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1uluyh | in movie scenes where a kidnapper asks for ransom money, why do they ask for non sequential bills? (extra credit: what are "marked bills"?) | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1uluyh/eli5_in_movie_scenes_where_a_kidnapper_asks_for/ | {
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"Because marked money can be tracked, sequential bills can be tracked. \n\nIn the case of the Lindbergh baby they wrote down the serial numbers of the bills and used them to track down the kidnapper/killer. \n\nSo lets say you kidnap someone and they pay the ransom. They keep an eye out for the bills they marked and notice them at a McDonalds, a Walmart and a Carwash. They know the area you've been in and now they can narrow it down to people who have been at these three locations in a specific time frame. "
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5lmc08 | Did the Soviet Union and former Socialist countries in Eastern Europe had minimum wage laws? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/5lmc08/did_the_soviet_union_and_former_socialist/ | {
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"Yes, countries of the Eastern Bloc ratified conventions of International Labour Organization which, apart form other issues, dealt with the minimum wage. However those laws were basically meaningless, as the wages were set by the government anyway."
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1xhwgg | why does beer foam subside so quickly when i touch my finger to the side of my nose, and then to the foam? | I know it must have to do with skin oils. But why? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1xhwgg/eli5_why_does_beer_foam_subside_so_quickly_when_i/ | {
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"Oils from your skin break the surface tension of the bubbles, and they just dissolve. It works with soda also."
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3y03h0 | why do people spoil movies? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3y03h0/eli5why_do_people_spoil_movies/ | {
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"There is an emotion called *schadenfreude* which means taking joy in other people's suffering. Some people are mildly sadistic and like to annoy others; it gives them a sense of power that might compensate for some bad feelings or lack of self-worth they are experiencing.",
"Have you ever solved a math problem before the rest of the class? You can sit there and wait for them to get it but sometimes people feel the need to blurt out the answer. It could be for attention, the false hope of praise, unintentional, they are impatient that others haven't gotten it, or maybe they just like being a dick."
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d8m9t9 | why do muscles take so little time to recover and grow compared to tendons and ligaments? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/d8m9t9/eli5_why_do_muscles_take_so_little_time_to/ | {
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"The really simple answer is that muscles are effectively made to be torn and damaged to regrow stronger. They're constantly getting minor \"damage\" as you use them, so major damage doesn't take too long to regenerate.\n\nLigaments and tendons can't really regenerate. You either have a partial tear - in which case, the ligaments/tendons don't regenerate, just form scar tissue which doesn't have the same functionality as the usual tendon tissue. Or you have a complete tear, and the body can't fix it on it's own, and you have to have surgical fixes.",
"The blood flow to ligaments and tendons is far, far lower than to the muscles. This means any growth and or repair is much slower, as the blood carries the vital clotting factors etc needed in the healing process.\n\nThe problem arises because the muscles are capable of generating much more force than the ligaments and tendons can withstand - that asymmetry can be dangerous when doing too much too soon. Getting strong muscles is relatively fast, strong ligaments and tendons take years to build up strength - and even longer to repair."
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2o7vcl | Does anybody know the value of a Ruble in 1860? | I'm currently reading Crime and Punishment. The importance of poverty and money is already clear 100 pages in.
The money of the time, as you know, was Rubles. They also use Kopecks, which I believe are the equivalent to a USD cent?
My question is: What is the current USD equivalent of one Ruble and Kopeck? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2o7vcl/does_anybody_know_the_value_of_a_ruble_in_1860/ | {
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"Are you talking paper ruble or metallic ruble?\n\nCatherine the Great started issuing paper rubles in 1768, and the value of these fluctuated greatly in the 18th and 19th centuries until the currency reforms of the 19th century.\n\nIn 1704, Peter the Great set the value of the metallic ruble at what is now about 12 grams of silver. ",
"To make some comparisons.\n\n1 Russian Ruble (100 Kopeks) = 12 grams of silver (thanks /u/The_Alaskan for this).\n\n1 British Shilling (12 Pence) = 20,98 grams of silver.\n\n1 US Dollar (100 Cents) = 24,06 grams of silver.\n\n1 Prussian Thaler (30 Silbergroschen or 260 Pfennig) = 16,7 grams of silver (the newer Vereinsthaler that started to come into circulation at this time contained 16,67 grams of silver).\n\n1 Swedish Riskdaler (100 Öre) = 6,38 grams of silver.\n\n1 Sardinian Lira (100 Centesimi) = 4,5 grams of silver.\n\n1 French Franc (100 Centims) = 4,5 grams of silver.\n\nUsing the measure how much an average worker woudl have to work to earn that amount then and how much he would earn if he worked as much today, one 1860 Shilling is worth £32,09.\n\nThe Ruble is then worth £18,35, which makes $28,79 today.\n\nHe's getting $33,11 for the watch, which I guess is a rather low Prince for a quality object."
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762ops | How long was the New Horizons probe in view of pluto and taking pictures for? | askscience | https://www.reddit.com/r/askscience/comments/762ops/how_long_was_the_new_horizons_probe_in_view_of/ | {
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"*New Horizons* practically always had a view of Pluto, it was just really far away. The probe was launched on January 19, 2006, and took its first images of Pluto on September 21-24, 2006. It woke up from hibernation on December 7, 2014, and took pictures on the approach. The main flyby, which occurred on July 14th, 2015, had 22 hours of radio silence because the probe was pointed towards Pluto instead of Earth.\n\nThe most reasonable answer is around 146 days; from the time it woke up out of hibernation to the end of its flyby."
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qi5kk | What causes genius burnout? | askscience | http://www.reddit.com/r/askscience/comments/qi5kk/what_causes_genius_burnout/ | {
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"Do you think that statistically geniuses exhibit more mental illness than the general public? ",
"In a psychology class I took, the professor said one contributing factor is that because of their intelligence levels, they do not relate well to others, view activities/people differently, and look down on most people as \"unintelligent\", focus on their work more. Basically, they isolate themselves, and this lack of normal human interaction can lead to \"eccentric\" behaviour. \n\nI do not know if people with high IQs have a higher percentage of actual mental disorders."
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2h4y0s | what causes that strange feeling you get when you accidentally miss a step? | Okay, so this may seem really weird, but whenever I exit my school, I always go down the ramp because nobody ever uses that door. However, I took the main door, and I forgot that there was a little step right outside it. Because of this, when my foot didn't hit the ground where it was supposed to, I felt like I was falling a great distance, and my body tensed up and I got scared. A similar sort of feeling happens to me when I play video games, and when it's a first person game, and I accidentally step backwards off a ledge without realizing it. Can anybody explain why this happens and how?
Thanks in advance! | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2h4y0s/eli5_what_causes_that_strange_feeling_you_get/ | {
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"Your body thinks you're losing balance and your defensive instincts or 'flight or fight response' kicks in to keep you unhurt."
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3ituyh | now that we know that "spooky action at a distance" is a confirmed phenomena of the quantum world, what does it mean? | I know whatever the average internet surfing Joe would know about Quantum mechanics. Mostly nothing.
What does this mean for general physics? I saw in the comments that this means we are all connected. Does that mean I am somehow connected to my plate of oreos? Or does this 'connection' work only from like to like, humans to humans, oreos to oreos. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3ituyh/eli5_now_that_we_know_that_spooky_action_at_a/ | {
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"Quantum entanglement, or 'spooky action at a distance', is a phenomenon that can occur when two particles are created. I'll use spin as an example of a property that can be entangled. If two particles are created that are entangled, their spins will have opposite values. You can only know the probability that a particle's spin will be in a particular direction. There's no way to be sure ahead of time.\n\nSay you measure the spin of one entangled particle to be clockwise. You now instantly know that the particle it is entangled with has a counterclockwise spin. Even though it's impossible to describe spin as anything other than a probability, the spin of the second particle is determined by the measurement of the first particle. Whatever measurement you get, the other entangled particle will measure the opposite way.\n\nThe second particle 'knowing' which spin to have based on the first particle's measurement happens instantaneously, and this bothered Einstein, the man who first referred to it as \"spooky\". According to relativity, nothing can move faster than the speed of light. Yet, the second particle's spin is determined instantly. Theoretically, the particles could be separated by light years, and measuring clockwise on the first particle's spin would guarantee that the second particle's spin would be counterclockwise.\n\nThis doesn't violate relativity, however, because there is no way to transmit information via entanglement. The second particle's measured quantity will always be determined by the measurement of the first particle, but what that measurement yields is inherently probabilistic. It's random, and the qualities of the second particle will be random too, just in the opposite way. So no physical laws are broken. You can't use quantum entanglement to send a message or intentionally make anything at all happen. And it's something that only really matters on the scale of individual particles. The chances of your left big toe being entangled with your right are about as likely as Jupiter spontaneously appearing in the Andromeda galaxy. It's technically possible, but the odds are so small that they're barely quantifiable.\n\nWhat does this mean for general physics? Nothing, because we've been aware of entanglement for quite some time now. All that has happened is that yet another rigorous experiment has upheld it to be true.\n\nAs an aside, Einstein's resolution to the problem was to say that the two particles contained hidden variables that determined what state they'd be in when measured. He had no evidence, but he imagined that there were some things that we just didn't yet know about the particles that would cause them to measure in opposite ways. The measurement of the first didn't determine the second because, to him, the information about what the measurements would be was contained within the particles all along, unknown to us. Many experiments have shown this to be false; quantum entanglement has withstood all experiments to date. Look up Bell's Inequalities if you want to know how we can prove that there are no hidden variables.",
"By the way, this is the lab who did the research and the experiment. \n\n_URL_0_\n\nI am an engineer in that lab, work never feels like work just one science playground "
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wiy7g | can broccoli really reduce estrogen in men? | askscience | http://www.reddit.com/r/askscience/comments/wiy7g/can_broccoli_really_reduce_estrogen_in_men/ | {
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"Perhaps you heard something like [this](_URL_1_)? \n > Indole-3-carbinol (I3C), a natural autolysis product of a gluccosinolate present in Brassica vegetables such as broccoli and cabbage, has anti-proliferative and **anti-estrogenic activities** in human breast cancer cells. \n\n[This study says](_URL_0_):\n > 3,3'-Diindolylmethane (DIM), a major in vivo product of indole-3-carbinol (I3C), is a promising anticancer agent derived from vegetables of the Brassica genus including broccoli, Brussels sprouts and cabbage. [...] Taken together, these results extend our previous findings of the ligand independent **estrogen receptor agonist activity** of DIM, and uncover an essential role for the stimulation in TGF-alpha expression and the TGF-alpha activated signal transduction pathway in the potent cytostatic effects of DIM in endometrial cancer cells.\n\n[This paper found](_URL_2_)\n > Previous studies suggest that the estrogen metabolite 16alpha-hydroxyestrone acts as a breast tumor promoter. The alternative product of estrogen metabolism, 2-hydroxyestrone, does not exhibit estrogenic properties in breast tissue, and lower values of the ratio 2-hydroxyestrone:16alpha-hydroxyestrone (2:16) in urine may be an endocrine biomarker for greater breast cancer risk. Vegetables of the Brassica genus, such as broccoli, contain a phytochemical, which may **shift estrogen metabolism** and increase the 2:16 ratio.\n\n[This paper reports:](_URL_3_)\n > These findings support the hypothesis that I3C-induced estrogen 2-hydroxylation results in decreased concentrations of several metabolites known to activate the estrogen receptor. This effect may **lower estrogenic stimulation** in women.\n\n\nSo unfortunately, nothing directly addresses your question, but there's some literature out there on the effects of broccoli metabolites on estrogenic processes in humans. I wouldn't place too large a value on the evidence as it stands right now, since there have been a fairly limited number of studies (~50 on pubmed that I looked through), without a clear consensus. As more evidence emerges this may change, but right now I wouldn't consider any of that strong enough to make medical decisions based on their findings.",
"Memorial Sloan-Kettering maintains a web site [About Herbs, Botanicals & Other Products](_URL_2_)\n\nHere's what they write about [Indole-3-Carbinol](_URL_0_):\n\n > Indole-3-carbinol, also called I3C, is a natural compound found in vegetables such as broccoli, brussel sprouts, cabbage, cauliflower, and kale. It is known to stimulate detoxifying enzymes in the gut and liver, but it has come under more study lately for its potential anti-cancer properties. Animals that are fed a diet rich in I3C have a slower growth of their cancers. **Laboratory studies show that it blocks estrogen activity by interfering with the estrogen receptor.** This suggests that I3C might be useful in preventing or treating estrogen-sensitive cancers (such as breast and cervical cancers), possibly in addition to tamoxifen, **but not enough studies have been done in humans to determine this.**\n\nThe last part (in bold) is the key.\n\n[This paper](_URL_1_) points out that:\n\n > Although in vitro studies have contributed significantly to our understanding, quite a number use concentrations orders of magnitude greater than those achievable in humans or toxic to normal tissues (exemplified by toxic concentrations of **indole-3-carbinol**, epigallocatechin-3-gallate, curcumin, and genistein for breast cells).\n"
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ad29n8 | why can cloth soaked in boiled linseed oil spontaneously combust? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/ad29n8/eli5_why_can_cloth_soaked_in_boiled_linseed_oil/ | {
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"I think what is happening is the oil gives off a tiny bit of heat when it evaporates from the rag. Now by itself, that is no big deal. \n\nBUT, if you have ten or twenty or fifty of these rags jammed into a can or box or whatever, that tiny bit of heat, all insulated by the other rags, can build up, and the more heat builds up, then the more oil evaporates, until it becomes a runaway chain reaction and eventually catches fire. \n\nCoal jammed into a bunker on a ship can suffer the same fate.",
"BLO polymerizes as it dries (hardens/crosslinks) and that process generates heat. Under the right conditions it can (and will, I've seen the aftermath) get hot enough to ignite.\n\nIf you want to reproduce an exothermic reaction in a controlled way, squirt some superglue on it paper towel. The surface area of the fibers allows the cyanoacrylate to set quickly and the paper gets very hot for a few seconds. "
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1z1iiz | how the hairs in geckos' feet help them stick to glass? shouldn't hairs actually make their feet slippier? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1z1iiz/eli5_how_the_hairs_in_geckos_feet_help_them_stick/ | {
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"The 'hairs' on their feet are incredibly tiny and there is a huge amount of them. The hairs are so small that they are able to interact with the surface on an atomic level. The gecko sticks to glass using something called Van der Waal forces, which is the attraction between two near by atoms. The attraction isn't a bond, it works in a way similar to magnets. Basically, they gecko's foot has < huge number > of hairs and each one is working like a tiny magnet with the atoms in the glass."
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1l5727 | What methods have been used to determine that space-time is 'curved'? | As I understand it, based on our current models, the universe is either infinite or it curves in on itself in something like a 4-dimensional sphere. Experiments have shown a measured 'curve' to the universe. I am curious as to what is measured to determine this. | askscience | http://www.reddit.com/r/askscience/comments/1l5727/what_methods_have_been_used_to_determine_that/ | {
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"[Gravity Probe B](_URL_0_) was an experiment that aimed to prove (and did) that space-time around Earth is curved due to it's gravity. \n\n",
"They waited till a solar eclipse and noted the positions of the stars located at the very edge of the sun that you can't normally see and they were not exactly in position they should have been due to the mass of the sun that curves space which bent the light and made the stars appear offset from the true location. This was done to prove einstines theory in the early 1900's."
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3vo2gi | why can't egypt take back their archaeological artifacts which have been stolen and are being displayed in the british museum and elsewhere? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3vo2gi/eli5_why_cant_egypt_take_back_their/ | {
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"Who were they stolen from? A \"country\" didn't own them at the time they were removed from Egypt. If there was a specific *family* that had previously had ownership of them and wanted to claim them back, there would be specific procedures that they could take legally , but \"Egypt\" as an entity, doesn't have such a claim.",
"The simple answer is that Egypt can take anything it wants from any country that it can over power militarily. The British have a military force that is quite capable of repelling the Egyptian military from an attack on the British home island.\n\nSo the Egyptians will have to use other means (i.e., diplomacy) to get their artifacts back.",
"They can't \"take them back\". I mean, they can't just march into the British museum and take them, right? They'd pretty much be arrested. \n\nThey can *request* the artifacts be returned -- and the have -- but the British Museum (and government) would have to decide to actually do it. So far, they have not. But Egypt (and Greece, and India, and any other country that claims that Britain holds artifacts that belong to them) don't really have much of a legal recourse, let alone the physical power it would take to force the issue. ",
"The Muslim leaders of Egypt ordered many artifacts destroyed for being idols. The artifacts are better off in UK and Egypt may not even want them.",
"In previous centuries, antiquities were often sold by government officials in Egypt, Greece, etc. to European countries as part of some kind of political deal, so they weren't always flat-out stolen, although of course you can claim that the government officials never had the right to sell them",
"Almost none were stolen. Many were exported in 19th century with agreement of Egyptian government. Many were sold by the Egyptian government: the national museum had a 'shop' where you could buy pretty much anything that came out of the ground or a tomb. MAny excavations since have had deals where finds are shared. Obviously some stuff was actually stolen, but that happens everywhere, and museums are pretty reluctant to exhibit stuff if they arent sure where it came from. Same goes for Greece, BTW.",
"There's an argument to be made that these artifacts aren't owned by any nation, Egypt or Britain, but are instead owned by *humanity*. In that context, Britain is a far better choice to look after these artifacts as they have so far done an excellent job keeping them in as good a condition as possible while simultaneously exhibiting them for public viewing and enjoyment. It is in *humanities* best interests that they stay where they are, even if that may not be in the best interests of modern day Egypt. And at this point modern Egyptians are hugely different ethnically than those who produced these artifacts, so the claim cannot be made by modern Egyptians that it is the work of their ancestors.",
"The British museum would be completely empty if they gave back anything. They can't start the precedent of giving stolen artifacts away unless they're willing to do it for everyone. Which will Never happen. David Cameron has basically said fuck off to India about the big diamond that's in the Crown Jewels. ",
"If an alien nation occupied France and pushed the French people out, would the new residents have the right to demand ancient French artefacts be returned to their original locations?",
"They (and other countries like Greece, where large numbers of antiquities were shipped abroad and now reside in foreign museums) *have* requested their artifacts back at times. In fact, just before the revolution, they were trying to request the famous Nefertiti bust in Berlin. The short answer is that short of force, they don't have a great chance of getting them back. In some cases, the return of antiquities *might* be part of negotiations around some larger issue, but these countries generally have bigger concerns.\n\nFrom the perspective of the countries/institutions that currently *have* the antiquities and artifacts, they have little motivation to give them back. Additionally, if the artifacts would go back to a country that's unstable or has poor infrastructure/funding available, researchers may be concerned that the artifacts will not be properly cared for (some need continual restorations/upkeep or have to be kept in very specific conditions to preserve them) - or they're worried about the items being sold or otherwise lost via corruption or instability. Sadly, this fear isn't totally unfounded - during the Egyptian revolution, some artifacts *were* stolen from the Egyptian Museum in Cairo.\n",
"A lot of artifacts that came out of China are, afaik, stolen. This is true for many things, such as urns, and ceramics. Some were stolen through the opium wars, such as when the Anglo-French coalition force burned the Emperor's Summer Palace. \n\nThat being said, many artifacts were probably preserved due to being stolen. In the Cultural Revolution for example, Mao moved the people to destroy many relics of the past. Of course, being kept on display in other countries means that people from the lands that produced them can't access them anyways. ",
"The government and culture that made them no longer exists. Those artifacts are global property and global heritage. They were not stolen, they were excavated by the British. "
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1jbdnt | how do completely different strands of species all share similar qualities? (ex: mammals and amphibians both developing eyes in a similar fashion) | I've always found this question interesting. How can so many creatures that are seemingly unrelated develop such similar organ systems? Is it simply that we all share a common ancestor and evolved a similar basis for these qualities and then differentiated from them over time?
Thanks in advance! | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1jbdnt/eli5_how_do_completely_different_strands_of/ | {
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"There are two factors at work here:\n\nOne is **common ancestry**. All living things share a fairly small set of common ancestors. Living things that are more closely related to one another share a more recent common ancestor than things that are less closely related to one another. For example, chimpanzees and gorillas share a more recent common ancestor with each other than either does with (for example) beetles.\n\nIn some cases, common body parts or functions are inherited from common ancestors. This is likely what we see in the opposable thumbs of chimpanzees and gorillas (for instance).\n\nIt's also possible to have **convergent evolution**. In the case of convergent evolution, the same features arises independently in separate lineages. This can happen by chance, and/or because a certain adaptation is very favorable. For example, flight in dragonflies and bats arose independently. We know this is the case because the structures responsible for flight are different in each, and the genes responsible for encoding those structures are considerable different in each.\n"
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38arht | how do animals recognize and remember humans? does this form of recognition vary between different species? | In a recent TIL, a man rescues a dying crocodile and nurses it back to health. He tries to release the crocodile to open waters but it kept coming back and they become "best friends" for 20 years. I've also read stories about people releasing animals they raised/took care of into the wild and after a few years, the animals greet the people affectionately! | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/38arht/eli5_how_do_animals_recognize_and_remember_humans/ | {
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"The answer to the second question is yes. Some animals will not remember humans because it is not a part they have required in their brains.\n\nThat being said, those that do remember humans have a number of ways similar to our own senses, but on a more advanced level. There are a lot of different ways animals remember people, but the most common are through scent, sound, and sight. While we can't tell ourselves, we have a unique scent to some animals. We sound unique as well to some animals. Visually, our mannerisms and physical features are also recognizable. Animals can also make memories like we can. Some animals will have bad memories of a person and will react so when around them. Like humans, animals also have an emotional response when they recognize someone they're familiar with. They have reactions to seeing, smelling, or hearing a familiar sight, scent, or voice just like we do to other humans."
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362dlh | What was the migration experience like from England/France/Ireland around 1800 to farmland in the interior US? | I've been doing a lot of genealogical research and found that most branches of my family arrived in the US from Europe in the late 1700s and then spent one generation on the east coast (NJ, VA, NC typically) then traveled in-land to TN, KY, MO between 1800-1820. I want to learn more about that process. Most of them seem to have been farmers who were too poor to have slaves/employees. Would they have been granted land in advance and known where they were going? If so, would they have had that information in Europe before they even came over? How big were the convoys, typically?
I'm particularly interested in finding some books on the subject if there are any. Thanks! | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/362dlh/what_was_the_migration_experience_like_from/ | {
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"Pre Erie Canal meant that they most likely went through the Cumberland Gap and became subsistence farmers and shopkeepers in the Kentucky/Tennessee area before maybe moving farther south or west, but not for another generation. The threat of Indian attacks was HUGE for a good portion of this time as the government did basically nothing to protect settlers from the Indians, so the Kentucky Militia essentially became a big ass private army for the governor and therefore frontier society was very martial. The people who were moving there were most likely people with roots already in the US or were Scotch-Irish immigrants to the Carolinas. \n\nAfter the Tecumseh Confederacy was demolished during the War of 1812 with Tecumseh's death, the old NW, which included Ohio, Indiana, and Illinois, suddenly became wide open for land settlement as the Indians moved west or north, or in most cases, died, as the winter of 1813 and 1814, with supply from Canada cut off, was devastating. TONS of people flocked to grab claims of land in those three states and made farms, and many were English and Scottish immigrants. The repeal of the Corn Laws in Britain made this a very proftable venture later on, and the population of those states exploded really quickly. Ohio had already undergone this process after the Erie Canal was finished as it allowed people to quickly ship goods to NYC. \n\nLater waves of German and Scandanavian immigrants would settle the further north regions of Michigan and Minnesota. \n\nBut the experience generally was one where people just simply took a boat over the Atlantic, made their way to some claim of land in the west that was available for dirt cheap, and then set up a farm or moved to one of the rapidly developing towns. \n\nEvery time an Indian tribe would bite the dust or agree to move west or north or settle down, land became available and immigrants were the first usually to claim it. "
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2glgcw | how does an imaginary number become an ordered pair? | I'm a 2nd year Computer Science major and I'm currently taking a pre-calc course. In class today we were going over complex numbers and the prof said, "We have expanded our mathematical system to include what are known as imaginary numbers... when you go on to higher mathematics an imaginary number can actually be used as an ordered pair." That shit blew my mind. It just doesn't make sense. I have a solid basic understanding of imaginary numbers. This wasn't the first course to introduce me to them, but how in the hell can a number that isn't real (cannot be placed on a number line) be a part of an ordered pair? I hope there is a reasonable ELI5 explanation. I'll even settle for ELI'mnotstephanhawking. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2glgcw/eli5_how_does_an_imaginary_number_become_an/ | {
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"First, your prof misspoke a little...he should have said *complex* numbers can be used as ordered pair.\n\nAll complex numbers are in the form *a + bi*, and it is sometimes useful to treat them as the ordered pair (*a*, *b*). When *a* = 0, you have an imaginary number in the form (0, *b*), and when *b* = 0, you have a real. ",
"Using complex numbers allows you to essentially add a dimension, the i or imaginary dimension. When you use a complex number it is like having a 2D plane instead of a 1D number line. In order to map that 2D plane, you need 2 numbers instead of 1, hence the ordered pairs."
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[],
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qh7dj | Is there any concrete scientific basis for hair going white after someone goes through a shocking experience? | I had a friend years ago who was 19 and had a permanent patch of white hair. She said it wasn't something that she had after birth but something that only appeared after she witnessed someone dying horrifically. The patch would not grow out- it remained in the same spot as her hair grew.
And I have seen sometimes in cartoons and movies a character's hair going white after being scared. Is there any basis for this happening being due to shock and not due to aging or genetically since birth? | askscience | http://www.reddit.com/r/askscience/comments/qh7dj/is_there_any_concrete_scientific_basis_for_hair/ | {
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"[Rogue](_URL_2_), but seriously there are several studies on this. [Here](_URL_0_) is a news article. [This](_URL_1_) is a scientific article that relates epinephrine to loss of pigment. Epinephrine is linked to flight-or-fight response system. Hypothetically stress, or a \"shocking experience\" indirectly would cause whitening of hair."
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"http://www.telegraph.co.uk/news/worldnews/asia/japan/5505630/Grey-hair-is-a-sign-of-stress-say-scientists.html",
"http://www.nature.com/jid/journal/v53/n2/pdf/jid1969122a.pdf",
"http://www.lookpictures.net/photos/registered_photos/1846-x-men-rogue-wallpaper.jpg"
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8xrt6d | what is the difference between hasidic judaism and standard judaism? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8xrt6d/eli5_what_is_the_difference_between_hasidic/ | {
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"There isn't one \"standard\" Judaism. There are 3 main branches - reform, conservative, orthodox. They differ on how strictly they follow the religion and how they observe. Reform are the most lax and have somewhat adopted practices of some Christian sects, such as musical instruments and choruses in services. They are also least likely to keep kosher, follow the sabath strictly, etc. Conservative are more tradition in service and more mixed in practice, ie. some don't keep kosher and only attend services on high holidays while others go to weekly services, keep kosher, observe parts of the sabbath rituals (maybe they don't drive, choosing to walk to temple). Orthodox follow the religion the most strictly, observing the sabbath and attending temple regularly, keeping kosher, modesty in dress, etc. But even within the Orthodox community there are different levels of custom/practice that often grew out of their originating community back in Europe or the Middle East and affect things like things like dress, assimilation with the general community outside orthodox Judaism. Because Hasidism arose in Eastern Europe, they tend to dress a certain way, speak Yiddish. And there are also certain practices and religious emphasis that's slightly different than other orthodox groups."
]
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6xd2zr | London is on a higher latitude than Montreal, why does it snow so rarely in comparison? | askscience | https://www.reddit.com/r/askscience/comments/6xd2zr/london_is_on_a_higher_latitude_than_montreal_why/ | {
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"The answer is [oceanic circulation](_URL_0_)\n\nThe eastern coast of North America is closer to the coldest ocean water, from the North pole. The gulf stream is responsible for Europe's milder climate.\n\nEurope however, enjoys the gulf stream. A warm current. \n\nThis allows NY to be way colder than Madrid whereas both share the same latitude. "
]
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1503pz | why don't we build pyramids anymore? | With the abundance of pyramids in ancient cultures, why don't we build them anymore? They seem to be structurally sound, and clearly stand the test of time. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1503pz/eli5_why_dont_we_build_pyramids_anymore/ | {
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"Why would we want to? Rectangles are more space efficient.",
"Because they aren't very efficient.\n\nLets say we use modern construction techniques and fill a pyramid with 'rooms' people would wanna live in. (I make this assumption because making a tomb that big for just one person anymore is silly on the face of it)\n\nSo now we have a 'use' for a pyramid. Lets say you are in a big city and you want to build an apartment complex or a house or something. So you buy up a city block, knock down the old square apartment building that had a foot print of 500m by 500m.\n\nNow you are gonna build your pyramid apartment in that spot. you decide you want the slope of the sides to be 45 degrees, which means the height of your building is at most 250m tall, which is fine.\n\nNow you realize that the volume of your pyramid (which represents the amount of space people can use) is 20,833,333.33 m^3. Which sounds like a lot untill it is compared to an equivalent 500x500x250 cube appartment which gets three times as much space with 62,500,000 m^3.\n\nBut wait it gets better. If you have a 6 foot tall person in a room with a 45 degree slope to one of the walls, there will be six feet of 'floor space' away from the wall in which they cannot stand without crouching. Given that the average room in an apartment is something like 12x12 that is approximately half of every room in every apartment which a slightly above averaged height person cannot access.\n\nDoing some very bad math this implies that of the 20,833,333.33 m^3 of total 'apartment space' in your building only a further fraction of that would be usable.\n\nYou can solve this problem by making the walls 'steeper' but even then that increases the instability of your building, and kinda ruins the whole 'pyramid' vibe in the first place.\n\nSo there you have it, rectangular faced buildings are more efficient both in absolute amount of space, and amount of usable space, and lets face it, if you aren't making your building out of giant rocks (which further limits the amount of space) It probably isn't going to make it hangout of that much longer 'long term' anyway.\n\n(fun fact) the tallest building in the world is 829.8 m. If this were a pyramid with a 45 degree slope to its sides it would cover approximately 2.75 square kilometers with its base.\n\nThis represents over 3% of the total area of manhattan. Which if it were located in it would displace over 50k people.",
"The buildings we design and build today are chosen based on a mix of durability, the resources we have available, ease of construction, and of course their intended use. The reason we don't build pyramids is because, first, they're less efficient in terms of space; we typically make better use out of cuboids and other variants with ninety-degree angles between walls and floors. Plus, we can stack rectangular (again, cuboid) buildings closer together and take advantage of large heights; pyramids loose a great deal of space \"above\" that a skyscraper could contain.\n\nAs to why we don't make classical stone pyramids, the answer is in what it takes to carve and move stone; yes, they endure, and may endure longer then our glass-and-steel constructs (long story; skyscrapers need maintenance), but the time and effort it would take to build one compared to the value we would get out of it makes them less valuable.\n\nOn the other hand, we *do* build pyramids (of modern materials) for ascetic reasons - a partial list [can be found here](_URL_3_), but just to point out the most notable examples:\n\n* [The Lourve](_URL_0_) in Paris is an art and antiquities museum which has this modern component added to its otherwise quite classical architecture (French Renaissance, if I undertand correctly), and the glass pyramid acts as the main entrance.\n* [The Luxor Hotel](_URL_1_) in Las Vegas takes the form of a pyramid; this is for aesthetics and to attract clientele. To phrase it another way, it's flashy and eye-catching, and thus attracts guests. And let's face it; to be eye-catching in Vegas...\n* The [Pyramid Arena](_URL_2_) in Memphis, Tennessee. In addition to the pure aesthetic value (let's face it; in all these examples it's cool to have a pyramid), it also ties into the city - Memphis is named after an [ancient Egyptian city](_URL_4_) famous for its pyramids.",
"Ancient cultures built pyramids because they're the easiest shape to build. Now that we are better and building things and can build rectangular skyscrapers, we don't need pyramids anymore.",
"We prefer phallic imagery over mammary imagery ^^^^^jokeanswer"
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2hshhc | Did the Romans charge citizens for the water that came through the massive aqueducts they built? | I posted this [link](_URL_0_) on /r/news and through discussion came to the posted question. So, using the power of reddit I ask you historians: Did the Romans charge citizens for the water that came through the massive aqueducts they built? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2hshhc/did_the_romans_charge_citizens_for_the_water_that/ | {
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"Yes and no is the answer. The public fountains were most people got their water from were free and available for all. However water that was delivered to private homes via the city's water mains and metered with officially calibrated nozzles was taxed, and two classes of service were available. Small houses were allowed a one half inch pipe connection to the water mains, while larger houses with baths were allowed a one and one half inch connection. The problem with that was since it was a sign of wealth to have a private supply of water people would often bribe officials to tap the aqueducts and steal water. Business would also do the same, here are some quote from Frontinus who wrote the book on the Roman Aqueduct system. \n\n\"There are extensive areas in various places where secret pipes run under the pavement all over the city. I discovered that these pipes were furnishing water by special branches to all those engaged in business in those localities through which the pipes ran, being bored for the purpose here and there by the so-called \"punctures\". How large an amount of water has been stolen in his manner, I estimate by means of the fact that a considerable quantity of lead has been brought in by the removal of that kind of branch pipe.\"\n\n\". . . a large number of landed proprietors, past whose fields the aqueducts run, tap the conduits; whence it comes that the public water courses are actually brought to a standstill by private citizens, just to water their gardens.\"\n\nSo in conclusion water was free unless you wanted it in your house in which case it was expensively taxed and monitored to the extent that people would rather bribe officials then actually pay the fees.\n\n_URL_0_\n\n\n*edit Thanks for the Gold stranger.\n"
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[
"http://www.uvm.edu/~rrodgers/Frontinus.html"
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4kpacq | Are there any estimates of how many Japanese citizens evacuated Hiroshima and Nagasaki due to the US Air Force's air dropped leaflets warning the public of what was about to happen? | Growing up I always assumed there was very little warning for the Japanese leading up to the nuclear strikes on Hiroshima and Nagasaki, however I recently learned about the US warning campaign (which can be read about here _URL_0_ ) which is something I haven't really heard brought up before.
My question is are there any estimates for how many people actually evacuated the cities due to these warnings? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4kpacq/are_there_any_estimates_of_how_many_japanese/ | {
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"[Here is an earlier answer that might be helpful](_URL_0_). The short answer is \"no-one\" and that _URL_1_ is a terrible source.",
"There were no specific warnings that Hiroshima, Nagasaki, or Kokura (the primary target for the second bombing mission) would be bombed. Hiroshima and Nagasaki have been asserted to be on lists of cities that had gotten generic \"we are bombing cities\" leaflets, but frankly I've never seen evidence of that. [They certainly got no specific warnings about the atomic bombings](_URL_2_). \n\nBut there is one interesting thing here that is not well-known. Citizens in Hiroshima had, in fact, worried that they might be getting bombed soon (not atomic bombed, of course, but bombed). Why? Because they had a military base there and they had been conspicuously _not_ bombed while [the rest of Japan was being turned to ashes](_URL_0_). So they figured something was coming their way. \n\nFrom the Preliminary Report of Findings on Atomic Bomb Investigating Groups at Hiroshima and Nagasaki, late November 1945:\n\n > Just previous to the bombing of Hiroshima plans were being made for the evacuation of unnecessary persons. The day of the bombing 40,000 extra people were brought into the center of the town for instructions on these evacuation plans.\n\nSo that intuition didn't help them very much. If they had been given warning, maybe they'd have gotten out of there earlier. As it was...\n\nNagasaki had been conventionally bombed several times already during the war, as recently as August 1st, 1945. Many of its \"non-essential\" people had already been evacuated to the countryside. This is one of the reasons that the death toll was fewer than at Hiroshima (there were geographical reasons as well). There were still plenty of civilians, though, especially in the area where the bomb went off ([which was mostly civilian](_URL_1_)). "
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"http://blog.nuclearsecrecy.com/2014/03/12/firebombs-usa/",
"http://blog.nuclearsecrecy.com/wp-content/uploads/2015/08/Nagasaki-damage-map-detail.jpg... | |
1ezmmi | What was Napoleon's life on St. Helena like? | I know he made complaints about his living conditions, and that some of the locals found him to a be charming person. Was he depressed at all about his failures? And did he have any contact with his family? Any intersting anecdotes, or recommended related reading, would be appreciated. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1ezmmi/what_was_napoleons_life_on_st_helena_like/ | {
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"Here’s the famous account by Emmanuel-Auguste-Dieudonné, Comte de Las Cases in his *Memoirs of the Life, Exile, and Conversations of the Emperor Napoleon* (trans 1894, p. 164). It’s vivid, but Las Cases was a fervent supporter of Napoleon and accompanied him in exile. His memoirs have been criticized for exaggeration:\n\n\n > The Emperor Napoleon, who but lately possessed such boundless power, and disposed of so many Crowns, now occupies a wretched hovel, a few feet square, perched upon a rock, unprovided with furniture, and without either shutters or curtains to the windows. This place must serve him for bed-chamber, dressing-room, dining-room, study, and sitting-room; and he is obliged to go out when it is necessary to have this one apartment cleaned. His meals, consisting of a few wretched dishes, are brought to him from a distance, as though he were a criminal in a dungeon. He is absolutely in want of the necessaries of life: the bread and wine are not such as we have been accustomed to, and are so bad that we loathe to touch them; water, coffee, butter, oil, and other articles, are either not to be procured, or are scarcely fit for use: a bath, which is so necessary to the Emperor's health, is not to be had; and he is deprived of the exercise of riding on horseback.\n\n > His friends and servants are two miles distant from him, and are not suffered to approach his person without being accompanied by a soldier. They are deprived of their arms, and are compelled to pass the night at the guard-house, if they return beyond a certain hour, or if any mistake occur in the pass-word, which happens almost daily. Thus, on the summit of this frightful rock, we are equally exposed to the severity of man and the rigour of nature! And how easy would it have been to procure us a more suitable retreat and more courteous usage. Assuredly, if the Sovereigns of Europe decreed his exile, private enmity has directed its execution. If policy alone dictated this measure as indispensable, would it not have been essential, in order to render the fact evident to the world, to have surrounded with every kind of respect and consideration the illustrious victim, with regard to whom it had been found necessary to violate law and principle?\n",
"Probably not particularly pleasant. Longhouse (where he was quartered) was damp, windy, and he was essentially isolated from anyone he could communicate with--keep in mind this is an island thousands of miles from land, so news of the outside world was sparse. St Helena is virtually barren for about 85% of its territory (due to idiotic sailors bringing goats to the island, who proceeded to tear up massive amounts of the endemic flora), and so there is little vegetation to stop the wind. By most accounts, he barely left Longhouse, and he passed the time by peering at his guards through little peepholes in the shutters. The brits didn't mess around--they built half a dozen batteries capable of fending off an invasion on the island in order to dissuade any French attempts at rescue. His life was strictly regimented. The food on the island wasn't great either--the majority of fresh food had to be imported from S Africa. Having been to St Helena, I can tell you that while it is a beautiful island, the area where Longhouse is located is really bleak. The climate is sub-tropical, but not particularly warm. \n\nOn Elba he was allowed his own guards and companions--here he almost completely isolated. He died of either stomach cancer or arsenic poisoning, depending on who you believe. They found arsenic in his hair, some think that it came from the wallpaper in Longhouse, which was an arsenic-based delightful shade of purple. Some french historians treat Napoleon's death as an assassination, which is probably a little unfair to the British. \n\nMy dad could tell you more, as he owns probably the world's largest private collection of books specifically about St Helena, no joke. \n\nMy source for all this is an extended visit to the island (my parents lived there for a number of years, and we took a trip there recently), and my experiences working for my dad's little company buying and selling books about St Helena. Sorry about being unable to cite sources. I just wanted to share what tidbits I remember about the man. ",
"There’s one particular scene from his days on St. Helena from a year before he died that I like:\n\n > “In 1820 he took to gardening, and attacked its problems with martial courage and discipline. He conscripted his entire colony to join in the enterprise, and they gladly turned from their old routine to the novel business of digging, carting, planting, watering, and weeding. Sir Hudson Lowe, in a new gesture of amity, sent his prisoner plants and tools. The garden, well watered, soon produced fresh vegetables which Napoleon consumed with delight. His health visibly improved. But when the garden’s harvest had been consumed, and bad weather set in, Napoleon returned to his former indoor indolence.”\n\n— Will & Ariel Durant, “The Story of Civilization, Part XI: The Age of Napoleon”\n\nWhen you take the quotes found in other comments in this thread into account, in particular describing his rather bad condition and mood, at least in comparison to the previous hight of his glory, it can be quite poignant or comical, perhaps both at once."
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4f1f5s | What makes electomagnetic waves able to propagate without a medium and other not other waves?? | askscience | https://www.reddit.com/r/askscience/comments/4f1f5s/what_makes_electomagnetic_waves_able_to_propagate/ | {
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"You could say that electromagnetic (EM) waves *do* propagate in a medium, if you take that medium to be the electromagnetic field. In this picture you can think of an EM wave (or a group of photons if you prefer) as an *excitation* in the electromagnetic field that moves from one region of space to another.\n\nIn reality the way EM waves propagate is not all that different from how say a water wave behaves. Imagine you are sitting on the edge of a lake on a windless day and the water appears completely calm. If you throw a pebble into this lake, you will [create ripples that will spread outwards](_URL_1_). In other words, you are creating an excitation where water is both the medium through which the ripples travel and it is also the stuff that is jiggling up and down at every point as each ripple passes.\n\nDeep down EM waves work pretty much exactly in the same way. For this analogy to click, the trick is to realize that no matter where you are in the universe, you are always surrounded by the electromagnetic field. This field is as big as the universe, it exists wherever space itself exists. Even in the depths of outer space, where at first it may seem like there is nothing around, if look more closely you will see that the EM field is still there and produces measurable effects (e.g. see the [Casimir Effect](_URL_0_)).\n\nNow just like the surface of that lake, the EM field normally looks still (in the sense that you won't detect any photons), but that doesn't mean it's not there. In fact you can still measure it and you can still interact with it. Just like you can throw a pebble to create a water wave, you can add energy into the EM field (e.g. by firing up a flashlight) and you will see this excitation spread outwards in the EM fields like the ripples in the lake.",
"This question has been asked here before:\n\n_URL_0_\n\nIt requires an understanding of quantum electrodynamics to truly understand our (current) interpretation. /u/crnaruka did a good job explaining it in layman's terms however.",
"While I enjoyed reading the comment comparing this to a wave on a pond, what you must realize is that light is a particle as well. It does not need a medium because it is it's own medium. This is explained by the fact that a photon produces an electric field, which in turn produces a magnetic field and continues to self propagate through any medium or lack thereof. ",
"This question is based on a sort of false assumption, that a wave needs to have a medium. Macroscopic waves, like water ripples and sound waves (and [hamon](_URL_0_)), do propogate through media, but that is because they are meta-waves, energy moving through the interactions between various types of materials. Sound does not travel in space because sound is a property of relatively high density gasses, a consequence of how the material works that allows for the propagation of energy in that manner.\n\nElectromagnetic waves are disturbances in a field that exists everywhere, and because they are unconstrained and massless they propagate at the speed of light.",
"You've had some good answers focused on EM waves, but I wanted to stimulate some thought about other waves.\n\nTake sound waves for example. Sound waves aren't some independent wave just waiting for a medium to propagate through. Sound waves are a description of changes happening *to that medium*. \n\nThere's nothing inherently voicey about you thinking words and making them happen. All you're doing is pushing air. If you try to speak in a vacuum, it's not that your voice can't find a medium to propagate through, it's that your vocal chords don't have a medium to manipulate anymore. \n\nIn a sense, the wave doesn't *need* a medium, the wave *is* the medium.",
"They're also particles. \n\nEM waves are a way to represent quanta, little packets of energy. They can also be represented as particles, and in reality they do behave as both. You can describe them as photons, or as EM waves, but they're actually both. \n\nExactly how they can be both requires some understanding of quantum physics, but essentially the wave is more of a probability wave that describes the range of positions in space (and other states) the quantum can be in at any point in time. \n\nThe quantum itself doesn't exist in one spot (for the most part anyway. There may be a 99.99% chance of it being in one specific place, but there's still a non-zero chance it exists anywhere else in the universe). It exists as this 'probability wave'. Which is why, depending on how you measure it, it can appear to be either. If you try to pinpoint it's location as you would a particle, it will be one. Try and measure it's frequency or something like that, it'll be a wave. \n\nBasically, they're waves that describe the existence of particles, but the particles only exist as said waves. The particles actually *are* the waves that describe them, and vise versa. ",
"In short, Faraday's and Ampere's laws. Changing magnetic fields induce an electric field and changing electric fields induce magnetic fields. EM waves are combinations of electric and magnetic fields and hence propagate themselves. They require no medium. If they did, it would give a preferred reference frame which goes against Special Relativity. \n\nSource: Neutrino Physicist"
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1vosex | why did the 1997 asian financial crisis take place? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1vosex/eli5_why_did_the_1997_asian_financial_crisis_take/ | {
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"The depreciation of value of Thailand's currency combined with the lack of financial policy to handle the event is the starting point. Thailand and some other countries had fixed or semi-fixed currency exchange rates which contributed to deficits in value and, in turn, the value investors placed on those currencies. Domestic companies with loans in foreign currencies found themselves needing to pay more money for the same loan amount due to the decline in value of the currency. Panic ensued in the markets and the rest is history. \n\nTL;DR - too much risk in the currency exchanges without protective policies allowed bad investments which caused massive sell-offs. "
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4kfbdb | When building, how did the Romans maintain and measure the aqueduct water gradients? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4kfbdb/when_building_how_did_the_romans_maintain_and/ | {
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"Fairly certain there is something here in De architectura\n_URL_0_\n\nSearched for you, page 244\n\"let the bed of the channel have a gradient of not less than a quarter of an inch for every hundred feet\"\n\nThe next question is 'why,' and in this Vitruvius has always be a little light in the details. He was a pragmatist and it was because it was what worked.\n\nChapter 4 explains how they found the gradient.\n\nInteresting enough, Vitruvius also advised to not use lead pipes for drinking water (ahem... Flint; 2,000 years later) \"Hence, water ought by no means to be conducted in lead pipes, if we want to have it wholesome.\""
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51z6oz | how can reducing the size of an object increase its surface area? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/51z6oz/eli5_how_can_reducing_the_size_of_an_object/ | {
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"I believe that what they mean is that more surface area in *total* is exposed, increasing the reaction rate. \n \nSay you have a perfect sphere, submerged in liquid. Right now, the area exposed to the liquid is the surface area of the sphere. \n \nNow say you cut the sphere in half. Now, the area exposed is equal to the surface area of the original sphere, *plus* the two circular faces which you have just created by cutting the sphere into halves. Does that make sense?",
"A really easy everyday example of that principle in action is a loaf of bread. The outside of the bread is the surface area. Now cut the loaf into slices. You still have all that outside surface area but now the front and back of each slice is also surface area. You've cut it into smaller pieces and massively increased the surface area. \n\nTL:DR - cutting something up turns some of the inside into surface area too. ",
"Reducing the size of an object does not increase it's surface area. When you cut an object into pieces, you are creating multiple objects. Rather than jumping into surface area, I'll explain with perimeter, since I feel like that's easier to understand. Imagine you have a 2x4 inch rectangle. There's 2 2-inch sides and 2 4-inch sides. The total perimeter is 2+2+4+4= 12 inches. Now split the rectangle apart into 2 2x2 squares. Each square has 4 2-inch sides. So the total perimeter of both squares is 2x(2+2+2+2) = 16 inches. \n\nWhen you split apart an object, you're creating at least two new faces. One on the outside of each object. These new faces get added in when calculating the total surface area. So a 2x2x4 rectangular prism with total surface area of 2(2x2)+4(2x4)=40 inches^2 can become two cubes with a combined surface area of 2(6(2x2))=48 inches^2 ."
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1zg6xk | why aren't more policemen (who are seemingly losing cases) allowing people to demonstrate their right to record them? why are they still trying to stop the recordings? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1zg6xk/why_arent_more_policemen_who_are_seemingly_losing/ | {
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"In general, cops don't want to be recorded while working as if they make a mistake or push the boundary too far, it can bite them in the ass later. \n\nI'm not sure what your job is, but how would you feel if every action you took in a dangerous situation was scrutinized? Sometimes things aren't always black and white, and actions in a grey area can result in you getting fired. Video doesn't always show things in the correct context and can make things appear to be worse than they are. For example, a video shows a cop attacking a suspect. Was he abusing his power, or was he trying to protect himself and subdue an armed and violent individual?\n\nThat said, there are also cops that flat out break the law and hide behind the badge, these cops don't want to be recorded at all as it would be impossible to justify their actions.",
"In some jurisdictions, it *isn't* always legal to record police officers. It's relatively new for most people to even have the ability to do this, so not all officers are super well trained on what the law is."
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jiqm7 | how does a plane fly? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/jiqm7/eli5_how_does_a_plane_fly/ | {
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"The plane is pushed forward by either propellers or jet engines. Propellers work just like a fan and push air backwards. Jet engines also push air backwards, but push much harder. This is why Jets can go faster.\n\nThe wings on the plane are tipped a little bit so that as the plane is moving forwards, they push the air down. Pushing the air down pushes the plane up and keeps it in the air.\n\nYou can feel this for yourself in a car. If you hold your hand out the window while driving and tilt it a little, you will see that it is either pushed up or down depending on how it is tipped!\n\nSource: My 5 year old daughter asked me this question a few weeks ago.",
"Much like your hand out a car window. Almost exactly. \n\nAs your hand moves through the air, if you tilt the front edge up slightly your hand will rise because air is hitting the underside of it more, pushing it up. IF you tilt it down, the opposite. This tilting is called 'Angle of Attack'.\n\nThis is basically how wings work (il5 explanation). So put 2 wings on either side of a plane, make it move fast enough forward through the air (with and propeller/jet engines), tilt the wings back slightly and they'll rise up, pulling the plane with them.\n\n\nThe wings also have a special shape (airfoil) which cause a slight amount of lift themselves, but negligible in contrast to the angle of attack. Most people will try and give you this explanation (about airfoil) but it's not entirely correct (to the point of being not worth talking about), and only a (very small) part reason what planes fly. A plane will still fly without any airfoil, but will not fly without air moving over the wings.",
"The plane is pushed forward by either propellers or jet engines. Propellers work just like a fan and push air backwards. Jet engines also push air backwards, but push much harder. This is why Jets can go faster.\n\nThe wings on the plane are tipped a little bit so that as the plane is moving forwards, they push the air down. Pushing the air down pushes the plane up and keeps it in the air.\n\nYou can feel this for yourself in a car. If you hold your hand out the window while driving and tilt it a little, you will see that it is either pushed up or down depending on how it is tipped!\n\nSource: My 5 year old daughter asked me this question a few weeks ago.",
"Much like your hand out a car window. Almost exactly. \n\nAs your hand moves through the air, if you tilt the front edge up slightly your hand will rise because air is hitting the underside of it more, pushing it up. IF you tilt it down, the opposite. This tilting is called 'Angle of Attack'.\n\nThis is basically how wings work (il5 explanation). So put 2 wings on either side of a plane, make it move fast enough forward through the air (with and propeller/jet engines), tilt the wings back slightly and they'll rise up, pulling the plane with them.\n\n\nThe wings also have a special shape (airfoil) which cause a slight amount of lift themselves, but negligible in contrast to the angle of attack. Most people will try and give you this explanation (about airfoil) but it's not entirely correct (to the point of being not worth talking about), and only a (very small) part reason what planes fly. A plane will still fly without any airfoil, but will not fly without air moving over the wings."
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17g08g | How were the dead, enemy and friendly, dealt with after a battle(s) in your area of study/research/expertise? | How were the dead, enemy and friendly, dealt with after a battle(s) in your area of study/research/expertise?
Were they immediately buried? Burnt? And if not, did this ever have any grave ramifications for any army in the sense of disease?
I am familiar with Islamic empires, that they would command their people/soldiers to immediately give their (friendly) dead an Islamic burial as soon as possible, but was this extended to foe as well?
And is there a book that deals with this topic extensively that you would recommend? Or any monographs that deal with specific areas after battles?
Was there ever any universal/unanimous (that is, cross-cultural) development toward dealing with the dead over time?
Much appreciated. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/17g08g/how_were_the_dead_enemy_and_friendly_dealt_with/ | {
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"During the Siege of Tobruk (North Africa, 1941. Australia plus some Commonwealth and Poles vs Germans and Italians) it wasn't uncommon, in fact it was somewhat common, for a truce to be declared after a battle to clear the battlefield of the dead and wounded. Medics and doctors from both sides would treat any wounded soldier they came across regardless of which side they were on.\n\nAs Rommel said about the war in North Africa, \"Krieg ohne Hass,\" which means, \"War without hate.\""
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1j4b5g | If animals have no awareness of death, where does the "playing dead" reaction come from? | askscience | http://www.reddit.com/r/askscience/comments/1j4b5g/if_animals_have_no_awareness_of_death_where_does/ | {
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"A concept of death isn't required for the playing dead instinct to develop. All that is required is that playing dead function successfully as a defense.\n\nIt is important to note, most predators prefer fresh killed animals, and ignore scavenging dead prey. Now envision a (simplified) scenario:\n\nTwo tiny cute defenseless creatures are born. One with a mutation that leads it to collapse when overstimulated by fear, and one which does not. \n\nA large predator that prefers live prey enters the vicinity. Both creatures become fearful. One creature attempts to flee. The other, in response to the mutation it possesses, collapses. The predator ignores the apparently dead prey, chases the moving, apparently living, prey, and devours it.\n\nThe prey with the 'collapse' mutation survives to pass on its trait, the other does not. At no point does the animal 'know' it is playing dead, or even have to know what death is.\n\nFor [more](_URL_0_)",
"\"Playing dead\" can be a result of the animal feigning death, or a tonic state in which the animal is paralysed. These reactions to predation, for example are not a result of any sort of \"awareness\". It's an adaption selected for by natural selection. A mutation in physiology or behaviour that benefited the animal and increased its organismal fitness! \n\nBesides. How would we know if any animal was \"aware\" of the concept of death? Ask them?"
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3nc44q | how do companies discover that they've been hacked? | If you're a smart hacker, couldn't you figure out how to access information without anyone knowing that you did it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3nc44q/eli5_how_do_companies_discover_that_theyve_been/ | {
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"If a good hacker didn't leave a footprint then the company wouldn't know about the leak, and you would never hear about the company having a leak.\n\nThe Sony hack wasn't noticed by Sony. It was the hacker group that publicly exposed the hack.",
"So. I worked in a global company when it was hacked. It was during a nuclear plant being built, and some of the foreign investors turned out to be part of there countries intelligence services. While they were being shown around, one of them put a pen drive in a USB port of one of our computors.\n\nA week later nobody really noticed anything. A few more spam emails got through the firewall, but nothing major. But then, I got an out of office reply from someone I'd not sent an email too. I looked into it, and the service desk was getting a few calls like this. Weird. Then I was sending an email, and wanted to recall it, looked in my sent items and a whole list of unknown emails were there. Again the serivce desk looked into it, locked down my email address and called in help. There was a program in the email system for a month (since the pen drive was inserted) that had propigated slowly from that one PC, to all the PCs it emailed, and onwards. All it did was send a copy of the emails from infected PCs onwards, it wasn't really possible to track how or where as it sent thousands of dummy mails everywhere. They assume the aim was to get a copy of directors discussing commercial issues etc, which they certainly will have managed.",
"Network intrusion and detection tools (along with people reading the reports) can catch things. Some of those tools monitor real time, some produce daily/weekly reports and that is when you find things. Something as simple as a virus on your computer they gets found by a definition update to your antivirus and you can figure out when it was installed/changed last. Which might be several days ago. \n\nBut yes, lots of times companies don't know they were hacked or the extent of the hack until.... \n\nHacking data isn't generally done for fun. It's criminal and can land you in a lot of shit if you do it badly. Hackers who can get data and get away with it are worth a lot of money, and they expect to be paid, extortion of the hacked company, bank or cc fraud (usually they sell this data to other hackers who specialize in this sort of thing). So hacked data to be worth anything shows up on hacker websites fairly quickly, or is used for extortion fairly quickly. And once you know what was taken (even part of it) you can work back through logs and see what was accessed from where and know the extent of the hack (not necessarily the real origin though). ",
"When they find their shit on bittorrent 2 years after the fact, most commonly. If you don't catch it real-time (using IDS equipment and good monitoring practices as explained in other posts), you basically have to get lucky to find it.\n\nBelgacom BICS found out GCHQ hacked them because their Exchange server was continuously crashing, because of a bug in the malware they planted in there. That bug was fixed in other versions of the same malware they found in other places of the network."
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vpeba | How are pre-Gregorian dates handled? | I'm hoping this is a simple question with a simple answer.
What's the convention for dates before the invention of the Gregorian calendar? Can I assume that they're Julian dates?
For example, Joan of Arc died on 30 May 1431. This is what's listed everywhere. I would assume that this date is based on contemporary documents, and it hasn't been converted more than strictly necessary.
So the Gregorian date, if we have a calendar stretching back continuously to the beginning of time, would really be 8 June 1431.
_URL_0_ | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/vpeba/how_are_pregregorian_dates_handled/ | {
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" > The Gregorian calendar can, for certain purposes, be extended backwards to dates preceding its official introduction, producing [the proleptic Gregorian calendar, ](_URL_0_)but this proleptic calendar should be used with great caution.\n\n > For ordinary purposes, the dates of events occurring prior to 15 October 1582 are generally shown as they appeared in the Julian calendar, with the year starting on 1 January, and no conversion to their Gregorian equivalents.\n\nSo, it seems your Joan of Arc assumption is correct: she died on 30 May 1431 using Julian calendar dating, the contemporary calendar. And [Wolfram Alpha agrees](_URL_1_) that this can be converted to 8 June 1431 in the proleptic Gregorian calendar.\n"
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3wr1cz | How come The majority of cars run on internal piston combustion engines over turbofan engines? | how come 99% of fossil fuel driven cars use a piston engine? planes, helicopter, and even tanks have switch to more effective methods, i.e. gas turbine engines, and havn't used piston driven engines since WW2. I know there were projects to make gas turbine cars, Chrysler had a car _URL_1_ as well as jaguar has a super car _URL_0_ and a couple others if you look on the turbo fan wiki page. My question is why arent these engines being fitted into present day cars? and what would the draw backs be of cars with turbofan engines? | askscience | https://www.reddit.com/r/askscience/comments/3wr1cz/how_come_the_majority_of_cars_run_on_internal/ | {
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"Turbines become much less efficient as you scale them down. Turbine speed is limited by the blade tip velocity, which must stay below the speed of sound. Smale turbojets run at tens of thousands up to a hundred thousand rpm. This is extremely loud and it takes a very long time to speed up. It's also extremely hard to get gears to work at that speed. There are many reasons but practically size is the really big one, and cost is a close second.",
"**Turbine engine disadvantages (over piston engines):**\n\nPrice per horsepower\n\nIdle and low power setting fuel efficiency\n\nThrottle / power response\n\nNeed for a gearbox to convert high RPM, low torque turbine output to low RPM, high torque power\n\nDoesn't scale well to small (sub-500 horsepower) applications\n\nMaintenance costs\n\n\n**Turbine engine advantages:**\n\nMass per horsepower\n\nVolume per horsepower\n\nHigh altitude performance\n\nScales well for very high power applications (1,000 - 150,000+ horsepower)\n\nLongevity / reliability\n\nLooking at those, you'll see that a lot of the advantages of turbine engines are not useful for automobiles and the disadvantages like price, idle/low power efficiency and response time are very detrimental to an automobile application."
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4e5f3b | how does my stone age brain manage to drive a car safely, while my mind wanders into oblivion and thoughts about sex | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4e5f3b/eli5how_does_my_stone_age_brain_manage_to_drive_a/ | {
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"By scaring the shit out of all the drivers around you so that *they* have to pay close attention to their driving. And thank their lucky stars that at least you aren't eating a donut.",
"Cars are designed by people to be easily driven by people. Learning how to drive isn't any different than learning any other skill.",
"Your brain does operations in parallel. Just because your thinking about something, doesn't mean your brain isn't thinking about something else. Like keeping your heart working, breathing, and motor skills that you don't need to think too hard to do anymore.",
"Your brain is evolved to watch out for dangers while your mind \"wanders into oblivion\". There isn't such a big difference between watching out for traffic and watching out for snakes or lions.",
"In the same manner as you can walk and chew gum at the same time - for most (all?) learned skills during learning, the various parts of your brain develop connections that are, in essence, a 'neural net' engine that does those things - usually, with no conscious processes required, those connections generally are not accessible to the small part of your brain that \"runs\" consciousness.\n\nThe part of your mind that is able to wander into oblivion and thoughts about sex isn't able to drive a car anyway. It has limited throughput and that is not sufficient to handle all the tasks required. It shows up quite nicely as people learn to drive - first, they consciously manipulate the pedals and steering wheel and are unable to do anything else beyond that such as paying attention to traffic lights and mirrors; and even the actual task of pressing the pedal to the exact desired amount is done quite poorly. With some time, that (part of) task gets learned and can be done \"automatically\" with the conscious mind merely initiating the process.\n\nAfter some more time, the other, more complex parts go the same way up to the extent that (some?) people occasionally can drive home without even consciously acknowledging and paying attention to the process, much less having their conscious mind actually making any decisions about the details of that trip..",
"Part of it is to do with different memory types. Driving, like riding a bike, is largely procedural, i.e. its doing something. Unlike episodic memory (things that have happened to you or matter, events/people) etc, its implicit. Which means its not something you're aware of really, you don't 'remember' how to ride a bike in the same way you remember that sex you had once. Its not an active process, kinda like muscle memory, where you simply draw on that memory to use it. So you drive almost on automatic, and can think about other things. At the same time, part of your attention is still engaged by driving and we have finite attention, so the less attention you pay to driving, the more likely you are to have an accident."
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zdjf3 | with the proper suit would it be possible to space jump? | I understand entering the atmosphere would be one of the bigger issues, I'm just curious if it would be a viable idea as a last resort to get home from the space station. | askscience | http://www.reddit.com/r/askscience/comments/zdjf3/with_the_proper_suit_would_it_be_possible_to/ | {
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"Space and orbit are different things. From space, sure. You just fall down the same as anywhere. There's no terminal velocity while outside atmosphere so you just keep on gaining speed. The shielding you need then depends on what your speed is when you do enter atmosphere.\n\nOrbit in a very real sense means that you are in free fall but are continuously missing Earth. If you already are in free fall, then jumping off of a space station isn't going to change anything. You just keep on being in free fall, in other words orbiting the planet. To reach Earth, you need to stop missing it with your fall. To do that you must reduce your horizontal speed. How much depends on how you want to enter the atmosphere. The shuttle reduced it just enough to hit the upper parts of atmosphere which will then slow down the shuttle more. But it enters the atmosphere at huge speed (because it had huge speed at orbit and reduced it only slightly) so it needs all that heat shielding. If you reduce the speed a lot, like cancelling all your horizontal speed, then we return to the first case of simply falling to Earth and requirements on heat shielding would be much less. But that would require a huge rocket, almost as big as you used to get up there in the first place. It is much easier to put on some heat shielding and use a tiny rocket than no heat shielding and a huge rocket."
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34kzuv | What are the major difference and similarities between a peasant living in southern France in 800 and one living in 1300? | On balance which are greater, the similarities or the differences? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/34kzuv/what_are_the_major_difference_and_similarities/ | {
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"There is a chance that your 'peasant' during the Carolingian period in southern France could have been a slave and not a free peasant, the odds depending on which historian's calculations you trust. By 1300 slavery had been extinguished in southern France, if not quite yet in the lands of their Spanish neighbours to the south. \n\nBy 1300 the wide gulf between Carolingian slavedom and free peasantry had narrowed and became, in custom and in law, a rather single entity: the peasant in servitude. But opportunity had also become more diverse with the development of technology and commerce. Southern France's position on the Mediterranean, with several important ports extant from antiquity (Marseille, Narbonne), had meant that import/export businesses never died off. But the south enjoyed a growth of towns perhaps faster than most other places in Europe in the 11-13th centuries. These towns were either brand new creations founded by either secular or ecclesiastical lords (*bastide* or *salvetat*, respectively) or based on Roman *oppidium* that had endured as villages. The rapid rise of towns was due to the huge growth of agricultural output and of commercial development it spurred.\n\nThese changes which spurred the growth of towns were founded on the lives of peasants, lives which changed in the 500 years between Charlemagne and the assertion of Capetian dominance over the French south. New lands were put to cultivation by more productive technology like 3 field rotation which made the earth more productive, horse collars which could pull faster and stronger, mouldboard plows which could turn heavier soil deeper, animal husbandry which resulted in greater animal variation to suit greater productivity. \n\nWhere the Carolingian peasant lived in earth and wood huts, 500 years later they could be living in stone houses; stone pulled from the fields by peasants' deeper, stronger plowing...or the cast offs of limestone mines for the castles and churches that sprang up across the south and which the peasants also built. It was a multitude of towns and castles and churches: some 200 new stone towns in the south sprang to life between 1100-1300. These towns drew in peasantry to work there in trades and industry, or to live behind the protection of walls and farm the fields beyond during the day. \n\nSo commerce and industry developed on the innovations of peasantry during this period such that the physical, agricultural world would have looked different over half a millennia.\n\nBut what of the spiritual world of the peasant?\n\nThe peasant of the Carolingian period, whether slave or free person, would have been Christian in name and identity. But in practice? They would have rarely been in a church or rarely seen a priest as we would know them, or as their descendants 500 years later would know them. By 1200 the Church was on a steady march into the souls of all the population, and perhaps no more so than the souls (and pockets) of the southern French peasantry.\n\nThe question of discipline of the average Christian in thought and action became paramount for the Church after 1000. Attendance to mass, sacraments like baptism and confession became obligatory and enforced by the 13th century. Marriage became subject to the Church. The entire life of the agricultural peasant in 1300 would have been enveloped by the Church (how effectively is another question).\n\nAnd to add to the greatly expanded influence of the cathedral and monastery, by 1300 thousands upon thousands of potential heretic peasants of southern France would have been disciplined - interviewed, approved and/or corrected - by the inquisition: from Toulouse to Narbonne, Montpellier to the deepest Pyrenees.\n\n & nbsp;\n\nSome reading:\n\nOn the transition of peasantry, Pierre Bonnassie, *From Slavery to Feudalism in South Western Europe*, \n(Cambridge University Press, 1991) and Georges Duby, *The Early Growth of the European Economy: Warriors and Peasants from the Seventh to the Twelfth Century*, (Cornell University Press, 1974).\n\nOn the 'world' of southern France in the middle of this period, Fredric Cheyette, *Ermengard of Narbonne and the World of the Troubadours*, (Cornell University Press, 2001).\n\nOn the inquisition, James Buchanan Given, *Inquisition and Medieval Society: Power, Discipline, and Resistance in Languedoc*, (Cornell University Press, 2001)\n\n"
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1kbjl7 | I've just learned about the fabulous life and horrible death of Ludwig II of Bavaria. What's a good source for the layman of more information about him? More questions in comments. | I'm scouring the internet at present in a state of wonderment. Questions I have:
* Was he really insane? He seems unbalanced in a tragic and fantastic way, but what I'm reading seems to fall short of what we would call insane today.
* Was he straight-up gay? I'm finding references to his troubles in finding his sexual identity, but what is the basis of this?
* What was the Chinese Palace, his never-built dream palace, to have been like? How far along was the planning for it?
* Is this account of events leading up to his death accurate: _URL_0_? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1kbjl7/ive_just_learned_about_the_fabulous_life_and/ | {
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"I'm kind of surprised and disappointed that no one has anything to offer on this topic. But that's infinitely better than a subreddit where people who know nothing speculate, so hats off to /r/AskHistorians anyway."
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1pzg8y | Why are Half Tracks no longer a prominent military vehicle? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1pzg8y/why_are_half_tracks_no_longer_a_prominent/ | {
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"This is more of a technology than history question, and it risks veering into speculation.\n\nMy take is that wheeled vehicles have simply gotten better. Tracks are primarily useful for gaining traction on soft ground with a heavy vehicle. Half-tracked vehicles are a sort of compromise, they are lighter than heavy armored vehicles but still need off-road traction. Today such niches tend to be filled by wheeled vehicles exclusively. If you look at, for example, the Czech made Tatra trucks you see how far wheeled off-road mobility has come. With high power and high torque engines, big tires, all-wheel-drive, modern transmissions, and other innovations even extremely heavy wheeled vehicles can have impressive off-road mobility.\n\nYou can see this trend clearly in the advancement of wheeled armored vehicles into the traditional domain of tracked APCs and light tanks. As with the Stryker, Pandur, BTR and many similar vehicles. You can also see a somewhat similar trend in civilian vehicles. Some very massive front loaders and excavators tend to be tracked, but there are many extremely large vehicles of those types that are wheeled. As are many dump trucks, even in the multi-hundred tonne capacity range.\n\nEdit: Here's a few other points that are probably relevant.\n\nWWII occurred prior to the interstate highway program in the US, which vastly increased the ability to move around the country via wide, well-paved highways. The same trend over the same period applies equally to many other countries around the world. It's just easier to get around on wheeled vehicles in most places.\n\nAnother important change has been improvements in air power. Today if some enemy army is holding some god forsaken piece of land where there are no roads, generally the thing to do is to just sit back and hit them with precision munitions. However, if you do end up fighting in remote regions it's likely that logistics and troop transport will be done via helicopter."
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5bsbsk | If two power plants feed AC voltage/current into the same electricity grid, how do we make sure they are in the same phase to not cancel out each other? | If two power generators feed a sinusoidal voltage into the grid, but one has a phase difference of 180° to the other, wouldn't the voltages cancel each other out?
So after the voltage of the power plant is transformed into the appropriate voltage, how do we make sure the voltages have appropriate phase differences? Or does it not make any difference what phase the feeded voltage of each power plant is? | askscience | https://www.reddit.com/r/askscience/comments/5bsbsk/if_two_power_plants_feed_ac_voltagecurrent_into/ | {
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"Power generators have to be [synchronised](_URL_0_) before connecting them to the grid.\n\nIf you imagine a single phase 240 volt generator being connected to the grid via a suitably thick cable, if it was 180 degrees out of phase you would effective have 480 volts shorted across a conductor. This would generally vaporise the connection with a significant, and possibly fatal to the operator, explosion.\n\nOnce connected the synchronisation is partly self regulating, as if the generator attempts to run faster than the grid frequency it will face higher load, and vice versa.",
"Answered here:\n\n_URL_0_\n\nOn the return question, the earth is the return and the circuit is closed loop; doesn't matter if the return terminates at the same power plant as the energy source.",
"Electrical engineer here and one of my labs was hooking up a generator to the live power grid. we actually did it by hand I'm sure that an automated control system could get it nearly perfect.\n\nTo answer your first question yes, if you connect out of phase things will go badly. think smoke and fire.\n\nA 3-phase generator has a Y frame in the inside each spoke 120 degrees apart with a winding on each. Each spoke generates one of the phases. The generator spins exactly 60 times a second to give use the 60Hz AC signal. \n\nSo now you are ready to hook to the grid but you are out of phase. All you need to do is briefly changes the speed of your generators. Something is driving the spinning of the generator mostly in power plants its a steam engine with the steam coming from burning a fossil fuel or a nuclear pile. So you adjust the steam engine to say 59.99 hz and now your phase difference relative to the grid that is at 60 Hz will start to move. Once it gets in phase you step up your engine back to 60HZ and connect.\n\nOver time you and the power grid won't both be exactly at 60 hz so you need to monitor the grid phase and have a feedback system to your generator to speed up or slow down in order to stay in phase.\n",
"Before making parallel, we use phasing sticks which are basically high voltage volt meters. When the difference in potential between two conductors is zero (or very close) it is safe to close the switch and make parallel. If they are out of phase you will get full line to line voltage and you do not want that. ",
"I've parallel a nuclear powered ship's (CGN-40) turbine generators with shore power at Norfolk more than once. The electric plant control panel had a Synchroscope _URL_0_ that displayed the phase/frequency relationship between the ship and shore power. If we had just docked, I'd match the shore voltage, then run the ship's generator frequency slightly lower than the shore frequency, and close the paralleling switchgear when the phase difference was zero.\nIt the phase difference is too great, you can motorize your generator, tearing it from it's mountings and cause great harm to ship and crew.",
"Seems like good answers have been given. An important concept I didn't see mentioned is that of the Interconnections, of which there are three in the US, Eastern, Western, and Texas. Each basically operates as its own giant machine (to which individual generators must synchronize), and it's impossible to connect between them, except through an HVDC link. ",
"Senior reactor operator here. \n\nPrior to connecting any generator to a bus, you need to match phase, frequency, and voltage. \n\nMost nuclear plants still do this manually, newer plants use automatic synchronization circuits. \n\nWhat we will do is turn on the synch scope. The scope is connected to the bus and the generator, and the resulting out of phase voltages cause the scope to move forward or backward. The scope is round with a needle, like a clock. When the arrow is facing straight up, that means both sources are in phase. \n\nSo how we will synchronize the generator, is after the synch scope is on, we check the voltage difference on a meter, and adjust generator voltage to match grid voltage. \n\nOnce voltage is matched, we adjust the turbine/generator governor to adjust frequency. We aim to have the synch scope rotating slowly in the clockwise direction. 1 rpm on the scope or less for a large generator. When the scope rotates clockwise, it means we are slightly ahead of grid frequency, and at less than 1 rpm, we are very close to grid frequency. Then we wait until the needle is about straight up (at the 12 o'clock position) where phase is matched. At this point we will close the generator output breaker. \n\nOnce the breaker closes, for the power grid, phase voltage and frequency of the generator will all lock onto grid voltage. The fact that we were slightly faster than the grid means that once we synchronize, we will be putting real power out onto the grid. (If we were slower, the grid would be reverse powering the generator and it would trip). \n\nAt this point we will raise governor settings up to put load on the grid and close our steam dumps, while also gaining margin to our reverse power trip. Finally we adjust the voltage regulator to set reactive power and bus voltage where the transmission operators want it. \n\nIf you have any questions let me know. I'll see if I can get a video of this in the next day or two from our simulator. ",
"While the OP asked about power plants, the examples of generators are a good analogy. Any two power 'sources' must be in synch before being paralleled. Golf you're talking about generators, you typically do this in the downstream switchgear. The two primary options are either PLC controls (Schneider M580) or a dedicated controllers (Woodward Easygen 3000). PLC's are more expensive but infinitely customizable to the needs of the user and the specific application. Controllers are configurable but offer less customization at a lower price point. Many times, mission critical applications perform paralleling with redundant Hot Stsndby PLC's where a fiber link between two PLC's keeps their memory in sync that if one fails you have continuity of operation. The PLC in these applications is just stepping through logic. It receives input from relays that are connected to the line (or bus) side voltage taps (Basler BEI-700). In medium voltage applications, potential transformers are used to reduce the voltage to < 600v. One of the critical things with paralleling generators is how fast they come online and sync to the bus. Once the two sources are paralleled, they keep each other in sync. ",
"Basically, they first synchronise the generator with the grid. Once it is synchronised they bring it online. From now on it's speed is basically locked by the grid. Trying to speed up cause it to send more power to the grid, taking extra power from the engine but don't make it speed up, just lead a bit more in phase. Going too slow cause the grid to feed back in the generator, turning it into a motor (no good at all). So, they control the power they send to the grid by making more power, which cause more phase shift, but since it is really locked by the grid, the shift is not that real. The grid don't see it. The heavier the load, the more it try to slow down all the generators. By carefully monitoring the production and consumption, they can still maintain about the right grid frequency. This is also one reason why the grid frequency vary slightly, as it get hard to sync all of them. With today's central that is all networked and they can predict most of the peaks (since it do not vary that much from week to week (but does day to day), they can also prepare some centrals and generators. During off peaks, they may shutdown some central and/or generator to save on wear and maintenance, but also to save on whatever \"fuel\" they use (I also include water as fuel). Since they are networked, they can make more fine adjustements, set more generators to their peaks efficiency. while maintaining enought generator on idle to handle some unexpected loads and equipment failure, while putting offline some other that will not be used. Ex: in canada, we mostly heat with electricity. This take an awefull lot of power. Why put all those generator online in... late spring or early autumn where there is no heating and no a/c?",
"There are systems called synchronizers at every power plant that wants to connect to the grid. Usually it works by matching zero crossing and time measurement at each end (generator side and grid side). The freq and phase are aproximatly matched but not perfect. The grid will tend to push or pull into synchronization the generator that is trying to connect (depending how much in or out phase it is) creating in-rush (motoring conditions: the grid will try to rotate de prime mover) or out-rush current surges that could damage the generator but this are kept low enough to not trigger synchronization protection relays (that are there to protect the generator for this kind of events).",
"I don't know if this is an urban legend or not, but here it is anyway.\n\nOur local electrical generator, Eskom, had a small coal fired power station, which was primarily used for training purposes. The station gets stripped down and rebuilt periodically, as part of their training. This includes removing and reinstalling the taps on the transformers that feed the frequency gauges.\n\nThis particular occasion, the taps were installed backwards, resulting in a reading that was 180 degrees out of phase. So when the dial speed spinning, indicating that they were in sync with the grid, and they closed the breaker, the grid effectively said Nope!\n\nSince the grid was backed by thousands of megawatts, and this was something like a 30 MW turbine, the grid won. The turbine stopped turning instantly, only to start turning again 1/60th of a second later. This resulted in a multiple ton turbine being launched out of the building and over the river several hundred meters away.\n\nThe facility was closed down, and never used again.\n\nAccording to my recollection of the story, this happened in the 1950's or thereabouts, which explains why i have not been able to verify the story.",
"The process of adding a (synchronous) generator to power grid is called synchronization. Basically, before connecting the generator to the grid, you have to spin in fast enough, do frequency matches grid frequency, all three phases match and there,s no time delay between grid and the generator. You have devices that can do that (tell you when the generator is ready to be connected) as they measure all of the parameters of generator and grid and compare them. Adding non-synchronized generator to grid is not a a good idea as every phase in both grid and generator is time dependant (its current value, also known as sin(omega*t)), so if there is time delay in between of them, you can actually get huge current which in my country we call equation current. Basically its value is dependant on voltage difference between grid phase and generator phase and total resistance between them.\n\nI hope I explained it well. :)",
"Using a device called a syncroscope that visually allows you to see phase synchronization as a unit of seconds. This allows for manual syncrhonization, usually indicated by a cardinal point like the 12 on a clock or a range (think between 11 and 2 on a clock). When the pointer is in that range, they parallel.\n\nP.s. proud to see all the fellow navy nukes going to answer this seeing the question my first thought was all the nukes are going to answer this, and you guys confirmed it",
"I've manually synchronized generators many times. Basically you use a syncrometer which connects to the power line and generator. The type I used had three flashing lights, one for each phase. The generator is started and the shaft RPM of is slowly changed until it matches the frequency of the line voltage. The bulbs will flash slow and stop flashing as generator output and line frequency match.\n\n If you get the bulbs to stop while on, they're out of phase but at the same frequency of the line voltage. If the bulbs are off, then the line frequency is the same and they're in phase. If, the line voltages are the same (adjust the field voltage if they aren't) and the syncro shows they're in phase, then you flip the switch to connect the facility to the generator and then disconnect the line power or vice versa. \n\nIt's actually quite easy. "
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e0ffne | How widespread was anti-Irish sentiment in the United States in the late 1800s-mid 1900s, particularly the infamous "No Irish Need Apply" signs? | While looking into information on the debate of Irish slavery in America, I spied a "No Irish Need Apply" sign, and remembered seeing one in a video game set in a steampunk Victorian-esque city (Bioshock Infinite). While information is clear that anti-Irish sentiment was rampant in the United Kingdom, to what degree was job-discrimination against Irish a factor in the United States?
As an aside, I remember hearing somewhere that the stereotype of Irish police officers and firemen was simply because no one wanted those jobs, and that the Irish would go on to earn the respect of the people of America by undertaking these dangerous jobs no one wanted, that also happened to be some of the few jobs that weren't discriminating against them. A second question I suppose, but it ties in to the main question enough I think, to be posted alongside it. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/e0ffne/how_widespread_was_antiirish_sentiment_in_the/ | {
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"I have [an earlier answer](_URL_0_) on \"No Irish Need Apply\" signs and ads (and how historians have talked about this). In the U.S., they were particularly prominent in jobs advertised to women--which definitely runs against common modern stereotypes of the 19th century.",
"As for your observation on the Irish association with the police force, it's actually an interesting topic in and of itself. During the mid-19th century, anti-Catholic/anti-Irish sentiment coincided with the formation of the first modern urban police forces. Before this time, you would usually see watchmen that worked for a few hours in shifts and \"policing\" was more apprehending criminals than preventing crimes from happening in the first place. In the more dangerous urban neighborhoods (many Irish), gangs formed and would work to control neighborhoods, which would often result in clashes and violence between rival gangs. In order to put an end to this and regain control of the cities, the modern police force was born. It took a few decades to iron out, but the idea was there by the 1850's (1).\n\n\nSo how did the Irish, who were despised, get jobs policing? It's simple: voting. During the early to mid-19th century, voting laws changed and now white male citizens who did not own land were given the right to vote (the year varies by state). Furthermore, in 1868, the 14th amendment was passed and granted citizenship to all males born in the United States, or naturalized, thus giving even more males the right to vote. All of this, coupled with rising Irish immigrant populations concentrated in the cities, gave the population huge voting power and the Irish were generally tightly-knit, connected communities through their parishes. Policing and firefighting required little education, so as the Irish entered the civil servant sector, this type of work was appealing. Then, once in, friends and family members would give each other jobs, and voila, Irish-dominated police and fire departments (as an aside, we could even talk about the Irish Mafia and public roles as they were generally connected, especially in Boston) (2, 3). This persisted well into the 20th century and can still be seen in some Northeastern cities, for example, Boston and its suburbs still have a lot of Irish policemen and it's still considered to be a legacy job.\n\n\nSources:\n\n1) Monkkonen, Eric H. \"History of Urban Police.\" Crime and Justice 15 (1992): 547-80. _URL_0_.\n\n2) Eisinger, Peter K. \"Ethnic Political Transition in Boston, 1884-1933: Some Lessons for Contemporary Cities.\" Political Science Quarterly 93, no. 2 (1978): 217-39. doi:10.2307/2148607.\n\n3) Glaeser, Edward L., and Andrei Shleifer. \"The Curley Effect: The Economics of Shaping the Electorate.\" Journal of Law, Economics, & Organization 21, no. 1 (2005): 1-19. _URL_1_.\n\n*Edited for formatting.",
"Any response to a question that involves NINA signs even tangentially must, of course, start by referring the reader to /u/sunagainstgold's [masterful answer on the subject](_URL_0_).\n\nThe Irish were discriminated against in America even before there was a United States - in the 1710s and 1720s, for instance, English colonists in New Hampshire harassed newcomers from Ulster (by way of Maine) attempting to start a new community nearby because they were \"unwholesome\", Catholic, and \"poor Irish\", despite being Scots-descended Protestants who had fought very recently for the British. Catholicism was, at the time, highly stigmatized by the English and Anglo-Americans as a dangerous and somewhat heretical ideology (several decades before, the king of England had been overthrown due to his Catholicism and the understanding that his newborn son would be raised in that religion), and which was a great part of the discrimination against the Irish. However, the simple fact of nationality was also a factor, which would in a few generations spur the push to use \"Scots-Irish\" as an ethnic identifier rather than simply \"Irish\" - to encapsulate the fact that they weren't like *those* Irish who lacked British ties and had stereotypical undesirable traits: the native Irish tended to be poor and under the thumb of English-descended landlords, which was taken to mean that they lacked intelligence and strength of character, rather than that they were unfairly exploited.\n\nBut the question is really about the nineteenth and early twentieth centuries, and employment. Male Irish immigrants and Irish-Americans were widely employed from the 1830s as contract laborers for construction projects like bridges, buildings, canals, etc. - while there was general sentiment about the Irish along the same lines as that described above, employers looking for \"unskilled\" manual laborers seem to have been perfectly happy to hire them. (To some extent, this does reflect the \"no one wanted these jobs\" issue you bring up. Early nineteenth-century native-born Americans in the working class were overwhelmingly likely to be born in rural areas and had a preference for agricultural work, particularly if they could manage their own farms, rather than nomadic or urban jobs under a foreman. However, the Irish weren't unique in this regard. It was true of all immigrant groups.) In Ireland, men had been organizing to protect their labor and livelihoods since the seventeenth century - groups like the Oak Boys and Whiteboys fought against evicting landlords and forced manual labor. The tradition continued in America, where violence erupted not just against unfair employers, but also fellow employees, mainly those from other western European immigrant groups that did not tend to stand alongside them in protest, but also those from different locations in Ireland who competed with them.\n\nIt has to be noted that despite the correlation between Irish laborers and unrest - in Noel Ignatiev's *How the Irish Became White*, eight riots/strikes are listed in five years on a single canal project in the 1830s - employers continued to hire them rather than writing them off as uniquely problematic. And as organized labor became more and more common in the United States, leaders of the movement started to unite disparate groups by downplaying the importance of religion and ethnic divides, helping to mainstream Irishness and Catholicism among laborers and artisans. At the same time, free *African-American* laborers in the northern cities faced a significant amount of discrimination from employers as well as from the white working-class unions and unofficial Irish ones.\n\nFollowing the Famine, Irish immigration to the United States increased, and in time, so did immigration from southern and eastern Europe. By this time (roughly 1875-1900), Irish-Americans had had several generations to establish themselves and develop strong ties to local institutions like the Democratic Party and the aforementioned labor unions; new Irish immigrants also tended to be English-speaking, literate, and to come from a culture fairly similar to America's, which helped them quickly assimilate. In contrast, the new immigrants usually spoke no English and had a much different culture - and of course the Jewish immigrants from Eastern Europe and Russia had a much different religion on top of that. \n\nThis is the context in which much of the \"No Irish Need Apply\" advertising discussed in the earlier answer takes place. As /u/sunagainstgold pointed out in it, the phrase turns up overwhelmingly in advertisements for female domestic servants, a field which was actually full of Irish/Irish-American employees. The well-to-do employers who posted these notices were not saying that anyone but an Irish woman could apply - the Irish were simply the least desirable of the applicants who could be expected to find and respond to the notices. Italian, Polish, and Ashkenazi women essentially did not need to be excluded because they couldn't read the newspapers where they were posted, and if they could, would understand that their ethnicities excluded them from employment as a maid or cook in Murray Hill. \n\nNow, the police and firefighters. Fire companies were made up of working-class men in the early nineteenth century, and were well-known for fighting territorial battles in the streets over the proceeds of fire insurance. These gradually became segregated by ethnicity (by white ethnicity, since African-Americans were basically not allowed to have their own); not all were Irish, but if the greatest proportion of a city's poor were Irish, then the fire companies would typically follow. Among the working classes, this was a desirable job, due to the pay and relative safety in comparison to construction or dockyard work, which could see a man hurt badly at any time. Public police forces came along a bit later, but developed a strong Irish base for much the same reason. Both also gave their workers a good foothold in local society and were positions of respect and power, while allowing members of a social group to \"protect their own\".\n\nDiscussions of discrimination against the Irish and Irish-Americans tend to look at the way they were treated in comparison to only native-born white Americans, without reference to the treatment of other immigrant groups, painting a picture in which the Irish (as you say) \"proved themselves\" to white America on their merits. But it's important to bear in mind that they didn't rise because they were inherently more respectable or civically-minded than other groups - they were able to leverage their advantages, in many cases at the expense of other immigrant groups that were less similar to the Anglo-American ideal.\n\nSources:\n\nMarta Deyrup, Maura Grace Harrington (editors), *The Irish-American Experience in New Jersey and Metropolitan New York: Cultural Identity, Hybridity, and Commemoration* (Lexington Books, 2014)\n\nNoel Ignatiev, *How the Irish Became White* (Routledge, 1995)\n\nKerby A. Miller, *Ireland and Irish America: Culture, Class, and Transatlantic Migration* (Field Day Publications, 2008)"
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ze8d8 | What are some good resources for learning how to name chemical compounds? | askscience | http://www.reddit.com/r/askscience/comments/ze8d8/what_are_some_good_resources_for_learning_how_to/ | {
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"IUPAC naming conventions for organic molecules: \n_URL_1_\n\nMore here:\n_URL_2_\n\nIUPAC inorganic nomenclature is summarised here:\n_URL_0_"
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4oi2o1 | why do so many websites have formatting issues with line breaks? | Like Reddit, for example. Why is it that some websites have no problem displaying line breaks in your text entry, while some websites need you to do something like and some brackets or symbols to indicate that there is a line break? Sorry I have a bad habit of rambling, so I'll leave it at that, I guess. Perhaps a better question would be why do they use different formatting systems than ones that just simply display what you typed, or your line breaks? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4oi2o1/eli5_why_do_so_many_websites_have_formatting/ | {
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"Pure HTML is whitespace-insensitive. That means that all blank space, except for a single space between words, is ignored. This is convenient from a developer point of view, because it means you can space your markup for easy editing without breaking the appearance of the page.\n\nComment systems, like the one on reddit, use different formatting languages. These languages are more WYSIWIG, which is intuitive, but less flexible."
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92x8a6 | what does chewing gum do to us? our teeth, mental all that | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/92x8a6/eli5_what_does_chewing_gum_do_to_us_our_teeth/ | {
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"The effect chewing gum has on the teeth really depends on the type of gum you are chewing. If the gum contains sugar, it might create an opportunity for bacteria on the teeth to multiply and cause tooth decay. However, just as with other forms of tooth decay, these harmful effects can be counteracted by brushing the teeth well. On the other hand, chewing sugarfree gum has been shown to increase the production of saliva in the mouth, which helps to wash away remains of food from between the teeth. Thus, eating sugarfree gum can actually help prevent tooth decay. \n\nEffects on the brain haven't been studied very much yet (as far as I know). However, a recent study (_URL_0_) did show that concentration might be increased up to 10% while chewing gum. No significant increases in other brain functionality were discovered in this study."
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1uy31m | What was the impact of the East/West split in Germany on modern nationalistic identity and culture? Do people identify as East/West/(region) German or just German? | I've always been interested on the impact that re-unification has had on Germany, rather, the impact of the split. Did people like the split at the time/when they were unified? What was its impact? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1uy31m/what_was_the_impact_of_the_eastwest_split_in/ | {
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"(As far as I know) most nationalists identify themselves as \"german\", and not as east/west/south/however-german. But of course there are always a few people identifying themselve more as a bavarian, or are exspecially proud of being from a certain place in generall, but that's also not much different from any other country.\nActually, many nationalists will claim that parts of today's France, Denmark, and exspecially Poland (and a few more areas) are part of \"their\" Germany, since huge regions there were taken away from Germany after WW II. Nowadays of course, nearly 70 years after the war, in these regions most people don't identify themselves as german at all anymore.\nSo I would guess, most nationalists saw and see the reunification as one step back to the \"old-time-germany\"and therefore as one state. \nSeperation movements (mainly only occuring in Bavaria, but by far not as strong as for example in Scottland) wouldn't be called \"nationalistic\" either way, since they are \"again the nation\". Hope that answers your questions.\n\nTL;DR Nationalists want \"the one Germany\", and therefore shouldn't identify as a certain \"type\" of german. But hey, these kind of people never appears to think very logical, so you never know...",
"To go more into the the identity of the average people; identifying with anything similar to nationalism is much less common then in other countries. So, you wouldn't say proudly \"Oho, Im from the West!\". But exspecially after the reunification, there sometimes occured slightly... Arrogance and denegotiation against each other, reflecting in terms like \"Besserwessi\". Still today, you may use the terms \"Wessi\" or \"Ossi\" for a person from the west or the east, respectively, but mostly only in a context of humor. The \"Ost-West-integration\" is still a big topic in today's politics, as for example the pensions, which are still slightly different between east and west.\nBut beside some jokes there is basically no serious distinction between east and west Germans anymore in the people's mind; as far as not concerning politics or the economy."
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3un1rw | How concrete was Christendom as a concept of European political union in the Middle Ages? | Came across [this](_URL_0_) post the other day and would like some further information about this bit in particular:
> Medieval politics, as I've already mentioned, was oriented around the idea of Christendom. The Christian monarchs formed a single community known as the Res Publica Christiana or, if you like, "Christian Republic". They were bound by particular obligations that, in theory, went back to the Code of Justinian of 529.
The current state of medieval scholarship is pretty bewildering to a layperson like me, and accordingly, any claim this substantial, I feel, deserves caution. Could someone please delineate how immediate/specific Christendom as a politically unifying concept was to European politics and law? For example, did the concept figure in local legal systems? Or was it applied merely in the mediation of "international" disputes? Did it influence legal doctrines around Europe? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/3un1rw/how_concrete_was_christendom_as_a_concept_of/ | {
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"The now-deleted writer of that post mentions *Res Publica Christiana* which frankly is something of a post-facto historiographic idea. It has a problem on two fronts. The first is that the self-conception as a Christian ruler is utterly obvious: no ruler would conceive of themselves otherwise; the 'binding' nature of this is a shallow analysis and doesn't help us understand medieval rulership. The second problem is \"went back to the Code of Justinian of 529\". This is total hokum: not many souls in western Europe knew anything about Justinian Code prior to around 1050: Justinian's Codex was an abortive effort in the Emperor's own time and had relatively no impact for centuries even within the Byzantine Empire.\n\nBoth problems above are the products of historians who believe that the way medieval rulers and their chancellories wrote about their decisions and beliefs were direct reflections of the world, and not polemical and strategic positioning. It's a source selection bias.\n\nClearing away the crap, we come to the question again. As I said above, 'Christendom' as some 'unifying concept' is really a shallow way of looking at medieval governance. It's utterly obvious and provides no explanatory power against the various interpretations of power by medieval rulers and their minsters. The best we can say is that 'Christian' was a polemical and ideological tool; this isn't to say that rulers and their ministers weren't devout Christians. But it is to say it's not enough of an explanation of how governance operated. \n\nWhen we come to discussing 'legal systems' or 'doctrines' we then must be very specific about epochs within medieval history. There is a fairly sharp dividing line between pre- and post-12th century western Europe. We cannot say there was a 'judicial system' of 'legal system' prior to the 12th century, not even within Carolingian society - there was no centralized 'judicial process' in early medieval Europe - it was driven by councils making decisions based on certain capitularies. But the form of those councils (*placitum*) and lower-level 'trials' were entirely customary. Even in the 13th century it was still taking shape. I wrote about one aspect of this shape-taking a few weeks ago [here](_URL_0_). \n\nNow, if we speak about 'legal systems', we need to separate two parts at this point. The first part is ideological: how did rulers, their ideologues, and the public conceive of rulership after say 1200? This is a subject that perplexes historians to this day, and I can't address it here in any way that is useful. \n\nHowever, the other part is about 'systems'. In my post I link to above I write at length about the development of some judicial processes in the 12-13th century. In fact, we can speak here of centralization, of systemization of legal processes; the opposite of the 'fragmented' systems of the early medieval period. Fragmented here must be explained: the word itself suggests some need for cohesion and consistency, some over-arching ethic. It would be wrong to think that prior to the 12th century western Europe was without law, without consistency. However, that law was customary and because it was customary it was subject to local opinion and patterns of use. It was not, however, bound by consistency of process across jurisdictions. The innovation of the scholars at Bologna, and of the Papacy, in 12th century was the resurrection of judicial processes, *ordo iudiciario*. This rapidly became 'internationalized' (that word is anachronistic for this period). This was the basis of the transformation of European legal systems, including common law systems of England (and thus the colonies like US and Canada). \n\nThe 12th century origins of our modern justice systems were in the Church and Canon Law; and it continued as such through the following 500 years. Canon and secular jurisprudence were tied together in universities, undivisible; this was called the *ius commune*. It wasn't until the nationalization of law in the 18th century that the *ius commune* was ruptured, and that local law ('customary law') was subordinated to national law.\n\nFrom the 12th century through the end of the middle ages and on into the early modern period, customary law still ruled to a great extent. Although its rule was bound by judicial processes that in fact created European legal processes (and a 'system') as of the 13th century.\n\nBy way of example, France in the late medieval period had 'parliaments', or King's Courts, in 13 locations. These courts dealt with inter-nobility appeals. But step down below high nobility and you were dealing with variable, local customary law, even if it was bound up in 'modernized' judicial processes (of evidence, witnesses, roles of appellant and defence).\n\nTo be perfectly honest, I believe any attempt to create an idea of 'international' legal relations anytime before the early modern period is anachronistic. Kings, lords, bishops, abbots, the Pope and his legates, all fought battles for power, most of which had little to do with 'law' so much as hubristic appeals to God, amongst other ideas. There was no international court of the Hague to fight these things; these things were dealt with on battlefields, in letters and missives, and sometimes in face-to-face meetings. But the idea of Christian as 'unifying' among rulers was only as good as the other party's willingness to concede a point; it was not for nothing that rulers would accuse each other of heresy.\n\n"
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"https://www.reddit.com/r/AskHistorians/comments/18zrj5/what_was_the_international_system_for_lack_of_a/c8jrvbl"
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"https://www.reddit.com/r/AskHistorians/comments/3qyw8y/how_exactly_did_the_papalmedieval_inquisition/cwjh6b6"
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qt1vw | Strongest Theoretical Earthquake/Seismic Wave? | I know the Richter Scale goes up to 10.0 at the minimum and that an increase in 1 is roughly equal to a 32 times increase in energy released. I also know that the highest recorded in Human History is about 9.5 on the scale, but never anything in the 10s. So I'm highly curious what the strongest theoretical earthquake is on Planet Earth. | askscience | http://www.reddit.com/r/askscience/comments/qt1vw/strongest_theoretical_earthquakeseismic_wave/ | {
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"This was [covered a past thread](_URL_0_); there was some good discussion."
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3ajfz0 | Why does water get larger when the temperature gets lower? With other materials happens the contrary | askscience | http://www.reddit.com/r/askscience/comments/3ajfz0/why_does_water_get_larger_when_the_temperature/ | {
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"Water exhibits this property because of Hydrogen bonds between adjacent H2O molecules. Basically, water is a polar molecule (Oxygen is the negative pole and the Hydrogens are the weaker positive poles), so the Oxygens in molecule A are attracted (NOT permanently bonded) to the Hydrogens in molecule B and vice versa. Thus, when water freezes, this results in an 'open' crystalline geometry with more empty space between molecules which is in turn less dense than similar non-Hydrogen bonded molecules. This unique structure is what causes it to expand as it freezes.\n\nTL;DR version- water exhibits Hydrogen bonding which causes its crystals to be less dense than other similar molecules, resulting in volume expansion.\n\nSource- AP chemistry",
"This is not true at every pressure, although it is true at atmospheric pressure, where water forms ice with a structure known as ice Ih. [This structure](_URL_2_) is such that the water molecules are organized in a way that is less dense than the [jumbled structure of liquid water](_URL_1_). Water molecules bond to each other through so-called 'hydrogen bonds', and these require the molecules to orient themselves in a certain way (hydrogens on one water molecule pointing to oxygens on the another) and with certain angles. When the temperature is high enough for it to be liquid, the kinetic energy is enough to break some of these hydrogen bonds. Without as many hydrogen bonds, the water molecules are able to get closer than they'd be otherwise. \n\nAt [higher pressures, water starts to form ice-III instead](_URL_3_), which has a [different structure](_URL_0_) that is in fact denser than the liquid water. This is because the pressure 'helps' push the molecules farther together.\n"
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cbgh5e | why do humans start feeling hot and sweaty when nervous? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/cbgh5e/eli5_why_do_humans_start_feeling_hot_and_sweaty/ | {
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"It’s the part of your nervous system that protects you when you’re in danger. Your body is designed to run away from tigers and such, not take tests or speak in public. Having your heart rate go up and moving your blood to different parts of the body is useful when fighting a wild animal but not as useful when you’re sitting in a desk - so it just makes you hot and sweaty.",
"Fight-or-flight response.\n\nBack in the 'caveman days' (not exactly an accurate term but a useful approximation), most encounters that would make a human feel what we now call 'nervous' would be something solved by violence or getting the heck outta there.\n\nBasically, your body is pre-gaming for a fight or for running away, because that's what 'nervous' means to it. It doesn't understand concepts like \"mid-terms\" and \"job interviews\" that can't be solved by running away or stabbing with a spear.\n\nYou get hot and sweaty due to increased blood flow, which is making sure your muscles are well-fed and have plenty of oxygen so they can operate at their best once the expected fight or flight starts. The sweat can also be preparedness on it's own; if you're already sweating when the action starts then it can start cooling you off faster.",
"Because in nature if you are getting nervous it means shits about to hit the fan, so body is getting you ready to book it at your max speed or fight what ever is making You nervous. \n\nTo do that it starts producing more energy to help you to do it. Heating is effect of that, same way car engine gets hot when it is working, and sweat response to your heat, its to make sure you dont overheat",
"besides increasing your oxygen levels(breathing techniques), what can help you control this response?"
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9roe48 | how do tanks (and similar vehicles) turn left/right? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9roe48/eli5_how_do_tanks_and_similar_vehicles_turn/ | {
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"The left and right tracks turn at different speeds. The engines have enough strength (torque) that they'll scrape across the ground as they rotate ",
"One turns forwards, the other turns backward (or just forward but slower), creating a spinning motion.",
"The two sets of tracks can be controlled separately, so to turn, you just spin one set of tracks faster than the other. IIRC, older tanks had two levers you could use to adjust the speed of the two tracks. "
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771kc3 | Did the Wehrmacht commit a disproportionally large amount of war crimes compared to, say, the Red Army or any other Allied forces? | I'm aware of the Clean Wehrmacht myth, but I'm just curious if they committed more war crimes than the Allies. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/771kc3/did_the_wehrmacht_commit_a_disproportionally/ | {
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"**Part 1**\n\nYes.\n\nThe Wehrmacht not only quantitatively committed more war crimes but also, and this can not be emphasized enough, the way they waged war during WWII was criminal from the outset as a matter of institutional policy. And not just in the way that the IMT in Nürnberg found that they were guilty of waging a war of aggression but the very way how they fought and what forms of warfare they encouraged was steeped in Nazi ideology.\n\nThis started from the very beginning of the war when the attack on Gleiwitz was faked in order to produce a casus belli against Poland, to the regular collaboration of the Wehrmacht with the SS and Police EInsatzgruppen in Poland, to the attack on neutral countries in the Benelux, to the blatant disregard to the laws of war in France where e.g. Rommel both used tactics such as setting civilians' houses on fire in order to mask his troops' advance to feigning surrender in order to draw French troops in, to the anti-Partisan operations in the Balkans, to the war against the Soviet Union being planned as a war of annihilation and thus constituting a war crime in itself, down to the lowest level of the units where massive violence against civilians and their property was encouraged as a tactic of warfare on a massive level.\n\nthe Wehrmacht as an institution superseded the \"normal\" function of an army within your average nation state (this is a bit simplified as neither a normal function or average nation state exists strictly speaking but I mean stuff like defense or fighting a war) and crossed the territory into becoming an institution heavily involved and complicit in the crimes of the Nazi state.\n\nThis came to bear in that the Wehrmacht and especially its higher echelons were by the time of the attack on the Soviet Union thoroughly nazified. The war against the Soviets was in their mind not a \"normal\" war but a war of annihilation. Meaning that civilians as well as the soldiers of the other side were perceived as such an existential thread that extreme violence and terror were the only appropriate measure in dealing with them.\n\nThe crimes of the Wehrmacht are numerous. To provide just a couple of examples:\n\n* The criminal conduct in the Soviet Union and against Soviet POWs\n\nThe probably most famous examples of Wehrmacht crimes are probably the Commissars Order and the Kriegsgerichtsbarkeitserlass. When preparing for the invasion of the Soviet Union, the Wehrmacht leadership in conjecture with the Nazi leadership issued orders that the war in the Soviet Union was not to be treated as a \"normal\" war but a war of \"Weltanschauung\", meaning they were not just fighting another country but rather Jewish-Bolshevism itself. To that end, the OKW gave the order that political commissars within the Red Army were not to be treated as POWs but were to be shot immediately after capture. Political Comissar included however not only people who held this position but also any member of the Communist Party of the Soviet Union as well as all Jews. In conjecture with this order, the Kriegsgerichtsbarkeitserlass decreed that no member of the Wehrmacht could be persecuted for any and all war crimes they committed while in the Soviet Union. So rape, pillaging, murder and burning down villages were all fair game for all members of the Wehrmacht. The Commissar Order alone lead to something between 60.000 and 140.000 victims.\n\nAdditionally, the Wehrmacht as an institution was responsible for Soviet POWs in general. In that function it was the Wehrmacht which basically let them starve to death in violation of all international treaties and conventions. Basically, the Wehrmacht built POW camps for Soviets by just putting up a fence and putting the POWs in there, letting them starve as a policy before the leadership of Nazi Germany needed them for forced labor in 1942. But even with that the death toll is staggering. Christian Streit estimates that about 3.3 million Soviet POWs or 57% of all Soviet POWs captured by the Wehrmacht died while in captivity.\n\n* The Wehrmacht as an occupational and security force\n\nThe Wehrmacht was an important part of the occupation of conquered territory and as a security force in that occupied territory. As such, it committed murder and war crimes. Taking Serbia as a territory that was directly administered by the Wehrmacht, Wehrmacht units shot 20.000 civilians alone in the time frame from September to December 1941 as part of a campaign of retaliation for Partisan attacks. The Wehrmacht commander of said territory, Franz Böhme, instituted a policy of 100 civilians shot for every dead German soldier and 50 for every injured German soldier. The vast majority of victims were not related to the attacks or the Partisans but rather male Jews or Roma and Sinti thus making Serbia the first territory outside of the Soviet Union in which Jews were systematically killed by the German occupation.\n\nCrimes such as these are numerous and extend even into the Western territories of Europe. For example, the Wehrmacht massacre of the Italian village of Marzabotto in October 1944.\n\nAlso, as an occupational force, the Wehrmacht was responsible for administering Nazi racial policy in its territories as can be read in detail in Dieter Pohl's book on the Wehrmacht in the Soviet Union.\n\n* The Wehrmacht and the Holocaust\n\nAs mentioned above, the Wehrmacht as an institution was involved in the Holocaust in Serbia, where it was Wehrmacht untis who killed the male Jewish population or when it came to Soviet Jewish POWs. But the Wehrmacht also collaborated closely with the Einsatzgruppen in the Soviet Union basically either transferring Jews into the hands of these mobile killing units or even lending a hand when it came to shooting Jews. Additionally, Wehrmacht units in Poland and the Soviet Union also were involved in killing the mentally handicapped and disabled.\n\nFurthermore, the Wehrmacht established Ghettos and provided transport for Jews to be deported to Auschwitz, e.g. in France and aided in registering and confining Jews to certain quarters in countries such as France and Belgium.\n\nThe Wehrmacht in fact encouraged its troops to use massive violence against a civilian population as a legitimate means to an end. Dating back to the Franco-Prussian war of 1871, the German army was almost notorious for its fear and hard line against Franc-Tireurs and irregular fighters. The German military doctrine was to employ hard reprisals against the civilian population harboring irregular fighters and security threats. This was allowed by the Hague convention and also used in accordance of it during for example WWI but it was a line of thinking that was quickly adapted to Nazi ideology, meaning that it was applied to Jews (\"Where there is the Jew, there is the Partisan, and where there is the Partisan, there is the Jew\" as the line from Erich von dem Bach-Zelewski ran) and other civilians perceived as a security threat.\n\nI have mentioned the Serbian example above but this is a general phenomenon in Wehrmacht occupation troops. Rather than punishing violence against civilians, numerous examples prove that the Wehrmacht encouraged violence. Klaus Michael Mallmann for example mentions in one of his articles that a Wehrmacht security unit in Poland was shown the movie \"Jud Süß\" and became so enraged by it and the copious amounts of alcohol they had consumed that they went out and hunted and shot all the Jews of the town they were stationed in.\n\nSimilarly, new research by Sönke Neitzel and Harald Welzer as well as Felix Römer based on newly discovered eve's dropping protocols from British and American POW camps shows that within the Wehrmacht a vast majority of soldiers considered violence against civilians, even women and children in some cases, as a legitimate form of warfare, especially when justified with Partisan warfare. Examples of this, specifically referenced by the Wehrmacht soldiers themselves, include using women and children to clear mine fields; burning down buildings with the inhabitants inside; and the use of public hangings in order to deter support for real or imagined Partisan groups.\n\nThe frequency of such happenings as well as the level of involvement on part of the individual soldier are hard to gauge but from all research up to date, it is possible to conclude that almost every unit involved in the war in the Soviet Union or the Balkans did commit atrocities in one form or another on regular basis. Similarly, it is hard to number the victims of Wehrmacht atrocities but even discounting the starved Soviet POWs the number of civilian murdered by the Wehrmacht runs in the several millions.\n\nAnd that only includes atrocities in the form of murder. The number of rapes committed by the Wehrmacht in the Soviet Union runs somewhere in between 2 and 3 million. This estimate comes from Wendy Jo Gertjejanssen who has her thesis in the subject online [here](_URL_0_)\n\nAlso Pascale R. Bos cites a German survey from 1942 in which the Wehrmacht estimates that 750,000 babies had already been born from contact between German soldiers and Russian women. This is a conservative estimate and covers only the time frame up to 1942. While not all of these might have come from rape it shows how endemic the problem was. You can find it in the article \"Feminists Interpreting the Politics of Wartime Rape: Berlin, 1945\"; Yugoslavia, 1992–1993 Journal of Women in Culture and Society, 2006, vol. 31, no. 4, p.996-1025. \n"
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jbg6d | When studying electromagnetic forces, how do you picture them? | While studying physics, I was always worse at these fields, such as electricity and magnets, for I couldn't picture them in my head as I could with Kinetics and Thermodynamics.
How does your minds eye see these forces, if not as themselves?
(I often pictured simple circuits as rivers for example) | askscience | http://www.reddit.com/r/askscience/comments/jbg6d/when_studying_electromagnetic_forces_how_do_you/ | {
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"Be careful with the language. An electromagnetic *field* is different from an electromagnetic *force*. A *field* occupies space like a [vector field](_URL_0_). An electromagnetic force is associated with a specific object, and can be pictured by a singe vector originating from the object to which the force is being applied. \n \nThe difference is illustrated by the image of the earth's magnetic field versus the force/pull/tug felt by a compass' needle. ",
"I found that the best solution is to stop trying to visualize stuff like electromagnetic in terms of what you already understand, because they are not like something you already understand. You should ofcause gain knowledge of how they work, but i like to rely on the equations and try not to reason to much about anything other than the math.",
"I just picture classical field lines.",
"Be careful with the language. An electromagnetic *field* is different from an electromagnetic *force*. A *field* occupies space like a [vector field](_URL_0_). An electromagnetic force is associated with a specific object, and can be pictured by a singe vector originating from the object to which the force is being applied. \n \nThe difference is illustrated by the image of the earth's magnetic field versus the force/pull/tug felt by a compass' needle. ",
"I found that the best solution is to stop trying to visualize stuff like electromagnetic in terms of what you already understand, because they are not like something you already understand. You should ofcause gain knowledge of how they work, but i like to rely on the equations and try not to reason to much about anything other than the math.",
"I just picture classical field lines."
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1o2vib | why household bathroom shower heads come from the wall and not the ceiling. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1o2vib/eli5_why_household_bathroom_shower_heads_come/ | {
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"The pipes are in the wall, and the water comes from beneath the house, so it is not efficient to pump the water any higher than necessary.\n\nThe way buildings are made today, there is usually a limited number of \"water walls\" that are slightly thicker than other walls to accommodate water pipes, and to have as many water fixtures on that wall as possible. This is why kitchens, bathrooms and laundry rooms often border each other, or are directly above or below each other in a multi-floor building.",
"It costs more money to bring it that high. Plus, most people cant reach that high....",
"Mine comes from the ceiling. I built it myself.",
"The plumbing is a lot easier to do in the wall, so comes from there, unless you want to pay a premium for a ceiling head."
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3azhxi | why we haven't taken any images of black holes? | Even a black region surrounded by warped light and a backdrop of stars would suffice... | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3azhxi/eli5_why_we_havent_taken_any_images_of_black_holes/ | {
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"Because all the ones we know about are really far away and shrouded in tons of gas and dust making them camoflouged.\n\nWe have xray images of the blackhole at the center of our galaxy, but they are only xrays. You can't really tell too much of what's going on.",
"Well we aren't close enough to any black holes to see a good 'disc of blackness' and it's worth noting space is pretty dark anyway, so it'd be hard to make out at the best of times. Would you notice if Jupiter was actually a black spot in the sky? Not easily, and it's a bigger disk than a distant event horizon would provide us. Most images of black holes involve extremely bright regions seen at great distance, due to the fact that the matter accreting around them gets very hot and shoots out a lot of high energy to our receivers. If there isn't matter around them, giving us a clear shot, well, they are really hard to find."
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4c6iwb | how directional speakers (and directional sound in general) work | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4c6iwb/eli5_how_directional_speakers_and_directional/ | {
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"Sound is the vibration of air particles. Taking to in a room is like standing in a swimming pool and splashing around, everybody gets wet. \n\nDirectional speakers are more like you holding one end of a slinky, and your friend holding the other, you can shake the slinky forwards and backwards as much as you want, but your other friend stood off to the sound won't feel anything.",
"It has to do with something called \"phase interference.\" Say you have \"point\" sources, meaning a sound wave is generated at a single point and expands omnidirectionally (in a sphere) from both points. If those two sources are located some distance from each other and generate the same wave, there is an interference pattern due to the fact that they create waves that are slightly out of phase, because there is a delay between the waves from each point source. When the waves from each source are 180^o out of phase (the time delay for that depends on frequency) you get total cancellation. \n\nNow a loudspeaker is modeled as a point source. You can get very crafty and put a bunch of speakers into an \"array\" (a 1-D array is a \"line array\" all speakers are aligned along a single axis, a 2-D array is usually a circle or square, a 3-D array can be a sphere). Then what you do is delay the same signal feeding each point source by differing amounts, doing so creates controllable interference pattern. You can make this pattern a \"beam.\" \n\nThat's sort of the way they can make a speaker array directional, it's used by the military to make sound spotlights where they blast loud noise at a concentrated area without anyone outside hearing it. You also see it in museums and other places where walking into the beam let's you hear the sound, but then you walk out and it's gone. \n\nThe same is true in reverse, you can make microphone arrays that do the same thing. Except you can get even craftier with mics and get multiple beams from one array. "
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[],
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6quj0f | why is it that some people need to adjust their sitting posture every 2 minutes but some people can sit in the same posture for one hour? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6quj0f/eli5_why_is_it_that_some_people_need_to_adjust/ | {
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"I was actually thinking about this the other day because I'm the kind of person seems to never get comfortable. I found out if you stretch and loosen up your muscles you'll have an easier time sitting still or even falling asleep at night."
]
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6wgzvy | AskHistorians Podcast 093 - The Holy Roman Empire in the Age of Martin Luther | [**Episode 93 is up!**](_URL_7_)
The [AskHistorians Podcast](_URL_11_) is a project that highlights the users and answers that have helped make /r/AskHistorians one of the largest history discussion forums on the internet. You can subscribe to us via [iTunes](_URL_5_), [Stitcher](_URL_3_), or [RSS](_URL_2_), and now on [YouTube](_URL_1_) and [Google Play](_URL_10_). You can also catch the latest episodes on [SoundCloud](_URL_0_). If there is another index you'd like the cast listed on, let me know!
**This Episode:**
In light of the upcoming 500th anniversary of the beginning of the Protestant Reformation, Professor Peter Wilson talks with us about the Holy Roman Empire in the 16th century.
Professor Wilson is known for books such as [Heart of Europe: A History of the Holy Roman Empire](_URL_6_) and [The Thirty Years War: Europe's Tragedy](_URL_8_).
**Questions? Comments?**
If you want more specific recommendations for sources or have any follow-up questions, feel free to ask them here! Also feel free to leave any feedback on the format and so on.
If you like the podcast, please rate and review us on [iTunes](_URL_5_).
Thanks all!
[Previous episode and discussion](_URL_4_).
Next Episode: u/AnnalsPornographie is back!
Want to support the Podcast? Help keep history interesting through the [AskHistorians Patreon](_URL_9_). | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/6wgzvy/askhistorians_podcast_093_the_holy_roman_empire/ | {
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"Listeners! Ignore not the reference to [Youtube](_URL_0_)! We are steadily working through the backlog of old episodes at the rate of one a day.",
"I just finished reading Q by Luther Blissett, a novel based around the political and religious conflicts and intrigues of this period and place, so this is going to be very nice context!",
"Oh wow! Big fan of Peter Wilson, hyped!",
"I'm a new subscriber, and the ending got me confused. 'Next week, we will be joined by Brian Wattson [that's what i heard, might not be the name]. Have a nice two-weeks, guys.\"\nSo are new episodes released every week, or every two weeks?\nThanks in advance.",
"I am so looking forward to this one!\n\nPeter Wilson's book *The Thirty Years War: Europe's Tragedy* is one of my favorite books on the defining conflict of the 17 century. \n\nAny chance that Dr. Wilson would be willing to do an AMA at some point?",
"Peter Wilson is my man! Loved his book on the thirty years war",
"I'm finally getting around to listening to the podcast! Thank you so much for all your work, as always. :)"
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12hox0 | As far as we know, is matter continuous or discrete? | I know that matter is made up of atoms, and that they are made of particles which are made of quarks, but do physicists think that we can keep dividing matter like this forever? Or, is there theoretically a "smallest" particle? | askscience | http://www.reddit.com/r/askscience/comments/12hox0/as_far_as_we_know_is_matter_continuous_or_discrete/ | {
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"There is a theorised smallest length, called the \"planck length\". In short, it's the absolute minimum length that it is theoretically possible to measure, regardless of how good our measuring technology becomes. I've heard it referred to as the \"pixel size of the universe\", which seems fitting if it truly is the smallest possible length. [Here's the Wikipedia link for further reading](_URL_0_)"
]
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"http://en.wikipedia.org/wiki/Planck_length"
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aw60gd | Did the Greeks have an "End of the World" scenario like Christianity and Revelations or the Norse and Ragnarok? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/aw60gd/did_the_greeks_have_an_end_of_the_world_scenario/ | {
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"Not really - or at least nothing so dramatic. \n\nIn his *Works and Days*, Hesiod (borrowing generously, if probably unconsciously, from Near Eastern myth) describes a succession of the five ages or generations of men who have populated the earth: the golden age, the silver age, the bronze age, the age of heroes, and the age of iron. Hesiod's own age/generation, the age of iron, is no picnic:\n\n\"\\[now\\] men never rest from labor and sorrow by day, and from perishing by night; and the gods shall \\[continue to\\] lay grievous trouble upon them.\" (176-7)\n\nIn the future, according to Hesiod, mankind will decay morally: \n\n\"The father will not agree with his children, nor the children with their father....Men will dishonor their parents as they grow quickly old...There will be no favor for the man who keeps his oath or for the just or for the good; but rather men will praise the evil-doer and his violent dealing. Strength will be right and reverence will cease to be; and the wicked will hurt the worthy man...\" (182-94)\n\nThis degeneration will be physical as well as moral; eventually babies will be born prematurely aged. At that point, Zeus will wipe out the human race from disgust. (179-80)\n\nThis theme does not reappear often in later authors. Ovid references it in the first book of the *Metamorphoses*, but without explicitly identifying humanity with the decaying men of iron. \n\nAnother more or less apocalyptic thread in Greek myth centers on the prophesied overthrow of Zeus and the Olympians. The most famous passage is in Aeschylus' *Prometheus Bound*. Prometheus, chained to a rock in the Caucasus, foresees the downfall of Zeus:\n\n\"Yes, truly, the day will come when Zeus, although stubborn of soul, shall be humbled, seeing that he plans a marriage that shall hurl him into oblivion from his sovereignty and throne; and then immediately the curse his father Cronus invoked as he fell from his ancient throne, shall be fulfilled to the uttermost.\" (907-12)\n\nPrometheus, as the later mythographer Apollodorus explains, is referring to Zeus' plans to have an affair with Thetis, the minor sea goddess who would later give birth to Achilles. If Zeus had conceived a son with Thetis, that child would have overthrown Zeus, and so destroyed the order of things that makes human life possible. (On becoming aware of the prophecy, Zeus married Thetis off to a mortal, Peleus, to preclude the birth of any future usurper). \n\nThere are various moments in Greek myth - most notably Zeus' tangle with Typhoeus, and the gods' battle with the savage giants - in which the divine order, and thus the human order, is threatened. But with the exception of Hesiod's pessimistic view of human destiny, there seems to have been little sense that it was all fated to end. "
]
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759h03 | - why does pr not have statehood? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/759h03/eli5_why_does_pr_not_have_statehood/ | {
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"See my earlier answer to your removed thread:\n\nPuerto Rico held four recent referendums to establish whether the population wanted a change in status. Until recently, the vote was either only narrowly in favour of statehood, or favoured remaining as-is.\n\nThe referendum held in 2012 showed 54% in favour of statehood, but 500,000 blank ballots were included in the numbers, and so Congress ignored the vote.\n\nIn the most recent one (2017), 97% of voters voted in favour of PR becoming a state. However turnout was low (23%) and so it was also ignored. The governor of Puerto Rico is now in favour of remaining an unincorporated territory, for economical, political and identity reasons.\n\nFor a history of why PR is part of the USA - you can blame the USA for occupying PR during the Spanish-American war in 1898.\n"
]
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r7iof | When looking at ferromagnetic compounds which form of iron is more magnetic, Fe2+ or Fe3+ or is there any real noticeable difference in magnetism? Also what is the difference between ferro- and ferri- magnetism? | askscience | http://www.reddit.com/r/askscience/comments/r7iof/when_looking_at_ferromagnetic_compounds_which/ | {
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"Insofar as magnetism can be somewhat proportional to the total number of unpaired spins in an atom..... it depends. Depending on the environment of the iron atoms, the relevant electrons that they have will be arranged differently.\n\nEssentially, both iron atoms have five orbitals that can hold up to 2 electrons each into which their electrons will be partitioned. These are called the d-orbitals. These orbitals don't have the same energy, and electrons will tend to occupy the lowest energy orbitals possible, unless repulsion from another electron is enough to bump them up into a slightly higher energy d-orbital. \n\nSo, the main difference between Fe(II) and Fe(III) is that they have 6 and 5 d-electrons, respectively. In most magnetic ores, the orbitals will be arranged such that the electrons will spread out evenly amongst the five d-orbitals. The result is that Fe(III) can fill the orbitals without having to pair up, but Fe(II) necessarily must pair up two of its electrons, reducing the overall unpaired spin that makes magnetism possible.\n\nNow, that doesn't have to translate into Fe(III) always having stronger magnetism, since ferromagnetism has more to do with how neighboring atoms align and create a net magnetic field, and how microscopic magnetic domains align with each other.\n\nFerrimagnetism occurs when you still have a net magnetic field, but not every atom's net magnetic field is pointing in the direction of the net magnetization; some of them are working against it to decrease the overall strength a bit."
]
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4kdkk2 | dark souls | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4kdkk2/eli5_dark_souls/ | {
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"There isn't really a storyline to Dark Souls. \n\n[Here](_URL_0_) is a video explaining a bit more."
]
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"https://youtu.be/LueVmefY_Kg"
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3m8r7s | can someone please explain zodiac signs and why people think they know you based on your "sign"? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3m8r7s/eli5_can_someone_please_explain_zodiac_signs_and/ | {
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"In our evolutionary history, spotting patterns was very advantageous. In fact, it was much better to spot a pattern when none existed than to not spot one that did exist. Consequently, people who were good at spotting patterns were more likely to survive and have children, and everyone became good at spotting patterns when none existed.\n\nThe Zodiac is just like that. \n\nIt also operates by using very vague descriptions that could apply to many people. For example, here is my \"horoscope\" for today (thanks _URL_0_):\n\n > It's important to communicate your feelings today. You tend to hold them inside and wait until they build up and erupt like a volcano. Emotional blocks in your system are clogging up the works and preventing new, healthier energies from moving in. Say what you need to say to the people who need to hear how you feel.\n\nMost people are bottling something up, so most people will read that horoscope and think \"oo, yeah, that's me right now!\". This has been shown scientifically - ask professionals to write horoscopes, then give half to the \"right\" sign and half to the \"wrong\" sign. The randomised ones will do just as well as the curated ones.",
"The zodiac signs are just self fulfilling prophecies of a person's personality. Essentially every zodiac sign specifies that a person will be born with X traits. Let's just use the Chinese zodiac for example because that's the one I'm most familiar with. People who were born on the year of the dog are said to display the qualities of loyalty and trust and people who are born on the year of the chicken are said to display traits such as egotism and ambition. This becomes a massive self fulfilling prediction of a person's traits because usually if a family believes that a child who is born with a certain zodiac sign will have these traits, they will raise the child with these traits in mind telling them they should act a certain way because of their zodiac sign. Consequently the child grows up a certain way because of their sign. People then notice these trends (general trends) and ascribe traits to you based upon your zodiac sign even if they don't know you.",
"It's a pseudoscience based on astrology that somehow the stars when you were born affect your personality. It is totally ridiculous and if someone actually thinks they know something about you because of your sign you should probably not trust them with anything important."
]
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exnjud | what’s the scientific meaning of medium? is it just the states of solid liquid and gas? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/exnjud/elif_whats_the_scientific_meaning_of_medium_is_it/ | {
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"I think it just means surroundings.\n\nIn Chemistry, if a reaction occurs in an 'acidic medium', the reaction will only occur when surrounded by acidic radicles.\n\nIn Physics, if sound travels faster in a 'denser medium', it would mean that the sound travels faster if there are more molecules around it (hence, denser).",
"A medium is the context or background in which something is contained, regardless of its phase.\n\nA copper wire is the medium through which electrons flow. Light is the medium through which visual information flows.",
"A medium is what something is in that is significant or required. Not just what happens to be nearby.\n\nSound waves travel through things. If they are traveling through the air, the medium is the air. The trees, lamp posts, etc nearby are not the medium as they are not what the sound is traveling through.\n\nLikewise for electrons flowing through a copper wire, the wire is the medium - the plastic lining of the wire is not."
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1fyl5i | How does anti-microbial plastic work? | I have at home a chopping board made from plastic which claims to be anti-microbial. I would like to know how the plastic or whatever is in/on it actually kills the microbes. Thanks! | askscience | http://www.reddit.com/r/askscience/comments/1fyl5i/how_does_antimicrobial_plastic_work/ | {
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"The material the fomite is made of helps to reduce or prevent the growth of colonies due to the non-porous nature of the material. It can't hold water and nutrients well, so the bacteria typically do not have a healthy environment to vegetate. While some materials actually can kill microbes (like certain metals) most antimicrobial plastics just reduce the likelihood of allowing the microbes to grow."
]
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7gsg9n | Did Western Europe ever have mounted archers? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/7gsg9n/did_western_europe_ever_have_mounted_archers/ | {
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"I think [this](_URL_0_) might help"
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1dyxs3 | why is the cleveland kidnapper only charge with 3 counts of rape, one for each victim rather than 10 years of rape? | Surely raping a person regularly of 10 years is more of a crime than raping them once. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1dyxs3/eli5_why_is_the_cleveland_kidnapper_only_charge/ | {
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"Becuase they have plenty of time to charge him with more later. They just threw out a few charges so they can hold him for now.",
"Because the charges will read Rape of Victim 1 with several dozen specifications. Rape of Victim 2, again with several dozen specifications, and Rape of Victim 3 with several dozen specifications. \n\nThe reason there is only the three charges with many specifications is that in order to get a conviction, the prosecutor only has to show **one** rape occurred for each specification. Each additional specification for each rape would only add to the sentence. If it was done the way you suggest, the trial would take centuries and the end results would be the same. ",
"We are not all native speakers of English so I'd like to explain a point of grammar and usage a helpful friendly manner. We know what you meant and here's some clarification.\n\n > re Surely ---ing a person regularly of 10 years is more ...\n\n\"a person of 10 years\" usuallly means a 10 year old person.\n\nI might have cut my hair a certain way for 10 years. \n\"_For 10 years\"_ is how we talk about duration.\n\n\nThat's all. Thanks for sharing.\n\n",
"The police need to file charges to be able to continue to hold him, so they start with what is easily proven. Now that he has been charged with something they can take their time, sort though all the evidence and figure out everything else he can be charged with.\n\nTL;DR - It's a stopgap measure."
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66gmqt | why can't mobile phones have optical zoom? | I get that you need space for the lens to move, but wouldn't a few mm already be enough for 2x or 3x optical zoom? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/66gmqt/eli5_why_cant_mobile_phones_have_optical_zoom/ | {
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"They can, I think iPhone 7 Plus reveal boasted it has 2x optical zoom. But it turned out while it is there the phone doesn't always use optical zoom first.",
"As others pointed out, some do. But the advantages can be questioned. Fixed lenses usually are much sharper for a cheaper price, increasing the resolution of the sensor will mostly be cheaper and show better results. I, like most people, wouldn't compromise on my phone's size to carry a mediocre camera. I guess there is just no demand. "
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q3tbn | Is it still possible to get aroused after having your testicles/penis removed? | I know it is possible to have your penis/testes removed to to cancer or other unfortunate events. So I was wondering, can you still get sexually aroused without testicles and/or penis? | askscience | http://www.reddit.com/r/askscience/comments/q3tbn/is_it_still_possible_to_get_aroused_after_having/ | {
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"There is an episode of TLC's \"Strange Sex\" where a paraplegic man is able to achieve orgasm via thumb massage. I cannot find a clip of this segment on the web, only discussion.\n\nHere is a link with some more information - borderline NSFW - [Wheelchair Sex](_URL_0_).\n\nTechnically, the genitalia are present, if completely insensate."
]
} | [] | [] | [
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"http://www.streetsie.com/spinal-injury-wheelchair-sex/"
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55o6l9 | Why is sodium chloride the dominant salt in seawater? | Why sodium instead of lithium, potassium, etc? Why chloride instead of sulphate, phosphate, etc? | askscience | https://www.reddit.com/r/askscience/comments/55o6l9/why_is_sodium_chloride_the_dominant_salt_in/ | {
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"So when considering this question, we have to consider two things. First, what are the concentrations of each element on earth? Second, what chemical form(s) is each element found in? To be found in seawater in large quantities, an element needs to preferentially form stable, water-soluble species. \n\n[This page](_URL_0_) shows the raw abundances of elements. As you can see, sodium is one of the most common elements on Earth. All of the more common elements are components of water, also found dissolved in water or tend to form insoluble chemical species. Chlorine isn't quite as common, but is still present in large amounts. However, the elements more common than chlorine don't prefer to form water soluble species in the presence of water, oxygen and each other. Thus, we are left with large quantities of sodium and chloride. ",
"This has to do with the \"steady state\" or the balance of input-output of these elements in seawater. The sources for these elements to the ocean is from the weathering of rocks on land, like all other major constituents of seawater. \n\nThe difference between sodium and chloride is their sinks from seawater a pretty different than other elements. The largest sink (exist mechanism from seawater) for these elements is basically drying up of ocean basins at the end of the Wilson cycle (the life cycle of oceans). This, as you can probably imagine, takes hundreds of millions of years. They are not significantly used in biological functions like other major constituents in seawater. \n\nOther major constitutes of seawater like calcium, magnesium, sulphate, ect. can get incorporated in the shells of phytoplankton or in their cells. That means these elements when the plankton die, or are consumed by the higher food chain and nicely packaged into fecal pellets are heavy enough to sink out of seawater and into ocean sediments. This is much faster in comparison to sodium and chloride.",
"Na and Cl are the most abundant salts in seawater because they have the slowest removal rates. \n\nThere's an easy way to figure out why this is the case - examine the concentrations of different ions in seawater compared to river water. Sodium and Chloride are the most concentrated ions in the ocean with respect to river waters (due to their extremely high solubility and low particle reactivity in the ocean). If it were due to sodium and chloride having the largest sources, they would also have to be the most abundant ions in river water, which they are not. \n\nSulphate and phosphate are used rapidly in the ocean by organisms and incorporated into organic matter. Lithium and potassium are certainly more soluble, but they have faster sinks - they can be removed by the hydrothermal circulation of seawater through the hot ocean crust. \n\nThis idea as a whole, is known as the kinetic model for seawater and is how chemical oceanographers understand the composition of the ocean - [Broecker 1971](_URL_0_ )\n",
"This is a good question. I've read some of the top upvoted comments and while there are parts of them that are close to the truth, they are all missing some *key* factors that adequately explain why Na+ Cl- are the dominant *ions* in sea water.\n\nFirstly, the comment by u/shieldvexor is accurate in the discussion of abundances (the usual term is crustal abundance, not concentration 'on earth'). Crustal abundance is a term used to describe the availability of a particular metal or element in the crust, since the crust is really the source of *most* of the elements we find in nature. This isn't 100% true, but it's true accounting for geologic time.\n\nSecond, We **must** look at solubility product of some other common salts in order to assess or conclude why those salts/ions are not more common in sea water. Lets take the obvious example of calcium carbonate. CaCO3 would be a strong contender for dissolved concentrations in seawater, given the incredible store of *solid phase* CaCO3 (consider all the detritus of millions of years of shellfish, bones and coral in the ocean), if the solubility product of CaCO3 was significantly lower, there would be a lot more Ca+2 CO3-2 in sea water, which would (could) make these ions contenders for the top salts. Lets look at another example: Since iron and oxygen are some of the most common elements on earth, we might expect that iron would make up a significant portion of of the ion strength in sea water. The reason iron isn't one of the top ions is because any iron that does go into the ocean is immediately precipitated out as iron oxy-hydroxide (FeOOH). Furthermore, iron which might have travelled down streams and rivers to the ocean would almost always be removed by settling out of the water column before it reached the ocean. Because iron oxy-hydroxide has a very , very low solubility product, there would be almost zero opportunity for any iron to reach the ocean unless mobilized by turbulent water. Since turbulent water hardly ever reaches the ocean (turbulent water carries a lot of energy and will erode mountains much more quickly than slow moving water, it means that turbulent water will always rapidly erode the source of the turbulence thus creating (eventually) a shallower slower moving river on account of the built up sediment. This slow moving water is a perfect place for iron precipitates to settle out of the water column.\n\nThirdly, and arguably most importantly, we have to account for source term liberation and mobility. Because sodium and chloride, potassium and some other mobile ions *are* mobile, they are rapidly leached out of rock. Since rock is gradually 'weathered' by wind and water, the process of weathering releases (liberates) the most mobile elements first. Other elements that are bound by higher energy bonds such as silica, aluminium, are slower to be released. This means that those elements that are released more rapidly are more heavily partitioned into the liquid phase, while elements (even when they are more abundant (e.g. iron, silica) are partitioned more heavily into the solid phase. We can consider the previous two points in context of this point: If silica or iron was not bonded so strongly, what would happen? The liberation would elevate water in contact with source terms, but, since mobility isn't as high (also KSP's lower) then transport from the source term to the ocean would still take longer, and thus other elements with higher mobility would still out-compete these elements.\n\nIn summation, the reason why Na, Cl is elevated in comparison to all of the other potential salts is because of source term liberation mechanics favouring partitioning into the liquid phase, higher mobility (higher solubility product) in water, and finally elevated crustal abundance concentrations in the source term.\n\nThere are a few other more technical reasons regarding extremely high salinity water adversely affecting solubility constraints and the hydration spheres (positive/negative ion density of the ions and associated water molecule arrangements) but I'm not going to go into detail on these because they are largely irrelevant given the scale of the differences we are discussing - hyper salinity will adversely affect *all* salts with the possible exception of some Ca+2, Na+ and K+ salts as a function of Debye & Huckel's observations (and others) as early as 1920's.\n\nThere is good reading on this topic and many advancements in the last 40 years (since the early 1980's) with special note to Kenneth Pitzer: _URL_0_\n\n\n"
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3icgpv | candidates love saying it, how exactly would we "abolish the irs"? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3icgpv/eli5candidates_love_saying_it_how_exactly_would/ | {
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"We would eliminate all income tax. The IRS (and all the things that go along with it; e.g. filing taxes every year) is a fairly new creation; for most of the USA's history the government acquired taxes on things like trade and property.\n\nThere's no reason why we couldn't go back to that. The IRS is a hideously inefficient system anyway."
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106i3o | Do humans have a sleep bank? | For a teenager, the recommended amount of sleep is 9.5 hours.
Now, for the average teenager, this number is close to impossible. But, if they take a 2 hour nap and then sleep for 7.5 hours do they achieve the same benefit if they to have slept for 9.5 hours?
Basically, does a nap add to the hours you slept that night?
| askscience | http://www.reddit.com/r/askscience/comments/106i3o/do_humans_have_a_sleep_bank/ | {
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"Not getting enough sleep can accumulates in what is called [sleep debt](_URL_0_). As for recommended amount of sleep, it varies from person to person, as each person's sleep cycle has a different duration. On average, you should get 3 sleep cycles at the bare minimum, and up to 6 sleep cycles for a good night's rest."
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dbeoi2 | what is a parsec | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/dbeoi2/eli5_what_is_a_parsec/ | {
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"It is short for Parallax of 1 arcsecond.\n\nBasically, it is the distance from Earth got an object has to be in order to appear to move one arcsecond in the sky over the course of a year. This translates into a distance of about 3.26 light-years.\n\nAn arcsecond is one sixtieth of ~~a degree~~ an arcminute, there are sixty arcminutes in a degree, and there are 360 degrees in the circle of the sky. Because the position in the sky was one of the most straightforward measurements astronomers could take, it made sense to come up with a unit of measurement that could be easily calculated given just that data. This makes it somewhat comparable to radians in geometry. Radians are also very uncommonly used to measure angles outside of certain mathematical fields that have to deal with coming up with the circumference of an arc based on an angle.",
"A parsec is a measurement of length or distance. It's used to measure very, very large distances between objects in space. One parsec is equal to about 31 trillion kilometers, or 19 trillion miles. For example, the nearest star to our sun is about 1.3 parsecs away. \n\n\nIf you're wondering how much a trillion is, it's one thousand billions. And one billion is one thousand millions. And one million is one thousand thousands. So a parsec, which is 31 trillion miles, is a looooooooooooooooong way.",
"Hold up your hand in front of your face and look at something that appears to be on the right of your hand. Move your head to the left until your chosen object is to the left if your hand. The object hasn't moved, but it appeared to, because your head moved. Now imagine that was the only way you could measure distance. You could use math (specifically, geometry involving triangles, aka trigonometry) to figure out how far away something is from you, by moving your head a little and seeing how far in your vision the object appears to move. The Parsec is a unit for measuring distances in space, where we can't, for example, put a ruler between two things, or bounce a laser off of something. If an object moves a specific tiny amount in our view of the sky, called an arcsecond, over the course of six months (the time from when the earth is in one position to when it's on the opposite side of the sun, aka as far away as it would ever get from the first position) it's one Parsec away. \n\nComes to about 3.26 light years.",
"[This article](_URL_0_) and especially the figures within might be helpful.",
"A parsec is just a measure of distance. It's about 3.26 light years, or about 3E13 kilometers.\n\nThings in space are really far apart so it makes sense to use a really big unit of measurements.\n\nBut we can't actually take a measuring tape to the stars. One of the easiest ways to talk about the relative position of stars is by the angle between them with us at the vertex. So you might notice that the angle difference between star A and star B is 2 degrees.\n\nThe problem is that this won't actually tell you how far anything is from anything else. But if we were to take two observations of the same star from two different spots that are sufficiently far apart we can do some basic trigonometry to find the distance.\n\nGiven the distances of space the only practical way to do this is to look at a star at multiple points in a year. That way the movement of the earth around the sun provides a known and big distance to base your calculations on.\n\nThe distance between the earth and the sun is defined as 1 AU. So a parsec is how far away that star needs to be in order to get 1 arcsecond difference between two observations that are 1 AU apart (assuming that 1 AU of movement is orthogonal to the direction of the star).",
"See [this](_URL_0_) right triangle? \n\nIf x = 1 arc second (1/3600th of a degree) and A = 1 astronomical unit (an AU, the distance from the sun to the earth), how big is B?\n\nThe answer is one parsec, 3.26 light years.",
"Something just dawned on me:This is a fixed distance unit.\n\nIf you took the parallax of an object further away the angle would decrease. You cannot just take a angle measurement and use its arcsecond value to get the distance in \"parsecs\".",
"Draw a right triangle with legs A and B. Let A be the shorter leg and B the longer one. Now, if the length of A is the distance between the Earth and the Sun (1 AU) and the angle opposite to A is 1/3600 (1 arc second), then the length of the longer leg B is approximately 1 parsec."
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4sxzm2 | Just 5 short years after the USA crushed their enemies, the Japanese, and helped defend their mainland, the USA and China would be at war in Korea. How did Chinese public opinion of the USA fluctuate in that time period? | Sorry if the title downplays Chinese involvement in WW2 or overstates American contributions, I'm not highly educated in the Pacific theater in relation to China and their part in the war, other than the atrocities committed to them by Japan. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4sxzm2/just_5_short_years_after_the_usa_crushed_their/ | {
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"Not my area of study and others are almost certainly better able to answer this question than I am, but the basic answer is that China fell to the communists. I'm more familiar with the changes in US public perception, for instance over the debate about [\"Who Lost China?\"](_URL_1_) But in those short five years you go from an Axis-Allies bi-polar world to a Communist-Capitalist bi-polar world. When the communists take over in China in 1949 it jumps to the other side of the ledger. Among other things, as a result of that change, \"public opinion\" matters quite a bit less than it would under a democratic system (not that Chang Kai-Shek was a democrat), but the US also substantively supported the other side.\n\nThe other, related issue is that the US, and MacArthur in particular, fundamentally underestimated the likelihood and impact of a Chinese intervention in the conflict. He was unable or unwilling to consider that a rapid advance to the Chinese border on the Yalu River would be viewed as a provocation to the Chinese, or that the Chinese communists would be so highly capable in their intervention. Were it not for rather extraordinary tenacity (to put it lightly), it seems likely to me that the entire 1st Marine Division (my grandfather among them, incidentally), would have been killed or captured at [Chosin.](_URL_0_)\n\nIt's pop-military history, but Martin Russ' *Breakout: The Chosin Reservoir Campaign, Korea 1950* is a great read."
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1u1vhm | How important was the Book of John the Evangelist to Cathar theology? | I've been doing research into the Cathar heresy, and I've been particularly interested in the theological tensions between orthodox doctrine and many pre-existing, local dualist beliefs in regions where Catharism gained traction. Given the relative lack of a non-hostile primary source base to outline a picture of Cathar theology, as well as the vast geographical differences, this is difficult.
But my main question relates to both the canonical Bible and the [Book of John the Evangelist](_URL_0_). To what degree were Cathars, both perfects and followers, engaged with either of these texts? How much did they know about what was written in them? And where did the Book of John the Evangelist even come from?
Thanks for your help, and I'd be glad to follow up on anything that is too vague in my question. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1u1vhm/how_important_was_the_book_of_john_the_evangelist/ | {
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"The Cathars did not exist.\n\nThat is to say, the heretics who have come to be described as Cathars of 12-13th century never called themselves that, there is scant evidence of actual organization of these heretics of this period into anything that could be considered formal enough to have a doctrine (as opposed to Waldensians), and there is even scanter evidence that these heretics have their origins in some sort of Eastern European Manicheaism (which would have accounted for citations of Book of John). \n\nBased recent research and analysis done by some of the pre-eminent current historians of French heresy in the high middle ages, most of our notions of a doctrine of Catharism are the result of confused historiography that has imposed Bogomilist dualist beliefs and doctrines on to the Occitan heretics.\n\nIt is only in the last 15 years that we have begun to unwind Cathar heresy from the deep confusion caused by books like Steven Runciman's The Medieval Manichee: A Study of the Christian Dualist Heresy (1947) which have assigned to so-called Cathar heresy a raft of dualist doctrines and texts which now do not adhere to Catharism under scrutiny.\n\nThe links we have between the heretics of southern France and Bogomil Manicheeism are thin, and it appears the historiography we've relied on turns on dubious evidence, the most important of which is the so-called Cathar Council, supposedly held at Saint Félix of 1167 attended by local senior heretics and - key to the connection to Eastern dualism - by the Bogomil Nicetas. Many, although not all, historians view this meeting as apocryphal, unproven, following Monique Zerner's compilation of the round table of historians discussing the matter in 2001, L'histoire du catharisme en discussion: le \"concile\" de Saint-Félix (1167) . \n\nIf the council were to be proven beyond doubt, we would still be a long way off from having any sense of the doctrines of the heretics, because the historiography that follows the Manichean influence of Bogomils is one of inference: because the Cathars must have had contact with Nicetas, they must therefore have taken in all doctrine of the Bogomils.\n\nNotwithstanding this critical yet unproven connection, the rest of the evidence is bereft of details on heretical 'doctrine' of 'Cathars'. Our two other sources of information are writings by monastics, chiefly Cistercians such as Bernard of Clairvaux and Alain de Lille, and inquisition records spanning decades. The Cistercians have nothing to say about heretical doctrinal details; they invoke Manicheeism, Arianism, and Donatism in abstracted, ideological forms inherited from Augustine. There are inquisition records of Toulousain, Lauraugais, Quercy, Agenais, Aquitaine, and so forth, thousands of submissions, and none refer to these supposed dualist doctrines of Catharism. \n\nWhat we do know with some certainty is that some heretics of southern France used the New Testament in parts, and they did perform certain offices but without the consistency that doctrine would require. These offices such as *consolamentum*, and heretical conditions such as *perfected*, come to us through the homogenizin effect of latin, orthodox Christian sources. We know more about the lifestyle of heretics, the *bons homes* or *Good Men*: it was Apostolic Christianity, the poor, wandering preachers at least by CE 1200.\n\nWhat you are interested in is Bogomilism from the medieval Balkans.\n\nFor a reasoned approach to medieval heretics in Occitania, , this web article by RI Moore is a really good grounding in some key issues in history of Catharism: [When did the Good Men of the Languedoc become heretics?](_URL_0_) . Moore is perhaps the greatest living English historian of high medieval heresy.\n\nAs I am not a biblical historian, I can't speak to your last question. You might try /r/AcademicBiblical.\n\nFurther reading:\n\n*The War on Heresy, R I Moore (London, 2012)\n\n*Beverley Mayne Kienzle, Cistercians, Heresy and Crusade in Occitania, 1145–1229 (York, 2001)\n\n*Mark Pegg, A Most Holy War (New York, 2008)\n\nEdit: The foregoing is in respect of the French Catharism which provoked the papacy to action in the form of a crusade, and not northern Italian Catharism of the mid-late 13th century. It is precisely the conflating of the two that has contributed to the mythologies.\n\n\n"
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13xydc | Is String Theory falsifiable? | String theory has been around for decades now, but I don't know how it suggests any observations that deviate from those suggested by the Standard Model.
So my question is: is String Theory falsifiable? If not, isn't just mathematical philosophy and not science? | askscience | http://www.reddit.com/r/askscience/comments/13xydc/is_string_theory_falsifiable/ | {
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"Not yet. It's not ready. It can take a long time to figure out what a theory implies.\n\nHowever, if you generalize your question and ask \"Can string theory as a technique make predictions about a non-stringy universe\" then the answer is yes: you can use holography to make predictions about heavy ion collisions and quantum entanglement. This is, as I said, is unrelated to whether the universe is stringy or not.",
"String theory is absolutely science. String theory predicts that the universe is quantum mechanical, Lorentz invariant, unitary, and that General Relativity is correct in the low energy limit. It predicts negative cosmological curvature, that the strength of gravity increases more rapidly at very short distances, string harmonics at very high energies, supersymmetry, magnetic monopoles, cosmic strings, holographic dualities, and coupling constant unification. Each of these predictions/postdictions are falsifiable. The big problem pointed out by its detractors is that they are not easily falsifiable *in practice*, only in theory. Is in unfortunate that practically speaking, string theory cannot be falsified at low energies without getting lucky. But technically string theory is not philosophy because factually speaking it is a falsifiable theory (we just need a particle accelerator that is 15 orders of magnitude more powerful in order to unambiguously be able to falsify it). "
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eppwky | What does data look like physically? | For instance, when I save an MS word document, or save data in a video game, those specific bits of info, what do they look like physically, and how is it stored? How does that work? | askscience | https://www.reddit.com/r/askscience/comments/eppwky/what_does_data_look_like_physically/ | {
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"depends on “where it is” is the computer.\nbut “physically” (go with me here):\n\nData is normally stored on a disk drive. Everything brakes down to binary which is 1s and 0s. \nIn the disk drive , the disk is magnetically charged to the atomic level. The more disks , the more data ect.\nWhen this atom , where the binary data is , it is read by the computer components , and is either charged or it isnt. This translates back to our binary 0 and 1.\nNot all data is stored together , the computer uses a complex algorithm of patching these strings of data together , using formulas , code to produce results.\n\nWhat also happens when you “defrag” your hard drive in the computer is moving these areas of charged data closer together , so in the disk drive the computer doesn’t have to move across the disk for different pieces of data. And therefore read data quicker.\nThe rest of data is arguably electrons flying around , mathematically to produce the computer. Its like a mini city when you zoom in with roads as channels , components like buildings doing stuff with electrons.\n\nYou cant see data physically its more like magic with electrons.\nHowever you could save a bunch of stuff onto a drive , break it open and look at it but it wont look different from other data",
"In a hard drive data appears as microscopic magnetic domains on top of a metal oxide. Looking at it as a human looks like the most perfect mirror you will ever see. \n\nAround the disc the data is organized into tracks, kind of like a record player. A modern hard drive contains millions of tracks. \n Within each track are specific domains, each with a different magnitude of their strength of the magnet. Each track contains 10s of millions of magnetic domains.\n\nIf you were walking along a track, and could see the magnetic domains as colors you would first see a section, a few hundred times per revolution where the magnetic flux is very very high. These sections are address markers, written into the disc to tell the hard drive head where it is in time/rotation.\n\nFollowing these markers is a steam of high amplitude magnetic flux that tells the hard drive which track it is on. \n\nAfter this the true user data begins. This data is now at much much lower amplitude and far higher frequency. At the smallest possible size ( dictated by the grain size of the metal oxide ) the magnetic state of each crystal changes back and forth. This data would continue on for a small bit ( enough for 1 sector or 4096 bytes + overhead ) and then you get another kind of marker.\n\nThese changes, along with their magnitude and frequency are read by a GMR read head, amplified enormously, then interpreted by a very advanced analog to digital converter. This digital data is then extracted, and pushed into internal DRAM on the hard drive.\n\nThe data is now stored in the charge, or discharge of millions of microscopic capacitors.",
"I'm giving this explanation not because I don't get what you're saying, but because I'm inviting you to rethink it.\n\nData does not have an appearance, because data does not exist pre-cognitively, like light molecules, and protein. It is strictly a post-cognitive phenomenon, much like pain, which also has no visual appearance. Data doesn't appear as a hard drive, nor as the electrons in a hard drive: that's just metal atoms and said electrons flowing around them. Nor is data ever even on a computer screen, as an object onto itself. It's only until it hits our eyes and goes through our neurons does it carry any meaning and become data. A cryptographic message, with a person reading it being unaware that it contains any message at all, is not data to that person. It might well take the appearance of a pretty drawing, and become a form of entertainment instead. A person who understands the code clearly sees data. \n\nAnd data can take many forms. The implicit underlying meaning in your question refers to digital binary data. But writing is no differently data, nor are the colors of an animal that inform other animals that it's poisonous to ingest. When we say data, we usually refer to a large collection of information that, as I said, is in digital binary storage. And this question is really asking what that digital storage looks like, not data per sr. However, even that question is tragically vague. What does it look like on CDs? What does it look like on a floppy disk? How about a flash drive? Moving platters? When it's floating across an ethernet cable? In each case it's vastly different, because we're really looking describing how those methods of storage physically appear. \n\nReiterating, data has no appearance, just like every other postcognitive phenomenon, but can -represented- through an infinite number of modalities (punch cards anyone?), which can take any and all appearances. It's only data when our brain perceives it as such. These appearances of data are completely subjective when represented in the physical world (How many ways has pain been represented visually in art? Aurally in music?Other post cognitive phenomena include proprioception, music in and of itself, fear and any emotion, thirst, and so many others. All are subject to the same subjectivity when we try to represent these things visually, or otherwise.\n\nIf you want to understand the why of why I took the time out to make this distinction, I have a B.S. in Cognitive Science. It might seem like a useless or pedantic distinction, but this understanding really helps us comprehend how we perceive reality, and therefore understand how we put it together in the brain.",
"Everyone seems to be forgetting that CDs and DVDs exist and are still commonly used. This is called optical media for a reason. Optical meaning that it is made or at least visible to normal light. I don’t know much about it but maybe someone will see this and realize they could explain it."
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ekd0ab | Why high concentration of smoke makes sky red? | askscience | https://www.reddit.com/r/askscience/comments/ekd0ab/why_high_concentration_of_smoke_makes_sky_red/ | {
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"Waves cannot generally be blocked by objects that are much smaller that their wavelength. For example, if you put a speaker behind a garbage can, the garbage can will effectively block the treble (short wavelength), but the deep bass (long wavelength) will just go around it. \n\nIt's the same way with light. \n\nRemember how blu-ray allowed for discs to hold a lot more data? That's because red light has a longer wavelength, and would therefore not be coherently bounced back by the especially tiny features on the surface of the disc required for that high data density. By using a blue laser (shorter wavelength) they could effectively read smaller features. \n \nThe particles produced by these fires are predominantly *similar* in size to the features on a blue ray disc - they will reflect higher frequency colors, like blue, back into space. But they're mostly too small to reflect red (low frequency) light, so a lot of that gets through to the ground. \n \nIt's kind of like of the sun was a giant speaker, and the smoke particles were all garbage can sized. They would block out the treble from the sun, but not the deep bass."
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c77zhn | what is generally the cause of death of bugs that only live a few days? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/c77zhn/eli5_what_is_generally_the_cause_of_death_of_bugs/ | {
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"Usually its just the adult phase that only lasts for a few days. Theyve evolved a tradeoff of digestive system (or even a mouth) for reproductive organs/anatomy.\n\nThe nymphal stages allow for a long and fulfilling life",
"Starvation in some cases. There are some bugs that dont have mouthparts or digestive systems and so cannot eat. They live as long as their initial supply of energy lasts - usually just enough to reproduce - then stop."
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1khtjz | Why did the U.S. Military switch from geographic units (20th Maine Regiment) to more standard formation (10th Mountain Division) | If I remember correctly there was a shift from an all-volunteer army to a standing army of regulars. Was it just a matter or organizing units into greater specialization? One could think of reasons where putting men from a similar geography into a unit could be advantageous for morale. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1khtjz/why_did_the_us_military_switch_from_geographic/ | {
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" > One could think of reasons where putting men from a similar geography into a unit could be advantageous for morale.\n\n The British have always gone in for regiments that recruited in one particular area. In WW1 they went a bit further and allowed men to join up together and then serve together in the so-called \"[Pals Battalions] (_URL_0_) The result, when faced with modern weaponry, was frequently tragic. \n\n So my guess would be, after the losses of Civil War, the Americans deliberately tried to avoid having too many men from one area in the same unit. That way one town wouldn't find their menfolk decimated in a morning.\n\n",
"Well that isn't exactly how it worked. The British Army actually was organized regionally in the Regular Army, as /u/TheMightyCheng points out, but not the US Army.\n\nThe US Regular Army has always been organized on roughly non-regional based lines. In the lead-up to the Civil War, the Regular Army was very small, but it was there, and composed of units like the 3rd US Infantry Regiment, which has existed since the founding of the country pretty much. It was heavily bolstered by the United States Volunteers, which is what you are thinking of, units like the 20th Maine or the Wisconsin Regiments that formed the bulk of the Iron Brigade. During peace time though, the Volunteers were disbanded, and the Regular Army would again be all there was... such as the 7th Cavalry Regiment during the Plains Wars. \n\nSo to answer your question, the US Regular Army has always used standard unit names. Those geographic ones are (were) pretty much just utilized in wartime when the military was augmented to meet the needs of the time."
]
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"http://en.wikipedia.org/wiki/Pals_battalions"
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7bxmw1 | why supersonic planes are designed with deltawings, and subsonic planes are designed with swept wings? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7bxmw1/eli5_why_supersonic_planes_are_designed_with/ | {
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"Long skinny wings have [less drag](_URL_1_) for the amount of lift they generate, so they're more fuel efficient. But you can't have a long skinny wing on a supersonic airplane: if the wings stick outside the [cone-shaped shock wave](_URL_0_) surrounding the plane, they may be damaged, and if not, the flight physics gets much more difficult.\n\nSo supersonic wings are tapered to stay inside the shock wave cone. They still need enough area to generate lift, though, so they need to be wider from front to back -- thus the delta wing shape.",
"The main reason is that, as you get close to supersonic and beyond supersonic, the air behaves differently, and thus the aerodynamics. This means that you'll need different wing geometry, especially in the transition between subsonic and supersonic."
]
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"https://physics.info/shock/",
"https://en.wikipedia.org/wiki/Lift-to-drag_ratio"
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925rnr | Did the Allies during WWI ever consider naval landings in Germany? | It seems logical that the Allies would try large scale naval landings in northwestern Germany to avoid the defensive lines of the Western Front, but no such landings ever occurred. Was this due to a fear of naval landings going poorly like Gallipoli? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/925rnr/did_the_allies_during_wwi_ever_consider_naval/ | {
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"I have answered similar questions before [here](_URL_2_), [here](_URL_1_) and [here](_URL_0_). "
]
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[
"https://www.reddit.com/r/WarCollege/comments/4hz4l4/bacons_folly_the_cancelled_1917_great_landing_in/",
"https://www.reddit.com/r/AskHistorians/comments/7se8ot/i_was_listening_to_the_podcast_on_the_battle_of/",
"https://www.reddit.com/r/AskHistorians/comments/45l3ap/was_landing_soldiers_behind_enemy_... | |
4y7cs7 | how do humans get electrocuted/pull power through their bodies when they aren't completing a circuit? | I've been learning about circuits and playing with power and I really don't understand how without holding power and ground of a dc circuit how can you get electrocuted, as it's difficult to complete the loop? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4y7cs7/eli5_how_do_humans_get_electrocutedpull_power/ | {
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" > how without holding power and ground of a dc circuit\n\nThe term \"ground\" is not just a quaint name for a terminal connection; the physical ground of the planet is \"ground\" for a circuit to complete. If someone grabs a conductor with electric potential it can go through them to ground out their feet."
]
} | [] | [] | [
[]
] | |
d2dj5f | Was there a real rivalry between the Templars, Hospitallers and Teutonic knights like is frequently shown? | Especially the Hospitallers and Templar's seem to have a real rivalry in pop culture and books I read, but how much of it is accurate? They're all dedicated to the same mission for the most part, but I guess there would be competition for sponsors and donors. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/d2dj5f/was_there_a_real_rivalry_between_the_templars/ | {
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"text": [
"Whilst there's always more to be said this [answer](_URL_0_) by /u/Rhodis might be interesting"
]
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[
"https://www.reddit.com/r/AskHistorians/comments/59hond/how_did_the_different_knight_orders_ie/d99rgld/"
]
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3xk9ea | Is it true the UN let the Srebrenica Massacre occur? | I saw a video about Bosnian Muslims attacking the Serbian prime minister at the 20th anniversary of the Srebrenica massacre and in the video it said the UN let the Serb forces advance without putting up a fight, Allowing it to happen, how true is this? Did the US/UK/Dutch forces plan this? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/3xk9ea/is_it_true_the_un_let_the_srebrenica_massacre/ | {
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"Hiya!\n\nThe UN absolutely did not 'let' the Srebrenica genocide occur in terms of 'intending to or allowing' the fall of the town and subsequent genocidal killings undertaken by Republika Srpska. The UN has, however, been heavily criticised for its poor handling of the situation that developed in Srebrenica between April, 1993 and the town's fall to Serbian forces on July 10-11, 1995. The video is correct in stating that UN forces allowed the town to fall without putting up a fight, but deliberately ignores the context of the situation and sounds like a conspiratorial attempt to paint the UN as willing murderers. To properly understand the reasons for the UN's failure to defend Srebrenica, we need to examine the wider situation surrounding Srebrenica prior to its fall in July 1995.\n\nThe town of Srebrenica and the region surrounding it were established as a 'safe zone' for Bosniak Muslims in the context of the wider Bosnian War. Prior to the safe zone's establishment in April of 1993, the Bosnian War had already seen widespread, systematic ethnic-cleansing, forced displacement and ethnically-motivated killing by both sides. Srebrenica had changed hands between Bosnian government and Serbian forces throughout the first half of 1992, but following its recapture by government forces in May, 1992, the town and surrounding region formed an isolated enclave of government control, surrounded by regions controlled by Republika Srpska. The appalling treatment of Bosniak civilians by Serbian forces in the surrounding region, including forced starvation, rape and masscres, resulted in a huge flow of Bosniak refugees into the relative safety of the Srebrenica enclave. By early 1993 the humanitarian situation within the town had become appalling as an effective siege by Serbian forces resulted in starvation and rampant disease. \n\nIn April, 1993, the UN acted to actively extend protection over the Srebrenica enclave. Fearing that the town's fall would lead to the massacre of Bosniak civilians by Serbian forces, the UN established a garrison to protect the enclave under the auspices of the United Nations Protection Force (UNPROFOR) and negotiated a treaty for the disarmament of Bosnian forces within the town and the withdrawal of Serbian forces threatening the security of the enclave. \n\nAlthough the UNPROFOR garrison - a force of Dutch soldiers, roughly 450 strong and supported by armoured vehicles and air support (and hereafter known as Dutchbat) was successfully established inside the enclave, the disarmament-and-withdrawal treaty negotiated by the UN was in practice ignored by both Bosnian and Serbian forces. The Bosnian garrison of the town, if it can be called that, the 28th mountain division, was in a horrendous state by April 1993. It was barely cohesive, and its soldiers were lacking training and suffering from shortages equipment weapons and uniforms - as well as being affected by the appalling humanitarian conditions within the enclave. By comparison, Serb forces besieging the enclave - some ~1,000-2,000 in April, 1993 (estimates vary) had access to tanks and heavy artillery. Dutchbat was not directed to disarm Bosnian forces within the town until Serbian forces withdrew to less threatening positions. As the Serbs never withdrew, the 28th remained, by and large, armed. The safe zone that had been established in April 1993 persisted into 1995, with the vast refugee population of the town almost entirely reliant on supply convoys. Bosnian forces from within the town frequently low-level raids into surrounding Serbian-controlled regions, attempting to secure desperately needed supplies, while Serbian forces maintained an effective siege against the enclave, disrupting supply convoys and frequently engaging in war crimes against Bosnians in the surrounding regions.\n\nBy early 1995, this already dire situation had deteriorated not just in terms of humanitarian conditions, but also strategically. It had become apparent to all involved that the Dutchbat garrison assigned to protect Srebrenica was in reality incapable of defending the town in the face of a determined assault. Dutchbat was now critically low on fuel and ammunition, and running low on food and medicine. Meanwhile, the Bosnian 28th Mountain Division had effectively ceased to exist as a cohesive unit, effectively dissolving into the morass of the Srebrenica enclave as the situation worsened and command-and-control became impossible. In this context, Dutchbat stood little chance of defending the enclave against the 1500+ Serbian troops^A, supported by armoured vehicles and artillery, that were preparing to assault the town.\n\nWhen Serbian forces launched an offensive against Srebrenica on July 6, 1995, this strategic situation came to a head. Dutchbat outposts around the town came under attack, and faced with the dilemma of withdrawing or risking annihilation, Dutchbat forces withdrew in the face of the advancing Serbs, allowing several outposts surrounding the town to fall. By July 10, Serbian troops were encroaching on the town proper. Dutchbat once again attempted to dissuade the Serbs by firing warning shots, but knew that, if they began actively defending against the Serbs and attempting to 'shoot to kill,' so to speak, then the battalion would likely be surrounded and annihilated in short order, and the enclave would fall anyway. Within this context, Dutch forces abandoned Srebrenica to the Serbs, attempting to begin the evacuation of women and children. They would, however, cooperate in handing over male Bosniak refugees under their protection to Serbian forces over the following days - actions that resulted in the deaths of those handed over, and have attracted widespread criticism.\n\nIn the aftermath of the Srebrenica genocide, Dutchbat received heavy criticism for their failure to defend the enclave, but far more reasonable criticisms were leveled at UNPROFOR for allowing the strategically catastrophic situation of July, 1995 to develop. Numerous studies and inquiries in the aftermath of the killings have concluded that Dutchbat had been given an effectively impossible task and provided with far too few resources with which to undertake it. UNPROFOR's failure to reinforce Dutchbat with additional forces, secure its supply lines (or indeed those of the Srebrenica enclave itself) or provide the garrison with adequate air support meant that any Dutchbat attempt to mount a determined defence against the Serbs would end in slaughter - and deterrence that can't deter isn't very useful.\n\nTo sum up, UNPROFOR and more locally Dutchbat did not plan, 'allow' or intend for the fall of Srebrenica. Dutchbat did everything within its power to deter the capture of the enclave by Republika Srpska, short of instigating a military engagement that would have resulted in the battalion being annihilated and the town falling anyway. At the higher level, however, the inaction and failure of UNPROFOR to provide Dutchbat with the resources or strategic support it needed to effectively defend Srebrenica was a critical contributing factor to the fall of the Enclave and the genocide that followed.\n\n---\n\n**Sources**\n\nA - Directly involved in the attack. /u/Polybios provides more accurate figures for the total number of Serb troops within the Srebrenica reigon.\n\n[NIOD Report on Srebrenica.](_URL_0_)\n\n[Report of the Secretary-General pursuant to General Assembly resolution 53/35: The Fall of Srebrenica.](_URL_1_) Warning, large PDF.\n\nRijsdijk, Erna. \"The politics of hard knowledge: uncertainty, intelligence failures, and the ‘last minute genocide’ of Srebrenica.\" *Review of International Studies* 37, 2011. 2221-2235. \n\nSpijkers, Otto. \"Responsibility of the Netherlands for the Genocide in Srebrenica : The Nuhanović and Mothers of Srebrenica Cases Compared.\" *Journal of international peacekeeping* 18, 2014, 281.\n\n\n",
"I have the same answer as /u/Elm11 but with a slightly different perspective :)\n\n------------------\n\nOn the 6th of July 1995 Srebrenica was attacked by Bosnian-Serb forces. Over the next 10 days, the Bosnian-Serbs expelled some 23000 Bosnian-Muslim women and children from the area and killed some 8000 Bosnian-Muslim men. The International Criminal Tribunal for the former Yugoslavia has ruled that these actions constituted genocide.\n\nHow true is it that the UN let the Serb forces advance without putting up fight? Mostly true, with some caveats. Did they allow the Serbians to massacre a large part of the population? That's hard to say, as it's unclear when exactly it became clear to the UN that a massacre was occuring, and what could realistically be done about it at that point. Did the US/UK/Dutch forces plan this? Absolutely not. The international community made many mistakes during the Bosnian war, and in hindsight it's clear they set themselves up to fail, but they didn't realise that at the time. \n\nNote I'll be using \"Bosnia\" as a short-hand for \"Bosnia-Hercegovina\" throughout this post. Convenience trumps accuracy in this regard.\n\n**Setting the stage**\n\nWhen Yugoslavia fell apart in constituent states, war engulfed the region. In Slovenia and Croatia the situation stabilised relatively quickly, but in Bosnia a drawn-out war was developing between Bosnian-Muslims and Bosnian-Serbs, the latter being supported by Serbian artillery and airforce, as well as irregular Serbian units.[1] The international community, chiefly the European Community and the United Nations, got involved by negotiating cease-fires and truces, but none held up. Nonetheless, an international peacekeeping force - UNPROFOR (United Nations PROtection FORce) - was sent to the region.\n\nA lot has been written on Srebrenica already and I'm not going to completely reinvent the wheel. Allow me to use large quote explaining UNPROFOR's situation [1]:\n\n > UNPROFOR's tasks in the disputed areas of Croatia were of simple peacekeeping kind. Its personnel was strictly neutral, while the local parties agreed to its presence in a buffer zone. In Bosnia, however, both the tasks of UNPROFOR and the prevailing situation were different. First of all, there was no peace to keep. Second, UNPROFOR's presence was not welcomed by all parties. Even its neutral role was questioned as, according to the logic of ethnic war, bringing humanitarian aid to the civilians of an other ethnic community, was equated to augmenting the stamina of the enemy. Consequently, in Bosnia, UNPROFOR was hardly tolerated by the stronger party. In the end, it was simply brushed aside when this party decided to eliminate the civilians UNPROFOR was supposed to help.\n\n > In Bosnia UNPROFOR was certainly not keeping the peace, and it was not enforcing one either. The international community, however, was too divided to redress this unfortunate situation. \n\nUNPROFOR units were sent to Bosnian-Muslim enclaves in Bosnian-Serb territory. These enclaves were nominally demilitarised and were called \"safe areas\" by the UN. Srebrenica was once such safe area. The main UNPROFOR presence in Srebrenica was Dutch military unit, about 500 strong, called DUTCHBAT. It had to be supplied through Bosnian-Serb territory though...\n\n**The lead-up to the attack**\n\nEarly in the morning of July 6th, 1995, a Bosnian-Serb army (BSA) attacked Srebrenica. The Bosnian-Serbs had up to 12000 soldiers, about 3000 of which from Serbia. The Bosnian-Muslim Army (BIH) had 3000 men defending. DUTCHBAT, as mentioned, had a total of about 500 men spread through the enclave. Their situation was difficult though, as Metselaar explains [2]:\n\n > The Dutch UN battalion was no real contester, handicapped as it was that some 150 of its members were unable to return to the enclave as a result of a well-planned blockade of the BSA, that only 16% of the operational requirement for ammunition was available, that its fuel supplies were mostly exhausted, that there was a structural lack of fresh food, drinking water, and (partly as a result of all these problems) that the morale of the battalion had become low. \n\nAnother problem was the complicated structure of UN command in the region. At the end of July 6th, the UNPROFOR force commander reported to the UN administration that it was \"overall a quiet day militarily\". Evidently the severity of the situation wasn't clear yet at UNPROFOR HQ. This is probably because communication from DUTCHBAT in Srebrenica had to routed through *Sector North East* in Tuzla, via *Bosnia Herzegovina Command* in Sarajevo, to UNPROFOR in Zagreb. Of course it didn't help that DUTCHBAT just hours before the attack (and after observing a convoy of tanks and APCs!) reported that \"the situation is calm and stable. We expect no major changes for the next 24 hours.\"[3] \n\n**July 6th**\n\nIn the morning of July 6th, the BSA conducted three infantry attacks in the south-eastern corner of the enclave. These were all repelled by the BIH. The BSA responded with heavy artillery fire, hitting a DUTCHBAT observation post in the process. The BSA infantry attacks continued in the east of the enclave; the BIH commander asked for assistance from DUTCHBAT, but that was refused. This angered the BIH, as they had understood the UN presence as meaning that the UN forces would help defend the enclave. However, politicians had severely restricted UNPROFOR's ability to (re)act by imposing strict Rules of Engagement - DUTCHBAT could only use their weapons for self-defence. \n\nFor instance, the Dutch commander Karremans did request Close Air Support (i.e. air bombardment) after the attack on the observation post. UNPROFOR command refused the request, since the rules of engagement stipulated that air support could only provided if UN forces were under fire. Since the observation post was no longer being fired upon (it was already heavily damaged), no air support could be provided. \n\n**July 8th**\n\nJuly 7th was relatively quiet, but on July 8th the fighting intensified. Heavy artillery fire forced the BIH to fall back. They asked DUTCHBAT to give them access to the weapons which had been collected as part of the demilitarisation effort, but DUTCHBAT refused. \n\nBSA tanks entered the enclave in the south-east. They fired on BIH positions and a DUTCHBAT observation post. BSA soldiers approached the observation post under a white flag, and told the Dutch soldiers that they had 10 minutes to leave. Since several tanks had trained their guns on the observation position, the observation post commander decided to retreat. \n\nAs the DUTCHBAT soldiers were retreating from the observation post in an APC, they were stopped by BIH soldiers constructing a barricade just 200 metres away. The BIH soldiers demanded the Dutch soldiers stayed. Not wanting to serve as human shields, the observation post commander ordered the APC to close the hatches and break the barricade. A BIH soldier responded by throwing a hand grenade before the hatches were fully closed, killing one Dutch soldier.\n\nIn the afternoon the DUTCHBAT commander once again requested close air support. The request was once again denied, but UNPROFOR did accept a NATO offer to fly a couple of fighter jets over the area as a show of force. An attempt by DUTCHBAT to re-establish an observation post near the lost observation post was stopped by BIH soldiers. In the evening another observation post was lost to the BSA. Civilians all across the enclave started fleeing to the city of Srebrenica proper. \n\n(continued below)"
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"http://www.un.org/en/ga/search/view_doc.asp?symbol=A/54/549"
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1wyfqd | how to play and win at eve online | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1wyfqd/eli5_how_to_play_and_win_at_eve_online/ | {
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"It's somewhere between having a full-time job and an alternate life. You have political alliances, hierarchies of power, very long-term planning, a complex economy, and more. It's a tremendous time sink."
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8hbzqi | how do thoae scammy top-down games make any money | I'm talking about those games that trick stupid straight guys with lots of anime breasts and claims that you can "raise your own dragon" but is actually just a really bad remake of Age of Empires \- how do they make any profit?
Like surely whatever they earn pushing paywall purchases must be negated by how much they need to spend to host and run the games, as well as paying people to keep it working etc? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8hbzqi/eli5_how_do_thoae_scammy_topdown_games_make_any/ | {
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"Cracked had an interesting article about this topic awhile back. It’s a comedy site, but the article is pretty well-sourced with hyperlinks.\n\n_URL_0_"
]
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"http://www.cracked.com/article_18461_5-creepy-ways-video-games-are-trying-to-get-you-addicted.html"
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5q98k1 | Can a black hole lose enough mass to be visible? | Considering the effects of Hawking radiation, it is known that black holes slowly lose mass as they take in negative energy from nearby virtual particles and it is possible that they will eventually evaporate completely given enough time.
Would it be possible, at least in principle, for a black hole to lose enough mass that it could no longer sustain an event horizon?
Or does it happen that they are simply too dense? Would it depend on other factors, such as whether or not there is a true singularity at the centre, or an ultra dense arrangement of matter contained in a finite volume of space?
How does our current understanding of physics explain this?
I'm very interested in all your answers and please correct me if my understanding abut any of the above is wrong / incomplete. Thank you. | askscience | https://www.reddit.com/r/askscience/comments/5q98k1/can_a_black_hole_lose_enough_mass_to_be_visible/ | {
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"Black holes in classical and semiclassical gravity always have horizons shrouding the interior. The interior is **never** exposed. When the black hole evaporates, the horizon just gets smaller. But nothing that is inside can ever get out.\n\nWith that out of the way:\n\nAt a certain point the horizon will have length of the order of the Planck length. This happens:\n\n- for uncharged, nonrotating BHs when the mass has shrunk down to close to the Planck scale.\n\n- for charged or rotating BHs when the mass has shrunk down to be almost equal to the charge / angular momentum and the BH is approaching extremality.\n\nNow since in these cases the horizon is ~ Planck length, full quantum-gravitational effects will contribute and you cannot say exactly what happens without knowing what quantum gravity is. For completeness, string theory predicts respectively for these two cases:\n\n- the black hole decays into a number of particles (strings) and simply disappears\n\n- the black hole becomes a D-brane, an object with no real horizon in the standard sense",
"/u/Rantonels has already explained the circumstances that cause black holes to radiate Hawking Radiation. But in fact there are many black holes of larger size that are observable because they are accreting matter, a process that produces radiation up to 50x as efficiently as fusion. The most luminous transient events in the universe (gamma-ray bursts) are thought to involve the formation of a black hole, and the most luminous steady sources (Active galactic nuclei) are thought to result from accretion onto a black hole.",
" > Would it be possible, at least in principle, for a black hole to lose enough mass that it could no longer sustain an event horizon?\n\nUntil it loses all of its mass, it will always have an event horizon.\n\nBut a black hole right now cannot actually lose mass faster than it gains it, unless it is very small (less than the mass of the Moon) and as far as we know there aren't any with that little mass. Even a black hole deep in intergalactic space would gain more mass from the cosmic background radiation than it loses to Hawking radiation."
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t7mvh | What would happen to someone if they were stabbed by a 1-atom thick sword made out of an indestructible material? | askscience | http://www.reddit.com/r/askscience/comments/t7mvh/what_would_happen_to_someone_if_they_were_stabbed/ | {
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"With a very quick google search I have found that this same question has been asked and answered. \n_URL_0_",
"On an atomic level, your body is mostly empty space.",
"What about large sheet 1-atom thick? Think about 4x4.\n\nCould you walk into it and stay there? Jump?",
"I've had this thought so many times, what if I had like the thinnest laser imaginable, but that would cut through anything no matter what, with infinite range. If I just flailed it around a bit, would nothing happen because it's so thin, or would I like, destroy the world?",
"I haven't seen this answered yet(I may have missed it) what does the minimum size of this sword need to be to feel anything at all and/or cause any immediate damage?"
]
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bci5wa | Hi all history buffs. So I'm a HUGE fan of the 1920. Especially Jazz, Cinema and the prohibition. But recently I've been fascinated with daily life in that decade. Any resources or anything to learn more? I've watched Ken Burns Prohibition documentary many times | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/bci5wa/hi_all_history_buffs_so_im_a_huge_fan_of_the_1920/ | {
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"I highly recommend Frederick Lewis Allen's 1931 classic [Only Yesterday](_URL_1_). It reminds me of the decade retrospectives (1960s, 70s, etc,) that CNN has - but Lewis wrote his classic long before CNN. Even by 1931 - in the wake of the Crash and so many other profound changes, the 1920s seemed like another time. Lewis speaks as a first-hand observer to other first-hand observers, but because of change, he also writes with a certain amount of historical perspective. It's a great place to start, to understand everyday life.\n\nMy copy - which dates to the late 1930s - was given to me by one of my professors who was born in 1920; he valued the resource, and when I first expressed an interest in knowing more about the 1920s, he gave me his copy.\n\nLewis wrote a sequel about the 1930s, [Since Yesterday](_URL_0_), which first appeared in 1939, intending to capitalize on the success of the original. It's very good as well, but \"Only Yesterday\" is a classic. (My professor gave me that copy as well; he also gave me my first-edition Oxford English Dictionary - all five feet! It's always a good idea to befriend old professors who are about to retire!!!)."
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"https://www.amazon.com/gp/product/1849022496/ref=dbs_a_def_rwt_hsch_vapi_taft_p1_i3",
"https://www.amazon.com/Only-Yesterday-Informal-Perennial-Classics/dp/0060956658"
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7gwmzl | Are there different types of electrons? | According to the standard model, each particle is an oscillation in a quantum field. There are different energies of photons. Similarly, can an excitation of the electron field have different levels?
I know that electrons have different energy levels in an atom, is this a separate concept from the one I described above? | askscience | https://www.reddit.com/r/askscience/comments/7gwmzl/are_there_different_types_of_electrons/ | {
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],
"text": [
"That is a separate concept. Every electron is fundamentally identical to every other electron, and same for photons.\n\nEach of these particles can have whatever energies you want (although an electron can never have an energy smaller than its mass), but they are still the same particle. Two electrons with different energies are still identical particles.",
"Your question was answered, but this is a tangential but interesting point:\n\nWhile electrons are indistinguishable from each other, there are \"extra electron-like\" particles in the Standard Model of elementary particles. Alongside the electron are two other particles, called the muon and tau particles (these three are usually called leptons). The muon and tau have properties basically identical to those of the electron, save for two features: they are much, much more massive (the muon is ~1/10th of a proton mass, and the tau mass is about ~1.8x a proton mass) and hence they have very short lifetimes, decaying down to other things (I think usually electrons + other things). We can produce them readily in particle colliders, and in fact muons that are generated in the upper atmosphere of Earth when cosmic rays slam into air particles can be detected all the way down here before the decay!\n\nIt's not quite exactly what you were asking about, but I thought it was interesting to mention!"
]
} | [] | [] | [
[],
[]
] | |
2ceet2 | what is "engine breaking" and why isn't it permitted? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2ceet2/eli5_what_is_engine_breaking_and_why_isnt_it/ | {
"a_id": [
"cjencyt",
"cjepo8k"
],
"score": [
7,
2
],
"text": [
"Engine braking is used to slow the vehicle by creating back pressure at the exhaust manifold. (The hot gas can't get out quickly - slowing the engine) Thus, braking via the pedal is reduced, prolonging brake life and keeping them cool during extended downhill areas.\n\nIt is not permitted in some places (usually near residences) because when exhaust braking (engine braking) is VERY loud. If you ever hear the big rigs in the mountains while going downhill - that is engine braking. Brr-rrr-rrr-rrr-rrr-rrrr-rrrr-rr-rrrr-rrrrr-rrrrrrr........\n\n:) Cheers!",
"A gasoline engine speed is controlled by the throttle valve. When you take your foot off the pedal the throttle closes. The pistons are still pumping, so a vacuum is created in the intake manifold. This tends to slow the vehicle, and helps the brakes. (ignoring overdrive transmission) This is not noisy and is not a problem in residential areas.\n\nA diesel engine (as used in most large trucks) does not have a throttle valve. The speed is controlled by the amount of fuel being injected into the cylinders. When you back off on the accelerator pedal no vacuum would be created to help slow the vehicle UNLESS there is an engine brake fitted (commonly known as a \"jake\"). This modifies the valve train when activated, and makes the familiar loud sound you hear when you are at the motel near the edge of town where the trucks slow down. Some jurisdictions prohibit the use of \"jakes\" in specific areas to make them more livable.\n\nI didn't make this all up: _URL_0_\n"
]
} | [] | [] | [
[],
[
"http://en.wikipedia.org/wiki/Compression_release_engine_brake"
]
] | ||
6mmeob | what is a 'gig economy', how does it work, and why is it becoming increasingly popular? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6mmeob/eli5_what_is_a_gig_economy_how_does_it_work_and/ | {
"a_id": [
"dk2ma7x"
],
"score": [
19
],
"text": [
"The \"gig economy\" is where, instead of having a steady job you go to for 40 hours and week and a stable income from that job, you make money by doing various things on irregular, self-set hours. Some examples might be driving for Uber, doing TaskRabbit tasks, picking orders for Instacart. You might even do these to supplement insufficient hours at a more traditional job, like bar tending or working as a barista, or to supplement income in addition to being a freelance writer/designer/photographer.\n\nIt's becoming increasingly popular because employers don't have to pay for set hours or offer benefits.\n\nFor those earning money that way, it's the freedom to set one's own hours based on income needs, works/school schedule, etc."
]
} | [] | [] | [
[]
] | ||
4cnhvk | Do neurons have their own genome? | My AP Biology always said that all the cells in a your body have the same DNA but a few articles on the internet like this one ( _URL_0_ ) say that neurons often have different ones and even unique to a specific neuron. So who is right? | askscience | https://www.reddit.com/r/askscience/comments/4cnhvk/do_neurons_have_their_own_genome/ | {
"a_id": [
"d1k1hya",
"d1k1p8c"
],
"score": [
4,
9
],
"text": [
"To be clear, most cells do not in fact contain the exact same DNA pattern. One simple reason: mutations. All DNA will undergo natural mutations. This article is saying that neurons have a high rate of mutations. So yes, their genome is different than a heart cell. But the heart cells genome are going to be different than liver cells. To extend it, epigenetics also change how the DNA is read. \n\nmore information about mutations: _URL_0_\n\nepigenetics: _URL_1_",
"Good question. All cells in your body start off from the same genome. Every time a cell divides, that genome gets replicated. DNA replication in humans is really, *really*, long-slow-whistle-sweet-baby-jesus accurate. But it's not perfect. [This guy](_URL_0_) did the math, and estimated that every time the genome is replicated, you get about 1/3 of a base pair change. Or rather, every three divisions you get one change. So if you plucked any two cells out of your body at random and compared their genomes, there's a pretty good chance that they won't have them *exact* same genome, even if they both descended from the same, original zygote. \n\nThe paper you linked to reports that neurons, which can live for decades, accumulate mutations over their lifespan. That's really cool! But since the cells they're studying don't divide, they don't replicate their genomes, so that's not really an option for acquiring base pair changes. That paper also reports that the source of those mutations is likely not from DNA replication but from *RNA transcription*. The idea is that every time DNA's double helix is opened to transcribe a gene, the bases of DNA are briefly more susceptible to mutation. \n\nYour teacher wasn't wrong, they were just simplifying things for the sake of understanding. Your teacher was right, but that paper is probably more right. "
]
} | [] | [
"https://www.sciencenews.org/article/brain-cells%E2%80%99-dna-differs"
] | [
[
"http://www.nature.com/scitable/topicpage/genetic-mutation-441",
"http://www.pbs.org/wgbh/nova/body/epigenetics.html"
],
[
"http://sandwalk.blogspot.com/2013/03/estimating-human-human-mutatin-rate.html"
]
] | |
1yubqn | When and where did pie throwing as a form on entertainment originate? | A pie being thrown into someone's face is a classic gag, but I am wondering where it got its origins? I assume it came about during the vaudeville era, but I still wonder how it came about. Thanks! | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1yubqn/when_and_where_did_pie_throwing_as_a_form_on/ | {
"a_id": [
"cfob95q"
],
"score": [
2
],
"text": [
"This reminds me of a [question](_URL_5_) that was asked some time ago, and was one of my favorite I've seen on this sub. We never answered it perfectly, but there was [a Google answer](_URL_2_) that did a decent job. \n\nLuckily, it seems your question has a clearer answer! \n\nYou are indeed right, that it appears to have originated during the Vaudeville era, right before the rise of cinema. In fact William Hammerstein (yes, Oscar Hammerstein's father), a very successful Vaudeville producer is sometimes [credited with inventing it](_URL_6_). However, like any good joke, the credit is widespread (and the sources for any inventor is suspect at best). Canadian [medicine show](_URL_7_) performer Thomas \"Doc\" Kelley is also widely credited with inventing the gag, [having seen an angry cook throw a partially-eaten pie at a kitchen worker](_URL_4_). \n\nWhat is clearer though, is the first instance of the joke on film: it takes place in a short slapstick film from 1909, [*Mr. Flip*](_URL_1_), where [Ben Turpin](_URL_0_) gets pied right at about 03:37. \n\nWithin a few years, the joke had taken off, to the point that it is now one of our most recognized trademarks of slapstick humor! \n\nAnd, side note, just because I love Chaplin, he was responsible for the first proper pie fight, at 18:45 in [*Behind the Screen* (1916)](_URL_3_). You can see how quickly the gag caught on! "
]
} | [] | [] | [
[
"http://en.wikipedia.org/wiki/Ben_Turpin",
"http://www.youtube.com/watch?v=WcJaN9n3W6Q",
"http://answers.google.com/answers/threadview?id=217280",
"http://www.youtube.com/watch?v=XrtKhhYxEKQ",
"http://books.google.com/books?id=oyLQn5zMtWMC&pg=PA124&lpg=PA124&dq=doc+kelley+pie+in+th... | |
1qalil | how does south park use strikingly similar product logos in episodes? | Wouldn't the companies claim they are too close to the real design and sue? Does South Park have some special circumstances? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1qalil/eli5_how_does_south_park_use_strikingly_similar/ | {
"a_id": [
"cdavd51",
"cdavwab"
],
"score": [
4,
2
],
"text": [
"Protected by parody laws. You're allowed to make fun of things. They would also be protected if they used the real logos because then they're be protected because those logos actually exist and they're not pretending that they are those companies. This is why you don't need Coca Cola's permission to have someone drink Coke in your movies. ",
"Thanks guys. good explanations."
]
} | [] | [] | [
[],
[]
] | |
6oh7py | what's the noise that trucks make when they stop, like air is being expelled? | I've always wondered. Sometimes it's just before they start moving again. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6oh7py/eli5_whats_the_noise_that_trucks_make_when_they/ | {
"a_id": [
"dkhael4",
"dkhaemt"
],
"score": [
3,
9
],
"text": [
"It is actually air being expelled.\n\nLarger vehicles use air brakes. They compress air and use that to work the brakes rather than (entirely) counting on hydraulics like smaller vehicles. The advantage to air brakes is the system can be tapped into at any time (adding or removing trailers and such), where hydraulics rely on a closed system (and therefor a set amount of fluid)",
"Air being expelled. Truck have air powered brakes as opposed to the fluid hydraulic brakes that you have in your car. \n\nIn fact, trucks have several different braking systems. One of those systems is the spring brake. The spring brake is an emergency brake that uses a powerful spring to keep the brake in place. While the truck is moving, air pressure actually keeps the brake from engaging. When the truck stops and parks, it works like a parking brake. Air is expelled and the brake engages. That's why you hear the air escaping."
]
} | [] | [] | [
[],
[]
] |
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