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5x4xhe | Will a more obese person burn more calories with the same daily activity as a thinner person strictly because of the amount of effort necessary to keep up? | Biology | explainlikeimfive | {
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"Yes, absolutely. Hauling a 300 pound body up a flight of stairs takes around twice as much work (and calories) as a 150 pound body.",
"That's right, it takes more calories just for a larger person to keep on living compared to a smaller one, simply because they have to fuel more cells. This also means that lots of exercises (even walking) burn more calories for larger people, who are moving a larger load.",
"This is also why \"fat people are sweaty\". The total energy being consumed and so re-expressed as heat, is maybe double but the surface area they have at their disposal to dissipate is not twice as large so they have to sweat more to mitigate that extra heat. Meanwhile, they are more resistant to cold since that surface area to volume thing reduces the rate at which they lose vital warmth when exposed to threatening cold. So there are a lot of sliders in the biological mixer that trades the various body types benefits and drawbacks.",
"Yes, and that's one of the reasons why people who are dieting, etc. see more weight loss early on and then the rate of loss slows as they progress. They no longer burn as many calories just living as they did when carrying more weight.",
"TL:DR - Yes. Source: I've recently lost 60 pounds. From 210 down to 150. I did it in about four months. Three step process 1. Cardio your guts out. Swim Bike Run 2-3 hours a day 2. Eat less than you burn. I averaged about 1100 cals a day in 3. Repeat every damn day In the beginning I could swim/bike/run for 45-60 each and I'd burn 1500 to 2000 a day easy. The first ten pounds flew off. The second ten came off easy. By the third ten pounds things slowed down. I was doing the same work. Maybe even harder (more resistance, incline, etc) and burning less. I had to talk to a trainer and discuss my situation to figure out that my body had someone acclimated and I needed to refocus. I went from long term cal burns to shorter burst of carb/cal burns with things like higher intensity reps with short intervals of rest between. I also adjusted my diet to actually eat a little more because I was eating to little. After that adjustment I was able to drop the second thirty pounds. Now if I do a swim/bike/run for 45-60 each (I'm preparing for Ironman!) I can burn about 1000-1200 ish with the same work that burned me 2000 before. It was not fun but I finished last November and haven't looked back.",
"By this logic, this must be the reason people lose a lot of weight when they first start dieting, but are always struggling to lose those last few pounds.",
"My slightly overweight wife and her obese mother joined Weight Watchers together. WW gave her mother twice as many \"points\" because she would have to eat much more just to keep herself going.",
"Check out \"base metabolic rate\" and play with the calculators a bit. Obese people even take more calories *just to survive daily* before they do anything, which is part of why it's a hard cycle to break, since you *need* more calories baseline as it is, but need to work in a deficit to lose weight as well, making the margin of error far slimmer.",
"So - I was curious about this as I had wondered how muscle mass played a factor. I suppose this depends on how you actually define \"thinner\" (i.e. lighter.. or more fit - but still the same weight). URL_0 EDIT: and the reason I was thinking about this is that I recalled hearing that once you start getting \"back in to shape\" the benefits are not linear as you might assume, because as you get thinner, but build muscle, the additional muscle requires more energy even at rest. And now I'm just talking out of my ass.. but I imagine this also becomes a thermodynamics problem. What if that thinner person generates a ton of heat just sitting there.. and the not-thin person has an idle temp much lower. I assume this would also play a factor.",
"Most exercise equipment that count your calories burned ask you to input your weight for this reason.",
"According to my Apple Watch, yes I see the daily move goals people set for themselves and I blow through those first few hundred calories within the first three I'm at work. I usually walk between three and 5 miles a day and up-and-down a single flight of stairs 20 to 30 times. Last week was the first opportunity I've had to get on the scale that could actually measure me in quite some time. I came in at 427lb (194kg, 31stone)",
"Does it take more energy to move 100 pounds or 200 pounds? That is your answer"
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5x4yxv | Why does water expand when it freezes. | I just can't understand why it does this. I always heard of things expanding when you warm them so why does water expand when it freezes? | Physics | explainlikeimfive | {
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"Water molecules (H2O) are made of an oxygen atom between two hydrogen atoms. They aren't lined up straight; they're bent at an angle, like a noodle of macaroni. When water freezes into solid ice, these macaroni shapes arrange themselves into hexagons, as shown in [this image]( URL_0 ). The empty space in the middle of each hexagon means that the overall structure takes up more space than if the H2Os just smashed together randomly (i.e. if they were liquid). So the overall volume of water ends up expanding as it freezes into hexagons.",
"When water freezes it forms a crystalline structure. This structure means molecules are neatly arranged with more space in between them than when they were a liquid. When water is liquid this structure doesn't exist and molecules are moving more freely and closer together."
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5x50mv | How can the economy keep growing every year if the planet has a finite amount of resources? | If every country's economy grows and is doing well won't we eventually run out of resources? Or can the economy grow without resource consumption? | Economics | explainlikeimfive | {
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"There are types/aspects of economic growth that are unsustainable. But not all growth is in the amount/size of products. For example a computer CPU is made out of very similar raw materials to a glass jar, yet the computer part is more valuable (by a lot). Technology, in short, allows us to get more practical function and definitely value out of the same resources.",
"It cannot. But don't expect many people to come out and admit it, as expected growth is the engine of the stock market - the giant gambling game that the super rich and banks use to suck up wealth. Don't expect them to admit to that either. Historically it was based on population growth (using resources, and then when you ran out, warring with the neighbors to get more), and then more recently - and they will tell you this is a way out, but it's not, it has somewhat been based on increasing technological efficiency. I.e. USA grows well without increasing population most years, by increasing productivity and efficiency. But even this has its limits. All systems have a sustainable limit, but as of yet we still pretend we're nowhere near ours. And we probably do have some time, if population is contained and all products are made with renewable resources and energy. But even renewables have limits within the system. Only recourse - space. Making the system bigger.",
"Peak oil, an event based on M. King Hubbert's theory, is the point in time when the maximum rate of extraction of petroleum is reached, after which it is expected to enter terminal decline.[1] Peak oil theory is based on the observed rise, peak, fall, and depletion of aggregate production rate in oil fields over time. It is often confused with oil depletion; however, peak oil is the point of maximum production, while depletion refers to a period of falling reserves and supply. Some observers, such as petroleum industry experts Kenneth S. Deffeyes and Matthew Simmons, predict negative global economy implications following a post-peak production decline and subsequent oil price increase because of the high dependence of most modern industrial transport, agricultural, and industrial systems on the low cost and high availability of oil.[2][3] Predictions vary greatly as to what exactly these negative effects would be. Oil production forecasts on which predictions of peak oil are based are often made within a range which includes optimistic (higher production) and pessimistic (lower production) scenarios. Optimistic[4] estimations of peak production forecast the global decline will begin after 2020, and assume major investments in alternatives will occur before a crisis, without requiring major changes in the lifestyle of heavily oil-consuming nations. Pessimistic predictions of future oil production made after 2007 stated either that the peak had already occurred,[5][6][7][8] that oil production was on the cusp of the peak, or that it would occur shortly.[9][10] Hubbert's original prediction that US peak oil would be in about 1970 seemed accurate for a time, as US average annual production peaked in 1970 at 9.6 million barrels per day.[11] However, the successful application of massive hydraulic fracturing to additional tight reservoirs caused US production to rebound, challenging the inevitability of post-peak decline for the US oil production.[12] In addition, Hubbert's original predictions for world peak oil production proved premature.[4] In short, \"Peak Oil\" is the way of all non-renewable resources. Unless we slow down and get local relationships and treat each other more like family, we run out really really fast. If, you really want to see some math involved (Which I don't recomend if you plan on being happy today) get on youtube and search \"Peak Oil\". Watch a few of the shorter (higher production value) documentaries.",
"1) The economy is measured in money which is basically infinite because it's made up. 2) You can have high economic outputs (stuff bought and sold) based on anything that a human puts value on and is willing to pay money for including non-tangible goods (things you can't touch like: software, bitcoins, xxx phone chats, naming a star, \"corn futures\", someone singing you a song, farmville game credits, naming rights, ad views etc.). 3) As long as there is enough physical infrastructure (food, shelter, wifi, power cells etc.) to keep humans alive and happy we can grow world economies while living sustainably (not using everything up) and produce nearly infinite non-tangible goods - all you need is a buyer, a seller and \"something of value\". It's already begun - look at the Konmari trend and the rampant success of youtube and Apps. The human population is also set to decrease eventually (More stuff share by fewer people). We are learning how to be rich and happy with less \"stuff\". The future is wonderful."
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5x5a1s | How does the Fourth Amendment prevent government reach into government cell phones? | In a recent [column]( URL_0 ), Andrew Napolitano said: > ...generally, a boss can look at an employee’s cellphone, as long as the employer of the boss and the employee owns the phone -- except when the employer is the government. The Fourth Amendment insulates government employees from governmental reach into its employees’ cellphones. Absent an employee's waiving his Fourth Amendment rights, the government may not seize work-related (governmental) or personal phones without a search warrant. I try to balance where I get news and opinion from, and make sure that I read all the different sides, and he usually hits pretty straight. In my searches, I can't come up with a single reason that the government wouldn't be able to seize government cell phones from government employees for absolutely any reason, at any time. Why would the interpretation of the fourth amendment be different when the device in question is owned by private business versus the government, specifically regarding technological assets? Wouldn't this interpretation cause significant issues with internet monitoring of government computers, etc? Does anyone have any insight? | Other | explainlikeimfive | {
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"Your quote provides the answer. The constitution including the bill of rights defines what the government can, and can't, do. (It does not apply directly to private employers, of course.) You don't automatically lose rights as a result of becoming a government employee; but you may waive those rights at times in exchange for something else, such as having a certain job."
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5x5bst | Do loud noises travel slightly faster than very quiet noises or does loud noise just travel further at the same speed? | Physics | explainlikeimfive | {
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"Sound travels at a constant speed through a medium (eg air). This is because sound travels by moving the surrounding molecules (usually air) back and forth. This causes pressure differences which is what we experience as sound. Sounds that are louder cause a larger pressure difference (move the molecules further) but since the molecules don't actually have any net movement (remember they just vibrate back and forth), how loud they are doesnt affect how fast the sound actually moves through the medium.",
"Sound travels at the same speed through any particular substance (\"medium\") regardless of how loud it is. So, for example, sound travels faster through water than it does through air. But a loud sound will travel the same speed as a quiet one in either medium."
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5x5c3k | From what I gather, Wikipedia seems to be a fairly neutral source. What prevents the polarization of facts on Wikipedia? | Technology | explainlikeimfive | {
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"There is a lot of arguing going on behind the scenes at Wikipedia. Visit the 'talk page' of the article on a controversial person or topic and there will be long discussions on what should be included and how it should be worded. Controversial topics also will have a lot of people watching their edits. If you want to wreak havoc at Wikipedia, then make an edit to an obscure article that nobody cares about.",
"Three points: 1) Wikipedia has a cadre of highly dedicated (occasionally fanatical) people who police the site and try to keep it on track. 2) Many fingers in the pot means that the version that survives the edit wars is the one that is most palatable to the widest number of editors. 3) Wikipedia really isn't that great. It is extremely useful and often well-done, but it also has a reputation for vicious flame-wars involving deeply entrenched factions, which often require moderator intervention. Ever notice how some Wiki pages are locked to prevent further editing? In most cases, that means the page attracted so much controversy and debate that the only way to resolve the problem is to shut it down entirely.",
"1. Community takes it very seriously 2. A demand for citation on *everything*, so statements are always backed up 3. No opinion pieces or anything like that allowed, just facts with no interperetation or opinion. Most places that consider themselves news sites (CNN, Fox News, whatever) also do \"opinion\" pieces, and while these are clearly labeled as such, if CNN runs \"Opinion: Donald Trump is a screwup\" some people will just treat that like a fact when it's really an opinion, a fact would be \"Donald Trump has done and said x y and z\" 4. No attempt to present articles that drive traffic. Most news sources try and put things on their front page that makes people hang around and read, which is profitable for them. This can often lead to cherry-picking juicy stories for more attention. Wikipedia doesn't try and present anything to entice readers other than information.",
"There are two core policies of Wikipedia work together to facilitate its neutrality: [Verifiability]( URL_4 ) and [Neutral Point of View]( URL_0 ). Verifiability means that all information of Wikipedia must come from a reliable source. Editors compile and distill this information in articles - they are not supposed to draw their own conclusions from the information (this is covered in more depth by the [No Original Research]( URL_3 ) policy). This makes Wikipedia a reflection of reliable information that already exists rather than a place that can develop its own ideas and biases. Neutral Point of View dictates that where there are conflicting statements *in reliable sources*, Wikipedia articles are supposed to represent the various viewpoints in reliable sources in proportion to their representation in the total literature of reliable sources. This makes the information on Wikipedia a neutral reflection of the (reliable) information in the world, not an arbiter of truth. See the essay [Verifiability, Not Truth]( URL_2 ) for more on this point. Of course, correctly identifying reliable and unreliable sources is central to all of this. Wikipedia's central guidelines on this are [here]( URL_1 ), but what is or isn't reliable ultimately gets hashed out in behind-the-scenes debates (which anyone can participate in!)."
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5x5fij | Why is it that we develop a tolerance to drugs, but not sex/masturbation? | Both drugs and sex/masturbation stimulate the reward centers of the brain and release chemicals like dopamine, oxytocin, etc. Why is it that if one takes drugs that stimulates those chemicals, they usually develop a tolerance to it and need more of the drug to get the same effect, but one doesn't get "used to" sex/masturbation like they do to drugs? | Biology | explainlikeimfive | {
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"In a manner of speaking, one can build a tolerance to sex, or at least to sexual stimulation. The classic example is a virgin male, who orgasms immediately during his first time having sex, compared to the same person at, say, his 100th sexual encounter. Similarly, if you view enough pornography of a similar style, you get used to it and need a change to get the same state of arousal that you used to achieve.",
"They do develop a tolerance. Look up sex addiction. But seriously, talking specifically about narcotics, one of the things they do chemically is damage neuroreceptors- the body's looking for the same dopamine (and serotonin), but it's getting starved at both ends; the body isn't producing as much, and the brain has a harder time taking in what is being made."
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5x5ktc | Crowd gps | I'm looking into Trackr or Tile and they both mention crowd gps. It seems simple, but I still can't wrap my head around it. Does that person get your GPS location? | Technology | explainlikeimfive | {
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"Crowd GPS apps are different in that they give your more real-time information such as obstructions in the road, red cam lights. All the added real-time information is gathered through different people who use that app. Functioning as a self sustaining community, people update the public map with new information wherever they are. Others can vote on whether this info is accurate or not in. The more people that apply to that \"community\" the more accurate and timely that info is."
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5x5n4z | How can NASCAR say they use "stock cars" when the cars used are far from being "stock"? | As far as I can tell, they only way they resemble a stock car is in the shape of he body (vaguely) and possibly the frame. Everything else seems to be modified or changed in some way. | Other | explainlikeimfive | {
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"And not even the frame - NASCARs have tube frames, nothing like their street namesakes. Its an anachronism. Originally stock car racing began as a way for moonshiners to race their bootlegging cars, which were only somehwat modified street cars. The term was coined to indicate these were modified street cars, not custom built race cars like formula 1 cars or dragstrip funny cars. Nowadways NASCAR and related series \"stock cars\" are, you're right, not anything close to the street car brands they supposedly represent. The original intent was to prevent special race cars to give any one driver an unfair advantage. In today's cars this is done through specific regulations that dictate how big the engine can be, how heavy/light the car is, the exact shape/profile of the body even is checked. Again, the intent is to keep a technological even playing field between drivers.",
"Former NASCAR team member checking in. The term goes back to the early days of the sport, when you could literally go down to your local Dodge, Ford or Chevy dealer and buy a completely stock production car, make just a few modifications for safety, (do whatever you wanted to the engine too) and take it to the race track. Think Lee Petty, Junior Johnson, Fireball Roberts, Ned Jarrett, etc. back in the fifties. By the late '60s, they had become more purpose built, but still had completely stock bodies. Now, of course, the cars are purpose built by hand from the frame up, and they only loosely resemble the factory cars that bear their names. TL;DR: Long ago, in the beginningof NASCAR they were actual stock cars, but mostly because of safety and the desire to keep anyone from having a big advantage, they've evolved into custom built machines."
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5x5tk6 | Why are some Moles cancerous while others can be completely harmless? | Biology | explainlikeimfive | {
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"It's more that you could have a mole growing on you, or you could have cancer growing on you, but without looking closely they look the same. It's not that the mole is cancerous, it's that you might ignore cancer because cancer might look like a mole."
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5x5zbu | AMD's new Ryzen processor. | I get that Intel dominated the market over years. But what is going on in the following thread? What are they all talking about? What is Zen? And what is that thing with the 3-5-7 number? And all this other stuff? I would be very grateful if you could please explain it like I am really 5 — or since my 7 year old cousin knows better than me how to handle an iPad please image for that case that I'm your 95 granny. Thank you! URL_0 | Technology | explainlikeimfive | {
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"Zen is a new processor architecture releasing pretty soon. The 3/5/7 is a marking nomenclature used to separate different models into mainstream/performance/enthusiast categories, very similarly to Intel's naming system.",
"Zen is a new architecture for AMD's newest lineup of CPUs, the Ryzen CPUs. 3/5/7 is just a way of dividing their processors into different categories, but also to match up with Intel's own 3/5/7 system (i3, i5, and i7). AMDs version will be the R3, R5, and R7 CPUs, with the R7s launching literally today. The biggest, most important bit of this new launch is the fact that AMD hasn't released a new CPU architecture in several years, causing them to really lag behind Intel in terms of performance. With the new Ryzen launch, AMD is selling processors of comparable performance to popular current gen Intel CPUs for a fraction of the price. As has been frequently pointed out, the R7 1800x (AMDs new top-of-the-line CPU) at $400 hands down beats Intel's 6900k, a current gen **$1000+** CPU. Ryzen's strong point definitely helps that last comparison out, as Ryzen CPUs (especially the R7s) are extremely competent at multi-threaded, intensive, more \"professional\" use tasks such as rendering 3D models and editing high resolution video. For gaming, Ryzen is definitely a little lackluster, offering little to no improvement over current gen Intel CPUs at simar price points.",
"If you want to understand all the hype the best way to look at it is through AMD's processors over the last 6 years. Throughout that time period AMD focused more on the integrated video processor built into their processors. What this means is that their processor lineup was not directly competing with intels processors because they were not as powerful at processing normal CPU tasks but rather the graphical elements like games or video rendering. This might sound like a good thing for gamers but realistically a gamer would have a dedicated graphics card to do that for them which would be drastically more powerful than anything that can be integrated onto a processor. This meant AMD had a very slim market. When they announced ryzen (originally titled zen) it was huge because this meant AMD would be competing with intels high end processors with actual processors again. This has not happened in over 6 years at this point. Over the course of these 6 years intel has charged a massive premium on their top of the line processors due to there being no competition. Everyone is excited not because AMD is making baller chips but rather due to this forcing intels prices down so the consumer isn't paying an unnecessary premium to get top of the line."
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5x610j | What does the 4th dimension look like, and how would we perceive it? | Other | explainlikeimfive | {
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"The 4th dimension can't be looked at by us or interpreted by us who reside in the 3rd dimension, no more than a 2D object has any awareness of the 3rd dimension. The reason for this is because us 3rd dimension people view time as a constant. This is untrue for the 4th dimension because time is viewed just as loosely there as we would view 'depth' here in the 3rd dimension. The easiest comparison is viewing a cube. Us 3rd dimensional beings would only see the shape of the cube from left to right and up to down, *AND front to back*. Conversely, a 2d being would only view this cube from left to right and up to down, but not front to back. In the 4th dimension, this cube is viewed according to a particular moment in time. So this cube you visioned 1 millisecond ago is viewed differently from now. How you say? Well this is where it gets tricky. Simply put, if the cube changes in shape, we can notice. If the cube is viewed by you right now, you can see the cube, but you don't know if the cube was there yesterday. In the 4th dimension, they can tell that answer by viewing the cube from a \"different angle\" much like we would to view the shape from a different angle in order to tell if the shape changed or not.",
"There is no 4th dimension. Like, dimensions of the universe is just a number. We live in 3-dimensional universe(more or less, actually it gets a bit fuzzy if you consider modern physics, but for our everyday experience, life is 3d), but there is no \"second dimension\". The world is 3-dimensional, that's a number 3, but there is no clear way of splitting that into 3 separate dimension. It's just a number. Like, answer this: what, in our 3d world, is the second dimension? So instead of asking \"what would 4th dimension look like\", your question probably should be, and you may have intended to ask, \"what would 4-dimensional world look like to us?\" Anyhow, a bit of clarification on dimension as a number: Basically, it tells you how many directions you have to choose from. If you run along a pre-determined path, then your jogging route is, for most intents and purposes, 1-dimensional. You can go forwards and backwards on that route, and that's it. If you have a piece of paper, then you usually think of it as having length, and height. These are kinda the \"canonical\" dimensions of 2d space. But they're not the only ones. You could also first choose a direction as an angle between 0 and 360, and then choose how much you walk towards that direction. 3d space has third option. In 3d space, you can for example choose to go backwards/forwards, left/right, and up/down. GPS has latitude, longitude and altitude as measurements it uses to locate people all around the planet. Different ways to do it, but you notice that the number 3 is the one that persists. No matter how you split the world, 3d world kinda has 3 parameters you're expected to fill. So 4d world would require 4th parameter. This new direction would allow all sorts of tricks, for example, knots(in specific mathematical sense) could not be made without them being untangeable. If you tried to measure how many little 4d cubes you could fit around you, you'd notice it's actually weirdly more than you're used to. So, let's stop with that for a moment. In 1d, you have line segment. Line between points A and B. In 2d space, you could kinda expand this line segment into a square, with 4 equal sides. If you have 2d square and your will it with squares that have half the side length of the big square, you can fit 4 squares in. But in 1d world, you can only fit 2 line segments on line that's twice as long as those segments. In 3d world, you could fit 8 cubes(half the side) inside a bigger cube. In 4d world, you could fit 16 hypercubes inside bigger hypercube. So you'd kinda have more to worry about right next to you. But the big problem we'd have is that, we don't have 4d \"width\". We are 3-dimensional creatures, and as such, we'd be like infinitely thin paper slides in a 3d world. As such, we really don't have a way we could live in 4d world. We also kinda lack in ability to view it. Again, starting from 2d world: 2d flatlander that had two eyes would see two colored \"lines\" of sorts. If you imagine being flattened to a piece of paper, you could only see one side of square, one side of circle, one side of triangle, and these would not have any height. We, in our 3d space, we see 2d images. Our eyes make two 2d colored images of what the world is like, and that's our window into this world. We could not even in principle see in 3d. But natural 4d creatures would need to see in 3d to navigate around the 4d world. We don't have that luxury, so without direct computer-to-brain interfaces, we simply cannot input the required 3d data into our brains to look at external 4d models. So we have to instead rely on mathematics, or vivid imagination. Vivid imagination however fails humans for whatever reason. Imagining 4th direction has turned out to be almost impossible for humans. So what we are left with is mathematics. We can slice the 4d objects into 3d slices which we then can use computers to show us 2d images of, which our brain then parses together into 3d understanding. Which can be somewhat helpful if you for example look at rotating hypercube, how it looks like in 2d projection of 3d slice: URL_0 But the unfortunate part is, there really ain't any particular shorthand to understanding 4d world beside cold and cruel mathematics. You can appreciate that there are 4 dimensions in 4d world, and that's it.",
"Are you talking about a fourth dimension *of space*? If so, there is no possible way to know what it would look like, because we have neither four-dimensional eyes or the necessary neurology or experience to decode information from them. Even if you could safely move into a fourth dimension of space, you'd only be able to see a single 3D \"slice\" of it at any given time. 4D objects would appear to warp and change shape in odd and nauseating ways as your view moved to different parts of the 3D volumes that make up the 4D shapes. However, even if such a space existed, you couldn't go there because you have no skin facing the fourth dimension. Your organs would spill out all over the place and you'd die a messy and horrible death. The closest we can get to seeing four dimensional objects is looking at their shadows. Just as 3D objects cast flat, 2D shadows on surfaces, 4D objects cast 3D shadows on volumes. [This]( URL_0 ) is the shadow of a tesseract, the 4D equivalent of a cube, made up 8 cubes all connected face-to-face at right angles, just as is the case with the edges of the sqaure faces that make up cubes. The tesseract casting the shadow is undergoing a simple 4D rotation. The cubes that make up the tesseract aren't actually moving through each other, but rather the large cube on the outside is the closest (in the 4D direction), and the small inner cube is the farthest. If you want to get a better grip on how a fourth spatial dimension would behave, I highly recommend [this]( URL_1 ) video. It explains a lot in an easy to understand way."
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5x63p3 | How does hashing work for single value like the letter "a"? | Technology | explainlikeimfive | {
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"You didn't specify what hashing algorithm, but in general, if the input wasn't long enough you would pad it by adding \"zero bits\" to it. Technically, even long strings often need padding as well. This is because to be able to work with the bit string properly it needs to be a certain length (or divisible by a certain length). Each algorithm has its own rules for such things. Sort of like if you had a number 42, but you actually needed a 10-digit number you would change it to 0000000042, but instead of using digits, you would use bits.",
"It depends on the specific algorithm. Generally some type of padding is added to bring the input to a proper length. Here's how the MD5 algorithm applies padding. > MD5 processes a variable-length message into a fixed-length output of 128 bits. The input message is broken up into chunks of 512-bit blocks (sixteen 32-bit words); the message is padded so that its length is divisible by 512. The padding works as follows: first a single bit, 1, is appended to the end of the message. This is followed by as many zeros as are required to bring the length of the message up to 64 bits fewer than a multiple of 512. The remaining bits are filled up with 64 bits representing the length of the original message, modulo 264."
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5x6618 | How did people slack off/waste time at their desks before the Internet or cellphones were invented? | Technology | explainlikeimfive | {
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"In the vicinity of a computer: minesweeper At home: television There are plenty of ways to procrastinate. You could even read a book. God forbid! Anything works when it comes to not wanting to work.",
"I predate the internet! When I had a private office, I'd chat on the (wired landline) phone. I'd make numerous long, meandering trips to the vending machine. I'd stick my head in other people's cubes to complain about the weather. I'd photocopy my hand and other body parts. I'd write letters (remember those?), or stories or a journal entry in my notebook. If I could get away with it, I'd read a book or magazine. Once computers were introduced, I'd play what few lame video games were available. If I was really desperate to procrastinate on a particular project, I'd do everything ELSE, like clean my desk or adjust the photos on my wall. Life was super boring back then. URL_0"
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5x68ew | Why social media apps take up so much storage? | Facebook, twitter, IG, etc all seem to take up 400MB or so each of data, and most of it is in "documents", why is this given the actual app is relatively light? | Technology | explainlikeimfive | {
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"I think the reason is primarily cached data. The apps download a bunch of content at once so it doesn't have to load progressively."
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5x69vt | Assuming a consistently dark environment, how do our bodies know when it is time to wake up/that we have had enough rest? | Biology | explainlikeimfive | {
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"Most likely the body wouldn't be able to work around it. I know you mentioned consistently dark environments, but if you attempt the opposite with a constant bright light for more than a day it really messes up your day/night cycle. Vsauce on youtube recently did a testing of this in which the show's host, Michael, spent 72 hours in a bright room with a bright light. After approximately one day his body started getting the time of day wrong. And from there it only escalated. It's a very interesting watch if you're into that sort of science.",
"Humans have two (known) systems that govern sleep pattern: the melatonin system and the adenosine system. The melatonin system is controlled by light (less light = more melatonin, which makes us sleepy). The adenosine system is basically just an accumulation of metabolites/waste which will increase during the day as our brain is active and they make us sleepy."
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5x6a5r | If humans were to colonize a new planet and could only send "X" number of people. What is the minimum number of people we would need to send in order to create a genetically diverse population? | Other | explainlikeimfive | {
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"I actually discussed this with my fiancée the other day. Realistically we would only send women and carry stored semen for the men. This is because in order to grow the numbers as quickly as possible we would want as many wombs at the start as possible, and men would be too much of a life support and weight burden for the population benefit. Also in the event that some of the crew is lost it would be a terrible thing if by happenstance all the women were killed. Considering we currently lack the ability to develop a child in an artificial womb that would mean the failure of the mission, so to maximize the allowable loss of crew every crew member should have a womb. Considering varied semen is much more compact than taking male colonists it shouldn't be any trouble at all to send excess genetic diversity for any proposed colony. Of course this implies that every colony would by its nature develop a matriarchal society as the founding members who are the most educated and skilled would all be women, and the first few generations would likely be purely women as well. By the time men are even allowed to come to term there would be far more women than men.",
"According to a Portland State University professor, you could do it with 10,000 people on a strict breeding program, or 40,000 people allowing for more natural pairings and attrition. [Source]( URL_0 ) EDIT: As shown in the article (but summarized here for simplicity), his program runs a 300-year simulation. Significantly fewer than 10,000 people would result in reduced genetic variation over that much time. As few as 150 people could last a few generations, but then all the permutations of pairings would effectively be used up.",
"[Seems like]( URL_0 ) if we wanted people to be happy and allowed to date, 160. But we could get that down to about 80 if we screened out groups genetics very carefully.",
"While not an actual scientist, I'm an undergraduate student of genetics and I don't think it's an issue. By the time were ready to send an interstellar colony ship, we'll have such an advanced understanding (the rate of gain of knowledge in the field of genetics is really really really fast) that low diversity won't be an issue. Maybe not a complete understanding but it wouldn't surprise me. Everyone in the population is a carrier of this gene and were at risk of massive portions of the next generation being born with a degenerative condition? That's ok, we'll cure it in zygotes and adults alike using this diversity library we bought? Oh no there are no extra alleles for this locus? That's fine we'll simulate a protein that can do the job better and add the code for that into the genome. Seems farfetched at the moment, but considering how far the field has come since its inception and even in the last 5 years it's not unlikely that 100 years from now we'll wield these abilities.",
"Ultimately it doesn't matter as the new population's genetic diversity will develop differently to the originals due to the founder effect (newly established populations are less genetically diverse then those they came from).",
"Everyone's doing this the hard way: All you need is 1,000 women and a sperm bank with 10,000 samples.",
"The best estimates can be found by looking at population bottlenecks. The population bottleneck caused by the Toba catastrophe 70,000 years ago reduced human population to an estimated 3,000 breeding pairs. Possibly as low as 1,000 breeding pairs. [This]( URL_0 ) study says that the native population of the Americas are descended from about 70 people. Not necessarily that there were only 70 individuals at any one time - in the same way [mitochondrial eve]( URL_1 ) wasn't the only woman alive at the time, but we're all related to her. But seeing as we would be able to select a genetically diverse group to begin with, use genetic screening, keep frozen sperm samples etc - I'd say less than 70 is viable."
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5x6a72 | The moon is bright enough to be seen from 240,000 miles away even in daytime, how could astronauts look directly at it during the lunar space landing? | Other | explainlikeimfive | {
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"The moon is just acting as a mirror. It is not producing it's own light. Take a regular mirror. Turn on a bright light. Set up the mirror about ten feet from the light. Now stand about ten feet from the mirror and look at the light in the mirror. Not too bright to look at. Now get right next to the mirror, less than a foot. The light should still be about the same brightness. Now consider that the moon is quite a bit less reflective than a mirror. It's gray dust. An interesting thing to note is that there is video from a moon landing in which an astronaut is in the shadow of the lander, and yet is fully visible. Conspiracy theorists say that this is proof of a secondary light source, a stage light. It's actually light being reflected from the surface *up* onto the astronaut.",
"Viewing objects from farther away does not make them dimmer, only smaller. The moon looks just as bright when standing on it as it does from the surface of the earth. Astronauts standing on the moon aren't dazzled by a tremendous amount of light because they can only see a very small fraction of the moon's surface and the rest of it is over the horizon. Elaborating on my original statement, as you view the moon closer up it will naturally appear bigger. Its total brightness will increase just because there's more of it to see but the brightness of its surface will remain the same. Stars and planets are different because they are so far away that you see them as only point sources; they have no visible size to the eye so there's no way for them to appear any smaller. Point-source objects do appear dimmer when viewed from farther away.",
"The Earth similarly can be seen from that distance, however it is not too bright for us to land on and exist in. As everyone else says, the level of brightness doesn't change as you get closer."
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5x6bjx | Why do they still make complicated stop-motion movies if there is more-efficient animation software available? | Why do they still make complicated stop-motion movies, like Kubo and the Two Strings, if there is more-efficient animation software available? | Other | explainlikeimfive | {
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"Because it has a very particular style. It's like why do people still paint with paint and brushes when they could do it on a computer, or why do people buy records when they can just get an mp4. New and efficient doesn't mean better in every way.",
"Why do people paint when photography exists? Sometimes the medium or methods used are more important than the final product."
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5x6dzb | How do banks know if a check has already been deposited? | Many banks allow depositing checks through mobile banking. I understand how a bank would know if the same check was deposited into my account two times, but if I had a friend with the same name, who belonged to a different bank, how would their bank know that the check had already been deposited? Does the bank look at the number on the check in the picture and then run it through some database of all the checks in the world to see if it has been marked as deposited? That doesn't seem feasible, so what is actually happening? | Other | explainlikeimfive | {
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"The bank that has to pay the check (the bank where the drafter's checking account is) usually has software to notice duplicate checks. Once a check is used once to withdraw money from the account the check info is saved and if the same check is used again it should be flagged. Say you use Check #1023 to pay me $100. Once the check is processed, it will be marked on your account that check #1023 for $100 was processed. If another Check #1023 for $100 comes through, it will get flagged. The problem is when someone uses remote deposit and then cashes the physical check before the drawee bank can process it. I think there are some services out there that are attempting to communicate among banks when a check is cashed to prevent this, but they're expensive right now so not many places use them. There can also be an issue if the person takes the paper check to a check cashing place that's not a bank since that place will pay cash before the check has a chance to process. While you can get away with depositing checks twice like that in the short term, the double charge will show up on the drafter's bank statement and it will be pretty obvious who did it. The threat of getting caught after the fact is also why most people don't copy your account number and routing number from the bottom of a check (which are in plain sight) and then use that information to commit wire fraud.",
"The bank won't know when you're making the deposit but as soon as they send the check information over to the bank that issued the check, it's going to come out that somebody's cheating the system. This seldom goes well for the cheater. It's illegal and you will get caught."
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5x6eqg | What causes the American South and Midwest to have so many tornadoes, and why are they so relatively rare everywhere else in the world? | Other | explainlikeimfive | {
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"The American Midwest is a flat steppe that runs from the Artic of Northern Canada, to the deserts of Northern Mexico. The lack of natural barriers(mountains) for such a long stretch allows cold Artic air to mix with hot tropic air which creates the conditions necessary for tornadoes to form.",
"I'll copy [one of my old answers]( URL_5 ). It's not exactly for five year olds, but I hope it's easy enough for the layman: There are many factors which go into making a large part of the US the perfect tornado breeding ground, but the most important are the following: 1. **Access to heat and humidity for a large portion of the country.** A major ingredient needed for tornadoes is heat and humidity near the earth's surface, as this allows for high [Convective Available Potential Energy (CAPE)]( URL_0 ), or atmospheric energy which can be converted into rapid rising motion found in strong thunderstorms. Because the eastern half of the US is north of the very warm Gulf of Mexico, and the central portion of the US is flat with very few terrain features, heat and moisture can easily stream north and cover a large portion of the country. 2. To expand on the above point, **large areas devoid of major terrain**. Tornadoes, while powerful, are quite sensitive to terrain variations. Tornadoes can occasionally form in mountainous areas, but it is much easier to form tornadoes in a flat region, such as that found in much of the central and southeastern United States, than it is in a mountainous region. Trees, however, have little or nothing to do with the prevalence of tornadoes: the southeastern US is heavily forested yet still sees [a great deal of violent tornadoes]( URL_1 ). A few people on my original post fairly criticized my point that tornadoes need a flat area to form. This may not be entirely true: the vast, flat plains of the central US do allow for warm, moist air from the Gulf of Mexico to easily flow northward, which is a major factor in making favorable conditions for tornadoes over a large area, but while [it's generally accepted that rough terrain may impede tornado formation]( URL_7 ), it's certainly not proven, and strong tornadoes can and [have occurred]( URL_3 ) in mountainous areas. 3. **Location in the mid-latitudes, 30-50 degrees from the equator**. This is important because further north tends to be too cold (which inhibits CAPE), while further south lacks access to the [jet stream]( URL_4 ), which provides upper-level winds that are required to maintain [supercell thunderstorms]( URL_6 ), which spawn almost all significant tornadoes. 4. **A large mountain range and high desert in the west**. This reason is quite complicated but arguably the most important. The high terrain allows for the formation of a warm, dry layer in the mid-levels of the atmosphere known as an [Elevated Mixed Layer (EML)]( URL_2 ), which is then transported eastward over the rest of the country. This EML works to promote tornadoes in three ways. First, the warm layer acts like a \"lid\" on the atmosphere, preventing thunderstorms from forming right away and allowing the sun to warm the surface for longer during the day. Second, once the storms do begin to form, only the strongest updrafts will make it through the layer, preventing weaker storms from using up the available instability. Third, once the strong storms do form, the rain evaporates in the hot, dry layer, which causes it to cool and increases the surface-based instability even more. Edit: as for why they are relatively rare in the rest of the world, most other areas lack one or more of the above ingredients, and those areas that do have all the same ingredients are much smaller. For example, the one tornado hotspot that probably rivals the central US in severity is Bangladesh and far eastern India, but this area is only about the size of Iowa, so tornado outbreaks tend to be smaller and less common.. I'm more than willing to provide clarification or answer follow-up questions.",
"A meteorologist is going to tell me I am wrong, and if that happens go with them over me! But the way the jet stream runs across America it is one of the few places on the world where you have vastly different temperature changes in a very short amount of time, while also having flat terrain for these temperatures to mix on. Desserts are hot, tundra's are cold, mountains are rough, valleys have odd wind currents. So when cold and warm fronts meet they spin around each other which is what causes tornados.",
"Southern England gets more tornadoes per square km than anywhere else in the world - it's just they're so weak that they're barely noticeable 99% of the time. I've seen two tornadoes in my 27 years of living in southern England, one in Cornwall and one in East Sussex - the total damage of which amounted to a couple of uprooted trees."
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5x6fgo | Why are we always told to make sure someone doesn't swallow their tongue when they go unconscious or have a seizure, when it isn't actually possible to swallow our tongues? | Biology | explainlikeimfive | {
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"**Don't do that!!** That's not state of the art. When someone has a seizure you shouldn't do anything to them. Remove all objects they can hurt themselves with, call emergency and wait. Do not place anything in the mouth (or attempt to, especially not your fingers) and do not restrict the person's movements.",
"Because it's a fun thing to say. People who don't know fuck all about shit feel important when they say it. A better fun thing to say would be is \"don't stick your finger into the mouth of a person with teeth who is experiencing involuntary muscles spasms\"",
"It's a myth. Care during a seizure is generally limited to laying someone on their side in a safe place, and timing the seizure. (If it lasts more than five minutes, or there's a second one soon after without regaining consciousness, call an ambulance.) Trying to jam anything into the mouth of someone who's seizing is a bad move.",
"If the person is unconscious (not seizing) their tongue will relax and fall back to close over their airway if they're on their back. That's why we're taught to put an unconscious person into the recovery position. Maybe the phrase comes from this idea?",
"That hasn't been protocol for years and if you stick your fingers in the mouth of someone having a seizure their jaw can clamp shut and you lose your fingers It is also impossible to swallow your tongue as it is attached to the floor of your mouth.",
"That advice goes back to the days when cutting a snake bite to let out the venom (actually helps venom spread) and getting someone with a nose bleed to put their head back (goes to stomach, can cause vomiting) were good ideas. None of these practices are a recommended any more because modern medcine has better understandings of conditions and treatments"
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5x6gjo | What is (if there is one) the difference between machine learning and AI? | My question started from a deep comment I made on /r/gadgets: URL_0 Kind of boiled down to my last question in the thread: > ...at what point does many machine learning data sets become an AI? Is this there a line in the sand where a program is one and not the other? Are there certain meta-characteristics that present themselves in a "legitimate AI"? Or is AI just a sufficiently well-rounded group of machine learning data sets? | Technology | explainlikeimfive | {
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"This looks like a version of the [Chinese Room argument]( URL_0 ). I'll summarize it here: Imagine that I put you in a closed off room, with no interaction with the outside world other than two small slots, an \"input\" and \"output\" slot. Inside of the room you have some paper and pencils, as well as a giant book (let's say infinitely large, since we're living in a thought experiment world) that has every question that you could ever possibly ask in the English language. After each question is listed the answer, but it's written in Chinese characters. Let's assume that you don't know any sort of Chinese, so to you, those answers are just a bunch of squiggles and squoggles. So I, outside of the box, write down a question in English and I slip it into the \"input\" slot. You, inside the box, will read the question, locate it in your magically large book, and you'll write the answer in Chinese script. And I'll receive it once you feed it through the \"output\" slot. From my perspective outside of this box, it sure looks like the person inside is fluent in both English and Chinese. In reality, you don't have to be fluent in either - you're just matching one pattern to another pattern. In essence, this is what a computer does... and the bigger the translation book, the closer the computer looks to true AI. But the question you're asking is \"Could that computer ever *learn* Chinese? Or is it always just matching an input to an output out of a very, very, very large book of I/O's like our Chinese book?\" And it's a really difficult question to answer. The link I shared has a few opinions on it, but since we aren't really certain we can agree on what \"consciousness\" is, it's pretty tough to determine when an artificial intelligence could be called \"conscious.\""
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5x6h33 | Why is "talked with Russia so bad? Isn't WHAT they talked about more important?/A Swede. | Other | explainlikeimfive | {
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"If you're talking about the Jeff Sessions thing, it's not necessarily that he talked to the Russian Ambassador, but that he lied to the Senate about doing it. The National Security Advisor resigned for doing the same thing. This all happened before they were in office, before Trump was president. Keep in mind, lying to the Senate got President Bill Clinton impeached, and he was just lying about a blowjob.",
"It's not bad in and of itself. The first issue is Sessions is the Attorney General and was supposed to be investigating Russian influence on the election. Obviously there would appear to be some impropriety there, so he recused himself. The second issue is that he lied about communicating with Russia during the campaign in his confirmation hearing. As he was testifying under oath, this could constitute perjury. For context, Bill Clinton was impeached for lying under oath about getting a blow job. So it would stand to reason that lying about meeting with Russian officials during a campaign that is suspected of undue Russian influence would be a big problem.",
"It's a big deal because of the Logan act. URL_0 It is illegal for US citizens to negotiate with a foreign government on behalf of the US government, to prevent private citizens from undermining/circumventing government policy. Considering that at least two Trump administration officials negotiated US policy with Russia while Obama was still president, there has been a lot of outrage. Also: they lied about it while testifying under oath. That is generally frowned upon... And is very illegal.",
"one thing the previous comments haven't really mentioned that *may* happen is because he is a lawyer he may (will) be brought infront of the state bar committee ...no lawyer wants this in the best of times fraud is one of the ABSOLUTE things a lawyer cannot do (you cannot harm the image that lawyers are supposed to be absolutely honest and ethical. it is more complex than that, but the basics are there) with that in mind the attorney general is essentially the 'chief prosecutor' of the nation. Could you imagine if he couldn't actually practice law (and again fraud is such a big 'no-no' that other states/districts will not accept you into the state bar) Because the justice department/judiciary are supposed to be free from politics it is virtually impossible for him to survive this and be capable of being the AG",
"It's not the fact that he talked to Russia. And unless there is evidence clearly showing direct collusion with the Russian government (or anything else illegal or unethical), it's not even really the content of his communication that matters. What matters is that during his confirmation hearing he *lied* to the Senate. He committed perjury. He was asked a direct question by the committee, and his answer was not truthful, and he *knew* that it was not truthful. And that's a crime in and of itself, but more worrying are the other implications: if he lied about that, then what else could he be lying about? And in addition to that, there has already been one member of Trump's cabinet who has had to step down as a result of being caught having inappropriate communications with the Russian government, so catching another person who has engaged in that behavior really does not look good at all for Trump's administration.",
"The most famous and important cases of American politicians getting removed from office or otherwise in major trouble aren't from immoral or unpopular things they did-- it's from lying and concealing it. Sessions did this.",
"1. The Logan Act, it's illegal for him to do that. 2. He directly said that he did not speak with Russians, *something he wasn't even asked, by the way*, while under oath. This is perjury. 3. Even if it wasn't perjury, it proves that he's a lying liarpants, who needs to be dragged into the street and pelted with eggs.",
"There are multiple layers to it, I'll try to be as thorough as possible. First of all, it's forbidden to talk policy with foreign entities as a private citizen under the [Logan Act]( URL_0 ). While Jeff Session claims that he was acting as a senator, it's disputable whether it was his function to talk with the Russian ambassador in private. There are certain protocols in place for such inquirie from foreign ambassadors. Kushner and others of the Trump campaign were certainly violating this law. Secondly, allegations of Russia meddling with the election have been making circles for just short of 6 months now. Trump himself was alleged to be compromised by the Russians in the Steele dossier, and a lot of his appointees have long standing ties with Russian officials. If those allegations hold true, then there may be criminal implications in the private, undisclosed talks to Russian officials. And lastly, for Session specifically, while it may not be inherently bad to talk to Russian officials, he was asked of such contacts under oath in front of the congress and chose not do disclose them. Lying under oath is perjury, a crime that is sentenced with up to 5 years in prison. For someone in his position as attorney general, that's not a good thing to have on your record. It also raises a lot of suspicions, naturally. If you haven't talked anything that could be subject of criminal implications, why would you lie about it/omit it in a hearing? With everything else going on, the implication is strong."
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5x6oun | How can they tell what started a wild fire? | Other | explainlikeimfive | {
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"Wildland firefighter here (Alberta). Sometimes it's impossible to tell. But most times it can be sleuthed out by examining the site specifics such as the fuel type, accessibility, any evidence or signs left behind. The indices of the day are an important tool, they help us understand the likelihood of ignition occurring. If an arsonist uses an incendiary device (time delayed ignition thingy) then there's going to be obvious evidence of this when personnel zero in on the origin site of the fire. At the origin, the fire is low intensity and doesn't burn hot enough to remove evidence like that. As the fire travels with the wind, it gains intensity and burns increasingly heavier fuels. But at the outset it's only really going to burn fine, flashy fuels. If the fire originates in the ditch of a quad trail, it's typically chalked up as having been started by an exhaust clinger from a quad or side-by-side. I've seen cases of this where the operators have stuck around to own up to it and offer statements, as well as cases where they've taken off. Hell, I've arrived on a fire where a Polaris side-by-side had apparently over heated and was fully involved by the time we got there. If the origin of the fire is downwind of a flare stack, typically there will be follow up with the operators at that work site if they weren't already involved. Occasionally, flare stacks will \"burp\" up some flaming bitumen bits and that'll cause a fire with the right indices. Or their flare will go out and they'll reignite it by shooting a flare pen/gun etc at it. This is illegal for obvious reasons. I've had to work on such a fire. Idiotic. When it's lightning caused it's fairly easy to figure out. There's typically a blown up/burnt /scarred tree at the origin site. Our province does a pretty good job keeping track of lightning activity and we know based on lightning frequency and indices how likely we are to see smoke puff up due to a lightning hold over. Sometimes fires are due to abandoned campfires and these are beyond obvious to identify. Burn piles left unattended (think farms, industrial lots such as forestry slash and such) can occasionally creep off and lead to wildfire. These are easy to tell. When a downed powerline is the cause, again, it speaks for itself. For the human caused fires, often there are witnesses. In these cases it helps a lot to remove any guess work.",
"Found the prospective arsonist! Various ignition sources leave telltale chemical signatures. As long as you know about the fire quickly you can narrow down where it started. Then forensic chemists head there and test for various residues.",
"Fire burns up hills (grades) and not down them, and it burns with the wind and not against it. I have worked fires that were tens of thousands of acres, and if you just walk into the wind far enough, you will find the point of ignition - usually a campsite with a fire ring, or a stump with a bunch of cigarette butts laying around it. Sometimes you can actually see the offending cigarette butt.",
"Couldn't an arsonist just kick some dry leaves into a pile and then use a propane torch to start it? I'm just spitballing here, but if they did it like that, there's no residue to speak of for a chemist to detect. And if the criminal walks away with the device used, there's nothing to find (versus a cigarette butt or something). I always wondered about that, there's this enormous forest fire and you hear on the news how they traced it all the way back to a cigarette butt or something. Always sounds near impossible to do.",
"There are some interesting answers here, but look at the common denominator: you have to know *where* it started. If you have a witness, then you pretty much go from what they say started it. From there, it's basically a guessing game. If they test something in the area and it comes up positive for whatever flammable chemical, then you blame it on that chemical, and it's arson if the chemical wasn't supposed to be there. If there is a campfire site in the area, then it's blamed on a campfire. If there are 4-wheeler trails in the area, you blame it on 4-wheelers. If there's a smoke stack upwind, then you blame it on that. Lightning strikes in the area and a blown tree are probably one of the more scientific findings. Fire investigation is not nearly as sound of a science as it's been made out to be. Texas executed someone recently based on this false science, which begs the question of just how many investigations these fire investigators/wannabe detectives have broken. Imagine how there have been entire conventions and training programs that are basically just Joe Blow fire-fighters teaching their peers their uninformed hunches, labeled as hard fact.",
"Over where i live they have an expert usually working the case. He's pretty serious about his job. He teaches everyone he meets about what to watch for. That dang smokey the bear is a sharp feller."
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5x6uma | What determines the noise or visual pattern of TV static? | i was wondering this for quite a while, and i just want to know what makes TV static look and sound the way it does. is there anything that makes some bits white and others black? Same for radio static | Technology | explainlikeimfive | {
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"For the most part, it's stray electromagnetic noise, with about 1% being background microwave radiation. As for why the picture is only white or black, it has to do with how your receiver interprets those signals. Most television receivers have automatic gain control, so the input to the TV is always at a proper 'loudness'. When you see static, that's because there's no actual signal, and what else is there is really weak, but the automatic gain control doesn't know what's a signal and what isn't, so it amplifies whatever is there. The rest of the receiver, or the TV itself, also doesn't really know that what it's getting isn't a signal, and just tries to display it as best it can. The reason you only have bits of black and white and not any other colors has to do with how color is encoded into the signal. Back when television first became a thing, they could only display black and white. So the signal was encoded such that a 'high' level was white, and a 'low' level was black. When color was coming onto the scene, they didn't want to create a whole new standard and leave out the people who still didn't have color TVs, so they made it so that a color signal still had the same brightness level as black and white encoding, but also a quickly vibrating signal overlaid on it that color TVs could interpret as color, but black and white TVs weren't bothered by. This quick vibration only works at one specific frequency though, and electromagnetic noise can't trick the color decoding on TVs. What does work still is the 'high' and 'low' level sensing for a black and white signal, so you get the white and black static field on the display. As for radio, it's really the same reason as TVs, since analog TVs used to primarily get their signal from radio antennas, just at different frequencies.",
"All I can tell you a about static is that it's background radiation. I think in the '60s or '70s, these guys with a microwave scanner kept getting background noise and couldn't figure out what it was. They were looking for microwave radiation to make the Big Bang Theory a *theory* and not just an idea. At the same time, some other scientists were also trying to find background radiation. Eventually they got in touch and as t turns out, static (radio for sure) is theorized to be leftover radiation from the Big Bang. I know it doesn't answer you're question, but there's some context. Check Scishow Space and Bill Bryson's A Brief History of Nearly Everything for more information and better details."
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5x6za3 | What causes pain during a headache? | I'm not asking what causes headaches, rather what is happening that causes you to be in pain? Also, are pains from a migraine caused by something similar? | Biology | explainlikeimfive | {
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"I think it varies a lot on the type of headache. The two main answers from this question when it asked was: There's actually an \"international classification of headache disorders\" that classifies the different types of headaches. The brain itself has no pain receptors, because all pain receptors send their signals to the brain. It's the thing that's doing the \"feeling\" of the pain. This is why awake brain surgery works as well as it does: the neurosurgeon can go in an electrically stimulate the awake brain and remove brain tissue without the patient feeling anything. As can be seen in the ICHD, there are many kinds of headaches. Some are caused by muscle tension in the head and neck. Others by inflammation pressing against nerves. Some even caused what's called \"referred pain\", which is when it feels like the pain is in one place, but that's actually a \"phantom\" pain being caused somewhere else. The classic examples are heart attacks and ice-cream headaches. In ice-cream headaches, the rapid cooling of blood vessels in the throat and mouth stimulate the trigeminal nerve which brings in pain information from the head, making it feel like your head is in pain when the stimulation is actually happening in the mouth. For other headaches, it's good to know about the three protective layers, called meninges, that cover the brain: thepia mater (soft mother), which adheres to the brain and is very fine; the arachnoid layer, which sort of provides a barrier between cerebrospinal fluid and the rest of the circulatory system; and the dura mater (hard mother), which feels very leathery, like bat wings, and holds in the cerebrospinal fluid. These meninges also help form the blood brain barrier and cover a lot of the fine blood vessels that supply the brain with blood. Both the blood vessels and meninges have pain receptors. The pain receptors in these regions can be stimulated by a lot of things. For example, meningitis is when these become enflamed due to infection. This inflammation is painful due to the stretching and pressure. Similarly, pressure changes brought about by dehydration or changes in blood salinity or what have you (like in a hangover) can also cause pain that we feel as \"headaches\". So in short: there's not one kind of \"headache\", and sometimes even though a headache feels like it's located in one place, it's not really because of the phantom stimulation from referred pain. **Credit (although he credits someone else who is unknown) : /u/falmingmanny** The second more simple answer was: Lot of the time it's related to the blood vessels in your brain they get smaller or bigger and put pressure on other structures such as the membranes that surround your brain. Example, if you are really hung over and have a head ache it is because you are dehydrated, how does this happen you may ask? Basically your brain is incredibly amazing and rather stupid at the same time. Body: shit were really dehydrated we need some water where can we get it. And your brain being the generous chap that it is steps up to the plate. Brain: hey I've got plenty of water here have some! And the membranes that envelope your brain don't shrink along with it as it loses water putting tension on then making your head hurt. That's just one example. By and large it has to do with the expansion and constriction of your blood vessels, unless there is some other underlying problem. **Credit: /u/Suicidebylifestyle**"
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5x73oe | How did Scientists create a 1.4 mb strand of DNA? | Biology | explainlikeimfive | {
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"It's a little complicated so bear with me. I won't go into the chemistry too much though. **Step 1** We start by chemically synthesising nucleic acids of the various types. Adenosine, Thymine, Guanine and Cytosine. There are many ways of doing this but we're interested in making molecules that are a bit different from the ones that the body uses. Ribose is a sugar with 5 carbon atoms in it. Off those carbon atoms are various chemical groups and one of those groups is the acid that gives the nucleic acid its identity. The other carbon atoms have hydrogen or hydroxyl (-OH) atoms connected. We can label the atoms 1' (read as one prime) through to 5' and DNA is connected with the 3' carbon linked to the 5' of the next nucleic acid. So 5' is the \"front\" and 3' is the \"back\". What happens is that researchers make nucleic acids \"protected\" by adding molecules to the carbon atoms that will not react. Essentially, they prevent the DNA chain from growing past that point. The short DNA chain is called an oligonucleotide. So, start with a solution of one type of nucleic acid. Add a second with a protected end and some enzymes to catalyse the reaction. Then wash with acid to remove the \"protecting\" molecule, add another nucleic acid and repeat. (this is VERY simplified). Eventually you get a chain of DNA with the exact nucleic acid order that you wanted. Of course there are errors here but you can weed them out by HPLC (high performance liquid chromatography) to separate out the oligonucleotides by mass and size. You know exactly the size and mass that you want so you can always get the right sequence here. **Step 2** So now you have a lot of oligonucleotides that, if chained together, will make up the sequence you want. Here you can either use special enzymes called ligases to link up the oligonucleotides. Of course they're going to link up fairly randomly but you can select for the one you want by sequencing the final ligated construct. Or you can use polymerase chain reaction if you were smart enough to use oliginucleotides that overlap a bit. PCR uses other oligonucleotides to start off normal DNA synthesis which will then use the overlapping oligonucleotides as a template. Again, you verify the result by sequencing it. **Step 3** Keep going, slowly getting bigger and bigger chains until you get to the size you want. It's laborious, time-consuming and incredibly painstaking work. Source: creating even short artificial genes sucks dogs balls. Major kudos to these guys for their patience and fortitude."
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5x766i | What happens to insects in winter? | In Europe, you see very few insects in winter. What happens to them? | Biology | explainlikeimfive | {
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"Many insects simply die in the winter. But they lay tons and tons of eggs all over the place that then hatch when it warms up. Many bugs also hibernate in hidden nests, protected from the elements. They enter a dormant stage where their metabolic processes slow down and they don't need much food or heat to live."
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5x76ae | Why do puppies always want to lick your face? | Biology | explainlikeimfive | {
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"Licking to show affection is a functional behavior that puppies learn from their mother and littermates. Maternal licking and licking among littermates helps strengthen family bonds. A dog licking your face is expressing his affection for you and trying to strengthen the familial bond he has with you.",
"My puppy loved to lick feet a lot. I think it's a way for a dog to identify who is who as well as understand chemical signatures of a person to judge your health, current mood etc. It's also something they do the same way human babies constantly hold onto things and grab things, it's part of them exploring. Dogs don't have hands so they use their mouths, nose, ears and tongue to explore, identify and classify. It is important to teach a dog to not bite but remember as puppies they don't bite down hard deliberately but to grip you like a baby does with his hands so don't get too angry when they do it, just remember to give them their shots before you let their teeth near you. A dog could remember a specific person by a particular characteristic smell, taste, voice and touch. Unlike us which we use our eyes to distinguish who is who and remembering names and personalities. Heck dogs could even remember the sound of the way your feet hit the ground and know exactly who that is as well as the type of sound you make when you close your car door. This is what people confuse with the dog's sixth sense, dogs use every sense in very unique ways that it surprises people that dogs can tell exactly who is coming from the parking lot to home without even having to see far off in the distance.",
"This is similar to asking the question: Why do people cry? Dogs will lick faces for a variety of reasons just like a humans will cry for a bunch of different reasons. Puppies specifically are likely trying to learn about you and the world around them. Human babies also do this, if you think about the first house you lived in and the floor there I bet you can remember how it tasted. Puppies also lick the faces of their mothers to trigger a regurgitation reflex so it is possible they are trying to communicate that they are hungry. Dogs in general will also lick a humans face for a variety of reasons. The salt on humans skins is often enjoyable to dogs and they lick it for this reason, they could be curious about your feelings as their noses and mouths are sensitive enough to sense chemical differences in a stressed human or a happy human. It could be that they are submitting to you, or it could be that their owner when they were a puppy indicated that they liked getting licked and so the dog continued to do so as a learned behavior. here is a link explaining other reasons as to why they lick: URL_0 TL;DR: Dogs lick for lots of reasons, puppies mostly out of indicating hunger and exploring the world around them like all babies do. In short: because they're good dogs, Brent. Edit 1: Was not expecting the ton of response from the floor licking thing. Yes I do remember what the floor in the first house I lived in tasted like. It was a carpet though I have almost no recollection of the house in general. Many people (though not all) will be able to remember this or something similar because it is one of the first memories that forms a negative experience and tell the brain 'Yeah. No. Don't ever do that again.' So it forms a very strong permanent memory. If you don't remember either you didn't care what the floor tasted like so that negative reaction isn't there, you have forgotten because brains are weird and awesome and complicated, or your parents kept you from doing it in some fashion.",
"Wolf puppies greet their mother by licking her corner of the mouth to trigger her gag reflex and vomit out food (she would do it anyway but it's a mix out of \"love you\" and \"food pls\" I guess)",
"As I understand it, dogs lick the faces of those above them in the pack order as a sign of submission, or as a sign of affection. They're making sure everything is okay.",
"Licking the face (self) is a sign of stress -- be that eustress (oh boy, yay!) or distress (oh boy, oh no!). Licking is often an appeasement gesture. Appeasement is not submission in the out-dated 1970s idea of wolves. Appeasement is more like \"Here I am, no threat, you can stop doing the thing I don't like.\" A dog may lick you if he is nervous about something or someone, including you. It's a deescalation social gesture, much like how humans raise hands out in a in front wide \"hey, it's okay, no worries\". We do this subconsciously to indicate our hands have no weapons, they are not in a position to throw a punch. Dogs also turn heads away, yawn, shake their heads, or scratch to help relieve stress. Licking can, of course, be due to taste such as lotions and sweat. Many dogs like to lick humans fresh out of the shower and seem attracted to the body wash remnants. Do not allow a dog to lick lotion, especially medicated lotion or sun lotion, off your hands or face. Like humans, dogs can develop OCD behaviors. Some classic dog OCD behaviors include a frantic attempt to 'catch' light that never ends, escalating to more and more diffuse light sources, and licking /gnawing at an existing wound, creating a point of infection that does not heal. It's important to interrupt and redirect any start of OCD type behavior and to consult a behaviorist as soon as possible if a dog can not be easily distracted from tail chasing, light chasing, or licking. The behavior can become consuming without intervention.",
"When a wolf pack returns from the hunt, puppies run up to lick their chins, which triggers an involuntary reflex to regurgitate part of their meal. The pup, either at the weaning stage or older (but still not ready to join in hunts), gets a prechewed meal - basically baby food - plus an infusion of gut microbes to help pass along beneficial digestive and immune-aiding bacteria. Pack members who don't want to share - either because they don't like the pups, or aren't closely related - won't let the pups lick their faces, obv. If a puppy licks your face, he is partly asking for nourishment, and partly checking to see if he would be protected & fed by you - just like when you seek kisses from a loved one (part oral fixation/nipple replacement, part communicating the affection to both of you).",
"From wolves- puppies lick their mothers face to make their mothers regurgitate their meal, and puppies could eat this partially digested meal. Dogs basically lick your face to let you know they are excited and hungry.",
"In animals that are domesticated you see neonate behavior into adulthood. In feral canids, licking adults mouths is how they get them to barf up breakfast. It's also a submissive behavior.",
"Just like human babies explore the world with their mouths, so do puppies... it's also a show of submission and affection through grooming",
"When you see a dog lick its balls, it's much the same thing. Anything that looks like balls gets a good lick'n.",
"Dogs licking your face/your mouth is not only a sign of affection, but also submission/subordination, as in \"You're the boss\"/\"i belong to you\"/\"You are my guardian\" Dogs don't only do this to humans but also their parents, other dogs and even other animals. [Wolves will also do this to discern their rank in the pack.]( URL_0 ) Licking the face of their alpha is to convey their own social standing as being lower and respecting the rank of the other. Usually they do it when there is tension, and one needs to make a point that it isn't a threat and isn't challenging the alpha. I should also mention that dogs are very much different than wolves. Their behaviors might stem from wolves, but they are thousands of years apart in genetics and behavior.",
"The face is the only place a dog cannot clean on its own, and it's the part of the body most susceptible to parasites. Dogs saliva contains an antiseptic. They lick faces the way chimps groom other chimps. It's a sign of respect and they instinctively believe they are providing you a valuable service.",
"I think the better question is, why do so many people like dog spit on their face?",
"There are a lot of cute answers here... but I think its salt right? Same reasons cats will lick you as well. They dont really care that its your face, its salty skin and it taste good.",
"man the top 3 are all wrong. i can't believe nobody knows this. dogs will lick the mouth to show affection and to show submission. they only lick the face of a dog above them in the hierarchy. it's not your face they want to lick. it's the mouth area. it's not just puppies, dogs of all ages will do this. you might think they want to lick your face because you avoid it when they try to lick your mouth."
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5x76j0 | What causes a human to want to pick at their scabs? | Biology | explainlikeimfive | {
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"Scabs cause slight irritation to the normal skin around it. Our instinct is to remove irritation because most of the time, they lead to infection in the wild",
"Scabs are very similar in feeling to a foreign body stuck to your skin. Cleaning foreign things off our skin is often a good thing, such as if you have a tick stuck to you, or a dried piece of cake batter on your face. Self-cleaning and grooming is important to stay healthy and sanitary. Thus if you can't immediately feel the difference between a scab and something foreign, your grooming instincts will kick in. If the scab is too large or fresh it may hurt to try to remove, so whether you continue to do so depends on the balance of your own innate desire to self groom, and the pain of removing the scab. Often scabs can be safely removed long before they fall off naturally, as the skin underneath has mostly healed. Just like pulling a piece of tape off your skin may be slightly painful, it certainly won't do you harm in the long run. Thus the grooming instinct very often wins out. Also, an additional tidbit that might motivate the grooming instinct for scab-picking is cosmetic reasons. Looking healthy/good/not-covered-in-scabs is important for a lot of people. Picking off a dark scab can often look better than the slight redness underneath (depending on personal complexion and how healed the wound is).",
"I have been doing this for most of my life. A lot of the time it is involuntary and I don't even notice it until I am bleeding. From what I have heard, it is a combination of nervous/anxious habits and possible endorphins being released. I notice it more when I am under a lot of stress at school. Additionally, it can be due to a more serious psychological issue similar to OCD in that the picking is a compulsion. I know this is not exactly a scholarly article but it describes this part of the explanation. URL_0 TL;DR: For me, anxiety.",
"Impatience. You know it will fall off naturally, but no one wants to wait forever for it to \"just happen\", so we instinctively try to hasten the process by picking at it (picking at the sides of a scab, in theory, would make the scab fall off sooner due to the fact that more air would be allowed under it). EDIT: or just rip it off prematurely, and start the process over again and hate your life.",
"Cats and dogs instinctively lick their wounds. I wouldn't be surprised if picking scabs evolved from similar behavior.",
"Theoretically, Scab-pickers have similar survival rates as non scab-pickers, therefore no evolutionary adaptation has taken place.",
"Cause it feels good when the endorphins hit?",
"Scabs itch and / or irritate your skin. Scabs also feel \"foreign\" to you, so you will subconsciously touch the scab.",
"No answer for you, but I pick at my skin on my fingers until it makes a scab. It was an anxiety thing and now it's a habit. I think there's some self harm rooted in there, too.",
"I have been a scab picker for as long as I could pick them. Why would you not pick them? Alot of the time the scabs stick out farther than the skin and may Feel weird when rubbing on clothing. Some of the scabs I end up with now are ingrown hairs. It's something that's irritating that has a very simple solution ;)"
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5x78gc | Why do bacteria/viruses/parasites that are host dependent eventually kill their host? | With the exception of bugs that get released once they kill their host and keep reproducing, why do some who can't survive with out their host eventually kill their host? Wouldn't they want to survive too? In my mind the ideal would be to keep them weak enough they can't fight back, but not so crippled that they die and then everything collapses. | Biology | explainlikeimfive | {
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"There are many reasons why pathogens would kill their hosts. I'll go through a few: 1. The host dies only after the bug gets transmitted to a new host. A good example of this is tuberculosis caused by the bacteria *Mycobacterium tuberculosis*. The bacteria infect a host and can multiply without symptoms (latent tuberculosis) for quite some time before occasionally transitioning to symptomatic or active tuberculosis. The symptomatic person can transmit the bacteria in their coughs, sneezes and breath. Only active tuberculosis kills and then only about half the time so the *Mycobacterium* can have a great time multiplying in a host, spreading **then** killing them. 2. The host dies because of an accident. Zoonotic is a fancy word that means that the disease agent came from another species. Ebola is a good example of a virus that almost certainly came from another species. As you probably know from many news articles, Ebola kills rapidly in quite a gruesome manner. This is because Ebola isn't well adapted to humans yet and kills them quickly. In their natural reservoir (host - probably bats), Ebola is largely benign and doesn't produce symptoms which allows it to be transmitted freely. 3. Genetic drift or shift. Generally there is a trade-off between how infectious a disease agent is and how quickly it kills the host. Some diseases are highly infectious (eg. influenza) but rarely kill. Those diseases generally undergo genetic drift which means that they slowly change their surface proteins (antigens) and are able to keep infecting a portion of the population as they change. However, sometimes those diseases undergo genetic shift to present a completely different set of antigens to the immune system. When that happens you get a disease that is both highly infectious and much more lethal because almost no one has any antibodies against it. Influenza is literally the textbook case for such a disease. Many diseases evolve to never kill their host. In fact, there are many diseases that have evolved to produce few or no symptoms. Our DNA is littered with [endogenous retroviruses]( URL_0 ) (ERVs) which are considered to be the remnants of ancient retroviral diseases which became inactive once they entered our genome. They are the ultimate opposite example to the point that you raised in the original question - they are diseases that have evolved so much that their host never dies and always passes them on, they are effectively immortal.",
"Because they do not have the ability to process cognitive thought and therefore cannot look at a big picture scenario like that."
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5x78mw | Does drinking a lot of water dilute stomach acid? | Biology | explainlikeimfive | {
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"Yes, a bit. Stomach acid is really strong so i dont think your stomach is big enough to dilute it significantly. milk will also neutilize it if you have heart burn"
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5x78ph | Why do candles smell strongest when you blow them out? | Some context, I was sitting in my bathroom doing my business when I realized it didn't smell so good. I considered lighting a candle but in my head I thought, "What good is it? It's not going to do anything until you blow it out." | Chemistry | explainlikeimfive | {
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"The scent is often oil based. If you burn the oil, you destroy the scent. But blowing it out, allows it to smolder thereby vaporizing the oil scent and filling the air with droplets of scent. (The same principle with incense sticks when you light them on fire, they smell stronger when you blow out the flame).",
"u/Sounds_of_Spokane is thinking about scented candles, but is overthinking. He's kinda accidentally half-right. What's happening is inefficient combustion. If you have perfectly efficient combustion, you'll have carbon dioxide, heat, and light as the three byproducts of a chemical reaction. All pretty well odourless. Candles are reasonably efficient when they're burning. When you blow out the candle, you remove a lot of the heat from the reaction, lowering the efficiency, allowing all sorts of other byproducts to emerge in greater quantities. These byproducts smell. You'll also notice that candles or matches rarely produce smoke when lit. It's when you extinguish them that you see the smoke. More smoke, more smell."
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5x79ee | How do musicians come up with chord progressions? | e.g. the guitar here has a tritone tuning, does that completely jumble up how you create chords? I know how scales work and how you can make chords from them, but how do people create a progression of many chords that work together, especially in complex music like this? URL_0 | Other | explainlikeimfive | {
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"That's where the art comes into it. It's intuition and taste. Sure, some people can write brilliant music with a mathematician like rigor, but I think most writers just feel it out. Trial and error."
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5x7n7z | If Potassium Iodide (KI) protects us from radiation, why we are not given KI before CT scans ? | I know it does not save all of the body, but would not it at least help? Pardon my ignorance, a brief google search did not help either. | Chemistry | explainlikeimfive | {
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"A few reasons. First of all, KI really only protects your thyroid gland. Your thyroid gland produces hormones that include iodine, so if you ate radioactive iodine, then eating more iodine (KI) helps reduce the amount of radioactive iodine that gets used in those hormones. The less used in the thyroid hormones, the less sticks around to harm you. That brings me to point two, KI only protects you when you ate radioactive iodine! It doesn't protect you from external radiation sources, for instance. And lastly, CT scans have low radiation doses, and there's really not much risk at all, unless for some reason you needed a ton of them."
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5x7nxa | Why does the History Channel not show more historical programming? | Other | explainlikeimfive | {
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"Remember when MTV used to show music videos instead of reality tv? Remember when the SyFy (Nee SciFi) network showed science fiction shows instead of professional wrestling? Remember when TLC (The Learning Channel) showed actual documentary type shows? (Insert obligatory \"Pepperidge Farm remembers meme here.\") Those aren't making money now, so they show whatever brings home the bacon regardless of the station's original intent and call letters.",
"That's commercial TV for you. The people who enjoy Ancient Alien Pawnshop Bake Off outnumber the ones that are interested in documentaries. The former costs virtually nothing to produce while giving higher ad revenue.",
"The History Channel will show whatever gets them views. Real History just isn't that popular compared to something like Ancient Aliens. Also, there are plenty people like me who just watch those shows for entertainment and don't believe a word of what they are saying."
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5x7spm | Why are headaches and toothaches much less tolerable other kinds of body pain? | Like its *really* hard to do just about anything with a headache/toothache than having a cut or some other form of pain. | Biology | explainlikeimfive | {
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"As far as teeth go, it's that teeth nerves are hardly shielded at all from debris and other shit. Cavities are basically tunnels leading to nerve endings. If we had our nerve endings exposed in such a way, it would also hurt quite badly. The equivalent of a cavity would be for someone to stab a hole in your skin, going into your nerve endings, except that your teeth do not heal naturally. As far as the head goes, it really does depend heavily on what kind of pain you're talking about."
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5x86h2 | How deep into the Earth could humans dig? (If any equipment was available) | Other | explainlikeimfive | {
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"\"The result was the Kola Superdeep Borehole and a drill-depth of more than 7.5 miles (12 kilometers). To put that in perspective, Kola descends further than the deepest point of the ocean, which lies at nearly 6.8 miles (11 kilometers). The borehole is located on the Kola Peninsula of Russia.Mar 11, 2015. \" URL_0 They had to stop drilling because of the heat.",
"The Russians drilled a hole just to see how far down they could go. It's called the [Kola Superdeep Borehole]( URL_0 ) and reached over 7.5 miles, but the ever increasing heat caused drill bits to fail.",
"Pretty sure there diamond mines that are 2 miles deep. As I recall the problem is that it is nearly a hundred degrees at that depth"
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5x8jb7 | Why can't we just surgically remove all the fat in a morbidly obese person in addition to the gastric bypass surgery? | Biology | explainlikeimfive | {
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"In small amounts, it's called liposuction. In large quantities, it's way too invasive and traumatic. Fat isn't just a tank of lard, it's actual living cells with blood vessels and everything.",
"We sort of can, but that's not really all or even a majority of the fat in a person. There's subcutaneous fat which is the layer of fat just below the skin, sort of like the layer of fat on the outside of pork belly bacon. Then there's the visceral fat that's wrapped around the organs, like the suet on beef kidneys. Then there's intramuscular fat, like the marbling on a steak. Liprosuction is an example of a fat removal procedure that can remove the subcutaneous fat. Removing the visceral or intramuscular fat on the other hand is far more difficult, if not impossible.",
"Its an extremely traumatic process on a large scale, liposuction effective tears out adipose (fat) cells. Those cells have capillaries supplying blood flow / oxygen, which on a large scale damage to these may lead to cardiovascular events. Plus the risk of infection, cardiac arrest, all the normal things that go with surgery as well. I don't have a link for proof of stats, but you are 20 times more likely to die from liposuction over general medical procedures. Not ELI5, but mortality stats - URL_0",
"You can remove a large amount of it *but* you encounter problems. One is that it's a traumatic operation, two is that the fatter someone is the more likely complications are to result from surgery. Morbidly obese people would likely die if you tried.",
"In addition to points already made about visceral fat, the maximum volume that can safely be removed by liposuction is 5 liters, depending on who you ask. Only a portion of this volume is actually fat due to a percentage of aspirated tumescent fluid, which is a mix of saline, lidocaine, and epinephrine injected during the liposuction procedure to decrease bruising, bleeding, and pain postoperatively. Higher volumes of liposuction aspirate increase risk of bleeding or more severe complications such as pulmonary embolism.",
"A lot of the health problems come from fat between the organs. That is the real source of illness due to volume of fat. Surface fat is not as large of a concern, though it still is. It is also seriously hard on the body . It took slot of work to get that fat, and liposuction isnt the magic cure that many people think it is.",
"As somebody who feels worse in his body AFTER losing 299lbs, this would have kicked ass if it were an option after having gastric bypass ten years ago.",
"The blood vessels to the skin pass through the subcutaneous fat. If you stripped away the fat layer, the skin would die for lack of blood supply. Similarly for belly fat. It's full of blood vessels that feed the intestines."
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5x8mkp | What category of taste does mint fall into because it doesn't seem to fit with any of the five tastes? (sweet, sour, bitter, salty and umami) | Biology | explainlikeimfive | {
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"Tastes are on your tongue (sweet, salty, sour, bitter, savoury), but **flavours** are in your nose, and all those other flavours is what gives your foods everything besides the 5 basic tastes. What makes an apple different than an onion is *flavour*. Mint also does something else that's not a taste or a flavour, and that's accidentally activating cold touch receptors in your mouth, giving a \"cooling sensation\", the opposite of a hot pepper that activates the hot touch receptors."
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5x8rv3 | Why does eating spicy food burn? | Like what exactly happens when the pepper goes in your mouth | Other | explainlikeimfive | {
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"text": [
"The spicy sensation is caused by capsaicin, which can be found in all spicy plants. It's an evolutionary defense mechanism, intended to put you off eating spicy foods by creating an unpleasant, burning sensation. I believe humans are the only animals to eat spicy plants *despite* their spiciness. NB: birds cannot taste 'spicy'. They lack the receptor that capsaicin interacts with."
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5x8wjr | How they manage to store data in DNA and receive it again. | Regarding this subject I'm 5 years old. Be gentle. | Biology | explainlikeimfive | {
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"There are companies who will produce DNA for you. You order a sequence: ACGTTGTA And they chemically make the DNA by adding the bases one at a time. To store and retrieve information as DNA, they had to choose how to *encode* their data as DNA. Binary has 0 and 1, DNA Has 4 bases, AGCT. You can therefore map 1 DNA base to 2 bits, A=01, G=10, C=11, T=00, say. If it was possible to create and read huge segments of DNA, you could just encode your data as one giant DNA Sequence. However, you cannot really synthesie or sequence large segments of DNA. Most DNA sequencing is done on an Illumina sequencing platform. They have maximum read lengths of ~600 basepairs, but you get better read depth on the machines which do ~300 basepairs. So if you split your data in to 400 bit chunks, then each 300 basepair segment can encode 600 bits, 400bits of message, and 200 bits of error corection codes and location information. You pay a company to make all of these 300 long segments for you. When you sequence the DNA, you get 100 million 300 base pair reads. Each one can then be decoded into a data bit, and a location. Then just assemble all the data, and you're done!"
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5x95e8 | If an elderly person is, literally, as fit and healthy as possible, what will eventually kill them? | Biology | explainlikeimfive | {
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"Basically, as we age, our cells make copies of themselves using a set of \"directions\" that gets worse with every copy as our life goes on. Eventually these cells cannot reproduce as efficiently, and our organs become less efficient as a result. No matter how healthy a person is, it can only slow down the imminent fate of death. But stay active, and you could live past 100. I believe the oldest man alive is like 120 or something in that range and he still tends the garden every day, but in an interview she said he's tired of living and wants to just die. When you get that old you have to keep moving though for the sake of it I suppose.",
"A ninety-two year old friend of Groucho Marx died. When another friend asked what he died from, Groucho said \"Too many birthdays.\"",
"Statistically: heart disease, cancer, or stroke. Of course, all of these violate your condition of being perfectly healthy, but no one stays perfectly healthy as they age. Some people stay healthier than others, and those people live longer. But dying \"of old age\" is just dying of some health problem when you are old enough that it's expected. \"Old age\" isn't a valid cause of death for legal purposes."
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5x9g4f | How are credit card numbers validated? | Technology | explainlikeimfive | {
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"The first step in that the first few digits will be checked to correspond to a certain company. For example an Amex card will start with 34 or 37 and will be 15 digits long. Where as a Visa will start with a 4 then the next 3 digits describe the issuer and card type, it will also be 13, 16 or 19 digits long. If it then passes this then a Luhn algorithm will be checked. You take every second digit(except the very last one) and double them. Any double digit numbers are added together to get a single digit. You then sum these numbers up with the other digits and get one whole number. The modulus 10 of this number should be 0 if it isn't then one or more digits is wrong. So if you have 80 then the modulus 10 is 0 so it works whereas if you had 23 then the modulus 10 is 3 and you know there's an error. Now that you have an entry that you know is accurate the machine then contacts the bank to verify it with the CVV and expiry date to authorise the purchase."
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5x9ge2 | - Ryzen Cpu's? What's all the fuss about? | I get that they're AMDs new CPU's, but there seems to be a damn lot of fuss being made. Have AMD changed the game or something? Or same old same old? | Technology | explainlikeimfive | {
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"Long story short: For roughly the last 10 years, Intel have dominated the performance CPU market. For the last 5 years, Intel have dominated it to such a degree that they've practically stopped trying to push performance forward in any meaningful way, with gains of little more than 20% in their last five generations of desktop processors. As workloads have increased, people have become more and more unhappy with Intel's reluctance to push performance forwards, and their high prices. Intel have gotten away with coasting for so long because AMD (the only other desktop CPU manufacturer left) haven't offered any sort of competition. With Ryzen, AMD promised to change that. As we learned yesterday when the reviews embargo lifted, AMD were only partially successful - they've released a series of new CPUs that can offer, depending on use, the highest level of processing power of any CPU on the market, at less than half the cost of the equivalent Intel chip. That's brilliant. What's not so brilliant is that Ryzen isn't particularly efficient where it comes to the performance loads placed on a CPU by gaming, which has lead to a bit of a backlash from the gamer community. Ryzen's performance *will* improve over the coming months and years, as microcode tweaks fix certain issues with the chips, and as software developers come to optimize their code for AMD's architecture, where before they had only optimized for Intel's. As to whether it's a game-changer or not, it absolutely is. There is now, for the first time in 5 years, actual competition in the processor market. That's going to lower prices and push performance forward for everyone.",
"They have re-entered the game in a splash. Half the price for equal or in certain scenarios better performance of their Intel counterpart. Basically all the amd fanboys have their jimmies in the air because there is a *viable* alternative now. It's exciting. Even if you don't like them, competition is going to be good for us."
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5x9klz | If radiation exposure causes cancer, why do they use it to treat cancer patients? Won't it just guarantee they will develop more cancer in the future? | Biology | explainlikeimfive | {
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"Radiation exposure damages cells, including their DNA. Cells with damaged DNA can become cancerous because the damage can cause them to replicate uncontrollably, which is what a cancer is. But enough radiation exposure will kill a cell outright, including those which are already cancerous. So doctors administer radiotherapy in a carefully targeted way such that it only attacks the cancerous cells of a tumour, killing them but leaving the surrounding cells mostly undamaged. Because of the requirement for careful targeting, not all cancers are able to be treated with radiotherapy.",
"When DNA of a cell is damaged from radiation, it attempts to repair it. If that fails, the cell is very likely going to die - but there's a small chance that it mutates, and mutated cells in turn sometimes become cancerous. For a cancer patient, the radiation therapy causing another tumor is a very real thing, but it's not a big issue: It takes years for a cancer cell to develop to a large enough tumor to be threatening. If the patient actually survives until it's grown up, that means he survived the original cancer for years. The bigger threat from radiation therapy is the immediate effect of radiation: If too many healthy cells die due to radiation, the tissue can be damaged permanently. But there's a very neat thing about cancer cells: The same mutations that make them cancerous make it less likely for them to be repaired successfully when their DNA is damaged by radiation. So when you expose a tumor to radiation, the cancer cells are more likely to die from radiation than the healthy cells. Each time the patient undergoes treatment, the radiation dose is calculated so that it doesn't kill so many healthy cells to cause lasting damage, but does a lot of damage to the cancer. In addition to that, the radiation beam can be shaped so that has the largest effect on the tumor, but affects as little healthy tissue as possible. It is also usually aimed at the tumor from multiple directions, like [this]( URL_0 ) - the lines in this image are the shape of the radiation beams, and the color indicates the radiation dose in the tissue. This way, the dose is spread out outside the tumor, but concentrated within.",
"My best friend had really aggressive multiple sclerosis that she said had been lurking in her family's genetics and was \"triggered\" by trauma (she was in a bus that rolled off a mountain). When it got really bad, they treated her with stem cell replacement, which involved radiation and chemo to kill off whatever m.s. bullshit was in her body while growing her own stem non-m.s. cells outside her body (obviously, I'm not an expert, just a friend). Then when she was \"clean,\" they reintroduced the \"clean\" stem cells and the m.s. went into remission and stopped attacking her myelin sheath, but she was still left with the damage that had already been done. (Bedridden and very little use of her arms/hands) But then she developed leukemia. Treatment? More chemo and radiation and another stem cell transplant, this time from her twin sister. Leukemia was gone, but then it became apparent that the trauma of the radiation and chemo had re-triggered her m.s. and she died. She was a nice person and I really miss her.",
"As the saying goes, chemotherapy is the strategy of killing the cancer just ever so slightly faster than you're killing the patient. Hopefully you can catch it and stop in that sweet spot where the cancer is dead and the patient isn't.",
"Well, quite simply yes - all our current cancer cures are carcinogenic themselves. Radiation quite obviously, chemotherapy (at least the toxic kind) depletes stem cells and can damage healthy cells. If radiotherapy is done right only the actual cancer cells receive a high dose. On the surface easy enough, use beta radiation and hit only the tumour. If the thing is deeper you move the radiation around so that while each instance of surface tissue gets 1 dose the tumour gets 10 doses. So, the tumour gets killed and the surrounding tissue gets mild (hopefully mild enough the body can recover) damage."
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5x9ltx | why is a building called a building and not a built | Other | explainlikeimfive | {
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"Linguist here! I'd say it probably has to do with the process element to it. You see it with other nouns - like how a painter creates a painting or a writer produces writing: a builder produces a building. It's interesting though, I've never really considered WHY we'd refer to them in that way, but it fits the pattern of a bunch of other transitional activities, so I'd say it's probably just an offshoot of that."
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5x9q6l | Why does the last 15% of my phone battery life disappear so much faster? | When my phone gets to the last %, normally around 15%, it visibally starts to fall! It only lasts a few minutes! | Technology | explainlikeimfive | {
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"So generally there are a few causes to that. 1. power = voltage * amperage, The lower cell is charged the lower the output voltage will be, li-pols range is 4.2V to around 3.0V, so between 100% and 5% there will be 1.4 times as much drain because the amperage will have to increase to sustain power draw. 2. Resistance inside the cells is different depending on how charged it is, its connected to the cells chemistry. 3. After a few hundred charging cycles the battery is starting to break down, and it's capacity is getting smaller, its possible that the phone sensor doesnt pick it up and guesses that there is more juice in the cells than its actually there. The phone is showing 15% but for real you are left with like 5% battery."
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5x9vms | why/how does your nose continuously produce so much snot when you or sick or have allergies? | Biology | explainlikeimfive | {
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"Snot (aka mucus) is produced by cells designed to keep your airways safe from infection. Some cells are in charge of producing it, while others are specially shaped with bristles (aka cilia) to \"sweep\" the mucus produced deep in your airways out the exits like your nose/throat/mouth. When you get a respiratory infection (cold/flu or other airborne virus) they target cells in your respiratory tract. Your immune system tells your body to make more mucus and sweeping it out, your body is getting many of the viruses trapped in the sticky mucus and removing them so they can't get lower into your lungs. Since allergies are your immune system reacting to something it thinks is a danger, this is why we also produce mucus during allergy seasons as well."
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5xa9in | Why are ejaculations so much more powerful when a guy has been horny or really turned on? | Other | explainlikeimfive | {
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"> has been horny more semen built up > really turned on a harder penis makes the tubes/muscles work more efficiently. This all makes sense when viewed from an evolutionary context. If a man has fewer chances to have sex, you want those encounters to have a higher chance of fertilization. more semen+more back pressure= more boots on the ground if you know what I mean."
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5xaa13 | Puts and Short Selling stocks | I understand that you're betting on a decline, but don't understand the mechanism.... | Economics | explainlikeimfive | {
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"Alice has 100 shares of ABC, and ABC is currently trading for $50. Bob thinks that the price of ABC is going to go down. Bob doesn't have any shares of ABC. He borrows them from Alice, for a small price, say $0.50 per share, and sells them to someone else for $5000 at $50/share. He now has $5,000 minus the $50 he paid Alice to borrow the shares. He still has to return those shares to Alice by a specific date, in say, 30 days. If the price goes down, he can buy back the shares at a lower price and keep the difference. So 30 days later, the price of ABC is down to $45. Bob buys 100 shares at $45 and gives Alice her shares back. Bob just made $450 by only spending $50 of his own money. Alice is a long term investor, so she can hold onto her shares and wait for the price to go back up, and she made $50 for loaning out her shares for 30 days. However, if the price went up, Bob would lose money. If the price of ABC after 30 days was $60, Bob would have to buy 100 shares at that price for a total of $6000, so he'd be out $1,050."
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5xadrf | Why are most DVD and video game cases still so big? | I know that DVD cases were meant to be the size of VHS boxes and then video games followed suit, but no one really uses VHS anymore. Is there a reason DVDs and video games still practice wasteful packaging, especially now that a lot of video game manuals are digital and rarely included in the case? | Other | explainlikeimfive | {
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"1) Marketing - people have been conditioned to look for the DVD-sized case ever since DVDs came out. 2) Theft deterrence - it's harder to fit big things in your pockets.",
"Stores want the packaging to be large enough that shoplifters can't easily stuff tons of them into their pockets, especially for items like these that are easy to trade for cash at used video game/movie stores."
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5xagby | Why we are told to consume some medicines before food and some after food | Biology | explainlikeimfive | {
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"As well as the gastrointestinal pH affecting drug absorption some drugs are purposely given with or immediately after a meal to slow down absorption or to provide short term protection against the acidic nature of the stomach contents (the presence of food raises the stomach pH towards neutral). Drugs mixed with food pass into the small intestine more slowly than drug mixed in stomach secretions alone. For some drugs it is necessary to control the rate of absorption to stop large quantities of the drug entering the blood stream quickly and giving what are known as peak plasma level side effects (typically nausea and vomiting from high plasma levels being reached quickly). Slower absorption from mixing with food can still let the same amount of drug into the blood but the levels do not get so high as those that cause the nausea and vomiting experienced by some patients. This is a very simplified picture (source: pharmacist involved in drug development for more than 30 years)."
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5xai2q | Why do zebras have a black and white hide? It seems as if these colors wouldn't be a suitable camouflage for their surrounding environment | Biology | explainlikeimfive | {
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"Because they travel in large herds. They don't use the surrounding environment to camouflage individuals, they use each other. Essentially what a predator sees is a blurring of black and white. The stripes makes it hard to pick out an individual among a running herd.",
"The stripes also appear to repel biting flies, which is good for the zebra. Of course, that just changes to question to \"why don't flies like to land on vertical stripes?\"",
"The reason a zebra has stripes is to break up its from. If your a plain white horse standing out in the wild, lions will look at you and recognize you as a zebra. If you're a zebra with a bunch of stripes to break up your form, the lion has a harder time seeing you. The US navy actually used this technology called dazzle camouflage in WW1 to break up ship's outlines and make them harder to see in the oceans. URL_0"
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5xao6f | Why do we tear up when we yawn | Biology | explainlikeimfive | {
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"Not 100% sure if this is the correct answer, but the act of yawning presses against the glands which produce tears. These glands are like a sac, so pressing against these sacs make the tear flow regardless of if you need it or not",
"I thought i were just weird. So to yawn, i would go to a private place and afterwards pinch myself to neutralize the urge",
"I don't know, but you're a wizard casting magic onto me as I just yawned and for sure did tear up too.",
"To yawn, a nerve impulse is triggered to all the muscles. It just so happens that the same nerves also affect the tear glands, triggering them simultaneously.",
"Whenever something on a film (or sometimes even an advert/commercial lol) gets me to tear up I pretend to yawn for the benefit of other people in the room ha"
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5xap5f | military strength in Europe compared to Russia | A few days ago, the Danish minister of defence said that NATO would not be capable of a serious defence against Russia without American support. I was looking at the numbers, and counting only France, GB, Germany and Italy Europe spends well over twice as much as Russia on military. Why can't NATO defend against Russia without the US? (I know that not all European countries are in NATO, but most are, and chances are all would support NATO if it came to that) | Other | explainlikeimfive | {
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"Oh buddy it's spreadsheet time! So I went over to [GlobalFirepower]( URL_0 ) and pulled up a bunch of numbers for all countries involved. I was disappointed I couldn't aggregate all of NATO together so I just used the 4 largest members minus the US and Turkey who's kinda iffy right now. So we have France, Great Britain, Germany and Italy as the bulk NATO force in Europe. We'll compare them against both Russia and the US on a number of important stats. So first. You are correct. Top NATO spends way more than Russia at 160.3 billion versus 46.6. Something interesting though is how long these places can keep paying for a military. Countries have reserves of cash and gold so I did up a bit of a ratio. NATO has a 4.18 ratio budget to reserves. So theoretically it has 4 years worth of cash on hand to pay for the army they have. Russia oddly enough has 8.11. (The US has 0.22). So Russia can theoretically keep a war going longer. So lets get into shooty bits. NATO has 855,000 troops ready to go right now against Russias 766,055. But Russia has a larger reserve force nearly 5 times NATO. 564,770 to 2,485,000. The US has 1.4 million regular and another 1.1 million in reserve. Fast and furious now! (NATO/Rus/US) * Tanks 1,824/15,398/8,848 * AFVs 25,652/31,298/41,062 * Artillery 1,352/14,390/4,564 * Fighting Aircraft 1,661/2,667/6,050 So Russia brings multiple times more guns than NATO. Much of it is still cold war era stuff but when they have any tank and you don't, it's still an unfair fight. NATO really needs the US to balance those numbers If we want to get into the navy we can but basically Russia doesn't have much of one and it's roughly the same size as NATOs and the USN blows everyone else out of the water with more carriers, destroyers and submarines. So the point is that NATO doesn't have much of a stand up army, because the US does. NATO has enough stuff to put up a fight but really needs the US to push back and actually win against a Russian invasion."
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5xaqjz | How do Atomic bombs work? Is it just one atom torn apart? | Chemistry | explainlikeimfive | {
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"There's an ideal ratio of protons to neutrons for an atomic nucleus to be stable. Even when their protons and neutrons are at the right ratio, big atoms have a nucleus that is kind of wobbly and unstable to begin with. Over time those big atoms, left to their own devices, will tend to split into fragments. This is called *radioactivity*. Exactly what fragments an atom splits into depends on what kind of atom it is (which is determined by how many protons and neutrons were there in the first place). When a big atom gets hit by a neutron, an already-unstable atom has its proton-to-neutron ratio suddenly be \"wrong.\" Which causes it to become extremely unstable and split into fragments almost instantly. A bunch of binding energy is released which causes the fragments to fly apart, like what happens when you cut a tight-stretched rubber band. How fast atoms are moving determines *temperature*, so when an atom is split, it creates heat as well as fragments. Leo Szilard, a Jewish physicist who left Germany when Hitler became chancellor, realized that if we could find some atom that splits into fragments that include multiple neutrons, you could create a *chain reaction*. In a chain reaction, one atom breaks and releases two neutrons, which breaks two more atoms, which releases four more neutrons, which breaks four more atoms, which releases eight neutrons...Szilard convinced other influential physicists, including Einstein, to advise the US government that this was possible and might be able to be used to create a powerful bomb. If you have only a small amount of the right kind of atom, the chain reaction can't get properly started -- too many neutrons escape off the edges of the sample. But once you have enough atoms -- a condition called *critical mass* -- the chain reaction will be able to sustain itself. If you're just over critical mass, the sample will start to heat up and get hotter and hotter until it melts itself and its container, this is called *meltdown* (the flow will eventually spread it out enough that it stops being critical and cools down, but before that it can cause lots of damage in places that are difficult / impossible to safely repair because of radioactivity). If you have way more than critical mass, then incredible amounts of heat and neutrons will be produced very quickly, which causes an enormous explosion. One use of this chain reaction phenomenon is to build a power plant: Use neutron absorbing rods which can be inserted/removed from a sample to keep it near critical mass, enough so that it heats up enough to boil water to create steam and generate power, but not to the point of meltdown. Another use is to build a bomb: Use regular explosives to smash two samples together to create a single sample far above critical mass, which will cause a very powerful explosion. The right kind of atom for this process, a kind of uranium, turns out to be fairly common all over Earth, but since it is unstable, a lot of it has split into fragments over the billions of years that have passed since it was formed. The remaining amounts of useful uranium are mixed with large amounts of useless uranium that doesn't release multiple neutrons. So the useful uranium needs to be separated from the useless uranium. Normally when scientists or engineers want to separate things, they will rely on different properties of the things they want to separate. For example, you can melt the sample and let the liquid settle into different layers (taking advantage of different liquid density). Or by making the sample hot enough for only one of the mixed things to boil away (taking advantage of different boiling points). Or by adding chemicals which react differently with the things they want to separate (taking advantage of different chemistry). But none of this works for uranium, because the two kinds of uranium are very similar and have almost identical properties. The best method they found for separating uranium involves vaporizing the uranium into gas and then spinning the gas really fast with a machine called a *gas centrifuge*. The two different kinds of atoms weigh different amounts, allowing the right kind of uranium to be separated and purified. This process is incredibly expensive and inefficient, which is a good thing. Hobbyists or terrorists can improvise regular bombs fairly easily, but can't feasibly build a nuclear bomb in their backyard. Even for a government, in the age of satellites it's not really feasible to hide the enormous facilities needed, so countries basically know which other countries can / are trying to build bombs, and can pressure each other not to create weapons.",
"A neutron is fired into a cluster of unstable radioactive particles. HOWEVER it must go at a certain speed; too slow and the bomb won't explode, tok fast and the particle will go right through it. The amount of energy released will split the rest of the particles in the reaction, causing the huge energy released. The neutrons are fired from a small cell within the bomb, via electricity (or magnetism) This is what prevented Germany from figuring out how to make the bomb and the US being successful; Germans fired the neutron as fast as they could while the US figured out it has to go at a certain speed",
"So a nuclear weapon uses fissile material. A fissile material is one that both undergoes fission (the atoms of a given isotope are unstable and will decay) and can sustain chain reactions (a decay byproduct includes neutrons that strike adjacent isotopes that cause them to decay). This is primarily Plutonium and Uranium, and I think there's one or two others that are fissile. You can also \"breed\" fissile materials, which is how we get plutonium from uranium, and thorium will break down into uranium. So of the few isotopes that are fissile, U235 is preferred over U233 because it's more energetic, and Pu239 is preferred over Pu241 for the same reason. Plutonium is preferred over uranium because it's much more energetic, meaning they need a lot, lot less, but uranium is used often enough because it has a longer shelf life and is more abundant. The goal of kicking off a nuclear explosion is to get the fissile material to go \"super critical\", in that chain reactions occur at an exponential rate. They do that by compressing the \"configuration\" (shape is as important as total mass) to where the neutrons from decay can't be avoided and there's a cascade effect. There are two ways of doing this. One is the \"gun type\" weapon, where a \"puck\" of uranium is fired into a \"plug\" of the same. The puck is fired using conventional explosives down the barrel of a cannon, and the plug is at the end. The two smash into one another and compress. It takes about 90-120 lbs of uranium to pull this off. It can't be done with plutonium because reasons... The other method is the \"implosion type.\" A hollow sphere is encased with conventional explosives which are detonated in a precisely timed sequence so the shockwaves evenly compress the fissile material. It takes about 30 lbs of uranium or as little as 4.5 lbs of plutonium. The configuration is extremely important, the shape of the mass, the explosives, the shockwave, the timing... These are complex weapons to get right. A hydrogen boosted weapon uses a glass bead of hydrogen inside the fissile sphere, the nucleus of hydrogen is a neutron. It only takes about 100 hydrogen atoms to get a sufficient multiplier in efficiency. There are other things you can add to increase efficiency, such as beryllium on the outside to reflect neutrons back into the mass, and lithium-6 and lithium-7 which rapidly decays, releasing neutrons. Castle Bravo was the largest test shot by the US because we miscalculated what lithium-7 would do. At 15 MT, it was several orders of magnitude larger than expected. A thermonuclear bomb uses hydrogen like a boosted weapon, but the goal is to use the nuclear explosion to generate heat and compression to cause the hydrogen to fuse into helium, lithium, and beryllium. Castle Bravo was also the first thermonuclear test. You can actually use a nuclear weapon to kick off another nuclear weapon. Instead of surrounding a core with conventional explosives, surround it with nuclear weapons! These are multi stage nuclear weapons, and they make very big booms. Russia built the largest such weapon called the Tsar Bomba, and it used 3 stages. The bomb itself was so big the carrier had to be gutted and modified to hold it, and it hung out the bottom of the plane. They wanted to demonstrate a 100 MT explosion but such a detonation would have covered the Earth in 1/4 worth of all nuclear fallout of all weapons ever tested to that date, so they dialed it back to a 57 MT explosion. In 1815, Mount Tambora, a volcano, exploded, completely obliterating the island it was on and killing *everyone instantly* in the surrounding *100 or so miles*. So much ash was thrown into the atmosphere, 1816 was in perpetual winter, world wide. It was called the year without a summer. That explosion was estimated to be around 400 MT, just for comparison.",
"The first neutron hits an atom of U-235 or Pu-239. These are special, unstable atoms. The atom splits in half, and releases 2 neutrons. These hit the next 2 atoms, which release 4, ... Many atoms are split. The rest of the special physics is trapping the very rare and unstable radioactive materials in a casing where they can be forced together well enough that the first 10% of the reaction doesn't just vaporize the rest of the weapon. It's very difficult, and mostly against international treaties, to make them.",
"Nuclear fission starts when a neutron hits a heavy nucleus, the reaction produces more neutrons and so on and so on. The more atoms you have in a contained space the faster fission will be and more energy will be created. Uranium fueled nuclear bomb is a ball of uranium surrounded by an explosive. During ignition the explosive is pressing the atoms together going to critical mass(when fission is self sustained) and over that to the point when a lot of fission happens at once producing a lot of light and heat. Little boy contained 64.1 kg of U-235 but only 0.8 kg went through fission and only 0.1% of that was changed directly to heat and light. The rest 63.3 kg was scattered around Hiroshima during the blast."
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5xas34 | Why do we get black circles under our eyes when we don't get enough sleep? | Biology | explainlikeimfive | {
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"The concept behind dark circles under your eyes relates to fluid retention. The skin under your eyes is extremely thin, and therefore, more transparent. When you've neglected sleeping one of the responses the body has is in the increase in the amount of the hormone Cortisol. Cortisol, which is sometimes referred to as the stress hormone, will increase blood flow (vasodilation). This is subsequently seen in the skin under your eyes!",
"I have hereditary black circles around my eyes, white people get it but it's more common in Indians and Africans, does it have something to do with melanin? Skin thickness, or circulation?",
"This isn't 100% but it it's because when you're awake more often, you; 1. Don't receive the proper amount of oxygen your body needs, and blood flow begins to thin out. This thinning out will shrink your blood vessels at and near your eye or possibly bleed, causing the black tint. 2. Your eyes move around a lot, so the longer you're awake and use your eyes, the more tired the muscles in your arm gets, let's excess blood or fluid in the tissue around your eye, giving you the black tint. TL;DR: blood around your eyes from lack of oxygen and muscle tiredness in eyes",
"Bags appear because the skin tone changes and becomes puffy. Sleep deprivation makes the skin paler and thinner, allowing the blood vessels to show more (hence the dark appearance). This is due to a number of hormones like cortisol altering blood flow. Once you're well rested the hormones return to normal, and the bags go away.",
"As a follow up, what's the reason that this only happens to some and not others? I was awake for 5 days straight once and never developed bags or discoloration",
"So clearly this is why raccoons always have black circles around their eyes. I've never seen one sleep at night! Mystery solved! Thanks for the thoughtful question",
"As a follow up, how can someone reduce the blackness? I know sleeping enough fixes this. But what if you want to revert this and get rid of those?",
"The tiny muscles that control your eyes and eyelids get tired, and need more blood to keep up. The skin around your eyes is very thin with a lot of blood vessels, so you can see the extra blood as dark circles under the eyes."
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5xatdu | Travelling from Canada to Asia. Why can't planes fly west instead? Wouldn't it be faster? | Been travelling from Canada to Asia a couple of times last year. Usually takes 16 hours from Vancouver to Hong Kong. Why can't planes fly west side, skipping middle east and just going straight to Asia? | Physics | explainlikeimfive | {
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"From Quora > Because the Earth is a three-dimensional sphere and not merely a two-dimensional flat, East-West surface. Because of this spherical shape, often times the shortest distance is flying more north and south, up over the Northern latitudes and the North Pole, rather than flying east/west over the Pacific. When you see the [picture]( URL_0 ) it's more clear.",
"What's interesting is that every time I've flown to Asia (Minneapolis or Chicago - > Tokyo), I have flown over the Pacific. The earth is a sphere, however, and they use what are called great circle routes to determine what the shortest amount from point to point is, even if it doesn't appear to be shortest on a flat map.",
"The direct path (10300 km) goes via Alaska, Kamchatka, Sakhalin, North Korea. While Alaska is fine, Russia [doesn't like]( URL_0 ) planes flying over their islands, and I can imagine that North Korea is avoided as well. There are many flights going a bit more south than the direct connection, however. Flying via the middle east (~17000 km) is way longer than necessary. It might be cheaper, but that depends on the specific flights."
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5xavwv | How is it determined whether or not citizens of a country need a visa to travel to another country? | Other | explainlikeimfive | {
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"Every country sets rules for what admission policies they set for people from other countries. Basically, you start with the idea that everyone needs a visa. Then, you make exceptions for other countries -- some countries you have agreements with that both of you will accept the other's citizens without a visa. And some countries won't make that agreement with you, but its in your economic best interest to allow people from certain countries into yours without a visa -- say a poor country that wants businessmen and vacationers from wealthy countries to be able to get in easily and spend money."
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5xawd4 | How do they declare certain aquatic organisms as extinct, when we haven't explored a huge majority of the oceans? | Apparently, we've only explored around [5%]( URL_0 ) of the Earth's oceans. How do they declare some aquatic organisms to be extinct, when we don't know what lies in the unexplored regions? > *Note that I'm talking about ancient and recent species here.* | Biology | explainlikeimfive | {
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"The same way we do on land, really. It is basically the reasoning of 'if we haven't seen any trace of species X in a good number of years, most likely they are extinct.' Sometimes those assumptions are correct. sometimes they are very false. (Like with coelacanths) Though note that unexplored parts of the ocean don't necessarily have to mean you can't know if an animal species is extinct. Many species have very specific habitats they don't deviate from. If you have a species that can only exist in shallow water or tide-pools, for example, then the fact that the deep sea has not yet been explored is not really an issue. That is not where those animals could live in the first place. Additionally, you don't always need to have explored a region. A lot of this is based on traces of their survivals, but that doesn't necessarily mean seeing the fish in the flesh. Finding remnants of them in the stomachs of other fish, finding them in fishing nets, finding them washed up on beaches. all of that can count towards being able to tell a species exists still or not. And if there is a huge change in that (for example, we used to find X species frequently in the stomach of dolphins, but they haven't been spotted there in 30 years) that can be a good indicator said species is gone. Again, not ever 100% and some species have clung onto life in places unknown to us at first, but still a reasonable guess."
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5xazc3 | Why do we get a runny nose when we're cold? | Biology | explainlikeimfive | {
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"It's to compensate for the air being dry. Lungs need to be wet inside, and if they dry out you will have some very major health problems very quickly. But if the nose is runny, it humidifies the air before it gets to the lungs and makes sure they stay functional."
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5xb248 | Why do the countries that used to be a part of the British Empire (Canada, New Zealand, Australia, etc) have a dollar ($) for a currency, instead of a pound (£) like Britain? | Just a thought I had, and it made me wonder. You'd think that when Britain gave Australia, Canada, and whatnot, their independence that they would have the pound as the currency. It's like they decided to join America on the dollar bandwagon. | Other | explainlikeimfive | {
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"New Zealand and Australia used their own independent pounds, shillings and pence for some time after they had independence. When they decimalised, they found people worked in shillings. So they came up with a system where the cent was similar in value to the old penny, and 10 cents was a worth one old shilling. To keep it decimal, they needed a new currency worth 100 cents, and so they picked the name \"dollar\" because it's understood as a currency name, and other proposals were unpopular. Other countries weren't straight for their own currency, and adopted a decimal currency with a similar value to their neighbours. Dollars were recognizably different from pounds, so made sense.",
"Why did you leave the US out of this list?",
"The Spanish Dollar (aka \"pieces of eight\") weighed about the same as a Crown coin. A crown was worth 5 shillings or 100 pence, so it was the natural unit to convert to when you're trying to decimalize with existing coins. Also, during the 19th century the Japanese, French, Americans, and British minted \"trade dollars\" of equal weight to the Spanish dollar as it had become the de facto currency of trade in Asia. So to many the Trade Dollar appeared to be on its way to being a global currency. This notion fell apart in the early 20th century. The UK did not do this because they decimalized very late and was less interested in fixing value to the pence or the crown but in retaining the \"very British\" pound. So they kept the unit and reminted all the coins (which is more expensive, but not as challenging in the modern age).",
"Malaysia has been under the British Empire but does not use dollar for currency. Malaysian Ringgit (MYR) is used.",
"You literally answered your own question. But I love how you assume they copied The United States. The US dollar is actually based on the Spanish dollar, so you really should be adding the USA to that list.",
"Australia used to have the pound but we're in Asia, so I guess it made \"cents\" to transfer to a decimal currency. That and if you look at the old currency, shillings, half Pennies and Guineas its freakin nuts."
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5xb3tk | How is Snapchat valued at over $30 billion but they have a loss of $500 million last year? | Other | explainlikeimfive | {
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"A valuation is the total value of all the shares of stock issued, based on the current trading price. The valuation is not based on anything else. The trading price reflects what investors are willing to pay to own that stock, presumably because they believe their investment will be worth more in the future. Many companies that are not profitable have high valuations. This reflects that the investors have faith in the company _in the long-term_. In other words, investors are not buying stock in Snap because of what it did last year; they're buying stock in Snap because of how they believe the company will perform over the coming years.",
"Welcome to the world of venture capital-backed start ups. Idea here is simple: Imagine you have a healthy, profitable, company, but the company isn't _that_ big, and you could be making more money. So you invest some money towards building more features into your product, you invest in marketing and sales to get people to use your product, etc etc. All this money you're spending on making your company bigger eats into your profits. If you're aggressive enough with the investment, you'll turn your profitable company into an unprofitable company _right now_, but you're betting that a loss today will turn into a lot of profit later on. The maximum amount of money you can invest like this is limited by how much money you have in the bank. But maybe if you had more money available to you, and spent even more aggressively, you might be able to produce even better results. There's two ways you can achieve this: Take a loan, or sell a portion of your company for cash. This is where VCs come in. They're companies with a tonne of money at their disposal (often some sort of investment fund), who specialise in finding companies that both need the money now, and are likely to become very valuable in the future. They then buy a fraction of the company for cash, so that the company can use that cash to fuel their growth. You can, and often do, run a company like this for years, having several funding rounds where you sell a bit more of the company for more money. In this world, growth is the performance indicator people really care about: Are you growing your client base and/or revenue fast enough? If you are, then becoming profitable is relatively easy, and the fact that you're in the red right now is kind of unimportant. You might never actually have that \"healthy profitable\" starting phase at all, as long as investors believe enough in your idea and your capacity to execute it.",
"Mostly because those things are only loosely related. Snapchat is valued at $30B because people are willing to pay that much per share of the company... though to be honest actually buying the company would cost more than that. It's operating loss is a concern, but companies have long lives and nearly every business starts out by losing money. So that is being factored into the price and they investors still think they are worth it."
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5xb991 | what is diarrhea? What causes it to happen? The cramps, the sounds, the smell, the result. | Just spent the morning on the toilet, so I had some time to wonder about why this thing happens to our bodies when we eat something that doesn't agree with us. Why does my body feel like it's eating itself? | Biology | explainlikeimfive | {
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"The final stages of digestion happen in the large intestine. The last bits of nutrients are absorbed, but most importantly, the large intestine absorbs most of the water back out of the digestive waste. Food, as it's digested, is mixed with a whole lot of water and basically turns into a soupy mess. But you don't want to poop out all that water, or you'd dehydrate yourself. So the large intestine re-absorbs nearly all of it, leaving the semi-solid poop we're familiar with. If your body feels that it has been poisoned, it has an \"oh shit\" button. It says screw re-absorbing the water, we need to clear this poison out of the body. So it expels everything out of the large intestine, water and all. That's diarrhea.",
"Diarrhea is poop with too much water in it, for any reason. The colon (large intestine) pulls water out of the slurry of digested food that comes out of your small intestine. The idea is to spend enough time in the colon to get most of the water back, but not so much time that pooping is difficult. Various things can lead to diarrhea, but mostly it comes down to stimulating the colon to move stuff faster, or getting more water into the colon. There's a lot of nerve input which can speed things up, say if you've just eaten and need to make room, or for any number of other reasons. Some laxatives stimulate the colon, while others pull water in by osmosis. Disease can produce increased stimulation in an attempt to get rid of everything, or lead to inflammation that increases water loss across the bowel wall. Alternately, some infections directly act on the bowel wall to cause more secretion of water and salt; cholera is notorious for producing buckets full of watery stools that way."
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5xbguy | Answer to Darwin's first dilemma | Firstly, why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms? Why is not all nature in confusion instead of the species being, as we see them, well defined? URL_0 I read the answer in the article, but I still don't understand it. Especially why "innumerable transitional forms" exist in asexual organism only? ************* edit: In other words, why not all living things forms one ring species? URL_1 And therefore, why do ring species even exist in the first place? | Biology | explainlikeimfive | {
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"> why not all living things forms one ring species? Take your ring species. We'll use the [Larus gull]( URL_0 ) from your link. It forms a ring. Each 'link' in the ring can interbreed with the adjacent link except where the ring meets at the end points. As an aside, ring species highlights an interesting dilemma inherent in categorizing organisms with discrete labels in the first place, but I digress. The ring species only presents an interest because of the existence of the intermediary links that can interbreed. If some catastrophy eliminated those links, leaving behind only the non-interbreading end points, there would be nothing of interest to discuss; you'd just have two separate species of organisms. Take this example then, and flip it on its side. Instead of considering the ring species as some phenomenon that exists due to geographic separation, consider it as a phenomenon that exists due to temporal separation. Pick any two existing species, and you can draw a similar ring with the present examples being the end points, and the intermediary links extending backwards through time. Starting at one, you will go backward in time to the most common ancestor, then forward again, down a different branch of descendants, to the other. In this way, we have mapped out a \"ring species\"; it just happens all of the intermediary links are dead, as we considered in the previous gull example. All that is left are the two end points who are sufficiently different to be considered two different species. As to the answer provided in the article, it basically said that there are reasons why transitional species operating in the same space will tend toward seciation. The more different species you have in an area, the smaller the population must be for each species (since they are all occupying the same physical area). The smaller the group, the harder it is to find a mate and reproduce. Unless things remained in perfect balance (nigh impossible due to the chaotic nature of ... well, nature) then what will happen is one or more of those groups will, for whatever reason, outproduce the others. The increase in size in one group has to come at the expense of a decrease in size of another (again, since they all occupy the same physical space) and the larger group will have a reproductive advantage, since there are more members and they can more easily find mates. This creates a feedback loop. Larger groups can more easily reproduce getting even larger and reproducing even more easily. Smaller groups have a harder time reproducing, getting smaller, and having an even harder time. The end result is that only a handful of those initial \"transitional\" species will get larger and basically outproduce the others (by chance or some slight advantage in fitness) and the others will eventually wither away. So the transitions disappear, leaving behind more distinct species.",
"> In other words, why not all living things forms one ring species? And therefore, why do ring species even exist in the first place? Ring species need to have similar environments. A ring won't form if there is a desert on one side and a jungle on the other. If the environment on only one side of the ring changes enough, the ring will be broken and true* speciation will happen. ^(*the definition of 'species' is fuzzy. it's a long story)",
"> Why is not all nature in confusion instead of the species being, as we see them, well defined? Because there are a limited number of niches and a limited number of combinations of biological traits that work well in those niches. This is related to the concept of *punctuated equilibrium*. Species tend to rapidly adapt until they are optimized to their niche, then remain genetically stable. Only when that niche is disrupted by climate change, an invasive species, or a novel mutation does rapid evolution change commence again. It is not unlike sand on a paved road. If the sand is spread at random, and if each car that passes moves it at random, how does it bunch up in the middle and at the sides of the road? It is because certain locations are more likley to be disturb and others are more likely to remain undisturbed."
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5xbkh2 | Why do the Air Force One pilots get switched with every president? | Other | explainlikeimfive | {
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"They don't switch just because a new president arrives. Air Force One is piloted by Air Force pilots (typically O-6, O-5 or O-4 - very senior guys - it's a high profile gig) and each tour of duty (like the rest in the military) typically lasts 3-5 years, so they will naturally rotate out over time during a presidency and overlap with multiple Presidents depending on timing in their career. edit: Here's a great National Geographic Documentary on this and what goes into planning each mission: URL_0 edit2: /u/since_ever_since mentioned that only full bird (O-6) colonel's could be Aircraft Commander of AF1. The other pilots/navigators could be lower ranks. It is a prestigious gig, so pilots are typically selected for it as a good deal tour of duty",
"They don't. Many Air Force One pilots have flown for multiple presidents, even from different political parties.",
"You never do any one thing for that long in the military. Each set of orders is about 3 years pretty much wherever you go.",
"The AF1 pilots and Marine 1 Pilots all work for the Military Chief of Staff in the white house. That guy also controls Camp David and secure bunkers. A million years ago I knew a very cool Captain that rose to that position.",
"When I was 6 or so, I met the Air Force One pilot for George W Bush. The pilot gave me a box of peanut M & Ms with the American seal on it and the president's personal signature on it in sharpie, next to the printed signature. I ripped it open, ate it and threw it away. Apparently stuff with his actual signature is worth around $300 now. Drat."
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5xbsct | Why would my dad be labeled as [my mom's] husband rather than [my] father on my birth certificate? | I do believe that my dad is in fact my biological father (the resemblance is undeniable), so why would he be listed only on my certificate of live birth as my mom's husband and not have the normal "father" section I see on all other examples? | Other | explainlikeimfive | {
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"The rules regarding which name must appear vary by state (or country) and marital status guidelines. There are a whole bunch of reasons this may be the case. In most cases, if a woman is married at the time of her birth, her husband is presumed to be the biological father so it's sufficient to list him as such. Does your certificate have BOTH a section for \"father\" and for \"mother's spouse\"? Since there is no standard for how a birth certificate should look, it's most likely you just have a different format that doesn't use the word \"father\" or something. Perhaps your parents were (or are) not certain that he is your biological father."
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5xbsiu | How do new species originate? | If organisms of different species can't reproduce with one another because their genes are different, how is it that new species come into existence from existing species and reproduce? | Biology | explainlikeimfive | {
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"So speciation is a very complex process, and there are many **many** forms of it. I'll cover some of them here the best way I can. So it's incredibly difficult to actual define a species, and it's usually a mixture of several different concepts with the main one being: -The biological species concept-which states that organisms of a population that can interbred and produce viable, fertile offspring are of the same species. To flip that around: If two animals cannot breed, or their offspring is either non-viable (can't live) or non-fertile (can't breed) than they are separate species. There are a lot of flaws in this, but we are going to ignore them and just pretend that the above concept is a perfect explanation of species. There are 2 main modes of speciation, **Allopatric** and **Sympatric**. Allopatric speciation occurs with non reproductive barriers, so for example geographic problems. Say you have a population of red tufted squirrels. These squirrels live near a river. One day the river changes course and splits the population in half. Over thousands or millions of year, the population on the right side of the river evolves the trait for blue tufts. If the river was to shift again and the two populations were to mix again, most likely they wouldn't breed, and now you have two species. There are a lot of things within allopatric speciation but I don't want to over explain. Sympatric speciation occurs **within** a population, through various ways. Back to our red tufted squirrels. Let's say that in order to find a mate, male red tufted squirrels have to dance the polka, well a couple males start dancing a waltz. Most females ignore them, but if somehow they are able to attract enough for those genes to be passed on, after many generations you have two kinds of squirrels who no longer mate with eachother. I know this is super long, but hopefully it was helpful. Feel free to ask me to clarify."
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5xbu3n | If the net worth is based on shares, how can it be spent? | Economics | explainlikeimfive | {
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"People who have most of their net worth tied up in a company they founded that's publicly traded, like Mark Zuckerburg, typically have automated trading set up so that every month/quarter it'll sell a set amount of shares so that they have money for living expenses, are able to diversity their investments, etc. By automating it, it removes the ability to intentionally or inadvertently act in ways that might be construed as insider trading. They could also make manual trades to sell shares, but would have to make sure to do so only in periods when there aren't trade blackouts (or quiet periods), say right before earnings releases or an acquisition is announced. Yes, if shares are sold then the founder's holding would decrease and whomever bought would have a part of the company -- that how public companies work. The whole point of buying stock is to profit later from the company doing well. In the case of companies that are not yet public, the founders can borrow money using their stake in the company as collateral, or they can sell to private investors like venture capital firms. This is often why start-ups take on additional rounds of funding... they don't need the cash to fund the company, but instead the founders want to take some money off the table.",
"He can sell the shares, trade them directly for other assets or borrow money using the shares as collateral to secure the loan."
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5xbv8k | Does everyone on earth actually have a different fingerprint? | I have heard some mixed consensus on this. Does identifying someone's fingerprints at a crime scene really rule out every other human on earth? Is it as accurate as DNA matching? If my phone has a fingerprint reader, will it really lock out every other person and only let me in? | Biology | explainlikeimfive | {
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"> Does identifying someone's fingerprints at a crime scene really rule out every other human on earth? No, mainly because we can't tell them apart, not because there are no tiny differences. But that doesn't matter because most cases aren't hinging on if every person on the planet is ruled out. The issue of if the guy with blood in his trunk and matching fingerprints on the murder weapon isn't really damaged that much if some person in Mongolia also has indistinguishable prints."
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5xc3h1 | how do our eyelids stay open? Are we constantly engaging muscles to keep them open? | Biology | explainlikeimfive | {
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"The main muscle that controls the eyelids (palpebrae) is the orbicularis oculi. This has two parts that are responsible for closing the eyes. The orbital part surrounds the whole orbit and is for closing the eyes tightly. The palpebral part is over the eyelid and functions for blinking. The main muscle that opens the eyelids is called levator palpebrae superioris. This pulls the top palpebra upwards and it even has a smaller muscle connected to it called the tarsus that is activated during a sympathetic response to open up the eye further. I believe the full resting state is mostly closed, but just because gravity acts on the top eyelid. To finally answer the question, yes, the eyes are always using muscles when they are open. Edit: I just read that linked comment, and now I feel like I wasted a bit of time typing this.",
"Check out [this]( URL_0 ) post!! It may help you out! Looks like there is no natural state for an eyelid, but happy reading!"
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5xc57e | How does my phone know what traffic is like around me? | Other | explainlikeimfive | {
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"So long as you allow it to, your phone periodically sends GPS data back to Google/Apple servers about where you are and how fast you are traveling. If Google gets a bunch of reports that people are on a 65mph road but only traveling at 15mph, they are able to extrapolate that there is a traffic incident there."
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5xc7wq | Why is Africa, as a whole, such an impoverished continent? | Economics | explainlikeimfive | {
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"Economics student here with a focus on developmental economics. I'm late to the party but hopefully a few people can get me some upvotes for visibility. Africa is impoverished for many reasons. In no particular order, I will list some: #All tropical areas tend to be more impoverished because they are more prone to disease -- You may notice that Northern areas and very Southern areas tend to be better off than Equitorial areas, especially wet ones. Places like the US, Canada, Europe, Australia, and New Zealand. Argentina used to be among that list of prosperous countries but had bad governance, and Chile is now quickly joining them. This is because of disease. Until very, very recently (as in, since maybe the 1980s) people in those areas could not rely on being healthy tomorrow. Tropical diseases of many sorts, as well as diseases also common to temperate areas, ravaged them. This leaves working age people disabled or dead. Without a good ratio of healthy people to sick, an economy cannot be productive. #Africa has suffered from bad governance --Since European contact, Africa has suffered from bad governance -- mostly from Europeans but also from African leadership as well. For a few hundred years, Europeans **really** wrecked the place with extortive policies aimed to overtly impoverish the population. This eased European rule and thus the capacity for Europeans to extract what they wanted from the area. Immediately upon independence, bad governance continued in many, but not all areas. Why? Because those areas wanted to practice *autarky* (autarky is the opposite of free trade & open migration -- Trump loves autarky if that makes it easier to understand). Why did they want to practice this policy? They wanted to close their borders because of their history of subjugation at the hands of foreigners. So they decided to not trade with anyone, not accept investment, and not allow labor migration. This left them without a means to transfer technologies from more technological areas, and without a way to get out of destitute poverty since they could not generate investment from exports or from foreign aid, or from foreign direct investment. They couldn't build industries at home because they had no source of income. Today, many many African countries are much better managed. But, they've got a lot of growing to do. Nigeria, Botswana, and Kenya are some of the best examples of growing prosperity. #Africa has recently been suffering from armed conflict, as is common among newly independent states -- Whether it was the fall of apartheid, the genocide in Rwanda, child soldiers in Sierra Leone and Uganda, or the ongoing civil war in the Congo, many Africans have not had their most fundamental need -- safety -- met. Without safety there is usually economic contraction, and often it is severe. This means that these areas, which were already poor, become more destroyed and more poor due to ongoing war. Any political revolution, on the short and medium term, tends to cause economic contraction due to a loss of faith in contracts and jeopardizing safety. Some revolutions tend to cause economic growth -- sometimes huge growth -- on the long term. An example of this is of course the American revolution. Another would be the fall of Apartheid, from the fall of Apartheid until the rise of Jacob Zuma South Africa had very robust growth (but Zuma killed that with tribalist division). #Africa lacks mature, essential institutions. This one can unfortunately be blamed mostly on colonial powers, as most African nations haven't been independent long enough to have developed fundamental institutions. It also falls as part of bad governance, but should be cited on its own. While public schooling in Africa is becoming fairly common **now**, previous generations often were illiterate or had not finished elementary school. So, until this generation grows up the workforce in Africa -- while cheap -- is unviable. Sure, African workers will work for less than those in Bangladesh... but they can't read. They can't read instructions. Again, not all. The region is in a period of huge transition right now and places like, say, Kenya or Botswana, or South Africa are much further along than, say, the former Zaire or Sierra Leone. Additionally, they lack banking industry. They lack large corporations and large bureaucratic structures. They lack a fully fleshed out police force especially in rural areas. A farmer in Namibia cannot, unlike an American farmer, enter in to a long term contract with a large purchaser to sell all of his, say, grain for the next two years at a fixed price. He can't do this because there aren't good courts and if there were then even if he won there aren't police out in the boonies where he lives to make the person pay him. He has his word, his family, and their collective weaponry to enforce agreements, and that's it. This limits the capability of investment and tends to cause disastrously volatile pricing which is extremely dependent on local conditions for that season. #The keys to prosperity in this world are fairly intuitive. We need safety -- not only from violence, but from disease and dirty water too. Then, we need justice. -- those in power cannot be performing backhanded deals or serving their own profit. Finally, we need to be open -- freely exchanging with our fellow man and allowing the inflows and outflows of goods and people. Africa had none of these things until recently. Now they need time.",
"This is probably going to get buried in the comments but Paul Colliers book titled, *The bottom billion* does a great job explaining this. He boils down poverty and economic disparity to these 4 main problems: 1. Never-ending conflict (countries plagued with conflict will never be economically successful in any meaningful way. Without security there's no economic success) 2. The natural resource trap (poor nations who are blessed with a few natural resources that should theoretically make them rich end up squandering the money and concentrating all their efforts into these resources while neglecting all other industries) 3. Being landlocked (Surprisingly this actually has a huge impact on the success of developing nations. Countries on the coast or those with access to the sea have a greater ability to trade and move around goods and people. If you're landlocked then you're in trouble because you're dependent on neighbours for trade and if they happen to be a neighbour that's in conflict, poor or badly run then it's not just unfortunate but your own economy will suffer as a result). 4. Bad governance (this one pretty much speaks for itself and unfortunately most countries in sub-Saharan africa suffer from this) The book goes into depth about all these points but it's easy to read and really informative. Highly recommend! Edit: words",
"EDIT: It is my opinion that the hypothesis I've written about below is one that *adds* to the discussion rather than explains entirely why Africa has had developmental problems. I am also aware that aspects of it may sound racist, however that does not warrant completely ignoring the hypothesis. It's not my hypothesis, and while I do believe it may have some truth, I don't fully agree with it nor the economists who espouse it. There is a fascinating concept called the \"geography hypothesis\" that might explain the economic hardships faced by subsaharan Africa. There are wide ranging causes of economic despair across the globe. When looking at a globe however, there seems to be a noticeable divide between the wealthy nations and nations with low income levels. Nations that lie in the tropics are on the wrong side of the tracks when it comes to economic prosperity. According to economist Ricardo Hausmann, these tracks exist at twenty degrees latitude and nations below this line are cursed with stagnant, declining, or slow economic growth rates as well as noticeably shorter life expectancy rates. Nations in the temperate zones exhibit overwhelming economic success by comparison. The temperate zones contain twenty-seven of the thirty wealthiest nations, the three exceptions being Brunei, Hong Kong, and Singapore. These nations seemed to have escaped the curse by having extensive coastlines allowing them access to global markets. Singapore for example is a small and flat island with few natural resources other than, arguably, the sea that surrounds it and allows the nation to enjoy low import and export costs. The rest of the tropical zone is not so lucky, and economists who subscribe to the geography hypothesis have three main reasons for this: the tropics are geographically prone to diseases, tropical agriculture cannot use technology from other geographic zones because the different climates produce equally different crops, and the countless landlocked nations of the tropics face exorbitantly high transportation costs for imports and exports. Many nations in the tropics face all three of these geographical obstacles simultaneously, and without the resources to overcome them these nations will continue to experience little or no growth. Malaria is a useful example to study for this topic due to the vast amount of data collected on the disease, and it has such strong associations with the economically impoverished tropics that it has been dubbed the ‘disease of the poor’. Ninety-eight percent of all malaria deaths occur in thirty-five countries, five of which are in Asia and the other thirty are in Sub-Saharan Africa. Malaria is often treatable depending on the severity of the strain, however the most severe strains are virtually exclusive to Sub-Saharan Africa where they cause jaundice and frequent loss of consciousness in their victims. The disease also claims more lives there than anywhere else. One out of every twenty children under the age of five in Sub-Saharan Africa dies from malaria and adults, while more likely to survive, suffer frequent and long-term debilitation. The crippling effect malaria has on workforces in Sub-Saharan Africa has made investors wary and growth elusive. The disease has effectively isolated the region from international trade and tourism by raising transactions costs to prohibitively high levels. This unfortunate reality is sustained by the geographic attributes of the topics. The tropical climate allows malaria to thrive year round, whereas colder temperatures spare temperate zones from having to contend with the disease as an economic hurdle. Malaria continues to pester tropical economies as relentlessly as the mosquitos that spread it.",
"I assume you're asking about Sub-Saharan Africa, yes? Because the African Mediterranean coastline has always done pretty okay, at least in comparison to parts further south. And it ought to be pretty clear why *Saharan* Africa is pretty poor: for the most part it's a godawful wasteland where almost nobody lives. So I'm assuming that you're really interested in Sub-Saharan Africa here. As to that, the simplest answer I can come up with is that Africa is a continent where just about everything wants you dead, from lions on the macro scale, to microbes on the micro scale. European explorers/colonists travelling to Africa had a distinct tendency to *die like flies*. There's a reason European countries spent almost three centuries colonizing North and South America before seriously turning their attention to Africa (which they'd *always* known about!), and this is a big part of it. Infectious diseases endemic in Africa--yellow fever and malaria in particular--contributed to such a high European mortality rate that Africa was known as the \"white man's grave,\" and not for no reason. The climate is about as fantastic a breeding ground for the spread of infectious disease as one could imagine. The parts of Africa that aren't tropical are sub-tropical. It almost *never* freezes, meaning microbes and the bugs that carry them never have to go dormant. Well if Europeans died in such large numbers, how did Africans survive? Part of the answer is that African populations do seem to have developed a certain resistance to some of the more common tropical diseases. For example, there's a recessive genetic disease, sickle-cell disease, that's pretty miserable for people who have it. But for people with only one copy of the gene carrying the sickle-cell traits, it provides a fairly robust resistance to malaria. Sickle-cell carriers can get malaria, but it's a lot less severe when they do get it. There are some other examples, but that's a classic one. But the other part of the answer to how Africans survived in places Europeans died so much is that they *basically didn't*. European mortality rates in Sub-Saharan Africa during the colonial period could be fairly described as \"catastrophic\". African mortality rates in Sub-Saharan Africa during the colonial period, by contrast, could be described as merely \"pretty damned bad\". Life-expectancy in Sub-Saharan Africa has pretty consistently been among the lowest in the world for a *very* long time. Assuming the lions (or whatever) didn't eat you, and the monsoons cooperated to the point that you could bring in at least *something* in the way of crops, there was *still* a really decent chance you were going to catch some bug and die. There are certainly other reasons. European colonial misadventures certainly didn't do the continent any *favors*, that's for damned sure, and certainly contributed to Africa *staying* poor a lot longer than most of the rest of the world. But Africa has trailed more temperate regions in terms of physical prosperity for a *very* long time. It's just a really tough place to live.",
"You can read \"Why Nations Fail\" jointly written by a developmental/growth economist at MIT and political scientist at Harvard that answers this exact question (among other impoverished countries) and are frankly far more qualified to do so than some of the other books and theories out there, they are THE top researchers at the forefront of this subject, period. Basically they have poor governments which can't enforce even basic property rights and rule of law - preventing any investment which would boost living standards. Also, the political institutions are so extractive they disincentivize anyone from seeking wealth because it will simply be taken either by criminals or the government itself. Also, the book strongly disputes the answer the other person has given, that access to natural resources plays a significant role edit: a lot of people in this comment thread are bringing up objections that are thoroughly answered in the book. For example, a government that is an awful human rights violator does not always equal a government that doesn't protect property and attract business",
"Born and bred West African here who spent the first 24 years of his life on my beloved continent. Problem numero uno in my opinion is bad leadership. One thing you always have to remember about Sub Saharan Africa is that a lot of these nations are artificial non homogeneous creations by European powers. Take my home nation of Nigeria as an example. There are three ethnic groups within its borders with populations of over 20 million each. Sure they may have all looked black to the British but these groups are as culturally and linguistically different as Russians are from Chinese (if you think this is not a problem, imagine aliens invading Earth and declaring that henceforth, Greece, Turkey and Russia will be one country). Throw in another four or five groups with populations roughly equivalent to that of Ireland and another 20 or so numbering over a million and you have a recipe for chaos as individual groups jostled for power. It's no accident that the Nigeria of my childhood was wracked by constant military coups. In such a situation, it's not the cream of the crop with drive and vision who rise to leadership. It's the most brutish and the most unscrupulous who force themselves into positions of authority. Something else people tend to forget is that the colonial period is still relatively recent. When I was a toddler, Zimbabwe, Angola and Mozambique were still engaged in conflicts related to their wars for independence. Apartheid was still a thing in South Africa. Heck, 7 years before I was born my own country was engaged in civil war. These conflicts were devastating and take time to recover from. Overall, I'm optimistic about Africa. I believe the younger generation are far less hung about ethnic identity than previous generations. People now take as much pride in being Nigerian, Senegalese or Ghanaian as they do in being Igbo, Wolof, Yoruba, Akan etc. Skilled African migrants are returning home to setup businesses as a kind of reverse brain drain. The internet has made the world a lot smaller and you can sit in a small village and pick up valuable skills by browsing MIT Courseware. The politicians are still no prize but they are a lot better than they were when I was growing up. I choose to remain positive. Give it 50 years and I think this is a story that turns out well.",
"Simple. Terra Nuills. It caused the decline of most of Africa's Kingdoms and Empires. Heres an overview of the continents history. Firstly West Africa should be considered one of the most important area for civilisations in the world. The richest man ever to live came from here, Mansa Musa, who on a pilgrimage to Mekka, sank the gold price for almost a decade in every country he visited. West Africa was also home to the Kingdom of Benin, notable because of two main things. First is Benin City, whose walls “extended for some 16,000 km in all, in a mosaic of more than 500 interconnected settlement boundaries. They covered 6,500 sq km and were all dug by the Edo people … They took an estimated 150 million hours of digging to construct, and are perhaps the largest single archaeological phenomenon on the planet”. [[1]]( URL_1 ) The second is the bronze's of Benin, the best in the world at the time. They demonstate a complex knowledge of metallurgy. These great Benin artisans refined that technique until they were able to cast plaques only an eighth-of-an-inch thick, surpassing the art as practiced by Renaissance \"masters\" in Europe. The cities populace were also versed in complex mathematics: > Benin City’s planning and design was done according to careful rules of symmetry, proportionality and repetition now known as fractal design. The mathematician Ron Eglash, author of African Fractals – which examines the patterns underpinning architecture, art and design in many parts of Africa – notes that the city and its surrounding villages were purposely laid out to form perfect fractals, with similar shapes repeated in the rooms of each house, and the house itself, and the clusters of houses in the village in mathematically predictable patterns. > As he puts it: “When Europeans first came to Africa, they considered the architecture very disorganised and thus primitive. It never occurred to them that the Africans might have been using a form of mathematics that they hadn’t even discovered yet.” [[1]]( URL_1 ) This knowledge of mathematics and science was mirrored in the more northerly (but still sub-Saharan) city of Timbuktu, where a university was founded (perhaps the oldest in the world, boasting 25,000 students in city with a population of 100,000). The Tumbuktu manuscripts are perhaps the best example of an advanced knowledge of astronomy and mathematics in sub-Saharan Africa. In an episode of Sahara with Michael Palin, he is shown one manuscript which might even suggest they discovered that the sun was the centre of the system, many years before Europeans did. As we move further south we come the Kingdom of Kongo on the West African coast. In 15th when the Portuguese, the first Europeans who sailed the Atlantic coasts of Africa “arrived in the coast of Guinea and landed at Vaida in West Africa, the captains were astonished to find streets well laid out, bordered on either side for several leagues by two rows of trees, for days thet travelled through a country of magnificant fields, inhabited by men clad in richly coloured garments of their own weaving! Further south in the Kingdom of the Kongo, a swarming crowd dressed in fine silks’ and velvet; great states well ordered, down to the most minute detail; powerful rulers, flourishing industries-civilised to the marrow of their bones. And the condition of the countries of the eastern coast-Mozambique, for example-was quite the same.” For example the Kingdom of Congo in the 15th Century was the epitome of political organization. It “was a flourishing state in the 15th century. It was situated in the region of Northern Angola and West Kongo. Its population was conservatively estimated at 2 or 3 million people. The country was fivided into 6 administrative provinces and a number of dependancies. The provinces were Mbamba, Mbata, Mpangu, Mpemba, Nsundi, and Soyo. The dependancies included Matari, Wamdo, Wembo and the province of Mbundu. All in turn were subject to the authority of The Mani Kongo (King). The capital of the country (Mbanza Kongo), was in the Mpemba province. From the province of Mbamba, the military stronghold. It was possible to put 400,000 in the field (Edit: they never did put this many in the field though, in the Battle of Mbwila the Portuguese reported facing an army of 100,000, thought the figure is likely to be lower).” (African Agenda - PD Lawton) Here's a picture of the city of M'Baza Kongo: URL_0 I could go onto talk about the stone castles of Great Zimbabwe. The carbon steel of the Africans who lived on the shores of Lake Victoria, created over a thousand years before it was discovered in the West. A shout out to the Lunda and Luba empires of Central Africa. And of course, the Tanzanian city states of the East Coast who filtered out the steady stream of resources from Central Africa to the trade routes which ended in China. Kilwa Ksiwani is the most notable, especially for it's [beautiful stones buildings and elegant arches]( URL_2 ). Terra Nullius led the destruction of most of the continents ancient structures, and a stripping of the continents natural wealth. And racial prejudice meant archaeology is only now catching up with the continents history. Edit: The African's are a people ignorant of their own history (not all obviously), and it leaves them without a grounding to base their progression upon. They lost all their knowledge and traditions. It can be pretty devastating.",
"Its a really long answer - if you'd like to really understand it, I would recommend reading _Gun, Germs and Steel_ by Jared Diamond; it addresses this _exact_ question. At a high level, Europeans had better/easier access to high calorie food stuffs and animals fit for domestication, which allowed them to more easily form large and complex communities. This allowed for people to start specializing in their labors and knowledge, which led to further advancements of civilization and technology. When they reached the point of being able to explore the world, they were able to conqour less developed civilizations (like those in sub-Saharan Africa) and colonize them. Colonization is, as a general rule, not great for the economic health of the colony.",
"African here (South Africa). In recent times, black South Africans have taken up the mindset that the only reason that Africa is impoverished is because of European greed. This really puts a big divide between people of African descent and those of European descent (with \"give back the land\" being the flavour of the month, with leaders like Julius Malema calling for people to take any piece of land that they like for themselves). Basically, where my tangent is going is that the sentiment from impoverished South Africans is mainly that the Europeans took everything from them. While I do agree that this could very well have been a catalyst, examples such as Zimbabwe prove that wealth redistribution in its simplest form (reappropriation without compensation) does not work in the current African climate. TL;DR: Africans mainly blame Europeans. However, taking the stuff away from the Europeans and giving it to the Africans leads to screwups like Zimbabwe.",
"Parts of Africa are doing reasonably well and lots of countries are improving economically SIGNIFICANTLY every year, the development there is insane. Cities in West Africa, places like Nairobi and the east, and of course South African cities are very diverse and well-developed, and often very international too. The obvious major barriers to a lot of development with impoverished nations comes from their origin as a 'nation-state,' which is from colonially drawn artificial lines, sort of like how Iraq was never a country and was just drawn up on a map. That, followed by the mass rape and pillage of resources, means there was a 'late start.' As for what's going on now, though the rapid development in Africa is grossly understated in media (but its obvious to those who visit every few years and see how much changes each time), there is also major problems involving international trade. Check out the Doha rounds, the most recent World Trade Organization set of rounds began in 2001, and STILL hasn't become solved. This is because trade standards are set by the WTO (and IMF), where developed countries have a massive vote majority. It wasn't until Doha that developing countries finally banded together. The problem, essentially, is that developed countries have forced open trade involving most goods *except* things like agricultural goods and textiles. These happen to be the only things many developing countries actually have a comparative advantage in and would benefit from selling. The capital-intensive countries get to use their trade advantage, then keep tariffs and subsidies to prevent developing countries from using their point of advantage, essentially an unfair system. URL_0 URL_1",
"The book *Prisoners of Geography* does a good job at explaining sub-Saharan African poverty. Basically, it's because the interior of the continent has historically been full of people who literally, because of geographic factors (thick, impassable jungles, few navigable rivers, diseases, poor land for agriculture etc.) have been cut off from most of the world. If you think in the 21st century, we would be over geographic limitations...you'd be wrong. We absolutely are not. TL;DR - geography matters, A LOT. It's not the only thing, but it can really set a region back.",
"During the time Europeans were colonizing, they either set up an \"extraction state\" where the goal was to get as many resources back to their motherland as fast as possible or an \"investment state\" where they would develop institutions like railroads and education systems since they planned on settling there. These institutions usually help countries e.g India prosper through trade later on. Europeans decided what type of state to set up greatly based on mortality rate. Africa had especially high mortality rates because of many fatal diseases, so the Europeans extracted their resources and hightailed the fuck out of there (at risk of oversimplifying)! You can see the effects of whether an \"extraction\" or \"investment\" state was set up by looking at the GDP of those countries today. Fascinating stuff!",
"To be very brief, one of the biggest reasons is Colonialism and Imperialism. European countries realized many African countries were rich in natural resources (unfortunately this also included viewing the actual citizens as a resource) and they wanted access to them. To name a few - England, France, Spain, Italy, Belgium used military force to establish colonial settlements in almost all African country's which were governed by military, authoritative rule. What happened in Africa during the Industrial Revolution was genocide. Tens of thousands were killed, their culture was demolished, they were forced to live in abject poverty with no access to education, no rights, they were property. A means to an end. It's been less than a hundred years since African countries were given their independence. That's not a long time to recover.",
"I've always looked at it as this: warm climates usually don't need to advance. Life is simple and slower because you don't have to worry about not having enough to eat as much. In a colder climate you need to prepare for the winter. This makes you that much more dependent on innovation. When it's warm, why would you have to even try and innovate? Life is already easy. In my own experience I see this at the company I work at. Our Mexico and even in southern US divisions, people answer emails much slower while our northern and Canadian divisions all are usually quite timely.",
"Every single upvoted answer here looks at external factors ignoring mentioning the inhabitants. They have bad governance, they lack institutions, they have armed conflicts, and they have diseases. 3 out of these 4 are strictly caused by people. And diseases: Europe lost 1/4 of its population just to the black plague. Again, all the answers given are nicely packaged and superficial, and made for 5 year olds to feel good. But the messy reality is that a huge impact is the local population.",
"The short answer is Imperialism. Africa was ravaged by the developed nations of Europe. Divided into a mess of colonies and incurring multiple small wars. The real problems began when imperialism left, practically overnight, following WWII. You see the colonies were not set up to be self sufficient or sustainable. They were made to gather, process, and export the natural resources of the land to their imperial masters while remaining dependent on the empire for basic things like infrastructure and security. When imperialism packed up it left a massive power vacuum as well as an entire continent that was in no way prepared to sustain itself.",
"Lack of innovation, statistically lower I.Q then other regions. Its pretty cut and dry but reddit censorship will claim this is racist even if its the actual reality.",
"They were kings and queens and built the pyramids with mind power alone but the white devil and stole everything from them and reduced them to slavery.",
"The real question is, why are Europe and North America so prosperous? After all, poverty is the natural condition. And the reason is very simple. The relative political anarchy in Europe, as well as the advent of liberalism (and I use this term not as it is used today, as synonymous with social democracy, but to be broadly in favour of human freedom) led to the development of laissez-faire capitalism. And because the USA and Canada were founded by European settlers the ideology of capitalism and freedom came with them. That is why Europe and North America became so much more prosperous than all the other continents, because there was a great deal of economic freedom. Because of laissez-faire capitalism. But unfortunately not many African nations had a good deal of economic freedom throughout their history, and so they remained impoverished. Of course sub saharan africa in particular had the added problem of being cut off by oceans on three sides and the most brutal desert in the world on the other, which didn't help matters. Africa is also home to a particular economic miracle, the nation of Botswana. During the 20th century Botswana was for many decades the world's fastest growing economy. And the reason was simple, Botswana had extremely limited government.",
"I have a good friend who lives in Ghana, and he was telling me that a big problem is that foreign corporate interests come in and buy up all the natural resources, so Ghana gets basically nothing from all the resources they're sitting on. People there haven't been shown how to open businesses, run companies, and make a profitable life for themselves, or even see that as an option. They're literally sitting on gold mines but nobody has shown them how to make that resource profitable, so they sell the land to outside companies who are much better at playing the cash flow game than they are.",
"I don't know about Africa in particular, but why in general: -Was used for its resources by other countries, which leads to a system where wealth is resource dependent and not diversified -Bad governance, which often is a symbiotic relationship with a natural resource based economy -Not taking advantage of poverty; meaning China, for example, used its low wage laborers to its advantage by being the efficient place to make goods; even if people in Africa are poorer and would work for less, companies don't move if the government isn't coherent and organized and if they've already reached agglomeration in another place -Being landlocked is another factor that leads to less investment and trade -Also people don't trust the institutions, including banks, so those who have wealth in poor places tend to send it elsewhere where they know it's safer and they tend not to invest where they live",
"Without immediately going into a: \"Everything is the white man's fault\" rant (You will find that in the other comments) It's mostly infrastructure. Everyone bar none needs water and food. The climate in about 80% of the continent, the part dividing it in two unfortunately, is very inhospitable to human settlements. This means that unlike most other continents, siberia is similarly difficult but also more sparsely settled, people living there need to spend more time out of there day obtaining food and water. That means that there's less time to build infrastructure to help shorten the time spent getting the basics to survive. That means it's harder to develop industry, etc... that would help further free time to educate children etc... There's a lot of other society economic factor and internal fightings that compound the problem but we start getting away from ELI5.",
"My father has spent a lot of time in Africa and once told me that this is partially because the government's don't want their people to get educated and socially mobile. The vast majority of Africans are peasants, most of them either work in agriculture or are self sustaining with very little income. This is good from the government's point of view because the more money their people have, the more educated they become, and the more they begin to see how corrupt and unfair the government is. Basically, they are kept poor because the government is scared that with an educated population, they will be replaced. Many African countries have the resources and huge potential to improve life for their citizens but sadly it won't happen soon due to this reason. This, when coupled with the disease, famine, and war that takes place in Africa makes it difficult for the continent to truly prosper.",
"Africa has some of the hottest climates on the planet. Due to this and the abundance of resources, especially food, Africans didn't have to go through the agricultural revolution to survive. The first agricultural revolutions in Africa started 4,000 years after those on the Eurasian continent. Even before, they never had to struggle as much to survive like those on the Eurasian continent did. The climate was more hospitable, and the seasons, were much more tame than in Eurasia. Over thousands of years these environmental pressures led to differently adapted evolutionary traits. Climate is highly correlated with intelligence, warmer areas having indigenous populations with lower intelligence, and colder areas having indigenous populations with higher intelligence. Intelligence is directly and strongly correlated with the wealth of nations. Lower intelligence populations on average create countries with lower economic status. We even see this in America and Europe, where the lower IQ black population enjoys a much lower economic standing than those of European descent.",
"It's not impoverished \"as a whole\". You must have an American or European perspective. The only portray poverty, hunger and violence in your TV and literature",
"Like the American Indian the Sub Saharan African was inferior to the Europeans in technology by several thousand years. Basically living like they have been since the Stone Age when Europeans first started to explore the equatorial and southern regions. What happened afterwards was bound to happen when a more powerful and organized people take advantage of such a situation. How it happened is inexcusable of course. The climate and geography is not as strong of a factor. If your going to use that as a factor then you must explain Iceland, they seem to have done ok for themselves since about 900AD.",
"@FatJokes101 Mallence explains it quite well in this TED Talks: URL_0",
"Trying to make this not a race issue but wasnt south africa doing pretty well up until about 10 years after the end of aparthied? Serious question.",
"There are a myriad of factors but one that is often overlooked is the effect that the Cold War had on post-colonial Africa. The height of Cold War tension and the independence wave of Sub-Saharan Africa happened concurrently. As a consequence of the Super Power's obsession with the global dominance of their systems the US and USSR were willing to support oppressive dictators as long as they declared themselves nominally capitalist or communist. For example Mobutu of Congo, a horrible authoritarian kleptocrat, enjoyed large support and aid from the US for 30 years just because of his anti-communist stance. The same for the USSR supporting The Derg in Ethiopia. After the Cold War ended these kinds of dictators are now frequently condemned, pressured and isolated by the USA and the west (e.g. Mugabe, Museveni). Who knows how things might have gone differently if the Super Powers had put the same pressure on the newly independent African leaders.",
"3 reasons: 1. Geography - the geography of the continent stretches north-south, not east-west, so it is divided both climate and by geography. This limits many nations to thin slices of the coast (Ghana, Somalia), inaccessible parts of the interior (CAR, Burundi), or areas dominated by difficult terrain (Mali, DRC). This makes it hard to get around. It's also largely deficient in things like good deep water ports, navigable rivers, and arable land suited for cereal crops that can support large populations. 2. Ethnography - as a result of geography, Africa is also heavily divided along ethnographic lines. There are thousands of languages, dozens of language families, and hundreds of ethnic groups. That makes it hard to get together and form things like cities and countries. 3. History - because of the first two factors, Africa has a several thousand year history of being exploited by outsiders from places without those disadvantages. This creates cultural expectations that are also hard to overcome. Africa isn't a poor continent. It's resource-rich, and has a third of the world's population. In any century but perhaps the past 2, it would be the wealthiest place on earth. However, it's politically divided for the reasons above, which make it relatively poor compared to other places.",
"Libya is now poor because it wanted to form its own currency with other N.African countries, and was bombed into smitherines as a result. Also, as a whole, more money in the form of minerals leave Africa than is returned. Imperialist capitalism at its finest.",
"Follow up - is Africa really that bad? Population has exploded. A quote from former British Prime Minister David Cameron \"In 1950 the population of the Middle East and Africa was equivalent to half of the population of Europe. By the end of this century, it will be eight times the size of Europe’s. \"",
"It's not. Africa is rich in natural resources. Vast swaths of the continent are ideal for farming and the continent possesses wildlife suitable for domestication and exploitation. For whatever reason the people inhabiting Africa have not been successful capitalizing on the vast opportunity the continent provides. The reasons people give for this will likely be incredibly controversial, ideologically motivated, and anything but impartial. However, the idea that Africa is some dreadful continent consisting only of arid wasteland without civilization potential is not true.",
"Well one of the most important reasons is that due to imperialism that continues to this day (distinct from the colonialism of the 1800s), a lot of nations are subjugated and their natural resources and labor are exploited. It is not uncommon for warlords in for example the Democratic Republic of the Congo to be on the payroll of various companies, who pay them to oversee the cheap and resource rich labor in their territory. Furthermore should be noted that several attempts to organize against these forms of imperialism are met with extreme hostility, with anti-imperialists like Nelson Mandela being labeled terrorists, and the African National Congress being seen as dangerous, the reason for the invasion of Libya was not over the issue of human rights, if that was enough, the Shah would never have had power, and Saudi Arabia would not continue, the real reason that Libya was invaded is because Gaddafi proposed a gold based currency to trade oil in, which threatened American hegemony.",
"I would recommend the book Prisoners of Geography by Tim Marshall. The chapter on Africa is incredible.",
"\"Architects of Poverty: Why African Capitalism Needs Changing\" is the book I'd recommend you reading, by Moeletsi Mbeki, if you want to find the full comprehensive answer. Compares African liberalization, to Asian liberalization which started happening at the same time.",
"One interesting theory I heard of was natural food availability. If you look at what kind of animals and crops are available throughout the world Europe has almost all animals you can farm and eat, and a great range of crops that will grow there happily. Various wheats, chicken, sheep, cows, pigs etc.. Not animal that is edible can be farmed though, some die, some don't reproduce. If you look at crops I think the yam is one of the few crops you can grow. Lack of stable foods to be grown leads to less culture, as culture generally develops in cities and cities require farmers to be able to exceed sustenance. As a result, Africa is not in the most favourable of circumstances.",
"Here's a short and helpful video that breaks down [**why are some countries poor and others rich**]( URL_0 ) & nbsp; Essentially, the 3 main factors are: 1) **Institutions** (e.g. health, transportation, education, etc.) * Corruption within large institutions and degree of poverty are directly linked. * In comparing the top richest and poorest countries, those with greater corruption in their institutions \"can't collect enough taxes to get the good institutions they would need to escape the poverty trap.\" 2) **Culture** * This relates greatly to religious beliefs, with statistics showing that \"the less people believe, the richer they stand a chance of being.\" * 19 of the 20 of the richest countries in the world have 70% of their population saying that religion is not a tool important to them (with the exception being the US). 3) **Geography** * Poorer countries are overwhelmingly located in the tropical regions. * In hotter climates, food production is negatively affected by several factors: (1) foods that grow in warmer climates tend to have fewer carbohydrates, (2) the soil quality is poorer, (3) the climate is disadvantageous to photosynthesis. * Tropical regions = Increased risk for (LOTS of) diseases Each of these factors are explained in more detail in the video for those interested in learning more!"
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"https://www.theguardian.com/cities/2016/mar/18/story-of-cities-5-benin-city-edo-nigeria-mighty-medieval-capital-lost-without-trace",
"https://theculturetrip.com/africa/tanzania/articles/kilwa-kisiwani-the-ruins-of-east-africa-s-greatest-empire/"
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5xc801 | Why is the 'pink' lake in Australia, pink? Like I am a high school kid ? | Chemistry | explainlikeimfive | {
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"The odd hue comes from an algae known as Dunaliella salina. There is another pink lake, in Senegal, named Lake Retba, that is pink for the same reason. Both lakes, from the air, are a bubble-gum pink, but from the shore, they're much more translucent, though still pink-tinted. The pink hue is even visible if you gather a bucket of either lakes' water. The algae produces a red pigment to aid in absorbing like, which provides energy to create ATP. ATP is Adenosine Tri-Phosphate, a small molecule used in cells for energy transference."
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5xc9rr | How would the gravity and environment of Mars affect the people that colonized it? | Biology | explainlikeimfive | {
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"There is almost no atmosphere on Mars (1% of Earth's Sea Level pressure). This means Humans who colonize Mars will either be indoors or in a pressure suit all the time. That's a key feature in the design of their air-tight structures and vehicles.",
"This is a complex topic with many possibilities, and much uncertainty, but I'll do my best to ELI5. We can separate the effects on 2 levels: **Physical** and **Psychological.** On a **psychological** level, its hard to predict how it would affect the first colonizers. The feeling of belonging to a new place wouldn't be there right away, but with generations to come, it would eventually settle. Those 2nd generation Martians would be introduced to the science fields and exploration much sooner than your average Earthling. They could also develop a feeling of entrapment, due to not being able to experience the same things as people on Earth. With enough time elapsed, routines would be created which would eventually give birth to a new set of habits, maybe even a culture. On a **Physical** level: Mars gravity being 38 % of Earth's brings some problems like muscular/bone atrophy, eyesight problems, sleep disturbance. But since the first colonizers, would not experience the **raw** environment and gravity of Mars, it wouldn't be much different from the astronauts who now live on the ISS. If there was a 2nd generation born on Mars, those people could experience differences in body morphism, like being taller and having leaner body parts. Also they would probably not be able to come to planet Earth without hurting how their body works, much less being able to move/walk."
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5xccc5 | What purpose does VEVO serve? Why do artists let VEVO put their music on youtube? | Other | explainlikeimfive | {
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"Vevo is a platform owned by Universal and, if I remember correctly, Sony that favors premium advertisments in order to have a stable revenue for sponsored artists (and labels). That *should* prevent unauthorized uploads from people who are basically stealing money from labels and artists by monetizing their videos.",
"Essentially, VEVO is an ad network within Youtube. Similar to ad networks such as Machinima. The point of an ad network is that they strive to collect video channels of a similar purpose so they can have a more specific demographic. The more specific the demographic, the more appealing they are to advertising companies. The more appealing you are, the more you can charge per ad. Youtube still collects a cut. But it's a cut out of a bigger pie tha VEVO shares with the labels, and in theory, the artists. In other ad networks, any ads they can't run are replaced by ads that Youtube collected. It pays less but they have a bigger pool of ads to play. If you're an independent artist, nothing is making you join VEVO. VEVO is just another ad network to you. Major labels Artists are typically forced to have their songs on VEVO so that VEVO gets more money, which means the label gets more money, and allegedly the artist gets more money. (Kanye shrug on the last part)"
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5xcg8p | what happens to the baby if a mother uses cannabis during pregnancy? | I have a friend that is pregnant and refuses to stop using cannabis during her pregnancy. I try telling her it's a bad idea but I don't have any evidence, I just base my suggestion on common sense. | Biology | explainlikeimfive | {
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"This isn't really an ELI5 type of question, so it's difficult to give an ELI5 answer. [Marijuana Use During Pregnancy and Lactation]( URL_1 ) > It is difficult to be certain about the specific effects of marijuana on pregnancy and the developing fetus, in part because those who use it often use other drugs as well, including tobacco, alcohol, or illicit drugs, and in part because of other potential confounding exposures. [Lasting impacts of prenatal cannabis exposure and the role of endogenous cannabinoids in the developing brain]( URL_2 ) > Marijuana abuse during pregnancy and adolescence represents a major health problem owing to its potential consequences on neural development. Prenatally cannabis-exposed children display cognitive deficits, suggesting that maternal consumption has interfered with the proper maturation of the brain. [Cannabinoids and the human uterus during pregnancy.]( URL_0 ) > Both endogenous and exogenous cannabinoids exert a potent and direct relaxant effect on human pregnant myometrium, which is mediated through the CB(1) receptor. This highlights a possible role for endogenous cannabinoids during human parturition and pregnancy. These results also support the view that the use of exogenous cannabinoids during pregnancy is not linked independently with preterm labor. Because THC exerts a psychoactive effect, we believe it effects fetal brain development. There is no evidence that marijuana use causes pre-term birth or low birth weight, however a lot of observational data is confounded by the presence of other substance usage that is known to cause pregnancy complications and have adverse effects on a developing fetus.",
"First off, how is she taking it? Smoking, eating?",
"URL_0 Jamaica did a study about this subject with some pretty cool results.",
"In general, pregnant women don't sign up for clinical trials so we are left with those who voluntarily give info. I have two kids. I was perfect with my first. Never sipped alcohol, went to prenatal yoga, ate a balanced diet, breastfed, you name it. Second child, I was stressed out (legitimately, I promise) and I hit the bowl somewhat regularly. If I needed a cigarette or a shot, I allowed myself if it calmed me down from the extreme stress. Not every day or every week, just in the times of need. And before I get the downvotes, they both turned out to be fine. They are healthy, loving, smart and talented children. I wouldn't change a thing. Happy mom happy baby.",
"It can do harm to babies. Generally it's similar to any exposure to cannabis during development. One reference: > What about long-term effects? A few studies have found that after 3 years of age, children born to marijuana-smoking mothers score slightly differently on cognitive and behavioral tests compared with other babies. A decade-long Canadian study found that at 4 years old, children born to mothers who used marijuana on a daily basis during pregnancy scored lower on memory tests, though there was no impact on overall intelligence scores. At age 10, kids had a slightly increased risk of hyperactivity, inattention and impulsivity. URL_0 It's not on the severity level of something like heavy drinking, but it's still bad. Especially if she's using it heavily or regularly."
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5xcjeh | Does a body absorb the same 2,000 calories whether it is eaten in one sitting or spread out over five days? | Biology | explainlikeimfive | {
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"To begin, a Calorie isn't exactly \"absorbed.\" All a kcal is is a measurement of energy required to raise the temperature of one kg of water 1 degree celsius at 1 atmospheric pressure. And, in physics, the amount energy in the universe is fixed. We use the energy, but release energy as well as heat, as matter, etc. So, with that out of the way, your body definitely would metabolize 2,000 Calories in one sitting versus several days completely differently. Your stomach generally holds onto food for 3 - 6 hours, depending on how much fat content is in it; fats take longer to break down because they must be emulsified first, and then broken down into fatty acids and glycerol, absorbed through your intestines into lacteals, which are a part of your lymphatic system, and then disbursed throughout your body. The biggest factor to consider concerning metabolization and Caloric intake is which type of macro nutrient we are talking about. Ignoring vitamins and minerals, fats, carbohydrates, and proteins are broken down in different ways. Simple sugars and carbohydrates are the easiest to break down, and are a preferred source of energy in some ways, because of their high bioavalibility; sugar is excellent for bursts of energy, ya know, to outrun lions, or catch the rabbit for food. Fats require a lot of oxidation to be utilized, so when you are walking, sitting, sleeping, studying, pooping, or anything that does not raise your heart rate very much, (IE: using oxygen rapidly as energy in conjunction with sugar for your muscle cells) your body will use the oxygen to oxidize fats for energy. This is why we say fats give 9kcal per gram. Proteins are a different beast, that I will not get into. TLDR; the way Calories are metabolized depends on the activity you are, or are not doing. And, there is a timer in which foods consumed will be utilized for energy, or stored for later use, and this time period is just a handful of hours--much less than one day.",
"Your body will not hold onto the food for five days. It will either absorb it as it passes through our it will pass some of it out in about a day if it cannot absorb it all. Most likely your body will be able to absorb 2000 calories eaten in one meal."
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5xcjnc | What exactly is the difference between "cores" and "threads" on a CPU? | I see some CPUs have cores equal to threads, but some have twice as many threads as cores. What are threads here? | Technology | explainlikeimfive | {
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"In a CPU core, various types of calculations are actually done in physically different parts of the CPU. For example, integer arithmetic runs on a different part of the silicon than floating point (decimal) arithmetic. A CPU with multiple threads takes advantage of this by letting two programs run on a single CPU core at the same time as long as both programs don't need to do the same type of instruction at the same time. This is why running two threads on a single core isn't usually a doubling of performance, because if both programs are trying to do integer arithmetic at the same time for example, they need to wait for each other. To make it more ELI5, imagine a CPU core is a kitchen. A program that wants to run is a recipe that needs to be prepared. The various parts of a CPU core are the various areas of the kitchen. You only have 1 oven, 1 stove, 1 cutting board, etc. Adding additional cores is like adding an entire extra kitchen. Adding CPU threads to a core is like adding another chef to the kitchen. Sure, you can now cook multiple dishes in that kitchen now, but only as long as they don't both want the oven at the same time. EDIT: As an anecdote, I used to do a lot of work with [POV-Ray]( URL_0 ), a free open-source 3D rendering app. In my 4-core (8 thread) i7-3770, if I tell POV-Ray to only run with 4 threads so it only uses 1 thread in each core, then run a full 8 threads, it only gains about a 10% speed increase because the extreme majority of POV-Ray's work is floating point math, so it can't effectively take advantage of a multi-threaded CPU core."
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5xcsuk | How Thomas DeMarse made a brain from rat brain cells and taught it to fly a plane | There's more here: URL_0 How does this work in simple terms? | Biology | explainlikeimfive | {
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"Its not a 'brain' as in self-thinking or self-aware. It is a biological computer. The cells are just randomly run through the program long enough that the correct actions/responses to continue are stumbled upon and connections built. (As an aside. Keep in mind that the source material is a press release from the University so its alot more hyped than it should be)"
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5xcvah | Why is it "Gramps" and not "Granps"? | Sometimes we use "gramps" instead of the longer versions (Grandpa and Grandfather). Why do we change the N to an M? Shouldn't it be "Granps"? | Other | explainlikeimfive | {
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"In English, an n often shifts to an m when it precedes a p or a b. For example, when you add the in- prefix to possible and balance, you get impossible and imbalance.",
"The English letter M is pronounced as a bilabial nasal. That means your two lips (bilabial) are together and wind is passed through your nose (nasal) while your vocal chords are making noise. The English letter P is pronounced as a voiceless (your vocal chords are not making noise) bilabial (two lips together) stop (air is prevented momentarily from leaving your mouth). Both sounds are bilabial - your lips are together, so there's a smooth transition from the vowel (where your vocal chords are active, but nothing obstructs the flow of air) A to bringing your lips together into M to simply stopping the flow of air momentarily as you shift from pushing through your nose (nasal) to the stop (P) to the vowel at the end. Trying to pronounce it with the N, which is an alveolar nasal - your tongue is pressed right behind your top teeth (the alveolar ridge) - requires shifting awkwardly between two different mouth positions. You have to make the M mouth shape anyway to get to P, so unless you prematurely stop the voice (basically \"Gran. Pa.\") you will accidentally say \"-mpah\" anyway. Because M and N are both nasal consonants, it's easier and still intelligible to use M instead, and even if you specifically said \"granpa\" it would almost certainly *sound* like \"grampa\" anyway. It's actually from \"gran**d**pa\" (from father - > pah, +grand like grandfather). The D stops the sound like the P, but again D is an alveolar stop, so you still have to shift to the P. That also means stopping the air twice in a row (once for D, another for P) which sounds weird and is inefficient. It's much more efficient to stop the air once and skip the D entirely, which still leaves you with \"granpa\" and that awkward N - > P shift. EDIT: Since N is an alveolar nasal and D is an alveolar stop, you have the same easy shift from the nasal N to the D stop, which is why the word \"grand\" rolls off the tongue as easily as \"gramp\" does, but \"gramd\" would be just as awkward as \"granp\"."
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5xcyrm | The Fed announced they will likely be raising interest rates soon. What does this mean for people who are in the process of picking out a house to buy? | Link to Article: URL_0 | Economics | explainlikeimfive | {
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"Interest rates are likely to be higher than lower. The change is probably small, 0.25%, but you should expect that banks will pass the cost on to you. Much of the increase is already baked into estimates, so don't expect a square wave in rates the next day."
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5xdagi | Why haven't we started domesticating tiny bears? | Biology | explainlikeimfive | {
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"What practical purpose would domesticated bears serve? All of our domesticated animals came from a practical need. Dogs? Descended from wolves that we captured as pups and raised. Dogs were (and still are) a pretty effective security system. Cats were domesticated for pest control. A house with a cat was healthier than a house without a cat, because it would kill off some of the rats and mice that spread disease, and scared off the rest. So, what benefit would a bear have in the house that would outweigh the costs and risks of keeping it?",
"i dunno. why haven't you started domesticating tiny bears that eat 100 pounds of meat a day?",
"You could get [a dog that looks like a bear,]( URL_0 ) and he won't try to tear your face off.",
"Among the other things listed, animals that are good for domestication are generally social animals. Wolves are very social, so it was easy to teach them how to be around humans, relatively. Dogs aren't very bright animals in general, but they're amazing in terms of social intelligence. Bears aren't social. They mostly stick to themselves outside of mothers with children. That means they have no instincts to work together or to spend time with others."
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5xdee6 | What actually causes/are palpitations? | I'm sure most people are familiar with the feeling of your heart going too quickly or pounding/racing, but what actually is it? Is it really your heart skipping a beat? Or is it something psychological and completely unrelated to the mechanics of the heart? | Biology | explainlikeimfive | {
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"Although there are many serious ailments that can cause palpatations (and you should have a routine check-up to rule them out), many occasional palpatations in otherwise healthy individuals are caused by dehydration. The subsequent lack of blood volume results in the heart trying to move a decreased amount of blood, causing irregular heartbeats, or palpitations. When you feel them, stop and drink a bottle of water or Gatorade/coconut water (for added electrolytes) and see if they improve/stop. And keep in mind how many diuretic drinks (soda, caffeine, alcohol, iced tea, etc.) you have in a day. Maybe try to make every third one a water to prevent palpatations."
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5xdhdn | Why are we using a loud, obnoxious *BEEP* to censor curse words? | Other | explainlikeimfive | {
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"I was thinking the beeps are used for a humorous effect. If we can't have curse words out in the open in case there's children watching, we can at least have a laugh at the obnoxious beeping.",
"I'm curious also, although I have heard the loud BEEP a lot less the past few years. Nowadays it seems to be mostly a small moment of silence to censor the curse words.",
"If we go back in time to when audio was recorded on tapes, the way to censor something is to record over it. If you just record silence over it, you'd still hear the censored content, albeit likely quieter. If you put a nice solid tone over it, it'll for sure eliminate the ability to hear what's underneath."
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5xdik1 | If booze actually makes your core colder, why do you feel warmer? | Explain this, please. | Biology | explainlikeimfive | {
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"text": [
"Booze makes your core colder because it increases blood flow. This lowers your body temperature overall, but your surface temperatures increases significantly as heat transfers out through your skin. This makes you feel warmer. And is also why you don't drink in the cold, because you will freeze faster.",
"when your body starts to get cold your blood vessels in your extremities constrict. it does this to force more blood away from your arms and legs and towards the critical organs in your head and torso (brain, heart, liver and all that). heat is lost more quickly in the arms and legs because there is more surface area per unit of volume, so keeping your warm blood closer to core will help you to conserve heat. drinking alcohol causes the blood to become thinner. that makes it easier for the blood to get into the smaller blood vessels. so while it may make you *feel* warmer because your hands and feet arent so cold, its lowering your core body temperature. thats probably not so bad if you have just come in from the cold and you have a hot drink while warming up next to the fire, you're not in critical danger of organ failure. its not so useful if you're trapped outside in the middle of a blizzard."
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5xdlea | If sound is air escaping things, why does hitting a metal fork against a glass sound different then hitting a plastic fork against a glass? | Physics | explainlikeimfive | {
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"Sound is not just air escaping things, it's a wave travelling through air. It is characterised by compressions and expansions of air, which vibrate our eardrums allowing our brains to interpret it. Things sound different because they produce different waves. Real life waves are not the simple sine waves you commonly see diagrams of - they have numerous different components which define the texture of the sound. This is why different instruments playing the same note have different sounds, even though the dominant frequency is the same. A plastic fork vibrates differently to a metal fork, which in turn produces a different sound wave."
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5xdllh | What makes someone allergic to a certain thing? | What makes someone allergic to peanuts, bee stings, etc. etc. Bonus question: why are some allergic to these things while others are not? | Biology | explainlikeimfive | {
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"You have an allergic reaction to something when your immune system incorrectly identifies it as a threat. As everyone is different, and has different immune systems and different exposure histories, they have different reactions to different things. It's currently understood that early exposure to peanuts as an infant or toddler can prevent allergic reactions later in life as the body learns that they're OK. I, for example, get hay fever; I'm allergic to grass pollen. Makes every Spring a nightmare. Grass pollen is not a threat to me, but my immune system believes otherwise.",
"Okay - my immunology is rusty, but here goes: First part: It's a part of your immune system called the Immunoglobulin-E (IgE) -mediated inflammatory response. What it's supposed to do is clear out parasites; but it can go awry. Immunoglobulin responses use these clever little protein keys to lock onto proteins in pathogens. That flags them as a threat, and a whole cascade of immune response comes hammering down on the threat. That includes things that make your tissues swell and heat up. That's great when its something dangerous like nasty bacteria or parasites, but it's not so good when it's something benign. A person with an allergy is someone whose immune system is sensitive to things it doesn't really need to be sensitive to, like peanuts or latex or bee stings. Bonus second part: In the womb, you develop an immune system that is naieve - it hasn't been keyed to be sensitive to anything; but it hasn't been told to be in-senstive to anything either. During gestation (and your early childhood), your immune system goes through a editing process to make sure it doesn't accidentally become sensitive to its own proteins (when it does, that's an autoimmune disorder like diabetes I), or stuff that's common in the surroundings (like peanuts or bee venom). Most people's immune systems seem to just edit out things like peanuts or bee venom as being not that big a threat, or just not common enough to warrant having a pre-keyed response ready to rock and roll. However, some people, for reasons not completely understood have a response ready to go to allergens. To make matters worse, some allergens in particular (like nuts and latex) seem to get the immune response more and more keyed-up each time it's exposed, to the point where the response will kill you (usually by causing swelling in the throat that chokes you).",
"Okay, but have I gained new allergies over the years? Starting when I was 12, I was suddenly allergic to cats -never was before. Then I became allergic to grass, then shellfish, then apples and peaches. It's really obnoxious. I used to eat all of those things growing up but now I can't, and it's extremely frustrating (though not the shellfish as I am a vegetarian now)."
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5xdroz | What are "multiverses" and why do we treat them differently than groups of different galaxies? What is the difference in classification? | Physics | explainlikeimfive | {
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"A universe is a collection of galaxies, stars, everything else. The multiverse is a collection of universes. It's just a hypothesis whether it exists - it all trails from the many worlds interpretation of quantum mechanics, which while it fits the observed evidence, is not the only interpretation which does, nor is it the more commonly accepted/used one. The idea basically states that every time anything happens, e.g. a decision which can result in A or B, then a universe in which A happens and a universe in which B happens are created. As you might expect, this results in a very, very large amount of universes very, very quickly so it tends to run on the idea that there is a universe out there for every single possibility of events from the start of the universe to the present day. As we said, there's absolutely no conclusive evidence that it exists, it's just a nice idea. As for multiverse**s**, by definition you can't really have more than one."
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5xdrp0 | Why do most online games feature beta testing phases, but offline games are released untested by the public? | Technology | explainlikeimfive | {
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"An online game needs to be exceedingly \"balanced\" in order to be successful. That means that a knight, a wizard, and a thief need to be all about as powerful as the other guy, else everyone who wants to play a knight will be disappointed if he's forced to play a wizard in order to be accepted into group content. Beta testing offers thousands if not millions of data points for the development team to study in order to balance the game properly. Even more so if the game offers a player versus player mode. Sure it's fun to be super overpowered in a single-player game, but in multiplayer games, one person having heaps of fun means that there's probably another 10 miserable ones. Server stress tests. When you release an online game, you are committing a ton of computing power from your own company to running the game. During beta testing, you get to see how do your servers react to a multitude of players and connections, something you can't really simulate without the testers. If there are server issues, you get to fix those ahead of release instead of having disappointed customers on day one. Also, an online game makes a lot of its revenue from continued subscriptions or \"item\" sales. Single player games get bought when they get released and their popularity dies down after that. By releasing an almost finished product as a \"beta test\", you get players to demo your game for free - so once the game is released for real, they will be even more willing to buy it and subscribe to it for a long time.",
"If your game design calls for a single player (as \"offline games\" do), you can hire X testers, put them each through the single-player experience, and determine if your game is bug-free, stable, fun, etc... If your game design calls is for a \"massively multiplayer\" game (eg: expect to support X thousand simultaneous players without the frame rates dropping to power point speed, for instance), then you probably can't afford to hire X thousand players times K number of permutations you need to test. Plus, there's all the \"marketing\" aspect of involving the community of potential players early, generating hype, to get funding in the early stages, etc etc...",
"The biggest reason for beta-testning is not to test the game, but the servers. Renting servers costs a lot, so you really want to make sure you only use the absolute minimum.",
"Open betas before a release are generally used to stress test the servers and try to make sure that the servers are able to handle the number of users. Plus since they are free and limited it adds to marketing"
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5xdszm | Why does drinking alcohol when hungover make you feel better? | Biology | explainlikeimfive | {
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"for much the same reason as it made you feel good the first time. The dehydration and other hangover symptoms are still there, but the new rush of alcohol numbs you the same way it did the night before.",
"The alcohol in drinks is mostly a chemical called ethanol, but another chemical, methanol, is also present. These chemicals are both broken down by your liver. When ethanol is broken down, the byproducts are fairly benign. But when methanol is broken down, it creates toxic chemicals like formaldehyde and formic acid that make a hangover much worse. Your liver prefers to deal with ethanol before tackling methanol. If you drink more alcohol while hungover, there's fresh supply of ethanol in your body to break down. Your liver will then stop breaking down methanol and creating nasty chemicals. This delay gives methanol a chance to leave your body through other ways like your breath and pee."
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5xduev | Why cant My dad use his propane heater indoors? But we can use a natural gas stove? | The bloody thing says "do not use indoors carbon monoxide warning" but he still continues to use it indoors. I open a door to save my own ass and let the cold air in and he gets pretty mad. How can I explain to him why he cant use his heater in the garage. He says the garage has a draft so therefore its ok? | Chemistry | explainlikeimfive | {
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"text": [
"imperfect combustion creates carbon monoxide. that stuff kills you if you inhaled enough of it. gas stoves also produce carbon monoxide. but most people don't turn their stoves on for hours at a time. so the concentration is much lower.",
"Get a Carbon Monoxide smoke detector. Get several. They are required by the NFPA regs exactly because of this behavior. CO is odorless, non-flammable, lighter than air, and highly toxic. It will kill you. Dead. But it is a painless death."
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5xe3t1 | Why do we use urine to test for pregnancy? | I would guess that it has something to do with hormones, but wouldn't swabbing your vagina be a better way to do this? | Biology | explainlikeimfive | {
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"Do you have a vagina? Why would anyone want to swab their vagina instead of pee? Peeing is less invasive.",
"The vagina doesn't just secrete hormones. Hormones are carried by blood, so when the kidneys filter blood to make urine some of the hormones are filtered out as well. A blood test is far more accurate at determining pregnancy than urine which is another reason why to go to the doctor if you get a positive test. Urine tests are really only used for at home purposes because they are far simpler to do compared to blood tests.",
"Before you even ask why do we test urine instead of swabbing the vagina for pregnancy, you have to first understand what a urine test is looking for to determine pregnancy. Swabbing a vagina would literally tell you nothing but what type of bacteria you have in your vagina. However, by testing the blood, it looks to see if a woman has any HCG, or human chorionic gonadotropin, in their urine, which is a hormone that is produced after a fertilized egg attaches to the wall of a woman's uterus."
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5xe6tv | The concept of abstraction in computer science | What is it? Why should I know it? How is it used? Thanks! | Technology | explainlikeimfive | {
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"Abstraction is the idea that the user of some function or method doesn't need to understand how the function works, the only thing they need to know is how to operate it (i.e. the input and output). Abstraction is incredibly important for building complex programs or circuits because each level of abstraction brings an increased amount of overall complexity and there comes a certain point when it becomes unreasonable to necessitate that the user understand all the minute details of some function. Functions that have their inner workings hidden are often called \"black boxes.\" For all intents and purposes, the user just considers it to be this magic box where you put something in and you get something out. Sometimes it's actually useful to understand on some level how the black box works because you can have two black boxes that do the same thing in different ways, and depending on the type of input you're giving it, you might want to choose one over the other due to efficiency concerns. Abstraction isn't just something computer scientists use, it's used for computer circuits, networks, weather models, scientific theories, psychology, economics, business etc. You use abstraction every time you drive your car. You understand the inputs to the machine, your gas pedal to go faster, your brake to go slower, your gear shift to park, go in reverse or go forward, your steering wheel to change direction. Most people don't really understand how cars work on a reductionist level, they just understand the high level idea of what input does what. I'll give a less 5 year old explanation: consider computer circuits. The fundamental unit of the computer is the transistor. A transistor is simply a gate that either allows current to flow or turns that current off. If you put a few of these transistors together in certain configurations, you can create logical gates like AND, OR, NOR, XNOR, XAND, NAND etc (Google these to see what they do). Using these gates, you can then build small circuits that output certain values given certain inputs. You can also make circuits that store information (these are called flip flops). You can make circuits using these flip flops and logic to create circuits that can add two numbers, that can make RAM, you can make circuits that display an image on a screen, and all the other things that computers can do. Each level of abstraction: * the transistor (which is itself an abstraction of quantum physics) * The logic gate (you don't have to worry about how the transistors are configured to make the gate) * The logic circuit (you don't have to worry about how the logic gates are configured) * The functional circuit like an adder, a CPU, a GPU (you *generally* don't need to worry about exactly how all the individual components are configured to make the complex circuit) Using abstraction, we are able to create programs and circuits and models of soaring complexity.",
"Say I make two classes with direct references to each other. This makes them tightly coupled, hindering them to be used individually elsewhere in the code. This often leads to the having to rewrite parts of code in other areas and making it a nightmare when you have to update the code a year later and only remember to update in once place. It also makes it difficult to test either class by itself, so debugging means effectively treating the two as a larger, more complex class. So the solution to this problem is to use abstraction to keep classes decoupled. You make an interface or abstract class that provides or describes some base functionality, and then anything implementing those can be used in operations throughout the code. This allows easier modification and testing, as you can add and remove classes without having to update existing code that operates on the abstracted level. And you can test the generic-handling code without relying on specific implementations of various classes. A basic example is sorting things. The sorting algorithm doesn't care what the things actually are, just what the outcome is when you compare two of them to each other. So making that an interface with some compare function, you can now implement a sorting algorithm that works with anything that implements that interface. Or perhaps message parsing. If you know your messages all build off an abstract class telling what kind of message they are and how big they are, the parser can look at this abstract level to obtain the relevant data to pass the message on to the appropriate parsing function. Or even further, perhaps the abstract class also has virtual methods to parse data, so now a generic message handler can tell the message to parse, knowing that all implementations know how to do that."
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5xec26 | How do medications get their chemical name? | Ex: Aspirin 2-acetoxybenzoic acid | Chemistry | explainlikeimfive | {
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"It is named based on the chemical structure and orientation of atoms in the molecule. Look up organic molecule naming conventions to learn more detail.",
"Functional groups (specific groups of atoms) have their own names, and a molecule is usually named from the base structure and functional groups. In the case of asprin, we start off with a benzoic acid (a 6-member aromatic ring with a O-COOH group) There is also a acetal group in a carbon directly adjacent to the carbon holding the larger group, hence the 2- designation. Can't really Eli5 this due to the nature of organic compounds naming.",
"Are you asking how drugs get assigned a generic name like paracetamol (acetaminophen) for Tylenol? The World Health Organization maintains a list of international non-proprietary names (abbreviated to INN) for chemical and biological substances that are used or have been investigated for use as medicines. This list is published on the WHO website and is regularly updated. There is a long list of rules that have to be followed when a company proposes a new INN for a compound that it has discovered and submits that proposal to WHO. WHO publishes these draft INNs for comment before the name can be formally adopted and published in the official list. The INN is shorthand for the compound and is used in place of the trade name (which is often different in different parts of the world) in scientific and medical literature so that it is clear that the same compound is being discussed. Another advantage of the INN is that it is short in comparison to the full chemical name of a drug substance and is easier to write and say. Source: I work in the pharmaceutical industry and deal with this on a daily basis."
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5xecdd | how can the value of currencies change compared to each other, like during Brexit. Pound:Euro and Pound:USD | Economics | explainlikeimfive | {
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"Before brexit (June 10th). If you had 100 Pound, and you wanted Euros, you could find someone who would give you 127 or so Euros. You wouldn't find anyone who would give you 130, so the price was 126.79 EUR. After brexit (July 10th). If you had 100 Pound, and you wanted Euros, you could find someone who would give you 117 or so Euros. You wouldn't find anyone who would give you 120 anymore, so the price was 117.33 EUR. Basically, people wanted Pounds less, so you'd have to pay them more pounds to get euros, so the price changes."
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5xegx5 | Why do coupons have a little note that says that their cash value is 1/100 of a cent? | Other | explainlikeimfive | {
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"I vaguely remember Co-Op Green Shield stamps. My parents were queuing up, looking to redeem them, and there were cabinets of items to be redeemed on display. I was around 7 y/o, I saw some adjustable roller skates, thought to myself, \"Huh. I bet me and my sis don't get those.\" After waiting approximately 3 eternities, my parents did come back - amazingly with 2 pairs of roller skates, one for each of us kids. I was thrilled! Much fun and many skinned knees occurred that day.",
"When I was a kid in the 1960s, my grandmother used to shop at Acme supermarkets in Philadelphia and collect trading steps all year. Then around November she would give the books of stamps to my brother and I and we would use the stamps to buy Christmas presents for our parents and grandparents.",
"Follow up question(s): If a coupon has a cash value, does that value expire, as does that coupon's intended effect? What I'm trying to get at is: should I stop throwing away expired fast food coupons in order to save up for a shiny new penny or would it be for naught? And if they do expire, then would it even be possible to ever redeem them for the cash value? Can I redeem, say, an individual coupon worth 1/100 of a cent before it expires and get a check or something? Or do you have to redeem them in 1 cent multiples?"
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5xeiqw | Why did the Nazis call themselves Socialist if they hated communism? | Other | explainlikeimfive | {
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"In theory, \"National Socialism\" meant \"socialist (not Marxist) principles applied to a nation, rather than internationally\". Fascist movements in the 20th Century developed not necessarily out of, but alongside leftist movements. For example, the first Fascist manifesto in Italy had some rather progressive goals in labor rights and wanted to redistribute wealth generally. However, they were emphatically *not* Marxists or communists - they rejected both historical materialism (the foundation of the Marxist left) and proletarian internationalism, in favor of \"racial science\" and nationalism. Nonetheless, they professed to stand for worker's rights, hence the \"Socialism\". In reality, however, this was never more than a neat trick to get workers on their side. Hitler liquidated the left of his party (led by the Strasser brothers) and privatized a great deal of German industry, as well as reining in trade unions.",
"Marxist Communism was a particular, and at the time new, form of \"socialism\". It has since become the dominant understanding of the word, but that wasn't so much the case in the 20's and 30's when NAZIism was on the rise in Germany. The real identifying quality of various \"socialist\" philosophies is the idea that the economy should controled and made to serve the society rather than the individual (as opposed to classical liberal and capitalist philosophies). National Socialists would then view 'Society' as the cultural nation (German, then later Aryan in this case), where Marxism generally rejected national identity for worker/proletariat identity and idealized ending in a stateless, nationless society. That, and the Communist party were a political threat to the NAZI party, largely regardless of philosophy, in the same way that Republican and Democratic parties in the US are at each other's throats, in spite of being closer to each other in many ways than any party in Europe or South America. On this level, it's not so much about policy differences, it's about who weilds power."
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