Subset (10)

eli5 · 25k rows

Split (1)

train · 25k rows

query stringlengths 20 300	positive listlengths 1 1	negative listlengths 1 1
What happens to a compass when in the ISS or on The Moon?	[ "/u/RobusEtCeleritas has the answer for a traditional magnetic compass. However, many systems now use a [gyrocompass](_URL_0_), [ring laser gyroscope](_URL_2_), or an [inertial navigation system](_URL_1_). These systems have different reference points than the magnetic north pole, such as a local pole (on the moon)...	[ "Suction cups work by creating a vacuum inside a chamber, and outside air pressure pushing down on the object. Space is a vacuum. It does not have outside air pressure Thus... no. It would not work. _URL_1_ _URL_0_" ]
How do the textures in our irises develop?	[ "The brown iris you linked has what are called prominent contraction furrows. These furrows, or folds, are due to the contractile nature of the iris. In dimly lit environments, the iris dilates to allow more light to reach the retina. Conversely, bright light causes the iris to constrict. Other visible features of ...	[ "It is down to the combination of the genes you get half the genes from your mother and half from your father but those genes are an almost random selection of those genes which go to make up each so can be combined in trillions of different ways. Like saying you get half a pack of cards from one parent and half fr...
Why does it feel so good to put my feet up after a long day of work?	[ "it's because your feet swell a little bit due to gravity causing blood/fluid to pool, so putting your feet up lets them drain, reversing the swelling." ]	[ "Evolution. People who didn't get that weird feeling when dangling their limbs from the trees they were sleeping on were killed by cheetahs." ]
How can a console transmit images to a stadium screen with the same ease as a TV screen?	[ "The console has no idea what's on the end of the cable, it'll be putting out the same signal it always does, at the same resolution. It's the stadium screen's problem to deal with interpreting that signal and displaying it." ]	[ "Imagine you have a computer on your house. Now you want to connect that computer to your friend 100 miles away. How do you do it? You could lay a 100 mile cable, but do you have the permissions to dig up roads and pathways? You would use a company whose cables were already there, and just use that network of cab...
Which United States presidents had documented mistresses/habitually cheated on their wives?	[ "Related question: I heard a story on Radiolab recently that claimed that, prior to Gary Hart, journalists generally didn't report on a politician's infidelity even if they knew about it, since it wasn't seen as relevant to their leadership ability. Regarding these presidents who are known to have had mistresses, w...	[ "This submission has been removed because it is [soapboxing](_URL_1_.), [promoting a political agenda, or moralizing](_URL_0_). We don't allow content that does these things because they are detrimental to unbiased and academic discussion of history." ]
The Iowa Caucus and why it is or isn't important?	[ "Its not important in terms of electoral votes (what decides who is president), it's just that its the first ballot towards the presidential election is then sometimes used as an indicator to who might win." ]	[ "You might get the chance to shake hands with Al Gore or the doofus who invented whatever social media platform is so hot right now. You also might get the chance to throw a venture capitalist bone to the whiz kid there pimping his \"next big thing.\"" ]
Why does it take so long for results to come in from an election?	[ "In a recent election I was involved in, all ballots were cast on paper, and counted by hand. This was in a single time zone, and polls closed at 8 PM. Results started coming in by 8:20 from more populous areas, where they had a full contingent of people counting the votes by hand and reporting the numbers. In outl...	[ "They have to make sure it's in stock (add some time to get it, if not), check with your doctor, check for interactions, and check with however many insurance companies, then count, double, and triple-count the pills, all while doing this with other customers." ]
In Leyman's terms, how do you split an atom?	[ "You fire a neutron at the nucleus to destabilize the atom. I once heard a great analogy between atoms and water balloons. The nucleus of an atom is similar to a water balloon in the sense that as each become larger they are less stable and more prone to \"bursting\"." ]	[ "> I'm not asking if this is even close to a favorable reaction, but could it in theory be possible on a small scale? What do you mean by \"possible\"? If you want to talk about \"possible\" but not \"favourable\" reactions, you must understand that the stability and reactivity of every chemical bond is a statistic...
How does one have a monotone voice and not know it	[ "We don't hear our voices in the exact way they come out of our throats/mouths. Because of the echoing of bone and sinuses in our heads, the sound is different to ourselves. Someone could easily believe they are emoting more with their voice than they really are, because the subtle little changes might only be hear...	[ "Can everybody just chill out with the tinnitus diagnosis? Tinnitus is comparatively rare, and what OP is talking about sounds like what basically everybody who's ever been in a silent space has noticed." ]
Why do Scandanavian women have last names like "Thorisdottir or Brynjarsdottir", but men have names that end with "Sen or Son".	[ "Your last name is your father's first name plus \"son\" or \"dottir\" as might be appropriate. And yes, this does make tracing lineage beyond a generation or two more difficult. So Anders Thorbjornsen and Annie Thorisdottir probably aren't siblings (or maybe they have the same mother and are half siblings), but An...	[ "There is an area of high pressure over Scandinavia. As far as I know, this is a common phenomena in winter. But much lower pressure over the North Atlantic usually results in the high pressure spreading out and moving on. This year, though, the pressure over the North Atlantic has not been as low as usual, allowin...
Why do we call giving someone the middle finger. “flipping the bird”?	[ "bird (3) \"middle finger held up in a rude gesture,\" slang derived from 1860s expression give the big bird \"to hiss someone like a goose,\" kept alive in vaudeville slang with sense of \"to greet someone with boos, hisses, and catcalls\" (1922), transferred 1960s to the \"up yours\" hand gesture (the rigid finge...	[ "You don't want to inject air. It's difficult to fill a syringe without having at least a small air bubble. Putting the needle up and flicking will get any air bubbles in the syringe up to the end, you then push out the bubble and you know when it's all out of the needle when liquid flows through. Even when you're ...
Do we posses technology to detect and stop a nuclear missile?? If yes how does it work? If no is there hypothetical solution that could be developed in the near future?	[ "Detect an incoming missile? Absolutely. We've been able to detect ICBMs shortly after launch with over-the-horizon radar (now supplemented with satellite surveillance) since we began developing them in the 1950s. Stop an incoming missile? Much harder, and whether we could do so today is an open question. There are...	[ "Our clocks slowing down relative to what? You can't really answer this sort of question unless there's some fixed notion of time to compare our clocks to." ]
X-Post from /r/electronic_cigarette - Vaping and pumping gas...Is it safe?	[ "Gasoline has an approximate ignition temperature of 280°C. [According to the FDA](_URL_0_) temperatures in an atomiser can run as high as 280°C. I would adopt the precautionary principle and avoid using electronic cigarettes in a petrol station. (Or gas station as you north Americans call them)." ]	[ "Don't know about the states but here we have a lot of new cars with stop/start engines. When you out the car into neutral, it turns the engine off when you release the clutch! The engine starts again when you press down the clutch. Freaky sitting in a SILENT car in traffic. For cars without this, I imagine the we...
Theoretically why can't objects go faster than the speed of light?	[ "The short version in this case is because F=ma is a rather large simplification of the Conservation of Momentum, and this simplification only works for non-relativistic cases. Once you start dealing with the long forms of the equations involved, it becomes apparent that for something with mass to accelerate to the...	[ "To say what would happen, you need a reliable theory. But there are no reliable theories in which ftl travel is possible. There are plenty of crazy theories with ftl travel, so I guess you could pick one and use that, but it would be no less scientific to save yourself the effort and just make it up :)" ]
Physicists of Reddit, please help me come one step closer to appreciating the madness of Quantum Theory.	[ "Imagine two people holding the ends of a jump rope, with one person shaking their hand up and down but neither of the people moving their arms much. There are only so many shapes waves can take along the rope. [These](_URL_0_). This is the principle behind the wavefunctions: there are only so many shapes they can ...	[ "Water runs down a mountain to the lowest point. There's a lip halfway up the mountain where the water can catch and form a puddle. The \"true vacuum\" (lowest possible energy state) is at the bottom of the mountain, so the puddle is in a false vacuum because the water could fall lower, but it would need to be push...
How do bots work to buy Hype items? Supreme had items drop today that sold out in less than 3 seconds. How does the bot know where to click to get the item and size, as well as overcome Captcha?	[ "It doesn't generally have to \"click\". Your browser sends a message to the server saying \"I want to buy this\" and then does some other messaging to send payment info. A bot could do these things without a browser. A second option is to write scripts in your browser to do it. A webpage has a structure that a pro...	[ "Sputnik's transmissions were on, if I recall, 20001 kHz. This is smack dab in the middle (...somewhat) of what is known as the shortwave radio spectrum, which is from 3000 to 30000 kHz. Shortwave radios were common back then, especially compared to now. To intercept the signal, it's pretty simple. One would need a...
What is the history of Islamic young-Earth Creationism?	[ "Could you please show your sources for Islamic young Earth creationism? I realized this is anecdotal but as a Muslim I've never heard of such a concept" ]	[ "Correction: Biblical scholars tend to prefer the Greek and Hebrew. ;) But seriously--the Oxford transation of the Quran seems to be pretty standard from what I know. I'm not an expert, though. _URL_0_" ]
Why is the goat associated with Satan/Hell?	[ "Before Christianity took hold in Europe, various pagan gods were worshiped, including goat gods usually associated with fertility. Fertility rites, as one might imagine, were pretty popular, so when Christianity came to town, they were among the most difficult to put an end to. One technique they used was casting ...	[ "For a long time, it was the default for Microsoft Word (by far the most common word-processing program), thus becoming the de facto standard." ]
Why is some content available in the US only?	[ "It's a holdover from Pre-Internet days, basically. Studio2 makes a movie but can't afford to distribute it in Europe (or just doesn't want to pay for the various localizations). Studio3 and Studio4 both operate in Europe and have no problem doing the legwork. Studio2 and Studio3 sign an exclusive contract (where S...	[ "Country specific ones follow the laws of that country. You can search for Tibet freedom on _URL_0_. but not _URL_1_ or Google.can Google was given a choice by Chinese gov. Either you make the search engine follow our rules, or you don't do business in China at all and China blocks _URL_2_ entirely" ]
When someone says "The Corporations run America"	[ "corporations, through lobbying, corruption, bribery, and false litigation, pass laws that benefit only them, elect congressman that benefit only them, and silence both opposition and honest creativity that endangers their current way of life. Concurrently, the economy and creativity suffer, as large corporations m...	[ "I was always informed it was based on the focus of the website. A company would have a .com An organization would have a .org A database or network might have a .net The government has a .gov Meanwhile, the endings in .uk (England), .ca (Canada), .us (USA), .jp (Japan) are short for country cod...
Why do fast spinning objects, such as wheels, sometimes create a pattern as if it's slowing down in the direction it is spinning and then speeding up in the opposite direction?	[ "It is only when you're observing it via something with a refresh rate like a video camera. The most common occurrence is under fluorescent light, which turns off and on really fast (60 cycles per second for the US). Most energy efficient lights have this property these days. There is no eye refresh rate. You won...	[ "Think of a surface as something that has a lot of peaks and valleys. Sandpaper generally wears away the peaks and doesn't hit the valley, so the surface gets more level. Typically, you'll go from a rough grit to a fine grit. Finer grit sandpapers wear away the peaks from the scratches of the rougher grits." ]
What are farm subsidies and how do they work?	[ "Farmers can be their own worst enemy. They want to grow as many crops as they possible can. The problem is when they all have a good year, there is an oversupply, prices plummet, and they all lose out. The gov't tries to fix this with subsidies. They either pay farmer not to grow when it looks like there will be a...	[ "This is a very common question. You can use search to find [all the other really good answers](_URL_0_ ). This is instant, and faster than ust typing in your question every time. It's a way of cheating elections. Read the others, and then ask a more specific question." ]
How do antacids neutralize stomach acid?	[ "Antacids contain a mild base such as calcium carbonate. Acids and bases neutralize each other and leave salt water. Try putting a very small spoonful of baking soda (mild base) into a cup of vinegar (mild acid). The bubbling is the acid & base reacting to form water and salt. Add another small spoonful and you wil...	[ "It is simply that toothpaste contains a small amount of abrasive. It's meant to rub micro gunk off your teeth, like sandpaper would, but it can also rub off the edges of scratches, making them much less visible." ]
What is the difference between 'Gifted' students and regular students?	[ "Regular students do well, and generally don't have any problems. Gifted students do well, and always finish half an hour earlier than the rest of the class. Then they sit there bored and get annoyed that other people are so slow" ]	[ "I would check out It's Okay to Be Smart on youtube. They do a good episode on this (im bad at links)" ]
What happens to the absolute centre of a rotating beer mat (or any disk)	[ "I know its a bit off topic, but I can't resist linking to a [relevant Calvin and Hobbes strip](_URL_0_)" ]	[ "It actually can be solved (for nonzero net angular momentum, at least), in the sense that we have an analytic expression for the solution in the form of a power-series. Unfortunately, the power-series converges so slowly (meaning that you need a ridiculously large number of terms to get a remotely accurate appro...
How did the Germans gain so much power during World War 2?	[ "Tactical and technological superiority. They never had the numerical or industrial advantage, but they managed to overwhelm Polish and French defenders by pioneering a new kind of war that other nations weren't prepared for. France was definitely ready to fight WW1.5, with all the trenches and mustard gas and mach...	[ "Britain was occupied by Rome from 43 AD to 410 AD, which is shorter than most other areas. During that time, the island was never fully occupied, and they always lived besides the Anglo-Saxons in Scotland. The geographic isolation also plays an important role. On the main land, Spain, France and Italy may have be...
If someone were to receive a blood transfusion from someone with leukemia, would they "catch" leukemia from the blood donor?	[ "This is actually an interesting question for not only leukemia, but all cancers. The reason is that there are circulating tumor cells CTC present in the blood. These CTCs are thought to be responsible for metastatic tumors. So, can a CTC plant itself in another person and develop into a tumor? This question was ad...	[ "> but also people who go somewhere like chernobyl, what do they use for protection? Unless you plan to work at the reactor side: Nothing. Don't go to the reactor ruin, don't eat things that grow in the exclusion zone, don't take material from there elsewhere. Ideally stay on the roads and other cleaned areas. The ...
What causes physical pain to be a pleasurable sensation to some people?	[ "In short, Neuroplasticity. Pain and pleasure are both literally \"just in your mind\". By that, I mean that what our minds interpret as pain or pleasure is dictated by the firing of certain neurons in our brains. The pain and pleasure areas lie fairly closely together in the brain. Neurons from one \"area\" can gr...	[ "Short answer: consumption of capsicum (spicy foods) release endorphins. Like your five: eating spicy foods makes your mouth do a dance that makes you happy in your brain." ]
What sort of lab/equipment is used to study quantum entanglement of particles?	[ "Usually this is done by parametric downconversion of light from laser. The light goes through fibers, not much to see. Here is a diy method with gamma photons from positron annihilation: _URL_0_" ]	[ "I do telephone and we use a TDR (time domain reflectometer) that sends a pulse out and times how long it takes an echo to return the unit (based on a given gauge of wire) and it shows the length on the wire. We have records that indicate what the distance should be and compare that to the result." ]
Why have desktop app stores not gotten similar development as mobile app stores?	[ "Developers don't like app stores. They take a 30% cut, restrict what your app can do, make you wait to get your app released, don't allow upgrade versions, etc. You don't get direct access to your customer, you can't get their email to try and sell them more crap. On most mobile devices developers don't have any ...	[ "Look at the geometry of the door and the rear wheel well. Most sedans don't have enough space in the rear door to put the whole window." ]
How does radio and chemotherapy kill cancer cells?	[ "Suicide isn't the only way in which a cell can die; these therapies' objective isn't to induce the cell's apoptosis, but to murder the cell, if you will. Radiotherapy causes damage (mutations) in DNA, the idea being to create so many mutations that the cell can't continue to divide and function properly, and thus ...	[ "> I think it's just a delay in the OS's process to update the display And you are almost correct. It's not the display (which can be updated immediately), it's the OS that takes a little time trying to reconnect to the network before deciding it is really down. Your roommate doesn't know what he/she is talking abo...
Are gravitational forces additive?	[ "Yes - this is exactly what gives rise to [Lagrange points](_URL_0_)." ]	[ "Powders with a spherical morphology that can slide past one another will behave like a liquid even with a rather large particle size. I have some spray dried silicon nitride powders at work that are ~30-40 um spherical agglomerates and you would think I was pouring liquid if you saw it come out of the bottle. The ...
What prevents us from harnessing the full potential of thunderstorms for electricity?	[ "An average lightning bolt has ~1.5 GJ of energy, there are ~1.6 billion lightning strikes a year, resulting in a total energy of ~2.4 * 10^9 J, world energy consumption is 5.4 * 10^20 J. So, if you could capture every single lightning bolt with %100 efficiency, you could supply less than half a percent (%0.44) of ...	[ "A lightening bolt creates a radio signal. These are easy to pick up. With ~~two or more receivers~~ you can calculate it's position. Edit Should be three or more receivers." ]
If there is an infinite amount of numbers between 1 and 2, is there an infinite amount of time between 1 second and 2 seconds?	[ "If time is continuous you can say that there is an infinite amount of moments in a duration of one second. That doesn't mean there is an infinite amount of time, of coruse: the interval is still one second long, much like the interval [1,2] still has measure or length 1, even if it is an infinite set. > thus cont...	[ "Think about things bouncing around. Imagine a box with a fan in it. Put 20 balls in ithe box. Now imagine a basket to one side just the right size for the balls. Turn on the fan. The balls jump around randomly. At some point a ball will fall into the basket. This will happen at a given rate which will depends on h...
What is a single photon made from? And how?	[ "No one can give you a meaningful answer to what is is, but you can get a meaningful answer to what it does and how it acts. Classically, it's a propagating wave of oscillating electric and magnetic fields. Quantum mechanically it's a wave that interacts directly with matter as a particle. It's behavior is describe...	[ "They use extremely fast camera shutters to capture a very short moment so you can see the light beam. However they can not reset the camera in time for the next frame so they cheat a bit by sending a new beam of light for the next frame. They make sure to synchronize the short beams of light with the camera shutte...
How is work divided in a communist country?	[ "In theory.....Under communism, the end result of socialism, work is voluntary and lacks any material incentives. The number of mentally and physically healthy people who would not want to work, especially when work has become less alienating and less strenuous, is minuscule. A post-scarcity society can more th...	[ "Amway and cutco make you buy there products to resell them or use them as demos. These are always overpriced. So you are losing money going into the job. At any other marketing firm you get paid a salary. The person working in the mail room does not have to purchase the companies products to get paid." ]
If Reddit has over 1 Million unique visitors per day, why do the Top links only get around 2,000 - 5,000 Upvotes in a day?	[ "- Not all visitors have accounts - Not all visitors with accounts vote - Reddit automatically fuzzes votes by downvoting" ]	[ "Listen to me. It's sleep cycles. People have been posting questions like this to ELI5 for months now. I got this answer form a previous ELI5. The answer is sleep cycles! Each sleep cycle is 90 min. If you wake up in the middle of one, you feel tired all day. So be sure to sleep in intervals of 90 min: 90 min, 3 ho...
Folklorists, neolithic archaeologists: What's the deal with Laurasian Mythology?	[ "I just read the article, and Witzel isn't even telling a just-so story -- he's telling an \"it's so whether it's so or not\" story. Take a look at this statement, as just one example among many: > Apart from the feature of drift, certain motifs that widely appear in Laurasian and non-Laurasian mythologies may bel...	[ "Well it all started in 1152 or so when this wee lad from Wexford called Dermot went off with this lassie Dervorgilla, from Co Meath whose husband was horrid upset he was and nobody talks about...... Anyway, I dont know the show but if you put any specific questions to me I will give you a straight answer." ]
Why do people hate Comcast?	[ "Everything I've read is about their terrible customer service. They don't solve problems for customers, they create them. Of course, like anything, people don't post a lot when things are going well, mostly only when there are problems." ]	[ "\"Just about everyone here\" Where is \"here\" for you? It sounds like your question's premise is based on a small sample set based on personal observation. Before your question is addressed, you should be making sure the premise is valid..." ]
Why do we get vitamin D from the sun? Could we make a light that gives off vitamin D?	[ "Vitamin D is produced in the skin in a reaction that is triggered by exposure to UVB radiation, which is a particular subset of the UV spectrum. So we don't get vitamin D from the Sun, but rather get the necessary component to make it ourselves from the Sun. UVB light can be produced artificially, so in principle ...	[ "When cells divide they make pretty much exact copies of themselves. Introduce radiation to the equation and the copying process goes screwy and the new cell is different. Rinse and repeat over and over and you end up with body cells which are completely different in shape size and function to what they were origin...
What is the difference between raw fish and sushi grade?	[ "Sushi grade means the fish was frozen at -20c for 7 days, or -35c for 15 hours. This kills any parasites in the fish. Edit: see below about bacteria." ]	[ "Here's a pretty good explainer. _URL_0_ Basically it comes down to different memory, different promises (reliability and service life), and different marketing." ]
Why does the US have so many federal law enforcement agencies, many with overlapping objectives instead of having just one or two for all crimes?	[ "Lawyer and former state-level prosecutor here, How: That's the way history happened. The Federal Gov't has limited power, and didn't really do much in the early years, e.g., under Pres. Washington. Each time a need for a specific task would arise, say to investigate counterfeiting, a new police force would be born...	[ "Let's say you're starting a business and I loan you the money to get started. You make your payments and manage to keep the lights on. Soon, you start making a profit. I, who loaned you money, don't come demanding more money because you're making the payments on which we agreed. Your buddy Jeff has a business, to...
Is there a gene that all cells have a form of and could not live without? is there a most common gene across the domains?	[ "There are many many many such genes. Off the top of my head, most things dealing with DNA synthesis (DNA polymerases), RNA synthesis (RNA polymerases), and protein synthesis (the ribosome, which is made from a bunch of different genes). The you have tRNA genes too." ]	[ "So I was just wandering around Google, looking up the whole \"4 chord\" theory -- which suggests that there are 4 main chords that morph into the most popular and \"hit\" songs. I read this really cool article a few years ago discussing the science behind manufacturing \"hit music\" in the pop genre. I'm going to ...
Is there a theoretical limit to the size of ocean vessels?	[ "Check out the square-cube law if you're interested in how a given shape eventually becomes structurally unfeasable as you scale it up. As you scale your ship up the weight and buoyancy will increase at the same rate since they're both based on volume, but the stress will also increase at a cubic rate while the str...	[ "It's way, way, WAY, too expensive. The power plant alone would probably be more expensive than the entire lifetime cost of an average bulk carrier. Not to mention the insane mess of regulation that is involved with running a nuclear reactor. Basically, big ships run on bunker fuel, and bunker fuel is ludicrously...
Why is Civil War Re-enactment a thing?	[ "Because some people want to LARP without being elves." ]	[ "You mean the Animal Planet one? Hype and marketing. Then it became a euphemism for menstruation (I'll fill you in if you want, but it's gross sex stuff...) and took on a life of its own." ]
Out of all online games, why are MOBAs (LoL/DotA/Smite) have the least trouble with hackers?	[ "MOBAs are \"server-side\", meaning everything you do has to be greenlit by the server before you actually can do it. The server knows how much gold your character has, how much agility points or whatnot, how much said agility will increase by if you buy item X. Where you're moving, how fast, what you can see or n...	[ "In the ancient near east/middle east in the Hebrew Bible era (say before 1000 BCE) deities were very regional and it was generally held that a certain god held dominion over a region and its people and a different god (or pantheon, like in Egypt) had dominion elsewhere. Common people generally held that a god wors...
Why watches, weather apps etc. indicate the phase of the moon. Why is the moon phase so significant that people need to know?	[ "Some people use moon phase, rise, set and when it is directly overhead, or underfoot along with the position of the sun to determine the best times to fish or hunt. The moon does have an effect on some animal behaviour, along with affecting tides. Everything else equal, I've found that fishing during a new moon o...	[ "Radio stations do a lot of clever work to fit more information in the audio stream then just the audio. Originally an FM station were just a simple mono audio signal. However they found out that the signal quality were good enough to deliver audio signals at much higher frequency then the humans can hear. So they ...
Organisms that consume SO2 (for energy)?	[ "First, plants do not take in CO2 for energy. The energy of photosynthesis comes from light, and this energy is used to build biomolecules, some of which are energy-storing (sugars), some of which are not (proteins, nucleic acids, etc). The purpose of the CO2 is to the builing block that these bio-molecules are mad...	[ "Ok so I worked in Zinc Oxide which is used as a catalyst for the rubber curing. I only did a bit on the rubber side so hopefully someone can come and fill that in, but yes Sulphur I presume works to form di/trisulfide bridges similar to what it does with amino acid structure. Oxygen is more likely just to burn it ...
If a lack of light over a period of time can cause one to lose their eyesight, how come people who are in comas (eyes shut) for years don't lose theirs?	[ "People who are in long term comas have all sorts of vision problems. It's just movies where people wake up from comas after 20 years and are just fine." ]	[ "As far as I'm aware it's fairly simple, falling out of trees sucks. You're a monkey! You love being in trees, swinging from branches and all that jazz, in fact you love trees so much you even sleep in them. But, if you are sleeping you can't see what's going on, you can't move about when you don't have a full pic...
Why and how is borax a danger to fertility and the unborn child?	[ "It really probably doesn't. The lowest observable adverse effect level in rats is about 10x higher than that measured in cases of chronic occupation exposure, which was considered the \"worst case\" chronic exposure scenario. Those same populations also had biomarkers of fertility measured and no reproductive toxi...	[ "Likely the store was not able to sell it for a high enough price, compared to the price the distributor was willing to give for the return. It literally would cost them money to sell you the product, making it \"toxic\" As for the later call, they probably were denied the return, meaning they had to get rid of the...
Why did the Twin Towers collapse the way they did?	[ "Because skyscrapers are deliberately constructed to do that. A skyscraper that did not collapse vertically would be extremely dangerous." ]	[ "When an engine is brand new all the parts have a near perfect fit. As time goes on things start to wear and get a bit sloppy. As a result items that are supposed to rotate begin to get a bit of lateral wobble and in the cylinders pressure starts to get past the pistons on the outside." ]
How much gasoline is actually wasted at a stop sign?	[ "0.00314248 gallons, or 0.0118956 L. Assumes: car must accelerate to 25 mph after stopping. Car weighs 2000 kg. Efficiency of engine is 30%. Gasoline energy density is 35 MJ/L. No other energy losses during acceleration (e.g. no friction). My work in Mathematica: _URL_0_" ]	[ "Only if you see oil as a carbon sink (along the lines of carbon sequestration techniques). By taking it out and burning it you are putting that carbon back in the atmosphere which is believed to contribute to global warming." ]
What's happening atomic level when I rub a balloon against my hair causing the balloon to become super staticky?	[ "[Bits of charged material transfer from one object to the other](_URL_0_)." ]	[ "When you drive, your wheels are always between you and the road. Does this mean that you do not move up and down with the road? (Negating the effects of your shocks) you will still feel the entire topography of the road as if you were in direct contact with it. To avoid confusion it is better not to look at the fo...
Dear physicists. Mass can be converted to energy during a fusion reaction. But law states that energy cant disappear, NOR BE CREATED. What am I misunderstanding?	[ "The energy is in the form of mass initially." ]	[ "The general idea is that the technological capabilities of a species can be determined by the amount of energy they can harness. First it was just muscle power, then fire, now it is into fossil fuels, nuclear, etc. Capturing the energy which falls onto our planet limits the amount of renewable energy available tho...
what just happened to the Australian and Chinese stock market	[ "What goes up, must come down. The Chinese economy has been slowing recently, but political reforms have also been encouraging greater transparency, and earlier this year, the Chinese central banks were making it easy for people to invest. So we had the odd situation that the Chinese stock market roughly doubled i...	[ "Victoria (u/chooter) was let go/fired from Reddit today, and because she does a lot of the background work behind r/IAMA it left that subreddit and a few others that also require her in a state of clusterfuck. [Here](_URL_0_) is a link to the explanation given by u/karmanaut on the whole situation." ]
volume change on speakers/earphones, how does it work?	[ "It works with a resistor that has a variable resistance. As the resistance decreases, the electromagnets that move the conus of the speaker get pulled on harder, more movement, higher amplitude, more volume. Of course there is a pretty elaborate explanation why the electromagnets actually pull harder with more pow...	[ "Each time you set it to shuffle it generates a new song index. Clicking prev/next just iterates through that list." ]
How voltage travel in a wire at the fundamental level?	[ "The electrons do move. It's just that a very small increase in the number of electrons causes a very large increase in the force, so there's negligible electric current before the system stabilizes. It's sort of like [Pascal's law](_URL_0_) of fluid mechanics. If you increase the pressure on a fluid, it increases ...	[ "Quoting [Wikipedia](_URL_0_) (a bit naughty, but it's a nice way to express what I think): > The proposed theory is inconsistent with quantum mechanics and critics have ruled it out on those grounds. Which is essentially saying what you pointed out, yes. If what they're doing is as easy as it sounds - just runnin...
Are galaxies neutrally charged?	[ "Not necessarily, but the charge differential is so insignificant in proportion to galactic distances and local gravity that the electromagnetic force does not play a part in galactic trajectories. Edit: There are many events that can cause galaxies to expulse matter, and in many of these, such as a black hole jet ...	[ "Any physically straigth line will always appear arc shaped if it covers long enough area of your vision. Its just our brains can make us realise they are really straigth if there is enough context. For the case of milkiway center there isnt. Cameras can cause further confusion. Its like inverse version of the prob...
From a software perspective, what does a 'Soft Reset' do?	[ "Restarting a program can fix glitches the same way you can restart a list of instructions from the top when things go awry. Something has gone wrong that's usually outside of your control so scrapping what you've done so far and starting from scratch can often lead to success. Soft/hard resets are more generally a...	[ "Imagine driving a long distance on the road. Your destination is 160 miles away, so you drive along the highway at about 80mph and figure that you need about 2hours total. Then, in the middle of that 160mi, the road gets very bad (you had no chance of knowing that) so you can drive only 50mph. You don't know if th...
Why do we walk with straight arms, but run with bent arms?	[ "To keep balance we need our arms to swing roughly in time with our legs, when at walking pace this is quite slow and easy to do, when running we need to do it quicker. By bending the arm it lets us move it forward and backward quicker so is better for running, but when walking the energy required to keep the arm b...	[ "Human engineering, which Don Normal originally called \"The Psychology/Design of Everyday Things\", influences many modern design choices. The classic example is the Norman Door Bar. When you approach a glass door, should you pull the handle bar or push it? If you write a sign, then you have to presume everybody r...
Why does not looking directly at where you are trying to look offer better night-vision?	[ "Your eyes have two types of light-detecting cell in the retina (back wall). Light comes through the lens in front and lands on either rods - which are good at detecting whites/greys/darks and work okay in the dark - or cones - which are good at detecting colors but fail at lower light levels. This is why when ligh...	[ "It is. It's just not blocked much. It's like running: running through the air is pretty easy: not much getting in your way. Running through the water is harder; and running through a solid object is even harder. Light works the same way, only it moves differently, so some things (like smoke) allows your movement t...
why do we need coin currency? Why not set prices to a flat dollar amount?	[ "The fractal amounts are still meaningful in many transactions. For example, if gasoline could only be sold for $4/gallon or $5/gallon would make a huge difference to the vendor and the consumer alike. Also, some industries live off those fractions. Credit cards, for example, charge the vendor a small fraction of t...	[ "Explain it like you're five? So somebody like an American version of Justin Bieber isn't swept into office because of his fan base." ]
why do you get the weird "butterfly" feeling in your stomach when going down a hill or drop fast?	[ "It is much like a car accelerating, but instead of forward, you accelerate downward. When you are at rest, your stomach and intestines are resting in your abdomen. But when are falling and accelerating downward, your organs are in effect \"falling\" in midair, as they abdomen they usually rest in is also falling, ...	[ "Our brains didn't evolve with cars in mind. They evolved with, like, being hunted by a jaguar (or whatever) in mind. So your brain doesn't know what to do with a car. It thinks hey, we're sitting, our body's not really doing anything physical, there's very little activity or stimulus... this seems like a good time...
Was the fall of the Soviet Union expected, or a surprise?	[ "I heard Ambassador Matlock speak recently (American Ambassador to the USSR from 1987-1991) and he said that the American diplomatic corps was actually discussing the imminent collapse with their Soviet counterparts back into 1988. He referenced the incredible confidentiality of the talks as a factor that helped th...	[ "This question is getting a lot of traffic after being [tweeted by @reddit](_URL_5_), so I thought I'd welcome those of you that haven't visited /r/AskHistorians before to the subreddit. Please do bear in mind that in order to keep the quality of answers here high we have [strict rules on comments](/r/AskHistorians...
Would it be possible to create a sunscreen-like substance for radiation of other kinds? Specifically, radiation caused by a nuclear explosion/accident?	[ "The reason that sunscreen works is that the material absorbs the UV radiation instead of your skin and emits it as a less harmful wavelength. Higher energy photons like X-rays are more and more difficult to block. In dentist offices they use lead vests because lead is a very dense material and therefore the photon...	[ "In theory yes. To get a kernel of popcorn to pop all we have to do is supply enough energy to the kernel to increase the temperature and pressure to the point that it explodes. This is most commonly done by directly heating the kernels, or by microwaving them, which uses radiation easily absorbed by the water mol...
The difference between designate/waive/release in baseball	[ "[This article](_URL_0_) does a good job explaining them. Gist of it is: -Release = adios/see ya/cutting all ties. -Waiving a player puts the player on waivers, and teams (starting with those who have the worst record) have the ability to claim the waived player. The team who then waived the player can either work ...	[ "Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s): You can find the basic answer with a google / wiki search. Please start there and come back with a more specific question. If you disagree with this decision, please send a [message to the moderators.](_URL...
Why is Pripyat, the town where the Chernobyl nuclear disaster occurred, abandoned/uninhabitable but Hiroshima and Nagasaki are inhabited?	[ "Chernobyl had a lot of radioactive materials that were deposited relatively close by, because it wasn't that hot (compared to an atomic bomb). Hiroshima and Nagasaki had a much more limited amount of radioactive materials that were largely heated to such temperatures that they didn't deposit on the ground nearby a...	[ "1- It was really more disease that doomed the French more so then anything. 2- Southerners were scared shitless by the Haitian rebellion, and for good reason. Although a few people supported Haiti in secret, such as John Adams, it was not in your political interest to side with the rebels. The United States went o...
Why do we get eye-floaters, and what are they?	[ "Eye-floaters are just proteins in the fluid of your eye that have unfolded and outlived their usefulness and become visible. They are not bad unless you have many of them constantly. Otherwise they're just a natural life cycle of proteins. They get absorbed back into your body through the bottom of your eye and ge...	[ "You mean like the ones you only notice when you're watching someone sleep really closely for hours on end? Don't know." ]
when the moon comes up, it's gravity is strong enough to rise the tide. How come small particles don't go flying as well?	[ "Probably the biggest thing to understand is that the moon's gravity doesn't create the tides \"all in one go\". As the Earth rotates, the pull of the moon has a constant very small effect that over time builds up a sort of standing-wave front that we call the tides. It's the cumulative effect that causes the tides...	[ "Inside those clumps is dry flour. The surrounding flour holds the water tension creating the clump. Thats why you have to mix the flour thoroughly in order to break the water tension in each indivual clump. EDIT: I had used the wrong spelling for the word \"tension\"." ]
When did the French become obsessed with food and culinary pursuits? And why didn't the British and English follow the same path?	[ "As far as I can tell from accounts of how dishes came into being, it was a combination of France becoming a major cultural power that exported fashion and architecture as well as food and France's development of court cuisine as a dedicated specialty with an almost academic structure of training and discourse. Ins...	[ "Our bodies need a lot of different things in order to be healthy. Vitamins, minerals, etc. Different foods may have different toxins that the body has to deal with and expel, or it may have different vitamins that are absorbed differently and that enhance or inhibit absorption (ie: vitamin C and iron... calcium a...
Why we close our eyes when we kiss???	[ "You heighten your sense of touch on your lips for brief moment by blocking your sense of sight, making the kiss feel more intense." ]	[ "The safest place in nature is a hole or cave where you're protected on 5 sides and only exposed on one. Evolution favors safe behavior like this, so it has become instinct. An open box is the modern equivalent-only open on one side, danger can only come from one direction, so they feel safe. It's also the reason c...
The passing of Neil Armstrong got me thinking: If the moon revolves about its axis at the same rate as it orbits the Earth, how can the Earth 'rise' or 'set' when viewed from the Moon?	[ "You are correct. The Earth does not rise/set on the moon. The NASA astronauts called their famous photograph 'Earthrise' because as they were orbiting the moon, they were coming around the near side, making the Earth appear to rise. I am sorry I do not have a source for this information, but I do remember reading ...	[ "It's all about having an atmosphere, since that's what helicopters need to fly. [This article explains it quite nicely ](_URL_0_) Here's a relevant quote: *\"Elysium was that—unlike an airplane cabin—its atmosphere wasn’t canned up in some hollow tube. A landing spacecraft could enter its air like it would on Eart...
Why Are Some Children So Resistant to Eating?	[ "There are a LOT of potential answers to this, and I expect that others will have better explanations. However: \\- A major and important point of child development is learning to say \"no\" -- essentially, learning that you have control over your own body and are that you are capable of setting boundaries. Because...	[ "Hospitals, like most services in the U.S., are a business. It is hospital policy to not perform such operations unless some form of payment is secured. This payment could be credit, of course, where the person then pays their credit debt; or in some cases, a payment plan can be established where that patient is in...
What tests are scientist's willing to invest in now that there's water on Mars, whereas before they wouldn't?	[ "Well I imagine now they would be more interested in searching for signs of life, as they now know that is a distinct possibility with liquid water." ]	[ "I imagine you are talking about the internal combustion engine (ICE)that is commonly used around the world in automobiles. Think of the classic \"fire triangle\" when thinking of these engines. You need 3 things to make something burn: Fuel, Oxidizer, and heat. In an ICE these components are a Petroleum product s...
Question regarding the speed of electrical signals through wire	[ "Your signal is actually a TEM mode electromagnetic wave travelling down you pair of cables, which is a transmission line. There is a finite propagation velocity, dependent on the geometry of the cables, and the material between the two." ]	[ "Lets say that you are drinking juice from a cup with one straw, you are getting the juice into your mouth but now you try two straws, you are getting more juice in less time in you mouth, you try three, it is faster ect. the same goes with 802.11n g b a. they each send more information at one given time to your co...
If moment of inertia is greater when the distance from the rotational axis is greater, why is it easier to rotate something when it has a larger axis of rotation (in terms of torque)?	[ "Simple mix up - the moment of intertia is a function only of the mass distribution of the object that we are spinning. It has nothing to do with where we apply the force. The angular acceleration experienced by the spinning object can be found with Newton's 2nd law: torque=moment_of_inertia * angular_acceleration ...	[ "Question: Suppose I give you an infinite number of sets. Can you pick out an element from each of those sets and give me back all of your choices? Turns out you can't prove whether or not this is possible with the other axioms of set theory. You have to either accept or deny it on faith. (That's why they're called...
What stops rain from freezing while in the clouds into one city size block of ice and crushing us all?	[ "Weight. That would be massively heavy. There's a reason the largest hail stone was the size of softball. It's too heavy to stay in the air." ]	[ "Unless you live in a desert, it's generally quite humid in the summer and that humidity plus you (you breathe out moisture) means too much humidity and it will condense onto the windshield. Therefore you use your AC to defog in the summer and make sure it's on recirculate. Don't want to keep bringing in humid air ...
Political systems in ancient Greece	[ "I am no expert on the topic, but a wikipedia search of \"athenian forum\" may shed some light on Athenian politics. You can also use the \"simple english\" language mode for pre-made ELI5 types of encyclopedia entries. The same goes for a search of Spartan government." ]	[ "This sounds like a \"polltype question\" which is not appropriate for askhistorians. sorry." ]
Is concrete a heterogeneous or homogeneous mixture?	[ "In a chemical point of view, from most scales, entirely heterogeneous. Concrete is, by definition, a mixture of cement (a paste that could in certain scales be considered homogeneous) and rocks. They do not, in optimal situations chemically react in any way. The rocks are bonded by the cement by simple physical c...	[ "Inclusion of all the colors of the rainbow man :) Things are not just \"black\" and \"white\", heterosexual or celibate. There are a variety and ranges and shades of humanity and human sexuality." ]
How can I make a Citizen's Arrest?	[ "The legal right to make a citizens arrest will depend on jurisdiction. It's totally illegal in some places. However, it's basically just restraining someone and waiting for the cops to show up. Even if you are technically allowed to do it, there's very few reasons why you'd ever want to. Not only are you expos...	[ "You can learn it quite easily by following some of the tutorials on YouTube - I learned to do it without references in a couple of hours. It takes NO skill to just solve it - doing it really fast though, is something else." ]
From what I heard, Yoko Ono is responsible for the break up of The Beatles. Please elaborate.	[ "You know how glass can fracture, but still kind of stay in place until someone touches it? Yoko Ono can be seen as that touch. But really, she was an easy scapegoat that allowed the Beatles to break-up without it being the fault of any one Beatle." ]	[ "In the 1832 Supreme Court case Worcester v. Georgia, Chief Justice John Marshall, in the majority opinion, ruled that the Cherokee nation was its own distinct community and not subject to the laws of a particular state. How, Andrew Jackson chose not to enforce that ruling, thus paving the way for the Trail of Tear...
How did Japan become sustainable while isolated from the rest of the world?	[ "Can you clarify what you mean by 'sustainable?'" ]	[ "There's an interesting [article in Discover magazine Oct 2004](_URL_6_) about traditional [Inuit](_URL_5_) diets. Diets were heavy in wild animal protein & oils/fats from fish/shellfish, land & marine mammals, and birds. Vitamins A & D is found in oils/fats. Vitamin C - necessary to prevent scurvy - is found in ra...
If water is incompressible, how do fish swim?	[ "You're missing a fundamental part of the equation: Water is a fluid. As the fish moves through the water, the water flows around the fish. There doesn't need to be \"space\" behind the fish for the water to flow into, because water is flowing behind the fish before the space can be created. In fact, it is due to...	[ "The pressure doesn't keep increasing. It's pressurized to a certain level and stays there. Just as a balloon can hold pressure for days without the pressure increasing and bursting it. Edit: Or how a heavy book on a shelf doesn't press harder and harder until it breaks the shelf. The pressure has stabilized." ...
Why was the British Empire able to become so big/powerful when the UK is so small?	[ "Just to add an extra question. Would the beginnings of the industrial revolution, starting in Britain, have had a place in the role?" ]	[ "That is not always true. In the Americas, for instance, the most developed part was in Mexico, a tropical country (the Aztecs and Mayas). And in Asia, India has been a center of high culture despite its warm climate. Further west, Egypt and Sumeria were pioneers of culture despite a sweltering climate. Parts of Ch...
How do you as historians treat information gathered illegally or through espionage?	[ "Archivists and librarians are held to a strict ethical code, which notably prescribes they won't disclose confidential information held by law. I come over secret or private documents when i work a the archives, and there are a lot of things i can't disclose to the public or in my works. Sometimes it's because of...	[ "Hello prospective respondents. Everyone loves to talk about food (and drinks!), so just a reminder of which sub we're in: it's /r/AskHistorians so no personal anecdotes, urban myths or conjecture. Respondents here are expected to have expertise in the subject, offer in-depth information and cite *reputable s...
What was Prophet Mohamad's religion prior to Islam? Do we have any information about religion in Quraish or the surrounding area?	[ "I recommend [Fred M. Donner's](_URL_0_)Muhammad and the Believers. It's a nice breakdown of the early spread of Islam with reasonable and succinct analysis of a period wrought with issues in sound primary source material." ]	[ "hi! not discouraging more contributions, but FYI racism is a common topic in this sub, so there have been a few similar questions. I pulled up a few by searching 'racism'; check these out for previous responses: * [Europe had normal diplomatic relations with non-white nations before turning explosively racist to j...
why do so many stores in the U.S. sell things with a .99 at the back? E.g. 9.99, 1.99, 999. Why not just use 10.0, 2.00, 1000?	[ "It’s a technique used to make the average person think at a first glance that $1.99 is not $2 and is only $1. Sorry if this is explained bad, I heard this from my 7th grade teacher" ]	[ "Doing that is the only way to differentiate between the top students. If the test is easy, and 5 people get 100%, then the professor has no way of knowing what advanced topics those students are struggling with. Be making the test difficult enough that no one gets 100%, it becomes possible to rank the top studen...
How are squareroot, cuberoot, powers, sine, cosine, tanh, erfc etc. complex functions computed on various platforms when all computers can really do is add/subtract/multiply/divide?	[ "Calculus, for the most part. It turns out that you can represent the vast majority of things you need to calculate with what's called a power series. So you take a function and, through some algorithm, turn it into a power series. A power series is an infinite sum of some more easily solved function, where you j...	[ "Software can optimize images and fonts to render well with your monitor. See [hinting](_URL_0_) and [anti-aliasing](_URL_1_) for details. With macs, the software is more standardized, which makes this easier to accomplish. For other systems, a bit of tweaking may be required, but the same effect can be achieved. ...
What material remains/artifacts you consider most significant for the understanding of Greek civilization and why?	[ "_URL_0_ Mainly because it blows wide open the idea of civilisation at that time being technologically primitive. This thing is extremely advanced, both in its construction and in some of the complex calculations that they now think it was designed to perform." ]	[ "I can't speak for all items, but guns and uniforms were common war trophies. Soldiers were permitted to bring back captured small arms and uniforms and other similar items. A token form had to be filled out, but this was not always enforced. Generally, this was just a permission to possess the captured arm. Here i...
Products, such as glue, that are purple but disappear/turn clear--how do they work?	[ "I don't know for sure, but it's almost certainly solvatochromism: _URL_0_ Briefly, the color of something can depend on the environment, particularly the polarity of the solvent. When the solvent evaporates, the environment changes and so does the color. Less likely possibilities are the dye being volatile and eva...	[ "Around 1669, there was a German alchemist named Hennig Brand. He was in search of gold, and thought that it came from within man. What color is gold? It's a shade of yellow. What else is yellow that everyone is familiar with? Urine. So off went Hennig on a quest to extract gold from pee. He boiled down 5,500 liter...
Why does the DTFE rendering of the near universe have that shape?	[ "The image you refer to is the result of an observation know as the 2dFGRS which stand for \"2 degree galaxy redshift survey\"- redshift being a measure of a galaxies distance. It's shape is like an hour glass because it was focused on the north and south galactic poles. They did that because the disk of our galaxy...	[ "On the earth end the communication is done with very large, highly directional radio dishes (essentially radio telescopes), for example, the [Deep Space Network](_URL_4_). The high directivity of the antennas lets you receive more signal while at the same time ignoring most of the background noise. There isn't rea...
- The OJ Simpson trial, and why is it important?	[ "he killed someone, he was uber famous, he got away with it. one of the primary examples of celebrity priviledge in law." ]	[ "I have a question for you. Do you want the version that is super, super long and includes a write-up on what actually went down at Munich, and the subsequent responses back and forth? Or do you want the shorter version that only talks about media coverage of the incident and how it changed things?" ]
Why isn't lunar energy a thing?	[ "The moon doesn't emit light. It reflects light from the sun towards Earth. And, assuming we're talking about a full moon...reflected moonlight is about [400,000 times](_URL_0_) weaker than the light that comes directly at the Earth from the sun." ]	[ "They are working on it. In NYC's East River, a third generation turbine is under development. The first was destroyed by the current. Pretty sure there is a project in Maine too. I'm sure there are more, but it is in its infancy." ]
How do video games save the position of many objects?	[ "The game saves the coordinates and orientation of each item in a relatively small area (like a city in skyrim) and does this for all areas. Interiors like houses are separate areas. The state of the items are only loaded when you are in that area, it doesn't load the whole world at once. If you haven't visited a...	[ "To answer your question of which file extensions are used, that doesn't really matter. File extensions are just naming conventions, which helps an operating system know what programs can open that file. But ultimately it's just part of the file's name, and can be anything, or even nothing. On consoles, they're pre...
With our new ability to measure changes in gravity, could information from within the event horizon of a black hole be communicated by creating gravitational waves within the black hole?	[ "Gravitational waves cannot escape a black hole. On the subject of \"the gravity escaping the black hole\" [read here](_URL_0_)" ]	[ "In the theory, wormholes are non-traversable, so there is no real \"connection\" in the sense that even an unbound excitation could cross from one spatial region to another. It's also possible that the whole ERB thing is a map-territory issue. You first see an ERB emerge in the idealized model used to formulate t...
how is it so difficult to go to the moon in 2019 even after all the technological advances - why haven’t we been back?	[ "It’s expensive and useless. What would we go back for? Another publicity stunt? Drones and rovers are leagues cheaper and more scientifically useful. We went once to prove it could be done, there is no practical reason to go back. It would be easier than it was the first time with modern equipment, but theres ju...	[ "That's just it. It takes a while to amass information and use it. An animal just does whatever comes natural, aka 'instinct'. But humans are taught and trained and learn and practice and... and... Layers and layers of information and training to get us to the point where we can actually achieve more than the previ...
Why is patient zero of such significance?	[ "Viruses mutate as they travel to different hosts, so the first patient to get it has the most basic form of it that has the most in common with the daughter strains, which may evolve in completely different directions. Thus, if you find a cure based on the original patient, is has the highest likelihood of working...	[ "You mean the Animal Planet one? Hype and marketing. Then it became a euphemism for menstruation (I'll fill you in if you want, but it's gross sex stuff...) and took on a life of its own." ]
Fast Fourier Transform	[ "It's basically a group of algorithms for calculating the discrete Fourier Transform. You should familiarize yourself with the discrete Fourier transform to understand the rationale behind fft algorithms. I don't know where you are in your mathematical development, but fourier analysis is often covered as a senior ...	[ "EE here, a rf low pass filter followed by a Rf detector forms a crude fm demodulator. In this case the wiring and passive components form the filter, and nonlinearity in the audio amp causes it to act like a rf detector." ]
What would happen if you put a magnetic ball inside a hollow metal sphere?	[ "As a purely theoretical question if the forces in all directions were balanced it would just float in the middle (assuming no gravity, etc.). However this is impossible to recreate and so due to imperfections in either the regularity of the objects or starting conditions it would stick to the inside of the metal b...	[ "Yes! Matter can exhibit a similar behavior. This is called [spin polarization](_URL_0_) and depends on how the spin of the object relates to some direction. A common application is electron polarization. If this direction is the direction of motion, then it's referred to as helicity." ]
Why do different countries have different sign languages, couldn't there just be one standard one especially due to the lack of "signers"?	[ "The issue was that sign languages evolved independently, in different countries back in days when communication across nations wasn't as easy. And unlike writing letters, or even using telephones, sign language isn't as easy to teach other people to use when not in person to see the actual signs. So it wasn't unti...	[ "Imagine a water pipe. If you're the only person using it you get full pressure. The more connections to that pipe the weaker the pressure." ]

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