title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Why do clouds have flat bottoms? Why do they seem to just stop?"
] | [
false
] | When I look at clouds, cumulus to be exact, I notice that at the bottom, they appear to be flat. I just want to know why that is. I assumed that it had to do with the atmosphere but Im not sure. | [
"As air rises, warmed up by the ground, the temperature falls by adiabatic effect (fall in pressure) to an average rate of 0.65 C per 100 m of altitude. ",
"At 15 C (the average temperature worldwide) a cubic meter of air can contain 14 grams of water. No more. ",
"As the rising air cools down, it has less and ... | [
"When water evaporates, it rises since a water molecule is lighter than your average air molecule. It tends to rise together in large clumps. As it rises, air pressure drops, which brings the temperature down with it. At some point, the water vapor condenses into tiny droplets. Once this happens, it becomes visible... | [
"a cubic meter of air can contain 14 grams of water",
"This is by calculating the Saturation Pressure of Water Vapor, which is a function of Temperature, then using this pressure you calculate Density of Water Vapor which is a function of Pressure and Temperature. At 15C it is actually closer to 13grams, I must ... |
[
"Why does the smell of flatulence vary between people?"
] | [
false
] | I am sure that we've all noticed that not only does our own flatulence smell differently from other people's (probably because we've gotten used to that smell), but it even varies noticeably between different people. It varies between men and women and between fat and thin people. I can think of several potential reasons for this, including diet, different compositions of the chemicals in the intestines and stomach, but what is the factor that decides the smell of flatulence? | [
"Don't forget your flora! Personal experience: Never EVER be around when people working in worm labs release gas! The contaminations that grow in their cultures can apparently hop to places ;)"
] | [
"The main factor is ",
"; but other factors include quantity (how much one eats), how long it sits in the digestive track, the amount of digestive enzymes one personally has, body temperature, how active one's parasympathetic nervous system is..."
] | [
"Oh god, thanks for the heads up!"
] |
[
"What determines if a leaf can be eaten as green vegetable, such as in salads?"
] | [
false
] | null | [
"1: That it's not poisonous",
"2: That it tastes good",
"3: That it has a nice texture",
"4: That is has any nutritional value to us (although stuff like iceberg lettuce we eat just for pleasure)",
"There's a lot of vegetation around us that is safe to eat, but would taste awful and not feel nice to chew an... | [
"Oh man, iceberg lettuce has no value?"
] | [
"Well not none, but a lot less than other types of lettuce or greens we eat"
] |
[
"If i had a stick that was 1 light year long, and at one end displaced it forward by say 1cm, wouldn't that displacement occur instantly at the end 1 light year away? Couldn't this be seen as information traveling faster than light?"
] | [
false
] | null | [
"No. Every material has a property called the \"",
"speed of sound",
"\", which is actually the speed that energy travels through that material.",
"When you push one end of the stick, the whole stick will ",
" move at once. You'll actually cause a ripple through the stick -- a compression wave -- and that c... | [
"that is an awesome question... can i assume that this \"speed of sound\" is dependent on the materials that that stick is made of? if so, could a material be made that would maximize this speed? if we had a super stick of some kind of space age alloy that allowed for a compression wave of say, .99c, would time d... | [
"This is in the ",
"FAQ",
" btw."
] |
[
"If humans could invent a way to travel instantly to a far off galaxy(far enough that the light hasn't reached it yet(since the universe is still expanding, the light would theoretically never stop)), and we had a telescope powerful enough, could we see the beginning of the universe?"
] | [
false
] | null | [
"No need to travel, we can already see the beginning of the universe. Using radio astronomy, the ",
"Cosmic Microwave Background",
" is the after-image of the big bang itself. ",
"EDIT from the wiki:",
"When the universe was young, before the formation of stars and planets, it was smaller, much hotter, an... | [
"the furthest you could see is ~13.7 billion light years in any direction, same as for earth.",
"Careful there. This is false due to the expansion of the universe. The observable universe has radius 45.7 billion light years. A long time ago, the distance between the Earth and the farthest thing in the observable ... | [
"Never having been this far away, any speculation is without proof, but what would happen, according to present theory, is that you would see a part of the universe that you can't see on earth.",
"Imagine that there is a bubble around each point in space that is expanding out at the speed of light - this is the v... |
[
"Does being exposed to confrontation/danger on a daily basis naturally increase testosterone levels?"
] | [
false
] | [deleted] | [
"Perhaps it's not the question you are really trying to ask, but the implication would be women and children who have lived with threatening partners or parents for large portions of their lives would then have extremely high levels of testosterone. Not sure that pans out. ",
"Testosterone isn't the stress hormo... | [
"I dunno about testosterone levels. ",
"Half of our troops come home with ptsd, which is the current name for an age old problem with leaving humans in stressful situations for too long. ",
"Stress eats at you like a disease. Too much, for too long, and it destroys your humanity. ",
"It could also be sleeps c... | [
"Depends... Do the person ENJOY being exposed to this danger daily ? Does it stress him ? Does his support net assist him to overcome the stress ? ",
"A High stress enviroment is generally associated with a decrease in T Levels... BUT, (And here I will extrapolate) My guess is that if the person seeks that dange... |
[
"How do scientists know what the structure of receptors look like?"
] | [
false
] | For example, the structure of melanopsin... I see alot of 3d renders, but no actual photos. What tools and methods are used to determine what it looks like? | [
"There are three main methods:",
"1.) X ray crystallography is the original method used. It solves the 3d structure by shooting radiation at bonds and measuring what comes back to determine distance, angle etc. However, for something with a repeated structure like an ",
"alpha helix",
", you can know without ... | [
"Whole lot of different ways really. These should be the more common ways as I was taught.",
"One key part is just isolating isolating a single protein from a soup of cell bits. Its's going to be some variant of chromatography which separates proteins into groups with different characteristics, like size, or d... | [
"This is a good general answer, but it doesn't really address OPs specific example of melanopsin, which as far as I can tell, has never had a crystal structure solved. This can happen if a protein is particularly difficult to isolate in a stable form, or if it doesn't like to crystallize in a uniform manner. In cas... |
[
"How do You Make KNO3 From Scratch?(AKA: Potassium Nitrate, or Niter)"
] | [
false
] | null | [
"Hello,",
"We can’t help you with this here.",
"Best."
] | [
"Hello,",
"Why not? Is there not a chance that someone in the community knows about this?"
] | [
"We don't offer assistance with personal projects.",
"Best."
] |
[
"An article I saw on r/physics today announced Fermilab's discovery of xi-sub-b, a baryon that had been predicted, but not previously observed. How exactly do the CDF/LHC and other particle detectors conclusively observe and determine the existence of a particle if it has never been observed before?"
] | [
false
] | edit: Another thing that confuses me is why a particle would appear in some instances of a collision, and not in others; from the article: " the Xi-sub-b was observed in 25 instances among almost 500 trillion proton-antiproton collisions." What occurred in those 25 instances that resulted in the detection of the Xi-sub-b? Was it present in the other collisions but simply not detected? | [
"It's likely a combination of both. ",
"When two particles collide the result is not deterministic. The slew of particles that result from the collision and the resulting decays is probabilistic. This is the nature of quantum mechanics. Though I don't know the details of the experiment, the creation of a Xi-sub-b... | [
"As far as I know the particles that have been discovered have all been hypothesized to exist beforehand, so I assume they are looking for specific properties. What I don't get is how exactly these properties are observed. Another thing that confuses me is why a particle would appear in some instances of a collisio... | [
"I see, so yes that is a good question, as I said not a scientist. "
] |
[
"Are there \"degrees\" of color blindness? The optometrist always tells me I am red-green colorblind, but I've never experienced any practical deficiency."
] | [
false
] | [deleted] | [
"There are different varieties of colorblindness.",
"You most likely have deuteranomaly. This means that your green-vision cells are not quite what they should be and activate on frequencies closer to red than they should.",
"However, some people have deuteranopia, which is a complete lack of green-vision cells... | [
"So...deuteranomaly is bad enough to fail all the tests, but not bad enough to actually see any effects in normal situations? Shouldn't the tests have been calibrated to distinguish this from deuteranopia? Or are there tests for that and I just never knew about them?"
] | [
"Your vision appears normal to you, and it is unlikely that you would know that you were colorblind if it were not pointed out to you explicitly in the tests for colorblindness. This accounts for the phenomenon you are describing. "
] |
[
"Is there a layer of steam around Europa's core?"
] | [
false
] | My current understanding (based largely on wikipedia) is that Europa is mostly water. The crust, to an unknown depth, is solid ice, followed by a mantle layer of liquid water and a hot iron core. What would the transition from the water mantle to the iron core look like? Specifically would the heat of the core be enough to generate an insulating layer of steam (the Leidenfrost effect)? | [
"The internal structure of Europa is not well understood, but there is certainly not a layer of steam between the water and the iron core for a couple reasons. 1) Water vapor is less dense than liquid water, so it would rise above the liquid. 2) The physical state of the water depends on both temperature ",
" pre... | [
"Europa is ",
"almost entirely a rocky planet",
", so it is unlikely that water from its oceans is being heated en masse by the inner core. You can see for yourself if you simply calculate Europa's density, which I find to be ~ 3000 kg/m",
" Since water is 1000 kg/m",
" this means that most of Europa cann... | [
"Thanks, this is the image I was missing."
] |
[
"What is oobleck and what does it mean for something to be non-newtonian?"
] | [
false
] | I keep on reading that it is a "non-newtonian" solid. What does non-newtonian mean exactly and how can we say that it is not liquid? Why does applying pressure to the corn starch and water mixture cause the liquid to harden? How is this able to act as it does on a molecular level? Sorry that my questions are all jumbled up. This thing is so bizzare to me. | [
"What does non-newtonian mean exactly",
": roll a ball along the floor. When you give 1 unit of \"push\", the ball rolls 1 unit of \"distance\"; 2 units of \"push\" = 2 units of distance; 3 = 3. etc. It's predictable according to Newtons laws of viscosity.",
": roll a ball along the floor. When you give 1 ... | [
"Ketchup. Ketchup gets more liquid when you hit it, which is why you have to thump the bottle sometimes to get it to come out. Materials that do this are called shear-thinning."
] | [
"Hard impacts make it feel solid but once you let it sit for a min it turns to liquid. Non-newtonian refers to that fact that it doesnt follow Newton's law of viscosity. I.E. constant viscosity independant if stress. Non-newtonian fluids change viscosity under force to either more liquid or more solid."
] |
[
"A (most likely misunderstood) problem I can't get out of my head: regarding Heisenberg's uncertainty principle."
] | [
false
] | I may be wrong from the start here, but for this problem I've been treating the uncertainty of position of my small but massive particle (may as well be a proton) as a perfect mathematical sphere, whose centre is a measurement of position I made of the proton, i.e it is somewhere in the sphere but we'll be damned if we know where. Now for potentially false assumption two: If we were to accelerate the proton to a large percentage of the speed of light and continued to measure it's position while it orbitted around us, (I have been assuming) the uncertainty of the proton would contract in a Lorentz-like way, reducing the volume of the sphere to the observer. As (delta)position(delta)momentum>h/4pi; would the uncertainty of position increase as a reaction to the loss of volume of the imaginary sphere? That is assuming that everything that I've assumed is true. I am fairly sure that things just don't work like this, with any of the assumptions I've made. Hopefully you guys and gals can put my on the right track? | [
"when you boost into another frame the length goes like x-> x/g where g is the gamma factor and momentum goes as p-> g",
"p, the g's cancel. On a more fundamental note the product of a momentum and a velocity is called action (its actually more complicated than that, but we'll ignore that for now.) And unlike mom... | [
"Don't accelerate the proton: instead, consider the different observations of two observers of the proton. One observer observes from the rest frame of the proton; the other observer observes from a frame with a relative velocity which is a significant fraction of the speed of light. Also, as the relative velocity ... | [
"My intuition is that the uncertainty doesn't change. Seeing as the uncertainty isn't a physical thing, I'm not sure why it would be subject to Lorentz-contraction. I think possibly, to get a real answer, would require reconciling quantum mechanics with relativity...",
"It's been awhile since I've done any QM, bu... |
[
"Why can there not be an n=0 mode on a waveguide?"
] | [
false
] | Take an elastic membrane for example. My physics notes say there has to be at least one oscillation in the x direction: why can it not be flat in the x direction, and a wave travelling down the z direction like normal? | [
"Shouldn't the excitation at the z=above,below boundaries be 0? Yet for a n=0 node, your membrane is flat along the x-direction. If it's both 0 at a point and constant, your wave won't be much of a wave. To be certain, I'd need more information as I don't even understand the diagram you just posted. Usually it's cl... | [
"thanks, that made thinsg clear even if my question wasn't"
] | [
"The question as you've asked it is a bit vague. Based on the linked picture I'm going to consider a rectangular (hollow?) waveguide. In this case you'll have indices m,n for x,y in cartesian coordinates. In the case of a TE waves it is entirely possibly for n=0 mode as long as m is non zero, ie TE_00 is not allowe... |
[
"I was recently identified as a potential stem cell/marrow donor for someone, what makes me special?"
] | [
false
] | Several months ago I joined the Onematch stem cell and marrow network . They called me up and told me that I was a match for a sick person and asked me to take some additional blood samples to make sure. The patient is anonymous to me. I am curious why mine? Wouldn't a close relative be better? Is it based on Blood type? A-, B+ etc? | [
"Firstly, congratulations on being fortunate enough to be given the opportunity to save somebody's life!",
"The ABO and Rh blood types apply only to giving blood to somebody. They are less relevant in organ donation, and even less so in marrow donation.",
"The important in marrow donation is the HLA (Human Leuk... | [
"Complete genetic chance. The HLA pattern is encoded in your DNA. You randomly inherited 1/2 of your pattern form your mother, and the other half from your father.\nInteresting note: Because distinct ethnic populations generally arise from a common ancestral group (i.e. all south asians arose from ancestral south a... | [
"Wow! Thanks a lot for the very informative answer. So is it complete genetic chance, or has my specific actions in life changed HLA pattern to match?"
] |
[
"Why are there Hadley cells, Ferrel cells, and Polar cells? What causes the air to sink between cells?"
] | [
false
] | Ok, so all the videos about global air currents start with convection and imagine an Earth that was still warm at the equator but cold at the poles but did not rotate. This Earth would have one two big cells where air travels from the equator to the poles and vice versa ( ). I know the Coriolis Effect means that the air wouldn't travel in a straight line, but why aren't there still two big cells? What causes the air in the Hadley cell to sink? And why three cells per hemisphere? | [
"This should clear things up",
"",
"https://sites.google.com/site/moreapesfiles/home/documents/Atmospheric%20Circulation%20%26%20Climate%20slides.pdf?attredirects=0&d=1"
] | [
"Some of the air has to sink if other air is rising, since the amount of air at each altitude is at equilibrium. So if you've got a band of uplift near the equator you've got to have an area of subsistence somewhere else.",
"I'm not sure about why there are three bands, but I suspect it has to do with Earth's spe... | [
"As you rightly mentioned the coriolis effect acts to deflect moving air masses away from a latitudinal orientation like you might expect on a non-rotating body. The magnitude of this deflection is large enough that air masses eventually follow the longitudes or align E-W or W-E. The general dynamics of the corioli... |
[
"Why are some insects attracted to bright lights, but others aren't?"
] | [
false
] | Wouldn't it be counter-productive to their survival by making themselves more visible when it gets dark? Also, why is this primarily something that some insects do, but not mammals or birds? | [
"They aren't \"attracted\" to the light. They use moonlight instinctively to navigate. Artificial lights mess with their guidance system, causing them to fly circles around the light or into it.",
"Mammals and birds don't use moonlight to navigate, as don't some insects.",
"It would be like if there was a big m... | [
"Why are some insects attracted to bright lights, but others aren't?",
"Insects are actually attracted to the UV light, which we and presumably some other insects can't see.",
"Wouldn't it be counter-productive to their survival by making themselves more visible when it gets dark?",
"Not necessarily. How many... | [
"Ok, and why are they attracted to UV light? And does a normal light bulb emmit lot of UV light? Thank you "
] |
[
"How far away are we from possibly creating a Dyson sphere (around the sun for example)?"
] | [
false
] | For those of you who do not know: So, when could such a structure ever be built, and how much would it cost? | [
"See ",
"http://en.wikipedia.org/wiki/Kardashev_scale",
"We're basically a Type I civilization, and most likely looking at several thousand years until we get to Type II, and the ability to construct a Dyson sphere. At that point, cost will probably (hopefully) be a concept of the past. "
] | [
"If we assume it to be 1m thick and at the orbit of mercury (0.3au) then it will have a volume of ",
"2x10",
"m",
". The volume of Earth is 1/20 of that so there is actually a lot of leeway in saying we would basically need to convert all of the terrestrial bodies in our solar system into it.",
"This would ... | [
"Perhaps through a post-scarcity economy if you're into that sort of thinking. "
] |
[
"Why isn't ejaculation after penetration instantaneous?"
] | [
false
] | null | [
"The female body makes changes to the reproductive tract during sexual intercourse to maximize chances of conception, and these take time to occur. ",
"The male body also undergoes continuous changes during sexual intercourse, which ultimately lead to ejaculation.",
"Female",
" and ",
"male arousal",
", r... | [
"And if the female has not warmed up and the male ejaculates, the chances of conception are lower. If one sex has to “warm up”, the other one must wait as well."
] | [
"Everyone, can we please have a nice, mature, scientific discussion about this? Keep it factual, keep it mature, and keep up the citations. "
] |
[
"Can the static tension of tectonic plates be quantified, or how are predictions about future quakes made?"
] | [
false
] | null | [
"Can the static tension of tectonic plates be quantified?",
"So, the way we as geologists would discuss this would be in terms of measuring the magnitude and direction of stress(es) within the crust. There are a variety of ways we can directly measure stress, e.g., ",
"borehole breakouts",
", ",
"overcoring... | [
"Amazing explanation, thanks so much!"
] | [
"Yeah, so, this is completely antithetical to everything I just laid out. I.e., you're effectively asking for a prediction after I just spent a significant amount of time trying to explain why these are not possible. PSHA maps for a given region are going to be the best bet for effectively background risk. As new e... |
[
"How can we differentiate so many simultaneous sounds?"
] | [
false
] | So I understand that sound waves are vibrations in a medium; for example, a drum sends a wave of energy through the air that eventually vibrates the air molecules next to my ear drum, which is then translated into a recognisable sound by my brain, as opposed to actual air molecules next to the drum being moved all the way over to me. But if I'm listening to a band and all the instruments are vibrating that same extremely limited number of air molecules inside my ear canal, how is it that I can differentiate which sound is which? | [
"Disclaimer: I know very little biology. I did a project in school that simulated a type of cochlear implant's performance and I know a fair bit about the psychosomatics of sound, but my medical terminology is poor. I may make mistakes.",
"The structure in the ear which detects sound is called the cochlea. It'... | [
"To add to this, when multiple sounds are playing together in the same airspace, you still only end up with one waveform that is an aggregate of all of the sounds present. The cochlea basically untangles that single waveform into a series of individual frequencies and sends that data to your brain, which analyzes t... | [
"Neuroscientist here.. Actually, it's very different.",
"In terms of the signal itself (as opposed to its location), our vision is much more limited than our hearing. Imagine you could only hear three different frequencies, in the sense that you could detect the whole range, but they'd always sound like some mixt... |
[
"Has anyone ever made a star chart not from Earth's perspective, Alpha Centauri A for example? How much would it differ from Earth's chart?"
] | [
false
] | null | [
"Yes. Here's one example:",
"http://www.astronexus.com/endeavour/chart",
"It starts at looking from Earth toward Orion. Replace \"Earth\" with \"Alpha Centauri\". As you might expect, the sky looks mostly the same, but a few of the nearby stars have moved. For example, Sirius is right next to Betelgeuse, and th... | [
"Hadn't realized that Sirius is in Orion as seen from Alpha Centauri! Right next to Betelgeuse."
] | [
"elite dangerous",
" does a great job too, and looks like it's based off the same data."
] |
[
"what is the optimum setting for efficiency on my storage gas water heater?"
] | [
false
] | null | [
"Lower temperature setting will always use less energy. Eventually you will run out so keeping the temp at the lowest setting you can without running out is best."
] | [
"In terms of the shower... the temperature of the shower times the amount of water used is the only thing relevant. It doesn't matter if the temperature is achieved by all 40 degree water from the storage tank - or a mixture of cold water and 60 degree water - the same total energy is needed for heating.",
"Which... | [
"If the tank and pipes were perfectly insulated, and the heating perfectly efficient - the temperature of storage doesn't matter.",
"That's a very good point, I never thought about it in that way. I think that's why I have felt so confused about the question."
] |
[
"Is the DWave machine a quantum computer or not? And how can they market it as a quantum computer if what it does isn't clear?"
] | [
false
] | null | [
"It is a quantum computer in the sense that it, at least in principle, uses quantum mechanical effects to compute. ",
"It is not a quantum computer in the sense that even if the machine were expanded to have infinitely many qubits, it is not believed to be able, even in principle, to solve all problems that could... | [
"Yes, it's a quantum computer",
"There is zero evidence for that. And even if there was, it still wouldn't be a quantum computer, it would rather be a dedicated solver for a class of problems that isn't even proven to be hard."
] | [
"It is a quantum computer in the sense that it, at least in principle, uses quantum mechanical effects to compute. ",
"I strongly object. Consider a gas tank filled with oxygen gas. Oxygen molecules are quantum objects, and the gas in the box \"computes\" things like temperature and pressure of the tank. Does thi... |
[
"Did not know that there had been so many Nuclear tests. Could they be partly responsble for climate change?"
] | [
false
] | Is a map/video showing the sheer number of nuclear detonations that have occured since the 40´s. But i have never heard much about the enviromental impacts they could have had on the planet. | [
"Most of those were below ground, and the above ground tests would have produced a slight cooling effect due to kicking up particulates."
] | [
"The ",
"largest nuclear test ever",
" released about as much energy as the sun imparts on the earth every second. Considering the sun has been shining for about 2*10",
" seconds since the first nuclear detonation, its energy is much, much greater."
] | [
"The total energy of the nuclear tests may not be significant compared to solar irradiation, but there could be other factors that contribute to global warming.",
"There are instances of erupting volcanoes that lead directly to global cooling",
"However, since exploding bombs do not kick up as much matter as vo... |
[
"How do cells know to grow into organized structures?"
] | [
false
] | When an animal or even a plant is growing, certain cells will develop in different areas to perform different tasks. What governs the cells ability to know what type of cell it should be and where it is within the structure? How do cells organize themselves into complex structures like veins for example? I'm assuming its an emergent process governed by simple-ish rules. I would sort of like to simulate this behavior in a computer, but I think I'm overthinking the rules governing a cells awareness of its location within the structure. Anyone have any ideas about this? | [
"This is rather complex, and the exact \"how does a cell know\" is very difficult to specify, but is mostly mediated by gene expression. I'll do my best to explain, but someone more versed in morphology might do better. When a zygote begins to divide and forms a blastocyst, a process known as gastrulation occurs, w... | [
"There's no single answer across the whole body.",
"In some cases, such as during brain and spinal cord development, there are proteins produced from one side of a structure that can diffuse across the structure, and cells can \"read\" these gradients to determine what position they occupy. In the developing cere... | [
"So this is actually a pretty complicated process, which the ",
"Wiki",
" can give you a brief idea of.",
"To generalize though, there are two broad modes of interaction that can help determine cell fate, specifically external and external signalling. External signals can include things like ",
"Matrix Stif... |
[
"Will the current ebola outbreak in Africa be a threat to Africa's primates?"
] | [
false
] | In the past Gorilla's have been threatened and died to ebola viruses . How much of a threat is the current strand to the Gorilla (and other primate) population and is there anything that is done to quarantine endangered animals susceptible to these kinds of outbreaks? | [
"Interesting question, experts still aren't certain which species are hosts, although they believe the fruit bat may be a major player in the spreading of the virus, as to this strain, it's hard to say, no large animals have been reported dead from this recent outbreak, this strain of Ebola In particular doesn't se... | [
"Since the fruit bats may be the biggest offenders in spreading the disease, does this mean that ebola likes a sugary host? "
] | [
"The short answer to that would be no, or not likely, I could be wrong but I've never read any journal on correlation between sugar and ebola homeostasis and or/survival benefits. The fruit bats fill a niche where they are likely to pick up the disease, it's worth noting that bats, are merely carriers of the disea... |
[
"At this point in time, are we able to simulate nuclear bomb tests by a computer with similar accuracy to a real life test? If so, are these test done as frequently as in the Cold War?"
] | [
false
] | null | [
"So the \"holy grail\" of nuclear simulation is to go from the subatomic scale all the way up to the macroscopic. That's like 15 orders of magnitude of distance from the femtometer to meter scale (even more so if you blow the nuke up!), with a ridiculous number of interactions that come into play, and huge amounts ... | [
"I mean a system in which you've got a live warhead on a live missile. There was only one of those — the Frigate Bird test."
] | [
"It's not a stupid question. The degree of confidence you require is not a technical answer, it's a question of values and strategy. Some countries have tended to want a ",
" of confidence that they know what would happen in the event of a nuclear war — the US is historically sort of obsessed with this, and desir... |
[
"If I eat two days' worth of calories, then the next day eat nothing, what are the effects on my body?"
] | [
false
] | Lets say I eat 5000 calories one day, then I fast the next day and eat nothing. How does that compare to eating 2500 calories each day? Is it any worse on my body/health? Thinking about things in the food like carbohydrates, salt, fat, etc - do they absorb at different rates? I wonder if a lot at once is better/worse than a moderate amount twice. | [
"OP specifically mentioned a two day experiment and wanting to know what happens. This is neither unhealthy nor the beginning of a Binge eating disorder outbreak. And using the word starving for not eating one day makes it worse. ",
"A healthy body will be able to store vitamins, minerals, etc for more than a day... | [
"OP specifically mentioned a two day experiment and wanting to know what happens. This is neither unhealthy nor the beginning of a Binge eating disorder outbreak. And using the word starving for not eating one day makes it worse. ",
"A healthy body will be able to store vitamins, minerals, etc for more than a day... | [
"No source here, just regurgitating information from a human nutrition course. It takes months to years to develop vitamin deficiency assuming a specifically nutrient-void diet, depending on the vitamin of course. "
] |
[
"How can you estimate the temperature of an arc discharge in air generated through high-frequency AC?"
] | [
false
] | Hi everyone. I'm wondering if it is possible or if there are methods to estimate the temperature of a plasma generated from an high-frequency arc discharge in air, like arcs generated from an arc lighter. Would it be dependant on the frequency, the distance between the electrodes or other things? The closest thing I found is related to the concept of electron temperature, but I haven't found any clear way to compute it. Thanks for your help and have a nice day! Edit: it would be in order to build an arc furnace capable of reaching temperatures up to 2100°C, to melt corundum | [
"An important thing to consider in these types of plasmas is exactly what you mean by \"temperature.\" A plasma includes, at the very least, very light electrons and heavy ions. These populations do not exchange energy with each other very easily so they are often at very different temperatures. In most low tempera... | [
"The simplest way is to look at the emission spectrum and compare it to ",
"black body radiation",
"At lower temperatures you can tell the temperature by just finding the right colour on something like ",
"this chart",
". Arcs are generally hot enough that you'd struggle to tell the difference in colour, ev... | [
"For a somewhat less simple but more quantitative option, you can make a papercraft spectrophotometer (usually based on a CD as a diffraction grating). Some versions are designed to attach to a phone, in order to record the results.",
"Example",
"."
] |
[
"Does counting \"one-one thousand, two-one thousand...\" after seeing a flash of lightning until you hear thunder actually give you a good estimate how far away you are from the flash?"
] | [
false
] | null | [
"Sound travels 1 mile in 4.7 seconds (or about 1 km in 2.9 seconds). We can round them up to 5 seconds and 3 seconds, responsively. If your counting of \"one-one thousand, two-one thousand...\" is a good approximation of a second (and that's why we add the extra \"one thousand\"; to force a pause in our speech of ... | [
"Follow up question: Why does a thunder clap last longer than a lightning flash??"
] | [
"My first thought was \"Doesn't the vertical distance of the lightning matter?\"",
"Then, I realized something profound - the fact that lightning stretches from the ground to the sky completely explains why the sound of a thunderbolt persists over a few seconds, rather than being an instantaneous CLAP. The sound ... |
[
"[META] Bots and AI tools on r/askscience"
] | [
false
] | Over the past few days we have seen a surge of accounts using bots/AI tools to answer questions on . We would like to remind you that the goal of is to be able to provide high quality and in depth answers to scientific questions. Using tools like GPT-3 chat not only do not provide the kind of quality that we ask for but they are often straight up wrong. As with all bots on this subreddit any account using those tools on will be and banned. | [
"Usually the comment will restate the question, for example if you ask \"is water wet?\" the comment will contain \"Researchers say that water is wet because...\". The comment also often doesn't really answer the question or contain any actual information. ",
"Those bots are also often posting way too much, too f... | [
"I had no idea that this was happening. Are there any post characteristics that we can keep an eye out for that would point to an account using these tools?"
] | [
"Ai is ruining every sub. Low effort ai art also constantly floods fan Reddits."
] |
[
"What would happen on the outside of a spinning spacecraft?"
] | [
false
] | I understand the physics of centripetal force creating a sense of gravity (inside of a spinning spacecraft, for instance) but I could never figure out what would happen to a person standing on the outside of the craft. | [
"Take a single point attached to the outside edge of the object, as if you were following it in time. Now, at any instant it will have a given velocity that is tangent to its rotation. For example, if the spacecraft is circular the velocity would be tangent to the ship. The centripetal force causes this point to ... | [
"You could have them wear magnetic space boots to keep them held on!"
] | [
"That sounds very very bad. Well, there goes an entire chapter from my short story. No spacewalks on generation ships, apparently."
] |
[
"When you lose a pound, how does it get out of you?"
] | [
false
] | null | [
"Mostly through your breath, the remainder through urine."
] | [
"A lot of that is water weight, the permanent weight loss is almost all through your breathe (CO2). "
] | [
"A lot of that is water weight, the permanent weight loss is almost all through your breathe (CO2). "
] |
[
"Do negatively charged phospholipids affect the resting membrane potential of a cell?"
] | [
false
] | null | [
"We're getting right to the edge of my knowledge here, as surface charge is a pretty esoteric area these days. But my understanding is essentially: no, but it depends. Specifically, if you think of the resting membrane potential as something that is the property of an entire cell, e.g. this cell is at -70 mV, then ... | [
"Well when it comes to Neuroscience textbooks, the go to should be \"principles of neural science\" by Kandell Schwartz and Jessel. \"Ion channels of excitable membranes\" probably has a chapter or two of use. But one that will get to this level of depth? I'm not sure. I would reckon most text books will stick to \... | [
"Well when it comes to Neuroscience textbooks, the go to should be \"principles of neural science\" by Kandell Schwartz and Jessel. \"Ion channels of excitable membranes\" probably has a chapter or two of use. But one that will get to this level of depth? I'm not sure. I would reckon most text books will stick to \... |
[
"What is infrasound, and how was it used to estimate the size of the Russian asteroid?"
] | [
false
] | How useful was any of the other evidence accumulated (videos and damage reports) in estimating the size? | [
"Infrasound is just a word used to describe very low frequency sound waves (below 20 Hz). They propagate just like normal sound waves, but carry further because atmospheric losses increase with frequency. As a result, you can measure these waves very far away with great accuracy, with the right equipment.",
"Beca... | [
"Infrasound are low frequency sound waves (20 Hz and under). At this range they can penetrate further through the Earth so are often used for stuff like earthquake monitoring.",
"As to how specifically it was used for the meteor strike, I do not know."
] | [
"Could this or could this not be used with the right amount of sensors to monitor any combustion reaction of a certain size within the atmosphere?"
] |
[
"What do \"tangent,\" the trigonometric function, and \"tangent\" the line that intersects a circle at one point, have to do with each other?"
] | [
false
] | Also, how do a secant in trig and a secant on a circle have to do with each other? I am doing trigonometry in school right now and I was wondering what the relationship between the two were. | [
"The tangent is the length you get when you project an angle onto the tangent line in a specific way. Here's a drawing of the tangent:\n",
"http://upload.wikimedia.org/wikipedia/commons/c/c7/Tangent-unit-circle.svg",
"If you have a secant of length 1 on a circle, and you draw the diameter at one of the end poin... | [
"The inverse tangent function maps slope (derivatives) to angles. The slope of a tangent line is (the limit of) d",
"/d",
" = ",
"'(",
"). The angle this line makes with the horizontal axis is arctan d",
"/d",
" = arctan ",
"'(",
").",
"The secant represents ",
"this length",
". I don't think ... | [
"This small collection of gifs helps make trigonometry more intuitive, at least to me. The last one is most relevant to your question, but I find them all useful.",
"http://www.businessinsider.com/7-gifs-trigonometry-sine-cosine-2013-5",
"EDIT: ",
"Imgur",
" link instead."
] |
[
"Are neurons in the brain simply put just complex multi-function logic gates, or does their function go much deeper than that?"
] | [
false
] | null | [
"Good question.",
"It is certainly very tempting to conclude that neurons, generally, yes. But of course, you need to extend the metaphor, as a neuron doesn't just have two inputs, it (usually) has thousands (though numerous classes on have 1-4). And of course, it isn't just any two inputs (usually speaking again... | [
"Depends on exactly what you mean by input. It also depends hugely on the cell type in question. I just published a paper showing that in a particular cell type, all input, no mater where it comes from in the cell, is the same size once it gets to the cell body. So, so long as you exclude inhibition, you should be ... | [
"Neurons certainly aren't literally a gate. But then, neither are any physical logic gates. They are only logic gates if used correctly. Or put more generally, there are certain regions within the parameter space that the abstraction of the circuit to a logic gate is legitimate. It could very well be the case that ... |
[
"You shoot a bullet out of the back of a jet. Does the bullet fall flat?"
] | [
false
] | If I'm standing on the tail of a jet facing its trail and fire a bullet, from my point of view it will travel at normal bullet speed away from me, right? To someone on the ground, would the bullet appear to fall flat? This makes the assumption that jet speed = bullet speed. | [
"Yes. ",
"Video of experiment."
] | [
"Yes, basically that is exactly what would happen."
] | [
"You'd also be hurt by the acceleration. In the video, the ball is going from rest to 60mph in a split second. Think of how bad you would be hurt if you went from 60 to 0 in that amount of time. It would be like crashing into a brick wall."
] |
[
"What is happening on a circuitry level when I turn the brightness up or down on my phone?"
] | [
false
] | null | [
"For LCD screens the LED backlight is set to a lower PWM duty cycle. Instead of being on 100% of the time, it'll flash on and off, spending some time off (more time off = darker). ",
"LEDs are funny; you can technically control their brightness by controlling the voltage/current, but tiny changes in electricity... | [
"It’s not the frequency which is changed, it’s the duty cycle (i.e. how long it is on and off during each period)"
] | [
"Assuming your display is LED based, the brightness adjustment is most likely a pulse width modulated(PWM) signal. A PWM (in this context) is a square wave that changes in frequency. If the frequency is fast enough it is effectively always on; if slow enough it is effectively off. LED dimmer often use PWM to introd... |
[
"Does the rule preventing homosexuals from donating blood make any sense?"
] | [
false
] | Many countries ban homosexuals from donating blood, presumably due to AIDS, but does that rule actually save more lives than the ones that would have been saved if homosexuals were allowed to donate? or is that rule in place due to homophobia? | [
"Yes, it does, from an administrative perspective. ",
"The numbers can be googled, but I'll limit myself to describing the principle. The target is having less then x% chance of a disease being transmitted through blood donations, say one in 100k. You know the incidence of the diseases you're interested in is hig... | [
"The rule is in place to save lives, because gay men are at a higer risk of getting HIV, and since gay men make up a rather small amount of the population, it is safer and easier to just exclude them from donating blood.",
"http://www.thebody.com/content/art13321.html",
"\nThis article is okay, search for \"Wha... | [
"Please check out the ",
"window period.",
"It is possible to be infected with a disease, yet test negative even with our 'superior screening'."
] |
[
"Why is there such a high rate of leukemia for children?"
] | [
false
] | I've read a statistic that says one third of cancers for kids below the age of 14 are leukemias. Why is that so and why does this rate change when you grow up? | [
"Children have a very low rate of all cancers, including leukemia: most cancers are caused by accumulated damage from lifelong exposures (e.g. smoking, obesity, sunlight) and children haven't yet racked up much exposure. However, it's not as clear what causes most leukemias, and it doesn't seem to be mostly exposu... | [
"Yes. ",
"Leukemias are most common in middle age: see here: ",
"https://seer.cancer.gov/statfacts/html/images/age_distribution/Age_Dist_New_Cases_Site_086_Sex_0.png",
"Unfortunate that they don't have a population-corrected graph: I suspect the rate rises throughout adulthood, but the population also shrink... | [
"I think the genetic causes are mostly due to chromosomal translocations that can occur during embryonic development. So children can be born with a predisposition to leukemia. Since translocations are common in leukemias (blood cancers) and sarcomas (cancers of connective tissues), but not as common in carcinomas ... |
[
"Why is the brain split into two?"
] | [
false
] | So why is the brain split into two sides instead of being a singular mass of tissue? I understand that separate parts operate different cognitive and behavioral functions. What I want to know is why we actually have two visible physical hemispheres rather than being a single mass. | [
"Well, ultimately it is a product of our bilaterality and need for specification, the wiki on lateralization is pretty awesome:",
"http://en.m.wikipedia.org/wiki/Lateralization_of_brain_function",
"The two hemispheres are something that Pre-dates us for quite a bit:",
"http://www.scientificamerican.com/articl... | [
"And adding to this: the brain's computation occurs in the surface of the brain, which is heavily wrinkled to maximize the neuron count. The fact this structure is chosen rather than some other is probably an evolutionary accident, but since surface area is important, we have this wrinkled organ."
] | [
"Well no. The sphere has the lowest possible surface area for a given volume. If you accept as a given that surface area is important for brain, then the smooth, spherical brain would be the worst possible choice for a given volume."
] |
[
"What caused dinosaur evolution to lead from larger terrestrial animals (dinosaurs) to smaller flying ones (birds)?"
] | [
false
] | null | [
"The stuff about atmospheric oxygen is bullshit. We all read that in Jurassic Park, but it's simply not true. Dinosaurs appeared in the Triassic and became dominant in the Jurassic, but the atmospheric oxygen was actually LOWER then than it is today. See ",
"this graph",
", where you can see that the peak was d... | [
"Thanks, I didn't know this"
] | [
"One notable feature is the extinction event which ended the Cretaceous period, and all non avian dinosaurs. Theorized to be an asteroid event, the suspected resultant obscuring of sunlight would have led to a decline in photosynthesis, and thus a major collapse in food chains which would seriously afflict large an... |
[
"How do reflective surfaces (like a mirror) differ physically from non-reflective surfaces? What makes them reflect light?"
] | [
false
] | null | [
"Reflective surfaces are generally smooth on their surfaces and this allows light rays to reflect at mostly the same angles (uniform reflection). When the reflection of light is uniform, and when they enter your eyes, your brain is able to form back the image as it perceives light rays to be straight. \nOn the othe... | [
"So virtually anything could be a mirror if you had the means to smooth it out?"
] | [
"If you rearrange the structure at that level, is it still the same thing?",
"If you went through a paper shredder, would you still be you?"
] |
[
"When I'm driving steadily up a hill, what's going on in my car's engine?"
] | [
false
] | Let me see if I can be more specific. My car is an automatic, 4-cylinder, gasoline model, and a bit under-powered. When I approach a large hill, I begin pressing more on the gas pedal to open up the throttle. If I do this slowly, I am able to pretty much maintain steady speed up the hill without causing the car to downshift, which would cause the RPMs to increase. I can keep the RPM needle steady while pushing the pedal down quite far while going up a significant hill. What I'm wondering is, if I depress the pedal like this and the car doesn't decide to downshift, is the engine burning more gas even though the rev counter doesn't change? | [
"if I depress the pedal like this and the car doesn't decide to downshift, is the engine burning more gas even though the rev counter doesn't change?",
"An engine's fuel consumption doesn't depend solely on engine speed. So if you're asking if your car burns more fuel when going up the hill than on a flat, the a... | [
"Yes. The car's engine time specific fuel consumption is the product of only two things, the speed of the engine in RPMs, and the amount of fuel injected per cycle. By depressing the pedal you are doing 2 things (when the car does not downshift), first it opens the throttle a adjustable plate that covers the air ... | [
"When you go up a hill the road load increases (kW) To maintain speed the engine output must increase. This takes more energy, I.e., fuel. The transmission and drive ratio mechanically link the engine speed to wheel speed. So when the road load kW increase the engine torque must increase, since engine speed is fixe... |
[
"If everyone frequently washed their hands how much would the spread of disease be stopped?"
] | [
false
] | [deleted] | [
"umm... Source? (for pretty much the whole thing.)",
"For example this statement",
"antimicrobials will selectively breed microbes to resist them, until you get nasty, nasty shit like MRSA becoming more and more common",
"Is false. Bacteria such as MRSA came from the incorrect usage of antibiotics, not from w... | [
"If everyone washed their hands very regularly, before and after every meal, and didn't touch their face without having washed their hands first, would disease still spread as much from person to person?",
"http://www.sciencedirect.com/science/article/pii/S0140673605669127",
"Here is just one study that suggest... | [
"http://en.wikipedia.org/wiki/Anthroposophical_medicine",
"Anthroposophical medicine is a complementary approach to medicine[1] that integrates the theories and practices of modern medicine[2] with homeopathic medicines, physical and artistic therapies and biographical counseling.[3] The medical approach has its ... |
[
"Why are cats able to develop on their own but people are not?"
] | [
false
] | Taking into account the feral child case ( ), where a child was deprived from human interaction for thirteen years, and once freed was incapable of ever catching up to where a normal 13 year old would be with speech, or even however old she is now. Also, she was incapable to walk normally from what I've learned (had a more animal approach to walking). But when you see cats they all have the same abilities of "talking" which I guess would be a meow? Why is this? I guess an obvious answer would be that they are with their mothers for a little while when they are first born, but later in life when they live on their own they pick up the same habits as a wild cat or any cat that lives with a family for at least a little while. I guess this could be interchangeable throughout the different species of animals. Tagging this psychology because I don't know what else it'd be | [
"Humans are a highly ",
"altricial",
" species. \"Altricial, meaning \"requiring nourishment\", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born\". The amount of energy, time and knowledge gained required to be able to... | [
"You assume talking and walking upright is innate. Or is it culture?",
"(I'll let the actual social scientists take over from here.)",
"As an aside: cats meow to communicate with humans, not each other. See: ",
"http://en.m.wikipedia.org/wiki/Cat_communication"
] | [
"You assume talking and walking upright is innate. Or is it culture?",
"That's an interesting one. It's innate for humans to talk and walk upright given a normal environment. But a part of a normal environment is having other humans around, and so, eg, what language you wind up speaking is culturally determined... |
[
"How does being blind at birth affect someone's sexuality?"
] | [
false
] | null | [
"I am legally blind (with a guide dog) and I'm studying psychology at a university. Unfortunately I don't think there's much research on this topic, but I've read some books about disability and sexuality and I think the other stimuli from someone (voice, the way their body feels, personality) is what attracts mos... | [
"From Dick Swaab's ",
" (We Are Our Brain), page 89:",
"Even though it is said often that development after birth is influential to sexual orientation, the evidence is absent. Children that grow up with two mother or fathers do not have higher odds of being homosexual themselves. ",
"Page 88:",
"Twin and fa... | [
"At risk of sounding crude and without much scientific basis... He can still TOUCH. He can still envision what a body looks like. Men and Women have different personalities, vocal traits, scents. The, uh, physical sensations of more intimate interactions would vary as well. There are more ways gender exists be... |
[
"How many of an average human's genes are mutations?"
] | [
false
] | How many of our genes are not simply reshuffled from previous generations in whatever form was expressed in one of our parents? I suppose this would be something like average mutation rate per b.p. x average length b.p. length of genes x number of genes in genome, or is there something I'm missing? | [
"As arumbar points out, the human mutation rate is now estimated at around 1.1*10",
" mutations per base pair per generation. There are ~ 6 billion bases in a human genome, so that yields about 66 new mutations in every individual. Approximately 1.5% of the genome is coding sequence, so under the assumption that ... | [
"This paper",
" cites the mutation rate at ~1.1e-8 per bp per generation. Beyond that, it gets muddled because you don't know how the mutations are distributed (eg clustered in a few genes or distributed across many), and what types of mutations they are (eg silent vs missense vs nonsense)."
] | [
"Thanks, but that's not what I was asking. My post title may not have been clear enough, but I think I clarified it in the body. How many new mutations are produced in an average individual?"
] |
[
"What's my brain doing? I've done this my entire life, it's involuntary, and I've never met anyone else who does it. (X-post from askreddit)"
] | [
false
] | null | [
"\"Medical advice is always off-topic and inappropriate. Please consult with a doctor regarding issues of health. Please do not ask for, listen to, or offer diagnoses, treatment advice, or personal medical opinions.\" ",
"Per Rule #4 in sidebar."
] | [
"Not sure he's seeking medical advice. If you were to actually read the post and watch the video, you would see that whatever is happening does not negatively affect his quality of life."
] | [
"I did both. I love being loosey-goosey with this rule, but the place where he says \"My plan is to see a Neurologist, assuming my insurance would make it affordable. But hey, maybe one of you knows what's up.\" Shows pretty clearly the intention is to get medical advice. He addresses his question to \"Neurology b... |
[
"How well do we really understand hieroglyphics?"
] | [
false
] | Are there older languages we understand better? | [
"There are still some graphemes that we don't know either what they do/mean and/or what sounds they might have represented. However, the vast majority of known graphemes across the recorded history of Egyptian's development are known to us. And we understand how they were used systematically. Namely, we know that t... | [
"We have comparative evidence from (the descendant language) Coptic (older descriptions, when it was still alive, and its current ecclesiastical form), from related languages like Hebrew and Arabic and from reconstructions of their ancestors (cousins to Egyptian), and from renderings of Egyptian names/words in the ... | [
"But the answer to the question, isn't \"we don't know.\" The question doesn't make sense because it misunderstands how languages work on a fundamental level and therefore doesn't make sense as a question. "
] |
[
"What are the stains in my glasses when I look at the computer screen through them with sunglasses?"
] | [
false
] | When I look at the screen through my regular eyeglasses and sunglasses lens combined, I find out that there are stains in my regular lenses. What are they and are they harmful to my sight? Photos: | [
"Oh oh this is so exciting!!! This relates directly to my area of specialty!",
"First of all: they are not stains, and they are not harmful to your sight.",
"So light has a property known as ",
"polarization.",
" The following metaphor isn't perfect, but its good enough for now. The basic premise of it is t... | [
"Follow up question: Why are you using sunglasses to look at your computer monitor?"
] | [
"Minor thing: sunglasses aren't universally polarized sunglasses. Plenty of sunglasses, especially cheap ones, are simply dark-tinted lenses without any polarization."
] |
[
"What is the largest a sun could possibly be?"
] | [
false
] | How large could a star physically be without collapsing upon its own weight? How large could one be with natural processes? What is the largest star we know? | [
"http://en.wikipedia.org/wiki/List_of_largest_known_stars",
"\"There are theoretical reasons for expecting that no stars in our galaxy are larger than approximately 1,500 times the sun, based on evolutionary models and the Hayashi instability zone.\"",
"\"UY Scuti is a red supergiant star in the Scutum constell... | [
"That is only for volume and the temperature assumption is only true for stars that have exited the main sequence. The opposite is true when a star is on the main sequence. The heaviest a star can be is thought to be ~300 solar masses. This is called the Eddington limit. The reason why stars can't be larger is not ... | [
"The largest star that we know of (and that we have accurately measured the size of) is VY Canis Majoris, which is approximately 2000x the size of the sun. Put it in our solar system and it would extend past the orbit of Saturn.",
"As to the biggest possible, I'm not sure. I've seen a source that says that about ... |
[
"What is Anaphylaxis and how does Epinephrine reduce the impact of an episode?"
] | [
false
] | I understand the why we have EpiPens, but I'd like to know the how it works too. | [
"Anaphylaxis is basically a very severe allergic reaction characterized by one or more of the following:",
"a very itchy rash, typically in the form of hives",
"vomiting",
"swollen tongue, throat, lips, eyes, or all of the above (also known as angioedema)",
"low blood pressure due to vasodilation",
"short... | [
"The two previous answers are very good, I'd just like to add on a little bit of information. All of the symptoms that come with an anaphylactic reaction are due to the release in the blood stream of substances (chemical mediators) from some specific cells : mast cells or basophils. Epinephrine or adrenaline here i... | [
"To add to this, people with true anaphylaxis will need more than one EpiPen shot and the ER will likely give more epinephrine before they mess with any of those other drugs. Some people even require intravenous infusions of epinephrine. As the previous answer stated, epinephrine keeps the airways open and the bloo... |
[
"Could we create gravity waves by spinning a massive 'rod' in space at high speed?"
] | [
false
] | Because it would not be spherical like everything else in the universe it's 'spot mass' would change drastically, thus the gravity would fluctuate while the systems forces could remain in equilibrium. | [
"Yes and no. In theory, any accelerated mass will radiate gravitational waves, but in practice, only the most energetic sources of gravitational waves (like supernovae and colliding black holes) will produce a signal that could ever be detectable. ",
"Additionally, even if your rod is very long and very fast and ... | [
"Moving a charged particle \"up and down\" causes EM radiation.",
"Moving a particle with mass \"up and down\" cases gravitational radiation.",
"Whether or not we could be able to detect this infintesimal fluctuation in space-time is another story."
] | [
"In theory, any accelerated mass will radiate gravitational waves",
"That is not the theory. Accelerating mass can be in a non-radiating condition. A spinning star will not generate gravitational waves if it has symmetry about the axis of rotation, and it very nearly does.",
"The spinning rod could be in a radi... |
[
"Effectively, how are nuclear weapons regulated? I remember reading (on here somewhere) that Uranium 238 isn't regulated, but rather the technology of making it into 235 is. Is this true, and how is this achieved?"
] | [
false
] | null | [
"Separating U-238 and U-235 is a difficult process. The issue is that you want U-235, but that is only 0.7% of naturally occurring uranium. Being isotopes of the same element with only a ~1% weight difference makes traditional chemical separatations not feasible. ",
"So, what do you do? A few things. ",
"You do... | [
"Uranium-238 and uranium-235 are really hard to separate. They are both uranium, and have identical chemical properties, and the difference in physical properties is minuscule. Therefore, you need very complicated technology to separate them.",
"You don't make it into 235, it does not work that way. But, you can ... | [
"Just as a clarification: the Calutrons of WWII were one one of the three methods of enrichment used during the Manhattan Project. Thermal diffusion and gaseous diffusion stages were all used before electromagnetic. After the war, the gaseous diffusion plant was made to operate without any additional stages, and co... |
[
"What are the actual differences in breathing at high altitude, what makes it hard, is it simply less oxygen?"
] | [
false
] | Is it that simple or are there other factors at play? | [
"I think there are 2 main things at play here:",
"We breathe by creating pressure differentials, so the pressure of our surroundings (Ps) determines how much total air flows in to our lungs. During inspiration, inspiratory muscles contract to expand the chest wall, which ultimately decreases the pressure in our a... | [
"As a pilot all I know is that it is not less oxygen. It is the reduced pressure that no longer allows the oxygen to pass the membrane in your lungs and then onto your blood cells. The concentration of atmospheric gasses is nearly uniform throughout most altitudes; it is only a reduction in pressure at higher altit... | [
"Some back-of-the-envelope calculations using generally accepted figures. ",
"Starting at sea level:",
"\nAir is always around 21% oxygen at all altitudes. The average person moves about 6 litres of air through their lungs every minute at rest. Exhaled air has around 15% oxygen content. So let's say that, in th... |
[
"What is the biggest limiting factor keeping videogames from looking photorealistic?"
] | [
false
] | recent post on got me thinking about why even some of the most impressive combinations of hardware and painstakingly developed player modifications still seem to mostly fall short of looking realistic. The screenshots are very impressive, yet something about them makes me think, had someone handed me a printout of one of them, I would probably recognize them as computer generated rather than a photo. I can't put my finger on it, but I was wondering if science has identified that limiting factor. | [
"The short answer is, as you might imagine, \"software and hardware aren't there yet.\" But a more detailed answer would be that 1) we haven't yet developed efficient (real-time) algorithms for reproducing a lot of what we see in the real world in a 1:1 way, 2) even if we had those algorithms today our hardware wou... | [
"In the past, one of the things that we could scale up to make things look realistic most easily was the total number of polygons in a scene; every year, as videocards got faster, we could draw more and more polygons to the scene concurrently. This made all the shapes that we see look smoother and smoother, but it ... | [
"One of the fundamental areas of research and study in computer science is the study of data structures - how data is organized and represented in an abstract sense by the computer. When I say \"abstract sense\", I mean it as in \"I know that character strings are all in the computer as zeroes and ones, but let me ... |
[
"Controlled hunting programs keep species from going extinct? Is this a valid statement?"
] | [
false
] | I see this argument lately (specifically, in defense of the ). Is this valid? Have there been studies to defend/refute this line of reasoning? Sorry if this the wrong place to post. | [
"This claim is potentially true depending on the relevant facts. Normally, the ideal case would be that zero individuals of an endangered species are killed by humans. But perhaps the national parks (and countries) where the species lives are not able to provide the necessary resources to prevent poaching.",
"I... | [
"This is basically a communism work \"in theory\" situation "
] | [
"For this to be effective you really need to meet a few requirements:",
"You need to have a very good understanding of the population dynamics of the species and their life history. I.E. how many individuals there are in each age-sex class, how long it takes individuals to mature, how many individuals typically s... |
[
"What factors lower the tide in this video by 12 meters? Why is it lowered so briefly?"
] | [
false
] | null | [
"This is probably a particularly low tide. It's worth remembering that the tides are not entirely due to the moon (explanations given to Bill O'Reilly to the contrary) and in fact the sun's tides are about half as strong as the moon's. When the two tides are in sync, they constructively interfere, leading to what... | [
"All well and good but that was John Hurt, not David Attenborough.",
"Source: ",
"http://en.wikipedia.org/wiki/Human_Planet",
"\nSource: ",
"http://www.imdb.com/title/tt1806234/"
] | [
"c'mon, please not in a science sub-reddit. Let's not pollute, mmkay?"
] |
[
"Do our bodies have much empty space inside?"
] | [
false
] | The reason I'm asking is this image (NSFL, leg with a cut in it, from ): It looks like there's a lot of empty space inside...in my head that makes little sense, I thought everything is very closely aligned. What's the deal here? | [
"Very little, outside the body cavity (and not a lot, there, really). That gap is actually a result of the opposite being true: there is enough pressure against the skin from all the stuff filling its insides, that when it is opened, it gapes."
] | [
"Actually, in your friend's case, the flesh has been pulled apart for finding and removing any foreign objects (shards of glass inside the body are extremely dangerous), so it \"seems\" like there is empty space there. The doctors will press the flesh together, and will stitch it up afterwards.",
"If you open up ... | [
"that space is an artifact of the plasticizing process. Those spaces aren't there in life."
] |
[
"What is the minimum size necessary for an object to cause planetary destruction while moving at the speed of light?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/estimation",
"/r/theydidthemath",
"guidelines",
"/r/askscience",
"If you disagree with this decision, please send a ",
"message to the moderators."
] | [
"Thanks! Sorry about that!"
] | [
"Thanks! Sorry about that!"
] |
[
"What was the world like before life?"
] | [
false
] | I am doing some amateur research on the origins of life, and am fascinated by the extent to which organisms effect their surroundings. I find it hard to imagine a world without trees or grass or micro-organisms. How different would the composition of the atmosphere or seas for example, be without the influence of living organisms? | [
"Indeed, life does have a significant impact on Earth and its evolution through time. The presence of oxygen, amount of CO2 etc.",
"The earth before life is pretty hard to constrain with actual data as we don't have many rocks that are that old that give definitive evidence for the presence or absence of life. Th... | [
"If I read the original question correctly, it's more about what the Earth would look like today if life had never taken hold here than it is about what primordial Earth was like.",
"That means plate tectonics would still be a factor, and there would be an ocean regardless of whether it was built by comet bombard... | [
"ilovemud",
"\"So, what do you do?\"",
"\n\"I study mud.\"",
"\n\"Oh! Um... how about them Red Sox, huh?\"",
"\n\"No no, mud's really very interesting! Let me explain...\"",
"\n\"I just remembered I have to return a library book, gotta run!\""
] |
[
"Can someone put \"pair production\" into layman's terms for me?"
] | [
false
] | Specifically as it relates to the modern supporters of the Expanding Earth hypothesis. Since the guy who came up with the hypothesis (Neal Adams) is a comic book writer and not a scientist, I'm quick to dismiss it, but alas I am no scientist myself so I cannot find the grounds to do so. | [
"So e=mc",
" right. Mass is energy.",
"You probably know that certain things are conserved. Energy is conserved, momentum is conserved, and charge is conserved.",
"An electron or positron has 511,000 electron-volts of energy, or 511 keV. The pair of them has 1,022,000 electron-volts of energy, or 1.022 MeV... | [
"\"4-momentum\" is conserved, mass isn't. That's why nuclear power plants work. Mass is a form of energy - it's just the energy that a particle has when it's in rest. "
] | [
"That's not really the main reason nuclear power works. It's just binding energy. It's really the same principle as chemical energy. When we burn coal we convert chemical binding energy into thermal energy through a chemical reaction. When we do nuclear fusion, we convert nuclear binding energy into thermal energy ... |
[
"What is the difference between neurons in different parts of the brain?"
] | [
false
] | If different parts of the brain perform different processes(visual,motor, somatic etc.) what is the difference between neurons in different parts of the brain? somehow i made too much of the word "different", still it makes sense :) edit: thank you all for your answers, it was interesting to see the brain from a deeper perspective. @PKThundr7, i was just thinking one day about the brains and thought that in different parts of the brain neurons should be somehow different and i wanted to check if it's true. sorry that i didn't reply earlier, i just forgot that i posted this question here until now that i checked again my reddit overview of activity. | [
"Good question.",
"I'm going to take a slightly different tack to the others, and say this, highly controversial statement:",
"There is no fundamental difference between different brain cells in different regions of the brain.\n",
"Already, some of the more educated readers will be outraged, and any neuroscie... | [
"/u/NeuroBill",
" is right, but so are the other two responders so far. What you need to do is clarify your question. What level of analysis do you care to measure? If you only care about the output of a neuron (action potentials) then ",
"/u/NeuroBill",
"'s analysis is spot on. A neuron is a neuron, they rec... | [
"Well! There are a lot of phenotypic differences when you look at neurons in different areas of the brain and body. A lot of the really cool work showing gross phenotypic differences was done over a hundred years ago by a dude named Santiago Ramon y Cajal. His adapted a guy named Golgi's method of staining to make ... |
[
"If planes are pressurized why do we have our ears popping?"
] | [
false
] | I mean, there is supposed to be a constant pressure in the plane and the pressure is supposed to be independant of the outside pressure, so why do we have our ears popping when the plane is gaining altitude? | [
"Aircraft ",
" maintain constant ground level pressure in their cabins. They’re required by law to maintain a ",
" pressure, which is equivalent to the pressure at an altitude of 8,000 feet. So when a plane takes off, the pressure in the cabin falls until it reaches the minimum required by law, and then remains... | [
"Plane cabins don't typically pressurize to sea level (or wherever you are starting from) but can range anywhere from that to up to a cabin pressure equivalent to 8000 ft of elevation (according to the FAA at least). As you climb the pressure will gradually decrease from your starting pressure to whatever the cabi... | [
"Remember that commercial jets typically fly above 30,000 feet anyway, so yes, they can actively increase the air pressure in the cabin. Typically they bring in air compressed by the engines' turbines."
] |
[
"How does Google know my location even when I am using a laptop or a device with no GPS?"
] | [
false
] | I have been wondering everytime I open my browser with location services enabled, it knows my location with a high accuracy. How does it manage that? I know my IP address plays a part but, I am sure you cannot just know exactly where I am using my IP address.Thanks in advance ya'll. EDIT: Thanks a lot to everyone who replied. Much appreciated. | [
"IP addresses can be used for a rudimentary location fix, but they're typically rather inaccurate (limited to the general region at best).",
"Much better location data can be obtained by analyzing which WiFi networks your device is able to see. Google has a database of WiFi networks and their physical location (s... | [
"If there isn't much to work with, then location accuracy will falter obviously.",
"Note that not broadcasting SSIDs doesn't really do anything, because even if you have set your router to hide the SSID, it's still broadcast in different ways. Hiding SSIDs only keeps out the most casual of listeners."
] | [
"Two ways: WiFi networks and IP Geolocation.",
"Google keeps an absolutely massive database of known WiFi networks and their corresponding MAC address.",
"If you have WiFi on, your phone will be able to see a pretty unique set of wireless access points and their signal strengths. Since the effective broadcast ... |
[
"How would/does microgravity affect the function of an induction motor?"
] | [
false
] | How does/would microgravity affect the function of an induction motor? If the stator was not anchored to anything would part of it's torque be transfer to itself resulting in the stator spinning counter directionally to the rotor and decreased rotational speed for the rotor relative to the initial position of the stator? For another example on Earth a motor spins it's rotor clockwise at 1rpm, would and attempt to run this motor in microgravity result in the rotor spinning clockwise at .5rpm and stator spinning counterclockwise at .5rpm? How does the mass of rotor and stator play into this? Basically in space will the stator stay? | [
"It would mostly not affect it. In a running motor, the electromagnetic forces dominate, and do not depend on gravity. ",
"The momentum of the motor would of course have to go somewhere. If you start a motor with a stator that is free to rotate, the stator will of course start to rotate. This could be demonstrate... | [
"At first I thought there would be no effect, maybe reduced wear on bearings, but then I saw that it might not be anchored. Yes, if it were not restrained, the rotor and stator would take off in opposite rotations. Power lines might twist, or a battery might be involved. Rotation speeds would depend on the rota... | [
"It depends on the mass of the parts. Think about using an electric screwdriver in a space ship. The screw is much smaller than the person holding the screwdriver, so the screw will spin freely while the person remains stationary. But once the screw is fully home and has become part of the ship, suddenly it beco... |
[
"What's in the way of creating a natural-sounding voice that doesn't rely on pre-recorded words?"
] | [
false
] | In other words, when I get directions from a navigation device or the announcer on public transport there's usually either a pre-recorded message (e.g. "examplestreet") or a combination of an established set of words, such as "head" "right" "next" "turn", resulting in a rather jarred sentence. I realized there's a lot to a voice and humans are great at noticing even the slightest mistakes, but considering how incredibly great we got at rendering facial expressions and the astonishing sound design in various media I couldn't yet figure out what's keeping us from creating such thing. I also have no clue wether this is the correct flair, sorry. | [
"It's really important to note that this Yamaha synth was hardly new, and was in fact built on the better part of a century of research. Formant synthesis underlay basically every kind of early speech synthesis, although the inventors of the earliest goes didn't exactly understand what they were doing. But people h... | [
"If a big part of it is computational cost, does that mean it's possible to naturally generate a synthetic voice, but not in real time? Like even though it only takes a couple seconds to say \"Hello, nice to meet you.\" that you could generate a naturally sounding voice clip of that phrase in a few hours? Assuming ... | [
"If a big part of it is computational cost, does that mean it's possible to naturally generate a synthetic voice, but not in real time? Like even though it only takes a couple seconds to say \"Hello, nice to meet you.\" that you could generate a naturally sounding voice clip of that phrase in a few hours? Assuming ... |
[
"Why does water all freeze at once at 32 Fahrenheit (0 Celsius) instead of gradually getting thicker/harder as it cooled?"
] | [
false
] | null | [
"Because of symmetry breaking. Phase transition is not a process, but a state for few molecules. Molecules attract each other pretty much like weak fridge magnets. Let's pretend the molecules are like these weak magnets, in a glass box being shaken vigorously. They attract each other, but as soon as they can bind t... | [
"Precisely. as we increase the temperature, molecules have more kinetic energy and can more easily break free of the forces holding them together. EDIT: more heat = more kinetic energy."
] | [
"The ",
" water has no in-between \"thicker/harder\" state is because of its simple molecular structure. You're probably considering an analogy between other substances like sugar perhaps, which can change its viscosity depending on its temperature. However such materials have more complex molecules, with opportu... |
[
"Are there any historical or current examples of cultures in which it is common or acceptable for \"settled\", unrelated* families of equal social status to share housing**"
] | [
false
] | *By "unrelated" I mean they do not consider the other families they share housing with to be their kin ** By "share housing" I mean share rooms to do at least 2 of these 3: sleep, cook, or do laundry. Please only include examples where the families shareing the housing are of equal social status. Please exclude examples such as these: people of the same tribe sharing housing in the manner mentioned or families sharing housing where, say, a noble family shares its house with its servants who are commoners or a family that ownes slaves living in the same house as their slaves. Also, please exclude things like religious or socialist communes or perhaps more generlly communes accociated with widely recognized recent (i.e. in the last 200 years) historical movements (e.g. social movements commonly associated with religious or ideaological movements). I don't have much of a background in anthropology, archeology, or history. I took one course at a community college in anthropology and one at the same place in history, so I'm sorry if my question seems vague or ignorant. | [
"You might have more luck asking in ",
"/r/AskHistorians"
] | [
"Kommunalkas",
" were a very common form of living in the former USSR. A lot of it was a function of economic necessity / lack of other options, but they were considered normal and acceptable. Most people who lived in them had a desire to move into more private residences but I imagine that a lot of modern-day ... | [
"Yes there are examples of this. Domestic residence patterns vary highly from culture to culture. An example that springs immediately to mind are the apartment compounds at Teotihuacan. These were large, multi-room compounds that had shared public spaces and courtyards. Some were likely composed only of extended fa... |
[
"Why would this crab rip off its own claw?"
] | [
false
] | [deleted] | [
"It is probably injured. Crabs can regenerate their limbs, so it will grow back.\n",
"Here is a video of a crab amputing his claw after getting in a fight with boobies"
] | [
"Does this show that the crab has foresight, or are they just reacting to stimuli? Does the crab think \"my claw is damaged, I'll rip it off and grow a new one later.\" Or does it simply feel pain in it's claw and rip it off, without realizing it will regenerate and regardless of the extent of the damage?"
] | [
"Unfortunately, I don't think that is an answerable question. We don't really have access to what a crab is thinking."
] |
[
"If I were in a helicopter above a city when an earthquake hit, what would it look like was happening?"
] | [
false
] | Since you wouldn't be able to feel the shaking, would you be able to see the ground moving around, or would it just look like buildings are falling down for no reason? | [
"I think we're still misunderstanding each other, but perhaps the fault is mine. I think OP was asking what the ground would look like. I.e. would it be undulating, pulsating, bouncing up and down... I think the helicopter is just there to provide a stable viewing platform not affected by the ground's motion. B... | [
"The question was, though, what would it look like? Not, what would happen to the helicopter."
] | [
"http://science.howstuffworks.com/nature/natural-disasters/fly-over-earthquake.htm",
"This says that you likely wouldn't feel it and you wouldn't hear it above a certain altitude (at least not over the sound of the engine). I've flown helicopters and fixed wings before, but Askscience does not like personal anecd... |
[
"Quick question for Sulfuric acid."
] | [
false
] | What materiels wont Sulfuric Acid melt through? We are making a science project in school, and cant seem to find an answer anywhere. Reddit you are my last hope. | [
"Depending on my concentration, I can be kept in various types of glass/plastic containers.",
"Lead and Tungsten are ",
"resistant to me."
] | [
"As mentioned, sulfuric is commonly stored in glass, lead, or plastic. ",
"Glass however, is unmachinable, unweldable, and brittle. It also has poor thermal conductivity and a slew of other properties that are undesirable for large scales. Plastic and lead have a low melting point. Tungsten is unweldable and ... | [
"When in doubt, PTFE (polytetrafluoroethylene aka Teflon): ",
"http://www.vp-scientific.com/Chemical_Resistance_Chart.htm",
"This pertains to storage. ",
"Zero's post is quite good regarding the sulfuric acid in industry. Due to environmental disposal problems, most companies have either switched to solid aci... |
[
"Why are we looking for exoplanets?"
] | [
false
] | We can't live on them considering the distance alone, so what are the current goals in the exoplanet search? Just to learn about the universe? | [
"Being able to get a better handle on number, location, size, and make-up of expolanets is fundamental for a number of reasons. It gives us a much better idea of how common other life might be in the universe. It gives us perspective on how 'special' the Earth is. It allows us to better understand solar system f... | [
"Because it's interesting."
] | [
"I think it's worth pointing out that science doesn't like the idea of special cases. So far, life on Earth seems like a special case - we haven't found life anywhere else. So we're looking for life anywhere we can find it. Currently, we're looking for evidence of life on Europa and other moons in the outer part... |
[
"What's the difference between Special Relativity and the Lorentz transformations?"
] | [
false
] | Einstein is famous for special relativity, but the Lorentz equations that it uses predate his theory and was developed by Lorentz apparently to explain the same phenomena. What's the difference? | [
"He came up with a consistent framework for kinematics and electrodynamics that made use of the mathematical tools developed by Lorentz. A decade later he formulated a theory of gravity that was consistent with the principle of relativity."
] | [
"He does, the symmetry is named after him."
] | [
"The Lorentz transformations are an integral part of SR. They are how you transform between different inertial reference frames."
] |
[
"Can our DNA be used to guess at our fingerprints?"
] | [
false
] | Or vice versa? Are the patterns on our hands and feet are result of specific alleles in our genes, or are they a result of our environment instead of our DNA? | [
"Not much is known about the specifics, but enough is known to answer your question. ",
"We know that there is a genetic component to fingerprint formation. For instance, a mutation to the regulatory gene SMARCAD1 can yield adermatoglyphia--a rare condition that results in no fingerprints forming. ",
"We als... | [
"Usually much more similar compared to non-twins, but still quite distinguishable. ",
"This study",
" measures \"Minutiae matching between twin–nontwin scores a 3, whereas matching between twins scores matching score of 38 -- both on a scale of 0–999.\" "
] | [
"Are the patterns on our hands and feet are result of specific alleles in our genes, or are they a result of our environment instead of our DNA?",
"A little of both. Twins have similar fingerprints, which shows there is a genetic component, but they are definitely different, due to local, random events during fe... |
[
"Has the total number of organisms on earth at a given time increased, decreased, or remained generally static over the last 500 or so years (more recent history)"
] | [
false
] | null | [
"Are you including prokaryotes (i.e. bacteria and archaea)? If so, the number is so large as to be more or less incomprehensible.",
"There are something like 10",
" bacterial cells (each one being considered an individual organism) in your body alone (also interesting to note: that's ten times as many of \"your... | [
"Yeah, I guess I didn't really complete my thought there.",
"I guess my point was that when dealing with numbers that large, I'd be skeptical as to whether we can even take a reasonable guess.",
"ninja edit: excluding microbes might get us a better chance at coming up with an answer, but I'm not the person who ... | [
"I'm not looking for specifics so much as I am a general trend in their change.",
" Ok, for the purpose of fulfilling the intent of the question, lets disregard single-celled organisms."
] |
[
"How dangerous are lead glazes, really?"
] | [
false
] | This question is specifically about glazes on ceramic mugs. Is there a stable way manufacturers can use lead glazes that doesn't lead to leaching of the Pb into liquids? What factors influence leaching? | [
"The factors that influence leaching are a combination of the relative solubility of lead in the glaze versus liquids in contact, and kinetics.",
"Relative solubility tells you how lead would be distributed between the glaze and the liquid if the liquid were left in contact for a very long period of time. Howeve... | [
"They actually leach out very quickly, I have seen Secondary Ion Mass Spec data from crystal decanters and there is a lead depletion zone on the surface. I believe pH has a big affect on the solubility of lead compounds so acidic foods and lead glazes would pry be bad.",
"If you were alive before the 80s when lea... | [
"They actually leach out very quickly ... a lead depletion zone on the surface.",
"Does that mean that after rinsing/soaking them (with acid?) enough, they'd become pretty safe since the surface lead had all leached out?"
] |
[
"Aside from height, did homo sapiens look significantly different in the distant past?"
] | [
false
] | As I understand it, modern humans have been around for about 150,000 years. Did we look significantly different then? What about 10,000, 1,000, or even 500 years ago? | [
"As I understand it, modern humans have been around for about 150,000 years. Did we look significantly different then?",
"This doesn't have a simple answer",
".",
"One identifiable group from about 160,000 years ago was ",
"Homo sapiens idaltu",
"Some images of what Homo sapiens idaltu might have looked l... | [
"Keep in mind that the pictures are somewhat guessy recreations of what they looked like. Sure we know where all the face muscles go but there is a certain amount of artistic freedom taken in this type of recreation.",
"Another thing is their facial features may have looked as modern as the recreations show but t... | [
"I see. From those pics, I bet I wouldn't look twice at a homo sapiens idaltu if I saw one. Looks like a modern human to me. Thanks for the answer."
] |
[
"What's the limiting factor in making bipedal robots?"
] | [
false
] | After the somewhat recent DARPA robotics challenge, its pretty clear that we have a very long way to go before we get to machines like the police robots seen in chappie and the like. My question is, what's stopping us? I'm referring mostly to the problem of balance/walking. I understand that this is certainly not a simple problem, but I would think that current accelerometers have a high enough polling rate and servos are fast enough that this wouldn't be an issue anymore. When it can get reading from sensors 100s of times per second and react with minute changes, wouldn't balancing and running be possible with good programming? | [
"If you just need it to move on an infinite plane, it would be easy. Walking up stairs and over obstacles is more complicated than just walking normally and trying to balance. And if the robot can't walk up stairs and over obstacles, wheels would be better."
] | [
"The CMU robot seemed to be a hybrid: mostly bipedal, but occasionally used four legs. And the legs had treads, too. "
] | [
"But that's just it, I would understand it being considerably more difficult on uneven terrain, but it seems like even on a flat plan, it hasn't been done yet. A brief Google search brought me to examples like this ",
"https://m.youtube.com/watch?v=gBA-9PelR5E",
"And this ",
"https://m.youtube.com/watch?v=lPE... |
[
"Which part of the body has the highest Pain Threshold?"
] | [
false
] | null | [
"Your back and thighs have the lowest density of pain fibers. The skin on your back, especially between your shoulder blades is much thicker compared to your thighs, so the pain receptors are less likely to be activated.",
"It really depends on what you mean by pain threshold. Each of the nerves is going to hav... | [
"Any location where you build up a high density of dead epithelium on the surface and low nerve induction. The back of the elbows could be argued."
] | [
"Thanks guys! I'llbe sure to include this in my research! You guys helped a lot!"
] |
[
"Do Chloroplast also get dna from the maternal line."
] | [
false
] | null | [
"In terms of sexual reproduction, I think maternal chloroplast inheritance is more common than paternal chloroplast inheritance (at least in what's been studied so far), but it is definitely not the rule. There are several organisms that show near exclusive paternal chloroplast inheritance and some that show a mix... | [
"How are chloroplasts in pollen? Or do plants do it differently than human cells that inherit the actual mitochondria from the mother and ovum cell?"
] | [
"Chloroplasts are plastids specialized for photosynthesis. There are a lot of other forms of plastids (chromoplasts that make flowers colorful, amyloplasts that store starch in potato tubers, elaioplasts, etc.) All of these plastids have the plastome, not just chloroplasts. Pollen stores a lot of the energy it need... |
[
"Do simple carbs release more insulin than complex carbs per carb consumed?"
] | [
false
] | I was discussing with a friend who studies this and he was saying that it all matters about the area under the curve. Simple carbs spike insulin to a peak but wear off quickly whereas complex carbs raise it to a steady level for a longer period but the insulin release is the same. Is this correct? | [
"Your friend is correct. The islet cells in the pancreas (that secrete insulin) use ATP as their marker for how much glucose is floating about (glucose is of course broken down and used to produce ATP)-- the pertinent ion channel is called Kir6.2 and we have drugs for diabetes that target their co-receptor to stimu... | [
"There are many factors that influence insulin resistance e.g. just being south Asian puts you at risk. The manner in which different carbohydrates do is controversial- lots of conflicting studies. Dietary studies are inherently difficult. However, losing weight does seem to reduce insulin sensitivity, thought to b... | [
"Great response. In regards to the complex carbs, even though the same insulin is released, does that longer process help dissuade insulin sensitivity when compared to the spike from simple carbs? Or does it not have an impact at all?"
] |
[
"Why are so many types of \"special\" functions orthogonal to each other?"
] | [
false
] | [deleted] | [
"Well... orthogonal functions are useful right? And functions that are dense, i.e. functions that can be used to approximate other functions are also useful, right? The most useful thing is therefore functions that are dense ",
" pairwise orthogonal.",
"The good thing is: Give me a dense set of functions and a ... | [
"We can forget about the QM, but we can't forget the abstract vector space stuff. It all works for physics ",
" we work in these spaces (a consequence of superposition).",
"Maybe I'm just not making the connection between the abstract linear algebra and the more concrete differential equations.",
"It all boil... | [
"We can forget about the QM, but we can't forget the abstract vector space stuff. It all works for physics ",
" we work in these spaces (a consequence of superposition).",
"Maybe I'm just not making the connection between the abstract linear algebra and the more concrete differential equations.",
"It all boil... |
[
"Does electric stimulation actually build muscle?"
] | [
false
] | In "Return of the Dragon" a movie based on Bruce Lee's life, he uses them. I have tried looking for other evidence that it actually stimulates the muscle in a similar way to exercising, but there seems to be none on it. Couldn't constantly exposing your body to electric current cause other problems as well? I also wanted input from actual experts, not broscience, that is why I posted to /askscience | [
"http://www.reddit.com/r/askscience/comments/k28kg/why_cant_i_build_muscle_by_electrically_shocking/"
] | [
"Unless I'm terribly confused, you shock your muscle and ",
" means your body is still doing some work. But as I recall from discussing this with some physical therapists and athletic trainers and a couple exercise physiologist (I run in some weird circles, believe it or not) part of the problem is that it doesn'... | [
"Thanks. I tried searching but it did not show up. Looking at that thread though still leaves the same question unanswered: why is Ems so rarely used? "
] |
[
"My mom is convinced cancer is contagious. Obviously it's not, but she wants the \"opinion\" of medical students/doctors, not a lowly premed such as myself. Would you mind debunking this?"
] | [
false
] | null | [
"Couldn't you just get a note from a doctor, if you're premed and working at a clinic it shouldn't be terribly hard to find an MD"
] | [
"I won't start for a couple weeks. It's more of a spur of the moment debate that I'd like to settle before I fly back out to school."
] | [
"Cancer is an out of control cellular growth that develops out of environmental or genetic reasons on a cellular based level. Someone sneezing on you will not make your cells begin to grow without necessity. It's not like one can high five prostate cancer into yours. It's much more complex than that and if her thou... |
[
"Is it normal for metastudies to discard vast majority of considered individual studies?"
] | [
false
] | I was browsing through a list of studies on beneficial effects of alcohol, and ran across . Abstract states that Of 4235 studies reviewed for eligibility, quality, and data extraction, 84 were included in the final analysis. That's less than 2% of the studies, which seems surprisingly small. Is that normal? Also, am I correct in assuming that with such small fraction, even a slight change of study selection criteria may substantially affect results? | [
"Yes. Typically, the authors will specify some search criteria for finding all studies that could possibly be related to the issue at hand. Then they will select from those studies ones that fit certain criteria. The initial search criteria may be overly broad, to ensure that no studies are missed.",
"Fig. 1 i... | [
"Tons of grad students. :)"
] | [
"Yes and No",
"1- A good meta-analysis allowing good conclusion needs good material like prospective randomized studies without bias and with a sufficient number of patients included, which are not the majority of the studies.",
"2- The selection criteria is defined before the inclusion of the studies in the me... |
[
"Can you siphon air?"
] | [
false
] | I understand you could siphon a dense gas, but could someone siphon air on earth? | [
"Siphoning water works because water has suface tension, not because of a difference in atmospheric pressure. There was an experiment in 2014 by Dr Hughes that showed siphoning in a hyperbaric chamber. Since air doesn't have intermolecular adhesion that siphonable liquids do you couldn't \"siphon\" it."
] | [
"I was wondering this myself... I would think at a column of enough air would be buoyant enough to overcome the pressure of water, and thus rise to the surface, creating a negative amount of pressure behind it...",
"But like Anonymous_scientist pointed out, water works by surface tension, if air rises, it could... | [
"Siphoning requires something above the fluid pushing down on it. You can't siphon water on the moon. It only works because of air pushing on it. You could siphon air if you stuck something lighter, like hydrogen or helium, on top of it."
] |
[
"Do passing asteroids have an effect on for example the tides?"
] | [
false
] | Seeing as how a relatively big asteroid passed earth at "only" 200.000km last Sunday I wondered if passing asteroids (or other things) affect the tides. | [
"What's interesting about gravity is that it has an infinite range, which is not true for the other 3 forces (strong, weak nuclear and magnetism). Because of this, you could say that every atom of matter in the universe has an effect on the tides of our oceans, this includes you! You walking around has an effect on... | [
"What makes you think electromagnetism has a limited range?"
] | [
"(not OP) It has infinite range, but it is so strong that all macroscopic objects tend to be close to neutral, typically leading to very small electromagnetic forces over long distances."
] |
[
"Is there estimated upper limit for mass of a star before becoming a black hole? Is mass the only determining factor for if a star becomes a black hole or not, or what are the other factors?"
] | [
false
] | [deleted] | [
"http://en.wikipedia.org/wiki/Chandrasekhar_limit"
] | [
"When discussing whether or not a star will become a black hole the only thing considered in most discussions is the mass of the black hole. In fact, the initial mass of a star pretty much determines that star's entire lifetime of evolution. However, there is one major assumption that we use in these discussions: w... | [
"I believe that is the symbol for the sun, and should be read as 0.1 solar masses."
] |
[
"What does it mean for a coordinate to be timelike?"
] | [
false
] | In the wikipedia article about Schwarzschild black holes, it says : For r < rs the Schwarzschild radial coordinate r becomes timelike and the time coordinate t becomes spacelike. What does it mean for a coordinate to be "timelike" ? Does it just mean that an object must move forwards in that coordinate? | [
"It's referring to the sign that that coordinate gets in the metric.",
"For example, in the Minkowski metric in the (-+++) convention, the metric is ",
"ds",
" = -c",
"dt",
" + dx",
" + dy",
" + dz",
".",
"The dx, dy, and dz terms are all positive, while the dt term is negative. So t is a timelike... | [
"There are lots, one example is ",
"Kruskal-Szekeres coordinates",
"."
] | [
"Well then you’ve missed one of the major points of general relativity, coordinate invariance. There’s nothing special about a set of coordinates, they’re just labels for points in spacetime. You can choose to label the points in your spacetime however you want, and it should not affect any physics. As a corollary,... |
[
"Can you demonstrate why cycling through a one-time-pad encryption key that's shorter than the message is not secure?"
] | [
false
] | I wrote a in python, to try to better understand one-time pad encryption. (Warning: Does not work with python 2.x, use Python 3). The program works as follows: Though it's obvious in the first example why cycling through an encryption key shorter than the message to be encrypted is not secure, it's not so obvious in the second example. Could you explain what would be the approach to decipher the message in the second example? : Updated sample code to work with unicode. | [
"The reason the standard one-time pad is perfectly secure is that regardless of the message, the distribution over ciphertexts is always identical. Once you recycle your key, this is no longer true. For example, (working over a binary alphabet of 0 and 1), if your key is 3 bits long, then no matter what, if your me... | [
"Let's assume the attacker knows the length of your secret key and aligns your message like so",
"short key\n---------\nThis a lo\nng messag\ne and sho\nuld be so\nmehow dec\nipherable\n",
"He knows \"s\" combined with first column (\"T\",\"n\",\"e\",\"u\",\"m\",\"i\"), \"h\" combined with second column etc. Th... | [
"By repeating a shorter key, it becomes a Vigenère cipher rather than a one-time pad. The Vigenère cipher is vulnerable to frequency analysis. Assuming the plaintext is in a natural language, then the frequency of letters for writing in each language is well known. For English, we expect an index of coincidence ... |
[
"How do hand sanitizers work? (in chemistry terms)"
] | [
false
] | null | [
"It's not really like soap and water. But has some of the same end results.",
"Saponification yields polar molecules capable of micellars formation which results in dirt and microbes being surrounded and washed away while polar molecules can also break apart phospholipid membranes and cause cellular damage.",
... | [
"I'd also suspect some of it has to do with diffusion of water. The concentration of alcohol exterior being high (60% or greater) means a good amount enters the pathogen as well. This allows it to act on both the exterior and interior of the cell. ",
"Additionally, I'd like to add there is some variation between ... | [
"Crenation lysis and protein denaturation.",
"Among other disruptive effects. I'm not sure it readily traverses the envelope or membrane though, you don't hear much about that."
] |
[
"Could I make liquor from a chocolate bar or candy?"
] | [
false
] | Ok, so I've heard that if you let a Twinkie ferment for a while you end up with a pretty nasty liquor, I'm not sure if that's a myth or not. I know that alcohol is made from distilling fermented sugars so theoretically, if I had a still, could I know make alcohol from a chocolate bar or candy? | [
"So long as you have clean containers and equipment, essentially any sugary item that is mixed with water or is liquid already and not too saturated with sugar, can be mixed with yeast to initiate safe fermentation. You could also begin fermentation in unclean containers, but you risk letting other fungi or bacteri... | [
"I wonder how many chocolate bars I would need to fill a 20L bucket and what it would yield",
"This is a crazy path to go down. I'll outline why and answer your question.",
"I'll assume you want as much alcohol as possible to begin with to make distilling faster and more productive, and I'll assume you're using... | [
"Good beers get their distinctive taste from the yeast and i assume wines as well (i don't know much about wine.) Brewing stores have many types of yeast and it is impotent to use the correct yeast for the style of beer you are brewing. I think that the taste from the yeast is less important for distilled spirits b... |
[
"Is Fuzzy Logic used in science, and more specifically in Quantum Mechanics?"
] | [
false
] | So I am self studying Fuzzy Sets from . Chapter 1 concludes with a discussion on paradigm shifts, and how fuzzy logic is a new paradigm that will change science considerably. The book was written in 1995 though. So did scientists adopt this new paradigm, and more specifically did this new paradigm make its way to quantum mechanics? | [
"I've never seen fuzzy logic used in quantum. Quantum mechanics is a probabilistic theory, sure, but we still work within well-defined sets (i.e., a normed vector space). It sounds like fuzzy logic works with a different sort of set.",
"It's possible that this is because our language about quantum mechanics is ba... | [
"It appears that there are some relations between fuzzy logic and quantum logic. I know near nothing about fuzzy logic, so I cannot give a very knowledgable answer to the question, but I did find a ",
"paper",
" that discusses exactly this topic."
] | [
"Of course fuzzy logic is used in science. Computer science.",
"As for how or if it is related to QM, well, first understand that people who know about QM probably don't know much about quantum computing or fuzzy logic/computer science, and vice versa. So each person who is the expert in each field will probably ... |
[
"What causes the black halos around bright objects in some 1950s television programs, such as the those around the participants of this game show?"
] | [
false
] | null | [
"It appears to be an artifact of the imagine capture technology.",
"http://en.wikipedia.org/wiki/Video_camera_tube#Dark_halo",
" "
] | [
"Observe more carefully. For instance, when Dali paints on the board moments later, there are large, dark halos around the white paint."
] | [
"I want to mention that shows in the '50 were so much more entertaining than today.",
"The TV cameras back then were an exact mirror image of a CRT (Cathodic Ray Tube). The light hit the photosensitive glass panel, and generated a positive charge while an electron beam scanned the surface of the glass. The black ... |
[
"Why don't refineries reclaim their flare's energy to heat water or the distillation stack?"
] | [
false
] | null | [
"I worked at a refinery. And we did use hot exhaust from the refining process to fire a steam plant that powered a ",
" 10MW co-generation plant that mostly powered the refinery with a small amount of sell-back to the power company.",
"\nBut that hot exhaust was a continuous part of the ongoing process, not tem... | [
"Most modern refineries already use flare gas compressors to win back their base load flaring. This way, you don't have a flame in a normal operating scenario. The compressed gas will then be reused. Only in case of an emergency, you depressurize to the flare, and then you can see a flame. Because of this intermitt... | [
"Yes. It was small. I guess. The turbine was in a 4 story building with the top half of the unit on the 3rd floor and the bottom half in the ceiling of the 2nd floor, and the plumbing on 1st and 2nd floor.",
"\nIt ran at 60 cycles a second = (60 x 60) = RPM and sat on \"gas bearings\" which I think was really jus... |
[
"I want to string together about 300ft of power cables. Googling around tells me that this is a bad idea, but doesn't explain why. What happens when you (a) join to extension cords together, and (b) run very long distances?"
] | [
false
] | I'm trying to power my laptop about 300 feet from the nearest outlet. I'm curious for the reasoning behind all the warnings against daisy chaining cables. | [
"There are ",
"online calculators",
" that tell you the needed wire gauge for a given amp draw and circuit length. Assuming a 60 watt power consumption from your laptop you would need a 14 gauge cord. ",
"The problem is this assumes one continuous cord. If you are chaining cords together you will get addition... | [
"You could try ",
"/r/AskElectronics",
" for advice on what to do"
] | [
"You are wrong. If the cables are the same thickness and material resistance is constant per unit length or cable and the heat will be dissipated easily by said cable length. The issue is overall resistance will drop the voltage. Or if the cables become coiled they could create induction and heat up."
] |
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