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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 ?