Will my undergraduate GPA affect my graduate admissions?

Question: I have a very low undergraduate GPA. I used to play a sport at the state level and thought I could cope up but didn't. Failed in multiple papers, completed a 3-year degree in 5 years. In the end, I had a 2.0 GPA (On the 4.0 scale). However, I got admission at one of the top universities in my country for my master's because the bachelor's GPA wasn't a prerequisite, and having a degree was enough plus I had to give an entrance exam as well as sit for an interview. I got a full 4.0/4.0 GPA in my master's and now am a research intern at one of the top institutes in my country, and have a publication to my name. I also was a research intern in the Research and Development laboratories of 2 companies during the summer and winter. I will be applying this fall to universities abroad, and I wanted to know how much my chances of getting in will be affected before spending money on GRE and university applications.
Comment: For this specific question (will my bachelor's gpa be looked at?), no. You will find this when going over instructions how to apply online - unfortunately on a university by university basis. To talk to a professor you would love to work with generally, and if the conversation goes well describe your issue, maybe. If you google around a little, you'll find many questions on students intending to apply to graduate school contacting professors (should I? How? When? What (not) to do?) on this site too. GL!
Comment: I recently checked related rules of my graduate alma mater (there was a similar question to yours here a little while back) which is highly ranked on the West Coast. There, and as to GPA, they will *only* look at your bachelor's gpa, not your masters at all. So this could spell trouble, but of course your other credentials might help. Other schools might have different procedures; it might also depend on your field.
Comment: Probable duplicates: [Doing bad in undergraduate but good in a masters program](https://academia.stackexchange.com/questions/1066/doing-bad-in-undergraduate-but-good-in-a-masters-program) and [How do you get a bad transcript past Ph.D. admissions?](https://academia.stackexchange.com/questions/324/how-do-you-get-a-bad-transcript-past-ph-d-admissions)
Comment: If you contact a faculty member, I suggest you contact the Department Head or the Chair of the Admissions Committee. They might give you advice on how they value your degrees and grades. They cannot give you a concrete answer unless you apply for admission. There is no point in talking to other faculty members; they will properly refer you to either the Department Head or the Admissions director.
Comment: @gnometorule is it a good idea to contact a professor in the department I will be applying to before I fill out the application if that's the case?
Comment: @DavidSmith Thank you. I am planning to email them in October after my GRE and TOEFL results come out. I heard that in many universities, if I have a low undergrad score, a good GRE score often makes up for it.
Answer: This varies by country and even by university, but in general, most people will give your recent work more weight in a decision than earlier work. People grow and change and it is usually recognized.
But ultimately, the only way to know for sure is to apply. GRE might help in some places. But a few applications will give you solid information. A wild guess (not a prediction) is that you will be ok.
Answer: In the US, M.S. degree grades are expected to be high, since masters programs tend to give relatively high grades because people are paying so much to be there.  Undergraduate grades are considered more meaningful because not everyone does well.
Your undergraduate GPA is going to hurt you, especially at big programs that get a lot of applicants.  I worked at a lab at well-known Massachusetts university a few years back, and I helped screen graduate applications for one of the engineering programs.  They got so many applications that they would essentially throw out anyone below a relatively high GPA cutoff, so with a 2.0 GPA in that program you would not even be looked at. That is an extreme case because everyone in engineering applied to that particular school and they couldn't go through it all.  In other places, there are fewer applicants and people have time to more carefully review applicants, in which case having a publication and a lot of additional training looks very good.  There are plenty of less famous programs in the US that get fewer applicants and would more holistically evaluate someone with good recommendations, research experience and a publication.
I would put together a list of a few programs you're interested in that are not MIT/Harvard/Stanford/etc.  Look for ones with research you would be interested in.  Reach out to a few professors you would want to work with, briefly state that you've published and are interested in applying to their program, and you want to know if you'd have a chance.  'I've published in X, I'm interested in Y, I have a M.S degree in Z but I did poorly in undergrad for personal reasons.  Am I wasting both of our time applying here'.  If you're not spamming everyone but actually emailing people interested in what you do you'll probably get a few answers.  It is in their interest to answer since if you're not qualified and you apply they have to read through what you send in anyway.  See what they say and reevaluate.
GRE has become dramatically less popular in the US, especially in sciences/engineering/math where everyone does well in math. Depending on your field, you may not even need it at a lot of schools. Double check that before you take it.
Comment: Thank you for the tips. I would be applying to Europe as well not only the US. Also, my field of study is statistics. As far as I know, there are several universities that are offering PhDs in Data Science, Biostatistics, and related fields. Maybe I could apply to those departments which are a bit less popular. Also, I am pretty sure with my grades I won't be getting into a top 15 uni so I am at this moment focused on whether I am wasting my time applying or should I focus on looking for a job. Do you think emailing a professor before applying changes an applicant's chance of getting in?
Comment: @NilanjanDebnath I can't specifically give you advice for statistics, but in a lot of fields I don't think you would be wasting your time, but you do have to find the right places to apply.  It is unlikely emailing will change your chances of getting admitted, but maybe you can get feedback before you apply.  I think different places and also to jobs makes a lot of sense.  You never know where you'll get a good offer that makes this moot.
Comment: I disagree with the first paragraph. Students don't "pay professors" for their education. There is no incentive for a professor to give a good grade for poor work. It is insulting to suggest it. There is, of course, a filtering process so that more capable students, on average, are likely to be seen in a masters. I think the standards are the same, but the audience is different. Such a practice would also reflect very poorly on the reputation of a university. And reputation is what they most want to protect.
Comment: @Buffy Maybe other countries work differently, but in the US system, students absolute do pay to be in a masters program, usually tens of thousands of dollars per year.  Furthermore, in many programs getting a C grade is grounds for probation or even expulsion from the program.  This is a severe step for the student, and it costs the program a lot forfeited tuition.  As a result, everyone has a strong incentive to compress grades into the A-B range, and so lower grades rarely given.  Conversely, at the undergraduate level, C grades are more widely given (I definitely had some in college).
Comment: Yes, they normally pay to be in a masters only program. But they don't pay the professors directly. Most professors are probably completely unaware of the financial contribution of any student. Professors do the grading and set the standards. It isn't a "pay to play" system at all. And yes, I'm in the US and have taught in such programs. If you got a B from me, you earned it. No freebies. Why would I want to demean myself? Again, it is the audience that is different, not the standards.
Comment: @Buffy No one said they pay the professors directly.
Comment: But you certainly implied a link between payment and grades. Sorry, but it isn't there.
Comment: @Buffy You're welcome to your opinion on the extent to which organizations respond to financial incentives, but we should keep this on topic. You said you disagree with the first paragraph, so you think grades in a masters program would matter more than undergraduate?


In Luke 18:8, does the Geek word translated "quickly" mean "suddenly" in this instance?

Question: We know that in our lives on planet earth the Lord does not always quickly protect those who are suffering injustice. Definitely, he will on the day of his visitation correct injustices and he will rule with perfect justice during the millennium. But it seems that many people, while living on planet earth, undergo major and continuous injustice even though they pray frequently for God to relieve the injustice.
I do not have sufficient knowledge of the Greek to understand how verse eight is true if I understand it to be translated "quickly."
Answer: The word is τάχος Strong 5034 which Thayer (see the link for Strong) renders as 'quickness' or 'speed'.
So in the construction used in verse 8, ἐν τάχει, Thayer tells us that the meaning is quickly or shortly (as in Acts 12:7; Acts 22:18; Romans 16:20) or it may mean speedily or soon (as in Luke 18:8; 1 Timothy 3:14 ; Revelation 1:1; Revelation 22:6).
Thus the execution of judgment is speedy, when the time comes to execute that judgment.  However the verse is not stating that there will not be a delay, ere the time of execution will occur.
It is only stating the rapidity of executed judgment, when the time for judgment to be appropriate arrives.
We know, from many other scriptures (such as the entire book of Job, or the forty years that Moses spent in  Midian, or the hundreds of years during which God waited before flooding the whole earth) that there may well be reasons, in God's purposes, for time to pass, until it is the right time for a reconciliation to occur.
But once that period of time has elapsed, the judgment falls swiftly, as exampled in the days of the Flood during Noah's lifetime, or as exampled in the judgment upon Sodom and the cities of the plain in the days of Abraham and Lot.

In Luke 18:8, does the Geek word translated “quickly” mean “suddenly” in this instance?


Chainring compatiblity for FC6570

Question: Hey guys I want to know which chainring can fit on Shimano FC-6750 crank arms? Ive tried to find it in a app called carousell(a place where you sell products) and I can't find any. I had to go google search and is able to find one but can't ship to my country. Thanks
Answer: Look for 110 BCD (or PCD) chainrings for 5 arm spiders, for 10 speed. That's an Ultegra crank. They may not specify "Shimano", or "Ultegra" compatible. Then, look if chainrings' bolt area looks like as yours.
You may have more luck with AliExpress. It's not hard to find chainrings for Ultegra's. At AliExpress, there are plenty..
Answer: As previously stated, the 6750 is a compact crankset meaning the chainrings have a BCD (Bolt Circle Diameter) of 110 mm.  Shimano had several gear combinations, all of which had 110 mm BCD's:  52/36, 50/34, and 46/36 for cyclocross racing. If replacing the large ring, for best shifting performance you'll want the same size chainring.
If you're replacing the large chainring, I have not tried other brands of 5-bolt chainrings on the Ultegra 10 speed cranksets, but for aesthetic reasons I don't think another brand will look good. The 105 chainrings will work just fine and are less expensive but they are anodized a slightly different color.
For the small chainring the different color won't show up and from a functional point you'll be fine with Ultegra or 105 10spd chainring.

Chainring compatiblity for FC6570


how can i connect the usb cable from my lg p350g into my computer to transfer its stuff?

Question: i have done it before but the notification does not appear its charges my phone but cannot connect the phones internal SD to my computer. Please help
Comment: If you go to *Settings* and follow the *More* item in the *Network* section, do you find an entry like *USB connection mode*? Or, when you connect your device, do those settings not pop-up asking you to connect?
Answer: When you connect your phone to your computer, You get a pop-up showing a green android with one hand being a USB.
There, click on Mount SD card or an option similar to that.
You should be able to use the SD card as a flash drive.


what are the available components i can use in a Custom Theme Layout

Question: I am trying to create a custom theme layout but the lack of proper documentation is a little frustrating.
The following is the only information I could find about supported Aura.Component[] names. But I am missing the notifications section.
<code><aura:attribute name="search" type="Aura.Component[]" required="false"/>
<aura:attribute name="profileMenu" type="Aura.Component[]" required="false"/>
<aura:attribute name="navBar" type="Aura.Component[]" required="false"/>
</code>
Is there any other documentation that I am not aware of, or a way to re-use that compactHeader that is used in the other salesforce Themes?
Thanks in advance!
EDIT:
I think the previous text was not very clear, what I am trying to do is to create a Theme layout using the Build your own theme, that has no navigation header.
I see that the other themes available are using this compactHeader but I cannot seem to be able to re-use, so I am trying to recreate it, I can work with the std component mentioned earlier but I am missing a key feature that is the notification section.
I am trying to find some documentation listing all the possible component names available (if exists) or a way of reusing the compactHeader.
Answer: Found a solution to my issue using forceCommunity:notifications/
Comment: Please include some more details about how this solution works, e.g. include a code sample. See [answer] for how to produce a clearer answer.


Effective length factor of a polymer in solution

Question: If one wants to calculate the force needed to buckle a polymer in solution with Euler buckling, what would the effective length factor be? The polymer is free to move and rotate in solution as it sees fit (though it is still subject to stresses), but the ends cannot move very far with relation to each other, nor can they rotate freely with respect to each other.
Answer: It's not an easy question to answer within the limitations of space. This is a full-fledged research problem. I was working on a similar problem 2 years ago without any success. I would suggest you to look at this thesis where you fill find the necessary details and then reframe your question for specifics.
https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/3557
This thesis deals with the buckling instabilities of filaments in biological systems and uses a renormalization group technique to calculate the critical length of a filament to buckle under an applied force and vice versa. Filaments of the cytoskeleton are semiflexible polymers, i.e., their bending energy is comparable to the thermal energy such that they can be viewed as elastic rods on the nanometer scale, which exhibit pronounced thermal fluctuations. Like macroscopic elastic rods, filaments can undergo a mechanical buckling instability under a compressive load. In cells, compressive loads on filaments can be generated by molecular motors. This happens, for example, during cell division in the mitotic spindle.
The author here investigates how the stochastic nature of such motor-generated forces influences the buckling behavior of filaments and reviews briefly the buckling instability problem of rods on the macroscopic scale and introduce an analytical model for buckling of filaments or elastic rods in two spatial dimensions in the presence of thermal fluctuations and presents an analytical treatment of the buckling instability in the presence of thermal fluctuations based on a renormalization-like procedure in terms of the non-linear sigma model where the author integrates out short-wavelength fluctuations in order to obtain an effective theory for the mode of the longest wavelength governing the buckling instability and calculates the resulting shift of the critical force by fluctuation effects and find that, in two spatial dimensions, thermal fluctuations increase this force.
You will find many more details pertaining to the problem you are studying in the document.
Comment: This is basically a link only answer, which tend to get deleted here. Could you edit your post to include a summary of the document?
Comment: Added more info. Please remove the infraction.


What is WETH and why can't we just use ETH?

Question: can someone explain why we need WETH? what's the purpose of WETH, can't we just use plain ETH? it's not like it removes the tx fees or something. Hopefully someone can shed light on the concept.
Answer: Ethereum's native token, ETH, doesn't follow the ERC20 standard.
The standard for tokens is ERC20, so in order to trade directly eth with alt tokens, ETH is wrapped into an ERC20 token, WETH.
See here for the contract code.
Answer: WETH or wrapped ether is usually used in defi protocols where specific features of ERC-20 standard are needed (such as transfer approval, permit, limit orders, etc). ETH, on the other hand, is the native coin of the Ethereum network which is used for staking and paying transaction fees on the network.
The point that you should keep in mind is that WETH is issued by a third entity and is riskier than native ETH (i.e. it's seizable and subject to smart contract vulnerabilities).


Does "Thanks to" in the sentence express "Thanks"?

Question: "Okey! Thanks to Danny giving us a brief overview of the production line. It seems it is the most profitable line. " Here, is "Thanks to Danny" the meaning of "Thank Danny"? or just means "Due to"?
Comment: Thanks to everyone for giving these comments. I have also another question. In the original sentence, "It looks like it will be our frofitable line yet." here, is "yet" used here the meaning of "up to now"?
Answer: In your example, the speaker is using thanks to to express gratitude to Danny. This usage is often preceded by a pronoun:

(Let's give) our thanks to Danny for giving us a brief overview of the production line.

Thanks to can also have the meaning (as you suggested) of "due to/because of." When it is used with this meaning, the expression may have either a sarcastic/negative or sincere/positive connotation that is usually evident from the context of the statement. For example:

Thanks to my little brother, my phone is broken.

This sentence indicates that the speaker's little brother broke the phone and the speaker blames him for it. Thanks to has a sarcastic/negative connotation.

Thanks to my fitness coach, I am now much stronger and healthier.

This sentence indicates that the speaker's fitness coach was responsible for his improvement. Thanks to has a sincere/positive connotation.
Answer: When you say (with a bit of correction):

Okay! Thanks to Danny for giving us a brief overview of the production line. It seems it is the most profitable line.

Here you are thanking him.
But if you said something like:

Thanks to Danny, everyone will need to work overtime to fix his mistake.

it means "due to Danny". Using "thanks" is a bit facetious as used here.


Java in OR: Which non-constraint solving libraries do you use?

Question: If you're programming OR challenges in Java, besides using constraint solvers, which other libraries do you typically use? Maybe for common tasks such as data reading, etc. Why? How do they make your life easier?
Answer: A few key ones that I use are:

algs4 -- a variety of programs/utilities from an online course at Princeton (Go Tiger!), including some graph/network libraries
Various Apache Commons libraries -- for reading/writing CSV files, doing operations on collections that Java currently does not directly support, and so on
Renjin -- let's me execute R code inside a Java program (not something I do often, but it has come up once or twice)
SQLite JDBC -- for pulling data from/pushing data to SQL databases (handy when you're running a bunch of experiments with different combinations of problem/algorithm/parameters and you want to store results in a coherent manner)
Watchmaker Framework -- Java framework for genetic algorithms (not under active development, and there are several other Java packages for GAs, some newer, but I like Watchmaker)
XStream -- converts Java objects to XML and back

I've also had reason to use a Java matrix library, but I've yet to find one that I like and, importantly, trust, so I'm not naming any here. (I've tried a few that exhibited a "good enough for government work" attitude about computing matrix ranks and doing rank-revealing QR decompositions.)
Comment: Thanks for sharing! I am using apache commons often too, but I find writing/reading CSV files very work-intensive none the less. Same for XSLX with POI. This is something I envy the Python programmers on (although I'd love to have my cake and eat it too: python easiness and still Java statically typed data).
Comment: You could use R to read/write CSV and XLSX files (via Renjin), but I suspect that the extra "plumbing" you'd be adding to do this would be about as inconvenient as what you're currently doing.


Any free Text To Speech for browsers?

Question: Wondering if there is any Text to Speech software available as a plug in for IE or Firefox.
Comment: For those that might be marking this down as a non-programming related question, keep in mind that web developers would need a TTS browser to accurately test the accessibility of the websites they build.
Comment: There are some text-to-speech JavaScript libraries, which don't require any plugins. http://stackoverflow.com/questions/11279291/a-good-text-to-speech-javascript-library
Answer: WebAnywhere is a university project aimed at creating a site that allows you to use text to speech from any browser at any location, without installing anything or using any plugins.
You can try it out and see for yourself. I was pretty impressed with it when I first heard of it.
Answer: There is also NVDA (NonVisual Desktop Access) which is an open source general purpose screen reader for Windows.
Answer: It is built in for Safari on Mac OSX.  Highlight any text and go to the menu, Safari > Services > Speech > Start Speaking Text.
Answer:
Fire Vox
Fangs
Comment: Fire Vox - clever clever name
Answer: I know you asked for plugins for IE and Firefox but I thought I'd just add that Opera supports text to speech (both for issuing commands and for Opera to read web / email to you) out of the box (in Windows and possibly Mac OS).
See the Opera Voice page.
Answer: Windows Narrator is part of a default XP installation, and can be used in any browser.  I also suggest you try out Thunder, which is free and can work with IE and most other Windows apps.
Answer: For Firefox, there is LowBrowse, which has text to speech for the
paragraph that the cursor is in.

Any free Text To Speech for browsers?


Perform Callout, get byte[] and view pdf

Question: I have a requirement to perform a callout, get response (byte array) that is a PDF base 64 encoded. Then, i need to show the pdf, without saving any data in Salesforce. I just need to view the response in PDF.
So, is there a way to achieve this?
What i have done is:
I have created an LWC to perform the callout on rowaction of a Lightning data table. So onRowAction a JS function is called which calls Apex. Apex performs the callout, gets response and then i need to render the result in PDF. I have tried opening a Visualforce page (calling it either from JS Controller of LWC or from Apex, but i could not find solution... I could not pass my parameter to the page so the PDF was always blank.
Please find below a high level diagram of the problem that i am facing and what i want to do..
Answer: You could do something like this in VF.
<apex:page>

</apex:page>

Unfortunately, LWC does not allow rendering data: and blob: urls in an iframe as it violates CSP. Alternatively, for LWC, you can try implementing PDF.js or PDFTron but it could be costlier both time and effort wise.
Comment: Hi Jay and thanks for the response. So, as per my understanding, you suggest making the callout directly from the vf page instead of making the callout in lwc and passing the blob to the vf page. Correct ?
Comment: @GiorgosGalaios Yes, this is a VF only solution. You can also do a hybrid LWC + VF solution. Embed VF into LWC using iframe. Do the callout in LWC, pass received base64 to iframe using postMessage API. iframe, i.e, VF page when receives base64 will render in another iframe.
Comment: Ok i will try it and see if it works. Thank you Jay!
Comment: Thanks for the help Jay! It worked :)


how to keep a wet edge applying poly to the floors of a whole house

Question: My floors are ready for poly. Is it possible to keep a wet edge, when the whole house needs poly, and every room conects to another with 2 diffrent doorways? Every path i can think of to take will end up with me runing in to a dry edge before i can finish a coat.
Comment: If you can get a helper or two, you might be able to plan a route that would let you start in various rooms and meet in the hallway to avoid a wet edge.
Answer: I see the pros use a large applicator, specific for floor finishing, looking a lot like a household mop. Not the old stringy style, but a sponge mop, theirs having a cotton pad instead of sponge. This way you can cover a lot of area. If any of the doors have the flooring running across the door rather than running through it, cut along one of the joints in the floor. The lap of the finish will be disguised by that joint. This will give a small bit of relief from the hustle.
If you go this route, have another person to check the progress and quality of your passes with the mop. A 4" brush is used to cut in the edges before "mopping".


PCB controlled impedance

Question: Hi) I want to calculate the width of my 100Mb Fast Ethernet MDI diff pairs. I've got some software (TXLINE 2003 Microstrip). I have 4 layers. The second layer is GND, the third is power, top and bottom are signal layers. I have one diff pair on the top and one on the bottom. For the top everything is clear, I took the height parameter as distance between top layer and GND. But what should I do for the bottom layer? What layer should I choose to calculate the distance (Power layer or GND)? I have also heard that if one chooses Power layer as reference layer for calculation of width then one need to place 10nF capacitors between power and GND on boths sides of MDI diffpairs. Is this correct?
Answer: If your routing a diff pair you need a ground plane underneath it that is continuous, as the capacitance between the traces and ground needs to be controlled to some degree. One of the best ways to do this is to have the top layer be signal and the second layer be ground. (There are more than one ways to have an impedance controlled trace, for simplicity I'll describe only one)
The idea behind a microstrip is that the current flows on the signal, and the return current flows back on the ground plane below, this keeps impedance low and lets it function like a transmission line, an you can minimize bad things like reflections and attenuation that would reduce the signal that the trace carries.
Don't use a power plane for the basis of a microstrip, this interferes with return current (needs to be through ground) and will result in undesirable characteristics of your transmission line.
While it is possible to to build a microstrip transmission line with a power plane, this is a bad practice. Why? because if you do use the power plane you'll need stitching caps, and each cap will have on the order of 10nH of parasitic inductance, this will inhibit the return current. If your ok with increasing the inductance and lowering the rise time then go for it.

Edit:
If your routing PCIE keep the diff pairs on the top layer with ground underneath, here is a guide:
PCIE Express Routing
Comment: Thank you for the respone!) The matter is that I am using PCI Express x1 connector. And it has one diff pair on the A side and one on the B side, so I think that I'm bound to spread diff pairs on two layers. What is the perpose of the stiching cups and how should I use them, should I connect ground plane to the power plane using caps along the signal line or just near IC output? And also what is the distance I should use to calculate the trace width to match impedance? Should I use  the distance to ground or to power plane in the case if the signal is referenced to power plane?
Comment: https://meta.stackexchange.com/questions/126180/is-it-acceptable-to-write-a-thank-you-in-a-comment

PCB controlled impedance


Can a Baofeng UV5R receive airport radio transmissions?

Question: I have tried programming approach frequencies into my baofeng and cannot hear any transmissions.  Freq programming was done using a desktop computer connected to the radio to frequency 121.9MHZ.  Nothing was heard, just standard background static.  Here is the  radio:  https://www.amazon.com/Baofeng-Warranty-Dual-Band-Radio-Improved/dp/B00HX03AMA  Baofeng UV5R v2
Comment: Also, the person best able to answer your question is you: look at the specs of your device, and find out whether it covers the frequencies you're interested in.
Comment: Also, you don't specify what you're trying to demodulate. Also, again, there's no such thing as standard background noise.
Comment: There's no such thing as "standard baofeng". You'll need to specify which model you use.
Comment: So @Marcus, you are getting too far in the weeds, and as I am new I don't just "know" what to look for or specify.  The model is there, but it is not pertinent as I am wondering if the frequency is somehow coded or modulated in a way that a BAOFENG UV-5R is not designed to receive due to regulations against just anyone being able to receive the transmissions.
Comment: And I would say there is standard background static, as in nothing out of the ordinary was heard such as odd pulsing or even silence indicating the radio does not work.  Feel free to vote me down more, but the question is fair.
Comment: first of all, great that you've edited your question a couple of minutes ago and added the radio type! So, to what kind of modulation did you program your UV5R to?
Comment: (and noise is not always the same – I could go on for hours about the mathematical/physical properties of different kinds of noises, but that really doesn't help here)
Comment: I entered 119.3, our local tower into my radio, but it said 'Cancel' at the last digit, even though I was on VHF.
Answer: As far as I've read, all Baofeng radios do FM only. The majority of aircraft communications uses AM, so whether or not it can be tuned there, you would not hear the audio, just approximate silence (quieter the stronger the signal).
This is because to a FM receiver's perspective, an AM signal is unmodulated (the frequency stays constant), and vice versa (in a FM signal the amplitude stays constant).

In some cases, the speech may be very faintly audible, due to imperfect circuits in both the transmitter (causing frequency variation in the transmitted signal) and the receiver (having unintended sensitivity to amplitude variations).
In the reverse case — attempting to receive a FM signal using an AM receiver — this can actually be used practically (improvised "slope detection", tuning with an offset and allowing the frequency modulated signal to be converted by the edge of the receiver's filter to an amplitude-and-frequency modulate signal).
Comment: Thanks, that about sums up what I was trying to find out....most airband is on AM versus FM.
Comment: You got it.  FM receivers are funny, though.  If the signal is below the threshold of the limiter you can sometimes hear it.  To try this out, set it to WFM and maybe try smaller antennas to see if you can hear anything.  Those radios are a great deal for the price.  Lots of fun.  Just be careful to NEVER transmit in that band.
Answer: From the amazon page you've linked to:

Frequency Range: 136-174 / 400-479.995 MHz.

So, no, you can't receive 121.9 MHz.
Comment: "not about frequency ranges, but about physical capability": supported frequencies **is** the most fundamental *physical capability* of any radio.
Comment: I worry less about someone facing legal enforcement over abusing that part of the spectrum than I worry about that spectrum being accidentally abused by Op - to be completely frank, he doesn't seem to be the most competent
Comment: Looks like the software change on the radio only allows for display of the frequency.  However, my question wasn't really about the frequency ranges, but was about whether the radio had the physical capability to accomplish this....such as filters would still allow other frequencies through.
Comment: Maybe the most fundamental, but not what he was looking for.  My biggest concern about physical capability is the chance of actually transmitting in that band.  The way they are coming down on people with laser pointers, just imagine how they would react to interference to their communications.  No thank you very much.
Answer: It is far from being ideal, but it is possible. UV-5R can get below the specified range (google Chirp) and although it is an FM radio, it can (under some conditions) receive an AM modulated audio signal. The quality is bad, but if the signal is strong, it is audible. I've tested this on ATIS from a nearby airport (~131 MHz). What also helps is to set WFM and tune slightly off the carrier frequency (in my case 6 kHz up was the sweet spot).
Seems to be working approx. down to 126 MHz. Although the frequency can be set even lower, it doesn't seem to receive anything (tried with TinySA).
!Never ever transmit on that band (rather even disable the TX capability in VHF band in the SW)!
Answer: I believe the tower & aircraft are on digital, not analogue systems. Though i think it's possible to receive transmissions from ground crew (fuel tankers, gangway vehicle & other airside staff), who communicate on certain analogue frequencies. Tugs, baggage train's etc. Haven't done this myself but have been told it is possible to receive them in the UK.
Answer: Yes, it can receive air band transmissions but upper the frequency limit is 127 MHz or 128 MHz. I can get the airport but the speech very faintly audible. This is because from an FM receiver perspective, an AM signal is unmodulated.
Anyway, I can receive AM signals with a Baofeng UV5R but the sound is awful.


mysql replication: one master with lots of databases, two slaves - one for all DB's and one - only for one of DBs

Question: I have a production mysql server. And one server for backups, with mysql slave running on it. As development continues I want to setup a small development server replicating only one of databases from master, ignoring binlogs for all other databases existing on master. Is it possible?
Answer: Yes, and it easy. See http://dev.mysql.com/doc/refman/5.1/en/replication-rules.html for details.
Answer: Yes, but you should be aware that always the full binlog for all databases is sent to all slaves. This can be important if you have large databases and want to replicate over a slow network connection. The transfered data will be the same regardless of the size of the specific database you want to keep.


Designing signal conditioner to convert current source to voltage output

Question: I've seen a lot of signal conditioners online for converting a 4-20 mA current loop signal to a 0-10 voltage output. However, they seem extremely expensive for the task they are achieving. Are the high costs due to protection against spikes in the input/other extreme events?
Comment: packaging , volume and distributor [profits] make all the difference
Answer:
Are the high costs due to protection against spikes in the input/other extreme events?

Yes, this would be a standard expectation in industrial control systems. Many also include isolation between the input and output signals and this will push the cost up significantly. This eliminates ground loops and allows, for example, the PLC to be electrically isolated from the sensor loop.

simulate this circuit – Schematic created using CircuitLab
Figure 1. Conversion doesn't have to be expensive.
If you can tolerate 2 - 10 V from the conversion then a 500 Ω precision resistor will do the job. These are available in 0.1% tolerance from the big suppliers such as RS.
Just as the 4 mA gives a "live zero" (which means that you can tell the difference between a sensor giving a zero indication as opposed to a sensor that has become disconnected) the 2 - 10 V can be used in the same way if you can set the scale and span of the input you are feeding.
Comment: @coolro: A solid state relay is an on-off device. You don't drive it directly with a 4 - 20 mA signal (or 0 - 10 V either). That's not how SSRs are designed to be operated. What are you really trying to do? By SSR do you mean a dimmer-style AC phase-angle controller?
Comment: Then you need a major edit to your question. It has little to do with the problem tou are trying to solve and my answer is irrelevant.
Comment: Would the drop with a precision resistor be sufficient to drive a solid state relay's input? I wasn't sure how an applied voltage works with current draw for something like an opto-isolator when there is a current source instead of voltage source
Comment: The circuit is not reversible for V to I but I to V on a PCB costs~$4 https://wiki.dfrobot.com/Gravity__Analog_Current_to_Voltage_Converter_for_4~20mA_Application__SKU_SEN0262  then V to I could be similar
Comment: @Transistor I have a 4-20 mA output on my controller that I'd like to use to control a random-fire SSR. I don't intend to use the whole range of the 4-20 output just min and max values to turn the SSR on and off


Expand / Collapse Swimlane (Domain Specific Language) C#

Question: I have multiple swimlanes on the surface, Is it possible to have expand / collapse functionality to these swimlanes?. My swimlanes are going to contain different shapes (Image Shapes), Geometry shape etc.
I have tried the nesting of a geometry shpes but it only contains the geometry shapes not image shapes i.e. I have already created a Geometry shape with it's type as a RectangleD and by writing its partial class I have overridden the Expand() and Collapse() methods but to no avail because this particular Shape (Container) going to contain only Geometry shapes and not the Image shapes.
Now I am trying to expand / collapse the swimlanes itself. Please let me know if anyone has done this before.
Answer: Did you try to set its Width to 0?


When we talk about the Higgs mechanism, is it a quantum effect?

Question: I have heard assertions that in QFT, the Higgs mechanism and Yukawa Couplings are calculated "at tree level" making the effects only classical in nature, not quantum. What does this mean, and is it accurate?
Answer: The question has two parts: (1) What does "tree level" mean, and why are tree-level effects said to be classical in nature? (2) Is the Higgs mechanism classical in nature?
 Tree level $\to$ classical
Solving linear differential equations is easy. Solving nonlinear differential equations is hard, usually too hard. If the nonlinearities are small enough, then we can start with a solution of the linear version and add successively-refined corrections to account for the nonlinear part. That technique is called perturbation theory. The word "theory" here doesn't mean any hypothesis about how nature works. It's just a technique for doing calculations.
In field theory, both classical and quantum, perturbation theory can lead to cumbersome mathematical expressions. We use a graphical notation called Feynman diagrams to summarize those expressions. In quantum field theory, Feynman diagrams can have loops. In classical field theory, they can't. A diagram without any loops is called a tree. Even if we're using quantum field theory, we often use an approximation that only includes tree diagrams. Since those diagrams can also be generated by a classical field theory, we can call this approximation "tree level" or "classical."
Two caveats:

A classical approximation can also include nonperturbative effects — effects that are not visible in perturbation theory at all, no matter how far we iterate it. Example: instantons.

The kind of "classical" field theory that we would need to use to reproduce the Standard Model's tree diagrams still includes some ingredients — like fermions — that we would not ordinarily include in classical field theory. It's called classical (in the tree-diagram sense) because all of its observables commute with each other, even if it involves some otherwise distinctly quantum ingredients.

 Is the Higgs mechanism a classical effect?
I'll answer a different question first, because it's easier: Is the  Higgs mechanism a tree level effect?
The answer to that question is no. The Higgs mechanism rearranges the vacuum state compared to what the vacuum state would be if interactions between the Higgs field and gauge field were absent. Determining the vacuum state is the archetypical nonperturbative problem: it is extremely hard, usually too hard, even when the nonlinearities are very small. Perturbation theory does not work for determing the vacuum state. Sometimes, we can work around that obstacle using things like experience, intuition, and lots and lots of consistency-checks. That's how we "know" that the Higgs field in the Standard Model leads to the Higgs mechanism.
Once we know that the Higgs mechanism occurs, then we can use perturbation theory to study many other processes. In this case, we're using perturbation theory to add successive refinements to a modified ansatz that already accounts for the Higgs mechanism. We can use this modified perturbation theory to do systematic calculations for many different scattering processes, and the tree-level approximation is often good enough. But this only works because we already know about the Higgs mechanism, and we know that only thanks to nonperturbative insights.
Now, back to the original question: Is the Higgs mechanism a classical effect? Well, we can use intuition from classical field theory to anticipate the Higgs mechanism, which is exactly how most textbooks introduce the subject. That intuition is really just an analogy, not a true derivation, but maybe that's enough of a reason to justify saying that the Higgs mechanism is a "classical" thing. I would say it isn't, but I would say that without much conviction, because I rely on the classical intuition/analogy just as much as everybody else does.
Comment: Suppose you have an Abelian Higgs theory with a negative mass term and you have a large parameter multiplying your action (like large N or $\hbar^{-1}$). You can do an expansion in that parameter and look at the lowest order which is classical. Since you would see spontaneous symmetry breaking at lowest order, it's classical.
Comment: @octonion That's a good argument. Thinking of the Abelian Higgs model on a lattice, where the "bare" parameters are finite, having a Higgs potential with a double-well shape doesn't necessarily produce the Higgs mechanism unless the wells are sufficiently deep. That, and the fact that the Higgs phase can be analytically connected to the confinement phase, made me reluctant to say it's "classical." But there are counter-arguments to both of those things, and your large-$N$ argument is a very good one.
Comment: My point is mostly that this is about saddle points. The larger that $N$ or $\hbar^{-1}$ gets the better a simple saddle point approximation gets. The naive thing to do in treating spontaneous symmetry breaking is to consider the minimum of the potential with a constant field, and that is exactly what a saddle point is. With your consideration on a lattice you are not taking the classical limit since you are summing up all sorts of configurations. If you did lattice theory with $\beta\rightarrow \infty$ that would be more what I'm talking about.
Comment: $\beta$ being an inverse temperature multiplying the action, thinking of the lattice theory more from a statistical field theory point of view.
Answer: I'll give a brief answer that is somewhat at odds with Chiral Anomaly's answer. When we do quantum field theory we expand about some 'saddle point' of the action, i.e. some place where the variation of the action vanishes and thus we can think of it as classical. When you are playing around with just the Lagrangian in quantum field theory, you are looking at these classical saddle points.
Often there is a saddle point where all of the fields vanish which is the ordinary thing we do in perturbation theory. But in the Higgs mechanism there is a non-trivial saddle where some fields get non-zero vacuum expectation values. This can't be seen (easily) by doing perturbation theory about the wrong saddle where all the fields vanish so in that sense it is 'nonperturbative' and that is what Chiral Anomaly's answer focuses on. But in another sense we are finding lowest order of the Higgs mechanism by just looking at the Lagrangian and as I am arguing in my first paragraph, that is as classical as it gets.
Comment: I don't know if I agree that "leading-order" automatically implies "classical". IIRC, even tree-level scattering amplitudes can contain nonzero powers of $\hbar$. Can't the classical limit be completely trivial, and the leading nontrivial order already be semiclassical?
Comment: If I consider a classical field theory based on some action that involves the Higgs mechanism, would I still see something like a Higgs mechanism? Of course, the textbook treatment just looks at what the minimum of the potential is and makes an appropriate gauge transformation.
Answer: What does "at tree level" mean? Look at this question. It means that you look only at diagrams that contain no "bubbles" attributable (in colloquial language) to "bubbles"",  which are attributable  {in colloquial language) to pairs of whatever particles-antiparticles. These particles-antiparticles are somehow connected more to quantum effects than the reactions you are looking at. They do happen though, but with a look probability, so they can be ignored. So one says that the process is classical (just as leaving out these bubbles in electron-electron scattering renders it "classical, meaning that, for example, the magnetic moment of the electron is exactly two, and not quantum corrected).


How to remove Address Bar in Safari in iOS?

Question: Old trick with window.scrollTo(0,1); doesn't work. And even worse, the address bar moves only a bit and gets stuck halfway out sometimes.
Answer: It is a combination of many things as I have found when researching this issue for myself.
Here's the code that properly works on iOS5:
(I know I'm a little late, but an answer is an answer, hopefully it can help people in the future)
<!DOCTYPE html>

<title>Hide Address Bar</title>
<meta name="viewport" content="width=device-width, initial-scale=1">

Content

Source: http://24ways.org/2011/raising-the-bar-on-mobile
Example: http://jsbin.com/isenax/
Comment: Instead of specifying the height in the CSS style, you can also add an additional entry in the viewport meta-tag. You can specify height=device-height. This way, the bar will still be hidden even if you change the orientation of the device.
Comment: For the new iPhone 5 display you'll have to bump the min-height up a bit. My experience showed 505px to be enough. Depending on your application you might want to set this dynamically depending on the user's device.
Answer: i guess the code should still work..
anyways here is the correct way to tell mobile safari that you want the full screen:
click me
e.g. use
<meta name="apple-mobile-web-app-capable" content="yes" />

EDIT
Apple uses a new mobile-ui property to display a minimal UI in safari:

A property, minimal-ui, has been added for the viewport meta tag key that allows minimizing the top and bottom bars on the iPhone as the page loads. While on a page using minimal-ui, tapping the top bar brings the bars back. Tapping back in the content dismisses them again.

use it like this:
<meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1.0, maximum-scale=1.0, minimal-ui" />

source: https://www.perpetual-beta.org/weblog/ios-7-dot-1-mobile-safari-minimal-ui.html
Comment: I want it to work without adding the app on the homescreen, that's the thing.
Comment: Tried all the meta tags, I need the old behaviour that can hide the address bar after the page is loaded without adding it page to the home screen.
Comment: In my situation the change only worked, after i put the app on the homescreen again.
Comment: If your page doesn't fill the full height of the browser, the address bar won't hide. Try setting "height: 100%" on something.
Answer: Since IOS7 the window.scrollTo trick doesn't work anymore. There is no work around for the moment except to invite the user to add your website to Home Screen.
http://www.mobilexweb.com/blog/safari-ios7-html5-problems-apis-review
Is it possible to hide the address bar in iOS 7 Safari?
Impossible to hide navigation bars in Safari iOS 7 for iPhone/iPod touch
Answer: On iOS 7 you can use the minimal-ui meta tag. Unfortunately, that was removed in iOS 8.
For iOS 8 there's a project called brim that is supposed to bring back the minimal-ui type functionality. It can be found here: https://github.com/gajus/brim


How do I stop this lag?

Question: When I do something on my Minecraft server, the world changes, but after a small period, my position and inventory goes back to where I was before. When I put stuff in a chest, it stays in the chest, and then I go get reset to my former inventory and position, and the stuff is still in the chest, so I have a duplicate. When I build, the building stays. But I just reset my position and inventory. This is happening to other players, by the way. How do I stop this lag?
Comment: what are the specs its running
Answer: This is called desync and rubber banding(because your position moves back and forth like a rubber band). What this basically means is your server can't keep up with what's happening in game and is ticking behind. This is why it appears like you have 2 of the same item, the client is desynced from the server (which sees only one). Assuming you have access to the console you can check to see if you get a message like "server is overloaded" or "last tick took x number of seconds"
If you are locally hosting you can try to allocate more ram to the server by modifying the run.bat file (or whatever it happens to be named) to allocate more ram. If this doesn't fix it you can look into getting a better cpu or IF your cup is compatible and you have PROPER(preferably water) cooling you can try overclocking your cpu.¹
If you are cloud hosting you can purchase(or in some cases earn) better computing resources. Or check if you can allocate more.
Independent of where you are hosting you can install plugins/mods that aim to reduce server lag, this isnt a mod like optifine which is client side, rather these are server side that run on the server to reduce lag. This answer showcases a few popular mods for fabric that do just that.
¹I am not responsible for any overclocking related hardware or software failures or damages that may be caused by overclocking your cpu
Comment: Is there a way to cause this on other servers?
Comment: both desync and rubberbanding can be caused by a slow internet connection or high ping, however i assumed this wasnt whats happening because that would be client side localized, meaning for only one user. you can of course overload other servers with lag machines or just too many players

How do I stop this lag?


Install an application so that it can be launched from the terminal

Question: I had to update my Firefox from ver 3 (i.e. the one that Ubuntu 10.04 ships with) and move it to Firefox 7.
So firefox gave a tar.gz file to extract the browser from. I ran sudo apt-get remove firefox, and then extracted the contents of the tarball to /opt/. But when i type the command firefox in the terminal it responds by saying firefox not installed. I am now using a launch shortcut to open firefox, but what i want to know is
How can I install the application so that I can open it from the terminal?
Answer: The programs to be executed are searched in the directories defined in the environment variable PATH.  You can see what you have defined using:
$ cat $PATH

Assuming you have the executable available in /opt/firefox/bin, then you can do:
$ export PATH=$PATH:/opt/firefox/bin

To make permanent, you have to add that line it in your ~/.bashrc.
Comment: How will I add this line to the `./bashrc` ?. I have tried adding the complete line but it does not work.
Comment: Note the file is .bashrc, not bashrc.  It has to be in your home directory.  For what it is worth, you have to omit the dollar sign.
Answer: For a single user:
ln -s /path/to/firefox ~/bin/firefox

For all users:
sudo ln -s /path/to/firefox /usr/bin/firefox


Are orbits possible in de sitter space?

Question: Since the de sitter space has constant positive curvature does that mean that objects can't orbit around other objects?
Answer: Couchyam's answer is for undeformed de Sitter space - empty if you will. So no orbits in that.
What you are asking is if one put an object the mass of the earth in a de Sitter space, could objects the mass of the moon orbit the earth thing?
It would seem that the earth like mass would follow a prescribed path, but since its a rule in General Relativity that any small patch of space is flat, the moon like thing can orbit the earth like thing.
In fact our universe is likely well modelled by a de sitter space: https://en.wikipedia.org/wiki/De_Sitter_universe so its obvious that orbits can exist.
You have to be careful with definitions here. Saying that our universe is a de Sitter space is only an approximation. That's where Couchyam's answer comes in - for a true exact de Sitter space, which is necessarily smooth and featureless with only vanishing small test particles allowed.
You can also look at the limiting case in a lumpy de Sitter like universe that we are in. If you take a completely flat spacetime, then anything can orbit anything else at any distance, but with a de Sitter universe at some point the expansion would rip extremely weakly bound orbits apart.
Comment: Nice answer, but I thought I should comment that I accounted for deformed de Sitter at the beginning of my answer in the parenthetical remark.
Comment: Thanks - I saw that but I think its a bit hidden, so I wanted to expand a bit for the lumpy de Sitter like case.
Answer: I'll assume you are asking about geodesics in de Sitter (If the objects contribute to the energy-momentum tensor they perturb the metric and perform orbits).
De Sitter space can be thought of as the set of points in 4+1-dimensional Minkowski space that satisfy
$$
X_1^2+X_2^2+X_3^2+X_4^2=1+X_0^2.
$$
Cross sections of constant $X_0$ are 3-spheres, so you might think that time-like or null geodesics can go in orbits around the spacetime. However, if you start at a certain value of comoving coordinates (say on $S^3$), it turns out that there is no time-like or null geodesic that returns to your starting point.  The easiest way to see this is through a Penrose diagram for de Sitter.
The Penrose diagram for de Sitter is shown below: (from Les Houches 2001)

Penrose diagrams encode the causal structure of spacetime. Every point in de Sitter corresponds to a point in the above square, and diagonal lines at $45^\circ$ angles correspond to the world-lines of null geodesics or light rays. Two light rays are shown above, going from the line $I^-$ to $I^+$.  The 'North Pole' and 'South Pole' are antipodal points on $S^3$, while $I^+$ and $I^-$ correspond to points at the infinite future and infinite past (if you want, you can think of these as equivalence classes of time-like geodesics).  Hence, a ray of light has 'just enough time' in the lifetime of a de Sitter universe to travel from $\theta=0$ to $\theta=\pi$, and can't get back to its original comoving position at $\theta=0$. In fact, it's clear that any two time-like geodesics that attempt to go around $S^3$ will intersect at most once.

Are orbits possible in de sitter space?


Blender 2.81 bad shadows (missing settings)

Question: Seems like new version has no shadow settings. I read that new version should calculate and make setting automatically for better results. But it look much worse. Any ideas?
2.80
2.81
Settings:
2.80
2.81
Comment: It's hard to tell without know what settings you are using. Perhaps add a screenshot of your lamp and global eevee shadow settings
Comment: Of course. Question edited.
Answer: Blender 2.81 has better shadow algorithm, the final result will deliver a higher quality shadow, but it needs more samples in order to get to that result.
Go to the Properties Render tab and in the Sampling panel increase the number of samples.
Comment: This doesn't help, before I used to adjust Exponent to get the contact shadows to the exact look I wanted (there had been light leaks), now the parameter is missing and the light leaks are back
Answer: In the Render properties panel there is a section for Shadows:

These affect the Eevee render engine globally.

Cube Size affects point and area light shadow maps
Cascade Size affects sun light shadow maps

The rest of the controls are quite self explanatory.
Answer: I know it feels like it is kinda obvious, but I say it: have you tried restarting it?
I'had been looking for an answer for that question, and nothing helped. I was fed up, closed it, but it bothered me so much, that in a half an hour I've started it again, and voila, the problem was gone.
Comment: If it doesn't work on the first attempted restart how many more  to be sure?  Apologies for the terrible attempt at sarcasm. ... but...  _Have you tried restarting?_ could  be the answer to everything, rarely solves anything.
Comment: Sorry for the bad wording. I state it again: after several attempts, I did just that, and the problem was gone. Maybe my pc was doing it weird, maybe... I have zero ideas about why it worked. When I modified something, I always resetted the value to the original, to avoid an effect caused by several factors, but none of it solved the issue. In this case, what should I say? It helped with none of the issues before, but it did in this case. If you say I should, I will just delete my answer. Now I see, your way works much better /sorry for the terrible attempt on sarcasm/
Comment: NP with you leaving it.  Added comment as it came up in late answers review...  will see if it makes thru the others (review is 2020 version of Spanish inquisition)  wouldn't be able to count how often someone comes to me with a computer problem and gets same advice.. when they ask what the problem was.. "_No Idea_ ".  Welcome to BSE 8^)


Is there a rule of conduct to handle supposedly ill-minded requests?

Question: I've been following a post that was asking to spoof an email sender.
OP was asking for details on how to spoof a sender's address. Downvotes were pouring in, while a lively communication in the comments section took place. I flagged the post for deletion, but as you know this is a process that might take a while. So my question is, is there a code of conduct to handle requests that seem to give offense to a netiquette or otherwise appear to be ill-minded, and how to handle such requests by the community?
Comment: Note, this isn't nearly as malicious as yacc is making it out to be. Adding an alias to the email's "FROM" header is quite common.
Comment: related, if not a dupe: https://meta.stackoverflow.com/questions/267699/how-do-we-handle-questions-that-are-potentially-or-blatantly-illegal-or-maliciou
Answer: If you feel a question is in violation of SO's rules, flag it.
If anything, you don't do this:

"If I could I'd stop this piece of crap of a request at once. @AbhishekD" – yacc 22 mins ago

Comments like that are in violation of SO's "Be nice" policy, and will be flagged.


Center of Mass Velocity Question

Question: How does the center of mass of a collision change after a collision has occurred compared to before. For instance, I know that it is moving, but does the velocity change and if so does it depend on whether the collision is elastic or inelastic
Comment: Possible duplicate of [Can the velocity of the center of mass of two spheres change after a collision?](https://physics.stackexchange.com/q/83583/)
Comment: -1 *I recall hearing things about how the COM can not move* is rather vague. A good question provides evidence, rather than appeals to vague memories.
Comment: See also [Conservation of Linear Momentum at the point of collision](https://physics.stackexchange.com/q/59515)
Comment: The centre of mass of an object depends on what you define as the object. A totally inelastic collision will lead (if not to destruction) to the objects sitting adjacent to each other and moving as one, so it may (depending on the application) lose meaning to talk of their centre of masses independently.
Answer: If you have a system which consists of two blocks then the velocity in a given direction of the centre of mass of the system of two blocks does not charge if there are no external forces acting on the blocks in that direction.
So if the blocks are moving on a flat and friction-less horizontal table the horizontal velocity of the centre of mass of the two blocks will not change irrespective of what type of collision they undergo.
Answer: The collision is said to happen in an instant, changing the velocity and rotational speed of a body, but the position and orientation do not change.
The change in velocity can be expressed as $$ \Delta v = \frac{1}{m} \int F\,{\rm d} t $$
where the force $F$ is short lived and very high in value such as the impulse $J = \int F \, {\rm d}t$ is a finite value. The result is that $\Delta v$ is finite.
But the change in position is zero because the finite velocity is multiplied by an infinitesimally small time
$$ \Delta x = \int v\, {\rm d}t \rightarrow 0 $$

Center of Mass Velocity Question


Which city was attacked by Nazi-German war flights in India during WW2?

Question: Nazi-Germany ran a bombing raid over India, in WW2. Which city was bombed, and what effect did it have? i.e how many casualties were inflicted, was transport closed down, or was there other damage to infrastructure?
Comment: Welcome to History.Stack-Exhcange. I've made several edits and changed the question slightly so that it fits the QA a bit better.
Comment: @T.E.D . Yo you are right man. Chennai(Madaras) city was attacked by german warship named "EMDEN". [Chempakaraman](http://en.wikipedia.org/wiki/Chempakaraman_Pillai) was the person involved in this attack. Some of the unexploded bombs thrown from this ship are still in available in [Government museum chennai](http://www.chennaimuseum.org/draft/gallery/02/04/arms4.htm).
Answer: Madras* was bombarded by a German warship during World War I. That's the only instance I could find in either war of an Indian city coming under that kind of fire from German regular armed forces.
Germany had no aircraft carriers, and their only real long-range bomber in WWII, the Heinkel HE 177, appears to have only been used in the Eastern and Western fronts in Europe. I don't believe Germany ever held any territory that would have been within the HE-177's 5,000 KM operational range from India. (The Eastern Ukraine is a wee bit further than that from New Dehli).
* - Now Chennai
Comment: Actually, Germany sent a few planes to Irak to support an anti-English coup, so they were way closer than Ukraine. That said, I found no report of those being used to strike outside Irak, and they did stay in Irak only for a small period before being overrun by the British.
Comment: @SJuan76 - As near as I can tell, the bombers sent there were HE-111s, which had a range in the general vicinity of 2,000 KM. About 3,000 KM would be needed from there. The 177 I mentioned above was not produced until about a year after the end of the insurrection.
Comment: @DavidBlomstrom - Pretty much. The captain's rationale is reported in (a translation of) his own words if you click the link at the top of the answer.
Answer: Agree with TED that German warships did not attack any Indian city. But a thing of interest is that of Japanese warships: Kakinada and Vishakapatnam were two cities that were attacked by the Japanese in 1942. It was believed that Madras would be under attack soon, but it wasn't eventually.
Comment: Quite. If the question was about **Japan**, then the answer gets very different indeed. Particularly if you take "India" to mean the British territory (including Bengal and Burma), rather than the boundries of the modern country.
Comment: The final Japanese offensive to Imphal and Kohima took place in the borders of India and Burma, on the Indian side.
Comment: Japan actually airstriked those cities on 5 April 1942 followed by Colombo.....


how to raise ambient light in a animation

Question: I am making an animation of a flying object and would like it to be lit with overall ambient lighting. I am using a transparent background (alpha chanel) From the sun the underside is too dark and if I add more lights it gets reflections off of them which does not look natural.
yeah -- I'm a really noob at this. Thanks
Answer: Try adjusting the world background. A brighter color will result in more lighting. This setting is located in the World tab of the Properties editor. You can also add an HDRI by clicking the Use Nodes option, then selecting Environment Texture under the Surface options.
Comment: This does not seem to work in 2.79 (menu quite different and washes everything out to grey??)
Thanks -- after much head banging I realized you were in 2.8
and works as I thought - my colors look much better too
now just have to spend the next 30 hours relearning 2.8 and unlearn 2.79
Comment: I am in 2.79, just with a different color theme, sorry for the confusion. This menu is located at the right of the screen in the default layout. You have to click on the tab with the spherical globe icon to show what I have in the screenshot.


Moment of Inertia and Total Kinetic energy about the pivot versus centre of mass explanation

Question:
I understand that the Total Kinetic energy can be determined by finding out the rotational kinetic energy about the pivot or by finding the rotational kinetic energy about the centre of mass and then adding the linear kinetic energy about the centre of mass. I have even proven this to myself mathematicaly they are equivalent. I don't understand from a physics point of view why this is the case. Any explanations would be appreciated.
Comment: you may want to read this https://en.wikipedia.org/wiki/Parallel_axis_theorem
Comment: Yeah I know the parallel axis theorem and understand thats how we can change the axis of the moment of inertia. My question more specifically is related to why by taking the moment of inertia by the pivot do we ignore linear kinetic energy.
Answer: About the pivot, the body can be viewed to be in pure rotational motion since the pivot is the center of rotation of each particle of the rod. Here, the center of mass has no special significance.
On the other hand, if we are not willing to take advantage of the fact that the motion of each particle is perfectly circular, we may view it as combined motion: (about the center of mass) + (of the center of mass).
The second method is particularly useful if it were not possible to classify the motion of the body as circular about some stationary axis. Here the motion of each particle from the ground frame would be really complicated. So it helps to break it down into two parts, which is how we express combined motion. In this case we will have circular motion about an axis through the center of mass(since the body is rigid) and the center of mass could have some arbitrary path.
The two methods are just different ways of describing the motion of the entire body. So one can expect to get the same kinetic energy in both cases.Mathematically, the parallel axis theorem can be used to prove that the two expressions for kinetic energy are indeed equal.


Why user_pass column in wp_users table is varchar(64)

Question: while working on a project, I found that "user_pass" column in "wp_users" table is varchar(64). WordPress always stores user password in md5 which is a 32 char ASCII string. So why not store it in char(32) with ascii collation. I am asking because I am working on a table that stores user password. Is there any other advantage of using varchar(64).
Comment: I don't think that WordPress uses md5. It uses [phpass](http://www.openwall.com/phpass/)
Comment: phpass is a hashing framework which supports different hashing algorithms, md5 is one of them. However, it is true that WordPress no more uses md5.
Answer: It is because of different encrypted algorithm. Sometimes users will override the MD5, which is the default algorithm, and add their own, which might need a little longer length to store the password.
Take a look at the Q&A's »What data type to use for hashed password field and what length?«, having detailed information about hashes and their length, at Stackoverflow for reference.


My older cat is very aggressive towards my 6 week old kitten

Question: I have a cat about 2 months old who is very aggressive he attacks my feet when I walk and any time I try to pet him he bites (hard) we got a very small kitten today who is very sweet and loving and the older cat is trying to play with it but is getting to aggressive. How can I stop this?!
Comment: Is the older cat two months old, or have you only had it for 2 months. A 2-month-old cat is still a kitten.
Comment: This is a great question that gets asked a lot. The short of it is cats often don't like new cats moving in and you have to introduce them carefully. See http://pets.stackexchange.com/questions/4371/recommendations-for-introducing-adult-cats-to-newly-adopted-adult-cats
Answer: This is a common behavioural problem.
Play with them as much as possible in such way that both take part but don't have to interact directly with each other, after some time the antagonism will subside and they will get along without hitch.
The issue is caused by cats being territorial: your kitten grows up, starts to become adolescent and attempts to pressure the elder into submission. In essence it always look different, but comes down to it.
P.S. If the fights are agressive, break them up by using water spray. For this purpose, use clean window cleaner spray bottle and pour full of water, they will break up and run off to lick the fur clean. Just make sure the bottle is cleaned properly so it does not contain any chemical residues.


Facebook startForPostWithGraphPath completionHandler block not called if run from background thread

Question: I am adding error handling to my code that post a message to Facebook, but am hitting an odd behavior that I am trying to understand.  In my completion handler for FB's startForPostWithGraphPath I check to see if there is an error, if there is then I wait a few seconds before trying to post again.  The issue I am hitting is that when I try to call the method to post this message a second time, I run it on the main thread it works fine.  If I try to run it on the background thread it fails silently.  As in the completion handler is never called the second time.
works
dispatch_after(popTime, dispatch_get_main_queue(),
               ^(void){
                    [MYSocial shareToOpenGraph:poll];
               });

Fails
dispatch_after(popTime, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
               ^(void){
                 [MYSocial shareToOpenGraph:poll];
               });

I am curious if anyone else has any experience with FB request methods needing to be called on the main thread.  It seems to me that calling retry logic on a background thread is the correct behavior, but obviously is not working for some reason.
Answer: i can confirm that the request works on the main thread & fails on the background thread in my application.


Presence of Muhammad in Battle Of Karbala

Question: According to some Hadith book written by some scholar,During the Battle Of Karbala, Salma went to visit Muhammad's wife Umme Salamah. In the Convesation between them,Salama told she had seen Allah's Messenger with dust on his head and beard. She asked him what was the matter and he replied, `I have just been present at the slaying of al-Husayn.' Does such thing really happened ? If Muhammad present in that battle field why he didn't save Al-Hussain ?
Comment: If you're looking for the confirmation of a hadith, you really could show more research effort than "some Hadith book written by some scholar".
Answer: First, the significance of this is to prove that the prophet actually have seen his grandson in the battle of Karbala, this means that he knew what happened to him, who killed him and everything happened there.
Now, your problem is that you feel that Al Hussain was actually in trouble to be saved. Shia believe that Al-Housain was able to survive but he didn't he chose to sacrifice his life to save Islam. please read more about battle of Karbala .
Comment: @user689 and warriorprince,  'we' may be the voice of God himself. becuse it came from sky, voice of 'all muslims' coming from the sky doesnot make sense
Comment: Thanks for the source..I wish i read this if i know Arabic...Ya actually in the battle field according to shia tradition,A void from the skies says "We are satisfied with your deeds and sacrifices". Please clarify me What is "WE"..I mean who and all satisfied with his sacrifice to save islam ?
Comment: @Warrior I think I understood this wrong, MAKZ is right. In arabic 'We' signifies the greatness of god.
Comment: @Warrior sorry for that source, this guy has something in his description about karbala please read it: http://islam.stackexchange.com/users/67/battle-of-karbala
Comment: MAKZ.."Voice of God himself"..There is only one prophet right..I can't able to find the meaning behind "WE"


Where should you go if gravity pulled sideways?

Question: If the entire Earth's gravity immediately shifted so it was pulling from East to West, what should people do?  Keep in mind that this is not reversed, but merely tilted sideways, and maybe at an angle slightly downward so that everything doesn't just fly off into space.  Would it be better for everyone to stay put, or try to find a common meeting place.  My initial thought was the Svalbard seed vault or some place similar, although there would be terrible constant rainstorms (the oceans would be falling), and it might become so icy that travel would be nearly impossible.  How long could anyone survive, and how should they do it?
Comment: Uh... I don't think you understand how gravity works....
Comment: @Aify Since this question is in regard to a world where gravity *doesn't* work properly, I'm not sure knowing how actual gravity works is terribly important.
Comment: what happens at the poles?
Comment: @MozerShmozer because what OP describes doesn't make sense. "Gravity that pulls slightly downwards" is relative to the person the gravity is affecting, and where they are on the planet.
Comment: World*building* ... not.
Comment: Earth's gravity is not "Earth's" gravity, it's just the sum of the gravitational force of each particle with mass in each atom of Earth. It's not the case that things fall toward the center of things; it's just things attracting each other in from all directions.
Comment: I feel like you're trying to rationalize some of the levels from Super Mario Galaxy, in which case, don't. It plays pretty fast and loose with the rules of the universe as it is.
Answer: The Earth would fly apart. Gravity pointing downwards is all that keeps this ball of dirt and metal holding together in space. If that force is no longer pointing downwards, I would expect something like this would happen (as viewed from a point above the Earth's north pole):

It is important to note that "East" points in completely different directions depending on where you are on the Earth's surface, hence the rotational symmetry of the above images.
In this scenario, the Earth is reduced to a disk of rubble rapidly spreading out into space. Nobody survives. NoTHING survives, except maybe lithophagous bacteria living deep inside rocks.
Comment: I wish I could upvote once for the concept and againg for the graphics :v
Comment: +1 please may I request u replace Earth with Sun I like to see supernova for once.
Comment: Thanks for the graphics, although I did put in a stipulation that gravity would pull at an angle slightly downwards to keep it from falling apart.
Comment: @margalo The effects on the Earth's structure would still be catastrophic. Millions of tons of rock would shift thousands of miles in the mantle. I don't know what shape the Earth would turn out in, but assuming the surface stayed intact it would probably become a raging ocean of lava.
Comment: @ApproachingDarknessFish I don't think humanity would be around long enough to enjoy it though.  The massive, global tsunamis would wipe us all out fairly quickly.
Answer: Greg Egan wrote a story about that!  You can read Bit Players on-line for free.

Sagreda looked back over her shoulder, only to be dazzled again by the rising sun. "Can you tell me what's happened to the world?" she pleaded.
"Are you saying you've forgotten the Calamity?" Gerther asked skeptically.
"What calamity?"
"When gravity turned sideways. When it stopped pulling us toward the center of the Earth, and started pulling us east instead."

Not only does it cover the absolute absurdity of the idea within the story itself, but the characters exploit the nonsense physics to produce power and start an advanced civilization underground.
It is well worth reading the full short story. Anything by Egan is recommended as masterful lessons in worldbuilding.
Since the premise is nonsensical, to the point that handwaving and unknown extra details are needed to make a small cave setting work at all, we really can't answer your question. You, the author, would need to introduce other unexplained details or inconsistencies to further your plot, and can make it "work" however you needed it to work out.

An older novel, On by Adam Roberts (pointed out by a4android) also has a plot of a sideways gravity world that presents as an endless cliff.  I've not read it, but it involves a great deal of travel and adventuring in this environment.
This might be the real novel mentioned in the short story and expresses Egan's own impression of the concept:

It was as if someone had tried to invent an exotic new world, but knew so little about the way the real one worked that all they could come up with was a dog's breakfast of contrivances and inconsistencies.
…this world is based on an obscure pulp novel called East, by a man named William Tush."

William Tush appears to be a fake name, and zero point energy is mentioned in the story, and the form of the character's names (Tighe, Wittershe vs Johnhis, Gissher, also noted as silly within Eagan's story) is clearly mimicing the other, so I suspect Eagan's story is a reaction to the shoddy worldbuilding in On.  Others agree.

After all, there were no premises that could give rise to both the believable local physics of the everyday objects around her and the Road Runner cartoon laws that the world required to hold up on any larger scale.

I suspect that anything the OP does with the concept would share the same fate, unless it's full blown meta "this universe is ridiculous" like with Bit Players, or the effect is thought out better somehow.
Comment: Appreciate your addition of the link to Roberts' ON (2001). Excellent expansion of your answer to include the possibility of Egan reacting to Roberts' worldbuilding. That really puts the icing on the cake. Well done, sir.
Comment: Thanks a lot— I didn't realize the concept had been explored so much already.
Answer: Setting the where aside for a moment, I think the first question is how would your average person go anywhere in that case?
If gravity were to suddenly start pulling everything sideways at 9.8 m/s², then anyone who happened to be outside at the time is probably already dead.  They would have "fallen" sideways (or been dragged along the ground, if the pull is sideways and slightly downwards), accelerating until either they reached terminal velocity or until they slammed into the nearest building, tree, or cliff.  Basically anyone more than about 20 feet from a vertical surface is likely to sustain serious injuries when the gravitational pull shifts, if they're not killed outright.  In either case, those people aren't likely to be going anywhere.
Your most likely survivors will be people who were inside of buildings at the time.  And probably only smaller, wider buildings, with a low center of gravity, as skyscrapers probably cannot withstand a 1G horizontal load.  So a person inside of a house, for instance, has a decent chance of surviving the transition.  So too does the house, if it has a deep/well-anchored foundation.  The person inside could move around (inside the house, that is) by walking on the walls.  Once they want to go outside, it's another problem entirely.
If gravity is pulling things sideways, then essentially every door in every house/building now opens to a sheer cliff.  To go anywhere, a person needs to traverse that cliff.  Which for a person of average strength/physical fitness and not in possession of advanced rock-climbing knowledge and equipment is going to be virtually impossible over any nontrivial distance.  Maybe a professional climber who happened to survive the initial event unscathed and had their equipment on them at the time would be able to make some progress.  However Joe Average is probably screwed once all the food in the house is gone.
But let's assume you've got someone who survived the gravitational transition and is able to move about (and let's assume that the planet hasn't torn itself apart or otherwise been rendered completely uninhabitable...which is liable to happen from a strictly scientific standpoint but also not really any good for storytelling).  Where do they go?  I can think of a few options:

Forests - If you can safely reach a dense forest (and it's still standing; taller trees may well suffer the same fate as skyscrapers), you may be able to use the trees to move around more easily.  Moreover, they may provide a source of shelter, and any birds and other small woodland critters that survived may provided a source of food (which is easily accessible, as "climbing" a tree is now as easy as walking horizontally along its trunk).  Over time you could potentially construct walkways/bridges and similar structures to make moving around easier and safer.
Shopping Centers - Think grocery stores, malls, and similar buildings that tend to be large, short, wide, and solidly constructed.  These may still be largely intact, would provide a decent-sized surface to move around on, and will contain extensive stores of preserved goods that you're going to need in order to survive.  If you can get inside they might provide some decent shelter as well, although the typical layout (large, cavernous interior spaces) might make this quite hazardous.  Given sufficient time and resources, however, you could potentially rework all of that interior space in a way that better accommodates sideways gravity.
Natural Cliffs - Ideally you want to get back into a situation where a large area of solid ground exists in the "downwards" direction.  The best option for that sort of thing would be eastward-facing cliffs, and/or mountain ranges (if they're steep enough).  Cliffs located near farmland/fertile soil might be ideal, as with a bit of effort you should be able to liberate some of that soil (if the gravitational transition didn't do so on its own) and relocate it to your cliffs.  Then you could look at reestablishing basic agriculture, expanding your living area by quarrying the surrounding area, and possibly creating a tunnel network to access nearby locations of interest.
Comment: (1) You say, "every door in every house/building now opens to a sheer cliff." But in fact, some walls will be "horizontal", and some will be sloped. (2) You mentioned staying in your house until all the food was consumed. You should note that toilets probably won't work correctly. (3) My first thought on reading this was "Forests! — That's brilliant!" But, on further thought, wouldn't tall trees have the same problem as sky scrapers? (Consider what wind can do to a tree. Compare to a persistent (permanent) lateral force that's equal to the weight of the tree.) Continued ...
Comment: ... Continued: (4) You mention "westward-facing cliffs." I may be confused, but I believe that eastward-facing cliffs would be the safe ones. But how many cliffs are perfectly aligned along a north-south meridian? It might be better to find a tall/steep mountain. (If it's round enough and big enough (in circumference), then it will have a "top" surface, just like a tree.) (99) Good answer!
Answer: If the entire Earth's gravity immediately shifted so it was pulling from East to West, what should people do?
Nothing. Everybody would be dead within the next 15 minutes (at max). Most would be dragged brutally on the surface and slammed against buildings, trees or mountains. Others would be brutally hit by rocks, vehicles, other people, animals and all other heavy things which would be rolling westwards at a speed which begins at 35 km/h and increases by 35 km/h every second.
I haven't done any in-depth research, but I would wager all human population would be dead within the next 15 minutes, all mammals within 1 hour, all vertebrates within 90 minutes and practically every form of macroscopic life within the next 1 day.
Answer: First, we have to ignore...
We ignore the destruction of the planet itself. We ignore physics, too. So we'll set that aside and treat this as more of a problem for life on earth than a fundamental problem with the universe itself.
First moments
In the first moments after gravity goes sideways, everyone who is outside is gone. Hikers, joggers, walkers, people going about their daily lives on the planet's surface suddenly shoot sideways and fly out into space, accelerating at 9.8 meters per second per second until they reach terminal velocity. Or until they impact with a building or a mountain , etc. between them and space -- those folks become a red smear on the side of whatever they hit. Much like a bug on a windshield. Either way, they die. So do all the other animals. There will be much screaming.
And all the kids' toys and cars and trucks, and loose pebbles, and large rocks, and landfills full of garbage, and your Amazon delivery sitting on the front porch, and anything else not attached to the planet goes flying off into space. Suddenly the debris field surrounding out planet just got more crowded.
People inside factories or garages or anywhere where sharp things exist in the path of your decent towards the wall will be impaled and die either quickly or slowly, depending on the nature of the impaling item. There will be much screaming.
People in restaurant or home kitchens will have to worry about falling into hot stoves, deep fryers and other nasty things. Or having those things fall into you. Hot grease flies out of deep fryers. Knives and chopping blocks and hot pans and vats of hot soup go flying into people and buildings. There will be much screaming.
Indoors and underground
Indoors and underground, people, furniture, pets, house plants, dishes, TVs, and everything else suddenly slams with extreme force into the walls. People will die. Other people will have broken limbs or bloody noses. Some people will die later because there's no way to get them to hospitals. People in the hospitals will face a harder time. Some things will slam into windows, shatter those windows, and become part of the debris cloud around the planet. There will be much screaming.
Mobile homes and houses that aren't well anchored will also fly off to join the debris cloud. Probably shattering into rubble as they fly off. Rocks and cars will impact against buildings, destroying them and adding to the flying maelstrom of death.
Some people will die in the clouds of debris. Others will die of asphyxiation once they get far enough out. Or cold. Regardless, there will be much screaming along the way.
Planes, trains, and boats?
At any given moment, about 5,000 airplanes are in the air. These planes will have some seriously bad turbulence. The pilots, strapped into their seats, should be okay once they get control of the planes. The ones near the ground will probably crash as gravity flips them out of control for the first few moments. The ones higher up will avoid that fate, but they probably cannot land. Sure, they could approach the ground. But they cannot land, because if they slow below stall speeds, they'll fall with gravity. So they'll die more slowly than the rest, at least.
Boats will slip sideways in the ocean. This will either flip them over on their sides (since the keel of the boat will be pulled slower than the portions out of the water), or will lift them entirely from the water. Either way, bad day to be at sea.
Trains will derail instantly, then crash out into space. Subways will derail and slam into the walls of subway tunnels. Those who survive this crash might be able to escape by climbing out of the tunnel walls. Maybe.
Submarines, if they don't smash into the sea floor, will probably give you the best odds of survival for the short term of any transportation means. The sub can rotate until down is down, and keep going for as long as the ocean is stable.
Goodbye, ocean
The ocean won't be stable for long. It will surge over land and, eventually, into space. Coastal regions will either become landlocked within minutes, or be washed away in the worst tidal surge ever, depending on whether they are east or west coastal facing.
Goodbye air
And then, of course, let's not ignore the hurricane-force winds that will rip things apart as all of our air flies off into space.
Final results.
The Earth is a cold, desolate, lifeless region with no hopes of recovery. You know, after all the screaming is done.
I feel like this should be an XKCD What-If response.
Comment: *"The earth is a cold, desolate, lifeless region with no hopes of recovery."* But planet Earth is still there?
Answer: Well first things first gravity would not just suddenly be pulling to the west, although polar shift is a thing
http://www.nasa.gov/topics/earth/features/2012-poleReversal.html
and there are actually several fantasy books that use this as one of there story driving forces although any titles escape me at the moment.
HOWEVER: baring the fact that it doesn't happen lets say a god or gods go and say "yeah, all this stuff.... its gonna start falling this way".. the first thing that would happen would be that anything on the western side of the planet would be gone into space, even when you say that it is slightly angled downward there is always a place on a sphere where slightly downward is going to (unless gravity started moving in a circular motion essentially from east to west but that is a whole other problem.) result in being pulled off of said sphere (earth).
so here are my 10 predictions that i think would happen NOTE: I am not a physicist or gravitational scientist of any kind just some one who enjoys these kinds of problems.
1: the western hemisphere would be uninhabitable to a point.
2:Anyone who was in the Western hemisphere is probably dead or really badly injured.
3:ocean levels would sink in the east and rise in the west, by how much i have no idea.
4: our atmosphere would maybe begin to siphon off (not sure on this one)
5: things like building, monuments, and the such would collapse due to stress they were not designed for killing millions.
6: people caught up in this would "fall" sideways probably dragging on the ground until they could grab something and/or die from getting dragged into a building or something.
7: cars would not work even if they were right side up due to gravity pulling gas down into the gas intake pipe (or whatever it is called.)
8: most (if not all) animals and fish would loose their balance and in the case of underwater mammals (i.e. dolphins) would drown as they swam against gravity trying to surface for breath.
9: birds would not be able to fly unless they figured out how to  fly upside down. (same goes for planes, they would have to launch only in the east and never fly into the west or they would loose and be sucked into space.
10: Life would most likely end for Planet Earth.
SO to be totally honest i would try and make my way to a swing-set and at least be able to sit comfortably and see a really unique sunset and wait for the world to end.
Comment: (1) If the OP says that gravity will suddenly start pulling to the west, what basis do you have for saying, "No, that won't happen"? (2) What is "the western side of the planet"? (3) "cars would not work even if they were right side up" Huh? What? (4) Dolphins normally "swim against gravity" when they go to the surface. It's not clear what would happen to the oceans, but I don't see dolphins drowning as being a problem. (98) I believe you're misunderstanding the premise of the question. See the other answers to understand the question. (99) Please use correct capitalization/punctuation, etc.
Comment: A polar shift has nothing to do with gravity.  The theories on that are about magnetic fields, with the more extreme also including a shift in the axis of rotation.
Comment: Again like i said in the question im not a physicist or anything like that this is just where my mind went while reading the other answers/comments and i am well aware that polar shift has nothing to do with gravity, this just reminded me of it and therefor made the statement that it was a thing. I never said that it affected gravity.
Answer: Gravity is so powerful, every object on the earth would suddenly be pulled to the "east".  When I say on the earth, I mean if it isn't rooted several hundred feet into the crust.  If there was only a slight downward pull to keep the earth from flying apart, there would be nothing but dust as everything was ground into a fine powder against the surface of the earth.  Of course the ocean's, lakes, and rivers would turn that dust to mud.  You'd end up with a planet of swirling mud.
There would be no safe place for a human in such a world.  Except maybe a surfer or snowboarder...they might survive until they starved or fell asleep and fell off their boards.


How does a quantum circuit calculating the inverse of a non-injective function act?

Question: Lets say I have a non-injective function $f()$, adding image for reference. Now lets say I build a quantum circuit to calculate $f^{-1}()$. If the input register has the value $i$, does the output register have all the values $j$ in superpostion, such that $f(j)=i$ ?
Comment: what would you think $f^{-1}(A)$ would be?
Answer: This is essentially a matter of definition. If you design and build a function which you are claiming to be $f^{-1}$, you first have to define what the output will be if the input is $C$, and what you define will determine how you implement it. Outputting some sort of superposition might seem like a reasonable option, but mathematically the function is unlikely to behave how you would expect it to. But that might all come down to the context you're using it in.
Comment: The context I'm using it in is to find the different inputs which have the same image under $f$. You can think of $f$ as a function calculating some cube-roots in a finite field where cube-roots are not injective.
Answer: Any operation on a quantum computer has to be reversible, measurement and reset being an exceptions. In your case the operation is not reversible as for C you have two possible inputs - 3 and 4. To implement your operation on QC you have to distinguish between 3 and 4. The most general approach is to copy input state together with the output. For example if input is $|3\rangle$, then output will be $|3\rangle|C\rangle$ and for input $|4\rangle$ you will have $|4\rangle|C\rangle$. Now, your operation is reversible.


minimum application size for my iphone application?

Question: i am developing a application which contains many images which appear on different buttons click and has an mp3 file too..When i checked the size of my .app file it is around 6.8 mb which i think might be too large?? is there any way i can reduce the size of my .app file though i think reducing the size of my images(already around 15kb) wont be the solution.
Answer: 6.8mb is fine and is small enough that people can downloaded it over 3G (the limit is 20Mb; you need wifi if it's more)
Answer: One thing to keep in mind is sales! On any app you do now or in the future you will want to keep the total size under 20mb.
Think about how many users want to "instinctively buy" your app. They saw a friend with your app and want to download it right then and there, but ohh wait... cant do it till ya get home! LOST SALE - More than likely that person will forget by the time they get home.
In your case 6.8mb is nothing compared to many apps that are games. I've seen 200 - 300mb apps that take a while to download on wifi. (WSOP Poker , Gamebox)
Good Luck my friend!


Image cache present in which config file

Question: I am new to drupal and was learning about image cache.So far its going good but I want to know where exactly the image cache config is getting saved.I mean to ask which file I have to browse to see image cache setting?If my doubt is silly then please forgive me.Thanks
Answer: Image cache is core in Drupal 7 IIRC. So you can access its config and settings via /admin/config/media/image-styles. The cached images themselves are saved in your theme/files dir as defined in /admin/config/media/file-system.
Comment: Thanks.As per my research even I have concluded the same.I was curious in which ".file" this image cache settings(code) are saved or getting append.Does my imagination works or not in drupal?
Comment: I'm not sure what you want exactly. The core functions reside in /modules/image/*. User-defined config presumably resides in db.image_styles and db.image_effects tables. You really don't want to be touching these files and tables directly however, which is the point of a UI.