Subset (10)

eli5 · 25k rows

Split (1)

train · 25k rows

query stringlengths 20 300	positive listlengths 1 1	negative listlengths 1 1
Why is 10000 steps a day the magic number?	[ "> Is it just because it's a round number? You got it. There is nothing special about that number, because the benefit of the \"steps\" vary wildly across individuals. They picked a number that was high enough to have a benefit, and round enough to be remembered and repeated." ]	[ "It is hard to start a motor, it would take a long long time to start on low. Going 0 3 2 1 let's the fan start on High which gets it up to speed in a timely manner" ]
A question about Titanic's water-tight bulkheads.	[ "Think of it as an open window between the two compartments. I am fairly sure there was literally an open space allowing water to pass through." ]	[ "As a footnote to this podcast: in between recording this podcast and now, I read John Brook's The Battle of Jutland. In this, Brooks casts doubt on the story about Room 40 I repeat in the podcast. Apparently, the German messages giving the British information on German plans weren't broken until after the messag...
when a police officer commits a crime why is the police department in charge of the investigation?	[ "there is a division in law enforcement specifically for this. It's called internal affairs." ]	[ "A correlation in statistics becomes a causation when you can find a theory that accurately describes a link between the two. Ice-cream sales and drownings are correlated but there is no causation. The thing that causes the correlation is that people swim more and eat more ice-cream in summer. Drinking and driving ...
how does gravity work?	[ "You might be interested in the responses [here](_URL_0_), where this question was asked 50 minutes ago." ]	[ "i just drop like a sack of potatoes. So if there is such a mechanism i want to ask the follow up question why mine doesn't work?" ]
Why does American Baseball have a "world series " when its only americans participating?	[ "It wasn't only Americans when the Toronto Blue Jays were contenders..." ]	[ "Article III, Section 2 of the US constitution says that states or citizens can sue foreign governments in the US Supreme Court. It's one of the very few cases where the Supreme Court has original jurisdiction. And sure, they could just not show up -- the same way you could choose not to show up if you were sued. B...
64 and 32 bit, and the differences?	[ "32 or 64 Bit describes the length of numbers in binary the processor calculates with, which means there's a maximum number the processor can handle. For 32 Bit that is 2^32 - 1 so about 4 billion. 64 bit means bigger numbers, bigger calculations. 64 Bit can handle 2^64 - 1, which is 9,223,372,036,854,775,807. But ...	[ "Up until recently, Android devices didn't employ [TRIM] (_URL_0_), reducing performance over time as \"fresh\" blocks in the flash drive became rarer and rarer. That's one specific example of an effect that could reduce performance over time. The other posters are correct in that 95% of the time, it's because the ...
what is the reason for the surge in superhero movies that have been released recently?	[ "Hollywood chases success. Spiderman and the X-Men were big hits ~15 years ago due to their mainstream appeal and their built-in fanbase of comic nerds. Comic book movies became much more frequent then, and the trend took a huge uptick when Marvel started it's cinematic universe. The MCU films and their continuous,...	[ "Data. Pure, gooey, delicious data. Seriously though - the Airlines are collecting data on a massive scale. If they notice an uptick in travel to/from one city they will use that information to update how their resources are distributed." ]
My grandfather always told me that during WW2 the grand majority of soldiers on both sides during battle would pretend to fight by purposefully misfiring or purposefully not shooting a fatal area, how true is this?	[ "How true? \"Very controversial at best\" I would say. I've written on this some time ago, which can be found [here](_URL_0_)." ]	[ "Muskets generally did not have a flared mussle. A Blunderbuss was a rudimentary shotgun, it could be loaded with anything from pellets, nails, or whatever shrapnel was around. The flare helps increase the spread to cover a wide area. The weapons are already inaccurate as hell, so it woud benefit the attacker to be...
Why does China feel the need to censor the internet?	[ "The CCP is ultra sensitive to criticism and the power of technology to cause disruption. They pragmatically understand that they need to keep a lid on dissent. The lesson they learned form Tiananmen Square was that free association and unfettered access to information would be bad for their regime - and in their v...	[ "I'm a journalist. I can tell you straight up : it's for audience. These videos create shock, which is the best hook television news has over the viewer. The whole ethics speech they'll give you about people having the right to see it is BS. Television is a business, news or not, sadly. This is even more true in th...
Why are roof shingles so small?	[ "A larger tile is going to be subject to a lot more force from wind. It would need to be thicker to avoid breaking if wind gets under it. It also takes more to hold it in place. When it does get damaged, it's more expensive to replace a large tile than a small one." ]	[ "There are authors who claim the practice began during the colonial period as an early \"mens\"/ \"ladies\" designation for an illiterate populace (the sun and moon being popular symbols for the genders during those times). The book : The Little Red Schoolhouse: A Sketchbook of Early American Education has the fo...
Why is it called Alternating Current and Direct Current instead of Alternating Voltage and Direct Voltage?	[ "Both are entirely correct, as the voltage change is what drives the current change. Back in the early days of electricity, it seems more members of the public understood the notion of current." ]	[ "Venmo deposited basically by using your debit card in reverse. Those transactions happen nearly instantaneously. The paypal transfers are done through ACH (basically an electronic check) and since those are done in a few daily batches rather than through a card processing network, there's a day or two delay in tho...
Could we create gravity waves by spinning a massive 'rod' in space at high speed?	[ "Yes and no. In theory, any accelerated mass will radiate gravitational waves, but in practice, only the most energetic sources of gravitational waves (like supernovae and colliding black holes) will produce a signal that could ever be detectable. Additionally, even if your rod is very long and very fast and very ...	[ "only if it's structure is perfectly non-[amorphous](_URL_0_) so that it wouldn't start contorting with the inertial effect commonly known as the [centrifugal force](_URL_1_). This would rule out glass and many plastics Also it would have to also be in a perfect vacuum so that air resistance, or friction with the a...
Why can we not use a pump to circulate blood through the brain of a dead person to keep them alive?	[ "Such a thing is (more or less) routinely done in experimental animals (mostly guinea pigs, for some reason). Google \"isolated perfused whole brain prep\" to get into the literature. I've talked to people who have used IPWBP. Mostly it's scoop out the brain then perfuse via the carotid arteries. They don't use blo...	[ "_URL_0_ The short answer is that when you set up a siphon like this, were the water comes out has to be lower than where the water starts from. A more theoretical answer would be what is driving this siphon is the potential energy in the raised body of water. If you expend that energy to move the water the most it...
High School student, how does college work?	[ "Major- Primary area of study. Often 40-60 credits taken in this area. Minor- You've taken enough credits to have an idea of the field, but did not heavily concentrate in it. Usually 18-24 core credits. Technical School- Typically offers vocational and trade programs; mechanic, nurse, IT, etc Associates - 2 years, ...	[ "This is a very common question. You can use search to find [all the other really good answers](_URL_0_ ). This is instant, and faster than ust typing in your question every time. It's a way of cheating elections. Read the others, and then ask a more specific question." ]
Why do games nowadays get sold at normal price unfinished? Is it just for money, or is the gaming industry creating such massive games they can't release all the content at once?	[ "I'm 33 years old and was heavily involved in gaming when I was a teenager. I'm not the most OG guy around, but I remember a \"back in the day\" story or two. You are remembering with rose colored glasses what \"then\" was like. Back then games were routinely released with game killing bugs. While we did not see th...	[ "To ensure all of the bacteria are actually dead. If you quit when the symptoms subside it's very likely the infection isn't entirely gone yet. Not only that but the bacteria remaining are the ones that were best able to resist the antibiotics thus making it harder and harder to get rid of the infection entirely. P...
how did Ask Bongo and similar services that were popular a number of years ago find out so much information about me so quickly?	[ "I worked for one of these. We googled you. You'd be surprised what we could find out, especially when Myspace was still a thing and nobody had anything on private. Also remember it's not just your own profile, it's anyone else's that has your full name. We also could see your message history with us. A surprising...	[ "This is possible and if you have a smart phone that has the facebook app on it, most likely happening. The technology is possible because in your pocket you are carrying a device that has (among other things): -A microphone -A connection to the internet. That's it. That's all it takes. The only way to 100% ensure ...
Why is it so difficult to tell if clothes are damp or just cold?	[ "It helps to first realize that there isn't really a \"cold.\" When you feel something, like a metal door knob, that appears cold, it's actually because your body is warmer than the knob, and what you feel is your hand actually heating the knob up! The knob robs heat from you. Clothing can also be at a lower tempe...	[ "\"One of the most common ingredients used was dihydrogenated tallow dimethyl ammonium chloride (DHTDMAC), which belongs to a class of materials known as quaternary ammonium compounds, or quats. This kind of ingredient is useful because part of the molecule has a positive charge that attracts and binds it to negati...
In the early 20th century, when ads for cigarettes were claiming their products were "supported by doctors," was there actual scientific evidence (biased or unbiased) that doctors used to make these claims at that time?	[ "I would like to encourage more history of science questions here. However, if you don't find an answer, you could try /r/askhistorians or /r/historyofscience" ]	[ "This is askscience, Respond with sources and credentials please." ]
Why does wind make the air feel colder?	[ "There are several factors: 1) Your body constantly warms the air around you (assuming it's colder), wind blows the warmed air away and thus keeps the air next to your skin at the lower degree. According to thermodynamics, the higher the temperature gradient, the higher the heat transfer, so you lose heat quickly. ...	[ "I'm pretty sure part of it has to do with water (sweat) molecules being knocked off of your skin (evaporating) more easily, and water evaporating off your skin takes some heat with it, which is why you sweat in the first place" ]
Help with non-Newtonian fluids?	[ "I suggest that you start reading about [rheology](_URL_0_); see 'Deborah number' and 'Reynolds number'. In theory, the Navier-Stokes equations describe fluid flow for any system, but the solutions to the NS equations have not necessarily been found yet." ]	[ "Oobleck is the closest you will get _URL_0_ It's cornstarch and water mixed together Water has one of the highest surface tensions, so that's your best bet, but oobleck stiffens under pressure, so if you jump around, it's ok" ]
What are the requirements for a new religion to be legally recognized?	[ "US laws don't recognize religion. so there isn't a legal anything." ]	[ "Your answer was removed shortly before you posted this question. It did not meet our standards. We ask that answers in this subreddit be in-depth and comprehensive, and highly suggest that comments include citations for the information. In the future, please take the time to better familiarize yourself with [the ...
Why is high voltage used to transfer electrical energy through long distances?	[ "Rearranging Ohm's law presents the following relationship > Power = Current² x Resistance Power loss in the transmission cables is undesirable, so there are two ways to reduce this. The first is to drop the resistance in the cable, requiring larger cables or more expensive materials. The other is to drop the cu...	[ "Probes like the Voyager are actually just following a pre planned trajectory, NASA never has to send them coordinates of where to go. When a probe like that is launched it is given enough velocity in order to escape the gravitational pull of the Sun, this is called the escape velocity. NASA just timed the launch s...
How does FOREX work?	[ "You buy pesos with dollars. When the price of pesos goes up, you sell the pesos for dollars and now have profit. You can do the inverse too." ]	[ "If you don't have even a 5 year olds level of understanding then why do you want to get into it? If you are actually interested then I can explain some of it, but you won't make money, trust me." ]
Drugs/drug culture in Ancient Rome.	[ "[This](_URL_1_) page has a bit of information on this (pretty cool) subject, which could maybe be used to find better sources. > The Greeks and Romans used opium, anticholinergics, and numerous botanical toxins to induce states of mental euphoria, create hallucinations, and alter their own consciousness; this i...	[ "[This previous discussion](_URL_0_) might help. In a nutshell: homosexuality was known to happen, but was frowned upon. Sex without the possibility of procreation was considered morally offensive to the divine guardians of fertility." ]
Why does shining a blue laser at an LED turn it on?	[ "I'm assuming it was a white LED. They work by shining a blue LED at a phosphor which causes it to emit a mix of red and green light. Together with some of the blue, they mix to make white. Any blue light shining on the phosphor will make it glow to some extent. The blue laser is intense enough to make it apparent...	[ "Interpreting perfectly green paper as meaning a piece of paper that only reflects 520nm wavelength light and absorbs all other wavelengths and red flash meaning it only emits 650nm light then the green paper would absorb the flash, not reflecting any light, so in the picture it would show up as black." ]
How to study history? Should I use Durant? Also, reputable intro texts on historiography?	[ "I strongly believe in following your own interests. I would pick an area you like or have questions about and then build your reading up from a broad base. Start with a general survey that gives the basics then follow with more specific works. The reading lists here will help and so will the bibliographies in othe...	[ "Get a feel for what you are reading. Ask yourself do all their arguments follow? Are they sometimes making leaps of logic? Are they priviliging/relying one group of sources, if they are do they explain why? What perspective is the book written from, how might this affect the focus of the book? Are they making bad/...
I have a fairly new computer but am able to do a recovery of thousands of images	[ "When you go to a web page, and there is a picture, the picture is downloaded to your browser cache. The browser deletes them when it's used how every much space you allocated for it, not usually a whole lot." ]	[ "You used your account to post this, didn't you? Who told you you have to make a new one? Or are you banned from a particular subreddit or something? You should consider verifying your email (use a throwaway email if you want) - that usually lessens the posting restrictions." ]
How do stormproof matches work and should I be adding them to my normal survival kit?	[ "Stormproof matches are basically regular matches with a light coating of wax to keep them waterproof. Scratching the match on a surface removes the wax, then simply strike like normal. You can easily make your own waterproof matches by simply dipping regular matches in melted candle wax. Cover the head of the matc...	[ "In NZ where the weather is similar to the UK our houses all had food safes; this was a box that was often on the outside of the house with a door on the inside of the house. The exterior had mesh windows which allowed air through. You could use it to store things like milk, cheese, meat (for a very short time), et...
How is it possible that almost every country in the world is in debt? Wouldn't that just mean that there is not enough money in the world?	[ "The debts aren't just countries oweing other countries money. It's also governments oweing their citizens money." ]	[ "We aren't really sure why, but it doesn't seem that something like that can be done. Think about it like your bladder; you can build up a need to urinate, but you cannot urinate so much that your bladder is more than empty." ]
Why does the ACA/"Obama Care" recently seem to be failing with both consumers and insurance companies? Whose fault is it and why? Looking for an UNBIASED, non-partisan answer.	[ "Obamacare in a nut shell is a wealth transfer from young people to old people. Young relatively healthy people are being asked to subsidize older less healthy patients. The penalty from not complying is rather weak, and many younger healthier people are effectively resisting the wealth transfer by just taking the ...	[ "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 ...
Was Fetal Alcohol Syndrome a problem back when alcohol was the go-to drink?	[ "According on [one study](_URL_0_) of 400,000 women, no adverse affects were found when the women drank < 8.5 drinks per week. Other studies have found no ill effects when women had fewer than 14 drinks per week. So, it's really the major alcoholics that struggle with this. (Though, the exact amount of risk is unkn...	[ "It was always prevalent, it's just that with the advent of social media and similar things that the stories spread like wildfire instead of being local stories that aren't able to gain any traction. The advent of everyone having a phone with a camera on it as well is leading to the rise of mass awareness, as befor...
How does Donald Trump Stand a chance at winning the presidential election?	[ "He doesn't, why would you think he would? He'll get some votes from the \"lol fuck it why not?\" crowd, but that will be at most a couple percent of the voting population." ]	[ "So the TL:NR is going to be \"That line doesn't really do jack\" here's why: Like someone using music or audio without consent saying \"Blahbity blah belongs to such and such, no claim to copyright is made\" or some such gives you no legal protection in court should that person decide to sue you the same is going ...
When two countries declare war on each other, what happens to any civilian ships that are in the now enemy port?	[ "Ships belonging to hostile belligerent countries get seized and impounded. Their crews are usually sent home through a neutral third party." ]	[ "Because the judicial system is only meant to see if the person is guilty of committing a crime or not. And then deciding his punishment. You're grandmother could take him to civil court, where it would be handled as that is what civil courts are for. Essentially, it's two different court systems. Imagine you had t...
If a company continuously issues new equity and a (colluding) investor always keeps on paying higher prices for the new equity, could they create an artificial stock market bubble?	[ "Firstly, a stock market bubble in involves the stock market, not a single company. So...no, even were what you're describing legal then at most it would inflate the value of the shares in single company. Secondly, what you just described is always illegal. Its a price fixing scheme and his wholly illegal for a pub...	[ "Say there are 100 school kids and they all enjoy cheap cheap jello. When 4 of the kids decide they want all the jello (for whatever reason) - It's tasty - It's sexy - It makes them feel rich(er) - religious reasons. Supply and demand kicks in. They buy up all the jello and that drives up the price. Fun fact...
Why are there more carnivores and herbivores than omnivores?	[ "Specializing helps with optimization. Cows can't eat meat, but their teeth and multiple stomachs are ideal for eating grass. Humans have to have sharp teeth for meat and grinding teeth for plants and our digestive system is inefficient at processing plant matter. Versatility is obviously useful, but there are trad...	[ "If you are looking at it from an emissions or energy standpoint then yes. [This](_URL_0_) Peta site is a good source of info, such as \"It takes more than 11 times as much fossil fuel to make one calorie from animal protein as it does to make one calorie from plant protein.\" Interesting information on burger prod...
Why do people feel the urge to vomit when seeing or hearing another person vomit?	[ "Yes. Humans are communal animals and tend to eat together. So if you see one person vomit up whatever was just consumed, its an advantage to yack it up before you get poisoned as well" ]	[ "Well, how we react to different tast is quite deep in our animalic past. Bitter was for exampe a dangerouse taste since it hinted to poisons. Blood on the other hand was something our animalic ancestors tasted when they were able to get their hands on meat. It is quite far into our history, but before we cooked ou...
WW2 German Tracer colors	[ "I've seen ammo boxes for tracer ammo in 8mm that indicated yellow, orange, white, and green to red. I haven't been able to dig up any original sources that talk about why a given color was used though. Some other armies would use different colors based on ambient lighting conditions, and others to differentiate ...	[ "Tangential question: do we in fact often tell stories of heroic actions of resistance within Germany and Italy? I've only seen one or two films about German resistance, and none about Italian resistance. What are some good examples?" ]
Why do redditors "cringe" when someone says "upvote to you sir" or just "sir" in general?	[ "Because people don't use \"sir\" in that context in real life. It sounds like someone pretending to be from the 1920s, which comes off as pretentious." ]	[ "Because most people will see it as a lower value. Just like stuff are advertised for 19.99 and a lot of people will think of that as \"less than twenty.\" 3.699 gets rounded in people's heads as three-sixty, not three-seventy. In a couple of days you can train your self to see the real value, 19.99 actually means ...
How much damage did resistance forces in World War II cause?	[ "A unique feat in the history of the Holocaust was accomplished by the Belgian Resistance in 1943. They succeeded in [stopping a train filled with Jews and Gypsies headed for Auschwitz](_URL_0_) and liberating many. In total 231 people escaped (115 were not recaptured or killed). In the grand scheme of things, thi...	[ "Awesome question, you’re right that the research about this kinda sucks. If you are good at interpreting/understanding research articles then check this out, if not then I’ll cover the details below so don’t worry: _URL_0_ Generally, research of this nature is done using model organisms, in the case of this study...
What keeps a river or lake from seeping into the ground?	[ "The ground below it is saturated. So, in my area, that means that the ground is relatively non-permeable. There'll be a layer of sand, but if you dig down below that, my entire state is basically built on top of a granite slab, so you run into solid rock. In other areas, the sand goes much deeper, but is fully sat...	[ "To perform tasks computer programs must allocate certain amounts of memory to them. An application is usually composed of many different smaller programming sequences and those programs each will allocate a certain amount of memory to them, do whatever they needed to do, then release the memory to be reassigned. T...
Why don't we put remote controlled rovers on the moon like we do Mars?	[ "I'm going to quote the red text in the comments section of reddit posts when there are not posts: \"There doesn't seem to be anything here\"" ]	[ "Cost, safety which is a component of cost, and the reception of the consumer to having to order and pay in some kind of interface when a large group of people can't even figure out credit card terminals at the grocery store. Additionally, wherever the food comes out you'd have to make sure it got I the right perso...
How was the value of a foreign coin determined when it was acquired by trading/from merchants.	[ "This thread might help a bit! Not sure if it will answer it all though. _URL_0_?" ]	[ "There is an episode of This American Life that explains it really well: _URL_0_ They say that the real money is made of incentives from the manufacturer to sell the cars - they just need to move a set number of cars, it really doesn't matter how much they sell them for. And then they get big payouts from the manuf...
How to differentiate nuclear blasts from earthquakes	[ "Earthquakes are sinusoidal and logarythmic.. bombs make 1 wave and then small echoes are seen." ]	[ "What's the point of supersoldiers when everyone has enough nukes to destroy the planet in the event of war?" ]
Opportunity cost of paying off low interest rate mortgage early.	[ "When you pay your loan off, you're getting a 3-4% return on your investment. This isn't an awesome return. It's also an investment with low liquidity, there are high fees to borrow against your house and selling it to liquidate your investment - that's a super-sized hassle. On the other hand, a low cost ( < 0.2%) ...	[ "A company will often invest 50k in loss leaders like this to build trust in an online store. It's cheaper than a marketing campaign." ]
Why does scratching your fingernails on a chalkboard bring chills down ones spin?	[ "Due to the way the human ear is built, certain frequencies of sound are amplified or made louder (the reasons for this can get a little technical, but if you're interested you can read about it [here](_URL_0_)). Sounds with a frequency of 2000-4000Hz (such as nails on a chalk board) resonate in a certain way in ou...	[ "Finally! Something I can answer! Notice many of the things you hate to hear a very high pitched? well just think, a human scream is about 3000 hz and most of the things that people \"cringe to hear\" are around that frequency. I think you can guess why you hate it! As always, it's all because of your ancestors!" ]
Are there any examples of animals that behave monogamously?	[ "Yep. Take a look [here](_URL_0_); the sorts of animals that are monogamous are actually pretty diverse." ]	[ "Orcas exist at both poles. To my knowledge though, they do not migrate between them. _URL_2_ Blue whales are also found in both regions. I have no idea whether they migrate between them or not. _URL_1_ Arctic terns, on the other hand, have the longest migration in the world. Every year, arctic terns breed in polar...
Difference between character progression and character development.	[ "Character developement basically means that a character gets fleshed out, whereas character progression means that a character changes. I'll give examples from Harry Potter, since it's a fairly well-known story. Dumbledore doesn't have much character progression, his character is pretty much the same at the end of...	[ "Salt & Pepper season our food. They make it taste better. Spices & Herbs flavor our food. They make it taste different. Season everything. source: Chef." ]
Did tipping in the US become common so that employers wouldn't have to pay former slaves?	[ "[This](_URL_0_) earlier answer touches on this in a follow up which might be of interest to you." ]	[ "Interesting; also, standing ovations at performances. Just as you said, they're somewhat expected now, despite the fact that they were probably once \"special\". I once heard this discussed on NPR (I think both topics were mentioned) & I hope someone has an answer!" ]
When you learn languages you do so by translating and comparing it to your native language. How do you learn your first language when there's nothing to go off of?	[ "Think about it like this. When learning an additional language you are suggesting that you learn it in the following manner: New Language -- > Known Language -- > Association with actual object or action. So, when learning a language for the first time, you simply have no middle man. You are associating the word d...	[ "Muscle memory and learning. You don't instinctively know exactly how to throw a baseball to get it on target as a toddler. You can get it in the general direction, but only through practice and the brain having an opportunity to learn through experience do you become capable of throwing a ball accurately" ]
the "Equal Employment Opportunity" survey at the end of job applications	[ "It's used by Human Resources (HR) for data collection. One use is they can see if they need to reevaluate their outreach/hiring practices. If they notice that an overwhelming amount of applicants is from a particular race/ethnicity, they might want to change something. But you're right, like any data collection, t...	[ "They usually provide, in the very small print, a second way to enter, such as by mailing them a post card. Clearly they'd prefer you buy the product. :-)" ]
question here... when the continents collide in 150,000,000 years, what will happen to the north pacific gyre?	[ "I'm not sure if I understand the question. but.... Gyres exist in all the sub-tropical ocean basins (North Atlantic, North Pacific, South Atlantic, South Pacific, Indian) because of the action of the wind. These gyres exist regardless of the details of the basin geometry - the details of the circulation certainly ...	[ "It's important to understand it was a belief in contemporary Japanese superiority. Even the most ardent nationalist could not deny the influence China has had in Japan. Rather, it was believed that China had become a Western puppet and had lost the mandate of heaven. The Chinese people had become corrupt; enter ...
How are galaxies named?	[ "Galaxies don't just get names, they are listed in catalogs and therefore have a designation. These designations can differ, because one and the same galaxy can be in different catalogs. The Andromeda galaxy for example has amongst others the designations M 31, NGC 224 and UGC 454, because it is in the Messier cata...	[ "At the first part of the disk (where ever that is, first track, first cylinder, first head, first platter) there is an index of partitions. At each partition, there is an index which explains what file system is used. And each file system has it's own way of storing the directory structure. So to be short: You don...
Why is that when you touch an open wound (or the “white meat”) under your skin with your finger, it burns?	[ "Because the nerves that bring sensations like pressure, heat and cold to your brain get the info from special structures around nerve endings that are deep in your skin. If you touch an open wound you stimulate directly your nerves and give them a much greater stress. The other case where this happens is when your...	[ "I'm not an expert in Australian weather terms, but here in Canada we actually have two different terms for this kind of thing: humidex and wind chill. The humidex is used in summer, and is typically higher than the \"real temperature\", because humid air feels hotter than drier air. The body cools itself by swea...
How Does One Die Instantly?	[ "For all practical concerns, the brain is what counts for life. If the brain is destroyed faster than it can react to the destruction, then death is effectively instantaneous." ]	[ "As others have said, nitrous oxide (dental anesthetic) and morphine will conk you out like magic. However, the \"chloroform rag\" trope is bullshit. Chloroform will make you a little drowsy after smelling it for a while but it's not the insta-KO the movies make it out to be. Source: I'm a synthetic chemist and use...
Why is Radio Shack going under (bankrupt)?	[ "As a former employee let me tell you why, first off the internet has cheaper prices, no joke. Secondly, They stopped caring about parts and starting pushing cell phones as their main product. I was pressured to sell phones, my paycheck was based on selling phones. One week I didnt sell a phone (they put me on the ...	[ "This is like asking \"why does a fire burn itself out - what's the point of using up all the fuel if it can't sustain itself?\"." ]
Why can't we store excess solar energy (or any variable source for that matter) as kinetic energy in some massive spinning turbine?	[ "It already exists. It's called flywheel energy storage, the huge wheels are called flywheels." ]	[ "When you shoot an arrow from a bow, the energy of the bow is transferred to the arrow. It gradually (doesn't seem like it, I know) pushes the arrow downrange, from a full stop at full draw, to full speed when the arrow leaves it. All that pent up energy of the bow at full draw is efficiently transferred to the arr...
Why haven't the USA and Russia ever gone to war?	[ "Generally, a country will only choose to go to war if they believe that the benefits of winning are worth the losses they will take getting that victory. The thing about the Cold War is that there were very few upsides to any potential conflict and a mountain of downsides." ]	[ "Not enough energy to. It's like lighting a match in a snow storm and expecting it to melt everything. Sure, the match is hot, but theres a lot more cold than there is hot." ]
What is the purpose of the spirals painted on airplane engines?	[ "So that people (ground crew) will know if the engines are turning." ]	[ "I know Air travel and contrail contribution to cloud clover definitely changes surface temperature in cities. In the 3 day stand down of (almost) all air traffic in the days following the 9/11 attacks, there were measurable decreases in surface temperature . I can only assume the effect would contribute in other m...
Why do some people believe that Oskar Shindler doesn't deserve to be called a hero?	[ "I don't know of anyone who wouldn't call him a hero--he saved large numbers of people at great risk to himself. However, he shouldn't technically qualify as one of Yad Vashem's \"Righteous Among the Nations\". One of the requirements is that aid rendered cannot have been given with the expectation of financial rew...	[ "Before I answer, may I ask who the speaker is for this particular lecture? Or if you have a link for me to listen to? I would like to know where they are coming from in their argument." ]
If engagement rings weren't a thing before the 1940s campaign to sell diamonds, what did people do when they got engaged?	[ "[The previous answers](_URL_3_) from the FAQ may also prove illuminating." ]	[ "[Here](_URL_0_) is a good NPR article answering that exact question. ----------------------------------- To start, we need something for a currency. Life is way easier with something for a currency. So what do we use? We need: * Something rare but not too rare * Something that's not a gas * Something that won't ex...
[Computing] How to compute the determinant of a large matrix with optimal precision?	[ "Decompose your matrix M using LU decomposition (into two lower- and upper-diagonal matrices) which you can achieve with a modified Gauss-Jordan elimination [1] in 2n^(3)/3 FLOps and then calculate the determinant as: `det(M) = det(L) det(U)`, which for triangular matrices is just the product of the entries in t...	[ "How much detail of the process do you want? You can write a whole book about it. First you need to extract your DNA from cells and purify the DNA. Then sequence it. This video is a good start about sequencing. _URL_0_ Or have a look at Sanger sequencing. These colorful blocks at the end of the video will the have ...
Why is it that when we’re exhausted suddenly everything becomes so much more funny? Does this have to do with a possible correlation between lack of sleep and brain function?	[ "One of the common themes of comedy is things not meeting our expectations. When we're very fatigued, our mind doesn't have the ability to predict things quite as well - so we're more likely to find something doesn't match our expectations, and thus amusement." ]	[ "Two social psychological concepts come to mind here. State dependent memory encoding and Erickson Arousal theory of learning. State dependent learning states that what ever state of mind you are in during encoding is the state of mind where recall would be optimal. Erickson arousal theory states that learning is m...
How feasible is it to put inductors under short stretches of highway to produce power from every vehicle that goes by?	[ "Any electrical power energy produced would have to come from the car engines. It would be easier to just use a normal gas powered generator. There's no such thing as free energy." ]	[ "Quoting [Wikipedia](_URL_0_) (a bit naughty, but it's a nice way to express what I think): > The proposed theory is inconsistent with quantum mechanics and critics have ruled it out on those grounds. Which is essentially saying what you pointed out, yes. If what they're doing is as easy as it sounds - just runnin...
Why were wolves so easily domesticated to dogs? Why can't we domesticate say, lions?	[ "Dogs were relatively easy and beneficial because of how similar we are; - a) They are a social pack animal much like humans. Lions are the most social cat but still it's more the females that hunt in groups and the males don't work very well together. - b) Lions are primarily nocturnal hunters which doesn't match ...	[ "People are very bad at assessing long term risks. We haven't evolved to handle dangers and risks of long term activities. Even though we intellectually know the risks, it is hard for us to translate that intellectual knowledge into behavior, as it does not tell our instincts that it is dangerous. We instinctively ...
why don't power plants that rely on pressurized steam double as water plants which create distilled water?	[ "The steam gets re-used after every cycle, it doesn't just get thrown out after if leaves the turbine." ]	[ "Imagine you have a computer on your house. Now you want to connect that computer to your friend 100 miles away. How do you do it? You could lay a 100 mile cable, but do you have the permissions to dig up roads and pathways? You would use a company whose cables were already there, and just use that network of cab...
What would you say are the greatest/most important contributions of black culture in the US?	[ "OP, you should ask this question on /r/blackculture or /r/blackpower" ]	[ "Technology builds on top of itself. Think about how much we can do now that we have computers that would have been simply impossible to do prior, no matter how smart we were. Really, though, it seems that the big leap forward occurred when we invented the written word (although there could be some confirmation bia...
why does time slow down as we approach the speed of light? Is it only our perception of time? Has this been proven or is it a theory?	[ "First, gotta be a stickler about this one. \"Theory\" in science refers to a framework for describing phenomena and making predictions. A scientific theory can be used to make predictions about untested phenomena and those predictions end up being true, ergo the theory is true. If it's not exactly correct it's clo...	[ "How far away the earth is from the sun is directly proportional to how fast it travels around it. For non-five-year-olds, the equation is: v = sqrt(GM / r) So if you double the speed around the sun, the distance closes proportionally to v^2 so we'd suddenly be four times closer to the sun. All life would die, and ...
How close are we to discovering Room-Temperature Superconductors, and how would that revolutionize the world?	[ "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...	[ "Such hypothetical / speculative / open-ended questions are better suited for our new-ish sister sub /r/asksciencediscussion. Please consider reposting there instead." ]
In the Islamic World, a Hafiz is one who has completely memorized the Quran. Were Medieval Christians aware of such a practice and did they try to replicate it in any way?	[ "I'd be interested in hearing a more general answer than this, namely, is there evidence of \\any\\ transfer of religious practices or beliefs from the Islamic to the Christian world during the medieval period." ]	[ "How about the \"knight-errant\" that is central in Don Quixote? Same idea as a hedge knight? Any basis in reality?" ]
How are sentences by judges that are aimed at making an example out guilty parties not a violation of "Equal Justice Under Law", and therefore unconstitutional?	[ "Each type of crime has a valid minimum and maximum sentence. As long as the judge stays within these guidelines, it is 100% legal." ]	[ "Imagine a city with no streets or no road signals. Although it makes it extremely fast to get from point A to point B, you never really feel safe because everybody is driving around independantly. One day, the city proposes to build roads and signs to avoid crashes. Now although this makes you mad because you can...
Was there a preferred theater of WW2 to be assigned to if you were an average US Army infantryman?	[ "\"preferred\" is not really quantifiable in this context. Can you expand on that?" ]	[ "Off the top of my head, the reforms of Gaius Marius seem to be the most relevant topic to start with. Marius raised armies from the Head Count, which were a teeming mass of the lowest class of citizens in Rome. Previously, armies had been raised from landholders and their sons, but as Rome had more land to protec...
If airline pilots can "make up" for delays by altering the route or the altitude, why not just do that in the first place?	[ "It may have cost a fair bit more in fuel - but the airline decided it was better to spend that and catch up so the plane would be in the right place for it's next trip in time and so the customers were happier." ]	[ "Because we can predict their passing in the sky with accuracy (diabolical accuracy might I add) That is the power of Newton's mathematics. (Next time your kids ask you what is math good for this is a good example: math can explain and predict basically everything that is going on in the universe) By calculating i...
How did explorers of the past create such intricate maps?	[ "Hi, hopefully one of the historians of cartography will be able to answer your specific questions, but meanwhile, you may find this section useful: * FAQ section [History of Cartography](_URL_0_) - the posts are arranged roughly chronologically, so start at the top if you're interested in \"ancient\" maps The post...	[ "\"If a service is free, you're not the client - you're the product.\" Google Maps allows Google to collect data from its users - where you are, what kind of restaurants you like, which places you like to visit. They can use this data to show you ads, or they can charge businesses to make them appear first in your ...
What do we know about historical Troy?	[ "There are Hittite royal letters about a fief of a City called Asuwa (iirc), with a king called Aleksandu. The letters also contain other names and places similar to those of the Iliad. Then there is antheory that the Trojans were the Sea People who raided the Egyptian coast. Just remember that the Iliad was writte...	[ "This is a pretty common question here; here's some links from the FAQ: _URL_2_ _URL_4_ and a few others that have been posted over the years: _URL_3_ _URL_1_ _URL_0_ Most posts agree that it is largely a post-war pop phenomenon with fairly little evidence to support it." ]
How do services such as Spotify and Overdrive make sure that you don't permanently download their material?	[ "The files are not in a standard format. You couldn't just take the files and play them using another media player app. The Spotify player knows how to decode the files into a normal audio stream and then sends it to your sound card. If the process used to encode the Spotify tracks was known, then it could be rever...	[ "I work for an ISP The Internet is like a series of roads. Let's say you built a road from your house to your friends. You and your friend could go real fast to each other's houses. But what if you wanted to go to some else's house? Or the mall, or school? You would have to connect your road with your towns road. ...
Why is the speed of light the speed that it is?	[ "You're thinking of it backwards. The speed of light is much more fundamental to the way everything works than units of distance and time. Everything scales to it--not the other way around. If light were \"half as fast,\" distances between everything would be half as far. And you would have no way of knowing it bec...	[ "The formula E = mc^(2) holds only when in the rest frame of the particle (or system of particles). A single light particle has no rest frame, and so it's not the correct formula. The full formula, valid for all particles (massless or not) and in any frame is E^(2) = (mc^(2))^(2)+(pc)^(2), where p is the mo...
Why aren't cars' front lights neon-powered?	[ "Cars' headlights need to be carefully focused and shielded so they throw strong light down the road but not in the eyes of oncoming drivers. That means the light has to come from a small source (a single point would be ideal) so the surrounding mirrors and lenses can focus it. Neon and/or fluorescent lights can't ...	[ "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...
Could a human survive temporarily being swallowed by a large animal like a shark or whale? What would the process of death be like, and could they survive if they weren't bitten/crushed in the mouth?	[ "The first thing that would kill someone who is swallowed alive is probably lack of oxygen. Assuming you're a scuba diver being swallowed by a whale, if you can avoid being forced into the whale's digestive track and stay in the mouth, you can live as long as your oxygen holds out and you aren't crushed by the mout...	[ "Steps: 1. Flight or flight, adrenaline, sympathetic kicks in. 2. Blood leaves GI tract because who needs to digest when a bear is clawing my ass. 3.blood leaving GI = heart sank. EDIT: I was corrected it is indeed sympathetic." ]
Why are most random number generators said to be "pseudo-random" rather than truly random? What is the difference between true randomness and pseudo-randomness?	[ "Let's start with the definition of deterministic. A deterministic process or system has one future for each state. In phase-space, the trajectories don't cross. So you can usually predict the future state of a particle given the particles current state. Random processes/functions/systems (whatever) can have multip...	[ "A sociopath is really a person with extremely antisocial tendencies and lack of conscience. A psychopath is one who actually often interacts socially and can often be undetectable. Still however, they lack the ability to express or feel certain emotions, such as guilt. I actually watched a very interesting [TED Ta...
Did any Royal Family member of Europe die from the Plague?	[ "Of course they did. For example there's Anne of Bohemia who married Richard II of England for 12 years and died of plague. According to Agnes Strickland's Lives of the Queens of England from the Norman Conquest, Richard was devastated by her death and made many bad choices. The period until his overthrow was kno...	[ "As a reminder, [top-level answers](_URL_0_) in this community need to be \"comprehensive and imformative.\" Single-links to Wikipedia and unsourced opinions do not clear that bar. This question already rests on a part of history hamstrung by the fuzzy diagnostics of diseases in the past and an almost unavoidable b...
What is the point of exercising in the ISS?	[ "Their workout equipment is designed to work around the fact that they're in microgravity. They don't just use free weights. Imagine something like a bowflex. It still provides the same exercise, even though there's no weight." ]	[ "The Schwarzchild solution describes the vacuum outside of a spherically symmetric mass distribution. So if you drew a big sphere around a large enough part of the universe and removed all of the mass outside it, that would be sphere with radius smaller than the Schwarchild radius. But since there is mass outside a...
What would happen if a black hole with mass < < Earth's mass came in contact with the Earth?	[ "A black hole of that mass would evaporate faster than you could really observe it." ]	[ "So, you don't actually observe the astronaut crossing the event horizon. What happens, from your frame of reference, is that the astronaut gets more and more time dilated, and moves slower and slower as they approach the event horizon. This means that the light gets dimmer and dimmer, because the time between each...
What determines our threshold for emotions?	[ "There are lots of contributing factors. The person may be genetically predisposed to being more or less emotionally hardy or robust. This person's experiences over their lifetime will also impact how they experience and express emotion. Their biochemistry will also affect their mood and how they respond to stimuli...	[ "I think it is hardwired into us. [Tommy Edison](_URL_0_) explains it better." ]
If π = 3 + .14159..., and that decimal extends infinitely, is there a set of decimal points where the decimal repeats exactly once from the start (ie .114159, .1414159..., .14114159...)?	[ "Let's take a real number at random, and consider its digits. The probability for the first digit to be the same as the second is 1/10. The probability for the first n digits to be the same as the next n digits is 1/10^(n). I might be mistaken, but I think the probability that it happens is around 11%. However, if...	[ "What does it prove? That Jeff Tupper is awesome. What does it achieve? Nothing, by itself. Tupper's formula is strongly related to the concept of a [Quine](_URL_0_ (a program that produces its own source code as output), which is itself strongly related to the concept of [fixed point](_URL_1_ (roughly, a fixed poi...
Why is the drinking age in the US 21?	[ "One big thing that the other two folks haven't hit on is that the 21 restriction effectively bans alcohol from High School. If 18 year olds could legally purchase, it would make it much easier for younger teens to get ahold of it. There's much less social network overlap between college age and High School age gr...	[ "Horse meat isn't rare at all. You can get it in many parts of europe. Tastes ok too. Anyway, that's culture. The same reason we think that bacon and eggs is a breakfast food, and don't eat grasshoppers." ]
Does a piece of meat stuck In your teeth grow bacteria at the same rate as an outside environment of similar heat and moisture or does your saliva help reduce the bacteria's growth?	[ "Saliva is both hypotonic ( < /=15mM NaCl compared to 154mM NaCl in plasma/interstitial fluid) and contains an enzyme called lysozyme, which hydrolyzes specific peptidoglycans composing the cell wall of Gram Positive Bacteria, contributing to bacterial lysis. There are much better mediums than saliva to support ba...	[ "As with antibiotics, over use can be bad. Say that the sanitiser contains a drug that kills 99% of the bacteria on your hands. The 1% that survive are the most resistant to the drug. If you allow those 1% remaining to reproduce to use the food etc. that the dead 99% aren't eating, you've now increased the populati...
How/why do cats purr?	[ "The short answer to both question is we don't know. Cats don't have a purring organ that we can find. Most scientist think they purr by vibrating their vocal folds and/or the the larynx while inhaling and exhaling. Not all cat species Purr and they don't sound the same but many big cats can purr. The reasoning be...	[ "I could try to explain it to you, but this video is all you really need: _URL_9_" ]
Why do we sometimes have an urge to smell disgusting things?	[ "You mean like our poop? It's an evolutionary drive. Because animals often track other animals by scent, when we smelled our own poop we could gauge how strong the smell is and therefore gauge the level of danger we would be in after having defecated. The stronger the smell is, the further and faster it would trave...	[ "Our ancestors when in the wild would enjoy a fresh kill, body still warm. If you came across a dead animal that had been there a while, well you wouldn't want that would you. Evolution has taught us warm is preferable to cold. Unless of course you are eating mint chocolate chip ice cream." ]
if Kim Jong-un died today, who would the successor to N.Korea be?	[ "He does not want that to be established. It is standard operating procedure for total dictators to have no one designated as the heir apparent. If their were someone it would be too easy for an accident to happen to him." ]	[ "It varies from one dynasty to another, but early rulers of China had a tendency to name the dynasties they found after the places they hailed from, or are strongly associated with them. E.g., in the case of Han, as stated in its Wikipedia page:_URL_0_ , the first emperor Liu Ban was once appointed as the prince of...
Are the authors of "Warfare in Medieval Europe 400-1453" related? Is it common for medievalists to have the last name Bachrach?	[ "They're father and son, though I have no idea what their family dinners are like." ]	[ "The Nicole Etcheson book was offered by the History Book Club when it first came out. It was the first serious historical work on the topic of Bleeding Kansas in thirty years, when it was published, back in 2004. Amazon still has a paper back edition for sale, but the History Book Club no longer stocks the hard co...
If Black Holes have supposedly infinite density and gravity has infinite range why is the entire universe not pulled into it?	[ "Infinite density does not mean infinite mass, so as your mass is still some finite value, it behaves similarly to a gravitational point source. For example, if the Sun turned into a blackhole right now, I would only notice 8 minutes later when it suddenly looked like someone decided to turn off daylight, otherwis...	[ "It isn't expanding into anything. Imagine an infinite loaf of raisin bread rising as it bakes. Each raisin in the loaf will be further away from every other raisin, since the loaf is expanding and the distance between all of the raisins is growing." ]
Why do they always qualify shootings as the n^th deadliest in modern US history?	[ "Looking through the search results is fairly depressing how frequently this question gets asked. Not that it is a bad question just that it seems to be continuously relevant. There are a couple good answers in two different posts, but many of the posts go unanswered. The first goes into the various tragedies and p...	[ "Hi there -- while we've approved this question, we would like to remind potential respondents of our [current events](_URL_0_) (AKA \"20-year\") rule -- it's fine to discuss events through 1997 (inclusive) and their effects, but not events after 1997. Thanks!" ]
Was ever Math expressed in another way than numbers?	[ "Hey there! Could you clarify your question a little bit more? As you mention, there have been many different ways of representing numbers, be those Roman numerals or [knotted strings](_URL_0_), but at their heart they all represent numbers. What would you consider \"math\" if it does not deal with numbers?" ]	[ "You know how authors write long stories using letters and words and the rules of grammar and writing? Its just like that. With enough knowledge of how to read (math), these kinds of explanations make sense. Dont feel bad that you cant read it. Its just like if you tried to read a story in a language you dont know....
Expansion of the Universe	[ "Physics doesn't know what happened at the big bang. All galaxies are not moving away from all others. Some are merging. All sufficiently distant galaxies are moving away from each other. Gravitationally bound systems are not expanding." ]	[ "We use a frame of reference where the cosmic microwave background has no velocity, which is about 600 km/s from the velocity of the Sun. This is the \"CMB rest frame\". In practice, most galaxies, stars, and planets move at < 1000 km/s relative to each other, so relativistic effects are so small that they're compl...
How do disinfecting wipes "kill" viruses?	[ "So I looked into the product you mentioned and it contains these active ingredients: * Benzalkonium chloride - This is probably the ingredient that 'kills' viruses. It can disrupt intermolecular interactions, which has a profound effect on things like enzymes (or other proteins) that are highly dependent on interm...	[ "Your computer keeps a list of where all your files are located on the hard drive. When you make a new file, it checks this list to make sure you don't use space that other files are using. So when you delete a file, your computer just deletes that file's entry from the list. Then, if you make a new file and try ...
Are there any good books about the Hittites that you would recommend?	[ "Anything by Trevor Bryce. Specifically: * The kingdom of the Hittites (Oxford, 1998) * Life and society in the Hittite world (Oxford, 2002) * The world of the Neo-Hittite kingdoms (Oxford, 2012)" ]	[ "FAQ; fantastic responses on [the general how/why here](_URL_1_) and specifically on the impact of [Constantine’s conversion here](_URL_0_) both by u/talondearg. There’s also “the rise of Christianity” by Rodney stark, although it’s a bit dated and disputed now. Pretty sure talon would have an opinion on it; and t...
Can someone explain how the "correcting spheres" on a binnacle works?	[ "I used to work on a ship where we called them the \"navigator's balls.\" These spheres were used to correct for the magnetic deviation induced on the compass caused by all of the various ferromagnetic components on the ship. The ship would be turned through the compass directions and the distances of the spheres w...	[ "When a body orbits another body in space, they are actually both orbiting a single point in space, which is their combined center of mass (known as the barycenter). [Here is an example of what it looks like](_URL_0_) if the two bodies have a similar but slightly different mass - imagine that the larger body is t...
Why are some Muslims so radical? What is written in the Koran that makes them lash out to such extremes?	[ "There is extremism in all forms of religion. Look at all of the deaths that have occurred in the name of Christ, whether it be the crusades or a crazy having a killing spree. The constant civil unrest in Africa is another good example of extreme radicalism. Just because the news focuses on extremes does not mean i...	[ "People care less about obeying rules when they are about to die. At this point what do they have to lose? Did Jerry over in cell D12 make a rude comment about your mother? Maybe Jerry should get stabbed 12 times with a sharpened tooth brush. What are the guards going to do about it? Kill you? lol!" ]
why do the southern and central states of the US remain typically conservative where as the northern and coastal states show typically liberal outlooks?	[ "It has less to do with geographic location and more to do with population density. People in more sparse rural tend to be more conservative on average, while people in urban areas tend to be more liberal on average. The reason for this is mostly that people in rural areas live among few people who are mostly very...	[ "Potentially. Different neurotransmitters occur in different concentrations in different parts of the brain and the receptors that they interact with occur as different subtypes and in different densities in different regions. So a drug, either agonist or antagonist, may preferentially act upon on anatomical region...
How long does it take for food to “store as energy” (fat) within a human body? Why does the body burn muscle instead of fat when starving?	[ "Think of fat like a savings account, and muscle mass as expenses. If you spend a little more than you take in in a particular month, you can withdraw a little from savings to cover the difference. But let's say you lose your job and have no money coming in (Starvation). Spending your savings is only going to work ...	[ "Genetics. Chimps have muscle that works differently to ours. It is complicated, but the simple version is that during our evolution, we sacrificed 'strong' muscle for very fine control over our muscles - it's what lets us be able to use tools so well. Chimps have great strength, but bad penmanship. Edit: Here's a ...

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