Subset (10)

eli5 · 25k rows

Split (1)

train · 25k rows

query stringlengths 20 300	positive listlengths 1 1	negative listlengths 1 1
What is the specific reasoning for teaching a lot about the industrial revolution in school? Why don’t they cover more topics related to war and peace?	[ "It's a singular unique event that massively shaped society like nothing ever before it. It also even reshaped war itself in huge ways Vs. War. War never changes Jokes aside, war is lots of the same shiza repeated over and over for slightly different reasons and outcomes. So only the most important/impactful are c...	[ "Robots and machines are really really expensive to build, develop, and maintain. People in Bangladesh are dirt cheap labor that can accomplish the same thing at small fraction of the cost of said robots and machines. Clothes being an easy item to construct, a cheap item, and a safe item, it doesn't make a lot of s...
How do US (and other countries') companies move manufacturing to China?	[ "It could be a bunch of ways. Either they buy their own factory, move the equipment etc. i.e. they just want the cheap labour. This is the more expensive route, but if you want to own the quality aspect, and/or you're looking a little more long term (like you know you'll be making this or similar products for decad...	[ "Let's say toll roads are run by Wal Mart. They then offer a discount - you can drive to Wal Mart for free, but still have to pay a toll when you go anywhere else. Sounds good, right? But then next year they double or triple the toll. Soon you can't afford to shop anywhere EXCEPT WalMart. Every other store then go...
Why do trees lose their leaves in winter if they need them to breathe?	[ "They need them to make sugar, which they store during the Winter as they don't need to use it." ]	[ "Nothing \"tells it to\" the changes dont happen during a creatures life, the changes come from mutations in the genes of offspring and nature decides which ones live and which ones die. When a mutation happens its usually bad but rarely a mutation can be beneficial. Take polar bears. Some time a long time ago a be...
Where did religion come from	[ "Humans are, and always have been, extremely curious. We have a huge problem with things we don't understand, to the extent that if we can't figure it out we're more comfortable making something up than just admitting it. Religion likely started as people trying to explain stuff they saw around them but couldn't e...	[ "The governing hypothesis of the origin of blood types, is that it confers a resistance to certain infections because of similarities in the AB-antigens, for example, and antigens on the surface of specific microbes. _URL_0_ [Wiki](_URL_1_)" ]
What happened to the culture and people of the Indus Valley Civilization?	[ "Piggyback question, how accurate are [these](_URL_0_) [photos](_URL_1_) in the National Science Center in Delhi, depicting everyday Indus Valley Civilization life" ]	[ "No. And to discuss why involves discussion of burden of proof. \"Extraordinary claims require extraordinary evidence.\" Sailing across either the Atlantic and Pacific, and making contact is a pretty extraordinary claim. Books such as \"Peru Before the Incas\", and \" The Last of the Incas\" have nothing to say abo...
What is the actual current that flows through the human spinal cord?	[ "What [mc2222](_URL_0_) said. The nerve fibers in the spinal cord propagate signals as waves of depolarization. Charge-carrying particles shuffle in and out of the nerve fiber radially, orthogonal to the direction of travel of the action potential, meaning no net current along the fiber. (Note, at the synapse of on...	[ "There is an [industry consortium](_URL_0_) that has standards for wireless device charging. From their web page: > Inductive Power Transmission Shielding - shielding necessary to prevent inductive power transmission and wireless battery charging from causing interference to other radio users. Also the frequency t...
Why does ELI5 have the requirement to start posts with ELI5?	[ "It distinguishes posts from other subs like askreddit or askscience for users scrolling the front page or all." ]	[ "\"Simplifying\" is not the same as \"dumbing down\", for one. Take the rules of this sub, for example - we don't literally explain things like we're talking to a 5-year-old even though we do try to simplify to the degree a layperson can understand. And that's another point. Say I'm a high-level network securit...
Where do our memories go when you can't remember them temporarily.	[ "it's not so much that the memory has \"gone\" anywhere, but more that the right neural circuit hasn't been lit up yet. imagine your brain like a tree with a bit trunk and then big branches that go into smaller branches to smaller and smaller branches and then to twigs, and the memory is a leaf. you have to access ...	[ "Similar questions have been asked several times before. You may be interested in the following posts: _URL_3_ _URL_8_ _URL_6_ _URL_0_ _URL_1_ _URL_4_ _URL_7_ _URL_2_ _URL_5_ _URL_9_ There are lots of really great questions and answers in /r/askscience that unfortunately get buried because of the high volume. It's ...
Why 1 GB = 1024 MB not 1000 MB	[ "Actually, it's both - depending on who you ask. In computers, everything is stored in binary (base 2). This makes it convenient to use powers of 2 to express sizes and memory addresses. 1024 is 2^10, the power of 2 which is closest to 1000. So computer engineers used the term gigabyte to denote 1024 megabytes (as ...	[ "Playboy is a household name. 0G Juggs isn't. One looks good on any modeling resume (not to mention the contacts), the other is kinda limited." ]
Why are crushed stones placed on railway tracks?	[ "The ballast spreads out the weight on the rails, holds the ties and thereby the rails in place, and allows water to drain off the rail line. Smaller particles would be more easily moved out of position by water, freeze/thaw cycles, wind, vibration from passing trains, and all that stuff." ]	[ "Round here (Telford, UK) the local one stores salt for de-icing roads in winter. There's another one around which has a riding school in it." ]
What's was different with the earth for it to spawn the creatures we have now oppose to large creatures like the dinosaurs once again	[ "_URL_0_ This phenomenon has occurred in specific areas throughout the history of all life due to special circumstances in their adaptation vs. abundance with a pinch of environment. In pre-cambrian times, the atmosphere was a tad different, but the underlying mechanisms that drive mutations and hence, an organism'...	[ "This question is rather ambiguous. Could you clarify? Do you mean creation of new mass, splitting atoms into their composites, or making new elements? TL;DR more stuff, dissecting stuff, or new types of stuff?" ]
Why is it that we laugh more when we watch a movie with others than we do when we watch the movie alone?	[ "Laughing is primarily a social signal that is used to indicate solidarity with others. If we are laughing along with other people, it indicates to them that we are similar to them (because the laugh shows that we like the same things). Robert Provines is a psychologist who has studied laughter and found that peopl...	[ "When you talk normally, you're generating the words, tone, and rhythm from your head before you open your mouth; when it's time to read, you have to look at the words manually and recite them one at a time, and you may not be able to anticipate how the entire sentence or line is supposed to sound. If you get a cha...
Does every piece of matter in the universe really affect every other piece (even negligibly)? (Physics of Douglas Adams's Total Perspective Vortex)	[ "An important consideration here is the finite speed of the propagation of information (the speed of light), which means that an event can only influence other events in its future light-cone; therefore it has no effect on anything which is occurring simultaneously with it. A piece of cake on earth would eventually...	[ "If you know the full Hamiltonian for your system and the initial state, you in principle know how the system will evolve for all time. The time evolution is governed by the [time-dependent Schrodinger equation](_URL_0_). However you don't necessarily know what the results of measurements will be. For example, if y...
Why are humans so weak (pound for pound) compared to many other animals?	[ "Because we evolved large brains and use tools to control our environments and protect ourselves. We never needed to be that hench to get by." ]	[ "Infants and children need bonding and attachment. When they get hurt, they aren’t sure what to do and rely on the adults around them for comfort and care. We as adults teach children that it’s ok to fall and get back up from it to keep going. It’s what we were taught as children and now as adults it’s easier to st...
I understand that plants (specifically flowers) are killed when we cut them from their original location, but how does placing them in vases of water and plant food keep them alive for a little longer?	[ "I would disagree with the statement that you kill the plant if you cut them. Plants are not like animals so you done have organs in some location that you need to survive or blood supply to transport oxygen. they are more distributed and uniform in the construction. Cutting plants and putting them in water result...	[ "The heart doesn't work alone to pump blood. When you exercise, a lot of other systems kick in to help blood get through the body easier and recycle to the heart more efficiently. Movement of other muscles and one-way valves pushes blood along and veins dilate and contract to direct flow. Exercise makes those syste...
Why does light have a speed limit?	[ "Need a foundation of the universe to explain this. We live in a four dimensional world, with time being the fourth dimension. We are always moving through time. Similar to the way inertia shifts when you make a turn from going straight to going right. Something similar shifts from time as something speeds up. At a...	[ "> I don’t even know if this question makes any sense I’m just curious. It makes sense in that I understand what you're asking, but it doesn't make sense in that it's a meaningless question; it has no answer. A photon is always traveling at c in all reference frames, and to measure the passage of time, that can't b...
[Medicine] Is ultrasound therapy a legitimate means to treat calcification in the achilles tendon (or similar conditions)?	[ "Yes. Speaking as an Occupational Therapy student who has studied the effects of using ultrasound as a modality I have seen the positive results. The settings of the ultrasound should be on continuous to penetrate the tissue and create a deep heat. This promotes tissue healing by increasing the blood flow to the ar...	[ "Edited: I have heard two things... * Rockets sent up to record various aspects of the test. * Vertical smoke flares which are used to observe the shockwave Edit 2: [Seems like it is a combination of the two](_URL_0_): > Sounding rockets or smoke flares may be launched just before a device explodes so that their v...
Can you find exactly how many grams of sugar are in a liquid, using nothing but a hydrometer?	[ "Assuming that the solution is just sugar water then yes, you can get a pretty good answer. Sugar water doesn't have a significant volume change upon solvation, so if you know the volume and the specific gravity it is straight forward to figure out the mass of sugar." ]	[ "Humidity. When it's a higher humidity. The air contains more moisture. Our bodies sweat to combat heat. Sweat evaporates. It's easier to evaporate in low humidity because the air is willing to take in more water. When water in the air is high. Sweating no longer helps us because the air can't talk in as much moist...
How do Starbucks pay it forward chains work?	[ "By the time you get to the window, the guy behind you has most likely already made his order. So you say to the barista \"Hey, can you actually add his order to my check?\" The barista complies with your request, and then you pay for it. When the guy pulls up to the window, the barista tells him the check has alr...	[ "I’m not a scientist, so I can’t explain like you’re 5. However, it’s a combination of a few things. Space is empty, so there’s nothing to interfere with the signal, unless a satellite momentarily dips behind a planet. Basically there’s a network of satellites around Mars that pick up a signal from the ground on M...
Why does it seem like airplanes with wings that curve up like the F4U-Corsair are more maneuverable than straight wing aircraft?	[ "in fact, that upward curve, called dihedral makes the plane inherently stable and thus less manoeuvrable. Which is why modern fighter jets have wings that point downwards. That makes them hard to control but that is compensated for by onboard computers." ]	[ "Yes, the transiting planet should more or less pass between the our telescopes and the star, which of course is a limitation. There are some alternatives that do not require the planet's plane to intersect our line of sight, such as Astrometry. It involves measuring the wobble of the star as the planet orbits aro...
Where does the image and origin of the wizard( in popular culture & imagination) come from? 🧙‍♂️	[ "Without discouraging further discussion, since it answers only part of your broader question, u/TheLionHearted wrote [an answer] (_URL_0_) about the iconic pointy hat." ]	[ "not discouraging anyone from contributing more info on this topic - especially with regard to how common pets were - but FYI there have been lots of questions about pets, so check out these posts for previous responses. [When and why did people start keeping pets?](_URL_2_) [When did it become common for people ...
Why is dental care considered to be "separate" from other kinds of medical care? Is it this way outside the US/Canada?	[ "It's another way to save money. They say that dental care is a way for \"fashion\" or for an \"appearance\". With much of it being considered as a fashion accessory, there isn't reason to consider it for regular healthcare or medical care. And so with that being, that's why you usually pay for dental care from you...	[ "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." ]
Why do people blur/blackout license plates when posting vehicle pictures online? When I can obviously see everybody's license plate while out in public.	[ "Online, pictures of cars are often pointing out what an awful job they did parking or driving or whatever. Also, reddit specifically asks that we don't post personal information. If we could see the plate for the guy that parked like a jack-ass at the local Goodwill, some other jack-ass might look up their informa...	[ "When a photograph is trying to reach the level of \"art\" it is trying to say something. Black and white, while not the only way to make a photograph worthy of being called art, has several advantages that let the photographer \"say something\" to you more easily. Black and white images force you to look at the s...
How does the optic nerve know what color a particular photoreceptor in the eye is responsible for?	[ "I think a useful way of understanding OPs question is this: how does the optic nerve represent color information? The answer will be something like the spatiotemporal pattern of firing of the retinal ganglion cells which constitute the optic nerve. A vision expert can elaborate." ]	[ "The most intense light is in the red orange part of the spectrum, look at the solar spectrum. Since a plant isn't likely to expend energy to produce a whole range of different molecules for energy production it is more expedient to use one that absorbs what the sun is putting out more of, I.e. red ight. Every ener...
How come old people tend to wear those really big eye glasses? What's wrong with smaller glasses/contacts and/or laser surgery?	[ "Your field of vision gets larger the larger the glasses. The older you get the less you care about looks and you start to care more about what works best. As far as lasik surgery goes i can understand some peoples fear of the laser and others simply cant afford it or their insurance wont cover it." ]	[ "Can you screenshot some examples? That would be very helpful. The most likely answer is that those shows haven't been remastered and are instead using VHS transfers. Most TV shows were on 35mm film just until a few years ago. 35mm film rivals 4K in terms of quality. Look up \"Seinfeld Answering Machine\" on YouT...
- How does the American Health Care system work?	[ "If you get hurt, you go to the hospital. If you have insurance, you give them your information. Insurance decides what it will cover. Then you get a bill for the rest. If you don't have insurance, there are some government programs that can help, but they don't give much assistance. If it's life threatening, and y...	[ "Hi, hopefully someone can drop by to address your specific questions, but fyi there have been several discussions about the electoral college recently; this one is a good starting point * [Question about the electoral college](_URL_0_) featuring /u/uncovered-history" ]
If energy can't be created or destroyed what happens to sound energy after it can't be heard anymore?	[ "The kinetic energy of, say, air molecules, that causes sound by making them vibrate in a specific pattern, gets dispersed to other nearby molecules as they collide." ]	[ "I'm not good at breaking things down to ELI5 levels but AFAIK sound is a wave that requires a medium to travel through in this case air is that medium. Sound will travel further in a more dense medium meaning the apparent volume will be higher. Air at night is colder than air during the day because the sun isn't d...
If the sun disappeared, just vanished, would we be able to tell something has happened before it all goes dark?	[ "According to general relativity, gravity also propagates at the speed of light, as does any other information we could measure about the Sun. Unless we had some way of detecting the event that was about to cause the sun to disappear, we wouldn't notice it until 8 minutes later." ]	[ "This video created by Vsauce 3 (Jake Roper) does a very good job explaining this: _URL_1_ I hope this answers your question. He also did another video on a simmilar line of - could you survive: _URL_0_" ]
Why do some games (e.g. Minecraft) need a launcher instead of directly launching the game ?	[ "There are at least a few reasons. The launchers that many games have now allow the game to check for updates when you open the launcher. It also allows for in game stores and advertising. There are probably many technical reasons as well, but this is why a lot of companies have launchers for games you would not th...	[ "YouTube changed how they pay youtubers to be based on how frequently they upload and the length of their videos. Let's plays, and other game play videos can be very long and don't take much time to make. Not saying they're bad, but these videos are so perfect in the eyes of YouTube they get paid more than basicall...
What do eye doctors use to dilate our eyes and how does it work?	[ "The size of the iris is controlled by a sphincter muscle, those eye drops are muscle relaxant, which blocks the nerve signals that control the muscles, so that they can't contract." ]	[ "A few different ways; - [Lasers](_URL_0_) for really close things like the moon. - [Parallax](_URL_2_) used for nearby planets and stars. - [Standard candles](_URL_1_), the brightness of a specific type of supernova which gives a good range. - [Red Shift](_URL_3_) for things very far away. For more detail on how a...
How does the 'back' option on a browser know exactly where to scroll down to, even though the URL is the same as before?	[ "The browser simply stores the last scroll location in memory so even if a new request is sent (it may well just load a locally cached version depending on settings/browser) it can jump straight to it." ]	[ "A lot of the data your brain uses to control balance is visual. Try walking a balance beam with your eyes closed. This phenomenon happens sometimes because your brain doesn't realize that the object it is using as a stationary frame of reference for your movement, is itself moving. Your brain really thinks you ar...
Why don't I see MORE picture in a 1080p resolution vs 720p	[ "> why isn't the field of view larger as you go from 720p to 1080p? Quite simply, it's because the entire point of higher resolution is usually better quality, not a larger field of view. No one wants a better display just so they can see more of a scene at the same low quality. Instead, they want to see the same a...	[ "Simply put for the same reason drinking water when you're not thirsty isn't as refreshing as when you're REALLY thirsty. Anticipating the bodies' needs doesn't trigger the same reward responses in the brain as fulfilling a need that is already present. Your muscles don't NEED to stretch right now, so you can't ant...
Why, especially in older software, does software load times not decrease significantly with a faster SSD?	[ "I would have to guess probably the efficiency of the code itself. I wrote a program that converts images to black and white in real time (shows the conversion on screen) and before I streamlined the code it didn't matter how fast the pc was it took the same length of time to process basically. once i streamlined i...	[ "Simply put for the same reason drinking water when you're not thirsty isn't as refreshing as when you're REALLY thirsty. Anticipating the bodies' needs doesn't trigger the same reward responses in the brain as fulfilling a need that is already present. Your muscles don't NEED to stretch right now, so you can't ant...
Film restoration: How is it possible that old lo-res films can be "restored" to HD or even 4k resolution?	[ "If the film is actual film then it doesn’t really have a resolution except what you scan it at. So you scan it at a higher resolution to digitize it. Then you fix any bad parts and/or run some filters to make it more modern." ]	[ "HIV infects CD4 T cells, a subset of immune cells in our body. The virus makes a reservoir in those cells by integrating its DNA in the host cell genome. So, infected adults who seek treatment are harboring multiple copies (tens of thousands) of the integrated genome and are pumping out viruses like no tomorrow. W...
Why does "lots of pulp" orange juice still have 0g fiber?	[ "I believe dietary fiber is indigestible fiber, the kind that keeps you regular. If pulp is digestible it would not qualify. I believe orange juice pulp is digestible." ]	[ "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 Chinese restaurants boast "NO MSG!" so much?	[ "There was some sensationalism about MSG being bad for people, and while it turned out not to be quite true the stigma remains for some people." ]	[ "They don't. They just care about your money. Come Easter they will remind you that the best way to commemorate the sacrifice of the lord and saviour Jesus Christ is to lease a 2016 Ford Escalade < /sarcasm >" ]
How can Dell buy EMS when EMS is quoted at being worth twice as much as Dell?	[ "First of all, it's not just Dell buying EMC, it's a consortium including MSD Partners (Michael Dell and others), Silver Lake (a private equity firm), and a Singapore-owned investment company. Oversimplified, they are buying EMC the same way you'd buy a house that is a multiple of your net worth: via borrowing (deb...	[ "I'm not familiar with any case matching that exact description (among other things, an unmarried woman in England in the 1800s would have been legally able to own land without any need for a legal sex-change). The closest case I know of is that of [Sir Ewan Forbes](_URL_2_), though that was in the 1900s. Born in 1...
How and Why deep web exists and why can't we access it through 'normal' browsers?	[ "The Internet is a space of IP messages. \"Normal\" browsers use one kind of IP message to talk to web servers. A different IP message is used by mail transport agents to relay email from server to server until it gets to the destination. The email web is \"dark\" to browsers, because they don't process the message...	[ "This video created by Vsauce 3 (Jake Roper) does a very good job explaining this: _URL_1_ I hope this answers your question. He also did another video on a simmilar line of - could you survive: _URL_0_" ]
Why didn't the Iberian Peninsula play a more prominent role in WW2?	[ "This is a common question so here are some previous answers i could find: On the topic of Spain there are many, [this one](_URL_2_) by u/tobbinator is good to start with but there are many more. I found less on Portugal but [this one](_URL_0_) by [u/vonadler](_URL_1_) Here's a [bonus one](_URL_3_) about a treaty ...	[ "Although you have received very complete answers, I would like to point out some more (although I am not a historian). From pre-Roman times you can find several archeological remains such as the [bulls of Guisando](_URL_3_), the numerous Celtic villages in the North of Spain and in Portugal, called [castros]( _URL...
Why can we "feel" sound waves?	[ "Because sound waves are nothing more than an actual compression wave of air/water/whatever-medium-you-are-in. So a sufficiently loud noise will move not only the very sensitive parts in your ear, but your entire body. And a big gust of wind also produces a sound, it's just often too low for you to hear." ]	[ "Envision jello on a plate. Now envision hairs are growing out of the plate and in to the jello, and the jello is topped with small pebbles that are stuck to it. If you tilt the plate, the weight of the pebbles being pull ed down by gravity causes jello to skew, bending the hairs inside in that direction. That is h...
What would medieval knights or soldiers eat while on patrol or when out fighting?	[ "Going to keep this simple. A lot of people imagine this to be a time of hardship but armies were usually well fed, a very high priority as it is now a days. They had wheat, rye, oats and barley for breads and beer production; beans and peas for soups; apples and berries for fruits; asparagus, beets, carrots, celer...	[ "It depends on how much money they had. In a one way migration from town to town, If they were poor or even middle class they had it on them in a physical way, either in cash, coinage, or mostly they bought supplies with it (wagon, oxen, rifles, etc) before they left. Later migrations they might have a check or a b...
When I go pee I sometimes shiver. Or get the Pee Jitters.	[ "There's a theory that it happens as a reaction from the removal of heat from the body." ]	[ "A friend of mine invited me to the church once for this huuge meeting and I saw others doing it so I started to mock them.. and people thought I was a devoted Christian and started conversations after the whole thing was over.. I can only imagine how many people act on a weekly basis" ]
Why are there war crimes when it is a war?	[ "International humanitarian law attempts to reduce the impact of war on civilians, to finish wars quickly, and to ensure the political goals of a given war are met. It is not a war crime to shoot paratroopers from the sky, it's a war crime to shoot people parachuting from aircraft in distress. When they land, the...	[ "It's not practical or just. If you break my toy and I break yours then now we have two broken toys. A better approach is that if you break my toy then you replace it. Likewise, if you cut off my arm and I cut off yours then we're both screwed and I'm still down one arm. Better if you compensate me somehow than me ...
Water is more dense as a liquid than as a solid. Is there anything about it on the molecular level that would let us predict this behavior?	[ "Hydrogen bonding! In a solid state, the average kinetic energy of water molecules is low enough that hydrogen bonding can happen. This creates a highly ordered crystalline structure with lots of space between molecules. In liquid water, however, the kinetic energies of the molecules overcome the hydrogen bonding e...	[ "Sometimes the surface of the ice will melt when it first touches the bottom/sides of the container you place it in since the container is usually warmer. The bulk of the ice is well below the freezing point. The cooler bulk of the ice cube can sometimes refreeze the ice at the interface faster than the heat from t...
Why do eskimos have a darkish tint of skin color?	[ "They had a relatively recent migration, probably from the Far East, and haven't had time to lose the pigment. American Indians are also pretty brown. Actually if you look at the DNA relationship Eskimos are very close to the natives of Japan (most people living in Japan now are not the original natives). Those peo...	[ "Follow-up question: I once read on this sub that the Tasmanian Aborigines of Australia gradually lost the technology of cold-weather gear after Tasmania was separated from the mainland. Well, it gets bloody cold in Tassie, so how did they cope?" ]
Why does semen turn into rubber cement when exposed to heat (e.g. a hot shower)?	[ "You know how meat gets a little tougher as it cooks? Well, so do unborn babies." ]	[ "Imagine a flamethrower and a crowd of X-Men kids. there's a range of powers. Burn the crowd for 20 seconds and they all die. Burn them for 10 seconds, and maybe that thick skinned or overly hydrated kid survives. He wouldn't have survived the assault for 20 seconds, they would all have died. But now he survived. X...
Did cannibal societies really exist?	[ "Many human cultures have practiced cannibalism throughout history; this isn't in dispute. But it's generally a ritualistic practice, or an act of desperation. I'm not aware of any cultures that have ever engaged in cannibalism as an exclusive form of sustenance, either because the people preferred human meat, or...	[ "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 black people have lighter skin on the inside of their hands?	[ "Everyone does, not just Black people... The reason is because the palms of our hands and the soles of our feet contain very little melanin due to receiving far less ultraviolet rays than the outer regions. And when our palms and soles do receive ultraviolet rays, they don't allow the rays to pass through as easily...	[ "Before DNA science was practical in criminal cases, the only evidence left on a gun would have been fingerprints, which gangsters (both real and fictional) would prevent either by wearing gloves or covering the handle of guns with fingerprint-resistant tape. If there were no fingerprints on the gun, then the only...
The Suez Canal Crisis	[ "Wikipedia has a pretty good summary on the subject: [_URL_1_](_URL_0_) Israel, France, and Britain were less than pleased that Nasser nationalized the Suez Canal (which could lead to him blocking foreign shipping if he so chose). The three countries invaded to try and maintain control over the canal, but internati...	[ "Follow-up question: How much did the Aswan dam affect the system? Did the construction of the dam have a significant effect on the benefits brought by the floods?" ]
Why is benzene a carcinogenic and why is toluene safe?	[ "What makes you say that toluene is safe? _URL_1_ Toluene, along with benzene, are in a class of volatile organic compounds (VOCs) called [BTEX](_URL_0_), which include benzene, toluene, ethylbenzene, and xylenes. These are all considered hazardous and the contamination of groundwater with these compounds is taken...	[ "Casein in milk binds to fats and oils and other things, my guess is it binds to the oils/fats in your mouth to clear them (cleaning your palette), unlike water which would just spread the oil around. Clearing the palette will make the next bite taste like that first bite, which is always the most delicious." ]
The relationship between UNIX, LINUX, and Ubuntu	[ "Think of it like Lego. Unix is the set of rules that define how the different bricks connect to one another. Linux is the bricks themselves. Ubuntu is a Lego set that you'd buy that completes a certain project. OSX is Mega Bloks (follows the same rules outlined by Unix, but has different bricks) Windows is K'Nex (...	[ "Having never heard of _URL_0_ and just looking on their website. Are they like Dropbox or an online hard drive?" ]
Are humans the only species with such a wide range of weight levels?	[ "Consider dogs from a Chihuahua to a Mastiff. Of course that is a size difference. If you are asking can animals get morbidly obese then yes, they certainly can. We don't see it in the wild since they would get killed by predators and/or be unable to catch their prey and die. Pets however can easily get fat since t...	[ "Why are noses different in size, why are people different heights, why do we have different hair colors?" ]
what happens to a program crash report after i send it?	[ "The main purpose is to find out which faults occur most frequently. I'd imagine that this is automated, so no, no one looks at your crash dump routinely if you're referring to an actual person, but it will certainly be analysed. Engineers then try to fix the most common faults first. Before they can fix a fault, t...	[ "Imagine a needle in a haystack that is 10 kilometers wide, and there are only 10 people designated to finding said needle. It would take them an insanely long time. They might find a few of the needles in their allotted time frame, but likely not all of them. When a game is released to the public, it's the same wa...
Can someone explain hair to me?	[ "1. The different colors is just pigmentation just like skin pigmentation, or lack there of. 2. Genetics plays a huge roll in that, I can't remember the scientific names for it but there's a difference between Caucasian, African, and Asian descent hair. 3 & 4. No idea." ]	[ "Leasing is basically just long term renting. You agree to pay a monthly fee/payment to use the car which is often restricted by how many miles per year you can put on the vehicle. However, they will often have warranties and/or allow you to trade in the car for a new/newer one at the end of the lease for relativel...
Why does chelation therapy not work on thallium poisoning?	[ "From what i read, there are solutions which can treat thallium poisoning. \"The optimal therapy for thallium intoxication is currently considered to be the administration of Prussian blue, combined with forced diuresis with furosemide and mannitol, which may be supplemented by hemodialysis. Activated charcoal may...	[ "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...
When the forecast shows something like 20% humidity what does that mean? 20% of what? Shouldn't the air just turn to water at 100% or something?	[ "Percentage humidity is based on the amount of water air can hold. The amount of water that can be dissolved in air is related to temperature and pressure. Warmer air can hold more water than cooler air. The % is the amount of water in the air for the conditions that the forecast is making." ]	[ "Let's say you want to travel to Chicago from Atlanta by car. Can you predict your exact position at any given time? No. You can predict where you are going to be in the next few seconds but as you look further ahead you lose accuracy. Sure, you could say, \"I'll be near Indy around 6pm on this road, but you don't ...
What would happen if you stood 'inside' the northern lights?	[ "You would be floating at an altitude of 100 km above the surface, so I'd imagine the first thing to happen is that you'd have a hard time breathing, then be dead. If some collisions happened before that, you'd get to see the northern lights for a bit." ]	[ "> I see pictures like this: _URL_0_ and long to see this sight for myself. I think those types of pictures are taken using decent cameras with high ISO settings and a long exposure time (maybe 25 seconds or more). They don't reflect what you'd see with the naked eye, unfortunately. Here's one photographer's rendit...
Why does Turkey hate the Kurdish region?	[ "The Kurds want a state of their own. The land which the Kurdish people live in covers sections of the countries of Iraq, Iran, Syria, and Turkey. The Turkish government is unwilling to give up a significant chunk of the land which it considers part of Turkey, and hence has refused to allow the Kurds to declare ind...	[ "Hi, I've approved the post, but just a note to you and potential respondents: this subreddit has a 20-year rule against discussing current events, so any answers will have to cut off at 1997. If you're looking for answers that can include 1998-2012, do consider x-posting elsewhere, eg. a foreign affairs sub like /...
What was the Great Arab Revolution, and what is its significance?	[ "For centuries, the area that we know today as the Middle East was controlled by the Ottoman Empire, which was based in Turkey. During WWI, the Ottoman Empire fought on the side of the Germans. To hurt the Ottomans, the Allies, especially Britain, encouraged the Arabs to revolt and gain their independence. When WWI...	[ "I've asked this before but I will again. Peter Hagendorf was a soldier in the Thirty Years' War who kept a famous diary of his service that seems very unique but I'm completely unable to find any English translation of it anywhere either online or in print. Do any Thirty Years' War experts know where I could find ...
Is there anyway to genetically alter a dog or any other domestic animal to keep it small and young? For example: Keeping a dog the size of a puppy and to look like a puppy forever	[ "To some degree. That's exactly what was done to modern dogs, in fact; at all stages of growth they more closely resemble wolf pups than adult wolves (and some breeds don't grow past the size of wolf pups). You can't actually prevent aging though." ]	[ "The issue is related to file format/encoding, most likely. Some sources like video games, Youtube and phone cameras compress the frames using very space\\-saving algorithms. This means using parts of one frame \$the keyframe\$ of video for the next and so on. It's called \"long\\-GOP\" compression. This makes it...
How does silver nitrate turn glass into a mirror?	[ "Silver nitrate contains silver. You need to dissolve the silver nitrate into solution... usually with a strong base, like sodium hydroxide. If you place glass in this solution and heat it, the silver will come out of solution and stick to the glass in a very thin layer. Most mirrors today are made with aluminum a...	[ "Whenever you see that rainbow surface, there is usually some interference going on. Which means that you have a thin film of something and light rays of different wave lengths are reflected in such a way that some wave lengths are canceled out depending on the angle you look at it. Another example would be oil on ...
What does "crisp" and "dry" mean when it comes to beer?	[ "When speaking of alcoholic beverages, \"dry\" is the opposite of \"sweet.\" If a fermented beverage has a lot of residual sugar in it, it will be sweet. if the sugars all get used up by the yeast, or if some other method of reducing the sweetness of the beverage is employed, it will be called \"dry.\" Beers use ho...	[ "Sliding is simply reading a magnetic strip sequence. There's no security to this and it's easily replicated by someone wishing to defraud you if they get a hold of your card in anyway. A chip is a lot more sophisticated and harder to replicate making it a stronger security measure, coupled with a PIN it's a very s...
Why is there a notable distinction in taste between food that is hot and cold?	[ "Not quite like you're 5 but.... All foods we eat have fats and oils right? Well heat can make food break down making it easier for our taste buds to recognize certain flavors and aromas. As with anything cold, it tends to dull our senses. When your taste buds get cold, it makes it harder for your body to recognize...	[ "Neural adaption. Basically, your brain only cares about a change in stimuli rather than every stimulus that comes along. Your brain knows how to ignore a stimulus if it isn't changing. So, if you are tasting/feeling the same thing all the time, your brain is going to ignore it." ]
How do you destroy a virus sample, like smallpox?	[ "In an autoclave, usually. An autoclave is basically a medical steamer, heating up its contents with high pressure, high temperature steam. This causes most biological molecules to fall apart. Aside from that, anything that can denature proteins can damage the virus. Drown it in acid, heat it to high temperatures, ...	[ "No where actually, all the data is still on your hard drive. Your computer has just marked that files spot as usable space, eventually it'll get overwritten. There are special programs that can fully erase a file by writing a bunch of zeroes over it." ]
How do illegal contract breaching gets resolved	[ "A contract to commit an illegal act is unenforceable. It falls apart under its own weight basically. The player in your example is just screwed out of their money basically. No legal recourse exists for them." ]	[ "As a follow-up to this, in general, how vulnerable are black markets to economic lurches such as this? Does operating outside the law afford some insulation, or are the effects worsened due to complete lack of regulations and protections?" ]
How did WW2-era Japanese nationalists reconcile the cultural debt Japan owes China with their belief in Japanese superiority over the Chinese?	[ "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 ...	[ "It would often depend on the religion and it's practices. They could occasionally see some of their gods in another religion, and co-opt them in a way; Egyptian religion was the big one, with most of their gods being compared or equated with others. The Greeks and the Romans did it between themselves; many Roman g...
Does listening to music at a higher volume (on a phone) use more battery?	[ "This has been asked before here: _URL_0_ . TLDR: Yes." ]	[ "I would imagine they're head pretty similar thing to us, although they wouldn't be able to comprehend the meaning behind the song. Most animals are able to detect patterns, so it would be interesting to see what kind of experiments you could test out with music. What if you play a certain song every time you feed ...
on the lines of the fact that its an evolutionary advantage for trees/plants to create fruits to help reproduction and general survival, why would it be an advantage to make one thats unbelievably spicy?	[ "Birds do not have capsaicin receptors, so they are more likely to eat it and may spread the seeds further than other animals." ]	[ "Capsaicin in chili peppers binds to spots on the tongue that make the brain think the mouth is literally on fire, and the best way the body has to flush it out is a runny nose and watery eyes. Also, this gets asked fairly often. Better to search first." ]
If there are no lions in Europe, why are they all over European heraldry?	[ "modern europeans largely have a greek/roman lineage, to some degree (at least culturally). romans had lions. Lions are depicted in the bible. Lions territory used to be quite large as well, living in southern europe." ]	[ "On mobile, sorry for the formatting. Based on this Norwegian text (\"The Historical Northern Lights\") _URL_0_ There is disagreement on wether northern lights are mentioned in the Edda. According to some, NL in norse mythology are explained as reflected light from the shields of the valkyries. The first certain (...
If I'm paying a computer technician to speed up my computer, what do they actually do?	[ "Laugh all the way to the bank. Seriously, all the things you're seeing in these posts are simple. Learn how. You're going to own computers for the rest of your life." ]	[ "The way I understand it, it gets \"marked\" to be overwritten. Meaning when new data is put onto your hard drive, it goes into space on the drive waiting to be written to. This space could be empty or have data on it that is \"marked\". There are programs that will overwrite this free space numerous times to ensur...
What makes bright reflective paint, like the ones on license plates, reflective?	[ "Retroreflective paint works because of geometry. In most cases, the paint consists of either tiny beads of glass or glass-like material, or microscopic corners set at 90 degrees from each other. This means that any light that comes in is reflected back in the direction it came from. Since that is generally about w...	[ "Speculative, as I know of no scientific study on the subject, but I am an electronics technician and electronic warfare specialist who works with various radio and radar equipment. It's possible that the angle of your radio station relative to the freeway (and thus overpasses) is such that just as you go through t...
How do fever blisters "decide" what part of the mouth to sprout up on?	[ "Basically, there are T-cells (type of white blood cell) in your skin that are meant to fight the infection but they're not always evenly distributed and if the virus is able to attack an area with a low t-cell count then a cold sore/fever blister will appear. The [source](_URL_0_) I could find references HSV2, bu...	[ "They make an agreement with a salesman for the local distributor. Usually they pick whoever will make them the better deal." ]
What kind of food did the Romans eat? In Rome itself, say about the time of Augustus.	[ "hi! there have been a few questions about Italian cuisine, so check these out for previous responses [What was Roman/Early Middle Ages food like in Italy?](_URL_4_) [How different is food preparation/taste 2,000 years ago vs today?](_URL_0_) [What were some Old World cuisines like before the Columbian Exchange?](_...	[ "Follow up: what materials were used in the construction of various homes/commercial properties? And who constructed them - did they have architects, etc for homes of regular folk? Or did poor people build their houses themselves?" ]
Why does a sound sound different after you've heard it more than once in a row?	[ "When your brain notices repetition, it filters out what stays the same so it can better notice what changes." ]	[ "I think we develop a \"been there, done that\" mentality in ways. I can not watch cartoons now. No matter what the topic. The irony is I just can't pay attention to cartoons." ]
If a certain result has a 1/x chance to occur per action, on average which iteration will it first occur on?	[ "1. Ask this question on r/learnmath if you want the most correct answers to be upvoted. 2. The first occurrence occurs the xth time on average. To see this, consider a long experiment consisting of, say, 1,000,000x trials. The event will happen about a million times, which means that the average gap between occurr...	[ "Fast internet and faster servers. Human reaction times are on the order of 100ms or so. Ping time, which is round-trip packet flight time is often on the order of half that or so. Round trip is therefore on the order of human reaction if you give the server a little time to do stuff. Also, the server only sends b...
How much did hunter-gatherers walk and run on a typical day?	[ "Check out the article on [persistence hunting](_URL_1_). Basically, we think early humans hunted by chasing after animals until their prey collapsed from exhaustion. Humans are uniquely suited for this because: * We run on two legs, which isn't as fast as running on four legs but is much more energy efficient, all...	[ "As far as my studies have gone, it's instinctual. Some birds use the earth's magnetic field, some use their parents and follow them and learn the path, others are genetically engineered to just know where to go. There's a term in ecology that we borrowed from German - zugunruhe. It's basically how animals exhibit ...
Why does meat go from pink to white/brown when you cook it?	[ "Myoglobin is a protein present in meat, which gives meat its red pigment. When your raise the temperature, the myoglobin molecules re-arrange themselves and that results in a colour change. The same applies to white meats, but with significantly less myoglobin." ]	[ "Analog TVs had a circuit called the [\"color killer\"](_URL_0_). It was designed to eliminate any color from the screen when B+W programming was being received. The B+W signal did not have a [color burst](_URL_1_) reference signal, and it is the absence of this color burst which triggers the color killer. Static m...
How did Werner Van Braun feel about being taken to the US?	[ "German scientists were taken to some sanatorium at Gorodomlya island at Seligyor lake, they lived there much more comfortably than most of Soviet scientists. They actually had made a contract to work there and were allowed to take with them wives (or mistresses) and children. German engineers were paid quite well ...	[ "This has been asked a few times, but there's never been, as far as I can tell, a comprehensive and well-sourced answer. So, I encourage people to provide one. That said, there have been _good_ answers. Here's [one](_URL_1_) with some good debate about what McCarthy got right or wrong, and [another](_URL_0_) that ...
What is the original cause for the apparent deep rooted and centuries old antisemitism in some parts of the west?	[ "Basically the Jews are one of the only groups to have survived from antiquity to today. You exist long enough, and you'll make some enemies. Keep existing, even outliving your enemies, and their stereotypes and prejudices will morph through the ages. The real beginnings of it seem to be split between ancient Gree...	[ "Because to our primitive ancestors, different usually meant bad. That tuber smells different? Probably rotten, don't eat it. Your dog acting weird? Might have rabies, stay away. That stranger looks different than you? Probably from a rival tribe, and up to no good." ]
Why can't we harvest blood from a dead person like we do organs?	[ "It's impractical. Blood coagulates quickly and most of the situations where the person is ideal for organ transplant (e.g. young and healthy) are situations where the person dies of some sort of trauma, which of course usually leads to large amounts of blood loss." ]	[ "It takes a ton of energy, and the cost is prohibitive. [Here is a good explanation why](_URL_0_) Here are some other discussions on this topic. _URL_2_ _URL_1_ _URL_3_ _URL_4_" ]
Why is it our eyes capture much attention from blinking lights compared to a continuous lighting ?	[ "It's not your eyes, it's your brain. We are wired to detect motion and change, as this is extremely important for survival. The ability to perceive motion developed a very long time ago (right after light/dark differentiation) and seems to be common to every organism regardless of other features of their visual sy...	[ "Because the thing you wanted to do next came to your mind BECAUSE you were doing the other thing. Say you were unloading the dishwasher, you saw that one glass with Anna from Frozen on it, which reminded you of the fact that you promised your daughter that you would fix her Olaf figure before she comes home from k...
How are emergency numbers (e.g. 911) handled near borders of countries?	[ "Well in the EU it's the same for all countries and they route 112 to the nearest emergency dispatch. While standing in one country and being connected to a different countries cell tower could cause issues they generally inform the correct emergency service and worst case a German ambulance will pick you up in Bel...	[ "US states can't deny the validity of legal documents in other states. So if I own some property in Texas, and I bring that up as evidence in an Oklahoma court case, the court can't decide it doesn't count because it's from the wrong state." ]
What is the difference between the European Union and the European Commission and the European Community?	[ "As explained earlier, just a bit different. The European Union is a group of (now) 28 countries which have agreed to enhanced economic, fiscal and political cooperation and integration. The European Community is the older name for it. The European Commission is the civil service of the European Union, and their j...	[ "Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s): You can find the basic answer with a google / wiki search. Please start there and come back with a more specific question. If you disagree with this decision, please send a [message to the moderators.](_URL...
When did cars begin to outnumber horses and horse-drawn carriages?	[ "[This](_URL_1_) provides some idea of the horse population in the US. [This](_URL_0_) provides a graph the number of registered motor vehicles year on page 13. Comparing the two there were more horses than cars in 1925 (22million to 20 million) but more cars than horses in 1930 (26.3 million to 18 million) . So yo...	[ "Niépce's house is now a [museum](_URL_1_) and photography is not allowed inside, so unfortunately there is no modern photograph of the view from the window that I can find. That said, [on the website of the Harry Ransom Center](_URL_0_), you can see a sketch done by the historian Helmut Gernsheim, who rediscovered...
How are ballistics from casings and weapons unique?	[ "Ultimately there's a lot of loose tolerances involved, which leaves enough room for individual differences to emerge even in brand-new firearms. There is no need for those weapons to be more precisely machined (I wonder what would happen if the CSI had to deal with a one-of-kind $20000 sniper rifle manufactured to...	[ "[The Fordham Internet History Sourcebooks](_URL_1_) are pretty much go-to in terms of finding major/commonly-assigned primary documents in simple text format. The faculty in my department use Fordham docs a ton in assigning readings. I use the [Public Records Office of Northern Ireland](_URL_0_) online selection, ...
Help: Discerning sources about Mao's Cultural Revolution	[ "Tbh as someone who studied Chinese and modern Chinese culture, you'd be hard pressed to find kind things about Mao outside a sort of socialist /Marxist or Chinese community. Within those communities, however, views varry , but often paint Mao in a mostly favorable light. I have some books on the cultural revolutio...	[ "Way too quiet in here! Everyone seems to be watching the World Cup... A technical question: How does everyone search for book reviews? Is jstor's search usually comprehensive enough when it comes to history/humanities journals?" ]
I am a paratrooper preparing to drop into Normandy on June 5th 1944, the day before D-Day. What equipment am I issued by the US army, and what equipment am I likely to have that is not GI?	[ "Leg Bags these were a British invention issued to American units. the idea is simple, a bag full of kit strapped to your leg, after you've jumped and your 'chute has been deployed, you lowered your leg bag. this acted as a land anchor, as it was quite common for parachutist to land, and then get blown about by the...	[ "The Voyager spacecraft were launched in the 1970s. They actually did use (and still do today!) digital transmission. They were one of the earliest successful uses of a type of error-correcting digital code known as Reed-Solomon. Quite a triumph of 1970s technology. (Today, CDs and DVDs use a similar form of digita...
What are curlers screaming about?	[ "When you sweep a rock it does 2 things. It makes it go further and it makes it go straighter. Generally the Thrower and Skip call the line because they can get down low and look right down the ice. They will tell the sweepers to sweep if the rock is curling too much. The sweepers are in charge of making sure the r...	[ "I used to work for our local TV station, Ch3 WEAR, in the master control department, and one of our jobs was to prep all commercials ran locally prior to them being loaded into our playlists. So, that meant checking captions, volume levels, run time, etc. If any of these were off by a certain margin, we had to con...
Why do mobile phones cost more than feature-comparable tablets?	[ "Because it's more expensive to make components that have comparable performance, but are smaller." ]	[ "Its the software not the hardware that does that. The same way your screen is made up of an array of pixels, the touch portions is an array of sensors. When you touch the screen it sends a signal saying \"I've got a touch centered at X1,Y1\", then you slide your finger it keeps reporting where it sees the touch. T...
If I exercise my left biceps, it will get more blood. Will my right biceps get a similar increase in incoming blood?	[ "Your body has mechanisms to locally control blood flow. Little rings of smooth muscle called precapillary sphincters can contract or relax to decrease or increase the amount of blood going into your capillaries, which is where oxygen exchange takes place. There is also smooth muscle lining your arteries (which car...	[ "First, let's separate out language and it's writing system. Writing isn't language as much as a representation thereof. There are \"right-handed\" and \"left-handed\" languages in the way you suggest. Second, considering that the Pheonician scribe was the origin of both the Latin and Cyrillic systems (left to rig...
How does an octopus know what color its environment is when it blends in to hide?	[ "All octopus are colorblind, but they do have very acute eyesight and are able to consciously match their skin pattern to the background they see. Their ability to match the color in their surroundings comes from special light-reflecting cells within their skin. So they basically have no conscious control over the ...	[ "Have you ever walked into a room that had an odd smell, but three minutes later you couldn't really tell that the smell was there? Have you ever suddenly realized how hungry you are when someone passes by with a tasty looking snack? Have you ever had to pee, but you were busy doing something so it didn't really se...
How do some kids under age 12 get into college/university?	[ "The program I know of is the University of Washington's Robinson Center, that attracts young students who participate in the [Center for Talented Youth](_URL_0_)'s Talent Search (students with 99th percentile standardized scores are allowed to take the SAT starting at 12). Students who get a high enough score (it ...	[ "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." ]
How are trace amounts of chemicals detected in a sample?	[ "I'll add ICP-AES since no one has mentioned it, yet. [Inductively couple plasma atomic emission spectroscopy](_URL_10_) is used for trace metal analysis. Soil scientists use this method frequently. It's also used for trace metal analysis on both industrial and reagent grade chemicals, like if you need HCl with as...	[ "Online tracking is easy. Whenever you click on an ad, it sets a cookie on your computer that marks you as arriving to that site from the ad. Your each activity on that site is tracked and noted when you make your purchase. Offline is a bit different. Depending on the size and marketing efforts of a company, they m...
Why do black fabrics bleach to orange?	[ "Black has a lot of underlying pigments that when lifted will show. Starting from black bleach will lift it to red, then red orange, then orange red, then orange, then orange yellow, then yellow, then pale yellow, then finally white. I'm no scientist, hairstylist actually, so this is the fundamentals of hair colori...	[ "Robots and machines are really really expensive to build, develop, and maintain. People in Bangladesh are dirt cheap labor that can accomplish the same thing at small fraction of the cost of said robots and machines. Clothes being an easy item to construct, a cheap item, and a safe item, it doesn't make a lot of s...
How were the Cheka and the Okhrana different from each other?	[ "You might be interested in some previous threads comparing the Cheka and the Okhrana: * [Was the USSR's method of keeping order (especially under Stalin) similar to the old tsarist way?](_URL_1_) - 4 comments, over 1 year old. * The commenters here explore the goals of, methods used, and punishments inflicted by b...	[ "Follow-up question; when did the Greek phalanx go out of fashion in favour of the Macedonian style, and why?" ]
Wed. AMA on the Middle Ages: Carolingians to Crusades ( & Apocalypse in between)	[ "> why I hate the 19th century Arrow to my heart Why do you hate the 19th century?" ]	[ "I don't have the time to answer this in depth, but 1913: The Year Before the Great War by Charles Emerson seems to be exactly what you're looking for. Be careful not to adopt a teleological view of history - even though it's obvious to us that WWI 'will happen', people at the time weren't quite so convinced. T...
The theory that black holes can be used for time travel.	[ "First it's important to realize that Black Holes aren't really holes, they're just an astronomical amount of stuff all compressed down to a relatively small size. But with all that stuff in such a small area of space comes a lot of gravity. Gravity does not just affect 3-dimensional space such as an object or a pe...	[ "The amount of information that's possible to store in a given chunk of space depends on its surface area instead of its volume. This is weird; the number of hard drives or sheets of paper you can store depends on volume, so why would a more efficient storage medium only scale with surface area? You can mathemati...
Why do dry erase boards become so dirty and difficult to erase fully even with a new eraser and proper pens?	[ "This is because the special surface wears out ove time. My office actually used Dry erase paint and turned our walls into a giant dry erase board, once it starts getting hard to erase, a new coat of paint will fix it up! _URL_0_" ]	[ "Imagine your hard drive as a giant wall, like the Great Wall of China. Now imagine that your files are painted on this wall (Images, text, music notes). When you delete a file, your computer finds the spot on the wall where that file was painted, and marks that section of the wall as \"free\". It doesn't scrub o...
What causes that sudden sinking, heavy, hot flush feeling when you become anxious and how are the effects felt so rapidly?	[ "I have that exact same « hot flush » feeling when I get anxious so I know what you mean and the best answer I found was on _URL_0_ . I copied-pasted the interesting part : « Body heat rises as a result of what's known as vasoconstriction. With a functioning fight/flight system, your body needs to be able to prior...	[ "Nobody knows for sure, is the short answer. The slightly longer but still short answer is that the best guess anyone has is that it's a temporary \"short circuit,\" of a sort, involving your long-term and short-term memory. Your knowledge of things that happened to you two seconds ago comes out of your short-ter...
Why are pancakes round, and what's the role of gravity and surface tension in this?	[ "When pancake hits griddle, gravity exerts a force on every single particle on the pancake. The ones that are immediately against the griddle stay in place, because they're already pretty cooked, but the free particles on top want to move down. With other particles in the way, they can't, but since there is a peak ...	[ "> A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the r...

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