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2o0mxm | What's the current consensus on drinking alcohol? | You hear people talk about alcohol as being beneficial as long as you drink the right kinds (most often citing wine as beneficial).
That being said there was a recent study which stated that only certain people who possess a specific type of gene would benefit from alcohol consumption.
My question, do we know yet if alcohol is good or bad for us? | askscience | http://www.reddit.com/r/askscience/comments/2o0mxm/whats_the_current_consensus_on_drinking_alcohol/ | {
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"Not the right kinds. The right amounts. Small amounts as is typical in wine (which also contains stuff like antioxidants that may or may not have additional health benefits depending on who you ask) can be beneficial for reducing the risk of cardiovascular diseases like coronary heart disease (although it seems the data is conflicting). However, too much alcohol consumption over long periods of times leads to all kinds of organical damages like liver cirrhosis (and its accompanied complications like hepatic encephalopathy), chronical pancreatitis, dilatative cardiomyopathy (which also means that high amounts cease to be heart protective at all, but actually become cardiotoxic) and korsakoff's syndrome (long term damage caused to the brain by lack of vitamin B6). These risks are accompanied by general nutritional deficiencies and social and emotional isolation in extreme cases of alcoholism. And of course, acute overdose leads to liver intoxication.\n\nAn alcoholic beverage is only better in regards of the contained alcohol and how likely you are to overdo it. From a clinical perspective it is favorable to just stay abstinent as much as possible, or if you find yourself in the situation just don't drink too much."
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13ks0d | why are lethal injections unreliable? | There are a surprising number of cases where the first "lethal" injection of a condemned prisoner was insufficient to actually kill them.
It doesn't seem like it should be that hard to kill someone quickly and painlessly, given modern science. Why aren't we using chemicals and dosages where there is no possible way any human could survive? And why are we bothering with these unreliable, expensive, messy techniques in the first place when we could do something a lot simpler and more reliable like just hook them up to a helium tank? Seems like this would be cheap, quick, painless, and have a 100% success rate. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/13ks0d/eli5_why_are_lethal_injections_unreliable/ | {
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"The problem is that there's no real way to test whether it's painless, since if it works it ends up with a person unable to report whether they felt pain.\n\nThe problem is that with any drug, there's no dose which leaves absolutely zero possibility of surviving, and most of the time we'd be talking about a pretty long, horrible, process if it did. Injecting a buttload of morphine doesn't work the way it does in the movies.\n\nThe way a lethal injection is *supposed* to work is first a painkiller, and then a sedative, finally something that stops lung and heart function. The problem is that too much of any of those things could (a) cause the procedure not to work, or (b) be painful. \n\nI'm not sure why you think a helium embolism would be quicker or less painful than a lethal injection, though. And if you mean to suffocate them, that's awful.",
"potassium is used in lethal injections. Electrical impulses are sent through nerves by moving potassium into a cell and sodium out. A cell in the axon of a nerve starts with a -60 to -80 millivolt charge differential between the outside of the cell and the inside. Potassium is pumped into the cell and sodium is pumped out changing to charge to +40 millivolts and causing the nerve to fire. This signal is carried down the nerve as each cell does this. When Too much potassium is outside of the cell it will be forced into the cell because of the osmotic pressure. This causes the nerve to constantly fire and in no particular order. When this happens in the heart it causes fibrillation and eventually will stop the heart. The process is painless because before the person is injected with potassium they are injected with either sodium thiopental or pentobarbital both of which will render a person unconscious within seconds. The process often looks painful for the victim because potassium makes all muscles contract and spasm even after the heart has already stopped. The reason it is said to be unreliable is because it is hard to determine how much potassium it will take to kill an individual and sometimes multiple doses must be administered. The person really just feels like they fell asleep because of the barbiturate. now whether it is ethical or not is up to you.",
"I don't know either. For animals, we usually first give an anesthetic so when the lethal drug is administered, they are already asleep. Even if the lethal dose doesn't stop their heart, you can easily administer more with no pain to the patient, who is already peacefully unconscious. ",
"One of the biggest reasons, as quoted by Jay Chapmann who invented lethal injection, is, \"I never knew complete idiots would be carrying them out.\"\n\nThe personnel who carry out the lethal injections are often not sufficiently trained to establish a reliable intravenous line. In addition, the drugs administered are given via a set series of protocols which do not account for age, gender, body weight, tolerances, or outstanding medical conditions. All of these things can greatly influence whether or not the dosage given will be sufficient to kill them. \n\nAlso, because a person is being injected with so many drugs at once, they interact in an unreliable fashion. \n\nLet's take sodium thiopental to start. It's typically administered in surgeries (like propofal) to induce unconsciousness. It's liked because it's a very fast-acting anesthetic which isn't particularly harmful to a person because after about 5 minutes it is flushed out of the brain to the peripheral tissues. \n\nYou can probably guess where I'm going with this. Bad freaking idea for a lethal injection since thiopental is not reliable for *continued* anesthesia. The victim will often start to wake up before the other drugs have been pushed. \n\nWhy isn't there more of a big stink about this? Glad you asked. The second drug administered is pancuronium bromide. It's also used in surgeries. As a paralytic. It freezes all muscle control, and that includes breathing. Normally a person receiving it must be put on a respirator, but the purpose here is to actually kill the victim, so they just let them choke. This prevents onlookers from seeing the victim wake up and begin to suffocate. \n\nThen comes the potassium chloride. It screws with the sodium/potassium pump in the heart and inhibits proper pumping. It also burns like the living bejesus, as the Nazis found out when they experimented with it on the Jews. The problem is that, by now, the victim has just had a whole ton of fluid titrated into his veins. Depending on the metabolic function of the victim, the potassium chloride may be much too diluted to actually do anything more than hurt and cause tachycardia, leaving the poor bastard to choke. \n\nA new method in some states is being proposed in which an intravenous overdose of pentobarbitol is administered, followed by a whopping intramuscular overdose of midzolam and dilaudid. Essentially the midzolam produces an amnesiac affect which, combined with the respiratory depression of the pentobarbitol and dilauded, knocks a person to sleep and keeps them that way until they stop breathing. Supposedly a lot less painful since actual opiates are used. It would also be more effective in victims where a reliable IV line cannot be established.\n\nPersonally, I think an ongoing anesthesia by gaseous inhalation of halothane, in conjunction with the dilaudid, potassium chloride, and pentobarbital would cover the bases more effectively. \n\nBut, you're right, hypoxia induced by pure nitrogen inhalation would probably be the best way to go. You just get light headed, dizzy, then fall asleep. Not even any respiratory distress like in the gas chamber or carbon monoxide poisoning."
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45hglr | Is there an evolutionary reason that aquatic reptiles (such as ichtyosaurs) moved their tails horizontally, while aquatic mammals move their tails vertically? | askscience | https://www.reddit.com/r/askscience/comments/45hglr/is_there_an_evolutionary_reason_that_aquatic/ | {
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"Marine mammals and reptiles do not only use their tails for swimming, they use their whole body. The direction of undulation (lateral in reptiles and dorso-ventral in mammals) came from their respective terrestrial ancestors. Reptilian locomotion on land retained the ancestral state of the early tetrapods and is, interestingly, constrained by their breathing pattern-- one side of their lungs get compressed while they walk. The terrestrial mammals solved this problem by having an erect stance, so they can run and breathe at the same time. When members of each of these groups went back into the ocean, they retained their locomotion pattern. \n\n[Source](_URL_0_)\n\nPS. Unlike what has been said, the aquatic mammal tails did not come from fusing hindlegs. In the case of the pinnipeds, their tails have been lost; in the case of the cetaceans and manatees, they lost their hindlimbs but retained and modified their tails."
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5cd5kk | why have americans become even more polarized in the 21st century despite the emergence of the internet as a medium where people can easily reach out to each other to learn about their opinions? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5cd5kk/eli5why_have_americans_become_even_more_polarized/ | {
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" > despite the emergence of the Internet as a medium where people can easily reach out to each other to learn about their opinions?\n\nIt's also easier to find people who agree with you and a lot of websites will just feed you stuff you already like, so everyone just ends up in their own little echo chambers where everyone is like them and any other ideas or opinions are tossed out.\n\nIn order to find other opinions you'd have to go look for them. And nobody does that.",
" tl;dr You seek out people with similar opinions. You avoid people with contradictory ones. You can meet anyone, so why would you meet people you disagree with?\n\n---\nFull response\n\n\n The internet allows you to reach out to almost anyone online and find all kinds of other new and interesting opinions.\n\n It also allows you to find other people who think just like you do. You might be the only one in your whole town who likes something, but thanks to the internet you can find someone 1000 miles away that also likes the same thing, and you can talk about it with them!\n\n Then you two can then find even MORE people who like the same thing you do. Eventually you have a big group of people online who all talk about the same thing and all like the same thing you do.\n\n But now that you have this big group, you don't want it to break apart. You keep finding like minded people, and avoid people who don't like what you like. If you add people who don't like the same things, all you'll do is fight. That's not what you want. Eventually you become part of a large group that views itself as a family, and views everyone else as \"outsiders\" who are \"against\" what you like.\n\n",
"The monetization of information following the deregulation of American media in the 1980s led to a more entertainment-oriented approach in news coverage. The companies running news divisions found they could get more viewers by drumming up controversy and sensationalism, turning everything into a dispute rather than simply reporting objective facts.\n\nThis led to bifurcation of the public as two different sets of emotional groups were found, corresponding roughly to left and right, and it was found more profitable to enhance discord rather than seek meaningful discussion.\n\nBy the time the internet came into its own, this was already ingrained into how people consumed news, and was continued online. The retreat into echo chambers was exacerbated by malignant botting and trolling that disrupted forums meant to facilitate discussion.",
"Methinks the US has *always* been this polarized. It's just more obvious because of internet and faster ways of getting ideas and communication across.",
"People don't like being told they're wrong, so they tend to group with people who already think similarly. They discourage any opposition to the current dominant views, so those people form their own groups. Both groups become echo chambers rapidly in the absence of any challenge.\n\nThe internet makes this significantly easier than it would be in the past because you can just choose to never be confronted with any contrary beliefs or opinions.\n\nSee: Leftists, Right-wingers, SJWs, feminists, MRAs, etc. \n\nFor a specific example, look at /r/politics. Although the subreddit is supposedly for neutral political discourse, it has always leaned left to the extreme. Due to the nature of reddit popular views are upvoted and anything else is voted to the bottom. People holding views outside the dominant leave because there is no reason to stay."
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41u7j8 | Why does silly putty break if yanked and stretch if pulled slowly? | Asking for my inquisitive kid, who noticed that if he pulled hard on his silly putty, it would break cleanly. But if he pulled gently, it stretches. You can even combine these by pulling gently to stretch it, and then doing a quick yank to break it cleanly. What is the science behind that? Thanks! | askscience | https://www.reddit.com/r/askscience/comments/41u7j8/why_does_silly_putty_break_if_yanked_and_stretch/ | {
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"Materials may have different reactions to different amounts of force applied. This happens with aqueous cornstarch solutions: the viscosity is dependent on the amount of pressure applied to the surface of the solution. You can [bike across a cornstarch pool](_URL_0_)! The woman even comments that it's like silly putty.\n\nEdit: stress ≠ force.\nEdit 2: other answers much more accurate and informative. See above and below.",
"To expand on the above answer, I'll provide more of a molecular level explanation. Silly putty contains a couple of different things, mostly a soft flexible polymer and a bit of finely ground silica. The polymer is linear, not crosslinked (like a rubber band is), but the silica is able to act like a physical crosslinker giving the silly putty a more solid mechanical response. Basically that just means that the polymer interacts with the solid fillers, but the interactions are not permanent and are constantly breaking and reforming. When your kid quickly stretches the putty, many of those polymer-filler interactions are broken at the same time, and they aren't able to reform quickly enough to prevent new surfaces from forming. Once a new surface is formed, then the putty tears pretty easily as that crack propagates. There are additionally some polymer entanglement considerations that add to the viscoelastic behavior, and I'm unsure of how much those contribute. "
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bbonoo | is the alcohol in mouthwash the same type as found in wine and beer? | I have a friend that refuses to use any mouthwash containing alcohol (i.e. Listerine) because she states it contains alcohol; however, she happily drinks wine, beer, and many other alcoholic drinks. I also stated that you don't drink mouthwash, you gargle with it. After some research, I found that ethyl alcohol is generally what's consumed. If that's true, then does mouthwash and alcoholic drinks basically have the same alcohol, just different concentrations? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/bbonoo/eli5_is_the_alcohol_in_mouthwash_the_same_type_as/ | {
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"The alcohol in mouthwash is indeed food grade ethanol, there are some alcoholic people who do consume it to get drunk as sometimes it's cheaper and more accessible than regular alcohol. It's not a great idea to drink it though because the high concentration of fluoride and other tooth strengthening/cleaning and breath freshening compounds can make you sick if ingested in large quantities. \n\nAll drinkable alcohol is just flavored diluted ethanol, whether it's obtained from fermented juices, molasses, corn etc... Any sugar source can be converted into ethanol. Only ethanol can be consumed, any other type of alcohol like isopropanol or methanol are extremely poisonous to humans. \n\nPeople were doing the same thing with ethanol based hand sanitizer gel recently also.",
"Can you clarify her reasoning? \n\nIf she doesn't use it simply because it contains alcohol and she also drinks alcohol, then it doesn't make any sense. \n\nOn the other hand if she doesn't use it because alcohol in mouthwash makes the problems worse, then she might have a point. Alcohol in mouthwash kills both good and bad bacteria, and may cause mouth dryness, making it a more likely place for bad bacteria to live.",
"It's the same alcohol -- ethanol. It's in relatively similar concentrations. The old-school yellow-bottle formulation of Listerine is around 54 proof. So, not quite as strong as hard liquor but stronger than wine.\n\nYou shouldn't drink recreationally though. The active ingredients -- the germ killing agents -- mean that it is considered a 'denatured alcohol'. You could probably get drunk off it, but you'll also get sick in other ways.\n\nMany people avoid alcohol in mouthwashes for other reasons. Many consider it hard on the insides of your mouth and worry that long-term use of these types of mouthwashes can increase your risk of oral cancer. I don't know valid these worries are, but they are common enough worries that many 'alcohol-free' options are available for mouthwash."
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4mb0oa | how does a toilet actually flush from water being added to the bowl? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4mb0oa/eli5_how_does_a_toilet_actually_flush_from_water/ | {
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"[Toilet Crossview](_URL_0_) for reference.\n\nAs water is added to the bowl, it rises up the pipe following that blue line. When enough water is added, it overflows the other side and gravity takes over. That water overflowing creates a chain of negative pressure and the remaining water/contents of the bowl are basically sucked out through the pipe.\n\nEdit: [Video of the process in action](_URL_1_). When the video mentions the siphon created in the back/pipe of the toilet, it's the negative pressure I was referring to."
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223svh | How does scraping scissors blades against ribbon cause it to curl? | Is the friction sufficient to break and reform the chemical bonds, similar to perming your hair? | askscience | http://www.reddit.com/r/askscience/comments/223svh/how_does_scraping_scissors_blades_against_ribbon/ | {
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"If sufficient force is applied to the material to stretch the polymers beyond their elastic limit, they will be permanently deformed. When the change is not uniform throughout the material it will cause it to curl as one 'side' of the ribbon is now 'longer' than the other. Materials that don't break down, i.e. satin ribbons, will not curl effectively as they're made of individual threads. An interesting demonstration of a similar concept can be done by heating bimetallic strips. One side of the strip expands at a different rate than the other, causing it to curl. This property has practical applications in timekeeping, thermostats, thermometers, heat engines, and electronics.\n\nSources: _URL_1_\n\n_URL_0_\n\nEdit: Big credit to /u/atmwarrior for explaining it as a curve which is much simpler and intuitive.. \"Simplicity is the ultimate sophistication.\" - Leonardo da fucking Vinci",
"I'm not sure if it adds to the discussion or aids in addressing the question asked but if anyone was curious about the perm part I can explain how that works. \n\nThe hair is wrapped in perm rods and soaked in an ammonia based perm solution which acts to break down the disulfide bonds of the hair. Think of the disulfide bonds as the framework of a house. With the perm rods still in, neutralizer is poured over the hair and left to set in order to restore the ph of the hair and solidify the restructuring of the disulfide bonds of the hair in the shape the hair was wrapped around the perm rod. The perm rods are removed and the hair is now magically curly thanks to science. \n\nSo there's that. ",
"it's not that you're not scraping it, it's that you are folding the ribbon, a million little times one one side. you're pressing your thumb on the other side which is squishy enough to deform around the blade making a crease in the ribbon, as you pull on the ribbon you are putting another crease and another and another and another.... \n\nalong that same side. the harder you press your thumb into the ribbon into the blade, the more pronounced the crease and the tighter the curl."
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5bfcis | what is 'dead' and what is 'alive'? | What differentiates between the state of death and the state of living? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5bfcis/eli5_what_is_dead_and_what_is_alive/ | {
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"Funny enough:\n\nNobody has a clear cut.\n\nBest example:\n\nScientists are STILL debating wether or not a VIRUS is alive.",
"In the context of medicine, death is defined as brain death, a lack of electrical activity in the brain.\n\nIn the context of basic biology, something is alive if it:\n\n* reproduces itself\n\n* has a metabolism\n\n* maintains homeostasis (regulates its internal environment)\n\n* is composed on one or more cells, and\n\n* responds to stimuli.\n\nHowever, both of those definitions are controversial. For the basic biology definition, I tried to list the points in order of least to most controversial.",
"\"Life\" is very hard to define and we can't really make up our mind. Obviously, the difference between a human and a rock is obvious, but as you go up the evolutionary tree the line becomes quite blurry.\n\nHowever, despite it being such a controversial question, we do have some sort of a definition of a living organism. An organism is \"alive\" if it shows the following characteristics:\n\n* **Homeostasis** - regulation of internal environment, for an example maintaining a constant temperature \n\n* **Organization** - composed of one or more cells\n\n* **Metabolism** - transformation of energy (eating, breathing etc)\n\n* **Growth**\n\n* **Adaptation** - changing in a response to the change in environment, crucial for evolution\n\n* **Response to stimuli** - whether it be moving towards food, facing light or running away from danger, living organisms react to their surroundings \n\n* **Reproduction** - all living organisms create more organisms\n\nViruses are very interesting here. They're clearly more than just random molecules, they cause diseases and catastrophes and they have their role in evolution. Even though they replicate, we still don't consider them living because they don't quite fit our description of a living organism. They don't have a cellular structure, they don't react much, they don't grow.\n\nBut then we have bacteria. A lot of people mix these up because these guys cause diseases too, but they're much more advanced and \"alive\" than viruses. A fun fact is that some (mycoplasma) can be smaller than some viruses, but they still show a very clear cellular structure, growth, reaction, adaptation, metabolism and homeostasis. \n"
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efonqi | different types of spicy? | So, as we all know what spicy is. That doesnt really need explanation. But, is their a difference between different kinds, is their different names for these? For example, spice that comes from peppers usually involves capsicum, but horseradish and wasabi doent have this, where does its spice come from? Why is it feel so different? And is there a name for these different kinds of spicy? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/efonqi/eli5_different_types_of_spicy/ | {
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"There are different chemicals that cause spiciness. One of the better known ways of measuring spiciness is the Scoville Scale. The test works by diluting (mixing with water) the spicy thing and measuring how much water is needed before the spiciness can barely be tasted. Spicier things need to be diluted more. The test can measure things other than capsicum.\n\n_URL_0_ and _URL_1_ are insightful about this (and what the other chemicals are).",
"There's a protein called the \"transient receptor potential cation channel subfamily V member 1\" (TrpV1, to its friends) that's responsible for signaling pain due to temperature/acids and other things - it's this protein that signals \"spicy pain\" for BOTH hot peppers and wasabi/horseradish. The reason they feel so different is due to the difference in the chemical properties of the \"active ingredients.\" Capsaicin is very water-insoluble (meaning it will linger in the receptor, providing a long-lasting burn), and basically nonvolatile (since it doesn't evaporate easily, you feel it on your tongue and not in your nose). Allyl isothiocyanate, the active component of wasabi/horseradish is more water soluble and very volatile. This is why you feel it all over your mouth and in your sinuses at once (it evaporates off your hot tongue, wreaking havoc), but it quickly dissipates as it dissolves in your saliva or evaporates out of your mouth entirely.\n\nSometimes wasabi is referred to as \"pungent\" instead of spicy."
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1adprj | Why are neurons more sensitive to incorrect protein misfolding than other cells? | I've learned that if there are mistakes in protein folding, then this can lead to aggregation of the misfolding proteins, which in turn leads to either degradation of these incorrectly folded proteins, or if it gets bad enough, cell death.
Supposedly, neurons are more sensitive to this process than other cells, often resulting in neurodegenerative diseases; but why? What makes neurons different from other cells? | askscience | http://www.reddit.com/r/askscience/comments/1adprj/why_are_neurons_more_sensitive_to_incorrect/ | {
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"They have the same problem with storage diseases, where enzyme deficiencies cause a backup of metabolites.\n\nIt's commonly accepted that, because neurons don't replicate, these things are allowed to build up into a problemed level without cell division to \"dilute\" them away. Neurons also serve many functions, so they Produce a large variety of proteins and/or molecules (unlike cardiac muscle cells, which also don't really replicate but aren't subject to as many miss folding diseases, but only need to make motor proteins) and a misregulation of this diversity can easily lead to cell death.",
"A lot of the more famous neurodegenerative diseases like Huntington's, ALS and Parkinsons are not only characterized by protein misfolding, but by the aggregation of these proteins in complexes with other stuff around the cell (proteins, RNA, proteosomes). Here's the really weird thing, we don't actually know if it's the aggregation that's causing the disease in these neurons. In fact, when you specifically stop the aggregation from happening, the cells die even faster and things get worse. So even though it seems obvious when you're looking in a microscope that aggregation of crappy protein = bad, scientists don't actually know what's causing the disease! Is it the loss of normal protein function? The aggregates? Are the aggregates stopping the cell from using some other really important thing (protein or mRNA)? Is it mucking up the cellular machinery that normally breaks down proteins? We just really don't know.\n\nSo, with all that unknown stuff, I don't think there is a conclusive answer to this."
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76z6b9 | Why can’t we trust ancient sources implicitly? | I’m aware of how foolish I sound as of this moment, and I totally understand the need to take sources with a grain of salt. (Or several)
But I was listening to the Dan Carlin’s Hardcore history podcast “the Celtic Holocaust” today and at one point he mentions how a hundred years ago many historians would just take some sources at their word if they didn’t have express reason to disbelieve them. (Like Caesar) Nowadays we are more strict.
That’s awesome, we should look deeper into historical documents and try to get the most accurate picture possible.
But why must we assume everyone is lying? For instance Dan mentions several times how Caesar is putting good arguments and reasons into the mouths of people he supposedly wants his audience (the people back in Rome) to want him to defeat, and Dan goes into detail talking about all the possible cynical reasons for doing this. Why is pure honesty ruled out though?
Is it really so hard to believe that not all ancient writers were attempting to pull the wool over our eyes? Sure the individuals writing have their own biases, but we modern people don’t always have such a hard time looking past those to write objectively.
What if people like Caesar are actually being as honest and straightforward with their audience as they possibly could?
Sure they could still possibly be inaccurate, but why abandon believing someone’s word without explicit evidence to the contrary? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/76z6b9/why_cant_we_trust_ancient_sources_implicitly/ | {
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"Hi there -- not to discourage further answers here, but you may be interested in our six-part series on [Finding and Understanding Sources](_URL_0_), particularly parts 3, 4 and 6 which deal with primary sources specifically. "
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2fnh2c | why do modern wars seem to be less deadly and brutal than previous wars? | Obviously any war is bad, but when reading the news I can't help but feel like the death tolls mentioned are small when compared to wars like Vietnam/Korea/WW2 etc.
The war in Ukraine has < 3000 deaths according to wikipedia, even the Syrian civil war is around 200,000, much less than Koreas 3,000,000+ in the same 3 years. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2fnh2c/eli5_why_do_modern_wars_seem_to_be_less_deadly/ | {
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"It depends which wars you're comparing, but a lot of it is technology and strategy. I hope some war historian comes to write a lengthy explanation, because I enjoy reading those, but the short, simple answer is twofold: 1) we have better weapons now, and 2) war combatants are not the same entities as before. \n\n1) With any weapons, there are two main factors that determine its effectiveness: accuracy and range of impact. It's better to have high degrees of both, but barring that, it's better to compensate by increasing the other. For example, if you're trying to kill Bad Guy X, you could probably do it with a single bullet, if you had a very accurate gun and a good shooter. High accuracy, and it has enough range of impact to kill Bad Guy X. On the other hand, if you can't get a clear shot at him, you could always throw a grenade -- much lower accuracy, but much greater range of impact. However, if you do this, you kill not just Bad Guy X, but everyone around Bad Guy X as well. \n\nThis can be applied to all types of weaponry. If you're trying to destroy an enemy base, you could launch a guided missile to do the job... or you could just drop a nuke, and kill everyone else too. We didn't really have fancy computer-aided weapons until after Vietnam, so that's part of it. \n\n2.) One major difference between previous wars and current wars is that the combatants were on somewhat equal footing. The Allies had armies and navies and air forces, and so did the Axis powers. The Korean War involved thousands of troops on both side shooting at each other, and so on. \n\nOn the other hand, there is no Taliban Air Force, Saddam did not have an aircraft carrier, and so on. They can't just assault US forces in a frontal attack, because they'll be crushed within days, and they know this. So they have to resort to sneaky things like roadside bombs and suicide bombers to achieve their mission. While the death toll is still very high, it's still going to be a lot lower than if you have two equal sides just raining fire on each other. ",
"One answer, which is quite simple, is the number of combatants. \n\nNo subsequent war has come close to the number of combatants involved in World War II. Any changes in the casualty rate of modern warfare due to technological or strategical advances are dwarfed by the sheer scale of previous conflicts. "
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7yv4os | Apart from the emancipation and winning the civil war, what did Lincoln achieve as president? What were the more mundane policies he enacted? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/7yv4os/apart_from_the_emancipation_and_winning_the_civil/ | {
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"So, the only trick to answering this is to keep in mind that the office of the president was perceived somewhat differently in the 1860s: Lincoln and many others held to this belief that the president should not shepherd through legislation or dictate what should be passed, instead leaving it to Congress to pass laws for his review. So keep in mind that a lot of these accomplishments were the purview of the Republican party in Congress, and not Lincoln proper. \n\nThe Civil War actually sees the passage of a number of Republican/Whig/Free Soil goals that were separate from the war. In many cases, the South had operated as an obstacle to these bills or the hopes behind them, meaning that when a host of Southern Democrats leave, the floodgates opened in Congress.\n\nOne immediately obvious one is the Homestead Act of 1862. Republicans and their antecedents in the Whig and Free Soil parties had hoped for the passage of a bill that would open up public lands in the west cheaply, and this first Homestead Act did exactly that: people could apply to work a 160 acre plot of land, and if they did so for five years and made \"improvements\" to it, they could receive title. There's been a lot of ink spilled as to whether this benefited speculators or farmers, and for that matter how effective it was: large parts of the areas west of the Rockies are too arid for small-plot farming, leading to a great many farm failures. I'll leave the assessment of the act to somebody who's better versed in all of that scholarly literature, but in any event, the estimate is something like 600,000 farmers had received title to a combined total of 80,000,000 acres of land by 1900 (of course, there were successive Homestead Acts after 1862 that account for some of that). Even if you come down on the side of big businesses and railroads using it predominantly for speculation, it exerts a powerful influence on the history of the American West.\n\nSpeaking of railroads, I would be remiss if I left out the transcontinental railroad, which was authorized through the Pacific Railroad Act in 1862. It provided for a route that would link the east and west coasts in exchange for land grants to the railroad companies as well as government-backed bonds to finance the project. This gave the railroads incentive to build while also helping to settle parts of the country that had heretofore been too remote for most settlers to consider. This also reinforced the impact of the Homestead Acts, which in turn helped reinforce railroad construction: without people to settle near railroads (and preferably to buy up those lucrative land grants), the companies would have lacked incentive to build in the first place. This helped to fuel further railroad construction as well, because as places became settled, there was in turn demand for more access.\n\nThe first income tax is passed during the Civil War. While it's only a temporary measure that ultimately expires in 1873, it set an important precedent with the idea of a progressive national income tax that's eventually enacted into law with the 16th Amendment in 1913. \n\nThe national banking structure was also reformed by Banking Acts that tried to standardize and strengthen weak legislation around banks by requiring federal charters; this was to try and put an end to so-called wildcat banks and instead put banks on stable financial footings. Perhaps most immediately, it created a uniform national paper currency, the greenback, that could redeemed for gold and silver. This was a major step towards having a uniform currency in the United States separate from specie (previously, banks could issue their own notes that could be redeemed for gold; this meant that a whole host of paper notes proliferated from hundreds of different banks).\n\nLastly, there was the the Morrill Land-Grant Colleges Act, which created state colleges that would be financially supported by land grants. These were supposed to be agricultural colleges, and today they form the basis of many states' higher educational systems. "
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21rnn1 | why does the combination of cigarettes and coffee seem to be a natural laxative? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/21rnn1/eli5_why_does_the_combination_of_cigarettes_and/ | {
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"Because both on their own are natural laxatives. So.... Together they're extra powerful.",
"Coffee (caffeine, specifically) *is* both a laxative and a diuretic, it doesn't just 'seem to be'."
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jf6yo | what's happening with european economies right now? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/jf6yo/whats_happening_with_european_economies_right_now/ | {
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"One currency is used by multiple countries, each with their own economy. Some of these economies are pretty shitty, and so they aren't able to pay their debt, or money they borrowed (from other countries, private businesses, all types of people).\n\nThe usual way a country can deal with this is either to print more money, which makes their own money worth less (since there's more of it); or they can default, or effectively say \"fuck you, we're not paying you\" to all the people they borrowed money from. Both of these are pretty bad for the economy, but defaulting is especially shitty, because nobody will want to lend to a country that can't afford to pay off the money it borrowed. \n\nUnfortunately, because the European economy shares the same currency across multiple countries, a failing country can't just print more money -- they don't have the authority to do that, and no one really wants to devalue the currency of every country in the Euro just because one country is doing shitty. So that leaves the other option, to default -- but this is also really bad for the Euro, for basically similar reasons why it's bad for any country with their own personal currency. This puts the better functioning countries in a terrible position, where either choice hurts them because some other country has a shitty economy or too much debt, and no one wants to pay cause someone *else* is unable to.",
"One currency is used by multiple countries, each with their own economy. Some of these economies are pretty shitty, and so they aren't able to pay their debt, or money they borrowed (from other countries, private businesses, all types of people).\n\nThe usual way a country can deal with this is either to print more money, which makes their own money worth less (since there's more of it); or they can default, or effectively say \"fuck you, we're not paying you\" to all the people they borrowed money from. Both of these are pretty bad for the economy, but defaulting is especially shitty, because nobody will want to lend to a country that can't afford to pay off the money it borrowed. \n\nUnfortunately, because the European economy shares the same currency across multiple countries, a failing country can't just print more money -- they don't have the authority to do that, and no one really wants to devalue the currency of every country in the Euro just because one country is doing shitty. So that leaves the other option, to default -- but this is also really bad for the Euro, for basically similar reasons why it's bad for any country with their own personal currency. This puts the better functioning countries in a terrible position, where either choice hurts them because some other country has a shitty economy or too much debt, and no one wants to pay cause someone *else* is unable to."
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225v3p | How does my computer speakers intercept phone calls? | Every now and then I hear someones phone call come through my computer speakers. Usually for a quick couple seconds and the clarity varies. What exactly is going on physics wise? | askscience | http://www.reddit.com/r/askscience/comments/225v3p/how_does_my_computer_speakers_intercept_phone/ | {
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"Some cordless phones use [amplitude modulation](_URL_0_) to encode an audio-frequency signal (someone talking) in a radio signal at much higher frequency. If an AM signal is \"rectified\" (the parts below the horizontal axis there are taken out), then what you get is a combination of audio- and radio-frequency components. Extracting the AF component gives you the original signal.\n\nTo get this sort of speaker break-in, you need something that acts as an antenna (a long enough piece of wire will work) in order to capture the radio signal, and you need something to rectify the signal (slightly loose/corroded electrical contact can do that). The speakers themselves can only play back the audio-frequency component (the radio-frequency component can't really get through the speaker's coil, and even if it could, you can't hear that high a pitch anyway). This isn't a very *good* receiver design, so it only works with fairly strong signal -- like a transmitter very close by, and even then, reception depends on what's in the way, what's reflecting the signal to where, etc. The conventional solution to speaker break-in is to clamp ferrite beads on the speaker wire to keep the RF signal from passing."
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6o1om5 | why aren't stainless steel countertops, like in restaurant kitchens, magnetic, but stainless steel knives are? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6o1om5/eli5_why_arent_stainless_steel_countertops_like/ | {
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"Mechanical engineer here (some material engineer might come around and give a better explanation):\n\nIt all has to do with the crystalline composition of your Stainless Steel. Most of the Stainless steel is made of Ferritic SS, which is cheap to fabricate and can be transform quite easily. Austenitic SS is the most corrosion resistant steel and is mostly used for specific application. The 304 series are usually used for Food grade purpose for example. Both of them are non magnetic.\n\nMastensitic SS is highly durable, very hard and easy to machine. Those 3 properties makes it very good for kitchen knives. It is also (almost?) the only type of SS that is magnetic.\n\nHope that helps.",
"Stainless steel used for knives uses an alloy with less chromium to allow for heat treatment which will make the skin of the knife harder so that it keeps an edge better. -given the right circumstances, these knives will rust. \n\nCountertops don't need that hardenability, but benefit from the increased corrosion resistance that a higher chromium alloy offers. \nThe breakover point for magnetism is 20% chromium. Above that, no magnetism, below that, magnets stick. ",
"Several people have mentioned the different alloys and which ones are/aren't magnetic, but no one has mentioned the reason. I'll take a stab at it but it's been a while since I learned the theory. Maybe someone else can go into more technical detail. \n\nThe molecules of different materials have different resistance to realigning their poles in the presence of a magnetic field. In pure iron, the domains move more freely, and in stainless, the extra metals added interfere with that temporary realignment. Think of the magnetic field as water flow, and the metal as a bunch of tiny tubes all jumbled up and not connected. Iron allows the tubes to realign into a flow path for the field, whereas stainless can't realign as easily. Once there's a path for flow, the field holds on to the metal it has realigned, creating the force that you feel when you try to remove the magnet. ",
"Everyone's talking about what makes a steel ferromagnetic or not, so I'll talk about the other side of the question: countertops in particular.\n\nIf you have a *private* countertop that's not ferromagnetic, that's probably because a higher chromium content makes it easier to polish, and if you're choosing stainless steel for the home instead of granite or marble, it's probably because you want the look of shiny, polished metal.\n\nCommercial kitchens have work surfaces intended to be durable, easily cleaned, and cheap. (It's really expensive to start a restaurant, and they don't tend to last very long, so you get cheap prep tables.) A variety of steel alloys work for that purpose, some of them ferromagnetic and some not.\n\nIf you went to a restaurant kitchen and found that it had a stainless steel countertop that was not ferromagnetic, it was probably because the manufacturer found a source of reasonably priced metal that fit their requirements that happened not to be ferromagnetic.\n\nConversely, I have a stainless steel countertop from a restaurant supply store. It was cheap. I have a bunch of magnets attached to it right now."
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8ukty0 | Does the moon’s surface experience the same heat intensity from the sun as Earth’s surface? | [deleted] | askscience | https://www.reddit.com/r/askscience/comments/8ukty0/does_the_moons_surface_experience_the_same_heat/ | {
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"Since there is no atmosphere on the moon to block radiant heat, and half of the moon's orbit is closer to the Sun than the Earth is, the Moon's surface receives more radiant heat from the Sun than the Earth's surface does.",
"One of the more recent temperature surveys points out some interesting things. The temperature variance of the surface near the equator is right around 300 Kelvin, from a low of around 95 K (just above the boiling point of liquid oxygen) to 395 K (a fair amount above the boiling point of water). But above or below a latitude of 40 degrees the temperature begins to fall off considerably.\n\nWhen one considers that the huge variance happens every two weeks and the plunge from one extreme to the other happens very fast and quite unevenly (half of any spacecraft is in its own shadow at sunrise, when the upward spike begins), I have to wonder about the mechanical stresses of all that heating and cooling. It looks like one more really good reason to dig under the surface and maybe even keep vehicles under a tarp or a hangar, if people plan to try to live there.\n\nEdiot: Oh yeah, the link: [_URL_0_](_URL_0_)"
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cxxlw6 | how is ebola diagnosed? | I read that they do something called "RT-PCR" or "antibody testing". I'd like to learn about these methods. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/cxxlw6/eli5_how_is_ebola_diagnosed/ | {
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"RT-PCR is reverse transcriptase polymerase chain reaction. What that means is it takes a sample, takes all the RNA present in the sample and converts it into DNA. Then you mix it with a special mixture of specific DNA pieces and certain proteins and you can amplify certain DNA strands that we’ve found that are specific to the virus and quantify them. A normal person’s sample wouldn’t make any of those DNA strands.\n\nAntibody testing in general just uses antibodies, which are Y shaped molecules normally used to tag certain things for destruction by our immune system, and instead use it to tag certain cells or proteins or other molecules in a sample. So we make an antibody that will only stick to Ebola or Ebola proteins and make a way for us to see how much antibody is binding to see whether someone has a detectable quantity of Ebola"
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2fedq8 | why was nato willing to intervene in afghanistan (a country in another region), but is not willing to intervene in ukraine (which actually borders nato members)? | NATO formed ISAL to go into Afghanistan to help in a fight against radicals. But Afghanistan is all the way in the Middle East, so why would NATO now be unwilling to help Ukraine fight against rebels (and possibly Russian soldiers), when Ukraine actually shares borders with multiple NATO members. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2fedq8/eli5_why_was_nato_willing_to_intervene_in/ | {
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"Nuclear bombs. Russia is powerful.",
"It's one of the unwritten rules of modern international politics: No direct conflict between nuclear powers.",
"I believe it is article 5, which paraphrasing here states: if a member is attack the other members are obligated to respond.",
"Article 5 of the North Atlantic treaty, requiring member states to come to the aid of any member state subject to an armed attack, was invoked for the first and only time after the 11 September 2001 attacks, after which troops were deployed to Afghanistan under the NATO-led ISAF.\n\nAfghanistan attacked US, an attack on one NATO member is an attack on all. \n\nUkraine is not a NATO member, so NATO has no duty to get involved.",
"In the former case, NATO was searching for a new reason to exist; in the latter case, NATO is afraid of its original reason for existing."
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dnakw9 | what function does dust serve? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/dnakw9/elif_what_function_does_dust_serve/ | {
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"Where would you prefer your dead skin cells to go?",
"Things dont need to serve a function. Dust is entropy, entropy is part of life. Things, all things, break down and wear away. Dust is one of the last detectable stages of that.",
"Dust doesn't have a specific function, other than being the end step of other different functions.\n\nDust is the debris left behind as a lot of other items decay - for example your body is constantly producing new skin, and allowing the topmost layers of old skin to flake off (done so gradually you never notice it). This skin costs around and settles as dust.\nSimilarly very fine dirt that had been blown around will settle as dust, the fluff that falls off your clothing, hair, food and any other small debris that is easily blown around.\n\nIt doesn't serve a purpose as much as it is the end result of a whole load of other processes."
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f0ozwv | how does nasa know exact trajectories and locations of space craft in interplanetary space? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/f0ozwv/eli5_how_does_nasa_know_exact_trajectories_and/ | {
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"2 things. First is simple physics. Once a spacecraft is on a trajectory, it doesn't change. Once you calculate a trajectory and burn the engines to put the spacecraft on said trajectory, you know it's there because there's nothing to make it go anywhere else. Second is tracking. We have to communicate with spacecraft, which means sending and receiving radio signals. If we're sending and receiving radio signals, we obviously know where they're coming from and where they're going. That tells us where. To get a trajectory, we just track the signals over a period of time and then plot out the rest, because, again, the laws of physics allow us to calculate it."
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coa9nd | I remember playing Assassin's Creed IV Black Flag. And a slave owner in the game didn't wanna convert slaves to Christianity because he think he is not allowed to have fellow Christian's as slaves but non Christian's are ok. Did this practice really occure IRL? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/coa9nd/i_remember_playing_assassins_creed_iv_black_flag/ | {
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" I should say first of all that I don’t really know about the age of piracy, but that practice really did occur in the medieval period, going back to the 12th and 13th centuries at least. By then, the Catholic church’s canon law prohibited Christians from enslaving other Christians, but they were allowed to own Muslim slaves. \n\nThe reason for this actually goes back much further to the Roman period when the emperors converted to Christianity and Rome effectively became an officially Christian empire. Back then there were only Christians, Jews, and pagans, but the Christians figured they should be in charge of everything, so Jews and pagans began to prohibited from doing all sorts of things that would put them in any position of power of any Christian. They weren’t allowed to be teachers, judges, serve in municipal councils, etc., and above all they weren’t allowed to have Christian slaves. Christians, of course, also couldn’t have Christian slaves, but everyone could have Jewish or pagan slaves.\n\nJump forward a few centuries to the Middle Ages, and all of that stuff was codified in church law (canon law). By then there also Muslims, but the church didn’t really know what to do with them, so for legal purposes they were usually considered to be “pagans” too, so it was okay to have Muslim slaves. Anywhere where Muslims and Christians lived together, there were Muslim slaves - Spain, Sicily, and the crusader states in particular. But since Christians could not be slaves, the law allowed for Muslims to be freed...as long as they converted to Christianity.\n\nThis really did happen in the crusader states, where there weren’t many crusaders compared to the rest of the population, so they depended on slavery for agriculture and construction work among other things. But the slaves figured out they could convert to Christianity and be freed. The crusaders were opposed to this because they were losing their work force, and also they were convinced their slaves weren’t really sincerely converting, they were just pretending, and would then go back home to Muslim territory. (Which is presumably exactly what was happening, the slaves figured out how to game the system!)\n\nSo the crusaders simply stopped letting their slaves convert. Initially the church complained about that, but eventually it concluded, contrary to its own canon law, that slaves would be allowed to convert, and they would no longer be freed from slavery. Of course that made no logical sense, since Muslim slaves weren’t going to convert (sincerely or insincerely) if they were still going to be slaves. But the whole situation shows that yes, they definitely had Muslim slaves, and they weren't really supposed to have Christian slaves.\n\nI don’t have sources at hand for similar things happening in Spain or Italy, but the church was also concerned about exactly the same thing happening in Sardinia, so presumably it was happening all throughout the medieval Mediterranean. I can only assume it still occurred in the early modern period too.\n\nFor information about the crusader states and Sardinia, my main source is Benjamin Z. Kedar, *Crusade and Mission: European Approaches toward the Muslims* (Princeton, 1984)"
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c1rhnl | why don’t women ‘save up’ their eggs when they take the pill which stops periods? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/c1rhnl/elif_why_dont_women_save_up_their_eggs_when_they/ | {
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" In fact when a woman reaches menopause, whether she took the pill or not, she isn't \"out of eggs.\" It's a hormonal thing, not a lack of eggs thing.",
"Because the egg is still released, the womb just doesnt prepare for the implantation.\n\nA period is the lining of the womb that was created to hold a fertilized egg, if the egg passes unfertilized, the prepared womb rids itself of the lining, causing a the bleeding\n\nIt doesn’t prevent an egg from releasing, it only stops the hormones that tells the body to prepare for a potential pregnancy. Since the womb isnt ready for an egg, even if its fertilized it passes without implantation"
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2cgxqn | how good or bad is the situation involving people crossing the border into the us from mexico? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2cgxqn/eli5how_good_or_bad_is_the_situation_involving/ | {
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"There is no easy answer to this question. Having been to several parts of the US/Mexico border, and having grown up in Texas, I can say that crossing the border in many locations is very dangerous. It's a desert, and the easiest crossing locations are fairly well guarded.\n\nI would say that a majority of the people crossing the border are just trying to make a better life for themselves. They aren't really hurting anyone, and they are filling jobs that would otherwise go unfilled. Legally immigrating into the US is virtually impossible for most of these people.\n\nAt the same time, the amount of drugs flowing north and the amount of drug money and weapons flowing south across the border is staggering. Look at the drug use rates in the US and imagine that a large chunk of that is coming and going across the border.\n\nPolitically it's a lose/lose situation. If you support weakening border control, then you risk an increase in the drug supply, which drives violence on both sides of the borders. If you do the opposite, than you are throwing money at an unstoppable force with little return.\n\nIf you support amnesty, then you risk encouraging more people to break the law by entering illegally. If you support increased deportation, then you risk destroying families and sending people back to a country that they don't even remember.\n\nIf you loosen immigration regulations, then you risk letting the \"terrorists\" in, or creating another wave of immigrants that the country may not be ready for. If you tighten the regulations, it forces more people into trying to cross illegally.\n\nAll around it's not going to have an easy solution."
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mxobv | Most "genetically distant" human population? | Is there one or several human populations that stick out by being significantly different, genetically, from most other human populations? Not just y-haplogroups or whatever but throughout the genome? Is there, for example, a significant difference between the DNA of genetically isolated populations like the Khoisan, the Andamanese and the the Tasmanian Aboriginals, and other less isolated populations?
Edit: does anybody know of any data on the genetic distance of the Andamanese, specifically, to other populations? | askscience | http://www.reddit.com/r/askscience/comments/mxobv/most_genetically_distant_human_population/ | {
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"Overall most humans are genetically almost identical; however, certain groups obviously have different genes that are unique to their own populations. However, since it has been discovered that on average all humans of non-African decent have about 1-4% neandertal DNA all other populations are more closely related to each other than African modern humans, African humans are strictly Homo Sapiens and have no neandertal DNA.\n\nThere has also been another group of humans, the Denisovans, recently discovered that are similar to neandertals and could have possibly interbred with Asian humans (which in the end is seen in immunities possessed by the Asian population) but the jury is still out on that, so to say.\n\nAs far as isolated populations in the world go, most of them have only been isolated in the past 10,000 years (when the sea levels rose) such as Tasmanian aboriginals and that isn't nearly enough time to become genetically distinct from the rest of human populations.",
"There are slight differences in genetics among populations, with the exception of certain parts of Africa. Certain populations in Africa have been found to contain significantly diverse genetic profiles.\n\nSource: _URL_0_\n\nIn terms of how significantly different they are....that depends on how you look at it. All humans on earth are still relatively inbred compared to many species of mammals.\n\n",
"There are genetic differences among all populations, throughout the genome. These correspond nicely to archaeological evidence about human migrations: every time a subset of a population migrates to a new place, it carries only a subset of the population's genetic diversity. This is called a genetic bottleneck. So Africans have extremely high genetic diversity, as they're geographically the closest to the origin of mankind, while East Asians and Native Americans have the lowest diversity as their ancestors migrated the farthest.\n\nIf you like graphics, [here](_URL_1_) is a tree showing the relationships between various human populations, and [here](_URL_0_) is a map of ancient human migrations.\n\nEDIT: clarified",
"The majority of genetic variation amongst humans is within a minority of the population. Most importantly native and isolated populations, though bottleneck effect and genetic drift resulted in this. Outside of the native pockets of variability most large populations are more genetically uniform.",
"TIL Indians are caucasians.",
"Basque people are different to warrant mentioning. They're mRNA differs from ours as does their linguistic history.\n\n_URL_0_",
"I submitted an article about this two years ago: [\"The three primary genetic divisions of humanity are the Hadzabe, the Ju|'hoansi, and everyone else.\"](_URL_0_)\n\nThese two African peoples, despite both speaking a click language, are more genetically dissimilar from each other than any other two populations on Earth.",
"The CCR5-D32 allele, which confers resistance to HIV infection, is present in about 16% of the Lithuanian population. ",
"Funny you should ask this. I created a website that shows genetic distance across 51 native worldwide populations and how their genetic risk of disease differs. Here is the URL: _URL_0_.\n\nThe vertical length of each branch is genetic distance.",
"In a similar vein, *how* do you measure genetic distance? It's been bouncing around my mind for a while and seems like a really tough question. Do you do it by chronological splits (further back split = greater distance)? Otherwise, doing it via some measure between the actual sequenced genomes seems like a crazy hard/interesting problem.",
"Socotra Island off Yemen, has some of its population whose genetic code is not shared by any others on earth. Also has some of craziest flora/fauna on earth.\n\n_URL_0_\n",
"Recent evidence has shown that there was a people concurrent to homo sapiens and Neanderthal, called the Denisovans. This people interbred with homo sapiens much like the Neanderthals did. They were present around the south asia regian and above the alps of india. As such there are populations in places like Papua New Guinea with a 4.5% similarity to the Denisovan race where we have very little to none. However they have very little to no similarity with the Neanderthal genome, whereas we are at roughly 2%.\n\nWith several Genomes in the mix there is a broad spectrum of genetic difference. So some people will be more genetically distant to you than others.\n\nThere is a some stuff, including a video here:\n\n[Stuff](_URL_0_)\n\n[Video](_URL_1_)\n",
"Is it beneficial to mate with someone of a different genetic background?\n\nWhat would be optimal if this is true?",
"according to this - _URL_0_\n\nitalians are the closest genetically to africans, spec. african bushmen?",
"Overall most humans are genetically almost identical; however, certain groups obviously have different genes that are unique to their own populations. However, since it has been discovered that on average all humans of non-African decent have about 1-4% neandertal DNA all other populations are more closely related to each other than African modern humans, African humans are strictly Homo Sapiens and have no neandertal DNA.\n\nThere has also been another group of humans, the Denisovans, recently discovered that are similar to neandertals and could have possibly interbred with Asian humans (which in the end is seen in immunities possessed by the Asian population) but the jury is still out on that, so to say.\n\nAs far as isolated populations in the world go, most of them have only been isolated in the past 10,000 years (when the sea levels rose) such as Tasmanian aboriginals and that isn't nearly enough time to become genetically distinct from the rest of human populations.",
"There are slight differences in genetics among populations, with the exception of certain parts of Africa. Certain populations in Africa have been found to contain significantly diverse genetic profiles.\n\nSource: _URL_0_\n\nIn terms of how significantly different they are....that depends on how you look at it. All humans on earth are still relatively inbred compared to many species of mammals.\n\n",
"There are genetic differences among all populations, throughout the genome. These correspond nicely to archaeological evidence about human migrations: every time a subset of a population migrates to a new place, it carries only a subset of the population's genetic diversity. This is called a genetic bottleneck. So Africans have extremely high genetic diversity, as they're geographically the closest to the origin of mankind, while East Asians and Native Americans have the lowest diversity as their ancestors migrated the farthest.\n\nIf you like graphics, [here](_URL_1_) is a tree showing the relationships between various human populations, and [here](_URL_0_) is a map of ancient human migrations.\n\nEDIT: clarified",
"The majority of genetic variation amongst humans is within a minority of the population. Most importantly native and isolated populations, though bottleneck effect and genetic drift resulted in this. Outside of the native pockets of variability most large populations are more genetically uniform.",
"TIL Indians are caucasians.",
"Basque people are different to warrant mentioning. They're mRNA differs from ours as does their linguistic history.\n\n_URL_0_",
"I submitted an article about this two years ago: [\"The three primary genetic divisions of humanity are the Hadzabe, the Ju|'hoansi, and everyone else.\"](_URL_0_)\n\nThese two African peoples, despite both speaking a click language, are more genetically dissimilar from each other than any other two populations on Earth.",
"The CCR5-D32 allele, which confers resistance to HIV infection, is present in about 16% of the Lithuanian population. ",
"Funny you should ask this. I created a website that shows genetic distance across 51 native worldwide populations and how their genetic risk of disease differs. Here is the URL: _URL_0_.\n\nThe vertical length of each branch is genetic distance.",
"In a similar vein, *how* do you measure genetic distance? It's been bouncing around my mind for a while and seems like a really tough question. Do you do it by chronological splits (further back split = greater distance)? Otherwise, doing it via some measure between the actual sequenced genomes seems like a crazy hard/interesting problem.",
"Socotra Island off Yemen, has some of its population whose genetic code is not shared by any others on earth. Also has some of craziest flora/fauna on earth.\n\n_URL_0_\n",
"Recent evidence has shown that there was a people concurrent to homo sapiens and Neanderthal, called the Denisovans. This people interbred with homo sapiens much like the Neanderthals did. They were present around the south asia regian and above the alps of india. As such there are populations in places like Papua New Guinea with a 4.5% similarity to the Denisovan race where we have very little to none. However they have very little to no similarity with the Neanderthal genome, whereas we are at roughly 2%.\n\nWith several Genomes in the mix there is a broad spectrum of genetic difference. So some people will be more genetically distant to you than others.\n\nThere is a some stuff, including a video here:\n\n[Stuff](_URL_0_)\n\n[Video](_URL_1_)\n",
"Is it beneficial to mate with someone of a different genetic background?\n\nWhat would be optimal if this is true?",
"according to this - _URL_0_\n\nitalians are the closest genetically to africans, spec. african bushmen?"
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5uyxbe | Why is it so difficult for particle accelerators to increase in energy, seeing as you need about 10000000 Tev for ~one Joule? | Couldn't we just pour an amount of energy measured in joules in, and see what happens? | askscience | https://www.reddit.com/r/askscience/comments/5uyxbe/why_is_it_so_difficult_for_particle_accelerators/ | {
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"Is your question more along the lines of \"Why is the SI unit for energy so much greater than elementary particle rest mass energies?\"",
"Particle accelerators do not have 100% \"efficiency\". Yes, a few Joules is a very small amount of energy on a macroscopic scale, and yes, it's a *huge* amount of energy for a microscopic particle. But the energy that it takes to power an accelerator and all of the related systems does not all go into actually accelerating the particles. It's not a trivial feat to give an electron a Joule of kinetic energy, there are technological limitations.",
"You're essentially asking about what limits the center of mass energy of colliders. In all colliders, particles are accelerated by an electric field. The problem is that the faster a particle goes, the least time it spends in the field, and so the least efficient the field is at accelerating. Colliders are therefore limited by length.\n\nCircular colliders have an infinite length (just have the particles do as many turns as you want). However, curving the trajectory of a particle is done by magnetic fields, and these have to be higher the faster the particle is going to maintain the same amount of curvature.\n\nThis means that increasing collider energy implies either building bigger circular accelerators (which costs a lot of money, mainly because of excavation) or discovering ways to make better magnets. The LHC uses 8.3 T magnetic fields, which is among the strongest man-made ~~ferromagnets~~ magnetic fields.\n\nFor lighter particles, synchrotron radiation is also a problem in circular accelerators. A curving particle will radiate a quantity of energy that increases with a smaller mass and higher momentum.",
"When you heat up a sample by 1 Joule it's not all going into one particle. When we say that the LHC has a collision energy of 13 TeV we're saying that you're taking two 6.5 TeV protons and colliding them together. The actual beam itself will have a lot of particles in it (~10^30? I can never remember) so it's not like the energy of the beam is only 13 TeV...\n\nThe limiting factors for circular accelerators is different between electrons/positrons and protons/anti-protons (mainly based on their mass). For protons (which the LHC uses) the limiting factor is how strong a magnetic field you can produce (the more momentum a particle has the less a given magnetic field will bend it). For electrons the limiting factor is a phenomenon called Larmor radiation - accelerating charges emit radiation - eventually ~all the energy you put into them is then radiated out again...",
" > Couldn't we just pour an amount of energy measured in joules in, and see what happens?\n\nLet me ask you the related question to illustrate the problem:\n\nHow?\n\nHow do you put one joule of energy into a particle? Do you have an answer? That's problem... neither does anyone else. The problem of energy transfer is a deep issue that pervades most of science and engineering, not just particle accelerators.\n\nA chocolate bar has about half a million joules of energy in it. If you could transfer that power into a bullet, you could launch it at 10km... per *second*. At that speed you could flip over tanks.\n\nOkay, let's do it! I'll stick my bullet into a chocolate bar and light it on fire and it should go at 10km/s right?... yeah no.\n\nRight now, we don't have any mechanism of efficiently transferring the chocolate bar's chemical energy into the bullet's kinetic energy. We have very roundabout systems that can burn the chocolate bar, produce heat, maybe drive a compressor and then launch the bullet. But much of the energy is wasted. Even if it wasn't wasted there are engineering limits to how much acceleration can be applied.\n\nSame thing with our particle accelerators. We can easily get terajoules from a nuclear reactor, but we have no way of directly applying that to the particles. Instead we go through a roundabout method of using magnetic and electric fields. You might be asking \"well why don't we increase those fields?\", we can certainly try but often times we're at the engineering limit. If we actually did increase those fields we would literally break the magnets. The stress they're under is too great. We can keep engineering better and better systems but that costs money. \n\nSo going back to your question: \n\n > Couldn't we just pour an amount of energy measured in joules in, and see what happens?\n\nI'll tell you exactly what happens: the magnets would explode long before that energy is transferred to the particle. \n\nDo you think it's as simple as turning a knob on the LHC from one to eleven? The knob's already been maxed out. Turning it further would literally break the machine.\n\nWhat we need is better machines. And that goes back to a fundamental problem we still haven't figured out:\n\nHow?\n\n\n(EDIT: spelling and grammar)\n",
"You might want to rephrase your question, as people are confused.\n\nYou seem to be asking:\n\n > why is it hard to accelerate particles in a particle accelerator when the total energy per particle is small (in macroscopic scales)?\n\nA few people have given good answers, but let's try to be more concise:\n\nIn order to make something go fast, you either need to accelerate it at a high acceleration (which is hard) or for a long distance (which takes space and resources).\n\nIn order to get up to relativistic speeds we do both: we create extreme electrical fields, and we let the particles spend as much time as possible in them, by letting the particles travel in circles.\n\nWhen a charged particle is accelerated it gives of light. This means we need to push harder, and also means we want to avoid turning too sharply as turning increases losses. This forces us to make large circles. The LHC is absolutely gigantic."
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292k9v | in movie scenes of gambling and betting, people throw up tons of cash for bets - how do they keep track? | People just yell out their bets with a fistful of cash and the bookie just grabs it - is someone taking notes on what they bet on, how much they gambled, and gave them a receipt? Does this happen in real life? It seems so complicated. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/292k9v/eli5_in_movie_scenes_of_gambling_and_betting/ | {
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"Some gambling venues have \"odds\" tickets. So if you want to bet on a fighter that has 1:10 odds on winning (underdog), you would receive a ticket with those odds that correspond to that fighter. Say you purchased 5 1$ vouchers, the person in the crowd of people would take your money and hand you 5 vouchers. Now let's say your fighter won, you then redeem your vouchers at a cash window and collect your winnings. Venues will have their own methods of tracking which are winning vouchers and which aren't. ",
"They don't keep track because it's a just movie and those aren't real bets. \n\nIn real life you walk up to the betting counter after waiting your turn in line, place your wager, it's entered into the system through a computer and you are given a receipt. \n\n",
"You see this mostly on the craps table. They take the cash or chips and place it in a certain spot on the board that indicates which area of the table you're standing at. It's also exaggerated in moves and is more manageable in real life. ",
"What you're describing is usually depicting the illegal \"numbers\" or betting process in early to mid 1900s. The way they show it in the movie is relatively accurate to what took place in real life. If you notice, the bookie usually has a pencil and paper to record bets. OR if he doesn't than the bets are usually taking place between friends/close associates and he would just remember; \"Jimmy said 50...jimmy always bets 50..50 on Jimmy\". In any case, memory or assumed accurate note taking is the only record of audit for the bet and any discrepancy would be between the person betting and the bookie. In this situation, the person betting would have little to no choice but agree with the book keeper. The reason being broken legs, never being able to bet with that bookie again or fear of being in bad standing with the mafia or whatever crime syndicate is backing the book keeper/numbers runner.",
"Casinos in Nevada can accept cash wagers, so they may call out something like \"Cash to the table max\" meaning you have made a cash bet up to the limit of the table.",
"I always imagined that if you were spending that kind of money you were usually good at gambling and was good at numbers. Also, a lot of those larger games usually have someone running them.",
"Hi, I worked for a horse racing bookmaker in Sydney for 10 years or so.\n\nThe process at your basic bookmaker stand at the races is this : \nYou have a bag man taking cash, an operator entering the bet on the computer system, and a bookmaker overseeing it and modifying the odds on the fly.\n\nThe punter places a bet, the bagman takes the cash, the computer operator prints out a ticket, the bagman checks it and hands it to the punter.\n\nThat ticket will have the race number, horse bet on, type of bet (win / place / eachway), amount bet, odds at the time you placed the bet and how much you can expect back if the result comes in. \n\nAt the end of the race, the results are entered into the computer, the punter will bring back the ticket, it's scanned to check it's authenticity and cash is payed by the bagman to the punter. Kinda hard to stuff up, unless it's really busy and you're inexperienced and all the punters are drunk and there's money everywhere... which happens sometimes. \n\nHowever, there have been times when the power has gone out AND the backup generators have blown and so the computer system has gone down.\n\nIn these cases, some of the older bookies would use an older method known as penciling (which is more what you're talking about)\n\nBasically, same process, computer removed. \n\nPunter comes to put a bet on, and instead of a printed ticket they get an abbreviated handwritten stub from the bag-man saying the horse number, the bet and the odds, which they keep as proof of wager.\n\nA corresponding entry is made in a ledger kept with the bookmaker.\n\nThat's what you're seeing in the movies. Once you get good at it the process can take less than a second per bet.\n\nTake the cash, write and give a ticket, someone else fills in the ledger and NEXT.\n\nIt can get frantic when it's busy, and when I watched the process at a muay thai match in thailand I noticed a lot of hand signals being thrown around to communicate over the din, but everything is on record.\n\nAnyway, hope that answers your question."
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16z2zj | How did cricket get so popular in India | How did cricket get so popular in India? Obviously it has something to do with the British influence on the region, but soccer appears to have taken off in other countries that were under previous colonial occupation (regardless of coloniser), even though it was invented in the UK as well. So does anyone have a more comprehensive answer for this? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/16z2zj/how_did_cricket_get_so_popular_in_india/ | {
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"Cricket was one of the popular sports, not the 'the popular' one; It used to be so until 1983. To be fair; wrestling, kabbadi, kho-kho, field-hockey, volley ball, badminton were more popular. Indoor games are even more dominant and were popular pastimes in both rural and urban demographics. Some (games)[_URL_0_] are very akeen to cricket, so cricket is not really a stranger (it had it's origins in the hands of cowherds).\n\nTo understand the reason, cricket was relatively heavy on the pocket and a bit boring, compared to the rest. Historically India's claim to fame was [Dhyanchand](_URL_1_), Wrestling was another sport which had hold in rural India. Infact, India's medal tally comprised on wrestling medals if commonwealth games are used as a bench mark for this period. This was in the era where skilled players were encouraged irrespective of choice of sports. Every college used to have sports tournaments (and rightfully, five-day test cricket matches were rarely included).\n\nIn 1983, India won the world cup. Cricket which was considered to be game of refined folks (5 days of play remember!), not for those who had to work for their wages. Most of the Indian cricket teams till that time were lead by aristocrats and princes. This was the time young India was booming was needed motivation. Victors and Victories are remembered, songs are sung and glorified. After one-day cricket came into prominence and India's triumph over West-Indies (analogous to David vs. Goliath), things fell in place. \n\nCricket became a heroic distraction to the unemployed and young, Leading to greater time spent on dusty fields. The lack of infrastructure (grass lawns and bouncy turf) was a handicap (swing/fast bowling needed this). On the other hand, coarse fields helped eager training ground for spinners. Indias' rather dismal off-shore record (on greener grounds) shows this.",
"Actually, football WAS quite popular in India in the 50's and 60's. In the 70's, cricket started to become more and more popular because of the players proving to be unbeatable, especially at home. Then, in the early 80's, almost two dozen top-notch football players in India walked out of the preparations for Asian Games (which was a prestigious tournament in which the Indian football team had bagged gold, twice). They walked out because the All India Football Federation (AIFF) put them on a two-year training schedule which completely hampered their club football play. That, coupled with the legendary Kapil Dev winning the cricket World Cup in 1983, turned all the limelight on the sport that was slowly but surely winning a lot of hearts.\n\nBy the late 80's, the whole country was taken by a storm called Sachin Tendulkar who after having played first-class cricket at the tender age of 15, impressed enthusiasts worldwide with his batting. Oh, and there were people like Azharuddin, Dravid, Ganguly, and so on, who are all legends in their own rights. So, basically, the AIFF screwed up a lot and the BCCI played all their cards right."
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f5i1e0 | how are threads for clothes made? | i'm referring to the synthetic, hairline, super thin, almost microscopic threads that are used to make thicker threads, what are they made of and how are they made? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/f5i1e0/eli5_how_are_threads_for_clothes_made/ | {
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"The individual fibers are twisted together, like a rope, but on a smaller scale. As each fiber binds up through torsional friction, there are more fibers added, this lengthening the piece. Then, they take these individual strands of fibers and wrap them together to create a thread.\nOnce you have enough thread (of whatever material), you begin weaving it into a fabric. \n\n[Here](_URL_0_) is a kind of cool video in a larger scale about lariat making (which should give you some idea of what I’m describing).",
"What is perhaps the most common type of synthetic fiber, Polyester, is a plastic that is melted down and squeezed out of tiny holes to reach the desired diameter. Here's a video outlining the whole process if you're interested: [_URL_0_](_URL_0_) . Many other synthetic fibers are also plastics manufactured in a similar manner."
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6i1iu0 | the difference between the nazi army, ss, and the wehrmacht. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6i1iu0/eli5_the_difference_between_the_nazi_army_ss_and/ | {
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"The Wehrmacht was the German Army. It existed well before the Nazis came to power. The SS replaced the SA. It was a paramilitary organization with different arms doing different things. Some were State security units, some were guards at Concentration camps, some were actually infantry and armored regiments that engaged the enemy in combat. ",
"The Wehrmacht was the German Army, an organization that long predated the Nazi Party and the same army that fought in WWI. Being from aristocratic backgrounds, many high-up Wehrmacht officers actually disliked the populist Nazis, and some even conspired to kill Hitler (see: Valkyrie). Despite their occasional disdain for the Nazis, however, the officers of the Wehrmacht were fully supportive of the war and of Germany, ruled by Nazis or otherwise.\n\nThe SS started as the political paramilitary wing of the Nazi party, replacing the SA, but later developed fully militarized units known as Waffen-SS that fought on the front as a regular army unit would. But unlike the Wehrmacht, it was completely part of the Nazi party.\n\n\"Nazi army\" isn't really a proper term for anything. It probably most accurately describes the Waffen-SS, army units that were part of the Nazi party. But since the Nazi party and the German state became identical during Nazi rule, people probably also use the term to mean the German army as a whole, even though the Wehrmacht was not a Nazi organization, and elements of its officer corps even opposed the Nazis.",
"Leading into WW2, Germany had a military comprised of three specific forces. Those being the Heer (also known as the Wehrmacht), the Luftwaffe (airforce), and Kriegsmarine (navy). The Heer had existed for quite some time prior to the war, in various iterations, but had been largely modernized during the last years of WW1, and the inter-war period prior to Hitler's rise.\n\nDuring Hitler's rise to power, he befriended a para-military group known as the Sturmabteilung, or the SA. The SA's name is taken from specialized troops used during WW1, and gave rise to the term of \"Stormtrooper\". Basically that's what Sturmabteilung means anyway, so it's understandable. In any case, prior to Hitler's rise within the Nazi party, there were a number of problems faced by the many members and ranking officials. The chief problem being that there was often fighting between other parties, not the least of which being the German Communist party. To protect the party leaders and members, the SA took on a bodyguard role.\n\nAfter Hitler's rise to Fuhrer, some aspects of the SA became troublesome for Hitler, based on what he was preaching and saying to his followers. Not the least of which was the fact that most of the high command of the SA were homosexual. So, in a coup, Hitler had all high ranking leaders arrested and then executed. What was left of the SA were absorbed into a new organization known as the Schutzstaffel, or SS. \n\nSo the differences? Well it depends on which SS you're talking about. See, there were actually two distinct groups of SS. The first was the regular Schutzstaffel who acted as bodyguards for Hitler, as well as the guards at the many concentration camps. Though their organization was much like the Heer's military, their commander only reported to Himmler, who in turn reported directly to Hitler. The second group is the Waffen-SS, the armed military group of the SS. Logistically speaking, the Waffen-SS and the Heer were almost identical, with both pulling from the same military support lines and training. However, where they really differed was in weaponry. The Waffen-SS, unlike the regular Heer, tended to be given the best and most modern weapons, while the Heer had those, but in a far more limited quantity. Operationally, Waffen-SS units reported to whatever Heer commander they were serving under, and only tangibly reported to SS command. \n\nThere were also other minor differences. For example, the Heer were not required to do the Hitler salute until sometime around 1943, or 44. While the SS only used that salute. The SS favored a camouflage uniform, while the Heer tended to default to the usual gray. SS units would rarely surrender, while Heer units were more likely to do so when under duress. \n\n"
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bbnlo5 | Why is there such a large Indian community in Africa? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/bbnlo5/why_is_there_such_a_large_indian_community_in/ | {
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"The short answer is colonialism.\n\nIf you look at the areas with an Indian diaspora, you will notice an interesting thing, nearly all areas were formally part of the British Empire. This is no coincidence as the British were largely responsible for large scale population movements across their empire. Importing laborers from India was a British peculiarity and led to sizable populations of Indian groups outside of their homelands. Some other significant diasporas are the Upland Tamils of Sri Lanka, the Malaysian Tamils, the Indo-Guyanese, and, yes, the South African Indians. \n\nThe British utilized indentured and bonded laborers heavily in their projects, drawing especially from South India and Hong Kong. These bonded laborers were essentially slaves, although their treatment was far better than chattel slaves at the time and they, at least theoretically, could buy their freedom eventually. Especially after slavery came to an end across the British Empire, bonded workers were increasingly used as Britain consolidated its hold over their colonies and undertook large-scale construction processes.\n\nImporting workers had two major benefits. One is that in unfamiliar territory, they could not flee or rebel effectively and were thus both pacified and reliant on the British. The other was that the British created a sense of division between groups. Rarely would a foreign worker gain any real power in the British system, but over time, the British began to rely more heavily on administrators, especially Indian, from their colonial holdings. \n\nIn any case, these foreign workers largely stayed put after being moved, mostly for economic reasons than any sense of belonging or homeland, and developed distinct communities. Most retain a strong sense of \"Indianess\" however in since the end of the colonial era, these diaspora groups have often strongly identified with their home country above India, especially as they mix with other groups."
]
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[]
] | ||
7pbxd8 | why won't most domestic freezers work in cold temperatures? | Shopping for a new freezer recently, and was puzzled to learn that most aren't suitable for outbuildings/garages that reach cold temperatures in winter. You would think they would work better by being in a colder environment as they don't need to achieve such a big drop in temperature? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7pbxd8/eli5_why_wont_most_domestic_freezers_work_in_cold/ | {
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"A freezer/fridge is essentially a heat pump, where is pumps the heat, or lack of cold air out of the container. It does this by decompressing a gas that is pumped through tubes in the freezer. As the gas moves it pulls the extra heat from the fridge and moves along and out the back again. Here it releases this heat as it is compressed and dissipates into the surroundings. Then goes back to the compressor and starts all over. \n\nSo when the gas is trying to release the heat it pulled from the fridge, and it has an easier job doing so. Better right? Nope. Because it is so cold it actually has a chance to cool by the time it gets back to the compressor, which drastically lowers the efficiency of the system. This is basically the system falling out side of ideal conditions. It will get cold, but it will take much longer. "
]
} | [] | [] | [
[]
] | |
3gxw3p | how did bill cosby's statements about quelludes surface if they were "sealed" by the court? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3gxw3p/eli5_how_did_bill_cosbys_statements_about/ | {
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"The court unsealed them. Cosby's lawyers argued they should stay sealed but the judge disagreed, saying there was a strong public interest at stake, Cosby portrays himself as a public moralist, so this information is very important and should be known to the public. ",
"A suit was filed in 2005. The seal was temporary. The seal was going to lapse, but the case settled so the court never lifted the (temporary) seal.\n\n~8 years later the Associated Press sued and said that the seal should be lifted. They said that temporary seals are automatically lifted after 2 years unless there's a good enough objection -- \"good cause\" -- from the person who wants to keep them sealed.\n\nCosby objected. The court found that his objections weren't good enough; he had spent a lot of time advertising himself as a moral compass so the public deserves to know things like this. Yes, it would embarrass him; no, the fact that it would embarrass him isn't good enough to keep it sealed considering that he spends tons of time advertising himself as a moral dude. \n\nAdditionally, the judge in the 2005 suit wasn't shown the settlement agreement. And that judge wasn't asked to make the seal permanent. Combine those facts with the fact that the public has an important interest in knowing and the court found that it was better to not keep it sealed."
]
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[],
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2h2imt | What language(s) were the books of the Old and New Testaments originally written in? | I've read conflicting things. If anyone knows, I'm also interested in where, when, by whom, and why they were written, though I expect that the answers to those questions are less clear. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2h2imt/what_languages_were_the_books_of_the_old_and_new/ | {
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"Your basic question is uncontroversial. The Old Testament is predominantly written in Hebrew, with a few portions (parts of Ezra and of Daniel) in Aramaic. The New Testament was written in Koine Greek. I don't see how you could get conflicting reports on that, it is beyond reasonable doubt.\n\nWhere, when, by whom, and why are much more complex questions, and in fact should generally be dealt with on a book by book basis. Each book in the Bible originates in its own context, with a particular purpose, by one or more authors and/or composers/editors, sometimes over a period of time."
]
} | [] | [] | [
[]
] | |
1c1lj9 | Can we use light to transmit data? | So, my limited understanding is, that light travels in little "bursts" called photons.
These photons act like little packets. Light isn't a single stream, but essentially a huge number of the packets.
Would it be possible to somehow encrypt information or data into these packets, or photons? That way, even if humans can't travel at the speed of light, at least our information can.
Btw, if I have an incredibly flawed understanding of how light works, correct me. Just please be polite about it. | askscience | http://www.reddit.com/r/askscience/comments/1c1lj9/can_we_use_light_to_transmit_data/ | {
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"That is how all wireless information works, actually, be it cell phone, satellite, Wifi, or even your remote control - those are all ways of transmitting data via light.\n\nOn the more obvious fronts, your monitor is displaying information right now, via light. A navigational light is transmitting data on location. You can use a flashlight to transmit Morse code.\n\nThere are thousands of ways it is done.",
" > Would it be possible to somehow encrypt information or data into these packets, or photons?\n\nYes. [Here is the wiki article on fiber optics.](_URL_0_) Literally cables that transmit light.\n\nHere is the article specifically on [communications/data transmission applications of fiber optics.](_URL_1_)\n\nMany internet service providers, like Verizon and AT & T already use fiber optics. Verison FiOS is one example. [\"FiOS\" stands for \"fiber optics\".](_URL_2_)",
"Pretty much been answered, but I'll expand, as this is very much in line with my studies.\n\n\"Light\" is essentially all EM waves, from radio - gamma. Any wireless transmission you receive is technically \"Light\".\n\nAs for \"Light\" in the more traditional sense of what we can actually see, it's wavelength is small enough that we can examine it as both a particle (photon) and a wave. \n\nIn order to transmit information via photons it would have to be a sort of OOK (ON OFF keying). Since photons aren't measured but calculated it wouldn't be wise to try to send a specific amount of photons to represent a single message, there is too much room for noise, and the system would be far too complicated for what it's worth.\n\nGoing back to OOK, light can be used for communications in that sense, essentially sending a pulse of light for a 1 and nothing for a zero. If sampled at the correct times you can distinguish a proper binary signal. More traditionally, however, light is treated as a wave and communications are encoded in it as they are in radio waves (Digital versions of AM/FM).\n\nFinally, the reason that it is generally better to encode light with digital modulation schemes instead of OOK is that you can do a lot more with them than just turning it on and off. For instance, OOK gives you a 1 or a 0, but QPSK gives you a 00, 01, 11, 10. Not to mention the interference from multiple OOK systems through a fibre optic line. Another neat thing you can do when you treat it as a wave is share a spectrum. Think red light carrying a message, lets say your phone conversation. While it's carrying your conversation it's also carrying say 2 other people's conversation at the same time, this is essentially what cell phones do. You can't do that with OOK, at least not very easily or reliably."
]
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[],
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"http://en.wikipedia.org/wiki/Optical_fiber",
"http://en.wikipedia.org/wiki/Fiber-optic_communication",
"http://en.wikipedia.org/wiki/Verizon_FiOS"
],
[]
] | |
6rsi8s | When and why did revolving doors go out of fashion? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/6rsi8s/when_and_why_did_revolving_doors_go_out_of_fashion/ | {
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"Revolving doors haven't so much gone out of fashion as not being needed as much - you certainly can still find them.\n\nThe revolving door primarily exists to control air flow - particularly in tall buildings. (they can also be used to control the flow of people for security - one-way revolves that use bars to block the opposite flow) For situations involving a low flow of people they work fine, but they are inefficient for larger flows.\n\nCompounding this are safety issues - the deaths at the Coconut Grove nightclub fire in the 40s were due in part to a single revolving door. Ensuing legislation to make emergency exiting more available (side doors or collapsible rotators) just make the use of revolving doors are the more problematic. \n\nI would suspect that advances in HVAC - as well as the development of \"air curtains\" - have reduced the temperature-control aspect of the revolving door "
]
} | [] | [] | [
[]
] | ||
3chcp2 | why do old people keep "chewing" even when they're not eating anything? | I seen a lot of older folks do this, but I never had the courage to ask anyone this, it's kind of a weird question. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3chcp2/eli5_why_do_old_people_keep_chewing_even_when/ | {
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"Playing with their dentures.\n\nSimilar to when people who have tongue-studs play with them in their mouth, the elderly have the same habit of orally maneuvering their dentures. A better question would be, \"what causes people to orally maneuver foreign particles in their mouths?\"",
"I've seen this happen, but only with denture users. My grandmother used to constantly do that and when I asked her about it, it was because the goop she used to keep them in place after her gum ridge eroded would \"feel funny\" after chewing extensively, like during a meal. She said it would eventually stop feeling weird and she would rest her chops after the goop \"was back where it belonged\". Weird question; weird answer. \n\n",
"it's usually either dentures, the onset of a brain condition like Alzheimer's or - more and more these days - the side effect of a drug they're taking to stop the aforementioned brain condition. "
]
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[],
[],
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] | |
hsc4i | What just happened to my bottle of water? | I put a bottle of water horizontally in the freezer (an unopened bottle of Fiji brand water, 1 liter size if that matters) about two hours ago on the "quick freeze" shelf. When I opened the freezer and noticed that the bottle and its contents were perfectly clear, which I thought was weird because the water should have frozen at least somewhat in that time period.
I picked up the bottle and when I looked at it a second or less later, noticed that a portion of the inside had become cloudy. To my astonishment, the cloud was spreading throughout the bottle until the whole inside was cloudy. This happened within three-five seconds of when I picked up the bottle. After those five seconds, almost all of the bottle was a block of ice with a sleeve of liquid water on the outside.
What process did I witness with the cloudiness spreading when I picked it up? Why didn't the bottle appear how I expected it to (like a piece of cloudy ice) when I first saw it? How can I replicate what I saw? It was pretty amazing and I would like to see it again if I can. Thanks! | askscience | http://www.reddit.com/r/askscience/comments/hsc4i/what_just_happened_to_my_bottle_of_water/ | {
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"crystallization\n_URL_0_\nof supercooled water",
"I've seen this several times on the Internet and on tv. If I remember correctly, you supercooled the water. That is, you cooled it below its freezing point without the water freezing. By disturbing the bottle you caused it to freeze near instantaneously, although I don't remember how this happens.",
"The same thing works with beer. Pretty epic party trick to win yourself some monies. Put a beer (with no bubbles) in the freezer for an hour and a half (might have to tweak how cold your freezer is). Tap the beer and watch that sucker freeze in less than 3 seconds. The aftermath makes for a yummy beer icee on a hot day :D",
"[obligatory answer from mythbusters](_URL_0_)",
"QUIT BUYING FIJI WATER!!!\n\nFor the love of Archimedes, just stop buying bottled water! It's the stupidest thing you can do - import a natural resource that is in plentiful supply right in your own kitchen!\n\nTap water is cheap, safe, and ecologically friendly. If you feel some overpowering need to have fancy water - buy and install a reverse osmosis filtration system for about $150 and you'll have water that's ultra pure and doesn't require a fuck-tonne of diesel to be hauled SIX THOUSAND MILES to your local grocer!\n\n/rant\n\nsorry people. I don't do much for my planet, but when I see some yob drinking water from a tiny island in the pacific that requires 250g of fossil fuels to produce and deliver, it pisses me right the fuck off. \n\nEdit: just to be clear - if you buy a bottle of Fiji water and fill 1/2 of it with diesel, that's what it takes to get it to you. Sickening. ",
"I do a lab for my Meteorology 101 students on supercooled water (plays a big role in hailstone formation) and that's exactly what this sounds like. "
]
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"http://www.youtube.com/watch?v=wHvGCKRZY5I"
],
[],
[],
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"http://www.youtube.com/watch?v=CzEC7WWeNyA"
],
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8xuqrh | how come shanghai tower (632m) and mia khalifa (828) can stand so tall without breaking from wind? concrete doesnt bend does it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8xuqrh/eli5_how_come_shanghai_tower_632m_and_mia_khalifa/ | {
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"Are you sure you didn't mean “Burj Khalifa?”"
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57kdv3 | When joining the corps back in WW2, could one choose which theater they would fight in? | For example, when the US was at war with Germany and Japan could you join and choose to fight in either Europe or the Pacific, or was it allocated? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/57kdv3/when_joining_the_corps_back_in_ww2_could_one/ | {
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"For the most part, no. When it came to the Army, placement of enlistees and draftees after they had signed up or were drafted (and as a result, eventual theater assignments) was generally completely random, pursuant to the calculated needs of the service at that time. All-volunteer Army units such as the Rangers or parachute infantry units filled their quotas by selecting men who had placed a preference after enlistment or induction, and then met the requisite physical and mental qualifications. [**For the experience of the Army draftee, see this earlier answer I gave.**](_URL_3_) The same kind of system existed for the Navy and the Marine Corps, except that they did not begin tapping the pool of draftees until early 1943.\n\nThere were six draft registrations during WWII:\n\n**Draft Registrations:**\n\nRegistration|Date|Criteria for Registration\n:--|:--|:--\n1|October 16, 1940|Men who were 21-36 years old\n2|July 1, 1941|Men who had turned 21 since October 16, 1940\n3|February 14-16, 1942|Men who had turned 20 on or before December 31, 1941, and were not older than 45 by February 16, 1942\n4|April 25-27, 1942|Men who were at least 45 on or before February 16, 1942 and not older than 65 on or before April 27, 1942\n5|June 30, 1942|Men born after January 1, 1922 and before June 30, 1924\n6|December 10-31, 1942|All men who had turned 18 by December 31, 1942\nExtra|November 16-December 31, 1943|Men living abroad aged 18-45\n\nAfter the sixth registration, all men who had reached their 18th birthday were required by law to register with their local draft boards.\n\nWith the signing of Executive Order 9279 on December 5, 1942, President Franklin D. Roosevelt eliminated voluntary enlistment into the military for those men who were between 18 and 37 years old. Those men who were 17, and those who were 38 to 45 (i.e. those men who were considered old enough for service, but not actually subject to the draft) could still enlist voluntarily into the military provided that they met its qualifications for service.\n\n > After the effective date of this Order no made person who has attained the eighteenth anniversary and has not attained the thirty-eighth anniversary of the day of his birth shall be inducted into the enlisted personnel of the armed forces (including reserve components), except, under provisions of the Selective Training and Service Act of 1940, as amended; but any such person who has, on or before the effective date of this Order, submitted a bona fide application for voluntary enlistment may be enlisted within ten days after said date.\n\nThis order was made so as to not disrupt vital war industries and farm labor by having men essential in these occupations run off and join the military. It also controlled how many men the military received at a time. The Selective Service set a quota of drafting around 200,000 men per month.\n\nIn contrast to the Army, the Navy, until the signing of Executive Order 9279, remained \"free\" of any Selective Service constraints due to sufficient enlistments and a rocky relationship with the Service itself. The Navy had refused to participate in the Selective Training and Service Act of 1940 (a request granted by the President himself) and had complained several times to the Secretary of War as to why it should be able to remain volunteer-only. Extremely aggressive recruiting processes (including assigning officers with sales backgrounds to recruiting offices and an extensive advertising campaign) had annoyed the Selective Service to the point where, in early 1942, they refused to provide the Navy with lists of men from local draft boards classified 1-A!. Voluntary enlistments, especially after Pearl Harbor, managed to carry the Navy to Executive Order 9279.\n\nThe Marine Corps (as a part of the Navy) also used an entirely voluntary system of enlistment through the first years of the war, and this proved to be successful. With the war on, it was realized that utilizing the draft's manpower pool would be necessary to provide enough Marines. The Marine Corps issued their first personnel quota on February 1, 1943, with the first draftees arriving to training later that month. Two weeks before President Roosevelt signed Executive Order 9279, the Marine Corps had arranged to send liaison officers to state and local draft boards to identify inductees who had made an explicit request to serve in the Marine Corps upon draft registration, or those that wished to. The liaison officers had the authority to funnel willing men into the Marine Corps or postpone the inductions of those men who wished to join the Marine Corps until vacancies existed (see below) They also had the authority to discharge prospective Marines from the Selective Service System, to allow them to re-enlist voluntarily and avoid the stigma among Marines of being drafted. Of 224,323 Marine draftees, less than 70,000 chose to keep their \"inductee\" status. Of the 275,985 men who entered the Marine Corps between February 1, 1943 and July 31, 1945, 58,927 were 17 year old volunteers.\n\nEach month, the services submitted a manpower requirement to their respective Secretary, who then presented this figure to the Director of the Selective Service. At Selective Service Headquarters, a total call was made up. Quotas of men needed were then issued to the states, where they were divided up among the local draft boards. A ratio was calculated between the Army and Navy (which included the Coast Guard and Marine Corps)\n\n > Each of the induction stations allotted inductees on the basis of this ratio. To assure equitable distribution of manpower by quality, categories were set up according to age, education, and occupational skill. The quotas for the Army and Navy were to be made up of proportionate numbers from all these categories. The Navy quota at each induction station was then broken down into Navy, Marine Corps, and Coast Guard components, again by use of a ratio. Selectees at induction stations also had the option of picking their branch of service, provided vacancies existed in the quota of the service of their choice.\n\nSources:\n\n[Executive Order 9279](_URL_1_)\n\n[Administration of the Navy Department in World War II, chapter VII](_URL_0_), by Rear Admiral Julius Augustus Furer, USN\n\n[Administration of the Navy Department in World War II, chapter XIV](_URL_2_), by Rear Admiral Julius Augustus Furer, USN"
]
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"http://www.ibiblio.org/hyperwar/USN/Admin-Hist/USN-Admin/USN-Admin-7.html",
"http://www.presidency.ucsb.edu/ws/?pid=60973",
"http://www.ibiblio.org/hyperwar/USN/Admin-Hist/USN-Admin/USN-Admin-14.html",
"https://www.reddit.com/r/AskHistorians/comments/561vrb/what_was_boot_campmilitary_training_lik... | |
2q3gxj | why is it common practice for companies that i already do business with to call me up with "special offers" that are just trying to scam me out of more money? | Seriously, it makes me want to do business with people who treat me like a human not a stack of bills. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2q3gxj/eli5_why_is_it_common_practice_for_companies_that/ | {
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"Essentially, because you have spent money with them in the past, you're more valuable to them as a customer. Your purchase has proved you a) have money and b) are willing to spend it with them, so marketing additional products to you is more likely to succeed than, say, advertising to random yobbos on the street."
]
} | [] | [] | [
[]
] | |
5kxc2k | What is the farthest wind has traveled? | askscience | https://www.reddit.com/r/askscience/comments/5kxc2k/what_is_the_farthest_wind_has_traveled/ | {
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"\"Wind\" is more of a concept than a physical object you can measure like that. There's always some wind everywhere (except in very controlled indoor conditions) and it's always moving, so you can't really say it travels *x* miles.",
"not an expert on this in any way (engineering major at University), but isn't wind just waves of air particles traveling from high pressure to low pressure? The question doesn't really seem to make sense as wind isn't really a thing that \"travels\" per say, but someone in the field might have a better scientific answer and might be able to answer the question you were trying to ask which is probably the farthest continuous distance at which wind is created, but i'm not exactly sure.",
"After the eruption of [Krakatoa](_URL_0_), shock waves were detected on barographs all around the world for days afterward. If you accept the premise that a shock wave through the atmosphere counts as \"wind\" (which, I'll grant, might be a bit of a stretch), the answer to your question would be \"around the whole earth, several times\".",
"What kind of wind are we talking about here?\n\nThe solar wind from our Sun travels out to the heliopause, about 18 billion km.\n\nStellar winds from Wolf-Rayet type stars can persist several light-years (50 trillion km) from their source."
]
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5eu61w | why does the body need metals like zinc? | I understand the need for metals like iron in foods. However, some, especially zinc, seem very odd to be needed. Even in small amounts, what purpose does eating zinc provide in the human body? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5eu61w/eli5_why_does_the_body_need_metals_like_zinc/ | {
"a_id": [
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"text": [
"Some special type of enzymes need them to work. They are also part of some cellular structures. So if you do not have them, some cells do not work properly and some chemical reactions made by these enzymes just not happen."
]
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[]
] | |
4uyous | is it actually legal for a police officer or fbi agent to demand i let them use my car in order for them to continue a high-speed chase? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4uyous/eli5_is_it_actually_legal_for_a_police_officer_or/ | {
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"text": [
"Yes. \n\nAn officer of the law has the right to commandeer any vehicle or vessel they need to in the course of pursuing a suspect and the city/department will compensate you for any damages incurred. "
]
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[]
] | ||
1ha257 | I have read that anechoic chambers make people "go crazy", feel uncomfortable, and even hallucinate. Why would sensory deprivation cause this kind of distress/altered perception? | askscience | http://www.reddit.com/r/askscience/comments/1ha257/i_have_read_that_anechoic_chambers_make_people_go/ | {
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"While the article everyone talks about is sensationalized and not very accurate, the reason people start to have \"hallucinations\" or altered perception is that our sensory systems operate with automatic gain control which when faced with minimal input, allow concious perception of \"sensor noise\" which would normally be imperceptable.",
"Is there any evidence to suggest that being in an anechoic chamber *actually* makes people \"go crazy\" and/or hallucinate? Or could it be that while the experience is quite stark and unnerving for people experiencing it for the first time - while also being told that they will \"freak out!\", they would, after a time, get used to it?\n\nI've only ever heard anecdotal evidence on TV shows and such.\n\nPlus, wouldn't humming or whistling or tapping your fingers totally negate the silence and the supposed \"being freaked out by the sound of your own X\" phenomena?"
]
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[],
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atefdv | Why do so many continental Germanic surnames (German, Yiddish, Swedish, etc) have topographic features like "stein", "wald", and "berg"? | These kinds of names are strongly associated with Germans and Ashkenazi Jews, and these kinds of names dot the German historical landscape: the Goldberg Variations, the Gutenberg Bible, the physics contributions of Albert Einstein and Werner Heisenberg, Nazi genocidaire Alfred Rosenberg and repentant Nazi officer Kurt Gerstein. The topographic names "Stein", "Steiner", "Berger", and "Bergmann" are among the top 100 in Germany. In Sweden, a whopping *29 out of top 100 surnames* [end in -berg.](_URL_0_).
"Stone" is an English surname, but a particularly uncommon one, and often the Anglicized version of Stein. So what causes this great break between the Germanic names of continental Europe versus the British Isles? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/atefdv/why_do_so_many_continental_germanic_surnames/ | {
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"In \"Anglo\" names, I think there are actually a lot of hidden meanings in topographical surnames that might not be transparent to a modern English speaker. This is because a lot of the place names in the British Isles (especially in England), retain their Anglo-Saxon or Viking names, while the English language has incorporated a lot of Latin/Old French words that have replaced them. Examples include names that end in \"-by\" that come from the Norse word for \"town\" (for example, Grimsby in Lincolnshire) or \"-thorpe\" (which derives from the Norse word for \"village\", for example Scunthorpe, also in Lincolnshire). The Anglo-Saxon equivalent of \"-by\" was \"-ton\" (shown in places like Luton in Hertfordshire), while the suffix \"ing\" meant \"people of\". For example, the town \"Hastings\" in East Sussex derives from the fact a man named \"Haesta\" set up the town. People who came from these towns often took these names as surnames, and their descendants bear them even if they are not from those places.\n\nA similar thing obviously happened in Germany, where ethnic Germans or Ashkenazi Jews took place names as surnames. For example, the surname \"Waldorf\" is built of the preffix \"Wald-\" (meaning forest) and the suffix \"-dorf\" meaning village. Both words are comprehensible to a German speaker today. In contrast, the modern English word \"village\" is from the Latin \"villa\" (meaning country house) via Old French, brought into the English language by the Normans. Therefore, a modern English speaker would not recognise \"thorpe\" or \"by\" to mean town or village, and may just be able to make a connection between town and \"ton\". In contrast, Scandinavians would recognise these suffixes, as a Swedish speaker would use \"by\" to mean village, and a Danish or Norwegian speaker would use \"by\" to mean town.\n\nAs for why \"Berg\" and \"Stein\" are more common topographical surnames in Germany and Scandinavia than in the British Isles may be due to the topography of these countries. I am no expert, but on the whole, I think England (where a lot of these surnames originate) is a lot flatter and less wooded than Scandinavia or Germany. In the areas of the UK where there are more hills and woods, particularly Wales and Scotland, there seems to be a preference for making surnames out of clan names and family connections. In Scotland, this was due to the long-entrenched clan system which didn't end until the 18th century (see the many Scottish surnames beginning with \"Mc\" or \"Mac\"). According to UCL, the top 11 surnames in Wales are all derived from mens first names - Jones (John), Williams, Davies (David), Evans (Ifan), Thomas, Roberts, Lewis, Griffiths (Gruffydd), and Edwards. You have to wait until number 12 to get to \"Smith\" (an occupational surname) and then 13 to 18 are all again linked to mens names. This is probably due to the fact that in Welsh speaking areas, using patronymics was more common than surnames even into the modern period. For example, if you were a Welsh man named Evan and your father was called Rhys, you would be \"Evan ap Rhys\". Slowly overtime, this could merge into a surname. For example, the surname \"Price\" is thought to derive from a shortening of \"ap Rhys\". A famous example would be the Tudor royal family which gave us Henry VIII and Elizabeth I - the first Tudor to take the surname was Henry VIII's great-grandfather Owen Tudor (d. 1461), whose father was called \"Maredudd\" (pronounced Meredith), and whose grandfather was \"Tudur\". Therefore, on moving in English circles, Owen ap Maredudd ap Tudur became \"Owen Tudor\".\n\n**tl;dr** There are topographical suffixes in Anglo surnames, but they tend to be hidden because of the way English has changed. Germany and Scandinavia is more hilly and forested than the British Isles, hence the frequency of \"wald\" and \"berg\". Hilly/woody places in the UK favoured patronymics or clans name to topographical surnames.",
"They are toponymic names (ger. Herkunftsnamen), usually hailing back to the names of medieval German nobility that were following the pattern of \\[first name - from - name of the holdings\\], not unlike English medieval names like William of Ockham (a reductionist principle named after him is a good example of the process, as logically, it should have been called 'William's Razor', as 'Ockham' is the name of place he came from, not his actual surname). In high middle ages (around 12th-13th century) such names were also adopted by the burghers who slowly rose to prominence with the development of urban patricians and burgeoning merchant class. \n\nThe particle '-berg' is very popular, as it literally means 'mountain' but may also come from the bastardised 'burg' ('fort', later 'city', cf. 'tun'/'town'). It has indeed been popular since at least High Middle Ages, as among 31 Land Masters of Prussia in Teutonic Order who held the position between 1230 and 1324, names of 11 end with '-berg' or '-burg' (these are names of their holdings rather than surnames, mind) giving a good insight into the prevalence of such place names. Other popular toponymical particles of the German names also refer to the landmarks and natural phenomena such as '-stein' (stone), '-furt' (ford), '-bach' (stream), '-heim' (home) or '-t(h)al' (vale). not unlike their English counterparts.\n\nEvery language and culture has its own rules of onomastics and toponymy, so the prevalence of particular names may differ, especially given that unlike Germany, British Isles were inhabited people speaking languages that belong to at least three different families (Celtic, Germanic and Romance) and thus they show greater versatility with prevalence of Latin and Celtic words being the most distinct difference. The numerous migration could lead to very complex changes in onomastics, with York being a nice example. Its earliest name was Brythonic 'Eburos' that was slightly changed into 'Eburacum' by Romans in 1st century BC, what was against changed possibly via popular etymology into 'Eoforwic' (lit. boar place) by Anglo-Saxons somewhere in 5th century AD and then into similary sounding by having a different meaning 'Hjorvik' (Hjor's haven) by Danes and sometime around 11th century was morphed to 'Jork' and finally took graphical form or modern 'York'.\n\nThe explanation above is quite relevant to the original question, because, while it is not too intuitive due to language diversity in the history of Britain, the toponymous personal names derived from the word 'mountain' are not that rare in English, but simply are derived from the language different than the one used nowadays. For example, there are many names containing the part '-ton' that is derived from Old English 'tun' meaning 'hill' or 'mountain' (Gladstone, Clifton, Norton, Middleton, Clinton, Ashton, Dayton, Leighton, Barton, Ea(s)ton, Brixton, Pinkerton, Harrington, Hampton and many more). The particle '-ton' may also be a hybridisation of 'stone', thus making the name 'Silverton' a direct counterpart to German 'Silberberg' or 'Silberstein'.\n\nNow, the Jewish (not necessarily Yiddish) names have a slightly different history. In late 18th/early 19th century Jews inhabiting Prussia, Austria, Russia and the Polish territory claimed by those two countries during partitions between 1772 and 1795 were forced by the absolutist administration to adopt regular hereditary surnames. The latter territories are quite important, as Poland had the highest number of Jews both as percentage and total number of all countries and because many of the Polish Jews were fresh immigrants who moved there due to persecutions and as representatives of different cultural subset, they have not integrated as well as the Jews living in Poland for centuries and thus were less prone to adopt local surnames or proto-surnames in the form of nicknames, popular among commoners, including Polish Jews and thus retaining their traditional, patronymical naming conventions. Aforementioned laws, issued in 1785 and 1787 in Austria, in 1796 in Prussia and in 1804 in Russia (also repeated in 1835 and 1844) mandated that all Jews should adopt a regular surname within two years time. Many of the names were being invented according to the general rules of German onomastics rather than selected from the list of existing names, and with toponymical surnames deemed to be the most natural and neutral, vast number of such surnames follow the pattern mentioned in the original question. According to S. Kurzweil, author of the short historical summary of Jewish naming convention in Poland published in Warsaw Jewish community magazine in 1937, local officials were not above accepting bribes for a nicely sounding name, derived from flowers or precious materials, initially proposing less desirable names derived from animals or common objects. On a curious note, the office responsible for creation and assignation of the surnames in Warsaw (then belonging to Prussia) was held in the years 1803-1806 by a writer and jurist E.T.A. Hoffman who is credited with inventing names that despite following common patterns where at this moment either nonexistent or extremely rare (Rosenbaum, Goldblum, Silberstein). Given the sheer number of Jews forced to change names, it is no wonder that the prevalence of the German-sounding names in Central Europe rapidly increased in the early decades of 19th century. Subsequent emigration of ethnic Germans and Central European Jews to America further increased popularity of such names worldwide."
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fim2kf | why do white fabrics or transparent silicones seem to “yellow” out of nowhere? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/fim2kf/eli5_why_do_white_fabrics_or_transparent/ | {
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"There are two primary reasons, the clothes absorb dirt and oil from you body and they build up over time, and some detergents don't wash out completely and they absorb dirt and oil. Even 100% cotton t-shirts that can be bleached are going to turn yellow because it's impossible to get all the dirt, there's eventually enough in the fabric to change the color.\n\nWashing white clothes and sheets immediately helps, the oils don't soak into the fabric and set, but it's pretty difficult to keep things white if you use them regularly. Drying outside can help somewhat, the sun bleaches clothing. Dryers, even on low, can cause stains to set in fabric, and the remove some of the fabric each time as lint. A shirt is going to have a tiny bit less material each time, and the dirt is going to be more concentrated.\n\nAny sort of caulk tends to yellow because even after drying it's somewhat sticky and the surface holds onto dirt."
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10j6iu | Do plants need "rest"? | Can plants go through photosynthesis nonstop without a break? Or do they need some time to slow down?
EDIT: Let me rephrase, if a plant is given light 24/7, watered when needed, and new/changed soil when required, would it work itself to death? | askscience | http://www.reddit.com/r/askscience/comments/10j6iu/do_plants_need_rest/ | {
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"In general, most plants have increased photosynthesis rates during the day and decreased or no photosynthesis during the nights. This is simply because there is light during the day which is necessary for the light dependent reactions of photosynthesis (the light independent reactions of photosynthesis do not require light but occur alongside the light dependent reactions). Stoma pores also open during the day and close during the night for gas exchange (photosynthesis needs carbon dioxide and releases oxygen).\n\nOne interesting exception to this is CAM plants. CAM is a specialized type of photosynthesis that exists in plants from extremely hot, dry, or windy climates. CAM photosynthesis has adapted to these particular conditions. Adaptations include the stomata opening during the night instead of the day for gas exchange. This is because hot, dry, or windy conditions cause evaporation of water from leaves or other plant material to occur faster. So for example, cacti and other CAM plants store carbon dioxide in the form of an organic acid during the night, and release the carbon dioxide for use in photosynthesis during the day when there is light.",
"This isn't 100% related, but: chloroplasts (the light capturing organelles that contain chlorophyll) relocate themselves according to light intensity. During the peak sunlight hours, a plant may need to protect its chloroplasts from damage, so the organelles will line up behind one another and \"hide\" from the sun. The opposite response is also true for low-light conditions. So when there is very little light, plants will optimize their chloroplast arrangement for maximum light capture... meaning that they will flock to the surface and increase their light capturing area.\n\nCheck out [this](_URL_0_) link for a diagram."
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"http://books.google.com/books?id=aQR__H2XBnUC&pg=PA236&lpg=PA236&dq=chloroplasts+relocates+according+to+light+intensity&source=bl&ots=OXZEPB9pwc&sig=Ejhi0pyuOzo1cSm3VwJcdGRMIyM&hl=en&sa=X&ei=z8VjUNa4AYa0igL-k4DoBQ&ved=0CCcQ6AEwAQ#v=onepage&q=chloroplasts%20re... | |
whabs | On a rainy day, how fast would you have to be moving in order to get killed by raindrops? | askscience | http://www.reddit.com/r/askscience/comments/whabs/on_a_rainy_day_how_fast_would_you_have_to_be/ | {
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"A [water-jet disruptor](_URL_0_) that is normally used to help disarm bombs uses water at 360 m/sec.\n\nGiven their ability to lance through certain products, I would hazard an estimate that one would be capable of breaching the thoracic cavity and penetrating the heart, causing enough injury (either through physical damage or production of emboli) to cause death.\n\nHow that might correlate into size of raindrop versus a small jet stream- I don't know."
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6cvmnp | what happens to the human body under extreme pressure? | So I really don't know. What would happen to a body (dead) under high pressure? Like the Mariana Trench pressure. I have seen burials at sea and most people think fish food, but what happens to the body at extream depths going down. Let's say for argument sake 20 kg of chains tied to the feet? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6cvmnp/eli5_what_happens_to_the_human_body_under_extreme/ | {
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"Past a certain depth, the pressure exerted on the body is greater than the bodies ability to maintain structural integrity. Soft tissues would compress and rupture, bones would break and your body would basically fall apart.\n\nTL;DR: Squish."
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5clmfp | Was the rise of fascism in pre-WW2 Germany largely split between rural supporters and urban opposers, as we see in the US today? Or was it along some other demographic or economic/cultural line? | As it becomes clear how much the US is culturally divided between the rural and urban populations, I wonder if this dynamic was at play in pre-Nazi Germany? Thanks! | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/5clmfp/was_the_rise_of_fascism_in_preww2_germany_largely/ | {
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"I think you mean the rise of national-socialism, not so much of fascism in pre-war Germany, but putting that aside for a moment;\n\n\n\n\nThe first electoral breakthroughs enjoyed by the Nazis came in Protestant rural areas, such as Schleswig-Holstein and Lower Saxony, where peasant voters had earlier registered discontent with their traditional representatives from the DNVP (German National People's Party or Nationalists). In fact this was more than a little ironical, as Nazi propaganda had initially targeted urban workers, and the Nazi agrarian programme developed in 1928 was only in response to the expansion of support in these areas. Subsequently the constituencies with the highest proportion of Nazi voters were in Protestant farming communities; and by 1932 the stream of peasant deserters to Hitler's party had become a torrent. Many rural labourers, often influenced by the estate managers, voted for the NSDAP in July 1932. Indeed, the scale of agrarian support for the party in that election suggests the Nazis were able not only to win the support of peasants and rural labourers but also that of some large landowners.\n\n\n\nVoters in large urban centres were less susceptible to Nazi electoral propaganda. In July 1932, the NSDAP's support in the Grosstadte (over 100,000 inhabitants) was 10 per cent lower than the national average. Though there had been a significant increase in support among German workers between 1930 and 1932, this was less marked in the larger cities; and nearly half the working-class newcomers to the party ranks between 1925 and 1932 came from villages of under 5,000 inhabitants. And proportionally few of the working-class storm-troopers of the SA came from the big cities.\n\n\n\nIn part this pattern reflects the point that Hitler and his followers were able to build support in small provincial towns and rural areas more effectively than in the large cities precisely because political mobilisation was less developed in the provinces and the countryside. SPD (Social Democrat) and KPD (Communist) support had been and was still concentrated in the big cities, and the electoral drive of the NSDAP encountered powerful traditions and loyalties there. This urban/rural divide was reinforced by another factor: the Nazis were relatively unsuccessful in gaining the electoral support of the unemployed, who were also concentrated in Germany's largest cities.\n\nSource/much more : [Dick Geary, Professor of Modern History at the University of Nottingham.](_URL_0_)\n\n"
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5iczeq | how are cpus made? | Say there's a brand new cpu out on the market. How does it go from being an idea, to a finished, working cpu? Also what makes it superior to other cpus; new competition and older models? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5iczeq/eli5how_are_cpus_made/ | {
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"That's lots of questions really so....\n\nCPUs are designed in a variety of ways, but the complexity of working out the specifics is, I believe, down to a computer program. The designers tell team program what they want on the chip, and the program works out how the circuitry needs to be laid out. I may be wrong about this bit.\n\nThe design gets printed out pretty big so that the detail can all be captured properly, then a process called lithography uses light to miniaturise it while keeping all of that detail intact. The light imprints the picture onto the silicon, which allows for the small size of the package which we use.\n\nThere's a number of ways one CPU can be superior. One is the \"length\" of the lithography process. This is a measure of how small and close together the individual bits of circuitry on the chip can be. The smaller and closer they can be, the faster the circuitry can operate - although heat dissipation is an issue.\nThe other major way one could be superior is the circuit design. Optimisations of the way in which data gets processed can make a difference to either the speed, or the efficiency.\n\nSince we're struggling to keep making them smaller, optimisations of the circuitry is a major battle between manufacturers.\n\nEDIT: \"e\"s aren't always good",
"There aren't really 'ideas', excepting for new chips. A new processing method is discovered, and the potential for denser, faster chips arrives, and so they put more onto the chip.\n\nThere are a few factors in speed:\n\n* Pitch size: the minimum distance between elements on the CPU. Smaller gaps, faster signal transfer, lower power consumption, etc. This is the nm 'process' you see advertised on new chip lines.\n\n* Gate count: influenced heavily by pitch size and chip size, the number of elements on the chip. More elements, more things can be done at once -- larger memory, specialized processing pathways, etc.\n\n* Layout: inline with pitch size, the distance between features on the board influence how fast a signal can get there.\n\n* Gate configuration: finally, the gates on the board are laid out to perform logical operations. Certain gate configurations are better than others. New solutions aren't too common, but they do show up from time to time. Now, I suppose multicore processors might fall under this section, so it's not to be underestimated.\n\nThese days, most of chip design is done by machine. They can solve the layout issues [synchronizing path lengths, minimizing travel time for statistically predictable operations, etc.] much faster than we can, so we generally only tell the machine what structures we want, how many we want and how much space is there.\n\nThey are better because they are faster -- unfortunately, there really isn't much to this one. Sometimes they consume less power for their performance, some times it's just more performance.",
"Here are some videos about the fabrication process: \n* _URL_1_ \n* _URL_0_ \n* _URL_2_",
"Other users have explained it from a circuitry level, but I will give my two cents of it from an architectural level.\n\nGenerally speaking, an architecture is for executing basic instructions in assembly code (the code that is in binary that runs in your computer. Most people write code that is easier to read nowadays with other programming languages). The architecture is basically a set of \"black boxes\" which do things with this assembly code. A very simple example is a black box that does addition with two binary numbers. Of course, there are more of these black boxes which are used to determine when a certain instruction should execute, what data do they write, etc. \n\nOnce this \"black box\" architecture has been designed to execute assembly code, it should be coded in a Hardware Design Language (HDL) to prove that it can actually work on a real chip. The architects will test their code on a FPGA (field programmable gate array, basically a multi-purpose computer chip). If it's a good, working product, then the design is sent to people who design chips at the transistor level (the lowest level of computing) who will then use a nano-fabricator to build the CPU that is put into your computer.\n\nWhat makes other models better depends on a multitude of things: Smaller transistors, larger amounts of memory, etc. Some more things that aren't really easy to ELI5 are:\n\n* Faster, more elaborate branch predictors\n* Different hierarchies of caches (or just faster cache memory) with fewer cache misses (this lowers memory usage time)\n* Grab instructions from memory that you know will be executed early (prefetching)\n* Scalability (Copy your CPU 2, 4, or 8 times and make them all do a portion of the work. Multi-core processors).",
"Also: why aren't they bigger?",
"I work in the semiconductor industry and my job is to develop new materials that go into computer memory. We use a lot of the similar processes as cpu development, so I may be able to help out.\n\n\nIt takes a lot of people (over 100, for sure) to get something from design, to testing, to final product. \n\n\nThere's a group that looks into what consumers are interested in, and then push those specs to an integration team. This team is broken up into individuals who are each responsible for certain aspects of the device. Their area of focus may involve people from all over the R & D unit, so they'd talk to people who focus on thin film depositions, people who focus on etching, and people who focus on photolithograpy. Then those people would form a team and try to make that level of the whole piece work. Then, we take our working piece and try it in the overall device and see how well it works with everyone else's. \n\n\nThe easiest development work comes from building on previous technology. Like we can make devices smaller because we've optimized our manufacturing tools or our designs. It's a bit harder when there's a new technology, because sometimes the equipment we need to do our work doesn't exist yet, and we need to work with tool vendors to design better tools. \n\n\nTimeline from idea to product? Not all of them make it, but it can take a number of years for a new technology. Also, you can prove a new technology works, but getting it to work while also being cheap enough to manufacture is a whole other challenge. ",
"Oooh, I kinda know this one from college.\n\n1. Use some software (used to be Xilinx in my day) to bundle transistors into little packages (crash course - if you put transistors together in a certain way you can make little logic circuits that can add numbers together and junk.\n\n2. Get the packages of transistors and spam them like *crazy*.\n\n3. Somehow connect them together so it form memory, logic units, buses, registers and what have you.\n\n4. Test the design in slow motion by having the computer simulate the circuit actually working. So, pretend there was electricity going through it.\n\n5. Print out the design, except instead of using a printer and some ink, use an X-ray machine which has resolution that makes the Hubble telescope blush, is the size of a bus (probably) and costs like a billion dollars (maybe). Also don't print out one, print out like 500 in a grid. Don't use paper, user silicon.\n\n6. Stick the whole thing in some acid (not sure about this one)\n\n6. Cut it into bits and put each tiny chip into its housing, which is just some ceramic to help heat dissipation plus the gold pins that go in the computer.\n\n7. Basically sell each crummy thing you made for like 1 cent for $500.\n\nAny questions?",
"The idea for the CPU comes from the things people need to do on the computer. This is a super trivial example, but imagine that early CPUs only did simple arithmetic: addition, subtraction, multiplication, etc. If you need to calculate an exponent, you'd have to multiply in a software loop. The manufacturer would see that exponents are slow and add a specific circuit into the CPU that can calculate it much faster. You could say that the CPU has an ADD instruction, DIVIDE instruction, etc. and that for each instruction there is a bit of logic circuitry that performs that instruction. You can speed up exponents by adding a EXP instruction circuit. In reality it is more nuanced than just adding a circuit for each instruction, but that is the gist. The [SSE instructions](_URL_0_) are an example of how modern CPUs have evolved to improve things like multimedia playback.\n\nConstructing a physical CPU is a process with thousands of steps. The chip is like a layer cake made of different kinds of silicon (N-doped, P-doped, etc.) and metal. The specific materials are beyond an ELI5 explanation. Suffice to say, it is created layer by layer using chemicals to deposit silicon and metal in a very specific pattern. In fact, this process is so difficult that many of the chips produced have defects. This leads to the CPU designs being modular, so that defective parts can be turned off. Many CPUs in a product family are actually the same chip, but the ones with more defects have parts turned off and sold as a lower model.",
"There are a LOT of steps to making a CPU. I worked in a fab (semiconductor fabrication plant) that made processors for phones, which are much simpler, and those still take a long time beginning to end.\n\nThe production part is what I'm familiar with, I never designed CPUs. Once the design makes it to the fab and the fab has made its test runs to work out any problems in creating that design in a production volume, the production stream has several different types of steps that are repeated in the appropriate order to make the processor work. The steps (in no particular order) are\n\nImplanting ions into the wafer to make the silicon into a p-type or n-type semiconductor material to create the gates\n\nDiffusion grows the crystals from the p and n doped substrate\n\nThin films are deposited onto the surface of the wafers to make either metal layers for interconnecting wiring or oxide layers to insulate between these metal layers\n\nPhotolithography applies a layer of photoresistive coating to the wafer, which can be fixed in place by shining a wavelength of intense light onto it. The light shines through a reticle , which is like a really big version of the pattern of light that will go onto the chip. The light shines through and only the pattern is fixed in the photoresistive coating (think of this stuff as a layer of paint). The rest can be washed off. Then a layer of thin film can be put on, or etched off \n\nEtching cuts out parts of the thin films that aren't wanted. you can't lay a wire that size onto a microchip, so you have to put a thin layer (so thin, the thickness is measured in angstroms) of whatever substance you want (metal, oxide, etc) onto the wafer, then the photolithography and etching steps can remove everything but the wiring pattern.\n\nChemical mechanical planarization is a fancy term for basically polishing the surface layer of the wafer. makes it smooth and level so the next layers can go on properly.\n\nThe thicknesses of these layers are mind-bogglingly small. They're measured in angstroms and at least to me, moving at a mass production scale while achieving something that precise is pretty amazing. My background is metals, (specific part of thin films) so I really can't go into detail about the rest of the process",
"This is one thing that cannot be eli5. There is a ton of things that go into making a CPU. From design to fabrication, the process is extremely elaborate. You'd have to ask a more specific question. As a 4th year electrical engineer, I'm STILL learning what goes into what you asked if that is any indication.",
"I work at Infineon, it's a semiconductor fabrication plant, I basically operate a laser/robotic track system that coats a silicon wafer (a 6-12 inch diameter disk) in a chemical and puts a pattern on it for further processing! Ama if you're curious, it's some interesting technology in a NASA quality clean room !",
"In order to understand how a CPU is made, we need to look at how really any [digital circuit](_URL_2_) is made into a [silicon wafer](_URL_4_) to be placed onto a [printed circuit board](_URL_0_) or even just a \"black plastic box with exposed pins\" ([integrated circuit](_URL_1_)) as this is how most digital circuits appear to us by the time we interact with them.\n\nIf you follow the link attached to \"digital circuit\" you'll see shapes you may or may not be familiar with, these are called logic gates. \n\nA digital circuit takes input signals and produces output signals, on a conventional CPU with hundreds of gold pins sticking out of the bottom the only way to know which pin provides which signal is to read the documentation provided by the manufacturer, something only those who will be designing motherboards for these processors would do.\n\nThe specifics of what the CPU does doesn't really matter to answer this question, but it's important to think about the CPU as a device that, based on certain inputs, where an input is either ON or OFF and cannot hold any other value, needs to provide predictable output signals that get routed to other things on your motherboard like your memory (RAM), your PCI bus that may contain a graphics card, sound chips, the BIOS chip, SATA devices and dozens of other peripherals that we expect to work 100% of the time.\n\nWith this in mind, a modern day CPU is clearly a product of decades of refined methodology about how computers should be designed to interact with many different components at once, but perhaps more impressive than that is the advanced manufacturing that allows designing a new CPU to be done in (roughly) the following steps:\n\n1. HDL design and design verification. HDL stands for Hardware Description Language; new digital circuits actually can be written in code and tested using simulation software such as Modelsim or Quartus. Verilog is an example of a commonly used Hardware Description Language.\n\n2. Synthesis, Netlist Generation and Post-Synthesis Verification. The issue with an HDL design is that it's often far more abstracted than discrete logic gates. A synthesis tool is needed to turn the HDL code into a massive list of pure logic gates and simple components, this list is still HDL code and therefore can be simulated using the same simulation software as the original design. The post-synthesis netlist will be tested to make sure timings are met (if you know much about electronics/electricity in general, parasitic capacitances on wires can be an absolute nightmare to deal with at these small scales!). It has taken a long time to create software that accurately portrays how a physical circuit will behave, so it's crucial that the engineers provide the software with the correct information (i.e. what kind of transistor is going to be used, what should be the delays for each logic gate) so that in the event that the device is manufactured, it actually works as it did in development.\n\n3. Device Layout. Now that we have a list of all of the components that are needed for this design, we need to physically lay them out so that it can be manufactured. This means that we will need to turn those logic gate symbols into actual blocks of transistors, and connect these blocks together in the same way that they are virtually connected in software. Let's say we have a highly modular design, CPU cores are module A, and there are four types of caches B, C, D, and E. Let's say this is a new i7 processor and there are 8 module A's. Maybe each core gets its own B cache, but all of the cores share caches C, D, and E. As you may be starting to gather, routing all of these modules together is certainly non-trivial and needing to create long wires to connect things can actually throw off the timings and render the design useless! \n\n4. Manufacturing. This is where my knowledge of making CPUs comes to an end. As far as I know, the physical layout can be manufactured through a combination of exposing certain wavelengths (think laser-etching) of light to refined-silicon ingots that have been sliced extremely thin. The exposed areas can then be exposed to a chemical so that the material is removed and then certain areas of the silicon are \"[doped](_URL_3_)\" with phosphorus/boron (many others) to be slightly more positive or negative, as silicon as an element has 4 valence electrons which can be considered electrically neutral. This concept is the basis of how any semiconductor-based circuit functions.\n\nThis is as much as I know as an undergraduate (5 semesters) Computer Engineering student.\n\n An interesting anecdote: normally a company like Intel will try to make as many of the best processors they can, but due to small imperfections in the manufacturing process not all wafers perform similarly, the ones that don't perform as well just have the dodgy cores disabled and get sold as i3s and i5s!\n\nEDIT: Thanks a lot for the gold, this is my first noteworthy comment. I had to update the image for \"digital circuit\" with something new as the first one died (if anyone is even still around to read this).\n\nOne thing I'd like to mention to anyone who sees this update is to read some of the comment replies, a few individuals have offered great supplementary information to what I have provided. Also, I realize this answer makes an assumption that the reader knows what role a CPU plays in a computer, if you know your computer has a CPU but aren't sure what exactly it does, think of it as the brain, where, a brain is processing inputs and making decisions on what outputs to send, just like a human brain!\n\nTo learn more about computers it can often require a highly intimate conversation that's catered to what each of us might already know. I hope this has inspired some of you to learn more! (:",
"You start with sand.\nReact it with HCL to get a liquid. Strain and vaporize it to get rid of impurities. Flow the vapor through heated graphite to get deposits of elemental silicon.\n\nOnce you get enough elemental silicon, heat it up until its a liquid. Difuse boron gas through the mixture to make initial doping levels. Take a silicon crystal that has the right orientation and dip it into the mixture. Rotate and pull it out. As the silicon around the crystal cools, it matches the orientation of the crystal and forms a bigger crystal.\n\nThe rotations cause the cooling silicon to form into a collumn as it is pulled upwards. Eventually you end up with a REALLY BIG COLLUMN with a point on one end.\n\nCut your collumn into very thin circles called wafers. (Right now, ours are p-type because of the boron we put in earlier.) This is where the real magic begins.\n\nThe air will create a resistive coating of oxide around the semiconductor. We will now apply a series of masks on the wafer to make the chip itself.\n\nLets make some mosfets. Heat up the wafers to drive off moisture. Apply a thin layer of compound (photoresist) that reacts when exposed to UV light. Shoot light at it with the right pattern to create some areas where the resist is cured and some where it is not. Dump the wafer in a solution that removes the non-cured photoresist. Push hot vapors of aluminum or manganese toward the cooler wafer. They will only reach areas where the photoresist was removed. This created the n-wells for our p- mosfets.\n\nLet the oxide grow back and deposit a layer of polysilicon to act as our gate insulator for the mosfet. Apply a mask that only covers the gates, and etch away the rest of the oxide with short wave uv light. Now push hot vapors of Boron toward the wafer to create higher concentrations of boron on both sides of the pmos gate.\n\nRepeat the whole Boron thing we just did with aluminum to create npn gates.\n\nPush hot nitrogen toward the wafer, apply the photoresist and etch it away to make insulating boundaries between the p/n regions and the gates.\n\nDeposit metal on to the substrate. Apply photoresist. Etch it away to make conductive metal that goes to the different gates.\n\nTLDR: sand - > purify - > molten SI - > doped molten SI - > giant collumn - > cut into wafer - > apply photoresist - > cure photoresist - > remove uncured photoresist - > etch photoresist - > deposit stuff - > repeat the photoresist stuff a lot\n\nNewer cpu = more detailed photoresist = smaller mosfets = more mosfets that are better ",
"Something else you may be interested in is a small piece of code a professor showed me once. The program creates what i believe is called an \"H-Tree\". Its a simple recursive design that draws a large H and then adds a smaller H at every end point for any number of iterations. See linked example: _URL_0_ What is interesting about this design is that the end/tip of each of the smallest H's is exactly the same distance from the starting point. This can let you transmit power, information, timing signal, etc to X number of nodes at exactly the same time. I'm not sure if it is still the case, but the designed is used for synchronizing the transistors in your cpu. ",
"The entire process is a long arduous one. It takes about 3-4 years (if not longer) before a chip comes to market. Most chips these days are refinement, it still take a few years before it hits the market though. \n\nThe idea needs to be \"written down\". Designers no longer create/design chips by circuit layout. Instead, they use high level language, called hardware descriptor language (eg: Verilog, VHDL, and SystemVerilog). \n\nTo verify that the HDL is doing what you intend, there are two types of validation. Simulation and Functional Verification. At early stage, you simulate your HDL and validate the output. (Tools from Mentor, Synopsys and Cadence)\n\nOnce you are happy, you go through the actual process of converting your HDL into the final silicon wafer, using tools mainly from Synopsys or Cadence.\n\nHDL is passed through a compiler that optimize the HDL and produce logic gates. (Designers will use formal verification to verify that the logic gates matches the RTL).\n\nThe logic gates are then given to a placement and routing tool that will assign location to gates and route the \"wires\", i.e. connections between the gates. (Designers will use formal verification gain to verify that the optimization during placement and routing hasn't introduced a logical bug).\n\nThen the clocks of the circuit are optimized and routed. (Designers will validate that the timing of the circuit will match the specifications)\n\nIt then goes though layout tools that does the mask creation.\n\nFinally given to the foundry to actually manufacture the chips.\n\n",
"If I'm talking to a typical 5 year old I'd start off saying. Do you know how red stone works in Minecraft to let you control stuff?\nWell real CPUs pretty much work the same way except we make them really small. \n\n\nHow do we do that? We start off by drawing it regular size. Then we take that picture and print it out on a special printer that is made to print out things as small as it possibly can be printed.\n\n\nThen, since that still isn't small enough, we take that super small drawing and shine it through a magnifying glass only backward so that it makes an even smaller picture.\n\n\nThen we shine the light from that picture on a computer chip covered with a special film that turns hard wherever parts of the picture hits it. \n\n\nAfter some parts of that film turn hard we use a special soap to wash away just the soft parts and then fill in the gaps with Red stone.\n\n\nWe repeat this process a few times building up one layer after another until we have the machine we want.\n\n\n\n",
"1. There are different types of CPUs that target specific markets. Eg servers, mobile, laptops etc. So when a company decides to build a CPU, they design it for a market and they design it with the idiosyncrasies of the market in mind. For mobile primary concern would be low power, for super computers it would be flops etc .. (Technically speaking mobiles dont have \"cpus\" in the traditional sense, they have SoCs or System on a Chip which is an another beast, but for this discussion let's just assume cpu)\n\n2. Ok now that we know which market you are targeting, you know what new features you can add to improve the performance. So your Biz Dev + strategy team and product team come up with a list of features and performance targets that can be achieved. This list is your product definition. You now know what to build. (This depends on the company culture. Some companies are bottom-up, which means product and engineering teams tell management what they can build and it is biz dev , sales' job to go market and sell it. Some companies are top-down. Manangement + biz dev tells the engineering team, go build this and hands them a list. I'm being very simplistic here. All cpu companies also have an R & D team which is always trying to improve stuff and try new things by experimenting. Some of the experiments fail, the ones which don't, get added to the new product. Some companies also have Research teams that do proper research and publish papers in top tier journals.)\n\n3. OK now we have a list and we can start designing. A cpu consists of thousands of parts and components. Each part will have its dedicated team of engineers and designers and testers. Eg:- Just to design and test and implement the clock circuitry you'll have a 60-70 person team. Ok but how are they designed you ask ? You first implement the logic of each part in software and simulate it. You test for functional correctness. Then you design it in SystemC or SystemVerilog or a bunch of other shit. By design, i mean build. Basically all these are circuits and you're building circuits. So every team does this. Slowly, you have a bunch and circuits and you tack them on together and you end up with a whole design for the cpu. Now you give it to a Layout team. This team redesigns the circuit so that the _physical_ components of the cpu follow certain rules and don't take up unnecessary space. So now you have your circuit diagram. At this point, this has been thoroughly tested and various levels and many engineers have had sleepless nights because some new addition broke tests that passed. Remember they are used in safety critical conditions, so they are tested thoroughly. But, only the logic has been tested because we still don't have a physical product in our hands.\n\n3. There are two types of cpu companies, fabless and ones with a fab. A fab is a factory that takes in design diagrams from customers and produces physical chips. Intel have their own fab, AMD doesn't, and have to go use the services of fabs like TSMC, Global Foundries. So now that you have your circuit diagram, you simply email or ftp it to them and have your account manager talk to their account manager to figure out the amount, time, quality etc etc. \n\n4. Then one day you get back the first batch of the new chips. This is the most crucial part. You have to figure out ASAP if everything is alright and all the tests pass again and make sure the fab didn't fuck it up or even if you missed something. If you catch something now you can tell the fab and they can fix it. You don't want a situation where you figure out a harware bug after a million chips have been produced. Too big of an investment. So more engineers have sleepless nights to make sure everything is alright. If you find anything off you let the fab know and send them new designs. By the first two weeks you'll know if it needs a rework. \n\n5. Ok now you have a working product. While we did all this, the marketing team and sales team have figured out ways to sell this thing. They have marketing campaigns and advertisements and conferences and conventions. The sales team finds partners and leads and builds deals with the customers etc .. like Best buy or HP or Lenovo etc ..\n\nHopefully this has answered your question. I've tried to keep it very simple. There is no 'eureka' idea moment. Companies have road maps and they know what they are going to build for the next few years .. ie Intel and AMD know what chip is going to come out in 2019 .. They have a plan and stick to it.\nFor superiority, you have industry standard metrics that measure performance and companies try to beat the competition by one upping + saving their customers money. ",
"For anyone who is seriously interested in knowing how a computer works, I can highly recommend a course offered through Coursera called \"[NAND to Tetris](_URL_0_)\". They take you all the way from learning about logic gates, to memory structures, arithmetic logic units and finally, the entire CPU. You literally build a computer yourself. Not physically of course, but simulated. \n\nEdit: This is highly rewarding course. I am a IT professional and did this purely for fun. And it was. ",
"I used to work at a major CPU manufacturer. Very possible that something I worked on is sitting on your desk. (These are my own views not the views of any employer.)\n\nDesign/manufacturing CPUs at scale is really a very, very, very large machine. If we are talking about a major chip, there are tens of thousands of people, maybe a hundred thousand, in different places all over the world that are involved at some stage of the process. \n\nTo give you some sense of the scale of it, in addition to the obvious things like design and actually running a factory, there are a lot of other pieces of the puzzle. Example, the manufacturing tolerances of CPUs are so tiny (on a molecular level, really) that basically something goes wrong with every part. So, as a stage in the assembly line, each chip is tested, and a decision is made about how to sell it (e.g. 1 of 4 cores doesn't work – sell as a 3-core chip). Just testing CPUs as they come off the assembly line is a whole business unto itself. To get some idea of the scope [see one of the machines in action](_URL_1_). A major manufacturer would have many *distinct* test stages in their pipeline, so what goes in as one part may come out as 50+ after sorting through dozens of machines. And that is just the testing piece of the puzzle.\n\nBut to answer the question you asked:\n\n > How does it go from being an idea, to a finished, working cpu?\n\nGenerally, somebody sees a market opportunity based on some combination of the current product and projections about what the competitive landscape will be 6 months from now. e.g., you notice that a lot of people are asking for 4-core chips, you wonder if the trend would continue for 6 cores but nobody knows. So you go to the engineering team, one third of them splinter off into some [crazy-ass 8-core moonshot that requires years of R & D](_URL_0_), another third of them try to squeeze 2 cores into the free space in the next die shrink and decrease the error rate so they won't be disabled on the assembly line, and one third of them works on removing silicon that \"nobody uses\" and emulating in software to free up space. One of those projects will fail, one will basically work but can't be manufactured reliably and so it becomes a specialist part until somebody figures out how to do it reliably, and one of them becomes a mass-market part. And that's basically how new CPUs are made.\n\nI guess what I'm trying to say is, it is a lot of iterating on existing designs. A major design company might have somewhere between 1-3 \"master\" designs and be working on 20 different \"projects\" that tweak some piece of the master design that individually are in some stage between whiteboard and manufacturing. But nobody tries to design a chip from scratch, that's too hard. It is all about how to lay out some section of the master design more efficiently etc.\n\n > what makes it superior to other cpus; new competition and older models?\n\nWell in addition to e.g. specs, there are a lot of things consumers don't normally think about. The primary customer for CPUs are OEMs (e.g. Dell, Apple) that are buying 10s of millions of units. So \"superior to other CPUs\" means in practice superior *for Dell*, so things like a low failure rate, diagnostic tools, good documentation, thermal limits / clearance are really important and those may not be the primary purchase drivers for the enthusiast market.\n\nThere are also a lot of \"specialist\" markets, for example \"extreme conditions\" (think fire/police/military/space) or special workloads (say you run a popular cloud-computing service and need a CPU you can split to 36 tenants) where the difference is somewhere between just testing the chip more thoroughly to adding unique features for the segment. The enthusiast market (e.g. \"Intel Extreme Edition\" \"AMD FX\", ) are really just \"yet another specialist market\" that is sold at retail instead of to OEMs.",
"Basically they take pure silicon and put it in a tanning bed with mask over it and zap it with light. The light burns in the transistors they want. \n\n[This 60's era video produced by Fairchild Semiconductor is instructive](_URL_0_)\n",
"Wow this is a tough one to ELU5, but:\n\n\nA CPU is really a lot of ideas put together in one chip- like a circuit board run through a shrink ray.\n\nLots of people work on improving the inside of the CPU.\n\nThey use light and chemicals to make small circuits.\n\nMost of the time a CPU is considered better if it is a) smaller and b) can run faster without getting too hot.",
"- Have silicon wafer\n\n- Slap coat of stuff onto it\n\n- Cut fancy patterns onto coat of stuff\n\n- Stick layer of metal stuff on top of that\n\n- Cut more fancy patterns\n\n- Slap more stuff on\n\n- Give it coat of stuff that changes under UV light (like when mum sleeps in her sunbed) \n\n- Shine UV light through fancy pattern\n\n- Chop up wafer into chips (do not eat chips)",
"If you want to know how computer is made, this amazing [book](_URL_0_) explains so clearly from scratch in order so you can understand next chapter to the end.\n\nIt explains in scratch from Morse code, to electricity circuit with battery + flashlight, to telegraphy and relays with more advanced electricity circuit, to how numbers are understood in logic sense, to binary digits (0 and 1), to explaining how you can do so much with just binary digits and how barcode works, to logic and switches in algebra and advanced electricity circuits with binary/boolean, to logic gates, more advanced electricity circuits stuff, to bytes and hexes, how memory functions, to automation... ah this is halfway through the book now.\n\nThe way how he writes is very clear, understandable, and everything what he wrote has a meaning for you to be capable to understand what he wrote further in the book.\n\nYou'll know EVERYTHING about electricity and behind-the-scene how computer works, how RAM works, how hard drive works, how CPU works, how GPU works, everything, after you finish this book.",
"Nobody's really gotten into chip manufacturing so I'll get into that a bit. Everything else has been covered.\n\nSilicon is melted down into a vat with some intentional impurities (dopants.) A silicon crystal (a \"seed\") is dipped into the molten silicon and slowly drawn out. As the seed is drawn out, the molten silicon grows the seed into an ingot. The ingot is spun as its drawn out. The process looks something like [this](_URL_2_). The ingot, when finished, is about 3-4 feet long and weighs around 250 kg.\n\nFrom here out, the work is done in clean rooms. One piece of dust can ruin a wafer. The ingot is sliced using diamond-tipped or wire saws into blank wafers. These wafers are buffed and polished to as perfect a surface as possible. If a polished wafer were scaled up to the size of a football field, the height from the highest peak imperfection to the lowest trough imperfection would be a few millimeters.\n\nVarious process are used to essentially 3D print the pieces of the circuit onto the wafer, including:\n\n* photo-lithography: liquid photo-resist is deposited onto the wafer. Light is shined onto the wafer using a template of the design to be imprinted on the current layer (the substrait). Depending on whether positive or negative photolith is being done, either the resist will harden under UV light or will harden without the light. Whatever resist has not cured will be washed away, leaving what is essentially a mould (the \"mask\") of the substrait to be created. [Image](_URL_0_)\n\n* ion beam implantation: ions are blasted at the substrait to dope the Silicon to create P and N-type semiconductor. These can be made next to each other to create transistors (a PNP \"sandwich\" of semiconductor will be called a \"p-type transistor\", similar NPN \"n-type\") these transistors are creatively connected together to create logic gates, which make computers work.\n\n* molecular beam epitaxy and chemical vapor deposition: metals are heated up into a gas and pushed into a vacuum to deposit on the wafer and substrait, creating the \"traces,\" or actual wires inside the chip.\n\n* thermal oxidation: the wafer is heated in an oxygen rich environment to create silicon dioxide, which will insulate the substrait and various traces from touching each other.\n\n* etching: strong, concentrated acid is used to dissolve the cured photo resist and any extra materials that have deposited on it after the substrait has been built. Another insulating material might be deposited over the entire wafer, followed by the wafer being ground and polished until contacts from the initial substrait are visible to make contact with the next layer of substrait. Etching can also be used to essentially \"dig\" into the wafer where resist is not protecting it.\n\nBetween pretty much every step, the wafer is polished and ground in order to make sure the heights of everything are as expected and contact between layers is available where it needs to be. A single wafer for a one layer chip might go through photolith, CVD, etching, more photolith, ion beam implantation, more CVD, more etching, more photolith, thermal oxidation, and more etching. [This](_URL_1_) is all done to create one layer of troughs in the wafer. Imagine doing all these steps for every set of jobs that needs to be done for every layer of the chip.\n\nI definitely missed some stuff, so feel free to add more if anyone knows this stuff better than me. Or ask questions and I'll do my best to answer.\n\n[10 min video showing the above steps with animations](_URL_3_) \n\nOne CPU might be better than another due to several factors. The layout might be more efficient with less heat losses, allowing the clock speed to be increased (which increases heat losses), making the CPU faster, without damaging the components. It might also use a better manufacturing process with tighter tolerances, allowing better design and performance. ",
"I think the best way to understand CPUs might be to start with a painfully simple computer. ENIAC was (arguably) the first real computer. This paper provides the details of how it was created what it was created for. _URL_0_\n\nObviously modern CPUs are much more complicated than ENIAC, but many of the same basic principles are the same. ",
"Computer engineer here. This is how I actually explained it to my 6 year old... \n \nYou know a light switch? Imagine a million of them connected in just the right way to make it do something cool, like watch YouTube, or play games. But a million light switches is too big, so we make them small. So small you barely see them, and a million small ones can fit on your fingernail. \n \nTo answer your questions: \n \nHow does it go from being an idea, to a finished, working cpu? There are thousands of things we want the cpu to do. We split the task up so that each engineer can do one of those thousand things, one at a time. They might need to use a few light switches, maybe even a hundred light switches, just to do one of those things. When they finish making the thousands of little things (using light switches, remember?) they put it all together to make the cpu. \n \nWhat makes it superior to other cpus? You can make it do more things (which require more light switches). You can make it do more things at the same time. You can make the light switches use less electricity. You can make the light switches smaller.",
"I've read some great explanations here, but none at the 5 year old level. Easier said than done, but whatevs.. here goes:\n\nJack and Jill each take turns doing the household chores like laundry. Each time they do it, they leave behind a token to let the other know it's their turn to do a chore the next time. Jack uses blue tokens, so when he finds the laundry basket full, he does the laundry and replaces the blue token with one of Jill's pink ones. Between all of the household chores like laundry, cooking, cleaning, there are a lot of tokens that add up so they decide to do it a different way.\n\nAt first they replaced the use of tokens with a switch that could be up for Jack and down for Jill. This worked out better because they didn't have to deal with all the extra tokens, but then Jill came up with an even better idea of putting all the switches in the same spot and labeling them. \n\nThey soon learned they could talk to each other by adding a few more switches to each task. So for Laundry, Jill could flick an additional switch to let Jack know how soon he needed to do it by. Jack could also let Jill know whether he wanted pizza or pasta for dinner with a new switch in the cooking section.\n\nAs they grew older and they needed to plan more and more, they needed so many switches they couldn't fit in the same spot. Jack found a way to make the switches a lot smaller by using what's called a transistor, and because they were too small to flick by hand, you controlled them with a mouse and a TV screen that showed them all. This was basically a CPU, and it worked great!\n\nOver time, they made the switches smaller and smaller, to the point where you could put as many on one small device as there were people in the world. This made things so easy that eventually the switches could self-regulate themselves, and Jack and Jill knew what they had to do just by reading and occasionally making some changes.\n\nJack and Jill have a great life now, and they soon plan to make a little robot called itsy bitsy that will do all of the chores for them.",
"Rather than describe the whole process, let me explain the biggest quantum leap forward that led to the revolution where average Joe now has CPUs in his pocket.\n\nSo, it's always been possible to create something mechanical that could do logic. You can imagine a machine with two levers, and only if you pulled both levers up (in any order) some mechanical display would change, and then change back if you pulled one or both of the levers back (this is now called an \"AND\" gate). Lotsa ways to do that mechanically, but it was less than 100 years ago that someone finally figured out a way to do this electronically, with transistors.\n\nSweet! We could now build something that could compute stuff without any moving parts. Everyone was stoked to build huge giant power-eating mammoth computers that would like, add up the national debt or something.\n\nThe holy-fucking-shit moment came when someone figured out that the conductive properties of silicon could be altered by shining light on it, and that let you make transistors via a process sort of like developing a photo. Just make a kind of 'negative' of your CPU, shine the outline on some silicon, and you're in business. Now this stuff can be crazy small and mass produced almost like newspapers.\n\nIt's gotten a little more complicated than that, you can see from the other responses. But that whole thing where we figured out the deal with silicon is where the whole world changed.\n",
"I'd like to describe the beginnings of a CPU design in a simple way (\"an idea to finished\"). \n\nTransistors are just 3 terminal switching elements (I'm discussing MOSFETs specifically). One terminal is the gate, and the gate is used to control the switch. Depending on the type of FET (field effect transistor), the gate being on will either open or close the channel (the channel is the path for electricity to go through). For ELI5, don't worry about the names of the other 2 terminals, they are just the start and end of the channel.\n\nSo turns out we can combine FETs that open with FETs that close when the gate is on to make some more complex logic. This is called CMOS logic, and the group of transistors acts in a generic manner we call a logic gate. Logic gates represent certain binary logic such as AND, OR, XOR, NOT and so. Have a look yourself: _URL_1_ I'm sure the truth table section makes some sense to you.\n\nNext level, more advanced combinational logic. What if I want to add some numbers? I can make an [adding circuit](_URL_0_) out of logic gates! I can make other stuff too, like multipliers and even multiplexers that let me connect different wires based on the inputs. This is how most of the logic ends up operating, but we also need memory and stuff that may not be made only of transistors.\n\nThere is a nice advanced answer about how the next level of design works, and honestly, it is kind of complex so I'll leave it.\n\nSo where are the transistors and wires in a modern CPU? They are etched into die of the CPU package. The gold pins go into a plastic PCB and then into the bottom of the die, which is covered in a lid stamped with the model number. You can see in [this image](_URL_2_) that the die is a silvery metal looking thing. That is a piece of silicon with a billion transistors in it, made at a foundry out of a large silicon wafer, which has transistors etched on it using chemicals and light.\n_______________________________________________\nSo, you can see, this is some complex stuff, and there are very few people who have a role in the big picture. Almost everyone working on CPUs fits in only one particular level of their design.",
"We stand on the shoulders of giants. Part of the picture is transistor count. Part is design. Part is the process that is used to translate the design to silicon or another material. (Silicon is used now but that is not needed as a blank) \nIntel was one of the fist to create a modern CPU and a founder of Intel said his rule was to double transistor count every 18 months. This was in the 1970's and is still true.\nWorking idea has always been to improve. Allen Turing gets credit for the first real working digital computer aka a Turing machine, Intel stands on his shoulders. \nThe term there is nothing new under the sun is not false, we basically improve an older invention always.\nIt is not hard to do a plus one to anything older. Now they add cores, even further proof they just add plus 1, or plus 3 or 7 or more.",
"This is ELI5, so I'm going to explain things a little differently.\n\nA CPU is, in a very real sense, an extremely small photo, printed on rock. The process of printing this photo isn't completely different than what we used to do to print film -- make a negative, shine light through it, use various chemicals to make the image stick. We even do things similar to drawing on top of the picture, of course at a much smaller scale.\n\nWhat's special is, when you run electricity through this \"rock photo\", weird things happen. Sometimes the power goes through, sometimes it doesn't. That's because Silicon -- rock -- is a semiconductor. It's not random, there are rules. What we burn onto the rock, decides how the CPU works.\n\nIt's worth noting that there are layers to a chip, sort of like layers to a cake. Photos are flat, but there's a little bit of 3D to CPUs. This is a thing the printing process allows, and is definitely used.\n\nIt's also worth noting that not every photo comes out! So we print many, many photos onto a big surface -- a \"wafer\" -- and then see what actually worked. We do something called \"binning\" too, where the really high quality \"pictures\" sell for more than the stuff that's slightly imperfect. Sometimes we even print extra stuff onto the chip, so that imperfections can just be skipped over.\n\nAt this point, heat is the major factor limiting what a chip can be made to do, so disabled components aren't a performance loss because we couldn't run power through the entire chip anyway.",
"Lots and lots of people have already stated most of how a CPU is made... i guess since i used to work in a smaller Fab, i got to see a lot of the process because we do have some downtime.\n\nA fab usually consist of the following, a metal deposition room, a liftoff room(removal of metal and substance), an wet etch room(cleaning), dry etch (plasma cleaning), photo (prep designs), backside(prep the back of the chip) and last is test. All of this is enclosed in a clean room, although some people say if there is a single particle on it, it would destroy the chip, but it actually depends on how sensitive that layer is. crucial layers will require less, others may not make a huge difference. \n\nThe designs are on long long pages of paper or on the computer. The least ive seen is like 50 pages, the most ive seen is 200 pages long. \n\nSo we always start with a common silicon base. its thin, silver. The typically go to photos first to put a design on it. The designs are actually done on Canon machines(which is my guess why its called photo). They basically put on a thin layer of wax(or metal resistant material) on where a layer should not be. that way, when u put the metal on, it only sticks to the design required area. After this, it goes to the Metal room.(usually)\n\nMetal is where i was placed in. There are 3 different ways to put metal on, Evaporating, Sputtering(spraying), and plasma spray. Evaporators will heat a metal up to its liquid state in a vacuum, then released onto the wafers. Sputtering is basically a spray(also under pressure), theres also plasma but im not sure how that works.\n\nAfter that, it is sent to liftoff where it is cleaned either by hand or by machine by using acetone to wash off the resistant layer. After this, it can go to any place, photos, dry etch, wet etch.both the dry etch and wet etch is basically a process to really clean the wafers. \n\nAfter that, once the majority of the chip is done, it is sent to backside, where the backside is prep. it usually just a bunch of gold attached to it.\n\nAt the very very end of the line, it is sent to testing to where a machine would test each chip. Then its sent to the customer.\n\nAlthough my ex-company did not manufacturer CPU we did a lot of wifi chips, which i would assume is close to a CPU. My knowledge of chip manufacturing was only about a year of being in the fab and able to explore such a small lab in the middle of night(graveyard shift) Sorry, if i sound confusing."
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3mgj8j | how did rockstar actually manage to create/model the gigantic map in gta5 ? | Like it seems like no two places inc the city are the same, how did they even design the whole thing ? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3mgj8j/eli5_how_did_rockstar_actually_manage_to/ | {
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"You never design one complete thing. The map is kinda made in that way. The map is divided into many tiny parts and then compiled as one. When we look at the bigger picture we can only see the entire map when we are totally zoomed out or most of the times we see regions or details of those regions. When the user is playing the computer only has to render the parts the user is in or where he might be. \n\nWhen it comes to making a game all the work is divided into tiny bits and pieces. Different teams are given different parts to make and then all the work is kinda compiled into one big game. Same goes for the maps. Here someone or a group might have decided first what all to include in the city and they after dividing it carefully given it out to teams to do it."
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10exfw | ionic bonding, molecular compounds, and covalent bonding | Can someone explain chemical bonding to me? What is the difference between covalent bonding, covalent-network bonding, polar bonding, non-polar bonding, etc? What is an ionic compound? What is the Metallic-Bond model? The VSEPR Theory? Hybrid orbitals? When do you use parentheses when you're bonding elements? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/10exfw/eli5_ionic_bonding_molecular_compounds_and/ | {
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"Well, elements are extremely unstable when left alone. An individual atom is basically a nucleus with an equal number of electrons and protons. these atoms want to achieve stability by either sharing or donating electrons to achieve a stable outer shell. _URL_0_ If you look at this periodic table, you notice a pattern in the colors. Lets look at B, C, N, O, F, and Ne. Neon has an atomic number of 10, so we can assume it has 10 electrons, right? Well, there is a cool trick to figuring out the electron configuration of an element. You have S (2 electrons) orbitals, P (6 electron) orbitals, D (10 electrons) orbitals, and F (14 electrons) orbitals. The column with Li has a S orbital with one electron (it wants to lose an electron to be stable). Be has an S orbital with 2 electrons (it wants to lose 2 electrons to become stable). Now, back to B, C, N, O, F, and Ne. These columns valence electron shell involves the P orbital (which can have 6 electrons in it). Ne has a full shell of 8 electrons surrounding it, which is the most stable. Think about it, we have a 1S2 2S2 2P6 electron configuration. 8 valence electrons! F also wants a stable configuration, but he only has 7 valence electrons. F wants to gain an electron so he carries a -1 charge. O only has 6 valence electrons, but really wants 8 as well. O carries a -2 charge (gains 2 electrons) to achieve a valence shell of 8. So O has an 1S1 2S2 2P4 and wants to achieve 1S1 2S2 2P6 configuration. \n\n\nThe periodic table is set up so that each column has the same number of valence electrons. Li, Na, K, Rb, etc. all have one valence electron. They carry a +1 charge so they can have a stable configuration. Na, which is sodium, secretly wants to be like Neon, so he loses an electron by donating it to another element. This is **Ionic bonding** such as the donation of an electron from Na to Cl. Both Na and Cl achieve a stable configuration by bonding to each other. Bonding is just a method to achieve stability. \n\n\nIonic bonding occurs when an element such as an alkali metal (Li, Na, K, Rb) donate an electron to another element. Keep in mind, the elements must both benefit from the bond formation, otherwise it is very unlikely to happen. All elements want to achieve stability in their bonds, and the bonds are directly related to the number of valence electrons. \n\n\nPolar bonding and hybrid orbitals might be too complicated to explain without a few models, so I might answer that separately. \n\nVSEPR theory basically states that bonded species (elements or electrons) repel each other as much as possible. If you have Carbon as a central atom surrounded by 4 hydrogen atoms, (remember, carbon wants 10 electrons in its outer shell) it forms a tetrahedral model. These elements are sharing electrons for stability and this is called **covalent bonding**. Why are the hydrogen atoms not in a square around the carbon? Well, each angle between the individual hydrogen atoms would be 90* in a square. They would rather be further apart than that because the hydrogen atoms want to be as far apart as possible. Combined the central carbon and it's hydrogens form a molecule with 109.5* angles between each hydrogen (called a tetrahedral bond formation). Now the hydrogen atoms are as far apart as possible, therefore as stable as possible in this molecule. There are many types of bonds and elements, but the best examples to look up are, carbon, nitrogen, oxygen, and Fluorine for bond behaviors. Silicon will bond to elements similarly to carbon because they are in the same column of the table. F, Cl, Br, and I will all bond the same because they are also in the same column.\n\n\nI will try to answer the rest of your questions in another post. \n\n**Edit** I don't think I'll be able to explain hybrid orbitals or polar/nonpolar bonding sufficiently without the use of models. This would likely be one of the first things taught in a college level organic chemistry class, and I am no chemistry teacher :( \n\n_URL_1_ Look at figure 15 to help understand hybrid orbitals. \n\n"
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77otu6 | How do audio books, printed books, and videos differ in terms of how our brains retain and process the information? | If I read a book compared to listening to it.. how does that affect my brain differently? Is there any difference? | askscience | https://www.reddit.com/r/askscience/comments/77otu6/how_do_audio_books_printed_books_and_videos/ | {
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"I know video and books are definitely different. but paper books and audio books are processed in the mind almost identically. so when you listen to an audio book it is nearly as if not better than reading the book and handled almost identically in the mind.\n\nBetter with a particularly good reader as they can help you engage better.\n\nit seems reading words and listening to words uses the same \"portion\" of the brain.\n\n_URL_0_\n\nthere is a forbes article back to 2011 saying the same thing but I can't read it any longer (ad block blocker)",
"I'd like to know how this would vary across the different \"types of learners\" as well (kinesthetic, visual, auditory etc). E.g. is an audiobook better for an auditory learner? If someone could verify if those learning types have any scientific basis or if they're just made up nonsense that would be good too.",
"I remembered reading this article when I saw your question: _URL_0_\n\nGranted it is a small study, but I can identify. When I read physical books or listen to them, I remember a lot of detail. When I read digitally, I don't remember much at all. I'm halfway through a book on my Kindle right now and I can't tell you the name of it, the author, or any of the main characters' names.",
"The Marines/Navy did a study in the 60s on how people learn the best.\n\nThe study was done over 10 years.\n\nWhat they found is some people learn better by listening, some by reading, and some by doing. \n\nAnd you even the people who are best at one form of learning can have it reinforced by another.\n\nSo the military especially in basic training try to teach everything 3 times in 3 ways. You get the information told to you, you hear others being corrected and you yourself being corrected... as well as responding or repeating. You do it hands on in many different ways and under varying levels of stress. The third method you get a book of knowledge and they have you study it in any down time. \n\nNow another thing they don’t do that was found in the 90s\n\nRecord yourself reading your notes. They need to be recorded in 15 seconds or less snippets. Making each an audio file of its own. Play it back to yourself on repeat and shuffle. Your brain interprets your voice as your inner monologue and builds pathways based on what you hear. If data is only memorized in one sequence then you remember it like that. But if it’s memorized as short bits of data that’s how you remember it. So you end up with a better recall because the information isn’t dependent on something else, and the pathways get linked all over the place to different bits of similar data. \n\nYou read it multiple times, see it, read it out loud, and hear it. Each time your brain makes a link among the data it links everything that it associates with that information."
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16kjph | How can it be almost the same temperature (80˚F) here in Florida mid-January? | I assume between winter and summer there is an average of about 40-50˚F difference (in summer it's 90˚+, during winter it's usually around 40-50˚ here, maybe freezing sometimes).
Wouldn't it being 80˚ right now mean that when you add the extra heat of summer it should be way hotter than just 90-100? If two objects (Florida this season vs. Florida in the past) are of different temperatures (80˚ today vs. 40˚ two winters ago) and you apply the same change of new energy (the seasons changing, tilt of the earth, etc.) shouldn't one summer be clearly warmer?
TL;DR: How is it *hot* during winter? Shouldn't it be super hot in the summer now? Is this global warming? | askscience | http://www.reddit.com/r/askscience/comments/16kjph/how_can_it_be_almost_the_same_temperature_80f/ | {
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"Global warming refers to an increase in the average temperature of the earth's atmosphere and oceans. It's not really applicable to a difference in year to year / month to month temperatures at a location. That's more probably a matter of air currents and where your current surface air mass has traveled from (i.e. somewhere warm). ",
"First let me say that weather is a very complex phenomenon, and there are many variables to account for why one place is warm and another cool. That being said, there are some global trends. \n\nThe first is, the closer you get to the equator, the less variation in temperature you'll see due to seasons. Right at the equator, there is no variation of sunlight regardless of when in the year it is. At the poles, it is sunlight half the year, and darkness half of the year. Thus, Florida being further south means less variation from season to season. \n\nSecondly, the closer you are to large bodies of water, the less variation you have. That is because water is a huge heat sink. It takes a whole lot of heat to raise its temperature, and a long time to cool it down. So when you are near large bodies of water, temperature remains more constant. Florida is surrounded on both sides by ocean, thus it receives a lot of temperature moderation by this effect.\n\nAnd finally- local temperature does not indicate global climate, and cannot be used to predict climate change. "
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1gqf8x | How did Soviet schools/media portray the American "founding fathers"? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1gqf8x/how_did_soviet_schoolsmedia_portray_the_american/ | {
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"As far as we can tell, there's no documented Communist or Stalinist diatribe against American founding fathers in particular. There are plenty of media examples regarding both the corruption and selfish attitudes of the American capitalist aristorcracy and military made evident in both [Encounter at the Elbe](_URL_2_) - in 1949 and in [The Extra Ordinary Adventures of Mr West in The Land of the Bolsheviks](_URL_1_). The point has been made on this board before that the point of Soviet propaganda wasn't necessarily to make out Westerners to all be savage or evil capitalist. But to characterize them as oppressed workers under the grip of greedy capitalist leaders and oppressive military juntas. \n\nIn Soviet Film and propaganda - if the workers of the west were properly exposed to, or understood the apparent 'equity' and 'fairness' of the Soviet Union and Bolshevik cause - they would eschew their capitalist ideals and values. The enemy of the soviet people was not the workers, but the capitalist leaders and Bourgeois of the West that they had overthrown in their own civil war. \n\nThe founding fathers didn't really come into play because most Russians didn't really have any association with them as historical figures. Educated Russians may well have known about them - but it wouldn't be very useful to the Soviet leadership and Ministry of Film to use them as material. It'd be like using [Dzokhar Dudayev](_URL_0_) as a figure to outline the dangers of nationalist separatism to an American audience - they would have no idea who you were talking about. "
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"http://www.imdb.com/title/tt0042029/"
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2exfe6 | why do the pronunciation of some words seem to match the meaning so well? | It seems like some words are just in place to describe something and are very ordinary, like computer, tomato, etc.
However, some words feel like the pronunciation really captures the object the word refers to, such as emotions and such.
For example: loathe, slut and c*nt (feels like very dirty words to me), vehemently, jubilant, and so on.
Is it that we're taught the meaning of the word, so we associate that emotion or feeling to the pronunciation, or is that the word was tailored specifically to describe that thing? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2exfe6/eli5_why_do_the_pronunciation_of_some_words_seem/ | {
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"I'm not an etymologist, but a linguist.\nI would say that rather than words being tailor made, it's a combination of association and usage that make you have certain \"feelings\" towards a word.\nI say this only because words weren't made at one time and then have been that way since. they are constantly evolving, changing, adapting and even being stolen.\nfor example, fanny and pussy. words that now you have such \"ditry\" feelings towards because of the association of porn etc. but just around 50 years ago, there was absolutely no wide spread use of these words other than a girls name (fanny) and a kitty cat (pussy). And I'll bet people thought these were soft and very fitting names for those things.\n\nTL;DR words are subjective and relative to temporal context."
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3oelu3 | What food or edible item contains the most calories in one tablespoon (15ml)? | askscience | https://www.reddit.com/r/askscience/comments/3oelu3/what_food_or_edible_item_contains_the_most/ | {
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"In terms of volume (i.e. mL) I can't find any data, but I can find the densities as well as the energy densities. Fat sits somewhere between 37-39 kJ/g, where the closest after that is alcohol sitting at 29 kJ/g, and then carbohydrates and proteins at 17 kJ/g.\n\nDensity of fatty acids or fat is approximately 0.9 g/cm^(3) or 0.9 g/mL.\n\nDensity of carbohydrates is approximately 1.6 g/cm^(3).\n\nDensity of alcohol is approximately 0.8 g/cm^(3).\n\nDensity of protein approximately 1.3 g/cm^(3).\n\nThis means fatty acids have ~33-35 kJ/cm^(3), alcohol has 23 kJ/cm^(3), carbohydrates sit at 27 kJ/cm^(3) and proteins sit at ~22 kJ/cm^(3).\n\nThus, feeding someone a 15 mL teaspoon of fat is the best way to fill them full of delicious calories.\n\nEDIT: Joules rool, calories drool."
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2oyrr6 | why is cheap labor frowned upon but outsourced jobs aren't? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2oyrr6/eli5_why_is_cheap_labor_frowned_upon_but/ | {
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"Every time a factory closes in the Netherlands because it has been outsourced to (most likely) Poland, a lot of people frown. Meanwhile, people still buy China made cheap products. I'd say the opposite is true.",
"Because cheap labour is taking jobs away from \"real citizens\" while outsourced jobs are in a different country, and are of little importance because it doesn't matter *here*./s"
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9pqf7l | how do we have information about ancient events? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9pqf7l/eli5_how_do_we_have_information_about_ancient/ | {
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"They wrote about their important news. Scrolls, books, chiseled in stone...\n\nIt's not hard to preserve books for thousands of years, actually. Keep them dry is about all that's required. Ancient Rome, have some scribes make copies of the important stuff Caesar did, take them to Egypt where the desert is dryer than you can possibly hope, put them in a sealed chamber in the pyramids or even a smaller building like the Library of Alexandria, and voila.\n\nThey knew about preserving things in antiquity. Keeping wine from spoiling, preserving foods, preserving bodies, preserving books and other objects of value."
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krbc3 | add/adhd and adderal. | How does adderal and other stimulants help ADD/ADHD? If the condition causes the person to have too much energy how would a stimulant help? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/krbc3/eli5_addadhd_and_adderal/ | {
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"Well, I'm not a doctor or anything, but I have vested interested in knowing something about this kind of stuff, and I take a different stimulant medication for ADD. So I'll give it a go.\n\n(If you decide to do your own research, I'm taking most of this from \"Adult ADD: The Complete Handbook\" by David B. Sudderth, MD and Joseph Kandel, MD. The one I have was published in 1997, and because this is a field of study that is constantly evolving, it's showing its age a little bit, but it did help me a lot to get a handle on this thing with which I struggle.)\n\nThere are lot of things that might cause ADD or ADHD, but a lot of the reasons have to do with chemicals in your brain. These chemicals control things like your mood, or your ability to focus, or all kinds of other things about how you act and how your mind works.\n\nSometimes people have ADD because the part of their brain that is supposed to create a certain chemical isn't doing it fast enough, or because another part of their brain which is supposed to suck up that chemical isn't doing it fast enough. One thing a stimulant can do is make those parts work faster. If the stimulant affects a part of the brain that is causing ADD by not working quickly enough, then the extra energy and the extra ability to focus and follow through on things will balance each other. In fact, some people say that people with ADD don't really get high from cocaine--it just makes them focus! But don't do that. I think I'll go into all the reasons not to do cocaine when you're a little bit older. And your parents are here.\n\nBut they are still stimulants. So when a person is taking a stimulant medication for ADD, they have to make sure that they're eating enough and doing healthy things, because any stimulant can have bad side effects, especially if you take them over a long time, like you do with ADD medicine. Even healthy people can lose weight and get a higher heart rate and higher blood pressure.\n\nSo basically: the stimulant stimulates that part of the brain that isn't doing what it's supposed to do. This allows the person taking the medicine to channel that extra energy into something productive.\n\n(If there's a redditor with medical training passing by, please do feel free to correct me if I've misunderstood some nuance.)\n\n\n\nOn a personal note: I have found that if you find the right dosage for the medication, you can experience the benefits of the medication without too much in the way of stimulant side effects. I can focus during the day a lot better, but I'm not jittery. I had a little bit of that kind of thing when I was still trying to find the right dosage with my doctor and we shot a little high, but the key to stimulant medications is basically to take the smallest effective dose, stick to a regular schedule, and make sure you keep up a healthy lifestyle to offset the unavoidable side effects. Sticking to a regular schedule means that your body's natural rhythms can adapt to having the medicine hit your system at a certain time every day, and it won't keep you up at night or anything. Living a healthy lifestyle is just necessary to ward off things like hypertension. It's also possible to have all kinds of weird mood side effects. The only thing I know to do about that is to keep a regular checkup on your mental health in addition to your physical health (like seeing a counselor once a week or something) or switching to something that doesn't mess up your brain chemistry like that.\n\nI hope this makes sense!\n\nedit: spellcheck",
"Here is how I remember a doctor explaining it to me: In the course of being awake, the brain receives incredible amounts of input from the senses -- but amazingly there are systems and chemicals in the brain which allow it to decide which to focus on and which to ignore. Some people have a part of their brain (perhaps it is the amygdala) that is \"asleep\", and when it is asleep the brain cannot filter properly -- the deficit is that ATTENTION gets paid to everything essentially, with no proper priority. *** Here's where the stimulant comes in: it wakes up the part of the brain that controls focus. *** Caffiene has been talked about as doing this, but not as well -- this is why ADD/ADHD kids don't get crazier when they drink soda or coffee, they actually calm down and pay attention, much to the confusion of parents of regular kids.",
"I'm 28 and was diagnosed this last March with ADHD. I take 20mg of AdderallXR a day, and what it does for me isn't give me energy. What it does is put my thoughts in order. Inside my head everything is just a big ball of picturescolorsmemoriesthoughtstexturesfeelings and it gets very overwhelming, but the Adderall is like a stocker at a grocery store that takes the items people have left around and puts them all in the right place. My thoughts are in straight lines instead of all in a big jumble and it makes it easier to concentrate on the things I'm supposed to and do well at my job.",
"It's actually very similar to coffee.",
"ADD doesn't mean you have too much energy. It means your brain requires more stimulation to keep you focused. That's why kids with ADD can sit for hours playing video games: they're very stimulating. Homework and classwork, on the other hand, is not. Adderall and other stimulants stimulant the brain, and the user interprets that stimulation as coming from whatever they're doing, be it homework, chores, video games, etc.\n\nI'm on a prescription of Vyvanse and it feels like my mind is locked in on whatever I'm doing.",
"First of all, there are different types of ADHD. \nADHD/H - Hyperactive and Impulsive. It's as if the 'filter' between their mind and their actions doesn't exist. It's like they don't fully think before they do something.\nADHD/I - Inattentive or Predominantly Inattentive (PI). Previously referred to as ADD. Daydreamy, easily distracted, unorganized, procrastination are all characteristics that tend to affect this group. Consequently, this subtype can lead to other problems such as low self-esteem, anxiety, mood disorders and substance abuse.\nADHD/C - Combined subtype.\nADHD/unspecified - Possess some of the characteristics of different groups but not enough to make a full diagnosis. Nevertheless, these problems still interfere with their daily lives.\n\nNow, stimulants, such as Adderall, are not the only treatments on the market. Individual brain chemistry and mental condition can vary greatly from person to person. Sometimes, the only thing necessary to manage symptoms to a reasonable level is good exercise, enough sleep, productive habits, good time management, which can be achieved through therapy or other self-help resources.\n\nStimulants, though, currently remain the most effective treatment (by most effective, I mean affects most people positively; different people respond to different medications differently).\nStimulants used to treat ADHD such as amphetamines (Adderall, Dexedrine) and methylphenidate (Ritalin, Concerta) are quite different than caffeine. \nCaffeine acts as an adenosine antagonist, which basically means it reduces the amount of chemical in the brain that says \"I'm tired\". \nAmphetamines and Methylphenidate, though possessing different mechanisms of actions, produce a similar effect. They inhibit the reuptake of the neurotransmitters dopamine and norepinephrine, which basically means it blocks the brain's \"clean up crew\" for certain chemicals in the brain that control attention, arrousal, pleasure, etc.\n\nWhile people without attention issues who take Adderall get energetic, sometimes even manic, people afflicted with ADHD tend to get calmer, their thoughts organized. \n\nYou know sometimes when you're changing the radio station and you stop in between two channels, it plays a little of both channels overlapping each other, fuzzy and incoherent? Now imagine the radio dial was broken. This is somewhat analogous to having ADHD, and Adderall (and other medication) temporarily fixes the dial and gives the ability and flip to whichever you want. Now if you took a huge dose or wasn't affected by ADHD, having a super lubricated radio dial wouldn't be very fun; a small motion would flip through a bunch of channels, and landing on the one you want might be troublesome.\n\nSomething fun to know: amphetamines (Adderall) is a cousin to methamphetamine (crystal meth, ice) and has a similar mechanism of action (meth is much more potent). Methylphenidate (Ritalin) is chemically similar to cocaine and possesses a similar mechanism of action.\nI have ADHD, and in the past, before I was getting treatment, I did cocaine once with a few of my friends. It was very weird seeing my friends energetic and sweating while I experienced a more sedating feeling. The effect was, in a way, similar to when I started taking medication: the brain \"fog\" was lifted, colors seemed brighter, 'illogical' anxiety (social and otherwise) was squelched.",
" > How does adderal and other stimulants help ADD/ADHD? If the condition causes the person to have too much energy how would a stimulant help?\n\nThe ELI5, simplified, child-friendly explanation is this:\n\nThere's a part of your brain that takes in everything you're doing and everything that's going on around you, and hands that information -- call it an Awareness Report -- to another part of your brain, a part that makes decisions. This second part looks at it, decides what's important, how much energy it should be spending, what it should be spending it on, etc. This is the part of your brain that puts you on standby when you're driving for the tenth straight hour on a quiet highway. The brain's power saver.\n\nIf you have ADHD, half of that awareness report is lost along the chain. The decision-making part of your brain looks at the unfinished report, and says \"Oh, doesn't look like much is going on.\" There are two or three different ways people's brains respond to that -- subtypes of ADHD like PI or PH -- but all of them are a result of that first part of your brain mishandling its report.\n\nWhen you take adderall, or methylphenidate, or cocaine, it basically tells your brain \"Holy shit, everything is so intense and interesting, you better be paying full attention to this\". If you've ever used speed or cocaine or been with someone who's on it, you know what I mean. In an ADHD person, that message balances out what's missing from the awareness report. Half of the report is still missing, so it still says \"Yeah, I guess we're participating in a debate on live TV, not much going on I guess, we can go into standby mode\", but in big black marker all along the bottom of the page is \"HOLY SHIT EVERYTHING IS REALLY INTENSE ALL GUARDS STANDING AT ATTENTION, YOURS TRULY, AMPHETAMINES\", so you behave more or less the way you would have if the brain had accurately realised how important what you're doing is. \n\n > If the condition causes the person to have too much energy \n\nADHD does not cause a surplus of energy. ADHD-PH, the second-most-common type, involves the decision making part of the brain saying \"Nothing important is happening, *so look for something more useful for us to do*\", meaning that the sufferer is never satisfied by any activity and constantly switches between tasks. In children, who are most easily diagnosed, that's usually a physical game or fidgeting in class, but in adults it's most commonly manifested as wildly veering conversations. It's the brain looking for stimulus wherever it can find it and trying to create some in its absence. This is why drugs that get other people high will make ADHD-PH sufferers calm; it's bringing the brain up to a level where it's usually satisfied by what it's doing.\n\n",
"Does anybody else here have a uncomfortable \"comedown\" from taking ADD/ADHD medications ? I was taking 36mg of Concerta Time Release before breakfast everyday (roughly 6am) and having a dirty and uncomfortable feeling at around 4pm - 5pm everyday.",
"The front of your brain makes all the good decisions and keeps you from getting into too much trouble. A person with ADD/ADHD has trouble because their whole brain is firing rapidly making them distractable. Stimulants make the front of the brain stronger so they can make good decisions again.",
"Well, I'm not a doctor or anything, but I have vested interested in knowing something about this kind of stuff, and I take a different stimulant medication for ADD. So I'll give it a go.\n\n(If you decide to do your own research, I'm taking most of this from \"Adult ADD: The Complete Handbook\" by David B. Sudderth, MD and Joseph Kandel, MD. The one I have was published in 1997, and because this is a field of study that is constantly evolving, it's showing its age a little bit, but it did help me a lot to get a handle on this thing with which I struggle.)\n\nThere are lot of things that might cause ADD or ADHD, but a lot of the reasons have to do with chemicals in your brain. These chemicals control things like your mood, or your ability to focus, or all kinds of other things about how you act and how your mind works.\n\nSometimes people have ADD because the part of their brain that is supposed to create a certain chemical isn't doing it fast enough, or because another part of their brain which is supposed to suck up that chemical isn't doing it fast enough. One thing a stimulant can do is make those parts work faster. If the stimulant affects a part of the brain that is causing ADD by not working quickly enough, then the extra energy and the extra ability to focus and follow through on things will balance each other. In fact, some people say that people with ADD don't really get high from cocaine--it just makes them focus! But don't do that. I think I'll go into all the reasons not to do cocaine when you're a little bit older. And your parents are here.\n\nBut they are still stimulants. So when a person is taking a stimulant medication for ADD, they have to make sure that they're eating enough and doing healthy things, because any stimulant can have bad side effects, especially if you take them over a long time, like you do with ADD medicine. Even healthy people can lose weight and get a higher heart rate and higher blood pressure.\n\nSo basically: the stimulant stimulates that part of the brain that isn't doing what it's supposed to do. This allows the person taking the medicine to channel that extra energy into something productive.\n\n(If there's a redditor with medical training passing by, please do feel free to correct me if I've misunderstood some nuance.)\n\n\n\nOn a personal note: I have found that if you find the right dosage for the medication, you can experience the benefits of the medication without too much in the way of stimulant side effects. I can focus during the day a lot better, but I'm not jittery. I had a little bit of that kind of thing when I was still trying to find the right dosage with my doctor and we shot a little high, but the key to stimulant medications is basically to take the smallest effective dose, stick to a regular schedule, and make sure you keep up a healthy lifestyle to offset the unavoidable side effects. Sticking to a regular schedule means that your body's natural rhythms can adapt to having the medicine hit your system at a certain time every day, and it won't keep you up at night or anything. Living a healthy lifestyle is just necessary to ward off things like hypertension. It's also possible to have all kinds of weird mood side effects. The only thing I know to do about that is to keep a regular checkup on your mental health in addition to your physical health (like seeing a counselor once a week or something) or switching to something that doesn't mess up your brain chemistry like that.\n\nI hope this makes sense!\n\nedit: spellcheck",
"Here is how I remember a doctor explaining it to me: In the course of being awake, the brain receives incredible amounts of input from the senses -- but amazingly there are systems and chemicals in the brain which allow it to decide which to focus on and which to ignore. Some people have a part of their brain (perhaps it is the amygdala) that is \"asleep\", and when it is asleep the brain cannot filter properly -- the deficit is that ATTENTION gets paid to everything essentially, with no proper priority. *** Here's where the stimulant comes in: it wakes up the part of the brain that controls focus. *** Caffiene has been talked about as doing this, but not as well -- this is why ADD/ADHD kids don't get crazier when they drink soda or coffee, they actually calm down and pay attention, much to the confusion of parents of regular kids.",
"I'm 28 and was diagnosed this last March with ADHD. I take 20mg of AdderallXR a day, and what it does for me isn't give me energy. What it does is put my thoughts in order. Inside my head everything is just a big ball of picturescolorsmemoriesthoughtstexturesfeelings and it gets very overwhelming, but the Adderall is like a stocker at a grocery store that takes the items people have left around and puts them all in the right place. My thoughts are in straight lines instead of all in a big jumble and it makes it easier to concentrate on the things I'm supposed to and do well at my job.",
"It's actually very similar to coffee.",
"ADD doesn't mean you have too much energy. It means your brain requires more stimulation to keep you focused. That's why kids with ADD can sit for hours playing video games: they're very stimulating. Homework and classwork, on the other hand, is not. Adderall and other stimulants stimulant the brain, and the user interprets that stimulation as coming from whatever they're doing, be it homework, chores, video games, etc.\n\nI'm on a prescription of Vyvanse and it feels like my mind is locked in on whatever I'm doing.",
"First of all, there are different types of ADHD. \nADHD/H - Hyperactive and Impulsive. It's as if the 'filter' between their mind and their actions doesn't exist. It's like they don't fully think before they do something.\nADHD/I - Inattentive or Predominantly Inattentive (PI). Previously referred to as ADD. Daydreamy, easily distracted, unorganized, procrastination are all characteristics that tend to affect this group. Consequently, this subtype can lead to other problems such as low self-esteem, anxiety, mood disorders and substance abuse.\nADHD/C - Combined subtype.\nADHD/unspecified - Possess some of the characteristics of different groups but not enough to make a full diagnosis. Nevertheless, these problems still interfere with their daily lives.\n\nNow, stimulants, such as Adderall, are not the only treatments on the market. Individual brain chemistry and mental condition can vary greatly from person to person. Sometimes, the only thing necessary to manage symptoms to a reasonable level is good exercise, enough sleep, productive habits, good time management, which can be achieved through therapy or other self-help resources.\n\nStimulants, though, currently remain the most effective treatment (by most effective, I mean affects most people positively; different people respond to different medications differently).\nStimulants used to treat ADHD such as amphetamines (Adderall, Dexedrine) and methylphenidate (Ritalin, Concerta) are quite different than caffeine. \nCaffeine acts as an adenosine antagonist, which basically means it reduces the amount of chemical in the brain that says \"I'm tired\". \nAmphetamines and Methylphenidate, though possessing different mechanisms of actions, produce a similar effect. They inhibit the reuptake of the neurotransmitters dopamine and norepinephrine, which basically means it blocks the brain's \"clean up crew\" for certain chemicals in the brain that control attention, arrousal, pleasure, etc.\n\nWhile people without attention issues who take Adderall get energetic, sometimes even manic, people afflicted with ADHD tend to get calmer, their thoughts organized. \n\nYou know sometimes when you're changing the radio station and you stop in between two channels, it plays a little of both channels overlapping each other, fuzzy and incoherent? Now imagine the radio dial was broken. This is somewhat analogous to having ADHD, and Adderall (and other medication) temporarily fixes the dial and gives the ability and flip to whichever you want. Now if you took a huge dose or wasn't affected by ADHD, having a super lubricated radio dial wouldn't be very fun; a small motion would flip through a bunch of channels, and landing on the one you want might be troublesome.\n\nSomething fun to know: amphetamines (Adderall) is a cousin to methamphetamine (crystal meth, ice) and has a similar mechanism of action (meth is much more potent). Methylphenidate (Ritalin) is chemically similar to cocaine and possesses a similar mechanism of action.\nI have ADHD, and in the past, before I was getting treatment, I did cocaine once with a few of my friends. It was very weird seeing my friends energetic and sweating while I experienced a more sedating feeling. The effect was, in a way, similar to when I started taking medication: the brain \"fog\" was lifted, colors seemed brighter, 'illogical' anxiety (social and otherwise) was squelched.",
" > How does adderal and other stimulants help ADD/ADHD? If the condition causes the person to have too much energy how would a stimulant help?\n\nThe ELI5, simplified, child-friendly explanation is this:\n\nThere's a part of your brain that takes in everything you're doing and everything that's going on around you, and hands that information -- call it an Awareness Report -- to another part of your brain, a part that makes decisions. This second part looks at it, decides what's important, how much energy it should be spending, what it should be spending it on, etc. This is the part of your brain that puts you on standby when you're driving for the tenth straight hour on a quiet highway. The brain's power saver.\n\nIf you have ADHD, half of that awareness report is lost along the chain. The decision-making part of your brain looks at the unfinished report, and says \"Oh, doesn't look like much is going on.\" There are two or three different ways people's brains respond to that -- subtypes of ADHD like PI or PH -- but all of them are a result of that first part of your brain mishandling its report.\n\nWhen you take adderall, or methylphenidate, or cocaine, it basically tells your brain \"Holy shit, everything is so intense and interesting, you better be paying full attention to this\". If you've ever used speed or cocaine or been with someone who's on it, you know what I mean. In an ADHD person, that message balances out what's missing from the awareness report. Half of the report is still missing, so it still says \"Yeah, I guess we're participating in a debate on live TV, not much going on I guess, we can go into standby mode\", but in big black marker all along the bottom of the page is \"HOLY SHIT EVERYTHING IS REALLY INTENSE ALL GUARDS STANDING AT ATTENTION, YOURS TRULY, AMPHETAMINES\", so you behave more or less the way you would have if the brain had accurately realised how important what you're doing is. \n\n > If the condition causes the person to have too much energy \n\nADHD does not cause a surplus of energy. ADHD-PH, the second-most-common type, involves the decision making part of the brain saying \"Nothing important is happening, *so look for something more useful for us to do*\", meaning that the sufferer is never satisfied by any activity and constantly switches between tasks. In children, who are most easily diagnosed, that's usually a physical game or fidgeting in class, but in adults it's most commonly manifested as wildly veering conversations. It's the brain looking for stimulus wherever it can find it and trying to create some in its absence. This is why drugs that get other people high will make ADHD-PH sufferers calm; it's bringing the brain up to a level where it's usually satisfied by what it's doing.\n\n",
"Does anybody else here have a uncomfortable \"comedown\" from taking ADD/ADHD medications ? I was taking 36mg of Concerta Time Release before breakfast everyday (roughly 6am) and having a dirty and uncomfortable feeling at around 4pm - 5pm everyday.",
"The front of your brain makes all the good decisions and keeps you from getting into too much trouble. A person with ADD/ADHD has trouble because their whole brain is firing rapidly making them distractable. Stimulants make the front of the brain stronger so they can make good decisions again."
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20uvys | why am i repulsed when i hear the sound of my own voice? | This seems to be a common phenomenon. When you hear your voice played to you on a recording or video, not only does it sound vastly different than it does in your head while you're speaking, but a fair amount of people are embarrassed, asking "Is THAT what I sound like?!" in disgust. What gives? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/20uvys/eli5_why_am_i_repulsed_when_i_hear_the_sound_of/ | {
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"When you speak, the sound you perceive is due more to the conduction of sound waves through your bones and tissues than it is through air. You build an idea of what you sound like over the many years. When you hear a recording, it's with the sound waves conducted through air. It sounds unfamiliar and strange.",
"Your repulsion comes from the \"uncanny valley\" effect.\n\nThe [uncanny valley](_URL_0_) refers to the sudden drop in comfort level that people feel about things that are almost, but not quite, lifelike. People are comfortable with things that are not at all lifelike, and things that are a little lifelink but clearly not, but at some point, as objects either look or act (or both) approach being cannily life-like, there's some point at which people experience deep discomfort.\n\nYou are recognizing the voice as your own, but missing the element of bone-conduction that fills out your voice. It feels weird because it's almost, but not quite familiar, and so the recording is like a near-miss your own lifelike voice. ",
"While I agree with the other comments about bone conduction and how our voice sounds different to others than ourselves because of our biology, there's another factor at play that often gets ignored when people answer this question: the recording medium itself.\n\nAll microphones don't all pick up the same frequencies, and the quality of the microphone makes a huge difference in how the human voice sounds. Also, which part of your body the microphone is pointed at makes a difference - pointed at the mouth usually makes things sound higher pitched, while pointed at the chest usually gives a bassier timber. The sweet spot, used for professional filming, is to point the mic at the chin from above, to get both.\n\nRecording formats like tape, vinyl, and compressed digital, can emphasize or discard some of the frequencies. Analog tapes and vinyl typically emphasize the lower frequencies, while modern digital recordings often emphasize mid ranges and cuts highs and lows (especially for Voice-Over-IP, like Skypeor Google Hangouts)\n\nAnd lastly, speakers rarely reproduce all frequencies faithfully. The sound recording systems themselves introduce a lot of distortion into the system, and depending on how they are calibrated (a lot of people prefer a bass-emphasized system) can significantly affect how the voice sounds.\n\nAnd none of that is to mention deliberate changes in equalization, the effect of ambient noise and echoes, or the myriad of other small factors technology plays in distorting audio recordings.\n\nWe rarely notice this when listening to the recordings of other people, because our memories of how their voice sounds are not as good as our memory of our voice - unless they are there to compare with the recorded sound, our brain will 'calibrate' itself to hear their voices right."
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1odeo3 | how can we breed dogs and change their physical bodies? | I see shows that talk about how a dog is bred to be physically different for a job. For instance, the corgis were bred to have short legs to be better herders by biting the ankles of other animals. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1odeo3/eli5_how_can_we_breed_dogs_and_change_their/ | {
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"Every puppy in a litter is a little bit different. Pick the one that is the closest to what you want out of a dog, then wait until it can have puppies. Repeat for many generations."
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by49tb | What does it mean chemically to be high? And why don't all psychoactive substances make you feel high? | [deleted] | askscience | https://www.reddit.com/r/askscience/comments/by49tb/what_does_it_mean_chemically_to_be_high_and_why/ | {
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"It is unknown exactly how nutmeg acts in the body. The main psychoactive compounds are elemicin and myristicin which are thought to act as anticholinergics. \n\nPeppercorn is known to act on the endocannabinoid system but the exact reason it can reduce the effectiveness of THC is unknown.\n\n‘What does it mean chemically to be high’ is a very difficult question to answer because every drug acts differently. To name just a few cocaine blocks dopamine transporters, MDMA (ecstasy) triggers presynaptic release of monoamime neurotransmitters and LSD activates 5-HT2A receptors. This is not exhaustive and these drugs will effect multiple systems but this is their main action. If you wanted a more detailed explanation I’d need to know a specific drug you had in mind.\n\n‘Feeling high’ is a result of changes in our perception due to a drugs effects, some substances may not act to alter our perception and therefore not make you feel high. Although it’s worth noting that ‘feeling high’ is subjective so ‘high’ to one person might not be the same as to another.\n\nIts best to avoid the term psychoactive substance as it is far too vague imo. The WHO defines a psychoactive substance as ‘a substance that when taken or administered into ones system affects mental processes’. This can apply to a variety of things that you wouldn’t consider to be ‘drugs’ which is normally what people are referring to using this term.\n\n_URL_0_"
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foijvj | how are manufacturers going to suddenly switch to manufacturing ppe/ventilators? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/foijvj/eli5_how_are_manufacturers_going_to_suddenly/ | {
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"Here is an example. A ventilator company said they needed plastic parts to make more ventilators, but their supplier was in China. They had molds, but needed plastic pellets and the specific injection machine their Chinese supplier uses. GM said they had several such machines, I think they use them to make taillights or engine covers. The ventilator company sends the molds over and some GM plastics molders are stamping out ventilator parts."
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6x75kd | Does the Doppler effect have any noticeable consequences on wireless Internet connection? | Let's say I'm downloading a file and run towards my router at significant speed, will that make the file download faster, or cause errors? Does it matter whether the signal is AM or FM? | askscience | https://www.reddit.com/r/askscience/comments/6x75kd/does_the_doppler_effect_have_any_noticeable/ | {
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"So... okay, wifi uses radio waves (at a particular frequency) to exchange information between your computer and your router. Radio waves are a kind of electromagnetic radiation, just like light, X-rays, etc. but their frequency is much lower. This means they carry less energy, so they're not harmful, unlike gamma rays at the opposite end of the [spectrum](_URL_0_). \n\nNow, because radio waves are electromagnetic radiation, they travel at the speed of light (c = 3 x 10^8 m/s) which is... really fast. The speed is slightly lower in air, but this is still a good approximation. \n\nDoppler shift is when, due to relative motion, a wave is \"squished\" or \"stretched\". In light, when the wave gets \"squished,\" since the speed at which it travels remains unchanged but either the object receiving the wave or the object emitting it are in motion, the frequency increases and the wavelength gets shorter. [Here](_URL_1_) is a visual explanation of what frequency and wavelength are, just in case anyone reading this doesn't know. When the frequency of a light wave increases, the color you see is closer to violet. This is what blue shift is. The opposite happens when the wave gets \"stretched\": frequency decreases and wavelength gets longer, so we see it as closer to red (red shift). \n\nSo supposing you were to run toward you wifi router, since the radio waves traveling from it to your computer don't change their speed, the frequency at which they reach your computer's antenna would be higher (but only very slightly) because you'd be \"squishing\" the waves, so to speak. If you ran away, the frequency would be lower.\n\nUnless you were able to move at very high velocities relative to your wifi router, the difference wouldn't be very meaningful. Remember that these waves are traveling at the speed of light, and that's 300,000,000 m/s. A person walking moves at about 1 m/s. As far as the radio wave knows, there isn't much difference between you staying still and you moving at, say, 3 m/s. (I actually don't know how fast people run, but this is simply a random number). For the wave, you're pretty much essentially staying still anyway. This is why we can't actually *see* red shift and blue shift, even though we hear it. Sound waves travel at much lower speeds than light does, so the difference there is audible, but since light moves so fast, our eyes can't really detect the slight (very slight) difference in color. \n\nSo your computer receives the wifi signal at a very slightly different frequency. This wouldn't affect download speed in a noticeable way. If you were moving fast enough, then it may cause errors, though. The reason is that wifi is basically a kind of radio, so your computer receives the signal through an antenna. The antenna is capable of receiving signals at a range of frequencies. I'm not sure how big it is in wifi antennas, but my handheld radio uses the same antenna for a range of about 4MHz and another one for a range of about 30MHz (this one is at a higher set of frequencies). In other words, your computer will be able to receive the signal and should be able to interpret it unless you're able to move fast enough that the change in frequency falls outside the channel it's \"listening\" on. Due to nature, a radio wave at a frequency in particular actually \"spills over\" onto neighbor frequencies (and you may even hear harmonics on farther away frequencies), so it's not a neat signal that exists exclusively at that specific frequency. There's a bit of leeway.\n\nI'll answer the bit about AM and FM in the afternoon, though, I'm late for class. But short answer: it shouldn't matter either, unless you're moving really fast. Then, the FM signal would have issues that the AM signal wouldn't- but if you're moving fast enough for that to happen, then you're not gonna be receiving the signal correctly to begin with because it'll have changed frequencies beyond what the radio can receive.",
"Yes it can actually have a pretty significant effect on communications. [In particular, if S(f) is the spectrum of your original signal, S(*a*f) will be the spectrum afterwards (PDF).](_URL_1_) Here *a* is relatively close^(1) to 1, basically 1 - v/c where c is the speed of light and v the velocity of the object. At most the shift will be a few Hz.\n\nThe shift in Hz is not a problem, in fact [phase lock loop](_URL_4_) are already usually applied so that the receiver can reap the gains of using coherent demodulators (PDF) [see here (PDF)](_URL_3_). Phase lock loops help to account for artifacts such as signal drift, and so on. The point being this is not where the problem comes in.\n\nThe big problem is what occurs with multi-path communications. If your signal has multiple reflections (like, if you are in a room of some sort instead of in an open field). When moving now, there will be a different velocity shift depending on the angle of arrival of the wave. And because of this the signal, being the sum of the different waves, can experience a wide arrange of channels. ~~Some of these channels will begin to have different interference patterns.~~ This is problematic though as the capacity (maximum amount of bits/second that can be sent over it) basically defaults to the minimum rate achievable over all possible channels simultaneously (see [Theorem 1 (PDF)](_URL_2_)). ~~Thus if one of those bands you pass over has a really bad channel, there goes your ability to connect in general.~~ While the variation due only to doppler shift will be small (about 80 Hz for 5 mph over 5GHz), it is just on the edge of what is considered to not be completely trivial.^(2)\n\nAnytime you transmit a code with a higher rate than the capacity of the channel, an error will occur. As a result a moving source does increase the probability of packet error, with the probability increase depending on the speed and strength of the reflections. \n\nThe same principal applies to AM and FM radio. Although both of which are horribly inefficient in terms of transferring information, so it is unlikely that it would have a noticeable impact. To put it in perspective, a WiFi router is trying to transmit at the very edge of comprehension, while AM and FM require the signal to be easily understandable. Adding a little bit more noise to the WiFi signal will move it past the point of comprehension, while for AM and FM the added noise will still result in a large enough SNR for it to not make a difference. \n\nEdit-- \n\n1 - correction due to /u/devman0 \n\n2 - Added later, as was pointed out by /u/dirtyuncleron69 and /u/dayzstu. Crossed out what is not directly attributable to the doppler shift. \n\nAlso, while on the edit, for a much more in depth discussion about how we model movement and the impact this has on communication, please see [Wireless Communications by Andrea Goldsmith](_URL_0_). She is the most prominent authority on the subject. Chapter 3 in particular talks about this exact scenario in realistic environments, and chapter 5 the impact on capacity. ",
"I think you're confusing modulation frequency and the wave frequency. The wave frequency is in 2.4GHz or 5.8Ghz. *That* is what would change if you were to run towards or away from the router. So you would be slightly shifting the frequency away from it's channel but you would have to move very fast for this to exceed the lock range of the receiver. The modulation rate (how fast the waveform is changed to encode data) would not be affected. So there is no way to make it go faster by moving. But if you move fast enough (way faster than running) to cause transmission errors and trigger retransmissions, you might make it slower.",
"The phase shift of the wireless data signals from the Malasian Airline MH370 aircraft was actually a significant piece of data that contributed toward determining approximately where it went.\n\nModern equipment is designed to compensate for this effect where it is necessary, but the Inmarsat satellite logged all the correction factors it used when receiving the data from MH370, and those became the missing link in localizing the unknown transmission location.",
"The Doppler effect does affect radio waves, but you can't move yourself fast enough for it to have a measurable effect on your wifi connection. Even if you could at best it would do nothing or degrade your signal due to the frequency shift. It's certainly not going to help in any way.\n\nThe shift magnitude is dependent on both speed at frequency. At aviation speeds at microwave frequencies the shift can become significant. At satellite speeds it becomes significant down at VHF frequencies. Here are some interesting experimental results from flying 10ghz ham radios on aircraft. Even then it looks like they saw shifts of up to 1khz; that small of shift is unlikely to throw off WiFi, which also operates at lower frequencies hence would have a smaller shift. _URL_0_\n\nWhen communicating via low earth orbiting satellites the Doppler effect can be significant as the frequency is shifted by several kilohertz as the satellite passes overhead. Iridium satellites e.g. will only communicate with other Iridium satellites moving in the same direction. _URL_3_\n\nThe Doppler effect was also used to try and locate the MH370 crash, without much success unfortunately. _URL_2_\n\nThe Doppler effect is also used by police radar guns to measure car speed. It's also used in weather radar to determine storm velocity. _URL_1_",
"As people have noted, \"running\" is too small.\n\nThe entire concept of time is not totally fixed to begin with. A receiver has a crystal it uses to generate its sense of time, that can be slightly different from the transmitter and both are going to be \"off\" by some small amount from the global standard for time references. Also it has a filter of resistors and capacitors that are far less precise, but it's got more tolerance for error there.\n\nThe magnitude of frequency shift from Doppler in a jet plane is still less than shift from normal component inaccuracy.\n\nThe receiver circuitry typically employs a phase locked loop which reconstructs the carrier wave exactly, not just in frequency but phase. So not only does it say \"this is a 2.4000000000002 GHz carrier by our time standard\" but \"the next wave starting point is exactly... now... now... now...\" Minor error in frequency is well-tolerated.",
"Typically, you can't move fast enough on earth to see this phenomenon. There was a Railway extension to the GSM specification which bolstered the original spec to handle stations aboard trains moving at high speed, but this was mainly minimizing the time it took to connect to, and hand off from base stations.\n\nLow Earth Orbit satellites travel fast enough to exhibit this behavior, and their signal will be higher in frequency as they approach you, and right on as they pass overhead, to becoming lower in frequency as they travel away from you. Usually this doppler shift is taken care of automatically (Iridium) but sometimes it's not (ham radio).",
"Yes, very much. In fact this is the method the [speed guns](_URL_0_) cops use to measure your speed. Without a doppler shift phenomenon this wouldn't have been possible. This is also why things like redshift happen where the wavelength increases to match red instead of a small wavelength.\n\nVisible light is made up of the exact same thing as your wifi signal by the way. So whatever physics apply to visible light applies to your wifi, just with different properties because they are simply different frequencies. \n\nNote that walking speed has no practical effect on a wifi signal. However something like an airplane does get affected at high speeds when communicating with \"stationary\" objects(satellites, base stations). [Here](_URL_1_) is a random article where a new project where airplanes have to communicate with base stations had the issue of correcting this shift in frequency. In fact it was one of the bigger challenges.",
"Actually it heavily depends on the kind of modulation you are using. E.g. OFDM (right now most commonly used) is really sensitive to frequency shifts, and it is used in 802.11 a/n/AC (WLAN), but your speed should not result in Doppler shifts large enough. However, for mobile networks, your speed can have a huge impact (think of moving in a car/train). In fact, LTE uses OFDM(A), while 3G uses WCDMA and 3G is much less sensitive to Doppler shifts (but OFDM and some other techniques in LTE are speed wise and in general superior)",
"I worked on 3g/4g mobile phone baseband. Doppler effect has a major role there. Exactly as the other posters said, the multiple paths that the signal takes to get from the base station to your mobile's antenna combine in ways that make resulting received signal fluctuate wildly both in phase and amplitude. Dealing with this is one of the main tasks of the \"baseband\" processing chain. In fact, the mobile phone performance test specs have different test cases to cover a range of conditions, including different values of Doppler shift.\n\nOne other note. Doppler shift is significant even when there is no multipath. Imagine a mobile phone on a high speed train in Japan. Base stations are sometimes located near the train tracks. So the Doppler shift changes rapidly from, say plus 2kHz to minus 2kHz as the train zooms past the base station. So the AFC (automatic frequency correction) in the phone gets exercised heavily.\n\nEDIT. I want to add that many of the other posts here, including the top post, have minor inaccuracies or misleading statements. The main missing piece of information that everyone has missed so far is that all current wireless systems use phase modulation. Either QAM or at least QPSK. This means that the information is encoded in the phase of the signal. Even the smallest amount of Doppler shift makes the phase rotate over time. The receiver has to constantly compensate for this effect. This is also one of the reasons why the mobile radio signal structure (encoding and modulation) is quite complex. This is also why Wi-Fi can't be used when mobile. Wi-Fi can't cope with high speed Doppler.",
"Test your theory. Run back and forth from your router while checking your internet speed. Then let us know your results. Statistically you should do this 30 times to gather the best data, unless you plan on bootstrapping your data. Good luck.",
"Another thought: Think of the over the air link as a fifo memory (first in first out). If you run towards the base station, not only do you Doppler shift the receive signal, but you get an ever so slight increase in data rate as you shorten the fifo memory. The base station is playing data into the over-the-air \"memory\" and your phone is receiving data from that memory. Running towards the base station plays out data at a rate that is slightly greater than the data rate feeding into \"over-the-air\" memory. (Until you hit the base station after which you can get no closer). ",
"No the file will not download faster. Modern Wifi transmits using AM (actually QAM which is the same except it uses complex numbers) on hundreds of evenly spaced frequencies. Each transmission on those frequencies is constant for a fixed amount of time. The amount of time each transmission is constant for is decided by the base station's clock. Any amount of movement at your end (even at relativistic speeds) doesn't change that symbol time. Your modem will simply have to adjust its internal sense of time to compensate for the Doppler shift in frequency. If the symbol time doesn't change then the datarate doesn't change either.\n\nThe Doppler effect *is* a potentially significant impairment though. This shifts the frequency which must a) be measured by your wifi chip and b) must be corrected. If the *change* in frequency is slow, there's no problem – the wifi chip is designed to handle it. But if the change is fast, it will fail to keep up, fail to decode the data and it will have to be retransmitted, lowering the datarate. This is not a problem for walking speeds. But on a high speed train (moving relative to the wifi basestation), it might be a problem.",
"Another thought: Think of the over the air link as a fifo memory (first in first out). If you run towards the base station, not only do you Doppler shift the receive signal, but you get an ever so slight increase in data rate as you shorten the fifo memory. The base station is playing data into the over-the-air \"memory\" and your phone is receiving data from that memory. Running towards the base station plays out data at a rate that is slightly greater than the data rate feeding into \"over-the-air\" memory. (Until you hit the base station after which you can get no closer). ",
"No the file will not download faster. Modern Wifi transmits using AM (actually QAM which is the same except it uses complex numbers) on hundreds of evenly spaced frequencies. Each transmission on those frequencies is constant for a fixed amount of time. The amount of time each transmission is constant for is decided by the base station's clock. Any amount of movement at your end (even at relativistic speeds) doesn't change that symbol time. Your modem will simply have to adjust its internal sense of time to compensate for the Doppler shift in frequency. If the symbol time doesn't change then the datarate doesn't change either.\n\nThe Doppler effect *is* a potentially significant impairment though. This shifts the frequency which must a) be measured by your wifi chip and b) must be corrected. If the *change* in frequency is slow, there's no problem – the wifi chip is designed to handle it. But if the change is fast, it will fail to keep up, fail to decode the data and it will have to be retransmitted, lowering the datarate. This is not a problem for walking speeds. But on a high speed train (moving relative to the wifi basestation), it might be a problem.",
"Another thought: Think of the over the air link as a fifo memory (first in first out). If you run towards the base station, not only do you Doppler shift the receive signal, but you get an ever so slight increase in data rate as you shorten the fifo memory. The base station is playing data into the over-the-air \"memory\" and your phone is receiving data from that memory. Running towards the base station plays out data at a rate that is slightly greater than the data rate feeding into \"over-the-air\" memory. (Until you hit the base station after which you can get no closer). ",
"No the file will not download faster. Modern Wifi transmits using AM (actually QAM which is the same except it uses complex numbers) on hundreds of evenly spaced frequencies. Each transmission on those frequencies is constant for a fixed amount of time. The amount of time each transmission is constant for is decided by the base station's clock. Any amount of movement at your end (even at relativistic speeds) doesn't change that symbol time. Your modem will simply have to adjust its internal sense of time to compensate for the Doppler shift in frequency. If the symbol time doesn't change then the datarate doesn't change either.\n\nThe Doppler effect *is* a potentially significant impairment though. This shifts the frequency which must a) be measured by your wifi chip and b) must be corrected. If the *change* in frequency is slow, there's no problem – the wifi chip is designed to handle it. But if the change is fast, it will fail to keep up, fail to decode the data and it will have to be retransmitted, lowering the datarate. This is not a problem for walking speeds. But on a high speed train (moving relative to the wifi basestation), it might be a problem."
]
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"https://cdn.miniphysics.com/wp-content/uploads/2011/07/electromagneticspectrum.jpg",
"http://images.tutorvista.com/cms/images/83/frequency-wavelength-image1.PNG"
],
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"https://wsl.stanford.edu/~andrea/Wireless/SampleChapters.pdf",
"https://pdfs.semanticscholar.org/2aed/1ae6a8739069d3bc6f63875... | |
erl3fe | what part of the brain realizes a memory? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/erl3fe/eli5_what_part_of_the_brain_realizes_a_memory/ | {
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"There is not going to be an answer for your question...we still don't know enough about our own brain to understand it at that level.\n\nWe know approximately where memories are stored and using functional MRI we can see part of the process as it happens but we still don't know.\n\nIt is an excellent question."
]
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[]
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4r5os3 | What exactly happens in our brain when we daydream/space out? Is it similar when we are sleeping? | askscience | https://www.reddit.com/r/askscience/comments/4r5os3/what_exactly_happens_in_our_brain_when_we/ | {
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"**TL;DR:** Daydreaming brain and sleeping brain states are quite different from one other. \n\nWe have a brain structure, more accurately, a type of neural network formed in parts of the brain, called the \"[Default Mode Network](_URL_1_)\".\n\nThis network, linking several parts of cortical areas and the limbic system, which are known to be involved in sensory experiences. When this network is active, as we learned from [Buckner et al](_URL_0_), the individual is not focused on outside stimulus, but instead is turned inside, hence the daydreaming. (More accurately called [Mind-wandering](_URL_3_) ) When this default network is active, it provides its own stimulation. In layman's terms, it's entertaining us, but we are not far away from our wakeful state.\n\nSleeping, on the other hand is a complex state of entire organism that plays a key biological role such as building up or the repair of immune and muscular systems as well as other syntheses. To be absolutely fair, we are not crystal clear on how the sleeping mechanics of the brain interacts with each other. However, we know that mostly by virtue of the [VLPO](_URL_2_) and thalamus of our brain, a cornucopia of neurotransmitters are controlled, which is assumed to help our brain switch between sleeping and wakeful states. When sleep occurs, a variety of signals of wakefulness are interrupted and most outside stimuli is blocked, which is quite different from what happens in the state explained before.\n\n\n\n\n",
"There's an electrophysiological feature that's shared between non-exploratory waking behavior (e.g., drinking water, spacing out) and NREM sleep, in every mammal studied so far: hippocampal sharp wave / ripples. Brief (~50-200ms) cell firing bursts with a ~150Hz oscillation in region CA1 of the hippocampus, involved in memory formation/consolidation. "
]
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"https://www.ncbi.nlm.nih.gov/pubmed/18400922",
"https://en.wikipedia.org/wiki/Default_mode_network",
"https://en.wikipedia.org/wiki/Ventrolateral_preoptic_nucleus",
"https://en.wikipedia.org/wiki/Mind-wandering"
],
[]
] | ||
6qpoa4 | How do orbital mechanics and our meteor showers work? | Searching online I was seeing how meteor showers form and if there are any maps with orbit paths and why we have these showers seemingly at the same time each year. | askscience | https://www.reddit.com/r/askscience/comments/6qpoa4/how_do_orbital_mechanics_and_our_meteor_showers/ | {
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"Most meteor showers are moving debris fields left behind by comets. They are in a particular area of Earth's orbit and have a particular trajectory so that's why their timing and apparent direction is so predictable.",
"Comets that enter the inner solar system tend to disintegrate while doing so because they are made up substantially of ices (water, CO2, ammonia, etc.) which evaporate as they get closer to the Sun. This evaporation leaves gaps in between other material (dust, pebbles, rocks, etc.) but it also creates forces which push that material away from the comet. This creates a tail of debris which lends comets their distinctive appearance from Earth. This debris trail is mostly in the same orbit as the original comet, but not exactly.\n\nThe way orbits work is that for the most part any small amount of movement won't change the overall orbital characteristics much. You might change the orbital eccentricity a little, or the semi-major axis a little, but overall the path the material takes around the Sun is going to be very similar, it takes a lot of delta-V to change that. However, any change to the orbital period will compound for each orbit. Let's say you have a comet with a 1 year orbital period, and a little bit of debris from that comet has a 360 day orbital period. That means every single year the debris will end up 5 more days \"ahead\" of the comet itself. After 36 years the debris will be on the opposite side of the solar system from the comet.\n\nWhat this means is that the debris from a comet will spread out sideways from the comet's orbit only a little, but it will spread out across the entire orbit a lot. If the orbit crosses near Earth's orbit then there will be a time every year where Earth plows through the debris cloud, creating an opportunity for a meteor shower.\n\nFor example, comet Swift-Tuttle orbits the Sun with a period of 133.28 years, and has done so since at least 69 BC (which is at least 15 orbits), if not much longer. During the time it's been passing through the inner solar system it's been shedding debris and that debris cloud has been stretching out along the orbital track over the centuries, as each little bit with a slightly different orbital period falls behind or pushes ahead. The Earth passes through the orbital path every year around August 12th, and some of the debris enters the atmosphere, creating meteors, this is the Perseid meteor shower. Other debris clouds for other comets also intersect Earth's orbit, which creates other periodic meteor showers."
]
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[],
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] | |
q9q1p | How did the idea of light having a speed come about? | askscience | http://www.reddit.com/r/askscience/comments/q9q1p/how_did_the_idea_of_light_having_a_speed_come/ | {
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"A good history is available [here](_URL_0_).\nAll modern theories of light include a finite speed, although it is sometimes neglected in calculations for the sake of convenience.",
"the first human that had the idea that light had a speed, was a greek philosopher by the name of Empedocles, he argued that light was something in motion, and thus took some time to travel. Aristotle disgreed, saying that light was the actual presence of something, not a movement of something from the presence to the observer. later, other scholars like Euclid and Ptolemy agreed that light came from the eyes, and enabled sight that way. Heron of Alexandria, based on that theory, said that light has infinite speed because, if you open your eyes, you see the stars right away. ",
"I know that Galileo attempted to measure the speed of light by having himself an an assistant stand on two opposite hills and opening/closing lanterns, but light is too fast for that to work. I am not sure if he concluded based on this that it was instantaneous or just very fast.\n\nAstronomers concluded that light had a finite speed based on observations of the moon of Jupiter in the seventeenth century, although I believe they were off by 30% or something similarly large. The first more accurate measurements were, I believe, made by Fizeau in the nineteenth century, and the actual speed of light was derived by Maxwell a few decades later. "
]
} | [] | [] | [
[
"http://en.wikipedia.org/wiki/Speed_of_light#Early_history"
],
[],
[]
] | ||
fgp7vr | why do city construction projects cost so much? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/fgp7vr/eli5_why_do_city_construction_projects_cost_so/ | {
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"Signs near roads have to be very safe. Wind and storms can apply enormous forces, particularly something that's 80 feet long. The cost would be the same on private land, unless the owner didn't worry about the liability.",
"Materials, unions, labor, insurances, lawyers, permit fees by the city. The list goes on and on."
]
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[],
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1ag8es | Could a black hole that's big enough, cause a "Big Bang" large enough to create a new universe? | I don't know much about black holes, but I'm wondering if they can get so big and heavy, that they explode in some way to create what we would perceive as a big bang.
I like the idea of there being multiple universes, and that the universe can be born again and again infinitely, so I thought about what it might look like if a person zoomed out far enough to see what the universe looked like, with other universes around it. I tried to think about patterns we see on small scales and large scales, and came up with this sketch I made _URL_0_
Since the big bang comes from one point, I thought it might look like a bubble of some sort, and if it came from an exploding black hole (White hole?), maybe there could be others too.
The image I made would try to show a cross section of entire universes created by big bangs. Other universes would collide with eachother, forming big concentrations of galaxies and matter of all kinds, making huge black holes that we have not even seen yet. At these super concentrations of galaxies and stars, there would be a lot of black holes, all converging and eating eachother until there was one big enough to get too big to exist, and explode. That is, if black holes ever explode.
I'm using the word 'universe' in a way that makes it sort of just an area in space created by it's own big bang. Like how we call a swirling group of stars orbiting a super-massive black hole a galaxy.
I'm not very educated on the matter, just been to high school, so forgive me if this idea and question sounds silly! | askscience | http://www.reddit.com/r/askscience/comments/1ag8es/could_a_black_hole_thats_big_enough_cause_a_big/ | {
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"Black holes do explode, or die violently, but sadly only small ones do. In fact very massive black holes are incredibly stable and emit very, very little energy. I'm talking less then the power of a small LED. Also it's best not to think of space as nothingness, even empty space is something and the Big Bang was the beginning of space itself. As for your sketch it looks a lot like the dark matter distribution maps, take a look if your interested.\n_URL_0_"
]
} | [] | [
"http://i.imgur.com/tQCfksU.jpg"
] | [
[
"http://scienceblogs.com/startswithabang/files/2011/08/dark_matter_millenium_simulation.jpeg"
]
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2jjz4o | Before our knowledge of genetics took off, how did most ancient cultures view inbreeding and marriages within the family? | I'm currently studying genetic disorders, and a friend of mine asked the above question. I know it's still a big cultural divider today, but how, and more importantly WHY, did ancient cultures hold their views on inbreeding? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2jjz4o/before_our_knowledge_of_genetics_took_off_how_did/ | {
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"text": [
"The magic legal-history words you're looking for are \"[consanguinity](_URL_2_)\" (degree of relationship by blood).\n\nThe degrees of consanguinity and affinity which are allowed have drifted and changed over time, however there is a long-term consensus around a consanguinity line at 4 (allowing first-cousin marriage but no closer). \n\nIn 1775 [Samuel Halifax notes](_URL_0_) that in comparison to ancient Roman civil law, the English law of the time was more permissive. For example, marriage of first cousins was at times denied by the Romans around the time of Emperor Justinian (6th c. AD), but was then allowed by the English crown. \n\nIn 1215 the Fourth Lateran Council set the limits of affinity at 1 and consanguinity at 4 ([canon 50](_URL_3_)) after they had previously been set much higher (meaning, more difficult to find a legitimate spouse). \n\nModern law (for example California) also [sets the consanguinity line at 4](_URL_1_).\n\nAs to the why, I'm not entirely certain, but hopefully this can get you started."
]
} | [] | [] | [
[
"http://books.google.com/books?id=P10UAAAAQAAJ&pg=PA12&lpg=PA12&dq=roman+civil+law+consanguinity&source=bl&ots=BLcPNs6s0v&sig=Buut3AGCR0x22L6pM3QoCCTQo5E&hl=en&sa=X&ei=9-1BVIRwhenxAZnLgOgI&ved=0CE0Q6AEwBw#v=onepage&q&f=false",
"http://www.leginfo.ca.gov/cgi-... | |
7josyp | Arguments for being a Loyalist during the American Revolution | I'm an American, and also an Anglophile. Like everyone else, I've become obsessed with the musical *Hamilton*, and I started to wonder which side I would have come down on if I'd been alive at the time. We don't hear much over here about the reasons for remaining a Loyalist. What, in your view, are the best reasons for an American colonist to remain a Loyalist leading up to and during the Revolution? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/7josyp/arguments_for_being_a_loyalist_during_the/ | {
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"Im sure there would've been many factors. Mind at the time the British empire had what was widely regarded as the most powerful military force in the world. Certainly staying under the protection, and avoiding the wrath, of this military power would have been a large factor for many. \n\nFor some it would likely have been as simply as not wanting to give up their national identity as citizens of the Empire.\n\nFor a long time the loyalist perspective was actually the majority, however the \"patriots\" were keen to publicly shame or attack those who expressed such beliefs.\n\nInterestingly, during the war, the british promised to free any slave who rebelled against their revolutionary master, and at the end of the war some 20000 african americans were evacuated by the british and resettled as free people.",
"They generally fell into one of two categories. Category A were those who legitimately felt a connection to the Mother country. No different than than an American with the \"my country right or wrong \" mentality. It would be extremely heart-wrenching for many Americans to de liberately abandon their country AND commit treason against it. John Dickinson for example, simply wished to get his rights as an English subject. \n\nCategory B were those who felt the winning side was going to be Britain. Also not difficult to see the reasoning. John Adams estimated, and it's still relatively an accurate statement, that roughly a third supported the Patriots, a third were Loyalists, and another third didn't much care either way. So looking at it from a military standpoint: one side has arguably the best Navy in the world, a standing army of tens of thousands, money, equipment, powder, musket, and cannon production, plus leadership and training. The Americans had no real government structure, a semblance of a military, ill-trained with often little or poor leadership, literally no formal navy, few resources or facilities to produce weapons of war, and barely a third of the populace supported their cause. Many assumed the Patriots didn't stand a chance and acted accordingly. \n\n(I'll have to edit tomorrow with sourcing, gotta get out some books and a grad-level paper I wrote on Loyalists)\nEdit: Sources:\nBoucher, Jonathan. Reminiscences of an American Loyalist: 1738-1789. Edited by Jonathan\tBouchier. New York: Houghton Mifflin, 1925. Reprint, Port Washington, NY: Kennikat\tPress, 1967.\n\nBerkin, Carol. Jonathan Sewall: Odyssey of an American Loyalist. New York: Columbia\tUniversity Press, 1974.\n\nBurke, Edmund. Speeches and Letters on American Affairs. Introduction by Very Rev. Canon\tPeter McKevitt. London: J.M. Dent & Sons, 1908. Reprint, 1961.\n\nNelson, William H. The American Tory. Oxford: Clarendon Press, 1961.\n\nGalloway, Joseph. The Claim of the American Loyalists Reviewed and Maintained Upon\tIncontrovertable Principles of Law and Justice. The Loyalist Library. The American\tRevolutionary Series. Boston: Gregg Press, 1972.\n\nJohnson, Elizabeth Lichtenstein. Recollections of a Georgia Loyalist. 1836. New York: The\tBankside Press, M.F. Mansfield and Co., 1901.\n\nThe Journal of Samuel Curwen: Loyalist. Edited by Andrew Oliver. Vol. I. Cambridge:\tHarvard University Press, 1972.\t\n\nLetters of Hugh Earl Percy From Boston and New York, 1774-1776. Edited by Charles Knowles\tBolton. Boston: Charles E. Goodspeed, 1902. The Loyalist Library, The American\tRevolutionary Series. Boston: Gregg Press, 1972.\n\nLetters of James Murray, Loyalist. Edited by Nina Moore Tiffany and Susan I. Lesley. Boston:\tn.p., 1901. The Loyalist Library. The American Revolutionary Series. Boston: Gregg\tPress, 1972.\n\nSiebert, Wilbur Henry. The Loyalists of Pennsylvania. Columbus: Ohio State University, 1920.\tThe Loyalist Library. The American Revolutionary Series. Boston, Gregg Press, 1972.\n\nUpton, Leslie F.S. The Loyal Whig: William Smith of New York and Quebec. Toronto:\tUniversity of Toronto Press, 1969.\n\n"
]
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2mqr2u | How did royalty from the middle ages smell? | Weird question. But due to not having proper sanitation did even royalty smell pretty bad? I don't know if this is true but I heard that some rooms in the palace of Versailles, spare rooms were used for defecation. Is that true? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2mqr2u/how_did_royalty_from_the_middle_ages_smell/ | {
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"Just to point this out, Versailles only gained relevance in the 17th century:\n\n > hunting lodge built there between 1623 and 1624. In the early 1630s he had architect Philibert Le Roy rebuild it in stone and brick and purchased the seigniory of Versailles.\n\n_URL_1_\n\n > Versailles was certainly the last major achievement of this great architect of the middle of the 17th century. After the Grand Divertissement of 1668, Louis XIV entrusted Le Vau, Chief Architect to the King since 1654, with the extension of the brick and stone palace of his father Louis XIII.\n\n_URL_0_\n\nSince many people attribute phenomena that would more accurately be placed in the renaissance or later to the middle ages, you may want to clarify your question.",
"Well it depends on where this royalty is from (what region/kingdom). \n\nI will not speak for the whole of Europe, but I do know quite a bit on bathing in Hungary (also take note that when I refer to Hungary, I mean the medieval kingdom, i.e Greater Hungary). As you may know, Hungary has an abundance of thermal springs, and its bath culture has existed since the foundation of the kingdom. However, the first thermal baths were built around the time of Mathias Corvinas (~1450). Once the Turks invaded, they also brought their bathing culture, and the ruins of many Turkish baths can still be found in Hungary. \n\nNow for the aristocracy: Hungarian aristocrats during the medieval era were prolific bathers, which can actually be derived from their behaviour during the Renaissance and the Enlightenment. While the nobles of other countries were wearing wigs to prevent headlice (due to poor hygiene), Hungarian nobles in general preferred to grow out their hair naturally. Take a look at some portraits of Hungarian nobles if you want to see this (there are some exceptions, such as nobles that allied themselves with the Austrians). Another example can be found in Miklós Wesselényi's journal, when he mentions that while staying in a castle in the Holy Roman Enmpire, he had to open all of the windows in his room to let out the stench, and thus his room was freezing. This again highlights the culture of hygiene in Hungary, although I admit, it is a few hundred years after the medieval era. \n\nIn conclusion, a Hungarian noble would actually smell quite rosy in the medieval ages. However, I did not address perfume, because I know very little of it, and I hope that someone else will help you out in that department. One of my sources is a very simple, yet descriptive account in English of some of the points that I have mentioned, but I refrained from including too many Hungarian language sources, because I doubt there are many people who will bother reading them.\n\n_URL_1_\n\n_URL_0_"
]
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"http://en.chateauversailles.fr/history/versailles-during-the-centuries/the-palace-construction/louis-le-vau-1612-1670",
"http://en.chateauversailles.fr/index.php?option=com_cdvfiche&view=cdvchapitre&template=blank&idr=4D3FD00F-F6ED-57A2-47D9-2440778646B0&idc=A4052ECD-0DE9-21B4-4AAC-455A15... | |
oa70e | Are all viruses descended from a single common ancestor? | If not, how often and from where have they emerged?
*Edit:* Is it known whether DNA or RNA viruses evolved first? | askscience | http://www.reddit.com/r/askscience/comments/oa70e/are_all_viruses_descended_from_a_single_common/ | {
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"According to this _URL_0_\n\nNo. \n\nCheck out figure 2\n\n_URL_0_/figure/F2",
"This question hasn't been satisfactorily answered, and probably won't be for a while, but I can tell you what I do know. There are multiple ideas as to the origin of viruses and i'll tell you the top two i've come across. \n\n* The first theory is that viruses are escaped genes from other organisms. This theory would mean that somehow, maybe through death or harm, an organisms DNA broke off, and it was complex enough to self-propogate. Viruses could have developed independently multiple times, or it could have happened just once and this \"Eve\" of viruses could have mutated and self-propogated to create a whole diverse range of modern day viruses\n\n* The second theory is that viruses originate in parasitic cells that evolved to rely on parasitism to such an extent that its non-parasitism coding DNA was slowly lost and the cell \"regressed\" into what we know as viruses.\n\nThe thing about all this is that these \"theories\" are basically just possibilities that have been supported by an \"eh\" amount of evidence. There are definitely multiple other theories as to what may have occurred. But don't put too much weight in them yet. \n\nVery interesting stuff though. Viruses are always intriguing",
"How do STDs begin? ",
"A little late to the game here, sorry. The best answer is that we just don't know. Viruses are too complex for their origins to be studied in a chemistry lab i.e. the [Miller-Urey experiment](_URL_0_) but too simple to be examined among early cells in the fossil record. \n \nAlso, all the major theories have some pretty significant shortcomings. The so-called \"escape\" hypothesis is attractive because we can observe segments of bare DNA to exhibit some properties similar to viruses. Transposons, for instance, can \"jump\" from one section of the genome to another in certain species under certain conditions in the same cell. These are a far cry from a real virus, though. Ask anyone who's spent time trying to transfect plasmids into bacteria and they'll tell you DNA is most definitely not inherently \"infective.\" \n \nThe other two theories basically state that viruses have come to be from either more or less complex structures. Either they were once cells that lost their ability to function without a host, or they were once simple molecules that gained complexity through mutation and selection (as can be applied to molecules, not mutation in the strict sense). Both are intuitive theories but unfortunately are very hard to test and to my knowledge haven't been tested thoroughly. Perhaps as computing power increases some smart computational biologist can model the \"gain complexity\" theory, but as it is now we don't have enough power to [model protein folding](_URL_1_). \n \nYeah, so tl;dr, this is one evolutionary biology question we just don't have the answer to (yet).",
"\nBasic lab work in microbio has taught me that [horizontal gene transfer between unrelated species](_URL_1_) is commonplace. It's not difficult to imagine this travelling information taking on a life of its own.\n\nIf you want a eukaryotic example, check out [canine transmissible venereal tumor](_URL_0_).\n\nI think whatever form the early replicators that eventually gave rise to life on Earth took, it is likely that our boundary definitions of what means what would be inadequate to explain them. I also think that basic forms of competitive advantage would arise early & frequently, but there's no way we can currently prove this one way or the other.\n"
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"http://folding.stanford.edu/"
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1vd5sv | at what point does sound become destructive? | Since sound is a wave, if I pumped thousands of decibels (dB) at a structure, could I blow it up? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1vd5sv/eli5_at_what_point_does_sound_become_destructive/ | {
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"Most of the damage caused by an explosive is from the pressure wave, which is technically a sound wave, so yes. You can destroy things with sound.",
"There are some good answers here, but there are two more, equally cool answers. \n\nSo first, yes, a powerful sound wave is actually just a powerful pressure wave, which can break things if strong enough. \n\nBut you can build on this. One way to amplify this sound is to use two equal sound waves. There are predictable points where the sound waves will interfere with each other. At some of these points, the waves will cancel each other out. At other ones, it will double the amplitude of the wave. (This is how they treat [internal kidney stones without surgery](_URL_1_).)\n\nThe third possibility is much more subtle. Every solid thing has what's called a resonant frequency. This means if that thing is vibrated at that frequency, it will start to shake harder than the amplitude of the wave hitting it. You can use sound waves to make a thing vibrate at its resonant frequency. The sound doesn't have to be all that loud either. If the amplitude of the sound is high enough, you can get those things to literally break apart from their own vibrations. [Check out this wine glass being destroyed](_URL_0_) by resonant frequency."
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4xsqr7 | Will we see any major constellations lose stars in our lifetime (next ~60+ years or so)? | askscience | https://www.reddit.com/r/askscience/comments/4xsqr7/will_we_see_any_major_constellations_lose_stars/ | {
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"Not noticeably by eye. [Barnard's Star](_URL_1_) is the star with the highest proper motion, which is how much it moves across the sky (an angle) per unit time, which is 10.3 arcseconds per year. If you hold your arm out and hold up your pinky finger, that's about one degree. One degree is made up of 60 arcminutes, and one arcminutes is made up of 60 arcseconds. So Barnard's Star, which has the *highest* proper motion of any star, is moving 1/6th of 1/60th (i.e. 1/360th ~0.003) of the width of your pinky. For a bit of a weird comparison, that's the same ratio as a circle drawn around the entire sky to your pinky (since there are 360 degrees in a circle, that's 1/360th).\n\n[Here](_URL_2_) is an example of how the Big Dipper and Orion will change over the span of 150,000 years. Note that stars are different distances away from us with different three-dimensional velocities, so that's why some features persist longer than others (e.g. [Orion's belt](_URL_0_) consists of three fairly distant stars though none very close to each other).",
"Betelgeuse is [scheduled to go supernova](_URL_0_) at a random time between right now and the next million years. If you are very lucky you will temporarily have a star brighter than a full moon in the sky for a few days, and then Orion will appear to lose his left upper shoulder as the remnant fades.",
"If you mean a star dying, then no, probably not. There is a supernova somewhere in our galaxy once every hundred years or so, but the vast majority are distant stars we can't see with the naked eye.\n\nIf you mean due to proper motion, a star exiting one constellation and entering another, the star Rho Aquilae crossed over the border from Aquila into Delphinus in 1992. I'm not aware of any other stars visible to the naked eye that will do this in the near future."
]
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"http://earthsky.org/brightest-stars/betelgeuse-will-expl... | ||
dkdny4 | If the recipient of an organ donation dies before the donor, could the donated organ be returned to the donor? | I've been re-watching the TV show Lost, and if you're not familiar with it, one character donates a kidney to another. Later in the show, the recipient of the kidney dies, and the SO of the donor jokes, "Maybe he left you a kidney."
Could the donated kidney theoretically be returned to the donor's body? If so, what might be the medical implications? Would it transfer the recipient's illness to the donor? Would immunosuppressants need to be given to the donor?
Thanks in advance for any answers or suggestions where to learn more! | askscience | https://www.reddit.com/r/askscience/comments/dkdny4/if_the_recipient_of_an_organ_donation_dies_before/ | {
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"Lots of practical and logistic reasons not to do it, and the organ may not be in great shape after all its been through (handling, anti-inflammatory medication, stress)... But as far as the question of \"would it still be a match?\" Yes. The organ will still be composed of the same cells, same DNA and same HLA profile as the original donor. Returning it back to the donor would immunologically be an \"autologous transplant\". \n\nAutologous transplants (of viable tissues) are generally highly successful (may include stem cells, bone marrow, blood, fat, tendon). _URL_0_",
"Usually most donors are cardiac or brain dead so generally not. We do use live living donors but hopefully you wouldnt harvest with a moribund recipient. Domino surgery ( ie take heart and lungs out and give heart to somebody else ) used to take place before surgical and immunosppresent techniques improved. Any organ recipient who has been on long term immunosuppression will develop alloimmunity complications and their organs are damaged by this. They are also at increased risk of malignancies. It is as others have said theoretically possible but very rare.",
"It could, but we never do it. This scenario happens all the time. Recipients are generally sicker people than donors, and as a result, many do not out live their donors. There are other technical factors with the organ as well, such as length of renal artery/vein/ureter that come into play. Returning the kidney to the original donor is unnecessary surgery without any real benefit. HLA does not change. Genetic makeup of the kidney does not change. \n\nSource: I’m a surgeon \n\nFunny story from surgical residency: performed a transplant where a male patient received a female’s kidney. While rounding on the patient the next day, he asked, “since I now have a female kidney, does this mean I have to sit down to pee?”",
"No. I asked my heart transplant team, if I were to die in a wreck or something on the way home, immediately after you've just verified my heart is in great condition, would they be able to transplant it into someone else? And they said no, that the transplant center that they're part of (and possibly all of them) won't re-transplant the same organ. My other organs though are useable.\n\n\nEdit: only read the title at first, answered that instead of the question in the post. Whoops.",
"Doubtful, unless they can keep the organ alive while they prep another person who requires the same organ with the same blood type, this takes hours, it usually takes place while the organs are in transport so it's a very tight schedule as it is",
"Follow up question, if the person set to receive the organ dies right before they receive the organ, would they return the organ to the person that just donated it? (I’m talking like healthy person just got it cut out and it’s being walked over to sick person timing)",
"There are lots of reasons not to, but the foremost is technical. It is 10 times easier to operate on virgin tissue and there is 10 time the risk of any given complication doing revision surgery. We as surgeons take complications and mortality very seriously and revision operations should only be done by exceptionally talented surgeons with extensive experience and only when the implications of not doing the surgery are particularly grave for the patient. There are types of suffering that are fates worse than death, and some of those can be induced by major complications of surgery. It would be unacceptable for everyone involved for those to happen when a procedure was not even necessary."
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3e1kdw | Before the American Revolution, what was the present-day US called? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/3e1kdw/before_the_american_revolution_what_was_the/ | {
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"In English-language discussion, the British colonies that became the USA were sometimes called the \"American colonies\" (or \"North American colonies\"). Examples:\n\n* [*The Justice and Necessity of Taxing the American Colonies Demonstrated*](_URL_3_) (London, 1766)\n* [*The Grievances of the American Colonies Candidly Examined*](_URL_0_) (London and Providence, 1766)\n* [*Memorial on the General Culture of Lands in Our American Colonies*](_URL_2_) (Edinburgh, 1766)\n\nOf course, Britain had many colonies on the American continent other than the thirteen who became the United States: [this list from 1774](_URL_1_) includes Hudson's Bay, Labrador, Newfoundland, \"Canada\" (i.e. Quebec), Nova Scotia, and East and West Florida -- not to mention the Caribbean islands such as Jamaica and Barbados. However, I'm not aware of any usage of the phrase \"Thirteen Colonies\" until after the revolution.\n\n"
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"https://books.google.com/books?id=qBpWAAA... | ||
2v2dim | where do people who break iphone's and samsung's, in youtube videos, get the phones in the first place? | I just can't find a reasonable explanation as to how they get 15 iPhone 6's to do "break tests" on. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2v2dim/eli5_where_do_people_who_break_iphones_and/ | {
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"Two reasonable ways are they're sponsored to do so because they're popular on YouTube and get the phones free. Or they already make a shit ton of money and buying them doesn't mean much to them."
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28ha2l | youtube will block independent music videos | So, I can still post a video called "Silly Cat Falls Down Stairs"
But if I post a video of my band playing the song "Silly Cat", it gets deleted?
Because I didn't pay YouTube a fee, like VEVO did? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/28ha2l/eli5_youtube_will_block_independent_music_videos/ | {
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"Essentially, Music companies are fed up with people downloading their artists music for free and uploading them and monetizing them. YouTube are fed up with having music companies threaning to sue. To stop this happening, YouTube is going to make the music section a simple pay to listen sort of deal with the option to download a song for an additional fee. This is why you need to pay a fee to upload music. Because you could upload a full random album off someone and make money from it without the consent of the record label.\n\nAlso, this is why certain artists such as Arctic Monkeys and Adele are getting removed, because the record labels are being forced into ridiculous contracts by YouTube just so the music can be shared."
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9yadu3 | why do your eyeballs roll up when you close your eyes? | Is this exclusive to humans/mammals? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9yadu3/eli5_why_do_your_eyeballs_roll_up_when_you_close/ | {
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"What? I think this might exclusive to you. You mean when you close your eyes, like having a rest, your eyeballs go up as if you would be looking up ? That’s some weird shit "
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5acuyn | To what extent were the events of Russia in 1917 inevitable? | Was the downfall of tsarism and the coming to power of the Bolsheviks inevitable, or precipitated by other factors?
Also, do you know of any historians who argue that the events were inevitable? I've scanned the internet for specific historians, but can't find any :( | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/5acuyn/to_what_extent_were_the_events_of_russia_in_1917/ | {
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"I don't think it was always inevitable but after sometime it became that way.\n\nI asked a similar question about [9 months](_URL_0_) ago that /u/International_KB answered better than I can so I'd advise you to check that out. \n\nThey also cite works by Peter Waldron, David Saunders and Hans Rogger which you may find useful in your search for historians who hold this view. "
]
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"https://www.reddit.com/r/AskHistorians/comments/42ukow/the_reigns_of_russian_tsars_nicholas_i_alexander/czdp726/"
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1zupqz | how come even the simplest medicines have so extreme adverse effects mentioned in the leaflet? | So I was just wondering - in almost all of the medicines we come across, there are tons of adverse effects listed in the leaflet inside the box. Sometimes they mention that such and such effect was spotted in some 1 in 10.000 patients but sometimes they don't and there is just a list of things to watch out for. How is this list composed, is it really a thing that over the course of some clinical tests, they found some patients to have hallucinations or cardiac arrest because of some simple anti-fever water-soluble powder with mostly paracetamolum in it? If so, how come it comes to market in the first place? Or maybe the more extreme adverse effects are just what may happen if you devour a whole box on the spot or use it contrary to the instruction? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1zupqz/eli5_how_come_even_the_simplest_medicines_have_so/ | {
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"Its Acetaminophen . and to answer your question, Its mostly cya on the part of the pharmacy company. and scientific due diligence and throughness.\n",
"No, certain adverse reactions given on the drug are more often allergic reactions or rare, but numerous reaction to drugs within that family of drug.\n\nIf people report a certain reaction after being on morphine, then they may add a warning on prescription bottles of codeine, even though the reaction weren't reported with codeine, it's still in the same family of drug. and therefore you may have the same reactions.\n\nIt's like if someone has a bad reaction to eating carrots, you may warn them against other root vegetables as well, such as turnips, radishes and potatoes."
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llfbi | how do anonymous hack into servers? | I understand small password hack techniques, but how do they get in to quite secure webservers that may have large passwords? e.g. HBGary would of had a secure password, how can they get through that? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/llfbi/eli5_how_do_anonymous_hack_into_servers/ | {
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"Computer programs are not perfect. The computer program running at HBGary is not perfect. So long as a hacker can find an imperfection in the program, he or she can exploit that imperfection to the extent of their computer abilities.\n\nThere is no one hacking method, not a secret trick that works every time. It is merely exploiting that which is exploitable. I couldn't tell you what Anonymous did, but I can tell you that it will likely be patched in the next update for their server software, and that Anonymous will have to find something else to do to gain access.",
"It's not all about password guessing or trying many passwords until the right one is found (so-called \"brute forcing\"). Some may use techniques like SQL injection. This is a situation where hackers will attempt to \"get into\" or retrieve information from a database by using specially crafted statements that are inserted into input fields or even URLs. If an admin or web developer hasn't correctly implemented security or input filtering, then the server will execute the code that is injected. This code can do things like log a user in with admin privileges (privilege escalation attack) or retrieve an entire database worth of information. \n\nSocial engineering can be even more effective. This is where the hacker poses usually as an important/authoritative figure and requests someone else to make a change on a system that will ease their attempts to access whatever info they seek. This plays upon the weakest link in a security system: people. They are coerced into making a change that is against company policy for fear of reprisal by a boss for limiting his access. \n\nThere are other methods, but those three methods are very common. ",
"You would be surprised. \n\nComplex web servers are generally ran by an engineering team, which runs day to day operations. A development team is responsible for writing the actual code for the web site and it's various directories, pools, and extensions (essentially controlling what happens when you interact with the site). In order to test these items, staging or development servers are set up to first deploy these code packages to. Developers (as well as any non-security minded IT folks) don't understand and/or care about password requirements. They establish servers with 6-8 character passwords. When the code is deployed to the live system, these passwords are generally hardcoded into the code rather than changing the code, the engineering team changes their passwords to match.\n\nSo now these various passwords are running as 6-8 characters. When a password is stored on a system, it is not stored as it looks (cleartext). Instead, it is hashed with a salt (a string of random characters). These hashes are then stored in a file, database, or some other media. When a password request is made, the system does the opposite -- it uses the salt and derives the password from the hash. \n\nA complex system of password cracking uses a \"rainbow table\", which is a file that contains a massive amount of these hashes and compares the hash of the system to the hash in the rainbow table to find the password. \n\nThis is the easiest way to crack passwords. However, web server vulnerabilities are not generally passwords. They are vulnerabilities in the server type (IIS, Apache, etc). Generally, live web servers are not patched immediately when the patch is released. Certain patches (specifically Microsoft patches) have a tendency to break web code. Larger companies lose a massive amount of money when the site is not accessible (certain sites like Amazon and eBay measure this by the second). Because of this, newer vulnerabilities can sometimes be exploited on large websites and access to the underlying server can be gained. Once there, it's simple to alter the website any way you like, or access various data directories or tables to download information. \n\nFinally, Anonymous employs certain database injection techniques to gather information from databases. These attacks are literally some of the easiest things a hacker can do. Websites generally have search options or forms that execute database queries on the underlying database server. When prompted for user entry, an SQL statement (database language) can be passed through this user input. If the programming team is not security conscious, the input will be passed as a query and the website will spit out any information requested. Almost everything is stored in databases and can be accessed like this. Credit card numbers, phone numbers, social security numbers, etc. \n\nHope that helps. ",
"Nice try, CIA.",
"It is like asking your mommy for candy, but she says no. So you go to your daddy and you ask again for candy and he says yes. You find the weakest link and exploit it. There is no 1-way solving method, but there are always some exploits out there, if you write a program who automates the proces of finding the exploitable links, you'll save yourself some time and now the less smart people can hack too (scriptkiddies). But these are the people who never heard of proxies (hiding) etc and get caught.\n\nThere are several ways of \"hacking\" a system, you could inject your own code (sql injections, buffer overflows, ...). A computer has to store its information in order to do that, it reserves some memory. If the program expects a value to be between 0 and 255 and you give it a 257 it has no space to store it and it will flip if it doesn't know how to catch it. You could simply be listening to what other computers are saying and filter through the crap to find some passwords (smartphones (3G), wifi, ...). ",
"[Just like this.](_URL_0_)",
"I am not a hacker, but I have spent a little time trying to piece this together for myself. There are a couple of different answers to how this is done, but they all basically involve reverse engineering, either technically or logically.\n\n\nThe logical reverse engineer involves thinking backwards through how you became a netizen, basically, and set up accounts and so on. Most of us, if we are standard, non paranoid web-users, have a junk email account or two which we use to set up accounts, do registrations for dumb sites which require such, and tasks of that nature. Personally I tend to hold on to old email accounts for this purpose. And generally, if we are incautious people, as most of us are statistically, we have some passwords stored inside email, etc. Remember now that there are procedures to follow at most email providers for lost passwords, which generally rely on another piece of information that \"only you could know\" such as the name of your first grade teacher, the name of your first pet, your favorite brand of pipe tobacco, or whatever. \n\nSo follow it through - you have a large number of people in a corporation who have basic access to the network. Many of them are statistically incautious, no matter what assurances their IT department might offer after the fact. So all you have to do is figure out the name of one of those people's first grade teacher, or pet or pipe tobacco or whatever, do the reset password thing, get into their Hotmail or AOL email, then follow up the chain from there. You're likely to find a mention of their password doing a basic search on the files in their sent folder. For a lot of people, if you find one password, you gain access to about half their shit because they aren't bothered to change it. \n\n\nSo that's the gist of this technique - you figure out, person by person, how to access each new level into a place. This is more or less exactly how they hacked something of Palin's last year, but I have only sort of a vague memory of that and don't remember what or why. I'm kind of baked, honestly. Shit - would you say that to a five year old? Probably not. Probably wouldn't say shit either, but you never know - kids can be cool about that stuff sometimes.\n\n\nAnyways, so the other type of reverse engineer is to think technically backward through the pipes on a web server. When you think about it, much of the data on a web server is publicly available by design. Otherwise surfing the web would involve entering a lot of passwords and shit (earmuffs!) to just look at normal stuff. Plus, a lot of the features on a web server are by design interactive, so they are reacting to data which you give them and giving you results, as in a search feature, for instance, or a form. Now, when that data gets passed back and forth - there's a lot of capacity for failure in the exchange. All of those interactions involve giving instruction to the web server, like \"find me all of the puffy pictures you have on this server\". So in a nutshell, hackers try to include more instructions with that literal line and often that works. So they basically add a line of code that says \"find me all of the puffy pictures you have on this server, and by the way, what's the root password to your database?\" And a lot of the time, the server is configured wrong and tells you both answers. That's SQL injection in a very simplified way from a guy who's never done it. Just another reliable piece of internet information, basically.\n\n\nThere are more complicated ways to hack web servers, but all of them are basically aimed at getting the root password for the server, at which point you can wreak complete havoc on anything you want. So that's what they need - one keyphrase that is human readable and probably known by 3 or 4 people at the very least. Given just that simple fact, it's pretty easy to see how any basic web system can be hacked given enough time, people, and determination.",
"Computer programs are not perfect. The computer program running at HBGary is not perfect. So long as a hacker can find an imperfection in the program, he or she can exploit that imperfection to the extent of their computer abilities.\n\nThere is no one hacking method, not a secret trick that works every time. It is merely exploiting that which is exploitable. I couldn't tell you what Anonymous did, but I can tell you that it will likely be patched in the next update for their server software, and that Anonymous will have to find something else to do to gain access.",
"It's not all about password guessing or trying many passwords until the right one is found (so-called \"brute forcing\"). Some may use techniques like SQL injection. This is a situation where hackers will attempt to \"get into\" or retrieve information from a database by using specially crafted statements that are inserted into input fields or even URLs. If an admin or web developer hasn't correctly implemented security or input filtering, then the server will execute the code that is injected. This code can do things like log a user in with admin privileges (privilege escalation attack) or retrieve an entire database worth of information. \n\nSocial engineering can be even more effective. This is where the hacker poses usually as an important/authoritative figure and requests someone else to make a change on a system that will ease their attempts to access whatever info they seek. This plays upon the weakest link in a security system: people. They are coerced into making a change that is against company policy for fear of reprisal by a boss for limiting his access. \n\nThere are other methods, but those three methods are very common. ",
"You would be surprised. \n\nComplex web servers are generally ran by an engineering team, which runs day to day operations. A development team is responsible for writing the actual code for the web site and it's various directories, pools, and extensions (essentially controlling what happens when you interact with the site). In order to test these items, staging or development servers are set up to first deploy these code packages to. Developers (as well as any non-security minded IT folks) don't understand and/or care about password requirements. They establish servers with 6-8 character passwords. When the code is deployed to the live system, these passwords are generally hardcoded into the code rather than changing the code, the engineering team changes their passwords to match.\n\nSo now these various passwords are running as 6-8 characters. When a password is stored on a system, it is not stored as it looks (cleartext). Instead, it is hashed with a salt (a string of random characters). These hashes are then stored in a file, database, or some other media. When a password request is made, the system does the opposite -- it uses the salt and derives the password from the hash. \n\nA complex system of password cracking uses a \"rainbow table\", which is a file that contains a massive amount of these hashes and compares the hash of the system to the hash in the rainbow table to find the password. \n\nThis is the easiest way to crack passwords. However, web server vulnerabilities are not generally passwords. They are vulnerabilities in the server type (IIS, Apache, etc). Generally, live web servers are not patched immediately when the patch is released. Certain patches (specifically Microsoft patches) have a tendency to break web code. Larger companies lose a massive amount of money when the site is not accessible (certain sites like Amazon and eBay measure this by the second). Because of this, newer vulnerabilities can sometimes be exploited on large websites and access to the underlying server can be gained. Once there, it's simple to alter the website any way you like, or access various data directories or tables to download information. \n\nFinally, Anonymous employs certain database injection techniques to gather information from databases. These attacks are literally some of the easiest things a hacker can do. Websites generally have search options or forms that execute database queries on the underlying database server. When prompted for user entry, an SQL statement (database language) can be passed through this user input. If the programming team is not security conscious, the input will be passed as a query and the website will spit out any information requested. Almost everything is stored in databases and can be accessed like this. Credit card numbers, phone numbers, social security numbers, etc. \n\nHope that helps. ",
"Nice try, CIA.",
"It is like asking your mommy for candy, but she says no. So you go to your daddy and you ask again for candy and he says yes. You find the weakest link and exploit it. There is no 1-way solving method, but there are always some exploits out there, if you write a program who automates the proces of finding the exploitable links, you'll save yourself some time and now the less smart people can hack too (scriptkiddies). But these are the people who never heard of proxies (hiding) etc and get caught.\n\nThere are several ways of \"hacking\" a system, you could inject your own code (sql injections, buffer overflows, ...). A computer has to store its information in order to do that, it reserves some memory. If the program expects a value to be between 0 and 255 and you give it a 257 it has no space to store it and it will flip if it doesn't know how to catch it. You could simply be listening to what other computers are saying and filter through the crap to find some passwords (smartphones (3G), wifi, ...). ",
"[Just like this.](_URL_0_)",
"I am not a hacker, but I have spent a little time trying to piece this together for myself. There are a couple of different answers to how this is done, but they all basically involve reverse engineering, either technically or logically.\n\n\nThe logical reverse engineer involves thinking backwards through how you became a netizen, basically, and set up accounts and so on. Most of us, if we are standard, non paranoid web-users, have a junk email account or two which we use to set up accounts, do registrations for dumb sites which require such, and tasks of that nature. Personally I tend to hold on to old email accounts for this purpose. And generally, if we are incautious people, as most of us are statistically, we have some passwords stored inside email, etc. Remember now that there are procedures to follow at most email providers for lost passwords, which generally rely on another piece of information that \"only you could know\" such as the name of your first grade teacher, the name of your first pet, your favorite brand of pipe tobacco, or whatever. \n\nSo follow it through - you have a large number of people in a corporation who have basic access to the network. Many of them are statistically incautious, no matter what assurances their IT department might offer after the fact. So all you have to do is figure out the name of one of those people's first grade teacher, or pet or pipe tobacco or whatever, do the reset password thing, get into their Hotmail or AOL email, then follow up the chain from there. You're likely to find a mention of their password doing a basic search on the files in their sent folder. For a lot of people, if you find one password, you gain access to about half their shit because they aren't bothered to change it. \n\n\nSo that's the gist of this technique - you figure out, person by person, how to access each new level into a place. This is more or less exactly how they hacked something of Palin's last year, but I have only sort of a vague memory of that and don't remember what or why. I'm kind of baked, honestly. Shit - would you say that to a five year old? Probably not. Probably wouldn't say shit either, but you never know - kids can be cool about that stuff sometimes.\n\n\nAnyways, so the other type of reverse engineer is to think technically backward through the pipes on a web server. When you think about it, much of the data on a web server is publicly available by design. Otherwise surfing the web would involve entering a lot of passwords and shit (earmuffs!) to just look at normal stuff. Plus, a lot of the features on a web server are by design interactive, so they are reacting to data which you give them and giving you results, as in a search feature, for instance, or a form. Now, when that data gets passed back and forth - there's a lot of capacity for failure in the exchange. All of those interactions involve giving instruction to the web server, like \"find me all of the puffy pictures you have on this server\". So in a nutshell, hackers try to include more instructions with that literal line and often that works. So they basically add a line of code that says \"find me all of the puffy pictures you have on this server, and by the way, what's the root password to your database?\" And a lot of the time, the server is configured wrong and tells you both answers. That's SQL injection in a very simplified way from a guy who's never done it. Just another reliable piece of internet information, basically.\n\n\nThere are more complicated ways to hack web servers, but all of them are basically aimed at getting the root password for the server, at which point you can wreak complete havoc on anything you want. So that's what they need - one keyphrase that is human readable and probably known by 3 or 4 people at the very least. Given just that simple fact, it's pretty easy to see how any basic web system can be hacked given enough time, people, and determination."
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wxyfb | Why are there so few Mongolians? | Even Genghis Khan's direct patrilineal descendants out number the number of Mongols in the world. Understandably, Mongolia can't really support a large population - but why wasn't Mongol culture and language adopted by residents of the empire?
Like, compare them to the Turkic people - many Mongol successor-states adopted Turkic languages, and the those countries conquered by Turkic people became Turkicized e.g. the populations of Azerbaijan and Turkey adopted Turkic culture and language.
Why wasn't Mongol culture and language similarly adopted? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/wxyfb/why_are_there_so_few_mongolians/ | {
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"The short answer is that the Mongols were much more interested in conquering and receiving spoils than they were in administration. Part of the reason their expansion was so successful is because they let local intermediaries handle a lot of the business of ruling and moved on to the next place to conquer. As long as taxes kept rolling in, they didn't really care about spreading their language and culture.\n\nI am by no means an expert on Mongols or this time period, but we cover their Empires in the \"East Asia to 1600\" lower division class that I TA once a year. Please correct me if I am wrong.",
"Not quite on-topic, but it's worth noting that the region of Inner Mongolia in China has more Mongolians than Mongolia itself.",
"I don't have much to add, but if you live in the Chicago area, I suggest you visit the Genghis Khan exhibit at the Field Museum. It is interesting and might help answer your question.",
"As I understand it they were just interested in conquering. In Europe a a comparison can be drawn between the huns and the magyars for example, they went on extensive military campaign but you don't really see any Huns in Europe and Magyar culture really only established in Hungary. As opposed to the romans or vikings who settled much of europe and became the the cultural roots of any overall European culture, well that and also the Slavs and Celts to a lesser extent.\n\nEdit: Europe, not euope"
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7tf4e3 | When a program crashes and asks to send an error report, does this actually do anything in terms of making the program better? | askscience | https://www.reddit.com/r/askscience/comments/7tf4e3/when_a_program_crashes_and_asks_to_send_an_error/ | {
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"Yes and no. This really depends on the program and the intent of sending reports by the company.\n\nSome companies will have a good error report capture system and will be able to see if the application keeps crashing for the same reason, allowing programmers to prioritize fixing the defect and have information about it, and may fix it in an upcoming patch/release.\n\nSome applications don't really capture the reports well, or they're lost or ignored for a variety of reasons, so it doesn't much help.",
"Yes. I was a software developer working on Microsoft Office in the 2000s. When we made service packs, they typically included fixes for the highest frequency crash reports that were sent to us. So consider sending crash reports something like voting: it doesn't guarantee you'll get the outcome you want, but it improves the odds.",
"[Related question](_URL_0_).\n\nAt best, your crash report is grouped with others to help identify or prioritise a problem for a fix.\n\nAt worst, it ends up processed manually by a human, choking their workload. Or ends up ignored. Depends on your point of view. :)",
"Maybe.\n\nI used to own doing this for a team in a large company. \n\nGenerally, what happens is that the information gets passed off to the company and feeds into their system. All of the reports are grouped together based on the issue and ranked based on how often they occur.\n\nThen, the company draws a line somewhere and divides the issues into \"important enough to fix\" and \"not important enough to fix\".\n\nHow that line is drawn depends on the company, the group within that company, and a lot of other factors. Some groups fix a lot of bugs, some groups fix a disappointingly small number.\n\nSending the report does increase the chance that it will be fixed. "
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4671cn | How can gravitational waves be measured using light (optical path distance), when the space itself (including the light) is stretched? | I'm sure I'm missing something here.
It seems like you're measuring the length of some line of space with a rubbery ruler. When the space is stretched, the ruler is also stretched, so you're not able to actually tell the space is any bigger...
Does it even make sense to talk about space being stretched? What is the space being stretched relative to? | askscience | https://www.reddit.com/r/askscience/comments/4671cn/how_can_gravitational_waves_be_measured_using/ | {
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"A beam is split into two beams that run orthogonally to each other (at 90 degrees), to a separate mirror and back. If the beams combine and cancel each other out, the two distances are the same.\n\nAny variation in the distance causes the waves to not completely cancel out, and the resultant signal is a candidate event.\n\nThis works because the gravity wave compresses space in one direction, while stretching it in another. Making the beams orthogonal gives them a chance to detect the wave. Ideally there would be a third dimension involved.\n\nHaving two such detectors, thousands of miles apart, and due to the curvature of the earth, at different angles, means that the same event can be detected in two different physical locations, at very slightly different times, ie how long it takes a gravity wave to travel thousands of miles. This helps determine the direction the wave came from.\n\nBut you're right, the thing being measured is being measured by a ruler that stretches as well. But having two of them at 90 degrees means they won't always stretch the same.",
"You're absolutely right about rulers stretching with space - by itself, a single ruler could never measure any distortion in space, for the reasons you mention.\n\nThe trick to making such a measurement is to compare two different rulers in areas of space with different amounts of stretching. This is what LIGO does using a couple of very large Michelson interferometers: one laser path goes one way, while the other goes at right angles to it. When the beams are recombined, it's the *difference* between the two paths, not any single distance by itself, that tells you that space is distorting. That is, the ruler in one direction is stretched *more than* the one in the other direction, which is measurable even when the absolute stretching of a single ruler isn't."
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u1zs4 | What makes certain musical time signatures easy to follow? | In music, time signatures such as 3/4 and 4/4 are naturally easier to count, as opposed to odd signatures such as 5/4 or 7/8. Why is this? Are we simply used to hearing music this way after all the music in the past, or is there a psychological reason of why our perception of certain signatures are easier to follow?
If we are simply used to hearing music in 3/4 or 4/4, what makes it hard to adjust to complex time signatures? | askscience | http://www.reddit.com/r/askscience/comments/u1zs4/what_makes_certain_musical_time_signatures_easy/ | {
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"Idk if this comment is on topic/ in the guidelines (I don't have an answer, but I want to ask another relevant question). Why are certain groupings in music easier to count? For instance it's easier to count 4/4 rests in groups of 4 or 8 or 16, e.g. 3.",
"We have few concrete answers on this. Rhythm was likely the first element of human music to manifest, and so its origins lie tens of thousands of years prior to recorded history. Some musicologists (Elena Mannes is one name off the top of my head) have hypothesized that our sense of rhythm and tempo in music derives from our heartbeats and our walking/running pace. This makes sense and is consistent with the data: the average human heart beats at about 60 bpm, the average human walking pace is about 120 bpm, and most of our music is at or near these tempos or feels fast or slow relative to them. 2/4 and 4/4 time are symmetrical, which means that as we walk the same foot will always land on one. 3/4 and 6/8 mirror the rhythm of our heartbeat when you include both the first and second heart sounds (DUB-(pause)-lub-DUB-(pause)-lub-DUB). But ultimately this is just informed conjecture that fits the facts.\n\nAnd while 3/4 and 4/4 are very common in human music in general, they're much more common in Western music, so there's definitely a cultural element at work. 5 and 7 show up frequently in the indigenous musics of South America, and 7 and 11 show up frequently in Greek music. \n\nAs for the second part of your question, enjoyment of music is largely related to the brain's ability to identify and predict patterns. 4/4 (and 3/4 or 6/8 to a lesser degree) are sufficiently common in Western music that, for anyone who has grown up listening to it, they are a fundamental pattern that the brain *always* expects to be in place, and it bases its analysis of all the other patterns in the music, in part, in the consistent presence of that pulse. If it's not there, and your brain hasn't incorporated odd time signatures into its pattern recognition schema by repeated exposure to it, it throws a *huge* wrench in the gears."
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a31jal | Are the divisions of sound frequencies into musical notes arbitrary or do they correspond to something in nature? | askscience | https://www.reddit.com/r/askscience/comments/a31jal/are_the_divisions_of_sound_frequencies_into/ | {
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"The frequency ratio between notes are what matters, not necessarily the absolute frequency. Specific ratios of frequencies sound nice to our ears, for example, two notes an octave apart have a frequency ratio of 2. A fifth has a frequency ratio of 4/3. Why these particular ratios sound nice has to do with superposition of sound waves and can get into some complex mathematics... so I can't give you a great explanation there, sorry.",
"In Western music, the smallest note step is a diatonic semitone. This is pretty arbitrary, basically you take an octave -- which is a natural thing since it corresponds to doubling frequency -- and divide it into 12 equal parts (semitones). Dividing it into 12 is arbitrary.",
"They're not arbitrary. They're a pragmatic approximation of small integer frequency ratios. \n\nThe \"pragmatic\" part is the equal division of the octave, which was done to make it easier to play in any key. \n\n12 notes per octave were chosen because it [approximates the most consonant natural](_URL_0_) frequency ratios, like 3:2 perfect fourth, 4:3 perfect fourth, etc.\n\nThese small integer frequency ratios are based in nature, since we usually produce sound using harmonic motion, which produces multiple tones at integer multiples of the root. When you play multiple such instruments in small integer frequency ratios, many of their harmonics align, and the ones that don't are far enough apart that they don't beat, so the combination tone remains smooth and sounds good to us. Harmony is actually fractal in nature, with increasingly dissonant intervals between each consonant interval.\n\nNon-harmonic instruments are possible, too, like drumheads, vibrating bars, gongs, or bells, but we usually modify them to sound roughly harmonic anyway.\n\nSome people make music using scales based on the natural ratios instead, which is called Just (\"natural\") Intonation: _URL_1_ (And singers and some instrumentalists adjust to this without thinking about it.)"
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buvqm3 | how do birds last so long flapping their wings non-stop? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/buvqm3/eli5_how_do_birds_last_so_long_flapping_their/ | {
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"4.5 billion years of evolution. They're made to do it. It's like asking how humans can last so long walking.",
"Also, they generally don’t go non-stop. Flap, flap, glide for a while, etc. \n\nThey also follow air currents. use uprises, and fly in formations to minimize air resistance.",
"they think hard about baseball scores or spiders when they think they can't last much longer"
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wzr8w | light in space | I'm not sure if this should be in /r/askscience or /r/AskShittyScience, so I'll put it here.
There is no sound in space because there isn't any matter to vibrate, or something along those lines. Then how is there light, shouldn't it need something similar? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/wzr8w/eli5_light_in_space/ | {
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"You're exactly right about why there is no sound in space. Sound is the propagation of a pressure wave through a material (such as air). Without some material, there can be no sound.\n\nIt was long thought that light *did* need an underlying material to \"vibrate\" through. Scientists called this the **luminiferous ether**. This belief grew stronger in the mid-19th century, when electomagnetism (and light) began to be described as a wave. Yet how can you have a wave without a material for it to propagate through? Ether solved this problem. But there were questions: what is this ether? Can you detect it? Does it move? Etc...\n\nIn 1887, some brilliant chaps named Michelson and Morley devised an experiment to prove or disprove the concept of ether. They observed that, since the earth would have to be moving through ether, you should be able to measure a very small difference in the speed of light as the earth moved in one direction vs. another. Their experiment was called the Michelson-Morley experiment, and it's considered one of the most famous experiments that \"failed\" - it did produced completely ZERO evidence for a light propagating ether.\n\nAnd so, the ether theory fell rapidly out of favor, and nowadays we know that light does not need a medium in which to propagate. You may have heard of the wave-particle dual nature of light, in which sometimes it behaves as a wave, and sometimes as a particle. Well, its ability to propagate in a complete vacuum (similar to space) is explained by its particle nature.",
"Light does need something similar, but the 'something' that vibrates is the electromagnetic field\n\nThis 'field' is really just a mathematical description, but since you are five, I will explain as follows: \n\nEveryone, even little kids should understand gravity. It is the thing that causes a jumping person to go down to earth instead of flying off to space. That thing is a type of 'force' that points to the ground. The region of space around the earth we feel this gravity is called a 'gravitational field'. Of course, teh strength of this field varies. As we move further away from the earth, gravity gets weak, and that is why astronauts float. To reiterate, the space where we feel gravity is called a gravitational field. The force of gravity felt within this field varies, i.e. the force felt is NOT the same everywhere.\n\nTake this concept of 'fields' and make it more general, and a little out of the realm of a five year old. Magnets have this thing called a magnet field, their own special variation of gravity, that only affects other magnets. Electrical objects, such as protons and electrons, that have 'electrical charge' exert an electrical field on other electrical objects. \n\nThese fields, magnetic and electric fields, exist in everywhere in space. Additionally, magnetic and electrical fields interact. The result of this interaction is called the 'electromagnetic field'. As the earth moves, the earth's gravitational field moves with it such that the field near the earth is always the strongest. Similarly, the electric or magnetic field can change in intensity when its source moves. \n\nWhat does this have to do with light? A moving charge will cause the a change in the electromagnetic field. When the said charge is not just moving, but accelerating, we see this as light."
]
} | [] | [] | [
[],
[]
] | |
1xaien | Suppose Earth followed the same orbit as Mars. How would life be different? Could we still survive? | In this hypothetical there is no fear of a collision with Mars, nor has the Earth stopped spinning, or felt any kind of relocation effects. | askscience | http://www.reddit.com/r/askscience/comments/1xaien/suppose_earth_followed_the_same_orbit_as_mars_how/ | {
"a_id": [
"cf9zhcl"
],
"score": [
2
],
"text": [
"The insolation (incoming sunlight energy) at Mars' distance from the sun is about 44% that of earth due to increased distance from the Sun. So down from about 1350W/m^2 to about 600W/m^2. Then it gets reduced by the atmospheric scattering, dust, etc.\n\nIt's way more complex than this, but a first shot at back of the envelope calculation would be to just look at a map of average insolation on Earth, then reduce everything to 44% of current values. \n\n _URL_0_\n\nSo, much of the USA would suddenly have the insolation of Arctic Canada, Europe would be be so low that it is worse than the North Pole, and the hotter parts of Africa would suddenly have the insolation of Northern Europe.\n\nHowever, that is assuming clouds and weather remained the same, which they wouldn't.\n\nOne big change would be the fact that colder air holds less water vapor (air at freezing point only holds about 1/10 the water of air on a summer day) , and water vapor is the most important greenhouse gas, contributing about 50% of Earth's greenhouse effect, without that... things would be even colder. Check out Figure 7 in this paper, Then imagine if half of the greenhouse radiation were lost.\n\n_URL_1_"
]
} | [] | [] | [
[
"http://upload.wikimedia.org/wikipedia/commons/7/78/Insolation.png",
"http://web.archive.org/web/20060330013311/http://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/RadiationBudget.pdf"
]
] | |
49ky1c | what's the difference between a hard link and a symbolic link in windows? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/49ky1c/eli5_whats_the_difference_between_a_hard_link_and/ | {
"a_id": [
"d0sn6te"
],
"score": [
2
],
"text": [
"A hard link is directly pointing to a physical location on the hard drive. A symbolic link is like a shortcut - it points to a hard link. A symbolic link can point to a different hard drive and make it appear to the user that it is merely a directory."
]
} | [] | [] | [
[]
] | ||
2uu7h2 | Why do some mentally ill people mumble their stream of consciousness? | So, I live in a city with a huge homeless population. While walking on the street, I frequently pass people who just continuously mumble their stream of consciousness. I'm impressed they can talk so fast without ever stopping to breathe, and it's interesting to hear an unfiltered version of what's going through someone's head.
But I'm curious -- is this a symptom of a specific mental illness? What makes them do this? | askscience | http://www.reddit.com/r/askscience/comments/2uu7h2/why_do_some_mentally_ill_people_mumble_their/ | {
"a_id": [
"coca5l7",
"cocacth"
],
"score": [
2,
2
],
"text": [
"Rapid speech ([tachylalia](_URL_1_)) could be indicative of [racing thoughts](_URL_0_), but it could also be an unrelated speech impediment. It's hard to know without a proper differential diagnosis. ",
"Depending on what they are saying, it could be a concept known as [word salad](_URL_0_) which is seen a lot in schizophrenics. "
]
} | [] | [] | [
[
"https://en.wikipedia.org/wiki/Racing_thoughts",
"https://en.wikipedia.org/wiki/Tachylalia"
],
[
"http://en.wikipedia.org/wiki/Word_salad"
]
] | |
3k8ywx | why do cars use steering wheels, instead of other control systems such as motorbike handles or jet joysticks? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3k8ywx/eli5_why_do_cars_use_steering_wheels_instead_of/ | {
"a_id": [
"cuvmx6q",
"cuvnw08",
"cuvx9ua"
],
"score": [
2,
13,
2
],
"text": [
"When cars first came out, they used \"rack-and-pin\" systems so they NEEDED steering wheels. Basically the wheel was connected to a gear that turned a rack (basically a gear laid out in a straight line).\n\nNowadays they're technically not necessary, but they allow for better control. ",
"Before power steering, you had to turn your wheels with muscle power alone. This could take a lot of strength, especially at low speeds.\n\n A steering wheel allowed you enough leverage to really bear down and crank the wheel when needed. It remains an important backup safety feature in case your power steering fails.",
"We could theoretically go to a \"steer by wire\" set up an use anything as input: wheel, joystick, etc. Compared to a joystick, the wheel has several advantages. One being it's easier to hold a constant turn. You couldn't relax your grip on the joystick, assuming it's self-centering. Also, if the joystick gets accidently nudged it would change the direction of the car. Bumping the steering wheel probably won't cause it to rotate."
]
} | [] | [] | [
[],
[],
[]
] |
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