query stringlengths 20 300 | positive listlengths 1 1 | negative listlengths 1 1 |
|---|---|---|
How long does the collapsing phase of a supernova last? | [
"From what I see [here](_URL_0_), you're talking about a few seconds. The gravitational compression becomes too much for electron degeneracy pressure to withstand, and the collapsing material hits about 23% of the speed of light. The collapse of the inner core is abruptly halted by neutron degeneracy pressure, and ... | [
"First, the USSR under Gorbachev in no way tried to transition to capitalism. Gorbachev was, by all counts, a committed communist who believe that the USSR needed reform but that reform could make socialism* work. So that means your question has to be either (A) why did the soviet union suffer a political collapse... |
I pick up an ant going in one direction, I put it down facing another direction, and it continues walking in the new direction. Did it never have an original set destination, or does it now have a new destination? | [
"Ants follow trails of chemicals left by other ants. It will walk aimlessly till it finds a trail. Ants do not have a lot of thought going on individually and have limited sense of direction, it might finds its way back, though it won't think much of it follow whatever order it picks up."
] | [
"They can only go to a single destination: Home. You have to raise carrier pigeons in a location that you want people to deliver messages to. Then you take them further and further away and release them to fly home so that they learn the area. After that, you have to physically carry them to whoever you want to be ... |
When you die, are all of the memories stored in your brain immediately terminated? Are memories something physically present in the brain held together by tissue, or are they more abstract? | [
"Nobody knows exactly how memory works, but it probably has something to do with the connections between the brain's neurons. When enough brain cells die, there's no way of getting them back."
] | [
"The vast majority of the energy in your body is the mass of the atoms that make it up. These atoms will survive unaltered. The thermal energy of your body will quickly dissipate into the environment until the body is the ambient temperature. The chemical potential energy of many of the compounds in your remains wi... |
Is it possible to convert heat into electrical energy? | [
"It is not particularly accurate to refer to infrared radiation as *heat*. Heat refers to the transfer of kinetic energy. Although energy transfer through radiation can be a part of this, it is erroneous to refer to infrared radiation as heat. To answer your question, solar thermal collectors can and do use solar e... | [
"For that you need mountains, with two lakes above each other, and a river to replenish the evaporated water. Most, if not all suitable sites are already used for that. *Construction is expensive, and the energy content is relatively low. As a theoretical exercise you can calculate the 'lake' sizes and heigh... |
"The WHO estimates that more than 500,000 people around the world die each year as a result of eating too much trans fat." What exactly does this mean? | [
"It's an estimate based on A) The number of people in the world exposed to high levels of trans fat, and B) The measured increased risk of death by heart disease to people exposed to high levels of trans fat. So basically it's an estimate that every year, 500k more people die from heart disease than WHO estimates w... | [
"The exponents are typically called \"share weights\" because they are the share of income that the consumer will spend on that good. So if u(x,y)=(x\\^a)\\*(y\\^b), the consumer will spend a/(a+b) of her income on good x and b/(a+b) of her income on good y. What that means in practice is that in a Cobb-Douglas wo... |
If everyone says girls mature more quickly than boys, why do boys seem to have a higher sex drive than girls while teenagers? | [
"because sex drive and maturity have nothing to with each other?"
] | [
"It's determined at fertilization - it depends on which sperm makes it to the egg. Your genetic code is made up of 26 chromosome pairs. The 26th pair is the sex pair. Females have two X chromosomes (XX), a symmetric pair. Males have an asymmetric pair: one X and one Y (XY). When you reproduce, you give one chromoso... |
blue lights at night | [
"The eye has a lens. Lenses, in general, don't bend all colours of light by the same amount. The human eye is optimised around the green portion of the spectrum, which means red light falls slightly behind the retina, blue slightly in front of it. During the day your pupil contracts, which makes the eye approximate... | [
"Yes, in fact that actually happened: _\"When a massive power outage struck southern California in the 1990s, Los Angeles residents reportedly called 911 to express alarm about strange clouds hovering overhead; they were seeing the Milky Way for the first time.\"_ _URL_0_"
] |
If the expiration date of bottled water due to the decay of the plastic in the water, would an expired bottle be safe to use if its contents were emptied? | [
"Yes, you can reuse that bottle, it's not as if it's going to suddenly melt into a pool of poison."
] | [
"Imagine getting a balloon and filling it with air, and diving down to the very bottom of a deep swimming pool with it. The air in the balloon will be crushed by the water pressure, causing the balloon to shrink dramatically, right? The balloon can't withstand the pressure. Now imagine diving down to the bottom of ... |
How can large company executives get paid in huge amounts of company stock and sell that stock without being charged for insider trading? | [
"Exec's sell stock on publicly available schedules. They announce to the public they're going to sell X shares of stock in 3 months. It's not private info anymore"
] | [
"Likely they just bought it. Cyanide is useful for things like rat poison or insect fumigant and is perfectly legal for purchase from a variety of vendors. Assuming they lived in a rural area they may have a local supplier from which to purchase to chemical directly."
] |
how do our brains determine when something that changes very gradually has changed a notable amount? | [
"That is actually a really good question; it's obvious that you do tend to ignore gradual change up to a point. It would make a nice psychological experiment; maybe if you try at /r/askscience, someone knows if any has been done on the topic."
] | [
"Just like how we learn to walk by putting one foot in front of the other as babies/toddlers. Eventually your motor functions get so good at these \"menial\" tasks from repeating them so much that you don't need to think about every individual step, just where you want to end up. I'm no expert though."
] |
Why does this hockey puck "explode" when put in an industrial press | [
"Hockey Pucks are very tough stuff, made of very tough rubber. However, rubber tends to fail catastrophically, as shown in the video (and every balloon you've ever popped). Apply enough pressure, and WOW that was a lot of pressure, and the tiniest flaw starts the failure. The failure/crack/rip/whatever spreads at h... | [
"Chemical reaction to oxygen. Like you are five: Once the stuff inside the compressed tube meets the air...it goes all crazy and changes."
] |
How much does the "visible light spectrum" vary from person to person? Would some people be able to see infrared light coming from a TV remote, on account of an ocular abnormality? | [
"This episode of radiolab addresses that, especially the one about the \"perfect yellow\" _URL_0_ They found a woman who kinda had a \"fourth\" spectrum of color perception outside of the RGB peaks we see for human eye acuity."
] | [
"In the video, the first part you can see the pilots actually moving (big cross hairs) the ATFLIR's view to keep the thing in view - this is manual or they can slave the view to the aircraft radar to some extent. Next, when that expanding box appears, the system has been told by the pilot to start picking up a the... |
Why cant we use the earths heat as an unlimited thermal energy source? | [
"Part of the problem is the [thermal conductivity](_URL_0_), in W/(m.K), how many Watt an area of 1m² can conduct through a certain material thickness and a certain temperature difference. A ~32cm diameter pipe (1m² per meter) in [Rock, solid (k=2-7)], can collect 2-7W/m² per ⁰K through a 1m thickness, 20-70W thr... | [
"They *did* do that. Some people just claim that research funded by oil companies doesn't count as \"extensive research\", because they think it's too likely to be biased."
] |
why hasn't there been any attempt to push for an universal language for us to use? | [
"There has been. Esperanto was designed after World War 2 to reduce the possibility of war due to miscommunication."
] | [
"Too expensive, little or no benefit. The people that benefit from metric (scientists, engineering) already switched over long ago. For everyone else: Does it really matter if the speed limit is in mph or kph? Are you having trouble converting the speed limit to feet per second on a daily basis? No? Then we're fine... |
If the boiling point of water is 212°, then why does it evaporate at room temperature? | [
"Boiling point is where it *must* be a gas. At lower temperatures, it seeks an equilibrium between liquid and gas. A liquid is a big jiggling mass of molecules loosely stuck together. Because they are moving randomly, occasionally a molecule at the edge will be shaken loose and bounce away. That's evaporation. Simi... | [
"Your sense of smell works by picking up molecules from the air. Many things emit these molecules regularly. \"Volatility\" is a measure of how frequently something will emit an odor-causing molecule. When temperatures increase the speed of atoms increase, which leads to an increase in volatility. Basically, you s... |
Is it possible to make a 100kW nuclear reactor that's not an RTG? | [
"I don't work in a nuclear power plant but I have some background in nuclear energy. RTGs are really the only kind of \"portable\" nuclear energy that I think would be feasible. If you look at a nuclear power plant, it's a big compound, but the actual nuclear fuel and reaction chambers don't make up most of it. The... | [
"For that you need mountains, with two lakes above each other, and a river to replenish the evaporated water. Most, if not all suitable sites are already used for that. *Construction is expensive, and the energy content is relatively low. As a theoretical exercise you can calculate the 'lake' sizes and heigh... |
Why do my eyes feel "pain" when looking at a bright light, even though it isn't touching/hurting me physically? | [
"the light actually *is* touching the receptors in your retina (the back wall of your eye) physically...translation of that reception by the brain yields your perception of the pain [animation here in Clip1](_URL_2_) is well done, IMO. edit: [here's another animation on eye function](_URL_2_)"
] | [
"I found this article about it: _URL_0_ Here's the tl;dr of it: Atoms emit photons occasionally. Our retinas occasionally pick these photons up, even if the source is inside your own body. Plus, photons can sometimes stimulate other nerves directly."
] |
Did unemployment exist in the Soviet Union? | [
"Hi there, the mod team has already had to remove several responses in this thread because we do not allow [personal anecdotes](_URL_3_). While they're sometimes quite interesting, they're unverifiable, impossible to cross-reference, and not of much use without more context. [This comment](_URL_3_) explains the rea... | [
"This question is getting a lot of traffic after being [tweeted by @reddit](_URL_5_), so I thought I'd welcome those of you that haven't visited /r/AskHistorians before to the subreddit. Please do bear in mind that in order to keep the quality of answers here high we have [strict rules on comments](/r/AskHistorians... |
How does phone number spoofing work? How can two phones communicate without knowing each other's real numbers? | [
"The phone number sent to caller ID is **not** the actual routine circuit number. That's because phone circuits are dynamically assigned, a throwback to before everything was just IP packets. It's just \"documentation\" to display on the caller ID device. The reason for this is that many companies have more extensi... | [
"I was curious about this as well, so I did some google-fu and found some results. This is all secondhand so take it with a grain of salt. It seems that the stations contract survey companies to get a rough estimate based on a sample population in the area. Arbitron is one of those companies. How do they do it? The... |
If I was playing middle C on a stationary piano and there was a second piano playing middle C while strapped to a rocket, how fast would the rocket have to be moving for me to hear a perfect 5th chord via the Doppler Effect? | [
"If the other piano was moving towards you, then to hear a perfect 5th, you'd need to hear the note G4 (middle C is C4). The frequency of C4 ~ 261.63 Hz, and the frequency of G4 ~ 392.00 Hz, and the Doppler equation for sound is: f*_2_* = (c*_s_* * f*_1_*) / (c*_s_* - v) * f*_1_* is the frequency of the sound when ... | [
"A \"chord\" is made up of 3 or more notes. A note is a single sound, like when you whistle, that's a note. Sounds make waves, and that's what we hear. Imagine you're in a pool with water like glass. You gently tap the pool at one end with your finger, while a friend lightly taps the water at the other end at the s... |
Why do people sometimes shake their heads when they say something wrong or think a bad thought? | [
"The reaction to thinking things you don't want to think is generally along the lines of \"no, don't think that.\" Since talking to yourself is associated with crazy people, most people don't say anything out loud. But because they're trying to overcome a negative thought using just willpower, extra \"force\" gener... | [
"I always wondered about the same thing and quite recently I discovered that the hushing sound is the most common sound you can make with your mouth to calm down a newborn baby: they naturally calm down when they hear vibrations and white noises. I wouldn't be surprised it just came out from this: a lot of pèarents... |
What was crime and punishment like among Native Americans? | [
"This question is as broad as \"What was crime and punishment like in Asia\""
] | [
"This submission has been removed because it is [soapboxing](_URL_1_.), [promoting a political agenda, or moralizing](_URL_0_). We don't allow content that does these things because they are detrimental to unbiased and academic discussion of history."
] |
HSA (Health Savings Account) vs. PPO (Preferred Provider Organization). How does it all work? | [
"HSA is simply an account anyone can contribute money into pretax for approved health related expenses, it is not an insurance plan. The two are not necessarily related. A PPO (an actual insurance plan) contracts with a bunch of different independent health care providers so you can get cheaper service (called in n... | [
"The Hungarians in '56 and the Czech's in '68 revolted against Soviet hegemony. The Czech's helped put down the Hungarian uprising, and the Hungarians helped put down the Czech uprising (among troops from other Warsaw Pact nations). Soviet troops were generally stationed in Warsaw Pact nations helping to ensure loc... |
Why does scratching feel so good? | [
"Particle on skin may cause danger, scratching removes particle (hopefully), relief of the damaging particle releases feel good chemicals into blood. At the same time scratching slightly damages skin, skin damage releases feel good chemical into blood to counteract pain. So kind of a mix of both."
] | [
"Some have suggested that it causes dopamine responses. Similar brain mechanics to forms of addiction (alcoholism, smoking, drug abuse etc). _URL_0_"
] |
Why is metal glowing when you heat it up? | [
"Light is made up of electromagnetic waves of different frequencies. Everything gives off electromagnetic waves - this is what's known as [\"black body radiation\"](_URL_0_). The frequency of black body radiation depends on the temperature of the object. Most objects at everyday temperatures give off infra-red ligh... | [
"Different elements and compounds emit different wavelengths of light. The study of this is called spectroscopy. By looking at the particular wavelengths, we know the particular compounds."
] |
What would have happened to slaves who were caught doing homosexual acts? | [
"I'm assuming you mean in the ante-bellum US, is that correct?"
] | [
"This might be easier for people to answer if you gave a specific time and place. Are we talking about Italian renaissance choir boys or Chinese imperial officials? Edit: specific time not a specific Tim"
] |
How did the Colombian Exhange impact the cuisine of indigenous American cultures? | [
"I want to preface this that I'm not an expert in food history- however, I have done work relating to colonial america and might have some details you find interesting. In terms of domestic animals, I know sheep were brought from Spain by conquistadors and these sheep, called Churro sheep, were raised by the Navajo... | [
"Do you mean using coins as adornment, as though they were beads? Such as this [Amerindian Dress](_URL_0_)?"
] |
How did Gavrilo Princip think of the war? | [
"This question has already been answered [here](_URL_0_) by u/HistoryLord"
] | [
"You can find some excellent answers about this [in the wiki](_URL_0_). I especially like [this answer](_URL_1_) from /u/Georgy_K_Zhukov **TL;DR: Your friend is almost as wrong as wrong can be.**"
] |
Is there an academic consensus about the role of the church in spreading literacy across Europe ? | [
"Academics are not prone to consensus on such topics. The Catholic church encouraged literacy among its monastics and clergy, but did not seem to be particularly active in spreading literacy across the lay people of Europe. Protestant churches, because they translated the Bible into local languages, instead of usin... | [
"It looks like it's different editions of the same book. The first book you linked is the [US paperback edition](_URL_1_), the second book is the [UK ebook edition](_URL_3_). There's also an [UK paperback edition](_URL_0_) and a [US ebook edition](_URL_2_). It is not unusual for there to be a slight delay between e... |
Why are liberals on the "left" and conservatives on the "right"? | [
"This custom came from the French Revolution. In France, the members of the National Assembly that supported the King sat on the right side while those that wanted reform sat on the left. Therefore, conservatives became right wing and liberals became left wing."
] | [
"World map drawing started in Europe. So Europe was the center. Asia is in the east, the Americas are in the west, so I guess you get the picture. There are other layouts - Japan and China for example have themselves in the center, making Europe the west and America the east. Usually the one who draws the map wants... |
How public key encryption and PGP e-mail encryption works. | [
"Say you want a friend to mail you a box full of secret stuff, but you don't trust your mail man, and you don't want him to be able open the box, so the box needs a padlock. Your friend could go and buy a lock, but then you wouldn't have the key. And if your friend also mailed you the key, the mail man could steal ... | [
"Many medications depend on the pathway of the disease. For example, diabetes insipidous (not the typical glucose diabetes) is characterized by excessive urination and thirst, which washes out lots of your ions and other important compounds. It has 2 causes. Either your brain isn't releasing ADH, a compound that pr... |
If the border between two countries or states is a river, what happens to the border when the river changes course over time? | [
"Either the border stays where it is, or the countries or states involved negotiate land swaps so that the border can be corrected. [Here](_URL_0_) you see the French-German border along the Rhine river, but at a couple of points it cuts across land where the river has silted up slightly, a process I imagine was ac... | [
"Basically, in countries that have private ownership of land, land surveyors give their opinion on where property lines actually are on the earth. We research deeds, maps, etc. to determine where the lines are thought to be and then go to the property to find evidence of where the original survey marked it. The ins... |
What's the point of giving someone the "Key to the City"? | [
"It's an award it doesn't really do anything in itself. What comes with the award is up to the city. Its more of a tradition then anything else."
] | [
"Your employer takes money out of your paycheck throughout the year to pay your local, state, and federal taxes. The amount they take out, however, is just an estimate how much tax you will probably owe at the end of the year. There's no way for the state, local, and federal governments to know what you actually do... |
will mass from a Neutron star "expand" into known elements if removed from the gravitational effects of the star ? | [
"Yes, it will explode because the neutrons in neutron stars have huge amounts of kinetic energy. The neutrons could capture onto nuclei and make them larger. In fact, [neutron star material thrown free during collisions may produce half of the heavy elements in the universe via the \"r-process\"] (_URL_0_). Any neu... | [
"You should in theory be able to move about at any point in the sun; it's plasma all the way through, and is never solid. It does get very dense near the center ([Wikipedia](_URL_0_) says 162 g/cm^(3), that figure being obtained from computer models since we can't exactly measure it directly - for comparison, water... |
Is it possible to use sound waves to shape or mold physical material? | [
"There's [ultrasonic plastic welding](_URL_0_) and [sonication](_URL_2_). And when pouring concrete, a heavy-duty vibrator (see _URL_3_ ) is used so that the concrete penetrates into crevices. Aaaaand, [ultrasonic humidifiers](_URL_1_)."
] | [
"That's like trying to harness the power of a mach-5 railgun slug with a windmill. The powers involved are incredibly forceful, incredibly brief and pretty unpredictable. The device would have to be extremely robust to withstand such forces, cheap enough to be deployed en masse to take advantage of infrequent thund... |
Why aren't counties used for voting lines? | [
"Districts are redrawn in response to the census to ensure proportional representation. This is not feasible for counties, which are political entities with their own governments and laws. You'd have potentially thousands of people waking up one morning to a new set of laws and ordinances they'd have to obey. It'd ... | [
"For starters the extra costs to the manufacturer and the customer are not worth it. And second saftey, they could be dangerous closing down on little children & even adults."
] |
How does the gas meter on a car work, and why does it only work when the engine is on? | [
"Depends on the year of the vehicle. My old 1975 ford had a mechanical float and showed the fuel level at all times. On newer cars and it's electrical there's most likely a float in the tank still except it's connected to a sensor. The reason it only works when the car is on is so it doesn't drain the battery. Whil... | [
"The price of oil (and by extension, gas) fluctuates wildly in response to geopolitical events and supply factors that state governments have no control over. Rather than try to budget in advance for such an impossibly unpredictable revenue source many governing bodies opt to impose a tax on volume instead. It's no... |
Why do tattoos stay on "forever"? | [
"The ink is injected deep into your skin, so it's below the layers that rub off."
] | [
"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."
] |
In what manner does antimatter-matter annihilation release energy? | [
"Typically, when a positron and an electron annihilate, two photons are produced, each with an energy of 511 keV, the mass of the electron (times c^2 ). If the particles had significant kinetic energy before annihilating, the photons can have more energy, or other particles can be created if the electrons were goi... | [
"The key thing here is [Noether's theorem](_URL_0_), one of the most beautiful results in all of physics. Noether's theorem connects symmetries of nature to conserved quantities. For example, when physics is independent of spatial position, momentum is conserved. Or when physics is unchanged by rotating your view, ... |
Why are we born with two sets of teeth (Baby & Adult)? Is there an evolutionary reason? | [
"Children have smaller skulls than adults, so it’s impossible for them to accommodate a full array of adult teeth. So they have temporary teeth until there skulls are large enough for adult teeth. At least that is one theory."
] | [
"What seems to be simultaneous sound is actually far more complex, but your mind helps you to perceive that complexity as \"one sound\" that makes sense. Your ears are positioned on opposite sides of your head. This leads to: * Sound getting to one ear slightly faster that the other ear * Sound getting dampened as ... |
Why are strawberry seeds so nicely devided over the strawberry? | [
"The fruity fleshy bit of a strawberry is jummy and sweet. The seeds are not. If you were a bird and had the opportunity to eat either the jummy and sweet bit or the seeds, you'd only eat the jummy and sweet. By spreading evenly arcoss the strawberry you make sure that as many seeds spread as possible. Thus creatin... | [
"[Striped shirts](_URL_0_) tend to cause problems with video recording and, if the pattern is fine enough, photos. It is due to the creation of a [moire](_URL_1_) pattern where 2 sets of parallel lines that are not quite parallel (the lines on the shirt and the pixels on the sensor) create a illusion of density wav... |
Why was Swedens Army so effective in the 17th Century? | [
"I can't help but I know one person who can. Paging /u/VonAdler"
] | [
"The definitive book of the finds from the battle is [Bengt Thordeman's Armour from the Battle of Wisby: 1361](_URL_0_). This is the definitive published work by the archaeologist who excavated the original site. I do not believe it is a full and complete catalog of each item, but it provides extensive detail and i... |
Why is gentrification considered bad? | [
"Mainly because it prices people out of their homes. The neighbourhood gets nicer, people with more money want to live there, rent and other living costs go up. The people who already lived there now struggle to afford it."
] | [
"This CGP Grey video does a really good job of explaining it all. _URL_3_"
] |
I am allergic to cats. What would happen if I ate one? | [
"I think cat allergies are normally to the fur/dander so I doubt it would impact you if you ate the meat."
] | [
"If you can't find an answer here you can always try e-mailing whatif@xkcd.com and hope it gets featured there, because it sounds like a question that would fit. Sorry I can't help any further =/"
] |
U.S. Navy plans for "Mobile Landing Platform" ships | [
"The things that make a good seagoing ship (deep hulls, lots of capacity) make it tough to use in landings (low draft, fast, maneuverable). The MLP provides a stable platform that lets the Marines easily transfer cargo like fighting vehicles and supplies from things like [Maritime Prepositioning Ships](_URL_0_) to ... | [
"interesting.... this is from the front page of _URL_1_ today _URL_0_ it is the radio wave recordings of the recent sunspot release"
] |
How does a rocket propel in space? | [
"When you suck on a straw, it isn't the suction pulling the milk shake up. It's the weight of the column of air above the milkshake, extending into space pushing down on top of the milk shake as air pressure. All you did by sucking was remove the weight of air on top of the milkshake straw that was holding it down.... | [
"The computer has files of varying sizes. These take up varying amounts of spaces on the hard drive. Say you write to the hard drive 3 different files. One takes up 5 \"spaces\" the next 2 spaces, and the last 5 spaces. Later, you delete the 2 space file. Now you've got 5 occupied spaces, 2 free spaces, 5 occupied... |
Is the wind speed that we measure an instantaneous speed, an average speed, or something else? How is it affected by the terrain, buildings, etc.? | [
"Short answer: It depends on who is measuring, and with what intent. I used to be an airline pilot, and wind speeds (for us) are measured at ground level (2m height) over an average of 2 minutes every 8 minutes. If the spread of these measurements was significant, a \"gust factor\" was added. i.e. 270/18g30 means t... | [
"So there was a mythbusters about drafting and how to reap the benefits of it. You are assuming that they air that the drafting is collapsing in such a way that the second car is experiencing more drag force from the air, when good drafting puts you in the pocket of air before it collapses. Then when they use the s... |
Please help me clear up a few things about the Cosmic Background Radiation. | [
"1: [Yes](_URL_0_) 2A: The CMBR being uniform means *either* that we're in a very special place in the universe, or that the universe looks uniform from everywhere. We have no reason to believe we're special, so we assume it's uniform throughout. We extrapolate to suggest the entire universe is much larger than the... | [
"When we say the age of the universe is about 13.8 billion years, we mean as elapsed in the so-called *isotropic frame*, which is operationally defined as the CMB rest frame (the unique frame in which the CMB is isotropic). For more details, see [this thread](_URL_0_)."
] |
Is it easier to do physical work in moon-gravity compared to earth-gravity? | [
"Objects on the moon *weigh* less. But they still have the same *mass*. Basically, it will be easier to lift objects, you need less energy to lift objects because g_Earth > g_Moon. However moving stuff laterally will still need the same amount of energy."
] | [
"I want to hear more detail. The smaller forces would mean if you dip below your point of neutral buoyancy it would take longer for you to rise back up. And similarly if you gave a particularly powerful stroke while treading water and rose above the surface some you would sink back down much slower. So I can only i... |
Is the alcohol in mouthwash the same type as found in wine and beer? | [
"The alcohol in mouthwash is indeed food grade ethanol, there are some alcoholic people who do consume it to get drunk as sometimes it's cheaper and more accessible than regular alcohol. It's not a great idea to drink it though because the high concentration of fluoride and other tooth strengthening/cleaning and br... | [
"Germs need food, too. If it was pure water, then no, germs wouldn't grow. But if you backwashed then likely there would be some cells, mucous and other goodies from the saliva for them."
] |
What will airlines do when fossil fuels run out? | [
"> So, are aviation-grade biofuels possible? Is it feasible/possible to have a jet engine capable of running on 100% biofuel? Absolutely. It's a huge focus in engineering R & D by all the major aircraft/engine manufacturers. [You can read about it here.](_URL_0_) There have been many commercial flights that used a ... | [
"War. EDIT: Oh. Super sorry about that. I mean that because of WWI the aviation industry made some massive leaps in a very small amount of time to try and get an edge in the war. Same with WWII. The technology they had at the beginning of the wars was obsolete once or twice over by the end. I have a source somewher... |
Does heat make honey toxic? If so, why? | [
"Given that honey is often pasteurized, i.e. heated in order to reduce the already low chances of bacteria... I can only suggest this is nonsense."
] | [
"Cooking externalizes a portion of the digestive process, making more energy available from most food sources. Oddly enough, they proved this in an experiment with snakes where one group was fed cooked meat and another raw. The snakes eating cooked meat grew larger, faster. Cooking has been a Human trait since befo... |
How do hairs know when they've grown to a certain length? | [
"Hairs don't know. Your hair follicles go through a timed cycle - they grow for a period of time, then they rest, then they shed the old hair and grow a new one. The length of the growth cycle determines the maximum length of the hair."
] | [
"If your alarm has been the same for a long period of time, it just becomes a routine, like turning on your bathroom light when you walk in. Considering your body perfectly times heartbeats, breath, blood flow, etc, it's not that hard to believe it can time very accurately. :P It's completely subconscious."
] |
If Israeli citizens cannot enter Saudi Arabia, what happens if an Israeli Muslim wants to visit Mecca? | [
"Jordan will issue temporary passports for Israeli Muslims going on the Hajj. I used to work with someone who did that."
] | [
"The Sun does create radio interference in such a situation (even though in most cases the Sun does not completely occult the signal Mars), and such an alignment occurs every 26 months. While I do not know the protocol for Curiosity, the way NASA has handled this in the past for Spirit and Opportunity is as follows... |
how does icy hot lotion work? Why does it feel so HOT?!?! | [
"You put it somewhere sensitive or something? Anyway it's not physically hot or cold, the sensations are caused by a chemical acting on your nerves to make them send the signal to your brain that there's a hot or cold sensation there. Which by the way is why you're not supposed to overuse the lotion, and never stic... | [
"Capsaicin in chili peppers binds to spots on the tongue that make the brain think the mouth is literally on fire, and the best way the body has to flush it out is a runny nose and watery eyes. Also, this gets asked fairly often. Better to search first."
] |
In Assassin's Creed Origins' new discovery mode, the section on the Roman military tells us that civic soldiers were granted the right to vote in return for their military service. Is this true? | [
"Haven't played the game, but what this is might be referring to is that if you were not a **citizen** of the Roman Empire but lived in its territory, you would be a *peregrini* and could serve in the *auxilia*. After serving your full term, 25 years under Augustus, you and your family and your descendants were gra... | [
"Follow-up question: Was their rank of any specific religious significance?"
] |
Why did/do East & South Asian nations have such higher population density? | [
"Rice is also a labor intensive and elastic good, meaning that the more people, the more output, causing women to have much higher birth rates (of around 5-6 children per woman) so that more hands could work."
] | [
"Each property owner had his/her own idea of what purpose the building would serve and a different budget to make it happen. They may appear to share walls, but they did not. They are built wall to wall, but they usually did not share a wall. And they were tightly packed like this because most people did not own ho... |
Why do we (still) need toe nails? | [
"It's like a vestigial thing leftover from back when we did need them. Basically, it doesn't hurt our odds for survival, so it just sticks around."
] | [
"Evolution. People who didn't get that weird feeling when dangling their limbs from the trees they were sleeping on were killed by cheetahs."
] |
How did commoners before the advent of photographs recognize "Famous people" in the past without seeing them before? | [
"Correct me if I'm wrong, but wasn't Louis XVI caught during the flight to Varennes when someone actually recognized him when he went to pay for something because his face was on an assignat?"
] | [
"Usually, historians look at how much of a certain crop - often things like wheat or barley or something similar. It varies with the region - could've been bought with a certain amount of money. If you then look at how much of that crop could be bought with today's currency, you've got some frame of reference about... |
why is sulfuric acid a liquid at room temperature, though it has strong intermolecular interactions? | [
"most of the time it is actually dissolved in water. works the same way that salt does. i've never seen pure h2so4 before."
] | [
"Not sure of this is more chemistry or biology, but noses are more sensitive to certain smells than others. I would venture that molecules stick around relative to their affinity for the substrate (skin, cotton, etc.), but a tiny amount of skunk thiols would smell more intensely than whatever makes roses smell as s... |
Why is it that "mom and dad" is much smoother and natural to say rather than "dad and mom"? | [
"It just has to do with the way our mouths shape the sounds. \"Ma Mand Ad\" flows together nicelike, the end of \"and\" and beginning of \"dad\" are natural because there are no more than two consonant sounds together and they are a single syllable sound. \"Da Dan Dmam\" is awkward because you have the NDM sequence... | [
"It’s not a matter of which direction the electricity is flowing when the appliance is on (because it’s AC as you pointed out) but which side of the circuit is live when the switch is off. In the US, polarized plugs use the smaller prong to supply current to the appliance and the wider prong as the neutral. If bot... |
How do the nuclear forces work? | [
"The weak force has short range because it's mediated by massive vector bosons. The weak potential due to a pointlike source goes like exp[-mr]/r, where m is a constant related to the mass of the W/Z boson and r is the distance from the point source. For a force like electrosmgnetism, where the exchange particle is... | [
"Are you talking about the [nucleon-nucleon potential](_URL_0_)? The repulsive core comes from Pauli exclusion between the quarks. If you have two nucleons very close together (less than 1 fm), you can think of the wavefunctions of the valence quarks overlapping strongly. Because quarks of the same flavor are ident... |
How easy was traveling within the Third Reich? | [
"If I can piggy back off of this question: Currently the stigma of a police state is portrayed as a lot police checkpoints. Was this true traveling through Germany, where you were asked for your papers in order to go anywhere?"
] | [
"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... |
Why do our voices sound shaky when we're nervous? | [
"Nervous means that additional adrenalin is being pumped around your system, which is great for powerful muscles and movement like running, however it plays havoc with fine motor/muscle control including the control of your voice."
] | [
"I'll try an ELI5. Sound goes into the mic, sound gets amplified, sound comes out of the loudspeaker, the mic pics up that sound again from the speaker, and amplifies it again-in a loop. There is a slight delay in the electronics, and then a longer delay (speed of sound) in the time the sound goes from the speaker ... |
Isn't a transistor essentially pointless? | [
"You've actually sort of stumbled upon one of the most useful applications of transistors! The fact that you can the output of one switch be the input of another is what allows us to create [logic gates](_URL_0_)! Logic gates are transistors chained together in such a way that they can create logical \"operators\" ... | [
"> how it really amounts to a bunch of bologna I don't have an answer, but I do need to point out that bologna = lunch meat. Baloney = nonsense."
] |
In early times, where brothels and prostitutes were a part of everyday life, how did the prostitutes avoid getting pregnant? | [
"In ancient Roman times, there were a number of potions or plants that women could take to avoid pregnancy or abort a pregnancy later. Some of them didn't work, but there were a number of options that could lead to some success. Silphium was a plant that was popular for use either in preventing a pregnancy or termi... | [
"Hello everyone, Unfortunately, we have already had to remove a number of poor quality responses in this thread, including many asking about the deleted comments, which merely compound the issue. If you're here to answer the question, please make every effort to *answer the question*, not talk about the show, make... |
Why do animals need to sleep? | [
"The truth is that sleep is a huge mystery even to the best scientists in the world."
] | [
"Instinct. You can't see predators coming for you when it's dark."
] |
Has there ever been an openly gay world leader? | [
"Point of clarification: Are you asking about historical openly gay world leaders? I ask because this might not be the best place for this question. There are current examples but they would break the 20-year rule of thumb for this sub."
] | [
"The only example I can think of is Saddam Hussein's son used one in Iraq. Uday Hussein kept an iron maiden in his torture chamber. _URL_0_"
] |
If the universe is constantly "accelerating" away from us and is billions of years old, why has it not reach max speed (speed of light) and been stalled there? | [
"Because the acceleration due to expansion does not peak out at the speed of light. The reason for this expansion is not due to the motion of two bodies away from each other, but due to the space between the bodies being \"stretched\" (or added to). The amount of \"stretching\" depends directly on the distance betw... | [
"It isn't expanding into anything. Imagine an infinite loaf of raisin bread rising as it bakes. Each raisin in the loaf will be further away from every other raisin, since the loaf is expanding and the distance between all of the raisins is growing."
] |
I know this may be stupid, but why are the majority of plants green? | [
"The simplest answer is because [chlorophyll](_URL_0_) looks green. Are you asking in a deeper sense, like why aren't plants black (to absorb more wavelengths), or why does the chlorophyll molecule look green?"
] | [
"so depending on the monitor technology it works something like this... side view ~ | -- > ~ | -- > ~ | -- > Where the ~ is white light the | is the screen and the -- > is the colored light you see What the screen | does is it sends any light waves you don't want to see in other directions, and it lets the w... |
How important was the Paris Commune and First International in growing socialism? | [
"The Paris Commune was hugely important to Marx and Engel, the latter of whom looked on the commune as a model for his 'dictatorship of the proletariat': A directly democratic system, in which public servants were elected for short terms, paid like other workers, and based on universal suffrage. Marx vision of a d... | [
"Follow-Up question: Were the Great Leap Forward and Four Pests Campaign disastrous?"
] |
Why can’t infants drink water? | [
"They can drink water, but they don’t need to as they get enough water from breast milk or formula. Also if you fill their bellies up with water, they run the risk of being too full to drink milk and might not get enough nutrition."
] | [
"Becaus for most if them their frontal lobes aren’t developed yet and are very easily molded by repetition and hype. Adults have the ability and experience to see the BS in ads."
] |
Why can you not put diesel fuel in a gasoline burning engine? | [
"The difference between the two items is this.... Gasoline burns via a combustion based ignition, I.e. Gasoline burns because a spark ignites it. Diesel fuel is a compression based ignition, I.e. Diesel burns because there is so much pressure that the diesel ignites. So if you put gasoline in a diesel engine, the e... | [
"Because the third party candidate is not going to win and you deprive your second choice a vote. For example lets use the last election between Obama, Romney and lets say Joe Blow as the third party. Lets say Joe Blow is my favorite, but if he doesn't win I would rather Obama then Romney. Well if I vote for Blow a... |
Did Christopher Columbus really think he landed in India? Popular knowledge says so because he referred to the natives as "Indians". But the Spanish pronunciation of "indigen" sounds like "indi-hen", which is awfully damn close "Indian". | [
"Columbus didn't think he was in India as we think of India today. Instead he thought he was in the Indies (what we'd call Indonesia today). Upon his return to Europe, he wrote a letter to be sent ahead to King Ferdinand, saying \"Since I know that you will be pleased at the great victory with which Our Lord has cr... | [
"The word for German in German is Deutsche. The Netherlands was founded by a Germanic people, whose language was functionally similar to German."
] |
Why doesn't a pistol shrimp's snap boil water? | [
"Not enough energy to. It's like lighting a match in a snow storm and expecting it to melt everything. Sure, the match is hot, but theres a lot more cold than there is hot."
] | [
"The gun-type design is extremely inefficient - the Wikipedia article on Little Boy claims only 1% of its U-235 underwent fission. Implosion is better, with about 20% of the plutonium fissioning in Fat Man. Presumably > 50 years of nuclear weapons design has since improved on these figures. A reactor's fuel rods ca... |
What Are Super Acids? | [
"Typically, [superacids](_URL_0_) are prepared by combining a suitable Lewis acid and Bronsted acid - the typical example is antimony pentafluoride and hydrogen fluoride together make fluoroantimonic acid. They're extremely powerful acids, capable of - among other things - protonating hydrocarbons, which is essent... | [
"That's your salivary glands secreting extra saliva to \"dilute\" the sour food. They kind of go into hyperdrive so they hurt..."
] |
what are "kills" in new york and parts of Pennsylvania? And why are they named like that? (ex: Fishkill) | [
"\"Kill\" means \"creek\" in Dutch. The Dutch are who colonized that region and named most of the places."
] | [
"For example: I'm going to keil you, bitch! could also be I'm going to keil [sic] you, bitch! It's a direct quote that acknowledges that there is a spelling error, but also that it is being left in there and is not a mistake by the people publishing the quote."
] |
monstrous and umbral moonshine. | [
"These are *very* advanced math topics. I took a lot of math in university and didn't even come across the subject areas that they are a part of. You may need to ask in /r/askmath."
] | [
"Gelatin is a good guess, but They're actually [Polyvinyl Alcohol](_URL_0_). Source: Used to work for the company that makes the material that cascade makes its pouches out of."
] |
How is Amazon getting away with these "sales?" | [
"The list price is a manufacturer's suggested retail price (MSRP) and for the most part, the value itself is meaningless; you could set it to whatever you want and in many cases, the retail price is probably artificially inflated to give the impression that the item is worth more than it actually is. It's a dirty b... | [
"someone earlier on ELI5 asked why Snoop Dogg could talk about smoking weed and not get arrested, and this is similar. It's just not worth police time chasing down minor offenses that they see on TV. Especially when they have no way to prove what they saw on TV was real"
] |
Why do dreams tend to end on a cliffhanger as you wake up? | [
"Someone came up with[ a plausible answer](_URL_0_) some time ago, in which dreams are created in moments before you wake up ;)"
] | [
"Simply put for the same reason drinking water when you're not thirsty isn't as refreshing as when you're REALLY thirsty. Anticipating the bodies' needs doesn't trigger the same reward responses in the brain as fulfilling a need that is already present. Your muscles don't NEED to stretch right now, so you can't ant... |
what happened on Natalie Dormers AMA that got everyone so riled up? | [
"I figured this was more of a /r/outoftheloop question, and what do you know, I found this: _URL_0_"
] | [
"One of the best comments ever posted on reddit: [Why exactly nothing can go faster than the speed of light](_URL_0_) Anything else is a pale imitation."
] |
If someone brought a dossier back with complete scientific information on how to build a nuclear weapon, would it have been possible for a nineteenth century power to build a bomb, all other factors being the same? | [
"Building a nuclear weapon isn't that complicated. The hardest part is enriching the uranium, which requires a [gas centrifuge](_URL_0_) which isn't a super complex device. With some good plans and a lot of money, I think it would have been possible. Building a rocket to launch it on would be much harder."
] | [
"This is just a meta comment, but you really don't want experts of the Cold War here. You want experts on periods _prior_ to the Cold War. It is worth noting that pretty much all of the millenarians of the past — the people who believed the world was close to ending — believed it was going to be because of divine ... |
In Christianity, from where the thought "love and fear our lord" originates from? | [
"Many times when followers of the Abrahamic faiths say \"fear of God,\" they mean it in the sense of reverence rather than what we think of when we hear the word \"fear\" (being afraid and cowering). The [Catechism of the Catholic Church](_URL_3_) describes the fear of God as one of the seven gifts of the Holy Spir... | [
"Infants and children need bonding and attachment. When they get hurt, they aren’t sure what to do and rely on the adults around them for comfort and care. We as adults teach children that it’s ok to fall and get back up from it to keep going. It’s what we were taught as children and now as adults it’s easier to st... |
Why do things prefer to be in the lowest energy state? | [
"Things in a higher energy state can spontaneously transition to a lower energy state, even of nothing else is around, by releasing energy. But they cannot spontaneously go to a higher energy state if nothing else is around, as thank to energy conservation, this requires an input of energy."
] | [
"Let's say your computer is a line of students (programs) in primary school waiting to be served lunch (processing resources). Skyrim, the school bully, has the notorious reputation of beating other kids up to get the Fullscreen pass which allows him to cut in front of the lunch line so he gets the highest priority... |
Where do asteroids come from? | [
"Astroids are rocks. Often born from leftover matter not consumed by terrestrial planets and moons. Part of the planetary process."
] | [
"Satellites are on a set orbit. The scientists put the satellite into that orbit to begin with, so they know when and where in space the satellite is going to be. When they launch a new satellite, they just calculate the appropriate trajectory and launch time to get the new satellite into space without hitting the ... |
How do waves transfer Energy | [
"thermal energy in earths magma below crust > kinetic energy in tectonic plates (earthquakes underwater) > kinetic energy in water. the energy is then lost in a lot of ways, im guessing, at a fundamental level, because work is done against gravity as it moves out of the sea, but also friction with everything the ts... | [
"Imagine you have a computer on your house. Now you want to connect that computer to your friend 100 miles away. How do you do it? You could lay a 100 mile cable, but do you have the permissions to dig up roads and pathways? You would use a company whose cables were already there, and just use that network of cab... |
How do large companies send bulk letters? | [
"I worked at a company where I spent one whole week with just printing letters (I had data from excel worksheet), putting them into envelopes and then bringing them to post office. I had to take one colegue with me, because every day, it was like 60 kilograms of envelopes. So it’s mostly repetitive boring work som... | [
"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 ... |
Certain institutions (the Catholic Church, British government, Subway, etc.) seem to put an incredible amount of effort into covering up pedophiles in their ranks. Why? What's the logic there? Is there an argument FOR protecting sexual predators? | [
"In what way did Subway protect Jared Fogel? I never once heard them accused of that."
] | [
"Mostly because Pandas never really needed to blend in to survive. They don't really have any predators and they don't hunt for their food. If they had something to hide from, then the least robust pandas would survive and generations down the line, they would not be as patchy and more closely resemble their surrou... |
Any good books on the Reconquista? | [
"A lot! O'Callaghan is a good general history. Also check out: [Medieval Spains](_URL_2_) -another good general work [Reconquest and Crusade in Medieval Spain](_URL_4_) - another O'Callaghan, talking in particular about the philosophical underpinnings of the Reconquest [Medieval Iberia](_URL_1_) - a collection of p... | [
"Check out 'East of the Sun'. It is a history of Russian conquest of Siberia from the middle ages to Soviet times. _URL_0_"
] |
How does being poor cause failure in school? | [
"Other commenters got a lot of the big reasons. In addition to those already mentioned, poor children often have received poor nutrition, which makes it difficult to learn: it's hard to learn if any of your basic needs aren't met, if you're hungry, or scared, or homeless, learning is not your first priority. Poor k... | [
"Above the threshold of the oracle at Delphi were three inscriptions which are characteristically Greek. The one to focus on here would be \"nothing in excess\". The Greeks believed that people should live life on a fine line where they sought to achieve personal excellence while at the same time remembering their ... |
When you point a laser at an object, what is the pattern we see when it hits? | [
"It’s called a [speckle pattern](_URL_0_). The laser sends out light in organized waves, not willy-nilly, so you get interference patterns. In some places, the waves cancel each other out, and in others, they sync up. Most of the time you are seeing subjective speckles. The cool thing is that even if you blur the d... | [
"It would reflect off the mirror forever. However, there's no such thing as a perfect mirror, so you couldn't actually do this."
] |
What happened to property owned by Loyalists after the independence of the USA from GB? | [
"I find the assumption that the Loyalists fled \"back to Britain\" a bit problematic. The majority were not born in Britain but were rather North American colonists living in the thirteen colonies who remained loyal to and \"rendered service\" to the crown. More than 50,000 (about half of those who fled) went to th... | [
"_URL_0_ It's amazing how often buildings are owned by a different company than the one that occupies it. For example, a hotel company may not own the hotel, a retail company may not own the store. Sometimes when a high-rise is constructed, a certain percentage of the building will be sold off to become individuall... |
why objects in video game cutscenes look unnatural when a character is holding them? | [
"When you pick something up in real life, you are manipulating the object. When doing 3D modeling for a cut scene, the objects are manipulated with animation and the character is not actually holding it, rather the objects motion with the character is a separate animation. It's like the characters are puppets and t... | [
"Okay. So let's say that you want to bake a cookie just like the ones that grandma makes. You could try to eat her cookie, and then using your knowledge of baking sort of reverse engineer it, but it would be an incredible hassle and very hard to do. But if you had the recipe she used, it would be very easy to figur... |
How do calculators work? | [
"Basically its a chip that performs basic arithmetic math known as an ALU (Arithmetic Logic Unit) which takes in inputs and outputs/converts to a display. Edit: I know this is ELI5 but this stuff is very complex. I gave a high level answer and if you want to know more maybe /r/askscience would be a better place for... | [
"\"magic\". This question is repeatedly asked. You need to ask more specific questions as there are a lot of things to answer."
] |
why is it that when i wrap myself tightly in my covers and pillows that my anxiety eases? | [
"Could it be that it resembles the feeling of the womb? Purely biological."
] | [
"Our brains didn't evolve with cars in mind. They evolved with, like, being hunted by a jaguar (or whatever) in mind. So your brain doesn't know what to do with a car. It thinks hey, we're sitting, our body's not really doing anything physical, there's very little activity or stimulus... this seems like a good time... |
Why does Windows create input lag when not in fullscreen? | [
"The full answer to this is pretty complicated, but in simple terms, it's because in fullscreen your PC has less to do. When a game (or any other application) renders in fullscreen, it essentially \"owns\" the display. 100% of your computer's graphics power can go to it. When you're in a windowed mode, your compute... | [
"When you take too big a swallow, it stretches your esophagus, causing it to spasm. This hurts."
] |
Do people with no arms/legs have less blood meaning they have more chance to die due to blood loss? | [
"Yes. It's a ratio thing. Smaller choo choo trains have smaller gas tanks. So when they lose a gallon it's a lot more than a big choo choo train losing a gallon."
] | [
"They don't directly connect, but they have pads with sensors that are pressed up against the skin of whatever is left of the limb. With training, the amputee can learn how to trigger the sensors to get the desired movement out of the limb."
] |
Why don't we invent new sports? | [
"We invent new sports all the time. My favourite is [Ultimate Taser Ball!](_URL_0_) Edit: [Video of people playing Ultimate Taser Ball](_URL_1_) and also the [Official Website](_URL_2_) of UTB."
] | [
"Inflation. Let's put it this way, in America it used to be that you could buy a steak dinner for let's say $5. Then today that same steak dinner would cost $50. How much we pay for things, and how much we get paid has increased slowly over time. In other countries, it has increased way faster, so something that us... |
Was there a contingency plan during the American Revolution should Washington be captured/killed? | [
"There wasn't a clear contingency plan, but they wouldn't really need one. As you've mentioned, there was a pool of Major Generals one rank beneath General Washington. Upon Washington's death, command would pass to the most senior Major General until such time as Congress named a replacement. Between 1777 and 1780,... | [
"Follow-up: What was the the next course of action if the patient didn't improve with the standard remedy of their time?"
] |
Why does air have high resistance to electric flow? | [
"Electricity is only carried by charged particles. Metals are good for this as they have loads of electrons (negatively charged) that can move freely and are quite closely packed. Not only is air not very closely packed, it's normally quite neutral, so any charges in it can't carry electricity very well."
] | [
"A few more interesting facts: 1) The earliest morse code transmitters used to establish the first intercontinental radio links were nothing more than rotating disc dragging a series of conducting plates across a metallic lead and generating a shower of sparks (google SPARK GAP TRANSMITTER). As discussed elsewhere ... |
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