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Why do I faint when I see lots of blood from a serious injury?
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[
" There's a short answer, and there's a long answer.\n\nThe short answer is that nobody knows why that causes you — or any of the many people like you — to faint. It's a complete mystery.\n\nThe longer answer, though, is that the *mechanism* by which you faint is well understood. It's called *vasovagal syncope.* Syncope is the medical term for a transient loss of consciousness; if you black out for no external reason and recover seconds or minutes later on your own, that's syncope.\n\nThis particular type of syncope is called vasovagal, *vaso* referring to the vascular system and *vagal* indicating a relationship to the vagus nerve, an important nerve in your chest.\n\nWhen it happens, your body's *parasympathetic* nervous response ramps up, while your *sympathetic* nervous response is diminished. In broad terms, the parasympathetic response is responsible for what they call \"feed and breed\"; it handles things like digestion and sexual arousal, stuff that happens to us when we're relaxed and feel safe. The sympathetic response handles what people commonly call \"fight or flight,\" which happens when your body is spurred into attentiveness and readied to expend a ton of energy in a short burst.\n\nYour parasympathetic and sympathetic responses are normally kept in balance, ebbing and flowing more-or-less in a rhythm. Your parasympathetic response makes you want to lay down and sleep at night, and your sympathetic response makes you want to wake up and be active in the morning.\n\nBut the vasovagal response upsets the balance of these two systems. It suppresses the sympathetic response and amplifies the parasympathetic response. This has several effects, but the ones that matter most are the *cardioinhibitory* effect and the *vasodepressor* effect. Basically, your heart rate slows down and your blood pressure drops. As a result, your brain is (mildly and temporarily) deprived of both oxygen and glucose, and you lose consciousness.\n\nBut as soon as you're out, the vasovagal response fades away, and your parasympathetic and sympathetic responses reassert themselves. Your BP and heart rate both come back up, and you wake up again, usually just seconds later.\n\n*Why* this happens is a bit of a mystery. Evolutionary biologists occasionally throw out the notion that the vasovagal response to stress is in some way an adaptation, that it's like a \"play dead\" reflex that deters predators … but nobody really buys that as anything other than amusing speculation. Too many things about our bodies just *work they way they do* and have no reason or rationale behind them.\n\nSo the upshot is that the sight of blood triggers your vasovagal response, which in turn triggers your \"sleep time now\" reflex, and you faint. As soon as you do, your body returns to its normal state, and you wake up again. The only danger is that you might bump your head on your way down, but aside from that, it's both harmless and *entirely* within the normal range. Not everybody gets the vasovagal response from the sight of blood, but many do, and *everybody* gets it sometimes, regardless of individual differences in trigger stimuli."
] |
[
" ELI5: When you are standing up, gravity pulls your blood down. When you faint, your body goes limp and the blood gets to your head more easily.\n\nELI15:Say you are walking around, then something happens, like you get a stroke, or your blood pressure drops rapidly due to blood loss, or any situation where blood can't get to your brain. As a medic, if someone is going into shock, we elevate their feet about a foot above the patient's head so the blood can get to their head. This will get the much needed blood to the brain as brain cells (generally) don't grow back. \n\nAlso, thats why if you see someone faint, then they \"wake up\" only to stand up and faint again. (Blood pressure in their head drops when they stand up). And if someone faints in a wheelchair... well they are screwed.\n\nEDIT: To answer your question... There is no kill switch for the brain. Its when the blood pressure drops too low and your brain *can't* function. That's why Air Force Pilots must be trained because the maneuvers they do go up to really high Gs which would cause MOST people to black out. \n\nAnd I think the only benefit of fainting is to get more blood to your head.",
" Yes you faint because you're brain gets less blood, but that happens because of a sudden drop in blood pressure. This sudden drop in blood pressure is a defense mechanism for when we are injured to keep us from bleeding out. For some people this mechanism is more sensitive and they'll faint at the sight of blood without being injured."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How do lymph capillaries collect the lymph?
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[
" They are the lowest pressure in the system. They have no elasticity like arteries. Muscle movement raises the pressure outside them temporarily. So they fill.From there they journey and collect. It is not an active process. \n\nIf an IV infiltrates the skin turgor increases. Slowly this will drain away through the lymph channels. There are no little pumps working away. It is a drainage system."
] |
[
" Your heart pumps blood away from itself in arteries, these branch out into narrower arterioles, and these branch out into narrower still capillaries, which exchange material with the cells of your body. The capillaries then join back up into wider venules, which join up into veins, returning the blood to start the cycle over.\n\nBasically, veins and arteries are simply the largest branches of a huge network.",
" Cold causes the capillaries in the nose to shrink, squeezing lymph and other fluids out into the nasal cavity and sinuses."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Employers of reddit: Why do you put "minimum work experience of X years required" into entry-level job postings?
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[
" I once saw a job posted online as an \"entry-level\" position for which, between 10 different categories of experience required to apply, they expected applicants to have a total of 60 years' worth of experience. I may be wrong, but I think the reason why this is done is simply to cut down on the number of applicants. You have to imagine that, for every job posted with the entry-level designation and no particular required experience, the HR department would have thousands of applications to sift through."
] |
[
" Used to work in recruitment. Now, what one needs to bear in mind is that recruiters will state what they *want*, but that's not necessarily what they'll *get*. Even they know this. But they pitch high, hoping that someone that fits that description applies for the job. They will get a bunch of people without experience applying too, and they may very well interview them and hire then. \n\nThis is often the case, but not always. A more cynical interpretation is that the company is looking for an experienced recruit but paying them on an entry-level salary, at least in their own scales. As far as that company is concerned, all entry-level positions require experience.",
" The job is going to pay an entry level wage, but managers selfishly want someone who is way overqualified and will be able to overperform for that low wage. They think those overqualified people won't need as much supervision. \n\nI hate this practice, but I had a manager that purposely put a wishlist of requirements in job descriptions. She put \"Adobe Suite\" in every job listing, even when it had absolutely nothing to do with the position, because she just wanted someone in the department to have that skillset. When I was promoted, she posted my old job, and I called her thinking there had been a mistake. I told her I've had this job and I don't qualify to apply! She had years of budgetary experience, managerial experience, and Adobe Suite listed. None were needed for the position. \n\nI personally HATE this practice, because it completely distorts who you get applying. Perfectly qualified people don't apply, because they don't have those unrelated skills. No one that overqualified is going to be happy at that pay, at least not for long. And, in my experience, a lot of the people who apply when they don't have those bogus qualifications, also don't have some of the actually necessary ones - they have a bigger tendency to overestimate their qualifications in general."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How does an LED bulb work? How is it different from fluorescent?
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[
" When you run a current through a gas like mercury, it shoots off ultraviolet light. If you put a phosphorescent coating next to the gas, it absorbs the ultraviolet light and glows with visible light. That's how fluorescent lighting works. \n\nIncandescent lighting is slightly different, it's called black body radiation. Essentially the heating of an object causes it to give off energy in the form of light. \n\nLEDs use semiconductors, where a controlled number of electrons move through a piece of material with an excess of electrons into a material with \"holes\" or places for electrons to go. The free electron material generally has them floating at higher energy level than in the material with \"holes\" so when the current flows and electrons cross the junction they drop energy levels, emitting the photons or light. It's called the photo electric effect.",
" LEDs work because electrons and holes are created when a current is passed through a semiconductor material. The resulting interaction of the electrons and holes produces photons. \nFluorescent bulbs are an ionized gas producing UV light which hits a phosphor coating that brightens the room with the familiar light we know."
] |
[
" As far as I'm aware, it's simply that LED bulbs have a much smaller light-emitting region, so for a given brightness the light density is much higher. Fluorescent and incandescent bulbs tend to be frosted for consistency and aesthetics, whereas with LED bulbs you're often looking straight at the diode itself. There are frosted LED bulbs: I'd expect those to give you roughly the same experience as staring at the other two.",
" Incandescent lights work by heating up a strip of metal until it's hot enough to glow. This uses a lot of electricity and produces a lot of heat, both of which are bad things.\n\nFluorescent lights work by adding energy to mercury gas. The mercury stays high-energy for a little bit, then loses that energy in the form of invisible ultraviolet light. This light, in turn, hits a special coating inside the lightbulb which glows under UV light (much like your teeth glow under a blacklight). This is more efficient than incandescence, but still inefficient since there are so many steps to the process. It is not heat-based, so that is an advantage over incandescent lightbulbs. It requires mercury, which is toxic. Finally, it is not a steady process, but a series of very fast zaps of electricity, which produces a flicker (but the flicker is so fast that the human eye can't normally detect it). \n\nLEDs basically work the same as fluorescent lights, but cut out some steps. Instead, they directly send energy to a substance which produces visible light, instead of UV light like mercury does. With fewer steps involved, this is much more efficient, and can be kept \"on\" steadily instead of flickering like a fluorescent bulb."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why does touching something really hot sometimes feel cold for a second?
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[
" Or vice versa, touching something really cold feels really hot. \n\nI believe it has to do with how your pain receptors work. First you touch something with a temperature difference which causes pain, and the pain you sense is just that. Pain. The neurons associated with pain will fire first. \n\nYou have to be above a certain threshold for this to hold true do, but as soon as you touch something that has a temperature that causes you pain, you will feel the pain and not the temperature first."
] |
[
" For the same reason why when you stick your hand in really really cold water, the first instant feels like fire hot. It's a sudden shock to your nerves and impulses to your brain saying \"HOLY COW WHAT THE HECK DONT TOUCH THIS.\" The nerves in your hand didn't have enough time to register heat in that fraction of second you first made contact, just really really stimulus.",
" The answer is actually that you're feeling different volumes of air. \n\nWhen you exhale with your mouth wide open and your hand near your face, you feel your hot breath. \n\nWhen you hold your lips together, you increase the air speed exiting your mouth, and this is actually pushing ambient air over your hand, and you feel cold because the pushed ambient air is removing heat from your hand due to forced convection. \n\nIf you bring your hand close to your face, and blow air with your lips close, you can feel the hot air that's actually coming from your mouth."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
What is the "reptilian" part of the brain and why is it labeled as such?
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[
" The reptilian brain, also known as the basal ganglia, is the part of your brain that keeps your heart beating, lungs breathing, basic motor control, and other automatic, reflexive, and instinctive behaviors. These parts are very similar among reptiles, birds, and mammals, and to a lesser degree, amphibians and fish. This indicates those features were present in a common ancestor.\n\nThe cerebrum is responsible for thinking and reasoning and is the part that becomes much larger and convoluted in more intelligent animals.",
" A better way to say it would be \"This is the part of your brain that has changed very little and still has much of the same function as the equivalent area in other amniote tetrapods (everything that shares a common ancestor with both reptiles and us).\"\n\nThese are the areas of your brain that accomplish every deep, basic functions of homeostasis and very basic information processing. They haven't changed that much because they are already very well adapted for their complex function, and other parts of the brain have seen more changes in response to differing needs in organisms (in humans, for example, we have radically more cerebrum with a lot of folds to increase surface area because that's the primary area where our abstract and complex thoughts occur.)"
] |
[
" Reptiles (Reptilia) no longer exist. The group (clade) is called sauropsida now. You can see it come from saurian who mean lezard in grec. Your question is legitimate because it's exactly why we switched the classification.\nSo vulgarized, yep, birds are reptiles or at least, they are related by an common ancestor.",
" The left hemisphere of our brain generally controls the right side of our body, and vice-versa for the right hemisphere. \n\n\n\n\nThe brain can be divided into three sections. The R-Complex, the Limbic system, and the Neocortex. \n\n\n\n\nThe smallest is the R-Complex situated where the spine connects to our brain, overlapping that is the Limbic system, and overlapping that is the Neocortex. \n\n\n\n\nReptiles only have the R-Complex, it is sometimes referred to as the lizard brain. Mammals have both the R-Complex and the Limbic. Humans have the Neocortex. \n\n\n\n\nThe Neocortex is where language develops. Specifically in the left hemisphere. The right hemisphere focuses more on spacial awareness and motor control. A baby's language center develops faster than it's spacial awareness, an evolutionary advantage supported by how long human babies are allowed to develop before having to fend for themselves. \n\n\n\n\nSince the left hemisphere has more development early on than the right, babies tend to use their right hand more than their left."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why is anal extremely painful to some, "weird" feeling to some, and pleasurable to others?
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[
" I think any person can experience pleasurable anal, it is just that a lot of people don't know what they're doing. You can't just raw dog it and shove your dick right up there for the first time and expect the other person to enjoy it. The anus needs to be played with and stretched until it can accommodate a penis. Most importantly of all you need to use lubrication. There is also a huge difference in pleasure between men and women because men have a prostate.",
" It really isn't painful to anyone, just extremely uncomfortable. It can be pleasurable to *every* male person, simply by stimulating the prostate.\n\nIf you are anxious about it and tense it will be more uncomfortable in the rectum.\n\nA majority of it is psychological but physiological differences including proper lubrication, size of anus and the object entering it, and stress levels.\n\nBut I think its safe to assume on any given night after a glass of wine and you are feeling relaxed, a lubed up finger in the butt can be fun for everyone."
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[
" Recent MSc neuropsychology graduate.\n\nThere is no single answer to the question as the human mind varies so greatly between individuals in how it copes with life experiences. Additionally, there are many types of fetishes, each with their own unique triggers to how one became enthralled in them. However, I can make some rudimentary associations. \n\nMild or \"vanilla\" sexual fetishes such as light pain stimulation, or stimulation of taboo body areas (anal regions) may arise from the simple discovery of pleasure when one experiences these sort of stimulations. They may occur naturally through self exploration or via an adventurous partner who pushes our line of comfort. In this case, an individual realize that they enjoy this sort of stimulation, and continue to explore this sort of fetish on themselves, and on others. The knowledge that a specific stimulation on one's own body causes pleasure, also produces pleasure when we provide the same sort of stimulation onto a partner. Thus, someone who likes to get their toes sucked, may also experience pleasure from sucking their partners toes. \n\nFetishes of attraction, such as attraction to older/younger partners, cosplay and incest seem to stem from the natural attraction an individual may have towards that source/person. For example, the common attraction to MILFs stems from the fact that men are naturally attested to their own mothers as children, and this may develop into an attraction for friends mothers, and eventually into an attraction for all mothers/older women. The same can be said about a \"sexy\" cartoon character which then stimulates attraction towards people in costumes for example.\n\nThe last type of fetishes will discuss are more hardcore, such as slave/dom relationships, cuckold, and more extreme pain and exhibition fetishes. It seems that these more extreme pleasures stem from the childhood, whether it was parental/social abuse which led to repeating the same patterns as an adult in the bedroom, or non-present parents which led to more extreme strategies to gain affection from future partners. Again, we are all human and differ widely. What may be a destructive pattern for one person, may be a form of pleasure another person stumbled upon.\n\nThere is alot more to talk about but its time for bed.",
" The anus and rectum are full of sensitive nerve endings. To some people they feel good when stimulated. \n\nMore importantly, in men, the prostrate can often be stimulated via anal penetration (which most men find pleasurable; often equating it to a woman's gspot). In women, pressure through anal penetration can reach their actual gspot through the tissues of the body. It also may impart a similar sense of \"fullness\" that one gets from traditional vaginal penetration. \n\nA buttplug is often shaped so that the part on the actual anus is thinner. This allows a larger object to be inside the body without putting continuous stress on the sphinkter. The flared end on the outside prevents it from moving too deeply into the which can be quite dangerous as, unlike a vagina, there is not an \"end\" to the area inside the body."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How is it that a very small wire sliver in my fingertip can hurt a lot, especially when moved, but a relatively larger sliver of wood sometimes won't hurt at all?
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[
" The wire could have been much sharper than the dull piece of wood. Every movement jolted the sharp wire into cutting up your finger while the edge free wood was relatively stable. \n\nIt's kinda like the difference between getting shot with an arrow vs a musket ball. The arrow makes a smaller hole in your body, but every movement causes the sharp edges to tear your apart. The ball will cause a much larger hole butis more likely to wedge itself firmly inside you."
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[
" It's smaller, so the pressure doesn't get distributed across your skin. Smaller, sharper objects tend to hurt more. It doesn't help that LEGOs are almost completely edges.",
" iirc, it's because while a scrape is usually larger in surface area, it just scrapes off a few layers of skin. While a papercut will cut farther down to expose nerve endings which is why it hurts more than a scrape."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why are inner cities so universally poor to the point where "inner city" is a synonym for poor?
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[
" You may be taking \"inner center\" too literally... many big cities do have a prosperous, nice center city where businesses, government agencies, and higher end housing is located. Elsewhere within the city proper there are poor areas, and then surrounding those are wealthier suburbs. \n\nFor example, Chicago's Loop business district is gleaming and full of skyscraper office buildings and flanked by parks and museums. The neighborhoods directly to the South (South Loop), West (West Loop, River West), and North (River North, Gold Coast, Streeterville) are all nice/expensive residential areas, and the nice areas extend well north (Old Town, Lincoln Park, Lakeview) and northwest (West Town, Wicker Park, Bucktown, Logan Square) from downtown. Further west of downtown and much of the South side of Chicago are what you'd consider to be \"inner city\" with poverty, crime, gangs, etc.",
" Well first of all, I suppose that your \"universal\" vision is in fact a US model where the city center, beside the [CBD]( _URL_0_), can have several boroughs poorer than the suburb.\n\nThis model is far from universal as the European cities have their \"inner city\" often overlapping the historical center that can be rather weatlhy, if not the wealthiest part of the city."
] |
[
" Where money and wealth are considered moral goods, and so the poor are considered moral failures, the wealthy tend to stigmatize the poor. This keeps the poor quite poor indeed.\n\nSo there is a vicious cycle of trying to keep the (ugly name for any racial or social out-group here) \"in their place\" offset to the tune of surprise that the economy isn't doing better.\n\nMeanwhile wealthy, middle-class, and even \"barely comfortable\" lower-middle classes don't want to move their families and businesses into some decaying hellhole.\n\nAnd there's nobody in that decaying hellhole to buy most products anyway so there's no impulse to move in nice stores that sell nice clothes and good food.\n\nIn the blue parts of blue states - and I phrase it that way because, in fact, most states and places are actually \"purple\" - suficent money is spent year-after-year to keep the schools reasonably funded and to socially de-stigmatize the poor and give the out-groups resources they need to bootstrap their lives into better circumstance. That raises incomes, which raises taxes, which both pays back the bootstrap money but also raises the entire standard of living and standard of services. This, in turn attracts businesses and families.\n\nAt the core, \"in my humble opinion\" of course, is the difference in the view of \"entitlement programs\" and \"giving\".\n\nOne type of person says \"I suffered, so I don't want to see anybody suffer like that\".\n\nAnother type of person says \"I suffered, so why should other people be spared from suffering like that\"?\n\nThe deadlocked ideas of \"people are only poor because they are lazy\", \"nobody helped me, so why should I help\", and \"charity is for the weak so I will neither give nor _accept_ charity\" taken as a whole perpetuate economic failure.\n\nGo to the net-giving areas and you will find healthy and reasonably vibrant communities for all the out-groups. People of color? yep. \"Questionably legal\" workers and their absolutely legal families? yep. Various religious minorities? yep.\n\nGo to the failing areas and you'll find a whole lot of \"you aint from around here, are you boy?\"...\n\nIt's strong correlation, but there's a heck of a lot of causation.\n\nBasically \"economically unwell\" areas are pathologically \"socially unwell\" too. Neither is the \"first cause\", but both create and sustain each other on an ongoing basis.\n\nThe desire to cut \"entitlement programs\" and other \"federal funding\" is just a symptom of that \"poverty is a moral failing\" attitude mixed with the implicit message that \"if my city, state, whatever needs federal funds then it must be a moral failure.\"\n\nThe the bad reasoning goes \"if we get rid of the charity then we'll obviously retake the moral high-ground\".\n\nPlus, of course, \"if my representative is encouraging such funding then he must be encouraging moral turpitude!\" just rides along.\n\nIt is, at its core, a failure of basic reasoning.\n\nNote that I am \"teh olde\" and when I was a kid the whole Republican Southern Strategy was in full force and I lived in, or very near, \"the south\". I would regularly hear \"If it's good for the ni & & ers it can _not_ be good for me\" in that many words.\n\nSo literally, the poor white racists _demand_ that the ni & & ers get nothing, no matter what it costs the poor white racists personally.\n\nThis isn't just a liberal rant. There's a cognitive bias that makes the bottom of the economic scale become very dog-eat-dog. It's a kind of risk/loss aversion. The poor racist doesn't want the poor black-fella to \"pass them\" on the economic ladder. So anything that benefits both of them is a danger to the one who perceives themselves as only slightly ahead.\n\nThis is the \"keeping up with the jones'\" mentality but down at the hunger games level.\n\nThe whole thing is just pernicious and stupid.",
" Because dealing with poverty by kicking all the poor people out of the city isn't considered an ethical solution."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Do I share DNA with all my ancestors, or just 2 branches?
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[
" It's quite possible, likely even, that you do not have DNA from all of your ancestors. Chromosomes do recombine, which would keep the DNA in the family longer, but with more generations the likelihood that some genes don't make it into the next gets higher. You share more than two specific lines, but definitely not with everybody."
] |
[
" Because 99% of our *human* DNA is similar to chimps, but 1% of it is non-human DNA.\n\nHalf of your DNA comes from your mother, and half from your father. You are essentially a perfectly equal mixture of your parents. Your sibling is similarly a perfect mixture, but you randomly share half of your genes from the same parent, while the other half is from different parents. \n\nYou, your mother, your father, your sibling, all share half of your all-human DNA with each other. If you had an identical twin, then you'd have 100% DNA with no variations.",
" We don't actually share 50% of our DNA with siblings, half of our DNA came from each parent, but there's no assurance that your sibling would get genes in a way that you'd share exactly half of them (in reality, a vast majority of your DNA is \"Default Human\" DNA that everybody shares). It's just a convenient shorthand when talking about human to human genetic relations. The actual amount of DNA you share is random. It's possible, although *extremely* (like extremely, extremely, extremely) unlikely that you and a older/younger sibling could get the exact same genes and be genetically identical. It's equally unlikely that you could have none of the same DNA at all.\n\nThe \"99% with chimps\" is more like the overall human genetic structure (think of it like the \"average\" of all the humans) is very similar to the \"average\" of all chimpanzees."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Malaria and sickle cell anemia and why natural selection hasn't eliminated sickle cell disease.
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[
" If you are a carrier of sickle cell, malaria has difficulty properly infecting you, and even when infected you recover quicker and with less symptoms.\n\nYou survive a malaria outbreak with others, you all do what survivors do, 9 months later babies born with a pair of the carrier gene express sickle cell and are sick. \n\nNatural selection selects for sickle cell because sickle cell is a survival trait. You see similar for Cystic Fibrosis in Caucasian populations where there's a high level of certain toxins which a CF carrier can deal with due to some unique mucosa/gut traits.\n\nPut 2 carriers together, and you have someone with a terrible disorder.",
" Besides the malaria thing, sickle cell isn't usually fatal in childhood. Anything that doesn't prevent you from reproducing natural selection has a hard time weeding out."
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[
" Lots of diseases are good for you. The two that come to my mind immediately are cystic fibrosis and sickle cell.\n\nFor sickle cell, being even a heterozygote makes you virtually immune to malaria. They believe that's what that particular disorder was selected for. Sickle cell was most seen in areas that are endemic for malaria. That's why the percentage is so high in black people. \n\nFor cystic fibrosis, it is thought that it prevents the devastating effects of vibrio cholerae. If your ion channels are messed up, you can't get the voluminous diarrhea. CF is also seen more in white people.",
" Disclaimer: I am not an expert on genetics, nor am I an expert on malaria. I only know what I know from the few years I spent as a biology student and from what I've read about malaria online. If I am wrong about any of this, PLEASE PLEASE PLEASE correct me. I'd rather be chided for telling a half-truth or untruth than give someone incorrect information. Thank you. Also, sorry, I'm not really explaining it like you're five, I'm more just giving a semi-technical explanation.\n\nSimply put, there is a link between sickle cell being prevalent and areas where malaria is commonplace, and this is because people with the sickle cell trait tend to be more resistant to malaria. The precise mechanisms are unknown, but you can find plenty of info by googling \"are people with sickle cell more resistant to malaria.\"\n\nTo get into a little deeper detail, you first need to know some introductory genetics. Many traits are passed down via alleles, which are forms of a gene (formed by mutations - hair color, eye color, and many other traits are determined by alleles. Eye color is a very common example) that get passed down by your parents. For any given allele, there's usually only one version per parent/chromosome. \n\nThere are many different ways that alleles can react with each other, but we'll look at the sickle cell allele simply as a \"has it\" or \"doesn't have it\" allele, in which having one \"has it\" allele and one \"doesn't have it\" results in mild sickle cell, two \"has it\" alleles result in severe sickle cell, and two \"doesn't have it\" alleles result in no sickle cell. This may be wrong, so as with any of this, I ask that someone please correct me if I'm wrong. I haven't dealt with genetics in a while, and I've never formally learned about the way sickle cell is passed on. \n\nSo assuming that the sickle cell trait is inherited purely by the presence of one of two possible alleles in a person, we can map out a simple Punnet square. That's a little tough to do without fancy formatting, so bear with me. So the two possible alleles for this will be \"S\", which codes for \"has it\", and \"s\", which codes for \"doesn't have it.\" Assuming that both parents have mild sickle cell (Ss), there are 3 possible outcomes for offspring, with different likelihoods:\nSS (25% chance) = severe sickle cell - while highly resistant to malaria, significant complications can result from the severe case of sickle cell.\nSs (50% chance) = mild sickle cell - resistant to malaria, but there is a chance of complications from the sickle cell disease.\nss (25% chance) = no sickle cell - no longer resistant to malaria, but also no sickle cell.\n\nIf one parent had the genotype SS and the other ss, you'd see a distribution of 100% Ss alleles. If one was SS and the other Ss or one ss and the other Ss, it'd be 50% SS, and 50% Ss.\n\nSo an answer why the \"races\" found in those regions are more susceptible to sickle cell is the same as why they have darker skin than Europeans: it's an adaptation to their environment. While sickle cell doesn't necessarily seem like a beneficial adaptation, it became so prevalent because it gave those with it a better chance of successfully reproducing. And ever since then, it's been passed down through the generations - even in areas without malaria - because we've found ways to treat it instead of letting everyone with sickle cell die young because of it. \n\nThe percentage distributions I listed above are by no means absolute, either. They're just in a perfect statistical world. So while you'd expect a much larger portion of the population to carry a sickle cell allele, but in reality, it turns out to be a far lower number."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why can't camera phones always film in landscape mode no matter what direction they are being held?
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[
" Because the camera sensor is rectangular. You could have such a setting, but you'd have to lower the resolution of the final image.\nUsing this as an illustration:\n_URL_0_\n\nBlack outline is the phone, blue outline is the sensor (though it's far smaller in real life). The red outline is what would need to be used if filming horizontal video while phone was being held vertically."
] |
[
" If you're using a phone, it's because the lens has a wide field of view. \n\nSome lenses have the opposite effect.",
" Your phone camera has a wide angle lens. This allows you to fit more stuff into a single shot, but the side effect is that everything in the distance becomes smaller to fit into the frame.\n\nThe same thing happens with the moon. Since it is far away, it becomes smaller on a cell phone camera picture.\n\nThe opposite is also true: if you take a picture of the moon using a telephoto lens, the moon can appear absolutely massive relative to the foreground."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why, when making a bank deposit, does it take a few days for a check to clear yet direct cash deposit seems almost instantaneous?
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[
" When you deposit a check at a bank or credit union, at that moment your bank does not know whether or not the check is good. There might be a stop payment on the check, or insufficient funds, or the account may be blocked, or half a dozen other possibilities. Your bank needs to contact the other bank first, and that can take a day or two (used to take longer, but nowadays the info is passed back and forth electronically instead of the physical checks themselves like they did ten years ago). \n \nSo, why does the bank usually make some of the money available right away? Well, that's because a federal law (Reg. CC) requires the bank to make some of the money available on a set schedule, even if the bank is not sure whether or not the check is good. Also, if your account is in good standing and you've been with the bank for a while, they will also make some money available right away based on you being a good credit risk. \n \nOkay, then, we live in the modern age, you ask, why can't the bank just contact the other bank at the time you are depositing your check to make sure it is good? Good question, but that's not really the way bank accounts really work. Banks and credit unions will \"batch\" all the transactions for the same business day, and then re-order the transactions based on a set of rules and policies. \n\nSo, for example, on Wednesday you have an ACH debit to your gas company at 9AM, a bill payment comes out of your account at 11AM, a check is presented against your account at 1PM, and you make a deposit at 3PM. At the end of the day, the bank reorders the transactions so the deposit counts first, then the other three transactions in order from smallest to largest. (FYI, that's just an example, other banks may have different ordering policies). \n \nBecause of this, if you contact the bank at a *specific* time of the day to check whether the account is in good standing, they can't really answer at that very moment - because the transactions could be reordered and there might be other transactions that happen after the call that may count first. \n \nThere's some more stuff (like the ability to place a stop payment *after* the check is presented, believe it or not, or force paying the item on the next day), but that's getting a bit more complicated."
] |
[
" They send you a fake check, per various laws, the bank must give you the money in your account before the check clears. Most people think that the money showing up in the account means it cleared, that's not true, you don't really know for about 2-3 weeks, and it can be even longer. The scammers tell you that 3 days is enough.\n\nThey either overpay and ask for some cash back, or just take the item your selling. A few weeks later it bounces and the bank takes all the money back, you're left with minus any cash you gave them, and without whatever item you were selling.",
" > When I paid for the early upgrade they got this payment almost instantly\n\nNo, they didn't. The money left your account instantly, but it took 3-5 working days for it to show up in their account.\n\nLikewise, when a refund was issued, the money left their account instantly, but takes 3-5 working days to show up in your account.\n\nThis all comes down to how banks operate. When money is transferred between accounts at different banks, it takes several days for the transaction to be verified before the money is released on the other side of the transaction.\n\nMost people just aren't aware of this, because most people aren't on the receiving end of this type of transaction very frequently."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why is Germany taking so many refuges?
|
[
" Lots of bad answers so far...\n\nWithout a doubt it comes down to the German people, at least so far, being extremely reflective upon the actions of their elders and ancestors during the time of the Nazi regime, and taking ownership of that legacy and a perceived obligation to better their society and be as much as they can a positive force in the world.\n\nGermany is a very interesting place. More than any other country that I know of, they wear the injustices committed historically by their society on their sleeves, and remember those injustices in modern decisions that they make.\n\nWhat other countries are so reflective? Many Americans prefer to downplay things like treatment of native americans and blacks, the japanese internment camps, our treatment of japanese war adversaries, and many other immoral or questionable actions that have been taken in the name of America. Our saving grace is that pretty much every other country is the same, they downplay their historical injustices. Germany is different. They own them. Even Austria, the country next door to Germany that by most accounts was at least as complicit in the Nazi regime (considering that Hitler was Austrian, and that he was more popular there than in Germany, and that more Austrian volunteered for Nazi military service than Germans as a percentage of population), to this day mostly denies any responsibility, considering themselves victims of the Nazi regime rather than mostly willing collaborators.",
" As a result of WWII, Germany adopted very liberal laws regarding asylum seekers. On top of that, Germany is seen as wealthy in the states where most of the refugees come from. That makes it a bit of a \"promised land\" for them."
] |
[
" The USA is in so many countries like Germany because the military presence they provide is a commodity. \n\nCountries like USA were on the winning side of the most recent wars. When Germany admitted defeat and surrendered, a part of their surrender was that we could maintain bases there. They were there for several reasons. Not all of them were \"bad\". The USA spent a lot of money, time, and other resources into rebuilding Germany into a functional country. Actually investing in their people and their country (very unlike the German defeat of WWI, which eventually lead into WWII).\n\nNow we have lots of military treaties, most namely, NATO. We're no longer in Germany as a requirement of past wars, but because of mutual agreements between countries.",
" 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."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Can someone please explain how a "space-time crystal" works?
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[
" The article is kind of silly and wildly misleading, but the physics is actually pretty cool. Just forget you read it, a lot of what the writer said was outright wrong.\n\nSo, first, what is a \"spacetime crystal\"? Well, the defining characteristic of a regular crystal is that its structure is repeated and regular. The structure of quartz, for example, looks like [this](_URL_0_). Note that the same shape repeats itself over and over as you move along: in math and science, we call that *periodicity*. Something that is periodic repeats itself over and over. For example, the swinging of a pendulum is a periodic motion.\n\nTo be more precise (it's important), the structure of a regular crystal is periodic in space. If you go up, down, left, right, forward and back, the shape repeats itself. That means it's periodic in three dimensions, the ones we're used to.\n\nHowever, physicists always talk about time being the fourth dimension. What if there was a structure that was periodic in space, like a regular crystal, but also periodic in time? That's what a spacetime crystal is, and it's also where stuff gets a little confusing.\n\nThe basic idea here is that they've constructed a material that, under the correct conditions, has the traditional crystalline structure, and has the property that it is periodic in time. What that means (loosely) is that if I took a \"video\" of it, there would be no way of telling what I recorded from 0:00 to 0:01 and 0:05 to 0:06 apart (or 0:10 to 0:11 or 0:47 to 0:48 and so on). In the same way that you can't tell one part of the crystal structure apart from another because it's repeating itself, you can't tell different times apart in the recording because the system's behavior repeats itself as time goes on.\n\nNow, there's lots of things you're familiar with that repeat themselves in time: pendulums, watches, swingsets, wheels. The other key distinction between a spacetime crystal and those devices is that the spacetime crystal is in its lowest possible energy state.\n\nTo exploit the pendulum analogy, the lowest possible energy state of a regular pendulum is when it's not swinging at all. What that means is that as time goes on, a pendulum slowly slows down, because it loses energy to friction and air resistance and that sort of stuff. No matter how well you make it, it will eventually get to a point where it's not swinging anymore, because that's the lowest possible energy state, and thermodynamics tells us that things eventually always get to the lowest state possible.\n\nThe spacetime crystal, though, is exhibiting that swinging pendulum-like periodicity in its lowest state. It's like you had a pendulum that couldn't *not* swing, or a mechanical watch that never needed to be wound. This is obviously pretty cool (at least to me). The spacetime crystal will never stop spinning, as long as they keep their machine running (which maybe makes it sound less cool).\n\nNote also that this is *not* perpetual motion, at least in the traditional sense. You could not power anything with it: it has no spare energy to give away."
] |
[
" Digital clocks work thanks to Quartz crystal oscillation.\n\nBasically, if you take a quartz crystal and pass an electronic current through it, it will oscillate at a specific frequency. \n\nMost work at about 32,768hz, which is 2^15 cycles per second. Basically, a computer chip counts the oscillations. Every 32,768 oscillations, the clock moves forward one second.\n\nThis is very accurate and reliable, generally speaking. The issue is, pressure and temperature affect how fast the crystal oscillates. A 10C difference can cause about 2min/year to be lost, a 20C difference can be a difference of 10min/year. If your unit gets hot, or sits in a hotter than normal area (like over a heater, on a sunny window sill), it can have a noticeable difference.",
" Space-time is a concept of how our universe generally works. It's made up of three spatial dimensions, and one time dimension. Fabric in this sense refers to how space and time, while different in many ways, are actually fused together. They are a single construct, not two different things interacting with each other.\n\nIf you were to take all the threads out of sheet that were going left-to-right, the entire thing would be a useless mess. the threads that go the other direction are useless alone. They only work when woven together. Likewise, our universe only works when space and time are working together, neither can exist without the other, because they are the same.\n\nIts a difficult concept for humans to really process and imagine, because the idea is so distant from the way we interpret things. referring to it as a fabric makes it just a little easier on us."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How do members of Anonymous remain anonymous? How do they get caught?
|
[
" Anonymous is more of a movement than an organization. There isn't a fixed number of \"members\" behind Anonymous. In a sense, anyone can put on a mask and make videos on Youtube and claim being part of Anonymous. And that's what makes Anonymous so intriguing.",
" Just guessing here. But anyone can claim to be part of Anonymous, how can you verify it? Probably just go into a cafe with a spoofed mac and burned linux cd. There's no way you can hide from your home network, but then again who is really trying to catch them? The NSA isn't. I guess they're not a big priority to catch. Plus most of the attacks they launch are social engineering to get DNS accounts or just plain botnet attacks. It's hard to get the admin of a botnet, and you can use voip to call companies. Just some thoughts."
] |
[
" They hack websites and cause general malicious chaos. That tends to piss some interested parties.\n\n'Anonymous' is a catch-all moniker, not so much a group. You can hack a website, release a statement saying Anonymous did it, and now you're Anonymous, hurrah. There's no telling how many 'groups' are using this moniker, but since there really is nothing else to go buy, Anonymous is referred to as one group.\n\nSo for example, the guys that hacked one site may be entirely unrelated and disconnected to the guys that hacked site two, but they both call themselves Anonymous, so the media places the credit/blame on the \"group\" Anonymous.",
" Generally if its something credible the larger Anonymous twitter accounts will pick up on it to spread the word. If no major Anon Twitter account is talking about it you can generally just ignore it."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
If a movie production has $5,000,000 (estimated) Budget, must some of that money go to the actors? or only movie's production quality?
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[
" The movie budget includes for the actors but also all the staff that is needed, equipment, supplies, costumes, stages & sets, etc.\n\nIf the movie is being financed by a major studio, it most likely is bound by union rules by the Screen Actors Guild (SAG), which it is now partnered with the American Federation of Radio and Television Artists (AFRTA) to form SAG-AFTRA.\n\nThere are standardized pay rates and benefits that actors must be paid, so this is figured in to the budget.\n\nThere are also guidelines for a movie that is being produced by an independent filmmaker with a low-budget (which is usually under $2.5 million) that uses actors that are members of SAG-AFTRA.",
" Yes, if its a 5 million dollar budget then it will most likely be a union show. This means that most if not all of the actors will be in SAG. SAG has minimum day rates for all performers. The bigger names in the cast will usually negotiate their rates through their agents and managers. Every crew member from the Director of Photography to the the production office to the lowly Production Assistants has a day rate that they are paid and if they are in a union its a set hourly rate, with overtime almost every day of production. Then theres cost for equipment rental location fees etc."
] |
[
" Budget. Most of your budget goes on the actors and the film crew. Script and soundtrack take a back seat.",
" In some cases actors are given producer credit rather than a raise.\nThis keeps production costs from getting out of hand due to salary demands, but let's the actors make up the money on the back end, including a share of sindication money for years down the road."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How is a FLAC file smaller than a WAV file without losing data?
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[
" This is like asking how a ZIP is smaller then a TXT\n\nFLAC is compressed via [Golomb Coding](_URL_0_).\n\nYes this is like RAR file but for audio (kinda its complex).\n\nWAV is just raw samples of what the input voltage was at once time. If you decode/read a WAV file its literally\n\n0.0000: 0.5\n\n0.0001: 0.65\n\n0.0002: 0.75\n\nThey're huge",
" FLAC uses loss-less compression. Stuff like MP3 uses lossy compression.\n\nImagine for a second that you want to give me some information on a piece of paper. The information is \"01\" written a hundred times in a row. Wave would be just writing out the whole sequence: \"0101010101...\" all hundred times\n\nWith loss-less compression you remove redundant information. So maybe you just write \"01 x 100\". You have to tell me that that code means \"write a sequence of numbers with 01 a hundred times\". But once I know the code, this makes for way shorter messages. If the sequence was a random set of numbers, you would not be able to compress it without loss of information.\n\nLossy compressiom does the same, but in addition it tries to remove some of the least important data. This is probably easier to explain in images. Imagine you have a photo of your room, and you want to show me where you have hidden a treasure or something. For me to replicate the image, I need the color-values for each pixel. Some of them will probably be the same, so you could use loss-less and say that evey pixel named \" X\" is completely black.\n\nExtreme lossy compression of that image would be a simple line drawing. I don't need details or accurate colors. All the unimportant info is removed, and you're left with the essentials.\n\nDid that make any sense?"
] |
[
" Here's probably going to be the only reason to get a FLAC.\n\nMP3s are lossy which means some of the audio data literally just gets thrown away when encoded. That's why they are smaller. However the algorithms are really good at keeping the parts you hear, but not perfect.\n\nHowever, you will probably never be able to tell the difference if the MP3 is encoded at a good quality. Unless you have a good ear and high quality audio equipment.\n\nA FLAC is not lossy. The algorithm compresses what it can, but when it can't compress anymore it just stops. Where the MP3 would start throwing samples away to make it even smaller. This is why FLACs are bigger.\n\nThe problem with MP3s is if you ever want to re-encode it again to something else. If you re-encode an MP3 to a newer format it will never sound better than the original MP3. The audio data that was thrown away in the original encoding can never be gotten back and you'll lose more by re-encoding it.\n \nSo, one reason you may want to get a FLAC is if you want sort of a master version of the audio. Take the FLAC and make an MP3 of it for your iPod for now. But if a newer better audio format comes out in a couple years then you could go back to the FLAC and have the original source to make a better quality encoding.\n\nIf you don't care about that I would just get the MP3.",
" **Technical explanation:** The more you compact and condense audio information into a smaller filesize, the more audio detail you lose, particularly in the high end and low end. Think of it like a jpeg becoming gradually more grainy and blurry as you decrease the quality of the compression and lower the filesize.\n\n**Practical explanation:** Assuming you don't have crappy headphones or a crap sound card, do an experiment some time.\n\nDownload an album of classical music or something without much noisy instrumental to it (so no heavy metal or dubstep) in the lossless FLAC format.\n\nThen listen to the same songs but encoded at a standard 128kbps mp3 format. The FLAC will not only have more clarity, but more atmosphere to it (depending on how it was recorded).\n\nIt doesn't make a difference for all types of music, but if I am listening to something like the OST for Skyrim, you bet I am going to prefer it on a lossless codec such as FLAC or at least 320kpbs CBR mp3. Anything less and you start to lose details in the music. If the instrumental is grungy and noisy to begin with however, it becomes more difficult for each instrument and aspect of the song to be lost with the audio data being taken out.\n\nIt also makes little difference when recording singular things such as the human voice.\n\nThe downside to lossless is that the filesize is much bigger, which is why the current standard is a relatively low quality one. The smaller songs are on average, the more songs a company can claim will fit on their mp3 players."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
What is Confucianism?
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[
" It is a system of beliefs based on the teachings of the Chinese philosopher confucius. It is based more in practical observation of the world than in any belief in some form of supernatural deity.\n\nIn other words, we should act in ethical ways because it is the right thing to do and benefits society as a whole, not because we could go to hell or be punished by God."
] |
[
" Feng Shui is a Chinese system of aesthetics which emphasizes that certain arrangements of design elements in a room or building can positively or negatively impact the flow of \"energy.\" This energy is qi (chi), which you may have heard about from martial arts films- it's the energy of the universe which we can channel through our bodies.\n\nFeng Shui has been around for a few thousand years, and there are a number of different schools. Some Feng Shui schools believe that the design of a place should be relative to the environment- nearby features like mountains or rivers have energy that should influence the design. Some Feng Shui is more astrological, orienting room design on cardinal directions, sun or moon cycles, or constellation houses. Some schools base themselves on the elements. Some base themselves around the individual- i.e. based on who owns the home, certain layouts match their their astrological traits, palmistry, etc. Some feng shui schools are more aesthetic.\n\nIs there a European equivalent? To some limited degrees. When you look into the designs of some religious buildings, you'll get some similar ideas. In a lot of traditional European magic schemas, like traditional Norse God worship, the altar is supposed to face north. \n\nAre their any lasting benefits, or is it all Chinese mysticism? Depends on the school. The existence or non-existence of \"qi,\" is highly debatable (depending on how you define it), but there really isn't any evidence to suggest that it exists. Probably the closest that you'll get to benefit is that some neuroesthetic research suggest that surrounding yourself with beauty is psychologically beneficial, and is feng shui is an organizing principle which allows for some degree of beauty, then it might be useful to you. I would personally be hesitant to suggest that your energy connection with the universe will be blocked by an ugly misplaced couch, but I think it's fair to say that having a nice couch that fits your room well will give you a certain sense of satisfaction and pride in your home.",
" I haven't seen anyone here mention Confucianism. There is a perverse strain of taking those ideas to the utmost extreme throughout Chinese history. Devotion to the state was a central tenant within the Confucian movement, and there are plenty of individual records I could point to where people allowed themselves to be subsumed to what they believed was their duty. I don't think it's a massive stretch to see the transition from monarchist feudal states to a broader communist state with the duty minded Confucian overtones."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
asking for a job
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[
" Bring a resume with you and ask to speak to a manager if possible. Tell them you would like to apply for a job and chances are they will have their own application form you will need to fill out."
] |
[
" I often would wonder this myself. Especially when it's a minimum wage job. When I was a teenager and got interviews for the food industry, they'd ask \"So why here?\" And I would say something bullshit like \"Oh I love this restaurant I've always wanted to work here\" but in reality it's \"because you called me back and I need money\"",
" I said \"blah blah and... Because i need the money\" to get the job i have now. My employer said he was relieved because no one EVER says it even when it's obviously true. No one aspires to work in a gas station."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why does it appear to be much less turbulent within an aircraft flying toward the eye of a hurricane than it does flying into a thunderstorm?
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[
" Turbulence is caused by unstable wind currents. It's when the plane gets swatted around in different directions in rapid succession.\n\nIf you look at [the air currents in a thunderstorm](_URL_0_) you have columns of air rapidly rising or falling. This will push the airplane up & down, causing turbulence.\n\nA hurricane is a cyclone - this means the air currents are mostly swirling around in a single direction. As long as you're not moving between \"bands\" of the hurricane, you're going to have a relatively constant wind. It might be a high wind, but it's not batting the plane around in different directions."
] |
[
" It's because the strongest winds of Irma are in its northeast quadrant, and are blowing water away from the region offshore of the Bahamas. In effect the winds are piling up water ahead of them, leaving a depression where the waters are blown from. This sucks in the surrounding waters, especially noticeable in the Bahamas which is a very shallow, broad submerged area in the direction of Irma.\n\nContrary to what others are saying here, it's [*mostly not the result of the low air pressure of the storm itself.*](_URL_5_) Pressure drops result in about 5% of the surge of a powerful hurricane, and that would be directly under the eye. Wind surge affects a much larger area and much greater height.\n\nThis makes sense if you do a back of the envelope calculation: One inch of mercury of pressure difference is about 13 inches of water. The center of a strong hurricane may be ~~two~~ three inches of mercury lower pressure, e.g. ~27 vs ~~~29~~ ~30, which converts to around three feet of water difference. So the sea level difference due to pressure is negligible- at most a bit over ~~2~~ 3 feet vs a total of 30 feet or whatever from a strong surge. \n\n In this case the effect of the wind-driven storm surge leaving land high and dry is exacerbated by the shallow shelf area that the Bahamas rest on.\n\nEdit: Normal atmospheric pressure is closer to 30 not 29 inHg, so adjusted my numbers. Also, [storm surge can be up to 50 feet, although such large surges depend on the interaction with seafloor and land topography](_URL_4_).",
" There are several different types of turbulence. \n\nLow down, just after take-off or before landing, the wind can become turbulent as it blows over buildings, trees and especially mountains. Also, the sun heats the ground, which in turn heats the lowest levels of the air - and hot air rises, so it's common to experience turbulence close to the ground on hot afternoons due to the air rising.\n\nIt can be turbulent inside certain clouds, especially \"cumulous\" clouds, which are the lumpy ones. Very big cumulous clouds are called \"cumulonimbus\", and they're what give us thunderstorms. These can often be so turbulent they are dangerous, and airline pilots will avoid them even if it means taking large detours.\n\nFinally, there's \"clear air turbulence\". This occurs at high levels, such as where aircraft cruise, and it's very difficult to detect. One of the causes (although it needs to be combined with other things) is the jet-stream - the very fast winds which aircraft take advantage of when crossing the Atlantic. Because of this, aircraft on trans-Atlantic routes will always be in contact with aircraft ahead to get weather reports, and if there are reports from pilots ahead about clear air turbulence, then it's possible to change level (or sometimes route) to avoid it."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why is "Lb" used for "Pounds" (Weight)?
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[
" It's a hold-over from the Latin word Libra (scale or weight), specifically in the phrase \"Libra Pondo\", or a pound of weight.",
" lb stands for libra, translated literally: scale (like the one your drug dealer uses, not those on a fish). Oz for ounces is from the old italian \"onza\" which was presumably anglicized into ounces."
] |
[
" The British pound is a share in the British economy, it's value is determined by how many pounds there are AND what the future of the economy is.\n\nLikewise for American dollars, but it just so happens that while the American economy is a LOT bigger than the British economy, there are WAY WAY more dollars than there are pounds, thus a dollar represents and even smaller amount of an albeit larger economy.",
" Remember how many times reddit reminded you to use the search function before submitting a new post? First, the \"request an explanation\" button changes to \"please search first\". Then, on the submission page, this button is repeated.\n\nThe sidebar also states:Search before submitting with keywords from your topic. The search box is in the upper right corner of the subreddit.\n\nThen, when you type in your post it says: \n\n > submitting to /r/explainlikeimfive\nSEARCH FIRST SEARCH FIRST SEARCH FIRST\nSEARCH FIRST SEARCH FIRST SEARCH FIRST\nSEARCH FIRST SEARCH FIRST SEARCH FIRST\nSEARCH FIRST SEARCH FIRST SEARCH FIRST\nSEARCH FIRST SEARCH FIRST SEARCH FIRST\nSEARCH FIRST SEARCH FIRST SEARCH FIRST\nSEARCH FIRST SEARCH FIRST SEARCH FIRST\nSEARCH FIRST SEARCH FIRST SEARCH FIRST\n\nSo let's see what a precursory search turns up:\n\n[ExplainedELI5:Why is the abreviation for pounds LBs?](_URL_5_)\n\n[Why is the weight unit \"pounds\" abbreviated \"lbs\" instead of something else that makes sense?](_URL_5_)\n\n[ELI5: Why do we use 'lbs' for an abbreviation to pounds? Where did it come from and what does it mean?](_URL_5_)\n\n[ELI5: In the Imperial Measurement System, why are \"pounds\" abbreviated as \"lbs.\"?](_URL_5_)\n\n[ELI5: Why do we use Lbs to abbreviate pounds?](_URL_5_)\n\nThe top one is flagged as \"Explained\", so that might be a good place to start. Or alternatively, this question is easily answered via a search engine."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Are all those buttons on airplanes and spaceships necessary?
|
[
" My oath they are! Every single one of those buttons and knobs serves a purpose. Whether it be pressurization, air conditioning, lights, navigation, radio, autopilot, fire safety, hydraulic control, engine bleeds, or any of the hundreds of other controls they are all necessary."
] |
[
" > Why exactly do aircraft that wish to turn left- or right-wards need to bank? I understand that it's necessary, but not really very keen on the why.\n\nBecause it allows you to use the entire surface of the wings to cause the airplane to change direction - whereas, if it didn't bank, you'd only be using the control surface on its vertical tail, and even it would have to fight against the airplane's inherent aerodynamic stability.\n\n > (Also, am I correct in assuming that banking in space would be needless/pointless, and that shows and films showing spacecraft doing that are wrong?)\n\nYes, airplanes need to point roughly in the direction they're moving because of air. In space, there's no air, so no matter which way you turn, you'll keep moving in the same direction.",
" Believe it or not, the controls in most conventional airplanes are not really so elaborate. For example, you have a control column or a joystick that rolls the plane left/right and pitches it up/down, just like the controller joystick. The rudders are there primarily to keep your turns coordinated (another lesson), but this is not as important in video games, and may or may not be part of the game controls. Your throttle or power/thrust levers essentially make you go faster or slower. There are a lot more systems for flying a real airplane (things like trim, propeller rpm, mixture/fuel, electrical systems) and most casual video games don't account for them, but overall the controls are the same.\n\nAs a fixed-wing (airplane) pilot, I won't comment too much on helicopter controls, but I do know the physics are a little more complicated, and the controls are a lot more simplified for most video games."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How do animals identify what is food and what is not?
|
[
" > But even artificial food made by humans like pet food is eaten fairly quickly by an animal that has never seen it before\n\nHmmm not so true for all animals. I don't know for others but rats in lab have a huge neophobia, like they fear everything new, including the food we give them.\n\nIn order for them to realise that it's food and that it can be eaten, you have to litteraly put them on food restriction so they are \"starved\" and start eating the food. They are really headstrong.\n\nAs for how does animals know what is food what is not ? I can't really answer you but I can tell you that rodents are very good at discriminating \"bad\" food from \"good\" food. They associate good food with salty/sugary aliments and bad food with acid/bitter ones, if they taste something bitter, they will (unless they don't have the choice) avoid the bitter food. \n\nAnd rats have a very good memory for bad food experience. Let's say a rat got a sick stomach from food A. Well if you put the rat in a room with food A, the rats will not eat it. And that works up to a year after a bad food experience."
] |
[
" Animals don't need any kind of logic or special thought to notice the absence of something. It's like how dogs don't have object permanence - they don't necessarily understand *where* it's gone and that it still exists, they just know that something was there and now it's not. Like understanding dark and light.",
" The answer varies depending on which animals we are talking about.\n\nMammals learn what to hunt and eat and what to fear from their parents. A baby gorilla will learn what is safe and good to eat the same way you did. It's mother will eat the plant and hand some to the baby. Whether you are a panda or a hedgehog this is basically the process, learning from your parents how to live, until they become adults and may sample new foods if they smell good, your nose is a tool that for the past billion years or so has evolved to allowed you to identify thousands of chemicals in an effort to keep you alive, it is decent at identifying things that you shouldn't eat. The smell of rotting meat makes you gag to get you to remove any rotten meat you might have accidentally eaten from your stomach. \n\nHowever for other creatures without parental care it is all instinctual, a rattle snake will strike at a mouse pretty much from birth it is hardwired with the knowledge that small warm bodied fuzzy creatures that smell like rodents are food. Some, like a jellyfish, just get lucky they make no effort to avoid predators or find food it is a floating trap and some certainly die from catching the [wrong creature](_URL_0_) in their tentacles."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Are 87, 89 and 91 octane really just the same fuel? Why can they come from the same hose but E85 and diesel need their own?
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[
" 87, 89, and 91 octane gas is the same gasoline with a different amount of additives added to boost the octane. So if you accidentally put 91 octane in a car that expects 87 you likely won't damage the engine (and visa versa) unless you do so over long periods of time. And even then the computers in cars these days can usually detect it and control the parts of the engine to compensate.\n\nHowever, if you put E85 gas in an engine not equipped to handle it you will likely put holes in your fuel line as the extra ethanol requires a different type of plastic tubing than is standard in non-E85 burning cars.\n\nSimilarly, putting diesel in a gasoline car will likely damage your engine.\n\nSo they separate the hoses and vary the sizes of the nozzles to help protect customers from making a mistake that could damage their engines."
] |
[
" 88 octane won't do any harm, but it won't gain you anything either.\n\nRead the owner's manual, if it says flex fuel is ok, then you can use that. Expect worse mileage on E85 gas though.",
" 89 octane, or mid grade gasoline, is required by some engines, and the owner's manual will indicate this. If your engine requires 89, but you use 87 (regular), it will still run, but at lesser efficiency, and you may experience engine knocking, as gasolines of different octane ratings behave a bit differently with regard to detonation and exhaust products. Engines are typically designed with a particular grade of fuel in mind for smooth running and optimum efficiency."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Since marriage is a right, why do we allow the government to control it at all by issuing licenses?
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[
" You have a right to spend your life with whoever you want. Getting married is just a practice recognized by the government to publicly proclaim your relationship. The marriage license is just a document that legally recognizes the relationship, and allows you to benefit from it (like filing taxes).\n\nThink of it this way: the government just controls who it *recognizes as partners*. A gay couple has the right to be together (married in all but legal status), but not every state recognizes their status (at least, not yet). I hope that makes sense.",
" Marriage is a legally binding contract, just like anything else you sign. Since it gives you certain legal benefits (i.e. taxes), the states need to know who is married and who is not. A marriage license is essentially just a license that says: you can now file your taxes jointly."
] |
[
" A marriage license must be issued so that two people can legally be married and receive the benefits a wed couple has (social security, tax, healthcare-there are thousands). You can have a *wedding*, but it would not fall under the governmental definition of a marriage.",
" Marriage certificates are granted by states, no the federal government. When the church performs a marriage ceremony that power is granted to them by the state, not the federal government."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why does Super Glue fasten my fingers together almost instantly but takes forever to glue anything else together?
|
[
" Actually, the superglue is cyanoacrylate, which is a compound that \"sets\" when it contacts water. Your fingers are moist while toothpicks aren't. Try dampening the toothpicks and they will set very quickly.This is why superglues have warnings about skin contact."
] |
[
" Many hardening glues need something to start the chemical reaction that turns it from liquid to solid. This is obvious in two-component glues. One component is the glue, the other is the hardening agent. \n\nThe hardening agent for super glue is in the atmosphere: water vapour. The air inside the bottle is completely dry, so the glue doesn't harden in the bottle. \n\nThis is why super glue (cyanoacrylate) is so good at gluing your fingers together: your skin contains a lot of moisture. In fact super glue is used in medical operations to close wounds without stitches.",
" I believe it's because as the glue dries, it loses volume and shrinks, and both the glue and paper are stuck, so it contacts and wrinkles."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
degrees of black belts
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[
" Note that the whole belt system only dates back to the 1880s, so it is not exactly an ancient tradition. \n\nEvery school does their own thing. Your typical strip mall McDojo will pretty much give you all the black belt degrees you want, if you stick around long enough and your checks clear each month. In other schools, it might take ten years to get your black belt to begin with.\n\nAlso, beyond black belt, it becomes less about being a \"badass\". In fact, most martial arts are less about self defense, and more of a stylized fighting sport. You'll note that UFC looks nothing like Jackie Chan or Bruce Lee. Beyond black belt, other factors, like instructing, come into play.",
" It basically has to do with experience. I'm a first Dan in Taekwondo(first degree) and I should be testing for my second at the end of the year. The black belt isn't the end of the martial arts journey, but rather the beginning. Like another poster has said, many martial arts are more sports than anything else. So between your white and black belt, you're just learning how to be a black belt. See the colour belts as educational degrees, and the black belt is graduation. While you're in school, you're learning how to work in your field. After you graduate what do you do? You work. Dans or degrees signify mostly your experience. I'm a first Dan but I have beaten third and fourth dans in competitions. A higher rank doesn't mean you're better, but rather you have a lot more experience. So those girls weren't better fighters than me, but they've probably been doing Taekwondo for their entire life! Also, degrees can show where you are as an instructor. 1-3 dan is an instructor. 3-7 master. 7+ grand master, if I remember properly. Martial arts are sports but also education. \nYes, you test for your dans. Your master decides his pre requisites.\nIf you reach the level of your master or no longer really have one, you seek testing from someone higher. Eventually, yeah you test in front of a \"council\" essentially.\nFeel free to ask any other questions."
] |
[
" First thing to remember is that the belt rankings are a fairly recent innovation. They were created in the late 19th century.\n\nSecond creating a new ranking or degree is no different than any other arbitrary rank. A bunch of people agree on what this ranking means and you have to pass those standards to achieve this rank. \n\nThe important thing to remember is that because people are coming up with the standards there will be people that will be able to achieve those standards as soon as they are created. You are not going to create a standard that no one can achieve, you will pick somethong that is difficult but not impossible.",
" practice, practice, practice. I could state physics as an explenation of how it happens, but instead i'll use a quote from Bruce Lee that i saw playing the UFC game on Xbox\n\n > I fear not the man who has practiced 10,000 kicks once, but I fear the man who had practiced one kick 10,000 times.\n\nwhen your punches, kicks, and blocks are perfected you have much more control over how hard and how accurate you can be. It's quite difficult to explain, but it's not some secret magic power you get at lv. 25+, it's practice\n\n\nsource: Blackbelt in Taekwon-do (ITF), we needed to break boards for our gradings and in competition, it was always my favourite"
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why is it perfectly normal in America to have churches, TV channels, etc... specifically for black people, yet terribly wrong if white people have those same things? (serious)(not a racist)
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[
" There *are* white churches, and white TV channels. You may not notice it if you're white, because you think of them as just \"regular\". Look, nobody's preventing white people from attending \"black\" churches or watching \"black\" TV channels. It's just that when most TV channels show relatively little content aimed at black audiences, and lots of content aimed at mostly white audiences, it's useful to have one channel that focuses on things black people want to see. Anyone can still watch them.",
" They idea is that main stream culture is white. That since the majority of the population of the United States is White there is no need for special churches for them since all churches except for ones started by minorities are white. Mainstream news and entertainment is aimed at a white audience and uses largely white actors and reporters etc. The reason there are specific black churches and channels is to create a cultural space for black people in which there culture can be expressed and they can see themselves depicted media and religion. \n\nTldr. Mainstream society is white so black aimed TV and churches try to create a cultural space in which they feel represented."
] |
[
" Because most christians are taught incorrectly and believe incorrectly. They have heard that the hording wealth is good, that the poor are just lazy, and that sharing is the devil. It is a symptom of the southern baptist movement and wealth based preaching. In the past, it had different reasons, but this is the way it is in modern times. Look at all the six flags over jesus style mega churches...what denomination are they? Baptist.",
" One is a minority with a long history of being treated less than human, the other doesn't. That includes stuff like TV- if you want to find a show that's relevant/includes that culture, you often (not always) have to look specifically for a channel that caters to it.\n\nFor white channels, it's considered a faux pas, because it's the \"default\". You don't need a separate channel for a specific interest, because other channels already are. If you're trying to distinguish yourself that way, the assumption is you're doing so because you're racist, because you don't need to.\n\n_URL_0_\n\nA lot of these will go into more detail. They're all basically the same thing.\n\nedit:\n\nIt's been getting better than it was historically, but we haven't quite hit the tipping point. It's always going to be a mix of historical events + minorities are always going to have to band together because you won't find it otherwise.\n\nIf you want to think of a less controversial version, it's basically the difference between Tinder and Grindr, or okcupid and christian dating sites. Gay people on average are ~2% of the population. It makes a lot of sense to have their own platform\n\nedit2:\nAnd as far as exceptions- rap music is probably one of the biggest ones (and relatively recent). It's one of the few types of culture that has really been fully assimilated."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Epigenetics: what the heck is it?
|
[
" Epigenetics refer to the study of genes _beyond_ the DNA sequence. This often includes modifications of DNA - for example, a common modification is _methylation_, the introduction of a methyl group (-CH3). These can change how genes are expressed or how they're regulated.\n\nIn a way this revives [Lamarckism](_URL_0_), which states that changes during the lifetime is passed onto the offspring. This is very much against traditional Darwinism, but now we have a process by which such changes could be inherited, since physical strands of DNA - modifications included - are passed onto the offspring."
] |
[
" There's an exciting new field of studies, called epigenetics. This refers to changes in DNA expression of the gametes -- eggs and sperm -- based on experiences within the body of the person who has those gametes. Like they've found that if a child's father was starving at some point in his life, then certain genes in their children and grandchildren will be expressed, while other genes will be dormant. I don't know if this works with women because sperm is produced anew throughout a man's life, while the eggs a woman has all exist before she is even born.\n\nAnother way, potentially, is that when the fetus is in utero, the fetus is being exposed to hormones from the mother via the umbilical cord. This exposure could pre-dispose the resulting child to certain reactions to hormone exposure, such as a more dramatic reaction to stress hormones, or a more calm reaction to stress hormones.",
" DNA contains the genetic information for the development and function of the entire organism. However, which sections of genetic information get utilized differ from cell to cell, and that is regulated by something called epigenetics. These are basically chemical marks on the DNA that control which genes are \"on\" and \"off.\" Imagine a contractor handing out copies of the blueprint to all his workers, but redacting the parts that they don't need. The painter doesn't need to know about the electricians work, so his version of the blueprint has that information blacked out, while the part that matters to him gets highlighted. Each cell in the body works on a similar principle."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
1) General and Special Relativity 2) Why "Space-time" actually includes "time"
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[
" Special relativity is the theory derived from the principle that the laws of physics are the same if you're traveling at any constant speed. General relativity is the theory derived from the principle that you can't tell the difference between being pulled down by gravity and being pushed up by some other force.\n\nIt turns out that if you apply geometry to both space and time taken together, the equations of relativity get a lot simpler. So instead of using the phrase \"geometry of both space and time taken together\", we use the phrase \"geometry of spacetime\"."
] |
[
" Simple Wikipedia is a great place to easily learn about this. \n \n > The central idea of general relativity is that space and time are two aspects of spacetime. Spacetime is curved when there is gravity, matter, energy, and momentum. \n \nSpacetime - is when space is viewed as the 3rd dimension and time is viewed as the 4th dimension. \n \nIf you watched Interstellar, you would have seen that people experiencing different amount of gravity experienced time differently.",
" You can split the theory of relativity into two part based. Special and General relativity. Special relativity is the effects of things moving RELATIVE to each other. In short, it states how time seems to differ based on how fast someone else if moving from your perspective. If you are moving very quickly, if you were to look out the window, you would see time move much faster for everyone else, and thus slower for you. This can lead to a version of time travel where you can sit in a very fast moving object for a long time and the world around you will have aged more.\n\nGeneral relativity is much more complex and deals with accelerations, and in particular, gravity. It explains that gravity is caused due to the bending of space and time. This is a very difficult concept to grasp, but it works the same was if you put a bowling ball on a trampoline. If you were to roll a smaller ball past the bowling ball, since the trampoline has dipped, the smaller ball will have its path curved towards the centre of the bowling ball. The same kind of thing also occurs with time. This means that things with no mass, such a photon (light) can still be attracted to planets.\n\nIm sorry its not very ELIF, but I can try to help if there was something you didnt understand."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
how does cryptographic salt and pepper work?
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[
" When encoding information:\n\nSalt is/are random string(s) of numbers used when storing information. If you want to save a password in a database, you can't use plaintext, so you encode it. The sequence the encoder used to base its encription can be called the salt. You can now store the encoded password with the salt. The only way to check if someone used the right password is to run what they entered through the encoder using the matching salt. If what the person entered matches what you stored, it's the right password. However, this method is risky, as anyone using exactly the same encoder can still check passwords if they have the matching salt.\n\nPepper is related to salt. Using the same hypothetical encoder, pepper would be an action done consistently to every password before it goes through the encoding/salt steps (like adding \"s6hk4\" to the end). This adds an extra variable to be accounted for when checking passwords. With pepper, in theory, even if you have access to the same encoder, the correct stored(encrypted) password, and salt, you still would need to guess the pepper, which is stored in a different location.\n\n\n[phone spelling]"
] |
[
" So, I am sure you have done this or seen it on a TV show/move. Turn the alphabet into numbers. For instance, A=1, B=2, etc.\n\nSo, AES encryption works like that, but it uses bigger numbers, math and multiple conversions to convert the characters.\n\nAES encrypted data gets obscured by Salt, Pass phrase and an Initial Vector.\n\nSalt adds to the encrypted data so that even if it is decrypted, you have to know where the salt is and where the data is.\n\nPass phrase is used to help build the encryption key.\n\nInit Vector is used to initialize the translation matrix (number replacement pattern).",
" Public Key Cryptography in a nutshell:\n\nYou have two keys: a public key (that you can give out to anybody) and a private key (that — you guessed it — you keep private). Both of those keys can be used to either encrypt or decrypt messages. If you encrypt with one key, you can decrypt with the other. By giving out your public key, people can encrypt messages with it so that they know only you can read them (by decrypting with the private key). Encrypting with the private key is useful for digital signatures — we'll get there in a minute.\n\nHash functions in a nutshell:\n\nCryptographic Hash Functions are mathematical constructs that allow you to summarise data into a fixed size summary (called a \"digest\"), in a way that for the same message you always get the same digest, where you can't recover the original message from the digest, and where you can't easily find another message that produces the same summary.\n\nThis is quite useful, for example, for validating that a downloaded file is correct (For hashes in current use, digests are usually like 20 or 32 characters long, irrespectively of the size of the message being hashed), or for digital signatures (we're getting there!)\n\nDigital signatures in a nutshell:\n\nEncrypting messages is annoying, because it forces the people on the reading end to have decryption software at the hand to be able to read them. This is fine when you need to keep messages secret, but sometimes what you actually need is to prove to people that it was actually you who sent a message that can perfectly well be shared publicly.\n\nA neat way to solve this: You hash the message you're going to send, then encrypt the resulting digest with your private key. It's this encrypted digest that is called a digital signature. Then you add the encrypted digest to the message. The message is still readable as-is, but now it has the signature. Anybody who has your public key can then do the following:\n\n- Hash the message themselves\n- Decrypt the signature with your public key, retrieving the digest you calculated on your end\n- Compare the digest they calculated with the one in your signature.\n\nIf they match, then they have proof that you wrote the message yourself (the public/private keys ensure that you encrypted the digest, and the difficulty in finding two messages that hash to the same digest ensures that this is actually the right message)\n\nSo what's the deal with the request to Julian Assange?\n\nJulian Assange has published his public key in the past, and that key is widely known. By asking him to sign a specific message, that user was basically asking JA to prove his identity — Presumably, only JA has the private key that goes with the public key we know to be his, so nobody else would be able to sign the message such that the signature would be valid as coming from JA. By choosing the message himself, he made it impossible for a fake Assange to reuse a message that the real Assange had signed in the past as a way to \"prove\" his identity. There's also the question of whether Assange himself still has access to those keys."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why is the SATA III standard (6 Gb/s) needed if standard r/w speeds are much lower?
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[
" Because you can have multiple drives on a SATA host. It doesn't matter much if you have a single drive, but if you have several drives, you'll need a faster bus speed to avoid becoming I/O bound."
] |
[
" Way too high system requirements made it slow as fuck at release. It needed over 50% of the ram on a standard pc back then. Like if windows 8 would need 6gb ram. For todays pcs the requirements are insignificant of course.",
" DDR3 is a memory standard. There are speeds (called frequencies) that RAM runs at. Very roughly, it's a measure of how quickly it can read and write data, so higher is better. DDR3-1866 is faster than DDR3-1440, for example (those numbers might be made up but it doesn't matter). Unless you're a really serious performance geek, your RAM frequency will make absolutely no noticeable difference, so it's not something to worry about. Your motherboard and processor will have certain allowed frequencies, so just get one that's compatible.\n\nDDR2 is the older standard, and it's not as fast as DDR3. I don't think you can really even buy DDR2 these days.\n\nThere's no such thing as DDR5 RAM. There's **G**DDR5, which is VRAM (video card RAM). Your video card is like its own little computer, and it has its own RAM so that it can do video card things. GDDR5 is very fast video card RAM. It's actually based on DDR3 RAM, I don't know why they pick the names in such a confusing way.\n\n/r/buildapc is a great general resource for this kind of stuff if you have more questions about actually choosing specific parts and stuff."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
how "cracking" a joint or your back in a certain area relieves the pain/tension you're feeling in that area.
|
[
" Great minds think alike. Yer not alone in askin', and kind strangers have explained:\n\n1. [ELI5: Why does it feel good to crack your back? ](_URL_3_) ^(_7 comments_)\n1. [Why does it feel so good when I crack my back? ](_URL_6_) ^(_ > 100 comments_)\n1. [ELI5: What does \"cracking your back\" do, and why does it feel good? ](_URL_4_) ^(_10 comments_)\n1. [ELI5: What is actually going on when i pop my back? How does this compare/contrast to when I crack my knuckles? ](_URL_7_) ^(_ > 100 comments_)\n1. [Why does cracking your back feel so good? ](_URL_1_) ^(_2 comments_)\n1. [Why does cracking my back feel so good? ](_URL_0_) ^(_2 comments_)\n1. [ELI5: Why does it feel good to crack my back? ](_URL_2_) ^(_5 comments_)\n1. [ELI5: Why is it really bad to crack your Back and Neck? ](_URL_5_) ^(_14 comments_)"
] |
[
" I'll give this a brief go.\n\nIt isn't officially known what it is for definite which makes the cracking noise but it seems to be widely accepted that the cracking is the formation of a bubble between the bone joints (ie. The knuckles) as oppose to common thought being that a bubble is popped. \n\nAs for feeling good (once again this is all more theories than dead fact) it could be due to this bubble between the joints allowing more space for flexion, extension etc. So that could be why you feel better after cracking your spine for example. \n\nSource-Med Student",
" Yo ho ho! Yer not alone in askin', and kind strangers have explained:\n\n1. [Why does cracking / popping your back feel so good? ](_URL_4_) ^(_47 comments_)\n1. [ELI5: Why does cracking your knuckles/back/neck feel good? ](_URL_7_) ^(_29 comments_)\n1. [ELI5: why does cracking your neck and fingers feel so good? ](_URL_8_) ^(_4 comments_)\n1. [ELI5: What cracking your neck actually does. ](_URL_1_) ^(_2 comments_)\n1. [ELI5: What happens when you pop your neck and is it dangerous to do to yourself? ](_URL_5_) ^(_5 comments_)\n1. [ELI5: What exactly happens when you \"pop\" your neck or any other body part? ](_URL_3_) ^(_26 comments_)\n1. [ELI5:What happens when I crack my neck/back, and why does it give me relief? ](_URL_6_) ^(_2 comments_)\n1. [ELI5: Why do we feel relief when we \"crack\" our knuckles/joints? ](_URL_0_) ^(_20 comments_)\n1. [ELI5:What happens when I crack my neck? Why does it feel better than just stretching? Is it harmful or helpful?? ](_URL_2_) ^(_1 comment_)"
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
how does fracking cause earthquakes?
|
[
" Well, it doesn't. What does cause earthquakes are wastewater injection wells. These are heavily used in the area of Oklahoma and Kansas that have seen a significant upturn in the number of earthquakes in recent years. These are called \"induced earthquakes\".\n\nFracking has gotten a lot of attention because of pollution of groundwater and so a lot of people get confused about the induced earthquake issue. But these are very different things.\n\nTo answer the meat of the question, from the [USGS](_URL_0_):\n\n > Earth's crust is pervasively fractured at depth by faults. These faults can sustain high stresses without slipping because natural \"tectonic\" stress and the weight of the overlying rock pushes the opposing fault blocks together, increasing the frictional resistance to fault slip. The injected wastewater counteracts the frictional forces on faults and, in effect, \"pries them apart\", thereby facilitating earthquake slip."
] |
[
" Fracking does NOT cause earthquakes! Disposing of produced brine water in disposal wells does IN SOME VERY LIMITED CASES. There are hundreds of thousands of disposal wells in the world and < 0.05% have been proved to increase seismic activity.",
" Fracking is a mining method to create cracks in deep ground formations. The goal is to break down formations and/or to open underground reservoirs of liquids or gases.\n\nIt is done by using frac liquids under very high pressures. These liquids cointain officially quite low relative amounts of chemicals (around 0.01 %). In reality the amount of used liquids is so tremendously high, that the used relative amount of chemicals could become a threat to the environment.\n\nNormally fracking companies are only allowed to frack in grounds which are naturally sealed, which means that natural rock formations create a barrier and the frac fluid cannot escape the reservoir.\n\nHere is why people all around the globe are against fracking: no one can can say if a reservoir will leak the toxic fracking fluid. There are numerous examples of fracking liquid contaminating the environment and contaminating natural drinkable water ressources (which are very important for everyday water usage). Once it leaks, it is impossible to undo the damage. Once water ressources are contaminated, the area is destined to die (plants draw water from the ground, animals eat the plants and so on)"
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why do some people have higher pain thresholds? Why are childrens'lower?
|
[
" There are both biological and psychological reasons that pain is different for different people. The sensation of pain is a complicated biological process with many places where genetic differences can lead to differential pain signaling. In particular, people with a mutation in a voltage gated sodium channel expressed in a specific population of neurons can be rendered completely insensitive to pain, while still being able to discriminate pressure and temperature. On the other hand, people can learn to tolerate more pain by exposing themselves to it and learning to control their reactions. This probably explains why children seem more sensitive to pain. \n\nTL;DNR: Genetics and environment contribute to an individual's uniqueness.",
" Pain has an obvious evolutionary purpose - when something injures our body, pain is the negative feedback we get to discourage us from doing it again. Someone who didn't feel pain would be less likely avoid dangerous activities, and less likely to survive as a result.\n\nPhysically, it's hard to know whether children feel pain more strongly than adults would experience the same event. However, pain can be more scary for children. They don't have as much of an understanding of things like why they're hurt, how long it will last, and what will make it feel better.\n\nAs adults, we can minimize our reaction when we experience pain because we understand why we're feeling it."
] |
[
" I can't remember 100%, but in uni I remembering learning about how genetics is a huge factor, but of course environment plays a role too. So neurons in general have to reach a certain threshold to \"synapse,\" and in the case of pain/sensory neurons, the synapse=pain felt. If you have a higher threshold to reach in order to have a synapse, then you'll be less likely to feel pain for certain triggers, whereas someone with a lower threshold will have neurons that are \"triggered\" more often. Different people are born with different thresholds, but like a lot of people are saying in the comments, environmental factors can modify it! So in theory, you can become more tolerant to pain.",
" Because leg pain means it's harder for you to live. Genital pain means it's harder for your child to ever live. Natural selection favored the one that had a bigger reason to protect his groin."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why is it considered bad table manners to use your hands to eat?
|
[
" It's not in every country (Middle east and southeast asia it is actually pretty common.)\n\nIn western culture it is because of the status symbol of silverware in the 1700's. If you were rich, you used silver-wares, spoon and forks (wares) made of silver, instead of your hands like the peasants. That carried into modern day as the divide between poor and rich was the way they ate their food. Now days, because silverware is pretty cheap, and because it is accepted custom that you don't use your fingers, everybody uses forks and knives because they don't want to be seen with bad manners (which came from not wanting to appear poor)."
] |
[
" From my personal experience this occurs only because of 2 reasons:\n\n1. You are in a formal/semi-formal setting where out of courtesy everyone leaves the last one for someone else who they think might really want it. But since everyone thinks the same way, no one ends up eating it. And if you do end up devouring that last bit, I must warn you that you're now THAT guy.\n\n2. There are probably occasions when the last portion left is either the most unwanted part i.e. the best stuff has been eaten and it's the least yummy part of the dish.\n\n3 (bonus). People you're dining with have such poor table manners that you it is no longer palatable. Risk being called a snob here.\n\nNot sure if this is what you were looking for or a more scientific explanation.",
" As for why some cultures eat with their hands, I think you will find that trend most pervasive in cultures that have flatbread or tortillas with every meal. The idea that people JUST use their hands is not really true. People use the bread as the utensil.\n\nIn Europe, the weather is very conducive for making risen yeast breads. European style bread is not as easy to use as a utensil, but nevertheless people did! They used stale pieces of bread even as edible plates called \"trenchers.\"\n\nNonetheless, spoons have been in use since ancient times, and are really the precursor implement to all cutlery. Combine the less useful nature of european bread with an improvement in woodworking and metallurgy and you have the ingredients for a silverware boom -- in addition to the individual historical incidences that actually made the shift real."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why are some actors referred to as "character actors"? Doesn't every actor play a character?
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[
" A character actor is an actor who mostly plays unusual or eccentric characters.",
" A 'character actor' is one who plays character roles that the script writer hasn't really spent time developing. For example, the script writer may have a character who's simply described as an 'Italian Plumber' or 'Mad Scientist'. The writer hasn't really done anything to develop this character further (such as give the character a full name, background story, personality, etc.). Character actors are the actors who fill these roles and bring their own 'character'/personality with them to fill the gaps in character development."
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[
" Casting director here; we often use words like \"character\" to imply 'not classically handsome'. Our industry isn't exempt from political correctness or heightened sensitivity to people's social expectations; but that doesn't stop people from putting out casting calls using words like \"hot, sexy\" etc. \n\nThere's no shortage of confident and charismatic people that aren't conventionally attractive, and it's an actor's job to know what kind of roles they'd be good for. In fact, they often emphasize the very features that differentiate them from attractiveness expectations. If a role requires a seriously obese person, and that was effectively dictated by the casting call, it's common for actors to show up in outfits that emphasize that characteristic, which is at least a suggestion that they are going to be at least outwardly comfortable with the subject matter. \n\nOn the talent side, talent knows that being friendly and agreeable, even if they find the material offensive or distasteful, is an implied expectation; and if you can't hide your disgust for the subject matter, you're probably not a good enough actor to carry the role anyway.",
" It's sort of like how Will Smith in Fresh Prince was a character played by the actor of the same name. Certain elements may or may not play in, but they are otherwise a fictional representation of a person with the same name."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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Do heart transplant patients need to be of the same blood type as the donor?
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[
" As others pointed out the heart does not make the blood, that's the bone marrow. But the blood type for a heart transplant needs to match just as it would for a blood transfusion or there will be acute rejection.\n\nHLA compatibility is a factor, but blood type takes priority, and all heart transplants are cadaveric so there is less choice in HLA compatibility. You aren't likely to closely match a random person. \n\nThey do blood tests to determine HLA compatibility.\n\nThis is as opposed to kidney transplants where if you have a close relative who can donate then the HLA compatibility will be better. \n\nRecipients are given immunosurpressive medications to prevent rejection."
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[
" It has to do with something called the patient's HLA (human leukocyte antigen) haplotype compared to the donor's HLA haplotype. The issue occurs when a family member has a similar, but not exactly the same haplotype. Let's say the patient expresses proteins we'll label the \"XY\" haplotype on the surface of their cells. The patient's body knows its his/her own cells by seeing the \"X\" or \"Y\" proteins on those cells. A close family member has a haplotype \"XX,\" which is very similar, but not quite the same as the original \"XY\" patient. These \"XX\" white blood cells which only have the \"X\" proteins on their surface are transfused into the \"XY\" patient. The patient's body knows to identify its own cells by looking for the \"X\" or \"Y\" proteins on the cell's surface. So the patient's cells see the \"X\" proteins on the donated cells' surfaces and that is enough to satisfy the host body's cells to identify the donated cells as \"self.\" Unfortunately for the patient, the donated white blood cells are only satisfied by seeing the \"X\" proteins on the surfaces of other cells, and do not recognize the \"Y\" proteins as \"self,\" so when these donated white blood cells get into the patient's body and see foreign \"Y\" proteins everywhere, they attack everything in sight and the host immune system is unable to defend itself, because it sees the donated white cells as its own \"self\" cells.\n\nEDIT: In the case of red blood cell donation, this issue is often mitigated by both leukoreducing the blood packs through apheresis and irradiating the packs in some cases to make any white blood cells left unviable. The issue of family member donation being more dangerous is when tissue donation is involved when these same steps cannot be taken to reduce the amount of white blood cells being introduced to the patient.\n\nFor more information on this subject, look up graft vs host disease.",
" This is a very interesting question, and one that often comes up when considering organ transplantation.\n\nYou can think of your genetic makeup as coming from your mother and father equally (50% each). This is because, of the two sets of chromosomes in each of your cells, one set must have come from each of your parents.\n\nNow lets consider siblings.\n\nBoth your father and his brother also received 1 chromosome set from each of their parents. This means that there is a spectrum of genetic similarity that can exist between the two, because they get their genes from the same pool of possible genes (ie your paternal grandparents genes). In turn, they can range from being very similar, to being not similar at all. On average though, they will be around 50% similar, just due to probability. \n\nThis is why organ donation from a sibling can lead to much better outcomes, and a lower rejection rate, because there is a chance that their compatibility is greater than the unchanging 50% similarity you get with your own child. \n\nHope that helps. Source: Medical Student"
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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Why is it socially acceptable to vilify Scientology and other religious sects?
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[
" You're confusing the vilification of a belief with the vilification of an organization. It's generally not alright to vilify someone's beliefs. There are villainous beliefs, of course, like \"muahaha I believe tha I should torture puppies for no reason!\", but the basic tenets of Scientology aren't so prima facia villainous, and nobody deserves to be vilified for accepting them.\n\nOn the other hand, the Church of Scientology, as an organization, has something of a nasty record for dealing with its people. All sorts of stories have come out over the years, starting with what is effectively slave labor, then moving on to kidnapping, beatings, and of course financial ruin. Often the members of scientology are not seen as villains so much as victims, while the leadership itself is vilified.\n\nYour question compares this to Islam. The difference here is that Islam is no longer a Caliphate, and there is no single voice that speaks for the religion as a whole. I can't condemn a muslim as a bad person because some other person claiming to also be a muslim thinks that Islam means that he should do bad things. The first person hasn't done anything wrong and claims to have different beliefs than the second person.\n\nIf I were a Christian, and some other person screamed \"praise Jesus\" before blowing up a building somewhere, I wouldn't expect people to hate me for it, and I extend the same courtesy to others.",
" There are three levels to this: individuals, religion, and organization.\n\nAt the level of individual, it is acceptable to recognize a person's religion (\"What religion are you a part of?\"), and to question them about the actions of an organization they are an active participant in.\n\nAt the level of religion, it is acceptable to question religious beliefs, the interpretation thereof, and to challenge those beliefs. Within certain limits, it is acceptable to parody or poke fun at beliefs.\n\nAt the level of organization, it is acceptable to question the actions of the organization, and the membership of the organization, especially when said actions are in service of the organization. And organizations are open to a much wider range of attacks, both in conversation, and in comedy.\n\nBasically, religion is most vulnerable to parody, organization most vulnerable to attack, and individuals protected to some extent from both\n\n\nThe problem is that in the case of the Church of Scientology, there is no clear line between the group of believers, the religion, and the organization.\n\nExamples: \n\n- Regarding Pedophile priests, it is not acceptable to question individual Christians (individual), nor other priests (religion), but it is acceptable to question the Church (organization)\n\n- Conversely, it's more acceptable to parody Christianity (religion) than any specific Church (organization). But parodying Christians for their belief is usually unacceptable, unless they are a member of an organization, or a public figure.\n\n- In almost all cases, individuals who merely attend religious ceremonies are insulated from the actions of both religion and organization.\n\n\nWith the Church of Scientology, there is a much less visible line between the religion of Scientology, the organization of the Church of Scientology, and the membership of the organization: partly because anyone who tries to practice Scientology outside of the Church is at risk of lawsuit. The Church of Scientology now is more like the Catholic Church in Europe before 1517 (when Martin Luther wrote his 95 Theses): there is no practical difference between the religion and the organization.\n\nA Christian today can exist separate from the Church, from all Churches even; and participation with one Church does not imply membership in that Church: I can attend a service any church in the city I live in without having any connection to that church. \n\nHowever, all Scientologists are both practitioners of the religion of Scientology and members of the Church of Scientology. Which means that individuals, group, and organization are all the same. And therefore are all subject to the full range of parody and questioning. Because the Church has done so much to maintain its control over the religion, and has required people who wish to attend services to join the organization, it has opened up itself and its membership to the full range of socially acceptable parody and criticism; which also allows both to be more pointed."
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[
" The Church of Scientology is an organisation. That organisation has its own actions. All Scientologists are paying members of that organisation, and so share in responsibility for that organisation's actions. Those actions include abuses of human rights, government infiltrations, and sabotages of health care organisations, leading to the Church being considered a criminal organisation in many areas. Anyone who criticises these actions is declared SP and expelled from the Church, making them no longer Scientologists. There's no such thing as a Scientologist who opposes Church actions, so it's not and cannot be an \"only 30% are doing this!\" thing.\n\nBuddhism, Christianity, Judaism, Hinduism are not represented by a single organisation to which every single member belongs; even when Buddhists, Christians, Jews and Hindus are part of an organisation they do not *have* to pay to support it; and there are many Buddhists, Christians, Jews or Hindus who oppose some behaviours of their organisations.\n\n(Scientologists who continue professing their beliefs after being expelled are termed 'Squirrels'; there are an estimated 150-200 of them worldwide and there is a unit of the church, the Squirrel Busters, dedicated to keeping them under surveillance.)",
" The Church of Scientology is an organization devoted to the practice and the promotion of the Scientology belief system.\n\nThe Church of Scientology claims, based on its original study of cases and continuous affirmation from ongoing subjects, that a human is an immortal, spiritual being (termed thetan from the Greek word 'theta' meaning life force), that is in a physical body. The thetan has had innumerable past lives and it is observed in advanced Scientology texts that lives preceding the thetan's arrival on Earth lived in extraterrestrial cultures. Based on case studies at advanced levels, it is predicted that any Scientologists undergoing auditing will eventually come across and recount a common series of events. \n\nNow the reason that Scientology is so controversial is because they charge a lot of money for the courses and counselling (aka \"auditing\"). I know people who've spent hundreds of thousands of dollars. \n\nThe church goes after critics, playing Nixonesque dirty tricks. They stalk critics with PIs and operatives, all sorts of appalling things. Google Operation FreakOut + Scientology. \n\nIf a member is expelled, they are declared to be a suppressive person. If he or she has family or friends in the church, those people will NOT be allowed to communicate with him or her, even if they are his or her child or spouse. So the church breaks up families. \n\nPhysical abuse of staff, particularly in the Sea Organization (Their \"religious order\". Not all staff are Sea Org, but many are). Bad living conditions in it. Insane punishment details. Google RPF+ Scientology (or Rehabilitation Project Force). Basically a gulag. \n\nthey take up more and more of a person's time and money. Lower to middle echelon staff work either during days or nights, but are supposed to come in other times for staff study. If their \"stats\" are low, they end up staying up very late to get more work done. They get far less than minimum wage and many go hungry. If they are in the Sea Org, they get food and board, but they are stacked up tightly in bunk beds, their stuff is gone through and sometimes confiscated, and the food isn't so good. Medical care is doled out and often denied.\n\nThe list goes on and on about why they are controversial but its for this reason that they are not a religion but a cult and the only reason they are considered a religion in many countries is due to their influence and their ability to infiltrate (perfect example Google operation snow white)."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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Why does it seem like being allergic to gluten is a trend?
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[
" Because it is. Its become a very weird trend diet to avoid gluten.",
" It depends on where you draw the line. You can have two different reasons for a gluten aversion (probably more, but two that I know of): wheat allergy or Coealiac disease. A wheat allergy is pretty much your run-of-the-mill food allergy, where Coealiac disease causes inflammation of your intestines. This is bad, because your intestines are usually pretty busy trying to digest all of the stuff they're holding, and they don't have time for any of this bullshit, they've got a person to keep alive.\n\nCoealiac disease is becoming more well-known, so people who have noticed they often feel ill, or are anaemic (decreased red blood cells) or fatigued may try to cut gluten out of their diet, where in the past they would have just lived with it, with no idea what to try in order to feel better. Some of those people will feel better without gluten, either by placebo effect or because they actually are treating a mild case of Coealiac.\n\nNow you have all of these people running around saying that they quit eating gluten and they feel *so much better you guys you don't understand you have got to try it seriously, Coeliac disease is more common than you think, come on try it for just one week.* This is fair, because they actually do feel better, and they're just trying to help their friends. Their friends try it, some treat their mild Coeliac disease, some feel better by placebo, some just go along with it because this is now the most interesting thing about them (that third group is of boring people) and some go back to their old ways. The cycle repeats.\n\nAs a whole, people love to talk about what they eat/don't eat and why they're making a better choice than you in regards to their health. It's like when I say I'm on a diet, when I really mean I'm just limiting my beer intake so I can drop 15 pounds."
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[
" My cousin developed an allergy to gluten (celiac disease) at the age of 35. Talk about changing your way of life! There's gluten in so many things! I don't know how he developed it so late in life, but he did.",
" While a lot of it has to do with better detection of celiac disease and various grain allergies, there is a rather silly notion among a lot of people that food falls along a spectrum of \"purity\" and that \"lower-purity\" foods have a bunch of unnamed contaminants or toxins in them. In this light, gluten is seen as a product of people rejecting more \"natural\" foods, and is considered a product of our modern agricultural system. Supposedly, our ancient ancestors didn't eat gluten, so this means it must be bad for us. \n\nMy theory is that people have always, since ancient history, restricted their diets in order to feel a sense of purity, and this latest fad is an extension of that. Lots of people claim that they've felt much better since stopping eating gluten, even when there's no evidence that they have celiac disease or a grain allergy. But then, the placebo effect can be incredibly strong.\n\nThat being said, celiac disease is very real. My mom has it, and she can have a bad reaction just from breathing in a bit of flour dust. And she's gotten reactions from all sorts of products that you would never expect to have gluten in them, but upon further research, she's found out that they do."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
|
Democratic Socialism
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[
" Socialism is the idea that workers should own the means of production; that is, all the tools used to make things should belong to the people who use them, rather than capitalist investors.\n\n*Democratic* socialism is the idea that socialism should be achieved through democracy. The term exists to differentiate them from *revolutionary* socialists, who think that some kind of political revolution should occur and force socialism to happen."
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[
" Socialism can mean a lot of things, but the core concept is workers' control of the production. It's basicly the idea of \"economic democracy\". Some socialists advocates a decentralized economy of workers cooperatives (i.e. syndicalism or \"market socialism\") while others believe in centralized democratic control of the economy (\"state socialism\") . Most I think believe in a combination. \n\n\nCommunism is the percieved long-term result of socialism, when the classes and the state institutions are completely abolished and society is run through free associations alone. \n\n\nCapitalism is private control of the economy, and It's run through private capital owners using money to make more money. Those who suceed - no matter how - expand and those who don't disolve. Thats the core logic of the system. Simple but dynamic. \n\nSocialists are against capitalism for two reasons: because it's not democratic and because socialists don't believe in Adam Smiths idea that actors competing for egoistic motives will bring about the most favorable overall result. Instead they think that human needs and wants would be better satisfied through democratic decisions in some form or another.",
" Worth pointing out that in most places on earth other the the US, what Americans tend to think as Democratic Socialism is actually Social Democracy."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
|
Why Did Princesses/Princes Get Forced to Get Married For Alliances Instead of Just Forming an Alliance?
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[
" Marriage solidified the alliance. Back when divorce wasn’t really an option that was allowed, alliances wouldn’t break if thy were bound by marriage because it would pit husband vs wife, and if that happened then both sides would be in trouble with the church who, while they had less outright power than the crown, still held a lot of power with the people (as they were a tool used to sway the people)"
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[
" Because modern political alliances are based on modern political conditions, not on historical colonial relationships. If conditions change, relationships will change.",
" Historically marriage was a ceremony for joining two people in union and often had a economic benefit. For example a family with a a young daughter might take a dowry (large gift) to give her hand in marriage to a guy who was courting her. The family might receive livestock or something valuable in exchange for giving their daughter away. In many places having kids before marriage was also considered taboo so getting married was necessary to procreate and to have kids. To me these are the primary reasons people got married.\n\nNowadays there is really no reason to get married. There is really no economic benefit of getting married. In many places common law couples have the same taxable benefits as married people. It is also more culturally acceptable in the western world to have a kid before marriage. Furthermore, the average initial start up cost of getting married (large venue, wedding dress/cake/photography, reception dinner, honeymoon etc) act as a deterrent to many people. \n\nMy belief is that in the next few generations marriage will be less and less common."
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Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
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What is with "German" engineering?
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[
" I used to work for a German company. German products are often over - designed. Since German engineers get paid if anything they have a patent on gets used, they force their patented technology into everything, even when it isn't appropriate.",
" There is certainly a degree of truth to it, perhaps even a high degree of truth.\n\nMuch of the association is historical, but many German firms are reknown for producing products that are of remarkable high quality. It may be something simple such as using a higher grade of steel in a part where a lower grade would suffice, tightening machining tollerances to a level beyond that which is strictly necessary to ensure mechanical compatibility, or using a heavy rubber sheath on a power cable that is expected to be dragged along rough surfaces all day rather than a cheaper plastic one.\n\nWhat it boils down to is that there are a limited number of products in the world which one can look at and say \"someone put some serious thought into this\" and a lot of them happen to be produced by German manufacturers.\n\nFor example, consider C. & E. Fein GmbH. Compare a Fein powertool to one produced by Bosch (another German manufacturer), one from DeWalt (American), and one from a DIY private label. The Fein powertool will be 1.5x-3x the price of the Bosch/DeWalt powertool, and 5x the price of the DIY tool. The functionality between them is roughly the same, but the Fein powertool looks like it will last forever."
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[
" I don't know about reliable when it comes to German, but quality I suppose. Cars come to mind as the common focus of German quality. If we look at cars we see that the last decade or so German cars have really embraced plastic, including under the hood. Think plastic trains fluid pans that warp, plastic dip stick tubes that crumble into the motor, plastic all the things! BMW had coolant leak related problems across a wide range of their engines. That problem was incredibly expensive to fix, many thousands of dollars, so people came up with bodge job products specifically for those engines to avoid fixing it the factory way which required basically disassembling most of the engine.\n\nNot sure if German quality is anything more than a legend at the moment, at least when it comes to cars. I will never own a second hand German car again, ever ever ever, sell that shit before the warranty runs out.",
" Because the german people are hardworking and industrious.\n\nSame with Japan.\n\nDemography is destiny, as they say."
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Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How do people who wear corrective lenses(concave) are able to see far off things a bit clearer when looked through a very small hole (without wearing glasses)?
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[
" Every point in a scene you're looking at sends out a bunch of light rays in all directions. A bunch of those rays arrive at your eye, in different locations and slightly different angles. A properly shaped lens takes all of those rays from one point in the scene, and focuses them back to one point on your retina. If this happens for every point in the scene you're looking at, you get the whole scene clearly in focus on your retina.\n\nIf the lens is not shaped properly, however, light rays from one point in the scene don't focus to a single point on your retina, they each focus to a slightly different place on your retina. So rays from that point gets blurred, and overlapped with blurred images of every other point in the scene. So you can't see clearly. The important thing here is each ray is still focused to a point, but the multiple rays from the same point in the scene get focused to different points on your retina.\n\nLooking through a tiny hole restricts the incoming light rays that can hit your eye. In the case of an infinitely tiny hole, only one light ray from a given point makes it to your eye. The lens focuses this to a single point on your retina, so it looks sharp. The same happens with light rays from every other point in the scene, so you get a sharp image.\n\nThe down side is the smaller the hole, the less light can get through. So as the image get clearer, it also gets darker. That's why our eyes have a lens in the first place rather than a tiny hole, and why pinhole cameras need such a long time to expose film.\n\nI'm leaving out diffraction since that would just confuse the explanation of why looking through a small hole helps."
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[
" Squinting shrinks the 'input' hole for your eye; the light that enters. What this does is effectually shrinks the [aperture](_URL_0_) of your eye. Just like a camera, a smaller aperture allows images to be focused clearer at longer distances, since the light is less dispersed and more focused on a point (think of a garden hose hole vs a fire hose hole). The trade-off is of course, there is less light entering the eye/camera, and so therefore the image you \"see\" (the world) becomes darker. This is also the same exact reason why as it get's darker out, your depth perception tends to get significantly worse, and why when it is super bright out, you can often see floaters and all sorts of weird stuff in your eyes. If you've ever had your eyes dilated, such as during an eye exam, you know that it is nearly impossible to read things close to you. This is because the aperture (your pupil) is so large, the light cannot be accurately interpreted at short distances. Hope this helps.",
" Okay, sorry for the repost, but a bunch of incorrect answers are getting voted up, so I'm reposting my reply in another thread to a top level answer:\n\nIt's actually an effect surrounding what is called the Acceptable Circle of Confusion.\n\nThere is only one mathematical point at which a lens focuses light beams onto a surface. In this case the lens is the one in your eye and the surface is your retina.\n\nWhen everything is perfect then that focus area is a very small point. If it's not perfect then your lens is putting the focal point either slightly behind your retina or slightly in front.\n\nIf you imagine light coming through the lens and converging as an hourglass on its side, you are in focus if the middle of that hourglass it perfectly centered on your retina. Where that hourglass intersects your retina is called The Circle of Confusion, and when the hourglass is in the right place the CoF is at it's smallest and everything is sharp. \n\nBut consider what happens if the lens isn't doing its job and the hourglass is a little too far forward or back. The more off it is, the bigger that circle is because the hourglass gets wider and wider as you move away from the exact center. The bigger that circle is, the more out of focus things are.\n\nSo why does squinting work? Because you are artificially looking through a smaller hole, and smaller holes essentially stretch the middle of that hourglass, so that even if it's a little too far forward or too far back that circle stays small.\n\nYou also don't need to squint to see the effect. Photographers take advantage of it when they close down the iris on the lens of their camera to increase depth of field, or you can use a small hole in a piece of cardboard as makeshift glasses.\n\nIf you want to see a diagram of lenses and how irises affect the Circle of Confusion [they have one on Wikipedia.](_URL_2_)\n\nHope that helped.\n\n**EDIT:** Regarding the ophthalmologist's answer involving the pinhole occluder -- partial credit for that answer. Looking through a pinhole, even an ophthalmologist's fancy pinhole, is the same phenomenon as squinting and has the exact same effect.\n\nI spoke above about squinting creating a very small hole and decreasing the size of the Circle of Confusion -- that's exactly what a pinhole occluder does too.\n\nTo say, however, that its effect is only due to sending light directly into the center of lens, and the focus improvements result because that's where the lens aberrations are minimized is not entirely correct. Or at least it's a little misleading. Think of it this way:\n\nSomething being out of focus, or having a wide Circle of Confusion, is a *convergence error.* Light rays that head straight into the eye aren't bent at all, so it doesn't matter there, but light rays that hit other parts of the lens are bent so they (try to) converge on the focal point. If the lens is not focused correctly, the bent beams don't converge into a tiny spot, they converge into a wider messy spot -- a wider Circle of Confusion.\n\nWhat the pinhole occluder does is ensure that all the light is coming straight into the eye so there's nothing to converge. No convergence means no convergence errors which means we're back to a tiny Circle of Confusion.\n\n*But...*\n\nThe place where the statement is misleading is the implication that you get your focus benefits because you are avoiding problems in the lens. The reality is that you would bring more things into focus by squinting or with a pinhole occluder *even with a perfect lens.*\n\nIf you have a lens that is perfectly focused and defect-free at 10 meters, and then put an iris in front of it you can make it perfectly focused from 9 meters to eleven meters. Close that iris even more and everything from 5 meters to 15 meters is in focus because you're forcing light to come in straighter and straighter and minimizing your convergence error. So your Circle of Confusion gets smaller and smaller simply by virtue of closing the iris.\n\nFinally, take it to the extreme, and make the iris very, very tiny and throw away the lens -- that's a pinhole camera, making in-focus pictures simply because of the tiny hole."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
What is the engineering and science involved in making the weather forecasts accurately ?
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[
" Modern forecasts are generated using computer simulations. Several times a day supercomputers operated by a variety of countries will ingest data about current conditions around the world. The data comes from satellites, radars, weather balloons, ground monitoring stations, and various other sources. The supercomputers will then run models to simulate what is likely to happen several days into the future.\n\nDifferent models are going to produce different results, so the job of the meteorologist is to use their training and local knowledge to consolidate the different model outputs into a single cohesive forecast. For example, a meteorologist might know that a particular model tends to overestimate rainfall in a certain area or perform worse in certain conditions, and correct the forecast accordingly.\n\nThe science and engineering that goes into improving forecasts tend to fall into one of several categories. You can try to improve the programming behind the models, which are based on our understanding of how weather systems work. You can build faster supercomputers so that you can run the models at higher resolution. And finally, you can improve the quality and quantity of data going into the models, by launching better satellites and installing more ground equipment. There are lots of people who work on all three areas."
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[
" Climate data and weather trending, ist' an inexact science but you can make some really good predictions. When you factor in climate data and monitor the position/trends of climatic events, you can get a fairly accurate prediction of what will happen.\n\nMeteorologist have a wealth of data at their disposal and train for literally years to be able to accurate predictions. Often enough there will be repeat events or patterns that make it easier to predict what'll happen in the mid to far future, for example:\n\n & #x200B;\n\nYou had a particularly hotand dry summer but comparison you can say there's a good chance you'd get a colder and wetter winter. conversely the same is true, a cooler summer, could indicate a warmer/dryer winter.\n\nIf you then need to consider event like El nino/La nina which have global implications, and may alter the outcome you were expecting.\n\nThen look at the varying degreee of annual events, such as how much as the gulf stream moved? what was the median ocean temperature in the last 3 months.\n\nPut it all together and there's your prediction. The Met office continuously gathers, processes and forecasts so that they always have an accurate model of what will happen based on what's happened and happening. \n\n\n & #x200B;",
" Weather forecasting will never be perfect.\n\nWeather is hard to predict because tiny differences in the current weather can have large effects on the future weather. You can't measure the weather with perfect precision, so the measurement uncertainty is enough to ensure that there are always tiny differences.\n\nDangerously oversimplified but hopefully instructive example: you don't know if the temperature at a weather station is ACTUALLY, say, 56.71736 degrees or 56.71800 degrees Fahrenheit because your instruments aren't sensitive enough to detect that difference. However the difference could have a large effect on the future weather because tiny differences get greatly magnified."
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Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
What is the state of matter "plasma"?
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[
" Sorry if I don't explain this as well as you would like. Plasma is the 4th state of matter. It is a superheated gas with positively charged ions. It is created in fusion reactions and can not be contained as of yet. The longest it has ever been contained was about 5ms by a company called Tri-Alpha. When it passes through living matter it either tears it apart or causes defects; for example cancer",
" Plasma is the next state of matter after gas. If a gas gets hot enough, its atoms are \"broken up\" into elections and ions. These particles can be affected by electric and magnetic fields, which is what makes it different from a gas (gas cannot be contained by a magnetic field, for example).\n\nWhat's interesting is that most people only learn about the first 3 states of matter, even those those states only make up less than 1% of the matter in the universe. Plasma makes up the other 99% (this is because stars are primarily plasma, not gas as is often said).\n\nYou can also see plenty of examples of plasma on earth. Lightning, neon signs, and fluorescent light bulbs are all plasma."
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[
" You are seeing photons emitted as atoms combine to form molecules. In the case of fire in normal air, you're seeing atoms of oxygen combine with whatever is burning. \n\nThe flames are a gas.\n\n(It is not a plasma. A plasma is a state of matter where the electrons have been stripped from the nuclei of their original atoms. It is similar to, but is not, a gas.)",
" Plasma forms when you heat up a gas to really high temperatures. The electrons get ripped away from the atoms due to their high energy. This is called ionization. This makes plasma highly electrically conductive. Plasma is its own state of matter because its properties are so fundamentally different from a gas, in the same way that a liquid's properties are fundamentally different than a solid's."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How do zip files compress information and file sizes while still containing all the information?
|
[
" Most of these explanations are not eli5. \n\nZip files compress information in the same way you do in conversation every day, they're just more efficient at it. For example, when I refer to them in this sentence, notice I'm not repeating the words \"zip files\" over and over again, that'd be too long. Instead I replace their full name with \"them\" or \"they\" because of the context you know what I'm talking about. File compression works in much the same way. With context you can express much more complicated ideas with fewer bits of information. It's just in file compression, that context is something that's more meaningful to the computer than to you. Never the less, it allows the computer to store information in a much smaller footprint.",
" Zip uses a compression algorithm called DEFLATE, which is really just 2 other algorithms packaged together, LZ77, and Huffman.\n\nLZ77 basically records runs of the same or similar data, and Huffman assigns the most common bytes shorter bitstrings."
] |
[
" hopefully this is a simpler answer than the others. basically imagine a file is a book with a bunch of words in it. you have words like \"the\" and \"because\" and \"Mississippi\" and some are repeated many times and others are used more rarely. what zip does is it goes through the book and matches each word to some sort of shorter series of characters. for example, the word \"the\" probably appears a lot in the book, so instead of using the word \"the\" you could have a table that says \"the\"=1. So you would go through the whole book and replaces all the \"the\"s with 1s. You would have the space that \"the\"=1 takes up minus 2 characters for all of the the- > 1 substitutes. you do this with all of the words and the file can come out smaller than the original. of course to be read again it would need to be decompressed, but thats easy since you have the table. on computers, instead of words there are bytes and bits and what not and if the file repeats a lot of the same byte patterns the file ends up smaller. of course it i also possible for file compression to make files larger to.",
" Technically speaking, you could compress a near infinte amount of data into a small size if the data is uniform. A Zip Bomb is a form of this. You can put terabytes of all 0's into a small file. Since it is all 0's, there is only one pattern that needs to be compressed. This could be represented in a simple form like \"this file has a zillion 0's\"."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
What jobs are there which only a citizen, and not a permanent resident, can do? Why is this the case?
|
[
" Federal jobs require a citizen. You also have to be a citizen to hold certain positions in the military.",
" Generally, only jobs regarding national security are reserved for citizens. Governments assume that non-citizens might be less loyal.\n\nIn some countries only citizens may own land or do certain economically powerful activities. This is a way of trying to avoid foreigners \"taking over\" a country's economy."
] |
[
" Because they didn't want to give those rights to non-citizens, because then people could just walk across the border and demand things without having to be born here or go through a process to make them american.\n\n > Also why can the NSA spy on non-citizens outside the US?\n\nBecause everyone does it, and no one really wants to do anything to stop it.",
" The is nothing to be explained other than the person that hire those illegal immigrants are of the same nationality of the person that complains about it. \nVery often those who hire illegals are complaining about it too since they feel that they cannot compete legally. \n\nFinally, \"Taking jobs\" that most citizens don't want is a very bad argument. Most of the jobs that illegals \"take\" are daily jobs with little money that provide no income security nor benefits."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why do I always wake up early after I drink alcohol?
|
[
" Alcohol is a depressant. Your body tries to counteract the depressant by releasing stimulants. Alcohol wins the race so you go to sleep. However, your body processes the alcohol out of your system and you are left with the (longer-lasting) stimulants, which is why you wake up earlier.\n\n_URL_0_",
" Alcohol (something that will stop you from growing big and tall if you keep drinking at such an age!) pulls the water from your body and makes you go potty more often than you usually would. Your body wakes you up early because it is thirsty. If you drink some water before you go to sleep, though, you should be able to sleep in a bit longer without your body waking you up out of thirst."
] |
[
" On a side note, if I ever encounter severe insomnia, I usually try to stay awake thought the whole day and not touch my bed until it's bedtime, I almost always fall asleep after imbibing a beer, since alcohol makes me drowsy and calms me down a lot. Maybe it counteracts the adrenaline/cortisol.\n\nI guess this isn't something I should reccomend, but it has worked for me.",
" I wake up at 6am after drinking heavily, but with a hangover."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How does the octopus know what colors to change to?
|
[
" You're aware of your environment; if a tennis ball is thrown at your stomach, you know where it'll hit and also exactly what muscles to tighten to protect yourself and/or dodge out of the way.\n\nYou also know how to hide behind a tree, for example, and whether you're actually hidden, from the point of view of the person who is trying to find you.\n\nCamouflage is similar to hiding; the octopus sees the surrounding environment, and \"knows\" which [pigments to squeeze](_URL_0_) on the surface of its skin to mimic the environment."
] |
[
" Damn. Came in here hoping there would be answers to how animals like chameleons and octopus know what colour to change to (if they actually do know).",
" The how is like everything else in evolution. At some point, some ancestor of the octopus genetically mutated and found itself able to somewhat change its appearance in either texture or colour. When this helped it survive (by hiding), it passed on this mutation. Many similar mutations later, each one reinforced by superior survival (and hence a greater chance of reproduction), some species were now capable of very advanced camouflaging.\n\nThis also covers the why. *To survive, and breed.*"
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
how can single celled organisms form a multi celled single organism?
|
[
" The in-between state happens when a single-celled organism forms a *colony.* In other words, it reproduces but the new cells stick right by the parent cell.\n\nIn the next level, the cells start to *specialize* a bit. For example, the cells on the outer edge of the colony form a protective exterior, but those inside the colony don't.\n\nFor an amazing example of such a transitional organism, check out *slime mold.* Very impressive.\n\n_URL_0_"
] |
[
" Mitochondria divide on their own. In single-celled eukaryotes such as protists, the mitochondrial division is synced with the cell division so that the two new cells both have mitochondria. In multicellular organisms such as humans, mitochondria are completely independent and divide when the cell needs more energy. Thus, for multicellular organisms the new cells just get whatever mitochondria happen to be present at the time they're split.",
" Single cell organisms came together and evolved into more complicated species. The mitochondria is thought to have external origins and even has its own dna."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How did people discover that some poisonous foods (such as blowfish) are edible if prepared a certain way?
|
[
" Based on assumption, trial and error. Let's say there is an abundance of bananas in an area. Many people would grab the bananas and attempt to eat it whole, based on the way they eat other fruits. People will do this and quickly realize that the skin isn't very edible. However, humans' natural instinct to eat will eventually lead to them finding a way to consume that banana. They will use their past knowledge and the knowledge of others in order to find a healthy and safe way to consume the fruit.\n\nThe same holds true for poisonous delicacies such as blowfish, except the process is much deadlier. Many people would have died before they realized that there is a specific way to prepare the blowfish that will allow for safe consumption. Basically it all rides on human determination and ability to apply past knowledge to a new situation.",
" As far as I know, the most poisonous parts of blowfish are the organs, which sequentially tend to be eaten last. Most of the meat itself isn't all that toxic, as its not the blowfish itself that is deadly but the bacteria present in its organs that it itself is immune to.\n\nEven in primitive times, it didn't take a genius to make the connection when people would be totally fine eating the flesh, but then keel over in paralysis after eating the organs."
] |
[
" I'm reminded of some science fiction stories by Vonda McIntyre, where the ambassadors from Earth and from the Four Worlds (the aliens who were sponsoring Earth's application into the Galactic Civilization) had their first, tentative, gathering: the hors d'oeuvres were water and cotton candy—of all five species present, those were the only things compatible with everyone's metabolisms.\n\nThe answer really depends on how alien that life is: if it uses silicon and ammonia where we use carbon and water, then there's no hope: everything there is toxic and might even burn us to touch it.\n\nIf it's mostly like Earth life, but there's a little twist like it's version of DNA uses arsenic instead of phosphorus, then that's even more annoying: it might smell and taste delicious but be totally poisonous to us.\n\nThe best scenario is where it's really, really Earth-like. Then we'd do it exactly like PoundNaCl says: it might be surprising but we don't have a fancy tricorder that would scan the alien life and say whether it was good to eat or not: if it's close enough to be remotely digestible, the only way to know whether it has hidden poisonous properties is to do exactly the same thing we do with mysterious Earth berries or whatever: taste a little tiny bit and wait to see if it makes us sick. Repeat with larger and larger amounts until you're satisfied.",
" My first reddit contribution, here goes nothin! \n\nThe human brain changes the way it perceives certain flavors as a survival mechanism. For instance, we develop a tolerance for the spiciness of peppers after the brain becomes aware of the good nutrients they contain. \nAnother example is a dude lost on a raft at sea for months but has a steady supply of fish he can easily catch. He just eats the meat at first, but after a time he gets cravings for the parts he originally found repulsive-organs and eyes- which contained vitamins he had become deficient in. His brain's innate ability to adjust his flavor perception kept him in good health by making him want to eat nasty stuff. \n\nSource: _URL_0_\n\nEdit: thanks to Roscoj for the vid link. Putting it here at the top. Skip to 8:10ish for the part relevant to this topic."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
What is Unraid?
|
[
" It’s an operating system you can buy for a computer. Like windows or Mac. But it’s intended for storing files and making them available to other computers on a network at home or in an office. It’s in the category of things we call “NAS” or Network Attached Storage. Unlike your computer, it’s typical for NAS servers to have more than one hard drive. \n\nIt’s called Unraid because most NAS or file serving computers rely on a concept called RAID to prepare for and recover from the failure of one of the hard drives. The goal for most NAS systems is for it to be possible for one drive to fail without causing the server itself to fail. When a drive fails, it can simply be replaced and no data is ever lost in the process.\n\nAs I mentioned, RAID is the way most systems do this. Some people feel that RAID is too complicated a technology and prefer a simpler approach. Those people worry that in a RAID system, if one drive fails you can’t simply read the data from the surviving drives: you have to replace the failed drive and allow the RAID technology to rebuild your data from the surviving drives. (These people are reminded that one must back up all file servers, whether they are protected by RAID or not.)\n\nUnraid also provides protection from a scenario when one hard drive fails, but one important difference is that after a drive has failed, whatever data is on the remaining drives can still be read, even if those drives are removed from the system and installed in another computer.\n\nI use Unraid at home to store video files and make them available on my TV, among other things. AMA."
] |
[
" Unsolved and unsolvable are different (if potentially overlapping) categories. The [halting problem](_URL_1_) (Entscheidungsproblem) is a problem that has been proved to be *unsolvable* - it is impossible to determine whether an arbitrary program will halt or run forever. (You can simulate the program and maybe determine whether it will halt given a particular input - but you can't come up with a general way of determining this for *any* program.)\n\nOn the other hand, there are many problems which have not been solved, but which have not been proved to be unsolvable. It is possible that a solution will be found in the future. For example, Grigori Perelman solved the Poincaré conjecture, one of the seven [Millenium Prize problems](_URL_0_), in 2003. (These are all very complicated problems, most of which I do not particularly understand.) They are not unsolvable, merely very hard to solve.",
" THAAD stands for **T**erminal **H**igh **A**ltitude **A**rea **D**efense and is a missile system placed in South Korea by the US ostensibly as a defense against North Korea. China doesn't like it because it reasons it could be used against China, so has taken lots of actions against South Korea as a form of protest or objection."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How fast would the earth have to be moving through space for us to feel it (if we could feel it at all)?
|
[
" You cannot feel speed. You can feel acceleration, but we could be going near the speed of light and you wouldn't feel anything.",
" You dont really feel speed. What you feel is a change in momentum. The earth is rocketing through the universe at a ridiculous speed. If it suddenly slowed down or sped up 1 mile per hour you would feel it, but then the momentum of your body would catch up or slow down and you wouldnt feel it any more."
] |
[
" You feel acceleration, not speed. The Earth is not accelerating. Or at least, not at a feelable speed.",
" There really isn’t a good answer to this without some speculation being involved. The universe as we know it is constantly expanding from what we believe is an event known as the “Big Bang”, which unleashed an incredible amount of energy and mass. To observe what’s beyond the universe you would need to move very fast for much longer than the average human lifespan. \n\n\nModern science estimates the speed of expansion or Hubble constant to be about 71.9 kilometers (44.7 miles) per second per megaparsec (one megaparsec equals about 3.3 million light-years). Assuming you could move faster than the expansion, and you lived long enough to reach the “edge”, you might find another universe or absolute nothingness. For all we know you’d find a tentacle monster that would fall in love with the human species if you’re a fan of Futurama."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why would you put a severed toe/finger on ice to preserve until reattached when they would amputate it if frostbitten?
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[
" First off, only incredibly severe frostbite requires amputation, mild frostbite will heal on its own or at worst leave minor scarring. \n\nNow, frostbite occurs when blood flow is restricted to your cells for an extended period of time, causing them to die. Since the finger or toe in question is already severed, that's not really a concern (or, more accurately, you're already at the worst-case scenario). \n\nSecondly, frostbite typically occurs at temperatures *well* below freezing. The lowest a finger on ice would get is 32 degrees F. \n\nFinally, cold really is a great preservative. It slows the degradation of your cells and prevents infection. While you certainly wouldn't want to keep a finger on ice for days, having a severed finger in an ice bucket for an hour or two while you make it to the hospital can definitely help preserve it for reattachment."
] |
[
" I had a first joint almost full amputation of my middle digit finger (basically cut off my finger to right below the cuticle). I had to have a snip of finger bone trimmed that was approximately 1/8th inch long. \n\nThe surgeon I had to repair it was fresh out of medical school, and told me the tip of my finger had the potential to regrow due to recent studies of cuticle tissue. \n\nIt's been 4 years and although my finger doesn't look perfectly normal, I have gained at least a 1/4 inch and re-grew a fingernail.\n\nThe body regenerates some, atleast on your fingertips! \n\nEdit.) link for the interested \n _URL_0_\n\nThis only talks about children, but I was 24 when I slammed my finger in a truck door. I don't believe it's limited by age.",
" I do this for sprained fingers often, see cold water immersion or ice therapy. Pretty safe in my book"
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why are highway and street signs usually white text on green (at least in the US)?
|
[
" You're correct that white and black would provide the greatest contrast, but the primary issue isn't contrast. Highway signs are \"retroreflective,\" meaning that at night, when you shine your headlights on them, the light not only illuminates the sign, but the sign also directly reflects a good amount of that light back at you. Black backgrounds would not be efficient retroreflectors (since black absorbs most light, reducing reflectivity), plus they would be difficult to see at night since the sky is black. Green was chosen since the eye is highly sensitive to green, it is clearly visible day and night, and it is a good retroreflector. Green is a common choice in many countries, including Canada, Japan, China, and Australia. Many European countries opt for blue backgrounds with white text or white backgrounds with black text."
] |
[
" Most local jurisdictions have codes that specify what color an exit sign needs to be, so builders just follow the building codes in their areas. Most building codes require either red exit signs or green exit signs or they give the builder the option to choose.\n\nRed and green have become the most popular choices because those colors tend to stand out in most buildings and they are also more visible through smoke, etc. than other colors.\n\nRed is chosen in a lot of places in the US on the theory that red is an emergency color (and easier to see than most other colors). However, some people criticize red because it's also the color for \"Stop\" and \"Do Not Enter\" which could confuse non-English speakers.\n\nGreen is chosen a lot elsewhere in the world because, like red, it's easy to see in hazardous conditions compared to other colors. It's chosen over red because it can't be confused with flames or fire (being green), green typically means \"go\", and it supposedly has a better psychological effect on people in general.\n\nThe National Fire Protection Association (NFPA) is an organization that recommends fire safety regulations for local governments in the US and some other countries. They don't take a stance on a particular color and instead just say it should be \"distinctive\"\n\nThe International Organization for Standardization (ISO) recommends a pictograph sign in green with a man running through a door, like [this](_URL_0_).",
" The two answers so far are pretty spot on. For interstate routes, even numbers run East-West and get higher as they go north, odd numbered roads run North-South and get higher as they go east. These are the roads with blue and red shields. 3 digit road numbers are related to the roads that share the last 2 digits with it, such as being a bypass, loop, etc. For example, I've seen various instances of I-495 connected to I-95. I-99 is famously out of place, due to politics. The ones with white shields, US Routes, are pretty similar, except that the numbers get higher as you go south and west."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
The r/atheism mod fight
|
[
" Basically. /r/atheism is a default sub (you're automatically subscribed to it when you make a reddit account). The \"founder\" of the sub /u/skeen had been a very inactive mod for his entire tenure as the head moderator. This led to a lot of low quality content making it to the front page of /r/atheism and subsequently /r/all \n\n/u/jij saw that skeen had been inactive for a while, basically skeen hadn't looged onto his account or done any actual modding. So jij did what any right minded person would do, assumed skeen was away permanently and requested to become the head mod of /r/atheism \n\nThe head mod is above all the other mods i.e they can't be removed by mods unless they break the ToS. jij seeing the place /r/atheism had become with its low quality memes and facebook \"pwns\" decided that all image submissions had to be made in a self post to try and balance out the submissions so higher quality content was making it to the front page.\n\nThe drama started when the petulant teenagers, [a \"40 year old PhD graduate\" who later turned out to be a fraud](_URL_0_) and a host of other people started having a tantrum over the whole thing.\n\nThey were either not listening, or were just too enlighhtened to understand that images weren't banned they just had to be made in the form of a self post. Lots and lots of drama followed. But to be honest, the quality of /r/atheism (minus the bitching) has improved 100 fold since the new rules were brought in. I hope they stay."
] |
[
" Mods are people just like anybody else, and this means that they have a political leaning of one kind or another. In this case, mods of r/news decided they didn't want it known or publicized that a radical Islamist was responsible for killing 50 people, because it disagrees with their worldview. By removing posts that point out the religion of the terrorist, the mods were hoping to prevent people from blaming Islam for the attack.",
" The short answer is the libertarian streak in Atheism. \n\n(Major) Religion (generally) works well to create a hierarchy where men are on top. However, without this religious hierarchy in place, women have no need to be subservient to men. This is where male atheists get upset: that accepting atheism means accepting women. The backlash against feminism is an attempt to preserve this hierarchy within a secular framework."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why is it better to inhibit reuptake (SSRIs), rather than just agonize receptors?
|
[
" ELI5: When you tickle someone really hard for a long time, eventually they will get tired and the tickling won't work anymore. Instead, it's better to tickle them medium-hard so you can have fun longer.\n\nWell the short answer is that it isn't better, it just appears to serve a different purpose, clinically.\n\n[There are lots of useful serotonin receptor agonists.](_URL_0_)\n\nNow, hopefully a pharmacologist will come and elaborate, but I would guess that it may have to do with increased tolerance development with agonists as opposed to reuptake inhibitors.\n\nTolerance develops when the brain produces more receptors to make room for an increased level of the molecule. An agonist would be drastically increasing the available molecules. Conversely, a reuptake inhibitor doesn't increase the total amount of available neurotransmitters rather it just forces them to remain available to stimulate receptors for a longer period of time.\n\nSSRI's usually are prescribed at a dose that does not change once a therapeutic level is achieved and can remain at this dose for a long time. Agonists would need to be increased exponentially over time and lead to dependence and withdrawal when used over the same time frame.\n\nEDIT: forgot to explain like you're five"
] |
[
" Because there are other, related classes of drugs that inhibit reuptake of serotonin *and* something else - most commonly, norepinephrine (SNRIs) or dopamine (SDRIs). The \"selective\" means that SSRIs *only* inhibit *serotonin* reuptake. SRIs are the whole broader class, and include various antidepressants and also cocaine (which inhibits reuptake of serotonin, norepinephrine, *and* dopamine), among other things.",
" I'll just touch on the most common type of antidepressant, which are SSRIs, or \"selective serotonin reuptake inhibitors.\"\n\nSerotonin is a chemical transmitter that we understand to be important for regulating mood and other \"higher\" functions. It's released from neurons in certain parts of the brain, where it binds to neurons elsewhere and tells them to do things. Without getting too complicated, this brain activity helps make us feel \"normal,\" or not depressed. People with depression tend to have low stores of serotonin to release, or don't release as much as they should.\n\nThe purpose of an SSRI is to make that available serotonin last longer. Naturally, the brain recovers serotonin that's been released, and recycles it for later. As the name implies, a \"reuptake inhibitor\" will stop the brain from recovering that serotonin, so it has more time to float around and do its job.\n\n**True ELI5 Answer:** If you imagine serotonin as kids running around being happy in a playground, SSRIs are equivalent to giving them snacks and water so they can play all day. That, or like slashing their parent's tires so they literally can't leave."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
why does humidity make it so feel so much hotter?
|
[
" Humidity makes it feel hotter because it interferes with your body's cooling mechanism: sweating.\n\nThe point of sweating is that the sweat must evaporate. Evaporating sweat costs energy, which comes from your body temperature, which is why you cool down. But, if the air is too humid, your sweat can't evaporate as easily, preventing your body to cool down, and therefore making it feel hotter.\n\nAlso, your mind has learned to associate sweat with heat. More sweat = \"gee, it's hot\"."
] |
[
" Another fun fact, the temperature can never be lower than the dew point. As water evaporates into the air when it rains, it raises the humidity in the air and the dew point goes up as the temperature goes down. This is evaporative cooling and it is why it is cooler when it rains and you feel cold when you are wet.\n\n It also partially explains the \"heat index\" as when it is hot with low humidity your sweat evaporates much faster and helps cool you. When it is humid, no as much evaporation occurs and you feel hotter. This is why 95 degrees with very high humidity can feel more uncomfortable that 105 with low humidity.",
" Most likely due to less humidity inside, drier air tends to feel cooler because it interferes less with your body's ability to shed heat through sweating.\n\nCould also be due to not being exposed to the sun."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
If Carbon Monoxide is colorless and can not be seen, how do CO alarms detect it?
|
[
" Just because it is colour less and can't be seen doesn't mean t can't be detected. The same thing could be said for air, or helium, or any number of gases. As it was said, there are ways to detect it chemically.",
" Google says they contain a gel that changes color in the presence of CO. Sensors detect this color change and trigger the alarm."
] |
[
" CO isn't manufactured or stored, like natural gas or propane. Carbon monoxide is usually generated because of an improperly operated or maintained machine; you can't really \"add\" a scent to a product of poorly executed combustion, without using some kind of CO detector that releases a foul smell when it detects CO. At that point, it's more effective to just sound an alarm.",
" If the part of your blood that carries oxygen sees carbon monoxide AND oxygen, it would much rather carry the carbon monoxide. This has to do with the energetics of the chemical reaction. Carbon monoxide slides nicely into the space that was supposed to carry oxygen via you blood to the rest of your body. \n\nIn the end, your cells need oxygen to carry some electrons after a ton of chemical reactions in order to make energy. Carbon monoxide prevents that from happening, and you can no longer make energy aerobically. Your body might be able to create energy via alcoholic or lactic acid fermentation for a very, very short time, but you'll soon pass out and die (and likely experience severe cramping beforehand). \n\ntl;dr - you breathe it in (even mixed with oxygen), it out-competes oxygen for a spot on your blood cells. Your blood cells deliver CO instead of O to your tissues, which can't use the CO in the same way. Individual cells die all over your body until you lose consciousness, stop breathing, and the rest of your body wastes."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why did Star Wars start on Episode IV back in the 70s and not Episode I ?
|
[
" The original film was titled \"Star Wars\", the subtitle (Episode IV: A New Hope) was added in later releases to make it constant with the sequels. Episode numbers started with V in \"Empire Strikes Back\", when Lucas decided to write backstory for many of the characters which could be (and were) made into prequel films.",
" Lucas had an overall story in mind when he started out, but looking at the early drafts of the first Star Wars movies that story doesn't seem to have much in common with the one we eventually got.\n\nThe whole idea was to make a movie based on the stuff he enjoyed in his youth (which is something that is true for almost all his projects) and ended up making something that was a lot like the Sci-Fi serials of old. There are numerous nods and references to that legacy even in the newer movies. He mixed it with standard mythology motives like following the Campbell's \"Hero with a thousand faces\" to give the whole thing more epicness and adding touches from WWII war movies and Kurosawa movies.\n\nWhen the first Star Wars movie started taking form he created something that had both a history of stuff that had happened before and a future of stuff that might happen later, but it was mostly a stand alone story without and Episode number.\n\nWhen the whole thing was more successful than anyone expected, Lucas decided he could add somethings from the stuff he had earlier cut out and dropped.\n\nTo give it more of serial feel he renamed and numbered the first movie as Episode IV: A New Hope. That gave the whole thing a certain in-medias-res quality like watching a serial episode halfway into the series without having seen the first few episode.\n\nIt made everything look grander and more epic and opened up the possibility of creating prequels to show the first three episodes and the adventures of a young Anakin Skywalker. Which is what he eventually did."
] |
[
" Frankly, it's because people are *much* less creative than they think they are. Most of what we create is actually a mash-up of things we have already seen. Consider: Star Trek is basically a World War II Pacific-theater naval adventure moved to outer space. Star Wars Episode IV is explicitly a remake of a Western cowboy adventure moved to outer space, converting at the end to a World War style aerial battle. Lots of fantasy realms are basically The Hobbit or Knights of the Round Table.",
" All of the other answers are using specific examples that might be confusing to someone who has not seen the movies, when it's really as simple as this: George Lucas decided to use computer special effects to make numerous alterations to the original STAR WARS films, both to improve elements he personally thought were lacking or wrong and to make things more in-line with the prequels that nobody likes. The mere fact that the films were altered from their original presentation irks people, especially because the original versions are not widely available in an acceptable format."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why did we evolve to the point where we have to wipe our ass when no other animal has to do so?
|
[
" Who says we have to?\n\nMainly we wipe our asses because with our bipedal body plan we can't exactly get our own heads back there to lick them clean like every other animal. So we just have to make do.",
" we didn't evolve to where we have to wipe, we evolved out of the ability to lick our own a-holes and into the ability to understand teamwork and hierarchy."
] |
[
" The basic answer is because we (and they) evolved that way. Remember the evolution starts as something random.\n\nTake a bird. One day a bird is born with a longer beak. This longer beak allows the bird to reach deeper into the ground for food. Over time that bird has kids and they have a longer beak. Then their kids have a long beak. Eventually there is a drought and there are no worm to be found near the surface of the ground. Only birds with long beaks can get food. So the short beaked birds die and the long beaked birds survive.\n\nSomething similar happened with humans a long time ago. Instead of evolving to be stronger or hairier we evolved to be smarter. Being smarter meant we don't need brute strength to survive. Instead of being strong or fast or having claws we learned how to make spears. Instead of growing longer hair or fur we learned to make clothes. So strength, agility, or other features weren't necessary.\n\nOther animals didn't evolve to be smarter. They evolved in a different way to survive. Dogs evolved for speed and agility. They also evolved to have fangs, claws, and fur. This allows them to survive in the cold and hunt prey.\n\nApes and monkeys took a different path than us. They didn't evolve to be very smart. They evolved to have more strength and less brains. This allowed them to survive challenges that they faced.\n\nVery few animals that are smaller than humans are actually stronger. Some are, such as apes or monkeys. Physically this can be explained by their physiology, or how their body is made up. They contain a different ratio of kinds of muscles that allow them to \"burst\" strength better (but at the cost of being able to be strong for long). Their muscles also attach to their bones differently, giving them more strength at the cost of fine muscle control. Other animals, such as dogs, are not stronger than humans. They can appear that way as when they're trying to do something that they're good at. Consider how much a human can carry compared to the animal in question. Humans can carry over their body weight, if properly attached to themselves, for quite a long time. Other animals will struggle.\n\nTLDR: Humans evolved for intelligence rather than raw physical capabilities. We also evolved for fine muscle control and stamina over brute strength. Very few smaller animals are stronger than humans.",
" Because we were first to reach the threshold of self awareness. Since then we have beaten down and destroyed anything that hasn't curled up at our feet or ran away at the very sound of us coming. You know what we did to Neanderthals? We ate them."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How did Helen Keller learn to communicate and what would her thought process be like while doing so?
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[
" Read her autobiography. There is a way for blind deaf to communicate through touch. Helen Keller got a teacher who knew this technique and would teach both Helen and the rest of her family how to communicate by touching the palm of the hand in special patterns based on the letters of the word. The way Helen learned the language was the same as any other kid would learn language, by repeating the words back to the teacher as it is associated with things. For example one of the first words Helen learned was \"water\" as this was a very distinct feeling she could touch. So the teacher would put her hand under water and sign \"water\" to her repeatably until Helen herself signed back. This process would be repeated for every word."
] |
[
" There's a great picture in my psych 101 book that shows a since-birth blind deaf kid on a swing glowing with a huge smile. The caption was something like 'emotions are experienced, not taught'. Same with 'abstract' words like those. There was nothing wrong with Helen Keller's brain and she would felt the same emotions as everyone else, perhaps frustration more than anything. As an example, she would have experienced profound triumph in that little hand-under-running-water scene where she learned that the symbols being spelled on her hand MEANT something. \n\nFrom there, it's only a matter of intelligence to read that word \"exquisite\" in a novel somewhere, once she learned to read braille, and apply it to her own emotional experiences and memories.",
" She does describe this in her book. First off ideas is not based on language, that is just how you perceive them. So even if you are blind, deaf or both you can still manifest thoughts and ideas. Helen Keller were also able to learn several different ways of communication. For example she were fully able to read and write braille. And the process of writing a book does not end at the authors typewriter but goes though a lot of people at the publishers who will suggest and make different kind of changes. An author is rarely responsible for the typesetting for instance. So the publisher would need someone to translate braille to Latin characters. I also suspect there was a lot of changes suggested by the publisher to make the sentences flow better as rhythm and flow would be things that Keller would be unfamiliar with."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How does standard deodorant really work?
|
[
" Deodorant just covers the smell. Like spraying the room after you fart. Fart is still there, it just is now covered by roses and tropical breeze. Antiperspirant blocks your sweat glands so you don't sweat as much. That's like a glue keeping your butt from farting in the first place. That's what the aluminum does. I dont think antiperspirant and deodorant stop bacteria from growing. That's what showers are for."
] |
[
" Antitranspirants lower the amount of sweat that leaves your body. Usually by clogging up the pores (afaik that is what the aluminium salts are for) or making the pores close up by themselves and forcing your body to get rid of the sweat another way (which it surprisingly can). A deodorant only prevents the build up of bacteria (your sweat does not smell but the bacteria that feed on it and break it down produce the smell). Some really bad ones just mask the smell. \nThat is why perfume is no substitute for deodorant but a different thing that should never be put under your arms.\n\nThey are safe to use but some sources claim aluminium salts are unsafe because aluminium builds up in our body and causes major harm. If you suffer from excessive sweating you might want to see a doctor. Last I heard BOTOX into the armpits deactivates the sweat glands there. Otherwise I recommend using deodorants. It lets your body sweat to control the temperature and it kills the smell. I recently bought an all natural deodorant and it surprisingly is the best one I had to date. Insanely expensive though and smells of white chocolate since cocoa butter is the main ingredient.\n\nAntiperspirants usually feature deodorant like qualities as well. If your problem is smell but you do not have a problem with the moisture you need to find a deodorant that works for you and very importantly a soap or shower gel that cleanses you well because getting rid of old bacteria is half the effort of preventing smell. After a day almost everyone develops a mild smell, even with deodorant. Regular showers are imperative to fight body odour if you have any.\n\nAlum works to some extent because it is an astringent that pulls the pores closed. It is not particularly strong though and only works for some people. For me it did not.",
" I'm in a similar situation, OP. A cheap and extremely-effective alternative is to use sodium bicarbonate, better known as baking soda. Not only does it dry your underarms, but it works by counteracting the smelly chemical those bacteria make, called propanoic acid. Thus, the bacteria never develop a resistance to something that doesn't affect them, and your underarms remain smell-less and dry for much longer than I have experienced with deodorant. Also, baking soda has no smell, so there is never this over-powering perfume smell."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Can languages be more efficient than other languages? If so what's the most efficient?
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[
" Languages aren't inherently more efficient, but some words do not have translations in other languages, or are difficult to translate without changing the meaning.",
" There was an article in Forbes, in 1987 about how Sanskrit is the most efficient language for AI and computational purposes. I have not read that issue, but I have learned a little bit of Sanskrit in school & it was an extremely versatile language. The constructs and grammatical twists that one can accomplish in the language seem limited only by one's creativity. There was this poem that in it entirety told two different stories, one of them absolutely false, so you knew which story it was talking about. Also, contrary to common world opinion, Sanskrit is not yet dead, there are very small pockets in India where Sanskrit is still spoken."
] |
[
" The same reason there isn't one car or one phone to rule them all. Different languages have different uses - some are better for writing high-performance game engines, some are better for building websites, and some are better for writing large data systems. Also, people have their own preferences - some people like Java, others like C#. No language is perfect, and each language has its advantages and disadvantages.\n\n > It just seems to me with the thousands of languages out there, somebody somewhere had to have said \"i'm gonna fix this.\"\n\n_URL_2_",
" Hmmm. This is hard because a lot of languages are general purpose, and there are few hard rules, but I can give an overview of the general cases.\n\n* C: systems programming, writing operating systems, and \"low level\" services that need to be very fast, such as web servers, and often other programming languages. The Apache and Nginx web servers are written in C, as well as the Linux kernel, and languages like Python and Ruby. Also, embedded systems are written almost exclusively in C or C++. Things like microwaves or industrial robots, etc.\n* Java: server-side application programming and cell/smart phones. Many websites are written in Java, especially big ones because it's quite fast. It's not as fast as C, but it's easier to use so it's considered better for making specific applications (eg _URL_0_) instead of generic applications like an email server (a load of people). It's also the main language used for the Android smartphone operating system, as well as the Blackberry OS, and on many types of dumbphones.\n* Python: Wide variety of things. Web applications like Java, developer tools like package managers and version control systems, and interestingly, lots of games. Civ 4 and Battlefield 2 use Python extensively. Python, like many scripting languages, is used where describing what you need to do is more important than describing how to do it in very fine detail. For example a python program may describe the menu system of a game, and all the options and those interactions, because typically you click less than 60 times per second so speed is less of a priority.\n* Ruby: a lot of similar things to python, though it's most popular as a web application programming language. For a while it was considered a one-trick pony in that regard, though it's usefulness as a general scripting language has evolved.\n* C++: This language is serious shit. It's notorious for it's complexity and difficulty to master, but it's extremely powerful. Projects which have both extreme performance and complexity requirements such as game engines are written in C++. Google also uses C++ for their web services, but they are one of the only companies who does so, because C++ is so \"hard mode\".\n* Javascript: a programming language that used to only run in the browser, it now runs as a regular scripting language thanks to work done by google and joyent (v8 and node respectively). It's used to write glue code for user interfaces, especially websites but increasingly it's being used for actual desktop interfaces. Gnome3 for Linux is one such desktop environment that uses javascript. It's also seeing limited use on servers for certain types of applications with specific requirements.\n* Objective-C: Apple. Used for desktop applications on Mac OS X, as well as apps on the various iDevices. Little to no use elsewhere.\n* C#: Rip off of Java, though arguably a better language (learning from Javas mistakes), similar uses to Objective-C but for Microsoft Windows.\n\nIn general, there are two types of languages. Compiled languages and scripting/interpreted languages. Compiled languages like C, C++, Java, Objective-C, and C# all are designed to run pretty fast, but are generally slower to program in. They also tend to have more facilities for writing extremely large programs, especially Java.\n\nScripting languages like Python, Ruby, and Javascript are designed to be easy to write in, and don't need to be precompiled. They usually feature dynamic runtimes, which has a lot of additional implications but essentially it means you can do really sweet stuff really slowly. Slow is relative, for most simple programs at the scale a 1st or 2nd year student is working at, the difference will not even be noticeable. In this day and age you need to have billions of something trying to happen to notice a significant difference, thus the recent rise in popularity happening for scripting languages as general purpose languages."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why is prostitution allowed in some countries, but not brothels?
|
[
" In places that dont allow brothels but have legal prostitution they kinda self employed or contractors. They might work at an escort agency, that \"manages\" clients and the hookers simply travel to their homes, or hotels. some times a building might exisit that they can conduct their work with security and lights and stuff like in Nederlands and the De Wald district or in berlin where they allow prostitutes to access a hotel for the sole purpose of conducting their business. \"Street Walkers\" don't exist in these places as the transactions have safe or regulated enviroments provided. \n\nCountries might prefer a self employed model over a brothel because Brothels can become large corporations that focus too much on profit. They tend to abuse legislation that helps more legitmate businesses be profitable, for example bringing in Visa workers. They also lack some legal framework like standard employment contracts, labour unions, government regulation or a government regulator organisation. \n\nYou might ask why they don't just create all those laws and regulations. Governments chose to ignore its presence because creating all this legal framework is time consuming, and most politicians think the electorate would never appreciate such measures being funded by the government. It more convient to adopt a self regulating model that gives the power to the workers as opposed to the employer",
" I think it's to ensure sex workers are doing it of their own free will...brothels can hide a lot of secrets like trafficked workers whose passports have been taken and live in fear each day and are therefore deterred from speaking out to authorities"
] |
[
" short answer. prostitution is illegal because the governing body of a locality (aka government) deems it illegal.\n\nlong answer. most governments are rooted in religious background and just haven't caught up to modern times. there is also the issue of human trafficking or forced sexual servitude, by making prostitution illegal, you [un]successfully prevent/reduce those crimes as well.",
" Many communities find prostitution to be immoral and as a result don't want to allow in their areas. Many countries have legal prostitution and in the US prostitution is decided at the state level."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Does the health tip "Eat Your Colors" have any basis in actual nutrition?
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[
" It's not a principle so much as a useful rule of thumb: eating a wide variety of colors means eating a wide variety of plants, which means that you'll be consuming a wide variety of nutrients. \n\nMore specifically, some nutrients have bright colors (famously, beta-carotene) but that's less significant than the simple \"eat many different things\"",
" It's a general guideline that has some nutritional basis.\n\nAs you process food more and more, the food loses it's color and nutrition. This is why processed, packaged food often has to add additional food coloring and flavors just to restore it enough so that it seems appetizing. However, processed food is nutritionally poor so people who have access to no other food end up eating more processed food just to fulfill their nutrition requirements. This is why poor communities without access to fresh food often have high rates of obesity.\n\nNot all foods lose nutrition with processing. Some processing can increase nutrition. For example, your body gains more calories from cooked meat because it is easier to digest compared to raw meat.\n\nAnother color-related nutrition tip is to not stick to eating the same color. If you only eat the same types of food, you may not get all the nutrients you need. By eating different-colored food, you have a much better chance of getting necessary nutrients like vitamins."
] |
[
" Healthy is a very undefined term. I kind of hate it in real life too. \nDrinking 2 litters of milk is healthier than drinking 2 litters of cola.\nOr drinking 2 litters of orange juice is healthier than drinking 2 litters of cola. \n\nThe simple fact is, you body needs a certain amount of nutrition, this is subjective per person and highly depends on your age, weight, height, race and other countless factors.\n\nAny fruit will usually provide you with some vitamins, a lesser amount of minerals and some fatty acids if you eat the seeds. \n\nIf we look at strawberries from a nutritional perspective.\n_URL_0_\nThey're awful at everything except Vitamin C and Manganese. \n\nSo they're healthier in the same terms Milk vs Cola is. \n\nMilk will give you a lot more nutrients but also has 60 kcal per 100g\nCola will give you almost no nutrients but has 41 kcal per 100g\n\nIs drinking 2 liters of milk a day healthy? Absolutely not. Thats 1200 kcal of calories just from a liquid food and you will eat other solids. This will lead to incredible weight gain over a long period of time. The same thing with cola or beer. Beer and Cola are easy to drink and have diuretic compounds and salt. That means you will piss a lot and you elecetrolite levels won't go down. So you can easily drink 4 liters of cola or beer in a day. But you will take in the equivalent of a 2 days worth of solid food calories by doing it. And thats incredibly unhealthy.\n\nTL;DR\n\nThere is 0% difference in nutritional value from a sweet or non sweet strawberry except the sugar content.",
" Our bodies absorb more of a food's nutrients if it's... Y'know, food! We get nutrients and vitamins from pills and whatnot well enough, but it's not as efficient! \n\nAnecdote:\nMy doctor prescribed a course of magnesium supplements to ease my migraines. They didn't work so well, so I found what foods are high in magnesium (leafy greens!) and began eating them instead of the pills. I actually felt a marked improvement!"
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How are the atoms split? Is the fission process the same for nuclear power plants and the nuclear bomb?
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[
" If you shoot a neutron at an atom at the right speed (not too fast or too slow), the atom will break into pieces. If you organize things right, those pieces will hit other atoms and break *them* apart too. It's the same underlying process in bombs and power plants, but the difference is in how the atoms are organized. In a bomb, a split atom hits many other ones, creating a violent reaction. In a power plant, it doesn't hit as many others, so the overall reaction is less violent.",
" The fission *event* where a single atom is split is the same for a nuclear reactor and a nuclear bomb. The fission *chain reaction* is different, though. \n\nFissionable atoms are unstable, and if you whack them with a neutron just right, they'll fly apart energetically. This process releases some neutrons itself; those neutrons are called \"prompt neutrons\". IF the fissionable atoms are arranged just so, and there's enough of them, those prompt neutrons will go on to cause more fission events in a self-sustaining chain reaction that consumes large numbers of atoms in the blink of an eye. That's a nuclear explosion. \n\nIn a nuclear reactor, the fissionable atoms are carefully arranged so that this *doesn't* happen, for obvious reasons. However, the leftover halves of the fissioned atom, called \"fission fragments\" are themselves unstable, and undergo radioactive decay. Among the results are more neutrons, and those neutrons go on to cause more fission events. \n\nThe very important difference here is that the neutrons that come from the decay of fission fragments are *delayed*. This means that not only does it take longer for the fuel to be consumed, but also, it takes longer for the reaction rate to change. That's because the rate of fission events depends heavily on what has *been* happening in the reactor core over the last minute or so. That makes the reactor controllable, because you have time to react if the power--the rate of fusion events per second--starts creeping up or down from where it should be. \n\nSource: Former Navy Electronics Technician (Nuclear)"
] |
[
" There are two different types of nuclear weapons: \n\n * Fission bombs. In these, the nucleus (center) of an atom is split. When it is split, a tiny bit of the atom turns into a huge amount of energy. This is the simpler type of nuclear bomb, like what the US dropped on Japan, and the kind you hear about N. Korea/Iran/etc. developing. \n\n * Fusion bombs. These are both more difficult to build & more powerful. They work by putting two atoms together into one atom. When that happens, also a tiny bit of the atoms involved, turns into a huge amount of energy. However, it takes a lot of energy to start this process - so much so that it's started with a small fission bomb. These are also known by the term \"thermonuclear weapons\". \n\nThat's a start, and I'm thinking much more detailed than that, would maybe be best found via Wikipedia, or something outside of this subreddit...but, what else did you want to know?",
" An atomic bomb achieves an explosion by fission or splitting atoms. The typical fuels of which are Uranium 235 and plutonium. A hydrogen or thermonuclear bomb explodes by fusion or sticking atoms together. Thermonuclear bombs use atomic bombs to supply the necessary energy to kick off the fusion reaction and are far more powerful than atom bombs."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
why do we try to reduce the swelling in the ankle/wrist after an accident? Surely our bodies evolved to swell up as it is somewhat beneficial after an injury, so why do we think it better to try to stop it/reduce it?
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[
" Looks like nobody got it yet so I'll answer. Swelling is a natural splint. Back in our hunter gatherer days, when we hurt ourselves, there were no time outs. You kept going or you died. If you've partially torn some of your ankle ligaments, you still may need to walk or even run on it. The swelling immobilized the joint to reduce the risk of further damage. May have taken a long time to heal, but at least you kept up with the rest of the clan.\n\nNow we try to reduce swelling. Why? Because the fluid around the joint is relatively stagnant and deoxygenated. Not the best environment for tissue healing. This is why we ice, to reduce swelling so fresh blood can get to the injury and start the healing process. But what about that nice natural splint, you ask? Well now you don't have one, so stop hobbling around on it and put it up on the coffee table, ferchrissakes!",
" Swelling, or inflammation, in the case of say an ankle sprain is the result of damage associated molecular patterns (DAMPS). Think of these DAMPS as markers that injured tissues and dying cells release to signify to the immune system that the body is hurt. Immune cells such as macrophages, dendritic cells, and other will respond to these DAMPS by secreting pro-inflammatory chemicals called cytokines. These cytokines act to recruit other immune related cells to the injured site and increase blood flow. A large part of the swelling and redness that you see, is the result of mast cells. Mast cells are stimulated to degranulate histamine and heparin by the locally circulating cytokines or the binding of DAMPS to antibody on their surface. Histamine and heparin cause the blood vessels in the area to leak allowing extra-cellular fluid to build up in the area. The purpose of all of this is to facilitate trafficking of cells such as neutrophils and macrophages which can fight off any invading pathogens if there might of been an open wound and to clean up any damaged tissue. Eventually cells called fibroblasts would be recruited to move in and lay down scar tissue where damaged tissues were unable to regenerate themselves. All this immune system activity is vital to protect us from infection and to clean up damaged tissues, but often times (especially w/ a sprained ankle) the inflammation is a bit over kill and can lead to more pain, slows healing, and lead to more scar tissue. Therefore, reducing swelling in situations like these is beneficial to healing and reduces pain. Hope that helped, I tried to keep things simple but educational."
] |
[
" Like the body's response to anything, too much or too little swelling is bad. There is an ideal amount of swelling that is beneficial in the Acute Inflammatory Response (right after an injury occurs). For most people, swelling only becomes truly problematic in the case of extreme injury or chronic exposure to an insult. \n \nLet's use the example of a cut in the skin. The cells that were damaged in the cut spill their contents into the surrounding tissue. The body recognizes injury because certain \"intracellular\" molecules are only found outside of cells after injury has occurred. Endothelial cells - the cells that make up the walls of blood vessels - recognize these substances and allow the walls of the blood vessels to become \"leaky.\" This leakiness causes swelling. \n \nThe leakiness is beneficial because it allows immune cells of the body to recognize and invade the site of injury as quickly as possible. Endothelial cells express molecules on their surface that signal to immune cells \"the injury happened over here\". These molecules help immune cells \"dock\" on the blood vessel walls, then help them escape the blood vessel into the site of the injury. \n \nSo it's not necessarily the swelling that is beneficial - it's what the swelling represents in the body. Swelling represents leaky blood vessels, which in turn (99% of the time) represents the cells of your immune system acting appropriately.",
" Swelling and inflammation is associated with and part of the body's response mechanism to injuries and infections, it is caused by a build up of fluids in the surrounding tissues. The reason why it is important to reduce swelling is it can cut down on blood flow to that area or any area which are fed blood through that area, if the swelling is great enough it can lead to further infection and potential of gangrene."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why don't we have dinosaur sized animals any more?
|
[
" We had some very close sized animals in the very recent past. Not completely dinosaur sized because of a number of climate reasons (less atmosphere, lower temperatures, etc), but still very impressive.\n\n[The Megatherium](_URL_2_), a 20 foot long sloth.\n[Woolly Mammoths](_URL_1_), who could sometimes weigh up to 10 tonnes.\n[The Elephant bird](_URL_0_) of Madagascar, which existed less than a millennium ago, was 10 feet tall and weighed almost 900 lbs.\n\nAll of them were killed by either climate change or humans, or both.",
" Selective pressures have pushed for smaller animals on land. For instance, the asteroid which rendered the dinosaurs extinct likely had a hand in this by damaging food chains (it blocked light from the sun with dust, killing plants). Larger animals, needing to consume more food at a higher rate, would have been more adversely affected by the significant reduction in available food. \n\nSmaller creatures and scavengers would have been more able to survive.\n\nHowever, as barc0de points out, we not only *do* have dinosaur sized animals still, we have *larger* than dinosaur sized animals."
] |
[
" The largest animals ever known to have lived are alive today, specifically the blue whale. Additionally, our perception of the size of animals in the past is skewed. Bigger animals make better headlines, and bigger fossils are easier to find. There were *plenty* of small animals just as there are now.\n\nNow that being said, we do see a fair number of large terrestrial animals from that time. One theory for land animals in the past is that they grew in size as a sort of arms race. Prey became larger to be harder to kill for predators (just as an adult elephant has little to fear from today). Predators became larger to kill those prey, and so on.\n\nHowever, this is just one 'strategy' among many that may be pursued, similar to having a hard shell, producing lots of young, and so on, when it comes to evolution. So life doesn't particularly *aim* for being big, but being big might arise if it is an advantage. \n\nAnd it isn't always an advantage. The extinction event that wiped out non-bird dinosaurs would have quite possibly made large size become a significant disadvantage, because it disrupted food chains by diminishing photosynthesis. If you're a large animal, you need a lot of food. A sudden loss in food availability is bad. Advantage goes to smaller animals and scavengers.\n\nLarge animals have existed between then and now as well, but there's a new *huge* disadvantage, and that is humans. If you are big, you need lots of space, you need lots of food, and you are potentially dangerous.\n\nWell now the world is full of humans. We divide land, we remove ecosystems, and we *really* don't like danger. So being big today means you are quite probably at odds with us, and generally speaking this is a very dangerous place to be for an animal. We have eliminated a great many large animals ourselves.",
" No. Most prehistoric animals were small, just as most animals today are small. We are biased in our exploration of the fossil record because larger skeletons can be easier to preserve and easier to find. Additionally, it's easier to sensationalize giant animals, so big cool creatures like the T-rex make more news than your average compsognathus.\n\nLarger animals exist today than any animal that we have found yet in the fossil record.\n\nOne major factor that eliminated many large animals in the past was the KT extinction event which eliminated all non-bird dinosaurs. This was likely at least in part due to the collapse of food chains, there was so much dust in the air that plants couldn't photosynthesize. If you were a huge plant eater, this is a big survival problem. If you eat huge plant eaters, and they all starve, this is also a big survival problem.\n\nThere have been other large animals between then and today, but there is a new serious threat to being a large animal now. Primarily humans. If you are big, you need lots of land and food. Humans have divided up the land and occupy much of it for themselves. Again, this is a big survival problem."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why are IP(v4) addresses usually represented in decimal while colors are usually represented in hex?
|
[
" Note that, while it's a pretty obscure thing to actually use, most modern software still supports representing IP addresses as hexadecimal. Try visiting [_URL_1_](_URL_1_)."
] |
[
" decimal, binary, hex are just different representations/encodings of the same information.\n\n192.168.1.43/24 is CIDR notation and stands for an IPv4 range. To understand the systematics, you best play around with some numbers by yourself, for instance with this calculator: _URL_0_\n\nTransition from v4 to v6 is not easy, as old routing equipment has to be replaced. v6 is based on 128bit while v4 on 32bit.",
" The # prefix is optional, just identifying it as a hex code. It is then typically followed by three numbers in hex format, from 0-255 (00 to FF) representing each color channel. \n\nEg. #FF0000 is bright red because it's 255 red, 0 green, 0 blue."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
If bribery is illegal, how does lobbying exist?
|
[
" The politicians aren't getting payed by lobbyists, that would be bribery. Lobbying refers to the practice of hiring lawyers or legal advocates with connections to push legislature. None of the money spend on lobbying goes directly to the politicians. In addition to this, lobbying is a very regulated and, for the most part, transparent process.\n\nTL;DR Lobbying=/=bribery."
] |
[
" Not much I'm afraid. Their pretty much the same thing with bribery being illegal but lobbying legal. Also, lobbying usually includes a bunch of parties but bribing only 2",
" Bribery requires proof of quid pro quo.\n\nbribery = \"Here is $1, You vote to pass X bill.\"\n\nlobbying = \"Here is $1, I trust that you'll vote the way I want, or when re-election comes around, you won't get another dollar\"\n\nYou can argue those are the same things, but the law disagrees."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why launch into space from the ground as opposed to something like a high-altitude aeroplane?
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[
" Hopefully I'm not too late for this. It's not quite an ELI5 answer, but hopefully it's simple enough to understand. I'm a Current aerospace engineering student (admittedly not a great one) so hopefully I'm remembering all my coursework correctly.\n\nFirst misconception I read: Rockets take off vertically. While initially true, that is only just to clear the launch pad. In actuality, rockets take off vertically and then perform an aerial maneuver so that they are travelling horizontally relative to the Earth's surface. In order to achieve orbit, an object has to be moving fast enough horizontally around the earth so that it \"falls\" around the horizon. [See this link from Wikipedia to understand what I'm talking about.](_URL_0_) If you launched a rocket straight up, it would just fall straight back down to Earth. If you strapped a rocket to an airplane and then launched from cruising altitude, what you would need to do is light your rocket from on top of or underneath your plane and then have it travel horizontally away from the plane. Not nearly as complicated as was postulated earlier in the comments (vertical launch from the airplane).\n\nSecond misconception: it doesn't take the same amount of energy for a rocket to get to the same altitude as an airplane. Actually, it takes the same amount of energy, but a rocket engine is much less efficient than a jet engine. So, the jet wastes less energy on its way up than the rocket does and thus requires less fuel.\n\nNow, as to why you wouldn't want to launch from a plane. The reason is that planes don't fly high enough to make it worth while to reach orbit. The ISS orbits at a relatively low orbit of about 400 km above the surface of the Earth. [In comparison, a Boeing 747 cruises at 11 km.](_URL_3_) This is nowhere near high enough to make launching from a plane to orbit worthwhile.\n\nAdditionally, the max takeoff weight of a 747 is 975,000 lb. [In comparison, the external tank of the shuttle, not including the shuttle itself, weighs 1,680,000 lb at takeoff.](_URL_2_) It doesn't make sense to try and modify or design a plane to lift enough weight to carry a rocket that is designed to make it to orbit.\n\nFinal note, while this concept doesn't make sense for launching rockets to orbit, there are commercial planes designed to launch suborbital vehicles. These vehicles are designed for short trips to the edge of space so tourists can see the curvature of the Earth. [See SpaceShipTwo and its carrier vehicle, WhiteKnightTwo.](_URL_1_)"
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[
" The air at high altitudes is less dense because there is less air stacked on top of it pressing it down. This reduces drag (drag slows airplanes down), and enables engines to use less fuel to achieve the same fuel/air ratio for combustion to occur. This means that the engines use less fuel to do the same amount of work, and there is less work to be done in the first place.\n\nIt is also importation to note that although aircraft climb slow, they descend very quickly (gravity is helpful for once). Therefore a lot of time seemingly lost in the climb is made up for descending.\n\nSource: I have a piece of paper from the government that says I can fly.",
" The main problem that rockets face is that in space there's nothing to push against. Planes flying in the air can suck air in the front and shoot it out the back, giving them thrust, and they can direct air around the wings to produce lift. Rockets are designed with the knowledge that they will not be able to do this.\n\nOnce you realize that you're going to have to use a rocket engine for the later stages of your flight you have to ask what you're going to do for the first stages of flight while you're still in the atmosphere. It turns out that this is a small enough part of the flight (maybe a minute or two before you're above the altitude where wings or jet engines are effective) that it's a reasonable decision to just forego jet engines and work with a rocket that has fewer stages.\n\nThe idea of using a horizontal takeoff is an attractive one, though, and it's been used on a number of space vehicles. The Pegasus Rocket, for example, is carried to a high altitude where it is launched mostly horizontally to boost a small satellite into orbit. Virgin Galactic's Spaceship One is carried to altitude by White Knight One where it launches into a suborbital trajectory (it doesn't have nearly enough fuel to make it into orbit). The SABRE engine that's in development is *claimed* to allow a craft to take off from a runway and to use its engines in an air-breathing mode until it gets to a certain altitude, where they operate more like conventional rockets.\n\nIt's worth pointing out that when you're trying to get to orbit you have to go really, *really* fast. Getting to a high altitude is also important, but it's not nearly as high as most people initially think. If you try to go orbital velocities while you're still in the (useful) atmosphere then you would just burn up—the SR-71 Blackbird went about 1/8 the speed you need for orbit and it was pushing the limits of material technology of the day for sustained flight. Most of the acceleration has to be done at an altitude above where most of the atmosphere is, so carrying jet engines and wings that won't be useful for most of your flight is wasteful. The exception is if those jet engines and wings are either reusable during the vacuum part of your launch (e.g with SABRE), or if they're a fully independent aircraft that can go home and land (e.g. Virgin Galactic, Pegasus)."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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Why are there so many homeless in America?
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[
" i don't know the actual number of homeless in usa or nz. but just b/c you don't see them doesn't mean they aren't there. i'm guessing that you just don't go to areas where the homeless are in nz. \n\nas to why they're homeless? well, there're many factors."
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[
" Homeless is a lay term that macarades as a technical term. How one person defines homelessness is different than another. Everyone agrees that people we see sleeping on the street are. What about those with a shelter bed (still legally homeless)?. Couch surfing with family (not legally homeless). Couch surfing with friend (sometimes homeless). Sleeping in a car (homeless). About to be evicted by landlord (not homeless until the sherif arrives).\n\nEnding homelessness is easy and simple. Provide everyone with a safe and secure place to lay their head. It's less expensive than you think. In my city of 2m+ (Philadelphia), the official nightly street homeless count is 750.\n\nMany people require stable housing before working on the causal issues that got them there. Old notions of requiring 90 days of sobriety as a condition to a housing subsidy will never solve the problem. It just results in paying social workers to be the housing police and not doing what they were trained to do - help connect people to available resources and help achieve positive outcomes.\n\nVeterans have dedicated pools of funding and in Philadelphia there was a big flashy announcement that we are at functional 0 veteran homelessness. Even the people making the claim understood that it came with many caveats.\n\nMy organization (MHASP) is working on some innovative ways to use technology to help people experiencing homelessness who are resistant to accessing services to come to a center, have some immediate needs met while also being educated on what is out there to help.\n\nUpworthy just released the following video (over 1M views): _URL_1_",
" Well the simple answer may surprise you. \n\nThey aren't. \n\nVeterans are only slightly over represented in the homeless population. 7.3% of Americans are classified as Veterans, and Veterans comprise 8% of the homeless population. However, even that doesn't tell the whole story. \n\nGiven the preponderance of the military in drawing members from backgrounds of lower socioeconomic status, the rate of homelessness among Veterans may actually be lower than the general population."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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What does the puff in the eye test do at the eye doctor, and how does it work?
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[
" It's a test for glaucoma, which is elevated pressure inside the eye. The puff of air pushes on the eye and by measuring the response to that external pressure, the internal pressure can be estimated. There are other, more accurate tests, but the air puff is the easiest to do."
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[
" They use a device called an [autorefractor](_URL_0_). It projects an image onto the retina, and uses a camera to see if the image in is focus. It then rapidly adjusts the focus of the projector until the image on the retina is in focus, which allows it to calculate how out-of-focus your eye is.\n\nThey often uses autorefractors for adults' eye exams, too, to quickly get a good starting point for further refinement.",
" Either you eventually blink it out, or it gets caught behind your eye, you get a huge infection, and need to go to the doctor. Most likely the first one though."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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- Why did humanity create new languages when they migrated? If we all spoke the same language wouldn’t international communication be much easier?
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[
" Languages aren't consciously created. Have you ever talked to someone from your hometown (thus you speak the same language) but they say a phrase you don't recognize or pronounce a word differently than you? Now imagine a few people start doing this, then more and more, and the variations become more and more extreme. Over the course of centuries or millennia, this creates a new language.\n\nFor another example, Shakespeare used the same the language as you and me (English), but if you've ever tried to read Shakespeare, it's clearly different. If you account for differences in pronounciation (which doesn't come across from just reading) it would be completely unrecognizable. Also, look up the original text of Chaucer's Canterbury Tales compared to a modern rewritting. Both are English, but Chaucer's English is completely unrecognizable to us.\n\nThese differences between old and modern English came about the same way we no longer say \"radical, man\" but we do say \"hey man, 'sup?\" Now just repeat this process over many, many, many years and it becomes a new language.\n\nThat said, yes, if everyone spoke the same language things would be much easier. That's the idea behind some constructed languages (\"conlangs\" for short) which are languages that were artificially constructed rather than natural languages (like English, Chinese, Navajo, ASL, etc). Esperanto is the most common conlang created with the purpose of being a universal language."
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[
" Humans evolved to think and communicate. Communication had evolutionary advantages that allowed ancient humans to form societies and survive over other species.\n\nIt seems natural to think that the human brain, the vocal cords, the tongue, and the lips evolved at the same time to produce complex sounds, and with them the creation of spoken languages. Thus, different voices also allow us to get information (male or female, young or adult, ill or healthy, etc.), and this complements our various systems of communication.\n\nAs I know, dolphins and whales also have different \"voices\". They use sound waves of different wavelengths, some inaudible to us. Their speech evolved differently because they have to communicate in water, while our vocal cords need to produce sound waves that travel in air.\n\nWe don't know if other animals have different voices. I'd say we cannot really call \"voice\" most barking and similar grunts. I don't think most animals have complex communication systems. And even if they are communicating, I'd say our ears are not tuned enough to distinguish the differences, so it all sounds the same to us.",
" When we humans were settling in the lands, looking for our own territories to raise families in, we may have had something of a language at the time. Although the further people traveled, the more they saw new things that weren't part of their language. They would have to invent new words, and sometimes, those words just didn't stick over time. Some words just changed because people didn't like them, or they came up with better/easier to pronounce versions. \n\nEventually, language became what we know (and love) now. Just hundreds upon hundreds of years of word evolution, eventually changing to fit the culture it belonged to. People had no way (until relatively recently) to communicate with one another, so there was no way to share words. A person who knew of a 'bear' in the Americas, would have called it a 'Kuma' in Japanese, and neither was at all aware the other existed."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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What do military drum lines do?
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[
" Keep the rest of you rhythm deficient SOBs stepping correctly. The drummer is a champion of tempo and rhythm. In the military marching and drilling are rhythmic activities. Having someone keep the beat helps. In years past the drummers cadence would also be used to communicate with other units over a distance. Today the drum line is largely ceremonial."
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[
" First off, keep in mind that the terms sometimes vary by country, so this might not always hold true.\n\nAn army is the portion of a country's military that fights primarily on land. A navy is the portion of a country's military that fights at sea. An air force is the portion of a country's military that fights in the air.\n\nEach of these main branches (army, navy, and air force), are divided into several parts. One of these parts is the infantry. Their primary role is to destroy the enemy. Both armies and the navies have infantries. In an army it is simply called the infantry; in the navy, it is either called a naval infantry or the marines.\n\nOriginally, marines' main task was to provide security on a ship (mainly from it's own crew who was often [pressed](_URL_0_) into service), to board other ships, and to repel boarding. Additionally, they would help conduct land raids. Over the centuries, their role has moved more towards these amphibious kinds of missions.\n\nThe US Marine Corps, being quite large, has gone even further than this. Often, they are not just used as an initial landing force for a naval invasion, but an expeditionary force, going in before other forces, even in places far from the sea.",
" Parade uniforms for military in formation on foot and drum players in a band rest on the chin. The straps on Cavalry and wind players in a band go under the Chin. \n\nThe original purpose on Cavalry was to keep the hat on your head, but on infantry was to help deflect saber slashes and use to be metal. \n\nThe Marching Band uniform is based on the old military uniform and so they have the chin straps but they get in the way of playing your instrument when they rest on top of your chin so wind players move them under their chin and traditionally percussion keep them in the same place an the infantry. But some band have started having percussion wear them under the chin to be more uniform with the winds."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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. Could a body be far enough away from a fired bullet that it does not pierce flesh but maybe bounces off.
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[
" Would be dependent on bullet shape, bullet initial muzzle energy, angle of impact to skin, skin toughness, etcetc. Human skin is not as tough as hog skin or rhino skin. For most bullets, the answer is never.\n\n\nQuote from wiki: \n\nFirearms expert Julian Hatcher studied falling bullets in the 1920s and calculated that .30 caliber rounds reach terminal velocities of 90 m/s (300 feet per second or 204 miles per hour). A bullet traveling at only 61 m/s (200 feet per second) to 100 m/s (330 feet per second) can penetrate human skin."
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[
" To expand on /u/TheLastSin 's point, its all about the location of the bullets.\n\nThe body is pretty tough (surprisingly) and bullets are not very big. If no bullets hit major organs, arteries or veins (and no infection sets in) its not unreasonable for the body to keep on moving. \n\nThere are numerous cases of people getting hit by waaaayyy to many flying pieces of metal and staying alive. The human body is well built, tough and has a number of redundant systems. Unless a bullet breaks something really important (or medical care is too far away to avoid shock/bleeding out) \"you'd be surprised what you can live through.\"",
" It's unreliable. Legs are small targets, and glancing shots do negligible damage, unless you're unloading buckshot. They're trained to aim for centre of mass, that's your torso. Contrary to popular media opinion, they're not taught to finish you off, so if you play dead, you have a very good chance to survive that kind of shooting."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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why is it that I can go on Google Earth or Google maps and see a photo taken by a satellite of anywhere in the world and satellites have good enough cameras to read the license plate off of a car but countries struggle to to find the exact location of terrorist groups?
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" Because they are actively trying to conceal their identity and are not static. It is sort of like trying to track all the bugs in your house. You have all the (theoretical) capability to track them (cameras, tracking software, etc.), but you still can't, because they hide in walls and so on. \n\nImaging satelites, because they orbit the earth, can only take a sweep of pictures but can't hover over a specific point for an extended period of time. This makes tracking terrorist movements difficult, since you don't have a continuous feed. Similarly, this is why surveillance drones are still used. \n\nSecond, terrorists typically don't just broadcast their affiliation so it can be read from space. Yes, you see ISIS \"parades\" but I'm pretty sure they don't do that all the time while they are on the move. \n\nThird, often the terrorists are hiding indoors and satellites can't see them there. As well, they try to look like \"normal\" people, so it is much harder to pick them out of the crowd (they don't go around with AQI bumper stickers)."
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[
" The most basic answer is that it's significantly harder to \"fly under the radar\" in general. \n\nPhone and internet communications are monitored on a level and scope that was simply nonexistant even as recently as 10 years ago. \n\nThere is a reason that Mexican cartels had to set up their own \"underground\" cell phone network just to operate. \n\nSmart phones are pretty awesome. They're incredible pieces of technology but at the same time they're so awesome that we've pretty much all willingly purchased a personal tracking device that we dutifully carry with us almost everywhere we go.\n\nquick edit cause I didn't really answer:\n\nThe level of gov't surveillance we live in is pretty unprecedented. For a terrorist it's usually not a good risk/reward gamble to attempt such a large operation anymore. The amount of people and communication that would be required beforehand is such that your odds of getting caught before pulling off the grand attack are too large to justify the time and money investment that would go into it. This is why we now see most Jihadi groups advocating and promoting \"lone wolf\" attacks like Hebdo or the Texas cartoon thing - it's just significantly more difficult for gov't to catch wind of prior to it's occurrence due to it being a smaller plan involving less people.\n\nLess people, less snitches/federal informants. Less phone calls and purchases, less attention. Etc.",
" Firstly, if you are talking about Google Maps, all the close shots are from planes, not satellites. Secondly, they do many flyovers over a period of time and select the best one, you can see all the attempts on Google Earth."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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Why do NBA big men struggle so much with free throws?
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[
" To make it in the NBA as a not-big-man you need a very impressive skill set including speed, jumping, passing and typically the ability to make points from a distance. Free throws use that making points from a distance skill. \n\nHaving a great deal of size is such an advantage in basketball that you can still be successful without an accurate distance shot. And indeed it isnt practiced that much because you don't usually shoot out there, so better to spend time perfecting your inside game. \n\nIn other words, NBA big men often struggle with fre throws because they can struggle and still be successful, and because once successful they don't spend as much of their time shooting from that distance."
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[
" Well one thing is the way the game is played. With football, it is such a physical sport that you dont have time really develop guys because of the beatings those guys take week in and week out. Running backs typically fall apart when they hit the 30 year old mark. The only positions where you can be successful for a long time are qbs and kickers because they do not typically take a beating. College is basically the minors for football. You dont have the body or time to go from college to the minors to develop because one hit in football and your career is done. With baseball you can see guys playing well into their 40's so they have time to develop their game before going pro.\n\n In basketball, athleticism goes a very long way. There is only so much you can learn after college ball in the pros that you haven't already learned. Big man can learn post moves yeah but they typically can contribute right away with rebounds, put backs and easy dunks. Guards are pretty much who they are going to be when they come out of college. They are good shooters who only get better with time, passers and those you get the whole team involved really happens with playing with the actual team you will be on and not a D-league team. Most basketball players fit a typical mold of a player. And also with their bench being as small as it is, usually the people in front of the incoming player is not going to be as good as the college player. \n\nNow with baseball, it is more of a finesse game. Sure athleticism and raw talent do go a long way but fine tuning of your swing, or your pitching mechanics is what makes you great but it also takes time and patience. Hell the best player ever Babe Ruth wasnt a shining example of athleticism. It takes time to turn the raw talent into good baseball mechanics and it easier to take those guys in early and teach them how the coaches want them to be taughtand not some highschool or summer league coach who probably is giving them bad advice. It's really hard to change a good swing that gave you good success in high school or even college into a great swing that can compete in the pros, especially when they've probably had that same swing their entire playing career and muscle memory is a hard thing to change. Also the season is REALLY LONG. Looking at pitchers alone, a 5 man rotation will probably have a lot of changes through out the year from injuries, guys not doing so well, weird scheduling that makes them call up guys for a game or two. That's starting pitching alone. Now take into account most teams will have a bullpen of 7 or 8 guys that only go out between 1 to 5 times a week and you have a lot of potential for injuries. Also, guys just lose their spots to better players in the minors. Now take into account a 25 man roster over the course of 162 games and you can see why teams need minor league teams. Also, like i said before the lingevity of a baseball career is what keeps younger players in the system longer. You may have a good 20 year old prospect but the position he plays is taken by your all star caliber player. Its not like in basketball or football where you can sub him in and sub back the other starter. Once a starter in baseball is subbed out he's done for that game.\n\nSorry if this is a lot of text i didnt really proof read either but hope this helps",
" Partially, it's because there are other similarly tall/fast/strong defenders trying to prevent them from dunking, which means that when there is an opportunity to dunk in a game, it's probably the result of that player beating his opponent in some way. Dunking *over* somebody is a direct way of displaying dominance over your opponent.\n\nBut, probably more importantly, for the elite players dunks can be simply awe-inspiring displays of athleticism. Example: Lebron is 6'8\" tall, sure, but he's also 250+ lbs and still able to jump high enough that he has to avoid [hitting his head on a 10' high rim](_URL_0_). Even within the realm of NBA athletes, that's a rare gift."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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Where did the "Humans only use ten percent of their brains" myth come from, and is there any truth behind it?
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[
" pretty much, it's a case of scientific discovery taken completely the wrong way by the media. There was a major revelation that different parts of your brain are made for different things, and you only use one or two parts at a time. The news media flipped out over this, with offal like \"we only use 10% of our brains at a time, what could happen if we could unlock all of it???\"\n\nAs for the myth, it is true that you only use a small percentage of your brain at a time, but it is in the same way that you only use 33% of a traffic light at one time. Is it really better to have all the lights on at once? Not really. \n\nHowever, it should be noted that there are people who can use 100% of their brains at once. There are millions of them out there right now. The scientific term for these people is \"having a seizure\" and most of them will be dead pretty soon."
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[
" It makes no sense whatsoever for 90% of our brain to be unused at all, as some type of untapped mental power. It sure sounds cool for new age spiritual/supernatural believers, but it's just plain wrong. You can't tap into this 90% and gain telepathy or the ability to see the future, or whatever else people think this extra power can do. \n\nFact is: You use your entire brain. You only use a certain percentage at any given time, though I'm sure it's more than 10%. Every part of the brain has it's function, and when called upon, it does whatever it's suppose to do, normally.\n\nIf 100% of your brain was active at once, then you'd be having one massive, probably deadly seizure.",
" There is nothing to debate. The left brain/right brain myth is exactly that; a myth. All parts of the brain are used by all healthy people throughout their entire day. Specific portions of the brain are more dominant during specific activities, but there is absolutely no merit whatsoever to the idea that someone can be \"left brain dominant\" and therefore \"more creative or artistic\"."
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Given a question, retrieve the highest voted answers on Reddit forum
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eli5
|
Most (but not all) male mammals are larger than females, but most (but not all) female insects, arachnids and fish are larger than males. Why does female-male sexual dimorphism vary by biological class?
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" Arthropods and fish lay masses of eggs which are large in comparison to the size of their bodies; that is their reproductive strategy. Mammals in comparison do not lay eggs but just produce tiny ova which, if fertilized, will then gradually grow into a baby. The biological requirements for these different reproductive strategies necessitate different body sizes. In mammals, the primary evolutionary pressure has been for larger, stronger males who can successfully compete with other males for access to females. In fish, the primary evolutionary pressure has been for large females who can produce large quantities of eggs."
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[
" First, we'll need to specify what is meant by *dominant.\n\nLet's talk about sexual dimorphism first of all. Sexual dimorphism is an apparent physical difference between sexes in a given species. For example, male lions have manes and lionesses do not. Male narwhals grow tusks, females do not. Peacocks are brilliantly coloured and have a large fan tail, peahens are brown and have a short tail. Good? Good.\n\nMale humans could be defined as \"physically dominant\" (ie, larger, heavier, stronger) in the sense that the average adult male can physically overpower the average adult female. In terms of sexual dimorphism, male humans have broader shoulders, thicker brow and jaw bones, more muscle mass, and body hair than females - to name a few main things. Anthropologists believe that before the agricultural revolution about 10,000 years ago, most human societies lived a hunter-gatherer lifestyle. Men were mainly the hunters and defenders and their physical strength lended itself to this role. \n\nNow, physical strength is one thing, but dominance and strength aren't the same thing. When we look at our closest relaive, the bonobo chimpanzee, the males are stronger but bonobo society is matriarchal. In gorillas, the males are stronger and gorilla society is patriarchal. So dominance is more about how the individuals make up the society and less about strength. \n\nA few more examples:\n\n-Male elephants are stronger than females but elephants are strictly matriarchal\n-Male orcas are much larger than the females but orca society is also strictly matriarchal \n-Male elephant seals are 3 times the size of females and the males govern the beach colonies during mating season\n-In birds of prey, the females are most often larger and stronger than the male and they dominate the males\n-Male wolves are usually slightly larger than the females but the pack is governed by a dominant pair\n\nSo differences in size and strength exist all throughout nature, but to say \"stronger equals dominant\" as a general rule is wrong.\n\nBack to humans. Prior to the agricultural revolution 10,000 years ago, many human societies were matriarchal. All over the world many societies were led by respected elder female members of the tribe. The Inuit, Apache, Navajo, and Iriquois are a few good examples from North America. These cultures existed for thousands if not tens of thousands of years. Many societies were also egalitarian, and decisions for the tribe was made by a council of mixed elders.\n\n_URL_0_\n\nSo when did this change? With the advent of wealth accumulation. As us humans started keeping more \"stuff,\" we were also building farms and houses and cities. We developed currency. All this land and wealth needed to be physically protected to ensure the survival of that particular society. Men, being physically stronger and suited to protect resources and attack to acquire resources, became the dominant sex in most wealth accumulating societies. This is almost always true. While women sometimes were able to attain a high status ( female kings in ancient Egypt, a lady emperor in feudal China), at the time they still were not regarded as equal to their male counterparts and most of these women got shut down at some point. The further humans have developed, the deeper these power structures have become entrenched. \n\nIt is only in the last century that things have started to change. While developed nations (\"first world\" countries) have experienced a higher degree of movement towards gender equality, developing nations (\"second/ third world\" countries) are still struggling.",
" I'm not sure it's true that they are often smaller than males. There are many species where females are larger than males. The Wikipedia page on [sexual dimorphism](_URL_0_) has some examples of both.\n\nA species will evolve one way or the other (or with no sexual dimorphism at all) based on what works best for their niche. In some species the females are larger because it's advantageous for them to be larger to carry the fetus, as you said. In others the male is larger because that is the trait that appeals to females, so females select larger males as mates. There isn't really one broad answer, the reasons are different for every type of animal (and some plants)."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How does hacking work? I understand the idea behind it, but what does a hacker actually do?
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[
" While the idea of a hacker (or cracker, the terms are pretty much synonymous these days) is someone finding the tiniest holes in security systems, a sort of digital Solid Snake if you will, this image is very inaccurate. A lot of \"hacking\" is actually done with no more than a phone, an email client, and a Web browser. \n\nYou can find all kinds of info on people through Google, Facebook, and so on. And you can use this information for a number of things: finding out answers to security questions, finding out a device's default password (you'd be surprised how many people don't change their router password, for instance), finding contact information, or in rare cases even finding passwords. \n\nYou can call people saying you're a comcast employee, and tell them you've had a database problem, and you need their username and password to recover the database. Do it with enough confidence, and you'll eventually find someone who gives you their details. \n\nYou can email someone with an address like [email protected], and tell them you need their password for verification. Do it in an official manner, and eventually someone bites. \n\nNeed someone's Facebook? Copy the Facebook layout, images and all, make a website on a domain like _URL_5_, and ask them to login there. Store The entered username and password, and voila. \n\nAnother problem is that people usually have one password for everything. You manage to get your hands on their Gmail password, chances are you can log into Facebook as well. \n\nAlso, a lot of people have very standard passwords or answers to security questions. Birthdays, pet's names, or even just \"password\". Favourite food? Usually pizza. \n\nI've never done these things, but a lot of people are amazingly stupid when it comes to these things. \n\nTL;DR: use the phone, Luke"
] |
[
" By logging in. \"hacking\" is the process of finding a weakness that allows you to or, more often, tricking somebody into helping you to log into the system. At that point, you win. \n\nHacking doesn't work like it does in the movies. You can't type furiously for ten minutes and then get into some system. You either need a password, or you need a way to trick the computer into doing what you want without a password, for example, [encoding instructions into database input fields to mess with the database](_URL_0_), or giving an [invalid input to a software such that it fails in a malicious way.](_URL_1_)",
" One type of hacking involves \"exploits\" - bugs in software that allow the hacker to run his own code on a machine. A computer works by basically following a long list of instructions the programmer gave it. Sometimes the instructions are not perfect (aka a bug). Some bugs can actually cause some of the instructions to be altered. When a hacker finds a bug like this, he can often send the right data to not only cause the bug to change the instructions, but to change them to his own instructions. For example, if there's a bug in the instructions for displaying a jpg, the hacker could create a special broken jpg that includes his own instructions. When you open that jpg, the computer hits the bug in the original instructions to show the jog, and now the hacker owns your computer.\n\nAnother type of hacking involves social engineering - instead of a bug in the instructions, the hacker emails you a program and convinces you to run it (e.g. look at this poon video!).\n\nSide note: this is often referred to as cracking instead of hacking.\n\nFolks have mentioned running scripts and such. Once a hacker finds an exploit, he often wraps it up as part of a script package and releases it. \"Script kiddies\" take these scripts and use them wherever."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
|
What is it about water that is so good at putting fires out?
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[
" Water is *decent* but not great at putting out fires. Its main effect is to cool the items off so they stop being hot enough to burn. It can also smother the fire.",
" Fire requires heat, fuel, and oxygen to burn (the so-called \"fire triangle\"). Water works by removing the heat element. It's also pretty cheap and readily available in most places, which is why it's used.\n\nHowever, you should definitely *not* use water to put out all fires. There are four classes of fire, and using water on three of them makes shit worse. Class A fires are combustibles like leaves, wood, paper, and so on. Use water on it, you'll be good. Class B fires are flammable liquids (gasoline) and gases (natural gas), Class C is electrical fires, and Class D is flammable metals (sodium, cesium)\\*. If you used water on a Class B fire, you're only going to spread it around. And in a Class C or Class D fire, ***water is going to become fuel***. To put out a Class B or C fire you want to interrupt the flow of oxygen by using a dry, non-flammable powder and/or a halogen-type gas or foam. To deal with Class D fires, call FEMA\n\nThere's also Class K, which is flammable cooking oils and fats. It's a subclass of Class B, and any Type B effective fire extinguisher will also work on Class K\n\nLuckily, the majority of commercially available fire extinguishers are combined Class ABC**, and unless you work in a lab, you'll never need to deal with Class D fires.\n\n*Note this is only true in the US. In Europe and Australia Class B is flammable liquid, Class C is flammable gas, and electrical fires as Class E\n\n**I assume that in Europe/Australia they're Class ABCE fire extinguishers."
] |
[
" there's 3 key elements to a Fire: 1) Heat, 2) Fuel, 3) Oxygen. The Fire Triangle.\n\nWater is great at cooling down the fire and then turned into steam/smoke (surface cooling). The steam/smoke acts as a blanket to smother the fire (smoke cooling). With less heat, wet fuel and less oxygen the fire will most likely extinguish with enough water.\n\nhowever, you shouldn't put out all fires with Water. IIRC, kitchen grease fires should be put out by Milk/Salt/Baking Soda/etc.",
" It is burning from natural gas. Even if it was covered in water, the constant bubbling of natural gas would likely remain alight. Typically water would put out a fire by smothering the fuel source and preventing its access to oxygen, but water cannot wet natural gas."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
|
In an expanding universe the farther away something is the faster it’s moving away from your position. Is there a distance where the recession approaches light speed? If so, would that be an event horizon, seen from the inside?
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[
" > In an expanding universe the farther away something is the faster it’s moving away from your position.\n\nThe universe is not expanding. It's our measurement of its size that is increasing. General Relativity tells us that the Red Shift of our universe is caused by time dilation. Time dilation is the ratio of two times measured by two observers for the same event.\n\nNearby galaxies have little Red Shift, so there is little time dilation between them and us. Far away galaxies have larger Red Shifts, so their time dilations are larger. The Red Shift of the cosmic microwave background (CMB) is 1091, so its time dilation is 1091. Since it is 13.8 giga-annum (Ga) old, it should be 13.8 giga-lightyears (Gly) in radius. But factoring in the time dilation, it is only 12.6 mega-lightyears (Mly) in radius.\n\n > Is there a distance where the recession approaches light speed?\n\nThat implies an finite time dilation, which means an observer with frozen time can exist. This does not seem possible given our understanding of physics.\n\n > If so, would that be an event horizon, seen from the inside?\n\nIt may approach the speed of light but it never gets there."
] |
[
" The universe is believed to be infinite in all directions. We reside within an observable universe, which is the spherical region around us that has had time for its light to reach us. This is expanding and it is called the particle horizon. As time passes, further regions have had time for their young light to reach us.\n\nSo you'd think over time we'd see more and more new light.\n\n*But* there is another sphere, the Hubble Volume. This relates to the expansion of the universe. Objects beyond this range are actually receding from us at greater than the speed of light due to the expansion of space.\n\nIn an accelerating universe, which we believe ours to be, this volume will lag behind the particle horizon. What this means is that in actuality, the universe we can see is shrinking, at least in 'contents' as objects near the edge over take the Hubble Boundary. At that point, the light they emit at that time will (once it travels all the way back to earth) be the last we ever see of it. They will essentially disappear from our universe. \n\nI believe this is already happening with the most distant possibly visible objects, although I am not certain we are actually able to see them with our technology.",
" The light isnt getting \"sucked in\", the space bends toward the hole, the light follows the bend. When it passes the event horizon it is essentially heading toward the center at the speed of light, but space is bending faster. Thats why it never comes out again"
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
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How come cockroaches don't die from a heart attack when you try to kill them?
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[
" They kinda sorta do actually.\n\nThere's a neat little experiment you can build (it's probably undergrad university level) to measure a cockroach thoracic movement due to its heart beat using a tiny neodymium magnet glued to it and building a hall effect probe.\n\nSome students I was working with did it and couldn't get a signal from the sensor they built. After *much* stuffing around they did further literature research and found that cockroaches have to basically stop their heart to process visual input - not enough brain power for both was the way it was explained to me. Having the students standing over it messing with their probe caused it to focus its limited processing power on its vision and stopped heart stopped - hence no signal. Put a box over the cockroach and apparatus and the sensor worked beautifully. (Have you noticed that cockroaches freeze and then run when you turn the light on rather than just run)\n\nAs to why it can restart everything and doesn't die - no idea. Maybe because everything is small enough for gasses to diffuse and the neural circuits are simple enough they can turn off and on unlike ours, and the whole process is over in under a second anyway?\n\nedit: and I watched them do this experiment 15 years ago, so no citations will be forthcoming. Sorry - I know that's poor form"
] |
[
" I assume cockroaches have evolved to be elusive around us because they have co-evolved with us. The ones who were not afraid and sat out in the open got squished, while the ones who feared us and hid and lived to reproduce - simple natural selection. Flies and moths do fine in environments without humans, but cockroaches are actually largely parasitic of human waste.",
" The explosion itself would kill roaches, just like any fire would. Radiation is much less of a threat to roaches than to humans, though. Cells are most sensitive to radiation when they are dividing. Humans and other mammals have cells that are dividing all the time. In fact, chemotherapy works because cancer cells divide rapidly and the radiation from chemo kills rapidly dividing cells (that's also why you lose your hair and why men become infertile during chemo - hair cells and sperm cells divide rapidly).\n\nRoaches and many other bugs don't have cells that divide all the time. Instead, a roach's cells only divide around the time it molts, which is about once a week when it's growing up. Molting is when a bug sheds its old exoskeleton as it's growing bigger. Since cells are usually vulnerable to radiation when dividing and a roach's cells only divide about once a week, there's only a small window during each week when radiation would kill a roach.\n\nIf there were enough radiation in the area to last a couple weeks it could still kill roaches since the young ones would have to molt at some point.\n\nThere's no reason this is specific to cockroaches. A lot of insects are more resistant to radiation for this reason."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
|
why do things curl when thinly cut?
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[
" Just a guess here:\n\nWhen slicing an item, you are also exerting a compressing force on the surface of the item touching the blade. This can make the side facing the blade slightly shorter than the other side, which would cause the item to curl. For this to happen, the compression force must be stronger than the pull of gravity on the item, the overall strength of the item, etc."
] |
[
" Because the nail acts as a tiny spring. Your nails are naturally curved, and are forced, during the cutting, into a more straight shape by the cutting force. As the clipping is fully cut away, that tension can suddenly release itself - which, just like compressing a spring between your fingers and then releasing it, causes the clipping to fly away.",
" This is actually a well studied phenomena and the reason is pretty cool.\n\nBasically you are stretching one side of the material more than the other side and that deformation persists after you run the blade down the ribbon.\n\nSince one side contracts more than the other side it tends to curl naturally."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
|
What determines whether a pair of consecutive earthquakes are classified as a foreshock and earthquake versus an earthquake and aftershock?
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[
" They reclassify them if a stronger one occurs during the sequence. So, the strongest one is the mainshock and the weaker ones before it are the foreshocks and the weaker ones after are the aftershocks. If a stronger one suddenly happens during the aftershock period, then all of the others are now classified as foreshocks."
] |
[
" As you may know, an earthquake occurs when two slabs of rock move relative to one another over a surface called a \"fault\". Moment magnitude is simply the product of the area of the fault ruptured, the relative movement across the fault, and the stiffness of the rock (called the shear modulus). It is closely related to the energy released in the earthquake, but the relation is not trivial.\n\nThe moment magnitude does not take into account any other factors, so ignores the depth, duration, size of area affected, and so on. The moment magnitude is an important quantity in academia because it is directly related to the fault rupture itself. However, it is not of huge benefit for working out impacts because other parameters like proximity to population centres, building quality, depth and surface geology (the waves that cause the damage are surface waves that only represent a tiny fraction of the total earthquake energy, and these waves can be amplified or suppressed depending on the geology at the surface) are a lot more important than the moment magnitude. \n\nYou may be interested in the USGS's [PAGER program](_URL_0_) which tries to take these factors into account to estimate the economic and humanitarian impact of earthquakes when they happen.",
" In a logarithmic scale, every 1 step up on the scale *multiplies* the intensity of what you're measuring by some value (often 2, 10, or *e*). Earthquakes are a well-known example: going up one magnitude on the Richter scale requires an earthquake ten times more powerful. So a magnitude 5 earthquake is a tenth of a magnitude 6, a one-hundredth of a magnitude 7, a one-thousandth of a magnitude 8, and so on."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
"Floating Point" Numbers
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[
" When programming, if you need a number, like 2 or 27 or -3, you use an integer. This is just a binary representation of of an integer number. In order for the computer to be fast, these numbers are limited by the number of bits in a computer word. For example, on a 32 bit machine, integers are represented by 32 bits in binary, which corresponds to a range of -( 2^31 ) to ( 2^31 - 1 ). This is about -2 Billion to +2 billion.\n\nWell, what if you want a decimal, like 3.25? Or a number larger than 2 billion? This is when we use floating point. Instead of being represented as one binary number (ie, 5 = 101) we store it as a *mantissa* and an *exponent*. For example, in a certain 32 bit floating point scheme, maybe you'll have a mantissa of 21 bits, an exponent of 10 bits, and one bit for positive/negative. The mantissa is the number, and the exponent is the power of 2 to multiply that number by. (i.e. mantissa * 2^exponent).\n\nThat is not the best ELI5 explanation so here's an example in 8 bit math (split into 4 bit bytes to be easy to read):\n\nInteger format: first bit is 0 for positive and 1 for negative, the next 7 bits are the number in binary.\n\n Integer +5: 0000 0101\n\n Integer -3: 1000 0011\n\n Integer +8: 0000 1000\n\n Integer -8: 1000 1000\n\nFor floats, the first bit will again be the negative/positive bit, the next three will be the exponent, and the last four will be the mantissa.\n\n Float +0.25: 0110 0001 - > + 1 * 2^-2 = 1 * 0.25 = 0.25\n\n Float -2.50: 1101 0101 - > - 5 * 2^-1 = 5 * 0.5 = 2.5\n\n Float +5.00: 0001 0101 - > + 5 * 2^+1 = 5 * 1 = 5\n\nYou'll note that I don't have enough precision to represent 0.1 with this scheme, so if I tried to represent that I'd just have to get as close as I could. This is why when you write something like 3 * 0.1 in a computer, you usually get something like 0.300000000000000000012321 instead of 0.3. The way around this limitation (and if you need to represent REALLY large numbers) is to use a BigDecimal representation that is much slower but guaranteed to be accurate.\n\nNOTE: In real computers, I think the mantissa and exponent are laid out differently, and integers are usually represented in 2's complement, and there are several other concepts like NaN that I have left out in the interest of simplicity.\n\nEDIT: formatting",
" A floating point number represents a number as sums of various powers of 2. \n\nSo 0.3 ~= 2^-2 +2^-5...\n\nIn computers it is laid out like scientific notation in decimal. one portion of the number is the decimal (1.56) and another part is the exponent (E+02). So the number 0.3 would look like (2^-1 + 2^-5 ...)^(2^0)\n\nIn programming you use floating point numbers to more easily represent numbers with decimal points and non-discreet values."
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[
" MIPS - Millions of Instructions Per Second.\nFLOPS - Floating Point Instructions Per Second.\n\nA floating point instruction is basically arithmetic on a decimal (real) numbers, in contrast to whole numbers (aka integers), and other kinds of instructions that a CPU does.\n\nFLOPs and MFLOPS (Mega-FLOPS=millions of operations per second) are traditionally performance figures that the scientific computing community are most interested in for running their simulations of physical phenomena (e.g. weather simulation, materials simulations, protein folding etc, things which are mostly done using decimal/real numbers).",
" AFAIK, float has precision to up to 7 decimal places, while double has precision to up to 14."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
how come we never hear about Acid Rain anymore?
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[
" Mostly due to concerted effort to eliminate the emissions that cause it. In the 80s when a bunch of legislators got tired of having the rain eat the leaves off their trees, they got off their butts and made laws banning emissions of acidic causing pollutants, mostly sulfur dioxide. These laws (google Helsinki Protocol and the US-Canada (arguably the two most affected countries) Air Quality Agreement) put emissions caps in place, mandated that scrubbers be used on smoke stacks etc. \n\nAnd it actually worked - acid precursor emissions peaked around 1991 and have been reduced to about 30% of that peak so far and trending - along with greenhouse gas emissions - downard.",
" Sulfur Dioxide emissions were the main source of acid rain and almost all countries have done extremely well at eliminating SO2 emissions. \n\nIn the US, a [wildly successful](_URL_0_) cap and trade scheme that brought down emissions by 75% over 35 years."
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[
" There are still music scenes, but now thanks to The Internet, a lot of artists are getting exposure outside of their local areas, there's more interaction outside of those scenes. It might not be a perfect answer, but it's a lot to do with it. \n\nAnother thing is that those scenes took a lot to build, and often had a people getting it all together. The Seattle scene that became \"Grunge\" was around a decade before anyone knew about it, and it took time to explode. A lot of the scenes develop around people, venues, or labels (CBGB in New York, for instance), and have long stories behind them. Those venues and disappearing, labels struggle, so on. \n\nThere are plenty of scenes still out there, but there's less pressure to uproot your band and go where your own kind are. I'm sure at some point, something really cool that's been brewing will surface and take the world by storm for a little while.",
" Mythbusters tested the acid one. IIRC they found that the acids claimed in the movie were not sufficient, but they consulted with chemists and got the job done with a different mixture. That much is real enough, just with enough Hollywood obfuscation to prevent people from trying it at home.\n\nI'm not familiar with the poison beans, so I can't comment there, but there's probably *something* poisonous in beans.\n\nA chemist would have the best shot at cooking the highest quality meth, especially if they can get ahold of high quality equipment. After all, chemists \"cook up\" drugs all the time for pharmaceutical companies.\n\nMeth was unknown at some point and consequently there was no law against it. That's how any drug winds up going—you don't make broad, sweeping prohibitions; you wait until a drug pops up and is being abused and you outlaw it then. In the case of Meth the outlawing came in 1970, while it was first developed in 1919 from the previous creation of amphetamine in 1887. It was openly used in World War II to keep troops alert, so it wasn't something that was squashed as soon as it arose, either. During this time you can be certain that it was produced under the supervision of chemists at pharmaceutical companies, tying back to the previous question."
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Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How Do Hotel Star Ratings Work?
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[
" Some rating systems are also based on the amount of available rooms. Some hotels are only able to reach five stars even with high level luxury amenities because of limited capacity",
" A lot of hotels are \"self rated\" and do not adhere to the standards set in place by governing star rating bodies."
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[
" I am friends with many people that work at one of the largest hotel software management companies in the world. They have software that tracks room use and selects a room based upon multiple factors:\n\n1) Is a room with your requests available (two queens or a king)\n2) Has the room been cleaned and is ready\n3) Is the room ready, but has a known problem. Some times they'll avoid using rooms with a leaky faucet until maintenance can fix it. However, if the hotel is busy, they'll use the room anyways and hope you won't mind.\n4) Lastly, they keep track of wear and tear on the room. If one room is being used disproportionately, they'll modify its selection. This will depend upon how hotel management wants to replace items. Do they want to do a complete building renovation every five years or do they want to do a rolling renovation as rooms become worn.",
" TV ratings would be my guess. \n\nThe sort of “boutique” films you’re thinking of that win Oscars still have famous stars in them. People tune into the Oscars to see the stars.\n\nPeople tune into the Grammys for the same reason: to see the stars. But in the music world, music that is lesser known is also by artists that are lesser known. The big stars are the ones making the popular music.\n\nAt the end of the day, the Grammys and Oscars are about making money from the TV show broadcast rights, and acting as an infomercial for their industry. They do that with their star power."
] |
Given a question, retrieve the highest voted answers on Reddit forum
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eli5
|
If water is held in clouds, why isn’t it always raining where there’s clouds?
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[
" Water isn't held *in* clouds. Water **is** clouds. A cloud is just fog that's really high in the sky. So it's the same reason that it doesn't always rain inside fog. Atmospheric conditions have to be right to cause the water vapor to condense into small enough droplets to start falling out of the fog/cloud."
] |
[
" Clouds aren't just water bodies floating in mid air. When water evaporates for the ocean and other bodies if water, it forms water vapor. In the air, there are billions of tiny little dust particles. The water vapor cools down and condenses (becomes liquid water) on these dust particles that are small and light enough to float. So clouds are made up of lots if water droplets, they are not one large floating lake. When clouds become big enough, more and more water droplets come together so that they eventually cannot stay afloat any longer and fall as rain (just water), snow (if it is cold enough up high, and cold down low), sleet (rain that freezes when it touches the ground if it is cold enough), etc.",
" It's a complex process, so ELI5 is a bit difficult. \n\nWhat you see in a cloud are droplets of water that condense due to air rising (all except for fog). \nAs air goes up and cools down, water condenses into droplets and keeps going up. If the air goes down the water evaporates and disappears again (vapour is invisible to humans). A cloud is the area where these droplets are condensed, but water is going in and out of the cloud all the time. \nIt only rains if the droplets get together into bigger and bigger droplets until they are large enough to fall past the evaporation process and get to the ground. This happens when a) air keeps rising into the cloud much faster than it evaporates so it accumulates until it's saturated or b) the cloud drops its temperature because it moved into a colder airmass or rose. \n\nIf you want to make an experiment that repeats this, get a sheet of newspaper and rip it into tiny little pieces and throw it from a tall building, preferable downtown. The pieces will rise, flutter and travel without falling fast, like the water droplets only that they do not evaporate below a certain level. This doesn't mean paper is not heavier than air. Then get another sheet the same size, roll it into a ball and drop it and it will fall down to the ground. This is as if the tiny pieces of paper joined into one big blob, like what happens when you have many droplets that combine into a raindrop."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How do missiles "lock-on" to aircraft?
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[
" Most tracking missiles lock onto aircraft using thermal imaging (as jet engines are very hot). \n\nThis is why many military aircraft carry flares (to confuse the missiles and cause them to go after a flare instead of the engine). \n\nSome specialty missiles use EMF or electronic tracking, where they target an aircraft's transponder or other electrical systems. \n\nThe \"lock on\" showed on TV and in movies is when the missile is directed at a specific heat or electronic signature. That way it does not easily go after the wrong plane. \n\nHave a great day! :-)"
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[
" Short range, air-to-air missiles use infrared homing to lock onto the heat of the target's engine. Longer-range missiles depend on radar guidance.\n\nRadar guidance can be \"active\" or \"semi-active\". If it's semi-active, the missile depends on an external source of radar (for example, the plane that launched it) to track the target. The plane tells the missile where to go.\n\nIf it's an active missile, the missile itself carries a radar and it tracks targets all by itself.\n\n & #x200B;\n\nSome missiles use both: when the missile is first launched, the plane's radar keeps feeding info about the target. The missile then switches to active targeting once it gets close.",
" Holy fuck a lot of nonsense here.\n\nThere is traditionally three types of \"locks\".\n\nWith heat seekers:\n\nThe sensor on the missile detects heat contrasts. Uncaging the missile widens that contrast, but once the missile warms up, sensitivity is lost. So generally it is only uncaged once you're about to fire.\n\nNewer heat seekers like the AIM 9x are a combination of radar guided from the FCR and the above method of tracking, and they're all aspect so you don't have to be behind the plane to get a solid lock.\n\nRadar guided:\n\nOlder missiles like the Sparrow require STT, or \"single target tracking\", in which missile guidance is relayed to the missile via the aircraft's radar. In a passive scan mode the missile will not track, it needs to be \"locked\" up in the onboard radar by singly tracking the target for proper guidance input.\n\nNewer missiles have their own onboard radar, and typically use a combination of FCR control with on-board, where its switch to terminal guidance activates its onboard guidance independantly.\n\nThe newest missiles have their own guidance entirely, and are true \"fire and forget\". Meaning the pilot doesn't have to \"lock\" anything, but simply bugs a target on their screen and fires. In this way, a pilot can engage as many targets as he has missiles at a single time."
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Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why are the legislative and executive branches of government seen as corrupt and bad, while the judicial branch (especially the Supreme Court) is so revered and respected?
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[
" It's important to note that things are always changing in regards to this question and people's personal views are also different. The Executive and Legislative branches are by definition run by a majority political party. The people within those positions are purposefully advocating for their ideology.\n\nThe judicial branch is supposed to not engage in any ideology and keep their personal views private. They are supposed to rule their cases purely on the law and try their best to set aside their personal views when making decisions. If you watch the State of the Union the Supreme Court sits before the President, but they won't clap or smile like other people in the room. They are supposed to at all times keep up appearances of impartiality. For example, let's say the President usurps his authority and puts out an assassination request on you, an American citizen, denying you your due process rights. If you take that case to the Supreme Court it would be very unfair if half the court was smiling and clapping while the President was addressing Congress and the nation about how he's really good at ordering his military to send a drone after people and doesn't care if they are US citizens or had a trial to establish guilt or not.\n\nThis is also why Supreme Court justice positions are for life. They are supposed to be above the politics and feel free to make decisions on cases based purely on the law and not public or personal opinion. They aren't supposed to fear losing their job because they make a ruling that is unpopular.\n\nHowever, everyone has personal biases and not every judge attempts to be impartial. Some, embrace it. For example, we currently have a Supreme Court justice who has publicly stated she hopes that by being a female latina woman she'd come to a better judicial decision more often than not than a white male by virtue of the life experiences her skin color and vagina provided her... not because she studied the constitution any better, but because she has brown skin and a vagina she suddenly believes she is better capable of interpreting the law. Additionally, Ginsburg recently has started going on talk shows and advocating for positions of a party platform and publicly wore her dissent around her neck after our new president-elect won the election. She has had to apologize a few times in recent memory for speaking out of punditry on a series of issues.\n\nSome also believe that the court gets decisions wrong and that they allow their political or religious views to influence their decisions on cases involving abortion, campaign finance, etc. When these issues should not be a factor any more than someone's skin color or genitals at interpreting what the law is.\n\nLong story short, not everyone has the same view that the Judicial branch is impartial and highly respected. There is something called Judicial Activism. This is basically what happens when the Legislative branch can't pass the laws they want, they hope to fill the Supreme Court with enough ideologues that they can get the court to redefine the law in ways that don't exist to fulfill their political agenda. And in many cases it works. This is why many considered the Supreme Court nominations under the next president to be so important. For example, one politician wanted to tear up the 2nd Amendment and the other politician wanted to hinder Roe v Wade and have a judicial impact on the status quo of abortion law.",
" The judiciary can not actually \"legislate from the bench\". Basically their only real power is to say \"no\" when it comes to the kinds of things that corruption pivots on. I mean you can buy a verdict, particularly one of criminal innocence, in theory. But even then, someone above you can just say \"no\" to the bad ruling.\n\nSo the judicial branch has vertical integrity that the other branches lack. There is no district congress, then congress of appeals, and then supreme congress. so in congressional matters you only have to corrupt one level to achieve a corrupt end.\n\nEvens so there are imfamously corrupted judicial regions. For instance if you have in intellectual property claim you _will_ prevail in the District of East Texas. So patent trolls always try to bring their actions there. And it's a huge financial windfall for the region. So that's corrupt as fuck, but the average person doesn't think they have to care.\n\nAlso grand juries tend to indict whatever comes before them with a basic rubber stamp. We even say they \"fail to indict\" when they actually do their jobs. The \"tough on crime\" mentality gives prosecutorial overreach a complete pass in this country. That's how we ended up with over-full for-profit prisons.\n\nSo really, the judiciary is generally less corrupt, and even where it is corrupt most people don't care until they get arrested or sued. And at that point it's too late to get upset about it."
] |
[
" The US government is split into three branches, and are arranged to have a system of checks and balances between them. \n\nThe Legislative branch (congress) makes laws. The Executive branch (the president) enforces the laws. And the Judicial branch (the courts) makes ruling on whether or not people have violated the law, as well as making sure that the law consistent with itself and with the constitution.\n\nIf the executive branch tries to enforce a law in a way that violates some other law, the judicial branch can strike down that action. The way to override that would be for the legislative branch to create/alter the law so that the thing that the executive branch wants to do becomes legal. \n\nAnd if any law that the legislative branch makes violates the constitution, then the judicial branch can strike down *that* law, which can then only be enforced if the legislative branch amends the constitution (which is **really** hard to do, and requires 75% of the states to agree to it).",
" Because that's not the way it works, and for a good reason. Each of the 3 branches has its own purpose when it comes to the law.\n\nThe Executive branch (the president) enforces the law\n\nThe Legislative branch (congress), writes the law\n\nThe Judicial branch carries out the law\n\n\nThe Legislative branch was broken into two branches to balance out the powers of large states vs smaller states, which was a great concern. The house of representatives is made up of a number of members divided up by proportion of the population in each state, so larger populous states have more member than smaller populous states. The senate on the other had was created because of concerns that the smaller states would be strong armed to the will of the bigger ones, so a branch was created where each state has a fixed number of representatives, 2, both branches have to hammer out and finalize a bill before it can become law, and thus in theory if a law is written that favors the bigger states over the smaller ones it will get killed because it won't pass the senate."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
What is happening in Greece? Why is everyone in Europe freaked out?
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[
" Greece is in trouble because of the money they owe and that they are not able to pay back. The economy is stuck, high unemployment rate, and the machine is not making enough money anymore to pay back its creditors. \n \nThis situation is going on for years and years now.\n \nIf Greece exits Europe, it means that they wont pay back the billions Euros they owe and it also gives a very bad example to other countries in the Union. \n \nEventually, other countries could also decide to leave the EU (aka Portugal, Italy, Spain), which could lead to the political and financial destruction of the Euro Zone (and this could be a major disaster). \n \nAs a global citizen, if Greece economically collapses and exit the Euro Zone, you wont be directly affected as long as you don't eat salad with feta and you don't pay your taxes in the Euro Zone. \n \nVery sad because this is an awesome country."
] |
[
" Because it's a bit more complicated than simply a debt problem. It was the massive capital influx into the periphery after the Euro was created that caused this. Suddenly, investors had these poor countries with a strong currency, which made them safer to invest. Money flew from the strong economies into the weaker ones.\n\n[As a result the wages in the periphery rose](_URL_0_). The problem with this is that the South has a competitiveness problem and our main strength (up until this point) was that labor costs were relatively cheap. Suddenly, we lost our edge, economies struggled and financial (Ireland) and housing bubbles (Spain) formed because money was easy to come by.\n\nNow, the shit has hit the fan. For one reason or the other, these countries need help because the money well dried up. Instead of making fair proposals to help the recovery, the troika (IMF, European Union and the European Central Bank) are demanding sharp cuts in an almost impossible deadline. And they're demanding these cuts in the face of great suffering and they are unwavering in any plea that the people of Greece have asked for.\n\nThe people of Greece are saying: Please give us more time to get ourselves together. And Germany is saying: No, you created this problem, you have to do it as we say. But the reality is that the situation in Greece is dire. Americans are furious for having a 7% unemployment rate? Greece has 25%. Their pensions are being slashed, their taxes are higher and higher. People have committed suicide because they don't have any more for the most basic things.\n\nGreece has almost no say in what they can do. Everything is imposed on them without much discussion, from countries that benefited greatly from the Euro. Germany is a powerhouse and the Euro is a weaker currency than their own would be, meaning their goods get cheaper to export.\n\nAnd if you know a bit about European History, let's go back a few decades to a Germany that was in crisis, being forced to pay an absurd amount of money for the damages of World War I, and to follow an unjust treaty imposed to them by other countries. They soon gave their support to the politician that spoke out against it: Adolf Hitler.\n\nCurrently, the Greek Parliament has 18 seats occupied by the [Golden Dawn](_URL_1_). A right wing extremist party that opposes any treaty with the EU as well as being anti-immigration and having several ties with anti-semitic vandalism acts and hooliganism.\n\nWorst of all, this crisis revealed the hypocrisy of the european integration project.",
" Greece isn't asking for a bailout really. What they're asking for is a change in interest rates and repayment schedules to something that is actually sensible, and in line with reality. In effect that's sort of a bailout, but it's not the massive loans of previous bailouts. \n\nBut even if it was, greece is in the mess it is, because it agreed to the last bailout, which gutted their economy. They should have (and still should) leave the euro, immediately. \n\nWhat the EU is asking for is madness. No country in the EU could sustain what the EU is asking for. They're asking for a primary surplus of 4.5% of GDP, which is essentially impossible unless greece could attract massive foreign investment. \n\n_URL_1_\n\nThe ELI5 ish, analogy. \n\nLets say you make 100 dollars a year. Things happen and you need to borrow 100 dollars, at 3% interest. So you've borrowed 100% of GDP. But now you only make 97 dollars a year all else equal, 3 dollars goes off to whomever you borrowed from. No now the reason you borrowed that money is that things are going badly - you're now only making 70 dollars a year, and you still owe 3 in interest. What was a debt of 100% of GDP has become 142% of GDP, and what was 3% of your yearly income on interest has become 4.5%. \n\nThe real numbers for greece are something like 343 billion dollars in income, \n410 billion in debt (120% of GDP), income which shrank to 242 billion dollars in income. They're paying more like 3% of GDP in interest. But government revenue is not all of GDP, and debt servicing comes out of government spending. \n\nThe EU rules about a 4.5% surplus - that is government revenue - expenditure ignoring interest rates is absurd. It's absurd for a lot of reasons. First, that translates into money that could be paid to employed people to do work in greece. Healthcare, police, schools etc. Second, 4.5 is more than should be needed. \n\nThe best way for the EU to get its money back is for the greek economy to recover (and remember, Greece has something like 27% unemployment, so there's around 1.5 million greeks who could be working, but aren't). There are lots of possible ways that could happen. But none of those ways are happening. So.... people need to start looking at solutions that might actually work, or at least make things better. \n\nOne last thing to keep in mind. The EU has open borders (though language still impose barriers to permanent moves). This makes anywhere doing badly in the EU essentially into detroit. All the unemployed in greece can just leave, and the most educated and capable do just that. Leaving greece worse off, and in a more difficult position to pay back its debts later."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why doesn’t the body return to its original shape after gaining weight after liposuction? Why don’t the fat cells come back?
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[
" Because you're only given a certain amount of fat cells. \nPeople that weigh 800 pounds have the same amount of fat cells as they did when they were 150 pounds, the difference is how bloated those fat cells are, so liposuction actually removes these fat cells- never a healthy option if you plan on living an active life because you're literally removing cells that store and give you energy."
] |
[
" Fat cells are stored energy so when your body runs low on its energy systems it will use the fat as a resource to fuel the body. This is why you should consume less calories to lose weight so your body can expend fat for energy. Muscles, unlike fat, does not come or go. It gets bigger or smaller through swelling of tissue after repairing microtears from lifting weights or putting stress on a muscle.",
" The fat cells actually never leave, until or unless that cell dies off naturally, as all cells eventually do. \n\nWhen you lose weight, you burn off the energy that the cell contains. This is like drinking the water out of a glass -- the glass is still there, but the content is less. \n\nThis is why it's very easy for a formerly fat person to re-gain the weight. The cells are already there, and are already used to storing excess fat."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
Why was the Iceland christmas advert about the orangutan banned for being too political?
|
[
" In the UK, TV broadcasting first started with the BBC, which is funded by a television licence. As such the BBC required no advertising to pay its way.\n\nCommercial broadcasting came along later, and with it came worries about the power and persuasive influence of TV advertising. Because of this laws, regulations and codes of conduct were drawn up to restrict what could be shown.\n\nOne of the very first things to be banned was any form of political advertising. Instead TV channels are required to give space during elections for parties to air their own Party Political Broadcasts.\n\nIt is this restriction that the Iceland advert has fallen foul of. Because the advert is not selling a service, but promoting a cause - it been judged to have contravened the above rules."
] |
[
" Because politicians have learned how to play people (theists and atheists alike) like a fiddle. \n\n\n\n\nThe arguments revolve almost completely around social issues now. Abortion, same sex marriage, welfare, things that honestly the government should have no say over.",
" Part of it is publicity, part of it is an effort to shift the [Overton window](_URL_0_). This is the idea that the public has a narrow range of ideas they consider acceptable, but if you deliberately push extreme ideas outside that range, you can shift it in your direction, as people try to pick a middle ground.\n\n\"Meat sure is tasty, but PETA says milk is genocide and owning pets is slavery. That's going too far, of course, but I did decide to go vegetarian at least.\""
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How are cranes transported, constructed and deconstructed in a construction site?
|
[
" As an example, a business site is being constructed directly adjacent to my office. The crane is assembled from modular pieces, big segments of 'tower.' These are trucked in n flat beds. \n\nA truck that extends a crane of its own is driven in, along with a pallet of numerous counter weights. The truck-crane assembles the tower pieces, using the counterweight to allow it to extend. Then it brings the pieces of the crane itself to the top of the tower, where they are assembled."
] |
[
" [This](_URL_0_) post was from a year ago, so feel free to check it out. But here's the top comment from the post if you're feeling lazy.\n\n > When a tall building, the crane is quite literally dismantled... piece by piece. Most cranes are designed to be easily taken apart. Usually the large crane will hoist up a smaller crane that is connected to the top of the skyscraper. This allows workers to detach pieces of the primary crane and slowly lower them back down to the ground. The mast itself and the base of the crane are lowered down by the same hydraulic rams that lifted them up, with each level of the mast being taken apart before the base is lowered.\nTo remove the second crane, a third crane is often sent up, even smaller, to lower the pieces of the second crane down. This third crane is small enough to be taken apart by hand and removed through lift shafts or other inner passageways, leaving the skyscraper intact and all the crane pieces disassembled on the ground.\nSometimes cranes at the center of complicated tall buildings cannot be removed like this and in those cases the pieces are taken away by powerful helicopters, although this is a much rarer method.",
" Cranes used to build tall buildings are initially assembled with another smaller truck-mobile crane at ground level, and then are capable of adding sections of tower to themselves so they can grow as the building is constructed. \n\n_URL_0_\n\nThe process is reversed to remove them."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
How does tilt-shifting a photograph trick the brain into thinking it's looking at a small scale model?
|
[
" It is only because we are used to looking at highly magnified photos of small things, and recognise what these photos look like.\n\nThe appearance of a photo of something small is all about the size of the lens, compared to the size of the thing being photographed. When photographing a tiny insect, the camera lens can be larger than the insect. It is hard to focus this, so only the insect is in focus, and the things just in front of and just behind the insect are out of focus. You do notice this, and remember that photos of very small things look like that.\n\nOur eyes work like cameras, so what we see with our eyes also follows this pattern. But most people cannot focus close enough to really see this effect.\n\nAt 'tilt-shift' photo is one where that pattern of focus is produced, either by tricky use of special lenses, or by artificially blurring parts of the photo with a computer after it is taken. Because the pattern of focus reminds us of those photos of small insects, our brains tell us that this is a photo of something small.",
" When we look at various photos during our life, we \"learn\" that photos with a very small sharp plane-like area somewhere, surrounded by blurry areas, are usually photos of very small things taken in a close-up situation. This effect occurs because of the way the image in the camera is generated optically. \n\nWith tilt-shift lenses or Photoshop, you can simulate this effect quite well also for large scale scenes by composing sharp and unsharp areas in a similar way, thus also tricking the brain into applying the learned fact that this has to be a photo of something very small.\n\ntl;dr: Your brain knows how photos of small things look like, and you can fake that effect artificially for large things, too..."
] |
[
" It's because a scene viewed close up, either by the human eye or a camera lens, has one very distinct visual characteristic. A tilt-shift lens can simulate that characteristic. I'll explain.\n\nCamera lenses can only truly focus on a single distance from the lens at any given time, however anything close enough to that distance will appear to be focused as well. The size of that nearly-focused area is called the \"depth of field\".\n\nThe closer the subject is to the lens, the smaller the depth of field, so more of the image is out of focus. You will see this often in photographs of small objects: insects, flowers, etc.\n\nThe tilt of a tilt-shift lens can be used to approximate the look of a small depth of field, by forcing certain areas out of focus. Your brain recognizes this look from all the times in the past that it has seen small objects close up, and mistakenly interprets the subject as a miniature.\n\n**Edit:** removed an unnecessary speculation",
" When you look at objects close up, your eyes focus on them and the surrounding objects come out of focus. When you look at things far away, your eyes focus on that longer distance and objects around what you're looking at still in focus. So your brain has become used to small things, which are close up when you look at them, being surrounded by out of focus objects while far away things are surrounded by objects also in focus. Tilt shift causes objects around the focused object to be blurred, so it gives your brain the signal that you're looking at small object close up."
] |
Given a question, retrieve the highest voted answers on Reddit forum
|
eli5
|
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