Subset (10)

eli5 · 25k rows

Split (1)

train · 25k rows

query stringlengths 20 300	positive listlengths 1 1	negative listlengths 1 1
How do people learn they're allergic to something?	[ "Ideally, you go to an allergist as a kid. They prick your arm a bunch of times and add allergens and see which cause a reaction. Many allergic reactions get worse as you get older. A child may have much more mild allergic reactions to peanuts, but as an adult that reaction may be deadly. That's why you should watc...	[ "In short, chemistry! For a longer answer... There are a lot of standard chemical 'building blocks' and standard methods for attaching them. That's pretty much the nature of chemistry. You can see [three different lab syntheses of melatonin here](_URL_0_). So how do you know that what you've made is actually melato...
What would happen if a desert started to get a lot of rainfall?	[ "Hopefully you'll get better answers but to my limited knowledge, it's not so much about the lack of rain so much as it is the soil not absorbing it. So in certain deserts when there is a huge rain fall the soil locks up like cement, causing floods." ]	[ "The sugar in the candies is causing the a change in the relative concentration of sugars (and other things) compared to the cells in your cheek. In an attempt to re-balance the concentrations, fluid from your cheek flows into your mouth. Leaving your cheek, dry (sore) and wrinkled." ]
How does the NBA draft work?	[ "You do realise that Australia has the AFL Draft right?" ]	[ "This CGP Grey video does a really good job of explaining it all. _URL_3_" ]
Why are there that many homeless people in california?	[ "well... not all homeless are really homeless. many are panhandling as a career and can do quite well at it. those that are homeless probably know places to find restrooms, public places like libraries, mass transit, ect. though Im sure some just pee in an alley if its more convenient. as for why california? might ...	[ "Different gasoline taxes. Different distances between the nearest refinery. Different blend requirements for the gasoline(California). Different requirements on who's allowed to pump gasoline into a car(Oregon/New Jersey). Different minimum wages. Different property values for a gas station sized plot of land. Dif...
What does US shale have to do with falling gas prices?	[ "From what I've heard, shale is only profitable to mine for oil when oil is more than about $60 per barrel. Trying to lobby for permits to extract the oil from the shale takes a long time. If OPEC can continue to push oil prices down below that $60 mark, then everyone important loses interest in shale, starting the...	[ "Repeal of Glass-Steagall caused it. There really isn't any controversy among financial experts, including Greenspan. It was Glass-Steagall that prevented the banks from using insured depositories to underwrite private securities and dump them on their own customers. This ability along with financing provided to a...
If I tilt my head to the side when I'm looking at an image, the image seems to stay "upright" until around 90 degrees or so, then it suddenly snaps to being a rotated image. What kind of processes are going on in the eyes and brain?	[ "The brain's occipital lobe is capable of making corrections to \"raw data\" from the eyes based on assumptions based on other sensory input. When you look at the slightly crooked image, your occipital lobe is able to compensate and show you what you \"want\" to see by using data from your other senses, in this cas...	[ "Your body is trying to regulate it's temperature constantly. Areas like your hands and feet can be allowed to get cooler without any damage, but the core of your body (especially your brain) must stay within a degree or two of 37 degrees Celsius otherwise you will die very quickly. Your eyes are embedded in y...
Why does it seem like women prefer me more when I'm in a relationship compared to when I'm single?	[ "Having a job implies you're employable, whereas not having a job leaves it in question. Apply this to relationships." ]	[ "You open a pizza shop and hire your nephew to take phone orders. For the first few weeks, you only get two or three calls per evening, so you get by with just one phone line and only your nephew assisting you. Then, someone posts a fantastic review of your place on reddit and the business explodes. Now you've got ...
How is it possible that socalled "red meat" affects our body more then fish and chicken?	[ "Red meats have a much higher concentration of myoglobin, a protein that makes red meats look \"redder.\" Myoglobin is similar to hemoglobin, the protein that makes your blood red and both proteins also contain iron. Myoglobin and hemoglobin are used to store oxygen, one of the vital compounds needed for our body t...	[ "If you are looking at it from an emissions or energy standpoint then yes. [This](_URL_0_) Peta site is a good source of info, such as \"It takes more than 11 times as much fossil fuel to make one calorie from animal protein as it does to make one calorie from plant protein.\" Interesting information on burger prod...
Why are math, tech and science majors paid more than literature, art and social studies?	[ "Basically, you should rarely think about pay as anything other than \"how much money can i likely make for my boss\" and secondly \"how hard would it be if i left.\" The idea of jobs being paid according to importance, or worthiness, or \"value to society\" is very rarely the case. It is \"how much is this work wo...	[ "I would check out It's Okay to Be Smart on youtube. They do a good episode on this (im bad at links)" ]
If the US replaced all of the states' currencies with the national one, why is Bitcoin allowed?	[ "Because Bitcoin is not a state currency. It's not backed by any government at all." ]	[ "Greetings everyone. In the few minutes this sub has been up, it's attracting sub-standard responses. Just a reminder of a few of the rules: * no responses covering events/conditions post-1994, per this sub's \"20-year rule\" prohibiting discussion of current events * no anecdotes * no speculation OP: your question...
Why does the label on my MSG say it has 0% protein?	[ "Nutrition labels are mandated by law. Like when you buy a bottled water, the nutrition label tells you that it has 0% everything. The deinition of what's protein and what's not is determined by the FDA (in America). _URL_0_" ]	[ "The whole bag is made of that material, it's just the front is printed to fit the advertising goals of the company. It's a cheap, hermetically sealable material, so it doesn't cost much to use." ]
What's more economically efficient to boil my water, an electric kettle or an electric stovetop?	[ "An insulated kettle with the element inside. That keeps waste heat to a minimum." ]	[ "From [IPCC](_URL_1_) lifecycle emissions in gC02eq/kWh min/median/max: * Hydropower 1.0 / 24 / 2200 * Geothermal 6.0 / 38 / 79 * Nuclear 3.7 / 12 / 110 * Wind onshore 7.0 / 11 / 56 * Wind offshore 8.0 / 12 / 35 * Concentrated Solar 8.8 / 27 / 63 * Solar PV -- utility 18 / 48 / 180 * Gas 410 / 490 / 650 * Coal 740 ...
Do proteins dissolve in water?	[ "It is not true that all proteins are soluble in water. Proteins are typical macro-molecules having a large range of solvents in which they dissolve including water. The property of solubility of different proteins is governed by their three-dimensional folded structures. Many proteins have exposed polar groups wit...	[ "Its all about density. Specifically, whether or not the average density of everything below the water line is more or less dense than water. For example, a solid iron bar will sink because iron is more dense than water, but a metal boat can float because a lot of what is under the water line is just air (because t...
If we devoted one year to working REALLY hard on fixing up the environment, could we stop global warming?	[ "For one year? No. Halting humans' effect on the environment will require a permanent shift in how we act. At the moment, this permanent shift won't be too painful - however if we put it off for more than a couple of years it will be. It would require everyone to produce less greenhouse gas - to use less electricit...	[ "What makes your beliefs the right ones? To you they are right but to the leaders of other countries they are not. Leaders in that country are probably asking each other the same thing about countries where homosexuality is accepted. They will be wondering how the leaders of those countries can allow such a thing. ...
Did historical pirates actually use the words and phrases we currently associate with them?	[ "The pirate accent is West Country English, and it is that way because the pirates in \"Treasure Island\" by Robert Louis Stevenson were from that part of the world. At least that's what I was always told." ]	[ "Hi - we as mods have approved this thread, because while this is a homework question, it is asking for clarification or resources, rather than the answer itself, which is fine according to [our rules](_URL_1_). This policy is further explained in this [Rules Roundtable thread](_URL_3_) and this [META Thread](_URL_...
What are the benefits of Stop Motion Animation over CGI?	[ "High quality CGI can be vastly more expensive than other methods. Of course, each creator has to choose the artistic style they want their work to be in, that is certainly a consideration -- but so is cost, and it may be a tradeoff" ]	[ "Are you watching blu ray? Is it a good transfer? (Example: despite being made in the early 80's Blade Runner Ultimate Director's cut blu-ray is one of the best you can buy) How good is your blu ray player? Is it a ps3? All of these factors contribute to what you determine as a home viewing experience being inferio...
Does the spin of all the particles in an atom's nucleus face the same way? If so, does this also affect the electrons?	[ "No, they don’t all face the same way in general. There are special cases, like the deuteron, where the proton and neutron spins are aligned in the ground state." ]	[ "Normal microscopes use visible light, which reflects off of the object you are looking at, back through the lens, and into your eye. The constraint to that is that light has a specific wavelength, and it is very difficult to see things that are smaller than the wavelength of light you are using. Electron microscop...
Homophobia in Russia	[ "As other commenters said, religious thing is more important than you might think. One more fact to consider is, in USSR homosexuality was illegal. But also there's a fact that \"russian anti-gay laws\" is for large part is an anti-russian propaganda. There's currently no law against being gay. There's a law agains...	[ "Hi, I've approved the post, but just a note to you and potential respondents: this subreddit has a 20-year rule against discussing current events, so any answers will have to cut off at 1997. If you're looking for answers that can include 1998-2012, do consider x-posting elsewhere, eg. a foreign affairs sub like /...
In March of 2012 It was 80 degrees this whole week where I live, this year the week wont top 30. Is this attributable to climate change or just random variation?	[ "Global surface temperatures have increased about 0.74 degrees C since the late 1800s ([source](_URL_4_)). Global warming isn't going to cause a huge swing over the course of one year; it's a very slow process." ]	[ "Air is like fluid. Different densities can stack and create fronts. Sometimes these stacks or fronts, are huge and create long lasting weather patterns. Sometimes they are thin layers and can pass in a day or two." ]
How can a person be non-verbal? Like, what is going on with their brain that they can't speak?	[ "Imagine you are going about your business on a normal day. A genie appears and gives you sixty seconds to respond to this question: \"You will receive 60 - t million dollars to donate to a charity to prevent world hunger deaths, where \"t\" = how many seconds it takes you to respond to this question. Also, I will ...	[ "Your voice cords need a certain minimum air pressure to get to vibrate and create tones. Without them vibrating you're getting a toneless whisper." ]
Why do teachers get tenure?	[ "One of the main justifications is to guarantee academic freedom. A teacher has a responsibility to educate their students to be best of their knowledge and experience. Sometimes, this isn't always what's most popular. Tenure ensures a teacher doesn't have to be worried about being fired because they're teaching so...	[ "This is a very common question. You can use search to find [all the other really good answers](_URL_0_ ). This is instant, and faster than ust typing in your question every time. It's a way of cheating elections. Read the others, and then ask a more specific question." ]
Two Drones Flying Away From Each Other Along the Equator; Does the Earth's Rotation Affect the Length of Ground Covered By Each Drone?	[ "Two quibbles: \"Variable wind resistance\" doesn't make much sense in this context. \"Variable wind\" does. \"Fixed speed\" is meaningless unless you specify with reference to what. Ordinarily, an aircraft flies at a fixed airspeed: i.e., speed with reference to the airmass. The rotation of the earth will have z...	[ "In simple terms, most circuits that make sound or play back digitally recorded sounds use a timing circuit (like an oscillator) to send out the sound waves at a constant rate. More expensive toys will use crystal-based oscillators and low-battery cutoff circuits to keep things from getting funky as the power level...
Did the Ostrich ever have a flying ancestor, or does it have yet to evolve flight?	[ "Ostriches definitely had a flighted ancestor! I have an [answer on another post](_URL_0_) that talks about the evolution of flight in dinosaurs, and birds are (for the most part) flying dinosaurs. More than that, the current thinking is that flight was lost multiple times in ratites, the group that includes the os...	[ "What about a fly buzzing around? They're not attached to the bus so therefore don't benefit from the momentum of the moving vehicle so why don't they splat into the back of the bus?" ]
Why has auto-correct in Word been unable to tackle transitory letters between words yet?	[ "Word autocorrect is a dictionary file, meaning you have a misspelling associated with the correct spelling. For example, \"odg\" might be in your auto correct dictionary to \"dog\". It is not really context aware, so it looks at each spelling mistake in isolation." ]	[ "Because they would get sued. The legal system isn't like some kind of beep-boop robot that overlooks totally obvious loopholes. Any company that claimed \"No, we were really advertising the endorsement of Bill Gates, plumber, from Bumfuck, Nebraska.\" would get laughed out of court. As /u/Snewzie pointed out with ...
Why do retail stores want fewer products in the store during their yearly inventory?	[ "Inventory involves counting every item in the store. It's horribly boring. If you can reduce the stock significantly, you can do inventory a lot faster. I'm not sure if there's any research into the cost benefits of liquidating stock before inventory, but from a human perspective, it makes a huge difference." ]	[ "Short answer, money. Slightly longer answer: religion, anti-intellectual movement, funding, social issues, and things that are used to ‘measure’ performance. Tests are easy to use to see if a kid can produce the answer to a given question. Which is great if you are playing Jeopardy but generally useless day to day...
What gas is inside a sealed coconut?	[ "[This paper](_URL_0_) might be what you’re looking for. Essentially it’s a mix of various volatile organic compounds." ]	[ "Humidity. Ever wonder why farts stink so bad in the shower? Humidity. Air conditioners take humidity out of the air, so you can't smell the scents in the air as well. When you switch to fan mode, no humidity is lost, so you can smell all of those scents." ]
Can anyone explain the ergodic hypothesis simply?	[ "The ergodic hypothesis is the statement that all states of a system with a given energy are equally likely to occur over long periods of time. Adopting the ergodic hypothesis allows one to compute the average behavior of a system over time by instead performing an average over states." ]	[ "It is pretty simple. The average of whatever experiment you are doing (flipping coin/rolling dice) should approach the expected value the more times you repeat the experiment. For example, if you are rolling a die, the expected value is 3.5. If you only roll the die a couple times, you might have averages pretty d...
How does a "nationwide saline shortage" occur?	[ "A majority of its manufacturing is done in Puerto Rico and the restoration of the island is not a priority for the current administration. It may just be ‘saltwater’, but it’s medical grade and there are very stringent regulations on its manufacturing to ensure quality and patient safety. The facilities must be li...	[ "An important incident was the loss of the [five Sullivan brothers](_URL_1_) aboard a single ship in 1942. The incident resulted in a 1944 [film](_URL_0_) and also helped inspire a change in [policy](_URL_2_)." ]
Can radiation be 'removed' or neutralised in anyway? (Even if just in theory)	[ "By removing the radioactive isotopes producing it. Without this source, the radiation in an area will escape/be absorbed very quickly. This can be done by sealing the material in concrete or something else dense enough to absorb all its radiation. The problems start when the source material is particulate or solub...	[ "For the most part, people who don't have cancer are people who are beating it successfully. We all have cells that are cancerous and we're constantly beating them back. What we mean when we say a person \"has cancer\" is to say that they've not been able to beat it. So...to answer your question, probably not. Ther...
How can states legalize marijuana when using/having it is a federal offence?	[ "Through the 10th amendment. Powers not expressly delegated to the federal government in the constitution are reserved for the states. The only way to (legally) grant the federal government additional powers is by constitutional amendment. States with marijuana initiatives are asserting that the federal drug laws a...	[ "The word is that the Denver Colorado dispensary was funded by money received from Mexican drug cartels. The DEA got word through an informant and shut it down. Tldr: local$$= ok Cartel $$= fed jail" ]
Why is the US dime smaller than the nickel?	[ "The value of coins used to be based on the precious metals they contained. Pennies were copper, and other coins were silver, which is why the dime was smaller than a quarter or half-dollar, and about the size of the less valuable penny. There used to be a coin called a half-dime, which was even smaller than a dime...	[ "America has regulations for this: _URL_0_ > * Illustration must be less that .75 or more than 1.5, in linear dimension, of the currency > * Illustration must be one-sided. > * Destroy or erase anything used in the making of the illustration that contains an image or part of the illustration." ]
Why are car rides soothing for babies?	[ "Some people will say it's because the car environment reminds babies of the womb. That may be true. It's not a testable hypothesis, though. The noise and vibration of the car's engine create a monotonous sound and vibration that allow a baby to relax; there is nothing new to see, hear, feel, or do because the car'...	[ "Song lyrics rhyme and have a set pattern. Brains love patterns, because they are predictable. Easier to work when things are predictable, and your brain is working all the time." ]
What would happen if you nuke a nuke?	[ "The non-detonated nuclear bomb would be destroyed. To detonate a nuclear bomb, a, very specific set of circumstances and mechanical processes have to happen." ]	[ "This video created by Vsauce 3 (Jake Roper) does a very good job explaining this: _URL_1_ I hope this answers your question. He also did another video on a simmilar line of - could you survive: _URL_0_" ]
Ok, so how incompetent was the Italian military really in WW2?	[ "I don't think it was totally incompetent. The RMI (The Italian Navy), despite being vastly outnumbered and outgunned by the Royal Navy, put up a pretty good fight in the Mediterranean in the early years of the war. The rank and file, as well as the actual line officers of the navy were pretty competent, but it suf...	[ "Here are some others to check out: Marincola, J. (2011). Greek and Roman historiography. Oxford: Oxford University Press. Kraus, C. S., Marincola, J., Pelling, C. B. R., & Woodman, A. J. (2010). Ancient historiography and its contexts: Studies in honour of A.J. Woodman. Oxford: Oxford University Press. Pausch, D. ...
Distance is proportional to the square of time	[ "When you're accelerating at constant rate, yes there's a linear relationship between distance and the square of time... How about a little more context about where you heard this?" ]	[ "Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That's relativity. Albert Einstein" ]
Why are old 90s PC games so twitchy and fast on current computers?	[ "Because many of them tie their internal timing to the speed of the cpu clock, making the game run faster the faster your cpu is, not unlike how many console games on PS2 and earlier were coded. Not all games were coded like this, however." ]	[ "The models used in those programs are much more complex, for one. Second, the algorithms used to render those scenes are much more complex. They take into account things like reflecting light and such. The more reflections you take into account, the more processing has to be done... exponentially." ]
Do all warm-blooded animals have the same body temperature or does it change between species?	[ "Here's a list of a few common ones. ([Link](_URL_0_)) The thing is, most of these animals are actually quite closely related in evolutionary time, so their proteins are similar and will break down at similar temperatures. That being said, birds are the warmest on that list, which makes sense because they're the mo...	[ "B0Boman's explanation is basically right. The rate of radiative heat transfer depends on the temperature of the reservoir (because the reservoir is radiating heat to the object; radiative power varies as T^4). A window that \"sees\" a wall that's at freezing temperatures will radiate less heat than one that \"sees...
Who sold the United States all those guns?	[ "The Dutch republic was one source of weapons and ammunition. They were sold to the Americans via the small island of St Eustacius (in the Carribean). This arms trade was one of the reasons for the fourth Anglo-Dutch war, which the Dutch, badly, lost. See .e.g. Barbara Tuchman's First Salute." ]	[ "Because most people who do not live in a cave realized decades ago that this has been going on. Very few people and/ or countries are that naive, not to know that this is going on in every country in the world" ]
Why haven't we received any video footage from the Curiosity Rover on mars?	[ "[This report on the NASA website](_URL_0_) written by the engineering camera team lead includes the reasoning behind the lack of video footage. They do actually take video footage, just very few as the files are very large and their downlink each day is limited. As you mentioned in your question the still photos t...	[ "A show like Jimmy Kimmel isn't on YouTube for the revenue, they're on YouTube because it's free advertising. They don't want you to watch all the back-episodes, they want you to tune in and watch the show as it's airing." ]
Parents of identical twins, how did you tell your twins apart when you took them home from the hospital until they became old enough for phenotypical differences?	[ "My sister has identical twins, they put a dot of nail polish on the big toe to tell them apart. Turns out it isn't really necessary, there are slight differences that parents get to reliably know." ]	[ "People are tribal, by instinct that comes from our DNA. We naturally want to identify who us \"us\" and who is \"not us\". Any group of more than about 200 people will tend to break into smaller groups. This instinct is so strong that we look for reasons to form these different groups, even if the reasons are sill...
If alongside almost a decade of schooling, Medical Doctors are required to pass three 9 hour medical exams before they can practice, why aren't Presidents required to sit through some comparable test of competency?	[ "Once you start including strict requirements for public office or voting, it becomes very easy for the party in power to bias the fuck out of the system in their favor & exclude people opposed to them. It's expected that the voters will have high enough expectations of their leaders to ensure that unqualified cand...	[ "It takes minutes to safely fill a battery, because your electricity is driving a chemical reaction. You can fill a super capacitor in milliseconds, provided you have a suitable power supply. Similarly, it takes minutes to safely drain a battery, the chemical reaction tends to generate heat. You can dump a supercon...
Follow-up to the "How 'complex' does life have to get to require sleep? " post earlier .... Have virtual neural networks ever demonstrated sleep like behaviour?	[ "A challenge with virtual (artificial) neural nets is that they largely demonstrate the effects you train them to. I've, for instance, trained a recurrent neural net to replicate a sinusoidal output and I could therefore interpret that as a \"wake\" and \"sleep\" cycle if I like. You'd need complex and uninhibited ...	[ "Google deep dream was developed as a test of Google's image recognition software. Basically, they're running it backwards - rather than taking a picture of a dog, and asking the software \"Is that a dog\"; they take a random picture and ask the software \"show me what looks like a dog\". By seeing what the softwar...
How does my body filter out the stomach acid that mixes with the water I drink, so I don't pee acid?	[ "You don't filter it out instead it is neutralized by sodium bicarbonate secreted in the Duodenum (the first part of the small intestine directly connected to the stomach. stomach acid + sodium bicarbonate =salt + water + carbon dioxide (that you breath out after transported to the lungs)" ]	[ "Here is a good video on what you're talking about: _URL_0_ Basically the esophagus and the trachea are separated by the epiglottis. So when stuff goes down the wrong tube it means your food went down your trachea instead of your esophugus." ]
How come you can feel whether or not your flatulence is going to smell very bad or not at all before it even leaves your body?	[ "You can't. What you're experiencing is a [confirmation bias](_URL_0_). Basically, whenever you correctly predict whether or not your fart will stink, you reinforce the belief that you can in fact predict it. When you incorrectly guess, you tend to ignore the fact that you were wrong. You can make educated guesses ...	[ "The hot pan causes water from the sausage (or whatever you are cooking) to evaporate quickly. This forms a sort of cushion of gas (water vapour) between the food and the pan, allowing movement with far less friction, so the food moves around a lot more. This is the same effect as when water drops on a hot iron jum...
Why do college applications and job applications even ask for your race, ethnicity and gender? Wouldn't it be more fair to screen applicants without that knowledge?	[ "For colleges there are scholarships and grants that are limited to specific races, ethnicities, and genders. For both jobs and colleges they need to know that information for legal purposes in case they get sued for discrimination in the future." ]	[ "Your credit report itself is free to view once per year from each of the three credit reporting bureaus, Experian, TransUnion, and Equifax. You can look at it by going to _URL_0_ and entering in your information. The number used to report your credit score, the FICO score, is proprietary information and it is ca...
How serious is an accusation of malicious selective quotation? [this is in the context of the Holocaust, so I'm nervous]	[ "Honestly that's what we historians do sometimes. We find the evidence we're looking for, whether or not it's there. What I mean is, if you look for something you'll generally find it even if it's not there. Weber talks about doing this in ~~Imagined Communities~~ Peasants into Frenchmen. He says that he finds evid...	[ "First off, don't use the term 'leech' - it implies that you do LOTS of downloading. Second, you won't get a dismissal; the MPAA/RIAA would LOVE to get a court ruling that says you can't download copies of stuff for which you own (other) liceneses." ]
Why is being too loud rebuked by another loud, prolonged sound? (SHHH!)	[ "In the grand scheme of things that SHHH! is going to attract your attention and through conditioning we are programmed to associate that sound with quieting down." ]	[ "Imagine you wanted to send a digital file to a friend of yours, but all you have is a telephone and the binary data contents of the file. You tell your friend \"when I say beep you write down 1, when I say boop, you write down 0\", and then you read the contents of the file to him over the phone \"beep beep boop ...
Why does the moon appear to tilt on its axis over the course of its transit across the sky each night?	[ "_URL_0_ Imagine standing inside this so that it was whirling around you but you were flat and level with the ground. if you looked at someone at their highest point, they would seem to be inline with a vertical line in the sky/perpendicular to the horizon, because their tilt (relative to vertical) is directly towa...	[ "If you have thin film of transparent material the light reflect on both top and bottom surfaces of this film the additional distance the light that reflect on the bottom of the film makes difference in the phase of the light wave function. As the phase of wave functions of the same light are shifted now, they star...
Does metal tarnish/corrode/rust in space?	[ "Well I'm a little late to the show, but here's [an article from New Scientist](_URL_1_) that discusses corrosion in space (paywall warning). Additionally, the wiki article on [corrosion in space](_URL_0_) provides several good sources for information on the topic. Searching for 'corrosion in space' or 'corrosion ...	[ "Me and a buddy of mine at a NASA internship got a chance to get inside the JPL cleanroom the Curiosity was assembled in. He had to take 2 special showers before he went in, and wore a special anti-static robe, mask, and hairnet. Before they let us in they detailed the extraordinary precautions they take before let...
Is there a material that can change permeability based on electric charge?	[ "There are piezoelectric valves that can handle some relatively extreme pressures and operate with a great deal of precision. They're used in pneumatics as well as vehicle fuel delivery. I think that tech misses the point of your question, though. The piezo crystal material is made to change shape in front of an or...	[ "Quoting [Wikipedia](_URL_0_) (a bit naughty, but it's a nice way to express what I think): > The proposed theory is inconsistent with quantum mechanics and critics have ruled it out on those grounds. Which is essentially saying what you pointed out, yes. If what they're doing is as easy as it sounds - just runnin...
Could strong radio wave bursts be used for space ship propulsion?	[ "Yes this is pretty much what a photons rocket is. You can use photon momentum to propel yourself. However the thrust to power ratio is really bad. The maximum electrical power that can be generated in space at the moment is in the order of a hundred kilowatts. From memory this gives you less than a millinewton of ...	[ "Scooby Doo really confused me as a child when Shaggy \"threw his voice\" across the room to distract the monster. Humans cannot do this, it's impossible. A single directional speaker can, but we are like normal speakers and eminate sound waves in all directions from our mouths." ]
Is there footage of German soldiers swearing loyalty to Karl Dönitz and saying "Heil Dönitz"? I have been unsuccessful in my search so far. Audio only is also OK.	[ "I don't think this exist. The Dönitz or Flensburg government existed only from May 2 to May 23, when they were arrested and the Allies took control of all government functions in Germany. While they notably signed the unconditional surrender of Germany, I do not think that any swearing-in ceremonies took place bet...	[ "The Papacy responded by attempting to convert the Mongols. The Order of Preachers, or Dominicans, were usually assigned the task although it is likely Franciscans were also involved in the effort. Initially the local leaders were curious about the Christian religion and had many misconceptions, including the idea ...
Why online videos featuring advertisements play perfectly during the ad, but may barely buffer for the featured video?	[ "Video sites will often cache popular videos on a server that is very close to you. So an advert, which is viewed by many people, will be streaming from a nearby server, but the actual video, which may be something a bit more obscure, is being served from the other side of the world." ]	[ "Depends on the country. Some countries have laws in place that ensure equal service for all providers using the same network, i.e. the network owner aren't allowed to diminish the service in any way for providers who \"rent\" their network. As for your particular example, they're both owned by the same corporation...
How would a nonbaryonic dark matter blocks collision behave?	[ "The general assumption is that it would just pass through. It's actually visible with telescopes too ! The [bullet cluster](_URL_0_) is the most famous example of this behavior. What is displayed here is in red is \"usual matter\" (galaxies, gasses, ...) while in blue is what is thought to be dark matter (inferred...	[ "[Here's a java demo of a double mass-spring system](_URL_3_). The motion of these types of systems can often be described as a sum of [normal modes](_URL_4_). In the geometry you described, a common normal mode is for the masses to sort of [pass the oscillation back and forth](_URL_0_). There are plenty of other s...
Shouldn't trained crew members sit next to the emergency exit doors over the wing? Why are untrained passengers who can panic seated there?	[ "The number of lives lost each decade that could have been saved by having a professional door opener is probably statistically indistinguishable from 0 per year. Compare that to the cost of paying for at least 2 professional sitters on every flight and the cost of not selling all those seats. This cost either come...	[ "Lots of airlines use the hub and spoke model. Rather than have a flight from every city to every other city, they have flights from the small cities to a few big cities, called \"hubs\". You then fly from the hub to your destination city, or perhaps to another hub, from which you fly to your destination. So let's ...
How can we measure how much dark energy or dark matter there is?	[ "We look at galaxies and measure how much visible mass there is. We notice that hmm, there simply isn't enough mass in those stars to hold that galaxy together with gravity. It would need at least 3 times that mass to hold itself together, yet, it seems to be fine. We deduce, then, that there is some form of matter...	[ "We do use antimatter currently for practical uses, ever heard of a PET scan? It would be the ultimate energy storage medium because gathering meaningful amounts of antimatter from nature is impractical. The best place to find it now is in the van Allen radiation belts." ]
Why north and south Korea want reunification yet can't achieve it?	[ "Each side wants reunification on their own terms. North Korea wants all of Korea to worship the Kim family, which isn't going to happen. South Korea wants all of Korea to be a modern country, which won't happen as long as the Kim family remains in power." ]	[ "There's an experimental plant called [ITER](_URL_0_), still under construction. The trouble with fusion is that you're basically putting the sun in a bottle, but we're still figuring out how to make the bottle." ]
How does the Pauli exclusion principle keep neutron stars from collapsing?	[ "Neutrons are fermions, and fermions obey the Fermi-Dirac statistics. This means that no two fermions can be in the same quantum state. This is called the Pauli exclusion principle. Now if you take a starfull of neutrons and start squeezing them, Pauli exclusion principle requires you to excite the neutrons to high...	[ "Alzheimer's disease involves amyloid plaque. No one quite knows why, although there are theories. [For some reason, amyloid protein breaks down and forms \"plaque\", which are blobs of goo that the brain can't remove.](_URL_0_) Alzheimer's also involves tangles of Tau protein, which is a structural support that gi...
In American football, other than the quarterback, why do most players never pass the ball?	[ "Well it's not their job or position. Each individual position has a specific job. The quarterback's is to pass. The running back's is to carry the ball. The wide receiver and tight end's is to catch. The Offensive Line is to block. It's like asking why the shortstop doesn't pitch in baseball." ]	[ "Sure there are. Roman consuls (equivalent to a presidential office) were expected to lead Rome's armies in times of crisis, which they did. In the late republic and on, Rome was dominated by military men like Marius and Caeser, who all led men into war and fought alongside them. William Duke of Normandy, before he...
Do all galaxies have a very massive object at their center? If so, is it necessarily a black hole?	[ "No and no. Many galaxies - such as the [Large Magellanic Cloud (LMC)](_URL_2_) have no obvious centre. The LMC has many high-energy sources. Some are probably neutron stars, and some may be black holes. There is no exceptional mass in the LMC centre. Although the LMC is clearly a first-class galaxy, it's not a cla...	[ "When a lot of stuff floats around it tends to group up... as those groups form they get more and more attracted to eachother. The more stuff there is the more gets attracted (gravety). Eventually there is so much stuff that the middle gets very hot! Everything there turns into this super dense ball. it keeps pulli...
Why does Americans associate Liberalism with Socialism?	[ "The shortest answer possible is that in North America, the word \"liberal\" became associated with the liberal application and/or proliferation of legislation. To support a liberal governmental policy is to support greater powers of law and more laws and regulations. The word \"conservative\" became the opposite, ...	[ "\"Just about everyone here\" Where is \"here\" for you? It sounds like your question's premise is based on a small sample set based on personal observation. Before your question is addressed, you should be making sure the premise is valid..." ]
How do scientists go about directly measuring entropy?	[ "I wrote [a brief PDF collecting ways to relate entropy and entropy changes to other, more easily measurable, thermodynamic quantities](_URL_0_)." ]	[ "It's a mix. There'll always be a human element but new technology is always being introduced. Players do wear things that can track things like how far or fast they're running. When I was in college they always made a big deal when ESPN came to talk to the statistics majors and hire a few to work for the company."...
How does the stock market work?	[ "People buy and sell portions of ownership in companies. That's what a stock market is. How they work? That's why you're going to business school, to learn! In reality, the answer is too long to type here." ]	[ "This CGP Grey video does a really good job of explaining it all. _URL_3_" ]
Why is everyone in Dubai so rich?	[ "Not everyone in Dubai is rich. There are far more millionaires in London or New York. The average income is high for a developing country but lower than the following countries, for example: * Australia * Austria * Canada * Netherlands * Germany * Sweden * USA Would you say everyone in those countries is \"so rich...	[ "Supply and demand. I know this is a simplistic answer, and I'm not trying to be flippant, but that really is the answer." ]
What is all that noisy crap an inkjet printer has to do before it prints anything?	[ "If somebody pushed your buttons forcing you to immediately wake up and get to work chances are you'd grumble a bit to." ]	[ "Do you ever repetitively click a pen? Or jingle the change in your pocket? Or chew your nails? Or throw a baseball with a friend or your kid? Or play with a stress ball? Or... Or... or... or... Why do people do those things? I think you're right that you're probably over thinking it and it's just a toy." ]
Why are some people tone deaf or incapable of getting the rhythm of music?	[ "depending on the degree you're talking about, it's actually a literal brain defect called amusia. one of Oliver Sacks's books (\"Musicophilia\") is all about the brain and music, and he talks about tone-deafness. basically, the part of your brain that recognizes pitch (or tempo, rhythm, etc.) is missing or damaged...	[ "The numbers might be misleading because of how they calculate the admission rates. I'm a musician. In the music, theater, and fine art departments of my alma mater, a student's application is not analyzed by the school until the student passes an audition - for me it consisted of a performance part plus a written...
How come some defendants during court proceedings and/or sentencing either are wearing prison/jail issued uniform or a suit?	[ "It will depend on the state/county/jurisdiction but typically the people in suits will have been on bail, and the people in jumpsuits will have come straight from prison where they were held on remand. Some places allow remand prisoners to wear suits to trial as wearing prison clothes tends to make you look guilty...	[ "I know this one sort of! Back in yon olden days, caskets were a luxury item that could only be afforded by the rich. So, rather than just dump their dead in a hole (ironically: because ghosts), the poor would wrap them in sheets and blankets. When it was scaring time and people wanted others to think they were gho...
Why are US license plates short and fat while European license plates are skinny and long?	[ "One thing that may explain it that in the UK and maybe all of Europe, a car keeps its license plate for the life of the car. So they need a format to basically print a VIN number." ]	[ "1. The East was settled first, most people chose to \"stay\" there. 2. West of that \"split\" is much less hospitable (geographically speaking). Lots of high plains, deserts, mountains, canyons, etc. The weather here can be very extreme. Compare this to the flatter, greener, less tornado-prone eastern half of the ...
Has there ever been a full year in the last 2000 or so years in which no wars were fought?	[ "Its not really an historical answer, but there would be several as a \"war\" requires a specific set of criteria to be considered one. Individual skirmishes and interventions do not really count as wars. So do you mean no conflict of any type?" ]	[ "Political parties are not an official part of the US government. People appear on the ballot representing themselves, not necessarily representing a party. Anyone who meets the requirements to be president can file paperwork to run with the Federal Election Commission and can file in each state to appear on the ba...
The metal thing they press on fighters faces between rounds.	[ "Hits to bony areas usually cause large swelling very quickly. There is no fat/muscle to blunt the force. The piece you see is actually an \"eye iron.\" It is simply a cold piece of metal. That piece is applied and pressed into the swelling to minimize/reduce it. It literally \"pushes\" the swelling down. The co...	[ "Film guy here. Movies were edited by watching different reels on a machine that looks like this: _URL_0_ which lets you play and listen to different clips and/or the whole assembled movie. Film Footage was cut apart and taped together with blades and special tape with a device that looks something like this: _URL_...
Why is New York City nicknamed "The Big Apple?"	[ "The term, first coined in 1909, was used in John G. Fitzgerald's popular horseracing column \"Around the Big Apple,\" beginning in 1924. New York had many racing tracks, and the purses in New York were some of the biggest in the sport. Concurrently, the term was also used by jazz musicians, referring to New York a...	[ "C'mon this is explainlikeimfive Linux - Legos - there are sets you can get or you can just build whatever you want. Might need a manual for some things. Windows - GI Joe - Everyone knows it and there are all kinds of cool accessories for it, but still a GI Joe in the end. Vulnerable to dogs and little ...
Can pathogens survive on primary documents? If so, are there any cases of historians falling ill from archival research?	[ "Might want to go to /r/AskScience! They might know if it would be at least possible." ]	[ "Hi - we as mods have approved this thread, because while this is a homework question, it is asking for clarification or resources, rather than the answer itself, which is fine according to [our rules](_URL_1_). This policy is further explained in this [Rules Roundtable thread](_URL_3_) and this [META Thread](_URL_...
What is the best available literature on English on the First Avar Khaganate?	[ "Literature on the First Avar Khaganate in English is probably the problem you're having. They're mainly in German, Serb, Hungarian, Romanian, or Bulgarian. Overwhelmingly in German, though. Pohl's [Die Awaren](_URL_0_) is the basic reading, and is in German. I know of no comprehensive English works on the Avar...	[ "To start, I go into the general features of Zoroastrian theology [here](_URL_0_). I will have a look at my sources and see if I there is enough material to put together an answer adressing more specific to your question. The problem you face here is that there are very, very few native sources for the Achaemenid p...
Why does cold air smell different than warm air?	[ "Warm air is more humid, so the moisture soaks into absorbent stuff around you (carpet, upholstery, clothes, etc), which causes different smells to bloom. Now, warm air is also more humid because it can \"hold more stuff\", if that makes any sense--more can be dissolved in it. So in warm weather, scents will be hel...	[ "The molecules in the steel bind with the sulfur molecules left on your fingers from things like garlic and onions, and when you rub your hands against the steel under cold water, the molecules are washed away." ]
What was Argentina a believed hotspot for Nazis during and after WWII?	[ "German speaking people from all over Europe started emigrating to Brazil and Argentina in the 1870s, and continued to do so in fairly significant numbers right up until 1939, and of course after the war. What makes Argentina kind of different is that a lot of those people lived in enclaves all over the country and...	[ "You may be interested in this similar earlier thread. _URL_0_ See responses by Blanglegorph, jonewer and myself. The short answer is that any positions of relative advance (e.g. Rocketry) tended to be out of desperation, whilst Allied advances (e.g. Computers) tended to be more a case of doing things they could af...
Do the human body produces the same amount of blood after one person loses his/her limbs? Or the blood production would be adapted to the body without the missing part?	[ "You would have less blood overall, as the concentration of haemoglobin and protein/electrolytes are regulated within a certain concentration. Same for blood pressure - if we kept the same amount of fluid within a smaller elastic system, blood pressure would increase, and promote fluid loss through the hormonal (RA...	[ "The go to way is to take a bunch of sensor units, attach them to whatever muscles are left in the stump, and convert their muscle movements into electric signals. These signals are then used for rather rudimentary commands. Hand prostheses for example are either \"pull to open\" or \"pull to close\". If you don't...
When I call customer support why do I have to answer a ton of automated questions only to finally reach an agent who asks me THE EXACT SAME QUESTIONS!!! Why do companies do this?	[ "When you answer those automated questions, you're being routed to the correct department that could best handle your situation. When you get the advisor on the line, all they're doing is verifying the information on screen to make sure there are no inconsistencies so they can help you as fast as they can. **Sourc...	[ "The captcha isn't checking that you clicked the box. But how you clicked the box. What was the path of the mouse cursor movement. What was the delay in movement. What was the speed of the movement. What were the initial and ending coordinates Applying heuristics, it can give a confidence level if it matches any ...
How were steam tables generated experimentally?	[ "Enthalpy, entropy and internal energy are derived from first principles using the laws of thermodynamics and the definition of these terms. The constants in each case for example the specifix heat capacity is determined experimentally. Using the equations and imperial data you get the desired value. Am I being too...	[ "Yes. A nonrelativsitic ideal gas and an ultrarelativistic ideal gas have different specific heat capacities, for example." ]
To reach the Sun, less delta-v is required if you go "out" first, and then descent, compared to going straight to the Sun from Earth. How is this consistent with conservation of energy?	[ "If you go out first, you shoot the rocket fuel backwards, reducing its kinetic energy (in the reference frame of the Sun) while increasing your energy. You hit the Sun with a higher energy. If you go inwards directly, you shoot the rocket fuel forwards, increasing its kinetic energy (in the reference frame of the ...	[ "Every kind of power generation scheme generates a lot of heat, simply because we use that energy in various ways and entropy takes over. Even if your power source was somehow 100% efficient in generating electricity from fuel, your computer or washing machine still convert all that energy into heat. Some industria...
How do the parasites that infect insect brains and such actually manipulate the host body's movements ?	[ "Screws with the hormone system (eg serotonin) . Doesn't make the ant do things, more it changes the way the ant behaves. EG. not make the ant climb, but make it really like the feel of sunlight so it goes and seeks that high place clear of shade." ]	[ "Well, it's not an ability exactly. At some point in the past the species that eventually became the viceroy butterfly produced a member or members that kinda looked like a nearby poisonous species, which would become the Monarch. Because the similar looking ones were less likely to be eaten, more of them survived ...
why is it that sometimes when you wake up your eyes and throat feel painful?	[ "Mostly drying out. You just spent a lot time not refreshing your water supply, and if you weren't amply hydrated your body will make short-term cuts to the amount of water it sends to various places to conserve it. That includes your mouth and eyes. The \"slime\" and \"eye crusties\" are partially dried out collec...	[ "The sphenopalatine ganglion, a nerve cluster that among other things contributes to control of mucus flow, is inhibited during sleep." ]
Fire. What exactly is it and how does it work?	[ "If you're talking about the flames, they are glowing hot gases with some hot particulate ash thrown in sometimes. The way it works is: oxygen in the air reacts with stuff that contains carbon and/or hydrogen to form CO2 and H2O, releasing a ton of energy that was pent-up in the chemical bonds of whatever it is tha...	[ "\"magic\". This question is repeatedly asked. You need to ask more specific questions as there are a lot of things to answer." ]
how astronomers can observe for a prolonged period of time a tiny part of the sky, with the earth rotating around its axis and the sun	[ "They mostly use a device called a heliostat. This is a device which you add to your telescope mount and configure it so that it aligns with the plane of the rotation of the planet. There is a motor attached to it, or you can turn it manually, that will rotate your telescope once every 24 hours. So the end result i...	[ "[The comments on this gif](_URL_0_) explain it, specifically [this one](_URL_0_csz5f42): > It's called retinoscopy. You shine a narrow beam through the pupil and focus it on the retina. Then you move the beam up and down. If the beam moves up or down on the retina too fast or too slow compared to your own movemen...
Why didn't the Egyptians have hieroglyphs for some things?	[ "As the name suggests, hieroglyphics (God's words) were not a vernacular written language in the same way English is. Egyptian commoners didn't use hieroglyphics to write road signs and letters to each other. I don't know enough to say for certain, but I'm guessing that there was no written language for the lower c...	[ "I've deleted this post. \"Throughout history\" questions, as stated in our rules, [are too broad for this subreddit](/r/AskHistorians/wiki/rules#wiki_no_.22in_your_era.22_or_.22throughout_history.22_questions). Moreover you're obviously trying to make a point about the way this subreddit is run which makes me doub...
Why do we lose saturation in our colors for several minutes when we are in the sun for a couple hours?	[ "It's been about 2 years since I studied this, but I think I can take a crack at it. Your cones have the ability to adjust to a wide range of photons/second hitting your eye. For example, a tv screen might have 10^6 TIMES less photons hitting a cone than a bright summer day, but you'll see both just fine. To adjust...	[ "While there are still a lot of unpopped kernels and only a few already popped, the energy is absorbed by the unpopped kernels. It is only until a few unpopped kernels are left, that the already popped kernels start to absorb energy and get burnt. Copy pasted my top answer from: _URL_0_" ]
What's the current consensus among scientists on what's the actual driving force behind osmosis?	[ "The system is seeking diffusive equilibrium. If the chemical potentials are different on the two sides of the semi-permeable membrane, solvent will cross the boundary in order to equalize them. The solute is not allowed to cross the boundary because the membrane is only semi-permeable." ]	[ "Hit a tennis ball with a tennis racket There's no pressure opposite the racket (on the side of the ball not getting hit by the racket), however the ball gets compressed It's the same idea with a fluid. A fluid has inertia and drag. A shock wave is \"hitting\" the fluid and causing a localized increase of pressure"...
What is holocytochrome C?	[ "A protein in general can have cofactors, that are not aminoacids, in their structure. For example the hemoglobine has the heme group that interacts with the oxygen. The protein without the cofactors, just the aminoacid chain, is called holiprotein In your case the holocytochrome c is the Cytocrome C withoit the he...	[ "My undergraduate adviser was an expert in this! He wrote this while still in school: _URL_0_ If you have any specific questions, feel free to ask. I also wrote quite a bit on the subject, but mostly as an example of indigenous communities within the colonial context and ad hoc systems of administration working in ...
Why did the Bretton Woods system fail?	[ "bit of a lay answer but - Russia had more gold than us, Nixon had to deal with Vietnam debt, and Japan and Germany had started to recover enough to not take as many imports as they did, and start exporting themselves. Also, imports of oil from the middle east skyrocketed around this period. Bretton Woods worked be...	[ "Any idea why Petra came into existence so far from an ideal location?" ]
Why does burning a candle help with slicing an onion?	[ "It creates a chimney effect. It is the same reason you see fires started by rioters. That's not just to create effect, that actually moves the CS powder clouds up and away from the ground. Basically, it moves the air around so it doesn't linger." ]	[ "> Nothing about it makes sense to me. How does this work? It is simple: Saps pay money for a red LED light and believe any pseudoscientific nonsense that is tossed their way. The scam artist makes a load of money off this fad. Of course it doesn't do anything, there is no evidence that the \"therapy\" works, but t...
How do solar panels work?	[ "There are two kinds of solar panels. In photovoltaic panels, light from sun beams can interact with electrons laying in the outer layers of the atoms. If this energy is sufficient, electrons are \"kicked\" out of the atom and become free too move in the material, which is the definition of an electric current. Wit...	[ "Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s): You can find the basic answer with a google / wiki search. Please start there and come back with a more specific question. If you disagree with this decision, please send a [message to the moderators.](_URL...
Why does an increase in a conductor's temperature lower its resistance?	[ "In general, electrical resistance [increases with increasing temperature](_URL_1_). What you're describing is the opposite effect so I'm not too sure, but at very low temperatures one can see the sort of behaviour you described (though I've only come across it for semiconductors). The resistance depends on the num...	[ "There's not a particularly simple way of calculating this universally. The rate of heat transfer via [conduction](_URL_1_) requires knowledge of lots of properties of the individual system you're investigating: probably most importantly the surface areas of contact and the [thermal conductivity](_URL_0_) of all ob...
Why do streetlights sometimes turn off as I walk under them?	[ "High pressure sodium street lights cycle on and off as they near the end of their life. Since they turn on and off repeatedly, the odds of turning off as you pass are much higher. I've always thought it was odd they always turn OFF when I pass, but finally I recently had one turn ON for the first time I remember."...	[ "I recommend listening to Feynman describe the sum-over-histories model of quantum electrodynamics (for which he and two other men won the 1965 Nobel prize in physics): [Here's the video.](_URL_0_) There are a lot of amplitudes, phases, and little spinning clock analogies involved. Essentially, light takes all poss...
If water is a great conductor of electricity, why would a lightning stike lose its lethality when covering large bodies of water.	[ "Water in and of itself is actually a poor conductor. What makes a current flow through a medium is the mobility of charged particles called ions. Pure, distilled water has no minerals or dissolved ions while regular old tap/sea water will have some minor amount of salt. The salt is made of ions, which can carry cu...	[ "Wet things usually have a higher heat transfer coefficient then the dry version. Also their heat capacity generally increases so it takes more heat to raise their temperature. For a coin, it will feel wet at first while it sucks the heat out of your skin quickly (metal is a bad insulator), but gradually its temper...
The message/meaning of Fight Club	[ "The main message of the film is laid out to you right at the start with the warning message you expect to be about piracy but then turns out to be this: _URL_0_" ]	[ "The books and movies probably get more popular than the t-shirts. The copyright owner is not going to bother unless the person infringing on their copyright starts making significant money." ]
Why does Earth look so large from Saturn, compared to how small Saturn looks from Earth?	[ "This picture was taken by Cassini when it was about 753,000 miles away from Saturn. Both would be fairly tiny if viewed with the naked eye, but a telescope magnified them both." ]	[ "The Theory of relativity. The same reason time seems to pass In a blink when you're enjoying a night with friends, yet seems to last an eternity during the last 10 minutes of work." ]
How am I stronger than people who appear very muscular?	[ "Muscle size is an awful indicator of strength and it often comes down to the type of muscle fibers the person has, how much torque those muscle fibers can generate and the neurological ability of that person to combine those muscles to apply force. Some of it is genetic ability but often it comes down to specific...	[ "I don't think you are going to get a valid answer. Music in and of itself is a confusing scientific phenomena. Our attachment to it is a strange byproduct of various cortical functions. We don't really understand why it exists (though there are many theories, none with anything close to proof). The most likely exp...
Are birds in any way related to dinosaurs?	[ "Most researchers now support the view that birds are a group of theropod dinosaurs that evolved during the Mesozoic Era. [Source](_URL_0_)" ]	[ "A pyramid is the easiest type of building to make. Any group of people who want to make a large structure are always going to start with a pyramid. Staircases are always going to take more work. So, if you want to walk to the top you will always make one section a stair case which is always going to be straight up...
How do boxers and MMA fighters have careers spanning years, while some people are killed with one punch in a street fight?	[ "People who get killed from one punch in a street fight often die because they hit their head on something hard on the way down. That's not a concern in a boxing or mma ring. Also, boxers and martial artists have been trained to defend against attacks. Most people would be destroyed if they joined a hockey or footb...	[ "Non-musicians don't give a shit about solos, they just think they're boring because they don't know how difficult it is for the musician to do what they're doing. Back in the day it was all about \"what band has the best guitarist?\" \"What band has the best drummer?\" Now it's all about \"What band has the catch...
Can sleeping with a fan on you/your face make you sick?	[ "It can't make you sick insofar as creating bacteria to infect you, however sleeping with the fan on your face can dry out your mucous membranes which prompts inflammation which is an immune response. This can lower your body's ability to fight off germs already in your system causing you to be more susceptible to ...	[ "As /u/SwedishBoatlover has said it causes the blood in your body to increase in pH. Everything in your body, including the CO2 that you produce, exists in an equilibrium. Our bodies were designed to have certain ratios of these things in our system and it relies on them to keep everything normal. In the case of yo...
- How are large crowds at rallies and events calculated?	[ "Assuming there is no door they have to enter through or some other choke points you can count them at the only way to do it is with math. So you pick an area, say 100 sq ft, then you count the number of people in several of those sized areas, then you take your counts and average them together. Now that you have...	[ "This is actually a very deep question. Philosophers still can't agree on what it really takes to \"know\" something. Suffice to say that our brains are kind of like very advanced computers that use past experiences to make predictions about the future. So if someone understands an equation, they have the experienc...

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