Subset (10)

eli5 · 25k rows

Split (1)

train · 25k rows

query stringlengths 20 300	positive listlengths 1 1	negative listlengths 1 1
the study(ies) that brought the theory of a "wage gap" between men and women into the forefront of modern society and why it is controversial.	[ "The studies that support the wage gap take the total population of women and their wages and compares it to the total population of men and their wages. They are controversial because they do not account for a lot of things. They do not account for different industries paying different wages, different positions ...	[ "I have a question for you. Do you want the version that is super, super long and includes a write-up on what actually went down at Munich, and the subsequent responses back and forth? Or do you want the shorter version that only talks about media coverage of the incident and how it changed things?" ]
why do crows seem to buck their head out when they walk?	[ "Almost all birds have stationary eyes; they cannot move their eyes like humans can to look at something. In order to see anything while walking, instead of just a blur, birds keep their heads stationary and move their body. Then they move their head forward and repeat. It kind of looks like they are bobing their h...	[ "How do you know a year has passed without looking at a calendar? I imagine they sense the temperature/climate changes like anything else." ]
What language has the least overlap of English speakers?	[ "Given the sheer number of languages in the world (around 6000), it's quite difficult to get a handle of even reliable estimates of how many speakers each one has, let alone how l of its speakers also speak a language other than its national language. But there are hundreds of languages across the world in non-Angl...	[ "Forming words and sentences is a different skill set to matching heard words with their translated counterpart. You can hear cheval and connect that with a horse but being able to know you want the word for horse and that the word is cheval is harder. Basically multiple choice being easier versus short answer on ...
Why does everyone hate Obama now?	[ "Most likely because he has went back on what he promised whilst campaigning." ]	[ "Follow up: When did 666 become widely seen as The Devil's Number?" ]
What can be done to make Sears brick and mortar stores live on?	[ "In the present configuration, it can't. There may be an opportunity for a handful of the still-strong stores to emerge again following the impending bankruptcy and, hopefully, selection of new leadership. But whatever that will look like, it will be very different from what Sears was in its heyday or what it is pr...	[ "Discovery Channel, TLC, The History Channel, they started out as niche channels...inexpensive programming aimed at a specific audience it was easier to target ads for. Then came Mythbusters, a big hit that appealed to a broader audience. Soon all the networks wanted to try to reach a wider range of viewers, and ...
Why is a mouse more accurate than a joystick on a controller	[ "Because with a computer mouse you move it exactly X distance on the table so the cursor moves Y distance. With a joystick, you essentially 'toggle' the cursors movement in any given direction, for a certain length of time, until the cursor reaches what you need. It's also less accurate because you're dealing with ...	[ "Mac Pros: relatively malware free, reliable, \"easy\" to use, looks nice Cons: Expensive, closed garden, software limited PC Pros: Inexpensive, infinitely upgradeable, easily modified Cons: Windows is susceptible to malware, bloatware is often preinstalled, hardware isn't \"pretty\"" ]
Do the large genome sizes of organisms like Marbled lungfish, P. Dubium, and P. Japonica provide any sort of evolutionary advantage in and of themselves?	[ "Disclaimer: all of my knowledge comes from genetic algorithms in the realm of computer science, not biology. This argument doesn't seem to apply to biology, as the probabilities of modifying the coding DNA shouldn't decrease, but it's interesting. In computer science genetic algorithms, a lot of noncoding DNA prot...	[ "Sure. Look at (domestic) cats and dogs. They differ physically far more than humans do. If you think that's an unfair example because we've been breeding them for a long time, then look at the eastern gray squirrel. They come in grey and black versions, which vary by location. Here in the Toronto area they are alm...
Can ∞ be used with a point. Like is x.∞ valid?	[ "You are confusing the concept of ∞ with the absolute value of numbers: ∞ is always infinite, any number you can think of is not infinite. You are thinking about a small subset of repeating decimals. it would be : 4.999..., where the ... specify the repeating of the last series of numbers. Or 4.(9), where the numbe...	[ "Because those characters have meaning in the file path: the string used to identify the location of the file. For instance, the file \"data\" in the folder \"2012\" and the file \"2012/data\" would both have file path \"/2012/data\"." ]
If the date we live by is related to religion, why don't all religions live by different dates?	[ "Because it's the calendar of European Business, which is pretty much the standard way of counting dates for all of the world that us descendants or members of cultures that have been conquered/subsumed usually interact with. Started back when Europe started colonizing everywhere and took the Christian calendar wi...	[ "Your employer takes money out of your paycheck throughout the year to pay your local, state, and federal taxes. The amount they take out, however, is just an estimate how much tax you will probably owe at the end of the year. There's no way for the state, local, and federal governments to know what you actually do...
How/Why does Cathodic Protection work?	[ "Think of the cathodic protection system as a battery of sorts, except the electron flow doesn't power anything. The anode used for protection (typically zinc on boats) react more readily than the steel/aluminum hull of the vessel with salt water. The zinc \"eats\" all the free floating electrons the hull reacts wi...	[ "The most common forms of [condensation polymerization](_URL_0_) are polyesters and polyamides. This happens two ways. The first is as an alternating copolymer (ABABAB...) where one monomer has two acids and the other monomer has two alcohols (or in the case of a polyamide, two amines). The second way is a single m...
How did the man-dog relationship developed to what it is right now? Why did we choose dogs to be mankind favorite animal?	[ "Humans and dogs likely coevolved. The modern dog's prehistoric ancestors probably followed around human's prehistoric ancestors to eat scraps left behind. Over time, animals that were more friendly and useful were welcomed into the group, while others were excluded or killed. This would cause evolutionary changes,...	[ "These sort of questions are really hard to answer under the auspices of \"science\". Someone can probably tell you a story based on a sort of \"evolutionary reasoning\" (and these stories are where a lot of evolutionary studies begin), but unless they can cite a serious research program that has investigated this...
Why are some elements referred to as synthetic or artificial?	[ "It's not necessarily impossible for these elements to be created naturally, it's just we have no indication that it's happened. Odds are, some supernova somewhere did create elements heavier than Californium, but all the synthetic elements are unstable enough that we almost certainly wouldn't be able to detect the...	[ "Basically, instead of responding to your argument, I make up an easier argument to fight, pretend that it's what you mean, and respond to that instead. Typically the fake argument (the \"straw man\") is a more extreme version of the original argument, but not always. So if you said something like \"I think we shou...
What was the typical composition of armor units in WW2?	[ "The problem with the Germans was that there was no such thing as typical in reality. The Germans were quite fond of Kampfgruppen which were ad hoc units. A Kampfgruppe was a force put together to accomplish an objective. When the objective was accomplished, or the objective was given up, the Kampfgruppe was disban...	[ "You may be interested in this similar earlier thread. _URL_0_ See responses by Blanglegorph, jonewer and myself. The short answer is that any positions of relative advance (e.g. Rocketry) tended to be out of desperation, whilst Allied advances (e.g. Computers) tended to be more a case of doing things they could af...
What would happen in a pressure chamber divided by a thin sheet, with a vacuum on each side?	[ "The sheet wouldn't split, because there's nothing to fill the gap that would form in the middle of the sheet. As long as you kept the vacuum pressure the same on both sides, there should be no effect on the divider at all. Pressure itself doesn't damage solid objects (like your aluminum sheet), but differences in ...	[ "You seem to be describing a variant of the [ladder paradox](_URL_0_), just using a train and tunnel instead of a ladder and a garage, he he. > What does the outside observer see? The outside observer sees the front guillotine make a cut, then later after the train has passed further through the tunnel, the back g...
How are anti-smoking agencies profitable?	[ "They aren't. They are non-profit institutions. The most famous one, the Truth Initiative was started after the four major tobacco companies were sued by a coalition of 46 states. The settled the lawsuit and had to pay 206 billion dollars over 25 years. About a billion dollars went towards an anti-smoking advocacy ...	[ "In most places, there are few laws regulating what prices a retail store can charge. They charge what the market will bear, and with a captive market it will bear a lot more than normal. Keep in mind that most such shops have a high overhead, since they have to pay special fees to the airport operator to sell in t...
Is that spinning circle of leaves that spins around a few times technically a tornado? Why does it happen?	[ "The way air moves can create a 'vortex' (like water spins as it goes down a plughole) the leaves actually make the vortex seeable. Vortexes of wind happen pretty often." ]	[ "This is a type of helicopter that uses the NOTAR (NO TAil Rotor) system. Inside the tail of the helicopter (where there would normally be a tail rotor) is a fan that creates air pressure that which exits via slots in the tail creating a boundary layer of air. This can change the direction airflow around the tail o...
Are there certain characteristics associated with different blood types?	[ "Some black Africans have variants of the Duffy antigen on their RBCs which can provide some resistance to malaria. I'm not sure about anything that has cancer/cold/flu resistance. If there's something \"special\" about a specific cell, it can only be \"special/resistant\" against something that is designed to inva...	[ "Since this is a homework question, we expect a little more effort from you. What research have you done so far for your paper? What are your findings so far? Is there anything specific you have a question about?" ]
Why do movies with intro-credits spell out the character name of the last person, e.g. 'starring Maffis as the OP' but not the characters of the other actors?	[ "It's called last billing. It's used when you have an actor who is notable enough that they should stand out in the credits, but doesn't have the lead role, which is listed first. Billing order is important. Actors want to be listed first, but if you can't be first, you want to be last. A last-billed actor will be...	[ "When playing Blackjack, there are a set of odds for how much a player can be expected to win based on how the House(the casino) plays and the likelihood of a player getting Blackjack. As the game progresses, more cards are shown, leaving less than a full deck inside. In Blackjack, having a deck full of high cards...
Why is the weight of a molecule in atomic mass units not exactly equal to the sum of the protons and neutrons?	[ "/u/RobusEtCeleritas has a good explanation. It is also important to know that the masses of atoms are measured in amu (atmic mass units), where 1 amu is 1/12 the mass of a carbon 12 atom. This takes into account some of the binding energy that was brought up, but not every atom has the same binding energy per nucl...	[ "Because what's considered \"high amounts\" of things in air is actually quite a tiny amount. For example, pollen count is measured in grains of pollen per cubic meter of air, and the websites that I see to track it have \"very high\" pollen levels at around 10. That's 10 grains of pollen per cubic meter. Hardly so...
why do people in extremely poor countries have children that they will not be able to feed or adequately look after?	[ "The kind of extreme poverty you're talking about is actually pretty rare. Dying of hunger and thirst are usually caused by a period of bad weather, and are in a sense more like localised events than sustained realities of x country. Generally speaking people don't live in places that can't sustain life. /u/the_or...	[ "Hi OP, this is a cultural question, so it would greatly assist anyone considering answering if you could specify which culture you're asking about. For example, the name of a cultural group / country / geographic region, plus a rough time period. Otherwise, this question is simply too broad, as it encompasses almo...
Why did the US/NATO/UN let Saddam Hussein stay in power after the gulf war?	[ "You might be interested in some previous threads on Saddam Hussein being left in power after the first gulf war: * [Why was Saddam Hussein left in charge of Iraq after the Persian Gulf War?](_URL_0_) - 14 comments, over 1 year old. * This thread discusses the issue as a matter of obeying the terms of the UN resolu...	[ "Greetings everyone. In the few minutes this sub has been up, it's attracting sub-standard responses. Just a reminder of a few of the rules: * no responses covering events/conditions post-1994, per this sub's \"20-year rule\" prohibiting discussion of current events * no anecdotes * no speculation OP: your question...
What is the difference between Anglicanism and Catholicism?	[ "The Head of the Church of England is Her Majesty Queen Elizabeth II. The Head of the Catholic Church is His Holiness Pope Francis." ]	[ "_URL_0_ Of all places, this thread has the answer. Their names are long and foreign: they are shortened and localized for ease of use. Mark Antony is probably the single most Anglicized name." ]
Why does standing in the receding water from a wave bury my feet in the sand?	[ "Sand is constantly being moved by wave action. It is pushed up onto the beach when the wave comes in, and pulled back out when the wave recedes. When you stand on it, the waves pushes sand up and, as it can't go under your foot, goes over and around it. However, sand can come out from under your foot. So, when the...	[ "Your glasses either diverge or converge rays of light that are coming in parallel to each other, depending on what they are correcting for. If they converge the rays, just like a [magnifying glass does](_URL_0_) they're casting a shadow because they focus the light into a point. Look at the linked picture of an il...
how does warmth or exercise loosen muscle, tendons, etc?	[ "Exercise generates heat, which makes the liquid between muscles more flowy, so they move more smoothly and more easily against each other. You're basically lubing up your muscle fibers." ]	[ "I'm sorry that I'm no expert, but I remember reading about this the last time a similar question was asked: _URL_0_ Basically, you percieve time faster after your run because of endorphines released during the work out, which means that the music seems slower. This is apparently also why a lot of rock musicians pl...
If the universe is expanding, do planets get smaller the further away they are from where the Big Bang occured?	[ "The Big Bang didn’t happen at a specific place. It was not the explosion of a dense ball into an empty void, it was the transition of the universe from hot and dense everywhere to cool and mostly-empty everywhere. Space itself grew, causing the overall density of the universe to drop." ]	[ "If you have a 30W light bulb right in front of you and a 100W light bulb on the other side of the football field, the 30W bulb will appear much brighter because it's so close. By the time the 100W bulb's light gets to you, it's scattered so much that there's barely anything left to come straight at you. Stars ar...
Why are data transfer speeds on measured in multiples of bits and everywhere else data is measured in multiples of bytes? It's confusing.	[ "For the record, the use of bits per second predates the internet. So anyone who claims marketing is the reason doesn't know much about the history of networking. Basically, bits/second is used because there's only one bit on the wire at a time (at least in serial communication). A byte really only exists on a comp...	[ "Different sensations are carried by different types of nerve fibres in the body. Basically it's like this: there are sensory fibres that tell the brain what your muscles and tendons are up to (called 'Aα' fibres), whether there's vibration ('Aβ'), or pressure / touching and cold ('Aδ'). So-called 'C fibres' mostly...
Why are English language keyboards configured the way they are?	[ "The QWERTY layout was designed for typewriters to minimize the chance of the arms becoming jammed. People learned to type on the layout, and even after typewriters became obsolete, the layout stayed since that's what most people knew." ]	[ "In the 1600s, the K was pronounced. Pilgrims in America said \"kuh-nife\" and \"kuh-nee\" for knife and knee. It died out around then, but spelling had become set, So we kept that." ]
Why do our voices sound differant to everyone else besides us?	[ "Because you hear not only the vibrations of your voice in the air, but also the resonances of your own body, through your bones, sinuses, etc." ]	[ "Anyone feel free to add but according to a PHD in physics: \"They do, and you've just never noticed. But if you have a big enough mirror and can point it toward a radio tower, you can test it out yourself. Point this big mirror at the FM radio tower, and get out a portable FM radio. Now start at the mirror and sta...
Does the expansion of spacetime have an effect on the fundamental forces?	[ "It does, and it is extremely important in cosmology. Basically, the expansion implies a change in the temperature of the content of the Universe. In particular, in the radiation-dominated period of the early Universe, temperature was inversely proportional to the scale factor: aT = constant. The strength of intera...	[ "Any faster than light travel will violate causality. It doesn't matter how you get from A to B, but if you got there faster than it could take light to get there, according to any observer, then that is equivalent to time travel, and you can break causality. I wrong a long comment about this quite a while ago, b...
What happens when a currency 'dies'?	[ "Typically the government prints a new currency, and for a limited-time period, they offer you to exchange the dying currency with the new one. In Zimbabwe's case, they abolished their old currency in 2009 and just started using foreign countries' currencies like US dollars and South African rands. People stopped u...	[ "Usually, lack of interest over time. These kind of projects don't have many funds (even not at all) to promote themselves. People who join don't compensate for the people who left. However most of these projects are still active due to a dedicated community with a lot of computing power - and a good part of them ...
What makes rubber bands "dry out" (become brittle)? Is there a way to make them last longer?	[ "Ozone. Natural rubber is attacked by the trace amounts of ozone in ground-level air, and this turns them brittle. If the rubber band manufacturers included anti-ozonants in their rubber recipe, the bands would last a lot longer. However, rubber bands are made to be cheap, and so no anti-ozonants are added. Anti-o...	[ "Johnny loves math, he's very good at it. But every summer break in between grades, he doesn't practice his math. He does other things like skating, baseball, and playing spin the bottle. No math equations or learning takes place all summer long. When Johnny returns to school, his brain hasn't kept up on math what...
Why can't we use a centrifuge to de-salinate ocean water?	[ "A centrifuge is typically used to separate a heterogeneous mixture of solid and liquid by spinning it. Salt water is a solution, so if it is even possible, I am sure the energy, time and expense are enormous." ]	[ "It's way, way, WAY, too expensive. The power plant alone would probably be more expensive than the entire lifetime cost of an average bulk carrier. Not to mention the insane mess of regulation that is involved with running a nuclear reactor. Basically, big ships run on bunker fuel, and bunker fuel is ludicrously...
Why can extreme couponing exist in America, but not in Europe?	[ "Those extreme coupon shows are highly contrived, and it's a lot more difficult to do than the TV shows make it seem." ]	[ "They don't. It's a marketing ~~lie~~ gimmick. I used to work for a company that did a similar thing by mail. New customers were supposed to sign up by a certain time for special rates but as a specific matter of policy we'd give those rates to anyone who mailed back the special offer." ]
Why is Antarctica setting all time record lows while the North Pole is melting?	[ "No-one knows for sure. There are some [competing (or overlapping) hypotheses](_URL_0_)." ]	[ "If you want a slightly biased but accessible and interesting source for a lot of the factors that have played into this phenomenon, you should check out \"before the flood\" documentary by Nat Geo. It came out pretty recently and is really informative, while being pretty engaging. The best part is that rather than...
Why does the U.S. typically use Blue to indicate the left wing and red to indicate the right wing when the rest of the world seems to do it the other way 'round?	[ "hi! you may be interested in this section of the FAQ (link on sidebar): [Why Red vs. Blue?](_URL_0_)" ]	[ "Get a protractor, tape or glue a straw to the straight edge, and tie a weighed down string to the middle. When you get on the plane, look down the straw at a star that you can easily pick out from the night sky (hope you're travelling at night!) and is viewable from both hemispheres, and mark where the string hang...
If i bark/meow at my cat or dog, do they think of us as a fellow dog or cat? or do they know we don't really do that?	[ "Meowing is not a common form of communication between cats. Mother cats might meow to get the attention of the kittens, but adult cats mainly communicate with each other through body language, hisses and growls. Occasionally outright screaming. Meowing is used mostly to \"communicate\" with people." ]	[ "There is a big difference between mimic a sound and understanding its meaning. Birds have a significant portion of their brain devoted to developing complex songs and sounds. They also have a voice box similar to our own, called a syrinx, that enables them to make these complex sounds. So not only do they have the...
Are there tides underground?	[ "Have a read of [this report, especially the graphs on page 13 and 14](_URL_0_). It shows how the tides [affect](_URL_2_) the water level underground. Essentially with underground wells and groundwater, the water level moves up and down in cycles in much the same way as other large bodies of water like the sea. [Th...	[ "Yes. One famous experiment uses the gravity between metal spheres. _URL_0_ Also, you pull on the earth just as much as the earth pulls on you. It is just that your pull on the earth is hardly sufficient to effect this extremely massive object." ]
Can someone please explain what exactly is happening in this video?	[ "What you're seeing looks like a mud pot, not mud volcano. They're both real things. _URL_0_ > A mudpot — or mud pool — is a sort of acidic hot spring, or fumarole, with limited water. It usually takes the form of a pool of bubbling mud. The acid and microorganisms decompose surrounding rock into clay and mud. Ed...	[ "In simple terms, most circuits that make sound or play back digitally recorded sounds use a timing circuit (like an oscillator) to send out the sound waves at a constant rate. More expensive toys will use crystal-based oscillators and low-battery cutoff circuits to keep things from getting funky as the power level...
When a circular membrane - a drum - is struck, how many modes become excited?	[ "Making some simplifying assumptions (eg friction doesn't exist)... yes, all of them become excited. This is true for 1D strings too, not just for circular membranes. To illustrate, let's model a \"pluck\" of a string as meaning that at t=0, the string at rest but is deformed into a perfect triangle shape. Then we ...	[ "The SEIR model is one way of projecting how many individuals in a population are Susceptible Exposed Infected and Recovered when considering an epidemic that allows an infected individual to immediately transfer the parasite to another individual. Some parasites have latency periods where an indiv...
How can a star emit light at minus degree temperatures ( C )?	[ "The fact that in Celsius scale the temperature is negative has no effect on the light. In fact, the [cosmic microwave background](_URL_0_), the oldest light in the universe, has a color temperature of 2.72K (that's -270.45 degrees Celsius), meaning that a pefect black body emitting that radiation would have that t...	[ "Binding energy from the nuclei. Binding energy is negative. In proton-proton fusion p + p - > d + e + ν_e, the mass of the products (deuterium + electron, neutrino is basically massless) is lower than the sum of the masses of the reagents by 0.42 MeV - remember that mass equals the internal energy (that's what E=m...
Why do humans get goose bumps when they see scary-looking bugs?	[ "Two things - Goosebumps when cold was a physiological trait that created more insulation - which is useless to us now, we dont have enough hair. When threatened - it increased our size AND gave indication to the opposing threat that we were indeed threatened. ( like a dogs hair standing on end)" ]	[ "Your understanding of how heat work in atomic level is correct. But when you have bunch of atoms together, you will get a slightly different thing that react to heat differently. Your skin is made up of many big molecules (molecules= many atoms bonded together into one thing), and they need to be in a very specifi...
How is energy concerved when light bends around large gravitational bodies?	[ "Your question does not have to be specific to light. In your diagram, the light could just as well be a bullet. In either case energy/momentum is conserved by Newton's 3rd law: the large mass feels an equal and opposite force that the photon/bullet feels. The large mass exerts a gravitational pull on the photon/bu...	[ "By measuring the wavelength of light arriving from different stars and galaxies we can determine whether they are moving towards us or away from us and how fast. Taking measurements of lots of them we can construct a model showing the overall trend, which appears to show the universe expanding outwards." ]
- How does chemotherapy work?	[ "There's a lot of different kinds of chemo these days, but usually the agents target rapidly diving cells. The faster a cell divides, the better the chemo kills them. This causes a lot of problems with side effects as there are a lot of rapidly diving cells in your body that are not cancer (such as your hair follic...	[ "It basically has a list, if it doesnt have the answer, it asks other dns servers untill one does, or it figures out that the server doesnt exist" ]
Why are Herbs tasty? No plant benefit...	[ "> My question is to whether the plants evolution did this intentionally It should probably be noted that neither plants, nor evolution possess the capability for intention :)" ]	[ "Surface area difference of food to taste buds/nasal passages. Sipping a drink versus chugging a drink makes for very different tasting experiences." ]
Why do countries need a gold reserve? For instance, america seems to have 8k tons of gold. When would they ever need to use it? Also, do they gradually buy and sell it?	[ "They no longer need gold reserves. Countries having them was a hold over from when countries used the gold Standard to back their currency. No country currently uses the gold standard so all gold reserves are just a point of investment now." ]	[ "Advertising. Companies spend billions of dollars to instill that \"need to buy something\" in you, by bombarding you with messages (both overt and subtle) telling you that your value as a person is tied to owning things or \"treating yourself\". > Buy this $499 barbecue grill and be the envy of your neighbours! W...
Why does Major League Baseball not make the World Series a true World Series by allowing international teams to compete?	[ "That's what the [World Baseball Classi](_URL_0_)c is for." ]	[ "National radio stations' content has to be rebroadcast by local stations. Local stations sell advertising and just broadcast that during commercial breaks the national broadcast contains. It's similar to how you can watch Jeopardy (a national broadcast program) and still see an ad for a local restaurant." ]
Where did all the bugs go?	[ "Most of this year's individuals die, and the \"next\" generation overwinters. Lots of variation, however. Many solitary bees overwinter as mated females. Social bee like honey bees overwinter as a whole, smaller colony with their queen. Many ants do the same. Some flies overwinter as pupae, some as larvae, some ev...	[ "What about a fly buzzing around? They're not attached to the bus so therefore don't benefit from the momentum of the moving vehicle so why don't they splat into the back of the bus?" ]
Why can our eyes only see visible light?	[ "You have it a little backwards. We only label a portion of the spectrum as \"visible\" because that's what our eye-meat can see. There is light above and below what we see and that light is the same as what we do see except a little more or a little less wavelength. The spectrum we see began with ocean dwelling o...	[ "There are none, we have mapped every frequency in our visual range." ]
I encrypt a message with keyA, then with keyB. Is there now a keyC that could decrypt the message in one go, instead of using keyB and keyA?	[ "It depends on the encryption scheme used. In the simplest scheme, the one time pad XORed with the plaintext, the answer is yes. XOR is associative so ciphertext = key_A XOR (key_B XOR plaintext) = (key_A XOR key_B) XOR plaintext. So the expression (key_A XOR key_B) becomes the new effective key. However in most ot...	[ "Logarithms are a way of summarizing how big a number is. I'm pretty sure you already know an easy way of summarizing how big a number is: you just count the digits. You're doing this whenever you talk about \"earning six figures.\" But $120,000 isn't the same size as $800,000, is it? It'd be nice to have a way of ...
Nitrogen Decompression Sickness (DCS), more commonly known as 'the bends'.	[ "At higher external pressures, more gas gets dissolved in your blood, as dissolved gas takes up less space than gaseous gas. Gas dissolved in blood transports to the other cells of your body. Most of this is N2 so thats what mostly dissolves. Go up and reduce pressure and this nitrogen bubbles out of your blood ag...	[ "Visual cues, basically. Check out this [description](_URL_0_) by astronaut Scott Kelly, who spent almost a year on the ISS: > I would wake up convinced that I was upside down, because in the dark and without gravity, my inner ear took a random guess as to how my body was positioned in the small space. When I turn...
Why do dogs hump human beings even though they know they are not dogs? Why do other mammals not hump the way dogs hump?	[ "Humping is a show of dominance in the dog world. Don't let your dog hump you, you hump him. It'll learn really quickly who is in charge." ]	[ "By response of said stimuli. When it goes too far a, say, kitten will signal it with body language and sound. And their partner will respond by licking the damaged area and going on a little less violently. If you have a kitten at home you can easily try this. If your kitten scratches or bites too hard, let out a...
Why does an automobile depreciate in value the minute you drive off the lot?	[ "Let's say a brand new Ford Focus costs $16,000. Would you be willing to pay $16,000 for a Focus that someone bought, drove around for a little bit, and then returned for some reason. The average consumer is always going to choose the new car over the slightly used car, so dealerships are going to have to offer th...	[ "commercialism. if you were happy with your old stuff, you wouldn't need to buy new stuff. all the designers and manufacturers come out with new looking stuff and market the old stuff as ugly and new stuff as pretty in order to make money. our tastes are hugely influenced by others." ]
Why are isotopes with a large number of neutrons unstable?	[ "Check out the [Semi-Empirical Mass Formula.](_URL_1_), specifically the equation for binding energy. It shows that there are many factors in determining nuclear stability, specifically volume, surface area, coulomb repulsion, symmetry, and pairing. The article does a better job explaining each than I would so I'll...	[ "I don't have your exact answer but a relevant fact: nuke plants are considered slow to start and stop, and are therefore treated as part of the baseload (left on for long periods of time), while other types of plants (such as natural gas, hydroelectric) are pretty quick to adjust and are used for most adjustments....
What difference between an elephants brain and a humans that allows humans to have complicated, advanced, abstract thought and imagination?	[ "A follow up question: Is it possible that they are potentially as smart as we are, but the lack of hands, appropriate communication (etc.) limits their ability to develop their potential?" ]	[ "Ask Reddit is for personal opinions, stories, and the like. Essentially subjective answers to questions without hard answers. Something like \"whats your favorite food\" is a good post there ELI5 is for getting a simplified answer or explanation to a question that you don't understand. A good thread here would som...
What would happen if u aimed the barrels of two guns directly against each other and pulled the triggers at exactly the same time?	[ "How far apart are they? if they are a modest distance a part, the bullets would collide (assuming everything is identical between the guns and the ammo used) in the middle either causing them to fall where they impact or more likely ricochet in some unknown direction due to minor flaws in each. If the barrels are ...	[ "You actually still can. It's called [check kiting](_URL_2_) and it's super illegal, you will get caught, blah blah, disclaimer. Get three separate checking accounts. Write a check from account 1 to account 2 for whatever you would like. Go to bank 2 and cash it. Now you can either run like the full force of the FB...
How do hospitals stay bug-free?	[ "Mosquito and flies like damp and warm environments. Hospitals, do their best to keep their environment dry and cool/freezing. Compared to the inside of a hospital, the incests prefer the garden outside where it is warmer, more wet. Nothing magical here." ]	[ "To piggyback on this. I've always wondered if it all goes through some type of decontamination process of some sort....?" ]
Why can't we create underwater breathing technology	[ "We are endothermic and have a high metabolic requirement--one that is further stressed when we are submerged. Animals with gills, on the other hand, are almost exclusively poikilothermic and require much less oxygen. For us, the challenge is getting enough oxygen from the water to sustain our metabolism." ]	[ "Actually it is being worked on presently, maybe you've heard of stem cell research? Same principle, but usually grown outside the body (currently), however there is a lot of talk about using straight injections for some issues, with spinal paralysis being a big one." ]
how do computers tell time?	[ "They don't really \"tell\" it, they're just given it or get it from the internet and then keep track of it. Computers use a quartz crystal to keep time, as do almost all watches. The main element in quartz crystal, called silicon dioxide, has a piezoelectric potential which means when heat, pressure or any type o...	[ "It uses lovely old GMT. Greenwich Meantime, also called UTC by traitorous colonials." ]
Why is it that lakes and the ocean seems to calm and be "still like glass" towards and through the night?	[ "There is a wind effect. Land will start warming as the sun rises. So the air above it rises. This means a wind toward the land from water. As the sun sets it ceases to heat the land. So this warming land wind effect ends. No wind means it is still." ]	[ "Your eyes work by constantly producing chemicals that is broken down by light. By measuring how much chemicals is in your vision cells you can find out how much light they receive. When it is light there is very little chemicals present and when it is dark there is lots of chemicals. However it takes your cells ab...
Do different salts in water have different electrical conductivity?	[ "Yes, salts are comprised of different ions with different mobilities. Larger ions move slower for a given field so the conductivity is lower. Salts also have different formula units, so a mole of sodium chloride will have fewer ions than a mole of sodium carbonate." ]	[ "It's called the oligodynamic effect. Here you can read about it, but usually it's pretty easy to google these types of questions: _URL_0_ Apparently several heavy metals do it including copper (Brass is an alloy of copper) and silver. Basically heavy metal ions bond with bits of proteins in bacteria and make them ...
Why do the fastest runners tend to be black?	[ "A couple of speculative answers, in addition to /u/MrAloha808's point. \"Black\" and \"White\" aren't really groups, as there's as much variation between as there is within. Nonetheless people with black skin outnumber people with white skin, so their best runners are recruited from a larger population. Also, if y...	[ "\"Just about everyone here\" Where is \"here\" for you? It sounds like your question's premise is based on a small sample set based on personal observation. Before your question is addressed, you should be making sure the premise is valid..." ]
Is light mass-less? (other Qs)	[ "Light is generally thought to be massless. If a photon does have mass, [it must be less than 10^-54 kg](_URL_0_) (an electron is 10^-31 , for comparison) in order to be consistent with with experimental observations." ]	[ "How long an explanation do you want? The first thing to note is that massless particles do not have a rest frame. By definition massless particles move at c in any inertial frame, so there is a clear contradiction if you try to construct one with a massless particle at rest. There is also a geometric explanation w...
Why is it legal for states to ban gay marriage if church and state are separated?	[ "Sure, religion accounts for the opposition to gay marriage. But the government can define marriage (the legal contract) however it wants. In some states the government defines marriage as something that must include a man and a woman. Its like how most government offices are closed on Sundays. It's because church ...	[ "Governments give tax breaks and subsidies to corporations to lure them in to their area. The idea is that bringing that business to the area will, ultimately, bring more business and jobs to the area which, theoretically, will bring jobs to the locals and more tax revenue for the government. Again, theoretically, ...
Where do we get the "every dollar we spend on space, the U.S. economy receives $8 of economic benefit" data?	[ "This was asked before, but the data was used irresponsibly. It said for every dollar spent in R & D, you would expect to see around $8 of ROI. They took this and specialized it to space research without any thought of how space would be profitable." ]	[ "Most of the time the people who go to these places are either already successful or some kind of athlete. The majority of the people you are talking about already have a lot of money to finance these trips. The alternative is usually some kind of athlete like the ones you see on YouTube doing extreme sports (base ...
A question about thermodynamics and refrigerators.	[ "I can't imagine you have any cool air left in the refrigerator after you're finished putting everything away either way. I could figure it out, but I'm going to take a guess instead: depending on the type of refrigerator you have, all the air could escape in a matter of 5-20 seconds. It's probably more likely that...	[ "We're still pretty far off, we don't even completely understand how superconductors that operate above 30K work. The applications of room temperature superconductors are extremely broad, a few examples would be loseless power transmission, smaller and less expensive MRI machines and integrated circuits that genera...
Why do we use the term 'sister' to describe things that are close together? Sister species, sister companies, etc.	[ "It has to do with the terms used in a phylogenetic tree and direct lineage. Think for a moment about siblings and sexual reproduction. As you know males are XY in their sex chromosome and females are XX. In terms of the mom (the main store) the one X is ALWAYS conserved (in the case of a male) or both conserved (i...	[ "It depends on the aerodynamics of the cars involved. Pull your minivan a couple car lengths behind a semi-trailer, you'll feel the drafting effect. If you have two fast cars with good aerodynamic coefficients, you need to be less than a foot apart." ]
Is there a scent that distinguishes all (or most) female mammals from males? Can animals tell the difference between females and males of other species?	[ "Although no proper scientific studies were made, anecdotally it was observed amongst transgender patients who were subjected to extended periods of hormonal treatment that animals categorically treat them different, including pets that are hostile towards a certain sex no longer recognising the person as hostile a...	[ "With things like cosmetics & hygeine products, we've already done an absolute shitload of testing & know which ingredients are safe. There's just not a lot of reason to test a slightly blend of ingredients X, Y & Z when you've already been selling XYZ for 20 years. Not only does it sound good, it saves you a bunch...
On a cellular level, what causes a sore throat?	[ "First read about [pharyngitis](_URL_1_). Then read about this [inflammation](_URL_0_). Then ask any questions you have. I don't mean to sound condescending but watching the episode of The Magic School Bus where they go inside Ralphie when he is sick will really help visualize everything. [link](_URL_2_)" ]	[ "Most phones are capable of talking to other carriers that use the same networking technology. For example, in the USA, AT & T T-Mobile and I think a couple others all use the same GSM system. However, if you buy a phone through one of those carriers, they put a piece of software in place that checks who you're ...
Is there a correlation between the average number of cells per individual in a species and that species’s cancer risk?	[ "Elephants rarely get cancer. There are many mechanics that protect the integrity of DNA and many more that destroy curupted cells. The likelihood of a species \"getting cancer\" is more directly a factor of the effectiveness of these mechanics than its overall cell count." ]	[ "Basically no - cells need so many different nutrients that it would never be cheaper than just burning the sugary fuel or reacting it in some kind of fuel cell. Though I think it would be interesting to design an electric eel so that the stacked cell membranes of its electric organ preferentially pass different is...
whenever a Championship/Playoffs Series goes to Game 7 (World Series, Stanley Cup, etc.) and both teams now have a shot at winning the Series, what happens to the losing teams "champs" gear?	[ "It is typically donated to the needy in a place that has never heard of the sport. In some distant corner of the word, there is a group of people who think the Buffalo Bills had the greatest football dynasty ever." ]	[ "The US Army did not. (as in, going back and studying the conflict and its lessons.) However, the US Marine Corps did and it was these experiences in counterinsurgency which built the foundation for the several experiments of proper counterinsurgency that was done through the USMC in the Vietnam War. For example, t...
Why do some mammals regularily produce more than one offspring per pregnancy?	[ "There is a trade-off between producing more offspring and their ability to survive to adulthood. If conditions are good (abundant food, few predators, etc.) for the length of the rearing period, and multiple births are physiologically possible for a species, evolution should favor more offspring since it allows fo...	[ "It's similar to the way 125% subprime mortgages spread (without getting into the debate about whether that caused the recession) - you get a few groups who think a similar way, with broadly the same ideas, motivations, worldview, that sort of thing, and when one of them comes up with a policy that fits those ways ...
At the Panama Canal, why is the sea level for the Pacific Ocean 8 inches higher than the Atlantic Ocean?	[ "That explanation is half right. The difference is due to density differences (the Pacific is less dense than the Atlantic) as well as the different ways water is piled up on the Pacific side vs. the Atlantic by prevailing currents (I guess this is what was meant by \"weather\"?). Source: _URL_3_ Prevailing ocean ...	[ "From the exact same XKCD article that you linked: > (Climates can be hard to predict—for example, in our world, Somalia and French Guiana both sit on the equator, at the eastern coast of a continent, and seem like they should both receive a tropical sea breeze. But coastal French Guiana is dense rain forest while...
Why build streetcars/trolleys when busses work fine?	[ "In addition to what Teekno says, developers like streetcars and subways better than bus routes. Developers take public transportation into account before investing in building a new project. A bus line can be moved on a whim, so they are less sure it'll be there. A subway or streetcar line will not be moved easily...	[ "[The Straight Dope covered this](_URL_0_). Basically, they started out as being made by two different production teams, but after a certain point, they became essentially interchangeable, but they kept both names going." ]
Are metals thermally conductive for the same reason that they’re electrically conductive?	[ "Yes, free electrons in metals act as both thermal carriers and electrical carriers. This is the basic principle behind things like the Wiedemann–Franz law." ]	[ "The coffee with two scoops will cool faster, and it has nothing to do with color. Water has higher heat capacity than coffee, which means that the higher relative water content, the more heat it needs to lose for it to decrease in temperature. _URL_0_" ]
The height of the average American male has risen roughly 3 inches in the past 200 years. Is this an example of evolution, coincidence, or something else?	[ "It is probably due to better nutrition. People are more likely to reach their genetic potential." ]	[ "The popularity of comic book characters and acceptance of the geek subculture, mainly. people aren't scared to show that they enjoy these things anymore." ]
Is there a way to quantify the amount of life it took for a given source of fossil fuel expenditure? I.E. It took a Tyrannosaurus Rex worth of oil to get to work today.	[ "> A staggering 98 tons of prehistoric, buried plant material – that's 196,000 pounds – is required to produce each gallon of gasoline we burn in our cars, SUVs, trucks and other vehicles, according to a study conducted at the University of Utah. [Source (unsure on legitimacy)](_URL_0_) That is a fucking shit-ton ...	[ "To make a movie of a thing, you just point a movie camera at it and shoot. Say it's cars driving across a bridge. You start the camera. It takes 24 frames per second. You stop the camera. You're pretty much done. You have a minute's footage of cars on a bridge. 1,440 frames. Now you need a giant robot destroying ...
If "cancer" is nothing but the body's cells multiplying, can "cancer" be used to grow new body parts?	[ "You cannot do this with cancer, unfortunately, but you're on the right track to learning about a different phenomenon: stem cells. In a nutshell, like cancer cells, stem cells have the ability to differentiate into different types of tissue and (potentially) regenerate completely new tissue. Only, unlike cancer (w...	[ "So you're in a war against an alien enemy you've never seen before. A scout party (Dendritic Cells) manages to destroy one and yanks off a piece of their armor (Antigen). They report back to their base (Lymph Nodes) to show (present) this piece of armor to everyone and to see if anyone has any answers on how to de...
When people randomly call you up from overseas trying to get your credit card details or identification through a scam: What exactly is their job and how do they get hired?	[ "... It's not a company, it's a person. Or maybe a collective of people with the same goal." ]	[ "It is not the number to the police station. It is the number of the emergency call center. The local phone company knows where your phone is and what ECC serves that area. When you dial 911, they route your call to that location. You can get police, fire, and other emergency services by talking to a trained operat...
how does the moon control the tides?	[ "The moon is really heavy. So heavy, in fact, that its gravity pulls the water on Earth closer to it. On a cosmic scale, the effect is tiny: A fraction of a fraction of a percent of the distance between Earth and the Moon. But that fraction is pretty big on our scale, so the water being pulled towards the Moon move...	[ "That depends on the construction of your balance. Normally, you would want the pivot point for a balance to be above the center of mass. If you tilt the balance (with equal weights on both sides), you shift the center of mass away from the line going down from the pivot point. Gravity then takes care to bring it b...
I'm 27 and I'm starting to notice something. Are adults looking and acting younger? Or is it my perspective on age that's changing?	[ "I think it's the fact that you're aging. I'm in my early 40's and I see little kids driving cars and working, having spouses and even babies! Little kids I say. The \"hot\" young guys look like potentially hot men. I don't look at them and think, \"Hmm, I could eat him up.\" Instead, I think he will be a good lo...	[ "Bigger, because a) the Universe is expanding, and b) as time goes on, light travels farther so there are more parts we can have observed. BUT, it turns out that if you factor out the expansion - i.e., if you just consider whether we can see more or less stuff over time - it turns out that the bit of Universe we ...
If a movie production has $5,000,000 (estimated) Budget, must some of that money go to the actors? or only movie's production quality?	[ "It has to include equipment, pay for employees (all cast, crew, and extras), fees, food on larger productions, constryucting sets, making costume,s all of the makeup artists, set design, sound guy, camera guy, lighting guy, dozens of other specific jobs, and yes, the actors." ]	[ "It kind of does. Picture and sound are actually recorded quiet separately. Usually they're literally recorded separately — using separate machines — but sometimes they're recorded in the camera but using separate recording mechanisms. What matters is just that picture and sound end up synchronized. The fundame...
When the bourgeois and proletariat were fighting, did they call themselves that, and what did they point at in history to sway arguments?	[ "A fight between the Bourgeois and Proletariat is primarily associated with Marxist philosophy. This didn't really occur during the French revolution. In the traditional Marxist historiographical view, the French revolution was primarily a fight between the Bourgeoisie and the Aristocrats, with the Bourgeois throwi...	[ "\"Democrats\" and \"Republicans\" are just labels, there is no hard definition on the party platform that each party must abide by. Each party's platform changes depending on major issue of the time and sometimes there are major shifts within the party (look up \"realignment election\"). [See the FAQ page on this ...
What is a "flat universe"?	[ "A flat universe is an universe that at large scales has zero spatial curvature. It doesn't mean that the universe is two-dimensional, but rather that its geometry is Euclidean: parallel lines don't cross, the Pythagorean theorem works, and the sum of the angles of a triangle is 180º." ]	[ "Imagine you draw a bunch of dots pretty close to each other on the surface of a deflated balloon. Then blow it up. The dots are much bigger and farther apart." ]
Is it possible to outrun a lightning bolt?	[ "Sure if you can run at 3700 miles per second." ]	[ "I have nothing useful except that this is one of those questions that's both original, interesting and testable without expensive equipment. Makes my high school teacher's heart beat faster. This is a perfect end-of-year question to engage my 15-year old pupils with. It'll be great fun to have them try to answer w...
if all the countries are in debt, who do we actually owe the money to?	[ "Most of the debt is owed to people and companies within the country and companies overseas." ]	[ "This CGP Grey video does a really good job of explaining it all. _URL_3_" ]
Airports and airlines? Does a city own an airport and rent tarmac space to airlines? Or is it a private company that does the same? Or something totally different?	[ "Some are publicly owned, others privately, others are public-private partnerships or government-created corporations. Generally speaking, commercial airports sell \"landing slots\", in other words they'll charge ABC Airlines a certain amount of money for the right to land one plane between 12:30 and 12:31 every da...	[ "How do we continue to slowly get smaller and smaller architecture in processors? I guess I am trying to understand what limits the shrinking of architexture. Essentially, why cant architexture rapidly decrease in size faster than Moores law predicted? Sorry, if this is a super complicated answer, I just always hav...
why is cereal (and dried milk) so hard to clean off a bowl if you let it dry?	[ "It's mostly the dried milk to blame. Milk is full of dissolved protein, the same sorts of molecule found in eggs and meat. Dried protein makes a very good glue, and once it's dried it's very difficult to re\\-wet and remove. If you just ate the cereal with water \$an unpleasant thought\$ and let it dry, then you...	[ "This is called the [Cheerios Effect](_URL_1_). I find this amusing. Basically, when something is floating in a liquid, a [meniscus](_URL_0_) forms around it. (In the case of the bubbles, it's a concave meniscus.) Since the bubbles float, they want to be at the highest point achievable on the surface of the liquid,...
Can I get intoxicated by smelling alcohol?	[ "Yes, and no, sort of. Since smelling is the act of collecting physical molecules of a substance in your nose you will inevitably get some of it in your respiratory system where it will end up absorbed and in your blood stream. It's actually this method that some people are exploiting when [alcohol vapor is inhaled...	[ "I have no idea about the actual air saturation, but the skunk's spray is composed of chemicals known as mercaptans (thiols) that can be detected by humans at really low concentrations (i.e., 10 parts per billion)." ]
Why is the NRA so powerful?	[ "Any special-interest group (e.g. National Rifle Association (NRA), National Organization for Women (NOW), United Auto Workers (UAW)) gains power from membership. The more members an organization has, the more money it has to promote its cause and the more voting power it can wield at the ballot." ]	[ "They don't. It's a marketing ~~lie~~ gimmick. I used to work for a company that did a similar thing by mail. New customers were supposed to sign up by a certain time for special rates but as a specific matter of policy we'd give those rates to anyone who mailed back the special offer." ]
Why do some spicy foods stay in your mouth while others are only spicy til you swallow?	[ "Food, like anything, is made of chemicals. The chemicals that are called spicy all have to touch cells in your mouth or nose for you to notice them. Some chemicals are called \"volatile\", which means they have an easy time getting into the air and staying there. Some chemicals are called \"pungent\", which means ...	[ "When you blow to cool things down part of the air comes from your lungs, but a greater part is pulled from the surrounding air by the vacuum you create blowing. When you blow to heat something up you get much closer and try to minimize the surrounding air. There is a good video I will try to find asking people how...
What happens to the people that were on their way (in the air) to the US from one of the now banned countries? Do we get a situation like Tom Hanks in "The Terminal"?	[ "That is exactly what's happening right now. There's a protest a JFK to release the people who are being detained for coming over." ]	[ "Kind of like if you're looking through some legos for a number of different parts, you usually come across one that you need so your search goes quickly until there's one last part you need. It might take you awhile to find that last specific part. That explanation is probably wrong but that's what I would say to...
How do we know for certain that the observable universe is almost entirely matter, and not partially antimatter?	[ "Intergalactic space isn't exactly empty. It's filled with incredibly sparse gas and dust etc. At the boundaries between matter and antimatter galaxies (or galaxy clusters or even bigger structures) there should be enough annihilation events to produce a tell-tale gamma-ray signal, which is not observed. In additio...	[ "By measuring it. There are so many contributing measurements that it is difficult to list them all in a reddit comment. [Wikipedia has an article](_URL_1_). The small uncertainty is simply a result of very precise measurements." ]
Why are curse words censored?	[ "Curse words are censored in order to make the show more appealing to a wider audience, which in turn makes these shows more appealing for advertising. Some people find curse words to be upsetting or they don’t want their kids hearing them. As for how curse words came about I’m not sure how they originated." ]	[ "To make it cheaper. Simply put we don't pay anywhere near enough to pay for the shows we watch" ]
How does plasma work?	[ "A plasma is a gas that is ionised, where some of the electrons leave the atoms resulting in a mixture of positively charged ions and negatively charged electrons. Because a plasma now is composed of charged particles it behaves very different to a regular gas. It becomes electrically conductive, reacts to external...	[ "Pictures on TV screens and computer screens are made from a whole bunch of teeny-tiny dots of lots of different colours. More dots, all jammed really, really close together, means the picture looks better. 'Cause the dots are less noticeable. And there's way more details. That's hi-def. More dots." ]
I've got a social anxiety about eating in front of certain people. What would cause an odd social anxiety like that to develop, and what can be done to get rid of it?	[ "Important: Go to a professional. There are people who help solve problems like this for a living. The most effective treatment is often a combination of medication and therapy, but in the end it's your call. There's been a fair bit of research into social anxiety, but the very nature of the condition makes it har...	[ "Because of how we hear our own voice is actually not like how others hear your voice. Your voice sounds different to you than to others. The voice originates in you and the sound going out from your mouth doesn't go straight to your ears, but by bouncing a lot. Not all sound actually goes out of your mouth, it als...
Why is mercury so dangerous?	[ "Mercury replaces calcium, sodium, and iodine in body chemistry, disrupting the workings of these dependent bodily functions. For example, your thyroid will absorb mercury instead of iodine, it will disrupt your immune system functions. Your body uses calcium and sodium to transfer oxygen through cell membranes, me...	[ "Large areas are covered with lead paint, often where there's lots of casual contact and rubbing off onto people. As lead paint ages, it crumbles into flakes (sometime very tiny) and even rubs off as powdered lead, which is easily eaten or inhaled. Most people don't come into direct contact with lead in solder sinc...
Why there are "big" cats but not big dogs.	[ "Because [large wolves](_URL_0_) died out, either due to climate changes at the end of the ice age or human eradication." ]	[ "The size of cerebral cortex matters - that's the surface of your brain. Humans have the most brain folds, largest brain surface and therefore the highest intelligence." ]
How does a vending machines verify a dollar bill vs. counterfeit?	[ "Vending machines use several mechanisms to scan bills and weed out counterfeits, but for smaller bills (1s and 5s) few counterfeiters will bother with using magnetic ink because its expensive and would cut into their margins. Vending machines then detect that the bill doesn't contain the magnetic ink and rejects i...	[ "They're either on a timer or on a sensor. Ever approach an intersection and see vertical and horizontal cuts in the pavement? That's where workers buried the sensors. Those work by detecting metal, not the weight of the vehicle." ]
What is the difference between real power, complex, average, reactive, and apparent power?	[ "Also, power is commonly used to describe electricity, which is AC in the United States. Because the current is a wave function, the power changes with time at the frequency of the wave function, which is 60 Hz in the US. That's why it's typically described in terms of average power. There's a pretty good summary o...	[ "Say you live in the US. You make $100,000 a year. Now say you live in China, but you make $50,000 a year. You could say that the person living in the US is twice as rich as the Chinese person in absolute terms. But consider that lunch (a sandwich) costs $10 in the USA. It costs $1 in China. So an American can buy ...
Do we know anything of large scale Native American battles in the pre-Columbian era?	[ "For clarification: are you asking about what battle strategies/tactics were like, or are you asking if we know pre-Colombian American war history (what battles were fought between whom, when, etc.)?" ]	[ "There's room for discussion, perhaps the section [Natural Disasters](_URL_0_) from our FAQ will answer your inquiry. You might also be interested in this [NPR article](_URL_1_) on how Kiowa recorded events like tornadoes." ]

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