title
list | over_18
list | post_content
stringlengths 0
9.37k
⌀ | C1
list | C2
list | C3
list |
|---|---|---|---|---|---|
[
"Does freezing dead bodies kill any diseases they may have?"
] |
[
false
] |
[deleted]
|
[
"Bacteria are highly resistant to freezing and viruses don't care at all. The usual storage conditions for bacterial culture samples in the lab are -78°C, they stay viable at that temperature for years. So, freezing doesn't help much in that regard. What freezing can do is killing multicellular parasites, though. But I don't know if those are a problem with snakes."
] |
[
"Basically the more complex the organism is the more that can go wrong with it, and the more extreme environments will adversely effect it."
] |
[
"Aye. And bacteria that can sporulate have an additional advantage there, since in their dehydrated state, ice formation isn't a concern."
] |
[
"If I were in a helicopter during a very large earthquake, would I be able to see the seismic waves moving across the ground?"
] |
[
false
] |
I don't think I would be able to, but I was thinking about it. Second, how large would it have to be in order to see the ground move from a normal helicopter flight?
|
[
"No, these waves are not considered to be detectable by the human eye. Although some people claim to have seen them this is more likely to be caused by the stroboscopic effect when the seismic waves disturb the air above them in synchronization. ",
"See here.",
" And cause an illusion or mirage. This effect would probably not be detectable from a helicopter due to the viewing angle being higher. The closest you'd get would be watching the sea during a tsunami where you could see the seismic sea waves like ",
"this helicopter view",
"."
] |
[
"these waves are not considered to be detectable by the human eye. ",
"Is that because of their low amplitude, their high speed, or both?"
] |
[
"Almost certainly not.",
"The reason being that the wavelength of these waves is on the order of kilometers, and the amplitude is on the order of meters. If you're far enough up to see the wavelength, you're too far away to see the amplitude. They're also very fast moving (km per second).",
"Close enough to the ground you could see the effects of the quake (buildings and trees moving etc), and there may just be a sweet spot high enough up, with a big enough earthquake that you could perceive a wave with good enough eyesight, but I'm not sure where i would ballpark it. "
] |
[
"Why do some people sneeze multiple times in a row?"
] |
[
false
] |
Lately at work I've noticed how differently some people sneeze from one another. When I sneeze, which is often triggered by sunlight, it is always one big boisterous sneeze. Pretty loud and violent reaction relatively speaking. Sometimes I might sneeze once and then sneeze again 5-10 seconds later. My boss on the other hand ALWAYS sneezes 5-6 times in a row. Why does this reaction vary from person to person? How common is it for people to sneeze many times in a row like my boss?
|
[
"This comment gets to live",
"."
] |
[
"Just a heads up, if you're writing \"u\" in your comment in place of the second-person pronoun, the comment probably isn't appropriate for ",
"/r/askscience",
". Also, you make use of personal anecdote, and even admit your comment is based off \"speculation.\" You provide no supporting links, and in fact you don't even really attempt to answer the posed question. You've practically done everything wrong here, lol. Unfortunately, it's going to get deleted; I wouldn't waste my time writing something here if I can't substantially back it up, it never works",
"This'll be deleted too"
] |
[
"Just a heads up, if you're writing \"u\" in your comment in place of the second-person pronoun, the comment probably isn't appropriate for ",
"/r/askscience",
". Also, you make use of personal anecdote, and even admit your comment is based off \"speculation.\" You provide no supporting links, and in fact you don't even really attempt to answer the posed question. You've practically done everything wrong here, lol. Unfortunately, it's going to get deleted; I wouldn't waste my time writing something here if I can't substantially back it up, it never works",
"This'll be deleted too"
] |
[
"Why is both helium 3 and deuterium required for a fusion reaction?"
] |
[
false
] |
I was watching a video ( ) (yep I’m not too versed) and they said that both deuterium and tritium or helium 3 was required for the fusion reaction. Why can deuterium not fuse with itself? If the plasma was hot/dense enough would this be possible?
|
[
"I didn’t watch the video, but deuterons can definitely undergo fusion with other deuterons. DT fusion has a higher Q-value, which means more total energy released, but DD is possible as well.",
"The Coulomb barrier depends much more strongly on Z than on A, so since deuterium and tritium and both isotopes of hydrogen, the barrier is essentially the same for DD and DT."
] |
[
"Tritium can be bred while the reactor is operating, so I think that should be taken advantage of in a fusion reactor for power generation."
] |
[
"Take a look at this reaction rate chart, which was made using data provided by the US Navy's Plasma Physics Division: ",
"https://upload.wikimedia.org/wikipedia/commons/d/d0/Fusion_rxnrate.svg",
"Keep in mind the y-axis, fusion reaction rate, is in log scale (so is the x-axis, temperature). Until you reach temperatures around 10 billion kelvin, D-T is vastly more reactive than either D-D or D-He3. And for most of that time, D-He3 is itself more reactive than D-D.",
"Since once of the major hurdles with nuclear fusion power is the ratio of power-in to power-out, working with more reactive materials is generally assumed to be better for achieving sustainable power.",
"https://en.wikipedia.org/wiki/Nuclear_fusion#Important_reactions",
" Lists many of the nuclear fusion reactions that are considered viable candidates for powering a reactor.",
"There are also more differences than just the reactivity and energy output at a given pressure/temperature. There is also the matter of what, exactly, is generated. D-T fusion releases most of its energy (80%) as fast neutrons, which cannot be confined by electromagnetic fields, and tend to undergo further nuclear reactions with surrounding material, resulting in what is called \"neutron activation\". The effect of this is to render some materials radioactive, and they can also weaken solid materials.",
"Fast neutrons can still be harnessed for energy, but mitigating these problems adds to the cost. D-D reactions release a minority of their energy as slow neutrons (11%), and the rest as charged particles, which are much more versatile as a product, since they can be confined and directed with electromagnetic fields. Slow neutrons are also far less problematic than fast neutrons.",
"D-He3 reactions release all of their energy as charged particles, so this also makes it a very attractive fuel source, in addition to being more efficient than D-D at most temperatures.",
"None of this is perfect, though. Side reactions can always happen, especially in a fuel containing D. This is because even in a D-He3 setup, D-D reactions will still happen, and produce T. D-T reactions will then happen anyway. Any fusion reactor design has to take into account undesired side-reactions.",
"All nuclear fusion reaction energy will also get converted into thermal energy, and thermal emissions (photons) as the products interact with the rest of the plasma."
] |
[
"How close to the earth was the moon (estimated to be) originally?"
] |
[
false
] |
Assuming the impact theory is correct, what was the likely original distance from the earth our satellite originally was? Would it have been noticeably larger if we were able to view it? Sorry for the kind of specific questions, I just find stuff dealing with the ancient earth (continental shift, etc) interesting.
|
[
"The simulations also imply that at the time of its formation, the Moon sat much closer to the Earth - a mere 22,500km (14,000 miles) away, compared with the quarter of a million miles (402,336 km) between the Earth and the Moon today. ",
"[Source]",
"Yes, it would have looked much larger."
] |
[
"That also means that the length of the day on Earth was much shorter, due to conservation of angular momentum. I've read that it was about 6 hours long."
] |
[
"I can give you a highly rounded average that is definitely not the exact number, but it's relatively close to it. ",
"The Moon moves away from Earth at an average of 3.8cm / year. Multiplying that with the Moon's age gives us 171,380 km. ",
"Take that from the current average distance to the moon which is 384,400 km and we end up with 213,020 km (~132,072 miles)",
"That is once again an extremely inaccurate result, since all numbers were rounded averages but if you look up another comment it quotes an article which says 22,500 km. This is how much difference it can make if your numbers are rounded or not."
] |
[
"In light of the European ban on neonicotinoids, how strong is the science supporting their link to colony collapse disorder?"
] |
[
false
] |
[deleted]
|
[
"tl;dr There is very strong evidence that neonicotinoids seriously harm bees, but only weaker evidence that this is the sole cause of colony collapse.",
"The Guardian",
" has a summary of some of the issues, but I'll make a few comments here also.",
"It isn't a total ban, only ",
"three neonicotinoid insecticides are banned",
" (which ignores that the entire class of insecticides appears to have the same risks), \nand only from certain crops (which ignores the frequent spread of pesticides to adjacent fields), and only when flowering (which ignores that bees also feed on ",
"guttation",
" and that the plant absorbs the insecticide through its roots or leaves and the insecticide .",
"The ",
"European Food Safty Agency",
" did a six month study of all available evidence and concluded that bees feeding on treated crops suffered significant harm. By significant they mean that even diluted 400,000 times, a single exposure to a neonicotinoid insecticide will half the number of bees in a hive within 30 days. The effective does to kill unwanted pests is usually a 1,000-4,000 times dilution, so it's easy for bees to accidentally get 1% of that dose.",
"The argument on the other side came entirely from the pesticide producers who believe banning these pesticides would hurt farmers, while there was no evidence of any sort offered to support these claims.",
"It isn't completely clear that neonicotinoids alone are enough to cause all of the hive collapses seen. There are lots of things that can harm bees, and in many cases the cumulative effect is also important to consider. Some of the standard threats like ",
"Varroa mites",
" aren't a problem for a healthy hive, but a poor summer can lead to a hive that is weak enough for the mites to kill it. It could be that weather conditions, existing diseases and neonicotinoids together are too much for the bees."
] |
[
"I don't think you're being entirely fair to DulcetFox.",
"The wide spread use of neonicotinoids is relatively recent, so could explain the timing. Unfortunately there are lots of other things that both show correlation and which could logically be causes. Climate change, mites, the use of high fructose corn syrup to feed hives (which appears to affect the bees' immune systems), use of antibiotics, and even EM fields have all been suspects precisely because they also pass the same tests.",
"Having said that, at this point we have not just a strong correlation both globally and region by region, and the suspicion that pesticides could be a problem, but good studies showing how trace amounts of neonicotinoids will wipe out a healthy colony in a few months. The last of these is the real smoking gun, and the correlation with CCD just gives it greater strength.",
"Obligatory ",
"XKCD",
"."
] |
[
"I don't think you're being entirely fair to DulcetFox.",
"The wide spread use of neonicotinoids is relatively recent, so could explain the timing. Unfortunately there are lots of other things that both show correlation and which could logically be causes. Climate change, mites, the use of high fructose corn syrup to feed hives (which appears to affect the bees' immune systems), use of antibiotics, and even EM fields have all been suspects precisely because they also pass the same tests.",
"Having said that, at this point we have not just a strong correlation both globally and region by region, and the suspicion that pesticides could be a problem, but good studies showing how trace amounts of neonicotinoids will wipe out a healthy colony in a few months. The last of these is the real smoking gun, and the correlation with CCD just gives it greater strength.",
"Obligatory ",
"XKCD",
"."
] |
[
"If milk contains lactose, why isn't milk naturally sweet?"
] |
[
false
] |
I have been told lactose is a sugar just like glucose etc but why is milk not naturallly sweet
|
[
"Not all sugars are sweet. Sweetness levels of various sugar and nonsugar compounds are measured relative to sucrose, and lactose falls pretty low on the scale: ",
"http://www.elmhurst.edu/~chm/vchembook/549sweet.html",
"\nSome substances are sweeteners without being sugars. For instance, Neotame is several thousand times sweeter than table sugar (sucrose), but its chemical structure does not qualify it as a sugar.",
"http://en.m.wikipedia.org/wiki/Neotame"
] |
[
"I think the interesting question is why do you not find it sweet. I personally find milk very sweet. ",
"There was a study done on milk sweetness preference: ",
"http://www.sciencedirect.com/science/article/pii/0031938485901507",
"They found that obese people preferred less sweet, higher fat milk than normal weight people. "
] |
[
"Lactose is made of glukose and galactose. Only when the bond in the molecule of lactose is broken, we can feel the sweetness. Usually we don't keep milk in mouth long enough to let this bond break. If you've ever tried warm milk then you probably noticed it's sweet."
] |
[
"Would a rock placed in a vacuum erode?"
] |
[
false
] | null |
[
"Within the solar system, rocks in vacuum are slowly eroded by solar wind, micrometeorite impacts, and photochemical reactions on their surface. A completely isolated rock kept in a vacuum with literally no other mass might experience some slight erosion due to internal radioisotope decay, but this would slow over time. If, as many physicists suspect, protons are not quite stable, the mass of the rock would gradually decay over the course of 10",
" to 10",
" years, depending on the exact proton half-life. If not, infrequent fusion events would eventually cause the rock to turn to iron over 10",
" years."
] |
[
"Quantum tunneling makes spontaneous fusion of lighter elements possible (though by no means likely). ",
"It stops at iron because it's the point where fusion is impossible with no further energy input."
] |
[
"I had a chemistry teacher tell the class that a solid in a vacuum would very slowly sublimate over time. I know the process would be very slow, but over the course of millions of years in a vacuum would that have an impact?"
] |
[
"Does weather have any influence on geothermal energy?"
] |
[
false
] |
Geothermal has much to do with the convectional flow of heat inside the earth, but what role does weather play in it?
|
[
"Well, since no one has answered your question, I'll give it a shot.",
"Geothermal is just heat. To actually get anything done with that heat you have to convert it to work. Getting work from heat relies on a difference in temperature. Since the temperature of the geo source won't vary much, a lower air temperature would allow for a greater amount of work to be extracted.",
"See: ",
"https://en.wikipedia.org/wiki/Carnot%27s_theorem_(thermodynamics)"
] |
[
"It's a good question, and I understand your logic, but weather has essentially zero effect on geothermal energy. Firstly, you have to look at the average geothermal gradient on the continental crust which is 25 C/km. This means that on the average area of land, you will have to dig 1 km down before the temperature of the surrounding rock is 25 C. Effectively, the deeper the hole, the higher the temperature. This happens because of increased pressure caused by the immense overburden of the rock above and other sources of heat which I will explain later.",
"As you probably know, geothermal energy uses rocks as a heat source to boil water which then creates steam, turning a turbine, and winding a generator which creates power. So you can imagine that on the average area of land you would have to dig down approximately 4 km before you reached the correct temperature to boil your water. Digging a 4 km hole is an expensive and very difficult thing to do. So we need to find the areas on the crust that have a naturally high temperature, think lava fields and igneous intrusions. Igneous intrusions occur when magma works its way up from the mantle and rises up within the crust. These intrusions are often >65% silica and are therefore very bouyant (no time to explain that, research: Isostatic Response and Magma Viscosity + Density). These intrusions are often Granite Plutons, which are full of Uranium 235. The Uranium 235 decays into Thorium, and less commonly Plutonium which creates heat as electrons are transferred. The heat created can raise the geothermal gradient so that you have up to 220 C/km, meaning a lot less digging. In effect it is a nuclear reactor. ",
"Now to answer your question about the weather. There are 3 ways in which I see the weather could have a minor effect on this process. 1: The heat that results from the suns rays heats up the earth in arid areas which increases the geothermal gradient and makes geothermal energy more viable in that area. 2: (indirect) The weathering surface processes, over tens of thousands of years expose an outcrop of granite to the surface, allowing it to become a very useful source of geothermal energy. 3: A higher temperature caused by sunny weather can very slightly increase the rate at which the water is boiled.",
"But considering this is a nuclear reaction, that happens within a very large, hard and resistant rock outcrop, the weathers effect would be minimal."
] |
[
"This largely depends on what sort of geothermal energy source one considers: shallow geothermal energy is effected by weather and the daily variations in temperature, while deep geothermal energy is largely independent of those factors. ",
"Shallow geothermal energy means, that one would bury a geothermal device that contains fluids with large heat capacity in the soil. Deep geothermal energy, in contrast, makes use of the geothermal gradient, that in turn is related to burial depth, tectonic pressure and other factors. ",
"An exception form the geysers on e.g. Iceland, the heat of which corresponds to the same energy as is being found in the deep subsurface."
] |
[
"Is it possible to divide the frequency of the light?"
] |
[
false
] |
In electronics there are devices named "frequency dividers" which basically reduce the frequency of the incoming signal by counting zero-crossings. For example 1000 Hz oscillation on the input could be turned into 500 Hz. Would it be possible to sense the light as an oscillation and consequently divide its frequency to lower ones? Dare I say – audible ones? As I understand, it is actually tera-hertz range and regular electronics don't work well in such high frequencies.
|
[
"Yes, it is possible to reduce or increase the frequency of light. See ",
"Nonlinear Optics",
". Dividing the frequency exactly in half would be a special case of ",
"spontaneous parametric down-conversion",
", but there are many other ways to use one or more photons to create other frequencies.",
"Nonlinear optical processes are generally quite inefficient, but light is routinely produced in the kHz range using ",
"acousto-optic modulators",
", for example (of course, light would never be audible).",
"Using electronics would in principle work as well, except that as you imply, metals are terrible conductors at optical frequencies. The field of ",
"optical antennas",
" attempts to overcome this and other limitations. "
] |
[
"Nonlinear optical processes are generally quite inefficient",
"It depends, doesn't it? Depending on the process they can be very efficient. Spontaneous parametric down-conversion from your example is very inefficient, but second harmonic generation within an optical cavity can reach efficiencies that exceed 50% by a lot. Difference frequency generation, which might be more relevant to this question, can reach at least tens of percent efficiencies if I recall correctly."
] |
[
"Yes, there are cases where it's efficient. But the nonlinear susceptibility, chi",
", is typically around 10",
" per order, implying a base efficiency of around 1/10000 per additional photon. If we're clever we can do better."
] |
[
"Could we deplete the earth's core of heat?"
] |
[
false
] |
Geothermal energy confuses me and I couldn't figure out how you could deplete the energy from the PV=nRT equation in the earth which causes it to have a greater Temperature due to pressure. If you removed that Temperature wouldn't the pressure still be the same because the force of gravity would increase it? I'm 100% I'm mistaken because it would disprove the law of thermodynamics, but I need an explanation!
|
[
"Could we deplete the earth's core of heat?",
"No. Not in any realistic scenario. We are too puny. Also, the geothermal energy is slowly dissipating in space even without our help.",
"The equation you are using is about ",
" gases, and the Earth core is neither of those.",
"More importantly, pressure by itself does not sustain heat.",
"It is the change in pressure that produces heat. So if you had some air and compressed it, it would heat up, but it would start cooling down as soon as you started compressing it (usually slower than you are heating it up. So, once it is compressed and some times has passed the air would have cooled down."
] |
[
"So could you explain the reasoning behind the Temperature b/t pressure, and how it would keep putting pressure in it for a long time it would have an infinite amount of heat? Sorry I have very little understanding of the topic. "
] |
[
"To pressurize something you either add heat with constant volume )which will increase temperature), add material with constant volume (which will increase pressure), or reduce volume (also increases pressure). But keeping something under pressure alone will not retain heat, because to increase pressure you have to do something to your system. ",
"If you have a higher pressure and a constant volume, T must increase. But in order to get that increase in pressure you had to add energy from elsewhere in the system. ",
"For instance, you added heat or did work to compress the gas. Once this is energy is added, the system is at an equilibrium position and stays constant. ",
"To answer your original question, you seem to have a fundamental misunderstanding of temperature versus heat. If you take away X amount of material at temperature Y, the remaining material is still at temperature Y. The total amount of energy has decreased but by the same amount as the mass at that temperature decreased. We aren't taking temperature away from the Earth, we are taking heat (energy). ",
"So in the case of geothermal energy production, the heat input that changes the temperature of the liquid or gas we are using to generate power comes from the core of the Earth. This will have some tiny effect on the temperature of Earth's core since we are pulling heat away. Ignoring the fact that PV = nRT is not a valid equation because we aren't talking about ideal gases, the amount of heat we are extracting from the Earth is tiny in comparison to the amount of energy available. "
] |
[
"P-value and mean doesn't add up. Do I always follow the p-value?"
] |
[
false
] | null |
[
"Can you clarify what you mean when you say the p-value and mean don't add up?"
] |
[
"i used \"add up\" as a figure of speech.\nThe means for both condition just appear to be on average.\nTrust= 5.66, Distrust= 5.05. \nIt's that huge of a difference yet the p-value is =0.03. \nWould I always follow the p-value regardless of how questionable the mean/average looks? "
] |
[
"If I understand what you're asking, I can clear up the misunderstanding. The mean of the scale doesn't matter here. What the t-test is doing is testing the means of two groups to determine if they are different. In this case, you're investigating the trust condition compared to the distrust condition.",
"The t-test compares the central tendency (mean) of two distributions, and in this case there is a significant difference.",
"Figure 5 on this page is a good visualization of what I'm referring to.\n",
"http://esa21.kennesaw.edu/modules/basics/exercise3/3-8.htm"
] |
[
"Does gravitational time dilation impact a star's lifetime?"
] |
[
false
] |
Does gravitational time dilation impact a star's lifetime? If so, is there a "normalized" stellar lifetime which takes this into account? What sort of observational evidence, if any any, suggests that nuclear processes in the star happen faster/slower than we would expect in the lab?
|
[
"Does gravitational time dilation impact a star's lifetime?",
"Not really.",
"In fact, ",
"I did the calculation over the weekend that time dilation between the earth's surface and the sun's surface is only a matter of 66 seconds per year.",
"The time dilation factor grows like 2GM/R, and if the mass grows with the volume then the time dilation factor only grows like R",
" - and that's assuming stellar density. Giants tend to be less dense. Even the most massive stars are only around 100 solar masses, and assuming a solar composition I expect the time dilation factor won't be too considerable. ",
"Stellar lifetimes are getting a bit out of my area, but I can honestly say I've never seen stellar lifetimes calculated including time dilation for mass. ",
"Lifetimes are pretty rough numbers",
" that depend highly on composition, formation history, and especially on dynamical interactions with a companion. Neutron stars are closer to my area, and you only get time dilation factors of about 0.85 there - 10 years on earth is about 8.5 years on a NS. "
] |
[
"Yeah, time dilation is really significant for them. For a neutron star, the flow of time looks roughly like ",
"this",
". The y-axis is the flow of time, 1 being normal, and zero being stopped. The x-axis is distance from the centre of the star. In simulation units, the star has roughly a radius of 2. As you can see, time inside the star flows at roughly ",
" the speed as time for a distant observer.",
"That simulation was taken from ",
"this paper.",
"The simplest model is the so-called ",
"Tolmann-Oppenheimer-Volkov equations",
", which makes some pretty significant simplifying assumptions. ",
"For black holes, the effects are even more extreme, and not completely understood for astrophysical (as opposed to eternal) black holes. From our perspective, something falling into the event horizon of an eternal black hole appears to freeze as time stops passing for it at all.",
"There are even speculative ideas like ",
"this one",
" that we see a black hole as existing for billions of years, but from the \"perspective\" of the matter behind the event horizon, only a few fractions of a second pass between stellar collapse and the end of the lifetime of the black hole."
] |
[
"66s/yr amounts to about 20,000 yrs over a 1 solar mass star's lifetime (10By)"
] |
[
"Why can Iodine diffuse through a cell membrane?"
] |
[
false
] |
I've searched google and my results showed that Iodine would diffuse through the cell membrane. This seems counter-intuitive to me because of its negative charge and the impermeability of almost every other ion (H+,Cl-,Mg++,Ca++, etc.). I was hoping someone here could answer my question. Thanks!
|
[
"Keep going. Iodine is a solid at room temperature and pressure."
] |
[
"Keep going. Iodine is a solid at room temperature and pressure."
] |
[
"The sodium-iodide symporter",
" might be of interest here.",
"Also, just to confirm - the citations you found of the cell membrane's permeability to iodide were for proper cell membranes (or physiologically relevant mimics), correct? If you could share them, we might have a better idea how to address your inquiry. "
] |
[
"Electron cloud question - Do they appear and disappear faster than light?"
] |
[
false
] |
So, in the electron cloud model, rather than orbiting the nucleus of an atom, electrons actually appear and disappear incredibly quickly around the nucleus (in the shape of valence electron shells.) I was once told by an astronomy professor that electrons in an electron cloud don't really travel, they just reappear somewhere else. "The fastest speed is simply " he said. Is there any truth to this? and if so, does that mean that electrons "travel" faster than light?
|
[
"The electron cloud model is a little like Newtonian mechanics in the sense that it ignores the speed of light. It is assumed that the speed of light is infinite. If you want to account for relativistic effects, you need to abandon quantum mechanics and do quantum field theory, specifically quantum electrodynamics."
] |
[
"Electron clouds are basically ",
"standing waves",
" of electron. The electron isn't in any one place in the cloud, it ",
" the cloud.",
"When an electron is bound to a nucleus in a particular orbital, we say it's in a momentum eigenstate. That means its momentum is well defined, but other properties, such as its position, are not well defined. If we were to observe its position, say by hitting it with a photon, we would necessarily lose our information about its momentum. It doesn't really \"jump\" to a certain place. The cloud just tells us where we're likely to find it when we look for its position."
] |
[
"Actually the uncertainty principle doesn't really say that we can't know the position and momentum of a particle at the same time. It says that when a particle has a well defined momentum, it ",
" a position, and vise versa. There's not some \"hidden\" information that we can't observe. There just isn't more information to be had than this.",
"Einstein had a hard time accepting this idea, too. He believed, as you suggest, that there were ",
"hidden variables",
" which account for the \"unknown information.\" He devised a bunch of ",
"thought experiments",
" to try to prove the existence of hidden variables, but later a physicist named Bell ",
"proved",
" that if there were hidden variables like this, quantum physics wouldn't work the way we observe it to work. This has been ",
"verified experimentally",
"."
] |
[
"Are GMOs actually bad for us?"
] |
[
false
] | null |
[
"In short, there's not enough research to be conclusive!!!",
"IMO: I'm fine consuming GMO's that are the process of selective breeding such as corn and wheat which have been bred to be bug resistant or drought tolerant. I'm not exactly sure about the more intensively lab manipulated foods. ",
"Please remember though, food is ingested and gets annihilated by the hydrochloric acid the stomach produces. We're talking about pH's of 1 and 2 here. It starts breaking down what we eat instantly!! And what gets absorbed by the lower GI system are the remaining, more simple amino acids, carbs, fats and simple proteins. ",
"Remember, cancers caused by teratogens happen because they are absorbed into cells and interfere with normal cellular division. Just because something is labeled a \"Franken-food\" doesn't mean it will give you cancer. As long as the food is able to be broken down into the simple pieces by the digestive tract as naturally occurring food, it will be used the same way. (i.e. as long as the GMO version of corn doesn't cause it to uptake obscene amounts of chromium or something like that, you're good) Its a very complex and broad topic, but I hope that gives you an idea."
] |
[
"Modification is only bad or good on the basis of each specific modified trait. \nAs far as health goes, I'm not aware of any evidence that any GMO has deleterious effects on human health. \nMonsanto et al may have obscenely reprehensible business practices, but their food is probably fine for you and there's absolutely no scientific reason that genetic modification should be anything but good. "
] |
[
"There is no evidence as such, however opponents of the GMO industry believe that problems could arise years in the future. There is no easy way to test that hypothesis. GMO food has been around for awhile and no adverse effects have been found though."
] |
[
"How close are we to getting rid of the aging of skin or at least the appearance of aging?"
] |
[
false
] |
Can a laser be made to get deep enough and remove a lot of skin to reveal newer, better-looking skin? Or is that "newer skin" damaged (DNA damage I guess?) to where it will just look old also? , I saw a program on TV about a girl that got an infectious, flesh-eating disease of the skin (I think it was Mystery Diagnosis) and it ate away almost all of her skin. She said that her doctor said that she will have "baby skin" and look 30 years younger than her age for the rest of her life. Could that principle be safely introduced into some sort of therapy? I doubt millions of people would be flocking to have 98% of their skin removed but just curious.
|
[
"A lot of the visible signs of aging (wrinkles, sagging skin, etc) are a result of elastin and collagen slowly breaking down, and a steadily decreasing efficiency of replacing them. Elastin is what's responsible for the stretchiness of your skin, unsurprisingly. Some people have a lot of it and are able to do all sorts of crazy things with their skin. Collagen is the underlying support structure for a great many systems in the human body, almost like the glue that holds things together."
] |
[
"Take a look at ",
"this",
"This describes some of the causes of the lack of collagen. Collagen formation is partially controlled by the hypothalamus (like a lot of body functions) which is part of the midbrain. This ",
"wiki article",
" describes the effects of cortisol creation which can negatively affect the elasticity of the skin by blocking the formation of collagen.",
"What I am getting at with all of this is that by controlling the amount of cortisol in the body (drugs, vitamins, meditation, etc) and decreasing cell damage, you can reduce the effects of aging on your skin yourself.",
"It will only be a matter of time before we have a drug to control these that is over the counter but drug companies and cosmetic companies\nhave very little interest in creating it. It's not a great business model."
] |
[
"One of the important building blocks of collagen is Ascorbic acid, aka vitamin C.",
"Humans and some other primates, have lost the ability to create our own ascorbic acid internally due to a mutation so we must ingest it.",
"We know that we die from the lack of it (scurvy), but preventing scurvy is simply the bare minimum ammount we need to survive. Alot of anti-aging and longevity regimes include megadosing vitamin C (well above recommended intake) for its antioxidant properties as well as collagen production and maintenance.",
"I'm sure its up for debate though. But take your vitamin C!"
] |
[
"what am I considered? alpha, beta or something else"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"We chose not to adresse personal questions. If you want a personal psychological evaluation you need to talk to a qualified professional. "
] |
[
"We chose not to adresse personal questions. If you want a personal psychological evaluation you need to talk to a qualified professional. "
] |
[
"What's the biggest obstacle keeping us developing warp drive technology?"
] |
[
false
] |
I've heard warp drive kinda-sorta possible in the fact that it doesn't break any of Einstein's theories like FTL travel does. So why haven't I heard about anyone working to develop it? What difficulties are keeping us from moving forward?
|
[
"Whether or not it violates some physical law is still an argument in physics.",
"To be clear, what a warp bubble is is a chunk of flat spacetime. Just in front of the bubble is a region of contracting spacetime, while just behind the bubble is a region of expanding spacetime. A spacecraft could sit in the middle of the bubble, and it would be the space that the craft is sitting in that moves faster than the speed of light, not the ship itself. Relativity constrains inertial rest mass to move slower than ",
", but it makes no restraints on how quickly spacetime is allowed to expand or contract. This method of propulsion is known as an ",
"Alcubierre Drive",
".",
"In my opinion, the biggest hurdle is proving that such bubbles actually exist, and generating these bubbles. To create a region of spacetime which is expanding, we'd need to be able to create a region of negative mass-energy density. Unfortunately, I don't think we as a species currently have an effective way of doing that. The question of whether warp bubbles exist is actively being explored in research. The current probe is to set up a sensitive interferometer, and to look for variations in the interference pattern. A warp bubble that passes through one leg of the interferometer would affect the effective distance of that leg, and thus would change the interference pattern. If we can show they exist, the problem still remains generating one, and then controlling it."
] |
[
"I believe it's much worse.",
"Popsci tries to sell this as:",
"warp drives need ",
" that ",
" and maybe ",
"but this is incorrect. It's better stated, in my opinion, as",
"Warp drives need ",
". Warp drives need the stress energy tensor of something to be ",
". In fact, anything really freaky - CTCs, warp drives, all that - turns out to need these kinds of things.",
"It's not like \"we need something stronger to build this tower\", and we go out and discover a new metal. It's like \"we need a round stone that is actually square. Maybe geologist will find it in the near future and we will conquer the galaxy.\""
] |
[
"Also, the Alcubierre warp drive requires negative mass to work* and nobody knows yet if negative mass can exist.",
"*It was announced some time ago that improvements in the design had greatly reduced the amount of negative mass required, but it's still necessary. On the other hand, the ",
"White–Juday warp-field interferometer",
" (an instrument used to measure the existence/strength of warp in the lab) does not seem to need any negative mass, so it may be necessary only at larger scales. I am definitely not an expert on this and will defer to one if one appears."
] |
[
"why don't we keep our mother's immunity?"
] |
[
false
] |
newborn babies are protected by antibodies passed on from their mothers for a short time after birth. why doesn't this immunity persist?
|
[
"These antibodies are proteins with a limited half-life.",
"If the mother were able to pass some memory B-cells, they would last indefinitely and keep producing antibodies."
] |
[
"First, what capy_capybara said is partially true. If you are constantly exposed to foreign antigens during the first year of life, your chances of developing tolerance are 100x. Nonetheless, your mother's lymphocytes and antiboides could attack your tissues (similar to Graft-vs-host disease or Rh incompatibility). ",
"Second, the placental barrier only allows molecules of certain size to pass... the largest antibodies that do are IgG. Otherwise, maternal antibodies would seriously harm you. (Think of Rh incompatiblity/Erythroblastosis fetalis)"
] |
[
"so why doesn't this happen? or maybe to put it another way, if memory b-cells were extracted from the mother and passed on to the child, would this produce immunity or is there some reason this wouldn't work?"
] |
[
"Fact or Myth: An ungloved hand can be dipped in liquid nitrogen without being damaged."
] |
[
false
] |
[deleted]
|
[
"That is absolutely true. That phenomenon, known as the ",
"Leidenfrost Effect",
" is the same reason that water appears to 'dance' on a hot skillet. But be careful, you need to be fast, or else the liquid nitrogen will eventually contact your skin. And Cryo burns are not fun. You can also dip a ",
" finger in molten lead for this reason. ",
"Aside, Berkeley FTW!"
] |
[
"Just DON'T drink it!"
] |
[
"To be doubly safe, cover your wet hand in molten lead before dipping in liquid nitrogen."
] |
[
"Just how strong is 3D printing?"
] |
[
false
] |
I read an article on the front page about how scientists are developing new materials to 3d print in order to better build electronic devices. I was thinking about the implications of this and I'm now thinking about how long it will take to improve the technology enough to build architectural structures out of this material. Maybe not buildings yet, per se, but what about a small bridge or at least components of architectural structures? This is totally exciting, and we're in the middle of a huge technological innovation here. I can't wait to see where this goes.
|
[
"3D printing isn't necessarily advantageous for something like a bridge. It's better at limited-production runs and prototyping. For a bridge, there are well-established construction methods, and costs are pretty well-defined for each. Printing a bridge would require printing many small parts, and nothing would be gained, as steel trusses, wood beams, and steel cables are stronger and much, much less expensive.",
"Homebuilt 3D printers don't have material allowables, but commercial printers do have allowables for many different materials."
] |
[
"Most 3D printers use polymers that are deposited in layers. The bond between those layers tend to be pretty weak structurally speaking. And polymers aren't the strongest materials to begin with. However with powdered metal process improving you can print using a metal powder and resin solution that can be sintered to be almost as strong as cast metal. The problem is it takes like 16 hours to print a single object that can be cast at a rate of 100's a day"
] |
[
"Yes, you would be correct, my bad."
] |
[
"Is there a way to demonstrate that the speed of light is finite using household objects?"
] |
[
false
] |
Given the high tech equipment now available, such as DSLR cameras, laser pens etc, is there a simple experiment I can do at home to measure the speed of light? It would be a great teaching demonstration. Thanks.
|
[
"I saw a demo once with an oscilloscope, it's not exactly a household object but you could carry one into a classroom...",
"You could probably make a michelson interferometer out of household objects. Probably not what you're thinking of though...",
"You can measure the ",
" of light pretty easily with a laser pointer and a small object of known size by measuring the spacing of the diffraction pattern.",
"Out of ideas at the moment, I'll try to think about it :/"
] |
[
"The method discussed in this talk seems really cool, and extremely low tech, though I don't know how practical it would be for a teaching demonstration, since it might require a bit of prep (and some long unobstructed distances): ",
"http://ed.ted.com/lessons/how-simple-ideas-lead-to-scientific-discoveries"
] |
[
"It would likely be fast enough, though if you cut slits in the CD to make the teeth, I would be concerned about safety, since structurally deficient CDs have been known to shatter. Perhaps a model airplane propeller could be repurposed somehow?"
] |
[
"A couple Big Bang questions"
] |
[
false
] |
Does the Big Bang theory describe only how the modern universe developed or does it actually postulate that the universe actually began from nothing? What is the leading model for pre-expansion matter creation? I've done a bit of research on the quantum vacuum model described by Krauss, but I've heard that Hawking purports a different model utilizing gravity. Does anyone have a layman's description of Hawking's model?
|
[
"The Big Bang theory posits the conditions that existed a fraction of a second ",
" the universe began - not ",
" it began, or what came before it. ",
"As an aside, I see a lot of people referring to it as an explosion; this is a misnomer. The big bang was a universal expansion of spacetime. That is to say, ",
" rapidly expanded during this event. Pick a point in space - the big bang happened there."
] |
[
"This",
" is a good start to give you an idea of the different epochs that cosmologists think of.",
"There are a ton of proposals for pre-inflation cosmology (basically how to get inflation in the first place from various models). I think by expansion you mean inflation (when the universe rapidly accelerates to what it looks like today) since the universe was always expanding. Matter that we see today was actually created ",
" this inflationary period, and was created from the \"release of energy from inflation\".",
"I think your question might secretly be \"what is the leading mechanism for getting inflation\" in disguise, for which I don't think there is any leading model right now, but I'm not up to date on that community."
] |
[
"There are a number of things that could be called Big Bang models. Most of the time, people are talking about inflation, (p)reheating, baryogenesis/leptogenesis, and then regular stuff like big bang nucleosynthesis (BBN).",
"None of these things actually adress \"how the universe began\". We've got more tenable problems to work on (specifically, all of the above ",
" for BBN -- that one is in the bag).",
"There are some \"how the universe began\" models. It doesn't really fall into the scope of things we know how to deal with, so it's really speculative and doesn't have much (or any?) testability."
] |
[
"Does the visual cortex get 're-purposed' in blind people?"
] |
[
false
] | null |
[
"According to ",
"this study,",
" yes. They put stereo headphones on 12 sighted people and 12 blind people and had them point to where they thought the sound was, all the while under an MRI. In the blind the visual cortex showed more activity than it it did in the sighted. They did the same experiment, but instead of stereo headphones they used electric vibrators on each finger and had the participants tell them which finger was stimulated. Again under the MRI. The blind participants showed more activity in the visual cortex than the sighted people. ",
"\"That tells us that the visual cortex in the blind takes on these functions and processes sound and tactile information which it doesn't do in the sighted,\" he says. \"The neural cells and fibers are still there and still functioning, processing spatial attributes of stimuli, driven not by sight but by hearing and touch. This plasticity offers a huge resource for the blind.\"",
"This ",
"NewScientist",
" article has further examples."
] |
[
"Unless they did the same experiment on the same people before they went blind it's impossible to tell with certainty. But it's generally accepted that when someone is blind their other senses \"heighten\" or get better."
] |
[
"Does it actually lead to notable improvement?"
] |
[
"Can anyone explain the effect on the motor when I stop a fan with my hand?"
] |
[
false
] |
I tried this question on and didn't get a very satisfactory answer, nor do I know how to cross post so I'm giving it another shot over here. When I stop a fan from spinning with my hand what effect does that have on it's motor, if any? My thoughts are that the energy going into the motor causes it turn with a certain amount of force that is countered by your hand stopping it, so no negative effect on the motor. However I have heard of motors burning out, and a friend who is an HVAC technician said he has witnessed compressors draw more amperage when they do more work. This makes me think there is something ( chip perhaps? ) that tells it to draw more power to maintain a certain output. I digress, could anyone shed some light on what happens when I stop the fan with my hand?
|
[
"An AC motor is nothing but a set of rotating electromagnets. While it's rotating, the changing electromagnetic field (EMF) keeps the complex resistance high, so that current flow is limited by the rotation speed designed into the motor for the given voltage (free speed).",
"As stated above, as you increase load towards stall, current increases, until you hit stall, when your complex resistance falls to real resistance, the relatively tiny Ohm value of the copper windings. Since these windings are usually thin to allow more of them, thus increasing EMF (and motor) output, and are sheathed only in an epoxy or varnish sheath rather than substantial plastic like house or appliance wires, the wire heats up, the sheath melts, the wires touch, the current shorts.",
"Then you have a dead motor and a tripped breaker (hopefully). Further current simply keeps it heating up until you have a fire.",
"There are a multitude of motor designs that prevent this, but a commercial grade fan doesn't use complex electronics, simply robust design and near-universal circuit breakers.",
"If you get lucky, the circuit breaker trips before the motor burns out. If not, you buy a new fan. Either way, stalling a motor that shouldn't be isn't good for it.",
"(If anyone is more up to date on the math of the complex resistance, I'm more than happy to let you correct me. My electrical classes were a loooong time ago!)"
] |
[
"The motor winding's will heat up until they burn out because there is no where for that energy to go."
] |
[
"It's not a simple transformation. It's Ohm's law. Generating an EMF field using a coil winding causes resistance when you use AC current.",
"The motor doesn't decide to draw more current. It draws current in response to the resistance of the coils. Heavier loads put on more resistance, requiring more resistance.",
"Operating speed is mostly due to motor design. You set a target speed and design the coil structure to support it.",
"I wish I still had that textbook. I kept the ones I figured would be useful, but as a poor college student I sold the rest. I wish now I'd kept ALL of them. Wiki Ohm's law and electric motors, that will give you a good basis for the terms."
] |
[
"Why are penises darker than the rest of the body?"
] |
[
true
] | null |
[
"Pheomelanin",
" is a pigment that produces a pink/red hue to the skin, and is found in higher quantities in the tissue of the penis than in other skin areas."
] |
[
"It is probably because penile skin has a higher amount of a hormone named dihydrotestosterone (DHT) that is necessary for normal development of the gonads and normal erectile functioning. DHT is a derivative of testosterone when it's converted by an enzyme called 5-alpha reductase. "
] |
[
"Why would it be on the skin of the penis and not somewhere else? "
] |
[
"Why do bacteria evolve and express a receptor for bacteriophages that would potentially compromise their survival? Are the receptors specific or do they just happen to be recognized by the phages?"
] |
[
false
] |
I'm taking a microbiology course and this baffled me. My professor didn't quite make it clear for me. Sources from where I could learn more about this would be much appreciated.
|
[
"It's the phage that recognizes an already existing protein in the bacteria as their receptor, not the other way around.",
"For example, the ",
"Phage Lambda",
" binds to an outer membrane protein in ",
" involved in Maltose uptake."
] |
[
"Though I'm sure it is the former.",
"Really? I'm sure it's mostly the latter. Viruses evolve crazy fast (much faster than bacteria) and kill bacteria a lot more than they promote diversity."
] |
[
"Though I'm sure it is the former.",
"Really? I'm sure it's mostly the latter. Viruses evolve crazy fast (much faster than bacteria) and kill bacteria a lot more than they promote diversity."
] |
[
"Could someone help me identify this tool?"
] |
[
false
] |
I am a high school science teacher. I found this tool while cleaning out the lab room. The top cone part is made of copper and is engraved with the text "made in west Germany". The silver blade part is not sharp, and swivels in and out of a groove on the copper cone. Help me identify this tool, Reddit!
|
[
"We have one of these in my lab. It's for making a sharp end to a piece of tubing. Like ",
"this",
", but smaller and smoother.",
"You insert the cone into the end of the tube, pull the blade closer and spin and the blade will shave off parts of the tube to give you a bevelled end. ",
"I can't find an example or the name of the instrument, but I'll ask my labmate who uses it and get back to you with the answer."
] |
[
"Okay, I've got an update. That tool is a sharpener for ",
"cork borers",
".",
"The borers are tubes used to cut cylindrical holes through rubber or cork stoppers, this tool keeps the borers sharp. The cone is so that the sharpener works on borers of multiple diameters.",
"This one looks like yours",
". "
] |
[
"Oh wow that would explain the cork borers I just found in the same drawer. I really appreciate all of the help. Now I am going to bore some cork with the kids next week!"
] |
[
"Could you make Helium-3 with Uranium-235 fission?"
] |
[
false
] |
Note: I am not sure if this should go under the Physics or Chemistry flair, so feel free to correct me. Fission using Uranium produces loose neutrons which speed away fast enough to embed themselves into other Uranium atoms, starting the reaction again. In theory, could this process be used with He-2 to make He-3? Say a reactor was built and the fuel was a careful mix of U-235 and He-2. This system should create He-3 as the loose neutrons from the Uranium attach to the Helium. Or is this not possible? Would the loose neutrons simply not want to attach to the Helium atoms?
|
[
"Fission using Uranium produces loose neutrons which speed away fast enough to embed themselves into other Uranium atoms, starting the reaction again. In theory, could this process be used with He-2 to make He-3?",
"Helium-2 is unbound, so it decays on a timescale of 10",
" seconds. So no chance we're able to use helium-2 for breeding helium-3.",
"When a fission reaction occurs, all kinds of particles can end up in the final state. In some small fraction of all fission reactions on ",
"U, you may end up with a helium-3 nucleus in the final state. This would not be a very efficient way to produce helium-3."
] |
[
"There is a helium-2 resonance, it's just not a bound state."
] |
[
"I agree with the statement that \"There is no ",
"He which can be put into a reactor\", but I do not agree with the statement \"There is no ",
"He\"."
] |
[
"[X-post from Astronomy] Night sky sighting that I cannot identify - Astronomers, please help!"
] |
[
false
] |
. I was biking home from a festival, heading east, in Groningen, the Netherlands. At approximately 00:05 today on 28-8-2011, I looked up and noticed a bright reddish blob in the sky, at about 45 degrees from the horizon. At first I thought it was a hot-air balloon or chinese lantern, so I pulled off onto the sidewalk to have a better look. At this point, I notice it is moving a bit slower than a satellite would be, faster than a hot-air balloon at that distance, and didn't move like a chinese lantern in the wind. As it moved further east, towards the horizon, it faded in intensity, changed to a more yellow hue, and then disappeared entirely. The whole event from discovery to disappearance lasted about 60 seconds. After it was gone, I thought it was an iridium flare. I have seen them before, and the fading out was very similar, except the color was just nuts. Heavens-Above tells me it was certainly not an iridium flare, nor the ISS. Apparently a magnitude -8 is coming straight over-head at 04:00 tonight, but I can't convince my wife to stay up to watch it... Anyway, what do you think it might have been? My suspicion is that it's actually a chinese lantern after all. Has anybody seen one at a great distance? Could it be some other satellite? It didn't look like any meteor I've ever seen or seen videos of, and was so very slow... I'm really at a loss!
|
[
"I think that the festival part of the story makes the chinese lantern theory highly plausible.",
"Depending on wind and atmospheric conditions they can appear quite unlike how you'd expect them to.",
"I had a similar experience a little while back: ",
"http://lookupandwonder.com/M51-And-UFOs"
] |
[
"OK possible explanation.... it might have been a bird. ",
"I know, sounds ridiculous, but let me finish :-) First off, the biggest problem is that you do not know the distance of the object. It could be a lot closer by than we think, and than our brains interpret high-speed motion. This is the problem with most UFO sightings.",
"A bird's flight is silent, so we do not hear an engine or anything, which again throws us off in distance determination. The light can be explained by simple reflection of street lights. Any chance there were those orange street lights around (Sodium lights)? They give off a ghostly glare, and often are poorly shielded, lighting things up above them as well. Explaining the orange hue, even the change in color as it changes position regarding the light or catch another light, and of course the disappearance.",
"Anyway, I saw the exact same effect when I was in Amsterdam on top of a tower. There were 6 orange objects flying in formation and it was incredibly eerie. But taken the fact that we were studying astronomy and I was with my fellow astronomy students, I called the UFO out to them, so we all saw it. And as the formation came closer we suddenly could see that they were a formation of ducks. ",
"So... valid questions: were there lights? And to directly offer a concern... midnight is not a normal time for birds to fly, but than again, not impossible."
] |
[
"Amateur astronomer here. Satellites just reflect the sun's light, so they wont shine reddish light at you. Iridium flares generally last of the order of a second or two. Meteors are far faster than any satellite (up to 10x faster notwithstanding any effects of perspective, and certainly ",
"no slower",
") and if a meteor did last for 60 seconds, ",
"it would turn night into day",
".",
"Does sound like a lantern, from what I've seen of them."
] |
[
"Does the Earth’s revolution around the Sun depend on frame of reference?"
] |
[
false
] |
If motion is relative, why do we say that the Earth revolves around the Sun? Doesn’t it depend on whether your frame of reference is the Sun or the Earth?
|
[
"Motion is relative but acceleration is not. The heliocentric frame of reference is an inertial (ideally) reference frame where Newton's laws of motion hold. Changing to a geocentric view makes your reference frame non-inertial and introduces fictitious forces that other non-inertial frames will not agree upon.",
"Of course, either view is mathematically valid and the physics is just a transformation of each other, but one is simpler and more consistent between multiple reference frames."
] |
[
"Yeah but then you have to deal with curved spacetime. GR in most cases is like using a sledgehammer to hang a picture frame, you'll create more problems than you solve."
] |
[
"But from a GR perspective, the earth just follows a geodesic around the sun, with no forces involved."
] |
[
"Why does the western part of North America have so many named, smaller deserts, despite seemingly all being next to each other? Why don't we name it as one single desert like we do with the Sahara?"
] |
[
false
] |
Reading through the on deserts in NA, I noticed that there's no single name for the desert on the western half of the continent, but it's seemingly broken up into smaller parts. Why is this? I suspect that part of it may be that, since it's oriented by longitude, the desert in British Columbia is different from Baja California or Mexico, but I'm not sure.
|
[
"They are broken up largely through a mixture of geography (i.e. portions of deserts separated by mountain ranges), history (i.e. native peoples / settlers established distinct names / extents for a variety of reasons), and ecoregions (i.e. different flora and fauna that characterize these regions). ",
"This is not unique to the North American deserts, i.e. your counter example actually is broken up into ",
"13 deserts",
" including the Tenere, Tanezrouft, Dijurab, Tin-Toumma, Libyan, White, Eastern, Nubian, Bayuda, Sinai, Blue, and Atlantic Coastal Deserts. These largely correspond to ",
"ecoregions",
" within the Sahara, but some of the deserts listed above occupy the same ecoregion. Not being an expert on the Sahara, I would suspect that history and/or geography account for the other desert divisions."
] |
[
"also sahara on its own just means desert in arabic so the name is meaningless without the qualifying sub-names you mention. "
] |
[
"They are largely different geological and ecological systems. I'm from Yucca Valley California originally, which is in the southern edge of the Mojave Desert. Mojave means \"high desert\" and it is very high altitude. Just down the hill (5 miles or so) is the Sonoma Desert which is completely different in what plants and animals you find. It is also hotter and dryer in the Sonoma than the Mojave for the most part. The Mojave even gets snow in winter."
] |
[
"What is the best way to determine if an exoplanet is suitable to sustain human life?"
] |
[
false
] |
Just say in some near future we send out a bunch of probes in various directions to try and find a suitable planet for permanent colonisation down the track. What is the most effective test that can be performed in order to determine with 100% confidence that a planet is suitable for us to live on? Bonus question: how do we get the message back? I'm imagining some kind of self destruct that would produce a specific frequency of RF (although that is probably not even possible).
|
[
"It's an interesting question you ask... ",
"But... there will NEVER be a 100% confidence-probability that an alien planet will be biologically-perfectly suitable for humans (as we exist today), unfortunately! ",
"When it comes to real life, in the real world, you can forget about the idea of \"100% guaranteed\". The real universe doesn't come with 100% guarantees of the type you are seeking. ",
"The term \"100% guaranteed\" is best left with sketchy late night advertised products! ",
"For example: it's actually considered unethical for doctors and lawyers to use phrasing such as \"100% guaranteed\", because nothing can ever be 100% assured to happen. ",
"So ya... again: such a test, and such a planet will NEVER exist. ",
"ALSO: ",
"It's worth noting that Earth is barely habitable to humans... and we evolved here! ",
"Out of nearly 400,000 plant species on planet Earth, barely 100 of them (give or take) are edible to humans! And that's only after countless centuries of gradual cultivation of that plant species to make it more edible for humans. ",
"That means over 99.9% of plants (on our own home world) will kill us, if you try to eat them in sufficient quantities! ",
"And of the tiny few that are eatable and nutritious to us, you can still die by eating them, due to contamination by bacteria and viruses. So even the edible plants can kill us. ",
"Overall, life on Earth is VERY hostile to humans... let alone an alien planet. ",
"NEXT: ",
"As for ranking the habitability of alien planets, for humans, the best testing factors to consider will likely be:",
"1) Its temperature, ",
"2) Its location in the solar system (warm, habitable zone),",
"3) Its gravity level,",
"4) Its day/night cycle,",
"5) Its geological stability,",
"6) The stability of its star,",
"7) The composition of its atmosphere.",
"NOTE: Water is, of course, also highly important. But if all the other 7 factors above are there, except for water, then water can \"easily\" be brought in from other parts of the alien-solar-system. ",
"(I say \"easily\" because if we have the technology to make it to another solar system, then shifting water around that other solar system would be trivial.) ",
"So the presence of water isn't crucial, as many might initially think (provided the other factors listed above are favorable). ",
"In order to determine these factors we need LARGE telescope arrays to be launched into space. ",
"SpaceX and Blue Origin might be able to launch those telescope-arrays for us, in the near future, cheaply. (Hopefully!).",
"Until we have those telescopes, then forget it: we will not be able to determine a planet's habitability ranking. ",
"FINALLY... ",
"as for the bonus question you asked, involving some type of \"self destruct\", unfortunately... I don't understand your question at all! ",
"I think perhaps my brain is too foggy this morning, and I'm still too sleepy! But ya, I don't know what you are asking there with that last question?"
] |
[
"Part of the problem is we have a sample size of 1. Basically impossible to draw hard conclusions from. ",
"One key metric I've seen talked about is the presence of free oxygen. Oxygen is very reactive, if it is present in large quantities in molecular form it seems reasonable to infer that a process like life is creating it (e.g. photosynthesis). ",
"Liquid water also seems to be an important pre-requisite, as life needs a solvent in which to mix all its magical molecules. ",
"If we spotted a planet at the correct temperature for liquid water that also had large amounts of molecular oxygen people would get very, very excited. "
] |
[
"Yes that's completely right. ",
"There could be other things about Earth that turn out to be important, like the axial tilt, magnetic field, presence of the moon, and so on. A lot of potential Earths seem to be tidally locked - that also seems like a big variable that would have a huge affect on the prospects for life. ",
"FWIW, my prediction for Europa is that we'll find some kind of life there. It seems to have an energy gradient, seems to be well shielded from the harsh Jovian radiation environment, and has a vast volume of water that has been stable for billions of years. The surface crust seems thin enough to allow occasional melt-through (can be seen from rafting features at locations like Conamara Chaos), giving some cycling of irradiated materials from the surface down to the subsurface. "
] |
[
"Is it possible to create a paint that corresponds to ultraviolet frequencies? Or, more generally, any portion of the light spectrum outside of visible light?"
] |
[
false
] |
Nothing is particularly 'special' about visible light objectively; we distinguish it from the rest of the spectrum only because it corresponds to the frequencies we can perceive. So what about the rest of the spectrum? Is it possible to invent an 'invisible paint' that will be the 'color' of non-visible light frequencies?
|
[
"'Invisible' paint has already been invented. ",
"Blacklight paint"
] |
[
"I take it you have never been to a museum (or even Chuck E Cheese) where they stamp your hand with UV paint upon paying so that they can check later that you paid but you don't have an ugly visible stamp on your hand for the next two days."
] |
[
"The reason paint (or just about anything) is of a specific color, is not due to the light it gives off, but rather due to the colors it reflects or absorbs. Wavelengths that are not absorbed and are reflected are then perceived as colors.",
"As you've guessed, there are many types of molecules that absorb, or do not, in other areas of the spectrum. There are ",
"insulative paints",
" that reflect IR (and often visible) light; many molecules with double bonds absorb in UV; gamma rays are stopped by heavy nuclei in a dense material, etc. There are quite a few ways in which E-M waves interact with matter and each of those can be exploited to produce materials that absorb or reflect certain wavelengths. "
] |
[
"Why is boron trifluoride toxic?"
] |
[
false
] | null |
[
"BF3 is a fairly strong Lewis acid which can be dangerous, but where it gets really bad is that upon exposure to water it generates very dangerous hydrofluoric acid.",
"While not a strong acid, it is very good at penetrating tissues due to its small size and the fact that it doesnt readily dissociate. Once inside your body the fluoride ions can react with calcium ions to precipitate out.",
"Calcium is important for a wide variety of cell signalling processes, and without it many important biological processes shut down. In severe cases of HF poisoning the cause of death is usually heart failure, but only because that kills you before the horrible agonizing pain of the rest of your organs failing does."
] |
[
"The answer to the hypothetical is no.",
"BF3 is worse when it is exposed to water, but it is still an aggressive Lewis acid. It will go hunting for electrons and if it can't get the from water it will get them from somewhere else.",
"Biological systems are very tightly maintained in specific conditions, throwing anything that is very chemically reactive almost always messes something important up."
] |
[
"Actually in the absence of water the B-F bonds are quite stable and strong.",
"The Lewis acidity comes from the vacant P orbital on the Boron; it is very low in energy so readily accepts electron pairs."
] |
[
"Magnets bending light? This youtube video shows just that, however I can't make any sense of it with my understanding of EM theory. Can somebody explain to me what is going on here? https://m.youtube.com/watch?v=L9pqAeUtUV8"
] |
[
false
] | null |
[
"Quack"
] |
[
"Thank you, thats what my instincts are telling me too. However, I still don't understand what is going on. So do you have an reasoning behind that claim, or a theory about what we are seeing, please let me know. "
] |
[
"Random images with a guy rambling?"
] |
[
"Why do the fundamental forces dominate at different length scales?"
] |
[
false
] |
Do we know why, or is it simply accepting the observations?
|
[
"There is a problem with answering this question ",
"the problem is well explained by Mr. Feynman",
".",
"So what exactly do you want to know? Eventually everything comes down to \"simply accepting the observations\" but there are lots of levels of explanation between knowing nothing about it and there. So, again, what do you want know?"
] |
[
"\"Why\" versus \"how\" is either semantics or just fastidious avoidance of your question. I was once involved in a project looking at gravity on submillimeter length scales. Simply put, looking for variation from the 1/r",
" dependence. The theory was that gravity might be wound up more in the higher dimensional space predicted by string theory. ",
"Here is a Forbes article on similar more recent work which pushed the measurement to below 100microns",
". If gravity was wound up in higher dimensions at very small scales then that would explain it's relative weakness. The idea of being wound up in higher dimensions at small length scales is often likened to an ant on a tightrope. A large scaled human can only walk back and forth, but the smaller scale ant can go back and forth and around the rope."
] |
[
"There are two solid reasons why this is the case, but as it turns out they raise a new problem, why are the forces different strengths?",
"See, ideally all forces would be like gravity and electromagnetism, and they would have infinite range. The strong and weak forces however are very short range, and for two completely different reasons.",
"The strong force lives up to its name. it's incredibly, mind-numbingly powerful. The potential energy of two objects attracting each other increases with distance, but as we know, potential energy is always minimized by interactions. At sufficiently large distances, the potential energy is so great that there's enough the energy in question overflow and is converted into quark-antiquark pairs. Energy becomes mass and the potential drops to nearly zero",
"As for the weak force, the bosons that carry it, the W and Z bosons, have mass, and lots of it. Like potential energy, mass wants to get broken down into kinetic energy, so massive particles decay into less massive ones with more kinetic energy. The W and Z bosons are so massive that they decay pretty much instantly."
] |
[
"Use of bra-ket notation in quantum mechanics?"
] |
[
false
] |
So, I've been reading up on some Wikipedia articles on bra-ket notation, spin, etc. And I noticed that the difference between bra-ket notation and normal vectors is that bras <A| are complex conjugates with kets |B>. I can understand a usefulness of complex conjugates with respect to pure mathematics, but what are some examples of variables in physics that use complex or imaginary values?
|
[
"There are cases where ",
" is convenient (optics, waves, oscillations, complex impedance), but in quantum mechanics, the use of ",
" and complex numbers is intrinsic to the equations. ",
"The fundamental way to see this is that the way the uncertainty principle is encoded mathematically intrinsically involves ",
". Below, I describe how that arises.",
"Observables in quantum mechanics take real values, and so they are represented by objects called Hermitian operators. The uncertainty principle arises when you have two observables whose operators do not commute, that is, operators ",
" and ",
" (like position and momentum) for which ",
" is not equal to ",
". The way we characterize this is to look at the ",
" of ",
" and ",
", namely ",
".",
"And here's the punchline: If the uncertainty principle says that ",
" and ",
" cannot both be known simultaneously, ",
" must take imaginary values (that combination is an anti-Hermitian operator), that is, it must be ",
" times a real number or ",
" times an operator that takes real values."
] |
[
"Waves. It's much easier to work with oscillations written in the form y = e",
" than it is to work with them in the form of y = cos(x). And in quantum mechanics, waves and wave functions are everything."
] |
[
"Physical observables might be restricted to real values, but we often need complex numbers to express the state of the of a system. The bras and kets are used to represent state vectors. These are generally written in the form of a set of numbers that represent the decomposition of the vector with respect to a certain basis set. You can always choose a funky basis in which the state of a system is a vector with complex numbers in it.",
"Physical observable, however, are always expectation values of operators with real eigenvalues, and hence are always real."
] |
[
"Is our solar system (sun) orbiting the milky way black hole?"
] |
[
false
] | null |
[
"Not really!",
"We are orbiting the supermassive black hole in the centre of the galaxy only in the sense that we are orbiting around the centre of the galaxy and there is a supermassive black hole there. However, if you removed that supermassive black hole, we would still orbit around the centre of the galaxy!",
"The supermassive black hole is, as the name suggests, quite massive. However, it makes up only a tiny fraction of the mass of the galaxy. It is millions of times more massive than the Sun. But there are ",
" of stars in the galaxy. And this isn't even counting the dark matter, which makes up the majority of the mass. So the supermassive black hole in the centre of the galaxy doesn't really contribute very much to gravity on a large scale.",
"It's still important, because it's a lot of gravity concentrated in a small area. While it doesn't affect our orbit, it can tear apart nearby stars. A supermassive black hole also acts as a sort of power source, where incoming material gains a lot of energy from gravity. This energy can be radiated out as the material tries to shed its energy and fall into the black hole. The radiation can be incredibly bright - one of the brightest things in the universe - and we call these bright objects \"quasars\" (or \"active galactic nuclei\" when they're a bit dimmer).",
"This is the true importance of supermassive black holes: not as a source of gravity for the galaxy as a whole, but as an ",
" source of gravity that can produce huge amounts of power in a small region."
] |
[
"Mostly yeah - without dark matter, a big chunk of the galaxy would be above escape velocity"
] |
[
"That's fascinating. I always thought the SBH was the driver (of the rotation) of galaxies, and dark matter was something like the invisible glue that connected everything to the SBH. ",
"Does this mean that dark matter is the only reason galaxies stay together at all? "
] |
[
"If the human eye was a camera, what would its resolution be? (in pixels)"
] |
[
false
] | null |
[
"For those who don't feel like reading through all that, around 576 megapixels.",
"Obviously that number can change depending on many factors, but if you just want a ballpark estimate, there you go."
] |
[
"For those who don't feel like reading through all that, around 576 megapixels.",
"Obviously that number can change depending on many factors, but if you just want a ballpark estimate, there you go."
] |
[
"So my eyes are roughly 30 times better than cameras, and yet I still need glasses to make out letters that are 3 feet from my face? Thanks mother nature."
] |
[
"Are there any studies on otherwise healthy adults purposely using ritalin/adderall as a study/work/programming aid?"
] |
[
false
] |
Programmers are perpetually trying to chase a mental state sometimes referred to as "The Flow"/"Hack zone"/"In the zone" where you're simultaneously hyper-alert but also calm and able to juggle more thoughts in your head without confusion. As a software developer I regularly self-medicate with caffeine and sometimes alcohol in order to reach that mysterious mental state (and certainly go through other behavioral rituals as well). I'm curious to know if other chemicals performance enhancing effects have been tracked – particularly within narrow fields like software development. Has there been any real study to measure benefits?
|
[
"Hi Gilgoomesh,",
"Looked into your question and it seems there are a few studies, all smale scale though. ",
"http://www.ncbi.nlm.nih.gov/pubmed/21859174",
" and ",
"http://www.ncbi.nlm.nih.gov/pubmed/21368261",
".",
"From personal experience I can say, yes there is a benefit. You will be more focused for a few hours. I wouldn't advise using this to often though as long term use is correlated with adverse cardiac events. Since it remains a strong stimulant.",
"cheers"
] |
[
"To add on to reasons why it would be a bad idea to use these drugs, there is actually an adderall shortage right now because so many people are using it recreationally, such that some people with actual disorders who need the medication can't get it. "
] |
[
"Ritalin and Adderall are two different drugs that can have very different effects on people. Adderall was pulled from the market in Canada because of concerns. I recall seeing news stories about how it made some people have serious lapses in sanity. Ritalin is different. They both can give you the ability to hyper focus on things and can be very effective for adults with ADD. I have had both prescribed for me and can tell you that Adderall made me feel like I was losing my mind. Ritalin (actually Concerta) made me feel like I finally got it back. "
] |
[
"In terms of getting the most nutrition out of food; how efficient is the human digestive system in comparison to other creatures?"
] |
[
false
] |
[deleted]
|
[
"Well you were each eating different food, so that makes cross animal ranking somewhat dubious... Dog, human, and cow for example each have really different efficiencies for different foods because they by definition evolved to fill different niches. Dog cannot get much nutrition out of grass, but cow has a specialized ",
"4 chambered stomach",
" that it uses to extract energy from tough plant carbohydrate polymers. Any material left over is coughed up and re-chewed, before a second round of digestion. Dog has a really acidic stomach that can quickly break down the high protein carnivore diet. Human is somewhere in between, and may overall have a reduced digestive tract compared to other hominid omnivores due to a long history of cooking meat. We don't break down the majority of plant cellulose, but do have some symbiotic bacteria like ",
", that help us get more energy from oligo-sacchrides. "
] |
[
"There is an interesting discussion of the different types of digestion ",
"here",
"."
] |
[
"Well ruminants have very modified foreguts for the digestion of cellulose and hemicellulose, where they keep all sorts of symbiotic critters around that aid in the digestion of that stuff.",
"Humans can't digest cellulose to any major degree. Cows aren't carnivores though, and even carb-rich meals will apparently make them very ill (my professor had cows and apparently they got into some wheat once and were afflicted with diarrhea suddenly - just googled it, it's called enterotoxemia.* Silly cows.) So I'm not sure if you'd rank us above them for having the ability to eat carb-rich stuff and meat, or below for their ability to digest cellulose.",
"*Basically, since ruminant digestion is really slow, a crap-ton of carbs sitting around in their rumen will let bad bacteria flourish. "
] |
[
"How does an electric motor work, and how does it differ from a homopolar motor?"
] |
[
false
] |
Which one is more efficient, provides more torque and how is it used? Sorry if this is a bit to general, if you could even just link an article that'd be helpful!
|
[
"A homopolar motor is an electric motor. There are other kinds, of course. The basic principle relies on the \"right hand rule\" which means this: hold your right hand out like you're giving a thumbs-up. If there were a current running out of your thumb, there would be a magnetic field coming out of your fingers. This magnetic field can interact with metals, other magnetic fields, and other electric fields. The configuration of how the wires are wound (typically in an assembly called a stator because it stays still) and a magnet or other chunk of metal (a rotor because it rotates) determine what happens when you apply a voltage across the terminals."
] |
[
"Homopolar motors have a huge problem: they are essentially a \"one-turn coil.\" They require short, enormously thick connecting wires, and operate at millivolts and enormous amperage. They require huge sliding contacts, preferably using liquid metal.",
"To fix the problem, just use a many-turns coil. This lets us use connecting wires hundreds of times thinner, and employ relatively large voltage at low current. Their sliding \"brushes\" no longer need be the size of the rotor, and we can even take Tesla's path and eliminate sliding contact entirely.",
"Visualize things like this: an electromagnet can be a single thick copper ring, or it can be a stack of hundreds of thin rings which add up to give the same magnetic field ...or all those rings can be connected electrically in series to form a spiral. All three use the same wattage and produce the same field. But it's ",
" easier to use a spiral of wire and deal with 100 volts at an amp, rather than than 1/10 volt at 1000 amps of the one-turn coil.",
"Electric motor triva: a large number of inventors were building motors with ",
"all kinds of crazy designs",
" (most resembling steam engines with pistons.) Then the inventor Zenobe Gramme was demonstrating a new type of smooth-output DC generator during an invention show, and connected two of his units together. The first one drove the second as a motor. This \"",
"Gramme Machine",
"\" led the way to the development of modern DC motors, motors with smooth torque output using a large number of interleaved coils on the rotor, and a large number of copper segments in the sliding commutator."
] |
[
"An excellent explanation. You're a great help!"
] |
[
"Are Magnetospheric Eternally Collapsing Objects a plausible alternative to black holes? Why or why not?"
] |
[
false
] | null |
[
"What is an eternally collapsing object?"
] |
[
"http://www.scitopics.com/Eternally_Collapsing_Object.html"
] |
[
"So, something destined to be a black hole but so perfectly balanced that it collapses at an imperceptible rate?",
"Color me dubious.",
"These things all have tipping points. You are on one side or the other. Not in some near-perfect equilibrium.",
"And by \"near-perfect\" I mean it. There is no room for error. A bit more or less mass is all it takes. Even one atom will tip the scale. Such a small difference would not be noticeable at first but the scale is tipped and over time the difference would magnify till it was very apparent."
] |
[
"AskScience AMA Series: I am Dr. Laura Kloepper, a biologist who studies the emergence and echolocation dynamics of large bat cave colonies. This summer I am traveling and camping with two female students as we record bats across the Southwest. Ask Me Anything!"
] |
[
false
] |
Hi Reddit! I am Dr. Laura Kloepper, an Assistant Professor of Biology at Saint Mary's College in Notre Dame, Indiana. My research involves using audio, video, and thermal imagery to understand the emergence, flight, and echolocation dynamics of large (1 million +) colonies of Mexican Free-tailed bats. These bats leave the cave at densities of up to 1,000 bats per second, flying at speeds of 25 mph, beating their wings ten times per second, and rarely run into each other. Their primary mode of navigation is using echolocation, or making a loud sound and using the information in the echoes to create a visual representation of their surroundings. Everything we know about biology, mathematics and physics says that they should not be able to successfully echolocate in these large groups. My main research involves trying to understand how they are able to successfully navigate via echolocation without interfering with one another, and these findings have technological implications to improve man-made sonar. I am also interested in flight dynamics in large groups, factors that control the emergence timing, and unique characteristics of bat guano. This summer I am traveling with two female undergraduate students and my trusty field dog as we visit 8 caves across the Southwest to tackle multiple research projects. We will be doing a lot of camping, consuming a lot of canned food, and putting close to 7,000 miles on our rental SUV. We will be documenting our journey on our blog, , or on our Twitter and Instagram (@smcbellebats). I will be here from 12:00pm EDT to 2:00pm EDT to answer your questions...AMA!
|
[
"Out of curiosity, why was it necessary to mention that the two students assisting you were female?"
] |
[
"How do the bats avoid crosstalk? Do they all echo locate at different frequencies, or is it highly directional? Or do they rely on some kind of \"near field\" communication with a couple of key bats doing the ranging for the group?"
] |
[
"This is exactly what I am studying! So far most of our knowledge is from bats in pairs or small groups in the laboratories. Bats in general make very short, directional echolocation sequences, but there is a lot of overlap in call frequencies. When bats fly together, data show that they will slightly adjust their call frequencies away from each other. But when they are in massive groups, such as the ones I study, you can only adjust your call so far before it overlaps with another conspecific. My hypothesis is that bats have sort of an acoustic fingerprint and my pilot data indicate that the way the frequencies change over time can vary from bat to bat. "
] |
[
"What do gravitational waves propegate through? What is the medum?"
] |
[
false
] | null |
[
"There is no traditional medium. Much like electromagnetic waves, gravitational waves propagate as oscillations on a field. The tricky part is that while EM waves propagate on an electromagnetic field which fills all space, gravitational waves propagate on space itself.",
"Whether you wish to call this \"aether\" is up to you, ",
"Einstein did albeit with a modified definition",
", but most physicists just drop that language and talk about fields instead as old-aether ideas historically imply several things we know to be wrong today."
] |
[
"That's true but the issue I'm trying to raise is in your final phrase there:",
"The spacetime manifold is important to how the electromagnetic field behaves.",
"The metric is not the manifold, it is a field on the manifold very much like any other. It just happens to tell us how to measure distances with physical objects."
] |
[
"The tricky part is that while EM waves propagate on an electromagnetic field which fills all space, gravitational waves propagate on space itself.",
"I'm not sure what distinction you are trying to draw here. Gravitational waves are perturbations of the metric just as EM waves are perturbations of the EM field. The metric is no different in being a field on the manifold than any other field."
] |
[
"How bright does the sun appear from space, in orbit around the earth?"
] |
[
false
] |
I assume the atmosphere scatters the light a lot - does that mean that the sun looks like a really bright point source?
|
[
"It depends totally on atmospheric conditions, and where on the Earth you are, and you elevation, and so on.",
"At the equator, during clear weather, if the sun is at a 45 degree angle, only about 70% of its photons are reaching your eye. So it would, conversely, be about 40% brighter if you were in space.",
"EDIT: this only accounts for visible photons."
] |
[
"How is that calculated?"
] |
[
"There's a fairly simple set of equations to use which tell you what percentage of photons pass through the atmosphere at a given angle at sea level. Things get more complicated if you take in higher/lower STP, or elevation, or smoggy/cloudy conditions, and so on (which is why I kept all the assumptions null).",
"The variables to calculate are \"atmospheric extinction\" and \"atmospheric refraction\", if you're curious about learning them yourself. I pulled the data from my previous post from memory, but ",
"this",
" looks like a good resource to use."
] |
[
"What is live culture yogurt and how does it aid in digestion?"
] |
[
false
] | null |
[
"Live culture means that when it was packaged there were live bacteria present within the yogurt. In fact, the reason it's yogurt in the first place is due to bacteria. After mixing together all the ingredients in yogurt (milk, sugar, etc.) it's boiled to kill off all the undesirable bacteria, then specific cultures are added to this tasty mixture. The bacteria find this mixture quite tasty as well, and start feasting on it. They are allowed to grow, and as they grow they start breaking down the lactose in the milk which produces other tasty byproducts and makes it the lovely thick texture you know yogurt as. These bacteria can also aid in digestion because they can help break down certain proteins and so forth in your gut.",
"In total, you use bacteria to produce yogurt, then you eat the bacteria, and it eats the food in your stomach to aid in digestion."
] |
[
"Loosely, this is correct. Consuming ",
"probiotic",
" cultures stabilizes gut microbiotia and provides various beneficial effects to the consumer. In the case of live culture yogurt, the ",
"specific type of bacterium",
" used in production is the probiotic culture that provides the beneficial effects. We commonly know live culture dairy products (kefir, yogurt) to be good for bowel regularity. It is believed that consuming them and allowing them repopulate your gut aids in this by their production of antibiotics that inhibit the growth of bad ",
"gut flora",
" (yeasts, pathogentic bacteria, etc.) while allowing the good ones to thrive.",
"The consumption of probiotics is becoming increasingly well known and well studied by scientists who study gut and immunological diseases such as ",
"IBD",
". The immunological moderation by good gut flora has been known to ",
"ease the symptoms of IBD",
" and other diseases (note, that article is 7 years out of date). ",
"Healthy gut flora provide increased digestion, immunological tolerance, a healthy immune system, reduce risk of pathogenic infection of the gut (E. coli, etc), provide vitamins for the host, and countless other benefits. We have not yet identified all benefits of the mechanisms behind the benefits, but they are being studied rigorously in the current scientific climate."
] |
[
"Read the container! Usually its strains L. acidophilus.",
"It helps because the bacteria produce enzymes that aide in breaking various proteins and fats."
] |
[
"Is there an 'opposite' of ADHD?"
] |
[
false
] | null |
[
"disorders of the brain do not generally fall along a neat linear continuum the way that some disorders of the rest of the body (eg endocrine hypo or hyper activity) do. this is because disorders of behavior are incredibly complex.",
"there is no such thing as the opposite of ADHD or schizophrenia or personality disorders. you could make some argument for depression being the opposite of mania, but even that is an oversimplification."
] |
[
"He's saying that the actual differences in the brain are so complex that there is almost no chance of finding exact opposites. Say insomnia and narcolepsy, they seem to be opposites but how they're affecting the brain, and which parts of the brain are affected are not related in any way."
] |
[
"He's saying that the actual differences in the brain are so complex that there is almost no chance of finding exact opposites. Say insomnia and narcolepsy, they seem to be opposites but how they're affecting the brain, and which parts of the brain are affected are not related in any way."
] |
[
"Today I found what appears to a be a plant that repaired a broken limb with as smaller support limb. What is going on with this? (Pics inside)"
] |
[
false
] |
So I am calling it a buttress, but I don't really know what this phenomenon is called. I have been unsuccessful in googleing any information on the matter. Please excuse my fuzzy phone pics. PS: I posted the same gallery in to see if they could identify the plant itself, in case that helps. EDIT: Thanks for all of the responses. The AskScience community is awesome! I was hoping I would get some lovely *tropism kind of word to help me get a better handle on the subject. It seems many people are suggesting inoscculation and/or gravitropism combined with stem damage. Upon further inspection I realized that the smaller, connecting, stem grew from a node closer to the end of the parent stem and re-attached to a point on the same stem, but closer to the stalk. It was able to do this because of the bend in the stalk. I am wondering now if the leaf stem's grafting behavior wasn't triggered by the bending/damage to the parent stem.
|
[
"I realize this may not be of any help for this particular post, however, when trying to identify a plant species you need a picture or it's full form, an upper leaf, under leaf, the bud, branching pattern, and any fruit or inflorescence , also knowing the location and whether it is a high and dry site or low and wet (near a ditch) is also very helpful. "
] |
[
"Hello, plant guy here. what you are seeing is common in the plant world. it is not a respons to the broken limb, its a respons to growing toward the ground and hitting it then looking like it was ment to be that way. "
] |
[
"I have a very large beech tree growing beside my house. It has a similar thing, but with massive branches, as big around as some smaller, younger trees. I always thought it was an interesting formation. If anyone's interested I could take a few pictures of it.",
"Edit: ",
"Took some pictures",
", please excuse the horrid exposures and often blurry focus. I had the ISO cranked high as it'd go and the shutter speed down in order to get a decent shot, and was either on my back or bent over halfways to get it in view. "
] |
[
"How can I preserve a dying family member's genetic material?"
] |
[
false
] |
[deleted]
|
[
"Freeze a tissue sample at -80C."
] |
[
"Human hair is a pretty good source of DNA (",
"source",
"). Moreover, it looks like hair samples degrade the least when they are frozen at at least -20C in a non-freeze/thaw freezer within 6 months of obtaining the sample (",
"source",
")."
] |
[
"It doesn't matter if the cells die if you just want to preserve the DNA."
] |
[
"Do men go through any physiological changes when their partner is pregnant?"
] |
[
false
] |
When a woman is pregnant she goes through a lot of hormonal and physical changes as she come to term. Do men typically experience any hormonal or physical changes as their partner progressing in the pregnancy?
|
[
"Try ",
"this",
" one. Expectant fathers have elevated prolactin & cortisol (before the baby is born; compared to levels from earlier in pregnancy).",
"See also ",
"this review",
" on ",
"Couvade syndrome",
", the psychological & physiological changes that occur in some men when their partners are pregnant. Couvade syndrome has historically been explained in purely psychological terms, but it's also quite possible that some of these effects are hormonally driven. Couvade syndrome often includes weight gain. Now here's where it gets fun. It's recently been demonstrated (",
"here",
") that marmosets and tamarin male monkeys also show weight gain when their partners are pregnant. Marmoset males put on a whopping 10% in weight, tamarins 5%. They gain weight on a different trajectory than their female partners, so they are not just eating-when-she's-eating. Marmosets & tamarins also show \"biparental care\", like humans (often) do, so it's been suggested (",
"ref",
") that male primates in such species are fattening up when their partners are pregnant so as to store up some fuel for the intensive parental care after the birth. Ziegler (previous 2 refs) suggests prolactin is the direct physiological trigger for the weight gain & other aspects of Couvade syndrome in primates in which males help care for the young. "
] |
[
"Yes. New fathers have increased levels of prolactin (same with mothers). Artificially increasing prolactin levels leads to increased paternal care in some species. ",
"Source.",
"Edit: I should say that this article only has data on prolactin levels AFTER the birth of a child, not when the mother is pregnant. Also, I don't remember seeing anything in this article about oxytocin, which is also elevated in new dads."
] |
[
"Awesome. Thanks."
] |
[
"Why is Dark Matter called 'matter'?"
] |
[
false
] |
Aside from the fact that the word 'dark' is a placeholder term. As far as I understand we have only measured unexplained gravitational effects. Wouldn't it be more accurate to call it 'dark gravity'? Is matter literally the only thing we know of that could produce such effects?
|
[
"We really do believe it is most likely an actual form of matter. It is the simplest explanation, and doesn't require arbitrarily changing the fundamental laws of physics to fit our observations.",
"And that's really the only alternative to dark matter - just inventing new laws for gravity. This is tricky, because General Relativity is really a beautifully minimalist theory. It's the simplest possible result you get from a very small number of assumptions. But if you want to make GR more complicated, there are very few constraints on what you can do - you can modify it however you want. This makes it very hard to prove that these theories actually describe gravity, and aren't just fudging the physical laws to get the right answer.",
"On the other hand, dark matter being made up of some exotic particle is much easier to constrain and understand. We already know there are particles that are invisible and don't interact electromagnetically - neutrinos, for instance. We also know that we probably don't have a full catalogue of all subatomic particles - there are apparent holes and symmetries, and there are very natural places for possible dark matter particles (basically, fat neutrinos) to live. And, as kinematic particles, we can quite robustly simulate what a distribution of dark matter would do, even if we don't exactly know what it's made of - it turns out it doesn't matter if something is a cloud of black holes, or a cloud of stars, or a cloud of dark matter particles, they all follow the same basic dynamical equations. So we can test things more robustly. Rather than setting up dark matter to fit our observations, we can throw a near-uniform distribution of dark matter into a simulation and see what it produces. And what we get is galaxy-sized blobs of dark matter, with just the right mass profile to give the rotation curves we observe.",
"One specific \"smoking gun\" though is the direct evidence of the Bullet Cluster. Here, two galaxy clusters have collided. Galaxy clusters have 99% of their visible mass in gas, and this gas has smushed together where the galaxy clusters first hit each other. However, the stars just flew past each other, as should the dark matter. Using gravitational lensing, we can find out where the mass is - and we find that the mass is not in the gas, where 99% of the visible mass is. Instead, it's around the stars, where the dark matter should be. If you modified gravity instead, you'd still expect to find gravity concentrated on the gas, but that's not what we see."
] |
[
"Great explanation. If you don’t mind, maybe we can add it to the FAQ?"
] |
[
"The dark matter component should be 5-10x more massive than the total of gas & stars, so the gas & stars do make a difference, but not enough to stop the dark matter in its tracks. What really happens is you get a \"halo\" (a blob) of dark matter, which captures gas inside it, that forms stars - it's the dark matter that dominates the motion of the gas, rather than vice versa.",
"Here, both stars and dark matter are \"collisionless\". Basically, stars don't really bump into each other. Two galaxy clusters, if they're going fast enough, will just shoot straight through each other. The stellar orbits will be disturbed, but the bulk of the stars end up just passing straight through. Dark matter also doesn't bump into itself, so the two dark matter halos also just go straight through each other. But gas particles ",
" smash into each other. So the gas spluts in the middle, and the stars and dark matter shoots straight through."
] |
[
"What's the difference between a sociopath and a psychopath?"
] |
[
false
] |
I know that there is a difference, but I'm unsure as to what the actual difference is. Can someone explain symptoms-wise, and possibly even psychologically what's different, please?
|
[
"If you read \"Without Concious\" by Hare (who is the guy who deemed the construct psychopathy), he essentially says that there is no difference between the two terms. He goes on to say though that a psychopath probably has more genetic roots to their behavior whereas a sociopath likely has more environmental roots to their behavior (but arguably this occurs pre age 6, so they are going to look the same). ",
"Also - if you are interested in it generally, I cannot say enough about that book. It is written for everyday person and I have Masters degree in psych with an emphasis in forensics and it still explains it better than anything else I've ever seen. "
] |
[
"To clarify the distinction: the difference in nomenclature - and that's all it is, really - is mostly a reflection of the attitudes of the author. Whether someone calls someone a psychopath or a sociopath is mostly whether the author attributes the traits to a genetic predisposition or societal and institutional influences. There are however as of yet no good ways to figure out the etiology of psychopathic personality traits and as such the distinction is a matter of opinion, not fact."
] |
[
"I have been unable for a number of years to find a source which provides a distinction between the two, although I have read works which essentially equated the two concepts. Do you have one you can cite?"
] |
[
"How can Greenland Sharks live up to 500 years and why can't humans live as long?"
] |
[
false
] | null |
[
"https://oceanservice.noaa.gov/facts/greenland-shark.html#:~:text=But%20even%20at%20the%20lower,deep%2C%20cold%20waters%20it%20inhabits",
".",
"“The largest shark they found, a 5-meter female, was between 272 and 512 years old according to their estimates. Carbon dating can only provide estimates, not a definitive age. Scientists continue to refine this method and may provide more accurate measurements in the future. But even at the lower end of the estimates, a 272-year lifespan makes the Greenland shark the longest-lived vertebrate.",
"One theory to explain this long lifespan is that the Greenland shark has a very slow metabolism, an adaptation to the deep, cold waters it inhabits.”",
"TLDR: Seems their extremely slow metabolism and living at depths of 700-2200 meters in arctic waters allows for them to grow more slowly. ",
"https://pubmed.ncbi.nlm.nih.gov/20704872/#:~:text=That%20is%2C%20metabolic%20rate%20is,rate%20live%20slower%20and%20longer",
".",
"“That is, metabolic rate is thought to be inversely proportional to maximum lifespan, which means that species that live fast will die young while those that have a slower metabolic rate live slower and longer.”"
] |
[
"In addition to resilient hearts, Greenland sharks have an extremely low risk for cancer and infectious diseases. Their autoimmune system paired with their body’s high ammonia levels make their bodies unfriendly to viruses, bacteria, and diseases that affect most other animals."
] |
[
"Thank you. This is a very clear and informative answer."
] |
[
"What is the latest and greatest theory of the origins of life on Earth?"
] |
[
false
] |
I have heard that the 'Primordial Soup' model most of us were taught in grade school is largely regarded as discredited. What is the current thinking?
|
[
"Some version of the primordial soup is right; there were lots of free organic molecules floating around, some how they got into the right configuration to start self replicattion. Most of the current work has been focused on what order the core aspects of life arose in and where.",
"Key things you need for life are 1. metabolism 2. heretibility and 3. structure that contains the other pieces.",
"So we have two main schools of thought; metabolism first theory, and RNA first theory. Both propose that specific component showed up, and the others came later. ",
"Key evidence for the RNA first is that there are RNA molecules that are self-replicating. There are also reasonable precursors to RNA that could fulfill the roll that have more favorable energy characteristics. ",
"The container problem seems to be reasonably easy; phospholipids self organize into spheres and wave energy mixing things up would eventually get the right molecules within the right sphere.",
"Where it happens; people have proposed life originating in deep space, or chemosynthetically at deep ocean vents as well as the warm little pond. A recent paper supported the warm pond style hypothesis by examining the proteins that all known life has in common, and concluding based on something (not sure what!) that Earth's surface temperature/pressure was optimal in some way.",
"Hope this helps!"
] |
[
"We don't know. There are a lot of potential ideas and the current favorite seems to be archean volcanoes. We have yet to really see when life began (it goes back to 3.8 billion years ago). So we don't know in what time period it would have started and therefore don't know the conditions that were prevailing at the time. If life did start before 3.8 billion years ago (which seems probable since the life we have evidence for at 3.8 billion years ago may have been capable of photosynthesis) we have a problem because the rock record only goes back to 4 billion years ago. Before that we rely on hadean zircons which go back to 4.3 billion years ago. ",
"TL;DR: We have no idea when or how life began"
] |
[
"Jack Szostak is investigating this in his lab.",
"Here's a paper"
] |
[
"Where do the dead bodies of the deep-sea creatures go?"
] |
[
false
] |
Human dead bodies that are usually dumped in the ocean, tends to float and usually gets found near the shores. So why haven't we found any of the dead bodies of the mysterious creatures that live in the deep sea, i.e. in areas where the sun light doesn't reach? Don't these dead fishes float? Or have they occasionally been found by fisherman but just tossed away without much scientific study done on them?
|
[
"Many organisms sink after death. The deep sea ecosystem depends on these infrequent food sources. ",
"Abyssal Megafauna",
" are adapted to survive relatively long periods between opportunities.",
"Blue whales, for example, will float at the surface for a short period of time as the bloat and gasses build in their body cavities. However, once the integrity of the carcass fails, they sink and provide an ",
"ecosystem unto their own for years."
] |
[
"Because when they die, other creatures eat them. It's a long way to float from the deep sea to the beach."
] |
[
"http://www.youtube.com/watch?v=rdI3eFrTGs8"
] |
[
"Best copy of \"On the Origins of Species\" to buy."
] |
[
false
] |
[deleted]
|
[
"It's one hell of a dry read, you can ",
"download it here",
" if you really want to read it. It's not really a book for the general public though. I've got a slightly damaged copy from the late 1800s which I got from ebay for under $10.",
"tl;dr: We can make new breeds by \"artificially selecting\" dogs, pigeons and horses for breeding, to get the traits we want. Nature does \"natural selection\" based on environmental conditions, which results in new species.",
"My favourite book on evolution is The Ancestor's Tale by Richard Dawkins, it's much longer than The Origin, but it's broken into small digestible chunks. It's 40 short chapters split into sections which describe a branch in the tree of life, going back to the start. Dawkins basically describes what we know, why we know it, what we don't know, what the different arguments are, and what he reckons is most likely when there's no evidence. ",
"The introduction and parts on human evolution and where the evidence comes from were a bit boring IMO, but later on when he gets into things like how whales returned to the sea after being hippo-like animals, how the peacock's tail evolved, or why the social insects work together it's really interesting. My favourite parts were the chapters on microbes, there should have been more of that. Oh and ",
"ring species",
", those are awesome!",
"Don't let his books on religion turn you off, he's a world leading authority on evolutionary biology."
] |
[
"Don't be surprised if the words/terms are archaic, and his arguments seem somewhat haphazardly organized. In the early days of such theories, people hadn't fully figured out the relations between all these new concepts, yet.",
"Also, don't be surprised if Darwin's understanding of natural selection is slightly different from the one we have today. He may have been the first to propose it, but it was refined in the many decades since, both theoretically and experimentally.",
"Lastly, he repeats himself, a lot. That was the style back then, in which he pretty much wrote an extremely long essay, gathering more and more evidence - very verbosely - but repeating his arguments and conclusions every time. But, you see, he had to convince a lot of people who've been educated against evolution.",
"(To be honest, I would suggest reading the modern books that others have suggested, to get a strong basis of understanding of the theory and where we are today, and then reading Darwin's texts to see how they link up.)"
] |
[
"Isn't there one that comes with a forward from kirk cameron that has a bunch of modifications? I would avoid that one unless you want to laugh."
] |
[
"What's the name of a phenomenon where we tend to notice some things much more while we are constantly thinking about them?"
] |
[
false
] |
For example, one day you just start noticing birds, and end up noticing much more than usual and you could swear there weren't so many birds before, but in reality there was the same number of birds every day, only your mind was occupied with searching for them. I hope I am being clear enough. Is there a term for this specific phenomenon?
|
[
"Availability heuristic",
" or ",
"priming"
] |
[
"Frequency illusion is also popularly known as Bader-Meinhof phenomenon."
] |
[
"Frequency illusion is also popularly known as Bader-Meinhof phenomenon."
] |
[
"Is there an opposite of albino? Can a white person be born black?"
] |
[
false
] |
[deleted]
|
[
"The disease exists, but I haven't found evidence of it in humans. Its called Melanism.",
"EDIT: Black Panthers are an example of this"
] |
[
"As DarkGrenchler rightly pointed out, Melanism is your culprit, but I thought I would cover the 'evidence in humans' part.",
"Dr. David Henley points out",
" that the closest presentation in humans is ",
"Peutz-Jhegers Syndrome",
".",
"It is a condition characterised by colonic polyps and patches of hyperpigmentation on the lips, gums, inner lining of the mouth, and facial skin, genitalia, and palms. There is a Familial version that is inherited, and a Sporadic version that isn't.",
"He notes a more general dark skin presentation can happen in ",
"Addison's Disease",
", but it isn't as close of a match to your question (opposite of albino)."
] |
[
"Thank you for adding this, because I was a tiny bit confused. Seriously."
] |
[
"If Scientists want to clone a Mammoth using Mammoth DNA, why don't Scientists try to clone early Human life using DNA found."
] |
[
false
] |
I think it would be really cool to clone a neanderthal and show him the new world!
|
[
"I'm not sure if the genetic material preserved in such cases is of adequate quality to attempt cloning.",
"Even if there were, contemplating the political/ethical/religious backlash would be make any public-facing researcher decide against attempting such a thing. ",
"However, given a permissive political/ethical/religious environment, adequate funding, and well-preserved genetic material, the technical barriers to attempting such a thing would be easily conquered."
] |
[
"They only have about 60% of the Neanderthal genome at present as far as I'm aware. And this is from only 3 individuals. ",
"http://www.time.com/time/health/article/0,8599,1987568,00.html",
"http://www.huffingtonpost.com/2012/03/20/neanderthal-eyes-brown-dna-study-genome_n_1367426.html",
"I do wonder if it would be possible to extract and isolate Neanderthal DNA from modern humans."
] |
[
"Does anyone know of any papers reviewing the cases of decently well-preserved hominid remains?"
] |
[
"Ask Anything Wednesday - Engineering, Mathematics, Computer Science"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"The sum of all integers is a divergent series, and because it's a divergent series, it doesn't sum to anything. In fact, with divergent series, you can often times make them \"sum\" to almost anything. Look at a slightly different version of your series:",
"1 - 2 + 3 - 4 + 5 - 6....",
"Note if you decide to put parenthesis like this:",
"(1-2) + (3-4) + (5-6)... you get -1 + -1 + -1.... and you head towards negative infinity. But if you instead rewrite the sum as:",
"0 + 1 - 2 + 3 -4 + 5 - 6.... and do the same grouping you get",
"(0 + 1) + (-2 + 3) + (-4 + 5).... and so now you are heading towards +infinity. ",
"The fact is, sums of divergent series do not exist, so there is no answer to what the sum of all positive numbers equals. That being said, there are useful techniques for assigning a value to divergent series, and the one that assigns it -1/12 is called the ",
"Ramanujan summation",
"."
] |
[
"The sum of all integers is a divergent series, and because it's a divergent series, it doesn't sum to anything. In fact, with divergent series, you can often times make them \"sum\" to almost anything. Look at a slightly different version of your series:",
"1 - 2 + 3 - 4 + 5 - 6....",
"Note if you decide to put parenthesis like this:",
"(1-2) + (3-4) + (5-6)... you get -1 + -1 + -1.... and you head towards negative infinity. But if you instead rewrite the sum as:",
"0 + 1 - 2 + 3 -4 + 5 - 6.... and do the same grouping you get",
"(0 + 1) + (-2 + 3) + (-4 + 5).... and so now you are heading towards +infinity. ",
"The fact is, sums of divergent series do not exist, so there is no answer to what the sum of all positive numbers equals. That being said, there are useful techniques for assigning a value to divergent series, and the one that assigns it -1/12 is called the ",
"Ramanujan summation",
"."
] |
[
"PEMDAS is a set of evaluation rules. They are a mnemonic of conventions which exist to eliminate ambiguity of notation:",
"It's perhaps worth noting that certain calculators ignore this by construction, and evaluate an input expression on each operator input: they cannot properly evaluate expressions like ",
"1 + 2 × 3",
", and the user must input it appropriately if they want the right output (7) ",
"2 × 3 + 1",
".",
"Besides the commonly-encountered infix notation, seen above in ",
"1 + 2 × 3",
", prefix or postfix notations which are well-formed are unambiguous and do not need parentheses and other precedence rules.",
"If different notation rules were employed, the way we write formulas would change. It is not foundational to mathematics. It may have some non-trivial consequences on programming languages (associativity enables a lot of optimisations)."
] |
[
"I just sat in my kitchen in silence for an hour and didn't notice the clock on the wall ticking until thirty seconds ago. How does the brain prioritize sound?"
] |
[
false
] | null |
[
"It's not so much prioritization, it's more that the auditory section of your brain underwent ",
"neural adaptation",
" to the stimuli (clock ticking) so that you no longer consciously registered it. ",
"This process occurs for much of the information taken in by your sensory system - for instance, you're probably not aware of your clothes touching your skin or the objects in your peripheral vision until I call attention to them. ",
"Generally, the brain only remembers novel, emotional or interesting stimuli, and much of the information we take in is subsequently discarded and thus not stored in memory.",
"The neural mechanisms behind this habituation were worked out by Eric Kandel in the ",
"Aplysia model",
", for which he won the Nobel prize."
] |
[
"It is maddening to hear a clock ticking all the time - as novice hearing aid users can attest",
"When hearing deteriorates this adaptation to background sounds is lost. If you don't hear a sound then there's nothing for the brain to adapt to.",
"When people start using hearing aids, sounds like the ticking of a clock can be really infuriating. The brain has lost its adaptation to the usual background sounds of life. Everything is unusual so it's all treated as potentially threatening and you pay attention.",
"It takes weeks, maybe months, for the adaptation process to be restored so that the background is no longer noticed"
] |
[
"Your brain doesn't have the power to process all of the information that is sent to it at any time. It has to pick and choose what to focus on and what to ignore. Inconsequential things, like the clock ticking or your clothes touching you, are ignored so more important things can be processed."
] |
[
"If I have a meal that is only 1 cup of olive oil (i.e. 100% lipid) ... how will my body synthesize it? Will excess be stored as fat, excreted in feces, or other? What parts of the digestive system will it strain?"
] |
[
false
] |
Of course it's not a healthy meal .. but lets ignore the aspect of lacking other nutrients for a moment. I'm interested to know what the body does if we consume more lipids than we need in a meal.
|
[
"1 cup of olive oil is about 237ml which is somewhere around 219.55g of olive oil. Give or take a little error most fats work out around 9cal per gram. So your cup of olive oil is about 1975.95cal. This is going to be around the entire per day calorie consumption for many folk.",
"So what is going to happen if you chug this down? First up it will completely overwhelm your stomach. I happen to know that there is a good chance you will just bring back up that kind of volume of fat (don't ask I was young and stupid).",
"If you keep it down the the fat will leave your stomach and enter your duodenum. This is where your digestive system emulsifies the fats you've eaten so they are dissolvable and can be digested. Your digestive system uses bile acids as the emulsifier but there is only so much bile acid on hand for any given meal. Your gallbladder has a capacity of about 40-70ml so that's as much bile as you might have on hand. A high fat meal will cause the gall bladder to empty over the course of an hour of digestion. Although bile is very concentrated and capable of emulsifying a lot of fat but because your meal has neglible water content not a great deal of fat will emulsify. The emuslfied fat forms 'droplets' of fat 4-7nm across.",
"Moving forward the emulsified fats are now available to lipase enzymes which will start to break the fats in to shorter chain fatty acids and monoglycerides. As this happens the breakdown products pinch off from the emulsified droplets in to tiny micelles (1µm in diameter). These micelles now facilitate fat absorption by the gut lining.",
"At this point there are two fates for the fats your consumed. The first is to be absorbed and metabolised in the body and the second is to pass down through the gut and encounter the bacterial populations in your lower intestine. ",
"Fat metabolism is mind-bogglingly complicated but I'll give you the fairly brief overview. The tiny, tiny micelles break up and reform continually and when their contents are exposed they are available for the cells lining the gut to absorb. This is how the chain fatty acids and monoglycerides get in to the gut cells. Inside these first gut cells the fatty acids and monoglycerides are re-assembled in to TAG: triacylglycerol (3 fatty acid chains and bound to a glycerol). The TAG is then exported out of the cells in to the lymphatic system packaged up inside of the first of the lipoproteins, a chylomicron which is the least dense of the lipoproteins.",
"Chylomicrons make their way in to the blood stream where they circulate in the body and deliver the TAG contents to various tissues, fat tissue, muscles, the brain etc... Typically the liver breakdowns and recycles lipoproteins, by entering the lymphatic system first this ensures that fats you've eaten get taken round the body and delivered first.",
"The liver is the site of the recycling of lipoproteins and it is responsbile for building the other main classes of cycling lipoproteins. Any chylomicrons that make it to the liver will be broken down, which controls their build up in the blood steam. The liver can also synthesise its own chylomicron-like lipoprotein particles; VLDL (very low density lipoprotein). When the body's demands for fats is high the liver increases it's synthesis of these particles. The new TAG for these particles is synthesised from the sugars in your diet and from recycling bits of the chylomicrons and so on. The liver also breaks down TAG in to keton-bodies. These are small molecules which cells can use as fuel (instead of sugars). When you \"burn\" fats they must come out of your fat tissue, get transported to your liver in a lipoprotein particle and then be broken down to ketone bodies which then circulate in the blood and are taken up as fuel ",
"But you've eaten A LOT of fat so you've likely got a large excess of chylomicrons or VLDL circulating. The body will try and store excess fuel and for fats this is under the control of insulin. Your insulin levels cycle during the day under 2 controls; firstly you have a circadian cycle where insulin levels begin to rise just before meal times and in part initiaite hunger (this is likely a trigger for waking in the moring too), over laid on to that glucose consumption causes the pancreas to output extra insulin. ",
"Insulin principally signals 2 things: It tells your fat tissue to start taking up TAG and tells your muscles to stop taking up TAG. Insulin tells your muscles (and brain) to preferentially take up and burn the sugars in your blood stream and to store any circulating fats. Under a normal diet this is good, you store some of the fats furing and after eating so that between meals (and especially during sleep) you can metabolise the stored fats. One hypothesis here is that a diet high in sugar and fat will see you store lots and lots of fat because the continually elevated levels of insulin ensure you only ever have the \"store fat\" signal turned on.",
"But this isn't what your cup of olive oil meal looked like. The likely outcome in this case is that some fats will be stored in response to the circadian increase in insulin but in the main the chylomicrons and VLDL that are circulating will continue to do so. Over enough time the TAG in these lipoproteins will be broken down to ketone bodies and burnt as fuel so in this scenario you likely\nwon't feel hungry for quite some time, as you might predict if you chugged a cup of oil.",
"In the meantime the excess fats you consumed which couldn't be absorbed are passing through your gut. Once they hit your large intestine they encounter and ever increasing population of bateria. Fats in your diet preferentially favour different populations/species of bacteria such as Bilophila, Turicibacter, and Bacteroide lactic acid bacteria, Actinobacteria, and Verrucomicrobia. In the main bacteria are somewhat less optimised to digest fats than they are to digest sugars and we can expect a measurable amount of the olive oil to pass through to the colon.",
"High fat in the colon causes stools to be pale or fragmentary or very light (or some combination of all 3). If you regularly pass pale, floating stools and your diet is normal you may have a fat digestion problem that needs checked out. Otherwise under the \"cup of olive oil\" meal you might expect one or two subsequent stools to be a bit 'odd' and then for everything to go back to normal."
] |
[
"great detail - thank you.",
"now this begs two followup questions : ",
"(1) i often will have a big salad with maybe half a cup of oil (and some vinegar or lemon juice) as dressing (i'm italian, so it's ok, we love olive oil). will these extra ingredients, including the leafy greens, tomatoes, onions, cucumbers, etc dilute any of what you have described?",
"(2) ok, now lets add a thick steak to the above meal. I understand this has a fair amount of fat built in. We are now close to consuming a full cup of oil. Again, how does all this extra chunk of animal protein affect the overall digestion.",
"Maybe i've overestimated the total amount of lipid .. perhaps it's only half a cup total .. but then the question is at what point is it \"too\" much oil for a desired meal?",
"thx again!"
] |
[
"I'd guess that you are probably over estimating the amount of oil (maybe not). 2 tablespoons of oil on a side salad would make it noticeably greasy.",
"Nevertheless in either the steak or salad scenario the additional food will both slow down the rate of passage of the food and make the fat less concentrated. Your stomach and intestine have more matter to process. This will mean that what you're eating will spend more time in your small intestine so there's a good chance you'll manage to emulsify more of the fat and in turn digest more of it.",
"but then the question is at what point is it \"too\" much oil for a desired meal?",
"This very much depends on what your lifestyle and diet look like and who you are willing to believe about what constitutes a balanced diet.",
"The conventional advice would place the RDA for fat around 70 to 90 grams per day. That is quite a bit shy of half a cup. However RDA advice assumes a balanced diet ought to derive the majority of its daily calories from carbohydrates. There are certainly several schools of thought here and different human populations, that appear to be healthy, consume the balance of their calories quite differently. Traditional Inuit populations have tended to have very, very high fat and low carbohydrate diets. People following paleo diets will also skew in that direction. RDA guildelines were mostly drawn up during a period where it was believed that high fat consumption was linked to heart disease risk but the evidence shows that there is no link between lifetime fat consumption level and incidence of heart disease (for metabolically normal people). This suggests RDA guidelines are much too conservative on the acceptable daily fat consumption.",
"Wherever you fall on these issues a balanced diet is probably best thought of as one which provides you with no more and no less calories than you need each day and provides you with sufficient protein, vitamins and minerals. The exact split of fat to carbs in your diet likely isn't too important as long as you are nor over consuming food."
] |
[
"I have a disgusting question about rotting bread."
] |
[
false
] |
[deleted]
|
[
"Maggots don't just appear when things get old and moldy...All you need is a fly to lay eggs in it. I once read that the time frame between eggs being laid and maggots hatching is only about a day. ",
"I would conclude that the bakery probably has a fly problem. Some flies laid eggs on your bread, and within a day or two, the maggots hatched. "
] |
[
"So do flies not normally lay eggs in bread? I've never seen a maggot in bread before, even old bread that is open to the air."
] |
[
"I'm not sure where flies prefer to lay eggs, but I do know that fly larvae aren't exactly the most mobile creatures. Some how, eggs did end up in your bread."
] |
[
"How do today's computers know not to \"hyperprocess\" old apps and games made to run on a 200MHz processor, for example?"
] |
[
false
] |
I was rummaging through my shelf and found a copy of 102 Dalmatians, and old childhood memory. Made in 2000, for Windows 95/98 computers, needing only 32MB of RAM and a 233MHz processor and only 100MB of space to install, it's and very lightweight game for today's computers. I installed it on my desktop with its 2.9GHz Pentium and 4GB of RAM, and it installed and runs fine....but how does my computer know not to run the game at lightspeed and make everything sped up by 20x? I didn't configure any extraneous execution settings, such as Compatibility Mode or anything. It just installed and runs at a smooth 30 FPS. It's locked at that, but it never goes any lower than that. To add on, I also have a copy of Cabela's 4x4 Offroad Adventure (again made for 95/98 but also XP) and it run super speed. Haven't found a way to fix it.
|
[
"I'm not sure what they do use, actually - maybe someone with more experience in the area can answer that.",
"All simulation happens in terms of \"delta-time\" or the length of a single frame, typically measured in seconds as a floating point number, and there are two general approaches to it:",
"The operating system offers an API",
" ",
" ",
" which gives accurate (down microsecond precision, sometimes even better) measurements of how much time has elapsed since some arbitrary reference point in time (often the point when the program was launched.) As the game's simulation is iterated, after each iteration the time spent between frames is measured and propagated throughout the simulation. E.g. for a very simplistic simulation, for an object moving at velocity ",
"v",
", you would update its position to be ",
"x_1 = x_0 + v * dt",
". This is called ",
"An alternative to passing along the measured time is to instead fix the simulation to a certain frame rate, for example 60 frames per second. For this purpose the operating system offers an API that lets your game process sleep (not move forward to the next iteration) for a certain amount of time; supposing 60fps, your frame should take 16.66ms to process but if it only took 5ms then you would sleep for 11.66ms to match the desired rate. An alternative API is one that allows you to wait for the video output system's vertical synchronization point (vsync). In this case the program may be hard-coded to always use exactly the expected frame time for its simulation, even if it doesn't correspond to reality. This is called "
] |
[
"They don't know not to \"hyperprocess\". It's a matter of how the game was programmed. If it uses the actual clock rate of the processor as its timer, it will not run properly on processors other than those in the range it was designed for. As you noticed, some older games are like this - it was such a problem that some manufacturers used to put \"Turbo\" buttons on their computers so that you could artificially slow the processor to play old games properly. But modern games don't use the processor as their clock. I'm not sure what they ",
" use, actually - maybe someone with more experience in the area can answer that. But the fact remains that instead of being directly tied to the processor's clock rate, they get their timing from somewhere else."
] |
[
"Ironically enough, pressing the Turbo button actually ",
" your computer to the 4.77MHz clock rate of the original 8088.",
"Many processors now have something called \"Turbo Boost\" (Intel) or \"Turbo Core\" (AMD) which do what you'd think: speed up the processor. That's unrelated."
] |
[
"We can find Martian meteorites on Earth. But can we find Terrestrial meteorites on Mars ?"
] |
[
false
] | null |
[
"Yeah, there's no particular reason we shouldn't be able to, but finding meteorites is rather difficult, even on Mars where there's much less atmosphere to stop them. We just haven't explored the planet thoroughly enough with rovers to find any coming from Earth yet."
] |
[
"They’re also pretty easy to find on earth. Most of the Mars meteorites found have been found in Antarctica. They fly along at low altitude over the ice and look for rocks. If they find a rock on top of the ice, chances are it’s extraterrestrial."
] |
[
"In theory yes but they would be much rarer than Martian meterorites, since Earth is much more massive than Mars so has a higher escape velocity, we have a much thicker atmosphere so more energy is lost to drag and meteors are much less likely to reach the surface.",
"Tl;dr You basically need to hit the Earth with a much bigger rock to knock bits off into deep space than Mars."
] |
[
"What causes cankersores and how can you prevent/heal them quicker?"
] |
[
false
] |
[deleted]
|
[
"Also, avoid toothpastes with ",
"Sodium Lauryl Sulfate",
"."
] |
[
"http://www.webmd.com/oral-health/guide/canker-sores"
] |
[
"<grin> It was such an easy web search..."
] |
[
"If Jupiter is gas giant does it have a surface that you could theoretically stand on ?"
] |
[
false
] | null |
[
"This is a cool question with a (scientifically) cooler answer: We have no idea!",
"Nothing we have, no sensor or probe or anything, can grind through the chaos that is Jupiter's ever thickening layers.",
"These guys at NASA",
" are pretty smart though, and they say that at some point you're going to encounter liquid metal hydrogen.",
"Let me just say that again, because it's pretty friggen cool:",
"LIQUID METAL HYDROGEN!",
"Ahem, anyway!",
"We're talking about (theoretically) temperatures hotter than the surface of the sun. Physics and chemistry kind of take a vacation when you get that deep, and just start making stuff up.",
"But I'm betting that rather than being able to stand on it, you would melt in a rather pretty fashion.",
"Edit: To remove my excited swearing.",
"Edit 2: Yes, I know that physics and chemistry still apply. I was anthropomorphizing science, because we all know what a big sexy beast she is, even when she goes off the deep end.",
"Edit 3: Hey, pro_astronomer is here, you should probably check out his posts since he's... a pro astronomer. :)",
"Edit 4: Gah, didn't realize the thread would take off. o-o Right ",
"liquid metalic hydrogen",
". In a nutshell, when you take hydrogen and put it under four MILLION bars of pressure, you get liquid metalic hydrogen (there are other ways to produce it, but we're talking Jupiter of course). It's hydrogen that flows like Mercury, and likely is the (or one of the) source(s) of Jupiter's magnetic field. It's likely a ",
"superconductor... AND a superfluid",
", trasitioning between these phases. This is kind of the upper limit of my knowledge of the stuff, please don't hurt me.",
"Final Edit: Thanks for the love guys, I'm off to bed here in the UK. Plenty of experts here now, who I'm sure will love to answer your questions! =)"
] |
[
"Fluid gasses? o.o"
] |
[
"Fluid gasses? o.o"
] |
[
"In this pic of Mercury, what is the giant flat plain? This is the only picture of Mercury showing this plain and I cannot find any information on it."
] |
[
false
] | null |
[
"As others have mentioned, your map of Mercury was built by assembling lots of pictures taken by Mariner 10, and the \"flat plain\" is an area where data is missing. But the missing data problem is worse than it looks! Your map shows the ",
" side of Mercury. Here's a rectangular map that shows everything we knew about Mercury until a few years ago:",
"https://www.nasa.gov/images/content/285929main_img5.1.jpg",
"Your strip of missing data shows up, but ",
" We had no idea what this side looked like until the Messenger spacecraft arrived 40 years later in 2011.",
"The reason is kind of interesting: Mercury rotates on its axis 3 times for every 2 times it goes around the sun. The Mariner 10 spacecraft flew by Mercury once every 2 times Mercury went around the sun... and so each time it flew by, the same side of Mercury was facing away from the sun, in darkness and impossible to photograph.",
"NASA knew about this, of course, but there wasn't enough fuel to get Mariner 10 into a better orbit."
] |
[
"Great explanation, thanks!",
"It's crazy to me that people understand orbital mechanics well enough to calculate the best trajectory for maximum surface coverage for stuff like this. ",
"Or the one that orbited that asteroid like 11 times before landing. Unrelated but this just is just incredible: ",
"https://i.imgur.com/TUkKuhf.gif"
] |
[
"According to ",
"this site",
" there has only been one mission to mercury. It said only 45% of it has been mapped. I'm assuming that the blank is not a giant plaine, but the 5% of that side of the planet that was not mapped.",
"Edit: The source is outdated. There has been a more recent mission to mercury that took better pictures. Read other comments for more details. "
] |
[
"A friend described plastic particulate in the ocean as being just as dangerous for organisms living there as sharp broken glass lying around is for us. Is this a fair comparison?"
] |
[
false
] | null |
[
"You might have wondered this because it's already been researched."
] |
[
"You might have wondered this because it's already been researched."
] |
[
"And is there?"
] |
[
"How does the brain interpret the passage of time?"
] |
[
false
] |
For example, we are all capable of counting down (ie we have an internal stopwatch). What mechanism allows us to monitor time passage relatively accurately?
|
[
"That's of course not true. The ability to measure time across a broad range of scales is necessary for proper brain function. And by function, I mean to do things like walk, perceive, and plan actions and sequences of actions. We know this also from psychophysical experiments. Time estimation follows normal pschophysical laws, and just noticeable differences in time tend to run at about 10% of the base time over a variety of scales (but breaking down when you get to less than a tenth of a second as the base time - a kind of floor limit).",
"The precise mechanisms are not known, but studies implicate certain brain regions like the striatum and cerebellum and prefrontal cortex, and here is a review going over the necessity of time estimation to the brain, and the current status of the field. ",
"http://www.jneurosci.org/content/25/45/10369.full"
] |
[
"Humans rely on environmental factors to monitor the passage of time. The most primitive of which being the sun, and how our circadian rhythms relay back to our brain when a day has passed. If we were locked in a window-less room, we would be very inaccurate at telling the time. We could guess based on our own bodies i.e length of beard, amount of times we urinate etc etc, but these guestimates are purely based on past experiences we accrued from our environment before we went in this room. We would have no idea, for example, how long we had slept ( which is very common anyway after a heavy night out! ).\nTo summarise, we are not genetically predisposed to tell how much time has passed, and rely heavily on environmental factors."
] |
[
"I think this only partially answers the OP's question. How does the brain measure time exactly? Is there a neural structure that measures time passing like a pendulum clock? I understand the cerebellum is largely responsible for rhythm, but is there a subconscious effort at play as well?"
] |
[
"Do solid or porous objects with open pores actually deform under uniform hydrostatic pressure, such as under water?"
] |
[
false
] | null |
[
"Yes, in general they will, but not because the pores collapse. Provided that the surrounding fluid can enter the pores, the main compression is elastic compression of the solid itself, which should generally result in a self-similar shrinkage (provided the solid is a uniform material)."
] |
[
"Note, however, that the decrease in volume is generally tiny because the bulk modulus of condensed matter is quite large. This may be what the question is getting at. The bulk modulus of a polymer is generally a few GPa; even if you move a solid cube of plastic to the bottom of the Mariana Trench, it'll compress by just a few percent on a side. Water would be similar, metal even more dimensionally stable. That's why we can generally idealize condensed matter as incompressible.",
"EDIT: This point is often confused. ",
"Even on Stack Exchange",
", one of the members claims that \"squashy\" neoprene would compress a great deal under hydrostatic pressure. This is not true. Solid neoprene has small shear and Young's moduli (meaning it's easy to shear and stretch), but its bulk modulus is still very high (side note: the imbalance results in a Poisson's ratio of just about exactly 0.5). It's just about as hard to push the C atoms together in neoprene as it is in any other organic polymer."
] |
[
"Good point!"
] |
[
"Can extra organelles be added to cells?"
] |
[
false
] |
[deleted]
|
[
"Yes, it's not easy but scientist have done something like that in zebrafish:",
"Agapakis, Christina M., et al. \"Towards a synthetic chloroplast.\" PLoS One 6.4 (2011): e18877.",
"There is also a slug that can do something like that by stealing chloroplast from algae."
] |
[
"Mitochondria and chloroplasts have their own DNA, so its a bit different from other organelles. The first cell that absorbed a mitochondrion or a chloroplast didn't have to reprogram their DNA as such initially, they would have just divided with the mitochondria dividing inside also. Its a pretty huge change though, picking up a symbiont successfully and then becoming one organism, so there is a reason it has happened only twice to our knowledge. It would also be more complicated with multi-cellular organisms. I think the answer would be yes theoretically but unlikely and difficult to do artificially."
] |
[
"Mitochondria and chloroplasts have their own DNA, so its a bit different from other organelles. The first cell that absorbed a mitochondrion or a chloroplast didn't have to reprogram their DNA as such initially, they would have just divided with the mitochondria dividing inside also. Its a pretty huge change though, picking up a symbiont successfully and then becoming one organism, so there is a reason it has happened only twice to our knowledge. It would also be more complicated with multi-cellular organisms. I think the answer would be yes theoretically but unlikely and difficult to do artificially."
] |
[
"Do vaccines prevent or reduce the likelihood of mutations?"
] |
[
false
] | null |
[
"The part that is not flawed premises has been recently asked. Vaccines can and do entirely prevent replication, and there have been questions about the effect of vaccines on mutation (global prevention because of reducing the pool of variation)."
] |
[
"Do you have a source on this? I'm completely out of the loop and would like to read up more about this."
] |
[
"Multiple previous questions on ",
"r/askscience",
"."
] |
[
"What exactly is it about lack of sleep that creates or worsens undereye bags?"
] |
[
false
] | null |
[
"That location of skin is thinnest on the body. What you are seeing is happening to all of the skin but most visible due to the thinness.",
"Sleep is when many of the adrenal hormones (glucocorticoids, epinephrine) are replenished. Without sleep there is a lack of these hormones. These hormones also police blood pressure, without enough the veins sag, causing the dark color (the blue combines w skin tone to create dark). ",
"There is also dehydration going on in sleep deprivation. All these factors contribute to create circles which eventually become bags.",
"EDIT: I got gold for askscience!? This is my nerd dream. Thank you so much!"
] |
[
"Hormones control a ",
" of what keeps you in working order.",
"Here's an article about adrenal hormones and how they help control things like salt balance in your bloodstream.",
" Too little aldosterone -> too little salt in your blood -> less osmotic pressure hydrating your cells. The water just doesn't get absorbed.",
"A source that talks more directly about how osmotic pressure is needed:\n",
"http://www.vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/absorb_water.html",
"This isn't my field though, so if anyone more expert could chime in that would be welcome.",
"EDIT: While checking up on my first source I found that it's a chiropractor promoting \"holistic\" approaches to health, but at least he doesn't seem to be a nutjob so far. Just trying to promote healthy living. At any rate, there are other sources backing up his characterization of aldosterone's involvement in salt retention.\n",
"http://en.wikipedia.org/wiki/Aldosterone"
] |
[
"Why would sleep deprivation cause dehydration?",
"Assuming you keep drinking fluids, wouldn't you remain adequately hydrated?"
] |
[
"How do we recognize people when they are too far away to see distinct details?"
] |
[
false
] |
While driving today I noticed someone a fair distance away and immediately thought it was a coworker of mine, and I was right. I could't see her face, and there isn't anything unusual about her, so how/why did I think it was her? What are we recognizing when we can't see faces or other obvious identifiers, but still know who we are seeing?
|
[
"We use a whole host of cues. One surprisingly effective cue is (biological) motion - how we walk (",
"Troje et al, 2005",
").",
"For example, have a go playing with the ",
"biomotionlab app",
" to see what information you can extract from basic modes of articulation."
] |
[
"Ooo, you gave me a source! Thank you!",
"If I'm understanding it right, although motion is a effective means of identification, we aren't sure why, or what exactly it is we are picking up on. Do you know of some other sources that explain a bit more about identifying through motion?",
"What are some of the other clues we use? "
] |
[
"It does, thank you. "
] |
[
"How do plants know when to start blooming?"
] |
[
false
] |
Do plant hormones have something to do with it? Is it triggered by temperature?
|
[
"It has to do with the number of hours of light the plant gets each day. ",
"Here's an example: Indoor marijuana growers all know to initially grow their plants with 18 to 24 hours of light each day when they are young. When they want the plants to flower, they cut the light down to only 12 hours per day. That's what starts the process. "
] |
[
"According to the ",
"florigen",
" hypothesis, you would have to actually graft a leaf on to another plant to get it to flower and this may not work in all plants. ",
"Grafting is actually how the florigen hypothesis was discovered. The leaf would have to be producing a particular protein called FLOWERING LOCUS T ",
"source",
".",
"Assuming the hypothesis is true then the proteins that are involved are not volatile and there is no evidence in scientific literature that one flowering plant can trigger another plant to flower just by being in close proximity. ",
"edit grammar"
] |
[
"Since we're at it, can you explain how autos work? AFAIK they trigger flowering stage on their own."
] |
[
"AskScience AMA Series: I'm Jon Schwantes from Pacific Northwest National Laboratory, and my team is working to uncover the origin of uranium \"Heisenberg\" cubes that resulted from Nazi Germany's failed nuclear program. Ask me anything!"
] |
[
false
] |
Hi Reddit, this is Jon Schwantes from PNNL. My team and I are working to uncover one of history's great mysteries. During WWII, the United States and Nazi Germany were competing to develop nuclear technology. The Allies thwarted Germany's program and confiscated 2 inch-by-2 inch uranium cubes that were at the center of this research. Where these cubes went after being smuggled out of Germany is the subject of much debate. Our research aims to resolve this question by using nuclear forensic techniques on samples that have been provided to us by other researchers, as well as on a uranium cube of unknown origin that has been located at our lab in Washington for years. I'll be on at 10:30am Pacific (1:30 PM ET, 17:30 UT) to answer your questions! Read more here: Username:
|
[
"Did Heisenberg willingly obstruct/prevent the progress to an atomic bomb or was he genuinely trying to create one for the Nazis? \nIs there any scenario where they could have succeeded or was this impossible as they were unable to match the resources to match the manhatten project? \nThanks"
] |
[
"Since they have answered, I'll just chime in as a historian of nuclear weapons. The answer to the Heisenberg question, so far as serious historians can tell, is \"neither.\" Heisenberg was not trying to obstruct progress, but he was also not trying to create an atomic bomb for the Germans. The German atomic program was not a bomb program. It was a reactor program, sort of a \"pilot\" program to what you'd need to do to produce useful nuclear reactors. There is no evidence that Heisenberg tried to sabotage it (this was a postwar myth spread mostly by people ",
" Heisenberg, though he sort of implied that ",
" that was why they were so relatively unsuccessful). ",
"Rather, the evidence from the time indicates that the German physicists a) did not think an atomic bomb was possible to make ",
" (a key distinction), b) did not want to try and promise the German government that they could do this (since they didn't think it was likely possible to do), c) that an atomic bomb was ",
" for a German victory at the time (mid-1942) that they made this decision, and d) that getting the Germans to fund a small reactor program was plausibly military-enough to get funding, and would allow them to preserve a \"nucleus\" (if you will) of the German physicist community from the ravages of war. ",
"So in mid-1942, the German government decided not to pursue a bomb, but instead to pursue a modest reactor project. That is what these cubes are from. Even if they had gotten the reactor at Haigerloch working, it would not have been enough to make plutonium for a bomb. You would have needed a much larger reactor. The ",
"Hanford B Reactor",
" gives a sense of the size they would need — it could produce 200 g of plutonium for every ton of fuel cycled through it, and could cycle 30 tons per month. So that's basically 1 bomb core per month. The US built three of these reactors as part of the Manhattan Project, and it took over a year to build each one. Just to give a sense of size and scale. And even then, the Germans would have to simultaneously develop the means of extracting the plutonium from spent fuel, designing a bomb that could use it, working out the means of delivery (it would have been too heavy for a V-2), etc... they were not anywhere close to making a bomb. ",
"The last part of your question is the really interesting one: if they did spend a Manhattan Project's worth of resources (or a V-2 project's worth, for that matter), might they have been successful? It's impossible to know, but one thing that would have played a huge role for the Germans that didn't matter to the Americans is that Germany was under heavy aerial bombardment from the Allies by the late stages of the war. The US in particular was targeting any factories it suspected had a connection to atomic bomb research for bombing, and were also sampling river water for evidence of reactor usage. So the Germans would have had to defend their project against active attack, by an enemy who was looking for it. The US did not have to worry about this and could build ",
"gigantic",
" facilities without serious risk of enemy attack. The Germans would have either had to be very discreet, or be very lucky. ",
"If the Germans had ",
" the war, the wartime work could have led to a later bomb program, sure. But their wartime program was not expected to produce a weapon. The size of the endeavor was not nearly large enough. (During the height of the Manhattan Project, the US was spending more ",
" than the German program spent during its entire existence. The US program employed approximately 100X more people than the German one. Just to give you a sense of the relative scales. It was not really a \"race for the atomic bomb.\")",
"The best histories of the German atomic programs are by the historian of physics Mark Walker. His ",
" (Cambridge University Press, 1989) is the standard technical reference work. His ",
" (Perseus, 1999) is a very nice overview that is less technical and dives into the personalities (like Heisenberg) more. Both are excellent."
] |
[
"1st Question: I've read several times about the famous \"demon core\" accidents. Cubes seem like a very easily stackable form factor, are there concerns and/or regulations and/or common handling practices for the shapes fissile materials are produced in, to reduce the likelihood of a critical amount being stacked too close together?",
"2nd question: \"Lost Nazi Uranium Cubes (!!!)(!)\" is one heck of a sensational phrase! Has this been subject to any conspiracy theories, History Channel specials, or other wild rumors over the years, or was it too classified or obscure?"
] |
[
"How do light waves activate photosynthesis?"
] |
[
false
] | null |
[
"Actually, it was only very recently that the mechanism of converting light into energy via photosynthesis was discovered.",
"It's actually an incredibly complicated process that leverages some very interesting quantum properties of light and substrate interactions. ",
"Obviously, the structure, at the macro and microscopic level, of the chloroplasts has been known for quite some time, but the mechanisms for the conversion of light into stored energy within the chloroplasts is the tricky part.",
"For the basics: Leaves and most chloroplasts are green because they absorb almost all the other light wave frequencies and reflect those in the green spectrum, so why green? Well it turns out that there are a number of different chloroplasts that absorb different parts of the spectrum, and the minimal overlap just happens to be the green part of the visible spectrum. It's not only a reflection issue, because when a chloroplast absorbs a photon, it strips a certain amount of energy and emits a photon at a lower wavelength, and the ",
" of the different pigments' energy extraction and re-emission (known as chlorophyll fluorescence), and substrate reflection results in an observed 'green' energy level. When plants begin to hibernate for the winter, their leaves change color because certain chloroplast with specific pigments die faster than others, resulting in various shades of yellow or red becoming the prominent reflected color. ",
"Also, light is both a wave and a particle, and wavelengths represent increasing energy levels of the photons, a chloroplast is only capable of extracting a finite amount of energy which is depends on multiple environmental factors and can be quite variable across all the various pigments (resulting in about3-6% of the total energy available in a photon being utilized).",
"Now, as for how these organelles are able to take a packet of light and extract energy from it in a form other than heat / radiation, is through a process called quantum walking.",
"When a photon is absorbed into the photosynthetic cell (called a chromophore), the photon is converted into a quasiparticle known as an exciton, which virtually / simultaneously travels from cell to cell as a wave until the wave determines the most efficient path to the bottom of the chromophore. The wave propagation is very limited in size, so there are a series of points where the wave will convert to a particle (during a walk) and then convert back into a wave of a lower frequency (meaning energy has been extracted and captured by the chromophore). ",
"This energy is utilized to fuel the electron transport chain to synthesize ATP (light dependent reaction / photophosphorylation) which is used to combine carbon dioxide and hydrogen (provided from water) into a simple carbohydrate (CH2O + H2O) (light independent reaction); known collectively as the Calvin Cycle.",
"References:",
"http://en.wikipedia.org/wiki/Light-dependent_reactions",
"http://en.wikipedia.org/wiki/Light-independent_reactions#Calvin_Cycle",
"http://en.wikipedia.org/wiki/Chromophore",
"http://en.wikipedia.org/wiki/Quasiparticle",
"http://en.wikipedia.org/wiki/Quasiparticle",
"http://en.wikipedia.org/wiki/Photosynthetic_efficiency"
] |
[
"Very exhaustive answer, but I think you've used \"cell\" instead of \"molecule\" in a couple of places toward the end? Chromophores aren't a type of photosynthetic cell, but rather part of the light-receiving molecule; the exciton doesn't travel from cell to cell, but within or between molecules."
] |
[
"What I meant by cell wasn't in a biological sense, but in a more mechanical sense; as in sort of a quantum bucket where photons drop into. "
] |
[
"Why do we need dark matter and energy to explain accelerated expansion of the observable Universe?"
] |
[
false
] | null |
[
"There's a few things wrong with the assumptions behind the question. The universe is not expanding from a literal point in space, and dark matter is not part of any explanation of the accelerated expansion we observe, except maybe as a counter force to the expansion since it's exerting a pull. ",
"We also would not expect to see the universe expand at an accelerating rate without something acting on it to cause the acceleration. We don't know what that is, which is where \"dark\" part of the term dark energy comes from. We know something is increasing the expansion rate but it remains a mystery what that something is."
] |
[
"Thanks for your response. Putting dark matter here was a mistake.",
"Also, I thought that that Big Bang was like actual explosion, and expansion of Universe was a galaxies moving through space because of impulse they get as result of that explosion.",
"But it's the space expanding itself plus the galaxies moving through space. And in order to explain that last part, we need this extra force, correct?"
] |
[
"Pretty much, calling it the big bang is rather misleading since it wasn't an explosion but rather all of space rapidly expanding from a single point. We don't know how the universe will end but there are 3 solutions based on wether or not expansion continues, stops or reverses. The big crunch suggests that the universe will at one point stop expanding and instead, contract into an Infinitely small point. This theory also allows for the oscillating universe theory which suggests that the universe continuously expands and contracts, if this is the case then our universe may not actually be the first. The next theory, the big freeze suggests that eventually expansion just stops, nothing really happens after that, and then the big rip suggests that expansion will continue forever and will eventually reach a point where objects are so far away that the light will never reach them.",
"If there is something that I got wrong here then please do correct me."
] |
[
"Why does MRI use helium as cooling?"
] |
[
false
] |
I have read a bit about helium shortage and I just wonder why MRI-scanners does not use high temperature superconductors which could be cooled by nitrogen but is instead cooled by helium. Is the high temperature ones not strong enough, durable enough or what is the reason behind this choice by the manufacturers?
|
[
"The answer that I got to that from my old NMR grad-course teacher, was that that high-temperature superconductors can't handle the (huge) amounts of current required."
] |
[
"It's also that high-Tc superconductors tend to be brittle ceramic materials and can't be made into wires the same way that metallic superconductors can."
] |
[
"I guess that sounds logical. Thank you for your answer!"
] |
[
"Does a female express/pass on epigenetic changes in their germ cells?"
] |
[
false
] |
[deleted]
|
[
"A lot of the fun correlates that have been found (and are often cited on Reddit)",
"The \"grandparent starvation > grandchild obesity\" link the example I've heard. It seems to me there are many alternative explanations that don't involve epigenetics. For example, socialization, prenatal stress or selective mating patterns during periods of resource scarcity.",
"Females can influence chromatin states through the expression of noncoding RNA, which can be passed onto a developing embryo.",
"Do you mean that noncoding RNA from the egg cells persists after fertilization? If that's true, it could affect the gene expression in the zygote. But the embryo doesn't form until 2-3 weeks later, so I doubt it would affect the embryonic development. The half-life of miRNA/lncRNA is only a few hours, right?"
] |
[
"First things first, we are not sure how much epigenetic changes can be inherited. We know that sperm and eggs can have marks and packaging, but when the embryo is developing it appears to erase most marks and reform its chromatin state ",
"[1]",
". This is a less sexy idea but it is important to keep in mind. In my experience scientists who study this want direct evidence that an epigenetic state is inherited rather than assuming it is. That being said we do know that genomic imprinting and differentially methylated regions exist and influence gene expression. ",
"To me, ",
"this review in Nature Communications",
" does a nice job of explaining the state of the field. A lot of the fun correlates that have been found (and are often cited on Reddit) have either A.) Not been replicated or B.) Been tied to an underlying genetic mechanism (see review for good examples). It is very easy to correlate a condition to an epigenetic state, it is much more difficult to actually prove that is the origin.",
"On to your actual question, I should also make it clear that epigenetic reprogramming is not necessarily reliant on cell division. Chromatin remodeling complexes and DNA methyltransferases (the workhorses here) are able to act on cells that are not actively dividing. I am not a human researcher so I do not know if germline cells have any sort of restriction on activity, but I have never heard of it. Females can influence chromatin states through the expression of noncoding RNA, which can be passed onto a developing embryo. Whether or not this is epigenetic or not is up for debate and largely based on how you define things."
] |
[
"Do you mean that noncoding RNA from the egg cells persists after fertilization? If that's true, it could affect the gene expression in the zygote. But the embryo doesn't form until 2-3 weeks later, so I doubt it would affect the embryonic development. The half-life of miRNA/lncRNA is only a few hours, right?",
"I was referring to ncRNA that can pass from mother to child through the placenta ",
"[1]",
". I have also heard of a crowd chasing ncRNA in breast milk, but I have no idea what the validity or state of that is. The half-life of all ncRNA (and there are a lot of different variants) varies greatly, and I am not totally thrilled with our understanding of it currently. However, I would not expect it to live 2-3 weeks.",
"I should put a giant asterisk here and say that I am not a mammalian researcher. I listen to lots of their talks and read some of their papers, but I am definitely going to miss some of the story when you are referencing people (especially when it comes to development)."
] |
[
"Is There Any Scale Where The Distribution Of Electric Charge Within A Neutron Is Relevant?"
] |
[
false
] |
A neutron contains valence quarks with both positive and negative charges so tightly bound that on most if not all conventional scales the baryon as a whole can be treated as a single electrically neutral particle. My simplified layman’s understanding is that the strong force typically dominates the electromagnetic force on scales for which it’s relevant at all, but is there any scale where the electromagnetic force operating on the charged components of a neutron is relevant to understanding the behavior of those components or the neutron as a whole? Is this expected to change at sufficiently high energy states (e.g before discrete atomic nuclei formed)?
|
[
"The charge distribution asymmetry of a neutron would manifest itself as an electric dipole moment, but so far there has been no nonzero measurement of the neutron electric dipole moment. So, it's safe to say that it's pretty irrelevant. If we could detect it, it might indicate \"beyond standard\" physics, because the standard model prediction for it is so tiny.",
"The magnetic dipole moment, however, is non-negligible, to the point that neutron beams can be controlled with magnetic fields. Neutron scattering is an extremely useful tool for learning the magnetic properties of materials, because they bypass those pesky electrical properties."
] |
[
"It's really cool to see my area of research here. I work on the neutron electric dipole moment experiment for Oak Ridge National Labs. So far, searches for the neutron EDM have found nothing to the level of 10",
" e*cm. This is so small that, if you blew up the neutron to the size of the earth, the separation between quarks would still be smaller than a virus (this, of course, isn't separation in the traditional sense). ",
"The standard model of particle physics predicts something called CP (Charge Parity) violation, and implies that the neutron EDM, which also violates CP, should be around 10",
" e-cm. CP violation is one of the criteria needed to have more matter than anti-matter in the early universe, but the proportion is off, there exists a far higher fraction of matter than this CP violating term in the standard model predicts. There are many corrections to the standard model that theorists have proposed to fix this discrepancy, and among them, supersymmetry predicts the EDM of the neutron at 10",
" to 10",
" e-cm. ",
"Our experiment at ORNL is attempting to measure the nEDM on the order of 10",
" e-cm. If we measure it, this will be good evidence for supersymmetry, and some related theories. If not, then it just narrows the field of possible models even more"
] |
[
"As a layperson, it's equally cool to see such an interesting question addressed by someone who's hands-on with current research. Thanks so much for the contribution. :)"
] |
[
"Why do all the gas giant planets exist past the asteroid belt?"
] |
[
false
] |
[deleted]
|
[
"I'm also not an expert on planetary formation, but I wanted to point out that the sun is powered by fusion, not fission. "
] |
[
"I can't tell if you're trolling, so I'll just leave this here:",
"\n",
"https://en.wikipedia.org/wiki/Nuclear_fusion"
] |
[
"I'm more of a rocky planet guy, but I'll relate what I learned in graduate school. The gas planets formed on a much smaller timescale than rocky planets, and seemed to do so without accretion (the process by which rocks collide to form meteors collide to form planetessimals collide to form planets). A little over 4 billion years ago, where our solar system is now, there was a nebula of gas and dust. It seems that the sun formed by a process called gravity collapse, where a slightly higher concentration of matter near the current center of mass pulled more material into it than the rest of the ~uniform nebula. Suddenly, the most massive thing around in a growing ball of matter in the center of the nebula, which attracts all the surrounding matter, becoming more massive, and so on. This drew in a huge amount of surrounding material and fusion started. Now we have a \"doughnut\" of material just beyond the distance needed to suck into the sun (I don't know that distance, but lets say its some appreciable fraction or multiple of the asteroid belt's radius). Slight variations still exist in the distribution of matter in this disk. These slight variations cause smaller gravity collapses at a few locations in the remaining nebula, creating the gas giants. It's possible that the gas giants formed about the same time that the sun was forming.",
"Much of what is left between the gaseous planets and the sun is dust and rock trapped in orbit around the star. The process of accretion in the inner solar system was then underway. Again, as a disclaimer, this story may have changed since I studied solar system evolution."
] |
[
"How does a transplanted heart get signals from the body post op? As far as I've seen in me brief research they only reconnect the blood vessels, not the nervous system."
] |
[
false
] |
Without signals coming from the brain, how does the heart know to increase rate when the muscles and brain require more oxygen during exercise? Is it a chemical process, or is there something else at play?
|
[
"The heart has an inbuilt natural pacemaker (SA node). The brain controls the heart rate chemically through the blood stream with norepinephrine and adrenaline."
] |
[
"This is broadly correct, but it's worth pointing out that a non-trivial number of people receiving a heart transplant require a permanent pacemaker to achieve a satisfactory heart rate - I don't recall the precise figure, and I don't have access to journals at this computer, but I believe it's around 15%.",
"Left to its own devices, the SA node will generate around 110 bpm, though this number declines as the age of the heart (as opposed to the age of the patient, since we're discussing heart transplants) increases. The SA node is primarily innervated by the Vagus (Parasympathetic) and Accelerator (Sympathetic) nerves - and most people will have significant Vagal tone at rest, suppressing the SA node and resulting in a heart rate closer to 60 bpm.",
"One might therefore expect that transplanted hearts would beat too ",
", but in reality the most common outcome amongst patients who require pacemakers is bradycardia arising from damage to the SA node itself, resulting in a heart rate markedly lower than that required to maintain good function - and the lack of sympathetic innervation precludes the body's primary mechanism for increasing heart rate.",
"Edit: Vagal -> Vagus, my Anatomy teacher would tut sadly."
] |
[
"Here",
" is a very interesting research article on exactly the topic of your question! The previous posters have already touched on the more important parts of their conclusion, but in case you don't read this understand that heart rate post transplantation is caused to increase during exercise due to: the catecholamine epinephrine, stretching of the myocardium as a result of ventricle filling (which is actually more prominent post transplantation due to the pericardium of the heart being left open in some cases), and something called respiratory sinus arrhythmia (RSA) which usually inhibits actions of the vagus nerve but in this case is hypothesized to control cardiovascular activity innately - the mechanisms of which are still not quite understood. Hope this helps!"
] |
[
"What happened to the hole in the ozone layer?"
] |
[
false
] | null |
[
"Here's a neat article about it: ",
"http://www.smithsonianmag.com/science-nature/ozone-hole-was-super-scary-what-happened-it-180957775/",
"Though I know most don't come here for a long read so here's the tl;dr:",
"The hole being discovered contributed greatly to its reversal. Had it not been, it would have been quite a catastrophe. It's expected to be completely healed by 2050."
] |
[
"Two things:",
"The ozone hole has always been a temporary phenomenon. It occurs in early spring in the Southern hemisphere for a period of a few weeks to a few months depending on conditions. This is due to the dynamics of ozone creation/depletion and the buildup of ozone destroying chemicals in the upper atmosphere along with conditions that maximize ozone depletion (polar stratospheric clouds and, ironically, ultraviolet light from the Sun) overwhelming the rate of ozone creation.",
"Over the past few decades the acknowledgement of ozone depletion as a serious environmental problem led to international efforts to curb CFC production and emissions which has dramatically reduced CFC pollution and brought ozone depletion under control. CFCs are fairly long-lived in the atmosphere (which is why they were used and why they are problematic) so it will take decades for the ozone layer to fully \"heal\" but currently we're on track for that to happen within the next 25-40 years or so."
] |
[
"Thalidomide is actually quite interesting. There's a type of thalidomide that is completely harmless and works as it should. The other causes horrible birth defects but still works. These two types come from stereochemistry when producing the compound. It is very possible to separate the two types. Sounds great, right? Let's bring it back with only the good type. The human body actually, unfortunately, converts the drug between the two types in a 50/50 mixture meaning that the drug can never be safe"
] |
[
"We can only notice the progression through time relative to our own immediate environment. If there were a spaceship far away, how would they calculate time in relation to Earth's relative time?"
] |
[
false
] |
[deleted]
|
[
"You mean like if you wanted to keep an accurate Earth calendar, for historical reasons or whatever? The difference would be on the order of microseconds per day, at the absolute most. I don't feel like doing the maths to figure out the time dilation between the surface of the Earth and flat space right now, but it's 38 microseconds a day between the surface and low Earth orbit, factoring in both gravitation and relative velocity. It'd take years for the calendars to drift even a day out of sync. And since the separation would be light-years, or even light-",
" it couldn't possibly matter on any time scale shorter than millennia."
] |
[
"More than you'd care to do. There'd be tensors involved, let's just put it that way.",
"In practice, you'd just use pulsars. There are hundreds of them, they're extremely well mapped, and most of them are sufficiently rigidly periodic to be used as reliable clocks wherever you happen to be in the universe, as long as you have line of sight on them and an agreement with everyone else you care about with regard to their use."
] |
[
"More than you'd care to do. There'd be tensors involved, let's just put it that way.",
"In practice, you'd just use pulsars. There are hundreds of them, they're extremely well mapped, and most of them are sufficiently rigidly periodic to be used as reliable clocks wherever you happen to be in the universe, as long as you have line of sight on them and an agreement with everyone else you care about with regard to their use."
] |
[
"How close to a black hole could a human get before death?"
] |
[
false
] |
And how would we die?
|
[
"It really would depend on the size of the black hole. But this entry on ",
"Spaghettification",
" explains it fairly well."
] |
[
"Wouldn't most black holes have a fury of particles circling them at relativistic speeds. So when you reach anywhere near event horizon you just \"burn away\"?"
] |
[
"I am only speculating on this, but if the black hole is not actively feeding you aren't likely to encounter enough high energy particles to kill you. "
] |
[
"What is the significance of parity violation in physics?"
] |
[
false
] | null |
[
"This issue is not easy to summarize concisely. Parity violation is now known to exist, it is not a welcome addition to physics because it requires an unpleasant \"gimmick\" added to an otherwise nice symmetrical theory, but it also may explain why there is any matter at all.",
"It turns out that, if there were perfect symmetry, i.e. no parity or other symmetry violations, there would be no matter in the universe, only energy. This is because the Big Bang is thought to have initially created a perfect mix of matter and antimatter, which would combine and produce only energy with no matter residue. The fact that this is not the case was one clue that the prevailing theory wasn't a complete explanation.",
"But the Big Bang wasn't always accepted, and it was the Big Bang's conditions that required a rethinking of physical assumptions. If there had been no Big Bang, there also would be no moment when all mass-energy was created and had to sort itself out into energy, matter and antimatter.",
"This is all relatively recent physics. Antimatter was theorized to exist in the early 1930s (Dirac) and was discovered shortly thereafter in 1932 (Anderson). The Big Bang wasn't really accepted until the 1950s. Before this time, the parity conservation issue, and the fact that there is more matter than antimatter, just didn't seem to be a problem requiring an answer.",
"CP violation and the matter–antimatter imbalance",
" : \"The Big Bang should have produced equal amounts of matter and antimatter if CP symmetry was preserved; as such, there should have been total cancellation of both- protons should have cancelled with antiprotons, electrons with antielectrons, neutrons with antineutrons, and so on for all elementary particles. This would have resulted in a sea of radiation in the universe with no matter. Since this is not the case, after the Big Bang, physical laws must have acted differently for matter and antimatter, i.e. violating CP symmetry.\""
] |
[
"Er, I think that OP was just asking about P violation, though."
] |
[
"Yes, I noticed that, but without a larger context it might not seem to be very important -- or easily explained."
] |
[
"Do the eyes have any type of influence on what we \"hear\"? Details inside."
] |
[
false
] |
So, interesting problem that happened to me. I am viewing this image of a maze, it's black on white color, and it's in a zoom to where the density of the black and white pixels become somewhat disorienting. Now the interesting part: when I zoom in to a certain extent, I hear a high-pitched sine-wave-like whine in my ear. When I zoom in another time, I then hear a slightly lower pitched tone. And it's definitely not like a sine-wave this time, but rather it has a slight "vibration" to it, if you will. My speakers were turned off when I continued experiments with this. I am not on any medication. When I switch to another window the sound goes away, which helps my hypothesis that the sounds are coming from a visual source. Is something in my brain just messing up the images and making it a sound?
|
[
"I don't know what's happening in your particular case, but the answer to the topic is \"yes\".",
"The ",
"McGurk effect",
" is an example of how our vision can affect what we hear. And if you want to see/hear it for yourself watch this: ",
"http://www.youtube.com/watch?v=G-lN8vWm3m0"
] |
[
"Sounds like synaesthesia to me"
] |
[
"It seems like it's the monitor making the noise. I continue to hear the noise even when I look away. I'll leave the explanation on why the monitor buzzes to someone smarter."
] |
[
"If laughing is caused by a surprised brain/learned something new, why isn't learning Algebra funny?"
] |
[
false
] |
Video I came with the though from:
|
[
"Laughter is much more complicated than that. "
] |
[
"Because math isn't funny, ",
"it's pain incarnate."
] |
[
"This isn't very scientific, but there's a word for this in Buddhism called \"satori\" -- similar to \"awakening\". It's sort of an \"ah ha!\" moment, as far as I understand. In that sense, the two things you've described are both \"funny\". "
] |
[
"Why are the planets in our system different?"
] |
[
false
] |
Aren't the elements and compounds which our planets are made of forged from the same star? Why is mars so different in composition than earth? Why are all Jupiter's moons so unique if the stuff they are made from comes from the same place wouldn't we expect more uniformity? Are the elements distributed unevenly in our solar system?
|
[
"I can't give you a complete answer, but seeing as no one's commented yet, I do know that a major factor is the ice line; the distance from the sun within which water in space does not exist as ice. When the planets start to form, the ones within this line can only form from dust, while the ones outside form from dust and ice, so they get much bigger much faster, and soon reach the point where they start accumulating large atmospheres of hydrogen gas, which gives you gas giants. This also means that some of the moons of these gas giants--such as Ganymede or Europa--can have ice as a major component, whereas the inner planets do not."
] |
[
"Not necessarily: We've observed gas giants around other stars that orbit extremely close, closer even than mercury. Since they can't form that close, so we assume that they slowly migrated inwards after formation."
] |
[
"Also if a planet in Earth's zone got to the size of Jupiter, gravity would cause it to fall into the Sun."
] |
[
"Can a inductor limit DC transient currents?"
] |
[
false
] |
Let's say I have a DC constant voltage source. I plug a resistive load subject to voltage transients (infrequently but periodically adding and removing loads at intervals, loads that vary from one steady state to another under operating conditions, etc). If I want to limit the transient currents while holding the steady state current the same, would using an inductor be appropriate? Seems like this is a no brainer. Under steady state DC an ideal inductor is just a piece of wire. When subject to a short, sharp voltage rise the current through the inductor doesn't rise right away but rather rises as I = V/R(1-EXP(-t/tau)) where tau is the time constant tau = L/R. This limits the peak current due to storing the transient of the energy in the magnetic field of the inductor. Am I missing anything? is it really this easy to limit DC transients?
|
[
"To a certain extend you are absolutely right, inductors are definately used for exactly that reason. But you kind of have to be careful how exactly you use the inductor because the back-emf that they generate when you change the load can also appear in the rest of your circuit. This all depends on where you put them. Good practice is to also add a shunt capacitor both in the smaller ranger and larger ranges to capture the back EMF but be sure if you use caps like Elco's that they have a maximum voltage. Put an electrolytic and normal non-polar cap in parallel since electrolytic capacitors tend to have quite a lot of parasitic inductance themselves which sort of defeats the purpose. The small cap catches the really sharp spikes and the elco the larger spikes. This also helps the inductor supply more current when the inductance of the power supply isn't able to catch up. Also remember that the exact same process occurs on your return path (usually ground line) and that depending on how you wire your circuit, you might see ground bounce when your load changes. Make sure to wire your return path appropriately and add enough decoupling capacitors around the crucial components if the ground bounce is a problem (often in signal electronics such as opamps but also digital components). ",
"Clayton Paul wrote an amazing book on the subject of Electcromagnetic compatibility which also covers this exact question."
] |
[
"a resistive load subject to voltage transients (infrequently but periodically adding and removing loads at intervals, loads that vary from one steady state to another under operating conditions",
"With an ideal DC source and a resistive load, you should not have large transients from changing loads. Reactive loads can create large transients. ",
"Inductors and capacitors are used to smooth DC supplies. Additional filtering is often used close to the load especially in digital electronics where each IC will have a bypass capacitor across the supply voltage. "
] |
[
"Thank you for the help and book suggestion. So for a single switched load that is not information carrying and has a duty cycle longer than the inductor discharge time, there's no issue. An inductor in series with the load is OK.",
"To capture back EMF, putting an electrolytic and small capacitor in parallel with the inductor is OK.",
"What is it about ground bounce?"
] |
[
"How much force would I really need to push a steel rod that is 1 light-year long, on a distance of 1 m?"
] |
[
false
] |
Such a long rod would have an astronomic mass, that seemingly would be impossible to move with human-accessible forces. However, as the movement would take a very long time (50 000 years according to by of another question). So according to my understanding, I could push the rod with a much lower force, as my extremity of the rod would not "know" the rod is so heavy. It seems the part of the rod that is several light-minutes away would not affect my push. Am I right? What would happen eventually? Would the rod gradually bounce back the whole meter? Or only half of it? Also, would it be correct to guess that there wouldn't be notable differences between pushing a rod 1 light-year long, and a rod that goes up the way to Andromeda galaxy?
|
[
"Yes. Here's the calculation of what you outlined.",
"Suppose it's steel. 200 GPa modulus (Y) and 8000 kg/m",
" density (rho). The characteristic impedance for compression wave propagation is sqrt(rho Y) = 40 x 10",
" sqrt(N kg/m",
" = 40 x 10",
" sqrt(N",
" s",
" / m",
" = 40 x 10",
" Ns/m",
" or 40 x MPa/(m/s). The yield strength of steel is more than 2000 MPa (often much more) so pushing with 4 MPa (e.g., 400 N on a 1 cm",
" cross section rod) should be feasible, and yield 0.1 m/s velocity of the end you are pushing on. So after 10 seconds of sustained force you have moved the end one meter.",
"That might seem surprisingly easy, but remember that springs in series get softer and this is a very long spring—in ten seconds the wave has gone 50 km, so there's a lot of elasticity involved: each meter only compresses 1/50000 of the total 1 m of compression."
] |
[
"You're missing the entire point of the question. It's not to apply Newton's law, it's how the sound transmission will effect how you push it. He's probably right, your push wouldn't see anywhere near that much mass like you are calculating, the elasticity of a metal rod would likely approach some value on an infinite limit. You wouldn't move the rod, unless you continued pushing with immense force even against the reflected waves years later, but you would see a certain inertia to start moving the end you are pushing before it decays along the length. What that is, I have no clue, but it's very similar to an electrical transmission line that I am familiar with. Even if you apply gravity and insist it collapses and ignore the heart of the question, applying Newton's law like you are still doesn't answer it. Pushing the earth is not as hard as you imply initially as you hit elasticity and the speed of sound well before you start pushing the other side of the Earth or the other side of the Earth knows you are pushing it. The answer basically the same as smacking the ground with a hammer. It will move, you don't need to move the whole earth, but it will reflect back after some time."
] |
[
" ",
"u/kilotesla",
" ",
" ",
"The rod will still have to obey the laws of physics, in particular Newton's second and third laws. The second law tells us that F = m·a, so the force we need to apply depends on how much acceleration we want to impart on it. The third law tells us that as we push on the rod, the rod pushes back as well. If we want to move the rod, we need to push it \"against\" something else. In space, we use rockets to do this. By burning fuel in a chamber, we can spit exhaust gases out a nozzle really fast — we're effectively pushing the rocket \"against\" those gases. You could sit on the end of the rod and throw rocks into space for the same effect, but that is a lot more inefficient.",
"Now for some numbers. Assuming a density of 7.85 g·cm",
" and a diameter of 1 m, the mass of this rod will be 5.83×10",
" kg, which is around the mass of a large asteroid like ",
"10 Hygiea",
". If such a rod was somehow brought into existence, it will quickly collapse into a more stable shape due to its own gravity. Applying any force to one end will simply make it buckle and collapse faster. To give us a better shot at getting anywhere, we'll let it collapse into something resembling an asteroid, so we can get a handle on how much force is needed to move it.",
"The ",
"F-1 engine",
" used for the Saturn V rocket has a vacuum thrust of 7,700 kN; five of these were used in the first stage for a total thrust of 38,500 kN. This stage fired for 150 s before burning out. 13 Saturn V rockets were built, but for the hell of it we'll just strap 13,000 of these onto our lump of steel. This gives us a total thrust of 501 GN. I'm ignoring the mass of the fuel used here, which turns out not to matter because the mass of the steel far eclipses everything else. Firing all 13,000 Saturn V rockets for 150 seconds will give us a final speed of... 1.3 μm·s",
". Bamboo grows nearly 10 times ",
"faster than this",
". At 1.3 μm·s–1, it will take 9 days to move our lump 1 m.",
"So no, you will not be moving this amount of mass anywhere without some ",
" force.",
"EDIT: The same rod stretching to Andromeda (778 kpc) will have a mass of 2.96×10",
" kg, which interestingly is almost exactly half an Earth mass — honestly I'd have thought it would be a lot more massive. Suffice to say this rod will ",
" turn into a planet."
] |
[
"When I brush my teeth, what's more important—the brushing or the toothpaste?"
] |
[
false
] |
Which would leave my teeth better off: brushing my teeth with no toothpaste for a year or putting toothpaste on my teeth for a year without brushing?
|
[
"Brushing the important part, the mechanical action of the bristles break up the biofilm created by bacteria, loosening up the bacteria so they can be rinsed out and of course clears out food residue that may be stuck in crevices.",
"If you go without brushing, but just gargle with toothpaste and regular mouth wash you will get substantial buildups of bacteria which cause decoloration, plaque buildup, gingivitis and cavities. Your gums will be very vulnerable as you have no way to clean the crevace between your teeth and gums.",
"Brushing with just water is very effective, although flouridation has been shown to help as it can kill residual bacteria left after brushing and rinsing.",
"Many animals and humans in undeveloped societies use fibrous material to help clean teeth, such as fibrous wood, dried fruits or dried animal skins."
] |
[
"The fluoride in most toothpaste does help in a variety of ways: making the enamel less soluble, remineralizing the enamel, and reducing the acidity of plaque-causing organisms . ",
"source"
] |
[
"Many apes and monkeys do, as well as dogs and some predators who chew bones and hide."
] |
[
"How can the body survive without blood? How does the body get oxygen? Human trials of suspended animation is scheduled to begin soon at the UPMC Presbyterian Hospital. They plan on replacing the patients blood with chilled saline, in order to slow down bodily functions and prevent blood loss."
] |
[
false
] |
It seems strange for me to take out the blood in order to save the body from blood loss. I wouldnt think the body could last long without blood.
|
[
"From the linked article in OP's article:",
"In this state, almost no metabolic reactions happen in the body, so cells can survive without oxygen. Instead, they may be producing energy through what's called anaerobic glycolysis. At normal body temperatures this can sustain cells for about 2 minutes. At low temperatures, however, glycolysis rates are so low that cells can survive for hours. The patient will be disconnected from all machinery and taken to an operating room where surgeons have up to 2 hours to fix the injury. The saline is then replaced with blood. If the heart does not restart by itself, as it did in the pig trial, the patient is resuscitated.",
"The heart of the patient has already stopped (or they have lost so much blood that it makes no difference). They are looking into gun shot or stab wounds which have a survival rate of 7%.",
"The point of the saline is not to replace the role of the blood, but to rapidly cool the brain and then the rest of the body. This slows down the chemical processes in the cells and allows them to survive on little or no oxygen.",
"They replace the blood with saline to prevent the patient from dying from the effects of no blood: lack of oxygen."
] |
[
"Cold blood is also very viscous, and can crystallize. It probably couldn't pump very efficiently. "
] |
[
"If we had enough blood to do that, we wouldn't even need to do the freezing thing. Blood supplies are valuable. Also blood is a complex mixture which is likely harder to cool (takes more energy) than just saline. "
] |
[
"What kind of adaptations would be expected for life that's been in a cold, Antarctic lake without light for 20 million years?"
] |
[
false
] |
Would anything even still be alive?
|
[
"I don't know. A lot of deep sea creatures have photo receptors of some sort. Other species down there have evolved bioluminecense to cater to exactly those eyes!",
"I am hoping they find a stargate down there, personally... "
] |
[
"I don't know. A lot of deep sea creatures have photo receptors of some sort. Other species down there have evolved bioluminecense to cater to exactly those eyes!",
"I am hoping they find a stargate down there, personally... "
] |
[
"Organisms would use chemosynthesis; look up Blood Falls under Taylor glacier for example."
] |
[
"What is the definition of observation (in a quantum mechanical sense)?"
] |
[
false
] |
What is it about looking into the box in schrodinger's experiment makes it pick a position? the gravity and what not of the alive/dead cat (whose spacial position would change based on living or dead) and surely other things would effect the world outside the box effectively as much if i looked in the box or not... also, why cannot the cat be in superposition after the box is looked in?
|
[
"An observation is just an external interaction. It's not quite the same thing (there exist interactions which do not count as observations), but for most purposes you can treat them as the same. So the fact that something interacts with the inside of the box is what causes the superposition to collapse.",
"Of course, you're right that the inside of the box ",
" be completely isolated in any real world scenario. That's why Schrodinger's cat is a thought experiment; it requires that the inside of the box be entirely disconnected from the outside world, which we cannot do for something the size of a cat."
] |
[
"\"Schrödinger's cat\" is ",
" It's not even a ",
" experiment. It's just a metaphor.",
"If you ever find yourself thinking about the ",
" of cats and boxes — as you appear to have here — you've gone off into the weeds. You need to pull yourself back to reality."
] |
[
"Then the next question is \"well what's the cutoff between classical and quantum and why is it there?\". People just don't find any answer to that question satisfactory, so I make sure to dodge it whenever possible."
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.