Split (2)

train · 226k rows

question stringlengths 3 301	answer stringlengths 9 26.1k	context list
how does a random function work?	A random number generator like the one typically used by a computer to generate random numbers isn't actually random. It is what is known as a pseudo-random number generator. It generates numbers according to a certain algorithm that first is initialized with a value called seed. For different seed values, differen...	[ "A random function is a type of random element in which a single outcome is selected from some family of functions, where the family consists some class of all maps from the domain to the codomain. For example, the class may be restricted to all continuous functions or to all step functions. The values determined b...
why can some brands completely rip off other brands designs on certain products?	Per a quick google search, they are often lawsuits for this. However, I’d hazard a guess that court costs and lawyer fees are factored in before moving forward. Generic copy at Walmart maybe only profits 40k$, but the lawsuit would cost 200k for both sides. It’s now a loss to sue and not worth moving forward. Adidas su...	[ "Designer branding is sometimes associated with a higher quality of manufacture and a higher price. The ownership and display of such products of quality is frequently marketed to suggest that the wearer will automatically embody a personal characteristic of quality by association. Designers have identified this an...
does convolution of signals have an intuitive explanation like the water-flow example for voltage and current?	Have you heard of convolution reverb? Basically, you take an impulse response from, say, a cathedral, and then you can convolve it with any sound signal to make it sound as if it were in the cathedral. So i guess a convolution is kind of like an echo. A bit like sonar - when there is something x-metres away, you'll g...	[ "In the \"water-flow analogy\", sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage (difference in electric potential) is likened to difference in water pressure. Current is proportional to the diameter of the pipe or the amount of water flowing at that pressure. A resisto...
the definition of “literary theory”	I suppose there isnt one definition but a literary theory woukd be a way in which yoi can understand/interpret literature. For example you could read a text in a feminist or post colonial way and theyre both literary theories. Or you could theorise on what literature itself is, for example literary theorist Roland Ba...	[ "As a consequence, the word \"theory\" has become an umbrella term for a variety of scholarly approaches to reading texts. Many of these approaches are informed by various strands of Continental philosophy and of sociology.\n", "A theory is a contemplative and rational type of abstract or generalizing thinking ab...
Mistakes Germany made on Russia	Wall of text- I'm sorry but it's a really complex answer that I've already really pruned down. I'm going to direct your attention to a frequently underappreciated aspect of the historiography- differing conceptualisation of warfare at an operational level. Under appreciation for this level of history stems from a West...	[ "As Russia's war losses increased, so did anti-German hysteria. They were held responsible for the disastrous course of the war and were accused of being spies and saboteurs betraying Russia. Anti-German measures reached a nadir with the government's so-called Liquidation Laws, of February 1915, authorizing it to e...
Paper vs Electronics	To add to that, how much difference is there between an e-ink e-reader and an actual book?	[ "Electronic paper, also called e-paper, is a display technology designed to mimic the appearance of ordinary ink on paper. Electronic paper reflects light like ordinary paper and is capable of holding text and images indefinitely without drawing electricity, while allowing the image to be changed later. Application...
How come Denmark ruled the Kalmar Union during 14-16 centuries, while Sweden was humongous in territory and Norway was considerably larger as well?	Well, first let's sort out what the Kalmar Union _was_ (and wasn't). It was a personal union, where three different countries had the same monarch. All three Scandinavian countries had elective monarchies at that time, albeit with a preference for electing people within he same dynasties. So the nobles (or _stormän_,...	[ "The Kalmar Union (Danish/Norwegian/Swedish: \"Kalmarunionen\") was a series of personal unions (1397–1520) that united the three kingdoms of Denmark, Norway and Sweden under a single monarch. The countries had given up their sovereignty but not their independence, and diverging interests (especially Swedish dissat...
how do we know what prehistoric life was like?	We have a good understanding of biomechanics, how the shape of bones, their growth and wear patterns, how ligaments were attached, and a lot of the details that tell us how the moved, how they ate and hunted. Teeth can tell you a lot about what sort of food an animal ate. The design of the head tells you how big the...	[ "In addition, fossil remains of some hitherto undescribed prehistoric species have been found. The oldest comes from the Late Miocene (Tortonian, some 7 to 12 million years ago) of the Bahía Inglesa Formation in Chile.\n", "The idea of prehistoric animals surviving into the present day was not new, but had alread...
What was the fire rate of the matchlock musket, and how did it compare to wheel locks and flintlocks?	16th century sources do indeed tend to be pretty unclear when it comes to firearm's rate of fire. Humfrey Barwick was a strong proponent of firearms at the end of the century and as such is probably represents the upper end of what might be expected in terms of fire rate. While serving as a mercenary for the French arm...	[ "At the end of the 17th century, a flaw within the design of matchlock muskets became more apparent. Since the matchlock musket used a slow burning piece of twine known as a slow match, the twine sometimes would accidentally set fire to the gunpowder reservoir in the musket prematurely setting off all of the gunpow...
what's a good source of hydration during a hurricane if water supply in stores is sold out?	The point is to stock up beforehand. Water comes out of your faucet for hundreds of times cheaper than in the store.	[ "To prevent casual use or misuse, the hydrant requires special tools to be opened, usually a large wrench with a pentagonal socket. Vandals sometimes cause monetary loss by wasting water when they open hydrants. Such vandalism can also reduce municipal water pressure and impair firefighters' efforts to extinguish f...
why does canceling a credit card with a zero balance hurt my credit score	Assuming you have other credit and you have outstanding balances. Canceling increases your credit utilization %.. Lets say you have two cards and one has a balance A:$50/$100 B: $0/$100 You are using 25% of your available credit. You cancel card B Your are now using 50% of your available credit. Credit scores are a...	[ "Because a significant portion of the FICO score is determined by the ratio of credit used to credit available on credit card accounts, one way to increase the score is to increase the credit limits on one's credit card accounts.\n", "However, this law did not prohibit all forms of universal default. Credit card ...
Do computer screens have a direct effect on our levels of melatonin?	The short answer is: yes, [computer monitors suppress the natural release of melatonin during the biological night](_URL_8_). But this is not unique to computer monitors -- all artificial and natural light that is bright enough suppresses melatonin, including blue and other colors of light. Here is how melatonin rel...	[ "Interest lies in the fact that MDA and MDMA may not themselves be responsible for their neurotoxicity, as an intracerebroventricular injection does not appear to cause neurotoxicity. While many studies suggest excitotoxicity or oxidative stress as likely mechanisms, which may be an effect of MDMA itself, this has ...
why do indian reservations have such high unemployment?	Very true and in case you have forgotten, the reservations were the tracts of mostly worthless land nobody wanted, far from civilisation. That should explain the dismal prospects ofvthe denizens.	[ "Native American reservation inequality underlies a range of societal issues that affect the lives of Native American populations residing on reservations in the United States. About one third of the Native American population, about 700,000 persons, lives on an Indian Reservation in the United States. Reservation ...
how do motor boat engines not get water logged?	Same reason your car motor doesn't get water logged when you drive in rain or puddles. The motor is not in the water. It's spins a shaft which is also attached to a propeller, that goes into the water.	[ "The Amphicar's engine was mounted at the rear of the craft, driving the rear wheels through a 4-speed manual transmission. For use in the water, the same engine drove a pair of reversible propellers at the rear, with a second gear lever engaging forward or reverse drive. Once in the water, the main gear lever woul...
Are there any good book (for layman) about climate changes and their impact on the course of human history/prehistory? Hopefully with maps.	Although comprehensive only in the sense that it attempts to cover the whole globe across most of the seventeenth century, with special focus on the impact of the Little Ice Age and associated abnormal El Nino episodes, Geoffrey Parker's book The Global Crisis (2013) is a major contribution by a senior historian to ...	[ "Field Notes from a Catastrophe: Man, Nature, and Climate Change is a 2006 non-fiction book by Elizabeth Kolbert. The book attempts to bring attention to the causes and effects of global climate change. Kolbert travels around the world where climate change is affecting the environment in significant ways. These loc...
reverse entropy	imagine you have a jar of marbles that you tip over. The marbles all go out in different directions, ricochet off of eachother, and settle. Now, you must put them back how they were before. How? That's impossible, that's so much data to somehow learn, which way each marble went and what it hit and how at what angle and...	[ "The linear entropy then is obtained by expanding ln \"ρ\" = ln (1−(1−\"ρ\")), around a pure state, \"ρ\"=\"ρ\"; that is, expanding in terms of the non-negative matrix 1−\"ρ\" in the formal Mercator series for the logarithm,\n", "A reverse salient refers to a component of a technological system that, due to its i...
how do companies like walmart profit from selling gift cards to other services when a gift card costs the amount of credit it's worth?	it is a strategy used to get people in the door, much like a sale, it is ok to not make as much money on one or two items because usually when people come in they buy more than they were intending to in the first place, it happens. so to get people in the door it is actually more profitable to sell some things at a red...	[ "In fact, many sellers could not qualify for a credit card Merchant account because they lacked a commercial credit history. The service also appealed to auction buyers because they could fund PayPal accounts using credit cards or bank account balances, without divulging credit card numbers to unknown sellers. PayP...
Why are owls associated with intelligence?	To answer the former question: Athena was the protector of Athens. Athena had an owl because owls were abundant in Athens. There's a proverb that says "bring owls to Athens" for a pointless venture. edit: I was answering the question of why owls are associated with the Greek goddess Athena.	[ "BULLET::::- Although owls are often associated with wisdom and intelligence, this is not universal, nor a timeless image. During the Middle Ages owls were seen as stupid and evil helpers of witches. In many paintings of Hieronymus Bosch the bird is seen as a symbol of stupidity and/or evil. The Dutch profanity wor...
sound effects	Yes, sometimes they just go out to a shooting range or go out driving with a bunch of sound equipment. Usually for movies they just buy the sound effects from someone who already did that and is selling all the sound effects. Either way, studios end up with libraries of sound effects they use.	[ "A sound effect (or audio effect) is an artificially created or enhanced sound, or sound process used to emphasize artistic or other content of films, television shows, live performance, animation, video games, music, or other media. These are normally created with foley. In motion picture and television production...
How important are cyanobacteria to keeping the earth's atmosphere oxygenated?	Indeed, they are very important. [Here](_URL_0_) is a Nat. Geo. article on this very topic (though they are talking about all phytoplankton, but just cyanobacteria). It's a bit old (2004), but still agrees with several other more recent sources I found. The short answer is that, yes, photosynthetic unicellular marin...	[ "While prokaryotic cyanobacteria reproduce asexually through cell division, they were instrumental in priming the environment for the evolutionary development of more complex eukaryotic organisms. Cyanobacteria (as well as extremophile Gammaproteobacteria) are thought to be largely responsible for increasing the am...
is it true that if you eat human flesh your body will uncontrollably shake? if so, why?	It could happen, yes. It's due to a prion disease called Kuru: _URL_0_	[ "In modern humans, necrophagy (eating of dead/decaying flesh) occurs rarely in most societies. This is likely an adaptation to the risk of disease, due to humans having lower levels of protective acids in the digestive tract, compared to species that are dedicated scavengers. Many instances have occurred in history...
how is the sugar coating on sour candy so much different than table sugar?	From Wikipedia: Sour sanding, or sour sugar, is a food ingredient that is used to impart a sour flavor, made from citric or tartaric acid and sugar. It is used to coat sour candies like Sour Patch Kids or to make hard candies tart, such as acid drops or SweeTarts. It's not quite the same thing.	[ "Sugar candy is made by dissolving sugar in water or milk to form a syrup, which is boiled until it reaches the desired concentration or starts to caramelize. Candy comes in a wide variety of textures, from soft and chewy to hard and brittle. The texture of candy depends on the ingredients and the temperatures that...
how are airplanes able to travel through the air despite being heavier than air? also, what exactly is jet propulsion?	Airplanes fly by generating lift. Their wings are shaped in such a way that when they are moving through the air, the air passing over the top of the wing is moving faster than the air moving under the wing. The faster that air moves, the lower pressure it has. Since the faster moving air on top of the wing has less pr...	[ "There are different approaches to flight. If an object has a lower density than air, then it is buoyant and is able to float in the air without expending energy. A heavier than air craft, known as an aerodyne, includes flighted animals and insects, fixed-wing aircraft and rotorcraft. Because the craft is heavier t...
when you forget something, why does retracing your steps often make you remember? (such as going back to a webpage you closed or redoing the activity you were doing)	For me, it tends to be that something in what I was doing was the impetus for the thought to begin with. When that stimulus occurs again, the thought happens again in the same way it did initially.	[ "There are two theories that can explain directed forgetting: retrieval inhibition hypothesis and context shift hypothesis. The Retrieval Inhibition Hypothesis states that the instruction to forget the first list hinders memory of the list-one items. This hypothesis suggests that directed forgetting only reduces th...
Is radioactive decay temperature-dependent?	Typically is not, the nucleus is so much smaller than the atom that it doesn't "care" what's happening around it (imagine a marble at the center of one of those giant human hamster balls). There are maybe a few small exceptions. One could argue that the electron-capture mechanism (sometimes called inverse beta decay)...	[ "The mathematics of radioactive decay depend on a key assumption that a nucleus of a radionuclide has no \"memory\" or way of translating its history into its present behavior. A nucleus does not \"age\" with the passage of time. Thus, the probability of its breaking down does not increase with time, but stays cons...
batteries: rechargeable vs disposable	Rechargable batteries have different chemistry from disposable batteries. And the different chemistries result in various pros and cons. A NiMH AA has a voltage of 1.2, but an alkaline AA is 1.5. But most electronics tolerate these small differences. A more significant difference for a user would be the problem of...	[ "A rechargeable battery, storage battery, secondary cell, or accumulator is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or primary battery, which is supplied fully charged and discarded after use. It is composed of one or more elect...
why was microsoft criticised for bundling a browser and media player with their os, but is apple allowed to bundle a computer with their os?	Microsoft was leveraging its monopoly to put a much smaller rival out of business.	[ "The plaintiffs alleged that Microsoft had abused monopoly power on Intel-based personal computers in its handling of operating system and web browser integration. The issue central to the case was whether Microsoft was allowed to bundle its flagship Internet Explorer (IE) web browser software with its Windows oper...
why do some nutrition labels read "total carbohydrates 30g" but sugars will say "sugars 22g"?	Sugars are a simple type of carbohydrate. Fibre (cellulose) is technically a carbohydrate, but it is not digestible and has no direct nutritional value. It is therefore not included in the total carbohydrates of food.	[ "This is a list of sugars and sugar products. Sugar is the generalized name for sweet, short-chain, soluble carbohydrates, many of which are used in food. They are composed of carbon, hydrogen, and oxygen. There are various types of sugar derived from different sources.\n", "Sugar is the generic name for sweet-ta...
what do the schrödinger and dirac equations describe and what's the difference?	The Schrödinger equation (ih d/dt psi = H psi) is a very general statement about quantum mechanics: the phase of a state changes (it ”turns”, in a way) proportional to its energy. It can describe many different things as long as you use the correct H. Note that I’m NOT talking about the common formulation ih d/dt psi =...	[ "the Schrödinger equation is turned into an integral equation. The \"in\" and \"out\" states are assumed to form bases too, in the distant past and distant future respectively having the appearance of free particle states, but being eigenfunctions of the complete Hamiltonian. Thus endowing them with an index, the e...
English (Latin?) certainly made its view of left-handed people clear (sinister - left handed) but are there any cultures were left-handedness is seen as better than right-handedness?	You might try /r/Askanthropology. There may be someone here with the answer, but this other sub has a concentration of people with a background in comparative ethnography.	[ "Moreover, apart from inconvenience, left-handed people have historically been considered unlucky or even malicious for their difference by the right-handed majority. In many European languages, including English, the word for the direction \"right\" also means \"correct\" or \"proper\". Throughout history, being l...
obama's new jobs bill.	You can read about it [Right Here](_URL_0_) from a previous ELI5. Cheers.	[ "The American Jobs Act () (H. Doc. 112-53) and (H.R. 12) is the informal name for a pair of bills recommended by U.S. President Barack Obama in a nationally televised address to a joint session of Congress on September 8, 2011. He characterized the proposal as a collection of non-controversial measures designed to ...
what makes the noise in an engine?	Its either the engine lifter's noise, valve noise, the combustion, bearing noise, or the exhaust of the car itself you're talking about at the moment. Vroom vroom.	[ "In recent years, the engine has developed a noise, referred to as \"The Squeak\". While the cause of this noise is not definitively known, it is presumed to come from the low pressure valve. There are no physical indications of scuffing, galling, or damage to components indicating a metal-to-metal contact. The squ...
what is al qaeda fighting for?	Its not a simple answer because Al Qaeda is NOT a simple terrorist group. The point of Al Qaeda, as laid out by Bin Laden, is not a single group with a single goal, but as the Arabic translation plainly tell us, to be "the base" for multiple related but not 100% similar groups, causes, and goals. This is NO single t...	[ "Al-Qaeda operates as a network of Islamic extremists and Salafist jihadists. The organization has been designated as a terrorist group by the United Nations Security Council, the North Atlantic Treaty Organization (NATO), the European Union, the United States, the United Kingdom, Russia, India, and various other c...
why does styrofoam melt when it comes into contact with superglue/adhesives?	Super glue and other adhesives contain some organic solvents (e.g. acetone, ethyl acetate). Styrofoam is made from thousands of styrene molecules linked together. Styrene by itself really wants to dissolve in these organic solvents, but since so many of them are linked together it can't because it's simply too big. So ...	[ "Two: Adhesion: Polyamide materials are basically high performance hot-melt adhesives. The adhesive properties of polyamide is what seals a chosen substrate. The type of adhesion is purely mechanical i.e. no chemical reaction takes place.\n", "Hot-melt adhesives are as numerous as they are versatile. In general, ...
how do services like pandora and spotify work	same way any business operates. sell it for more than you buy it. if it costs $10,000 for Pandora to buy the rights for a song, and they play it on 1million users and get advertising $0.01 per play, then that's profit.	[ "Pandora (also known as Pandora Media or Pandora Radio) is an American music streaming and automated music recommendation internet radio service powered by the Music Genome Project. The service, operated by Sirius XM Satellite Radio, is available in the United States. The service plays songs that have similar music...
putting down animals in zoo	Did you read the rest of the article? They explained exactly why they did it. They didn't have the money to relocate the animals, and the new animals they were getting would have killed the old animals -- euthanasia makes a little more sense than a zoo snuff show. It's more important to look at the population of the ...	[ "Formerly the reptile house, Zoo At Home is a zone for pet animals. It was adapted with the assistance of Pets At Home. It is also currently home to the zoo's Madagascan giant jumping rats. As of September 2012 the area became the Animal Cafe, where visitors can eat as they watch the animals.\n", "On 2015 it was ...
why is it easier to fall asleep to background noise (radio, tv etc.) than just the plain dark?	This happens because when there's noise around us we feel that someone is near us. Thus we feel safe and can let go of the tension and fall asleep. This is an evolutionary thing and has been embedded in our DNA. Humans are primarily social animals and keep each other safe.	[ "Noise can make sleeping difficult on occasions, whether from snoring, talking and social activities in the lounge, people staying up to read with the light on, someone either returning late from bars, or leaving early, or the proximity of so many people. To mitigate this, some wear earplugs or eye-covering sleepin...
how are amputees able to control the fingers in their bionic arm ?	The company I work at actually exclusively works on this! /u/WashingtonFierce post is incorrect, we do not yet have commercial technology designed specifically to physically interact with the brain and detect limb movement. The amount of time, money, and risk is prohibitively monumental. Imagine being an ethics revi...	[ "The Lancet published a 2012 UPMC study of two 9 year quadriplegics being able to move a robotic arm by thought, to pick up objects, shake hands, and even eat. Wiring the brain around spine damage to restore arm and leg muscle function was successful using robotic arms controlled via an embedded computer to transla...
I have a weird question about micro-gravity.	I'll attempt to answer part of this question seriously. I wouldn't know anything about the first two questions, but in terms of the third question you may be interested in [this nice Slate piece](_URL_1_) which has quite a bit of information. In addition, you have several problems with radiation. Cosmic rays can dam...	[ "The term 'micro' gravity refers to a gravitational state that is 'low' (i.e., 'micro' in the sense of 'small' and not necessarily a millionth of Earth's normal gravity) such that the influence of buoyancy on physical processes may be considered small relative to other flow processes that would be present at normal...
why haven't we seen the us (and its partners in the fight against isis) engage in a siege of raqqah, the "de facto capital of isis"?	1. Raqqa is surrounded by other territories controlled by Islamic State, so to surround it you need to fight IS on at least two fronts (both sides of the Euphrates). 2. Any effective form of siege could have to involve cutting off food, water, or electricity, which would result in massive civilian casualties and would...	[ "On 3 August 2014, ISIL captured the cities of Zumar, Sinjar and Wana in northern Iraq. Thousands of Yazidis fled up Mount Sinjar, fearful of the approaching hostile ISIL militants. The stranded Yazidis' need for food and water, the threat of genocide to them and to others announced by ISIL, along with the desire t...
Was there any ethnic tension between Germans, Slovaks, Slavs, etc... in the early 1900's and leading into the second World War? If so, what was it like?	Of course there was. In the early days of Czechoslovakia, tensions between Czechs and Germans were a major issue that would later play a part in the months preceding the Second World War and the occupation of Czechoslovakia, and that would only be resolved until after the war. And even then only via the highly controve...	[ "After World War I, the population expanded with an influx of Gottscheers—an ethnic German population from Slovenia who were dislocated in the aftermath of World War I—and Irish, followed soon after by Italians. In April 1934, a large, 9,000-person boycott of Nazi Germany resulted in brawls between Nazi sympathizer...
when did the storefront name of "arcade" go from being a kids' video-game hangout, to being an 18+ slot machine parlour?	It happened due to home gaming consoles. Older redditor here. I used to play the quarter-munchers back in the days before everyone with teens or kids had at least a couple game consoles... and the earlier generations were really shitty. So you'd go to the "pinball arcade" to play games with much better features like a...	[ "The arcade was built by Watertown native Loveland Paddock and designed by architect Otis Wheelock. It was based on similar arcades built during that era in the United States and Europe. Shops occupied the bottom floor, while the upper floors were used for office space.\n", "The name of the arcade version was a r...
what is the difference between readings books (any kind) and reading various reddit articles/threads?	Reddit posts & articles are usually fairly short. There's not a lot of depth or nuance going on - especially the front page, which is full of image, memes and other such easily digestible things (not to mention all the articles that get commented on by people who never read the link). A book, or long-form article r...	[ "Reading, by definition, is the ability and knowledge of a language that allows comprehension by grasping the meaning of written or printed characters, words, or sentences. Reading involves a wide variety of print and non-print texts that helps a reader gain an understanding of the material that is being read. Read...
Was Cato the Younger a Pleb or patrician?	> When Clodious , who was from a minor patrician family Minor?! The gens Claudia was one of the largest and most prestigious patrician gentes, outstripped only in surviving patrician lines by perhaps the gens Cornelia. To call Clodius a member of a minor family is like calling the sun a little hot. [You're c...	[ "The real Cato was much younger than his fictional counterpart appears: in 52 BC, the year the series opens, he was 43, seven years younger than Caesar. He was also not as contemptuous of plebeians as the series makes him: he established a provision of state-subsidised grain to poor Romans, and Cato was himself a p...
Why did the Irish Rebellion in 1798 fail?	In short (don't have much time, so perhaps someone can expand on this) 1. Three of the United Irishmen's top brass were arrested on the eve of the uprising. 2. Artillery stationed in Ireland had been upgraded and increased in size. One Lieutenant was to describe that the 'Grapeshot (cannister) worked like a wonder' ...	[ "The Irish Rebellion of 1798 was assisted by a French invasion force under Jean Joseph Amable Humbert. The rebellion and the invasion failed. To secure control of Ireland, the Parliament of Ireland and the Parliament of Great Britain negotiated a merger of the two kingdoms. The Act of Union 1800 resulted in the for...
why can paying off your student loans hurt your credit score? it seems like it would be a good thing.	Part of a credit score is being able to prove you can pay off debt, which requires having debt to begin with. That’s why people who have never had a credit card or loan generally don’t have good credit. Without any debt, you can’t prove you have the ability to pay it off, hence the lower score. To summarize, lots of d...	[ "In coverage through established media outlets, many borrowers have expressed feelings of victimization by the student loan corporations. There is a comparison between these accounts and the college credit card trend in America during the 2000s, though the amounts owed by students on their student loans are almost ...
What was the primary warship of the Indian Ocean before the advent of the modern period?	One particular aspect of maritime situation in the Indian ocean in the second half of fifteenth century which is often emphasized by scholars, is the relative peacefulness and absence of large scale naval conflicts. The accent here is really on the word relative as piracy was abundant and there was plenty of nava...	[ "For the most of the 16th century, the Portuguese India Armadas and fleets, then the world leader navy of shipbuilding and naval artillery, dominated most of the Atlantic Ocean south of the Canary Islands, the Indian Ocean and the access to the western Pacific.\n", "In the 1830s, the Portuguese Navy incorporated ...
when i'm tired, every now and then i will go through bouts of extreme drowsiness where i can't even keep my head up and eyes open, but after about 5-10 minutes i am awake again and completely fine. what are these cycles and how do they work?	This can't be as abnormal as other posters are making it out to be. I experience the same problem sometimes if I did not get much rest the night before and I am doing something uninteresting. I try to think about how important it is that I stay awake in a meeting with my boss, for example, but sometimes I find it legit...	[ "The wake maintenance zone generally lasts 2 to 3 hours, during which one is less inclined to fall asleep. While potentially useful for completing urgent tasks, it may have a potentially unwanted side-effect of keeping one awake for several hours after the task has been completed. The hypervigilance and stimulation...
suitjacket, sportcoat, and blazer? which situation calls for which jacket?	Sport coats have patterns, unlike blazers, which are solid and have contrasting buttons. Suit jackets are smooth, have tonal buttons, and should never be worn with anything other than matching suit trousers.	[ "A sport coat, also called a sport jacket (sports coat or sports jacket in American English), is a men's lounge jacket designed to be worn on its own without matching trousers, traditionally for sporting purposes. Styles, fabrics, colours and patterns are more varied than in most suits; sturdier and thicker fabrics...
why are so many large companies headquartered in minneapolis?	Minneapolis has a well educated population, the standard amenities of a major city, is a hub for a major airlines, has a high livability index, and still maintains a relatively low cost of living compared to other major cities.	[ "In 2011, the 20 largest U.S.-based companies by revenue were Walmart, ExxonMobil, Chevron, ConocoPhillips, Fannie Mae, General Electric, Berkshire Hathaway, General Motors, Ford Motor Company, Hewlett-Packard, AT&T, Cargill, McKesson Corporation, Bank of America, Federal Home Loan Mortgage Corporation, Apple Inc.,...
why are b.c. (before christ) and a.c. (after christ) the reference points we have chosen to use for historical measure, as opposed to any other major historical event?	Nowadays you often see “BCE” which stands for “Before the Common Era.” “BC/AC” was just a handy reference since many Western historians were/ are Christian.	[ "BULLET::::- Dionysius Exiguus, Scythian theologian-mathematician, inaugurates at Rome the practice of using A.D. (Anno Domini) for calendar dates after the birth of Jesus Christ (who was actually born in 7 B.C. or later). Dionysius produces also his tables for computing the date of \"\"Cyclus Paschalis\"\" (\"East...
if most psychopaths become psychopathic due to their childhood or a birth defect, why are most psychopaths male?	The debate about whether psychopaths are the result of nature vs nurture is still very much ongoing. If and to the extent it is due to nature then the sex difference in psychopathy is likely to be due to the sexual dimorphism in the brain. Both women's and men's brains are mainly formed by estrogen, but the male estro...	[ "Psychopathy has been associated with commission of sexual crime, with some researchers arguing that it is correlated with a preference for violent sexual behavior. A 2011 study of conditional releases for Canadian male federal offenders found that psychopathy was related to more violent and non-violent offences bu...
What problems was fascism intended to solve?	Hi there. There's always room for more discussion (and follow-up questions) but you might be interested in [this older answer of mine](_URL_0_) about the prelude to Mussolini's rise. [This great answer](_URL_1_) by u/Klesk_vs_Xaero is also great overview of Italy's descent into dictatorship	[ "\"Fascism is the concentrated expression of the general offensive undertaken by the world bourgeoisie against the proletariat... fascism [is] an expression of the decay and disintegration of the capitalist economy and as a symptom of the bourgeois state’s dissolution. We can combat fascism only if we grasp that it...
Why is it that the inside of fresh water pipes that feed houses don't need regular cleaning?	They are designed so that there are no blind ends or dead angles, where bacteria or deposit could build up. An example of how this failed was a case where the cooling system of a power plant had a blind end in their piping. Legionella bacteria found the place, made a little colony and then spread around the area with...	[ "Moreover, because the acidic or basic drain cleaners themselves are washed down the drain, this contributes to pollution in the water supply. The heat generation can also soften plastic PVC pipes, and the pressure buildup by gas generation can cause older pipes to burst. Commercial chemical based solutions can cau...
what makes our ears ‘clog’ in high altitudes and what makes them pop by yawning?	When you go from a lower altitude to a higher altitude, the ambient air pressure decreases. Because the air inside of your eardrum is semi-trapped (you can clear them) it expands as you go higher and puts pressure on the eardrum. When you yawn/chew/etc it helps open up the eustachian tubes that go from the backside of ...	[ "During a yawn, the tensor tympani muscle in the middle ear contracts, creating a rumbling noise from within the head. Yawning is sometimes accompanied, in humans and other animals, by an instinctive act of stretching several parts of the body, including arms, neck, shoulders and back.\n", "A similar hypothesis s...
Imagine an empty room with no windows/doors or any point of entry and escape with just a light bulb inside and a light switch outside. What will happen to light if I open the light for 10 seconds and turn the switch off? Will the brightness remains or will fade? Why?	The light will fade almost instantly. As the light strikes the wall, part of it is reflected and part of it is absorbed. The reflected light will bounce away from the wall until it hits another wall (or floor/ceiling) and then again, part of it is absorbed and part reflected. With every bounce the intensity of the rema...	[ "The width of the rooms is further subdivided into three sections of and this module determines the width of doors, windows and passages between rooms within the apartment. The wooden windows have two sets of nine movable slats that can be independently controlled to modulate the natural light in the room, they can...
why are surgical gowns, masks, and gloves green or blue?	They used to be white. There's a sort of 'surgeon legend' about the green being used because it was easier to see in a surgical field (brightly lit + whites = too bright). But then also that green/blue is actually opposite red and makes it easier to see blood. But I think it's kind of one of those "was written down som...	[ "All gowns, other than the dress gowns of doctors, are made from black material. The dress gowns of Doctors of Philosophy and other doctors of this level (such as DBA, DArch and EdD) are made in claret, while those of higher doctors are made from scarlet cloth. For this purpose, the degree of Doctor of Medicine was...
In medieval times, how long could a knight physically fight in a battle? The swords were heavy, the armor was heavy. Nutrition was poor. Could they last more than 30 minutes?	This doesn't directly answer the question, but I think you may be overestimating the weight carried/worn by a knight. The average sword weighed somewhere around 3lbs, an M16 with full ammo weighs about 9lbs. A suit of full-plate would generally weigh less than 60lbs (sometimes significantly less), such armor was also...	[ "BULLET::::- According to the given statistics, the Knight had a size advantage of 1 inch and 10 lbs; roughly equal by the standards of Deadliest Warrior matchups. However, the Knight's gear was 50 lbs heavier.\n", "BULLET::::- According to the given statistics, the Knight had a size advantage of 1 inch and 10 lb...
If I were to travel ten light years going the speed of light, would it seem like an instant to me, but ten years for an outside observer?	You cannot travel at the speed of light, so this question becomes pseudo-scientific. But let's say you were travelling really close to the speed of light. Like really, really close. Like 99.999...999% with a billion, billion 9s after the decimal place. Then yes, what you say is correct. To you, the journey wou...	[ "Since one might not travel faster than light, one might conclude that a human can never travel further from the Earth than 40 light-years if the traveler is active between the age of 20 and 60. A traveler would then never be able to reach more than the very few star systems which exist within the limit of 20–40 li...
How does pilot wave theory account for quantum fluctuations?	The guided particle doesn't move through space, it moves through the space of possible positions of all particles, which instead of just 3 dimensions has 3N dimensions, where N is the number of particles. The positions of particles in a measurement device is included in this, so the question of what kinds of measuremen...	[ "The pilot wave model, originally developed by Louis de Broglie and further developed by David Bohm into the hidden variable theory proposes that there is no duality, but rather a system exhibits both particle properties and wave properties simultaneously, and particles are guided, in a deterministic fashion, by th...
AskScience AMA Series: I am Jamil Zaki, professor of psychology at Stanford University and director of the Stanford Social Neuroscience Lab. I wrote a book called The War for Kindness, which shares stories and research about how to fight for empathy even when it feels impossible to some days. AMA!	Are there empathy building exercises that have tangible impact in practical life ? Do such exercises really work or are just scoffed off by adult participants ?	[ "G2Conline is an interactive educational website that provides extensive background information on key topics in neuroscience and brain disorders. There are many video clips of interviews with scientists, including Nobel laureates James Watson and Eric Kandel.\n", "APS publicizes psychology research in an effort ...
Does Anybody have any information on the "Phantom Divisions" of the United States Army during World War II? (Cross Posted From r/Military)	Could they be similar in role to the [Ghost Army](_URL_0_)?	[ "This is a list of formations of the United States Army during the Second World War. Many of these formations still exist today, though many by different designations. Included are formations that were placed on rolls, but never organized, as well as \"phantom\" formations used in the Allied Operation Quicksilver d...
why does it seem easier to get stuck in a comfort zone as an adult?	In the old days, life changed very slowly. The way the world worked when you were 5 years old was the same when you were 75 years old. So by the time you had reached adulthood you pretty much had figured out what there was to figure out.	[ "A comfort zone is a psychological state in which things feel familiar to a person and they are at ease and (perceive they are) in control of their environment, experiencing low levels of anxiety and stress. In this zone, a steady level of performance is possible.\n", "Ambivalent attachment is characterized by a ...
Constellations disappearing:	Stars rarely just go missing, but the constellations will change over time due to stars moving at different velocities. Here's [what some of them will look like in 50,000 years](_URL_0_).	[ "The constellation appeared in later star atlases through the 19th century but was rarely used by the end of the century; Richard Hinckley Allen noted its most recent use had been in 1878 in Father Angelo Secchi's planisphere, but stated \"it is seldom found in the maps of our day.\". The stars were later absorbed ...
Why did Britian use the bolt action Lee-Enfield as their primary battle rifle when repeating technology (M1 Garand, Gewehr 41, etc) was already developed and working?	hey, sorry for the very late answer, i hope i don't break any rules by digging up old unanswered questions. To answer this question you have to understand how the adoption of a self loading rifle would have worked in britain in the 1930's. To get a new rifle adopted, someone in the board ordnance has to be persuaded...	[ "The British Army looked at the M1 as a possible replacement for its bolt-action Lee–Enfield No.1 Mk III, but it was rejected when rigorous testing suggested that it was an unreliable weapon in muddy conditions. However, surplus M1 rifles were provided as foreign aid to American allies; including South Korea, West ...
conservation of mass says matter can't be created nor destroyed. do we have any theory of how this fundamental law was originally ignored to create the big bang?	The original question not entirely accurate. Mass/energy (they are the same thing) cannot be created or destroyed, but mass can be turned into energy, and vice versa. Nuclear reactions attain their vast energy outputs by converting a small (but non-trivial) amount of mass into energy. Even chemical reactions are th...	[ "Mass and Energy Balances is a fundamental \"laws of physics\" states that mass can neither be produced nor destroyed. It is only conserved. Equally fundamental is the law of conservation of energy. Although energy can change in form, it can not be created or destroyed also. The beauty of this algorithm is the capa...
The Norse people were shown to be capable raiders, especially in the British Isles. The Anglo-Saxons despite divided were socially and militarily organised, why did they, or others, never seek or attempt to attack Scandinavia?	I afraid that I cannot offer a single definitive answer to 'why X didn't Y' type question of OP. Instead I'll make some corrections to OP's premise below. First of all, there was no known unified large-scale kingdom in Scandinavia before the middle of the 10th century (until the rise of the Jelling dynasty in Denmark...	[ "Almost by definition, opponents of the Vikings were ill-prepared to fight a force that struck at will, with no warning. European countries with a weak system of government would be unable to organize a suitable response and would naturally suffer the most to Viking raiders. Viking raiders always had the option to ...
What happened to Dutch painting in the 18th century?	Apparently during the 18th century the Dutch Republic was seen as being in a decline. Instead of commissioning new works by comtemporary artists, patrons preferred to obtain works from the Golden Age, when their country was more stable and prosperous. And in 1718, Dutch artist Arnold Houbraken published his first vol...	[ "The enormous success of 17th-century Dutch painting overpowered the work of subsequent generations, and no Dutch painter of the 18th century—nor, arguably, a 19th-century one before Van Gogh—is well known outside the Netherlands. Already by the end of the period artists were complaining that buyers were more inter...
how does an led change colors?	A color changing LED isn't one LED in a package but three LEDs along with a small computer to drive them. The LED is made up of red, green and blue LEDs each of which can be controlled by a microcontroller. Since the two legs on the LED that supply the power are connected to the microcontroller and not the LED elements...	[ "By selection of different semiconductor materials, single-color LEDs can be made that emit light in a narrow band of wavelengths from near-infrared through the visible spectrum and into the ultraviolet range. As the wavelengths become shorter, because of the larger band gap of these semiconductors, the operating v...
How will it affect US economy if bill gates were to transfer all his money to some other country ?	The exact disposition of Bill Gates' personal wealth isn't information we can get our hands on, since he's a private citizen and it's none of our business. So instead let's make up a person with the same order of magnitude of wealth, imagine how he would store his wealth, and then answer the question based on that. So...	[ "In 1999, his wealth briefly surpassed US$101 billion. Despite his wealth and extensive business travel, Gates usually flew coach in commercial aircraft until 1997, when he bought a private jet. Since 2000, the nominal value of his Microsoft holdings has declined due to a fall in Microsoft's stock price after the d...
Is there a way to conceptualise complex integration?	In complex analysis, an integral is less like the "Finding the area under a graph" integral of calc 1, and more like the line integrals of vector fields in calc 3. These path independence results are actually there in normal multi-variable calculus. In this context, integrating a differentiable complex function is simi...	[ "Integration by parts is a heuristic rather than a purely mechanical process for solving integrals; given a single function to integrate, the typical strategy is to carefully separate this single function into a product of two functions \"u\"(\"x\")\"v\"(\"x\") such that the residual integral from the integration b...
cannabis strains classification.	It's both. There's a classification system to differentiate between plants, and from the same family of plants. And with cannabis, naming the strains means that you can get the same product again without confusion; but you can name any strain the name you want. There's no science behind that.	[ "The scientific debate regarding taxonomy has had little effect on the terminology in widespread use among cultivators and users of drug-type \"Cannabis\". \"Cannabis\" aficionados recognize three distinct types based on such factors as morphology, native range, aroma, and subjective psychoactive characteristics. \...
Why are siphonophorae considered "colony organisms"? What's the difference between a morphologically specialized zooid and an organ?	We consider siphonophores to be a colony organism because of how they develop and are organized compared to other cnidarians. The cnidarians body plan generally falls into one of two categories. The medusa or the polyp. The most common example of a medusa form cnidarian is a jellyfish, and a common example of a polyp ...	[ "Siphonophores are of special scientific interest because they are composed of medusoid and polypoid zooids that are morphologically and functionally specialized. Each zooid is an individual organism, but its integration with others is so strong that the colony attains the function of a larger organism. Indeed, mos...
Historians, how many of you speak/ have fluency in languages relevant to your areas of study? How important would knowledge of such relevant languages be to you?	I work in ancient materials, so it's reading, not speaking that's needed. Reading wise, I'm pretty solid in Hebrew and Greek, ok in Syriac. In terms of modern academic languages I can read/write/speak German pretty well. I got a relatively late start on languages and actually consider myself somewhat behind. Before com...	[ "The history of foreign-language education in the 20th century and the methods of teaching (such as those related below) might appear to be a history of failure. Very few students in U.S. universities who have a foreign language as a major attain \"minimum professional proficiency\". Even the \"reading knowledge\" ...
why airlines don't sell empty seats on flights at cheap rates	Because people who purchase tickets last minute usually have to travel and will pay the full price. It's rare that a plane will be relatively empty. When that happens, it's probably just a fluke. If a route regularly has a lot of empty seats, they airlines will drop one of the flights and put it on a more profitable...	[ "Airlines may ask for volunteers to give away their seats or refuse boarding to certain passengers in exchange for a compensation that may include an additional free ticket and/or an upgrade in a later flight. They can do this and still make more money than if they booked only to the plane's capacity and had it tak...
Part 1: What causes a person with Tourette's to shout obscenities? Part 2: What would happen if they never learned any curse words?	I would just like to point out that not all verbal tics are curse words— [here is an article about a woman with Tourette's Syndrome who involuntarily says the word "biscuit" ~900 times an hour.](_URL_0_) The article also mentions that > "Fewer than 10 percent of all patients [with Tourette's] swear or use socially in...	[ "The typical clinomorphism of Tourette's is both an oversimplification and a conflation of various aspects and conditions pertaining to some persons with Tourette syndrome. Some people with Tourette syndrome do have involuntary offensive speech which is termed coprolalia and is sometimes clinomorphised into the ter...
why can't we use the ocean to dump onto fires?	Saltwater changes the pH of soil and can really hinder the regrowth of plant communities. If you consider an area that seldom receives rain then you have a very long time before enough freshwater (rain) has fallen to restore soil chemistry.	[ "In some cases there is sufficient heat, fuel, and oxygen to allow spontaneous combustion and underground fires to smolder for some considerable time, as has occurred at a natural reserve in Spain. Such fires can cause surface subsidence, presenting an unpredictable physical hazard as well as environmental changes ...
Tuesday Trivia \| Missing and Destroyed Documents	I deal with formerly classified documents pretty much every day. Government secrecy makes the terms "missing" and "destroyed" a little tricky to use, because they may be effectively missing and destroyed to most historians, but in reality they are often just being denied to us. Some secret documents do go missing, howe...	[ "Some of these documents deteriorated due to chemical treatment performed by Firkovich. Other documents which were suspected forgeries disappeared; Firkovich claimed they had been stolen. The collection was moved to the Imperial Public Library in 1863.\n", "In 1697, an Austrian general Eugene of Savoy, raided the...
To what extent was the Japanese government aware of the Manhattan project or similar nuclear weapons project prior to the deployment of the nuclear bombs during WWII? Was there any awareness that such a thing was possible?	Practically all physicists knew that atomic bombs were theoretically possible after the discovery of nuclear fission and the nuclear chain reaction in the early months of 1939. Most thought that they were a technology that was not going to emerge for another decade or so, and if they were interested in chain reactions,...	[ "In addition to developing the atomic bomb, the Manhattan Project was charged with gathering intelligence on the German nuclear energy project. It was believed that the Japanese nuclear weapons program was not far advanced because Japan had little access to uranium ore, but it was initially feared that Germany was ...
What causes absorption of right- or left- circularly polarized light by chiral molecules?	The answer lies in the polarized nature of the electric and magnetic fields induced by the light. Polarized light, like all light, will induce magnetic and electric dipoles within the matter it interacts with. These induced dipoles are distortions of the electron clouds around the molecule, and can thus be seen by look...	[ "Simply put, since circularly polarized light itself is \"chiral\", it interacts differently with chiral molecules. That is, the two types of circularly polarized light are absorbed to different extents. In a CD experiment, equal amounts of left and right circularly polarized light of a selected wavelength are alte...
[META] Merry (UTC) Christmas and Happy Holidays to AskHistorians! As an extra-special gift from the Asia flairs, we've completely revamped our book recommendation list! Links below!	Now we get to the comments thanking the contributors to the list. Firstly, I’d like to give special thanks to three flairs whose contributions are not (at present) immediately apparent on the list itself. * Firstly I’d like to thank fellow Asia flairs /u/keyilan [Moderator \| Historical Linguistics \| Languages of Asia]...	[ "\"A Long Vacation\" reached number two on the Weekly Oricon Album Chart and was the eighth best-selling album of the 1980s in Japan. The 20th anniversary edition reached number 13 and the 30th anniversary edition peaked at 19. Following Ohtaki's death in December 2013, the 30th anniversary edition jumped to number...
does piracy actually hurt the profit of corporations?	If any brainy person with data can answer this well, I hope they also take into consideration the affect of franchise knock-on, which is often not discussed. And arguably makes up a larger long term profit and vertical integration, or market synergy and all that. For example people who may pirate a show still love ...	[ "In the 21st century, however, the company began to lose revenue due to the piracy of the video and album releases, with chief-executive Marie To commenting, \"Profit? We are barely making it.\" Works released by the company are also banned in Vietnam, which has the largest source of pirates.\n", "Some countries ...
Why does male pattern baldness follow the pattern it does? i.e. from the top of the head down, often in a perfectly straight circle around the head.	It doesn't. Sometimes the hair line recedes all the way to the back of the head, sometimes a bald spot appears on top of the head and increases in diameter over time. Sometimes there is even a patch at the front that is missed leaving a little island of hair. _URL_0_	[ "The head patterning is controlled by \"orthodenticle\", a homeobox gene which demarcates the segments from the top-middle of the head to the more lateral aspects. The ocelli are in an orthodenticle-rich area, and the gene is not expressed by the time one gets as lateral as the compound eyes.\n", "Hair on the bac...
how did some neighborhoods in america came to be known as 'black neighborhoods'? is it mainly because of segregation?	Housing segregation enforced by redlining and blockbusting and white flight. So, you take a neighborhood, and you line it. Red lines are where black people are able to live. Banks would (and still do) deny black people loans to live outside of the red lines, and designate the loans inside of the red lines high risk. ...	[ "The formation of black neighborhoods are closely linked to the history of segregation in the United States, either through formal laws or as a product of social norms. Despite the formal laws and segregation, black neighborhoods have played an important role in the development of African-American culture.\n", "T...
why were african, australian and native american civilisations so technologically inferior compared to european and east asian civilisations?	For one thing, it's cold enough in East Asia and Europe (note they're at similar latitudes) for germs to die every winter, so people live longer and technology can advance accordingly. In the case of Australia, humans inhabited the continent and killed off all the big game before they domesticated anything, so they did...	[ "China, India and South-East Asia were industrial powerhouse for major parts of human history. These countries and regions suffered great loss of industrial production due to colonization during 18th-20th centuries. After many decades of their independence, these countries have started reindustrializing themselves....
When I donate blood, I sometimes wonder: What happens if the blood recipient is allergic to something I recently ate?	Food allergies typically act on tissues the food encounters before digestion, such as the oral and esophageal mucosa, resulting in swelling or rashes of the throat leading to constricted airways. Once the food enters the stomach the allergens are broken down before entering the bloodstream, so blood to blood transmissi...	[ "Allergic reactions from blood transfusion may occur from the presence of allergy-causing antigens within the donor's blood, or transfusion of antibodies from a donor who has allergies, followed by antigen exposure.\n", "An allergic reaction will not occur on the first exposure to a substance. The first exposure ...
what exactly does this mean (pic in post)?	In some locations, failing to upkeep a property means it can be forfeited to a new owner who does want to care for the property. The sign was posted by essentially squatters who want to prove no one cares for the property. Its called adverse posession.	[ "A pictogram, also called a pictogramme, pictograph, or simply picto, and in computer usage an icon, is an ideogram that conveys its meaning through its pictorial resemblance to a physical object. Pictographs are often used in writing and graphic systems in which the characters are to a considerable extent pictoria...
why does my cat insist on having me constantly feed him, even though he still has food in the bowl?	Cats are assholes?	[ "Once inside the cat searches for food in the kitchen, but comes up empty. His luck finally changes when he finds a can of cat food. He quickly opens the can and out of the can pops a mouse who is plopped down onto a dinner plate. The cat is about to dig in with a fork but the mouse puts a quick stop to that. He sa...
swingset physics	In the absence of friction (or other energy sinks), a swingset, or indeed any simple pendulum, would simply continue to oscillate indefinitely between the two high points. At one extreme, when the pendulum is highest and its speed zero, the system has maximum gravitational potential energy, and zero kinetic energy. At ...	[ "The poi are swung in a forwards direction in phase with each other (same time). The hands are then both moved in front of the swinger so that the poi traverse a circle in front of the spinner - the left poi spinning clockwise, the right poi counter-clockwise. Their angles are \"very\" slightly offset to prevent th...
Which planet, if it disappeared, would affect Earth the most?	If Jupiter were to magically disappear I expect we'd quickly be exterminated by an asteroid impact. The solar system is, to first order, the sun. Pretty much everything that goes on can be pretty thoroughly described if you just know the distance to the sun, its mass, no matter where you are in the solar system. To s...	[ "If Earth is not destroyed by the expanding red giant Sun in 7.6 billion years, then on a time scale of 10 (10 quintillion) years the remaining planets in the Solar System will be ejected from the system by violent relaxation. If this does not occur to the Earth, the ultimate fate of the planet will be that it coll...
how do we know that we 'mixed' with other human species?	Scientists are able to analyze DNA and determine your ancestors. Certain areas/species have specific genes, and we have recently discovered Ozzy Osborn has traces of Neanderthal heritage: _URL_0_ That's how we "know". But evolution occurs at such a slow rate, so it's not like two subspecies of humans birthed the moder...	[ "Some hybrids between similar species have been achieved by housing males of one species and females of the other together to limit the choice of mate. To create a \"natural\" macropod hybrid, young animals of one species have been transferred to the pouch of another so as to imprint into them the other species. In...
If one clock orbits Earth moving very fast, why does it measure less time when, relative to the orbiting clock, Earth-bound clocks are moving equally fast?	See the [Wikipedia article for twin paradox](_URL_0_), specifically the resolution part.	[ "According to the theory of relativity, due to their constant movement and height relative to the Earth-centered, non-rotating approximately inertial reference frame, the clocks on the satellites are affected by their speed. Special relativity predicts that the frequency of the atomic clocks moving at GPS orbital s...
During the Holocaust what was the difference between the death camps and the work camps? Also how was it decided who went where?	_URL_0_ u/commiespaceinvader answered a lot of my questions in this post, but I'm still unsure of how it was decided who went to what camp	[ "In 1942, Auschwitz II (Birkenau), originally intended to house slave laborers, began to be used instead as a combined labor camp and extermination camp. Prisoners were transported there by rail from all over German-occupied Europe, arriving in daily convoys. By July 1942, SS doctors were conducting \"selections\" ...
A friend of mine tells me every culture around the world has a myth of a great flood wiping out the whole world, and that the timelines match up indicated they are talking about the same flood. How true is this likely to be?	[Mark Isaak has collection about a gazillion flood stories.](_URL_0_) That is a lot, but not every country has one. Nor is there all that much similarity across the stories. Boats are common, but you expect boats in a flood story. Some destroy the world and we go to a new one, some just destroy the local area. Nor is t...	[ "Cultures around the world tell stories about a great flood. In many cases, the flood leaves only one survivor or group of survivors. For example, both the Babylonian \"Epic of Gilgamesh\" and the Hebrew Bible tell of a global flood that wiped out humanity and of a man who saved the Earth's species by taking them a...
How can I learn history on my own and take steps to be a buff?	History is arguably the science of the specific. At least, that's what I argue, so I suppose it must be arguable. Which is to say, while understanding the vast sweep of history is great, it's also hard to really dive into because so much of what makes history fascinating, informative and fun is the details. Often the b...	[ "As a teacher, Lewis believes one is better able to teach what one knows, stressing firsthand experiences particularly when it comes to history. He recreates history for his students by retracing the routes of (for example) famous nonviolent protests, often interviewing participants or relatives of original partici...
Why were (or even how) the battle tactics of Mesoamerican peoples so different from those of the old world at the time of contact?	The idea that the "Aztecs were looking to gain captives in combat" is really quite overblown. While the taking of prisoners was important for advancement in social and military rank, the number of prisoners to gain high status was quite small -- as few as 4 captives depending on the circumstances. That the upper echelo...	[ "The jungle terrain of Mesoamerica made it difficult for large armies to reach their destination. The warriors who were familiar with the battle landscape could strategically retreat into familiar wilderness. Other war tactics included the siege of cities and the formation of alliances with lesser enemies to defeat...
why flight attendants close the windows during the night?	So people can sleep. Night destination-time may not correspond to night at the longitude the plane is currently over. For example, you may be arriving in Europe early in the morning, but flying partially during daytime.	[ "At window seats there are window shields for protection from sunlight. They have to be slid up during landings and takeoffs by ICAO regulations and/or law. This rule is in place to provide visibility into and out of the aircraft during emergencies. Some airlines also require passengers to keep the window shields d...
Does metric expansion of the universe apply to the dimension of time? If not, why not?	I'm going to try to do this without any equations. It'll make it harder, but let's see if I can pull it off. Think for a moment about what space and time are, just to get the distinction between them clear in your head: Space is that thing that separates events that are simultaneous. Time is that thing that separates ...	[ "Technically, the metric expansion of space is a feature of many solutions to the Einstein field equations of general relativity, and distance is measured using the Lorentz interval. This explains observations which indicate that galaxies that are more distant from us are receding faster than galaxies that are clos...
why do most power plants convert heat into electricity by heating water into steam and then using it to spin a turbine? is there not a more efficient way to do it?	Steam turbines are actually quite efficient and they have the advantage in that the steam can be condensed back into water at the end of the process and reused.	[ "Power plants that use steam-driven turbines commonly use heat exchangers to boil water into steam. Heat exchangers or similar units for producing steam from water are often called boilers or steam generators.\n", "For the sake of efficiency, it is desirable to minimise the steam content of the generator. Heat ca...
what is the significance of having headphones in the correct ears when listening to music?	There isn't one from a music perspective, (some songs have differences in the left-right channel, but it doesn't really matter if it is reversed). The problem is with the shape of the headphones themselves. The right headphone is shaped for the right ear, so if you put it in the left ear then it will be backwards and w...	[ "Supra-aural headphones or on-ear headphones have pads that press against the ears, rather than around them. They were commonly bundled with personal stereos during the 1980s. This type of headphone generally tends to be smaller and lighter than circumaural headphones, resulting in less attenuation of outside noise...

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