Split (2)

train · 226k rows

question stringlengths 3 301	answer stringlengths 9 26.1k	context list
movies breaking even	when you say a movie "grosses" 1 billion dollars, youre takking about total ticket sales. this doesnt include the what the theater gets, sales taxes, or other expenses. for a $10 ticket, the studio sees about $4 of that.	[ "Due to its extremely graphic content, the \"Broken\" movie was never officially released, but was leaked as a bootleg which became heavily traded on VHS in the 1990s, and more recently via the Internet. Reznor once said that the \"Broken\" movie \"...makes 'Happiness in Slavery' look like a Disney movie.\" While h...
why are there people on the floor at the nyse?	Most of the people on the floor these days are just there for the TV cameras. It's more of a TV set these days than a place where people actually do stock trading.	[ "New York City and the surrounding New York metropolitan area dominate the economy of the state. Manhattan is the leading center of banking, finance, and communication in the United States and is the location of the New York Stock Exchange (NYSE) on Wall Street. Many of the world's largest corporations locate their...
Where did Roman legionaries keep their money when away from home for years?	I guess there are good answers about the subject in this other thread here: [_URL_1_](_URL_0_)	[ "During the Pax Romana, a rank-and-file Roman legionary would be paid 225 denarii per year. This was increased to 300 denarii during the reign of Domitian. However, during the third century crisis, inflation and chaos disrupted a legionary's pay, with emperors often letting legionaries seize goods from civilians. T...
Can nerve endings get fatigued?	Sure they can, but not really in the way that you're describing. To illustrate this, consider opiods. Opiods are a class of drugs that work by increasing the production of dopamine-- in essence, making a neuron activate. If you give a mouse a lever to press that administers opiods into their brains, they'll press real...	[ "Nerves control the contraction of muscles by determining the number, sequence, and force of muscular contraction. When a nerve experiences synaptic fatigue it becomes unable to stimulate the muscle that it innervates. Most movements require a force far below what a muscle could potentially generate, and barring pa...
When did flintlock firearms start getting replaced by self-repeating firearms? (Such as a classic revolver for example)	The first major improvement to the flintlock musket was the percussion musket, which began to appear in military arsenals in the 1830s. The discovery of fulminates in the early 1800s made possible the creation of the percussion cap. When placed on a nipple and struck by a hammer, the percussion cap detonated and sent...	[ "Firearms using some form of flintlock mechanism were the main form of firearm for over 200 years. It was not until Reverend Alexander John Forsyth invented a rudimentary percussion cap system in 1807 that the flintlock system began to decline in popularity. The percussion ignition system was more weatherproof and ...
how high can most commercial helicopters go? what is the typical cruising altitude of helicopters?	Commercial helicopters almost universally aren't pressurized, meaning they cannot go above 14,000 feet MSL at all, can't go above 12,000 feet MSL for more than 30m without oxygen, and typically don't go above 10,000 feet or so. Cruise altitude is much lower than that, usually 2000 feet or lower.	[ "BULLET::::- August 14 – Alexei M. Cheremukhin, co-designer (with Boris Yuriev) of the Soviet TsAGI 1-EA pioneering single lift rotor helicopter, takes the 1-EA to an unofficial record altitude for helicopters of the era, of 605 meters (1,985 ft).\n", "BULLET::::- The Canadian AeroVelo Atlas human-powered helicop...
if a president has already served his 2 term limit, become vice president, and then the president dies. who would take on the presidency?	The Twenty-Second Amendment prevents someone being elected to a third term as President, so it shouldn't stop him serving as President after being elected as Vice President. However, the Twelfth Amendment says that "no person constitutionally ineligible to the office of President shall be eligible to that of Vice-Pr...	[ "In the event of the death, resignation or removal of the President, the Vice-President ascends to the presidency, which he or she holds as acting President. The Vice-President nevertheless cannot succeed to the presidency in case of dismissal, resignation or death of the head of state but he can be nominated by th...
are skyscrapers built to last forever or do cities have plans to demolish them once their 'lifespan' has expired?	The old joke in Manhattan is that it will look really nice if they ever finish building it. Most of the time a building the decision isn't so much one of structural integrity and age as economics. Frequently there is a need to replace it with a larger building that generates more rental income per square foot of land i...	[ "The civilization of the Old Ones is implied to have collapsed because of the replacement of magic, which could last forever, with technology, which would disintegrate if left unattended, but which nevertheless was allowed to be responsible for maintaining the Beams of the Dark Tower. \n", "Skyscraper projects re...
why do we have a hard time repeating a word we hear in another language, but not words we've never heard in our own language?	Because they mean something to you. Can you remember this?: The brown cow jumped the fence. Can you memorize this?: 5678449291234902399298301 Same number of characters. But the number string is dramatically more difficult to memorize. Because it has no inherent meaning. Things with meaning are naturally eas...	[ "Of course, the reason why children need to learn the sound distinctions of their language is because then they also have to learn the meaning associated with those different sounds. Young children have a remarkable ability to learn meanings for the words they extract from the speech they are exposed to, i.e., to m...
Did FDR, Churchill or Stalin ever communicate directly with Hitler during WWII? Phone? Telegram?	Stalin and Hitler never met, nor did they ever actually talk to each other. The same goes for Churchill and FDR who never talked to Hitler either. The only allied leader that I can think of who actually met and talked with Hitler and then later fought him in World War Two was Canada's prime minister, William Lyon Macke...	[ "Soviet propaganda to Germans during World War II was at pains to distinguish between the ordinary Germans and their leaders, the Hitlerites, and declaring they had no quarrel with the people. The only way to discover if a German soldier had fallen alive into Soviet hands was to listen; the radio would announce tha...
why is capsaicin the only spicy molecule? why doesn't anything else taste hot?	It isn't. It's just a very well-known and potent one. There exist [chemicals](_URL_0_) many many thousands of times more spicy than capsaicin. [Piperine](_URL_1_) is a totally different type of molecule, and is responsible for the spiciness of (the spice) pepper.	[ "Because of the burning sensation caused by capsaicin when it comes in contact with mucous membranes, it is commonly used in food products to provide added spice or \"heat\" (piquancy), usually in the form of spices such as chili powder and paprika. In high concentrations, capsaicin will also cause a burning effect...
[Astronomy] What is happening with Betelgeuse – and how "unique" is what we are currently observing?	“Dimmed by a factor of 2” just means it is now half as bright as it was. Bear in mind that the star could go supernova “immediately”, meaning any time in the next 10,000 years or so. Unfortunately the odds of that happening in our lifetimes are slim.	[ "Due to misunderstandings caused by the 2009 publication of the star's 15% contraction, apparently of its outer atmosphere, Betelgeuse has frequently been the subject of scare stories and rumors suggesting that it will explode within a year, leading to exaggerated claims about the consequences of such an event. The...
Arising of chirality	I went to a very interesting talk by Ron Breslow from Columbia about this last year. His main hypothesis was that highly energized circularly polarized light emitted from pulsars could create a chiral imbalance, for as you learned chiral light interacts with different enantiomers in different ways. From there, he noted...	[ "Chirality in supramolecular chemistry implies the non-symmetric arrangement of molecular components in a non-covalent assembly. Chirality may arise in a supramolecular system if one of its component is chiral or if achiral components arrange in a non symmetrical way to produce a supermolecule that is chiral.\n", ...
When we look at a star through a telescope, do we see it at a different point in time than we would looking at it with our eyes?	No. Stars emit light. When the light hits our eyes that light is translated into an image for our minds. Stars (besides the sun) are large numbers of light years away from us. This means that light emitted from a far away star must travel for large numbers of years before it reaches us and our eyes. This means, wh...	[ "Viewed from the same location, a star seen at one position in the sky will be seen at the same position on another night at the same sidereal time. This is similar to how the time kept by a sundial can be used to find the location of the Sun. Just as the Sun and Moon appear to rise in the east and set in the west ...
what is the double slit experiment? why is it important?	[The experiment look like this](_URL_1_), you send electrons into a screen with two slit, and behind this you got a screen on which you can see where the electrons land. If you believe the electrons are particles, in the sense that they are like a very "small ball", you would have points on two spots on the second scr...	[ "The double-slit experiment (and its variations) has become a classic thought experiment, for its clarity in expressing the central puzzles of quantum mechanics. Because it demonstrates the fundamental limitation of the ability of the observer to predict experimental results, Richard Feynman called it \"a phenomeno...
There's a lot of talk about carcinogens all around us, can we evolve to resist/coexist with them?	In short, yes, but keep in mind that it took tens of thousands of years for differences in melanin to develop. There are so many carcinogens that interfere with an unsurmountable amount of biological processes, which leads to cancer. So many of these biological processes would have to change their mechanism or the enzy...	[ "Anticarcinogens that may help prevent cancer can also be found in many food especially fruit and vegetables. Antioxidants are important groups of compounds that may help remove potentially harmful chemicals. It is however often difficult to identify the specific components in diet that serve to increase or decreas...
weighted average cost of capital	Getting money to grow your business costs money. This can be the interest rates on loans, the dividends from investors and other costs. These costs vary by source but you can average them to get a weighted cost of capital. It's used as the hurdle rate for whether something makes sense to use cash for. If the WACC is 30...	[ "The weighted average cost of capital is an approach to determining a discount rate. The WACC method determines the subject company's actual cost of capital by calculating the weighted average of the company's cost of debt and cost of equity. The WACC must be applied to the subject company's net cash flow to total ...
doxing	It's really just detective work. For example, you can to through someone's complete post history, if you were so inclined, and get an idea of where they live, what they do for a living, etc. For example: Let's say someone says in a post on Reddit where they work. Then you Google their username and discover they've...	[ "Doxing (from \"dox\", abbreviation of \"documents\") or doxxing is the Internet-based practice of researching and broadcasting private or identifying information (especially personally identifying information) about an individual or organization.\n", "\"Doxing\" is a neologism that has evolved over its brief his...
how did the woodpeckers constantly moving their head back and forth without getting tired?	Wood peckers are designed to do this. It's just like a hummingbirds wings flapping. They have evolved to move this quickly with extreme efficiency. What you should really be asking is how can a hummingbird slam it's head into a solid object simulating hundreds of G forces without dying. Which is a way cooler question....	[ "Many of the foraging, breeding and signaling behaviors of woodpeckers involve drumming and hammering using the bill. To prevent brain damage from the rapid and repeated powerful impacts, woodpeckers have a number of physical features which protect the brain. These include a relatively small and smooth brain, narro...
In medieval European art, angels are depicted with rainbow or coloured wings. Modern angels have white wings, though. When was there a shift in wing colour? Why? What triggered it?	I can't give a total answer to this, but I can make some observations which may help. Firstly, the habit of depicting angels with colourful wings has never actually been fully abandoned. [Here](_URL_3_) is a mural from 17th century Italy. [Here](_URL_6_) is a French painting of the 19th century, and a 20th century [Iri...	[ "It is believed that this practice arose from medieval liturgical dramas and mystery plays, in which the actors portraying angels wore garments covered with feathers to emphasize their power of flight, often standing on \"clouds\" of wool. Costumed angels also might be introduced for one-off special occasions: at t...
how come when you burp while drinking soda and exhale the air through your nose, it stings?	Soda is carbonated water. The act of carbonating the water converts some of it into carbonic acid. This acid is what stings your nose when you exhale (tiny amounts of it in the air), or belch in my case!	[ "Nasal insufflation (known colloquially as \"snorting\", \"sniffing\", or \"blowing\") is a common method of ingestion of recreational powdered cocaine. The drug coats and is absorbed through the mucous membranes lining the nasal passages. Cocaine's desired euphoric effects are delayed when snorted through the nose...
As gamma waves became CMB, at what rough time in the Universe's history did they red shift through visible light?	The CMB hasn't been around forever, as the early universe was opague to photons. It was formed some 380 000 years after the big bang during what's known as the recombination era. By then, the universe was cool enough to form atoms that wouldn't interact with photons as easily as plasma. This happened at around 3000K, ...	[ "Lange's research interests focused on the Cosmic Microwave Background (CMB) and instrumentation for its study. The CMB is believed to be the light of the Big Bang, red-shifted from the visible into the sub-millimeter range by the cosmic expansion in the intervening 13.8 billion years. He developed a new generation...
how does it work that flat mirrors make you look thinner?	Those funhouse mirrors _aren't_ flat. I suppose you could shape a mirror like a [Fresnel lens](_URL_0_) but then you might notice the funny texture. The direction its parts are facing would still show curvature as usual. Do you have a concrete example if you don't think any of this is the case? One shape that would ma...	[ "Mirrors with curved surfaces can be modelled by ray tracing and using the law of reflection at each point on the surface. For mirrors with parabolic surfaces, parallel rays incident on the mirror produce reflected rays that converge at a common focus. Other curved surfaces may also focus light, but with aberration...
how do scientists get animals to interbreed?	They don't have to wait for the animals to do anything. Artificial insemination has been going on for a long, long time. That said, many animals will breed with whomever is available. Scientists probably have a harder time preventing this than getting it to happen.	[ "Inbred strains (also called inbred lines, or rarely for animals linear animals) are individuals of a particular species which are nearly identical to each other in genotype due to long inbreeding. A strain is inbred when it has undergone at least 20 generations of brother x sister or offspring x parent mating, at ...
Are there any diseases/conditions that affect the relative amount/distribution of spongy bone vs. compact bone in humans?	[SOST-related sclerosing bone dysplasia](_URL_1_) is a disorder of bone development characterized by excessive bone formation that results in bones that are denser and wider than normal. While it's not quite as drastic as what you were inquiring about, it can cause people to be taller than normal and more resilient to ...	[ "Age-related bone loss is common among humans due to exhibiting less dense bones than other primate species. Because of the more porous bones of humans, frequency of severe osteoporosis and osteoporosis related fractures is higher. The human vulnerability to osteoporosis is an obvious cost but it can be justified b...
why if someone uses my glasses they see blurry, but they never see my eyes blurry when looking at me?	It's different focal ranges to which the glasses aim to match. So when you wear them, the glasses don't match your focus. Just like how a camera works.	[ "BULLET::::- Research has confirmed that when nearsighted subjects remove their corrective lenses, over time there is a limited improvement (termed \"blur adaptation\") in their unaided visual resolution, even though refraction indicates no corresponding change in refractive error. This is believed to occur due to ...
the difference between aaa, aa, c, and d batteries.	It is just a difference in the physical size of the battery, which changes how much charge they hold. They are all 1.5v batteries Small, low drain devices need a small light battery, so they use AAA. Heavy drain devices like remote control cars need a lot of charge, so they use D size. And so on	[ "An AAA or triple-A battery is a standard size of dry cell battery commonly used in low-drain portable electronic devices. A zinc–carbon battery in this size is designated by IEC as \"R03\", by ANSI C18.1 as \"24\", by old JIS standard as \"UM 4\", and by other manufacturer and national standard designations that v...
why don't medical professionals rule out the worst diagnoses earlier in the process?	If you see hoofprints, you think of horses, not zebras. Meaning that you go to the most likely candidates. 90% of the time, blood in the urine is a UTI. So they work with that until something happens that isn't UTI. Not to mention sometimes the tests for those worse things are intrusive, painful and just unnecessary ...	[ "Medical professionals often jump to conclusions. Jerome Groopman, author of \"How Doctors Think\", says that \"most incorrect diagnoses are due to physicians' misconceptions of their patients, not technical mistakes like a faulty lab test\". Many doctors jump to conclusions in the following ways: they assume the p...
Did Saxon England have any thing like a parliament?	Hope I'm not too late! Now this is an interesting question and I'll try to bring in some historiography at the end because that it very important in gaining a full understanding. Now if were going into semantics during the Anglo-Saxon period 'England' as a polity didn't exist because there were many kingdoms and it wa...	[ "By the 7th century, England was almost entirely divided into kingdoms ruled by the Anglo-Saxons who had come to Britain two hundred years before. The kingdom of Mercia occupied what is now the English midlands. The origin of the kingdom is not recorded, but royal genealogies preserved in the \"Anglo-Saxon Chronicl...
do women serve in combat roles in the us military?	Women (at the moment, but changing or will be) do not serve in direct combat positions (e.g. infantry, artillery) but women do provide support roles that put them in combat situations indirectly. Women are also armed as well.	[ "The role of women in the United States armed services became an important political topic in 1991. Women military personnel had engaged in combat in the most recent U.S. military actions: Grenada in 1983 Panama in 1989, and the Gulf War in 1991. Senator William V. Roth (R-DE) introduced a Senate bill in 1991 to cl...
Looking for an introductory explanation of Strange Attractors	If you heard about strange attractors in a motivational speech, the speaker likely didn't understand them and was just making a crappy metaphor that sounded nice but would offend mathematicians. I've tried to come up with a short easy explanation but the topic is difficult to distill and I'm not that good. If you're...	[ "An attractor is called strange if it has a fractal structure. This is often the case when the dynamics on it are chaotic, but strange nonchaotic attractors also exist. If a strange attractor is chaotic, exhibiting sensitive dependence on initial conditions, then any two arbitrarily close alternative initial points...
What causes the equatorial orbit around the sun?	I think this should do you well: _URL_0_	[ "If a geosynchronous satellite's orbit is not exactly aligned with the Earth's equator, the orbit is known as an inclined orbit. It will appear (when viewed by someone on the ground) to oscillate daily around a fixed point. As the angle between the orbit and the equator decreases, the magnitude of this oscillation ...
How effective is the influenza vaccine?	First of all, the question of vaccine effectiveness is complicated. There are lots of different measures of vaccine effectiveness, and talking about them without specifying which measure you are talking about gets very confusing very fast. Thankfully, the CDC has a [very detailed writeup](_URL_1_) on the topic of vacc...	[ "\"Adjuvanted vaccines appear to hold the greatest promise for solving the grave supply-demand imbalance in pandemic influenza vaccine development. They come with obstacles—immunologic, regulatory, and commercial—but they also have generated more excitement than any other type of vaccine thus far. [In August 2007],...
How did so many underage WW2 soldiers manage to enlist?	I don't have great answer to this, but I think there were several aspects: 1) The armies needed the manpower, so unless the man applying was visibly clearly way too young or otherwise physically unqualified to enlist (too short, physical disability, etc) the recruiters didn't look for reason to disqualify a potentia...	[ "At the outbreak of war, on 3 September 1939, the Military Training Act was overtaken by the National Service (Armed Forces) Act, and the first intake was absorbed into the army. This act imposed a liability to conscription of all men 18 to 41 years old. Men could be rejected for medical reasons, and those engaged ...
How where harems organized ? Was there a "bottom girl" to keep the others in line? How would a poorer man go about these things ?	The Ottoman harem is the subject of an excellent 1993 study by Leslie Peirce, called The Imperial Harem: Women and Sovereignty in the Ottoman Empire. Anyone with any interest in this topic should pick it up. Really a great book. Peirce's study is mainly about the way in which female power was exercised in the Ottoma...	[ "A menagerie was mostly connected with an aristocratic or royal court and was situated within a garden or park of a palace. These aristocrats wanted to illustrate their power and wealth, because exotic animals, alive and active, were less common, more difficult to acquire, and more expensive to maintain.\n", "Alt...
what makes two colours 'go well together'?	I'll take a shot at this. First off, I'll be trying to make some connection between things I've read in different books and websites, but I will not be able to cite any sources so any and all I say should be up for scrutiny and further independent research: Alright. First off; usually when two colours "go well togeth...	[ "Contrasting colors may be chosen in various ways. A common choice is to take a complementary colors from one of the several color wheels (e.g., blue and orange, green and red), or to choose a pairing that occurs in nature, e.g., yellow and red.\n", "Analogous colors are groups of three colors that are next to ea...
Why were Scots the first to rebel against Charles I in the late 1630s?	A lot of Scots were Calvinists, a protestant sect similar to Puritanism. Charles was attempting to impose a version of the Book of Common Prayer which was in disagreement with Calvinist theology. The Scots were trying to show that they did not agree with this imposition of a religious text they did not agree with. Thi...	[ "The Scottish uprising triggered civil war in Charles' other two Kingdoms, first in Ireland, then in England. Charles and his minister Thomas Wentworth were unable to persuade the English Parliament, which itself was unhappy with Charles's civil and religious policies, to pay for an army to put down the Scots. As a...
I recently read about a lamp that uses salt water and magnesium & carbon rods to create electricity for its power source. What exactly is going on here?	This thing is a battery (this type of battery is called a wet cell), the only difference is that you add an electrolyte instead of having it come in the battery. This particular type of battery wouldn't be very good for high power applications (lithium batteries would be better). Sea water should be fine as an el...	[ "Glenwood Springs was one of the first places in the United States to have electric lights. The original lighting was installed in 1897 inside of the Fairy Caves in Iron Mountain. Later, a dam was built in Glenwood Canyon, providing water for the Shoshone power plant. The plant began producing power on May 16, 1909...
why do some people say women make less money than men?	The average woman makes less than the average man, mostly because they do different jobs. Women sometimes are paid less for the same job compared to men, but that only accounts for a small part of the overall difference. It's illegal for companies to pay women less because they are women. Although sometimes women don...	[ "In general, women have lower personal financial assets than men. This means that for a given opportunity and equally capable individual, women must secure additional resources compared to men in order to exploit the opportunity; because, they control less capital. The question of whether women have a harder time g...
Since we now have superconductors that exist well over the boiling point of liquid nitrogen, why haven't we built super excellent power storage facilities with them?	Because a superconductor will wind up storing any power that you put into it in the form of a magnetic field. One of the fundamental properties that separates a superconductor from a "perfect" classical conductor (just a metal with infinite conductivity) is that a superconductor will expel magnetic field lines from its...	[ "High-temperature superconductors (HTS) promise to revolutionize power distribution by providing lossless transmission of electrical power. The development of superconductors with transition temperatures higher than the boiling point of liquid nitrogen has made the concept of superconducting power lines commerciall...
how come your nose is often the coldest part of your body in the winter?	Like your ears, it's mostly cartilage with very little muscle to help generate heat or fat to help insulate. On top of this, the way we often dress in the winter leaves the nose exposed while ears and other areas that get cold to a similar extent remain covered.	[ "The common cold, also known simply as a cold, is a viral infectious disease of the upper respiratory tract that primarily affects the nose. The throat, sinuses, and larynx may also be affected. Signs and symptoms may appear less than two days after exposure to the virus. These may include coughing, sore throat, ru...
the farmer's almanac	No, it's not accurate, although the publication itself claims to be. For one thing, the predictions are like two years in advance. It doesn't predict weather in the sense that it says, "In Austin, next week it will rain". It covers regions or "climate zones" and trends. There's more to it than weather prediction. I...	[ "The Farmers' Almanac is a compendium of knowledge on weather, gardening, cooking, remedies, managing your household, preserving the earth, and more. Published every year since 1818, it was founded by David Young, Philom. In 1949, Ray and Ann Geiger obtain the rights to Almanac Publishing Company/Farmers’ Almanac. ...
What voltage does the human body use to control muscles?	The way the body controls skeletal muscles are through a connection of your nerves, which usually start from your brain, to their associated muscles. Most of the time, your nerves are at rest, at -70mV relative to the rest of your body, which is set by an equilibrium of ion pumps and leak channels on the cell surface. ...	[ "Transcutaneous electrical muscle stimulation (EMS) is the use of electric current to stimulate muscle activity. This method is theoretically utilized to prevent muscle atrophy and weakness. The efficacy of this approach was tested in a 30-day bed rest study done by Duovoisin in 1989. Though the patients showed dec...
why does apple not like jailbreaking ?	In no particular order: - Loss of revenue. People are installing, and in some cases paying for, apps, whilst bypassing the App Store. - General security. The fact that it's possible to jaolbreak at all shows that there is a hole in their security, which they want to fix before it gets used for nefarious purposes. - ...	[ "While Apple technically does not support jailbreaking as a violation of its EULA, jailbreaking communities have generally not been legally threatened by Apple. At least two prominent jailbreakers have been given positions at Apple, albeit in at least one case a temporary one. Apple has also regularly (though possi...
Why did the U.S. quickly conclude that Castro was not a leader we would support when he initially declared that he wasn't a communist?	Well this is a debate amongst historians on the topic: was Castro "pushed" into the arms of the Soviets by the U.S, or, were Castro's intentions all along to break ties with the U.S diplomatically and economically? To first answer this question, we must decide what we believe Castro's political persuasion was. First,...	[ "Although refusing to categorize his regime as socialist and repeatedly denying being a communist, Castro appointed Marxists to senior government and military positions. Most notably, Che Guevara became Governor of the Central Bank and then Minister of Industries. Appalled, Air Force commander Pedro Luis Díaz Lanz ...
astrocytes and their function within the brain.	Astrocytes are part of the glial tissue in the brain, which is like a support tissue (like connective tissue is in the rest of the body). It helps neuronal cells do their functions, by maintaining the homeostasis, providing energy, building structures (myelin) etc. It might also have a role in protection from patologic...	[ "Studies have shown that astrocytes play an important function in the regulation of neural stem cells. Research from the Schepens Eye Research Institute at Harvard shows the human brain to abound in neural stem cells, which are kept in a dormant state by chemical signals (ephrin-A2 and ephrin-A3) from the astrocyte...
does carbonated water act as a better solvent than regular tap water? why?	Carbonated water is more acidic. Carbonated water is made by adding a lot of Carbon Dioxide to Water. The Carbon Dioxide combines with Water to make Carbonic Acid.	[ "Modern variants of water coolers have been equipped with options for sparkling water as a result of increasing demand for carbonated beverages and also a greater awareness to healthy living, resulting in preference for carbonated water over sweetened carbonated beverages. This works with the addition of a mixer ta...
why do cops have such a hard-on for id? (see comments)	The information on an ID is important to police becuase it's how they can tell whether you have any warrants out for your arrest, if you have any priors, and what your name is in case they detain you and have to fill out a report. Police also like asking for ID because it's kind of a nerve test. If someone produces a...	[ "The same police officer also noted that these criminals are often technologically savvy and create profiles using fake information and other people's photos from cyber cafés or public libraries, making them difficult to trace.\n", "Corrupt and inadequately trained police officers can be complicit in sex traffick...
How would someone who is infected with COVID-19 but is asymptomatic spread the disease to others, if it is spread by respiratory droplets from coughing and sneezing?	It's in their saliva and they also produce fomites. You make a good point that it's not spread as effectively as someone who is regularly propelling droplets into the air, but a lot of people just randomly cough. Tomorrow, keep a mental note of how many times you sneeze or cough. It probably won't be zero. If you want ...	[ "BoHV-1 enters the animal through the mucous membrane in the respiratory tract or genital tracts. The main mode of disease transmission is direct nose-to-nose contact between an infected and a susceptible animal. This is made possible because of the virus sloughing off into the mucus. Aerosols have to be exhaled, s...
why it sometimes costs less to buy something from walmart online and pick it up in the store than it is to buy it from the same store where it's already in stock?	When you are online, it is easy to price shop, so Walmart has to compete with Target and Best Buy and whomever. But once you are in the store, you are less likely to drive around to those other places.	[ "Some major retailers, such as Target, are attempting to battle showrooming by selling products exclusive to their stores. Walmart is allowing customers to avoid the shipping charges of online purchases by picking up the items in the stores. The same practice is expanding to European countries.\n", "One advantage...
why do windows updates need to be installed in two phases, namely when shutting down and booting up? can it not be done together in a single phase?	Windows locks certain files while the operating system is in use, and such files can only be modified when they're not in use (such as while booting up).	[ "Also introduced with Windows 8, Refresh re-installs the Windows OS but retains user files, the pre-installed applications, and those installed by the users. Running the reset option is advised only if Refresh fails to resolve the issue. \n", "Since reinstalling Windows (or installing a new version) often require...
why do rates of growth use exponents and rates of decay use euler's number?	They both actually use the same formula: N = a(1 + r)^t where a = initial value, r = growth rate (negative for decay), t = time However, this formula assumes discrete growth/decay, like interest compounded monthly. When you have a bacterial culture, the bacteria don't wait until the end of each hour to divide, th...	[ "For simple population models, \"R\" can be calculated, provided an explicit decay rate (or \"death rate\") is given. In this case, the reciprocal of the decay rate (usually 1/\"d\") gives the average lifetime of an individual. When multiplied by the average number of offspring per individual per timestep (the \"bi...
Does temperature change if you go faster?	It's actually ambiguous as to how temperature should transform between different frames of reference. See the discussion [here](_URL_0_).	[ "At high speeds through the air, the object's kinetic energy is converted to heat through compression and friction. At lower speed, the object will lose heat to the air through which it is passing, if the air is cooler. The combined temperature effect of heat from the air and from passage through it is called the s...
If we shot Jupiter and Saturn into the sun, roughly how much longer would the sun undergo fusion before turning into a red giant?	You've got it backwards. You want to take mass away from the sun to make it live longer. The more massive a star is, the shorter its lifetime. This happens because the extra gravitational pressure from added mass increases the rate of fusion in the core a lot, so even though there's more hydrogen/helium, you burn thr...	[ "However, this situation is going to change subsequently to a close encounter with Saturn during the second half of the year 2312 (0.8 ± 0.1 AU). This will bring the comet's perihelion distance (reduced to 5.58 AU in 2400) in precarious vicinity to Jupiter's orbit, which will lead to a very close encounter with Jup...
why don't they package soda and beer the same? like why do we have 30 racks of beer and not soda?	There ARE 30 packs of soda. Walmart sells them. [Here's a link for 30 cans of Diet Mt Dew](_URL_0_) If you want to see other examples you can google 30 pack of soda, thats how I found that link.	[ "A peculiarity not found in many other states is that brewed or malt beverages can be sold for off-premises consumption in quantities less than 192 ounces (generally 6-packs and 12-packs of beer). Thus, many bars and restaurants double as beer stores.\n", "In five states (Colorado, Kansas, Minnesota, Oklahoma, an...
Is there a time-out to sleep debt?	I'm not sure I understand the question. I'm interpreting it to mean something like "how long does it take to adapt to a restricted sleep schedule?" That is, normally you sleep 8 hours a night but now you are only sleeping 6 and thus building up a sleep debt. How long will that debt continue to build up until you adapt ...	[ "There is debate among researchers as to whether the concept of sleep debt describes a measurable phenomenon. The September 2004 issue of the journal \"Sleep\" contains dueling editorials from two leading sleep researchers, David F. Dinges and Jim Horne. A 1997 experiment conducted by psychiatrists at the Universit...
What are atom shells made of? I can’t find a clear answer anywhere	Atom 'shells' aren't 'made of' anything. They're just regions in which electrons exist.	[ "Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the \"n\"th shell can in principle hold up to 2(\"n\") electrons. Sin...
What happens on a cellular level when you improve muscle flexibility?	Nothing much, really. Increasing muscle flexibility is more to do with reprogramming the nervous system so it offers less resistance when it is stretched to a level it deems unsafe. For example, a person under anaesthesia can be made to do a split (though it would be unprofessional), because their nerves are not firin...	[ "Flexibility can be simply defined as the available range of motion (ROM) provided by a specific joint or group of joints. For the most part, exercises that increase flexibility are performed with intentions to boost overall muscle length, reduce the risks of injury and to potentially improve muscular performance i...
why does it take them so long to open the doors after landing and parking the airplane?	Part of it has to do with the engines. When an aircraft arrives at the gate, no one is allowed near the aircraft until the engines are shut down. This includes the gate ramp operator. The engines will take a brief time to spool down once the engines are commanded off. In addition, I’ve maybe heard about grounding ...	[ "As the aircraft began its right turn off the runway, approximately 10 seconds before it stopped, one of the two flight attendants in the rear of the aircraft, probably the No 3 stewardess, opened the right rear door and deployed the emergency chute, but no one escaped through this door because it was blocked by sm...
Who is this? Is it worth anything?	The inscription to the left of the head says it is St. Basil, who was one of the Cappadocian theologians. The colorful, onion-domed cathedral on Red Square in Moscow that you have (perhaps) seen pictured is named for him. edit: With apologies to the mods, the [wikipedia article](_URL_0_) looks pretty good.	[ "The most iconic object in the museum is probably the yellow cedar sculpture \"The Raven and the First Men\" by Bill Reid, which was depicted on the Canadian twenty-dollar bill from 2004 to 2012 (the Canadian Journey Series).\n", "Items that have been in direct contact with a famous athlete can have significant m...
why do newly paved roads sound so much quieter than older ones?	Because they are new and smooth, old roads have dents and other imperfections that make wheels and axle more noisy	[ "Instead of metal wheels on metal tracks, rubber-tired wheels on a concrete track are used making it very quiet. Also, the windows mist within of (mostly) HDB apartment blocks ensuring residents' privacy. 19 individual cars (which can be coupled in pairs if necessary during peak hours) were purchased.\n", "Asphal...
Were the D-Day attacks known about before hand by general population?	It wouldn't have come as a surprise to most Americans or Britons. It was obvious to many Britons, who could see the influx of men and war material. Many American families had relatives who'd been sent Britain and could easily guess why so many GI had been deployed there. But the exact date and location of the landings...	[ "During the preparation for D-Day in the spring of 1944, the Allies launched the Transport Plan, carrying out intensive bombing of railway junctions and transport networks across northern France and Belgium. Many of these targets were in towns near densely populated civilian areas, such as La Louvière and Kortrijk ...
Why didn't Western Europe have a Red Scare?	Firstly, several countries did have similar worries about communist spies, revolutionaries and militias. And in fact, this was at times true: far-left revolutionaries and terrorists were actually a problem in some western European countries, for example in Germany the Red Army Faction (better known as the Baader-Meinho...	[ "With the start of the Cold War a curse on the Anti-Westernization was proclaimed, mirroring the American Second Red Scare to some extent. For instance, in the 1950 edition of \"The Ordeal of Sevastopol\", censors made over three hundred cuts, screening the book's references to Frenchmen as \"a people of very livel...
What was it like to stay at an inn through the centuries?	In 19th century Paris, you had a couple of options. First, if you were staying for longer than a couple of days, you could rent waht they called a hôtel garni. These were basically small, studio or one bedroom apartments that were furnished with old and cheap furniture. They were considered to be trashy, and not at al...	[ "By the seventeenth century, the Inns of Chancery began to turn into societies for attorneys and solicitors; they became residences, offices and dining clubs. The greater part of the old Inn was taken down in Charles I.'s time, and a new building erected in its stead. Although it survived the Great Fire of London, ...
Why are there no photos of a battlefield covered with thousands of bodies?	There's an obvious safety hazard in taking photographs or video during a pitched battle, particularly in an age where the requisite tools would be very burdensome and require purposeful inclusion in planning. Taking D-Day as an example, NPR and Fresh Air just broadcasted an interview centered around media, propoganda,...	[ "One of the most noticeable actions was the publication of several hundred photos depicting the coffins of U.S. soldiers fallen in Iraq. These were obtained by Kick by filing a request based on the Freedom of Information Act. The photos sparked a controversy regarding the publication of war photos, public opinion a...
why do we perceive height and depth different from length?	We evolved on flat plains in Africa - our eyesight is used to estimating horizontal distances so we don't do so well with vertical distances. It's a pretty well known effect with looking at mountains, called foreshortening and we do it with depths too. We tend to underestimate vertical distances but something like a ...	[ "Depth perception is the visual ability to perceive the world in three dimensions (3D) and the distance of an object. Depth sensation is the corresponding term for animals, since although it is known that animals can sense the distance of an object (because of their ability to move accurately, or to respond consist...
when a program crashes, is it my computers fault or the programs fault?	It depends on the certain circumstances, but regardless it happens because somewhere something went wrong that puts the wrong data in the wrong place and the computer does not have a way to figure out what is wrong so the program cannot do what it is trying to do. I explained this over Easter to some family, so i'll us...	[ "Software faults occur through the following processes. A programmer makes an error (mistake), which results in a defect (fault, bug) in the software source code. If this defect is executed, in certain situations the system will produce wrong results, causing a failure. Not all defects will necessarily result in fa...
What was life like for Native Americans during the American Civil War? Did life change amidst the chaos? Were they largely unaffected?	I'm not a historian, but I have looked into some of this a little bit for personal reasons: At the the time the Dakota alliance in southern Minnesota was strongly divided between pro-war and anti-war factions; both sides unhappy with recent treaties but disagreeing on how to respond. The pro-war faction explicitly argu...	[ "By the beginning of the American Civil War, many remnant Native Americans in the Upper South struggled to survive and their status continued to decline. Since 1790, Native Americans in the southern states were enumerated as \"free persons of color\" on the local and federal census, included with free African Ameri...
Does octave equivalency show any sort of property in physics, or is it a completely perceptual phenomenon?	Yes. First thing to understand is timbre. When you play a note, you hear a collection of frequencies. The note you're playing is the loudest frequency but there are other more quiet frequencies being produced concurrently. This is what gives an instrument's tone character, and makes a flute and a trumpet sound differe...	[ "Deutsch also produced illusions using sequences of tones that were clearly defined in terms of pitch class (note name), but ambiguous in terms of which octave they are in (known as \"Shepard tones\"). In particular, she discovered the tritone paradox. Perception of this illusion again differs substantially from on...
why did people want near field communication (nfc) on the next iphone, and how does it work?	1. As the name suggests, it's Near Field Communication. Meaning, the communication only takes place between two objects that are near, like phone to phone or phone to register, Etc. This has the potential to be very useful. For instance, you could tap your phones together and instantly sync contact information, in...	[ "A new \"Core NFC\" framework gives developers limited access to the near field communication (NFC) chip inside supported iPhones, opening potential use cases in which apps can scan nearby environments and give users more information.\n", "Following rich discussions about mobile television, video, music and gamin...
ipv6 and how to deploy it?	So, on the internet, every computer has an address. You can think of it like the post address you have. When you know a computer's IP address, you can send him a message, just like you can write a letter to a person. Note that message does not mean e-mail or facebook message or something like that, but a really basic t...	[ "6rd is a mechanism to facilitate rapid deployment of the IPv6 service across IPv4 infrastructures of Internet service providers (ISPs). It uses stateless address mappings between IPv4 and IPv6 addresses, and transmits IPv6 packets across automatic tunnels that follow the same optimized routes between customer node...
basic roller coaster physics	I would assume they would all be going the same speed since they are all connected.	[ "A roller coaster is a machine that uses gravity and inertia to send a train of cars along a winding track. This combination of gravity and inertia, along with g-forces and centripetal acceleration give the body certain sensations as the coaster moves up, down, and around the track. The forces experienced by the ri...
why do i get canker sores in my mouth when i'm stressed out?	The stress negatively affects you immune system and mucus membranes in your mouth, which leads to the initial canker sore. After it starts it take quite a long time to heal. Stress can also cause other health problems.	[ "Patients with mouth infections usually complain of pain at the affected tooth with or without fevers. Inability to fully open one's mouth, also known as trismus, suggests that the infection has spread to spaces between the jaw and muscles of mastication (masseter, medial pterygoid, and temporalis). If an abscess h...
How would a British/HMS Frigate built in 1715 differ from his Napoleonic (say, 1790's+) descendant? What improvements would be made and did it's paint pattern or any aesthetics change?	This is quite a difficult question to answer as in the early 18th century the individual design of each frigate would have been down the the master ship builder at each individual dockyard. The idea of building to class doesn't come in until the 1740's, when ships began to be built under contract. This means a great d...	[ "The classic sailing frigate, well-known today for its role in the Napoleonic wars, can be traced back to French developments in the second quarter of the 18th century. The French-built \"Médée\" of 1740 is often regarded as the first example of this type. These ships were square-rigged and carried all their main g...
why do people still have to pay child support if the kid isn't theirs?	I don't get why people in the comments support this or are okay with this. If its provably not a guys kid, why the fuck should he have to pay at all? I'm all for children getting support, but it should be from the person responsible.	[ "Payment is not made to children but between parents and the payee is not required to account for how child support money is spent. Critics of child support argue that, as a result, the support payments do not need to be used to support the child and can be regarded as a punishment to the parent who is paying child...
why is right considered "better"?	Everything you mentioned tends to align with how we view the world due to cultural upbringings and language. We read and write from left to right so it's easier to conceptualize things like video game levels and charts in terms of left to right. You can get used to the other way easily enough but it would require more ...	[ "Currently in United States of America, the Left is branded as socialist, baby-killing anti-Semites by the Right, while the Right are called hypocrites, pro-life anti-vaxxers. These ideas are further encouraged by politically-motivated news outlets contributing to media bias in the United States. “Left” and “Right”...
why do screens have a minimum brightness setting?	There is a minimum amount of energy for a pixel to become energetic. This creates a minimum brightness.	[ "Brightness, as it is most often used in marketing literature, refers to the emitted luminous intensity on screen, measured in candela per square metre (cd/m). The higher the number, the brighter the screen.\n", "In LCD screens, the LCD itself does not flicker, it preserves its opacity unchanged until updated for...
why do my legs ache after a night of drinking?	Do you exercise frequently? Or do you sit at your job most of the day? Typically a night of drinking involves a lot of standing, walking or dancing. And if you aren't in shape, that can leave your legs sore.	[ "The metabolic processes required for alcohol elimination deplete essential vitamins and electrolytes. Furthermore, alcohol is a diuretic, causing excretion of electrolytes through urination. After a night of drinking, the resulting lack of key B and C vitamins, as well as potassium, magnesium, and zinc may cause f...
how do super nintendo game save batteries last so long?	The memory chip that holds the data acts as a passive component and only requires a tiny current to keep the bits within from flipping. Powering an active circuit, like a clock where components change state constantly, takes many times that much power.	[ "Nintendo claims the battery lasts a maximum of 10 hours under ideal conditions on a full four-hour charge. Battery life is affected by multiple factors including speaker volume, use of one or both screens, use of wireless connectivity, and use of backlight, which can be turned on or off in selected games such as \...
how do people get morbidly obese?	At the end of the day, these people have eating disorders. That's to say, it's not just about excess calories, not enough exercise and/or slow metabolism; there's also a huge psychological component to it. It's the same way with people who are very thin vs. people with Anorexia Nervosa, for example.	[ "Today, over one third of American adults are considered \"obese\" and nutrition psychology aims to explain what psychological reasons may be behind this and other health trends. Nutrition psychology looks at the internal psychological effects of why people do what they do, and how they are shaped and influenced by...
[Biology] Why was there a lack of domesticable animals in the Americas?	Domesticated animals are descendants from animals that aren't exactly friendly to humans. Europe wasn't home to cows and pigs and chickens in their current form in the wild at any point. See dogs from wolves. There are wolves in the Americas. Cows were domesticated from aurochs, native to Europe and western Asia. B...	[ "While not as widespread as in other areas of the world (Asia, Africa, Europe), indigenous Americans did have livestock. Domesticated turkeys were common in Mesoamerica and in some regions of North America; they were valued for their meat, feathers, and, possibly, eggs. There is documentation of Mesoamericans utili...
Is it theoretically possible to measure the superposition of a particle without disturbing it?	Strictly speaking, no. Measurements are by nature interactions, and interacting with a system will disturb it. Typically probability distributions are determined statistically by running many experiments and compiling the data. There is an experimental technique called [weak measurement](_URL_1_) which allows you to c...	[ "If the supersymmetry theory is correct, it should be possible to recreate these particles in high-energy particle accelerators. Doing so will not be an easy task; these particles may have masses up to a thousand times greater than their corresponding \"real\" particles. \n", "For most short baseline neutrino exp...
- if my injected flu vaccination can't give me the flu, what is causing the crappy feeling side effects?	Your immune system still reacts to the inactive virus. Some of the crappy feeling you have when sick is actually caused by your immune system's reaction, not the virus itself.	[ "While side effects of the flu vaccine may occur, they are usually minor. The flu vaccine can cause serious side effects, including an allergic reaction, but this is rare. Furthermore, the common side effects and risks are mild and temporary when compared to the risks and severe health effects of the annual influen...
How much independence from Moscow and the central party did Soviet Republics enjoy? Did the bureaucracy of the USSR contribute to the development of these states at all?	Mongolia wasn't a Soviet Republic.	[ "However the politics in Moscow took a different course of events, and eventually the accession of Joseph Stalin saw a new policy adapted Socialism in One Country. In accordance to which, expansionist and irredentist claims were removed from Soviet ideology, which instead would focus on making regions economically ...
Would the human body be able to mentally and/or physically adjust to the day length of another planet? Could a 45 hour day, for instance, eventually become second nature? What about a 15 hour day?	Without time cues (amount of light, types of animals heard characterizing time of day, etc.) the sleep-wake cycle can become as long as 36 hours. (_URL_0_) If Earth's day length can shorten the sleep-wake cycle by 12 hours, lengthening it by 9 seems possible. a 15 hour day I'm not sure of. Hopefully someone can clear ...	[ "The circadian rhythms of humans can be entrained to slightly shorter and longer periods than the Earth's 24 hours. Researchers at Harvard have shown that human subjects can at least be entrained to a 23.5-hour cycle and a 24.65-hour cycle (the latter being the natural solar day-night cycle on the planet Mars).\n",...
Physics question: limits of gravity equation?	Your everyday observations never really see anything get close enough to anything else for this to come up. For example, you are currently about 6380 km from the center of gravity of the Earth. Solid objects have a finite size that is much, much greater than the sizes required for this to be relevant, and Newton's law ...	[ "On 8 November 2016 Erik Verlinde published his new theory of gravity, where gravity is not one of the four fundamental forces of physics but, rather, gravity is emergent from other fundamental forces. In this work, he argues that unlike in anti-de Sitter (AdS) space, holography and the area law do not apply exactl...
How does a neutron emit an electron when it consists of quarks?	A neutron is heavier than a proton, which makes it unstable outside of a nucleus; if a particle is heavier and there is an interaction that allows it to decay to another it will eventually. It decays into a proton, an electron, and a electron anti-neutrino. It's actually one of the down quarks that decays into an up qu...	[ "Inside a nucleus, a proton can transform into a neutron via inverse beta decay, if an energetically allowed quantum state is available for the neutron. This transformation occurs by emission of a positron and an electron neutrino:\n", "This process is mediated by the weak interaction. The neutron turns into a pr...
how are trade agreements like nafta and tpp considered bad deals for the u.s. economy?	This is very complicated and not all economists even agree on the basic facts. Moreover it's very difficult to seperate the effect of NAFTA from the effect of other macro-economic things happening at the same time, like automation. That said, economists agree on a few general principles: 1. Lower tariffs in genera...	[ "PAFTC believes that the North American Free Trade Agreement-World Trade Organization model of globalization has failed the US and trading partners when since 2000 Pennsylvania has lost over 200,000 manufacturing jobs.\n", "When two countries enter into a bilateral trade agreement, they are essentially giving one...
Where did the lore of trolls, elves, dwarfs etc originate from? Are they from the same source or time period?	This is a difficult question to answer. First a minor point of clarification: the term "troll" can mean many things depending on the location in Scandinavia. I think it is safe to assume that you are referring to the array of supernatural beings that figure in popular fantasy literature and films and that the trolls yo...	[ "Among Gnomes and Trolls (), is a popular Swedish folklore and fairy tales annual and children's fairy tale anthology published since 1907. One of the most noted of the early illustrators is artist John Bauer.\n", "Troll (Norwegian), trolde (Danish) is a designation for several types of human-like supernatural be...
What do people from past centuries say about man ever walking on the moon?	[A similar question](_URL_0_) from recently.	[ "The first person to stand on the Moon was Neil Armstrong, who was followed 19 minutes later by Buzz Aldrin, while Michael Collins orbited above. Five subsequent Apollo missions also landed astronauts on the Moon, the last in December 1972. Throughout these six Apollo spaceflights, twelve men walked on the Moon. Th...
Where do humans fall in terms of population size compared to other species?	Just to put your first point into context - there's estimated to be [less than a million elephants on the planet])_URL_0_), while our current population is over 7 billion. So there's at least 7000 of us for every elephant	[ "One demographic consequence of a small population size is the probability that all offspring in a generation are of the same sex, and where males and females are equally likely to be produced (see sex ratio), is easy to calculate: it is given by formula_1 (The chance of all animals being females is formula_2; the ...
on average by mass, weight, or other objects (oceans or mountains) is the earth truly spherical?	We don't judge how round something is by mass. We try to see how closesly the given object matches a perfect sphere. Earth is vastly more spherical/smoother than something like a poolball. But if you were to scale an electron up to the size of earth, it'd be a perfect sphere within the error of a human hair.	[ "Earth is not a sphere, but an irregular shape approximating a biaxial ellipsoid. It is nearly spherical, but has an equatorial bulge making the radius at the Equator about 0.3% larger than the radius measured through the poles. The shorter axis approximately coincides with the axis of rotation. Though early naviga...
how cigars are rated and how to choose the correct one for the occasion.	Cigar smoker here. Assuming they are non-cigar smokers, it's not going to matter much. It's like asking for a 12 year old to pick out the individual flavors from a shot of whiskey. I recommend Macanudo as while experienced cigar smokers tend to avoid them, they are mild and easy to smoke, perfect for a group of ciga...	[ "Evaluating the flavor of cigars is in some respects similar to wine-tasting. Journals are available for recording personal ratings, description of flavors observed, sizes, brands, etc. Some words used to describe cigar flavor and texture include; spicy, peppery (red or black), sweet, harsh, burnt, green, earthy, w...
why do sinks in america have built in death blades (garbage disposal)?	Not all sinks do, but they're increasingly common. The simple answer is that they're in demand. Consumers like them because it's convenient to be able to dispose of food waste in the sink.	[ "In past centuries, when urban streets did not have sanitary sewers, street gutters were made deep enough to serve that purpose as well; responsibility for operation and maintenance of the dual-purpose street gutter was cooperatively shared between the local government and the inhabitants.\n", "The toxics compone...
why doesn't hiv pass through saliva, sweat, or tears, and could it evolve to be passed through these methods?	HIV infects white blood cells. There is very little or no HIV in the blood plasma and most other body fluids, because these are free of cells and don't come into close contact with the blood system. Theoretically, the virus could change to become present in saliva, etc. But the virus would again need to get into con...	[ "Kissing on the lips can result in the transmission of some diseases, including infectious mononucleosis (known as the \"kissing disease\") and herpes simplex when the infectious viruses are present in saliva. Research indicates that contraction of HIV via kissing is extremely unlikely, although there was a documen...
what is earth’s magnetosphere?	The Earth has a magnetic field (is a magnet). The magnetic field extends into space and forms, roughly, a sphere of space around the Earth where it's strong enough that you can "feel" it (with objects made of iron, which are affected by magnets). The Sun constantly spits out charged particles (this is called the sola...	[ "The magnetosphere is the region above the ionosphere that is defined by the extent of the Earth's magnetic field in space. It extends several tens of thousands of kilometers into space, protecting the Earth from the charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmos...
how do anti-virus companies develop malware "footprints" to later use to detect malware on customer's machines?	> it's my understanding that one would require the executable file to create a hash They have the executable file. It can be obtained from any infected machine. They employ people to analyse malware executables, figure out how they work, how they can be removed and how they can be detected. The difficulty is, a sim...	[ "Traditional methods of virus detection involve identifying malware by comparing code in a program to the code of known virus types that have already been encountered, analyzed and recorded in a database – known as signature detection.\n", "Most anti-virus software and intrusion detection systems (IDS) attempt to...
what happens when we inhale? how does our body generate the suction?	Air Pressure. When we inhale, Our muscles pull on the lungs, making them a little bigger. This creates more space than there is air, resulting in negative air pressure. Air outside our body gets sucked into the lungs to fill up the space. When we exhale, it's the reverse. The muscles squeeze the lungs, creating less sp...	[ "Inhalation begins with the contraction of the muscles attached to the rib cage; this causes an expansion in the chest cavity. Then takes place the onset of contraction of the diaphragm, which results in expansion of the intrapleural space and an increase in negative pressure according to Boyle's law. This negative...
how does movement from a moving wheel create electricity?	Moving a wheel doesn't create electricity We often use rotational energy to move wires through a magnetic field to create electricity, but it doesn't require a spinning wheel	[ "The principle is applied to spinning robots, where the driving wheels are normally on for the whole revolution, resulting in an increased rotational energy, which is stored for destructive effect, but, given perfect symmetry, no net translational acceleration. The drive works by modulating the power to the wheel o...
How do people calculate things like this: "1 in 5 people don't know they have X disease"? Is it a guess?	They take a control group size (maybe 100 or 1000 or 10000 people) to research and then extrapolate that to the population size.	[ "Even if the whole group in question is susceptible, \"x\" is generally smaller than the basic reproduction number for the disease. That is defined as the number of individuals each infected individual will go on to infect themselves, in a population with no resistance to the disease. The basic reproduction number ...

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