Split (2)

train · 226k rows

question stringlengths 3 301	answer stringlengths 9 26.1k	context list
is it possible for an object in space to have zero velocity?	Velocity relative to what?	[ "The zero-velocity surface is a concept that relates to the N-body problem of gravity. It represents a surface a body of given energy cannot cross, since it would have zero velocity on the surface. It was first introduced by George William Hill. The zero-velocity surface is particularly significant when working wit...
why do abandoned buildings exist in cities like san francisco and manhattan when housing is in such high demand?	Myriad reasons. The owner may have it tied up in court or in regulation. It could have environmental issues. They may be shopping around for a buyer. It may be unclaimed (owner died etc). It could be owned but the owner just doesn't care now because they have long term plans for it. It may be a part of a bigger deal th...	[ "After a wave of arson ravaged the low income communities of New York City throughout the 1970s, many of the residential structures in East Harlem were left seriously damaged or destroyed. By the late 1970s, the city began to rehabilitate many abandoned tenement style buildings and designate them as low income hous...
why do phone numbers call houses and not say anything?	Telemarketers, to save time, don't phone one person at a time, they phone half a dozen, increasing the chance they have at least one person pickup. They will complete the call of the first person to pickup and the rest essentially get dropped. They will however use the data to know that you are available at that time t...	[ "Single number means that the mobile phone and the desk phone share an extension number. So only one phone number need be given out to receive calls on either a mobile or desk phone. But the cell phone likely still has its own number, it’s just that one need not give it out to anyone. To make business calls from a ...
how does wifi speed get increased	Your WiFi speed isn't changing, it's the speed of your internet connection. DOCSIS 3.0 - the standard that cable modems use - is capable of handling over 1000 mbps if the provider is willing to send that much data & has the bandwidth to support it. These sorts of upgrades can be done by flipping a switch and/or upg...	[ "As of July 2006, these applications generally serve to improve dial-up, broadband and other connections from which users may not be getting the best speed. Many users can achieve a 2- to 10-times speed increase in average browsing experience, while some report a 5- to 20-times speed increases for specific web site...
What was the significance of being a left handed sword fighter in the ancient world? Are there any reports of it having an advantage/disadvantage in battle?	The major concern for a left-handed swordsman is that you would not fit into a tight formation of heavy infantry, such as a Roman maniple or Greek phalanx, which required uniformity and discipline to work. Your shield protected the man to your left as much (if not more) as it protected you. If went into such a formatio...	[ "Soldiers in ancient Indian subcontinent are recorded as carrying a shield and spear in their hands while a sword, dagger, and battle-axe were held at the waist. These included both straight swords and slightly curved sabres. The stout, straight sword appears to have been common and can be seen in early sculptural ...
Why does gas flow more violently the first time pouring coke in a glass than when there's already some in it?	Little bits of debris and rough surfaces along the the glass act as sites where CO2 will grab and come out of the liquid. The bottom of the glass is a lot of surface area all at once. That initial pour will clean off the surface a bit sometimes too. There's generally a small later of crud all over everything in you...	[ "During blowing, thinner layers of glass cool faster than thicker ones and become more viscous than the thicker layers. That allows production of blown glass with uniform thickness instead of causing blow-through of the thinned layers.\n", "When Guinness is poured, the gas bubbles appear to travel downwards in th...
what is the difference between the radiation from electronics (e.g. laptops and phones) and carcinogenic radiation?	The radiation concerned with electronic items (such as phones and things) is an electromagnetic wave, usually in the radio frequencies (just like a stereo). These waves are near harmless, and we're constantly being bombarded by radio waves from space and from our modern lifestyle. There have been many studies into the ...	[ "Not all types of electromagnetic radiation are carcinogenic. Low-energy waves on the electromagnetic spectrum including radio waves, microwaves, infrared radiation and visible light are thought not to be because they have insufficient energy to break chemical bonds. Non-ionizing radio frequency radiation from mobi...
Why were there no significant Marine units in the European theater of World War 2?	When you asked this you probably had no idea how complex (and in my opinion interesting) the answer to this question really is. The reasons touch on the development of technology, national pride, inter-service rivalry, prewar military contingency planning, strategic views and disagreements on how to fight the war with...	[ "Although there was very little effect in creating a formidable unit because the outset of World War I and the Gallipoli Operations due to the lack of Marine Corp personnel by the Isolationism of 1920-1930s. Also drawbacks concurred while most of the Marine forces were engaged in conflicts of China and Nicaragua.\n...
how does universal health care lead to longer wait times and why is it difficult to solve?	Providing medical care requires training, skill and often specialized equipment and facilities. These are scarce resources and in the US many don’t seek healthcare because of the costs. But there is a demand there and if it were free they would seek care. But from the same scarce resources, so thus waits must occur for...	[ "Waiting times in American health care are usually short, but are not usually 0 for non-urgent care at least. Also, a minority of American patients wait longer than is perceived. In a 2010 Commonwealth Fund survey, most Americans self-reported waiting less than four weeks for their most recent specialist appointmen...
bullet calibers and grains.	"Caliber" is the diameter of a bullet, either in inches or millimeters. Gun & ammo manufacturers take liberties with this, however, and the true diameter is often slightly different than what is advertised. "Grains," as used by ammo makers, refers to the weight of the bullet, not the propellant used to fire it. ...	[ "Bullet sizes are expressed by their weights and diameters (referred to as \"calibers\") in both imperial and metric measurement systems. For example: 55 grain .223 caliber bullets are of the same weight and caliber as 3.56 gram 5.56mm caliber bullets.\n", "BULLET::::- caliber/calibre: in small arms, the internal...
why do famous musicians use older instruments?	Funny fact, some of the old instruments are better than modern ones (the best examples are Stradivarius). For others it's just relative rarity, legend around them and personal preferences (like in some electric guitar cases).	[ "Vintage musical equipment is older music gear, including instruments, amplifiers and speakers, sound recording equipment and effects pedals, sought after, maintained and used by record producers, audio engineers and musicians who are interested in historical music genres. While any piece of equipment of sufficient...
When, how, why did every military on the planet adopt a more or less identical hierarchy of ranks?	To our readers: Please keep in mind [our subreddit rules](_URL_3_) when posting. Particularly, please make sure [to write an in-depth answer](_URL_2_), [to not just speculate](_URL_0_), and [not to just post a link](_URL_1_).	[ "After the World War II when the Enver Hoxha regime took power, military ranks were radically changed in looks and in naming. The original design for ranks for the UPS came from the Soviet Union and the Eastern Bloc. In May 1966 military ranks were abolished following the Sino-Soviet Split switching over to the Chi...
Why the mass inside a black hole is a "singularity" and not just a very dense body like a neutron star?	With a neutron star, it is held up by neutron degeneracy pressure counteracting gravity. (White dwarfs are held up by electron degeneracy pressure) When you form a black hole, it's the proverbial straw that broke the camel's back. A little extra mass means the neutron degeneracy pressure can't hold it up anymore and t...	[ "It might be thought that a sufficiently massive neutron star could exist within its Schwarzschild radius (1.0 SR) and appear like a black hole without having all the mass compressed to a singularity at the center; however, this is probably incorrect. Within the event horizon, matter would have to move outward fast...
How do cables/cords all work and what differs between things such as a HDMI cable vs a USB cable vs fiber optic cables?	Your usb cables are a bunch of wires. They carry electrical impulses. The optical cables are just that, optics. They carry light and are basically made of glass. That accounts for the differences in throughputs without getting into plasmonics and things like that. The "upgrades" for your usb cables are almost cert...	[ "Networking cables are networking hardware used to connect one network device to other network devices or to connect two or more computers to share printers, scanners etc. Different types of network cables, such as coaxial cable, optical fiber cable, and twisted pair cables, are used depending on the network's phys...
how high up do you have to be above water for it to be fatal when you hit the surface?	Just on a side note: Do we have to worry about you asking such a question?	[ "BULLET::::- Hitting the water flat (non-diving position) from a height of 10 meters will bring the pilot to a stop in less than 1 foot which can cause serious bruising to the body and internal organs. It also strains the connective tissue securing the organs and possible minor haemorrhaging of lungs and other tiss...
how do you help someone during a panic/anxiety attack?	I'd recommend avoiding the terms "calm down” or “chill out” etc. may sound dismissive. Ask what they need. If it’s the place, is there a stimulus to remove etc	[ "Treatment of panic attacks should be directed at the underlying cause. In those with frequent attacks, counselling or medications may be used. Breathing training and muscle relaxation techniques may also help. Those affected are at a higher risk of suicide.\n", "With panic disorder, a person has brief attacks of...
What were Wilhelm II's views on jews, really?	There is debate on this subject given that his public and private positions often seem to be at odds, but I can provide at least one notable example of his thoughts on this subject from only a year after the end of WWI. By way of providing background for other readers: the Kaiser notably abandoned the throne near the...	[ "On 7 October 1898, Eulenburg summoned the leader of the Zionist movement, the Hungarian journalist Theodor Herzl to Liebenberg to announce that his master Wilhelm II wanted to see a Jewish state established in Palestine (which would be a German protectorate) in order to \"drain\" the Jews away from Europe, and thu...
If stars create other stars when they die, why will the universe still eventually come to an end?	Stars are very far from 100% at recycling old stars. Only the most massive stars go supernova, but even then they retain some of their mass as a black hole or neutron star. A large fraction is launched into the "interstellar medium", where it mixes with other gas and eventually may be incorporated into new stars, but ...	[ "Most stars will eventually come to a point in their evolution when the outward radiation pressure from the nuclear fusions in its interior can no longer resist the ever-present gravitational forces. When this happens, the star collapses under its own weight and undergoes the process of stellar death. For most star...
forex trading and other programs of the sort	It's literally gambling. There are PhDs and masters in finance and economics doing these activities at banks professionally, like for a living (my former macroeconomics professor actually did this for over a decade). The margins in the long run are EXTREMELY low on these trades. A professional will need to move around ...	[ "Program trading is defined by the New York Stock Exchange as an order to buy or sell 15 or more stocks valued at over US$1 million total. In practice this means that all program trades are entered with the aid of a computer. In the 1980s, program trading became widely used in trading between the S&P 500 equity and...
calculus	Hopefully this is for your own curiosity rather than for a class! Calculus, at the most basic level, deals with rates: how quickly or slowly certain variables (like distance) change when other variables (like time) are changed. For example, people often say that sprinters run at x miles per hour. In reality, that's th...	[ "Calculus is a branch of mathematics focused on limits, functions, derivatives, integrals, and infinite series. This subject constitutes a major part of contemporary mathematics education. Calculus has widespread applications in science, economics, and engineering and can solve many problems for which algebra alone...
You always hear about greenhouse gases as the cause of global warming. Is the sheer amount of heat released by humans a factor too?	Total human energy consumption (1.5 x 10^13 W) is about 0.01% of total solar energy input to Earth (1.7 x 10^17 W). So it's a very small effect compared to factors that modify the Earth's ability to radiatively cool (e.g., greenhouse gases). Waste heat is much more significant on local scales, e.g., leading to [urban h...	[ "Humans are one of the biggest influences on global warming. The biggest cause is the use of fossil fuels which creates COformula_1 that later gets trapped in the atmosphere. COformula_1 in the atmosphere then traps heat and changes the temperature of its climate. Some smaller but also meaningful human influences i...
Is it possible for a spaceship traveling around Earth to generate electricity?	Like this? _URL_0_	[ "Nuclear-electric or plasma engines, operating for long periods at low thrust and powered by fission reactors, have the potential to reach speeds much greater than chemically powered vehicles or nuclear-thermal rockets. Such vehicles probably have the potential to power solar system exploration with reasonable trip...
tax cuts & job acts 2017?	I would still keep track of your miles. If you're driving a car that you own for work there is a 99% chance you're wrong and will still be able to use your miles. Also most people have a mileage sweet spot where they get the most savings, so it's not always wise to report the entirety of your miles.	[ "The law cut taxes by 231 million in its first year, and cuts were projected to total 934 million after six years. They eliminated taxes on \"pass-through\" income (used by sole proprietorships, partnerships, limited liability companies, subchapter S corporations, for the owners of almost 200,000 businesses, and cu...
why does opening things hurt more in the morning?	It takes a bit of movement to get the fluid in your joints working. But you might have arthritis go see a doctor.	[ "On the eighth night, the old man awakens after the narrator's hand slips and makes a noise, interrupting the narrator's nightly ritual. But the narrator does not draw back and, after some time, decides to open the lantern. A single thin ray of light shines out and lands precisely on the \"evil eye\", revealing tha...
when using carbon dating and similar techniques, how do we know the age of the object it made up, rather than the age of the carbon or other isotope from when it was formed in a star?	Carbon dating works of the natural rate at which Carbon 14 (an unstable isotope) decays based on its half life. When things are alive, everything in an environment has an equilibrium of C14 as carbon is being continually being transferred between organisms. When they die however, there is no more carbon addition, and t...	[ "Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.\n", "The precision of a dating method depends in part on the half-life of the radioactiv...
Are slave narratives from the Federal Writers' Project regarded as legitimate sources?	They are largely regarded as legitimate by those who study and use them (including myself), but as /u/The_Alaskan said, they need to be taken with a grain of salt. Depending on the time and date of the interview as well as the race or gender of the interviewer, the responses given by the interviewee are going to be dif...	[ "Notable projects of the Federal Writers' Project included the Slave Narrative Collection, a set of interviews that culminated in over 2,300 first-person accounts of slavery and 500 black-and-white photographs of former slaves. Many of these narratives are available online from the above-named collection at the Lib...
Neville Chamberlain: Was he really a mild-mannered appeaser or was he buying time to mobilize the British military?	When we talk about the „appeasement“ of Hitler, you have to remember that the word did not have such a negative connotation at the time. Those attempting to pacify Hitler used the word openly to describe their strategy, and outside observers, such as American policymakers, praised the likes of Neville Chamberlain for ...	[ "The \"Wall Street Journal\" compared Neville Chamberlain to Rowling's Cornelius Fudge, saying both were eager to help their constituents look the other way to avoid war. \"Throughout the '30s, Chamberlain, fearing that Churchill was out for his job, conducted a campaign against his fellow Tory. Chamberlain tried e...
why do our lungs remain full when we hold our breath?	First of all, the air you breathe in only contains about 18% Oxygen of which you only take in 3%(in relation to the original 100! not the 18). In addition to that, while your blood takes in oxygen, it gives out carbon-dioxide. This results in the total amount of air in your lungs to not change enough for you to perc...	[ "The lungs are not capable of expanding to breathe on their own, and will only do so when there is an increase in the volume of the thoracic cavity. This is achieved by the muscles of respiration, through the contraction of the diaphragm, and the intercostal muscles which pull the rib cage upwards as shown in the d...
Why do electrons have discrete energy levels they can occupy, and jump from between orbitals, yet do not revolve around the nucleus in orbits?	An electron in an atomic bound state has a well-defined energy, but not a well-defined position or momentum. It’s in an eigenstate of the energy operator, but not of the position or momentum operators.	[ "Additionally, an electron always tends to fall to the lowest possible energy state. It is possible for it to occupy any orbital so long as it does not violate the Pauli exclusion principle, but if lower-energy orbitals are available, this condition is unstable. The electron will eventually lose energy (by releasin...
why is k-12 a state issue when most citizens look to the federal government?	In the US if the Constitution does not specifically give the power over something to the Federal Government it belongs to the State. Education is not specifically given to the Federal Government so they are only allowed to put a few regulations on it. And what do you mean by "most citizens look to the federal governm...	[ "Since its inception, public K–12 has been debated, with several waves of reform throughout the last 50 years. In the 1980s, Reagan's 'A Nation at Risk' initiative provided provisions requiring public education to be evaluated based on standards, and teacher pay to be based on evaluations. In the 1990s, the Goals 2...
When did Europeans begin to believe that people of African descent belonged to an 'inferior race'	Pre-Follow-Up Question: Maybe this will help to get closer to the answer: what is the earliest evidence we have of 'racialist' beliefs being espoused?	[ "As slavery became a racial caste system, persons of only partial African ancestry and majority European ancestry were born into slavery. African descent became associated with slavery. By hypodescent, persons of even partial African ancestry were classified socially below whites. By the late 18th century, there we...
why is it that despite how much cgi has improved in the last 20 years it is always possible to tell when human faces are digitally rendered?	The term is “uncanny valley.” And yes it is much harder to make something real look realistic. Our brain is much better at finding something strange about things that we are used to.	[ "As the film/television industry continues to grow, so do the capabilities of the technologies behind it. Since the debut of newer technologies, many have feared that CGI (Computer Generated Imagery) will put practical SFX makeup out of business. More can be done with CGI than can be done with makeup as some things...
Omega-3s are essential but they're not that widely available.How is that humans survived and thrive even w/o it?	They are passed from mother to offspring during gestation, at the expense of the mothers stores of those fats. Prior to seafood consumption, they were available by eating the most concentrated land-based sources of those EFA's, namely the brains of other mammals, especially ruminants(although the EFA's are present in ...	[ "The elements listed below as \"Essential in humans\" are those listed by the (US) Food and Drug Administration as essential nutrients, as well as six additional elements: oxygen, carbon, hydrogen, and nitrogen (the fundamental building blocks of life on Earth), sulfur (essential to all cells) and cobalt (a necessa...
why do credit card companies send pre-approval letters for loans? how does this help their business?	They are in the business of loaning money to people, and they make a profit off the interest. The more people they get borrowing money from them, the more money they make. If the send out letters encouraging people to apply for credit, then they'll make more money.	[ "Business credit cards offer a number of features specific to businesses. They frequently offer special rewards in areas such as shipping, office supplies, travel, and business technology. Most issuers use the applicant's personal credit score when evaluating these applications. In addition, income from a variety o...
If all landmass was leveled, how high would the water above it be?	[Wikipedia](_URL_0_) actually has the calculation, taken by dividing the estimated volume of water on Earth (1.332×10^9 km^3) and dividing it by the known surface area of the Earth (5.1×10^8 km^2). This calculation gives an average height of 2.7km for the uniform shell of water.	[ "Water depths reached . Depending on the location, evidence for water levels of or even above sea level have been found; in the former case the lake may have occupied an area of no less than . There is also evidence of shorelines at altitudes of above sea level; if they reflect a lake stand at that altitude, this s...
how does china's great firewall work?	Not sure if this totally answers your question, but here goes: 1. All Internet connection provided in China is provided by the same "company". Imagine if everybody in the US only got internet from Comcast and there were no competitors. 2. The basic idea of the internet is little packets of information being sent and...	[ "The Great Firewall of China (GFW) is the combination of legislative actions and technologies enforced by the People's Republic of China to regulate the Internet domestically. Its role in the Internet censorship in China is to block access to selected foreign websites and to slow down cross-border internet traffic....
Why does lack of good rest, stress create over time the darkened skin tone around the eyes?	According to [this article](_URL_0_), if the primary reason is due to inadequate sleep, it's caused by combination of collagen weakening (hence skin sagging) from the periorbital area and a redistribution of fat towards the infraorbital area, causing visible veins immediately below the eyes and a fatty prominence sligh...	[ "Stress has effects on the immune system, which may explain why some cases directly correlate with stress. It is often stated that in studies of sufferers who are students, ulceration is exacerbated during examination periods and lessened during periods of vacation. Alternatively, it has been suggested that oral pa...
how our stomach "know" how much acid it have to use to digest some food?	Food introduces relatively basic material into our stomach. pH receptors in our cells tell the stomach to produce more acid as its contents become more basic. After the food is sufficiently digested, the pH becomes increasingly acidic as more acid than food is being added into the mixture. Once it gets to a certain pH ...	[ "Beaumont also used samples of stomach acid taken out of St. Martin to \"digest\" bits of food in cups. This led to the important discovery that the stomach acid, and not solely the mashing, pounding and squeezing of the stomach, digests the food into nutrients the stomach can use; in other words, digestion was pri...
what makes an iceberg invisible?	For a few reasons. 1. Blue Ice. It's when an iceberg stays in one position over a long period of time, meaning the part above the water and at the waterline erodes and the water leaves it. This makes the icebergs white at the top. After this, the iceberg tumbles and the part that was under the water is now above the w...	[ "An iceberg is a large piece of freshwater ice that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Small bits of disintegrating icebergs are called \"growlers\" or \"bergy bits\".\n", "A blue iceberg is visible after the ice from above the water melts, causing the smooth por...
Why are there no fencing manuals before the 1300s?	I can't give a greatly comprehensive answer because we simply don't know if there aren't things like Fechtbucher in between Vegetius and Ms. I.33 that we just haven't found, or if they just weren't written. I can answer a bit about the context of the Fechtbucher corpus that starts with I.33, and unsurprisingly, ...	[ "Although there is a considerable gap in extant Italian treatises, between 1696 and 1800, we can see from the earliest 19th Century treatises that the style had changed very little during that period. The only changes were the addition of certain techniques suitable for the somewhat lighter blades of the dueling sw...
if stem cells can be used to create any tissue and the reason we age is to do with damage occurred during cell reproduction. why can't we stop aging using stem cells gained from embryos?	Yes, theoretically, but embryonic stem cells have a tendency to not do precisely what you want, and we still have lots and lots and lots of learning to do before we can use them effectively to "stop" aging, and even to slow it down in any material way. The problems to solve include getting them to where they need to ...	[ "Stem cell function becomes impaired with age, and this contributes to progressive deterioration of tissue maintenance and repair. A likely important cause of increasing stem cell dysfunction is age-dependent accumulation of DNA damage in both stem cells and the cells that comprise the stem cell environment. (See a...
How much does shivering affect core body temperature when cold?	It's difficult to be positive since it's difficult to separate shivering from other things the body does. For example, to raise the body core temperature blood flow to the extremities decreases, which decreases heat loss, but doesn't affect heat generation like shivering does. In [one study I found](_URL_1_) it appears...	[ "The functional capacity of the thermoregulatory system alters with aging, reducing the resistance of elderly people to extreme temperatures. The shiver response may be greatly diminished or even absent in the elderly, resulting in a significant drop in mean deep body temperature upon exposure to cold. Standard tes...
Sun Tzu’s The Art of War is considered by many to be one of the most influential works of strategy and warmaking. Once translations made it to Europe how was it initially regarded? and Was there any obvious changes in strategy once the book made it into foreign hands?	Hey maybe, just maybe one I can answer. I've never had a whole lot of success posting on this sub, which makes me love it even more. Okay, so I guess I need to explain how I know about this... My dad was an infantry officer in the US Army between 1974 and 2006. He enlisted, hit sergeant, went to college, became and of...	[ "The newly discovered text provided historians with a different perspective on the Battle of Guiling and Battle of Maling. In addition, when compared to Sun Tzu's \"The Art of War\", \"Sun Bin's Art of War\" contained one major difference from the former. The former advised against siege warfare, while the latter s...
I'm a temporary worker in the US trying to learn more about this country's history. What basic historical facts about the US should I know.	I'm a an engineer working in Oil and Gas. I'm from Brazil. I have been in the States for over a year but realized there are a lot of things that I don't know. Like when and why they said "The British are coming"? Why they threw tea in the Boston harbor? I have a general understanding of the civil war, like it was about...	[ "BULLET::::- \"The National Cyclopaedia of American Biography: Being the History of the United States as Illustrated in the Lives of the Founders, Builders, and Defenders of the Republic, and of the Men and Women who are Doing the Work and Moulding the Thought of the Present Time\", J. T. White company, (1900)\n", ...
Phalanx Exceptionalism: what distinguishes the Greek Hoplite Phalanx from the next shield-wall of violent men with pointy sticks?	There are essentially two ways of picturing the Greek phalanx: 1. As a direct predecessor to the Macedonian pike phalanx: a tightly packed infantry formation with touching or overlapping shields, presenting a wall of spear points to the enemy, with as many ranks as possible sticking their spears over the shields of th...	[ "The hoplite phalanx of the Archaic and Classical periods in Greece (c. 800–350 BC) was the formation in which the hoplites would line up in ranks in close order. The hoplites would lock their shields together, and the first few ranks of soldiers would project their spears out over the first rank of shields. The ph...
Are there any (theoretical) ways of eradicating High levels of radiation besides time?	Some things have very short half lives, and will decay (on average) in the range of microseconds to minutes. Other isotopes have much longer half-lives, whether on the order of years or billions of years, it doesn't make much difference. Strontium 90 is a good example. It is produced in relatively large amounts in fi...	[ "Releases of radioisotopes can expose future generations to ionizing radiation and the calculation of the collective dose from such releases will contain uncertainties. For example, it is impossible to be sure of future population sizes and habits (e.g. diet and agricultural practices). Also the effects of a given ...
I've seen a lot of photos of samurai in armour from the very end of the Edo period. As I understand it Japan had been at relative peace for decades at that point, did that amour actually serve any practical purpose? if "no" why did they still have it?	It's important to remember that being a samurai wasn't simply a job that one picked up. It was very much a social caste that members were born into, able to trace their family's/clan's lineage and history as samurai, and maintained their role in society was as a caste of professional warrior vassals. **Armor and weap...	[ "During the Heian period (794 to 1185) the Japanese cuirass evolved into the more familiar style of armour worn by the samurai known as the . Japanese armour makers started to use hardened leather along with iron in their armour construction and lacquer was used to weather proof the armor parts. By the end of the H...
What is a scientific principle/invention that comes from Europe during 570 to 1240?	What you've posted already seems to be a fairly sensible rebuttal of the concept of the Dark Ages. I do have a basic problem of the term "Dark Ages" meaning a slowing of scientific advance--'scientific' being a bit of an iffy word during that period and, according to most people using the phrase, only means 'things we ...	[ "Among the earliest inventions were the abacus, the \"shadow clock,\" and the first items such as Kongming lanterns. The \"Four Great Inventions,\"the compass, gunpowder, papermaking, and printing – were among the most important technological advances, only known to Europe by the end of the Middle Ages 1000 years l...
how do uhaul and car rental companies get their cars and trucks back when they are dropped off in different states or cities?	Because other cars and trucks are being driven from other cities to that location. It's a constant network of vehicles flowing in and out. I'm sure if there's too much of an imbalance between locations they transfer vehicles without them being rented. But that is easy enough.	[ "In the sharing economy, transfer cars, relocation cars, or driveaways are rental cars that need to be transferred back to their original branch after a one-way rental. Rental car companies have traditionally used truck and train transporters to re-position their fleet until this model was disrupted by websites whi...
who/what are the russian "separatists" involved with today's downed airliner?	This part is factually settled: They're living in a part of Ukraine that they currently have taken control over and want to reincorporate into Russia. This part is still unclear: Russia may have given them the surface to air missiles. But, the problem is that since Ukraine is a former part of the USSR, all their mi...	[ "In an interview with Reuters on 23 July 2014, Alexander Khodakovsky, the commander of the pro-Russian Vostok Battalion, acknowledged that the separatists had an anti-aircraft missile of the type the Americans had said was used to shoot down the aircraft, and said that it could have been sent back to Russia to remo...
How did soldiers in the front line protect themselves against spears when charging the enemy?	Soldiers didn't just ram themselves onto spears. When faced with a line of heavy infantry who were standing in close order and fully prepared to receive a charge, they knew that slamming full-force into that line would probably be ineffective. A scene from the siege of Majorca in 1229 illustrates the difficulties of ge...	[ "In one British form of the tactic, three or four officers rush at a group of violent or disorderly people, with two of the officers carrying batons and the others a shield. The officer with the shield rushes the most violent in the group and forces the subject between the shield and a fixed object, while the other...
what happens to headphones when one of the ear buds stop working unless the cord is in the sweet spot?	Inside the bud itself, the wires are soldered onto connecters attached to the speaker part that makes the noise. Because of how thin the wires are, and how cheap ear buds tend to be, they work themselves out of the solder pretty easily. What you're hearing (or not) is the wire actually physically breaking connection ...	[ "A disadvantage of using phone connectors for balanced audio connections is that the ground mates last and the socket grounds the plug tip and ring when inserting or disconnecting the plug. This causes bursts of hum, cracks and pops and may stress some outputs as they will be short circuited briefly, or longer if t...
Were the Taliban pro or anti opium? How did their stance on this issue shift and why? (Only pre-invasion, please)	Not to be a debbie downer on what is an interesting question, but my understanding is that the Taliban only became a player on the scene around 1994, so on the near side of /r/AskHistorians' 20 Year Rule.	[ "While the Taliban were considered a threat both to the human rights of Afghans, and to other areas of the world by providing a sanctuary for transnational terrorists, they also demonstrated an ability to strictly enforce a moratorium on opium production. Since their overthrow in 2001, stopping their enforcement wi...
What was the last empire that fell and broke into today's countries?	The Soviet Union dissolved in 1991, and many other eastern bloc countries broke loose. Czechoslovakia dissolved in 1993, but I'm not sure that it meets the definition of empire.	[ "The empire eventually died out because of many factors such as substantial loss of territory and imperial authority caused by their own erstwhile feudatories, as well as the invasion by the Huna peoples (Kidarites and Alchon Huns) from Central Asia. After the collapse of the Gupta Empire in the 6th century, India ...
Why didn't Han China have slaves like Rome did?	Slavery was abolished prior to the 1st Dynasty of China, before 200 BC. There was never any official abolition of slavery. The institution of slavery simply became outdated culturally that the Chinese simply didn't bother to enforce it any more. The other reason is, the Emperor technically owned all property in Chin...	[ "Many Han Chinese were enslaved in the process of the Mongol invasion of China proper. According to Japanese historians Sugiyama Masaaki (杉山正明) and Funada Yoshiyuki (舩田善之), there were also a certain number of Mongolian slaves owned by Han Chinese during the Yuan dynasty. Moreover, there is no evidence that the Han ...
What’s the current status of Zika? The news hasn’t been reporting it as threatening as it was before- is this because the news is bored of it and it is just as bad as it was a year or ya ago or is it actually subsiding? Do we have a vaccine available?	Not sure, but I'd probably check with the WHO, [_URL_1_](_URL_1_), and [_URL_0_](_URL_0_) & #x200B; TLDR; it's still a problem	[ "In February 2016, WHO declared the outbreak a Public Health Emergency of International Concern as evidence grew that Zika is a cause of birth defects and neurological problems. In April 2016, WHO stated there is a scientific consensus, based on preliminary evidence, that Zika is a cause of microcephaly in infants ...
masturbation, oral sex, and other non-intercourse from an evolutionary perspective	its a way to bond and resolve conflict within groups. like with the bonobos.	[ "Sex at Dawn: The Prehistoric Origins of Modern Sexuality is a 2010 book about the evolution of monogamy in humans and human mating systems by Christopher Ryan and Cacilda Jethá. In opposition to what the authors see as the \"standard narrative\" of human sexual evolution, they contend that having multiple sexual p...
brain focusing and unfocusing	Unfocusing is just paying attention to something else, whether it's something in the environment or your own thoughts it doesn't matter. I believe you are trying to ask whether it's better to look at the "whole image" (the whole act, the magician and his stage) rather than focus on something more specific(for example h...	[ "A tendency to focus attention tightly has a number of psychological implications. While monotropism tends to cause people to miss things outside their attention tunnel, within it their focused attention can lend itself to intense experiences, deep thinking and flow states. However, this hyperfocus makes it harder ...
how is lip syncing done in movies like "kubo and the two strings"	The dialog is recorded ahead of time, so all of the audio can be timed and charted for the animators. Each scene length is (generally) set in stone, too. So the chart says, "According to the audio track for this scene, the character should be making an 'S' sound at frame 47." I'm not sure what Laika's charts look like...	[ "In film production, lip-synching is often part of the postproduction phase. Dubbing foreign-language films and making animated characters appear to speak both require elaborate lip-synching. Many video games make extensive use of lip-synched sound files to create an immersive environment in which on-screen charact...
So, the mandate of Heaven: In the Han Dynasty, did the emperor's mandate of heaven simply mean that he was allegedly approved of by heaven, to discourage coups and assassins, or did the Chinese believe that this made the emperor literally infallible, and un-touchable?	He who wins is the king; He who loses is the rebel. Let’s begin with an overview for anyone who might not be totally familial with what - exactly - the “Mandate of Heaven” really is, as well as where it came from, and its role in Chinese dynastic rulership. Then we’ll get to the main part of your question of whe...	[ "The Mandate of Heaven was the idea that the Emperor was favored by Heaven to rule over China. The Mandate of Heaven explanation was championed by the Chinese philosopher Mencius during the Warring States period.\n", "In ancient China, the Emperor of China was regarded as the \"Son of Heaven\", who administered e...
what is happening in missouri right now?	All is calm in St Louis so far. Still waiting on that Grand Jury for the decision though. Most of the protests have been peaceful, but the governor declared a state of emergency and preemptively called in the national guard in case people are upset by their decision and start rioting again.	[ "Missouri had a population of 5,988,927, according to the 2010 Census; an increase of 137,525 (2.3 percent) since the year 2010. From 2010 to 2018, this includes a natural increase of 137,564 people since the last census (480,763 births less 343,199 deaths), and an increase of 88,088 people due to net migration int...
How common were incestual relations in medieval times outside of royal families?	Just a question for clarification. By your phrasing, I assume that you aren't asking only about immediate-blood relations (sibling-sibling; parent-child), but also about close relations such as first- or second-cousin marriages, yes?	[ "In the 18th century people were still executed for incest even when they were not related by blood, because relations by marriage were considered by religious criteria to be equivalent to blood relatives. There was a similar case in Västmanland, where Brita Johansdotter ran away from her husband with her stepson M...
Where is a good place to look for primary sources regarding escapism and consumerism in the US during the 1920's?	If you're studying escapsim and consumerism, have you tried looking at collections of vintage ads online? What sorts of primary sources do you anticipate will have exactly what you're looking for? I'll ask the classic librarian question to help you narrow down your search: If you could describe the perfect resource f...	[ "In North America, there was a DIY magazine publishing niche in the first half of the twentieth century. Magazines such as \"Popular Mechanics\" (founded in 1902) and \"Mechanix Illustrated\" (founded in 1928) offered a way for readers to keep current on useful practical skills, techniques, tools, and materials. As...
Could birds mistake whistling for bird calls?	When hunting for water fowl/turkey people will often call the animals in with small flute like devices. These work quite well. In fact some people can do these said calls very well with only their mouth: _URL_0_ So in theory yes you can call birds.	[ "The numbers of these birds have declined in some areas due to loss of habitat. They are still fairly common but are more often heard than seen. They prefer to escape on foot and hide than to take flight. These birds make cooing and clucking sounds, usually in early morning or near dusk.\n", "It is a noisy bird w...
i got hit in the nuts with a soccer ball lastnight, why did i feel such pain in my stomache?	Every fetus starts out female; the reproductive organs all start out in the gut. If you are finally a male, the organs drop out of the body and dangle precariously in a thin, vulnerable pouch of skin. But the nerves in the organs still register as in the gut.	[ "Ball was partly inspired by two encounters he had in the early 1990s. In about 1991–92, Ball saw a plastic bag blowing in the wind outside the World Trade Center. He watched the bag for 10 minutes, saying later that it provoked an \"unexpected emotional response\". In 1992, Ball became preoccupied with the media c...
why is it easy to type from the thoughts/words in your head, but difficult to type the alphabet?	Muscle memory. You are used to type these short words over and over. You have very few words that have more than ABCD or BCDE or CDEF ect connected. Same reason you can easliy read last names you are used to read but a very foreign name will have you trying to reconnect syllables and hesitate on the word.	[ "Once the algorithm is understood, one can type almost any character with a little practice, even if one hasn't typed it before. Muscle memory will make sure that frequent typists using this method don't have to think about how the characters are actually constructed, just as the vast majority of English typists do...
why do the countries that used to be a part of the british empire (canada, new zealand, australia, etc) have a dollar ($) for a currency, instead of a pound (£) like britain?	New Zealand and Australia used their own independent pounds, shillings and pence for some time after they had independence. When they decimalised, they found people worked in shillings. So they came up with a system where the cent was similar in value to the old penny, and 10 cents was a worth one old shilling. To keep...	[ "In the economy of the Americas, the Canadian dollar plays a similar role to that of the Australian dollar (AUD) in the Asia-Pacific region. The Canadian dollar (as a regional reserve currency for banking) has been an important part of the British, French and Dutch Caribbean states' economies and finance systems si...
In the end, was Julius Caesar considered a friend or foe of Rome ?	I don't think there is a consensus on Caesar. He's the kind of guy you have to take a position on one way or another, and very little historical judgment goes into taking those kinds of political positions. For the record, I'm a Caesarean, if the word carries any meaning anymore. What Caesar had on his side: * the...	[ "Julius Caesar leaned considerably toward Epicureanism, which e.g. led to his plea against the death sentence during the trial against Catiline, during the Catiline conspiracy where he spoke out against the Stoic Cato. His father-in-law, Lucius Calpurnius Piso Caesoninus was also an adept of the school.\n", "At t...
3/4, 12/8 and similar notations in music. also, 3/4 = 6/8 in this context?	The top number denotes beats per measure while the bottom denotes which note gets the beat. 2/4 time would mean two beats per measure and the quarter note gets the beat. 2 beats per measure is duple meter, 3 is triple, and 4 is quadruple. 3/4 and 6/8 time sound very similar, but 3/4 time is usually seen with slow...	[ "According to this definition, with the twelve notes of a chromatic scale it is possible to define twelve different tritones, each starting from a different note and ending six notes above it. Although all of them span six semitones, six of them are classified as \"augmented fourth\"s, and the other six as \"dimini...
what are gas future that i've been told affect our price at the pump so drastically?	So this is how it goes: gas has been transformed in a financial asset! What that means is that you can, today for instance, say to somebody "I will buy from you 3 papers that represent gas. But I won't buy them today, but ten weeks from now and I'll give 10$ for each paper." If the other person accepts, ten weeks from ...	[ "BULLET::::- June 10: Federal Reserve Chairman Alan Greenspan notes that rising natural gas prices in the United States could have a negative impact on the economy in the months ahead if prices remain at high levels. States Greenspan, \"I have no doubt that...if we stay at these very elevated prices we're going to ...
what is the difference between decriminalization and legalization?	Decriminalizing simply removes criminal penalties, legalizing involves the process of creating infrastructure for regulation and taxation.	[ "The term 'legalization', on the other hand, is usually used in the context of prostitution to refer to the use of criminal laws to regulate prostitution by determining the legal conditions under which prostitutes can operate. Legalization can mean anything from rigid controls under a state-controlled system to mer...
Did bronze or iron equipped armies ever clash with iron or steel equipped armies? What was the outcome?	This is not directly answering your question, but rather correcting a misconception you seem to have. Bronze is not necessarily a much worse material than the rudimentary low-grade steel they would be using in the transition period. The real answer to the Bronze/Iron age divide is not that Iron is stronger, but rat...	[ "Leonard R. Palmer suggested that iron, superior to bronze for weapons manufacturing, was in more plentiful supply and so allowed larger armies of iron users to overwhelm the smaller bronze-equipped armies that consisted largely of Maryannu chariotry.\n", "It is uncertain when Iron weapons replaced Bronze weapons...
If the electromagnetic and weak forces have been unified into the electroweak interaction, why do we still say there are four fundamental forces?	EM and the weak force become united at higher temperature regimes. In everyday day life, the forces are not unified and manifest themselves differently. Both ways of saying are technically correct, although the unification could be more confusing to laypeople.	[ "Although the weak and electromagnetic forces appear quite different to us at everyday energies, the two forces are theorized to unify as a single electroweak force at high energies. This prediction was clearly confirmed by measurements of cross-sections for high-energy electron-proton scattering at the HERA collid...
how does paying off a house work?	You put a downpayment on a house. A downpayment is a large sum of cash you have on hand. Obviously, most people can't pay for a whole house at once. They go to a bank. The bank checks their credit rating, which is based on paying payments for credit cards and other things on time. The bank also makes sure you can a...	[ "This unique way of renting a house is called \"jeonse\"; a renter makes a lump-sum deposit on a rental space instead of paying monthly rent, at anywhere from 50 to 100% of the market value, and gets back the whole deposit when the rent contract ends. The home-owner is free to invest the deposit as wanted, as long ...
In pistol duels throughout history (wild west, Burr-Hamilton, etc), what determined the moment the opposing parties would fire?	There are different ways, but generally it would be upon a signal, and then either with a time limit or not. One of the most common would be for one of the seconds (chosen by lots) to give the signal, and then count to three. The duelists had to fire within that window, or else they forfeited their fire. Less refined...	[ "All first-hand accounts of the duel agree that two shots were fired, although the seconds disagreed on the intervening time between the shots. It was common for both principals in a duel to fire a shot at the ground to exemplify courage, and then the duel could come to an end. Hamilton apparently fired a shot abov...
how does sound move onboard the international spacestation?	No, sound is not significantly affected by gravity. Sound on board the ISS is the same as it would be if the ISS were stationary on the ground. And as a side note, there is no lack of gravity on the ISS -- it's in free fall which creates an experience much like zero gravity, but as it's very close to Earth, there is...	[ "The default version of \"Orbiter\" has no sound, however a popular add-on called \"XRSound\" is available. It provides engine noises, ambient sounds in the cabin, radio chatter and other sounds including playlists. Options enable the user to maintain a realistic silence when the craft is viewed externally during s...
What caused and what ended the Cryogenian era in Earth's history?	Exactly what causes periods of "snowball Earth" is not completely known, though several factors are considered important. It's necessary for there to be significant continental land-masses in tropical latitudes. Weathering of continental rocks removes CO2 from the atmosphere, cooling the Earth slightly and causing the ...	[ "The Cryogenian period was ratified in 1990 by the International Commission on Stratigraphy. In contrast to most other time periods, the beginning of the Cryogenian is not linked to a globally observable and documented event. Instead, the base of the period is defined by a fixed rock age, that was originally set at...
How can 2 black holes possibly merge? Wouldn't one black hole have to "pull something" into itself? But if the other blackhole doesn't give up matter... then there is nothing to "pull in"?	Layman here - My biggest roadblock to understanding black holes for a while was the overloaded term 'matter'. When talking about black holes, there are no fermions inside the event horizon, 'matter' and 'mass' refer to the energy content of the singularity. Experts - do I have this right?	[ "Some simulations have concluded that after crossing a certain distance, the energy dissipation of two approaching black holes ceases, result in them not getting closer any further. However, the merger of black holes is expected to occur during the collision of galaxies. This unsolved problem is known as the final ...
Why has present day Saudi Arabia been untouched throughout many empires?	Saudia Arabia is, minimally, the combination of three rather different cultural zones: the Hejaz region on the West Coast which contains the Muslim holy cities of Mecca and Medina, the Najd desert and oasis region in the center, the historically mostly Shi'a East Coast along the Persian Gulf. The desert center was di...	[ "Scholar Vitaliĭ Vi͡acheslavovich Naumkin argues that even before the fall of Communism, Saudi Arabia had substantial influence on Islam in Central Asia because of its prestige as the location of the holy places of Hejaz, its financial resources and because of the large number of Central Asian pilgrims (and their d...
How good is a goats eyesight?	I think I found an answer to your question. It looks like the answer is, no. This is an excerpt from an article that covers whether or not and how a goat can detect a harmful worm on their food. It’s not a spider but it’s relatively the same size. _URL_0_ “We tested the goats’ ability to detect webworms using sig...	[ "Although the elephant nose fish was once thought to have poor eyesight, it is now known to have good low light vision. Its eyes use a combination of photonic crystals, parabolic mirrors and a clustered arrangement of rods and cones.\n", "Goats have horizontal, slit-shaped pupils. Because goats' irises are usuall...
how do e-cigarettes work?	Imagine this. You have a piece of paper, and you have a really hot light. You move the paper close to the light but it doesn't touch the light. The heart from the light causes the paper to burn, thus releasing smoke. The E-Cig is essentially doing the same thing although instead of paper you have some sort of liquid t...	[ "An e-cigarette is a handheld battery-powered vaporizer that simulates smoking, but without tobacco combustion. Once the user inhales, the airflow activates the flow sensor, and then the heating element atomizes the liquid solution. The different kinds of trigger sensor or sensors used are acoustic, pressure, touch...
how do scientists know we're not simply still in the expansion phase of a "big crunch scenario?"	It's because of the very fact that the expansion seems to be speeding up (accelerating). If you think of Big Bang as an explosion, the highest velocity is always at the initial time and point. In the Big Crunch hypothesis, with gravity exerting its force, the universe will continue to expand but it would be expanding a...	[ "The Big Crunch scenario hypothesized that the density of matter throughout the universe is sufficiently high that gravitational attraction will overcome the expansion which began with the Big Bang. The FLRW cosmology can predict whether the expansion will eventually stop based on the average energy density, Hubble...
how do any thing that lay eggs fertilize them?	Eggs that don't have shells, such as those laid by fishes and frogs, are usually fertilised after being laid. The female produces the eggs and then the male covers them in sperm. It's an inefficient method, which is one reason why these creatures usually lay large numbers of eggs. Eggs in shells, however, such as thos...	[ "The egg is the organic vessel containing the zygote in which an embryo develops until it can survive on its own; at which point the animal hatches. An egg results from fertilization of an egg cell. Most arthropods, vertebrates (excluding mammals), and mollusks lay eggs, although some, such as scorpions do not.\n",...
NYTimes: "smoking increases the chance that an HPV infection will become chronic." Is this statement true?	No, it's not about promiscous behavior. And a chronic infection is not one acquired repeatedly, but one that is persistent (an acute infection can become chronic if it doesn't heal quickly). Smoking impairs the immune response, so that will increase the chances of an HPV infection to become chronic. Also, tobacco sm...	[ "Infection with some types of HPV is the greatest risk factor for cervical cancer, followed by smoking. HIV infection is also a risk factor. Not all of the causes of cervical cancer are known, however, and several other contributing factors have been implicated.\n", "A 2007 survey of American women found 40% had ...
Question for historiography: Handling classified materials	So I have a long [post here](_URL_1_) about accessing sources _without_ a clearance. _With_ a clearance presents very different issues. I've never had (or wanted!) a clearance, so I can't speak to those authoritatively. But I do know official historians (and have read accounts by them) of how this has worked. Histori...	[ "Because published materials differ in significant and fundamental ways from the collections of interrelated and unique materials found in archives, there are significant differences in bibliographic and archival description. A bibliographic description represents an individual published item, is based on and deriv...
Are there any surviving food recipes from the Romans? If so are they easy to follow?	Well, last time I answered a question on Roman food I got in a lot of trouble with the Thirty, but here we go: & nbsp; Yes, there are tons of Roman recipes and a lot of them are really simple. A lot of them are collected in a late Roman "cookbook" often attributed to a person named Apicius (who is fictional). This...	[ "The earliest collection of recipes that has survived in Europe is \"De re coquinaria\", written in Latin. An early version was first compiled sometime in the 1st century and has often been attributed to the Roman gourmet Marcus Gavius Apicius, though this has been cast in doubt by modern research. An \"Apicius\" c...
how does time dialation work?	Imagine standing in a train, rolling a ball on the floor. The train is moving at 70 mph. From your perspective inside the train the ball is rolling at 10 mph. From the perspective of someone outside the train the ball is moving at 80 mph. As your velocity approaches relativistic levels the length of time in a second...	[ "In time management, timeboxing allocates a fixed time period, called a timebox, within which planned activity takes place. It is employed by several project management approaches and for personal time management. \n", "The on-time marker, the exact moment which the time code identifies, is the leading (negative-...
Is it possible for a single, random atom to split on its own, at any time?	Yes, this happens all the time in some radioactive elements. It's called alpha decay: the atom splits into two, and one part is a helium nucleus, also called an alpha particle. For example, a radium atom splits into one radon atom and one alpha particle. If you observed a single radium 226 atom for 1600 years, it...	[ "Because there exist formula_13 ways of splitting each cluster, heuristics are needed. DIANA chooses the object with the maximum average dissimilarity and then moves all objects to this cluster that are more similar to the new cluster than to the remainder.\n", "If there are multiple breaks in a time series, the ...
why do lips start to stick together when closed for long times?	We use our tongue to keep our lips moist and when we don't do that, lips lose their moisture- this also happens when we are dehydrated. So when the moisture on the lips dry up, the left over thin coating which is made up of a sticky substance which comes from the mucus of saliva makes lips to stick together.	[ "Small defects of the upper and lower lip can be closed primarily. For the upper lip, defects of up to 1/4 (25%) of the lip may be closed primarily. For the lower lip, defects of up to 1/3 of the lip may be closed primarily. This means the edges of the defect are simply sutured together in three layers: oral mucosa...
How do moons work? Would it be possible for a planet to gain or lose moons, and could we see it happen? Why do planets farther from the sun seem to have more moons? Can a moon have a moon?	Hi, > How do moons work? They work by simply orbiting a planet. That's essentially how a moon is defined. Regarding gravity, those are simple two-, three-, or multiple-body systems around a common barycenter and therefore work like any other system with mass (be it planets around stars, double stars, etc.) > ...	[ "Moons are created when a debris field is large enough to form together. The largest debris fields will yield a maximum 20 percent chance of creating a Moon, and they will also create the Moons with the most available space. Players in an alliance will often give each other \"moonshots\" by attacking a certain numb...
why do bigger document scanners cost exponentially more?	The main reason is that the market for these devices is very small, so they don't benefit from the economies of large-volume manufacturing and competition.	[ "The range of hardware available to turn paper documents into digital images has increased considerably in the last 10 years. Although desktop scanners and multi-function devices (MFDs) are now very affordable and well suited to small office or departmental scanning requirements, the need for high speed, high volum...
How does clothes dye work?	Many common dyes require a basic environment to work, and soda ash is basic so it is a common way to accomplish this. There are several different types of fabric, but in general you can think of protein fibers (wool, silk, and nylon), and cellulose fibers (cotton, paper, hemp, line, and rayon). There are also a lot o...	[ "Product dyeing, also known as garment dyeing, is the process of dyeing products such as hosiery, sweaters, and carpet after they have been produced. This stage of dyeing is suitable when all components dye the same shade (including threads). This method is used to dye sheer hosiery since it is knitted using tubula...
how did we come to decide which words mean what? are sounds just randomly formed into words or do they carry some sort of meaning?	Originally? We don't really know. However new words are created all the time and gain meaning by their shared use. As far as I know, theres no human universal "meaning" to any particular sounds, it's just whatever the language evolved to use. Most of the words in english come from pretty easily identifiable sources, ...	[ "A key component of language is its arbitrariness and what a word can represent, as a word is a sound created by humans with attached meaning to said sound. No one can determine the meaning of a word purely by how it sounds. However, in onomatopoeic words, these sounds are much less arbitrary; they are connected in...
Whilst Russia underwent a huge "destalinisation" process after his death, why does China still revere Mao even now, when the country is capitalist?	I'm more familiar with the Soviet side of things but my understanding is: * Mao and Stalin's leadership positions were kind of different towards the end of their rule. The Cultural Revolution is often interpreted as Mao trying to change the balance/structure of power, with Mao not technically in charge of the governme...	[ "After Joseph Stalin's death in 1953, Nikita Khrushchev became leader of the Soviet Union. His denouncement of Stalin and his purges, the introduction of more moderate communist policies and foreign policy of peaceful coexistence with the West angered China's leadership. Mao Zedong had been following a strict Stali...
The science behind keto: How does the ketogenic diet work, do we know if it's safe for anyone, does it lead to weight loss even when calories exceed daily recommended intake for weight loss, and what studies are there on the keto diet for weight loss rather than epilsepsy?	Carbohydrates consumed elevate glucose in the bloodstream. Dietary glucose levels are measured in the portal vein (from the small intestine). A high level of glucose stimulates the release of insulin. Insulin stimulates glycogen synthesis and fat synthesis. When carbohydrates are not consumed, the level of insulin fall...	[ "Because the ketogenic diet alters the body's metabolism, it is a first-line therapy in children with certain congenital metabolic diseases such as pyruvate dehydrogenase (E1) deficiency and glucose transporter 1 deficiency syndrome, which prevent the body from using carbohydrates as fuel, leading to a dependency o...
What do prisms of non-visible electromagnetic radiation look like?	Prisms spread out the component colors of white light because of something called dispersion. Dispersion relates the wavelength or wavenumber of a wave to its frequency. This is equivalent to saying the speed of a wave depends on the wavelength (i.e., the color) of the wave. In vacuum there is no dispersion and all w...	[ "In optics, a dispersive prism is an optical prism, usually having the shape of a geometrical triangular prism, used as a spectroscopic component. Spectral dispersion is the best known property of optical prisms, although not the most frequent purpose of using optical prisms in practice. Triangular prisms are used ...
I sat in disbelief as my physics professor told the class that cell phones emit EM waved that will fry your brain because they are the same thing as microwaves and UV waves. Was he BS'ing or am I just terribly misinformed?	You're correct; (Edit: The poster, _not_ the professor's assertion, since some people apparently don't read more than the title) Cell phones emit in the microwave region, which is non-ionizing. UV is also non-ionizing, but have far more energy. Enough to excite electrons in many organic compounds, which causes chemica...	[ "\"Wi-Fried?\", an episode broadcast in February 2016 featuring American epidemiologist Devra Davis courted further controversy by claiming that electromagnetic radiation emitted by devices such as mobile phones lead to an increased risk of brain cancer in heavy users, contrary to the mainstream view that exposure ...
how come certain videos on youtube can use copyrighted material and others can't, even if it's the same material?	It's not fine to simply include commercial music in your videos, even if you see others include the music in their videos. What you did was an explicit copyright violation. You are only permitted to incorporate the music into your video when you have explicit master and synchronization rights. For some music, such as...	[ "The law in the United Kingdom does allow people to use copyrighted material for the purposes of parody, pastiche, and caricature without infringing on the copyright of the material. Copyright owners are only able to sue the parodist if the work contains hateful or discriminative messages. If the case is then taken...
What is the cardinality of the set of the cardinalities of all sets?	There are too many cardinalities to form a set, so it doesn't have a cardinality. Proof. Let S be a set of sets so that every set is equivalent to one set in S. Let P be the powerset of the union of all sets in S. This set must necessarily have a strictly greater cardinality than any set in S, and so canno...	[ "In mathematics, the cardinality of a set is a measure of the \"number of elements of the set\". For example, the set formula_1 contains 3 elements, and therefore formula_2 has a cardinality of 3. There are two approaches to cardinality – one which compares sets directly using bijections and injections, and another...
Historians, how has studying history affected your understanding of religion?	It has shown me that Robert Orsi is correct. Religion is fundamentally ambivalent. It is a system that can be used for unprecedented evil. It can also be used for unprecedented good. I can only really speak to Christianity, but it holds true for the other religions as well. I spend my time with the more deplorable end...	[ "Historians for centuries focused on the theological developments of their own religious heritage. Social scientists in the 19th century took a strong interest in \"primitive\" and comparative religion. In the 20th century the field focused mostly on theology and on church organization and development. Since the 19...

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