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Which types of animals need the most/least amount of sleep? Why?
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[Koalas](_URL_1_) can spend up to 20 hours per day sleeping (or resting at a low metabolic state). [Horses](_URL_0_) spend only a few hours (2.5-4) asleep.
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Why is static friction stronger than kinetic friction?
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There is no simple answer to this question, and it is a rule "in general" not a hard and fast rule. As a rule, when an object is moving, the small imperfections on the surface get smoothed out a little bit, all facing the same direction, and thus the friction between the surfaces will decrease. If you have two smooth, clean pieces of metal, you will often find the coefficients of static and kinetic friction are the same.
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Is there a reason hard drive space is often measured in 2^x gigabytes (eg iPhones come in 16, 32 or 64Gb)?
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Actually you'll usually find that memory comes in powers of two (kernelhacker explains why), while hard drive sizes are more marketing driven. They'll have sizes like 20 MB or 100 MB or 500 GB or whatever. iPhones don't have hard drives.
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Does our universe expand faster than the speed of light?
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1) According to our best models and data, the universe has no edge. It's either wrapped back around on itself like a three-dimensional sphere or (more likely) infinite in extent. 2) According to our best models and data there are and have always been objects far enough away that their recession velocity as a result of expansion exceeds the speed of light.
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If a blocked nose is caused by inflamed sinuses, them how come when you lie down, the nostril closest to the pillow gets more blocked while the other clears up?
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Inflamed sinuses can be a reason for a blocked nose because they're associated with fluid buildup. This fluid can have trouble draining from the sinuses around the nose ([paranasal sinuses](_URL_3_)) because the openings to these sinuses are in weird places. This has a lot to do with how [flattened human faces are](_URL_2_). The maxillary sinus in particular, which I suspect is what you're referring to, is especially silly (in my expert opinion). The sinus lies just below the eyes, above upper jaw, and on either side of the nasal cavity. The silly bit is that the opening to drain the maxillary sinus [is located at the top of the sinus](_URL_1_) in the [semilunar hiatus](_URL_0_). There are cilia (hair-like projections) that beat in the direction of the opening to move fluid towards it, but they're working against gravity. When someone lies down the sinus can usually drain more easily. Depending on how that sinus is oriented, one might drain while the other has more difficulty draining.
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Why does string theory require the concept of 11 dimensions?
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I also have a question about this. We can only make string theory work with a crazy number of extra dimensions. However, we have not ever observed these extra dimensions. All the evidence we have suggests that there are 3 spatial dimensions. Why don't we then stop there, and say that string theory must obviously be wrong? The theory does not agree with observations. Surely the scientific thing to do is to then discard the theory? How is it any different from saying "My XYZ theory requires invisible pink unicorns, therefore invisible pink unicorns may exist" rather than "My XYZ theory requires invisible pink unicorns, therefore my XYZ theory is probably wrong"
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Why does string theory require eleven dimensions?
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To expand on OP's original question - what do the additional dimensions do in string theory? Are they required to tunnel information between standard model particles to express forces or exchange energy that is not visible in the 3 dimensions we can see? Is time one of those 11 dimensions, or is it yet another dimension, if you consider it to be one?
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Does honey production/consumption help or harm the bee population?
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Not sure if there is a good conclusive scientific answer, grounded in reliable data, to this question. It might be context sensitive. I've read reports that in London, at least, the "grass roots" effort to help the bees [are doing more harm than good](_URL_1_). But then, there is also [this](_URL_0_), touting how bees in urban environments benefit from more abundant resources. Not sure if honey consumption (or bee products in general, ie beeswax lip balm, candles, soaps, etc.) or other commercial impingement has as big of an impact as you assume. I live in California, where lately, bees have been in the news because almond growers here are desperate to get sufficient pollination of their crops. If anything, a perfectly efficient economy would see honey prices drop due to over supply.
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How does vitamin D and sunlight work?
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The vitamin D you are probably talking about (there are actually different forms of vitamin D) is created by using the energy of UVB in the sunlight to "rearrange" 7-Dehydrocholesterol which is present in the epidermis (outermost layer of the skin) into Cholecalciferol by means of an [electrocyclic reaction](_URL_1_). [Here](_URL_0_) is a pathway from Wikipedia that displays the process.
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Is the tongue really the strongest muscle in the human body? If so, in what sense is it "strongest"?
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The tongue is not the strongest muscle in the human body. It's a common myth. The strongest muscle in the human body, defined by the it's size versus how much force it can exert is the Masseter muscle^[[1]](_URL_5_) located on both sides of your jaw. It's function is to help chew and crush the food you eat. The [library of congress](_URL_2_) has a list of "strong muscles" which includes the tongue, but the tongue is nowhere near the strongest muscle in the body. It is easily outmatched by the larger muscles such as the latissimus dorsi^[[2]](_URL_4_) , pectoralis major^[[3]](_URL_0_) , quadriceps femoris^[[4]](_URL_3_) , and gluteus maximus^[[5]](_URL_1_) . Each of these muscles can easily outperform the tongue when it comes to force exerted, as these large muscles play a major part of your everyday function. The tongue was romanticized as "the strongest muscle" in your body, but it is not true and it is a myth.
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Maximum and minimum rotational speed for habitable planets?
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> Is a habitable, tidally locked world possible? If not, what is the minimum rotational speed that allows for habitability? Yes. The habitable zone around a red dwarf star can be close enough that a planet would be tidally locked. Now, the side always facing the star would probably be too hot to support life, and the side always facing away would probably be too cold, but along the terminator, the area right around the edge of the planet when night crosses into daylight, the temperature could be in the range where human/Earth life could survive and even thrive. You would build your cities just across the terminator on the night side, and grow your food just on the edge of the day side.
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If the white light is all colors combined, why does bleaching something turn it white? Does it add all pigment colors?
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When we talk about color, there's actually two different paradigms: the color of light, and the color of pigments. Light color is determined by the wavelengths of photons. White light, as you know, is the equal combination of all the wavelengths humans can see. So a light source that emits all wavelengths appears white, and something that emits zero light appears black Pigment color is sort of the opposite. Things that appear red do so because when they are hit by full spectrum (white) light, they absorb all colors *except* red. They reflect the red, and so appear to be red because that is the light that actually reaches out eyes. So a pigment that absorbs all wavelengths of light appears black, and one that reflects all wavelengths appears white. So, when it comes to bleaching pigments, you are removing the ability of the pigments to absorb colors. Now, instead of absorbing some colors and reflecting others, the bleached pigments reflect all colors, and thus appear white.
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Do bees know they’ll die if they sting another animal?
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I can't find the study just now, but your quick answer is "no." When a bee stings and loses his stinger (and therefore rips out his guts), it has to do with physics and the tensile strength of what he stung. Human skin, for some species (not specific to bees) is strong enough to cause that in stinging "bugs." The bee is the most well-known, but there are others. Bees (like any other species) attack or defend at need. Please forgive both my use of "bugs" along with the possibility that the period belongs outside of the quotes.
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What causes our muscles to sometimes involuntarily twitch for extended periods of time?
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The medical term for this is *[fasciculation](_URL_0_)*. What's happening is that part of your nervous system is a little overactive. You can picture it sort of like static on an audio channel. The nerve fiber controlling your left bicep has more "static" in its signal, and since your muscle can't tell the difference between random noise and an intended signal, it interprets the static as a command to contract. The internet can't diagnose what's causing it for you specifically, but there are lots of possible causes. The most common are stress, anxiety, stimulants (like caffeine), and dehydration. Electrolyte imbalance is another big one, especially magnesium deficiency. And in relatively rare and severe cases it can be a symptom of underlying neuromuscular disease.
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GMOs- engineered genes in crops don't spread into the wild, into other species, do they?
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If you mean by [horizontal gene transfer](_URL_0_) that is very rare in nature and there is no reason to expect it to be any more common with GMO.
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In regards to red shift, why does light emitted from stars that are moving towards us shift to blue and not violet?
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A more precise description would be shifted to shorter and longer wavelengths, which is what blue and red shifts ultimately are used to mean. Honestly using violet instead of blue would hardly make the term more exact since e.g. if you're dealing with UV light, then shifting it to a longer wavelength would be a "red-shift," even if the resulting light would be blue. In other words, just recognize that these are colloquial terms for shifting to shorter or longer wavelengths, don't read too much into the actual words themselves.
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Why did we have to send a probe to Pluto to get a photo of it?
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The photo of the black hole is not a "photo" in the sense you are thinking. It is a visualization of very high-frequency radio waves. While these are still electromagnetic waves just like visible light, they are way outside of our visible range. This is necessary to "penetrate" through all of the super-heated matter that surrounds the black hole. In the visible spectrum, all we would see is a big ball of light ([_URL_0_](_URL_0_)). Pluto does not emit radio waves on the scale of a supermassive black hole (if at all), so we cannot get a similar image.
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If it took approximately 100 million years for the first stars to form, does that imply that for the first 100 million years the universe was in absolute darkness?
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~~Photons (light particles) were created [10 seconds after the big bang](_URL_0_) and for a while everything *was* light.~~ EDIT: See Silpions correction below. We can still see light from when the universe was [300 000 years old in the form of Cosmic Microwave Background Radiation](_URL_1_).
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How has light had time to reach us from distant stellar phenomena?
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> More precisely what I mean is, if our universe is only 13-14 billion years old, how has light from objects that are 40 billion light years away reached us. The objects were much, much closer when they emitted the light. Over time, the distance between us and the light and the distance between us and the object expanded. As a result, the light took 13 billion light-years to reach us, and the object got to be 40+ billion light-years away.
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Do humans photosynthesize Vitamin D the same way that plants photosynthesize glucose?
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Yes and no. They are both photochemical reactions, but a little different in nature. Vitamin D is the result of UV activation of a precursor molecule in human skin. See [this diagram](_URL_1_) for good overview of the process. The UV light here actually changes the chemical structure of the precursor molecule itself. In [photosynthesis](_URL_0_), the energy from light is used to excite electrons into higher energy levels in photosystems II and I. The energy in these excited electrons is then stored in ATP, a mediator molecule, which is then used by the Calvin Cycle to generate sugars. So, both use energy from the sun in their synthesis, but activation of vitamin D uses UV radiation directly while photosynthesis uses lower energy light to excite electrons whose energy is then stored in ATP before finally being used for sugar synthesis. Hope this helps.
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Can any animals ACTUALLY smell fear?
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It seems that they can detect(by smell) emotional states in their own species, but this is highly unlikely in different species. The highest likelihood is that the animals can read body language very well, and pick up on these physical queues. _URL_0_
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Is there such a thing as a resolution of photons? If so, how far away from a star would we have to be to detect these "pixels" of photons.
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The pictures you are seeing from Hubble really aren't in high resolution. Hubble still has a slightly blurry picture, it is corrected with software and active optics and a reduced field of view so it looks better, but its still not what it should have been. Also, galaxies and galactic structures tend to look crisper because there is no fine detail for you to attempt to make out. When you are looking at a picture of a galaxy you can no longer make out individual stars you can only make out star clusters and neighborhoods, each pixel is actually light years wide at the target distance. Hubble also spends days staring at the same chunk of space gathering all the light it can, this helps to get decent pictures of dark objects. If you want a super good image you need a massive aperture, or you can cheat and use several much smaller apertures like the VLT array with its 4 main telescopes all working together to provide resolution close to that of Hubble but with atmospheric distortions.
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How does the ISS removes the heat absorbed from the sun?
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[Here](_URL_0_) is an article that talks about this very question. It involves using aluminized Mylar, which effectively blocks *all* radiation from the sun. It's also good for keeping heat in. The biggest cause of temperature gain at the ISS is actually from the electricity being used inside the ISS. Heat exchangers are used to disperse the excess heat through ammonia based aluminum radiators (so called because they radiate heat, air circulation not required).
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How does the ISS get rid of heat?
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Hey there! [Ever seen a photo of the station?](_URL_1_) The solar panels are immediately recognizable, they are the huge, in-this-image vertical, golden panels. See the horizontally-aligned panels? They are smaller, and duller, grayer? Those are called radiators. See [here](_URL_0_) for a diagram, and you can read about the system a little too, if you'd like. It is called the *External Active Thermal Control System*. Bit of a mouthful, huh? Anyway, essentially how it works is pipes of ammonia run throughout the station, and pick up excess heat. These ammonia pipes then run through to those radiators we see, where the extremely large surface area allows them to cool through radiative cooling, the same process which makes hot things feel hot from a distance. A great example of this is the heat of the sun on your skin. There is, of course, a little more to it than that, but there is the basic rundown.
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Why can we only synthesise 11 of the 20 essential amino acids?
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Actually, the term ["essential amino acids"](_URL_0_) refers to those amino acids that we can't synthesize.
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Why can't we make the 9 essential amino acids?
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There is also an element of random chance in evolution. Someone developed the mutation that meant they could not make an amino acid, and if it wasn't a huge disadvantage, the mutation can get passed on a lot by chance, or if that person has other advantageous traits. Genes can 'hitchhike' on other genes through evolutionary history like that. Also, some of the amino acids we lost are chemically related to each other, so when we lost the ability to make a common precursor, we lost the ability to make (for example) both leucine and isoleucine.
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Does the number of moons a planet has affect its ability to support life?
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The short answer is, of course, we don't know - we only know of life in one place, and it does have a moon, but one data point isn't enough to extrapolate from. I think it's fair to say that life on Earth wouldn't have evolved in the same way without the moon, but it's quite a jump to go from that to saying that it couldn't have happened without it. _URL_0_
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Why do cookies get soft when they go stale, but bread gets dry as it goes stale?
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What kind of cookies do you have that go soft?
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If an electromagnetic wave's penetrating power is proportional to its frequency, why can visible light penetrate glass, yet UV light, with a higher frequency cannot?
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The energy of a photon is proportional to frequency, but this energy must match the energy of some transition in the absorbing matter. The electrons in bonds in glass have transitions in the UV, but not the visible range. This is the same reason why high energy X-rays are used for imaging: muscle and tissue are mostly transparent to X-rays, while the calcium in bones absorbs them.
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Where does gas go when released into the vacuum of space?
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It diffuses into the near vacuum of space.
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Is the speed of light contingent upon the speed in which the universe is expanding at?
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No, the speed of light in a vacuum is always the same.
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[Engineering] Why has no one made an engine where the cylinders are of varying sizes?
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Vibration would be a big factor. Straight 6 and V12 engines have the best balance/lowest vibration. Most others are compromises of space and vibration. If you have different sized cylinders everything becomes way more complicated and less efficient.
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Were all humans pigmented the same way "out of Africa"? Or differently? Did climate and location dictate skin color?
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If you consider our common ancestors then it is most likely that variation in skin pigmentation existed before we separated from chimpanzees. Chimpanzees exist with a wide variety of skin coloration, from very light to very dark.
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If photons lose kinetic energy when colliding with objects but by definition travel at the speed of light and have no mass, where does that energy come from? Can a photon’s energy level be reduced to the point of being below the speed of light?
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The photon doesn't lose energy by slowing down. When it exchanges energy with a particle (e.g. [Compton scattering](_URL_0_) ) it loses energy by becoming lower frequency (longer wavelength), by the equation *E=hf*, where *E* is the energy of the photon, *h* is [Planck's constant](_URL_1_) and *f* is its frequency.
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If I was in intergalactic space such that a nearby galaxy filled up my entire field of view, would I be able to see it clearly? Or would it still be as dim as the milky way is in the sky here on earth?
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Follow-up question. The center of the galaxy is quite a bit brighter than the rest of it, and the center of the Milky Way is only dim on Earth because there is a "dark nebula" in the way. You can see that [here](_URL_0_). How bright would the center of the galaxy be if the dark nebula was not in the way?
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[Mathematics] How do people find new prime numbers?
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The largest prime numbers we know are Mersenne primes. These primes can be written in the format M = 2^n - 1, where n is an integer. The current largest known prime number is 2^74207281 - 1. Obviously not all numbers of this format are prime, but having this format narrows our search by giving us lots of candidates. Once we have a candidate, we use an algorithm called the [Lucas-Lehmer primality test](_URL_0_), as it's the most efficient known way of determining if a number is prime.
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Why do things like eggs or dough become more of a solid when they are heated?
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> On my limited science background, I am aware that when energy (heat) is added to something, it would tend to progress from a solid to a liquid to a gas from the freed molecules. This is true for physical changes. > However, when cooking eggs or baking something from dough (cookies, bread) it toughens up under heat. Why does this occur? This is a chemical change. _URL_0_
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Does the "Monty Hall Problem" apply to Deal or No Deal?
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No, because the key part of the monty hall problem is that the host is giving you information by opening another door and showing you what is behind it (because he knows it is not the prize beforehand). In deal or no deal, the host doesn't do anything that could provide you information about the location of the prizes - he never opens any boxes for you or provides any information about their contents. All you know about the remaining boxes is what you can deduce about the boxes you have already opened, which is totally straightforward. I would guess that Noel Edmonds doesn't even know the contents of the boxes in the first place.
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Have apes that have been taught sign language ever been found to use it to communicate with other apes or only with their trainers?
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There are some chimpanzees at CWU that not only used sign language with each other, one of them taught its offspring sign language without the trainers prompting it, and they also have started hybridizing certain signs to invent new words, for example "run" and "play" have been combined to specifically mean "let's play tag", and it's not just that they were signed together as a phrase, they were actually combined into a new sign. EDIT: citations for you! _URL_2_ _URL_0_ _URL_1_ _URL_3_
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Can man made elements be found on other planets?
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864 degrees is nothing compared to the forces we use to create elements. But the real reason we won't find high-level synthetic elements on other planets is because they are unstable, radioactive, and that radioactivity causes them to rapidly decay. an atom of Einsteinium, for example, lasts only a year. Some last only a few seconds! After that, they are but ordinary heavy metals like lead, iron, uranium, etc.
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[Physics] Considering that the photons would never be absorbed by the 100% reflective mirror, what would happen inside? It's in the realm of a thought experiment since you'll never be able to measure the result.
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I think that he is asking about the inside of a perfectly reflective box. Yes it would bounce around forever, here's why: The photon is an electromagnetic wave in a vaccum, and is classically defined as a pair of coupled wave equations: _URL_0_. Imagine a mirror in 1-D propagation. A perfect mirror, (100% reflection) can be mathematically modelled as a specific boundary condition at the physical boundary, (lets say, X = 0 and X = L), which governs the energy transfer and reflection from the surface. In this case, (1D), the wave equation is v^2 f_XX(x, t) = f_TT(x,t). With an initial condition of f(x,0) = initial_trapped_wave(x) and f_t(x,0)=0, (some initial waveform, and no first order temporal derivative). The boundary condition is such that there is no restoring force acting on the wave front at the boundaries, so something like f_tt(0,t)=0, f_tt(L,t)=0. Then, without loss of generality, expand this to 3-D and limit wave propagation to some box in R^3. It will just keep reflecting.
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What do scientists do to adult stem cells?
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If you subject an adult stem cell to a specific set of conditions and the right transcription factors are present (Oct4, Nanog, Sox2), you can create what are known as induced pluripotent stem cells. They do not have the same potential as an embryonic stem cell, and the degree of imprinting varies based on the type of stem cell you are working with- so trying to redifferentiate the iPSC is tricky, but you can reprogram the iPSC with transcription factors specific for the cell type you want it to become.
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If solar panels convert sunlight into a different kind of energy than heat, then are solar panels basically air-conditioners for the outdoors?
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No, photovoltaic panels don't convert heat into electricity. They use photons to dislodge electrons from special materials and generate electric current as those electrons "fall" back into place. Thermoelectric materials can take advantage of a temperature difference to generate electricity, but even these don't cool the environment, as energy is obtained by letting heat flow from a hot source to a cold sink, which on Earth is the surroundings.
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Why don't our teeth heal?
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For the purposes of evolution the most important thing was that we lived long enough to pass on our genes. Our teeth generally last long enough to accomplish this goal and likely would have lasted longer before humans started consuming soda and candy.
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What is the difference between sugar and sugar alcohol?
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Sugar alcohols are simply sugars that have had their ketone/aldehyde group reduced to an alcohol. They're often used as artificial sweeteners, especially in gum. Normally, the bacteria in mouth use sugar for metabolism, producing acidic byproducts that cause tooth decay. However, the bacteria aren't able to utilize sugar alcohol. While sugar alcohols aren't completely absorbed in the intestine, studies are showing they can raise blood sugar levels. Large amounts can cause bloating and diarrhea as well.
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How do alcoholic drinks have sugar in them if yeast consumes sugar in order to make alcohol?
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Depends on which yeast you use, they consume various degrees of different kinds of sugars. Depending on the kind of drink, the yeast's consumption might stop at some point in the process, either by killing or removing the yeast (which is quite common in large-scale beer production) or the yeast might die from the alcohol it creates (I would guess this can happen in wine, but I have never made any so I wouldn't know). Yeast might also learn to consume sugars we don't want them to, which is one of the reasons why a yeast that has fermented a beer is not reused again.
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How does data compression work?
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Here's the simplest idea that will sort of explain it: Let's say we have a file that looks like this: "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" Now we'll compress it: "153 zeros." We just took the same data and represented it twice. The first way has lots of redundancy, that we removed.
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How efficient is recycling?
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**Are they inflating their worth?** **TLDR** It's a lot like saying "McDonalds saved customers $42 million on groceries in 2010!" Which prices did you use to measure that, and what's stopping people from just going to Burger King instead? Yes. It's likely an overestimation. Their reasoning probably goes something like "We recycled enough paper materials to equal 42 million trees worth of pulp." But that doesn't necessarily mean that they've saved that many trees. First, because virgin paper is more superior to recycled paper- in part- because the fiber length gets shorter each time the paper is recycled. Virgin paper is stronger and that confers a lot of benefits. Second, because recycling 42M trees worth of pulp doesn't necessarily mean that 42 million trees weren't cut down. With virgin paper being more expensive to make, you have to assume that the market would have responded to the paper price hike and done *wonderful* things like cut back on phone books and junk mail.
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If captchas are supposed to differentiate between man and machine, how does the server confirm I wrote the correct letters?
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Some processes are easy to do in one direction but hard to undo. It's easy to take a series of letters or numbers and to apply a series of random effects to it, but it's hard to figure out exactly what those effects were. Even if you knew that one of the effects was "draw a black line from one random point to another" it could be difficult to work out which pixels were part of that random black line and which ones were part of the original letters.
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is there any animal who commits suicide?
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[Here](_URL_0_) you will see how some penguins commit suicide by separating from the colony to wander aimlessly in the wilderness. It is not direct suicide, but suicide none-the-less.
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Is there an opposite to clinical depression, a sort of "chronic happiness" or something like that?
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To be classified as disorder, the condition must have negative effects to the person, his ability to to function, or to his environment. Mania is in some sense opposite of depression, but it comes in cycles in almost all cases, even if not every bipolar person has clear depression between manic episodes. I think [hypomania](_URL_0_) in some cases might be what you are looking for.
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How did we come to realize that some planets are gaseous while others are not?
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You need to calculate the density of the planet, then you can match that to its general composition (rock, gas, plasma). In order to get the density, you need the mass and the volume. The mass can be easy, just calculate the force of gravity it exerts on its neighbor. IIRC, you don’t even need to know the mass of the second object, just the distance between them. The volume can be trickier, you need to get the general size, and our eyes/teloscopes can’t do that at large distances. So we use the earths orbit (and the planets orbit) to trianglate the size. Kinda like how the gap between your eyes gives you a 3D view of the world, except the gap is the earth’s whole orbit. (see the comment below for a better/more modern way to do this) Then divide mass by volume and presto! You’ve got the density of a planet!
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Why is drinking milk after spicy foods better than drinking water?
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Nonpolar substances tend to dissolve other nonpolar substances, and polar substances tend to dissolve other polar substances. "Like dissolves like." Hydrocarbons such as capsaicin tend to be nonpolar, i.e., positive and negative charges are more evenly distributed and cancel each other out. Water molecules, on the other hand, have polar regions, i.e., they have partial positive and partial negative charges. The arrangement and orientation of the atoms within a molecule help determine its polarity. Since water is polar and capsaicin is nonpolar, capsaicin is less soluble in water than it would be in a nonpolar solvent. The capsaicin would still be free to interact with receptors that cause pain. Milk and other dairy products contain casein, a nonpolar protein that is better at attracting the nonpolar capsaicin than the polar water molecules. If capsaicin is interacting with casein instead of the receptors that cause pain, then the burning sensation is lessened/neutralized.
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Why does our throat "tighten" when we're at the edge of tears?
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It's called the globus sensation which has associations with hypertonicity of the UES, the upper esophageal sphincter, as well as GERD. The purpose of the UES is to keep food in and air out. Stress, can cause the UES to tighten, the exact etiology of that action isn't known, but there is an association with stress and rapid breathing and losing your lunch, both things the UES interacts with.
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Why do you feel a jerk when a car comes to a complete stop?
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Many of the deleted comments here were incorrect or based on a very superficial understanding of classical mechanics. Other deleted comments were irrelevant personal anecdotes. If you are not an expert in this particular topic, **do not even attempt to offer an explanation**. We do not allow layman speculation, anecdotes, or off-topic discussion on AskScience.
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How bad/dangerous is second-hand smoke?
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> ETS is a human lung carcinogen, responsible for approximately 3,000 lung cancer deaths annually in U.S. nonsmokers. That really is a trivial number compared to the witch-hunt against smokers. I'm not saying that non-smokers don't deserve a smoke free environment, but the issue is distorted beyond all reason. far more people develop cancer after being exposed to pesticides (without actually using them, but simply by living in a farming area)
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If I'm listening to music while I yawn or stretch, the pitch of the music will audibly change while I'm yawning/stretching. Why is this?
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I'll answer quickly but I'm on my iPhone so I won't be linking a source. Shame on me. When you yawn, breath in deeply, or breath out forcefully, you create a pressure gradient between your chest cavity and atmospheric pressure. Try an upper airway Valsava maneuver, you should feel your ears "pop." Your ear canals have an anatomical connection to your nasal passages (this is where I would link a picture of the appropriate anatomy). When you change the pressure in your upper airway, the pressure changes in your inner ear. When the pressure changes in your inner ear, the ear drum now has a different gradient between the outside atmosphere and the inside inner ear. Sound is simply a pressure wave of air that you hear because it causes your eardrum to vibrate. In summation, if you tweak the pressure of your inner ear (by yawning), your perception of tone will change slightly because the vibration will adjust accordingly. TL;DR: My answer was confusing and unsourced. Hope it helps.
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Is a medications expiry date related in anyway to its packaging method?
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It certainly can have an effect. If a medicine contains compounds that are air or water sensitive (i.e., they decompose over time under those conditions), then taking them all out and putting them into a bottle would decrease their effective lifetimes. Only your pharmacist could answer that question for certain.
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If photons have no mass, how can E = mc2?
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E = mc^2 only applies to objects at *rest*. Light can never be at rest (any observer will see it travelling at the speed of light), so it will never be subject to that equation. E = mc^2 is a subset of a more complete equation, E^2 = (mc^(2))^2 + (pc)^(2), where p is the object's momentum. For an object at rest (p=0), this becomes E=mc^(2). But for a massless object, like a photon, this becomes E=pc, which is a well-known formula relating a photon's energy to its momentum, which is in turn related to its frequency.
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What causes my dog to age and die much faster than my kid?
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There is no concrete answer to why different animals have dissimilar life spans. One theory is that the life span is dictated by how long creatures need to stay alive in order to ensure the survival of their spieces. Some animals can procreate within two months and die within 2 years (mice) so as not to overcrowd their environment. Others, like humans take ~12 years to reach puberty, take care of our young for ~17 years on average, and need to stay alive to defend and provide for the race. We don't have any natural predators, so we don't need to multiply like rabbits to ensure our survival. This is the strategy evolution has funneled us into. Another theory is that each animal has a certain metabolic rate that relates to their life span. Basically, some animals live fast and die young while others live slowly and die old.
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Lottery strategy problem: 10% chance of winning $10k vs. 50% chance of winning $2k. Over a hundred times played is there a better strategy?
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As other have pointed out, both strategies have the same expected payout ($100K), but the first strategy has a greater variance. With the first strategy, there is a greater chance of getting more than $200K, for example, but also a greater chance of getting less than $50K. [Here's what the probability density of the winnings looks like](_URL_0_). The first strategy is in blue and the second one in red.
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Can multiple optical telescopes be used in the same way as radio telescopes like the Very Large Array?
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Yes, it can be done. Read [this](_URL_2_) from 2002 about a 6 optical telescope array and a little of what was involved in getting it working. You can also find a list of [optical and infrared interferometers](_URL_0_) on Wikipedia, with a guide to the wavelengths [here](_URL_1_).
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Do any other species, apart from humans, cry violently as newborns?
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Not only do other mammal offspring cry, the sounds are similar enough that mule deer mothers will respond to the cries of a large variety of mammals ranging from [fur seals to dogs to humans to bats](_URL_0_). There was a recent study about it. Mammals generally cry for the obvious reason: they want their mothers-either for safety or because they are hungry.
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Do drought-resistant GM plants maintain nutritional quality?
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If you rephrase your question, substituting 'a different variety' for 'a GM plant' then you may get the drift of your question. The GM variety will have whatever characteristics that were 'bred' into it as well as the drought resistance that you specify.
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Will moths ever have the brain capacity to evolve to the point where they are no longer "tricked" by unnatural sources of light (such as streetlamps)?
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IIRC insects use light sources (i.e. the sun or the moon) to navigate. the sun usually stays in the same spot no matter where you are standing (more or less. this is good enough for the insect to fly in straight lines). Now the street light is a lot closer that the sun and as the insect flys the streetlight moves, too. this will cause the insect to slowly spiral towards the light where it will then constanly be flying around. So unless insects develop a new way to navigte, I doubt they will ever adapt to artificial lighting.
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Has anyone detonated a nuke in space?
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Yes, as long as you're not picky about your definition of "in space". A nuclear bomb was tested at an altitude of more than 300 miles in 1958. That's still within the atmosphere by any reasonable definition, but it's higher than the space shuttle flew, so call it what you like.
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What exactly determines mucus's color?
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Basically the amount of cells and proteins present in the mucus. Clear is just water and minerals whereas green would be chock full of immune cells and potentially even the pathogenic organism. Red to brown mucus would indicate blood. And fun fact of the day: black mucus can be caused by bismuth sulfide, a Pepto-Bismol byproduct.
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How big were the biggest ancient trees? Would they dwarf the giant trees of today?
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Not until the seed plants (especially conifers) started to dominate the landscape in the Mesozoic period did we really start to see very large trees because early "trees" didn't have the structures and growth patterns necessary to support large trunks. Most of the early trees didn't seem to get about 30 m in height and about a meter or so in girth. Most of these trees had the capability to increase their height, but not their girth like the large conifers we know of today. I would wager that the largest trees we know of today (in terms of girth and height) are about what we would have seen in prehistoric times, if not a little larger.
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Why don't humans have a mating season, or do we?
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Most of Africa has very mild seasonal changes so it was better to just reproduce whenever we can. Women have periodic (heh) fertility/infertility but don't go in and out of estrous. Pheromones don't reveal fertility very strongly either, men don't respond much to pheromone changes that still exist. This is probably because sex has evolved to have stronger social value in humans than other animals.
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What is the least massive star visible to the naked eye?
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Here is list of the nearest stars to the Sun. _URL_1_ The apparent magnitude is how bright it will appear on Earth. The general definition is that anything dimmer than magnitude 6 (meaning the magnitude is greater than 6) is not visible to the naked eye under the best sky conditions. The absolute magnitude is if the stars were all put at the same distance (10 parsecs or 32.6 lt-yrs) away. Going down this list would give you 61 Cygni B which has a mass of 0.63 times the Sun. It's part of a binary system so you would also see its slightly heavier companion with it as well. _URL_0_ Actually Alpha Centauri A is 1.1 times the mass of the sun and is easily visible from the Southern hemisphere.
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If we see galaxies moving away as a redshift. Would we see parts of our own galaxy redshifting too?
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Any time an object is moving away from you it will be redshifted and any time it's moving toward you it will be blue shifted. This effect is used in observational astronomy as discussed [here](_URL_0_). Note that this effect is actually distinct from the redshift observed in distant galaxies. In the former case it's a result of relative motion and is called the relativistic Doppler effect, while in the latter case it's directly attributable to the expansion of the universe and is called cosmological redshift. As mentioned in the above article, there is also a gravitational redshift that occurs when the light is coming from a region with stronger gravitational fields.
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Why is the skin on our lips different from the skin on the rest of our body?
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From what I remember from my development lectures, the reason your lips are different is because when embryos are developing the endothelium of the gut extends when the embryo folds in development, the endothelial tube then presses through the epiderm so that the tube opens at one end and leaves at the other, the endoderm at the end then fuses with the epiderm and is slightly exposed on the end. Eventually these develop into your lips and ass. I'm probably remembering wrong so I would check my facts if I were you, I'm too hungover right now to do this myself. Hope this helps
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Is the path of the earth’s (or any other planet’s) orbit around the sun on a constant plane or does that path rotate?
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Why the Solar System is usually represented in 2D is a frequent question, please try searching. Short answer is: all planets orbit *almost* in the same plane. Only smaller bodies have high inclinations, some asteroids are nearly perpendicular to the orbits of most planets. For the part of your question about that path changing, the answer is no. Or almost no. A single planet orbiting a star would be always on the same plane (conservation of angular momentum). When several planets affect each other with their gravity, they can exchange some angular momentum and change each other's orbital inclination by a tiny bit. (This is really negligible but for theoretical correctness this possibility must be considered). But the sum of the momenta of all planets stays constant, this defines the so-called [invariable plane](_URL_0_) of the system. That wiki page also contains a table with the inclination of each planet, you can see how small the numbers are.
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How does a fish know what kind of fish it is?
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The olfactory system is a strong part of fish identification of each other. Fish will even choose a mate based on smell. I'd like to find a better reference, but _URL_1_ talks about how acidification of oceans is ruining fishes sense of smell and they can no longer identify their own kind as well. Ok, got some. So for [zebra fish](_URL_0_), not only is chemical sensing (smell) important, but their [first 24 hours alive](_URL_2_) they will have imprinting of who their kin is based on the smells they learn. There are [more papers that go into different fish](_URL_3_) that also find smell, or chemoreception as it's called is the major factor for recognition.
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If Light has no mass, why is it affected by gravity?
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What mass does is it distorts space-time so that light will follow a curved path. One of the most fundamental principles in optics (which arises from one of the most fundamental principles in physics) is that light will travel a path between points A and B such that the time of flight between them is a minimum. Normally, the shortest rout between two points is a straight line. However, we've all seen light get bent as it goes into a glass of water - this is because the shortest time of flight when going between two materials means the light gets bent at the interface (I can talk more about this if you like). Since mass distorts space, it also distorts the path of least time for a photon to travel. What was a straight line in un-deformed space becomes a curved line in the presence of a massive object. This leads to things like gravitational lensing and the like. This type of path is called a geodesic and massive objects tend to warp geodesics in their local vicinity.
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Why do your ears make a ringing sound when the room is dead silenced?
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Nerves can become sensitized and experience after effects. Also, you're used to hearing noise. Dead silence is something the nerve endings don't necessarily know how to interpret and they try to hear "something". I couldn't find the studies I was looking for to answer this, but this study on [the brain creating sounds](_URL_0_) kind of illustrates the point. Anyway, there was a documentary I watched once where they put people by themselves in a sound-proof room, they could hear their heart beats, their breath moving in and out, their clothes rustling, etc and it drove them nutty for the time they were in there. There's also electricity in "empty" rooms, there are insects, there's wind...something that your ears can pick up and try to translate.
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Why do you hear a faint ringing sound when in a silent room for too long?
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[Tinnitus](_URL_2_) can have a lot of causes. Probably everyone has it to some degree, but they never notice it unless they're in a very quiet place. [Here's some recent news about it:](_URL_1_) > U-M researchers previously demonstrated that after hearing damage, touch-sensing “somatosensory” nerves in the face and neck can become overactive, seeming to overcompensate for the loss of auditory input in a way the brain interprets – or “hears” – as noise that isn’t really there. So it's possible that what you're hearing is your brain creating sounds in an attempt to normalize auditory inputs. If you really want to hear what's going on in your brain, go camping overnight in someplace like [The Big Bend](_URL_0_). It's so quiet there, you might have a hard time falling asleep at night.
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Why do many poisonous household substances advise that you should not induce vomiting if you accidentally consume them?
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Because a doctor can pump your stomach in a clean and efficient way as opposed to the messiness of vomiting. Vomiting has the potential to spread the material in question into your sinuses and, in the case of something corrosive, to burn you further by exposing your esophagus a second time. I would hazard a guess that induced vomiting might be necessary if no medical facilities are available. However, ~~assuming you are within easy driving distance of an emergency room, drinking milk to dilute the potential poison and~~ seeking prompt medical attention is the ideal.
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Why do most poisonous household products say “Do not induce vomiting?”
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Some substances, like bleach, can also do harm going back up your esophagus. So, if you drink something that burns your insides on the way down, why force that same harmful, corrosive substance back up? Also, depending on the substance, the way to treat it is sometimes simpler than vomiting it up and going through all that added stress on your body.
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Is there a limit to the total mass a planet of a given size can trap in its orbit?
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Gravity works independently. If I'm alone in a room I'm not lighter when that room was filled with people. The force gravity exerts on an object is dependent on the gravitational constant, mass of the object and the distance.
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How close can two celestial bodies of roughly the same size and mass orbit around each other?
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It doesn't really matter if they're in a solar system or not. The limit is when they're big enough that they extend outside their [Roche lobes](_URL_0_). At that point, the outer layers will start to slough off and fall into the middle of the system, and they'll eventually settle into one larger planet.
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Why do "dead" batteries work when I take them out of my remote and out them back in? Sometimes it works if you just wiggle them.
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The chemical reaction that occurs in a battery to create electricity also produces hydrogen bubbles. When these bubbles are created faster than they can dissipate, they can cover the anode in the battery which stops the chemical reaction. Removing the batteries from a circuit allows the bubbles over the anode to dissipate thus allowing the battery to work again. _URL_0_
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Why does a dead battery work for a second when I remove it and put it back in the remote?
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A battery is basically just two electrodes, and a permeable barrier between them that lets ions pass but not electrons. At each electrode there are chemical reactions, the reactions at the negative electrode deposits electrons at the terminal, the reaction at the positive electrode removes electrons from the metals and move those electrons into the other reacting chemicals. So both those reactions occur at some rate, a slower rate as the battery is depleted. When the battery is installed in a device, electrons move from the negative terminal, through the circuits, back to the positive terminal. So, the voltage of the battery is determined by the amount of free electrons on the negative terminal compared to the positive terminal. When you take away the drain of the circuitry, the number of electrons, and hence the voltage, is allowed to build up by the chemical reactions at the negative and positive terminals.
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Why is there no more room for any other elements in the Periodic Table?
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It sounds like he's talking about **naturally-occurring** elements. We may have discovered all of the naturally-occurring elements, but we've certainly not discovered all of the possible elements.
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If the force carrier for the electromagnetic force is the photon why don't magnets emit light?
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Light can be thought of as an electromagnetic wave. From [Maxwell's equations](_URL_0_), electromagnetic waves are caused by the interaction of *changing* electric fields with magnetic fields, and *changing* magnetic fields with electric fields. In order for the magnet to generate an electromagnetic wave, the magnetic field it produces would have to oscillate in time. You could force it to do so by wrapping a coil of wire around it and running AC current through the wire, and then you could emit electromagnetic waves. The waves wouldn't be light though, they would probably be in the radio part of the spectrum.
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If photons are the force carriers of the electromagnetic force, why don't magnets emit light?
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Magnets do emit light, if you shake them back and forth. (The light won't be visible light, though--it will have the same frequency as your shaking, on the order of a few Hz.) A more accurate statement is that photons are the *quanta* of the electromagnetic field; this sometimes gets misconstrued as all EM fields being made of photons. They're not. Oscillating EM fields carry energy which is quantized into photons. (Virtual photons are a mathematical approximation and don't actually exist.)
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Why haven't species developed more eyes?
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Species don't develop new traits specifically to accommodate some need. Mutations are entirely random and only "stick" if it increases survivability long enough to become homogeneous among the population.
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Did eyes evolve only once on Earth? Is there something about the small band of "visible" light that makes it optimal for eyes to evolve to see? Or is it just a coincidence that most animals see in the same spectrum?
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So eyes evolved many times as already mentioned, but a very curious thing is that the photoreceptor used in all eyes appears to have evolved once. All "eyes" use a descendant of this same photoreceptive protein. The only arguable exception is the "pit organ" in some snakes, but this is really a directional heat sensor rather than an eye - the infrared rays do not directly excite any receptors.
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We always hear that the European explorers brought over new diseases; however, did they catch (similar to smallpox) any that were native to the Americas but deadly to Europeans?
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This is more speculative than I would like for this sub, but some believe syphilis is a new world disease, others believe it existed in Europe unrecognized. Edit _URL_0_
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So, plants grow against gravity, and towards light. What happens if a plant has light below it for it's growth process?
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Most seeds as they germinate don't react to light (though the presence of light may stimulate or inhibit germination, depending on the plant), so initially the effects of gravitropism will overshadow phototropism, with the radical growing down and the shoot upwards. As the shoot grows phototropism starts ramping up. The shoot may begin to hook to the side if the sole or strongest light source is coming from below. The extent of the bending would be dependent on how strong a response that type of plant exhibits. This should be a pretty simple experiment. Many seeds germinate easily with just water. Get a petri dish (or a CD jewel case will work just as well) and place a few seeds (beans or corn kernels work well) near the middle, making sure to space them out. Cover with wet paper towels, enough so that when you close the case the seeds are pressed snugly between the towels and the plastic. Place upright over a light and observe.
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Is there a name for the nebula our Sun was born from and does it still exist?
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I found a great answer on Yahoo Answers, complete with a source from arxiv. > Yeah, the nebula is long gone, but it might have been somewhere in this region surrounding the galaxy (the sun has a circular path around the galaxy). But it probably contained 1000 - 5000 proto-stars, some/many which may have grown to massive sizes, exploding as a supernova. We know that one exploded near to the Proto-solar system and spiked our system with exotic elements. And, surprisingly, even after all this time, It may be possible to track down a few (say, 50) of the suns siblings (born from the same dust cloud) > Title: The lost siblings of the Sun Authors: S. Portegies Zwart (Amsterdam) _URL_0_ (96kb, PDF) [Source](_URL_1_) edit: URL correction (thanks Verdris)
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Are there precious resources (ie gold, copper, titanium) on the moon? Would it be possible to mine them?
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The moon actually has a fairly high abundance of titanium compared to most bodies in the solar system--so far as we're aware--and in general you should expect to be able to find all metals on the moon in rates comparable to Earth. It's nonmetals like carbon, nitrogen, and phosphorus--all necessary to life--that are hard to come by (oxygen is present in water ice and in silicate and other oxide minerals).
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How does carbon dating work?
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There are some good previous answers on the theory of Carbon Dating available in [this thread](_URL_1_), but perhaps someone could expand more on the techniques used? ([Wikipedia](_URL_0_) does cover sample preparation and measurement quite well, but it seems a bit long winded)
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Why are lenses round, while photographs and movies are rectangular?
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Most lenses are round because all lenses start off as round. This is a because lenses are ground from round glass blanks. A rectangular lens starts off as a round lens, but the edges are cut to form a rectangular. (This is how eyeglasses are manufactured.) Quite simply, round lenses are cheaper. Another reason why is that many lenses rotate to change the focal length (zoom) or to adjust the focus. If the lens is square, an edge may crop a corner blocking that part of the image. And finally the is no good reason not to use a round lens. Rectangular lenses simply don't offer any real benefits.
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Why do butterflies fly so erratically?
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Some insects use irregular flying patterns to help avoid birds and other predators, especially if they are relatively 'palatable' or 'tasty.' _URL_1_
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Do solar sails us the mass of photons in order to propel a spacecraft, or do they utilise "solar wind" and gain their momentum via particles emitted by the sun?
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1) Photons are massless, as far as we can tell. 2) Photons do have momentum, which they can impart to the solar sail, which is how the solar sail works. Compton scattering describes how a photon can behave similar to a particle with mass, when it collides with an atom: _URL_0_
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Cleaning Products that kill 99.9% of germs: are these not simply leaving the strongest 0.1% to survive and repopulate?
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Most of those cleaning products use alcohol or something similar, and germs can’t evolve a resistance to that in the same way that they can adapt to antibiotics. The germs that survive antibiotics have a mutation that makes them more resistant, but the 1% that survive those cleaning products don’t do so because of a mutation, they only survive because there will almost always be some small surface area that isn’t fully exposed to the cleaner. So we aren’t really leaving the strongest germs behind, just the luckiest, and that’s not an adaptation they can pass on.
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How is the universe "flat" when it exists in 3 spatial dimensions?
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The word "flat" is used in a different way than you are thinking. When used to describe 3D space and 4D spacetime "flat" means that the geometry is Euclidean (in 4D, it's called "Minkowskian"). This means that there is no curvature. A curved 2D surface has a radius of curvature (think of a balloon). Similarly, curved 3D or 4D geometry has a "radius", which is the distance over which non-Eudlidean geometrical effects become important. We don't observe these effects in our universe, so we say that it's "flat".
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Does drinking straight hard alcohol put more strain on the liver than a mixture?
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Well, both cases will cause the liver to work equally as much. Water is processed through your body much quicker than liquor is, obviously, so you're still left with the same 8 fl oz of 43% abv gin in your system, to be filtered through. That's why mixed drinks aren't much better than drinking straight shots. You're still consuming the same amount of liquor, the same amount of liquor needs to pass through your system, just the other homogenous parts of the beverage get absorbed faster .
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Why don't humans have mating seasons?
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There have already been some good answers to your question. I would like to point out however, that human females still experience estrus (in heat) duration, and males respond to it. [Here](_URL_3_) is a study that was done on this topic, that correlated tips earned by erotic dancers with their menstrual cycles.
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