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5eqkcd | When does a bullet reach its maximum velocity? | I was wasting my time on youtube watching gun videos and this got me thinking. The bullet has to reach Vmax from standstill in some time, then is slows down due to air drag. It should be somewhere in the barrell, but is there a way to know when and where?
Also is this related to the force the gun kicks back with? | askscience | https://www.reddit.com/r/askscience/comments/5eqkcd/when_does_a_bullet_reach_its_maximum_velocity/ | {
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"Probably right as it leaves the barrel. For many cartridges, firing the same bullet from a longer barrel will result in higher velocity because it doesn't \"waste\" as much of the gas expansion. Imagine a very snub nosed revolver: there's a huge flash of fire out the barrel *around* the bullet, and all that gas expansion is \"wasted\" (it doesn't push the bullet any more) ",
"Generally, the muzzel velocity (when the bullet leaves the barrel) is the Vmax for a bullet from a gun. This is due to the loss of propulsion and the overtaking of friction and drag. No more push, just slow-down after that.",
"yes the recoil is related to the bullet flying away. It is newtons third law: Actio=Reactio \nThere is a force that is accelerating the bullet away from the gun, but at the same time a force has to act on the gun in the opposite direction. That is the recoil. ",
"For a properly designed firearm, the bullet reaches maximum velocity as soon as it leaves the barrel. This is because the expanding gas behind the bullet no longer accelerates it. \n\nThe bullet should never be decelerating inside the barrel due to friction; if that were the case then you'd just shorten the barrel."
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jko32 | How did the first replicating RNA or DNA begin to result in organelles with functions? | askscience | http://www.reddit.com/r/askscience/comments/jko32/how_did_the_first_replicating_rna_or_dna_begin_to/ | {
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"At least some organelles seem to be the result of endosymbiosis - i.e. they were formerly independent life forms which became symbiotic with other life forms (like our ancestors). \n\nMitochondria, which are in every cell in your body keeping you alive, in particular are thought to have originated in this way. \n\n\\- _URL_3_ - \n\n\\- _URL_1_ -\n\n\\- _URL_0_ - \n\n\\- _URL_2_ - ",
"At least some organelles seem to be the result of endosymbiosis - i.e. they were formerly independent life forms which became symbiotic with other life forms (like our ancestors). \n\nMitochondria, which are in every cell in your body keeping you alive, in particular are thought to have originated in this way. \n\n\\- _URL_3_ - \n\n\\- _URL_1_ -\n\n\\- _URL_0_ - \n\n\\- _URL_2_ - "
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1e1tjh | Is this Pearl Harbor picture authentic? | _URL_0_ | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1e1tjh/is_this_pearl_harbor_picture_authentic/ | {
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"To be exact, it's a picture of [Mahan-class destroyer USS Shaw](_URL_0_) exploding. The ship wasn't destroyed however, and went on to continue fighting in the war before being retired after World War II ended."
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"http://i.imgur.com/b8ERPVm.jpg"
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"http://www.history.navy.mil/photos/events/wwii-pac/pearlhbr/ph-shw.htm"
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1753oe | Is there any credence to the concepts of wet cold and dry cold? | Given the current freezing temperatures here in Montreal, this discussion seems to have popped up, notably on the front page of reddit in [this thread](_URL_1_).
However, upon some brief googling, I found the following [article](_URL_0_) which states that this is all nonsense.
So is there any truth behind feeling a wet cold or a dry cold? | askscience | http://www.reddit.com/r/askscience/comments/1753oe/is_there_any_credence_to_the_concepts_of_wet_cold/ | {
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"I answered this question [here](_URL_0_) about a month ago: \n\n > After much reading, and some calculations, here's what I've found:\n\n > 1. People on online forums like to argue about this topic. These same people tend to rely heavily on broscience and hand-waving. (\"I can feel the water particles against my skin and I lose my body heat into the air much quicker.\" -actual forum quote)\n\n > 2. The math shows that the conditions are nearly identical, from a heat transfer perspective. The main reason is that at cold temperatures, there's almost no difference in air properties of saturated and dry air, which is, in turn, because the air just doesn't hold much water. The thermal conductivity only differs by a tenth of a percent, and the specific heat difference is about one percent. Neither of these figures would account for a perceivable difference.\n\n > 3. Meteorologists use humidity for heat indices, but almost exclusively use only wind speed for cold sensation (which is obvious since it's called the wind chill). Note: AccuWeather uses RealFeel, which apparently does factor humidity for cold conditions.\n\n > Furthermore, I can find no scientific evidence to back up the claim that damp cold takes more body heat than dry cold. None.\n\n > From this, I would conclude that all of the claims to your point are merely anecdotal. To further this point, Craig Bohren proposes in his book, What Light Through Yonder Window Breaks: More Experiments in Atmospheric Physics, that the cause of these claims is that humid places are often cloudy, and, therefore, feel colder than a cold, sunny place, where direct sunlight warms people. This comes from a chapter in his book dedicated to the \"Water Vapor Mysticism,\" and is backed by math and experimental data.\n\n(My answer is at the bottom of the other thread because amateur scientists tried to answer the question with speculation, and those posts were upvoted before I was able to work out the numbers to prove that the heat transfer is nearly identical in both wet and dry air scenarios, but I'm certain this is correct.)"
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"http://www.cbc.ca/news/technology/story/2013/01/23/wdr-wet-cold-dry-cold-environment-canada.html",
"http://www.reddit.com/r/pics/comments/174idn/this_is_a_picture_of_montreal_this_morning_its_36/"
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17esk8 | How do Positrons form and what exactly are they? | So my chemistry textbook said that "Positrons have the same mass as an electron but they possess a positive charge. They form when a proton decays into a neutron" I don't know why but I just don't quite understand that explanation. Also, I always thought Neutrons were made up of a Proton & an Electron? So can someone please explain this to me in simple terms?
Edit: Guys these are all great comments... But I don't do physics. I'm in my last year of high school and I do chemistry. Because I wasn't doing physics, I promptly forgot everything I learnt in 10th grade (sophomore year for you Americans :) ) about physics & the structure of an atom. Dumb decision. We just got to a unit about Nuclear Chemistry. I don't understand what all this means. How does a proton decay into a neutron? Up quark, down quark, neutrino, anti-electron, anti-electron-neutrino... All these terms are confusing me. | askscience | http://www.reddit.com/r/askscience/comments/17esk8/how_do_positrons_form_and_what_exactly_are_they/ | {
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" > Also, I always thought Neutrons were made up of a Proton & amp;amp;amp;amp; an Electron?\n\nYou forgot something. Neutrons decay into a proton, ~~anti-electron (aka positron)~~ electron, AND an anti-electron-neutrino.\n\nA down-quark in the ~~neutrino~~ neutron gets turned into a up quark and emits the positron and anti-electron neutrino.\n\nedit: fixed an obvious goof up.",
"Positrons are what we call the anti-particle to the electron. They have the same mass, but opposite electric charge. When a positron and electron meet, they can annihilate, destroying both and converting their mass energy into two photons (or Z bosons, at high enough energy). This is why we don't see positrons very often. With the abundance of electrons around us, any positron formed will rapidly find one and annihilate.\n\nNow about the questions with the neutrons. Neutrons can decay into a Proton and Electron and Neutrino, but this does not mean a neutron is made up of these things. This decay, known as beta decay, is mediated by a force we call the weak force. There are other ways a neutron can decay. A proton can decay as you said into a neutron, a positron, and neutrino. This is also mediated by the weak force, and can only occur within a nucleus for conservation of energy to work.\n\nThese facts don't really make sense in combination classically, which I think is leading to your confusion. In these decay processes, the particle is **not** broken down into constituent parts. Matter and energy are **transformed** by the weak force. Here is an analogy: Imagine I smash a clock with a hammer, but instead of a bunch of gears and junk flying out, I get three little watches. It really is that weird, and there really isn't a great way to explain it in simple terms, but this is about the best I could do. \n\nI'll clarify points if needed. Also, I think this would be better labeled as a physics question, since it involves nuclear reactions, rather than atomic reactions."
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3fddke | what happens when drugs consume your body/mouth? | Multiple times I have seen pictures of drug addicts with awful mouths and body parts (including legs).
How does it work?
Is it a "chunk of meat" falling off?
How much time does it take until a change is seen?
Does it hurt?
P.S.: I don't use drugs. I'm just very curious. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3fddke/eli5_what_happens_when_drugs_consume_your/ | {
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"I believe this is something to do with a combination of dehydration and a general lack of taking care of ones self. Can't confirm, but someone should be able to. \n\nI know that's what \"meth mouth\" comes from. ",
"1. Smoking anything will eat away at your teeth over time. Even tobacco cigarettes will give you yellow teeth. Meth-smoking is particularly known for this, giving people \"meth mouth\". Smoking also leads to dry mouth, which can worsen tooth decay. \n\n2. Heavy drug users will often spend long periods of time totally neglecting their personal hygiene. If you're strung out for days at a time, you're not going to be brushing your teeth.\n\n3. Many drugs can cause addicts to compulsively pick at their skin, either because they feel itches or have the sensation of insects crawling on or even *under* their skin. If you pick and scratch long enough you'll get nasty sores.\n\n4. A particularly fucked-up type of morphine is called \"krokodil\" which first started being used in Russia and Ukraine. It's laced with some pretty gnarly chemicals and can turn skin scaly and cause enormous open sores to form, often literally eating away at the flesh. This is probably where you've seen someone with legs that look like chunks were taken out of them. "
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36l8l4 | how do tv broadcaster/tv show creator work? | Does the broadcast company pay the creators, or is it the other way around?
Bonus questions, who is getting the short end of the stick? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/36l8l4/eli5_how_do_tv_broadcastertv_show_creator_work/ | {
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"Broadcast companies, think of these like channels, Discovery, NBC, etc make their money from advertising. So they seek out or have pitched to them show ideas , and hire production companies to create shows. They hire directors and writers to work on the show, so they are basically employed by the broadcast company. Who is getting the short end of the stick? Well, the entire cast and crew is at risk of getting cancelled if the show is doing poorly. The broadcast company very rarely ever gets the short end of the stick as they are the top dog and can basically make the staff do whatever they want. But these companies that make changes in the script or story for various reasons often run into push back from the creative staff. "
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1usx8c | How was Cuba like before the Revolution? | Some people say it was doing pretty well by Latin American standards while others say it was a shithole and the brothel of the Americans. What's the truth? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1usx8c/how_was_cuba_like_before_the_revolution/ | {
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"Which Revolution? There have been several."
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1jpbm6 | texas is running out of lethal injections- how/why, can't they order/make more? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1jpbm6/eli5_texas_is_running_out_of_lethal_injections/ | {
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"Many companies are starting to refuse to sell drugs for executions. So they can't find anyone to order more from. (Drug manufacturing has huge startup costs, so it wouldn't make sense for Texas to start making their own.)",
"The pharmaceutical companies that make the drugs for lethal injections no longer are interested in continuing their production. Many see it as bad PR for the company as a whole or for some drugs that they sell since they can be used for legitimate medical purposes as well as in executions. Would you feel comfortable using a substance used in executions regardless of if your doctor ensured that it was ok at \"this level\"? That kind of association is bad for business. \n\nSome states are looking into hiring smaller firms to custom make the drugs for them. \n",
"Other people have given the gist of why they're running out, but they could easily 'make more' by changing their formulations... in theory. In practice it'd be a big hassle no doubt to try and work out legally that it's a sufficiently humane way to do it, sufficiently likely to kill everybody, etc.\n\nThere's nothing particularly special about the formulation used now, and there are plenty of drugs out there that can be very lethal but also have very valid uses and therefore are easy enough to find in a hospital. (Morphine for example.)",
"As the US constitution forbids cruel punishments, there are only a few drugs which may be used for lethal injections. The idea is that those drugs guarantee a „clean death”, which is, according to the Supreme Court, not a cruel or unusual punishment.\n\nThese drugs were chosen in the seventies, after the suspension of the death penalty. Quite a few of these drugs are obsolete for their original use by now, and so are no longer commercially viable to produce.\n\nOne of these drugs is only manufactured by a European company. European right sees capital punishment as unlawful, an infringement of the unalienable right to live. It is a serious crime to export substances or tools to countries that might used them to ~~murd~~ execute their citizen. Thus this European company no longer exports to the US.\n\nIt's noteworthy, however, that this law was not intended to prohibit exports to the US, and it is not tested before court whether it really would apply here."
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3p6dz0 | in baseball, why does the catcher call out pitches to the pitcher? what does the catcher know that the pitcher does not | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3p6dz0/eli5_in_baseball_why_does_the_catcher_call_out/ | {
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"The pitcher and the catcher both need to know the pitch. One of them has to call it out. The batter is looking directly at the pitcher, so it makes more sense for the catcher to call them out. The pitcher will then nod or shake his head to accept or reject the pitch suggestion.",
"The catcher needs to know the pitch so they know what is coming. That means there has to be some sort of communication, catcher to pitcher, or pitcher to catcher.\n\nHaving the catcher do it makes more sense, because the batter can't easily see it. The catcher also has a better view of the base runners, and can call pick offs and pitch outs.",
"There are a few parts to it. (1) The catcher needs to communicate with the pitcher so they both know whats coming. A curveball could mean a ball in the dirt so being prepared for that is very useful (2) The catcher has a better view of the field so he can alert the pitcher to keep certain base runners honest. (3) The batter cant see the pitches being called out by the catcher. (4) I think this is the most important one-- the catcher has the best idea of what the strike zone is and can align the pitcher to certain corners and spots to ensure accuracy. Plus they can talk to the umpire and help figure this one out since their both back their chilling together. (5) Note Most of the time coaches call pitches. That's the way it was when I played. When I got free reign it was rare. ",
"The other posts covered the primary reason, but one additional factor is that catchers at a higher levels of the sport can / do spend more to study the opponents, and their weaknesses at the plate. (And/or getting them relayed in from a coach). Pitchers have enough to worry about keeping their pitches accurate. ",
"Something not mentioned is how the catcher relays pitches from the coach to the pitcher. A guy I know who was a pitcher taken in the first round back in the 80s, but blew out his arm, said a bunch of coaches actually call every pitch for certain pitchers. He said it is more common than you think. ",
"High School and a lil bit of college catcher here. Me and the pitcher usually have a strategy set up for certain batters in the lineup and basically ill call the pitch and if he agrees hell nod so were on the same page as to whats coming. Also as a catcher, i sometimes took signs from the coach in the dugout to relay to the pitcher.",
"Explain like Im British?",
"Piggy backing off this what makes for a \"super star\" catcher? Like Buster Posey is supposed to be an amazing catcher in the league, what does he do that makes him so much better?"
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1dhw8m | What is the historical significance of the last legal trial by combat in France? | If you could also refer me to some sources about it that would be great! | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1dhw8m/what_is_the_historical_significance_of_the_last/ | {
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"meh, you really just have people doing the same, but with honor being the guiding principal rather than some kind of legal system.\n\n\"For French historians of the subject, the duel that stands at the boundary between the judicial duel and the later duels of honor was one that took place on July 10, 1547, between Guy Chabot, Baron de Jarnac, and Francois de Vivonne, Sieur de La Chataigneraye.\"\n\n\"Their duel is a judicial duel without its umpire, presiding authority, or official setting; it has broken loose from its proper legal and feudal moorings. The Duel of honor would quickly develop its own rules, often elaborate codes and ceremonies, but it never had the identities of the many combatants who engaged in it throughout its history.\"\n\n_URL_0_[1]\n\nRethinking Chivalry and Courtly Love by Jennifer G. Wollock\n\nHad to find an old post to dig that one up. "
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"http://books.google.com/books?id=2JvZquS-7W0C&pg=PA32&lpg=PA32&dq=ovid+chivalry&source=bl&ots=7Bh_dxmWUU&sig=Cl7EHG2COQv2iFuDp913V0QxbNw&hl=en&sa=X&ei=F9oZUZuLIOXRigLZu4Ew&ved=0CEcQ6AEwBA#v=onepage&q&f=false"
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8rmwib | If methane is so abundant why is it not used in homes and such like the gas we normally use that's so expensive to obtain? | [deleted] | askscience | https://www.reddit.com/r/askscience/comments/8rmwib/if_methane_is_so_abundant_why_is_it_not_used_in/ | {
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"Methane is the primary constituent of natural gas used to heat homes and hot water. If it's expensive in your area that may be due to transportation costs, or lack of local supply. Transporting natural gas can be problematic in the absence of extensive pipelines."
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2oacv5 | with oil prices plummeting, shouldn't gas prices be falling respectively? | Gas prices haven't budged considerably despite the significantly lower cost of crude... Is this just an old fashioned swindle?? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2oacv5/eli5_with_oil_prices_plummeting_shouldnt_gas/ | {
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"Where do you live? Gas is extremely low in the US right now (at 4 year low).",
"Has it not? My local station is at 2.24 a gallon, down from 2.99 just last month. Was 3.22 just two months ago. ",
"First off, crude oil prices dont correlate directly to refined good retail price.\nIt depends wildly on where you live, but here in Canada, crude price is only half the cost of gas at the pump. [There's taxes, cost of transport to the gas station, refining costs (refineries are expensive to build and run).](_URL_0_)\n\nSecond part, gas prices only go up rapidly and only go down slowly with eventual competition on price between retailers. I mean what else are you going to do? Not drive? Switch to peanut oil? Not likely for most of us.",
" > haven't budged considerably\n\nWow, the gas stations near you are *fucked up*, then. Gas is down more than 25% here, at a rough guess. That's not as much as oil has dropped, but there are fixed costs in refining gas, and it takes time for the lower cost of oil to work its way through the supply chain anyway.",
"Not sure where you live but gas prices in my town have dropped quite a bit. "
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vu5ow | Could there be an intelligent civilization in the ocean that we just haven't found yet? | As far as I know, most of the deep ocean is very poorly explored. Could there be a species with human-level intelligence down there that we haven't made contact with? | askscience | http://www.reddit.com/r/askscience/comments/vu5ow/could_there_be_an_intelligent_civilization_in_the/ | {
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"Deep ocean is mostly cold, empty and has little energy and nutrients (almost all of that falls from the surface). Brains consume lots of energy, if your food is sparsely distributed and there is very little of it, big brains don't make evolutionary sense. No matter how smart you are, your options are limited by environment. \n\nIf there would be intelligent species in the deep ocean, it would probably be like Eskimos. Small population trying to survive in demanding environment. If you want to build civilization and advanced culture, you need to concentrate many individuals on same place, have free time and specialization. Farming enabled humans to create civilization. I don't think it would be possible in the ocean. No sun, no energy. [Advanced civilizations consume lots of energy](_URL_0_)\n",
"It's not really fair to use a human standard like IQ to judge other animals, they will always disappoint. But if you look at a dolphins brain, they have the same kind of swollen look in their social lobes that we do in our frontal lobes. It's really quite remarkable when you think of how much information can be transmitted via sonar squeaks coupled with this brain power. Kinda like... All the talent we have building, creating and discovering, dolphins and other higher marine mammals have being social with each other. \nAnd then we put them in sea world all alone to deal with noise pollution, no wonder the original flipper killed herself :("
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6x4acw | why atoms feel bad when they don't have 8 or 4 electrons in their outer shell, so theytry to get hid of electrons if they're 1, 2 or 3, or try to get more if 5,6 or 7 ? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6x4acw/eli5_why_atoms_feel_bad_when_they_dont_have_8_or/ | {
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"So you've got an element with an incomplete outermost shell. Its greatest hope and desire is to have a complete outermost shell, by giving penny taking.\n\nSodium is so close to being perfect, it just got that one darn extra. Chlorine is so close too, it just needs one. They know which end they're closer too.\n\nCarbon? Carbon is really on the fence. Does it give four electrons away? Does it take four? Nothing sways it in either direction, because it's valence electrons are in the exact middle of the possible numbers of valence electrons.\n\nIf it were to take four, it'd take them from a metal, so you can get metal carbides, like calcium carbide. If it were to give four, it'd give them to a non-metal, but that's a covalent bond so it just shares instead.",
"Atoms don't really want a full shell, its just that the full shell is the maximum of bonding energy. When you consider an atom that has a single electron in its outer shell, and another one that has 1 less than is needed, those are completely fine by themselves. They might not be in the most stable electron configurations but if there is nothing to interact with they dont care. When you bring them together though, they need more energy in total to maintain their less than ideal states than they would if they were to share their electrons in a molecular orbital so there is potential energy waiting to be released and also end up with a more stable configuration.\n\nHow likely that is to happen at a given temperature depends on how big and attractive their respective positive nuclei are and also how many full shells they already have, as the higher energy shells are less attracted by the nuclei."
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3u2w9x | why do people of the uk oppose the investigatory powers bill (computer surveillance) with such zeal? (read text) | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3u2w9x/eli5_why_do_people_of_the_uk_oppose_the/ | {
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"text": [
"Because privacy. If you like being preemptively identified as a criminal, you can volunteer that information. If you trust your government with it. And they don't get hacked. And if no one evil gets elected.",
"A) ...until they decide that something you're into is wrong, or you jokingly set off a keyword monitor. \n\nB) This is bollocks. What they'll get is broad permission from the Home Secretary and abuse it. \n\nC) How much freedom are you willing to give up for your safety? And how much freedom do you think you can stand to lose before the terrorists have won? There's no real evidence that it will increase security or prevent terrorism and no evidence that there aren't better ways. \n\nD) They need a defendable cause and they need to obtain a warrant. In those cases there is nothing wrong with them searching your data - if they can show a need. What they *will actually* do is use it to dig for dirt as they have done so many times before. \n\nE) Watching what someone does in public is a lot different. They need to build a case and get permission for anything more than that, generally. \n\nF) Do you ever close your house/bedroom door? Do you lock the bathroom door? Do you own curtains? What are *you* trying to hide and why shouldn't you be investigated to find out why you are being so secretive and suspicious? \n\nThe right to personal privacy isn't something that needs to be justified, breaching it requires the justification. \n\nThere may be some use to the powers they're asking for but that is far from being proved and there has been enough historical abuse of police powers that people are right to feel nervous about being spied on."
]
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[],
[]
] | ||
3gjex4 | why do scam websites that claim to sell "a revolutionary product" all look the same? | I think we've all at one point when using the internet encountered these websites. They claim to sell an undiscovered way to get fast abs, or a new, better and "cheap" alternative to viagra or some other kind of bullshit. But the thing about these websites is, why do they all look the same?
I'm talking about big flashy titles and quotes, a video about the product that auto-plays the second you visit the website, webpages that go on for 100 paragraphs containing the same bullshit sales-pitch over and over again on why you should buy their product. I can't find an example website at the moment but my question is: why don't they make a professional looking website so people actually buy the whole story? I mean, whenever I see one of these website, as a young person who knows how the internet works, I immediately know that these sites are a scam. Maybe some older people will fall for this, but I know that the internet-savvy person won't. So why don't these people put a little more effort into these sites to make it look legit?
Edit: I just found an example website: _URL_0_ You even get a pop-up when trying to leave their site... But it perfectly illustrates the examples of the website lay-out I've given. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3gjex4/eli5_why_do_scam_websites_that_claim_to_sell_a/ | {
"a_id": [
"ctyp7c8"
],
"score": [
3
],
"text": [
"Because they work. Scam artists and lazy people see an idea that brings money for little work, and they emulate that idea. Why fix something that isnt broken, right? Similar idea to why there are a million different versions of Minecraft and Bejewelled. The people peddling these things aren't innovators. They don't desire to expand on previous formulas and improve the world. They just want quick cash, and the easiest way to do that is to do the exact same thing other people have done. "
]
} | [] | [
"http://makemoney-athome.com/"
] | [
[]
] | |
3pnur5 | how do fast chargers (like the one that comes with the galaxy s6) work? why don't we just use those for all phones/laptops/tablets? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3pnur5/eli5_how_do_fast_chargers_like_the_one_that_comes/ | {
"a_id": [
"cw7vodi"
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"score": [
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"text": [
"The charger that came with my S6 has two different output modes listed: 5V 2A and 9V 1.67A. The default voltage is 5V, in accordance with USB power standards; phones can request the higher voltage mode, which sends more power across the cable. If you do the math, the default mode is capable of about 10 watts, the higher power mode sends just over 15 watts. More power means faster charge time.\n\nHigher voltage is necessary as USB cables aren't rated for higher currents."
]
} | [] | [] | [
[]
] | ||
5s1w9c | what law guides the confessions in a r.catholic confessional?suppose a catholic priest decides to give data on a penitent to the cia?or the fbi puts its staff in the seminary? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5s1w9c/eli5what_law_guides_the_confessions_in_a/ | {
"a_id": [
"ddbteao",
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"text": [
"*Canon law*- the religious law of the Catholic Church (the Orthodox and Anglican churches have their own Canon law, too, I think)- provides for the immediate and automatic excommunication, which can only be lifted by the Pope, of any priest who reveals information obtained through confession.\n\nIn parallel to that, in the United States, there's a legal principle called *confessional privilege,* according to which priests (and officers of other religions with a role similar to priests) can't be forced to testify about what they know through confession or other private religious communications. The details of how this rule is applied are, unfortunately not ELI5 material: they're technical, and vary from state to state, because each state writes the Rules of Evidence for its own courts.\n\nAs for the last part of your question, *what if the government planted its own agent to pose as a priest,* well, all I can say is that there would be a spectacular legal fight about it that the government would almost certainly lose, either because of the First Amendment's establishment clause, or because of confessional privilege.",
"Ordinarily, if you have information that is relevant to a legal case, you can be compelled to provide that information. This is called a *subpoena* (suh-pee-na). But there are circumstances in which a person cannot be compelled to provide certain information. The most well-known is the right not to incriminate oneself — you cannot be compelled to provide information that could incriminate you. Invoking this right is often called “pleading the fifth”, after the Fifth Amendment which guarantees this right.\n\nBut there are other situations in which information could be deemed *privileged*. These situations are defined by law to preserve civil rights or to serve some other higher purpose:\n\n- *Priest-penitent* privilege prevents a court from compelling a member of the clergy to reveal information that was divulged under a religious guarantee of non-disclosure. The prime example is the Catholic sacrament of confession. To force a priest to break the seal of the confessional would violate both participants' freedom to practice their religion.\n- *Attorney-client* privilege protects conversations between a lawyer and their client. To force a lawyer to reveal information that their client divulged in confidence would compromise the client's right to due process.\n- *Physician-patient* privilege protects conversations between a doctor and patient. This is to guarantee that a patient can be totally honest with their doctor about drug use, criminal behavior, or embarrassing medical problems or personal habits without fear that these could be used against them.\n- *Marital* privilege protects private conversations between spouses.\n- *Executive* privilege protects confidential discussions between the President and their advisors. This is to guarantee that these discussions can be totally open and honest without any self-censorship.\n\nThese privileges all work differently and have different rules and exceptions. For example, married person may in many circumstances keep their spouse from testifying, even if the spouse wants to; however, when one spouse is suing the other, the privilege largely vanishes. Or, a doctor may be compelled to report that a patient intents to harm someone, even if this was confessed in confidence. Or, Nixon's attempt to invoke executive privilege to avoid handing over taped conversations was denied by the courts, and he was forced out of office when those conversations proved his guilt."
]
} | [] | [] | [
[],
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] | ||
3jso4l | why has pizza delivery in "30 minutes or less" become uncommon? | I've noticed when ordering pizza recently, even for carryout, I'm commonly told it will be 45 minutes or more. I just ordered online and my confirmation said the estimated delivery time is 55-65 minutes. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3jso4l/eli5_why_has_pizza_delivery_in_30_minutes_or_less/ | {
"a_id": [
"curxkhd"
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"score": [
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"text": [
"About 20 years ago, there was a multi-million dollar judgement against Domino's (who was most famous for the 30 minutes or less thing) when a woman was hit by a pizza delivery driver who was not operating the vehicle safely. This caused a lot of bad publicity for the \"fast pizza delivery\" deal, and as a result Domino's dropped it's \"30 minutes or free\" guarantee, and other pizza companies backed off delivery guarantees as well."
]
} | [] | [] | [
[]
] | |
666kfq | the news talking heads are freaking out about n. korea. what is different today vs the last 20+ years of threats from them? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/666kfq/eli5_the_news_talking_heads_are_freaking_out/ | {
"a_id": [
"dgg1tmy"
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"text": [
"This time there is a guy in charge who might actually take them seriously. Not because they are more serious then the last twenty years, but because the guy in charge doesnt know anything about how not seroius they have been for the last twenty years.\n\nAlso someone is desperate for a justifiable war. Any war. War time presidents are good right?"
]
} | [] | [] | [
[]
] | ||
177nun | gills | How do gills turn water into oxygen? How long does it take for the water to become usable oxygen? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/177nun/eli5_gills/ | {
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"Gills don't turn water into oxygen. Nor do they extract the oxygen atom from water molecules. They filter out oxygen that is dissolved in the water.\n\nGills are essentially areas extremely densely packed with blood vessels. The water is usually 'pumped' over the gills by the organism by various mechanisms and the oxygen diffuses across into the blood vessels.",
"They don't turn water into oxygen. They *extract dissolved oxygen* from water.\n\nThink about your lungs for a second. One entirely reasonable way to think about the air you breathe is to imagine that it's oxygen dissolved in nitrogen. (A chemist would disagree strongly with that, but for reasons that, while valid, don't actually apply here.) Your lungs extract the \"dissolved\" oxygen from the nitrogen around you.\n\nGills, similarly, extract dissolved oxygen from water. That's why aquariums — aquaria? — include a way to oxygenate the water, dissolving oxygen in it so the fish and other aquatic animals can breathe. Without that, it'd be like sticking you in an airtight room full of nitrogen gas. You'd *breathe* just fine — in the sense that you'd move the air in and out of your lungs — but because there's no oxygen dissolved in it, you'd quickly expire."
]
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[],
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zqg40 | Why is the 4th rover to land on Mars being heralded as such a historic achievement? | askscience | http://www.reddit.com/r/askscience/comments/zqg40/why_is_the_4th_rover_to_land_on_mars_being/ | {
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"To some extent, you are right that we have successfully landed on Mars before, even with rovers.\n\n[The size is a big factor of why this rover is different.](_URL_0_) This rover was so big our previous method of descent - which more or less amounted to wrap it in an airbag and hope it doesn't hit a pointy rock - wouldn't work any more. So, for the first time, a rover landed on Mars that was under controlled, powered descent. We used something called a skycrane: [here's a computer simulation of it.](_URL_3_)\n\nBut a large part of the fascination people have is the massive publicity drive that accompanied this landing. As NASA funding falls, many space exploration advocates and enthusiasts are spreading the word about just how awesome it can be. Curiosity was popularized and discussed more than Spirit and Opportunity ever were. \n\nIf you also think that space exploration is worth continuing, then you may be interested in a fairly popular campaign to double NASAs budget to one percent of the national budget. You can learn more at [_URL_2_](_URL_1_)",
"I refer you to the [Askscience Mars Curiosity Rover thread](_URL_0_) for a longer discussion and more Q & A.\n\nBut, quickly, why is this a big deal when we've landed rovers on Mars before? (Also, I am not sure that the media attention really is more compared to Spirit & Opportunity, the most recent previous mission, or even for the Viking landers in 1976.)\n\n(1) The landing site is a potential gold mine (metaphorically). This was the payoff the landing scheme (see point 3). This scheme allowed for a much more precise landing, which meat the ability to land in a scientifically especially interesting area (exposed rock that might reveal up to billions of years of Martian geological history). Past missions could not land with anything close to this precision, and therefore had to go to area that were flat and safe over a large region.\n\n(2) The rover is comparatively huge (nearly 1000 kg), and is bigger, faster, and better, from engineering and scientifc perspectives. More importantly, it has an array of scientific instrumentation of a sophistication never before deployed to another planet. Just one example: it has the abilitiy to fire a laser and do spectroscopy to determine the chemical composition of rocks from a distance, whereas previous rovers might have to take a full day to get to the rock, dust it off, and take a sample.\n\n(3) The landing scheme was extremely complicated, but the best solution they were able to design to bring a rover that size on Mars. The ability to execute this is a major engineering triumph, and represents, in my estimation, a real leap forward in our ability to land spacecraft on Mars. The multi-step process (atmospheric braking, parachute, thrusters, skycrane) is amazing, and opens up new possibilities for what we can explore in the future.\n\n\n\n"
]
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3i6e7c | the possibility/situation of a wwiii | I'm hearing some people say a WWIII is very likely to happen and that international laws in place are very weak/fragile and essentially useless... | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3i6e7c/eli5the_possibilitysituation_of_a_wwiii/ | {
"a_id": [
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"I wouldn't say that WWIII is VERY likely to happen, well not any time soon, but I guess people in 1913 didn't think anything was going to happen either.\n\nIn very short terms (so this doesn't become an essay) there are resource problems especially in energy production which unless we go renewable in someway will only get worse and could cause resource wars.\n\nISIS are not a threat globally (as soon as they become one the big guns will come out) but instability could lead to external countries seeking gains in the Middle East (much like Russia-Ukraine atm) which sparks a domino affect. \n\nIt is clear by the current events in the Ukraine that international law is pathetic. Sanctions? pfft, they didn't help with Iran and they haven't helped this either. But then again maybe it is better to let Russia eat the Crimea then start WWIII as would probably have to happen.\n\nOther countries to look out for North and South Korea - they are tetchy all the time. Israel - serious long term problems. Iran and America for too many reasons to explain."
]
} | [] | [] | [
[]
] | |
1sjr76 | what's the mess with south africa's capital cities? | I have noticed that South Africa appears to have more than one capital city - Pretoria, Bloemfontein, Cape Town (maybe even more?). What's the difference? Why is that? Please :) | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1sjr76/eli5_whats_the_mess_with_south_africas_capital/ | {
"a_id": [
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"text": [
"South Africa was created by unifying four colonies, and all of them wanted to host the capital. In Canada and Australia, which had similar situations, they solved the same problem by creating a new capital city. In South Africa they decided to split the government across multiple cities. The two biggest and most powerful colonies, the Transvaal and the Cape, got the two big branches of government - the executive in Pretoria and the legislature in Cape Town. The Orange Free State got the smaller judicial branch with the Appeals Court in Bloemfontein, while Natal got financial compensation.\n\nCalling Bloemfontein a capital is actually a bit silly now, because the Constitutional Court (in Johannesburg) which was created in 1994 is now superior to the Appeals Court in Bloemfontein."
]
} | [] | [] | [
[]
] | |
1o8j44 | Did the idea of blacks being inferior predate their heavy use as slaves in the americas, or did they arise because of it? | I am speaking of the views of Europeans and Americans. | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/1o8j44/did_the_idea_of_blacks_being_inferior_predate/ | {
"a_id": [
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"score": [
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"text": [
"It certainly predates their use as slaves in the Americas, because [medieval Islamic scholars also thought of them as inferior.](_URL_0_) But they also of course practiced slavery, so that may have been the cause."
]
} | [] | [] | [
[
"http://www.colorq.org/Articles/article.aspx?d=2002&x=arabviews"
]
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3i4hvi | Why was Asia Minor full of empty cities? | I am reading Xenophon's Anabasis, and as he describes Cryus' army marching East he feels the need to note that when they come to a town it is οἰκουμένη, that is "inhabited." This sounds to me like there must have been lots of empty cities that the army marched past, so that Xenophon felt like he needed to specifically say a town was inhabited.
Did something make people abandon lots of towns? Was he referring to ruins of earlier civilizations? Am I reading too much into this? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/3i4hvi/why_was_asia_minor_full_of_empty_cities/ | {
"a_id": [
"cudc50k"
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"text": [
"Hello!\n\nI'm looking at the _URL_0_ translation at http://www._URL_0_/files/1170/1170-h/1170-h.htm#link2H_4_0005\n\nspecifically \n\n > Crossing it, he marched through Phrygia a single stage, of eight parasangs, to Colossae, an inhabited city (4), prosperous and large.\n\nThere's a footnote that says \n > (4) Lit. \"inhabited,\" many of the cities of Asia being then as now\n deserted, but the suggestion is clearly at times \"thickly\n inhabited,\" \"populous.\"\n\nSo one conclusion is that it means **densely populated**.\n\n---------\n \nIn other cases, cities are **uninhabited** because they've been evacuated or abandoned. In the above linked section (bk I.ii), the city of Tarsus \n > \"had been deserted by its inhabitants, who had betaken themselves, with Syennesis, to a strong place on the hills.\"\n\n---------\n\nAnother is that inhabited means simply \"lived in [by X]\". As in, \"Dallas is inhabited by Texans.\" OR \"Weirdos inhabit Florida.\"\n\n > From this point Cyrus pursued his march, through Syria a single stage—five parasangs—to [Myriandus, a city inhabited by Phoenicians](http://www._URL_0_/files/1170/1170-h/1170-h.htm#link2H_4_0007), on the sea-coast."
]
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"gutenberg.org",
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"http://www.gutenberg.org/files/1170/1170-h/1170-h.htm#link2H_4_0005"
]
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13hywl | James Webb Space Telescope question. | Someone told me that this telescope, when deployed, will actually be able to observe exoplanets; not just their gravitational pull on stars, or dark spots, but it will be able to take images of planets in other solar systems. Is this true? I haven't been able to scrape up any information on this claim. | askscience | http://www.reddit.com/r/askscience/comments/13hywl/james_webb_space_telescope_question/ | {
"a_id": [
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"text": [
"We have already taken pictures of planets around other stars, most notably this star: _URL_0_ ",
" > The four science instruments will be contained within the Integrated Science Instrument Module or ISIM. This unit will house the four main instruments that will detect light from distant stars and galaxies, and planets orbiting other stars.\n\nSo, what NASA says is that it will detect light from planets orbiting other stars, which can give us a whole bunch of information. But not specifically take pretty up close photos. \n\n > Webb's instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range.\n\n_URL_0_\n"
]
} | [] | [] | [
[
"http://en.wikipedia.org/wiki/HR_8799"
],
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"http://www.jwst.nasa.gov/"
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19ccoy | four-dimensional space. what would it "look" like? | Not related to time as a fourth dimension, I can't really wrap my head around how four-dimensional space would work. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/19ccoy/eli5_fourdimensional_space_what_would_it_look_like/ | {
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"You're not going to be able to. There *aren't* four spacelike dimensions. In order for there to be four spacelike dimensions, it'd have to be possible for four lines to intersect at mutual right angles. That can't happen.\n\nIt's kind of like trying to construct a mental picture of an elephant which isn't an elephant. You can't do it, because such a thing cannot exist.\n\nYou can do *math* on abstract geometries that can't actually exist, but it makes no sense to try to visualize them except in cross-section.",
"Ever draw a picture of a cube on a flat surface, like a piece of paper or a whiteboard? Notice how it looks something like [this](_URL_0_), and now look how none of the angles that you've drawn are actually 90 degrees - some are larger, some are smaller, but none of the angles in your sketched cube are exactly 90 degrees on paper. This is odd, because if you held an actual, three dimensional cube in your hands, you'd see that in fact, *all* of the angles on it are 90 degrees. How come a cube distorts its shape when you draw it on a 2D surface?\n\nWell, it's because of something called \"projection\". We can \"project\" the image of a 3D object onto a 2D surface, but in doing so, we distort the object somewhat to create an artificial illusion of depth. In the same way, you could project the image of a 4D object into 3D space, but it wouldn't look quite right. It would be a loose approximation at best, and wouldn't stand up to scrutiny. This is because there aren't enough dimensions in your display medium to accurately represent the original object. \n\nSo, to answer your question, it would \"look\" wrong. ",
"A mathematician was asked how they imagine a four-dimensional space and they replied \"First, I imagine an n-dimensional space, then let n = 4\"",
"I'll let Carl Sagan answer. [He does this so much better than any of us could.](_URL_0_)"
]
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"http://i.imgur.com/CudAjtO.jpg"
],
[],
[
"http://www.youtube.com/watch?v=oHhaDORZq_8"
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bu0g3e | why does the enzyme catalase break down hydrogen peroxide? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/bu0g3e/eli5_why_does_the_enzyme_catalase_break_down/ | {
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"text": [
"It takes hydrogen peroxide and combines together to make oxygen and water! That's why your not supposed to but hydrogen peroxide on your cuts because the bacteria on your cut are already exposed to the air and use it to live and divide. If you put hydrogen peroxide on them, since they are aerobes, they effectively dilute it! That's why you see bubbles when you poor it on the skin, it's the oxygen! Also hydrogen peroxide acts as a mechanical cleaner of the skin so it can actually harm our skin by killing our fibroblast cells. Source: college medical microbiology"
]
} | [] | [] | [
[]
] | ||
12mxz3 | What was advertising like in ancient times? | What was advertisement like in major cities prior to the industrial revolution? I'm particularly interested in advertising in ancient history, although any time period before the 1800s would be interesting.
I remember reading about advertisements and political campaign posters being discovered in Pompeii. What were those advertisements like, and how much did they resemble advertisements of today? Have we ever mistaken simple advertisements for more cultural works of art?
On a related note, did celebrity culture exist? What sort of things would people become famous for (outside of being an Awesome Soldier). Did that extend into 'celebrity endorsements' of a sort? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/12mxz3/what_was_advertising_like_in_ancient_times/ | {
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"My high school ancient civilization professor told us that in ancient Greece, shopkeepers sometimes hired beautiful girls to dress up/pose as Aphrodite and various other goddesses to try and push their wares. \"Celebrity\" endorsement, in a sense.",
"Roman history major/Classicist here; **I**. During elections, candidates would give out plates of food (mostly fruit) with their name at the bottom. Ref. modern samplers. **II**. There were some forms of oral advertising during the gladiatorial matches and circus races. IIRC it was just simple stuff; Quintus' wine is the best - go buy some! ",
"Powerful romans would give out coins with there name/face on them to boost their public image. This also had the unintended consequence of creating inflation. ",
"I know your question is really trying to get at print culture, so forgive me ...\n\nThe main form of advertising in cities: Shouting.\n\nUp even into the later 19th century (for some trades), hawkers would have distinctive calls and songs to identify themselves. Similar to an ice-cream truck, you would hear certain types of hawkers as they came down your street. The cacophony of hawkers' cries was considered one of the quintessential attributes of city life. The songs and cries would often pitch and describe their product. Ballad-sellers, of course, would actually sing the songs that they were selling. You might hear a song that you liked as you passed by and then stop and buy the lyrics.\n\n",
"If you look at some of the images of Pompeii you will find faded advertisements and political graffiti. Also in the stone there are carvings of penises and footprints to lead the customer to a local whore house. Pompeii was destroyed in 70 CE. ",
"We actually still have examples of advertising/graffiti from Pompeii:\n\n_URL_0_",
"- Roman pottery producers used stamps to \"brand\" their wares\n- Greek Olympic winners were paid to endorse the wares of merchants on markets",
"There was a strong celebrity culture, especially around Chariot racing and Gladiators. \n\nThe worlds highest paid athlete (adjusted for inflation) [was from ancient Rome.](_URL_0_)",
"Well you did have the town crier, but if your REALLY want to advertise\n\n_URL_0_\n\nsee the stone Dong? Its literally pointing the way to brothel. So lets say some things never change...they just might get slightly more tasteful\n\nI have seen handwritten notes as well, im sure word of mouth meant a lot then as well.\n\n"
]
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8p27mj | what is the purpose of all the different coloured lines on school gym floors? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8p27mj/eli5_what_is_the_purpose_of_all_the_different/ | {
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"Normally they are used for different sports, so you may have a basketball court outlined with red lines, 2 tennis/ volleyball courts outlined with green, and maybe something else like a soccer field or floor hockey set up. Each set of coloured lines represents it's own sport.",
"They indicate different playing fields.\n\nRed could be basketball court.\n\nBlue could be badminton.\n\nThere's not much space in a school and it's a way to maximize on space!\n\n\nRewrote as my first answer was deemed too simple. ",
"There are different lines for marking the playing areas for different sports and the colours are used to tell them apart. You might have black lines for a five-a-side football pitch with red lines on top splitting the area up into several badminton courts instead, for example.",
"Each color is for a different sport/activity. Blue lines might be for basketball, and white lines might be for volleyball. The main rule is that all lines that are the same color are for the same sport/activity. If blue lines are for basketball then ALL blue lines are for basketball. ",
"They are lines for different sports that may be played on that floor -- basketball, volleyball, etc. Typically different sports will be marked in different colors -- so basketball might be black, while volleyball is white, and badminton might be blue. In addition to different sports, there may also be different markings of same sport due to court size differences by age bracket, organization (ie. high school basketball court different from NCAA)"
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31h4ti | how are radio stations and websites allowed to report the locations of speed cameras? | I notice that people slow down in these areas, and as soon as they're clear they put their foot down. To me, it defeats the purpose of speed cameras completely. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/31h4ti/eli5_how_are_radio_stations_and_websites_allowed/ | {
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"Because it actually supports public safety by causing drivers to slow down in those areas.",
"The same way they are allowed to report the locations of accidents and general traffic conditions so that people can plan their trips.",
"The vast majority of speed cameras are a matter of public record. Knowledge of their locations also helps public safety as people will comply with laws more often when they know they are on camera. ",
"If you're talking about the US, don't you guys have some kind of constitution that covers this situation? This kind of thing isn't going to be affected by the same kind of limitation as, for example, your right to yell \"fire\" in a crowded room."
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suy16 | Forgotten technologies | Hello AskHistorians, I was wondering if any of you could recommend a book about "modern" technologies which were actually pioneered by the ancients and subsequently forgotten for thousands of years before they were rediscovered. Suitable for a layman, if possible. Thanks! | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/suy16/forgotten_technologies/ | {
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"Well, I'm no historian nor I have a book recomendation, but I heard that when the Roman Empire fell, the ability to use concrete was lost for another 1000 years.",
"although completely not academic, there is a good [cracked article](_URL_0_) that discusses this topic. It talks about steam engine, misplacing a giant gold Buddha statue, the cure for scurvy, methods to stop bleeding, evidence for a 1500 mile hedge in India, and how to create concrete. "
]
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[],
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639c2p | if we know that movies and shows are fake, then why so we still get teary-eyed or scared during certain scenes? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/639c2p/eli5_if_we_know_that_movies_and_shows_are_fake/ | {
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"There's a concept called \"suspension of disbelief.\" So we know it's not real, but if the movie is good, it can bypass our disbelief (suspend it, if you will) so that it sits on our mental back burner.\n\nBut then you could see the wire that is making the person fly through the air, and that ruins your suspension of disbelief.",
"One: because humans are storytelling creatures. Two: because humans possess empathy.\n\nFirstly, humans are evolutionarily accustomed to receiving important, even life-saving info, from other humans in the form of a story. Before the bard told us about the hero's fight with the werewolf, bob was telling us about how he got away from a bear. Stories are part of our past, thus we pay attention to ones that have a lot of emotional power.\n\nSecondly, humans can empathize with characters, because after suspension of disbelief the brain starts to think it's just watching an actual event unfold. We can put ourselves in characters' places and thus feel their emotions.",
"The human brain cannot distinguish between reality and that which is vividly imagined. This is why visualization works so well for rehearsal or skill practice. Ever made a mistake and thought someone wronged you? You react to your beliefs as if they are reality. Movies are often so well made that they act like our vivid imagination. Ever seen a poorly made movie? It takes you out of the 'vivid imagination' realm and then you just laugh, cringe, or turn it off. \n\nAnd the empathy thing"
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98vnlq | - why do potatoes get so hot? what makes the temperature inside a potato keep heat so high? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/98vnlq/eli5_why_do_potatoes_get_so_hot_what_makes_the/ | {
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"Potatoes are (according to Google) 80% water. Water takes more energy to heat (per gram per degree) than almost any other chemical known to man, and the ones that require more energy aren't edible. \n\nNow, in things like soup water cools down fairly quickly because it moves around a lot, letting hot water reach the surface for rapid cooling, but since the water in potatoes is trapped inside cells it can't do so. Instead, the potato has to slowly give off heat at the surface, allowing heat from deeper within to slowly make its way out. \n\nIn short, potatoes don't get any hotter than the water around them, it's just that they're a lot slower to give the heat away again. You can test this by grilling a whole tomato and trying to eat it without cutting it open and letting it cool for a while (but don't, you will burn yourself and be unable to taste what you're eating properly for days). "
]
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wc0oi | Whenever I see a spider indoors that isn't poisonous, I don't kill it in hope that it will eat other insects, is this a logical thing to do? | askscience | http://www.reddit.com/r/askscience/comments/wc0oi/whenever_i_see_a_spider_indoors_that_isnt/ | {
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"_URL_0_\n\nAll spiders are venomous, not all poisonous.",
"What the hell did I miss here?\n"
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"http://www.ipm.iastate.edu/ipm/hortnews/2008/12-10/spiderbites.html"
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9uaens | where do the winds go? | After being generated, where do winds stop (other than hitting a barrier)? What makes them stop? What generates them?
Do they behave like individual ‘streaks of air’ or is it like one whole bunch of air that, like when hurricane winds hit a barrier like a series of mountains, gets weak against something? Or if some of that ‘streak of wind’ didn’t hit the barrier, will it continue to cover more distance until it hits another barrier?
I’m not sure if they are generally created due to differences in atmospheric pressure and temperature. I wanna know more. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9uaens/eli5_where_do_the_winds_go/ | {
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"Air moves due to a pressure difference. High pressure moves towards lower pressure. Wind isn’t an entity that is trying to go somewhere, there are no streaks of air that act independently, the air just wants to even out its pressure. So on a calm still day you’re in the middle of a patch of fairly even pressure and the air molecules have no great impetus to go anywhere. However squeeze that air between two areas of different pressure and suddenly you have higher winds as the molecules are being pushed together and there’s a pressure gradient for them to flow down (in a manner of speaking)."
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4soqdg | How long has China known about the existence of the United States? | [deleted] | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/4soqdg/how_long_has_china_known_about_the_existence_of/ | {
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"[1784 at the latest](_URL_0_), but the Chinese government and relevant merchants would have probably been aware of the American Revolution as it was occurring. The Colonies were a major market for Chinese goods (notably tea) through the British East India Company.\n\nAs for how they took the Revolution, they just weren't very interested. Qing China ruled roughly a quarter of the world's population and a disproportionate amount of its wealth. Foreign affairs would have been a relatively minor matter until the First Opium War (1844) and the US was a minor player in the region until the Philippine-American war (1899).\n\n*Fateful Ties: A History of America's Preoccupation with China* by Gordon H. Chang"
]
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"https://history.state.gov/countries/china"
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23rzl7 | how come i can do two hours of cardio non-stop in a fitness class type situation but i can't run outside for more than ten minutes without stopping? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/23rzl7/eli5_how_come_i_can_do_two_hours_of_cardio/ | {
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"You're probably not working out as hard as you think you are in your fitness class.",
"It is definitely harder to run outside than it is to run (or do cardio) inside, because when you're outside you are not on flat ground and your muscles makes up for the different impacts you'll feel. Try running on sand and you'll see what I mean.\n\nAlso, in a class you have other people around that you are doing the exercise with which makes it more fun and you'll notice your exhaustion less. Plus you don't want to be the only person in class stopping from doing the exercise so you endure.\n\nThis is anecdotal.",
"psychological reason = you're motivated by others in your fitness class\n\nphysical reason = the routines in your fitness class vary the impact on your body; running jolts your body in the same way stride after stride\n\n\nps. why do you stop running? are you winded or do your legs hurt?...\n\n",
"Running is actually quite different from the types of exercise you do in a cardio class. Running works your joints and muscles in a different way because you're not only exerting force to propel yourself forward but also absorbing the shock of your feet hitting the pavement/track, stabilizing your core and keeping your balance, hitting wind resistance, etc. It's just more difficult than the types of in-place cardio stuff we tend to do indoors."
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1eiiam | why is radio still widely used for entertainment and communication? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1eiiam/eli5_why_is_radio_still_widely_used_for/ | {
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"It's well understood and reliable as a technology, propagates at the speed of light (since it **is** light), doesn't require much physical infrastructure to transmit or receive, and there's really nothing to replace it in cars.",
"As opposed to what?\n\nRadio is probably the only form of entertainment you can enjoy while driving, taking a bath, closing your eyes to go to sleep, mowing the lawn, and many other things. It's not going to go away any time soon!\n\nIt is going to change, though. Digital radio is gradually becoming more popular in the UK, I don't know about other places. I can switch my tv to my favourite radio station - and I often do, because I get better reception from my cable provider than through a radio aerial. This wouldn't have been possible a few years ago.",
"because sometimes your eyes have to be somewhere else. also, you dont need a tv to listen to music",
"Because nothing can replace it as of yet.\n\nYou don't have to pay for radio, unlike television.\nIt's accessible, it's cheap and it's extremely portable."
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8m5yb3 | why do car alarms have that one sound? | Is there any reason behind that weird consecutive combination of sounds car alarms make?
Does it symbolise or mean anything or is it just because of the simplicity of devices that create it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8m5yb3/eli5_why_do_car_alarms_have_that_one_sound/ | {
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"It's a collection of all the alarm sounds that were available for various things before that. What it tells *me* is that someone got an aftermarket alarm for their car that isn't particularly well designed/managed, and that I'm extremely unlikely to bother checking to see who set it off.\n\nThe OEM alarms that just use the car horn are almost as bad.\n\nThe GOOD ones are the ones that chirp a warning when movement is detected, and require persistent disturbance before they go off for exactly 1 minute with a shrill single warbling siren. After that, a tracking service is notified.\n\nThat's the only decent alarm system I've seen out there, but it's significantly more expensive than the useless ones most people install.",
"That sequence is actually from the ability to customize to just one of the available sounds. There were/are connections that can be cut inside to eliminate the unwanted sounds, playing only the connected sound(s).\n\nThe installation instructions told the dealers how to configure this option, but most dealers didn't explain that to the customers because of the additional time for deciding and the configuring what the customer had selected. \n\nI speak in the past tense, because I assume that those are a thing of the past now. ",
"Something to keep in mind: the vast majority of aftermarket alarms are made by the same company: Directed. Viper, Clifford, Python, Avitol, AutoMate are just a few of their brands. They are the Luxottica of aftermarket auto security. \n\nThey share a lot of technology and designs between their brands so that’s why that classic alarm sound seems so common. That setting is the default alarm sound for most of these systems. Most can be customized for one of those tones or just f’it play them all. ",
"My guess is that it is to alert everyone around that a car maybe is being robbed. If everyone had different car alarms, it would be hard for people to differentiate. "
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37hagl | What is the theory behind the "432Hz" music idea? What is the difference between 432 and 440Hz music? | What is the theory behind the "432Hz" music idea? What is the difference between 432 and 440Hz music? I work in a studio and so can't get my head around music being based on one frequency? Can someone explain this from scratch? I know frequencies etc but not this 432 theory | askscience | http://www.reddit.com/r/askscience/comments/37hagl/what_is_the_theory_behind_the_432hz_music_idea/ | {
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"It's just a convention. Hundreds of years ago, different orchestras played in different pitches, but after a while they started agreeing to play in one pitch, and that happened to be A = 440 Hz. There are some classical musicians who prefer 442 or 444 because they find that it sounds a bit sharper, but I don't know if anyone without perfect pitch could tell the difference or prefer one alternative.",
"this frequency is assigned to the note A. All other notes are tuned according to it. It was widely used in baroque music, especially vocal music - because of tradition, and perhaps lower base frequency means the top C for the mezzo soprano is also lower, and therefore the highest notes require less effort from the singer. Also it seems to better fit to natural voice scale of many famous singers who prefer it - because the 'distances' between sounds are a bit smaller.\n\nThe original Baroque pitch is even lower and is about 415 Hz. To this day most serious conductors when playing baroque music tune their orchestras to 430 Hz as a standard. \n\nCheck [this](_URL_0_) small recent thread on /r/opera for more."
]
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24ev67 | How come I can only see stars and other small lights in my peripheral vision? | If I look directly, they seem to disappear | askscience | http://www.reddit.com/r/askscience/comments/24ev67/how_come_i_can_only_see_stars_and_other_small/ | {
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"Without going into the specifics of the physiology, the eye has two receptors. Cones are designed to interpret color. They are concentrated near the center of the eye. Rods are the other receptor and are distributed all over the eye, but have a slightly higher density in a ring around the center. (As I recall. Someone feel free to correct me if I have forgotten the proper distribution.)\n\nThe important take away here is that cones are less sensitive to light than rods. So the center of your eye is not going to be able to pick up dim things as well as the ring around the center. So if you look off center from an object you are letting more light fall on to the rods than the cones. So if it is something faint, you can see it better. But you pay the price of not being able to focus on it well.\n\nThis technique is called averted vision [1](_URL_0_) by Astronomers. It lets you locate dim sources. A great example is to use it on the Pleiades (for the Northern Hemisphere folks) so you can see all the sisters properly. :)",
"The periphery of the [retina](_URL_0_) is more sensitive to dim light than the center. The center has more cones, which give you color vision but are not as good at detecting light as rods. There are more rods on the periphery.\n"
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5lzsa8 | Can a light intermittently blink on and off so quickly that we see it as always off? | askscience | https://www.reddit.com/r/askscience/comments/5lzsa8/can_a_light_intermittently_blink_on_and_off_so/ | {
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"you could drive an LED with fast electronics and produce nanosecond blinks. what's more important is the time interval between two light flashes. \n\ni think if the time interval was the same as the on time you'd always see the light (as permanently on). but with electronics you can do anything you want, so you could swith the LED on for a nanosecond and leave it off for a second. then you would not see anything of the blink. ",
"I think this has more to do with the response time of the photoreceptors in the eye. Once a receptor is stimulated it will signal the brain for a certain amount of time. If the frequency of flash is shorter than this time, you will see it as always on. With a sufficiently fast camera you will always see both the on and off cycles of the flash. ",
"Think of it this way. Imagine pouring water into a bucket. Then imagine that every hour someone visits the bucket, puts it on a scale, writes down how much the bucket weighs, then pours out the bucket.\n\nHow quickly could you add water to the bucket to cause the reading of the weight of water for that hour to be zero? We see that this question doesn't entirely make sense, no matter how *fast* you add water to the bucket, it'll still end up contained inside of it and able to be measured. The only thing that matters is whether or not the total amount of water added per hour is so small it can't be measured on the scale.\n\nThe situation is the same with an eye or a camera. If you flash a light extremely quickly what matters isn't just the duration of the light pulse but the total amount of light involved. An incredibly bright light source blinked very rapidly would still be visible, a sufficiently dim light source would not be visible, however, and the main effect of blinking the light source for a very short period would be to reduce the average luminosity below the visible level."
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akxyll | The historical source behind German children tales | I've heard that the source behind German children tales such as Hansel and Gretel with the motif of children stranded in the forest is a great famine in the 14th century leading to many parents abandoning their children in the forest. Is there any truth in this claim? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/akxyll/the_historical_source_behind_german_children_tales/ | {
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"In an [earlier post](_URL_1_) I pointed out the following:\n > Many on this subreddit (and elsewhere) mistakenly believe that \"most myths and legends are either based off some semblance of truth or attempt to convey some message...\" The belief that this is true can be regarded as a bit of modern folklore. Like many beliefs, it is often accepted as widely accepted and completely valid, but there is not evidence that at least the latter is true.\n\n > Folklorists Alan Dundes and Jan Brundvand independently attempted to \"chase down\" the original incident that inspired various modern \"urban legends.\" They consistently failed. Where these stories came from is extremely difficult to fathom, even though most clearly are modern and one would think with all the tools available in a modern age, that it would be possible to track down to their point of origin - whether as a real incident or as a fabrication. Given those failed modern attempts, it is even more problematic to track down what an older story was \"based on.\" In other words, we really need to accept, simply, that it was a good story that people told and retold, and where it came from is not likely to be known with any certainty.\n\n > That doesn't prevent people from attempting to find the \"real\" thing that was behind an older story. These efforts are always speculative. Some speculation is better than others and can be reasonably persuasive, but we cannot lose sight of the fact that in attempting to connect the dots between \"this story\" and this or that historic event/character is filled with speculation. It is a fun parlor game, but it is not anything that can be objectively accepted as fact. Good stories are, simply, just that, and we are all subject to a good story - and we like to repeat them.\n\nThat’s the context that causes me to be extremely skeptical about anyone who claims to know what is behind a given motif. The assertion that the motif in the folktale “Hansel and Gretel” provides a direct link to an earlier famine is pure speculation, it is unlikely, and it cannot be proven.\n\nThe folktale that appears in the Grimm collection is part of a large complex of folktales and their variants, which folklorists describe as [“ATU” Tale Type 327](_URL_0_). With the wide distribution and variation of these narratives, it appears that this tale type is old – and likely to predate the 14th century.\n\nUther, Hans-Jörg, The Types of International Folktales (Parts I–III) (Helsinki: FF Communications No. 284, 285, and 286, 2011).\n"
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1ii9a0 | [Earth Sciences] Why Is It So Cold High In The Sky? | If warm air rises, and being higher makes you closer to the Sun, why is it so cold up in the Himalayas or higher in the atmosphere? | askscience | http://www.reddit.com/r/askscience/comments/1ii9a0/earth_sciences_why_is_it_so_cold_high_in_the_sky/ | {
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"There's a good answer to that question [here](_URL_0_) - even phrased with the same premise of hot air rising.\n\nThe main reason is that most of the Sun's radiation passes through the atmosphere and warms the ground and surrounding air. If you were to somehow capture a fixed mass of warm, ground air and lift it high into the atmosphere, it would expand due to the lower pressure, and cool (as shown in ideal gas laws). Another way of thinking of it is that hot air can rise, but in doing so, thermal energy is converted into gravitational potential energy.\n\nIt doesn't matter that it's closer to the Sun at high altitudes, because the Sun is very far away, so a few hundred thousand feet make no difference. In fact, the eccentricity of Earth's orbit makes the Sun's distance vary through the year much more than this (but don't confuse this as the reason for seasons, which is actually a result of the angle in which sunlight strikes a given area)."
]
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5u068h | what is the purpose of the us marine corps? | what do they actually do that doesn't fall under the other branches' specialty? we have the army, specializing in ground war; the navy, specializing in water war; and the air force, specializing in air war. why do we have the marines? what do they even do? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5u068h/eli5_what_is_the_purpose_of_the_us_marine_corps/ | {
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"They are for warfare at the boundary between ground and water:\nThey are used for amphibious landings, since ships have a hard time coming ashore and the army tanks can't really swim :)\n\nSame as paratroopers are for warfare at the boundary between air and ground.\n\nOnce they have a decent beachhead, the army comes in to take the fight further inland",
"Historically, marines were ground forces which operated from a naval base. They would deploy from naval vessels which allowed for surprise attacks, fast deployment and fast withdrawal, and the ability to stage ground operations far from land bases (ie overseas war). In fact, the first war the US engaged in (after the war for Independence) was the First Barbary War in which the marine corps invaded Tripoli in Northern Africa.\n\nOvertime, the mission of each branch of the military has evolved along with each branch's specialties. The marine corps is still nominally used to project US military presence abroad, deploying from naval ships, and using fast-strike tactics. They are still a part of the Navy, although the Commandant of the Marine Corps sits on the Joint Chiefs of Staff."
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3y38yl | How much of the traditional story of the birth of Jesus is accepted as historicaly accurate? | I had trouble blieving that I couldn't find this question in a search, but it kept returning 'search failed'.
I overheard a discussion last night about the nativity. The topic was things that are commonly accepted but aren't true. A couple of examples being that Joseph and Mary likely stayed with relatives rather than at an inn, and that the three wise men were actually kings who visited some years later.
I also have read where the entire story was likely created in order to fulfill some earlier prophesies about the messiah.
I'm interested in what is accepted by historians as likely true based on evidence. Is there any?
EDIT: holy guacamole, my first front page. Thanks for all the interesting answers and discussion. | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/3y38yl/how_much_of_the_traditional_story_of_the_birth_of/ | {
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"There are two nativity stories in the New Testament, one in Matthew and one in Luke. Neither story is believed to have any historicity at all. The two stories are not even compatible with each other. They are set ten years apart with different, contradictory details and no real overlap.\n\nIn the view of mainstream scholarship, the Nativity stories were both independently invented by their authors as a means of getting Jesus born in Bethlehem in order to fit expectations and counter the perceived problem that he was from Galilee.\n\nThere are a number of details in each story which are either demonstrably ahistorical or highly implausible. Some problems with Luke, for example, include the fact that Augustus never ordered a census of the world, nobody ever had to travel to their ancestral towns to register for any Roman census and the census of Quirinius in 6-7 CE did not apply to Galilee and would not have applied to Joseph. Problems with Matthew are Herod killing all the babies in Bethlehem (almost certainly never happened), the obviously mythological nature of the star and the magi, the angels and flight to Egypt, etc.\n\nAs I said above, the stories also contradict each other. Matthew has Mary and Joseph starting out living in a house in Bethlehem, then has them flee to Egypt and then decide to relocate to Galilee only after they see that Herod's son, Archelaeus, has become Tetrarch of Judea. Luke has them starting out in Nazareth, only going to Bethlehem for the census, then going right back to Nazareth after presenting Jesus at the Temple. Their genealogies contradict. The census of Quirinius didn't happen until ten years after Herod died. Luke has no Magi, slaughter of innocents or flight to Egypt, Matthew has no census, no inn, no shepherds in the fields or singing angels. If you read the two stories together, you will see that they are not two different versions of the same story, but two completely different stories.\n\nMatthew was trying to draw mythological parallels of Jesus to Moses. Luke was trying to ground Jesus' birth in some kind of pseudo-historical context. Neither story is believed to be historical in any degree at all. It is generally believed by critical scholars that Jesus was born in Galilee, that this was seen as a problem because the Messiah was expected to be born in the same town that David was born, and the nativity stories were invented as independent attempts to solve that problem.\n\nThe definitive book on this is probably Raymond Brown's *Birth of the Messiah,* but these same main points are reiterated in pretty much any academic assessment you would find. Crossan's *Historical Jesus* is another one that really goes into this in detail.",
"Hello everyone, \n\nA friend of mine mentioned this discussion to me. Having briefly read over the discussion, I believe he is cherubim45 in this conversation. I created this reddit account so I could add my brief contribution to this discussion (btw, how cool is it that the username \"ntscholar\" wasn't taken yet?).\n\nFirst, a bit about me, I am a New Testament scholar and my academic focus is the use of Jewish symbolism and theology in the Pauline epistles, including Hebrews, which many scholars doubt was actually written by Paul. I did my graduate studies at a state school known for its religious studies program. I won't say more than this for two reasons: 1. I prefer to keep my life private and 2. one should weigh historical arguments not on the basis of who is saying it, but on the strength of the arguments and evidence provided.\n\nMy answer to the original question will unfold in two parts. First, I will highlight a bit about what exactly it is that historians do and don't do (or should and shouldn't do), and thus what historians may rightly conclude from assessing artifact and manuscript evidence. Second, I will explain how New Testament historians approach the Gospels and the Epistles of Paul. Third, I will discuss what \"mainstream scholarship\" means in the field of New Testament Studies. Finally, in light of these first two points, I will provide my answer to the original question.\n\nAs one surveys the history of history, she discovers that the discipline as practiced is much more complex than merely assessing the information available and reaching a clear conclusion. The historian must (or should) attempt to place herself in the shoes of the individual(s) who made or wrote the artifact. This involves asking questions such as what certain words, symbols, and entire stories meant to the groups in which they were used. It is also important that a historian not posit claims or conclusions beyond what the evidence justifies. Unfortunately, public demand for sensational \"history\" that is new and interesting, or \"history\" that bolsters already held beliefs sometimes sometimes leads historians to do just this. Additionally, historians as all human beings are influenced by the ideological trends of their eras and regions. This is why Marxist history (a historical method that emphasizes social class and economic constraints) saw an increase in the wake of the rise of political Marxism. Everyone holds ideological beliefs, but for the historian, if unmentioned or unchecked, these presuppositions can deceive the untrained reader. For instance, if the Marxist historian brings to his study the presupposition that historical outcomes are primarily the result of social and economic factors, this might prevent her from seeing that the primary agent of change in a certain event may have been ideological or environmental.\n\nI bring all this to light because New Testament scholars too are subjects of their environment, and thus what is important when assessing the arguments being offered by New Testament historians is not the majority opinion, since this often changes as ideological trends come and go, but the actual strength of an argument in light of the ideological presuppositions that are shaping it. Revolutions in historical thought happen all the time not only due to ideological shifts, but the discovery of new evidence. \n\nWhen a New Testament historian approaches the Gospels or the Epistles she asks (or, once again, should ask) several key questions. What is the genre? Why was this text written? What is the provenance of the text (Who, where, and when is the text from?)? Because the New Testament originated almost two millenia ago, it has been challenging at best and impossible at worst to provide answers to these questions. Nevertheless, New Testament historians have offered many interesting theories, varying in degree of persuasiveness. It is important to distinguish between theories supported by material evidence and sound logic and theories lacking one or both of these qualifiers.\n\nThe term \"mainstream scholarship\" is problematic for several reasons. First, history has become so specialized that \"mainstream scholarship\" on an issue might consist of the writings of only two people. Second, as mentioned previously, trends within these circles of specialization are constantly experiencing revolutions as a result of ideological changes or new discoveries. Finally, it is difficult to know what exactly one means by \"mainstream scholarship.\" For instance, some might exclude works published by seminaries even though most and some of the best New Testament scholarship comes out of these seminaries. In my estimation, throwing around the term \"mainstream scholarship\" risks being a fallacious appeal to majority that might not even exist at all. This isn't to say that what the majority of scholars accept on an issue is unimportant, but rather that it shouldn't be a point of conclusion. One ought to find out what the scholarly consensus is, how and why they have reached this consensus, and if there are problems with it. This is a major aspect of how historical discourse unfolds. \n\nFinally, the original inquirer asks \"How much of the traditional story of the birth of Jesus is accepted as historically accurate?\" I brought up the question of genre earlier and it is relevant here. The nativity stories, while they may have historical value, were not written as history, at least not as we understand the historical genre. Keep this in mind as I continue. The original inquirer's question can be assessed by dividing up the different propositions in the nativity accounts of Matthew and Luke and assessing 1) whether it is a question for the historical discipline, and 2) what evidence and consensus is available. I should state again, though, that given how far removed we are from the recorded events, it is difficult to provide a historical assessment of these propositions. Nevertheless, here is an assessment of probability:\n\n\n\n\n"
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3bvnce | why do pretty much all take-out coffee cups (like starbucks, etc.) say "do not microwave" on them? what would happen if i heated up my coffee in that cup? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3bvnce/eli5_why_do_pretty_much_all_takeout_coffee_cups/ | {
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"You're also potentially introducing chemicals into your coffee by heating the treated plastic and paper up. If your coffee is soaking into the paper, then it's just as likely something else escaped.",
"The paper take-out cups have a layer of wax on the inside. It's what makes the cup waterproof so it doesn't get soggy while holding a liquid. As you might imagine, heating in a microwave can melt this wax. Now you have wax in your drink, and a soggy and potentially dangerous cup full of hot liquid.\n\nStyrofoam coffee cups simply melt in a microwave. I hope it's obvious why this isn't a good thing.\n\nFinally, it's a legal thing. Cups aren't dangerous, microwaving liquids inside until they are way too hot is the only reasonable way to hurt someone or something. By telling you not to do it (and controlling the temperature of liquids going in there on their end) they can prevent quite a few lawsuits."
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di7l9h | why can we "think" along to songs in different languages, but we can't sing along to them aloud? | Even without music playing, I am able to seemingly perfectly recreate the vocals and phonetics to any song I'm familiar with in my head, even if the song is in a language I don't speak.
Granted: I wouldn't understand what I'm saying in terms of the linguistics, but shouldn't I be able to "pronounce" along to a song if I technically know how it sounds? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/di7l9h/eli5_why_can_we_think_along_to_songs_in_different/ | {
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"It's because singing is done by a different part of the brain than speech, it's also why stutterers can often sing just fine. The part that does the singing isn't verbally minded, so it just cares for the sounds it needs to make (as it sees your voice as a musical instrument).",
"Sound \"recognition\" and language comprehension are separate abilities in the brain. Think about the sounds birds, dogs, cats etc make: we can clearly differentiate the tone and rhythm of the sounds, and scientists have shown that they use different sounds to express different ideas and emotions, and we can even mimic the sounds ourselves, but it does not mean that we understand what the animal is expressing or are able to create new expressions with those sounds that the animal would understand in the way we intend.",
"There is also the technical aspect of singing. \n\nI can hear Pavarotti’s voice in my head, but I can’t physically sing the notes with the same speed, fluidity, volume, range, musicality etc.\n\nIt’s similar to drawing where you can imagine vivid shapes but physically recreating them can be impossible without a lot of practice and skill development."
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itzbe | Would a diamond break under enough water pressure? | askscience | http://www.reddit.com/r/askscience/comments/itzbe/would_a_diamond_break_under_enough_water_pressure/ | {
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"Yes, but whether or not that pressure is readily attainable or if observation at that pressure is possible is another question.",
"Pressure is pressure, no matter what medium is used to achieve it. ",
"Yes. Actually, you can break a diamond just by dropping it (or something on it) at exactly the right angle.\n\nAll diamonds are subject to fracturing along certain axis - this is how diamonds are first cut from their roughs. An experienced cutter can examine a rough and determine exactly the right angle to cleave the diamond on. It doesn't take but a simple stroke to split the diamond along that axis.\n\nEdit: Here, found you this... _URL_0_\n",
"If you define 'break' in the sense that it cracks or fractures, then no.\n\nIf you put a piece of diamond in a liquid-filled box and pressurised the box, the diamond will not break. This is because liquid pressure exerts force equally in all directions, so the side facing left will be compressed right, and the right-facing surface will be compressed left.\n\nOverall, there will be no overall force acting on the diamond. The effect of hydrostatic pressure on the solid is forcing the atoms/molecules closer together. Perhaps at very very high pressures something might 'break' at the atomic or subatomic scale, but I'm not familiar with this area.\n\nOf course, you can USE water pressure inside a hydraulic piston to push a cutting tool to cut the diamond, but that's cheating.\n\n\nSide topic: If you have graphite (pencil lead) and put it under great pressure, it WILL change phase into diamond. See phase diagram here:\n_URL_0_"
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7kblgp | haven't rockets always been reusable? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7kblgp/eli5_havent_rockets_always_been_reusable/ | {
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"They *crash* land in the ocean and are obliterated on impact. Much of it sinks.\n\nTheoretically you could fish it up, piece the shattered husk back together, and reuse it, but it's cheaper and safer to build a new one.",
"You’re thinking of the Space Shuttle booster rockets. Those are the *only* rockets (or at least the only common ones) that were reusable in that way. For the most part, rockets are not built with parachutes to slow their descent or the robustness to survive a landing in salt water (which, among other things, is very corrosive). They just crash into the ground or into the ocean (the people launching them do know where they’ll crash and can make sure that they won’t go into an inhabited area).",
"Nope, they've almost always been disposable. They fly appart and crash land in the ocean or float around in space.\n\nElements of the space shuttle were reusable but that accounts for a very small fraction of total rocket flights and was revolutionary in its own right. "
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dk0mfd | how can there be so much variation within the same species? | How come there are so much physical, chemical, and anatomical differences among humans but yet they are still considered of the same species? Are we just considering all humans to be of the same species for political reasons or is there something more behind it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/dk0mfd/eli5_how_can_there_be_so_much_variation_within/ | {
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"A species is usually defined as being able to interbreed however there are a few exception being animals such as lions and tigers. Also the physical look doesn’t matter as much as the genetic makeup",
"Genetically speaking humans have fairly small diversity compared to related species such as chimps or orangoutans. But we are adapted to seeing differences between each other. So we look amazingly different *to us*. A chimp would say we all look and smell the same.\n\nHowever, we are by definition the same species because every human group can have fertile children with each other. There is no biological reproductive barrier even between the most far flung people, just distance. Millennia of travel, trade and conquests have brought people from all over the globe in touch, and thus this has been thoroughly tested.\n\nSo that's got nothing to do with politics. True, political views for a long time insisted on playing up divisions between populations and dividing them into races, but biologically speaking those classifications have been found to be obsolete nonsense. They still retain some popularity with non scientists with particular political agendas.\n\n\nSource: I am an evolutionary biologist",
"Species have a biological definition - every human individual (non sterile) can mate with any other of the opposite sex and produce fertile offspring - of the same species. The genetic relatedness of humans is ridiculously low; humans outside of Africa have less genetic diversity than populations between themselves in Sub-Saharan Africa; and yet nucleotide diversity (the average portion of nucleotides different between two individuals) is 0.1-0.4%. For comparison, corn is about 20 times more genetically diverse than humans, and yet it is still all the same species."
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3jsl2i | how do companies like blue moon create beer with different alcoholic content to meet state standards yet maintain consistent flavor? | I live in Oklahoma were beer has to have less alcoholic content than regular beer. So Blue Moon beer has 3.2% alcoholic content in Oklahoma, but normally it contains 5.4%. How does Blue moon change their alcoholic content without changing the flavor of the beer.? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3jsl2i/eli5_how_do_companies_like_blue_moon_create_beer/ | {
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" > Available in cans, bottles and kegs, Blue Moon has 5.4% alcohol by volume.[5] In Oklahoma, Minnesota, Colorado and Utah, the alcohol content of all Blue Moon beers bought in grocery or convenience stores is 3.2% alcohol by weight (approximately 4.0% alcohol by volume).\n\n^ above from wikipedia\n\nThe 5.4 and 3.2 are in different systems.\n\nBlue moon goes from 5.4% to 4% alcohol by volume, or from about 3.9% alcohol by weight to 3.2 % alcohol by weight.\n\nSo it's really actually changing very little. It does affect the taste slightly, but usually not enough to really notice unless it was a very alcoholic beer. The taste is much more dominated by other factors at that level.\n\nif you had a 12 oz beer, the difference in the amount of alcohol you get is 0.168 fluid ounces\n\nin other words, If you took a normal can of beer and the reduced alcohol content can of beer, the different between them is one tenth of a normal small shotglass - pouring that much alcohol in would make them equal again."
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pp088 | Do we have any proof of evolution in humans in the last 2000-3000 years? No matter how insignificant it may be.. | askscience | http://www.reddit.com/r/askscience/comments/pp088/do_we_have_any_proof_of_evolution_in_humans_in/ | {
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"Just to point out - most species are not noticeably changed within the fossil record for periods of millions of years (in some cases tens or perhaps even [hundreds of millions](_URL_0_), which itself is incredible considering life only emerged out of the oceans less than 500 million years ago). While there are certainly differences between us and ancient man, you'll have a job pulling apart how much of that is genetic from the much larger picture which is due to lifestyle and dietary change.",
"in the last 100-200 years sickle cell anaemia happened in africa, granting those affected immunity to malaria",
"_URL_0_\n\nMilk tolerance.",
"(LAYMAN)\n\nLactose tolerance is a commonly cited example of recent human evolution. It's a little outside your date range.\n\n_URL_0_",
"New Scientist 2 April 2011\n\nEvolution in the fast lane.\n\nFore tribe of Papua New Guinea ate their deceased relatives and developed kuru, a degenerative brain disease (like mad cow disease). It killed many except the descendants of someone born about 200 years ago that had an unusual mutation in the prion protein that prevented the disease. If ritual cannibalism had not been stopped in the 1950's the genes would have spread to the majority of the tribal population.\n\n3000 years ago the Tibetans diverged from the Han population of China and evolved genes for higher red blood oxygen carrying capacity. ",
"Reduced brain size.\n\n_URL_0_",
"Human skin colour, but was going about 6-10K years ago. \n \nPathogen selective pressures is more recent and has likely been changing the distribution of HLA subtype distributions in the population. I seem to recall that it is thought that the black death selected against certain HLA subtypes rather heavily and that was about 600 years ago.\n\nBeta-thalassemia is the most famous example (as alcoholicbacon pointed out).\n\nLactase persistence in the last 7.5-10K years\n",
"Evolution related, although its kinda going in the wrong direction. \n\nThere's a handful of communities that were established from just a few individuals, such as the Amish and Church of Ladder Day Saints [EDIT: communities* within the Fundamentalist* Church of JC of Latter* Day Saints] . So they have relatively little genetic variation and have distinct occurrences of certain genetic disorders. \n\n_URL_0_\n\nEDIT: Corrections Appreciated :p",
"[Asian alcohol flush syndrome](_URL_1_)\n\nand fyi this is probably stuff that happened outside of the 2000-3000 years : _URL_0_",
"These will thoroughly answer your question:\n\n_URL_0_\n\n_URL_3_\n\n_URL_1_\n\n\nAlso, something easier to read: _URL_2_",
"[Ability to process milk after infancy](_URL_1_)\n[Immune system evolution](_URL_0_)\n\nAlso life expectancy in both males and females, as well as average height.\nEDIT: Formatting...",
"That's the wrong question to be asking of science. The right question is \"Do we have any *evidence* of evolution in the last 2000-3000 years?\"",
"HIV immunity.\n\n\"According to biologists at the\nUniversity of Liverpool the\nplagues of the Middle Ages have made 10 percent of Europeans HIV resistant.\"",
"Palmaris longus is a forearm muscle which is absent in approx 15% of the human population. \n_URL_0_",
"I have a question: with all of the advances we have in medical science, is it possible that we are actually slowing our own evolution? When we live longer lives, and the drugs that we take make us healthier...doesn't that kind of effect natural selection? ",
"Skin Color! For some reason it took me until the middle of college to fully appreciate that as we moved further away from the equator, our skin color lightened in order to make the most of the decreased amount of sunlight.\n\n(from wikipedia)\n\n1. From ~1.2 million years ago to less than 100,000 years ago, the ancestors of all people alive were from Africans which had dark skin.\n\n2. As populations began to migrate, the evolutionary constraint keeping skin dark decreased proportionally to the distance North a population migrated, resulting in a range of skin tones within northern populations.\n\n3. At some point, northern populations experienced positive selection for lighter skin due to the increased production of vitamin D from sunlight and the genes for darker skin disappeared from these populations.\n",
"The Black Death affected human evolution. The Black Death killed more people without the CCR5-Delta32 mutation than with, so now many more of us have the mutation than did before. This mutation also confers some protection again AIDS.\n\n_URL_0_",
"Also [Alcohol Tolerance](_URL_0_)",
"As mentioned several times here, the evolution of hemoglobin is a great example. The divergence of the \"globin\" proteins throughout evolutionary history (not just in humans) is a neat topic if you ever get curious.\n\nAnother one is clotting disorders. Basically, because we are so good at killing each other over our whole history, individuals who can clot better have a better chance of surviving a wound and living long enough to have kids. ",
"Yes. There's a group of indigenous people around Nepal who have evolved to be able to function normally in the relatively low level of oxygen they have available at such high altitude. This is apparently an aptitude that's unavailable to first generation settlers of the area.",
"in parts of africa there is a link between sickle cell anaemia and malaria. those who carry or have sickle cell anaemia are immune to malaria, but are likely to die anyway. those who carry live the longest so they are more likely to reproduce then those who can suffer from malaria. that is basically why sickle cell is so populous, because those with it live longer then without. ",
"The much higher presence of sickle-cell anemia in malaria-prone countries. Being heterzygous (i.e. carrying one of the two chromosomes required for recessive gene expression) for sickle cell anemia helps the body fight malaria, so regions with a history of malaria susceptibility (West Africa, the Mediterranean) have a much higher incidence of sickle cell anemia.",
"There's also the classical example of (I think) sub-Saharan Africans having a much higher rate of sickle cell anemia due to the fact that it helps prevent malaria related deaths. ",
"The fact our faces are increasingly unable to accommodate our third molars (wisdom teeth) is evolution in action. There are several possible reasons for our oral cavity decreasing in size over the past 10,000-20,000 years or so (I realize it's a bit past your range, but since it's an ongoing process, I felt it counted), but I think this theory from Noreen von Cramon-Taubadel is probably the most recent publication and points to dietary changes due to humans transitioning from hunter-gatherers to agriculturalists as a primary contributor.\n\n_URL_1_\n\nHere is a link to an Arstechnica article summarizing and citing the PNAS journal article in case you have no direct access to it:\n\n_URL_0_",
"I think it was in the BBC Horizon episode on human evolution that I saw a bit on Nepalese Sherpas. In their high altitude environment the conditions are so extreme that high hemoglobin levels are very strongly selected for. In other words, in the past, basically almost everybody died young if they had hemoglobin content in the blood below a certain level, so only the people with excessive amounts of hemoglobin reproduced and so nowadays, native Sherpas only have extreme hemoglobin levels. I think they compare their levels to levels of recent immigrants (as in, only a few generations) to rule out non-genetic factors. Furthermore, they look at descendants that don't live in the Himalayas anymore and they still have high hemoglobin levels.\nDisclaimers: I am only a physicist. And I am only remembering a documentary, so I may have mis-remembered some detail.",
"Many adaptations and changes to the human species have been observed but many are theoretical concepts in the context of evolution. Human vestigiality is a good example of how when the body has something with no function we start to see a decrease in the prominence of that phenotype. The higher instances of people being born with less or no wisdom teeth is a good example.",
"Eyelid differences in Asians developed as a result of migration north during the ice age; their distinctive eyelid shape is the result of a layer of fat which helps to protect their eyes in extremely cold weather. Can't find a source at the moment but will post one later if I get a chance. \n\nI also remember reading their population's black hair and brown eyes are the result of previous events of population bottlenecks. Also, they have a different kind of earwax and if I recall longer tendons in their legs. \n\nDisclaimer: I love Asians and don't intend this to be offensive or anything! ",
"Yes. According to Wikipedia: [lengthening of the reproductive period, reduction in blood pressure, cholesterol and blood glucose](_URL_0_) are all manifestations of genetic adaptions that humans have experienced as a result of living in urban and agrarian societies. \n \nYou can also look a disease resistance - when \"modern\" man came to North America, the microbes he brought alone were enough to wipe out a good portion of the native people. At the same time, winter in New England, which Native Americans had been surviving for hundreds of years (in a relatively primitive manner), nearly killed off European settlements within the first decades. ",
"Sure. We have plenty of vestigial body parts, meaning they have lost their original function, but we still have them. These include, the appendix, wisdom teeth, and canine teeth, just to name a few.\n\nA main reason for human's most recent evolutionary changes is the difference in the food we eat. Modern day, our food is much more processed, easier to get, to eat/chew, and to process.\n\nDoesn't really make us better, just different. \n\n_URL_0_",
"Blue Eyed people -\n\n\"ScienceDaily (Jan. 30, 2008) — New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.\"\n\nOne of the common mistakes of Creationism versus Evolution, is the typical dictionary definition of the word - evolution:\nWikipedia Dictionary\nev·o·lu·tion/ˌevəˈlo͞oSHən/\nNoun:\t\n1. The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the...\n2. The gradual development of something, esp. from a simple to a more complex form.\n\nCreationism incorrectly focuses on the second definiton, while biologic evolution is more correctly defined like this: \n\n\"In fact, evolution can be precisely defined as any change in the frequency of alleles within a gene pool from one generation to the next.\"\n- Helena Curtis and N. Sue Barnes, Biology, 5th ed. 1989 Worth Publishers, p.974 \n\nFor further details regarding biological evolution:\n_URL_0_\n\n",
"More humans are becoming tolerant to lactose: _URL_0_\n\nCall me old fashioned, but milk gives me flatulence.",
"_URL_0_\nA significant fraction of northern europeans are resistant to HIV infections due to a gene which inhibits the ability of the virus to infect white blood cells. The higher prevalence of this gene in the European population is thought to be due to it having a similar effect against Bubonic Plague during the Black Death. If you didn't have the mutation 700 years ago, you were much more likely to die of the plague, and not to breed/have children. If you had it, you lived and passed the gene on. ",
"It is interesting to imagine whether one of our hominid ancestors could, for example, drive a car, given the correct training. Is the major differentiating factor between us and our recent ancestors simply culturally transmitted behaviour? In the most part, yes. However, evolution has significantly altered the human genome in the last 2000-3000 years, and, in fact, there's even evidence that human evolution has sped up in the last 1000 years.\n\nFirst, as the top commenter has noted, human lactase tolerance is the 'go-to' example for recent human evolution. All mammals have the ability to metabolise milk at a young age. However, there is no selective pressure to be able to digest milk later in life as it is not usually available. In fact, genes for adult lactose intolerance may serve to facilitate the process of weaning. However, the development of dairy farming in human populations is believed to be responsible for the rapid spread of adult lactose tolerance in the last 9,000 years. While ancient DNA extracted from early Neolithic humans demonstrates no lactose tolerance, the trait is frequent in modern northern Europeans and pastoralist populations from Africa and the Middle East. However, the trait is absent elsewhere. Interestingly, in cultures with traditions for consuming fermented milk products, containing lower levels of lactose, adult lactose tolerance is at intermediate levels in the population. Similarly, dietary responses are overrepresented in recent genetic developments. For example, starch consumption is a feature of agricultural and pastoral societies. Individuals from population with high starch diets have, on average, more copies of a gene known as AMY1 than those with traditionally low-starch diets. Higher AMY1 copy numbers are thought to improve the digestion of starchy foods and buffer against the fitness reducing effects of intestinal disease.\n\nIt has been suggested that recent selection has shaped somewhere between “a few hundred and a couple of thousand” regions in the human genome. Such recent evolutionary change may in many cases be linked to cultural developments. While some of these examples may later be shown to be false positives, statistical analysis does reveal that there are some areas of the genome that are “overrepresented in recent evolutionary change”. For example, 28 out of the 56 human heat-shock genes exhibit recent change, as do many genes associated with brain development. Brain development genes are thought to be essential to human cultural practices such as recognition, cooperation and language. The Forkhead box P2 (FOXP2) gene appears to be crucial in language skills, and may therefore have evolved in response to burgeoning human culture and the advantages conferred by advanced communication skills. Other genes affecting brain development (such as ASPM and MCPH1) also show signs of natural selection and marked geographic structure. Additionally, they “co-vary with linguistic tone”: the use of voice pitch to convey lexical or grammatical distinctions.\n\nAnother example is given by evolution in response to human pathogens (some have argued that this is the primary selective pressure behind all evolution). . For example, it has been hypothesised that yam cultivation may have led to the spread of the “sickle-cell” allele. The removal of trees necessary to grow yams led to large pools of standing water; providing breeding grounds for malaria-carrying mosquitoes. Consequently, there is a higher selection pressure on the HbS ‘sickle-cell’ gene, as the heterozygous condition affords protection against malaria. Interestingly, evidence indicates that the standing water created in modern Asian tyre factories may also be having the same effect in other human populations. Meanwhile, the cultural development of human diets, particularly the ability to cook food, also precipitated genetic changes. For example, the deletion of the MYH16 gene in humans led to a massive reduction in the size of the jaw muscle. Such a development in the jaw may also have been a cause/effect of human language development. Additionally, traits for enamel thickness as well as those affecting the digestive tract may have been caused by the human cultural propensity to cook food. \n\n\nIn conclusion, human cultural evolution far outstrips genetic evolution. We are poorly adapted to modern environmental pressures, as evidenced by the increasing obesity epidemic (Diamond), breast cancer rates among women (Silove), drug abuse (Pani), but most of these discrepencies are dealt with through behavioural modifications. However, where selective pressure is strong enough (i.e. a certain trait corresponds with greater reproductive success) genetic evolution will occur.\n\nA controversial and not-widely accepted example of this is the increase intelligence evidenced in Jewish populations. \n* Ashkenazi Jews have unusually high incidences of many diseases, most of which are extremely detrimental to fitness, many even causing death in their homozygous form, as indicated by the table on the following page. However, it has been suggested that this is a side effect of “the unique demography and sociology of Ashkenazim in medieval Europe select[ing] for intelligence” (Cochran). Cochran postulates that Ashkenazi literacy, economic specialisation and reproductive isolation led to a social environment in which there was a high fitness payoff to intelligence, especially verbal and mathematical intelligence. (_URL_0_). Around the fourteenth century, the pattern of social organisation among Jewish populations required literacy while strongly discouraging intermarriage. In the middle of the fourteenth century, about 85% of the Jewis population were “independent owners of business enterprises” (Weinryb 1972). In such a community, intelligence led to economic success which in turn led to reproductive success. Ashkenazi Jews consequently have high levels of verbal and mathematical ability, scoring 0.75 to 1 standard deviations above the general European average in IQ tests, corresponding to IQs of 112-115, the highest average IQ of any ethnic group (Cochran). \nHowever, Cochran suggests that this selective pressure also caused a corresponding increase in many of the above disorders. In some cases, this may have been to simple linkage. On the other hand, many of the neurological disorders may in fact be pleiotropic effects of the same genes that increased intelligence. Genes that increase neuron development and linkage in gestation and childhood may also cause diseases such as Tay-sachs in later life. This is similar to the way in which calcium deposition is beneficial in the short-term, as it strengthens bones, but detrimental in the long-term as it builds up in arteries. Similarly, the BRCA1 gene, though associated with increased cancer risks in later life, is also expressed by embryonic and adult neural stem cells, and is involved in cell proliferation. As the long-term disadvantages of some of the diseases mentioned above do not manifest themselves until later in life, there would have been no selective pressure against them. However, many of the above diseases do strongly reduce reproductive fitness, even causing death, in their homozygous form. Nevertheless, even a very small heterozygote advantage, such as increased intelligence, would allow these alleles to remain in the Ashkenazi population. For example, there is “strong but indirect evidence” that Gaucher disease does indeed increase IQ. Similarly, sickle cell anaemia, which is very detrimental in its homozygous form, nevertheless persists in malarial populations due to the fitness advantage it confers in its heterozygote form. However, once this environment is reduced, or when life expectancy is extended, individuals with sickle-cell anaemia or Tay-sachs disease, or Gaucher disease, are considered to be maladapted. Cochran’s theory on Ashkenazi intelligence remains controversial, and others suggest that the intelligence and high incidence of certain diseases is merely the result of a genetic bottleneck. However, gene frequencies at a large number of other autosomal loci indicate that, if there was a bottleneck, then the subsequent gene flow from Europeans must have been very large. Large enough, in fact, to eliminate any other genetic evidence of a bottleneck.\n\n\nI realise this is an extremely long post. But it's something I feel very passionately about. I will try and upload links to my sources as I find them in my history (firefox crashed as I was halfway through this post) Read sources for info on haemochromatosis, the 'slavery hypothesis, and slective benefits of arthritis\n\n\nSources: Meals, Roy. \"Paradoxical Frequencies of Recessive Disorders in Ashkenazic Jews.\" Journal of Chronic Diseases (1971). \nMobley, James. \"Is rheumatoid arthritis a consequence of natural selection for enhanced tuberculosis resistance?\" Medical Hypotheses (2004): 839-843.\nSullivan, Roger. \"Revealing the paradox of drug reward in human evolution.\" Proceedings of the Royal Society (2008).\nDiamond, Jared. \"The Double Puzzle of Diabetes.\" Nature (2003).\n\n\n**tl:dr**. Humans evolve. Use as your go-to explanation for evolution\n\n",
"I've had a similar question.\n\nCould 'Nowadays Humans' and humans, of say, 100,000+ years ago, or a time prior to a 'population bottleneck', produce viable offspring?\n\nI only wonder, because, low level of genetic variation with humans wasn't always prevalent (unless it was?). Today, humans are all near clones of each other, with having less than 0.1 genetic variation, while chimps can have 2%.\n\nWhile I understand humans having 99% similar DNA as chimps is not the same thing having a 2% genetic variation within a species, it's always made me curious.\n",
"The theme of the October 2010 issue of the magazine *Scientific American* was \"Human Evolution is Not Over.\"\n\nOne article from this issue, [Culture Speeds Up Evolution](_URL_1_), states:\n\n\"'We found very many human genes undergoing selection, says anthropologist Gregory Cochran of the University of Utah, a member of the team that analyzed the 3.9 million DNA sequences showing the most variation. 'Most are very recent, so much so that **the rate of human evolution over the past few thousand years** is far greater than it has been over the past few million years.'\"\n\nAnother really interesting article from this issue gives a concrete example of recent human evolution. [How We Are Evolving](_URL_0_) talks about a gene variant identified in Tibetians, but was rare in other populations. The Tibetan plateau, 14,000 ft above sea level, provides an environment with low oxygen content. The gene variant was found to adjust red blood cell production in order to help the Tibetans survive their harsh surroundings. \"*One study estimated that the beneficial variant spread to high frequency within the past 3,000 years...*\"",
"Imperfect example: [Sickle cell disease](_URL_0_).\n\nSickle cell disease is caused by a recessive genetic variant (ie, you need 2 copies to get SCD). If you have only 1 copy, you are healthy, and additionally are more resistant to malaria. In places where malaria is common, the fitness risk of malaria is often worse than the fitness risk of losing 1/4 of your offspring to SCD. (which, btw, we should really do something about. Malaria, I mean.)\n\nLook at the prevalence of sickle-cell disease in west Africans (around 4%), and the prevalence in African Americans (~0.25%). One theory is that because African Americans aren't getting malaria, the SCD gene is getting selected out pretty fast.\n\nNot a perfect example. African Americans don't have 100% west African ancestry. There's a lot of genetic admixture there, which could account for the difference. But the lack of malaria is probably at least a part of the reason, and this would have taken place over the last 300 years.",
"Wouldn't lactose percistance count as a bit of evolution? That our (swedish) ancestors have been drinking milk for a longer time and created a lactase percistance. \n\n_URL_0_",
"Quick question:\nIs it possible to find out exactly when a mutation first, mutated? It seems like everyone is saying it first \"mutated\" when allele frequencies were large enough to be noticed a la population genetics. I do suppose that's when it became useful though.",
"How much of a factor is natural selection these days?",
"What about people who are now born without wisdom teeth? Just curious if this counts. Everyone in my family had them (and we're consequently pulled), but I wasn't born with them. ",
"milk tolerance, average height increase, changing frequencies of disease (look at malaria in relation to sickle cell anemia)",
"Worse eyesight. People (myself included) who are practically blind would have died a thousand years ago before the introduction of glasses. Since those with bad eye sight are living to reproduce, the trait has grown in the population.",
"Ok, no one is very likely to read this, but I know some things! \n\nBiologically, evolution doesn't happen over 2000-3000 years, sorry. However, our minds have been evolving for the lack of biological speed. We don't have wings, so we invented aircraft, we can't travel over the ground like a cheetah, so we made roads, bridges, and cars. \n\nTl;dr, our evolution has become external.",
"Tibetans have evolved to maintain normal hemoglobin levels even at high altitude. this has happened in the last 3000 years\n\n_URL_0_",
"Blue eye color is thought to have come from a single ancestor. The genes involved were so strongly sexually selected for that it spread to a large portion of the population - but estimated around 6000 years ago _URL_0_",
"The existence of your appendix, the tail bone, plica membrane and the one we all relate to is the bodies reaction to get goose bumps or the raising of hair on the skin. Go on any medical page or just a search and they all come back to evolution of the human body.",
"Dentist here. We've seen it in teeth. More and more people are born without 3rd molars (wisdom teeth), 2 premolars and/or laterals.",
"Human wisdom teeth",
"Hadn't really thought about it... but I don't know if this counts as just breeding or evolution per say, but I think of the people of African decent here in the USA whose ancestors were brought over as slaves. \n\nTo quote Jimmy the Greek:\nThe black is a better athlete to begin with because he's been bred to be that way — because of his high thighs and big thighs that goes up into his back, and they can jump higher and run faster because of their bigger thighs. This goes back all the way to the Civil War when during the slave trading, the owner — the slave owner would breed his big black to his big woman so that he could have a big black kid.\n\nWouldn't this be the start of a particular evolutionary change? Look at black people here in America vs most Africans. Most black people in america are decendants of those slaves, who were chosen based on size and strength. One only has to look to the NBA and the NFL to see the results. \n\nDisclaimer: This post is not intended, nor should be taken as racism. Just an observation. ",
"The Moken people of SE Asia, and their ability to see underwater: _URL_0_\n\n* I think to understand human evolution, you need a bit of a background in genetics, as well as a bit of an understanding of man's migration throughout the Earth (started in Africa, went to SE Asia and to Middle East, Europe). And Evolution is easier to see an \"isolated groups\", rather than the globalized persons imo.\n\n*man's migration: _URL_1_?",
"According to my dentist, wisdom teeth are starting to disappear in humans with each progressive generation.",
"Check out [Lactase persistence](_URL_0_)\n\nIt may have already been said, but anyone who can digest milk into adulthood has evolved from our ancestral state, which was in able to do so. \n\n\"Lactase persistence is the continued activity of the enzyme lactase in adulthood. Since lactase's only function is the digestion of lactose in milk, in most mammals species the activity of the enzyme is dramatically reduced after weaning.[1] However in some human populations lactase persistence has recently evolved[2] as an adaptation to the consumption of non-human milk and dairy products beyond infancy.\"\n\n\"Lactase expression persistence is largely due to natural selection. Natural selection is a component of evolution by which a trait affects the chances of the survival of organisms, and consequently, the trait becomes more prevalent in the population over time. Especially in Europe, the genetic variant -13,910*T has been strongly associated with lactase persistence and has been favored by natural selection in the past 10,000 years. Indeed, the consumption of lactose has been proven to benefit humans through adulthood.\"",
"\"Evolution is any change across successive generations in the heritable characteristics of biological populations\"\n\nAny change: doesn't have to be good. \n\nThere's an indication that myopia (nearsightedness) is increasing [in just the past few decades](_URL_0_). So, yes, evolution is happening. \n\nEvolution in the commonly-used form of \"getting faster/stronger/smarter/better?\" I don't know about that. It's hard to seperate out the effect of genes from other things like nutrition.\n\nI'd also guess that in the future, some genes will be artificially selected against as genetic screening and sequencing becomes more prevalent. Even if we don't get to gene therapy, we'll be able to tell if you're a carrier for cystic fibrosis, and that might influence you to adopt, for example.",
"I remember reading this recently. it is the most recent \"example\" of human evolution. It shows that Tibetans evolved to survive in climates with thinner air.\n\n_URL_0_",
"Not in the last 3000 years and not specific to humans, but the unnecessarily long path of the left recurrent laryngeal nerve is evidence of natural selection acting on an imperfect form/basis. This nerve is then suseptible to damage, especially with an enlarged aorta, tumors, and various lung diseases.\n\nSource: I have a degree in biology and am a medical student.",
"[There's some speculation that the Nepalese sherpa people have several genetic adaptations to live at great height](_URL_0_)\n\nSickle cell disease is genetic and leads to shortened life expectancy. Carrying a single sickle cell gene also leads to increased resistance and ability to handle malaria. [In a great example of natural selection human populations in area's where malaria is (or was historically) common can have a much higher than normal percentage of people carrying the gene. Sometimes up to a third of the population.](_URL_1_)\n\nEvolution doesn't necesarily mean that there's humans who are beyond the rest of us. Humanity is full of local populations carrying unique genetic traits simply because they conferred some kind of advantage or selective bias in their locality.\n\nIncidentally evolution isn't measured in years but generations. Traits are only passed down to the next generation. 3000 years isn't that many generations for humans. ",
"I have no wisdom teeth. I don't know how significant that is, but considering most people need them removed, it's a fairly handy adaptation.\n\nSource: my mouth.",
"It is extremely common for several amish populations to have Polydactily due to the Founder effect (Drift, in this case, is what is causing the evolutionary change). Notice that this is a good example for neutral evolutionary change which highlights that evolutionary change is, at its essence, nondirectional. The PBS article can be found [here](_URL_0_), and the scientific papers can be found in any number of places.\n\nSource: _URL_1_ College coursework",
"Laymen here, vote me down if I'm wrong.\n\nIt is my understanding that if we compared the DNA sequence of a lineage of humans starting from 3000 years ago up to the present day, we would see subtle changes in the genetic code that grow more and more different as time went on.\n\nIe: the DNA of the 3000 year old human would be slightly different than a 2750 year old human, while the DNA of a modern human would show more differences when compared to the 3000 year old human.\n\nWhether or not these subtle genetic changes manifest themselves in traits that we can readily identify (hair color, height, skeletal structure) or not is not the point -- evolution, by definition, is happening so long as the genetic code is changing from one generation to the next."
]
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"http://en.wikipedia.org/wiki/Lactase_persistence"
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"http://en.wikipedia.org/wiki/Lactase_persistence#Evolutionary_history"
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"http://discovermagazine.com/2010/sep/25-modern-humans-smart-why-brain-shrinking"
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[]... | ||
1sjvbe | what is a religion and why are there so many that exist? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1sjvbe/what_is_a_religion_and_why_are_there_so_many_that/ | {
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"According to Wikipedia, \"Religion is an organized collection of beliefs, cultural systems, and world views that relate humanity to an order of existence\"\n\nIn general, as humanity has grown out of the muck, stories such as oral traditions, mythos, legends, etc. have been an integral part of culture. In some cases, those traditions can become something more than just story, and take on a significance in the culture that is a way for a group of people to understand and interpret the happenings of life and death.\n\nFor instance, lets say we have a small village, of which a great warrior named Ug. Ug goes off and defends the village from many invaders, and eventually dies. They bury him, idolize him, and tell stories of him.\n\nPerhaps over time, the village considers the possibility (or perhaps such a concept already existed) that the soul/spirit of a person can remain behind, and so it is surmised that the spirit of Ug might still visit the village. Now the villagers begin to engage in simple rituals to honor/invoke Ug, either out of respect or in the hopes Ug's spirit will protect the village.\n\nAs more time passes, these original rituals may become more and more important, and the village may begin to craft a world view that holds Ug as central - things like the Weather, Crops, Health, enemy incursions, etc. all become associated with Ug.\n\nThe village has found Ug to be their way of interpreting the world around them. They have culture and history to support this, and Ug's worship becomes a part of their daily lives. Depending on how well the village does in the future, they may very well become an Empire founded on the shoulders of the Great Warrior Ug.\n\nAs far as 'why are there so many,' humans have a great many different cultures across the world, each with their own interpretations of how the 'world works,' so to speak. Depending on how that culture's oral/written traditions play out, the nature of a religious movement will vary. Sometimes as cultures intermix and intermingle, religious oral/written traditions become changed over time. For instance, in India, the Dravidian and Aryan cultures intermixed, and there are portions of both Dravidian and Aryan religious beliefs that can be found in Hindhuism today. "
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[]
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3izy8j | How does the dielectric constant of a material affect the wavelength of a ray of light? | I know that the wavelength of the ray is proportional to the inverse square root of the dielectric constant it is travelling through, but I don't really understand the mechanism by which this occurs.
Basically by asking this question I am trying to understand why the dielectric constant can affect the speed of light, but I think that I've narrowed it down to the process mentioned above.
Correct me if I'm wrong with any information. Thank you! | askscience | https://www.reddit.com/r/askscience/comments/3izy8j/how_does_the_dielectric_constant_of_a_material/ | {
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"This is actually pretty non-intuitive. I'll try and explain but the real answer is \"that's what Maxwell's equations tell you.\"\n\nA dielectric is a polarizable material--one that responds to an electric field, because the atoms distort (the nuclei and electrons are pulled in different directions and slightly separate). So, when light (an oscillating electric field; the magnetic field part is not important here) passes through, the material oscillates in response. But oscillating dipoles produce their own oscillating electric fields, and these combine with the incoming light (via superposition) to create a new oscillating electric field with the *same frequency* and *shorter wavelength* (for typical dielectrics with epsilon > 1). As a result, the wave travels at a different speed, since speed = frequency \\* wavelength.\n\nThe fact that the waves combine to give such a simple result--another wave with a different wavelength--is totally remarkable and not at all obvious. In particular it has nothing at all to do with 'absorption, delay, and reemission' of photons, which is a common misconception of the slowing of light in materials. It's entirely a classical wave phenomenon that is quite surprising."
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[]
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6hri3d | why as a teen do do you randomly get depressed for periods of time? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6hri3d/eli5_why_as_a_teen_do_do_you_randomly_get/ | {
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"Talk to a doctor. Not reddit. Not your best facebook buddy, not anyone else on the internet. Medical concerns should be discussed with a DOCTOR."
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1oku6t | how gifs work | I get the idea that they're a series of pictures, but how do they tell a computer how fast to play them? How are a bunch of different images saved as one file type? Also bonus question. Why can't I save on on my iPhone? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1oku6t/eli5_how_gifs_work/ | {
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"You know how a zip file can contain several other files inside of it? Same kind of deal with gif files - they can contain multiple separate images inside the same container file. The gif header contains information about what delay to use between frames, and any decent web browser or image viewer comes with code specific for decoding gif files and playing the frames in the right order at the right speed. It's almost like an mpg or an avi file but without the audio stream (and with different compression, but that's not terribly important to the point of this).\n",
"GIF files actually have a [header on the beginning of the file](_URL_0_) that tell the images dimensions, color depth, and the delay that it should play at, if a GIF is animated and has a set of images.\n\nThe only bad thing about them is that most programs limit them to have up to 256 colors (even though True-Color can be achieved by [using multiple block GIFs with different color palates](_URL_1_)) and the compression is not good enough, so there are limitations to how long and how large a GIF can get before you can't go any further, which means no movies in a single GIF.\n\nContainer formats like Quicktime, Matroska, and MP4 behave similarly, with a header at the beginning and a set of video and audio streams."
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2ahn8u | How much of the modern image of Vikings is made up? | Like do we really know what they looked like, how they dressed, what they ate, what their language was, and how their society worked? Also what exactly are vikings? Are they just big dudes with beards holding axes? Was that really how vikings looked? | AskHistorians | http://www.reddit.com/r/AskHistorians/comments/2ahn8u/how_much_of_the_modern_image_of_vikings_is_made_up/ | {
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"Firstly, while we today tend to refer to the population of Scandinavia as a whole as \"vikings\" today, in old Norse, the word referred only to the people who went raiding *or* trading overseas - \"*fara í viking*\", or \"to go on a *viking*\", (a phrase that appears in the Icelandic sagas) meant to go across the sea. The word stems from the word \"vik\", which means bay or inlet. \n\nSpeaking of words and where they come from, the language spoken would have been various dialects of Old Norse - one dialect of which was brought to Iceland with settlers in the 9th century, and while it is not identical, it is similar to today's Icelandic. The Icelandic Sagas can, with some modernised spelling and footnotes, be read by someone who knows modern Icelandic. \n\nA lot of what we know of the overseas raiders come from contemporary written sources from outside of Scandinavia, as Vikings as a rule did not write books. The Viking writings we do have tend to be runestones, comemorating big events - such as people returning from a successful voyage, or the death of someone important. These runestones can be found in various places in Scandinavia, standing in fields or forests (there's even rune-grafitti in [the Hagia Sofia!](_URL_5_)). Common inscriptions tend to be along the lines of \"Halvdan, son of Rolf, raised this stone in memory of his father who died in battle\", etc., etc. \n\nSeeing as how almost all of the contemporary written sources are foreign to the culture itself, they tend to be biased - especially since they were writing about the raiders, rather than the ones who stayed at home in Scandinavia. The Anglo-Saxon chronicle describes the Viking raid on the monastery at Lindisfarne like so: \n\n > \"In this year came dreadful forewarnings over the land of Northumbria, terrifying the people most woefully: these were immense sheets of lightning and whirlwinds, and fiery dragons were seen flying through the sky. A great famine soon followed these signs and not long after in the same year, on the sixth day before the ides of January, the harrowing inroads of heathen men destroyed the church of God in Lindisfarne by robbery and slaughter.” \n\nOur knowledge of what they looked like and how they lived is pieced together through contemporary accounts, carvings and statues from the period, as well as burials and archeological finds. Ibn Fadlan, who travelled among the people living in what is now Russia, but who were of Viking descent, describes their appearance in these words: \n\n > I have seen the Rus as they came on their merchant journeys and encamped by the Itil. I have never seen more perfect physical specimens, tall as date palms, blond and ruddy; they wear neither tunics nor kaftans, but the men wear a garment which covers one side of the body and leaves a hand free. Each man has an axe, a sword, and a knife, and keeps each by him at all times. Each woman wears on either breast a box of iron, silver, copper, or gold; the value of the box indicates the wealth of the husband. Each box has a ring from which depends a knife. The women wear neck-rings of gold and silver. Their most prized ornaments are green glass beads. They string them as necklaces for their women.\nIbn Fadlan, on the Rus merchants at Itil, 922.\n\nMuch of contemporary viking art tends to depict men with some manner of facial hair - often [beards](_URL_1_) of various [types](_URL_2_), while they depict women with [long hair](_URL_0_), often in [braids or knots](_URL_7_) (these images are variously of statues, ship carvings and decorations in stave churches). \n\nAs for societal structure, the Edda-poem Rigsthula (the lay of Rig) gives an account of how the societal structure came about, and describes a society consisting of jarls (the ruling class), karls (free men, farmers and craftsmen) and thralls (serfs or slaves). The poem also depicts the thralls as being dark, swarthy and ugly, the karls as being fairer and more pleasant, and the jarls as being pale and tall and handsome. There is some debate about when the poem was written, but the consensus seems to be that it is a fairly accurate representation of how viking age society functioned. The Rigsthula also wraps up with a description of how the youngest son of the first jarl becomes a king, which implies that in that *particular case*, the rule of primogeniture did not apply - though how true that was for the rest of viking society, I do not know. \n\n\nSources: \n[Danish History Museums article on Viking written sources](_URL_4_)\n\n[A summary of Ibn Fadlan's writings, courtesy of Judith Gabriel](_URL_3_)\n\n[Wikisource has the text of both of the Eddas](_URL_6_)"
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"http://www.saudiaramcoworld.com/issue/199906/among.the.norse.tribes-the.remarkable.account... | |
7hrp1m | what is it about meat going bad that means it can no longer be eaten after being cooked? doesn't the heat just kill any bad bacteria? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7hrp1m/eli5_what_is_it_about_meat_going_bad_that_means/ | {
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"Heat might kill the bacteria, but it doesn't remove the toxic byproducts that the bacteria produced before they got killed. Eating all that bacteria-poop is also bad for you.",
"The live bacteria are not always the threat. In fact more often it is the toxins they produce as a waste product and as they die that are the threat. Once a certain volume of these toxins has been reached the food is no longer safe to consume. ",
"If you're having a difficult time wrapping your head around u/cdb03b or u/WRSaunders answers, try thinking about it more abstractly.\n\nWe use water to \"kill\" fire.\nIf a building catches on fire, we call the firemen.\nThe fireman puts out the fire with water.\n\nThe fireman/water does not also repair the damage already caused by the fire, it just kills the fire. The roof caved in and all the contents are utterly destroyed by the fire, but at least the fire is gone now."
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c2jzri | How Do Waterproof Matches Work? | I know that water extinguishes a flame due to water removing energy from the system, preventing the reaction to go over the activation energy. I don't get how the wax on fireproof matches work. You need fuel, oxygen and heat for combustion but I don't see the wax helping any of these 3 factors in water. | askscience | https://www.reddit.com/r/askscience/comments/c2jzri/how_do_waterproof_matches_work/ | {
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"Waterproof matches wont keep the match lit underwater. The wax coating just prevents the wood and chemical head from absorbing water. Once struck you will need to keep water away from the burning portion or they will go out."
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nazkw | Capillaries? | Why does the relatively high blood pressure in the arteries not destroy the capillaries? | askscience | http://www.reddit.com/r/askscience/comments/nazkw/capillaries/ | {
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"Because the arterial pressure is spread over billions of capillaries. The surface area of your capilaries is about that of a football field. The pressure in any single capilary is very small.",
"Because the arterial pressure is spread over billions of capillaries. The surface area of your capilaries is about that of a football field. The pressure in any single capilary is very small."
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413rk9 | How do we know how far an animal can smell or hear something? | How do we know? How do we test it? Is it estimated? | askscience | https://www.reddit.com/r/askscience/comments/413rk9/how_do_we_know_how_far_an_animal_can_smell_or/ | {
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"You start with a reward based system. For instance; every time they hear a bell, a treat appears in the bowl across the room. Once they finally understand that sound = reward, you simply move the source of the sound further away until they stop noticing and take note of the distance. \n\nFor sight it's a similar process, only you associate it with a color or object. Then you study them until they notice the object and take note of the distance. \n\nSmell test can be similar to the sound or sight tests.\n\nYou could also just place the stimulus near the reward and see how far away the subject will notice it. "
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tuc31 | Are there any liquids that have boiling points under 100 degrees at normal atmospheric pressure? | If a liquid exists that boils, say around 80 - 85 degrees, would it not be easy to heat that liquid via geothermal? You wouldn't have to dig a really deep hole in the ground to obtain the necessary heat. You could then run a turbine from the steam and get cheap and safe electricity. | askscience | http://www.reddit.com/r/askscience/comments/tuc31/are_there_any_liquids_that_have_boiling_points/ | {
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"Tons of liquids boil at the range you want. \n\nIf you want hydrocarbons \n_URL_1_\n\nThough hydrocar can burn and react and cause all sorts of problems, because of this refrigerants were made (not for this task but for refrigeration) and they have similar boiling points\n\n_URL_0_\n\n\nI don't know specifically about geothermal heating and if this is useful but i do know that goethermal heating is being currently used. The problem here is that on the scale you want to run this type of system, the chemicals are going to expensive no matter what you choose. especially refrigerants. Not only will they be expensive these things can easily leak out into the crust, and cost even more to replace and may even be harmful to the environment.\n\nI assume the people who are doing these types of systems have already considered this and found the cost benefit to be bad.",
"All natural occurring gasses have boiling points below 100 degrees Celsius at atmospheric pressure.\n\nN - > 77K\n\nHe - > 4.2K\n\nO - > 90.2K"
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5gbh5c | How does the production of lactase decrease over time in individuals who are lactose intolerant? | I know that lactase production decreases because humans used to not require lactase after they were weaned, but how exactly does the body go about downregulating this genes (LCT via MCM6 I believe)?
| askscience | https://www.reddit.com/r/askscience/comments/5gbh5c/how_does_the_production_of_lactase_decrease_over/ | {
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"You are correct, [as per the wikipedia about lactose intolerance states.](_URL_1_) In simpler terms, and which I've heard many professors say, is \"use it or lose it\" - something you've probably heard many times before too. Your body is apt at producing things it needs, and ridding things that it does not, or rids things that take energy to produce yet are not beneficial in any way. Lactase decreasing can simply come from the negative feedback loop in our cells - if our body is producing lactase yet it is not being utilized, the transcription of the protein will slow and after awhile, the gene will simply cease to function very well. \n\n[In this paper](_URL_0_) the researchers tried to find similarities between the phenotype and genotypes of the world in regards to lactase production. The showed that: \"The first allelic variant that was shown to be strongly associated with increased lactase activity is a C > T change 13,910 bases upstream of the LCT gene in the 13th intron of the MCM6 gene [13]. Functional studies have indicated that this change may affect lactase gene promoter activity and increase the production of lactase-phlorizin hydrolase mRNA in the intestinal mucosa [14-17] but, as with all LP-associated variants, there remains the possibility that linkage to as yet unknown causative nucleotide changes may explain observed associations.\"\n\nThus, decreased lactase production would start with the slowing of the production of lactase-phlorizin hydrolase mRNA in the intestinal mucosa as it is not needed as much. As less and less mRNA is used over time, it will simply slow/halt the production of it itself. Someone with more knowledge on this should chime in as I'm not well-versed in the bimolecular epigenetic changes that could be occurring for this exact process - I do not know if DNA methylation is part of this chain and if so, how it initially forms. Hope this helped a bit though!"
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1tnsxd | how do they make the sex scenes on shows like game of thrones look so real? [nsfw] | For example: the scene with Jamie and Cersei Lannister in the tower, or whenever Khal Drogo is humping Danaerys doggy style. It looks extremely real, and the obly way I could think of faking it would be just tucking the penis out of sight, but with them both being completely nude and so close that seems very unlikely to even be possible. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1tnsxd/eli5_how_do_they_make_the_sex_scenes_on_shows/ | {
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"They have very good underwear for these scenes. Merkins and whatnot.",
"The males wear small (they'll tell you huge) flesh coloured pouches for their penis. After that it's all camera angles. ",
"which brings me to wonder...\nwould it be unethical if they actually had sex for the scenes? I mean, people already kiss for movies. ",
"I always wonder if there's a scene where an actor fully disrobes, but has his or her back to the viewer but is facing a fellow actor (say, before a love scene) . We can only see their back, but the other actor can see all their junk right ?",
"One thing I haven't seen mentioned is that it's generally taken very very seriously by the crew. Often times the director (or would it be the producer) will run a skeleton crew for the sex scenes. Only the very bare minimum of staff needed to be onsite will shoot the scene. Actors are allowed to have their SO onsite for the shooting if that makes them more comfortable. Everything is taken very serious and great care is taken to make sure the actors are made as comfortable as possible during the potentially awkward scenes. \n\n",
"Different techniques are used. Usually, camera angles are placed to hide actual genitals but show everything else. Also, men wear flesh-colored underwear that is just enough to cover the actual peepee. Ladyparts are all covered by a perfectly placed hand or sheet or something.\n\nAlso, since both actors know what is expected beforehand by reading the script, they know what has to be done and they go along with the creative director and/or cinematographer's requirements. It is upto the editors and the camera crew/director to ensure the final output seems 'so real'.",
"Using a clever combination of flesh colored \"garments\" covering the genitals, perfectly choreographed movements, and tricky camera angles/lighting and shadows.\n\nEverything is intricately planned and edited, and very often sex scenes are the most difficult scene to film for the director, actors, editors, and cameramen.",
"There are two kinds: simulated and unsimulated or explicit sex scenes.\n\nSimulated sex scenes have everything from wearing flesh colored pouches(as mentioned before) with aesthetic camera angles (meaning they try not to focus too much on the parts they wish to hide using various techniques like light/dark contrasting) to having full on body doubles play out the scenes. These sex scenes are usually \"softcore\" as actors only *portray* it happening but it never does, also, barely features full frontal male nudity but it does for females. (Meaning they dont show the cock, it is kinda considered a turn-off for some reason..)\n\nUnsimulated scenes have actors, I shit you not, actually having sex on camera, and yes, they do retakes ;-) . Some examples ( Admit it!I know you want them. ) include 9 songs, All about Anna etc. google \"unsimulated sex\" and you'll find a huge list of these movies. They are usually hardcore/pornographic sex scenes featuring full frontal nudity for both genders.",
"Hey, I actually starred in a miniseries earlier this year that required me to act in two sex scenes, so I think I'm probably qualified to answer this one. \n\nI've also had to simulate a masturbation scene in a short film and during my acting degree at university students take a course called 'Sex & Violence' that has them simulating fight scenes and sex on camera (not at the same time... ^*unless you're into that*)to prepare them for the big bad world. \n\nSo you're going to have sex on camera.\n\nYou've auditioned, got the part, read your script and bam - there it is. Your agent warned you in advance but hey - it's part of the job, right?\n\nMonths before the scene is shot, usually during contractual negotiations several provisions are made for the actors involved - they stipulate how the set will be closed down for the scene, which basically means only absolutely essential crew are involved. If the director knows they want to just run a song over the top and don't require on set sounds, they might not even have a boom (sound) operator. In most cases no on set stills are to be taken. Nudity clauses are discussed. If you are a female, will you be topless? will bare breasts/nipples be seen? Is it full frontal with bush?\n\nIf you're a male, full frontal is a lot less likely, but will your bum be shown?\n\nOn the day of shooting, the actors go to makeup. If the scene in in bed with lots of sheets and has little on camera nudity/a lot of sheets, usually we'll be sporting underwear. If it's a little bit more risque, things get interesting. Flesh coloured tape and dick-pouch interesting. We call them modesty patches, and they are applied over a woman's genitals, and for men a flesh coloured sock is applied and sometimes taped down onto your leg or even awkwardly back towards your ass crack. It's pretty hilarious. \n\nYou are given robes at all times when the scene is not being shot, and they lock the set down removing all non-essential personel. The actors and directors then rehearse the scene, and it is usually choreographed much like a dance. We discuss what positions to use, who is on top, the actors can discuss their boundaries - 'Can I touch your breasts? Can I kiss your neck?' and for camera angles - 'Should I have my right hand on her hip? or maybe holding her hair...' etc. \n\nDuring the actual take, it is a very mechanical, technical exercise for the actors - if you are shooting on location and not in a studio (as I was) we weren't allowed to use airconditioning because it interfered with the sound. Within minutes, the room is unbearably hot, and you're trying to keep each take as spontaneous and real as you can whilst acting within the set parameters you discussed earlier. It's not as easy as it looks, and when it looks extremely real - you know how hard the actors and crew have worked to make it that way. \n\nOr you're watching Shortbus.\n\nHope that helps",
"I work in film, so I can shed some light on this actually happens. When a script calls for nudity or simulated sex, there is an additional contractual discussion about what can and cannot be shown, the way in which the scene will be filmed, and many other aspects (they basically go through everything line by line, shot by shot, which is why you want a good agent and lawyer). Unlike the stories you may hear about the seventies, or some indie films, Hollywood is very strict about these scenes, and there are no surprises. A lot of the guidelines are regulated by the guilds, such as having bathrobes standing by, etc. \n\nKeep in mind that you are not going to be filming anything real, because you couldn't show it anyway if you wanted to get an R rating or below. Everything you can get away with at the R level or below can be faked. NC-17 (formerly X rating) is the kiss of death, because most theaters refuse to screen NC-17 films. That is why some films will choose to be unrated, or get into a fight with the MPAA like Blue Valentine or more recently Charlie Countryman.\n\nIf the scene is showing a lot, like Game of Thrones, the actors are probably naked, and the man will wear a small skin colored sock. The set is designated a closed set while filming, which restricts the set to only essential personnel. That would include the actors, director, cinematographer, assistant director, assistant cameras (possibly only the 1st AC), hair/make-up, and wardrobe. A few other people may be on set, and then others may be watching from the monitor depending on the scene, like the production designer.\n\nThe Assistant Director (AD) team would lock the set up, despite the grips trying to get a peek. In between every take, the wardrobe team rushes onto the set with bathrobes for the actors. Then for the actual act they are touching naked on screen, and it is very awkward but most actors will tell you it is not romantic in the slightest. I seriously doubt many people would enjoy being naked in front of a dozen people, starting and stopping every few minutes for a few hours while people run out periodically to adjust a light. Every situation is different and I am sure some actors are comfortable crossing the lines of professionalism, but this is how the vast majority of major films handle these scenes.\n\n\nA few funny anecdotes:\n\nI cannot remember which actor it was, but a male actor was quoted telling the actress before a sex scene the following, \"I'm sorry if I do, and I'm sorry if I don't.\"\n\nMy mentor also told me about the day she was walking across a backlot and a grip came running out of a sound stage in his boxer shorts. Apparently, the actress said, if I have to take my pants off then everyone watching does too. So the entire crew removed their pants to make her more comfortable while filming.\n\nEDIT: Grammer & to say, what an interesting post to answer on Christmas.",
"Have you ever filmed yourself having sex or watched someone else (outside of porn)? Honestly, it doesn't look that great. That's Hollywood with unrealistic glorified images, even sex itself. Anything on the screen is supposed to attract the eye. In realty, it's more crude. \n\nFor a more parallel \"realistic\" view, compare porn scenes to TV sex scenes and see what might be different or lacking.",
"It's fake. I know it seems impossible but it is. \nEven kissing is faked quite often.\nThey have skincolored underwear or socks on their genitals and things like that. Clever camera angles.",
"On the Spartacus set, they used these skin coloured pillows beteween the performers and skin coloured underwear. Some of the guys wore a prothestetic penis called \"Kirk Douglas\".\n\nThere is a lot of practice before the scenes are taken. Sometimes the actors would giggle when trying to play their parts.",
"The real answer we are all wondering to hear... is what happens if the male actor gets an erection?",
"Because they are real",
"I don't we should explain this to a 5-year-old.",
"I see someone else has been marathoning GoT this Christmas break...",
"They hire a stunt cock to do the scenes",
"Copious amounts of naked, awkward thrusting?",
"Plot twist: they are having sex",
"I've **never** had sex that was anything like the sex they have on Game of Thrones.",
"Sarah Silverman said she was in a sex scene & the dude kept ramming his hard on onto (not into) her vag so hard that the next day she was sore. I guess he didn't get a cock sock. ",
"NSFW but right after he stops giving her doggy he \"pulls out\" and then you see this _URL_0_",
"AMA Request for Celebrity Scene camera operator?",
"I was hoping to see a nice actress modelling her vj patch. Then I thought I'd settle for the picture of a penis sock. Found none.",
" > look so real\n\nYour virginity is showing, OP.",
"cock sock or no, I'd prolly nut just grinding on some of them girls in GoT.",
"I'll tell you when you're older sweetie. ",
"I would not dare explain this to a five year old",
"HBU needs to make a show about a detective that smells crime. Full Penetration will be the twist. There is always a twist.",
"SO all in all they are just dry humping each other? how does he not pop a stiffy."
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mscwo | youtube subscriber importance | Why is it that in many videos on youtube they always seem to emphasis to subscribe to them as if their life depends on it? Why is this so important to the poster?
"Don't forget to subscribe!"
"Please subscribe guys!"
"If you like this, subscribe!"
Are subscriber numbers some kind of popularity gauge? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/mscwo/eli5_youtube_subscriber_importance/ | {
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"People can earn a living from it if they are popular enough on youtube. Subscribing helps remind people to watch their videos as they come out, and the more people watching = the more ads being served, which = more revenue for youtube + the youtuber. ",
"People can earn a living from it if they are popular enough on youtube. Subscribing helps remind people to watch their videos as they come out, and the more people watching = the more ads being served, which = more revenue for youtube + the youtuber. "
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653uyf | how come when we exhale after holding our brearh we "get more air" | Weird title but, have you ever held your breath underwater as long as possible and noticed that when you exhale you can "Breath underwater longer"?
If you dont know what I mean just hold your breath right now and exhale when you just csnt hold it any longer. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/653uyf/eli5_how_come_when_we_exhale_after_holding_our/ | {
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"Your lungs are filling up with waste CO2 (carbon dioxide) which you feel an urgent, instinctive need to expel before it reaches toxic levels. Once you get rid of it you feel some relief.\n\nThis relief doesn't last, because you still need to get some fresh O2 (oxygen).",
"When you inhale, you inhale oxygen. Then your body turns the oxygen into carbon dioxide. Then you exhale that carbon dioxide.\n\nYour body responds to excess carbon dioxide before it responds to low oxygen. That way you catch the problem early. It's better to start feeling out of breath when you have extra carbon dioxide building up than when you are already out of oxygen."
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9n3vy1 | why are bullets bullet-shaped rather than football shaped? | I know that bullets are partially inside the shell prior to being fired. But wouldn’t having them be football shaped make them more aerodynamic, and this able to fly straighter for longer? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9n3vy1/eli5_why_are_bullets_bulletshaped_rather_than/ | {
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"Theoretically, sure. But the thing you have to remember is the bullet is being propelled from the gun. WIthout the flat surface for pressure to build against you're gonna have a hard time with it actually leaving the barrel.",
"I think it has to do with the firing mechanism. You want all the force from the explosion firing the bullet in line with the direction of the barrel, so it needs a surface normal to that force to be pushed out of the gun with as much energy as possible.",
"A football shape isn't actually a particularly great shape for stability. What's usually meant by \"aerodynamic shape\" when talking about droplet shaped objects is the reduced pressure loss drag and not their stability.\n\nBullets from rifles and guns are usually spin stabilized. They are spun up through the rifling in the barrel resulting in a rotation around their axis when leaving the barrel. This has 2 effects. 1 rotating objects tend to resist changes to their rotational axis. Much like how a yoyo is stable when spinning. 2 any asymmetries in the bullet shape will not change the bullet path in a particular direction. The asymmetry is spun around the bullets axis and will cyclicly produce the same forces in all directions so that they cancel out and the bullet path is stable.\n\nBullets can also be drag stabilized. So additional drag at the tail end can actually be desired to increase stability. If the bullet starts to fly sideways the tail end will get hit by the oncoming wind. This results in a force acting on the tail end of the bullet which pushes it inward and the bullet will return to its orientation along the direction of the flight path.",
"The reason the back of a bullet is flat, instead of tapered, is to make sure the force of the explosion that drives the bullet is even and effective. \n\nIf the bullet was tapered at the back the explosion wouldn’t push evenly on the bullet. And more importantly not all of the force of the explosion would press the bullet out, some would squeeze the tapered end. \n\nFinally, while a tapered end can reduce your drag force, the weight and speed of a bullet makes aerodynamics less effective. Bullets are so light and traveling so fast that making them aerodynamic doesn’t increase their travel speed or distance as much as just increasing the power behind them. "
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2p6yrc | when we toss/throw an object, what in our brains is telling us how hard/soft/hard to throw it? | Or is it a sight thing and just by looking at it we already know?
| explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2p6yrc/eli5_when_we_tossthrow_an_object_what_in_our/ | {
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"I'm confused.\n\nOur brains don't tell us, we tell our brains. And that happens because of neurons and lots of complicated signals from our brain that then tells our muscles how much force to use, etc.",
"I have heard of something called [muscle memory](_URL_0_).\n\nI believe that this is what happens when people practice swinging a tennis racket over and over again, or standing and swinging a baseball bat at batting practice."
]
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[],
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"http://www.wisegeek.org/what-is-muscle-memory.htm"
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6h7zoo | is it possible to 'change' our voice permanently, like if i put on a voice 24/7 would that eventually become my 'real voice? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6h7zoo/eli5_is_it_possible_to_change_our_voice/ | {
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"text": [
"its impossible to permanantly change your voice, \n\nThe only thing you could do is damage your vocal chords."
]
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1bqtky | When black holes radiates, wouldnt they grow as the particle not escaping the eventhorizon gets stuck in the black hole? | I'm by no means an expert on black holes but as I've understood Hawkings postulated that due to small quantum fluctuations at the eventhorizon small particle- anti-particles are created where one of the two escapes the black hole having the black hole radiate a little bit.
But the particle that doesn't escape the eventhorizon should get stuck in the black hole making it grow? | askscience | http://www.reddit.com/r/askscience/comments/1bqtky/when_black_holes_radiates_wouldnt_they_grow_as/ | {
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"The particle that doesn't escape the event horizon is allowed by quantum rules to carry a negative energy -- this is how the outcoming newly-real photon can have a positive energy. The negative energy is then \"added\" to the black hole's mass, which grows smaller.",
" > as I've understood Hawkings postulated that due to small quantum fluctuations at the eventhorizon small particle- anti-particles are created where one of the two escapes the black hole having the black hole radiate a little bit.\n\nYou should probably just forget all about the idea of virtual-particle pairs being involved in Hawking radiation, because there's really no theoretical basis for it. The whole idea is one *possible* heuristic explanation (among several) provided by Hawking; the actual derivation of Hawking radiation says nothing of the sort.\n\n > But the particle that doesn't escape the eventhorizon should get stuck in the black hole making it grow?\n\nThe idea here is that you start with a vacuum. Then two particles appear, \"borrowing\" energy from the vacuum. Normally, they'd re-annihilate almost immediately and the energy/time uncertainty principle can be invoked to say that the momentary \"drop\" in vacuum energy isn't a problem. But if you assume the two particles are separated quickly, and that one of them escapes to a detector far from the black hole while the other disappears, then you have a problem. Your vacuum can't have a lower energy than what it already had, so the only way that escaping particle can have energy is if the one that falls into the black hole *reduces* the mass of the black hole.\n\nOf course, as I said above, that whole description is based on nothing but Hawking's suggestion and a bit of intuition; there's no actual theoretical basis for it."
]
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[],
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8hac2t | why do rocket engines always go over 100%? | If the standard is say 104%, than why isn’t that 100%? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8hac2t/eli5_why_do_rocket_engines_always_go_over_100/ | {
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"The reference for 100% is max power at sea level. For shortperiods of time at altitude this can be safely exceeded. However, testing and quanification isn't done under those conditions.",
" > If the standard is say 104%, than why isn’t that 100%?\n\nThe engines were designed for a given output originally which becomes \"100%\". Afterwards there are tweaks and optimizations made which allow it to go over that output, but instead of redefining that output as \"100%\" they just say what its output is compared to the baseline specifications of the rocket engine. Unless you are familiar with what specific tweaks were made to that engine you wouldn't know how much thrust the adjusted 100% would equate to."
]
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[],
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cgjozl | can you make a brand new internet, like it would be completely empty with no data, no website no anything? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/cgjozl/eli5_can_you_make_a_brand_new_internet_like_it/ | {
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"I suppose so, but it doesn't make sense.\n\nThe internet is a network of connected computers. You could in theory create all the infrastructure to transfer data between computers without actually connecting it to anything but that isn't really an \"internet\", it is just a geographically large network.\n\nYou could connect a bunch of blank servers to that big network but I don't know why people would do such a thing. Usually you add a server to actually host something.",
"Yes. And you'll have to keep it from connecting to current internet. Otherwise it'll just be part of the current internet.\n\nYou'd have to get people to rerun millions of miles of cabling independently of all current connections. \n\nNot very cost effective",
"You certainly can. And in fact this is exactly what happens if you plug some computers into a router but don't connect that router to the public Internet — you just created your own tiny private Internet."
]
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[],
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2khbmr | how do tribute bands not have to pay royalties? | If I were to take a movie and remake it, nearly identical, I couldn't without facing a huge lawsuit. I have an idea for a "tribute" movie: Cosmos Chaos - Episode IV, a A Renewed Optimism. Similarly for a book. For example, my idea for a "tribute" book: Gary Rotter and the Wizards Wonders.
So, how do "tribute" bands get away with it? What are the rules for small, bar-bands playing someone else's music? Why are they able to profit from some other band's efforts? There are also "tribute" bands that do nothing but play music from another band. How? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2khbmr/eli5_how_do_tribute_bands_not_have_to_pay/ | {
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"Legally you must have a license to perform a copyrighted song. The right to license public performances are almost all held by one of three \"performing rights organizations\" (ASCAP, BMI, and SESAC). The venue usually takes care of obtaining the license and often does so in a package deal (so a venue might get the rights for any band to play all songs held by a performing rights organization). If you're playing at a nonprofit venue, such as a church or school, you may be exempt from having to pay for the license.",
"Tribute bands that play only at venues that have contract with a licensing agency (such as BMI or ASCAP) are covered by that for licensing. Or, a really popular tribute band may have directly handled the licensing. Many cover bands, however, are performing illegally, and just hoping not to get caught. A small bar band isn't likely to be noticed. if anything, the venue is more likely to be fined.\n\nHere's an interesting paper done on this:\n_URL_0_",
"It should be noted that tribute bands can't release a recording of them singing copywritten music without them paying a royalty to the original song writter. "
]
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[],
[
"http://www.kentlaw.edu/perritt/courses/seminar/katherine%20wardein%20Final%20Paper.pdf"
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ifayn | Can we harness energy from falling rain? | Say you have a large funnel type deal connected to a turbine that charges a battery.
the large funnel would collect the rain and hold it, similar to the way a watertower holds it. every time you pumped water from it, the water coming down from the reservoir would spin a turbine to create a small amount of energy that charges batteries. the kind of turbine we get from water-energy could be miniaturized/modernized. (i dont know the real name for it, the water wheel that spins from falling water, ya know?) | askscience | http://www.reddit.com/r/askscience/comments/ifayn/can_we_harness_energy_from_falling_rain/ | {
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"Yes. We call it hydroelectric power. Dams for generating electricity are based on the principle.\n\nIf you're interested in history, [wikipedia](_URL_0_) has a nice list of ancient European water-mills.",
"Kinda like [this thing](_URL_0_) right?",
"Yes. [Here's a diagram of a reservoir and power station near my hometown](_URL_0_). It was created when they built up basically a giant funnel using a saddle formation between two mountains. At the bottom is another reservoir, with a normal river outlet that regulates the water level. This is different from a normal river dam which just dams up a river's flow. This one regulates how much water is drawn from the reservoir based on how much power is needed, just as you described in your OP.",
"Come on, all these answers about dams are not what the OP is talking about. The OP wants to get the kinetic energy from the falling rain. When rain hits the ground it loses this kinetic energy. Yes, it gains more KE as it flows to lower altitudes, but this is not what the OP is talking about. ",
"In theory you could, I mean those drops do have kinetic energy. I would imagine a device that uses thousands of tiny paddle wheels hooked up to little generators.\n\nAssuming an energy of .08j a drop (drop mass of 8mg and a drag of -2m/s) and an efficiency of 40% (pretty high) you would need 2,500,000 of these little generators running to produce 1 watt or 250 trillion to match a 100MW plant. If each paddle was 6mm^2, you would need a 60mile^2 array to achieve this. This is not to mention a constant rain storm that covers that area and a million other little bits I glossed over.\n\nSo while it is possible it is ridiculously inefficient to do.\n"
]
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[
"http://en.wikipedia.org/wiki/List_of_Roman_watermills"
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"http://cn1.kaboodle.com/hi/img/b/0/0/b8/3/AAAAC5nW47sAAAAAALg9dQ.jpg?v=1268427728000"
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318rfu | What is the wave type of electromagnetic waves (transverse or longitudinal ) ? | Hello,
I wanna know if electromagnetic waves can be said as transverse or longitudinal waves?
If yes, then how ? Because they don't have medium and that transverse waves are those in which direction of energy is perp to direction of vibration in **medium**
If no, then why ?
Thanks,
Hemail. | askscience | http://www.reddit.com/r/askscience/comments/318rfu/what_is_the_wave_type_of_electromagnetic_waves/ | {
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"Electromagnetic waves are transverse when propagating in homogenous free space. (shorthand TEM waves)\n\nOr when their transmission line has a geometry and material distribution that causes the electric field lines to be continuous.\n\nbut there are transmission lines in which only one of the magnetic or electric aspect is transversal, and the other has a longitudinal component.\n\nThe most easy to grasp example is a metallic waveguide: basically a rectangular or cylindrical hollow metal tube.\n\nIn microwave engineering, the common convention is that z is the axis of the direction of propagation, x is the axis of the larger dimension of the rectangular waveguide ans y the axis of the shorter one.\n\nSo, in a TEM wave, if **E** and **H** are the vectors of the electric and magnetic field respectively:\n\n**E** = Ex**x0**+Ey**y0** and\n\n**H** = Hx**x0**+Ey**y0**\n\nEz = Hz = 0\n\nbut in a waveguide, the electromagnetic wave has several \"modes\" of propagation: depending on how many wavelengths can actually \"fit\" inside it, there are several shapes the electromagnetic wave can take.\n\nNow this null (or multiple nulls) can be either in the Magnetic or in the Electric component, and only either of them can be transversal, with the other having a longitudinal component as well.\n\nfor TE (transversal electric modes)\n\n**E** = Ex**x0**+Ey**y0** and\n\n**H** = Hx**x0**+Hy**y0**+Hz**z0**\n\nand for TM (transversal magnetic modes)\n\n**E** = Ex**x0**+Ey**y0**+Ez**z0** and\n\n**H** = Hx**x0**+Hy**y0**\n\nKeep in mind that the longitudinal oscillation is standing. That means it doesn't transfer any energy.\n\nIn fact if P is a vector that shows you the \naverage real power of a wave and its direction, then\n**P** = **E**x**H**.\n**P** is always on the z direction, and **E** and **H** only matter on the xOy plane. (the plane perpendicular to the z vector).\n\nThe power that oscillates back and forth on the z plane is called \"reactive\" power. In a way, it can be explained as the portion of the power needed to keep this mode going."
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55vcev | why do eli5 posts have to be longer than a sentence, when a five year old would probably appreciate and better understand a simple one-sentence answer? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/55vcev/eli5_why_do_eli5_posts_have_to_be_longer_than_a/ | {
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"So, this sub isn't ACTUALLY for five year olds. It's not \"Explain BECAUSE I'm Five\" but \"Explain LIKE I'm Five.\" The idea is to explain things to adults in a simpler manner, not to literally explain concepts to children. \n\nWhile I agree that there are times when a shorter answer would be better, requiring thought and length does prevent shitposting. ",
"From the sidebar: \n \n > E is for Explain - merely answering a question is not enough.\n \n > LI5 means friendly, simplified and layman-accessible explanations - not responses aimed at literal five-year-olds. ",
"I think that a significant number of studies have indicated two things:\n\na) questions with valid, useful, one-sentence answers don't really ask for an explanation. They should be referred to /r/AskReddit .\n\nb) One-sentence answers to questions which actually deserve an explanation distract from the civility of the sub, making folks cranky.\n\nThus we have the present rules."
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3m3xs1 | what exactly is _url_0_ ? it seems like a government site, yet there are a lot of papers supporting homeopathy as effective treatment, while many scientist have concluded homeopathy is fake science and just placebo. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3m3xs1/eli5_what_exactly_is_wwwncbinlmnihgov_it_seems/ | {
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"The National Institute of Health archives research from all over the place. Each paper's page links back to the original source. It's basically the Google of research- just a means of finding papers, not endorsing them."
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"www.ncbi.nlm.nih.gov"
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5mbb5w | why does pineapple hurt/irritate my tongue even though i'm not allergic to it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5mbb5w/eli5_why_does_pineapple_hurtirritate_my_tongue/ | {
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"Pineapple actually has a chemical in it called * bromelain*, which is a mixture of enzymes that essentially start to break down the tissues of your mouth as it sits there.\n\nYour mouth hurts because as you're eating the pineapple, the pineapple's sort of eating you, too."
]
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h61s9 | Why is it dangerous to daisy-chain surge protectors? | Surge protectors often come with warnings not to plug one surge protector into another. Many building and fire codes also prohibit this too.
Other than the manufacturer attempting to avoid liability, is there an electrical reason why it's dangerous to do this? (Assume that the total load on all the daisy-chained surge protectors doesn't exceed the maximum that any individual one is rated for.) | askscience | http://www.reddit.com/r/askscience/comments/h61s9/why_is_it_dangerous_to_daisychain_surge_protectors/ | {
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"It's just because people are idiots... seriously.\n\nWithout that warning, then people will assume you can plug ten power strips into a single outlet, quickly overloading the rating of the circuit. It's akin to something like [this](_URL_0_).\n\nIf you can somehow guarantee that you won't be overloading the circuit, then there is no problem.",
"Well... If you _know_ that the total current will not exceed the rated maximum of each power bar, then there won't be a reason why it's unsafe. Since it's often difficult to find out though, it's much safer to just do a blanket warning.",
"what i always understood is that hooking them up in series will potentially cancel the surge protection effect. i know there are different designs for surge protectors, and i don't believe [this](_URL_0_) is a typical design, but hooking these guys up in series would, i believe, leave you with capacitors in parallel.\n\nparallel capacitors' values are cumulative, and so if you design a circuit around a 1uf capacitor, and hook two up, the capacitors would discharge at half the rate. so essentially the trigger would be slower.\n\nother designs seem to use varistors, which i'm not overly familiar with as an audio diyer, but i would wager that if they're designed to bleed a certain amount of voltage into a shutoff circuit, connected in parallel, it would split the bleed among the parallel circuits, requiring more voltage to trigger the shutoff mechanism.\n\nanother reason for this is that if they offer you a surge protector guarantee, they want any excuse not to pay you for your broken gear.\n\nEDIT: correcting a stupid.\n\nEDIT: [another surge protector](_URL_1_), which seems like it would worth in series with others. but i don't know what the exact parameters for triggering it would be.",
"This advices applies primarily for the US, as I don't know the electrical laws of other nations.\n\nFirst off, daisy chaining surge protectors is a violation of OSHA regulations and the National Electric Code. Second, daisy chaining surge protectors is dangerous because it's easy to overload if you don't do the math properly. And getting the math wrong in eletrical work is _dangerous_.\n\nMost circuits in your typical US home are going to be rated 15A at 110/120V. (Yes, there are some instances of 20A, but it's safer to assume that everything is 15). These circuits will have one or more outlets, each outlet usually containing two plugs.\n\nThere are two types of maximum loads you need to be concerned with: maximum instantaneous load and maximum continuous load. Maximum instantaneous load is calculated by multiplying the amps and volts to get watts. In the typical home, 15A*120V = 1800 Watts.\n\nA continuous load is defined as any load which will be on for longer than three hours. For a 15A circuit, you should only draw a maximum of 12A for continuous loads. Again, for your typical home, 12A*120V = 1440 watts. It's a smaller load to work with.\n\nPower strips are designed to have a limited number of outlets. They are tested and rated to provide power to a limited number of items in a safe manner. When you daisy chain power strips, you eliminate this safeguard. Load too much on a power strip, and you can cause the plug to overheat and cause fires, you can flip breakers, etc.\n\nAs a final note, flipping circuit breakers is a _very bad thing_. It means you've done something wrong along the way."
]
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9xqjy0 | History of Nuclear Weapons Advancement and Production | Are there any books/documents that talk in depth about the advances in nuclear tech and production during the nuclear arms race? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/9xqjy0/history_of_nuclear_weapons_advancement_and/ | {
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"Yes, though the answer to which one depends on which aspect of the technology you care most about:\n\n* Are you asking about the specifics of warhead design and development? (e.g., the \"physics package\") If so, Hansen's _Swords of Armageddon_ is probably what you want, for an extremely \"in depth\" approach. \n\n* Are you talking about the delivery systems (the bombers, missiles, submarines, etc.)? Depending on which, there are different books for that, though Schlosser's _Command and Control_ gives a good overview of all.\n\n* Are you interested in the ways that the strategy changed (and was changed by) the technology? Freedman's _The Evolution of Nuclear Strategy_ is the best starting point.\n\nThere are other angles (political arrangements, cultural responses, etc.) that have other books, as well, of course, but it doesn't sound like you are asking about that."
]
} | [] | [] | [
[]
] | |
acs01j | bearer bonds. what are they? how do they work? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/acs01j/eli5_bearer_bonds_what_are_they_how_do_they_work/ | {
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"It's an IOU — a note for a debt — that says \"I owe you $___ and when due I will pay it to whoever brings me this piece of paper.\"\n\nAs opposed to a traditional bond, where the name of the person owed is written on it. A bearer bond can be handed off between people, since whoever holds it can collect the money."
]
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4anpd8 | what happens during a contested convention? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4anpd8/eli5_what_happens_during_a_contested_convention/ | {
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"The way that the primaries / conventions work is that states send a collection of delegates (voters in the convention) based on whomever won their state's primary. Some are winner take all, some are proportional, but either way the candidate gets a number of delegates pledge to them for the primary elections. Some states require that the delegates vote for the candidate that they were sent for and others don't (but most still vote along the lines of which candidate they were sent for).\n\nAt the convention, an initial vote is taken and if once candidate gets 50% +1 delegate, they are the party's nominee and the process is over.\n\nContested conventions happen when one candidate _doesn't_ get 50% +1 delegate in that initial vote. Once that happens, all of the previous rules about whom you have to / should vote for go out the window. The delegates are free to vote for whomever they want to - even if that person isn't running in the primary (which almost never happens, but it could). Backroom deals are brokered and candidates shift their support until one candidate is able to obtain the 50% +1 delegate in some subsequent vote.\n\nNormally, this isn't a big deal - the person leading in the primaries still normally wins because it is far easier to shift a smaller number of votes than a larger one. What is interesting about the RNC convention this year is that while Trump is the frontrunner and delegate leader, there is a large group of RNC delegates that do not want him to get the nomination - they would much rather see Cruz or Rubio. Now that Rubio has officially dropped out of the race, it is very possible that he and Kasich could ask their delegates to support Cruz rather than Trump, giving Cruz 717 delegates (by current count) to Trumps 661 - putting Cruz in the lead and giving him momentum to win the nomination. It would be an incredible upset, because the candidate who had the most delegates going into the convention might not get the nomination."
]
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11a6kz | Could a person live with a constant IV drip of minerals and vitamins our body needs? Or do we need some kinda of liquid/ solid in our stomachs? | askscience | http://www.reddit.com/r/askscience/comments/11a6kz/could_a_person_live_with_a_constant_iv_drip_of/ | {
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"Your basic premise is done fairly often with either enteric feeding (putting a tube into the stomach or even the intestines and pumping in nutrient solutions) or total parenteral nutrition (giving someone an IV with the necessary nutrients). This sort of thing is often done if someone has some sort of swallowing or esophageal defect. Most of the people I've spoken with who've been on an enteric feeding regimen or TPN report not feeling overly hungry (since hunger is determined by more than just distension of the stomach). There's no real limit to survival on this regimen - it's not ideal and may lead to a number of complications, but many people are on gastric tube feeds for many years. Hospitalized patients can also be on TPN for long periods of time. [Here's some info about enteric feeds](_URL_0_), and [here's an example of what's in TPN](_URL_2_). [Here's an example of a common liquid nutrient supplement.](_URL_1_) You may still have bowel movements (assuming healthy GI tract), since a large component of stool is bile excreted from your liver, via the gallbladder."
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"http://en.wikipedia.org/wiki/Ensure",
"http://en.wikipedia.org/wiki/Total_parenteral_nutrition#Total_parenteral_nutrition"
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alhzzn | What are the possibilities for glaciers and related geology on Saturn's moon Titan? | I'm imagining fjords and valleys and sharp pyamidal mountain peaks and braided streams. Glaciers and glacial lanforms are so beautiful on earth. What would it be like on Titan, if at all? | askscience | https://www.reddit.com/r/askscience/comments/alhzzn/what_are_the_possibilities_for_glaciers_and/ | {
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"[NASA JPL: Titan Touchdown](_URL_0_) \n\n\n On Jan. 14, 2005, ESA's Huygens probe made its descent to the surface of Saturn's hazy moon, Titan. Carried to Saturn by NASA's Cassini spacecraft, Huygens made the most distant landing ever on another world, and the only landing on a body in the outer solar system. This video uses actual images taken by the probe during its two-and-a-half hour fall under its parachutes \n",
"Slim. On Earth, we have water ice glaciers flowing down mountains made of rock. Titan definitely doesn't have that: it doesn't have rocks at its surface, its entire crust is *made* of water ice. This ice is 180 degrees C below its freezing point, so it's hard and brittle and doesn't flow at all. Water ice is Titan's version of bedrock!\n\nTitan has lakes, hills, river valleys, all carved into the water ice bedrock. Now, there's an interesting possibility that Titan might have glaciers made of some *other* kind of ice. It's been [suggested](_URL_0_) that acetylene -- used on Earth as a welding gas -- might form solid glaciers on Titan. However, there's not much observational evidence for this as of yet.\n\nTo sum up: water ice is too solid to flow on Titan, and forms Titan's \"bedrock\" instead. There might be glaciers made of other chemicals, but evidence is sketchy so far."
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7e84wq | With the death of Charles Manson, a lot of people are making posts partially crediting him with ending the Hippie Era. What did end it and how? | I should be clear that i'm specifically talking about the American hippie culture. Across the threads discussing his death, a common thought that's expressed everywhere is that his actions somehow contributed to the end of the Hippie movement and the culture that goes with it.
Is it true that it was really a contributing factor and if so, how could it impact a whole cultural movement on such a level? Isn't it a bit much to credit this event over other, more directly impactful factors? | AskHistorians | https://www.reddit.com/r/AskHistorians/comments/7e84wq/with_the_death_of_charles_manson_a_lot_of_people/ | {
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"Followup question. I just read this comment in another thread. Is there any truth to this?\n\n > From what I read, Atkins and Watson didn't even blame Manson until the police put that idea in their heads. Similarly the young women didn't blame Manson or say he brainwashed them until the cops inferred that he did. I see it this way: young white girls from middle class families committed these heinous crimes. This wasn't something that society was willing to accept as possible. Thus came the myth that Manson - a life long criminal from the lowest social class - must have brainwashed and controlled the women. I think that Manson will be somewhat exonerated by history. In so many ways he was the scapegoat for the actual murderers and since those were mostly young women who had an \"acceptable\" upbringing, everyone was all too relieved to put the blame on him. Because of Manson, white middle class America didn't have to experience a moral panic.\n\n",
"Amongst the counterculture in the 1960s, there was deep dissatisfaction with American capitalism/democracy and the way its imperialist instincts played out in the Vietnam War in particular. But by the 1960s, amongst the same people, Communism - and specifically the Stalinist and post-Stalinist versions of that - were widely seen as also fatally flawed. The hippie movement, in some respects was a response within the counterculture to dissatisfaction with both of these alternatives.\n\nInstead, the hippies wished to withdraw from mainstream society and its economics, and instead live in communities that were more aimed at human flourishing, without the restrictions of conservative American society or the restrictions of communism. The solutions that the hippies arrived at was a movement to live in small groups that could potentially be self-sufficient - hippie communes. This was also an era of 'humanistic psychology', where psychologists like Abraham Maslow made arguments about what humans needed to have in order to 'self-actualise' (in Maslow's terminology); to self-actualise was to become the potential person you were capable of becoming, to reach your full potential. For the young people attracted to the hippie movement, self-actualisation involved 'free love', the expansion of the mind with psychedelic drugs, and returning to nature, and perhaps all of that was best done in the kind of hippie commune where you could ignore the outside world. \n\nOne example of this logic was the way that The Beatles responded to the trauma of the death of their manager Brian Epstein by going to live for a month or two, from February 1968, in India on an ashram with the Maharishi Mahesh Yogi. One song written by John Lennon during the retreat to India was called 'Child Of Nature' which has lyrics like \"yes, the dream I had was true/ I'm just a child of nature\"; Lennon later thought better of the sentiment of the song and reworked that melody to become 'Jealous Guy' in 1971. And because the Beatles had become, in a way, the patron saints of the hippies, with utopian songs about how 'All You Need Is Love', the idea of going to live on a commune with your like-minded friends was in vogue.\n\nThe actions of Charles Manson and his Family, however, showed very vividly how easily the theory behind the hippie movement could be subverted, and how easily a charismatic psychopath could take the rejection of society implicit in the hippies in dangerous directions. To explain him in the context of hippie culture, let's talk about The Beach Boys. Circa 1964, the Beach Boys were personification of bright young American youth, and the best reply the USA had to the Beatles. But by 1966, they were becoming influenced by the counterculture, and by 1968, they had turned into what Richard Nixon definitely would have called a bunch of dirty drugged-out no-good hippies. Even their usual lead singer, Mike Love, had become a hippie. Love, by all accounts had resisted the Beach Boys move into hippiedom very strongly indeed (he hated drugs, he was the one saying 'don't fuck with the [surf, cars and girls] formula', and he was the one who spent years making fun of the experimentation on the Beach Boys album *Smile* (even if he denies it now, pretending that recordings of him doing so don't exist). Love's whole personality was the antithesis of the ideal hippie (read: [he comes across even in his autobiography as a gigantic arsehole whose vibe was harsh, man](_URL_0_), and the *New York Times* and most other outlets *ripped* into him in reviews). Nonetheless, Love had attended the Maharishi's ashram with the Beatles in February 1968 (and unlike the Beatles, become a lifelong devotee of the Maharishi). And Mike Love was the *least* receptive of the Beach Boys to hippie ideals; the most receptive was Dennis Wilson, the Wilson Bros. middle child, whose 1978 solo album *Pacific Ocean Blue*'s themes revolve around ecology and love.\n\nWhen Dennis Wilson picked up two cute hitchhikers and brought them back to his house in the spring of 1968 for what he hoped would be a threesome, it turned out that Dennis had bitten off more than he could chew. He did apparently have the threesome, and then they left, but then they returned later that day with a further bunch of female hippies, along with a dark-eyed guru they called Charlie Manson. Manson impressed Wilson very deeply by being able to get a roomful of women to take off their clothes on command. For Dennis Wilson this was an amazing Satyricon that had just turned up in his house unprompted, and so he was happy for Manson and his Family to move into his sprawling mansion.\n\nWilson became enamoured of Manson, quoting him in what are now deeply disturbing interviews of the time: \"fear is nothing but awareness, man\" - and he even recorded some songs by Manson, including 'Never Learn Not To Love' (which was released on the Beach Boys *20/20* album that led with their comeback single 'Do It Again'), along with introducing him to many of his hippie LA friends like producer Terry Melcher (the son of Doris Day, who had produced The Byrds' 'Mr Tambourine Man'). However, as Manson insinuated himself into Wilson's life, it became harder and harder to ignore his darker ideas about trying to provoke race wars and the like. Eventually Wilson grew tired of having Manson around his mansion, and kicked him and his Family out. \n\nManson did not take this well, and began to make threats on Wilson's life, and that of his stepson. Eventually, Manson turned up at the house Melcher had recently moved out of, and his Family murdered one of the new occupants, Sharon Tate, the pregnant wife of the movie director Roman Polanski, scrawling Beatles lyrics on the walls. The next day, he turned up at Wilson's door, demanding money; Wilson gave him some out of fear, and after he went away to Canada on tour and came back, he found that Manson had left a bullet on his doorstep. \n\nAnyway, you can read the gory details in plenty of sensationalist accounts of the murders, but the point is that Charles Manson was an incredibly prominent, living, breathing argument against the idea that the hippie lifestyle would help people self-actualise into better versions of themselves - he had all the free love he ever wanted, he knew the Beatles' music, and hung out with the hippiest Beach Boy. And despite it all, he was a charismatic, murderous psychopath. It very clearly showed how impossibly utopian the hippie dream was - even basically good-hearted people have negative emotions, let alone the likes of Manson. Conflict and evil cannot be so easily done away with by simply thinking nice hippie thoughts. After all, Manson had aped the tone of the hippies very well indeed - he co-wrote a song called 'Never Learn Not To Love' and found inspiration in Beatles lyrics...but that didn't stop the whole murderous psychopath bit.\n\nThe Manson murders not only made hippies feel sad about their ideals; it also changed the way that mainstream America viewed the hippies. Previously, hippies had been something of a curiosity, in the same way that millennials and their ability to kill a variety of industries by not spending their money on things are now something of a mainstream curiosity. But the Manson murders became a symbol of the moral bankruptcy of the hippies; *Los Angeles Magazine*, for example, published an article with the title 'Could Your Daughter Kill?'\n\nPresident Richard Nixon responded to Manson's arrest, argued Richard Perlstein, with the theory that it was the turning point that would make the 'Silent Majority' of Americans decide that enough was enough, and that they needed to put a stop to all these lefties and hippies (additionally after Manson had been arrested and imprisoned but before the murders had gone to trial, Nixon made deeply prejudicial comments about the case). And so, in between the arrest and the trial, pushback against the counterculture became much more visible. Most prominently, the Kent State shootings occurred in May 1970, where the Ohio National Guard shot at students protesting the Vietnam War, killing four. So beyond the way that Manson's existence soured the hippie dream, it also made being a hippie something more of a dicey proposition politically; being a hippie now attracted bad vibes. It harshed the mellow. As a result of all of these factors, the energy of the counterculture moved on from the kind of communal ideals and 'peace and love' vibes of the hippie lifestyle, with the 1970s famously styled as the 'me decade'. \n\nCounterintuitively, the tropes of hippie culture also became increasingly mainstreamed in the 1970s; the hippie bands of the 1960s who survived the era became the bands that really raked in the cash (e.g., Crosby, Stills, Nash and Young who released the song 'Almost Cut My Hair' in 1970, and whose stadium tours of the 1970s played a big role in the modern touring circuit for big rock stars). Even the conservative country music scene had a star in a longhaired hippie pot smoker called Willie Nelson. But nonetheless, the tropes of hippie culture that survived into the 1970s were more like familiar tropes rather than the stuff of serious counterculture, which is why you get Lester Bangs in 1971 writing articles titled 'James Taylor Marked For Death' bemoaning how safe the hippie stuff has become, and why you get the punk movement of the late 1970s positioning itself as the antithesis of all \"that hippie shit\" (to quote Sex Pistols lead singer John Lydon's autobiography, *Rotten*).\n\nSources:\n\n* *Encountering America: Humanistic Psychology, Sixties Culture & The Shaping Of The Modern Self* by Jessica Grogan\n* *Catch A Wave: The Rise, Fall & Redemption Of The Beach Boys' Brian Wilson* by Peter Ames Carlin\n* *Nixonland* by Richard Perlstein\n* *Revolution In The Head: The Beatles' Records And The Sixties* by Ian McDonald"
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1sjzva | why do game devs make games for one mobile system (e.g. android vs. ios) and not the other. | Two part question: I have noticed there are a number of games that are on ios that aren't on android. What stops game devs from changing their code and putting it on the other system.
2) It seems that a lot of games favour apple. This seems extra weird since Android is outperforming apple. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1sjzva/eli5_why_do_game_devs_make_games_for_one_mobile/ | {
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"So iOS and Android's ecosystems are significantly different. not just at the programming level, but even with how code is organized, what libraries are available, etc. In a company somewhere between 20-30 programmers, we had maybe 3-5 who were switch hitters between the two. Most were specialists in one language, and then further specialized with one thing (algorithm, UI, game theory, etc.)\n\nFurthermore, with iOS, you are designing with fewer issues of backwards/hardware compatibility. You program for the latest iOS, and know that it should cover at least a few years worth of hardware. You then only pick up the hardware you need to test with.\n\nWith Android, the hardware can be cheaper, but there is a *lot* of issues due to the decentralized nature of both the OS and the hardware. What works on a Galaxy S3/S4 might cause crashing on an HTC because of some weird custom launcher shit. Most of our QA with android phones involved figuring out why one particular popular model had issues where none of the other ones did.\n\nThat's not to rag on Android, but from a dev point of view, it could be challenging. That's not to say iOS didn't have its own issues - constant changes to the iOS libraries caused problems for us in general, and every time a new version of XCode came out a bunch of shit would break. At least with Android it was just Java, so the worst you had to deal with were new libraries. \n\nThere is also marketing - if you are making Game A, you have to decide where your customers are. If there are 100x games like Game A on the iOS store, but none in Androidland, then Android might be the better option since you can capture that market share. At the same time, iOS is still iOS - even if Android is making solid gains, from a marketing perspective having an iOS game is almost your default position. \n\nNow, to answer your question: code from one language doesn't just translate to another. Code from one OS doesn't just translate to another.\n\nOn iOS, you would design your code around Objective C, using the iOS libraries for drawing and graphics work. On Android, its all Java, and you use a *completely different set of libraries*. Hell, even the way that the UI is designed is different. In iOS you use Views and View Controllers. In Android you have activities and intents. They don't function exactly the same way, so there isn't a 1-to-1 translation.\n\nI've seen apps designed side by side between iOS and Android - not even the wireframes are the same. The only similarities are in the concept and how it should work - everything else, from the way the UI is designed and interacted with, down to the code, is completely different."
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4x4cfd | Are there any Miller-Urey-type experiments that are currently running continuously? | Hello, I have always been fascinated by experiments simulating the early times on Earth trying to answer the question of how life first arose. I was wondering if any of you know about Miller-Urey-type experiments that focus on running the experiment continuously and analysing the chemical composition at time intervals trying to create some primordial-like soup by performing a longer (in relation to time) experiment? | askscience | https://www.reddit.com/r/askscience/comments/4x4cfd/are_there_any_millerureytype_experiments_that_are/ | {
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70copy | what is calculus? how does it work? | I understand that calculus is a "greater form" of math. But, what does it does? How do you do it? I heard a calc professor say that even a 5yo would understand some things about calc, even if he doesn't know math. How is it possible? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/70copy/eli5what_is_calculus_how_does_it_work/ | {
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"Calculus does two things: Finding rates of change, and adding up infinitely small parts to find the area or volume contained by a curve or surface.",
"In algebra you learned to calculate the slope of a straight line.\n\nWhat's the slope of a curved line? Well, it's not just one number. It changes - it's higher when the curved line is steeper and lower when the curved line is flatter. You can actually graph this out and get a second line, the graph of the slope of the first line. Calculus is the set of mathematical tools that allow you to relate the first line to the second line: how to calculate one given the other, and so on.\n\nIt's quite handy for stuff like physics. For example, you may have an equation for your velocity and need to know your acceleration. Acceleration is the slope of velocity, so you use calculus to find that.",
"Calculus is the math of things that smoothly change, like the speed of your car, or the force of gravity between planets that are moving relative to each other.\n\nIf things didn't change over time or space, you wouldn't need calculus. \n\nAnd if they change abruptly, calculus runs in to challenges.\n\nBut if what you're trying to figure out is something like how fast does something fall through the air when you drop it, or how much water can you put into a pitcher of a given size or shape, then calculus is the tool you need. ",
"Think of when you are clipping your fingernails. You want to clip a curved \"line\" but you only have a flat tool (let's ignore the slight curve in modern clippers). The more smaller clips you make, the \"rounder\" your nail will get. The only way to get a truly round nail is to clip it infinitely many times. But that is impossible. One fundamental of Calculus is examining what happens as you clip more and more and get closer to infinity. ",
"The basic principle behind calculus is fairly easy to understand. Imagine painting the walls around a round ship window. It's got that neat brass stuff, and you don't want to paint that so you have masking tape. \n\n So how do use straight masking tape on a round window? You use some small strips. You can start with some big ones like the yellow in [this](_URL_0_). Well, that doesn't look right at all. You didn't paint close to the circle, and nobody likes it. Boss man gives you a second chance. OK, you use smaller strips and your outline is more like [this](_URL_1_). Much better! \n\nNow using the smaller straight strips were much better approximation to the actual window, but they were not perfect. To be perfect we need super tiny strips, and once they are absolutely tiny, they are perfectly accurate. \n\nCalculus breaks things down into those tiny strips to accurately measure curvey things. It works for straight things too, but kinda overkill. ",
"Calculus one (differential calculus) primarily deals with finding how quickly something is changing at any given time. E.g. Given a position of an object for some time interval, we can find how fast it was moving during any moment in that interval. We do this by finding derivatives of functions.\n\nCalculus two (integral calculus) deals with finding area/volume. E.g. given the velocity of an object over some time interval, we can find how far it has traveled by finding the area underneath its velocity vs time curve. We do this by finding integrals of functions.\n\nCalculus three (multivariate) deals with calculus in three dimensions. Finding the path that water might travel down a complicated hill, the volume of a three dimensional object, the circulation of fluid along a curve, or the flux of a liquid across a surface are a number of applications. It's ultimately the most useful in complicated engineering problems since the real world is three dimensions.\n\nSome related fields are analysis and differential equations. The former is more about establishing the theory that allows us to perform basic calculus, and the latter deals with equations involving the relation of certain quantities and their derivatives (big in physics).\n\nEdit: a taste of how calc 1 and 2 are done:\n\nCalc 1: So imagine you use a microscope to zoom in on a curve. The more you zoom the more the curve looks like a line. Theoretically, if you zoom in infinitely you see a line. The slope of that line is equal to the rate of change of the curve. So if you plot the graph of an objects position (given by our curve) and zoom in on that curve a lot, it looks linear. The slope of that line is the object's velocity at that position. That is calc 1\n\nCalc 2: The idea is to subdivide some closed region (think like an amoeba) into rectangles and use the formula for area of rectangles to find area under/inside a curve. We use two processes. The first is called limits (to make the rectangle width approach 0, which causes the error in our approximation to approach 0. Think about approximating a circle as a square. When we divide the circle up into more squares, our shape becomes closer to a circle and our error in approximation approaches 0. Let these squares approach infinitely small size.) Then we sum their areas using our rectangle area formula through a second process, which is called summation. This is Calc 2\n\n",
"Essentially, Calculus studies how a function works. There are two tools that are totally linked with the modern notion of Calculus: the derivative and the integral (or anti-derivative): in a nutshell if we derivate a function we obtain another function that is somehow related with the \"speed\" (if it changes rapidly, slowly... but also if it grows or decreases) of the first function, and if we integrate this new function we obtain the original.\n\nThe utility of the aforementioned is huge. For example, most of the physical phenomenons are described with a function (more precisely, with an equation where the thing to determine is not a number, but a function), so knowing how to study a function leads to obtaining a tool of studying physics. Functions are also used in economics, chemistry...\n\nThe idea of all this can be explained to a 5 year old as you said. The main notion of what underlies here is very easy to understand. You should look for the paradox of Achilles and the tortoise. It dates from the Greeks but wasn't completely solved until the development of the modern Calculus. ",
"I'm an undergraduate student in pure mathematics - i.e not an expert, but I have some experience and can hopefully give a good answer.\n\nCalculus really began by seeing that finding the area under a curve is extraordinarily important in for example physics. To give an example, let's say that you get paid 12 dollars an hour, and you work for 7.5 hours. This can be visualized as a graph staying constantly at y = 12. The area under the graph, from x = 0 (beginning of the shift), to x = 7.5 (end of shift) is then how much you have earned, and this is (as we know) 7.5 x 12 dollars. Now this is all well and good, but what if our graph is more complicated? What if you steadily get paid more pr. hour of work? Or what if your salary fluctuates up and down every single minute, depending on some factors? Then, we **still** want to find the area under the graph; but its harder. \n\nThe key thing to realize is that if our salary at x hours is S(x); then if we can find a function F(x) which (lets say we work from x = 0 to x = 7.5), is zero at x = 0 (i.e F(0) = 0), and at every point x between 0 and 7.5 **increases with speed S(x)**, then the total area under the graph is F(7.5)! Now; how the hell do we find the speed F(x) increases with, when x = 2, for example? Well, this is where differential calculus begins, and the main idea here is to \"zoom in\" at the graph at x = 2 so much that the graph of F(x) at this point stops looking like some organic curve and starts looking like a line; and then finding the slope of this line and calling this the derivative of F at x. Zooming in at the function f(x) = x^2 at x = 2, for example, makes the function look (locally) like the line f(x) = 4x - 4 which has slope 4! Thus in this case, the derivative of f(x) at x=2 is 4, typically written f'(x) = 4. (see here: [Wolfram alpha link showing x^2 and 4x - 4, for x between 1.5 and 2.5](_URL_0_)\n\nSure, these ideas can be explained to a child at least to some extent, but to do calculations with them one needs a lot of time and practice.",
"Calculus is basically all about the idea that you can take an infinite number of infinitesimally-small iterations, and they can sum to a finite number.\n\nFor example: imagine you're on a coordinate plane, and have to walk to a location one mile north and one mile east. Simple geometry tells you that the distance from your destination is √2 or ~1.4 miles away diagonally. Instead you walk 1 mile east and 1 mile north. You will have gone 2 miles. If you instead walk 1/2 mile east, 1/2 mile north, then 1/2 mile east again and another 1/2 mile north, your path will be closer to the diagonal, but the total distance is still 2 miles. If you break it up into 1/4 mile increments, you'll be even closer to the diagonal but it's still 2 miles.\n\nKeep iterating like that and your path is closer and closer to a straight diagonal line but still 2 miles total. But at some impossible point, after infinite iterations, the path becomes the diagonal and the distance becomes 1.4 miles. That's called a limit, and it's the foundation of what calculus is.",
"First, the pedantic definition: \"Calculus\" simply means \"The method of calculating something\". Similar to how the word \"Transportation\" means \"the way to transport things.\"\n\nSpecifically, what we call 'Calculus' is dealing with the calculation of things using *infintesimals*, or small pieces, and *limits*.\n\nThere are two main 'pieces' of Calculus:\n\n1. Figuring out the slope, or angle, of a curve, at a certain point. You do this by 'zooming in' *as small as we can*, and using a *limit*. \n\n2. Figuring out an area under a curve, in a certain range. You do this by adding up an 'arbitrarily large number' of *smaller pieces*. So by using *limits*, we can look at the area of smaller and smaller 'slices', and add them up into a final answer. \n\n > I heard a calc professor say that even a 5yo would understand some things about calc, even if he doesn't know math. How is it possible?\n\nI'm looking at an ant. It's crawling across the table, probably to get a taste of that drop of grape jelly. It has to crawl half way to the drop. Then half the remaining distance (1/4th), then half again (another 1/8 of the way)...and so on. But does the ant ever get the jelly? Or is it stuck, never able to cross that infinite number of steps to victory?\n\nYes, the ant does. Calculus teaches how an infinite number of smaller pieces can converge to a finite amount, or a limit. And the ant gets the jelly! And then Mom gets mad because you left a jelly drop on the table, and now there a ton of ants on the table. Clean up better next time...",
"3Blue1Brown did a good set of videos. I think people will like it.\n[Link](_URL_0_)\n\nBasically calculus is the math of small changes.",
"Calculus lets you do meaningful math on systems that change over time. \n\nFor example, your car's speedometer changes constantly depending on how hard you press the gas in any instant in time. You might guess that multiplying the speed readings at smaller and smaller intervals of time would result in the distance traveled by the car, and you would be correct.\n\nWhat your professor is saying is that Newton, Leibniz, Barrow, and others discovered that when the time units are chopped finely enough and added together, this simplifies into an astoundingly simple set of rules and patterns!\n\nMuch like this phone, you don't need to understand every detail of calculus to use it effectively.",
"There are two principle ideas in calculus, the derivative and the integral.\n\nThe derivative helps you answer one question: what's the slope of a function that's not straight? Here you build up tools to find a function that tells you the slope at any given point of another function, assuming the functions work well.\n\nThe integral answers another question: What's the area under a curve? Here you build up another set of tools which help you find a function which can be used to find the area under another function.\n\nIt turns out that, if you take the integral of the slope-giving function of one function, you get the original function back. This is called the fundamental theorem of calculus and relates the integral and derivative intrinsically.\n\nEverything else about calculus is learning the specifics and nuances of these.",
"Finally, my time to shine. Calculus isn't really any harder to understand that basic arithmetic once you learn the rules. I can teach a 5 year old the power rule, but they'd have no idea what they're doing. This is why people sometimes say ignorant things like \"Calculus is easy\".\n\nThere are different types of Calculus, but the one you're probably thinking of is known as Differential or Integral Calculus (which encompasses most of the fundamental stuff). Things like derivatives (or anti-derivatives) of polynomials, rational functions, trig functions, so on.\n\nA derivative is basically just the slope of a function at a given point. You can spend several weeks just learning how to find slope of very nasty functions just using derivatives. Then come integrals, or anti-derivatives. These are essentially derivatives in reverse. You can use these things to find solutions to initial value problems or some very basic differential equations. \n\nAt its heart, Calculus is a tool we mathematicians use to analyze function behavior. In a sense, we can \"see\" what a particular function does at certain values by using Calculus (This is still the 'baby' version of Calculus though). Most of the applications of 'baby' calculus are in engineering and physics problems, where you use it to solve some different types of differential equations. However, this is only a part of the story. \n\nOne of my favorite things you can use Calculus for is to make sense of factorials with fractions. For example, 3! = 1•2•3 = 6. But what about (1/2)!... well, the story gets messy here. You'd need a tool called the gamma and beta functions to help out (which are sort of messy integrals), but they work! I could go on for days, but I hope this helps some :) Cheers! ",
"calculus: a way to solve new problems, and solve some old problems faster, Calculus is useful for finding the volume of weird shaped items mathematically, or finding the instantaneous speed of an object. its basically just algebra 2.0",
"Calculus is the mathematical study of rates of change.\n\nSay you have a big water tank, and it has a hole in the bottom so water is leaking out. With algebra, you figure out how fast the water is leaking out and solve for how long it takes the tank to empty. Easy!\n\nExcept when you go to do this, you figure out there's a problem. As the tank empties, the pressure pushing the water out goes down. There more water in the tank, the faster it comes out; the less water as it drains, the slower. Uh oh!\n\nCalculus. ",
"There's a thing you can do with calculus called Optimization. \n\nImagine you are a corgi playing on the beach and your human throws a tennis ball into the ocean diagonally from you. You are a fast runner but a slow swimmer. \n\nYou can either jump right into the water and swim straight to the ball - pretty slow. Or you can quickly run along the beach until you are directly perpendicular to the ball, then jump in and swim to the ball (your path makes a right angle) - a faster option, but you travel the most distance this way. Still relatively slow. But there is a sweet spot in the middle where you run only a little ways along the beach and then jump in and swim the rest of the way - this is the fastest option and can be calculated using calculus. \n\nFun fact - most dogs do this instinctively :D\n\n",
"Calculus explains the relationship between a car's position, speed (change in position over time), and acceleration (change in change in position over time). People have intuitive understandings of these things, even without understanding calculus. ",
"Calculus is pretty much the algebra of infinities (and infinitecimals, which are easily understood as being like 1 over infinity, pretty much infinitely small). It's easiest to understand on a graph. \n\nYou first start with limits, which basically are a fancy way of saying what value does a function approach as x gets infinitely close to a number. These become especially useful because you can use them and say that f(x) is approaching infinity. You can't actually plug in infinity because it's not a number, but conceptually you can talk about f(x) as it goes *towards* infinity.\n\nSo okay, now you can do that, how is it useful? Mainly in defining the other two dig operations of calculus which are inverses of each other: derivatives and integrals. The first thing we do is take the slope of two points on a curve: which is (y2-y1)/(x2/x1), or for a function we use the values x and x+a (which is just \"a\" units away from x, like 5 and 5+2 = 7 where x = 5 and a = 2, so a is the distance between the two points) (f(x) - f(x+a))/(x-(x+a)). Let's take a break here and picture what's happening. [You're putting two points on a function and drawing the line that touches both of them.](_URL_0_) Back to math. Then we take the slope of the two points and shove it into a limit as \"a\" approaches 0. This means as the distance between the two points (picture them moving closer) gets infinitely close to 0, you are getting closer and closer to the exact slope at that point on the curve (also known as the tangent line aka. the line that only touches the curve at one point).\n\nNext, we do the opposite; if slope is dividing rise by run, we're now going to multiply them to find the area under the curve. We'll start by splitting the curve into rectangles with equal widths and heights at the function values (usually at the left, right, or midpoints of the intervals, but it can be anywhere really). [Here's a gif](_URL_1_) Add the areas all up and hey, this is a pretty good way to approximate the area, but there's all that extra area. We get closer and closer to the actual value as we make more rectangles. So we start going to infinity. Write a summation (fancy way of adding a lot of things) that adds the sums of width*height for all rectangles. Stick it in a limit, use the limit to say n (the number of rectangles) approaches infinity. Boom, you've got a perfectly accurate way of finding the area. Then you just find easier ways of doing this stuff and applying it to more things and build off of it. ",
"I see all these big paragraphs trying to explain calculus. To simply put it, its the study of change.",
"So, something that I don't see mentioned, that I think is incredibly important to talk about, is Limits. Basically, what happens as you're going along, getting closer and closer to something, but without actually reaching it. As u/ibdx suggests, what happens when you use pieces of tape that get closer to zero width, but without reaching zero width (cause that'd be silly).\n\nCalculus wants to know, what happens when (sin(x))/(x) gets reeeeeeeeeeeeeeally close to x=0? since at x=0, the equation is undefined. What happens when you take a straight line that goes through 2 points of a curve and move those 2 points really close together? (i.e. a tangent line) These and many more things can be done by taking a Limit as some variable approaches a number (or infinity) and that gives you the basis of Calculus.",
"I realise my lateness but I tell people this:\n\nderiving a function tells you *how fast* something is changing\nintegrating tells you *how much* something has changed\n\nSeems to find a nice pigeonhole in people's heads.\n\n",
"Calculus is the study of change. Basically, algebra has mostly linear equations where everything is nice and neat. However Calculus focuses on cases that are not so linear and therefore curved and ever changing. I wouldn't consider it a higher math, but rather a math that focuses on more real world problems because anything that happens in the real world is never perfectly linear and always has some difference somewhere. For example in physics, if you have a \"normal spring\" there is no friction and you can simply just use algebra to manipulate and solve for various variable. However, in real life there is no frictionless spring and the only way to deal with this non ideal spring is to use calculus. ",
"Calculus is all about continuous change. It's one of the fields of study in mathematics. It's not a higher form at all, it's just something new that you learn.\n\nLet's say you want to calculate the speed of a car from a graph at one second. You can pick a point at 0 and 2 or 0.5 and 1.5 or 0.999 and 1.001. This is discrete change.\n\nHow do you calculate the speed at EXACTLY 1 when you need at least two points? How do you calculate things like instantaneous speed or instantaneous acceleration or instantaneous heart beat and so on?\n\nCalculus gives us tools to deal with getting infinitely close to things. So instead of average speed between two discrete points, we get speed at exactly the point we want.",
"The study of continuinity; space and time. Most things are dependant of the two, yet humans tend to understand these things better in fragments, peices of the whole. Think of time, we divide it into minutes, hours, days to discretely make since of an past or future instance. Yet this is a mere approximation of the exact, precise, moment in time we are wishing to reference. Calculus gives judgment of how to estimate continuous ideas in discrete separate entities while providing the resulting error in doing so. ",
"I see a lot of people here talking about finding slopes and rates, and all of this is correct. There's also people mentioning the area or space under a curve/surface, which is also calculus.\n\nAll of this is true, but I want to add something that gets at the beauty of calculus a bit more, and doesn't even require notion of functions!\n\nAt its heart, calculus is the relationship between change (ie. rates, slopes, differentials) and content (ie. volume, area, distance, etc). It's a field that connects how big something is to how much it grows when small changes are made or, conversely, how knowing the rate that something is changing can tell you how much \"stuff\" you've accumulated.\n\nFor example, pretend you're in a vehicle where you can't see out the window. The only thing you can see in the car is the speedometer. As the car drives, you can keep track of the speedometer at every point in time and you'll know how much distance the car has traveled without being able to measure the distance of the car's path.\n\nI think it's beautiful that calculus connects two seemingly unrelated: change and content. This is what math is in general though - it is the study of taking seemingly disparate things in the world and showing that they are fundamentally connected.\n\nEdit: added a small point on functions",
"This is going to be a simple explanation, but probably not for a 5-year-old.\n\nA lot of people think that math is about numbers and computing things. Like, solve this equation, multiply these numbers, find the value of that side, etc. But that's not right. Really, math is about *understanding* things. Math is about *how* things work and *why* they work. Different branches of math are about how and why different types of things work. For example, arithmetic is about how operations with numbers work. Algebra is about how solving basic equations works. Geometry is about how shapes work. Etc. Well, calculus is about how really tiny things relate to one another and how they come together to make normal-sized things.\n\nWhen I was really little, I knew how to count and add and such. I liked to play with Legos, and my dad taught me how to multiply with Legos. So a 4x4 piece had 16 dots -- I could see the 4 rows of 4 dots each, and I could count the 16. So that's how you multiply. And that's also how to get the area of a rectangle. I understood those before I was 5; it was pretty easy! So it's clearly not so far-fetched for a 5-year-old to understand a little arithmetic and geometry, right? So why not a little calculus?\n\nThe easiest way to understand a little calculus is to sit in the middle seat and look at the speedometer in the car. What speed does it say? Maybe it says 31 miles per hour. This means that, if you keep traveling at this speed, you'll go 31 miles in an hour. Any kid can understand that (even if the kid doesn't really know how far a mile is). But then your dad slows down and stops at a red light. The speed is 0 miles per hour now. Did you actually go 31 miles in an hour? No; 31 miles per hour was your speed only at that instant in time. Now the speed is different. The idea that it even makes sense to *have* a speed at an instant in time is... calculus! You calculate speed by seeing how far you go and dividing by how long it took you to get there, but that only gives you *average* speed. For the speed *right now*, you have to see how far you go in a very, very, very tiny amount of time. You only go a very, very, very tiny distance. And you divide by that very, very, very tiny amount of time to get a speed in numbers that you understand. Calculus is when you make that amount of time tinier and tinier and tinier, and that makes the distance tinier and tinier and tinier too, so that, at that moment, the tiny distance divided by the tiny time is 31 miles per hour, but a second later it might be 30 mph or 32 mph or something else.\n\nYou generally use calculus to talk about how fast things change -- in the case of the car, it's how fast your position changes, but lots of things can change. How fast something is changing *right now* is called the *derivative*. Sometimes you know how the rate of change for something is related to other things. For example, if you have a weight on a spring, you can write how fast the *speed* of the weight is changing based on its position on the spring, and you can write an equation called a differential equation.\n\n(I'll show you an example that's way above ELI5, so you can skip it if you want: Hooke's Law says that the force F = –kx, where k is some number and x is the position away from the spring's equilibrium. Newton's Second Law says that F = ma, where m is the mass of the object, and a is the acceleration. Acceleration is how fast the speed -- well, actually, velocity, but let's not get confusing -- changes over time, and speed is how fast the position changes over time. So the speed v = x', where ' indicates a derivative with respect to time, and a = v', so a = x'', called a second derivative. Since F = ma and F = –kx, we get mx'' = –kx, and we want to solve for x as a function of time. This is a differential equation. The solution is x(t) = Acos(wt) + Bsin(wt), where A and B can be any numbers, and w = sqrt(k/m). In order to figure out A and B, you need to know how the weigh starts out. If the weight starts at the equilibrium position and it's not moving, then it's not going to start moving, right? A = B = 0. That's boring! But if the weight starts at x = 5 at rest, then A = 5 and B = 0. There are lots of possibilities. How did I solve this? Calculus! Not going to get into it here.)\n\nYou can also use calculus to talk about how lots of little things can add up to a big thing. For example, let's say you have an object, and you want to know how much it weighs. You can break it up into tiny little pieces, figure out the density for each piece, figure out how much each little piece weighs, and add them all together. That's calculus! (Or you can just put it on a scale -- that's physics.)\n\nThe calculus of how fast things change is called *differential calculus*, and the calculus of adding up lots of little things is called *integral calculus*. In differential calculus, you take a tiny little number and divide by another tiny little number to get a regular-sized number. In integral calculus, you add together a very, very, very *large* number of tiny little numbers to get a regular-sized number.\n\nNow, actually *doing* calculus is much more advanced, but it's not actually *hard*. You basically just memorize a bunch of formulas. For example, the derivative with respect to x of x^n is n·x^(n – 1). When you need to take a derivative, most of the time you can just use that rule and similar rules. There are a bunch of them, but they're not hard to learn. There are rules about taking the derivative of stuff multiplied together or added together or divided one by the other, and even when you have a function of a function. It's actually pretty easy once you get the hang of it! Integrals, it turns out, are the inverse of derivatives, so you have a different set of rules but they're just the opposite of the rules for derivatives (for example, ∫x^(n)dx = x^(n + 1)/(n + 1) + C; it's just the opposite of the derivative rule -- never mind the C for now). But the rules for multiplication and such are much more difficult, so a lot of the time you just *can't* take a nice-looking integral, not because you don't know how but because it's actually not possible without inventing new math (for example, people couldn't figure out how to do ∫dx/ln(x), so they just made up a new function [li(x)](_URL_0_) to be the answer). There are quite a lot of rules for taking integrals, but in the end, it's not really very difficult. You just have to learn how to do it, that's all!",
"physics major for a few years (then the actual physics happened and i changed majors, but i took all my calc classes)\n\n[integrals] (ANY kind of engineering, design, how computers calculate things for us)\n\nimagine you dont have a computer, and you want to perfectly measure a curve, or a slope, and the area inside of it. what if this curve is funky and weird? and you only know how to calculate the area of a rectangle? \n\na few people figured out that if you take tiny bits of this curve at a time, and transform them into rectangles, you could accurately measure the area under this curve, depending on how intense you wanna make these small rectangles (this is usually called a Reimann approximation).\n\nnow think about how many curved objects you see in your day to day life (this is also one specific example, theres TONS of things you can do with other aspects of calculus). when you use a 3D modeling software, you are basically doing this. same goes for 3D printing. the better processing power you have, the more accurately you can map that thing with millions of little shapes.\n\n[derivatives] (specifically used in physics, but again can be applied to anything)\n\nnow imagine you want to measure the speed, or velocity of a thing. people figured out you could divide the distance by the time. what if you wanted to measure the speed in a SPECIFIC moment, without having to know the entire time and speed? you *could* divide the time and the speed in half, right? you now do that instead of rectangles, and try to get it down the smallest data point possible. this allows you to create graphs of variable speeds (accelerations (speed divided by time)).\n\nhowever, you reach a point where you eventually will be dividing a super small distance by a super small time. these points essentially become zero, where dividing by zero is a big no no for mathematics. calculus (and derivatives) were essentially created to skirt the math laws and divide by zero. the Formal Definition of a Derivative is the landmark of calculus.\n\nthis formula is basically saying that as the limit of time approaches zero, you will receive an output of a derivative, at a certain point. several other math laws were created to support this (however there were many math schisms throughout the years debating notation), and it basically allows us to divide something by essentially zero. this lets you calculate the speed of a thing at any given point, which is absolutely essential for physicists and engineers, and many other different fields.",
"In short, calculus is understanding how functions change. A common representation is using a function (an equation with at least one variable such as x) of distance into a function to calculate the velocity of an object, but there are multiple scenarios where calculus can apply. The act of finding the rate of change in a function is \"finding the derivative\". You probably recall doing this in algebra with y2 minus y1 over x2 minus x1 to calculate slope. However calculus works on more complicated functions, not straight lines, and this is because functions that involve more curves are definitely more realistic when understanding the idea that a straight line will basically mean little to no rate of change at all. Now, integrals are almost like finding a derivative, but backwards. Given a differentiated (derivative) function, can you find the integral (the original function)? A good real-world example is, let's say you're given a function that represents the rate at which something sells, what is the integral of that equation which will help you understand how much in quantity did it sell over a period of time? The reason why derivatives/integrals are accurate is that a graph used to measure an output given various inputs (like distance for the y-axis given time for the x-axis, respectively). If you know that a curve represents that, then you could figure out the derivative, distance over time, is velocity, that being slope, a process of division which is simply rise over run. While velocity multiplied by time is total distance, which is multiplication, and it checks out because you multiply two numbers to find an area (base times height), or specifically the integral - the function of the area under the curve - because area changes over time with a curve. \n\nEDIT: BTW sorry for the shit load of run on sentences and bad grammar, it's 1 AM and I really am rushing trying to type this before i sleep.\n\nSource: Math undergrad, i like math.",
"You have a function, which takes one number as input and yields a number as output. You have a functional which takes a function as input and gives another function as output.\n\nMost functions have outputs which depend on input. The question that arises is how much does the output change if you change the input? Do small changes in input also yield small changes in output? How to measure this?\n\nThe answer is the derivative, which is a functional - it gives a function which tells the rate of change for an input given function. The derivative of constant functions is 0, because of no change; for the identity function is 1 because of constant change. One can compute the derivative of most functions (not all functions are derivable) by a simple formula: (f(x) - f(y)) / (x - y)) where y is a number very close to x, but not quite x; in mathematical terms a limit. The integral is just the opposite operation of the derivative.\n\nThis is just an analytical approach. Actual historical approaches were through physics/mechanics by Newton in describing instant speed and through geometry by Leibniz by measuring the slope of curves. ",
"I feel like all the answers so far have each given bits and pieces, like looking through a window at the part of the whole...\n\nCalculus is the study of changing things.\n\nThe most obvious use of this is change over time, associated with motion of objects. Drop a ball. Because of gravity, its speed changes. How long does it take to hit the ground and how fast is it going when it hits? Alternatively, drop a ball and it takes 5 seconds to hit the ground: how high was it? Calculus gives you the tools to answer those questions.\n\nSimilar to this, and one of the original problems that inspired Newton to develop calculus, was solving planetary orbits. The planets move due to gravity. How do their orbits work? Calculus lets you compute details about the orbit. Or alternatively, by observing the orbit, calculus lets you compute the mass and distance of the planet.\n\nThe most up-voted post on this thread so far is about approximating the shape of a circular window with straight segments. How to view that in terms of change? Imagine constructing the window by taking a radius of it, and then rotate that radius around 360 degrees until you have the window. Applying calculus to that process of the radius's change of direction over time, lets you calculate the area and perimeter of the window.\n\nRelated to that, one way to calculate the volume and surface area of curved solids (e.g. a sphere) is by taking a slice (a semicircle, in the sphere's case) and rotating it around an axis.\n",
"I think peoples descriptions in here are more complicated thsn they need to be.\n\ncalculus is the math of change. Specifically the math of the rate of change.\n\nOther maths will let you calculate things in a static (non changing) environment, calculus will let you calculate things that are constantly changing.",
"3Blue1Brown (the best math YouTuber ever) has a really nice series about it: Essence of calculus: _URL_0_",
"Check out [Calculus Made Easy](_URL_0_) by Silvanus P. Thompson. It's a very simple and amusing explanation of calculus. \n\nThe very lovely prologue:\n\n > Considering how many fools can calculate, it is surprising that it\nshould be thought either a difficult or a tedious task for any other fool to learn how to master the same tricks.\n\n > Some calculus-tricks are quite easy. Some are enormously difficult. The fools who write the textbooks of advanced mathematics—and they are mostly clever fools—seldom take the trouble to show you how easy the easy calculations are. On the contrary, they seem to desire to impress you with their tremendous cleverness by going about it in the most difficult way.\n\n > Being myself a remarkably stupid fellow, I have had to unteach\nmyself the difficulties, and now beg to present to my fellow fools the parts that are not hard. Master these thoroughly, and the rest will follow. What one fool can do, another can.",
"Really simple example of calculus application :\n\nYou have data about a car's acceleration value. You can use calculus to find the speed at which this car was going at any moment.",
"Actual eli5: when you turn on the bathtub faucet, the bath starts to fill up with water. When you turn it on more or less, the bathtub fills up quicker or slower. Calculus helps you figure out how long it takes to fill the bath (or how much the faucet is turned on by looking at how much water is in there).",
"I use calculus all the time in Economics - it measures relationships between two variables and how much one variable will change as a result of a change in another, e.g how much output will change if you add in an extra employee. It can be used for a whole bunch of other stuff too such as finding the area between a curve and the axis, which in turn can be used to calculate how much producer/consumer surplus there is when given supply and demand curves etc. ",
"I'm going to try to explain it using non-mathematical concepts that people already understand.\n\nBasically, calculus is about how you can take a big, complex problem, divide it up into parts, then simplify those small parts to be super easy (even if that simplification is a massive one), and then put them back together and bam, you've solved the big problem. Well, you solved it if you divided it up small enough.\n\nThat's a bit complicated, so let's use an example you're actively looking at right now: your computer screen. It's doing a very hard problem: showing you an image. However, there is absolutely no way it can really show you a full realistic image. Computer screens can't do that. So instead, it breaks it down into pieces. Your computer screen is made up of pixels. That's easy. Just have one little piece that's just one color. It's not an image, but an oversimplification of an image, just a dot. However when you put all of those pixels together, you get a computer screen that *fakes* an image. Again, it's not an image. It's just a collection of dots. However the more pieces you divide the problem into, the better the result. The more pixels, the closer you get to the real picture.\n\nHere's the real interesting part: when we're doing this with raw numbers and data, we can see trends as the \"pixel\" count increases. With those trends, we can extrapolate out to pieces that are infinitely small, and when that happens we are no longer dealing with an approximation. The sum of all the infinitely small pieces is now exactly the real thing. That's the miracle of calculus. It's a bit hard to wrap your brain around, but think about it this way: would a pixelated picture with infinite resolution really still be pixelated?\n\nThat's calculus. It's applications are huge because it turns out there are tons of massive problems that can be broken down into simpler chunks.",
"I'm late to the game and this won't see the light of day. I had another student explain it to me like this after having failed my calc class the first time. \n\nWhen you have an equation where you don't know a number, like 3 times \"something\" equals \"another something\", with \"something\" represented by \"x\".\nCalculus is how to do math on the \"x\" to add or remove it so you can solve it. ",
"Calculus in 10 seconds: calculus is the process of getting accurate approximations of something being measured. It works by splitting up the thing being measured into infinitely tiny pieces, then putting all the pieces back together to get an pretty accurate approximation of whatever is being measured. ",
"The most simple explanation I've ever had, was that Algebra is the language or tool that you use in Calculus and Calculus is how we fly planes and build bridges.",
"A definite integral is a SUPER adder. This magic symbol can add together an infinite amount of numbers, and give you a finite number. "
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4r5joj | exempt vs non-exempt | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4r5joj/eli5_exempt_vs_nonexempt/ | {
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"Exempt versus nonexempt what?",
"ELI5 is not a dictionary, but I'll see if I can help you out (assuming you're talking about what I think you're talking about).\n\nIf you are talking about classifications of employees, a non-exempt employee is entitled to overtime pay (since they are not exempt from the overtime pay laws) while an exempt employee is not entitled to overtime pay (which is useful for an employer since they don't have to track the employees hours no matter how much the employee works if they are paid on commission or on salary, and don't have to worry about paying overtime).\n\nExempt employees, however, are, by definition, the *exception* to the rule, so the employer and employee have to meet very specific criteria to fall into this category.\n\n"
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3aqvht | Are we lighter than we "should" because of earth's rotation? | So our body has mass so we are being pulled towards the centre of the earth with a certain force. The thing is: earth is rotating so is the centripetal force having any effect on our weight?
Would we be heavier if the earth stopped rotating? (assuming everything else stays the same) | askscience | http://www.reddit.com/r/askscience/comments/3aqvht/are_we_lighter_than_we_should_because_of_earths/ | {
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"The rotation of the Earth does lead to slightly lower gravity near the equator, both due to the centrifugal force and the oblateness of the Earth that it causes. However, the overall variation in field strength across the planet is less than a percent.",
"Weight is defined as mass times (edit: **acceleration due to**) gravity, so in that sense, our weight is unaffected.\n\nAlthough, since rotation does deform the earth's shape, we're farther from the earth's center when we're near the equator than when we're closer to the poles, so we would technically have less weight (by virtue of experiencing less gravitational pull) if we were near the equator. However, the same could be said if we were on a mountain (and the reverse if we're on the ocean floor), and the difference between the shortest and longest diameters (major and minor axes) of the earth is less than 25km.\n\nIn terms of what a scale might say, it would measure lower weights near the equator than near the poles due to the rotation, if it was precise enough. If you're under 289 pounds, you could take a one pound dump and make more weight difference than standing at the equator when the earth slows to a halt (\"an object experiences a centrifugal force equal to approximately 1/289 of standard gravity\").\n\n**tl;dr** You are lighter in that your feet will have to exert less force to hold you up, but not by your actual weight (unless you're considering the shape of the earth, which was partially caused by the rotation). It's definitely not nearly significant enough to be noticeable without instruments to measure it.",
"furthering the others' explanations, there is a third force which affects your apparent weight: the buoyant force.\n\nTechnically, when you are in air, there is an upward force on you equal to the weight of the air you displace. Much like the deviations from the spinning earth, these effects are too small to be concerned about in general."
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d1siek | how and/or when did the egyptians, greeks, vikings, etc came up with the name of their gods? | \*If these gods "existed" way before them (As in almost every civilization has primordial gods in one way or another), how or when did these gods received their names?
\*Or are these names something archaeologists interpreted from discoveries regarding said civilizations?
\*Are these names like Zeus, for example, a really accurate translation of their original names? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/d1siek/eli5_how_andor_when_did_the_egyptians_greeks/ | {
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"The Greek/Roman/Norse/Germanic gods developed alongside the languages. The names similarly changed. We do have texts written about all those gods in a phonographic alphabet so we know how they pronounced the names. For example Dyeus Phater (Day father or Light father) would be pronounced slightly differently in different regions of Europe over centuries and would become both Dipeter or Jupiter and also Zeus Peter in Greek and Roman languages respectively. In Germanic languages however Dyeus became Tiwaz and then in Norse Tyr. This is just like any other words in the language changes over time."
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9kwk5j | how can glass be cut using a laser? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9kwk5j/eli5_how_can_glass_be_cut_using_a_laser/ | {
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"Glass absorbs some of the energy from the light that passes through it. Look through a piece edgewise and it will look green or blue as a result. With a laser you can put a huge amount of energy into the beam. Even if the glass only absorbs 1%, a good CO2 laser can add enough energy to melt the glass under the beam.",
"in addition to glass not being perfectly clear, not all kinds of light pass through glass. glass blocks infrared, for instance. humanity uses glass in part because it doesn't significantly disrupt the part of the spectrum we can see. \n\nit's entirely possible to fire a laser of a wavelength that glass will absorb.\n\n"
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2o8ii7 | why is cyprus still split in half. | I understand why it was split with the Greeks and Turks fighting over it but why like 30 years later is it still divided? You would think a UN mandate or something would come through settling this issue. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2o8ii7/eli5_why_is_cyprus_still_split_in_half/ | {
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"The same reason Israel is still split with Palestine. The division runs deep. The north has actually declared independence and is backed heavily by Turkey. I briefly lived in Paphos in the west (Greek) in 1992/3. They lived as though the east didn't exist. Nobody seemed to talk about it, but the hatred is there.",
"Brief history:\n\n* Cyprus essentially becomes a British colony in 1878 (and officially in 1925)\n* the British grant Cyprus independence in 1960\n* sectarian violence between the Turkish and Greek Cypriots breaks out soon after, and is an ongoing problem\n* in 1974, a coup overthrows the Cypriot government, and seeks to become part of Greece\n* Turkey invades to protect Turks in Cyprus and to prevent Greek annexation\n* the Cypriot gov't is restored, Turkey stays anyway\n* Greek Cypriots are kicked out of the Turkish section, Turkish Cypriots move from the Greek section in a mass migration\n* in 1983, Turkish Cyprus declares independence, no one but Turkey recognizes it\n\nSince then, not much has happened. The has been a UN mandate condemning the Turkish occupation, but Turkey is a much more important ally to the West than Greece is, especially during the Cold War, so that is as far as it went.\n\nIn Cyprus, the Turks are in the Turkish section, the Greeks are in the Greek section, and it is probably more peaceful than before Cyprus was divided.",
"The turkish army invaded in 1974 because they claimed they wanted to protect the turkish community in cyprus who were settlers from mainland turkey when cyprus was still part of the ottoman empire.\n\nInstead they created a breakaway republic and actually allowed mainland turks to migrate to make it harder for greek cypriots who were the majority in the nowadays area under control of the turkish Cypriot republic, to regain it.",
"Because:\n\nTurkish military, inept politicians, ethnic hate and misunderstanding."
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z6yto | Is it possible to generate hydroelectricity, by placing turbines within downspouts? | Assuming this is in an area with heavy annual rainfall. The water is falling from the sky, and achieving maximum head. The problem seems to be with flow. It isn't constant and can be erratic. | askscience | http://www.reddit.com/r/askscience/comments/z6yto/is_it_possible_to_generate_hydroelectricity_by/ | {
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"You mean like off your roof?\n\nIt's technically possible, but I doubt you'd get enough to be worth collecting it.\n\nBut if you're way out off the grid, and needed to charge a battery, you could do something like this:\n_URL_0_",
"The water in a downspout from your roof doesn't fill the pipe as it flows down. It clings to the surface of the pipe and the center of the pipe will remain full of air. This even happens when there is a larger volume of water involved, such as in the waste pipe from a bath, there is still a large amount of air in the pipe. This will make a turbine unsuitable as a form of energy extraction.\n\nIt may be possible to rig up some kind of generator, but unless you have a large roof and have some way to divert all that water through the same downspout I doubt you'd ever recover your investment. You also have to deal with the debris that usually ends up in the gutters, such as leaves and twigs.\n\nedit: It may be worthwhile to just collect all the rainwater in tanks, maybe keep them as high as possible, just under gutter level. Then you could intermittently empty the tanks through a thinner pipe with a turbine inside it. That would avoid both of the issues mentioned above, but you'd still get a very small amount of power from it. \n\nIn my situation, I have 40 m^2 of roof and get about 1,000mm of rain per year. With a head of 3m and 40,000 litres of water, I only have a potential energy of 1,200KJ or 0.33 Kwh per year. That's about 6c worth of electricity where I live. Nah, not worthwhile for me at any rate. ",
"Well hold on: Failling from the sky has nothing to do with it's head in this case because it hits the roof and thus has however tall your structure is for head (If that makes any sense). \n\nIn any case, the amount of energy from it is going to be pretty small, even if you have a 50x50 ft roof and it rains 1\" in an hour, you'll get a whole 47 watts (assuming 60% efficiency) avg during that time. \n\nEDIT: I live in Seattle and we get about 5.8\" a month in our wettest months. Quillayte, one of the rainiest cities in Washington, gets 14.82\" in its wettest month. Which means you'd get .70kw/h of power from it on the rainiest month of the year, in an extremely rainy city. "
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2odhtz | why as an adult sitting on your knees is so painful compared to when you were a kid. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2odhtz/eli5_why_as_an_adult_sitting_on_your_knees_is_so/ | {
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"That possition puts your weight on a relatively small area.\n\nThis matters more when you're an adult than when you're a kid because of the square-cube ratio.\n\nThe square-cube ratio means that while your volume and mass increase by a power of 3, your surface area only increases by a power of 2.\n\nThis means as your size increases, the ratio of surface area to mass decreases, and you therefore have more pounds per square inch on your knees.",
"I have being practicing Aikido for 20 years. I can sit on my knees for days on end of needed without any issues. \n\nAs a kid you were more flexible, now you're an old fart and getting more stiff. ",
"\nAdults can kneel/squat pain-free with practice. When I lived in Japan, sitting on one's knees was an unfortunately common thing to do, but after a few months, it was like second nature. \n\nCoincidentally, elderly Japanese are flexible as hell knee and hip-wise. Years of kneeling/squatting keeps the knees and hips loose, and I saw even 85+ year olds crouch with ease. ",
"edit - now more eli5-y at the bottom\n\n/u/Sand_Trout 's [post](_URL_0_) deals with some of it, but another factor is the way stress works with growing sizes. It's similar to why a kid can make a bridge out of 200 Popsicle sticks that can hold 900 lbs, but we don't just recreate a giant version of that model out of Popsicle sticks. the material Popsicle sticks are made out of can only handle a certain amount of stress. As an object scales up, the stress exerted on it by itself (as in the force of its own weight) increases linearly as well. The same thing explains why there aren't giant insects - the biological materials that are so effective to allow ants to carry a thousand times their weight can only handle that stress when scaled down very small. \n\nCombining this with /u/Sand_Trout's post, your mass increases greater than the surface area of your knee. So, it's not even the linear stress that increasing size by a scale factor causes, it's even more, because your upper body might increase by an even bigger scale factor than your knee. Being on your knees as an adult causes a lot more stress on your joints and muscles than being on your knees as a child does.\n\nI'm sorry if this wasn't ELI5 enough, let me know if you want me to try again.\n\nFor some additional not ELI5 material, here's some math to go with what I said about stress. \n\nStress = Force / AREA (force being a perpendicular force to the surface area). Let's say a Popsicle stick is cylindrical, with Radius = 1cm (or .01m) and a length of 20cm (or .2m). The mass of this Popsicle stick is 5g (I 2don't know if that's reasonable or not, just made it up). \n\nThe surface area = A = pi*r^2 = 3.14*(.01m)^2 = 3.14(.0001)m^2 = .000314m^2 = A.\n\nF = the weight of the Popsicle stick = m*g = .05Kg*9.8 = .49N\n\nStress_1 = F/A = .49N/.000314m^2 = 1560.5 N/m^2\n\nNow let's scale this Popsicle stick up by a factor of 4. The new Radius is 4cm, and the length is 80cm. The volume of a cylindar is pi*r^2*length. We're doing pi*(4r)^2*4l = 48*pi*r^2*l, or 48 times the initial volume. The surface area is going to be pi*(4r)^2, or 16*pi*r^2. This is the Square Cube law, the volume of a cylindar increases by a cubic factor (cube of the scale factor), while the surface area is going to increase by a square factor. Since the volume increases by a cubic factor, the mass must also increase by a cubic factor.\n\nFor us, using m and r from the original equations, we get:\n\nstress_2 = F_2/A_2 = 48*m*g / 16*pi*r^2 = 48/16 stress_1 = 4*stress_1.\n\nSo, multiplying the dimensions by a scale factor of 4 also multiplied the stress by a scale factor of 4. But let's say the material the Popsicle stick was made out of can only handle a stress of .5Newtons/m^2. The original Popsicle stick is fine, because it only had a stress of .49N/m^2 which is less than .5N/m^2. However, our giant Popsicle stick has a stress of 4*.49N/m^2, which is almost 4x as big as .5N/m^2. The Popsicle stick just can't handle that stress and is going to break.\n\nGoing back to the original question, as you get older (and going from a child to an adult, we can assume bigger) your strain increases by a lot. Even more than the square-cube law, since you might get fat, as well. The amount of stress on your knee is going to be much bigger than the amount of stress there used to be on your knee, and thus much closer, or for some people, even exceeding, the maximum amount of stress your knee can handle. \n\ntl;dr stress increases linearly when you scale the size up, and the same materials you're scaling up can only handle so much stress.\n\nedit - ELI5 version:\n\nYou are building a tower out of play-doh. Play-doh can only hold up 5 lbs for every square inch of play-doh. That weight comes from the weight of all of the play-doh directly above the square inch at the bottom. Say we have 3 lbs above each square inch of play-doh. If we double the height, length, and width, we now have 2*w X 2 * l = 4*l*w or 4 times the number of square inches. However, each square inch has 2 * h inches of play-doh above it, which is twice as heavy as the first version of the tower. Now, instead of only 3 lbs for every square inch,we have 6 lbs for every square inch. The play-doh at the bottom can't hold up all of that play-doh, so your tower collapses. To answer OP's question, your knee is the bottom of the play-doh tower, and as you get older and weigh a lot more, you get closer to the point where your knee can't hold any more weight for every square inch.",
"You stop doing it so much as an adult, so you get soft.\n\nI meditate in seiza position daily, and it's not uncomfortable at all anymore. I also stock at a store, and I drop down onto my knees and slide around on them on concrete everyday. ",
"I always felt ashamed about this. Thought it was just me. ",
"How the fuck do you sit on your knees? ",
"Sitting on my knees was still painful as a kid. I was really fucking fat.",
"Simple.. It's painful because you spent so much time on your knees as a kid.",
"you're heavier. square cubed rule and all that.",
"It's not painful for all adults. If it is painful, it is because you don't sit that way normally, and your body isn't used to it. Your quadriceps are probably too tight. I am 49 years old, self-employed, rarely use chairs and sit on the floor most of the time. (My computer is on a table with the legs cut off.) I find that position very comfortable. Adults who do yoga or martial arts will have no problem with this. Edit: I'm assuming you mean this _URL_0_ "
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leihi | I read today that it takes around 30,000 years for light made at the core of the sun to reach our eyes on earth, how can that be? | How can the speed of light be reduced so drastically? | askscience | http://www.reddit.com/r/askscience/comments/leihi/i_read_today_that_it_takes_around_30000_years_for/ | {
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"The speed of light isn't reduced. The light produced in the center is adsorbed and remitted many many times. Each time it is emitted it goes in a random direction. Based off a 3 dimensional random walk calculation we find it takes 30,000 years for the light to reach earth. The calculation for a random walk considers radial distance (size of the sun), and interaction length (distance between absorptions).",
"Stars are huge. And full of stuff. Photons are absorbed and reemited whenever they run into something. Which is all the time. This takes some time to do. Ergo, it takes a long time for light to leave a star.",
"It's like leaving a crowded bar or theater. You're walking at 1.5 meters per second, but you keep bumping into people and having to change directions that it takes you a long time to get out.",
"The speed of light isn't reduced. The light produced in the center is adsorbed and remitted many many times. Each time it is emitted it goes in a random direction. Based off a 3 dimensional random walk calculation we find it takes 30,000 years for the light to reach earth. The calculation for a random walk considers radial distance (size of the sun), and interaction length (distance between absorptions).",
"Stars are huge. And full of stuff. Photons are absorbed and reemited whenever they run into something. Which is all the time. This takes some time to do. Ergo, it takes a long time for light to leave a star.",
"It's like leaving a crowded bar or theater. You're walking at 1.5 meters per second, but you keep bumping into people and having to change directions that it takes you a long time to get out."
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