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Why can't humans survive off of only vitamins? | Vitamins don't have calories, which humans use for energy. They also lack many of the micronutrients we need to survive (sodium, potassium, magnesium which we need a good amount of). | You absolutely need vitamins to live. For example, if your diet contained zero vitamin C you would get scurvy and die. However, it turns out that unless you're only eating one very specific thing it's hard to have a vitamin deficiency so severe that it negatively impacts your health. |
How do schemes like "pay $50 for 50,000 Facebook Likes" work? | By using click farms (a lot of people just clicking likes), the people who accumulate the likes are paid very little to work. They can be easy to detect sometimes but creating more is easy (I dont think you even need to create a capatcha or equivalent). To discourage getting caught they will usually just like everything, | This was a very big concern with early facebook. It was free with no ads and they were bleeding money like there was no tomorrow. They sold private equities to investors (basically, you agree with an investor that your company is worth 1B$, so if he wants 25% in it, it is going to be 250M$. The real valuation process is complex and the results are debatable). Usually the founders lose control of their business in this process, but it is not always the case. Multiple rounds of financing usually occurs before a company can make enough revenues to survive on its own. Once they have enough users attracted by the free service, they start to insert ads into the application / webpage or charge for usage or create "premium content" for paying users. I won't hide that most of those investors lose money, but everyone hopes to hit the next Facebook, or Twitter |
why does temperature seem to affect how food tastes? | A lot of the details in how food tastes comes from the smell. Increased temperature means the volatile compounds that our noses pick up are released more, so the smell (and corresponding flavor) is stronger. It also changes the texture of most food, which is also important. | Higher temperatures mean more molecular activity, which means more activation of the taste sensors on your tongue and more molecules evaporating into your nasal tract to create smells. This can for example make a drink brewed to taste sweet when chilled become cloyingly so when consumed warm. Cultural expectation and familiarity is also an important factor, though, as ungabungabunga pointed out. |
when people drown, do the instinctively stop breathing or do they end up trying to breath in the water? | Drowning is a pretty horrible way to die. After not trying to breathe (because of being underwater) for enough time, the body will instinctively try to breathe despite being underwater... leading to inhaling water... leading to death. It is supposedly excruciatingly painful. | You can't consciously hold your breath long enough to lower blood pH to lethal levels. As the concentration of CO2 in your blood increases, eventually it will reach the *breath-hold breakpoint*, where you will reflexively inhale. If you're still underwater at this point, you will inhale water, triggering coughing and vomiting, and further water inhalation. If you haven't made it to the surface or haven't been rescued by this point, you will die from water inhalation. It's possible to forestall this by lowering the concentration of CO2 (inducing hypocapnia) before you go underwater - by hyperventilating. This allows you to hold your breath longer, but if you do then lack of oxygen becomes an issue. Without elevated CO2 levels in the blood, you can pass out from hypoxia without ever knowing you're suffocating. This can happen in water of any depth, and is responsible for shallow-water drowning. You can find some informative CO2-O2 graphs on the [Shallow water blackout](_URL_0_) wiki page. |
How did the U.S.A. end up with the MM/DD/YYYY date format? | I believe that the format was used alongside DD/MM/YYYY in Britain during the 18-19th Centuries until it was slowly replaced in Britain by the DD/MM/YYYY format. For example, if you can find any old copies of newspapers such as The Times, the header is written 'July 4th 1862' or 'Month/Day/Year'. Unfortunately I'm not quite sure why it thrived and endured in the USA and faded away in Britain. Possibly some link to colonialism. Sorry I can't be more helpful! | Considering that the international standard is YYYY-MM-DD does it really matter? Everyone else is just engaging in local preferences anyway. It makes enough sense when you consider most English speakers, at least in the USA, would say today is May 29th 2015. |
What is a moving average, how is it different from an average, and why would it be used? | It's an average of just the most recent numbers, for example the daily closing price of a stock averaged *for the most recent 30 days.* It shows you the recent trend without as much bouncing up and down (volatility). Every day, one new number is included, and one oldest number is dropped. | Averages can be a little odd. It was explained to me this way: a typical class can be 30 while the average is 22 if you have enough smaller classes of 10 or 12 (either advanced, remedial, specialty or SPED classes can sometimes be this small). |
How can a current create a magnetic field when there is no time varying electric field? | It's the same way that an electric charge at rest creates an electric field even though there is no changing magnetic field. There are two different ways to make each type of field: charges and/or changing magnetic fields make electric fields, and currents and/or changing electric fields make magnetic fields. | If you look at maxwell's equations, a changing electric field begets a magnetic field and a changing magnetic field begets a changing electric field. If your change is linear with time, meaning your field isn't "accelerating" you can generate a static field of the other kind. Ultimately, this results from special relativity. If a solid rod of electric charge passed you, you'd see a "current" and thus a magnetic field, but if you sitting on the rod, you'd experience no magnetic field, only electric. You can read more about that here: _URL_0_ If special relativity is a bit too much to take in, I recommend just looking up the Lorentz force and Faraday's law of induction separately. |
Why is human sexual selection so focused on beauty [esp. facial beauty] when it has no survival value? | The majority of facial traits seen as beautiful are used to determine the health of the individuals. For example the greatest determination of person beauty is how symmetrical the persons face is, this is a sign of healthy growth though out the persons life time. Eye size which is common in women for attractiveness is used to determine the age of individual, since human women lose the ability to have children youth is important as a sexual trait. This is also while being skinny is so important. Red lips are a sign of good blood flow, Hair is a sign or good health, and the hour glass figure is excellent for having children. You can also see the these evolutionary factors in how different gender approach mating. Society seems to be more comfortable with a older man (Who can have children at almost any age.) with a younger woman, then the opposite. And women seems to be less choosy about appearance, when the man is able to take care of their children with wealth or power. | Since agriculture began, people haven't always chosen their mates. In many cases families would arrange marriages years before the participants were fully grown. In other cases marriages between adults were done for political reasons. In these cases attractiveness would play only a minor role. Also, I believe there is evidence that people "find their level" of attractiveness in finding a mate. Therefore people of lower attractiveness will often mate with others who are "in their league" and are thus likely to have babies who are about as attractive as they are. Finally: attractiveness isn't entirely physical. A pretty but vapid person might be far less attractive than a less beautiful but more intelligent one. Especially when thinking about having a family. |
How AC can be converted to DC without a source of electrons. Does DC drain electrons? | Using things called diodes. More specifically, a diode bridge. Even more specifically, a full wave bridge rectifier. A diode is like a one-way check valve. Current can only flow through in one direction, but not the other. Putting diodes in a bridge configuration, you can convert the AC to choppy DC. It's choppy because it has dips when it's switching phases. That can be smoothed out with a decent sized capacitor. (capacitor acts as a temporary energy storage unit that fills in those dips to make the output smoother like normal DC) It's very difficult to describe how the diodes are laid out for a full wave bridge rectifier, so here's a link to a quick youtube video that explains how they work: _URL_0_ | First of all, there are appliances that run better on AC power, so why waste effort on converting it? Items that involve motors or resistive heating either want AC power or are perfectly fine with it. Second of all, you don't know the voltage of all possible DC appliances. If you're going to need to transform your voltage anyway, you might as well just leave the power as DC. In theory, you can speculate about some future where all the power sockets in our homes are 5V USB-Q or something, capable of charging your cellphone or running your washing machine with equal facility. But we're not there yet. |
How can you extract ROMs from video games? | There are devices you can buy, called 'cart dumpers' that let you do exactly that - connect a cartridge to a computer. You would then need to run a program to pull the data off of it, depending on cartridge type. A bit of searching and I found these: * _URL_0_ - a community for the (now discontinued) Retrode cart dumper, which lets you plug in any Sega/SNES cartridge and pull the ROM data out of it as if it were a flash drive * _URL_1_ - a NeoGAF thread showing the process I described above. edit: formatting. | Emulating is legal, if you own copies of the game, and rip the ROMs from those copies by yourself (you have to make the roms from your own copies of the game using special tools). Anything else is copyright infringement and can be prosecuted as such. Of course, with some emulators, like PS2 emulators, you can just put a the game disc in your computer drive and play it. *That* is by definition 100% perfectly non-infringing, because emulators don't infringe anything. Roms and ISOs are where copyright infringement exists. |
How did "Chinese" food in the U.S. get so standardized? | The Chinese Exclusion Act in the 1800s banned Chinese immigrants from doing pretty much any good jobs which drove Chinese Americans to slums. Chinese food was considered dirty and for poor people as a result. The act was repealed during WWII because China was considered an ally. As a result Chinese food didn't really catch on in the US until fairly recently. During this time, the majority of Chinese immigrants to America came from a handful of places in China, most of them ended up in New York, and most of them were illegal immigrants who found work in restaurant kitchens. They adopted their cooking styles to what was locally available, i.e. General Tso's Chicken is just chicken nuggets smothered in sauce. There's a very good documentary on Netflix called ~~General Tso's Chicken~~ The Search for General Tso which better answers your question. Edit: thanks u/deuce232 for the correction | No one knows exactly why, but mostly, it's because very long ago, China really was the cultural center of Asia. So a lot of the reason why Koreans and Japanese eat rice is because ancient Chinese people ate a lot of rice. So why did Chinese people start eating rice and not wheat or barley? It turns out the climate around the Yangtze river is almost perfect for growing certain types of rice. It was easy to grow, easy to store, and lasted a long time. So it became the grain of choice just because it was easy to feed people with it. Since a lot of people lived near the Yangtze river, they starting making other things from rice, such as wine, cakes, and even special holiday meals. So over time, the traditions and cultures got passed down. But fun fact, In North China (where I am from) rice is traditionally not as common as you think. We still have it, but in fact wheat and barley are also very important grains in those regions. |
Is there an actual problem with the police in the USA? | For the most part, police officers and police organizations are just fine. I mean, they can be seen as a little dickish because no one likes getting a speeding ticket or whatever, but in general they are OK. But there are enough officers who are actually dickish - racist, sexist, overly violent, corrupt, and so on - that it's not impossible to come in contact with a really bad situation. And police officers do have kind of a brotherhood thing going on which means that the bad cops get backed up by the good cops, so the bad ones tend to drag the good ones down to their level. | Some people feel that it would prevent the police from being able to do their job if they are going to be scrutinized by the public and risk losing their job over every little incident. |
How is water managed and supplied in Trains ? | Pretty much like in an RV. There are tanks to hold clean water, typically refilled with a hose at the ends of the line. These are usually mounted above the sinks and toilets, so gravity delivers the water. The drains all connect to storage tanks under the cars, which are pumped out at the end of the line. | It all goes out of the house in the same pipe. Then it goes to a water treatment facility that filter, cleans, and treats the water and sends it either into the water table or back into the water supply for the city (I'm honestly unsure if it gets recycled directly back to the city or not) |
How can American Airlines file for bankruptcy but continue to buy brand new planes? | They're in Chapter 11 bankruptcy. In a Chapter 11, a business continues to operate as usual, it just goes through a judicial proceeding to create a "plan" to restructure its debt. There are certain restrictions on what a business in Chapter 11 can or can't do, but for the most part it's business as usual. | [Great video by Healthcare Triage](_URL_0_) on the topic. Healthcare related debt is the primary cause of bankruptcy in the US, but that's not that common of a thing to happen, you probably dont know anyone who has filed for bankruptcy either. As for where to look, I can't offer much help on that (im from the UK so don't know much about individual insureres in the US). |
If we say there are no privileged frames of reference, was the Catholic church technically wrong when they said the Sun revolved around the Earth? | There are no privileged *inertial* frames of reference, but rotation is a non-inertial frame. Of course, the sun itself is revolving very slightly around the center of mass of the Earth-sun system, but it's still less wrong to say that the Earth orbits around the sun than vice versa. _URL_0_ | I'm a mathematician, not a historian. Still, maybe I can help. I doubt that anyone ever thought that *all* the planets were stationary, as all that a person would have to do is keep track of a planet's position for a little while to see that that couldn't possibly be true. In antiquity, however, people thought that the earth was stationary and that the planets, the sun, and the moon all orbited around it. This idea was called geocentrism. According to the [Geocentric model](_URL_1_) wikipedia page, [Copernicus](_URL_2_) was the first to [suggest](_URL_0_) that the planets actually orbited the sun in 1543. Now, in the absence of any absolute frame of reference, neither is really *true*. The point, however, is that taking the sun as the frame of reference simplifies the mathematics involved in understanding the dynamics of the solar system. |
If a person was born with a defect in their brain that did not flip images from the eye right side up would they live a normal life in an "upside down" world? | There is no "flipping". There is no little person ([homunculus](_URL_0_)) in your head that is looking at the image on your retina like at a movie screen. Your brain does not need to flip anything because the information at the bottom of your retina simply corresponds to the upper part of the world and that's all there is to it. It's only from the perspective of an outside observer that you can say that the image on the back of the retina is inverted (up-down and left-right). | Years ago, an experiment was conducted giving subjects glasses that flipped everything upside down. Initially they had great trouble feeding themselves and moving around. But after just a few days their brains adapted and they functioned the same as they did prior, even to the point of insisting that everything looked upside down with the glasses off. It would be simple to construct a pair of glasses that simulated having eyes on the sides of your head rather than forward facing. If you wore them, you would likely have difficulty at first. Everything would seem distorted and strange. But soon your brain would adapt to the wider field of vision and when you took the glasses off you would feel like you had a crazy tiny field of view. Youd also lose depth perception while wearing those glasses. That's not something your brain would be able to correct for. |
Why were huge blimps such as the Hindenburg pursued in the first place? | First of all, the *Hindenburg* was not a blimp, but a dirigible, a rigid airship. Second, when airships were invented, heavier-than-air flight was in its infancy, and it certainly wasn't capable of carrying people across oceans. You can't compare airship travel to any kind of airplane travel, as such a thing really didn't exist then. Airships competed against ocean liners. 'Ships like the *Hindenburg* were luxury hotels in the air, more or less. Best of everything for the passengers, no expenses spared, and all that. | Airships had reached the limits of their possibilities in the 1930's, while planes were making rapid advances in speed, range, ceiling and rough-weather capacities. The Nazi's weren't very interested in airships, and a number of other disasters before 1940 (USS Akron, USS Macon and British R 101) has shown the weaknesses of airships. |
Are other stars surrounded by "clouds" like our Oort Cloud? | First you should ask whether ours is. The Oort Cloud is, for the most part, an inference based on the observation of long-period comets. All we have is estimates of what its characteristics might be. Granted, if the Sun has an Oort cloud then it won't be unique in that respect. But without some actual observations, we can't accurately predict what stars might or might not have such clouds. | Nope! These types of clouds only live for 10s of millions years. They live long enough for portions of the cloud to collapse into stars, but those stars soon heat up the gas and the cloud dissipates, and you end up with an "open" star cluster without much gas. After 5 billion years, the cloud that formed our solar system has been thoroughly mixed into the general mess of the galaxy's gas. So we won't have any chance of seeing the cloud we came from, because it doesn't exist any more. But in particular: the Orion Nebula is only a few million years old while the Sun is about five thousand million years old, and the Orion Nebula is over a thousand light-years away anyway. |
Why does cracking your knuckles/back/neck feel good? | Usually when you crack your joints you relieve the pressure that was building over the cartilage, which mostly happen because your joints aren't that tight anymore as they were when you were a kid, so they start "slipping" to a position where they were not actually supposed to be, but are not entirely wrong (as in a dislocation, which usually hurts). Pressure, most of the times, is not painful, just unsettling, so when you release it you get that pleasury feel. | Great minds think alike. Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why does it feel good to crack your back? ](_URL_3_) ^(_7 comments_) 1. [Why does it feel so good when I crack my back? ](_URL_6_) ^(_ > 100 comments_) 1. [ELI5: What does "cracking your back" do, and why does it feel good? ](_URL_4_) ^(_10 comments_) 1. [ELI5: What is actually going on when i pop my back? How does this compare/contrast to when I crack my knuckles? ](_URL_7_) ^(_ > 100 comments_) 1. [Why does cracking your back feel so good? ](_URL_1_) ^(_2 comments_) 1. [Why does cracking my back feel so good? ](_URL_0_) ^(_2 comments_) 1. [ELI5: Why does it feel good to crack my back? ](_URL_2_) ^(_5 comments_) 1. [ELI5: Why is it really bad to crack your Back and Neck? ](_URL_5_) ^(_14 comments_) |
At what point did people start referring to "The United States" as a singular entity? Did any debate occur around the shift? | From about the 1840s to the 1920s. [Source](_URL_0_) courtesy of [this thread](_URL_2_) Antebellum statesmen avoided the term altogether, preferring "the Union" or "the Republic". It was popularly believed that the shift was chiefly a result of the Civil War, where the grammatical debate parallels the political division of the time, though it seems the shift occurred independently of the war. The idea was promoted by Basil Lanneau Gildersleeve, a classics scholar and former Confederate soldier, though the shift and its connection to the war was noticed as early as 1887. There was debate for decades over the matter, based on the Constitution's use of the term as plural and its political implications. [Source](_URL_1_) | Follow up question: were there similar trends across the rest of the United States at that time? |
Why is car and motorcycle insurance so cheap in the USA compared to the rest of the world? | Pricing is based on statistical data gathered for each ZIP code (postal areas). It includes (and I'm sure I'll forget some things) the current value of vehicles involved, the statistics of that specific vehicle being involved in collisions (My Mini was cheaper to insure than my Mazda, even though the mini was a more expensive car because Minis get in fewer collisions) The driving record of the individual (this gets filled in by statistical data if the driver has insufficient driving experience). The distance that a person drives on a regular basis (commute usually). The expense of repairing the specific type of vehicle The calculations are meant to take things like that into consideration and still give out less money than they take in so they can be profitable. If other parts of the world have higher costs in those areas, that would lead to higher insurance rates (or the chance that the insurers charge more for higher profit) | Inefficiencies. Who gets the money in the long run. Are we paying extra just because private practices cost more or the stupidity that is insurance? |
How do fingerprint readers / touch IDs maintain security without the need for frequent changes like a normal password? | A password is something you know. It's knowledge. Knowledge can be given away, or stolen. So if you haven't changed your password, maybe someone has figured it out. So, for security reasons, you should change passwords frequently. But biometric security, like fingerprint scanners, are based on something you *are*. You're not likely to lose your finger or have it stolen, so it's much safer to keep that as an ongoing method of identification. | If you mean something like Touch ID on an iPhone then there is a crystal coverglass that protects the sensor and a metal ring to detect when a finger is in contact with it. When your finger touches the sensor, a ultra high resolution snapshot of the ridges and shape of your finger is taken, even the layers under the skin are measured (stops spoofing with fake finger). To take this "image", the sensor detects tiny tiny differences in capacitance (electrical charge) in-between ridges in your fingerprints, which makes up a full picture. These images are taken during the set up process, and then this image is turned into a mathematical hash, a one way operation, and stored on the phone. When you scan later to unlock, the "image" is snapped as you touch the sensor, the hash of that new image is generated and if the new one matches the stored one, the phone unlocks. & #x200B; TLDR; tiny sensor measures differences in electrical charges between ridges and bumps in your fingerprint. |
What do they mean specifically when they say they will "tighten up security" at places like airports? | They may have more bomb sniffing dogs walking the airports, extra police walking around observing... most of the security is at one checkpoint, checking people who are about to board a place. But as the Belgian attacks showed this week, there is also a need for more patrol of people who have no intention of going through the metal detectors. | At the end of the day, a prison is a building with a security system limiting what goes in and out of it, and security systems are subject to flaws unforeseen by those who create them. Consider how often we hear about security breaches in million dollar, professionally built computer systems. Hackers look for flaws in those systems to exploit and gain entry. In a similar vein, those who are able to escape from prisons have simply found a way to hack the prison's security system. Perhaps a door that must be manually locked is forgotten or missed by a lazy or tired guard. Or poor maintenance has led to a section of fence which can be pushed open. When you have an imperfect security system being analyzed on a daily basis by a group of people who would like to break through it, sooner or later one of them will succeed. |
What does it mean when a video game is in pre-alpha/alpha/beta? | It means that the game is not done. Imagine you are building a house. You start with the foundation that might be called pre-alpha. You ave an idea of the shape of the house but it's not realy a house yet. Then frame in the walls. Then you insulate it and put siding up. At this point it might be called an "alpha" house. People can look at it, but if anyone gets to close they will clearly see that it's not finished yet. At some point, late in the construction process, you invite a whole pile of people over to the house so they can jump up and down in it and make sure it stays standing. This would be the bata stage. The house is mostly done, but not polished. You are just kind of testing it out to make sure it's structurally sound. | Some games come to PC first and to consoles later (Diablo 3). Some games come to consoles first and PC later because the developers want to optimize the game more or add new features (GTA 5). Some games come to PC later because Sony and/or Microsoft will pay a developer to wait so that the first release of the game is on their console (Assasin's Creed Syndicate). And sometimes games just come out on all of the platforms at the same time (Overwatch). |
What is it about 7up, and other similar sodas that are good for an upset stomach? | Its typically ginger ale that is recommended for an upset stomach. That is because ginger is an actual herbal remedy for 'upset stomach' and motion sickness. | Bad for you isn't exactly the right question, here is the answer on why there is a health issue regarding diet soda. Diet soda contains a chemical called aspartame which is used as an artificial sweetener instead of sugar. There has been some controversy over the safety of this chemical, though after much further research since the 70s, most experts now agree it is quite safe or at least not any less safe than other additives or sugar. |
What is ISO and how is it possible to record in so dark conditions and make the images look bright. | ISO refers to the sensitive of the film, or it's equivalent on the sensor of a digital camera. A lower ISO number used an emulsion of including a smaller grains of silver halide, which capture more detail but are slower to react to light exposure. A larger ISO number uses larger grains, which react faster, but produce a "grainy" photo and capture less detail. For further information: _URL_0_ | Sorry. I know this has been answered very well already but I came upstairs and turned on my computer just so I could share this video. [Video is here](_URL_0_) This is how I finally understood ISO, Shutter Speed and Aperture. It's ELI5 but in video form and i've had it bookmarked forever. |
When it is silent, why does the ticking of a clock change pitch? | It's a psychological effect in our constant attempts to find patterns in things. If you try to switch the ticks and tocks you would be able to. Except for minute differences in the gears leading to small pitch differences, the pitch is usually identical. | There's a separate battery to run the clock even when it's turned off. [Source](_URL_0_) |
Why does MSG taste so good? | MSG is monosodium glutamate. You have special receptors for glutamates on your tongue, and it is one of the five tastes you can perceive (with salty, sour, sweet, and bitter). The perception of glutamates is called [umami](_URL_0_). That page also has a fair description of the activation and signal properties of receptors if you were interested. [MSG is not a health concern.](_URL_1_) Interestingly, I had Chinese food tonight as well. | MSG is a compound that has a strong savory flavor (savory is roughly the thing that makes meat and fish seem "filling"). It's not any worse for you than salt is. Some people claim to have MSG sensitivity, but scientific tests have repeatedly shown that this doesn't exist as more than a psychosomatic effect; people recognize the taste, and *think* it should make them feel bad, and this thought makes them start feeling bad. There is a very rare genetic condition which means you can't process MSG properly, but you'd know about it if you had it, because it also keeps you from eating a lot of other things. |
why consoles can't mod games like GTAV on PC | Sony/Microsoft/Nintendo(and maybe game developers) don't want to release the tools(the dev kits are real hardware and the software isn't made for the public) they use to make games on consoles. And on PC modding is not associated with niche little modifications to the game or bad things like making games unplayable online(try to play GTA Online on PS3/Xbox360 without any modders that gives you 5millions $ in game for no apparent reason...) Also on PC even if the developers make modding "impossible" the modding community *almost always* find workarounds to get mods working. | You can mod both. But modding is much more common on the PC, because modding is much easier on the PC; consoles aren't designed to run things that aren't games. |
Why do humans have such a bad grasp of time? | While we survived and grew as a species by being able to remember what didn't work from the past and plan for advancements in the future the main survival instinct has always kept us focused in the now. The now is there immediate danger is, where hunger and thirst are. The need to survive moment to moment is the main line of perception with the others all supporting and guiding it. Information that is not useful is abandoned,and often that includes the when of an event, as only the how and what were really necessary. Of course this doesn't show up the same in all people, some have powerful concepts of time and others have nearly none. | It's very possible that time is just something we came up with to be able to understand how the world around us works. Then we get to the first cause "origin" of the universe and time itself, our explanations right now aren't scientifically satisfactory, I'm sorry to say. |
Why can't we freeze a person for a couple of years and bring them back to life without killing them? | Living beings, including humans, are mostly water. When water is frozen it crystalizes and expands. These two effects taken together can burst cell walls causing massive systemic damage to living systems. It **is** possible to induce hypothermia to slow down body functions such as breathing and heart rate, but doing this for more than a couple of days is very risky. | The answer to this question requires to understand *how* you want to bring them back to life. |
When I turn on the lights in my room, the interference on my AM radio is greatly reduced. What's going on here? | You have a dimmer switch in your room? I don't know the science behind it, but they are notorious for messing with radio reception. | This is common in RF systems. You are becoming part of the antenna and the signal is coupling across you. |
Soap; Considering soap is a relatively new thing in the grand scheme of life, and is considered extremely important (obviously) so that we don't catch disease, how did people in the history of humanity survive without it? | 1: Soap is old. Thousands of years old, in fact. There are other substances that will do something similar to what the soap is doing. Most ancient cultures had something like it. 2: Soap is not necessary for life, and neither is hygiene, for all types of human settlement. Larger cities have more issues and need higher levels of hygiene to avoid awful sickness but wide spread tribes need a lot less. Various transmission vectors are cut off so the spread of disease is not as easy. 3: Once you remove soap from the equation, the human body balances various skin oils and becomes fairly "clean" all on its own. We definitely start to smell more animalistic, but that's not a big deal. It's pretty mild. Really, it's our dense society and propensity to touch things that cause all the problems. Having soap doesn't really make your body much "cleaner" (or less covered in bacteria) but does wonders for your hands. | When humans grubbed about in the dirt and mud, we got dirty. Often times sticky liquids used to fall on us, like sap or blood. Normal water in the rivers was enough to wash ourselves of dirt and blood, but humans noticed that fats helped in removing these sticky resins from our skin. That was the early precursor to soap and from there humanity basically used it as a way to keep ourselves clean of macroscopic things rather than as antibacterial as its used today (not good imo) |
How can a company like Amazon never make a profit, and yet it increases in value? | Amazon has so many businesses that they can lose money on one when they expand into the market. The company is profitable as a whole, but profit is accounting, while bills are paid in cash. From operating their businesses in 2016 Amazon generated $16,443,000,000 after expenses. They then invested 9,876,000,000 into new things, and then paid down 3,740,000,000 in debt. Only having a net increase in cash of 3,444,000,000. Sears generated NEGATIVE 1,381,000,000 from operating it's business in 2016 and made ends meet by selling assets and taking on 1,236,000,000 in additional debt. That's why ones growing and ones failing. | Investors believe that Amazon is temporarily losing money in order to expand and control a lucrative market in the future. Amazon isn't in the red because nobody's buying from them, in fact their sales are higher than ever before. They are in the red because they are spending a lot and growing rapidly. Once their growth slows then they'll be in a much stronger and will easily make up for a few years of negative profit (so the thinking goes). |
Why is it that when we have fevers, our body temperature goes up but we feel extremely cold? | Its because the body sends a signal to the hypothalamus (a part of your brain that controls temperature, among other things) to raise the body's temperature to fight a virus or infection. Immune cells responding to the infection release a protein that travels to the hypothalamus to say "hey, this guy is *totally* cold. Turn the heat up, will ya!" When the fever breaks, you will get all sweaty so the body can cool itself back down. This is when you must keep up the fluids to prevent dehydration. | A fever is when your body gets itself extra hot to kill all the little buggies that are invading it. So you don't sweat when you *have* a fever because that would cool you off, and your body doesn't *want* to cool off, it thinks 102°F is just swell, thank you. That's why you usually don't feel hot when you have a fever, if anything the room feels cooler. Then when the war against the buggies is won (or your mom gives you some Dimetapp), your body's thermostat gets turned back down to the usual 98°F or so, and the cooling system says "HOLY CRAP WE'RE BURNING UP HERE" and turns the sweat up to eleven. And you wake up a hot, sweaty mess. Thanks, immune system! |
Why is "Always-Online" DRM so universally reviled? | Two points: 1. There has never, since I was a kid, been a game that has had a single player experience I've wanted to try and I've been unable to locate a copy to steal online. Usually, the stolen copies are very convenient and easy to use, with little hassle once you get it set up. 2. Even though I have a "persistent" internet connection, occasionally my router fucks up and drops the connection for a while. Sometimes the internet company drops the ball and I don't have service for a bit. Sometimes I'm in a car or on an airplane. "Always-Online" DRM doesn't actually stop pirates, but it does severely limit me as a user for no practical purpose. In fact, I'd have less trouble running a stolen copy of the game than a legitimate one. | _URL_0_ They're forcing you to always be logged in to their server to play a SINGLE PLAYER game. Annnnnnd, icing on the cake, the servers have been down since launch, which means no one can play it. Its a direct blow to the face, and a big-ass I TOLD YOU SO. DRM is Digital Rights Management, a way for them to copy-protect their game. Other forms of DRM include having to put in a CD key when you first install a game, for example. Its a way so that you can't just install the game, and give it to your buddy to install too. They're selling you a crippled game (limited city size... in a city-building game... that you reach the city size in under an hour? OH, don't worry, a future Download (that will cost $20) will unlock bigger cities for you!).... Stuff like that is really pissing people off. |
If lie detectors (polygraph) are a pseudo science the why are they still used in court cases and by law enforcement? | They are still used for their original purpose: to intimidate witnesses into telling the truth, because they think the machine works. | They're expensive. They produce a lot of results that would require further investigation, which would be even more expensive. Most of the investigation would determine that nothing worth worrying about was wrong. |
why does Bismuth crystallize into such a weird square shape? | > it doesnt make sense for bismuth to look like this when most crystalline metals are much less orderly structured. Literally the definition of a crystal is that it has an ordered [e: repeating] long-range structure. You're right that we don't see the crystal structure very often, and that's because [e: many of] the things we see that are crystalline at the microscopic level are made up of many small crystals instead of a few big crystals. Generally speaking, the faster something is cooled, the smaller the crystals are. Bismuth has a low melting temperature, so it's relatively easy to cool it down slowly and end up with only a few relatively large crystals instead of a large number of small crystals. But the crystalline structure of other metals, like iron, is often visible. If you've ever seen sort of "splotchy" galvanized steel that looked [something like this](_URL_1_), you've seen zinc crystals. You can see similar nickel-iron crystals in the [slice of this meteorite.](_URL_0_) | [This Wikipedia article on hopper crystals](_URL_0_) is illustrated with the famous shape of bismuth, but it mentions that the phenomenon also applies to water crystals: under the right circumstances the crystal growth is strongest at the edges and corners. In its most extreme form it creates the "flake" shape. |
Will water freeze if the windchill is below 32* but the temperature is above 32*? | The freezing point of water isn't affected by windchill. Humans feel heat/cold by the rate of heat gain/loss. We radiate heat so the air right against our skin gets warmed. When there is no wind this air provides somewhat of a cushion against the rest of the cold air. We're still losing heat but we aren't feeling the full 35° because the air we warmed from our skin is still hanging round in the general vicinity and keeping the area warmer than the actual temperature. When you introduce wind, it basically blows away all the warm air away and leaves your skin exposed to the full 35°. That's why it's called windchill, because it's caused by wind. It doesn't actually make it colder, it just makes it cold faster. | Yes, but not much, and only under pressure. [Here is a phase diagram](_URL_0_). At ~2000 times the atmospheric pressure water can exist up to 22 K below the usual (atmospheric pressure) freezing point. |
It is said Ragnar Lodbrok was killed by a pit of snakes. How common was death by snakes? | It's usually suggested that this story (which dates only to the 12th century, about 350 years after the supposed events it describes) is a poetic invention - and even the historicity of Loðbrok himself is in some doubt. [This earlier thread](_URL_0_), featuring u/alriclofgar, goes into the problem in more detail. The thread also mentions other instances of snake pits being used as a method of execution. As an aside, only one species of venomous snake - the adder - is indigenous to the British Isles, and it is scarce. While its bite can be fatal, it is not invariably so. So a pit full of adders would be hard to populate and not hugely efficient as a method of execution. | Depends on the snake. Many of them build up immunity in order to protect themselves in the case of an accidental bite. |
How do animals with large antlers like Deer and Moose get through the forests without getting tangled constantly. | First they tend to walk on established animal trails, which from centuries of animals grazing along side the are cleared of most snags. Second they do hit tree branches all the time, they just keep walking and get untangled or back up. Very rarely does an animal get so badly tangled that it starves to death. If you Google search for deer tangled, you'll see plenty of pictures of a deer tangled in something, typically wire fencing,.but a few trees too. | Well, when they start "sprouting" from the head they are covered in felt, within this felt they are mineralized and grow, including in other directions. They don't get exposed as bone til the deer start rutting and scrape the felt off, usually with a tree. Then the antlers fall off and the process starts over again. To be more detailed about the points it's similar to finger or toe formation, with growth factors on one side and inhibitors/apoptosis factors on other sides such that a "branch" is formed. |
Love at First Sight. How can someone develop strong feelings the moment they meet someone? | It's not that people immediately progress to the feeling of "love" at first sight. It's more so that there was an immediate infatuation or attraction that existed, which, with further interaction, turned into love. There's probably many instances of immediate infatuation in someone's life, many of which may have been one-sided. Other times, mutual infatuation may turn into a relationship but personalities or lifestyles clashed. However, the relationship that started with immediate infatuation and resulted in long-term love is generally classified as "love at first sight". | **ELI21**: Essentially there is a strong release of neurotransmitter chemicals when you first meet someone. That's what causes the "love at first sight." Not everyone has it, but many people like you and I do. It's more of an attraction at first sight, not love, where we are attracted to either their physical attraction or a specific feature of their personality. Obviously, the more we know about them (in general) the less we find them attractive. It becomes true love when find them more attractive as time goes on. **ELI5**: You know when you bought that new power ranger toy and fell in love with it so that you couldn't stop playing with it? Then you eventually learned all of its quirks and started to dislike it until you stopped playing with it at all? It's like that. |
How you can make an SOS call without phone service? | Just because you do not have service with your particular carrier, it does not mean that you are not in the coverage of another service network. By law, all cell phone carriers are required to allow emergency calls to be made on their networks regardless of the phone's primary carrier. Edit: Gold for this? Seriously? This isn't even rocket science and somebody thinks this is gold worthy? Goddammit, this is not the sort of comment I wanted to lose my Gilded-Virginity with. | basically, you're being called by a computer, not a person. the computer just keeps dialing from a list of numbers until someone picks up, and the computer hears you going "hello?". then you're connected to a person who's waiting. |
If toxic and edible mushrooms are so easy to confuse, then why are poisonings from market-bought mushrooms so rare? | 1. They're not so easy for *experts* to confuse. 2. Most of the ones at markets are farmed, not found in the wild. 3. Most of the popular market species aren't the ones that look very similar to poisonous species. | Molds are a type of fungus, like mushrooms. Like some varieties of mushrooms, some varieties of molds produce stuff that's poisonous to humans or other animals called Mycotoxins. |
why do credit cards not have a PIN number attached to them? | They do on Europe. Americans are resistant to the change and they don't wanna risk losing customers over forcing them to have a PIN to use their card. Ruh roh, I hope this answer isn't so small it gets autobaleeted. | Merchants pay to use credit cards. If the credit card company doesn't give favorable terms to the merchant, they can decide to not use that credit card, at the risk of annoying their customers. |
Why is it that antisemitism was/is so much higher in Black Americans than the general population? | To direct this question in a historical way (the original post doesn't frame it so clearly): It hasn't always been that way. A strong Black-Jewish Alliance and other nonracial organizations existed during the Civil Rights era, and some Jewish activists paid for their advocacy with their lives, [including two of the three CORE (Congress of Racial Equality) workers murdered in Mississippi in 1964](_URL_1_). Jonathan Kaufman's [*Broken Alliance*](_URL_0_) (1995) might be a place for you to start. But someone with more knowledge of recent US political history might be able to give you a synopsis. | While an interesting question, I would suggest also putting this in the [Black History AMA going on right now!](_URL_0_) |
I've heard that a secret goal of the space race was to put nuclear weapons in orbit. If this is true, why didn't we follow through with it? | I'm not sure where you heard that. I mean, the space race was always dual-use — you can use a rocket to put a satellite into orbit, or a nuke onto another country. There were some ideas, from early on, about how you would weaponize space, both with nuclear and non-nuclear weapons. But it isn't anything fancy to put a nuclear weapon into orbit, in and of itself. There were ideas about developing "weapons platforms" but they were never the main reason that the US or USSR were interesting in going into space. From a strategic point of view, there are many disadvantages to putting weapons permanently into orbit, as opposed to just keeping them on the ground (where you have physical control over them) and launching when needed. As for why space remained weapon-free, it's because of the [Outer Space Treaty](_URL_0_) of 1967. It very clearly prohibits all militarization of space, especially with nuclear weapons. | This is a viable strategy, and lots of people have thought about doing just that. Indeed, certain spacecraft like Dawn and Hayabusa employed ion engines once lofted into orbit by chemical rockets, much like you describe. As for nuclear...some day. Maybe once we as a species learn that we're supposed to be afraid of the *weapons* part of nuclear weapons and not the *nuclear*. |
Why do some all-organic, natural healthy etc. fruit juice drinks have 0% vitamin C? | Grapes have very little vitamin C. But I am not aware of any case where the fruit *does* have plenty of vitamin C and then its juice *doesn't.* Can you please provide a link to such a product? | Take a look at the ingredients list. I bet you that what's happening is that the juice on the left has a lot less orange juice in it than the juice on the right. Apples provide about 4.6 mg of vitamin C per 100g; oranges provide 53.2 per 100g. |
Why do many people on reddit mark their editing with posting "edit: ... " instead of just editing the comment? | Most of the time it's an honesty thing. So you don't look like a dbag who went back and edited a downvoted post to say something completely different. As a result, people just got into the habit of always tagging their edits. | Because if someone asks a question you could give one answer, then when you realize it's wrong you could completely change your answer, and then all the people replying to you pointing out how wrong you were would look crazy. It's just good form to point out when you have made an edit, since there's no other way to figure it out. |
Why do most of us stick out our tongues in some fashion when we're concentrated on doing something? | Sticking your tongue out or biting your lip while concentrating is not really that weird. Michael Jordan was famous for his tongue sticking out while going up for a dunk. It is an example of what’s called motor overflow or motor disinhibition. It happens sometimes when our brains are working really hard at something. Normally, the brain keeps the brakes on the parts of the body it doesn’t want to move. However, when we concentrate really hard on a tough task, sometimes the brain lifts the brakes on other parts of the body (most often the face, lips, tongue, etc.) making them move without our control. As we get older our brains get better at controlling the brakes (inhibition) and the motor overflow goes away most of the time, but some people still have this happen when they are grown ups. There are studies that show it is more common in people with ADHD. | Tongues and lips have a ton of nerve endings in them so it feels good to do it. Also there are many hormones that can be transfered via saliva. |
"FDA admits Arnesic use in chicken" How accurate is this? It was blowing up on my FB feed. | It's real, but not as bad as the sensational headline would suggest. There is/was an arsenic-containing compound fed to chickens, and a bit of the arsenic does make it's way into the meat. The key law of toxicology, however, is "the dose makes the poison". There's no evidence that the levels of arsenic found in chicken are harmful to humans. In fact, the age-adjusted incidence of cancer in humans has been falling over time. | Person who handles food here. Not sure how in US but in Canada when chicken goes to market only 1 of every 10th grt inspected as oppose to beef where every single cow get inspected. Chicken skin 70% chance that it has salmonela on it. On beef its different bacteria that doesnt cause too much damage. |
how does moving your legs on a swing make you go faster? | It's not just your legs, but your hands as well. You are basically shifting your center of mass to be on one side of the swing's chain/rope or the other. This causes the chain/rope to accelerate in one direction or the other according to Newton's law. | When your legs are in front of you, your center of mass changes to be closer to the front of your body. When you swing them back, it changes to be closer to the back. The changing of your center of mass creates kinetic energy. |
In EU4's 1444 start date I see the oddly named nation qara qoyunlu around in the middle east. Can someone tell me more about it? | Don't get me wrong here, I think it's great that you're interested in something like that on the basis of a game. That said, it is not really an appropriate question for this sub. It's more for specific questions. Just wanting to know more about *everything* related to the Qara Qoyunlu can usually be sated using Wikipedia or similar internet sources. To give an example, asking "What led to the fall of the Qara Qoyunlu?" would have been a potential question. | It comes from old western European cultures, who when trading with Asia referred to it as the far east because, well, it was far away and east of Europe. the middle east was kind of in between, hence the name that has stuck around |
[Mathematics] How is it possible to use the cross product, which is defined only in three dimensions, to calculate the area of a two dimensional object? | The magnitude of the cross product A x B is equal to the area of the [parallelogram whose sides are A and B.](_URL_0_) Similarly, if you cut that parallelogram in half you can make a triangle with two sides A and B whose area is half that of the parallelogram. In the case that A and B are parallel vectors the area of your parallelogram is zero, and your cross product is zero. Fun! | If you draw a little parallelogram and label two consecutive sides **u** and **v**, you can put the common corner of **u** and **v** at the origin of an x-y coordinate system and figure out the coordinates (u1, u2) and (v1, v2) of the ends of the labeled sides. The area of the parallelogram can be calculated to be A = u1\*v2 - u2\*v1 which is the same formula as the determinant of the matrix with columns given by **u** and **v**. Knowing that formula for Area of a parallelogram **you can define the determinant to be area (or volume in many dimensions) of the shape defined by the columns of the matrix**. |
Why can drinking too much alcohol cause you to go blind and what is the biology/chemistry behind it? Is it specifically because you absorb too much too quickly (like with moonshine/liquor/spirits), or is there something else that causes it? | Drinkable alcohol is ethanol; it's what in the beer and spirits you buy at your liquor store. Moonshine that isn't distilled correctly builds methanol which the body metabolizes into formaldehyte (which is toxic) and then further into formic acid which will harm your nervous system, beginning with the eyes (causing blindness). | Alcohol is a chemical that affects almost every organ in the human body, but in particular it interferes with the brains' cells abilities to communicate with each other. If you drink alcohol faster than your liver and kidneys can process it, it begins to build up in the bloodstream and hence gets carried to your brain, where it basically blocks some of the normal brain behaviour from occurring. [This paper explains alcohol's physical effects](_URL_0_) in a reasonably simple to understand format. |
Why does breaking your spine result in permanent paralysis? | It's not the spine so much as the spinal cord. It's the most delicate system in our body that doesn't have a backup, which is why it is encased within a very thick layer of bone (the vertebrae). You can break your back, even crack vertebrae, and as long as the spinal cord itself is undamaged you can recover. [Gloria Estefan](_URL_0_) was in a horrible bus accident in 1990, in which her back was broken; she was able to make a full recovery. [Christopher Reeve](_URL_1_) was in a much less severe accident - a simple fall off of a horse - and was much less lucky, because his spinal cord was severely damaged. | The New Yorker did a pretty good article recently on spinal injuries [here.](_URL_0_) TL;DR: It depends where the injury occurs, generally the higher the injury, the more severe. That's why if you "break your neck" it's usually going to paralyze you, if not kill you outright. Additionally, we've yet to see anyone regain motor function after becoming a paraplegic because those nerves just won't regrow. This article explores a guy that just had a procedure that might change that. |
Why do people feel more tired when it's raining? | I think as an addition to /u/DanceAmbulance 's text, it's worth mentioning that the human eye recognizes how much natural light there is around it, and if the sun isn't shining, it may think that night is coming and you need to go to sleep. Also the air is fresh during/after raining so that might help. + the rain's sounds are so calming. | When sunlight hits the optic nerve, melatonin secretion decreases, and you feel more awake as a result. On rainy days, there is less sunshine, so this stimulation is reduced, and you feel sleepier as a result. You can think of melatonin as a sleep hormone. It helps let your body know it's time to sleep. Without it, your body can feel more awake. In terms of how this works, sunlight hits retinal ganglion cells which signal the SCN which is responsible for our body's circadian rhythms. The SCN signals the pineal glad which controls the production of melatonin. Besides melatonin, sunlight leads to increases serotonin production which makes you happier in general, which could result in more enthusiasm for the day on sunny days and less energy on rainy days. |
What does being able to see polarized light allow a Cuttlefish to do? | According to [this link](_URL_0_), cuttlefish can also alter the way in which their skin affects the polarisation of light reflected from it. This may allow them to communicate silently and 'invisibly' as other animals will not be able to detect the changes in polarisation | Many arthropods, including most flying insects, are able to detect polarized light. In insects, there are usually two or three ocelli on the 'forehead' of the insect, in between the compound eyes. These are sensitive to polarized light, and are thought to be involved in navigation and predator detection. In flying insects, it's thought that the polarized light may act as something like an artificial horizon, helping the insect to maintain orientation with the sky above and ground below. In marine environments, stomatopods (aka mantis shrimp) have eyes that sensitive to a wide range of colours (up to 16 different types of cones, compared with our 3), can pick up multiple spectra, including ultraviolet, and detect polarized light. What exactly they do with this supervision is still a matter of debate. |
How warlike were hunter-gatherer societies? | Remember that hunter-gather societies vary enormously. One could compare and contrast !Kung / Inuit / Australian Aboriginals but it is impossible to make a general statement about warfare and violence in hunting gathering societies. There is simply too much diversity. Lastly, hunting gathering societies have existed for something like 100,000 years, in many different environments, and the ones we have anthropological records of have come into contact with non hunting gathering societies. Do you have a specific hunting gathering society you are interested in? | Hey man, sorry to be the bubble burster here, but this question would fall under [poll-type questions that are against the rules of the subreddit.](_URL_2_) Maybe you could split up some of the smaller questions? Such as the hunter-gatherer one - "How idyllic was the lfiestyle of a hunter-gatherer tribe?" The problem is, as you said, the fact that the question itself is incredibly subjective. Sorry! |
Why do most animals have very similar eyes, when everything else about them is different? | Eyes vary a great deal! Check out just these differences in pupils: [cuttelfish](_URL_4_) [goat](_URL_0_) [mantis shrimp](_URL_1_) and of course compound eyes like in the [fly](_URL_3_) There are also some fascinating differences (and similarities!) in [octopus eyes](_URL_2_) also. | Very distantly related species can separately evolve similar traits to adapt to similar environments. There are many examples of this in the animal kingdom, but the separate evolution of wings in insects, birds, bats and so on is an easy one to picture. This is called 'convergent evolution'. Similarly, closely related species can develop differing traits if they move into different environments or occupy different niches. In the case of small cats and big cats, the different pupil shape may be to do with a different focusing system in the eye, different prey (small cats tend to hunt very small prey, whereas a lot of big cats hunt animals larger than they are), or different sleep behaviour (small cats are more likely to be out at night). _URL_2_ |
What happens when you remove a brain tumour? What grows in its place, if anything? | Well two things are possible... One, you removed all the tumor cells (harder than you think). Nothing grows there. The brain of an adult doesn't grow under normal conditions. Two, you didn't get all the cancer cells. A tumor will eventually recur there. | Depends on the kind of cancer. Most often it is because the tumor invades existing tissue and replaces it with non-functional tumor. Say you have a tumor of your liver and that invades your kidney. That effectively removes your kidney. Brain and spinal tumors can compromise the CSNto the point it does not function. That results in coma and death. Lung tumors can cause respiratory collapse. Cancer can also invade your bone marrow and reduce your body's ability to make new blood cells. It all depends on where the tumor is and what kind of tumor it is. |
Why do CRT screens drift? | There's a lot of analog circuitry in a CRT, and analog things are generally less "stable" over time as compared to digital. Your CRT appears to be failing where it can't keep the image centered (it's supposed to); this problem was solved long ago for CRTs. | If you mean on really old CRT screens, the whole picture was drawn by a single point flying across the screen very fast, horizontally, then stepping down a vertical level and repeating. When you turn it off, the inputs driving that beam go to 0v. The outputs of that beam are at high voltage so take a little while to drain, causing the beam to sort of sit on one line, which eventually shrinks to a point, before the power source of the beam dies too. |
How did so many children around the world come up with the "floor is lava" game individually? | My twin brother and I started playing the lava game after watching the lava scene in Aladdin. That's how we learn it. I think it also stems from playing on a jungle gym, you spend a lot of your time on the equipment but you don't touch the ground, and so playing the lava game in your living room, you'd be standing on couches, ottomans, tables, and then making the living room your personal jungle gym | Agility games are popular in children, like jumping from obstacle to obstacle. Kids just happen to set limits with the most obvious danger- lava. Here's a good read in a thread of the past: _URL_0_ |
Why do I have to pee so often when I'm drunk? | Alcohol is an antidiuretic hormone (ADH) inhibitor. ADH makes sure that your kidneys put back the excess water that they filter out to make pee. When alcohol blocks ADH secretion it means that the kidneys don't put that water back, meaning your bladder fills up more quickly and making you have to pee more often. | You make a hormone called vasopressin. One of the functions of it is to maintain water in your body. Alcohol inhibits the production of it. As a result, your kidneys don't reabsorb as much water as they would otherwise, and instead you whizz it out. |
Why does Iran, India, and Australia have 1/2 hour time zone increments? | This isn't an explanation but newfoundland Canada also has a half hour time zone | They don't "have different time zones". We created time zones. Once we realized how the earth moves around the sun we knew that noon was going to be at different points at different places on earth. Time zones are a way for us to make more sense out of time when we became able to move faster between different areas (when trains developed). |
Does youth unemployment necessarily cause social unrest? | Almost all unrest and violence occurs amongst the young in a society. When your demographics are skewed towards the young, this tends to cause problems. When your demographics are skewed towards the young *and* they don't have much supervision or anything useful to do with their time, the problem is exacerbated. High youth unemployment also tends to follow from a demographic skew towards youth. When you have a lot of older people in comparison to younger people, there's a strong demand for workers to replace the retiring/dying older people. When you have the reverse situation, the demand is much lower. | OP, please see the link below. It is an article that deals with the work of Fuller and Goldstone who have studied "population bulges". Essentially, a large population of young unemployed men correlates with civil wars and may have played a role in WWI and WWII as well as the Marxist regime changes in Latin America. > Between 1970 and 1999, 80 percent of civil conflicts occurred in countries where 60 percent of the population or more were under the age of thirty, according to the PAI report. Today there are sixty-seven counties with youth bulges, of which sixty of them are experiencing social unrest and violence. _URL_0_ |
How the hell does a calculator gets the square root of pi in no time? | Computers don't have infinite precision, meaning they can only store up to a certain number or decimal points. So for pi, that's something like 15 digits (in that ballpark). Calculating the square root of 3.1 is no more difficult than calculating the square root of 3.14159 as far as the computer is concerned..... because inside the computer, both numbers are stored with the same number of binary digits, or bits. One way of doing it is called a "Taylor series" approximation, where you can write any function like sqrt (x) as a polynomial (a + bx^2 +cx^3 .....). For a computer that's nice because it breaks the operation down into multiplies and adds, which are two operations the processor has hardware for. | Just because you can't write down a number in a convenient form doesn't mean it doesn't exist. We can't write pi down as a finite number in any number base (base ten, base two, etc.) besides base pi (or a multiple or fraction of base pi), but most people agree that pi exists, because it has a definition. If pi exists, then we can just _define_ the square root of pi to be a number (well, really, two numbers, the positive and negative versions) that, when multiplied by themselves, make pi. If you're wondering how we calculate it -- well, the same way we calculate a value of pi to some decimal place. We make an approximation, and cut off calculating at some point. |
Why don't we get products cheaper when we use the self-checkout? | There is really no incentive for the store to give a discount. The lines are used regardless. In addition, there are costs associated with self checkout (for instance, a staff member to assist people and the cost of the machines). | Two reasons (one for non-physical products). For physical products, packaging. It's much less expensive to package and ship 1000 products in the same container to the same location than 4 packages of 250 units to 4 locations. For all products, assurance. Imagine the following: You're a freelance photographer and portraits for 5$ apiece. An company approaches you to take pictures for all of their employees but will only give you 4$ apiece. You have two choices here, a) refuse, get 5$ a photo but you don't know when or if you'll be making money later in the week b) accept for a smaller profit, but you're guaranteed to be making money all week. This principle applies to everything. Chocolate bars sold by a grocery store go 1-by-1 but they don't know if they can sell all 40 that they get in a box. When costco sells you a 40 bar box though, they won't get the same cash-per-bar value but they know that they will sell all 40. |
Why are crickets so hard to locate from their "chirp". | It is because their chirp is very periodic in time. The period of repetition is usually around 5 kHz which is a period of 200 us and a wavelength of about 7 cm (340 m/s / 5 kHz). Part of the way your brain localizes sound is by comparing the time of arrival at each ear. The problem with periodic noises is that there is a fundamental ambiguity because you can shift the waveform by multiples of 200 us (or 7 cm) in either direction and it looks about the same. Your ears are farther apart than 7 cm so there are multiple possible directions of arrival that all result result in a time difference that is a multiple of 2 ms. Your brain cannon easily distinguish between those directions. | The short answer appears to be no. I researched this a while ago when I heard about them and my BS meter went off. I found [this](_URL_0_), which unfortunately doesn't actually directly link to the studies. It seems that they will work on crickets, at least until they get habituated to the noise and ignore it. Apparently the FTC even warned companies that produced these devices that they need to back up their claims, with one company even being sued for violating the warning. |
Why mist can contain salt (salt mist) but water vapor does not (desalination via distillation)? | Salt mist as in sea mist is literally tiny drops of sea water splashing into the air, so it contains everything from the sea, including the salts. Water vapour is evaporated, the water boils into a gas and then condenses onto a cooler surface or in the cooler air, so it is chemically pure h2o. | Two reasons: 1) It costs a lot of money to desalinate water, it's a very energy intensive process. 2) There's no good way to get rid of the leftover salt. Desalination plants generate millions of gallons of toxic brine that can't be discharged back into the ocean. |
How the hell do they build Dam's? | They divert the flow of the river during construction then redirect it back to the dam once it's finished. | Usually you divert the river, build the dam, and then set the river back straight. EDIT: So, check out [this diagram.](_URL_1_) The river is redirected, and then walls called [cofferdams](_URL_2_) are built to hold the rest (if any) of the water out. The area surrounded by the cofferdam is then pumped dry, and construction occurs. The cofferdam can then be removed, the diversion filled in, and the dam functions as intended. Here is a [short article](_URL_3_) on dam construction which should clear it up. Here is [another article](_URL_0_), which is shorter and should clear up what the earlier diagram was showing. |
What uses more gas, driving with the AC on or with the windows down? | This depends on the speed of driving and the aerodynamics of the car. At 0 mph, it is definitely more efficient to have the windows open. At 250 mph, it is definitely more efficient to have the AC on. At some point there is a crossover. I've heard various estimates for this point, from 30 mph to 50 mph. | This question misses the main reason for the lack of understanding regarding the MPG 'myth' of air-conditioning, and that is if you don't use the AC, then I bet you use a competing method to keep the car cool: windows. So, from a scientific point of view we need not compare AC alone. We should compare two competing scenarios for maximum MPG: 1. Roll down the windows - turn off the ac 2. Roll up the windows - turn on the ac. In each scenario there are aerodynamic requirements (drag) as well as mechanical requirements (provide power to the AC.) The key result is that under a certain speed (Without checking a reference, I'd speculate 25-35 mph) it is slightly more efficient to roll down the windows and shut off the ac. However for high speed the negative effect of drag overwhelms the cost of running the AC. |
Do objects physically change the wavelength of light or just absorb certain wavelengths and reflect others? | When light hits an object, certain wavelengths are absorbed. In the process, the material's molecules move into a higher energy state (electrons go to higher energy orbitals). The molecules stay in those higher energy states for a variable amount of time (which depends on the material) and then "relax" down to their original state. In doing so, the energy initially added by the light either gets converted to heat, in the former of increased molecular motion, or, more rarely, is given off by emission of a new photon, which we call fluorescence or phosphorescence. Substances are coloured because their molecular structures lead them to absorb (and convert to heat) certain wavelengths of light and not others. There are cases where substances "scatter off" light at a different wavelength, but this effect (called the Raman effect) is incredibly weak and not detectable without specialized equipment. | As Dubanx says, the arrangement of electrons in a molecule dictate what frequencies of light it absorbs and emits. So if you shine a light through a sample while varying the frequency, and you see which frequencies are more strongly absorbed, you can match that to the absorption frequencies of known substances. This is called spectroscopy, and it's a powerful tool but not the only one. For example, [this](_URL_9_) is what the spectrum of cocaine looks like; you can see that light is strongly absorbed when there are about 1750 wavelengths/centimeter. |
if liquid helium is the coldest thing around at 4.2 Kelvin then what freezes it into a solid? | Freezing is not the lowest temperature a substance can be. So, while solid hydrogen or helium has the lowest freezing point, we can get things even colder than that through advanced refrigeration techniques. So, the thing that freezes helium is "something colder than the freezing point of helium". What that would be exactly, I don't know, but that's basically it. | At near-zero pressures, the answer is no, not everything becomes solid no matter how much you cool it down. Almost everything does, but Helium-3 and helium-4 don't freeze solid at low pressures (below around 25 atmospheres) because the atoms always have zero-point energy from the quantum mechanical jitter that all particles experience and since helium has very little self-interaction as an unreactive noble gas, this tiny zero-point energy is enough to keep it from solidifying at any temperature as long as the pressure is low. See these phase diagrams for [helium-4](_URL_2_) and [helium-3](_URL_1_) and compare them to the phase diagram for a more typical substance like [hydrogen](_URL_0_), which does freeze solid at low pressures if you lower the temperature enough. |
Were there any illegal drugs in ancient Rome? | [This](_URL_0_) is a great discussion of drug use in Ancient Rome, and u/x3k suggests that there was no taboo about drug use. | Not to discourage any further answers but /u/cleopatra_philopater answered: [I'm a wealthy young Roman at the height of the empire with money to burn and a brain to fry. What sort of drugs- illicit or otherwise- are available to me?](_URL_0_) |
When glaciers scraped away so much soil and other material during the Ice Ages, where did it go? | Gargatua already gave great answer. I'd like to just give one example of a place where the matter carried by glacier has formed a clearly visible large landmark. In Finland there are three ridges called [I, II and III Salpausselkä ](_URL_12_). They were formed around 12 250–12 050, 11 790–11 590 and 11 300–10 400 years ago. I Salpausselkä and II Salpausselkä are easily visible on [height map](_URL_14_) too ([map source](_URL_13_)). | Glaciers. While the bedrock of eastern Canada is incredibly old, most of it was under glaciers until very recently (14,000 years ago), which left behind brand new soil. As [wiki](_URL_1_) says, "The multitude of rivers and lakes in the entire region is caused by the watersheds of the area being so young and in a state of sorting themselves out with the added effect of post-glacial rebound." Basically, the land was crushed downward under the weight of the ice, and expanded back up unevenly. One characteristic feature of this terrain is [kettle lakes](_URL_0_) -- small round lakes that fill in the low-lying areas of the irregular terrain left behind. Obviously, glaciers don't respect national boundaries. This is also why Minnesota is the ["Land of Ten Thousand Lakes"](_URL_2_). |
How is space dictated or can any country just put a satellite above another country? | ELI5 version: Sattelites in space move in really strange ways from our perspective on the ground. Because of this, the idea of something in space staying direclty "over" a country is almost impossible unless the country is really near the equator. The reality is that satellites fly over many, many countries depending on their orbit (e.g. the international space station flies over almost every single country every day or two). Any sovereign nation can place a satellite in space that flies over another. This is part of the reason why the Cold War did not escalate further, the Russians could see what Americans were doing and the Americans could see what Russians were doing. | Space more or less works like ships on the Ocean. Spacecraft belong to the country that built them, and that countries laws apply onboard, just like it would if you were sailing on a ship that flew that countries flag. This is a little more complicated on the International Space Station, where each individual module remains the terriroty of the country that built it. |
Why are school language classes not implemented in grade school, when kids are able to learn languages easier, and instead implemented in middle/high schools, when languages can be harder for children to learn? | I had Spanish classes since 1st grade through college (Ft.Lauderdale FL) I still probably only know about 15 words total. I think how we teach language needs a major overhaul. I live in SC now and there is an elementary school here that does half its core classes in a different language (either French or Spanish depending on the parents choice). From what I have heard these kids quickly gain fluency and understanding. | Because English largely fills this role, albeit incompletely. In general it's far more practical to get everyone to speak a language that at least some people already speak. It's at least incrementally harder to get people to speak a language that essentially _no one_ speaks. As for why we aren't "all in" on this, it's largely because it's vastly easier and feels better to communicate in a native tongue. Would you give up the ability to have a natural communication with your child in order to satisfy some utopian global communication ideal? Would you divert what little resources are already available for education in much of the world in order to learn a hypothetically useful language? Or...would you spend those resources on something more immediately practical? |
Why did the soviets named their most powerful nuclear bomb the "tsar" bomba ? | The Slavonic word "Tsar" derives from "Caesar", and like many similar words in other European languages means simply "Emperor" (German "kaiser", Swedish "kejsare" and Finnish "keisari" all have the same meaning and origin). So Tsar Bomba is literally "The Emperor of Bombs". The English (and French, Italian and Spanish) word for "Emperor" derives from Latin [Imperator](_URL_0_). It's true that they hated the tsarist regime, but the word has a more general meaning than that. Saying it's strange for them to have a bomb with that name is like saying that it would be weird for an American company to call itself "Burger King" because the US fought a revolutionary war against the British Crown. | /u/restricteddata went into the nomenclature of Tsar Bomba [here](_URL_0_). The long and the short of it is that the Soviets never called it that and the term arose in the West after the Cold War. Such creative naming of weapons is not without precedent, for example the US naval historian Samuel Elliot Morrison coined the term "Long Lance" for the Japanese Type 93 torpedo because he felt that such a significant weapon deserved a more fitting designation. |
What is the idea behind applying heat/ice to injuries? Does one work better than the other? | Heat and cold have different effects on blood vessels. Cold causes them to constrict, which can reduce swelling in the case of a rolled ankle. Heat causes them to expand which can help improve blood flow, which can ease pain. | Yes! Often when you have injured yourself, the inflammation created by the immune system creates a significant amount of pain, swelling, and damage. The body is gearing up to fight an infection which isn't going to come if you didn't break the skin open or don't have a bone exposed, for example. When you injure yourself, the broken cells release chemical signaling factors which cause blood vessels to dilate, allowing migration of the immune cells which cause inflammation. Ice cools the area, which causes blood vessels to constrict and prevents movement of these immune cells. It also works on the chemical reaction level (which all cells are: big continuous chemical reactions). It slows cells from performing their duties, which in this case are actually more harmful than good. This is the same reason we take anti-inflammatory drugs; the drugs prevent production of inflammatory signaling molecules, decreasing the swelling pain, and additional damage of inflammation. |
Which of these help keep bones from snapping at the joint: muscles, tendons, or ligaments? | Bones are held in place by a combination of all 3. Tendons attach muscles to bone, so the tendon /muscle combo are keeping things tight and together. Ligaments attach bone to bone so their main function is to just stabilize the joint. | Tendons and ligaments are both bands of tough, fibrous tissue designed to hold things together. Tendons connect bone to muscle (typically with the aim of aiding movement), while ligaments connect one bone to another bone (typically to serve as a stabilizing force). The third type in that group are known as a 'fascia' and they connect muscle tissue to other muscle tissue. |
How is water both an acid and a base, and is it ever in a non- aqueous state? | Water is not both an acid and a base, it is *either* an acid *or* a base, depending on the ion concentrations within the fluid. Aqueous is defined as being in solution in which water is the solvent so the term "aqueous" doesn't even really apply. You can, of course, freeze it so that it's not longer a fluid, but that's another thing entirely. | Liquid is just like you think, a liquid state. Aqueous means dissolved in water. The formula you have right here describes the phenomenon of a tiny fraction of H2O being split into H+ and OH-. This always happens in water but only a tiny bit of water is like that and it basically reacts back into water immediately. A good example of a formula would be NaCl(s) ⇌ Na+(aq) + Cl-(aq) Meaning that solid salt splits into 2 ions which are dissolved in the water, when you put the solid salt in the water. |
Why tires appear to be spinning the opposite way | I'm not sure how to ELI5 it, because I don't really understand it myself (and it seems like there is no solid theory yet) but there's a Wikipedia article on it, it's called the [wagon-wheel effect](_URL_0_) | Basically due to the strobe effect. Your eye can only see at a certain number of frames per second. You are capturing frames while the wheel is moving forward, *but* those frames happen at a time when the spokes appear to be slightly behind where they were in the first frame. If the car changes speed while you are watching, you'll "see" the wheels slow down, almost stop, and then reverse to the correct direction! |
What exactly is that cramp in your side you get while running? | As far as I know, it has to do with the jolt of your right leg hitting the ground when you walk or run or work out. The jolt smacks into your diaphragm, which retaliates by cramping up. I think. With this in mind and with personal experience in mind, it helps to lean over a little and breathe deeply until it passes, then try to change your breathing patterns, trying to coordinate your exhale with your left foot hitting the ground, rather than the right. And I'm really sorry if this is completely wrong. It's just what I've read a couple of times. | Your muscles are cramping. It can come from dehydration or lack of proper electrolytes. Drink more water. Eat foods with calcium, magnesium, and potassium. |
Are arthropods cold-blooded? | Like fish and reptiles, arthropods are unable to regulate their body temperature. However they don't exactly have "blood", so describing them as "cold-blooded" may be a little off. | All insects, including bugs, are "cold blooded". I used quotations because generally speaking species are *mostly* cold blooded, or *mostly* warm blooded, but very few (if any) are entirely one or the other. For example, last night I was drinking a beer on my balcony and I moved from the shade in to the sun to warm myself a little. And it worked. And contrary to David Icke's claim, I am not a space reptile, I'm a warm blooded human. |
Why are there no books on China in the "Allied Countries" section of the World War II book list? | The booklist has been put together by *volunteers* on a rolling basis - that is, nobody sat down and worked for eight hours straight on creating a comprehensive list of The Best and Most Important History Books. As such, each section generally represents someone with a specific area of expertise contributing the works that they can best judge, and as a result, yes, there are holes. If you (or anyone else) has expertise in China during WWII and can contribute both titles and reviews of relevant books - as you can see, we include a snippet from a professional review with each book in that section - we'd love it if you/they sent them to us via modmail for inclusion. | Xinjiang is very much in the news recently, so the absence of a section in the booklist for Xinjiang under Chinese rule has been a major omission. However, as of a couple days ago I've updated the Central Asia booklist to include three recommendations for books on Xinjiang under the Qing: [see here](_URL_0_). |
What changes for a body to reject the consumption of dairy products when prior to the change it was fine? | It's possible that you've developed a lactose intolerance. lactose is a sugar that gets broken down into galactose and glucose in the digestive tract by an enzyme called lactase, all humans are able to process lactose as a child to be able to digest breast milk, when the need to drink breast milk stops, so does the production of lactase. However because of the domestication of cattle many Europeans evolved to be able to produce lactase for longer periods of time, to be able to take advantage of the newfound food source. Without the lactase being produced the lactose would be too large a molecule for the body to easily absorb which would cause the irritation and gassiness that is usually associated with lactose intolerance. So really it could just be that you've lost the ability to produce lactase enzymes. | The human body changes over time. Absent the genetic mutation that humans developed a few thousand years ago, humans are born producing lactase (the enzyme that breaks down lactose) but stop producing it once they stop breastfeeding. |
Why do we like to kissing so much? | There are a lot of theories, a leading one being that it's a biological way for us to test whether someone's a good partner based on their immune system. Basically, we like to mate with people with different immune systems, so our offspring will have the best of both our immune systems (yay evolution!). By tasting someone's saliva, we can (subconsciously) tell what their immune system is like. Someone with a varied immune system from ours will be more agreeable/pleasant to kiss, because our bodies want us to make babies with them. On the other hand, it could just be a social habit of affection. Or it could be a subconscious fixation on the mouth, or... well lots of stuff. But I like the immune system theory. | Of 168 studied cultures around the world, less than half practice kissing in a romantic-sexual way. It is definitely not a natural universal behavior. There are numerous cultures that find it utterly disgusting. _URL_0_ |
I am allergic to cows while around them, though when I eat beef there is no reaction. Why is this? | Short answer is that you are likely allergic to animal dander and saliva. The "meat" muscle tissue you consume does not contain the same antigenic proteins to which your allergic reaction is specific. | An allergic reaction is just our immune system trying to attack what it percieves to be a foreign threat to your body. Usually people develop allergies to things because they either weren't exposed to it enough when they were young or genetic reasons. Your body perceives the animal hair as a potential foreign body attempting to enter your body so it causes an allergic reaction. It may cause you to feel itchy in the area in an attempt to scratch it away or any other of the reactions our body has for these. |
Why don't all animals bleed during menstruation? Are there others, besides humans, that do? | First, only [mammals menstruate](_URL_0_. That is because you need a uterus with a uterine lining (endometrium) to bleed. Even among mammals, only a few actually bleed visibly [Most mammals actually reabsorb the uterine lining if they don't conceive](_URL_1_). Moreover, cycles differ between animals. Some only come into heat once a year for a few days, others only come into heat every week, some are monthly (like us), others longer then a month. The mammals that do menstruate are mostly restricted to primates - but even then only certain ones do. The general trend is that the closer a primate is related to us through our family tree, the more likely they are to have overt rather then covert menstruation. I don't think dogs are considered to have true overt menstruation, but there may be some disagreement on that between scientists (some animals may bleed even though the majority of the lining is reabsorbed). | No, female dogs do not get menstrual periods. Female dogs *will* bleed at the beginning of their oestrus cycle (heat cycle) as their bodies prepare themselves for ovulation / possible pregnancy, however this bleeding is not comparable to a woman's period. For human women, the period marks the *end* of her menstrual cycle. When a woman is on her period what happens is that her uterus is shedding the layer it built up in preparation for a pregnancy, but which went unused as no pregnancy occurred. Animals do not do this (barring a few rare exceptions like the Elephant shrew) Animals reabsorb the lining they create for a potential pregnancy fully. Humans only absorb about 2/3rds of it back into the body and the rest comes out as waste. |
why doesn't Japan just shoot down N. Korea's missiles? | They could, but that might be interpreted as an escalation by North Korea. Also, if they were to shoot down a missile, they better not miss. This was not an actual attack, but if an interception missed, it would signal to North Korea that Japan's anti-missile technology was unreliable and might make North Korea even more willing to use missiles in the future, knowing they won't be intercepted. | A few things: 1) China is protective of North Korea (China stepped in and fought the US during the Korean war). China is a military superpower with nukes. 2) While it may be possible to kill Kim Jung Un you cannot kill the whole leadership in one, swift go. The next bad guy would just step in to the vacuum left by Kim Jung Un. 3) North Korea has nukes and such a strike may prompt them to lash out. They can't quite attack the US but can certainly attack important US allies such as South Korea and Japan. 4) Even if they do not throw nukes around North Korea has a massive amount of artillery all within striking range of South Korea's capital Seoul. This artillery is enough to be nearly equivalent to a nuke with a few minutes firing on Seoul. Seoul is a city of about 10 million people. It would be disastrous. Basically NK defends itself with their version of MAD (Mutually Assured Destruction). While they can't threaten the world they can threaten enough to be left alone. |
How do ISPs identify people who torrent illegal stuff at public access points such as Starbucks? | ioneupyourstory pretty much got it. but, to explain like you're five: Every computer has an internet talking box inside,or attached.This is called a network card. Every network card has a unique code -kinda like a computer fingerprint. This is called a "MAC" or machine address code. If you go get stuff illegally at a public network site, they can keep a picture of your MAC/fingerprint. The company that fuels your home network (internet service provider) usually also has a copy of your MAC/fingerprint. If lawyers somehow learn that someone was naughty at the public site, they can get an order from a court, and ask every major internet service provider in town for the matching MAC/fingerprint, home address, and name of the person on the account. From here, comes trouble. one more note: very sneaky people can change their MAC/fingerprints when out in public, so they are harder to catch. | Imagine a classroom of kids passing around the answers for a test, the teacher may find the piece of paper on a kid, but has no way of knowing if he wrote the answer, used it or was just passing it on. Tor which is one of the programs that lets you browse the deep web will go through a number of nodes to fetch you the site you are looking for, and authorities don't know if you are looking for, hosting or accesing the illegal website or simply passing it on. |
Why do diesel engines sound different from petrol ones? | Diesel engines use the only the compression of the piston stroke to ignite the air/fuel mix, whereas a gasoline engines air/fuel mix is ignited by a spark plug. Gasoline is much more resistive to detonation due to high compression (self ignition from being compressed) than diesel, which is why gasoline engines require an ignition source (spark plug). The extra noise produced by Diesel engines is the result of the 'detonating' air/fuel mix resonating through the piston head and engine block. If a gasoline engines if ignition timing is overly advanced or the combustion temperatures overly hot, the gas/air mix can detonate on it's own resulting in a typical 'knock' sound due to the same resonance. In short the difference is sound is a result of the different timing of the combustion event in each engine relative to piston and valve movement. | A lot of people don't like the sound & vibration of a diesel engine, they are "rougher" than the regular engines. If you're on the fence, take one for a test-drive you'll be a convert like me, the torque of a modern diesel is something to experience. |
Why do some bowls/cups pour clean off the edge, while others run down the side? | It's a balance between gravity and surface tension. One is trying to get the liquid out quickly, and the other is trying to keep the fluid molecules together and stuck to the walls of the container. So it really depends on how fast you pour (gravity), the shape of the rim (smaller area to stick to, and more water pressure), the material the cup is made from (changing how sticky it is), the texture of the cup (changing the surface area that the fluid can stick to), and the fluid itself (again, changing the surface tension). | Side of the bowl. The water hits it at an angle and bounces downward towards the water. When hitting the water it’s forced upwards. Additionally, forget the cleaning issue. Hitting the water is disgusting, loud and horrible for anyone else within a city block to have to listen to. |
How come that when you forget something, and are given a list of options, you can still pinpoint the thing you forgot? | Because you didn't actually forget it. Your brain tucked it away in long term memory and you need a stimulus for your brain to bring it back into working memory. | In the prevailing theory of memory, your hippocampus stores a bunch of memory "traces" that are brought up every time you try to remember something. A lot could go wrong with this process of recollection and bringing back the memory traces but I don't think neuroscientists truly understand forgetting. It could be that you lose the memory trace and the mental processes recruited by the recollection command simply can't find it or maybe those memories have been overwritten by other memories. Given the brain's high degree of plasticity, I'm inclined to believe it's more of the latter - that old memories are written over to form new ones. |
How in movies when we see a character look into a mirror and see their reflection, how come we don't also see the camera? | They shoot from an angle. This isn't just to hide the camera; despite what you might have heard, actor's heads are not actually transparent. You can't film through the back of their head, so you can never get a straight-on view in a mirror of their face. | Well, when a camera takes a photo usually from left to right. It's doesn't take the picture all at once. So something can be one way in the picture on the left side, and different as it goes right. This is a great example of this effect: _URL_0_ When the photo was taken, the kids eyes were closed, but the reflection, which was scanned a fraction of a second later, he had opened them so that's what's seen in the reflection. |
Why do birds shake their head while walking? | The shaking comes from their eyes usually not pointing the in the same direction, like human's do. They need some other way to judge distances, so instead of 'overlapping' two slightly different images like we do. they must move their heads to see what things move infront of other things which gives them a rough idea of what is closer and what is farther away. Bird's whose eyes can both look forwards, such as Owls and Eagles, don't do the head-shaking as they walk, because they can overlap the images from both eyes. However they might still bob their head around a bit when looking at something in particular, they will be combining both effects for an even greater understanding of what they're looking at. | When we walk, our eyes actually bob a little to keep our gaze. Birds don’t have this mechanism. Instead they Bob their heads. It allows them to keep their head in the same position for the maximum amount of time before moving so their image/view is stable. Some birds don’t bob their heads though. Which is an interesting phenomenon. |
If HSV-1 is stored in the nerves in your lips, why can't we just burn the nerves that house it? | Nerves do important things. Burning them out is a bad idea, science isn't really confident in its targeting. This means that we'd have to nuke all the nerves in our lips... which would suck. | Herpes resides in your nervous system, not your lips. The infection you see as a cold sore is an inflammation response to a newly reactivated bit of virus at the tip of a nerve under the skin that colonizes some minor damaged tissue on the lips. The reason it is reactivated is not clear: herpes is usually dormant for awhile after infection then spontaneously pops up due to signals we don't entirely understand. It can cause sore on just about any place with lots of nerves or weak tissue, so it can get in the eyes or on the fingers. But as for the reason it doesn't spontaneously shift it is likely the same reason you don't immediately get cold sores after your first infection: newly infectious virus particles don't cause immediate symptoms, and you already have antibodies and a latent infection. This is borne out by the fact that immunocompromised people do get long spreading lesions called "knife cut" lesions and potentially life-threatening outbreaks. |
Is this true that cooked foods have more calories than raw foods? Or are they just implying that the type of foods that are cooked tend to have more calories then the type of foods that are eaten raw? | Anything your body does requires energy, including digesting food. When you cook food, you are essentially predigesting it. Since it is predigested somewhat, your body does not need to spend calories digesting it, and thus you have a greater net caloric intake from it. | As for your question about what happens when you cook *any* food, for one thing, [cooking food allows your body to more efficiently extract calories from the food.](_URL_0_) In the case of toasting, though, the bread is technically already cooked, so I don't know how much of an effect that would have. As for the effect on other nutritional aspects of the food, I don't personally know. |
Why aren't tattoos applied by a printer like machine? Why do we only have tattoos drawn by hand? | The big problem with using tattoo printers is that skin doesn't act like paper. In addition to being curved, skin has different thickness/resistance at different places. You can't just tell the computer to apply x force for each pixel. | Tattoo ink isn't injected into cells, it sits between cells and can't be destroyed by the body. |
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