title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Did cannonballs spin and exhibit the Magnus effect?"
] | [
false
] | null | [
"Yes. Cannonballs were fired from smoothbore cannons, so they would develop some random spin when fired. The Magnus effect then caused the cannonball to veer off target.",
"http://pencilcricket.blogspot.com/p/magnus-effect-in-leg-spin-bowling.html?m=1"
] | [
"Imperfections of the ball/barrel and inconsistency of the blast (the powder won't ignite at the exact same time and would be unevenly packed down)."
] | [
"Imperfections of the ball/barrel and inconsistency of the blast (the powder won't ignite at the exact same time and would be unevenly packed down)."
] |
[
"What is the most current description of a vacuum?"
] | [
false
] | I'm aware that a vacuum in space is not truly empty, as shown by the Casimir effect and other experiments. What exactly is a vacuum then, and does this affect how physicists view real matter? I'm particularly interested in something I read that described a vacuum as being nearly infinitely dense and that real particles exist only when an excitation in a field "knocks" the particle out of the vacuum. Here is the quote I'm going off of: In the 1930's Dirac proposed that the vacuum was a near infinitely dense sea of particles in which all of the possible quantum states were filled. Matter as we know it, is what exists in quantum states above the vacuum. When a particle is knocked out of the vacuum, it leaves a hole called an anti-particle. Strong electromagnetic fields can effect the interactions of electron positron pairs which alter the observed electromagnetic field. The effect is called vacuum polarization and it has been experimentally observed. Is the above quote correct? | [
"The best current description (and this describes everything we've observed in terms of high energy physics) is that spacetime is filled with quantum fields. It turns out that quantum states of these fields correspond to a number of particles with particular properties. e.g. we may excite the electron field to have... | [
"It is indeed possible, and was recently ",
"demonstrated",
"."
] | [
"I'm sure my question will be well off-base, but as I have absolutely no education in these matters, I'm willing to ask the stupid question in order to be educated:",
"Granted, I don't really understand what you mean by quantum fields, but the way you phrased your answer makes me curious if it is possible to exci... |
[
"Dear Reddit, blacksmith needs advice on a sundial."
] | [
false
] | I am an apprentice blacksmith and i have been asked to make a Sundial as a 100h project. It is to be exhibited at the 15-17 June, hopefully I will sell it there as well. I don't want to make this post too lengthy so here is the question: What is the angle of the gnomon in relation to the ground? I live outside Warwick (Warwickshire) in the UK, the latitude 52 degrees 16 minutes and 48 seconds north. Now i don't consider myself stupid, however, for some reason I cannot wrap my head around this. I know the dial plate needs to be 90 degrees to the gnomon as this will align it with the equator. I have also heard that 55 degrees should work pretty well but I have no idea why. Hopefully I asked the proper subreddit. I'm sorry for the bad English, it's not my native language. Have a smashing day! | [
"The angle of the gnomon with the horizon should be equal to the latitude. This way, on average, it will be about perpendicular to the Sun and will cast the strongest shadow. You can build the dial plate perpendicular to the gnomon (like ",
"this",
"), or parallel to the horizon (like ",
"this",
"). Depe... | [
"The angle of the gnomon alone is not the only thing that's important for you. Its the relationship between the point of the gnomon and the marks indicated on some surface. That, plus orientation to north, is all that geometrically defines a sundial. Any arbitrary angle btw the ground and the gnomon, and btw the... | [
"Upvoted for correct answer. I have an excellent book on sundials, called \"Sundials, their construction and use\" by R Newton Mayall & Mrgaret W. Mayall, Sky Publishing Corp, P.O. Box 9111, Belmont, MA 02178-9111. It was originally published in 1938, but there have been several re-printings. Pretty much a defini... |
[
"What are these tiny creatures that keep appearing on my window sill (on the inside)?"
] | [
false
] | null | [
"Try ",
"/r/whatsthisbug"
] | [
"oh thank you, didn't know it existed...should i delete this post?"
] | [
"Probably makes sense to delete it here, and just post on ",
"/r/whatsthisbug"
] |
[
"Are LCD monitors more or less stressful to our eyes compared to CRT monitors?"
] | [
false
] | over a given time span, which would be more stressful/strenuous to our eyes? | [
"No expert here, but after some googling this is what I found. Eye strain is not necessarily caused by the monitor (LCD or CRT), but rather by staring at a fixed spot for extended periods of time and not blinking enough.",
"Link",
" and ",
"link2",
" \nfor more info"
] | [
"This is a supposition based on personal experience, sourceless.",
"Then you should have stopped right there and not commented."
] | [
"This is a supposition based on personal experience, sourceless.",
"Then you should have stopped right there and not commented."
] |
[
"Is there a certain area of the body that is more susceptible to changes in temperature?"
] | [
false
] | For example, if one wanted to cool down and had an ice pack, what part of the body could he place the ice to make his body cool down the fastest? Is there a certain part that controls our sense of temperature more than the other parts? | [
"For example, if one wanted to cool down and had an ice pack, what part of the body could he place the ice to make his body cool down the fastest?",
"Place the ice pack on an area which exposes a lot of veins and arteries. This will stop the cooling being mostly localised, because of the blood which is circulatin... | [
"The face is perceptively more susceptible and triggers different responses to cold than a lot of the rest of the body. In terms of actual cooling ability, armpits and behind the knees provide the best options."
] | [
"The palms of the hands are the best place to cool down your body temperature from because they have a large number of blood vessels near the surface. Instead of an ice pack though you should use something around 70 degrees Fahrenheit (I think that's the number) as this will prevent your blood vessels from constri... |
[
"What is the biological basis for physical sensations related to your \"third eye\" (that space on your forehead between your eyebrows)?"
] | [
false
] | null | [
"You can make many places on your body seem to tingle just by attending to them. Nothing special. Your brain just naturally ignores a lot of these sensations when you are not attending to them explicitly."
] | [
"But it ",
" special. Maybe that happens a tiny degree but nowhere near as strong. There's no way I could do this with like...a random spot on my upper arm, or my belly button, or the back of my hand."
] | [
"We can't answer why you specifically have some kind of experience, but anatomically there is nothing special about the spot on between your eyes"
] |
[
"Why do camera recordings get digital artifacts when receiving physical strain(during impacts, for example)?"
] | [
false
] | Like this: | [
"The artifact you see is from a packet loss: the video is encoded blocks by blocks and then transmitted. Because losing adjacent packets (blocks of data) is likely, blocks are shuffled so that we lose less ",
" blocks, and it looks less crappy. There are ways to conceal losses but when they're too numerous, block... | [
"The shock can momentarily cause connections to break. Then remake. All electronics use connectors to attach things together. They are spring loaded. So a large enough shock can cause the spring loaded connections to bounce."
] | [
"I think this isn't actually a physics question, it's a computer science question! Modern video encoding algorithms don't store ",
" the details about a scene: they pick and choose what's most important for the eye to see, and store a certain amount of information about details and changes in the scene per secon... |
[
"What evidence is there that there is a smallest particle? Is it possible that even the smallest particle we know about could be composed of smaller particles, composed of even smaller particles ad infinitum?"
] | [
false
] | I understand that elementary particles are supposed to be 'elementary', because they have no measurable internal structure. But could it be that we are just unable to measure an internal structure made up of ridiculously small particles? And if that is the case is it theoretically possible that even those particles have internal structures of even smaller particles? Is there evidence against this, if so what is it? EDIT: So basically as I understand it. Nobody has any fucking clue. | [
"From the outside it would indeed seem theoretically possible but let me expand upon this quickly in two ways.",
"The internal structure of protons and neutrons (well all hardons, particles made up of quarks) is not just a result of theory there is ",
"experimental evidence",
" that they are made up of quarks... | [
"The internal structure of protons and neutrons (well all hardons, particles made up of quarks)",
"Pretty sure you meant hadrons, but that is a hilarious typo."
] | [
"A particle physicist's dirty talk:\n\"I'll show ",
" a hadron!\""
] |
[
"AskScience, can someone please explain this weather-radar anomaly?"
] | [
false
] | Is it just a radar anomaly or something more sinister? This showed up about a month ago. Haven't seen it again since. | [
"Out of curiosity, do you know what date and time this screen capture was taken? I would like to compare it to raw radar data, because I think there was an issue with the radar in Warner Robins, Georgia at this time making the odd circle. The map you are looking at is a composite reflectivity image of all of the W... | [
"Birds form concentric circles when migrating?"
] | [
"Birds form concentric circles when migrating?"
] |
[
"The movement of rotating things and the movement of a weight hanging on a spring and can both be described with sine waves. What does rotate in a mass/spring system and what does oscillate like a spring in a rotating system?"
] | [
false
] | null | [
"The other two comments are correct, but i wanted to try to give you some mathematical insight as to ",
" the two things are described by the same mathematics.",
"The crucial feature of a spring (or a pendulum, or ...) is the existence of a ",
", which is ",
". In math, this looks like ",
" = -",
" ",
... | [
"Circular motion can be described by sine and cosines. ",
"Here's an animation I created explaining that",
". So that's the connection. The two phenomena are related by the same functions. That's all there is to it, pretty much."
] | [
"So, why is the position (along an axis) of a point that rotates about a pivot point proportional to the second derivative of the position of said point? "
] |
[
"How much is Iceland's climate and temperature affected by the Iceland hotspot?"
] | [
false
] | I know that the main reason for Iceland's very mild climate is the North Atlantic Gulf stream, but since Iceland is right above a volcanic hotspot, I assume that volcanic activity in some way adds to Gulf streams effect. Am I right about this, and to which extent does it affect the climate? | [
"The heat flow to the surface due to volcanic activity on Icealnd is insignificant compared to the solar energy input.",
"This paper:",
"HEAT FLOW FROM THE EARTH'S INTERIOR: ANALYSIS OF THE GLOBAL DATA SET",
"Describes the heat flow from the iinterior as 65 and 101 mW/M",
" for the land and ocean res... | [
"If we look at the bare bones of the argument, it is infinitely dependant on the hotspot, as without, the climate would be very much like the North Atlantic and very little like an island. "
] | [
"Geology student who recently visited Iceland here,",
"Not much more to add -- but the main utility of the hotspot is to harness the geothermal energy related to it. I believe Iceland is the only country in the world not dependent on fossil fuels that has an excess of energy, and they are trying to find out ways... |
[
"A question about intersteller travel and navigation"
] | [
false
] | I was (not) watching some show about space last night as i was trying to fall asleep and had a thought maybe you all can help me wrap my mind around. Let's say somehow tomorrow we find/are given/discover a method of space travel that would allow you to get in a ship and go explore any star in our galaxy (or others). Somehow your ship can move across the vast expanse of space in a timely mannor. My question has to do with navigation. When we plan a trip to say Mars, we can figure out what path to take by doing the math for where we are and where Mars is and adjust for where it will be when we get there right? How could we do this with a distant star? One thats light took years just to get to us? Can we track the movements of a distant star well enough to to "jump" to a point near it and on the correct plane or better yet near a planet? I know it's dumb to bring movies into this, but in films ships always "jump" across space to a just outside of a planets orbit where they can then pilot down into the atmosphere. If we had such a ship, is there anyway we could figure out where to go? | [
"Astronomers can track star movements across the sky and can estimate distances pretty accurately. As long as you had those two pieces of information for your destination and knew how long it would take to travel that distance (to adjust the flight path for the illusion of a distant star's location in the sky) you... | [
"One option is to use ",
"pulsars to define cosmic location",
". Individual pulsars are readily identifiable by their rate of spin (pulsation)."
] | [
"Could we calculate it so you could put your ship to within a hundred miles of the surface of a planet on the other side of the milky way?",
"I guess i got overwhelmed (as i often do when confronted with the sheer number of stars in our galaxy) last night thinking about the complexity of navigating a ship between... |
[
"Is the \"Island of Stability\" possible?"
] | [
false
] | As in, are we able to create an atom that's on the island of stability, and if not, how far we would have to go to get an atom on it? | [
"The current theoretical best estimate for the location of the island is Z = 114, N = ",
" 184. We have produced some isotopes of the element with Z = 114, but they have less than ",
" 184 neutrons.",
"The nuclides near and at the island of stability may exhibit enhanced stability relative to their neighbors ... | [
"Since supernovae produce all super-heavy isotopes, couldn't we make the argument that if the island of stability exists, we should see the corresponding spectral lines in a fresh supernova, but not if the island of stability does not exist?",
"Or are we talking about the difference between half-lifes of microsec... | [
"We don't know whether superhevay nuclides are produced in non-negligible quantities in supernovae. We have no reason to believe that species near the island of stability are produced. But yes, even in the island of stability, the lifetimes could be very short on practical timescales."
] |
[
"How would I go about making an electromagnet stronger than the average man?"
] | [
false
] | null | [
"/r/AskEngineers",
" is probably the most suitable place to ask about this. The answer is most likely that it is possible, but there are a lot of practical considerations that makes it pretty complicated. For once, you'd need a powerful electromagnet, which is big. Thus, its probably easier to hide the magnet on ... | [
"Can you think of a feasible alternative?"
] | [
"My initial idea would be something that latches onto some hinges that pop out of the box. But it would be kind of hard to rig everything so that you could put the box down and have the latches automatically come out. "
] |
[
"In a vast universe, is it possible that a solid gold planet exists?"
] | [
false
] | Edit: What a great discussion! A lot to think about here, especially regarding the implications of infinity. So it seems that the verdict is that yes, it is in reality POSSIBLE for this to happen, and though it would be incredibly unlikely that a planet consisting of only a single type of ANY element would exist, in a truly infinite universe, this scenario SHOULD occur at least once! Now for extra credit, does that mean that a solid gold planet would exist an infinite number of times?!?! Thanks again for all the great comments everyone! | [
"It's really really unlikely. Gold is produced in highly energetic events like supernovae that come with a lot of accompanying matter. ",
"On a lower energy chemical scale, gold binds to iron really well (which is present in the same events) and makes it highly unlikely to get a planet made purely of gold. "
] | [
"Hydrogen is the most common element in the universe by a fair margin at about 75%. Jupiter is already about 90% Hydrogen, so it seems that that would be the most plausible.",
"Especially if there was a gas giant around a first generation star before most of the other elements were formed."
] | [
"A metal is a material where the electrons in the outermost 'shell' of the atom interact with the rest of the material in a way that they are not bound to single atoms any more. The silvery appearance of most metals is a direct consequence of this physical fact. ",
"Some materials that aren't metals can become me... |
[
"Is it possible to find the algorithm for a random number generator by studying the sequences it produces?"
] | [
false
] | null | [
"For the sake of brevity, we will talk neither about the seed, i.e. the number that is given to the algorithm to bootstrap its pseudo random generation process, nor the environment it is executed in, and from which it can draw some randomness (time, temperature of the CPU, etc.). We will only talk about a determini... | [
"That was a really interesting read! I'm pretty sure it went in one eye and out the other but while it was in there, I found it really informative."
] | [
"/u/linschn",
"'s answer is great from a theoretical perspective, but from a practical everyday perspective, I think there's an equally interesting answer.",
"First, there are two kinds of pseudo-random number generators (PRNGs): cryptographically secure (CSPRNG), and non-cryptographic (PRNG). The short answer ... |
[
"Why do carbon dioxide levels cause climate change when it was all originally drawn from the environment in the first place?"
] | [
false
] | null | [
"The carbon is being released due to burning of fossil fuels.",
"This carbon was removed from the atmosphere during the Carboniferous geological age (~360-300 million years ago), before the dawn of the age of dinosaurs.",
"When stored underground this carbon was not contributing to the greenhouse effect, and do... | [
"Some of the CO2 currently in the atmosphere used to be trapped in the earth in the form of trees, coal, natural gas, other hydrocarbons, ect. Since it was trapped in those things, it had a very different effect on the environment.",
"Humans came along and found out that we could burn these things to make our liv... | [
"Today’s CO2 levels are some of the lowest in earth history. It’s been that way for about a million or so years. ",
"Plants have taken what was about 2400 ppm down to about 300-400 ppm by locking it away. Plants starve if the CO2 is less than about 200ppm."
] |
[
"Noise Cancelling Technology + Radiation Will it work?"
] | [
false
] | [deleted] | [
"Optical waves and sound waves behave very similarly and both exhibit destructive and constructive interference. Interferometers can give you destructive interference at one point (at the cost of constructive interference at another point).",
"Doing this \"real time\" like is done in headphones by employing some... | [
"To address this to the concept of nuclear radiation you might be better off thinking of radiation as particles in this case. All you have to do is stop the particle, which is what lead walls and thick concrete do. In theory you can fire other particles with exactly the same momentum at the radiation particles an... | [
"OH...OH GOD oh no I horribly misunderstood your question then. You were talking about nuclear radiation like from a nuclear reactor. ",
"I was talking about radiation meaning any form of light. Please discount my initial response."
] |
[
"Would flipping your body every 30 seconds for an hour get you just as tan as lying on both sides for 30 minutes each?"
] | [
false
] | null | [
"There are two ultraviolet lights at work in tanning: UVA and UVB. UVA causes the oxidation of melanin present in the skin, which causes a short term darkening of the skin. UVB triggers the production of melanin (which takes around 72 hours to have an effect).",
"\nAlthough these processes are very different, the... | [
"so being tan is skin damage?"
] | [
"It's caused by skin damage and is the body's mechanism to protect itself. We don't have a permanent tan because we also need to use the light for vitamin D (so can't just block it all using melanin)."
] |
[
"How are bats' organs adapted to sleeping upside down?"
] | [
false
] | I know why they sleep upside down and that tendons in their legs "cramp up" to make sure they hold on pretty tight. But how are their internal organs arranged? Doesn't blood flow to their brains like in humans turned upside down? | [
"Humans are close to 2m tall. Bats is close to a quarter of that. This basically means that they only have to deal with a quarter of the pressure difference a human does.",
"They probably have some adaptions in addition."
] | [
"Only the largest bats (some of the fruit bats) are that big. Most bats are mouse sized or squirrel sized. So yeah, they're dealing with a tiny fraction of the pressure difference that a human would experience. "
] | [
"If the bat is roughly a quarter of the human's demensions, wouldn't that equate to about 1/64 the pressure, due to the square-cube law? "
] |
[
"Is it possible to \"make it rain\" in the literal sense (not urban)?"
] | [
false
] | If possible how is this done? Side effects? | [
"Cloud seeding",
" has been shown to give a 10% increase in precipitation. Not exactly a mad-scientist-style weather control machine.",
"There really are no side effects since the clouds are seeded with such a small amount of silver iodine dust. The increased exposure is 2 orders of magnitude less than the norm... | [
"I thought every attempt at this just lead to a hurricane being redirected somewhere else."
] | [
"I recently saw half of a short film/documentary[?] by the BBC and Discovery Channel called \"Superstorm\" in which they were attempting to precisely control the direction of hurricanes --I don't know how much fiction it is but according to it, China successfully did deviate a hurricane to the Gobi desert or someth... |
[
"Does compression effect the electrical conductivity of a material?"
] | [
false
] | Not necessarily to the point of trauma, but does pressure alter the flow of electrons through, let's say, copper in any meaningful way? | [
"Yes it does. However, there isn't a clearcut relationship. For example, noble metals like copper and silver get more resistive under pressure, whereas tin and indium get less resistive. And that's just metals, the simplest conductors. When you get to nonmetals and semiconductors and ionic liquids and whatnot it ge... | [
"Exactly.",
"\nThis phenomenon is exploited in sensing technologies. The resistance in a conduit is manipulated by the stretching of the materials, giving a signal reading that can be interfaced to read a real physical value. It is well known, and largely exploited. But like our other friend said already, differe... | [
"It does indeed, to add to ",
"/u/iorgfeflkd",
", straining silicon in order to enhance its electron mobility is actually a huge part of modern computer chip designs. Strain in that case isn't coming from \"compression\", as you may be thinking (i.e. by putting a weight on it), but rather by growing the silicon... |
[
"Is there a set amount of energy in the universe?"
] | [
false
] | Due to the conservation of energy, where energy cannot be created or destroyed and only converted from one form to another, would that mean that there is a set amount of energy within the whole universe? | [
"Actually no. Conservation of energy predicates on time-translation symmetry. But our universe is expanding, so it lacks such symmetry. In more mathematical term, there is no time-like Killing vector in Friedmann–Lemaître–Robertson–Walker metric, the metric modelling our expanding universe. Consequently there is no... | [
"On small scales and in \"flat\" spacetime, energy is conserved. When you get to larger scales and take expansion into account then conservation of energy can no longer be applied."
] | [
"So does this mean that energy on large scales can diminish but not increase? Does the energy released in the big bang represent the upper limit on the energy in our observable universe?"
] |
[
"Under what circumstances will a star collapse?"
] | [
false
] | null | [
"Interestingly, not all stars that explode do so from collapsing. Lighter weight white dwarf stars (which began their lives as stars less massive than the approximately 8 solar-masses needed to form a neutron star) with companions can add mass over time and enter a period of runaway fusion reactions which blows the... | [
"A star will collapse when gravity is sufficient to overcome the outward force usually created by the star during its lifetime. This usually occurs after the star has fused hydrogen and helium into heavier elements such as carbon, oxygen, and iron, around the end of the lifetime of the associated star. The outcome ... | [
"above a certain threshold, the star will collapse into a black hole. Otherwise the star, having shed its outer layers, will become a white dwarf and meet a comparatively calmer end.",
"There's a pretty big mass range in between these two that results in the formation of neutron stars as well.",
"The processes ... |
[
"Does cold water extinguish fire more effectively than hot water?"
] | [
false
] | null | [
"It's negligible. Yes the entire purpose of putting water on fire is too remove the heat source side of the 3 sides of the fire triangle (heat source, fuel, oxygen). However, most of this energy transfer occurs as the water turns to steam (so I am told, I do not know the particulars of this). And therefore, the ... | [
"Even if we ignore the heat absorption from changing water to steam, ",
"an ordinary candle burns at temperatures over 1,100 °C / 2,000 °F",
". Compared to that, the difference between hot and cold water is still negligible."
] | [
"When we're applying water to a fire we're not trying to take away the heat source, most of the time we are actually trying to take away the fuel source. The argument is when using water what we are trying to do is cool the fuel, so that it can't reach its ignition point, this in turn reduces the amount of sustain... |
[
"Can an open reading frame be expressed without a stop codon"
] | [
false
] | Say you have a start codon and the required promoters but there is no stop codon, and some other mechanism stops transcription, could you have a functional gene? | [
"Yes. Yes is the answer to your question technically, however let me start with some definitions to be sure I am answering the question you are really asking. A gene is the common term for the part of the DNA that gets transcribed through the process of transcription. What we most commonly think of are protein c... | [
"Let me look around, these would be pretty old. I do know of several people who have done it accidentally. It is something you are warned about when cloning. It is one of those things that is so common a mistake a paper on it would not be accepted.",
"Here",
" is something that may interest you, it is about st... | [
". the stop for transcription are the ",
"termination bases",
". mRNA are further modified before translation, removing introns. They wrap and fold and are subject to degradation. A very large mRNA would likely be unstable and not usable for the ribosome. Now lets say teh revers the termination sequence is bef... |
[
"How does CPR work?"
] | [
false
] | null | [
"It really depends on the situation.",
"If someone goes into cardiac arrest, there is the possibility time lapse between the arrest and someone initiating CPR. Every second that goes by without CPR is a second those organs are starving without oxygen. If the arrest is witnessed, and CPR is quickly initiated, the ... | [
"http://www.kingcounty.gov/healthservices/health/news/2013/13090401.aspx",
"http://en.wikipedia.org/wiki/Seattle_%26_King_County_Emergency_Medical_Services_System",
"http://www.komonews.com/news/health/King-County-may-be-the-best-place-to-have-a-heart-attack-210592381.html",
"That top link is particularly rel... | [
"I read your links, and it makes me slightly nervous that you are attributing that 57% cardiac arrest survival rate to CPR. First, none of what you posted mentions traditional CPR at all, furthermore, that survival rate is not from compressions/breaths CPR, but to early and effective defibrillation, and likely to a... |
[
"Would it be possible to create a larger scale experiment of a straw holding water?"
] | [
false
] | So if u put something over the top of a straw as it is in water, could u then create the same scene but say 10 times larger. Would this work? would the force of gravity pull it down? | [
"Excellent question! The bottom surface of the water in the straw (with water above it and air below) would be an unstable surface if not for surface tension. That is to say, although it's in equilibrium (if the surface were PERFECTLY flat and it were in a hypothetical zero-vibration environment nothing would happe... | [
"In fact, we can do even better than this! Based off of the discussion of the linearized Rayleigh-Taylor instability in the Wikipedia article, I find that the maximum wavenumber of an unstable mode is sqrt(g * density / surface tension). Since I think the correct boundary conditions mean you have to have at least o... | [
"For fun let's calculate the critical width for some different liquids:",
"Water: 8.4 mm",
"Water + 11% ethanol (similar to wine): 6.7 mm",
"Vegetable oil: 6.0 mm",
"Ethanol: 5.2 mm",
"Hexane: 5.2 mm (gasoline is similar)",
"Liquid helium: 1.6 mm",
"Liquid nitrogen: 3.3 mm",
"Mercury: 8.0 mm"
] |
[
"Lorentz Transformation into a superluminal frame"
] | [
false
] | Using the laws of special relativity, we can show that if an airplane was travelling at a superluminal velocity in one frame another frame would exist where that plane is travelling backwards through time. My question is, what would happen in the frame of the plane itself? The Lorentz factor in the denominator would suggest it is travelling through imaginary space and time as it sees itself. In the context of special relativity only, is this correct, or is there a better interpretation? | [
"What you're describing is just the argument for why this is impossible. It would violate causality - a fundamental assumption of relativity. Therefore, if you want to consider superluminal velocity, you are no longer working with relativity."
] | [
"How does what he's saying violate the Lorentz transformation"
] | [
"We throw out the solution because its physically inconsistent with our expectations, but there is nothing mathematically forbidding an object with superluminal velocity in special relativity, correct? Isn't that what a tachyon is, at least hypothetically? If this is the case, then for a \"non-moving\" reference fr... |
[
"What causes the throbbing in my head during a bad headache?"
] | [
false
] | [deleted] | [
"Typically headaches are caused by blood vessel inflammation in the dura of the brain. The dura is one of the most highly innervated areas of the body. These inflamed blood vessels are prone to spasm and tend to spasm severely with rapid changes in blood pressure (ie standing)",
"Therefore the combination of den... | [
"The vascular theory of migraine has problems. For one thing, blood vessels routinely dilate and constrict without causing pain. And experiments in which blood vessels in the head and neck were artificially dilated by infusing saline solution failed to induce migraine-like symptoms.",
"Migraine headache is accomp... | [
"Adenosine.",
"Adenosine is the endogenous (originating within the body) neurochemical that causes headache pain and associated vascular dilation."
] |
[
"The \"face\" of the moon is always visible because of tidal locking. Are there any other common examples of this phenomenon that might help a rube like me to understand it?"
] | [
false
] | null | [
"Good question. ",
"Think about tides on earth. As the moon rotates around the earth it pulls a bulge of water around with it. It doesn't just effect the wate though, the moon also pulls the solid surface of the earth a little bit more on the closer face than on the other side.",
"A similar effect happens becau... | [
"A semi-related fact: there are no maria on the lunar far side. Recent publication says that the maria (which are volcanic outflows) are the result of Earth's glow when the Earth was still molten, causing the lunar near side to also stay hot millions of years longer than the far side. ",
"article"
] | [
"Because it's had lots and lots and lots of time to act on the water. It's like pushing someone on a swing. You give them a little bit of a push, but with the right timing (resonant frequency) the small pushes add up until the person is swinging with a much larger amplitude than the initial push alone would have do... |
[
"What happens to one's body after orchiectomy?"
] | [
false
] | I'm a 24 year old heterosexual male who has no intention of building a family or dating girls but instead dedicating my life to science and other pleasures. I'm interested if there are any negative side-effects (even the smallest one possible) of orchiectomy. Since I'm not interested in what most people want from life, I would be much more productive and focused on my interests if I had no sexual desire. Thank you. | [
"For those wondering, here is a ",
"link",
" explaining what an Orchiectomy is.",
"Edit:\nLayman speculating, I believe you would have a hard time finding a doctor willing to perform this procedure unnecessarily."
] | [
"I agree that most doctors would be reluctant to perform this operation on an otherwise healthy man. They would probably require you to visit a psychologist and get approval from the hospital's ethics board before performing it."
] | [
"It doesn't look like we are going to get a well detailed or scientific answer here. I applaud you for your decision, I have often thought of doing the same thing, but I fear the shadow of my time has grown too long while I played in the pools of destruction. I would encourage you to try to find other, similarly th... |
[
"How Might Universal Expansion Affect Black Holes?"
] | [
false
] | I just had a field day with Wikipedia on the subject of black holes, so you'll have to forgive my layman' understanding of the subject. As I understand it, expansion will, at some point (assuming acceleration continues) lead us towards a "Big Rip" that will tear apart structures when expansion overcomes the strength of a given force holding that structure together. I also know that as space expands, the universe cools, so I would assume that once a given black hole reaches it's equilibrium point because of that, it will start shrinking (ignoring any matter that may still be falling into it). My question is, specifically, concerning the "direct" effects of expansion on a black hole, rather than its surroundings. So, would a "Big Rip" scenario rip up a black hole too? (If so, what would the fireworks look like? That energy has to go somewhere, right?) Or is the black hole itself immune to the ripping effect inside it's event horizon? (Or is it "apparent horizon" now? I don't quite remember how that one was resolved) Could expansion somehow accelerate the evaporation of the black holes? (If I remember right, the Rip, if it happens, will occur much sooner than the expected lives of most black holes, even in an empty universe scenario) [edit] Fixed some spelling. | [
"IIRC: black holes are expected to evaporate before any such \"big rip\" would occur."
] | [
"As far as I remember, the Big Rip's most optimistic date is a meagre 103 billion years away (10",
" -ish years), where the expectant lifespan of black holes with only a single solar mass (most are far bigger than that) is the the order of 10",
" -ish years. I don't even think there's a name for that! And keep ... | [
"oh well so it is. I was mistaken in thinking about the big rip vs. just the general accelerating heat death of the universe. I guess the answer to your question probably depends on the nature of dark energy then. I don't know much about those two scenarios. I think some recent data suggested one scenario was more ... |
[
"Why is styrofoam squeaky?"
] | [
false
] | null | [
"There was a good answer to a very similar question ",
"here",
" a few months ago:",
"Styrofoam is mostly air, and is otherwise walls of the polymer polystyrene. The reason that it is so squeaky is that when something rubs against it, on the microscopic level, there is a \"stick-slip\" interaction between the... | [
"There's a name for the effect: stiction",
"http://en.wikipedia.org/wiki/Stiction"
] | [
"That name is proof that scientists can have fun too."
] |
[
"Why does voltage increase when the resistance increases?"
] | [
false
] | Correct me if I'm wrong but I think that's what happens but I don't understand why it works like that. | [
"The V = IR law we learned in school has a lot of analogies to other physical phenomena, like fluid flowing through a pipe.",
"Voltage is like pressure",
"Resistance is like the width of the tube",
"Current is like...well...the current, the speed of the fluid",
"If you imagine, increasing the resistance by ... | [
"Thanks that goes in to more detail. I understand it now. Thanks again"
] | [
"I think of current more like the volume of water, not the speed. All electricity moves at the same speed. ",
"It all depends on what you hold constant. If you increase resistance in a normal circuit powered by a constant voltage source, like a battery, you will therefore decrease the current. If you want to main... |
[
"What variables make some viruses deadlier than others?"
] | [
false
] | null | [
"Most of the deadlier viruses display a certain type of homing behavior in specific groups of human cells through epitope matching on viral structures, like surface glycoproteins. This makes certain viruses difficult to control and eradicate by your immune system. For example, HIV uses Th4 lymphocytes and macrophag... | [
"For example one may target more important cells like the immune system. Whereas another may target the resperatory sytem.",
"These are not variables, but specific behaviors as a consequence of the genotype.",
"Variables would include, in this context, for example, e.g. RNA mutation rate with defined mutations ... | [
"It would be in the genetic information carried in the virus, deadly viruses carry instructions to self replicate and destroy the body in the process. As such some viruses are more harmful because they contain instructions that are better. For example one may target more important cells like the immune system. Wher... |
[
"Is there a commonly accepted theory on how life evolved from single celled organisms to multi-celled organisms, or is it a complete mystery?"
] | [
false
] | null | [
"This is an odd way to formulate the question, but we can take a stab at a satisfactory answer. Multicellularity has evolved numerous times, multicellular organisms are not one lineage. The genus Chlamydomonas has developed lineages which differentiated cell types only to eventually revert back to unicellularity, w... | [
"This depends, to a great degree, on what exactly one considers to qualify for multicellularity. I cannot provide a definition that will be satisfactory to all people in the field. ",
"I think we could refer to the nature of some ",
"desmids",
" where an isthmus divides a single cell into two distinct functio... | [
"Thanks for the answer! Would you say then that the first multicellular organism only had two cells? Or would it have been a clump of attached cells sharing nutrients? "
] |
[
"If I am standing still on earth, how fast am I moving from a third person universal standpoint."
] | [
false
] | I know I'm sure it has to do with inertial frames and relativity but this problem has stumped me for a long time. Accounting for earths rotation, revolution around the sun, the solar system floating through our galactic arm, the entire galaxy rotating, and gravitational interactions between galaxies how fast are we really moving if a person were watching you outside of gravity's hold. | [
"You still have issues with how you define a stationary observer. I believe that you could make a case up to the galactic level to defining the galaxy center as stationary, but above that I believe that it would be difficult to justify defining a reference frame as stationary."
] | [
"The view point you're talking about doesn't exist. ",
", ",
"here's a site",
" that will probably give you what you're looking for."
] | [
"yes, that site is very helpful but like they said at the end, those results are just added together, they have nothing to do with vectors :(. As for the view point. If you were say at the exact place where the big bang happened and not moving at all, everything would be moving away from you so you could use that a... |
[
"Is there any evidence that playing a frequency similar to that which our brains interpret would cause it to temporarily change?"
] | [
false
] | null | [
"Are you asking whether human bodies have some kind of resonant frequency in the way that, for example, a wine glass does? I don't really understand your question."
] | [
"My bad. That is a very good point. In that case, would the human body have a resonant frequency? If it does, is it possible to find out what it is? Will it have multiple resonant frequencies? ",
"Thanks for your response :)"
] | [
"I think OP is just taking about Abby effects on the body from specific frequencies. There are a lot of different ways for this to happen though. The aforementioned resonance frequency as well as the brown note (mythbusters), effect of high amplitude frequencies outside hearing range, frequency patterns changing br... |
[
"How far back in history would I have to go before people couldn't understand the modern english I speak?"
] | [
false
] | null | [
"It looks as though the comments so far are suggesting around the time of Chaucer, and they seem to be doing so based on how intelligible ",
" Middle English is to a modern reader. However, this is misleading; English pronunciation has changed much more than our spelling has. Looking at the written text is NOT a ... | [
"I would just like to add that even the excellent audio links you provided under-demonstrate the actual difference between spoken Modern English and earlier varieties, because those recordings are of Modern English speakers reading ",
" language slowly and carefully. If you were to drop in and talk to your averag... | [
"As a foreigner who has learned English as their third language and now speaks it fluently (living in the US), I'd be curious to find out if there have been studies about near-native speaking foreigners understanding these type of recordings better.",
"I'm curious, because anecdotally, I actually understand all o... |
[
"Why don't the tides bring the moon closer to the Earth?"
] | [
false
] | [deleted] | [
"To put it colloquially: ",
"Imagine the moon suddenly went twice as fast. Its speed would be so large it would \"overshoot the corner\", escape earth gravity and float further and further away from earth.",
"Imagine the moon suddenly lost all its speed. It would no longer orbit, but fall straight down."
] | [
"A spacecraft in orbit that accelerates forwards ends up in a higher orbit. Even if you fire forwards/downwards at an angle. You increase the energy and angular momentum, which leads to a higher orbit. Same for the Moon.",
"For an idealized circular orbit the radial force doesn't even matter for orbital changes. ... | [
"Because it increases energy and angular momentum.",
"The radial force is not strong enough to keep the Moon on its circular orbit at the increased velocity. A trajectory that is curved less goes to a larger radial distance."
] |
[
"Does anyone know the Emissivity of Molten Aluminum?"
] | [
false
] | I can find all kinds of charts for oxidized, polished etc, but not molten. | [
"12% at 700 C\nSee ",
"this book",
", page 57."
] | [
"Emissivity is usually provided as a number between 0 and 1. Like a percentage is. Emissivity of 0 is a perfect reflector, emissivity of 1 is a perfect black body. "
] | [
"It was in the book that ron_leflore pointed to in the first response of this thread. 12% (or 0.12) at 700C. "
] |
[
"How does the body create so much mucus so fast and where is it stored?"
] | [
false
] | [deleted] | [
"You have specialized cells in all of your mucus membranes (mouth, sinus, GI tract, etc.) called goblet cells. They are interspersed within the cells that line the cavities and are always producing mucus to lubricate and protect the surrounding cells. When you have an infection, mucus production is sped up as a f... | [
"No you should. Your body views your sinuses, mouth, GI tract, lungs, ect. as external areas because they are open to the environment. By blowing your nose you are increasing infectivity to other people but what your body cares about is to keep the infection in its \"external\" environment. (if it's bacterial, t... | [
"This is a good answer. :)"
] |
[
"How does gravity work in a Dyson sphere?"
] | [
false
] | Let's say that a Dyson sphere has the same mass as Earth with the same circumference. If you were on the inside surface would gravity pull you toward the center of the sphere or toward the surface? | [
"This is why Ringworlds are more likely constructs than Dyson spheres. You can spin up a ringworld for artificial gravity."
] | [
"The gravity inside a spherical shell of uniform density vanishes. No matter where you are, gravity pulls you from all directions, resulting in a net force of zero (this is a lot of handwaving, as it works only for a spherical shell, but I think you get the gist). That is, the Dyson sphere would have no effect what... | [
"what would happen to the atmosphere in a spinning Dyson ? "
] |
[
"Can fish survive in carbonated water, or would they suffocate?"
] | [
false
] | Would there be any other side effects if the carbonation is not grounds for suffocation? | [
"Saltwater fish?"
] | [
"Saltwater fish?"
] | [
"/u/divestrong",
"'s post says \"saltwater are less salty than the surrounding water,\" and ",
"/u/NegativeX",
" is just trying to clarify divestrong meant saltwater fish."
] |
[
"If electrons in an atom are actually in probability clouds instead of a set orbit, then how can London Dispersion Forces exist?"
] | [
false
] | null | [
"Electrons don't have to be discrete particles for the dispersion to occur. They can change the shapes of the \"probability clouds\" of electrons in other molecules, though, because electromagnetic forces still very much come into play in quantum mechanics.",
"LDF actually relies on quantum mechanics."
] | [
"The orbitals are very dynamic. Just because the Bohr model of an electron orbiting around the nucleus is wrong that doesn't mean that the electron distribution doesn't change as molecules move around and interact with each other. "
] | [
"Yap. Orbitals have distinct shapes that we can/have calculated, so it makes total sense that the shape could be altered by an external field."
] |
[
"Are the risks associated with vaccinating against tetanus greater than the risk of contracting the disease?"
] | [
false
] | I am very pro vaccination; however, my hippy friend is always posting shit against vaccination on Facebook. She did make a fairly good point (if it's true). "You get 5 doses by age 6. Side effects include swelling of entire limb (1/30), vomiting (1/50), seizure (1/14,000) and permanent brain damage (1/1Mill.). 50% occurs in folks over the age of 50 with an average of under 30 cases per year. Which led me to wonder what kind of chances of getting tetanus are? That is 1/10Mill. So you have a higher chance of permanent brain damage than actually getting tetanus." | [
"The reason why there's a 1/10,000,000 chance of tetanus is because vaccinations have helped lead to eliminating tetanus in countries that vaccinate. ",
"Also, seizures and brain damage can be the result of a pre-existing condition. That's always a possibility. But there isn't any real evidence stating there i... | [
"That's the way I understand it. People who don't vaccinate weaken our herd immunity. This is why it angers me so much. I understand there will be stupid and ignorant people and I've stopped caring as I know you can't change them.",
"But it really heats me up when their ignorance can potentially harm my child.... | [
"There's an episode of House that kind of explains it. Probably not the most credible source, but they did their research for the show.",
"Usually people who don't vaccinate claim it's government conspiracy for health care profits and chemicals. And if they do know what a vaccine is, they don't understand why i... |
[
"With current technology, how high can we build a skyscraper."
] | [
false
] | Theres lot of talks about space elevators and etc. How about a spiral road to space? haha yea pretty stupid, but i can still dream. | [
"I heard that we don't really have a material that is strong enough to support itself to construct a space elevator. Can you provide any evidence one way or another?"
] | [
"I heard that we don't really have a material that is strong enough to support itself to construct a space elevator. Can you provide any evidence one way or another?"
] | [
"Limiting factor is definitely structural. It's not the height that matters, though. It's the shear force. A tower of any height is going to be affected by wind. The elasticity of the material has to be enough to hold the mass of the tower in place when the bottom is anchored in place and the top is being blown aro... |
[
"Does octave equivalency show any sort of property in physics, or is it a completely perceptual phenomenon?"
] | [
false
] | null | [
"Yes. First thing to understand is timbre. When you play a note, you hear a collection of frequencies. The note you're playing is the loudest frequency but there are other more quiet frequencies being produced concurrently. This is what gives an instrument's tone character, and makes a flute and a trumpet sound di... | [
"Pitches an octave apart are in 2:1 ratio with respect to their frequencies. This is true of all octave intervals. The brain experiences then as similar because their information content (in terms of pitch) ",
" very similar."
] | [
"This is an excellent explanation and what I was going to say. If you listen to pure sine waves at octave intervals, you can hear it, but not as definitely as in an instrument, and this is specifically because of the shared overtones you hear on top of the pitch."
] |
[
"Why must a vacuum be 'filled'?"
] | [
false
] | This is something that's always bothered me. I understand the idea of a vacuum and suction, but I always wondered why it happens. Why is it that a vacuum cannot exist beside matter? What is it that causes nature to fill the vacuum? Lastly, where does the energy to facilitate the movement of the matter come from? It seems to me that it is quite literally that is pulling the matter into the vacuum, and I can't make sense of it. | [
"Random movement of particles results in a transition of molecules from a place with high density to a place with low density.",
"Let's assume that there are two enclosed regions - one is filled with air and one is a vacuum. In the one filled with air, the air molecules are colliding with each other and with the ... | [
"There is an unbalanced force of air on the opposite side of your hand. ",
"\"Suction\" is actually an emergent phenomenon, it isn't a real force. What is happening is that there is higher pressure on the opposite side of your hand, and the unbalanced force of the multitude of particles striking your hand on that... | [
"Why does a vacuum literally suck onto my hand if i were to suck the air out of a bottle, and put my hand on it.",
"Is that just air pressure?"
] |
[
"What is the most habitable celestial body besides Earth? If we had the technology, what would the best celestial body be to move to?"
] | [
false
] | This is obviously inspired by NASA and SpaceX wanting to get to Mars. SpaceX want to inhabit Mars but as it seems like a hellish place to live, what other celestial body's are out there that are closer to Earth. There are so many factors here like does the body have a thick atmosphere, magnetic sphere, water and breathable air. Has there been study's of the many celestial objects we've observed to find out which one is the most Earth-like? | [
"rotating habitats inside the holes we’ve drilled in asteroids to mine them",
"it protects from radiation, provides the precisely desired artificial gravity, and is way easier to transport to/from than the gravity well of a planet",
"plus there’s way more room in the solar system for these habitats than there i... | [
"Few asteroids are likely to have the structural strength to hold together under rotation. You'd probably want to process the material into something more robust and cohesive."
] | [
"no asteroid rotation is required",
"cylindrical rotating habitats within holes drilled in asteroids from mining doesn’t turn the asteroids"
] |
[
"What is going on in this picture?"
] | [
false
] | null | [
"I am going to take a stab at this, and offer a hypothesis. The arm does not move in straight lines, but in arcs. I would assume that as the hand is moved down, there is a tendancy for it to also move toward a natural position in front of the shoulder. If this is the case, then the only scratches directly below the... | [
"Right-handed vs Left-handed people?"
] | [
"This is on the right track. It's probably a combination of where you are standing when you swipe your card (directly in front of the machine or offset), and whether you use your left or right hand to swipe.",
"Just as an experiment, hold your arm out in a \"swiping\" position, and try to recreate the mechanics o... |
[
"What is happening when we focus on one particular noise?"
] | [
false
] | [deleted] | [
"Auditory Scene Analysis",
" is a branch of cognitive psychology, I believe. Like you said, humans are able to focus on specific streams in a loud environment. Also, humans are able to cue in to ",
" conversations that were previously not being listened to. This is called the ",
"Cocktail Party Effect",
". ... | [
"I've noticed that when there's nobody with me, I can turn the tv way down and still catch everything that's being said. If there's a noise though, it takes a few seconds to get back on track. It's pretty interesting how much processing goes on when you hear."
] | [
"Yes, I can be in a very crowded, distractingly loud environment, but if somebody says my name, I can hear it clear as day. I didn't know there was a name for it."
] |
[
"Is reading on a higher resolution display (such as Apple's Retina Display) any better on your eyes then reading on a display with lower DPI or is the difference purely aesthetic?"
] | [
false
] | null | [
"For the sake of this post, lets assume we are looking at text with the same font size on both screens, but one is obviously a bit more pixelated (say, comparing a PDF at 100% zoom on an iPad 2 vs. an iPad 4). "
] | [
"It's mostly the size and not the DPI that matters if you are getting a headache from reading too much on your screen(also the light from your screen compared to the light around the screen), unless you are having a REALLY low resolution.",
"If you have high resolution then many texts will be smaller than normall... | [
"As long as you have a decent resolution, it's size of the font that matters, not super high resolution. Eye strain is worse when reading small text."
] |
[
"Why don't we feel pain we haven't noticed yet?"
] | [
false
] | If I scrape my knee and don't realise it's bleeding, it won't hurt until someone points it out later. And then it REALLY hurts. If I saw myself get damaged though and therefore have some level of assumption that it's going to be damaged, I can feel the pain already. It's just kinda funny, whats the point of a 'damage attention alert' system if we have to already perceive the damage before it goes off? | [
"Pain has unusual perceptual qualities compared to other sensory inputs. It is significantly gated by things like attention and anxiety. There are lots of reports of fairly significant injuries being sustained in sport or battle that are largely unattended until the sport or battle alert lessens. ",
"The point o... | [
"When we're talking about intensive stuff like sports or battle, isn't adrenaline also a factor in this?"
] | [
"People use the term \"adrenaline\" generically to refer to a heightened state of arousal/attention caused by some context. In that sense, yes. In a chemical sense, no, as the blood-brain barrier is essentially impermeable to adrenaline from the adrenal glands. Because it cannot impact the central nervous system, i... |
[
"How does the iterative process that provides Graham's number not violate the pigeon hole principal?"
] | [
false
] | [deleted] | [
"How would it violate the Pigeonhole Principle? ",
"Do you mean \"Why can we describe Graham's Number, even if we can't write it down in base 10?\" This comes down to the meaninglessness of decimal expansions and the power of mathematical notation and human invention.",
"Decimal expansions tell us next to ",
... | [
"Could you outline your reasoning? I don't know why you would think that.",
"Graham's number is \"compressible\" in the sense that it has a relatively small Kolmogorov complexity(for a number as big as that): you can write a computer program that computes it and is way shorter than actually writing the number out... | [
"It's a property of the number, but nothing intrinsic about it. You're comparing how it looks compared to 10 rather than discussing properties of the number. ",
"Intrinsic properties of a number include whether it's prime or not. Slightly related, how many primes divide the number. The sum of the divisors of a nu... |
[
"Is it possible to invent an engine with the same efficiency as the Carnot cycle?"
] | [
false
] | I know the Carnot cycle is the maximum efficiency in which any cycle could have, but is it possible to even achieve that in an engine? | [
"The short answer is no. The Carnot efficiency is, as you said, the maximum efficiency that a heat engine can have. It assumes that things like friction, wear on moving parts, vibrations/sounds induced in the engine, etc do not exist. These things will always be present. Friction is certainly not going anywhere... | [
"At that point the assumptions behind the model of a heat engine go out the window. Quantum effects allow you to get around various classical laws in very controlled conditions."
] | [
"I can't find a mention of efficiency in that article."
] |
[
"Would Spacetime Curvature Affect Gravitons?"
] | [
false
] | I've always been confused as to how to reconcile gravity being a pseudo-force (space curvature) with a quantum mechanical idea of gravity. If gravity IS just curvature of spacetime, would gravitons still move through it? Or is gravity just affecting objects in some non-fluid space in a way that makes it SEEM like space is curving? | [
"There's been several historical approaches to handling gravity quantum mechanically and the general consensus is that any effective spin-2 massless field theory is by default a theory of gravity",
"It's better than that. There's exactly one massless spin-2 theory (which is local, 4D, ghost-free, etc.) and that i... | [
"There's been several historical approaches to handling gravity quantum mechanically and the general consensus is that any effective spin-2 massless field theory is by default a theory of gravity (this is the position a lot of string theories take since they have such fields--therefore a lot of string theories are ... | [
"There's something I've never quite understood about the quantum gravity discussion; does the particle-based interpretation of gravity replace the geometric interpretation as the actual \"story\" of what's going on in the universe? Or is it more that the geometric explanation of gravity occurs as a consequence of t... |
[
"Why, when you continue to burn ash, do the ashes eventually change from black to white?"
] | [
false
] | Whenever you burn wood, plants, or other organic material, the residual carbon becomes black ash. However, if you continue to burn that material, eventually the ashes will turn white. What are the mechanisms involved in further combustion of the material that result in the ash changing from a compound which essentially absorbs all photons in the visible spectrum making it appear black, to a compound that largely scatters light in the visible spectrum appearing white? Thanks! | [
"If you have something black during a combustion process that‘s not ash but the remaining carbon. The carbon reacts with oxygen in the air to form carbon dioxide, a gas. Ash is the product of oxygen reacting with everything not containing carbon: calcium, magnesium, and a few other metals. The oxides of those metal... | [
"Interestingly, most of these are basic oxides, meaning that they form very alcaline solutions in water. This was exploited in ancient times to prepare soap from fat."
] | [
"It's important not to mix up terms here. What you get after combustion are oxides: Na2O, CaO, K2O, MgO, etc (probably some superoxides as well, but I digress). These are not oxidants, because the metals are in very stable oxidation states. But they are very reactive towards water: the oxide anions \"steal\" proton... |
[
"If time is relative to speed, what happens when we stop moving?"
] | [
false
] | null | [
"Which means that the spacecraft moving away from the earth in one direction would have time slow more for them as they accelerated than the spacecraft flying in the opposite direction.",
"Nope! The effects of time dilation are also relative. In other words, if you're an observer on Earth looking at the clocks on... | [
"You can find many past threads by ",
"doing a quick search",
".",
"...if you could be perfectly still relative to the universe?",
"There is no such a thing. Speed is always relative, and there isn't really a \"reference frame of the universe\". For example, if I'm driving past a lemonade stand, the girl si... | [
"Speed is always relative, and there isn't really a \"reference frame of the universe\". ",
"I understand that everything is moving in space, and there is no way to observe space itself to see if it has its own point of reference because anything we can observe is matter moving through space.. But saying that all... |
[
"I'm learning about Henrietta Lacks right now, but have a question about the HeLa cells"
] | [
false
] | [deleted] | [
"There can be the accumulation of mutations in the cells that get propogated with each generation. These are what caused the cells to turn cancerous in the first place and that hasn't stopped just because the cells are in vitro. ",
"Also, as cells are grown for a long time in culture there are other non-genetic... | [
"I think you'd like this wikipedia section on ",
"immortalized cell lines",
". There are actually several cell lines like this and they're used for production of biologic pharmaceuticals.\nKeep in mind that HeLa cells are cancer cells, so they're not a kind of cell you would want living & reproducing forever i... | [
"I'm wondering of we can learn anything from them in order to manipulate our own cells to live longer/continute dividing and surpass the limit (I forget what the limitation is called) that we understand cells to have. "
] |
[
"Does the placebo effect work on infants?"
] | [
false
] | [deleted] | [
"First, different fields use the term 'placebo' and 'placebo effect' differently. Psychology tends to use it in the strictest sense - a neutral intervention that produces a positive change due to the ",
" of treatment in the patient (a negative change is called a ",
"nocebo effect",
", btw). Medicine tends to... | [
"Thank you for responding!"
] | [
"In medicine, use of a placebo control is done to rule out quite a few different explanations for improvement. If the only thing involved was regression to the mean, placebo treatment wouldn't be necessary, as a no-treatment arm would rule out such.",
"Placebos work to blind patients to whether they're in the tr... |
[
"How small can nuclear power plants become?"
] | [
false
] | I know that the Nimitz-class and the Gerald Ford-class aircraft carriers use nuclear power in order to meet their energy needs. This makes me wonder: if it is possible to fit a nuclear power plant on an aircraft carrier, how small can nuclear power plants become right now? Are there any developments now that can make these power plants become smaller in the future? | [
"They're small enough to fit in nuclear submarines and the basements of apartment buildings, the submarine case being of interest as they operate as completely sealed units with magnetic torque couplings to manipulate their internals through sealed walls. ",
"Are there any developments now that can make these p... | [
"This is kind of a trick question. When people talk about the nuclear in nuclear power plants they are really talking about fuel. See most power plants tend to use the rankine cycle as there basis for generating power(",
"http://en.wikipedia.org/wiki/Rankine_cycle",
"). This cycle in its most simplistic form th... | [
"The ",
"Toshiba 4S Nuclear Battery",
" is pretty small although I haven't heard anything about it since the 2011 Tsunami and subsequent de-nuclearization of Japan."
] |
[
"What's the difference between a proton and a Δ+ baryon?"
] | [
false
] | I've been reading about quarks recently and I came across the Δ baryons. The Δ+ has the same component quarks as the proton, but a different angular momentum (3/2). How / why does this happen and what makes it different from a proton? | [
"It's not that they have different angular momentum, they have different isospin. Isospin isn't as fundamental as regular spin, which is associated with angular momentum. Instead isospin has to do with the properties of the strong nuclear force.",
"The delta particles were predicted and discovered long before t... | [
"Astronomy|Star Formation|Galactic Evolution",
"That is an impossibly cool tag."
] | [
"For the technically minded, it may be worth adding that the proton and delta+ have the same isospin projection, but they're part of different multiplets.",
"For the less technically minded, describing the delta+ as an excited state of the proton is probably good enough..."
] |
[
"Can the common house fly(Musca domestica) see window glass?"
] | [
false
] | Well flies keep flying into my window every minute or so. There isn't a major difference of light between inside and out, and there isn't any smell that would attract them inside my house. | [
"there isn't any smell that would attract them inside my house.",
"That you can readily detect. Flies, especially the more highly derived ones, are quite capable of picking up on very minute olfactory cues. "
] | [
"True.... "
] | [
"A family friend of mine swears by filling up a sandwich ziplock baggie with water and hanging it by your doors or windows. She says that the water confuses the flied because of their strange eyesite and helps repell them."
] |
[
"Are all galaxies moving in the same direction? If not why?"
] | [
false
] | So me and a friend of mine (who is an astronomy major) were sitting around talking about the universe and galaxies and some stuff he was explaining to me didn't quite make sense and I was wondering if a experienced astronomer could enlighten me. From what I understand the universe is constantly expanding from a central point from the big bang or huge cosmic explosion or what have you, but at the same time our galaxy is also moving toward another galaxy, the Andromeda galaxy, while it is also moving towards us. So I guess my question is are both of our galaxies flying in one direction but at the same time moving closer together? Like if you were to throw two magnets in a single direction and they link up in the air? or is our galaxy or the Andromeda galaxy moving at a slower rate than the other and one is simply catching up? Also are all galaxies really moving away from a central point or do we have any evidence that some might be moving in the wrong direction and how would this be proven? I'm sorry if this is a lot and if I'm not asking a very clear question but I just can't seem to get this question out of my head and I would love a good explanation to some of these questions. | [
"From what I understand the universe is constantly expanding from a central point from the big bang or huge cosmic explosion or what have you",
"There is no central point. The Big Bang wasn't an explosion. See the ",
"FAQ",
". It was an event in which the whole universe began uniformly expanding. All points s... | [
"Stars and galaxies moving away from us seems weird and very earth-centered, but its actually not.",
"I will use the overly-used example to illustrate this: consider a balloon. You can draw a grid on the balloon. Since you can choose two axis, you know each grid points have their coordinates, for example (0,1) or... | [
"This never made sense to me though. Taking the balloon example, as you add air the balloon gets bigger and all the points move away from each other (I get that). However, everything is then moving away from the center of the balloon, or the point at which the balloon was the smallest. How is it then incorrect that... |
[
"If I put a rock in say water, would it ever dissolve like a cube of sugar due to diffusion so I'd have a glass of rock water?"
] | [
false
] | Edit: assuming that the glass and the surrounding environment stay the same eternally. | [
"That depends on the Ksp of whatever mineral makes up the rock, the size of the rock, and the volume of water."
] | [
"It really depends on the rock, and on how big it is compared to the volume of water. If you dropped a chunk of halite, which is just table salt, in there, it'd dissolve pretty quick, unless it's a big chunk in a small glass, in which case it might eventually reach saturation. Some carbonates, such as limestone, wi... | [
"No. Eventually the water would be saturated with as much of the rock as it could possibly dissolve and the system would reach a state of equilibrium, where atoms were deposited back onto the rock at the same rate at which they were dissolved. You can see the same thing with sugar, where if you put enough sugar i... |
[
"What is the most efficient method of removing contaminating bacteria and viruses from a person?"
] | [
false
] | null | [
"In what context? Does the person still need to be alive afterwards? Simply incinerating the person would certainly remove all contamination.",
"If the bacteria/viruses are only on the skin, then they should be relatively easy to remove with soap and water (or bleach if needed).",
"If the person is already infe... | [
"I'd say the most efficient way would be for the person to have already been immunized against the bacteria or virus, so that the immune response just gets rid of them.",
"However, I feel like that answer is kind of cheating. So lets say you didn't pre-immunize. The methods will be different for bacteria and viru... | [
"Yeah I agree completely. For some viral infections that lack vaccines, monoclonal antibody treatment has been helpful for improving disease outcomes for things like ebola, but its not what I'd call fully efficient."
] |
[
"If the immune system \"learns\" and \"remembers\" viruses, how and where is this information created and stored?"
] | [
false
] | My understanding of vaccines is that we take "dead" viruses, and inject them into the body so that our immune systems can learn to fight them before we first get them. My guess is that somehow the white blood cells (?) adapt to the virus somehow, but in what way? Do they unzip parts of DNA like cells do when they replicate? What would they even do with these pieces of DNA or whatever information they learn? ie. how does that information help them kill the virus? Do they then go and hide out until later waiting for the next infection? | [
"To simplify greatly, there are immature immune cells present in your body. Certain types have \"hypervariable\" regions which, for complex reasons, are able to develop with incredible diversity on a molecular level. Enough diversity that virtually any complex protein (which are absolutely essential for life but ar... | [
"This is a good answer. The \"hypervariable\" regions ",
"/u/mstrgrieves",
" mentioned is not an easy concept and topic to understand, but this is essential to recognizing and combat any past, present, and future infections. To put an insanely high number to the amount of hypervariable combinations possible, it... | [
"Good question! To continue to trend of simplifying the vastly dynamic and complicated world of immunity, the body \"practices\" in that you have cells that present antigens (called professional antigen-presenting cells, or APCs) to your developing B- and T-cells all the time. The ones that recognize your self-anti... |
[
"How long might it take for humans to evolve significantly enough to see noticeable differences from humans today, either physically or mentally?"
] | [
false
] | null | [
"It depends on how you define \"evolve.\" We are taller than we used to be just 100 years ago (and live a hell of a lot longer on average) and we are also much more knowledgable as a society as a whole than we were just 20 years ago. You may have also heard recently the population growth in India predicted to suc... | [
"What about intelligence? Certainly it's a complex thing and difficult to understand, but do you see cultural or social systems leading to an interbreeding of more intelligent members in any way (for example isn't it encouraged in some countries for academics to intermarry)?",
"Would it therefore produce perhaps ... | [
"What about intelligence? Certainly it's a complex thing and difficult to understand, but do you see cultural or social systems leading to an interbreeding of more intelligent members in any way (for example isn't it encouraged in some countries for academics to intermarry)?",
"Would it therefore produce perhaps ... |
[
"How does the body know if a gene is recessive or dominant?"
] | [
false
] | [deleted] | [
"First of all, genes are not dominant or recessive; alleles are. ",
"If you are unfamiliar with the terms, then allele is roughly a specific thing that you might have in your DNA (such as \"blood group A\") where as a gene is a set of specific things you might have in your DNA (such as \"blood group\"), but a gen... | [
"A small nitpick. Your dangerous protein example would be referred to as dominant negative. "
] | [
"Well, it doesn't really, it basically just does as it is told. Both genes are there in each parent, it's just to what probability will the dominant alelle be expressed and how fully will it be expressed. I know that's not the most helpful answer. Could you maybe rephrase your question?"
] |
[
"Why does Earth's iron core generate a magnetic field?"
] | [
false
] | Also, what is special about the specific directions of the north and south poles? | [
"We do and we don't. We know that earth generates a magnetic field. We know that this magnetic field changes polarity intermittently. ",
"The thing we don't know is WHY. The popular theory (known as Dynamo theory) theorizes that the earth's core (inner and outer) is made of iron and nickel. Because the outer core... | [
"Iron in the outer core rotating is basically what causes it. If you want you can read about it in more depth.",
"http://en.wikipedia.org/wiki/Dynamo_theory"
] | [
"The magnetic field is generated by moving currents inside the outer conductive metallic core. These most likely are driven by convection produced by the the release of heat due to solidification of the inner solid core. ",
"Here",
" is a reasonable summary. The spin of the inner core and of the layers outside ... |
[
"Is there an inherent difference between a nuclear explosion and a conventional explosion other than radiation released?"
] | [
false
] | Someone posted a photo of operation Minor Scale Where large amounts of explosives were used to simulate a small nuclear explosion. My question is, other than a lack of radiation released, does detonating a nuclear weapon actually equate well to the equivalent amount of explosives. Does a 300 kiloton nuclear warhead explode the same way 300 kilotons of TnT would? | [
"interestingly, our current nuclear warhead design (as far as a lay person can tell) seems to be:",
"Chemical reaction (conventional explosives) compress fissile material driving a fission reaction. That fission reaction then (through a rather brilliant design, I think) drives a fusion reaction. But that fusion r... | [
"A conventional explosion relies on the electromagnetic force; the energy stored in chemical bonds is released through a variety of methods - but fundamentally, it is the breaking of chemical bonds that is the energy source. ",
"A nuclear explosion relies on the Weak Force (or perhaps more appropriately, the inte... | [
"In a sense, to simplify for OP, could you say \"A nuclear explosion is much, much brighter per kiloton\" using \"brighter\" oversimplified to imply visible and ir/uv/xray/gamma photons?"
] |
[
"What would be the immediate effects of a supervolcano eruption at Yellowstone?"
] | [
false
] | ...I don't mean a piddly one like the eruption 70,000 years ago, I mean a full-scale eruption along the lines of the one 640k years BP. Who is in range of the blast radius, and how far out and in what directions does the deadly ash cloud go? Does the eruption set off already-volatile faults in California? Alaska? Asia? What about the poisonous fogs? Does the East coast survive? West coast? Midwest? How about Boise? Billings? There are articles talking about 10 years of problems, but I'm wondering about the first 10 . | [
"Well everybody nearby would die, and a large region would get covered in ash. In 1883 a massive volcano exploded in Indonesia and there was so much ash in the atmosphere that the whole world experienced a temperature decrease for a year. I imagine this would be worse."
] | [
"This actually contains one of the reasons I asked this question. They say \"tens of thousands would die.\" After explaining how a chunk of Earth roughly the size of Oahu would be atomized and blown into the stratosphere with sufficient ",
" to make it a permanent fixture of the air for a decade they go on to not... | [
"Nom nom sweetastrophe nom nom"
] |
[
"(Astronomy) Why is the sun white?"
] | [
false
] | I've heard that the sun is white, and that the atmosphere makes it look yellow, but it's surface temperature of about 6000 degrees Celsius would place it as a yellow star in the HR diagram. Is the sun not white then? | [
"The HR diagram was created in 1910 when we knew much less about stars and their spectral power distributions. The color range on the diagram was arbitrarily based on visual observations. There are a lot of traditional holdovers like this in astronomy that remain because they don't really get in the way of the scie... | [
"The colors on the HR diagram are exaggerated. Most mid-range main sequence stars would look white in real life, as we can see when we observe stars at night (though admittedly that sample is biased towards larger, brighter stars)."
] | [
"oh ok"
] |
[
"Why did NASA use a skycrane to deliver Curiosity to Mars?"
] | [
false
] | How did NASA come to the conclusion that the skycrane was the best way to land a heavy rover on the Martian surface? What were some of the other strategies considered for the EDL (entry descent and landing) of Curiosity and why weren't those used instead? | [
"It should be noted that the EDL system used by the Mars Exploration Rovers, Spirit and Opportunity, was by necessity very elaborate as well:"
] | [
"It's atmosphere is too thin to use a parachute and ",
". ",
"Can you explain the bolded part? I don't understand why the thickness of Mars' atmosphere would preclude the use of rockets to land. "
] | [
"It's atmosphere is too thin to use a parachute and ",
". ",
"Can you explain the bolded part? I don't understand why the thickness of Mars' atmosphere would preclude the use of rockets to land. "
] |
[
"[Physics]Can ALL physics be represented mathematically?"
] | [
false
] | Sorry for such a simple question, a quick google didn't give me what I wanted. I have been working in computer simulation with physics engines and got to wondering, are there any psysics that don't have a definate mathematical equation to represent it? | [
"Just a protip: you don't need to type \"[Physics]\" in your title because you can add it with the \"flair\" button after you post. I've gone ahead and done that for you. It'd be nice if more submitters would do this since it makes it easier for experts to home in on their questions. (Right now the moderators are j... | [
"Oh I was wondering how that was done. I thought it would automatically color it if I wrote it that way. Thank you."
] | [
"We've yet to find something we can't approximate through math.",
"There's a few problems for which there aren't very good closed forms, even in simple Newtonian mechanics."
] |
[
"Why is biomedical research to computationally expensive, and what exactly is being 'researched'?"
] | [
false
] | [deleted] | [
"There are at least two large, inter-related fields: one is bioinformatics, which involves high-level comparison/interpretation/extrapolation of genetic data. The 2nd is molecular simulation, where the three-dimensional structure/function of macromolecules such as proteins or nucleic acids can be predicted and/or c... | [
"For computational biology (bioinformatics), the data sets are very, very large - they could be the entire human genome, or the output from some short read sequencing. The data often lists the nucleotide or amino acid makeups of a certain item - such as our genome (ie, ACTTTGCTGCTA, except many, many times longer).... | [
"Similiarly for molecular simulation the complexities are vast. For example, protein folding simulations ideally take into account individual atoms, including the surrounding water molecules. ",
"Then the algorithm itself would be a numerical iteration where you start with an initial \"push\" to the starting conf... |
[
"If Titanic had not sunk 100 years ago, could it still be used as an ocean liner?"
] | [
false
] | [deleted] | [
"With proper maintenance, yes. There are much older ships than it that are seaworthy.",
"However, whether it would be economically feasible is an entirely different story. Maintenance and operating costs are probably much higher than a modern cruise ship, and those only increase with age. There's likely a point a... | [
"Medina. Built for Mallory Line. Completed 1914. Last reported in service with Good Books For All as a floating ministry/bookshop. It was announced in November 2009 that she would be withdrawn from service on 31 December 2009 after surveyors discovered that she needed major repairs. In March 2010 she was handed ove... | [
"It would have most probably been stripped of its steam turbines and received a diesel makeover because of the more than double efficiency of the latter, as companies ",
" care about money. Other than that, only if it would have received proper care, because boats and the sea are not friends."
] |
[
"How do I explain the density of the observable universe in an easy to understand way?"
] | [
false
] | In the aftermath of a discussion I found the density of the observable universe through wolframalpha (I assume there will be different views on the validity of this number, and although not my primary concern here further insights would be interesting too), but I really struggle coming up with a couple of easy to understand similes since the number is so low. This might be a little different than the usual questions here, but you guys are usually amazing at giving relatable and easy to understand examples, so if you feel like it, have a go :-) (or point me to a better subreddit if I'm trampling all over some rules here) | [
"Maybe give a term such as, \"it would take this number of houses (or square feet (assuming a certain height)) to give one breath of air\". "
] | [
"Can't you just say that for the most part it's a vacuum? 1 O atom in a swimming pool, if it were enclosed, would qualify. "
] | [
"I really don't think there are. To explain a density, you have to explain it as a mass divided by a volume. If you want a mass that is everyday familiar, you wind up with a volume that is too big to be everyday familiar. If you want a volume that is everyday familiar, then you wind up with a mass that is too small... |
[
"Is there an extreme level(high or low) that would disable smell or taste?"
] | [
false
] | [deleted] | [
"You mention that if a room is dark people will go blind. I read that researchers were having people learn Braille and used a group of students wearing sleep masks to cover their eyes so they were \"blind\". They left them on for a few weeks and learned Braille. When they took the masks off they actually couldn't s... | [
"This is also \"state-dependent memory\". When you learn something under a specific condition, it would be easier to recall when you are placed in the same condition. Indeed, it's very interesting stuff."
] | [
"Closing your eyes isn't the same thing as having a mask on for an extended period of time. I mean, you can see light through your eyelids."
] |
[
"Can we mine the moon?"
] | [
false
] | Is there resources there that we can harvest and ship back to Earth? It seems if we want to whole world to be advanced, we will definitely need more resources, because the way we live now is destroying the planet, and not even the entire planet is advanced. I don't understand why the government doesn't try and spend money on improving technology and make it more green. It seems just most companies pick up the tag as Green, to make them better to people, and are really just fighting over consumers. The biggest problem will probably be the cost/power of shipping it back to earth. But if the government would fund programs to research that stuff, not just spend it on retarted shit. idk, it feels like everyone is looking down to try and fix their problems, when we should be looking up. | [
"Is there resources there that we can harvest and ship back to Earth?",
"Sure. Near the top of the list is ",
"helium-3",
" : \"The abundance of helium-3 is thought to be greater on the Moon (embedded in the upper layer of regolith by the solar wind over billions of years) \"",
"Helium 3 is a potentially ve... | [
"This leaves us with only one option: preemptively nuke the moon."
] | [
"This leaves us with only one option: preemptively nuke the moon."
] |
[
"[Space] If all the stars in the night sky appeared at the same brightness to us on earth, would the entire sky be light?"
] | [
false
] | Would there be any dark patches, or do stars (there are a lot of them) fill in all the gaps? | [
"You might be interested in this wiki-article:",
"https://en.wikipedia.org/wiki/Olbers'_paradox"
] | [
"If you apply this to every star in the observable universe there would not be any patches. There are 100-500billion galaxies out there, and on a scale as large as this, our universe is almost perfectly uniform. Our nigth sky would be compleatly filled without any noticable spots or holes. And saying that stars in ... | [
"If you apply this to every star in the observable universe there would not be any patches. There are 100-500billion galaxies out there, and on a scale as large as this, our universe is almost perfectly uniform. Our nigth sky would be compleatly filled without any noticable spots or holes. And saying that stars in ... |
[
"If swelling/inflammation is our body's method of sending essential blood cells and nutrients to a site of damage, why are most treatment efforts after, say, an ankle sprain concentrated on reducing swelling?"
] | [
false
] | [deleted] | [
"Hey, so it seems no one is really answering your question, so I guess I'll take a stab at it. I'm a human biology major, and while I may not have the credentials as most people have on here, we definitely discussed the subject of inflammation quite thoroughly, and I believe I can answer your question.",
"Basical... | [
"The primary reason to reduce swelling is to prevent additional damage caused by pressure on the cells. In a traumatic injury, the increase of fluids into the interstitial spaces(especially confined spaces) can cause physical damage to the surrounding tissues. Additionally, the swelling increases localized pressure... | [
"Ive always wondered the same thing about the fever response, if its not dangerously high, >103°, is it just for patient comfort? "
] |
[
"Is there a diamond equivalent for silicon?"
] | [
false
] | I understand that silicon shares certain properties with carbon. Can it arrange itself into a diamond-type structure? | [
"Yes. Silicon is already naturally occurring (or I should say ",
"naturally arranges itself",
" ) in a diamond structure. Unlike carbon which occurs mostly in its graphitic form at ambient pressure. ",
"There are also ",
"P-Si",
" which is easier to produce than monocrystalline silicon.",
"There's al... | [
"The qualitative explanation for the non-existence of a graphitic allotrope of silicon is the fact that pi-bonding is relatively weak for elements below the second row of the periodic table. In the diamond structure, each atom has 4 sigma bonds. In the graphite structure, each atom has 3 sigma bonds and one pi bond... | [
"There is indeed a \"graphitic\" form of silicon. Its single layers are called ",
"silicene",
", but contrary to graphite the structure is slightly bucked and not completely flat."
] |
[
"Would doing a belly flop into a pool filled with a non-newtonian liquid such as ketchup hurt more or less than would water?"
] | [
false
] | null | [
"Ketchup should hurt less, since it's sheer-thinning and at an appreciable belly flop speed, the viscosity will be lower than water. That initial impact is where most of the pain comes from, and in the case of ketchup, that impact is smoothed out."
] | [
"shear thinning"
] | [
"Cornstarch with water would be close to jumping on asphalt. "
] |
[
"Does the radiation from the sun/sun's radiant energy change over time?"
] | [
false
] | Are there any differences in the composition of the radiation from the sun in it's early days and the present? Also as the sun ages/dies, will the composition change? | [
"Yes, very much so. Here's a star migrating over a ",
"Hertzsprung-Russel diagram",
". The vertical axis is luminosity, from darkest to lightest, and the horizontal axis is temperature, from hottest to coolest. Most stars, like our sun, are on the \"main sequence\" depicted as the black line. The way the sun mo... | [
"Thank you. This was very helpful."
] | [
"also, the sun's energy output increases by about 10% every billion years. This means that as time goes on, the habitable zone around the sun gets pushed a little farther out. Maybe someday in the future, the Earth will look a little more like Venus as the sun cooks us into a delicious, sulfuric, greenhouse mess."
... |
[
"Marine biologists use submarines with bright lights to film deep sea creatures, many of which have very large, sensitive eyes. Are the retinas of these animals damaged by these lights, and do they try to avoid the subs?"
] | [
false
] | null | [
"Marine Biologist here, to answer your question the most truthful answer is \"we dont know\". Thats due to a lack of research, species specific responses and difficulty of accessing the deep sea. But that's not very fun or elaborate.",
"An interesting report here",
" covers most of the bases. It seems in most s... | [
"Do we know what spectrum their eyes actually \"care\" about? I know when I go deer hunting I can wear LED headlamps and it doesn't bother the deer in the wee hours of the morning whereas if I was wearing a Halogen lamp they would avoid me like the plague. "
] | [
"Thats another \"we dont really know\" question. However, we do know that no surface light reaches past 200m, and anything from 100-200m will only receive blue light.",
"Our current understanding is that fish would be seeking out that far reaching blue light, especially if the species is vertically transient. We ... |
[
"Why is Plutonium considered to be so dangerous?"
] | [
false
] | It has a very long half life so it's not throwing out a lot of radiation, yet it is still considered to be bad. | [
"Plutonium isotopes that have a long half life are not considered deadly for their radioactivity as much as their toxicity. Plutonium is incredibly toxic, even a small amount can kill you/seriously mess you up if ingested. In fact, in this regard, the long half life actually makes the situation worse because it doe... | [
"In fact, in this regard, the long half life actually makes the situation worse",
"If its lifetime would be so short that it would decay notably while in the body, then its radioactivity would be a problem. You wouldn't win."
] | [
"You wouldn't win.",
"When ingesting it. We would certainly win when it comes to the safe disposal of it."
] |
[
"Subtractive colors: Does a yellow filter just let yellow wavelengths through, or does it let green and red through?"
] | [
false
] | Are there different kinds of yellow filters? If a yellow filter only let yellow wavelengths through, then when it was stacked with a magenta filter, no wavelengths should get through... (rather than red)...? | [
"Depends on the filter. There's sunglasses that can treat colorblindness by being very selective on which wavelengths they let through. A perfect yellow filter would just look opaque, since almost no light would be exactly the right wavelength."
] | [
"Ordinarily yellow filters let through the wavelengths that we see individually as red, orange yellow and green in large amounts. If they didn't they wouldn't work for subtractive mixing. In the same way, bright yellow objects like lemons and yellow paints reflect wavelengths throughout the ROYG range in large amou... | [
"There are indeed many different kinds or of yellow filters. Your thinking is actually along the right track. If you have a perfect yellow filter that only allows yellow wavelengths to pass, say for example it passes 100% of light from 565-575nm, but completely blocks all other light, it would become black when s... |
[
"Educating myself on the MCAT topics. Recommended reading?"
] | [
false
] | null | [
"The MCAT prep books are not terribly good for you - they are based more on the principle of ",
" you first year concepts than actually teaching you. The answers to the practice questions often include explanations, but they may only include key words designed to jog your memory, without ",
" explaining them. A... | [
"For Ochem, check out ",
"Ochem as a second language I and II",
". It goes over your basic concepts including orbital theory, nomenclature, mechanisms, NMR, etc with pretty good explanations to help get the concepts across. I used this as supplemental material to my real ochem book. Also, if you want to lear... | [
"I think your best approach would be to read one of the MCAT prep books. I used the Princeton Review CBT book and I believe it was pretty thorough in its material. The point of these prep books is to review concepts that are expected to be known on the exam, but without going into to much depth because it to be u... |
[
"How did scientists estimate the age of Earth before the advent of radiometric dating?"
] | [
false
] | null | [
"There were a lot of different attempts that largely relied on estimating the rate of something and then extrapolating that to estimate the age of the Earth, i.e. there is Y quantity of this, it changes at X rate today, we'll assume it started at Z condition has always occurred at X rate and from there we can estim... | [
"Pretty much all of these estimation techniques missed the mark by at least a few billion years, largely because of incomplete understanding of the processes",
"But in the nineteenth century context their answers usually served to advance the scientific conversation, they discredited the Biblical creation story, ... | [
"Poorly.",
"One estimate was based on the estimated age of the sun, which derived by assuming that the sun was powered by gravitational collapse, since nobody knew about nuclear fusion. So they got a figure between 20 and 100 million years. Likewise the cooling rates of the Earth, which would have been way off ... |
[
"Does the Earth gets bigger trough the Seafloor Spraeading ?"
] | [
false
] | Today in school we learned sth about plate tectonics and the seafloor spreading. But does the Area of the earth gets bigger because of the Seafloor Spreading ? (srry for my bad English) | [
"No, new seafloor (oceanic lithosphere) is created at ",
"mid-ocean ridges",
" but this, on average, is balanced by seafloor being destroyed at ",
"subduction zones",
", meaning that the surface area of the Earth is constant (but this destruction and creation of oceanic lithosphere are the primary mechanism... | [
"No, because old sea floor is pushed back down into subduction zones where it melts again, at about the same rate that new seafloor is created and spreads out.",
"Anyway, even if this didn’t happen, there is only a finite amount of material that makes up the earth. The earth couldn’t get bigger without new materi... | [
"Thx"
] |
[
"How far can the Earth actually move towards or away from the Sun and still be okay?"
] | [
false
] | I was always told that if it were to move even 10 feet then we would all die. I know this isn't true but what is the exact distance that the Earth's can get from the Sun and still be habitable by humans? | [
"I was always told that if it were to move even 10 feet then we would all die. ",
"This is a myth especially common among Christian communities, the insistence that any tiny deviation in the Earth-Sun distance would obliterate life on the planet being convenient for argumentation about the Earth having been crea... | [
"This is referred to informally as the ",
"Goldilocks",
" zone after the fable. It extends inward for our solar system to about Venus and extends past Mars.",
"While such drastic orbital changes would undoubtedly wreck our climate, these represents the regions where it's plausible to find a temperate planet. ... | [
"The Earth's orbit is not a perfect circle, it varies between 152.10 million kilometers and 147.10 million kilometers, so 5 million kilometers, from the sun. The difference we feel in weather between the two is completely overshadowed by the effects of the earth's tilt."
] |
[
"[chemistry] Why does Cl- not form Cl2 in water?"
] | [
false
] | I work in water treatment but I'm not a chemist. I'm seriously considering further education because the more I learn the more I want to know. I use drop-test kits and a typical water sample can contain 30ppm Cl- (chloride) , 0.3ppm ClO- (free chlorine) and 0.4ppm Cl2 (total chlorine) What stops the Cl- from becoming Cl2? Why does my total chlorine test kit not pick up the chloride? What would have to change in order to make the Cl- form covalent bonds and become Cl2? What are some good sources of information on water chemistry? | [
"Cl- is a chloride anion. It has a negative charge because it has one extra electron in its valence shell (it would've gained this by forming an ionic bind, a bond where one atom gives up an electron entirely, typically a metal). ",
"Water is a polar molecule so ionically bonded compounds such as NaCl can disasso... | [
"Yes, if the Cl- ions want to form neutral Cl atoms (or essentially Cl2) then they need to find a species that would happily take their electrons away. As it turns out, in water alone there aren't any species that would rather the electrons than chlorine.",
"Electrolysis is one way to remove the electrons in a co... | [
"This doesn't really explain why chloride couldn't be oxidized to chlorine, one way or another; that has to do with electronegativity."
] |
[
"If oxygen is thought to be the \"enemy\" of food, and can cause certain foods to spoil, how would an oxidizer like sodium nitrate cause meat to NOT spoil?"
] | [
false
] | It seems counter intuitive, help me understand! Thanks. | [
"Because nitrite was found to inhibit the growth of C.botulinum (Reddy, Lancaster, Science, 19 August 1983: Vol. 221 no. 4612 pp. 769-770) "
] | [
"Oxygen is bad because it allows bacteria to grow. Bacteria consume nutrients in the food and can be toxic to the human body. By itself, oxygen isn't bad at all, but it just has the secondary effect of promoting aerobic bacteria to grow. That's why vacuum-sealing processed food helps to keep it from spoilage. Of co... | [
"Sodium nitrite is actually the main preservative used in cured meat. Nitrate is converted to nitrite in the food, and it's the nitrite that does the job. Actually, it does several jobs: it binds to hemoglobin and preserves the red/pink color, it affects the taste (the characteristic \"sausagey\" taste of cured mea... |
[
"Do we ever see instances of infidelity among species that have been identified as \"mate-for-life\" types?"
] | [
false
] | null | [
"Yes! In fact, there is a huge difference between sexually monogamous (individuals only mate with their SO) and socially monogamous (pairs will live and associate together and take care of their young together, but will mate with other individuals). There is fairly strong evidence that sexual monogamy doesn't actua... | [
"There's a whole section in the book Dr Tatiana's Sex Advice To All Creation about this. The author is the evolutionary biologist Olivia Judson. It's an interesting book, I'm enjoying it. She gives TONS of interesting examples behind the evolution of sex and the sexual practices of different creatures. ",
"Sh... | [
"Male angler fish have no infidelity. You can't exactly cheat on your SO when you're fused to her and everything but your testes has atrophied down to nothing."
] |
[
"When looking in a mirror, do animals understand that they are looking at themselves?"
] | [
false
] | null | [
"Some do! This is actually a common test of animal intelligence: ",
"the Mirror Test",
"Unsurprisingly, several species of apes pass the test, but so do dolphins and orcas, Asian elephants, magpies, and according to one study at least three species of ants."
] | [
"Ants? How on earth would you even objectively asses that? "
] | [
"Ants don't have sophisticated vision but they do have vision. It's a good sense for not bumping into things."
] |
[
"Why can't we treat depression (or just become happy) by actually injecting serotonin?"
] | [
false
] | I've heard that our happiness is purely controlled by our dopamine and serotonin levels, and that depression is mostly a lack of serotonin. Depression is currently treated using SSRIs which control the uptake of serotonin by the body. But why can't we just supplement our serotonin levels to achieve this more effectively? | [
"Couple issues.\nFirst, a physical barrier. Serotonin (5-HT, 5-Hydroxytryptamine), cannot cross the blood brain barrier (BBB) the BBB is a physical boarder that separates/filters what components of our blood can reach our brain. ",
"http://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier",
"Serotonin isn't one... | [
"\"I've heard that our happiness is purely controlled by our dopamine and serotonin levels, and that depression is mostly a lack of serotonin.\"",
"You often hear this, but neither part is quite true. Neurotransmission is not a simple process. The monoamine hypothesis has been firmly shown to be lacking, and does... | [
"I don't think that SSRIs work the way you think they do. The name serotonin re-uptake inhibitors doesn't refer to diet or the blood. When serotonin is released from nerves in the brain, the serotonin then interacts with it's receptors, producing multiple effects in multiple nerve types, one of which is improving m... |
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