Datasets:

leoleoasd

/

learningq_ted_ed

like 0

germanium is the first element in the periodic table , beginning at hydrogen , that ’ s named after a country : it is named after germany . there are other elements named after france and poland and america but we will come to those later . one of the things about germanium and what really makes it important in the periodic table is that this is one of the elements which was unknown when mendeleev constructed the periodic table and he predicted its existence and when it was found it had many of the properties that he had predicted based on the change in properties as you go down and across the periodic table . so this is a small sample of germanium , named after germany , so you can see the wonderful shiny surfaces . germanium is used quite widely as a so-called semi- conducting material . if you look at it in visible light it looks like a metal . germanium na , na , n-na na . i have used germanium mirrors in some of my experiments . the lasers that i used when i was younger had a germanium mirror that let the light out at the front of it and germanium is used quite widely in electronics . this is quite a nice piece of germanium . unfortunately i broke it somewhat earlier in my career , but you can see very nicely how this material looks like a piece of metal but on the other hand if you shine infrared light through it , it ’ s transparent so the infrared light will through but visible light doesn ’ t .

if you look at it in visible light it looks like a metal . germanium na , na , n-na na . i have used germanium mirrors in some of my experiments . the lasers that i used when i was younger had a germanium mirror that let the light out at the front of it and germanium is used quite widely in electronics . this is quite a nice piece of germanium . unfortunately i broke it somewhat earlier in my career , but you can see very nicely how this material looks like a piece of metal but on the other hand if you shine infrared light through it , it ’ s transparent so the infrared light will through but visible light doesn ’ t .

germanium is in the same group as carbon and silicon , but while both carbon and silicon have the stable oxidation state of +4 , what about germanium ? why is this the case ?

at pixar , we 're all about telling stories , but one story that has n't been told very much is the huge degree to which math is used in the production of our films . the math that you 're learning in middle school and high school is used all the time at pixar . so , let 's start with a very simple example . anybody recognize this guy ? ( cheers ) yeah , so this is woody from toy story , and let 's ask woody to , say , walk across the stage from , say , left to right , just like that . so , believe it or not , you just saw a ton of mathematics . where is it ? well , to explain that , it 's important to understand that artists and designers think in terms of shape and images but computers think in terms of numbers and equations . so , to bridge those two worlds we use a mathematical concept called coordinate geometry , right ? that is , we lay down a coordinate system with x describing how far something is to the right and y describing how high something is . so , with these coordinates we can describe where woody is at any instant in time . for instance , if we know the coordinates of the lower left corner of that image , then we know where the rest of the image is . and in that little sliding animation we saw a second ago , that motion we call translation , the x coordinate started with a value of one , and it ended with a value of about five . so , if we want to write that in mathematics , we see that the x at the end is four bigger than x at the start . so , in other words , the mathematics of translation is addition . alright ? how about scaling ? that is making something bigger or smaller . any guesses as to what the mathematics of scaling might be ? dilation , multiplication , exactly . if you 're going to make something twice as big , you need to mulitply the x and the y coordinates all by two . so , this shows us that the mathematics of scaling is mulitiplication . okay ? how about this one ? how about rotation ? alright , spinning around . the mathematics of rotation is trigonometry . so , here 's an equation that expresses that . it looks a little scary at first . you 'll probably get this in eighth or ninth grade . if you find yourselves sitting in trigonometry class wondering when you 're ever going to need this stuff , just remember that any time you see anything rotate in one of our films , there 's trigonometry at work underneath . i first fell in love with mathematics in seventh grade . any seventh graders ? a few of you ? yeah . my seventh grade science teacher showed me how to use trigonometry to compute how high the rockets that i was building was going . i just thought that was amazing , and i 've been enamored with math ever since . so , this is kind of old mathematics . mathematics that 's been known and , you know , developed by the old dead greek guys . and there 's a myth out there that all the interesting mathematics has already been figured out , in fact all of mathematics has been figured out . but the real story is that new mathematics is being created all the time . and some of it is being created at pixar . so , i 'd like to give you an example of that . so , here are some characters from some of our early films : finding nemo , monsters inc. and toy story 2 . anybody know who the blue character in the upper left is ? it 's dory . okay , that was easy . here 's a little harder one . anybody know who 's the character in the lower right ? al mcwhiggin from al 's toy barn , exactly . the thing to notice about these characters is they 're really complicated . those shapes are really complicated . in fact , the toy cleaner , i have an example , the toy cleaner there in the middle , here 's his hand . you can imagine how fun it was to bring this through airport security . his hand is a really complicated shape . it 's not just a bunch of spheres and cylinders stuck together , right ? and not only is it complicated , but it has to move in complicated ways . so , i 'd like to tell you how we do that , and to do that i need to tell you about midpoints . so , here 's a couple of points , a and b , and the line segment between them . we 're going to start out first in two dimensions . the midpoint , m , is the point that splits that line segment in the middle , right ? so , that 's the geometry . to make equations and numbers , we again introduce a coordinate system , and if we know the coordinates of a and b , we can easily compute the coordinates of m just by averaging . you now know enough to work at pixar . let me show you . so , i 'm going to do something slightly terrifying and move to a live demo here . so , what i have is a four-point polygon here , and it 's going to be my job to make a smooth curve out of this thing . and i 'm going to do it just using the idea of midpoints . so , the first thing i 'm going to do is an operation i 'll call split , which adds midpoints to all those edges . so , i went from four points to eight points , but it 's no smoother . i 'm going to make it a little bit smoother by moving all of these points from where they are now to the midpoint of their clockwise neighbor . so , let me animate that for you . i 'm going to call that the averaging step . so , now i 've got eight points , they 're a little bit smoother , my job is to make a smooth curve , so what do i do ? do it again . split and average . so , now i 've got sixteen points . i 'm going to put those two steps , split and average , together into something i 'll call subdivide , which just means split and then average . so , now i 've got 32 points . if that 's not smooth enough , i 'll do more . i 'll get 64 points . do you see a smooth curve appearing here from those original points ? and that 's how we create the shapes of our charcters . but remember , i said a moment ago it 's not enough just to know the static shape , the fixed shape . we need to animate it . and to animate these curves , the cool thing about subdivision . did you see the aliens in toy story ? you know that sound they make , `` ooh '' ? ready ? so , the way we animate these curves is simply by animating the original four points . `` ooh . '' alright , i think that 's pretty cool , and if you do n't , the door is there , it does n't get any better than that , so . this idea of splitting and averaging also holds for surfaces . so , i 'll split , and i 'll average . i 'll split , and i 'll average . put those together into subdivide , and this how we actually create the shapes of all of our surface characters in three dimensions . so , this idea of subdivision was first used in a short film in 1997 called geri 's game . and geri actually made a cameo apperance in toy story 2 as the toy cleaner . each of his hands was the first time we ever used subdivision . so , each hand was a subdivision surface , his face was a subdivision surface , so was his jacket . here 's geri 's hand before subdivision , and here 's geri 's hand after subdivision , so subdivision just goes in and smooths out all those facets , and creates the beautiful surfaces that you see on the screen and in the theaters . since that time , we 've built all of our characters this way . so , here 's merida , the lead character from brave . her dress was a subdivision surface , her hands , her face . the faces and hands of all the clansman were subdivision surfaces . today we 've seen how addition , multiplication , trigonometry and geometry play a roll in our films . given a little more time , i could show you how linear algebra , differential calculus , integral calculus also play a roll . the main thing i want you to go away with today is to just remember that all the math that you 're learning in high school and actually up through sophomore college we use all the time , everyday , at pixar . thanks .

it 's dory . okay , that was easy . here 's a little harder one .

design a character that would be really easy to describe mathematically . what makes the design easy ?

is it a flying comma , or a quotation mark chopped in half ? either way , you may already be well-versed in how to use the apostrophe , but here 's a quick refresher on its usage . the apostrophe can be used in three ways : to mark possession , to mark contraction , to mark the plural of single letters . most of the time , if you see an apostrophe hovering helpfully near a word , it 's trying to mark possession or contraction . first , let 's look at how the apostrophe marks possession . as you can see , the placement of this punctuation mark can really change the meaning of a sentence . `` those robots in the sand are my sister 's . '' `` those robots in the sand are my sisters . ' '' `` those robots in the sand are my sisters . '' when showing possession , the apostrophe belongs next to the noun that owns or possesses something . the noun can be singular or plural . proper nouns work , too . so if lucy needs to get her robots under control before they cause mayhem , those dangerous creatures would be `` lucy 's robots . '' but what if lucy was lucas ? would we write `` lucas ' robots '' or `` lucas 's robots '' ? and what if lucas gave his robots to the robinsons family ? would it be `` the robinsons ' robots , '' or `` the robinsons 's robots '' ? the truth is , even grammar nerds disagree on the right thing to do . the use of 's after a proper noun ending in s is a style issue , not a hard and fast grammar rule . it 's a conundrum without a simple answer . professional writers solve this problem by learning what 's considered correct for a publication , and doing that . the important thing is to pick one style and stick with it throughout a piece of writing . one more wrinkle . certain pronouns already have possession built in and do n't need an apostrophe . remembering that will help you avoid one of the trickiest snags in english grammar : its vs. it 's . `` it 's '' only take an apostrophe when it 's a contraction for `` it is '' or `` it has . '' if you can replace `` it 's '' with one of those two phrases , use the apostrophe . if you 're showing possession , leave it out . otherwise , contractions are pretty straightforward . the apostrophe stands in for missing letters , and lets common phrases squash into a single word . in rare cases , you can have a double contraction , though those generally are n't accepted in writing , with the exception of dialogue . so it 's possessive , it 's often followed by s 's , and it 's sometimes tricky when it comes to its usage . it 's the apostrophe .

certain pronouns already have possession built in and do n't need an apostrophe . remembering that will help you avoid one of the trickiest snags in english grammar : its vs. it 's . `` it 's '' only take an apostrophe when it 's a contraction for `` it is '' or `` it has . ''

as the english language evolves , so do english grammar `` rules '' and `` style '' choices . why ?

the biggest kidney stone on record weighed more than a kilogram and was 17 centimeters in diameter . the patient did n't actually swallow a stone the size of a coconut . kidney stones form inside the body , but unfortunately , they 're extremely painful to get out . a kidney stone is a hard mass of crystals that can form in the kidneys , ureters , bladder , or urethra . urine contains compounds that consist of calcium , sodium , potassium , oxalate , uric acid , and phosphate . if the levels of these particles get too high , or if urine becomes too acidic or basic , the particles can clump together and crystallize . unless the problem is addressed , the crystals will gradually grow over a few weeks , months , or even years , forming a detectable stone . calcium oxalate is the most common type of crystal to form this way , and accounts for about 80 % of kidney stones . less common kidney stones are made of calcium phosphate , or uric acid . a slightly different type of stone made of the minerals magnesium ammonium phosphate , or struvite , can be caused by bacterial infection . and even rarer stones can result from genetic disorders or certain medications . a kidney stone can go undetected until it starts to move . when a stone travels through the kidney and into the ureter , its sharp edges scratch the walls of the urinary tract . nerve endings embedded in this tissue transmit excruciating pain signals through the nervous system . and the scratches can send blood flowing into the urine . this can be accompanied by symptoms of nausea , vomiting , and a burning sensation while urinating . if a stone gets big enough to actually block the flow of urine , it can create an infection , or back flow , and damage the kidneys themselves . but most kidney stones do n't become this serious , or even require invasive treatment . masses less than five millimeters in diameter will usually pass out of the body on their own . a doctor will often simply recommend drinking large amounts of water to help speed the process along , and maybe taking some pain killers . if the stone is slightly larger , medications like alpha blockers can help by relaxing the muscles in the ureter and making it easier for the stone to get through . another medication called potassium citrate can help dissolve the stones by creating a less acidic urine . for medium-sized stones up to about ten millimeters , one option is pulverizing them with soundwaves . extracorporeal shock wave lithotripsy uses high-intensity pulses of focused ultrasonic energy aimed directly at the stone . the pulses create vibrations inside the stone itself and small bubbles jostle it . these combined forces crush the stone into smaller pieces that can pass out of the body more easily . but zapping a stone with sound does n't work as well if it 's simply too big . so sometimes , more invasive treatments are necessary . a rigid tube called a stent can be placed in the ureter to expand it . optical fibers can deliver laser pulses to break up the stone . stones can also be surgically removed through an incision in the patient 's back or groin . what about just avoiding kidney stones in the first place ? for people prone to them , their doctor may recommend drinking plenty of water , which dilutes the calcium oxalate and other compounds that eventually build up into painful stones . foods like potato chips , spinach , rhubarb , and beets are high in oxalate , so doctors might advise limiting them . even though calcium is often found in stones , calcium in foods and beverages can actually help by binding to oxalate in the digestive tract before it can be absorbed and reach the kidneys . if you do end up with a kidney stone , you 're not alone . data suggests that rates are rising , but that world record probably wo n't be broken any time soon .

stones can also be surgically removed through an incision in the patient 's back or groin . what about just avoiding kidney stones in the first place ? for people prone to them , their doctor may recommend drinking plenty of water , which dilutes the calcium oxalate and other compounds that eventually build up into painful stones .

what is happening to the incidence of kidney stones in the human population ?

despite advances in medicine , cancer remains one of the most frightening diagnoses patients can receive . what makes it so difficult to cure is that it 's not one illness , but a family of over 100 diseases occurring in different types of cells . and one type of cancer has the unfortunate distinction of afflicting children more than any other type . this is leukemia , a cancer that begins in stem cells found in the bone marrow . a stem cell is a bit like an infant , undeveloped but possessing great potential . many stem cells specialize and become cells of organs , like the liver , brain and heart . but in some tissues , they can continue to divide into new stem cells throughout development , and into adulthood in order to frequently generate new cells and keep up with the body 's needs . one example is the bone marrow , where stem cells differentiate into many types of blood cells . that includes red blood cells , which carry oxygen from the lungs to all tissues , platelets , which help stop bleeding by sticking to damaged blood vessels , and white blood cells , which patrol the body , destroying potentially harmful invaders . every once in a while , something goes wrong during a stem cell 's specialization process and harmful mutations occur in the cell 's dna . cells with compromised dna are supposed to self-destruct , but some damaged cells ignore this order , replicating uncontrollably , even as they lose their original function . these are what we know as cancer cells . it is not yet clear why leukemia is the most common childhood cancer , but one contributing factor may be that leukemias are often caused by just one or two dna modifications , while most cancers require many of them , allowing leukemias to arise faster than other types of cancer . moreover , some dna alterations can occur in white blood cells during fetal development , further increasing the risk of early leukemia . but though it affects more children than any other cancer , adults constitute the majority of leukemia patients overall . once leukemia strikes , the damaged cells reproduce in the blood and the bone marrow until they take up all available space and resources . when the bone marrow can no longer produce the required amount of functional cells , the blood becomes depleted . the lack of red blood cells means that muscles do n't get enough oxygen , the reduced number of platelets is not sufficient to repair wounds , and the dearth of functional white blood cells impairs the immune system , increasing the risk of infections . to restore the normal function of the blood , leukemic cells have to be eliminated . but because leukemias are not solid tumors , they ca n't be removed surgically . instead , the cells are killed inside the body using various treatments that include chemotherapy , a combination of drugs that destroys quickly multiplying cells . unfortunately , this has the side effect of killing healthy cells , such as those found in hair follicles or intestines . and in some cases , the dosage required is so high that it kills all cells in the bone marrow , including stem cells . when this happens , the body is no longer able to create new blood cells on its own . fortunately , outside help can come in the form of stem cells from the bone marrow of a donor . once transplanted into the patient , they rapidly repopulate the bone marrow and the blood . however , bone marrow transplants are a complicated process requiring antigen compatibility between the donor and recipient to keep the transplanted cells from from attacking the patient 's own cells as foreign bodies . unlike with blood transplants , there are thousands of hla types , and even siblings and close relatives may not have compatible bone marrow . if this is the case , the search is expanded to a database containing the genetic makeup of millions of voluntary bone marrow donors . the more potential donors there are , the more patients lives can be saved through successful transplants . leukemia may be a frightening disease , but there is strength and hope in numbers .

to restore the normal function of the blood , leukemic cells have to be eliminated . but because leukemias are not solid tumors , they ca n't be removed surgically . instead , the cells are killed inside the body using various treatments that include chemotherapy , a combination of drugs that destroys quickly multiplying cells .

doctors ca n't use surgery to remove leukemia because :

brady haran : hey there , everyone . today 's video is about richard feynman -- a lot of people 's favorite scientist -- and safe breaking . but i just wanted to point out at the start that most safes , or secure filing cabinets , actually have one dial . and if you 've got a three number combination , for example , you 'll turn that dial in one direction , then the other direction , and then back in the other direction . and that 's how you open it . but the mock up that we 've used in this video -- and it is a mock up , i can assure you . it 's about as far from a safe as you could get . we 've used three dials . that kind of makes things a bit more visual , a bit easier to understand looking at it in that way . but in most cases , the sort of safes we 're talking about will actually be using one dial . i do n't want to get all the safe enthusiasts out there too fired up and angry in the comments section . but for now , here 's professor bowley with his pretend safe and the story of richard feynman and his world war ii safe cracking . professor roger bowley : i 'm talking about feynman and how he managed to crack safes when he was working on the atomic bomb project in los alamos in the early '40s . his wife had died . so early in the 1940s , his wife died . and he was stuck in the middle of los alamos , not able to get out . it was a sort of desert area around there . he was stuck with lots of other theoretical physicists . so he needed something for amusement . and as a hobby , he tried cracking open all the safes in los alamos . now , they had new , purpose built safes with locks on them made by the mosler lock company . you can imagine 100 numbers for this , 100 numbers for that , 100 numbers for that -- a million , a million possible settings . and if you fiddle them around , it 'll take about five seconds to do it . so if you tried to crack it , it will take you about 60 days . on the average , it 'd be 30 days , but 60 days if you screw up and it takes the last one to open it . well , feynman was a group leader . so he was given one of these in his office to keep all the top secret files that he might come up with . so he knew how this worked mechanically , because he fiddled around with it . he 'd just fidget with anything . he wanted to know how it worked . and he found by trial and error , suppose the number should be 20 , it was set at . actually , it started at 25 , and a lot of people did n't change it from 25 , naught , 25 . that was the default . and if he wanted to crack the safe , a lot of times , people left it in the default setting , because it 's the easiest one to remember . suppose he set it at 20 . now , he found that if he tried to set it at 20 and it opened , he could also set it to 21 and it would open , or 22 . there was some slack on this . this was not mechanically perfect . so there was a bit of tolerance , plus or minus 2 on every single number , which meant that if you set it at 20 , it could be 21 or 22 or 19 or 18 -- and the same for this dial and the same for this dial . so now , if you go through all the combinations , you only have to do 3 , 8 , 13 and so on -- every fifth one -- to make sure you cover them all . now , there are only 20 settings for this , 20 for that , and 20 for that . so automatically , that 's gone down , oh , i ca n't do it . can you do it in your head , brady ? it 's really quite difficult . 8,000 different settings -- now , that becomes doable mechanically . it will take you something like 10 hours working solidly overnight . and you could do it . and he could do that . he worked out how to do it . he found out other ways of doing this . he found that most people will set a birthday , an anniversary , some well-defined date that -- i do n't know , the independence day in the united states of america , whatever . and it would not be an ordinary number , because if it 's going to be , say , my birthday , which is the 21st of april if anybody wants to send me presents . there 's the 21st . 04 -- 04 is there . and i 'm born in 1946 , which is down there . so for the top one , which is the days of the month , there are typically 30 days in a month . so let 's suppose there are just 30 and never 31 . 30 days in the month , you would need to set it in six different positions . now , for the months , there 's 12 months in the year , so you may need not two , but three for that . so now , we 've got six settings here , three settings there . and for the year -- well , now , the year , if it 's some date , it 's going to be something in the past . so how long back in the past is somewhat arbitrary . but suppose 45 would do , and then it would be 9 . he was doing it 1942 or '43 or '44 . all right . so the test would be somewhere around there . so 45 is a natural number to look at , because then you do n't have to go back into the previous century . 6 for this one , 3 for this one , and 9 for that one . and you multiply them together . and you get out 162 . so that 's 162 different settings . five seconds for each , 162 -- that 's 800 seconds . it 's about 12 minutes . so he could go in and if somebody had chosen one of those dates , instead of having 8,000 , he 's got 162 . and he can do it in 12 minutes . on the average , it will be six minutes , because he might be reach it in the first go or he might reach it after 12 minutes . but he would only require 12 minutes . so he would go in and make a big fuss of going into the office and say , i 'm not going to show the secrets . these are top secret stuff . i do n't want everybody to know my secrets . and he 'd carry in a bag with tools -- screwdrivers , picks , all sorts of things that people would think you crack safes with -- shut the door , and in 12 minutes , he would do it . he 'd take a magazine in with him . sometimes , he 'd get it done straight away and he 'd do some exercise and wait for 20 minutes just to make everybody believe it was tough work doing this . and then he 'd come out with a bit of sweat on his brow , saying , that was hard work . so those were the main techniques that he used . 162 means that this is n't safe and using your birthday or anniversary is not safe . but after that , he learned another trick . and he got the number down to 20 . out of all these million , there were 20 . and it turns out that if you open the safe and leave it open , and there 's a little draw on the bottom . and he goes into somebody else 's office . he chats to them . and the safe is open . he fiddles with all the knobs . and after two years of practice , he got these two sorted out by fiddling around with the knobs when the safe was open in somebody else 's office . he 'd go back afterwards -- and they do n't realize he 's been doing this -- and writes down these two numbers in a little book and says such and such . so by the end of the war , he could go into anybody 's office . he 's got the last two numbers . there are 20 settings . it takes him a minute and a half to open the safe , or less . so he really has to spin it up . he has a reputation of safe cracking . and everybody thinks he knows how to use picks . but he 's just used human nature , the tolerance of all this , and deviousness , just to show how clever he was . he was doing it just to show how clever he was . he was obnoxious . he would like to be one up on everybody else . but there was a security problem there . and the guy who he shared a room with was the guy who gave the secrets of the bomb to the russians , which is klaus fuchs . he was a roomie of his . brady haran : but for all his showing off about safe breaking , it turns out the real spy was in the room with him . professor roger bowley : yes . but i do n't -- well , yes . when you look at this , now that we live in worlds where you have a little security code for everything , this seems unbelievably primitive -- phone hacking and everything else going on . but people were n't -- if you 're a scientist , you 're not really looking at the other guy next door and wondering whether he 's letting all your secrets out .

i do n't want to get all the safe enthusiasts out there too fired up and angry in the comments section . but for now , here 's professor bowley with his pretend safe and the story of richard feynman and his world war ii safe cracking . professor roger bowley : i 'm talking about feynman and how he managed to crack safes when he was working on the atomic bomb project in los alamos in the early '40s .

why did richard feynman start cracking safes ?

right now , you 're probably sitting down to watch this video and staying seated for a few minutes to view it is probably okay . but the longer you stay put , the more agitated your body becomes . it sits there counting down the moments until you stand up again and take it for a walk . that may sound ridiculous . our bodies love to sit , right ? not really . sure , sitting for brief periods can help us recover from stress or recuperate from exercise . but nowadays , our lifestyles make us sit much more than we move around , and our bodies simply are n't built for such a sedentary existence . in fact , just the opposite is true . the human body is built to move , and you can see evidence of that in the way it 's structured . inside us are over 360 joints , and about 700 skeletal muscles that enable easy , fluid motion . the body 's unique physical structure gives us the ability to stand up straight against the pull of gravity . our blood depends on us moving around to be able to circulate properly . our nerve cells benefit from movement , and our skin is elastic , meaning it molds to our motions . so if every inch of the body is ready and waiting for you to move , what happens when you just do n't ? let 's start with the backbone of the problem , literally . your spine is a long structure made of bones and the cartilage discs that sit between them . joints , muscles and ligaments that are attached to the bones hold it all together . a common way of sitting is with a curved back and slumped shoulders , a position that puts uneven pressure on your spine . over time , this causes wear and tear in your spinal discs , overworks certain ligaments and joints , and puts strain on muscles that stretch to accommodate your back 's curved position . this hunched shape also shrinks your chest cavity while you sit , meaning your lungs have less space to expand into when you breath . that 's a problem because it temporarily limits the amount of oxygen that fills your lungs and filters into your blood . around the skeleton are the muscles , nerves , arteries and veins that form the body 's soft tissue layers . the very act of sitting squashes , pressurizes and compresses , and these more delicate tissues really feel the brunt . have you ever experienced numbness and swelling in your limbs when you sit ? in areas that are the most compressed , your nerves , arteries and veins can become blocked , which limits nerve signaling , causing the numbness , and reduces blood flow in your limbs , causing them to swell . sitting for long periods also temporarily deactivates lipoprotein lipase , a special enzyme in the walls of blood capillaries that breaks down fats in the blood , so when you sit , you 're not burning fat nearly as well as when you move around . what effect does all of this stasis have on the brain ? most of the time , you probably sit down to use your brain , but ironically , lengthy periods of sitting actually run counter to this goal . being stationary reduces blood flow and the amount of oxygen entering your blood stream through your lungs . your brain requires both of those things to remain alert , so your concentration levels will most likely dip as your brain activity slows . unfortunately , the ill effects of being seated do n't only exist in the short term . recent studies have found that sitting for long periods is linked with some types of cancers and heart disease and can contribute to diabetes , kidney and liver problems . in fact , researchers have worked out that , worldwide , inactivity causes about 9 % of premature deaths a year . that 's over 5 million people . so what seems like such a harmless habit actually has the power to change our health . but luckily , the solutions to this mounting threat are simple and intuitive . when you have no choice but to sit , try switching the slouch for a straighter spine , and when you do n't have to be bound to your seat , aim to move around much more , perhaps by setting a reminder to yourself to get up every half hour . but mostly , just appreciate that bodies are built for motion , not for stillness . in fact , since the video 's almost over , why not stand up and stretch right now ? treat your body to a walk . it 'll thank you later .

it sits there counting down the moments until you stand up again and take it for a walk . that may sound ridiculous . our bodies love to sit , right ?

sitting may help your brain function better .

you 've probably heard of the human genome , the huge collection of genes inside each and every one of your cells . you probably also know that we 've sequenced the human genome , but what does that actually mean ? how do you sequence someone 's genome ? let 's back up a bit . what is a genome ? well , a genome is all the genes plus some extra that make up an organism . genes are made up of dna , and dna is made up of long , paired strands of a 's , t 's , c 's , and g 's . your genome is the code that your cells use to know how to behave . cells interacting together make tissues . tissues cooperating with each other make organs . organs cooperating with each other make an organism , you ! so , you are who you are in large part because of your genome . the first human genome was sequenced ten years ago and was no easy task . it took two decades to complete , required the effort of hundreds of scientists across dozens of countries , and cost over three billion dollars . but some day very soon , it will be possible to know the sequence of letters that make up your own personal genome all in a matter of minutes and for less than the cost of a pretty nice birthday present . how is that possible ? let 's take a closer look . knowing the sequence of the billions of letters that make up your genome is the goal of genome sequencing . a genome is both really , really big and very , very small . the individual letters of dna , the a 's , t 's , g 's , and c 's , are only eight or ten atoms wide , and they 're all packed together into a clump , like a ball of yarn . so , to get all that information out of that tiny space , scientists first have to break the long string of dna down into smaller pieces . each of these pieces is then separated in space and sequenced individually , but how ? it 's helpful to remember that dna binds to other dna if the sequences are the exact opposite of each other . a 's bind to t 's , and t 's bind to a 's . g 's bind to c 's , and c 's to g 's . if the a-t-g-c sequence of two pieces of dna are exact opposites , they stick together . because the genome pieces are so very small , we need some way to increase the signal we can detect from each of the individual letters . in the most common method , scientists use enzymes to make thousands of copies of each genome piece . so , we now have thousands of replicas of each of the genome pieces , all with the same sequence of a 's , t 's , g 's , and c 's . but we have to read them all somehow . to do this , we need to make a batch of special letters , each with a distinct color . a mixture of these special colored letters and enzymes are then added to the genome we 're trying to read . at each spot on the genome , one of the special letters binds to its opposite letter , so we now have a double-stranded piece of dna with a colorful spot at each letter . scientists then take pictures of each snippet of genome . seeing the order of the colors allows us to read the sequence . the sequences of each of these millions of pieces of dna are stitched together using computer programs to create a complete sequence of the entire genome . this is n't the only way to read the letter sequences of pieces of dna , but it 's one of the most common . of course , just reading the letters in the genome does n't tell us much . it 's kind of like looking through a book written in a language you do n't speak . you can recognize all the letters but still have no idea what 's going on . so , the next step is to decipher what the sequence means , how your genome and my genome are different . interpreting the genes of the genome is the part scientists are still working on . while not every difference is consequential , the sum of these differences is responsible for differences in how we look , what we like , how we act , and even how likely we are to get sick or respond to specific medicines . better understanding of how disparities between our genomes account for these differences is sure to change the way we think not only about how doctors treat their patients , but also how we treat each other .

you probably also know that we 've sequenced the human genome , but what does that actually mean ? how do you sequence someone 's genome ? let 's back up a bit .

if there are 3 billion letters in the reference genome , how much did it cost per letter to sequence the first human genome ?

since the dawn of humanity , an estimated 100.8 billion people have lived and died , a number that increases by about .8 % of the world 's population each year . what happens to all of those people 's bodies after they die and will the planet eventually run out of burial space ? when a person 's heart stops beating , the body passes through several stages before it begins decomposing . within minutes after death , the blood begins settling in the lower-most parts of the body . usually eight to twelve hours later , the skin in those areas is discolored by livor mortis , or post-mortem stain . and while at the moment of death the body 's muscles relax completely in a condition called primary flaccidity , they stiffen about two to six hours later in what 's known as rigor mortis . this stiffening spreads through the muscles , and its speed can be affected by age , gender , and the surrounding environment . the body also changes temperature , usually cooling off to match its environment . next comes decomposition , the process by which bacteria and insects break apart the body . many factors affect the rate of decomposition . there is , however , a basic guide of the effect of the environment on decompositon called casper 's law . it says that if all other factors are equal , a body exposed to air decomposes twice as fast as one immersed in water and eight times as fast as one buried in earth . soil acidity also greatly affects bone preservation . high-acidity soils with a ph of less than 5.3 will rapidly decompose bone , whereas in a neutral or basic soil with a ph of 7 or more , a skeleton can remain in relatively good condition for centuries . different cultures throughout history have developed unique approaches to burials . as far back as the first neanderthal burials , death was accompanied by rituals , like the positioning , coloring , or decorating of corpses . traditional christian burials decorate the body in dress , while in traditional islam , a body is wrapped in a piece of ritual fabric with the face oriented toward mecca . traditional hindus ceremonially burn the body , and zoroastrians , followers of one of the oldest monotheistic religions , traditionally place bodies atop a tower to expose them to the sun and scavenging birds.` before the industrial revolution , burials were simple and accessible . these days , with suitable burial land running out in high-population areas , purchasing private gravesites can be costly , and many people ca n't afford simple burials . even cremation , the second most common burial practice in the world , comes with a high cost . as for the question of running out of space , the issue is n't so much about total land in the world as it is that large populations cluster together within cities . most of the big cities in the world may run out of suitable burial grounds within a century . for london , it 's even sooner . that may happen by 2035 . so are there alternatives to traditional burials that might help with the space issue ? in some countries , skyscraper cemeteries enable vertical burials . some options focus on the body 's relationship with the environment . promession , for example , freeze-dries and pulverizes the body , creating a powder that can turn into compost when mixed with oxygen and water . there are also green burials that use special materials , such as biodegradable caskets , urns that sprout trees , and burial suits that grow mushrooms . eternal reefs take that concept to the depths of the ocean using a mixture of ashes and cement to create marine habitats for sea life . death is an inevitable part of the human condition , but how we treat bodies and burials continues to evolve . we may each have different spiritual , religious , or practical approaches to dying , but the ever-increasing demand for burial space might give us a push to be creative about where our bodies go after the final stages of life .

these days , with suitable burial land running out in high-population areas , purchasing private gravesites can be costly , and many people ca n't afford simple burials . even cremation , the second most common burial practice in the world , comes with a high cost . as for the question of running out of space , the issue is n't so much about total land in the world as it is that large populations cluster together within cities .

what is the second most common burial method ?

the secrets of the x chromosome . these women are identical twins . they have the same nose , the same hair color , the same eye color . but this one is color blind for green light , and this one is n't . how is that possible ? the answer lies in their genes . for humans , the genetic information that determines our physical traits is stored in 23 pairs of chromosomes in the nucleus of every cell . these chromosomes are made up of proteins and long , coiled strands of dna . segments of dna , called genes , tell the cell to build specific proteins , which control its identity and function . for every chromosome pair , one comes from each biological parent . in 22 of these pairs , the chromosomes contain the same set of genes , but may have different versions of those genes . the differences arrive from mutations , which are changes to the genetic sequence that may have occurred many generations ago . some of those changes have no effect , some cause diseases , and some lead to advantageous adaptations . the result of having two versions of each gene is that you display a combination of your biological parents ' traits . but the 23rd pair is unique , and that 's the secret behind the one color blind twin . this pair , called the x and y chromosomes , influences your biological sex . most women have two x chromosomes while most men have one x and one y . the y chromosome contains genes for male development and fertility . the x chromosome , on the other hand , contains important genes for things other than sex determination or reproduction , like nervous system development , skeletal muscle function , and the receptors in the eyes that detect green light . biological males with an xy chromosome pair only get one copy of all these x chromosome genes , so the human body has evolved to function without duplicates . but that creates a problem for people with two x chromosomes . if both x chromosomes produced proteins , as is normal in other chromosomes , development of the embryo would be completely impaired . the solution is x inactivation . this happens early in development when an embryo with two x chromosomes is just a ball of cells . each cell inactivates one x chromosome . there 's a certain degree of randomness to this process . one cell may inactivate the x chromosome from one parent , and another the chromosome from the other parent . the inactive x shrivels into a clump called a barr body and goes silent . almost none of its genes order proteins to be made . when these early cells divide , each passes on its x inactivation . so some clusters of cells express the maternal x chromosome , while others express the paternal x . if these chromosomes carry different traits , those differences will show up in the cells . this is why calico cats have patches . one x had a gene for orange fur and the other had a gene for black fur . the pattern of the coat reveals which one stayed active where . now we can explain our color blind twin . both sisters inherited one mutant copy of the green receptor gene and one normally functioning copy . the embryo split into twins before x inactivation , so each twin ended up with a different inactivation pattern . in one , the x chromosome with the normal gene was turned off in the cells that eventually became eyes . without those genetic instructions , she now ca n't sense green light and is color blind . disorders that are associated with mutations of x chromosome genes , like color blindness , or hemophilia , are often less severe in individuals with two x chromosomes . that 's because in someone with one normal and one mutant copy of the gene , only some of their cells would be affected by the mutation . this severity of the disorder depends on which x got turned off and where those cells were . on the other hand , all the cells in someone with only one x chromosome can only express the mutant copy of the gene if that 's what they inherited . there are still unresolved questions about x inactivation , like how some genes on the x chromosome escape inactivation and why inactivation is n't always random . what we do know is that this mechanism is one of the many ways that genes alone do n't tell our whole story .

now we can explain our color blind twin . both sisters inherited one mutant copy of the green receptor gene and one normally functioning copy . the embryo split into twins before x inactivation , so each twin ended up with a different inactivation pattern .

what is one cause of colorblindness ?

testing , testing , one , two , three . when your band is trying to perform , feedback is an annoying obstacle , but in the grand orchestra of nature , feedback is not only beneficial , it 's what makes everything work . what exactly is feedback ? the key element , whether in sound , the environment or social science , is a phenomenon called mutual causal interaction , where x affects y , y affects x , and so on , creating an ongoing process called a feedback loop . and the natural world is full of these mechanisms formed by the links between living and nonliving things that build resilience by governing the way populations and food webs respond to events . when plants die , the dead material enriches the soil with humus , a stable mass of organic matter , providing moisture and nutrients for other plants to grow . the more plants grow and die , the more humus is produced , allowing even more plants to grow , and so on . this is an example of positive feedback , an essential force in the buildup of ecosystems . but it 's not called positive feedback because it 's beneficial . rather , it is positive because it amplifies a particular effect or change from previous conditions . these positive , or amplifying , loops can also be harmful , like when removing a forest makes it vulnerable to erosion , which removes organic matter and nutrients from the earth , leaving less plants to anchor the soil , and leading to more erosion . in contrast , negative feedback diminishes or counteracts changes in an ecosystem to maintain a more stable balance . consider predators and their prey . when lynx eat snowshoe hares , they reduce their population , but this drop in the lynx 's food source will soon cause their own population to decline , reducing the predation rate and allowing the hare population to increase again . the ongoing cycle creates an up and down wavelike pattern , maintaining a long-term equilibrium and allowing a food chain to persist over time . feedback processes might seem counterintuitive because many of us are used to more predictable linear scenarios of cause and effect . for instance , it seems simple enough that spraying pesticides would help plants grow by killing pest insects , but it may trigger a host of other unexpected reactions . for example , if spraying pushes down the insect population , its predators will have less food . as their population dips , the reduced predation would allow the insect population to rise , counteracting the effects of our pesticides . note that each feedback is the product of the links in the loop . add one negative link and it will reverse the feedback force entirely , and one weak link will reduce the effect of the entire feedback considerably . lose a link , and the whole loop is broken . but this is only a simple example , since natural communities consist not of separate food chains , but networks of interactions . feedback loops will often be indirect , occurring through longer chains . a food web containing twenty populations can generate thousands of loops of up to twenty links in length . but instead of forming a disordered cacophany , feedback loops in ecological systems play together , creating regular patterns just like multiple instruments , coming together to create a complex but harmonious piece of music . wide-ranging negative feedbacks keep the positive feedbacks in check , like drums maintaining a rhythm . you can look at the way a particular ecosystem functions within its unique habitat as representing its trademark sound . ocean environments dominated by predator-prey interactions , and strong negative and positive loops stabilized by self-damping feedback , are powerful and loud , with many oscillations . desert ecosystems , where the turn over of biomass is slow , and the weak feedbacks loops through dead matter are more like a constant drone . and the tropical rainforest , with its great diversity of species , high nutrient turnover , and strong feedbacks among both living and dead matter , is like a lush panoply of sounds . despite their stabilizing effects , many of these habitats and their ecosystems develop and change over time , as do the harmonies they create . deforestation may turn lush tropics into a barren patch , like a successful ensemble breaking up after losing its star performers . but an abandoned patch of farmland may also become a forest over time , like a garage band growing into a magnificent orchestra .

a food web containing twenty populations can generate thousands of loops of up to twenty links in length . but instead of forming a disordered cacophany , feedback loops in ecological systems play together , creating regular patterns just like multiple instruments , coming together to create a complex but harmonious piece of music . wide-ranging negative feedbacks keep the positive feedbacks in check , like drums maintaining a rhythm . you can look at the way a particular ecosystem functions within its unique habitat as representing its trademark sound .

how do all the feedbacks together in an ecosystem create harmony ? one important mechanism is :

imagine if half the people in your neighborhood , your city , or even your whole country were wiped out . it might sound like something out of an apocalyptic horror film , but it actually happened in the 14th century during a disease outbreak known as the black death . spreading from china through asia , the middle east , africa and europe , the devastating epidemic destroyed as much as 1/5 of the world 's population , killing nearly 50 % of europeans in just four years . one of the most fascinating and puzzling things abut the black death is that the illness itself was not a new phenomenon but one that has affected humans for centuries . dna analysis of bone and tooth samples from this period , as well as an earlier epidemic known as the plague of justinian in 541 ce , has revealed that both were caused by yersinia pestis , the same bacterium that causes bubonic plague today . what this means is that the same disease caused by the same pathogen can behave and spread very differently throughout history . even before the use of antibiotics , the deadliest oubreaks in modern times , such as the ones that occurred in early 20th century india , killed no more than 3 % of the population . modern instances of plague also tend to remain localized , or travel slowly , as they are spread by rodent fleas . but the medieval black death , which spread like wildfire , was most likely communicated directly from one person to another . and because genetic comparisons of ancient to modern strains of yersinia pestis have not revealed any significantly functional genetic differences , the key to why the earlier outbreak was so much deadlier must lie not in the parasite but the host . for about 300 years during the high middle ages , a warmer climate and agricultural improvements had led to explosive population growth throughout europe . but with so many new mouths to feed , the end of this warm period spelled disaster . high fertility rates combined with reduced harvest , meant the land could no longer support its population , while the abundant supply of labor kept wages low . as a result , most europeans in the early 14th century experienced a steady decline in living standards , marked by famine , poverty and poor health , leaving them vulnerable to infection . and indeed , the skeletal remains of black death victims found in london show telltale signs of malnutrition and prior illness . the destruction caused by the black death changed humanity in two important ways . on a societal level , the rapid loss of population led to important changes in europe 's economic conditions . with more food to go around , as well as more land and better pay for the surviving farmers and workers , people began to eat better and live longer as studies of london cemeteries have shown . higher living standards also brought an increase in social mobility , weakening feudalism , and eventually leading to political reforms . but the plague also had an important biological impact . the sudden death of so many of the most frail and vulnerable people left behind a population with a significantly different gene pool , including genes that may have helped survivors resist the disease . and because such mutations often confer immunities to multiple pathogens that work in similar ways , research to discover the genetic consequences of the black death has the potential to be hugely beneficial . today , the threat of an epidemic on the scale of the black death has been largely eliminated thanks to antibiotics . but the bubonic plague continues to kill a few thousand people worldwide every year , and the recent emergence of a drug-resistant strain threatens the return of darker times . learning more about the causes and effects of the black death is important , not just for understanding how our world has been shaped by the past . it may also help save us from a similar nightmare in the future .

as a result , most europeans in the early 14th century experienced a steady decline in living standards , marked by famine , poverty and poor health , leaving them vulnerable to infection . and indeed , the skeletal remains of black death victims found in london show telltale signs of malnutrition and prior illness . the destruction caused by the black death changed humanity in two important ways . on a societal level , the rapid loss of population led to important changes in europe 's economic conditions .

what proportion of the affected population was killed by the black death ?

with social media sites being used by ⅓ of the entire world , they ’ ve clearly had an major influence on society . but what about our bodies ? here are 5 crazy ways that social media and the internet are affecting your brain right now ! can ’ t log off ? surprisingly , 5-10 % of internet users are actually unable to control how much time they spend online . though it ’ s a psychological addiction as opposed to a substance addiction , brain scans of these people actually show a similar impairment of regions that those with drug dependence have . specifically , there is a clear degradation of white matter in the regions that control emotional processing , attention and decision making . because social media provides immediate rewards with very little effort required , your brain begin to rewire itself , making you desire these stimulations . and you begin to crave more of this neurological excitement after each interaction . sounds a little like a drug , right ? we also see a shift when looking at multi-tasking . you might think that those who use social media or constantly switch between work and websites are better at multitasking , but studies have found that when comparing heavy media users to others , they perform much worse during task switching tests . increased multi-tasking online reduces your brains ability to filter out interferences , and can even make it harder for your brain to commit information to memory . like when your phone buzzes in the middle of productive work . or wait ... did it even buzz ? phantom vibration syndrome is a relatively new psychological phenomenon where you think you felt your phone go off , but it didn ’ t . in one study , 89 % of test subjects said they experienced this at least once every two weeks . it would seem that our brains now perceive an itch as an actual vibration from our phone . as crazy as it seems , technology has begun to rewire our nervous systems - and our brains are being triggered in a way they never have been before in history . social media also triggers a release of dopamine - the feel good chemical . using mri scans , scientist found that the reward centres in people ’ s brains are much more active when they are talking about their own views , as opposed to listening to others . not so surprising - we all love talking about ourselves right ? but it turns out that while 30-40 % of face-to-face conversations involve communicating our own experiences , around 80 % of social media communication is self involved . the same part of your brain related to orgasms , motivation and love are stimulated by your social media use - and even more so when you know you have an audience . our body is physiologically rewarding us for talking about ourselves online ! but it ’ s not all so self involved . in fact , studies on relationships have found that partners tend to like each other more if they meet for the first time online rather than with a face to face interaction . whether it ’ s because people are more anonymous or perhaps more clear about their future goals , there is a statistical increase in successful partnerships that started online . so while the internet has changed our verbal communication with increased physical separation , perhaps the ones that matter most end up even closer . speaking of social media , we had you ask us questions on twitter , instagram , facebook , tumblr , google+ and every other social platform we could find and did a q & amp ; amp ; a video over on asapthought ! so if you feel getting some insider info on asapscience and behind the scenes , check it out with the link in the description ! got a burning question you want answered ? ask it in the comments or on facebook and twitter . we also finally got a po box , for all of you amazing science lovers who have requested to send us mail or other stuff over the years . and we ’ d love to hear from all of you ! so feel free use the address on the screen or in the description box . and subscribe for more weekly science videos !

or wait ... did it even buzz ? phantom vibration syndrome is a relatively new psychological phenomenon where you think you felt your phone go off , but it didn ’ t . in one study , 89 % of test subjects said they experienced this at least once every two weeks .

in your own words , explain phantom vibration syndrome . have you ever experienced it ?

if i say , `` venice , '' do you imagine yourself gliding down the grand canal , serenaded by a gondolier ? there 's no doubt that the gondola is a symbol of venice , italy , but how did this curious banana-shaped black boat get its distinctive look ? the origins of the venetian gondola are lost to history , but by the 1500s , some 10,000 gondolas transported dignitaries , merchants and goods through the city 's canals . in fact , venice teemed with many types of handmade boats , from utilitarian rafts to the doge 's own ostentatious gilded barge . like a modern day taxi system , gondolas were leased to boatmen who made the rounds of the city 's ferry stations . passengers paid a fare to be carried from one side of the grand canal to the other , as well as to other points around the city . but gondoliers soon developed a bad rap . historical documents describe numerous infractions involving boatmen , including cursing , gambling , extorting passengers -- even occasional acts of violence . to minimize the unpredictability of canal travel , venetian citizens who could afford it purchased their own gondolas , just as a celebirty might use a private car and driver today . these wealthy venetians hired two private gondoliers to ferry them around the city and maintain their boats . the gondolas soon became a status symbol , much like an expensive car , with custom fittings , carved and gilded ornamentation , and seasonal fabrics , like silk and velvet . however , the majority of gondolas seen today are black because in 1562 , venetian authorities decreed that all but ceremonial gondolas be painted black in order to avoid sinfully extravagant displays . apparently , venetian authorities did not believe in `` pimping their rides . '' still , some wealthy venetians chose to pay the fines in order to maintain their ornamental gondolas , a small price to keep up appearances . the distinctive look of the gondola developed over many centuries . each gondola was constructed in a family boatyard called a squero . > from their fathers and grandfathers , sons learned how to select and season pieces of beech , cherry , elm , fir , larch , lime , mahogany , oak and walnut . the gondola makers began with a wooden template that may have been hammered into the workshop floor generations earlier . > from this basic form , they attached fore and aft sterns , then formed the longitudinal planks and ribs that made up the frame of a boat designed to glide through shallow , narrow canals . a gondola has no straight lines or edges . its familiar profile was achieved through an impressive fire and water process that involved warping the boards with torches made of marsh reeds set ablaze . however , the majority of the 500 hours that went into building a gondola involved the final stages : preparing surfaces and applying successive coats of waterproof varnish . the varnish was a family recipe , as closely guarded as one for risotto or a homemade sauce . yet even with the woodwork finished , the gondola was still not complete . specialized artisans supplied their gondola-making colleagues with elaborate covered passenger compartments , upholstery and ornaments of steel and brass . oar makers became integral partners to the gondola makers . the venetian oarlock , or fórcola , began as a simple wooden fork , but evolved into a high-precision tool that allowed a gondolier to guide the oar into many positions . by the late 1800s , gondola makers began to make the left side of the gondola wider than the right as a counter balance to the force created by a single gondolier . this modification allowed rowers to steer from the right side only , and without lifting the oar from the water . while these modifications improved gondola travel , they were not enough to keep pace with motorized boats . today , only about 400 gondolas glide through the waterways of venice , and each year , fewer authentic gondolas are turned out by hand . but along the alleys , street signs contain words in venetian dialect for the locations of old boatyards , oar makers and ferry stations , imprinting the memory of the boat-building trades that once kept life in the most serene republic gliding along at a steady clip .

specialized artisans supplied their gondola-making colleagues with elaborate covered passenger compartments , upholstery and ornaments of steel and brass . oar makers became integral partners to the gondola makers . the venetian oarlock , or fórcola , began as a simple wooden fork , but evolved into a high-precision tool that allowed a gondolier to guide the oar into many positions .

why do you think that gondoliers and gondola makers appear less frequently in historical documents than , let ’ s say , politicians or bankers ?

translator : andrea mcdonough reviewer : bedirhan cinar you might have heard that we 're running out of fresh water . this might sound strange to you because , if you live in a place where water flows freely from the tap or shower at any time , it sure does n't seem like a big deal . it 's just there , right ? wrong ! the only obvious thing about fresh water is how much we need it . because it 's essential to life , we need to think about it carefully . right now , at this very moment , some people , women and girls in particular , walk hours and miles per day to get fresh water , and even then , it may not be clean . every 15 seconds , a child dies due to water-born diseases . this is tragic ! the most compelling reasons to think about fresh water , therefore , have to do with what we might call the global common good . this is not something we normally think about , but it means recognizing how much fresh water matters for the flourishing of human and non-human life on earth now and in the future . how do we think about something as local as our faucets and as global as fresh water ? is there a connection between them ? many people assume that fresh water shortages are due to individual wastefulness : running the water while you brush your teeth , for example , or taking really long showers . most of us assume , therefore , that water shortages can be fixed by improving our personal habits : taking shorter showers or turning off the water while we brush our teeth . but , global fresh water scarcity neither starts nor ends in your shower . globally , domestic use of fresh water accounts for only 8 % of consumption , 8 % ! ! compare that to the 70 % that goes to agriculture and the 22 % that goes to industrial uses . now , hold up - you 're not off the hook ! individual habits are still part of the puzzle . you should still cultivate water virtue in your daily life , turn off the tap when you brush your teeth . but still , it 's true . taking shorter showers wo n't solve global problems , which is too bad . it would be much more straightforward and easier if virtuous , individual actions could do the trick . you 'd just stand there for 30 seconds less , and you 'd be done with that irksome , planet-saving task for the day . well , that 's not so much the case . agricultural and industrial patterns of water use need serious attention . how do our societies value water ? distribute it ? subsidize its use in agriculture ? incentivize its consumption or pollution ? these are all questions that stem from how we think about fresh water 's value . is it an economic commodity ? a human right ? a public good ? nobel prize winners , global water justice activists , transnational institutions like the united nations , and even the catholic church are at work on the issue . but , it 's tricky , too , because the business of water became very profitable in the 20th century . and profit is not the same thing as the common good . we need to figure out how to value fresh water as a public good , something that 's vital for human and non-human life , now and in the future . now that 's a virtuous , collective task that goes far beyond your shower .

agricultural and industrial patterns of water use need serious attention . how do our societies value water ? distribute it ?

in your own words , explain how our societies value water .

translator : andrea mcdonough reviewer : bedirhan cinar right now , trillions of chemical reactions are humming away in the cells of your body . you never feel them , but without these reactions , you would n't be alive . unfortunately , each of those reactions needs some help . you see , most molecules are stable , they are happy just the way they are . the atoms in them are all bound-up and friendly with one another and would prefer to stay that way . the problem is , for a chemical reaction to happen , the atoms that make up those stable molecules need to break away from their friends and go buddy up with another atom . this break-up is where the molecules need a hand . this initial kick-start is known as activation energy . it 's used to destabilize the molecule , to push the bonds between the atoms to a place where they are ready to break . this unstable state is known as the molecule 's transition state . once a transition state has been achieved , the atoms become willing to leave their current molecular friends and go make new friends elsewhere . once they are convinced , it 's a piece of cake . bonds break , atoms rearrange , and the rest of the reaction happens automatically . after that first push , the body does n't need to put in any more energy to help the reaction along . left alone , most of these reactions would be very slow because it takes quite a while to build up the activation energy the molecules need to get started . enter the enzyme . enzymes are proteins that speed up , or catalyze , reactions by lowering the activation energy . they make it easier for the molecule , also known as a substrate , to get to the transition state . you can think of a reaction like a race . some racers are running along , while others have teammates to help them . meet sam the substrate . his team is the mods squad . together , his team is able to get to the finish faster , using less energy . there are four special enzymes in sam 's team . each has a different strategy for lowering the energy it takes to get going and speeding up the pace to get the mods to the finish line . the `` m '' stands for `` microenvironment '' . this enzyme creates a tiny , special environment for the substrate , resulting in a faster reaction time . he runs ahead of the pack , flattening out bumps in the road and misting cool water on his team of molecules . `` o '' is for `` orientation '' . sometimes two molecules must be positioned just right before they will react . like a friend at the finish line , the o enzyme provides his molecules with specially shaped spaces that allow the substrates to interact in just the right way . `` d '' stands for `` direct participation '' . every now and again , a little muscle is needed . and when his teammates are struggling to finish the race , teammate d is there to pick them up and carry them over the line . finally , `` s '' is for `` straining bonds '' . this guy pushes the team through some serious flexibility exercises : splits , lunges , backbends , the works . sometimes his substrate teammates just need to be stressed and flexed into their transition state . so that 's it . remember that all reactions need energy to get going . this energy is known as the activation energy . enzymes lower that activation energy and speed the reaction through team mods : microenvironment , orientation , direct participation , and straining bonds .

once they are convinced , it 's a piece of cake . bonds break , atoms rearrange , and the rest of the reaction happens automatically . after that first push , the body does n't need to put in any more energy to help the reaction along .

in a chemical reaction , atoms do which of the following ?

you might remember a pair of ted-ed lessons written and performed by two educators , brad voytek and tim verstynen . these two scientists used a drooling , hag-faced , animated zombie as a mechanism to model the symptoms and medical diagnosis process for various neurological conditions . for example , they spent time debating whether the zombie 's stiff gait was caused by basal ganglia damage , like that in parkinson 's patients , or by severe damage to the cerebellum , which can cause ataxia . in each lesson , brad and tim certainly showed us how the walking dead can help us understand neuroscience , but how can the walking dead help us understand animation ? or , more simply put , how did this one-eyed , decaying , and very much dead pile of pixels walk ? puppet animation is a relatively quick solution to creating 2-d animation of a hand-drawn character . since the character does not need to be drawn over and over again , it can be animated by moving each element individually . aside from their portrayal in a few great modern zombie flicks , these concocted carcasses are generally known for limited , stiff movements . their traditional stride is perfect for puppet-style animation . when designing a 2-d zombie puppet , or any other type of puppet , it is important to find a design that is both fun and functional in a flat environment . for example , you might not want to puppetize , say , julie andrews in the `` sound of music '' as she spins in circles . we used rotoscoping for her , but that 's another lesson . always begin by sketching and designing your puppet in a neutral pose like this . this will allow it to easily transition into and out of a variety of extreme positions . once a character transitions from concept stetches to final design , the next step is to break up the pieces in order to assemble a puppet , keeping in mind that each element needs to have an appropriate amount of overlap so that the zombie can bend at his joints . an understanding of anatomy is an integral part of designing any 2-d or 3-d animated character that needs to move realistically in the context of its environment . regardless of the number of dimensions your character has , you 'll need to create a skeleton , which in animation terms is known as a rig . once the rig is finalized and the range of motion is determined , the next step is to choose anchor points . each piece of artwork has its own anchor point , which essentially assigns the limb a hinge , which in this case is a joint . next , line the artwork up so that the anchor point for the forearm-elbow sits on the upper arm 's elbow area . once all the artwork is in place , you can use an expression script that creates links between the body parts . in this case , we used the expressions provided in after effects . by parenting one layer to another , you could teach the forearm to follow the upper arm and the hand to follow the forearm . this is what 's called forward kinematics . the alternative is inverse kinematics , in which a separate set of scripts control the motions . in this case , a controller is attached to the anchor point of the hand . the animator then uses the controller to position the hand . the scripts will then use an algorithm to make sure that the rest of the arm and body follows along . once the character is rigged , we can start animating . often times , puppet animation is done as straight-ahead action , which means moving a character frame-by-frame from beginning to end . another approach is pose-to-pose animation , which involves choosing your key poses first , and then filling in the intervals , or in-betweens , later . regardless of the method of motion , it 's important to think of your 2-d puppet as a piece of paper . it can move across a surface in a variety of poses , but it can not move in perspective . if your character needs to turn its head , then you will need to create additional art . we created three different zombie heads and six different hands to achieve different movements and angles that the neutral pose could n't accommodate . you can recreate almost everything you 've seen in this lesson with a pen , paper , and a camera . the method is called cut-out animation , and it was around well before the age of software . to create a stumbling 2-d zombie , or a speeding narwhal , or even an abstract character with some semblance of joints , simply print , cut , and fasten your character 's limbs together in a neutral pose . you can use fasteners , string , or even just place and move them each time . all the same rules and theories that we use in the computer apply to cut-out animation , except under the camera , the only way to animate is straight ahead .

you might remember a pair of ted-ed lessons written and performed by two educators , brad voytek and tim verstynen . these two scientists used a drooling , hag-faced , animated zombie as a mechanism to model the symptoms and medical diagnosis process for various neurological conditions . for example , they spent time debating whether the zombie 's stiff gait was caused by basal ganglia damage , like that in parkinson 's patients , or by severe damage to the cerebellum , which can cause ataxia .

the two educators used a drooling , hag-faced , animated zombie as a mechanism to model the symptoms and medical diagnosis process for various neurological conditions .

testing , testing , one , two , three . when your band is trying to perform , feedback is an annoying obstacle , but in the grand orchestra of nature , feedback is not only beneficial , it 's what makes everything work . what exactly is feedback ? the key element , whether in sound , the environment or social science , is a phenomenon called mutual causal interaction , where x affects y , y affects x , and so on , creating an ongoing process called a feedback loop . and the natural world is full of these mechanisms formed by the links between living and nonliving things that build resilience by governing the way populations and food webs respond to events . when plants die , the dead material enriches the soil with humus , a stable mass of organic matter , providing moisture and nutrients for other plants to grow . the more plants grow and die , the more humus is produced , allowing even more plants to grow , and so on . this is an example of positive feedback , an essential force in the buildup of ecosystems . but it 's not called positive feedback because it 's beneficial . rather , it is positive because it amplifies a particular effect or change from previous conditions . these positive , or amplifying , loops can also be harmful , like when removing a forest makes it vulnerable to erosion , which removes organic matter and nutrients from the earth , leaving less plants to anchor the soil , and leading to more erosion . in contrast , negative feedback diminishes or counteracts changes in an ecosystem to maintain a more stable balance . consider predators and their prey . when lynx eat snowshoe hares , they reduce their population , but this drop in the lynx 's food source will soon cause their own population to decline , reducing the predation rate and allowing the hare population to increase again . the ongoing cycle creates an up and down wavelike pattern , maintaining a long-term equilibrium and allowing a food chain to persist over time . feedback processes might seem counterintuitive because many of us are used to more predictable linear scenarios of cause and effect . for instance , it seems simple enough that spraying pesticides would help plants grow by killing pest insects , but it may trigger a host of other unexpected reactions . for example , if spraying pushes down the insect population , its predators will have less food . as their population dips , the reduced predation would allow the insect population to rise , counteracting the effects of our pesticides . note that each feedback is the product of the links in the loop . add one negative link and it will reverse the feedback force entirely , and one weak link will reduce the effect of the entire feedback considerably . lose a link , and the whole loop is broken . but this is only a simple example , since natural communities consist not of separate food chains , but networks of interactions . feedback loops will often be indirect , occurring through longer chains . a food web containing twenty populations can generate thousands of loops of up to twenty links in length . but instead of forming a disordered cacophany , feedback loops in ecological systems play together , creating regular patterns just like multiple instruments , coming together to create a complex but harmonious piece of music . wide-ranging negative feedbacks keep the positive feedbacks in check , like drums maintaining a rhythm . you can look at the way a particular ecosystem functions within its unique habitat as representing its trademark sound . ocean environments dominated by predator-prey interactions , and strong negative and positive loops stabilized by self-damping feedback , are powerful and loud , with many oscillations . desert ecosystems , where the turn over of biomass is slow , and the weak feedbacks loops through dead matter are more like a constant drone . and the tropical rainforest , with its great diversity of species , high nutrient turnover , and strong feedbacks among both living and dead matter , is like a lush panoply of sounds . despite their stabilizing effects , many of these habitats and their ecosystems develop and change over time , as do the harmonies they create . deforestation may turn lush tropics into a barren patch , like a successful ensemble breaking up after losing its star performers . but an abandoned patch of farmland may also become a forest over time , like a garage band growing into a magnificent orchestra .

when your band is trying to perform , feedback is an annoying obstacle , but in the grand orchestra of nature , feedback is not only beneficial , it 's what makes everything work . what exactly is feedback ? the key element , whether in sound , the environment or social science , is a phenomenon called mutual causal interaction , where x affects y , y affects x , and so on , creating an ongoing process called a feedback loop .

describe three examples of positive feedback and three of negative feedback , in other systems that have many interacting parts – such as economic , social , political systems .

when you hear the word art , what comes to mind ? a painting , like the mona lisa , or a famous sculpture or a building ? what about a vase or a quilt or a violin ? are those things art , too , or are they craft ? and what 's the difference anyway ? it turns out that the answer is not so simple . a spoon or a saddle may be finely wrought , while a monument may be , well , uninspired . just as not every musical instrument is utilitarian , not every painting or statue is made for its own sake . but if it 's so tricky to separate art from craft , then why do we distinguish objects in this way ? you could say it 's the result of a dramatic historical turn of events . it might seem obvious to us today to view people , such as da vinci or michelangelo , as legendary artists , and , of course , they possessed extraordinary talents , but they also happened to live in the right place at the right time , because shortly before their lifetimes the concept of artists hardly existed . if you had chanced to step into a medieval european workshop , you would have witnessed a similar scene , no matter whether the place belonged to a stonemason , a goldsmith , a hatmaker , or a fresco painter . the master , following a strict set of guild statutes , insured that apprentices and journeymen worked their way up the ranks over many years of practice and well-defined stages of accomplishment , passing established traditions to the next generation . patrons regarded these makers collectively rather than individually , and their works from murano glass goblets , to flemish lace , were valued as symbols of social status , not only for their beauty , but their adherence to a particular tradition . and the customer who commissioned and paid for the work , whether it was a fine chair , a stone sculpture , a gold necklace , or an entire building , was more likely to get credit than those who designed or constructed it . it was n't until around 1400 that people began to draw a line between art and craft . in florence , italy , a new cultural ideal that would later be called renaissance humanism was beginning to take form . florentine intellectuals began to spread the idea of reformulating classical greek and roman works , while placing greater value on individual creativity than collective production . a few brave painters , who for many centuries , had been paid by the square foot , successfully petitioned their patrons to pay them on the basis of merit instead . within a single generation , people 's attitudes about objects and their makers would shift dramatically , such that in 1550 , giorgio vasari , not incidentally a friend of michelangelo , published an influential book called , `` lives of the most excellent painters , sculptors and architects , '' elevating these types of creators to rock star status by sharing juicy biographical details . in the mind of the public , painting , sculpture and architecture were now considered art , and their makers creative masterminds : artists . meanwhile , those who maintained guild traditions and faithfully produced candelsticks , ceramic vessels , gold jewelery or wrought iron gates , would be known communally as artisans , and their works considered minor or decorative arts , connoting an inferior status and solidifying the distinction between art and craft that still persists in the western world . so , if we consider a painting by rembrandt or picasso art , then where does that leave an african mask ? a chinese porclein vase ? a navajo rug ? it turns out that in the history of art , the value placed on innovation is the exception rather than the rule . in many cultures of the world , the distinction between art and craft has never existed . in fact , some works that might be considered craft , a peruvian rug , a ming dynasty vase , a totem pole , are considered the cultures ' preeminent visual forms . when art historians of the 19th century saw that the art of some non-western cultures did not change for thousands of years , they classified the works as primitive , suggesting that their makers were incapable of innovating and therefore were not really artists . what they did n't realize was that these makers were not seeking to innovate at all . the value of their works lay precisely in preserving visual traditions , rather than in changing them . in the last few decades , works such as quilts , ceramics and wood carvings have become more prominently included in art history textbooks and displayed in museums alongside paintings and sculpture . so maybe it 's time to dispense with vague terms like art and craft in favor of a word like visual arts that encompasses a wider array of aesthetic production . after all , if our appreciation of objects and their makers is so conditioned by our culture and history , then art and its definition are truly in the eye of the beholder .

in fact , some works that might be considered craft , a peruvian rug , a ming dynasty vase , a totem pole , are considered the cultures ' preeminent visual forms . when art historians of the 19th century saw that the art of some non-western cultures did not change for thousands of years , they classified the works as primitive , suggesting that their makers were incapable of innovating and therefore were not really artists . what they did n't realize was that these makers were not seeking to innovate at all .

what are some of the ways in which renaissance culture changed people ’ s views of the role of art—and artists—in western society ?

if i were to distill the 20 years of elephant research that i 've done into one sentence , what would it be ? what could i tell you ? i would say that elephants are just like us ! and what do i mean by that ? it takes a lot of patience to be out there in the field and trying to figure out patterns of these very slow and intelligent animals . but over time , it is true they are very similar to us . and you think , `` well , how can i say that ? look , they have huge ears , they have really long noses . what do you mean they 're like us ? '' well , in fact , their families are very similar to ours . and family is extremely important to elephants . they grow up in very tight-knit families and they have extended families . and it 's just like our family reunions where you have all the aunts gathering around with all the food they 're going to bring and plan , and all the boys are thinking , `` are we going to play our video games together ? are we going to spar ? '' it 's very , very similar , and it 's jubilant , and screaming , yelling , it 's really amazing to see . but , as soon as you get that family gathering , it 's just like a wedding or anything else , all of the sudden the family politics come out , and the lower-ranking individuals in this scene , you see the arrow off to the back , the lower-ranking individuals already know their station , they 're going to drink at the muddiest part of the pan because the whole family 's here and we ca n't drink at the best water because that 's reserved for the top-ranking family . what 's also very similar is that you have elders in the group that everyone reveres . this is the matriarch , and the other female is reaching over and doing what 's called a trunk to mouth placing her trunk in the mouth , and it 's a sign of respect , it 's kind of like a handshake , but it 's also like a salute . and this salute is learned at a very young age . now , ritual and bonding within the family also facilitates coordinated activities . so , here 's a young female whose calf has fallen into the trough and she does n't know what to do and she panics . well , the older female , that 's the matriarch , she says , `` no problem here , '' she just scoops the baby out . now , that 's not true for a lot of different families , they ca n't coordinate very well , the younger females do n't really know what to do , but the older ones will just get down , kneel down together and pick the baby out . another thing that 's very similar is the coming of age of teenage boys . male elephants at the age of about 12 to 15 . the biggest elephant in this photograph here is an elephant who 's about the leave the family . he gets too big , he gets a little fresh , the adult females had enough of him , but he also is independent , he wants to go out and play with the guys . so what happens then is that you have this all male society , very ritual male society . greg is our main dominant bull here , you can see him in the middle . he 's got a huge posse , his following reveres him . and it 's very interesting how very good leaders , very good dominant individuals know how to titrate the carrot and the stick . this guy 's a master at it , and there 's other bullies out there that want to kind of want to create their own little following , but they ca n't do it because they 're too agressive . and so when he 's not around they try and sweet talk the underlings to come into their fold , and they actually become less agressive . so it 's very interesting to see how politics play out in these male and female societies . now back to the ladies here . in a core family group you 'll have a mother , maybe even a grandmother , her daughters and all of their offspring , the male and female calves . and what 's very interesting here is that how character makes a difference . so each matriarch has a very different character . these two characters are kind of curious , they 're uncertain , whereas these other two characters are really agressive . `` we 're going to charge first , ask questions later . '' but then there are also matriarchs that say , `` forget it ! i 'm going to run first and then figure it out when we 're in the bush and it 's safe . '' but the wisest matriarch , the matriarchs that succeed best in all of the studies that have been done , is the one that assesses the danger and decides is this worth running away from or is this not a big deal at all . now being social is super important for elephants and of course right at the beginning , just like early childhood development , socialization is very important . bathing together , eating together , playing together , rough housing , this is all very important for social development . and who has n't tried to beat their sibling to the head of the line coming into the water hole ? and these relationships from the beginning is just like best friends forever for real . these females are going to live together for life . now if it 's a male , female they might know each other for life , but it 's really important to develop those bonds early on . those are the relationships that are going to save you later . i 'll show you a little schoolyard scenario here . where , i think if you just focus on what 's happening here you can see that we have the bully , he 's pulling on the trunk of this baby calf , and then we have the diplomat who 's reaching over and saying , `` no , do n't do that ! stop doing that ! '' and then , of course , we have the bystander . and how do you get these three different characters within the family ? it 's kind of fascinating to think that elephants really are just like us . and so i got curious about this and i thought , `` well , what if you measure the difference in character of a dominant female 's calf versus a lower-ranking female 's calf , and see what happens in their growing up . '' and so we started doing this . and you can see this little guy with his ears out , really charging at you . the difference between that character and the character who holds back , wants to touch mom , is n't so certain about what 's going on here . but the other one 's charging ahead all confident . well , we started measuring how far away a calf will stray from mom , how often do they touch others , how often do they initiate play , and then look at the dominance of the females , of their mothers . and what we found is that socializing with the dominant calves actually socialize more significantly more than the lower-ranking calves . and what it looks like is it 's not that the lower-ranking calves do n't want to play , they 're actually not allowed to interact with the higher-ranking calves . they get swatted away from the dominant females . and so this is kind of the downside of , okay we are very much like elephants , elephants are as much like us , but it 's kind of for better or for worse because i can also see this happening in humans and maybe we should take a lesson from that . one last thing that we found is that the males will be the risk-takers , they 're more independent and they 're more likely to spend more time away from mom . and that 's very true in human societies and with other social animals . so i hope i 've convinced you that we have very similar lives to elephants and that elephants have very individual , durable characters that we 've measured across years . the bully always tends to be the bully unless there 's some kind of social upset , and he decides he better be a softy or else he 's not going to gain favor at all . and then you have the gentle giants that are always going to be gentle . the young males really need mentoring from the elders , and those gentle giants are very good at doing that , soliciting them . leaving family is a really hard things for the males , but they survive and they figure out who to hang out with . so , just to end here , i just wanted to say that since they are so similar to us , and have these characters , i hope when you see them on tv or you go out and you 're lucky enough to see them in the wild , that maybe you 'll think of them as individual characters deserving of our attention , and also deserving of our protection . thank you .

well , in fact , their families are very similar to ours . and family is extremely important to elephants . they grow up in very tight-knit families and they have extended families .

when an extended family group of elephants meets up at a waterhole when they haven ’ t seen each other in a while ________ .

this is a tomato plant , and this is an aphid slowly killing the tomato plant by sucking the juice out of its leaves . the tomato is putting up a fight using both physical and chemical defenses to repel the attacking insects . but that 's not all . the tomato is also releasing compounds that signal nearby tomato plants to release their own insect repellent . plants are constantly under attack . they face threats ranging from microscopic fungi and bacteria , small herbivores , like aphids , caterpillars , and grasshoppers , up to large herbivores , like tortoises , koalas , and elephants . all are looking to devour plants to access the plentiful nutrients and water in their leaves , stems , fruits , and seeds . but plants are ready with a whole series of internal and external defenses that make them a much less appealing meal , or even a deadly one . plants ' defenses start at their surface . the bark covering tree trunks is full of lignin , a rigid web of compounds that 's tough to chew and highly impermeable to pathogens . leaves are protected by a waxy cuticle that deters insects and microbes . some plants go a step further with painful structures to warn would-be predators . thorns , spines , and prickles discourage bigger herbivores . to deal with smaller pests , some plants ' leaves have sharp hair-like structures called trichomes . the kidney bean plant sports tiny hooks to stab the feet of bed bugs and other insects . in some species , trichomes also dispense chemical irritants . stinging nettles release a mixture of histamine and other toxins that cause pain and inflammation when touched . for other plant species , the pain comes after an herbivore 's first bite . spinach , kiwi fruit , pineapple , fuchsia and rhubarb all produce microscopic needle-shaped crystals called raphides . they can cause tiny wounds in the inside of animals ' mouths , which create entry points for toxins . the mimosa plant has a strategy designed to prevent herbivores from taking a bite at all . specialized mechanoreceptor cells detect touch and shoot an electrical signal through the leaflet to its base causing cells there to release charged particles . the buildup of charge draws water out of these cells and they shrivel , pulling the leaflet closed . the folding movement scares insects away and the shrunken leaves look less appealing to larger animals . if these external defenses are breached , the plant immune system springs into action . plants do n't have a separate immune system like animals . instead , every cell has the ability to detect and defend against invaders . specialized receptors can recognize molecules that signal the presence of dangerous microbes or insects . in response , the immune system initiates a battery of defensive maneuvers . to prevent more pathogens from making their way inside , the waxy cuticle thickens and cell walls get stronger . guard cells seal up pores in the leaves . and if microbes are devouring one section of the plant , those cells can self-destruct to quarantine the infection . compounds toxic to microbes and insects are also produced , often tailor-made for a specific threat . many of the plant molecules that humans have adopted as drugs , medicines and seasonings evolved as part of plants ' immune systems because they 're antimicrobial , or insecticidal . an area of a plant under attack can alert other regions using hormones , airborne compounds , or even electrical signals . when other parts of the plant detect these signals , they ramp up production of defensive compounds . and for some species , like tomatoes , this early warning system also alerts their neighbors . some plants can even recruit allies to adopt a strong offense against their would-be attackers . cotton plants under siege by caterpillars release a specific cocktail of ten to twelve chemicals into the air . this mixture attracts parasitic wasps that lay eggs inside the caterpillars . plants may not be able to flee the scene of an attack , or fight off predators with teeth and claws , but with sturdy armor , a well-stocked chemical arsenal , a neighborhood watch , and cross-species alliances , a plant is n't always an easy meal .

they can cause tiny wounds in the inside of animals ' mouths , which create entry points for toxins . the mimosa plant has a strategy designed to prevent herbivores from taking a bite at all . specialized mechanoreceptor cells detect touch and shoot an electrical signal through the leaflet to its base causing cells there to release charged particles .

one of the defense strategies that mimosa plants use against herbivores is :

anyone who has played a claw machine can relate to the experience of having the claw perfectly positioned only to see it weakly graze the prize before pulling back up . `` no man ! '' it may seem like the machine is n't even trying . and well ... `` it is not your imagination , those claw machines are rigged ! '' there are a couple of beloved stuffed animals that i have that are from a claw machine , a koala and a bear . that is vox.com writer , phil edwards . `` i looked at the instruction guides for a few of the biggest claw games out there . take for example , the manual for black tie toys advanced crane machine . if you look at page 8 , section subheading claw strength you will see a horrifying piece of information . `` managing profit is made easy . simply input the coin value , the average value of the merchandise , and the profit level . the machine will automatically calculate when to send full strength to the claw . '' alright , so if it cost 50 cents to play the game , and the prize inside cost 7 dollars . to make a profit of 50 % full power will be sent to the claw only about once every 21 games or so . that sucks . they also randomize that winning game within a range so that players ca n't predict when exactly it will happen . and you might notice a subheading that says `` dropping skill '' they can program the machine to make you think you almost won . they taunt you with it . you see the stuffed animal flying in the air . and then it drops it . and that just ruins everything . so , most of the time claw machines are more like slot machines , than like skeeball or wack-a-mole . `` who 's in charge here ! '' `` the claw ! '' the question of whether claw machines are a game of skill or chance goes back decades . the earlier versions back in the 1930s had very little element of skill and were marketed as highly profitable for their owners . this was the depression era and people were desperate for ways to get money moving . during a crackdown on organzied crime in the 1950s federal law classified claw machines as gambling devices and prohibited the transporation of them across state lines . after those laws were relaxed in the 1970s newer claw machines from europe and asia spread throughout the united states . they actually started calling them `` skill cranes '' because the joystick gave players more precise control . but owners had increasing control over profits as well . and they 've been met with a patchwork of state and local laws and regulations . if machine operators want to make that claw really really unfair against the players , there 's not a lot stopping them . most of the regulations focus on the prize size , not the strength of the claw . that 's a reason that you might see fewer of the `` win a free ipad '' claw machines or `` win a free iphone '' claw machines around . and more of just old fashioned stuffed animals . it 's great if players know what they are up against . especially since sites like youtube have enabled claw machine enthusiast to broadcast their victories . like this guy . `` i 'm matt magnone . join me as i venture out and win as much crap as i can from claw machines ! '' my best outcome of this is not that all the claw machines go away . since i first wrote this article , i 've spent a dollar on claw machines ... and i 've lost . all i want for people to know is that they are not the problem . the claw machine is the problem . `` ah , you piece of crap ! ''

and that just ruins everything . so , most of the time claw machines are more like slot machines , than like skeeball or wack-a-mole . `` who 's in charge here ! ''

the first claw machines were explicitly marketed as highly profitable for owners . when were they invented and why were they so popular at the time ?

good morning , john ! today is the day after thanksgiving here in america . traditionally , the day when we buy all the things ! actually , more traditionally at my house , it 's the day when we do n't leave the house ; because black friday.. terrifies me . for people who are n't american , the very ominous-sounding black friday is an accident of history . so , back in 1621 , it was hard livin ' here in america ; and the first english settlers had a really bountiful crop . apparently . this is somewhat mythological ... and , it was on a thursday ; and they were thankful ! that inspired a holiday ; which is a nice kind of idea for a holiday , where you just talk about the things that you 're thankful for . and eat a bunch of food ! you also eat a bunch of food . until the 1860 's , different states celebrated this holiday on different days . until abraham lincoln said : `` this.. is the day ! we 're gon na have a national day . `` ; and , the south was like : `` we 're not even part of you anymore . what are you talking about ? ! '' but then , when we got back together again , that was good ; and it became the national holiday . the fourth thursday in november . now , because it 's a national holiday on the thursday , you also sort of get that friday as a de facto day off . 'cause you do n't want to go back to work for one day and then have the weekend ; that 's just dumb ! in the '60 's [ 1960 's ] , because so many people were going on vacation on this day , or , to a lesser extent , going shopping ; this became such a terrible traffic mess that police and taxi drivers started calling it `` black friday '' . as stores , and also just general consumerist cultures , started pushing the idea of christmas shopping further and further away from christmas ; the big block in the road , where you ca n't push it back any further , is thanksgiving . 'cause that 's its own holiday . you ca n't start christmas before thanksgiving . and so , black friday became the official tipping point into the consumerist bonanza that is the holiday shopping season ! despite the fact that it has kind of this ominous-sounding name , it has been billed as the biggest and most important and best holiday shopping day of the year ; which is actually not true . we are.. a nation of procrastinators ; and thus , the biggest shopping day of the year is christmas eve . it seems a little bit upsetting that the day after we all get done telling the world why we should be satisfied with our lives , we are.. barraged with an advertising blitz showing us all of the things that we lack ! at the same time , it is very important to the american economy . i mean , you ca n't really get angry at people for wanting to give each other things ... and yes , dftba.com has its own black friday and cyber monday deals ; and you can go to dftba.com and check those out now . it 's also our 4th anniversary of being a company , which is very exciting ! and , to celebrate that fourth anniversary , all shipping within the united states this weekend , starting tomorrow , i think , is just $ 4.00 ! no matter what you buy ! ! but , i do think it 's important that we do n't just scrub the idea of satisfaction and thankfulness out of our brains as soon as we 're done for thanksgiving . and so , on this black friday , i want to continue being thankful . i 'm thankful to my wonderful and supportive parents ; to my beautiful , and intelligent , and hilarious wife . i 'm thankful to my new wii u . if you want to go to youtube.com/hankgames , you can see us playing the new super mario brothers there soon . i 'm thankful to all of my great friends here in missoula and across the world . i 'm thankful to finally have a robust and stable forum that can handle the weight of nerdfighteria . there 's a link in the description . i 'm thankful to youtube and google for funding scishow and crash course , and for supporting vlogbrothers , and all of our endeavors through the years . i 'm thankful to reddit , and qi , and mental floss magazine , for making sure that i keep learning interesting things . i 'm thankful to jonas salk for giving away the patent to his polio vaccine to the world , so that it could be less expensive to manufacture ; and tim berners-lee for doing basically the same thing with the internet . i 'm thankful to the nerdcrafteria minecraft server and tumblr , and the ning ; and all the other places on the internet where nerdfighters do nerdfighter things . and , i 'm thankful to all the wonderful , thoughtful , intelligent people who watch and support the things that i do on the internet ; even when it 's sappy , silly videos like this one . and i 'm thankful , of course , for my brother who 's always driving me to do new and interesting and difficult things ; and who 's raising a wonderful family , and who says wise and intelligent things on tumblr . and john , i 'll see you on tuesday . *music plays*

despite the fact that it has kind of this ominous-sounding name , it has been billed as the biggest and most important and best holiday shopping day of the year ; which is actually not true . we are.. a nation of procrastinators ; and thus , the biggest shopping day of the year is christmas eve . it seems a little bit upsetting that the day after we all get done telling the world why we should be satisfied with our lives , we are.. barraged with an advertising blitz showing us all of the things that we lack !

what is the biggest shopping day of the year in the united states ?

if you ever find yourself gazing at falling snow , why not catch a few snowflakes on your glove and examine their shapes ? you might notice that they look symmetrical , and if you look closely , you 'll see they have six sides . you could say a snowflake is simply frozen water , but compare one with an ice cube from the freezer , and you 'll realize they 're very different things . unlike ice cubes , formed when liquid freezes into a solid , snowflakes form when water vapor turns straight into ice . but that still does n't explain why snowflakes have six sides . to understand that , we need to delve deeper into the physics of water . water is made out of two hydrogen atoms and one oxygen atom . a single water molecule thus has ten protons and ten electrons , eight from oxygen and one from each hydrogen atom . the two electrons from oxygen 's outer shell are shared with two electrons from both hydrogens as they bond together , and the remaining four outer shell electrons from oxygen form two pairs . we call the bonds between these atoms covalent bonds . the pairs of electrons are all negatively charged . similar charges repel , so they tend to stay as far away from each other as possible . the pairs form four electron clouds , two of which are where the hydrogen and oxygen share electrons . the repulsion between the unbonded pairs is even stronger than repulsion between the shared pairs , so the two hydrogens get pushed a little further to an angle of 104.5 degrees . the water molecule as a whole is electrically neutral , but oxygen gets a larger share of electrons , making it slightly negative and the hydrogens slightly positive . due to its negative charge , the oxygen in one molecule is attracted to the positive charge of the hydrogen in another molecule . and so a weak bond between the two molecules , called a hydrogen bond , is formed . when water freezes , this bonding occurs on repeat , ultimately forming a hexagonal structure due to the angle between hydrogens and oxygen within each molecule . this is the seed of a snowflake , and it retains a hexagonal shape as it grows . as the snowflake moves through the air , water vapor molecules stick to the six sharp edges and expand the snowflake outwards , bit by bit . a snowflake 's developing shape depends on atmospheric conditions , like humidity and temperature . as a snowflake falls , changes in weather conditions can affect how it grows , and even small differences in the paths two snowflakes take will differentiate their shapes . however , since conditions at the six sharp edges of one snowflake are similar , a symmetric snowflake can grow . weather conditions affect snow on the ground , as well . warmer ground temperatures produce a wetter snow that is easier to pack because liquid water molecules help snowflakes stick to each other . melted snow also plays a critical role in another wintry activity , skiing . completely dry snow is very difficult to ski on because there 's too much friction between the jagged snowflakes and the ski surface . so what 's happening is that as skis move , they rub the surface of the snow and warm it up , creating a thin layer of water , which helps them slide along . so technically , it 's not really snow skiing , but water skiing . but it is true that no matter how hard you look , you 're almost definitely not going to find two identical snowflakes , and that 's a mystery that scientists are still trying to solve , though we know that it has to do with the many possible branching points in snowflake formation , and the differences in temperature and humidity , and while we wait for the answer , we can enjoy watching these tiny fractals falling from the sky .

completely dry snow is very difficult to ski on because there 's too much friction between the jagged snowflakes and the ski surface . so what 's happening is that as skis move , they rub the surface of the snow and warm it up , creating a thin layer of water , which helps them slide along . so technically , it 's not really snow skiing , but water skiing . but it is true that no matter how hard you look , you 're almost definitely not going to find two identical snowflakes , and that 's a mystery that scientists are still trying to solve , though we know that it has to do with the many possible branching points in snowflake formation , and the differences in temperature and humidity , and while we wait for the answer , we can enjoy watching these tiny fractals falling from the sky .

why can a skier slide over snow ?

in 1985 , three researchers on a dolphin-studying expedition got a little bored . to lighten things up , one pretended to be poseidon by placing a seaweed garland on his head and then throwing it into the ocean . moments later , a dolphin surfaced with the seaweed crowning her head . sure , this could have been a coincidence , but it 's also entirely possible that the dolphin was mimicking the scientist . that 's because dolphins are one of the smartest animals species on earth . so exactly how smart are they ? like whales and porpoises , dolphins belong to the group of aquatic mammals known as cetaceans who comprise 86 different species , and share a common link with ungulates , or hoofed animals . originally land mammals , the first cetaceans entered the water about 55 million years ago as large predators with sharp teeth . then , a shift in ocean temperatures about 35 million years ago reduced the availability of prey . one group of cetaceans who survived this distruption , the odontocetes , wound up smaller with less sharp teeth , but also larger and more complex brains that allowed for complex social relationships , as well as echolocation to navigate and communicate . jump ahead to the present , and modern dolphins ' brains are so large that their encephalization quotient , their brain size compared to the average for their body size , is second only to humans . dolphins have evolved to survive through their ability to form complex social networks that hunt , ward off rivals , and raise offspring together . for example , one group of florida dolphins practices a sophisticated form of cooperation to hunt fish . a dolphin designated as `` the net-maker '' kicks up mud while another gives the signal for the other dolphins to simultaneously line up and catch the escaping fish . achieving a goal like this requires deliberate planning and cooperation , which , in turn , requires some form of intentional communication . dolphins pass down their communication methods and other skills from generation to generation . different dolphin populations exhibit variations in greetings , hunting strategies , and other behaviors . this sort of cultural transmission even extends to tool use . one group of bottlenose dolphins off the australian coast nicknamed the dolphin sponge club , has learned how to cover their rostrums with sponges when rooting in sharp corals , passing the knowledge from mother to daughter . dolphins have even demonstrated language comprehension . when taught a language based on whistles and hand gestures , they not only understood what the signals meant , but that their order had meaning : the difference between bringing the ball to the hoop and bringing the hoop to the ball . so they were able to process two of the main elements of human language : symbols that stand for objects and actions , and syntax that governs how they are structured . dolphins are also one of the few species who pass the mirror test . by recognizing themselves in mirrors , they indicate physical self-awareness , and research shows they can recognize not just their bodies , but also their own thoughts , a property called metacognition . in one study , dolphins comparing two sounds could indicate a same , different , or uncertain response . just like humans , they indicated uncertainty more often with difficult trials , suggesting they 're aware of what they know , and how confident they feel about that knowledge . but some of the most amazing things about dolphins are their senses of empathy , altruism , and attachment . the habit of helping injured individuals extends across the species barrier as evidenced by the many accounts of dolphins carrying humans to the surface to breathe . and like us , dolphins mourn their dead . when we consider all the evidence , we may wonder why humans still hunt dolphins for meat , endanger them through fishing and pollution , or imprison them to perform tricks . the ultimate question may not be whether dolphins are intelligent and complex beings , but whether humans can empathize with them enough to keep them safe and free .

this sort of cultural transmission even extends to tool use . one group of bottlenose dolphins off the australian coast nicknamed the dolphin sponge club , has learned how to cover their rostrums with sponges when rooting in sharp corals , passing the knowledge from mother to daughter . dolphins have even demonstrated language comprehension .

the dolphin sponge club :

in 1996 , 56 volunteers took part in a study to test a new painkiller called trivaricaine . on each subject , one index finger was covered in the new painkiller while the other remained untouched . then , both were squeezed in painful clamps . the subjects reported that the treated finger hurt less than the untreated one . this should n't be surprising , except trivaricaine was n't actually a painkiller , just a fake concotion with no pain-easing properties at all . what made the students so sure this dummy drug had worked ? the answer lies in the placebo effect , an unexplained phenomenon wherein drugs , treatments , and therapies that are n't supposed to have an effect , and are often fake , miraculously make people feel better . doctors have used the term placebo since the 1700s when they realized the power of fake drugs to improve people 's symptoms . these were administered when proper drugs were n't available , or if someone imagined they were ill . in fact , the word placebo means `` i shall please '' in latin , hinting at a history of placating troubled patients . placebos had to mimic the real treatments in order to be convincing , so they took the form of sugar pills , water-filled injections , and even sham surgeries . soon , doctors realized that duping people in this way had another use : in clinical trials . by the 1950s , researchers were using placebos as a standard tool to test new treatments . to evaluate a new drug , for instance , half the patients in a trial might receive the real pill . the other half would get a placebo that looked the same . since patients would n't know whether they 'd received the real thing or a dud , the results would n't be biased , researchers believed . then , if the new drug showed a significant benefit compared to the placebo , it was proved effective . nowadays , it 's less common to use placebos this way because of ethical concerns . if it 's possible to compare a new drug against an older version , or another existing drug , that 's preferable to simply giving someone no treatment at all , especially if they have a serious ailment . in these cases , placebos are often used as a control to fine-tune the trial so that the effects of the new versus the old or alternative drug can be precisely compared . but of course , we know the placebos exert their own influence , too . thanks to the placebo effect , patients have experienced relief from a range of ailments , including heart problems , asthma , and severe pain , even though all they 'd received was a fake drug or sham surgery . we 're still trying to understand how . some believe that instead of being real , the placebo effect is merely confused with other factors , like patients trying to please doctors by falsely reporting improvements . on the other hand , researchers think that if a person believes a fake treatment is real , their expectations of recovery actually do trigger physiological factors that improve their symptoms . placebos seem to be capable of causing measurable change in blood pressure , heart rate , and the release of pain-reducing chemicals , like endorphins . that explains why subjects in pain studies often say placebos ease their discomfort . placebos may even reduce levels of stress hormones , like adrenaline , which can slow the harmful effects of an ailment . so should n't we celebrate the placebo 's bizarre benefits ? not necessarily . if somebody believes a fake treatment has cured them , they may miss out on drugs or therapies that are proven to work . plus , the positive effects may fade over time , and often do . placebos also cloud clinical results , making scientists even more motivated to discover how they wield such power over us . despite everything we know about the human body , there are still some strange and enduring mysteries , like the placebo effect . so what other undiscovered marvels might we contain ? it 's easy to investigate the world around us and forget that one of its most fascinating subjects lies right behind our eyes .

in these cases , placebos are often used as a control to fine-tune the trial so that the effects of the new versus the old or alternative drug can be precisely compared . but of course , we know the placebos exert their own influence , too . thanks to the placebo effect , patients have experienced relief from a range of ailments , including heart problems , asthma , and severe pain , even though all they 'd received was a fake drug or sham surgery .

list some of the benefits that patients have been known to experience while under the influence of placebos .

many of the inanimate objects around you probably seem perfectly still . but look deep into the atomic structure of any of them , and you 'll see a world in constant flux . stretching , contracting , springing , jittering , drifting atoms everywhere . and though that movement may seem chaotic , it 's not random . atoms that are bonded together , and that describes almost all substances , move according to a set of principles . for example , take molecules , atoms held together by covalent bonds . there are three basic ways molecules can move : rotation , translation , and vibration . rotation and translation move a molecule in space while its atoms stay the same distance apart . vibration , on the other hand , changes those distances , actually altering the molecule 's shape . for any molecule , you can count up the number of different ways it can move . that corresponds to its degrees of freedom , which in the context of mechanics basically means the number of variables we need to take into account to understand the full system . three-dimensional space is defined by x , y , and z axes . translation allows the molecule to move in the direction of any of them . that 's three degrees of freedom . it can also rotate around any of these three axes . that 's three more , unless it 's a linear molecule , like carbon dioxide . there , one of the rotations just spins the molecule around its own axis , which does n't count because it does n't change the position of the atoms . vibration is where it gets a bit tricky . let 's take a simple molecule , like hydrogen . the length of the bond that holds the two atoms together is constantly changing as if the atoms were connected by a spring . that change in distance is tiny , less than a billionth of a meter . the more atoms and bonds a molecule has , the more vibrational modes . for example , a water molecule has three atoms : one oxygen and two hydrogens , and two bonds . that gives it three modes of vibration : symmetric stretching , asymmetric stretching , and bending . more complicated molecules have even fancier vibrational modes , like rocking , wagging , and twisting . if you know how many atoms a molecule has , you can count its vibrational modes . start with the total degrees of freedom , which is three times the number of atoms in the molecule . that 's because each atom can move in three different directions . three of the total correspond to translation when all the atoms are going in the same direction . and three , or two for linear molecules , correspond to rotations . all the rest , 3n-6 or 3n-5 for linear molecules , are vibrations . so what 's causing all this motion ? molecules move because they absorb energy from their surroundings , mainly in the form of heat or electromagnetic radiation . when this energy gets transferred to the molecules , they vibrate , rotate , or translate faster . faster motion increases the kinetic energy of the molecules and atoms . we define this as an increase in temperature and thermal energy . this is the phenomenon your microwave oven uses to heat your food . the oven emits microwave radiation , which is absorbed by the molecules , especially those of water . they move around faster and faster , bumping into each other and increasing the food 's temperature and thermal energy . the greenhouse effect is another example . some of the solar radiation that hits the earth 's surface is reflected back to the atmosphere . greenhouse gases , like water vapor and carbon dioxide absorb this radiation and speed up . these hotter , faster-moving molecules emit infrared radiation in all directions , including back to earth , warming it . does all this molecular motion ever stop ? you might think that would happen at absolute zero , the coldest possible temperature . no one 's ever managed to cool anything down that much , but even if we could , molecules would still move due to a quantum mechanical principle called zero-point energy . in other words , everything has been moving since the universe 's very first moments , and will keep going long , long after we 're gone .

translation allows the molecule to move in the direction of any of them . that 's three degrees of freedom . it can also rotate around any of these three axes .

a large protein consisting of 94 atoms has ____ vibrational ‘ degrees of freedom . ’

some people ca n't see the forest for the trees , but before stephen sillett , no one could see or even imagine the forest in the trees . stephen was an explorer of new worlds from the start . he spent his boyhood in harrisburg , pennsylvania reading tolkien and playing dungeons and dragons with his brother scott . but when the sillett family visited their grandparent 's cabin near gettysburg , their grandmother helen poe sillett , would take the boys into the nearby mountains and forests to bird-watch . they called grandma sillett poe , and she taught the boys to identify songbirds , plants and even lichens , creatures that often look like splotches of carpet glued to the shady sides of rocks and tree trunks . looking upwards , both boys found their callings . scott became a research scientist specializing in migratory birds . stephen was more interested in the trees . the tangle of branches and leaves attracted his curiosity . what could be hidden up there ? by the time stephen was in college , that curiosity pulled him skyward to the tallest trees on earth : the ancient coast redwoods of northern california . rising from trunks up to 20 feet in diameter , redwoods can grow up to 380 feet , or 38 stories , over a 2,000 year lifetime . but no one had thought to investigate the crowns of these natural skyscrapers . were there more than just branches up there ? stephen decided to find out firsthand . in 1987 , stephen , his brother scott and his friend marwood drove from reed college in oregon to prairie creek redwoods state park in northern california . deep inside the park , stephen picked the tallest redwood he could find . its lowest branches were almost 100 feet up , far beyond his reach . but he saw a younger , shorter redwood growing next to the target tree . with a running start , he leapt and grabbed the lowest branch , pulled himself up and scurried upwards . he was free climbing without ropes or a harness , one misstep meant death . but up he went , and when he reached the peak , he swayed and leapt across the gap of space onto a branch of the target tree and into a world never seen before . his buddy marwood followed him up , and the two young men free climbed high into the redwood 's crown . stephen came across lichens like grandma poe had shown him as a boy . he noticed that the higher he went , the thicker the branches were , not the case with most trees . he found moist mats of soil many inches thick , made from fallen needles , bark , other plant debris and dust from the sky piled on the tops of the large branches . he even found reiterations : new redwood tree trunks growing out from the main trunk . the redwood had cloned itself . when stephen reached the pinnacle , he rested on a platform of crisscrossing branches and needles . growing in the soil mat was a huckleberry bush with ripe berries ! he ate some and waited for his friend . stephen had discovered a new world hundreds of feet above the ground . his climb led to more excursions , with safety equipment , thank goodness , up other ancient redwoods as he mapped and measured the architecture of branches and additional trunks in the canopy of an entire grove . stephen became an expert in the ecology of the tallest trees on earth and the rich diversity of life in their crowns , aerial ecosystems no one had imagined . there are ferns , fungi and epiphytic trees normally found at ground level like douglas firs , hemlocks and tan oaks whose roots had taken hold in the rich wet soil mats . invertebrates such as ants , bumblebees , mites , beetles , earthworms and aquatic crustacean copepods make their homes alongside flowering plants like rhododendrons , currant and elderberry bushes . ospreys , spotted owls , and jays search the canopy for food . even the marbled murrelet , a pacific seabird , flies many miles from the ocean to nest there . squirrels and voles peek out of penthouse burrows . and the top predator ? the mighty wandering salamander ! sillett 's research has changed how we think about tall trees , and bolstered the case for their conservation , not just as impressive individual organisms but as homes to countless other species . so when you look up into the branches and leaves of a tree , ask , `` what else is up there ? '' a new world might be just out of reach . so leap for it .

he noticed that the higher he went , the thicker the branches were , not the case with most trees . he found moist mats of soil many inches thick , made from fallen needles , bark , other plant debris and dust from the sky piled on the tops of the large branches . he even found reiterations : new redwood tree trunks growing out from the main trunk .

soil mats form on the large branches over long periods of time . explain the importance of these soil mats in the redwood canopy ecosystem .

how many times can you fold a piece of paper ? assume that one had a piece of paper that was very fine , like the kind they typically use to print the bible . in reality , it seems like a piece of silk . to qualify these ideas , let 's say you have a paper that 's one-thousandth of a centimeter in thickness . that is 10 to the power of minus three centimeters , which equals .001 centimeters . let 's also assume that you have a big piece of paper , like a page out of the newspaper . now we begin to fold it in half . how many times do you think it could be folded like that ? and another question : if you could fold the paper over and over , as many times as you wish , say 30 times , what would you imagine the thickness of the paper would be then ? before you move on , i encourage you to actually think about a possible answer to this question . ok. after we have folded the paper once , it is now two thousandths of a centimeter in thickness . if we fold it in half once again , the paper will become four thousandths of a centimeter . with every fold we make , the paper doubles in thickness . and if we continue to fold it again and again , always in half , we would confront the following situation after 10 folds . two to the power of 10 , meaning that you multiply two by itself 10 times , is one thousand and 24 thousandths of a centimeter , which is a little bit over one centimeter . assume we continue folding the paper in half . what will happen then ? if we fold it 17 times , we 'll get a thickness of two to the power of 17 , which is 131 centimeters , and that equals just over four feet . if we were able to fold it 25 times , then we would get two to the power of 25 , which is 33,554 centimeters , just over 1,100 feet . that would make it almost as tall as the empire state building . it 's worthwhile to stop here and reflect for a moment . folding a paper in half , even a paper as fine as that of the bible , 25 times would give us a paper almost a quarter of a mile . what do we learn ? this type of growth is called exponential growth , and as you see , just by folding a paper we can go very far , but very fast too . summarizing , if we fold a paper 25 times , the thickness is almost a quarter of a mile . 30 times , the thickness reaches 6.5 miles , which is about the average height that planes fly . 40 times , the thickness is nearly 7,000 miles , or the average gps satellite 's orbit . 48 times , the thickness is way over one million miles . now , if you think that the distance between the earth and the moon is less than 250,000 miles , then starting with a piece of bible paper and folding it 45 times , we get to the moon . and if we double it one more time , we get back to earth .

how many times can you fold a piece of paper ? assume that one had a piece of paper that was very fine , like the kind they typically use to print the bible .

if we fold the paper ten times , how thick would it be ?

mastering any physical skill , be it performing a pirouette , playing an instrument , or throwing a baseball , takes practice . practice is the repetition of an action with the goal of improvement , and it helps us perform with more ease , speed , and confidence . so what does practice do in our brains to make us better at things ? our brains have two kinds of neural tissue : grey matter and white matter . the grey matter processes information in the brain , directing signals and sensory stimuli to nerve cells , while white matter is mostly made up of fatty tissue and nerve fibers . in order for our bodies to move , information needs to travel from the brain 's grey matter , down the spinal cord , through a chain of nerve fibers called axons to our muscles . so how does practice or repetition affect the inner workings of our brains ? the axons that exist in the white matter are wrapped with a fatty substance called myelin . and it 's this myelin covering , or sheath , that seems to change with practice . myelin is similar to insulation on electrical cables . it prevents energy loss from electrical signals that the brain uses , moving them more efficiently along neural pathways . some recent studies in mice suggest that the repetition of a physical motion increases the layers of myelin sheath that insulates the axons . and the more layers , the greater the insulation around the axon chains , forming a sort of superhighway for information connecting your brain to your muscles . so while many athletes and performers attribute their successes to muscle memory , muscles themselves do n't really have memory . rather , it may be the myelination of neural pathways that gives these athletes and performers their edge with faster and more efficient neural pathways . there are many theories that attempt to quantify the number of hours , days , and even years of practice that it takes to master a skill . while we do n't yet have a magic number , we do know that mastery is n't simply about the amount of hours of practice . it 's also the quality and effectiveness of that practice . effective practice is consistent , intensely focused , and targets content or weaknesses that lie at the edge of one 's current abilities . so if effective practice is the key , how can we get the most out of our practice time ? try these tips . focus on the task at hand . minimize potential distractions by turning off the computer or tv and putting your cell phone on airplane mode . in one study , researchers observed 260 students studying . on average , those students were able to stay on task for only six minutes at a time . laptops , smartphones , and particularly facebook were the root of most distractions . start out slowly or in slow-motion . coordination is built with repetitions , whether correct or incorrect . if you gradually increase the speed of the quality repetitons , you have a better chance of doing them correctly . next , frequent repetitions with allotted breaks are common practice habits of elite performers . studies have shown that many top athletes , musicians , and dancers spend 50-60 hours per week on activities related to their craft . many divide their time used for effective practice into multiple daily practice sessions of limited duration . and finally , practice in your brain in vivid detail . it 's a bit surprising , but a number of studies suggest that once a physical motion has been established , it can be reinforced just by imagining it . in one study , 144 basketball players were divided into two groups . group a physically practiced one-handed free throws while group b only mentally practiced them . when they were tested at the end of the two week experiment , the intermediate and experienced players in both groups had improved by nearly the same amount . as scientists get closer to unraveling the secrets of our brains , our understanding of effective practice will only improve . in the meantime , effective practice is the best way we have of pushing our individual limits , achieving new heights , and maximizing our potential .

mastering any physical skill , be it performing a pirouette , playing an instrument , or throwing a baseball , takes practice . practice is the repetition of an action with the goal of improvement , and it helps us perform with more ease , speed , and confidence .

how is slow practice beneficial in the development of complex , coordinated skills in dance , sports , the martial arts , and playing a musical instrument ?

some superheros can move faster than the wind . the men in apollo 10 reached a record-breaking speed of around 25,000 miles per hour when the shuttle re-entered the earth 's atmosphere in 1969 . would n't we save a lot of time to be able to move that fast ? but what 's the catch ? air is not empty . elements like oxygen and nitrogen , even countless dust particles , make up the air around us . when we move past these things in the air , we 're rubbing against them and creating a lot of friction , which results in heat . just like rubbing your hands together warms them up or rubbing two sticks together makes fire , the faster objects rub together , the more heat is generated . so , if we 're running at 25,000 miles per hour , the heat from friction would burn our faces off . even if we somehow withstood the heat , the sand and dirt in the air would still scrape us up with millions of tiny cuts all happening at the same time . ever seen the front bumper or grill of a truck ? what do you think all the birds and bugs would do to your open eyes or exposed skin ? okay , so you 'll wear a mask to avoid destroying your face . but what about people in buildings between you and your destination ? it takes us approximately one-fifth of a second to react to what we see . by the time we see what is ahead of us and react to it - time times velocity equals distance equals one-fifth of a second times 25,000 miles per hour equals 1.4 miles - we would have gone past it or through it by over a mile . we 're either going to kill ourselves by crashing into the nearest wall at super speed or , worse , if we 're indestructible , we 've essentially turned our bodies into missiles that destroy everything in our path . so , long distance travel at 25,000 miles per hour would leave us burning up , covered in bugs , and leaves no time to react . what about short bursts to a location we can see with no obstacles in between ? okay , let 's say a bullet is about to hit a beautiful damsel in distress . so , our hero swoops in at super speed , grabs her , and carries her to safety . that sounds very romantic , but , in reality , that girl will probably suffer more damage from the hero than the bullet if he moved her at super speed . newton 's first law of motion deals with inertia , which is the resistance to a change in its state of motion . so , an object will continue moving or staying at the same place unless something changes it . acceleration is the rate the velocity changes over time . when the girl at rest , velocity equals zero miles per hour , begins accelerating to reach the speed within seconds , velocity increases rapidly to 25,000 miles per hour , her brain would crash into the side of her skull . and , when she stops suddenly , velocity decreases rapidly back to zero miles per hour , her brain would crash into the other side of her skull , turning her brain into mush . the brain is too fragile to handle the sudden movement . so is every part of her body , for that matter . remember , it 's not the speed that causes the damage because the astronauts survived apollo 10 , it 's the acceleration or sudden stop that causes our internal organs to crash into the front of our bodies the way we move forward in a bus when the driver slams on the brakes . what the hero did to the girl is mathematically the same as running her over with a space shuttle at maximum speed . she probably died instantly at the point of impact . he 's going to owe this poor girl 's family an apology and a big fat compensation check . oh , and possibly face jail time . doctors have to carry liability insurance just in case they make a mistake and hurt their patients . i wonder how much superhero insurance policy would cost . now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .

that sounds very romantic , but , in reality , that girl will probably suffer more damage from the hero than the bullet if he moved her at super speed . newton 's first law of motion deals with inertia , which is the resistance to a change in its state of motion . so , an object will continue moving or staying at the same place unless something changes it .

newton ’ s first law of motion deals with inertia , which is

so i 'm here today to encourage you to think about new york city , and not just as one of humanity 's greatest achievements , but as home to native wildlife that are subject to a grand evolutionary experiment . so take this forested hillside in northern manhattan , for example . this is one of the last areas left in the city where there 's clean spring water seeping out of the ground . you could drink this out of your hands and you 'd be ok . these tiny little areas of seeping water contain huge populations of northern dusky salamanders . these guys were common in the city maybe 60 years ago , but now they 're just stuck on this single hillside and a few places in staten island . not only do they suffer the indignity of being stuck on this hillside , but we divided the hillside in two on two different occasions with bridges crossing from the bronx into manhattan . but they 're still there , on either side of the bridges , where you see the red arrows -- about 180th street , 167th street . my lab has found that if you just take a few segments of dna from salamanders in those two locations , you can tell which side of the bridge they came from . we built this single piece of infrastructure that 's changed their evolutionary history . we can go study these guys , we just go to the hillside we know where they are , we flip over rocks so we can catch them . there are a lot of other things in new york city , though , that are not that easy to capture , such as this guy , a coyote . we caught him on an automatic camera trap in an undisclosed location ; i 'm not allowed to talk about it yet . but they 're moving into new york city for the first time . they 're very flexible , intelligent animals . this is one of this year 's pups checking out one of our cameras . and my colleagues and i are very interested in understanding how they 're going to spread through the area , how they 're going to survive here and maybe even thrive . and they 're probably coming to a neighborhood near you , if they 're not already there . some things are too fast to be caught by hand . we ca n't pick them up on the cameras , so we set up traps around new york city and the parks . this is one of our most common activities . here 's some of my students and collaborators getting the traps out and ready . this guy , we catch in almost every forested area in new york city . this is the white-footed mouse -- not the mouse you find running around your apartment . this is a native species , been here long before humans . you find them in forests and meadows . because they 're so common in forested areas in the city , we 're using them as a model to understand how species are adapting to urban environments . so if you think back 400 years ago , the five boroughs would 've been covered in forests and other types of vegetation . this mouse would 've been everywhere [ in ] huge populations that showed few genetic differences across the landscape . but if you look at the situation today , they 're just stuck in these little islands of forest scattered around the city . just using 18 short segments of dna , we can pretty much take a mouse somebody could give us a mouse , not tell us where it was from , and we could determine what park it came from . that 's how different they 've become . you 'll notice in the middle of this figure , there are some mixed-up colors . there are a few parks in the city that are still connected to each other with strips of forest , so the mice can run back and forth and spread their genes , so they do n't become different . but throughout the city , they 're mostly becoming different in the parks . so i 'm telling you they 're different , but what does that mean ? what 's changing about their biology ? to answer this question , we 're sequencing thousands of genes from our city mice and comparing those to thousands of genes from the country mice , so , their ancestors outside of new york city in these big , more wilderness areas . now , genes are short segments of dna that code for amino acids . and amino acids are the building blocks of proteins . if a single base pair changes in a gene , you can get a different amino acid , which will then change the shape and structure of the protein . if you change the structure of a protein , you often change something about what it does in the organism . now if that change leads to a longer life or more babies for a mouse , something evolutionary biologists call fitness , then that single base-pair change will spread quickly in an urban population . so this crazy figure is called a manhattan plot , because it kind of looks like a skyline . each dot represents one gene , and the higher the dot is in the plot , the more different it is between city and country mice . the ones kind of at the tips of the skyscrapers are the most different , especially those above the red line . and these genes encode for things like immune response to disease , because there might be more disease in very dense , urban populations ; metabolism , how the mice use energy ; and heavy-metal tolerance . you guys can probably predict that new york city soils are pretty contaminated with lead and chromium and that sort of thing . and now our hard work is really starting . we 're going back into the wilds of new york city parks , following the lives of individual mice and seeing exactly what these genes are doing for them . and i would encourage you guys to try to look at your parks in a new way . i 'm not going to be the next charles darwin , but one of you guys might be , so just keep your eyes open . thank you . ( applause )

this guy , we catch in almost every forested area in new york city . this is the white-footed mouse -- not the mouse you find running around your apartment . this is a native species , been here long before humans .

munshi-south and his colleagues are analyzing dna from the white-footed mouse in order to

translator : andrea mcdonough reviewer : jessica ruby how big was that fish you caught ? this big ? this big ? this big ? without photographic evidence , there 's nothing that proves you caught a whopper , and that 's been true since the dawn of fishing . in fact , hundreds of years ago , long before photography could capture the moment , japanese fishermen invented their own way to record trophy catches . they called it gyotaku . gyotaku is the ancient art of printing fish that originated in japan as a way to record trophy catches prior to the modern day camera . gyo means fish and taku means impression . there are several different stories about how gyotaku came about , but it basically started with fishermen needing a way to record the species and size of the fish they caught over 100 years ago . fishermen took paper , ink , and brushes out to sea with them . they told stories of great adventures at sea . since the japanese revered certain fish , the fishermen would take a rubbing from these fish and release them . to make the rubbing , they would paint the fish with non-toxic sumi-e ink and print them on rice paper . this way they could be released or cleaned and sold at market . the first prints like this were for records only with no extra details . it was n't until the mid 1800 's that they began painting eye details and other embellishments onto the prints . one famous nobleman , lord sakai , was an avid fisherman , and , when he made a large catch , he wanted to preserve the memory of the large , red sea bream . to do so , he commissioned a fisherman to print his catch . after this , many fisherman would bring their gyotaku prints to lord sakai , and if he liked their work , he would hire them to print for him . many prints hung in the palace during the edo period . after this period , gyotaku was not as popular and began to fade away . today , gyotaku has become a popular art form , enjoyed by many . and the prints are said to bring good luck to the fishermen . but the art form is quite different than it used to be . most artists today learn on their own by trial and error . before the artist begins to print , the fish needs to be prepared for printing . first , the artist places the fish on a hollowed out surface . then the artist spreads the fins out and pins them down on the board to dry . they then clean the fish with water . when it comes time to print , there are two different methods . the indirect method begins with pasting moist fabric or paper onto the fish using rice paste . then , the artist uses a tompo , or a cotton ball covered in silk , to put ink on the fabric or paper to produce the print . this method requires more skill and great care needs to be taken when pulling the paper off the fish so the paper does n't tear . in the direct method , the artist paints directly on the fish , and then gently presses the moist fabric or paper into the fish . with both of these methods , no two prints are exactly alike , but both reveal dramatic images of the fish . for the final touch , the artist uses a chop , or a stamp , and signs their work , and can hold it up to say , `` the fish was exactly this big ! ''

in fact , hundreds of years ago , long before photography could capture the moment , japanese fishermen invented their own way to record trophy catches . they called it gyotaku . gyotaku is the ancient art of printing fish that originated in japan as a way to record trophy catches prior to the modern day camera .

what was the original purpose for gyotaku ?

translator : andrea mcdonough reviewer : bedirhan cinar being human , we each view ourselves as a unique and independent individual , but we 're never alone ! millions of microscopic beings inhabit our bodies , and no two bodies are the same . each is a different habitat for microbial communities : from the arid deserts of our skin , to the villages on our lips , and the cities in our mouths . even every tooth is its own distinctive neighborhood , and our guts are teaming metropolises of interacting microbes . and in these bustling streets of our guts , we see a constant influx of food , and every microbe has a job to do . here 's a cellulolytic bacteria , for example . their one job is to break down cellulose , a common compound in vegetables , into sugars . those simple sugars then move along to the respirators , another set of microbes that snatch up these simple sugars and burn them as fuel . as food travels through our digestive tract , it reaches the fermentors who extract energy from these sugars by converting them into chemicals , like alcohol and hydrogen gas , which they spew out as waste products . deeper in the depths of our gut city , the syntrophs eke out a living off the fermenters ' trash . at each step of this process , energy is released , and that energy is absorbed by the cells of the digestive tract . this city we just saw is different in everyone . every person has a unique and diverse community of gut microbes that can process food in different ways . one person 's gut microbes may be capable of releasing only a fraction of the calories that another person 's gut microbes can extract . so , what determines the membership of our gut microbial community ? well , things like our genetic makeup and the microbes we encounter throughout our lives can contribute to our microbial ecosystems . the food we eat also influences which microbes live in our gut . for example , food made of complex molecules , like an apple , requires a lot of different microbial workers to break it down . but , if a food is made of simple molecules , like a lollipop , some of these workers are put out of a job . those workers leave the city , never to return . what does n't function well are gut microbial communities with only a few different types of workers . for example , humans who suffer from diseases like diabetes or chronic gut inflamation typically have less microbial variety in their guts . we do n't fully understand the best way to manage our individual microbial societies , but it is likely that lifestyle changes , such as eating a varied diet of complex , plant-based foods , can help revitalize our microbial ecosystems in our gut and across the entire landscape of our body . so , we are really not alone in our body . our bodies are homes to millions of different microbes , and we need them just as much as they need us . as we learn more about how our microbes interact with each other and with our bodies , we will reveal how we can nurture this complex , invisible world that shapes our personal identity , our health , and our well-being .

every person has a unique and diverse community of gut microbes that can process food in different ways . one person 's gut microbes may be capable of releasing only a fraction of the calories that another person 's gut microbes can extract . so , what determines the membership of our gut microbial community ?

one person 's gut microbes may be capable of releasing only a fraction of the calories that another person 's gut microbes can extract .

4,000 years ago , the ancient sumerians made a surprising discovery . if they scraped the bark off a particular kind of tree and ate it , their pain disappeared . little did they know that why they 'd found was destined to influence the future course of medicine . what the sumerians had discovered was a precursor to the medicine known today as aspirin . aspirin 's active ingredient is found commonly in willow trees and other wild plants , which is how it came to infuse the medical traditions of sumer , ancient egypt , ancient greece , and other cultures . around 400 bc , hippocrates , thought of as the father of modern medicine , first recommended chewing willow bark for pain relief and making willow leaf tea to ease the pain of childbirth . but it took over 2,000 years for us to comprehensively investigate its potential . in the mid-18th century , an englishman named edward stone ran five years of experiments , showing that willow bark crushed into a powder and eaten could cure a fever . it took nearly another 70 years for a german pharmacist , johann buchner , to finally identify and purify the substance that made all this possible , a compound called salicin . by then , doctors were routinely using willow bark and other salicin-rich plants , like the herb meadowsweet , to ease pain , fever , and inflammation . but identifying the exact compound suddenly opened up the possibility of manipulating its form . in 1853 , a french chemist managed to chemically synthesize the compound , creating a substance called acetylsalicylic acid . then in 1897 , the pharmaceutical company bayer found a new method and began marketing the compound as a pain reliever called aspirin . this was widely recognized as one of the first synthetic pharmaceutical drugs . originally , aspirin was just bayer 's brand name : a for acetyl , and spir for meadowsweet , whose botanical name is spiraea ulmaria . soon , aspirin became synonymous with acetylsalicylic acid . as its influence grew , aspirin was found to ease not just pain , but also many inflammation-related problems , like rheumatoid arthritis , pericarditis , which enflames the fluid-filled sack around the heart , and kawasaki disease , where blood vessels become inflamed . yet , despite aspirin 's medical value , at this point , scientists still did n't actually know how it worked . in the 1960s and 70s , swedish and british scientists changed that . they showed that the drug interrupts the production of certain chemicals called prostaglandins , which control the transmission of pain sensations and inflammation . in 1982 , that discovery won the researchers a nobel prize in medicine . over time , research has also uncovered aspirin 's risks . overconsumption can cause bleeding in the intestines and the brain . it can also trigger reye 's syndrome , a rare but often fatal illness that affects the brain and liver in children with an infection . and in the late 20th century , aspirin 's success had been overshadowed by newer pain killers with fewer side effects , like acetaminophen and ibuprofen . but in the 1980s , further discoveries about aspirin 's benefits revived interest in it . in fact , the 1982 nobel prize winners also demonstrated that aspirin slows production of thromboxanes , chemicals that cause clumping of platelets , which in turn form blood clots . a landmark clinical trial showed that aspirin reduced heart attack risk by 44 % in participants who took the drug . today , we prescribe it to people at risk of heart attack or stroke because it cuts the likelihood of clots forming in the arteries that supply the heart and brain . even more intriguingly , there 's a growing body of research that suggests aspirin reduces the risk of getting and dying from cancer , especially colorectal cancer . this might be due to aspirin 's anti-platelet effects . by reducing platelet activity , aspirin may decrease the levels of a certain protein that helps cancer cells spread . these discoveries have transformed aspirin from a mere pain reliever to a potentially life-saving treatment . today , we consume about 100 billion aspirin tablets each year , and researchers continue searching for new applications . already , aspirin 's versatility has transformed modern medicine , which is astounding considering its humble beginnings in a scraping of willow bark .

in fact , the 1982 nobel prize winners also demonstrated that aspirin slows production of thromboxanes , chemicals that cause clumping of platelets , which in turn form blood clots . a landmark clinical trial showed that aspirin reduced heart attack risk by 44 % in participants who took the drug . today , we prescribe it to people at risk of heart attack or stroke because it cuts the likelihood of clots forming in the arteries that supply the heart and brain .

aspirin is one of the various strategies used to prevent heart attacks . what are some of the other approaches people could take to reduce their risk ?

in 1984 , an enterprising australian doctor named barry marshall decided to take a risk . too many of his patients were complaining of severe abdominal pain due to stomach ulcers , which are sores in the lining of the upper intestinal tract . at the time , few effective treatments for ulcers existed , and many sufferers required hospitalization or even surgery . desperate for answers , dr. marshall swallowed a cloudy broth of bacteria collected from the stomach of one of his patients . soon , dr. marshall was experiencing the same abdominal pain , bloating , and vomiting . ten days later , a camera called an endoscope peered inside his insides . marshall 's stomach was teeming with the same bacteria as his patient . he 'd also developed gastritis , or severe inflammation of the stomach , the hallmark precursor of ulcers . dr. marshall 's idea challenged a misconception that still persists to this day : that ulcers are caused by stress , food , or too much stomach acid . marshall thought the culprit was bacterial infections . initially , his idea was considered crazy by the brightest medical minds on the planet . but in 2005 , he and dr. robin warren received the ultimate validation when they were awarded the nobel prize for medicine . our stomachs are j-shaped organs with surprisingly intricate ecosystems awash in hormones and chemicals . the stomach is under constant attack by digestive enzymes , bile , proteins , microbes , and the stomach 's own acid . in response , it produces bicarbonate , mucus , and phospholipids called prostaglandins to maintain the integrity of its own lining . this delicate balance is constantly regulated and referred to as mucosal defense . since the mid-1800s , doctors thought stress alone caused most stomach ulcers . patients were given antidepressants or tranquilizers and told to visit health spas . this belief eventually shifted to the related notion of spicy foods and stress as culprits . yet no convincing study has ever demonstrated that emotional upset , psychological distress , or spicy food directly causes ulcer disease . by the mid-20th century , it was widely accepted that excess hydrochloric acid prompted the stomach to eat itself . fervent proponents of this idea were referred to as the acid mafia . the biggest hole in this theory was that antiacids only provide temporary relief . we now know that some rare ulcers are indeed caused by too much hydrochloric acid . but they make up less than 1 % of all cases . dr. marshall and dr. warren pinpointed a spiral-shaped bacteria called helicobacter pylori , or h. pylori , as the real offender . h. pylori is one of humanity 's oldest and most frequent companions , having joined us at least 50,000 years ago , and now found in 50 % of people . previously , we thought the stomach was sterile on account of it being such an acidic , hostile environment . yet h. pylori survives the acidic turmoil of the stomach with a variety of features that disrupt mucosal defense in its favor . for example , it produces an enzyme called urease that helps protect it from the surrounding gastric acid . h. pylori can make over 1,500 proteins , many of which are dedicated to maximizing its virulence . we still have unanswered questions , like why specific people develop ulcers at particular times . however , we do know individual genetics , other medical problems , use of certain medications , smoking , and the genetic diversity of helicobacter strains all play a role . in particular , certain pain medications used to reduce inflammation in joints have been discovered to work with h. pylori to create more severe stomach ulcers . dr. marshall ended up being fine after his famous , albeit dangerous , experiment . he ingested a course of antibiotics similar to the ones taken now for ulcers . to be treated by simple antibiotics is a modern triumph for a disease that previously needed surgery . marshall 's work also reminded us that scientific progress is not always smooth . but there 's value in trusting your proverbial , and sometimes literal , gut .

but they make up less than 1 % of all cases . dr. marshall and dr. warren pinpointed a spiral-shaped bacteria called helicobacter pylori , or h. pylori , as the real offender . h. pylori is one of humanity 's oldest and most frequent companions , having joined us at least 50,000 years ago , and now found in 50 % of people .

which of the following factors most influences when helicobacter pylori prompts the development of ulcers ?

in 1978 , louise brown became the world 's first baby to be born by in vitro fertilization , or ivf . her birth revolutionized the field of reproductive medicine . given that approximately one in eight heterosexual couples has difficulty conceiving , and that homosexual couples and single parents often need clinical help to make a baby , the demand for ivf has been growing . ivf is so common , that more than 5 million babies have been born through this technology . ivf works by mimicking the brilliant design of sexual reproduction . in order to understand ivf , we first need to take a look at the natural process of baby making . believe it or not , it all starts in the brain . roughly fifteen days before fertilization can happen , the anterior pituitary gland secretes follicle stimulating hormone , fsh , which ripens a handful of follicles of the ovary that then release estrogen . each follicle contains one egg , and on average , only one follicle becomes fully mature . as it grows and continues to release estrogen , this hormone not only helps coordinate growth and preparation of the uterus , it also communicates to the brain how well the follicle is developing . when the estrogen level is high enough , the anterior pituitary releases a surge of luteinizing hormone , lh , which triggers ovulation and causes the follicle to rupture and release the egg . once the egg leaves the ovary , it is directed into the fallopian tube by the finger-like fimbriae . if the egg is not fertilized by sperm within 24 hours , the unfertilized egg will die , and the entire system will reset itself , preparing to create a new egg and uterine lining the following month . the egg is the largest cell in the body and is protected by a thick , extracellular shell of sugar and protein called the zona pellucida . the zona thwarts the entry and fusion of more than one sperm , the smallest cell in the body . it takes a man two to three months to make sperm , and the process constantly renews . each ejaculation during sexual intercourse releases more than 100 million sperm . but only 100 or so will ultimately make it to the proximity of the egg , and only one will successfully penetrate through the armor of the zona pellucida . upon successful fertilization , the zygote immediately begins developing into an embryo , and takes about three days to reach the uterus . there , it requires another three or so days to implant firmly into the endometrium , the inner lining of the uterus . once implanted , the cells that are to become the placenta secrete a hormone that signals to the ovulated follicle that there is a pregnancy in the uterus . this helps rescue that follicle , now called the corpus luteum , from degenerating as it normally would do in that stage of the menstrual cycle . the corpus luteum is responsible for producing the progesterone required to maintain the pregnancy until six to seven weeks of gestation , when the placenta develops and takes over , until the baby is born approximately 40 weeks later . now , how do you make a baby in a lab ? in patients undergoing ivf , fsh is administered at levels that are higher than naturally occuring to cause a controlled overstimulation of the ovaries so that they ultimately produce multiple eggs . the eggs are then retrieved just before ovulation would occur , while the woman is under anesthesia , through an aspirating needle that is guided by ultrasound . most sperm samples are produced by masturbation . in the laboratory , the identified eggs are stripped of surrounding cells and prepared for fertilization in a petri dish . fertilization can occur by one of two techniques . in the first , the eggs are incubated with thousands of sperm and fertilization occurs naturally over a few hours . the second technique maximizes certainty of fertilization by using a needle to place a single sperm inside the egg . this is particularly useful when there is a problem with the quality of the sperm . after fertilization , embryos can be further screened for genetic suitability , frozen for later attempted pregnancies , or delivered into the woman 's uterus via catheter . common convention is to transfer the embryo three days after fertilization , when the embryo has eight cells , or on day five , when the embryo is called a blastocyst , and has hundreds of cells . if the woman 's eggs are of poor quality due to age or toxic exposures , or have been removed due to cancer , donor eggs may be used . in the case that the intended mother has a problematic uterus , or lacks one , another woman , called the gestational carrier or surrogate , can use her uterus to carry the pregnancy . to increase the odds of success , which are as high as 40 % for a woman younger than 35 , doctors sometimes transfer multiple embryos at once , which is why ivf results in twins and triplets more often than natural pregnancies . however , most clinics seek to minimize the chances of multiple pregnancies , as they are riskier for mothers and babies . millions of babies , like louise brown , have been born from ivf and have had normal , healthy lives . the long-term health consequences of ovarian stimulation with ivf medicines are less clear , though so far , ivf seems safe for women . because of better genetic testing , delayed childbearing , increased accessibility and diminishing cost , it 's not inconceivable that artificial baby making via ivf and related techniques could outpace natural reproduction in years to come .

in 1978 , louise brown became the world 's first baby to be born by in vitro fertilization , or ivf . her birth revolutionized the field of reproductive medicine .

although many patients want twins , a common phenomenon with in vitro fertilization , why has there been a push to try to reduce the number of twins born from ivf ?

figs are one of my favorite foods . they 're sweet and floral , and there 's something about the texture that i find so delightful—the outside is soft , but the seeds in the middle give you this totally satisfying crunch . but it turns out that many species of figs contain the bodies of dead wasps . i 'm anna and this is gross science . figs are n't exactly your typical fruit . you can think of them as packages that contain all of the fig tree ’ s flowers within them . but if the flowers are trapped inside the fig how do they get pollinated ? well , that 's where fig wasps come in . in most species , pregnant female fig wasps carrying pollen are attracted to young figs . they enter through a tiny opening at the fig ’ s bottom that ’ s highly selective—it usually only lets in the exact species of wasps that pollinate it . but , even the pollinators have a hard time getting in . most lose their wings and antennae in the process . the wasp ’ s goal is to find a home for her babies . and the perfect home is inside the fig ’ s female flowers—those are the ones that would produce seeds if they were fertilized . so , the mama wasp drops a fertilized egg inside as many of the female flowers as she can—sometimes , up to a few hundred . but she ca n't get to all of them . along the way , she winds up fertilizing the rest of the flowers with the fig pollen she 's carrying , and those flowers begin developing seeds . once the wasp is finished laying eggs , she usually dies inside the fig . each baby wasp begins to grow , encased in a protective structure that the plant forms called a gall . the male wasps mature first . when they emerge , they find the galls of the female wasps , many of whom are their sisters , poke inside , and impregnate them before they 've even hatched ! then , the males die inside the fig , but not before boring tiny holes through the fig ’ s skin . when the females do emerge , the fig has just started producing pollen . the female wasps pick up some of that pollen before making their way through the holes their brothers drilled , and go off to find a new fig to start the cycle again . but the story 's not over . at this point , our fig ’ s seeds are finally mature and ready to be planted . and that happens when the ripe fig is eaten by animals , which poop out the seeds , spreading fig plants far and wide . of course , humans eat figs , too . so , when you bite into a fig are you actually eating the bodies of dead wasps ? well , if you ’ re getting your figs from the supermarket , then most likely not . see , humans and figs have a really long history—we ’ ve probably been domesticating them for over 11,000 years . so , while there are over 750 species in the world , most of the figs we eat are a species called the “ common fig , ” which humans have had a huge hand in creating . in fact , some common figs are seedless and don ’ t require pollination at all . other varieties of common fig do need to be pollinated , but have separate male and female trees , and we only eat fruits from the female ones . i ’ ll put a link in the description to a great explanation of how common fig pollination happens , but long story short , female wasps can only manage to lay eggs in the the figs from male trees , not female ones . but they can ’ t tell the difference between the two types of trees . so , if a wasp does enter a female fruit , she ’ ll pollinate it , and either manage to escape or die inside the fig . and then that fig might make it to your table . frankly , one wasp here and there isn ’ t enough to deter me from eating these things . but if you 're still feeling squeamish , just think about it this way : by eating that fig , you 're benefitting from a complex and in my view , beautiful partnership—or , what ’ s called a “ mutualism ” — between two very different species . one that ’ s been delicately crafted by around 90 million years of evolution . and that certainly whets my appetite—at least for curiosity , if not for dinner . mmmm ! but also ew .

but if the flowers are trapped inside the fig how do they get pollinated ? well , that 's where fig wasps come in . in most species , pregnant female fig wasps carrying pollen are attracted to young figs . they enter through a tiny opening at the fig ’ s bottom that ’ s highly selective—it usually only lets in the exact species of wasps that pollinate it .

before the newly-hatched female fig wasps leave the fig , they pick up some pollen , then bore their way out through tiny holes . so when they enter a new fig what two tasks are they accomplishing ?

translator : andrea mcdonough reviewer : bedirhan cinar this is zeno of elea , an ancient greek philosopher famous for inventing a number of paradoxes , arguments that seem logical , but whose conclusion is absurd or contradictory . for more than 2,000 years , zeno 's mind-bending riddles have inspired mathematicians and philosophers to better understand the nature of infinity . one of the best known of zeno 's problems is called the dichotomy paradox , which means , `` the paradox of cutting in two '' in ancient greek . it goes something like this : after a long day of sitting around , thinking , zeno decides to walk from his house to the park . the fresh air clears his mind and help him think better . in order to get to the park , he first has to get half way to the park . this portion of his journey takes some finite amount of time . once he gets to the halfway point , he needs to walk half the remaining distance . again , this takes a finite amount of time . once he gets there , he still needs to walk half the distance that 's left , which takes another finite amount of time . this happens again and again and again . you can see that we can keep going like this forever , dividing whatever distance is left into smaller and smaller pieces , each of which takes some finite time to traverse . so , how long does it take zeno to get to the park ? well , to find out , you need to add the times of each of the pieces of the journey . the problem is , there are infinitely many of these finite-sized pieces . so , should n't the total time be infinity ? this argument , by the way , is completely general . it says that traveling from any location to any other location should take an infinite amount of time . in other words , it says that all motion is impossible . this conclusion is clearly absurd , but where is the flaw in the logic ? to resolve the paradox , it helps to turn the story into a math problem . let 's supposed that zeno 's house is one mile from the park and that zeno walks at one mile per hour . common sense tells us that the time for the journey should be one hour . but , let 's look at things from zeno 's point of view and divide up the journey into pieces . the first half of the journey takes half an hour , the next part takes quarter of an hour , the third part takes an eighth of an hour , and so on . summing up all these times , we get a series that looks like this . `` now '' , zeno might say , `` since there are infinitely many of terms on the right side of the equation , and each individual term is finite , the sum should equal infinity , right ? '' this is the problem with zeno 's argument . as mathematicians have since realized , it is possible to add up infinitely many finite-sized terms and still get a finite answer . `` how ? '' you ask . well , let 's think of it this way . let 's start with a square that has area of one meter . now let 's chop the square in half , and then chop the remaining half in half , and so on . while we 're doing this , let 's keep track of the areas of the pieces . the first slice makes two parts , each with an area of one-half the next slice divides one of those halves in half , and so on . but , no matter how many times we slice up the boxes , the total area is still the sum of the areas of all the pieces . now you can see why we choose this particular way of cutting up the square . we 've obtained the same infinite series as we had for the time of zeno 's journey . as we construct more and more blue pieces , to use the math jargon , as we take the limit as n tends to infinity , the entire square becomes covered with blue . but the area of the square is just one unit , and so the infinite sum must equal one . going back to zeno 's journey , we can now see how how the paradox is resolved . not only does the infinite series sum to a finite answer , but that finite answer is the same one that common sense tells us is true . zeno 's journey takes one hour .

now you can see why we choose this particular way of cutting up the square . we 've obtained the same infinite series as we had for the time of zeno 's journey . as we construct more and more blue pieces , to use the math jargon , as we take the limit as n tends to infinity , the entire square becomes covered with blue .

an infinite series :

meet our chemist , harriet . she has a chemical reaction that needs to occur more quickly . a chemist has some processes at her disposal that can help her speed up her reaction , and she knows of five ways . and to remember them , she thinks back to her days as a high school student , and the day she got a date for the dance . harriet was in high school , studying between classes . she had lost track of time and was going to be late to class . unbeknownst to her , harold , who was just around the corner , was running late , too . they both sprinted to class and , as it happened , sprinted directly into one another . now , this was no small collision . they ran squarely into one another in such a way that he knocked the books right out of her hand . `` i 'm sorry , '' he said . `` let me help you with your books . '' he kindly helped her re-collect her belongings , and politely offered to walk her to class . and you 'll never guess who went together to the dance later that year . yup , those two . so as we can see from this example , the key to getting a date for the dance is to collide with someone and knock the books out of their hands . now , you 're probably already aware that not all collisions lead to dates for the dance , thankfully . the collisions must have two important characteristics : one , correct orientation that allows books to be knocked from one 's hands ; and two , enough energy to knock the books out . shortly after this incident , harriet decided to tell me , her chemistry teacher , all about it . i noticed some interesting parallels between her story and chemical reaction rates , which happened to be what she was studying in the hallway the day of the collision . together , we decided to set out on two missions . harriet wanted to help all chemistry students and chemists remember how to speed up the rate of chemical reactions and i , being the nice guy that i am , decided to make it my mission to help create educational environments in which more book-dropping collisions can take place to increase future chemists ' chances of getting a date for the dance . in order to facilitate this improved dance-date-getting process , i propose five changes to all schools that parallel harriet 's five ways to increase chemical reaction rates . first , i propose that we shrink the size of the hallways . this will make it more difficult to safely navigate the hallways and will cause more collisions than in larger hallways . and by increasing the number of collisions , we increase the likelihood that some of those collisions will have the correct alignment and enough energy to create a date to the dance . now , chemically speaking , this is equivalent to lowering the volume of a reaction vessel or a reaction mixture . in doing so , the individual particles are closer together , and more collisions will occur . more collisions means a greater likelihood that collisions with the appropriate energy and configuration will happen . second , i propose increasing the overall population of the school . more students equals more collisions . by increasing the number of particles available for collision , we create an environment where more collisions can take place . third , we must reduce the time allowed between classes -- heck , let 's just cut it in half . in doing so , students will need to move more quickly to get from one class to the next . this increase in velocity will help make sure collisions have the appropriate amount of energy necessary to ensure book-dropping . this is analogous to increasing the temperature of the reaction mixture . higher temperature means particles are moving faster . faster-moving particles means more energy , and a greater likelihood of the reaction-causing collision . fourth , students must stop traveling in packs . by traveling in packs , the students on the outside of the pack insulate those in the middle from undergoing any collisions . by splitting up , each student has more area exposed that is available for a collision from a passing student . when particles travel in packs , the surface area is very small , and only the outside particles can collide . however , by breaking up the clumps into individual particles , the total surface area is increased , and each particle has an exposed surface that can react . fifth and finally , we hire a matchmaker . is this colliding and book-dropping too violent ? is there an easier way to get a date that requires less initial energy ? then a matchmaker will help with this . the matchmaker makes it easier for a couple to get together , by coordinating the match . our matchmaker is like a catalyst . chemical catalysts function by lowering the activation energy -- in other words , by lowering the energy required to start a reaction . they do this by bringing two particles together and orienting them correctly in space so that the two can meet at the correct configuration and allow a reaction to take place . so , to sum up : if a future chemist wants a date for the dance , he must collide with another person and knock the books out of their hands . and if a chemist wants to make a chemical reaction occur , the particles must collide in the correct orientation with an appropriate amount of energy . and both of these processes can be accelerated , using the five methods i 've described .

in order to facilitate this improved dance-date-getting process , i propose five changes to all schools that parallel harriet 's five ways to increase chemical reaction rates . first , i propose that we shrink the size of the hallways . this will make it more difficult to safely navigate the hallways and will cause more collisions than in larger hallways . and by increasing the number of collisions , we increase the likelihood that some of those collisions will have the correct alignment and enough energy to create a date to the dance .

in this analogy , shrinking the hallways is analogous to :

there are many stories that can be told about world war ii , from the tragic to the inspring . but perhaps one of the most heartrending experiences was that of the akune family , divided by the war against each other and against their own identities . ichiro akune and his wife yukiye immigrated to america from japan in 1918 in search of opportunity , opening a small grocery store in central california and raising nine children . but when mrs. akune died in 1933 , the children were sent to live with relatives in japan , their father following soon after . though the move was a difficult adjustment after having been born and raised in america , the oldest son , harry , formed a close bond with his grand uncle , who taught him the japanese language , culture and values . nevertheless , as soon as harry and his brother ken were old enough to work , they returned to the country they considered home , settling near los angeles . but then , december 7 , 1941 , the attack on pearl harbor . now at war with japan , the united states government did not trust the loyalty of those citizens who had family or ancestral ties to the enemy country . in 1942 , about 120,000 japanese americans living on the west coast were stripped of their civil rights and forcibly relocated to internment camps , even though most of them , like harry and ken , were nisei , american or dual citizens who had been born in the us to japanese immigrant parents . the brothers not only had very limited contact with their family in japan , but found themselves confined to a camp in a remote part of colorado . but their story took another twist when recruiters from the us army 's military intelligence service arrived at the camp looking for japanese-speaking volunteers . despite their treatment by the government , harry and ken jumped at the chance to leave the camp and prove their loyalty as american citizens . having been schooled in japan , they soon began their service , translating captured documents , interrogating japanese soldiers , and producing japanese language propaganda aimed at persuading enemy forces to surrender . the brothers ' work was invaluable to the war effort , providing vital strategic information about the size and location of japanese forces . but they still faced discrimination and mistrust from their fellow soldiers . harry recalled an instance where his combat gear was mysteriously misplaced just prior to parachuting into enemy territory , with the white officer reluctant to give him a weapon . nevertheless , both brothers continued to serve loyally through the end of the war . but harry and ken were not the only akune brothers fighting in the pacific . unbeknownst to them , two younger brothers , the third and fourth of the five akune boys , were serving dutifully in the imperial japanese navy , saburo in the naval airforce , and 15-year-old shiro as an orientation trainer for new recruits . when the war ended , harry and ken served in the allied occupational forces and were seen as traitors by the locals . when all the akune brothers gathered at a family reunion in kagoshima for the first time in a decade , it was revealed that the two pairs had fought on opposing sides . tempers flared and a fight almost broke out until their father stepped in . the brothers managed to make peace and saburo and shiro joined harry and ken in california , and later fought for the us army in korea . it took until 1988 for the us government to acknowledge the injustice of its internment camps and approve reparations payments to survivors . for harry , though , his greatest regret was not having the courage to thank his japanese grand uncle who had taught him so much . the story of the akune brothers is many things : a family divided by circumstance , the unjust treatment of japanese americans , and the personal struggle of reconciling two national identities . but it also reveals a larger story about american history : the oppression faced by immigrant groups and their perseverance in overcoming it .

the brothers not only had very limited contact with their family in japan , but found themselves confined to a camp in a remote part of colorado . but their story took another twist when recruiters from the us army 's military intelligence service arrived at the camp looking for japanese-speaking volunteers . despite their treatment by the government , harry and ken jumped at the chance to leave the camp and prove their loyalty as american citizens .

what was the primary reason harry and ken akune joined the u.s. army 's military intelligence service ?

in 1997 , a french woman named jeanne calment passed away after 122 years and 164 days on this earth , making her the oldest known person in history . her age was so astounding that a millionaire pledged $ 1 million to anyone who could break her record . but in reality , living to this age or beyond is a feat that very few , maybe even no humans , are likely to accomplish . human bodies just are n't built for extreme aging . our capacity is set at about 90 years . but what does aging really mean and how does it counteract the body 's efforts to stay alive ? we know intuitively what it means to age . for some , it means growing up , while for others , it 's growing old . yet finding a strict scientific definition of aging is a challenge . what we can say is that aging occurs when intrinsic processes and interactions with the environment , like sunlight , and toxins in the air , water , and our diets , cause changes in the structure and function of the body 's molecules and cells . those changes in turn drive their decline , and subsequently , the failure of the whole organism . the exact mechanisms of aging are poorly understood . but recently , scientists have identified nine physiological traits , ranging from genetic changes to alterations in a cell 's regenerative ability that play a central role . firstly , as the years pass , our bodies accumulate genetic damage in the form of dna lesions . these occur naturally when the body 's dna replicates , but also in non-dividing cells . organelles called mitochondria are especially prone to this damage . mitochondria produce adenosine triphosphate , or atp , the main energy source for all cellular processes , plus mitochondria regulate many different cell activities and play an important role in programmed cell death . if mitochondrial function declines , then cells and , later on , whole organs , deteriorate , too . other changes are known to occur in the expression patterns of genes , also known as epigenetic alterations , that affect the body 's tissues and cells . genes silenced or expressed only at low levels in newborns become prominent in older people , leading to the development of degenerative diseases , like alzheimer 's , which accelerate aging . even if we could avoid all these harmful genetic alterations , not even our own cells could save us . the fact remains that cellular regeneration , the very stuff of life , declines as we age . the dna in our cells is packaged within chromosomes , each of which has two protective regions at the extremities called telomeres . those shorten every time cells replicate . when telomeres become too short , cells stop replicating and die , slowing the body 's ability to renew itself . with age , cells increasingly grow senescent , too , a process that halts the cell cycle in times of risk , like when cancer cells are proliferating . but the response also kicks in more as we age , halting cell growth and cutting short their ability to replicate . aging also involves stem cells that reside in many tissues and have the property of dividing without limits to replenish other cells . as we get older , stem cells decrease in number and tend to lose their regenerative potential , affecting tissue renewal and maintenance of our organs original functions . other changes revolve around cells ' ability to function properly . as they age , they stop being able to do quality control on proteins , causing the accumulation of damaged and potentially toxic nutrients , leading to excessive metabolic activity that could be fatal for them . intercellular communication also slows , ultimately undermining the body 's functional ability . there 's a lot we do n't yet understand about aging . ultimately , does longer life as we know it come down to diet , exercise , medicine , or something else ? will future technologies , like cell-repairing nanobots , or gene therapy , artificially extend our years ? and do we want to live longer than we already do ? starting with 122 years as inspiration , there 's no telling where our curiosity might take us .

those changes in turn drive their decline , and subsequently , the failure of the whole organism . the exact mechanisms of aging are poorly understood . but recently , scientists have identified nine physiological traits , ranging from genetic changes to alterations in a cell 's regenerative ability that play a central role .

why is it difficult to define aging ?

every year , about 1,000 new words are added to the oxford english dictionary . where do they come from , and how do they make it into our everyday lives ? with over 170,000 words currently in use in the english language , it might seem we already have plenty . yet , as our world changes , new ideas and inventions spring forth , and science progresses , our existing words leave gaps in what we want to express and we fill those gaps in several ingenious , practical , and occasionally peculiar ways . one way is to absorb a word from another language . english has borrowed so many words over its history that nearly half of its vocabulary comes directly from other languages . sometimes , this is simply because the thing the word describes was borrowed itself . rome and france brought legal and religious concepts , like altar and jury , to medieval england , while trade brought crops and cuisine , like arabic coffee , italian spaghetti , and indian curry . but sometimes , another language has just the right word for a complex idea or emotion , like naïveté machismo , or schadenfreude . scientists also use classical languages to name new concepts . clone , for example , was derived from the ancient greek word for twig to describe creating a new plant from a piece of the old . and today , the process works both ways , with english lending words like software to languages all over the world . another popular way to fill a vocabulary gap is by combining existing words that each convey part of the new concept . this can be done by combining two whole words into a compound word , like airport or starfish , or by clipping and blending parts of words together , like spork , brunch , or internet . and unlike borrowings from other languages , these can often be understood the first time you hear them . and sometimes a new word is n't new at all . obsolete words gain new life by adopting new meanings . villain originally meant a peasant farmer , but in a twist of aristocratic snobbery came to mean someone not bound by the knightly code of chivalry and , therefore , a bad person . a geek went from being a carnival performer to any strange person to a specific type of awkward genius . and other times , words come to mean their opposite through irony , metaphor , or misuse , like when sick or wicked are used to describe something literally amazing . but if words can be formed in all these ways , why do some become mainstream while others fall out of use or never catch on in the first place ? sometimes , the answer is simple , as when scientists or companies give an official name to a new discovery or technology . and some countries have language academies to make the decisions . but for the most part , official sources like dictionaries only document current usage . new words do n't originate from above , but from ordinary people spreading words that hit the right combination of useful and catchy . take the word meme , coined in the 1970s by sociobiologist richard dawkins from the ancient greek for imitation . he used it to describe how ideas and symbols propagate through a culture like genes through a population . with the advent of the internet , the process became directly observable in how jokes and images were popularized at lightning speed . and soon , the word came to refer to a certain kind of image . so meme not only describes how words become part of language , the word is a meme itself . and there 's a word for this phenomenon of words that describe themselves : autological . not all new words are created equal . some stick around for millennia , some adapt to changing times , and others die off . some relay information , some interpret it , but the way these words are created and the journey they take to become part of our speech tells us a lot about our world and how we communicate within it .

and today , the process works both ways , with english lending words like software to languages all over the world . another popular way to fill a vocabulary gap is by combining existing words that each convey part of the new concept . this can be done by combining two whole words into a compound word , like airport or starfish , or by clipping and blending parts of words together , like spork , brunch , or internet .

a way to fill-in a conceptual gap in a language is to :

today i ’ m going to tell you about one of my favorite creatures to ever grace this planet . it ’ s a frog that ’ s pretty bizarre but also weirdly sweet and adorable . sadly , it went extinct just before i was born , so i thought i ’ d never get the chance to see it . but a few years ago , scientists tried to bring it back from the dead . i ’ m anna and this is gross science . gastric-brooding frogs were first found in queensland , australia in 1972 . they looked pretty normal—just your average brownish , greenish frog . but there was nothing average about how they gave birth . a female frog would lay her eggs , and a male frog would fertilize them externally . so far so normal . but then , the mother frog would swallow the eggs—around 40 of them ! you ’ d think this would be a terrible idea . after all , stomachs—whether they be frog or human—usually contain strong acid to break down your last meal . but the eggs likely contained a chemical that made the mother ’ s stomach stop producing acid . that meant the mother couldn ’ t eat during her pregnancy , which from a human perspective seems awful , but the frogs seemed to make do . eventually , tadpoles would hatch from the eggs . and the tadpoles would release mucus that contained more of that acid-blocking chemical . the babies would continue to grow in the stomach for another 6 weeks , getting so big that they ’ d compress the mother ’ s lungs . luckily , these frogs could also breathe through their skin , so the mothers didn ’ t suffocate . finally , the tadpoles would metamorphose into baby frogs , and the mother would vomit them up—usually one at a time over a few days . though , when provoked some were known to projectile vomit all their babies out at once . while barfing up your babies sounds ... horrible ... it ’ s kinda sweet when you think about it . gastric-brooding , as this strategy is called , is a way to keep your babies close to you and safe while they ’ re most vulnerable . it ’ s really a lot like human pregnancy…only the babies come out the other end… anyway , there were two species of these frogs , but both went extinct by the mid-80s . the culprit was likely an invasive fungus—one that poses a major threat to amphibians worldwide , and that humans likely helped to spread around the globe . it ’ s called chytrid fungus and it affects a frog ’ s skin . because frogs use their skin for crucial functions like breathing , staying hydrated , and regulating their temperature , the parasite can easily kill its victims . and it ’ s highly contagious—by 2013 it had put 42 % of the world ’ s frog species in danger . losing all these frogs would be , in a word , devastating . not only would it have major impacts on ecosystems worldwide , and be a loss of beautiful biodiversity , but there is so much we still have to learn from these creatures that might be beneficial to human health and well-being . take the gastric-brooding frog . if we ’ d had more time to study it , maybe we could have learned more about how it turns off stomach acid production , potentially revealing some insights that could help humans with gi problems . consequently , back in 2013 , some scientists began a project to resurrect the gastric-brooding frog . they took cells from a frozen specimen , cloned the dna into the egg of another frog species , and ended up creating a living gastric-brooding frog embryo . it only survived for about three days , but they haven ’ t given up trying . and it ’ s made some researchers hopeful that “ de-extinction ” —the process of bringing extinct species back to life—will one day be a solution for reviving at least some of the valuable biodiversity we ’ ve lost , often due to humans ’ impact on the environment . obviously , this is a controversial idea . and , i think most scientists would agree that de-extinction is a last-gasp effort in conservation . it in no way means we should stop protecting and preserving the at-risk species we have . that said , while i can ’ t speak to the ethics of the situation , i will admit that there ’ s a pretty big part of me that would love to see a gastric-brooding frog vomiting up its babies . ew .

not only would it have major impacts on ecosystems worldwide , and be a loss of beautiful biodiversity , but there is so much we still have to learn from these creatures that might be beneficial to human health and well-being . take the gastric-brooding frog . if we ’ d had more time to study it , maybe we could have learned more about how it turns off stomach acid production , potentially revealing some insights that could help humans with gi problems .

what made the gastric brooding frog go extinct ?

you might just want to sneak up so you don ’ t sprinkle any dirt at the bottom of this place where we turned it over . yeah ok. look at that soil , it is all cake looking . yeah it is . where are we ? look up yonder . to the left oh wow ! ok , let me get the soil before you start whacking ok ? oh yeah . salt blast covered . here we can see evidence of the mining . now this mine closed , many years ago . the bottom is glass-covered houston . yeah , white glass . so if we look into the quarry in the normal daylight in the absence of the snow it would look a bit like a lunar landscape . no the black stuff that is that stuff is crystal , that is the crystal in rocks , now i say that for one specific reason because during the apollo programme the astronauts , they came back from the moon with bucket loads and bucket loads of moon rock and dust . that part of it is . very good . and upon analysis they were really , really surprised to find that there were a number of elements including yttrium which existed at a much much higher abundance on the moon which happens to be the deepest penetration that bowler made . so we are in ytterby in sweden and it ’ s a really nice day and we have come to the ytterby quarry , or ytterby groover , which is actually the birthplace for 4 of the elements and really the one we are going to talk about now is this one right here yttrium . it was first discovered in this quarry from a really horrible black lump of mineral which people thought was coal . and over a period of 40 years from the late 1700s on , some scientists over in arbo did a lot of work in refining this material and they found a new earth or yttria . ok this was yttrium and oxygen and they couldn ’ t get the oxygen out by using traditional reductive methods , metal making methods like burning with carbon and charcoal . so the yttria survived and it was known for about 40 years before the german scientist volla , decided to react the yttria with a much more reactive element , potassium . the potassium wrestled and ripped out the oxygen and he made yttrium metal for the first time . yttrium its used in a whole range of different things , it ’ s used in semi conductors , where there is yttrium , barium , copper oxides , the 1-2-3 complexes that we know of and it ’ s used for a whole range of applications . it ’ s used in laser technologies to make very intense pulses of light , for technologies like cds and leds etc. , etc. , but a massive , massive area . another activity of another use for yttrium is actually in the use of yttrium oxisulphide which is used as an additive in glass it makes glass really tough , like bullet proof glass it makes it very shock resistant and very very resistant towards temperature changes , so it is a very useful additive in glasses and glassy materials . make sure you don ’ t fall over the rock so yttrium itself is a really quite nice lustrous soft metal from group 3 of the periodic table , it burns really readily in an oxygen rich atmosphere and reacts quite well with water in the atmosphere as well . so you have to be very careful with yttrium because it oxidises and it is really quite easy to destroy . that ’ s yttrium metal , just as turnings . so we have to handle this under nitrogen because generally it will form an oxide layer and then you would not be able to do any chemistry with it . yttrium is an element which is not again particularly widely studied in chemistry , much less so than its neighbour zirconium , and but again it ’ s an area where chemists now are starting to focus rather more . if it is really finely divided then it might burst into flames , in fact , all metals if they are finely divided they are quite likely to spontaneously combust .

so if we look into the quarry in the normal daylight in the absence of the snow it would look a bit like a lunar landscape . no the black stuff that is that stuff is crystal , that is the crystal in rocks , now i say that for one specific reason because during the apollo programme the astronauts , they came back from the moon with bucket loads and bucket loads of moon rock and dust . that part of it is .

why does this video begin with images of astronauts from the apollo program walking on the moon ?

rising temperatures and seas , massive droughts , changing landscapes . successfully adapting to climate change is growing increasingly important . for humans , this means using our technological advancement to find solutions , like smarter cities and better water management . but for some plants and animals , adapting to these global changes involves the most ancient solution of all : evolution . evolutionary adaptation usually occurs along time scales of thousands to hundreds of thousands of years . but in cases where species are under especially strong selective conditions , like those caused by rapidly changing climates , adaptive evolution can happen more quickly . in recent decades , we 've seen many plants , animals , and insects relocating themselves and undergoing changes to their body sizes , and the dates they flower or breed . but many of these are plastic , or nonheritable changes to an individual 's physical traits . and there are limits to how much an organism can change its own physiology to meet environmental requirements . that 's why scientists are seeking examples of evolutionary changes coded in species ' dna that are heritable , long-lasting , and may provide a key to their future . take the tawny owl . if you were walking through a wintry forest in northern europe 30 years ago , chances are you 'd have heard , rather than seen , this elusive bird . against the snowy backdrop , its plumage would have been near impossible to spot . today , the landscape is vastly different . since the 1980s , climate change has led to significantly less snowfall , but you 'd still struggle to spot a tawny owl because nowadays , they 're brown . the brown color variant is the genetically dominant form of plumage in this species , but historically , the recessive pale gray variant triumphed because of its selective advantage in helping these predators blend in . however , less snow cover reduces opportunities for camouflage , so lately , this gray color variant has been losing the battle against natural selection . the offspring of the brown color morphs , on the other hand , have an advantage in exposed forests , so brown tawny owls are flourishing today . several other species have undergone similar climate-change-adaptive genetic changes in recent decades . pitcher plant mosquitoes have rapidly evolved to take advantage of the warmer temperatures , entering dormancy later and later in the year . two spot ladybug populations , once comprised of equal numbers of melanic and non-melanic morphs , have now shifted almost entirely to the non-melanic color combination . scientists think that keeps them from overheating . meanwhile , pink salmon have adapted to warmer waters by spawning earlier in the season to protect their sensitive eggs . and wild thyme plants in europe are producing more repellent oils to protect themselves against the herbivores that become more common when it 's warm . these plants and animals belong to a group of about 20 identified species with evolutionary adaptations to rapid climate change , including snapping turtles , wood frogs , knotweed , and silver spotted skipper butterflies . however , scientists hope to discover more species evolving in response to climate change out of 8.7 million species on the planet . for most of our planet 's astounding and precious biodiversity , evolution wo n't be the answer . instead , many of those species will have to rely on us to help them survive a changing world or face extinction . the good news is we already have the tools . across the planet , we 're making on-the-ground decisions that will help entire ecosystems adapt . critical climate refuges are being identified and set aside , and projects are underway to help mobile species move to more suitable climates . existing parks and protected areas are also doing climate change check-ups to help their wildlife cope . fortunately , it 's still within our power to preserve much of the wondrous biodiversity of this planet , which , after all , sustains us in so many ways .

critical climate refuges are being identified and set aside , and projects are underway to help mobile species move to more suitable climates . existing parks and protected areas are also doing climate change check-ups to help their wildlife cope . fortunately , it 's still within our power to preserve much of the wondrous biodiversity of this planet , which , after all , sustains us in so many ways .

humans will have to adapt to climate change too . predict the future for those people living in areas that will be most affected ( coastal areas , those in warmer climates , arctic areas ) .

flatulence , or passing gas , is a normal daily phenomenon . most individuals , yes , that includes you , will make anywhere from 500-1500 milliliters of gas and can pass gas ten to twenty times a day . but where does this bodily gas come from ? a small proportion may come from ingesting air during sleep , or at other times , but the majority of gas is produced by bacteria in our intestines as they digest parts of food which we can not . our intestine is home to trillions of bacteria living in a symbiotic relationship with us . we provide them with a safe place to stay and food to eat . in exchange , they help us extract energy from our food , make vitamins for us , like vitamin b and k , boost our immune system , and play an important role in gastrointestinal barrier function , motility and the development of various organ systems . clearly , it 's in our best interest to keep these bacteria happy . gut bacteria get their nutrition primarily from undigested food , such as carbohydrates and proteins , which come to the large intestine . they ferment this undigested food to produce a wide range of compounds , such as short-chain fatty acids and , of course , gases . hydrogen and carbon dioxide are the most common gaseous products of bacterial fermentation , and are odorless . some people also produce methane due to specific microbes present in their gut . but methane is actually odorless , too . well then , what stinks ? the foul smell is usually due to volatile sulfur compounds , such as hydrogen sulfide and methanethiol , or methyl mercaptan . these gases , however , constitute less than 1 % of volume , and are often seen with ingestion of amino acids containing sulfur , which may explain the foul smell of gas from certain high protein diets . increased passage of gas is commonly noticed after eating foods with high amounts of indigestible carbohydrates , like beans , lentils , dairy products , onions , garlic , leeks , radishes , potatoes , oats , wheat , cauliflower , broccoli , cabbage , and brussel sprouts . humans lack the enzymes , so the bacteria able to ferment complex carbohydrates take over , and this naturally leads to more gas than usual . but if you feel uncomfortable , bloated or visibly distended , this may indicate impaired movement of gas along the gastrointestinal track . it 's important not to just blame certain foods for gas and bloating and then avoid them . you do n't want to starve the bacteria that digest these complex carbohydrates , or they 'll have to start eating the sugars in the mucus lining of your intestines . your personal gas will vary based on what you eat , and what bacteria are in your gut . for example , from the same starting sugar , the bacteria clostridium produces carbon dioxide , butyrate and hydrogen , while propionibacterium can produce carbon dioxide , propionate and acetate . at the same time , methanogens can use hydrogen and carbon dioxide produced by other bacteria to generate methane , which can reduce the total volume of gas by using up hydrogen and carbon dioxide . so there 's a complex web among intestinal bacteria allowing them to flourish by either directly consuming undigested food , or using what other bacteria produce . this interaction largely determines the amount and type of gas produced , so gas production is a sign that your gut bacteria are at work . but in some instances , people may develop abnormal increased flatulence . a common example is lactose intolerance . most individuals have the enzyme for breaking down lactose , a sugar present in milk and milk-derived products . but some people either lack it entirely , or have a reduced amount , such as after a gastrointestinal infection , so they 're unable to digest lactose products and may experience cramping , along with increased flatulence due to bacterial fermentation . but remember , most gas is produced as a natural result of bacterial fermentation in the intestine , and indicates healthy functioning of the gut . the amount and type can vary based on your diet and the bacteria in your intestine . exercise social courtesy while passing gas , and do try to forgive your bacteria . they 're only trying to be helpful .

a small proportion may come from ingesting air during sleep , or at other times , but the majority of gas is produced by bacteria in our intestines as they digest parts of food which we can not . our intestine is home to trillions of bacteria living in a symbiotic relationship with us . we provide them with a safe place to stay and food to eat .

trillions of bacteria live in a symbiotic relationship with humans . why is this beneficial ?

everyone knows that stories are made up of words , from short poems to epic novels . but did you know that a single word itself can tell an entire story ? you see , just as we can look at a story 's plot , setting , and characters , we can also study the history of an individual word , where it developed , and the cultures and people who helped shape it . looking into the story of a word is like counting the rings of a tree . newer words , like google or cyborg , have shorter stories . but the older the word , the longer the story and the more it stands to reveal to us not only about itself , but about ourselves and our history . the oldest words in present-day english are those that come from old english , the ancestor of our modern language whose first seeds were planted about 1500 years ago . compared to languages like greek or chinese that date back thousands of years , english is just a sapling in the lexical forest . but the stories of its words often start long before english itself took root . one such word is the familiar word true , as in true stories . let 's take a look . true usually means factual , correct , or faithful to reality . it can also mean exact , properly positioned , upright , or straight . a true friend is loyal , reliable , faithful , and steadfast . the word true is a simple word , and we can add some affixes to grow its family tree with words like truer , truest , truly , truth , and untruth . but if we go in the other direction to look at the roots of true itself , we find even more relatives further up the family tree . the words trust , bethroth , and truce all derive from the same source as true , and these words all denote faithfulness or confidence . a thousand years ago , the word true looked and sounded different than it does today . in several old english dialects , the word treow was a noun that meant good faith or trust , a pledge or a promise . but it also had another definition , tree , and that 's no coincidence . if we trace the roots back even farther , we find that both meanings derive from a common origin , where some of the earliest expressions of the concept of truth were associated with the uprightness of an oak , the steadiness of a silver birch , and the fidelity of an orchard baring fruit year after year . this may sound like a stretch at first , but trees are the oldest living organisms on this planet . some that would have been called treow long ago still stand today . the fortingall yew in scotland is more than 2,000 years old . a californian bristlecone pine is more than 5,000 . and utah 's pando-quaking aspen grove has a single root system that dates back more than 80 millennia . trees have also held a sacred place in many cultures throughout history . the celtic peoples who first inhabited the british isles believed that trees housed deities . and , in fact , the ancient druids take their name from the same ancient root as tree . planting a tree is itself an act of faith and commitment . not only are trees upright and prototypically straight , but they are actual , solid , and real , something you can see and touch . and they are as reliable and steadfast to us today as they were a millennium ago , nurturing us , sheltering us , and providing the pages of our books . philosophers and poets , people in search of the truth , have often sought it in trees . `` what did the tree learn from the earth to be able to talk with the sky ? '' asked pablo neruda . `` a tree falls the way it leans , '' says an old proverb . just as trees mark our landscapes and witness our histories , the stories of words landscape our language , capturing the rains and sunshine of generations and sending roots and branches far and wide . as there is a whole orchard in a single seed , there is a whole story in a single word , and that 's the truth .

but the older the word , the longer the story and the more it stands to reveal to us not only about itself , but about ourselves and our history . the oldest words in present-day english are those that come from old english , the ancestor of our modern language whose first seeds were planted about 1500 years ago . compared to languages like greek or chinese that date back thousands of years , english is just a sapling in the lexical forest . but the stories of its words often start long before english itself took root .

english is not as old as some languages ; it dates back only about

in 1984 , an enterprising australian doctor named barry marshall decided to take a risk . too many of his patients were complaining of severe abdominal pain due to stomach ulcers , which are sores in the lining of the upper intestinal tract . at the time , few effective treatments for ulcers existed , and many sufferers required hospitalization or even surgery . desperate for answers , dr. marshall swallowed a cloudy broth of bacteria collected from the stomach of one of his patients . soon , dr. marshall was experiencing the same abdominal pain , bloating , and vomiting . ten days later , a camera called an endoscope peered inside his insides . marshall 's stomach was teeming with the same bacteria as his patient . he 'd also developed gastritis , or severe inflammation of the stomach , the hallmark precursor of ulcers . dr. marshall 's idea challenged a misconception that still persists to this day : that ulcers are caused by stress , food , or too much stomach acid . marshall thought the culprit was bacterial infections . initially , his idea was considered crazy by the brightest medical minds on the planet . but in 2005 , he and dr. robin warren received the ultimate validation when they were awarded the nobel prize for medicine . our stomachs are j-shaped organs with surprisingly intricate ecosystems awash in hormones and chemicals . the stomach is under constant attack by digestive enzymes , bile , proteins , microbes , and the stomach 's own acid . in response , it produces bicarbonate , mucus , and phospholipids called prostaglandins to maintain the integrity of its own lining . this delicate balance is constantly regulated and referred to as mucosal defense . since the mid-1800s , doctors thought stress alone caused most stomach ulcers . patients were given antidepressants or tranquilizers and told to visit health spas . this belief eventually shifted to the related notion of spicy foods and stress as culprits . yet no convincing study has ever demonstrated that emotional upset , psychological distress , or spicy food directly causes ulcer disease . by the mid-20th century , it was widely accepted that excess hydrochloric acid prompted the stomach to eat itself . fervent proponents of this idea were referred to as the acid mafia . the biggest hole in this theory was that antiacids only provide temporary relief . we now know that some rare ulcers are indeed caused by too much hydrochloric acid . but they make up less than 1 % of all cases . dr. marshall and dr. warren pinpointed a spiral-shaped bacteria called helicobacter pylori , or h. pylori , as the real offender . h. pylori is one of humanity 's oldest and most frequent companions , having joined us at least 50,000 years ago , and now found in 50 % of people . previously , we thought the stomach was sterile on account of it being such an acidic , hostile environment . yet h. pylori survives the acidic turmoil of the stomach with a variety of features that disrupt mucosal defense in its favor . for example , it produces an enzyme called urease that helps protect it from the surrounding gastric acid . h. pylori can make over 1,500 proteins , many of which are dedicated to maximizing its virulence . we still have unanswered questions , like why specific people develop ulcers at particular times . however , we do know individual genetics , other medical problems , use of certain medications , smoking , and the genetic diversity of helicobacter strains all play a role . in particular , certain pain medications used to reduce inflammation in joints have been discovered to work with h. pylori to create more severe stomach ulcers . dr. marshall ended up being fine after his famous , albeit dangerous , experiment . he ingested a course of antibiotics similar to the ones taken now for ulcers . to be treated by simple antibiotics is a modern triumph for a disease that previously needed surgery . marshall 's work also reminded us that scientific progress is not always smooth . but there 's value in trusting your proverbial , and sometimes literal , gut .

but they make up less than 1 % of all cases . dr. marshall and dr. warren pinpointed a spiral-shaped bacteria called helicobacter pylori , or h. pylori , as the real offender . h. pylori is one of humanity 's oldest and most frequent companions , having joined us at least 50,000 years ago , and now found in 50 % of people .

approximately how much of the world ’ s population has helicobacter pylori ?

look at your hand . how do you know it 's really yours ? it seems obvious , unless you 've experienced the rubber hand illusion . in this experiment , a dummy hand is placed in front of you and your real hand is hidden behind a screen . both are simultaneously stroked with a paint brush . no matter how much you remind yourself the dummy hand is n't yours , you eventually start to feel like it is , and inevitably flinch when it 's threatened with a knife . that may just be a temporary trick , but it speaks to a larger truth : our bodies , the physical , biological parts of us , and our minds , the thinking , conscious aspects , have a complicated , tangled relationship . which one primarily defines you or your self ? are you a physical body that only experiences thoughts and emotions as a result of biochemical interactions in the brain ? that would be a body with a mind . or is there some non-physical part of you that 's pulling the strings but could live outside of your biological body ? that would be a mind with a body . that takes us to an old question of whether the body and mind are two separate things . in a famous thought experiment , 16th-century philosopher rené descartes pointed out that even if all our physical sensations were just a hallucinatory dream , our mind and thoughts would still be there . that , for him , was the ultimate proof of our existence . and it led him to conclude that the conscious mind is something separate from the material body that forms the core of our identity . the notion of a non-physical consciousness echoes the belief of many religions in an immaterial soul for which the body is only a temporary shell . if we accept this , another problem emerges . how can a non-physical mind have any interaction with the physical body ? if the mind has no shape , weight , or motion , how can it move your muscles ? or if we assume it can , why can your mind only move your body and not others ? some thinkers have found creative ways to get around this dilemma . for example , the french priest and philosopher nicolas malebranche claimed that when we think about reaching for a fork , it 's actually god who moves our hand . another priest philosopher named george berkeley concluded that the material world is an illusion , existing only as mental perceptions . this question of mind versus body is n't just the domain of philosophers . with the development of psychology and neuroscience , scientists have weighed in , as well . many modern scientists reject the idea that there 's any distinction between the mind and body . neuroscience suggests that our bodies , along with their physical senses , are deeply integrated with the activity in our brains to form what we call consciousness . from the day we 're born , our mental development is formed through our body 's interaction with the external world . every sight , sound , and touch create new maps and representations in the brain that eventually become responsible for regulating our experience of self . and we have other senses , besides the typical five , such as the sense of balance and a sense of the relative location of our body parts . the rubber hand illusion , and similar virtual reality experiments , show that our senses can easily mislead us in our judgment of self . they also suggest that our bodies and external sensations are inseparable from our subjective consciousness . if this is true , then perhaps descartes ' experiment was mistaken from the start . after all , if we close our eyes in a silent room , the feeling of having a body is n't something we can just imagine away . this question of mind and body becomes particularly interesting at a time when we 're considering future technologies , such as neural prosthetics and wearable robots that could become extended parts of our bodies . or the slightly more radical idea of mind uploading , which dangles the possibility of immortal life without a body by transferring a human consciousness into a computer . if the body is deeply mapped in the brain , then by extending our sense of self to new wearable devices , our brains may eventually adapt to a restructured version with new sensory representations . or perhaps uploading our consciousness into a computer might not even be possible unless we can also simulate a body capable of delivering physical sensations . the idea that our bodies are part of our consciousness and vice versa also is n't new . it 's found extensively in buddhist thought , as well as the writings of philosophers from heidegger to aristotle . but for now , we 're still left with the open question of what exactly our self is . are we a mind equipped with a physical body as descartes suggested ? or a complex organism that 's gained consciousness over millions of years of evolution thanks to a bigger brain and more neurons than our distant ancestors ? or something else entirely that no one 's yet dreamt up ?

and we have other senses , besides the typical five , such as the sense of balance and a sense of the relative location of our body parts . the rubber hand illusion , and similar virtual reality experiments , show that our senses can easily mislead us in our judgment of self . they also suggest that our bodies and external sensations are inseparable from our subjective consciousness .

what can we learn from rubber hand illusion or other virtual reality experiments ?

in 1997 , in a game between france and brazil , a young brazilian player named roberto carlos set up for a 35 meter free kick . with no direct line to the goal , carlos decided to attempt the seemingly impossible . his kick sent the ball flying wide of the players , but just before going out of bounds , it hooked to the left and soared into the goal . according to newton 's first law of motion , an object will move in the same direction and velocity until a force is applied on it . when carlos kicked the ball , he gave it direction and velocity , but what force made the ball swerve and score one of the most magnificent goals in the history of the sport ? the trick was in the spin . carlos placed his kick at the lower right corner of the ball , sending it high and to the right , but also rotating around its axis . the ball started its flight in an apparently direct route , with air flowing on both sides and slowing it down . on one side , the air moved in the opposite direction to the ball 's spin , causing increased pressure , while on the other side , the air moved in the same direction as the spin , creating an area of lower pressure . that difference made the ball curve towards the lower pressure zone . this phenomenon is called the magnus effect . this type of kick , often referred to as a banana kick , is attempted regularly , and it is one of the elements that makes the beautiful game beautiful . but curving the ball with the precision needed to both bend around the wall and back into the goal is difficult . too high and it soars over the goal . too low and it hits the ground before curving . too wide and it never reaches the goal . not wide enough and the defenders intercept it . too slow and it hooks too early , or not at all . too fast and it hooks too late . the same physics make it possible to score another apparently impossible goal , an unassisted corner kick . the magnus effect was first documented by sir isaac newton after he noticed it while playing a game of tennis back in 1670 . it also applies to golf balls , frisbees and baseballs . in every case , the same thing happens . the ball 's spin creates a pressure differential in the surrounding air flow that curves it in the direction of the spin . and here 's a question . could you theoretically kick a ball hard enough to make it boomerang all the way around back to you ? sadly , no . even if the ball did n't disintegrate on impact , or hit any obstacles , as the air slowed it , the angle of its deflection would increase , causing it to spiral into smaller and smaller circles until finally stopping . and just to get that spiral , you 'd have to make the ball spin over 15 times faster than carlos 's immortal kick . so good luck with that .

too fast and it hooks too late . the same physics make it possible to score another apparently impossible goal , an unassisted corner kick . the magnus effect was first documented by sir isaac newton after he noticed it while playing a game of tennis back in 1670 .

which physics principal underlies the banana kick ?

a , c , e , d , b , k. no , this is n't some random , out of order alphabet . these are vitamins , and just like letters build words , they 're the building blocks that keep the body running . vitamins are organic compounds we need to ingest in small amounts to keep functioning . they 're the body 's builders , defenders and maintenance workers , helping it to build muscle and bone , make use of nutrients , capture and use energy and heal wounds . if you need convincing about vitamin value , just consider the plight of olden day sailors , who had no access to vitamin-rich fresh produce . they got scurvy . but vitamin c , abundant in fruits and vegetables , was the simple antidote to this disease . while bacteria , fungi and plants produce their own vitamins , our bodies ca n't , so we have to get them from other sources . so how does the body get vitamins from out there into here ? that 's dependent on the form these compounds take . vitamins come in two types : lipid-soluble and water-soluble , and the difference between them determines how the body transports and stores vitamins , and gets rid of the excess . the water-solubles are vitamin c and b complex vitamins that are made up of eight different types that each do something unique . these are dissolved in the watery parts of fruits , vegetables and grains , meaning their passage through the body is relatively straightforward . once inside the system , these foods are digested and the vitamins within them are taken up directly by the bloodstream . because blood plasma is water-based , water-soluble vitamins c and b have their transport cut out for them and can move around freely within the body . for lipid-soluble vitamins , dissolved in fat and found in foods like diary , butter and oils , this trip into the blood is a little more adventurous . these vitamins make it through the stomach and the intestine , where an acidic substance called bile flows in from the liver , breaking up the fat and preparing it for absorption through the intestinal wall . because fat-soluble vitamins ca n't make use of the blood 's watery nature , they need something else to move them around , and that comes from proteins that attach to the vitamins and act like couriers , transporting fat-solubles into the blood and around the body . so , this difference between water- or fat-soluble vitamins determines how they get into the blood , but also how they 're stored or rejected from the body . the system 's ability to circulate water-soluble vitamins in the bloodstream so easily means that most of them can be passed out equally easily via the kidneys . because of that , most water-soluble vitamins need to be replenished on a daily basis through the food we eat . but fat-soluble vitamins have staying power because they can be packed into the liver and in fat cells . the body treats these parts like a pantry , storing the vitamins there and rationing them out when needed , meaning we should n't overload on this type of vitamin because the body is generally well stocked . once we figured the logistics of transport and storage , the vitamins are left to do the work they came here to do in the first place . some , like many of the b complex vitamins , make up coenzymes , whose job it is to help enzymes release the energy from food . other b vitamins then help the body to use that energy . from vitamin c , you get the ability to fight infection and make collagen , a kind of tissue that forms bones and teeth and heals wounds . vitamin a helps make white blood cells , key in the body 's defense , helps shape bones and improves vision by keeping the cells of the eye in check . vitamin d gathers calcium and phosphorus so we can make bones , and vitamin e works as an antioxidant , getting rid of elements in the body that can damage cells . finally , from vitamin k , we score the ability to clot blood , since it helps make the proteins that do this job . without this vitamin variety , humans face deficiencies that cause a range of problems , like fatigue , nerve damage , heart disorders , or diseases like rickets and scurvy . on the other hand , too much of any vitamin can cause toxicity in the body , so there goes the myth that loading yourself with supplements is a great idea . in reality , it 's all about getting the balance right , and hitting that vitamin jackpot .

the system 's ability to circulate water-soluble vitamins in the bloodstream so easily means that most of them can be passed out equally easily via the kidneys . because of that , most water-soluble vitamins need to be replenished on a daily basis through the food we eat . but fat-soluble vitamins have staying power because they can be packed into the liver and in fat cells .

how many fruits and vegetables do you need to get enough daily vitamins ?

what 's the worst bug on the planet ? you might vote for the horsefly or perhaps the wasp , but for many people , the worst offender is by far the mosquito . the buzzing , the biting , the itching , the mosquito is one of the most commonly detested pests in the world . in alaska , swarms of mosquitos can get so thick that they actually asphyxiate caribou . and mosquito-borne diseases kill millions of people every year . the scourge that is the mosquito is n't new . mosquitoes have been around for over a hundred million years and over that time have coevolved with all sorts of species , including our own . there are actually thousands of species of mosquitos in the world , but they all share one insidious quality : they suck blood , and they 're really , really good at sucking blood . here 's how they do it . after landing , a mosquito will slather some saliva onto the victim 's skin , which works like an antiseptic , numbing the spot so we do n't notice their attack . this is what causes the itchy , red bumps , by the way . then the bug will use its serrated mandibles to carve a little hole in your skin , allowing it to probe around with its proboscis , searching for a blood vessel . when it hits one , the lucky parasite can suck two to three times its weight in blood . turns out we do n't really like that too much . in fact , humans hate mosquitos so much that we spend billions of dollars worldwide to keep them away from us -- from citronella candles to bug sprays to heavy-duty agricultural pesticides . but it 's not just that mosquitos are annoying , they 're also deadly . mosquitos can transmit everything from malaria to yellow fever to west nile virus to dengue . over a million people worldwide die every year from mosquito-borne diseases , and that 's just people . horses , dogs , cats , they can all get diseases from mosquitoes too . so , if these bugs are so dastardly , why do n't we just get rid of them ? we are humans after all , and we 're pretty good at getting rid of species . well , it 's not quite so simple . getting rid of the mosquito removes a food source for lots of organisms , like frogs and fish and birds . without them , plants would lose a pollinator . but some scientists say that mosquitos are n't actually all that important . if we got rid of them , they argue , another species would simply take their place and we 'd probably have far fewer deaths from malaria . the problem is that nobody knows what would happen if we killed off all the mosquitos . something better might take their spot or perhaps something even worse . the question is , are we willing to take that risk ? ( buzzing )

in fact , humans hate mosquitos so much that we spend billions of dollars worldwide to keep them away from us -- from citronella candles to bug sprays to heavy-duty agricultural pesticides . but it 's not just that mosquitos are annoying , they 're also deadly . mosquitos can transmit everything from malaria to yellow fever to west nile virus to dengue . over a million people worldwide die every year from mosquito-borne diseases , and that 's just people .

what do you do to prevent mosquitos from biting ?

( music ) quick ! what 's common between beef burgers , baseball training and auto mufflers ? tough question . let 's ask it another way . what 's the common factor between mcdonald 's , d-bat and meineke ? you may know the answer if , along with a big mac , you 've absorbed a fragment of the romantic story of ray kroc . he 's the salesman that created what became the world 's biggest fast food chain . he did it by making a deal with a couple of men called the mcdonalds . brothers they were , owners of a small restaurant chain , and the deal was , he could use their brand name and their methods . then he invited small entrepreneurs to open mcdonald 's , that they 'd run as operators , with an ownership state . very different than the business model where mom and pop stores have full ownership , but no similar support . all the examples in my opening question are a franchise operation . kroc is sometimes credited with inventing franchising , and so is isaac singer , the sewing machine magnate . not so . the real genesis of franchising was not in stitches or beef , it was in beauty . martha matilda harper was a canadian-born maid . she made the beds , cleaned house , did the shopping . in the employment of a doctor 's family in ontario , she acquired a secret formula for shampoo , one more scientifically based than the quackeries advertized every day in the newspapers . the kindly doctor also taught the maturing young woman the elements of physiology . martha had a secret ambition to go along with the secret formula : a determination to run her own business . by 1888 , serving as a maid in rochester , new york , she saved enough money -- 360 dollars -- to think of opening a public hairdressing salon . but before she could realize her dream , two blows fell . she became sick , and collapsed from exhaustion . mrs. helen smith , a healing practitioner of the christian science faith , was summoned to her bedside . the two women prayed , and martha recovered . no sooner was she better then she was told , `` oh no , you ca n't rent the place you 've eyed . '' you see , her venture was to be the first public hairdressing salon . a woman in business was shocking enough then . only 17 percent of the workforce in 1890 was female , but a woman carrying out hairdressing and skincare in a public place ? why , it was sure to invite a scandal . martha spent some of her savings on a lawyer , and won her case . she proudly displayed on the door of her new her salon a photograph of the barely five-foot martha as rapunzel , with hair down to her feet , but glowing with good health . her sickness , too , had proved a boon . her ambition was now propelled by christian science values . the harper method , as she came to call her services , was as much about servicing the soul as it was about cutting hair . in the therapeutic serenity of her salon , she taught that every person could glow with the kind of beauty she had , if spiritually whole and physically obedient to what she called `` the laws of cleanliness , nourishment , exercise and breathing . '' she was very practical about it . she even designed the first reclining shampoo chair , though she neglected to patent the invention . martha 's salon was a huge success . celebrities came from out of town to experience the harper method . they enjoyed the service so much that they urged her to set up a salon in their cities . and this is where martha 's ethical sense inspired her crowning innovation . instead of commissioning agents , as other innovators had done , from 1891 , she installed working-class women just like herself in salons exactly like hers , dedicated to her philosophy and her products . but these new employees were not provided a salary by martha . the women in what became a satellite network of 500 salons in america , and then europe and central america and asia , actually owned the harper 's salons . what was good enough in the nineteenth century for suffragette campaigners like susan b. anthony and was good enough in the twentieth century for woodrow wilson , calvin and grace coolidge , jacqueline kennedy , helen hayes and ladybird johnson must be good enough for the rest of the world . today , only the harper method founder 's shop remains in rochester , new york , but martha 's legacy is manifold . her health and beauty treatments have been copied , and her business model is dominant . in fact , half of retail sales in america are through martha harper 's franchising idea . so the next time you enjoy a mcdonald 's hamburger or a good night 's rest at a days inn , think of martha . because these franchises might not be the same without her inventing the model , over a century ago .

her health and beauty treatments have been copied , and her business model is dominant . in fact , half of retail sales in america are through martha harper 's franchising idea . so the next time you enjoy a mcdonald 's hamburger or a good night 's rest at a days inn , think of martha .

the expansion of martha harper ’ s franchising idea today drives half of all retail sales in america [ 5:07 ] . this means one woman has had a really remarkable effect on america ’ s economy . so why is she relatively unknown ?

we live in a society obsessed with music . we use music to worship , tell stories , to celebrate , to work , exercise , declare our love and sometimes our hatred , and , arguably most importantly , to dance . and , of course , we play music ourselves because , well , it 's a pleasant thing to do . thousands of years ago in ancient greece , when it came to music , things were n't much different . they might have had lyres and tunics instead of mp3 players and jeans , but the ancient greeks were just as obsessed with music as we are today . in fact , music was such an important part of ancient greek society that it makes us seem tame by comparison . to really understand just how integral music was to the ancient greeks , let 's begin by acquainting ourselves with a bit of their mythology . in ancient greek mythology , it was believed that human creativity was the result of divine inspiration from a group of goddesses known as the muses . while scholars have argued over the years that there are anything between 3 and 13 muses , the standard number accepted today is 9 . each muse oversees her own specific area of artistic expertise , ranging from song and dance to history and astronomy . it might seem strange to categorize history and astronomy as creative pursuits , but the ancient greeks saw these disciplines as more than just school subjects . these were the hallmarks of civilization in what , to their eyes , was a pretty barbaric world . an educated , civilized person was expected to be proficient in all aspects of creative thought inspired by the muses , and the common medium through which these disciplines were taught , studied , and disseminated was music . you see , it 's no coincidence that the word muse is very similar to the word music . it 's where the word originates . poetry , be it a love poem or an epic poem about a dragon-slaying hero , was sung with a musical accompaniment . dancing and singing , obviously , were accompanied by music . theater was always a combination of spoken word and music . history was recounted through song . even the study of astronomy was linked to the same physical principles as musical harmony , such as the belief held by many greek thinkers that each of the planets and stars created their own unique sound as they traveled through the cosmos , thrumming like an enormous guitar string light-years long . however , music pervaded more aspects of their lives than just education . ancient greeks considered music to be the basis for understanding the fundamental interconnectedness of all things in the universe . this concept of connectivity is known as harmonia , and it 's where we get the word harmony . music was used as a form of medicine to treat illnesses and physical complaints , as a vital accompaniment to sporting contests , and as a means to keep workers in time as they toiled away on monotonous or menial tasks . one of the most important applications of music in ancient greek society is found in the belief that music can affect a person 's ethos . a word we still use today , ethos is a person 's guiding beliefs or personal ethics , the way that one behaves towards oneself and others . the greek philosopher plato , one of the most famous and influential greek thinkers of the time , asserted that music had a direct effect on a person 's ethos . certain kinds of music could incite a person to violence while others could placate a person into a benign , unthinking stupor . according to plato , only very specific types of music were beneficial to a person 's ethos . one should only listen to music that promotes intelligence , self-discipline , and courage , and all other kinds of music must be avoided . furthermore , plato fervently denounced any music that deviated from established musical conventions , fearing that doing so would lead to the degradation of the standards of civilization , the corruption of youth , and eventually complete and utter anarchy . while plato 's fears can seem extreme , this argument has appeared in modern times to condemn musical trends such as jazz or punk or rap . what do you think plato would say about the music you listen to ? is it beneficial to your ethos , or will it degenerate you into a gibbering , amoral barbarian ?

according to plato , only very specific types of music were beneficial to a person 's ethos . one should only listen to music that promotes intelligence , self-discipline , and courage , and all other kinds of music must be avoided . furthermore , plato fervently denounced any music that deviated from established musical conventions , fearing that doing so would lead to the degradation of the standards of civilization , the corruption of youth , and eventually complete and utter anarchy .

pick one of the muses and think about the art form or science she influenced . what are some ways her discipline is expressed in music or art today ?

as far as we know , medieval england was never invaded by ice zombies , or terrorized by dragons , but it was shaken by a power struggle between two noble families spanning generations and involving a massive cast of characters with complex motives and shifting loyalties . if that sounds familiar , it 's because the historical conflicts known as the wars of the roses served as the basis for much of the drama in game of thrones . the real-life seeds of war were sewn by the death of king edward iii in 1377 . edward 's oldest son had died before his father , but his ten-year-old son , richard ii , succeeded to the throne ahead of edward 's three surviving sons . this skipping of an entire generation left lingering claims to the throne among their various offspring , particularly the lancasters , descended from edward 's third son , and the yorks , descended from his fourth son . the name of the ensuing wars comes from the symbols associated with the two families , the white rose of york and the red rose of lancaster . the lancasters first gained the throne when richard ii was deposed by his cousin henry iv in 1399 . despite sporadic unrest , their reign remained secure until 1422 , when henry v 's death in a military campaign left an infant henry vi as king . weak-willed and dominated by advisors , henry was eventually convinced to marry margaret of anjou to gain french support . margaret was beautiful , ambitious , and ruthless in persecuting any threat to her power , and she distrusted richard of york , most of all . york had been the king 's close advisor and loyal general , but was increasingly sidelined by the queen , who promoted her favorite supporters , like the earls of suffolk and somerset . york 's criticism of their inept handling of the war against france led to his exclusion from court and transfer to ireland . meanwhile , mounting military failures , and corrupt rule by margaret and her allies caused widespread discontent , and in the midst of this chaos , richard of york returned with an army to arrest somerset and reform the court . initially unsuccessful , he soon got his chance when he was appointed protector of the realm after henry suffered a mental breakdown . however , less than a year later , henry suddendly recovered and the queen convinced him to reverse york 's reforms . york fled and raised an army once more . though he was unable to directly seize the throne , he managed to be reinstated as protector and have himself and his heirs designated to succeed henry . but instead of a crown , york 's head acquired a pike after he was killed in battle with the queen 's loyalists . his young son took up the claim and was crowned edward iv . edward enjoyed great military success against the lancasters . henry was captured , while margaret fled into exile with their reportedly cruel son , edward of westminster . but the newly crowned king made a tragic political mistake by backing out of his arranged marriage with a french princess to secretly marry the widow of a minor noble . this alienated his most powerful ally , the earl of warwick . warwick allied with the lancasters , turned edward 's jealous younger brother , george , against him , and even briefly managed to restore henry as king , but it did n't last . edward recaptured the throne , the lancaster prince was killed in battle , and henry himself died in captivity not long after . the rest of edward iv 's reign was peaceful , but upon his death in 1483 , the bloodshed resumed . though his twelve-year-old son was due to succeed him , edward 's younger brother richard iii declared his nephews illegitimate due to their father 's secret marriage . he assumed the regency himself and threw the boys in prison . though no one knows what ultimately became of them , after a while , the princes disappeared and richard 's power seemed secure . but his downfall would come only two years later from across the narrow sea of the english channel . henry tudor was a direct descendant of the first duke of lancaster , raised in exile after his father 's death in a previous rebellion . with richard iii 's power grab causing a split in the york faction , henry won support for his royal claim . raising an army in france , he crossed the channel in 1485 and quickly defeated richard 's forces . and by marrying elizabeth of york , elder sister of the disappeared princes , the newly crowned henry vii joined the two roses , finally ending nearly a century of war . we often think of historical wars as decisive conflicts with clearly defined winners and losers . but the wars of the roses , like the fiction they inspired , show us that victories can be uncertain , alliances unstable , and even the power of kings as fleeting as the seasons .

raising an army in france , he crossed the channel in 1485 and quickly defeated richard 's forces . and by marrying elizabeth of york , elder sister of the disappeared princes , the newly crowned henry vii joined the two roses , finally ending nearly a century of war . we often think of historical wars as decisive conflicts with clearly defined winners and losers .

what were the ways in which henry tudor managed to finally end the war ?

hmmm , that 's not what we want , is it ? today 's digital cameras do a lot for us , but there 's no replacement for the human eye . it 's important to learn how cameras work with light to create an image , that way we 'll know what 's going on when it 's time to capture a moment . there are three variables that determine if you 're getting the right amount of light for the correct exposure . with a manual camera , we 're able to change any of the variable ourselves . different settings can result in really different pictures . let 's look at the process together . first , see this here ? this is the aperture . it 's the hole that light passes through . if we make the aperture big , we 'll have more light , true , but the sharpness of your photo will decrease very quickly from your focus point , backward and forward . this is what we call shallow depth of field . if we have a very small aperture , we 'll have less light but a deeper depth of field . for portraits , it can be nice to have a sharp figure separate from a somewhat blurry background so i would suggest a large aperture . aperture is measured in f-stops . this can get a little confusing because lower numbers mean bigger apertures and higher numbers mean smaller apertures . next , there 's shutter speed to think about . the shutter acts like a curtain that covers the sensor , and it only opens when you release the shutter button . if we want less light , we open the shutter for a shorter time . if we want more light , we open it for a longer time , but we run the risk of getting a motion-blurred picture . the speed is measured in seconds and fractions of seconds . for shooting sports or anything with a lot of movement , we 'll need faster speeds . for taking awesome night landscapes , longer exposures will be better , but we 'll need a tripod to steady the shot and prevent motion blur . another cool thing we can do with light exposures is light painting , drawing in the dark with a torch or the light of a cell phone . lastly , iso sensitivity controls how sensitive the sensor is to light . if we use low sensitivity , we 'll need more light to register a photo . with a higher sensitivity , we 'll be able to get a picture with less available light . 100 iso is a low sensitivity , while 6400 iso is a high one . if we increase sensitivity , we 'll be able to use faster speeds and smaller apertures , but we 'll get noisier images . good thing we have something to tell us if we 're getting the correct amount of light to get a good exposure , the light meter . sound good to you ? now it 's time to get out there and practice taking pictures under different conditions , so you know what to do any time you want to take the best picture .

if we increase sensitivity , we 'll be able to use faster speeds and smaller apertures , but we 'll get noisier images . good thing we have something to tell us if we 're getting the correct amount of light to get a good exposure , the light meter . sound good to you ?

imagine you are shooting an indoor basketball match . players move fast , but you don´t have a large amount of light . which exposure will you use to capture faster action ?

- when you get to space , because you 're in a zero g environment , some really funky things happen to your body . ( upbeat music ) i grew an inch . right now , i 'm 5'11 '' but in space i was six-feet tall . on the ground , gravity compresses your spine , it pulls you down , the force factor going down . in space , without gravity pulling your spine down , every vertebrae has a chance to move up , which gives you your extra inch of height . after my spine elongated , when i went to bed on the first night , i felt some back pain , some lower back pain , and so i actually curled up to kind of alleviate that pain , to kind of stretch it out even more . a few other ways the body can change in space are the heart gets smaller and changes shape because it 's not having to pump as hard to pull the blood up from your feet , 'cause now things are just floating and working inside your body so it 's pumping easier , therefore the muscle walls actually changes the shape and they get smaller . without gravity , your bones , they change shape and they lose calcium , and they become more brittle . so , we run on a treadmill that you strap yourself down to and you run on the treadmill to actually give loads into your bones to keep them from atrophying and losing bone density or calcium . for some people in space , your intracranial pressure changes with pushes on your eyeball and that changes its shape , therefore requiring you to wear glasses in space , so it effects your vision . so , we keep different prescriptions of glasses on board just in case someone 's vision changes . any changes in our bodies and anything that happens in space , it 's worth it for the spirit of exploration .

- when you get to space , because you 're in a zero g environment , some really funky things happen to your body . ( upbeat music ) i grew an inch .

4. from the description in the video , determine what the word `` atrophy '' means .

you probably know the feeling . your phone utters its final plaintive `` bleep '' and cuts out in the middle of your call . in that moment , you may feel more like throwing your battery across the room than singing its praises , but batteries are a triumph of science . they allow smartphones and other technologies to exist without anchoring us to an infernal tangle of power cables . yet even the best batteries will diminish daily , slowly losing capacity until they finally die . so why does this happen , and how do our batteries even store so much charge in the first place ? it all started in the 1780s with two italian scientists , luigi galvani and alessandro volta , and a frog . legend has it that as galvani was studying a frog 's leg , he brushed a metal instrument up against one of its nerves , making the leg muscles jerk . galvani called this animal electricity , believing that a type of electricity was stored in the very stuff of life . but volta disagreed , arguing that it was the metal itself that made the leg twitch . the debate was eventually settled with volta 's groundbreaking experiment . he tested his idea with a stack of alternating layers of zinc and copper , separated by paper or cloth soaked in a salt water solution . what happened in volta 's cell is something chemists now call oxidation and reduction . the zinc oxidizes , which means it loses electrons , which are , in turn , gained by the ions in the water in a process called reduction , producing hydrogen gas . volta would have been shocked to learn that last bit . he thought the reaction was happening in the copper , rather than the solution . none the less , we honor volta 's discovery today by naming our standard unit of electric potential `` the volt . '' this oxidation-reduction cycle creates a flow of electrons between two substances and if you hook a lightbulb or vacuum cleaner up between the two , you 'll give it power . since the 1700s , scientists have improved on volta 's design . they 've replaced the chemical solution with dry cells filled with chemical paste , but the principle is the same . a metal oxidizes , sending electrons to do some work before they are regained by a substance being reduced . but any battery has a finite supply of metal , and once most of it has oxidized , the battery dies . so rechargeable batteries give us a temporary solution to this problem by making the oxidation-reduction process reversible . electrons can flow back in the opposite direction with the application of electricity . plugging in a charger draws the electricity from a wall outlet that drives the reaction to regenerate the metal , making more electrons available for oxidation the next time you need them . but even rechargeable batteries do n't last forever . over time , the repetition of this process causes imperfections and irregularities in the metal 's surface that prevent it from oxidizing properly . the electrons are no longer available to flow through a circuit and the battery dies . some everyday rechargeable batteries will die after only hundreds of discharge-recharge cycles , while newer , advanced batteries can survive and function for thousands . batteries of the future may be light , thin sheets that operate on the principles of quantum physics and last for hundreds of thousands of charge cycles . but until scientists find a way to take advantage of motion to recharge your cell battery , like cars do , or fit solar panels somewhere on your device , plugging your charger into the wall , rather than expending one battery to charge another is your best bet to forestall that fatal `` bleep . ''

he tested his idea with a stack of alternating layers of zinc and copper , separated by paper or cloth soaked in a salt water solution . what happened in volta 's cell is something chemists now call oxidation and reduction . the zinc oxidizes , which means it loses electrons , which are , in turn , gained by the ions in the water in a process called reduction , producing hydrogen gas .

oxidation and reduction are processes through which _____

the onset of cancer usually begins as a solitary tumor in a specific area of the body . if the tumor is not removed , cancer has the ability to spread to nearby organs , as well as places far away from the origin , such as the brain . so how does cancer move to new areas , and why are some organs more likely to get infected than others ? the process of cancer spreading across the body is known as metastasis . it begins when cancer cells from an initial tumor invade nearby normal tissue . as the cells proliferate , they spread via one of the three common routes of metastasis : transcoelomic , lymphatic , or hematogenous spread . in transcoelomic spread , malignant cells penetrate the covering surfaces of cavities in our body . these surfaces are known as peritoneum and serve as walls to segment the body cavity . malignant cells in ovarian cancer , for example , spread through peritoneum , which connects the ovary to the liver , resulting in metastasis on the liver surface . next , cancerous cells invade blood vessels when they undergo hematogenous spread . as there are blood vessels almost everywhere in the body , malignant cells utilize this to reach more distant parts of the body . finally , lymphatic spread occurs when the cancer invades the lymph nodes , and travels to other parts of the body via the lymphatic system . as this system drains many parts of the body , it also provides a large network for the cancer . in addition , the lymphatic vessels empty into the blood circulation , allowing the malignant cells to undergo hematogenous spread . once at a new site , the cells once again undergo proliferation , and form small tumors known as micrometastases . these small tumors then grow into full-fledged tumors , and complete the metastatic process . different cancers have been known to have specific sites of metastasis . for example , prostate cancer commonly metastasizes to the bone , while colon cancer metastasizes to the liver . various theories have been proposed to explain the migration pattern of malignant cells . of particular interest are two conflicting theories . stephen paget , an english surgeon , came up with the seed and soil theory of metastasis . the seed and soil theory stated that cancer cells die easily in the wrong microenvironment , hence they only metastasize to a location with similar characteristics . however , james ewing , the first professor of pathology at cornell university , challenged the seed and soil theory , and proposed that the site of metastasis was determined by the location of the vascular and lymphatic channels which drain the primary tumor . patients with primary tumors that were drained by vessels leading to the lung would eventually develop lung metastases . today , we know that both theories contain valuable truths . yet the full stories of metastasis is much more complicated than either of the two proposed theories . factors like the cancer cell 's properties , and the effectiveness of the immune system in eliminating the cancer cells , also play a role in determining the success of metastasis . unfortunately , many questions about metastasis remain unanswered until today . understanding the exact mechanism holds an important key to finding a cure for advanced stage cancers . by studying both the genetic and environmental factors , which contribute to successful metastasis , we can pinpoint ways to shut down the process . the war against cancer is a constant struggle , and scientists are hard at work developing new methods against metastasis . of recent interest is immunotherapy , a modality which involves harnessing the power of the immune system to destroy the migrating cells . this can be done in different ways , such as training immune cells to recognize cancerous cells via vaccines . the growth and activity of the immune cells can also be stimulated by injecting man-made interleukins , chemicals which are usually secreted by the immune cells of the body . these two treatments are only the tip of the iceberg . with the collaborated research efforts of governments , companies and scientists , perhaps the process of metastasis will be stopped for good .

the war against cancer is a constant struggle , and scientists are hard at work developing new methods against metastasis . of recent interest is immunotherapy , a modality which involves harnessing the power of the immune system to destroy the migrating cells . this can be done in different ways , such as training immune cells to recognize cancerous cells via vaccines .

which of the following is not a type of immunotherapy ?

so comrades , welcome to the lecture . what i am going to do now , we ’ re going to begin with an experiment to illustrate this point that the oxygen molecule , o2 , has unpaired electrons . now we ’ re outside just to show you the reactivity of this lovely stuff here , liquid oxygen . so you can see wonderful liquid oxygen is a nice blue colour . so over here on the table we ’ ve got a tin tray which we ’ re going to use to contain the experiment that i ’ m going to show you next . so we ’ ve got our favourite liquid oxygen . strongly oxidising ; very , very reactive , and here i ’ ve got some cotton wool . so this is the same stuff we use to take make-up off , perhaps our partners or our girlfriends or our wives , and this is the same stuff we use to wipe our babies ’ bums . oxygen is an interesting element because it exists in two forms : the taught form which we breathe all the time is o2 , two oxygen atoms joined together ; and there ’ s another form called ozone , and which has three atoms arranged like the letter v , or letter v this way up . oxygen has unpaired electrons within the molecular orbitals , in the atomic orbitals around the structure , and these unpaired electrons give rise to colour and that colour is blue . so blue is often perceived to be the colour of solvated or unpaired electrons , and you can see here the lovely blue colour . now lots of chemists are really scared when they see the blue of liquid oxygen , because liquid oxygen is very , very reactive . generally you only make liquid oxygen by mistake . not like today when we ’ re making some on purpose . and if you ’ ve made it by mistake in an uncontrolled way , where there might be organic molecules perhaps simple organic chemicals like hydrocarbons , grease or perhaps a highly elaborate compound then , they tend to detonate and they tend to cause very energetic experiments . yeah it ’ s very fluffy it ’ s not very reactive . it doesn ’ t really burn , it cinders , might smoulder . but here we go , we ’ re going to pop it in the tray . so we begin with neil ’ s very high-tech piece of equipment , which is a test-tube on a piece of string . what we ’ re going to do is to put some liquid nitrogen in here . you can see liquid nitrogen – well you may not see – is colourless . ok ? so this is liquid nitrogen , and what i hope you can see is that this magnet , which is a pretty good magnet . let me just show you here with my keys , that they stick pretty strongly to the magnet . the magnet has absolutely no affect at all on the liquid nitrogen . i can pull the magnet and nothing happens . and then we ’ re going to fill up all of the void space , so all of the space in the cotton particles with oxygen . so you might want to stand back after this bit brady . so here we go , here ’ s our liquid oxygen . do you want to come in and zoom in on me ? it ’ s ok , i ’ ve got it zoomed nicely . ok , so here you can see the lovely blue liquid oxygen colour , going into the cotton wool particles . let ’ s try the same thing with liquid oxygen . careful of my shoes… so here we have a match on a stick , and i think you can see its probably alight , so we have our fire , we have our oxygen , and we have our fuel . now let ’ s see what happens when we put them all together . the liquid oxygen is a very nice blue colour today . so now let ’ s try , here ’ s the magnet again , and if i take the liquid oxygen you can see i can pull it right up here . it ’ s not as magnetic as my keys , but you can see there ’ s a really big difference . it sticks to the magnet . so you can see it really is magnetic . you ready ? ok. woohoo and there she blows ! and ozone is much more reactive than oxygen . so near the earth ’ s surface , where you and i are at the moment , ozone is really quite dangerous because if you breathe it in it can start reacting with any sort of molecule that has bonds between carbon . but in the upper atmosphere , ozone is extremely important because it absorbs ultra-violet light that comes from the sun and stops this ultra-violet light attacking the molecules in biological species on the surface . if it wasn ’ t for the ozone in the upper atmosphere all of us would be , if not dead , certainly very much less comfortable than we are at the moment . so neil ’ s now connecting up a piece of tube to oxygen cylinder and he is going to fill up this gas jar with oxygen and we are going to do a really classic experiment : the one that everyone learns at school and tests for oxygen , which is to relight a glowing splint . so we have a traditional gas jar full of oxygen . so here you can see we are burning a splint . ok , so this is the wood burning in excess oxygen around us , ok . so what we are going to do is we are going to take the splint out so it is just glowing . and if i blow on this splint you can see it gets brighter . now we are going to try and relight that splint by putting it into a very oxygen-rich atmosphere . so we ’ ll move over to the jar and we ’ ll put in our glowing splint and you can see the flame comes back to life . so that ’ s a test that everyone learns for an oxygen-rich environment . what happened ? what made that happen ? well the increased oxygen content/concentration reignites and reinitiates that oxidation of the wood or the burning of the wood . so we ’ ll do that again . so there we go : flame again .

so near the earth ’ s surface , where you and i are at the moment , ozone is really quite dangerous because if you breathe it in it can start reacting with any sort of molecule that has bonds between carbon . but in the upper atmosphere , ozone is extremely important because it absorbs ultra-violet light that comes from the sun and stops this ultra-violet light attacking the molecules in biological species on the surface . if it wasn ’ t for the ozone in the upper atmosphere all of us would be , if not dead , certainly very much less comfortable than we are at the moment . so neil ’ s now connecting up a piece of tube to oxygen cylinder and he is going to fill up this gas jar with oxygen and we are going to do a really classic experiment : the one that everyone learns at school and tests for oxygen , which is to relight a glowing splint .

in the upper atmosphere , we can find a high concentration of ozone . why is this ozone layer so important to us ?

you may know that it takes light a zippy eight minutes to reach us from the surface of the sun , so how long do you think it takes light to travel from the sun 's core to its surface ? a few seconds or a minute at most ? well , oddly enough , the answer is many thousands of years . here 's why . photons are produced by the nuclear reactions deep in the core of our sun . as the photons flow out of the core , they interact with matter and lose energy , becoming longer wavelength forms of light . they start out as gamma rays in the core , but end up as x-rays , ultraviolet or visible light as they near the surface . however , that journey is neither simple nor direct . upon being born , each photon travels at a speed of 300,000 kilometers per second until it collides with a proton and is diverted in another direction , acting like a bullet ricocheting off of every charged particle it strikes . the question of how far this photon gets from the center of the sun after each collision is known as the random walk problem . the answer is given by this formula : distance equals step size times the square root of the number of steps . so if you were taking a random walk from your front door with a one meter stride each second , it would take you a million steps and eleven days just to travel one kilometer . so then how long does it take for a photon generated in the center of the sun to reach you ? we know the mass of the sun and can use that to calculate the number of protons within it . let 's assume for a second that all the sun 's protons are evenly spread out , making the average distance between them about 1.0 x 10^-10 meters . to random walk the 690,000 kilometers from the core to the solar surface would then require 3.9 x 10^37 steps , giving a total travel time of 400 billion years . hmm , that ca n't be right . the sun is only 4.6 billion years old , so what went wrong ? two things : the sun is n't actually of uniform density and photons will miss quite a few protons between every collision . in actuality , a photon 's energy , which changes over the course of its journey , determines how likely it is to interact with a proton . on the density question , our models show that the sun has a hot core , where the fusion reactions occur . surrounding that is the radiative zone , followed by the convective zone , which extends all the way to the surface . the material in the core is much denser than lead , while the hot plasma near the surface is a million times less dense with a continuum of densities in between . and here 's the photon-energy relationship . for a photon that carries a small amount of energy , a proton is effectively huge , and it 's much more likely to cause the photon to ricochet . and for a high-energy photon , the opposite is true . protons are effectively tiny . photons start off at very high energies compared to when they 're finally radiated from the sun 's surface . now when we use a computer and a sophisticated solar interior model to calculate the random walk equation with these changing quantities , it spits out the following number : 170,000 years . future discoveries about the sun may refine this number further , but for now , to the best of our understanding , the light that 's hitting your eyes today spent 170,000 years pinballing its way towards the sun 's surface , plus eight miniscule minutes in space . in other words , that photon began its journey two ice ages ago , around the same time when humans first started wearing clothes .

the answer is given by this formula : distance equals step size times the square root of the number of steps . so if you were taking a random walk from your front door with a one meter stride each second , it would take you a million steps and eleven days just to travel one kilometer . so then how long does it take for a photon generated in the center of the sun to reach you ?

list the zones of the sun from the exterior to the interior . give one characteristic of each layer .

caffeine a legal stimulant that most of us are pretty familiar with , many of us use every day , and some of us are addicted to . if you are a caffeine user , you probably know your limits . for me one small cup of coffee in the morning can help keep me alert and focused , whereas two small cups of coffee in the morning can turn me into a cat on catnip . well for the purposes of this video and to best demonstrate the physical and mental effects of caffeine , i 'm going to get very very caffeinated very very fast . for science . go big or go home . caffeine is a stimulant drug that acts on your central nervous system . because caffeine is both lipid and water soluble it can easily pass through the blood-brain barrier and act on the interior of your brain once there , caffeine works by diminishing the effect of a neurotransmitter called adenosine . adenosine acts as a suppressor for your nervous system , reducing neural activity and slowing everything down . caffeine and adenosine have similar shapes so caffeine can bind to the same neuroreceptors that adenosine does . but because caffeine is not adenosine , it does n't turn these neuroreceptors on . this is called competitive inhibition . caffeine competes with adenosine to bind with the same receptors , and because caffeine is bound , adenosine can not bind and its effects are inhibited . long story short , caffeine prevents adenosine from slowing down your nervous system . so this explain part of why you feel more awake , alert and active with caffeine flowing through your veins . but adenosine inhibition is n't the only thing that caffeine does . oh no . caffeine also stimulates the production of adrenaline or epinephrine . adrenaline is a pretty well known hormone involved in the fight-or-flight response . it causes all sort of physiological reactions ! it increases your heart rate , increases the blood flow to your muscles , opens up your airways , causes your blood pressure to rise , and also causes you 're your liver to release extra sugar into your blood stream for an added boost of energy . it also causes your muscle to tighten up , which would be useful if you were the lone human on the savannah , deciding or not to fight or flee from that lion over the distance , but as a modern twenty something sitting in from of my camera , it just give me the jitters . finally caffeine also plays with the dopamine levels in your brain . awesome , yeah . caffeine increases the amount of dopamine present in your brain by slowing down its reabsorption , much in the same way that cocaine increases the amount of dopamine present by slowing down how quickly it can be sucked back into your brain tissue . this means that caffeine also makes you feel good and this interaction with dopamine is how you can actually build a caffeine addiction . so now you 're a happy , jittery , fight or flight ready bundle caffeine ! now what ? well the now what really depends on how your specific body metabolizes caffeine . the average half-life of caffeine in the human body is about six hours . so this means that if you have two hundred milligrams of caffeine in your average cup of coffee at 9am in the morning , then 6 hours later half of that will be left , so at 3pm you will have a hundred milligrams of caffeine left , and then another 6 hours later you will have half of the hundred you will have half of the hundred so you will have 50 milligrams of caffeine left at 9 o'clock at night . but dude , who stops at just one cup of coffee ? not this chick . so how much caffeine is too much caffeine ? a lethal dose of caffeine is about two hundred milligrams per kilogram so it would take about nine thousand five hundred milligrams of caffeine to kill me . now , there are about two hundred milligrams of caffeine in a standard cup of coffee , so that 's about forty eight cups of coffee , which is a surprisingly low number , but i would have to drink all 48 of those before my body started to metabolize the caffeine , which means i would literally have to chug 48 cups of coffee . i literally would n't be able to drink that much coffee , both because my stomach could n't hold that volume of liquid and also because as every coffee drinker knows , caffeine is a diuretic . before i got to cup forty anyways , the stimulant effect of caffeine would be jacked up so high that that the alertness and awakeness would be transformed into mania , disorientation and hallucinations ... great ! what would eventually kill you would be ventricular fibrillation , which basically means that your heart would caffeine jitter itself to death . so moral of the story , caffeine is a drug . it is a stimulant that has some pretty noticeable effects on your body , can cause addiction , and , in high enough doses , can kill you . so caffeinate wisely ! go forth , do science ! my hand is actually not shaking too bad right now . do n't try this at home , i know a lot of people do drink that much caffeine all on one day and sometimes i approach it , but i certainly do n't do it over the span of 20 minutes . i actually do n't feel as terrible as i thought i would have after that amount , but i certainly do n't feel good either .

oh no . caffeine also stimulates the production of adrenaline or epinephrine . adrenaline is a pretty well known hormone involved in the fight-or-flight response . it causes all sort of physiological reactions !

which of the following is not an effect of adrenaline ?

translator : andrea mcdonough reviewer : jessica ruby in the 11th and 12th centuries , most english commoners were illiterate . since they had no way to learn the bible , the clergy came up with an inventive solution : they 'd create plays out of certain bible stories so even people who could n't read could learn them . these were called mystery plays because they revealed the mystery of god 's word . at about the same time , the clergy also developed plays about the saints of the church , called miracle plays . in the beginning , the clergy members acted out bible stories on the steps outside the cathedral . the audience reacted so well that soon they needed to move out to the street around the town square . by building moving carts to put on each play and by lining up one after the other , they could put on cycles of stories , which would take the viewer from genesis to revelation . these movable carts , called pageants , looked like huge boxes on wheels . each was two stories tall . the bottom story was curtained off and was used for costumes , props , and dressing . the top platform was the stage for the performance . spectators assembled in various corners of the town , and the pageant would move around in the cycle until the villagers had seen the entire series . soon , the plays required more actors than the clergy could supply . so , by the 13th century , different guilds were asked to be responsible for acting out different parts of the cycle . the assignments were meant to reflect the guilds ' professions . for example , the carpenter 's guild might put on the story of noah 's ark , and the baker 's guild might put on the last supper . can you imagine what might happen to the story if the butcher 's guild put on the crucifixion of christ ? yes , without the clergy , the plays soon started changing from their true bible stories . by the end of the 14th century , a new form of drama , called the morality play , had evolved . faith , truth , charity , and good deeds all became characters on the stage . and , at the same time , the opposite virtues of falsehood , covetousness , worldly flesh , and the devil became the antagonists . the morality plays were allegorical stories in which these characters battled for the control of the soul . audiences loved the immoral characters , and spectators were encouraged to interact with the actors . throwing rotten food and even getting into scuffles with other spectators became very common . the character of the devil often would roam through the crowds and pull unsuspecting watchers into a hell that was depicted as a dragon 's mouth . the virtuous biblical stories had morphed into crude and sometimes comic stories . the clergy intended to teach against immorality . how ironic , then , that the morality plays actually encouraged vices as more popular than virtues . by the mid-15th century , the church started to outlaw these performances . town charters required that any theater must be built outside the city wall . one of the first theaters was built like a larger version of a pageant , with tiers of gallery seating encircling a grassy area in front of the stage . sound familiar ? a young william shakespeare developed his craft here at the theater that was eventually renamed the globe . the medieval morality play had led to renaissance playwrights who were inspired by the inner struggles and the conscience of man . and that , in essence , is how drama emerged as a literary art form .

can you imagine what might happen to the story if the butcher 's guild put on the crucifixion of christ ? yes , without the clergy , the plays soon started changing from their true bible stories . by the end of the 14th century , a new form of drama , called the morality play , had evolved .

why were the plays reenactments of bible stories ?

consider the classic white t-shirt . annually , we sell and buy two billion t-shirts globally , making it one of the most common garments in the world . but how and where is the average t-shirt made , and what 's its environmental impact ? clothing items can vary a lot , but a typical t-shirt begins its life on a farm in america , china , or india where cotton seeds are sown , irrigated and grown for the fluffy bolls they produce . self-driving machines carefully harvest these puffs , an industrial cotton gin mechanically separates the fluffy bolls from the seeds , and the cotton lint is pressed into 225-kilogram bales . the cotton plants require a huge quantity of water and pesticides . 2,700 liters of water are needed to produce the average t-shirt , enough to fill more than 30 bathtubs . meanwhile , cotton uses more insecticides and pesticides than any other crop in the world . these pollutants can be carcinogenic , harm the health of field workers , and damage surrounding ecosystems . some t-shirts are made of organic cotton grown without pesticides and insecticides , but organic cotton makes up less than 1 % of the 22.7 million metric tons of cotton produced worldwide . once the cotton bales leave the farm , textile mills ship them to a spinning facility , usually in china or india , where high-tech machines blend , card , comb , pull , stretch , and , finally , twist the cotton into snowy ropes of yarn called slivers . then , yarns are sent to the mill , where huge circular knitting machines weave them into sheets of rough grayish fabric treated with heat and chemicals until they turn soft and white . here , the fabric is dipped into commercial bleaches and azo dyes , which make up the vivid coloring in about 70 % of textiles . unfortunately , some of these contain cancer-causing cadmium , lead , chromium , and mercury . other harmful compounds and chemicals can cause widespread contamination when released as toxic waste water in rivers and oceans . technologies are now so advanced in some countries that the entire process of growing and producing fabric barely touches a human hand . but only up until this point . after the finished cloth travels to factories , often in bangladesh , china , india , or turkey , human labor is still required to stitch them up into t-shirts , intricate work that machines just ca n't do . this process has its own problems . bangladesh , for example , which has surpassed china as the world 's biggest exporter of cotton t-shirts , employs 4.5 million people in the t-shirt industry , but they typically face poor conditions and low wages . after manufacture , all those t-shirts travel by ship , train , and truck to be sold in high-income countries , a process that gives cotton an enormous carbon footprint . some countries produce their own clothing domestically , which cuts out this polluting stage , but generally , apparel production accounts for 10 % of global carbon emissions . and it 's escalating . cheaper garments and the public 's willingness to buy boosted global production from 1994 to 2014 by 400 % to around 80 billion garments each year . finally , in a consumer 's home , the t-shirt goes through one of the most resource-intensive phases of its lifetime . in america , for instance , the average household does nearly 400 loads of laundry per year each using about 40 gallons of water . washing machines and dryers both use energy , with dryers requiring five to six times more than washers . this dramatic shift in clothing consumption over the last 20 years , driven by large corporations and the trend of fast fashion has cost the environment , the health of farmers , and driven questionable human labor practices . it 's also turned fashion into the second largest polluter in the world after oil . but there are things we can do . consider shopping secondhand . try to look for textiles made from recycled or organic fabrics . wash clothes less and line dry to save resources . instead of throwing them away at the end of their life , donate , recycle , or reuse them as cleaning rags . and , finally , you might ask yourself , how many t-shirts and articles of clothing will you consume over your lifetime , and what will be their combined impact on the world ?

consider the classic white t-shirt . annually , we sell and buy two billion t-shirts globally , making it one of the most common garments in the world .

create a list of all the countries that may be involved in creating the t-shirt you might be wearing today .

in the early hours of august 13 , 1961 , east german construction workers flanked by soldiers and police began tearing up streets and erecting barriers throughout the city of berlin and its surroundings . this night marked the beginning of one of history 's most infamous dividing lines , the berlin wall . construction on the wall continued for the next decade as it cut through neighborhoods , separated families , and divided not just germany , but the world . to understand how we got to this point , we have to go back to world war ii . america , britain , and france joined forces with the soviet union against the axis powers . after they defeated nazi germany , each of the victorious nations occupied part of the country . the division was meant to be temporary , but the former allies found themselves at odds over their visions for post-war europe . while western powers promoted liberal market economies , the soviet union sought to surround itself with obedient communist nations , including a weakened germany . as their relations deteriorated , the federal republic of germany was formed in the west while the soviets established the german democratic republic in the east . the soviet satellite countries restricted western trade and movement , so a virtually impassable border formed . it became known as the iron curtain . in the former german capital of berlin , things were particularly complicated . although the city lay fully within the east german territory of the gdr , the post-war agreement gave the allies joint administration . so america , britain , and france created a democratic enclave in berlin 's western districts . while east germans were officially banned from leaving the country , in berlin , it was simply a matter of walking , or riding a subway , streetcar or bus , to the western half , then traveling on to west germany or beyond . this open border posed a problem for the east german leadership . they had staked a claim to represent the communist resistance against hitler and portrayed western germany as a continuation of the nazi regime . while the u.s. and its allies poured money into west germany 's reconstruction , the soviet union extracted resources from the east as war reparations , making its planned economy even less competitive . life in east germany passed under the watchful eye of the stasi , the secret police whose wiretaps and informants monitored citizens for any hint of disloyalty . while there was free health care and education in the east , the west boasted higher salaries , more consumer goods , and greater personal freedom . by 1961 , about 3.5 million people , nearly 20 % of the east german population , had left , including many young professionals . to prevent further losses , east germany decided to close the border , and that 's where the berlin wall came in . extending for 43 kilometers through berlin , and a further 112 through east germany , the initial barrier consisted of barbed wire and mesh fencing . some berliners escaped by jumping over the wire or leaving from windows , but as the wall expanded , this became more difficult . by 1965 , 106 kilometers of 3.6-meter-high concrete barricades had been added topped with a smooth pipe to prevent climbing . over the coming years , the barrier was strengthened with spike strips , guard dogs , and even landmines , along with 302 watchtowers and 20 bunkers . a parallel fence in the rear set off a 100-meter area called the death strip . there , all buildings were demolished and the ground covered with sand to provide a clear line of sight for the hundreds of guards ordered to shoot anyone attempting to cross . nevertheless , nearly 5,000 people in total managed to flee east germany between 1961 and 1989 . some were diplomats or athletes who defected while abroad , but others were ordinary citizens who dug tunnels , swam across canals , flew hot air balloons , or even crashed a stolen tank through the wall . yet the risk was great . over 138 people died while attempting escape . some shot in full view of west germans powerless to help them . the wall stabilized east germany 's economy by preventing its work force from leaving , but tarnished its reputation , becoming a global symbol of communist repression . as part of reconciliation with the east , the basic treaty of 1972 recognized east germany pragmatically while west germany retained its hope for eventual reunification . although the eastern regime gradually allowed family visits , it tried to discourage people from exercising these rights with an arduous bureaucratic process and high fees . nonetheless , it was still overwhelmed by applications . by the end of the 1980 's , the liberalization of other eastern bloc regimes caused mass demonstrations for free travel and demands for democracy . on the evening of november 9 , 1989 , east germany tried to defuse tension by making travel permits easier to obtain . but the announcement brought thousands of east berliners to the border crossing points in the wall , forcing the surprised guards to open the gates immediately . rejoicing crowds poured into west berlin as people from both sides danced atop the wall . and others began to demolish it with whatever tools they could find . although the border guards initially tried to maintain order , it was soon clear that the years of division were at an end . after four decades , germany was officially reunified in october 1990 . and the soviet union fell soon after . today , parts of the wall still stand as a reminder that any barriers we put up to impede freedom , we can also break down .

but the announcement brought thousands of east berliners to the border crossing points in the wall , forcing the surprised guards to open the gates immediately . rejoicing crowds poured into west berlin as people from both sides danced atop the wall . and others began to demolish it with whatever tools they could find .

the wall was built to :

physicists , air traffic controllers , and video game creators all have at least one thing in common : vectors . what exactly are they , and why do they matter ? to answer , we first need to understand scalars . a scalar is a quantity with magnitude . it tells us how much of something there is . the distance between you and a bench , and the volume and temperature of the beverage in your cup are all described by scalars . vector quantities also have a magnitude plus an extra piece of information , direction . to navigate to your bench , you need to know how far away it is and in what direction , not just the distance , but the displacement . what makes vectors special and useful in all sorts of fields is that they do n't change based on perspective but remain invariant to the coordinate system . what does that mean ? let 's say you and a friend are moving your tent . you stand on opposite sides so you 're facing in opposite directions . your friend moves two steps to the right and three steps forward while you move two steps to the left and three steps back . but even though it seems like you 're moving differently , you both end up moving the same distance in the same direction following the same vector . no matter which way you face , or what coordinate system you place over the camp ground , the vector does n't change . let 's use the familiar cartesian coordinate system with its x and y axes . we call these two directions our coordinate basis because they 're used to describe everything we graph . let 's say the tent starts at the origin and ends up over here at point b . the straight arrow connecting the two points is the vector from the origin to b . when your friend thinks about where he has to move , it can be written mathematically as 2x + 3y , or , like this , which is called an array . since you 're facing the other way , your coordinate basis points in opposite directions , which we can call x prime and y prime , and your movement can be written like this , or with this array . if we look at the two arrays , they 're clearly not the same , but an array alone does n't completely describe a vector . each needs a basis to give it context , and when we properly assign them , we see that they are in fact describing the same vector . you can think of elements in the array as individual letters . just as a sequence of letters only becomes a word in the context of a particular language , an array acquires meaning as a vector when assigned a coordinate basis . and just as different words in two languages can convey the same idea , different representations from two bases can describe the same vector . the vector is the essence of what 's being communicated , regardless of the language used to describe it . it turns out that scalars also share this coordinate invariance property . in fact , all quantities with this property are members of a group called tensors . various types of tensors contain different amounts of information . does that mean there 's something that can convey more information than vectors ? absolutely . say you 're designing a video game , and you want to realistically model how water behaves . even if you have forces acting in the same direction with the same magnitude , depending on how they 're oriented , you might see waves or whirls . when force , a vector , is combined with another vector that provides orientation , we have the physical quantity called stress , which is an example of a second order tensor . these tensors are also used outside of video games for all sorts of purposes , including scientific simulations , car designs , and brain imaging . scalars , vectors , and the tensor family present us with a relatively simple way of making sense of complex ideas and interactions , and as such , they 're a prime example of the elegance , beauty , and fundamental usefulness of mathematics .

what does that mean ? let 's say you and a friend are moving your tent . you stand on opposite sides so you 're facing in opposite directions .

you have walked to a friend ’ s house and suddenly get a phone call . “ where are you ? ” your sister asks . she wants to come and see you at your friend ’ s house . how do you use vectors to diagram the pathway to your friend ’ s house so your sister can arrive without getting lost ?

penguins have long captured the imagination and the hearts of people the world over . but while popular culture depicts them as clumsy , adorable birds with endlessly abundant populations , the truth is that penguins are exceedingly graceful , often ornery , and their populations are in rapid free fall . their real life situation is far more precarious than people think . and if current trends do not change , it may not be long before penguins can only be found in movies . there are many things about penguins that make them odd birds , so to speak . for one thing , they are one of the few bird species that can not fly , having evolved from flight-capable birds about 60 million years ago . surprisingly , their closest living relative is the albatross , a bird known for its enormous wingspan and extraordinary soaring abilities . it may seem strange that losing the ability to fly would be an evolutionary advantage , but the penguin 's short , flipper-like wings and solid bones allow them to swim faster and dive deeper than any other bird on earth , filling an ecological niche that no other bird can . penguins inhabit the southern hemisphere , being one of the few bird species able to breed in the coldest environments . but contrary to popular belief , they are not restricted to cold regions nor are there any at the north pole . in fact , only 4 of the 18 penguin species regularly live and breed in antarctica . most penguins live in subtemperate to temperate regions . and the galapagos penguin even lives and breeds right near the equator off the coast of south america . they are also found in south africa , namibia , australia , and new zealand , as well as on a number of islands in the southern atlantic , pacific , indian , and antarctic oceans . although penguins spend 75 % of their lives at sea , they must come to shore every year to reproduce and to molt their feathers . they do this in a variety of places , from the temporary ice sheets of the antarctic to the beaches of south africa and namibia , to the rocky shores of subantarctic islands , to the craggy lava surfaces in the galapagos . different penguin species have different nesting practices . some dig burrows into dirt , sand , or dried guano ; some nest in tussock grasses ; some build nests out of small rocks , sticks , and bones ; while others do n't build any nests at all . although most penguins lay a clutch of two eggs , the two largest species , the king and the emperor , lay a single egg that they incubate on top of their feet for approximately two months . unfortunately , 15 of the 18 penguin species are currently listed as threatened , near-threatened , or endangered by the international union for conservation of nature . in the last several decades , we have seen the world populations of most penguin species decline by up to 90 % , with two of them , the yellow-eyed and galapagos penguins , down to just a few thousand birds . penguins are an indicator species , the proverbial `` canary in the coal mine . '' simply put , if penguins are dying , it means our oceans are dying . and sadly , most of this decline is attributable to human activities . historically , penguins have had to deal with multiple disturbances . the mass collection of penguin eggs and the harvesting of the seabird guano they nested in caused the dramatic decline of several penguin species . if you 're wondering what humans would want with seabird poop , it was used as an ingredient in fertilizer and in gunpowder , being so valuable that in the 19th century , it was known as white gold . current threats to penguins include the destruction of both marine and terrestrial habitats , introduced predators , entrapment in fishing nets , and pollution from plastics and chemicals . there have also been several large-scale oil spills over the past 50 years that have killed or impacted tens of thousands of penguins around the world . but the two major threats to penguins today are global warming and overfishing . global warming impacts penguins in multiple ways , from interrupting the production of krill due to decreased sea ice formation in the antarctic , to increasing the frequency and severity of storms that destroy nests , to shifting the cold water currents carrying the penguins ' prey too far away from penguin breeding and foraging grounds . even though humans may be the greatest threat to penguins , we are also their greatest hope . many research and conservation projects are underway to protect penguin habitats and restore vulnerable populations . with a little help from us and some changes in the practices that impact our planet and oceans , there is hope that our tuxedo-clad friends will still be around in the next century .

and sadly , most of this decline is attributable to human activities . historically , penguins have had to deal with multiple disturbances . the mass collection of penguin eggs and the harvesting of the seabird guano they nested in caused the dramatic decline of several penguin species .

penguins are faced with multiple human-based disturbances , and even though they only inhabit the southern hemisphere , things that are done in the northern hemisphere impact penguins as well . what are some of the global practices that harm penguins ? what changes can you make in your daily life to reduce your impact on the environment and mitigate some of these harmful effects ?

meet our chemist , harriet . she has a chemical reaction that needs to occur more quickly . a chemist has some processes at her disposal that can help her speed up her reaction , and she knows of five ways . and to remember them , she thinks back to her days as a high school student , and the day she got a date for the dance . harriet was in high school , studying between classes . she had lost track of time and was going to be late to class . unbeknownst to her , harold , who was just around the corner , was running late , too . they both sprinted to class and , as it happened , sprinted directly into one another . now , this was no small collision . they ran squarely into one another in such a way that he knocked the books right out of her hand . `` i 'm sorry , '' he said . `` let me help you with your books . '' he kindly helped her re-collect her belongings , and politely offered to walk her to class . and you 'll never guess who went together to the dance later that year . yup , those two . so as we can see from this example , the key to getting a date for the dance is to collide with someone and knock the books out of their hands . now , you 're probably already aware that not all collisions lead to dates for the dance , thankfully . the collisions must have two important characteristics : one , correct orientation that allows books to be knocked from one 's hands ; and two , enough energy to knock the books out . shortly after this incident , harriet decided to tell me , her chemistry teacher , all about it . i noticed some interesting parallels between her story and chemical reaction rates , which happened to be what she was studying in the hallway the day of the collision . together , we decided to set out on two missions . harriet wanted to help all chemistry students and chemists remember how to speed up the rate of chemical reactions and i , being the nice guy that i am , decided to make it my mission to help create educational environments in which more book-dropping collisions can take place to increase future chemists ' chances of getting a date for the dance . in order to facilitate this improved dance-date-getting process , i propose five changes to all schools that parallel harriet 's five ways to increase chemical reaction rates . first , i propose that we shrink the size of the hallways . this will make it more difficult to safely navigate the hallways and will cause more collisions than in larger hallways . and by increasing the number of collisions , we increase the likelihood that some of those collisions will have the correct alignment and enough energy to create a date to the dance . now , chemically speaking , this is equivalent to lowering the volume of a reaction vessel or a reaction mixture . in doing so , the individual particles are closer together , and more collisions will occur . more collisions means a greater likelihood that collisions with the appropriate energy and configuration will happen . second , i propose increasing the overall population of the school . more students equals more collisions . by increasing the number of particles available for collision , we create an environment where more collisions can take place . third , we must reduce the time allowed between classes -- heck , let 's just cut it in half . in doing so , students will need to move more quickly to get from one class to the next . this increase in velocity will help make sure collisions have the appropriate amount of energy necessary to ensure book-dropping . this is analogous to increasing the temperature of the reaction mixture . higher temperature means particles are moving faster . faster-moving particles means more energy , and a greater likelihood of the reaction-causing collision . fourth , students must stop traveling in packs . by traveling in packs , the students on the outside of the pack insulate those in the middle from undergoing any collisions . by splitting up , each student has more area exposed that is available for a collision from a passing student . when particles travel in packs , the surface area is very small , and only the outside particles can collide . however , by breaking up the clumps into individual particles , the total surface area is increased , and each particle has an exposed surface that can react . fifth and finally , we hire a matchmaker . is this colliding and book-dropping too violent ? is there an easier way to get a date that requires less initial energy ? then a matchmaker will help with this . the matchmaker makes it easier for a couple to get together , by coordinating the match . our matchmaker is like a catalyst . chemical catalysts function by lowering the activation energy -- in other words , by lowering the energy required to start a reaction . they do this by bringing two particles together and orienting them correctly in space so that the two can meet at the correct configuration and allow a reaction to take place . so , to sum up : if a future chemist wants a date for the dance , he must collide with another person and knock the books out of their hands . and if a chemist wants to make a chemical reaction occur , the particles must collide in the correct orientation with an appropriate amount of energy . and both of these processes can be accelerated , using the five methods i 've described .

meet our chemist , harriet . she has a chemical reaction that needs to occur more quickly . a chemist has some processes at her disposal that can help her speed up her reaction , and she knows of five ways .

explain how a chemical catalyst helps change the rate of a chemical reaction and give two examples of actual chemical catalysis .

today , more than half of all people in the world live in an urban area . by mid-century , this will increase to 70 % . but as recently as 100 years ago , only two out of ten people lived in a city , and before that , it was even less . how have we reached such a high degree of urbanization , and what does it mean for our future ? in the earliest days of human history , humans were hunter-gatherers , often moving from place to place in search of food . but about 10,000 years ago , our ancestors began to learn the secrets of selective breeding and early agricultural techniques . for the first time , people could raise food rather than search for it , and this led to the development of semi-permanent villages for the first time in history . `` why only semi-permanent ? '' you might ask . well , at first , the villages still had to relocate every few years as the soil became depleted . it was only with the advent of techniques like irrigation and soil tilling about 5,000 years ago that people could rely on a steady and long-term supply of food , making permanent settlements possible . and with the food surpluses that these techniques produced , it was no longer necessary for everyone to farm . this allowed the development of other specialized trades , and , by extension , cities . with cities now producing surplus food , as well as tools , crafts , and other goods , there was now the possibility of commerce and interaction over longer distances . and as trade flourished , so did technologies that facilitated it , like carts , ships , roads , and ports . of course , these things required even more labor to build and maintain , so more people were drawn from the countryside to the cities as more jobs and opportunities became available . if you think modern cities are overcrowded , you may be surprised to learn that some cities in 2000 b.c . had population densities nearly twice as high as that of shanghai or calcutta . one reason for this was that transportation was not widely available , so everything had to be within walking distance , including the few sources of clean water that existed then . and the land area of the city was further restricted by the need for walls to defend against attacks . the roman empire was able to develop infrastructure to overcome these limitations , but other than that , modern cities as we know them , did n't really get their start until the industrial revolution , when new technology deployed on a mass scale allowed cities to expand and integrate further , establishing police , fire , and sanitation departments , as well as road networks , and later electricity distribution . so , what is the future of cities ? global population is currently more than 7 billion and is predicted to top out around 10 billion . most of this growth will occur in the urban areas of the world 's poorest countries . so , how will cities need to change to accommodate this growth ? first , the world will need to seek ways to provide adequate food , sanitation , and education for all people . second , growth will need to happen in a way that does not damage the land that provides us with the goods and services that support the human population . food production might move to vertical farms and skyscrapers , rooftop gardens , or vacant lots in city centers , while power will increasingly come from multiple sources of renewable energy . instead of single-family homes , more residences will be built vertically . we may see buildings that contain everything that people need for their daily life , as well as a smaller , self-sufficient cities focused on local and sustainable production . the future of cities is diverse , malleable , and creative , no longer built around a single industry , but reflecting an increasingly connected and global world .

but about 10,000 years ago , our ancestors began to learn the secrets of selective breeding and early agricultural techniques . for the first time , people could raise food rather than search for it , and this led to the development of semi-permanent villages for the first time in history . `` why only semi-permanent ? '' you might ask .

what led to the development of the first semi-permanent settlements ?

massive vines that blanket the southern united states , climbing as high as 100 feet as they uproot trees and swallow buildings . a ravenous snake that is capable of devouring an alligator . rabbit populations that eat themselves into starvation . these are n't horror movie concepts . they 're real stories , but how could such situations exist in nature ? all three are examples of invasive species , organisms harmful not because of what they are , but where they happen to be . the kudzu vine , for example , had grown quality in its native east asia , eaten by various insects and dying off during the cold winters . but its fortunes changed when it was imported into the southeastern united states for porch decoration and cattle feed . its planting was even subsidized by the government to fight soil erosion . with sunny fields , a mild climate , and no natural predators in its new home , the vine grew uncontrollably until it became known as the plant that ate the south . meanwhile in florida 's everglades , burmese pythons , thought to have been released by pet owners , are the cause of decreasing populations of organisms . they 're successfully outcompeting top predators , such as the alligator and panther , causing a significant reduction in their food sources . they 're not a problem in their native asia because diseases , parasites , and predators help to control their population size . and in australia , european rabbits eat so many plants that they wipe out the food supply for themselves and other herbivores . they 're a pretty recent addition , intentionally introduced to the continent because one man enjoyed hunting them . like the burmese pythons , various factors in their native habitat keep their numbers in control . but in australia , the lack of predators and a climate perfect for year-long reproduction allows their populations to skyrocket . so why does this keep happening ? most of the world 's ecosystems are the result of millennia of coevolution by organisms , adapting to their environment and each other until a stable balance is reached . healthy ecosystems maintain this balance via limiting factors , environmental conditions that restrict the size or range of a species . these include things like natural geography and climate , food availability , and the presence or absence of predators . for example , plant growth depends on levels of sunlight and soil nutrients . the amount of edible plants affects the population of herbivores , which in turn impacts the carnivores that feed on them . and a healthy predator population keeps the herbivores from becoming too numerous and devouring all the plants . but even minor changes in one factor can upset this balance , and the sudden introduction of non-native organisms can be a pretty major change . a species that is evolved in a separate habitat will be susceptible to different limiting factors , different predators , different energy sources , and different climates . if the new habitat 's limiting factors fail to restrict the species growth , it will continue to multiply , out-competing native organisms for resources and disrupting the entire ecosystem . species are sometimes introduced into new habitats through natural factors , like storms , ocean currents , or climate shifts . the majority of invasive species , though , are introduced by humans . often this happens unintentionally , as when the zebra mussel was accidentally brought to lake erie by cargo ships . but as people migrate around the world , we have also deliberately brought our plants and animals along , rarely considering the consequences . but now that we 're learning more about the effects of invasive species on ecosystems , many governments closely monitor the transport of plants and animals , and ban the imports of certain organisms . but could the species with the most drastic environmental impact be a group of primates who emerged from africa to cover most of the world ? are we an invasive species ?

a ravenous snake that is capable of devouring an alligator . rabbit populations that eat themselves into starvation . these are n't horror movie concepts .

one of the main problems caused by both the burmese python and european rabbit is :

this is a map of yellowstone national park for the most part the park is in wyoming but it extends a bit into montana and idaho this little 50 square miles section in idaho is what concerns us it 's called the zone of death because of a loophole that exists in the constitution of the united states if someone were to exploit that loophole they might be able to get away with murder yellowstone was established in 1872 before wyoming idaho and montana join the union it 's federal land and always has been but federal land across the u.s. is split up and divided into its corresponding state district courts except for yellowstone and this is where the loophole begins law professor brian c. kalt points out in his 2005 paper the perfect crime that yellowstone national park was assigned fully to wyoming 's district court even though small portions fall into montana and idaho unlike every other district the district of wyoming includes land in other state so kalt asks the question what happens if you 're caught for a crime you committed in that 50 square mile idea who region of the park the first thing law enforcement would do is bring you to cheyenne the hub of the district court of wyoming because the crime technically happened within wyoming 's jurisdiction but article 3 section 2 of the united states constitution says that the trial should happen in the state where you committed the crime if you 're a savvy murderer you invoke your right to a trial in idaho so they bring you back to idaho no big deal in the sixth amendment they said that they would require local juries and the language they use is that the jury has to be from the state and district where the crime was committed this is called the vicinage clause that leaves you with a sort of venn diagram you have the right to demand jury from that middle area where the state in which you committed the crime that 's idaho overlaps with the judicial jurisdiction where you committed the crime the wyoming district that has jurisdiction over yellowstone national park and here 's the problem nobody lives there there 's there 's no way for them to give you a trial and so i argue they should have to let you go this could also happen in the montana portion of the park except a few dozen people do live there so a jury could theoretically be called kalt has proposed numerous solutions to congress to fix the loophole but they have yet to act all they have to do is redraw the district line so that the district of wyoming is wyoming the district of idaho is in idaho and the district of montana in montana and if they do that it all goes away so if you 're planning a gathering of your adversaries exes and debtors maybe try yosemite

this is a map of yellowstone national park for the most part the park is in wyoming but it extends a bit into montana and idaho this little 50 square miles section in idaho is what concerns us it 's called the zone of death because of a loophole that exists in the constitution of the united states if someone were to exploit that loophole they might be able to get away with murder yellowstone was established in 1872 before wyoming idaho and montana join the union it 's federal land and always has been but federal land across the u.s. is split up and divided into its corresponding state district courts except for yellowstone and this is where the loophole begins law professor brian c. kalt points out in his 2005 paper the perfect crime that yellowstone national park was assigned fully to wyoming 's district court even though small portions fall into montana and idaho unlike every other district the district of wyoming includes land in other state so kalt asks the question what happens if you 're caught for a crime you committed in that 50 square mile idea who region of the park the first thing law enforcement would do is bring you to cheyenne the hub of the district court of wyoming because the crime technically happened within wyoming 's jurisdiction but article 3 section 2 of the united states constitution says that the trial should happen in the state where you committed the crime if you 're a savvy murderer you invoke your right to a trial in idaho so they bring you back to idaho no big deal in the sixth amendment they said that they would require local juries and the language they use is that the jury has to be from the state and district where the crime was committed this is called the vicinage clause that leaves you with a sort of venn diagram you have the right to demand jury from that middle area where the state in which you committed the crime that 's idaho overlaps with the judicial jurisdiction where you committed the crime the wyoming district that has jurisdiction over yellowstone national park and here 's the problem nobody lives there there 's there 's no way for them to give you a trial and so i argue they should have to let you go this could also happen in the montana portion of the park except a few dozen people do live there so a jury could theoretically be called kalt has proposed numerous solutions to congress to fix the loophole but they have yet to act all they have to do is redraw the district line so that the district of wyoming is wyoming the district of idaho is in idaho and the district of montana in montana and if they do that it all goes away so if you 're planning a gathering of your adversaries exes and debtors maybe try yosemite

yellowstone national park is mostly in which state ?

we check the time every day , all day long . but did you ever wonder - where did telling time come from ? why does it matter what time it is ? who determined the clock and why in the world are there so many different time zones ? the first form of telling time was the sundial and the earliest sundials known from the archaeological record are obelisks from nearly 5,000 years ago . sundials indicate the time by casting a shadow onto a surface . the object that casts the shadow is a stick in the center known as a gnomon . a well-constructed sundial can measure time with remarkable accuracy , and sundials were used to monitor the performance of clocks until the modern era . but sundials have their limitations too . obviously they require the sun to shine , so they do n't work at all during the night when it 's dark . many different devices have been used over the years to estimate the passage of time : candles and sticks of incense that burn down at fairly predictable speeds have been used , along with the hourglass . hourglasses are devices in which fine sand pours through a tiny hole at a constant rate and indicates a predetermined passage of an arbitrary period of time . the origin of the hourglass is uncertain , although beginning in the 14th century , the hourglass was used commonly , especially on board ships . the motion of the boat on the water did not affect the hourglass , unlike other time-measuring devices . the mechanical clock was invented in the 13th century which sparked a big change in traditional timekeeping methods . this modern clock relied on the swing of a pendulum or the vibration of a quartz crystal , which was far more accurate than sand or candles . today , the basis for scientific time is a continuous count of seconds based on atomic clocks all around the world , known as the international atomic time . why does it matter that we keep track of time ? well , time regulates our daily lives and makes it possible to accurately communicate with people all over the world . without a time system , we would have many challenges in farming , social structures , communication , and business . take the american railroad system , for example . in the mid-19th century , each railroad used its own standard time generally based on the local time of its headquarters , and the railroad 's train schedules were published using its own time . some major railroad junctions served by several different railroads had a separate clock for each railroad , each showing a different time . the distance between new york and boston is about 2 degrees , or 8 minutes , which can be the difference between making or missing your train connection . if the difference between new york and boston is 8 minutes , imagine the difference between boston and australia . the use of time zones irons out these differences and makes communication significantly smoother . a time zone is a region on earth that has a uniform standard time . there are 40 time zones on land because the earliest and latest time zones are 26 hours apart . any given calendar date exists at some point on the globe for 50 hours . so the next time someone asks you `` what time is it ? '' your answer may be a whole lot more complicated than it used to be .

who determined the clock and why in the world are there so many different time zones ? the first form of telling time was the sundial and the earliest sundials known from the archaeological record are obelisks from nearly 5,000 years ago . sundials indicate the time by casting a shadow onto a surface .

the first form of telling time was the :

in 1895 , a physicist named wilhelm roentgen was doing experiments with a cathode tube , a glass container in which a beam of electrons lights up a fluorescent window . he had wrapped cardboard around the tube to keep the fluorescent light from escaping , when something peculiar happened . another screen outside the tube was glowing . in other words , invisible rays had passed through the cardboard . wilhelm had no idea what those rays were , so he called them x-rays , and his discovery eventually won him a nobel prize . here 's what we now know was happening . when high energy electrons in the cathode tube hit a metal component , they either got slowed down and released extra energy , or kicked off electrons from the atoms they hit , which triggered a reshuffling that again released energy . in both cases , the energy was emitted in the form of x-rays , which is a type of electromagnetic radiation with higher energy than visible light , and lower energy than gamma rays . x-rays are powerful enough to fly through many kinds of matter as if they are semi-transparent , and they 're particularly useful for medical applications because they can make images of organs , like bones , without harming them , although they do have a small chance of causing mutations in reproductive organs , and tissues like the thyroid , which is why lead aprons are often used to block them . when x-rays interact with matter , they collide with electrons . sometimes , the x-ray transfers all of its energy to the matter and gets absorbed . other times , it only transfers some of its energy , and the rest is scattered . the frequency of these outcomes depends on how many electrons the x-rays are likely to hit . collisions are more likely if a material is dense , or if it 's made of elements with higher atomic numbers , which means more electrons . bones are dense and full of calcium , which has a relatively high atomic number , so they absorb x-rays pretty well . soft tissue , on the other hand , is n't as dense , and contains mostly lower atomic number elements , like carbon , hydrogen , and oxygen . so more of the x-rays penetrate tissues like lungs and muscles , darkening the film . these 2-d pictures are only useful up to a point , though . when x-rays travel through the body , they can interact with many atoms along the path . what is recorded on the film reflects the sum of all those interactions . it 's like trying to print 100 pages of a novel on a single sheet of paper . to see what 's really going on , you would have to take x-ray views from many angles around the body and use them to construct an internal image . and that 's something doctors do all the time in a procedure called a ct , computed tomography scan , another nobel prize winning invention . think of ct like this . with just one x-ray , you might be able to see the density change due to a solid tumor in a patient , but you would n't know how deep it is beneath the surface . however , if you take x-rays from multiple angles , you should be able to find the tumor 's position and shape . a ct scanner works by sending a fan or cone of x-rays through a patient to an array of detectors . the x-ray beam is rotated around the patient , and often also moved down the patient 's body , with the x-ray source tracing a spiral trajectory . spiral ct scans produce data that can be processed into cross sections detailed enough to spot anatomical features , tumors , blood clots , and infections . ct scans can even detect heart disease and cavities in mummies buried thousands of years ago . so what began as roentgen 's happy accident has become a medical marvel . hospitals and clinics now conduct over 100 millions scans each year worldwide to treat diseases and save lives .

a ct scanner works by sending a fan or cone of x-rays through a patient to an array of detectors . the x-ray beam is rotated around the patient , and often also moved down the patient 's body , with the x-ray source tracing a spiral trajectory . spiral ct scans produce data that can be processed into cross sections detailed enough to spot anatomical features , tumors , blood clots , and infections .

modern ct data are often collected when the x-ray source moves along _____ around the patient .

in this short video , we 're going to show you how we constructed and animated a pop-up book to explain earth 's tectonic plates . the supercontinent pangaea broke apart 200,000,000 years ago , but the pieces have n't stopped shifting . although with animation we can show this movement easily with drawings , we thought it 'd be more interesting to depict gigantic sliding slabs of rock using a tangible object that also moves and shifts . and the pop-up book idea was born . ( music ) to make your own pop-up book , you 'll need some basic paper tools , such as scissors , an x-acto knife , glue , double-sided scotch tape , a ruler , a bone folder or other creasing tool , and , of course , some paper . for this lesson , we first determined the visual style by making illustrations and deciding on the overall design , colors , shapes and elements we wanted on each page , or spread . you can have more detailed illustrations , but we wanted to illustrate this lesson simply by playing with shapes and colors . when you visualize your pop-up and choose a visual style , you will want to make a bunch of good old pencil sketches on paper and plan each movement for each spread . plan as much as you can : all the basic shapes and how they connect and how you want them to move , which parts you want to pop-up first . challenge yourself , and explore multiple possibilities of how your main element on the spread can pop up . for the next step , make a mock-up spread and see if your masterful paper engineering ideas translate from a sketch to the actual prototype . instead of using fancy paper , start with the cheap stuff and allow yourself to make mistakes and adjustments . this prototype lets you see how your preliminary sketches will come to life . you will want to first draw all individual parts on a single sheet , including all your main pieces , all the supporting pieces and the folds . you may be surprised that there are only two types of folds that can make your elements pop up the way you want : a step fold and a v-fold . here , you can see how we used a step fold to make each layer of the earth step out . then , cut all your individual elements and assemble using glue or double-sided scotch tape . ( music ) through trial and error , make sure that all the elements , shapes and placements are moving the way you imagined , and that they fold properly when closed and opened . ( music ) once your prototype is tested and complete , you can proceed to making the final product in color . draw or paint on your main pop-up elements as you see fit . for this lesson , we decided to just play with simple shapes in different colors to create the world of shifting continents we imagined . ( music ) when we were planning each spread , we knew we wanted some elements to move independently of the typical pop-up book using slight manipulations and animations . we had to plan well , but also use a few tricks . as always , when you 're making stop-motion , you may have to be creative and use all sorts of unusual tools and props to achieve the effect that you want . in this shot , the birds had to fly across and off the edge of the book , so we used fun-tak to move the clouds across the page . once they left the page , they had to be trimmed to get the illusion they flew off . when the pages of the book close at the end , we had to flip each page , supporting it in each position long enough to be photographed as an individual frame . we used binder clips , wedges , fun-tak , and almost every handy little thing you can think of . once all the individual frames were photographed , we put them all together and composited to make our pop-up book look like it 's moving on its own . so now , think of a special occasion where you can surprise someone with your own unique pop-up card , or an entire story that you want to tell , and start plotting the ins and outs of your pop-up book .

although with animation we can show this movement easily with drawings , we thought it 'd be more interesting to depict gigantic sliding slabs of rock using a tangible object that also moves and shifts . and the pop-up book idea was born . ( music ) to make your own pop-up book , you 'll need some basic paper tools , such as scissors , an x-acto knife , glue , double-sided scotch tape , a ruler , a bone folder or other creasing tool , and , of course , some paper .

why is it so important to create a prototype of your pop-up book ?

hi , my name is john green , this is crash course world history , and today we ’ re going to talk about the french revolution . admittedly , this wasn ’ t the french flag until 1794 , but we just felt like he looked good in stripes . as does this guy . huh ? so , while the american revolution is considered a pretty good thing , the french revolution is often seen as a bloody , anarchic mess , which ... mr. green , mr. green ! i bet , like always , it ’ s way more complicated than that . actually no . it was pretty terrible . also , like a lot of revolutions , in the end it exchanged an authoritarian regime for an authoritarian regime . but even if the revolution was a mess , its ideas changed human history - far more , i will argue , than the american revolution . [ theme music ] right , so france in the 18th century was a rich and populous country , but it had a systemic problem collecting taxes because of the way its society was structured . they had a system with kings and nobles we now call the ancien régime . thank you , three years of high school french . and for most french people , it sucked , because the people with the money - the nobles and the clergy - never paid taxes . so by 1789 , france was deeply in debt thanks to their funding the american revolution - thank you , france ; we will get you back in world wars i and ii . and king louis xvi was spending half of his national budget to service the federal debt . louis tried to reform this system under various finance ministers . he even called for democracy on a local level , but all attempts to fix it failed and soon france basically declared bankruptcy . this nicely coincided with hailstorms that ruined a year ’ s harvest , thereby raising food prices and causing widespread hunger , which really made the people of france angry , because they love to eat . meanwhile , the king certainly did not look broke , as evidenced by his well-fed physique and fancy footwear . he and his wife marie antoinette also got to live in the very nice palace at versailles thanks to god ’ s mandate , but enlightenment thinkers like kant were challenging the whole idea of religion , writing things like : “ the main point of enlightenment is of man ’ s release from his self-caused immaturity , primarily in matters of religion. ” so basically the peasants were hungry , the intellectuals were beginning to wonder whether god could or should save the king , and the nobility were dithering about , eating foie gras and songbirds , failing to make meaningful financial reform . in response to the crisis , louis xvi called a meeting of the estates general , the closest thing that france had to a national parliament , which hadn ’ t met since 1614 . the estates general was like a super parliament made up of representatives from the first estate , the nobles , the second estate , the clergy , and the third estate , everyone else . the third estate showed up with about 600 representatives , the first and second estates both had about 300 , and after several votes , everything was deadlocked , and then the third estate was like , “ you know what ? forget you guys . we ’ re gon na leave and we ’ re gon na become our own national assembly. ” this did not please king louis xvi . so when the new national assembly left the room for a break , he locked the doors , and he was like , `` sorry , guys , you ca n't go in there . and if you ca n't assemble , how you gon na be a national assembly ? '' shockingly , the third estate representatives were able to find a different room in france , this time an indoor tennis court where they swore the famous tennis court oath . and they agreed not to give up until a french constitution was established . so then louis xvi responded by sending troops to paris primarily to quell uprisings over food shortages , but the revolutionaries saw this as a provocation , so they responded by seizing the bastille prison on july 14th , which , coincidentally , is also bastille day . the bastille was stormed ostensibly to free prisoners - although there were only seven in jail at the time - but mostly to get guns . but the really radical move in the national assembly came on august 4 , when they abolished most of the ancien régime - feudal rights , tithes , privileges for nobles , unequal taxation , they were all abolished - in the name of writing a new constitution . and then , on august 26th , the national assembly proclaimed the declaration of rights of man and citizen , which laid out a system of rights that applied to every person , and made those rights integral to the new constitution . that ’ s quite different from the american bill of rights , which was , like , begrudgingly tacked on at the end and only applied to non-slaves . the doromac , as i called it in high school , declared that everyone had the right to liberty , property , and security - rights that the french revolution would do an exceptionally poor job of protecting , but as noted last week , the same can be argued for many other supposedly more successful revolutions . okay , let ’ s go to the thought bubble . meanwhile , back at versailles , louis xvi was still king of france , and it was looking like france might be a constitutional monarchy . which might 've meant that the royal family could hang on to their awesome house , but then , in october of 1789 , a rumor started that marie antoinette was hoarding grain somewhere inside the palace . and in what became known as the women 's march , a bunch of armed peasant women stormed the palace and demanded that louis and marie antoinette move from versailles to paris . which they did , because everyone is afraid of armed peasant women . and this is a nice reminder that to many people at the time , the french revolution was not primarily about fancy enlightenment ideas ; it was mostly about lack of food and a political system that made economic contractions hardest on the poor . now , a good argument can be made that this first phase of the revolution wasn ’ t all that revolutionary . the national assembly wanted to create a constitutional monarchy ; they believed that the king was necessary for a functioning state and they were mainly concerned that the voters and office holders be men of property . only the most radical wing , the jacobins , called for the creation of a republic . but things were about to get much more revolutionary - and also worse for france . first , the jacobins had a huge petition drive that got a bit unruly , which led troops controlled not by the king but by the national assembly to fire on the crowd , killing 50 people . and that meant that the national assembly , which had been the revolutionary voice of the people , had killed people in an attempt to reign in revolutionary fervor . you see this a lot throughout history during revolutions . what looked like radical hope and change suddenly becomes `` the man '' as increasingly radical ideas are embraced . thanks , thought bubble . meanwhile , france ’ s monarchical neighbors were getting a little nervous about all this republic business , especially leopold ii , who in addition to being the not holy , not roman , and not imperial holy roman emperor , was marie antoinette ’ s brother . i should note , by the way , that at this point , the holy roman empire was basically just austria . also , like a lot of monarchs , leopold ii liked the idea of monarchies , and he wanted to keep his job as a person who gets to stand around wearing a dress , pointing at nothing , owning winged lion-monkeys made out of gold . and who can blame him ? so he and king william frederick ii of prussia together issued the declaration of pillnitz , which promised to restore the french monarchy . at this point , louis and the national assembly developed a plan : let ’ s invade austria . the idea was to plunder austria ’ s wealth and maybe steal some austrian grain to shore up french food supplies , and also , you know , spread revolutionary zeal . but what actually happened is that prussia joined austria in fighting the french . and then louis encouraged the prussians , which made him look like an enemy of the revolution , which , of course , he was . and as a result , the assembly voted to suspend the monarchy , have new elections in which everyone could vote ( as long as they were men ) , and create a new republican constitution . soon , this convention decided to have a trial for louis xvi , who was found guilty and , by one vote , sentenced to die via guillotine . which made it difficult for austria and prussia to restore him to the throne . oh , it ’ s time for the open letter ? an open letter to the guillotine . but first , let ’ s see what ’ s in the secret compartment today . oh , there ’ s nothing . oh my gosh , stan ! jeez . that ’ s not funny ! dear guillotine , i can think of no better example of enlightenment thinking run amok . dr. joseph guillotine , the inventor of the guillotine , envisioned it as an egalitarian way of dying . they said the guillotine was humane and it also made no distinction between rich or poor , noble or peasant . it killed equally . you were also celebrated for taking the torture out of execution . but i will remind you , you did not take the dying out of execution . unfortunately for you , france hasn ’ t executed anyone since 1977 . but you ’ ll be happy to know that the last legal execution in france was via guillotine . plus , you ’ ve always got a future in horror movies . best wishes , john green the death of louis xvi marks the beginning of the terror , the best known or at least the most sensational phase of the revolution . i mean , if you can kill the king , you can kill pretty much anyone , which is what the government did under the leadership of the committee of public safety ( motto : we suck at protecting public safety ) , led by maximilien robespierre . the terror saw the guillotining of 16,000 enemies of the revolution including marie “ i never actually said let them eat cake ” antoinette and maximilien robespierre himself , who was guillotined in the month of thermidor in the year two . alright , so while france was broke and fighting in like nine wars , the committee of public safety changed the measurements of time because , you know , the traditional measurements are so irrational and religion-y . so they renamed all the months and decided that every day would have 10 hours and each hour 100 minutes . and then , after the terror , the revolution pulled back a bit and another new constitution was put into place , this one giving a lot more power to wealthy people . at this point , france was still at war with austria and britain , wars that france ended up winning , largely thanks to a little corporal named napoleon bonaparte . the war was backdrop to a bunch of coups and counter coups that i won ’ t get into right now because they were very complicated , but the last coup that we ’ ll talk about , in 1799 , established napoleon bonaparte as the first consul of france . and it granted him almost unlimited executive power under yet another constitution . and when he was declared first consul of france , napoleon proclaimed `` citizens ! the revolution is established on the principals with which it began . it is over . '' by which he presumably meant that france ’ s government had gone all the way from here to here to here . as with the american revolution , it ’ s easy to conclude that france ’ s revolution wasn ’ t all that revolutionary . i mean , napoleon was basically an emperor and , in some ways , he was even more of an absolute monarch than louis xvi had been . gradually the nobles came back to france , although they had mostly lost their special privileges . the catholic church returned , too , although much weaker because it had lost land and the ability to collect tithes . and when napoleon himself fell , france restored the monarchy , and except for a four-year period , between 1815 and 1870 , france had a king who was either a bourbon or a bonaparte . now , these were no longer absolute monarchs who claimed that their right to rule came from god ; they were constitutional monarchs of the kind that the revolutionaries of 1789 had originally envisioned . but the fact remains that france had a king again , and a nobility , and an established religion and it was definitely not a democracy or a republic . and perhaps this is why the french revolution is so controversial and open to interpretation . some argue the revolution succeeded in spreading enlightenment ideals even if it didn ’ t bring democracy to france . others argue that the real legacy of the revolution wasn ’ t the enhancement of liberty , but of state power . regardless , i ’ d argue that the french revolution was ultimately far more revolutionary than its american counterpart . i mean , in some ways , america never had an aristocracy , but in other ways it continued to have one - the french enlightenment thinker , diderot , felt that americans should “ fear a too unequal division of wealth resulting in a small number of opulent citizens and a multitude of citizens living in misery. ” and the american revolution did nothing to change that polarization of wealth . what made the french revolution so radical was its insistence on the universality of its ideals . i mean , look at article 6 of the declaration of rights of man and citizen : “ law is the expression of the general will . every citizen has a right to participate personally , or through his representative , in its foundation . it must be the same for all , whether it protects or punishes. ” those are radical ideas , that the laws come from citizens , not from kings or gods , and that those laws should apply to everyone equally . that ’ s a long way from hammurabi - and in truth , it ’ s a long way from the slaveholding thomas jefferson . in the 1970s , chinese president zhou enlai was asked what the affects of the french revolution had been . and he said , “ it ’ s too soon to say. ” and in a way , it still is . the french revolution asked new questions about the nature of people ’ s rights and the derivation of those rights . and we ’ re still answering those questions and sorting through how our answers should shape society today - must government be of the people to be for the people ? do our rights derive from nature or from god or from neither ? and what are those rights ? as william faulkner said , “ the past is never dead . it ’ s not even past. ” thanks for watching . i ’ ll see you next week . crash course is produced and directed by stan muller , our script supervisor is danica johnson , the show is written by my high school history teacher raoul meyer and myself , our graphics team is thought bubble , and we are ably interned by meredith danko . last week ’ s phrase of the week was `` giant tea bag '' ; if you want to suggest future phrases of the week , or guess at this week 's you can do so in comments , where you can also ask questions about today ’ s video that will be answered by our team of historians . thanks for watching crash course , and as we say in my hometown , don ’ t forget to be awesome .

they had a system with kings and nobles we now call the ancien régime . thank you , three years of high school french . and for most french people , it sucked , because the people with the money - the nobles and the clergy - never paid taxes . so by 1789 , france was deeply in debt thanks to their funding the american revolution - thank you , france ; we will get you back in world wars i and ii . and king louis xvi was spending half of his national budget to service the federal debt .

what conditions existed in france in 1789 that caused the french people to revolt ?

good morning hank , it 's tuesday . so earlier this morning , i was kayaking on the white river . i came to an island that only exists when the water is low , so i had to choose which stream to follow down . i thought as i always do in these situations of robert frost 's poem , the road not taken . you know , the one that ends in , `` two roads diverged in a yellow wood , and i took the one less travelled by , and that has made all the difference . '' so i followed the road that seemed the less obvious choice . it turns out that it was the less obvious for a reason . so hank , the road not taken is an interesting poem because 1. it 's kind of responsible for the death of the person it was written for and 2. what most people conclude from the poem is the exact opposite of what robert frost intended to conclude . and also , 3. this dissonance points at something terrible about poetry i think hank . but let 's start with 1 - that dead guy . so robert frost was inspired to write this poem by the many walks he took with his friend , the english poet , edward thomas . thomas was very obsessive and indecisive person , and every time they 'd come to a fork in the road , he would n't know which one to take . you know , like how if you 're in the english countryside and if you choose the wrong path , you might get eaten by a lion . but you ca n't know that until after you 've made the choice . i assume that there 'd be lions in england , at least dandy lions . in frost 's mind , the poem was gently mocking people who obsess over the importance of tiny , little decisions , right ? but as often happens with people who are mocked too gently , edward thomas did n't get the joke and took the poem very , very seriously . and so even though edward thomas was too old to be expected to enlist , he went ahead and took the road less travelled , joining the british army to fight in wii , where upon he was promptly shot through the chest and killed . since then hank , pretty much everyone , including me , has adopted edward thomas ' interpretation of the poem despite the fact that it , you know , killed him . i think there 's just something alluring about the idea choosing the less travelled is always a good idea . it would be very helpful if there was some overarching guideline , like `` follow the path that others do n't . '' also , following the road less taken has the added advantage of making everyone feel like a non-conformist , which is nice . but of course , there are a bunch of problems . for one thing , if everyone followed the road less travelled , it quickly becomes the road more travelled . furthermore , there are many times when the road more travelled is more travelled for a reason , because for instance , the road less travelled leads to a kayak unfriendly marsh . or because there 's something kind of nice about having a spouse and two kids and a mini-van . anyways hank , i 've been thinking about this a lot because over at our podcast , dear hank and john , we 've been getting a lot of questions from listeners who are making huge life decisions , you know , should i go into the military ? which college should i attend ? should i attend college at all ? as humans , we constantly have to make all these big , big decisions , with very limited information . like hank , we are both incredibly blessed to have great marriages and great spouses , but i had no idea what i was agreeing to on my wedding day . i thought i was saying , `` i want to be in a romantic relationship with you for the rest of my life . '' i did not realize that i was also saying , `` i want to be co-ceos of a company that raises children and mows lawns and stuff . '' anyways hank , the other thing about dear hank and john is that i insist on beginning each episode with a short poem . and so in the last few weeks , we 've had a bunch of discussions about poetry - whether poetry matters , what poetry does , etc . and i think we have the road not taken as one answer about what poetry can do . because poetry is so often musical and rhythmic , it has a way of sticking in our heads , like i memorized it almost by accident . frost thought that the poem was exploring how people experience choice making rather than offering advice , but precisely because it sounds good hank , it seems like good advice . and even though i know it is n't good advice , at least not consistently , i suspect that the next time i am facing a fork in the road or fork in the river , those iambic feet will wander back into my mind . and i will once again be biased , however minutely , toward the road less travelled . i guess that 's one example of how i think poetry can really matter in the real lives of real people , hank , and why i think that poets and readers alike need to be very careful with language . after all hank , we do n't want to end up like edward thomas , but we also do n't want to end up like the poet , who at least in a roundabout way , killed him . hank , i 'll see you on friday .

but of course , there are a bunch of problems . for one thing , if everyone followed the road less travelled , it quickly becomes the road more travelled . furthermore , there are many times when the road more travelled is more travelled for a reason , because for instance , the road less travelled leads to a kayak unfriendly marsh . or because there 's something kind of nice about having a spouse and two kids and a mini-van .

what did the speaker ( john green ) discover when he took the road less traveled while in his kayak ?

dear nickelodeon , i 've gotten over how spongebob 's pants are not actually square . i can ignore most of the time that gary 's shell is not a logarithmic spiral . but what i can not forgive is that spongebob 's pineapple house is a mathematical impossibility . there 's three easy ways to find spirals on a pineapple . there 's the ones that wind up it going right , the ones that spiral up to the left , and the ones that go almost straight up -- keyword almost . if you count the number of spirals going left and the number of spirals going right , they 'll be adjacent fibonacci numbers -- 3 and 5 , or 5 and 8 , 8 and 13 , or 13 and 21 . you claim that spongebob squarepants lives in a pineapple under the sea , but does he really ? a true pineapple would have fibonacci spiral , so let 's take a look . because these images of his house do n't let us pick it up and turn it around to count the number of spirals going around it , it might be hard to figure out whether it 's mathematically a pineapple or not . but there 's a huge clue in the third spiral , the one going upwards . in this pineapple there 's 8 to the right , 13 to the left . you can add those numbers together to get how many spirals are in the set spiraling steeply upwards . in this case , 21 . the three sets of spirals in any pineapple are pretty much always adjacent fibonacci numbers . the rare mutant cases might show lucas numbers or something , but it will always be three adjacent numbers in a series . what you 'll never have is the same number of spirals both ways . pineapples , unlike people , do n't have bilateral symmetry . you 'll never have that third spiral be not a spiral , but just a straight line going up a pineapple . yet , when we look at spongebob 's supposed pineapple under the sea , it clearly has lines of pineapple things going straight up . it clearly has bilateral symmetry . it clearly is not actually a pineapple at all , because no pineapple could possibly grow that way . nickelodeon , you need to take a long , hard look in the mirror and think about the way you 're misrepresenting the universe to your viewers . this kind of mathematical oversight is simply irresponsible . sincerely , vi hart .

in this case , 21 . the three sets of spirals in any pineapple are pretty much always adjacent fibonacci numbers . the rare mutant cases might show lucas numbers or something , but it will always be three adjacent numbers in a series .

what 5 numbers does the fibonacci sequence begin with ?

have you ever tried to picture an ideal world ? one without war , poverty , or crime ? if so , you 're not alone . plato imagined an enlightened republic ruled by philosopher kings , many religions promise bliss in the afterlife , and throughout history , various groups have tried to build paradise on earth . thomas more 's 1516 book `` utopia '' gave this concept a name , greek for `` no place . '' though the name suggested impossibility , modern scientific and political progress raised hopes of these dreams finally becoming reality . but time and time again , they instead turned into nightmares of war , famine , and oppression . and as artists began to question utopian thinking , the genre of dystopia , the not good place , was born . one of the earliest dystopian works is jonathan swift 's `` gulliver 's travels . '' throughout his journey , gulliver encounters fictional societies , some of which at first seem impressive , but turn out to be seriously flawed . on the flying island of laputa , scientists and social planners pursue extravagant and useless schemes while neglecting the practical needs of the people below . and the houyhnhnm who live in perfectly logical harmony have no tolerance for the imperfections of actual human beings . with his novel , swift established a blueprint for dystopia , imagining a world where certain trends in contemporary society are taken to extremes , exposing their underlying flaws . and the next few centuries would provide plenty of material . industrial technology that promised to free laborers imprisoned them in slums and factories , instead , while tycoons grew richer than kings . by the late 1800 's , many feared where such conditions might lead . h. g. wells 's `` the time machine '' imagined upper classes and workers evolving into separate species , while jack london 's `` the iron heel '' portrayed a tyrannical oligarchy ruling over impoverished masses . the new century brought more exciting and terrifying changes . medical advances made it possible to transcend biological limits while mass media allowed instant communication between leaders and the public . in aldous huxley 's `` brave new world '' , citizens are genetically engineered and conditioned to perform their social roles . while propaganda and drugs keep the society happy , it 's clear some crucial human element is lost . but the best known dystopias were not imaginary at all . as europe suffered unprecedented industrial warfare , new political movements took power . some promised to erase all social distinctions , while others sought to unite people around a mythical heritage . the results were real-world dystopias where life passed under the watchful eye of the state and death came with ruthless efficiency to any who did n't belong . many writers of the time did n't just observe these horrors , but lived through them . in his novel `` we '' , soviet writer yevgeny zamyatin described a future where free will and individuality were eliminated . banned in the u.s.s.r. , the book inspired authors like george orwell who fought on the front lines against both fascism and communism . while his novel `` animal farm '' directly mocked the soviet regime , the classic `` 1984 '' was a broader critique of totalitarianism , media , and language . and in the u.s.a. , sinclair lewis 's `` it ca n't happen here '' envisioned how easily democracy gave way to fascism . in the decades after world war ii , writers wondered what new technologies like atomic energy , artificial intelligence , and space travel meant for humanity 's future . contrasting with popular visions of shining progress , dystopian science fiction expanded to films , comics , and games . robots turned against their creators while tv screens broadcast deadly mass entertainment . workers toiled in space colonies above an earth of depleted resources and overpopulated , crime-plagued cities . yet politics was never far away . works like `` dr. strangelove '' and `` watchmen '' explored the real threat of nuclear war , while `` v for vendetta '' and `` the handmaid 's tale '' warned how easily our rights could disappear in a crisis . and today 's dystopian fiction continues to reflect modern anxieties about inequality , climate change , government power , and global epidemics . so why bother with all this pessimism ? because at their heart , dystopias are cautionary tales , not about some particular government or technology , but the very idea that humanity can be molded into an ideal shape . think back to the perfect world you imagined . did you also imagine what it would take to achieve ? how would you make people cooperate ? and how would you make sure it lasted ? now take another look . does that world still seem perfect ?

in the decades after world war ii , writers wondered what new technologies like atomic energy , artificial intelligence , and space travel meant for humanity 's future . contrasting with popular visions of shining progress , dystopian science fiction expanded to films , comics , and games . robots turned against their creators while tv screens broadcast deadly mass entertainment .

what was a major difference between dystopian fiction of the 19th century and the 20th ?

energy is not easy to define . things have energy , but you ca n't hold a bushel of energy in your hands . you can see what it does , but you ca n't see it directly . there are different types of energy , but the differences between them are manifested only in how they make stuff behave . we do know that the total amount of all the different types of energy in the universe is always the same . and , for chemists , two important types of energy are chemical potential energy and kinetic energy . potential energy is energy waiting to happen . think of a stretched rubber band . if you cut it , all that potential energy gets converted to kinetic energy , which is registered by you as pain . like a stretched rubber band , chemical bonds also store energy , and when those bonds are broken , that potential energy gets converted to other types of energy , like heat or light , or gets used to make different bonds . kinetic energy is the energy of motion , and molecules are always moving . they 're not necessarily going somewhere , though they could be , but they are vibrating , stretching , bending , and/or spinning . take methane , which is four hydrogens attached to a central carbon , as an example . drawn on paper , it 's just a still tetrahedron . but in real life , it 's a jiggling mess . the kinetic energy of molecules is exactly the same type of energy as the energy you have when you 're moving around , except that you can be still and molecules ca n't . if you suck the kinetic energy out of a group of molecules , they 'll move less , but they 'll never fully stop . now , in any group of molecules , some will have more kinetic energy than others . and if we calculate the average kinetic energy of the group , we 'd have a number mathematically related to temperature . so , the more kinetic energy a group of molecules has , the higher its temperature . and that means that on a hot day , the molecules in the air around you are spinning , stretching , bending , and generally shooting around much faster than on a cold day . now , hot and cold , by the way , are relative terms . they 're always used to compare one thing to something else . so , on that hot summer day , the air molecules have more kinetic energy than the molecules in your skin . so , when those air molecules crash into you , they transfer some of their energy to the molecules in your skin , and you feel that as heat . on a cold day , the air molecules have less kinetic energy than the molecules in your skin , so when you crash into those air molecules , you actually transfer some of your kinetic energy to them , and you feel that as cold . you can trace the path of energy around you . try it at your next cookout . you burn charcoal and the release of that chemical potential energy shows up as extreme heat and light . the heat then makes the molecules of your burgers , your hot dogs , or your vegetables vibrate until their own bonds break and new chemical structures are formed . too much heat and you have a charred mess ; just enough and you have dinner . once in your body , the food molecules in your delicious , or charred , dinner get broken down , and the energy released is used to either keep you alive right now or it 's stored for later in different molecules . as night falls , the hot summer air cools and the flow of energy into you slows . then , as the air reaches your skin temperature , for the briefest of moments , the flow stops . and then it starts up again in the opposite direction as energy leaves the warmer surface of your skin to return to the universe around you , that energy , neither created nor destroyed , but ever shape-shifting , the chameleon phoenix of our physical world .

there are different types of energy , but the differences between them are manifested only in how they make stuff behave . we do know that the total amount of all the different types of energy in the universe is always the same . and , for chemists , two important types of energy are chemical potential energy and kinetic energy . potential energy is energy waiting to happen . think of a stretched rubber band .

the total amount of all energy in the universe is ________ .

translator : denise rq reviewer : callum downs i just want to start with a little bit of a word of warning and that is my job here tonight it 's to be a little bit of a doctor bring me down . so bear with me for a few minutes , and know that after this , things will get lighter and brighter . let 's start . i know that many of you have heard the traveler 's adage , `` take nothing but pictures , leave nothing but footprints . '' well , i 'm going to say i do n't think that 's either as benign or as simple as it sounds , particularly for those of us in industries who are portraying people in poor countries , in developing countries and portraying the poor . and those of us in those industries are reporters , researchers , and people working for ngos ; i suspect there are a lot of us in those industries in the audience . we are going overseas and bringing back pictures like these : of the utterly distressed , or the displaced , or the hungry , or the child labor , or the exotic . now susan sontag reminds us that photographs in part help define what we have the right to observe , but more importantly , they are an ethics of seeing , and i think right now , is a good time to review our ethics of seeing as our industries of reporting , and research and ngo work are collapsing and changing in part by what it 's been happening in the economy , but it 's making us forge new relationships . and those new relationships have some fuzzy boundaries . i worked at the edge of some of these fuzzy boundaries and i want to share with you some of my observations . my ethics of seeing is informed by 25 years as a reporter covering emerging economies and international relations . i believe in a free and independent press . i believe that journalism is a public good . but it 's getting harder to do that job , in part because of the massive layoffs , because the budgets for international reporting are n't there anymore , new technologies and new platforms begging new content , and there are a lot of new journalisms . there is activist journalism , humanitarian journalism , peace journalism , and we are all looking to cover the important stories of our time . so we are going to ngos and asking them if we can embed in their projects . this is in part because they are doing important work in interesting places . that 's one example here : this is a project i worked on in the blue nile in ethiopia . ngos understand the benefits of having reporters tag along on their team . they need the publicity , they are under tremendous pressure , they are competing in a very crowded market for compassion . so they are also looking to reporters and to hire freelance reporters to help them develop their public relations material and their media material . now , researchers are also under pressure . they 're under pressure to communicate their science outside of the academy . so they 're collaborating with reporters because for many researchers is difficult to write a simple story or a clear story . and the benefit for reporters is that covering field research is some of the best work out there . you not only get to cover science , but you get to meet interesting scientists , like my phd adviser revi sterling ; she 's one of the magic research high tops there . and it was in a discussion with revi that brought us to the edge of the researcher and reporter , that fuzzy boundary . and i said to her , `` i was looking forward to going to developing countries and doing research and covering stories at the same time . '' she said , `` i do n't think so , girlfriend . '' that confusion , mutual confusion , drove us to publish a paper on the conflicting ethics and the contradictory practices of research and reporting . we started with the understanding that researchers and reporters are distant cousins equally story tellers and social analysts . but we do n't see nor portray developing communities the same way . here 's a very classic example : this is somalia 1992 . it could be somalia today . and this is a standard operating procedure for much of the news video and the news pictures that you see , where a group of reporters will be trucked in , escorted to the site of a disaster , they 'll produce their material , take their pictures , get their interviews , and then they will be escorted out . this is decidedly not a research setting . sometimes , we are working on feature stories . this is an image i took of a woman in bhongir village in andhra pradesh in india . she is at a micro-finance meeting . it 's a terrific story . what is important here is that she is identifiable . you can see her face . this also is not a research picture . this is much more representative of a research picture . it 's a research site : you see young women accessing new technologies . it 's more of a time stamp , it 's a documentation of research . i could n't use this for news . it does n't tell enough , and it would n't sell . but then , the differences are even deeper than that . revi and i analyzed some of the mandates that researchers are under , they are under some very strict rules governed by their university research review boards when it comes to content and confidentiality . researchers are mandated to acquire a document of informed consent , while as a reporter , if i hang a microphone on someone , that is consent . and when it comes to creating the story , i 'll fact check as a reporter , but i do n't invite company to create that story . whereas social scientists , researchers , and particularly participatory researchers will often work on constructing the narrative with the community . and when it comes to paying for information , checkbook journalism is roundly discouraged . in part because of the bias it introduces in the kind of information you get . but social scientists understand that people 's time is valuable so they pay them for that time . while journalists are well-placed to convey the beauty of the scientific process - and i would add the ngo process - what about the words ? what happens if a research project is not particularly well designed or an ngo project does n't fulfill its goals ? or the other kind of words ; that happens after dark when the drinks happen . research environments , and reporting , trips and ngos projects are very intimate environments ; you make good friends while you are doing good work , but there is a little bit of johnnie walker journalism after dark and what happens to that line between embedded and inbedded ? what do you do with the odd and odious behavior ? the point is that you 'll want to negotiate in advance what is on the record or off the record . i will turn now to some ngo imagery which will be familiar to some of you in this audience . ( video ) for about 70 cents , you can buy a can of soda . regular or diet . in ethiopia , for just 70 cents a day , you can feed a child like jaamal nourishing meals . for about 70 cents , you can also buy a cup of coffee . in guatemala , for 70 cents a day , you can help a child like vilma get the clothes she needs to attend school . leslie dodson : there is some very common imagery that 's been around for 40 years . that 's part of sally struthers ' famine campaign . some of it is very familiar ; it 's the madonna and child . women and children are very effective in terms of ngo campaigns . we 've been looking at this imagery for a long time , for hundreds and hundreds of years ; the madonna and child . here is [ duccio ] , and here is michelangelo . my concern is : are we one noting the genders in our narratives of poverty in developing communities ? do we have women as victims and are men only the perpetrators ? the guys with the ak 47s or the boys soldiers ? because that does n't leave room for stories like : the man who is selling ice-cream at the refuge camp in southern sudan , where we did a project . or the stories of the men who are working on the bridge over the blue nile . i wonder , are these stories inconvenient to our narratives ? and what about this narrative ? this is a for profit game , and its aim is to make development fun . one question is did they inadvertently make fun of ? another set of questions is what are the rights of these children ? what rights of publicity or privacy do they have ? did they get paid ? should they get paid ? should they share their profit ? this is a for profit game . did they sign talent wavers ? i have to use these when i 'm working with ngos and documentary film makers here in the states . in the states , we take our right to privacy and publicity very seriously . so what is it about getting on a long , whole flight that makes these rights vaporize ? i do n't want to just pick on our friends in the gaming arts , i 'll turn to the graphic arts where we often see these monolithic , homogeneous stories about the great country of africa . but africa is not a country , it 's a continent . it 's 54 countries and thousands and thousands of languages . so my question is is this imagery productive ? or is it reductive ? i know that is popular . we have usaid just launched their campaign `` forward '' -- fwd : famine war and drought . and by looking at it , you 'd think that was happening all the time , all over africa , but this is about what 's happening in the horn of africa . and i 'm still trying to make sense of africa in a piece of wonder bread . i 'm wondering about that . germaine greer has wondered about the same things and she says , `` at breakfast and at dinner , we can sharpen our own appetites with a plentiful dose of the pornography of war , genocide , destitution , and disease . '' she is right . we have sharpened our appetites , but we can also sharpen our insights . it is not always war , insurrection , and disease . this is a picture out of south sudan just a couple of months before the new country was born . i will continue to work as a researcher and a reporter in developing countries , but i do it with an altered ethic of seeing : i ask myself whether my pictures are pandering , whether they contribute to stereotypes , whether the images match the message , and am i complacent , or am i complicit ? thank you ( applause )

i do n't want to just pick on our friends in the gaming arts , i 'll turn to the graphic arts where we often see these monolithic , homogeneous stories about the great country of africa . but africa is not a country , it 's a continent . it 's 54 countries and thousands and thousands of languages .

dodson observes that the continent of africa encompasses

how do you know you 're real ? it 's an obvious question until you try to answer it , but let 's take it seriously . how do you really know you exist ? in his `` meditations on first philosophy , '' rené descartes tried to answer that very question , demolishing all his preconceived notions and opinions to begin again from the foundations . all his knowledge had come from his sensory perceptions of the world . same as you , right ? you know you 're watching this video with your eyes , hearing it with your ears . your senses show you the world as it is . they are n't deceiving you , but sometimes they do . you might mistake a person far away for someone else , or you 're sure you 're about to catch a flyball , and it hits the ground in front of you . but come on , right here and now , you know what 's right in front of you is real . your eyes , your hands , your body : that 's you . only crazy people would deny that , and you know you 're not crazy . anyone who 'd doubt that must be dreaming . oh no , what if you 're dreaming ? dreams feel real . you can believe you 're swimming , flying or fighting off monsters with your bare hands , when your real body is lying in bed . no , no , no . when you 're awake , you know you 're awake . ah ! but when you are n't , you do n't know you are n't , so you ca n't prove you are n't dreaming . maybe the body you perceive yourself to have is n't really there . maybe all of reality , even its abstract concepts , like time , shape , color and number are false , all just deceptions concocted by an evil genius ! no , seriously . descartes asks if you can disprove the idea that an evil genius demon has tricked you into believing reality is real . perhaps this diabolical deceiver has duped you . the world , your perceptions of it , your very body . you ca n't disprove that they 're all just made up , and how could you exist without them ? you could n't ! so , you do n't . life is but a dream , and i bet you are n't row , row , rowing the boat merrily at all , are you ? no , you 're rowing it wearily like the duped , nonexistent doof you are/are n't . do you find that convincing ? are you persuaded ? if you are n't , good ; if you are , even better , because by being persuaded , you would prove that you 're a persuaded being . you ca n't be nothing if you think you 're something , even if you think that something is nothing because no matter what you think , you 're a thinking thing , or as descartes put it , `` i think , therefore i am , '' and so are you , really . ( airplane engine )

how do you really know you exist ? in his `` meditations on first philosophy , '' rené descartes tried to answer that very question , demolishing all his preconceived notions and opinions to begin again from the foundations . all his knowledge had come from his sensory perceptions of the world . same as you , right ?

descartes rules out emotions and intuition as foundations for discovering truth . does this provide a fair understanding of human knowledge ?

your rich , eccentric uncle just passed away , and you and your 99 nasty relatives have been invited to the reading of his will . he wanted to leave all of his money to you , but he knew that if he did , your relatives would pester you forever . so he is banking on the fact that he taught you everything you need to know about riddles . your uncle left the following note in his will : `` i have created a puzzle . if all 100 of you answer it together , you will share the money evenly . however , if you are the first to find the pattern and solve the problem without going through all of the leg work , you will get the entire inheritance all to yourself . good luck . '' the lawyer takes you and your 99 relatives to a secret room in the mansion that contains 100 lockers , each hiding a single word . he explains : every relative is assigned a number from 1 to 100 . heir 1 will open every locker . heir 2 will then close every second locker . heir 3 will change the status of every third locker , specifically if it 's open , she 'll close it , but if it 's closed , she 'll open it . this pattern will continue until all 100 of you have gone . the words in the lockers that remain open at the end will help you crack the code for the safe . before cousin thaddeus can even start down the line , you step forward and tell the lawyer you know which lockers will remain open . but how ? pause the video now if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 the key is realizing that the number of times a locker is touched is the same as the number of factors in the locker number . for example , in locker # 6 , person 1 will open it , person 2 will close it , person 3 will open it , and person 6 will close it . the numbers 1 , 2 , 3 , and 6 are the factors of 6 . so when a locker has an even number of factors it will remain closed , and when it has an odd number of factors , it will remain open . most of the lockers have an even number of factors , which makes sense because factors naturally pair up . in fact , the only lockers that have an odd number of factors are perfect squares because those have one factor that when multiplied by itself equals the number . for locker 9 , 1 will open it , 3 will close , and 9 will open it . 3 x 3 = 9 , but the 3 can only be counted once . therefore , every locker that is a perfect square will remain open . you know that these ten lockers are the solution , so you open them immediately and read the words inside : `` the code is the first five lockers touched only twice . '' you realize that the only lockers touched twice have to be prime numbers since each only has two factors : 1 and itself . so the code is 2-3-5-7-11 . the lawyer brings you to the safe , and you claim your inheritance . too bad your relatives were always too busy being nasty to each other to pay attention to your eccentric uncle 's riddles .

3 x 3 = 9 , but the 3 can only be counted once . therefore , every locker that is a perfect square will remain open . you know that these ten lockers are the solution , so you open them immediately and read the words inside : `` the code is the first five lockers touched only twice . ''

what is the second locker to remain open ?

currently i think there are eight intelligences that i ’ m very confident about and a few more that i ’ ve bene thinking about . i ’ ll share that with our audience . the first two intelligences are the ones which iq tests and other kind of standardized tests valorize and as long as we know there are only two out of eight it ’ s perfectly fine to look at them . linguistic intelligence is how well you ’ re able to use language . it ’ s a kind of skill that poets have , other kinds of writers , journalists tend to have linguistic intelligence , orators . the second intelligence is logical mathematical intelligence . as the name implies logicians , mathematicians , scientists have that kind of intelligence . they ’ re able to do mathematical proofs . they ’ re able to do scientific reasoning and experimentation . and it ’ s great to have language and logical intelligence because most tests really focus on that . and if you do well in those tests as long as you stay in school you think you ’ re smart . but if you ever walk out into broadway or the highway or into the woods or into a farm you then find out that other intelligences are at least this important . so the third intelligence is musical intelligence and that ’ s the capacity to appreciate different kinds of musics , to produce the music by voice or by an instrument or to conduct music . and people say well music is a talent . it ’ s not an intelligence . and i say well why if you ’ re good with words is that an intelligence but if you ’ re good with tones and rhythms and timbres nobody ’ s ever given me a good answer which is why it makes sense to talk about musical intelligence . and at certain cultures over history musical intelligence has been very important . the fourth intelligence is spatial intelligence . that ’ s the intelligence which allows us to handle and work in space that ’ s close by . a chess player would have spatial intelligence . a surgeon would have spatial intelligence . but there ’ s another variety of spatial intelligence which we use for a much broader navigation . that ’ s what an airplane pilot or a sea captain would have . how do you find your way around large territory and large space . similarly with the fifth intelligence bodily kinesthetic intelligence it comes in two flavors . one flavor is the ability to use your whole body to solve problems or to make things . and athletes and dancers would have that kind of bodily kinesthetic intelligence . but another variety is being able to use your hands or other parts of your body to solve problems or make things . a craft person would have bodily kinesthetic intelligence even if they weren ’ t particularly a good athlete or dancer . the sixth intelligence and seventh intelligence have to do with human beings . interpersonal intelligence is how you understand other people , how you motivate them , how you lead them , how you work with them , how you cooperate with them . anybody at any workplace with other people needs interpersonal intelligence . leaders hopefully have a lot of interpersonal intelligence . but any intelligence can be used in a pernicious way so the salesman that sells you something you don ’ t want for a price you don ’ t want to pay , he or she has got interpersonal intelligence . it ’ s just not being used in a way that we might prefer . the seventh kind of intelligence is difficult to assess but it ’ s very important . it ’ s intrapersonal intelligence . it ’ s the understanding yourself . if we go back a way in history and prehistory knowledge of yourself probably wasn ’ t that important because people did what their parents or grandparents did whether they were hunters or fisherman or craftspeople . but nowadays especially in developed society people lead their own lives . we follow our own careers . we often switch careers . we don ’ t necessarily live at home as we get older . and if you don ’ t have a good understanding of yourself you are in big trouble . so that ’ s intrapersonal intelligence . the eighth intelligence which i added some years ago is the naturalist intelligence . and that ’ s the capacity to make important relevant discriminations in the world of nature between one plant and another , between one animal and another . it ’ s the intelligence of the naturalist , the intelligence of charles darwin . i missed it the first go around when i wrote about it but i tried to atone by adding it to my list . and by the way you might say well but nature isn ’ t so important anymore . but in fact everything we do in the commercial world uses our naturalist intelligence . why do i buy this jacket rather than another one ? this sweater rather than another one ? one hair style rather than another ? those all make just the naturalist intelligence because the brain is very adaptive . and when an old use of a brain center no longer is relevant it gets hijacked for something new . so we ’ re all using our naturalist intelligence even if we never walk out into the woods or into the savannah of east asia . the two other intelligences which i ’ m interested in , one of them is called the teaching or pedagogical intelligence . the intelligence which allows us to be able to teach successfully to other people . now you could have two people who have exactly the same expertise and knowledge in the field but one is a very good teacher and the other isn ’ t . that probably doesn ’ t surprise individuals so much . but what got me fascinated was as young as two or three kids already know how to teach . now what does that mean ? you show a child how to do something let ’ s say a three or four year old and then you ask the child to explain it to an older person or to a younger person . and even the three or four year old will explain it very differently to a young person , will go through details , point things and speak slowly . and with an older person it would be much more elliptical and say well you do this and that and then you can figure it out . so that shows as young as three let ’ s say we already have teaching intelligence . the other one is one which i think is going to be difficult to prove to a skeptic but i call it existential intelligence . and existential intelligence is the intelligence of big questions . philosophical questions , artistic questions . what does it mean to love ? why do we die ? what ’ s going to be in the future ? my pet bird might have more musical intelligence . the rats who are scurrying around the floor might have more spatial intelligence . but no other animals have existential intelligence . part of the human condition is to think about questions of existence . and i like to say every five year old has existential intelligence because five year old are always asking why this , why that . but the difference between a five year old and a philosopher is the five year old doesn ’ t pay too much attention to the answer whereas philosophers and other people who develop existential intelligence are really very interested in how we attack questions like that . so again where there ’ s eight intelligences or ten or twelve is less important to me than having broken the monopoly of a single intelligence which sort of labels you for all time . i think if we lived forever we could probably develop each intelligence to a very high degree . but life is very short and if you devote too much attention to one intelligence you ’ re not going to have much time to work on other kinds of intelligences . and so the big question is should you play to strength or should you bolster weakness ? and that ’ s a value judgment . scientists can not give you an answer to that . if , for example , you want to be a jack of all trades and be very well rounded then probably you ’ re going to want to nurture the intelligences which aren ’ t that strong . if on the other hand you ’ re dead set on really coming to the top of some particular heap then you ’ re probably going to find the intelligences that you ’ re strongest at and really push those . and , you know , if a parent came to me and said well should we supplement or should we accentuate i would say well tell me what you would like your child to do . or better let the child tell you what he or she wants to do rather than say well science says you should do one or the other . i think it ’ s a question of values , not of science . some people think there ’ s such a thing as humor intelligence . but , in fact , i don ’ t . i think humor intelligence is simply the operation of a logical intelligence in some realm like human nature or physical nature or the workplace . and what happens is in humor there ’ s a certain expectation and you flip that expectation so it ’ s logic but it ’ s logic that ’ s played out in different kinds of ways . people had mentioned there ’ s such a thing as a cooking intelligence , a humor intelligence and a sexual intelligence . and i quipped well that can ’ t be intelligences because i don ’ t have any of them .

interpersonal intelligence is how you understand other people , how you motivate them , how you lead them , how you work with them , how you cooperate with them . anybody at any workplace with other people needs interpersonal intelligence . leaders hopefully have a lot of interpersonal intelligence . but any intelligence can be used in a pernicious way so the salesman that sells you something you don ’ t want for a price you don ’ t want to pay , he or she has got interpersonal intelligence . it ’ s just not being used in a way that we might prefer .

what is interpersonal intelligence ? how can it be used in a pernicious way ?

indium is a very soft metal . i haven ’ t got a sample here . it melts at 150 degrees or so . this is an example of indium it is a really , really quite nice chemical element this one . we can use it for lots and lots of selective types of catalysis , but generally when it is forming a complex with other organic ligands . but here we can see a really nice example of indium and this is 99.9 % pure . but it ’ s a metal which has suddenly become very much more expensive because its oxide is transparent to light but will conduct electricity . so it is indium oxide that you find on every lcd display . here is a rather old computer and here is an old fashioned computer , the lcd display was quite small and gradually they have got bigger and bigger and therefore demand for indium oxide is more and more and probably you are watching this video clip through a thin layer of indium oxide . this sample although it ’ s very small , is 5 grams . so it is a really , really , dense metal , very , very expensive and very , very valuable as well . but indium is also used as solder for soldering various metals together and it is also quite useful if , i used it in my youth , when we were making low temperature apparatus and we wanted to screw two things together and get a nice seal in between them , you could screw them together with a thin sheet of indium , and that almost welded them together . so indium wire ; it is very , very malleable and very , very soft and very easy to form into shapes . i am not going to touch it though because it will cause some significant problems for me , because it does cause toxicity if it comes into contact with the skin ; so lovely piece of indium wire .

indium is a very soft metal . i haven ’ t got a sample here .

indium-113 and indium-115 are the 2 natural isotopes of this metal . what other radioactive isotope is used in medicine as a radiotracer to follow the movement of labeled proteins and white blood cells in the body ?

we live in a society obsessed with music . we use music to worship , tell stories , to celebrate , to work , exercise , declare our love and sometimes our hatred , and , arguably most importantly , to dance . and , of course , we play music ourselves because , well , it 's a pleasant thing to do . thousands of years ago in ancient greece , when it came to music , things were n't much different . they might have had lyres and tunics instead of mp3 players and jeans , but the ancient greeks were just as obsessed with music as we are today . in fact , music was such an important part of ancient greek society that it makes us seem tame by comparison . to really understand just how integral music was to the ancient greeks , let 's begin by acquainting ourselves with a bit of their mythology . in ancient greek mythology , it was believed that human creativity was the result of divine inspiration from a group of goddesses known as the muses . while scholars have argued over the years that there are anything between 3 and 13 muses , the standard number accepted today is 9 . each muse oversees her own specific area of artistic expertise , ranging from song and dance to history and astronomy . it might seem strange to categorize history and astronomy as creative pursuits , but the ancient greeks saw these disciplines as more than just school subjects . these were the hallmarks of civilization in what , to their eyes , was a pretty barbaric world . an educated , civilized person was expected to be proficient in all aspects of creative thought inspired by the muses , and the common medium through which these disciplines were taught , studied , and disseminated was music . you see , it 's no coincidence that the word muse is very similar to the word music . it 's where the word originates . poetry , be it a love poem or an epic poem about a dragon-slaying hero , was sung with a musical accompaniment . dancing and singing , obviously , were accompanied by music . theater was always a combination of spoken word and music . history was recounted through song . even the study of astronomy was linked to the same physical principles as musical harmony , such as the belief held by many greek thinkers that each of the planets and stars created their own unique sound as they traveled through the cosmos , thrumming like an enormous guitar string light-years long . however , music pervaded more aspects of their lives than just education . ancient greeks considered music to be the basis for understanding the fundamental interconnectedness of all things in the universe . this concept of connectivity is known as harmonia , and it 's where we get the word harmony . music was used as a form of medicine to treat illnesses and physical complaints , as a vital accompaniment to sporting contests , and as a means to keep workers in time as they toiled away on monotonous or menial tasks . one of the most important applications of music in ancient greek society is found in the belief that music can affect a person 's ethos . a word we still use today , ethos is a person 's guiding beliefs or personal ethics , the way that one behaves towards oneself and others . the greek philosopher plato , one of the most famous and influential greek thinkers of the time , asserted that music had a direct effect on a person 's ethos . certain kinds of music could incite a person to violence while others could placate a person into a benign , unthinking stupor . according to plato , only very specific types of music were beneficial to a person 's ethos . one should only listen to music that promotes intelligence , self-discipline , and courage , and all other kinds of music must be avoided . furthermore , plato fervently denounced any music that deviated from established musical conventions , fearing that doing so would lead to the degradation of the standards of civilization , the corruption of youth , and eventually complete and utter anarchy . while plato 's fears can seem extreme , this argument has appeared in modern times to condemn musical trends such as jazz or punk or rap . what do you think plato would say about the music you listen to ? is it beneficial to your ethos , or will it degenerate you into a gibbering , amoral barbarian ?

music was used as a form of medicine to treat illnesses and physical complaints , as a vital accompaniment to sporting contests , and as a means to keep workers in time as they toiled away on monotonous or menial tasks . one of the most important applications of music in ancient greek society is found in the belief that music can affect a person 's ethos . a word we still use today , ethos is a person 's guiding beliefs or personal ethics , the way that one behaves towards oneself and others .

what are some ways that you use or are exposed to music in daily life that someone from ancient greece would recognize ? are there ways that we use music today that an ancient greek citizen would find strange ?

translator : andrea mcdonough reviewer : bedirhan cinar hello , my name is christian rudder , and i was one of the founders of okcupid . it 's now one of the biggest dating sites in the united states . like most everyone at the site , i was a math major , as you may expect , we 're known for the analytic approach we take to love . we call it our matching algorithm . basically , okcupid 's matching algorithm helps us decide whether two people should go on a date . we built our entire business around it . now , algorithm is a fancy word , and people like to drop it like it 's this big thing . but really , an algorithm is just a systematic , step-by-step way to solve a problem . it does n't have to be fancy at all . here in this lesson , i 'm going to explain how we arrived at our particular algorithm , so you can see how it 's done . now , why are algorithms even important ? why does this lesson even exist ? well , notice one very significant phrase i used above : they are a step-by-step way to solve a problem , and as you probably know , computers excel at step-by-step processes . a computer without an algorithm is basically an expensive paperweight . and since computers are such a pervasive part of everyday life , algorithms are everywhere . the math behind okcupid 's matching algorithm is surprisingly simple . it 's just some addition , multiplication , a little bit of square roots . the tricky part in designing it was figuring out how to take something mysterious , human attraction , and break it into components that a computer can work with . the first thing we needed to match people up was data , something for the algorithm to work with . the best way to get data quickly from people is to just ask for it . so we decided that okcupid should ask users questions , stuff like , `` do you want to have kids one day ? '' `` how often do you brush your teeth ? '' `` do you like scary movies ? '' and big stuff like , `` do you believe in god ? '' now , a lot of the questions are good for matching like with like , that is , when both people answer the same way . for example , two people who are both into scary movies are probably a better match than one person who is and one who is n't . but what about a question like , `` do you like to be the center of attention ? '' if both people in a relationship are saying yes to this , they 're going to have massive problems . we realized this early on , and so we decided we needed a bit more data from each question . we had to ask people to specify not only their own answer , but the answer they wanted from someone else . that worked really well . but we needed one more dimension . some questions tell you more about a person than others . for example , a question about politics , something like , `` which is worse : book burning or flag burning ? '' might reveal more about someone than their taste in movies . and it does n't make sense to weigh all things equally , so we added one final data point . for everything that okcupid asks you , you have a chance to tell us the role it plays in your life . and this ranges from irrelevant to mandatory . so now , for every question , we have three things for our algorithm : first , your answer ; second , how you want someone else -- your potential match -- to answer ; and third , how important the question is to you at all . with all this information , okcupid can figure out how well two people will get along . the algorithm crunches the numbers and gives us a result . as a practical example , let 's look at how we 'd match you with another person . let 's call him `` b . '' your match percentage with b is based on questions you 've both answered . let 's call that set of common questions `` s. '' as a very simple example , we use a small set `` s '' with just two questions in common , and compute a match from that . here are our two example questions . the first one , let 's say , is , `` how messy are you ? '' and the answer possibilities are : very messy , average and very organized . and let 's say you answered `` very organized , '' and you 'd like someone else to answer `` very organized , '' and the question is very important to you . basically , you 're a neat freak . you 're neat , you want someone else to be neat , and that 's it . and let 's say b is a little bit different . he answered `` very organized '' for himself , but `` average '' is ok with him as an answer from someone else , and the question is only a little important to him . let 's look at the second question , from our previous example : `` do you like to be the center of attention ? '' the answers are `` yes '' and `` no . '' you 've answered `` no , '' you want someone else to answer `` no , '' and the question is only a little important to you . now b , he 's answered `` yes . '' he wants someone else to answer `` no , '' because he wants the spotlight on him , and the question is somewhat important to him . so , let 's try to compute all of this . our first step is , since we use computers to do this , we need to assign numerical values to ideas like `` somewhat important '' and `` very important , '' because computers need everything in numbers . we at okcupid decided on the following scale : `` irrelevant '' is worth 0 . `` a little important '' is worth 1 . `` somewhat important '' is worth 10 . `` very important '' is 50 . and `` absolutely mandatory '' is 250 . next , the algorithm makes two simple calculations . the first is : how much did b 's answers satisfy you ? that is , how many possible points did b score on your scale ? well , you indicated that b 's answer to the first question , about messiness , was very important to you . it 's worth 50 points and b got that right . the second question is worth only 1 , because you said it was only a little important . b got that wrong , so b 's answers were 50 out of 51 possible points . that 's 98 % satisfactory . pretty good . the second question the algorithm looks at is : how much did you satisfy b ? well , b placed 1 point on your answer to the messiness question and 10 on your answer to the second . of those 11 , that 's 1 plus 10 , you earned 10 -- you guys satisfied each other on the second question . so your answers were 10 out of 11 equals 91 percent satisfactory to b . that 's not bad . the final step is to take these two match percentages and get one number for the both of you . to do this , the algorithm multiplies your scores , then takes the nth root , where `` n '' is the number of questions . because s , which is the number of questions in this sample , is only 2 , we have : match percentage equals the square root of 98 percent times 91 percent . that equals 94 percent . that 94 percent is your match percentage with b . it 's a mathematical expression of how happy you 'd be with each other , based on what we know . now , why does the algorithm multiply , as opposed to , say , average the two match scores together , and do the square-root business ? in general , this formula is called the geometric mean . it 's a great way to combine values that have wide ranges and represent very different properties . in other words , it 's perfect for romantic matching . you 've got wide ranges and you 've got tons of different data points , like i said , about movies , politics , religion -- everything . intuitively , too , this makes sense . two people satisfying each other 50 percent should be a better match than two others who satisfy 0 and 100 , because affection needs to be mutual . after adding a little correction for margin of error , in the case where we have a small number of questions , like we do in this example , we 're good to go . any time okcupid matches two people , it goes through the steps we just outlined . first it collects data about your answers , then it compares your choices and preferences to other people 's in simple , mathematical ways . this , the ability to take real-world phenomena and make them something a microchip can understand , is , i think , the most important skill anyone can have these days . like you use sentences to tell a story to a person , you use algorithms to tell a story to a computer . if you learn the language , you can go out and tell your stories . i hope this will help you do that .

if both people in a relationship are saying yes to this , they 're going to have massive problems . we realized this early on , and so we decided we needed a bit more data from each question . we had to ask people to specify not only their own answer , but the answer they wanted from someone else .

what was the last data point that okcupid needed from each question ?

the earth intercepts a lot of solar power : 173 thousand terawatts . that 's ten thousand times more power than the planet 's population uses . so is it possible that one day the world could be completely reliant on solar energy ? to answer that question , we first need to examine how solar panels convert solar energy to electrical energy . solar panels are made up of smaller units called solar cells . the most common solar cells are made from silicon , a semiconductor that is the second most abundant element on earth . in a solar cell , crystalline silicon is sandwiched between conductive layers . each silicon atom is connected to its neighbors by four strong bonds , which keep the electrons in place so no current can flow . here 's the key : a silicon solar cell uses two different layers of silicon . an n-type silicon has extra electrons , and p-type silicon has extra spaces for electrons , called holes . where the two types of silicon meet , electrons can wander across the p/n junction , leaving a positive charge on one side and creating negative charge on the other . you can think of light as the flow of tiny particles called photons , shooting out from the sun . when one of these photons strikes the silicon cell with enough energy , it can knock an electron from its bond , leaving a hole . the negatively charged electron and location of the positively charged hole are now free to move around . but because of the electric field at the p/n junction , they 'll only go one way . the electron is drawn to the n-side , while the hole is drawn to the p-side . the mobile electrons are collected by thin metal fingers at the top of the cell . from there , they flow through an external circuit , doing electrical work , like powering a lightbulb , before returning through the conductive aluminum sheet on the back . each silicon cell only puts out half a volt , but you can string them together in modules to get more power . twelve photovoltaic cells are enough to charge a cellphone , while it takes many modules to power an entire house . electrons are the only moving parts in a solar cell , and they all go back where they came from . there 's nothing to get worn out or used up , so solar cells can last for decades . so what 's stopping us from being completely reliant on solar power ? there are political factors at play , not to mention businesses that lobby to maintain the status quo . but for now , let 's focus on the physical and logistical challenges , and the most obvious of those is that solar energy is unevenly distributed across the planet . some areas are sunnier than others . it 's also inconsistent . less solar energy is available on cloudy days or at night . so a total reliance would require efficient ways to get electricity from sunny spots to cloudy ones , and effective storage of energy . the efficiency of the cell itself is a challenge , too . if sunlight is reflected instead of absorbed , or if dislodged electrons fall back into a hole before going through the circuit , that photon 's energy is lost . the most efficient solar cell yet still only converts 46 % of the available sunlight to electricity , and most commercial systems are currently 15-20 % efficient . in spite of these limitations , it actually would be possible to power the entire world with today 's solar technology . we 'd need the funding to build the infrastructure and a good deal of space . estimates range from tens to hundreds of thousands of square miles , which seems like a lot , but the sahara desert alone is over 3 million square miles in area . meanwhile , solar cells are getting better , cheaper , and are competing with electricity from the grid . and innovations , like floating solar farms , may change the landscape entirely . thought experiments aside , there 's the fact that over a billion people do n't have access to a reliable electric grid , especially in developing countries , many of which are sunny . so in places like that , solar energy is already much cheaper and safer than available alternatives , like kerosene . for say , finland or seattle , though , effective solar energy may still be a little way off .

to answer that question , we first need to examine how solar panels convert solar energy to electrical energy . solar panels are made up of smaller units called solar cells . the most common solar cells are made from silicon , a semiconductor that is the second most abundant element on earth .

what is the carrier of the electric current from solar cells ?

caffeine a legal stimulant that most of us are pretty familiar with , many of us use every day , and some of us are addicted to . if you are a caffeine user , you probably know your limits . for me one small cup of coffee in the morning can help keep me alert and focused , whereas two small cups of coffee in the morning can turn me into a cat on catnip . well for the purposes of this video and to best demonstrate the physical and mental effects of caffeine , i 'm going to get very very caffeinated very very fast . for science . go big or go home . caffeine is a stimulant drug that acts on your central nervous system . because caffeine is both lipid and water soluble it can easily pass through the blood-brain barrier and act on the interior of your brain once there , caffeine works by diminishing the effect of a neurotransmitter called adenosine . adenosine acts as a suppressor for your nervous system , reducing neural activity and slowing everything down . caffeine and adenosine have similar shapes so caffeine can bind to the same neuroreceptors that adenosine does . but because caffeine is not adenosine , it does n't turn these neuroreceptors on . this is called competitive inhibition . caffeine competes with adenosine to bind with the same receptors , and because caffeine is bound , adenosine can not bind and its effects are inhibited . long story short , caffeine prevents adenosine from slowing down your nervous system . so this explain part of why you feel more awake , alert and active with caffeine flowing through your veins . but adenosine inhibition is n't the only thing that caffeine does . oh no . caffeine also stimulates the production of adrenaline or epinephrine . adrenaline is a pretty well known hormone involved in the fight-or-flight response . it causes all sort of physiological reactions ! it increases your heart rate , increases the blood flow to your muscles , opens up your airways , causes your blood pressure to rise , and also causes you 're your liver to release extra sugar into your blood stream for an added boost of energy . it also causes your muscle to tighten up , which would be useful if you were the lone human on the savannah , deciding or not to fight or flee from that lion over the distance , but as a modern twenty something sitting in from of my camera , it just give me the jitters . finally caffeine also plays with the dopamine levels in your brain . awesome , yeah . caffeine increases the amount of dopamine present in your brain by slowing down its reabsorption , much in the same way that cocaine increases the amount of dopamine present by slowing down how quickly it can be sucked back into your brain tissue . this means that caffeine also makes you feel good and this interaction with dopamine is how you can actually build a caffeine addiction . so now you 're a happy , jittery , fight or flight ready bundle caffeine ! now what ? well the now what really depends on how your specific body metabolizes caffeine . the average half-life of caffeine in the human body is about six hours . so this means that if you have two hundred milligrams of caffeine in your average cup of coffee at 9am in the morning , then 6 hours later half of that will be left , so at 3pm you will have a hundred milligrams of caffeine left , and then another 6 hours later you will have half of the hundred you will have half of the hundred so you will have 50 milligrams of caffeine left at 9 o'clock at night . but dude , who stops at just one cup of coffee ? not this chick . so how much caffeine is too much caffeine ? a lethal dose of caffeine is about two hundred milligrams per kilogram so it would take about nine thousand five hundred milligrams of caffeine to kill me . now , there are about two hundred milligrams of caffeine in a standard cup of coffee , so that 's about forty eight cups of coffee , which is a surprisingly low number , but i would have to drink all 48 of those before my body started to metabolize the caffeine , which means i would literally have to chug 48 cups of coffee . i literally would n't be able to drink that much coffee , both because my stomach could n't hold that volume of liquid and also because as every coffee drinker knows , caffeine is a diuretic . before i got to cup forty anyways , the stimulant effect of caffeine would be jacked up so high that that the alertness and awakeness would be transformed into mania , disorientation and hallucinations ... great ! what would eventually kill you would be ventricular fibrillation , which basically means that your heart would caffeine jitter itself to death . so moral of the story , caffeine is a drug . it is a stimulant that has some pretty noticeable effects on your body , can cause addiction , and , in high enough doses , can kill you . so caffeinate wisely ! go forth , do science ! my hand is actually not shaking too bad right now . do n't try this at home , i know a lot of people do drink that much caffeine all on one day and sometimes i approach it , but i certainly do n't do it over the span of 20 minutes . i actually do n't feel as terrible as i thought i would have after that amount , but i certainly do n't feel good either .

well the now what really depends on how your specific body metabolizes caffeine . the average half-life of caffeine in the human body is about six hours . so this means that if you have two hundred milligrams of caffeine in your average cup of coffee at 9am in the morning , then 6 hours later half of that will be left , so at 3pm you will have a hundred milligrams of caffeine left , and then another 6 hours later you will have half of the hundred you will have half of the hundred so you will have 50 milligrams of caffeine left at 9 o'clock at night .

what is the half-life of caffeine in the average human body ?

with every year , machines surpass humans in more and more activities we once thought only we were capable of . today 's computers can beat us in complex board games , transcribe speech in dozens of languages , and instantly identify almost any object . but the robots of tomorrow may go futher by learning to figure out what we 're feeling . and why does that matter ? because if machines and the people who run them can accurately read our emotional states , they may be able to assist us or manipulate us at unprecedented scales . but before we get there , how can something so complex as emotion be converted into mere numbers , the only language machines understand ? essentially the same way our own brains interpret emotions , by learning how to spot them . american psychologist paul ekman identified certain universal emotions whose visual cues are understood the same way across cultures . for example , an image of a smile signals joy to modern urban dwellers and aboriginal tribesmen alike . and according to ekman , anger , disgust , fear , joy , sadness , and surprise are equally recognizable . as it turns out , computers are rapidly getting better at image recognition thanks to machine learning algorithms , such as neural networks . these consist of artificial nodes that mimic our biological neurons by forming connections and exchanging information . to train the network , sample inputs pre-classified into different categories , such as photos marked happy or sad , are fed into the system . the network then learns to classify those samples by adjusting the relative weights assigned to particular features . the more training data it 's given , the better the algorithm becomes at correctly identifying new images . this is similar to our own brains , which learn from previous experiences to shape how new stimuli are processed . recognition algorithms are n't just limited to facial expressions . our emotions manifest in many ways . there 's body language and vocal tone , changes in heart rate , complexion , and skin temperature , or even word frequency and sentence structure in our writing . you might think that training neural networks to recognize these would be a long and complicated task until you realize just how much data is out there , and how quickly modern computers can process it . from social media posts , uploaded photos and videos , and phone recordings , to heat-sensitive security cameras and wearables that monitor physiological signs , the big question is not how to collect enough data , but what we 're going to do with it . there are plenty of beneficial uses for computerized emotion recognition . robots using algorithms to identify facial expressions can help children learn or provide lonely people with a sense of companionship . social media companies are considering using algorithms to help prevent suicides by flagging posts that contain specific words or phrases . and emotion recognition software can help treat mental disorders or even provide people with low-cost automated psychotherapy . despite the potential benefits , the prospect of a massive network automatically scanning our photos , communications , and physiological signs is also quite disturbing . what are the implications for our privacy when such impersonal systems are used by corporations to exploit our emotions through advertising ? and what becomes of our rights if authorities think they can identify the people likely to commit crimes before they even make a conscious decision to act ? robots currently have a long way to go in distinguishing emotional nuances , like irony , and scales of emotions , just how happy or sad someone is . nonetheless , they may eventually be able to accurately read our emotions and respond to them . whether they can empathize with our fear of unwanted intrusion , however , that 's another story .

there 's body language and vocal tone , changes in heart rate , complexion , and skin temperature , or even word frequency and sentence structure in our writing . you might think that training neural networks to recognize these would be a long and complicated task until you realize just how much data is out there , and how quickly modern computers can process it . from social media posts , uploaded photos and videos , and phone recordings , to heat-sensitive security cameras and wearables that monitor physiological signs , the big question is not how to collect enough data , but what we 're going to do with it .

a major problem for self-driving cars would be :

what do fans of atmospheric post-punk music have in common with ancient barbarians ? not much . so why are both known as goths ? is it a weird coincidence or a deeper connection stretching across the centuries ? the story begins in ancient rome . as the roman empire expanded , it faced raids and invasions from the semi-nomadic populations along its borders . among the most powerful were a germanic people known as goths who were composed of two tribal groups , the visigoths and ostrogoths . while some of the germanic tribes remained rome 's enemies , the empire incorporated others into the imperial army . as the roman empire split in two , these tribal armies played larger roles in its defense and internal power struggles . in the 5th century , a mercenary revolt lead by a soldier named odoacer captured rome and deposed the western emperor . odoacer and his ostrogoth successor theoderic technically remained under the eastern emperor 's authority and maintained roman traditions . but the western empire would never be united again . its dominions fragmented into kingdoms ruled by goths and other germanic tribes who assimilated into local cultures , though many of their names still mark the map . this was the end of the classical period and the beginning of what many call the dark ages . although roman culture was never fully lost , its influence declined and new art styles arose focused on religious symbolism and allegory rather than proportion and realism . this shift extended to architecture with the construction of the abbey of saint denis in france in 1137 . pointed arches , flying buttresses , and large windows made the structure more skeletal and ornate . that emphasized its open , luminous interior rather than the sturdy walls and columns of classical buildings . over the next few centuries , this became a model for cathedrals throughout europe . but fashions change . with the italian renaissance 's renewed admiration for ancient greece and rome , the more recent style began to seem crude and inferior in comparison . writing in his 1550 book , `` lives of the artists , '' giorgio vasari was the first to describe it as gothic , a derogatory reference to the barbarians thought to have destroyed classical civilization . the name stuck , and soon came to describe the medieval period overall , with its associations of darkness , superstition , and simplicity . but time marched on , as did what was considered fashionable . in the 1700s , a period called the enlightenment came about , which valued scientific reason above all else . reacting against that , romantic authors like goethe and byron sought idealized visions of a past of natural landscapes and mysterious spiritual forces . here , the word gothic was repurposed again to describe a literary genre that emerged as a darker strain of romanticism . the term was first applied by horace walpole to his own 1764 novel , `` the castle of otranto '' as a reference to the plot and general atmosphere . many of the novel 's elements became genre staples inspiring classics and the countless movies they spawned . the gothic label belonged to literature and film until the 1970s when a new musical scene emerged . taking cues from artists like the doors and the velvet underground , british post-punk groups , like joy division , bauhaus , and the cure , combined gloomy lyrics and punk dissonance with imagery inspired by the victorian era , classic horror , and androgynous glam fashion . by the early 1980s , similar bands were consistently described as gothic rock by the music press , and the stye 's popularity brought it out of dimly lit clubs to major labels and mtv . and today , despite occasional negative media attention and stereotypes , gothic music and fashion continue as a strong underground phenomenon . they 've also branched into sub-genres , such as cybergoth , gothabilly , gothic metal , and even steampunk . the history of the word gothic is embedded in thousands of years worth of countercultural movements , from invading outsiders becoming kings to towering spires replacing solid columns to artists finding beauty in darkness . each step has seen a revolution of sorts and a tendency for civilization to reach into its past to reshape its present .

here , the word gothic was repurposed again to describe a literary genre that emerged as a darker strain of romanticism . the term was first applied by horace walpole to his own 1764 novel , `` the castle of otranto '' as a reference to the plot and general atmosphere . many of the novel 's elements became genre staples inspiring classics and the countless movies they spawned .

the term “ gothic ” was first used as a derogatory term during the :

a , c , e , d , b , k. no , this is n't some random , out of order alphabet . these are vitamins , and just like letters build words , they 're the building blocks that keep the body running . vitamins are organic compounds we need to ingest in small amounts to keep functioning . they 're the body 's builders , defenders and maintenance workers , helping it to build muscle and bone , make use of nutrients , capture and use energy and heal wounds . if you need convincing about vitamin value , just consider the plight of olden day sailors , who had no access to vitamin-rich fresh produce . they got scurvy . but vitamin c , abundant in fruits and vegetables , was the simple antidote to this disease . while bacteria , fungi and plants produce their own vitamins , our bodies ca n't , so we have to get them from other sources . so how does the body get vitamins from out there into here ? that 's dependent on the form these compounds take . vitamins come in two types : lipid-soluble and water-soluble , and the difference between them determines how the body transports and stores vitamins , and gets rid of the excess . the water-solubles are vitamin c and b complex vitamins that are made up of eight different types that each do something unique . these are dissolved in the watery parts of fruits , vegetables and grains , meaning their passage through the body is relatively straightforward . once inside the system , these foods are digested and the vitamins within them are taken up directly by the bloodstream . because blood plasma is water-based , water-soluble vitamins c and b have their transport cut out for them and can move around freely within the body . for lipid-soluble vitamins , dissolved in fat and found in foods like diary , butter and oils , this trip into the blood is a little more adventurous . these vitamins make it through the stomach and the intestine , where an acidic substance called bile flows in from the liver , breaking up the fat and preparing it for absorption through the intestinal wall . because fat-soluble vitamins ca n't make use of the blood 's watery nature , they need something else to move them around , and that comes from proteins that attach to the vitamins and act like couriers , transporting fat-solubles into the blood and around the body . so , this difference between water- or fat-soluble vitamins determines how they get into the blood , but also how they 're stored or rejected from the body . the system 's ability to circulate water-soluble vitamins in the bloodstream so easily means that most of them can be passed out equally easily via the kidneys . because of that , most water-soluble vitamins need to be replenished on a daily basis through the food we eat . but fat-soluble vitamins have staying power because they can be packed into the liver and in fat cells . the body treats these parts like a pantry , storing the vitamins there and rationing them out when needed , meaning we should n't overload on this type of vitamin because the body is generally well stocked . once we figured the logistics of transport and storage , the vitamins are left to do the work they came here to do in the first place . some , like many of the b complex vitamins , make up coenzymes , whose job it is to help enzymes release the energy from food . other b vitamins then help the body to use that energy . from vitamin c , you get the ability to fight infection and make collagen , a kind of tissue that forms bones and teeth and heals wounds . vitamin a helps make white blood cells , key in the body 's defense , helps shape bones and improves vision by keeping the cells of the eye in check . vitamin d gathers calcium and phosphorus so we can make bones , and vitamin e works as an antioxidant , getting rid of elements in the body that can damage cells . finally , from vitamin k , we score the ability to clot blood , since it helps make the proteins that do this job . without this vitamin variety , humans face deficiencies that cause a range of problems , like fatigue , nerve damage , heart disorders , or diseases like rickets and scurvy . on the other hand , too much of any vitamin can cause toxicity in the body , so there goes the myth that loading yourself with supplements is a great idea . in reality , it 's all about getting the balance right , and hitting that vitamin jackpot .

finally , from vitamin k , we score the ability to clot blood , since it helps make the proteins that do this job . without this vitamin variety , humans face deficiencies that cause a range of problems , like fatigue , nerve damage , heart disorders , or diseases like rickets and scurvy . on the other hand , too much of any vitamin can cause toxicity in the body , so there goes the myth that loading yourself with supplements is a great idea .

humans need the correct amount of vitamins to function . too much or too little of any one vitamin can cause problems . list five vitamins and problems associated with too much of each one .

are you afraid of black cats ? would you open an umbrella indoors ? and how do you feel about the number thirteen ? whether or not you believe in them , you 're probably familiar with a few of these superstitions . so how did it happen that people all over the world knock on wood , or avoid stepping on sidewalk cracks ? well , although they have no basis in science , many of these weirdly specific beliefs and practices do have equally weird and specific origins . because they involve supernatural causes , it 's no surprise that many superstitions are based in religion . for example . the number thirteen was associated with the biblical last supper , where jesus christ dined with his twelve disciples just before being arrested and crucified . the resulting idea that having thirteen people at a table was bad luck eventually expanded into thirteen being an unlucky number in general . now , this fear of the number thirteen , called triskaidekaphobia , is so common that many buildings around the world skip the thirteenth floor , with the numbers going straight from twelve to fourteen . of course , many people consider the story of the last supper to be true but other superstitions come from religious traditions that few people believe in or even remember . knocking on wood is thought to come from the folklore of the ancient indo-europeans or possibly people who predated them who believed that trees were home to various spirits . touching a tree would invoke the protection or blessing of the spirit within . and somehow , this tradition survived long after belief in these spirits had faded away . many superstitions common today in countries from russia to ireland are thought to be remnants of the pagan religions that christianity replaced . but not all superstitions are religious . some are just based on unfortunate coincidences and associations . for example , many italians fear the number 17 because the roman numeral xvii can be rearranged to form the word vixi , meaning my life had ended . similarly , the word for the number four sounds almost identical to the word for death in cantonese , as well as languages like japanese and korean that have borrowed chinese numerals . and since the number one also sounds like the word for must , the number fourteen sounds like the phrase must die . that 's a lot of numbers for elevators and international hotels to avoid . and believe it or not , some superstitions actually make sense , or at least they did until we forgot their original purpose . for example , theater scenery used to consist of large painted backdrops , raised and lowered by stagehands who would whistle to signal each other . absentminded whistles from other people could cause an accident . but the taboo against whistling backstage still exists today , long after the stagehands started using radio headsets . along the same lines , lighting three cigarettes from the same match really could cause bad luck if you were a soldier in a foxhole where keeping a match lit too long could draw attention from an enemy sniper . most smokers no longer have to worry about snipers , but the superstition lives on . so why do people cling to these bits of forgotten religions , coincidences , and outdated advice ? are n't they being totally irrational ? well , yes , but for many people , superstitions are based more on cultural habit than conscious belief . after all , no one is born knowing to avoid walking under ladders or whistling indoors , but if you grow up being told by your family to avoid these things , chances are they 'll make you uncomfortable , even after you logically understand that nothing bad will happen . and since doing something like knocking on wood does n't require much effort , following the superstition is often easier than consciously resisting it . besides , superstitions often do seem to work . maybe you remember hitting a home run while wearing your lucky socks . this is just our psychological bias at work . you 're far less likely to remember all the times you struck out while wearing the same socks . but believing that they work could actually make you play better by giving you the illusion of having greater control over events . so in situations where that confidence can make a difference , like sports , those crazy superstitions might not be so crazy after all .

and somehow , this tradition survived long after belief in these spirits had faded away . many superstitions common today in countries from russia to ireland are thought to be remnants of the pagan religions that christianity replaced . but not all superstitions are religious .

many common superstitions come from history of :

you and nine other individuals have been captured by super intelligent alien overlords . the aliens think humans look quite tasty , but their civilization forbids eating highly logical and cooperative beings . unfortunately , they 're not sure whether you qualify , so they decide to give you all a test . through its universal translator , the alien guarding you tells you the following : you will be placed in a single-file line facing forward in size order so that each of you can see everyone lined up ahead of you . you will not be able to look behind you or step out of line . each of you will have either a black or a white hat on your head assigned randomly , and i wo n't tell you how many of each color there are . when i say to begin , each of you must guess the color of your hat starting with the person in the back and moving up the line . and do n't even try saying words other than black or white or signaling some other way , like intonation or volume ; you 'll all be eaten immediately . if at least nine of you guess correctly , you 'll all be spared . you have five minutes to discuss and come up with a plan , and then i 'll line you up , assign your hats , and we 'll begin . can you think of a strategy guaranteed to save everyone ? pause the video now to figure it out for yourself . answer in : 3 answer in : 2 answer in : 1 the key is that the person at the back of the line who can see everyone else 's hats can use the words `` black '' or `` white '' to communicate some coded information . so what meaning can be assigned to those words that will allow everyone else to deduce their hat colors ? it ca n't be the total number of black or white hats . there are more than two possible values , but what does have two possible values is that number 's parity , that is whether it 's odd or even . so the solution is to agree that whoever goes first will , for example , say `` black '' if he sees an odd number of black hats and `` white '' if he sees an even number of black hats . let 's see how it would play out if the hats were distributed like this . the tallest captive sees three black hats in front of him , so he says `` black , '' telling everyone else he sees an odd number of black hats . he gets his own hat color wrong , but that 's okay since you 're collectively allowed to have one wrong answer . prisoner two also sees an odd number of black hats , so she knows hers is white , and answers correctly . prisoner three sees an even number of black hats , so he knows that his must be one of the black hats the first two prisoners saw . prisoner four hears that and knows that she should be looking for an even number of black hats since one was behind her . but she only sees one , so she deduces that her hat is also black . prisoners five through nine are each looking for an odd number of black hats , which they see , so they figure out that their hats are white . now it all comes down to you at the front of the line . if the ninth prisoner saw an odd number of black hats , that can only mean one thing . you 'll find that this strategy works for any possible arrangement of the hats . the first prisoner has a 50 % chance of giving a wrong answer about his own hat , but the parity information he conveys allows everyone else to guess theirs with absolute certainty . each begins by expecting to see an odd or even number of hats of the specified color . if what they count does n't match , that means their own hat is that color . and everytime this happens , the next person in line will switch the parity they expect to see . so that 's it , you 're free to go . it looks like these aliens will have to go hungry , or find some less logical organisms to abduct .

the tallest captive sees three black hats in front of him , so he says `` black , '' telling everyone else he sees an odd number of black hats . he gets his own hat color wrong , but that 's okay since you 're collectively allowed to have one wrong answer . prisoner two also sees an odd number of black hats , so she knows hers is white , and answers correctly .

how many wrong guesses is the group allowed to have ?

as 1905 dawned , the soon-to-be 26-year-old albert einstein faced life as a failed academic . most physicists of the time would have scoffed at the idea that this minor civil servant could have much to contribute to science . yet within the following year , einstein would publish not one , not two , not three , but four extraordinary papers , each on a different topic , that were destined to radically transform our understanding of the universe . the myth that einstein had failed math is just that . he had mastered calculus on his own by the age of 15 and done well at both his munich secondary school and at the swiss polytechnic , where he studied for a math and physics teaching diploma . but skipping classes to spend more time in the lab and neglecting to show proper deference to his professors had derailed his intended career path . passed over even for a lab assistant position , he had to settle for a job at the swiss patent office , obtained with the help of a friend 's father . working six days a week as a patent clerk , einstein still managed to make some time for physics , discussing the latest work with a few close friends , and publishing a couple of minor papers . it came as a major surprise when in march 1905 he submitted a paper with a shocking hypothesis . despite decades of evidence that light was a wave , einstein proposed that it could , in fact , be a particle , showing that mysterious phenomena , such as the photoelectric effect , could be explained by his hypothesis . the idea was derided for years to come , but einstein was simply twenty years ahead of his time . wave-particle duality was slated to become a cornerstone of the quantum revolution . two months later in may , einstein submitted a second paper , this time tackling the centuries old question of whether atoms actually exist . though certain theories were built on the idea of invisible atoms , some prominent scientists still believed them to be a useful fiction , rather than actual physical objects . but einstein used an ingenious argument , showing that the behavior of small particles randomly moving around in a liquid , known as brownian motion , could be precisely predicted by the collisions of millions of invisible atoms . experiments soon confirmed einstein 's model , and atomic skeptics threw in the towel . the third paper came in june . for a long time , einstein had been troubled by an inconsistency between two fundamental principles of physics . the well established principle of relativity , going all the way back to galileo , stated that absolute motion could not be defined . yet electromagnetic theory , also well established , asserted that absolute motion did exist . the discrepancy , and his inability to resolve it , left einstein in what he described as a state of psychic tension . but one day in may , after he had mulled over the puzzle with his friend michele besso , the clouds parted . einstein realized that the contradiction could be resolved if it was the speed of light that remained constant , regardless of reference frame , while both time and space were relative to the observer . it took einstein only a few weeks to work out the details and formulate what came to be known as special relativity . the theory not only shattered our previous understanding of reality but would also pave the way for technologies , ranging from particle accelerators , to the global positioning system . one might think that this was enough , but in september , a fourth paper arrived as a `` by the way '' follow-up to the special relativity paper . einstein had thought a little bit more about his theory , and realized it also implied that mass and energy , one apparently solid and the other supposedly ethereal , were actually equivalent . and their relationship could be expressed in what was to become the most famous and consequential equation in history : e=mc^2 . einstein would not become a world famous icon for nearly another fifteen years . it was only after his later general theory of relativity was confirmed in 1919 by measuring the bending of starlight during a solar eclipse that the press would turn him into a celebrity . but even if he had disappeared back into the patent office and accomplished nothing else after 1905 , those four papers of his miracle year would have remained the gold standard of startling unexpected genius .

as 1905 dawned , the soon-to-be 26-year-old albert einstein faced life as a failed academic . most physicists of the time would have scoffed at the idea that this minor civil servant could have much to contribute to science .

einstein 's first `` miracle year '' paper , in march 1905 , put forth a surprising idea . he proposed that :

translator : jessica ruby reviewer : caroline cristal russia , with the largest territory in the world , has roughly the same total population as nigeria , a country 1/16 its size . but this similarity wo n't last long . one of the populations is rapidly growing , while the other is slowly declining . what can this tell us about the two countries ? population statistics are some of the most important data social scientists and policy experts have to work with . but understanding a country 's situation and making accurate predictions requires knowing not just the total size of the population but its internal characteristics , such as age and gender distribution . so , how can we keep track of all that data in a way that makes it easy to comprehend ? complex data is more easily interpreted through visualization , and one of the ways that demographers represent the internal distribution of a population is the population pyramid . here , the data is divided by gender with females on one side and males on the other . the population numbers are shown for each five-year age interval , starting from 0-4 and continuing up to 100 and up . these intervals are grouped together into pre-reproductive ( 0-14 ) , reproductive ( 15-44 ) , and post-reproductive years ( 45 and up ) . such a population pyramid can be a powerful predictor of future population trends . for example , rwanda 's population pyramid shows it to be a fast-growing country , with most of the population being in the youngest age groups at the bottom of the pyramid . the number will grow rapidly in the coming years . as today 's children reach their reproductive years and have children of their own , the total population is almost certain to double within the next few decades . for our second example , let 's look at canada , where most of the population is clustered around the middle of the graph . because there are less people in the pre-reproductive age groups than there are in the reproductive ones , the population will grow more slowly , as the number of people reaching their reproductive years decreases . finally , let 's look at japan . because the majority of its population is in its post-reproductive years and the number of people is smaller at each younger interval , this means that at current rates of reproduction the population will begin to decline as fewer and fewer people reach reproductive age . comparing these three population pyramids side by side shows us three different stages in a demographic transition , as a country moves from a pre-industrial society to one with an industrial or post-industrial economy . countries that have only recently begun the process of industrialization typically see an increase in life expectancy and a fall in child mortality rates as a result of improvements in medicine , sanitation , and food supply . while birth rates remain constant , leading to a population boom . developing countries that are farther along in the industrialization process begin to see a fall in birth rates , due to factors such as increased education and opportunities for women outside of child-rearing and a move from rural to urban living that makes having large families less economically advantageous . finally , countries in advanced stages of industrialization reach a point where both birth and death rates are low , and the population remains stable or even begins to decline . now , let 's take a look at the projected population pyramids for the same three countries in 2050 . what do these tell us about the expected changes in each country 's population , and what kinds of factors can alter the shape of these future pyramids ? a population pyramid can be useful not only as a predictor of a country 's future but as a record of its past . russia 's population pyramid still bears the scars of world war ii , which explains both the fewer numbers of elderly men compared to elderly women and the relatively sudden population increase as soldiers returned from the war and normal life resumed . china 's population pyramid reflects the establishment of the one child policy 35 years before , which prevented a population boom such as that of rwanda but also led to sex-selective abortions , resulting in more male children than female children . finally , the pyramid for the united states shows the baby boom that followed world war ii . as you can see , population pyramids tell us far more about a country than just a set of numbers , by showing both where it 's been and where it 's headed within a single image . and in today 's increasingly interconnected world , facing issues such as food shortages , ecological threats , and economic disparities , it is increasingly important for both scientists and policy makers to have a rich and complex understanding of populations and the factors affecting them .

finally , countries in advanced stages of industrialization reach a point where both birth and death rates are low , and the population remains stable or even begins to decline . now , let 's take a look at the projected population pyramids for the same three countries in 2050 . what do these tell us about the expected changes in each country 's population , and what kinds of factors can alter the shape of these future pyramids ? a population pyramid can be useful not only as a predictor of a country 's future but as a record of its past .

what factors might account for differences in population pyramids between cities within the same country ?

so , you 're thinking of moving to mars . have you picked out a spot for your new home ? no ? well , i 'm here to help . first things first , here are some of the things you 'll need to bring to the red planet : a high tolerance for cold , loneliness , and radiation ; a lifetime supply of breathable air and food ; a multibillion dollar spaceship ; a desire to just get away from it all ; and water . you 're definitely going to need water . so what sort of real estate are you looking for ? how about a mansion in the maze-like noctis labyrinthus ? a hideaway in the happy face crater ? a fortress on the face mesa ? an oceanview ? uh , bad news on the last one . you 're about 4 billion years late . we 're pretty sure that mars used to have oceans , lakes , rivers , the whole package . but over time , almost all of it froze beneath the surface , or evaporated off into space . there 's probably still some trapped beneath the seasonally expanding and contracting carbon dioxide ice caps , though . so what might mars look like today if it had surface water ? that , of course , depends on how much we 're talking about , but maybe something like this . the relatively flat northern hemisphere is below the average elevation , so it would become one giant ocean , while the crater-ridden southern hemisphere would stay mostly high and dry . that difference between hemispheres is a bit bizarre , and we do n't know why it 's like that . the southern half is probably much older , judging by features like the number of craters , and the evidence of increased volcanic activity in the north . okay , so who knows ? maybe one day mars will have oceans again , but for now , what we 've got is essentially one giant dusty desert . in fact , it 's similar enough to deserts on earth , that we 've been able to learn a great deal about mars on our home planet . for instance , martian sand dunes form and behave similarly to our sand dunes , though the martian versions often grow twice as large thanks to a gravitational pull that 's about a third as strong as ours . and mars has some features you wo n't see on earth , like tars , which are crestless sand dunes up to fifteen meters tall , whose formations we have yet to understand . you 're probably wondering , `` what do you get when you combine a planet-wide desert with an atmosphere that , like ours , is subject to wind-generating pressure differentials , dust storms ? '' these will be your main weather hazards on the red planet . they play a large part in making the planet red by distributing rusted iron particles across the surface and into the air . thanks to the low gravity and lack of moisture , these dust storms can last for months and cover the planet . so , you might want to build your home as high as possible . well , look no further . this is olympus mons , the largest volcano in the solar system . even if mars had a breathable atmosphere , you 'd find the views from the 25 kilometer summit breathtaking . or are volcanos not your thing ? then how about valles marineris , the largest canyon in the solar system ? it 's so wide that from one side , the opposite rim would be below the curve of the horizon . still , you 'll catch some spectacular blue sunsets in the normally red sky , which gets its color from the dust absorbing most of the blue light , and the way sunlight is scattered by the atmosphere . have you got spirit , curiosity , or are you just looking for opportunity ? then stop stalling and make the move to mars today . mars : redder than ever .

they play a large part in making the planet red by distributing rusted iron particles across the surface and into the air . thanks to the low gravity and lack of moisture , these dust storms can last for months and cover the planet . so , you might want to build your home as high as possible .

dust storms last longer on mars than on earth . what is the most important reason for this ?

the victory of the underdog over the favored team . the last minute penalty shot that wins the tournament . the high-energy training montages . many people love to glorify victory on the playing field , cheer for favorite teams , and play sports . but here 's a question : should we be so obsessed with sports ? is playing sports actually as good for us as we make it out to be , or just a fun and entertaining pastime ? what does science have to say ? first of all , it 's well accepted that exercise is good for our bodies and minds , and that 's definitely true . exercising , especially when we 're young , has all sorts of health benefits , like strengthening our bones , clearing out bad cholesterol from our arteries , and decreasing the risk of stroke , high blood pressure , and diabetes . our brains also release a number of chemicals when we workout , including endorphins . these natural hormones , which control pain and pleasure responses in the cental nervous system , can lead to feelings of euphoria , or , what 's often called , a runner 's high . increased endorphins and consistent physical activity in general can sharpen your focus and improve your mood and memory . so does that mean we get just as much benefit going to the gym five days a week as we would joining a team and competing ? well , here 's where it gets interesting : because it turns out that if you can find a sport and a team you like , studies show that there are all sorts of benefits that go beyond the physical and mental benefits of exercise alone . some of the most significant are psychological benefits , both in the short and long term . some of those come from the communal experience of being on a team , for instance , learning to trust and depend on others , to accept help , to give help , and to work together towards a common goal . in addition , commitment to a team and doing something fun can also make it easier to establish a regular habit of exercise . school sport participation has also been shown to reduce the risk of suffering from depression for up to four years . meanwhile , your self-esteem and confidence can get a big boost . there are a few reasons for that . one is found in training . just by working and working at skills , especially with a good coach , you reinforce a growth mindset within yourself . that 's when you say , `` even if i ca n't do something today , i can improve myself through practice and achieve it eventually . '' that mindset is useful in all walks of life . and then there 's learning through failure , one of the most transformative , long-term benefits of playing sports . the experience of coming to terms with defeat can build the resilience and self-awareness necessary to manage academic , social , and physical hurdles . so even if your team is n't winning all the time , or at all , there 's a real benefit to your experience . now , not everyone will enjoy every sport . perhaps one team is too competitive , or not competitive enough . it can also take time to find a sport that plays to your strengths . that 's completely okay . but if you spend some time looking , you 'll be able to find a sport that fits your individual needs , and if you do , there are so many benefits . you 'll be a part of a supportive community , you 'll be building your confidence , you 'll be exercising your body , and you 'll be nurturing your mind , not to mention having fun .

the victory of the underdog over the favored team . the last minute penalty shot that wins the tournament .

around what age does bone density begin to decrease ?

translator : marcia de brito reviewer : ariana bleau lugo ( guitar music throughout ) music is a language . both music and verbal languages serve the same purpose . they are both forms of expression . they can be used as a way to communicate with others . they can be read and written . they can make you laugh or cry , think or question , and can speak to one or many . and both can definitely make you move . in some instances , music works better than the spoken word , because it does n't have to be understood to be effective . although many musicians agree that music is a language , it is rarely treated as such . many of us treat it as something that can only be learned by following a strict regimen , under the tutelage of a skilled teacher . this approach has been followed for hundreds of years with proven success , but it takes a long time . too long . think about the first language you learn as a child . more importantly , think about how you learned it . you were a baby when you first started speaking , and even though you spoke the language incorrectly you were allowed to make mistakes . and the more mistakes you made , the more your parents smiled . learning to speak was not something you were sent somewhere to do only a few times a week . and the majority of the people you spoke to were not beginners . they were already proficient speakers . imagine your parents forcing you to only speak to other babies until you were good enough to speak to them . you would probably be an adult before you could carry on a proper conversation . to use a musical term , as a baby , you were allowed to jam with professionals . if we approach music in the same natural way we approached our first language , we will learn to speak it in the same short time it took to speak our first language . proof of this could be seen in almost any family where a child grows up with other musicians in the family . here are a few keys to follow in learning or teaching music . in the beginning , embrace mistakes , instead of correcting them . like a child playing air guitar , there are no wrong notes . allow young musicians to play and perform with accomplished musicians on a daily basis . encourage young musicians to play more than they practice . the more they play the more they will practice on their own . music comes from the musician , not the instrument . and most importantly , remember that a language works best when we have something interesting to say . many music teachers never find out what their students have to say . we only tell them what they are supposed to say . a child speaks a language for years before they even learn the alphabet . too many rules at the onset , will actually slow them down . in my eyes , the approach to music should be the same . after all , music is a language too .

too long . think about the first language you learn as a child . more importantly , think about how you learned it .

how did you learn the first language you spoke ? were you allowed to make mistakes ? how do you think those mistakes helped you learn the language ? how do you think that relates to learning to play a musical instrument ?

this room may appear to be holding 600 people , but there 's actually so many more , because in each one of us there is a multitude of personalities . i have two primary personalities that have been in conflict and conversation within me since i was a little girl . i call them `` the mystic '' and `` the warrior . '' i was born into a family of politically active , intellectual atheists . there was this equation in my family that went something like this : if you are intelligent , you therefore are not spiritual . i was the freak of the family . i was this weird little kid who wanted to have deep talks about the worlds that might exist beyond the ones that we perceive with our senses . i wanted to know if what we human beings see and hear and think is a full and accurate picture of reality . so , looking for answers , i went to catholic mass . i tagged along with my neighbors . i read sartre and socrates . and then a wonderful thing happened when i was in high school : gurus from the east started washing up on the shores of america . and i said to myself , `` i wan na get me one of them . '' and ever since , i 've been walking the mystic path , trying to peer beyond what albert einstein called `` the optical delusion of everyday consciousness . '' so what did he mean by this ? i 'll show you . take a breath right now of this clear air in this room . now , see this strange , underwater , coral reef-looking thing ? it 's actually a person 's trachea , and those colored globs are microbes that are actually swimming around in this room right now , all around us . if we 're blind to this simple biology , imagine what we 're missing at the smallest subatomic level right now and at the grandest cosmic levels . my years as a mystic have made me question almost all my assumptions . they 've made me a proud i-don't-know-it-all . now when the mystic part of me jabbers on and on like this , the warrior rolls her eyes . she 's concerned about what 's happening in this world right now . she 's worried . she says , `` excuse me , i 'm pissed off , and i know a few things , and we better get busy about them right now . '' i 've spent my life as a warrior , working for women 's issues , working on political campaigns , being an activist for the environment . and it can be sort of crazy-making , housing both the mystic and the warrior in one body . i 've always been attracted to those rare people who pull that off , who devote their lives to humanity with the grit of the warrior and the grace of the mystic -- people like martin luther king , jr. , who wrote , `` i can never be what i ought to be until you are what you ought to be . this , '' he wrote , `` is the interrelated structure of reality . '' then mother teresa , another mystic warrior , who said , `` the problem with the world is that we draw the circle of our family too small . '' and nelson mandela , who lives by the african concept of `` ubuntu , '' which means `` i need you in order to be me , and you need me in order to be you . '' now we all love to trot out these three mystic warriors as if they were born with the saint gene . but we all actually have the same capacity that they do , and we need to do their work now . i 'm deeply disturbed by the ways in which all of our cultures are demonizing `` the other '' by the voice we 're giving to the most divisive among us . listen to these titles of some of the bestselling books from both sides of the political divide here in the u.s. `` liberalism is a mental disorder , '' `` rush limbaugh is a big fat idiot , '' `` pinheads and patriots , '' `` arguing with idiots . '' they 're supposedly tongue-in-cheek , but they 're actually dangerous . now here 's a title that may sound familiar , but whose author may surprise you : `` four-and-a-half-years of struggle against lies , stupidity and cowardice . '' who wrote that ? that was adolf hitler 's first title for `` mein kampf '' -- `` my struggle '' -- the book that launched the nazi party . the worst eras in human history , whether in cambodia or germany or rwanda , they start like this , with negative other-izing . and then they morph into violent extremism . this is why i 'm launching a new initiative . and it 's to help all of us , myself included , to counteract the tendency to `` otherize . '' and i realize we 're all busy people , so do n't worry , you can do this on a lunch break . i 'm calling my initiative , `` take the other to lunch . '' if you are a republican , you can take a democrat to lunch , or if you 're a democrat , think of it as taking a republican to lunch . now if the idea of taking any of these people to lunch makes you lose your appetite , i suggest you start more local , because there is no shortage of the other right in your own neighborhood . maybe that person who worships at the mosque , or the church or the synagogue , down the street . or someone from the other side of the abortion conflict . or maybe your brother-in-law who does n't believe in global warming . anyone whose lifestyle may frighten you , or whose point of view makes smoke come out of your ears . a couple of weeks ago , i took a conservative tea party woman to lunch . now on paper , she passed my smoking ears test . she 's an activist from the right , and i 'm an activist from the left . and we used some guidelines to keep our conversation elevated , and you can use them too , because i know you 're all going to take an other to lunch . so first of all , decide on a goal : to get to know one person from a group you may have negatively stereotyped . and then , before you get together , agree on some ground rules . my tea party lunchmate and i came up with these : do n't persuade , defend or interrupt . be curious ; be conversational ; be real . and listen . from there , we dove in . and we used these questions : share some of your life experiences with me . what issues deeply concern you ? and what have you always wanted to ask someone from the other side ? my lunch partner and i came away with some really important insights , and i 'm going to share just one with you . i think it has relevance to any problem between people anywhere . i asked her why her side makes such outrageous allegations and lies about my side . `` what ? '' she wanted to know . `` like we 're a bunch of elitist , morally-corrupt terrorist-lovers . '' well , she was shocked . she thought my side beat up on her side way more often , that we called them brainless , gun-toting racists , and we both marveled at the labels that fit none of the people we actually know . and since we had established some trust , we believed in each other 's sincerity . we agreed we 'd speak up in our own communities when we witnessed the kind of `` otherizing '' talk that can wound and fester into paranoia and then be used by those on the fringes to incite . by the end of our lunch , we acknowledged each other 's openness . neither of us had tried to change the other . but we also had n't pretended that our differences were just going to melt away after a lunch . instead , we had taken first steps together , past our knee-jerk reactions , to the ubuntu place , which is the only place where solutions to our most intractable-seeming problems will be found . who should you invite to lunch ? next time you catch yourself in the act of otherizing , that will be your clue . and what might happen at your lunch ? will the heavens open and `` we are the world '' play over the restaurant sound system ? probably not . because ubuntu work is slow , and it 's difficult . it 's two people dropping the pretense of being know-it-alls . it 's two people , two warriors , dropping their weapons and reaching toward each other . here 's how the great persian poet rumi put it : `` out beyond ideas of wrong-doing and right-doing , there is a field . i 'll meet you there . '' ( applause )

from there , we dove in . and we used these questions : share some of your life experiences with me . what issues deeply concern you ?

what are the three questions that lesser used to help structure her conversation ?