Split (2)

train · 219k rows

question stringlengths 3 301	answer stringlengths 9 7.04k	context listlengths 7 7
If Einstein hasn't came up with relativity was anyone else working on the similar theories?	(As a warning, I got slightly jargony in this post. SR = special relativity GR = general relativity c = speed of light EM = electromagetism B-field = magnetic field) First off, SR probably would have been developed within a few years of Einstein's publication. This is because the root problem that Einstein was trying...	[ "Several experiments predating Einstein's 1905 paper are now interpreted as evidence for relativity. Of these it is known Einstein was aware of the Fizeau experiment before 1905, and historians have concluded that Einstein was at least aware of the Michelson–Morley experiment as early as 1899 despite claims he made...
how do zero gravity pens work?	They inject pressurized gas into the ink capsule, that constantly pushes the ink toward the tip regardless of gravity or orientation.	[ "BULLET::::- The Space Pen, also known as the Zero Gravity Pen, is a pen that uses pressurized ink cartridges and is claimed to write in zero gravity, upside down, underwater, over wet and greasy paper, at any angle, and in extreme temperature ranges. The ballpoint is made from tungsten carbide and is precisely fit...
Where do the photons go after the light is turned off in the room?	They get absorbed by the surroundings! Photons are electromagnetic waves, so when they come to matter, they "wave" the electrons in the matter around, so the photons lose their energy are are absorbed. This is why a wall in the sun feels hot! The light is being absorbed by the wall and all energy goes into the wall fee...	[ "Note that, because the points of emission of the photons can be at any place on the (normally straight line) trajectory of the particle through the radiator, the emerging photons fill a light-cone in space.\n", "If a single photon is emitted into the entry port of the apparatus at the lower-left corner, it immed...
how is it possible that sites like _url_0_ or any other movie streaming service violating copyright laws are still up and running?	Not hosted on a server in the United States, perhaps?	[ "Professor Jukka Kemppinen, an expert on copyright legislation, states that Pirate Cinema is a deliberate provocation, but that, despite it being illegal, there is no point in making a big issue out of it. Kemppinen states \"It is no more illegal than showing a legally rented DVD to residents of an apartment buildi...
How can a paper cup full of water not burn up on a 2400 degree billet of steel?	The reason is that, perhaps surprisingly, the paper simply does not get hot enough. Paper has an autoignition temperature (the temperature at which it will burst into flame) of about 210-250^o C. If you were to just put an empty paper cup on the hot steel, it would rapidly reach this temperature and start burning. Howe...	[ "The second section of the paper machine is the press section, which removes much of the remaining water via a system of nips formed by rolls pressing against each other aided by press felts that support the sheet and absorb the pressed water. The paper web consistency leaving the press section can be above 40%.\n"...
what is a probation?	Basically means he can live feely as long as he abides by certain conditions (not out after certain time, keep the peace, and/or abstain from drugs/alcohol, etc...).	[ "Probation is a period of time where an offender lives under supervision and under a set of restrictions. Violations of these restrictions could result in arrest. Probation is typically an option for first time offenders with high rehabilitative capacity. At its core, it is \"a substitute for prison\", with the goa...
what's the religious situation in the us?	Westboro Baptist Church isn't a religion. It's a bigoted and angry old man and his family. There are a couple members that aren't related to the Phelps family. There are a lot of family members who have dropped out of the church as well.	[ "The religious and cultural holidays in the United States is characterized by a diversity of religious beliefs and practices. However, the First Amendment to the United States Constitution provides that \"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof .....
what is the ndaa and why did obama veto it?	It's basically a defense spending bill. He vetoed it because it had provisions that prohibited removing spending cuts and prohibited the closing of Guantanamo Bay. [sauce](_URL_0_)	[ "On September 30, 2015, President Barack Obama threatened to veto the NDAA 2016. The reason for the veto threat by the Obama administration was that the bill bypassed the Budget Control Act of 2011 spending caps by allocating nearly $90 billion to the Overseas Contingency Operations (OCO) account, designating routi...
Does our moon have a name in common english?	The proper English name for the moon is "the Moon". ([source](_URL_0_)). "Luna" is sometimes used in literature, and is the name of the Roman goddess that was the personified moon to the Romans.	[ "Every human language has its own word for the Earth's Moon, and these words are the ones normally used in astronomical contexts. However, a number of fanciful or mythological names for the Moon have been used in the context of astronomy (an even larger number of lunar epithets have been used in non-astronomical co...
absolute and apparent magnitude	Apparent magnitude is how bright a star appears to an observer on Earth. Absolute magnitude is a measure of how bright the star would appear to an observer on earth if the star were 10 parsecs away. Absolute magnitude allows astronomers to compare the inherent brightness of stars since the variations caused by distanc...	[ "Absolute magnitude () is a measure of the luminosity of a celestial object, on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly , without extinction (or dimmin...
If Ulysses S Grant was such a bad president why is he on the $50 bill?	It's less to do with the substance of his Presidency, and more to do with him winning the Civil War for the United States as a General, and then being elected to the Presidency. When Grant first appeared on a $50 gold certificate in 1913, he'd been dead for nearly 30 years: long enough to forgive some of the bad thing...	[ "According to historian John Y. Simon, had Grant served only one term of office, he would have been considered a great President by more historians, particularly noted for his successful negotiations of the \"Alabama Claims\" under his Secretary of State Hamilton Fish, his strong enforcement of civil rights for bla...
To what extent did the typical 15th/16th century European peasant know about/be affected by the Age of Exploration?	Well, there was the introduction of the potato, sugar (in loaves) from canes (as opposed to beets) and coffee. Oh, and tobacco.	[ "In the wake of the Age of Exploration, roughly between the 15th and 18th centuries, there was an explosion in the number of commodities and availability of products. People were using newly created cartography and using these maps to explore the world on paper. There was an accumulation of more objects and a desir...
what the different url means	They're just supposed to denote what kind of organisation is using the website. The usual .com was originally intended for commercial sites, .org for nonprofit organisations, and .net for networking technologies (guess what .tv was supposed to be used for?), but they ended up being unrestricted so anyone can use mostly...	[ "As such, a URL is simply a URI that happens to point to a resource over a network. However, in non-technical contexts and in software for the World Wide Web, the term \"URL\" remains widely used. Additionally, the term \"web address\" (which has no formal definition) often occurs in non-technical publications as a...
How do astronauts tell how fast they are going in space?	It is just as valid for an astronaut to say they are still and all else is moving as it is to say the earth is still (we know it rotates on its axis and around the sun). There will be someone on the ground telling them by radio their speed and position relative to the shuttle/satellite/station.	[ "There was no mass or power available in the LESS for an Inertial Measurement Unit to measure acceleration and tell the astronauts where they were, where they were going or how fast they would be getting there, or even for a radar altimeter to show altitude above the lunar surface.\n", "In order to unambiguously ...
if a non-english speaker learns english from a natural english speaker, why exactly do they have an accent?	It's not as easy as you think to "emulate sounds". Basically, the older we get, the harder it is to learn new skills. Learning how to pronounce sounds is easy when you're a baby -- literally child's play. But once you're past puberty, it gets harder to learn new sounds. To actually make intelligible sounds that mean ...	[ "The speech of non-native English speakers may exhibit pronunciation characteristics that result from their imperfectly learning the sound system of English, either by transferring the phonological rules from their mother tongue into their English speech (\"interference\") or through implementing strategies similar...
If Earth had a huge equatorial ocean like it did in the past, would it be possible we'd observe persistent hurricanes lasting months or even years, like a mini-version of Jupiter's great red spot?	Not quite. Global winds and ocean currents on planets are based off numerous factors. - The tilt of the planet (not just seasons, but if influences the amount of sunlight at the equator and the poles) - Positioning of continents (alters ocean currents) - Positioning of continents (warm and cold air) - Speed of the...	[ "Storms do not only occur on Earth; other planetary bodies with a sufficient atmosphere (gas giants in particular) also undergo stormy weather. The Great Red Spot on Jupiter provides a well-known example. Though technically an anticyclone, with greater than hurricane wind speeds, it is larger than the Earth and has...
What physical properties make Iron, Cobalt and Nickel ferromagnetic?	It is complicated. Paramagnetism and diamagnetism can be explained in terms of electron spins and electron orbital motion around an atom. If there are too many spins that are unpaired then the spins align with the field (para), if the spins are paired then the spins play no role and it is all about orbital motion which...	[ "The workability and corrosion resistance of iron and chromium are increased by adding gadolinium; the creep resistance of nickel is improved with the addition of thorium. Tellurium is added to copper (Tellurium Copper) and steel alloys to improve their machinability; and to lead to make it harder and more acid-res...
what constitutes resisting arrest? if i just go ragdoll when arrested, would that count?	If you do not comply with the officers instructions, then you are resisting. They will instruct you to do certain things with your hands, and to get into certain positions, and if you just go rag-doll and refuse to comply then you will be treated as non-compliant and resisting arrest. It's passive resistance, not viole...	[ "A person commits resisting arrest by intentionally preventing or attempting to prevent a person reasonably known to him to be a peace officer, acting under color of such peace officer's official authority, from effecting an arrest by: (1). Using or threatening to use physical force against the peace officer or ano...
How strong/durable would a sheet of diamond be?	Diamond is the hardest naturally occuring substance, which means it's scratch resistant. But it doesn't mean it won't break. That's more of a toughness thing. Toughness measures how much energy it takes to break it. Diamond has a toughness of about 2.0 MPa m^(1/2). Glass is about 0.7 to 0.8 MPa m^(1/2). So diamonds ...	[ "Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. Diamond is an optically isotropic crystal that is transparent to opaque. Diamond is the hardest naturally occurring material known. Yet, due to important structural weaknesses, diam...
pulse vs hearth-rate	Heart-rate Your pulse can have a little extra information on your health. A heart rate is the number of beats per minute that your heart makes, but on top of that a pulse can add the strength and consistency of the heartbeat at the point where it's measured. For example, a pulse can be characterized as "weak and t...	[ "The pulse is the rate at which the heart beats while pumping blood through the arteries, recorded as beats per minute (bpm). It may also be called \"heart rate\". The pulse is commonly taken at the wrist (radial artery). Alternative sites include the elbow (brachial artery), the neck (carotid artery), behind the k...
how there can be so much money in network tv advertising and so little in comparative online advertising?	First off, Youtube is not struggling to profit; neither is Netflix. Netflix made more than $2 Billion in profit and $20 billion in revenue last year, far more than any TV station. Alphabet Inc (parent of Google/Youtube) is the 3rd largest company on earth with a value of $988200000000. Secondly, there are few TV stati...	[ "The advertising network market is a large and growing market, with Internet advertising revenues expected to grow from $135.42 bn in 2014 to $239.87 bn in 2019. Digital advertising revenues in the United States alone are set to reach $107.30 bn in 2018 which is an 18.7% increase from 2017 ad spend. This growth wil...
Need to explain gravity and falling objects to my 9yo...	A simple thing that no one's mentioned is to put the piece of paper on top of and underneath the book when you drop them, rather than side by side. If they actually fall at different speeds, they would separate in one case. They'll fall together in both though, because the paper is shielded from air resistance effects ...	[ "This particular equivalence often referred to as the \"Galilean equivalence principle\" or the \"weak equivalence principle\" has the most important consequence for freely falling objects. Suppose an object has inertial and gravitational masses \"m\" and \"M\", respectively. If the only force acting on the object ...
in the way that people are able to build their own pcs, how far away are we from being able to build our own cellphones?	The major issue there is that most cellphone technology is extremely compact and build to fit around preselected parts where computers have components that can come in diffrent shapes and sizes, the designs are also far less modular. When I replied my iPhones charging port I had to use tweasers to re attach some compon...	[ "The majority of people around the world still do not have access to personal computing. Many of the current efforts to bridge the digital divide are failing and it is difficult for organizations to make a dent in this large demand. The idea of providing a “laptop per child” sounds feasible in theory, but there is ...
what is programmatic advertising?	Using programming (computers) to buy ads. Some are sold in what's called real time bidding. Basically when you visit a website with the ad in question whoever is selling the ad starts a short "auction" among some competitors and whoever has the highest bid gets the add and that's what you see. So obviously this all ...	[ "While advertising refers to the advertising message, per se, advertising management refers to the process of planning and executing an advertising campaign or campaigns; that is, it is a series of planned decisions that begins with market research continues through to setting advertising budgets, developing advert...
why do you hear so much more regarding desperate and lonely men rather than desperate and lonely women? shouldn't there be more or less an equal amount of both?	Women have far better support systems available compared to men. It's socially acceptable for women to feel hurt and express those feelings. They usually get ample sympathy and support from friends, family, colleagues and the public. When a man tries the same, he's ignored, ridiculed and perceived as weak.	[ "Americans seem to report more loneliness than any other country, though this finding may simply be an effect of greater research volume. A 2006 study in the \"American Sociological Review\" found that Americans on average had only two close friends in which to confide, which was down from an average of three in 19...
how is orange juice economically viable when it takes me juicing about 10 oranges to have enough for a single glass of orange juice?	They use machinery that grinds the orange down to more or less nothing, and can extract every tiniest little drop of juice from it. The machinery pretty much grinds up the oranges whole, skin and all, and then extracts every drop of juice from the ground-up mess. So they get more juice per orange than we can by hand, o...	[ "BULLET::::- Orange juice is obtained by squeezing the fruit on a special tool (a \"juicer\" or \"squeezer\") and collecting the juice in a tray underneath. This can be made at home or, on a much larger scale, industrially. Brazil is the largest producer of orange juice in the world, followed by the United States, ...
Do we know of any contact between Ancient Egypt and East Asia ?	Ah. I enjoyed that book and it does an excellent job of telling stories, but yes, it's age shows in quite a few places. Short answer: no. Essentially, the book is proposing a model called diffusionism, although hyper-diffusionism might be more accurate. This was a theory, or more accurately a methodology, that propose...	[ "Eastward contacts are represented by objects and motific works of ancient Egypt found in the Near East, including modern Anatolia and Byblos and those ancient regions around Canaan and Syria. Some kings of Byblos have been found buried with Egyptian items.\n", "Foreign artifacts dating to the 5th millennium BCE ...
why do some women look super pregnant at 8ish months, yet others are barely noticeable?	The boring, obvious answer is that women have a wide variety of body types and sizes. A tall, larger woman will appear less pregnant than a short, small woman. A woman with a tiny waist will show a pregnancy more than a woman with wide hips.	[ "BULLET::::- Women are more susceptible to develop diastasis recti when over the age of 35, high birth weight of child, multiple birth pregnancy, and multiple pregnancies. Additional causes can be attributed to excessive abdominal exercises after the first trimester of pregnancy.\n", "Two months later, all women ...
Is the next generation of humans getting stronger and taller than the previous one? Also when would it stop?	Humans are generally getting taller and stronger than previous generations. Many scientists believe this is due to nutrition (increased calories, increased protein intake) rather than genetics. Given that vitamins and proteins are ubiquitous, it is unlikely that height would increase as a function of nutrition.	[ "Improved nutrition is another possible explanation. Today's average adult from an industrialized nation is taller than a comparable adult of a century ago. That increase of stature, likely the result of general improvements of nutrition and health, has been at a rate of more than a centimeter per decade. Available...
What is the place of the battleship Yamato in the Japanese consciousness/culture?	I would definitely say the Yamato has some sort of place in the hearts of the Japanese people even today. In the late 30s, when it was laid down it was praised for being the biggest battleship in history and at the time many people still thought that size was the most important feature for these kind of Battleships. In...	[ "\"Yamato\", and especially the story of her sinking, has appeared often in Japanese popular culture, such as the anime \"Space Battleship Yamato\" and the 2005 film \"Yamato\". The appearances in popular culture usually portray the ship's last mission as a brave, selfless, but futile, symbolic effort by the partic...
Going into the Korean war, did the US ever have the goal of completely absorbing the north into the south, or was an eventual retreat from the Yalu planned?	Going in was long before the Yalu. The intent was simply to keep the south from being incorporated into the north. Americans' concern was not to be embarrassed by having to retreat from Pusan. There was no UN mandate to do more which is why it was a UN police action, not a US war. Anyway, America was war weary after W...	[ "In the Korean War, the United States and the United Nations officially endorsed a policy of rollback—the destruction of the North Korean government—and sent UN forces across the 38th parallel to take over North Korea. The rollback strategy, however, caused the Chinese to intervene, and US forces were pushed back t...
Is there literally ZERO resistance in superconductors or is it just miniscule or neglectable (like stuff normally is in real-life as opposed to theory)?	The best theory we have suggests that the electrical resistance of a superconductor can be exactly zero. Unfortunately it's a bit tricky to definitively validate this result experimentally since we simply can't measure a resistance of 0. Even though [most experiments seem to show that the resistance vanishes](_URL_1_),...	[ "Superconductivity is the set of physical properties observed in certain materials, wherein electrical resistance no longer exists and from which magnetic flux fields are expelled. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradual...
Just how long has vinegar been around in any form?	Vinegar is created by acetobacter, a kind of bacteria that is naturally occurring- notably, occurring in the guts of fruit flies. When yeast ( a fungi) encounter sugar, they will start to ferment it into alcohol. If acetobacter bacteria are present ( and, of course, that can occur because fruit flies are going to ...	[ "Vinegar was known early in civilization as the natural result of exposure of beer and wine to air, because acetic acid-producing bacteria are present globally. The use of acetic acid in alchemy extends into the 3rd century BC, when the Greek philosopher Theophrastus described how vinegar acted on metals to produce...
When was the second first developed as a unit of time? Were there any areas where a different standard was used?	hi! I've got a pile of links for you, so settle in... First up, the FAQ has a couple of posts on [Hours, minutes, and seconds](_URL_11_) Origins * [Has everyone always used a 24 hour day?](_URL_5_) * [As far as I can tell, nearly all of the world divides a day into 24 hours, each of which in turn divides into 60 mi...	[ "In 1832, Gauss proposed using the second as the base unit of time in his millimeter-milligram-second system of units. The British Association for the Advancement of Science (BAAS) in 1862 stated that \"All men of science are agreed to use the second of mean solar time as the unit of time.\" BAAS formally proposed ...
When, how, and why did sports (in general) become such a high-dollar enterprise in the United States?	( I'm typing this on my phone, so please excuse any grammar/spelling mistakes) Although I'm not an expert, I would have to guess this happened around the late 1800s/early 1900s. During this time Americans disposable incomes and leisure time increased due to achievements by unions and other average Americans. Major lea...	[ "Many factors combined to produce an explosive growth in this new sport which had been imported from the United States. The number of teams grew from 8 in 1985 to around 40 by the end of the 1980s. In addition, the teams from larger cities were able to professionalise further by obtaining large sponsors, attracted ...
after showers, whenever i rub my skin i get rolls of dirt/dead skin cells. why is this?	You need to exfoliate better. Or shower more often. Grab a wash cloth or loofa and wash, don't just use your hands.	[ "In general, the skin becomes swollen, itchy and red. This is a result of compression of mast cells, which are hyperactive in these diseases. These mast cells release inflammatory granules which contain histamine. It is the histamine which is responsible for the response seen after rubbing the lesional skin.\n", ...
why does 25 mph on a bicycle seem so much faster than in a car?	You feel like you're going extremely fast on a bike because you feel more. Cars have very well developed suspension systems that "even out" the bumps on the road. As long as you're not dealing with a serious pothole or a speed-bump, the car's suspension is going to face-tank most of the shock so that you don't have ...	[ "A standard lightweight, moderate-speed bicycle is one of the most energy-efficient forms of transport. Compared with walking, a cyclist riding at requires about half the food energy per unit distance: 27 kcal/km, per 100 km, or 43 kcal/mi. This converts to about . This means that a bicycle will use between 10-25 t...
Zion Harvey got a double hand transplant at 9 years old. Will his hands continue to grow along with the rest of his anatomy as he ages?	Yes the cells will keep working normally and normal physiological growth is expected. Abnormal groiwth is also relatively common (please correct me) due to post transplant medication that supresses the immune system thus not stopping some spurs of organ/limb growth that medication would normally stop. PS: I'm by all ...	[ "On July 28, 2015, doctors at the Children's Hospital of Philadelphia performed the first successful bilateral hand transplant on a child. At the age of 2, Zion Harvey lost his hands and feet to a life-threatening infection. Six years later, at age 8, he had both of his hands replaced in a double hand transplant.\n...
where did trigonometric functions come from? and why do they work?	Trigonometric functions were developed by various ancient cultures, mostly dealing with measuring astronomic phenomenon which requires dealing with angles and triangles and such. Basically, we had a certain set of questions (if you know the sides of a triangle how to calculate its angles, and vice versa) that trigonom...	[ "In mathematics, the trigonometric functions (also called circular functions, angle functions or goniometric functions) are real functions which relate an angle of a right-angled triangle to ratios of two side lengths. They are widely used in all sciences that are related to geometry, such as navigation, solid mech...
what happened to telescoping fm antennas on cars?	Most new cars embed them inside the windshield or rear window which gives them a much better and bigger area of reception. The wire used is nearly invisible to the eye and you don't have to worry about a motor burning out or breaking it in the car wash as with the telescoping ones.	[ "The first 2,200 cars produced used a windshield-embedded antenna. This type of antenna proved to be unsuitable with poor radio reception. Oftentimes the radio would continually \"seek\", attempting to find a signal. A standard whip antenna, which was later changed to a manually retractable antenna, was added to th...
if heat rises up, why does global warming occur instead of the heat just dissipating through outer space?	global warming is the buildup of gasses that PREVENT exactly what you are talking about (heat dissipating up, its called albido). These gasses act like a mirror pointed back at earth, reflecting said heat back into the system.	[ "Here on earth, the sun delivers lots of bounce, and the atmosphere surrounds it with a wall that reflects the energy back in. In outer space, however, there’s nothing — a vacuum — and the bounce all disappears very quickly, leaving very little moving. Lack of motion means little heat, and almost no transfer — very...
Would we be able to detect an extraterrestrial spacecraft in orbit around our Sun?	[Voyager](_URL_2_) or [Voyager](_URL_0_)? :P In all seriousness though, [this](_URL_1_) says that by 2028 we hope to have detected 90% of all near-Earth asteroids of diameter 140 meters or larger. So it's very unlikely we'd detect a Voyager-sized spacecraft in orbit around the Sun (unless it happened to be at the sa...	[ "Interstellar spacecraft may be detectable from hundreds to thousands of light-years away through various forms of radiation, such as the photons emitted by an antimatter rocket or cyclotron radiation from the interaction of a magnetic sail with the interstellar medium. Such a signal would be easily distinguishable...
what is the catch with those auction sites that claim to sell ipads and high end laptops for $20?	You have to pay for each bid, and you can only improve the previous bid by a small increment each time. So as an example. Lets say an IPad costs $500. Each bid costs you $1. You can bid it up by .01 each time. So in aggregate people need to spend $2000 to win the right to buy the item for $20. And once people start bid...	[ "Amazon introduced Amazon Coins on July 13, 2013 in the United States and gave 500 free coins valued $5/£3 to all users of Kindle Fire devices, who could use the coins to purchase apps, games, and in-app purchases on the Amazon Appstore. However, in 2014, Amazon started allowing all Android users in Germany, the Un...
What were the casualties expected in an invasion of mainland Japan and how did they compare to the actual casualties caused by using nuclear weapons ?	The atomic bombs dropped on Japan killed at least 150,000, and probably more than 250,000 eventually died as a direct result of the bombings. Just to keep things in perspective, neither the bombing of Hiroshima or Nagasaki were individually as deadly as the March 9-10 1945 firebombing of Tokyo (100,000 dead). The inv...	[ "These casualty figures, as well as those from other island campaigns, were used by U.S. military planners to estimate that Operation Downfall, the planned invasion of the Japanese home islands, would result in well over 1,000,000 U.S. and 5,000,000 Japanese casualties. These estimates put the decision made to use ...
Is there proof of mutation introducing new material into the genome?	How your friend put it is a bit misleading. Mutations happen all the time. And they aren't noticeable because many don't cause any change in that gene's function. Point mutations occur in which bases (nucleotides in your DNA) are altered. There are insertions, deletions or frameshifts.. which I don't want to get into....	[ "A molecule that allows the genetic material to be realized as a protein was first hypothesized by François Jacob and Jacques Monod. Severo Ochoa won a Nobel Prize in Physiology or Medicine in 1959 for developing a process for synthesizing RNA \"in vitro\" with polynucleotide phosphorylase, which was useful for cra...
Why isn't the sky completely white at night?	You've hit upon a very old question called ["Olbers' Paradox"](_URL_0_). The solution relies on the fact that the universe is not infinitely old, so only finitely many stars and galaxies are observable and they collectively subtend an angle on the sky much smaller than the full sky.	[ "The nighttime sky on Earth is black because the part of Earth experiencing night is facing away from the Sun, the light of the Sun is blocked by Earth itself, and there is no other bright nighttime source of light in the vicinity. Thus, there is not enough light to undergo Rayleigh scattering and make the sky blue...
what causes a rolled up piece of paper to act like a spring and what other materials want to naturally return to a flat sheet when rolled	> Are there other elastic materials similar to these that would want to snap back to a flat sheet? Sure. They're everywhere. Metal, plastic, wood, rubber, and on and on. Pretty much any common solid material will snap back to its resting arrangement when you let go, provided you don't stress it too far. Think of...	[ "A paper roll is threaded between two hard rollers, usually made from steel. One or both of the steel rollers has a linen pattern engraved on it. As the nip pressure between the two hard rollers increases, the pattern from the engraved roller(s) is pressed into the paper. The end result is a pattern that looks like...
Wednesday AMA: I am Mr_Bimmler, ask me anything regarding WWII Weapons or Vehicles.	I have a question regarding the general reliability of military ground vehicles in WWII. How often would a German Tiger tank or an American Sherman need to be serviced? Could a Jeep travel thousands of miles with nothing more than filling it up with gas? Who would perform the actual maintenance if something were to ...	[ "Sonderkraftfahrzeug (abbreviated Sd.Kfz., German for \"special purpose vehicle\" or \"special ordnance vehicle\") was the ordnance inventory designation used by Nazi Germany during World War II for military vehicles; for example \"Sd.Kfz.\" 101 for the Panzer I.\n", "BULLET::::- Captured German WW2 vehicles - A ...
why is cyberbullying a problem?	> Basically my question is this, if you're being bullied over social networking (or even through your phone) why continue to participate? You don't have to participate directly for it to affect you. Even if you ignore the bully, if other people in your social group are still paying attention to them, it will eventua...	[ "Cyberbullying \"involves the use of information and communication technologies to support deliberate, repeated, and hostile behavior by an individual or group, that is intended to harm others.\" -Bill Belsey\n", "'Cyberbullying' is the use of technology to bully a person, or threatening an individual online. Cyb...
Cathedrals are large and ornate, necessitating significant investment to construct. Did Cathedrals they serve any practical purpose for the village/town/city aside from hosting religious proceedings.	There actually are a few ways that churches functioned aside from housing worshipers for Mass, but these are, of course, directly related to the church’s larger spiritual aims which took precedence in the Middle Ages. I can’t demonstrate every way that the space of the church was used at this time but I can give a few ...	[ "Because many cathedrals took centuries to build and decorate, they constitute a major artistic investment for the city in which they stand. Not only may the building itself be architecturally significant, but the church often houses treasures such as stained glass, stone and wood statues, historic tombs, richly ca...
Why does snow accumulate in stripes? (Pic)	It is because of wind. It works like sand dunes. You start with an even accumulation, then wind blows in one direction. Imperfections in the ground surface cause some flakes to stick, and others stick to them, until all of the snow is in drifts.	[ "In the natural environment, slush forms when ice or snow melts. This often mixes with dirt and other materials, resulting in a gray or muddy brown color. Often, solid ice or snow can block the drainage of fluid water from slushy areas, so slush often goes through multiple freeze/thaw cycles before completely disap...
how does soaking a piece of clothing in milk remove red wine stains?	You're extracting the compounds In wine by using density extraction. Milk is more dense than the wine compounds so it ends up pulling up the less dense components. Source: I'm a Biochemistry student	[ "The popular belief that carbonated water is a good remover of clothing stains, particularly those of red wine, is based on hearsay and anecdotal evidence. The dissolved gas in water acts as a temporary surfactant. There is no underlying chemical reason why carbonated water would be superior to plain water in stain...
Monday Mysteries \| Ancient Ruins	One particularly bizarre (to our eyes) archaeological feature are the mosaics found in Olmec cities like La Venta. [Here's an example](_URL_0_). These large patterns are made from serpentine (a kind of green stone considered to be a precious mineral by Mesoamericans). The weird thing about them is that they were buri...	[ "Ancient Ruins and Archaeology is a 1964 science book by L. Sprague de Camp and Catherine Crook de Camp, one of their most popular works. It was first published by Doubleday and has been reprinted numerous times by other publishers. Paperback editions since 1972 have generally reverted to the title Citadels of Myst...
how are my headphones playing a "ghost station"?	A nearby AM radio station is being picked up and rectified by the TV. A simple AM receiver can be made with a junction of two dissimilar metals or a metal needle point on a crystal. I suspect the electronics in the TV are performing the rectification and the headphone cable is the antenna.	[ "Another ghost is that of Stan Andrews. He is often heard wheezing around the backstage corridors at night, checking on his ushers. Also, a boy's choir is said to haunt the auditorium. The choir played their last song at the St. James during World War II before sailing off on tour. Their ship was never seen again a...
when using my smartphone camera why is video darker than photos for a given light level?	Exposure time. When you take a still-shot, the camera can pause to take in a large amount of light - after all, nobody is moving around much (hopefully) and there's no rush to get another shot in within the next few ms. When you're taking a video, however, the camera has at most 30 ms to take in light for each frame...	[ "The camera on the iPhone 5 reportedly shows purple haze when the light source is just out of frame, although Consumer Reports said it \"is no more prone to purple hazing on photos shot into a bright light source than its predecessor or than several Android phones with fine cameras...\"\n", "There is a flash on t...
what happens to the human body that makes it feel like cold isn't cold?	Your body can't actually sense temperature. It feels heat being absorbed or lost. So when you are losing heat your body tells you that your surroundings are cold. The more heat you lose the more you perceive your surroundings as being cold. Also, the greater the temperature differential between two things, the fast...	[ "Cold has numerous physiological and pathological effects on the human body, as well as on other organisms. Cold environments may promote certain psychological traits, as well as having direct effects on the ability to move. Shivering is one of the first physiological responses to cold. Extreme cold temperatures ma...
music equalization (as it pertains to mixing)- what's the deal?	Boosting = making a certain range of sound frequencies louder Cutting = making a certain range of sound frequencies quieter I'll post sample pictures in a bit. EDIT: Here is an [example](_URL_0_). So for me, I make hip-hop beats. When I'm making beats from sampling + chopping, I always cut the low / bass frequenci...	[ "Equalization is used in a reciprocal manner in certain communication channels and recording technologies. The original music is passed through a particular filter to alter its frequency balance, followed by the channel or recording process. At the end of the channel or when the recording is played, a complementary...
A balloon filled with helium goes in the opposite direction of earth's gravity. Not only does it overcome the force, but it also travels up. What would happen to a balloon in deep space? Would the helium stay put or would the balloon split and the helium go in all directions?	It is not fighting gravity. It is just lighter than the air around it. The air is pushing it up, much like air bubbles rise in water. Space is a vacuum, so it depends on it's initial course. If the helium escaped Earth's atmosphere it would not keep 'rising'. Earth's gravity would still pull it. But in a zero G vacuu...	[ "Fully inflated, a balloon of this size would contain just over of helium. Helium's lift capacity at sea level and 0 °C is 1.113 kg/m (0.07 lbs/ft) and decreases at higher altitudes and at higher temperatures. The volume of helium in the balloon has been estimated as being able to lift a total load, including the b...
how do fossils of an action or event get made?	That's not a "stone" type of [fossil](_URL_3_) but insects trapped in amber which is a [fossil resin ](_URL_2_). The insects got trapped in the [resin](_URL_0_) from a tree and that kept them intact over the ages when it turned into amber. [_URL_4_ article on the find](_URL_1_).	[ "Over geological time since, the rock was pushed so deep that heat and pressure hardened it much, before it came again to the surface. As a result, a common way to look for fossils in it was to break each lump with a sledgehammer, and after each blow to examine all new broken surfaces for cross-sections of bone. An...
After we get a cut, I read that our blood vessels have to grow back at the site of the wound. Do the blood vessels always grow back in the same pattern as before, or can they grow back in a different way?	When you cut your finger your body tries to fill the wound with a mixture of totally random capillaries and collagen-rich fibrous tissue. Later, most of the capillaries will die back and the wound will contract and turn white. [Vastly more on this here](_URL_0_) starting with the angiogenesis section. You can grow lar...	[ "Because the walls of the blood vessels are firmly attached to the fibrous tissue of the superficial fascial layer, cut ends of vessels here do not readily retract; even a small scalp wound may bleed profusely.\n", "It has been hypothesized that, during both wound healing of normal tissues and tumor development, ...
why does metal heat up so much when crushed under a hydraulic press?	Almost every metal is made up of crystals - ordered arrangements of atoms. Some metals are made of very small crystals, some are made of large crystals, and some very special metal parts can be made of a single crystal. These crystals aren't perfect - they have little atom-sized holes in them, and atoms stuck where th...	[ "In this process molten metal is poured in the mold and allowed to solidify while the mold is rotating. Metal is poured into the center of the mold at its axis of rotation. Due to centrifugal force the liquid metal is thrown out towards the periphery.\n", "Metallic yielding dampers, as the name implies, yield in ...
french politics and law	Please be more specific? Political parties or how politics work? All the laws would be challenging... do you have something in mind?	[ "French law is divided into two principal areas: private law and public law. Private law includes, in particular, civil law and criminal law. Public law includes, in particular, administrative law and constitutional law. However, in practical terms, French law comprises three principal areas of law: civil law, crim...
who started 'high-5s' and are they universal?	[Check out this Radio Lab podcast](_URL_0_), where they ask and attempt to answer this very question. Unfortunately, I can't find a transcript, but they refer to an ESPN article called [History of the high five](_URL_1_) which might also be interesting.	[ "High 5 was founded in 1993, as a collaboration between staff of the American Symphony Orchestra (Eugene Carr and Kathleen Drohan), the New York Times (Jeanne Shanley and Sharon Yakata), and Ticketmaster (Marla Hoicowitz and Connie Fitzgerald). In 1995, High 5 appointed its first full-time executive director, Ada C...
To what extent did resistance groups in WWII fight each other?	I am familiar in detail only with Yugoslav resistance groups. The two main resistance groups, Chetniks and communist partisans waged a civil war parallel with the war against occupying and quisling forces. Far from just occasional skirmishes this civil war in many ways determined the strategy of both, to the extent tha...	[ "Resistance movements during World War II occurred in every occupied country by a variety of means, ranging from non-cooperation to propaganda to hiding crashed pilots and even to outright warfare and the recapturing of towns. In many countries, resistance movements were sometimes also referred to as The Undergroun...
What differences, if any, were there between Soviet and Western (American, British, French) tactics in countering Blitzkrieg tactics in WW2?	Follow up. Was Blitzkrieg even a real German doctrine in WW2?	[ "During the 1930s, the resurgence of the German military in the era of the \"Third Reich\" saw German innovations in the tactical arena. The methodology used by the Germans in the Second World War was named \"\"Blitzkrieg\"\". There is a common misconception that \"Blitzkrieg\", which is not accepted as a coherent ...
why do turtles grow as large as their tanks?	It's not totally true. Turtles will grow as big as their genetics and nutrition and other factors let them. Turtles actually have their growth stunted in an unhealthy way by being in an environment too small, not due to the physical environment alone, but also by the nutrients available in said environment. The physica...	[ "The shape of the shell gives helpful clues about how a turtle lives. Most tortoises have a large, dome-shaped shell that makes it difficult for predators to crush the shell between their jaws. One of the few exceptions is the African pancake tortoise, which has a flat, flexible shell that allows it to hide in rock...
how can countries be banned from the u.s. based solely on their religious majority?	> How is this possible with rights guaranteed by the first amendment? Rights laid out in the US constitution only apply to US citizens, or people on US soil. If you're a foreign national in another country, the US doesn't have to give you any rights; that's the job of the country you're currently in. > Does the ...	[ "Religion in the United States has a high adherence level compared to other developed countries, as well as a diversity in beliefs. The First Amendment to the country's Constitution prevents the Federal government from making any \"law respecting an establishment of religion, or prohibiting the free exercise thereo...
Would a planet-sized ball of liquid water in space have a solid core of "hot ice" the same way Earth's inner core is solid?	At high pressures water will form a solid at any temperature. Wikipedia has a rather detailed phase diagram for water: _URL_0_ Of course the specifics will vary; it'd be very unlikely for a planet to form exclusively from water, so getting a water-only core becomes difficult.	[ "Solid nitrogen has several properties relevant to its formation of rocks in the outer Solar System. Even at the low temperatures of solid nitrogen it is fairly volatile and can sublime to form an atmosphere, or condense back into nitrogen frost. At 58 K the ultimate compressive strength is 0.24 MPa. Strength incre...
why has stop snitchin' remained so popular in low-income us populations?	People in low income situation usually have short term goals as opposed to long term goals. And in many low income areas criminal populations hold more power then government.	[ "Both in the United Kingdom and United States, they came out of social concerns about cities, poverty, immigration, and vagrancy following industrialization, as well as from a shift in society's attitude from retribution, punishing the miscreant to reforming.\n", "Jenny, as outbreaks of measles, mumps and whoopin...
Are Southern Chinese really Han Chinese?	Now firstly it must be made clear: "Southern Chinese" is not a single homogenous group. There are several major ethnic group that usually called Southern Chinese. These are: - Hokkien/Fujuanese: people from Fujian. This province is the most mountainous province in eastern China. During early Han period this period are...	[ "The Han Chinese people are bound together with a common genetic stock and a shared history inhabiting an ancient ancestral territory for over four thousand years, deeply rooted with many different cultural traditions and customs. The Huaxia tribes in northern China experienced a continuous expansion into southern ...
what is insomnia and why can't our brains shut off when we're excessively tired	Insomnia can be caused by many things, but one of the most common causes of insomnia is a non-functioning ability to produce the chemical that makes us begin to fall asleep. Our brain (neurotypically) naturally makes all of the chemicals we need on a given day to function. One of them, melatonin, is produced in low li...	[ "BULLET::::- Insomnia cannot be blamed for all the deficits the patient is experiencing in his daytime life (not all problems will go away once the patient is able to sleep), this is important to know, because it takes some of the unrealistic expectations off sleep.\n", "People with insomnia tend to excessively w...
What set the precedent for the "campy" style of early superhero pop culture? As opposed to the gritty/realistic style we see today.	can you clarify the timelines you are thinking about? The really campy stuff doesn't start until the 60s after the pushback from the book "seduction of the innocent," (where criticism of superhero books was included along with other violent comic books) sparking a moral panic and the comics code. As a result of the cod...	[ "Antecedents of the superhero archetype include such folkloric heroes as Robin Hood, who adventured in distinctive clothing, Penny dreadfuls, shilling shockers, dime novels, radio programs, and other popular fiction of the late 19th and early 20th centuries featured mysterious, swashbuckling heroes with distinct co...
Was there ever a time and place, before alcohol regulation, where it was acceptable for children to get drunk regularly?	You seem fairly familiar with the common practice of giving smaller children beer before potable water was widely available, and the idea of "drinking water" would have seem foreign to adults and children alike. There is another practice that might interest you, which involves giving a baby a small amount of brandy o...	[ "Alcohol consumption was also used to medicate both adults and children during illnesses. Because alcohol was held in such high regard, Korean ancestors took great pains to pass down drinking customs from generation to generation.\n", "Because of moral panic involving alcohol abuse among minors (a 16-year-old boy...
Can bacteria survive in a freezing enviroment?	[Psychrophiles](_URL_0_) thrive at very low temperatures. Such as wiki states, temps as low as -20C. They're part of extremophiles which cover all 'extreme' environments from high heat, to acidity, and metals.	[ "Three species of bacteria, \"Carnobacterium pleistocenium\", as well as \"Chryseobacterium greenlandensis\" and \"Herminiimonas glaciei\", have reportedly been revived after surviving for thousands of years frozen in ice.\n", "Three species of bacteria, \"Carnobacterium pleistocenium\", \"Chryseobacterium greenl...
Does hair growth add weight?	You would get heavier as you consumed food. Hair, in this analogy, can be seen like sweat. The only difference is that it's an excretion you retain, instead of one that evaporates.	[ "Scalp hair grows, on average, at a rate of about 1.25 centimeters per month, and shampoos or vitamins have not been shown to noticeably change this rate. Hair growth rate also depends upon what phase in the cycle of hair growth one is actually in; there are three phases. The speed of hair growth varies based upon ...
how come that in every mayor city there are hundreds of pigeons but you never see any dead ones?	Two words: Turkey buzzards.	[ "Feral pigeons often only have small populations within cities. For example, the breeding population of feral pigeons in Sheffield, England, has been estimated at only 12,130 individuals. Despite this, feral pigeons usually reach their highest densities in the central portions of cities, so they are frequently enco...
will you explain to me the chi-square model when applied to genetics?	The chi square model is a way for people who study genes to understand probability. If two traits are inherited by a child (like blue eyes and a small nose), what are the chances they were inherited together randomly, out of all the options it could have been? The other option is that these genes are linked, meaning th...	[ "The chi-square distribution is used primarily in hypothesis testing, and to a lesser extent for confidence intervals for population variance when the underlying distribution is normal. Unlike more widely known distributions such as the normal distribution and the exponential distribution, the chi-square distributi...
Why didn't Einstein get a Nobel prize for Relativity? Was the paper on the photoelectric effect really more important?	The first thing to remember about [Einstein's Nobel Prize](_URL_1_) is that it was given for "his service to Theoretical Physics, and especially for the discovery of the law of the photoelectric effect" So it was not strictly given to him for the photoelectric effect. But to understand why that theory was highlighted...	[ "Through these papers, Einstein tackles some of the era's most important physics questions and problems. In 1900, Lord Kelvin, in a lecture titled \"Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light\", suggested that physics had no satisfactory explanations for the results of the Michelson–Morle...
why are real number data types such as float and double called "floating-point"?	Let's say you have 8 "spaces" to store a number. There's a few different ways you can store numbers in it: 1. Unsigned Integers. ######## lets you store numbers from 0-99999999 but no negatives or decimals 2. Signed Integers. ±####### lets you store from -9999999 to +9999999, a smaller number than option 1 but cover...	[ "The floating-point form is used to represent numbers with a fractional component. They do not, however, represent most rational numbers exactly; they are instead a close approximation. There are three types of real values, denoted by their specifiers: single precision (float), double precision (double), and double...
why is it so difficult to figure out how life actually started?	Over time, the crust of the earth gets recycled. It gets pressed down into the mantle and eroded away, only to be replaced by cooling lava. In the past 4 billion years or so, almost all of the original crust is gone, only small portions in Canada, Australia, and Africa remain intact. That means most of the history o...	[ "One of the major challenges in studying the origin of life has been the inability to clearly define what life is. In her investigations, Walker has used the flow of information in systems as a means to distinguish life from non-life. She used the Boolean network model, information theory, and other models to disce...
Why does the ticking of my clock mess with the display on my TV?	Battery powered clock? Usually those use a pulsed electromagnet to advance the gearing once per second. They create a small "EMP" electromagnetic pulse. Tune an AM radio between stations, and it may pick up the one-second pulse as a click sound. But this shouldn't affect your TV unless it has a poorly shielded (b...	[ "A clock accompanied the look, which used GNAT (Generator of Network Analogue Time), resulting in the clock mimicked the movement of an analogue clock by moving the minute hand every second, rather than every 15 seconds as was found on previous station clocks. The counters on the clocks alternated between dots and ...
creative commons	Whenever a person creates a work like a photo, drawing, song, poem, etc., they own the copyright to it. That means that, aside from fair use, they have the exclusive right to distribute, sell, or otherwise use it. Creative Commons is basically a way for creators to allow others to use that work, usually with certain st...	[ "Creative Commons is an organization that “develops, supports, and stewards legal and technical infrastructure that maximizes digital creativity, sharing, and innovation.” It encourages the use of protected properties online for research, education, and creative purposes in pursuit of a universal access. Creative C...
why is it that we can't see gases in their pure form, yet we can see the shadows of gases on a sunny day?	Plenty of gases have color in their pure form. We can see shadows on hot days because air expands and then moves. And light changes a few properties when switching between mediums, so that movement of air and change in density is what makes the light wavy (gives interference patterns). But the gases in air do not ref...	[ "In principle, we cannot directly see a difference in temperature, a different gas, or a shock wave in the transparent air. However, all these disturbances refract light rays, so they can cast shadows. The plume of hot air rising from a fire, for example, can be seen by way of its shadow cast upon a nearby surface ...
What were the relative advantages and disadvantages of varying melee weapons during the middle ages?	Since a historian hasn't responded to your question, I hope I can post these video links from a TV show that looked at "alternative" weapons such as a flail, mace, falchion, etc. : _URL_2_ _URL_1_ _URL_0_ The host discusses some of the advantages and disadvantages of these weapons. Hope this post is OK, I can edit ...	[ "Later in the Middle Ages, massed archery techniques were developed. English and Welsh longbowmen in particular were famed for the volume and accuracy of their shooting, to which cavalry and poorly armoured infantry were particularly vulnerable.\n", "For most of the Middle Ages, warfare and society were dominated...
what does the 3-2-l mean in some automatic transmissions in cars, what are their purpose?	3rd gear, 2nd gear, Lowest gear. Automatic switches gears automatically of course, but doesn't always give you the power you may want, so those options allow you to manually downshift and give your car more power.	[ "There are currently four different engines available, the 1.6 L \"M16A\" I4 (petrol), 1.9 L \"F9Q\" I4 (diesel), 2.0 L \"J20A\" I4 (petrol) and 2.4 L \"J24B\" l4 (petrol). The transmission choices are a 5-Speed Manual or a 4-Speed Automatic Transmission (depending on engine and market). Some markets do not offer t...
why do my eyes become hard to keep open when i'm tired? is it the brain trying reduce stimuli and rest?	Eyes are controlled by ciliary muscles. As do all muscles, when you are tired you muscles start to become harder to use. E.G, when you lift weights, the longer duration you lift for, the more fatigued you get. Same principle.	[ "Primary reasons is eye fatigue as a result of excessive pressure on the eyes because of reading, watching TV, computer, poor lighting, etc. Some other reasons are poor posture, poor diet, lack of sleep, etc.\n", "When concentrating on a visually intense task, such as continuously focusing on a book or computer m...
Josip Broz Tito spoke Kyrgyz?	Tito did spend some time in what is now Kyrgyzstan during the Russian Civil War. From 1918 to 1920 he was hiding out in a village near Osh, the main city in the south of Kyrgyzstan, and eventually married an ethnic Russian from there. However it should be noted that the region is, and was, mainly full of ethnic Uzbeks...	[ "BULLET::::- 13: Yugoslav Army Colonel Draža Mihailović summons up the \"Yugoslav Army in the Fatherland\" which mostly consists of Serbs, but also includes Slovenes, Bosnians, and Croats. Mihailović treks from Bosnia into central Serbia, Ravna Gora, and issues an uprising call promising a struggle against the occu...
if volcano eruptions are from pressure buildup, why not just drill and relieve the pressure?	That's a monumentally risky endeavor for so little reward. You could get seriously burned, possibly trigger a real volcanic eruption, and release toxic gases into the atmosphere. Furthermore, as long as the core is hot, volcanos will still erupt, and the nuclear fission of the uranium in the core will keep it hot for...	[ "The sudden release of pressure causes the gases in the magma to suddenly froth and create volcanic ash and pumice, which is then ejected through the volcanic vent to create the signature eruption column commonly associated with explosive eruptions. The size and duration of the column depends on the volume of magma...
why is it that the federal reserve can print money but america has limited inflation?	Several reasons actually. The currency(not money) that is being printed/typed into the system has not, for the most part entered the system yet. It is given to large banks (particularly the ones that are a part of or have pull with the FED) and then put into the stock market. This is done by the FED to provide collater...	[ "Some protesters have argued that Federal Reserve notes (better known as dollar bills) are not actually money, because the Constitution only permits the government to \"coin\" money, and requires that such money be exchangeable for gold or silver; therefore, printed bills are instead symbols for use in bartering, a...
How did the titles of "Roman Emperor" and "King of the Franks", both held by Charlemagne, become separated?	So [this excellent post](_URL_0_) a week ago by /u/idjet explains the circumstances of the passing on of Charlemagne's imperial title, as well as whether he intended to do so or not. However, whatever the details were, after the division of the empire after the death of Charlemagne's surviving son Louis the Pious, the...	[ "For this reason, Charlemagne, the King of the Franks and King of Italy, was crowned Emperor of the Romans (\"Imperator Romanorum\") by Pope Leo III, as the successor of Constantine VI as Roman Emperor under the concept of \"translatio imperii\". The Eastern Empire eventually relented to recognizing Charlemagne and...
why acceleration is constant in a vacuum, and an airplane would fall at the same velocity as a tennis ball?	Because in a vacuum a moving object has no resistance acting on it. Clarify the second part of the question please.	[ "If a projectile, such as a baseball or cricket ball, travels in a parabolic path, with negligible air resistance, and if a player is positioned so as to catch it as it descends, he sees its angle of elevation increasing continuously throughout its flight. The tangent of the angle of elevation is proportional to th...
what is social engineering?	Social structures can be 'hacked' just like physical and digital structures can - and it's often easier to approach an intrusion problem from this standpoint. Actually hacking into the DMV database is a relatively difficult task. However, pretending to be an IT consultant and tricking those with passwords to the datab...	[ "Social engineering is a discipline in social science that refers to efforts to influence particular attitudes and social behaviors on a large scale, whether by governments, media or private groups in order to produce desired characteristics in a target population. Social engineering can also be understood philosop...
how do celebrities tweet and reply to other celebrities on twitter considering there are thousands of people tweeting them as well?	There are services and software you can use with twitter to let you know when a certain user tweets you or posts a tweet, chances are most celebrities don't even see their fans tweets unless a pr person alerts them to one they should reply to.	[ "The most popular United Kingdom celebrities on Twitter come from television with people like Stephen Fry and Jonathan Ross being amongst the most popular British celebrities on the site. Fry's success on Twitter is credited with being the same person on Twitter that he is off Twitter.\n", "Twitter is also used b...
Would it ever be possible to create a mirror that reflects 100% of the light it's exposed to?	Yes, but not in the traditional sense. Mirrors are normally made of a polished metal surface covered by glass. This kinds of mirrors are theoretically unable to achieve perfect reflection. It is possible to achieve perfect reflection using total internal reflection, and it has been done before. It wouldn't work lik...	[ "Almost any dielectric material can act as a perfect mirror through total internal reflection. This effect only occurs at shallow angles, however, and only for light inside the material. The effect happens when light goes from a medium with a higher index of refraction to one with a lower value (like air).\n", "A...
why are there airpockets in underwater caves that are clearly under sealevel?	The caves may have a hidden opening or cracks somewhere to allow air in. If not the air pockets may come from methane or carbon dioxide from degradation of organic matter on the sea floor or some kind of natural gas pocket. It's unlikely that any air pockets in an underwater cave would be breathable since sunlight woul...	[ "BULLET::::- This lack of bubbles allows wreck divers to enter enclosed areas on sunken ships without slowly filling them with air, which can accelerate rusting, and is also an advantage in cave diving if there is loose material on the ceiling which can be dislodged by bubbles, reducing visibility.\n", "The cave ...
How are the causes of airplane crashes identified?	Well, from the "something broke in the air" perspective; fractures that occured in the past look a lot different than fresh ones, and fractures from impact look a lot different than fractures [from other causes.](_URL_1_) Imagine a crack in a steel part, for example. If the crack slowly propagates until the part snaps...	[ "A first report by the Federal Bureau of Aircraft Accidents Investigation was published in May 2013. It listed the known facts of the accident without identifying a cause. The cause of the accident was still unclear .\n", "United States civil aviation incidents are investigated by the National Transportation Safe...
To what extent was Stalin responsible for the Korean war?	According to Halberstam's "The Coldest Winter" page 49 "Stalin was playing a delicate game, flashing a half-green, half-amber light on the invasion." Halberstam later states that Stalin gave Kim permission, but kept his involvement to a minimum and told Kim to rely on China for any material support. There's later an ...	[ "Despite the expenses and regardless of who paid them, it must also be said that the Korean War provided approximately thirty thousand Soviet military personnel valuable experience in waging local wars. The conflict also allowed the Soviets the opportunity to test several new forms of armament, in particular the Mi...
What would happen if we allowed exotic animals to go extinct?	> What would happen if we didn’t protect exotic animals and have laws on hunting and conservation? Its not just exotic animals that we protect, every country protects animals and their ecosystems within their borders. Also, the USA does not regulate how foreign countries manage their resources, ecosystems or endanger...	[ "Despite their relatively small size and secretive nature, some species may be susceptible to extirpation, mainly due to habitat alteration and introduced feral animals. The Navassa Island dwarf boa, \"T. bucculentus\", has not been seen for 100 years and is believed to be extinct.\n", "A 2010 report said that th...
how does cold air reach body temp in your lungs so fast?	There are small sacs in your lungs that bring the incoming air in close contact with your circulatory system. This quickly brings the air close to body temperature , as well as enabling the transfer of oxygen and carbon dioxide.	[ "BULLET::::- The wind chill factor measures the effect of wind speed on cooling of the human body below 10 °C (50 °F). As airflow increases over the skin, more heat will be removed. Standard models and conditions are used.\n", "In the lungs a temperature of 37 °C and 100% relative humidity (RH) is the ideal condi...
If I have a system of mirrors that makes 300 million meters could I see the speed of light?	Yes you can. This is used to determine the speed of light experimentally (There is an easy demonstration using fast rotating mirrors, look at how Fizeau and Foucault measured it in in the 19th century). You can also do an easy experiment if you have access to an oscilloscope. An electromagnetic signal moves at the spe...	[ "Another more accurate measurement of the speed of light was performed in Europe by Hippolyte Fizeau in 1849. Fizeau directed a beam of light at a mirror several kilometers away. A rotating cog wheel was placed in the path of the light beam as it traveled from the source, to the mirror and then returned to its orig...

Subsets and Splits

No community queries yet

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