Split (2)

train · 226k rows

question stringlengths 3 301	answer stringlengths 9 26.1k	context list
How long was an Earth day 4.6 billion years ago?	Yes the rotation of the earth has been slowing for a long time. In the precambrian 500 million years ago, the day was about 22 hours long. [Source](_URL_0_) The further back you go the more hazy the picture gets. I mean how do you measure the rotation of the earth when the surface was still molten? Generally what ...	[ "For the earth-moon system, d\"r\"/d\"t\" gives 1.2x10 meter per second, or 3.7 cm per year. This is a 1% increase in the earth-moon distance in 100 million years. d\"n\"/d\"t\" is 1.3x10sec, and for a period of 29.5 days is equivalent to 7 minutes in 1 million years, or 1 day (i.e. lengthening of the lunar period ...
do blind people/people with fake eyes, close their eyes when they sleep?	Yes. Just because you're blind doesn't mean you don't have eyes and you can't feel them getting dried out by being exposed to the air. If you were in a pitch black room, you wouldn't be able to keep your eyes open forever without them starting to bother you. As for people with glass eyes, more than likely they onl...	[ "Another study has indicated that sleeping with the light on may protect the eyes of diabetics from retinopathy, a condition that can lead to blindness. However, the initial study is still inconclusive.\n", "Night blindness is the difficulty for the eyes to adjust to dim light. Affected individuals are unable to ...
How did Truman decide to drop the bomb?	Truman didn't actually make a decision to use the atomic bombs (that is, the portrayal of him agonizing over authorizing its use is incorrect; he essentially deferred to military leadership on the topic, and the train was down the tracks). Here is a link from /u/restricteddata's recent AMA: _URL_0_ That comment is sh...	[ "Truman decides to drop the bomb, reporting afterward that he then \"went to bed and slept like a baby.\" The Allied leaders deliver an ultimatum to Japan \"to give them one last chance.\" In Tokyo, prime minister Suzuki tries to keep the army in line by declaring in a press conference that he will \"mokusatsu\" th...
Why does caffeine withdrawal cause headaches?	When you consume caffeine there are various physiological effects taking place. Certain receptors in your brain are blocked and prevent adenosine from making you drowsy. It also dilates the capillaries around the forehead. which can sometimes alleviate headaches. When the body becomes dependent on caffeine and then sud...	[ "Caffeine also causes the release of dopamine in the dorsal striatum and nucleus accumbens core (a substructure within the ventral striatum), but not the nucleus accumbens shell, by antagonizing A receptors in the axon terminal of dopamine neurons and A–A heterodimers (a receptor complex composed of 1 adenosine A r...
can someone explain the logic behind the roe v. wade supreme court decision to me?	Under the 9th amendment, you have rights that aren't actually in the constitution. After they added a few new rights to the constitution, they realized that they probably didn't have them all yet, so they basically added a line saying 'just because it's not in the constitution doesn't mean it's not a right'. Someone w...	[ "The Committee released a 2003 email in which Kavanaugh said, \"I am not sure that all legal scholars refer to [\"Roe v. Wade\"] as the settled law of the land at the Supreme Court level since Court can always overrule its precedent, and three current Justices on the Court would do so.\"\n", "According to Jamal B...
why do even the smallest shots in big movies take dozens if not hundreds of takes to make?	Large part of the job of directors is directing the actors, and that generally requires that the director first has some initial take to improve on. Like they have a first take, then the director finds something to improve, to change in the performance of the actor and gives additional instructions. And sometimes direc...	[ "Like most of Jancsó's films, this one uses extremely long takes, often as long as the camera would allow without stopping because of the film stock finishing. The entire 70 minute duration is covered by just twelve takes.\n", "A film with a shooting ratio of 2:1 would have shot twice the amount of footage that w...
What did the life of a Pre-Columbian Mesoamerican peasant look like? What did commoners do besides farm?	That really depends on the time, location, and culture of the person you are asking about. An Early Formative Olmec person would live a very different life from a Classic period Teotihuacan person or a Postclassic Maya person.	[ "In the Early Basketmaker II Era people lived a semi-nomadic hunter-gatherer lifestyle with the introduction of cultivation of corn, which led to a more settled, agrarian life. Some of the early people lived in cave shelters in the San Juan River drainage. Excavation of their sites yielded a large number of baskets...
why is winking so.. attractive?	I can think of many reasons. First it is a sign of acknowledgment which is of course attractive. Another reason is that winking is usually accompanied by slightly opening the mouth, which is associated with kissing and other displays of affection. Plus it can display healthy dentistry which has strong primal bases for ...	[ "Winking is one of the more subtle gestures, usually involving eye contact between those involved. In most cases it is only meant to be known by the sender and their intended receivers, but in some cases can be more widely intended.\n", "A wink could also be used as a somewhat humorous way to express sympathy, so...
When birds fly south for the winter, how exactly does the population Distribution change? Do they all fly south an equal distance and displace each other, or do those that spend summer farther north have to fly farther south to find unoccupied territory?	Totally depends on the species. I doubt you can make many generalizations about all birds. One that I know about is the Golden-winged warbler. They have a pretty wide summer breeding range, but are mostly rare breeders throughout. However, the whole population winters in a much smaller area in central America. Going do...	[ "Many bird populations migrate long distances twice a year. The most common pattern involves flying north in the spring to breed in the temperate parts of the northern hemisphere or the Arctic during summer and returning southward in the autumn to wintering grounds in warmer regions, often on the other side of the ...
can everyday exposure prepare your immune system just like a vaccine?	Your immune system in effect produces a cure for any disease it manages to beat off. So yes exposure to a given disease will act like a vaccine. There are two problems though. First you will most likely have to contract the disease in the first place including all its symptoms. Second of all diseases such as flu mu...	[ "Although immunological adjuvants have traditionally been viewed as substances that aid the immune response to the antigen, adjuvants have also evolved as substances that can aid in stabilizing formulations of antigens, especially for vaccines administered for animal health.\n", "In order to provide the best prot...
What distinguishes academic/professional historians from popular historians? - How do you make history academically useful rather than simply entertaining ?	The differences identified by the previous posters I think miss the really essential element that varies between academic and popular history-writing: the audience. Writing for different audiences then has several follow-on effects. At their core, academics write for other academics; they do so to be part of a scholar...	[ "Nothing is more concrete than history, nothing less interested in theories or in abstract ideas. The great historians have fewer ideas about history than amateurs do; they merely have a way of ordering their facts to tell their story. It isn’t theories they look for, but information, documents, and ideas about how...
Would trees grow taller in reduced gravity?	Gravity limits tree growth. The tallest trees on earth are believed to have reached this limit (~110m). Plants move water along a gradient of negative pressure. With increasing height the gradient is not sufficient to supply the leafs with water. You can find further information [here](_URL_0_).	[ "Tree height is influenced by species, genetics, age, stand density, soil type and depth, rainfall, aspect, altitude, protection from wind and snow damage, fire history and insect attack. Scientists believe that trees have a theoretical maximum height of , even though there are many historical accounts of taller tr...
why is the usa more conservative on attitudes about sex compared to other developed nations?	I think it's because the country was founded by Puritans who fled the United Kingdom because they were on the other side of religious persecution, being a minority religion in a majority Protestant country. In the New World, they were free to do the oppressing and forbid any fun activities. They kicked Roger Williams ...	[ "In addition, there are also non-Western countries of low religiosity where the contention surrounding gender equality remains. In China, a cultural preference for a male child has resulted in a shortfall of women in the population. The feminist movement in Japan has made many strides which resulted in the Gender E...
How did 19th-C immigrants to America learn English? Were there equivalents of modern ESL schools for older immigrants?	As it with many things, the answer to your first question is basically, "it depends." In this case, it depends on where the immigrant is from, who they know when they arrive, and where they're heading. That is, if they were from a country with a history of emigration to America, which meant time and people to establish...	[ "In the U.S. over the last twenty years, more than 70% of non-English-speaking school-age immigrants have arrived in the U.S. before they were 6 years old. At this age, they could have been taught English in school, and achieved a proficiency indistinguishable from a native speaker. In other countries, such as the ...
How come some illnesses are species-specific?	A great deal of it has to do with the difference in cell machinery. Think of a human cell like a machine, and a cat cell like a similar machine but with different parts. A virus that infects a cat works by using cat specific parts to replicate itself - the whole point of a virus's existence. When that virus comes in co...	[ "These orders span viruses with varying host ranges. The \"Ortervirales\" (Groups VI and VII), containing also retroviruses (infecting animals including humans e.g. HIV), retrotransposons (infecting invertebrate animals, plants and eukaryotic microorganisms) and caulimoviruses (infecting plants), are recent additio...
Some Questions about Plasma	Plasma physicist here. Let's get to some answers! 1) Plasmas are ionised gases. That means that the atoms are stripped of their electrons, leaving separate fluids of electrons and ions. The ions in the plasma need not be fully ionised (stripped of every electron). By having two or more separate fluids of charge partic...	[ "A plasma is any gas in which a significant percentage of the atoms or molecules are ionized. Fractional ionization in plasmas used for deposition and related materials processing varies from about 10 in typical capacitive discharges to as high as 5–10% in high density inductive plasmas. Processing plasmas are typi...
would two objects of the same density but different weights fall at the same rate underwater?	Not necessarily. if you have two pieces of the same type of steel alloy and one is heavier and shaped like a sphere and the other is lighter but stretched out like a thin piece of sheet metal they will fall through the water in different ways and the heavier spear shaped one likely will fall faster. You could also h...	[ "A small object immersed in a container of fluid subjected to a uniform gravitational field will be subject to a net downward gravitational force, compared with the net downward gravitational force on an equal volume of the fluid. If the object is \"less dense\" than the fluid, the difference between these two vect...
why are some train tracks rusty and some shiny	Trains regularly running over tracks wears out any rust on the load-bearing part. The rest of the rail is either structure or excess shape designed to protect the train from derailment. The type of steel in the rail is resistant to rust, and it doesn't corrode very quickly. Lots of the rail actually has rust on it to ...	[ "A more persistent problem is rust. Usually the railhead is kept clean of rust by the regular passage of trains' wheels. Lines which are not used regularly can become so rusty as to prevent vehicles being detected; seldom-used points and crossovers and the extremities of terminal platform lines are also prone to ru...
how do those prescription savings cards work?	Basically: many of them charge the pharmacy a small amount of the sale so that the pharmacy can offer a lower price to the customer.	[ "In addition PBMs (Pharmacy Benefit Managers) offer discount cards that act similarly to coupons. These cards work for both generic and brand medications and can save cash paying customers up to 75% on their prescription medication.\n", "The Acme Fresh Market Savings card is used to receive special discounts and ...
During the US Civil war, how many stars were on Union flags?	> Did they include the states which had left the Union? The practice of adding stars to the flag continued during the Civil War. They absolutely did still include the Confederate states. [This](_URL_6_) is the flag that flew at Ft Sumter. It had 33 stars representing all the states prior to Kansas. It should be no...	[ "The first official flag of the Confederate States of America – called the \"Stars and Bars\" – originally had seven stars, representing the first seven states that initially formed the Confederacy. As more states joined, more stars were added, until the total was 13 (two stars were added for the divided states of ...
how do show/ movie directors get shots and scenes of totally abandoned cities?	They're not in real cities. They're on a movie set, and the rest of the city is faked with CGI. Check out [this demo reel](_URL_0_) of how prevalent CGI is in TV shows.	[ "The film takes place in Los Angeles, and as part of the plot, the city is supposed to be void of human activity except for Neville. Several tricks were used to make the city appear deserted. This objective was accomplished in part by simply filming on a Sunday morning in the center of LA's business district, when ...
how exactly does the coriolis effect affect large-scale weather patterns?	_URL_0_ I could try to explain it myself but nothing is ever going to beat a video for this topic. I think the merry-go-round example is the best possible example and the last part of the video ties it into how it affects air.	[ "The Coriolis effect results in a deflection of fluid flows (to the right in the Northern Hemisphere and left in the Southern Hemisphere). This has profound effects on the flow of the oceans. In particular it means the flow goes \"around\" high and low pressure systems, permitting them to persist for long periods o...
If the universe is expanding constantly, what is going on at the edge where "new space" is getting created?	There is no edge. To the best of our knowledge, it's an infinite plane. the expansion isn't stuff being added to the edge, but a stretching of the stuff we have, like blowing up a balloon or pulling a rubber sheet.	[ "Based on a huge amount of experimental observation and theoretical work, it is now believed that the reason for the observation is that \"space itself is expanding\", and that it expanded very rapidly within the first fraction of a second after the Big Bang. This kind of expansion is known as a \"\"metric\"\" expa...
why do i need to urinate more when concentrating?	And what about when playing hide and seek?	[ "Focusing is a psychotherapeutic process developed by psychotherapist Eugene Gendlin. It can be used in any kind of therapeutic situation, including peer-to-peer sessions. It involves holding a kind of open, non-judging attention to an internal knowing which is directly experienced but is not yet in words. Focusing...
During The Troubles, why did the British Army have a much higher proportion of casualties when compared to the IRA?	Its a mistake to view the troubles as simply a war between the IRA and the British Army. The issue was more complex than that. It was primarily a conflict between the republican (IRA, INLA, etc) and loyalist (UVF, UDA, etc) sides. The IRA would view its actions as protecting catholics from loyalist gunmen like the U...	[ "The IRA therefore came to be very well armed in the latter part of the Troubles. Most of the losses it inflicted on the British Army, however, occurred in the early 1970s, although they continued to cause substantial casualties to the British military, the RUC and UDR throughout the conflict. According to author E...
how does lashing kill someone?	It's not that mysterious. [It causes death either through loss of blood, damage to internal organs, or infection.](_URL_0_)	[ "A lashing is an arrangement of rope wire or webbing with linking device used to secure and fasten two or more items together in a somewhat rigid manner. Lashings are most commonly applied to timber poles, and are commonly associated with cargo, containerisation, the Scouting movement, and sailors.\n", "A lashing...
Why do so many religions have names (Islam, Shinto, etc) but not the religions of ancient Rome/Greece/Egypt/Norse?	Possibly because the concept of religion that you're using can't be applied to the Greeks and Romans. Islam refers to a set of canonized beliefs, based on interpretation of a holy text. Even if there is much disagreement about what those beliefs should be and what that holy text means or says, following Islam (or Chris...	[ "There are no official naming practices for the Hellenic religion, and the ancient Greeks did not have a word for \"religion\" in the modern sense. Some informal naming conventions have developed since the formation of the first Hellenic religious organizations in the 1990s, based on academically accepted descripti...
what happens if you get shot in the stomach?	Please read this entire message --- Your submission has been removed for the following reason(s): * Straightforward or factual queries are not allowed on ELI5. ELI5 is meant for simplifying complex concepts (Rule 2). --- If you would like this removal reviewed, please read the [detailed rules](_URL_0_) firs...	[ "BULLET::::- Gastric dilatation volvulus (bloat): A painful and often fatal twisting of the stomach occurring in large or deep-chested breeds which can usually be prevented by feeding small meals and not allowing vigorous exercise immediately before or after eating.\n", "BULLET::::- Israeli forces shot and wounde...
What are the conditions that allow the oral herpes simplex virus to start "infecting" cells? What's the name for "infecting cells"?	The process of infection is different for every virus. They each have different cell surface proteins (some use glycoproteins) that they bind to. This is for all intents and purposes just a specific chemical reaction. Once the virus is bound to the cell surface protein it is usually endocytosed (brought into the cell i...	[ "Human herpesviruses are all double stranded DNA viruses that enter the nucleus of the host cell. HHVs replicate in the nucleus of the infected cells and can enter both a lytic and latent phase. In the lytic phase, the viral genes are being actively transcribed and many times ultimately lead to cell death. In the l...
what happened to the aristocracy? did the great wars/ great depression bleed the old money dry?	> why there isn't really a high society in America Why would you think that? The US has plenty of billionaires and other extremely wealthy people in. There is a lot of "old money" that has been passed down since before the Robber Baron era of turn of the Century. Names like Rockefeller and Kennedy have been part o...	[ "The great economic depression caused by the World War I brought miseries to the rural people of Sindh as they were unable to pay taxes and purchase day to day needs, other than grain which was the only source of survival produced by themselves. Thus from the year 1917-1942, all agricultural land-owners drowned in ...
One lightbulb has an output of 1300 lumens. Do 2 of these same lightbulbs have an output of 2600 lumens?	Generally, quantitative measurement of visible light is a really difficult study in the sense that our eyes are crap measurement devices. Our eyes measure blue green and red light in varying efficiencies. Meaning that the same amount of green photons and the same amount of blue photons hit your eyes, but your gut will ...	[ "The lumen is the photometric unit of light output. Although most consumers still think of light in terms of power consumed by the bulb, in the U.S. it has been a trade requirement for several decades that light bulb packaging give the output in lumens. The package of a 60 watt incandescent bulb indicates that it p...
Do we orbit the sun where it is right now, or where it was at the time that we are seeing its light?	We definitely have covered this before, but it's usually been in threads asking what would happen if the sun were to disappear. To a high degree of accuracy, we feel the force of where the sun is now. A similar thing happens in electromagnetism. The field of a uniformly moving charge essentially "predicts" where the...	[ "The Sun's inner gravitational focus point lies at minimum distance of 550 AU from the Sun, and is the point to which light from distant objects is focused by gravity as a result of it passing by the Sun. This is thus the distant point to which solar gravity will cause the region of deep space on the other side of ...
how do successful celebrities attract so much bad press and remain successful?	Well, the saying goes "there's no such thing as bad press". If you didn't believe it before, take Donald Trump who has made an entire career out of it. The crazier he sounds the more people talk about him. All of these things are more or less expected of celebrities. It doesn't affect their personal brand, becaus...	[ "Tabloid magazines and talk TV shows bestow a great deal of attention on celebrities. To stay in the public eye and build wealth in addition to their salaried labor, numerous celebrities have participating and branching into various business ventures and endorsements. Many celebrities have participated in many diff...
Did the Romans ever consider the preservation of old, derelict yet significant buildings?	The Romans preserved and restored old and damaged buildings all the time, as well as completely rebuilding structures that had been totally destroyed. It was a major part of the monumental building projects that made up such a crucial part of the urban economy, as well as preserving the dignitas of the restorers. Som...	[ "Many of the ancient buildings have been restored from their remains, as have the wall paintings of Herod's two main palaces, and the Roman-style bathhouses that he built. The synagogue, storehouses, and houses of the Jewish rebels have also been identified and restored.\n", "Roman times were a period of growth a...
how do they pick what camera angles to use in sport games?	All of the cameras feed to screens in a room, where a producer will decide which camera's stream is sent to TV screens, it's their decision as to which shot is best. There will also be editors available, who can grab important pieces of footage to assemble highlight reels and montages. In either case all of the footag...	[ "The game is mostly played through a bird's eye view perspective where the camera is either showing the country scape, a town or a dungeon. Each version 'zooms in' closer to the ground and the resulting view shows more detail. For combat, the game uses a side view, that is dynamically constructed from the location ...
Do the ants I'm flicking off of my backyard table feel pain?	No, they do not feel pain. Whilst invertebrates do possess nociceptive ability (the detection of noxious stimuli), they do not experience pain as we, mammals, do. Pain is a multifactorial experience in response to potential or actual tissue damage which has a sensory and affective components. This relies on the integra...	[ "Often, ants will stridulate while cutting vegetation by raising and lowering their gasters in a way that makes a cuticular file on the first gastric tergite and a scraper on the postpetiole rub together. This makes a noise, audible by people with great hearing sitting very close to them and visible using Laser-Dop...
why are there so many different shapes of water towers?	Not exactly an answer but remember that water towers do not supply water: they supply water pressure to the whole system. The key design feature is that the water has high potential energy to drive it through the whole system. [Like this](_URL_0_)	[ "The water tower is designed in the National Romantic style with inspiration from Medieval architecture. Built in a red brick, the cylindrical tower stands 32 metres high and has a diameter of 6 metres at its base. The uppermost part has timber framing. On three sides, four windows, arranged one over the other, pro...
What made the Norse/Scandinavians more willing to take the long and dangerous sea voyages they took?	The main reason the Norse were willing was that there were new opportunities through those voyages. Some would try to earn money and prestige through raids in the British Isles and Northern Europe, others would seek their fortunes as mercenaries, for instance as varangians serving the Byzantine emperor, and still other...	[ "Scandinavian shipbuilding technology failed to advance beyond that of the Viking days. The traditional Viking ships performed quite well in the relatively tranquil summer seas of the medieval warm period, but the stormier climates rendered these vessels particularly dangerous to the point of obsolescence. Viking t...
what's the purpose of the orange lights on top of larger trucks and tractor trailers?	I believe those are called "clearance lights." They're apparently required by law in the US and Canada on larger vehicles. For why I'm not sure, here's a few possibilities randos threw out from googlin': * They indicate to other drivers that the vehicle they're looking at is taller, larger/heavier, and probably wi...	[ "Amber lights are often used on vehicle involved in non-emergency work. Most utility companies, towing services, oversize load vehicles, slow vehicles, and certain types of construction equipment mount some type of lightbar or lighting system for a higher degree of visibility.\n", "These have two lights, usually ...
how come we don't have to pay for porn?	Your dad pays for it, you just happen to find it for free.	[ "Because there is free porn available on the Internet (e.g. thumbnail gallery post (TGP) and streaming video sites, not to mention piracy), and some individuals cannot afford to or do not wish to purchase paysite memberships, some consumers of pornography view only free pornography. However, paysites are often one ...
why can your weight change so quickly (like gaining weight after going off of a diet or losing weight after not eating for a few days) but it takes so long to get back to your original weight?	Short term weight changes are either due to water or colon content. It you eat like a regular person, you have about 500g og glycol stored in your body as short term carbohydrate store. These sugar molecules bind about 2kg of water. If you ran on a diet, your body will first metabolize those stores, so you'll lose abo...	[ "Fad diets tend to result in losing small amounts of weight, usually mostly water, in the first few days or weeks. Afterwards, the weight is almost invariably regained. According to Boston University School of Medicine, 98% of people who lose weight regain it within 5 years. Many diets fail to produce lasting weigh...
why does australia have 16/20 of the most venomous snakes in the world?	Yarr! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why is Australia choke-full of poisonous creatures, but New Zealand, despite the geographic proximity, has surprisingly few of them? ](_URL_4_) ^(_._) 1. [ELI5: Why exactly is everything so deadly and dangerous in Australia? ](_URL_1_) ^(_6 co...	[ "Although Australian snakes can be very venomous, comparatively little is known about the protein compositions of venoms from Australian snakes, compared to those of Asia and America. Wide access to antivenom and adequate medical care has made deaths exceedingly rare with only a few fatalities each year. Australian...
Is there a means to recover astronauts during spacewalk accidents?	The risk is extremely low. NASA astronauts on ISS always maintain some sort of tether to the station to prevent that from happening. Additionally, they always wear the SAFER equipment on their EVA suits. This is a small set of thrusters which would allow them to return to the station even if for some reason their tethe...	[ "Difficulties with standing, walking, turning corners, climbing stairs, and a slowing of gait are experienced as astronauts re-adapt to Earth's gravity, until terrestrial motor strategies are fully re-acquired. Adaptation to spaceflight also induces a significant increase in the time required to traverse an obstacl...
why hasn’t the united nations decreed a denuclearization of all 9 countries with nuclear weapons?	Because the UN does not have the power to do this. Such an order would have to come from the UN Security Council, where most of these countries have veto power.	[ "The Nuclear Nonproliferation Treaty (NPT), which entered into force in 1970, recognizes five countries as nuclear-weapon states (the United States, Russia, the United Kingdom, France, and China), who commit to pursue disarmament, and the right of other signatories to use nuclear technology for peaceful purposes, c...
What kind of weapons did the Ancient Egyptians use?	The one book I read on the subject, Robert Drews' The End of the Bronze Age, said that the backbone of the pharonic Egyptian army, and of most bronze-age empires, was the 3-man chariot archery team: driver, heavy archer, and an infantryman equipped with a heavy bronze rod (called a mace, but there's no thickening at ...	[ "Projectile weapons were used by the ancient Egyptians as standoff artillery, used to weaken the enemy before an infantry assault. Slings, throw sticks, spears, and javelins were used, but the bow and arrow was the primary projectile weapon for most of Egypt's history.\n", "In History of Ancient Egypt: Volume 1 (...
It seems as if philosophy has changed dramatically since Ancient Roman and Greek times, was there a event that spurred the change?	I'm not sure exactly what you mean by the question. The history of Western philosophy is generally divided by periods: Greco-Roman philosophy begins with the "Pre-Socratics." That is, philosophers like Thales, Anaximander, and Heraclitus who lived before the fourth century B.C. in Greece and Asia Minor. Their primary ...	[ "Greek philosophy entered a high level of abstraction. It adopted \"apeiron\" as the origin of all things, because it is completely indefinite. This is a further transition from the previous existing mythical way of thought to the newer rational way of thought which is the main characteristic of the archaic period ...
Do the changes in total mass of the ISS (docking spacecraft, supplies, people) cause it to orbit at different heights and / or speeds?	No. A docking craft would not, in itself, change the ISS' velocity and altitude. Why? Because before the craft can dock with the ISS, it has to match the velocity and altitude of the ISS. So if both craft are orbiting at the same velocity and altitude, and then they join, there would be no change in either craft's ve...	[ "The gross mass of the station changes over time. The total launch mass of the modules on orbit is about (). The mass of experiments, spare parts, personal effects, crew, foodstuff, clothing, propellants, water supplies, gas supplies, docked spacecraft, and other items add to the total mass of the station. Hydrogen...
why do climbers have to melt snow to drink it, why can't they just eat the snow?	"Snow and ice are obvious sources of water but always melt them before consuming. Avoid the urge to eat snow or ice as it will lower your body core temperature, hastening the onset of hypothermia and can cause dehydration. Eating ice may also cause blistering and sores in and around your mouth and lips." _URL_0_	[ "Proper snow throwing technique minimizes strains and back injuries. Recommended technique is that when lifting snow, the user bends their knees to collect the snow while maintaining a straight back, then straightening the legs to stand and lift. It is best to lift snow by using the shovel as a lever. Never lift sn...
why is asbestos looked at in such a bad light while other building materials like fiberglass and silica are seemingly similar and still currently used?	Asbestos is similar in chemical and physical structure (i.e., filaments), but it it way more friable. Friability means it breaks down into microfragments (tiny needles) that easily become airborne, hence the reason that asbestos causes mesothelioma and lung cancer. The tiny needles get lodged in lung tissue and repea...	[ "The North American Insulation Manufacturers Association (NAIMA) claims that glass fiber is fundamentally different from asbestos, since it is man-made instead of naturally occurring. They claim that glass fiber \"dissolves in the lungs\", while asbestos remains in the body for life. Although both glass fiber and a...
How is it that we know elephants have excellent memories?	It's interesting. References to elephant memory appear in the literature far more often as a metaphor than as part of an actual study of elephant memory. That aside, there are reports of elephant memory that seem remarkable given a common but unjustified prior assumption that most animals are stupid. Specifically, elep...	[ "\"Elephants Can Remember\" was cited in a study done in 2009 using computer science to compare Christie's earlier works to her later ones. The sharp drops in vocabulary size and increases in repeated phrases and indefinite nouns suggested Christie may have been suffering from some form of onset dementia, perhaps w...
How can the brain distinguish between someone looking in your general direction versus that same person locking eyes with you?	There is evidence that parts of the the human brain are [specialized in recognizing faces and facial expressions](_URL_0_). It is likely that the brains of many higher animals are likewise specialized in recognizing faces. Things with faces are either predator or prey, and [many animals develop natural camo to disguise...	[ "Intermediate directions are controlled by simultaneous actions of multiple muscles. When one shifts the gaze horizontally, one eye will move laterally (toward the side) and the other will move medially (toward the midline). This may be neurally coordinated by the central nervous system, to make the eyes move toget...
how do companies such as twitter, which has yet to turn a profit since it's creation and has lost $165 million this year so far, continue to run and how can they pay employees?	Source: I'm in-house counsel for a group of tech startups. Twitter has raised a tremendous amount of money: [1.82 billion, to be precise.](_URL_1_) This has been done by selling off bits of their company to investors. They also raised a shitload in this IPO. [They also have a tremendous amount of revenue - $317M last...	[ "In July 2009, some of Twitter's revenue and user growth documents were published on \"TechCrunch\" after being illegally obtained by Hacker Croll. The documents projected 2009 revenues of US$400,000 in the third quarter and US$4 million in the fourth quarter along with 25 million users by the end of the year. The ...
if we could see the entire spectrum of light, what colour would rainbows be?	Everything out of the visible spectrum has no colour and is invisible to us. You cannot see it in colours.	[ "Like most atmospheric optical phenomena, rainbows can be caused by light from the Sun, but also from the Moon. In case of the latter, the rainbow is referred to as a lunar rainbow or moonbow. They are much dimmer and rarer than solar rainbows, requiring the Moon to be near-full in order for them to be seen. For th...
why my theeth are yellowish if i brush them everyday?	It's your enamel, which you can't restore (though I believe researchers are working on that). The enamel is demineralized by sugars, like in candy and soda. Which is why if you have anything with a lot of sugar, you should drink some water to wash away the sugar.	[ "At the beginning, people show pin-sized dots with white plaque on them which constantly grow into flat, red areas hardly sourrounded by white plaque. Despite of the visible symptoms, patients in nearly all cases do not suffer from burning or itching, nor does it smell strange. Due to its analogy to a fungal skin i...
difference between gamma radiation and getting zapped with static electricity	Gamma radiation is actually electromagnetic radiation and not electrons being shot at you. It's like light, except much more energetic. You might be thinking of Beta radiation which is the emission of positrons and electrons. The diffrence between Beta radiation and static electricity is the speed with which the part...	[ "Gamma (γ) radiation consists of photons with a wavelength less than 3x10 meters (greater than 10 Hz and 41.4 keV). Gamma radiation emission is a nuclear process that occurs to rid an unstable nucleus of excess energy after most nuclear reactions. Both alpha and beta particles have an electric charge and mass, and ...
are gatorade-like sport drinks actually effective as it seems they are? if so, how do they contribute to the athlete?	In endurance sports, like triathlon, the race basically comes down to an eating contest. When you're really fit and have built the endurance, the upper limit for your endurance speed becomes how much energy the body can expend. It's very normal to see top level athletes expend 1000+ calories per hour. It's entirely...	[ "Sports drinks are beverages whose stated purpose is to help athletes replace water, electrolytes, and energy before and after training or competition, though their efficiency for that purpose has been questioned, particularly after exercise.\n", "The drinks are marketed as soft drinks. In response to the Oxford ...
Why does having a PhD entitle one to be called "Dr."?	"Doctor" comes from the Latin docere, meaning "to teach." The title originally concerned university lecturers in the Middle Ages rather than people in medicine, and remains in use because a Doctor of Philosophy is thus qualified to teach his/her subject at (we hope!) the highest level of understanding and knowledge. ...	[ "As the American term PhD (i.e. doctor of philosophy) is much more widely understood internationally, the degree is frequently translated as \"MD, PhD\". This, however, is somewhat misleading, as the PhD is officially considered a lower degree than the Dr.Med. in Denmark, where both degrees exist, and also because ...
how resilient are a man's testicles?	There would be no people if this were a problem. Testicular ruptures are a very serious problem, and surgery within a couple of days is needed to prevent serious complications that can include death. That said, 0.23% of the entries in the 2015 USA trauma databank have it. Most of these trauma cases involve car crash...	[ "In males with strong presentation of the cremasteric reflex, the testes can—during supine sexual activity or manual manipulation—partially or fully retract into the inguinal canal for a short period of time. In juveniles and adults with inguinal injury, retraction can be prolonged and potentially lead to overheati...
how does a company fire or let go of a ceo?	The Board of Directors. The CEO runs the company, but it is the Board of Directors that hold large stakes in the company (and decide its ultimate course of action). If they are unhappy with the CEO they can move to fire them.	[ "They concluded that the decision-making of firing a CEO is based on whether CEOs perform in expectation relative to shareholders expectations. Furthermore, they found that CEOs have a higher chance of being fired based on soft information rather than their previous performance (good or bad). Monitoring through the...
The Hundred Years' War vs. The Eastern Front of World War II--A Good Comparison?	Well, from my limited understanding of France in this time period; no. Perhaps you can make some stretch that the relative disunity of France in the Hundred Year's War (HYW) is comparable to the initial confusion and disorder present in the RKKA, but I'd say its too much of a stretch. The disorder in the RKKA in 1941 ...	[ "The Hundred Years' War was a series of conflicts waged from 1337 to 1453 by the House of Plantagenet, rulers of the Kingdom of England, against the French House of Valois, over the right to rule the Kingdom of France. Each side drew many allies into the war. It was one of the most notable conflicts of the Middle A...
How do jet engines find adequate O2 for combustion at high altitudes?	If I may, a related question: how do jet engines function in the rain? Don't they ingest massive amounts of water?	[ "During three more flights in the spring and summer of 1998, liquid oxygen was cycled through the engine. In addition, two engine hot firings were conducted on the ground. Researchers decided against a hot-fire flight test because of liquid oxygen leaks in the test apparatus. The ground firings and the airborne cry...
What is the science behind fame, celebrities, and the very distinct behavior human beings fall into when in the presence of high-status individuals?	I am by no means a psychological expert, but I watched a special that covered exactly this and an expert was interviewed. Basically it's about the campfire. At the end of the day humans crave social interaction, and social interaction requires topics to discuss. Celebrities provide this, because everyone knows who they...	[ "However, a great many celebrities are clearly not \"intellectual\" achievers nor notable for any cognitive or analytic powers, e.g. Kim Kardashian, professional sports figures or other athletes. While they may through sheer exposure become involved in causes or controversies (as Paris Hilton did in the US presiden...
why was prince a big deal?	He was a talent like the world had never seen. He played many instruments, had an amazing voice, was a brilliant songwriter, and had one of the greatest stage presences ever seen. He's one of the most successful recording artists in history. He won 7 Grammys, a Golden Globe, and an Academy award for Purple Rain's so...	[ "The prince is consistently described by friends as adventurous (almost to the point of recklessness), warm, tender and extremely generous. But of all his qualities, the one most often mentioned is that of loyalty to his friends. One account describes how William was particularly kind to friends who were either \"i...
why do men like strip clubs/strip teases?	Orgasm is not the only goal. 99% of all daily interactions aren't going to result in sex either. Looking at attractive females makes the straight male brain feel pleasure usually. That's why we are so bad about checking out girls that walk by, trying not to stare at cleveage, etc. It takes conscious physical exertion ...	[ "The strip club as an outlet for salacious entertainment is a recurrent theme in popular culture. In some media, these clubs are portrayed primarily as gathering places of vice and ill repute. Clubs themselves and various aspects of the business are highlighted in these references. \"Top Strip Club\" lists in some ...
why do calorie deficits work in burning fat on a non keto diet if the body can just use available glycogen storages instead of fat?	Your body doesn’t have an infinite supply of glycogen. Eventually it will run out and burn fat. 100% of diets that involve a caloric deficit will burn fat.	[ "Consumption of fat substitutes can assist in lowering total overall fat and calorie intake from foods. This has positive implications for those looking to reduce either one of these, especially when in a disease state associated with high fat diets. While fat substitution alone can reduce the percentage of kilocal...
why are nightmares so scary despite some of them being mild when we look back?	When you sleep, many parts of your brain operate at reduced capacity, including the part that evaluates reality. When faced with something nonsensical, instead of saying "that can't be right, let's take a closer look", your brain just kind of rolls with it. It is the reason when you can be an adult and in grade schoo...	[ "Nightmares portray some of our most deeply held fears, especially about family, according to the famous American horror observer, Joseph Maddrey. For example, he explains the huge appeal of the \"Nightmare on Elm Street\" franchise (1984 original directed by Wes Craven) as a result of its exploiting these fears. I...
what is happening when i accidentally crash an app or a program simply by clicking on the screen or clicking the mouse button when the software is loading?	Not really 'stress', more likely you caused a sequence of events to occur which the programmer never thought of and never planned for. Here's a possible scenario (warning, simplifications coming here): Since the programmer knows how they expect the program to work, they might wait patiently for all the loading and se...	[ "Some computer programs, such as \"StepMania\" and BBC's \"Bamzooki\", also crash to desktop if in full-screen, but displays the error in a separate window when the user has returned to the desktop. Crashes are usually caused by website failure or system failure.\n", "An application typically crashes when it perf...
what is the purpose of hoarding enormous university endowments?	> What is the purpose of hoarding such huge endowments that's tax free without making education cheaper or better You're assuming they dont. 36% of their revenue ($1.7 billion) last year was from endowments. Why not use it all? Endowments have restrictions set forth by the donor. They cant be accessed by Harvard un...	[ ", U-M's financial endowment (the \"University Endowment Fund\") was valued at $10.9 billion. The endowment is primarily used according to the donors' wishes, which include the support of teaching and research. In mid-2000, U-M embarked on a fund-raising campaign called \"The Michigan Difference\", which aimed to r...
Is it fair to say that Britain won the Intelligence and Espionage aspect of WW2 from the outset?	piggybacking: has anyone written on just WHY British intelligence was so much better than German? I asked the question before but got no response: > The Wikipedia article on m15 says that they caught all but one of the ~115 German spies sent into England, converting many to double agents. Another thread from this mo...	[ "In July 1939 the \"Biuro Szyfrów\" gave French and British intelligence all their results. Both countries were expanding their decryption efforts in anticipation of war, and this continued after the war started in September 1939.\n", "At that time Britain was in a difficult situation, badly in need of intelligen...
why does the consistency of food effect the taste?	In the case of bread, the hard piece may have been baked longer, and thus caramelized and had its chemical composition thus altered. In the case of other items, it may be a question of surface area: things chopped very fine may have a more intense flavor because there is a greater surface area And a greater area for ai...	[ "Another universal phenomenon regarding food is the appeal of contrast in taste and presentation. For example, such opposite flavors as sweetness and saltiness tend to go well together, as in kettle corn and nuts.\n", "Since then, his research has established that the sight, touch and sound of food can have large...
What were the social functions of the spectacles in the amphitheatre?	The games in Rome had multiple facets to their use; they were used as a political tool by the elite, a social control, and an exemplar of Roman power. The elite were the primary benefactors of the games as they were able to make use of them as sources of popularity and be able to build political careers from their popu...	[ "Amphitheatre has first appeared in Southern Italy in the second century B.C. and was specifically designed for putting on spectacular combats between gladiators or animal fights, this new type of construction took the form of two theatres set face to face with an oval arena which allowed everyone, wherever they we...
What makes light reflecting off of a surface, change its color to that of the surface?	> Additionally, what is happening when I shoot a strobe (flash) through an orange gel? Is that due to certain light being filtered out? Exactly, the material absorbs all colours except orange. The same goes for reflections - a red bowl absorbs all colours except red, which it reflects. Of course, nothing absorbs/refl...	[ "When light strikes the surface of a (non-metallic) material it bounces off in all directions due to multiple reflections by the microscopic irregularities \"inside\" the material (e.g. the grain boundaries of a polycrystalline material, or the cell or fiber boundaries of an organic material) and by its surface, if...
Does digestion create body heat?	The majority of your body heat occurs from cellular metabolism, your organs and your muscles. Let me quote: > (1) basal rate of metabolism of all the cells in the body; (2) extra rate of metabolism caused by muscle activity, [...] (5) extra metabolism caused by increased chemical activity in the cells themselves, e...	[ "The resting human body generates about two-thirds of its heat through metabolism in internal organs in the thorax and abdomen, as well as in the brain. The brain generates about 16% of the total heat produced by the body.\n", "Along with his theory of the role of vital heat in nutrition and digestion, Aristotle ...
If we had room temperature superconductors, could we build computers out of them that create no heat?	Nope, although they'd use less heat. A significant amount of what makes a computer work involves switching things - turning things on and off uses semiconductors rather than conductors, and you'd lose energy in those transitions.	[ "Components are often designed to generate as little heat as possible, and computers and operating systems may be designed to reduce power consumption and consequent heating according to workload, but more heat may still be produced than can be removed without attention to cooling. Use of heatsinks cooled by airflo...
American cuisine seems to have been meat centric from early on, and meat seems to have been affordable even to the poor. Why was it so much more ubiquitous than in many places in Europe where its inhabitants came from?	Wow this question is perfect for me since I wrote a whole book about this. On my phone so I can elaborate in the morning but for now I’ll summarise... Basically cheap meat (particularly beef if we are talking 19th century) was about land and distribution. Beef can be produced cheaply but to do so is very land intensiv...	[ "Although, due to the fact that the region was not always one of prosperity, not much meat was used in the kitchen there are still some regional specialties with meat, e.g. lamb roast with Spätzle or the fried onion roast. Many recipes use tripe which was inexpensive and therefore affordable for the common and poor...
How much direct power did the Chinese emperors wield?	In terms of direct power, it varied. Anything the emperor decreed was supposed to be treated as a sacred edict, and many dynasties worked to create strong central governments with local rule delegated to local officials. Some emperors, like Ming Taizu acted with extreme vigor and despotism, overseeing many aspects of h...	[ "In practice, however, the power of the emperor varied between different emperors and different dynasties. Generally, in the Chinese dynastic cycle, emperors founding a dynasty usually consolidated the empire through absolute rule: examples include Qin Shi Huang of the Qin, Emperor Taizong of the Tang, Kublai Khan ...
despite both being highly totalitarian, how are nazi germany and soviet russia polar opposites in political ideology?	Nazism was a nationalist movement, meaning that they were all about the (mythic, idealized) German people and German state. They were all about taking care of the German people first (and, obviously, horrible anti-Semitism and racism and so on) because they believed that Germany in particular was better than everybody ...	[ "The Soviet Union and Nazi Germany were both ideologically driven states (by Soviet communism and by Nazism respectively), in which the foremost political leaders had near-absolute power. The character of the war was thus determined by the political leaders and their ideology to a much greater extent than in any ot...
What are the evolutionary advantages of non-black people evolving less 'wide' noses?	Not every difference has an advantage.	[ "Marina L. Sardi of the anthropological division at the University of La Plata, Argentina, and Fernando V. Ramírez Rozzi wrote in 2012 that South African adults have neotenized relative facial heights and nose shapes in comparison to European adults, because \"Europeans\" develop relatively taller faces and relativ...
what happens when we choke on liquid substances such as water?	It goes down the air hole instead of the drinking hole. As a result the lungs work to eject the liquid that they have determined, rightly, should not be there. This comes in the form of coughing it back up, generally.	[ "Under normal circumstances, accidentally consuming too much water is exceptionally rare. Nearly all deaths related to water intoxication in normal individuals have resulted either from water-drinking contests, in which individuals attempt to consume large amounts of water, or from long bouts of exercise during whi...
Were there traffic control rules and signs prior to the invention of the automobile?	hi! there's lots of room for more input on this (particularly regarding more cultures), but you can get started on this section of the FAQ* [Traffic](_URL_0_) *see the link on the sidebar or the wiki tab	[ "The origins of the code can be traced back to 1920 when the Departmental Committee on the Regulation of Motor Vehicles announced that \"a compulsory and uniform code of signals for all road vehicles is to be brought into operation\". Drivers in London had evolved a system for signalling their intentions to turn ri...
How to compare different card shuffling methods?	As a gambling machine programmer, the best algorithm I've seen for deck shuffling in terms of time and space is to create a structure (array) of all the cards in whichever order you'd like. Go to the first element, pick a (pseudo)random number in the range of the structure, and swap the first element with the randomly...	[ "Most similarly to the way humans shuffle cards, it can be defined as a random cut and riffle. The deck of cards is cut into two packets; if there are a total of \"n\" cards, then the probability of selecting \"k\" cards in the first deck and \"n\" − \"k\" in the second deck is formula_1. Then, one card at a time i...
Can a stray balloon make it to space?	No, for most definitions of space. Balloons don't really push themselves up, it's more that the air around them is pushing down harder than they do, and the air pushes them out of the way, thus up. As you get higher, there's less air to push the balloon higher. Eventually one of two things happen: 1. the total densi...	[ "High-altitude balloons are used as high flying vessels to carry scientific instruments (like weather balloons), or reach near-space altitudes to take footage or photos of the earth. These balloons can fly over 100,000 feet (30.5 km) into the air, and are designed to burst at a set altitude where the parachute will...
Ancient China (back when it was an empire). If a household lost all their males, leaving only women behind. What would happen to these women?	Adoption was very common, and acceptable. In the western tradition, we think that the family may only be continued by a blood relation, but this wasn't necessarily true in China. During the Song/Yuan/Ming period (~AD 960-1644) an heirless family had two adoption options to continue the line. One, they could adopt a ...	[ "In ancient China, women did not have social status. A woman could only obey and rely on her husband; even if her husband was dead, she was still not allowed to remarry. While the man could have many wives and many concubines, the emperor had imperial harems. The general dignitaries also had many wives and concubin...
Where did the specific make-up and behavior associated with circus clowns come from?	As a circus clown, I take exception to your friend's assertion. Circus clowning has roots as far back as tribal shamanism. Circus clowning also took a lot from the Italian Commedia dell'arte theatrical tradition of the 16th century. These masked "stock characters" were common from troupe to troupe, and allowed f...	[ "Clowns have always been an integral part of the circus, offering a source of amusement for patrons and providing relief from the array of animal acts and performances by acrobats and novelty artistes.\n", "Many circus clowns have become well known and are a key circus act in their own right. The first mainstream...
Filled 4s and partially filled 3d orbitals question.	3d^(1)4s^(2) arises because of electron-electron repulsion. Imagine the Sc^(3+) ion (3d^(0)4s^(0)) and adding a single electron to it. At this point in the PT 3d is lower in energy than 4s so you get 3d^1 as the configuration for Sc^(2+). Now add another electron - what happens? Electrons repel each other, and the ene...	[ "Single locations in 4D space can be given as vectors or \"n-tuples\", i.e. as ordered lists of numbers such as \"(t,x,y,z)\". It is only when such locations are linked together into more complicated shapes that the full richness and geometric complexity of 4D and higher dimensional spaces emerge. A hint to that co...
Why did Britain server its "special relationship" with Canada after WWII?	I think the post you quote here misrepresents what happened after the Second World War. As far as I know, the closest thing to a "special economic relationship" between Canada and Britain would have been something like imperial preference, which set up favourable tariffs between Britain and its colonies. This idea die...	[ "Loyalty to Britain still existed, however, and during the darkest days of the Second World War for Britain, after the fall of France and before the entry of the Soviet Union or the USA, Canada was Britain's principal ally in the North Atlantic, and a major source of weapons and food. However, the war showed that t...
why did the 1892 populist party in the united states demand inflation through free and unlimited coinage of silver (what was its benefits)?	It wasn't inflation. You had uncoined silver that turned into coined silver. The uncoined silver already had purchasing power before it was coined. It is like the government purchased the silver, reducing the money supply and then increase the money supply by the same amount.	[ "Because of the Panic of 1873, governments depegged their currencies, to save money. The demonetization of silver by European and North American governments in the early 1870s was certainly a contributing factor. The US Coinage Act of 1873 was met with great opposition by farmers and miners, as silver was seen as m...
why are so many historic sculptures missing limbs and heads?	Religion! At least for some... when christians took over ancient greece they were scared the sculptures of greek gods etc would come to life/curse them or something - so they cut off the hands so it couldn't get them, cut off the genitals so it can't reproduce/ cut out the mouth/eyes or just cut off the head so it coul...	[ "Two skeleton sculptures have been found, one of which was constructed by Arthur Graves and the current Gormogon, the other by Jason Harkness and the current Gormogon. The former was completely made of bone, while the latter was still mostly silver. Not all the victims have yet been identified, but at least one bon...
what is all the fuss about facebook "censoring" news	The trending news section implies just that - Trending. Based on popularity, what people are actively discussing. If a story hit a certain activity threshold, it would show up in this section. The fuss is both about facebook censoring conservative stories even if they were genuinely trending, and likewise facebook in...	[ "BULLET::::- Censorship of Facebook, mainly in regard to political activists' profiles being suspended without notice, and also their apparent support of outright government-sponsored censorship in countries such as China and Syria.\n", "In March 2019, Facebook banned content supporting white nationalism and whit...
how come one power strip with 12 plugs is okay, but linking two power strips that each have 6 plugs is dangerous?	It's not inherently dangerous, but having too many things running off of one circult can overheat the wiring and either trip the circuit breaker or start a fire. A 20 amp circuit breaker can handle 2400 watts of power. You just need to use 12 gauge (or thicker) wiring to handle that much power. However, some powe...	[ "A power strip (also known as an extension block, power board, power bar, plug board, pivot plug, trailing gang, trailing socket, plug bar, trailer lead, multi-socket, multi-box, super plug, multiple socket, multiple outlet, polysocket and by many other variations) is a block of electrical sockets that attaches to ...
why are there frequently office buildings being constructed in close proximity to other office buildings that have oftentimes stood empty with "space for lease" in them for extended periods of time?	Often the empty one is no longer up to code; whoever buys/leases it will have to spend a ton on upgrades before they’ll be allowed to move in. New construction is sometimes cheaper, depending on what needs to be done.	[ "Because of the downtown area's office market's migration west to Bunker Hill and the Financial District, many historic office buildings have been left intact, simply used for storage or remaining empty during recent decades. In 1999, the Los Angeles City Council passed an adaptive reuse ordinance, making it easier...
why can you run for miles without your legs getting so tired that you can't keep going, but you can only do so many push-ups or curls before you can't do any more?	Probably because of 2 things 1. Early humans needed to run long distances to run animals to the point exhaustion 2. You use your legs way more than your arms/abs	[ "Leg muscles are important to take advantage of everything in the path of the pumping speed, to complete the whole way down. The torso and upper body are also important in the beginning, when it is important to be fast. If you are the fastest in the beginning you have a good chance to win because it can be difficul...
How do we know Earth has an elliptical orbit?	Long story short... One of the biggest problems with the Copernican model of the solar system was that the planets do NOT orbit the sun in perfect circles. Johannes comes along and uses some very precise measurements to show that ALL of the planets (including the Earth) orbit the sun in ellipses, where a circle is an ...	[ "Earth's orbit around the Sun is an ellipse. The semi-major axis of this elliptic orbit is defined to be half of the straight line segment that joins the perihelion and aphelion. The centre of the Sun lies on this straight line segment, but not at its midpoint. Because ellipses are well-understood shapes, measuring...
Is the water used to cool spent nuclear fuel rods radioactively contaminated? If yes, what is happening with it after it gets exchanged with fresh water?	Since I've been paged. I'm a current senior reactor operator at a US boiling water reactor. I'm going to be talking from a boiling water reactor perspective, but most of this is applicable to any primary coolant system. Also, heavy water reactors will have some different answers as they have a lot of tritium content....	[ "Although the radioactive water treatment system has not yet started full-scale operation, a total of 1,850 tons of radioactive water has been processed during test runs of the system. Today this decontaminated water is used to cool the reactors for the first time. TEPCO states that it will continue injecting 16 to...
What's the method used to arrive at such a precise figure for the claim that "1 in 200" men are descendants of Genghis Khan"?	Actually the method is described in the article. > As Y chromosomes are only passed from father to son, that would mean that the Y is a record of one’s patrilineage. Genghis Khan died ~750 years ago, so assuming 25 years per generation, you get about 30 men between the present and that period. In more quantitative te...	[ "There are no living males known to descend directly from Genghis Khan, or any of his nearest male relatives. Many researchers have attempted to infer his Y-DNA haplogroup, according to various criteria, from those now prominent in Mongolia and other areas formerly part of the Mongol Empire.\n", "A white paper by...
why is it that when sometimes you wear sunglasses and look through a car mirror such as a rear view mirror, and see a visible teal and purple checkerboard on other cars' windshields?	This is caused by the tempering process used on the glass. This is the process used to make the glass shatter into tiny little pieces instead of large ones. This makes it less likely to cause injury.	[ "A prismatic rear-view mirror—sometimes called a \"day/night mirror\"—can be tilted to reduce the brightness and glare of lights, mostly for high-beam headlights of vehicles behind which would otherwise be reflected directly into the driver's eyes at night. This type of mirror is made of a piece of glass that is we...
If hydrogen only has a few line spectra, why does the sun have a continuous spectrum of light?	The light from the sun isn't only from the hydrogen spectrum, in fact most of it is from the continuous blackbody spectrum.	[ "Throughout the universe, hydrogen is mostly found in the atomic and plasma states, with properties quite different from those of molecular hydrogen. As a plasma, hydrogen's electron and proton are not bound together, resulting in very high electrical conductivity and high emissivity (producing the light from the S...
if time 'stops' at the speed of light, how does anything happen to light itself?	Nothing does happen to light. The only "things" that can "happen" to light (and that's using the terms loosely) is that it can come into existence, and it can stop existing … and in the frame of reference of light, those two events happen at both the same instant and the same point in space. Say you have an atom. That...	[ "The second postulate of Einstein's theory of special relativity states that the speed of light is invariant, regardless of the velocity of the source from which the light emanates. The extinction theorem (essentially) states that light passing through a transparent medium is simultaneously extinguished and re-emit...
How long can bacteria survive on everyday household items without nutrients and water?	Depends on the strain and species. If it's a spore forming bacteria, it can survive for almost forever. Normal households won't be free of water or nutrients, as there are naturally in the air. But in ideal conditions, as to your question, a few days to a few weeks.	[ "The lifespan of microbes in the home varies similarly. Generally bacteria and viruses require a wet environment with a humidity of over 10 percent. \"E. coli\" can survive for a few hours to a day. Bacteria which form spores can survive longer, with \"Staphylococcus aureus\" surviving potentially for weeks or, in ...
What distinguishes species from their predecessors?	> at what point would evolutionary biologists say that the animal was no longer a chicken? At what point does [this](_URL_0_) bar become black? Why is the point immediately to the left not black? "Species" is not a well defined term in biology. It is an attempt to impose discrete measurements on a fundamentally non...	[ "An evolutionary species, suggested by George Gaylord Simpson in 1951, is \"an entity composed of organisms which maintains its identity from other such entities through time and over space, and which has its own independent evolutionary fate and historical tendencies\". This differs from the biological species con...

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.