title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Why do satellite orbits appear as waves when projected onto world maps?"
] | [
false
] | I'm referring to screens like . | [
"This is mostly because of our choice of map projection. If we projected the map so that, for example, the poles weren't at the top and bottom, then the lines of longitude would look like waves as well (",
"example",
").",
"Notice in the example that there are still straight lines, but those lines are differe... | [
"They are circles (or ellipses) around the sphere of the Earth. When you map the spherical Earth to a plane those are circular paths. Think about what the path would look like on a globe."
] | [
"Well, if a satellite is in a polar orbit then it ",
" look like a line of longitude when its orbit is projected onto a map. And an equatorial orbit looks like the equator.",
"However, many satellites are in orbits that are neither polar nor equatorial, but rather orbit in a plane which is tilted by some angle ... |
[
"If our cells can only divide ~80 times before dying off, how do high turnover body tissues like the stomach that regenerates itself almost every day last a lifetime?"
] | [
false
] | null | [
"What you're referring to is the Hayflick Limit (",
"http://en.wikipedia.org/wiki/Hayflick_limit",
"). Replication shortens the telomeres which are protective regions of DNA - after too many replications the DNA is at risk of damage and the cell stops replicating.",
"Stem cells (such as in the crypts of intes... | [
"And the stem cells will create ",
"progenitor cells",
" which DO have limited divisions, but will do the bulk of the replicating and transformations into specific cells. These are often called transit amplifying cells and they are to preserve the stem cells. ",
"This is a useful image to picture it"
] | [
"For a couple reasons. One is that a single mutation is not sufficient to cause cancer. You need a bunch of mutations working in concert to do that. Since mutations are rare, and since mutations don't always abolish the function of proteins the gene encodes, it takes a while for enough mutations to build up to caus... |
[
"Are gravitational forces additive?"
] | [
false
] | Can two gravitational forces influence each other? So for instance if two equal forces overlapped, is it possible to get stuck in some kind of gravitational equilibrium between the two? | [
"Yes - this is exactly what gives rise to ",
"Lagrange points",
"."
] | [
"This phenomenon is also responsible for why when inside a perfect spherical shell, anything inside that shell feels no gravitational force. [",
"http://en.wikipedia.org/wiki/Shell_theorem",
"]"
] | [
"You can never have stable equilibrium points, even if orbits are involved. (See ",
"Earnshaw's theorem",
".) None of the Lagrangian points are stable."
] |
[
"Can the spin constant of a Kerr Black Hole that houses a quasar be calculated independently of data from the quasar itself?"
] | [
false
] | null | [
"How would we even know it exists without data?"
] | [
"I wanted to know if there was any other data than the quasars themselves e.g. some other kind of radiation from the black hole's accretion disk."
] | [
"The radiation from the accretion disk and jet is how we know it's a quasar. I'm still not sure what you're asking about. Even if it's infrared or X-ray or radio, it's all still \"the quasar\". ",
"Outside of EM radiation, when two black holes merged, gravitational wave sensors like aLIGO can put constraints on s... |
[
"How can new wireless standards improve bandwidth without changing frequency?"
] | [
false
] | null | [
"Most short-range wired connections are simply a series of high/low signals. Each 'symbol' on the wire is one bit and the bit rate is equal to the frequency.",
"With wireless and optical communications, you don't use a digital signal but an analog waveform.",
"Analog waveforms have three basic properties: ampli... | [
"The short answer is that in virtually all wireless standards, the bandwidth is much smaller than the frequency (or so-called \"carrier frequency\").",
"Use wifi as an example, in 802.11b, the bandwidth is 22MHz while the carrier frequency for wifi channel 3 is 2.422GHz (i.e., 2422MHz). What all of this means is ... | [
"I don't know if what you said about phase and frequency being the same is a convention in signal processing, but in physics, frequency is the number of cycles per second and phase refers to the shift in time between the wave and some reference wave.",
"According to the Wikipedia page, phase modulation for large ... |
[
"What puts out a fire better, hot or cold water?"
] | [
false
] | [deleted] | [
"But evaporation pulls much more energy from the fire than warming cold water. So you're right in that cold water is technically better, but I don't think the difference would be particularly significant."
] | [
"The heat of vaporisation of water is 2200 J g",
" , the specific heat capacity of water if 4.2 J g",
" K",
"So it takes 2200 Joules of energy to boil a gram of water that is already 100",
" C and it takes 2600 Joules of energy to boil a gram of water that is 0",
" C",
"The difference is significant, bu... | [
"Cold:",
"It takes longer for the water to evaporate ",
" ",
" it takes away more energy from the fire to do so. ",
"Also a fire needs 3 things: heat, fuel, and, oxidizer. By throwing cold water, you take away a lot of the heat element. "
] |
[
"If I would create a regular sized bowl with a hole the size of one water molecule in the bottom, how long would it take for me notice water outside the bowl?"
] | [
false
] | null | [
"I'm going to ignore single molecule wall and capillary effects as I honestly don't know how to model those in such a situation. Therefore we need to just assume some kind of flow rate through that orifice. For simplicity lets start with 1 molecule per second.",
"I'll go ahead and say you might be able notice w... | [
"Your containers surely have holes bigger than single molecules, if they are made out of plastic. The hole isn't perpendicular to the surface all the time, but there is most definitely defects in the amorphous plastic.",
"That being said, a hole that small is still 'tight' at atmospheric pressures. Especially con... | [
"This is tough to answer because if you make a pore that small then the exact molecular details of the channel are going to affect whether water bonds to the walls and jams up or even enters the pore at all. ",
"There is a water pore used by cells that is one molecule wide. It has an appropriate name: ",
"aquap... |
[
"Do different colours have different weights?"
] | [
false
] | null | [
"It all depends on what you mean by \"weight\".",
"If you mean \"mass\", then no light has any mass.",
"If you mean \"force of gravity\", then all light is affected by gravity the same. No matter the color, light rays will travel along geodesics.",
"If you mean \"momentum\", then the answer is \"kind of\". Li... | [
"on the most fundamental level, the answer to your question is \"no\". Weight is not a property of an object. Weight is a force that results when gravity acts on a body with mass (Weight)=(mass)x(gravitational acceleration). Since weight changes depending on the gravity the object is subjected to, we can not tal... | [
"This makes sense from a Newtonian perspective, but you can't use Newtonian mechanics when talking about light and gravity. Light ",
" have weight, in the sense that there's a \"force\" on light due to gravity. Light bends in gravitational fields, and light also gravitates (i.e., affects gravitational fields). So... |
[
"Is there a fundamental 'resolution' problem to looking at far away things (planets in other solar systems for example); or could (technology permitting) we potentially see planets on other solar systems with the same resolution our satellites currently see earth"
] | [
false
] | Title pretty much sums it up. I wonder if there is some potential completely unfathomed technological breakthrough that would allow us to 'infinitely zoom' into the cosmos, or, if there just isn't enough information making it to us to recreate high resolution photos/video. | [
"From the surface of the earth, the main problem is looking through the atmosphere -- that causes all sorts of problems. New technology telescopes have various ways to minimize the effects of atmospheric distortion, but these methods can only do so much.",
"Also, there is the issue of skyglow, caused by a number ... | [
"A ten meter telescope could resolve it, but couldn't \"image\" it in the layman sense - to see atmospheric phenomena and geography. To do that you'd need a traditional telescope kilometers in diameter."
] | [
"A ten meter telescope could resolve it, but couldn't \"image\" it in the layman sense ...",
"Yes, true. It would be barely resolvable at all. One could say about it that it was a planet, but nothing more than that.",
"To do that you'd need a traditional telescope kilometers in diameter.",
"Yes, traditional, ... |
[
"Are orbiting solar panels viable?"
] | [
false
] | Please excuse my limited knowledge on this subject. I was wondering.. If we where to for instance land on Mars and build a base on one of the poles. Could we use orbiting solar panels as a power source? We set up a base in orbit with a space elevator down to the land base and use solar panels as a power source and tran... | [
"Apparently someone is trying this",
"http://www.physorg.com/news183278937.html"
] | [
"A space elevator is a wonderful idea, but in reality, the technology behind that is a long way off. If we set up solar panels in orbit, the way to get the power down to the surface would be much simpler via a microwave dish - send the power down to a specific point in radio waves and use it at the surface to heat ... | [
"It is plausible, but there are a couple of problems."
] |
[
"Why are significant meteor showers on the same day every year?"
] | [
false
] | How are they exactly in sync with the earth's year instead of appearing every 17.3 months or something arbitrary? | [
"There are streams of meteroids that intersect the Earth's orbit. Each time the Earth passes through the stream, a bunch of the meteroids in the stream hit the Earth's atmosphere and turn into meteors. These streams are made up of the debris left behind by disintegrating comets.",
"There's a nice figure ",
"her... | [
"It's both - the stream is moving too, as it has to be in orbit to avoid taking into the Sun. It's just very long and moving along its length so we keep on encountering new sections of the steam at the same spot."
] | [
"So if I understand that picture right, they're not hitting us we're hitting them? And since it's in the same position we pass through it at roughly the same time every rotation?"
] |
[
"Photons move at the speed of light, so there is no relative time lapse. How do they oscillate at all?"
] | [
false
] | A photon doesn't experience local time at all. How then, in zero time, how does a photon oscillate between E and M fields with such a high frequency? To say it another way. If I was traveling at (or extremely close to) the speed of light and waved my hand, by the time I was finished one oscillation the Universe would... | [
"Let's ignore \"photons\" for the moment, as this stumbling block occurs even for classical pictures of light.",
"I'll ",
"repeat something I said earlier",
":",
"It's not useful to think of the reference frame of a photon, because it doesn't have one. Our equations work to describe anything in any referenc... | [
"Oh boy.",
"I was afraid that might happen. No, light is absolutely not tiny ripples in spacetime. That was the predominant theory for years until it was conclusively disproved by experiment. Light isn't tiny ripples in ",
" It's just light. It has the properties it has, and historically every attempt to descri... | [
"Photons do not oscillate. Modeling light as a self-propagating oscillation of the electric field (with a frame-dependent magnetic component) is a classical approach that works only on the aggregate."
] |
[
"Why do most mammals find being stroked/patted pleasurable?"
] | [
false
] | Humans, cats, dogs, pigs, horses etc. | [
"Mammals, humans included, have a specific sensory nerve endings on their skin and hair follicles that activate with deep pressure and petting. Activation of these receptors increases the release of endorphins and oxytocin (pain relief, relaxation, and bonding chemicals) and I know know of at least one study that s... | [
"But what about mammals like wild cats, which (who? I'm never sure) usually don't live in groups? Is it purely from their relationship between parents and offspring?"
] | [
"Wow, I can't believe the \"correct\" answer isn't here yet!",
"Essentially, mammals with fur and birds with feathers are susceptible to insect and mite infestation, bites, colonization, etc. and this requires cleaning and maintenance of hair, fur, and feathers. For instance, nest mites are a type of mite that sp... |
[
"How close to light speed can we get?"
] | [
false
] | I'm aware that it's impossible for anything with mass to reach light speed. But if we were to use magic to accelerate on object through space, how close to the speed of light would we be able to get? | [
"The Large Hadron Collider, the largest particle accelerator in the world, can send protons up to ",
"0.999999990c",
" at the current energy record."
] | [
"I just want to ask how is it even possible? How do they send it so fast..."
] | [
"It's pretty incredible. This is described in the link, on the design of the LHC. Basically they use many huge magnets to accelerate the particles in a ring. A crude cartoon can be seen ",
"here",
". The particles feel a force as they go through the circular magnetic field which accelerates them. The LHC has in... |
[
"How do we measure the mass of remote objects in space?"
] | [
false
] | [deleted] | [
"If there's another object in orbit around it, like a planet with a satellite, then it's trivial. The ",
"orbital period",
" depends only on the semi-major axis of the orbit and the mass of the central body."
] | [
"If the satellite is much smaller than the primary body, as is often the case, then the relative densities don't matter."
] | [
"T",
" /r",
" =4Pi",
" /GM "
] |
[
"What exactly is going on in your eyes and brain when you see something that's \"too bright?\""
] | [
false
] | null | [
"Rhodopsin is a protein that changes conformation in response to light, as a g-coupled receptor this passes the signal on to nerve fibres, which then passes it into the brain, and then in time resets itself. ",
"However, this therefore means it is a saturateable system, once all your Rhodopsin proteins change con... | [
"Does the brain recognize this over-saturation as harmful and thus makes seeing blindingly bright light feel painful?"
] | [
"Well yes, but inherently pain only exists as a manifestation of the signals sent to the brain, so the that could be said of any stimulus that causes pain it doesn't really mean anything. Your brain can't interpret the saturation as anything stronger than too much light, normally this can easily be mitigated by clo... |
[
"When going down a hill on a bike, what is the optimum strategy to \"preserve momentum\"?"
] | [
false
] | null | [
"It depends on how you define \"optimum strategy\". Do you mean what gets you down the hill the fastest? Or with the least effort? (The two have opposite answers). If you could clarify, it might make it easier to answer :)",
"EDIT: My confusion arises from you wanting to \"preserve momentum\", which would mean tr... | [
"While we're waiting for a physics panellist to pop in, I'll just point out that precisely which is most efficient will vary according to a number of factors. Off the top of my head key ones will include mass, vertical descent, aerodynamic efficiency, surface friction between bike and road, wind speed and direction... | [
"I mean which would require the least total effort over the entire trip."
] |
[
"Why is it ok to lay down all night when sitting all day is so detrimental to the body?"
] | [
false
] | null | [
"Thanks for your reply! I had assumed no one was going to respond. What prompted the question was I had heard that sitting for long periods of time causes muscle atrophy, and I wondered whether our muscles atrophied in our sleep as well. You briefly mentioned physical activity in your reply -- is this what you were... | [
"Thanks for your reply! I had assumed no one was going to respond. What prompted the question was I had heard that sitting for long periods of time causes muscle atrophy, and I wondered whether our muscles atrophied in our sleep as well. You briefly mentioned physical activity in your reply -- is this what you were... | [
"While sleeping, we often change position without waking, or at least without waking so long that we remember. Think about how long you can lie in one position while awake. An interesting example of this is that people with Parkinson's disease can experience a lot of sleep disruption if they do not take their medic... |
[
"What would happen if two galaxies collided?"
] | [
false
] | null | [
"Actually, we can observe two galaxies colliding with the ",
"Antennae Galaxies",
". Galaxies are mostly empty space though so most of the time, they would just pass through each other. And to answer the final part of your question, the Milky Way and Andromeda are actually on a collision course right now. Yo... | [
"So if I was to live 4.5 billion years how would the night sky change?"
] | [
"We are on a collision course with Andromeda, it seems. As far as the collision, it's going to be less spectacular than you think. Galaxies are mostly empty space, so the collision is going to be a lot more like two water drops merging than a car crash. "
] |
[
"Information theory: are there numbers which have infinite information content?"
] | [
false
] | There's an infinite number of irrational numbers, which can't be described using two natural numbers. Are there also an infinite subset of these that cannot be expressed by a finite-length computer program? If so, would these have infinite information? Is it possible for them to exist in reality, and if so, does this h... | [
"PhD student in Computer Science here. What you are describing are named ",
"computable numbers",
" and are closely related to ",
"computable functions",
".",
"Computable functions are the ones that can be described by Turing machines (\"finite-length computer programs\"). You can see a real number as a f... | [
"You should read about ",
"Kolmogorov complexity"
] | [
"Yup. See Omega. ",
"http://en.wikipedia.org/wiki/Chaitin\\'s\\_constant"
] |
[
"Is there any scientific basis to the oft-repeated layperson idea that the Mentally Handicapped have extraordinary strength?"
] | [
false
] | [deleted] | [
"Urban myth. There is no scientific basis that due to the measure of IQ relating to physical/kinetic potential. Consider flipping the hypothesis on its head: The super intelligent have extraordinary weakness. "
] | [
"The strength they exhibit is the same \"strength we have, but we are limited by our psychology. Can a woman lift a car? Not under normal conditions, but women have been known to lift cars off of their children. Same as the professional weight lifter that broke the 500 lbs mark that held for many years, his coach l... | [
"Is this a USA cultural meme? Italian here, and never heard of such a thing."
] |
[
"At the molecular level, what is the difference between a material that gains and loses heat slowly (eg. a heat rock), and a material that gains and loses heat quickly (eg. a metal cooking pot)?"
] | [
false
] | null | [
"Gaining/losing heat slowly/quickly is a combination of two material properties, volumetric heat capacity and thermal impedance. The time constant of a hot body to reach equilibrium with its environment is proportional to (thermal impedance/volumetric heat capacity). volumetric heat capacity is the product of densi... | [
"specific heat",
"According to Wikipedia, specific heat capacities for Aluminum 0.897, for Brick 0.840, for Granite 0.790.\n",
"http://en.wikipedia.org/wiki/Heat_capacity#Table_of_specific_heat_capacities",
"Metal and rocks have about the same amount of heat. "
] | [
"Contrary to what Apophilus says electrons do NOT carry heat out of these materials.",
"The major factor is how much energy something can actually hold.",
"Metallic bonds can only hold a small amount given there are a low number of modes in which to place the vibrational energy. So they loose heat (change temp... |
[
"How inefficient are non-intravenous injections?"
] | [
false
] | It is a popular movie trope that poison can be injected into someone and act quickly. Snake bites take time to take effect. How effective are non intravenous injections? When I was young a doctor injected a penecillian booster in my buttocks. I panicked, tensed my gluteal muscles and the drug literally fountained out s... | [
"Administration route by itself says nothing about efficiency. When one thinks of a proper treatment, (produce a desired effect on a body/organism) one has to consider all pharmacological factors involved. Proper drug, proper presentation, proper dose, proper route. ",
"The most effective route to achieve certain... | [
"90%~ bioavaiablity, 1-5min onset and 10min until peak effects for most stuff. If you wanna inject someone in a combat situation then afaik the carotid artery on the neck is the only plausible option as it's not impossible to hit while moving unlike a vein and doesn't take minutes to kick in like SC/IM. Diff meds ... | [
"Injections are not \"the old way.\" Some drugs are not absorbed well through the GI tract, so no matter how many pills you took it would just end up in the toilet with your next bowel movement.",
"Other drugs will be chemically changed by the liver, making them not effective (concept called \"first-pass metaboli... |
[
"Why is Turner syndrome a thing when extra X chromosomes are usually inactivated anyways?"
] | [
false
] | null | [
"Lyonization is the inactivation of one X-chromosome. However, it's important to remember that this chromosome is not ",
" inactivated",
". It's still being studied, but to my knowledge, the symptoms of Turner's arise due to haploinsufficiency of these genes that escape inactivation."
] | [
"Yes. This becomes apparent in other animals, such as cats (the calico color pattern). It's much less apparent in humans, but distinct differences can arise (e.g. the female body can be a collage of sweat producing and nonsweat producing cells). "
] | [
"As the person above stated, not all of the X chromosome gets hypermethylated (inactivated). "
] |
[
"How does my brain come up with people I have never seen / heard of / met before while I am dreaming?"
] | [
false
] | null | [
"The premise of this question is flawed. There's presently no way to test whether the people you dream about are people that you have seen, heard, or met before.",
"We have no way of cataloging everyone that we've ever encountered, and certainly no way of comparing such a catalog to people that appear in dreams, ... | [
"People commonly revert to such anecdotes when considering this question. But it's still not clear whether any of the dreamed scenes or people are really novel, or whether they are recreations of images you may have seen elsewhere (e.g., TV, movies, games, artworks). The only way to be sure of the novelty of any dr... | [
"Your follow-up question as well as your first question deals with a lot of different areas of cognitive psychology, cognitive neuroscience, and neuroscience which makes it difficult to answer comprehensively. The simplest approach would be to to account not just for how dream activity occurs, how the brain is sti... |
[
"How efficient is the average star?"
] | [
false
] | [deleted] | [
"We can't rate a star in efficiency, because efficiency is a rating of how much energy is turned into usable work. Since virtually none of a star's energy is turned into usable work, and virtually all of it is wasted by shooting off into space, we would have to say that stars are very, very inefficient. So any at... | [
"Hello there, Astrophysics PhD student here:",
"Here is one useful way to look at this problem (and it involves E=mc",
" The Sun is made up almost exclusively of hydrogen. What powers the sun is Fusion, also known as Stellar Nucleosynthesis. Now what does this mean? This means that all the Hydrogen atoms in... | [
"I'm not sure how to define efficiency in this concept. In general you define it as something like (desired output energy)/(input energy). So if a steam turbine is 30% efficient it means it 30% of the input energy, usually steam, is converted into, say, electricity or mechanical power. I have no idea how to answ... |
[
"Questions regarding Localized Surface Plasmon Polaritons"
] | [
false
] | I know it might be a bit too specific but I am really interested into understanding the mechanism. I am currently working on a TiO2 nanoporous film coated with gold nanoparticles. The photocurrent generation under 400 nm of visible light is not hard to understand, a 5d HOMO electron is excited into 6sp LUMO (on the gol... | [
"Essentially, the valence band and conduction band in Ti02 is a three dimensional surface in momentum space. Transitions from the valence band to the conduction band needs to obey energy and momentum conservation.",
"Consider a SPP with energy E as a function of k.",
"We will call this E_s(k_s).",
"The energ... | [
"In the same way an excitation such as light can be absorbed and generate an excitation in the gold, the SPP can be absorbed by the TiO2 bulk. The SPP eventually scatters and is absorbed by the bulk. Momentum and energy conservation requires an electronic excitation in the TiO2."
] | [
"Momentum and energy conservation requires an electronic excitation in the TiO2.",
"So basically the photoexcitatio of an SPP simply leads to electrons from the SP to drop into the conduction band of the semicoductor?",
"Can I inject electrons with the proper momentum or does the SP requires light to be excited... |
[
"How can one resolve electron capture with nucleon quark composition?"
] | [
false
] | So, electron capture says that: proton + electron --> neutron + electron neutrino In terms of elementary particles, that would be u+u+d+electron --> u+d+d+neutrino So, by conservation, would it not be true that: up + electron --> down + electron neutrino ? That doesn't make sense to me. It implies that these aren't ... | [
"It implies that these aren't elementary particles",
"No it doesn't.",
"and the mass doesn't add up.",
"It doesn't have to, the ",
" has to add up. If the mass of the products is greater, then the components on the left side need kinetic energy or the process won't occur.",
"Is energy conserved? Yes, if t... | [
"I strongly encourage reading Griffiths', it's very readable. It's a bit dated, but he's absolutely brilliant at making the physics accessible.",
" is a more recent alternative which outlines the same theory in a lot more detail, but you have to be prepared to work through a ",
" of formalism to start getting t... | [
"It would be more correct to say that the process does not violate angular momentum conservation (unlike e.g. a hypothetical scattering process from an even number of fermions to an odd number of fermions)"
] |
[
"What are the differences between Quantum Mechanics and Classical Mechanics, and how and why do they manifest?"
] | [
false
] | The equation x̂(t) = x̂(0) + p̂(0) t/m is arrived at after applying the commutator value [x̂, p̂] = iħ to the Heisenberg Equation of Motion for position of a free mass which says dx̂/dt = i[Ĥ,x̂]. In classical mechanics, x and p can be determined simultaneously with infinite precision, that is to say, the Uncertainty r... | [
"What actually makes CM different than QM?",
"The canonical Poisson bracket and canonical commutation relation look similar on the surface, but the interpretations of those equations are very different. Just look at the postulates of QM versus the postulates of classical mechanics (Shankar has a good comparison i... | [
"The deeper I get into theoretical physics (now doing a PhD) the more similar Classical and Quantum mechanics look to me. The differences are in fact extremely subtle, so be very skeptical of everything you read. Replacing Poisson brackets with commutators does nothing on the surface, it’s still the same algebraic ... | [
"This is a strong and interesting point. I think there was a paper that showed that classical mechanics could reproduce all tree-level results in QED, and field quantization was only relevant when loops became involved -- if you know what I mean, do you remember the authors? I'd love to read more about this...",
... |
[
"Has the time nature of quantum entanglement been tested?"
] | [
false
] | I'm a layman so please forgive me any misunderstanding or wrong use of terminology. I understand that theoretically communication using quantum entanglement has to be impossible because it would lead to time travel. For example suppose you put one particle of an entangled pair on a spaceship making a relativistic round... | [
"It seems very much like you're misunderstanding things. Can you provide some reference for this \"time passes for entangled pairs uniformly regardless of reference frame\" idea? I don't understand what it's supposed to mean.",
"Again, in practice, it's very simple: Particles that are part of \"entangled pai... | [
"No, you only get ",
" correlated measurement. If you keep making the same measurement (i.e. of spin along the same axis), you will keeping getting the same result, but that's true of any particle, entangled or not.",
"The only way to get a different result - your random series - is to subsequently measure alon... | [
"Entangled pairs are identical in all respects, including their behavior across time",
"That's not true. Entangled particles don't ",
" any differently to non-entangled particles, and they don't alter their behaviour based on what's happening to their partner.",
"in that the state measured on the particle und... |
[
"Is there any relation between the equations e=mc^2 and area of circle = pi * radius^2?"
] | [
false
] | Me and a buddy were having a very noob conversation about the universe and the speed of light after reading and I noticed the correlation between the two. Is there any reason for this, or is it just coincidence? | [
"No"
] | [
"There's a relation between ",
" and the fact all the points of a unit hyperbola in the ",
" plane satisfy the relation ",
" - ",
" = 1.",
"Here's the paper",
" wherein Einstein derived mass-energy equivalence. As you can see, the quadratic ",
" term comes out of the Lorentz relation between two movin... | [
"The c",
" in E = mc",
" is a constant. It shows that there is a linear relationship between E and m. The π in A = πr",
" is the constant of proportionality in that equation, or the equivalent of c",
" in the former equation. A = πr",
" shows a quadratic relationship between A and r. So no, not exactly.",... |
[
"Does subliminal messaging work? To what extent?"
] | [
false
] | null | [
"There's a type of subliminal messaging that's regularly used in psychological experiments. It's called priming. Basically, as our brains work in networks of interrelated nodes (neurons that fire together, wire together) thinking about one item makes you more likely to think of an item that is often thought of toge... | [
"I just read that one yesterday!",
" Got Baader-Meinhof'd.",
"To answer \"to what extent\", it targets the subconscious.",
"It will lose it's effect when it crosses to the conscious mind - if people realize they're being \"subliminally messaged\", or consciously catch themselves doing something they normally... | [
"The results show no significant difference between the Prime (M = 6.27″ SD = 2.15) and the No-Prime group (M = 6.39″ SD = 1.11) in the time necessary to walk along the hallway after the priming manipulation (F (1, 119)<1, η2 = .01).",
"But is says it didn't work...? Am I reading it wrong?"
] |
[
"So Earth's rotational axis is tilted. Does that mean all the other planets' axes in our solar system are parallel to the sun, and if so, why?"
] | [
false
] | null | [
"And Venus is just about tilted (haha) on its head at about 177 degrees, meaning it rotates in the opposite direction compared to other planets with small tilts."
] | [
"Other planets in our solar system have various axial tilts. Wikipedia has a nice list: ",
"http://en.wikipedia.org/wiki/Axial_tilt#Axial_tilt_of_selected_objects_in_the_solar_system"
] | [
"The Earth may be tilted because it may have been struck long ago by what we now know is the moon. Uranus has a tilt almost parallel to the plane of its orbit, giving the poles that face the Sun 42 year periods of dark and light-- probably tilted for the same reason as Earth, though the reason isn't truly known.",... |
[
"Does the orbital positions of the planets, impact the trajectory of the sun through the galaxy?"
] | [
false
] | For example: would a planetary alignment put enough gravitational drag on the star to move the entire solar system onto a new vector? Edit: I know a dragon won't affect orbital dynamics. | [
"The Sun has virtually all of the mass in the solar system, something like 99.5+, so while there'll be some effect it would be reasonably negligible I'd believe.",
"That said everything doesn't orbit around the actual centre of the sun, but a point roughly near it's surface, this is more because of the distance b... | [
"In addition to the Sun holding practically all the mass of the solar system (seriously the sun is huge), the planets will never come in to a perfect alignment due to a number of factors such as tilt, inclination etc. Their effect on the suns trajectory is beyond minuscule."
] | [
"Newton's laws state that everything has an equal force acting back on it, however because of the sun's mass in comparison to everything else, it is damn near impossible to see this effect at work. Still, everything is technically orbiting a point just slightly outside of the sun's center of mass, which is kind of ... |
[
"At what time during an illness am I most contagious: before symptoms, at the height of symptoms, or after? Do different viruses and bacteria have different degrees of contagiousness?"
] | [
false
] | null | [
"'am I' could just as easily be substituted for 'is one'. He also wasn't refering to a current existing illness that is affecting him."
] | [
"The fact that I am currently ill provoked the curiosity in me, but I am hardly soliciting medical advice. I only want to know more about how contagion works.",
"EDIT: Furthermore, I am asking about viruses and bacteria, not the human body."
] | [
"Depends a lot on the type of infection. Some viral infections become contagious after you get a big enough viral load (how much of the virus you have in your body). Most viruses won't be contagious without the necessary viral load and its also directly tied in with the onset of symptoms (symptoms appear at certain... |
[
"What gives something a \"smell\"?"
] | [
false
] | null | [
"Materials release particles into the air, which your nose detects when you breath in said air. For example, gasoline smells strongly because it is volatile and evaporates quickly, so a lot of particles are released into the air. "
] | [
"Just a technicality, but it's not necessarily particles that are released. It's just some kind of chemical (or chemical with functionality) for which you have a receptor in your nose.",
"On a side note - the number of smells we can smell is amazing considering they're based on chemical structure. There are lots... | [
"These materials have to match up nicely with receptors that exist in your nose (technically: olfactory receptors). These work much in the same way as taste receptors, but tend to be sensitive to much smaller concentrations.\nThese receptors exist on the surface of neurons which propagate a signal up to your brain ... |
[
"Will binaries compiled on the destination machine run more efficiently?"
] | [
false
] | If I recompiled every binary on my machine, for my machine, would it be faster than getting it from common repositories/sources as it has been made specifically for my hardware? | [
"A compiler should produce the same output regardless of where it is run. So as long as you're using the same compiler (and it doesn't choose different default options based on where it is running) the resulting binary should be ",
". Even if you \"cross compile\", where the machine you're compiling on can't e... | [
"Please note, though, that you can produce binaries that are faster than the ones you download by allowing the compiler to use specific features of your CPU that it might not otherwise utilize for portability reasons. But that is all about the CPU the compiler is targeting, not the one it is running on.",
"As the... | [
"The build process for many programs includes a configuration step, which selects settings used for the build. If you allow this configuration step to target your current machine, or you specify narrow options for the systems targeted, this can result in a faster executable.",
"When a program is distributed in bi... |
[
"Can charged ions increase airflow over a wing?"
] | [
false
] | Can an electric field potential increase velocity of air over a wing to produce lift? What if the angle of attack was was perpendicular to the chord line, and the velocity of airflow was accelerated by an electric field potential? I'm attempting to show that a 90° angle of attack creates upward lift if the air velocity... | [
"I recall reading an article about this: ",
"Flying with the Fourth State of Matter"
] | [
"The efficiency will be horrible and the ion flow won't keep a relevant net charge for long, but sure, the effect won't be exactly zero."
] | [
"There has been some work with ion thrusters on aircraft wings, for energising the boundary layer and aerodynamic control without moving parts. The long and short of it is that yes it works, it's not really efficient, and it's difficult to do wind-tunnel tests with because it generates large amounts of ozone."
] |
[
"I'll ask again. Can someone please explain the hologram theory of the universe?"
] | [
false
] | null | [
"Holography basically means that you can encode a piece of your space into a lower-dimensional space. There is not a single \"hologram theory\", but there are actually many cases where you can see holography appearing as a consequence of of your theory.",
"It all started when it was discovered that black hole ent... | [
"Just to clarify something: It's not really accurate to say that any reputable theory suggests the observable universe ",
" a hologram. This gets misconstrued all the time, so I think it's worth taking a moment to get specific about it. Instead, there are theories — very interesting ones — that suggest that any v... | [
"Heh, apparently so. In my defence I did say I was a complete layman! I just watched a documentary on space-time and a holographic universe was one of the theories they covered.",
"I mean kudos to the experts above who can answer fully informed and in-detail. I just felt their explanations weren't really \"layman... |
[
"NASA posted this picture of a black hole to their Instagram account. Is it real? Fake? Have we observed black holes?"
] | [
false
] | And also, if it was a computer generated approximation of what a black hole galaxy may look like, wouldn't it be a little bit disingenuous of them to present it like a "picture" - like the real images of space on their profile? | [
"That is not a picture of a black hole, that is a rendering of a black hole over a real picture of stars and galaxies. The warping of the image around the black hole may or may not be consistent with general relativity, it's not clear just from the image. ",
"This gif",
" showing the trajectories of stars in th... | [
"The IAU needs to hold a competition or process to name that thing. It really needs a proper name like the planets around Sol. Name it after some great beast or underworld monster from mythology. We need something better than ",
"Sagittarius A*",
". ",
"Just think about that thing for a second. It's the large... | [
"Definitely not the largest. According to ",
"Wikipedia",
", the black hole at the center of our galaxy has a (Schwarzschild) radius of less than 6.5 AU, yet the ",
"largest known star in our galaxy",
" has a radius of about 8 AU."
] |
[
"Going to sound stupid, but what is the difference between sound and heat?"
] | [
false
] | From my understanding, they are both the vibrations of particles... Edit: So, it looks like heat is the disordered vibrations, whereas sound is an ordered wave with a larger wavelength | [
"Heat is random motion on a very small scale, while sound is a cohesive wave on a much larger scale: the wavelength of middle C, for instance, is about 1.3 meters."
] | [
"That's not a dumb question at all."
] | [
"Yes. They use sound waves to burn tumours."
] |
[
"If we could see different wavelengths of light, would they be shown as completely new visible colors?"
] | [
false
] | null | [
"What do you mean by different?"
] | [
"ones not on the visible spectrum, like ultraviolet or infared"
] | [
"We can't really sense into IR so we don't know what that experience would be like. ",
"We actually are sensitive to UV, but the lens filters it out (for good reason). In the early days of cataract surgery, the lens was replaced with a material that did not filter UV and patients reported seeing deeper purples an... |
[
"How do we know that the river channels and other geomorphic features on the surface of Mars are attributable to liquid water and not a liquid of alternative composition (methane, ethane, etc.), like those that have been identified on other planetary bodies?"
] | [
false
] | [deleted] | [
"Mars today has a mean temperature of about 210K, though it can range from 120K to nearly 300K. In the past, it was probably a bit warmer if anything, since it likely had more atmosphere and leftover internal energy from formation. Methane boils at 112K, ethane at 185K. There wouldn't have been much of either in ... | [
"Kinda like asking, \"How do we know all the ice in Antarctica is water ice and not dry ice?\" Short answer is we are too close to the sun. Mars is also too close to the sun to have ever had liquid methane or ethane flowing freely on its surface."
] | [
"Good point about there once having been an atmosphere. My mind was focused on the lower energy of the faint young sun, but i didn't take atmospheric retained heat into account."
] |
[
"What would happen if there was no sunlight for 3 days?"
] | [
false
] | null | [
"never sun in the north pole",
"????"
] | [
"never sun in the north pole",
"????"
] | [
"Areas on Earth that do not receive sunlight for a period of time is very different from the Earth not receiving any sunlight at all. There's, you know, the atmosphere and oceans that conduct heat and indirectly heat those areas."
] |
[
"I am near-sighted, but when I look through a very small aperture, distant objects become clear to me. Why?"
] | [
false
] | null | [
"The aperture makes a pinhole camera with your eyes. You get a sharp image, but at the cost of blocking most of the light from reaching your eyes. "
] | [
"The image is always inverted on the retina."
] | [
"There are two effects as illustrated ",
"here",
"1)First effect (images 3 and 4): The small aperture provokes ",
"diffraction",
" which change the direction of the light, a bit like a diverging lens would. ",
"2) The second effect (images 1 and 2). The small aperture increase the depth of field. Contrary... |
[
"How much energy is contained within a strike of lightning?"
] | [
false
] | null | [
"Lightning bolts don’t last a second. You can’t just switch between joules and watts like that. "
] | [
"Yeah I found ",
"this resource",
" which claims that peak power is about 1 terawatt but the duration for the strike is about 30 microseconds. This gives an energy considerably lower (30 million joules, if power was uniform for 30 microseconds). That's about 6 days for our lightbulb.",
"Edit: there are 4ish s... | [
"Source for this statement? \"Giga\" is a standard SI prefix, and I have never heard anyone say \"jigga\" in any other measurements, before or after 2000.",
"I also don't see how it could be considered \"wrong\", as \"gig\", \"give\" etc all use this sound."
] |
[
"If the total energy of the universe is zero, does the universe cost nothing to create?"
] | [
false
] | I've read that the total energy of the universe adds up to zero. Does this mean that the big bang could have produced an infinite number of universes since the universe costs nothing to make? | [
"Yet when I reach the South Pole I am not limited by compass directions in where I can go. From the South Pole I can simply look up and see most of the universe - none of which is south of the South Pole.",
"The start of the big bang may be the farthest back we can go in our time dimension - just as the South Pol... | [
"Other people have already addressed the fact that this is not a proven theory. That aside, creating something with zero energy is not free. In order to get the reaction to happen that creates your object, you don't need to supply it's enthalpy (what we usually mean with energy), you have to supply it's ",
"Gibbs... | [
"I think it is a matter of discussion/belief. For example the inventers of inflation both refered to the universe as being a \"free luch\" (A. Guth) / \"the ultimate free lunch\" (A. Linde). For some discussion about the basic idea you should ust look for public talks by linde."
] |
[
"What happens when two photons collide head-on?"
] | [
false
] | null | [
"Many things can happen, depending on their center-of-mass energy."
] | [
"Okay. That sounds interesting. Please elaborate."
] | [
"They can scatter elastically, or produce particle-antiparticle pairs."
] |
[
"Is there any material harder then diamond?"
] | [
false
] | I've heard that carbon nano-tubes are supposed to be harder, or mure durable then diamond. (since diamond is hard but brittle) Is this true, and what makes it harder than diamond? Is there any other material that is harder than diamond, or does diamond has the perfect atomic structure for "hardness"? | [
"There are a couple, as far as I'm aware. Lots of man made carbon nano-materials are stronger than diamond. Also though, in the natural world, wurzite boron nitrate, which is like carbon but contains boron and nitrogen, and lonsdaleite which is like carbon but has a hexagonal structure; are harder than diamond. Bu... | [
"Researchers at North Carolina State University within the past few months discovered a new phase of solid carbon by the name of q-carbon that is supposed to be harder than diamond due to a shorter carbon-carbon bond. \nSources: ",
"https://news.ncsu.edu/2015/11/narayan-q-carbon-2015",
"\n ",
"htt... | [
"To the best of my knowledge, no, there is no material harder than diamond. Hardness is however not the only measure of a material's strength. Hardness (generally) means the ability to resist indentation. The article that AHundredAcreWoodsman links to seems to have tested the tensile strength of limpet teeth, not t... |
[
"What are the different 'phases' magma goes through in the eruption of a stratovolcano?"
] | [
false
] | I'm currently working on a music and art project featuring a volcanic eruption. An eruption from a stratovolcano (of course), for it's violent and explosive eruption. I would really appreciate some insight from you awesome people to better translate magma and the whole process of the eruption into music. By different p... | [
"Magma formed in the upper mantle (not the core, or even close - as far as the whole Earth goes, these processes are skin-deep) would normally migrate to a secondary magmatic chamber (not the best figures, but ok for our purposes: ",
"http://publishing.cdlib.org/ucpressebooks/data/13030/51/ft6v19p151/figures/ft... | [
"Thanks a lot for taking the time to respond so well!\nI'm trying to find a way of delving deep enough into the topic to get a good understanding of the processes at work whilst not losing myself in it. You have just helped me a lot with that, thanks. ",
"I think this subreddit is such an amazing place, where peo... | [
"It's been a pleasure! ",
"Feel free to ask should you have other questions. It might be worth taking the time of looking at pictures from layered igneous complexes such as the Lac Doré, Bell River, Bushveld, Muskox and Stillwater complexes to get a feel for the rocks and the processes.",
"Perhaps you can work ... |
[
"Is it true that Fish is a crude biological term and that one type of fish is more likely related to a land animal rather then another type of fish?"
] | [
false
] | null | [
"Unlike \"mammal\", \"fish\" doesn't refer to one evolutionary group. Instead, sharks and rays (Chondrichthyes), lungfish (Dipnoi), bony/ray-finned fish (Actinopterygii), coelacanths (actinistia), and a couple other groups I cant remember off the top of my head... they're all \"Fish\".",
"The lungfish are more cl... | [
"I am no biologist, and cannot answer your question about the validity of the term \"fish\", but I have some understanding of evolution.",
"It is true that certain species of fish are more recent evolutionary cousins to humans than they are to other fish. This is because all mammals and other land animals are de... | [
"heres a simplified ",
"tree of relationships",
"Tetrapods are the group that includes amphibians and reptiles and birds and mammals. So all the other groups are fishes and had a fish ancestor. So are tetrapods fishes? Well yes, if you say that we share a common ancestor with all the other fishes. But no if you... |
[
"What would a supernova look like in a hypothetical environment that had an Earth-like atmosphere?"
] | [
false
] | I recently saw a and thought it (kinda) looked like a supernova. Please take liberties with answering the question how you'd like as I might not have worded it properly. | [
"Are you asking how a SN would appear if the several light-years around it were composed densely with Nitrogen and Oxygen?"
] | [
"This",
" is what a SN does to the surrounding environment in space.",
"From ",
"Crab",
". ",
"The filaments are the remnants of the progenitor star's atmosphere, and consist largely of ionised helium and hydrogen, along with carbon, oxygen, nitrogen, iron, neon and sulfur. ",
"This would be essentially... | [
"I think you may be misinterpreting the crab nebula. It's not gas that was round the star before it exploded, it is the material thrown off the star during its explosion."
] |
[
"How *exactly* did the dinosaurs die out? Why did the mass extinction target some types of animals (dinos) but not others (mammals, fish)?"
] | [
false
] | I understand that the asteroid hypothesis is the most accepted one. But what exactly about the asteroid killed all of them? Did the dust block out the sun, kill out all the plants, and the dinosaurs that depended on them therefore die out? If that's so, why do we still have plants...and mammals, fish, insects, etc? ... | [
"Try Googling K-T extinction... there are a huge number of sites covering this very complex subject. No one here will be able to give you anywhere near the depth of information needed to properly address this question.",
"http://en.wikipedia.org/wiki/Cretaceous–Tertiary_extinction_event",
"http://www.ucmp.berke... | [
"My understanding is that birds are the descendants of dinosaurs. ",
"http://en.wikipedia.org/wiki/Feathered_dinosaur",
"http://en.wikipedia.org/wiki/Archaeopteryx",
"http://en.wikipedia.org/wiki/Origin_of_birds"
] | [
"Even if you were an archaeologist, you wouldn't be able to answer the question, as that's the domain of paleontologists."
] |
[
"Is a study with a small sample size less meaningful than one with a big sample size?"
] | [
false
] | [deleted] | [
"Your definition of a P value is better than most scientists could give!",
"However, your next statement is not exactly correct, at least in my opinion (though very understandable). In fact, you could probably ask 10 statisticians this question and get 10 different answers.",
"The clearest, and least controvers... | [
"All other things being equal, larger sample sizes lend greater credibility to a result. In mathematical terms, larger sample sizes tend to produce smaller p-values if all other things are equal. This is basically the ",
"Central Limit Theorem",
" at work.",
"Practically speaking, all other things are not equ... | [
". Does the small sample size actually affect how meaningful a study is?",
"Yes, depending on what you mean by meaningful. ",
"Having the same probability of a type I error doesn't imply that they have the same probability of a type II error.",
"which both have an identical p value, they should be equally rel... |
[
"Is it possible for a planet to be hollow?"
] | [
false
] | null | [
"The problem with this idea is that planets by definition are very large, and at those sizes everything behaves like it's liquid, so there aren't any materials that could support keeping a hollow shape at that pressure.",
"Although you could in theory have a planet that orbits in a donut shape and in that sense b... | [
"Not to mention the way planets form to begin with. They start out as small rocks that accumulate more and more debris over time giving it a larger diameter. I don't see how a planet could form with a uniformly hollow center."
] | [
"Like ",
"/u/MestR",
" said above, at such a large scale materials may as well be fluids. That is like trying create a warm wax ball and making it hollow then expecting it to hold it's shape. It just wouldn't work without an inconceivably strong material. That isn't to say that air pockets couldn't be present i... |
[
"Would a radiator disperse heat in space?"
] | [
false
] | If a hot metal radiator was in space and I put my hand 3 or 6 inches from it would I feel any heat? | [
"Yes, although not the same amount. A radiator as with all things transfers heat through three basic mechanisms: radiation, conduction, and convection. Radiation transfers through electromagnetism, so works just the same in space. Conduction and convection would not work because there is no air between your hand an... | [
"Yes, but not by any appreciable amounts, as radiation is relatively weak at close to room temperatures (compared to conduction or convection)."
] | [
"Yes, just not as much. You'd only feel the radiation. convection and convection transfers(through air) wouldn't work though."
] |
[
"when thrown into the air an infinite number of times, could a basket filled with motorcycle parts become a functional vehicle?"
] | [
false
] | the title says it all, i'm afraid. i have a good friend who is much smarter than me who insists that probability faced with infinity will yield amazing results. it causes the mother of all arguments edit: someone said this: I think that the throws are additive, so you could assemble it on a hundred impossibly lucky t... | [
"Everybody gets infinity wrong.",
"There are times when we can be careless with language to no great harm. There are strict rules for dealing with infinitesimals, for instance. But if we're just talking, we can skip over those rules entirely and say, \"Well, let's just stipulate that epsilon is small.\" Or whatev... | [
"I am having trouble appreciating how this challenge from the OP could have a nonzero chance of happening at all, based on the criteria we have been given for this challenge. ",
"The assembly of a functioning motorcycle occurring naturally from having all it's individual parts being thrown into the air in one thr... | [
"Given infinite time, who needs parts to begin with? Eventually a motorcycle will spontaneously materialize out of vacuum fluctuations. ",
"(If you ever witness this happening and you get a free motorcycle, it's bad form to complain about the paint color.)"
] |
[
"Why does travel sickness affect mostly passengers and not the driver of the vehicle?"
] | [
false
] | According to this post ( ) the nausea is most likely caused by conflicting sensory signals, but why does the effect differ depending on whether one is a passenger or a driver? I have also heard that sitting in certain locations on a bus can decrease the feeling of nausea, but I can't say I have ever felt noticeably wor... | [
"The best location for passengers is directly above, or slightly behind or forward of the rear wheels. Swaying motion is minimal.",
"This may minimise the swaying, but it is also important to have a good view of the outside of the vehicle so that what you see matches what you feel. So, depending on circumstances,... | [
"Because the driver can anticipate most of the sways, bumps, and other motion and is therefore prepared for them. Passengers cannot.",
"The best location for passengers is directly above, or slightly behind or forward of the rear wheels. Swaying motion is minimal.",
"On a related note, I remember reading years ... | [
"Good point. Anecdotally, I rarely experience motion sickness as a passenger, but if I look down for an extended period, say, trying to read a map or book, I definitely get queasy."
] |
[
"Is the total mass of oxygen atoms greater in the ocean or in the air?"
] | [
false
] | null | [
"Oxygen is about 23.20% of the atmosphere by mass, and the atmosphere has a total mass of about 5 x 10",
" kg. So the atmosphere contains about 1.16 x 10",
" kg of oxygen.",
"Oxygen is about 88.89% (16/18) of water by mass, and the oceans have an approximate mass of 1.35 x 10",
" kg. So the oceans contain a... | [
"Just using some quick values from Wikipedia:",
"Mass of Earth's oceans: 1.35x10",
" kg",
"Percent oxygen by mass",
": 85.84%",
"Multiply these values to get 1.2x10",
" kg of oxygen in the oceans.",
"For the atmosphere, oxygen is contained in O2, H2O, CO2, and some other minor gases such as O3, N2O, e... | [
"The pressure of the atmosphere is equal to the pressure of 10m water. The average depth of oceans is more than 4km, and if there was no land the average depth of oceans would be around 2.5 km. So a rough estimation is that the mass of oceans is 250x that of the atmosphere.",
" ",
" is almost 90% of water by ma... |
[
"How much notice would we get if a large asteroid were to collide with Earth or the moon?"
] | [
false
] | null | [
"There's no hard and fast answer to this question, unfortunately. There are programs that actively look for and track objects that cross the Earth's orbit, however anything below about 150m in diameter is very hard to detect. If the object is small, has a low albedo (doesn't reflect much light), and/or approaches... | [
"Tell that to Robert Farquhar and try not to let your ego cry when he laughs you out of the room."
] | [
"With decades of warning, just changing its speed by a few centimeters a second could be enough to result in a miss.\nIt could also be enough to turn a miss into a hit if the calculations are a bit off.\n(With a decade of warning the calculations have a very high chance of being \"a bit off\")"
] |
[
"Why is it necessary to reach a certain speed to breach our atmosphere into what is regarded as outer space, and why cant you do that with a much slower, constant speed?"
] | [
false
] | As if you were moving vertically at say a constant 100 mph instead of 25,000 mph. Why wouldn't you be able to break earths atmospheric bonds that way? | [
"Never mind 100 mph, you could walk into outer space if you had a long enough ladder. You just couldn't stay there; you'd fall back to Earth as soon as you stepped off the ladder.",
"Why doesn't the Space Station fall back to Earth? It does. It's falling back to Earth all the time. That's why people in the sp... | [
"If you had a propulsion system that could keep you going up at 100mph without needing air to function, then yes, you could leave the atmosphere at a slow speed. You just wouldn't be in orbit.",
"There isn't a fixed boundary of the Earth's gravity. You are always acted on by a force f=G m1 m2 / d",
" , pulling ... | [
"Never before has this sub done me as much justice as it has now thanks!"
] |
[
"How does Transatlantic cabling account for seismic activity?"
] | [
false
] | [deleted] | [
"Submarine cables are laid with sufficient slack so that they can be lifted to the surface for later repair/inspection. The slack needed for plate tectonics would be minor in comparison."
] | [
"Please, if the world of submarine cables even remotely interests you, do yourself a favor and read this amazing piece written about the industry by none other than Neal Stephenson (author of Cryptonomicon, Snow Crash, etc.) for Wired in Dec 1996. It is a serious chunk of text, (as most of his works are) but it is... | [
"Considering how long those cables are, a 2-3 cm lengthening would induce an insignificant strain in the cables."
] |
[
"If antimatter had 'won out' at the origin of the universe, could we hypothetically have wound up with a universe just like ours, but made of antimatter?"
] | [
false
] | I'd assume the answer is yes, unless there's something I'm missing here. Could the good people of help me out? | [
"Well, from antimatter's perspective, we are the antimatter."
] | [
"Antimatter and matter are indistinguishable from each other. So, yes."
] | [
"Wouldn't it just be called matter then?"
] |
[
"Why does a flu shot make your arm hurt a day or two later?"
] | [
false
] | I recently got my flu shot, and I noticed that a day or so later my arm was "sore". This wasn't from the needle, but it felt like I'd been punched and had a bruise (though nothing was visible). I realized that this happens for most vaccinations (I'm old enough that aside from a flu shot the only other ones are things l... | [
"The soreness is caused by your immune system reacting to the vaccine. It's not well understood why vaccines affect some people more than others or why some vaccines seem to have stronger reactions but it's assumed that there are simply differences in individual immune systems and sensitivities to pain.",
"Why do... | [
"This is vaguely related to questions like \"Why do many different viruses all cause the same cold-like or flu-like symptoms?\" ",
"The early phase of an immune response is pretty generic. The body senses that something is wrong, and begins to mobilize its defenses, but the earliest detection systems are very bro... | [
"Innoculation relies on introducing a sterile/attenuated antigen into your organism. In other words, you are given a weak infection to stimulate the creation of antibodies by your immune system.",
"The human body tends to overreact at a sign of infection and can cause symptoms after innoculation occurs, includin... |
[
"Are there any advanced subjects in physics, chemistry, biology, or engineering that are exclusively taught in school and not available in even the most expensive book or video lectures?"
] | [
false
] | null | [
"Speaking for biology and chemistry (but I'm pretty sure this applies to all branches of science), I can say that the latest, cutting edge science takes a long time to make it into textbooks and classes. You need journal subscriptions to read about that, but journals will be available at libraries and online ",
"... | [
"From a physics perspective:",
"As for being taught, yes, there are advanced graduate courses that professors sometimes teach which are focused on their own sub-sub-field, and sometimes no textbook exists with that material.",
"However, that information should exist in science journal papers, which you can cert... | [
"Upvote, was just coming in to post this.",
"I will quibble just a bit though with this answer. In addition, within whatever tiny niche of science you want the most breaking edge info, you need to be actually involved in ongoing research to be truely up to date. Even scientific studies take time to make publica... |
[
"Pot Bellies: Why is it that older people tend to develop larger abdomens? Is it fat? Intestines? What is contributing to all that size?"
] | [
false
] | Also, how do you prevent the development of a pot belly? | [
"It's a combination of two things; weak abdominal muscles, and body fat. ",
"Your abdominal muscles hold the viscera in place acting like a lid to a tupperware full of spaghetti if you will. Without proper conditioning these muscles weaken and the \"lid\" of your tupperware becomes more lax and succumbs to the ou... | [
"hey thanks for the great answer"
] | [
"You're welcome, I hope that made sense to you. "
] |
[
"Humanity just developed a FTL spaceship, and travels away from the sun. Does the front of the ship or back of the ship get lightened up?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"If you disagree with this decision, please send a ",
"message to the moderators."
] | [
"Ok 😢"
] | [
"I am sorry but the laws of physics as we currently understand them don't allow for FTL travel. So it is impossible to scientifically answer this kind of questions."
] |
[
"Antagonizing the sympathetic nervous system causes urination, so why does the fight/flight response also cause urination?"
] | [
false
] | Giving an alpha-1 adrenergic antagonist allows one to urinate more readily by relaxing the smooth muscles around the urinary sphincter (the one in the prostate, I believe). Why, then, does urination occur (with Epi/NE release) when you are terrified? Also - does an ACh agonist also cause increased urination? | [
"I answered a similar question some time ago ",
"here",
"."
] | [
"Good catch. The first half of my answer was not my own and was from the allexperts.com link. I skimmed it and it seemed correct at the time but upon further reading the original writer was incorrect. You are correct in writing that beta adrinergic activity is not responsible for bladder contractility, in fact, it ... | [
"Awesome - perfect response!"
] |
[
"Was recursion \"well understood\" by the 1960s?"
] | [
false
] | [deleted] | [
"How do you define well understood? I'm sure people out there knew of it, and you'll find various research papers on the topic. But was it used? Nope, a quick check on early fortran says it ",
"did not support recursion",
", partly because it would have been very difficult and slow to implement since there was ... | [
"APL in the mid 60s also supported recursion. I was an APL programmer in the 80s. I was sent on a course on algorithm design in about 1986 writing algorithms in a pseudocode. I wrote a sort algorithm recursively and the instructor marked it wrong. After much arguing it emerged that he had never heard of recursion a... | [
"Take a look at section 2.2 (Origins of Recursion) in ",
"this",
" paper.",
"I've been doing some googling to try to determine when recursion became widely used in computing, so far without luck. I would suspect that early implementations favored iterative implementations because they generally use less reso... |
[
"Considering all dogs have 38 chromosomes, can a very small dog mate with(in some manner) and give birth to a very large dog's pups?"
] | [
false
] | null | [
"I don't see what this has to do with the OP's question. "
] | [
"A family member of mine breeds dogs so I've seen newborn puppies firsthand. There were two simultaneous litters of puppies; one from a toy poodle, and one litter from a standard poodle. What was amazing is that these newborns were practically the same size, just the toy poodle had considerably less (2) than the st... | [
"Yeah, a lot of what we've done to dogs is actually to alter their maturation, but the puppies are (aside from color) more-or-less still wolf cubs. For example, bulldogs are born with normal snouts, dalmatians are born without spots, etc.",
"Still, puppies of larger breeds can (and sometimes do) run larger than ... |
[
"Question about pain"
] | [
false
] | [deleted] | [
"I do know from meditation techniques that you can reduce psychological suffering associated with pain, which is a very, very significant part of it. Try an experiment--stick your hand in a cup of ice water for several seconds. It will hurt, obviously, and you will begin to suffer. In fact, if you pay attention to ... | [
"Point of proof. ",
"http://www.pnas.org/content/102/51/18626.short"
] | [
"I didn't know you could \"meditate\" to reduce the pain, but what I was talking about is doing something mentally in half a second that can reduce pain. For instance, if you're in a fight and you get cut from your oppenent, you don't have time to meditate or go into a zen state of mind. I guess what I'm asking is,... |
[
"How Does Cancer Form In Your Body?"
] | [
false
] | Why does cancer form in certain parts of the body? How and why does it form? | [
"This fantastic article is likely to bring you few answers ",
"http://cancerbiologyprogram.med.wayne.edu/pdfs/hallmarks_cancer_article.pdf"
] | [
"Apoptosis (programmed cell death) is imperative for maintaining a normal amount of cells in a given tissue. If you think about an aging cell, it will eventually form defects or stop functioning as well. In order to die, it goes through apoptosis. Apoptosis is an orderly process of cell death which allows the body ... | [
"Can you explain how apoptosis, or downregulation of it, comes into the picture?",
"I read an article on inhibitors of inhibitors of apoptosis as cancer drug candidates and never really understood where it stands in the whole picture"
] |
[
"In Earth-like conditions, how much stronger gravity can a planet have to support life? If Earth had a stronger gravity (2x, 5x, 10x?), how life would have evolved differently?"
] | [
false
] | I've always wondered about this. If Earth was twice the size, and with twice the gravity, would we be 4 meters tall? Or twice stronger? Does gravity influences the speed we age? This may be specially pertinent given this: | [
"Surely it's all relative. Who's to say that the Earth is at some sort of sweet spot, where weaker would mean larger and stronger would mean smaller? (That's a question being asked, not just me sprouting off, well abit of both) ",
"Why couldn't you have a planet with 2x gravity and then still get big creatures an... | [
"I have read, though i apologize from my lack of source, that a higher gravity would lead to a denser atmosphere, which, in turn, would make flight easier. So, birds would probably still exist. Hopefully someone can confirm/deny. "
] | [
"It's not a sweet spot if weaker is larger and stronger is smaller... it's just a spot along a linear scale."
] |
[
"Does a nuclear explosion destroy matter?"
] | [
false
] | null | [
"Sort of. The total mass of the matter afterwards is less than the material at the start. However even for very large nuclear explosions the difference in mass from the start to the end is only a few grams."
] | [
"Yes. The law of conservation of matter is not a law of physics. Only a approximation we believed to be true before Einstein proved otherwise."
] | [
"But doesn't this violate the Law of Conservation of Matter?"
] |
[
"Is it possible to go fast enough horizontally that you break free of earth's gravity and reach space?"
] | [
false
] | So I was watching dragon ball z and one constant thing they do is show a blast leaving earth. When they shoot these blasts, they shoot them horizontally and eventually they zoom out to see the blast leaving earth. So this made me wonder. Is it possible to move horizontally fast enough that you are no longer affected by... | [
"Yes, you'd have to go about 11 km/s. The problem though is that Earth has an atmosphere, so an immense force would be required to compensate for drag."
] | [
"The simple fact is that this is what is done by all Earth escaping projectiles. ",
"It's pretty rare to launch directly upwards. That's super inefficient. Instead, pretty much everything is put into orbit.",
"An orbit is literally just \"moving so fast that you can't fall back to earth\".",
"If you go a ti... | [
"And an incredibly strong structure that wouldnt crumble and be torn apart and melted by the atmospheric drag and its effects."
] |
[
"Many electronics have very poor efficiency, releasing heat as waste. Considering the amount of electronics in today's society, does this heat contribute a significant amount to global warming?"
] | [
false
] | null | [
"You shouldn't, at least not for this reason.",
"The power of the sun's radiation, at Earth's distance from it, is about 1380 W/m",
" (a watt is a joule per second). The radius of Earth is about 6000 km, so the sun-facing surface of Earth is about 10",
" m",
" in area. So the Earth is receiving 1.5x10",
"... | [
"No.",
"The world uses roughly ",
"700 million barrels of oil per year",
", or about 100 billion kilograms. Oil has a chemical energy density of about ",
"40 MJ per kilogram",
", so this means that burning oil releases about 4 trillion MegaJoules (4 quadrillion kJ) of energy per year. Sounds like a lot, h... | [
"Note: The 'vampire draw' of electronics is really only an issue when you don't have your heat on.",
"Assuming you moderate your heating based on the temperature of your home, practically ",
" the energy used by your computer, television, phone, and other electronics goes towards heating your home, and thus red... |
[
"What would happen if one were to consume all necessary nutrients in their purest form?"
] | [
false
] | I.e vitamin pills, protein powders and such (or purer forms if possible), and drink only water. Would one feel constant hunger? (since your stomach would never be quite full) How long could one survive in this regimen? How would the metabolism process work? (would there be any excrement? ) Thanks! | [
"Your basic premise is done fairly often with either enteric feeding (putting a tube into the stomach or even the intestines and pumping in nutrient solutions) or total parenteral nutrition (giving someone an IV with the necessary nutrients). This sort of thing is often done if someone has some sort of swallowing ... | [
"Protein powders are not \"purest form\". They are doctored to make the taste acceptable. Pure aminoacids taste like shit. Back when protein powders were invented, it was a real challenge to swallow that whole concoction - bodybuilders thought of it as a test of manliness. Then manufacturers figured out ways to mas... | [
"Just to clarify, you're discussing two methods (I know you mentioned it but I think it's important to break it out)",
"Enteric feeding uses a tube that is fed through the nose and down into the stomach, a pump is used to push a liquid food into the stomach for normal digestion. It allows for feeding when people... |
[
"What does a microwave do differently when defrosting food?"
] | [
false
] | Title pretty much. Compared to how microwaves normally cooks food, what does they do differently when defrosting? | [
"Microwave ovens work by ",
"dielectric heating",
". This heats up the outer layer of a material (food) pretty rapidly. When a home microwave oven is set to 'defrost', it generates microwaves in short bursts -- typically a few seconds -- and then pauses for a few seconds while continuing to rotate the food an... | [
"Yes, but I've always felt severe facial burns were part of the ",
"."
] | [
"So if I used defrost on a hotpocket, it would take longer to cook but I would get a more consistent heating throughout? (Meaning no more magma hot edges and ice cold center?)"
] |
[
"If diarrhoea induced by lactose intolerance reduces calorie absorption of the food ingested then why does diarrhoea induced by laxatives not have this effect?"
] | [
false
] | It is said that laxatives only cause loss of water weight but it does not make sense to me. | [
"Any ",
" weight loss from laxatives is just water. Ditto for lactose intolerance - the effect of losing the calories from one cheese sandwich won't make any difference once you rehydrate, whether they were 'lost' through a laxative or a reaction to the cheese. ",
"However, chronic diarrhoea - whether due to... | [
"Don't do that however, as the constant diarrhea will have a negative impact on your electrolyte balance, your supply of important nutrients and vitamins, and your gut flora."
] | [
"Yup. At least until your body gets used to them and stops responding as vigorously. It's not a great strategy - aside from becoming less effective over time, you are also likely to end up short of essential nutrients that are whisked through faster than they can be absorbed, prone to dehydration, low on electrolyt... |
[
"Why does air pressure decrease as altitude hightens?"
] | [
false
] | *please warn me in case the flair is wrong. | [
"Air pressure is just the pressure exerted by the weight of the air piled on top of something. Basically imagine a \"pillar of air\" pressing down on you. The higher up you are, less and less of this pillar is above you and more of it is below you (and thus is no longer pushing down on you). Basically, imagine the ... | [
"We can consider the air pressure as the weight of the column of air above a surface. The higher the surface stands in the atmosphere, the shorter is the column of air weighing on it. A shorter column of air means less weight on the surface."
] | [
"When you dive into the deep end of a swimming pool, the deeper you go, the more pressure you feel on your ears. The pressure is from all the water piled up on top of you. The higher the pile of water, the more pressure on your ears. In fact, that's how dams that make electrical power work. It's the pressure of the... |
[
"How do they plan on supplying oxygen to the astronauts that go to Mars?"
] | [
false
] | It seems like the amount of oxygen that it would take for the year long trip would take up a lot of room, so are they going to have a method to convert stuff to O or are they just going to lug it all up at one time. | [
"The current primary oxygen source on the ",
"ISS is electrolysis",
". The Russian-built Elektron and American Oxygen Generating System crack water into oxygen and hydrogen (vented to space). Orion could use this. ",
"Apparently NASA is currently taking proposals for better oxygen recovery systems that can pu... | [
"Also, when you mention the mass of gas tanks, the cute thing is that the mass of a tank is roughly proportional to the mass of its contents. Holding pressure constant, ",
"that's because the necessary tensile strength (and thickness of the wall) increases linearly with the radius, while the area of wall follows ... | [
"To add to this, which is quite correct, the main issue we care about in space is ",
". It is a problem not only by itself due to the launch costs, but in the case of an interplanetary trip it's also a problem because it impacts on how much fuel you need in orbit, which in turn impacts again on launch costs.",
... |
[
"What is responsible for our sense's tastes? Be it literal taste, or sound, feeling, smell, or looks"
] | [
false
] | null | [
"I don't understand your question. Can you try rephrasing? What does a sense's taste mean?"
] | [
"Oh. There's no nice answer for that question. It's a combination of exposure, environment, culture, socioeconomic group, etc."
] | [
"Like what we like and dislike, for example you may like McDonald's but dislike Burger King or you may like Screamo but dislike Classical Music."
] |
[
"Is psychopathy an extreme end of a bell curve (or some distribution)? If yes, what is the other end ? extreme ?"
] | [
false
] | I'm assuming there are several degrees of psychopathy, I was wondering if the is an 'opposite' of a psychopath. If so, then what is it. | [
"IANAP (I am not a psychologist), so moddown/remove if needed. But if:",
"\"Psychopathy (/saɪˈkɒpəθi/[1][2]) is a mental disorder characterized primarily by a lack of empathy and remorse, shallow emotions, egocentricity, and deceptiveness.\"",
"(wikipedia)",
"then the opposite end of the spectrum is quite obv... | [
"Administering the psychopathy checklists is my regular job, and I can tell you that it is not on a bell curve. There are 20 characteristics to determine if a person is a psychopath, and no psychopath has to have all of them. So, there could be an opposite to a category like sexually promiscuous (a virgin), or to d... | [
"Psychopathy is defined by the presences of some or more psychopathic traits according to the most recent version of the DSM. As a result, the opposite of this would just be an absence of these traits."
] |
[
"What are Markov Chains?"
] | [
false
] | Specifically, how can they be used in algorithmic production of music? Also, what is the difference between discrete and continuous chains? | [
"if you go deep enough with this it starts seeming like the ramblings of a mentally challenged person which is a big improvement over garbage that looks like english",
"A good example of this is on page 7 (PDF).",
" Specifically, the 6th example shows what a markov chain looks like on words. "
] | [
"if you go deep enough with this it starts seeming like the ramblings of a mentally challenged person which is a big improvement over garbage that looks like english",
"A good example of this is on page 7 (PDF).",
" Specifically, the 6th example shows what a markov chain looks like on words. "
] | [
"Excellent answer. ",
"This blog",
" explains a bit, more visually."
] |
[
"Can tungsten survive lava?"
] | [
false
] | I read that tungsten boils at like, 3000 degrees Celsius, and that lava burns at around 900 to 1200 Celsius, so what would happen if you put tungsten in lava? (I'm assuming it's pure, because unpure is supposed to be brittle?) | [
"Tungsten ",
" at 3422°C (it boils at a much higher temperature). Pāhoehoe is one of the hotter types of lava, at about 1200°C.",
"So nothing would happen. It would get hot, but not melt. There are plenty of elements/metals that have melting temperatures hotter than 1200°C, like titanium, platinum, etc."
] | [
"Thank You."
] | [
"Well, if you were in a tungsten box, surrounded completely by lava, I suppose you could survive, but it depends on a lot of variables. Your biggest concern would be the fact that just because the box is not melting does not mean it won't get hot enough to cook you.",
"If you had enough insulation, or you and th... |
[
"What exactly will happen when Andromeda cannibalizes the Milky Way? Could Earth survive?"
] | [
false
] | null | [
"Not much. Space is mostly empty and with the distances between stars being as big as they are, the chances of an actual collision or short-range interaction between an Andromeda star and a Milky Way star are extremely small.",
"The gravitational interactions of the merger could result in some stars being flung i... | [
"Regarding life and Earth, plate tectonics will likely end in 1-2 billion years as the core cools and that will likely lead to a great weakening then ending of the magnetic field around Earth which will likely lead to us becoming Mars like as our atmosphere is eroded away by high energy particles from space. So, yo... | [
"Evolution seperating species takes place over something like tens of thousands of years, a billion years ago life was essentially bacteria and single-celled organisms. The Cambrian explosion which brought complex life into the scene happened around 540 million years ago, or half a billion years."
] |
[
"Human Genome Project"
] | [
false
] | How has the human Genome Project allow us to predict and prevent more diseases? Need to know for science but can't get my head around it. | [
"A collection of people of different backgrounds. However, a lot of it is ",
"Craig Venter",
", biologist, genius, ego-maniac!",
"He also suggested his personal genome (100% Craig) be used as the human reference and published it under the name \"HuRef\". In the end, it's not a huge deal as human are (litera... | [
"So, I never worked on the human genome project (HGP), it was just a bit before my time. But I have extensive background in high-throughput (sometimes called next-generation) sequencing. I've helped discover the causative variants for a number of (genetic) diseases, discovered genes for diseases we didn't know ex... | [
"I think one of the great failures of the \"human genome community\" is that we haven't come up with a comprehensive (or agreed upon) set of genes. Right now I'd say there were 4 or 5 collections of gene models (CCDS, UCSC, Gencode/ensembl, RefSeq) -- that mostly (90%) agree on protein coding genes, but differ on ... |
[
"Why do viruses mostly affect only one species?"
] | [
false
] | I hope my observation is correct. We talk about a virus jumping from one species to another as a special event, so the normal case seems to be that viruses specialize in one host organism. Most of the machinery of cells is universal, so I wondered why viruses need to specialize. | [
"It's because a lot of the machinery is NOT universal, especially the parts the virus use to get into cells, then into the nucleus, and then to use the DNA there to make more virus. Those parts are generally very specific to each species, and even to types of cells within a species."
] | [
"This is my area of expertise!",
"Let's first address the \"Most of the machinery of cells is universal,\" statement. While this is true in a sort of surface understanding, that eukaryotes share many basic fundamental processes, and these processes are carried out by related proteins, there are many details that ... | [
"To elaborate on your correct answer: cellular machinery is universally VERY similar, but ecen between 2 individuals within a species you see enough small variation in proteins and their structures to cause differences in outcomes when it comes to infection and other diseases. Between 2 different species: the varia... |
[
"Why do birds bob their heads forwards and backwards as they walk?"
] | [
false
] | null | [
"For the same reason your right arm goes forward when your left leg does. Balance!"
] | [
"Relevant",
" video of birds' perspective shows quite well how this happens. Basically the bird conserves brain processing power by keeping the head still while moving.",
"I also liked the \"raw science\" experiment here."
] | [
"It's also to stabilize their visual surroundings. I imagine keeping their heads stationary relative to their environment as often as possible allows a better picture of surroundings compared to if their heads were constantly moving like ours are."
] |
[
"Does body orientation affect how blood flows through the brain?"
] | [
false
] | For example, if I am lying on my right side, will the right half of my brain receive more blood flow. If so, does this result in any cognitive changes? | [
"We use this strategy sometimes in asymmetric lung injury. When one lung is disproportionately injured relative to the other, in critically ill patients one of the strategies is to put the \"good lung down\". I think this is more of a physiologic concept than something that has actually been demonstrated, but theor... | [
"This is not true. Arterial blood has higher pressure than your veins, and blood that has to travel up your legs to get back to the heart need the support of valves that prevent back flow. Gravity is definitely a factor in blood flow. It's much less of one the closer you are to the heart though, where blood pressu... | [
"This is not true. Arterial blood has higher pressure than your veins, and blood that has to travel up your legs to get back to the heart need the support of valves that prevent back flow. Gravity is definitely a factor in blood flow. It's much less of one the closer you are to the heart though, where blood pressu... |
[
"Whenever I see classic photos of the US space program, why are no Stars, or the milky way ever visible?"
] | [
false
] | For example, this famous photo, or where the sun is on the perpendicular angle, or perhaps this where the camera is clearly pointing away from the sun, and therefore stars should be visible. All I ever see in is completely empty black, not even universal background noise. As I understand it there is no atmosphere here,... | [
"It has to do with shutter speed of the camera and the light activation speed of the film. If the shutter stayed open long enough to capture the stars the main part of the photos will be whited out.",
"As film and cameras advanced, more and more stars started showing up on film, "
] | [
"This is a gif taken from the station on the dark side of the Earth",
". Orion can be clearly seen rising from the horizon."
] | [
"We see the Milky Way just like you can see the Miky Way on Earth. Like the question above, we aren’t a lot closer to it than you are, so we can both see probably just as well as you can see it. However, on Earth to see it, you will probably need to go somewhere where there aren’t too many city lights so you can id... |
[
"Is dream interpretation legitimate or a pseudoscience/BS?"
] | [
false
] | For example, I have a hard time taking sites such as seriously. Edit: To further specify: what use are dreams in terms of modern psychology? | [
"Cognitive psychology is extremely scientific. Lots of the other stuff is fluff."
] | [
"yes.",
"edit: when it's done scientifically."
] | [
"However, dreams are indicative of a person's general emotional state.",
"Thanks you! THIS kind of dream-interpretation is always real. Dreams aren't meaningless just because some nut decided to relate it to astrology.",
"edit: oh you already mentioned it in tl:dr :)"
] |
[
"During the eclipse this morning I noticed the shadow moved from top to bottom. Shouldn't it be the other way around?"
] | [
false
] | Seems the shadow cast by the earth would start from the bottom. What exactly was going on? | [
"The shadow of the Earth on the Moon appears to move that way because the Moon is actually orbiting our planet in a direction completely opposite of its apparent movement in the sky (the rotation of our planet makes it look like the Moon is travelling East to West when it's the other way around in reality)."
] | [
"Thank you! It is much more clear now. :)"
] | [
"If it helps further, check out the Moon on a daily basis... you'll notice that, at any given time of the day, it will appear farther east than it did the day before. "
] |
[
"How does a gaming console display decent graphics for cheap and it takes a good computer for the PC version of the game?"
] | [
false
] | How does a $200 gaming console display the game on a TV with decent graphics while a computer has to have high end processing capability to display the same graphics with good frame rate. | [
"Most console makers actually sell their hardware at a loss and hope to recoup that with game sales. So a computer that can run PS3 games would cost more than a console, but not because PC is more \"High-end.\"",
"I don't know if that's the whole issue, but it's definitely a big part of it."
] | [
"A PC is an order of magnitude faster than consoles. But the reason consoles seemingly keep up is because of the API driver overhead in PCs. With consoles, they can program much closer to the bare hardware and squeeze all the performance out of it.",
"Source: John Carmack. See this article:",
"http://www.comput... | [
"Eh you're kind of close. Gaming consoles have specialized hardware that never changes through the life of the console brand. So, game developers can heavily optimize their games to run on the platform. PCs have varying hardware, and such optimization a cannot be performed. Also, PCs have many components and softwa... |
[
"Why aren't power lines underground?"
] | [
false
] | This question comes out of frustration from the ice storm in Michigan knocking out power, and it isn't estimated to be back on until the 20th. All of this could be avoided if they were underground, no? | [
"First of all, many power lines are underground. But it is cheaper to put them on poles, so that is often what's done in many areas. "
] | [
"I believe there are three main reasons for this:",
"They are more expensive to bury. You have to dig up more than a ton of dirt for a small patch of a power grid. This requires much more equipment and labor that most power suppliers aren't willing to invest when there are alternatives.",
"There are all kinds o... | [
"I'm a construction engineer in the power industry and you're mostly right.",
"The biggest reason by far is cost. If the cable is not important, like most of the low voltage network that supplies houses, then it doesn't really make sense to bury it all, especially if you have to dig up every street.",
"I've nev... |
[
"How are diodes and mosfets related?"
] | [
false
] | [deleted] | [
"You may want to do a search or look in your textbook for the term ",
". This is a \"parasitic\" diode that forms from the structure of a MOSFET, and keeps the MOSFET from being a totally symmetric device like it is in theory."
] | [
"note that mosfets as in original question dont need NP junctions (as found in diodes). Complementary MOSFETS (CMOS) do have them as part of their construction."
] | [
"In a JFET the gate forms a diode junction with the drain-source channel, this limits performance because there is a leakage current, and if the gate becomes forward-biased with respect to either source or drain, regular diode conduction occurs, with drastic reduction of the input impedance. In the insulated-gate F... |
[
"Does torture elicit accurate information?"
] | [
false
] | null | [
"For ethical reasons, this isn't really studied in science. The last big examination was done over the CIA's program under Bush/Cheney. I won't force you to read the 6,000 page report, that would be cruel, perhaps even sadistic. The Wikipedia summary is here:",
"https://en.m.wikipedia.org/wiki/Senate_Intelligence... | [
"No, it does not. Torturing someone during an interrogation will only succeed in making the subject tell you what you want to hear. ",
"Source: Costanzo, M. A., & Gerrity, E. (2009). The effects and effectiveness of using torture as an interrogation device: Using research to inform the policy debate. Social Iss... | [
"That source really isn't great for answering the question. The paper is mostly about the effects that torture has on those involved, with only a small section actually talking about the effectiveness of torture. Within that section, the first half is mostly anecdotal, referencing testimony from both victims and pa... |
[
"With thousands of cellphone transmissions going about, how does my cellphone pick out its signal from the spectrum it receives?"
] | [
false
] | To my knowledge, the cellphone should simply receive a single spectrum that changes with time. How exactly does a cellphone decompose that and pick out its personal signal? | [
"The answer to this depends on what technology your phone is using and can vary dramatically.",
"In the case of 2G GSM (somewhat simplified): your phone is paged by the network (on a frequency/time channel that all devices listen to) informing it that the network would like to communicate. When the phone receives... | [
"Pseudo-random numbers are used in cellular communication systems in a couple ways. The first would be cyphering of user data, though this is not necessarily unique to cellular networks it is used.",
"Another much more unique application of PRNs would be in generating spreading codes in CDMA systems (DSSS). These... | [
"It is not a case of the phone receiving all frequencies at once and filtering the others out as in normal radio transmission. Rather it uses a temporarily assigned frequency determined by computer whenever a transmission is made or received. ",
"Each cellphone registers its presence whenever it enters a cell usi... |
[
"What happens if a pendulum swings with a high angle of deflection?"
] | [
false
] | My physics teacher taught me that a pendulum can approximate simple harmonic motion (where a perfectly elastic spring oscillates in a sinusoidal pattern). He told me, however, that SHM only applies to a pendulum with a small angle of deflection (under 15 degrees). What happens if it swings with a larger angle of deflec... | [
"What happens if it swings with a larger angle of deflection?",
"The equation of motion for a pendulum is of the form x'' + sin(x) = 0, where x is the angle of the pendulum measured from the resting position, and I'm using units where sqrt(g/L) = 1.",
"In the small-angle approximation this equation can be appro... | [
"Primes denote derivatives with respect to time. So that’s the second derivative of the angle of the pendulum."
] | [
"Thank you. By the way, what does x\" mean?"
] |
[
"Questions about a solar array that would be big enough to power the US."
] | [
false
] | I have heard that a 100 mile array could be built in the desert that could supply the US with all the power it needs. With current technology: What is the actual size we would need? What are the technical limitations/bottlenecks to creating this? What would be the cost of a project like this? Are there any plans to bui... | [
"Anecdotally, we have a 7kW array on our roof, and live in the desert. We get about 10\" of rain annually. The combination of wind and rain has kept the panels clean enough that dust buildup has never been an issue, and we've never had to even hose the panels off."
] | [
"We must be careful to use precise terminology here. It is a 10,000 mile",
" array, or (100 mile)",
"Here's",
" an article about it (from a political slant), with links to scientific articles and quotes from the folks who published the original article.",
"There are no plans to build an array that large tha... | [
"The limiting factor isn't so much the size of the array, but the size of the battery you would need to store the energy so you can watch TV on a cloudy day or listen to music at night. Solve the battery and overnight you will see PV and wind explode in popularity. "
] |
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