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[
"Are capital goods included in the calculation of GDP every year?"
] |
[
false
] |
Say I invested 500$ in a machine in year 2012-2013 and that machine is still running in the year 2013-2014. Will this 500$ be added for the fiscal year 2013-2014 GDP? Also, what about inventory?
|
[
"There are two ways of thinking about GDP and both ways have to be equivalent in the end as they are measuring the same thing. In Brazil your example, you've confused the two different ways.",
"Your earlier question stemmed from the difference between ",
" and ",
" in economics. The value of an existing capital good, like a house is a ",
". The creation of value, like the utility gained by living in the house or the income earned by renting the house, is a ",
". GDP is an annual economic measure. It measures ",
" - it is a measure of ",
". So the price of the house is not included in GDP but the rent earned by the house is.",
"Let's take a single person. That person has an ",
" which is a flow. There is also their ",
" which is a flow. And then there is their ",
" which is a flow. By simple accounting, every year:",
"Income = Expenditure + Change in Savings",
"If you wanted to know how much money the person made in a year, you could do it two ways: (1) measure the income directly; (2) measure how much they spent in the year and add that to how much their savings changed.",
"The same logic applies to GDP. There are actually two ways of measuring GDP.",
"The ",
" approach to GDP:",
"GDP = all wages paid to workers + all profits + all interest + taxes - subsidies",
"The ",
" approach to GDP:",
"GDP = Consumption + Investments + Exports - Imports + Government Expenditures",
"(BTW, just to be clear ",
" here doesn't mean existing investments - it means money spent to produce ",
" investments. The value of existing houses doesn't contribute to GDP. The expenditure spent on creating ",
" does.",
"In your product from Brazil you're making an argument about where a good was ",
" but the equation you're using is the ",
" equation - you're mixing the two different approaches, and so you're not getting the right answer.",
"Let's take the income approach. Did US resources produce whatever you think should be part of GDP? Did US workers get paid wages, was US capital or US land paid rent? For the product from Brazil, no, so it's not part of US GDP. And you're right about the general argument too: imports can't change the amount that the US ",
" so imports are not in the 'income approach equation' to GDP. ",
"OK, so that's good. But you're not using the income approach equation in your question, you're using the expenditure approach equation.",
"If we take the expenditure approach, we're interested in how people in the US spend their money - we don't care where the good was produced. So your product from Brazil. Let's say it is an orange fruit - it's already in our expenditure accounts as consumption then. Let's say it's a piece of manufacturing equipment we're moving to the US - then it's already in our expenditure accounts as investment.",
"So why in our expenditure equation do we have (Exports - Imports) at all?",
"Because we also want to track whether people in the US are spending money they've earned this year or whether they're spending savings they've accumulated in the past - we want to track the national equivalent of the single person's ",
". A nation earns the money it gets by selling ",
". A nation spends the money it gets by buying ",
". If we want to track the national ",
" we need to take the money earnt by exports and subtract the money spent by imports. If exports > imports, then the national 'change in savings' is positive - the nation has increased net savings in foreign countries. If exports < imports, then the national 'change in savings' is negative - the nation has decreased its net savings in foreign countries.",
"So I'm afraid you're wrong, you ",
" need to subtract the value of the Brazilian import in your equation. But your argument about production is correct - it's just that you're not using a production approach. Your equation is using an expenditure approach and so needs to track change in US national savings - and buying a product from Brazil by itself would decrease US national savings and so needs to be accounted for as such.",
"Final hopefully clarifying example: take a very small island nation that imports everything. Its only business is a tourist resort where everyone on the island works. Staff are not paid wages - they eat and live at the resort for free instead. The only people who pay for their time at the resort are the tourists. So the island's economy is essentially ",
" exports (the resort experience for tourists) and imports (the food and other essentials for the tourists and staff at the resort).",
"If we wanted to know the total production, the GDP, of the island, we could look at the income side: what was the revenue produced by the resort this year? That is the island's total ",
" after all. Or we could look at the expenditure side: how much money did the resort spend this year? But if we look at the expenditure side, we need to ask ourselves - did the resort make a profit? If so, it's revenue was more than it's spending and we need to add that profit to the resort's spending to estimate GDP. Did the resort make a loss? If so, it's revenue was less than it's spending and we need to subtract that loss from the resort's spending to estimate GDP. The profit or loss of the resort is equivalent to the (Exports - Imports) portion of the expenditure GDP equation."
] |
[
"No, GDP, the gross domestic product is the increase of production at a given time or period. \nGDP only aggregates what is produced/consumed so capital and and inventory aren't concerned. What you have are the differences of those variables. Inventory and capital would matter in the measurements if they had changed over the period, and basically we would only measure that change.",
"The mathematical formula for GDP is : \nGDP = Consumption + Investments + Exports - Imports + Government Expendituress"
] |
[
"Thanks for the quick reply! If I could I would like to ask a follow up question. ",
"If I buy a product from Brazil ( assume I live in USA) that does not factor into the reduction due to import, right? My reasoning is that the good wasn't produced in USA, hence its import shouldn't be subtracted from GDP. If my reasoning is correct, could you cite an example where an import leads to decrease in GDP. Once again, thanks!"
] |
[
"Why do we perceive red as running into violet on a color wheel if their light frequencies don't similarly run into each other on the light spectrum? [neuroscience]"
] |
[
false
] |
For all other colors that bleed into each other on a color wheel, there is a corresponding "bleeding together" of frequencies on the light spectrum. Why do we perceive color in this way? Would this be the case if the visible light spectrum was a different stretch of the light spectrum, for example if we could see only between yellow and blue, or infrared and ultraviolet? Please let me know if it's unclear what I'm asking. I also was unsure whether to tag this in neuroscience, biology, or physics.
|
[
"Color perception is a bit complicated, but essentially, our eyes don't detect color in the same way an instrument would. An instrument takes the light and disperses it into its component colors, like prism. It then measures where there is a strong intensity on the detector. If there is only red light, the detector lights up at the left side, for blue light, on the right.",
"In our eyes, we have 3 separate detectors, one that absorbs reddish light, one that absorbs greenish light, and one that absorbs bluish light. The combination of the activation of these detectors helps to tell us about color. But that's not the whole story.",
"Then the brain starts to get involved, and it does something called color opposition. Black, clearly, is the opposite of white. But to our brain, red is also the opposite of green, and yellow is the opposite of blue. Stare at a red light for a while, then look at something white. You should see a green \"afterimage\", while the red detection, which was really strongly activated, relaxes. So the reason why purple seems like both red and blue isn't because it is close to both red and blue frequencies, but because it activates the pathways of \"Not Green\" and \"Not Yellow\". Because of your opposition system, you equate that to being Red (Not Green) and Blue (Not Yellow) at the same time.",
"Now I will leave you with a related (non)question: what is the wavelength of pink?"
] |
[
"I'm not sure if bringing up the opponent process stage adds much to the explanation that violet light is the result of activating S and L cones at the same time. But the opposite color pairs your eyes detect are ",
"magenta-green and blue-yellow",
". They detect these color pairs through Cg cells and Cb cells respectively. There isn't a \"red-green\" difference detector. So violet (i.e. magenta) is light that is simply \"not green\", not a specific combination of \"not green\" and \"not yellow\". In other words, pure magenta should activate the Cg cells and neither activate or inhibit the Cb cells."
] |
[
"The tricky part about what you are asking is that \"violet\" is used to describe a range of colors. Your eyes have three cones - S, M, and L. We think of these as Blue, Red, and Green but the match up isn't perfect to the way these colors are used everyday. In particular, many people would consider the shortest wavelengths we can see, which only activate the S cone, to look like violet or indigo rather than blue. We tend to associate \"blue\" with something closer to cyan in common usage. So one source of \"violet\" light is pure activation of your S cones.",
"But there are also a ",
"range of violet colors",
" between blue and red on a color chart. The bleeding together of colors comes from the activation of at least two types of cones at once. When we see cyan, that is from the activation of S and M but not L. When we see yellow, that is from M and L but not S. And when we see magenta (and the purple colors nearby it on a color wheel), that is L and S but not M. ",
"For all these mixed colors, you can get them by combining multiple wavelengths at once, like we do with color monitors. But for cyan and yellow there are also pure wavelengths that activate two cones equally well. But our brain doesn't care which way the color is \"made\" - it only knows the cones are activated in equal amounts and the rest of the wavelength information is lost.",
"So, while there is no pure wavelength that bleeds together between red and blue to make purple, your eyes can still collect some red wavelengths and blue wavelengths at the same time to make different shades of violet. The continuum of perceived colors is independent of the continuum of frequencies. "
] |
[
"How are photons in light bent by stars if they don't interact with the higgs field?"
] |
[
false
] |
They must not interact with the higgs field, by my assumption, because they have no mass... but Einstein proved that light is affected by gravity, so how does that interaction work?
|
[
"They must not interact with the higgs field, by my assumption, because they have no mass",
"That's correct, at least insofar as one can make such statements in a non-mathematical way.",
"but Einstein proved that light is affected by gravity, so how does that interaction work?",
"Einstein's reformulation of gravity reinterprets Newtonian gravitation as a special case of a more general phenomenon. Specifically, gravity becomes the curvature of spacetime, with the curvature being determined by the local stress-energy. Mass ",
" to this curvature, but it's not the only contributor. Moreover, because gravity is the curvature of spacetime, the path of ",
" moving through spacetime, whether massive or massless, will be affected by that curvature. And that's what we see with the gravitational lensing of light."
] |
[
"Yes, that. I would also add that the Higgs field has nothing to do with gravity."
] |
[
"No no no. It's ",
" that curves spacetime. (And pressure, stress, and momentum, but you can usually ignore those.) Whether that energy happens to be intrinsic energy, a.k.a. mass energy, caused by the Higgs mechanism, or some other kind of energy, it doesn't matter."
] |
[
"Is there a tolerance band of possible values for the Law of Gravity? e.g. F = GmM•r^(2 +/- 0.00000000000000001)??"
] |
[
false
] |
I know the theory says that the exponent is 2, and that all experiments are consistent with it being 2, but is there anything that shows it must be precisely 2 as opposed to (say) 1.99999999999999999999998?
|
[
"You can show that it's two by assuming Poisson's law and knowing that we have three dimensions.",
"However, general relativity has some deviations from the inverse square law."
] |
[
"Out of my field as well, but isn't the R",
" a function of the fact that fields are proportional to area, which is a mathematical function of R squared? Thats the way it works with electrics I believe.",
"Of course there are uncertainties in the other parameters."
] |
[
"The experimental limits are length dependent. The most interesting are the short length scale limits because they put limits on the theories with extra-dimensions. Have a look at preprint below.",
"http://arxiv.org/pdf/hep-ph/0303057v2.pdf"
] |
[
"Are underground water turbines closed systems?"
] |
[
false
] |
I know you've got a lower lake and an upper lake; the water cascading down into the lower lake during high demand generates electricity. But what does it actually look like? Is the water in a great tube, or does it flow freely?
|
[
"Does this help?",
"http://www.tepco.co.jp/en/challenge/energy/images/16-01.jpg",
"I'm not sure exactly the context of your question, but there's no air in a generator turbine system under normal conditions. If you are imagining some kind of old-timey water wheel in there or something, it's not quite like that. Water turbines look more like the impellers in jet engines."
] |
[
"Hey thanks for your reply. I'm wondering for a book -- the whole context is, could a character sneak into a city through an underground power system in an abandoned mine? Would you maybe come out in an underground building that's kind of like an office if you snuck through old mine tunnels towards what's being used as a renewable energy system? Or could you come out with the water? Or would you just hit a dangerous generator/turbine?"
] |
[
"Trying to joyride through a working turbine wound invariably be fatal in the real world."
] |
[
"How did birds evolve from dinosaurs if their extinction was so abrupt?"
] |
[
false
] |
I don't question that birds did evolve from dinosaurs as even with my very limited knowledge I can see the similarities, but how, since the evolutionary process takes a very long time did this happen? since most theory's about the dinosaurs extinction imply that they all died out in a very short period of time, how was their DNA able to be passed on and share similar traits with modern day species of birds?
|
[
"To further elaborate on other posts, modern day birds are part of a group of dinosaurs called the ",
"theropods",
".",
"\"Among the features linking theropod dinosaurs to birds are the three-toed foot, a furcula (wishbone), air-filled bones and (in some cases) feathers and brooding of the eggs.\"",
"If you look at ",
"this",
" it gives you an idea of how complex this group was. Now, only the birds made it past the K-T boundary (65 mya - birds evolved before the extinction of the other groups of dinosaurs, but they did undergo further evolution after that time radiating into the many species we see today). Birds didn't come from dinosaurs...they are dinosaurs. They just survived and had many more unique adaptations after the K-T extinction event. (FYI Birds are contained in the last offshoot group within the theropods called avialae in this chart)",
"Some adaptations were already present in the theropods - like feathers and hollow bones, and birds took advantage of these in unique ways compared to other offshoot groups in the theropods. ",
"It didn't have to take long, ",
"Archaeopteryx",
" is thought to be the first fossil we have of a primitive bird which is capable of powered flight, and it was alive well before the K-T boundary (Archaeopteryx lived in the Late Jurassic Period around 150 million years ago). ",
"Now I must clarify, that while archaeopteryx is certainly though to be a primitive bird, it may not be a direct first ancestor of all living birds. It may be an offshoot group of theropod dinosaurs",
". To my knowledge this is an ongoing debate.",
"For more information see: ",
"avialae",
" is a clade (group) of dinosaurs containing their only living representatives, the birds (Aves), and the most immediate extinct relatives of birds. Archaeopteryx may or may not be included.",
"Edit: ",
"This evolutionary history of birds may also help you",
"Edit: how was their DNA able to be passed on and share similar traits with modern day species of birds?",
"It was never \"passed on\" in the sense that I think you are thinking of, they were always dinosaurs. Most traits that we see in modern birds evolved in dinosaurs long before modern birds came into existence. These traits may have had different functions - for instance feathers evolved before powered flight, so it its hypothesized that feathers first functioned as insulators, then later to help power flight. So hypothetically we might imagine the 'feather gene' appeared in some ancient dinosaur, some theropod. Eventually a group of theropods used this 'feather gene' not for insulation, but for flight. We call this group of dinosaurs with flight 'birds'. I hope this answers your ultimate question... I understand you didn't doubt that birds and dinosaurs are linked, its just you said \"birds came from dinosaurs\" which is wrong, because birds are dinosaurs."
] |
[
"Humans are apes, I think you meant humans did not evolve from chimpanzees."
] |
[
"All dinosaurs did not die at the same time. There are 335 kinds known so far from 165 million years, and no one kind lived for more than two million years or so. The only reason we think of dinosaurs as going extinct at one time, 65 million years ago, is that this last group of dinosaurs didn't get replaced later on by another group of dinosaurs as had happened before.",
"(",
"http://www.scholastic.com/teachers/article/dinosaur-extinction",
")"
] |
[
"Is there an absolute maximum value for a magnetic field?"
] |
[
false
] |
Is there a value of Amps per square meter that can not be exceeded? Or is it (theoretically) possible to have an infinite amount of Amps/m2?
|
[
"To my knowledge, there is no fundamental limit to the strength of a magnetic field. With that said, literal \"infinities\" do not exist in the physical world. It would take more material/energy than is present in the observable universe, and longer than the universe has existed, to make a magnetic field that is literally infinitely strong. When scientists say \"infinite\", they usually just mean \"really big\" or \"approaching really big in a well-behaved way\". ",
"With that said, extremely strong magnetic fields can lead to exotic effects that we don't experience with everyday magnetic fields. For instance, strong magnetic fields can enhance matter-antimatter pair production. The key is that a magnetic field contains energy, and when you get enough energy at a location, you can start creating mass and even gravity. ",
"EDIT: To make my last comment more clear, energy can turn into mass via E = mc",
" through pair production. Strong magnetic fields trigger pair production but cannot create mass by themselves. This is a purely quantum field effect. In a somewhat unrelated way, strong magnetic fields contain energy, and energy directly creates gravity without needing to be mass according to the Einstein field equations. This is a purely General Relativity effect. In principle, a magnetic field could become a black hole, which you could view as an upper limit on the magnetic field strength. But considering that very strong magnetic fields lead to interesting quantum ",
" general relativity effects, I don't think we will know exactly what happens until we have a solid theory of quantum gravity.",
"EDIT 2: Responding to several comments below, I should say infinities do not exist ",
" the physical universe. The universe itself may be infinite, but we would have no way of proving this without resorting to limits and assumptions of uniformity. When infinities do show up in physical theories (e.g. center of black hole), this is an indication that the theory is incomplete and not that the infinity literally exists. "
] |
[
"Yes. The energy density of an electromagnetic field is proportional to the square of the magnetic field strength (plus the square of the electric field strength). This is one of the terms in the Einstein field equations that govern the gravitational field, so, in principle, a sufficiently strong magnetic field could produce a black hole."
] |
[
"I've heard of a ",
"maximum information density",
" which is related to the surface area of a black hole's event horizon. Is there a magnetic field density that would create a singularity? I imagine that would be an upper bound."
] |
[
"What would happen if a regular black hole collided with an antimatter black hole?"
] |
[
false
] | null |
[
"There’s no distinction between a “normal” black hole and an “antimatter” black hole. Black holes are characterized by three parameters only: mass, angular momentum, and electric charge. They don’t come with labels saying that they were made by matter or antimatter. A black hole is a black hole, no matter what’s gone into it."
] |
[
"Strange, thank you. I have another question then. What would happen if antimatter was inserted into a black hole? Would it shrink? Or just become part of the larger black hole?"
] |
[
"It would make the black hole a little bit bigger, just like regular matter."
] |
[
"What is the weak nuclear force?"
] |
[
false
] |
[deleted]
|
[
"So... a particle travels from A to B, both places we observe it at. But since we don't observe it between A and B, we can't know for sure exactly what path it takes. Some of these paths involve interacting with other \"particles\" in other fields. And when an \"interaction\" takes place, momentum is exchanged. Changes in momentum are, technically, forces. ",
"(let's leave Z aside for the moment). The interesting behaviour is that when a particle interacts with a W boson, it changes \"flavour.\" An electron gives its charge to the W",
" boson and some momentum and the electron changes flavor into a neutrino. (for instance).",
"So some particle, say a muon, has a mass, and it interacts with W bosons. So between A and B it ",
" take a path where it temporarily interacts with a \"virtual\" W boson. (more about virtual vs. real in a bit). So remember the interaction. The muon gives its charge to the W",
" boson, and becomes a muon-type neutrino. The W",
" boson then travels on a little bit and decays down into an electron and electron-type anti-neutrino. So more specifically here, we observe a muon and then, later, an electron and a neutrino and anti-neutrino (well we almost never observe the neutrinos directly, but let's pretend we have a perfect experiment where we detect those too). ",
"So what? Well see, in the above, we had one particle with mass. That's only one way to arrange energy. Mass. But in the end, we have 3 new particles flying off in different directions from each other. And each has some mass, but their relative shares of momentum could all be very different. So there's many more ways to arrange the energy there. So entropy has increased. And the universe likes entropy increasing. So as the time between A and B increases, it's increasingly likely that the muon will have taken a path that includes a decay. Hence we see a \"half-life\" for muons that arises out of this scenario. ",
"So what's the deal with nuclei, then? Well... a nucleon, a proton or neutron, is 3 (valence) quarks bound together with the strong force. But when you get nucleons together, some of that strong force \"leaks\" out between them. And the energy of the strong force holding the nucleon together is about 90% of the mass of nucleon. So that leakiness means that the nucleus' mass ",
" just adding up the mass of however many protons and neutrons the nucleus has. (plus other quantum mechanics corrections, and the energy of forcing positive protons together)",
"So now we take a nucleus, and just like the muon above, let it travel. Well any of the quarks making up a nucleon can interact with W bosons. Up quarks can interact with W",
" bosons and Down quarks can interact with W",
" bosons. Well if any of those quarks, interacting with a W boson, can lower the overall mass of the nucleus... it's likely to. These are the various \"beta\" decays. W",
" bosons will be emitted from up quarks to decay into electrons and anti-electron neutrinos. W",
" bosons will be emitted from down quarks and can ",
" emit a positron and an electron neutrino, ",
" absorb an electron from the atom and emit an electron neutrino (and a gamma ray photon from the electron \"falling into the nucleus\") ",
"Z",
" bosons? Well these are not charged. And they don't participate in changing flavour. Think of them as massive photons that exchange momentum between particles that don't have to be charged (including exchanging momentum between photons). But they're so massive they rarely interact at all anyway, so they're pretty negligible all things considered.",
"Virtual particles: this is such a big topic... I'll link you my favorite article on the subject though: ",
"http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/"
] |
[
"Thanks for that link. I have been waiting for an article like that for years. I want to learn more about modern physics, but the laymen pop science books are a level or two beneath me, and I just don't have the time to go through a whole textbook or online course purely out of curiosity. If only this guy would write a book for me..."
] |
[
"/u/shavera",
" has a much more comprehensive answers but for a ",
" simplified answer just remember the weak force is responsible for beta radioactive decay.",
"A neutron interacts via the weak force to decay into a proton, an electron and an anti electron neutrino ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" Some other interesting things also happen because of the interaction such as ",
".",
"A neutron is made of 2 down and 1 up quark and a proton 2 up and 1 down quark which means the flavour of one of the down quarks are changed to an up quark. The energy difference emits a W boson ",
" which goes on to decay into a electron and neutino as described."
] |
[
"What are the benefits of our brain hemispheres controlling the opposite sides of our bodies?"
] |
[
false
] |
I understand that once when the fish saw a predator approaching, it needed to trigger the muscles on the other side of the body to flee, but what purpose does this design serve today? Would it be more efficient if each hemisphere controlled its side? Are there any creatures like that?
|
[
"While this is not an answer to your question, it will provide a way to ask a better question.",
"Your statement of opposite hemisphere control is a bit generalized. For larger functions, this is true in some cases, but hemispheres don't entirely work that way. There are ispilateral (same side) and contralateral (opposite-side) connections. Here's just a silly example for the ",
"LGN",
".",
"Additionally, things like language production (Broca's area) and language comprehension (Wernicke's area) are, in nearly all cases, localized to a single side of the brain.",
"But in short, the whole \"wiring diagram\" of the brain/nerve pathways is basically an \"engineering disaster\" and poorly \"designed\". "
] |
[
"Heres a related thread :) \n",
"http://www.reddit.com/r/askscience/comments/i1ggl/what_iswas_the_evolutionary_advantage_of_having/",
" "
] |
[
"That makes sense. Thanks."
] |
[
"How to make an ice cube last for a long time using ordinary materials?"
] |
[
false
] |
Hi askscience. I'm helping my 10 year old daughter with a school project. She has been tasked with creating something in which to put an ice cube and make it last as long as possible. She has gotten up to 2 1/2 hours with three trials. Later this week the kids will be competing to see who's contraption works the best. I'd love to help her rock this one out, but frankly I don't have any particularly good ideas. The only rule is that it can't use commercially produced insulation materials. Please don't jump my case for "cheating" on a school project... that's not the case. The three experiments she completed are the graded school project. She has written up her report and that will be what she submits for grade. This is only for the fun, non graded competition at the end.
|
[
"I don't know if adding sawdust will remove any criteria of the assignment, but consider making Pykrete.",
"http://en.wikipedia.org/wiki/Pykrete"
] |
[
"You might be able to approximate a vacuum flask. Take two glass jars with metal lids, one large and one small (such as a mayonnaise jar and a baby food jar.) You'll want to glue the lid of the small jar to the inside of the lid of the large jar so that it's suspended inside. However, don't just glue a metal lid to a metal lid, try using something like stryrofoam between them so that they can't conduct.",
"Now you have a jar in a jar. The only step left is to somehow suck the air out from in between. They sell hand vaccum pumps at auto parts stores, which are used for bleeding brakes and such. You can create a connection port to the jar by cutting a valve stem out of a bicycle innertube. Leave a \"shoulder\" of rubber around the stem, and use that to glue around the surface of the hole in the lid on the inside. (Edit: or actually, gluing it to the outside surface would work better as the vacuum will pull it tighter instead of trying to rip it off.) You'll need to remove the actual needle valve from the stem, as it's pointing the wrong direction, but you can get a tool for like a dollar that will do that. Then you can just attach the hand pump to the jar and try to create a vacuum. Once you've got that, pinch off the tube firmly and hopefully it will hold. Or you could leave the hand pump attached as it will usually have a nice vacuum gauge that will tell you how well it's holding and if you have any leaks."
] |
[
"Aside from the vacuum flask idea already proposed, air is about as good an insulator as you could want. An airtight sealed cardboard box full of (pre-chilled) rolled-up newspaper would be pretty effective."
] |
[
"Are there more shooting stars near the equator?"
] |
[
false
] |
I'm currently staying with some friends on an Island in Indonesia, and we have been seeing a LOT of shooting stars. Two nights ago we saw a massive meteor that visibly broke up into sections, and I thought it was a one in a lifetime event. Then we saw a very similar one last night. I go camping/hiking in Australia quite often, so I spend a lot of time stargazing, and I have never even seen anything close to what I have seeb on the last two nights. Was it simply a coincidence, or is the incidence of meteors more common near the equator? Or are we passing through a comet's tail at the moment etc.?
|
[
"I can't think of anything that would cause more meteors at the equator, but I can think of something that would cause you to see more meteors in Indonesia than Australia--light pollution. If you're hiking or camping within an appreciable radius of a major city, your ability to see lights in the night sky is greatly reduced.",
"Here's a nifty map of light pollution:\n",
"http://www.lightpollution.it/download/mondo_ridotto0p25.gif",
"From what I understand of meteors, while they are in a similar orbital plane to the Earth for the most part, they aren't so in-plane with earth that they would strike more often at the equator; many of them pass well \"above\" or \"below\" our orbital plane.",
"If we take the behavior of large/enormous meteorites to be similar to the behavior of smaller meteorites that don't reach the surface--this isn't necessarily the case though--then this list of major impact craters should give us a hint; there's no significant preference for equatorial latitudes in this list:\n",
"http://en.wikipedia.org/wiki/List_of_impact_craters_on_Earth",
"This doesn't really deserve a top level response--I'm not an expert by any means--but I wanted to give you something to start with at least. Someone with more information get in here."
] |
[
"According to ",
"this",
" website the Orionids are right about now, although other sources are indicating that the shower is typically later. That may have contributed to a higher-than-average number of shooting stars. "
] |
[
"I'm pretty sure it does--if you were floating in the middle of the Pacific on a perfectly clear moonless night I'm sure it would put all of our collective stargazing spots to shame. Once again: not an expert at all, but it's both my interpretation of this diagram and my personal experience."
] |
[
"How can you separate mixed dna samples?"
] |
[
false
] |
Every now and then, I have a memory from an old episode of Quantum Leap where Sam becomes a woman, and long story short, saves her son from being abducted by two men. At one point, the men discuss how if they both rape the boy, the authorities will be at a loss because the DNA would be mixed and impossible to identify. Obviously, this sounds like truth at the surface... but it's been close to a decade and half since that show aired (if not longer) and I can't imagine that it's true anymore. How do scientists identify who the culprits of a rape were when there have been multiple parties involved? Once DNA is mixed, be it blood or semen or anything else... how can science identify it with 100 certainty they aren't picking chromosomes from one person and chromosomes from another?
|
[
"They always have to do this to separate out the victim's DNA. Adding one extra isn't too tough - if you know there are two perpetrators, they test quite a bit of DNA and can get 3 different results. In a large gang rape, it gets increasingly difficult, but apparently is improving. Here's an interesting article on it:\n",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3990198/"
] |
[
"If you read further into a process referred to as STR profiling, it is a method that is used by forensic scientists to determine if a sample contains a mix of two or more DNA types. It basically involves the amplification of specific alleles through a method of Polymerase Chain Reaction (PCR); more specifically real-time PCR. Through the evaluation of certain trends in the data obtained, such as analysis of the allele peaks, it is possible to determine all contributors to a DNA sample. I studied forensic science for the past four years, and it is a pretty detailed process. However, I would recommend looking into it as the technology involved is quite groundbreaking :)"
] |
[
"thank you, I appreciate the article."
] |
[
"What's the science behind liking things? Why does one person like and identify with some things, while others choose differently?"
] |
[
false
] | null |
[
"\"Like\" can be divided into several underlying processes:",
"1) Interpersonal affection seems to be mediated by ",
"vasopressin",
" in males and ",
"oxytocin",
" in females.",
"2) The ",
"dopamine reward system",
" is responsible for many positive feedback sensations from drugs, food, certain behaviors.",
"3) Miscellaneous hormonal stimulation: In addition to the above pathways, when we eat, for example, a cascade of hormones signals (increasing leptin, decreasing ghrelin, for two) that give our body relevant biochemical information. The human brain is, above all else, an organ of learning and adaptation. Feedback signals that it interprets as good will result in positive sensations.",
"As to WHY you like classical music vs. death metal... We have no idea. We don't even know why we have such a fascination with music. We understand why someone might not like foods by their biochemical response (and even texture), but there is a lot of variance because of setting and other factors that shape experience dramatically. The \"Why's\" of enjoying almost anything are unknown at a complex level. The \"How's\" are honestly just barely understood.",
"Leading theories relate everything back to evolutionary drives. Why are certain colors more attractive than others? We have seen green for a thousand years, purples/reds are less common, our eyes naturally fall to brighter tones. This doesn't mean people will say those colors are their favorite, but at least when we track eye motions they tend to follow reasonable patterns of focus that show signs of evolutionary drives.",
"EDIT: Majidah is quite incorrect on his assertions. Evidence for innate eye preferences covered ",
"here",
". Please read what I said carefully before considering his baseless accusations and false statements."
] |
[
"I can't answer the question, but I know Paul Bloom (Yale) studied your question. He talks about it ",
"here",
". Maybe that helps to answer your question a bit! "
] |
[
"The truth to your question is, we have not yet reached a truly defined answer to this question. The question itself delves deep into many different fields and aspects of Psychology and brain science. However, the current modeling leads to the following hypothesis. Because we live our lives running backwards in time, in otherwords we always refer back to the known when facing the unknown, what your percieving is the brains recall of similar events. The brain operates efficiently and does so by only focusing on the most important or unknown portion of an event and relies on memory recall to fill in the rest of the story.",
"So, reasonably if something was pleasurable to begin with, the brain is going to encode it as such. The real issue is, why is it pleasurable, if I am understanding correctly. The answer is far more complex. The brain will encode things as pleasurable for many reasons and factors. Was their a release of serotonin due to a positive reaction to the action or reaction of an \"event\" creating conditioning, or was their base experience of the receptors in the tongue vision or ears registering a sensation that fell into an already conditioned response. We are finding these days that babies are born with far more experience, pre-recorded nueral pathways and biases than ever thought.",
"As I said, with the generalness of your question the answer becomes rather complex, but hopefully my answer can serve as a basis for an answer to you."
] |
[
"Can an aircraft wing or propeller cavitate like a boat propeller?"
] |
[
false
] | null |
[
"Cavitation happens when changes in pressure around the propeller are significant enough to cause some of the water to turn into vapor. The bubbles of gas collapse rapidly and cause damage. ",
"Air is already a gas, so it can't cavitate."
] |
[
"What if it were going fast enough to heat the air into a plasma? Like the Space Shuttle coming back from space, for example."
] |
[
"Agreed that it won't happen. However there are planes with supersonic props. ",
"Tupelov Tu-95 Bear",
"."
] |
[
"Does the frequency of switching a transistor on and off affect its performance/longevity?"
] |
[
false
] |
I know RAM wears out, and this is probably what limits the life of a computer, but does a similar thing happen to the core? Maybe the semiconductor loses its dopants? Just trying to lead the conversation, I could have no idea what I'm talking about.
|
[
"It doesn't \"lose it's dopants\", but high frequency operation does take it's toll on CMOS logic devices, in at least a few major ways. ",
"One major way is due to the fact that a static (non-switching) CMOS circuit has very low current flow in it, and therefore very low heat generation. Heat accelerates almost all failure mechanisms, and localized heating causes thermomechanical stresses that can be quite intense. The faster you switch a circuit, the more it heats up. Current surges through the transistors, charging and discharging parasitic capacitances in the interconnect. Generally this \"dynamic power\" dissipation is much greater than any static power dissipation component. Therefore it is responsible for most of the heat, and heat is responsible for making (most) all reactions go faster. ",
"The other way that switching hurts is that when transistors are conducting, the charge carriers are speeding through the channel at high velocity, and through collisions (phonon interactions) they can end up in unwanted places, such as at the channel/gate interface, or even within the gate dielectric itself. This mechanism is called \"Hot Carrier Injection\" or HCI for short. It is one of a handful of true wearout mechanisms. HCI used to be accelerated by current flow but ",
"celerated by high temperatures, but that is not so true any more. And the current flow matters more anyway. ",
"And, since switching means current flow, electromigration can occur. EM is one of the other major wearout mechanisms. With EM, the collisions are within metal conductors. This leads to stress buildup which causes the metals to creep, leading to high resistance or opens, and sometimes even shorts. It is influenced by current density, and is also highly accelerated by heat. ",
"There are some other secondary effects, such as increased power supply bouncing causing higher voltage stresses, but those should not be all that significant in a correctly designed device. ",
"FYI, I am a semiconductor reliability engineer. "
] |
[
"Transistors are rated for for different frequencies of operation, determined by how they are manufactured. IIRC the amount of doping is one factor while the semiconductor used is another. For example, silicon doesn't work well at really high freqencies (ie. gigahertz range). The fast on/off switching will cause too much heat to be produced and burn up the transistor. So for the transmitters/recievers in a cell phone which need to switch well in the GHz spectrum, doped Gallium Arscenide (GaAs) is used instead. Because it is a semiconductor that works better at high frequencies than silicon.",
"So in answer to your question, I would say it depends on how close the frequency is to the maximum recommended operating frequency of the transistor. If you are well below that frequency, then it shouldn't have an impact on the transistor's longevity."
] |
[
"I couldn't tell you, but you might want to try asking ",
"/r/electronics",
" as well, it's right up their alley."
] |
[
"How come vaccines don’t pass from mother to child?"
] |
[
false
] |
If they share the same blood before birth, which I’m 90% sure they do, wouldn’t their immune system keep information from when the mother got vaccinated?
|
[
"The mother and the fetus do not share the same blood. The function of the placenta is to facilitate the exchange of nutrients, gases, and wastes while keeping the blood supplies separate. There are a type of antibodies called IgG that can cross the placenta. They give some protection to the developing fetus in utero. After birth, IgG and IgA antibodies are transferred to the baby through breast milk. While the baby is breastfeeding, it has the same immunities as the mother does (including those the mother acquired through vaccination). Babies start to make their own antibodies by three months, but their immune systems will be supplemented by maternal antibodies until they are weaned. After weaning, maternal antibodies in the baby's blood eventually degrade, so they will have to be vaccinated to develop their own antibodies."
] |
[
"They pass stuff, but not all.",
"Vaccines trigger immune response to form a sort of imitation cell that they can automatically produce antibodies against. Think of it as a dossier of weapon against different enemies. When vaccinated, your body learns about the capsid or binders of the virus (that is why vaccines uses usually deactivated or just the skin/capsid of the virus), and save the weapon (antibody) manufacturing information so they can quickly produce antibodies the next time the body encounters the same virus.",
"Now, the antibodies do travel through the placenta into the fetus. So fetus, and usually the baby after birth, has some antibodies in the system which will break down soon. However, the importance of the vaccine is less about the antibodies (weapon) themselves but the knowledge on how to make the antibody. Because only very rare viruses can pass through the placenta, the same thing applies to vaccines. Vaccines, being parts of viruses, cannot pass through the placenta, and so the fetus/baby cannot learn to formulate the response.",
"I should add that they do not strictly share the same blood. There is a barrier between the parent and fetus. Only few substances, albeit some bad ones, can enter through. Viruses are usually not able to pass through this barrier."
] |
[
"That is correct the baby and the mother doesn't share their blood. It's the reason why a mother infected by the HIV (which is transmitted by exchange of fluides) doesn't infect her baby until she deliver. And by doing a cesarian you can greatly reduce the risk thus the baby isn't infected by HIV while the mother was.\nIf they were to share blood the baby would be infected as soon it is in contact with the mother's blood."
] |
[
"Can someone explain how Impedence Matching works?"
] |
[
false
] |
A is specialized cable which enables the transfer of Alternating Current with a frequency high enough that the length of the cable begins to matter. (Basically anything higher than mains power). At the end of the line there is usually an impedence-matched load resistor. What is that and how does it work? Does it simply absorb the wave pulse so that a return line is not needed?
|
[
"This is a great response. It should also be noted that when the two mediums are impedance matched, it also minimizes any reflections at the boundary. This helps to minimize signal distortions, so it helps in keeping the signal/noise ratio high. This makes it easier for a receiver at the end of the transmission line to pick out the signal. "
] |
[
"This is a great response. It should also be noted that when the two mediums are impedance matched, it also minimizes any reflections at the boundary. This helps to minimize signal distortions, so it helps in keeping the signal/noise ratio high. This makes it easier for a receiver at the end of the transmission line to pick out the signal. "
] |
[
"You should ",
" watch this ",
"video",
" from Bell labs, where the host use a wave machine to visually show how waves work. You can actually get an intuitive feel for what the impedence matching does, it's very interesting!"
] |
[
"Could neutrinos escape a black hole?"
] |
[
false
] |
So, let's assume, in line with the most recent (although still not accepted) observations, that there is a way of causing neutrinos to travel faster than light. My mate is in a spacecraft, orbiting a black hole. For convenience's sake, let's say he has a period of 10 seconds. He ejects me from the spacecraft in such a way that I'm stationary relative to the black hole. Also I'm carrying a superliminal neutrino emitter, which is sending out a continuous S-O-S pulse pattern. As I fall toward the black hole, and eventually past the event horizon, what does my mate in the spacecraft see with his amazing hand-held neutrino detector?
|
[
"We don't know. Our theories about black holes are based on relativity, which requires that nothing can travel faster than c. If neutrinos can, then relativity is false, and we don't know enough about how black holes work to say."
] |
[
"Because the escape velocity has nothing to do with black holes. You can't simply apply Newtonian physics here. It is actually only a coincidence that naively computing the escape velocity for a black hole yields the speed of light.",
"An easy way to see this is considering this: You don't actually need to travel at the escape velocity to escape the gravitational potential of a body. The escape velocity of earth is 11km/s, but our rockets fly slower than that. As long as they keep accelerating, no problem. Only if you stop accelerating you need to travel at the escape velocity in order to use the remaining momentum to leave the gravitational potential.",
"The more complicated and more correct way to see this is via the fact that the geometry around a black hole makes it so. The radial coordinate inside the event horizon becomes time-like, such that reaching the singularity is as inevitable as next thursday, no matter what kind of speed you have. Of course, all of these findings came from the assumption that special relativity is correct according to which nothing can go faster than the speed of light."
] |
[
"No. ",
"This comment by RobotRollCall is a beautiful explanation of why not.",
" - Gravity works by bending spacetime. Black holes are special because they effectively bend it all the way around to wrap up on itself. Once you are inside the event horizon, all trajectories through space bend back around to point at the singularity. ",
"Speed is irrelevant, because once you're inside, all directions only point further inside. Your neutrino beam can't get out because there is no \"out\" direction to point it."
] |
[
"Hydrogen peroxide (3%) in ears?"
] |
[
false
] | null |
[
"I wouldn't do this on a regular basis. Hydrogen peroxide (a weaker solution than above) is sometimes used to soften built up ear wax in order to remove it with a syringe. This should only be done if you have impacted ear wax that is causing problems.",
"Using peroxide routinely would likely remove, change, soften etc. the ear wax in your ear. Ear wax is essential -- it has antibacterial properties and keeps your ear clean and lubricated. If you remove the ear wax long term you might end up with ear infections or hearing problems. Ear wax is there for a reason, unless there is too much of it don't remove it!",
"If you think you have too much ear wax, go to the doctor and have them assess your ear before you start pouring things into this precious sensory organ."
] |
[
"Thank you for the precious information!",
"\nDo you also happen to know whether hydrogen peroxide diminishes the immune system due to the body's over-reliance of it as being an anti-infectant?"
] |
[
"It shouldn't diminish your immune system as you shouldn't be using it unless you have small wound (i.e. paper-cut, scrape etc). You should only be using it at a 3% solution (or less) for this purpose. You shouldn't be exposing your mucous membranes or really bad wounds to hydrogen peroxide.",
"Plus, hydrogen peroxide is present inside ALL of your cells naturally. Scientists believe that it may play a role in signalling white blood cells to converge on a site of a wound. Of course, this is in very small concentrations as signalling molecules generally tend to be.",
"In plants, it actually increases its immune response. Hydrogen peroxide is a plant hormone, increasing intracellular hyrogen peroxide will increase proteins that defend the plant from fungus and cold temperature. "
] |
[
"Two Time Dimensions"
] |
[
false
] |
What if there were two time dimensions? Would we represent it as a coordinate plane like we do for spacial dimensions? if so what would a point on this coordinate plane represent? (Also if we're thinking of it as a coordinate plane, what if we added the z axis, and thus a third time dimension?)
|
[
"It would be even more wibbly...",
"Though seriously, physicist Itzhac Bars has some ",
"interesting thoughts on two-time physics."
] |
[
"I'm not an expert in multiple time dimensions, but I like ",
"this overview on wiki",
"."
] |
[
"I've been working on this as a side project myself recently. Starting on the assumption that the Minkowski metric (for 2 time, 1 space) can be written as (-,-,+) and that Lorentz scalars must remain invariant under boosts, you can derive the form of the Lorentz transformation. For this metric, all you get is that the transform behaves exactly the same as a 2d+1t Minkowski space (as you would guess) except with the time and space dimensions interchanged. The only problem is that I'm not sure what kind of significance to ascribe to β, because as the ratio of velocity to c, it's ambiguous as to whether the velocity is dx/dt1 or dx/dt2... guess it depends on whether you're moving through t1 time or t2 time.",
"I have not tried it with a 2d+2t space yet, but plan to do so later when I have some time. That one should be a little more interesting. Sorry this doesn't answer your question, I kind of want feedback from some other physicists."
] |
[
"Are mitochondria significantly different in different species?"
] |
[
false
] |
If it were possible to replace the mitochondria in, say, a giraffe cell with mitochondria from a hyena cell, would it work?
|
[
"The current prevailing theory is that all mitochondria are descended from a bacterium that was swallowed by another prokaryote before the Eukaryotic cell even existed--so before animals, plants, fungi, algae, other protists, etc. split off from eachother. Because of that, it's believed that no living eukaryote developed mitochondria-like structures independently--they all come from the same original bacterium.",
"However, like everything relating to life, they have evolved quite a bit in different branches of the eukaryotic tree. In some eukaryotic microorganisms, ",
"it's been highly modified and may not even perform the same function",
". The mitochondria of plants and animals, which are about as far apart as you can get on the eukaryotic tree of life, are fairly similar in broad strokes but have some differences like ",
"the presence or absence of key enzymes",
"Within the animal kingdom, with a quick search I found that there are likely some biochemical differences between ",
"mammal and reptile mitochondria",
", but I couldn't find anything stating that there are major differences between the mitochondria in mammals. It's very possible "
] |
[
"If you didn't research this, why are you answering?? "
] |
[
"Not an expert, just got interested in the subject, please feel free to add:",
"http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0060213#s6",
" ",
"Additions: [[My thoughts on the subject, keep in mind my amateurism]]",
"The wealth of recent data from MA experiments across taxa provides a picture of the mutation spectrum that is far from evolutionarily constant. Mitochondrial genomes [[a mitochondrion has its own circular (not the X setup) DNA]] from yeast, worm, flies, and mouse experience qualitatively different mutational input [[So the DNA of the mitochondria can change]], yet maintain qualitatively similar nucleotide content [[Nucleotides are the building blocks of nucleic acids]] through a mutation-conversion-selection balance that remains to be explained. [[All the mitochondria can therefore create the same output with minor difference]]",
"While pervasive positive selection has recently been posited for the mtDNA, this theory remains controversial. The wealth of new MA data suggests that background selection must have strong effects on the evolution of a completely linked mitochondrial genome that experiences extensive purifying selection to remove mutations. Far from being a neutral molecule, the mitochondrial genome appears to have ample scope to be shaped by negative as well as positive selection.",
"[[So they have mostly the same role, got some only minor modifications but the extent of those modifications is unclear and controversial]]",
"Edit: for the last question, if technically possible, you could, this mitochondrion could do the minimum requirement. But IF a specific mitochondrion from a certain species got expert in reverting mutation (that's one of the theories) is inserted the giraffe (while at embryo stage) then the offspring of your mutated giraffe will mutate slower than the normal giraffe (because your mitochondria are cleaning every mutation you can have)"
] |
[
"If I put a refrigerator in a room with the lid open, does the room get warmer, cooler, or stay the same?"
] |
[
false
] | null |
[
"It depends if the fridge is plugged in and what sort of circumstances you want to contrive for the room. But generally speaking, the room gets warmer. ",
"If the refrigerator is plugged in and running it's still actively trying to keep its insides cold, so it is going to be using electricity which ultimately ends up as waste heat. All electronics do this, it's the same reason computers and laptops get warm. Using energy from electricity ends up converting that energy into heat. ",
"So the refrigerator acts as a heat pump, removing heat from the insides and pushing it to the outside, but it also adds a little extra heat in the process which is the waste from the electricity. As a consequence of the refrigerator being open there is a net positive heat flow into the room, which is the equal to the electrical energy the fridge uses. Curiously, this is the case even when the door is closed and the fridge isn't working overtime to cool itself down."
] |
[
"“it depends on if the fridge is plugged in”",
"Ok."
] |
[
"Is your refrigerator running? This entire thread is literally just a set up for that joke so let's get it out of the way now."
] |
[
"Why are position and momentum related by Fourier Transform?"
] |
[
false
] |
For the context, here is a brief description of my understanding level - I want to understand why the Heisenberg Uncertainity Principle is true and although, I feel like I am being thick headed or something, I really cannot figure out how we went from momentum is inversely proportional to wavelength to the Uncertainity principle. The most common answer is that it results in position and momentum being linked by Fourier transform, but I fail to make the jump. Does it come from Schrodinger equation or is it more fundamental than that? I would be really thankful if you can add some comments.
|
[
"The uncertainty principle is true for ",
" wave. It says that a wave can't be both constrained in space and in wavelength at the same time - the more constrained it is in space, the more spread out it is in wavelength. (I'm going to use wavelength and frequency interchangeably, because for a constant speed of light they're just different measures of the same speed).",
"If you have a wave - say, a sine wave - then the Fourier transform of that wave tells you what frequencies or wavelengths the wave it made of - essentially, what frequencies of sine and cosine waves do you need to add to get your wave. For a single sine wave, this is a single value, so the Fourier transform of a sine wave is a single spike (a delta function) at a single frequency.",
"So for a sine wave, the wavelength is extremely constrained - it's a single value. But what is the ",
" of a sine wave? It just keeps on going on forever with constant amplitude. It's ",
" really - its position is completely unconstrained.",
"So what you can do is add a bunch of sine & cosine waves together to make a ",
". Wikipedia has a nice ",
"gif",
" of what I mean. By adding together the right frequencies, you can get a wave that is all focused around one point. It's a little spread out, but it's not ",
". However, if you take the Fourier transform of this, you find that it's spread out over lots of frequencies. So we've gone from frequency being perfectly constrained but position being unconstrained, to frequency being quite unconstrained but position being quite constrained.",
"If you go through the maths (which I won't do here), you find that these things are anticorrelated: the more spread out the wave is in space, the less spread out it is in frequency (or \"Fourier space\"), and vice versa.",
"This is all true for any wave, and has nothing to do with quantum mechanics. It's just that waves genuinely can't have both a single position and a single wavelength at the same time - it's just not how waves work.",
"Next we add the quantum mechanics part, which is that massive particles are also waves, with a frequency proportional to their momentum. So instead of position being more constrained when frequency is less constrained, we can say that position is more constrained when ",
" is less constrained."
] |
[
"I actually don't like the fourier transform explanation for someone who knows math. It's a much more general rule than that, and honestly, ",
"wikipedia does a pretty good job of explaining the linear algebra derivation of it."
] |
[
"No, any pair of non-commuting observables obeys a minimum uncertainty relation, even if they’re not related by Fourier transform."
] |
[
"How many times has the water we drink today, been consumed by past generations?"
] |
[
false
] | null |
[
"Counting the number of times water is consumed would be incredibly difficult and has a few fundamental challenges:",
"1) Water molecules are created (hydrogen and oxygen atoms joining together as H20) and destroyed (braking water apart and the atoms forming other relationships) constantly. This is happening in your body right now. Given this, are we counting the life of water as the number of times the atoms in water are consumed or is it each molecule of water from formation to destruction? Even so, in the scheme of things the amount of water created and destroyed is a relatively small amount compared to what is just sitting in the oceans. But...",
"2) I would suggest the water molecules in your glass probably haven't been near each other before they entered the pipe in your house. For an idea of the number of molecules under standard conditions, in a glass of water (250ml, 8.5floz) there are 8x10",
" water molecules -- that's more than the ",
"number of stars in the observable universe",
". On top of that water is pushed around the world, mixing in the atmosphere, lake, rivers and oceans all the time.",
"So, I don't know how consumption was determined.",
"Does this mean dinosaurs consumed the same water we drink today?",
"I would hazard a guess and say 'yes', there would be molecules of water that have been consumed by dinosaurs (and even some water created by dinosaurs) that we would drink from time to time. However, I don't know if we would be able to determine how much is present today."
] |
[
"What? Why has it been consumed? "
] |
[
"But water is H2O and hydrogen can be removed from the oxygen atom to form OH- so it needn't be the same water molecule forever",
"Edit: or a hydrogen can be added to form hydronium"
] |
[
"What enables aquatic mammals to hold their breath so much longer than land mammals?"
] |
[
false
] |
Relative to body size, it doesn't seem like the lungs of aquatic mammals are any larger than those of land mammals; yet a sperm whale can hold its breath for an hour and a half and most humans can't hold their breath for more than a few minutes. Is there something special about their lungs? Is it due to metabolic differences? Are humans just especially bad at it?
|
[
"Excellent question!",
"Different Marine Mammals use different strategies for these problems. Here are the big evolutionary advantages developed within marine mammals, though different marine mammals use different ratios of each depending on their environmental constraints.",
"1.) Myoglobin: Basically, this acts exactly like hemoglobin, but is contained within muscles, rather than primarily in the blood. Humans have it as well, but Marine Mammals have an increased amount in order to store even more oxygen!",
"2.) Brachychardia: This is the slowing of the heart rate during dives, this reduces the amount of oxygen used.",
"3.) Blood Shunting: During dives, many marine mammals shunt their blood from their extremities towards their internal, and vital organs, and essentially only send blood to the vital organs necessary, which reduces oxygen usage.",
"4.) Overall Blood Volume: Even animals like a harbor seal have a 1.5-2 times larger blood volume than other mammals with respect to body weight. This increase of blood volume allows for more hemoglobin, and oxygen to be stored.",
"Their are other small behavioral aspects that aid these animals, but here are the big 4 that assist in Marine Mammal oxygen efficiency, and usage.",
"I should say that not all Marine mammals use all of these, but different animals use different rations of these 4 in combination to achieve the overall goal!",
"Source: I'm a Pinniped Biologist.",
"Edit: I forgot the usage of the anaerobic metabolism, which many species are able to switch to in the event of a dive, in order to drive their bodily functions without the use of oxygen!"
] |
[
"Whales exhale when they dive. Their enormous blood supply can hold an immense amount of oxygen. Aquatic mammals have a diving reflex (which can be partially activated in humans in experienced free-divers) which lowers blood flow to non-essential muscles and organs, reducing oxygen consumption."
] |
[
"All marine mammals have haemoglobin, but other organisms in the marine environment may use haemocyanin (a copper based oxygen binder found in crustacea and molluscs) or haemorhythrin (iron based, found in polychaetes) to carry oxygen.",
"edit: some fish don't even have any oxygen carriers at all, and carry oxygen dissolved in the blood!"
] |
[
"Why does Google's Deep Dream code add shoggoth eyes, creepy tendrils, and warped animal faces to everything?"
] |
[
false
] |
, , and . Seriously, I think I understand what it's designed to do, but why does it warp things into an oddly specific sort of nightmarish?
|
[
"It has to do with the training data and what sort of high-contrast, \"easy to find\" features it contains. Most photos interesting to Google have \"human interest\" aspects like people and animals, so that's what they train their ANN with. Eyes are a good example of a feature it's easy for the network to figure out. The tendrils seem to be animal legs.",
"I'd like to see the output of networks trained on other sorts of data sets. Like boobs, if you pardon my crassness."
] |
[
"So, I'm going to type this up under the assumption that Google is using a convolutional neural network, which I'm pretty sure is true.",
"So, having said that, I should start with what that is. CNN is basically an algorithm for training object detection models in image processing (most commonly, anyway). It kills at face detection, and other similar problems. ",
"To get a hazy idea of how it operates, we can start with convolution. Most detection algorithms work by taking fixed sized window in an image, and sliding it around, testing whether each region fulfills some criteria (is this a face?). Then you repeat the process at different resolutions. If you're looking for a face in a random picture, it could be anywhere in the frame, and at any size, so you have to search all of them. As you can imagine, multi-scale sliding-window computations can wind up being very time consuming, so most algorithms use some kind of trick to speed things up. The CNN's trick is ",
"convolution",
", which, long story short, is a fast way to take some template pattern (like an eye for instance), and matching it up against every region in an image. ",
"Then, there's the neural network part. Generally speaking, a neural network, or any machine learning algorithm really, is just a way to estimate a mathematical function. In this case, you have a bunch of images of, lets say faces and not-faces. You want some huge equation, which, given a set of pixels, will spit out a 1 if a picture is a face, or a 0 if a picture is a non-face. You can't figure out this equation by hand, it's got an impossible number of terms, and its very nonlinear. So, you gather a whole lot of labeled \"training data\", and let the network learn to fit such an equation to the data it's been given. ",
"So, you can get an idea of what the network's actually learnt by looking at the terms of this equation. So, in the CNN's case, the network is laid out in layers. What you may find in training such a model is that the outer most layer starts learning basic shapes, such as edges, circles, etc. When the model performs convolution, it tries to match these shapes across the image, and more or less comes up with heatmaps of where they occur, and how strongly. These maps feed the next layer, which winds up looking for specific combinations of these shapes (again, performed by convolution). So, some amalgamation of primitive shapes might make up an eye or nose, for instance. The next layer up does the same thing, but now it's looking for combinations of eyes and noses, and so on so forth, until you have enough layers to confidently identify a face. ",
"I haven't read up yet on how google uses the network to generate images, but, based on how CNN's work, you can definitely get an idea of what's going on. For instance, eyes and animal legs are evidently very prominent features in google's network. Going further, if you're not doing detection, what you're really left with is a collection of \"parts\" which the model has learnt, and their general spatial relationships. So if you have a pair of horse legs in the window you're looking at, the model understands that horse legs come in fours, so it's likely to add another pair. When you slide your window to the side a bit, you're only looking at one pair again, so you get yet another pair, and you wind up with freaky fractal looking patterns of horse legs and eyes and wheels, and anything else that's easily identifiable and comes in groups. ",
"The convolutional aspect of this is why all of the faces make sense in their immediate neighborhoods, but don't really jive with the big picture. It's obvious that the donkey's nose is, in fact, a donkey's nose, given the context of the whole image, but if you zoom in a bunch, and lose that context, the model might guess that it's looking at an eye, which then of course requires an accompanying eye, nose, and mouth. "
] |
[
"From what ive read, the way they generate the images is to run the CNN in reverse: they give it an image and ask it to generate (as opposed to locate) the 'eyes' or the 'dogs' or whatever the network was trained to detect"
] |
[
"What is the “colorful static” that some people see?"
] |
[
false
] |
So a couple years ago, I found out that not everyone can see this, but what it looks like to me is what I like to call “colorful static”. Basically it looks like your vision isn’t completely clear because of all these tiny dots flashing in front of your vision, but at the same time you can see everything just fine. I can see them better at night, and they’re separate from the eye floaters people get. What I’m trying to find out is what it is, and how it’s caused.
|
[
"Are you talking about ",
"visual snow",
"? We actually don't know the cause at the moment."
] |
[
"Like ",
"/u/albasri",
" said, we don't know the cause of it. So what I'm going to write here is purely speculative. Take it with a grain of salt.",
"Visual snow seems to be highly comorbid with high-pitched tinnitus (",
"68% in this case report",
"). There is reason to believe that the two sensory processing conditions are related. Both involve an increased excitability of neurons; neural noise. ",
"Increased stochastic firing seems to be a compensatory mechanism in the case of tinnitus",
", resulting from hearing impairment.",
"How can noise compensate for such an impairment? It increases sensitivity. The cells are more likely to fire at random, but they're also more likely to fire in response to legitimate sensory stimulation. A metaphor that may be useful is that they are more \"on edge\". Stress seems to increase both tinnitus and visual snow in those afflicted. Which makes sense. Threat detection is important. Failure to detect a threat can, evolutionarily speaking, result in death. An increased false positive rate is, in this context, an acceptable tradeoff.",
"Visual snow is also highly comorbid with migraine and migraine auras",
".",
"All of this is pointing to cortical hyperexcitability. Specifically, the primary visual cortex. ",
"And there is some preliminary evidence that this may be the case",
".",
"In terms of signal detection:",
"Enhanced excitability would result in an increase of both true positives and false positives.",
"The excitation/inhibition (im)balance of the neocortex has been linked to both schizophrenia and autism",
". Both of these disorders are characterized by aberrant sensory processing.",
"Since I'm already speculating, I'm going to kick it up a notch.",
"Stress-induced mutagenesis (SIM) is a phenomenon by which stress increases mutation rates",
". Mutation rate can be considered \"noise\" in the same way as the intrinsic excitability of neurons. It has an adaptive value: stress is a proxy variable for environmental fitness, so increasing plasticity relative to stress is an optimal strategy.",
"It may well be that visual snow and related disorders is related to an evolutionarily adaptive response. ",
"It reminds me of pain sensitization, which has been shown to have an adaptive value",
".",
"The link to enhanced vigilance and threat perception suggests to me that there is a connection. Again, this is all speculation."
] |
[
"Oh yeah I am! I didn’t realize it had a name"
] |
[
"slow light"
] |
[
false
] |
Does anyone know of any good books that do a thorough job of covering the material? Or a good review article? If anyone actually works on this, I would love to pick your brain. Edit: since I wasn't clear (sorry, I was on my phone), I'm looking into more on kind of effect. Specifically, I'm looking for a book that might cover the material well, or a good current review article. I'm posting here in the hope that someone works on something similar, or has encountered it in their studies.
|
[
"also, it doesn't ALWAYS travel at the same speed through a medium, it depends on frequency, intensity, and shape of the pulse. the intensity dependent changes are nonlinear effects of the medium that only start popping up for really intense pulses."
] |
[
"classical and quantum mechanical on-resonance nonlinear optical effects. its particularly well pronounced in BEC's because of the whole \"single quantum state\" thing, but it can happen in any medium where you can control the absorption."
] |
[
"something a bit more specific. mechanisms (EIT, SIT), theory, papers (eg. Hau's paper in nature circa 1999), information on stopped light, etc.",
"I know the general story, I want specifics."
] |
[
"Do magnets lose their magnetic properties over time? And why does dust seem to strongly affect how magnetic a surface is?"
] |
[
false
] |
[deleted]
|
[
"Do magnets lose their magnetic properties over time?",
"Over very long times (billions of years), when heated too much, with mechanical shock, or when put in strong external fields, yes.",
"I don't understand the second question."
] |
[
"Materials maintain magnetization for billion of years if they are not heat over the curie's temperature. That's the way how geologists recognize the movement of plates over million of years. "
] |
[
"Materials maintain magnetization for billion of years if they are not heat over the curie's temperature. That's the way how geologists recognize the movement of plates over million of years. "
] |
[
"How is our brain able to pinpoint specific voices in crowds and then focus in on what they're saying?"
] |
[
false
] | null |
[
"Because our hearing system is absolutely amazing. And I mean utterly, utterly incredible.",
"Sounds are made up of harmonics. These are, basically, a bunch of different frequencies that are mathematically related to each other, and the relative volumes of them all determine the ",
" or ",
" of the sound.",
"Even if our ears are being hit with lots of different sounds at once, all comprising of their own bunch of harmonics, our brain is able to take that jumble of noises and group the harmonics that belong together as one sound, another group of harmonics as another... it's how we can, for example, hear a bass guitar, a sax, and a vocal at the same time and be able to hear all three. Our brain knows how to group the frequencies hitting the ear into something that makes sense.",
"So, when we want to concentrate on one voice among a crowd of voices, our brain works as a frankly incredible signal processing unit, identifying which elements of the vibrations hitting your ear belong to the voice you want to hear, grouping them together and presenting them as one unified voice that you can understand.",
"There are other cues the brain can use too; your outer ear, the bit you can see, is designed to affect the time of arrival and tone of sounds depending on what angle they're arriving from and over time we learn how to interpret those to determine sound source direction. If the sound is to one side or the other, the speed of sound means that it'll reach the near ear before it gets to the far ear, and this is also used to determine direction.",
"So, what it comes down to is that your brain can parse the related parts of the audio signal coming in based on whether or not the harmonics are related, and because you have two ears and ear lobes it can also look for directional cues to help focus in on the sound you want to hear.",
"A short aside... as you get older, and also if you get hearing damage, your inner ear gets worse at knowing exactly what frequencies are reaching it - the margin of error gets wider, and loud sounds at a certain frequency will totally drown out quieter sounds around that frequency. The more hearing damage, the wider and deeper this effect will be. That's why as you get older it gets harder and harder to pick out conversation in noisy environments."
] |
[
"This problem, in acoustical psychophysics, is referred to as the cocktail party effect. It has been studied, quite a bit. Almost 100 years ago, scientists made recordings of 6 people reading books at the same time. A listener can attend to only one of the six. If you playback the recording, a listener cannot parse any of them. Even if you use two microphones, it is still nearly impossible. ",
"The cues of interaural arrival time and phase enable specific sounds to be localized in their angle of approach to the head. These cues are one of the major factors that make the cocktail party effect solvable. ",
"Holy cow there are a lot of my friends cited on this wikipedia page...\n",
"https://en.wikipedia.org/wiki/Cocktail_party_effect"
] |
[
"The cochlea is part of the inner ear, and is a snail-shaped (i.e. curled up) organ that starts out wide at the base and gets narrower and narrower towards the apex. The cochlea is topographically tuned to different frequencies, which means that higher frequency sounds are recorded at the wide base, while lower frequency sounds are recorded more towards the apex (with mid frequency in between). Neurons both run to, and emerge from, the cochlea along its length so in a sense different neurons will carry impulses from cells detecting different frequencies. ",
"The part of the cochlea that actually records sound is the hair cells. There are two types: internal and external, and the internal hair cells (IHCs) are specifically the ones detecting the sound (the mechanism is amazing, and if you want I can go deeper into the detail of how sound is picked up). The external hair cells (EHCs) function as amplifiers to amplify the vibration of the fluid filling the cochlea (for reference, IHCs detect sound based on vibration so the EHCs basically amplify the signal to the IHCs). The thing is, whether or not the EHCs are amplifying or just sitting there is regulated by the brain, so if your brain picks up a set of frequencies that it identifies as the target voice (either by you having previously heard the voice or coordinating the voice you're hearing with you visually seeing the target person's mouth moving), the brain will send a signal to the appropriate regions along the cochlea and the EHCs in those regions will amplify vibrations for the IHCs to pick up.",
"Basically, this translates into the brain being able to tell the ear which characteristic voices to focus on, and the ear will \"ignore\" other frequency combinations (= voices) by having the EHCs not amplify in those regions of the cochlea, or at least not have them amplify as much.",
"Source: neurobiology course "
] |
[
"Why aren't we moving at the speed of light?"
] |
[
false
] |
Velocities are relative - spaceship A zipping away from spaceship B at a million MPH is the same as saying spaceship B is zipping away from A at a million MPH. But what is one spaceship is a photon? The photon zips away at c - does that mean the spaceship zips away from the photo at c? The explanations elsewhere I've found boil down to "something with mass can't go c, so no", which is dissatisfying. Why aren't we all moving at the speed of light relative to photons? (Obviously we aren't because we experience time)
|
[
"How long an explanation do you want? The first thing to note is that massless particles do not have a rest frame. By definition massless particles move at c in any inertial frame, so there is a clear contradiction if you try to construct one with a massless particle at rest.",
"There is also a geometric explanation which is probably more satisfying but would take a LOT of explanation to even begin to make much sense."
] |
[
"The laws of physics are invariant under translation, rotation, and Lorentz transformation. Lorentz transformation lets you turn any slower-than-light velocity into any other slower-than-light velocity, but c is still c. There is no reference frame where the photon is not moving."
] |
[
"I think everyone has missed your real question, so I'll restate how I'm interpreting it. Ignore the photon, it is a red herring here and doesn't really get at the real question imo.",
"Say we have a spaceship and a planet. I'm on the planet and a monkey is in the spaceship. The spaceship is travelling away from the planet at some % of c, so we know time will pass slower for him and faster for me, but why? Couldn't you construct a reference frame where he is not moving and my planet is moving away from him at some % of c? Another question, does the time dilation only happen during acceleration/deceleration?"
] |
[
"I've heard that the Azolla fern could be used for carbon sequestration. How do you measure how much CO2 a plant is absorbing? Could an individual person measure how much CO2 a plant take in?"
] |
[
false
] | null |
[
"Just to be clear, you cannot just weigh the plant. It is mostly water. You have to dry it first.",
"Plants also do reactions other than photosynthesis, so the element ratio in the plant will not be the same as in the photosynthesis equation. Lignin has a higher carbon content than carbohydrates, so if you assume the plant has empirical formula CH",
"O, you'll underestimate the carbon content of woody plants."
] |
[
"Would it not simply be dependent on how fast the plant grows, which can be measured by weighing the plant with all other inputs (eg. water) controlled? The chemical equation for photosynthesis would enable calculation of the amount of carbon dioxide reactant. Wikipedia states that azolla fern can double its biomass in 1.9 days."
] |
[
"Here is an outline of an experimental design you could do at home to measure the carbon content of a plant: ",
"https://edu.rsc.org/feature/the-carbon-dioxide-problem/2020244.article",
". It's behind a signup wall but you get one free article.",
"Instead of waiting for the leaves to decompose, after sealing the containers, ignite the leaves, possibly by focusing sunlight with a magnifying glass. With appropriate precautions, adding an oxidizer like potassium chlorate to ensure complete combustion might be useful. I wouldn't use a nitrate oxidizer because I worry this would release nitrogen oxides that could contaminate the alkali and mess up the results."
] |
[
"How does inhaling marijuana smoke affect your mucosa?"
] |
[
false
] |
Specifically, how does the smoke from marijuana (asking here about both unfiltered and water-filtered smoke) affect your mucosa? Specifically, the gastric, oral, buccal, and bronchial mucosa are of interest. Specific questions regarding the mechanism of action of smoke on mucosal surfaces I have include: is cottonmouth a mental or physical phenomenon? Can irritation of the mucosa cause swelling, vasodilation, or water retention in the affected areas? Otherwise, I'd like to know generally what happens physiologically. Citations of studies instead of comments are just as appreciated! Reg
|
[
"There is only a little good info on this, but we ",
"can start here.",
"\nFor a study of this nature, I'm happy with what they published, and this is even a reasonable sample size. They also have good p values and stat's tests, excepting the results for Cocaine-Marijuana smokers.",
"Table 5 shows the rates of histological abnormalities in different groups. MS (Marijuana smokers) and TS (Tobacco Smokers) both show increases in a number of measures, and MTS (Marijuana-Tobacco Smokers) show additive increases.",
"The things that occur in order:",
" These are basically stem cells that replace the epithelium, ciliary cells, mucous or goblet cells and even Clara cells that are a specializied ciliary cell. More of these implies damage is occuring at an increased rate in the lungs and cells require more frequent replacement. While we can't say this alone is a precursor to cancer it would be foolish to expect it plays no role.",
" This refers to flattening of cells that are normally not flat or squamous, in shape. Mechanical damage like this is usually due to the inhalation of irritants.",
" This is overproliferation of goblet cells, or mucuous producing cells within the airway. This means the lungs are trying to secrete more mucus to protect from irritants.",
" This means we can see changes in the shape of the nucleus, or the structure of it, on examination and is a strong precursor to a number of diseases. Marijuana smokers alone don't exhibit enough of this for us to suspect a correlation.",
" The number of cells examined that are undergoing mitosis. Can be significant, but is not significant in the marijuana smoking population of this study.",
" This is a measure of the size of the nucleus in comparison to the cytoplasm. An increased ratio implies the cells being examined are more juvenile, as the nucleus decreases with age.",
" I'm going to cover both listings here. We note increased ECF (extra-cellular fluid) in these samples as well as increased white blood cell activity. Typically neutrophil infiltrates. It's not present below the epithelial layer in marijuana smokers however.",
" This damage while we haven't as last I checked positively completely correlated it with a restrictive lung disorder can be an early indicator of that. Restrictive disorders affect the diffusion rate of oxygen from the alveoli [air sacs] into the bronchial capillaries. The basement membrane of the airways is thickened as a result of inflammation and fibroblast proliferation.",
"The other mucosa will likely exhibit similiar effects, but I find little study showing such strong information. This should cover your question about irritation of the mucosa, as it's clear they show inflammation, which is what you described.",
"Cotton-Mouth",
" is a physical condition that can be caused by a number of conditions and has varying treatments depending upon the cause.",
"Marijuana smoke may actually harm your immune system.",
" It can also impair diffusion and the rest of their observations support the earlier studies histopathological findings.",
"Further support of these findings.",
"A good resource for lung histology, albeit nowhere near complete.",
" It has a good overview for the majority of what we've discussed here."
] |
[
"The DCO in Table 4 is also, albeit only slightly, below predicted, and is indicative of a restrictive lung disorder. Keep in mind however that wheeze, sputum production and acute bronchitic episodes in MS are elevated, which are obstructive disorders.",
"I personally feel it's reasonable to predict MS will see similiar combined disorders like COPD, but with an additive restrictive element.",
"The p values for all the MS analyses are of statistical relevance, meaning that the concerns of the other histopathologies noted are of concern and relevant. This could lead to cancer, bronchitis, or other obstructive respiratory illnesses.",
"I'm not familiar with anything regarding water pipes/ glass or metal pipes. Let me find traumazulu, he might."
] |
[
"Obstruction is more acute than restriction.",
"Obstructive lung diseases include asthma and COPD, and refer to the obstruction of airflow entering/exiting the lungs. They're generally related to inflammation and airway constriction due to irritation. Chronically they become worse due to the loss of lung compliance (elasticity of the airways) which causes collapse.",
"Restrictive refers to disorders that limit lung volumes, or mimic a decreased lung volume. Obstructive disorders can cause they when airways collapse, but we're typically thinking of things like fibrosis, silicosis etc. when thinking here. They prevent the oxygen from dissolving across the membrane from alveoli to capillaries properly. This is, at heart, a volume problem.",
"I'm trying to make this more clear, but it's tough without knowing your physiology background. Hopefully I've cleared things up instead of made them more confusing, and feel free to ask more!"
] |
[
"Is it possible that one of the gene edited Chinese twins is does not have their genes edited to fight HIV as part of a placebo study?"
] |
[
false
] | null |
[
"Who knows. That's not what they said they did. "
] |
[
"Well no shit that’s not what they said. The premise of my question wasn’t what they said it was the possibility of a placebo study. Granted a speculative question but your response neither adds to nor detracts from the discussion. It merely points out the most obvious by stating that they didn’t say that. As though what people say they do is exactly what they actually do. "
] |
[
"The question in your post is about what they did. What are you trying to ask? Is it possible to do a study where the genes of one fertilized egg are edited and the genes of another are not and then both are implanted? Sure, why not. "
] |
[
"Is there a function/equation for every different combination of graph?"
] |
[
false
] |
So as the title says, If I were to have a graph let's say showing sales over time for a specific time frame, would it be possible to actually form an equation for that specific graph? I'm not sure how feasible it would be but theoretically is there an equation for every single graph you can draw? So if I were to right now draw a random graph, could it be possible to find an equation for that graph no matter how many zig-zags there are in it etc?
|
[
"You have to realize that the functions that you learn about and use in school are very limited. You learn about polynomials, rational functions, trigonometric functions, exponential functions, logarithmic functions and that's basically it. Theses are the ",
"Elementary Functions",
" In the grand scheme of \"All Functions\", this is practically nothing. Almost all functions that exist are not elementary. They are like the content in a demo version of a game. There are many other functions that are used all the time that cannot be made from these. Functions like the ",
"Bessel Functions",
", the ",
"Jacobi Elliptic Functions",
", the ",
"Gamma Function",
", and many many more. None of these can be written using the familiar elementary functions. ",
"This being said, how general of an answer do you want? If you want to build things up from all of the functions that humans are currently aware of then no, there are definitely curves that cannot be written in terms of functions that all of humanity knows, since most functions are unknown to humanity. If you are asking if there exists a function for every possible graph that we can draw, known or otherwise, with infinite precision, then the answer is definitely yes.The graph is a bunch of ordered pairs like (x,y), where each x only appears in the first coordinate once. We can define the function F so that F(x)=y whenever (x,y) is an ordered pair in the graph. This is a function whose graph is, by construction, the original graph.",
"If you just want to get \"close enough\" and your curve is continuous (you can \"draw\" it without picking up a pencil) then you can always approximate it with polynomials (get as close as you like). Arguably, since a pencil, or any visible line, is \"fat\", then this means that you can find a polynomial that fits inside any continuous graph that you draw or see. See ",
"Stone-Weierstrass Theorem",
", and be thankful for ",
"Uniform Convergence",
". "
] |
[
"A function is a set of x-y coordinate pairs such that there is at most one y-value that gets paired with a given x-value. I assume that's what you meant by graph. So really the question is if there's an equation for every function.",
"But if you're asking about just ones that can be written out, the answer is no. There's only as many equations you can write down as there are natural numbers. If you have n symbols, then you can think of it as the number that would be in base n. Even if you allow infinitely many symbols, that's only enough to write one for every real number. Just do what you did before, but with a 0. at the beginning, and it will give you a real number between zero and one. There will be a few duplicates, but just do it in base n+1, so you never use the highest symbol, and you can't get the equivalent of point nine recurring.",
"The number of functions is equal to the cardinality of the ",
"power set",
" of the reals. That is to say, there are as many as there are combinations of real numbers. It's fairly simply to show there must be at least that many. You can make a function from functions to combinations of reals by looking at just the real numbers where that function is nonzero. That gives you every combination. And by ",
"Cantor's diagonal argument",
", a powerset has more elements than the set it's a powerset of. In other words, there are more combinations of real numbers than there are real numbers.",
"In short, there are more functions than there are equations, so there can't possibly be an equation for every function."
] |
[
"If I were to have a graph let's say showing sales over time for a specific time frame,",
"This is a special case, because you probably only measure \"sales\" at discrete intervals. Like every quarter or every month. ",
"Given a graph like this, with y values at discrete x intervals, you can always write an equation for a smooth function connecting the dots using ",
". In fact you could write infinitely many such functions for any such graph. The trick is to find a smooth function that matches our intuition about how \"sales\" are changing in the intervals between the measurements. There are various ways to do that, such as polynomial interpolation (with various choices of polynomial basis sets), spline interpolation, sinc interpolation, etc."
] |
[
"Are there contradicting phylogenic trees both based on genetics such as cytochrome c and something else? Or are they all very harmonious?"
] |
[
false
] | null |
[
"You can certainly have contradicting trees if you use different characters, genes vs morphological characters. You can even have contradicting trees if you use different tree searching methods (distance-based methods, or character-based methods), and choose unwisely, given the limitations of some methods in different cases. And you can get different trees based on what substitution model you choose. For example, maximum parsimony is subject to long-branch attraction, which is the incorrect grouping of rapidly evolving sequences (high rates of substitution (long branches)), and distance-based methods like minimum evolution assume that divergence rates are identical in lineages.",
"But let's assume you are using the same method, yes you can get different trees. You lose a lot of information when you ",
" use a discrete or continuous morphological character. By discrete I mean, the presence or absence of a structure (let's say a horn, 1 = present, 0 = absent), and by continuous I mean scale (if they all have horns, 1 = very long horn, 2 = medium length horn, 3 = short horn). The big downside to this is that it assumes that convergent characters do not exist, which really overlooks homoplasies which can show up in paraphyletic groups, or polyphyletic ones.",
"While I'm already discussing it, you can use mixed models, which take into account both genetic and morphological characters. Off the top of my head I do know that Bayesian inference can do mixed models, there may be others.",
"When I was doing work on bivalve phylogenetics, we were using several genes, 12S, 18S and COI, and were combining morphological and anatomical characters into the models."
] |
[
"In phylogenetics, we are usually concerned with estimating the \"Species tree,\" which reconstructs the order and timing of speciation events. For instance, we try to figure out which of the great apes shares the most recent common ancestor with humans. We can reconstruct this phylogeny using any type of inherited data, but DNA data is used most often these days.",
"Individual gene sequences, such as Cytochrome C, estimate the species tree imperfectly, because the gene contains a limited number of DNA characters. Also, the tree we build for cytochrome c may differ from the tree we build from hemoglobin. This is expected on any phylogeny due to a process known as \"Incomplete Lineage Sorting.\" ",
"This is not surprising to phylogeneticists. ",
"Mathematical models of how DNA evolves",
" on trees predict how likely it is that a gene tree will disagree with the species tree.",
"For instance, a recent paper (",
"available here for free",
") showed that about 0.1% of our genome is more closely related to orangutans, rather than to chimpanzees. If you were to build a phylogenetic tree using a gene from this 0.1%, it would show Humans and Orangutans sharing a more recent common ancestor than Humans and Chimpanzees.",
"However, the grand bulk of the evidence, coming from the other 99.9% of the genome, shows that chimpanzees share the most recent common ancestor with humans. ",
"One reason that genes may reconstruct different phylogenies is recombination. In your example, cytochrome c is a gene located on the mitochondrion, and therefore is only passed from mother-to-daughter and son. It will likely have a different gene history than a gene located in our nuclear genome, such as the gene for hemoglobin.",
"You can read more about the relationship between gene trees and species trees here, including some really good illustrations: ",
"http://biologos.org/blog/evolution-basics-species-trees-gene-trees-and-incomplete-lineage-sorting"
] |
[
"I don't mean to seem like I'm trying to nitpick your posts, but I have some points of clarification on this as well:",
"Weights are not assigned in Bayesian and maximum likelihood analyses in the way that they can be in parsimony analyses. What are probably most analogous (but still considerably different) to parsimony weights are the rates of character substitution for each partition. If a particular partition has a higher substitution rate than another, then changes in this partition will be considered to be more likely, and homoplastic substitutions will be more likely for this partition than for the partition with a lower substitution rate.",
"In a Bayesian analysis, one could assign a higher prior probability to a high rate for a particular partition, but I cannot recall ever having seen this done. Rather, flat priors are generally assigned to all partitions, and the substitution rates are then inferred in the analysis.",
"The answer to the ",
"/u/FurthurPenguin",
"'s question",
"How do you figure and weigh which genes are more important in mixed models?",
"is generally that you don't make a decision, but you allow the analysis to infer the rates of substitution from the data. How this is actually done is fairly complex."
] |
[
"Theoretically speaking, could antimatter be contained and stored?"
] |
[
false
] |
My understanding of antimatter is limited, but what I do know is that if antimatter meets regular matter then they destroy each other. With that in mind, is it possible in theory for antimatter to be stored? For example, a chunk of antimatter suspended in a vacuum by a magnetic field. I imagine it would take a lot of power and technology we're nowhere close to now, but is it possible? I've seen antimatter used as weapons in a few sci-fi stories so it got me curious about how it would be stored/manufactured.
|
[
"This is already done, in electromagnetic traps. It's really difficult, and the length it can be trapped for is limited."
] |
[
"There's always a probability that the antiatom will be found somewhere sufficiently far from the trap centre and annihilate with a regular atom."
] |
[
"Why is the time span limited? Is this something to do with the magnetic field or stability of the antimatter, etc?"
] |
[
"If an issue of aging is rising levels of cortisol, why not remove the Zona Fesiculata or else remove an adrenal gland when you have higher levels of Cortisol?"
] |
[
false
] |
From what I understand, Cortisol is only really useful during gestation and in small doses, stimulating the conversion of T4 to T3. As you get older, Cortisol is catabolic on everything, making you store fat viscerally around organs instead of subcutaneously (terrible for life span). At high levels, Cortisol will shut down TRH and TSH, inhibiting T$/T3, which lowers metabolism. Cortisol also lowers the reproductive axis, negatively effecting levels of GnRH, LH, and T. High levels of Cortisol also causes higher sodium reuptake, since it overwhelming the 11BHSD at the kidney that makes cortisol unable to bind to the Aldosterone receptor (since both cort and aldo can bind to the receptor). So, at high levels of cort, you get higher sodium reuptake, causing high blood pressure --> thus the need for low sodium diets hen you are older. Also, since CORT is a glucocorticoid, it ups the glucose in the blood, so even more high BP. Cortisol, since it is catabolic, also causes you to lose calcium from the bone (since it degrates the collagen, so there is no where for Calcium to be put on). Yes, while messing with the endocrine system can be dangerous, why isn't removing an adrenal gland (or at least the cortex) an option FOR WHEN YOU ARE OLDER? (unless it is, and I didn't know?) The adrenal cortex makes weak androgens, cortisol, and aldosterone, the only one of which is necessary for life is aldosterone. Seeing as you have higher levels of cortisol anyway, won't it be enough if you just have one adrenal gland working? This is just me thinking, and wondering what you all have to say about it! :) added older part.
|
[
"A number of thoughts come to mind about your assertion. I think you can claim a superficial level of plausibility, in as much that, nothing you say is actually wrong. However, I think the difficulty lies in the fact the system is so complex, that it is possible to find supporting observations for almost any hypothesis. ",
"It’s probably useful to break down what you are suggesting into more manageable bits and look at whether there is supporting evidence. ",
"Its certainly seems that we make more cortisol as we age, (although saying its “too much” is perhaps a bit loaded) and several studies have shown this (Purnell et al, JCEM 2004 for example).",
"These higher levels of cortisol contribute to mortality.\nHarder to say. There is a recognised association between higher cortisol levels and cardiovascular mortality, but that doesn’t mean that it is causative – it might be that sicker people have higher cortisol levels because they are sick, not the other way around.\nThere are some plausible mechanisms by which cortisol might lead to heart disease and stroke though, probably related to fat deposition and metabolic syndrome.",
"Removing an adrenal gland will reduce the cortisol levels and thus improve lifespan.",
"I think this is where you are making the big leap. First, what effect does removing an adrenal gland have on plasma cortisol concentrations? I don’t know of any literature on this, but I don’t believe having only one adrenal has any clinical significance, or any effect on adrenal testing for example. I would strongly suspect that if you removed one gland the other would compensate and bring your cortisol levels up to what they were before, thus making your intervention worthless. However, if it does have an effect, how would you predict it? – what cortisol level would you be aiming for and how would you know if adrenalectomy would achieve it?",
"Its worth looking at outcomes for people with glucocorticoid deficiency, as by your hypothesis, people with these deficiencies should perhaps live longer. Secondary adrenal insufficiency does not include mineralocorticoid insufficiency, but the data suggests theses people have a higher mortality rate (Tomlinson et al, Lancet 2001). Health related quality of life is also impaired in these people and many of them are on disability pensions. Adjusting the dose does not seem to make much difference (Riedel et al ,Exp Clin Endo 1993) which suggests things are probably a lot more complex than we realise.",
"I would suspect that one area of complexity would be differential tissue cortisol acitivity. You touched on BHSD activity in your post, and certainly differential regulation of this enzyme system will have profound effects on glucocorticoid activity in different tissues that wont be reflected by plasma levels. ",
"I think overall, one thing we have learned in medicine is that what seem to be simple interventions can have unforeseen outcomes. Cutting out an entire gland is perhaps a bit of big step to take based on speculation, even if it is informed ☺ "
] |
[
"first, i think you should really understand what cortisol does[wiki it, i know this is ask science but theres A LOT of information regarding cortisol; it interacts with so many aspects of metabolism and the body that its next to impossible to explain it briefly here. I've looked over the wiki article and its spot on]. A lot of the above are really nitpicky circumstances. They almost require a pathological state or exogenous use(either a cortisol or ACTH secreting tumor, pituitary adenoma, or someone who is taking steroids for autoimmune diseases or for recreation). ",
"Cortisol is responsible mainly for maintaining glucose levels in your blood, as well as to act as an antiinflammatory and inhibitor of cytokines[interleukin 2]. Without cortisol, you run into a whole list of problems, including death. see: ",
"addisons disease",
"High levels of cortisol caused by stress, for example, can suppress the production of TSH, leading to symptoms of hypothyroidism due to low hormone production. \n--",
"http://health.howstuffworks.com/human-body/systems/endocrine/understanding-thyroid-metabolism.htm",
"Yes, cortisol does cause fat accumulation; this is believed to be due to cortisone inhibition of lipolysis. \n-- wiki",
"suppression of sex hormones occurs only when cortisol levels are HIGH(again, pathologies); even at that its not a pronounced symptom(its more likely to be a prolactinoma/adenoma if someone comes in complaining of sexual dysfunction or performance anxiety).",
"Glucocorticoids aren't really responsible for sodium reabsorption. that is the job of aldosterone and to some extent ADH(antidiuretic hormone). \n--Cortisol inhibits sodium loss through the small intestine of mammals.[24] Sodium depletion, however, does not affect cortisol levels[25] so cortisol cannot be used to regulate serum sodium. -Wiki",
"\"Also, since CORT is a glucocorticoid, it ups the glucose in the blood, so even more high BP.\"\n--what do you mean? by increasing the glucose in the blood, you will not increase the BP via the sugar. BUT, GluCorts also have a synergistic effect with epineprine and norepenephrine, which can cause increased BP. ",
"Again, without glucocorticoids YOU DIE. You need some level of glucocorticoids in your body in order to undergo gluconeogenesis in times of starvation. Its one of the ways your body prevents you from going into a diabetic coma. Remember, you can live for days with blood sugars in the 500-600(normal is 100-120, its obviously not good but you won't die). Guess how long you live with a diabetic coma in which your sugars are low enough to make you unconscious? (say 40)...FOURTY FIVE MINUTES and you're dead or have severe brain injury! Crazy no? ",
"Cortisol, since it is catabolic, also causes you to lose calcium from the bone\n--this mechanism is not fully known, although it was tested on my boards. What the current thought is, is that glucocorticoids activate a RankL gene which is responsible for upregulating macrophages. the macrophage of the bone is the osteoclast. This is the reason behind steroid induced osteoperosis. Again, this requires long term use of steroids at high levels. Most patients are also given fosamax or some sort of calcium supplement to combat this effect. They are also told to do weight bearing exercises multiple times a week to maintain bone density(assuming they can be active on their own). the collagen degradation was only found in lab rats, thus is can not be extrapolated to humans. I have never heard of this but if you can show me an article with human subjects id be interested to read it :)",
"In medicine, we don't want to remove anything that isn't causing a problem(there's a whole new list of problems that occur after surgery). While steroids do have many of these effects, they really don't manifest unless a pathological state exists. As we age, a lot of patients get the problems above but its not necessarily due to steroids alone. Many of these people will get these problems via genetics or lifestyle choices. This is why the majority of statements above are really only applicable to circumstances where excess cortisol is being secreted(tumors). ",
"There are times where the adrenal gland is removed; ie pheochromocytoma. In this case, one or both of the adrenal glands are being removed due to excessive adrenaline(epi+norepi) production; this can cause arrhythmias, vasoconstrictive crisis, heart attacks, strokes, etc. When an adrenalectomy is performed, the patient must be placed on exogenous steroids for life(11-Deoxycorticosterone has effects similiar to aldosterone). In this instance, the risk of keeping the adrenal tumor is much higher than requiring the patient to take meds, unlike the instances in the OP. "
] |
[
"Thanks! That was the kind of answer I was looking for :) "
] |
[
"How do we know what the Milky Way looks like?"
] |
[
false
] |
You always see pictures of the Milky Way, but I assume this is just interpretations. How do we know its a spiral galaxy, and where we are in relation to the rest of it.
|
[
"From one of my previous answers to this question:",
"Star counts. Lots and lots of star counts. Mapping the galaxy is a very difficult, pain-staking, and error-prone process. The basic idea is that astronomers count the number of stars brighter than some value in various directions. As you decrease the lowest brightness, you probe farther distances. This is all confounded by the fact that stars have a large variety of luminosities and (especially) there is a lot of dust in the galaxy which obscures light. The fact that this dust is somewhat clumpy makes the problem even worse.",
"As a consequence of the dust, we can't really see much of the other side of the galaxy, particularly toward the galactic center, so we don't really know what's going on there. There could be a dwarf galaxy hiding behind the Galactic center and we wouldn't know it. (Although, in principle it would be possible to detect something like that due to its gravitational influence on the Galaxy.)",
"Another technique to determine the shape of the galaxy is to map neutral hydrogen gas by observing the 21 cm line in radio. Radio waves don't get obscured by dust, so this can be more useful for mapping out more distant parts of the Galaxy. ",
"Kinematics are also important. By measuring the direction and speed with which stars are moving, it is possible to determine (in conjunction with star counts) whether the galaxy has a bar, and if it does, how large a bar it has. "
] |
[
"The dust is a problem for optical light, but if you work in the near or mid-infrared, its extinction is much reduced and you can actually see stars through the dust. Of course, you still have to deal with the fact that any stars on the other side of the galaxy are at least ~30,000 lightyears away.",
"Also, the relative densities of pulsars (whose radio emission is mostly unaffected by intervening dust) can be used to trace the location of spiral arms."
] |
[
"Sky surveys and then models based on this. The Sloan Digital Sky Survey is one of the more modern spectroscopic surveys. This data can then be fed into models. (SDSS: ",
"http://www.sdss.org/news/",
")",
"There are areas of course that cannot be mapped, because they are 'out of view'. For example you cant look through the bulge of our galaxy because it is too dense. ",
"To try and map this region usually relies on models. The Milky Way is thought to be quite similar to M31 (Andromeda) which we can see the whole of, because it is handily face on, rather than edge on. ",
"This allows us to fine tune the models, and make a better interpretation of whats in the bits of the MW that we cannot see."
] |
[
"Books on the theory of evolution?"
] |
[
false
] | null |
[
"If you want to read everything, start at the beginning, which is slightly ironic since the topic is evolution, and thinking has, well, evolved:",
"On the Origin of Species by Means of Natural Selection",
"Warning PDF."
] |
[
"Thank you. And where do I go from there? I would also like to read the history of it all. The response it got and the arguments against it."
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"A good home for this question is our sister subreddit ",
"/r/AskScienceDiscussion",
". It might be too open-ended or speculative for ",
"/r/askscience",
". ",
"/r/AskScienceDiscussion",
" is also a better place for advice on education, book suggestions or general questions about working in STEM. Please feel free to repost there!",
"Please see our ",
"guidelines",
".",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"As a kid my mom told me not to freeze my plastic water bottles because the frozen water would attatch to particles on the plastic. Is this even remotely true?"
] |
[
false
] |
I had a lot of warm water as a child..
|
[
"There is a slight truth to it, in the sense that ice crystals need something to nucleate around, so if your plastic is a bit rough (on a microscopic scale) that will be where ice crystals will start to form during the freezing process. ",
"As others have pointed out, that won't actually cause the particles to get into the water, nor would it be bad for you."
] |
[
"The water isn't going to attach to anything, but plastics can decompose and get into the water and you end up drinking it... (after high temperature treatment, at least) and they can mimic certain hormones like estrogen which is one of the reasons for the shift away from using BPA-based plastics."
] |
[
"not really. and even if it did \"attach,\" that does not mean that the plastic molecules would detach and float around in the water. And then, even if they did, there is nothing that indicates they would do anything more than just pass harmlessly through the body"
] |
[
"What makes a battery or cell \"heavy duty\"? How does it differ from a \"normal\" cell?"
] |
[
false
] | null |
[
"Marketing, usually. Industrial batteries are designed to have a longer shelf life by sacrificing capacity. Battery manufacturers sometimes come up with ways of improving the capacity of consumer batteries, and market the \"new\" design as something like \"MAX!\" or \"Heavy Duty\", but the terms have no official meaning. They're just marketing fluff."
] |
[
"It doesn't really mean anything. It's usually just down to marketing."
] |
[
"Does that mean these \"heavy duty\" cells have a higher capacity in exchange for a poorer shelf life, in comparison to say, \"standard\" cells like the average alkaline?"
] |
[
"Calculating the time dilation for an object inside a black hole returns imaginary values, does this have a deeper meaning?"
] |
[
false
] |
[deleted]
|
[
"The Schwarzschild coordinate chart does not cover the region beyond the event horizon. To the faraway observer, the inside region doesn't even exist. It doesn't make any sense to talk about the time dilation factor between a faraway observer and an observer beyond the horizon. "
] |
[
"A Schwarzschild black hole singularity is always hidden behind a horizon. Naked singularities don't seem to exist but if they did, then, sure there could possibly be a single chart that covered all of the relevant spacetime. The Kerr metric for a superextremal black hole is one such example. ",
"The original question was why the time dilation factor gives an imaginary value. The simple answer is that the formula uses coordinates that are not valid for the interior region. Singularity or no, if the coordinates don't work for that region, then you certainly can't use any formulas derived from them. ",
"For instance, we can map the northern hemisphere of Earth to some disk in the xy-plane by simple downward projection. This coordinate chart would be invalid for the southern hemisphere. So any sort of formula that tells you how two points are related using these coordinates certainly can't be used to relate a northern point to a southern point. "
] |
[
"Hmm, what if cosmic censorship were wrong and we had a naked singularity? An object could be closer to the center of mass than the Schwarzschild radius and we would still be able to observe it."
] |
[
"[Physics]My 12 year old wants to know if a microwave oven would turn thermal paper black? And, of course, regardless of what the answer is, why?"
] |
[
false
] | null |
[
"Your 12 yr old may also be interested to know that rubbing alcohol will also turn thermal paper black. ",
"I'm actually not sure why this is but if anyone out there has an explanation, I'd love to see it. My guess is that the alcohol causes the activation temp of the paper to change, but again I actually have no idea why this works."
] |
[
"It's not only water molecules but also anything opaque to that frequency of light"
] |
[
"No, it is not the resonant frequency of water, that has absolutely nothing to do with it. It will heat a wide variety of dielectrics and conductors, not just water. Stop spreading this false rumour. ",
"2.4 GHz was chosen because:",
"It's fairly cheap and easy to generate high power waves with a magnetron, 2.4 GHz is in no way special though and there is a wide range that would work",
"It's a good frequency for dielectric heating (not resonant), which can heat a wide variety of things found in food besides water. Though once again, a wide range would have also worked. ",
"the waves need to have a wavelength small enough to resonate in the microwave oven itself. In other words, anything with a wavelength larger than the oven is out. My use of resonant here has absolutely nothing to do with water. ",
"and most importantly for 2.4 GHz being chosen specifically, it's an unlicensed bandwidth so consumer products are free to use it. Most of the spectrum is licensed to various things like telecommunications, satellites, air traffic, etc. so you can't just go off making a 1 kW transmitter in any frequency you please. It's the same reason why wifi and Bluetooth happen to use the exact same frequency. It has nothing to do with water. ",
"As for the natural frequencies of water's vibrational modes, ",
"they appear to be in the IR spectrum."
] |
[
"How can Olympic skiers jump the distance of a football field going 40+ mph without sustaining an injury?"
] |
[
false
] | null |
[
"Because the distance doesn't really matter (for the injury part). Imagine if they were on a horizontal plane. The height of the jump would not be that high relative to that plane.",
"Also, the angle of the landing zone to the angle of the skier when they touch down is small because the slope of the landing zone is similar to the trajectory of the skier."
] |
[
"Yup, adding to that last point, imagine throwing an egg or water balloon up in the air. If you try to catch it by just putting your hand out they will break. But if you continue with the egg/ water balloon's motion and slow it down more gradually then you reduce the amount of force that is experienced and decrease the likelihood of breaking the egg / balloon / a bone. ",
"If you want to get more physics-y, if you remember newton's law which states that force = mass x acceleration, essentially what all these are doing (and same as airbags and padding and pretty much everything we use to land safely on things without injury) is decreasing the acceleration by increasing the time it takes to stop. so instead of the skier going from X mph to 0 mph in a fraction of a second, they're taking much longer to slow down which means less acceleration and therefore less force of impact."
] |
[
"Because of the sloped landing. Also the terminal velocity of a flying skier is relatively low because their wide skis acturally generate lift. That's why it's crucially important for a ski jumper to maintain the correct pose and angle in flight - if one of the skis stalls the jumper will tumble down and slam into the landing at very high speed.",
"Watch this video",
" - notice how the jumper's left ski stalls due to the incorrect angle of attack and immediately sends him plummeting towards the landing."
] |
[
"Why are there common food allergens?"
] |
[
false
] |
[deleted]
|
[
"A theory of why people seem to be developing so many more food allergies is not just because or food sources are more globalized than ever, but due to the inflammation response. Your microbiome (all the bacteria living in your body) have a big effect on your immune system and how it responds to external factors. Breast milk selects for very specific bacteria in your gut that aid with development and your immune response. Many mothers have gone towards formula with \"prebiotics\" in them which enrich for bacteria, but are no where near as specific as human milk oligosaccharides.",
"Also, the diversity of the mother's diet can also have a big effect on food allergies. If the mother is a picky eater and tends to avoid certain foods or food groups, it is more likely that the offspring will have allergies to those foods. Again a lot of this stuff comes down to the antigens you are exposed to early in life, your microbiome, inflammation response, and how your immune system reacts to foreign antigens.",
"TL;DR Breast feed your children, eat a balanced diet to maintain good bacteria in your gut (also drink Kiefer)"
] |
[
"Several reasons have been given as to why peanuts are more allergenic than other foods. Seed storage proteins are extremely ",
" from heat, acidity, and proteolytic activities (Koppelman et al., 2010). Moreover, factors associated in the manner in which peanuts are processed can also lead to higher allergenicity. It has been suggested that roasting peanuts in high temperatures can cause ",
" versus boiling or frying, with the latter methods of preparation being found in cultures with a lower incidence of peanut allergy (Chung et al., 2003; Maleki et al., 2003).",
"source"
] |
[
"You drink a big ol' glass of Kiefer Sutherland, he will help support a healthy immune system...",
"Yes that was a typo, I meant Kefir. Thanks :p"
] |
[
"Is there any difference between a black hole made out of regular matter and a black hole made out of antimatter?"
] |
[
false
] |
Suppose we have two identical stars (size, mass) except that one is made of matter and the other of antimatter and they both implode into black holes? Are the two black holes identical? If not, what happens if they collide?
|
[
"No there is not. Black holes only have three properties: mass, spin, and charge."
] |
[
"Specifically, the \"no hair\" theorem— which says that black holes only have those three properties— implies that black holes don't conserve baryon number (or ",
"lepton number",
"). A black hole made from the collapse of a matter star would be indistinguishable from one made from the collapse of an antimatter star.",
"This is related to the black hole \"information paradox\", which is one of the places where general relativity and quantum mechanics disagree vehemently. There is speculation that a hole's Hawking radiation might radiate out some information, or an evaporated hole might leave behind a quantum turd, to make the numbers balance, but AIUI those are just speculations. It's an open question."
] |
[
"At Cern, a physicist I was talking to was in the middle of an investigation to determine whether anti-matter followed normally gravitational effects, because an element of string theory(pretty sure its super symetry but I could be wrong) says that anti-matter particles should 'fall up'. He also said the results would be published in a few years. Until then we can't definitively say whether an anti-matter star acts gravitationally the same as matter stars? maybe they implode to form black holes with an opposite gravitational charge?\n Of course he also said he'd bet a thousand euros that it would act normally and that he would merely disprove the current theory of supersymetry.\nBut its something to think about when talking about anti-matter."
] |
[
"Can water, if pressured enough, cut you?"
] |
[
false
] |
I have seen it happen sometimes in cartoons. The water would come out of a slit of a pipe and it would be so powerful that it would give the person a cut (it looked a lot like a paper cut). Is this possible? If it is how pressured would that water have to be? Also, I realize that my explanation is a bit messy, If you don't understand I will try to elaborate. EDIT: after what all the people have been saying, I'm beginning to look at my super soaker differently...
|
[
"Yes, there is an industrial cutting technique known as ",
"water jet cutting",
" which uses this method. Although, such methods usually mix in an abrasive compound to help with the cutting. I couldn't tell you the force required for the water to actually cut you, though."
] |
[
"Thanks! It's weird how a liquid can have such effects. "
] |
[
"Water, if pressured enough, can blow your limbs off."
] |
[
"My grandfather had schizophrenia. However, at my father's age it's safe to say that he does not suffer from the same disease. What are the odds of me having it?"
] |
[
false
] | null |
[
"We have strict guidelines against medical advice. If you have any health concerns, please see a physician."
] |
[
"This is not medical advice though, im just trying to get some information on my odds"
] |
[
"Please see the guidelines. Alternatively, you could as a more general question about the heritability of schizophrenia in general."
] |
[
"Eugenics from a purely scientific viewpoint."
] |
[
false
] |
I am interested in the cons and pros(if any) of eugenics from a purely scientific viewpoint, rather than historic, political, or moral perspective. It is my understanding that eugenics fails to be a scientifically valid model for creating the "supreme race" of humans, but I have yet to read any detailed explanation as to why. I am in no way a supporter of eugenics, but if we can breed a horse specifically for speed, or a dog to have a short nose, why can't we do the same with humans, or if we can, what BIOLOGICAL (not social/moral) effects will it have (either in the short term or the long term)? Again to make it clear, this is posted in askscience because I would like to avoid any moral/political discussion.
|
[
"Of course we could breed humans for whatever we would like, just like any other mammal. Humans however are slower at reproducing than cats, dogs or pigs, so it would take more time.",
"Biologically, well, we would probably see some of the same side effects we see in other artificially selected breeds of mammals: susceptibility to diseases and higher incidence of genetic defects due to inbreeding, and we would also select probably for not necessarily desirable but genetically linked traits (either by linkage or pleiotropy)."
] |
[
"Eugenics is dangerous from a biological prospective without accounting for morals and politics. Traits are linked together and selected for in complex networks that we're nowhere near understanding. By artificially selecting for one trait, we don't really know what we're pulling with it. ",
"The implications for disease are the easiest to think about, but there's a more important issue beyond genetic uncertainty: even if we completely understood our genome's level of ",
"epistasis",
" and ",
"pleiotropy",
" (i.e., interconnection), the future is unpredictable. Environments change rapidly and, consequentially, so do the traits that allow a species to survive. That's why genetic diversity is vital in a population: you increase your odds of someone having the right genes to survive in a given scenario. ",
"Eugenics would reduce that diversity, which in a species as homogenous as humans, is madness. ",
" Nature doesn't care what traits we think are the most valuable. Genetic variation is clutch for continuing our grip on existence. "
] |
[
"This has been covered a few times before, but I'll add a quick summary (leaving out the whole 'shallowing the gene pool' thing that others have covered pretty well). The biggest issues are:",
"1: Defining 'good' genes",
"The classic example for this problem is the mutation(s) that causes ",
"sickle celled anaemia",
". It causes a malformation of your red blood cells - sounds bad right? Well it is, unless you live in an area that has a malaria problem. People with one copy of the sickle-cell gene are less susceptible to malaria, so there is a certain advantage to keeping the gene around, though not too much as it causes a lot of other problems.",
"Not all cases are this black and white, but when it comes to trying to breed out genes, it can be difficult to weigh up the repercussions of deleting apparently 'bad' genes.",
"2: Polygenetic/ recessive disorders",
"Not all genes are easy to spot and remove - some are harmless unless people have the bad gene on both chromosomes (recessive). You have to breed the gene out of asymptomatic people.",
"3: Environmental/epigenetic effects/trait complexity",
"Some genetic disorders aren't really symptomatic unless the body is directly challenged in some way, to which certain genotypes might be less fit to respond. It's not really an illness, more of a potential weakness. How do you breed all of these genetic predispositions?",
"Also, some genes are only detrimental if combined with other genes or environmental conditions. Even seemingly benign things like pale skin which is a benefit in cold, dark places, but which causes huge skin cancer rates in sunny places like Australia.",
"It's not clear to what extent things have a genetic basis. Look at the controversy over the so-called ",
"'warrior' gene",
".",
"4: ",
" - we all carry deadly genes. Genes that would cause horrible illness if we produced children with the wrong people or if we ran into the wrong environmental conditions. You'd have to kill us all to get rid of everything."
] |
[
"How would a Vantablack coating affect a laser cutters ability to cut?"
] |
[
false
] |
[deleted]
|
[
"When a surface is black it means it is absorbing all of the light heat. If it were the opposite, vantawhite, little/no heat would be absorbed and the the laser would only be reflected and rendered useless. So, I'd bet that vantablack would be cut more efficiently by a laser, as it would more readily absorb the heat from the laser, because of this same principle."
] |
[
"So, I'd bet that vantablack would be cut more efficiently by a laser...",
"I agree. Especially since vantablack is made of CNT, carbon being VERY combustible.",
"However, the question becomes would the underlying material be cut more efficiently as well?",
"I don't know for sure, but my gut says no. In fact it may slightly hinder the cutting action due to the vantablack acting as an ablation material."
] |
[
"Vanta black works on the same principal as an anechoic chamber, it may absorb the heat, as that is what it is designed to do but that heat wouldn't be centralized it would be dispersed along the material, difference similar to some one standing on your foot with a stiletto or a boot, same weight but one is more concentrated and does more damage.."
] |
[
"Why does it appear that \"all of a sudden\" many people are allergic to gluten?"
] |
[
false
] |
Up until two or three years ago I had never even heard of Coeliac disease or Gluten free diets, or a Gluten/Wheat allergy. Now I know at least a dozen or so people that have lived their whole lives eating wheat products that no longer can. I also read on wikipedia that the prevalence is 1 in 105 in America, yet it is 1 in 1,750 worldwide. Why the sudden jump? Is it real? Or just a fad diagnosing spree?
|
[
"Celiac has been a thing for a long time, but you only heard of it in serious cases where continued consumption of wheat would end in death. That is very real.",
"In America we eat lots of wheat and we have advanced medicine to test for such things. Lots of places in the world don't have one or both of those so prevalence should be expected to be much lower.",
"In recent years there's been a popular idea that a significant portion of people or maybe everybody exhibits a certain amount of wheat sensitivity. This is different than celiac. The problem is that most of the people who'll say they have this are self diagnosed based on the advice of nutrition enthusiasts. It is not science, based on much hard evidence, free of placebo... etc. Nutrition enthusiasts tend to get annoyed when you point this out.",
"The fad might last, it might not. Maybe science will confirm or deny some of these cases. The problem is that the symptoms that are claimed are generally pretty mild and non-specific, the chance of any hard conclusion is low. ",
"ADD:",
"Most of the wheat-phobes I've encountered are entirely self-diagnosed. This is an important point to remember."
] |
[
"Worth noting:",
"Up until 70-130 years ago, most breads were sourdoughs. Sourdough is a combination of at least one lactobacillus (lactic acid bacterium) and at least one yeast (usually not Saccharomyces cerevisiae, common bread yeast- and, in fact, sourdoughs that are intentionally inoculated with S. cerevisiae usually shrug it off fairly quickly). The lactobacilli outnumber yeast about 100:1 to 200:1, and the relationship is fairly complex: one splits starches into smaller polymers of glucose for digestion by the other. It's really very interesting stuff.",
"However, the relevance to gluten disorders is that there are some recent data suggesting that sourdough fermentation may diminish the concentration of gluten found in breads. There are some data to suggest the concentration of gluten may be reduced to a point where it is safe enough for consumption by those with celiac disease.",
"Cite.",
" \"As shown by R5 antibody-based sandwich and competitive enzyme-linked immunosorbent assay (ELISA), selected lactobacilli and fungal proteases, routinely used in bakeries, degraded gluten to <10 ppm during sourdough fermentation.\"",
"Cite.",
" \"A 60-day diet of baked goods made from hydrolyzed wheat flour, manufactured with sourdough lactobacilli and fungal proteases, was not toxic to patients with CD. A combined analysis of serologic, morphometric, and immunohistochemical parameters is the most accurate method to assess new therapies for this disorder.\" (Note that 2/6 patients had to drop out because this didn't work for them.)",
"Cite.",
" \"Initial gluten concentration of 400 ppm was degraded to below 20 ppm only in the sourdough GF bread.\"",
"The incidence of the disease ",
"appears to be on the rise.",
" The Air Force study seems to be the best data to support this assertion, and it's a fascinating read.",
"It is conceivable that the combination of improved cultivars of wheat (with higher levels of the desirable gluten), in conjunction with changes in how bread is fermented (leaving breads to have a consistently high level of gluten) have led to this increased incidence of celiac disease.",
"It's worth noting that rye bread has less gluten than wheat bread; the pentosans are what allows rye bread to form a loaf, and it is presumably the remnant pentosans in sourdough breads that allow it to form a loaf of bread once the gluten is chewed up."
] |
[
"As this article demonstrates",
", the diagnosis was originally only considered and tested for in patients with gastrointestinal complaints. The golden standard was endoscopy and biopsy. The screening blood test was developed and is quite sensitive and specific and so testing has become much less invasive and cheaper. Celiac screening is now also done on patients non-classic/atypical complaints, but with other complaints or no complaints (\"asymptomatic\") and at risk (they may have other autoimmune disease such as type I diabetes). As a result, the frequency of diagnosis has increased because testing has increased and includes many individuals without classical symptoms.",
"The average frequency of celiac disease in the human population is about 1%",
" while the professed diagnosis is much higher, most of it self-diagnosis and not based on serum testing. The upside is that now for those who truly have celiac disease, more dietary options are available, more convenient to access and at a cheaper cost than previously.",
"A detailed summary of celiac disease"
] |
[
"What is the purpose of the white part of eyeballs?"
] |
[
false
] | null |
[
"They are thought to make it easier for humans to see what other humans are looking at, facilitating nonverbal communication."
] |
[
"\"Human eyes are somewhat distinctive in the animal kingdom in that the sclera is very plainly visible whenever the eye is open. This is not just due to the white color of the human sclera, which many other species share, but also to the fact that the human iris is relatively small and comprises a significantly smaller portion of the exposed eye surface compared to other animals. It is theorized that this adaptation evolved because of our social nature as the eye became a useful communication tool in addition to a sensory organ. It is believed that the conspicuous sclera of the human eye makes it easier for one individual to infer where another individual is looking, increasing the efficacy of this particular form of nonverbal communication. Animal researchers have also found that, in the course of their domestication, dogs have also developed the ability to pick up visual cues from the eyes of humans. Dogs do not seem to use this form of communication with one another and only look for visual information from the eyes of humans.\"",
"Source, ",
"The wikipedia article"
] |
[
"Do you have a source for that?",
"It doesn't seem obvious to me that that is strictly the reason why we evolved the white portions of our eyeballs."
] |
[
"Dear AskScience, why do humans create pendular motion with their arms while walking?"
] |
[
false
] |
I've always assumed it was to create forward momentum and balance, but please enlighten me on the actual physics behind the behavior. Thanks!
|
[
"To maintain balance, or, more specifically, to keep your centre of gravity over your feet. The left leg goes forward and the right arm goes forward too, and vice versa. Try walking with your hands straight down by your sides and without rotating your hips. Now try running (preferably somewhere where you won't get hurt if you fall over).",
"EDIT: corrected limb"
] |
[
"You may find that you are swivelling your hips or shoulders or swinging your elbows to compensate for the lack of arm movement."
] |
[
"As it says in the sidebar, personal anecdotes and layman speculation are unwelcome in this subreddit."
] |
[
"On the most fundamental level, what is a computer?"
] |
[
false
] |
Inspired by xkcd comic. What is a computer? When this guy , what exactly is happening?
|
[
"The word you're looking for might be \"",
"Turing Machine",
"\". It's a mathematical description of what a computer ",
" - on a purely abstract level, without concerning yourself over whether the computer is built out of transistors, rocks, redstone torches, or clockwork.",
"The original Turing machine described a machine that used an infinitely long piece of tape, on which a \"head\" would move back and forth, reading and writing little squares on the tape. Modern computers don't actually work anything like this, but they can simulate a Turing machine quite easily (except for the fact that the original Turing machine requires an infinite amount of storage space, but that's a minor nitpick). A device that can simulate a Turing machine is called ",
", and that's usually what people mean when they refer to a \"computer in Minecraft\", or a \"computer made out of rows of rocks\".",
"Incidentally, the first important result that was found in this area of mathematics was the existence of a \"universal Turing machine\", which is a Turing machine that can be programmed to simulate other Turing machines. This is the concept of a \"programmable computer\".",
"(Not all Minecraft computers are actually Turing-complete, by the way. Some Minecraft builds actually show a single component of a modern computer, like the graphics card or the arithmetic logic unit, and not the entire thing. This is no less impressive, but it means that the definition of a \"computer\" is fuzzier than I've made it seem here.)"
] |
[
"At the absolutely most fundamental level, it's nothing more than lots and lots of switches. Millions and millions of them. The switches are called transistors. Hooking up a couple transistors in the right way give you logic functions with 1's and 0's, which are really just high or low voltages. With logic functions (aka gates), you can make anything - an adder or a memory slot.",
"In a computer, there are lots and lots of memory slots (look up a gated D-latch). Every computer has a special set of instructions (assembly code) that take numbers from the memory slots, perform a calculation, and put the result somewhere else (or just move numbers around, etc).",
"So that guy in Minecraft? He just put lots and lots of switches together. But, he probably did it at a higher level - he almost certaintly wrote a script that allowed him to place a whole series of gates in one place - he didn't put down every switch."
] |
[
"Computer scientist here: This post isn't getting enough love. Other people are describing what an electronic, digital computer is made of/how it works, but at a basic level a computer doesn't have to be electronic or digital.",
"If your question is, \"Fundamentally, what is a programmable computer?\" this is the answer you want. If your question is, \"At the lowest level, how does my desktop PC work?\" that's a different question with a different (and more complex) answer."
] |
[
"What determines the smallest particle size for powders?"
] |
[
false
] |
Can anything be ground down 'to the molecule' ?
|
[
"Electrostatics, the amount of effort you're prepared to invest in production, the amount of effort you're prepared to invest in storage, and the amount of time you want your powder to last."
] |
[
"Further question: Wouldn't something ground down to 'the molecule' effectively be a gas/liquid?"
] |
[
"Not an expert, but as I recall it has to do with the current thermodynamic properties (temperature, pressure, etc) and phase boundaries of the material.",
"e.g. ice isn't a liquid/gas, even if you crush it up. "
] |
[
"A horse goes through puberty in its second year. Why is our physical development so slow?"
] |
[
false
] |
I can understand why our mental development would take a lot of time, since there is so much to learn - complex language and all the skills and knowledge we take for granted as adults. But human physical development is also remarkably slow compared to most species of comparable size. Why would this be? Wouldn't it be a rather sever disadvantage during our evolution?
|
[
"I'm away from home right now, or I could give you a more complete quote, but John Gottman in his book \"And Baby Makes Three\" talks about the evolutionary loss of our \"fourth\" trimester. Essentially, we are forced to be born too early because our greatest evolutionary asset (our brain) means that our heads would not naturally fit through the birth canal if we were carried to the ",
" full term.",
"He points out how many animals (such as horses) can walk minutes after being born, but human babies are 100% helpless and immobile: we can't even turn over for several months. "
] |
[
"A lot points to the kinds of foods we ate in the ancestral environment. Hunter gatherers specialized in high caloric, highly nutritious food that took much learning to sucessfully gather.\nThis specialization probably happened slowly. There are monkies that break open nutritious nuts with tools. It takes years for them to learn.\nHowever, the payoffs are big. Think fishing, or opening clams, or hunting, or knowing how to cook roots that are normally poisonous, or extracting honey. Hunter gathers produce a net calorie ",
" for the community until they get into late 20s or thirties. However, when the reach peak production, they can gather 10x more than they consume.\nTo sum up, our slow development (ie time learning with the community) and big brains were an adaptation that allowed us to fill a niche for high payoff foods that other animals could not fill."
] |
[
"Yes but carrying the baby in the womb is also a constant energy drain."
] |
[
"Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary 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!
|
[
"How scientifically significant is the fact that water is most dense at 4",
" Celsius? In other words, the fact that there can be liquid water below the ice.",
"\nIt seems to me that this property of water played a huge role in developing life on Earth.",
"\nAre there any other materials that have such anomaly? "
] |
[
"What are some of the present theories on the Great Attractor? What do we think is the cause of all the mass? How do we take anomalies like this into account when calculating for dark matter/energy? Are there other regions identified in other parts of the universe that also function as great attractors? "
] |
[
"The great attractor is not an anomaly. It's a region of some dozen(s) of Abel clusters in relatively close confinement. In a big universe - a universe as big as ours - you get regions with many huge clusters packed close together and regions with no galaxies, cosmic voids. There are for sure other great attractors in the universe, there just not that many. An anomaly implied it's unexpected, which is now the case. Two or three great attractors within 50 Mpc would be unexpected. But one is fine. ",
"On the other hand we also have the local void right next door. A huge region devoid of galaxies. That Tok is not an anomaly but also not that common. How deep the voids are and how high the density \"peaks\" are and how many of each there are, is a statistical quantity known as the power spectrum and it's exactly the same as what you would expect to see if you evolved under gravity a density field as contrasted as the CMB for 13.7 Gyrs. ",
"There are similar regions of attraction in the local universe. One of the most interesting is the Shapley super cluster, which undoubtedly is the greatest attractor in the neighborhood. "
] |
[
"About all those lonely trees falling in forests..."
] |
[
false
] |
Everything is observed due to every particle being gravitationally attracted to every other particle which makes every particle in the universe 'visible' to every other particle? ...Which boils down to: there is always someone within earshot of a falling tree. Does this sound about right?
|
[
"This would hold if all these signals were uniquely distinguishable. But how could you tell, from gravity, the difference between a mass m at some distance r, and a mass 4*m at distance 2*r ? All you see are the sum of the effects, without any way to disentangle the whole set, even if you had measurement accurate enough to do such a thing."
] |
[
"It seems like I need to explain this more clearly... I was talking about being within 'earshot' as in observing a gravitational pull. If a tree falls or a particle moves it will create a wave which will ripple through space-time. So if a tree falls and no one is around to hear it the change in gravity although extremely small is still there to signal to an observer in the universe that yes a tree has in fact fallen and was 'heard' gravitationally. "
] |
[
"This seems like it would belong more in ",
"/r/trees",
", no offense.",
"There ",
" always something in earshot of a falling tree, but sound is not gravity... Neither is light. Everything on our planet is linked through causality to some degree.",
"As for everything being causally linked in the universe, that is not necessarily the case. There are likely things outside of our observable universe that we cannot and never will observe."
] |
[
"How does abnormal (too low or too high) blood sugar affect blood vessels?"
] |
[
false
] | null |
[
"This is an enormous topic. Sugar is an energy source, a growth signal, and can form adducts with cellular proteins. If you have a more specific interest in one of these broad areas, can you narrow your question so we can tackle it more effectively?",
" perhaps this is an accessible introduction: ",
"http://en.wikipedia.org/wiki/Microangiopathy"
] |
[
"That article you linked to, while short, actually answered it perfectly. Sorry, didn't realize it was such a generalized and broad question, but thanks. :)",
"Are you a doctor by the way? Just curious."
] |
[
"Glad to hear it. I'm not a doctor yet, but I am a medical student."
] |
[
"Does music sound different on a space station?"
] |
[
false
] |
Does the lack of gravity affect the perceived quality of sound?
|
[
"As far as I can tell, no, it shouldn't. While there is, in fact, a term in the ",
"Navier-Stokes Equation",
" that represents the force on the air due to gravity, its effect on acoustic propagation is negligible. If there would be an effect, it would probably have to do with structural noise. One of the ways that vibrational energy leaves a system is that it radiates out as noise. That would be much more difficult with a vacuum surrounding the space station. That said, you would still have other losses, like heat losses, that would cause the vibrational energy to dissipate."
] |
[
"The ISS operates at sea level air pressure."
] |
[
"I agree. The only possible reason I can think of that could cause music to sound different would be long-term physiological changes in response to micro-gravity, e.g., redistribution of body fluids."
] |
[
"How are video games “ported” to other consoles and PC?"
] |
[
false
] |
When a video game is “ported” from one system to another, say PC to Playstation, how difficult is this process? Is the entire game rewritten in the code that each system reads? Or does a PlayStation interpret the same kind of programs/code that a PC interprets?
|
[
"Let's assume the video game you're talking about is written targeting a specific system architecture, and a specific framework. For PC a common example would be Windows x64 and DirectX. Let's say we wanted to port the game to PlayStation. That would entail rewriting all parts of Windows and DirectX-specific code to the (more or less) equivalent PlayStation-specific code.",
"\nAs to how difficult that process really would be is hard to tell, it depends on how well the developers of the original Windows version used software engineering principles like abstraction (which could make rewriting lots of platform specific code much easier), how large the codebase is, how similar the DirectX and PlayStation programming interfaces are, etc."
] |
[
"Programs including games are not written in a platform specific code, they are written in a more human-friendly language like C, C++, C#, Java etc. Those languages are quite abstract in the sense that they make very few assumptions about the hardware they are going to be executed on and you generally don't think about that either when you write programs.",
"Programs called compilers then convert programs written in a human-friendly language like C into something that a specific processor can execute. You feed your code to a compiler and ask it to produce executable code for a specific CPU, or a family of CPUs (for instance you can run the exact same code on AMD and Intel x86 processors, but not an ARM processor that Nintendo Switch uses).",
"Simply recompiling the source code for the different platforms solves a big chunk of the problem. Most of the actual gameplay code typically needs no changes at all to be able to be recompiled like that.",
"However in addition to the CPU architecture there are also parts that are very specific to the OS (operating system) your code runs on. These are things like talking to your input devices, tracking time, reading files, accessing the GPU etc. Every OS has its own way of doing it and this is the biggest headache for developers when porting games.",
"These days this is mostly solved by game engines that provide a unified way of working with these resources so you can write your game once and then rely on the engine to use the correct platform-specific implementation at runtime.",
" Since games are mostly written using high-level programming languages, all you need to do is to recompile your code. Parts of your code that interface with the OS and the hardware have to be re-written for every platform you want to support, however those parts are usually covered by the engine and you don't have to worry too much about that. ",
"Unless you're a game engine developer. Then your life is pain."
] |
[
"Apart from actually porting platform dependent Code as mentioned by Fuet, one of the more time intensive tasks is complying with platform holders’ technical requirements. Things like QOL requirements, where and how a game saves its data, what to report to its servers, and even trivial things like the correct displaying system messages (“don’t turn off the console while this icon is visible”) can be a huge pain in the ass. Even more so than porting the code itself. Mostly because the code changes are handled by the engine (or by the engine department), and doesn’t change too often. ",
"Source: I’m creative director at a game studio."
] |
[
"I have heard/read from a few sources that viral load is one of the factors influencing severity of the infection in Covid-19. How far is this true?"
] |
[
false
] |
For example, if person A gets a higher viral dose than person B, is his/her infection more likely to be more severe and has there been any research/studies conducted on this? Also, I'd like to know if there's a minimum viral dose that is needed for symptomatic infection, and if this dose varies from individual to individual. The new (mutated) strains of Covid-19 are said to be more infectious- does this imply that a smaller viral dose is required to cause symptomatic infection?
|
[
"In general, there is a positive correlation between initial inoculate and disease severity that has been shown for several viruses including this one. This at the population level, at the individual level it can be that 2 get infected by a similar inoculate but one does worse than the other etc."
] |
[
"I have spent much time looking for any type of study or experiment finding a link between inoculum and severity of symptoms of Covid.",
"But of course, I could not find one, because purposely infecting subjects with various levels of SARS-CoV-2 to see levels of Covid symptoms in unethical. And there does not seem to be a way to determine level of inoculum post accidental infection.",
"However, the closest experiment to what you are asking involves the purposeful infection of Syrian Golden Hamsters with SARS-CoV-2. The hamsters suffer symptoms and:",
"Using the Syrian hamster model, we demonstrate that the severity of pneumonia induced by the intranasal inhalation of SARS-CoV-2 increases with virus inoculum.",
"https://www.sciencedirect.com/science/article/pii/S2666379120301634",
"So yes hamster suffer worse pneumonia with higher inoculum.",
"But that's hamsters and unless someone can link to a study with humans it is still conjecture for now if severity of human Covid symptoms are tied to initial viral dose.",
"We don't know yet.",
"Edit: the closest thing I could find to an \"unintentional study\" where subjects were possibly given low doses of Coronavirus is this cruise ship that had high levels of masking: ",
"https://www.medpagetoday.com/infectiousdisease/covid19/88692",
" . The hypothesis is that many cruise goers had asymptomatic cases because they were exposed to only low doses of virus during initial infection because of the masks. Of course there is no control and it's just a theory but it's a data point."
] |
[
"Yes, it is conclusive and perfectly normal. Though when one sneezes for example there is a multitude of viral particles, many are not even viable. Besides that, those that do get inhaled have to find suitable host cells, infect and replicate potentially forming thousands of new virions from a single infected cell. So the initial number of virions matters both because many of them are not infectious anyway and because even a small increase in the initial particles that successfully infect the host cells will result in a massive increase of \"first generation\" virions, and therefore higher chance to defeat initial host defences."
] |
[
"If combustion requires oxygen, what happens if I put a piece of paper in a vacuum and heat it really hot?"
] |
[
false
] |
I know it's possible for paper to burst in flame with high heat even if there's no flame, but I was wondering if the same would happen in a vacuum. Also, since in space there's no oxygen, what would happen if you send a rocket towards the sun? Sorry for my lack of science knowledge..
|
[
"If paper is heated without the presence of oxygen, it undergoes thermal decomposition, also known as pyrolysis. This is similar to the process through which ",
"biochar",
" (and charcoal) is made. The carbohydrates and cellulose in the paper will break down into gaseous CO, CO2, CH4 and H2O, leaving a solid carbon residue.",
"Speaking practically, you would need ",
" molecules to be present between the heat source and the paper to transfer thermal energy (a vacuum is great insulation); you couldn't perform this experiment if the paper was ",
" in a vacuum.",
"Don't apologise for a lack of knowledge, this is ",
"/r/askscience",
", where it's far better to ask a question than pretend you know the answer! :-)"
] |
[
"What about radiation? Yes, you can't do conduction or convection in a vacuum, but radiation you can."
] |
[
"It turns to carbon in a sheet."
] |
[
"Why do women typically have higher voices than men?"
] |
[
false
] |
Is there an evolutionary reason for women to have higher voices than men? I'm assuming it has something to do with sexual selection, although I may be way off base. Also, does this happen in other animals? EDIT: I'm not asking HOW women have higher voices, I'm asking WHY. Also, I thought about the size thing, but regardless of size, a large woman still has that "feminine" element to her voice, while a small man still sounds like a man.
|
[
"I think it's the other way around: why do men have lower voices than women? Female is the default, the Y chromosome only has 45 genes in it, compared to 20,000 or 30,000 in the entire human genome.",
"Women find deeper voices in men sexier",
", testosterone lengthens a man's vocal chords to produce a lower voice, but that still doesn't explain ",
".",
"According to ",
"this article",
", \"evidence suggests men evolved deeper voices mainly for intimidating other men rather than attracting women\".",
"edit: I found some links which I posted later in this thread disputing the long held notion that female is the default gender."
] |
[
"I'm not professionally versed on this particular topic but I've done a fair amount of studying on it nonetheless. Compared to other primates, humans have been sexually selected to a much greater degree in favor of neoteny- the retention of childlike characteristics into adulthood. Comparing humans and other primates, this tendency for neoteny clearly this presents itself in several ways: our lack of body and facial hair, our larger brain and skull, and our shorter arms and longer legs, as well as others. ",
"Now getting back to your question, human females are even more predisposed to neoteny than males. The reasons for this are likely due to a combination of sexual selection factors which I won't get into but are expounded upon very well in this article: ",
"http://www.davidbrin.com/neoteny2.htm",
" ",
"So finally, women have higher voices because their mates seek out and prefer neoteny (higher voices are of course more childlike). Males who enjoy neoteny are more likely to have an interest in children, and therefore more likely to father them into their own eventual reproductive success. This has some interesting implications in regards to our species somewhat unique interest in pedophilia but that's a topic for another thread."
] |
[
"Well shit, my voice definitely isn't sexy then."
] |
[
"Why can't we make spaceships go faster?"
] |
[
false
] |
What is preventing us from increasing the maximum speed of the modern spaceship? Edit: Thanks everybody for the answers, they were all amazing!
|
[
"With current technology the speed of modern spacecraft are limited by the amount and type of fuel we deem economical to carry into orbit with us. We have to carry the fuel with us as we don't have the technology ready to create fuel for us in space. Right now the most efficient fuel we have is Hydrogen and Oxygen combustion. Chemically this releases the most amount of energy per pound for us without using stuff that is toxics. This is a chemical reaction and is bound by the limits of chemistry. There are other proposals that use nuclear fission, like VASIMR, but those are barely out of the R&D stage. Ion propulsion is possible if you don't care about how long it takes to accelerate to a certain velocity. Solar sails might be feasible, but like ion propulsion, take a long time to get up to speed.",
"In addition to that we are limited by the materials we have available to us. If we built a big nuclear reactor and launched it into space, we have the problem of how to cool the reactor. Since there is no atmosphere or bodies of water to provide cooling we have to rely on the heat to be radiated out by EM radiation, it takes a lot of special engineering to keep power sources cool in space. We would easily have a melt down. Our best materials can't withstand a nuclear melt down here on earth let alone in space.",
"With that being said it comes back to chemicals as the most viable and the limits of energy available to us in those chemical reactions. To get those chemicals into space we have to carry them with us. Which comes back to economics. Modern spacecraft are a balance of keeping the payload as small and light as possible to keep the overall weight of the craft low. This means less fuel and smaller rocket. This is one of the reasons why we are looking so hard for ice on other planes/moons/asteroids. If we can extract water we can then split it into fuel for our spacecraft."
] |
[
"Delta-v",
" is one of the most important concepts in basic space flight. In a way it describes how big a change of velocity the spacecraft is capable of performing. This includes both accelerating and deccelerating as well as making course corrections or changing direction when done using engines. Excluding things like solar sails and gaining speed by gravity assists, how much delta-v your spacecraft has is dictated by the ",
"rocket equation",
".",
"The delta-v in the rocket equation depends on two things, the ratio of your final mass and initial mass, and exhaust velocity of your engines. Exhaust velocity is simple, it's simply the speed at which the exhaust leaves your spacecraft, in other words the type of your engine determines the exhaust velocity. Delta-v depends linearly with this. Double your exhaust velocity and you get double the delta-v.",
"Initial mass is your whole rocket, payload, astronauts, power sources, life support, whatever else you have in there, and most importantly the propellant. Final mass is everything that's left after you've used all your propellant, that is the payload, all the systems and empty propellant tanks. The crucial part in the rocket equation is that delta-v depends logarithmically on the mass ratio. So to double your delta-v you need to square the mass ratio. So if the mass ratio is initially 10 (9 parts fuel 1 part payload) to double the delta-v with same engines you need to have a mass ratio of 100 (99 parts fuel, 1 part payload). In other words you need either 11 times as much fuel or reduce your payload mass to one tenth the mass (note that the payload here includes the engine itself and empty tanks etc). As you might guess, this gets very impractical very fast. Or I guess you could say that it already is very impractical with the rockets we have today but it gets even more ridiculous if you try to increase the delta-v significantly by just stocking more fuel.",
"So the best way to increase delta-v is to make better engines with better exhaust velocities. Ion drives have much bigger exhaust velocities than chemical rockets so they require much less propellant to achieve the same thing. Their downside is that the thrust is very small and so the acceleration is slow. Once you're in orbit it doesn't matter so much since there's no resistance forces, but to get off the ground you need more thrust and the chemical rockets are still the best option there."
] |
[
"I like both ",
"pozitron's",
" and ",
"Olog's",
" answers, but here's yet another way to put it:",
"Spaceships travel with rockets. Rockets work by conservation of momentum. If you want momentum ",
" you have to also create some momentum ",
" to balance it. You put all the ",
" momentum on something cheap (like burnt rocket fuel) and let it go away. That stuff is called \"propellant\". The rest of the rocket is now moving ",
" like you wanted.",
"The catch is that you have to get rid of some mass from the rocket itself - and there's only so much mass in the rocket to start with.",
"So to go fast you have to put ",
".",
"The difficulty is that loading momentum (mass * speed) onto propellant takes kinetic energy to do, and kinetic energy grows like (mass * speed",
" ). So loading more momentum onto each kilogram of propellant costs extra energy: you have to hurl the propellant fast to put momentum on it, and each additional bit of momentum costs more energy than the last.",
".",
"The Space Shuttle Main Engines use one of the most energetic chemical reactions known to create energy, which they then dump onto the burned fuel. It's not possible to make a much-more mass-efficient rocket engine that uses chemical fuel, because there just isn't enough energy available in chemical reactions.",
"Pozitron wrote about ion rockets and some other exotica, which are great in terms of mass efficiency (and are thus awesome for making and moving robotic probes more cheaply) but don't have the power you want for rapid interplanetary transit.",
"Nuclear reactions have a ",
" more energy available and can supply high power, but there are some problems associated with them - like you don't want to actually throw away the nuclear fuel as propellant, because you don't want to spray highly radioactive nuclear waste all over the Earth-Moon system. About 40 year ago, the Air Force developed a nuclear rocket (patented by Richard Feynman, IIRC) that used a nuclear reactor to ",
" propellant that was forced through it in little tubes, keeping all the nuclear fuel on-board -- unless (as rockets occasionally do) it blew up or crashed. That rocket was called NERVA, and it did about twice as well as the Space Shuttle Main Engines -- not bad for a little prototype.",
"But, because of the fear of blowing up or crashing, NERVA never actually flew and almost certainly never will.",
"There's another reason that fission nuclear rockets probably won't fly, which is the nuclear test ban treaty. That treaty forbids its signatories (the U.S. is one) from placing nuclear chain-reactors in space. The NTBT is one reason why deep-space probes use Pu-238 to generate electricity -- Pu-238 stays warm from natural decay, ",
" from a critical chain reaction.",
"Fusion rockets, if we ever manage to develop them, will open the solar system in much the same way that Interstate roads opened America. The energy (and power) densities that are in principle achievable with fusion are immense. You could cross the solar system in a couple of days with a suitable fusion rocket, and (again in principle) refuel it from any handy source of hydrogen. Larry Niven made his name in science fiction by writing about a society in which fusion rockets became feasible. He spent quite a bit of time thinking about the astrodynamics and engineering trades that people would be likely to make with them."
] |
[
"How can a real particle have negative energy?"
] |
[
false
] |
Hi, I'm reading Stephen Hawkin's "Brief history of time". There's a chapter where he talks about black holes and I assume is the precursor to hawking radiation, but basically it explains that at the event horizon there are particle-antiparticle pairs being created, some escape into space (particles as radiation, antiparticles annihilate pretty soon after their escape), but whenever a particle falls into the black hole it reduces it's mass (instead of increasing it). Hawkins says "Normally, the energy of the particle is still positive, but the gravitational field inside a black hole is so strong that even a real particle can have negative energy there". Cans someone elaborate on this? how is the possible? I mean to me it just sounds like "well, it has to be negative or else the black hole will grow, so lets just make it so" but doesn't really click (in my head)
|
[
"that explanation of hawking radiation (even if presented by hawking himself) is really just so laymen can feel they understand hawking radiation. it's not accurate. particles don't have negative energy. it's true that a positive energy particle would add to the mass, so your suggestion",
"I mean to me it just sounds like \"well, it has to be negative or else the black hole will grow, so lets just make it so\" ",
"seems accurate. "
] |
[
"a particle has positive energy.",
"mind I'm only talking about this explanation , that doesn't mean hawking radiation cannot be derived rigorously"
] |
[
"I just want to emphasize what he said: this explanation of Hawking radiation is an oversimplification intended to help a layperson understand sort of what Hawking radiation is, but it is an ",
" explanation. It's not totally wrong, but elements of it are wrong, and it's not the whole story. The idea of a real particle with negative energy is a wrong one, and that is one (of many) of the flaws of this particular explanation.",
"The failures of the explanation shouldn't be used to discredit the idea of Hawking radiation, but if you want to really understand the phenomena, you unfortunately need a substantial background in physics. Frankly, most physicists who don't specifically study black holes or models of quantum gravity don't fully understand what Hawking radiation is, either. "
] |
[
"Why have we not been funding/seriously researching transplanting brains and directly hooking in motor functions to artificial bodies?"
] |
[
false
] | null |
[
"I posted this, as a response, to ",
"/r/askreddit",
" and it did decently well, so I am finally deciding to post here and see if anyone can help or at least help me understand why."
] |
[
"Our question would be better suited to ",
"/r/AskScienceDiscussion",
". Please, consider resubmitting there."
] |
[
"Resubmitting now."
] |
[
"How do parrots talk like us if they have a beak and no lips to form sounds the way we do?"
] |
[
false
] |
Okay, maybe this is a stupid question but yesterday I was chatting with my sister and she brought up one of her patient's parrot and how he greets everyone, sings lyrical and even says goodnight. She actually told me she was scared at first because the first time she entered his house, she greeted the patient (Hello [name]) and she heard this robotic like voice saying "Oh [patient's name] who is this?" And then the question came up. How do they talk almost like us if they have a totally different mouth? We change sounds based on our tongue and lips, but they have a beak, yet they can still sound human! Thanks to anyone who might respond. :)
|
[
"Birds have an extra throat structure called a syrinx that’s a bit more advanced than the larynx in mammals. Humans have to add mouth shape to what the larynx can do to get our sounds, but birds do it all with their syrinx!",
"(Birds still have a larynx, but it doesn’t vocalize.)",
"The syrinx can even be separately controlled on each branch of the trachea, allowing a song bird to make more than one sound at the same time!",
"Source: ",
"https://en.wikipedia.org/wiki/Syrinx_(bird_anatomy)"
] |
[
"They do indeed! It’s a credit to both bird and human brains that birds parse and attempt noises they can’t quite make, and human brains fill in the gaps where needed."
] |
[
"I imagine that some of the sounds we make will give parrots issues too. P sounds, for instance."
] |
[
"Because temperature affects the speed of sound, how slow could the cold bring down the speed of sound?"
] |
[
false
] |
I assume it's not possible for sound to not move at all. I'm not exactly sure how this works other than temperature affecting energy levels.
|
[
"Well the limiting case is if you get it so cold that it becomes liquid, and then sound becomes much faster. If you treat nitrogen as an ideal gas down to the transition temperature, the lowest speed will be about 180 m/s, just over half as fast as at normal temperatures. "
] |
[
"I suppose a vacuum would reduce it to zero. however a quick googling indicates that decreasing pressure doesn't affect it much. I'm left to assume that as pressure approaches 0, something changes; can anyone explain?",
"got my info from ",
"https://en.wikipedia.org/wiki/Speed_of_sound#Dependence_on_the_properties_of_the_medium"
] |
[
"Thank you for the response. "
] |
[
"Why does the power rule \"shortcut\" for differentiation work?"
] |
[
false
] |
I know what the power rule is and that it works. I've read the , but the mathematical notation is a little confusing. I guess I'm asking for a logical, intuitive reason why I can just turn the old exponent into the coefficient and reduce the new exponent by one. Thanks!
|
[
"One reason is that you can look at the ",
"Binomial Expansion",
" of (a+h)",
" in order to find (a+h)",
"-a",
" in the numerator of the derivative. What you'll get is something like (a+h)",
" = a",
"+na",
"h+ (Terms with a higher degree in h). Subtracting out the a",
" will give na",
"h+h",
"(Some Polynomial). Dividing by h and then taking the limit to zero kills off that second term and we're left only with na",
".",
"That's kinda the formula version, working straight from the definition, but there are other interpretations. ",
"This Blog Post",
" talks about the ",
" nature of the Product Rule. This means that the Product Rule encodes how many ways a certain outcome can occur, and since you can see the power rule as a special case of the product rule, it turns out that the Power Rule has some combinatorial interpretations as well! Essentially, the power rule must be of the form d/dx(x",
") = Ax",
" and the number A must be the number of ways I can add up n things to equal 1, using no negative numbers. So the number of ways to do 1+0+0+0+0 = 1, 0+1+0+0=1 etc. Obviously, there are exactly n ways to do this hence the derivative is nx",
"."
] |
[
"Using the product rule to show why the power rule works is probably not very informative. Someone asking this question would likely have the exact same question about why the product rule works."
] |
[
"By the product rule d/dx x",
" = d/dx (x * x",
")= x*(d/dx x",
") + x",
" * d/dx x = x * (d/dx x",
") + x",
"Using the same process again for d/dx x",
" gives:",
"d/dx x",
" = x * (d/dx x",
") + x",
" = x",
" * d/dx (x",
") + 2x",
"Once more gives us ",
"d/dx x",
" = x",
" * d/dx (x",
") + 2x",
" = x",
" * d/dx (x",
" ) + 3x",
"You can convince yourself (maybe even write a prove?) that doing this n times will give you d/dx (x",
" ) = nx",
" "
] |
[
"5 year-old asked what life is. Help?"
] |
[
false
] |
After waiting up most of the night for relatives to fly in on the red-eye, and being awoken at 6am by our darling child, he starts looking a little down. Us parents as him what's wrong, and he turns to us, and in the most manner-of-fact manner possible, says: While I appreciate that the question is vague, I trust over the more religious/philosophical subreddits, and would frankly prefer to be able to give him a factual answer. I'm only one coffee into the day, and can't even begin to shape the beginnings of an answer. Any suggestions on what I can tell him?
|
[
"An operational definition is MRS GREN: Life is something with \n Movement\n Respiration\n Sensitivity\n Growth\n Reproduction\n Excretion\n Nutrition"
] |
[
"Well, at the very least it won't be some vague philosophical bullshit."
] |
[
"This is just about perfect. I can nut down to the details of each of those with him relatively easily - thankyou!"
] |
[
"Why do we divide the electromagnetic spectrum into different sections?"
] |
[
false
] |
Did we just arbitrarily decide where the divides between say X-rays and gamma rays are? Or does energy literally behave differently at these different levels?
|
[
"microwaves have wavelengt roughly the size of micrometres",
"They do not. Micrometer waves are infrared. \"Microwaves\" got the name \"micro\" from being shorter than radio waves, it shares the origin of the name with the SI prefix for 10",
" but they don't have micrometer wavelengths."
] |
[
"It's just a historic classification, based on the prominent experiments and application of the bands.",
"X-rays, also known as Röntgen radiation, was discovered as a typical bremsstrahlung when electrons hit certain materials. Wilhelm Röntgen called it \"X-ray\", the X standing for \"unknown\", because at first it wasn't quite clear what's coming out of his apparatus.",
"Gamma rays are a typical radiation you find in radioactive decays, which are typically termed as \"alpha\", \"beta\" or \"gamma\", depending on the type. This again was named, before it was clear what's exactly going on.",
"Radio waves are typically used for radio, microwaves have wavelengt roughly the size of micrometres, and so on...",
"There's no physical reason to divide them into different sections, and there's a fluid passage between them. But depending on the situation, some wavelength may have different effects, for example the wavelength at which a photon can ionize a specific molecule is a \"hard\" transition from \"can't ionize\" to \"can ionize\"."
] |
[
"The ionization energy is not dependent on the way you measure it, or which units you use. It's purely based on the forces within that specific molecule. You'll get different values if you measure in eV or in J, but an alien doing the same experiment on a different planet in completely different units will come to the same result (if we converted everything to the same unit): Up until a certain energy, a photon will not have enough energy to ionize the molecule."
] |
[
"How would we know when we become homo novus and not homo sapien?"
] |
[
false
] |
[deleted]
|
[
"Defining the breaking point between two species is always a tricky business, but it usually is agreed that when two populations are no longer interbreeding (due to behavioral/genetic reasons, not geographic reasons) they can be considered separate species"
] |
[
"Defining species is bad enough sometimes, but distinguishing when one species becomes another ",
" is much worse--especially when you are watching it happen and not looking at a couple of fossils seperated by 10 million years. People will draw some arbitrary line that may have little biological relevance, unless some sort of weird genetic divergence occurs quite rapidly. ",
"Also, you wouldn't necessarily expect to see the whole human species flip over to being a different species (though this is certainly possible). You'd expect to see some offshoot branch off and become a different new species. "
] |
[
"Species aren't that terribly well defined. Reproductive compatibility is the most common criterion, but in a world of genetic medicine and in-vitro breeding, who could tell and why would it matter?"
] |
[
"Is it possible for a brain tumor to inhibit emotional response?"
] |
[
false
] |
I've recently taken an interest in Neurology, or more accurately, in diseases of the brain. As a result, I have been wondering if it is possible for a brain tumor (malignant or otherwise) to inhibit the afflicted party's emotional response, or ability to express emotions in general. If the answer to the aforementioned question is affirmative, in which part of the brain would the growth be located in to illicit such an affect?
|
[
"Lesions of the amygdala have been associated with blunted emotional responses, so if the tumor results in damage to that area (or projections to/from it), then the answer is yes. ",
"More generally, it's well-established that emotional changes can accompany any kind of brain trauma (not just tumors); a famous case you may have read about was ",
"Phineas Gage",
" who had a ginormous iron rod blown through his noggin. He survived for more than a decade, but during that time he exhibited profound personality changes.",
"Disclaimer: I'm a researcher not a clinician, so perhaps an MD might chime in here with more information."
] |
[
"I would guess any kind of mass growing within the enclosed volume of the skull has the potential for doing damage. The stuff in there doesn't respond well to getting pushed on..."
] |
[
"Tumors which cause emotional ",
" are most commonly seen in the frontal lobe. Offhand, I'm unfamiliar with tumors near the amygdala, but it is certainly plausible that they could cause problems similar to what LabKitty described."
] |
[
"What am I hearing when I close my eyes and flex the muscles responsible for blinking?"
] |
[
false
] |
The sound is best described as a fairly low rumble as though a great herd of buffalo were on the move a fair distance away. It can be done voluntarily. edit:spelling.
|
[
"It's activation of the tensor tympani muscle, also activated when you yawn. Check out ",
"r/earrumblersassemble",
" for more info."
] |
[
"The sound you are hearing is actually that muscle contracting! muscles contract anywhere from between 10 and 70 Hz (times a second) - and we can hear those twitches! When you yawn, you're hearing the muscles of your head contract. crazy!"
] |
[
"Crazy indeed! Thank you both."
] |
[
"How significant is nose hair in protecting us from infection?"
] |
[
false
] |
It's common to see advice not to pluck nose hair because of it's supposed role in protecting us from infection. Late edit: I'll also add another reason I've posted this question; I'm 51 and my nose hairs are doing what they do in all of us after we reach middle age. If I could afford it, I'd consider permanent removal of them. Like most men my age, it's getting to the point where I could probably grow a bit of a mustache with just my nose hairs, now that they've changed the direction and length that they grow.
|
[
"The mucosal membranes are part of your immune system's first line of defense. Hair, mucous, and ciliated movements trap and expel foreign objects/antigens out and off the membranes and therefore out of the body. It's not that you're fucked without it, but every little bit helps."
] |
[
"To follow up on this, instead of starting a new thread:",
"How well do other bodily methods prevent infection, such as coughing, sneezing, ear wax, etc.?"
] |
[
"If you have a productive cough (a cough with a fair amount of mucous), you need to get it out of your system or you're just making things harder on your immune system.",
"Forgive the gruesome detail, but I imagined that after a wad of mucous was coughed up and then re-swallowed, it was leaving the respiratory tract and going down to the stomach, where it would be safely dissolved in acid.",
"Is this not the case, and all infected-coloured mucous should be spat out?"
] |
[
"Pelican found"
] |
[
false
] |
In Pacific Mexico, we found a bird looking like this with a smaller and sharper beak. It is seemingly lost and possibly juvenile, seperated from its family. Is there anything possible that we can do to save this bird? It stays in one place and lets humans touch it; the parents would probably reject it if found on account of the human scent. edit: Not a pelican. Went out today, and for the second day it was just standing, not caring about humans. When we got near, it opened its beak and positioned it vertically (hungry?). Please help, I have pics here!
|
[
"Look up for any animal shelters that take animals such as pelicans if its indeed abandoned/injured. I have no idea where you are in Mexico so you got to ask the locals and look up if there is one in the area."
] |
[
"You are correct,that is a myth. WHEN is that stupid myth going to die!?ಠ_ಠ",
"I used to be a wildlife rehabber and we always had babies brought in that should have been left ALONE..But no.\"My kid picked it up and so now we are giving it to your wildlife shelter to raise cause of a tired old myth.\""
] |
[
"You are correct,that is a myth. WHEN is that stupid myth going to die!?ಠ_ಠ",
"I used to be a wildlife rehabber and we always had babies brought in that should have been left ALONE..But no.\"My kid picked it up and so now we are giving it to your wildlife shelter to raise cause of a tired old myth.\""
] |
[
"In the course of Earth's history: Are separated continents less common than super-continents?"
] |
[
false
] |
This question only arises after I became curious about how Pangaea formed. I then saw that geologists believe there may have been four or so other super continents at one time or another. I was just curious if continents being separated (like there are in the current day) is just a transitional period before there is another super-continent or if those super continents were all created due to random circumstance? I was just curious if geologists had an idea of the frequency of each type of continent.
|
[
"Hi there, Geologist here:",
"Whilst I cannot comment definitively on the \"frequency\" of both (it's very difficult to work out, and there are many oppositing theories and interpretations) I can handle the rest of your question.",
"Regarding: \"or if those super continents were all created due to random circumstance\"",
"This is due not to random circumstance but to plate tectonics. Plate tectonics is a series of diverging and converging plates on which our Oceans and Continents sit. Since we live on a sphere (ish) what diverges in one place (say, the Mid-Atlantic Ridge) must Converge somewhere else (Alps, Himalayas, etc).",
"This pattern will repeat, sometimes change and move and even reverse. The end result is a Super continent which breaks apart, then will reform again where everything converges. ",
"I would estimate that Super Continents or separate Continents may occur in roughly the same frequency, with a slight preference to separated continents simply due to the time taken during breakups where they would indeed by separate.",
"This site has some great animations of plate movements:",
"http://serc.carleton.edu/NAGTWorkshops/geophysics/visualizations/PTMovements.html",
"In a few hundred million years we will be living on a new Super Continent because this process rinses and repeats until the tectonic system runs out of energy and ceases (such as on Mars)."
] |
[
"I see that site has geophysics in the URL thingy. Is it suitable for me to learn the very basics of geophysics in less than a week?"
] |
[
"Why the same land masses for so long, just cut up and moved around?",
"Shouldn't plate boundaries be creating new continents and destroying old ones, so that there's never a single supercontinent because land is forming on the other side of the Earth just as quickly as the continents are being smushed together elsewhere?"
] |
[
"Are there any human populations without any Neanderthal DNA? Are there measurable differences from that absence?"
] |
[
false
] | null |
[
"Native African tribes. Neanderthals lived in Europe and Western Asia, and only encountered humans after we migrated out of Africa. From there, we interbred with Neanderthals, and moved across the globe, first to East Asia, then the Pacific Islands and Australia, and finally North and South America. Since no human groups (that we know of) went back to Africa, most Southern African tribes and their descendants have next to no Neanderthal DNA. ",
"However, there isn't much of a measurable difference in our DNA because of this. Most Europeans and Asians only have about 2% Neanderthal DNA in their genome.\nAlthough, some studies have found that a higher concentration of Neanderthal DNA can possibly lead to a minor increase in risk for genetic diseases, like Crohn's Disease and lupus. Also, because Neanderthals and humans are nearly separate species (genetically), those with higher concentrations of Neanderthal DNA can have a higher risk of issues with their X chromosomes, which leads to a lower rate of fertility. But again, these changes have been part of us for tens of thousands of years, and are as much a part of us as any other human ancestor.",
"Daven Presgraves has even postulated that breeding with Neanderthals made it easier for our species to adapt to northern climates, since Neanderthals carried traits for lighter skin, hair, and eyes, as well as being shorter and heavier-set than us."
] |
[
"Since no human groups (that we know of) went back to Africa",
"... except for the ",
"Eurasian backflow",
", but your general point stands."
] |
[
"Second more speculative question. What would we be like had we never interbred with them? How would that have changed history and cultures?"
] |
[
"How does sorting by \"Relevance\" work? How does a computer determine what's relevant and what isn't?"
] |
[
false
] |
A lot of search tools let you change the thing you sort by. You can look at the most recent, the newest, or the most popular, and I can understand the criteria they're sorting by. But sometimes you have a sort by "relevance" option ( ), and I don't understand what that's doing. And just to be specific, I'm not talking about algorithms like pagerank that can use outside information like cross linking to determine the weights of specific entries, but specifically something like reddit's search, that only has the entries themselves to determine relevance from. Unless, of course, that's how all of these relevance sorts work on the back end.
|
[
"A whole lot of different websites use a whole lot of different information to sort by \"relevance\". One option would be to use the amount of times someone searched the same keyword and clicked a link from that search (thus making its relevance higher). Other options would be to use the searching user's own history of the site to check the relevance. Like, if reddit knows you go to x kinds of threads more often, it'll make those threads more relevant to you. A more simple way of doing it is to compare it to the metadata of the content; if your search term appears more often in the body, title, tags, etc of the content, then that content would be more relevant.",
"It's a very intricate kind of fuzzy logic that a lot of different companies work on, and most of these techniques delve a lot on the field of Machine Learning. Of course, the more accurate you can make your algorithm, the more people will prefer using your services, and the more income you can get... So I'd imagine the bigger companies keep those algorithms under lock-and-key."
] |
[
"To give an example of this that happens to be open-source, we can look at ",
"Apache Solr/Lucene",
", which is pretty widely implemented on a lot of big sites for internal site searches. Each possible search result is stored as a \"document\" (in this case, probably the text content of each possible page on the site) that Solr can give back when you make a query, and each document returned by Solr has a \"score\" value generated at the time of Solr's response.",
"Solr's determination ",
"works like this",
" (simplifying some things):",
"Using all these things together, a score is assigned to each result, making it easy to sort by 'relevance' - just stick them in numerical order, descending."
] |
[
"It's just a name, so don't put too much stock by it: the computer does not know what's truly relevant what's not; rather, the designers of the system have come up with an algorithm that is ",
" to find things relevant to your query, and so that's the label they put on it.",
"One popular algorithm if you type in multiple words is that sorting by relevance sorts first of all by how many of the words can be found in each item. So if you search for \"chocolate biscuits\" you'll find pages about chocolate biscuits before you find pages about hot chocolate or digestive biscuits - this is good because it's more relevant!",
"Nevertheless it often doesn't give you the stuff you want - because really \"relevance\" is just a name here. The trouble is, sorting by date and popularity - or price for example on Amazon - are easy to label. But the algorithms that are labelled as \"relevance\" don't really have an easy or intuitive name."
] |
[
"Nitrogen versus carbon dioxide in beer."
] |
[
false
] |
Probably asked before but I can't find it. Why when you pour a beer that uses nitrogen (nitrogonated?) like Guinness can you pour straight down and get a solid head without overflowing a pint but with carbonation it will just go everywhere. Specifically what is the chemical reaction that keeps the nitrogen from expanding as recklessly as CO2.
|
[
"I'm pretty sure this is wrong. It might not be entirely wrong, but it is not the main reason for OP's observations.",
"Guinness doesn't \"go everywhere\" because it's only carbonated to about 1.2 volumes of gas mix, whereas most other beers are carbonated to 2 - 3 times that amount. For instance, Bud Light is carbonated to 2.6 volumes CO2, all Sierra Nevada beers are 2.6 - 2.7 volumes, and some wheat beers and lambics are carbonated as high as 4.5 volumes CO2.",
"A volume CO2 in the beer industry means that 1 L of beer has 1 L of CO2 (at 1 atm) dissolved in it."
] |
[
"I'm pretty sure this is wrong. It might not be entirely wrong, but it is not the main reason for OP's observations.",
"Guinness doesn't \"go everywhere\" because it's only carbonated to about 1.2 volumes of gas mix, whereas most other beers are carbonated to 2 - 3 times that amount. For instance, Bud Light is carbonated to 2.6 volumes CO2, all Sierra Nevada beers are 2.6 - 2.7 volumes, and some wheat beers and lambics are carbonated as high as 4.5 volumes CO2.",
"A volume CO2 in the beer industry means that 1 L of beer has 1 L of CO2 (at 1 atm) dissolved in it."
] |
[
"But they're not pressurized to the same level; that's my point. That one fact fully answers the question. Guinness has 1/3 - 1/2 the dissolved gas as most other beers. And the pressure that the bottle can handle is irrelevant here."
] |
[
"Big Bang and the accelerating universe?"
] |
[
false
] |
[deleted]
|
[
"In the explosions you mention, the initial expansion accelerates because energy is still being put in (the fuel is burning). That is not happening in the accelerated BB expansion now.",
"In your examples, the expansion slows because they are pushing against the air and losing energy to it. The BB expansion isn't doing that.",
"Finally, the BB expansion had (we think) an initial acceleration, then deceleration, followed by the present day acceleration. This isn't compatible with your picture."
] |
[
"My phrase \"we think\" was only referring to the inflationary epoch during the very early universe. The other two periods (of deceleration, followed by acceleration) have been observed.",
"We certainly don't know everything (we never do), but the probability that \"all we thought today about BB was wrong\" is not very likely."
] |
[
"keep in mind the big bang was not an explosion actually.",
"\nRather it was a sudden , very energetic expansion of the time-space continuum. I.e. there was no space-time where sth existed , only a singularity which encompassed all , space - time - matter - energy - possibly other dimensions. ",
"The BB was a literal expansion of time and space. Not an explosion"
] |
[
"If a hammer is essentially made of atoms, and a nail is essentially made of other atoms, and on the outside of these atoms is an electron cloud, then is sound essentially the product of electrons banging into each other?"
] |
[
false
] |
I got to thinking, and sometimes things like this show up in my head. But if the outer "layer" of metal is just a bunch of atoms that have a nice pretty electron shell, then how is sound produced when nothing but electron clouds touch? How is sound different on one object than another when all elements have the same electrons?
|
[
"You can think of the atoms of the hammer as a bunch of weights attached to each other with springs. An illustration:",
"*—*—*—*\n| | | |\n*—*—*—*\n| | | |\n*—*—*—*\n",
"Where * is an atom with mass, and lines represent \"springs\" (the bonds between atoms). Now consider what happens if you punch one of the atoms on the left side. Obviously, it'll move, and drag/push neighboring atoms around. These atoms, in turn, move their neighbors around, etc. The whole thing will start to wobble and vibrate.",
"This vibration is sound. The vibration in the hammer will create vibrations in the air around it, which eventually reach your ear. Blammo!",
"The sound that reaches your ear depends on how the original object's atoms are connected to each other (e.g. how stiff the springs are and how massive the atoms are)."
] |
[
"Sound is the collective vibration of matter, not of individual atoms. Vibration of electrons produces photons, but that's a different story.",
"Electron clouds repel eachother. When you force some close to another, they resist (this is why the hammer can't go through the nail). As a result, this vibration transfers to nearby atoms, where the vibration wave propagates. It ends up vibrating the air around it also, and that's what you \"eventually\" hear."
] |
[
"If matter is composed of atoms, and atoms are mostly empty space, then why doesn't the hammer just go right through the nail!?",
"The answer is that pauli's exclusion principle prevents electrons from occupying the same quantum state. By trying to force the hammer and the nail to occupy the same space you come up against a repulsive force which is opposing shoving electrons into the same state.",
"So you can indeed say that nothing is actually touching, but this isn't necessary for there to be a transfer of energy and momentum. And this energy doesn't just go into driving the nail into wood, some of it sets up vibrations in the hammer and the nail and wood. This vibration sets up similar vibrations in the air molecules surrounding the system and this is what you hear as sound.",
"So the sound is produced because the energy of the impact is transferred from the electrons to the atoms and to the bulk materials that make up the hammer and nail system."
] |
[
"Do you use more energy when walking up the stairs by stepping on each step or by skipping every other step?"
] |
[
false
] | null |
[
"Your legs are more efficient at straightening when they're closer to straight (to a point) -- this is why for example racing cyclists will set their seats so that their legs are almost straight at the bottom of their pedal stroke.",
"So the deeper knee bend when going up two at a time means you do more work for the same amount of potential energy gained.",
"EDIT: This is assuming \"normal\" sized steps."
] |
[
"Posting this a reply here since it got buried under a negative comment.",
"Your legs are more efficient at straightening when they're closer to straight (to a point) -- this is why for example racing cyclists will set their seats so that their legs are almost straight at the bottom of their pedal stroke.",
"So the deeper knee bend when going up two at a time means you do more work for the same amount of potential energy gained.",
"EDIT: This is assuming \"normal\" sized steps."
] |
[
"Posting this a reply here since it got buried under a negative comment.",
"Your legs are more efficient at straightening when they're closer to straight (to a point) -- this is why for example racing cyclists will set their seats so that their legs are almost straight at the bottom of their pedal stroke.",
"So the deeper knee bend when going up two at a time means you do more work for the same amount of potential energy gained.",
"EDIT: This is assuming \"normal\" sized steps."
] |
[
"Can someone help me understand the arguments around Abortion?"
] |
[
false
] | null |
[
"Human Body"
] |
[
"Human Body"
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"This question is not answerable via the scientific method. Please see our ",
"guidelines",
".",
"Please see our ",
"list of related subreddits",
" for other options for your question.",
"It suffers from issues listed in the AskScience ",
"guidelines",
". The question may be written in a way we believe does not contribute to scientific discussion at ",
"/r/AskScience",
".",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"Psychologically, what's happening in my brain when I spin around really fast and get dizzy?"
] |
[
false
] | null |
[
"Its more physiological than psychological. There is fluid in your ears that (along with other mechanisms) help you orient and balance yourself. When you spin, the fluid moves outward due to centrifugal forces (ie: spinning a pizza moves the dough outward). This confuses your senses into thinking your still moving, so you feel dizzy."
] |
[
"On a related note this is basically why you get dizzy when you're drunk. Signals are not in [relative] sync (as alcohol inhibits brain activity) and what you see is not what you feel [balance wise] and it throws you off."
] |
[
"Your brain is trying to process two different signals about where it is and what it is doing. Once you stop spinning your eyes will be sending a message which should be interpreted as \" I am standing still\" at the same time the motion sensors in the inner ear are still giving the signal normally interpretted as \"I am moving\".",
"Immediately after spinning the fluid in the inner ear labyrinth, will continue to move due to momentum and therefor the now incorrect signal is sent to the brain."
] |
[
"If you've lost a limb like a hand or foot, what do your muscles do when your brain sends the signal to move that limb?"
] |
[
false
] |
Obviously there's no hand to move but is there still muscle contraction? Will the "stump" (for lack of a better word) move slightly? Will it hurt?
|
[
"I don't believe that the actual question has been addressed yet. Unless I'm mistaken, the question wasn't referring to signals unable to reach missing muscles after loss of a limb. It's asking about muscles still present which at one time had a part in controlling the missing limb, EG forearm muscles after loss of the hand at the wrist. Surely THOSE muscles still are able to contract. My guess would be that they atrophy, but that a surgeon may reattach the tendon at the end of the stump so the muscles don't ball up towards the elbow when they try to contract. \nPlease, somebody who knows better, am I way off base here?"
] |
[
"Typically called phantom limbs. So maybe searching for mirror phantom limb."
] |
[
"Any source on this? Very interested and not so sure what to search for."
] |
[
"What inferences, if any, can be drawn from an unrooted phylogeny?"
] |
[
false
] |
I know unrooted phylogenies are a useful simplification because each one encapsulates many different rooted trees. But if you look at an unrooted phylogeny itself, with no background knowledge as to where to root it, what can you say about the taxa involved? For example, in the first image here, one might be tempted to say that we can infer that humans are more closely related to chimps than they are to gorillas. But we can’t: if the tree’s root was actually at point B (hypothetical), then that’s false. So is the unrooted tree merely an intermediate step on the ultimate journey, with no insights to be gleaned? But then how can that be reconciled with their frequent appearances in journals, and the fact that some analytical methods for unrooted phylogenies really do mean to convey information (such as the hypothetical second phylogeny linked here)? Thank you so much for your help!
|
[
"You actually can tell relationships on an unrooted tree, the issue is you can't tell when things happened at the sort of starting point. If your example included neanderthals for example, you'd see them branched from the same line that leads to humans. Theres still no root. We don't know whats the next closest, but we can get a relationship. Your example isn't ideal due to how simple it is. There's a hierarchy of relationships. an unrooted tree won't show the broadest groups timeframe of divergence, but within that you'll find relationships. ",
"",
"In this unrooted tree for example they look at the divergence of myosin proteins in life. Looking at plants alone you can see the XI group had an explosion of diversification of the gene and that some are more recent than others. Sure I can't tell where it all started or if the absolute first amoebal myosin in class I is more related to class IV or XIV but I can see the subgroups within each of the different classes. ",
"https://www.dnabaser.com/articles/phylogenetic-tree/myosin-unrooted-tree-big.jpg",
"",
"no root means no base to the tree, no trunk, no starting point, but the whole tree analogy is about the branches. Some are big and alone, others have many smaller branches branching off of them. They aren't used often, and when they are its because were often looking at bigger pictures with a looot going on to begin with, meaning roots aren't as important."
] |
[
"That makes a lot of sense. Thank you. But when making inferences about relationships, isn't the only true metric of interest the time of the MRCA? So two sequences could be remarkably similar, sure, but if it only happens that way because of convergence (e.g., long-branch attraction) then they really can't automatically be said to be more closely related. So if you don't have that time metric, yielding the MRCA, then no conclusions about relatedness can be drawn period. Unless you're saying that all terminal taxa here are, by definition, more recent than any of the internal nodes? So the fact that, tracing back from humans, they would rendezvous with the Neanderthals before they (both) would reach the node connecting them with chimps, necessarily means that they're more closely related to Neanderthals than chimps?"
] |
[
"Well first of all you state \"time\" but in reality time isn't the best indicator of evolution. Time is an alright metric because mutations and genetic drift happen at constant rates, but under different conditions there can be faster or slower evolution of some traits in certain environments. So time is an ok estimate, but what is truly used when generating phylogenetic trees is genome similarities, gene identity and the sort. You can still identify convergent evolution based off DNA similarities as well as the same functional gene can be coded in different ways so you can look for those differences. ",
"",
"On all phylogenetic trees, rooted or not, the tips of a branch are the peak of all evolution up to the present and where those two tips touch are wherre there last mos common anscestor comes from. I linked a simpler phylogenetic tree where I can use examples to show stuff. If you look theres the circled area that is primates. it has a diverged spot that diverges twice again into human chimp colbs and maque. From this tree you can see that humans and chimps are more closely related based off the closest node connecting the two is higher up than the rest. The next lower node connects to the double branch of colbs and maque, showing that they are more closely related to humans than everything else on this tree than chimps.. If you go down from there it splits off and things begin to be less connected...",
"Using this same graph look at the aves and reptilia. You can pretty easily see that all the birds have fairly closely connected nodes. More interestingly though is that the next node from where all birds have diverged from has nodes that closely connect to the reptilia. The node that goes from Bdragon to the rest of the tree shows that theres a common ancestor to reptilia (the Bdragon and later on the tree Aligtr) and then the tree goes to other birds. The next closest node from Bdrgn starts to connect to other mammals. ",
"This isn't the most representative tree but shows a great example of how you can see relationships on an unrooted tree. they are really just a bit harder to read because you aren't given an outgroup, meaning you need to be able to compare by nodes and not by a starting line. ",
"",
"https://upload.wikimedia.org/wikipedia/commons/2/23/Unrooted_Phylogeny_tree_c1orf167.png"
] |
[
"[Physics] Why does it take around 100000 years for the energy from the center of the sun to reach the outside of the sun?"
] |
[
false
] | null |
[
"THe specfici reason though, is the density of the matter the photon is going through. It takes a long time to get retransmitted from molecule to moleclue."
] |
[
"It is just a typo, I'm sure, but could be a confusing one. It is fusion going on in the sun, and the typo looks like it could be you're saying fission. "
] |
[
"The radiation from the sun (such has heat energy and light) reaches us in only 7 minutes. The photons that originate from the center however do not have a clear path, and they are absorbed, ejected, and reabsorbed by the dense matter in the sun. It has been approximated to take over 100,000 years for those photons to exit to the outside of the sun and take the 7 minute trip to Earth."
] |
[
"How involved is the strong force in creating mass?"
] |
[
false
] |
It is my basic understanding that most of an atom's mass arises from the energy of the quarks inside nucleons. But since the strong force (via gluons) dictates how these quarks operate, how much of a hand (if any) does the strong force have in the creation of this mass vs. the sheer kinetic energy of the quarks?
|
[
"It is my basic understanding that most of an atom's mass arises from the energy of the quarks inside nucleons.",
"The vast majority of hadron masses is due to strong force interactions. And the vast majority of the mass of matter is from the atomic nuclei, which are made of hadrons (protons and neutrons).",
"But since the strong force (via gluons) dictates how these quarks operate, how much of a hand (if any) does the strong force have in the creation of this mass vs. the sheer kinetic energy of the quarks?",
"The kinetic energies of particles bound in some system in the center-of-momentum frame contribute to the mass of the system. So if you imagine a very oversimplified, classical picture of a baryon, you have three quarks moving around and interacting with one another. Both their kinetic energies and their potential energies (as well as their individual masses) contribute to the total mass of the baryon.",
"If you think in terms of perturbation theory and virtual particles (dangerous to do in QCD), you'd say that there are a bunch of \"sea quarks\" and virtual gluons, also with kinetic energies and interactions with the valence quarks.",
"If you want the technical details for how hadrons masses are actually calculated from QCD, you can find lots of papers out there on lattice QCD calculations. They tend to do ",
"pretty well",
"."
] |
[
"The vast majority of hadron masses is due to strong force interactions.",
"For light hadrons (including everything that makes up the matter around us), but not for all hadrons. If they have a charm or bottom quark (or more than one) their mass is mainly from these quarks."
] |
[
"Thanks so much! Can you offer a brief explanation of the graph?"
] |
[
"Can depression affect someone's memory?"
] |
[
false
] |
[deleted]
|
[
"Yes"
] |
[
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4561348/",
" depression can induce a decrease in episodic memory, with lessen reward for positive memory recalling."
] |
[
"I'm no expert but I have previously been taught about something called 'overgeneralised memory' which is, in the most basic way that i remember it, when a depressed person looks back and only recalls the memories related to general doom and gloom and misery in their life.",
"https://en.wikipedia.org/wiki/Overgeneral_autobiographical_memory"
] |
[
"When I transfer data to my external hard drive using a USB cord why does the rate of the transfer constantly change (60mb/s to 90mb/s) throughout the transfer when my computer is doing nothing else?"
] |
[
false
] | null |
[
"There's a couple factors that can influence this.",
"Are you transferring one big file, or a whole folder full of different sized files? There's overhead to create and finalize each file written to a file system, so lots of small files will slow down the overall transfer speed.",
"How populated is the hard drive? Disk fragmentation can happen when a disk has handled lots of writes/deletes over its lifetime, and its especially bad with plug and play drives that are formatted as FAT32. If there's a large uninterrupted block on your drive to write to, the speeds will stay high, but once it has to start searching for random places to store files, the speed goes down."
] |
[
" - Think of a parking lot with a lot of small spaces. You have an SUV (file) to park (write) and these spots (empty drive storage) look empty at first but as you check it out it has a motorcycle or Smart Car parked in it, or someone parked over the line and didn't leave you enough room (there is empty space on the drive, but not enough to write the file). You waste so much time driving around, stopping to look for spots.",
" - A ton of smaller files takes longer to write/read than a single larger file. Imagine you are writing/reading a bunch of letters. It would take longer to open single letters in individual envelopes, as you have to open each envelope, pull out the letter, then move onto the next envelope. On the other hand, opening one big envelope with many letters only requires you to open a single envelope, just one time."
] |
[
"HDD transfer rates vary by the location on the platter being accessed. The further towards the edge of the platter, the faster read/write will be. If the drive is constantly changing the location where data is being read/written, possibly because of bad sectors or disk fragmentation, this would account for the changes is speed you're seeing. "
] |
[
"I know that its a myth that we only use 20% of our brains, but we use small areas during different activities. What activity can I do to use the \"most\" of my brain at once?"
] |
[
false
] | null |
[
"A seizure!"
] |
[
"I remember seeing (a very long time ago) a 3D measurement of brain activity during various activities. This was all set up to try and show how the 20% can be BS. There were various activities of reading, watching TV and sleeping. All of those activities there wasn't much more than 20% activity or so. Then they recorded the brain of a fighter pilot in a combat simulation....The whole brain lit up like a christmas tree. So go dogfight in a plane."
] |
[
"ride a unicycle while juggling and reciting pi to 200 decimal places..."
] |
[
"If Dinosaurs got extinct by a meteorite hit or a megavulcano, why didn't the underwater sea-dinos survive? (f.e. Plesiosaurus, Mosasaurus,etc..)"
] |
[
false
] | null |
[
"ObNitPick: Plesiosaurs and mosasaurs are not dinosaurs. They aren't even archosaurs - they are lepidosauromorphs, more closely related to modern lizards than they are to dinos & birds.",
"In something as big as the Chicxulub/Deccan traps event, marine ecosystems are going to suffer, too. First there would be the reduced sunlight whch affects phytoplankton and thus deranges the marine food-chain from the bottom up. Second, those animals were littoral rather than pelagic, so cooling would expose much of the continental shelves and erase their habitat.",
"TLDR: Short-term food loss, long term habitat loss. Au revoir, specialized predators!"
] |
[
"There are two common misconceptions surrounding the K–Pg event ~65 mya: ",
"That all dinosaurs went extinct. This is not true, since birds are dinosaurs and they are alive today. ",
"Dinosaurs were the only group to experience widespread extinction. While dinosaurs are probably the most famous example of widespread extinction during this event its worth noting that many of the above mentioned groups (e.g. sharks) did experience widespread extinction. \"A wide range of species perished in the K–Pg extinction. The most well-known victims are the non-avian dinosaurs. However, the extinction also hit other terrestrial organisms, including mammals, pterosaurs, birds, lizards, insects, and plants. In the oceans, the ",
"K–Pg extinction",
" devastated the giant marine lizards (Mosasauridae), plesiosaurs, fish, sharks, mollusks (especially ammonites) and many species of plankton. It is estimated that 75% or more of all species on Earth vanished.\""
] |
[
"Other sea creatures like sharks, fishes etc survived, so why not those?",
"I'm uncertain from how you phrased your question, but I want to point out, other land animals survived as well, not just marine creatures. The extinction event was severe but not universal. However, the only dinosaurs that survived were the ancestors of modern birds."
] |
[
"Can cancer be contagious?"
] |
[
false
] |
I'm not referring to things like oncogenic viruses or infectious agents that can cause cancer; rather, if cancerous material from one individual (say a fleck of a tumor) enters another individual (say it got into their bloodstream through a cut), could it thrive in the host environment? I'm guessing the immune response would make this difficult, but given that cancers replicate so quickly and aggressively, could this happen?
|
[
"Almost invariably no. If you’re talking about humans, then almost never. ",
"There are four exceptions that we know of: A contagious cancer of dogs, a contagious cancer of Tasmanian Devils, a contagious cancer of clams, and a contagious cancer of hamsters that has been extinct since the 1960s. ",
"Canine transmissible venereal tumour: a review",
"A Devil of a Transmissible Cancer",
"Horizontal transmission of clonal cancer cells causes leukemia in soft-shell clams",
"CHROMOSOME STUDIES OF A CONTAGIOUS RETICULUM CELL SARCOMA OF THE SYRIAN HAMSTER",
"It’s not known why these cancers were able to become contagious. You’ll read speculation that it’s related to their immune suppressive/immune evasion properties, but all tumors have these properties and still can’t spread to other individuals. In the case of Tasmanian Devils, it may be related to a lack of genetic diversity in the devil population, but recently the cancer has spread to more genetically diverse groups, so that isn’t as clear any more. Certainly dogs are highly genetically diverse, and their cancer has been successful for over 10,000 years, so that’s not a requirement. ",
"In humans, most cases where cancers have been transmissible are where the recipient has been heavily immune suppressed (that is, organ transplants). There are a number of case where a kidney was transplanted, where the donors had had cancer, and the recipients subsequently developed the donors’ cancer. ",
"Renal Cancer in Recipients of Kidney Transplant",
"There are a very small number of cases of vertical cancer transmission - from mother to fetus. ",
"Transplacental and Other Routes of Cancer Transmission Between Individuals",
"There is also a case where a cancer spread because of a surgeon sticking himself with a contaminated scalpel. ",
"Genetic Analysis of a Sarcoma Accidentally Transplanted from a Patient to a Surgeon",
". This may suggest that more cancers are capable of taking root in a new individual, but don’t have a method for actually spreading. The Tasmanian Devil cancer is spread through bites, and the Canine cancer through sex."
] |
[
"It's very rare, but yes. Tasmanian Devils are one such species who suffer from contagious cancer called DFTD. This takes the form of facial tumors which can be spread from one to another through biting. This is very much the exception though, otherwise you only see metastasis within a singular creature's own body."
] |
[
"While most cancer is not contagious, it’s important to remember that the causes of certain types of cancer are contagious. HPV is a great example which is why they have a vaccine. Further, community exposure to the same free radicals might cause a certain form of cancer seem contagious."
] |
[
"If a quantum fluctuation caused matter and antimatter to come into existence, than is it possible for it to happen again during the lifetime of our universe? A second big bang?"
] |
[
false
] | null |
[
"There is an idea out there called the metastable or ",
"false vacuum",
". It's not held in wide regard, but... it exists. Specifically, that when the quantum state fluctuated down to its present state, there may have been a deeper state it could have gone to, and maybe someday it could spontaneously fluctuate down to that state, causing another inflationary period in our universe spreading matter too thin to make any difference."
] |
[
"Oh, that would suck."
] |
[
"So let me ask you a second question. ",
"How would we ever communicate with the other universe?"
] |
[
"In an a large asteroid or comet strike, does the angle of impact make a difference? Same with a ground vs. air burst."
] |
[
false
] |
Also, What if there was an impact was in deep ocean, would it make it to the ocean floor?
|
[
"Yes, they absolutely make a difference. Mybest advice is to spend some time playing with this ",
"http://impact.ese.ic.ac.uk/ImpactEffects/"
] |
[
"The major difference that angle of impact makes is whether or not it will explode in the air. ",
"At a low angle of reentry the meteor (comets work differently) has a longer time to heat up and flatten, this flattening causes more heat to be generated and the cycle self-accelerates. It reaches a point where it can no longer retain its shape and shatters, which causes a massive shockwave. ",
"The altitude at which this happens is dependent on the exact composition and size of the asteroid, the angle of entry, and the orbital velocity of the asteroid.",
"Air burst shockwaves do damage in the same fashion as air burst atomic weapons.",
"A ground impact has the difference of making a large crater and throwing large amounts of ash and debris into the air. It will cause a large shockwave, fireball, and debris plume. ",
"Water impacts are a bit different. If they happen in deep water, with a large impactor, they will both vaporize a large amount of seawater, and cause a terrible tsunami. Again, dependent on the size of impactor."
] |
[
"cool link. Thanks."
] |
[
"Are there any non alternating, infinite series', that diverge slower than the harmonic series?"
] |
[
false
] |
The harmonic series already diverges extremely slowly, I was wondering if there were any other series' that diverge slower than the harmonic.
|
[
"The series Σ 1/(n ln(n)) diverges and does so more slowly than the harmonic series.",
"In fact, given ",
" divergent series Σ a",
" with positive terms, there exists a divergent series Σ b",
" with positive terms such that b",
"/a",
" --> 0 as n --> infinity. So in this sense, the series Σ b",
" diverges more slowly than the series Σ a",
". There is ",
" a more slowly diverging series.",
"Similarly, given ",
" convergent series Σ a",
" with positive terms, there exists a convergent series Σ b",
" with positive terms such that b",
"/a",
" --> infinity as n --> infinity. So in this sense, the series Σ b",
" converges more slowly than the series Σ a",
". There is ",
" a more slowly converging series.",
"This also means there is no \"master series\" Σ c",
" that determines the \"boundary\" of convergence and divergence. For ",
"-series, there is such a \"master series\" and that's the harmonic series. But for general series, there is no such \"master series\"."
] |
[
"A series of the form Σ n"
] |
[
"Suppose you give me a series that goes to infinity. Chop it up into 'blocks' that each sums up to at least 1. Now divide n-th block by n. Now each block is smaller (except for the first one) than it was, but n-th block is at least 1/n - so summing over the blocks gives at least as much as harmonic series, i.e., infinity.",
"If you do it to series 1,1,1,1,..., you get harmonic series. If you do it again, you get something that converges slower than harmonic series. If you tell me you found the slowest converging series, I do the above and present you an even slower one."
] |
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