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44czgp | why is there a mass refugee problem right now from dozens of countries? wasn't this originally because of syria attacking their own people? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/44czgp/eli5_why_is_there_a_mass_refugee_problem_right/ | {
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"There were a lot of refugees from those countries you listed before Syria, however when the waves of Syrians came, a lot of other people saw it and thought this was their chance to start a better life. If these European countries are letting thousands of people in why not me.",
"There have always been refugees seeking asylum abroad. There have been Afghan and Somali refugees since before the crisis. But with the massive war going on in Syria, the number of refugees has increased dramatically as have the stakes. There's also been an increase because of ISIS along with new fears that ISIS members will sneak in disguised as refugees.\n\nBecause the numbers are so huge right now, some counties are trying to reevaluate their policies. \n\nAlso, Middle Eastern refugees are more likely to go to Europe because of geography. "
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669t3d | how did video game developers test their games in the days of cartridges? | Being an aspiring programmer I think about all the times I hit "compile", and it makes me wonder how developers back in the Atari and the NES days didn't go bankrupt printing off test carts for the latest version of the game. Especially third party developers who didn't work on the hardware itself, and who I assume couldn't go printing their own carts until they shipped the final build off to Nintendo. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/669t3d/eli5_how_did_video_game_developers_test_their/ | {
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"Do you have to burn a DVD every time you want to test the latest iteration of whatever you're working on? \n\nThey ran the tests on the development machines they were working on. Transfer to cartridge comes later, when it's ready.",
"Before the days of official Dev-kits for consoles game developers would often build their own customized game carts that could connect to a PC directly or be repeatedly rewritten with new code.\n\nThey were fairly expensive, but you can reuse them for multiple development projects.\n\n",
"A cartridge is most often a set of Read Only Memory chips. However you can get special cartridges with other chips that can be rewritten. Some cartridges have unused pins so you can use the same interface to program them as the console and some require you to connect an external interface or to remove the chip from the socket and place it in a programmer module. Today the most common is the latter but with SD cards. Computer chips are usually quite easy to hook together in any configuration you want. If you have a soldering iron you could easily connect a Commodore RAM expansion cartridge to an Atari cartridge with a ribbon cable so you can read and write the content of the game from the Commodore. The chips use the same protocol with the only difference being some extra pins for the RAM chips to facilitate writing. In addition programmers did learn to take a lot of extra care when writing software back when compiling and deploying took longer so they would spend more time making sure there were no errors.",
"There were 'development kits', modified consoles that could connect to computers of the time. The computer could load a game onto the console, and could also inspect the game in detail, pause it and step through it, and so on.\n\nThis is a video about developing for a Sega Mega Drive using a real development kit: _URL_0_"
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1r0p8h | what are organic photovoltaic solar cells? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1r0p8h/eli5_what_are_organic_photovoltaic_solar_cells/ | {
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"Solar cells utilize a class of materials known as semiconductors to absorb light and generate electrical power. Conventional semiconducting materials used in solar cells are derived from single elements (silicon & germanium) or combinations of elements (gallium-arside & cadmium-telluride), that do not contain carbon.\n\nOrganic solar cells work the same way, but they use semiconductors made from carbon-based molecules, otherwise known as polymers or plastics. These carbon-based molecules must be specially engineered and paired together to facilitate the necessary physical process to convert light into electricity.\n\nThe potential advantages of organic solar cells relate to cost reduction, not efficiency improvements. However, I believe that it is unlikely for organic solar cells to ever gain popularity over their inorganic counterparts. They presently suffer from low efficiency ( < 10%), and short life-span (~2 yrs) at best. Inorganic solar cells made from silicon and gallium-arsenide can have efficiencies greater than 20%, and have a useful life-span longer than 20 years."
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9qoxs7 | do the lungs of a fetus do oxygen/co2 exchange in utero, and how does a newborn go from not needing to "breathe" air in the "normal" sense (while in the amniotic sac) to suddenly needing to breathe room air after being born? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9qoxs7/eli5_do_the_lungs_of_a_fetus_do_oxygenco2/ | {
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"All oxygen perfusion to the cells occurs through the umbilical cord until birth. Upon delivery, the neonate expelled the amniotic fluid and starts to breath air for oxygenation. ",
"The mother supplies oxygenated blood to the foetus via the umbilical vein and receives deoxygenated blood via the umbilical artery. The mother essentially does 'double-duty' and acts as the lungs for the baby. In the womb, the heart has a hole that connects the two atria together (the two sides of the heart are usually separate, so one side pumps blood to the lungs, the other pumps blood to the rest of the body). \n\nAs soon as the baby comes out and coughs out the amniotic fluid and takes its first breath, a flap in the heart closes and the heart works as two separate chambers (technically four) and baby uses the lungs to oxygenate their own blood. ",
"The short answer is no. The mother’s lungs are in charge of getting oxygen and ridding CO2 for the fetus. Upon exiting the womb, a number of physiologic processes combine to cause the child to cough up the amniotic fluid currently filling the lungs and increase blood flow to the lungs, allowing normal gas exchange to begin",
"The blood circulation is different before birth then after birth. There is a opening between the right and left atrium called the foramen ovale. The ductus arteriosus a special connection between the pulmonary artery and the aorta. The result is that a lot less blod is circulated trough the lunge before you are born.\n\nThe Foramen ovale closed at birth because changes in pressure when the lungs start to work. The Ductus venosus closed in most case during the first week.\n\nThe lungs will exchange gas with the amniotic fluid before birth bur as it is enclosed in the amniotic sac there gas exchange with the surrounding is limited. So most gas exchange occur in the Placenta with the blood of the mother.\n\n\nI video that show the flow can be show here. _URL_0_"
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dmb1l0 | how are compact cameras able to deliver a better optical zoom with similar quality than a dslr camera? | I jumped on the dslr train about 7 years ago but was disappointed by the lack of versatility, unless you dump thousands of dollars into lenses. My mother, on the other hand, bought a $400 compact Sony camera and it vastly outshines my Nikon DSLR. She gets 30x optical zoom whereas to get something similar for my camera, I'd have to spend hundreds to a thousand dollars, while having a gigantic arm-sized lens on the camera.
The thing that gets me is that it doesn't seem to be much of a difference in quality. (I could be wrong as I haven't had my own lens to try.)
I don't know if this sub allows posting of videos, but I'll link a video in the comments using my mother's camera as an example of the zoom. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/dmb1l0/eli5_how_are_compact_cameras_able_to_deliver_a/ | {
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"Example video:\n\n**Excuse the quality for a few minutes while Google processes it. Normally it's excellent quality. It should be 1080p.**\n\n[_URL_0_](_URL_1_)",
"Smaller sensor. Compact cameras usually have a 2/3 inch sensor while DSLRs usually have an APS-C sensor or larger, which is 3-4 times wider and taller than a 2/3 inch sensor. \n\nThe smaller the sensor, the smaller the other optical parts of the camera need to be, mainly the lens system. So a DSLR lens needs to be 3-4 times larger (and longer) than a compact camera's lens."
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3q4puz | why would someone pay the electric company to install solar panels on their home? | I'm noticing my neighbors taking advantage of promotions offered by the electric company to install solar panels on their home. you want solar the electric company isn't your only option. Why would someone purchase the liberator of a resource from the supplier of that reasource? Isn't it like hiring your your lawyer spouse to represent you against themselves in your divorce? Isn't there a conflict of interest between them wanting to keep you on the grid and you wanting to get off it completely? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3q4puz/eli5_why_would_someone_pay_the_electric_company/ | {
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"At least in France, the electricity you produce through solar panels is \"sold\" to the company. I think you use it directly but you pay less for your electricity. It's more an agreement than a potential conflict of interest. In France the main electricity company is mostly public, the electricity that is not used in the country is sold to European neighbours so the fact that you consume less doesn't really impact EDF's economy and it actually helps the country for their goals of \"green energy production percentage\" ",
"OP I don't know where abouts you're from but in places like England if you pay to install solar panels (depending on) the electric company will pay you for generating electricity. To install them you need to get a Energy Performance Certificate (EPC) that grades a house from A to D depending on how efficient the house is. You can save around £400-700 a year on bills depending on how far south you live. So basically even though it may cost alot it saves money off the electricity bill cause you're generating your own electricity, the electricity that you don't use is put back into the grid and the government pay you for both. In essence its win win. You wouldn't see an immediate profit but you definitely would in the long run. Its just up to you to add up the numbers and decide if its worth it\n\n\nSome added bonuses are that they:\n\nalso increase the price of a house\n\npanels are low maintenance\n\nyou don't usually need permission to install them \n\nwhen used at the right time they you can max their value\n\nYou can still switch electricity provider when they're installed. "
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1s9qv1 | when stopped by police, why do police always ask where you have come from and where you are going? | They alwayd ask this and it seems irrelevant to a seatbelt check point or being pulled over for a minor traffic violation. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1s9qv1/eli5_when_stopped_by_police_why_do_police_always/ | {
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"They want you to talk to see if you slur your speech or are confused, indicating intoxication.",
"I work with a lot of cops, and have had many interactions with them on the other side of the law. Why they ask is to see if there are any inconsistencies in your response. An inconsistency may allow the cops to have reason to detain you or search your vehicle. \n\nSuppose you say you are coming from work and are heading home. The cop asks where you work, and you say Red Town and your license shows you live in Blueville. If you are pulled over in Green City, 50 miles north of Red Town and Blueville, he can ask you further questions. If you say you went to visit your buddy Tom, the cop can ask you Tom's address. If you don't know, he can ask you why you went to visit Tom and why don't you know Tom's address. \n\nEach response gives him more information to ask more questions if your answers don't make sense. If he gets enough inconsistent information, he may decide to find out what you are really up to. "
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550ol4 | how can the president giveaway us control of internet without congress approval | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/550ol4/eli5_how_can_the_president_giveaway_us_control_of/ | {
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"The US doesn't control the internet. In fact it doesn't even do anything with it's current authority, not that is could. Giving up it's oversight is nothing but a formality where literately nothing will change about how the internet is used.\n\nIt's like how the Queen of England is the figurehead to the commonwealth countries. She doesn't have any actual authority over the countries but then Canada decides they want to change that. They ditch the Queen and replace her with a beaver or something. Literally nothing else would change. "
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4y541a | why do countries adapt central bank systems? | Based on what I know it seems like a terrible system, yet many countries seem to have it. What are the pros of these systems? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4y541a/eli5_why_do_countries_adapt_central_bank_systems/ | {
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"What makes you think its a terrible system?\n\nA central bank is in charge of the monetary policy of a country which means it controls the availability of money to help the economy. \n\nIn bad economic times it tries to make money more available by lowering interest rates so that people can more easily start a business or buy a house. If they have the power they can also print more money. Of course, you can't simply print your way to prosperity it's about making sure there is enough money to flow around the economy.\n\nIn good economic times it tries to remove money from the economy so it doesn't over heat by people being reckless. To do this it typically raises interest rates.",
"Pros: \n- adds predictability in policy and stability to a countries economic growth (or contraction) by setting the base interest rate for lending. (If economy gets too hot they can make loans more expensive, too slow and they can make loans cheaper - this can stop economies growing too fast / bubbles forming eg. US real estate, Chinese manufacturing) \n- Some (depending on their constitutional remit) can also stabilise a currencies exchange rate by buying/selling currency reserves. \n- prevents political manipulation that could have disastrous economic effects eg. A government writing themselves generous loans to finance frivolous spending just to stay popular leading to high inflation and weak currency (Zimbabwe, Argentina etc.) \n- usually act as a 'lender of last resort' for governments, to prevent them being in sovereign debt to foreign countries / world bank. \n\n\nCons:\n- governments can't interfere too much (governments are usually more interested in social welfare, compared to a central bank which is primarily concerned with economic welfare)\n- economic booms can't always be maximised to their full extent (interest rates generally only change periodically eg. Quarterly) \n- recovery from recessions can be slow\n- they are not always well run / cooperative with the government of the day. "
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13ks0d | why are lethal injections unreliable? | There are a surprising number of cases where the first "lethal" injection of a condemned prisoner was insufficient to actually kill them.
It doesn't seem like it should be that hard to kill someone quickly and painlessly, given modern science. Why aren't we using chemicals and dosages where there is no possible way any human could survive? And why are we bothering with these unreliable, expensive, messy techniques in the first place when we could do something a lot simpler and more reliable like just hook them up to a helium tank? Seems like this would be cheap, quick, painless, and have a 100% success rate. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/13ks0d/eli5_why_are_lethal_injections_unreliable/ | {
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"The problem is that there's no real way to test whether it's painless, since if it works it ends up with a person unable to report whether they felt pain.\n\nThe problem is that with any drug, there's no dose which leaves absolutely zero possibility of surviving, and most of the time we'd be talking about a pretty long, horrible, process if it did. Injecting a buttload of morphine doesn't work the way it does in the movies.\n\nThe way a lethal injection is *supposed* to work is first a painkiller, and then a sedative, finally something that stops lung and heart function. The problem is that too much of any of those things could (a) cause the procedure not to work, or (b) be painful. \n\nI'm not sure why you think a helium embolism would be quicker or less painful than a lethal injection, though. And if you mean to suffocate them, that's awful.",
"potassium is used in lethal injections. Electrical impulses are sent through nerves by moving potassium into a cell and sodium out. A cell in the axon of a nerve starts with a -60 to -80 millivolt charge differential between the outside of the cell and the inside. Potassium is pumped into the cell and sodium is pumped out changing to charge to +40 millivolts and causing the nerve to fire. This signal is carried down the nerve as each cell does this. When Too much potassium is outside of the cell it will be forced into the cell because of the osmotic pressure. This causes the nerve to constantly fire and in no particular order. When this happens in the heart it causes fibrillation and eventually will stop the heart. The process is painless because before the person is injected with potassium they are injected with either sodium thiopental or pentobarbital both of which will render a person unconscious within seconds. The process often looks painful for the victim because potassium makes all muscles contract and spasm even after the heart has already stopped. The reason it is said to be unreliable is because it is hard to determine how much potassium it will take to kill an individual and sometimes multiple doses must be administered. The person really just feels like they fell asleep because of the barbiturate. now whether it is ethical or not is up to you.",
"I don't know either. For animals, we usually first give an anesthetic so when the lethal drug is administered, they are already asleep. Even if the lethal dose doesn't stop their heart, you can easily administer more with no pain to the patient, who is already peacefully unconscious. ",
"One of the biggest reasons, as quoted by Jay Chapmann who invented lethal injection, is, \"I never knew complete idiots would be carrying them out.\"\n\nThe personnel who carry out the lethal injections are often not sufficiently trained to establish a reliable intravenous line. In addition, the drugs administered are given via a set series of protocols which do not account for age, gender, body weight, tolerances, or outstanding medical conditions. All of these things can greatly influence whether or not the dosage given will be sufficient to kill them. \n\nAlso, because a person is being injected with so many drugs at once, they interact in an unreliable fashion. \n\nLet's take sodium thiopental to start. It's typically administered in surgeries (like propofal) to induce unconsciousness. It's liked because it's a very fast-acting anesthetic which isn't particularly harmful to a person because after about 5 minutes it is flushed out of the brain to the peripheral tissues. \n\nYou can probably guess where I'm going with this. Bad freaking idea for a lethal injection since thiopental is not reliable for *continued* anesthesia. The victim will often start to wake up before the other drugs have been pushed. \n\nWhy isn't there more of a big stink about this? Glad you asked. The second drug administered is pancuronium bromide. It's also used in surgeries. As a paralytic. It freezes all muscle control, and that includes breathing. Normally a person receiving it must be put on a respirator, but the purpose here is to actually kill the victim, so they just let them choke. This prevents onlookers from seeing the victim wake up and begin to suffocate. \n\nThen comes the potassium chloride. It screws with the sodium/potassium pump in the heart and inhibits proper pumping. It also burns like the living bejesus, as the Nazis found out when they experimented with it on the Jews. The problem is that, by now, the victim has just had a whole ton of fluid titrated into his veins. Depending on the metabolic function of the victim, the potassium chloride may be much too diluted to actually do anything more than hurt and cause tachycardia, leaving the poor bastard to choke. \n\nA new method in some states is being proposed in which an intravenous overdose of pentobarbitol is administered, followed by a whopping intramuscular overdose of midzolam and dilaudid. Essentially the midzolam produces an amnesiac affect which, combined with the respiratory depression of the pentobarbitol and dilauded, knocks a person to sleep and keeps them that way until they stop breathing. Supposedly a lot less painful since actual opiates are used. It would also be more effective in victims where a reliable IV line cannot be established.\n\nPersonally, I think an ongoing anesthesia by gaseous inhalation of halothane, in conjunction with the dilaudid, potassium chloride, and pentobarbital would cover the bases more effectively. \n\nBut, you're right, hypoxia induced by pure nitrogen inhalation would probably be the best way to go. You just get light headed, dizzy, then fall asleep. Not even any respiratory distress like in the gas chamber or carbon monoxide poisoning."
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5cd5kk | why have americans become even more polarized in the 21st century despite the emergence of the internet as a medium where people can easily reach out to each other to learn about their opinions? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5cd5kk/eli5why_have_americans_become_even_more_polarized/ | {
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" > despite the emergence of the Internet as a medium where people can easily reach out to each other to learn about their opinions?\n\nIt's also easier to find people who agree with you and a lot of websites will just feed you stuff you already like, so everyone just ends up in their own little echo chambers where everyone is like them and any other ideas or opinions are tossed out.\n\nIn order to find other opinions you'd have to go look for them. And nobody does that.",
" tl;dr You seek out people with similar opinions. You avoid people with contradictory ones. You can meet anyone, so why would you meet people you disagree with?\n\n---\nFull response\n\n\n The internet allows you to reach out to almost anyone online and find all kinds of other new and interesting opinions.\n\n It also allows you to find other people who think just like you do. You might be the only one in your whole town who likes something, but thanks to the internet you can find someone 1000 miles away that also likes the same thing, and you can talk about it with them!\n\n Then you two can then find even MORE people who like the same thing you do. Eventually you have a big group of people online who all talk about the same thing and all like the same thing you do.\n\n But now that you have this big group, you don't want it to break apart. You keep finding like minded people, and avoid people who don't like what you like. If you add people who don't like the same things, all you'll do is fight. That's not what you want. Eventually you become part of a large group that views itself as a family, and views everyone else as \"outsiders\" who are \"against\" what you like.\n\n",
"The monetization of information following the deregulation of American media in the 1980s led to a more entertainment-oriented approach in news coverage. The companies running news divisions found they could get more viewers by drumming up controversy and sensationalism, turning everything into a dispute rather than simply reporting objective facts.\n\nThis led to bifurcation of the public as two different sets of emotional groups were found, corresponding roughly to left and right, and it was found more profitable to enhance discord rather than seek meaningful discussion.\n\nBy the time the internet came into its own, this was already ingrained into how people consumed news, and was continued online. The retreat into echo chambers was exacerbated by malignant botting and trolling that disrupted forums meant to facilitate discussion.",
"Methinks the US has *always* been this polarized. It's just more obvious because of internet and faster ways of getting ideas and communication across.",
"People don't like being told they're wrong, so they tend to group with people who already think similarly. They discourage any opposition to the current dominant views, so those people form their own groups. Both groups become echo chambers rapidly in the absence of any challenge.\n\nThe internet makes this significantly easier than it would be in the past because you can just choose to never be confronted with any contrary beliefs or opinions.\n\nSee: Leftists, Right-wingers, SJWs, feminists, MRAs, etc. \n\nFor a specific example, look at /r/politics. Although the subreddit is supposedly for neutral political discourse, it has always leaned left to the extreme. Due to the nature of reddit popular views are upvoted and anything else is voted to the bottom. People holding views outside the dominant leave because there is no reason to stay."
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bbonoo | is the alcohol in mouthwash the same type as found in wine and beer? | I have a friend that refuses to use any mouthwash containing alcohol (i.e. Listerine) because she states it contains alcohol; however, she happily drinks wine, beer, and many other alcoholic drinks. I also stated that you don't drink mouthwash, you gargle with it. After some research, I found that ethyl alcohol is generally what's consumed. If that's true, then does mouthwash and alcoholic drinks basically have the same alcohol, just different concentrations? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/bbonoo/eli5_is_the_alcohol_in_mouthwash_the_same_type_as/ | {
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"The alcohol in mouthwash is indeed food grade ethanol, there are some alcoholic people who do consume it to get drunk as sometimes it's cheaper and more accessible than regular alcohol. It's not a great idea to drink it though because the high concentration of fluoride and other tooth strengthening/cleaning and breath freshening compounds can make you sick if ingested in large quantities. \n\nAll drinkable alcohol is just flavored diluted ethanol, whether it's obtained from fermented juices, molasses, corn etc... Any sugar source can be converted into ethanol. Only ethanol can be consumed, any other type of alcohol like isopropanol or methanol are extremely poisonous to humans. \n\nPeople were doing the same thing with ethanol based hand sanitizer gel recently also.",
"Can you clarify her reasoning? \n\nIf she doesn't use it simply because it contains alcohol and she also drinks alcohol, then it doesn't make any sense. \n\nOn the other hand if she doesn't use it because alcohol in mouthwash makes the problems worse, then she might have a point. Alcohol in mouthwash kills both good and bad bacteria, and may cause mouth dryness, making it a more likely place for bad bacteria to live.",
"It's the same alcohol -- ethanol. It's in relatively similar concentrations. The old-school yellow-bottle formulation of Listerine is around 54 proof. So, not quite as strong as hard liquor but stronger than wine.\n\nYou shouldn't drink recreationally though. The active ingredients -- the germ killing agents -- mean that it is considered a 'denatured alcohol'. You could probably get drunk off it, but you'll also get sick in other ways.\n\nMany people avoid alcohol in mouthwashes for other reasons. Many consider it hard on the insides of your mouth and worry that long-term use of these types of mouthwashes can increase your risk of oral cancer. I don't know valid these worries are, but they are common enough worries that many 'alcohol-free' options are available for mouthwash."
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4mb0oa | how does a toilet actually flush from water being added to the bowl? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4mb0oa/eli5_how_does_a_toilet_actually_flush_from_water/ | {
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"[Toilet Crossview](_URL_0_) for reference.\n\nAs water is added to the bowl, it rises up the pipe following that blue line. When enough water is added, it overflows the other side and gravity takes over. That water overflowing creates a chain of negative pressure and the remaining water/contents of the bowl are basically sucked out through the pipe.\n\nEdit: [Video of the process in action](_URL_1_). When the video mentions the siphon created in the back/pipe of the toilet, it's the negative pressure I was referring to."
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5bfcis | what is 'dead' and what is 'alive'? | What differentiates between the state of death and the state of living? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5bfcis/eli5_what_is_dead_and_what_is_alive/ | {
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"Funny enough:\n\nNobody has a clear cut.\n\nBest example:\n\nScientists are STILL debating wether or not a VIRUS is alive.",
"In the context of medicine, death is defined as brain death, a lack of electrical activity in the brain.\n\nIn the context of basic biology, something is alive if it:\n\n* reproduces itself\n\n* has a metabolism\n\n* maintains homeostasis (regulates its internal environment)\n\n* is composed on one or more cells, and\n\n* responds to stimuli.\n\nHowever, both of those definitions are controversial. For the basic biology definition, I tried to list the points in order of least to most controversial.",
"\"Life\" is very hard to define and we can't really make up our mind. Obviously, the difference between a human and a rock is obvious, but as you go up the evolutionary tree the line becomes quite blurry.\n\nHowever, despite it being such a controversial question, we do have some sort of a definition of a living organism. An organism is \"alive\" if it shows the following characteristics:\n\n* **Homeostasis** - regulation of internal environment, for an example maintaining a constant temperature \n\n* **Organization** - composed of one or more cells\n\n* **Metabolism** - transformation of energy (eating, breathing etc)\n\n* **Growth**\n\n* **Adaptation** - changing in a response to the change in environment, crucial for evolution\n\n* **Response to stimuli** - whether it be moving towards food, facing light or running away from danger, living organisms react to their surroundings \n\n* **Reproduction** - all living organisms create more organisms\n\nViruses are very interesting here. They're clearly more than just random molecules, they cause diseases and catastrophes and they have their role in evolution. Even though they replicate, we still don't consider them living because they don't quite fit our description of a living organism. They don't have a cellular structure, they don't react much, they don't grow.\n\nBut then we have bacteria. A lot of people mix these up because these guys cause diseases too, but they're much more advanced and \"alive\" than viruses. A fun fact is that some (mycoplasma) can be smaller than some viruses, but they still show a very clear cellular structure, growth, reaction, adaptation, metabolism and homeostasis. \n"
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efonqi | different types of spicy? | So, as we all know what spicy is. That doesnt really need explanation. But, is their a difference between different kinds, is their different names for these? For example, spice that comes from peppers usually involves capsicum, but horseradish and wasabi doent have this, where does its spice come from? Why is it feel so different? And is there a name for these different kinds of spicy? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/efonqi/eli5_different_types_of_spicy/ | {
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"There are different chemicals that cause spiciness. One of the better known ways of measuring spiciness is the Scoville Scale. The test works by diluting (mixing with water) the spicy thing and measuring how much water is needed before the spiciness can barely be tasted. Spicier things need to be diluted more. The test can measure things other than capsicum.\n\n_URL_0_ and _URL_1_ are insightful about this (and what the other chemicals are).",
"There's a protein called the \"transient receptor potential cation channel subfamily V member 1\" (TrpV1, to its friends) that's responsible for signaling pain due to temperature/acids and other things - it's this protein that signals \"spicy pain\" for BOTH hot peppers and wasabi/horseradish. The reason they feel so different is due to the difference in the chemical properties of the \"active ingredients.\" Capsaicin is very water-insoluble (meaning it will linger in the receptor, providing a long-lasting burn), and basically nonvolatile (since it doesn't evaporate easily, you feel it on your tongue and not in your nose). Allyl isothiocyanate, the active component of wasabi/horseradish is more water soluble and very volatile. This is why you feel it all over your mouth and in your sinuses at once (it evaporates off your hot tongue, wreaking havoc), but it quickly dissipates as it dissolves in your saliva or evaporates out of your mouth entirely.\n\nSometimes wasabi is referred to as \"pungent\" instead of spicy."
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2fnh2c | why do modern wars seem to be less deadly and brutal than previous wars? | Obviously any war is bad, but when reading the news I can't help but feel like the death tolls mentioned are small when compared to wars like Vietnam/Korea/WW2 etc.
The war in Ukraine has < 3000 deaths according to wikipedia, even the Syrian civil war is around 200,000, much less than Koreas 3,000,000+ in the same 3 years. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2fnh2c/eli5_why_do_modern_wars_seem_to_be_less_deadly/ | {
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"It depends which wars you're comparing, but a lot of it is technology and strategy. I hope some war historian comes to write a lengthy explanation, because I enjoy reading those, but the short, simple answer is twofold: 1) we have better weapons now, and 2) war combatants are not the same entities as before. \n\n1) With any weapons, there are two main factors that determine its effectiveness: accuracy and range of impact. It's better to have high degrees of both, but barring that, it's better to compensate by increasing the other. For example, if you're trying to kill Bad Guy X, you could probably do it with a single bullet, if you had a very accurate gun and a good shooter. High accuracy, and it has enough range of impact to kill Bad Guy X. On the other hand, if you can't get a clear shot at him, you could always throw a grenade -- much lower accuracy, but much greater range of impact. However, if you do this, you kill not just Bad Guy X, but everyone around Bad Guy X as well. \n\nThis can be applied to all types of weaponry. If you're trying to destroy an enemy base, you could launch a guided missile to do the job... or you could just drop a nuke, and kill everyone else too. We didn't really have fancy computer-aided weapons until after Vietnam, so that's part of it. \n\n2.) One major difference between previous wars and current wars is that the combatants were on somewhat equal footing. The Allies had armies and navies and air forces, and so did the Axis powers. The Korean War involved thousands of troops on both side shooting at each other, and so on. \n\nOn the other hand, there is no Taliban Air Force, Saddam did not have an aircraft carrier, and so on. They can't just assault US forces in a frontal attack, because they'll be crushed within days, and they know this. So they have to resort to sneaky things like roadside bombs and suicide bombers to achieve their mission. While the death toll is still very high, it's still going to be a lot lower than if you have two equal sides just raining fire on each other. ",
"One answer, which is quite simple, is the number of combatants. \n\nNo subsequent war has come close to the number of combatants involved in World War II. Any changes in the casualty rate of modern warfare due to technological or strategical advances are dwarfed by the sheer scale of previous conflicts. "
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21rnn1 | why does the combination of cigarettes and coffee seem to be a natural laxative? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/21rnn1/eli5_why_does_the_combination_of_cigarettes_and/ | {
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"Because both on their own are natural laxatives. So.... Together they're extra powerful.",
"Coffee (caffeine, specifically) *is* both a laxative and a diuretic, it doesn't just 'seem to be'."
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jf6yo | what's happening with european economies right now? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/jf6yo/whats_happening_with_european_economies_right_now/ | {
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"One currency is used by multiple countries, each with their own economy. Some of these economies are pretty shitty, and so they aren't able to pay their debt, or money they borrowed (from other countries, private businesses, all types of people).\n\nThe usual way a country can deal with this is either to print more money, which makes their own money worth less (since there's more of it); or they can default, or effectively say \"fuck you, we're not paying you\" to all the people they borrowed money from. Both of these are pretty bad for the economy, but defaulting is especially shitty, because nobody will want to lend to a country that can't afford to pay off the money it borrowed. \n\nUnfortunately, because the European economy shares the same currency across multiple countries, a failing country can't just print more money -- they don't have the authority to do that, and no one really wants to devalue the currency of every country in the Euro just because one country is doing shitty. So that leaves the other option, to default -- but this is also really bad for the Euro, for basically similar reasons why it's bad for any country with their own personal currency. This puts the better functioning countries in a terrible position, where either choice hurts them because some other country has a shitty economy or too much debt, and no one wants to pay cause someone *else* is unable to.",
"One currency is used by multiple countries, each with their own economy. Some of these economies are pretty shitty, and so they aren't able to pay their debt, or money they borrowed (from other countries, private businesses, all types of people).\n\nThe usual way a country can deal with this is either to print more money, which makes their own money worth less (since there's more of it); or they can default, or effectively say \"fuck you, we're not paying you\" to all the people they borrowed money from. Both of these are pretty bad for the economy, but defaulting is especially shitty, because nobody will want to lend to a country that can't afford to pay off the money it borrowed. \n\nUnfortunately, because the European economy shares the same currency across multiple countries, a failing country can't just print more money -- they don't have the authority to do that, and no one really wants to devalue the currency of every country in the Euro just because one country is doing shitty. So that leaves the other option, to default -- but this is also really bad for the Euro, for basically similar reasons why it's bad for any country with their own personal currency. This puts the better functioning countries in a terrible position, where either choice hurts them because some other country has a shitty economy or too much debt, and no one wants to pay cause someone *else* is unable to."
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6o1om5 | why aren't stainless steel countertops, like in restaurant kitchens, magnetic, but stainless steel knives are? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6o1om5/eli5_why_arent_stainless_steel_countertops_like/ | {
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"Mechanical engineer here (some material engineer might come around and give a better explanation):\n\nIt all has to do with the crystalline composition of your Stainless Steel. Most of the Stainless steel is made of Ferritic SS, which is cheap to fabricate and can be transform quite easily. Austenitic SS is the most corrosion resistant steel and is mostly used for specific application. The 304 series are usually used for Food grade purpose for example. Both of them are non magnetic.\n\nMastensitic SS is highly durable, very hard and easy to machine. Those 3 properties makes it very good for kitchen knives. It is also (almost?) the only type of SS that is magnetic.\n\nHope that helps.",
"Stainless steel used for knives uses an alloy with less chromium to allow for heat treatment which will make the skin of the knife harder so that it keeps an edge better. -given the right circumstances, these knives will rust. \n\nCountertops don't need that hardenability, but benefit from the increased corrosion resistance that a higher chromium alloy offers. \nThe breakover point for magnetism is 20% chromium. Above that, no magnetism, below that, magnets stick. ",
"Several people have mentioned the different alloys and which ones are/aren't magnetic, but no one has mentioned the reason. I'll take a stab at it but it's been a while since I learned the theory. Maybe someone else can go into more technical detail. \n\nThe molecules of different materials have different resistance to realigning their poles in the presence of a magnetic field. In pure iron, the domains move more freely, and in stainless, the extra metals added interfere with that temporary realignment. Think of the magnetic field as water flow, and the metal as a bunch of tiny tubes all jumbled up and not connected. Iron allows the tubes to realign into a flow path for the field, whereas stainless can't realign as easily. Once there's a path for flow, the field holds on to the metal it has realigned, creating the force that you feel when you try to remove the magnet. ",
"Everyone's talking about what makes a steel ferromagnetic or not, so I'll talk about the other side of the question: countertops in particular.\n\nIf you have a *private* countertop that's not ferromagnetic, that's probably because a higher chromium content makes it easier to polish, and if you're choosing stainless steel for the home instead of granite or marble, it's probably because you want the look of shiny, polished metal.\n\nCommercial kitchens have work surfaces intended to be durable, easily cleaned, and cheap. (It's really expensive to start a restaurant, and they don't tend to last very long, so you get cheap prep tables.) A variety of steel alloys work for that purpose, some of them ferromagnetic and some not.\n\nIf you went to a restaurant kitchen and found that it had a stainless steel countertop that was not ferromagnetic, it was probably because the manufacturer found a source of reasonably priced metal that fit their requirements that happened not to be ferromagnetic.\n\nConversely, I have a stainless steel countertop from a restaurant supply store. It was cheap. I have a bunch of magnets attached to it right now."
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cxxlw6 | how is ebola diagnosed? | I read that they do something called "RT-PCR" or "antibody testing". I'd like to learn about these methods. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/cxxlw6/eli5_how_is_ebola_diagnosed/ | {
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"RT-PCR is reverse transcriptase polymerase chain reaction. What that means is it takes a sample, takes all the RNA present in the sample and converts it into DNA. Then you mix it with a special mixture of specific DNA pieces and certain proteins and you can amplify certain DNA strands that we’ve found that are specific to the virus and quantify them. A normal person’s sample wouldn’t make any of those DNA strands.\n\nAntibody testing in general just uses antibodies, which are Y shaped molecules normally used to tag certain things for destruction by our immune system, and instead use it to tag certain cells or proteins or other molecules in a sample. So we make an antibody that will only stick to Ebola or Ebola proteins and make a way for us to see how much antibody is binding to see whether someone has a detectable quantity of Ebola"
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2fedq8 | why was nato willing to intervene in afghanistan (a country in another region), but is not willing to intervene in ukraine (which actually borders nato members)? | NATO formed ISAL to go into Afghanistan to help in a fight against radicals. But Afghanistan is all the way in the Middle East, so why would NATO now be unwilling to help Ukraine fight against rebels (and possibly Russian soldiers), when Ukraine actually shares borders with multiple NATO members. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2fedq8/eli5_why_was_nato_willing_to_intervene_in/ | {
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"Nuclear bombs. Russia is powerful.",
"It's one of the unwritten rules of modern international politics: No direct conflict between nuclear powers.",
"I believe it is article 5, which paraphrasing here states: if a member is attack the other members are obligated to respond.",
"Article 5 of the North Atlantic treaty, requiring member states to come to the aid of any member state subject to an armed attack, was invoked for the first and only time after the 11 September 2001 attacks, after which troops were deployed to Afghanistan under the NATO-led ISAF.\n\nAfghanistan attacked US, an attack on one NATO member is an attack on all. \n\nUkraine is not a NATO member, so NATO has no duty to get involved.",
"In the former case, NATO was searching for a new reason to exist; in the latter case, NATO is afraid of its original reason for existing."
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dnakw9 | what function does dust serve? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/dnakw9/elif_what_function_does_dust_serve/ | {
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"Where would you prefer your dead skin cells to go?",
"Things dont need to serve a function. Dust is entropy, entropy is part of life. Things, all things, break down and wear away. Dust is one of the last detectable stages of that.",
"Dust doesn't have a specific function, other than being the end step of other different functions.\n\nDust is the debris left behind as a lot of other items decay - for example your body is constantly producing new skin, and allowing the topmost layers of old skin to flake off (done so gradually you never notice it). This skin costs around and settles as dust.\nSimilarly very fine dirt that had been blown around will settle as dust, the fluff that falls off your clothing, hair, food and any other small debris that is easily blown around.\n\nIt doesn't serve a purpose as much as it is the end result of a whole load of other processes."
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f0ozwv | how does nasa know exact trajectories and locations of space craft in interplanetary space? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/f0ozwv/eli5_how_does_nasa_know_exact_trajectories_and/ | {
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"2 things. First is simple physics. Once a spacecraft is on a trajectory, it doesn't change. Once you calculate a trajectory and burn the engines to put the spacecraft on said trajectory, you know it's there because there's nothing to make it go anywhere else. Second is tracking. We have to communicate with spacecraft, which means sending and receiving radio signals. If we're sending and receiving radio signals, we obviously know where they're coming from and where they're going. That tells us where. To get a trajectory, we just track the signals over a period of time and then plot out the rest, because, again, the laws of physics allow us to calculate it."
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c1rhnl | why don’t women ‘save up’ their eggs when they take the pill which stops periods? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/c1rhnl/elif_why_dont_women_save_up_their_eggs_when_they/ | {
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" In fact when a woman reaches menopause, whether she took the pill or not, she isn't \"out of eggs.\" It's a hormonal thing, not a lack of eggs thing.",
"Because the egg is still released, the womb just doesnt prepare for the implantation.\n\nA period is the lining of the womb that was created to hold a fertilized egg, if the egg passes unfertilized, the prepared womb rids itself of the lining, causing a the bleeding\n\nIt doesn’t prevent an egg from releasing, it only stops the hormones that tells the body to prepare for a potential pregnancy. Since the womb isnt ready for an egg, even if its fertilized it passes without implantation"
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2cgxqn | how good or bad is the situation involving people crossing the border into the us from mexico? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2cgxqn/eli5how_good_or_bad_is_the_situation_involving/ | {
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"There is no easy answer to this question. Having been to several parts of the US/Mexico border, and having grown up in Texas, I can say that crossing the border in many locations is very dangerous. It's a desert, and the easiest crossing locations are fairly well guarded.\n\nI would say that a majority of the people crossing the border are just trying to make a better life for themselves. They aren't really hurting anyone, and they are filling jobs that would otherwise go unfilled. Legally immigrating into the US is virtually impossible for most of these people.\n\nAt the same time, the amount of drugs flowing north and the amount of drug money and weapons flowing south across the border is staggering. Look at the drug use rates in the US and imagine that a large chunk of that is coming and going across the border.\n\nPolitically it's a lose/lose situation. If you support weakening border control, then you risk an increase in the drug supply, which drives violence on both sides of the borders. If you do the opposite, than you are throwing money at an unstoppable force with little return.\n\nIf you support amnesty, then you risk encouraging more people to break the law by entering illegally. If you support increased deportation, then you risk destroying families and sending people back to a country that they don't even remember.\n\nIf you loosen immigration regulations, then you risk letting the \"terrorists\" in, or creating another wave of immigrants that the country may not be ready for. If you tighten the regulations, it forces more people into trying to cross illegally.\n\nAll around it's not going to have an easy solution."
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292k9v | in movie scenes of gambling and betting, people throw up tons of cash for bets - how do they keep track? | People just yell out their bets with a fistful of cash and the bookie just grabs it - is someone taking notes on what they bet on, how much they gambled, and gave them a receipt? Does this happen in real life? It seems so complicated. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/292k9v/eli5_in_movie_scenes_of_gambling_and_betting/ | {
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"Some gambling venues have \"odds\" tickets. So if you want to bet on a fighter that has 1:10 odds on winning (underdog), you would receive a ticket with those odds that correspond to that fighter. Say you purchased 5 1$ vouchers, the person in the crowd of people would take your money and hand you 5 vouchers. Now let's say your fighter won, you then redeem your vouchers at a cash window and collect your winnings. Venues will have their own methods of tracking which are winning vouchers and which aren't. ",
"They don't keep track because it's a just movie and those aren't real bets. \n\nIn real life you walk up to the betting counter after waiting your turn in line, place your wager, it's entered into the system through a computer and you are given a receipt. \n\n",
"You see this mostly on the craps table. They take the cash or chips and place it in a certain spot on the board that indicates which area of the table you're standing at. It's also exaggerated in moves and is more manageable in real life. ",
"What you're describing is usually depicting the illegal \"numbers\" or betting process in early to mid 1900s. The way they show it in the movie is relatively accurate to what took place in real life. If you notice, the bookie usually has a pencil and paper to record bets. OR if he doesn't than the bets are usually taking place between friends/close associates and he would just remember; \"Jimmy said 50...jimmy always bets 50..50 on Jimmy\". In any case, memory or assumed accurate note taking is the only record of audit for the bet and any discrepancy would be between the person betting and the bookie. In this situation, the person betting would have little to no choice but agree with the book keeper. The reason being broken legs, never being able to bet with that bookie again or fear of being in bad standing with the mafia or whatever crime syndicate is backing the book keeper/numbers runner.",
"Casinos in Nevada can accept cash wagers, so they may call out something like \"Cash to the table max\" meaning you have made a cash bet up to the limit of the table.",
"I always imagined that if you were spending that kind of money you were usually good at gambling and was good at numbers. Also, a lot of those larger games usually have someone running them.",
"Hi, I worked for a horse racing bookmaker in Sydney for 10 years or so.\n\nThe process at your basic bookmaker stand at the races is this : \nYou have a bag man taking cash, an operator entering the bet on the computer system, and a bookmaker overseeing it and modifying the odds on the fly.\n\nThe punter places a bet, the bagman takes the cash, the computer operator prints out a ticket, the bagman checks it and hands it to the punter.\n\nThat ticket will have the race number, horse bet on, type of bet (win / place / eachway), amount bet, odds at the time you placed the bet and how much you can expect back if the result comes in. \n\nAt the end of the race, the results are entered into the computer, the punter will bring back the ticket, it's scanned to check it's authenticity and cash is payed by the bagman to the punter. Kinda hard to stuff up, unless it's really busy and you're inexperienced and all the punters are drunk and there's money everywhere... which happens sometimes. \n\nHowever, there have been times when the power has gone out AND the backup generators have blown and so the computer system has gone down.\n\nIn these cases, some of the older bookies would use an older method known as penciling (which is more what you're talking about)\n\nBasically, same process, computer removed. \n\nPunter comes to put a bet on, and instead of a printed ticket they get an abbreviated handwritten stub from the bag-man saying the horse number, the bet and the odds, which they keep as proof of wager.\n\nA corresponding entry is made in a ledger kept with the bookmaker.\n\nThat's what you're seeing in the movies. Once you get good at it the process can take less than a second per bet.\n\nTake the cash, write and give a ticket, someone else fills in the ledger and NEXT.\n\nIt can get frantic when it's busy, and when I watched the process at a muay thai match in thailand I noticed a lot of hand signals being thrown around to communicate over the din, but everything is on record.\n\nAnyway, hope that answers your question."
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f5i1e0 | how are threads for clothes made? | i'm referring to the synthetic, hairline, super thin, almost microscopic threads that are used to make thicker threads, what are they made of and how are they made? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/f5i1e0/eli5_how_are_threads_for_clothes_made/ | {
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"The individual fibers are twisted together, like a rope, but on a smaller scale. As each fiber binds up through torsional friction, there are more fibers added, this lengthening the piece. Then, they take these individual strands of fibers and wrap them together to create a thread.\nOnce you have enough thread (of whatever material), you begin weaving it into a fabric. \n\n[Here](_URL_0_) is a kind of cool video in a larger scale about lariat making (which should give you some idea of what I’m describing).",
"What is perhaps the most common type of synthetic fiber, Polyester, is a plastic that is melted down and squeezed out of tiny holes to reach the desired diameter. Here's a video outlining the whole process if you're interested: [_URL_0_](_URL_0_) . Many other synthetic fibers are also plastics manufactured in a similar manner."
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6i1iu0 | the difference between the nazi army, ss, and the wehrmacht. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6i1iu0/eli5_the_difference_between_the_nazi_army_ss_and/ | {
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"The Wehrmacht was the German Army. It existed well before the Nazis came to power. The SS replaced the SA. It was a paramilitary organization with different arms doing different things. Some were State security units, some were guards at Concentration camps, some were actually infantry and armored regiments that engaged the enemy in combat. ",
"The Wehrmacht was the German Army, an organization that long predated the Nazi Party and the same army that fought in WWI. Being from aristocratic backgrounds, many high-up Wehrmacht officers actually disliked the populist Nazis, and some even conspired to kill Hitler (see: Valkyrie). Despite their occasional disdain for the Nazis, however, the officers of the Wehrmacht were fully supportive of the war and of Germany, ruled by Nazis or otherwise.\n\nThe SS started as the political paramilitary wing of the Nazi party, replacing the SA, but later developed fully militarized units known as Waffen-SS that fought on the front as a regular army unit would. But unlike the Wehrmacht, it was completely part of the Nazi party.\n\n\"Nazi army\" isn't really a proper term for anything. It probably most accurately describes the Waffen-SS, army units that were part of the Nazi party. But since the Nazi party and the German state became identical during Nazi rule, people probably also use the term to mean the German army as a whole, even though the Wehrmacht was not a Nazi organization, and elements of its officer corps even opposed the Nazis.",
"Leading into WW2, Germany had a military comprised of three specific forces. Those being the Heer (also known as the Wehrmacht), the Luftwaffe (airforce), and Kriegsmarine (navy). The Heer had existed for quite some time prior to the war, in various iterations, but had been largely modernized during the last years of WW1, and the inter-war period prior to Hitler's rise.\n\nDuring Hitler's rise to power, he befriended a para-military group known as the Sturmabteilung, or the SA. The SA's name is taken from specialized troops used during WW1, and gave rise to the term of \"Stormtrooper\". Basically that's what Sturmabteilung means anyway, so it's understandable. In any case, prior to Hitler's rise within the Nazi party, there were a number of problems faced by the many members and ranking officials. The chief problem being that there was often fighting between other parties, not the least of which being the German Communist party. To protect the party leaders and members, the SA took on a bodyguard role.\n\nAfter Hitler's rise to Fuhrer, some aspects of the SA became troublesome for Hitler, based on what he was preaching and saying to his followers. Not the least of which was the fact that most of the high command of the SA were homosexual. So, in a coup, Hitler had all high ranking leaders arrested and then executed. What was left of the SA were absorbed into a new organization known as the Schutzstaffel, or SS. \n\nSo the differences? Well it depends on which SS you're talking about. See, there were actually two distinct groups of SS. The first was the regular Schutzstaffel who acted as bodyguards for Hitler, as well as the guards at the many concentration camps. Though their organization was much like the Heer's military, their commander only reported to Himmler, who in turn reported directly to Hitler. The second group is the Waffen-SS, the armed military group of the SS. Logistically speaking, the Waffen-SS and the Heer were almost identical, with both pulling from the same military support lines and training. However, where they really differed was in weaponry. The Waffen-SS, unlike the regular Heer, tended to be given the best and most modern weapons, while the Heer had those, but in a far more limited quantity. Operationally, Waffen-SS units reported to whatever Heer commander they were serving under, and only tangibly reported to SS command. \n\nThere were also other minor differences. For example, the Heer were not required to do the Hitler salute until sometime around 1943, or 44. While the SS only used that salute. The SS favored a camouflage uniform, while the Heer tended to default to the usual gray. SS units would rarely surrender, while Heer units were more likely to do so when under duress. \n\n"
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7pbxd8 | why won't most domestic freezers work in cold temperatures? | Shopping for a new freezer recently, and was puzzled to learn that most aren't suitable for outbuildings/garages that reach cold temperatures in winter. You would think they would work better by being in a colder environment as they don't need to achieve such a big drop in temperature? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7pbxd8/eli5_why_wont_most_domestic_freezers_work_in_cold/ | {
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"A freezer/fridge is essentially a heat pump, where is pumps the heat, or lack of cold air out of the container. It does this by decompressing a gas that is pumped through tubes in the freezer. As the gas moves it pulls the extra heat from the fridge and moves along and out the back again. Here it releases this heat as it is compressed and dissipates into the surroundings. Then goes back to the compressor and starts all over. \n\nSo when the gas is trying to release the heat it pulled from the fridge, and it has an easier job doing so. Better right? Nope. Because it is so cold it actually has a chance to cool by the time it gets back to the compressor, which drastically lowers the efficiency of the system. This is basically the system falling out side of ideal conditions. It will get cold, but it will take much longer. "
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3gxw3p | how did bill cosby's statements about quelludes surface if they were "sealed" by the court? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3gxw3p/eli5_how_did_bill_cosbys_statements_about/ | {
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"The court unsealed them. Cosby's lawyers argued they should stay sealed but the judge disagreed, saying there was a strong public interest at stake, Cosby portrays himself as a public moralist, so this information is very important and should be known to the public. ",
"A suit was filed in 2005. The seal was temporary. The seal was going to lapse, but the case settled so the court never lifted the (temporary) seal.\n\n~8 years later the Associated Press sued and said that the seal should be lifted. They said that temporary seals are automatically lifted after 2 years unless there's a good enough objection -- \"good cause\" -- from the person who wants to keep them sealed.\n\nCosby objected. The court found that his objections weren't good enough; he had spent a lot of time advertising himself as a moral compass so the public deserves to know things like this. Yes, it would embarrass him; no, the fact that it would embarrass him isn't good enough to keep it sealed considering that he spends tons of time advertising himself as a moral dude. \n\nAdditionally, the judge in the 2005 suit wasn't shown the settlement agreement. And that judge wasn't asked to make the seal permanent. Combine those facts with the fact that the public has an important interest in knowing and the court found that it was better to not keep it sealed."
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3chcp2 | why do old people keep "chewing" even when they're not eating anything? | I seen a lot of older folks do this, but I never had the courage to ask anyone this, it's kind of a weird question. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3chcp2/eli5_why_do_old_people_keep_chewing_even_when/ | {
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"Playing with their dentures.\n\nSimilar to when people who have tongue-studs play with them in their mouth, the elderly have the same habit of orally maneuvering their dentures. A better question would be, \"what causes people to orally maneuver foreign particles in their mouths?\"",
"I've seen this happen, but only with denture users. My grandmother used to constantly do that and when I asked her about it, it was because the goop she used to keep them in place after her gum ridge eroded would \"feel funny\" after chewing extensively, like during a meal. She said it would eventually stop feeling weird and she would rest her chops after the goop \"was back where it belonged\". Weird question; weird answer. \n\n",
"it's usually either dentures, the onset of a brain condition like Alzheimer's or - more and more these days - the side effect of a drug they're taking to stop the aforementioned brain condition. "
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8xuqrh | how come shanghai tower (632m) and mia khalifa (828) can stand so tall without breaking from wind? concrete doesnt bend does it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8xuqrh/eli5_how_come_shanghai_tower_632m_and_mia_khalifa/ | {
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"text": [
"Are you sure you didn't mean “Burj Khalifa?”"
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2q3gxj | why is it common practice for companies that i already do business with to call me up with "special offers" that are just trying to scam me out of more money? | Seriously, it makes me want to do business with people who treat me like a human not a stack of bills. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2q3gxj/eli5_why_is_it_common_practice_for_companies_that/ | {
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"Essentially, because you have spent money with them in the past, you're more valuable to them as a customer. Your purchase has proved you a) have money and b) are willing to spend it with them, so marketing additional products to you is more likely to succeed than, say, advertising to random yobbos on the street."
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5eu61w | why does the body need metals like zinc? | I understand the need for metals like iron in foods. However, some, especially zinc, seem very odd to be needed. Even in small amounts, what purpose does eating zinc provide in the human body? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5eu61w/eli5_why_does_the_body_need_metals_like_zinc/ | {
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"text": [
"Some special type of enzymes need them to work. They are also part of some cellular structures. So if you do not have them, some cells do not work properly and some chemical reactions made by these enzymes just not happen."
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4uyous | is it actually legal for a police officer or fbi agent to demand i let them use my car in order for them to continue a high-speed chase? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4uyous/eli5_is_it_actually_legal_for_a_police_officer_or/ | {
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"Yes. \n\nAn officer of the law has the right to commandeer any vehicle or vessel they need to in the course of pursuing a suspect and the city/department will compensate you for any damages incurred. "
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fim2kf | why do white fabrics or transparent silicones seem to “yellow” out of nowhere? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/fim2kf/eli5_why_do_white_fabrics_or_transparent/ | {
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"There are two primary reasons, the clothes absorb dirt and oil from you body and they build up over time, and some detergents don't wash out completely and they absorb dirt and oil. Even 100% cotton t-shirts that can be bleached are going to turn yellow because it's impossible to get all the dirt, there's eventually enough in the fabric to change the color.\n\nWashing white clothes and sheets immediately helps, the oils don't soak into the fabric and set, but it's pretty difficult to keep things white if you use them regularly. Drying outside can help somewhat, the sun bleaches clothing. Dryers, even on low, can cause stains to set in fabric, and the remove some of the fabric each time as lint. A shirt is going to have a tiny bit less material each time, and the dirt is going to be more concentrated.\n\nAny sort of caulk tends to yellow because even after drying it's somewhat sticky and the surface holds onto dirt."
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6cvmnp | what happens to the human body under extreme pressure? | So I really don't know. What would happen to a body (dead) under high pressure? Like the Mariana Trench pressure. I have seen burials at sea and most people think fish food, but what happens to the body at extream depths going down. Let's say for argument sake 20 kg of chains tied to the feet? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6cvmnp/eli5_what_happens_to_the_human_body_under_extreme/ | {
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"Past a certain depth, the pressure exerted on the body is greater than the bodies ability to maintain structural integrity. Soft tissues would compress and rupture, bones would break and your body would basically fall apart.\n\nTL;DR: Squish."
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5iczeq | how are cpus made? | Say there's a brand new cpu out on the market. How does it go from being an idea, to a finished, working cpu? Also what makes it superior to other cpus; new competition and older models? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/5iczeq/eli5how_are_cpus_made/ | {
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"That's lots of questions really so....\n\nCPUs are designed in a variety of ways, but the complexity of working out the specifics is, I believe, down to a computer program. The designers tell team program what they want on the chip, and the program works out how the circuitry needs to be laid out. I may be wrong about this bit.\n\nThe design gets printed out pretty big so that the detail can all be captured properly, then a process called lithography uses light to miniaturise it while keeping all of that detail intact. The light imprints the picture onto the silicon, which allows for the small size of the package which we use.\n\nThere's a number of ways one CPU can be superior. One is the \"length\" of the lithography process. This is a measure of how small and close together the individual bits of circuitry on the chip can be. The smaller and closer they can be, the faster the circuitry can operate - although heat dissipation is an issue.\nThe other major way one could be superior is the circuit design. Optimisations of the way in which data gets processed can make a difference to either the speed, or the efficiency.\n\nSince we're struggling to keep making them smaller, optimisations of the circuitry is a major battle between manufacturers.\n\nEDIT: \"e\"s aren't always good",
"There aren't really 'ideas', excepting for new chips. A new processing method is discovered, and the potential for denser, faster chips arrives, and so they put more onto the chip.\n\nThere are a few factors in speed:\n\n* Pitch size: the minimum distance between elements on the CPU. Smaller gaps, faster signal transfer, lower power consumption, etc. This is the nm 'process' you see advertised on new chip lines.\n\n* Gate count: influenced heavily by pitch size and chip size, the number of elements on the chip. More elements, more things can be done at once -- larger memory, specialized processing pathways, etc.\n\n* Layout: inline with pitch size, the distance between features on the board influence how fast a signal can get there.\n\n* Gate configuration: finally, the gates on the board are laid out to perform logical operations. Certain gate configurations are better than others. New solutions aren't too common, but they do show up from time to time. Now, I suppose multicore processors might fall under this section, so it's not to be underestimated.\n\nThese days, most of chip design is done by machine. They can solve the layout issues [synchronizing path lengths, minimizing travel time for statistically predictable operations, etc.] much faster than we can, so we generally only tell the machine what structures we want, how many we want and how much space is there.\n\nThey are better because they are faster -- unfortunately, there really isn't much to this one. Sometimes they consume less power for their performance, some times it's just more performance.",
"Here are some videos about the fabrication process: \n* _URL_1_ \n* _URL_0_ \n* _URL_2_",
"Other users have explained it from a circuitry level, but I will give my two cents of it from an architectural level.\n\nGenerally speaking, an architecture is for executing basic instructions in assembly code (the code that is in binary that runs in your computer. Most people write code that is easier to read nowadays with other programming languages). The architecture is basically a set of \"black boxes\" which do things with this assembly code. A very simple example is a black box that does addition with two binary numbers. Of course, there are more of these black boxes which are used to determine when a certain instruction should execute, what data do they write, etc. \n\nOnce this \"black box\" architecture has been designed to execute assembly code, it should be coded in a Hardware Design Language (HDL) to prove that it can actually work on a real chip. The architects will test their code on a FPGA (field programmable gate array, basically a multi-purpose computer chip). If it's a good, working product, then the design is sent to people who design chips at the transistor level (the lowest level of computing) who will then use a nano-fabricator to build the CPU that is put into your computer.\n\nWhat makes other models better depends on a multitude of things: Smaller transistors, larger amounts of memory, etc. Some more things that aren't really easy to ELI5 are:\n\n* Faster, more elaborate branch predictors\n* Different hierarchies of caches (or just faster cache memory) with fewer cache misses (this lowers memory usage time)\n* Grab instructions from memory that you know will be executed early (prefetching)\n* Scalability (Copy your CPU 2, 4, or 8 times and make them all do a portion of the work. Multi-core processors).",
"Also: why aren't they bigger?",
"I work in the semiconductor industry and my job is to develop new materials that go into computer memory. We use a lot of the similar processes as cpu development, so I may be able to help out.\n\n\nIt takes a lot of people (over 100, for sure) to get something from design, to testing, to final product. \n\n\nThere's a group that looks into what consumers are interested in, and then push those specs to an integration team. This team is broken up into individuals who are each responsible for certain aspects of the device. Their area of focus may involve people from all over the R & D unit, so they'd talk to people who focus on thin film depositions, people who focus on etching, and people who focus on photolithograpy. Then those people would form a team and try to make that level of the whole piece work. Then, we take our working piece and try it in the overall device and see how well it works with everyone else's. \n\n\nThe easiest development work comes from building on previous technology. Like we can make devices smaller because we've optimized our manufacturing tools or our designs. It's a bit harder when there's a new technology, because sometimes the equipment we need to do our work doesn't exist yet, and we need to work with tool vendors to design better tools. \n\n\nTimeline from idea to product? Not all of them make it, but it can take a number of years for a new technology. Also, you can prove a new technology works, but getting it to work while also being cheap enough to manufacture is a whole other challenge. ",
"Oooh, I kinda know this one from college.\n\n1. Use some software (used to be Xilinx in my day) to bundle transistors into little packages (crash course - if you put transistors together in a certain way you can make little logic circuits that can add numbers together and junk.\n\n2. Get the packages of transistors and spam them like *crazy*.\n\n3. Somehow connect them together so it form memory, logic units, buses, registers and what have you.\n\n4. Test the design in slow motion by having the computer simulate the circuit actually working. So, pretend there was electricity going through it.\n\n5. Print out the design, except instead of using a printer and some ink, use an X-ray machine which has resolution that makes the Hubble telescope blush, is the size of a bus (probably) and costs like a billion dollars (maybe). Also don't print out one, print out like 500 in a grid. Don't use paper, user silicon.\n\n6. Stick the whole thing in some acid (not sure about this one)\n\n6. Cut it into bits and put each tiny chip into its housing, which is just some ceramic to help heat dissipation plus the gold pins that go in the computer.\n\n7. Basically sell each crummy thing you made for like 1 cent for $500.\n\nAny questions?",
"The idea for the CPU comes from the things people need to do on the computer. This is a super trivial example, but imagine that early CPUs only did simple arithmetic: addition, subtraction, multiplication, etc. If you need to calculate an exponent, you'd have to multiply in a software loop. The manufacturer would see that exponents are slow and add a specific circuit into the CPU that can calculate it much faster. You could say that the CPU has an ADD instruction, DIVIDE instruction, etc. and that for each instruction there is a bit of logic circuitry that performs that instruction. You can speed up exponents by adding a EXP instruction circuit. In reality it is more nuanced than just adding a circuit for each instruction, but that is the gist. The [SSE instructions](_URL_0_) are an example of how modern CPUs have evolved to improve things like multimedia playback.\n\nConstructing a physical CPU is a process with thousands of steps. The chip is like a layer cake made of different kinds of silicon (N-doped, P-doped, etc.) and metal. The specific materials are beyond an ELI5 explanation. Suffice to say, it is created layer by layer using chemicals to deposit silicon and metal in a very specific pattern. In fact, this process is so difficult that many of the chips produced have defects. This leads to the CPU designs being modular, so that defective parts can be turned off. Many CPUs in a product family are actually the same chip, but the ones with more defects have parts turned off and sold as a lower model.",
"There are a LOT of steps to making a CPU. I worked in a fab (semiconductor fabrication plant) that made processors for phones, which are much simpler, and those still take a long time beginning to end.\n\nThe production part is what I'm familiar with, I never designed CPUs. Once the design makes it to the fab and the fab has made its test runs to work out any problems in creating that design in a production volume, the production stream has several different types of steps that are repeated in the appropriate order to make the processor work. The steps (in no particular order) are\n\nImplanting ions into the wafer to make the silicon into a p-type or n-type semiconductor material to create the gates\n\nDiffusion grows the crystals from the p and n doped substrate\n\nThin films are deposited onto the surface of the wafers to make either metal layers for interconnecting wiring or oxide layers to insulate between these metal layers\n\nPhotolithography applies a layer of photoresistive coating to the wafer, which can be fixed in place by shining a wavelength of intense light onto it. The light shines through a reticle , which is like a really big version of the pattern of light that will go onto the chip. The light shines through and only the pattern is fixed in the photoresistive coating (think of this stuff as a layer of paint). The rest can be washed off. Then a layer of thin film can be put on, or etched off \n\nEtching cuts out parts of the thin films that aren't wanted. you can't lay a wire that size onto a microchip, so you have to put a thin layer (so thin, the thickness is measured in angstroms) of whatever substance you want (metal, oxide, etc) onto the wafer, then the photolithography and etching steps can remove everything but the wiring pattern.\n\nChemical mechanical planarization is a fancy term for basically polishing the surface layer of the wafer. makes it smooth and level so the next layers can go on properly.\n\nThe thicknesses of these layers are mind-bogglingly small. They're measured in angstroms and at least to me, moving at a mass production scale while achieving something that precise is pretty amazing. My background is metals, (specific part of thin films) so I really can't go into detail about the rest of the process",
"This is one thing that cannot be eli5. There is a ton of things that go into making a CPU. From design to fabrication, the process is extremely elaborate. You'd have to ask a more specific question. As a 4th year electrical engineer, I'm STILL learning what goes into what you asked if that is any indication.",
"I work at Infineon, it's a semiconductor fabrication plant, I basically operate a laser/robotic track system that coats a silicon wafer (a 6-12 inch diameter disk) in a chemical and puts a pattern on it for further processing! Ama if you're curious, it's some interesting technology in a NASA quality clean room !",
"In order to understand how a CPU is made, we need to look at how really any [digital circuit](_URL_2_) is made into a [silicon wafer](_URL_4_) to be placed onto a [printed circuit board](_URL_0_) or even just a \"black plastic box with exposed pins\" ([integrated circuit](_URL_1_)) as this is how most digital circuits appear to us by the time we interact with them.\n\nIf you follow the link attached to \"digital circuit\" you'll see shapes you may or may not be familiar with, these are called logic gates. \n\nA digital circuit takes input signals and produces output signals, on a conventional CPU with hundreds of gold pins sticking out of the bottom the only way to know which pin provides which signal is to read the documentation provided by the manufacturer, something only those who will be designing motherboards for these processors would do.\n\nThe specifics of what the CPU does doesn't really matter to answer this question, but it's important to think about the CPU as a device that, based on certain inputs, where an input is either ON or OFF and cannot hold any other value, needs to provide predictable output signals that get routed to other things on your motherboard like your memory (RAM), your PCI bus that may contain a graphics card, sound chips, the BIOS chip, SATA devices and dozens of other peripherals that we expect to work 100% of the time.\n\nWith this in mind, a modern day CPU is clearly a product of decades of refined methodology about how computers should be designed to interact with many different components at once, but perhaps more impressive than that is the advanced manufacturing that allows designing a new CPU to be done in (roughly) the following steps:\n\n1. HDL design and design verification. HDL stands for Hardware Description Language; new digital circuits actually can be written in code and tested using simulation software such as Modelsim or Quartus. Verilog is an example of a commonly used Hardware Description Language.\n\n2. Synthesis, Netlist Generation and Post-Synthesis Verification. The issue with an HDL design is that it's often far more abstracted than discrete logic gates. A synthesis tool is needed to turn the HDL code into a massive list of pure logic gates and simple components, this list is still HDL code and therefore can be simulated using the same simulation software as the original design. The post-synthesis netlist will be tested to make sure timings are met (if you know much about electronics/electricity in general, parasitic capacitances on wires can be an absolute nightmare to deal with at these small scales!). It has taken a long time to create software that accurately portrays how a physical circuit will behave, so it's crucial that the engineers provide the software with the correct information (i.e. what kind of transistor is going to be used, what should be the delays for each logic gate) so that in the event that the device is manufactured, it actually works as it did in development.\n\n3. Device Layout. Now that we have a list of all of the components that are needed for this design, we need to physically lay them out so that it can be manufactured. This means that we will need to turn those logic gate symbols into actual blocks of transistors, and connect these blocks together in the same way that they are virtually connected in software. Let's say we have a highly modular design, CPU cores are module A, and there are four types of caches B, C, D, and E. Let's say this is a new i7 processor and there are 8 module A's. Maybe each core gets its own B cache, but all of the cores share caches C, D, and E. As you may be starting to gather, routing all of these modules together is certainly non-trivial and needing to create long wires to connect things can actually throw off the timings and render the design useless! \n\n4. Manufacturing. This is where my knowledge of making CPUs comes to an end. As far as I know, the physical layout can be manufactured through a combination of exposing certain wavelengths (think laser-etching) of light to refined-silicon ingots that have been sliced extremely thin. The exposed areas can then be exposed to a chemical so that the material is removed and then certain areas of the silicon are \"[doped](_URL_3_)\" with phosphorus/boron (many others) to be slightly more positive or negative, as silicon as an element has 4 valence electrons which can be considered electrically neutral. This concept is the basis of how any semiconductor-based circuit functions.\n\nThis is as much as I know as an undergraduate (5 semesters) Computer Engineering student.\n\n An interesting anecdote: normally a company like Intel will try to make as many of the best processors they can, but due to small imperfections in the manufacturing process not all wafers perform similarly, the ones that don't perform as well just have the dodgy cores disabled and get sold as i3s and i5s!\n\nEDIT: Thanks a lot for the gold, this is my first noteworthy comment. I had to update the image for \"digital circuit\" with something new as the first one died (if anyone is even still around to read this).\n\nOne thing I'd like to mention to anyone who sees this update is to read some of the comment replies, a few individuals have offered great supplementary information to what I have provided. Also, I realize this answer makes an assumption that the reader knows what role a CPU plays in a computer, if you know your computer has a CPU but aren't sure what exactly it does, think of it as the brain, where, a brain is processing inputs and making decisions on what outputs to send, just like a human brain!\n\nTo learn more about computers it can often require a highly intimate conversation that's catered to what each of us might already know. I hope this has inspired some of you to learn more! (:",
"You start with sand.\nReact it with HCL to get a liquid. Strain and vaporize it to get rid of impurities. Flow the vapor through heated graphite to get deposits of elemental silicon.\n\nOnce you get enough elemental silicon, heat it up until its a liquid. Difuse boron gas through the mixture to make initial doping levels. Take a silicon crystal that has the right orientation and dip it into the mixture. Rotate and pull it out. As the silicon around the crystal cools, it matches the orientation of the crystal and forms a bigger crystal.\n\nThe rotations cause the cooling silicon to form into a collumn as it is pulled upwards. Eventually you end up with a REALLY BIG COLLUMN with a point on one end.\n\nCut your collumn into very thin circles called wafers. (Right now, ours are p-type because of the boron we put in earlier.) This is where the real magic begins.\n\nThe air will create a resistive coating of oxide around the semiconductor. We will now apply a series of masks on the wafer to make the chip itself.\n\nLets make some mosfets. Heat up the wafers to drive off moisture. Apply a thin layer of compound (photoresist) that reacts when exposed to UV light. Shoot light at it with the right pattern to create some areas where the resist is cured and some where it is not. Dump the wafer in a solution that removes the non-cured photoresist. Push hot vapors of aluminum or manganese toward the cooler wafer. They will only reach areas where the photoresist was removed. This created the n-wells for our p- mosfets.\n\nLet the oxide grow back and deposit a layer of polysilicon to act as our gate insulator for the mosfet. Apply a mask that only covers the gates, and etch away the rest of the oxide with short wave uv light. Now push hot vapors of Boron toward the wafer to create higher concentrations of boron on both sides of the pmos gate.\n\nRepeat the whole Boron thing we just did with aluminum to create npn gates.\n\nPush hot nitrogen toward the wafer, apply the photoresist and etch it away to make insulating boundaries between the p/n regions and the gates.\n\nDeposit metal on to the substrate. Apply photoresist. Etch it away to make conductive metal that goes to the different gates.\n\nTLDR: sand - > purify - > molten SI - > doped molten SI - > giant collumn - > cut into wafer - > apply photoresist - > cure photoresist - > remove uncured photoresist - > etch photoresist - > deposit stuff - > repeat the photoresist stuff a lot\n\nNewer cpu = more detailed photoresist = smaller mosfets = more mosfets that are better ",
"Something else you may be interested in is a small piece of code a professor showed me once. The program creates what i believe is called an \"H-Tree\". Its a simple recursive design that draws a large H and then adds a smaller H at every end point for any number of iterations. See linked example: _URL_0_ What is interesting about this design is that the end/tip of each of the smallest H's is exactly the same distance from the starting point. This can let you transmit power, information, timing signal, etc to X number of nodes at exactly the same time. I'm not sure if it is still the case, but the designed is used for synchronizing the transistors in your cpu. ",
"The entire process is a long arduous one. It takes about 3-4 years (if not longer) before a chip comes to market. Most chips these days are refinement, it still take a few years before it hits the market though. \n\nThe idea needs to be \"written down\". Designers no longer create/design chips by circuit layout. Instead, they use high level language, called hardware descriptor language (eg: Verilog, VHDL, and SystemVerilog). \n\nTo verify that the HDL is doing what you intend, there are two types of validation. Simulation and Functional Verification. At early stage, you simulate your HDL and validate the output. (Tools from Mentor, Synopsys and Cadence)\n\nOnce you are happy, you go through the actual process of converting your HDL into the final silicon wafer, using tools mainly from Synopsys or Cadence.\n\nHDL is passed through a compiler that optimize the HDL and produce logic gates. (Designers will use formal verification to verify that the logic gates matches the RTL).\n\nThe logic gates are then given to a placement and routing tool that will assign location to gates and route the \"wires\", i.e. connections between the gates. (Designers will use formal verification gain to verify that the optimization during placement and routing hasn't introduced a logical bug).\n\nThen the clocks of the circuit are optimized and routed. (Designers will validate that the timing of the circuit will match the specifications)\n\nIt then goes though layout tools that does the mask creation.\n\nFinally given to the foundry to actually manufacture the chips.\n\n",
"If I'm talking to a typical 5 year old I'd start off saying. Do you know how red stone works in Minecraft to let you control stuff?\nWell real CPUs pretty much work the same way except we make them really small. \n\n\nHow do we do that? We start off by drawing it regular size. Then we take that picture and print it out on a special printer that is made to print out things as small as it possibly can be printed.\n\n\nThen, since that still isn't small enough, we take that super small drawing and shine it through a magnifying glass only backward so that it makes an even smaller picture.\n\n\nThen we shine the light from that picture on a computer chip covered with a special film that turns hard wherever parts of the picture hits it. \n\n\nAfter some parts of that film turn hard we use a special soap to wash away just the soft parts and then fill in the gaps with Red stone.\n\n\nWe repeat this process a few times building up one layer after another until we have the machine we want.\n\n\n\n",
"1. There are different types of CPUs that target specific markets. Eg servers, mobile, laptops etc. So when a company decides to build a CPU, they design it for a market and they design it with the idiosyncrasies of the market in mind. For mobile primary concern would be low power, for super computers it would be flops etc .. (Technically speaking mobiles dont have \"cpus\" in the traditional sense, they have SoCs or System on a Chip which is an another beast, but for this discussion let's just assume cpu)\n\n2. Ok now that we know which market you are targeting, you know what new features you can add to improve the performance. So your Biz Dev + strategy team and product team come up with a list of features and performance targets that can be achieved. This list is your product definition. You now know what to build. (This depends on the company culture. Some companies are bottom-up, which means product and engineering teams tell management what they can build and it is biz dev , sales' job to go market and sell it. Some companies are top-down. Manangement + biz dev tells the engineering team, go build this and hands them a list. I'm being very simplistic here. All cpu companies also have an R & D team which is always trying to improve stuff and try new things by experimenting. Some of the experiments fail, the ones which don't, get added to the new product. Some companies also have Research teams that do proper research and publish papers in top tier journals.)\n\n3. OK now we have a list and we can start designing. A cpu consists of thousands of parts and components. Each part will have its dedicated team of engineers and designers and testers. Eg:- Just to design and test and implement the clock circuitry you'll have a 60-70 person team. Ok but how are they designed you ask ? You first implement the logic of each part in software and simulate it. You test for functional correctness. Then you design it in SystemC or SystemVerilog or a bunch of other shit. By design, i mean build. Basically all these are circuits and you're building circuits. So every team does this. Slowly, you have a bunch and circuits and you tack them on together and you end up with a whole design for the cpu. Now you give it to a Layout team. This team redesigns the circuit so that the _physical_ components of the cpu follow certain rules and don't take up unnecessary space. So now you have your circuit diagram. At this point, this has been thoroughly tested and various levels and many engineers have had sleepless nights because some new addition broke tests that passed. Remember they are used in safety critical conditions, so they are tested thoroughly. But, only the logic has been tested because we still don't have a physical product in our hands.\n\n3. There are two types of cpu companies, fabless and ones with a fab. A fab is a factory that takes in design diagrams from customers and produces physical chips. Intel have their own fab, AMD doesn't, and have to go use the services of fabs like TSMC, Global Foundries. So now that you have your circuit diagram, you simply email or ftp it to them and have your account manager talk to their account manager to figure out the amount, time, quality etc etc. \n\n4. Then one day you get back the first batch of the new chips. This is the most crucial part. You have to figure out ASAP if everything is alright and all the tests pass again and make sure the fab didn't fuck it up or even if you missed something. If you catch something now you can tell the fab and they can fix it. You don't want a situation where you figure out a harware bug after a million chips have been produced. Too big of an investment. So more engineers have sleepless nights to make sure everything is alright. If you find anything off you let the fab know and send them new designs. By the first two weeks you'll know if it needs a rework. \n\n5. Ok now you have a working product. While we did all this, the marketing team and sales team have figured out ways to sell this thing. They have marketing campaigns and advertisements and conferences and conventions. The sales team finds partners and leads and builds deals with the customers etc .. like Best buy or HP or Lenovo etc ..\n\nHopefully this has answered your question. I've tried to keep it very simple. There is no 'eureka' idea moment. Companies have road maps and they know what they are going to build for the next few years .. ie Intel and AMD know what chip is going to come out in 2019 .. They have a plan and stick to it.\nFor superiority, you have industry standard metrics that measure performance and companies try to beat the competition by one upping + saving their customers money. ",
"For anyone who is seriously interested in knowing how a computer works, I can highly recommend a course offered through Coursera called \"[NAND to Tetris](_URL_0_)\". They take you all the way from learning about logic gates, to memory structures, arithmetic logic units and finally, the entire CPU. You literally build a computer yourself. Not physically of course, but simulated. \n\nEdit: This is highly rewarding course. I am a IT professional and did this purely for fun. And it was. ",
"I used to work at a major CPU manufacturer. Very possible that something I worked on is sitting on your desk. (These are my own views not the views of any employer.)\n\nDesign/manufacturing CPUs at scale is really a very, very, very large machine. If we are talking about a major chip, there are tens of thousands of people, maybe a hundred thousand, in different places all over the world that are involved at some stage of the process. \n\nTo give you some sense of the scale of it, in addition to the obvious things like design and actually running a factory, there are a lot of other pieces of the puzzle. Example, the manufacturing tolerances of CPUs are so tiny (on a molecular level, really) that basically something goes wrong with every part. So, as a stage in the assembly line, each chip is tested, and a decision is made about how to sell it (e.g. 1 of 4 cores doesn't work – sell as a 3-core chip). Just testing CPUs as they come off the assembly line is a whole business unto itself. To get some idea of the scope [see one of the machines in action](_URL_1_). A major manufacturer would have many *distinct* test stages in their pipeline, so what goes in as one part may come out as 50+ after sorting through dozens of machines. And that is just the testing piece of the puzzle.\n\nBut to answer the question you asked:\n\n > How does it go from being an idea, to a finished, working cpu?\n\nGenerally, somebody sees a market opportunity based on some combination of the current product and projections about what the competitive landscape will be 6 months from now. e.g., you notice that a lot of people are asking for 4-core chips, you wonder if the trend would continue for 6 cores but nobody knows. So you go to the engineering team, one third of them splinter off into some [crazy-ass 8-core moonshot that requires years of R & D](_URL_0_), another third of them try to squeeze 2 cores into the free space in the next die shrink and decrease the error rate so they won't be disabled on the assembly line, and one third of them works on removing silicon that \"nobody uses\" and emulating in software to free up space. One of those projects will fail, one will basically work but can't be manufactured reliably and so it becomes a specialist part until somebody figures out how to do it reliably, and one of them becomes a mass-market part. And that's basically how new CPUs are made.\n\nI guess what I'm trying to say is, it is a lot of iterating on existing designs. A major design company might have somewhere between 1-3 \"master\" designs and be working on 20 different \"projects\" that tweak some piece of the master design that individually are in some stage between whiteboard and manufacturing. But nobody tries to design a chip from scratch, that's too hard. It is all about how to lay out some section of the master design more efficiently etc.\n\n > what makes it superior to other cpus; new competition and older models?\n\nWell in addition to e.g. specs, there are a lot of things consumers don't normally think about. The primary customer for CPUs are OEMs (e.g. Dell, Apple) that are buying 10s of millions of units. So \"superior to other CPUs\" means in practice superior *for Dell*, so things like a low failure rate, diagnostic tools, good documentation, thermal limits / clearance are really important and those may not be the primary purchase drivers for the enthusiast market.\n\nThere are also a lot of \"specialist\" markets, for example \"extreme conditions\" (think fire/police/military/space) or special workloads (say you run a popular cloud-computing service and need a CPU you can split to 36 tenants) where the difference is somewhere between just testing the chip more thoroughly to adding unique features for the segment. The enthusiast market (e.g. \"Intel Extreme Edition\" \"AMD FX\", ) are really just \"yet another specialist market\" that is sold at retail instead of to OEMs.",
"Basically they take pure silicon and put it in a tanning bed with mask over it and zap it with light. The light burns in the transistors they want. \n\n[This 60's era video produced by Fairchild Semiconductor is instructive](_URL_0_)\n",
"Wow this is a tough one to ELU5, but:\n\n\nA CPU is really a lot of ideas put together in one chip- like a circuit board run through a shrink ray.\n\nLots of people work on improving the inside of the CPU.\n\nThey use light and chemicals to make small circuits.\n\nMost of the time a CPU is considered better if it is a) smaller and b) can run faster without getting too hot.",
"- Have silicon wafer\n\n- Slap coat of stuff onto it\n\n- Cut fancy patterns onto coat of stuff\n\n- Stick layer of metal stuff on top of that\n\n- Cut more fancy patterns\n\n- Slap more stuff on\n\n- Give it coat of stuff that changes under UV light (like when mum sleeps in her sunbed) \n\n- Shine UV light through fancy pattern\n\n- Chop up wafer into chips (do not eat chips)",
"If you want to know how computer is made, this amazing [book](_URL_0_) explains so clearly from scratch in order so you can understand next chapter to the end.\n\nIt explains in scratch from Morse code, to electricity circuit with battery + flashlight, to telegraphy and relays with more advanced electricity circuit, to how numbers are understood in logic sense, to binary digits (0 and 1), to explaining how you can do so much with just binary digits and how barcode works, to logic and switches in algebra and advanced electricity circuits with binary/boolean, to logic gates, more advanced electricity circuits stuff, to bytes and hexes, how memory functions, to automation... ah this is halfway through the book now.\n\nThe way how he writes is very clear, understandable, and everything what he wrote has a meaning for you to be capable to understand what he wrote further in the book.\n\nYou'll know EVERYTHING about electricity and behind-the-scene how computer works, how RAM works, how hard drive works, how CPU works, how GPU works, everything, after you finish this book.",
"Nobody's really gotten into chip manufacturing so I'll get into that a bit. Everything else has been covered.\n\nSilicon is melted down into a vat with some intentional impurities (dopants.) A silicon crystal (a \"seed\") is dipped into the molten silicon and slowly drawn out. As the seed is drawn out, the molten silicon grows the seed into an ingot. The ingot is spun as its drawn out. The process looks something like [this](_URL_2_). The ingot, when finished, is about 3-4 feet long and weighs around 250 kg.\n\nFrom here out, the work is done in clean rooms. One piece of dust can ruin a wafer. The ingot is sliced using diamond-tipped or wire saws into blank wafers. These wafers are buffed and polished to as perfect a surface as possible. If a polished wafer were scaled up to the size of a football field, the height from the highest peak imperfection to the lowest trough imperfection would be a few millimeters.\n\nVarious process are used to essentially 3D print the pieces of the circuit onto the wafer, including:\n\n* photo-lithography: liquid photo-resist is deposited onto the wafer. Light is shined onto the wafer using a template of the design to be imprinted on the current layer (the substrait). Depending on whether positive or negative photolith is being done, either the resist will harden under UV light or will harden without the light. Whatever resist has not cured will be washed away, leaving what is essentially a mould (the \"mask\") of the substrait to be created. [Image](_URL_0_)\n\n* ion beam implantation: ions are blasted at the substrait to dope the Silicon to create P and N-type semiconductor. These can be made next to each other to create transistors (a PNP \"sandwich\" of semiconductor will be called a \"p-type transistor\", similar NPN \"n-type\") these transistors are creatively connected together to create logic gates, which make computers work.\n\n* molecular beam epitaxy and chemical vapor deposition: metals are heated up into a gas and pushed into a vacuum to deposit on the wafer and substrait, creating the \"traces,\" or actual wires inside the chip.\n\n* thermal oxidation: the wafer is heated in an oxygen rich environment to create silicon dioxide, which will insulate the substrait and various traces from touching each other.\n\n* etching: strong, concentrated acid is used to dissolve the cured photo resist and any extra materials that have deposited on it after the substrait has been built. Another insulating material might be deposited over the entire wafer, followed by the wafer being ground and polished until contacts from the initial substrait are visible to make contact with the next layer of substrait. Etching can also be used to essentially \"dig\" into the wafer where resist is not protecting it.\n\nBetween pretty much every step, the wafer is polished and ground in order to make sure the heights of everything are as expected and contact between layers is available where it needs to be. A single wafer for a one layer chip might go through photolith, CVD, etching, more photolith, ion beam implantation, more CVD, more etching, more photolith, thermal oxidation, and more etching. [This](_URL_1_) is all done to create one layer of troughs in the wafer. Imagine doing all these steps for every set of jobs that needs to be done for every layer of the chip.\n\nI definitely missed some stuff, so feel free to add more if anyone knows this stuff better than me. Or ask questions and I'll do my best to answer.\n\n[10 min video showing the above steps with animations](_URL_3_) \n\nOne CPU might be better than another due to several factors. The layout might be more efficient with less heat losses, allowing the clock speed to be increased (which increases heat losses), making the CPU faster, without damaging the components. It might also use a better manufacturing process with tighter tolerances, allowing better design and performance. ",
"I think the best way to understand CPUs might be to start with a painfully simple computer. ENIAC was (arguably) the first real computer. This paper provides the details of how it was created what it was created for. _URL_0_\n\nObviously modern CPUs are much more complicated than ENIAC, but many of the same basic principles are the same. ",
"Computer engineer here. This is how I actually explained it to my 6 year old... \n \nYou know a light switch? Imagine a million of them connected in just the right way to make it do something cool, like watch YouTube, or play games. But a million light switches is too big, so we make them small. So small you barely see them, and a million small ones can fit on your fingernail. \n \nTo answer your questions: \n \nHow does it go from being an idea, to a finished, working cpu? There are thousands of things we want the cpu to do. We split the task up so that each engineer can do one of those thousand things, one at a time. They might need to use a few light switches, maybe even a hundred light switches, just to do one of those things. When they finish making the thousands of little things (using light switches, remember?) they put it all together to make the cpu. \n \nWhat makes it superior to other cpus? You can make it do more things (which require more light switches). You can make it do more things at the same time. You can make the light switches use less electricity. You can make the light switches smaller.",
"I've read some great explanations here, but none at the 5 year old level. Easier said than done, but whatevs.. here goes:\n\nJack and Jill each take turns doing the household chores like laundry. Each time they do it, they leave behind a token to let the other know it's their turn to do a chore the next time. Jack uses blue tokens, so when he finds the laundry basket full, he does the laundry and replaces the blue token with one of Jill's pink ones. Between all of the household chores like laundry, cooking, cleaning, there are a lot of tokens that add up so they decide to do it a different way.\n\nAt first they replaced the use of tokens with a switch that could be up for Jack and down for Jill. This worked out better because they didn't have to deal with all the extra tokens, but then Jill came up with an even better idea of putting all the switches in the same spot and labeling them. \n\nThey soon learned they could talk to each other by adding a few more switches to each task. So for Laundry, Jill could flick an additional switch to let Jack know how soon he needed to do it by. Jack could also let Jill know whether he wanted pizza or pasta for dinner with a new switch in the cooking section.\n\nAs they grew older and they needed to plan more and more, they needed so many switches they couldn't fit in the same spot. Jack found a way to make the switches a lot smaller by using what's called a transistor, and because they were too small to flick by hand, you controlled them with a mouse and a TV screen that showed them all. This was basically a CPU, and it worked great!\n\nOver time, they made the switches smaller and smaller, to the point where you could put as many on one small device as there were people in the world. This made things so easy that eventually the switches could self-regulate themselves, and Jack and Jill knew what they had to do just by reading and occasionally making some changes.\n\nJack and Jill have a great life now, and they soon plan to make a little robot called itsy bitsy that will do all of the chores for them.",
"Rather than describe the whole process, let me explain the biggest quantum leap forward that led to the revolution where average Joe now has CPUs in his pocket.\n\nSo, it's always been possible to create something mechanical that could do logic. You can imagine a machine with two levers, and only if you pulled both levers up (in any order) some mechanical display would change, and then change back if you pulled one or both of the levers back (this is now called an \"AND\" gate). Lotsa ways to do that mechanically, but it was less than 100 years ago that someone finally figured out a way to do this electronically, with transistors.\n\nSweet! We could now build something that could compute stuff without any moving parts. Everyone was stoked to build huge giant power-eating mammoth computers that would like, add up the national debt or something.\n\nThe holy-fucking-shit moment came when someone figured out that the conductive properties of silicon could be altered by shining light on it, and that let you make transistors via a process sort of like developing a photo. Just make a kind of 'negative' of your CPU, shine the outline on some silicon, and you're in business. Now this stuff can be crazy small and mass produced almost like newspapers.\n\nIt's gotten a little more complicated than that, you can see from the other responses. But that whole thing where we figured out the deal with silicon is where the whole world changed.\n",
"I'd like to describe the beginnings of a CPU design in a simple way (\"an idea to finished\"). \n\nTransistors are just 3 terminal switching elements (I'm discussing MOSFETs specifically). One terminal is the gate, and the gate is used to control the switch. Depending on the type of FET (field effect transistor), the gate being on will either open or close the channel (the channel is the path for electricity to go through). For ELI5, don't worry about the names of the other 2 terminals, they are just the start and end of the channel.\n\nSo turns out we can combine FETs that open with FETs that close when the gate is on to make some more complex logic. This is called CMOS logic, and the group of transistors acts in a generic manner we call a logic gate. Logic gates represent certain binary logic such as AND, OR, XOR, NOT and so. Have a look yourself: _URL_1_ I'm sure the truth table section makes some sense to you.\n\nNext level, more advanced combinational logic. What if I want to add some numbers? I can make an [adding circuit](_URL_0_) out of logic gates! I can make other stuff too, like multipliers and even multiplexers that let me connect different wires based on the inputs. This is how most of the logic ends up operating, but we also need memory and stuff that may not be made only of transistors.\n\nThere is a nice advanced answer about how the next level of design works, and honestly, it is kind of complex so I'll leave it.\n\nSo where are the transistors and wires in a modern CPU? They are etched into die of the CPU package. The gold pins go into a plastic PCB and then into the bottom of the die, which is covered in a lid stamped with the model number. You can see in [this image](_URL_2_) that the die is a silvery metal looking thing. That is a piece of silicon with a billion transistors in it, made at a foundry out of a large silicon wafer, which has transistors etched on it using chemicals and light.\n_______________________________________________\nSo, you can see, this is some complex stuff, and there are very few people who have a role in the big picture. Almost everyone working on CPUs fits in only one particular level of their design.",
"We stand on the shoulders of giants. Part of the picture is transistor count. Part is design. Part is the process that is used to translate the design to silicon or another material. (Silicon is used now but that is not needed as a blank) \nIntel was one of the fist to create a modern CPU and a founder of Intel said his rule was to double transistor count every 18 months. This was in the 1970's and is still true.\nWorking idea has always been to improve. Allen Turing gets credit for the first real working digital computer aka a Turing machine, Intel stands on his shoulders. \nThe term there is nothing new under the sun is not false, we basically improve an older invention always.\nIt is not hard to do a plus one to anything older. Now they add cores, even further proof they just add plus 1, or plus 3 or 7 or more.",
"This is ELI5, so I'm going to explain things a little differently.\n\nA CPU is, in a very real sense, an extremely small photo, printed on rock. The process of printing this photo isn't completely different than what we used to do to print film -- make a negative, shine light through it, use various chemicals to make the image stick. We even do things similar to drawing on top of the picture, of course at a much smaller scale.\n\nWhat's special is, when you run electricity through this \"rock photo\", weird things happen. Sometimes the power goes through, sometimes it doesn't. That's because Silicon -- rock -- is a semiconductor. It's not random, there are rules. What we burn onto the rock, decides how the CPU works.\n\nIt's worth noting that there are layers to a chip, sort of like layers to a cake. Photos are flat, but there's a little bit of 3D to CPUs. This is a thing the printing process allows, and is definitely used.\n\nIt's also worth noting that not every photo comes out! So we print many, many photos onto a big surface -- a \"wafer\" -- and then see what actually worked. We do something called \"binning\" too, where the really high quality \"pictures\" sell for more than the stuff that's slightly imperfect. Sometimes we even print extra stuff onto the chip, so that imperfections can just be skipped over.\n\nAt this point, heat is the major factor limiting what a chip can be made to do, so disabled components aren't a performance loss because we couldn't run power through the entire chip anyway.",
"Lots and lots of people have already stated most of how a CPU is made... i guess since i used to work in a smaller Fab, i got to see a lot of the process because we do have some downtime.\n\nA fab usually consist of the following, a metal deposition room, a liftoff room(removal of metal and substance), an wet etch room(cleaning), dry etch (plasma cleaning), photo (prep designs), backside(prep the back of the chip) and last is test. All of this is enclosed in a clean room, although some people say if there is a single particle on it, it would destroy the chip, but it actually depends on how sensitive that layer is. crucial layers will require less, others may not make a huge difference. \n\nThe designs are on long long pages of paper or on the computer. The least ive seen is like 50 pages, the most ive seen is 200 pages long. \n\nSo we always start with a common silicon base. its thin, silver. The typically go to photos first to put a design on it. The designs are actually done on Canon machines(which is my guess why its called photo). They basically put on a thin layer of wax(or metal resistant material) on where a layer should not be. that way, when u put the metal on, it only sticks to the design required area. After this, it goes to the Metal room.(usually)\n\nMetal is where i was placed in. There are 3 different ways to put metal on, Evaporating, Sputtering(spraying), and plasma spray. Evaporators will heat a metal up to its liquid state in a vacuum, then released onto the wafers. Sputtering is basically a spray(also under pressure), theres also plasma but im not sure how that works.\n\nAfter that, it is sent to liftoff where it is cleaned either by hand or by machine by using acetone to wash off the resistant layer. After this, it can go to any place, photos, dry etch, wet etch.both the dry etch and wet etch is basically a process to really clean the wafers. \n\nAfter that, once the majority of the chip is done, it is sent to backside, where the backside is prep. it usually just a bunch of gold attached to it.\n\nAt the very very end of the line, it is sent to testing to where a machine would test each chip. Then its sent to the customer.\n\nAlthough my ex-company did not manufacturer CPU we did a lot of wifi chips, which i would assume is close to a CPU. My knowledge of chip manufacturing was only about a year of being in the fab and able to explore such a small lab in the middle of night(graveyard shift) Sorry, if i sound confusing."
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"https://www.youtube.com/watch?v=4FLBtQC0F0c",
"https://www.youtube.com/watch?v=aWVywhzuHnQ",
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3mgj8j | how did rockstar actually manage to create/model the gigantic map in gta5 ? | Like it seems like no two places inc the city are the same, how did they even design the whole thing ? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3mgj8j/eli5_how_did_rockstar_actually_manage_to/ | {
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"You never design one complete thing. The map is kinda made in that way. The map is divided into many tiny parts and then compiled as one. When we look at the bigger picture we can only see the entire map when we are totally zoomed out or most of the times we see regions or details of those regions. When the user is playing the computer only has to render the parts the user is in or where he might be. \n\nWhen it comes to making a game all the work is divided into tiny bits and pieces. Different teams are given different parts to make and then all the work is kinda compiled into one big game. Same goes for the maps. Here someone or a group might have decided first what all to include in the city and they after dividing it carefully given it out to teams to do it."
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10exfw | ionic bonding, molecular compounds, and covalent bonding | Can someone explain chemical bonding to me? What is the difference between covalent bonding, covalent-network bonding, polar bonding, non-polar bonding, etc? What is an ionic compound? What is the Metallic-Bond model? The VSEPR Theory? Hybrid orbitals? When do you use parentheses when you're bonding elements? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/10exfw/eli5_ionic_bonding_molecular_compounds_and/ | {
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"Well, elements are extremely unstable when left alone. An individual atom is basically a nucleus with an equal number of electrons and protons. these atoms want to achieve stability by either sharing or donating electrons to achieve a stable outer shell. _URL_0_ If you look at this periodic table, you notice a pattern in the colors. Lets look at B, C, N, O, F, and Ne. Neon has an atomic number of 10, so we can assume it has 10 electrons, right? Well, there is a cool trick to figuring out the electron configuration of an element. You have S (2 electrons) orbitals, P (6 electron) orbitals, D (10 electrons) orbitals, and F (14 electrons) orbitals. The column with Li has a S orbital with one electron (it wants to lose an electron to be stable). Be has an S orbital with 2 electrons (it wants to lose 2 electrons to become stable). Now, back to B, C, N, O, F, and Ne. These columns valence electron shell involves the P orbital (which can have 6 electrons in it). Ne has a full shell of 8 electrons surrounding it, which is the most stable. Think about it, we have a 1S2 2S2 2P6 electron configuration. 8 valence electrons! F also wants a stable configuration, but he only has 7 valence electrons. F wants to gain an electron so he carries a -1 charge. O only has 6 valence electrons, but really wants 8 as well. O carries a -2 charge (gains 2 electrons) to achieve a valence shell of 8. So O has an 1S1 2S2 2P4 and wants to achieve 1S1 2S2 2P6 configuration. \n\n\nThe periodic table is set up so that each column has the same number of valence electrons. Li, Na, K, Rb, etc. all have one valence electron. They carry a +1 charge so they can have a stable configuration. Na, which is sodium, secretly wants to be like Neon, so he loses an electron by donating it to another element. This is **Ionic bonding** such as the donation of an electron from Na to Cl. Both Na and Cl achieve a stable configuration by bonding to each other. Bonding is just a method to achieve stability. \n\n\nIonic bonding occurs when an element such as an alkali metal (Li, Na, K, Rb) donate an electron to another element. Keep in mind, the elements must both benefit from the bond formation, otherwise it is very unlikely to happen. All elements want to achieve stability in their bonds, and the bonds are directly related to the number of valence electrons. \n\n\nPolar bonding and hybrid orbitals might be too complicated to explain without a few models, so I might answer that separately. \n\nVSEPR theory basically states that bonded species (elements or electrons) repel each other as much as possible. If you have Carbon as a central atom surrounded by 4 hydrogen atoms, (remember, carbon wants 10 electrons in its outer shell) it forms a tetrahedral model. These elements are sharing electrons for stability and this is called **covalent bonding**. Why are the hydrogen atoms not in a square around the carbon? Well, each angle between the individual hydrogen atoms would be 90* in a square. They would rather be further apart than that because the hydrogen atoms want to be as far apart as possible. Combined the central carbon and it's hydrogens form a molecule with 109.5* angles between each hydrogen (called a tetrahedral bond formation). Now the hydrogen atoms are as far apart as possible, therefore as stable as possible in this molecule. There are many types of bonds and elements, but the best examples to look up are, carbon, nitrogen, oxygen, and Fluorine for bond behaviors. Silicon will bond to elements similarly to carbon because they are in the same column of the table. F, Cl, Br, and I will all bond the same because they are also in the same column.\n\n\nI will try to answer the rest of your questions in another post. \n\n**Edit** I don't think I'll be able to explain hybrid orbitals or polar/nonpolar bonding sufficiently without the use of models. This would likely be one of the first things taught in a college level organic chemistry class, and I am no chemistry teacher :( \n\n_URL_1_ Look at figure 15 to help understand hybrid orbitals. \n\n"
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"http://www.quantumwise.com/documents/manuals/VNL-2008.10_Manual/chap.molbuilder.html#fig.molbuilder.hybrids"
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2exfe6 | why do the pronunciation of some words seem to match the meaning so well? | It seems like some words are just in place to describe something and are very ordinary, like computer, tomato, etc.
However, some words feel like the pronunciation really captures the object the word refers to, such as emotions and such.
For example: loathe, slut and c*nt (feels like very dirty words to me), vehemently, jubilant, and so on.
Is it that we're taught the meaning of the word, so we associate that emotion or feeling to the pronunciation, or is that the word was tailored specifically to describe that thing? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2exfe6/eli5_why_do_the_pronunciation_of_some_words_seem/ | {
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"I'm not an etymologist, but a linguist.\nI would say that rather than words being tailor made, it's a combination of association and usage that make you have certain \"feelings\" towards a word.\nI say this only because words weren't made at one time and then have been that way since. they are constantly evolving, changing, adapting and even being stolen.\nfor example, fanny and pussy. words that now you have such \"ditry\" feelings towards because of the association of porn etc. but just around 50 years ago, there was absolutely no wide spread use of these words other than a girls name (fanny) and a kitty cat (pussy). And I'll bet people thought these were soft and very fitting names for those things.\n\nTL;DR words are subjective and relative to temporal context."
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2oyrr6 | why is cheap labor frowned upon but outsourced jobs aren't? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2oyrr6/eli5_why_is_cheap_labor_frowned_upon_but/ | {
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"Every time a factory closes in the Netherlands because it has been outsourced to (most likely) Poland, a lot of people frown. Meanwhile, people still buy China made cheap products. I'd say the opposite is true.",
"Because cheap labour is taking jobs away from \"real citizens\" while outsourced jobs are in a different country, and are of little importance because it doesn't matter *here*./s"
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9pqf7l | how do we have information about ancient events? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9pqf7l/eli5_how_do_we_have_information_about_ancient/ | {
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"They wrote about their important news. Scrolls, books, chiseled in stone...\n\nIt's not hard to preserve books for thousands of years, actually. Keep them dry is about all that's required. Ancient Rome, have some scribes make copies of the important stuff Caesar did, take them to Egypt where the desert is dryer than you can possibly hope, put them in a sealed chamber in the pyramids or even a smaller building like the Library of Alexandria, and voila.\n\nThey knew about preserving things in antiquity. Keeping wine from spoiling, preserving foods, preserving bodies, preserving books and other objects of value."
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krbc3 | add/adhd and adderal. | How does adderal and other stimulants help ADD/ADHD? If the condition causes the person to have too much energy how would a stimulant help? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/krbc3/eli5_addadhd_and_adderal/ | {
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"Well, I'm not a doctor or anything, but I have vested interested in knowing something about this kind of stuff, and I take a different stimulant medication for ADD. So I'll give it a go.\n\n(If you decide to do your own research, I'm taking most of this from \"Adult ADD: The Complete Handbook\" by David B. Sudderth, MD and Joseph Kandel, MD. The one I have was published in 1997, and because this is a field of study that is constantly evolving, it's showing its age a little bit, but it did help me a lot to get a handle on this thing with which I struggle.)\n\nThere are lot of things that might cause ADD or ADHD, but a lot of the reasons have to do with chemicals in your brain. These chemicals control things like your mood, or your ability to focus, or all kinds of other things about how you act and how your mind works.\n\nSometimes people have ADD because the part of their brain that is supposed to create a certain chemical isn't doing it fast enough, or because another part of their brain which is supposed to suck up that chemical isn't doing it fast enough. One thing a stimulant can do is make those parts work faster. If the stimulant affects a part of the brain that is causing ADD by not working quickly enough, then the extra energy and the extra ability to focus and follow through on things will balance each other. In fact, some people say that people with ADD don't really get high from cocaine--it just makes them focus! But don't do that. I think I'll go into all the reasons not to do cocaine when you're a little bit older. And your parents are here.\n\nBut they are still stimulants. So when a person is taking a stimulant medication for ADD, they have to make sure that they're eating enough and doing healthy things, because any stimulant can have bad side effects, especially if you take them over a long time, like you do with ADD medicine. Even healthy people can lose weight and get a higher heart rate and higher blood pressure.\n\nSo basically: the stimulant stimulates that part of the brain that isn't doing what it's supposed to do. This allows the person taking the medicine to channel that extra energy into something productive.\n\n(If there's a redditor with medical training passing by, please do feel free to correct me if I've misunderstood some nuance.)\n\n\n\nOn a personal note: I have found that if you find the right dosage for the medication, you can experience the benefits of the medication without too much in the way of stimulant side effects. I can focus during the day a lot better, but I'm not jittery. I had a little bit of that kind of thing when I was still trying to find the right dosage with my doctor and we shot a little high, but the key to stimulant medications is basically to take the smallest effective dose, stick to a regular schedule, and make sure you keep up a healthy lifestyle to offset the unavoidable side effects. Sticking to a regular schedule means that your body's natural rhythms can adapt to having the medicine hit your system at a certain time every day, and it won't keep you up at night or anything. Living a healthy lifestyle is just necessary to ward off things like hypertension. It's also possible to have all kinds of weird mood side effects. The only thing I know to do about that is to keep a regular checkup on your mental health in addition to your physical health (like seeing a counselor once a week or something) or switching to something that doesn't mess up your brain chemistry like that.\n\nI hope this makes sense!\n\nedit: spellcheck",
"Here is how I remember a doctor explaining it to me: In the course of being awake, the brain receives incredible amounts of input from the senses -- but amazingly there are systems and chemicals in the brain which allow it to decide which to focus on and which to ignore. Some people have a part of their brain (perhaps it is the amygdala) that is \"asleep\", and when it is asleep the brain cannot filter properly -- the deficit is that ATTENTION gets paid to everything essentially, with no proper priority. *** Here's where the stimulant comes in: it wakes up the part of the brain that controls focus. *** Caffiene has been talked about as doing this, but not as well -- this is why ADD/ADHD kids don't get crazier when they drink soda or coffee, they actually calm down and pay attention, much to the confusion of parents of regular kids.",
"I'm 28 and was diagnosed this last March with ADHD. I take 20mg of AdderallXR a day, and what it does for me isn't give me energy. What it does is put my thoughts in order. Inside my head everything is just a big ball of picturescolorsmemoriesthoughtstexturesfeelings and it gets very overwhelming, but the Adderall is like a stocker at a grocery store that takes the items people have left around and puts them all in the right place. My thoughts are in straight lines instead of all in a big jumble and it makes it easier to concentrate on the things I'm supposed to and do well at my job.",
"It's actually very similar to coffee.",
"ADD doesn't mean you have too much energy. It means your brain requires more stimulation to keep you focused. That's why kids with ADD can sit for hours playing video games: they're very stimulating. Homework and classwork, on the other hand, is not. Adderall and other stimulants stimulant the brain, and the user interprets that stimulation as coming from whatever they're doing, be it homework, chores, video games, etc.\n\nI'm on a prescription of Vyvanse and it feels like my mind is locked in on whatever I'm doing.",
"First of all, there are different types of ADHD. \nADHD/H - Hyperactive and Impulsive. It's as if the 'filter' between their mind and their actions doesn't exist. It's like they don't fully think before they do something.\nADHD/I - Inattentive or Predominantly Inattentive (PI). Previously referred to as ADD. Daydreamy, easily distracted, unorganized, procrastination are all characteristics that tend to affect this group. Consequently, this subtype can lead to other problems such as low self-esteem, anxiety, mood disorders and substance abuse.\nADHD/C - Combined subtype.\nADHD/unspecified - Possess some of the characteristics of different groups but not enough to make a full diagnosis. Nevertheless, these problems still interfere with their daily lives.\n\nNow, stimulants, such as Adderall, are not the only treatments on the market. Individual brain chemistry and mental condition can vary greatly from person to person. Sometimes, the only thing necessary to manage symptoms to a reasonable level is good exercise, enough sleep, productive habits, good time management, which can be achieved through therapy or other self-help resources.\n\nStimulants, though, currently remain the most effective treatment (by most effective, I mean affects most people positively; different people respond to different medications differently).\nStimulants used to treat ADHD such as amphetamines (Adderall, Dexedrine) and methylphenidate (Ritalin, Concerta) are quite different than caffeine. \nCaffeine acts as an adenosine antagonist, which basically means it reduces the amount of chemical in the brain that says \"I'm tired\". \nAmphetamines and Methylphenidate, though possessing different mechanisms of actions, produce a similar effect. They inhibit the reuptake of the neurotransmitters dopamine and norepinephrine, which basically means it blocks the brain's \"clean up crew\" for certain chemicals in the brain that control attention, arrousal, pleasure, etc.\n\nWhile people without attention issues who take Adderall get energetic, sometimes even manic, people afflicted with ADHD tend to get calmer, their thoughts organized. \n\nYou know sometimes when you're changing the radio station and you stop in between two channels, it plays a little of both channels overlapping each other, fuzzy and incoherent? Now imagine the radio dial was broken. This is somewhat analogous to having ADHD, and Adderall (and other medication) temporarily fixes the dial and gives the ability and flip to whichever you want. Now if you took a huge dose or wasn't affected by ADHD, having a super lubricated radio dial wouldn't be very fun; a small motion would flip through a bunch of channels, and landing on the one you want might be troublesome.\n\nSomething fun to know: amphetamines (Adderall) is a cousin to methamphetamine (crystal meth, ice) and has a similar mechanism of action (meth is much more potent). Methylphenidate (Ritalin) is chemically similar to cocaine and possesses a similar mechanism of action.\nI have ADHD, and in the past, before I was getting treatment, I did cocaine once with a few of my friends. It was very weird seeing my friends energetic and sweating while I experienced a more sedating feeling. The effect was, in a way, similar to when I started taking medication: the brain \"fog\" was lifted, colors seemed brighter, 'illogical' anxiety (social and otherwise) was squelched.",
" > How does adderal and other stimulants help ADD/ADHD? If the condition causes the person to have too much energy how would a stimulant help?\n\nThe ELI5, simplified, child-friendly explanation is this:\n\nThere's a part of your brain that takes in everything you're doing and everything that's going on around you, and hands that information -- call it an Awareness Report -- to another part of your brain, a part that makes decisions. This second part looks at it, decides what's important, how much energy it should be spending, what it should be spending it on, etc. This is the part of your brain that puts you on standby when you're driving for the tenth straight hour on a quiet highway. The brain's power saver.\n\nIf you have ADHD, half of that awareness report is lost along the chain. The decision-making part of your brain looks at the unfinished report, and says \"Oh, doesn't look like much is going on.\" There are two or three different ways people's brains respond to that -- subtypes of ADHD like PI or PH -- but all of them are a result of that first part of your brain mishandling its report.\n\nWhen you take adderall, or methylphenidate, or cocaine, it basically tells your brain \"Holy shit, everything is so intense and interesting, you better be paying full attention to this\". If you've ever used speed or cocaine or been with someone who's on it, you know what I mean. In an ADHD person, that message balances out what's missing from the awareness report. Half of the report is still missing, so it still says \"Yeah, I guess we're participating in a debate on live TV, not much going on I guess, we can go into standby mode\", but in big black marker all along the bottom of the page is \"HOLY SHIT EVERYTHING IS REALLY INTENSE ALL GUARDS STANDING AT ATTENTION, YOURS TRULY, AMPHETAMINES\", so you behave more or less the way you would have if the brain had accurately realised how important what you're doing is. \n\n > If the condition causes the person to have too much energy \n\nADHD does not cause a surplus of energy. ADHD-PH, the second-most-common type, involves the decision making part of the brain saying \"Nothing important is happening, *so look for something more useful for us to do*\", meaning that the sufferer is never satisfied by any activity and constantly switches between tasks. In children, who are most easily diagnosed, that's usually a physical game or fidgeting in class, but in adults it's most commonly manifested as wildly veering conversations. It's the brain looking for stimulus wherever it can find it and trying to create some in its absence. This is why drugs that get other people high will make ADHD-PH sufferers calm; it's bringing the brain up to a level where it's usually satisfied by what it's doing.\n\n",
"Does anybody else here have a uncomfortable \"comedown\" from taking ADD/ADHD medications ? I was taking 36mg of Concerta Time Release before breakfast everyday (roughly 6am) and having a dirty and uncomfortable feeling at around 4pm - 5pm everyday.",
"The front of your brain makes all the good decisions and keeps you from getting into too much trouble. A person with ADD/ADHD has trouble because their whole brain is firing rapidly making them distractable. Stimulants make the front of the brain stronger so they can make good decisions again.",
"Well, I'm not a doctor or anything, but I have vested interested in knowing something about this kind of stuff, and I take a different stimulant medication for ADD. So I'll give it a go.\n\n(If you decide to do your own research, I'm taking most of this from \"Adult ADD: The Complete Handbook\" by David B. Sudderth, MD and Joseph Kandel, MD. The one I have was published in 1997, and because this is a field of study that is constantly evolving, it's showing its age a little bit, but it did help me a lot to get a handle on this thing with which I struggle.)\n\nThere are lot of things that might cause ADD or ADHD, but a lot of the reasons have to do with chemicals in your brain. These chemicals control things like your mood, or your ability to focus, or all kinds of other things about how you act and how your mind works.\n\nSometimes people have ADD because the part of their brain that is supposed to create a certain chemical isn't doing it fast enough, or because another part of their brain which is supposed to suck up that chemical isn't doing it fast enough. One thing a stimulant can do is make those parts work faster. If the stimulant affects a part of the brain that is causing ADD by not working quickly enough, then the extra energy and the extra ability to focus and follow through on things will balance each other. In fact, some people say that people with ADD don't really get high from cocaine--it just makes them focus! But don't do that. I think I'll go into all the reasons not to do cocaine when you're a little bit older. And your parents are here.\n\nBut they are still stimulants. So when a person is taking a stimulant medication for ADD, they have to make sure that they're eating enough and doing healthy things, because any stimulant can have bad side effects, especially if you take them over a long time, like you do with ADD medicine. Even healthy people can lose weight and get a higher heart rate and higher blood pressure.\n\nSo basically: the stimulant stimulates that part of the brain that isn't doing what it's supposed to do. This allows the person taking the medicine to channel that extra energy into something productive.\n\n(If there's a redditor with medical training passing by, please do feel free to correct me if I've misunderstood some nuance.)\n\n\n\nOn a personal note: I have found that if you find the right dosage for the medication, you can experience the benefits of the medication without too much in the way of stimulant side effects. I can focus during the day a lot better, but I'm not jittery. I had a little bit of that kind of thing when I was still trying to find the right dosage with my doctor and we shot a little high, but the key to stimulant medications is basically to take the smallest effective dose, stick to a regular schedule, and make sure you keep up a healthy lifestyle to offset the unavoidable side effects. Sticking to a regular schedule means that your body's natural rhythms can adapt to having the medicine hit your system at a certain time every day, and it won't keep you up at night or anything. Living a healthy lifestyle is just necessary to ward off things like hypertension. It's also possible to have all kinds of weird mood side effects. The only thing I know to do about that is to keep a regular checkup on your mental health in addition to your physical health (like seeing a counselor once a week or something) or switching to something that doesn't mess up your brain chemistry like that.\n\nI hope this makes sense!\n\nedit: spellcheck",
"Here is how I remember a doctor explaining it to me: In the course of being awake, the brain receives incredible amounts of input from the senses -- but amazingly there are systems and chemicals in the brain which allow it to decide which to focus on and which to ignore. Some people have a part of their brain (perhaps it is the amygdala) that is \"asleep\", and when it is asleep the brain cannot filter properly -- the deficit is that ATTENTION gets paid to everything essentially, with no proper priority. *** Here's where the stimulant comes in: it wakes up the part of the brain that controls focus. *** Caffiene has been talked about as doing this, but not as well -- this is why ADD/ADHD kids don't get crazier when they drink soda or coffee, they actually calm down and pay attention, much to the confusion of parents of regular kids.",
"I'm 28 and was diagnosed this last March with ADHD. I take 20mg of AdderallXR a day, and what it does for me isn't give me energy. What it does is put my thoughts in order. Inside my head everything is just a big ball of picturescolorsmemoriesthoughtstexturesfeelings and it gets very overwhelming, but the Adderall is like a stocker at a grocery store that takes the items people have left around and puts them all in the right place. My thoughts are in straight lines instead of all in a big jumble and it makes it easier to concentrate on the things I'm supposed to and do well at my job.",
"It's actually very similar to coffee.",
"ADD doesn't mean you have too much energy. It means your brain requires more stimulation to keep you focused. That's why kids with ADD can sit for hours playing video games: they're very stimulating. Homework and classwork, on the other hand, is not. Adderall and other stimulants stimulant the brain, and the user interprets that stimulation as coming from whatever they're doing, be it homework, chores, video games, etc.\n\nI'm on a prescription of Vyvanse and it feels like my mind is locked in on whatever I'm doing.",
"First of all, there are different types of ADHD. \nADHD/H - Hyperactive and Impulsive. It's as if the 'filter' between their mind and their actions doesn't exist. It's like they don't fully think before they do something.\nADHD/I - Inattentive or Predominantly Inattentive (PI). Previously referred to as ADD. Daydreamy, easily distracted, unorganized, procrastination are all characteristics that tend to affect this group. Consequently, this subtype can lead to other problems such as low self-esteem, anxiety, mood disorders and substance abuse.\nADHD/C - Combined subtype.\nADHD/unspecified - Possess some of the characteristics of different groups but not enough to make a full diagnosis. Nevertheless, these problems still interfere with their daily lives.\n\nNow, stimulants, such as Adderall, are not the only treatments on the market. Individual brain chemistry and mental condition can vary greatly from person to person. Sometimes, the only thing necessary to manage symptoms to a reasonable level is good exercise, enough sleep, productive habits, good time management, which can be achieved through therapy or other self-help resources.\n\nStimulants, though, currently remain the most effective treatment (by most effective, I mean affects most people positively; different people respond to different medications differently).\nStimulants used to treat ADHD such as amphetamines (Adderall, Dexedrine) and methylphenidate (Ritalin, Concerta) are quite different than caffeine. \nCaffeine acts as an adenosine antagonist, which basically means it reduces the amount of chemical in the brain that says \"I'm tired\". \nAmphetamines and Methylphenidate, though possessing different mechanisms of actions, produce a similar effect. They inhibit the reuptake of the neurotransmitters dopamine and norepinephrine, which basically means it blocks the brain's \"clean up crew\" for certain chemicals in the brain that control attention, arrousal, pleasure, etc.\n\nWhile people without attention issues who take Adderall get energetic, sometimes even manic, people afflicted with ADHD tend to get calmer, their thoughts organized. \n\nYou know sometimes when you're changing the radio station and you stop in between two channels, it plays a little of both channels overlapping each other, fuzzy and incoherent? Now imagine the radio dial was broken. This is somewhat analogous to having ADHD, and Adderall (and other medication) temporarily fixes the dial and gives the ability and flip to whichever you want. Now if you took a huge dose or wasn't affected by ADHD, having a super lubricated radio dial wouldn't be very fun; a small motion would flip through a bunch of channels, and landing on the one you want might be troublesome.\n\nSomething fun to know: amphetamines (Adderall) is a cousin to methamphetamine (crystal meth, ice) and has a similar mechanism of action (meth is much more potent). Methylphenidate (Ritalin) is chemically similar to cocaine and possesses a similar mechanism of action.\nI have ADHD, and in the past, before I was getting treatment, I did cocaine once with a few of my friends. It was very weird seeing my friends energetic and sweating while I experienced a more sedating feeling. The effect was, in a way, similar to when I started taking medication: the brain \"fog\" was lifted, colors seemed brighter, 'illogical' anxiety (social and otherwise) was squelched.",
" > How does adderal and other stimulants help ADD/ADHD? If the condition causes the person to have too much energy how would a stimulant help?\n\nThe ELI5, simplified, child-friendly explanation is this:\n\nThere's a part of your brain that takes in everything you're doing and everything that's going on around you, and hands that information -- call it an Awareness Report -- to another part of your brain, a part that makes decisions. This second part looks at it, decides what's important, how much energy it should be spending, what it should be spending it on, etc. This is the part of your brain that puts you on standby when you're driving for the tenth straight hour on a quiet highway. The brain's power saver.\n\nIf you have ADHD, half of that awareness report is lost along the chain. The decision-making part of your brain looks at the unfinished report, and says \"Oh, doesn't look like much is going on.\" There are two or three different ways people's brains respond to that -- subtypes of ADHD like PI or PH -- but all of them are a result of that first part of your brain mishandling its report.\n\nWhen you take adderall, or methylphenidate, or cocaine, it basically tells your brain \"Holy shit, everything is so intense and interesting, you better be paying full attention to this\". If you've ever used speed or cocaine or been with someone who's on it, you know what I mean. In an ADHD person, that message balances out what's missing from the awareness report. Half of the report is still missing, so it still says \"Yeah, I guess we're participating in a debate on live TV, not much going on I guess, we can go into standby mode\", but in big black marker all along the bottom of the page is \"HOLY SHIT EVERYTHING IS REALLY INTENSE ALL GUARDS STANDING AT ATTENTION, YOURS TRULY, AMPHETAMINES\", so you behave more or less the way you would have if the brain had accurately realised how important what you're doing is. \n\n > If the condition causes the person to have too much energy \n\nADHD does not cause a surplus of energy. ADHD-PH, the second-most-common type, involves the decision making part of the brain saying \"Nothing important is happening, *so look for something more useful for us to do*\", meaning that the sufferer is never satisfied by any activity and constantly switches between tasks. In children, who are most easily diagnosed, that's usually a physical game or fidgeting in class, but in adults it's most commonly manifested as wildly veering conversations. It's the brain looking for stimulus wherever it can find it and trying to create some in its absence. This is why drugs that get other people high will make ADHD-PH sufferers calm; it's bringing the brain up to a level where it's usually satisfied by what it's doing.\n\n",
"Does anybody else here have a uncomfortable \"comedown\" from taking ADD/ADHD medications ? I was taking 36mg of Concerta Time Release before breakfast everyday (roughly 6am) and having a dirty and uncomfortable feeling at around 4pm - 5pm everyday.",
"The front of your brain makes all the good decisions and keeps you from getting into too much trouble. A person with ADD/ADHD has trouble because their whole brain is firing rapidly making them distractable. Stimulants make the front of the brain stronger so they can make good decisions again."
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20uvys | why am i repulsed when i hear the sound of my own voice? | This seems to be a common phenomenon. When you hear your voice played to you on a recording or video, not only does it sound vastly different than it does in your head while you're speaking, but a fair amount of people are embarrassed, asking "Is THAT what I sound like?!" in disgust. What gives? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/20uvys/eli5_why_am_i_repulsed_when_i_hear_the_sound_of/ | {
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"When you speak, the sound you perceive is due more to the conduction of sound waves through your bones and tissues than it is through air. You build an idea of what you sound like over the many years. When you hear a recording, it's with the sound waves conducted through air. It sounds unfamiliar and strange.",
"Your repulsion comes from the \"uncanny valley\" effect.\n\nThe [uncanny valley](_URL_0_) refers to the sudden drop in comfort level that people feel about things that are almost, but not quite, lifelike. People are comfortable with things that are not at all lifelike, and things that are a little lifelink but clearly not, but at some point, as objects either look or act (or both) approach being cannily life-like, there's some point at which people experience deep discomfort.\n\nYou are recognizing the voice as your own, but missing the element of bone-conduction that fills out your voice. It feels weird because it's almost, but not quite familiar, and so the recording is like a near-miss your own lifelike voice. ",
"While I agree with the other comments about bone conduction and how our voice sounds different to others than ourselves because of our biology, there's another factor at play that often gets ignored when people answer this question: the recording medium itself.\n\nAll microphones don't all pick up the same frequencies, and the quality of the microphone makes a huge difference in how the human voice sounds. Also, which part of your body the microphone is pointed at makes a difference - pointed at the mouth usually makes things sound higher pitched, while pointed at the chest usually gives a bassier timber. The sweet spot, used for professional filming, is to point the mic at the chin from above, to get both.\n\nRecording formats like tape, vinyl, and compressed digital, can emphasize or discard some of the frequencies. Analog tapes and vinyl typically emphasize the lower frequencies, while modern digital recordings often emphasize mid ranges and cuts highs and lows (especially for Voice-Over-IP, like Skypeor Google Hangouts)\n\nAnd lastly, speakers rarely reproduce all frequencies faithfully. The sound recording systems themselves introduce a lot of distortion into the system, and depending on how they are calibrated (a lot of people prefer a bass-emphasized system) can significantly affect how the voice sounds.\n\nAnd none of that is to mention deliberate changes in equalization, the effect of ambient noise and echoes, or the myriad of other small factors technology plays in distorting audio recordings.\n\nWe rarely notice this when listening to the recordings of other people, because our memories of how their voice sounds are not as good as our memory of our voice - unless they are there to compare with the recorded sound, our brain will 'calibrate' itself to hear their voices right."
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1odeo3 | how can we breed dogs and change their physical bodies? | I see shows that talk about how a dog is bred to be physically different for a job. For instance, the corgis were bred to have short legs to be better herders by biting the ankles of other animals. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1odeo3/eli5_how_can_we_breed_dogs_and_change_their/ | {
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"Every puppy in a litter is a little bit different. Pick the one that is the closest to what you want out of a dog, then wait until it can have puppies. Repeat for many generations."
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foijvj | how are manufacturers going to suddenly switch to manufacturing ppe/ventilators? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/foijvj/eli5_how_are_manufacturers_going_to_suddenly/ | {
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"Here is an example. A ventilator company said they needed plastic parts to make more ventilators, but their supplier was in China. They had molds, but needed plastic pellets and the specific injection machine their Chinese supplier uses. GM said they had several such machines, I think they use them to make taillights or engine covers. The ventilator company sends the molds over and some GM plastics molders are stamping out ventilator parts."
]
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||
erl3fe | what part of the brain realizes a memory? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/erl3fe/eli5_what_part_of_the_brain_realizes_a_memory/ | {
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"There is not going to be an answer for your question...we still don't know enough about our own brain to understand it at that level.\n\nWe know approximately where memories are stored and using functional MRI we can see part of the process as it happens but we still don't know.\n\nIt is an excellent question."
]
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fgp7vr | why do city construction projects cost so much? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/fgp7vr/eli5_why_do_city_construction_projects_cost_so/ | {
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"Signs near roads have to be very safe. Wind and storms can apply enormous forces, particularly something that's 80 feet long. The cost would be the same on private land, unless the owner didn't worry about the liability.",
"Materials, unions, labor, insurances, lawyers, permit fees by the city. The list goes on and on."
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1vd5sv | at what point does sound become destructive? | Since sound is a wave, if I pumped thousands of decibels (dB) at a structure, could I blow it up? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1vd5sv/eli5_at_what_point_does_sound_become_destructive/ | {
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"Most of the damage caused by an explosive is from the pressure wave, which is technically a sound wave, so yes. You can destroy things with sound.",
"There are some good answers here, but there are two more, equally cool answers. \n\nSo first, yes, a powerful sound wave is actually just a powerful pressure wave, which can break things if strong enough. \n\nBut you can build on this. One way to amplify this sound is to use two equal sound waves. There are predictable points where the sound waves will interfere with each other. At some of these points, the waves will cancel each other out. At other ones, it will double the amplitude of the wave. (This is how they treat [internal kidney stones without surgery](_URL_1_).)\n\nThe third possibility is much more subtle. Every solid thing has what's called a resonant frequency. This means if that thing is vibrated at that frequency, it will start to shake harder than the amplitude of the wave hitting it. You can use sound waves to make a thing vibrate at its resonant frequency. The sound doesn't have to be all that loud either. If the amplitude of the sound is high enough, you can get those things to literally break apart from their own vibrations. [Check out this wine glass being destroyed](_URL_0_) by resonant frequency."
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"http://www.webmd.com/kidney-stones/extracorporeal-shock-wave-lithotripsy-eswl-for-kidney-stones"
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2v2dim | where do people who break iphone's and samsung's, in youtube videos, get the phones in the first place? | I just can't find a reasonable explanation as to how they get 15 iPhone 6's to do "break tests" on. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2v2dim/eli5_where_do_people_who_break_iphones_and/ | {
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"Two reasonable ways are they're sponsored to do so because they're popular on YouTube and get the phones free. Or they already make a shit ton of money and buying them doesn't mean much to them."
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28ha2l | youtube will block independent music videos | So, I can still post a video called "Silly Cat Falls Down Stairs"
But if I post a video of my band playing the song "Silly Cat", it gets deleted?
Because I didn't pay YouTube a fee, like VEVO did? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/28ha2l/eli5_youtube_will_block_independent_music_videos/ | {
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"Essentially, Music companies are fed up with people downloading their artists music for free and uploading them and monetizing them. YouTube are fed up with having music companies threaning to sue. To stop this happening, YouTube is going to make the music section a simple pay to listen sort of deal with the option to download a song for an additional fee. This is why you need to pay a fee to upload music. Because you could upload a full random album off someone and make money from it without the consent of the record label.\n\nAlso, this is why certain artists such as Arctic Monkeys and Adele are getting removed, because the record labels are being forced into ridiculous contracts by YouTube just so the music can be shared."
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9yadu3 | why do your eyeballs roll up when you close your eyes? | Is this exclusive to humans/mammals? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9yadu3/eli5_why_do_your_eyeballs_roll_up_when_you_close/ | {
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"What? I think this might exclusive to you. You mean when you close your eyes, like having a rest, your eyeballs go up as if you would be looking up ? That’s some weird shit "
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1zupqz | how come even the simplest medicines have so extreme adverse effects mentioned in the leaflet? | So I was just wondering - in almost all of the medicines we come across, there are tons of adverse effects listed in the leaflet inside the box. Sometimes they mention that such and such effect was spotted in some 1 in 10.000 patients but sometimes they don't and there is just a list of things to watch out for. How is this list composed, is it really a thing that over the course of some clinical tests, they found some patients to have hallucinations or cardiac arrest because of some simple anti-fever water-soluble powder with mostly paracetamolum in it? If so, how come it comes to market in the first place? Or maybe the more extreme adverse effects are just what may happen if you devour a whole box on the spot or use it contrary to the instruction? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1zupqz/eli5_how_come_even_the_simplest_medicines_have_so/ | {
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"Its Acetaminophen . and to answer your question, Its mostly cya on the part of the pharmacy company. and scientific due diligence and throughness.\n",
"No, certain adverse reactions given on the drug are more often allergic reactions or rare, but numerous reaction to drugs within that family of drug.\n\nIf people report a certain reaction after being on morphine, then they may add a warning on prescription bottles of codeine, even though the reaction weren't reported with codeine, it's still in the same family of drug. and therefore you may have the same reactions.\n\nIt's like if someone has a bad reaction to eating carrots, you may warn them against other root vegetables as well, such as turnips, radishes and potatoes."
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llfbi | how do anonymous hack into servers? | I understand small password hack techniques, but how do they get in to quite secure webservers that may have large passwords? e.g. HBGary would of had a secure password, how can they get through that? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/llfbi/eli5_how_do_anonymous_hack_into_servers/ | {
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"Computer programs are not perfect. The computer program running at HBGary is not perfect. So long as a hacker can find an imperfection in the program, he or she can exploit that imperfection to the extent of their computer abilities.\n\nThere is no one hacking method, not a secret trick that works every time. It is merely exploiting that which is exploitable. I couldn't tell you what Anonymous did, but I can tell you that it will likely be patched in the next update for their server software, and that Anonymous will have to find something else to do to gain access.",
"It's not all about password guessing or trying many passwords until the right one is found (so-called \"brute forcing\"). Some may use techniques like SQL injection. This is a situation where hackers will attempt to \"get into\" or retrieve information from a database by using specially crafted statements that are inserted into input fields or even URLs. If an admin or web developer hasn't correctly implemented security or input filtering, then the server will execute the code that is injected. This code can do things like log a user in with admin privileges (privilege escalation attack) or retrieve an entire database worth of information. \n\nSocial engineering can be even more effective. This is where the hacker poses usually as an important/authoritative figure and requests someone else to make a change on a system that will ease their attempts to access whatever info they seek. This plays upon the weakest link in a security system: people. They are coerced into making a change that is against company policy for fear of reprisal by a boss for limiting his access. \n\nThere are other methods, but those three methods are very common. ",
"You would be surprised. \n\nComplex web servers are generally ran by an engineering team, which runs day to day operations. A development team is responsible for writing the actual code for the web site and it's various directories, pools, and extensions (essentially controlling what happens when you interact with the site). In order to test these items, staging or development servers are set up to first deploy these code packages to. Developers (as well as any non-security minded IT folks) don't understand and/or care about password requirements. They establish servers with 6-8 character passwords. When the code is deployed to the live system, these passwords are generally hardcoded into the code rather than changing the code, the engineering team changes their passwords to match.\n\nSo now these various passwords are running as 6-8 characters. When a password is stored on a system, it is not stored as it looks (cleartext). Instead, it is hashed with a salt (a string of random characters). These hashes are then stored in a file, database, or some other media. When a password request is made, the system does the opposite -- it uses the salt and derives the password from the hash. \n\nA complex system of password cracking uses a \"rainbow table\", which is a file that contains a massive amount of these hashes and compares the hash of the system to the hash in the rainbow table to find the password. \n\nThis is the easiest way to crack passwords. However, web server vulnerabilities are not generally passwords. They are vulnerabilities in the server type (IIS, Apache, etc). Generally, live web servers are not patched immediately when the patch is released. Certain patches (specifically Microsoft patches) have a tendency to break web code. Larger companies lose a massive amount of money when the site is not accessible (certain sites like Amazon and eBay measure this by the second). Because of this, newer vulnerabilities can sometimes be exploited on large websites and access to the underlying server can be gained. Once there, it's simple to alter the website any way you like, or access various data directories or tables to download information. \n\nFinally, Anonymous employs certain database injection techniques to gather information from databases. These attacks are literally some of the easiest things a hacker can do. Websites generally have search options or forms that execute database queries on the underlying database server. When prompted for user entry, an SQL statement (database language) can be passed through this user input. If the programming team is not security conscious, the input will be passed as a query and the website will spit out any information requested. Almost everything is stored in databases and can be accessed like this. Credit card numbers, phone numbers, social security numbers, etc. \n\nHope that helps. ",
"Nice try, CIA.",
"It is like asking your mommy for candy, but she says no. So you go to your daddy and you ask again for candy and he says yes. You find the weakest link and exploit it. There is no 1-way solving method, but there are always some exploits out there, if you write a program who automates the proces of finding the exploitable links, you'll save yourself some time and now the less smart people can hack too (scriptkiddies). But these are the people who never heard of proxies (hiding) etc and get caught.\n\nThere are several ways of \"hacking\" a system, you could inject your own code (sql injections, buffer overflows, ...). A computer has to store its information in order to do that, it reserves some memory. If the program expects a value to be between 0 and 255 and you give it a 257 it has no space to store it and it will flip if it doesn't know how to catch it. You could simply be listening to what other computers are saying and filter through the crap to find some passwords (smartphones (3G), wifi, ...). ",
"[Just like this.](_URL_0_)",
"I am not a hacker, but I have spent a little time trying to piece this together for myself. There are a couple of different answers to how this is done, but they all basically involve reverse engineering, either technically or logically.\n\n\nThe logical reverse engineer involves thinking backwards through how you became a netizen, basically, and set up accounts and so on. Most of us, if we are standard, non paranoid web-users, have a junk email account or two which we use to set up accounts, do registrations for dumb sites which require such, and tasks of that nature. Personally I tend to hold on to old email accounts for this purpose. And generally, if we are incautious people, as most of us are statistically, we have some passwords stored inside email, etc. Remember now that there are procedures to follow at most email providers for lost passwords, which generally rely on another piece of information that \"only you could know\" such as the name of your first grade teacher, the name of your first pet, your favorite brand of pipe tobacco, or whatever. \n\nSo follow it through - you have a large number of people in a corporation who have basic access to the network. Many of them are statistically incautious, no matter what assurances their IT department might offer after the fact. So all you have to do is figure out the name of one of those people's first grade teacher, or pet or pipe tobacco or whatever, do the reset password thing, get into their Hotmail or AOL email, then follow up the chain from there. You're likely to find a mention of their password doing a basic search on the files in their sent folder. For a lot of people, if you find one password, you gain access to about half their shit because they aren't bothered to change it. \n\n\nSo that's the gist of this technique - you figure out, person by person, how to access each new level into a place. This is more or less exactly how they hacked something of Palin's last year, but I have only sort of a vague memory of that and don't remember what or why. I'm kind of baked, honestly. Shit - would you say that to a five year old? Probably not. Probably wouldn't say shit either, but you never know - kids can be cool about that stuff sometimes.\n\n\nAnyways, so the other type of reverse engineer is to think technically backward through the pipes on a web server. When you think about it, much of the data on a web server is publicly available by design. Otherwise surfing the web would involve entering a lot of passwords and shit (earmuffs!) to just look at normal stuff. Plus, a lot of the features on a web server are by design interactive, so they are reacting to data which you give them and giving you results, as in a search feature, for instance, or a form. Now, when that data gets passed back and forth - there's a lot of capacity for failure in the exchange. All of those interactions involve giving instruction to the web server, like \"find me all of the puffy pictures you have on this server\". So in a nutshell, hackers try to include more instructions with that literal line and often that works. So they basically add a line of code that says \"find me all of the puffy pictures you have on this server, and by the way, what's the root password to your database?\" And a lot of the time, the server is configured wrong and tells you both answers. That's SQL injection in a very simplified way from a guy who's never done it. Just another reliable piece of internet information, basically.\n\n\nThere are more complicated ways to hack web servers, but all of them are basically aimed at getting the root password for the server, at which point you can wreak complete havoc on anything you want. So that's what they need - one keyphrase that is human readable and probably known by 3 or 4 people at the very least. Given just that simple fact, it's pretty easy to see how any basic web system can be hacked given enough time, people, and determination.",
"Computer programs are not perfect. The computer program running at HBGary is not perfect. So long as a hacker can find an imperfection in the program, he or she can exploit that imperfection to the extent of their computer abilities.\n\nThere is no one hacking method, not a secret trick that works every time. It is merely exploiting that which is exploitable. I couldn't tell you what Anonymous did, but I can tell you that it will likely be patched in the next update for their server software, and that Anonymous will have to find something else to do to gain access.",
"It's not all about password guessing or trying many passwords until the right one is found (so-called \"brute forcing\"). Some may use techniques like SQL injection. This is a situation where hackers will attempt to \"get into\" or retrieve information from a database by using specially crafted statements that are inserted into input fields or even URLs. If an admin or web developer hasn't correctly implemented security or input filtering, then the server will execute the code that is injected. This code can do things like log a user in with admin privileges (privilege escalation attack) or retrieve an entire database worth of information. \n\nSocial engineering can be even more effective. This is where the hacker poses usually as an important/authoritative figure and requests someone else to make a change on a system that will ease their attempts to access whatever info they seek. This plays upon the weakest link in a security system: people. They are coerced into making a change that is against company policy for fear of reprisal by a boss for limiting his access. \n\nThere are other methods, but those three methods are very common. ",
"You would be surprised. \n\nComplex web servers are generally ran by an engineering team, which runs day to day operations. A development team is responsible for writing the actual code for the web site and it's various directories, pools, and extensions (essentially controlling what happens when you interact with the site). In order to test these items, staging or development servers are set up to first deploy these code packages to. Developers (as well as any non-security minded IT folks) don't understand and/or care about password requirements. They establish servers with 6-8 character passwords. When the code is deployed to the live system, these passwords are generally hardcoded into the code rather than changing the code, the engineering team changes their passwords to match.\n\nSo now these various passwords are running as 6-8 characters. When a password is stored on a system, it is not stored as it looks (cleartext). Instead, it is hashed with a salt (a string of random characters). These hashes are then stored in a file, database, or some other media. When a password request is made, the system does the opposite -- it uses the salt and derives the password from the hash. \n\nA complex system of password cracking uses a \"rainbow table\", which is a file that contains a massive amount of these hashes and compares the hash of the system to the hash in the rainbow table to find the password. \n\nThis is the easiest way to crack passwords. However, web server vulnerabilities are not generally passwords. They are vulnerabilities in the server type (IIS, Apache, etc). Generally, live web servers are not patched immediately when the patch is released. Certain patches (specifically Microsoft patches) have a tendency to break web code. Larger companies lose a massive amount of money when the site is not accessible (certain sites like Amazon and eBay measure this by the second). Because of this, newer vulnerabilities can sometimes be exploited on large websites and access to the underlying server can be gained. Once there, it's simple to alter the website any way you like, or access various data directories or tables to download information. \n\nFinally, Anonymous employs certain database injection techniques to gather information from databases. These attacks are literally some of the easiest things a hacker can do. Websites generally have search options or forms that execute database queries on the underlying database server. When prompted for user entry, an SQL statement (database language) can be passed through this user input. If the programming team is not security conscious, the input will be passed as a query and the website will spit out any information requested. Almost everything is stored in databases and can be accessed like this. Credit card numbers, phone numbers, social security numbers, etc. \n\nHope that helps. ",
"Nice try, CIA.",
"It is like asking your mommy for candy, but she says no. So you go to your daddy and you ask again for candy and he says yes. You find the weakest link and exploit it. There is no 1-way solving method, but there are always some exploits out there, if you write a program who automates the proces of finding the exploitable links, you'll save yourself some time and now the less smart people can hack too (scriptkiddies). But these are the people who never heard of proxies (hiding) etc and get caught.\n\nThere are several ways of \"hacking\" a system, you could inject your own code (sql injections, buffer overflows, ...). A computer has to store its information in order to do that, it reserves some memory. If the program expects a value to be between 0 and 255 and you give it a 257 it has no space to store it and it will flip if it doesn't know how to catch it. You could simply be listening to what other computers are saying and filter through the crap to find some passwords (smartphones (3G), wifi, ...). ",
"[Just like this.](_URL_0_)",
"I am not a hacker, but I have spent a little time trying to piece this together for myself. There are a couple of different answers to how this is done, but they all basically involve reverse engineering, either technically or logically.\n\n\nThe logical reverse engineer involves thinking backwards through how you became a netizen, basically, and set up accounts and so on. Most of us, if we are standard, non paranoid web-users, have a junk email account or two which we use to set up accounts, do registrations for dumb sites which require such, and tasks of that nature. Personally I tend to hold on to old email accounts for this purpose. And generally, if we are incautious people, as most of us are statistically, we have some passwords stored inside email, etc. Remember now that there are procedures to follow at most email providers for lost passwords, which generally rely on another piece of information that \"only you could know\" such as the name of your first grade teacher, the name of your first pet, your favorite brand of pipe tobacco, or whatever. \n\nSo follow it through - you have a large number of people in a corporation who have basic access to the network. Many of them are statistically incautious, no matter what assurances their IT department might offer after the fact. So all you have to do is figure out the name of one of those people's first grade teacher, or pet or pipe tobacco or whatever, do the reset password thing, get into their Hotmail or AOL email, then follow up the chain from there. You're likely to find a mention of their password doing a basic search on the files in their sent folder. For a lot of people, if you find one password, you gain access to about half their shit because they aren't bothered to change it. \n\n\nSo that's the gist of this technique - you figure out, person by person, how to access each new level into a place. This is more or less exactly how they hacked something of Palin's last year, but I have only sort of a vague memory of that and don't remember what or why. I'm kind of baked, honestly. Shit - would you say that to a five year old? Probably not. Probably wouldn't say shit either, but you never know - kids can be cool about that stuff sometimes.\n\n\nAnyways, so the other type of reverse engineer is to think technically backward through the pipes on a web server. When you think about it, much of the data on a web server is publicly available by design. Otherwise surfing the web would involve entering a lot of passwords and shit (earmuffs!) to just look at normal stuff. Plus, a lot of the features on a web server are by design interactive, so they are reacting to data which you give them and giving you results, as in a search feature, for instance, or a form. Now, when that data gets passed back and forth - there's a lot of capacity for failure in the exchange. All of those interactions involve giving instruction to the web server, like \"find me all of the puffy pictures you have on this server\". So in a nutshell, hackers try to include more instructions with that literal line and often that works. So they basically add a line of code that says \"find me all of the puffy pictures you have on this server, and by the way, what's the root password to your database?\" And a lot of the time, the server is configured wrong and tells you both answers. That's SQL injection in a very simplified way from a guy who's never done it. Just another reliable piece of internet information, basically.\n\n\nThere are more complicated ways to hack web servers, but all of them are basically aimed at getting the root password for the server, at which point you can wreak complete havoc on anything you want. So that's what they need - one keyphrase that is human readable and probably known by 3 or 4 people at the very least. Given just that simple fact, it's pretty easy to see how any basic web system can be hacked given enough time, people, and determination."
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buvqm3 | how do birds last so long flapping their wings non-stop? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/buvqm3/eli5_how_do_birds_last_so_long_flapping_their/ | {
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"4.5 billion years of evolution. They're made to do it. It's like asking how humans can last so long walking.",
"Also, they generally don’t go non-stop. Flap, flap, glide for a while, etc. \n\nThey also follow air currents. use uprises, and fly in formations to minimize air resistance.",
"they think hard about baseball scores or spiders when they think they can't last much longer"
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wzr8w | light in space | I'm not sure if this should be in /r/askscience or /r/AskShittyScience, so I'll put it here.
There is no sound in space because there isn't any matter to vibrate, or something along those lines. Then how is there light, shouldn't it need something similar? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/wzr8w/eli5_light_in_space/ | {
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"You're exactly right about why there is no sound in space. Sound is the propagation of a pressure wave through a material (such as air). Without some material, there can be no sound.\n\nIt was long thought that light *did* need an underlying material to \"vibrate\" through. Scientists called this the **luminiferous ether**. This belief grew stronger in the mid-19th century, when electomagnetism (and light) began to be described as a wave. Yet how can you have a wave without a material for it to propagate through? Ether solved this problem. But there were questions: what is this ether? Can you detect it? Does it move? Etc...\n\nIn 1887, some brilliant chaps named Michelson and Morley devised an experiment to prove or disprove the concept of ether. They observed that, since the earth would have to be moving through ether, you should be able to measure a very small difference in the speed of light as the earth moved in one direction vs. another. Their experiment was called the Michelson-Morley experiment, and it's considered one of the most famous experiments that \"failed\" - it did produced completely ZERO evidence for a light propagating ether.\n\nAnd so, the ether theory fell rapidly out of favor, and nowadays we know that light does not need a medium in which to propagate. You may have heard of the wave-particle dual nature of light, in which sometimes it behaves as a wave, and sometimes as a particle. Well, its ability to propagate in a complete vacuum (similar to space) is explained by its particle nature.",
"Light does need something similar, but the 'something' that vibrates is the electromagnetic field\n\nThis 'field' is really just a mathematical description, but since you are five, I will explain as follows: \n\nEveryone, even little kids should understand gravity. It is the thing that causes a jumping person to go down to earth instead of flying off to space. That thing is a type of 'force' that points to the ground. The region of space around the earth we feel this gravity is called a 'gravitational field'. Of course, teh strength of this field varies. As we move further away from the earth, gravity gets weak, and that is why astronauts float. To reiterate, the space where we feel gravity is called a gravitational field. The force of gravity felt within this field varies, i.e. the force felt is NOT the same everywhere.\n\nTake this concept of 'fields' and make it more general, and a little out of the realm of a five year old. Magnets have this thing called a magnet field, their own special variation of gravity, that only affects other magnets. Electrical objects, such as protons and electrons, that have 'electrical charge' exert an electrical field on other electrical objects. \n\nThese fields, magnetic and electric fields, exist in everywhere in space. Additionally, magnetic and electrical fields interact. The result of this interaction is called the 'electromagnetic field'. As the earth moves, the earth's gravitational field moves with it such that the field near the earth is always the strongest. Similarly, the electric or magnetic field can change in intensity when its source moves. \n\nWhat does this have to do with light? A moving charge will cause the a change in the electromagnetic field. When the said charge is not just moving, but accelerating, we see this as light."
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49ky1c | what's the difference between a hard link and a symbolic link in windows? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/49ky1c/eli5_whats_the_difference_between_a_hard_link_and/ | {
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"A hard link is directly pointing to a physical location on the hard drive. A symbolic link is like a shortcut - it points to a hard link. A symbolic link can point to a different hard drive and make it appear to the user that it is merely a directory."
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3k8ywx | why do cars use steering wheels, instead of other control systems such as motorbike handles or jet joysticks? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3k8ywx/eli5_why_do_cars_use_steering_wheels_instead_of/ | {
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"When cars first came out, they used \"rack-and-pin\" systems so they NEEDED steering wheels. Basically the wheel was connected to a gear that turned a rack (basically a gear laid out in a straight line).\n\nNowadays they're technically not necessary, but they allow for better control. ",
"Before power steering, you had to turn your wheels with muscle power alone. This could take a lot of strength, especially at low speeds.\n\n A steering wheel allowed you enough leverage to really bear down and crank the wheel when needed. It remains an important backup safety feature in case your power steering fails.",
"We could theoretically go to a \"steer by wire\" set up an use anything as input: wheel, joystick, etc. Compared to a joystick, the wheel has several advantages. One being it's easier to hold a constant turn. You couldn't relax your grip on the joystick, assuming it's self-centering. Also, if the joystick gets accidently nudged it would change the direction of the car. Bumping the steering wheel probably won't cause it to rotate."
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1ph8pm | why do dry counties still exist in the u.s.? | I'm confused as to what real purpose they serve. I assume most people just go into the next county to get alcohol, so from a business point of viewwhy would you want to pass up on that revenue? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1ph8pm/eli5_why_do_dry_counties_still_exist_in_the_us/ | {
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"Because religion. Because politics. Because they dont want some store getting all the town yahoos tanked up n hangin all around town causing ruccus!",
"Some people believe the moral or societal cost of permitting alcohol sales in their county outweighs its prospective benefit. It's really as simple as that. People object to it on moral grounds, or on the basis they believe it will contribute to crime, poverty, etc.\n\nSource: I was born and bred in a dry county; there were maybe 3 places (all private clubs) you could go for a drink, and absolutely no liquor stores. The local churches had a stranglehold on the city council and the liquor licenses they issued, and nothing budged until relatively recently. Now serving liquor is permitted (subject to rather rigorous licensing requirements and a substantial excise tax), but there are still no liquor stores.",
"Because the citizens of the county don't elect leaders to change the law (or the citizens are happy with the way the current law stands). Perhaps they feel there would be too many problems attached with that revenue or they don't feel the law inconvenences them excessively. After prohibition ended local laws set their own rules, and people are allowed to choose locations that provide them with the most benefit. ",
"They tend to exist in *poor*, *rural* counties. In these places, there was a high correlation between domestic violence, vehicle accidents, alcoholism and availability of alcohol. Cities differ because they have public transportation and nosey neighbors with local PD on speed-dial. \n\nThe theory is \"dry counties\" protect families and save lives. These counties tend to be economically dead and full of old religious folks. Even if they overturn the local law - no liquorstore or bar would open up because there's never been a market for it.",
"I also think that with the added mobility and improvement in roads after WWII that anyone in a dry country that wants alcohol can get it. Either from the local private club (a lot of VFWs halls that sprung up after WWII do this) or from driving over the county line and bringing it back. This is a good reason for almost all laws having a sunset clause in them so they have to be renewed or they automatically go away."
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3i2g8s | why are bright white led lights allowed on cars for use at night when white light reduces your ability to see in the dark? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3i2g8s/eli5_why_are_bright_white_led_lights_allowed_on/ | {
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"We normally drive with our headlights set to a \"dipped\" position. This means that they are pointed down slightly, so you can see the road ahead of you, but the lights don't point directly at oncoming drivers and blind them.\n\nYour car will have a \"main beam\" setting which can be used on unlit roads when there is no one coming towards you, which *does* blind oncoming drivers like you've described. There's usually a warning light (blue, by convention) on the dashboard to warn you you're using this light, so you don't forget to turn it off.",
"It's because of regulatory lag and lobbying. Almost like e cigarettes. The regulations did not anticipate these lights being feasible and so did not regulate them. By the time it because apparent these lights and HID lights are a problem, too many vehicles have been fitted with them to retrospectively impose regulation. ",
"Hm lots of misinformation here. First, the DOT doesn't approve headlights. There are SAE tests for legal headlights. If your product passes the tests, it is DOT compliant and can have the lettering on it. As far as LED headlights, they're just vastly superior. AAA just put out a study which showed you could see almost 20% further with LED headlights. The color temperature that you speak of is also much better. Usually around 5200K, which is about the color of daylight. They last longer, typically 30,000 hours on low beam while halogens will last about 3,000 hours, and they are durable as hell. If you are seeing glare from an LED headlight, they are either not DOT compliant or they haven't been aimed properly. All headlights should be aimed. \n\nSource: work for a headlight company ",
"They are illegal in a lot of places to install improper hid kits, without the cutoffs. My hids project a beam like this: _/- from each light, which does not blind drivers unless I have my high beams on (which would always blind drivers) "
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75aiy4 | how does the earth (and everything else) just float, suspended in space? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/75aiy4/eli5_how_does_the_earth_and_everything_else_just/ | {
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"We don't just float. We are travelling very quickly around the sun. We don't just sit suspended in space.",
"The short answer is: it doesn't. We are constantly falling towards the sun. It's just that we're also moving sideways at the same time so that we never actually hit the sun, but keep going around it. The sun (and all the planets around it) are also falling, towards the middle of the Milky Way. But again, because the sun and planets are moving sideways relative to the center of the Milky Way, we keep going in circles around the center.\n\nIn the end everything is rotating around other stuff. There is no real up and down to fall to. We just keep falling towards other massive objects. ",
"It isn't. Earth is constantly being pulled toward the sun. But since it has a high tangential velocity (ie. it is travelling in a directly that would otherwise make it fly by the sun), the pull ends up making the planet orbit in an elliptical pattern. This applies to every planet in the solar system as well as every moon around those planets. And also extends the other way to solar systems orbiting a galaxy. They are all moving yet held in orbit by gravity. Celestial bodies that moved faster didn't stay in orbit, and bodies that moved too slowly were pulled into the larger bodies."
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3voxvz | i don't understand how something sealed in the freezer gets more and more ice in there after months/years. where is the water coming from exactly? | I put a box of individually wrapped egg rolls from Costco in my freezer a year ago. I've eaten them slowly and it's still half full of wontony goodness.
I've noticed that when they were new, there was no ice in the little packages. Then more, and more and more. Today I opened a few and my plate was so full of ice I had to wipe it off before cooking them. I would estimate 4 egg rolls had 2 TBSP of ice in there!
Where is this water / ice coming from?? The egg rolls appear to be exactly the same as new. They're not dried out freezer burned junk. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3voxvz/eli5_i_dont_understand_how_something_sealed_in/ | {
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"Every time you open the freezer door a little warm air gets in there and the moisture in the air cools and condenses sticks to everything. It's too small an amount to notice from 1 opening of the door to another, but it is noticeable after hundreds/thousands.",
"From inside the food. It's called freezer burn. Even if you seal it in a bag every time you open up the door and close it part of it begins to thaw. When it refreezes the water expands forcing itself to the surface of the food."
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7fr863 | why do we get vibration-like echoes when driving and we open the rear windows? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7fr863/eli5_why_do_we_get_vibrationlike_echoes_when/ | {
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"My best guess is that it has to do with airflow not being consistent. I notice this the most when only one window is rolled down and it seems to stop if I open another window on the other side of the car. I think it’s because the air is rushing in and out of the same window, causing alternating high and low pressure in the car. \n\nOr is it the same phenomenon as a wind instrument and the pulsing is just a really low frequency note that is created?"
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4h7sg0 | what are the little white table-looking things they put in the middle of take-out pizzas? | [deleted] | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4h7sg0/eli5_what_are_the_little_white_tablelooking/ | {
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"Those are props, or spacers, to keep the middle of the pizza box lid from collapsing and getting smooshed down on to your pizza.",
"They are to keep the top of the box from collapsing into the pizza, getting cheese all over the top, and ruining the pizza; it is like a support column to hold up the roof.",
"Its to hold the top of the box up so it does not collapse and fall into the pizza. Most pizza places I go to dont use them though. probably a question for r/askreddit ",
"They are there to keep the top of the box from pressing down into the top of your hot pizza. \n\nAlso..they are tables for doll houses."
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6gmwhb | in british politics, what are the politicians with 'shadow' in their title e.g shadow chancellor, shadow foreign secretary. what is their purpose? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6gmwhb/eli5_in_british_politics_what_are_the_politicians/ | {
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"They are the official opposition, so the government will have a health minister, the opposition will have someone who \"shadows\" that minister and in debates etc. asks questions and generally holds that minister to account for decisions that they make.",
"Britain has traditionally a two party system. Either Tories or Labour form the government. The other party builds the opposition. The oppositon party also has a kind of ''government''. Like in the real government they have ministers for all the different offices, called shadow cabinet. If after elections, the party who governs changes, often the memebers of the shadow cabinet will become part of the new government.\n\n_URL_0_",
"In a roughly two party system, one party gets the most MPs and forms the Government, with a number of them appointed as Ministers to head the various departments.\n\nThe minority party is in opposition, whose primary purpose is to hold the Goverment to account for it's actions. One way of doing that is to have a \"shadow\" for each minister who has a particular job to keep an eye on that department's actions.\n\nWhen a Minister introduces a proposed law bill to Parliament, the Shadow Minister will lead the \"against\" side of the debate.",
"I am 5 and I have been explained, thanks guys"
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6wtpgu | given that we started at $0 and we are now at countless zillions, where did all the worlds money come from? | I'm not talking about paper money, more how can we start with cave men of zero wealth to have built economies worth trillions. I'm assuming people will reply with two people trading with one another however how can either side get back more than what they started with? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6wtpgu/eli5_given_that_we_started_at_0_and_we_are_now_at/ | {
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"You're making the assumption that there was zero wealth to start off. If I'm a caveman and I pick up a shiny rock that other cavemen want, I now have wealth. Likewise if I make a tool out of wood and stone, others might want that tool and not necessarily want to take the time or have the expertise to make their own, so I have a thing to trade.\n\nSo now we have simple trading. I make tools, you farm food. I exchange some of my tools for your food. We both trade with the family that makes clothes. But this becomes unmanageable as you have more items for trade. How many X and you receive for Y when you have hundreds of options for both is just impractical. And when you have seasonal things, there may be times you have too much and others that you have not enough to trade with. Or things that simply can't be broken down for small trades such as if I raised oxen and want a simple tool that isn't really worth an ox.\n\nFrom here, civilization invented currency. Some common trading thing that could be easily quantized, carried, and traded for all other things. It had to be something relatively rare and have enough intrinsic value that others accepted it for trading. Things like shells, beads, and eventually metal coins have all been used by different civilizations. It's only extremely recently that civilization has moved beyond the necessity for currency to have intrinsic value.",
"Money appeared because barter sucks as a means of exchange. You need to have what the other person wants, and even if you do happen to have that, it's often in some hard to transport form (like a cow) or hard to divide up. So people came up with the idea of money to represent wealth. So where did the wealth come from? Someone had to first produce it. They needed something that was rare, portable, divisible and hard to duplicate. Gold served all those purposes, so at least in the old world gold and silver coins became a unit of exchange. Usually rulers made a monopoly on them - but since they couldn't produce gold from nothing, it limited the money supply. \n\nHumans tend to want more money, especially rulers. So they found ways of diluting coins, of shaving them, of counterfeiting them. Some countries experimented with cheap metal or even paper. Mostly these experiments failed, causing inflation. Eventually, long distance traders came up with the idea of promissary notes to take with them while trading, and banking was born. That allowed the money supply to grow dramatically - because the bank could lend money out to someone, who had the money, as well as keeping it for the person who deposited it in the first place. As long as not many people asked for their money back at once, everybody became richer - especially the bank. \n\nToday, money isn't linked to gold at all. Instead, it's given value based on what people believe it is. That's called fiat currency, and it means that the US dollar is worth what it is because people believe it's worth something. If the USA was to suffer a major disaster, a Civil War, or a government collapse, the dollar could become worthless overnight - as a few countries have found, much to their horror. But overall the system works! And it means that the money supply can be increased simply by printing money. Thus, there's more money in the world today than last year, and there will be more next year than this. ",
"Ogg is a good hunter and kills a deer, more than he can possibly eat on his own.\n\nOok is a really good firestarter. \n\nOgg prefers cooked deer, which lasts longer and tastes better. Ook is hungry - starting fires is a cool skill, but it doesn't feed you.\n\nOgg and Ook trade - Ogg shares his deer, and Ook helps Ogg start a fire.\n\nNothing has changed - there is still one deer and one fire guy, but the transaction has made them both wealthier than they were before - they both now have some cooked deer meat."
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mdrh9 | how a person with an accent sings without the accent. | How does a British singer sound exactly like an American one? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/mdrh9/eli5_how_a_person_with_an_accent_sings_without/ | {
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"Folk music perspective: British folk singers open their mouths far and have less \"twang\" and more \"warble\", most American folk singers go the okie/appalachia route and sing with a more closed mouth and more twang. This is why Joan\tBaez sounds more british than Joni Mitchel, even though both are Americans.",
"Let's look at how you learn to do each. Talking you just pick up from the people around you and unless you see a dialect coach no one ever corrects you. Trained singers are usually coached how to maintain pitch and maximize volume. Also in singing 'tone color' or \"tone quality' is very important and every genre has a different preferred color. Think of a singer preforming the Hallelujah Chorus while singing like a country star. Or a gangster rapper. I suspect the brits don't sound like americans, but rather all singers in any specific style strive for the same sound.",
"Folk music perspective: British folk singers open their mouths far and have less \"twang\" and more \"warble\", most American folk singers go the okie/appalachia route and sing with a more closed mouth and more twang. This is why Joan\tBaez sounds more british than Joni Mitchel, even though both are Americans.",
"Let's look at how you learn to do each. Talking you just pick up from the people around you and unless you see a dialect coach no one ever corrects you. Trained singers are usually coached how to maintain pitch and maximize volume. Also in singing 'tone color' or \"tone quality' is very important and every genre has a different preferred color. Think of a singer preforming the Hallelujah Chorus while singing like a country star. Or a gangster rapper. I suspect the brits don't sound like americans, but rather all singers in any specific style strive for the same sound."
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7lcfa0 | why did americans and soldiers hate jane fonda for sitting with that gun in a photo, even though she campaigned so much on the soldiers behalf? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7lcfa0/eli5why_did_americans_and_soldiers_hate_jane/ | {
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"The 1970's were a different time and place. However, even today you wouldn't find much sympathy for a celebrity who appeared sympathetic to our enemy to the point that U.S. Congress held hearings to establish whether her behavior constituted treason or not."
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6lc59x | how do they get the different colors that we see commonly in fireworks?? and why aren't there more blue and variations of blue fireworks??? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6lc59x/eli5_how_do_they_get_the_different_colors_that_we/ | {
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"They use them by adding metals to the fireworks. Different metals burn different colors. Iron for Red. Titanium for White. Copper for Green. I think Cobalt for blue? Quantum mechanics really, excited atoms of a given element produce light in a given part of a spectrum."
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7f7hf8 | what makes any given bacteria inherently beneficial or harmful to humans? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7f7hf8/eli5_what_makes_any_given_bacteria_inherently/ | {
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"In most cases this has to do with what type of stuff the bacteria produces, but also how aggressively it out-competes other bacteria and whether or not it's capable of penetrating tissue on its own. The gut is a good example of some of these variables.\n\nFor example, you've got E. coli in your gut all the time. Most E. coli is not bad for you. It helps break down certain food products so that you can absorb them. However, there are harmful strains of E. coli which are harmful because they produce a toxin. This toxin interferes with your gut lining and makes you really sick.\n\nThen you've got bugs like C. diff, also in the gut. We get exposed to this sometimes but we're just fine. However, when you're on really strong antibiotics, lots of the normal bacteria that helps out in the gut is killed. Dangerous C. diff strains aren't killed so easily, and it will populate all that new space really fast. This one also produces a toxin that'll make you sick when your gut is full of it.\n\nAfter that you've got stuff like salmonella, shigella, and campylobacter. These also produce toxins in most cases, but they tend to go one step further and actively invade the tissues lining your GI tract. Unlike normal gut bacteria, these guys are digging in and that doesn't feel very good.\n",
"A couple of factors play into this.\n\n1. How well can it grow inside the body. This includes how well it adapts to the environment inside our body and also how well it can evade death from our immune system\n\n2. Does it release toxins? This ones kind of a no brainer when it comes to harming the body.\n\n3. How does our body respond to its presence? A lot of bacteria don’t actually damage the cells themselves, but certain components of them activate such a strong immune response that the body actually starts to hurt itself\n\nThose are the three biggest things that make for harmful bacteria. Beneficial bacteria are generally bacteria that can grow within our GI tract that don’t cause us much harm at all in there, but instead outcompete other bacteria that may cause disease ",
"In biology, there's something called symbiosis. Contrary to popular thought, it just means that two organisms are living together and have some sort of relationship.\n\nMost bacteria have a commensal relationship to us. This means that whatever waste we produce, they happily eat and stick around. We don't get any benefit out of it. This is opposed to parasitic, where it leeches off of us like a leech or a vampire (that is, we're suffering because of it). Bacteria often digest stuff that we can't eat anyway so its not harmful.\n\nThough, some bacteria are considered to have syntrophy. This is where we don't need the bacteria, but they help us. This includes bacteria in your gastrointestinal tract and skin. They don't harm us, but the stuff we can't eat, they can eat and then provide crap that they can't use but we can. These include Vitamin K, short chain fatty acids and some can break down carbs we can't into sugar. \n\nGood bacteria can become bad. We're effectively enslaving bacteria by keeping them to certain places. We have essentially guards called lymphoid follicles made of white blood cells that stop them from spreading further than we want. When they do spread too far, they can become pathogenic and become bad bacteria. So the distinction is sort of if they're where we want them.\n\nHowever, there's exclusively bad bacteria like Staph Aureus (Golden Staph). These don't normally live in our body, sometimes can be found on the skin. However, when they get in, their exclusive role is to cause as much damage as possible to get nutrients from our body and then divide/proliferate and then leave, spreading to other people. They do this by producing exotoxins which they secrete causing destruction, or endotoxins. Endotoxins are basically their outer shell which gets picked up by our body as bad. However, if they're released when the cell dies, it harms our body.\n\nThat said, good bacteria also have endotoxins sometimes. But we're not really sure how the body recognises bad bacteria and kills them without killing the good bacteria. \n\nEven funnier yet, there are bacteria that just sit in our body and replicate. They don't really do anything, but as soon as our body recognises and attacks it, we're in big trouble and it starts causing a lot of nasty problems everywhere. They don't have endotoxins or exotoxins. Their destruction is caused by our bodyhurting itself trying to kill it. An example is TB. "
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2o51xc | how do we not run out of food and other natural resources? | It seems like the supply on earth is very limited and I'm surprised we haven't run out of things with the way our current population consume things. How do we do supply ourselves so well without draining the planet dry. | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2o51xc/eli5_how_do_we_not_run_out_of_food_and_other/ | {
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"There's more on earth than you might think. We produce more than enough food to feed the planet. The problem is distribution - the food is all concentrated in rich countries. Food is basically stored solar energy. Plants use the sun to grow and animals feed off plants. We're unlikely to run out of food anytime without a major catastrophe. \nSame with resources. Shortages are mostly economic. As supplies get scarce people either find substitutes or they mine previously uneconomic deposits. Oil is an excellent example. When the price is high we turn to fracking and shale oil. Now it's dropped down again those supplies will probably stop because they cost too much to produce. The oil doesn't disappear tho' so when the price rises again we will re-open those supplies. Over time we can darn the planet but it'll take a couple of thousand years and by then we could hope to be mining space."
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7w05uu | why can some large corporations get away with directly attacking other large corporations in their commercials without getting in trouble for slander/defamation? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7w05uu/eli5_why_can_some_large_corporations_get_away/ | {
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"Defamation (in US law) is a knowingly false statement of fact that causes damages.\n\n\"X sucks and is dumb and makes bad products\" isn't a statement of fact. It is an opinion, and opinion cannot be defamatory.",
"Technically since it's an ad, it would be libel, not slander which is an oral statement. And defamation is a broader term for either libel or slander. \n\nTake the recent Wendy's ad campaign. The basic message is \"Wendy's tastes better than McDonald's because we use fresh beef and McDonald's uses frozen beef\".\n\nWhat tastes better is a matter of opinion, and you can't defame by expressing an opinion. That McDonald's uses frozen beef is a verifiable fact, and it's not defamation if something is actually true. Making fun of a competitors claim is likewise not spreading an objective falsehood. The McDonald's statement \"our beef is flash-frozen to seal in flavor\" was mocked by Wendy's with \"Remember an iceberg sank the Titanic\". Nothing legally defamatory about that. Now if Wendy's ran an ad that said McDonald's used horse-meat for their burgers and they were contaminated with broken glass and *E. coli*, that would likely result in a lawsuit for defamation since it is neither opinion nor a true fact. \n\nThat \"better\" is subjective is settled case law. Papa John's was sued by Pizza Hut. The gist of the claim was that Papa John's statement slogan \"Better Ingredients- Better Pizza\" was not objectively true. They won in a lower court which ordered Papa John's to stop, but then upon appeal a higher ruled that \"better\" is a matter of opinion and thus not subject to libel.\n\n",
"Take note this is somewhat an American thing, some other countries have tended to be stricter to a degree. Direct gold sales ads are only allowed in India and USA."
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2jka90 | why does the air conditioner in my car "smoke" when it is raining out? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2jka90/eli5_why_does_the_air_conditioner_in_my_car_smoke/ | {
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"It's more of a mist than a smoke I suppose. ",
"Because there is so much moisture in the air that the evaporator in your car is not able to pull it all out. ",
"It's water vapor, cold air can't hold as much water vapor as warm air. When it's raining outside it's really humid but the air can hold more moisture when it's warm; so when you cool down that air the ability to hold that moisture is lowered."
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e64n8d | how come some drugs cause physical withdrawals (opioids) and others only psychological withdrawals (cocaine) or no withdrawals at all (nsaids) | & #x200B;
||||
|:-|:-|:-|
|||| | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/e64n8d/eli5_how_come_some_drugs_cause_physical/ | {
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"a lot of the time it depends on the parts of the brain that they effect along with the symptoms they create when you do them. I know when it comes to medication that covers up pain you have more severe withdrawals and typically physical because your body is trying to maintain the homeostasis that it has learned which in this case would be not having the pain. Psychological could be due to this as well depending on if they have more psychological effects when you use the drug vs. more physical symptoms when you use the drug. I'm guessing this so I'm not 100 percent sure but I'm basing this off of the different neuroscience and psychology classes that I've taken. Also, we've learned that \"neurons that fire together wire together\" so could be due to if they aren't firing anymore the effects of those neurons getting rid of the connection between them. Those are just my best guesses if that helps.",
"It all comes down to whether or not and how a drug affects brain chemistry. \n\nMost withdrawals are due to your brain’s natural tendency to try to counteract the effects of a drug that messes with its normal function. It does this by adapting the brain and body’s resting state to a new normal. For example alcohol is a depressant which means it decreases the activity in your brain. Well the brain likes a certain level of activity so that it can control your body properly, so when you are constantly drunk and your brain activity is too low for its preference it will try to increase its activity to try to re-achieve its preferred normal from before the alcohol was introduced. When you remove the alcohol, all of a sudden the brain is working in overdrive because the set point it adapted to with the alcohol present is now too high. This can lead to seizures and other bad outcomes from the overactivity in the brain. Think of it like this. I (your brain) want to stand in one spot and I don’t want to move. All of a sudden a man (alcohol) comes up and starts pushing on me constantly trying to get me to move. I don’t want to move so I push back hard to try to stay in that spot. All of a sudden the man disappears in a puff of smoke. What happens? I fly forward and fall on my face because lm still pushing even though he isn’t there. That’s what happens to give you physical withdrawals. \n\nFor stimulants like meth, the withdrawals are the opposite (fatigue, depression, etc.) because your brain set a new set point to try to adapt to the drug that is now too low once the drug is removed. \n\nIt also depends on how long the drug lasts whether your body will try to adapt to it. It takes sustained intoxication for the body to try to adapt to a new set point since the mechanisms involved are more long-term than a few hours. I suspect this is the reason drugs like cocaine usually don’t produce withdrawals, since it is relatively short-acting, and staying high on cocaine for weeks at a time is very hard and out of the realm of financial ability for most addicts. But I will admit this specific example I am not entirely sure the reason why you don’t get withdrawals. \n\nFinally, drugs like NSAIDs that don’t alter brain chemistry do not really trigger the brain to try to adapt to a new set-point. You can still develop tolerance from other organs adapting to the presence of the drug (I.e. the liver can get better at breaking down the drug) but since the brain hasn’t adjusted its activity, there aren’t really that many systemic effects when you stop.",
"Physical withdrawal usually results from when your brain/body makes physical changes from chronic exposure to a drug. Opioids are a good example: opioids shut off receptors in your brain that, in part, signal for pain. Overtime, an opioid addict's brain starts making more and more of those receptors. This leads addicts to using greater and greater doses to get the same effect. If they stop cold turkey, there is a ton of pain signals that can now get through, regardless of whether they are actually in severe pain. \n\nPsychological withdrawal is related to how your brain perceives rewards. Physically addictive drugs are also often psychologically addictive. Most recreational drugs (including less dangerous drugs like caffeine) and even things like sugary foods or pleasurable activities like gambling or sex \"make you feel good\" by stimulating your brain to release dopamine, the main signal for pleasure. It becomes an addiction if you can only \"feel good\" when you are on the drug , eating unhealthy food, or doing that addictive activity.\n\nThings that are non-addictive tend to not release dopamine and also avoid triggering your body to overcompensate by making excess receptors."
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436mwt | what is coal ash? is it really bad? are there any good benefits? | The reason I'm asking is because Republic Services' is getting closer and closer to dumping a lot of it in a landfill back in my old hometown. I have no knowledge of what it is,the effects of it,etc It sounds like really bad stuff and I just want it explained to me better. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/436mwt/eli5_what_is_coal_ash_is_it_really_bad_are_there/ | {
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"Coal ash is what's left over when a power plant burns coal. It's mainly silicon dioxide, aluminum oxide, and iron oxide, but does contain some heavy metals, so it can be a problem if it gets in the groundwater.\n\nBut unless you actually eat it or breathe it, it's not especially dangerous. It's often mixed into concrete as a way to recycle it, since it functions similar to Portland cement. "
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1hsnkt | the appeal of comic book superheroes | I never got it, and I feel like there is something I am missing. Everyone seems to love them (superman, batman, etc.) so much and I would like to join in the fun. What is great about them? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1hsnkt/eli5_the_appeal_of_comic_book_superheroes/ | {
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"Superman is the embodiment of the perfectly \"good\" person. He's the one we all wish we could be. He fights crime, saves the world, gets cats out of trees, and calls his mother every week. No task is too small or unimportant. \n\nBatman, we empathize with. The big \"what-if\". If we had his resources, and experienced the trauma of having our parents murdered, what would we do then?",
"You know how ancient societies loved their stories of heroes fighting monsters? Its like that. Superheroes are modern myths. Just like classical myths they serve several functions for the viewer; they allow us top escape into the world of the hero and we can create characters that somehow speak to our society and what we want from it in symbolic language. It's just that instead divine parents they get their powers from accidents.\n\nA few examples might help clear it up. When Superman was created in the 30's he represented not just the the immigrant culture but the change in american demographics. Like many Americans he came from a different society (krypton), a society he was proud of but also was proud of his adopted society as well (earth). He had to balance these two aspects of his life in his two identities. Like a growing number of people he was raised on a farm and came from a blue collar background but had moved to a city and became a white collar worker. Since aspects of american culture have changed he seems dated, but much of his story can still be relatable. The dual identity aspect should be something that many people can relate to at one point in their life. The destruction of krypton and it failure to heed the warnings of its lead scientist reminds me of climate change.\n\nThe X-men are metaphors for almost any oppressed minority who are being discriminated against. Like African Americans or homosexuals the x-men are being vilified by society for something that they have no control over because its just how they were born. At the same time they are an ideal minority because the are advocating acceptance instead of separation. Every time professor x beats magneto we are saying that the ideology of MLK is superior to Malcolm X.\n\nIron man was originally intended as an example of american industry being superior to Russian industry. Readers could cheer an American business man defeating Russian businessmen in exciting and physical ways. With the fall of the soviet union he has changed to suite our changing ideas about wealth. He works to make sure the government is abusing his technology. Instead of punching rival Russians, he takes on corrupt and evil american businessmen. Through his stories we get to see our ideal billionaire triumph over our evil ones.\n\nFor all that overthinking, there is one more aspect to their appeal. There is just something primal about the superhero. Everyone fantasizes about being able to fly or being invulnerable. Iron man wears a suite of armor and shots lasers, every kid knows how cool that sounds.",
"There are the unrealistic ones that most people idolize, and treat as gods. Then, there are the humans who are extremely skilled at a certain thing, and are much more relatable. All it is is another fictional character, but (mostly) with big muscles and/or boobs. Basically; in comic books, the superheroes are trusted with the fate of humanity, and once you have begun to read some, you will understand why people look up to them.",
"Total side note: the best super hero movie is and remains Unbreakable.",
"There isn't much to explain. If it's not to your taste, you're not going to like it. Are you a fan of sci fi or fantasy? Kinda similar to that in a way. Personally, I really enjoy (good) speculative fiction (obviously a lot of it's crap, so you need to get the good stuff) set in imagined worlds or scenarios that could never actually happen. It allows you to explore themes or issues in extreme or exaggerated ways. Not all superhero books try to do that of course, but one good example would be Invincible. In this comicbook series a teenage boy looks up to his father and sees him as a hero, but they fall out and fight a lot and he starts to really hate his father. So far, a very common trope, but the difference here is that the father literally is a superhero with incredible powers. I don't want to spoil it for you, but the crushing realisation the boy experiences, and the conflict created between the characters, when the boy discovers his father is not quite the man he thought he was, is similarly exaggerated from the common everyday experience. So by taking everyday life and amplifying it you can get great narratives. Most importantly though, superhero comicbooks are fun.",
"It's the same reason people watch action movies or read adventure novels. It gives you someone who is already noble or whatever, but then faces a stronger enemy and against all odds defeats them using wit, strength or some other sought after quality. You just gotta find a hero you like. I like the Flash a lot. Also Deadpool. You should play some superhero video games and watch some superhero cartoons and you might get it. I recommend Marvel Ultimate Alliance 2 and Justice League."
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dco8fk | why does hitting someone (or getting hit) hard causes a bruise? why is it blue? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/dco8fk/eli5_why_does_hitting_someone_or_getting_hit_hard/ | {
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"A sufficiently powerful impact will cause tissue and capilaries to break meaning you have a hematoma which is localized bleeding under the skin. \n\nNow for some reason some blood vessels like Veins will look blue or purple through the skin, but thats because blood carrying CO2 is darker then the bright red of blood carrying O2.",
"The bruise is blood that has leaked, and is being broken down by the body. The colour of the bruise is dependant on how far the blood has been broken down, so it changes from pink-red to blue-purple to green to yellow-brown over time. \n\nBlood with a lot of oxygen is red, blood with less oxygen is more bluish. \n\nThese colourings from broken down blood also affect the colour of feces and urine."
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cutywp | why there is a "tipping point" for the destruction of the amazon | I keep hearing things like "once we destroy 20/30/40% of the Amazon, we've reached the tipping point, and the rest will follow." what is the science behind this? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/cutywp/eli5_why_there_is_a_tipping_point_for_the/ | {
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"The trees in the Amazon create their own microclimate causing increased amounts of rain sustaining the conditions for the rainforest. The starting point for the rain is the Bodele depression in the Sahara _URL_0_ the trees prevent the water flowing rapidly back to the Atlantic with the warmth in the area meaning that some of the rain then forms more rainclouds which keep the area wet.",
"In terms of animal life, only so many animals can fit in smaller spaces. So, the less forest there is, the more species are lost. I forget the exact numbers but after a certain amount of loss, extinction and stuff picks up rapidly.",
"Positive feedback loops.\n\nLess trees = less transpiration = less rainfall = less growth = less trees.\n\nAlso less trees = more soil loss = less nutrients = less growth = less trees.",
"As a slight aside - for all of you wondering about climate change and increased CO2 being \"good\" for the trees and that they'll grow more: There is a pre-set rate at which osmosis occurs (the process where water travels from the roots up to leaves). Think of the commercials for Bounty absorbing water. You cannot increase that rate. As the temperatures increase, water will evaporate out of the leaves faster than the tree can draw water from the ground. When this happens the trees die. This is why global temperature increases are so dangerous - the plants stop working. Increasing CO2 levels are just like giving a dehydrated person a potato . . . its food, but they'll die of thirst. As more trees die, less shade, more heat, less trees, etc to tipping point. (edited for spelling)"
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3o11po | why does the recruiting/hiring process for most jobs move so ridiculously slow? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/3o11po/eli5_why_does_the_recruitinghiring_process_for/ | {
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"I work for a natural gas company. We have 1 engineering department. HR collects applications, but it's up to the engineering manager to determine out of all of the applicants which ones should qualify for an interview. In the meantime, that manager has a full day of work to do. Also, jobs are open for a certain amount of time, so from job posted to posting closed will be a couple of weeks before they look at the application/resumes.\n\nHuman resources won't be the ones who hire you, interview you, etc unless you're applying for a job at fast food. They're the ones that will hand your applications to the manager and manage your benefits after you get hired. If it's taking a long time, it's because the department that needs an employee is short-staffed and has to do their normal daily business.\n\nI'm in Information Technology, and for IT, you almost exclusively are brought in through consulting houses (fancy temp agencies) or referral via vendors (we use EMC for our data storage, so we would ask them if they know people who need a storage job, etc).\n\nIf you're looking to move faster, see if you can find your equivalent engineering placement agency, or try joining a startup company."
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6x4cbx | why most ammunition's dimensions have decimal number instead of round number? | Such as 7,62x49 instead of 7,60x49, and 5,56x49 instead of 5,50x49. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/6x4cbx/eli5why_most_ammunitions_dimensions_have_decimal/ | {
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"A reason for some strange values is that they were original designed in inches. \n\nThe 7,62 are developed from the .30-06 Springfield cartridge where a diameter of .3 inches was used. \n\n5,56 is derived from a .222 inch cartridge where the value make a bit more sene\n"
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k6drx | why is the swiss national bank saying it will buy all other currencies in unlimited quantities? eli5 | _URL_0_
I don't understand economics! | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/k6drx/why_is_the_swiss_national_bank_saying_it_will_buy/ | {
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"The Swiss Franc is actually too strong verses other currencies right now. This sounds like it would be a good thing and too a degree it is but Switzerland relies on exports as a major part of its economy and if no one can afford your exports then you have problems so they wanted to cap the value of the Franc verses the Euro at 1.2 Euros per Franc. \n\nNow capping your currency on paper is one thing but actions is louder than words so they feel they have to enforce this by buying the crap out of currencies in an effort to make the market do what they want it to do. The idea is, we set the cap, now we are going to buy currencies and make the currency market follow what we are doing.",
"Maybe not quite at the 5-year-old level, but here's a good podcast about this topic: _URL_0_\nAnd a blog post: _URL_1_\n\nThe gist is that because of all of the uncertainty in the markets, a ton of investors have been buying up the Swiss Franc over the last couple weeks drastically inflating its price and making their exports too expensive.",
"How much does one who lives it Switzerland earn? - could you work in Switzerland buy currency and retire in america like a king? ",
"The Swiss Franc is actually too strong verses other currencies right now. This sounds like it would be a good thing and too a degree it is but Switzerland relies on exports as a major part of its economy and if no one can afford your exports then you have problems so they wanted to cap the value of the Franc verses the Euro at 1.2 Euros per Franc. \n\nNow capping your currency on paper is one thing but actions is louder than words so they feel they have to enforce this by buying the crap out of currencies in an effort to make the market do what they want it to do. The idea is, we set the cap, now we are going to buy currencies and make the currency market follow what we are doing.",
"Maybe not quite at the 5-year-old level, but here's a good podcast about this topic: _URL_0_\nAnd a blog post: _URL_1_\n\nThe gist is that because of all of the uncertainty in the markets, a ton of investors have been buying up the Swiss Franc over the last couple weeks drastically inflating its price and making their exports too expensive.",
"How much does one who lives it Switzerland earn? - could you work in Switzerland buy currency and retire in america like a king? "
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601zze | why is china's role in ww2 such uncommon knowledge? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/601zze/eli5_why_is_chinas_role_in_ww2_such_uncommon/ | {
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"In the United States, it's because the war on Germany took precedence, so we learn more about the Western Front, briefly touch on the Soviet Union and the Eastern Front, and our experience with the other side of the world is mainly limited to the Pacific War with Japan. China's not covered because, to be honest, the vast majority of our servicemen were deployed elsewhere. All we ever hear about from the Chinese Theater of Operations is the Flying Tigers.",
"One reason is because it makes the chinese communist party really upset when you remind everyone that the only reason they are in power is because the actual democratic people's republic of china lost all it's military power fighting tooth and nail with the japanese imperial army. Mao Zedong's communists basically laid low like a bunch of opportunistic cowards during the war while the japanese raped and murdered everyone, and then moved in to take over the country after the republican government had exhausted all its man power. Then they went out of their way to rewrite history and pretend that they were actually the saviors of the people/fought the japanese. Since china is an important trading partner and chinese culture puts a huge emphasis on the concept of face (face basically means public respect), we all collectively agree to ignore it.",
"Much of China was occupied by Japan before and during WW2. China was also still largely an agricultural \"peasant nation\", not industrialized nearly the extent of Japan or western powers. Thus their capacity to mount resistance was limited. Their main role (from the allies' standpoint) was to force some extent of japanese troops tied up defending the territory, raid supply lines, sabotage war resources. Their history during WW2 is limited because their impact on the war was limited. ",
"After the war, our government was worried that Japan would become communist like Russia and China. A lot if the atrocities committed by Japan weren't made public since our politicians wanted to rebuild and make an ally of them. They wanted a presence in the region. There was really no way to talk about China without talking about what the Japanese did there.",
"Well, to sum it up simply, Japan had already conquered much of Asia by the time the US joined the war and those parts were generally not liberated. Japan still held that territory when they surrendered to the US, and during that part of the war Russia swept in to claim territory for the communists.\n\nIt made for a somewhat awkward ending to the whole thing and the Soviet land grab at the end sort of triggered the cold war stance that followed.",
"One of the simple reasons is because we call it the \"Pacific War\" on the eastern front. Where and when did it start? Pearl Harbor, December 7, 1941. This entirely takes out the starting point in which Japan began hostilities against China, September 18, 1931 during the Mukden Incident. An entire decade had passed before the USA joined the eastern front, but we don't even bother to mention it.",
"The history of countries that sometimes cause the US aggregation are seldom studied in depth in grade school. Very few people know about the rape of Nanking who haven't done some digging and research out of real curiosity because it's not talked about often. You could say the same for Vietnam before the war, or Korea before the war etc. World history is painted in with the broadest of strokes. ",
"China Marines and the Flying Tigers etc? Those were the main things other than Role as victims of the Japanese I knew of growing up.\n\nDisney doing the Patch for the Flying Tigers and Newsreel stuff.",
"Here in Britain we learnt about it. The Burma road and all.\n\nI'm really starting to feel like American teaching of history sucks.\n\nWho won the war in Europe? The Soviets obviously, I think the right statistic is for every German that died fighting Americans or British, 30 died fighting the Soviets. Yet you talk to Americans and they make out they won the war single handly. \n\nYea cheers guys thanks for selling weapons to both sides, getting rich then only joining the war when Hitler directly declared war on the US. ",
"The Rape of Nanjing occurred, where Japanese soldiers seized control of the Chinese capitol (at the time) and raped/killed as many people they could find. At the same time, Japan committed a lot of messed up medical research during WW2 through torture, some may say even worse than the Nazis did. Unfortunately, these findings were deemed important to the U.S., as they could help advance the search for cures of some diseases and other things. The U.S. made a deal with Japan to obtain the medical discoveries in return for no punishment for the Rape of Nanjing.\n\nIf this deal never happened and the Japanese got their rightful punishment for their crimes, I am very sure that we would hear of China's role in WW2 more often than we do now.\n\nWhat's even more messed up is that medical researchers would have made a *portion of these medical discoveries sooner or later. So stupid.\n\n*Edit: A portion, not all",
"It's well know in the majority of the world. The US education system is based on glorifying the US role. \n\nThis is how the fact that the US didn't help the Allies in Europe (particularly France) until ¾ of the way through WW1 isn't well known. And then it didn't want to help Britain and Europe in WW2. It demanded all of Britains wealth for assistance and sent it broke. No one remembers that either. \n\nSo it suits the US image of itself to tell the history that makes itself look good. \n\n",
"I was unaware of the atrocities committed by Japan in China until in undergrad my Chinese history professor gave us a good couple hour lecture solely on the subject. Eye opening to say the least. ",
"Because it ended with Mao, and it's a lot easier to forget why Mao got power and just accuse him of mass murder. It's hard to have an in-depth understanding of the factors that led to his popularity and still blindly accuse him of horrible things.",
"Because the nationalists lost the chinese civil war, a lot of WW2 history was used in favor of PRC propaganda. Little did people know that the communists ambushed the nationalist soliders in 1940, killing 40 thousand of them in one single battle while ignoring Japanese troops some 50 miles away.",
"The massacre of Nangking was awful. The Japanese had no humanity in such atrocious acts against the Chinese. ",
"It's due to the post war hostility towards communism. \n\n\nEssentially, there was two stories of WW2. The one that really happened, and the one where the US sallied in and kicked everyone's ass.\n\n\nNow guess which version cold war high school class rooms were teaching.\n\n\n\nThe result is the current state of affairs with a bizarrely warped perception of how and by whom WW2 was fought that persists to this day.",
"Yeah I'm from the NL and you can already guess what we talk about most. We did a really cool thing though where the teacher gave us a couple of subjects and we had to make a presentation about one of them. I chose operation barbarossa as it isn't that well known and I am a history fan. But I think western countries don't talk about the stuff they weren't involved in that much. I don't know about the situation in Germany or Japan but you'd think they'd learn more about the Eastern front and China. ",
"It's not well-known because we as Western countries wrote a history that shoehorned the China-Japan-Pacific conflict into the European-centered war. That's not necessarily wrong: the Japanese did attack European and American territories, and they did that (ultimately) because of their conflict in China. These things are absolutely connected. But the idea that China was a nation like Western nations, and that it had a \"role\" in the war like France or New Zealand is not quite accurate. China was horribly complicated in the 1930s.\n\nSo in China the Second World War has to be discussed in the context of their history. Most countries in the war operated together. We call the winning side \"the Allies\" because- with a few serious exceptions- they collaborated closely. China had the benefit of aid from the Soviets and Americans, but they did not have the ability to project power into other theaters or provide men or material in return. They didn't cooperate internally, much less with other governments on other continents.\n\nChina didn't even have a single government: it was a quilt of warlord territories, most of which had been assembled together by Jiang Jieshi (Chang Kai-Shek) into Kuomintang (Nationalist) territory like a syndicate. The Communists under Mao Zedong controlled roughly one province. Other warlords and potentates controlled their own provinces and regions, including places that still give the Chinese government a headache, like Tibet and Xinjiang out west. The efforts each government made differed too, with the Communists putting up remarkable resistance when they faced off against the Japanese, and the Nationalists losing ground continuously for eight years.\n\nWith all that in mind, it was not realistic to expect the Chinese to do much outside of China. Their place in the history of the war is crucial, but the story that we tell- about industrial superpowers, an engineering arms race, intercontinental strategy, and the wills of mad men- doesn't really fit with the events in China.\n\nSource: wrote thesis on China in the 1930s, lived in China for several years.\n\n\nFor my pet theory: the conflict with Japan should be put in the context of Chinese history broadly, under the idea that China has a cultural center (including places like Sichuan, Shanghai, and Bejiing) and a cultural border (including places like Japan, Manchuria, Vietnam, and Tibet). Every few centuries one of the border countries rides in and tries to take over the center. The Mongols and Manchus pulled it off. The Japanese tried but failed.\n\nThat theory will probably not hold water, but I'd like to try it out on some Japanese people anyway. \n\n\n",
" > **It’s a good reason to remember that on its own. I would say that one of the single facts, which is worth remembering if you want to annoy an official in the Chinese Communist Party, is to remind them that the reason, the primary reason, that China today has a seat in the permanent five on the United Nations Security Council, the top table of global diplomacy, is not because of anything that Chairman Mao did. It was because of the wartime efforts of Chiang Kai-shek, and essentially as a direct result of China’s involvement on the Allied side in World War II.**\n\n > China now finds itself — more than 65, 70 years nearly after the end of World War II — as the only non-European, non-white power to sit at that top table. So these things do have a great deal of significance today.\n\n > **When were they forgotten? Put very simply, China’s wartime experience, suffering, and contribution to the Allied cause fell into a hole created by the Cold War. Neither side had an interest in recalling what China did.**\n\n > On the Chinese side, after 1949 when the civil war was over, the Nationalists had been exiled to Taiwan, and Mao was victorious on the mainland, you had essentially a virgin history in the mainland of China — that the only people who had made a contribution to fighting and defeating the Japanese were the Chinese communists.\nThe contribution that had actually been made by the much larger Nationalist army was essentially either dismissed or wiped out of the official history that was taught in China itself. So there’s sort of an historical black hole there.\n\n > But we can’t put any of the responsibility by any means on the Chinese communists on the mainland. You have to remember that in the West, we very quickly forgot about that wartime contribution as well. The reason is that Chiang Kai-shek, the Chinese wartime leader, was essentially seen as a sort of embarrassment — this Cold War relic remaining on Taiwan, looking more and more irrelevant year by year, associated with incompetence and corruption, with a whole variety of qualities that the West didn’t find very attractive.\n\n > But what was forgotten was the leader, through a whole swath of decisions, many of them very problematic and difficult, had nonetheless kept China in the war against Japan. First of all, on his own for about four and half years, and then of course as part of the very difficult alliance with the West for another four years after that.\n\n_URL_0_",
"Usually in school, we just learned a handful of events (Pearl Harbor, Normandy, etc) and then to make it easier they just lumped countries into the good (US, GB, USSR, France) or bad (Germany, Japan, Italy), while China's role was a bit more complicated than a public school teacher would want to get into.",
"The same reason we think America won the European conflict despite Russia killing 90% of all Nazi forces, almost all the tanks and the eastern front being the clear deciding front of the war. Germany pulled forces away from the west, even after D-day, to stop the Russians, and some German officers intentionally surrendered early so that Britain/America could get to places before the Russians.\n\nThe west talks about the west kicking ass because the western soldiers came back with their stories. Very few Russian soldiers came back to make Hollywood films about the Eastern front. Very few Chinese soldiers made Hollywood films about their experiences. ",
"Not a direct answer but relevant. I'm travelling in China right now and got discussing history in general, Chinese history and Mao, the cultural revolution, the wars etc with some native Chinese young people I met at a hostel. They were mid twenties probably, and when we got discussing ww2, (which incidentally here they actually call 'the anti Japanese war'), none of them even knew who Adolf Hitler was. I mentioned his name, but they had not the slightest idea, never heard of him. Only one of them slightly recognised him when I showed them some pictures on the Internet. \n\nHistory is more often than not centric to where you live. They couldn't believe I'd never heard of x amount of Chinese and Japanese folks that they all know, the same way we know of Hitler and goring and goebbels (im tired forgive me for the spelling). \n\nSo in the west, we focus on the Germans, France, the UK, the US whereas here they basically learn, 'Japan was bad'. \n"
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68tduf | why do people in the us refuse pay raises to not get into higher tax brackets? | Is it because people do not understand how tax brackets actually work?
EDIT: I should've put "some people" in my title, now I sound really passive aggressive. My bad | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/68tduf/eli5_why_do_people_in_the_us_refuse_pay_raises_to/ | {
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"I never heard of that before, but if some people do that, it's because they don't understand how tax brackets work.",
"People think that if they get a raise that it will push them in a higher bracket and they'll overall net less income overall. \n\nThis isn't true thought because the tax brackets are marginal. This means the first $X amount is taxed in bracket 1, the second $X amount in bracket 2, and so on. ",
"Its not just about tax brackets, which other replies in this thread seem to maybe not understand.\n\nLets say I have a family of 3 with an income of $80800. With this, I see an estimate of [$8270 financial help](_URL_1_) with insurance. If I get a $1 raise, putting me at $80801, [I lose all of that assistance](_URL_0_)\n\n",
"There are a few things.\n\n1. Is a misunderstanding of how the income taxes work. With marginal rates, you only pay the higher tax rate on income above that amount. So if you make $50,000 and the tax rates are 10% on the first 15,000, 20% between 15,000 and 45,000, and 25% on everything above 45,000. You only pay 25% on the last 5,000, 20% on the middle 30,000 and 15% on the first 15,000.\n\n2. Is a real concern thanks to the stupid way most welfare type programs works. Many programs are setup only to provide benefits below an income threshold, so maybe you get $2000 of food stamps if you make less than $10,000 in income. So if you make $9,999, you get an additional $2,000 in food stamps, given you an effective equivalent income of $11,999. But if you income goes up $1, you no longer qualify for food stamps, so now you effective income is $10,000. This discourages raises because people will be worst off unless the raise is high enough to offset it. This is terrible design, and could be mitigated by having a gradual reduction, i.e. you lost $.50 of food stamp benefits for every dollar of income above $8,000 so that you are always noticably better off making more money. "
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1mdzjl | why does gold of the same amount of karats look different colors? | Beyond rose gold and white gold, why will some gold have brighter more yellow color thank other, even if it is the same amount of karats? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/1mdzjl/eli5_why_does_gold_of_the_same_amount_of_karats/ | {
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"The carat unit is the level of purity of the gold. If it's less than pure gold (24k) then the gold has been mixed with other metals. The various other metals create variation of colors.",
"It is common for manufactures to plate low carat gold with a higher quality to make it look nicer in the shop. _URL_0_ ",
"There are 4 different types of gold (Red, Green, Yellow, White) they look different at different karatage.",
"Great question! Karats refers to gold content only. The formula is 1 karat = 24x(mass of gold)/(mass of material). so 100 grams of pure gold is 24x100g/100g = 24 karat gold. However, if you have 12 karat gold such that 24x(50g pure gold)/(100g material) = 12 karats, that other 50g can contain other metals. \n\nAssuming that your jewelry isn't plated in any way, different colors arise from different alloying agents. [Here is a chart of what these alloys may contain.](_URL_0_)\n\nHope that answered your question!!"
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3guofv | how are the words in phonetic alphabets (such as the nato phonetic alphabet) chosen and why have they changed over the years? | How were the words chosen? Why have they changed in the past?
The NATO Phonetic Alphabet: Alpha, bravo, charlie, delta, echo, foxtrot, golf, hotel, india, julliet, kilo, lima, mike, november, oscar, papa, quebec, romeo, sierra, tango, uniform, victor, whiskey, x-ray, yankee, zulu | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/3guofv/eli5_how_are_the_words_in_phonetic_alphabets_such/ | {
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"From _URL_0_:\n\n > The final choice of code words for the letters of the alphabet and for the digits was made after hundreds of thousands of comprehension tests involving 31 nationalities. The qualifying feature was the likelihood of a code word being understood in the context of others. For example, football has a higher chance of being understood than foxtrot in isolation, but foxtrot is superior in extended communication.",
"The words are chosen because they are hard to confused with one another.\n\nThe point of the phonetic alphabet is to be able to easily distinguish the first letter of the the word from the first letter of other words.\n\nIf you had it be Apple, Bog, Cat, Dog, Era, Flame, George, Happy, India, Jericho, Kilo, Little, Map, Newton, Ontario, Prairie, Quiet, Roger, Sample, Tornado, Ultra, Victor, Water, Xylophone, York, Zebra then there are going to be some confusion.\n\nObviously things like \"Bog\" and \"Dog\" or \"Cat\" and \"Mat\" can be easily confused especially when you are doing other stuff. Even things like \"Apple\" and \"Sample\" can be confused with enough distractions and/or a poor radio signal.\n\nAnd then there are words like \"George\" and \"Xylophone\" where saying the word doesn't give a precise first letter. Some people spell \"George\" as \"Jorge\" and many don't know how to spell xylophone. \n\nSo they keep it simple and make sure each word has it's own unique sound at the beginning.\n\nAs for how they are chosen? Many of them have been around since codes were first invented and remain due to status quo. Alpha, Beta and Delta are actually names for the equivalent forms of \"A\" \"B\" and \"D\" from the Greek Alphabet. And others have been included because they work better and/or are easier to remember than their predecessors."
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4w50z9 | what is the most probable scenario for worldwide infection of some deadly disease? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4w50z9/eli5_what_is_the_most_probable_scenario_for/ | {
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"A significant international event, for example an Olympics. \nHeld in a place where an outbreak is occurring, Zika doesn't quite fit that bill.",
"There is no probable scenario for worldwide infection of some deadly disease, sorry - no Walking Dead Zombie Plague.\n\nWhen people are exposed to an infection, many of them fight it off. Even a specially engineered bioweapon wouldn't have 100% effectiveness.\n\nWhile there is widespread travel and traveling patients are a good vector for spreading a disease widely, it is not true that everybody travels. As we saw with Avian Flu and SARS, travel restrictions are imposed pretty quickly to block the spread.\n\nYou'd have to have an airborne disease that can cross into many types of animals with a long period until there were symptoms and a short time until the infected person was contagious. Aliens cook this sort of thing up in science fiction novels, but it's not a pathology we see in the real world.",
"As permafrost melts in the arctic, bodies of people and animals infected by bubonic plague or \"new\" types of influenza thaw out and the disease is passed on to humans via animal contact. "
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2he3l6 | why do so many americans believe in god? | As a Norwegian, I think northern Europe is very close culturally to America in so many ways, but here literally no-one, except some of the older generation, believe in god, while I have the impression that religion is a huge part of the lives of so many Americans. Why is that? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2he3l6/eli5_why_do_so_many_americans_believe_in_god/ | {
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"*gets on knee* America was founded by very religious groups of people from England and other parts of Europe called Puritans. They created a country based on religious freedom because they themselves were so religious. A large part of modern Americans come from these families. Their traditions and customs have become the America we know and hate today? ok? *gets up*",
"I think a better question is why ~76% of the population of Norway belong to the Evangelical Lutheran Church of Norway when literally no-one in Norway believes in god.",
"One of the principles that is highly protected in the US is religious freedom. This means that at times there have been large waves of immigrants who have come to the U.S., such as the influx of of Catholics from Ireland, Germany, Italy, and elsewhere in the 1800s.\n\nThe bigger issue, though, is the Cold War. During that time the Soviet Union was a secular state and there was a lot of propaganda that focused on this fact. When you have a person who has learned their morals through religion and you need to paint an entire union of nations as being inferior and immoral it is easy to attack them for their godlessness. This greatly strengthened the power of Christianity in the US. It is from that era that the motto \"In God We Trust\" found its way onto all of the coins and currency of the nation and that the pledge was amended to be \"One Nation, *Under God*\" \n\nThis culture is waning, though. The generation that was most strongly influenced by the effects of the Cold War is aging while there are young adults today who were born after the fall of the Soviet Union. \"No Religion/Athiest/Agnostic\" is the fastest growing religious (or lack thereof) philosophy in the country.",
"everyone who says AMERICA HATES CHANGE isnt right. I mean america was the champion to the freaken internet. America was founded and has always been very tied to Puritan beliefs this is why you dont see much nudity in american media. the folly of your logic is that america is simular to the Scandinavians when in fact they are very different. yes the houses my be similar but the people are very different ",
"* much of America was founded by people specifically looking to practice their religion without gov't interference\n* lack of a state religion mean churches are in competition for members and actively recruit and retain them...in European countries, a state religion came to dominate, and once established, didn't have to try very hard, and became tepid",
"I can't see this thread going badly at all. :^ )",
"America was founded by very religious groups of people, and was were numerous waves of religiously persecuted people came over the centuries.",
"people want magic, not logic.Not just in America, in other religious countries as well.",
"Thanks for the replies! I think I understand the historical aspect, but I still don't get why Americans haven't moved away from religion to the same extent as many (northern) Europeans the last 30-40 years, considering how big of a role science has in modern society, and especially since a lot of the scientific advantages are being made in the US. It's also weird hearing so many people thanking god in public (actors, the president etc). That would be really really strange in these parts! I'd dare to say almost cringeworthy."
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2y5jpg | how can full albums stay up on youtube for months if not years without being taken down, but full movies are taken down almost instantly? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/2y5jpg/eli5_how_can_full_albums_stay_up_on_youtube_for/ | {
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"Because the groups which manage the rights for music have got their shit together and negotiated deals with Youtube. GEMA (Germany) is the exception, so most of these albums are blocked in Germany."
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d0il1q | why wet slaps hurt more? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/d0il1q/eli5why_wet_slaps_hurt_more/ | {
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"Skin is soft, mushy, and full of lots of little cracks and holes. When you slap someone, a lot of the force from the slap gets cushioned by the skin and dissipated over the larger surface area created by those little uneven surfaces. This happens for both your hand and the slapped person.\n\nWhen your skin is wet, it pulls itself taut to help keep that moisture out. This tightens it out a bit to reduce surface area and makes it slightly less mushy. In addition, the water fills in some of the cracks and holes, making the surface more uniform. This reduces the energy lost and makes the slap hurt more.\n\nIf you wait even longer while wet, like long enough for your hand to get all pruney, the opposite will happen. All of those wrinkles increase surface area and make the skin even mushier, and so the slap will hurt even less.",
"It is surface area. The water fills the gaps in your skin of the hand and surface of the other area. Evenly dissipating the power of the slap onto its target. Creating more efficient energy transfer. \n\nYou ever tried to hit something, swing hard and just not get enough hand on it. Like a volleyball serve where your fingers engage before your palm, it will not go as far because you did not evenly transfer the power.",
"Good god!\nI asked this question on a whim\nI didn't know reddit was waiting for it.",
"the other commenters are mistaken, i think. it’s not a surface area thing, it’s an air cushion thing. the pain of a slap comes from the linear kinetic energy of the slap being transferred to the struck skin, and air lets some of the linear force become transformed into motion in a random direction via turbulence and subsequently into sound and heat. by making an airtight seal, a slap that occurs at a wet palm/skin interface compresses all of the air at once. you can think of it as a wrinkled vs a flat surface striking skin. as the rough surface comes toward the skin, the taller peaks of the surface will be “squishing” the air faster than the troughs, so those areas will experience a sharper rise in pressure. the adjacent troughs will be at a lower pressure and air will flow sideways to equalize this, stealing forward momentum that could otherwise be spent on pain. there’s only so much force behind the slap, and moving air isn’t free. more force spent pushing air sideways means less force pushing meat hard enough to hurt, less force means less pressure. \n\nwell, the why of a wet slap hurting more probably has something to do with the fact that the acceleration is happening quickly. i don’t know why sharper acceleration is more painful, but i’m pretty sure that’s the cause.",
"Its because water is not compressible, for the same reason that water is like concrete when an object hits it from a great height."
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wauo1 | why does gatorade hydrate you better than water? | explainlikeimfive | http://www.reddit.com/r/explainlikeimfive/comments/wauo1/eli5_why_does_gatorade_hydrate_you_better_than/ | {
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"Gatorade doesn't necessarily hydrate you better than water. What it has that water doesn't is high levels of sodium, which replaces the salt that you sweat out. It also has ingredients that replace lost electrolytes.",
"Because its got what plants crave.",
"Electrolytes, water doesn't have any and in large amounts can actually flush them from your system. Without electrolytes and sodium you get to die a very unpleasant death. Be better to mix water and Gatorade, or even pickle juice, as it's packed with electrolytes and tastes better. ",
"As they have already said, but here is the 5YO version. Your body is like a car battery. You need both water and electrolytes to make your battery work. When you sweat, you lose water, salt and electrolytes. When you drink water you replace the water, but not the electrolytes. Before Gatorade made Orange Bowl champions out of the University of Florida, the coaches would have water, ala Adam Sandler \"Waterboy\" kind of water. \n\nThe water will rehydrate a player, but the salts and electrolytes will still be depleted. If you add enough water, the player would lose a lot of electrolytes, and like you car battery overfilled with water, not have a lot of power. Gatorade adds the electrolytes. Too much so in fact. You are better diluting the Gatorade by half in order to keep the balance correct. "
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ccgof1 | why do a lot of out of tune people singing together sound not out of tune? or at least not as out of tune as compared to if they all sang as individuals. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/ccgof1/eli5_why_do_a_lot_of_out_of_tune_people_singing/ | {
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"Your brain is good at understanding patterns, and what things are \"supposed to be.\" If one person does something wrong, your brain says \"that's wrong!\" but if multiple people are doing different things wrong then your brain can pick out the \"right\" parts of the singing and focus on that. If everyone sang something completely wrong then it would be equally difficult to listen to.",
"Also it is much easier to sing in tune when you have a lot of other people singing with you. This is actually how I learned to sing, and I still can't sing most songs on my own, but I sound fucking great at those group songs. \nSomeone else can provide explain harmonizing in more detail. I think that's the concept you're experiencing."
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8hz8ig | what triggered the us to pull out of the iran nuclear deal? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8hz8ig/eli5_what_triggered_the_us_to_pull_out_of_the/ | {
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"Trigger #2 for 45 was that Obama admin negotiated it and he wishes to destroy everything Obama."
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8wbi27 | why is it that in radio frequencies, the lower the frequency the further range you get but less bandwidth? | Was reading bout 5ghz vs 2.4 GHz WiFi . Basically why is attenuation proportional to frequency? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/8wbi27/eli5_why_is_it_that_in_radio_frequencies_the/ | {
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"Think of a 5GHz signal as a fully loaded car, and a 2.4GHz signal as a fully loaded semi. \n\nWhich do you think is easier to stop?\n\nA 5 GHz signal is tiny, and cannot pierce through many solid materials like buildings or mountains. They can even be disrupted by rain.\n\nIn contrast a 2.4GHz signal is bigger in comparison and will pierce through more substances. \n\nAs for information sending, imagine the lower bandwidth signal is someone talking really slowly. You'll get the information, but it will take a while.\n\nThe higher the frequency the faster the talking.\n\nThis is how I understand it.\n\nSource: Radio Technician\n\nEdit: The semi vs car analogy wasn't about the data transfer rates but rather about how hard it is to stop something big. I realize in retrospect I should have used a different analogy. \nI'm leaving it up because it still makes sense to me.\nTake it as you will.",
"The ~~bandwidth~~ throughput reason is pretty straightforward: If you talk faster, you can have longer conversations in the same timespan. Higher frequency - > higher ~~bandwidth~~ throughput.\n\nAs for range, it's similar to driving a car: The faster you drive, the more noticable the windresistance becomes. High frequency radiation is dampened stronger than low frequency radiation, thus low frequency has a longer range.\n\nEdit: As has been pointed out, throughput is the word for data transfer rates. And according to u/TheDapperYank symbol-times are standardised and constant, so my first analogy is based on faulty assumptions anyway.",
"High frequency waves are more easily absorbed by materials. But just because 2.4GHz will go further doesn't mean you will get a better real life data rate due to many more devices being on the 2.4GHz band, shitty access points not choosing a non-overlapping channel, Bluetooth interference, USB 3.0 interference, etc.",
"Radio is a kind of light (just way lower frequency than red).\n\nRadio travels at the speed of light - no matter what frequency. High frequencies can carry more information in a given time because there there is more \"room\" for changes to be detected.\n\nThink of riding in a car over a bridge with the regular \"thump-thump .... thump-thump ... \" sounds. The only way to communicate information is to suppress (0) or amplify (1) these \"thumps\" or \"peaks in the radio wave\". The more \"thumps per second\" you have the more 1s or 0s you can transmit. ( [_URL_0_](_URL_1_) )\n\nAs for why high frequencies don't travel as far - it comes down to dispersion. Make waves in a lake or a bathtub. Slower waves are easier to see (peaks and troughs). Faster oscillating waves are easier to see closer to the sources ... but as you look further from the sources these waves become \"smooched\" together. You lose the \"thump-thump\" type features needed to convey information.\n\nNot a 100 & #37; accurate explanation what's going on at the physics level - but this is the start I give my kids.\n\nNote: Some answers given talk about materials absorbing certain radio frequencies - which is correct but the effect you're describing in your question will also apply in empty space without any materials messing things up.",
"A better lay definition would be that within a specific distance the intervening material will interact with a wave more often the shorter the wavelength is. You have to adjust for specific sizes of material having a stronger than normal impact if they match the wavelength of the transmission, but that's the general rule.\n\nA good (not perfect) visualization would be to scatter balls across a pool table. Then to simulate low frequency trace an s curve across the table with a stick and see how many balls you hit. Then zig zag back and forth 10 times (at the same amplitude) and see how many you hit to simulate high frequency. On top of this just one set of pool balls scattered on the table might be like passing through air, while 20 sets more like a cinder-block wall.",
"Bandwidth isn't the term you want. Throughput or capacity is the term you want. \n\nThis is going to be more of an eli13\n\nBandwidth is the span of frequency you're using, and it's functionally frequency independent. \n\nHow RF signals work is that they are generated at the frequency of the bandwidth you are interested in. So a 20Mhz wide signal is generated from 0-20Mhz. This is called the \"Baseband\". What happens next is the Baseband signal will get sent to the radio which will basically just shift it up to whatever your transmission frequency is. For wifi that's either 2.4Ghz or 5Ghz.\n\nNow as for why you TEND to get higher throughput at higher frequencies is mostly due to RF noise and interference. WiFi specifically uses a technique called Carrier Sense Multiple Access with Collision Avoidance. In short this means that all the devices that want to transmit will listen and wait until they don't hear anyone else transmitting before trying to transmit their data. So if you have lots of RF noise then the devices will refrain from transmitting till they think the RF environment is clear. That and noise will impact how efficient/dense the data being sent is. \n\nWiFi uses a waveform called Orthogonal Frequency Division Multiplexing (OFDM) where the spectrum is subdivided into smaller and smaller chunks of time and frequency that do not overlap, until you get to individual symbols. These symbols are functionally a sine wave, and based on and amplitude and phase of the individual sinewaves it represents a series of 1's and 0's. If the RF environment is clean then you can pack more 1's and 0's into a single sine wave.\n\nNow, for pathloss. RF through freespace is NOT actually attenuated. It just acts like it is because the RF energy is being spread out over the surface of an ever increase sphere the further away you are from the source. The reason why lower frequency (larger wavelength) signals have less pathloss because the aperture of an equivalently optimal antenna will be significantly larger, touching more surface area of the sphere of RF energy.\n\nDoubling the frequency is equivalent to doubling the distance from a pathloss perspective.\n\nSource: am RF/Telecommunications Engineer\n\n**edit:** spelling"
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bve6fq | how does cold transfer if it's just the absence of heat? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/bve6fq/eli5_how_does_cold_transfer_if_its_just_the/ | {
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"Cold sucks the heat out of other things. If you have a cold thing and a hot thing and put them together the heat will transfer to the cooler part until they both reach the same temperature as their surroundings.",
"Others have covered thermodynamics. There is a slight/not-really-exception to this which is convection. Warm gasses rise causing cooler gasses to fall, meaning in a tall room, the cold comes down. Also if you open a door on a windy day, physically cold air may blow in and replace your warm air. In a closed system the warm air would give its heat to the cold air in time, but this is why it annoys me that \"smart\" people poke fun at the commonly said \"you're letting the cold in\". You can absolutely let cold air in.\n\n/end rant.",
"Think of heat as a bunch of super bouncy balls. If you have big box and you pour a lot of these balls in one end of it, then they are going to be bouncing into each other and on the walls. This is the hot end of the box. \n\nIn the other end of the box there are no balls. This is the cold end of the box.\n\nNow, every time a ball bounces towards the hot end it's more likely to bounce of another ball, because there's loads of them. \n\nBut if it bounces towards the cold end it's got more free space and is less likely to bounce of another ball.\n\nThis way balls migrate over towards the cold end until the balls are pretty much evened out across the box. The cold end has become hotter and the hot end has become colder.\n\nBut the emptyness(cold) hasn't moved to the hot end, it's just that some bouncyness has moved from the hot end to the cold side so now the hot end is less hot (or less full of bouncy balls)",
"Cold doesn’t transfer, as in cold moving from one object to another. As you said cold is the absence of heat, so a colder space tends to attract heat. The cold isn’t moving into a new area, heat is being sucked away from said area into the colder space. Think of it like oxygen in a vacuum where the barrier between the two gets broken (window in space ship breaks. The vacuum isn’t moving into the oxygenated area, the oxygen is being pulled into the vacuum.",
"It was explained to me this way. There is no such thing as cold, it’s simply less heat, not necessarily the absence of heat. We can’t measure cold, we can measure heat. So even though something feels cold to the touch, it’s simply far less hot than your hand and therefore it transfers the heat from your hand faster than your hand can transfer the heat from the “cold” item. I’m no scientist and I’m sure others can explain better, but it helped me when explained that way.",
"Cold doesn't really transfer. The second law of thermodynamics states that heat transfer only occurs from hot to cold. In other words, heat will never move from a cold to a hot object. Heat will be transferred from a hot region to a cold region until there is no temperature difference.",
"Cold doesn't transfer but the difference in temperature between a cold substance and a hot one increases the rate at which the hot substance loses heat to the cold substance.",
"Cold do not travel as it is not a thing. It is heat that travel in the other direction. It is heat that travel from the warmer object to the colder object. The result that the warmer object the a colder and the colder object get warmer.\n\nThe transfer is exact the same as when heat is transferred. There is not fundamental difference between when it is warmer outside and it hear up a house compared to when it is colder outside and it cool down your house. \n\nThere is a practical difference and that is that you can generate heat by burning fuel or using electricity. Covering heat to other energy is a lot harder hand you need a temperature difference to do that. So it is a lot easier to warm stuff upp then to cool then down."
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4pfae1 | why is ups suddenly transferring so many packages to usps thus causing delays? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4pfae1/eli5_why_is_ups_suddenly_transferring_so_many/ | {
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"It's cheaper. The USPS has to deliver to every house. The government requires them to do that. UPS is a for profit company that doesn't have to follow the government's rules. They don't have to deliver to everyone themselves. It is expensive to send out a truck, so they try to make the truck to as many deliveries as possible. If your house is far out of the way, or there are no deliveries being made nearby, it's much cheaper to just pass it to USPS than send out a truck to make just a few deliveries.\n\nBut no, I don't know what specifically made them do it so much more frequently now."
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7i5qv4 | why is the lucas number superior to the fibonacci sequence in terms of calculating the golden ratio? | I just don't see the difference. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7i5qv4/eli5why_is_the_lucas_number_superior_to_the/ | {
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"You can get an approximation (estimate, if you prefer) of the golden ratio from lucas/fibonacci numbers by taking one element from the sequence, then dividing it by the previous element. So, for fibonacci numbers (1, 1, 2, 3, 5, 8, 13, 21, ...), your approximations are 1/1, 2/1, 3/2, 5/3, 8/5, 13/8, ... and for Lucas numbers (2, 1, 3, 4, 7, 11, 18, ...) they're 1/2, 3/1, 4/3, 7/4, 11/7, 18/11, ...\n\nBecause both of these are integer sequences, and the golden ratio is irrational, you can never get the exact value. However, the further along you are in either sequence, the better the approximation.\n\nSo... how good are these approximations? That's where the Lucas numbers are \"superior\" to the fibonacci sequence: After a frankly wonky start (because lucas numbers start weird, with the first term being bigger than the second), if you take the same number of steps (that is, for both sequences dividing the 11th element by the 10th element, or dividing the 28th element by the 27th element, or whatever else), then doing that same amount of work using the Lucas numbers gets you an approximation that's closer to the true value than you'd get with Fibonacci numbers.",
"A given Lucas number is twice the average of two Fibonacci numbers, those being the one just before and just after the ordinal position of the number in question. \n\nI.e. L(n) = F(n-1) + F(n+1).\n\nSo it's going to be a slightly smoother approximation that will be slightly closer to the golden ratio at any given time, but inconsequentially so. ",
"First lets define some things so that it doesn't get too messy. \nLet A := 1+sqrt(5) and B := 1-sqrt(5)\n\nThe Fibonacci and Lucas numbers can be defined as such: \nF_n = ( A^n - B^n ) / ( sqrt(5) \\* 2^n ) \nL_n = ( A^n + B^n ) / 2^n\n\nDividing the consecutive numbers by eachother we get the following ratios: \nF\\_(n+1)/F\\_n = 1/2 \\* ( A^(n+1) - B^(n+1) ) / ( A^n - B^n ) \nL\\_(n+1)/L\\_n = 1/2 \\* ( A^(n+1) + B^(n+1) ) / ( A^n + B^n )\n\nYou can rewrite this as: \nF\\_(n+1)/F\\_n = 1/2 * [A / ( 1-(B/A)^n ) - B / ( 1-(A/B)^n )] \nL\\_(n+1)/L\\_n = 1/2 * [A / ( 1+(B/A)^n ) + B / ( 1+(A/B)^n )]\n\nThese two are almost identical since B will be negative and as such the sign of B^n will flip for each step and both of these will converge to 1/2 * (A/1 ± B/∞) = A/2 as n goes towards infinity and they converge equally fast.",
"It cheats.\n\nLucas cheats because it's opening ratio of 2:1 is closer to Phi than Fibonacci's opening ratio of 1:1. Not only that, but Lucas's first two sequence numbers are simply Fibonacci's second two sequence numbers backwards.\n\nAlmost any starting pair of positive integers added in sequence like Fibonacci can reach Phi. A 9, 3... sequence reaches 4 digits of Phi (1.618) at the 11th step, same as Fibonacci."
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4wrs4t | why does a circuit require a neutral? why is it classified as 0v but has 230v traveling through it? | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/4wrs4t/eli5_why_does_a_circuit_require_a_neutral_why_is/ | {
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"Voltage is a difference in energy levels. There's no such thing as 230V without having some sort of reference whether that's a neutral pin of a power supply or ground.",
"Hey, so your question is worded a bit incorrectly because voltage doesn't exactly work that way. But that's why you asked the question, to find out how it does work!\n\n.\n\nSo to answer your first question: Why do circuits require a neutral. The answer is, they don't. Think of a simple 1.5 Volt AA battery. It has a positive end and negative end. This means the positive side is 1.5 volts higher than the negative side.\n\n.\n\nDoes this mean that the positive side is 1.5V and the negative side is 0V? Not exactly. An analogy we can use is to pretend that instead of voltage, we are talking about height. Let's replace our 1.5V battery (chemical/electrical potential energy) with a 1.5m cliff (gravitational potential energy).\n\n.\n\nWe know that the height of the cliff is 1.5m, but does that mean the bottom of the cliff is at 0m? Maybe, if you define the base of the cliff to be 0m. you could also define the top of the cliff to be 0m, which makes the bottom of the cliff -1.5m.\n\n.\n\nIn this simple battery system, there is no such a thing as neutral. Just a positive reference point and a negative one. So basically, the answer to your first question is, circuits don't require a neutral.\n\n.\n\nOf course the obvious next question is, well why do we have neutrals then? Or what are neutrals?\n\n.\n\nWhat you're probably thinking of is your electrical outlets at home that you plug things into. You'll notice there are three holes, the two 'eyes' on top and the mouth on the bottom. The two 'eyes' correspond to positive voltage and neutral, and the mouth corresponds to ground. (Simplified for ELI5 purposes since AC current in your house is a bit more complicated than that).\n\n.\n\nIn this case, all of the appliances in our house share the same neutral (it all connects back to the power panel in your home). So the neutral acts as a reference. This is like building a whole bunch of cliffs that all have a bottom at the same height, which you define at zero, so you can measure the heights with respect to that zero. (Again, a bit simplified since AC is a bit more complicated than that.)\n\n.\n\nNow, even though we are using the neutral for most of our household plugs, we don't HAVE to. What if we needed a bigger voltage drop? Well, in addition to the 'positive' height of 120V, our AC home system also has a -120V height. What this means is if we have a special appliance that needs 240V (for example, a clothes dryer or an electric hot water heater), We can set up our plug so that one 'eye' connects to +120 and the other connects to -120, giving us a total voltage drop of 240V.\n\n.\n\nOkay, as for your second question, why is the neutral classified as 0V but has 230V running through it, we can see that this question doesn't quite make sense. Voltage measures electrical potential (aka \"height\"), so the neutral doesn't have voltage running through it just like you can't have meters or feet falling off a cliff.\n\n.\n\nSo what is running through your wires? Electric current. Think of it as water falling off your 120m cliff. The energy of the water powers a turbine below using the energy from falling from the top of the cliff to the bottom. Your TV or computer or lights are powered by electrons \"falling\" from 120V down to 0V (your neutral) or even -120V as discussed above."
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9iy50c | sir michael atiyah's solution to the riemann hypothesis and what it means for mathematics if confirmed to be correct. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/9iy50c/eli5_sir_michael_atiyahs_solution_to_the_riemann/ | {
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"The early consensus seems to be that the alleged proof is deeply flawed, where “deeply flawed” is a euphemism for utter nonsense. The author is a renowned mathematician, but he's also 91 years old and he's been writing some very questionable stuff recently. Maybe someone will find something interesting in it, but it's likely that the alleged proof is not coherent enough to explain.",
"As has been said, the proof is most likely nonsense. \n\nBut, I’ll take a stab at your second question, which is what does it mean if it’s correct. \n\nHonestly, at this point, not that much. A lot of math has been developed on the assumption that the Reimann is correct (and on the assumption that it is not correct), so when it is proven/disproven, a good chunk of papers will become validated, and a different chunk will be invalidated. The key will be *how* the Reimann hypothesis is actually proved- whoever does it will likely have to invent some new cutting edge ideas, or relate it to something in a genius way. (The current proposed proof doesn’t do that, afaik, which is partly why there’s little hope for it). When a true proof does appear, the methods used in that proof will likely give rise to a lot of new and interesting math, which I can’t hope to guess at. "
]
} | [] | [] | [
[],
[]
] |
||
7329rw | why does the feeling of zero-g (without the physical resistance of water; like floating in the air) seem like a familiar feeling, despite never having experienced it? | To elaborate: doesn't the feeling of floating around, pushing off from a wall that's upside down or something with your feet and just floating towards something else, maybe grabbing onto something to stop your momentum, seem so familiar to you in a weird way? Isn't it just so easy to imagine that you can almost swear you've felt it before?
Not like swimming, where you can feel the pressure against you. | explainlikeimfive | https://www.reddit.com/r/explainlikeimfive/comments/7329rw/eli5why_does_the_feeling_of_zerog_without_the/ | {
"a_id": [
"dnn0pn0",
"dnn2or2",
"dnn30sf",
"dnn9trd"
],
"score": [
3,
4,
2,
2
],
"text": [
"40 weeks in a womb? ",
"I have a question: Having not experienced it, how do you know it feels familiar? You're just assuming the sensation you imagine is accurate at that point, are you not? In which case it's 'familiar' in that you have no basis for comparison.",
"As a Lucid Dreamer I can say I experience this very exactly feeling regularly. Do you LD? If so, maybe that is the case. Or maybe it is just a good feeling for a thing you really admire.",
"Maybe you're confusing familiar feelings with intuitive/adaptive movement? If you're swimming and get caught in a strong turbulent current, your movements will almost intuitively work to counteract the turbulence and restore balance even if you've never been in that situation before.\n\nI think this is a testament to how adaptive your mind is rather than familiarity with the situation. "
]
} | [] | [] | [
[],
[],
[],
[]
] |
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