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eax4lm | where does all the food go? | Especially if you have a high metabolism where you’re not gaining weight and not pooping an equivalent amount to how much you eat. Where is all this excess food going? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/eax4lm/eli5_where_does_all_the_food_go/ | {
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"Poop, heat, and consumed useful energy. You basically take the nutrients, break them down, make energy molecules, release a lot of heat along the way. Then, use this energy to build things like proteins from things you got from food (amino acids). If you're not gaining weight despite eating insane amounts, you either have very high metabolism (genetic, hormonal, age related, aerobic sports, etc) or you have very bad absorption (genetic, some GI disorder, etc) or something is stealing your food (parasite, tapeworm, etc).\n\nEdit: also, please note that the food that goes in is not even remotely similar to the one that leaves (poop). For some things it is but not most. You destroy its architecture, you squish everything into higher density (remove fluid and crush the organization). So if you really want to compare how much food is going out relative to in, you have to measure the mass not volume, and then measure water content because you absorb a lot of that (then water goes out in urine, sweat, breath, saliva, cum, or tears)"
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2uyt3g | if cellular radio waves are basically everywhere all the time, how do they not get blended with eachother? | Same goes for radio stations I guess. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2uyt3g/eli5if_cellular_radio_waves_are_basically/ | {
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"They all have slightly different frequencies, which makes it easier to tell the difference. \nImagine you're trying to pull one thing out of a box while blindfolded. There are three items in the box. Those three things are all apples, but you're trying to get a Granny Smith. The different frequencies would be like taking those same three apples, and coating the Granny Smith in sandpaper. \nMake sense?"
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2fd9va | how did we come to understand universal symbols for play, rewind, fast forward, and so on. what is the design of these symbols called? | Something I was thinking about recently is how a lot of devices like remotes, control panels, etc, all have these symbols that are shorthand for the function they perform.
Examples: _URL_0_
Like, 'star' has become pretty standard for favorite something, a heart/thumbs up is a like, and so on. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2fd9va/eli5_how_did_we_come_to_understand_universal/ | {
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"They become ICONS by means of a general CONSENSUS as to what they mean.",
"We all understand them because culturally we've been conditioned to know that a thumbs up means \"good/like\", a heart means \"favorite\", two right-facing arrows means \"faster\", etc. A baby has no idea what each symbol means; it's something we learn as we grow up. It's something we learn very early though, judging by how quickly my baby cousins have mastered Netflix.\n\nThe study of symbols is called semiotics.",
"[No one is really sure](_URL_0_), but the pause icon resembles the symbol for a break in electronic schematics, and the play symbol seems to imply forward motion. "
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"http://cache4.asset-cache.net/xc/466037403.jpg?v=1&c=IWSAsset&k=2&d=B53F616F4B95E5538F961FB2DF43F838F6C0FB6433A47A7438F76B61711082D1"
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88g8jl | what is bicarbonate? | I am learning about the means of transport of carbon dioxide in my college A & P II class right now and I learned that 70% of CO2 is transported as bicarbonate dissolved in plasma. The only chemistry background I have is junior year high school chem, so I’m very confused about what bicarbonate is, especially in relation to anatomy. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/88g8jl/eli5_what_is_bicarbonate/ | {
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"Bicarbonate is HCO3(-). It acts as a buffer keeping your blood within certain pH values. \n\nIt is formed when H2O and CO2 are combined in red bllod cells by carbonic anhydrase(an enzyme) to make carbonic acid, H2CO3. This carbonic acid quickly breaks down into H and HCO3. When it reaches the lungs the bicarbonate is separated back into H2O and CO2."
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1hxcls | what happens to prices/wages when a country implements euro as the currency? | I have friends in a country that is not in the eurozone yet, but there is talk of adopting euro as the currency. What would that mean in terms of prices? Even if the current food/domestic products prices may be way below the average EU price, I do not expect everything to stay at the same level. Will that mean people will earn more in comparison to before when the pay is 'translated' to euros? Will the prices go up? Will the prices remain the same, just in a different currency? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1hxcls/eli5_what_happens_to_priceswages_when_a_country/ | {
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"In theory (and largely in practice) prices and wages will stay the same, just in a different currency.\n\nYou're correct in your implication that this means that goods and services can vary widely in price across the eurozone.",
"If a country joins the Eurozone, their old currency is fixed to the Euro.\n\nSo, if you had a price in German Marks, you had to divide it by 1,95583 to get the same price in Euro. And that will never change. If I go and check under the couch and find old German Marks, I can still get them exchanged for that precise course.\n\nOne Mark *is* 0.51129188119 _URL_0_ difference, no change. They represent the same value.\n\nSo, if you have a job that pays a certain amount of money, it will simply be paid in the equivalent number of Euros after that.\n\n > Will the prices go up?\n\nThey will change. But that has nothing - or little - to do with things now being paid with different coins that have different numbers. It has everything to do with a new country joining a larger commercial union.",
"See where the money and the people are going.\n\nSay you run your country with your own currency. You get to set interest rates, and if your country slows down, you can lend money at a cheaper rate. The downside is that your currency may be cheap today and dear tomorrow, and people in other countries may not want to do business with you.\n\nSo you sign up to the Euro. Now this is not a peg, but a complete conversion of your old currency to the euro. You don't have the tools to change the value of your currency anymore - a euro costs a euro anywhere in the zone, and its value relative to the world's monies is set by the European Bank. Things that are cheap in your country now gets sold far and wide, whereas things that are expensive in your country gets replaced by imports.\n\nBut what if your country's economy slows down? Sorry, we're all in it together now, says Angela Merkel. If the whole of Europe were a real country, the rich part may help the poor part by transferring tax revenues until both get better in a new and stabler setting. But this is just the Eurozone, so you have to sit it out until your country recovers on its own. You can spend what you have in your piggy bank, but if you go bust nobody's going to want to take care of you. (Unless your tiny little country manage to sink the euro with it, that is. Then you become Greek.)\n\nNow, on to the flow of people. After eurozone comes Schengen Zone, guaranteeing the flow of people. And people follow the money, and the mobile people in your country will go abroad. Foreign Europeans will want to come to your pristine country and do serious business as well, so there is an exchange of labourers for investors.\n\nAny questions?"
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10g9gu | how can an animal eat its own kind with no side effects but human cannibalism causes brain damage? | Deep down we're all 'animals'. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/10g9gu/how_can_an_animal_eat_its_own_kind_with_no_side/ | {
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"Animals can't either; look up mad cow disease.",
"It isn't the human flesh that causes brain damage, it is the risk of parasites/prions in the human flesh. Thoroughly cooked human flesh won't hurt you, but if it is under cooked or you eat infected brain matter (as with the cows who got mad-cow disease) then you are at risk.\n\nGenerally you only find cannibalism in less developed areas and so the risk is greater.",
"related; are humans even safe to eat aside from things like vitamin A and diseases? Like, wouldn't toxin buildup from us being at the top of the food chain be too much to handle? I've read that large animals such as whales are actually declaired biohazards when they are found dead on the shore due to mercury, etc. ",
"OK, prions are a problem. But I'm healthy (I think) so if my doppleganger (assuming basically the same genetic structure to over simplify things) were to eat me, would he get sick? When exactly does it become a problem? Does having the prions in you make you sick, or ingesting them from another source make you sick?",
"Cannibalism is dangerous because all the things that are capable of harming you are most prevalent in your own species. It's no worse for humans than it is for animals."
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f4gvat | why are people born with photographic memories? how does this impact psychological childhood development? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/f4gvat/eli5_why_are_people_born_with_photographic/ | {
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"Photographic memory is a myth. Not a single case of it has even been found, so no one is born with it. Makes for great TV though. \n\n\nThere is such a thing as Eidetic memory, but only really found in children, disappears as they get older, and even this is often warped or flawed in some ways. \n\n\nThere is no such thing as perfect memory. A very few adults have unusual memories, but those usually come with some pretty severe mental problems in other areas instead."
]
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477hup | how were the first construction cranes built when there were no other cranes to reach or lift the heavy weights? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/477hup/eli5_how_were_the_first_construction_cranes_built/ | {
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"Cranes can construct themselves. You dont need a crane to build a crane. Its tricky but it can be done.\n\nYou could also easily build a crane by constructing scaffolding around it and putting it together that way.",
"We've had simple cranes being built thousands of years in the past, so putting together a small crane isn't an insurmountable task. Besides, you don't necessarily need a crane to put together another crane, as long as you've got something like a ledge to work with, or even a pulley system mounted to a higher point, like a building.",
"Gin poles were used for a long time. I haven't worked with them myself, but the previous generations of my trade could lift nearly anything with them. \n\n_URL_0_\n"
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ehh4n9 | how it is determined that people who died while texting-and-driving were actually looking at their phone at the time of (or time leading to) impact? | I always wonder how it is determined that people who died while texting-and-driving were actually looking at their phones at the time of (or time leading to) impact. I feel like it’s a pretty serious accusation to make - as it, in a way, provides a rationale for their death.
I should clarify that I’m the most anti-texting and driving person you’d ever meet. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/ehh4n9/eli5_how_it_is_determined_that_people_who_died/ | {
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"No way to know accurately. But some estimates based on witnesses that saw the driver texting. Seeing sent text messages with that time stamp, etc. In general cellphone in hand at the time of accident could be classified as driving and texting regardless of actual use.",
"Txt messages all have timestamps recorded on the phone and also on the telco side. You can match up the timestamps with the accident.\n\nA lot of accidents also have witnesses and it's really obvious when someone is using their phone while driving.",
"If the deploying airbag embeds the phone into the drivers cranium, then that’s a good indicator too.",
"One way is to look at the text box where you type in the meassage, and see if there's an incomplete word or sentance at the end."
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1aukj8 | how does my hair get tangled so quickly? | I swear it takes all of 10 minutes for tangles to appear in my hair. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1aukj8/eli5_how_does_my_hair_get_tangled_so_quickly/ | {
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"text": [
"Entropy. There are more ways for your hair to be tangled, than untangled. "
]
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rcbek | why do i look up and the right when i'm trying to remember something? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/rcbek/eli5_why_do_i_look_up_and_the_right_when_im/ | {
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"I look to the side, personally; I think looking in another direction helps you focus on something different quicker.",
"It's a microexpression. You're looking away as your brain tries to find the memory. \n\nPolice sometimes as you a random question to establish a baseline to refer back to. Your eyes might drift to the side as you recall a memory. \n\nLater, when they ask you where you were the night Bobby was murdered, if your eyes drift the same way, they know you're probably telling the truth. If you answer head-on without that glance, your brain's probably making things up because you didn't do that recall glance. "
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2sspgm | how do scientists determine how much water you need to drink? | The amount of daily water recommended seems ridiculously high. You would think that if your body is capable of doing anything naturally, it would be to tell you if you need water or not (such a fundamental resource). How do scientists determine that we should be drinking beyond what our bodies tell us? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2sspgm/eli5_how_do_scientists_determine_how_much_water/ | {
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"IIRC, the \"recommended amount\" of water per day has no real health benefits. Maybe a myth, may be a misconception.",
"The \"8 glasses of water per day\" thing is ridiculously high and is also a myth, apparently originally based on a misinterpretation of a 1940s article telling people to get 8 cups per day *including the water content of their food*. _URL_0_\n\nBut even that recommendation is somewhat suspect. Research hasn't conclusively shown what the \"correct\" amount of water per day is. There have been studies looking at health outcomes for different groups drinking different amounts, but again nothing really conclusive. \n\n"
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30odgd | why do we have summer and winter time? wouldn't it be easier to shift the clock half an hour in one direction and leave it that way all year? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/30odgd/eli5_why_do_we_have_summer_and_winter_time/ | {
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"It started as a way to help farm families manage work and school time. It stuck because it saves many millions of dollars in energy each year. Reduces stress on the power grid and other benifits. Adjusting humans can be done, the sun just is so set in its ways."
]
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2o7y6u | why is it conservative media in the us usually stands against minorities in alleged police brutality cases? | I'm black and am studying in the US, but my country of origin is elsewhere. I understand the rationale for conservative support for low taxes, less government regulation etc; but I don't get why they would be on the side of the police in cases of alleged excessive force. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2o7y6u/eli5why_is_it_conservative_media_in_the_us/ | {
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"I think you'd have to provide some specific evidence here. Most of the stuff I've seen is them pointing out in the Michael Brown case that the rest of the media was really quick to label him a blameless victim and pointing out all of the contrary evidence.",
"Conservatives in the us are not like conservatives in the rest of the world. The Republican Party supports \"traditional values.\" This is often one in the same with either Christian values or family values. This can largely encompass respect for authority and therefore they support the police officers. Also, all conservatives support stability and so they would be against revolting. Finally, conservatives stand firm that the ferguson case was self defense and not supporting wilsons right to protect himself is bad for guns rights. ",
"It's probably incorrect to treat any group as being monolithic and all members sharing the same rationale for supporting their position.\n\nHowever, as far as the United States is concerned, it's important to consider the impact that race has on this debate.\n\nThe police cases that have gotten the most publicity lately have involved white officers with black members of the public.\n\nIn the US, conservatives are largely members of the Republican Party. That party's members tend to be older and whiter than the the Democratic party, which is generally considered to be the liberal party. Democrats tend to be younger, with much more racial diversity.\n\nIn this context, the Republican party tends to focus on law and order, while Democrats tend to focus more on individual freedom and view police actions with more suspicion.\n\nRace is a big factor in this issue because the Republican party tends to dominate in the South where this is a long history of slavery and discrimination against blacks, and in wealthy suburbs where many whites have relocated to escape living around blacks. \n\nThus, when police actions and race collide, many Republicans tend to identify more with the white officer and view the person of color with suspicion, while many Democrats tend to identify more with the person of color and view the white officer with suspicion.\n\nThis is a gross over-generalization.\n\n\n\n"
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n2emz | why we think pirates talk the way they do | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/n2emz/eli5_why_we_think_pirates_talk_the_way_they_do/ | {
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"_URL_0_\n\nNumber 6.",
"What we came to know as \"Pirates\" (e.g. treasure maps marked with an \"X\", schooners, the Black Spot, tropical islands, and one-legged seamen carrying parrots on their shoulders etc.) all came from the novel Treasure Island by Robert Louis Stevenson (1823). \n\n\n\n ",
"I once heard a very old recording, of a sailor who was old when the recording was made, singing sea chanties. His accent sounded exactly like Popeye, but much stronger. \n\nDuring the classic age of sail, people in different parts of the world had very strong accents, as there was no broadcast standard for people to emulate. Sailors started out with these strong accents, and many grew up speaking different languages. All the world's English speaking sailors would have developed their own distinct, global dialect, while people from the North and South sides of London could hardly understand each other's speech.\n\nFor an analogy, see the [Military basic](_URL_0_) accent, in modern American English (middle of the page). Then imagine how much stronger the accent would be if the speakers didn't watch TV in standard English, or call home regularly.\n\nAs LindLTaylor points out, our ideas about pirates come from Robert Louis Stevenson. But the author, and readers at the time, knew sailors had a disticnt way of speaking.\n\nOh, crap, this is eli5. Old time sailors talked funny, sort of like Popeye. Our ideas about pirates come from one make believe story. The guy who wrote it knew sailors taked funny, but the book probably isn't quite accurate. ",
"_URL_0_\n\nNumber 6.",
"What we came to know as \"Pirates\" (e.g. treasure maps marked with an \"X\", schooners, the Black Spot, tropical islands, and one-legged seamen carrying parrots on their shoulders etc.) all came from the novel Treasure Island by Robert Louis Stevenson (1823). \n\n\n\n ",
"I once heard a very old recording, of a sailor who was old when the recording was made, singing sea chanties. His accent sounded exactly like Popeye, but much stronger. \n\nDuring the classic age of sail, people in different parts of the world had very strong accents, as there was no broadcast standard for people to emulate. Sailors started out with these strong accents, and many grew up speaking different languages. All the world's English speaking sailors would have developed their own distinct, global dialect, while people from the North and South sides of London could hardly understand each other's speech.\n\nFor an analogy, see the [Military basic](_URL_0_) accent, in modern American English (middle of the page). Then imagine how much stronger the accent would be if the speakers didn't watch TV in standard English, or call home regularly.\n\nAs LindLTaylor points out, our ideas about pirates come from Robert Louis Stevenson. But the author, and readers at the time, knew sailors had a disticnt way of speaking.\n\nOh, crap, this is eli5. Old time sailors talked funny, sort of like Popeye. Our ideas about pirates come from one make believe story. The guy who wrote it knew sailors taked funny, but the book probably isn't quite accurate. "
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1rsqkz | what is math and why does it work? | what is math. We have algebra,calculus etc.but what is math in real world? I know it might be a stupid question but is math only something we use to describe our world , or why does it even work ,what does it even study, did we discovered math or did we invented math, why there even is math?...you know, the thought before sleep | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1rsqkz/eli5what_is_math_and_why_does_it_work/ | {
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"One of the problems I see with a lot of the explanations here is that they are focused strictly on one type of mathematics. Mathematics is a large topic that encompasses many parts. As such I share the definition that I share with my students:\n\nBorrowed from \"The Language of Mathematics: Making The invisible Visible\"\n\nMathematics is the science of patterns...\n\nArithmetic and number theory study patterns of number and counting. \nGeometry studies patterns of shape. \nCalculus allows us to handle patterns of motion. \nLogic studies patterns of reasoning. \nProbability theory deals with patterns of chance. \nTopology studies patterns of closeness and position. \n\nEDIT:\n\nI feel it is necessary to address several of the comments and an edit is the best way to do so.\n\n1. **Saying Math is the Science of Patterns is too broad.** Yes you would be correct in that statement. Except there was also context provided with that statement. Looking at each of the main topics gave examples of each of the types of patterns studied. Math does not study every single pattern that exists, just ones that relate to it. \n\n2. **Math is no empirical to be considered a science.** I have one issue with this particular statement. If math is not empirical enough to be considered a science. How is it that we can use math to make other sciences empirical? Physics is a scientific field that is heavily influenced by mathematics. It uses it mathematical statements all the time as empirical evidence. Where the issue comes in, I believe is how math is empirical. In other fields of science, they use another field to give empirical evidence. Physics uses math, Chemistry uses math and physics, and so on and so on. In math to prove something, we use math. Which you would think creates this self-fulling prophecy but it really doesn't. TL/DR: If math isn't empirical neither is any other science as they are based on math.\n\n3. **Math is Logic.** Ehhh. Yes and no. Yes, math uses a lot of logic to help prove numerous statements. If you look at one of the parts of the definition though it says, \"Logic studies patterns of reasoning.\" Saying that math is logic only allows you to analyze a very small part of mathematics. Again, mathematics is a huge topic so we need to be careful when trying to define it. There is no perfect definition sadly and everyone will disagree on numerous points. Definitions of math is numbers, logic, or whatever else may have been said is extremely limiting though.\n\n4. **Math is a language.** While I do disagree with this statement it is an interesting discussion to have. The way we see math used on a daily basis is in a base 10 system. The notation we are familiar with was created to shorten statements down to \"equations.\" The notation we use was really just created to make creating multiple copies of books (back when everything was hand written) easier and to a degree when the printing press was invented. In the past, we would have said stuff like: \n\n\"When two numbers are added, their order is not important.\"\n\nWe would not write that as: a + b = b + a\n\nIf we want to talk about the patterns that exist outside of notation than I would agree with you that mathematics is a language.\n\n5. Final statements. Understand that math is an enormously large topic. It is easy to be focused on one specific part of math because that is what we have been exposed to most. Few ever see the entirety of mathematics and truly understand it. I wish I was one of those lucky people but sadly, I am not. \n\nI use this definition in my classes for the sheer fact that it hopefully allows my students to think beyond what they are exposed to on a regular basis. As a trial, I usually have them make their own definition before providing them this one. Typical answers usually include math is numbers, torture, or various other quips. Use this definition as not an end all be all, but a starting point. Let it open up your perception of mathematics beyond what you already know and explore other parts. Numbers and equations are such a small part of mathematics.",
"This is a very interesting question. I think you might find related the work of Hilbert, a German philosopher/mathematician, and those who were working at a similar time in related fields, such as Godel and Russell.\n\nMaths essentially works by stacking proofs on top of each other. Essentially, you take some things you know and re-arrange, combine and manipulated them so that they tell you something else. These proofs build on each other, and it's essentially that way that maths gets done.\n\nIn the early 20th century there was a movement, lead by Hilbert, pushing to try to logically ground all mathematics in a number of basic propositions (axioms) that were consistent, finite and complete - this was called the Formalist movement.\n\nIt all gets pretty complicated here. But the Formalist and Logicist (that is, a group trying to reduce all maths to logic) movements essentially failed. Godel's incompleteness theorems showed these goals to be essentially impossible.\n\nI'm not really sure where that leaves maths. I hope I've told this story well enough - it's not an area of expertise for me, only one of interest. I'm also not sure if it really answers your question all that well, but I may as well put it out there for people to see.",
"Mathemathics is a **very** big subject. People have been discovering new things for thousands of years that have all been classified as \"maths\".\n\nWhen you go about your daily life you do math all the time. Lets say you have a family of five, but only three pieces of candy. You then immediately know that there is not enough candy for everyone, you'd need two more.\n\n\"Formal\" mathematics is to take something like that candy situation, remove unneccesary details like the words \"person@ and \"candy\", then figure out a good way to write it down, for example \"3 - 5 = -2\". Once you've done that you have not only written down the solution to the candy problem, you have also defined the operation of subtraction. And that operation can be reused as often as you'd like.\n\nMore advanced maths is just the same thing for more advanced problems. You want to make a good map? Think about the problem, remove details, write it down, maybe use that clever subtraction operator from earlier to simplify what you wrote. Boom, geometry. Want to figure out how speed and acceleration are related? You're gonna need to invent some calculus for that.\n\nAfter thousands of years of clever discoveries we now have a huge toolbox of operations, methods, formulas and so on, which, if you know how to use them, will let you solve some really difficult problems.\n\nAs it turns out, people all across the world figured many of the same things out independently. It turns out math is the same everywhere. Mathematicians don't invent, they *discover*.\n\nThis means that we can use math to figure out how *anything* in the universe works. Physics is taking math then adding some details again. That's how we can look at a star in the sky, measure what color it's light is, check what elements make that color, then tell what the star is made of, what way it is moving in relation to the earth, how old it is, etc. All without ever going there, because we know that math is the same there too.",
"Who/how was it figured out that ten digits could be used to express so many things and that they all fit together in patterns?",
"In my opinion its counterproductive to start thinking about mathematical models of the real world when trying to understand what math is.\nFirst of all, math isn't a natural science at all. It's a science of structures. And the beauty of it is that you can study any structure you can think of. There is no actual need for validation in this universe when studying structures mathematically.\n\nNow, I don't know who said it, but one of my favourite quotes about this said something like \"Mathematics is the only science you can still do if the universe ceases to exist tomorrow.\"\nWhat most mathematics boils down to nowadays is pretty simple: You define a basic set of rules for a structure (mostly through axioms and properties of sets you wish to examine) and then, trough logic (in whichever logic system you chose), deduct further properties of your structure, mostly under new restrictions that are or seem interesting.\n\nNow what is a really good question indeed is why it \"works\" so well in our human world. People have been doing arithmetic for about as long as we have recorded documents of history. Euclidian Geometry has been around since, well, Euclid in ancient Greece, possibly longer.\nI'd argue that for the longest time, mathematics was merely a tool for other fields to better understand our world, but people for the longest time didn't think about the underlying structure of their thoughts regarding the tools. Most \"mathematicians\" like Newton, Laplace, Pascal, Eucild, Leibnitz or Pythagoras were'nt even mathematicians per se.\nThey studied nature and used mathematics when it was neccessary (and often developed new techniques for their cases). The \"modern\" way of mathematics started arguably with Cauchy, who was one of the first to regard mathematics as a discipline in itself.\nBut it's only natural for it to develop that way.\n Mathematics works because there seems to be a universal logic to the our universe. So while studying real objects, you come across these patterns and structures you can abuse to get to know a little bit more about yourself and the world you live in. Until at some point you realize\nthat there is a way to formalize these observations for more general objects and so on.\nThink about a lumberjack. He's using his axe to chop wood, and maybe learns a thing or too about his axe on the way to become more efficient. A mathematcian would dissect the axe, and come up with a way to describe the axe with very general outlines for structures (to stay with this picture, lets say the need for a \"handle\" and a \"sharp contact surface\").\nHe would break down the axe so far, you would'nt even recognize it. But by analyzing the underlying principles, he would gain a deeper understanding while reconstructing the axe from his assumptions.\n\nThe crazy thing is how efficient mathematics works in itself. There are so many fleshed out theories that don't have any use for \"real world problems\" yet. Absolving itself from the dependence on other natural sciences seems to have speed up the process.\nThere is of course the poster child of modern mathematics, Graph Theory, with it's direct links to computer science, but every field has results defying any connection to other fields.\nWhat's unique about mathematics is that you can obtain \"absolute truths\" in the set of rules and restrictions YOU defined. As long as human thinking and logic is consistent, mathematics allows for these kinds of judgement. \nThat is why proofs are so important. Instead of testing your theory with observation of the universe, you test it with logic on your assumptions for your structure. Proofs are a way to show the logic connection between results and assumptions.\n\nI don't know how much that helps, but these are my ramblings as I'm still studying at university right now. But here are some things I think Math is not (as in \"not only\"):\n\n1. Math isn't arithmetic. I haven't used a calculator since I started university.\n2. Math isn't numbers. There are tons of Theorems/Results or even branches of mathematics that don't even need numbers (or structures that act a lot like our number system, groups/fields/rings).\n3. Math isn't Applied Math. Every time someone asks what I'm doing all day it's hard to make people understand that you don't need an actual application of the findings.\n\nHere are some hints to topics that maybe help grasp the spectrum of mathematics a bit better:\n\n1. Zermelo-Fraenkel set theory in first order logic _URL_1_\n2. Functions _URL_2_\n3. Abstract Algebra _URL_4_\n4. Topology _URL_0_\n\nAnd last but not least, my favourite theorem and a good example of the difference between an application and a fleshed out, theoretic version of the \"same\" thing: Stoke's Theorem _URL_3_\n Note the difference between the usage in physics and it's modern version in mathematics using differential forms.",
"I'll explain by analogy. Think of a game, like chess. Chess has specific rules on what you can do and what you can't do. It has specific results for every action. Really chess is defined as just a set of rules and a specific environment (board and pieces) on which these rules apply.\n\nBut from a simple base structure like this, we can play a huge number of interesting games. It's mind-boggling how many different unique games are possible in Chess. Just a simple game with simple rules like Chess has given us millenia of interesting games and entertainment.\n\nThen there are other games like Tic-Tac-Toe, which are also simple but very limited in their possibilities. Here you have used a different set of rules, but generated only a small universe of possibilities, in stark contrast to Mathematics.\n\n---\n\nMath is exactly like that. Modern mathematics is rooted in specific axioms and rules, and we then explore the vast universes that are created by those rules. Say you define some objects with some properties and then some rules about what they can do. You have a system that you can explore now. Using only the axioms, you can prove certain things and disprove other things. The amazing thing here is, that if you can find ANY real life objects that happen to have those properties and follow those axioms, you will get the same result in a real-world setting.\n\nSo, the math that everyone is used to (numbers, functions, calculus) is really just describing some abstract objects that have to play by some abstract rules. The reason is work in the real world is because a lot of the objects in the real world behave like those abstract objects and follow those rules.\n\nThat said, there are many fields of mathematics where this is not true. You can come up with many systems for which you won't be able to find any tangible use because nothing you can think of or find, actually works like that. But regardless, if you did find something - you would know a whole lot about it as a result of the theorems you've proven.\n\nA lot of people feel the need to state that Mathematics is merely a system used to model the universe, but this is not true. There are many fields or spaces that you can explore in Mathematics that are not relevant or related to the physical universe. Whether or not this is the purpose of Mathematics is not a question I wish to address. Our's is but one universe that is explorable through the use of mathematics.\n\n---\n\nIn recent history, we've been getting better and better at abstraction to the point where we have almost captures all the fields of mathematics under one umbrella of rules. For a while, it was taught that set theory could be the complete foundation of mathematics, but now have found areas that don't come under set theory at all.\n\nThere is also the deal with how we define and approach logic. That's all very philosophical. You can read more up on [mathematical logic here](_URL_0_).\n\n---\n\nAt the heart of it, Mathematics is the art of taking some objects and some specific rules about what you can do with these objects and then exploring the universe that is created out of it.",
"I refer you to this: _URL_0_ which refers to a seemingly unique tribe living in the Amazon whithout numbers.\n\nA few paragraphs of reading will tell you they have great difficulty drawing a straight line or describing even simple numbers like one and two.\n\nThey can trade nuts they gather and women with neighboring tribes, but cannot count even after months of lessons. Neither can they describe their history or traditions beyond a generation or two.\n\nIt would seem from this evidence that numbering is an essential part of modern human society. That without numbering we remain simple hunter-gatherers without the ability to build a sophisticated society.\n\nPerhaps the cro-magnon did not have numbers either.\n\nMore than 60 years ago, amateur linguist Benjamin Lee Whorf argued that learning a specific language determined the nature and content of how you think.\n\nThat theory fell into intellectual disrepute after linguist Noam Chomsky's notions of a universal human grammar and Harvard University professor Steven Pinker's idea of a universal language instinct became widely accepted.\n\n\"The question is, is there any case where not having words for something doesn't allow you to think about it?\" Prof. Gordon asked about the Piraha and the Whorfian thesis. \"I think this is a case for just that.\"\n\n",
"Mathematics is the study and application of abstract reasoning.\n\nIt should be noted that our modern day notion of \"Mathematics\" did not always exist. Today, Mathematics is all about establishing a consistent axiomatic system and then making deductions. In the old days of the Egyptians, this was not the case. To the Egyptians, Babylonians and etc, Arithmetic and Geometry were practical sciences based off of empirical evidence and not sound reasoning. Because of this, these people made many gross errors which we would think obvious.\n\nExample: The Egyptians thought that the area of an arbitrary quadrilateral was A=(a+c)*(b+d)/4 where a,b,c,d are the lengths of the sides of the quadrilateral in adjacent order. The Egyptians saw that this formula was true for rectangles and squares, and it \"looked right\", so they accepted it as fact blindly.\n\nIt wasn't until Thales of Miletus came around at about 600 B.C. that our current day notion of Mathematics was born. He was the first to demonstrate that the circle is bisected by its diameter through deductive reasoning. The circle is bisected by a diameter not because it looks like it. The circle is bisected by a diameter because if it did not, then at least one commonly accepted assumption about circles must be false.\n\nThis is the heart of Mathematics. Something isn't true simply because we haven't found an example of it being false. Something isn't true simply because someone else said it is true. In Mathematics, something is true because it can be shown to be true through rigorous reasoning.\n\nSadly, most people go through their entire academic career being taught a subject called Mathematics which really isn't Mathematics at all.",
"I'll try answering this as simply as I can.\n\n > did we discovered math or did we invented math\n\n\nMath has been there all along, since the universe began. 1+1 has always equaled 2, whether humanity discovered it or not, right?\n\nWe chose to give specific meaning to specific things we call numbers and symbols so that we could start TALKING about the math that has been there all this time.\n\n > why there even is math?\n\nThere is math because some wise ancestor decided to count things and trade things with others. It became so complex because of all the contributions people made over so many centuries.\n\n > why does it even work\n\n\nMath works because it all depends on very basic assumptions. Think of them like building blocks. You have these 10 or 15 or 20 assumptions, and you start to come up with rules based on these assumptions. This works if we assume simple things, such as \"If we take any two points on any one piece of paper, and use a straightedge to connect them, we will have made a line.\"\n\nMathematicians use these assumptions to build new and exciting theories and results. Then someone else takes THOSE results and makes something out of them. Just like working with building blocks. If the logic of going from one building block to the next is good, then the result is also valid.\n\n > what does it even study\n\nThere are a LOT of branches of mathematics, and they're different (but very well connected). I can't really answer this one.\n\n > is math only something we use to describe our world\n\nMath can be used to describe any world, because it only depends on logic being valid.\n\n\n > what is math in real world?\n\nIn the real world, math is mostly finance, probability, and statistics. Businesses need to be able to add things up to do their taxes and other documentation. Probability and statistics are used to manage risk in the real world. In the real world, anything can happen, and probability and statistics are used to try and predict these things and work around them or with them.",
"\"Mathematics is the science of not getting laid.\"",
"Mathematics, at its core, is a series of logical patterns and conclusions that can be drawn from our observations of the world around us. Numbers themselves are a construct to represent the idea of an amount. Of what? Well, it doesn't really matter because it's just an abstraction.\n\nBasic manipulations of those numbers (\"I have 2 apples, I will get 1 more apple, I now have 3 apples\") leads to basic arithmetic. Above is an example of addition. In addition, we can demonstrate subtraction (\"I have 3 apples, I will throw 1 apple, I now have 2 apples\"). We can build up on that basic concept with more advanced manipulations (\"I have 3 apples. I will steal 2 apples for every apple I have right now\") to demonstrate multiplication. It's very, very difficult to make a logical statement that can disprove these sorts of rules, and any proof you can find will have some logical missteps in them.\n\nMany of these ideas can be derived purely from observation, and many of the more fundamental mathematical concepts can be made more concrete. For example, 2 + 1 = 3 is the previous apple example. Now, what if we wanted to use similar concepts for problem solving? Well, I know I can steal 2 apples at a time from you, and I want 20 apples. How many trips do I have to make while you're not looking? That leads us to super basic algebra, in the form of 2 * x = 20. This is one of the reasons why word problems are important when teaching kids math. It's supposed to teach them how a real-world problem can be boiled down to a math problem, which can be solved on paper. Or, more succinctly, how a real problem can become an abstract one, which is usually much easier to solve.\n\nThese sorts of ideas have led to a set of rules called *postulates*, of which there are many. I may be mistaken in this assumption, but it's very difficult or impossible to prove a postulate. They are the absolute fundamental building blocks of what we call math. [Check out this link for postulates](_URL_0_).\n\nFrom postulates, we've collectively as humanity derived a set of *theorems* that can be proven from those postulates. Think of the \"proving\" step like a logic puzzle. You have a goal (the theorem you want to prove), you have a starting point (postulates), see if you can get from point A to point B. There are several other ways to prove theorems (induction, contrapositive, and I'm sure I'm forgetting others) as well, but they tend to be more advanced.\n\nSo, **TL;DR**:\n\n* Math in the real world is what happens when you take patterns in reality and make it abstract\n\n* Math works because the fundamental rules we assume to be true to prove everything are based entirely on our observations of the world that always hold to be true.\n\n* Math is the study of patterns and logic. All postulates are derived from patterns we as humans noticed out in the wild. They're rules that have always held.\n\n* We invented math, but we did not invent what math represents. Math is a language to describe our world in order to boil it down to the purest, simplest, most abstract terms. Much like how I can use the word \"apple\" to mean a particular type of fruit, math is the language of reality.\n\n* Math exists out of necessity. From the earliest days of bartering, we needed a way to say \"a = b\", \"a > b\", and \"a < b\". Going even earlier than that, we needed a way to say \"165 pounds of Gazelle, minus X pounds of bone, minus Y pounds of skin, is going to leave Z pounds of meat to feed 12 people. Is that enough for everyone?\"",
"Mathematics is about looking around you and seeing what the pieces mean. In math, you get the luxury of a starting set of hypotheses -- axioms, as the Mathematicians say -- and you then ask the simple question: if these are true, what else is?\n\nThis is in contrast to science where we do the experiment and find the end result, but can never know for certain what the starting axioms actually are. When, for example, Einstein crafted his theory of relativity he did some science in guessing what the axioms might be, and then did a lot of math by asking what the consequences were (and subsequently working them out). ",
"Mathematics is a language used to put meaning to the patterns which persist throughout every level of size we have discovered in our observable universe. These patterns are thought to exist on all levels because all living and non living masses are all in possession of varying amounts of the same energy on the most fundamental scale. The language uses measurements to generalize information about the quantities of forces, masses and their interactions and how they all fit together to produce what we humans consider to be the physical world. etc. (Distances, forces, masses, volumes, temperatures, pressures, the list goes on and on). All math is a description of whats out there in the universe. Math does not exist because the universe does exists, the universe is not dependent upon the math for its function and survival. The math is a creation of the human mind used to express what we are all actively taking part in every day and witnessing transform stars in the sky. Math is the human attempt and accurately describing real life things like motion in a way that is specific enough to be reproduced by nothing other than the math itself. The units are defined by the speaker as he/she interprets them, so long as that interpretation of the units is constant throughout the sentence, or equation. Math is always a description of something..... No college experience or diploma here, just my opinion of what mathematics is after a high-school math education.",
"*[Something To Let You Maintain Your Puzzlement](_URL_0_)*",
"Okay so I'm not a mathematician, but I've done and am doing and will be doing a considerable amount of mathematics in my degree plan, and this is *my* interpretation of what math is.\n\nIt's some thing we made up. It doesn't 'exist', the universe doesn't check for a table of constants, or make this chemical reaction happen at this speed because there are that many molecules, it just *operates*. We, being a curious species, use our own conceptualization of numbers to explain the things we see in front of us. Read this:\n\n_URL_0_\n\nPi is a very 'important' number - especially if you're going to study any kind of science, pi is something that you will eventually start to use in some way. Pi isn't a number that is engrained in the universe, it just IS - and the 3.1415 . . . is a number we 'found' because of the way we interpret numbers.\n\nI know we operate on a base 10 mathematical system and I think I read somewhere that it is probably because we have 10 fingers off of which to count on, which influenced our evolutionary understanding of numbers. I'm curious to know how much constants like pi would change if we were operating on a different base system, would it change at all? Would all of our mathematic laws of physics and nature change if we were using say, a base 6 system?",
"Math is a way of telling a story about something, even if you never get to see that something.\n\n\"Michael brought bread to the table. Marie, Don, Fred, and James had Michael's bread, but Michael and David were unable to have bread.\"\n\nThere's something about this story that illustrates something about the bread that allowed Marie, Don, Fred and James to have Michael's bread, while Michael himself and David couldn't have any. There simply wasn't enough bread for all of them.\n\nWith maths, we can answer some questions about why only some of the people at this table could have bread. We can imagine that there are a countable number of people at this table, that there is an amount of bread one of them brings to the table. Also there's a matter of distance. Why David and Michael went without bread instead of just Michael.\n\nSure, there are plenty of questions that can come up that don't have to do with maths at all. Maybe David has a gluten allergy and chose not to partake of any bread. And maybe Michael was too busy setting the bread on the table that he was not able to take a piece for himself. And if that answer satisfies the listener, the dinner scene can continue.\n\nBut some folks are really curious about details. And maths lets us look for details into why only some people had bread and others didn't. Was David too far away from the table to get there in time before all the bread was taken? Some maths can answer that. Why didn't Michael use one hand to offer the bread and use another hand to take a piece for himself? Some maths can answer that too.\n\nMaths allows us to look for details about events regardless if we can see them directly, and many of us are very curious about how things happen. Maths is something we formed and agreed upon to find a way to share these details, and even sometimes find out things we didn't even know.\n\nSome maths out there are for things we sense. Some maths involve things that don't really exist. And that gets to people sometimes. How can you talk about things that don't exist? It takes a great deal of wonder and patience and practice to do so, but sometimes those imaginary things will surprise you by being a great way to look at the details of things that are real.",
"Mathematics is simply a tool we developed in order to describe the patterns found in nature, and like all tools, we designed it to help us understand those patterns better. So technically, mathematics is man-made, but its creation is inspired by patterns and concepts that are not easily explained without a use of tool.",
"Math was a thing the Scottish invented to trick the British into lowering their taxes. \n\n",
"when i was in second grade i asked my teacher this same question. i wanted to know why math worked more than how it worked. she got really angry with me because she didnt know how to answer and thought i was being a smart ass. i got detention and gave up on math being and interesting subject until adulthood. i wish i had had reddit back then.",
"Math is abstraction, a way to describe or symbolize pretty much anything. It's like kids draw stick figure and put some random lines and say it's daddy. And from that point to try make it simpler, ie, cave man draw many copies of animals to record \"many\" without precise amount, after you invent numbers, you can simply say 25 elephants.\n\nIt works because it starts from symbolize physical things, ie 1 ship can carry 25 soldiers, so 4 ships incoming you have maximum of 100 soldiers attacking. You give symbols(+,-,x,/) for what they suppose to do in a formula, and later everyone agree to use it the same way for better communication. \n\nMath does not study anything, human study math as a tool, and use math to try describe other things, be it observable(how long does it take for Earth to orbit sun) or just hypothetical( how fast will zombie spread if T-virus is real), thus new symbols are invented to describe new concept of doing complex calculation but don't take many pages to write it down in pages like idiot.( ie, 5x100 = 5 + 5 + 5 + 5...... )\n\nWe invent math symbols, but discover relationships of how some formulas can accurately describe real world things. Math is here because we need a system to efficiently book keeping instead of painting 200 cows on a small sheet of paper, but at the end people need to study all those symbols and formulas that all the previous smart people discovered.\n",
"using symbols to represent everything we can count or measure and playin with them and shit like that",
"Math is logic, except distilled to a shorthand form that makes it easier to explain a logical thread of information. \n\nSometimes we interpret the math wrong, and draw further conclusions from a logical conclusion than we should. See the Financial Crisis.",
"Consider a set of statements that are so obviously true no one would argue with them. Statements like: for any number x, x * 1 = x. Or, for any number x, there exists a number -x such that x + -x = 0. These statements are called axioms. They're things we accept as true without proof.\n\nMath is the process of figuring out what more interesting statements could be made from the axioms. For example, from a set of 9 axioms about real numbers, we can prove that x * 0 = 0 for any number x. These more complicated statements are called theorems.\n\nThe axioms needn't describe numbers. For example, there are the seven (I think) axioms of origami, describing the seven different way to define folds of paper. And from these axioms, Robert Lang has been able to prove a theorem that simply stated says \"If you can draw a stick figure of it, I can origami it.\" He's created wonderful works of art based on this theorem. I encourage you to look up Robert Lang if you are interested.\n\nAnd that's math.",
"I don't know if this is ELI anything under the age of like 16 but that would take tons of time. If you actually take Calculus 3 or so (for some it is 2 or 1) everything just clicks. Math is no longer boring and weird but it is actual beautiful. You go past the numbers and you understand it you understand what it is used for and why. I went up to Calc 4 and stopped, but I am sure it gets even cooler if you go deeper but ti understand you have to take some calculus IMO.",
"We invented math to describe what we can see of the math that already naturally exists.\n\nMath is taking one and making it many. Tangling, twisting, and bending, with out ever violating the one.\n\nMath is taking many and unrolling them, smoothing them, stretching them. Making one without ever violating the many.\n\nMath is gazing in awe at none. The none that rarely is.",
"I always liked the following definition of Mathematics:\n\nMathematics is the symbolic representation of logic",
"I'm in high school and I do a lot of extra math competitions and tests. I lose sleep over this question. People consider me to be good at math, but what is it that I'm actually doing? I don't know for sure, but this is the best explanation I could come up with so far:\n\nReligion is a man-made explanation of how things work. We turn to it to know what happens when we die; early peoples used it to help in things like farming or sailing, as well. Science is also a man-made explanation of how things work, but it's more accurate and relevant than religion in many non-existential respects. We now generally rely on science to help farm and sail. Mathematics, however, can exist entirely within itself. Although it's most often used for science, certain respects may have no practical application.\n\nI consider there to be two different ways to think of mathematics. The first way is as a system of thought. From some small but highly applicable set of basic, concise rules, so long as you can make infinitely many deductions that you can prove to be true or false from only those rules, the rules compose a form of mathematics.\n\nThe second way is as a discipline. This is the arbitrary selection of such rules that society as a whole considers to be true. For example, if I were to write \"2 + 2 = 4\", you would most likely immediately recognize a true statement. But the truth of this statement is arbitrary. Society could have just as easily made it so that \"2 + 2 = 5\" was a true statement. Only because the generally accepted set of rules can prove that \"2 + 2 = 4\" is true do we accept it as such.\n\nAs for why it works, I have much less idea. There can be topics of mathematics that don't work (have no scientific application), but I find it amazing that so many of them do. Personally, I like thinking that a mathematical universe is a requirement for intelligent life. I think that the Einstein quote sums it up best, though:\n\n > \"The most incomprehensible thing about the universe is that it is comprehensible.\"\n\nEdit: format",
"I've often asked myself this and and this is how I see maths. \n\nMaths is a language like any other, and is used for communicating ideas. What sets it a part from other languages is the precision it has in it's rules and definitions. \n\nLanguages need common understanding for communication to take place. Take English and I want you to pick up a phone. I could say 'pick up the phone' but that relies on both of us having a common frame of reference eg. what a phone is and what pick up means and so on. I don't need describe what a phone is and what all the elements of science tht make up the 'pick up' motion\n\nIn maths it's the same but the rules are be defined from a very very basic set of assumptions or very simple frame of reference (called axia) . Maths then defines the things based on these (both objects - like the phone in the above example) and processes (like pick up) to add more and more complexity. \n\nSo far it's like any other language and is used as a tool to communicate ideas about the world (both real and imagined). The big advantage is that because it's made up of so many smaller element s many of is components it has can be applied in many different ways to come up with completely new ideas, or new ways to express existing ones.\n\nI studied physics (high school) and it was at that point maths as a language became clear. Physics models (describes) reality at a very low level. It needs a language that describes it's ideas in a very precise way and this is where maths helps. You see something in the real world that has some properties that change (ice into water for instance). If you measure accurately enough you can plot some numbers that will give you a graph of the change. So now you have something real that is described in maths (a graph), and you can look at the data and say \"oh that's looks like an foobar function\". Then a maths expert could look at that an say - did you know foobar functions that have a starting point of 10 will always do something special. You can now look at you real world and think about what if your property started at 11 - would the property have done the same - what would if mean for the world if you did?\n\nAll I'm trying to convey is that it's a language that helps describe the world in a way that's useful to some people. It's like a very precise poetry.",
"One of my (computer science) professors in college described math as a modeling language. I've yet to come across a more concise definition.",
"Math is the observation of patterns. Essentially, it is a language to represent how everything works with absolute certainty.\n\n > Did we discover math or did we invent math?\n\nWe invented the symbols that we use (numbers, operations etc..) as \"markers\" for the ideas we discovered. For example, whether you refer to a single unit of measurement as \"one\" or \"1\" or \"uno\" is irrelevant; it doesn't change what is being represented.\n\n > What is math in the real world?\n\nA computer program can emulate reality and to do so, everything needs to be logical. Fundamentally, events occur as the result of IF\\THEN\\ELSE, as in, if x=1 then [do this] else [do that]. \n\nRegarding the \"real world\", the reason artificial intelligence is deemed to be impossible by some people is that we observe reality through the proverbial right side of the brain, where events happens more chaotically and *without* a line-by-line sequence of rational conclusions. We can make mistakes and not know why, whereas a simulation (in regards to being the opposite of reality) would have a very specific reason as to why something happens (such as an error in the coding).\n\nI think understanding how computers do what we want them to do is a great parable to seeing how math applies to everything around you. If you really want to get deep on the idea of what math is and how it really is a representation of everything, check out the concept of [simulated reality](_URL_0_).",
"In some ways this can't be an ELI5 without lying a little bit. Just recognize that this is very incomplete.\n\n Math is a lot of statements that you can make. Not a language by the way as some have said here. The symbols we use to communicate those statements are a language. But we could choose different symbols (different language) and it would reference the same statements. Anyways, whenever someone makes a statement in math you can ask them why that is true and they will explain it using other statements. You can keep asking why, and eventually you will get to a few statements that are just assumed to be true. These statements at the bottom of the tree of asking why are called \"axioms\".\n\nWhat pure mathematicians do is to work this process backwards. Start with the axioms, and build the trees from those. What we see is just the outer branches and leaves but all of that really springs from statements that lie at the bottom of the trees, even though the useful stuff is up top.\n\nAs for \"why does it work\". I hope this isn't a copout, but that is not really a valid question in my opinion. There is no why. They do work, insofar as we have picked our axioms wisely. In other words, we have chosen the right place to plant our tree and grow it out (sorry, I'll leave that metphor alone now). We appear to have done so.\n\nAnd let me emphasize again, this is all much more complicated than I'm letting on. And this is also not quite what I do for a living, so I might have missed some important stuff even at this basic level.",
"I've always found this picture to be helpful _URL_0_",
"Put simply, **math examines how and how much things are in relation to each other**.\n\n* How big a slice of cake needs to be when a certain number of people share (arithmetics)\n* How hard you must throw a ball for it to reach your team mate, the curve it describes, the way it travelled (integrals)\n* How big the chance is of you winning the lottery with a given number of tickets and players (statistics), or [how to behave in a game show](_URL_0_)\n* How the roof on your house must be angled for it not to be crushed by snow in the winter ([differential analysis](_URL_1_) among others), and how the angles are constructed by using lengths instead of angles (trigonometry)\n* How your optimal way of playing is when you play Risk with your friends (game theory)\n\nAnd while those are real-world examples of how quantifyable things can stand in relation to each other ensuring that math can be applied, **you can apply math to math** - and that's where it got really useful, as this allowed us to go beyond immediately observable relations and find out what the \"big\" connections may be, those that we can't see.",
"IMO, **mathematics is the pursuit of [Analytic Truths](_URL_0_) through dialectic means**. An Analytic truth is anything that is completely independent of the \"real\" world, what most would call the physical world (If you don't agree with the philosophical concept of [materialism](_URL_1_), then there is more to the real world than just the physical. For example, if souls and god exist as actual things and not just ideas, they count as part of the \"real\" world, even if they aren't objects). Any analytic truth is true because of what the words or symbols mean, not becuase of anything to do with the world. 1+1=2, and it would still equal two (as long as those symbols mean the same thing) if the real world were completely different in every way, or even if there was no universe and nobody to think it. By contrast, a Synthetic Truth is something whose truth relies on the real world. So \"All bachelors are married\" is a synthetic truth because it's true because of what the word bachelor means. It's kind of a trivial example, but that statement is an example of math. The statement \"Atmosck is a bachelor\" is true because of the fact that I, a part of the real world, am not married. \n\nWhen I say \"through dialectic means\" I mean as opposed to empirical means. If you come across a fact just by thinking about it (as is the case with math, or at least when a piece of math is originally discovered), you've discovered it through dialectic means. If you discover something using your senses (as is the case with all of science), then you discovered it through empirical means. Science is all about the real world, so **Science is the pursuit of Synthetic Truths through empirical means.**\n\nAdditionally, **metaphysics is the pursuit of synthetic truths through dialectic means**, and you could argue that most of philosophy falls under metaphyics or meta-questions like whether this is possible at all (or if any knowledge is possible at all). It's a popular view these days that metaphysics is impossible. But as an example, the [Ontological Argument for the Existence of God](_URL_2_) is supposed to be a dialectic argument (because it only relies on definitions an logical truths) with a synthetic conclusion (that god exists, in the real world). (Arguments that the ontological argument is faulty usually rely on the analysis that it has implicit empirical assumptions that are faulty.\n\nTo answer some of your questions directly, the truths of maths are things we discover, by reasoning. What truths of math we try to figure out are often motivated by the fact that they are often useful analogies for the real world. For example, given the rules of geometry, the facts of geometry would be true in any universe. But the reason we care about geometry with those particular rules is that we can describe our world in terms of that geometry. Often we change the rules just to see what would happen (what if a line had multiple different parallel lines that go through the same point) and study them just because they're interesting, and later find out that they are useful in science somewhere.\n\n**tl;dr** Math is figuring out, just by reasoning, things that are true and would be true no matter what the real world is like (you could never make 1+1=2 false just by changing things about the universe).\n",
"A long time ago, humans found they needed a way to keep track of quantities, and started counting things. This was step 1.\n\nEventually they realized they wanted to remember what they had counted, and decided to use symbols to write things down. This was step 2. Several systems came and went, but it's important to remember we invented the idea of numbers and how they get written down.\n\nUp to this point, really no math was being done. Most of the math you do in grade school to deal with addition and subtraction isn't so much real \"pure\" math, it's just learning the system of dealing with those symbols we made up. (Think of carrying the 1, and the idea that when you have 12 things it's written as a '1' followed by a '2', etc.)\n\nWhere real math started was when someone had to figure out how to invent that system that we now call 'numbers', and when someone had to make sure that set of rules we invented called 'arithmetic' are actually guaranteed to work. After all, we don't want to adopt a system of numbers only to find out that it breaks down in some odd unforseen case. So early mathematicians proved that 'arithmetic' works for our arbitrarily invented system called 'numbers', and by doing that in a very rigorous and specific way, they were able to prove 100% beyond any possible doubt that arithmetic is a valid way to work with numbers.\n\nInitially they started with addition and subtraction. Makes sense, you have some things over here and some things over there, and you want to put them together or separate them apart. But then, those early mathematicians realized that certain kinds of addition were repetitive, and quickly found that if you know 100% for sure that addition works, then another rule naturally arises that makes those scenarios much easier. They called it 'Multiplication' and proved that if addition is valid, so is multiplication.\n\nAnd so it went from idea to idea. Someone realized that because we know addition and multiplication are proven to be true, they could prove that you can work with numbers even if they're unknown, and algebra was born. Society needed to work with shapes, and since they knew arithmetic and algebra are proven to be true, they can use it on shapes. Geometry and trigonometry were born. Then they realized that since geometry is proven valid, there was a way to use it with lists of numbers, or continuous functions, and went about proving that Calculus is a valid way to work with numbers.\n\nSo, this is how society has used math, and what math has been to society, but it's not the best answer for \"what is math\". I went through that explanation because if you look closely there's a repeating pattern going on.\n\n**Math is the mental process of proving that something is 100%, absolutely known to be true.** (Within any constraints set by your initial assumptions.) It's frequently used to discover new ways of dealing with the world because \"if we know A and B are true, I can prove that C is also true.\"\n\nI went through all that explanation above because, without it, it could be hard to understand what that statement means. In the context of \"We had figured out that you can add numbers, and someone used math to realize that multiplication is a thing\" it makes more sense.\n\nDoing math depends on the discipline of being able to work with abstract ideas, and keeping good track of your initial assumptions. For example, as many people who played old NES games may have noticed, addition doesn't work when you're working with 8-bit binary numbers. If you add 100 to 200, you get 44. This happens because when binary numbers are limited to 8 bits, that disobeys one of the fundamental \"ifs\" that were in place in proving the validity of arithmetic. (Basically, you can't ever have a situation where if you keep adding 1 to your number you end up back where you started. Unsigned 8-bit binary numbers wrap around when you go past 255, so you can only use arithmetic on them if you avoid that situation.)\n\nIt also depends on the discipline of understanding that math happens in the abstract and not the real world, and making sure you're using a valid translation of math when you use it in real world scenarios. For example, I can't \"prove that math is wrong\" by showing that if you add one rock to one rock really hard, you get three rocks since one broke. That's not math being invalid, that's me (deliberately) applying it wrong. I started with the assumption that my rocks were indivisible units when I counted them as \"two\", and then broke that rule. This discipline is called \"Applied Mathematics\" because you're deviating from the realm of abstract ideas that work the way they were intended with no strings attached, and entering the realm of real things that behave according to the rules of real life. (e.g., if I tell you I have the number 1 but I need the number 2 so I'll break the 1 in half to get two 1's, you will easily tell me I'm doing it wrong. But if I tell you I'm going to break one rock into two rocks, your mind has no objection to that phrase.)\n\n**The TL;DR**:\n\nMath is used to prove that things are undeniably true. That's really the only definition that fits everything math does. Math is made entirely of things we invented, all the way down to numbers and the idea that adding 1 to 9 is 10, and adding 1 to 7 is not 10. Math works only on abstract concepts, until you choose to apply it to the real world, at which point the only flaws you have to worry about are any flaws in your logic of how you applied it to your real-world situation.\n\n[Edit] I foresee someone pointing out that this doesn't sound like what they do when they're \"doing math\". My counterpoint would be, you're not \"doing math\" you're \"doing arithmetic\" or \"doing calculus\". We as a culture just don't feel like splitting it all apart and talking in such annoyingly precise terms all the time, so we say \"Doing Math.\"\n\n[Edit 2] Why does it work? It works because it's been rigorously proven, and because it ultimately only depends on abstract things that we made up. Calculus works because geometery and algebra work, those work because arithmetic works, and arithmetic works because our system of numbers follows certain rules. Everything has been rigorously proven every step of the way, making all of it a complete pure certainty. (At least, until someone tries to apply it to the messy, unkempt real world.)",
"I like math- I might have something to add here....\n\n...reads commments...\n\n...I have nothing to add here",
"The universe is made of two things: matter and energy.\n\nMatter is stuff.\nEnergy makes the stuff move.\n\nWe created math to predict where \"stuff\" will \"move\" before (or after) it happens. ",
"We do not have good memory, but when we write something down, it allows us to keep note of it. As problems in everyday life became more and more technical, (like figuring out how to divide pieces of land in Babylonia) writing symbols down to keep track of our technical thoughts became the only way to easily solve these problems. As this became more commonly used, we started to develops a system around these symbols so people would not need to re-learn another's symbols every time they were looked at. This is what math is. It is a highly technical language that allows you to short cut writing out long sentences. Just like we use our thoughts to think through something, we also use those same thoughts for communication to others. Some one doing math could be thought of as thinking their way through a technical question instead of a literal one. This has extraordinary practical applications to modeling the physical world. Hope that helps.",
"1+1=2\n\nAnd everything else is just built up on top of that, because those numbers can mean anything.\n\nSubtraction is just the logical \"well that means that 2 - 1 = 1\"\n\nMultiplication is just rewriting that same thing. Technically the meaning of 1+1 is the same as \"hey, put 2 of that 1 together\". Rewrite it as 2 x 1 = 2. \n\nDivision is the opposite of multiplication.\n\nAlgebra is just saying it doesn't matter what the 1 represents. Heck, it could represent another number if you want. 1(apple) + 1(apple) = 2 (apples). rewrite that as 1x +1x = 2x. Or, if you want, write 1(3) + 1(3) = 2(3). Which conceptually is the exact same thing as writing 3 + 3 = 6. And that's basically just multiplication again. Doesn't even matter what it represents.\n\nEverything, all the way through calculus and the ends of our mathematical knowledge is just messing with these facts, and they all rely on a really really simple premise that 1+1 = 2. ",
"There are a lot of good answers... but nothing that seems geared for ELI5 that I've yet seen. So I'll give it a stab. \n\n\nImagine that the universe is actually a simulation - on a computer. \nWe exist within this simulation, but do not know the code that defines our reality. \nMath is us reverse engineering that code. The code *library* to be more precise. \nThe generic goal is to understand the 1 and 0s behind it all. \nBut we more often seek different high-level syntax's, which make some topic easier to deal with. \nPhysics, in this analogy, is the goal of understanding some existing bit of programming within the context of that syntax. \nAnd engineering is the use of that syntax to create something ourselves. \n\n\nThat said, we make up our own syntax. We lack access to the real library, and thus must create our own. So when people say that math is man-made that is what they mean. But it doesn't change the fact that what it is used to define is very real, and exists as *truth* regardless of our accepting it. ",
"OP, I actually find this question, and questions like it, to be profound and thoughtful. It's one of those big Why questions. Most people don't ever think to ask things like this. Good for you.",
"Math is just a series of logical arguments.",
"Not really an ELI5-answer but I liked the video the Idea Channel did on this subject on youtube [Ideal Channel](_URL_0_)",
"In physics we have found a way to predict the behavior of objects (like planets for example).\n\nTo each object you associate a number m, the \"mass\" of the object, which you can think of as corresponding to how difficult it is to accelerate the object.\n\nWhenever something is pushing on something else, we introduce a vector (a quantity with both magnitude and direction, which can be described by three numbers) which corresponds to how hard the thing is pushing, and also the direction in which it's pushing.\n\nPhysicists have found that these quantities can be given appropriate values such that equations such as the following are satisfied:\n\n-- F = ma (F is the total force on an object, m is the mass of the object, a is the acceleration of the object).\n\n-- If A pushes on B with force F, then B pushes on A with force -F.\n\nWith this approach, we can write down some equations that describe how a physical system (like a bunch of planets orbiting the sun) behaves. By solving these equations, we can predict how the physical system will behave in the future.\n\nThis is only one example of a \"mathematical model\". Mathematical models like this are used throughout physics, science, and engineering. The equations in the model may not actually be satisfied exactly, but hopefully they are close enough to being true that the model predicts reasonably well how the system will behave.",
"A lot of very smart people have been thinking about this for a long time. It is not assumed to simply be the \"science of patterns\". No five year old is going to have a clue about any of this (unless they spent like, 10 years working on it, at which point they would be 15. If my *math* is right). This might almost read as nonsense if you don't have a little background. There's probably an introduction to phil of math on youtube or something that would be better.\n\n\nFrom ( _URL_0_ ):\n\n > 1.Logicism\n\n > The logicist project consists in attempting to reduce mathematics to logic. \n\n > 2.Intuitionism\n\n > Intuitionism originates in the work of the mathematician L.E.J. Brouwer (van Atten 2004). According to intuitionism, mathematics is essentially an activity of construction. The natural numbers are mental constructions, the real numbers are mental constructions, proofs and theorems are mental constructions, mathematical meaning is a mental construction\n\n > 3.Formalism\n\n > David Hilbert agreed with the intuitionists that there is a sense in which the natural numbers are basic in mathematics. But unlike the intuitionists, Hilbert did not take the natural numbers to be mental constructions. Instead, he argued that the natural numbers can be taken to be symbols. Symbols are abstract entities, but perhaps physical entities could play the role of the natural numbers.\n\n > 4.Platonism\n\n > In the years before the second world war it became clear that weighty objections had been raised against each of the three anti-platonist programs in the philosophy of mathematics. Predicativism was an exception, but it was at the time a program without defenders. Thus room was created for a renewed interest in the prospects of platonistic views about the nature of mathematics. On the platonistic conception, the subject matter of mathematics consists of abstract entities.\n\n\nI think that in practice most mathematicians are platonists, if they even care about the issue at all. You don't need any of this to do most mathematics. It reminds me of Richard Feynman's quote about philosophy of science. “Philosophy of science is about as useful to scientists as ornithology is to birds”.\n\n\n",
"This question is a very deep one. The article linked below gives an interesting example. The first paragraph is a fun one. You can ignore the statistics jargon and get the full effect I think.\n\n_URL_0_",
"So this is a contentious topic. I'll start by explaining the logicist view and then suggest some problems with it.\n\nOne view is sees Mathematics as logical extrapolations from a set of axioms (assumptions). For example, Euclid's elements, which contains proofs of many of the basic theorem's of geometry (e.g. Pythagoras' theorem), arrives at these proofs by starting with a set of axioms. One such axiom is the [parallel postulate](_URL_1_), this axiom can't be derived from the other axioms Euclid uses. We might consider such an axiom to be (at least an approximation of) a fact about the real world, but nonetheless it is important that this axiom (like Euclid's other axioms) is not provable a priori.\n\nHowever, it may be possible to prove such axioms from some other, more basic set of axioms. Indeed, we might expect that the axioms that define integral and differential calculus can be proved from the axioms that define basic arithmetic and set theory. Showing this to be true would be no simple exercise.\n\nSuch a view of mathematics suggests that all of math could be described using some very basic set of axioms and then using deduction rules to arrive at more complex theorems.\n\nA deduction rule is a concept in formal logic. The idea is as follows: normally you might informally deduce something e.g. \"look, we know if John goes into the cinema then Stacy will go too. Well John is indeed in the cinema, therefore Stacy must be.\" By contrast, in formal logic you carefully define a set of formal rules that determine what sentences in your logical language follow from what other sentences. So one rule might be that a sentence of the form \"A if B\" and a sentence \"B\" together imply \"A\" (this is equivalent to the cinema deduction). In reality we use symbols rather than words but that is the basic idea. For some types of formal language and associated deduction rules we can check whether those rules are consistent (they never lead to a contradiction) and that they are complete (if one conclusion does indeed follow from a set of premises then it is possible to get from those premises to that conclusion using our deduction rules). Once a proof is written in this way it could be easily verified by machine whether the proof is valid.\n\nThe project of carefully defining mathematics in a formal language and deriving formal proofs using the deduction rules of some formal logical language is known as [logicism](_URL_0_) and gained momentum at the end of the 19th century. Thinkers like Bertrand Russell championed the project which had been initiated by Frege and Dedekind.\n\nThere are however a number of problems that face locisists. Firstly, Godel's incompleteness theorem shows that regardless of how you set up your formal logic version of mathematics (i.e. no matter how you set up your axioms and choose your deducation rules) for any system that could be used to describe even basic arithmetic, the system you set up can never be both consistent and complete, i.e. there will always be some true statements that your system cannot be used to prove to be true. This is not necessarily a rebuttal of logicism but it perhaps limits what logicism might hope to achieve.\n\nGodel's second incompleteness theorem also presents a challenge, it effectively implies that you can never prove that a formal system that includes basic arithmetic truths is actually consistent. This arguably answers your second question \"why does it work?\" the fact is it might not. We cannot formally prove the consistency of math, it is possible (if highly unlikely) that tomorrow someone could prove one thing and then prove the opposite of that thing is also true and hence destroy our entire conception of mathematics.\n\nThere are also deeper problems for logicism. Chiefly there is an argument that logical systems presuppose ideas about the natural numbers in the way those systems are set up. That the concept of numbers of things is built into the structure of logic, by talking about \"A and B\" perhaps we are presupposing a concept of 'twoness'. It has been argued that the essence of math is the natural numbers.\n\nThis is an ongiong debate and a very interesting one. Clearly logicism has had some major victories, it is likely true that at least a decent majority of mathematics could be derived formally from the basic axioms of set theory. But whether this such a view of mathematics would actually capture its essence is less clear.",
"Let me begin by saying that by *mathematics* I will not mean that which is taught at school. I don't know what that symbol-pushing, pattern-matching, number-crunching, soul-crushing thing is, but I know it is not mathematics.\n\nMathematics, as practised by us humans, is, quite simply, reasoned imagination. Nothing less. Unlike the other art forms, say poetry, it is not constrained by the universe, which is merely a particular kind of semi-riemannian manifold. \n\nWe mathematicians study manifolds, CW-complexes, varieties, schemes -- all vast generalisations of the notion of physical space. We(or at least Gromov) deal with spaces where each point itself is a Riemannian Manifold. We deal with an infinite sequence of CW-complexes all tied together in a strange dance, called Spectra. We routinely deal with spaces of infinite dimensions (hilbert space) -- in fact, a quantum system is a point moving through this space described by what is called a wave equation. \n\nWe study mathematical structures and objects, which are built up from axioms. However, mathematics is no more a game with axioms than music is a game of squigly marks on sheets of paper. What are mathematical structures and objects? Well, they are what mathematicians study. Let me explain by way of an example -- when Euler solved the Konigsberg Bridge problem, he did not think he was doing mathematics, but his solution and the subject he initiated is now a card carrying member of mathematics. The object he used in his solution, a Graph (I feel forced to call it a one-dimensional CW-complex), is now a mathematical object par excellence. \n\nThere are some who believe that capital R Reality, ultimately, in the end, at the very bottom, sub specie aerernitatis sort of a way, is a mathematical entity (which is frankly not as crazy as it sounds -- begin by thinking about Rutherford's experiments, escalate to a textbook on QFT). \n\nSo, the real question is not what is math in real world but where is the real world in math?\n\n\n**Edit** I am infering, from many of the answers given, that a lot people seem to be approaching this question from a CS or philosophy background (That 'model theoretic' answer of mhd-bhd reminded me of an undergrad logic class I had taken long ago). However, I just wanted to add that it is safe to say the majority of the (pure math) community do not view mathematics like this, but having said that I'm not sure how much that really matters actually.\n\nI just wanted to add that the 'axiomatic' way is just how we package our math. And although we care about 'proofs' and 'theorems' a lot, what we are really after is 'understanding' -- this is why we try to prove a significant result in as many different ways we can. As mathematicians we are trying to get the right concept or idea which we encode as a 'definition'. We are interested in proofs not just because of the certificate of certainty that they gives us, though that is important as well, but because they help us understand the mathematical landscape. ",
"I can't believe no one has pointed out that the definition of math and its relation to the material world (or what you might call *reality*) is [a whole branch of philosophy](_URL_1_). There are several interpretations on which level math operates: does it only live in our imagination, is it a brain function or is it even(identical to) nature? For an easy introduction you might be interested in [this video](_URL_2_) and [this](_URL_3_) and [that one](_URL_0_) gives you an idea about where the problems are on relating math to reality.",
"It's a model for the logic of reality. We know it works because we observe it working.",
"On the surface this may seem like a 'stupid' question to some, but this is a fantastic example of what ELI5 should be all about: explaining complicated topics and concepts that don't necessarily have a readily apparent answer. The philosophy of math is really cool.\n\nI've stickied this post to the front page as an experiment to see if we can encourage more thought-provoking content like this.",
"[There is no one answer for this.](_URL_0_) Simply put, mathematics is a system we use to model our universe. It stemmed from the dawn of humanity from tangible objects; we count in base ten because we have ten fingers and ten toes. So it's a model. We use addition to represent accumulation, and multiplication as a scaled up version of addition.\n\nThat said, there are also constants in math. Truths. Do numbers exist on their own? That is debated as well-- I'd recommend [this numberphile video](_URL_1_) which draws on the subject. We have values, like pi, e, and other constants and ratios that have a deeper meaning. Patterns emerge, and the numbers take on a life of their own. Math is a model for our universe, but it's also much more. I could elaborate on this subject for hours.",
"\"Mathematics is the language in which God has written the universe.\"\n\n* *Galileo Galilei*, Italian astronomer & physicist (1564 - 1642) ",
"Mathematics is really just logic, written with fancy symbols and equations. But it all boils down to very simple things that every human being, even children, can understand.\n\nOne of something is more than none of something. If I have one of something, I can't give it to you and still have one of something myself. \n\nFrom very simple observations like this come, eventually, algebra, calculus, and everything else."
]
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[],
[],
[],
[],
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"http://en.wikipedia.org/wiki/Topology",
"http://en.wikipedia.org/wiki/Zermelo%E2%80%93Fraenkel_set_theory",
"http://www.abstractmath.org/MM/MMFuncSpec.htm",
"http://en.wikipedia.org/wiki/Stokes'_theorem",
"http://en.wikipedia.org/wiki/Abstract_algebra"
],
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"http://en.wikipedia.org/wiki/Mathematical_logic"
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[
"http://www.jcrows.com/withoutnumbers.html"
],
[],
[],
[],
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"http://library.thinkquest.org/2647/algebra/post.htm"
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[],
[],
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"http://www.youtube.com/watch?v=TbNymweHW4E"
],
[
"http://en.wikipedia.org/wiki/Pi#History"
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[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
[],
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"http://en.wikipedia.org/wiki/Simulated_reality"
],
[],
[
"http://i.imgur.com/Vqo79.png"
],
[
"http://en.wikipedia.org/wiki/Monty_Hall_problem",
"http://en.wikipedia.org/wiki/Structural_analysis"
],
[
"http://en.wikipedia.org/wiki/Analytic%E2%80%93synthetic_distinction",
"http://en.wikipedia.org/wiki/Materialism",
"http://en.wikipedia.org/wiki/Ontological_argument"
],
[],
[],
[],
[],
[],
[],
[],
[],
[
"http://youtu.be/TbNymweHW4E"
],
[],
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"http://plato.stanford.edu/entries/philosophy-mathematics"
],
[
"http://www.dartmouth.edu/~matc/MathDrama/reading/Wigner.html"
],
[
"http://en.wikipedia.org/wiki/Logicism",
"http://en.wikipedia.org/wiki/Parallel_postulate"
],
[],
[
"http://www.youtube.com/watch?v=u7Z9UnWOJNY",
"http://en.wikipedia.org/wiki/Philosophy_of_mathematics",
"http://www.youtube.com/watch?v=TbNymweHW4E",
"http://www.youtube.com/watch?v=JmyLeESQWGw"
],
[],
[],
[
"http://en.wikipedia.org/wiki/Philosophy_of_mathematics",
"http://www.youtube.com/watch?v=1EGDCh75SpQ"
],
[],
[]
] |
|
odc57 | birth control statistics (nsfw) | I am actually asking this is a volunteer counsellor at a teen clinic. I've asked around but nobody seems to understand what the following statistics genuinely mean.
Let's say birth control pills are advertised as being 99.8% effective with perfect use. How exactly is that percentage determined? If I'm a girl who has sex once a month then obviously I am MUCH less inclined to get pregnant that a girl who has sex 100 times per month.
Where does this number come from?
Likewise, perfect condom usage is also 99.8% effective. What accounts for that .2%? Can sperm pass through the latex? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/odc57/birth_control_statistics_nsfw/ | {
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"I believe contraceptive statistics are quoted as \"pregnancy per year given perfect usage.\" So 99.8% effective means 2 out of every 1000 women using the pill correctly will get pregnant within a year despite perfect use.\n\nOf course this makes a lot of assumptions. \"Perfect use\" is hard to achieve. Maybe a woman was busy that night and forgot to take her pill. Maybe she wasn't able to get a refill before the pharmacy closed that night and had to take it the next day. The biggest problem is a lot of people don't know how to use condoms correctly or use them inconsistently.\n\nYou get at another assumption and that is \"average use.\" They assume an \"average\" rate of sexual intercourse. I believe it's 2-3 times a week or something. Obviously the rate would be a bit higher for those with more active sex lives.\n\n > What accounts for that .2%? Can sperm pass through the latex?\n\nI believe condoms are less effective than 99.8%. The Wiki says 98% given perfect use, 82%-90% given typical use. As you can see, **proper** usage is a definite problem. The problems likely come from what I mentioned above. Improper usage which leads to breakage, and not using one every time. It's a great method since it also protects against STDs which almost no other method does, but is not a very good long-term solution if you expect regular encounters. Condom + a different form is probably your best bet for your overall health.",
"The birth control failure rates you usually see quoted are derived by what's called the Pearl Index if you want to look up more details. The number people usually quote is roughly an estimate of the number of unintended pregnancies over 100 women-years of use of a particular method. So if it was 1% failure (99% effective) then if you took 100 women and had them all use the method for 1 year, then 1 of them would be expected to have an unintended pregnancy.\n\nSo it's important to note it isn't a \"per-use\" statistic. Although of course if you have more sex than the average person in their study you are obviously at higher risk, it doesn't mean you have 1% chance of getting pregnant each time you have sex. (Otherwise a person on 99% effective contraception, having sex each night would very likely be pregnant after a year.)\n\nTo work out how the statistics would be affected by someone having sex significantly more than the average you'd have to look at individual studies.\n\nTo answer your question \"where does the failure rate come from?\":\n\nYou obviously know about \"Perfect-use\" and \"typical-use\" rates, a perfect use rate is determined on a study where the rules of use are rigorously followed, whereas a typical-use study has people use the method as they would if they were left to their own devices. Now obviously there's still some room for error in the perfect-use camp, even if people are told to rigorously follow rules, they're only human. Some of this can be statistically accounted for, but other things account for part of the failure rate. Other factors to consider are manufacturing defects, condoms can be made with defects, pills can have imperfect manufacturing too, these factors contribute to the failure rates.\n\n\nSorry this answer has been some vague, but really the problem is these statistics are often very specific to the circumstances of the individual study, without looking at the details thats the best you can do.\n\n**Edit:** One more thing, I always think a useful statistic is the \"failure rate\" of nothing. Its approximately 85%, so after a year of having sex without any protection, 15% of women still wont be pregnant."
]
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[],
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1uo5ub | how are secret formulas legal? | For instance, products such as WD-40 do not list ingredients. Coca-Cola simply lists "flavoring" for some of their ingredients. How do we know such "secret ingredients/formulas" are safe and how does the government go about regulating these formulas? Is there a reason that this IS a legal practice? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1uo5ub/eli5_how_are_secret_formulas_legal/ | {
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"There are certain ingredients which are banned, and that can not be used in any capacity. Since the creation, importation, transportation, and use of these ingredients are strictly regulated, there is little fear that they are going to end up in consumer products, especially major ones that many people use.\n\nSo the government focuses on testing the product itself, rather than what's in it. Things like the [technical data sheet](_URL_0_) are compiled, determining the product's features and the risks associated with using it.\n\nSame thing, Coca-Cola has to submit to quality controls, and they have to have their sugar and caloric content independently verified. But as for what's in it, they don't really care. ",
"Foods and drugs are regulated differently than chemical concoctions like WD-40. If you have access to a mass spectrometer, it would probably be a short bit of work to work out what it's made of. Likewise, you can legally knock off any perfume with the same process. \n\nWhether something is legal or not can come from two approaches: legal unless proven harmful, or illegal until proven harmless. We take the former approach, because the latter approach is extremely costly, even for the things that're harmless. That cost limits the development of new drugs.\n\nThe FDA has had a long list of items that it has banned, time and resources permitting, that were commonly used as medicine. That's why you don't see Paregoric or Mercurochrome around even though these were common medicines in the past. Tylenol/acetaminophen might end up getting banned someday because of its \"narrow therapeutic window,\" the very small range of safe dosages for the drug that has come to light.",
"Things like WD 40 have something called an MSDS (material data safety sheet) that you can obtain by calling the numbers on the back of the can or emailing the company. (They reciently changed the names a bit and some of the label requirements - we just got retrained at work) They're required to list all chemicals that are potentially hazardous but there are materials called \"trade secrets\" that have no effect on the actual dangerous chemicals other than color or scent (such as the 'tide smell' that we all know). They don't have to list them because they aren't hazardous."
]
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"http://wd40.com/files/pdf/wd_40tec16952473.pdf"
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971lye | how does augmented reality graffiti work?? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/971lye/eli5_how_does_augmented_reality_graffiti_work/ | {
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"Augmented reality is a catchall term for the use of computer graphics overlaid on our view of the real world. A live video stream can be edited to include artificial elements, or people might look through a clear screen that displays such things to the viewer. In practice this can be a symbol such as a QR code which a computer recognizes and then places a graphic over within the pictured scene.\n\nThis can be used to produce \"augmented reality graffiti\" because the artificial graphic can be made much larger than the QR code which triggers the overlay. A small mark on a storefront could trigger AR viewers to overlay a massive graffiti graphic which obscures the entire storefront for example."
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||
2nbjaz | where did this "explain it like i'm 5" saying/concept originate? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2nbjaz/eli5_where_did_this_explain_it_like_im_5/ | {
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"_URL_0_\n\nIt's from the Office."
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"http://vimeo.com/27060669"
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||
2u9cgd | why is the crown victoria so popular within the police forces in north america? | It is a heavy, not so fast and probably not very fuel efficient.
It is my favourite car of all time, but i just can not grasp why they would use it over e.g. a Dodge Charger. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2u9cgd/eli5why_is_the_crown_victoria_so_popular_within/ | {
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"was, the Crown Vic is no longer made. Full size sedan, V8 engine, rear wheel drive, made it popular with the police and taxi companies.",
"They use chargers as well (at least where i live)\n\ncrown vics are actually pretty fast once they recieve police package upgrades (tranny cooling etc.)",
"The honest answer? It matched the specifications the police wanted and Ford won the contract to provide these cars for the government. If Chevy had won the bid you would be asking the same question about Impalas. ",
"The Crown Vic was a body on frame design. Where now most cars are a unibody design meaning the body is apart of the frame the Crown Vic's body is build separately from the frame. This allow police to do things like pit maneuvers reducing the risk of significant damage like bending the frame. It also allows for some damage to be done in there own shop for cheap compared to unibody would need a specialist. For example a fender is something that would like be damaged doing a pit maneuver. With a Crown Vic they are bolt on. It's the same reason why a lot of cab companies use them as well. \n\nThere are some significant disadvantaged like lack of crumple zones. This raises the risk of serious injury or death in a serious accident. ",
"Crown Vics and Chevy Caprice were pretty much made for fleet vehicle usage. American made, full size sedan, v8 engine, low redesign cycle, came pre-configured for police usage. With lots of other police departments standardizing on the same vehicle, companies make all kinds of police accessories designed for it. And most importantly inexpensive to purchase.\n\nIncidently, the crown vic after the fuel tank issue, has been discontinued, and designed as the \"police interceptor.\"\n\n_URL_2_\n\n_URL_0_\n\n_URL_1_\n\n",
"Ideal police vehicles, large and powerful. The interior could accommodate a cage separating the front and rear and allow for an acceptable amount of legroom. Wide and bold lines projected power and authority while the large engine could tolerate the endless demands placed on it. Great vehicle ",
"Thank you all for bothering to reply - my curiosity is satisfied and i hope one day to own one of these beautiful cars :)"
]
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[],
[],
[],
[],
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"http://www.gmfleet.com/specialty-vehicles/police.html",
"https://www.fleet.chrysler.com/lawenforcement/Pages/index.html",
"http://www.ford.com/fordpoliceinterceptor/"
],
[],
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ap9y3k | how does adding spin to a bullet using rifling make the gun more accurate? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/ap9y3k/eli5_how_does_adding_spin_to_a_bullet_using/ | {
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"It is conservation of momentum, in this case rotational momentum. One of the major problems with early ammunition was that it tended to tumble unpredictably and this would interact with the drag of the air to move them off target. A rotating bullet though tends to want to keep rotating which means that changing where it is pointing is difficult; think trying to turn a gyroscope. Thus rotation keeps the bullet pointing in the direction of the barrel which stops tumbling, increasing accuracy.",
"Objects that spin [maintain their orientation](_URL_0_). This happens because of the laws of conservation of angular momentum; an object that spins will want to continue to spin and not change its orientation or wobble to disturb that spin.\n\nSo the effect is that a bullet that spins will fly through the air point first, and the air will slide around it very nicely and not slow it down much. A bullet without spin will tumble through the air, head over tail, and the air will slow it down and cause it to go off-target unpredictably."
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3j7wsp | why do central banks use interest rates as the primary tool for adjusting the supply of money? | You could distribute new money in a number of ways. You could create money and just put it directly in people's bank accounts, you could fund government programs with the newly created money, or you could just drop cash from a helicopter. Why does pretty much every central bank use interest rates, then? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3j7wsp/eli5_why_do_central_banks_use_interest_rates_as/ | {
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"Because interest rates also let you adjust the supply of money 'down' too.\n \nCentral banks do have other ways to add money to the economy beyond interest rates. One of the most common is to buy/sell bonds. If the central bank buys bonds then they basically inject money into the banks, and the reduction in supply also will increase the price of the bonds that the banks still hold. This was how the whole \"quantitative easing\" thing that the US was doing worked."
]
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2zxtxo | why isn't chicken meat marbled? | Beef is always red and varying degrees of marbled. Chicken is either white or dark and not marbled. Why? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2zxtxo/eli5_why_isnt_chicken_meat_marbled/ | {
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"Actually if you have a corn fed chicken that us free range is has a small degree of marbling however because the fat is translucent and thin it nearly always acts like a baste for the bird (which is why many chickens when roasted tend to leech do much fat)"
]
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|
7fc0hi | why can't digital clocks retain the time when unplugged/powered down if phones and computers can? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7fc0hi/eli5_why_cant_digital_clocks_retain_the_time_when/ | {
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"Digital clocks tend not to have backup batteries, though some do and can keep time across power outages. If more models with this feature were sold then perhaps manufacturers would make it more common. They don't so apparently it's not worth it for people to pay the extra cost.\n\nIf you look at computer motherboards you'll find a small battery that can powers the internal clock and some other functions for 5+ years. This is possible because the clock circuit is designed in the same low-power way as digital watches. Mains-powered clocks mostly use a different principle, based on syncing to the 50/60Hz mains power frequency, and it's not so easy to add a low-power battery backup.",
"Computers have a small battery on the motherboard that typically lasts years and years. \n\nPhones use their internal batteries and additionally rely on the time provided by cell towers (which are connected to computers with little batteries on their motherboards).\n\nYour bedside clock might have a backup battery (mine does), but most of them have no ability to hold onto data when the power goes out."
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3oba50 | why are we so scared to introduce life on other planets? | I recently read on a reddit thread that if we were to send rovers to planets that are habitable, we'd have to make sure there are no bacteria and such on it so we don't introduce life on that planet.
Why does it matter? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3oba50/eli5_why_are_we_so_scared_to_introduce_life_on/ | {
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"We're not SCARED to, we're trying to avoid wrecking science.\n\nBy bringing in foreign contaminants, you're essentially wrecking any sort of science experience concerning native life. You'll never be able to tell if some discovered earth-like microbe is truly native, or just somehow survived the trip from Earth. \n\nSo unless there's tremendous care to avoid contamination you'd never be able to absolutely verify whether there was life on Mars or elsewhere like in the oceans of Europa. Someone could always argue that it was just brought along from Earth.",
"Because we want to see if there is life on other planets. If we carelessly send our rovers over contaminated with earth bacteria, we are jeopardising that research. Because then, when we find something, we are never 100% sure if it is actually something from Mars or something from Earth.\n\nAdditionally, our bacteria could become an invasive species on Mars. If there is an ecosystem of life on Mars, our bacteria might very well destroy it before we've had time to properly study it. "
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7zttct | who decided that the standards were 4:3 16:9 21:9 for aspect ratio? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7zttct/eli5who_decided_that_the_standards_were_43_169/ | {
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"It's because 4:3 is closest to our vision and is best to relay information, 21:9 was already the standard of cinema and is best to describe scenery. 16:9 is just the compromise between those two. \nAnd for where those numbers came from, there's only 1 word: compromise. The artist, engineers, and the market all fought with eachother with their own aspect ratios. Those that survive are the ones we use today. \nExample: there now exist mobile phones with 17:9 and 18:9 resolutions, due to how applications are layed out on the screen (vertical scrolling). Only time can tell if they survive and become the new standards."
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||
3en6hs | why does air conditioner cooling use electricity? isn't there an efficient way to absorb thermal energy to produce electrical energy? | Can't we convert the heat from our room to power something like a flashlight, and thereby cool the room and produce electricity?
| explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3en6hs/eli5_why_does_air_conditioner_cooling_use/ | {
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"If you search for \"air conditioner\" on here you'll get some great explanations for how they work. I'd like, however, to address your second question.\n\n > Isn't there an efficient way to absorb thermal energy to produce electrical energy?\n\nThe only way to create usable energy out of thermal energy is when you have a temperature *differential*. It doesn't matter if the air is 100 degrees if you don't have a place to transfer that thermal energy to. You have to have a place that you can dump the energy in order to harvest usable work out of the difference. This dump is often called a cold sink.\n\nSo, if you had hot air inside of a building and cold air outside you could create electricity by moving the heat from inside to the outside. But, at the end you'd eventually have the air inside and outside reach the same temperature and you can no longer create any work from the differential.",
"It might help if you think not of temperature as a value, but of temperature *differences*. In many ways heat is like a fluid -- it aims for equilibrium. In the case of a liquid it will flow from a high place to a lower one, and once there spread out evenly. In the case of heat it \"flows\" from a hot place to a cooler one, and once everything in a system is the same temperature then the flow stops.\n\nThis is the case with air conditioning. You have a hot room inside, and a hot exterior outside. There is no imbalance of temperatures, therefore no change will take place. The only way to overcome this situation is by forcibly changing the situation -- in the case of air conditioning this is done be causing gases to repeatedly expand and contract. And to move those gases around -- or to change the temperature equilibrium using any other method -- requires an input of energy, e.g. electricity.",
"The short answer is no, not really. Not unless you've already got a nice cold heatsink sitting around. \nProducing energy from heat requires a heat gradient. In other words, you need a hot side and a cold side. In a power plant, for example, they've got boilers or a nuclear reactor to generate steam on the hot side, but then they can use cooling towers or water from a lake or river for the cold side, because the steam is so far above the ambient temperature. \nOn the other hand, if it's just plain hot outside, there's nowhere for you to move that heat to create a heat engine. It might be possible to create a small Stirling engine that ran on heat from the air if you had a river or ocean or something to cool the cold end of the engine. But if you don't have cool water or something like that available, you'd be kind of out of luck.\n\nThere is actually an idea for generating power called [OTEC](_URL_0_) which uses the temperature differential between the sun-warmed surface water of the ocean and the deep water hundreds of feet down. And there's also something called earthtubing or passive geothermal which uses the difference between the warm air and the cooler temperature of the earth deep underground to circulate and cool water. Some homes use this very effectively, but it takes a LOT of excavation to install and doesn't actually generate any power; it just uses the fact that, deep underground, the temperature stays more or less the same, whether it's hotter or colder on the surface."
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7nruk8 | does darkness have a speed? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7nruk8/eli5_does_darkness_have_a_speed/ | {
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"Darkness is the absence of light. Since a lack of something isn't, in and of itself, a thing it has no bounds on how fast it may move.\n\nIn some setups darkness moves at the speed of light. For example, if you consider a spotlight shining out into space and briefly flash it then you shoot a cylinder of light. The front of the cylinder approaches at the speed of light, then the rear approaches at the speed of light. Arguably the end of this cylinder is darkness, so we could say that darkness was, in this case, moving at the speed of light.\n\nWhile that's the simplest setup it's not the only one. We could imagine a long corridor with a bunch of spotlights pointed down. At some point we could have these spotlights start turning off, one after another, going down the row. This causes a wave of darkness to move down the corridor at whatever speed we want. We could turn off lights 1 meter further down the corridor each second and the speed of dark would be 1 m/s, or we could turn them off 600,000 km further per second giving our darkness wave a speed of about twice the speed of light (note that for this setup we'd need to set things up with timers to allow for the speed of light signal delay, but that's an engineering problem, not a physics one).\n\nSince darkness is just the absence of light it's just as meaningful to look at the wave of darkness moving down the hallway as it is to look at the wave of darkness in our first scenario. In both cases we follow a wave where on one side there's visible light and on the other there's not. It wouldn't be proper to use the corridor experiment to argue that the speed of light is whatever you want because light is a thing in and of itself. You can meaningfully track the motion of an individual photon while no such concept can exist for the lack of photons. \n\nThis notion is similar to a shocking observation some astronomers made at one point. They saw what appeared to be something moving at many times the speed of light which cast doubt on various models until they realized that it was the interference between two large debris clouds. While the debris was not traveling faster than the speed of light the boundary of intersection between the two fields was. A boundary isn't a physical thing so it's not bound by the speed of light. ",
"I suppose it depends on just how you look at things. The speed at which electromagnetic radiation is no longer touching something is the same speed at which it came into contact with that thing in the first place.\n\nBut since some things remain illuminated for variable amounts of time after coming into contact with a light source, and nothing stays dark for a time after coming into contact with a light source, you could say that dark is slightly slower than light. \n\nOutside of that rather flimsy example though, the absence of light does not have speed."
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7dzxcs | if any distance can be halved, at what point do you stop touching something? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7dzxcs/eli5_if_any_distance_can_be_halved_at_what_point/ | {
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"Uh... if you're taking your finger off something, then the distance will increase, halving is a decrease.\n\nAlso, from a physics standpoint you never actually touch anything...\n\nAside from those, you're describing a form of one of Zeno's Paradox. Ultimately the solution is the fact that in the limit, 0.99999.... is equal to 1.",
"You're never touching anything - you are just as close as possible to it. The sensation you feel is effectively the force of the atoms \"pushing back\" against your fingers (and your fingers' atoms \"pushing back\" against the atoms in whatever you are touching). Think of it a bit like how two magnets push against each other, but much much stronger.",
"Planck length, the smallest possible measurement in the universe before the laws of physics break down."
]
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[],
[],
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] |
||
5c7m3m | how do contactless cards work? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5c7m3m/eli5_how_do_contactless_cards_work/ | {
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"text": [
"They use radio waves. The cashier's terminal powers the card and the card emits a signal containing info connecting it to your account and the necessary security details to make sure it's genuine. It's basically a wireless version of chip cards. The time it takes to complete the purchase depends on hardware of the terminal, how bloated the software on the terminal is (bunch of graphics on the screen and whatnot), and the Internet connection (speed and ping) of the business. \n \nContactless cards use RFID, which receive power to work; NFC payments like Apple Pay supply their own power. This is why you don't have to charge your card."
]
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[]
] |
||
1ockdm | why is it considered healthy to put oil on your salad, but not fry your food in it? | You always hear people say that oil and vinegar on a salad is a healthy choice, yet if I fry anything in the same oil it isn't considered healthy? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1ockdm/eli5why_is_it_considered_healthy_to_put_oil_on/ | {
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"text": [
"Putting fats on salads is good because it helps absorb the fat soluble vitamins in salad. Frying on the other hand isn't good because first off heating up fats to the point of frying isn't good for the fats and second off cooking food too much destroys food and produces carcinogens. ",
"Oil consists of different kinds of fat. Saturated, monounsaturated and polyunsaturated fats. You can think of them as a chain. Saturated fats are strong, whole chains, while monounsaturated fat have a weak link (mono = one). Polyunsaturated fats have more weak links. When you heat up the oil (or leave them for too long on your shelf) those weak links gets damaged by heat and oxidation, like rust on a chain. This damage causes the fat to become really unhealthy and can cause problems like cancer, atherosclerosis and all kind of other nasty stuff. [More info](_URL_1_). \n\n\nYou should always pick a cold pressed (not heat damaged) virgin (non-chemically treated) oil. [Many oils are treated with chemicals, heated and bleached](_URL_0_) (seriously!), all very damaging to the oil. A rule of thumb: the thicker the fat, and the less refined, the better. \n\n\nEdit: You could also look up the oils smokepoint as glycerol in oil is converted to acrolein when it starts to smoke and burn. That's one of the things in cigarettes that cause lung cancer. \n\nGood fats: Macadamia and coconut are great. Olive oil if you don't heat it. "
]
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[],
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"https://www.youtube.com/watch?v=omjWmLG0EAs&amp;amp;feature=youtube_gdata_player",
"http://onlinelibrary.wiley.com/doi/10.1111/j.1745-4506.2001.tb00028.x/abstract;jsessionid=D04D633146812B9AFE4F9CDB0E0C6B48.f01t02"
]
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|
5a0kxn | what is going on in south korea right now? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5a0kxn/eli5_what_is_going_on_in_south_korea_right_now/ | {
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"text": [
"[South Korean explained it well.](_URL_0_) Warning though it's from a chan board so it's highly offensive. It's a great explanation, but still offensive.\n\nEDIT: Made an imgur album for you with more information.\n\n_URL_1_",
"**Pasting this, and modifying this from a comment /u/flyawaystupidkite made. Send him your love.**\n\nIt's a bit insane. So I'll try going step-by-step from memory how this all turned about.\n\n1. A young high school girl fails to get into a prestigious university.\n\n2. The girl's mother (Choi Soon-sil) uses her influence to pay the girl's way into prestigious university. They package it as the girl receiving a scholarship for her equestrian skills.\n\n3. Girl doesn't do so well in school and later turns out she had a child during her high school years which was no-no for this school's policies.\n\n4. Girl decides to take some time off but still demands her grades to be given to her as if she had completed her semester.\n\n5. Professor says no. This incurs the wrath of the girl's mother who successfully convinces the professor to give her the grades. \n\n6. This leads to a massive 80 day protest from students of that university for unfair treatment and etc.\n\n7. This leads into investigation that eventually reveals the girl's mother had a personal relation with President Park.\n\n────────\n\nOh shit it's about to get real funky now.\n\n────────\n\n1) The girl's mother turned out to be one of like 15 known children of a famous cult leader (Choi Tae-min). Each child was known to have extreme assets from estimated 10s of millions to upwards of billions.\n\nEDIT: 1a) \"The elder Choi reportedly enjoyed considerable influence over Ms Park as a young politician, prompting diplomats to refer to him in private as “Korea’s Rasputin.”\nA newly released Wikileaks cable from the US embassy in Seoul described him as having “complete control over the body and soul of the president in her formative years. Both women are understood to have met decades ago and formed a close relationship when Ms Choi’s father allegedly helped the future president contact her late mother in the afterlife.\" Source: _URL_0_\n\n2) President Park had a scandal in the past (that many dismissed as they deemed highly improbable and a likely attack from opposing political parties) that said apparently she had a child with this cult leader while she was in her teens.\n\n────────\n\nSo how does this relate directly to the Korean people?\n\n────────\n\n1. As investigations ensued it turned out that the President Park had been exchanging emails regarding her speeches and other national policies and events with the girl's mother (Choi Soon-sil). Even going as far as asking her for edits and such.\n\n2. Journalists, during the investigation, received a tablet from President Park? Girls mother? That for some reason contained all the exchange between them. This is thought to be an unfortunate mistake by them and a fortunate mistake for the Korean people to know the truth. \n\n3. The investigative journalists are doing this via wikileak style and slowly releasing information. More and more information have been coming out each day.\n\n4. Latest news is what you've guys read. It seems the relationship between President Park and the cult leader's daughter (girl's mother) have been more intimate and influential than people thought. Even going so far as President Park, after a hard day, going to their residence to sleep over and discuss the problems and getting advice and what not. All national secrets out on the table for the cult family. \n\nEDIT: Choi, who is currently in Germany, says she is too ill to return to Seoul for questioning over the affair.\n\n“I am suffering from a nervous breakdown and I have been diagnosed with heart issues,” she toldSegye Ilbo, a South Korean newspaper.\n\n\n────────\n\nIt's still a developing story. Koreans are wondering why the President haven't stepped down yet. It's either that or impeachment and jail for her. \n\nIt's a sad day when people are saying Korea's best presidents so far were either the dictators or the ones who just didn't do any crazy shit while in office. \n\nAll this because of one spoiled ass girl dealing with a broken education system in Korea. \n\nP. S. Be careful criticizing that spoiled ass girl. She's been threatening to kill everyone criticizing her over the internet :)\n\n",
"I used to be someone who tell people that thinking a secret cult is behind the government is bullshit... now this shit will be the holy grail for those mother fuckers to keep saying that all governments are like this.",
"Obviously this is all batshit insane, but one of the worst parts is that Universities won't let you attend if you've had a child?! I thought Korea was better than that. "
]
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[
"http://imgur.com/UvJ8P3l",
"http://imgur.com/a/lsttr"
],
[
"https://www.google.ca/amp/www.telegraph.co.uk/news/2016/10/29/secret-advisers-nepotism-and-even-rumours-of-a-murky-religious-s/amp/"
],
[],
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] |
||
3biq6m | how can it be cheaper for a company to hire a contractor rather than new employees? | Wouldn't the contractors need to be paid basically the same amount as a theoretical new employee? And then wouldn't the contractor somehow need to turn a profit? It seems like contracted work would ultimately be more expensive than doing it yourself. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3biq6m/eli5_how_can_it_be_cheaper_for_a_company_to_hire/ | {
"a_id": [
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"text": [
"In my case, I had a small project that was supposed to run for a few months. I did not want to hire a full time employee, because I had nothing for them to do after this project. Hired a contractor, got the project done. Worked out well since the cost of using a contractor for a few months was within the project budget.",
"Employees have certain costs above and beyond a contractor. Even if you're paying less per hour, the total cost can be far more.\n\nContractors handle their own taxes, no need to pay an accountant or payroll company to do it for you.\n\nContractors are not eligible for company benefits. No 401k fees or contribution matching, no stock options, no insurance premiums, etc. (This is MAJOR).\n\nContractors are usually employed as needed. Just need 4 days of work? No problem, someone will be there in the morning and gone when you're done, just pay for the time they're there. Employees, on the other hand, need to be interviewed, trained, put through orientation, etc. Then, to fire them, there are all the processes involved, ERISA compliance with notifications, COBRA insurance continuation and administration, etc. It's wildly impractical for any sort of short term or \"overflow\" work.\n\nAs an aside, contractors often have their own training and equipment. For example, hiring a printer repair man makes no sense for most offices, and neither does having all the tools and parts to repair. Hiring a contractor to come in and fix machines as needed is a much better solution."
]
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[],
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|
3m41i8 | why has there been a new 3d printer getting fully funded on kickstarter every month for the past 3 years? | Every time I get on Kickstarter, there's always a new 3D printer that's fully funded for several hundred thousand dollars, but doesn't look any different from previous printers. This has been going on for years. What are they doing that is any different from the dozens of other printers already out there? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3m41i8/eli5why_has_there_been_a_new_3d_printer_getting/ | {
"a_id": [
"cvbtsc2",
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4
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"text": [
"There has yet to be a truly consumer friendly 3D printer on the market, they just need to much maintenance and calibration to remain useful. People keep coming along thinking they can solve this problem, but no one has so far.",
"I said the exact same thing 4 years ago, when I built my first 3d printer. Its because nobody had produced a model that is anywhere near perfect, and they are all ridiculously expensive. What you are seeing on kickstarter is not revolutionary, they are just making small adjustments. For example: The first repraps (such as the purusa, the original ones that were developed in basements) had accuracy to 0.9 mm thick per layer, and it did it very slowly and still looked terrible. The newer ones can go all the way to 0.01 mm thick. So if you were to invent a brand new 3D printer that could print to 0.01 mm per layer, and do it faster than anything out on the market, you could have a potential money maker that people might want to have."
]
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[],
[]
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|
21jr3h | why aren't pico projectors a huge thing now, and why aren't they the number one feature in all smartphones? | I understand power draw. Clearly they well annihilate a current smartphones battery. I'm saying why isn't this the next smartphone push? If you're phone can be the TV, it can then be the console, the set top box, the sports center.
Why isn't this being focused on more, at least publicly? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/21jr3h/eli5why_arent_pico_projectors_a_huge_thing_now/ | {
"a_id": [
"cgdp9fq"
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"score": [
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"text": [
"because they suck and everyone still has a laptop or a tablet. So...if you ask me, until they work better AND the phone can replace a laptop/tablet then it's just wasted money. If you're sitting there with your laptop/table and your pico projector phone and you wanna watch something it's not a hard decision. They just aren't \"there\" yet on the scale that can get them into a phone."
]
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|
5ox5s7 | why, when slowly opening a plastic soda bottle, does a little air come out when you crack it a little open, but then more comes out when you open more? | If the first crack is enough to let some air out, Spyker it be enough to let it all out? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5ox5s7/eli5_why_when_slowly_opening_a_plastic_soda/ | {
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"Most sodas are carbonated, this means that they have carbon dioxide gas (CO2) dissolved in them. There are a variety of things that can cause a solution (the soda) to release a dissolved gas (the CO2), heat and agitation being the two your soda is most likely to encounter.\n\nAdditionally, most sodas are overpressured with CO2 to make sure that they stay carbonated until they get to you. When you first crack open a soda, it's this CO2 that you hear leaving, and if you left it just barely cracked open long enough it certainly would reach equilibrium with the air around the bottle and you wouldn't hear any more gas leaving.\n\nSo the short answer to the question is yes. The very first crack is enough to let all the gas out *if you leave it long enough*. Think about it like this, if you had a 5 gallon bucket of water and you knock a small hole in the bottom, the bucket isn't going to empty immediately it can only empty as fast as the force pushing it and the fluid that it's pushing will allow. Your bucket will eventually empty, but not immediately. Now, if you got impatient with your small hole and decided to knock out the bottom of the bucket, it would empty immediately because now there's nothing holding the liquid back, like if you take the cap completely off of a soda.",
"Your whole high school is in the gym for an assembly. The presentation comes to an end and everyone needs to leave all at once. \n\nIf you never open the doors, people will never leave. \n\nIf you open one door, how long will it take for everyone to leave? \n\nIf you open all the doors, how long will it take for everyone to leave? \n\nRelate this to your problem. Basically, it doesn't matter how fast or slow you open the bottle, the air will equalize anyway. It's only a function of how fast it equalizes. "
]
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[],
[]
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|
f9dg2y | what is the culture around modifying cars and motorcycles to be louder? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/f9dg2y/eli5_what_is_the_culture_around_modifying_cars/ | {
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"Most of the times making a motorcycle louder can save a life. Loud pipes save lives when comes to two wheels.",
"Depends on the individual\n\n1. Some (often younger) think louder = cool. These are often the ones that drill holes in their exhaust to achieve that effect\n\n2. Some (often incorrectly) think the power gains achieved by increasing the size of the exhaust or removing sections of it (often those used to clean the air before it goes into the atmosphere) are worth it\n\n2b) You can swap an exhaust to gain power but still keep it quiet, and light \n\n3. Some do it purely to create a deeper, throatier noise that they prefer and will, legitimately, enjoy the driving experience far more\n\n1 and 2 is usually illegal. If you hear “pops and bangs” then it’s probably achieved through over-fuelling the car and removing a catalytic converter. \n\n3 is usually a case of swapping to an aftermarket exhaust and would be done on a car with a big engine (in terms of displacement - say 4L and above). For some, it’s a big deal\n\nThere’s a thread/blog somewhere online where someone went through about a dozen high-end, custom exhausts on a Porsche GT car in order to try and get the “perfect” sound"
]
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||
2am3py | how do i upload a website? | Assuming I've created a website in Dreamweaver, and I've also purchased a domain name, whats the best way to upload a website? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2am3py/eli5how_do_i_upload_a_website/ | {
"a_id": [
"ciwit7k"
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"score": [
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"text": [
"You haven't mentioned your hosting solution, so I'm assuming you don't have one.\n\nA domain name is just a pretty name that you use so that people don't have to remember an IP address. That's it. It does nothing else for you. (Well not for a simple website, anyway.)\n\nWhatever Dreamweaver crapped out is the code. (By the way I heartily recommend building a website properly, tools like dreamweaver make websites that are really hard to maintain or modify and are generally total crap for Google or other search engines to understand and index.)\n\nSo what's missing? Well something to actually send the code to people's browser when they try to visit your website. A server. \n\nWhat you need to do is find a hosting company, buy a package from them and use the control panel on the DNS provider you got the domain name from to set up an A record containing the IP address of the hosting server. (The hosting company will give you the IP somewhere.)\n\nAfter that you'll probably need to SSH into the server, set up Apache, nginx or LigHTTPD and FTP, then use the FTP server to move the files into the root directory of the web server you set up.\n\nIf this is all flying over your head, as it probably is, you should secure the services of a web developer to help you. (And well your're at it probably ask them to do the website by hand.)\n"
]
} | [] | [] | [
[]
] |
|
3f7fbe | why does netflix produce original content? isn't it a risky endeavor? what are they gaining by trying to be a streaming service and a production studio? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3f7fbe/eli5_why_does_netflix_produce_original_content/ | {
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"text": [
"If they produce original content they can guarantee *exclusive* access to potentially highly sought after tv shows.\n\n\nTake HBO. People subscribe to channels like HBO because of the high quality content they produce. Netflix wants people to choose them over rivals such as lovefilm/amazon-prime etc. by offering new content that none of the other services can offer.",
"It is potentially risky, but ultimately, when their core business is based on licensing agreements (which piss off a lot of people when stuff disappears due to licensing), if they can keep costs reasonable, having something in their control is meaningful, and it will likely always be available on the streaming service.\n\nYou could have said the same thing about HBO 25 years ago. At that point, I think standup comedy specials were the bulk of their original programming, and Netflix is very similar to HBO (they are a subscription service, and they likely get more per month per customer than HBO does). Then all of a sudden HBO becomes the go-to place for shows that aren't watered down by the FCC, and milquetoast boring shows to appeal to the broadest audience, and they win tons of awards."
]
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3r2byw | why does trying to read a scratched cd/dvd pretty much freeze up your computer? | Seems to have happened on pretty much every computer I've owned, what causes this? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3r2byw/eli5_why_does_trying_to_read_a_scratched_cddvd/ | {
"a_id": [
"cwkbdwv"
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"score": [
17
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"text": [
"Some things on a computer are never expected to take much time, so it sends the command to do it then just sits and waits for the result.\n\nWith a scratched CD/DVD the drive itself decides to try again over and over before giving up. The computer just sits there and waits. And waits. After a short timeout the drive gives up and moves on to the next sector of the disk. Unfortunately typical scratch damage affects tens or hundreds of sectors, so it all happens again, time after time and that short timeout gets multiplied up to much more.\n\nThe computer will have it's own timeout set after which it will give you a message about a problem reading the disk. This timeout is a balance between giving up too early and not managing to read an important disk that could have been recovered, and waiting too long and being really annoying.\n\nA defensively written program can handle it much better and give up on bad sectors more quickly, but most people don't do that, or can't justify the extra time it takes even if they know how to. It's only really worth the added complexity for things like data recovery programs which need to get back all the 'easy' sectors first before going back and retrying the bad ones.\n"
]
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|
503h1e | why do professional field sports use cleats? | Now, I know that cleats obviously provide more traction, and definitely provide an advantage over someone that isn't using cleats. But if everyone is using cleats, no advantage is gained.
Cleats also seem to drastically increase the risk of leg injuries in sports. It seems like the vast majority of leg injuries happen when force is applied to the leg in an odd direction, and the cleats anchor the foot to the ground, so the leg can't naturally give. This means something else has to give, which is going to be some bone/muscle/tendon that is the weakest point in the leg. It seems like if an athlete was wearing non-cleated shoes, the chance that their foot would just slide out, avoiding injury for the leg, would be much greater.
Also, leg injuries usually tend to be the most likely to end an athletes career, no matter what the sport, so you would think avoiding leg injuries would be a priority for any sporting organization.
So, why the hell haven't cleats been banned? Do they not actually increase injuries that much? If they do increase injuries, no advantage is gained by using them, since all teams use them. If no teams used them, the playing field would still be level. What gives? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/503h1e/eli5_why_do_professional_field_sports_use_cleats/ | {
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"They do not actually increase injuries much because it is against the rules to kick or step on your opponent, thus meaning it rarely happens. But they do prevent a lot of injuries by reducing your chances of your feet slipping on the grass. \n\nYour assumption of your foot being able to \"just slide out\" is true, but that causes more injuries instead of reducing them. ",
"Everyone having the same advantage doesn't remove the advantage. Everybody still has better traction. ",
" > So, why the hell haven't cleats been banned? Do they not actually increase injuries that much? If they do increase injuries, no advantage is gained by using them, since all teams use them. If no teams used them, the playing field would still be level. What gives?\n\nTwo big reasons. \n\nRemoving cleats actually would likely increase injuries. Slipping is dangerous and likely to cause lots of pulled muscles. Like you are right, in some ways. ACL injuries might go down without cleats (I am not positive about this though because I could see it also causing them) but overall injury rates would likely go up without cleats.\n\nSecond big reason is it makes the game more fun to watch, watching people slip as they cut and fumble around would be dumb compared to now. Pro sports are about entertainment afterall and people slipping all over the field especially if its wet is less entertaining."
]
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|
6r92m9 | if the speed of sound is about 340m/s how can normal things make sound? | Are our vocal cords moving at that speed? and even pressing keys on my laptop as slow as I can still make sounds | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6r92m9/eli5if_the_speed_of_sound_is_about_340ms_how_can/ | {
"a_id": [
"dl3d27d",
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"text": [
"No you are confusing the speed of propagation of the sound wave with the speed of the thing moving back and forth to generate the sound.\n\nWhile the thing moving back and forth doesn't have to move nearly as fast as the speed of sound, it does have to move much faster than you could say move your fingers. The highest frequency that a typical human can hear is 20kHz. To create that sound an object has to move back and forth 20,000 times a second. The lowest frequency we can hear is 20 Hz or 20 times a second. That's still much too fast for the average human to move their fingers. \n\nSo most of the sounds we create are by bumping or slapping objects and causes them to vibrate. Objects have a frequency that they tend to vibrate at based on their physical properties.\n\nTo finally answer your question, yes parts of your vocal cords are moving thousands of times a second to produce the sounds that come out of your mouth.",
"The speed of sound is related to how fast particles bump into each other, not how fast they travel. Keep in mind that air particles are constantly moving, they don't just sit around. \n\nThat said, the speed of the particles can be much higher than the speed of sound. \n\nWhen you hit something, like a key on your keyboard, the sound doesn't come directly from the motion of the key but rather the energy from friction and the impact dissipating through the material which causes it to vibrate very quickly. "
]
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|
2f5p5b | why do we not have international space program? | I can understand that many countries like keeping their civilian and military space programs separate but why do countries start and fund their own space programs? Wouldn't it be more beneficial to have one large space program that many countries fund rather than a number of small individually funded space programs? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2f5p5b/eli5_why_do_we_not_have_international_space/ | {
"a_id": [
"ck65j0h",
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"score": [
3,
2
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"text": [
"Yes, it it is typically more beneficial. That's why 20 nations have cooperated in the [European Space Agency](_URL_0_) for over 30 years now. ",
"**International Space** Station\n\nIt's even in the name."
]
} | [] | [] | [
[
"http://en.wikipedia.org/wiki/European_Space_Agency"
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] |
|
1zzx27 | how does the large hadron collider remain stable? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1zzx27/eli5_how_does_the_large_hadron_collider_remain/ | {
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"text": [
"You need to elaborate more on your question. What fo you mean by remaining stable?",
"I *think* the collision experiments themselves release only tiny amounts of energy. No chain reactions like fusion or fission are possible. If the particles miss each other, it's just one radiated particle. Which are all around us anyway. That, and union welding."
]
} | [] | [] | [
[],
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||
5ipvta | many in the u.s. are concerned for the future. can a modern, world super power actually fall similar to rome? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5ipvta/eli5_many_in_the_us_are_concerned_for_the_future/ | {
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"I question your premise. \n\nAnyway, the fall of rome was varied and slow. Yes there were actual conquests but a lot of it was gradual. \n\nWe probably don't have to worry about northern european hordes threatening us at the gate. \n\nWe probably do have to worry about a relative decline in power. But that wouldn't mean that the country fails or becomes undeveloped. \n\nSpain used to be the most powerful nation in the world, then France, then the UK. Citizens in all three countries are doing pretty well today even if their respective states have lost a lot of power/influence. \n\n"
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1pluyc | why are they cutting food stamps in the us? | I obviously know it's a budget issue, but why are they cutting back on something like food stamps? Is this related to the Affordable Care Act? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1pluyc/why_are_they_cutting_food_stamps_in_the_us/ | {
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"Edit 2: Since some people need further explanation, I do not claim that the views below are my own, nor do I claim that they are the correct way of thinking. What follows is just my understanding of the arguments presented by those who wish to cut back on expansion of food stamps in the US.\n\n\nThe reasoning behind it is as follows and I will do my best to leave my bias out of it. \n\n1. Food stamps are a drain on the countries resources. Doesn't matter how big or small the cost , we are paying for someone else's food. \n\n2. This is seen by some as a government handout that has been and will continue to be abused by individuals to the point where they decide to not work, and just live off of the government assistance. \n\n3. Even if the stamps were not abused, it is the opinion of some that we should not provide services like food stamps to people because not having it given to them will encourage them to work. \n\n4. Some people are also of the opinion that using tax dollars to fund programs like food stamps takes away from workers who earned their wage and gives it to people who do not deserve it. \n\nThose are the general ideas behind it, whether or not you agree with them is up to you. \n\nEDIT: words"
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2ux8xh | we see stories of people who lose half their brain and somehow survive. if you divide a human brain 50/50 are both halves equally viable to survive as a person given the right circumstances? | example person with half a brain:
_URL_0_
apparently there is also a surgical procedure:
_URL_1_
*added links
*i am selecting kitten1999 post as the answer | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2ux8xh/eli5_we_see_stories_of_people_who_lose_half_their/ | {
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"Uuhh... no. The brain is collosally complex organ that we understand less about then we do about any other part of ... almost anything. It can do a shitton of funky stuff and compensate for TONS of problems. but you might just as wel die as another might survive drom the same injuries. What or where the injury is seems to matter little to nothing. \n\nBasicly the brain is magic and we just dont know fuck about it.",
"It seems possible. \nThe two hemispheres are connected by the corpus callosum which is made of fibers that allow the two sides to communicate. When this is slightly severed, a lot of weird stuff happens. \n(See _URL_0_) \nBy that we can reason that if the corpus callosum was totally severed, there would be a seperate consciousness in each side. If the two hemispheres were seperated after the subject was born, however, there would not be a fully functioning brain on each side. Both sides of the brain become more specialized as we grow. Different areas of the brain eventually control different things, so one side may lack language skills and the other may lack something like facial recognition. \nIf a baby is born with a totally severed corpus callosum and survives, (or if it is severed shortly after birth) I believe that consciousness would most likely arise in both hemispheres, as if each was a seperate brain. I can imagine that there would be limitations, though, because of the smaller size. Also, one side would control the left of the body and the other the right. (right and left sides, respectively.) \n \nPlease keep in mind that this is only based off my personal understanding of this. I am not a scientist or a very smart person. "
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31kp4d | how does the movie 'birdman' look like one continuous take? how did they do it? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/31kp4d/eli5_how_does_the_movie_birdman_look_like_one/ | {
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"Whenever there's a scene where there is no characters in the shot and the camera is still.",
"It's easier to see the cuts once you know what you're looking for. Birdman wasn't filmed in one location: the stage and backstage portions, as well as the roof scenes, were on location at the St. James Theatre. Anything in the hallways and dressing rooms was in a different studio. So there's a cut any time a character leaves the dressing room/hallway areas. Same with any time there's a change in time (like the day to night time lapses). \n\nThe cuts that are easiest to see involve a black screen. It happens a lot when characters go up to the rooftop or out of the pub, where there's no light on the door so the screen goes black for a half-second. Another technique they used, going from the dressing rooms to backstage, was having an extra walk in front of the camera. Some of the less obvious ones have cuts when the camera is making a fast pan, like with the drummer while Riggan and Mike are walking outside the theatre. ",
"Like others said, it was done in the same way Rope was.\n\nSide question though, are there any movies that were done in one take? I know the rape scene from irreversible was, but i mean like a whole movie. Probably not.",
"There is a horror movie called Silent House that uses this effect. About 20 minutes into the movie I realized they hadn't made a cut yet, and started looking for it. They just did really long takes and made cuts while the camera pans away from the characters.\n\nSome people don't like the movie, but I felt it was really well done.",
"Actually that one take movie was already done with Russian Ark using a hard drive as a support and a long time before in Hitchcock's Rope... Hitchcock's movie tho was not really a one take as at the time it was technically not possible because of the lenght of the film, so there are actually three cuts when the film was nearly over, with a new take starting from the exact frame where it was stopped (for example on James Stewart's jacket) ",
"Different transitions. There's one where you cut right when the cameras moving quickly, creating a blur. Then you splice in a clip that starts with a blur in the same direction. You can see this in a multitude of films, it's fairly common. There's another where the camera will point up and and then zoom into a light. The light will eventually make one monochromatic color, so the editors can cut and put in a scene thats starts the same way the last one ends. You can see this in many of Gaspar Noe's films. There's an inverse to this transition too. Instead of flooding the frame with light then transitioning, they flood it with heavy movement and relative darkness, making it difficult what's going on screen. Here the editors can cut and go on to a new scene. There's many other tricks but these three are the most prominant.",
"I didn't really understand the film/film ending..anyone care to elaborate?"
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2bizcu | the main differences between baptist and pentecostal beliefs | Something that lets the outsider distinguish between the two groups. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2bizcu/eli5_the_main_differences_between_baptist_and/ | {
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"There are several. Here's three of the big ones, by doctrine: \n\n1. Baptists believe you're saved, then get baptised. Pentacostals believe baptism is a prerequisite for salvation.\n\n2. Pentacostals believe glossolalia (speaking in tongues) is evidence of baptism, while Baptists do not. \n\n3. Baptists believe that once you are saved, you're saved forever, while Pentacostals believe you can fall out of God's grace. "
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4hw41b | why weed and hops smell almost the same | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4hw41b/eli5why_weed_and_hops_smell_almost_the_same/ | {
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"They are extremely closely related, both belonging to the family \"cannabacae\". They share a vast amount of their genetics with cannabis so the smell is similar.",
"They're related plants. It stands to reason they would smell alike. (They also have in common an unusual-in-plants feature of having male and female plants, which makes cultivation more complicated, since in both cases, users want unfertilized female flowers.)"
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20ysyt | why doesn't my parents' dog recognize my face or voice when i call them on skype? | I've been studying overseas for the last year, and when I have made video calls to my parents, they sometimes bring the dog to the computer. Despite me calling her name, she doesn't react in the slightest. My brother's dog doesn't respond to my image or voice either. My parents have pretty good speakers so the sound quality is good. So why doesn't the dog react to me? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/20ysyt/eli5_why_doesnt_my_parents_dog_recognize_my_face/ | {
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"He probably does. He just knows you can't scratch his ears via Skype and there's no treats either.",
"Not sure about the lack of voice recognition, but dogs and cats see screens differently than we do. In order for us to detect fluid motion/activity on a screen, there needs to be around 15 frames per second. Think of it like a film reel. There aren't any major differences when you look at adjacent frames, but when they're played through a projector, they string together and we get the \"motion picture\". Dogs and cats require a higher frequency of frames in order to detect fluid motion (around 60ish). So, what we see as fluid movement on a screen is just still shots to them.",
"I have no facts or whatever to back this up, but dogs probably rely on smell a lot in individual identification."
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2gecm7 | if the smell of cut grass is a distress signal, what will the grass that receives the message actually do about it? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2gecm7/eli5_if_the_smell_of_cut_grass_is_a_distress/ | {
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"The grass sends it's nutrients etc. to it's roots so that they won't go to waste and can use them to regrow.",
"The smell itself is not the distress signal. Plants release ethylene and jasmonic acid particles into the air to warn other plants/other parts of the same plant that it is under attack. \n\nJasmonic acid frequently up-regulates anti-insect proteins in those plants, so when insects start chewing on those other plants they get a sore stomach/have seizures and die. (Up regulation means that more functional enzymes will be produced in cells, for those curious.) \n\nIf a sufficient amount of ethylene is sensed by other plants/the same plant senescence will take place, resulting in tissue death (aka leafs falling off/discoloration of leafs). But there has to be a LOT of ethylene for this particular result to take place. Ethylene produced in the damaged grass causes the very tip of the cut grass (the wound basically) to die and turn brown, preventing moisture loss.",
"The smell attracts predatory bugs that feed on the insects attacking the grass. ",
"I thought it was just a distinctive scent that attracts birds, which eat the insects that are eating the plant. \nAfter a farmer cuts hay/silage in the summer, the fields are always flocked with birds.",
"Are there any safe chemicals you could spray/across the lawn before mowing that would simulate this warning? ",
"It signals larger predator insects to come",
"I just wanted to say thanks for posting this. I had the exact same question and forgot about it.",
"How does the other grass detect these scents?\n"
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2ioon8 | how does the photo 51 of rosalind franklin show the evidence for a double stranded dna | I don't understand a lot of diffraction and all of that, but I would like to have some idea on how it shows that. Thanks! | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2ioon8/eli5_how_does_the_photo_51_of_rosalind_franklin/ | {
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"This page has an interactive walkthrough of the image explaining everything along the way:\n\n_URL_0_\n\nIt's not perfect but gives a decent understanding of it using simple terms.",
"The ELI5 is we understand the physics of how light scatters off crystals. Thus we know what kind of diffraction pattern we should see given a molecule with a specific structure. The X-Ray diffraction of DNA results in a pattern that we know would be produced by a molecule with a helical shape. Further details of the image tell us other things about the structure, but that is the basics. Some of those details are explained in the link provided by /u/boredgamelad\n\nedit: To give you an example unrelated to X-Ray diffraction, what does the raw output of an MRI scanner look like? [This.](_URL_1_) How do we go from that to something like [this](_URL_0_)? By understanding the physics that produces the first image, and developing a model for recomposing it into a more intelligible format. The X-Ray diffraction image is just like the first MRI image, it is the raw output of the diffraction experiment. The physics involved is understood well enough that you can tell a lot about what you are looking at just from that, but it is possible to do the same thing we do with MRI images, and transform the diffraction image into a model of the crystal that formed it."
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9rr63a | ; it’s not the volts that kill you, it’s the amps? | Biology because that’s the closest I can think of, but wouldn’t a whole bunch of volts kill somebody pretty quick?
Edit: wow ok this blew up overnight, was not expecting this. So what seems to be the most common answer was that volts are the potential, amps are the potential being realized, the saying is wrong, and that time is also needed to kill.
Thanks everyone! | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9rr63a/eli5_its_not_the_volts_that_kill_you_its_the_amps/ | {
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"Basically, voltage is electrical potential, amps is that potential being realized. Potential can't kill you, action can",
"The title statement is misleading because it takes voltage to make current flow. Together with resistance they form Ohm's Law: E=IR They are inextricably linked. \n\nVoltage is potential, while current is motion. To use the water analogy, water pressure alone can't do work. It takes a stream of moving water to do work. However that water stream won't flow without pressure to overcome resistance of the hose and the work resistance. \n\nEdited for clarity.",
"When going through the human body, one uniquely determines the other. If there is a constant voltage V across the body, it will generate the current I=V/R, and if there is a current I, it will have been caused by the voltage V = IR.\n\nHowever, both of these assume an ideal voltage source and an ideal current source, which are idealizations of real electrical systems. You can have capacitors which can build up a huge voltage but don't have a lot of charge - then discharging it might not hurt you because the voltage begins to drop rapidly, so the amount of actual energy going through you is not large.\n\nLikewise, a current source might rely on low-resistance objects like metal, and stop functioning on high-resistance objects like the human body.\n\nThe thing that kills you is energy, so the real measure of how much damage an electrical system can do to you is how rapidly and for how long it can dump energy into your body.",
"This isn't entirely true.\n\nVolts and Amps are tied together. I know this is ELI5 but I'm going to give a simple equation called Ohms law:\n\n & #x200B;\n\nI=V/R\n\nI is current, which is amps. Amps are to current as pounds are to weight.\n\nV is for volts. \n\nR is for resistance, which as you might guess is the resistance to the flow of electricity. Wood has a really high resistance, metal doesn't.\n\nFor a person the resistance is going to be \\*your\\* resistance. Unless your skin are wet or you have a cut (this allows electricity to just skip right through your skin) it's pretty much constant.\n\n & #x200B;\n\nSo because resistance is pretty much constant. The only way your current will go up is if voltage goes up. These two things are tied together. More voltage means you will have more current. You won't get shocked by 12 volts and end up dying, because you won't have enough amps. \n\n & #x200B;\n\nSo the question now is \"Why do we even say this.\" Well, a static shock is at 20,000 volts. For reference the voltage of an electrical outlet is 120 if you are in north america and 240 if you are in Europe. But obviously a static shock doesn't kill you but an electrical outlet can. So what's going on?\n\n \nWhat \\*\\*actually\\*\\* kills you is the \\*\\*energy\\*\\* that goes into you. Here's another equation (I know, I'm sorry)\n\n & #x200B;\n\nE=V\\*I\\*s\n\nenergy equals voltage times current times seconds. \n\n & #x200B;\n\nWith a static shock you have a really high voltage and remember that's a really high current \\*too\\*. But it's only for a few microseconds (1 million of those make a seconds) until the energy is used up. \n\n & #x200B;\n\nBut a toddler that sticks their fingers into an electrical outlet would be touching that for several seconds. Millions of times longer. So more energy gets transfer into them and they die. The same with a car battery, that things stores a ton of energy so if you touch it you die. ",
"Current, Amps, is a measure of the motion of electrons. Voltage is a measure of how strongly an electron is attracted to something else without actually moving. The problem with a lot of current is that you have all these electrons moving through your body hitting a bunch of atoms as they move through. There has to be enough voltage to pull the electrons along the path of least resistance but as the electrons travel along they constantly collide with everything along the way and each collision causes heat and all that heat build up and ends up burning whatever it's hitting. If there's only one electron, even if there's a high voltage and it's pulling that electron along really quickly there's not a whole lot of collisions so there's not much heat built up. If there are a lot of electrons there are a lot of collisions which causes heat build up and eventually burns.",
"Let me make an analogy. Wind speed is voltage, how heavy or massive the air is the amperage, and how much work that thickness of air, moving at a certain speed can do is like the wattage. \n\nHigh voltage with low amperage is like very thin air, like Mars atmosphere, blowing very fast. It's moving super fast, but it's so thin you barely feel it. You are aware of it, but it's not blowing you over. \n\nHigh voltage with higher amperage, is like thicker air, or even maybe water, moving at high speed. Now you not only feel it, but it can actually pick you up off your feet and kill you. \n\n\n\nThere are two ways that electricity can damage the body. \n\n1. Burns - Burns require amperage, lots of amperage, but not necessarily high voltage. Think of a 3 volt lithium battery melting a wire shorted across it. It's only 3 volts, but it can put out 20-30 amps, which is enough to heat up almost any material. Electricity moving through the body can [literally cook you](_URL_0_) with enough amps. Electrical burns are the primary reason why a person may need a limb amputated after an electrocution. The damage to the limb is severe enough it could kill the person if not amputated. \n\n2. Interrupting the [autonomic nervous system](_URL_1_) like the hearts rhythm or even the brain. This requires a high enough voltage to penetrate deeply into the body, an electrical path that brings it through the trunk of the body like from the hands to the feet, or in one arm, out the other. It also requires enough amperage to disrupt the bodies nervous system and the hearts natural pace maker. It can cause a dangerous arrhythmia and death. \n\n\nAnother way of thinking about it is the high voltage helps overcome the low electrical conductivity of the human body, and the high amperage plus high resistance = heat, much like a resistive wire in a vaporizer heating up and glowing red when electricity is passed through it. ",
"Electricity is like a garden hose. The water is the amperage, water pressure is the voltage, hose is the conductor and squeezing the hose is resistance. Getting wet is equivalent to getting shocked. ",
"e: revised the analogy.\n\nconsider a cliff, a tall one, with level ground on top and level ground at the bottom.\n\nand let's use water flow as an analogy to electric flow - water coming from the top creates a water-fall falling onto the ground below.\n\nif there's only a little water - and you stand under the cliff - you'll only get wet. but if there's a lot of water flowing and coming down the water-fall - you will get crushed. the amount of water is equivalent to electrical current or amps.\n\nnow imagine the same cliff but much much smaller - smaller in fact than a person. so that when you stand on the bottom the water only goes up to your shoulders or even your knees. that's equivalent to electrical resistance and electrical potential - if the height of the water fall (potential, volts) is lower than your face, even a large flow of water will not hurt you (ignoring for now the fact you are likely to be swept away) - in the same way a large flow of current (amps) that doesn't have enough potential (volts) to overcome your skin resistance (ohms) will not go through your body (ie you will not become part of the circuit).",
"It's not speed that kills you, it's the force!\n\nYou can easily drive 200 kph and stop without dying. It's the force of a sudden stop against a concrete wall that will kill you.\n\nBut while it's technically the force that kills you, it makes a lot of difference if you hit that wall with 200 or 20 kph.",
"P = IV\n\nIt's power that kills you.\n\nCase 1 : 500 Volts, 0.00001 Amps\n\nSure 500 Volts means that the electrons reallllly want to flow and hit you hard but 0.0001 Amps indicate there isn't many electrons in the first place so it won't kill you.\n\nCase 2: 0.0001 Volts and 500 Amps\n\nThere's a shit tonne of electrons ready to flow, but the potential isn't there for them to reallllly want to flow through so even though there's a lot of electrons, they don't hit you that hard and you don't die.\n\n & #x200B;\n\nCase 3: 5000 Volts 40 Amps\n\nP = IV = 5000 V \\* 40 A = 200 000 W = 200 000 J/s\n\nTwo hundred thousand joules per second. Good night. Forever.",
"An ELI5....\n\nIf you look at a dam, there is stagnant water up above and fast moving down below. This serves as a large potential between the two (voltage)\n\nNow, think of the fast moving water down below as the amperage, its the flow of electrons, in this case the flow of water.\n\nNow, when they say its the amps that kill you, its the water flowing at a fast rate. To answer your question it would be the electrons flowing through your heart which will kill you.",
"Even after closely reading the 20 different analogies offered here, my brain still has a hard time understanding electricity. :(\n",
"\"yes\" So the two are related. \n\n\nCurrent is what kills you. But current happens when voltage is placed across a load. In this case, the load is \"you\" and that's a load that's going to be in a very specific range. \n\n\nthis is going to be \"about right\" but it takes just a few milliamps across your heart to stop it. However, you can take a couple dozen milliamps across your whole body. This is because current takes \"every path availalbe\" rather than just the path of least resistance. \n\n\nI'm getting off in the wrong direction. Basicly you're a big resistor, to get enough current across your heart, you need enough voltage to do it. :-) Volts is what you need to worry about, amps \"take care of themselves\". ",
"It's a little bit bullshit. It's very similar to saying that it's not the fall that kills you but the ground. Voltage is potential, same as height. Without a lot of it, you can't drive enough current to be dangerous in a human body. Also the voltage and current relationship is linear. So given some constant resistance through your heart, it's the volts that drive exactly the amps that kill you",
"Two examples... \n\n12V car battery. If we assume the resistance of dry hands to be around 100k ohms, then placing your hands on both terminals causes 0.00012 amps of current to flow between your body. This isn't enough to even feel. The important point here is that the car battery is capable of putting out hundreds of amps, so if you place a wrench across those same terminals it would make a lovely lightning show.\n\nThe second example is a van de graff generator. Large ones can produce voltages of hundreds of thousands of volts. The metal ball on the generator acts like 1 plate of a capacitor, while the ground is the other. The ball is only able to store a very small charge, but at very high voltage. The current only flows long enough to discharge the spark, then stops until the voltage builds up again. When the capacitor just charges it acts like a high frequency wave so the current tends to travel through your skin instead of through your soft tissues which have much lower electrical resistance.\n\nIn summary, it is a combination of voltage, frequency, and the maximum current output of the power source. \n\n",
"Voltage is the name used to measure electrical potential energy. Amperes is used to measure current.\n\nVoltage is akin to a rock on a hill. It's harmless as long as there is no path for it to roll down and exert force on something. The higher the voltage, the bigger the rock.\n\nCurrent is the rock in motion. The rock can only be in motion if something opens a path for it to roll down. Current can only occur if there is something to conduct it from high voltage to low voltage.\n\nIf you are in the path of the current or rock, the rock will exert some force on you. Say you are in the path of the rock but you are running away and the rock grazes you, the rock exerted some force on you but since you did not resist it, it does little damage. But if you stand your ground and face the rock head on, it will exert more force on you and do more damage.\n\nThe human body can conduct a current but parts of our bodies also resist a current. Those parts of your body resist the current and some energy from the current is converted to heat which has no where to go but your body. This causes internal burns which causes death. On the same person, higher voltage will cause more current to be conducted which results in more heat dissipated causing worst burns. Our bodies also use electrical signals to communicate so current can also interfere with that and cause death through say heart or lung failure.\n\nIf you see a sign that says high voltage, don't touch it or go near it. And rubber gloves probably won't protect you if the voltage is high enough. :)",
"If this is ELI5, only the volts matter. High voltage will kill you. Dont touch anything over maybe 12V just to be safe. Don't worry about amps. That's all anyone that's not a technical person needs to know.\n\nSlightly more technically, the amount of current needed to kill a human is tiny. So tiny that virtually any circuit could deliver it. If the voltage isn't high enough though, there will be no current. Once the voltage is over maybe 50V, the circuit can possibly deliver enough current to hurt and/or kill.\n\nBoth of the aboves are pretty vast over simplifications, but that's the gist. Anyone who tells you 'it's the amps' either doesn't know what they are talking about or is an engineer being a sophist. Given the complex subject matter, that's about the best ELI5 you're going to get without resorting to the god awful water hose analogies or even worse, math.",
"Think about volts as the weight of a travelling object and amps as the speed of the object. A slow moving truck will be less likely to kill you than a fast moving bullet, although the truck has more weight.",
"That saying is just plain wrong. It’s the volts *and* the amps *and* the frequency *and* the duration that kill you. Sadly there is no really simple way to understand all the nuances of electricity.\n\nA typical static shock blasts you with a pulse of tens of thousands of volts, carrying about between 1 and 20 amps amps IIRC. 100 milli~~volts~~**amps** is enough to kill you, but that is for a sustained shock.\n\nIf you touch 170 volts DC from a source without current limiting, it will be pretty unpleasant, but you could definitely hold on to it for a bet; if you touch and hold on to 170 volts AC at a certain range of frequencies from a source without current limiting, you will die.\n\nIf you touch 5000V AC at 60Hz from a source without current limiting, you will instantly die. If you touch 5000V AC at 20,000Hz from a source without current limiting, you will get a nasty burn where you touched it, but you will live.\n\nElectricity and biology are bizarre beasts, which is what makes them so interesting! Electricity is an oddball because we can use relatable analogies to represent many of its behaviors (like water pressure and flow rate = voltage and current, one-way check valve=diode, etc.), but there are some behaviors that we can’t really relate to more accessible concepts.\n\nHere’s the most I could distill it down without being misleading or untruthful: *Voltage can push current (amps) through you, which can be lethal if enough current is pushed through you at certain frequencies for a long enough duration.*\n\n\n**TLDR: If it were just the amps that kill you, static shocks would be 100% lethal. It is a combination of the voltage, current, duration and frequency that kill you.**\n\n & nbsp;^(Edit: 100 milliamps, not millivolts)",
"Imagine a serine river flowing by. That’s a lot of water flowing by but you can stick your fingers in it. Now imagine that same amount of water forced into a pipe with a small opening in the side. The spray coming out would cut your finger off. The amount of water going by is the voltage and the pressure at which you can touch it is the amperage.",
"This saying is not true. Neither is more important than the other. With an excess of one and not enough of the other it is no more deadly than the other way around.",
"Think of it as water. There is a tank above your head. It has an opening in the bottom.\n\nIf there is one drop of water in the tank, it doesn't matter how big the opening is.\n\nIf the opening is 1/8 of an inch, it doesn't matter how much water is in the tank.\n\nThere are various combinations that of the two that will be a very bad result.\n\nThe volume of the tank is volts. The size of the opening is amps.",
"As those mentioned here, the saying is misleading and wrong. \n\nThere are three components we need to take into account; voltage, current (amps), and resistance (ohms). There are other ELI5 posts discussing how electricity works and water analogies so I won't get into it.\n\nThe most basic electrical formula (v=ir) restructured gives us current equals voltage divided by resistance. This means if we have a given voltage, 120 V, the current will depend on resistance. For example, electricity flows with less resistance through water. So if a conductive object is wet, it will have less resistance. \n\nSo I accidentally touch a 120 V supply that is capable of supplying 100 amps. If I am dry without broken skin (which I was in this real life scenario), I could have 100,000 ohms. This value varies from person to person. 120/100000 = 1.2mA. Looking at an electrical safety chart says I'd feel a tingling sensation which I did. It wasn't painful. If I was wet, then my body resistance could be 100 ohms. 120/100 = 1.2 A or 1200 mA. I'd be burned with internal organ damage and possibly died if this happened.\n\nSo it is about the current but only in respect to the supply voltage and the body's resistance at that moment.\n\n-----------------------\nA couple things for additional reading.\n\nYour outlet is capable of supplying more than 2 amps. But when you plug in your phone, a digital clock, or a low power device, the outlet is supplying only what the device is asking for. The phone will not receive 20 A while charging or you'd see magic smoke. This means these devices have internal resistences built into the wall wart, the device, and/or the power brick. \n\nSo even though, in my example above, the full service or supply is 120 Volts and 100 Amps, I only received 1.2 mA and Max would have been 1.2 A.\n\nI assumed DC voltage above for simplicity sake but in reality, it was 120 VAC. To get a DC voltage from this, we can calculate the rms value. 120 VAC * SQRT(2) = 170 Vrms. My dry body resistences is also in the range of 70000 ohms. So in reality, the tingling sensation was from 170V/70000 = 2.4 mA",
"Well, my potential for fully grasping this concept is currently at about... zero.\nLet's just say its a voltage-gated situation.",
"From experience. I touched 500v and it stung but clearly still alive. Right after my coworker asked if I was ok, I said this line as I was shaking. Was not pleasant, was not what I meant to do (lapse of attention) but clearly didnt kill me.",
"Think of it like water. Volts at how much water is in a tank. Amps are how much flows. Resistance would be the size of the pipe.\n\nSo an entire ocean couldn't kill you if it only went at a trickle (high voltage, low amperage), but a slug of water going fast enough to punch a hole in you could definitely kill you.\n\nThere might be more in depth, but I think a 5 year old could get this *shrug*",
"The huge semi truck sitting still won’t kill you. The huge semi truck driving into you will kill you.\n\nThe bullet sitting on the table won’t kill you. The bullet shot at you out of a gun will kill you.\n\nVoltage is electricity’s way of just sitting there waiting for something to do. Current is electricity’s way of doing something. They’re obviously related - you can’t have current without voltage, just like how you can’t be run over by a truck without the truck being there in the first place.",
"In my electronics degree, I found it useful to think of electricity like water. Because I can intuitively grasp plumbing more easily than electron flow.\n\nSo voltage (aka \"electric potential\") is akin to water pressure, or the \"head\" the water has (aka \"gravitational potential\"). A raindrop in a cloud has massive gravitational potential, but won't hurt if it drops on you.\n\nAmperage (aka \"current flow\") is akin to the current flow of the water. The more water that flows through a pipe each second, the higher its \"current\".\n\nOhmage (aka \"resistance\") is akin to the constriction or width of the pipe. Given the same water pressure, you can get more water per second through a wider pipe.\n\nWattage (aka \"power\") is how fast the water can do work: the current, times the potential. So a meandering river is low-power compared to the same river flowing over a waterfall (or a water-wheel!), even though they have the same current. You can consider it the \"flow speed\" of the water.\n\nJoulage (aka \"energy\", \"Kilowatt-hours\", \"Watt-hours\", \"Ampere-hours\") is the measure of capacity of a power storage, or the amount of work that the water has done. How much water has been lifted how high, and so forth.\n\nVariable resistors and switches are intuitively replaced by faucets and stops; resistors by pipe constrictions; diodes by one-way valves. A broken wire is a capped-off pipe. Capacitors are chambers with a diaphragm separating the two exits. Inductors are coils of soft pipe that swells depending on the pressure in them. Even more complex devices like transistors (a valve controlled by pressure in a third input), relays, voltage regulators, motors and so forth all have reasonably simple and intuitive representations, which illustrate the basic principles of how charge flows in an electric circuit. Only some effects seem impossible to mock up (electromagnets, heating elements, LEDs...).\n\nIt feels like there should be a teaching kit with a set of panels, each panel having a component and a plumbing equivalent; you'd be able to link the panels together to make both a hydraulic and an electrical circuit.\n\n\\---\n\nYou can't, with either electricity or water, say \"It's the \\[metric name\\] that kills you.\" A million joules, spread over a long time, won't hurt you. A massive current won't hurt you, if it's a wide, meandering river. A massive flow-speed won't hurt you, if it's a raindrop. A massive pressure won't hurt you, if applied and removed slowly.\n\nBut in combination, they can hurt and kill.\n\nWith a water leak, it's the bill that kills you."
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1a0zgs | how do you get into medical school in the united states? | I'm on my third engineering degree and someone was trying to explain to me how medical school works, from getting in to graduating. The actual process of graduating seems to be straightforward, but they seemed deeply confused by the whole admissions process. Is there some sort of algorithm here? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1a0zgs/eli5_how_do_you_get_into_medical_school_in_the/ | {
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"There are certain required courses which you must complete in college. If you haven't done them, you can't get into med school.\n\nAfter that, the most important factors are your grades and your score on a standardized test known as the MCAT. Medical-related volunteering is also important, but it's difficult to really stand out there, because most applicants are going to be volunteering whenever they can.\n\nEverything else is a minor factor at best. It's not known exactly how much they affect things, but you don't get into medical school by having strong recommendations.",
"1. Complete a pre-medical program during undergraduate. This includes the MCAT (Medical College Admissions Test), which is a test of your knowledge in subjects such as chemistry and biology as well as your thinking andreasoning skills. Your score will be included with your med school applications.\n\n2. Apply for medical school. This includes written and interview stages. Since there are very few slots compared to the number of applicants, you need to stand out from the pack. This usually means, at a minimum, a history of volunteer work and research lab work.\n\n3. If you're good and lucky enough, you'll be accepted. Medical school generally consists of two years of preclinical courses and study, followed by two years of work at a teaching hospital under more experienced physicians. You also work towards your medical license.\n\n4. After you graduate from med school, you are a Doctor but still don't have a medical license. You have to complete an internship and work towards completing your medical license.\n\n5. Congratulations, you're a licensed doctor and can now open your own practice."
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13w125 | if a muslim was on the exact opposite side of the earth from mecca, where would they turn to pray? | They'd probably be on a boat...idk where the opposite is. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/13w125/eli5_if_a_muslim_was_on_the_exact_opposite_side/ | {
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"They would probably move a bit.",
"It would indeed be in the ocean. _URL_0_\n\nIn that case they would simply point any direction they pleased.",
"You're right, they would be on a boat, [in the middle of the South Pacific](_URL_2_). (Lat/Long: 21° 25' 48\"S, 140° 10' 48\"W)\n\nFirst, let's make it clear that, no, they wouldn't stand on their head and face \"through\" the earth.\n\nSince the Earth is a 3-D sphere, you can just calculate it by sticking two pins in a map and tying the shortest line you can. Instead, it's calculated via the [*Great Circle* approach](_URL_1_).\n\nAccording to [this site](_URL_3_), using the latitude and longitude above and the *Constant Compass* setting, they'd want to face to a compass heading of 80 degrees, 50 minutes (a little above the compass heading of east, which would be 90 degrees).\n\nIt's also important to note that compasses face magnetic north, not true north, and the Earth's magnetic north actually moves. So, it sounds weird that you'd face just a little bit north of directly what your compass says is east, but the calculation made is taking Mecca's location in relation to the current location of magnetic north into consideration.\n\n[For comparison, here's the shortest flight path to Mecca](_URL_0_).",
"There's actually an app that will point you towards Mecca (MeccaLocator). I wonder what it would do?...",
"It might use some of the Space rules. (I'd link it, but I'm at work) basically it's a bunch of new rules to do away with the problems of their non terrestrial location. Examples being, since they're traveling much faster than the Earth beneath them, when do they prey (since sunrise, and sunset are relative notions in space) where do they look (relative locations in space) what the rules with fasting are (basically optional, which is neat) and other things besides.\n\nEdit: [Here is the only really good link on the subject that I could find. Yahoo and Reuters both have them originally, but it's shooting up 404's.](_URL_0_)\n ",
"Here's a related question:\n\nIs it more important to *actually* face Mecca, or that you honestly intended to and thought you were facing Mecca?\n\nI seem to remember a mosque or other prayer center that had the indicator in the wrong place for a time, but I don't remember what was said about it.",
"I'm not a muslim but I have a lot of muslim friends because I live in Indonesia. They turn to north west when they pray and very strict about it, unless when they're subconsciously forget the direction or don't know where they are.\n\nA little bit unrelated story..\nOne time, I asked a question : \"Where would a muslim turn to pray when he/she is on the moon?\"\n \nOne of my friends said that when they're on the moon, they would most likely just turn to earth.\n\nThen I asked again: \"What if you're unable to see the earth? or somewhere in a far-far away galaxy?\" \n\nand he said that if human being can reach that point, the direction wouldn't be important anymore as long as they had a strong intention to pray.\n\nWhen I looked up to the internet, I found out that it's not just a hypothetical question. It's a real trouble for muslim astronauts when they're not on earth : \n\n_URL_0_\n"
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j2eu9 | can someone explain general relativity? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/j2eu9/can_someone_explain_general_relativity/ | {
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"I'm not an expert on this, but I'm pretty sure you could sum it up like this:\nIt's basically a theory that explains gravity & it's effects on space, time, matter, etc.\nFor example, how light can bend around a planet because of the gravity field of that planet, how planets orbit around suns, how black holes work (the light is pulled in by so much gravity that it can't escape), etc.",
"This is more a question for r/askscience. ",
"Ooooh, not exactly something that you can explain in 5 minutes, but I'll give it a shot.\n\nKeep in mind that I am far from an expert and on top of that I'm kind of bending the rules to make things easier to explain. First off, when I say \"fast\" I mean something like 100 thousand kilometers per second. The speed of light is 300.000 kilometers per second, we call it \"c\", and yes, that is the c in E=Mc2. \n\nWhen I say \"heavy\" I mean the weight of a planet or a star. Because we weigh so little and move so slow, we almost never actually notice relativity. \n\n\nNow, we all grew up learning that time always goes \"forward\" with a fixed speed of 1 second per second. Space is also always the same, 1 cubic meter here, another one there. etc. Then, relativity came and messed things up:\n\n1. Nothing can ever go faster than the speed of light.\n\n2. If you measure the speed of light relative to yours, you will always measure it to be c.\n\n3. Heavy things can \"bend\" the space and slow time around them.\n\n\nWithout relativity, a measurement would go like this:\n\nYou are moving at 50km/h, a car passes you that is driving 120km/h. If you were to measure the speed of the car relative to you, you measure the car to go 70km/h *relative to you*.\n\n\nNow, let's look at relativity:\n\n\nYou are standing still and measure the speed of light *relative to you*. You measure the difference to be c.\n\nYou are moving at one half the speed of light and measure the speed of light *relative to you*. You measure the difference to be c.\n\n\nThe last one is funny. It would imply that the actual speed of light is c PLUS your own speed. But it isn't! Remember rule 2, it's always c! Looking at this some more, and remembering rule 2, we come to a funny conclusion: Time *seems* slows down when a person is going faster. I write \"seems\" because it isn't. It's just that *your* time is not the same as some other person's time. If you were to ask the other person about your time, he'd tell you that your time is going too fast.\n\nNow for rule #3. The sun, being a very heavy thing, bends the space and time around it. Time moves slower near heavy things. If you were to look at a clock on the surface of the sun, you would say it moves slower than yours. But it isn't, it just looks like that to you. If you were on the sun and looked at earth's clock, you'd say it goes faster.\n\nAnother mindbender: The earth isn't really going in circles around the sun. The earth is going in a straight line in space, but that space is \"bended around the sun\".\n\n\nYou might want to look up \"Time dilation\" and \"Twin paradox\".",
"This may be off-base, but this is how I've always thought about it:\n\nIf a frisbee is thrown at you, and you run towards it, it \"looks\" to you like it is faster than if you stood still. Likewise if you run away from it, it appears slower.\n\nThe bizarre truth is that this doesn't work for light. If you run towards a source of light, no matter how fast, you still see that light ray as moving at the speed of light. \n\nThis leads to all sorts of weird contradictions, and the only way to resolve them is to accept than when you move very fast, time actually \"slows down\" for you, as if to \"enforce\" the speed of light."
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73ppqq | how does physics work in calculus? | What exactly does calculus do to physics? Say we have a simple equation like Force=mass*acceleration. The second derivative means acceleration. So if you take the second derivative of Force what would it be and what does it mean? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/73ppqq/eli5how_does_physics_work_in_calculus/ | {
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"Acceleration is the second derivative of displacement with respect to time. The second derivative of force with respect to time isn't all that meaningful. I'm not entirely sure what you're asking, to be honest. Can you clarify a little bit?",
"You get something called jerk. Its how quickly an acceleration changes. For example, An object that goes from an acceleration of 20m/s/s to 30m/s/s over 2 seconds will have a jerk of 5m/s/s/s. ",
" > What exactly does calculus do to physics? \n\nA lot. Without a specific example in mind, it's hard to quantify. It's like asking what algebra does. The generic answer is if you want to know how some variable changes as you change other variables, that's calculus. ie, dx/dt is telling you if you change t a little, how does x change.\n\nTo give one example. Lets say i tell you you have an object under a constant acceleration (like say, a projectile under gravity close to earth). You could integrate twice, and get something like\n\nx(t)=x_0+v_0*t+0.5*a*t^2\n\nGiven an initial position and initial velocity, you can solve for the position of that object at some time t.\n\nYou could also do the reverse- if someone gives you the position as a function of time and you want the acceleration, take two derivatives with respect to time. In the generic example i gave above, if you took the derivative of x(t), you'll just get back to a=constant.\n\n > So if you take the second derivative of Force what would it be and what does it mean?\n\nJust because you *can* take a derivative, doesn't mean it's meaningful.\n\nIn this case, the second derivative of force (with respect to time) would give you something in terms of \"jounce\". (also called snap)\n\n_URL_0_\n\nIt's not really meaningful for the most part. Forces care about accelerations (for the most part).\n\nFor a lot of functions, they're either polynomials, or infinitely differentiable.\n\nTo use the constant acceleration example again, the jounce is just 0. But for a function like sin(wt), you can take as many derivatives as you want. But it's just a math exercise.\n\n > The second derivative means acceleration.\n\nThe second derivative of *position* (with respect to time) is acceleration.",
"What you are partly getting at is the more philosophical question of whether mathematics is invented or discovered. Calculus was \"invented\" as a way to describe natural phenomena in physics that people were observing. Those terms like velocity, acceleration, jerk, etc. are all qualities of an object in motion. Calculus just describes these properties that are already there in physics. Calculus doesn't \"do\" anything to physics, it's just a way to describe and understand how the natural world works. Which is where the philosophical question comes from: since the natural world obeyed these laws before humans understood them, is the math behind them something we invented or did it already pre-exist?",
"Calculus allows you to two things:\n\n* calculate the instantaneous rate of change, like the velocity of an object the instant it hits the ground\n* calculate the accumulation of a value over time, like the total distance travel by an object with changing velocity\n\n > The second derivative means acceleration.\n\nThe second derivate of *displacement* is acceleration. Physics describes many things that are not displacement.\n\n > So if you take the second derivative of Force what would it be and what does it mean?\n\nI am not aware of any special names the derivatives of force have. The first derivative of force would describe how force's rate of change varied over time, and would be measured newtons per second (N/s), or kg m/s^(3). The second derivative would be the change in the rate of change, and the unit would be N/s^2 or kg m/s^(4).\n\nThis is true for the derivatives of any measurement. The first is rate of change, the second is the rate of change of the rate of change. The ones for displacement just happen to have special names."
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2szseo | why do dogs cock their heads when their begging for something? | Is it just canine body language, or something more sinister? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2szseo/eli5_why_do_dogs_cock_their_heads_when_their/ | {
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"There are a few theories on why they do this.\n1. They're trying to hear better\nDogs have movable earflaps that help them locate the source of a sound, but they also have brains that can compute time differences between the sound reaching each ear. A slight change in a dog's head position supplies additional information that the canine can use to judge a sound's distance. Essentially, tilting the head can help the animal more accurately locate the location and distance of a sound.\n\n2.They're trying to understand us\nAccording to Steven R. Lindsay's \"Handbook of Applied Dog Behavior and Training,\" when a dog listens to your voice, he's trying to identify familiar words or tones that he associates with a reward, such as going on a walk or receiving a treat.The muscles of a dog's middle ear are controlled by a part of the brain that's also responsible for facial expressions and head movements, so when a canine tilts his head, he's trying to perceive what you're saying, as well as communicate to you that he's listening.\n\n3.They can't see our faces easily\nIn an effort to understand us, dogs not only use our words and inflection, but also facial expressions, body language and eye movements. Because of this, it's important for them to see our faces, so Dr. Stanley Corren reasons that when dogs cock their heads they're trying to see us better. He says that dogs with longer muzzles have difficulty viewing a person's entire face and compares it to how our vision is obstructed if we hold a fist to our nose and view the world as a dog does. Corren suggests that dogs may tilt their heads to view a speaker's mouth and aid in understanding what is being communicated. He hypothesized that dogs with flatter faces, such as pugs, Boston terriers and Pekingese, might tilt their heads less because they don't have to compensate for prominent muzzles. Corren conducted an Internet survey to test his theory. Out of 582 participants, 186 had dogs with flatter heads. Seventy-one percent of the people with large-muzzle dogs reported that their dogs often tilted their heads when spoken to, while 52 percent with flat-faced dogs reported frequent head cocking.\n\n4.We've taught them to do it\nWhen dogs tilt their heads when we speak, it's undeniably cute and we have a tendency to respond to the behavior with positive reinforcement. Perhaps we say \"aww\" in a pleasing tone of voice or offer the dog a treat. Reacting in such a way encourages the activity, and the more a dog is praised for cocking its head, the more likely he is to repeat the gesture in the future."
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aarlw2 | what will happen to the 0.1% of the germs that didn't get killed by the hand sanitizer? | Do the 0.1% of the germs get sick? Do they function properly like nothing happened? I honestly don't know. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/aarlw2/eli5_what_will_happen_to_the_01_of_the_germs_that/ | {
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"Those that survive will often pass on this genetic advantage to their offspring, which will then be slightly more resistant and so on...This is natural selection and evolution in action. Bacteria and viruses have already evolved/mutated in response to our modern medical treatments, which has created new classes of drug resistant pathogens (e.g. MRSA, VRSA, HIV, etc..). Alcohol kills germs differently than medications do, however the same basic idea applies It's actually becoming a bit of an issue in places like hospitals, which are in a constant arms race against newly forming, drug resistant infectious agents. Because we can never truly be 100% perfect at eliminating all germs at all times, a few will slip through the cracks and become ever more resilient. "
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2zstj2 | why does music in 4/4 time sounds more natural to us? | Is there a reason why weirder time signatures sound a bit more strange other than we are used to listening to simpler ones? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2zstj2/eli5_why_does_music_in_44_time_sounds_more/ | {
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"Part of it is what we are conditioned to listen to. Lots of music is in 4/4 so it has a context we can fit it into. As a professional musician, I've played lots of music in many mixed meters, so those don't sound or feel awkward to me anymore. I've been conditioned to have a way to understand them compared to lots of other examples. \n\nBut on a more biological level, a lot of it probably has to do with our two feet. Left, right, left, right. It fits the rhythm of 4/4 better than, for example, 7/8. ",
"I believe its mostly cultural conditioning, if we look at music throughout history its so varied and different that you can't really say 4/4 is somehow caused by our biological configuration. Having more/less limbs basically allows you to play more in a shorter period of time, it has little to do with the beat its self, HOW you chose to play that beat, or more importantly how you chose to write it down.\n\nBasically, time signature is completely arbitrary, its the result of how the notation system works in the first place. The reason 4/4 sounds more natural to you is because you're basically surrounded by it. Its literally everywhere.",
"It's not really natural or anything, it's just what most people have been exposed to all thier lives, and is the easiest to write in an clap along for a listener. In contrast, some thing in 7/8 time is harder to write in, and isn't uniform in downbeat. So mainly 4/4 just feels natural because it's just what you have been listening to your whole life",
"It's cultural. Many other cultures use very different timing. Indian music is one of note, I believe. \n\nI've often heard that a lot of religious music from ~400 years ago was in waltz form (3/4) as the 3 represented the holy trinity. ",
"I can't answer the question, but I had a similar thought a bit ago. I make beeps and boops on my PC so I was wondering what it would take to make an EDM song in a different signature.\n\n[This is what I came up with, it's basically metal but no guitars were involved. It says 3/4 but I think it's actually 12/8](_URL_1_)\n\n[This is one I found looking for dubstep in weird signatures, this is in 3/4](_URL_0_)\n\n[and this is in 7/4 (or 7/8 depending on how you count)](_URL_2_)",
"4/4 might be what sounds 'normal' to us, what we consider standard, but songs can even be cool in other time signatures. Heres a good example of a rap in 15/8: _URL_0_\n\n^[edit:typo]",
"Short answer: You most likely grew up listening to western music. Just what you are used to hearing.",
"3/4 or 6/8 sounds pretty natural too. Commonly used in modern pop music.",
"Technical deathmetal drummer here .. Most music is based on the brand typical western style 4/4 & you can figure in other forms such as jazz, blues and bigband from there as well which was majority based off the first composite number in the current counting system. From there it essentially grew up based from there in my opinion. As music progressed it just kind of stayed locked in that norm.. styles grew & progressed but wasnt truly noted i believe until the late 60s (Beatles - here comes the sun, all you need is love .. being some of the earlier & most notable ones) .. and from there the offtime setting just got little by little bigger & bigger .. \n\nHeres a list i happened to come across that has a ton of offtime signature songs & dates (i started typing this like 2hrs ago & forgot due to post knee reconstruction pains & attempted child fanagling during said pains \"joys of fatherhood\") but the list of songs actually go way back but dont get prominent until more recent\n\n\n_URL_0_\n\nTL:DR - started majority as 4:4 .. ppl got use to it .. then ppl started to get craycray more & more\n\nHAPPY BANGIN",
"As a classical and jazz musician, I find 3 and 4 to be equally natural.\n\n5 and 7 and 15 and the rest are awesome, but they always sound like a modification of a natural beat (e.g. 7/8 feeling like 8/8 with the last beat dropped), rather than a basic natural beat themselves.",
"The most common meters and most 'natural sounding' meters are duplet and triplets. that incapsulates 4/4, 2/4, 8/8, 3/4, 6/8, and even 9/8 or 12/8. Where things start to get weird is with odd meters. things that can't be divided evenly into twos or threes. Meters like 5, and 7 and 11, and 13 have to be divided into combinations of twos and threes for phrasing and counting purposes. The reason this feels weird to you is because in even and triplet meters you can tap your foot at a consistant beat and always land on the one of the measure. With five or seven, unless you're counting the whole measure as one giant 7-note beat, you have to have a half beat or a one and a half beat(relative to the tempo you're tapping out with your foot for example) to land squarely on the one of each measure. This stutter is what gives odd meters their odd feel. Good songwriters will generally use syncopation to try and smooth over some of the jankiness of odd meters. Dave Brubeck's take 5 is a classic example of this. If you wanna hear another good odd time song that does a good job of smoothing out some of the 'oddness' of an odd-meter, check out lazy lightning by the Grateful Dead. The Dead actually have quite a few songs that use odd meters and meter switches in a clever and seamless fashion. I can list a few if you like",
"It's cultural; we're just not used to it. Try listening, say, to some Senegalese popular music. I remember the first few times I heard [this song](_URL_0_) it just sounded like a total mess. After a few times things started falling into place."
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4tqhd2 | why has there recently been an increase in ultra-nationalism? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4tqhd2/eli5_why_has_there_recently_been_an_increase_in/ | {
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"Financial downturns always push populaces to the right.\n\n1. Have less money.\n2. Suffer more hardships.\n3. Look for scapegoat (with giddy help of local politicians)\n4. Identify simplest scapegoat as foreigners.\n5. Demand border closure to keep dirty foreigners out.",
"Talking EU here.\n\nBecause legitimate fears (of migration) of population are not being addressed, and are automatically dismissed as racism. \n\nPoliticians and journalists become completely disconnected from voters. Nationalistic groups tend to rise from working class (not political), and are promising to address these issues.\n\n\nAnd prosecuting people for Facebook discussions (in Germany) is pouring petrol to the fire, and will only cause more support and more radicalisation.\n",
"The sad truth is that it's because the economy is lousy. Historically, whenever there has been a recession or a famine, xenophobia has risen.\n\nWhen things are going well, good jobs are plentiful, and opportunity abounds, nobody really cares about people of different ethnicities and lifestyles. There's a perception that even if people are making the wrong choices, there's plenty to go around.\n\nBut, when things get bad, people start to wonder why. On an instinctive level, we don't understand the economy as it is (an interconnected, flowing exchange of goods and services) but understand it in a more primeval way, like a harsh winter making fewer berries and less game in the valley. So, we look to the other tribes, and feel that we'd have more if they went away. But don't worry, as soon as the Baby Boomers are able to retire and college grads once again find middle class jobs, it'll all go back to normal.\n\nIn other words, the human race just really needs a Snickers right now.",
"People have a natural tendency to value those close to them. Their spouse, children, family, neighborhood, city, state/province, country, etc. If humans came to earth and wanted to negotiate usage of resources...most people would side with earthlings. \n\nNearly everyone wants the same basic things... Peace and prosperity for everyone. But when increased peace and prosperity for someone else means less peace and prosperity for *us*... It's natural to have reservations about it. \n\n\nMore specifically to today's situation... If a group of people have a well functioning system and another group of people have a failing system. The successful group is typically open to accepting the failing group into their own, on one condition. They adapt to the successful methods. When the failing group comes into the successful group and wants to bring with them the same ideals that led to the failure of their other group; people will naturally start to \"circle the wagons\" to protect the system that is working for them. \n\nTo put an even finer point on it, a lot of the border discussions today are around religion. Free societies have proven successful, and religious states have typically failed. Now as these religious people are seeking asylum in other countries, they often have troubles (or outright *refuse*) assimilating with the culture. They essentially want to live the lifestyle that led them to ruin, while also enjoying the progress made by a free society. \n\n\nSo it's basically 2 fold. First you are asking people to share their resources with more people that are not adding much resources in return. And second we have the almost daily instances of violence where immigrants hold a severe disdain for their host country. \n\n\n",
"There's plenty of reasons, and they all compound on each other. A lot of answers here are lazy and want simple answers for complicated things. Most of the answers are right, but none of them really go all the way to explain it all.\n\nFor starters, the economy being in a slump is a huge part of it. People, for the most part, are doing worse now than they were 10-12 years ago. People want to blame this on everyone outside of their group, and at times they're right, and at times, they're just a scapegoat.\n\nBut another big part is that people keep being told that things are getting better, but a lot of people aren't feeling that. There are jobs reports that are coming out saying that things are getting better, and most people just aren't seeing that on their side. They hear that the markets have risen, and they're not getting a cut. The heads of state keep saying \"it's coming for you too\" and people are growing skeptical of it.\n\nOn top of it, with the messes in the Middle east, there's a huge amount of support to take care of outsiders from typically liberal countries, while their nationals feel like they're not being taken care of, so this builds resentment, especially when you see things like the multiple recent attacks in France, and every time it's an outsider.\n\nPeople feel disenfranchised because they keep getting told \"Everything's fine\" and they see people from other countries coming into their country, and getting the help from their government when they feel like they're the ones that need help.",
"What you describe is not \"ultra\" anything. \n\nNationalism, sure. I think you should read about Isolationism.\n\nI also think that the media is hyping things quite a lot as it is an election year and the mass media are a political beast. So take many pinches of salt.\n\nBrexit and the US presidential election aside, what ultra/nationalism are you asking about?",
"It's pretty normal to value those close to you more than those who are considered far away. This is simply evolution really, we value our family, our children, over other people's children, our families over other families. Extension of this logic brings us to the idea of a Nation state. We want to be surrounded by people who think as we do, share the same moral, cultural values. \n\nFurthermore, with the migrant crisis going on, and the rise of Islam (and attacks related with, i might add) there are many legitimate concerns that Europeans wish to express. However these are stifled by leftists trying desperately to virtue signal how enlightened and all loving they are, (you'll see a LOT of that on reddit) and flat out ignored by politicians. \n\nWhat do people do when they feel like they're being ignored? They start to get angry, they WANT to be heard, and as a result they feel like if their politicians aren't looking after their best interests, then it's time they elect ones that do. \n\nIt's very clear for example that Merkel has a very low value of Germany as a nation. She's been filmed disapprovingly removing a German flag from the stage at a press conference she was doing. Now most people could get past that, if they felt like their politicians were looking out for them, but seeing your nations flag tossed away, even if you aren't a nationalist, is often seen as indicative of a disdainful attitude to you. \n\nThen you look around and see crime on the rise, or your culture moving away from the values it has held for hundreds, maybe thousands of years and want them preserved. \n\nRemember also OP that we live in a world that pretty much automatically see's nationalism as racism at this point, so actually research these 'ultra' nationalist groups you're told about in the media and really ask if their views are so outlandishly hateful.",
"Because that's what the media wants you to believe. It's no longer acceptable to believe in your own country and its right to self-determination. So even the meekest display of patriotism is described as 'ultra-nationalist'. "
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jln8p | the fed and why people like it and dislike it | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/jln8p/eli5_the_fed_and_why_people_like_it_and_dislike_it/ | {
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"People dislike the federal reserve because they make money out of thin air every year which causes all of our money to decrease in value. This is much like a hidden tax on your currency on top of the taxes you already pay, and people hate taxes. At times they seemingly make money according to no set rules or plan, or for reasons that do not benefit us, and this often does very bad things to our economy.\n\nIf we however had a set amount of money in circulation and that never changed all of it would increase in value every year until the point in some distant future where a penny could buy a car, so there is reason to create money, they just do it to a point where goods cost more every year (even as the technology for making them becomes less expensive) instead of keeping the value of currency about the same, which from my point of view is better.\n\nWho gets the money that is created? Banks, the money is created from out of nowhere anytime a bank wants to borrow money to in turn play the role of a middle man to a person who wants to take out a loan from the bank, this is regulated by interest rates the fed sets. They don't necessarily just create X dollars per year, they choose the interest they wish to charge banks to borrow from them, and the lower they set the interest rate increases the amount of money people want to borrow and thusly more money gets created.",
"People dislike the federal reserve because they make money out of thin air every year which causes all of our money to decrease in value. This is much like a hidden tax on your currency on top of the taxes you already pay, and people hate taxes. At times they seemingly make money according to no set rules or plan, or for reasons that do not benefit us, and this often does very bad things to our economy.\n\nIf we however had a set amount of money in circulation and that never changed all of it would increase in value every year until the point in some distant future where a penny could buy a car, so there is reason to create money, they just do it to a point where goods cost more every year (even as the technology for making them becomes less expensive) instead of keeping the value of currency about the same, which from my point of view is better.\n\nWho gets the money that is created? Banks, the money is created from out of nowhere anytime a bank wants to borrow money to in turn play the role of a middle man to a person who wants to take out a loan from the bank, this is regulated by interest rates the fed sets. They don't necessarily just create X dollars per year, they choose the interest they wish to charge banks to borrow from them, and the lower they set the interest rate increases the amount of money people want to borrow and thusly more money gets created."
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1m95vj | why do shark cages have gaps in them, which look big enough for sharks to fit through? | Can sharks actually make their way through these gaps? Or do they have some sort of aversion to tight spaces? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1m95vj/eli5_why_do_shark_cages_have_gaps_in_them_which/ | {
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"Could be because most dangerous sharks are still too big to get in. Could also be that if a dangerous shark did get in, the diver could escape.\n\nEdit: I found a video in which a man uses the gap on the side to escape _URL_0_",
"Just an idea:\n\nOne might be that a lot of photography is done in cages and they need the gaps for viewing.\n\nAlso, if the gaps are too small, someone could inadvertently get an arm or leg suck hanging outside the cage."
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45uyjv | why does usb have fewer reliability issues than older interfaces? | NES cartridges are famous for their unreliable connections. We've seen people blowing on them to get games working. Also, I've had experience with (relatively speaking) more recent consoles like the DS or Gameboy having intermittent issues (needing to be re-inserted) as well. On the other hand, I still have USB devices and ports from the same era that rarely (if at all) require re-insertion to work, and most don't have any issues at all. How come USB, with its higher transfer speeds, fewer data lines (less redundancy?), and smaller contacts (think Micro USB) maintain connection integrity? Are there any software features that USB has to make it more reliable or is it mostly hardware design? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/45uyjv/eli5why_does_usb_have_fewer_reliability_issues/ | {
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"Not an engineer or anything, but i'm pretty sure that NES and other cartridges used many like 20+ connections. the more connections there are the more likely one or more of them might be unstable or slightly disrupted. Blowing them clears dust away which is usually the culprit. \n\nUSB's are designed so it really doesn't matter if a bit of dust gets in because the four (reasonably spaced, and also usually fairly high quality) connections contact quite snugly. With four connections versus say 16 the chance that one faulty connection will disrupt the traffic is much less.\n\nNow i don't know anything about the algorithm used to maintain and error-check the connection but others will surly oblige. But think of it like \"less is more\".",
"Nes cartridges were designed by a relatively small team - Nintendo, to be specific. USB is an international industry standard designed and tested by a much larger group *with different economic goals than Nintendo*. If a USB maker's product is unreliable, then customers -which are other companies, not individuals- are free to buy more reliable hardware elsewhere. \nUSB was designed so that devices work together with the least fuss possible. Nintendo's design team had an economic \"life expectancy\" - that is, how long will the market be interested in buying any one cartridge? How long will a console have market viability? If no one is going to be buying that console or its cartridges ten years from now, it's a waste to design for greater longevity. This is *not* stereotypical \"planned obsolescence\". This is just good business sense. But USB was intended as a single interface that would replace most, if not all physical interdevice interfaces in an era where wireless interconnections were advancing rapidly. ",
"The problem with NES cartridges is that they used an unnecessarily complex mechanism for aesthetic purposes. Nintendo wanted to capture the look & feel of a VCR to distance itself from other cartridge-based consoles. You need to remember that the NES came out following a *major* crash of the video game industry.\n\nLater NES models and the SNES used standard card-edge connectors and had very few problems with getting connected.",
"USB was actually built to be hot pluggable, so they've got the ability to shut it down, reload it, and refresh the drivers, device everything HOT. This means that if there's a hiccup, timing issue, or crash during load they can handle it. Whereas the old games and such were built very bare bones, streamlined for speed and performance, and much simpler and older languages in use. If there's a hiccup, timing issue, or a crash when it loads.. it has nothing to handle it, you need to reinitialize it to make it work. So, you have to turn it off, make reseat it, and power it back on."
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7apbrs | why every storm we get the radar shows it moving one way but the wind blows the opposite? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7apbrs/eli5_why_every_storm_we_get_the_radar_shows_it/ | {
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"You’re probably feeling the inflow feeding into the storm. Inflow winds will blow toward the storm system and be fairly warm. Outflow winds will be colder (rain cooled) and blow away from the storm. \n",
"Because the wind is not pushing the storm along. That's not how storms work. Wind moves from areas of high pressure, to areas of low pressure. A storm front is a low pressure area, so wind will flow from the high pressure area in front of the storm, back into it. This also moves the storm, because as the wind moves it moves the low pressure area along inn front of the storm. Of course there are many other factors involved, such as warm and cold air, up and down drafts, etc.",
"This detail depends entirely on where you are located.\n\nHowever, when this happens, the main reason is that the air different altitudes is moving in different directions. Storm clouds are typically thousands of feet above ground level."
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18vrg9 | in islamic countries, how are women who wear a face veil identified for official purposes? | There's a lot I don't understand here, not least how they identify each other in everyday situations. But what about getting a passport, visiting a prison, getting a library card, getting a driver's license (not relevant in ~~Iran~~ Saudia Arabia (thanks to buried_treasure) I know), passing through airport security or getting a bank card? The list goes on.
If you're wearing a [burqa](_URL_0_), a [niqāb](_URL_2_), or most of all a [boshiya](_URL_3_) then you won't be able to be identified at all.
I suppose someone will say that they just take them off but the Qur'an is really clear about who they can reveal their 'modesty' to. _URL_1_
I should clarify. I'm not just interested in how they're IDed in Islamic Countries but also how they're identified on entry to non islamic countries or when going about their business there. Could a women entering the United Kingdom with a face veil be asked to raise it?
Another edit: this is the passage that makes me wonder about female inspectors;
> [Women] should [...] not display their beauty except to their husbands, their fathers, their husband's fathers, their sons, their husbands' sons, their brothers or their brothers' sons, or their sisters' sons, **or their women**, or the slaves whom their right hands possess, or male servants free of physical needs, or small children...
Bold is my own. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/18vrg9/in_islamic_countries_how_are_women_who_wear_a/ | {
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"I don't know for sure but I believe that women go into a private area and show their face to a female officer. ",
"As I live in an arabic country, I can tell you, that on their passport, or official ID card, women have a picture of their face. This is taken by a female photographer.\nAt official purposes (such as imigration on the airport) they lift it just enough that the officer can check and the camera can scan the face.",
"In most Islamic countries there are separate sections for females where women officials work, like in airport the search for females is done is a separate room and same goes for everything else. ",
"When I lived in the middle-east (Oman), it was not uncommon to see women with everything covered except their face so it was relatively simple to identify them. As far as I know, women you are really orthodox and wear the full niqab, almost never have to do anything that requires them to show their face and depend on their husband or father for all their needs. I'm sorry if this sounds insensitive but they hardly ever leave the house and if they do, they are accompanied by their husband who vouches for their identity if needed. I remember seeing a few counters at the Govt offices that were staffed by women that served women who were in niqab. I hope this helps a bit even though I dont have a definite answer for you. \n\nEdit: words",
"Just to clarify a point of confusion:\n\nWomen in Iran are allowed to drive cars (although not ride motorcycles).\n\nIt's Saudi Arabia that refuses to grant women even that extremely minor privilege.",
"Women can and do drive in Iran, they even drive motorcycles often in downtown Tehran. It's only in Saudi Arabia that women aren't allowed to drive. ",
"Face veiling is very rare in iran, so not really an issue. very devout iranian women wear the chador not a burqa/niqab so identification is fairly simple. airport security does have separate queues but the reason for this is mainly to avoid getting frisked by a man.",
"I used to live in Iran and hated wearing the hijab, after reading this thread I guess, shit could have been worse! \n\nIn Iran women mostly cover their hair, not their face. ",
"In Egypt, where the niqab is not common but around, the government's attempt to control social culture and forcibly secularize the society during its mini-civil war with Islamists in the 1990's resulted in them barring women with niqab from entering government buildings and schools for a good portion citing \"security concerns\". If a government feels like suppressing Islamic customs, odds are it will do so and face the political consequences.",
"I remember there was a some sort of eye scan method when entering UAE (through Dubai airport) for the women who wore traditional clothing. Others took the normal passport line. Although Sheik families didn't really have to identify through the eye scanner, if I understood it right.",
"A girl in a veil had to be identified while registering for courses at a UK university. \n\nShe was taken to a screened-off area and nearby men were asked to vacate the vicinity. Her identity was then verified by a person of the female persuasion. \n\nThis way her dignity and her religious beliefs weren't compromised, and the University was able to confirm her identity. ",
"I once read that a woman's passport in Saudi Arabia showed a picture of her husband (or father or other male legal guardian). It worked because women never travelled unaccompanied. Was that incorrect?",
"I live in a western country with a very large Islamic population. Passport and ID card pictures here are 99% of the time taken by a machine instead of a person of any gender. The rules regarding the biometric photos state that women must remove head/face coverings (including stuff like glasses). ",
"Women in Iran do not have to cover their faces.",
"They are allowed to show their face. The extra concealing things they wear, like the burqa, are not mandatory, they are optional. Most muslims wear the hijab which only covers the hair and nothing else. The extra stuff is just tradition.",
"Women can drive in Iran.\n\nSource: my moms Iranian Drivers License",
"I lived in Kuwait and at any location where a search or ID was required, there was a female officer available to do it, and often they would go off into a little booth with a privacy curtain to do it. I have no idea if this satisfies the Koran but its what I saw.",
"They are identified by the men they are forced to travel with anywhere they go",
"Am I missing something completely obvious cuz nobody else seems to be asking this... but why did command+f \"fingerprints\" bring up nothing? \n\nSurely the answer should just be: \"fingerprints.\" No? \n\n",
" > Could a women entering the United Kingdom with a face veil be asked to raise it?\n\nThis actually crops up from time to time. The short answer is, it depends how PC the country, it's media, and policy makers are feeling at the time. Sometimes, you will have specialised female officers who will carry out whatever ID checks need to be done. Other times, no checks/minimal checks will be done out of fear of being labelled a racist or xenophobe.",
"\"Or their sisters' sons, or their women\" is one contextual statement.\n\nIe, their nephew's wives are allowed.\n"
]
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"http://en.wikipedia.org/wiki/Islam_and_clothing",
"http://upload.wikimedia.org/wikipedia/commons/thumb/b/be/Woman_in_burqa%2C_Aleppo.jpg/496px-Woman_in_burqa%2C_Aleppo.jpg",
"http://mythousandtrinkets.weebly.com/uploads/7/1/2/6/7126647/7899797.jpg?279"
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2lfujj | how does net neutrality continue to be threatened through legislation? haven't we already shot this down? | In reference to a [recent guardian article](_URL_0_). I feel like every few weeks net neutrality is being threatened. Don't courts say "yeah, we've already been through this" and put it down automatically? Something, something, legal precedent. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2lfujj/eli5_how_does_net_neutrality_continue_to_be/ | {
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"Unfortunately, there's no \"double jeopardy\" on bad legislation. They can try and try and try to pass it as long as they want.",
"It's not enforceable I don't think. Plus, the big companies that push for these bills to pass probably won't ever stop really. They want more money, they'll do whatever it takes."
]
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"http://www.theguardian.com/technology/2014/nov/05/net-neutrality-protest-hybrid-fcc-solution"
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8mstu1 | how does fat in the body create more flesh? | And when you lose weight how does the extra flesh vanish? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8mstu1/eli5_how_does_fat_in_the_body_create_more_flesh/ | {
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"You have dedicate fat cells that are specialized in storing energy as fat. To if you eat more food that you need you can stor it as fat in those cells.\n\nIf you eat food with less calories then you need you start to remove the fat from the cells and use it for energy. When you use fat for energy you convert fat+oxygen- > water +carbon dioxide. \n\nThe carbon dioxide is exhaled from you lungs to the air. The water is used or excreted like other water you drink.\n\nSo you convert fat stored in the body to thin that you excrete so you lose weight."
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4azd1j | what the scientific meme is? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4azd1j/eli5_what_the_scientific_meme_is/ | {
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"Are you talking about the Sociological concept of a meme? Well essentially it's a thought virus, a concept that quickly spreads from person to person. Most cultural norms would be considered memetic in nature."
]
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[]
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||
co7azr | what happens in the brain when you decide to move a hand or leg? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/co7azr/eli5_what_happens_in_the_brain_when_you_decide_to/ | {
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"It is a VERY long answer in reality, but I'll try to make it short. Your brain sends signals from the zones that are responsible for initiating movement to the muscles needed. It generates this signal based on various information (sight, balance, etc).\n\n\nWhile the muscles contract and perform said movement, your cerebellum, eyes, and inner ear check for any error and correct it by sending appropriate signals to the brain (that then convey the signal to the muscles to correct any error).",
"Somewhat related, but there’s a rather prominent theory that you don’t actually “decide” to move your hand or leg, your hand or leg moves for whatever reason (you get an itch etc) and your brain creates this narrative of choice in order to explain why it happened. Many studies have found that conscious experience of events happen after the sensorimotor processing."
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4as22c | the situation in brazil right now. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4as22c/eli5_the_situation_in_brazil_right_now/ | {
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"Okay.\n\nBrazil's economy is really bad right now. The public are blaming corruption at the federal level. President Dilma Rousseff is being accused of altering the countries financial records to make Brazil look less in economic disaster. She's also being accused of being involved in a grand scheme by many involved in her political party, the Workers Party, to use public funds for their own use by exploiting government contracts from a large corporation, which she was formerly the head of the board for.\n\nHer predecessor as President, Lula, had his phone calls tapped and it looked like he was aware of this corruption. The current president has made him immune to prosecution by appointing him as a minister on her cabinet. (He can now only be prosecuted by the Supreme Court.) Lula had been arrested and interrogated about these corruption charges.\n\nBasically, the public is sick and tired of the massive rampant corruption in the highest level of the government, but the President is not going to step down and she's claiming that all of this is a smear campaign meant to keep the Worker's Party, which was elected due to their socialist promises to help the poor of Brazil, from being re-elected.",
"Basically, the ex-president Luis Inácio Lula da Silva is under investigation in several corruption schemes alongside several other politics. During this week, more evidences surfaced and even a delation that digs his grave even deeper surfaced. Clearly he's been up to no good, most of the country knows this already. \n\nThe current President, Dilma Rousseff, seeking to save Lula's ass, offered him a position as a Minister (which he accepted) so he can avoid being judged by the Judge Sérgio Moro and gets judged by the Supreme Court of our country. That gives him time to recover and he could possibly buy his way out of the prison if he were to deal with them.\n\nThen, Judge Moro gave the order to tap Lula's phone so they could seek for more evidence of his crimes and, presumably, issue a preemptive arrest to keep the lawsuit against him going. In some of the recordings, Lula makes fun of the nation, insults the justice, and, in a talk with the president, it's mentioned the nomination is just a \"free out of the jail card\". \n\nThe people are asking for the President to step down because she's also involved in corruption scandals and she's harboring a known criminal with their own gain in mind, among other things like raping the economy with populist actions, cutting money from important things, and etc. \n\nSorry for my English, not a native. Hopefully this is easy to understand! "
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3itapo | why are some people so smart without even trying? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3itapo/eli5why_are_some_people_so_smart_without_even/ | {
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"I think there was some study about this saying that the brains in smarter individuals actually process information at a faster rate than average. Since the signals are going much faster, the brain can make links to similar situations/memories more quickly.",
"Genetics, just like some are born with faster building muscles, some are born with a brain that can make connections and send signals faster. ",
"I think smarter people tend to run simulations in their heads of the different possible scenarios and do types of ratios for different situations. \n\nThe rate that they logically go through those steps and calculations is probably faster than someone who is less intelligent. ",
"The path to knowledge is awareness.. Awareness is your everyday experience of everything. Letting yourself be open, and letting yourself think past areas you usually wouldn't (without being ridiculous) and having curiosity about the fabric of life and the universe, and a desire to understand without bias... Will lead you to having a whole bunch of basic understandings, upon which you can build upon and test against modern theories (keeping in mind everyone is just a person, and truths are re-written throughout time).. So that your understanding of the whole is -understood- rather than -memorised- from an external source. But, you have to make sure it's a real thing, the understandings that you have... If done without respect to the mental structure and societal structure, can lead to mental illnesses. (Psycosis, Alienation, Depression, Anxiety, ect.)Watch your ego, question everything, stay healthy. And you'll do much more with your brain than the majority.\n\nEdit: \nIt also has alot to do with things such as genetics, up-bringing, willingness to learn, passions, goals, environments, the potentiality to be affected by mental stigma... ect..\nGenerally, you have to think past everything that you know and form true conclusions... \n\n",
"Usually people who \"gets things quickly\" are able to do so because they can link a new concept to something they already know. If you spend a ton of time studying math, you will understand new concepts quickly. If you don't spend a lot of time studying, new concepts will have no context. ",
"Depends on how you define smart, do you mean about in terms of language, art, mathematics, coordination, memory or problem solving? It all comes down to genetics and how that persons brain is wired. Some people can draw/paint what they see, sure practice is needed but true artists have a gift they don't understand. Some people can play what they hear without any significant training. Creative problem solving would have to be one of the least understood gifts, some people can design solutions without having any real understanding of the individual components."
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1k3g1h | how is the universe constantly expanding when there is no edge? | I have heard explanations before but still never really got my head fully around it. How can there be no edge (it be infinite) and still be expanding? how can it expand on infinity? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1k3g1h/eli5_how_is_the_universe_constantly_expanding/ | {
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"The space between two points grows. Literally the space between them. It's not expanding *into* anything, and therefore the edge of space never becomes an issue.\n\nThe space between the Milky Way and the next Galaxy (in this case, Andromeda) literally grows. It just grows a very small amount. On a solar system-scale, the effect can be ignored. On a Galactic scale, it's negligible. Even on an *intergalactic* scale the space that gets added between galaxies is miniscule. But over the scale of the universe, over a long enough period of time and between objects on opposite sides of the observable universe... the effect is really quite large. \n\nSo the answer to your question is that space itself grows larger over time. "
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mixtb | how do escort ads still exist and how are they not all set ups? | I heard something on NPR not too long ago about backpage still having an escort section and I'm confused how they could even operate one. Would law enforcement just bait and hook all ads and how is that even legal to have those ads in the first place? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/mixtb/how_do_escort_ads_still_exist_and_how_are_they/ | {
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"A former escort posted an AMA, and explained it (I can't find a link, but she did it recently). Pretty much, you just pay for an escort's time. Whatever you two decide to do is between you guys.\n\nAt least according to this woman who worked in the UK.",
"I believe that \"escorts\" get away with prostitution because it's claimed that you paid for the escort but the sex was an unrelated activity that just happened. ",
"ELI5: have you been browsing my web history?!?\n\nThere are certain people who enjoy pie. They form an online community of pie lovers and pie makers. The pie makers get rated on their pies, from appearance to quality. If a pie maker hers a bad reputation, pie lovers will avoid in the future.\n\nSometimes, a new pie maker comes along. Usually, someone from the community of pie lovers will try the new pie (taking one for the team).\n\nThe pie lover isn't paying to eat the pie, but only to spend time with the pie. If the pie gets eaten, then it's between the pie lover and pie maker.",
"A couple points:\n\n - Escorts operate by you donating money to them, in return, they spend time with you. Escorts don't advertise explicitly what they'll do in that time, but you can infer what they'll do based on the type of advertisement. I knew one gal who was a professional escort and a good half of the guys contacting her just wanted to go out for dinner or go to a work party with a date. Other ads make it pretty clear that you're spending money on their time, and if they choose to do something sexual with you, that is something they're choosing to do while with you. It may sound like they're just playing with words, but it is an important distinction.\n - There are many, many cities out there. A quick look at Backpage shows at least a good 150 cities. Coordinating such traps would take a lot of time, money, and resources. Not to mention that, because you're hiring an escort and not a prostitute, you can just say that you were paying to spend time with them (which is true, even if you were hoping to get sex out of the deal). Proving an intent to pay for sex can be hard to do.\n - And if it isn't clear by now, there really isn't any legal steps they can take to take these ads down. There is no legal grounds for forcing a site to take down ads which don't advertise prostitution. The site may be forced to take down ads explicitly advertising prostitution, but even then, they could deflect that to the person who posted it.\n - As a last point, the reason that escorts haven't been made illegal is because it is a slippery slope. Not being able to pay someone for spending time with you branches into a number of innocent professions. Also, you can be sure that the pornography industry would block any steps that would make it so they couldn't pay their actors for their work.",
"Basically, an escort transaction breaks down into a series of actions, none of which is illegal on its own or in combination with the others, and most of which (other than the use of the term \"escort\") differ little from things that could occur in any ordinary online dating scenario:\n\n* A woman posts her name and contact info on a website: no illegal act committed.\n* She types the word \"escort\" beside her name: no illegal act committed.\n* A man finds the info and contacts the woman: no illegal act committed.\n* Man and woman meet and go somewhere together: no illegal act committed.\n* Man, of his own volition, gives woman some money (without any explicit or proveable link with sexual activity): no illegal act committed.\n* Woman and man have sex, both voluntarily: no illegal act committed.\n\n",
"Here in Australia, it's completely legal. \n\nCheck out our [yellow pages](_URL_0_) on the subject.\n",
"A former escort posted an AMA, and explained it (I can't find a link, but she did it recently). Pretty much, you just pay for an escort's time. Whatever you two decide to do is between you guys.\n\nAt least according to this woman who worked in the UK.",
"I believe that \"escorts\" get away with prostitution because it's claimed that you paid for the escort but the sex was an unrelated activity that just happened. ",
"ELI5: have you been browsing my web history?!?\n\nThere are certain people who enjoy pie. They form an online community of pie lovers and pie makers. The pie makers get rated on their pies, from appearance to quality. If a pie maker hers a bad reputation, pie lovers will avoid in the future.\n\nSometimes, a new pie maker comes along. Usually, someone from the community of pie lovers will try the new pie (taking one for the team).\n\nThe pie lover isn't paying to eat the pie, but only to spend time with the pie. If the pie gets eaten, then it's between the pie lover and pie maker.",
"A couple points:\n\n - Escorts operate by you donating money to them, in return, they spend time with you. Escorts don't advertise explicitly what they'll do in that time, but you can infer what they'll do based on the type of advertisement. I knew one gal who was a professional escort and a good half of the guys contacting her just wanted to go out for dinner or go to a work party with a date. Other ads make it pretty clear that you're spending money on their time, and if they choose to do something sexual with you, that is something they're choosing to do while with you. It may sound like they're just playing with words, but it is an important distinction.\n - There are many, many cities out there. A quick look at Backpage shows at least a good 150 cities. Coordinating such traps would take a lot of time, money, and resources. Not to mention that, because you're hiring an escort and not a prostitute, you can just say that you were paying to spend time with them (which is true, even if you were hoping to get sex out of the deal). Proving an intent to pay for sex can be hard to do.\n - And if it isn't clear by now, there really isn't any legal steps they can take to take these ads down. There is no legal grounds for forcing a site to take down ads which don't advertise prostitution. The site may be forced to take down ads explicitly advertising prostitution, but even then, they could deflect that to the person who posted it.\n - As a last point, the reason that escorts haven't been made illegal is because it is a slippery slope. Not being able to pay someone for spending time with you branches into a number of innocent professions. Also, you can be sure that the pornography industry would block any steps that would make it so they couldn't pay their actors for their work.",
"Basically, an escort transaction breaks down into a series of actions, none of which is illegal on its own or in combination with the others, and most of which (other than the use of the term \"escort\") differ little from things that could occur in any ordinary online dating scenario:\n\n* A woman posts her name and contact info on a website: no illegal act committed.\n* She types the word \"escort\" beside her name: no illegal act committed.\n* A man finds the info and contacts the woman: no illegal act committed.\n* Man and woman meet and go somewhere together: no illegal act committed.\n* Man, of his own volition, gives woman some money (without any explicit or proveable link with sexual activity): no illegal act committed.\n* Woman and man have sex, both voluntarily: no illegal act committed.\n\n",
"Here in Australia, it's completely legal. \n\nCheck out our [yellow pages](_URL_0_) on the subject.\n"
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24zw90 | why isn't there a list of ingredients on a pack of cigarettes, when it seems like anything else you buy has that information on their products? | I mean there is sugar in some cigarettes. Shouldn't there be a nutrition label on it as well? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/24zw90/why_isnt_there_a_list_of_ingredients_on_a_pack_of/ | {
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"There are labels in Canada...",
"Same reason there isn't an ingredients list on beer (assuming you're asking about the US). Food is regulated by the Food and Drug Administration, under the Department of Health and Human Services. Alcohol and Tobacco are regulated by the Alcohol and Tobacco Tax Trade Bureau, under the Department of the Treasury. Because of this, tobacco products don't have to comply with the FDA's labeling rules. ",
"Not enough space for all the large chemical names to fit on the tiny package at least big enough for you to read"
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bdmzgc | how is it that your veins/arteries don't simply cut off whenever you sit or compress the body in normal circumstances? | When you sit, what makes it so that our veins/arteries don't just immediately close under the pressure of your weight? Like a hose being cut off by someone standing on it. I understand that there is blood pressure, but is the heart really that powerful to create pressure that can suspend the veins/arteries enough for blood to pass? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/bdmzgc/eli5_how_is_it_that_your_veinsarteries_dont/ | {
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"For the most part veins and arteries are not on the surface so simply sitting won't compress them enough to \"cut off\" flow, but it can be significant enough to reduce flow to the point your leg \"goes to sleep\" , also why you should not have legs crossed when taking your blood pressure, etc. \n\nAlso the circulatory system is remarkably complex and closing one pathway often is compensated for by blood rerouting through alternate, less restricted, paths.",
"Many major vessels are fairly well protected by muscles and fat. Also vessel walls are fairly tough and can maintain their shape. Blood pressure does play a role in keeping the lumen (hollow part inside vessel) open, but I think for your question the better answer is just the veins and arteries being pretty well protected. \n\nIf you do put enough pressure on a vessel it will cut off flow (i.e. tourniquet) but you won't have immediate tissue damage. We use pneumatic tourniquets in the O.R. when doing some surgeries on extremities like hands, feet, or knees. But the maximum time they can stay inflated is 1-1.5 hours."
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55nfvu | p-hacking and how to detect it? | _URL_0_
> look for “p-hacking” by examining the distribution of p-values in the included studies
How does that work?
What is p-hacking? How and why do researchers do it? How can authors of meta-analyses detect it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/55nfvu/eli5_phacking_and_how_to_detect_it/ | {
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"The [paper that coined the term p-hacking](_URL_0_ ) is online, and an interesting read.\n\nTL;DR: P-hacking is the use of data mining to find patterns in data that can be presented as statistically significant, without first devising a specific hypothesis as to the underlying causality. Then a hypothesis is constructed that matches the previously found data.\n\nThe example from statistics is that 1970-1990 the Dow Jones index growth for the year is almost identical to the New York Yankees baseball game winning percentage.",
"_URL_0_ is probably the simplest example.\n\nSuppose you run a test on your data and find something that's highly unlikely to occur purely by chance: in fact, there's only a 1% probability it could occur by chance.\n\nThat result would seem important, unless we learn that you've run over 100 (independent) tests on your data. At that point, we'd say it's not important, because you've run enough tests to \"insure\" you'll get some unlikely results purely by chance.\n\nThe more tests you run, the worse it gets. If you run \"parametrized\" tests (where you combine test data using different weights until you find the \"best fit\"), the situation is worse, since you're effectively running an infinite number of tests (albeit not independent) with a very high chance of purely coincidental success.\n\nI could say a lot more about this and how it's been used to massively defraud people, but to answer the other part of your question:\n\n1. Insist on hypothesis PRIOR to experimentation. In other words, the experiments should test a given hypothesis. You should not use the experimental data to retroactively create hypotheses.\n\n2. Insist on replication. This is really the same as (1). If your experimental data shows an apparently important result, the result is null and void until you create a new separate experiment to test it. Simply using random coincidences in one study is insufficient evidence.",
"A lot of science and social science leans heavily on the [hypothesis testing](_URL_0_) regime, which is a systematic way of formulating and deciding whether to reject hypotheses. Probably one of the simplest examples of when you would use hypothesis testing is when you're trying to decide whether two randomly selected groups have a different mean. Suppose I wanted to know whether people who ate corn flakes as a child tend to be taller on average. I collect a large sample X of 1000 people who ate corn flakes, and another 1000 people Y who did not. In order to do the test, I will take the average height in the two groups and compare them. Now, we know that it's nearly impossible for the two samples groups to have the *exact* same sample mean. They will differ by some amount u = |mean(X) - mean(Y)|. But if the two *populations* have the same mean height, then we can figure out how likely it would be that our samples would differ by (at least) u. This probability is called a p-value, and it's at the heart of the standard hypothesis testing regime.\n\nI'll state it again because it's subtle and sometimes a little bit difficult to understand. We have collected numbers: the sample mean height of X and the sample mean height of Y. If we assume that the population means E[X] and E[Y] are the same, then under that assumption we can compute the probability that they would differ by u, which we call a p-value.\n\nNow, if our p-value is fairly large, say like 0.7, we should say something like \"well we didn't get u = 0, but we did get a u that would happen about 70% of the time, so this is would be a pretty typical result if eating corn flakes has no effect on average height.\" But if the p-value is small, say like p = 0.001, we'll say something like \"if corn flakes don't have an effect on height, then we have collected a very rare sample that would only happen about a tenth of a percent of the time. The most likely explanation is that cornflakes actually *do* have an effect on height.\" That is basically how hypothesis testing works.\n\nIn order to systematize this procedure, we need to pick a threshold for deciding whether p is large or small. The consensus in social sciences and other places is to use 0.05 as the threshold. So if we collect our two sample means and compute a p-value for the null hypothesis that the populations are the same, and we get a p-value of less than 0.05, we will conclude that we have *statistically significant* evidence that there is a difference in the means. Otherwise the evidence is not statistically significant.\n\nThat's the theoretical underpinning of p-values and hypothesis testing. But there are also some practical concerns: namely, we want to publish a damn paper. But nobody is interested in publishing a paper that says that corn flakes *don't* cause height imbalances between groups. So what can we do? Well, one thing we could try to do is go out and try to collect another couple of groups and do the experiment again. Another thing that we could do is start looking at subsets of the data. Maybe cornflakes don't make *everyone* taller, but maybe they make black people taller. Maybe they make people with blonde hair taller. Maybe they make women taller. You can look at all these subgroups and keep on doing the same hypothesis test, computing a p-value for the difference in means between the subgroups and seeing if it's less than 0.05.\n\nBut since a p-value computes the probability of seeing an effect size when there actually is no effect, then if there really isn't an effect, we should expect to see a \"significant\" result about 1 out of every 20 (0.05) experiments. So if we just keep chopping it up in different ways, we're bound to find one way where p < 0.05 eventually, which gives us the \"significant\" result that we're looking for.\n\nSo when we inevitably find out that corn flakes make people colourblind people who were born on a Tuesday taller, we can just claim that that's what we were trying to find in the first place and publish our paper. But really, we didn't discover anything. We just found one of the totally expected cases where the p value was less than 0.05 by chance."
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2xrqsk | why is honey and lemon good for singers when it never gets near the vocal cords? | or any fluid for that matter. if it bypasses our throat (and it does) how is lemon and honey going to have any effect whatsoever?
Water I understand as it hydrates from inside. But honey and lemon? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2xrqsk/eli5_why_is_honey_and_lemon_good_for_singers_when/ | {
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"Not sure what the honey does, but lemon water helps cut the phlegm in my throat. Makes it so I can sing without rattling or hitching.",
"Lemon is an astringent, in small amounts it will help clear mucous from your throat.",
"tl;dr: Its soothing, tastes good, promotes blood flow in the dried out, possible irritated tissues, and forces you to close your mouth and stop breathing across your throat tissues allowing them to re-hydrate.\n\nOne of the side effects of singing is diminished ability for saliva to lubricate the throat because its production is minimized and in spite of the air coming out of our lungs being moist, it is not enough to make up for having so much air flow and having your mouth open for so long without swallowing normally.\n\nShort version: it doesn't directly interact with the vocal folds (other than minute amounts of \"runoff\" as the glottal area closes off the windpipe), but it does help all of the other surrounding tissues by stimulating blood flow and providing direct moisture to the tissues above the opening of the vocal folds.\n\nHoney and lemon taste really good together so it's tempting to use them both although the actual influence of the honey (other than for taste) is debatable.\n\nIt's possible (although as far as I know unproven) that there is something about the reaction of honey and water that helps the tissues absorb more moisture, but I've never seen anything that leads me to believe it.\n\nLemon being slightly astringent is actually probably slightly the opposite of the desired effect so don't use too much. Just a bit for acidity. This \"tang\" causes your salivary glands to begin production.\n\nDoes your mouth start watering when I write \"super tangy, ultra tart, mega lemon\"?\n\nMine does just thinking about a fresh lemon.\n\nHad to swallow just now in fact. :D\n"
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coxf6d | what’s hpv and how does it differentiate from herpes | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/coxf6d/eli5_whats_hpv_and_how_does_it_differentiate_from/ | {
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"Hpv is a skin virus that typically causes warts. Most people have hpv at various places on their body occasionally throughout their life. One type causes genital warts which is an std. herpes is a disease that causes skin blisters and again becomes an std when on the genitals",
"They are both viruses and their symptoms are varied. \n\nThe [Human Papilloma Virus](_URL_1_) (HPV) is not one virus but more than *170* different types, most of which cause no symptoms. Some cause plantar warts which appear on the bottoms of the feet, some cause warts on the hands, knees, elbows, other areas, some are exclusive to the genital areas, and oral mucosa. Some are spread through casual contact, others through contact with surfaces, and others through sexual contact. About a dozen HPV viruses are directly linked to cancerous lesions (sexually transmitted HPV). \n\nHPV is the most common sexually transmitted infection/virus/disease (whatever one wants to call it). \n\nThere is currently no *definitive* treatment for HPV infection (meaning it cannot be cured), but typically the infection clears itself to undetectable levels within ~2 years in 90% of cases. \n\nThere is a vaccine against the more troublesome forms of HPV which lead to cancers in men and women. \n\n\n[Herpes simplex](_URL_0_) (I & II) is a virus that causes varied symptoms (painful, weeping blisters) and is separated into two types based on which areas it usually infects, although each type can occur in any area. Type I more *commonly* affects the oral area and Type II the genital region, but they aren't exclusive. If an infected person has Type I on their lip (a cold sore), they can transmit it to their partner's genitals via oral sex and vice versa. \n\nTransmission may still occur even when symptoms are not present but the risk is low. \n\nHerpes can occur on the hands, referred to as Herpetic whitlow, caused by Type I or II. \n\nAfter initial infection with Herpes, the virus travels along nerve pathways and becomes dormant in the nerve ganglion (a cluster of nerve cells). People often have reactivation of the virus due to non-specific causes but there may be an immune system link, such as when one comes down with a febrile illness, coincidentally, a \"cold-sore\" will appear as well. In others, it may show up in cyclical time with menses. The symptoms may appear along the same nerve pathway of original infection, or in other nearby areas also served by the nerve ganglion.\n\nThere is currently no vaccination available against Herpes simplex.",
"HPV is the 'Human Papilloma Virus' \n\nHerpes is HSV, 'Herpes Simplex Virus'. \n\n\n\nThey're two different viruses that affect the body in similar ways, kind of like how the cold and flu both cause upper respiratory tract infections. \n\n\nHSV and HPV both have genital and non genital virus types, both cause lesions or growths, both are linked to an increase in certain types of cancer (typically cervical). Herpes tends to stay on mucus membranes (mouth, genitals), HPV can infect the skin (hands, feet, etc). Just slightly different presentations."
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6c7tfi | is there a highest temputare the human body can feel? | can the human body tell the difference between a 1000 degree flame and a 1001 degree flame, and than a 1002 degree flame? Also is there a max temperature in total where after that you won't feel any more pain no matter how hot the fire is? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6c7tfi/eli5_is_there_a_highest_temputare_the_human_body/ | {
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"Well first, I don't think someone would notice the slight change of temperature. It's like feeling the difference between 73 degrees and 74 degrees but hotter. Also the heat would start to burn your skin and damage nerves which would tell your brain that it is hot. So the highest temperature someone could feel is the temperature is when their nerves are damaged enough to where they can't feel anything.",
"It is easier to think about this in percentages, going from 1000 to 1001 is only a change of 0.1% while going from 10 to 11 is a change of 10% (Assuming absolute quantities). This is just [Weber's Law](_URL_0_). I don't know what the difference threshold is for noticing a change in temperature, but it is most likely much greater than 0.1% so you would not feel a difference between a single degree at such high temperature. ",
"Seeing as how we all are roughly 70% water, water boils at 212F, coincidently skin melts at 212F, I would say that once you get to just about there you are going to stop feeling it. In the flip side nerve ending spaetzle is delicious. "
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2t18qe | how can lg and samsung produce amoled or oled screens for phones with great resolutions for relatively low price but can't do the same for tvs? | Basically, phone screens cost around 200-300 USD. Considering TV resolutions and panel technologies, TV's should have been cheaper with the same resolutions but they are not. Why is that? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2t18qe/eli5how_can_lg_and_samsung_produce_amoled_or_oled/ | {
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e5cc5m | why is it so much more difficult to chug cold water vs room temperature? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/e5cc5m/eli5_why_is_it_so_much_more_difficult_to_chug/ | {
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"Ik for me the cold water can make my teeth hurt and kinda gives my mouth and throat a sort of \"brain freeze\".",
"Because it will make your mouth and throat cold and the human body doesn’t like that?"
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5szdv4 | how do we know/guess how many died in historic plagues? | Hello all,
I've done a bit of hunting on the web, but don't seem to be able to clear this up- how do historians arrive at a number for epidemic- related death tolls?
Wikipedia lists epidemics going back centuries, and some of the numbers dead for the Antonine Plague/Black Death are truly astronomical- but it got me thinking- how do they know? I don't doubt many died, but to even get within an order of magnitude of the correct number would seem to be tricky if you are looking back a millennia or so.
Anyone got any experience in this field? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5szdv4/eli5_how_do_we_knowguess_how_many_died_in/ | {
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" > but it got me thinking- how do they know?\n\nPeople wrote stuff down. Even back then it was important if people died, and keeping track of population was important for things like taxation. Researchers can look at a period of time and see how the deaths differed from normal and deduce about how many people died from a certain plague."
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ao0lnx | what's the appeal of 4chan? every time i try to read it doesn't make sense | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/ao0lnx/eli5_whats_the_appeal_of_4chan_every_time_i_try/ | {
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"Much of what happens on 4Chan is what's called shitposting. I.e intentionally posting drivel (either harmless or inflammatory drivel). There are also lots of inside jokes and bits of jargon that originated on that site, which a new viewer might not know. Kind of like how redditors might joke about Kevin, or a young man breaking his arms, or decoy snails.",
"It's somewhere where the raw id of the internet comes out, for better or worse. There's no user accounts, so there's no 'reputation' or 'karma', and there's no upvotes or downvotes, threads are ordered literally by the most recent post in each thread. The principal appeal is that there are virtually no restraints on what you post and what other people post (other than illegal shit) and people have no need to put up any sort of facade the way they would if they were tied to a username.\n\nSo yeah when you get rid of all the constraints you get a stream of mostly garbage, but it's garbage that more authentically reflects the sentiments and thoughts of the posters.",
"I remember when most of the internet was like that, except for email. You crazy whippersnappers today giving out your real names and personal info left and right. *shakes cane*"
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6azgqp | how can we feel tense / bad atmospheres in certain places? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6azgqp/eli5_how_can_we_feel_tense_bad_atmospheres_in/ | {
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"It's a purely psychological effect. The \"atmosphere\" isn't real, but lots of symptoms are -- these can include an odd smell, an unusual quiet, the presence of nervous-acting people, or objects arranged in a manner that's unusually messed up or unusually tidied up."
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2xrpd1 | why do arcades use coins instead of quarters? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2xrpd1/eli5_why_do_arcades_use_coins_instead_of_quarters/ | {
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"I've always thought that people were more likely to spend \"coins\" as they don't see them as money in the same way. Plus coins lock a person into spending a certain amount of money, unlike quarters which can be easily taken elsewhere. ",
"Arcades can also give you more tokens than you would normally get quarters to entice you to spend more and use it all in one visit.\n\nSo, instead of 20 quarters for $5, they can give you 25 tokens for $5 and you're more likely to spend $5 than going to get 4 tokens for a dollar five times. $10 will get you 55 tokens and $20 will get you 120 tokens. \n\nPeople will see that the $20 is the best value and just put in a twenty. \n\nIt's harder to get someone to spend all 80 quarters if they get change for a $20.",
"If they give you real money, they'll have to replenish their supply of coins more often. Some people will just walk in and take out $40 of quarters for their laundromat money.",
"The answers here are good but I'd like to add that it reduces the risk of employee theft. If you have all the currency in a handful of token stations, it's easier to make sure that no employees can pocket that money. If you had every game filled with quarters, you have to deal with the significant risk that the employees who empty them will end up pocketing a few extra bucks in quarters."
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3iyph4 | how does solid state memory work with no moving parts? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3iyph4/eli5_how_does_solid_state_memory_work_with_no/ | {
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"Essentially, Solid State memory functions by creating \"cells\" that can be written on to, and require no energy to maintain.\n\nTo be more specific, like with the interior of a CPU, we encase super-tiny mechanisms called Floating Gate (FGMOS) transistors into divots in sheets of ultra-thin colorless sapphire (like what we use for high end watch faces). These tiny transistors can store very specific electrical charges for exceedingly long periods of time, as they are insulated with highly electrically resistant materials.\n\nWe essentially cram millions of these onto tiny chips, then stack several of these onto a single device. It's worth noting that as transistor sizes get smaller, SSD density rises. This is why a [1 TB USB 3.0 flash drive](_URL_0_) is possible.",
"It depends on the type of memory:\n\n* Static RAM stores data using [flip-flops](_URL_2_) - circuits with two stable states. One state is defined to be \"1\" and the other \"0\". Because the data is encoded in the state of the circuit, static RAM is volatile (it loses it's data when the power is cut). Static RAM is fast but expensive, so it's used for things like CPU caches, where speed is very important.\n\n* Dynamic RAM stores data using capacitors - components that store electrical charge. A transistor is used to control the current flow into or out of the cell. A charged capacitor can represent a 1 and a discharged capacitor represents a 0. Capacitors slowly leak their charge over time, so dynamic RAM must be periodically refreshed, during which the data is read out and then written back again. This happens many times per second. For this reason, dynamic RAM is also volatile. Dynamic RAM is slower than static RAM but requires fewer components for the same amount of storage. Most of the RAM in a typical computer is dynamic RAM.\n\n* Flash memory stores data using [floating gate transistors](_URL_0_). These are transistors that have an electrical insulator between the gate and the rest of the circuit. To turn the transistor on, a high voltage is applied, which causes electrons to \"jump\" across the gap by [quantum tunneling](_URL_1_). Once there, the electrical charge remains in place until a corresponding voltage is applied to remove it. The charge will remain in place even if the device is powered off; so flash memory is nonvolatile. Flash memory is commonly found in portable devices like USB flash drives and smartphones. Flash memory is also sometimes used as an alternative to magnetic hard drives, as they are faster than hard drives since they don't have to wait for the right area of memory to pass under the read head (because there is no read head)."
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5pb8p0 | why is heart cancer so rare? | The heart's an organ just like the brain, right? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5pb8p0/eli5_why_is_heart_cancer_so_rare/ | {
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" > Right?\n\nWrong, the heart is a muscle. (Technically a \"muscular organ\")\n\nThat isn't why there's no heart cancer though. It's because cancer is the unregulated and out of control division of cells that turns into a tumor. But heart cells don't divide, so there's no process to go haywire.",
"Cancer is the abnormal and unstoppable cell growing. Some types of cancer are very common (like prostate cancer) because the cells of that organ are growing continuously.\nThe heart stop growing at a very young age compared to other organs, and the rarer the cells are regenerate, the rarer the type of cancer is. \n\nThat's because heart cancer is such a rare type of cancer. ",
"Cancer is dependent upon cells that actually reproduce. \n\nThe more cells reproduce and replicate the more chances that antigen and genetic changes take place that actually produce cancer. Cancer isn't really a disease but a spectrum of diseases and changes that we call cancer. \n\nThe heart cells do not reproduce so cancer is rare. ",
"This is because muscle cells (also called muscle fibers) don't divide, and cancer is most common in cells that divide a lot. Dividing cells are primed for cancer because:\n1) a lot of the machinery needed to divide rapidly is already present in the cell so not a lot extra is needed to make it grow uncontrollably into a tumor/cancer\n2) the more a cell divides the more chances it has to make errors. DNA replication isn't perfect, and over time these errors can accumulate into dangerous mutations (this is also why cancer is more common in the elderly)\nThis is why we see a lot of cancer in tissues with a high \"cellular turnover\" rate - skin, liver, colon, etc. Cells that never divide (muscle fibers, neurons) almost never get cancer. Brain cancer is usually caused by a special type of brain cell that can divide (but not signal) call neuroglia, which forms the cancerous \"glioma.\"\nBonus biology fact - because muscle cells fibers don't divide, you have the same number your whole life. Arnold Schwarzenegger has the same number of muscle fibers now as he did as a baby, they're just more packed with the good stuff.\nSource - biochemistry major, medical researcher.",
"There is a very rare endocrine tumor predisposition syndrome called the Carney Complex which is characterized by the development of cardiac tumors called cardiac myxomas. Patients can also develop tumors in the various endocrine glands (thyroid, testis, pituitary, etc.). Heart tumors are rare for the reasons others have mentioned, but they are not entirely non-existent. \n\nSource: I got my PhD studying aspects of the Carney Complex.",
"The heart is a muscle, constantly contracting 24/7. It is extremely difficult for cancer cells (or, anything for that matter) to take up permanent residency in a space where there is zero fuel to spare (because it's always being sucked up by the muscle cells of the heart in order to continue to beat). ",
"Hear cancer is rare partly because heart cells rarely divide. Because of that the chance for a cancer to develop is [very small](_URL_0_).",
"From what I remember, In order for a person to get cancer, a cell has to reproduce with a mutation that is considered cancerous. Such mutation would cause that particular cell to keep producing without dying and creating more cancerous cells.\n\n\nHowever, tissues like our muscles don't reproduce, die and repeat, they continue to maintain, grow and shrink as they are needed. The Heart is an organ made mostly of muscle tissue, so it doesn't regenerate any of it's cells. In the event that it does, the new cell may or may not carry a mutation to make it cancerous.\n\n\nI would like to point out that not all cancerous cells are harmful, some are benign. Meaning the cancer cell exists but it's not gonna do any arm. Some are internal, some are external and people are covered in these (think of moles on the skin).\n\n\nHowever, some can turn malignant, the opposite of benign, that's the type you should worry about and your doctor will tell you more about that.",
"Others have given you the answer. I just wanted to mention that there was a Reddit member with heart cancer that did a great AMA about a year or so ago. ",
"A lot of people with super long answers. But here is my short answer. Heart cells don't undergo mitosis as much as other cells in the body. The more your cells divide the more chances there are of mutations that occur which eventually can lead to cancer cells. ",
"People's answers here have been good, but I just came to say that the lack of heart cell proliferation has a flip side in that damage to the heart is not easily repaired. This is why heart attacks can be so detrimental, any cells that die are not likely to be replaced.",
"1. Cancer is a set of diseases where cell division goes wrong and the cells divide uncontrollably. \n2. Your body is made up of many different cell types which have different rates of division.\n3. Skin cells are replaced every 2 weeks, red blood cells every 4 weeks, muscle cells every 16 years.\n4. The heart is made of muscle.\n5. Heart cells therefore divide *very* slowly, making division errors uncommon and heart cancer rare.",
"The heart doesnt change its number of cells much (no hyerplasia) or change cells much (metaplasia). Places like your lungs amd GI change a lot because of their environment and purpose making them susceptible. Like skeletal muscles though, the heart can become larger by the cells becoming larger (hypertrophy) from working harder such as in people with hypertension.\n\nThe grinch's heart didnt grow because of xmas, it grew because of severe hypertension."
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7ns9io | when your body is submerged in cold water, it feels freezing at first, then starts to feel warmer and warmer. when your body is exposed to cold air, it feels okay at first, then gets colder and colder. what causes this phenomenon? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7ns9io/eli5_when_your_body_is_submerged_in_cold_water_it/ | {
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"I'm no expert, but I think it has to do with body heat. In the water, your body heat and the temperature of the water find an equilibrium where both are at the same temperature, whereas in the air, it's always moving so it cools your body while your body heat doesn't have time to affect the air temperature.",
"Not an expert and could be wrong. Water will actually take body heat away about twice as fast as air will. So the average body temp is about 98.6 Fahrenheit. The body is always producing heat through metabolic and kinetic (muscle movement). It just so happens that 98.6 is the perfect temp your body has found for homeostasis. If you were to go into a body of water that was below that at 80 degrees you will start to feel cold sooner. your blood vessels will constrict in you extremities as your body tries to keep blood flow to more important organs (lungs, heart, and the such) to keep them warm. Then you will start to shiver. That's the body's way of producing heat as a last ditch effort. This is why scuba divers will use wet suits to stay warm even if the water is a high 70-80 degree Fahrenheit. Now you can go outside at those temperatures and feel comfortable in little to no clothes. But, if you were in a room set at those temperatures with no other form of energy to warm you up like the sun after a period of time you will get that cold feeling. As to your question i think there could be a couple answers. 1. Your mind tries to block the sensation so you can be more attentive to other things. An evolution perk so predators don't sneek up on us. 2. This might be the major cause. As your body constricts vessels and restricts blood flow to your limbs your nerve endings lose sensation and can't feel as well per say. Also since you have less blood flow to your hands the temperature of your hands drop. Like when you go outside in the freezing cold and then place your hands under room temperature water it will feel hot(don't do this for fun it can cause damage). So both are doing the same thing it's just that water does this faster than air.",
"If you mean cold water as in near-freezing, the warm effect comes from endorphins released to block the painful freezing sensation in order to maintain function to enable you to get the hell out of the freezing water.\n\nI disagree with the equilibrium theories proposed by others, unless you were to be submerged in a body of water that is only a small fraction of your total volume but still manages to cover you. If the water volume is greater than say a third of your own, you will dramatically cool down as the water in your body and the water around you begin to equalize their temperatures, unless measures are taken to increase your own heat generation. \n\nThe body has compensation mechanisms in place to prevent dying rapidly due to hypothermia, including the shivering reflex to increase muscular heat generation and constricting peripheral blood vessels to minimize heat loss from vital organs, at the cost of your extremities cooling down faster."
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2eq3a0 | if the airline industry is struggling, wouldn't it be better for them to sell unbooked seats for less at the last minute than operate at a loss? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2eq3a0/eli5_if_the_airline_industry_is_struggling/ | {
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"To a point, but remember that planes take fuel. It takes a certain amount of fuel to get your weight from A to B. If you want to fly you need to pay them AT LEAST that amount just to break even for the added weight you contribute. ",
"Airlines already do this. It's called \"flying standby\". You can show up to an airport at the last minute and try to get reduced fare for unbooked seats. However, there are a few problems with this.\n\n1. There are rarely empty seats. The budget problems have caused airlines to more frequently *over*book flights. Empty seats are much rarer than they used to be.\n\n2. Flying standby can get you on a single flight, but if you need multiple connections to reach your destination, you may discover that there are no empty seats on connecting flights, and now you're stuck in another city and have to pay full price and wait (potentially for days) to get an appropriate connecting flight either to your destination, or back home.",
"Basic economic models suggest that airliners should fill up every seat of their aircraft no matter how much they sell the last tickets for. After demand is expended at a \"standard\" price, the price should be lowered until the last seat is filled. The airline must pay for transport of a plane from place regardless of whether there's one person or one hundred. And after considering the weight of an entire aircraft, a couple thousand extra pounds won't spend their tickets' worth in fuel.",
"This is kind of handled by people flying stand by. But the most important part of the equation is this:\n\n*If everyone knew that the airline was willing to sell empty seats at cost or at a loss just before the flight, a lot more people would wait until the last minute to buy and they'd start selling MOST seats at cost or at a loss.* \n\nThey'd be digging their own grave.\n\nedit: some formatting",
"They do it to some extent, although lowering prices too much is very bad business practice.\n\n* People who tend to book last-minute NEED the flight urgently and are willing to pay a premium. Suppose if the ticket costs $1,000 and one person books it at the last minute - that gives the airline $1,000 of revenue. If they really wanted to fill up the airline they could reduce it to $200. However, that means that they need to attract at least four more last-minute customers to get the same $1,000 revenue (remember that your first last-minute customer is now happy he got the ticket for $200 when he was willing to pay $1,000!) Your profits also decrease due to extra fuel and service needed to serve the other four customers.\n* Repeatedly doing this trains customers to avoid booking until the last minute (or book cancellable tickets and then re-book at the end). This dilutes your revenue significantly if your pricing becomes predictable.\n* /u/Antechronos is right about flying standby - but realize that you need to show up at the airport at the last minute to do so. This is a tactic that allows the people who are absolutely willing to go through the pain of showing up at the airport to get the discounted ticket, while stopping everyone else from seeing the prices drop and cause the problems mentioned above.\n\nSource: I do revenue management in the hospitality industry.",
"Let's say you manage a pizza delivery place. At the end of every night, there are a few pizzas that got messed up that you need to get rid of, so you sell them for half price. Getting something for them is better than nothing, right?\n\nNot necessarily. If you wind up with a bunch of people hanging out at closing time waiting for a cheap pizza *instead* of buying one at full price, those pizzas might be eating into your regular sales. If you are losing more than one sale for every two cheaper pizzas you sell, you would actually make more money by throwing them away."
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eg3gwb | how can a government block targeted internet access once starlink is available vs traditional isp? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/eg3gwb/eli5_how_can_a_government_block_targeted_internet/ | {
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"The first and simplest way would be to demand that SpaceX stop providing service when the government demands. Almost certainly they are going to agree to do so.\n\nOtherwise the government doesn’t give them a business license and makes doing business with them illegal. Now most people can’t get access because they can’t pay, and it would be very unlikely that SpaceX would want to become involved with overtly illegal business in other countries, regardless of the reason.\n\nBut suppose it is free for some reason. Then the government just makes it illegal to access and flies aircraft over population centers with directional antenna tuned to the frequencies used to uplink to the satellites. They pick out anyone talking back to the satellites and then send some police on the ground to seize the equipment and whoever is using it. That relatively small portion of the population ends up in a mass grave somewhere.",
"A government can just ban the equipment necessary to connect to the network. For example, satellite dishes are illegal in Iran. Given that its hard to hide a satellite dish, enforcement of laws like this is fairly easy.\n\nThe signal that's being broadcast from the satellites is also fairly low powered, which makes it easy to jam. Equipment to jam satellite signals is also cheap and widely available. It might not be cost effective to jam the signal over an entire country with purpose built equipment, but jamming it over the major population centers isn't a big deal.\n\nThe radar systems of SAM installations, like the S-300 and S-400 radars, can easily be reconfigured to jam a satellite signal as well. And the kinds of countries that have good SAM radar coverage also tend to be the kinds of countries that would be looking to jam such a signal. So even if a worst case where there are vast stretches of a country that aren't covered by purpose built equipment, its still likely possible for a country to block the signal over much of its rural territory as well."
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fmzyo5 | how do the graphics card, ram, and processor all work together to determine performance of a pc? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/fmzyo5/eli5_how_do_the_graphics_card_ram_and_processor/ | {
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"CPU is its ability to do math. Everything a computer does is dictated by math, so this makes things faster. However you can't get faster than almost instant (dictated by speed of electrons wizzing around inside) so if the CPU is able to go at that speed, other things may slow it down instead.\n\nThis is where we get to RAM. RAM (Random Access Memory) is the computers ability to remember things quickly. The CPU can't remember things on its down, so if you want it to, say, remember the keys you are typing in your keyboard, it needs RAM to hold that information until the CPU needs it. If the RAM is smaller than is needed, we get issues. On solution is to temporary store information on your hard drive, that that is orders of manitude slower, so your CPU has to twiddle it non-existent thumbs and sit around and wait for the numbers it needs to get to it so it can do more math.\n\nThe Graphics card (GPU) is just another specialized CPU that has it's own RAM built in with it. 3D graphics involved LOT of very complicated math done very quickly. The GPU does that math so the CPU doesn't have to bother and it's custom build to do that specific math very well. If it's not good enough, you graphics will go behind. See the above two explanations for details, as either the GPU or it's dedicated RAM will be at issue. You're CPU can't handle it's own work and modern 3d graphics at once.\n\nThings that do not require 3d graphics do not use the GPU at all, usually. Crytocurrency happens to use similar math to 3d graphics, so that's why those are used for that. Hope that helps!",
"Think of a computer as a restaurant.\n\nThe CPU is the head chef and sou chefs that manages all the tasks and sets up the menus. The faster or more experienced chefs will increase the performance but they are expensive. These chefs work harder and faster than any individual worker but they can't operate an entire restaurant by themselves.\n\nMost of the work goes to the line cooks which are the GPUs. While they are slower and less experienced, there are a lot more of them and they are cheaper to hire. They work in parallel to cook individual steps of a dish and put it together. If they are well trained and work faster, the restaurant can serve food faster. More of them can also increase sales if the restaurant can scale to allow more demand.\n\nRAM is the kitchen space. You need tables to hold ingredients for processing food. More dishes means more tables. GPU RAM is the stoves and cooking areas. Food from the tables (RAM) need to be transfered to these areas for specific processing by the line chefs (GPU). If your kitchen is too small, you will end up with \"too many cooks in the kitchen\" and end up slowing the entire process.\n\nLastly, storage of food is the hard drive space. It takes some time to pull out the food and have it ready for the kitchen."
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69vk5l | why is the tip of the human nose made of cartilage? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/69vk5l/eli5_why_is_the_tip_of_the_human_nose_made_of/ | {
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"The actual reason, although rather vague, is that natural selection leads to traits that are more advantageous for survival to be selected for and thereby become more prevalent in a population. So having a cartilaginous tip to the nose allowed for better survival to reproduction. Probably because the nose sticks out relatively unprotected, and cartilage has some give that is more forgiving when hit compared to bone which would be more likely to break, possibly causing increased bleeding or chance of infection by breaking through the skin.",
"We are descended from other species where the nose is this way, possibly useful in those species as they may press their nose against the ground when following a scent. But in a sense evolution never provides a \"why.\" Some things just grew that way by accident."
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2bg72t | what exactly makes cheap beer taste much worse than something more expensive? | What in the process of brewing beer can be "cheapened" thus making a cheaper beer taste like crap? Is it just more watered down or is there more to it? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2bg72t/eli5_what_exactly_makes_cheap_beer_taste_much/ | {
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"Some of the big boys use rice in their beers. And their light beers are just overfermented then watered down. You can really taste poor quality ingredients.",
"Without going into too much detail the flavor of a beer is determined mainly by types of grain used, type of yeast and types of hops (or lack thereof more commonly in bad beer).\n\n\"Watering down\" beer is actually a bit more complicated than it might sound. The amount of alcohol will be determined by how much sugar is available to the yeast and making stronger beer would require more grain (more money). \n\nWatering down beer to a desired alcohol content is completely accepted practice, but a big brewery would get into tons of trouble if the alcohol content was lower than what the bottle says. They wouldn't be able to straight up \"water down\" their beer in other words.\n\nThat being said, you could in theory make \"beer\" of malt flavored molasses and yeast. The most basic DIY beer sets just give you liquid malt extract to mix with water in place of the [wort](_URL_1_) you'll end up with after [mashing](_URL_0_) so you can skip the mashing process altogether. \n\nMy guess would be cheap malt extract (custom mix with extra sugar), an effective yeast (doesn't have to be bad) and very little hops to add character.\n\n "
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2634p2 | why can my ipad play videos for hours straight without even having a fan, while my laptop reaches 85deg c and higher after streaming netflix for only 2 minutes? | I would think the technology in my Macbrook Pro surpasses that inside of my iPad, so why does video seem to be so much more taxing when played on the laptop?
I can watch hours and hours of Netflix and _URL_0_ without any heat coming from my iPad, but my laptop gets hot as hell after less than 5 minutes. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2634p2/eli5_why_can_my_ipad_play_videos_for_hours/ | {
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"Well your laptop has a full blown processor it running a full blown OS. That requires a lot of processing power to handle all the background processes and other elements that come with it. The ipad on the other has a risc(reduced instruction set) processor that is a simplified processor that was designed to use a little power as possible and a specially designed mobile OS that keeps things light wight and depends on dedicated apps to run things.",
" > I would think the technology in my Macbrook Pro surpasses that inside of my iPad\n\nNot really. Tablets are a miracle.\n\n",
"Every video you play on the iPad is a format that can be efficiently decoded in hardware with a minimum (none?) of other processes going on.\n\nIf you are playing a video in Netflix in your browser on a PC you are dealing with many layers of abstraction, some extremely inefficient (flash).\n\nOf course the real answer is not any if this \"iOS isn't a full blown OS\" bs. iOS is just as \"full blown\" (whatever that means) as any other. But it was designed from the ground up to be efficient. Windows wasn't designed to do anything in particular, stuff just kept getting added on top of old stuff for 30 years."
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1i785c | how do protesters have time to protest for days on end? | Don't these people have jobs or other responsibilities that require their attention? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1i785c/eli5_how_do_protesters_have_time_to_protest_for/ | {
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"One big reason people protest is lack of jobs, or lack of jobs that pay them enough to make working more appealing than trying to point out that their work sucks for the amount of pay they get.\n\nEssentially, people protest because they care a lot about what they're protesting about. Some people protest because they care deeply about the way the world is, and the way they want it to be tomorrow.\n\nAlso, many working class people don't protest, precisely because they are scared of losing their jobs. People who can afford to protest are therefore also often people with flexible hours or flexible work.",
"Generally speaking, they regard what they're protesting about to be more important than other duties, and arrange to take time off to do so - or simply take the time to do so anyway.",
"It may just be what they do. They could be retired or jobless, work odd hours, or something like that.",
"(I know, I know, not for literal five year olds, but this one was just too easy to convert)\n\nSo you know when you come home from school, and you get to play with your toys after a long day of fingerpainting and learning your letters? \n\nWell some people who care a lot about a certain issue, like, say, their nice teacher getting fired, use that play time to protest against the school authorities. The problem is that you only get to play AFTER you are done with school, so the amount of time you can protest is limited. But, there are other kids who go to school in the afternoon, meaning they can protest in the morning, and then as soon as they have to go back to school you can take over for them. \n\nAnd, there are some other kids whose parents will let them take a few days off of school to protest something that they really believe in. Those kids become sort of like anchors, and maintain the constancy of the protest. \n\nAnd there are also some kids who can only come out for a few minutes or a few hours, because their parents are very strict. Usually, the other kids will invite these kids to come only on big days when the need to show a big prescence, like when the superintendent is going to address the protesters, or when the governor is in town. \n\nSo, with all the different kids taking different roles and giving different time commitments, you can have a continous protest for days on end without giving up too much schooltime.\n\n**TL;DR - Most people who protest are employed, because most people are employed. Continous protests are maintained by cycling people in and out, with a few anchors to maintain continuity.**",
"hippies. they don't have jobs to go to.",
"Personally i used to earn a bunch of money as a freelancer, so i could take the day off and do some good (possibly). I used to be on the dole (welfare) and stood on the front line against the National Front (now it's the British National Party (fascists by any other name). My grandfather fought against fascism, my mother worked with Poles who had concentration camp numbers tattooed on their arms. Least i can do is make sure it doesn't happen again. Not on my watch.\n",
"Some of them are actually paid to protest. It's their \"job\" \n_URL_0_",
"You know how you have a friend how's always always too busy for you? Like every time you call him he has a date, or a picnic, or is going to travel with some friend and can't really come to your party because there is this really great concert and he promised someone he would be there? That guy doesn't have a lot of responsibilities. He just doesn't like you. \n\nWhen you like someone, when an issue really matters to you, or if you think it is worth it, you put the time for it. You will find the time to balance the responsibilities and protest. You can take vacations, you can ask your mother in law to take care of the baby for a couple of days, and you can paint that wall the next weekend. There is something wrong and you feel you can make a difference. \n\nEveryone put their time towards things they feel important, even you. And change are made by people who put change first. ",
"Nobody else seems to have mentioned this, but a well organised protest camp will have a wide range of people with varying \"real life\" responsibilities. Lots of people will turn up to demonstrate when they get off work. Some people work nights, which means it's possible for them to be there during the day, which for them would be early morning or evening. Also, popular causes can organise fundraisers to provide for subsistence for the core activists who have decided to dedicate their energy to the campaign. \n\nSo between people who work at different times, students, and people who are otherwise unemployed, it's not as hard as you'd think to run a permanent protest camp for a popular cause.",
"It depends on the protesters and even the protest. When there are issues like human rights violations, or an attempt to overthrow a brutal regime, people are willing to put their lives on hold to make sure things go there way. \n\nThen on the other hand you have special interest groups and the anti-everything crowd who are often paid protesters. Paid protesting is a relatively new concept to some people, so I will explain:\n\nSome protesters are higher ranked and get paid decently to plan and organize protests for special interest groups. Some protesters are much lower ranked and only get paid to fill a spot in order to increase the protest numbers. \n\nThe companies that pay them are usually special interest groups under the disguise of environmental groups - like Greenpeace for example. How can Greenpeace pay people to protest you might ask... Well that's simple;\n\nLet's say one of the USA's top oil suppliers like Venezuela wanted to ensure they remained a top supplier to the USA. They are aware of a pipeline being proposed from Canada to the USA which would significantly cut into their share of the USA oil market. So they would \"donate\" money to a special interest group to oppose this pipeline. That \"donation\" might filter through several companies/groups to make it less clear where the donation comes from, but the purpose will remain in tact. Once the money makes it to its final destination you will see several targeted campaigns against a specific company/proposal/etc...\n\nThat is why if you look closer at the thousands of people signing up for public hearings you will see that many are or have been affiliated with heavily funded special interest groups like Greenpeace. Likewise, that is why you often see what the police label as \"professional protesters\" getting arrested at events. They are labeled that because they are usually affiliated with those groups and/or have been arrested several times before at different protests.\n\nIt really is the best form of hypocrisy I have witnessed. I guess the best question you can ask is whether or not these protesters truly understand what they are protesting and why they are protesting it.\n\nIn the case of the human rights and over throwing brutal regimes, I would say yes. In the case of protesters like many of those from Greenpeace, I would say no. I say that simply because I think many of the paid Greenpeace protesters do believe they are doing what is best for the environment, etc.. However, believing and knowing are two different things and if they knew who was paying Greenpeace to protest for them I truly think they would not back Greenpeace.\n\nUnfortunately, like with many special interest groups, ignorance to them is bliss. That is why you will always get a very defensive and even retaliatory reaction when you oppose them. \n\n**TL;DR -** Some protesters are either paid or tricked into believing the idea they are protesting is something that it is not. In reality it is often just a competitor trying to maintain their market share by hindering the competitions expansion via protests. ",
"Most likely because they are paid to be there or are simply unemployed by force or choice. \n\nA few years back there was a group of black protestors in downtown Miami protesting a bank for unfair work practices. They would march is circle banging cans etc and holding nicely made signs. Several held a huge banner. Around 1 PM there brought hot food and this went on for weeks. They were all homeless and many slept in downtown. How did I know? I would watch them go back to where they slept every day. \n\nWhen Carnival cruise lines was being protested for paying 3% of their taxes every morning white Ford Econoline vans showed up with homeless people too. Same situation. Fed daily nice signs and the marching in circles. \n\nIt's propaganda and like politicians people will do anything for money or food when they are hungry. \n\nLook at occupy Wall Street someone was paying for the food. Who? The people looking to benefit. \n\n",
"Thank you for asking this. I volunteer for a rape crisis center and they're constantly sending out emails telling us about protests at the capitol... at noon on a Tuesday! Goddamn don't people have jobs? Can't we get our feminist hate on during weekend hours? ",
"Protesters are like TIE Fighters. For every one that goes home, more shoe up to take his or her place."
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8w6f6x | why do bugs when outside fly around the same area with a bunch of other bugs instead of being spread apart? typically gnat like bugs. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8w6f6x/eli5_why_do_bugs_when_outside_fly_around_the_same/ | {
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"They are making more bugs via the usual route. That requires them to be in close proximity. Think of it like you are walking through a bug night club."
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1dhx0f | music in dreams | Why is it that music in some dreams (I've heard multiple people say the same thing) are usually beautiful and songs that have never been heard before? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1dhx0f/eli5_music_in_dreams/ | {
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"Because your mind is beautiful and capable of an incomprehensible amount of creativity. ",
"This has happened to me before. I heard a beat while I was dreaming and just started rapping. I remember it being the dopest shit ever, but couldn't remember a word of it in the morning. My girlfriend was like \"you were rapping in your sleep last night\" ",
"I can't remember any dream having music, and I usually remember my dreams.",
"When you're asleep, your mind is less distracted and you may have many kinds of creative experiences. Different brains respond to music differently. Oliver Sacks, the famous professor of neurology, talks about this kind of thing in [one of his books] (_URL_0_)",
"Does anyone know if this music is really as amazing as it sounds and we just can't remember it? Or is it just nonsense? I've composed some absolutely amazing symphonies in my sleep that blow away anything I've heard. "
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"http://www.amazon.com/Musicophilia-Tales-Music-Revised-Expanded/dp/1400033535/ref=sr_1_5?s=books&ie=UTF8&qid=1367444787&sr=1-5&keywords=oliver+sacks"
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