title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"If CO2's sublimation point is -78.5C, and the coldest temperature recorded in the Antarctic was -89C, would there have been cardice on the ground as well as regular snow/ice? Were there any observations made about this?"
] | [
false
] | null | [
"Arguably the lowest recorded temperature is actually ",
"92ºC",
" observed via infrared satellite imagery. Theoretically, a ",
"large amount of dry ice",
" should be observable to the Landsat satellites, but Earth's atmosphere doesn't have enough CO2 for significant accumulation. ",
"The last askscienc... | [
"The main problem is that CO2 content in air is in the 300-400 ppm range and thus you won't see condensation at that temperature with such a low partial pressure. Dry ice would still try to evaporate (sublimate) if you had some and put it out in the open air, because it wants to make the CO2 content of the air get... | [
"The sublimation point is the equilibrium between dry ice and a 100% CO2 atmosphere (at sea level pressure). If our atmosphere would be pure CO2 then dry ice would have formed. The atmosphere is only 0.04% CO2, it has to be ",
" colder (about -140 C) before dry ice will form."
] |
[
"Today my professor taught us that Phosphorus is the primary limiting factor in fresh water ecosystems while Nitrogen does the same in salt water and soil systems. What is it about these systems that limits them to different elements?"
] | [
false
] | I am a first year ecology student and we have recently been learning about eutrophication and the effect of nutrient runoff into fresh and saltwater ecosystems resulting in hypoxic "dead zones". We studied a local example in Lake Washington where hypoxia was a result of phosphorus eutrophication from human waste/sewage dumped into the lake in the 50's. When phosphorus in the sewage was identified as the limiting factor causing the algal blooms, treatment plants were installed for the sewage and the water quality improved and surpassed initial measurements. A similar example in the gulf of Mexico is a result of nitrogen fertilizers running off the Mississippi watershed and causing a huge deadzone in the Mississippi river delta. I asked my professor what it was that made them dependent on different elements but he wasn't sure. I don't have a background in chemistry or biology so I was hoping someone could help me out! The only thing I can think of is something to do with salinity or the metabolisms of the primary producers due to pH/salinity differences in salt/fresh water systems. Could anyone with a bit more understanding try to put it in a way that a simple Geologist like myself would understand or point me towards some readings that may further my understanding of the processes at work? A bit on Hypoxia/Dead Zones in the Gulf Of Mexico Lake Washington Study | [
"1st thing of interest is the Redfield ratio number: the ratio of carbon:nitrogen:phosphorus is 106 C:16N:1P for marine life (dead or alive). For 1 molecule of phosphorous the life form had/needed 16 molecules of nitrogen and 106 molecules of carbon.",
"Nitrogen is not a limiting factor in freshwater systems beca... | [
"Thank you for this easy to understand explanation. I feel a little embarrassed since I study quite a bit of Geology as well and had a strong inkling that the phosphorus abundance in the oceans was related to a geologic process and nitrogen was more limiting due to it's atmospheric nature.",
"The Redfield ratio i... | [
"No problem. I wrote this before dozing off really late yesterday so I apologize for any typos. The nitrogen cycle is actually a bit more complex than the phosphorus cycle as different types of organisms can produce 4 classes of nitrogen products: ammonia based, nitrate, nitrite, and nitrogen. With phosphorus, it's... |
[
"Do other languages indicate sarcasm in speech the same way as English?"
] | [
false
] | That is, stressing and drawing out the sarcastic portion of the sentence, raising the pitch a bit. I.e., if you were at a concert and thought the band sucked but your friend liked it, "Isn't this band great? "Yeah, they're " I guess in other words, if you listened to a language you didn't understand, could you tell when the speaker was using sarcasm simply from the sound? | [
"Here is one journal that can be looked at for information: ",
"Acoustic markers of sarcasm in Cantonese and English.",
"Direct Cantonese-English comparisons revealed one major distinction in the acoustic pattern for communicating sarcasm across the two languages: Cantonese speakers raised mean F0 to mark sarca... | [
"Yes. The first study showed that English speakers indicate sarcasm by lowering the voice, while it's the opposite for Cantonese. French speakers draw out the words and raising the voice. Mexicans slow their speech and emphasize certain parts of the words.",
"So actually it's pretty different from language to lan... | [
"The prosodic marking of sarcasm (stress/intonation/etc) should vary a lot from language to language, simply because different languages have different prosodic systems, and emphasizing something you don't really mean will be done differently. ",
"But it's interesting to note that \"emphasizing something you don'... |
[
"Why doesn't your metabolism speed up when eating a lot of calories?"
] | [
false
] | I know that when you're fasting, your metabolism consumes less calories to conserve energy, so if you're eating to many calories, why doesn't your body burn calories faster? | [
"We do. Just not enough for some peoples' intake...\nPost-prandially (after a meal) we speed up our basal metabolic rate via 5-HT, insulin, secretin and a plethora of other hormones that respond to increases in blood sugar levels, satiety and even the lower GI stretching. (etc.)\nHowever, that is more aimed at prim... | [
"You are correct, but the heavier man uses more energy mainly because he ",
" more; he doesn't need more because he is big or something like that. This does not directly answer OP's question, which was why do we not burn more calories when we eat too much (presumably he meant when also corrected for our body's ne... | [
"It does. Metabolism is just the set of processes going on in an organism, and a shorthand for the energy consumed by those processes.",
"Your metabolism is based roughly on your mass, activity level, and food intake. Raise any of those and your metabolism goes up. A 200 pound man has a much higher metabolism t... |
[
"How powerful/fast of a CPU could we produce if it were the size of a typical video card? The size of an entire motherboard?"
] | [
false
] | [deleted] | [
"Yeah, making the circuits bigger would make it much worse. In general smaller circuits are more efficient because the same signal is transmitted over a smaller distance. Instead, you want to increase the effective area of heat dissipation, which is what all cooling devices do in some sense or another."
] | [
"They would be able to support higher temperatures, but they would be much slower. I don't remember the exact numbers offhand, but to illustrate - roughly - a CPU accessing its level 1 cache is 10 times slower than the processor speed. Level 2 cache is 100x slower, ",
". The same CPU accessing its RAM is about... | [
"The ",
"Larrabee",
" cpu was a ",
" large processor (it had 32 cores of with 4 hardware threads, giving an effective core count of 128 using 16-wide SIMD units), and was something like a ",
"square inch",
". The ",
"next generation CPUs",
" in that line are expected to be about double the number of p... |
[
"Does gravity work on the time 'dimension' or just the spatial 'dimensions'?"
] | [
false
] | I don't exactly know what I'm asking here. But if there were a of some kind that were slightly 'before' some other , would that bring the 'forward'? | [
"With a Newtonian view of gravity, such a question doesn't really make sense. Time is just a label that we use to distinguish different states of particles and how they change. So things at different times don't have effects on things at later times, except indirectly, by causing motion that changes the states at a... | [
"Yep, that's right. In fact changes in gravity propagate at the speed of light."
] | [
"Not only does gravity warp the time dimension, the fact that it does is really important in explaining why you appear to fall in a gravitational field.",
"Imagine a ",
"Minkowski diagram",
", with x as the position coordinate and time on the y axis. A slope of 1 represents moving at the speed of light. If yo... |
[
"How does quantum indeterminism affect macroscopic events?"
] | [
false
] | Can quantum indeterminant events snowball/butterfly effect into changes at larger scales, or does it not affect anything beyond the movement of particles? Do all states of affairs observable to us with the naked eye still obtain out of necessity as in classical determinism? | [
"Due to ",
"sensitivity to initial conditions",
" being a general property of many-particle systems, and macroscopic things being made out of ~10",
" atoms, certainly quantum indeterminacy generally produces ",
"butterfly effects",
" that propagate to large distance scales. The answer to your second quest... | [
"Quantum mechanics is a deterministic theory. Heisenberg's Uncertainty is a general feature of ALL wave phenomena, whether quantum wavefunction or ocean wave. ",
"Your first point depends on the interpretation. The second one is very debatable. Sure you can derive the Kennard uncertainty from the point of wave me... | [
"Right, I had the Copenhagen interpretation in mind when asking the second question."
] |
[
"Vodka used to treat dog with anti-freeze poisoning, what is the pathophysiology behind this?"
] | [
false
] | I'm curious as to how the worked on a biological level, as this is a treatment I've never heard of for humans. Is it something canine specific? How did the alcohol stop the renal failure? | [
"Antifreeze poisoning is due to the ",
"ethylene glycol",
" in it. Ethylene glycol by itself is not intrinsically toxic (and in fact has a rather sweet taste). However, it can be metabolized into glycolate, glyoxylate, and oxalate, which can cause organ damage (particularly to the kidneys) as well as lead to ... | [
"Humans can and do ingest ethylene glycol, this treatment is not really similiar to chronic liver injury due to alcoholism. It seemed like that's what you were implying, so I wanted to clear that up. "
] | [
"Works for people too. The ethanol binds to the same sites (enzymes? I don't really know specifically) as the alcohols in the antifreeze. The ethanol bond is much stronger and thus displaces the antifreeze, preventing the antifreeze from doing anything. You keep those sites loaded with ethanol until the antifreeze ... |
[
"Why do nails stick in car tires instead of being shot out due to tire pressure?"
] | [
false
] | null | [
"There is a lot of friction between the tire tread and the sides of the nail. There is only a very small surface area (the end of the nail) for the pressure to act on, so the net push outwards is very small, not enough to overcome the friction against the sides of the nail."
] | [
"Apparently, 2.4mm is roughly the diameter for \"13 gauge\" nails, commonly used in construction. So 1.2mm would be the radius, and we can calculate the area at pi * r",
" . Also, my tire pressure is roughly 207kPa.",
"The cross-section of the nail and tire pressure on that area will tell us how much pressure i... | [
"Mostly a first guess, based on the idea that you'll have a ring of contact between the two objects, the three parameters that I can see being the coefficient of friction between them, the thickness of the tire contacting the nail, and the circumference of the nail. Kind of a \"spherical cow\" approximation.",
"A... |
[
"Do automatic weapons have any other power source except for the explosion of the gunpowder in the bullets?"
] | [
false
] | You hear of guns that can shoot at so many hundred rounds a minute, but what determines this speed? Guns don't have batteries, right? So does it use some of the energy from the explosion of the gunpowder in the first bullet to move the second bullet in and fire that? So what would determine the number of rounds per minute? How much energy it has to do the change over and how much resistance in moving a round in? Could you speed it up somehow? I have no real experience with guns, so forgive me if this is a dumb question. | [
"It's only a dumb question if you don't learn anything from the answer.",
"Let me first explain the action of an M16, and then I can illustrate changes that'll make a difference, in order to address the other questions you raise.",
"We'll start with 1 round ready to fire, and the gun ready to go. When you pull ... | [
"Most automatic weapons redirect a small amount of the exploding gases to power the mechanism. Some larger automatic weapons may use an electrically or hydraulically driven mechanism. A few experimental-type pistols and rifles have used spring, electrically or pneumatically driven mechanisms, though none have ever ... | [
"I have never heard such a distinction before. Please provide some source for this.",
"Non-externally powered firearms usually considered machine guns include the M2, M1919, M1917, M60, M249, M240, and scores of others from non-US armies."
] |
[
"Could you fly a helicopter/drone on Enceladus?"
] | [
false
] | With NASA's planned Orbilander going to Enceladus, could it host a small rotorcraft like Perseverance did with Ingenuity? I read it does have an atmosphere of water vapor. | [
"No, to the point that it's not what you would informally call an atmosphere.",
"I was going to post something about so-called surface boundary ",
"exospheres",
", but it's not clear from an initial read to what extent Enceladus is hanging onto the outgassed materials for long enough for it to count."
] | [
"A prime candidate for flying helicopters/drones would be Titan; that moon is unique in being the only one in our Solar system with a considerable atmosphere. It's even ticker then Earth's. The problem is that it's very cold (90K)."
] | [
"NASA is working on a Titan helicopter: ",
"https://en.wikipedia.org/wiki/Dragonfly_(spacecraft)",
"Unlike Enceladus it has a significant atmosphere."
] |
[
"How close do a particle and its antiparticle have to be to annihilate?"
] | [
false
] | Would it also matter through wich interaction they annihilate by? Since the electromagnetic force has a much further range than say the weak force would electron-positron annihilation be able to then occur further away via electromagnetic interactions rather then weak interactions? | [
"For any interaction among fundamental particles (whether it counts as annihilation or not), there isn't a sharp cutoff. The probability of the interaction becomes lower as the trajectories of the incoming particles get further apart.",
"Each individual reaction has a cross section, and if you set that cross sect... | [
"The cross section for ",
" scattering under a Coulomb potential is infinite (under some approximations), but elastic scattering is where the two particles basically just bounce off each other, or even just perturb each others' trajectories a bit. That's not annihilation. To get the cross section for annihilation... | [
"I thought the scattering-cross section of a coulomb potential was infinite, so would the particles be able to annihilate at any distance just with less probability?"
] |
[
"What are the equations governing the Strong and Weak nuclear forces?"
] | [
false
] | The basic equations of gravity and electromagnetism are taught in high school. I've taken university physics (including basic problems with Schroedinger equations) and I've never seen an equation for the or the (even the wikipedia pages referenced here don't have them). I've never seen them in a textbook. I've never found something I recognize as an equation for them online. Why is that? How is the force of interaction calculated? | [
"Strong force",
"Weak"
] | [
"There aren't any is the short answer.",
"Force, as classically defined, is about a change in momentum. We've come to learn that all of these momentum exchanges are governed by the exchange of particles called \"gauge bosons.\" Each force has at least one boson associated with it. EM exchanges photons, Weak excha... | [
"great answer."
] |
[
"Question in regard to science news."
] | [
false
] | null | [
"Hello: This submission is stuck in the spam filter, and probably won't be let out mainly because it is not something we really discuss here. However, you might be interested in looking at the sites ",
"physorg",
", and ",
"ScienceDaily",
". Thanks! "
] | [
"Thank you very much! :)"
] | [
"You're most certainly welcome. And, if you find some scientific ideas in those sites that you don't understand, or want to know more about, come back and ask a question, and hopefully one of our panelists can help!"
] |
[
"Is the radiation we receive throughout our lifetime from everyday electronics even close to harmful to us?"
] | [
false
] | Im talking about things like computers, microwaves or cellphones. I know its not a huge significant amount, but over long periods of time(years, not hours) can they have effects on humans? | [
"Radiation isn't a summing process. Either the radiation has enough energy to cause damage, or it doesn't. Computers, microwaves and cellphones do not emit or receive radiation with enough energy to cause ionization in your body. "
] | [
"Because they are exposed to ionizing radiation, which is able to damage cells or RNA. A microwave oven for example only emits weak non-ionizing radiation. It cannot cause damage to your body. "
] | [
"Keep in mind that microwaves and radio waves carry less energy than visible light. So if ",
" waves are energetic enough to damage cells, then we're screwed anyway :)"
] |
[
"A sphere is the solid with the highest volume/surface area ratio. Is there a solid that's the opposite of it? That is, that has the lowest volume/surface area?"
] | [
false
] | null | [
"Another easy example where one can verify this property oneself is this: Consider a cube whose sides have lengths a=b=c=1. Now, double a and halve b. Do this again. And again and again. After n steps, you end up with a new solid whose sides have lengths a'=2",
" b'= 2",
" c'=1.",
"\nThe volume here is still ... | [
"No, there can't be. There are families of solids (for example, those used in the construction of the ",
"Menger sponge",
") whose surface area increases without bound while the volume tends to zero; given one solid in the family, you can always find another one with a lower volume to surface area ratio. The li... | [
"Yes many fractals can be constructed in such a way to have positive or 0 measure with positive surface area."
] |
[
"What keeps us from re-capturing CO2 at the source?"
] | [
false
] | According to article, a company is re-capturing CO2 from the atmosphere, turning it into carbon pellets, and then into diesel fuel. Why can't we make those carbon pellets straight off of the exhaust pipe? Or can we? | [
"Sure you can, but then you need to use a good deal of the energy you get out of burning your fuel in the first place just to do this. ",
"CO2 is formed because it is the stable product of carbon and oxygen combustion. The actual energy you release and use to power your car comes from breaking the more unstable... | [
"Actually, the energy you need to break the carbon-oxygen bonds is the same as the amount you can gain from burning the fuel you make afterwards. Since nothing we do is done at 100% effectiveness, the result is a net energy loss, and in turn even more CO2 released.",
"If the point is to save CO2, we are better of... | [
"The biggest pet peeve of any engineer that understands thermodynamics is when people want to string energy conversions in series."
] |
[
"How will Voyager 1 keep its antenna pointed at Earth once it crosses the heliopause?"
] | [
false
] | Does the spacecraft have thrusters or does it use torquing coils to interact with the heliosphere? How does communication actually find its way back to Earth (if its not LOS that is)? | [
"Voyager 1",
" is at about 122 AU from Earth. Earth's entire orbit ",
"subtends an angle",
" of less than 1 degree, about twice the angle subtended by the moon viewed from Earth. It has a ",
"3 axis thruster system",
", and has only used about half of the fuel it started with."
] | [
"What were you thinking would knock it out of it's current alignment?"
] | [
"Well I was thinking along the lines of them not using a very tight beamed transmission. At the distance they are at relative to each other, a few degrees of spread in the broadcast would cover the whole region of the target. Given there aren't many patterns in natural radio wave sources the return would stick out ... |
[
"Explaining Mechanical Advantage in Rope Pulley Systems"
] | [
false
] | I was hoping that someone would be able to show me how to calculate how much mechanical advantage someone gains from a rope pulley system ie. 3 to 1, 5 to 1, how do you figure this out? | [
"I think it's useful to count the number of strands pulling ",
" on an object. Since the tension must be the same in the entire rope, each loop adds an extra force of tension to the system. (need pictures to illustrate...)"
] | [
"In a block and tackle system, you've usually got a standing block and a moving or running block. The mechanical advantage is the number of \"parts\" of the line that run through or are attached to the moving block.",
"Here's a diagram of several ways you can reeve a tackle system: ",
"Picture",
".",
"In t... | [
"I drew us a picture: ",
"Picture"
] |
[
"Why is electricity cheaper at night?"
] | [
false
] | I'm in the UK and my electrical company charges less for electricity at night when I assume night time is when more people are at home and using more electricity for lights, televisions, computers and heaters. Is it more efficient to produce and distribute electricity at night? Sorry if this question is more economical than science . | [
"Residential demand is only a piece of the puzzle. Business demand during the day outweighs that at night.",
"Take a look at ",
"this",
". Overall demand is higher during the day. ",
"This image",
" shows demand from a hot California day in 1999 -- commercial demand peaks during the day, and even reside... | [
"It's cheap because homes, offices and other power hungry places are mostly switched off. It takes a lot of work to power down power plants and so by offering incentive for people to run washing machines and such overnight, can even out the demand."
] | [
"not only that but they literally need to put it somewhere. That's why they'll sell it to other markets [like Canada to the states] at a loss."
] |
[
"Rockets need to expell mass to go forward, but if you expell the mass at greater speed then less mass need to be expelled, couldn't Rockets just expell the mass at very high velocity to reduce the amount off mass needed to be carried?"
] | [
false
] | The biggest problem with rockets is that they need to carry a large amount of fuel, but what I'm wondering is that a possible future solution to this is to use ion drives that use magnets to expell some amount off mass but to just use a nuclear reactor to increase the amount of energy in the magnets and expell the mass at higher speed to carry less off it. Also could it then be possible to expell only a few particles at extremely high velocity to only have to carry an extremely low amount or am I missing something? Now I know that you can't expell the mass at or beyond the speed of light but even then you can still add and ever increasing amount of energy and therefore momentum giving you greater thrust. Is this possible or is there some physical reason of why it can't happen, I'm speaking from a purely hypothetical standpoint and using technology in the distant future, maybe using super conducting magnets or something. I would love to know some thoughts on this. Thank you P. S. I'm new to reddit so I'd just like to say hi and sorry if I'm doing something wrong, I'm not too clear yet on the rules :) | [
"It's true, that the faster your exhaust travels, the less fuel you need. However, it costs energy to accelerate your exhaust, and higher exhaust speeds require more energy. The result of this is that you also have to budget for how much energy you can generate, as well as what the energy efficiency of your exhaust... | [
"This is exactly what rocket scientists have been working on for decades, and is the principle behind ion engines. As a matter of fact, a measure of a rocket's capability is \"specific impulse (Isp)\" which describes the power of an engine by its exhaust velocity. This is factored into the Tsiolkovsky rocket equati... | [
"By inefficient, i mean energy inefficient. You spend more energy for less delta V. So the tradeoff you get is that although you need to carry less reaction mass, you now need to carry more energy."
] |
[
"Why doesn't HSV-1 transfer to other parts of your lip? Does genital herpes function the same way?"
] | [
false
] | null | [
"Herpes resides in your nervous system, not your lips. The infection you see as a cold sore is an inflammation response to a newly reactivated bit of virus at the tip of a nerve under the skin that colonizes some minor damaged tissue on the lips.",
"The reason it is reactivated is not clear: herpes is usually dor... | [
"I would like to clarify a bit on immunocompetence and herpes spreading. Herpes does not spread in immunocompetent individuals because their immune system is able to control the herpes infection. However, a competent immune system is not able to develop sterilizing immunity to HSV because it develops latency. Durin... | [
"The mechanism is poorly understood but we do know what herpes genes are activated first. Since PNS neurons lack DNA polymerase, the LAT activates transcription of the herpes own thymidine kinase genes in order to replicate. Also, the protein ICP0 has been shown to be required for initiation of transcription of man... |
[
"How close are we to \"test tube babies\"?"
] | [
false
] | null | [
"I'm not sure exactly what you mean, but we've had \"test tube babies\" (in vitro fertilization) since the 70s... "
] | [
"Oh I see. In that case, not at all close"
] | [
"Yes. But how close are we to continuing that process and keeping it outside the body for the duration of pregnancy"
] |
[
"After the heart stops, how long do synapses keep firing? And other questions."
] | [
false
] | [deleted] | [
"Archives d'Anthropologie Criminelle, 1905:",
"\"Here, then, is what I was able to note immediately after the decapitation: the eyelids and lips of the guillotined man worked in irregularly rhythmic contractions for about five or six seconds . . . I waited for several seconds. The spasmodic movements ceased. The ... | [
"The electrically active cells will fire at their basal rates until they can't maintain their electrolyte gradients (Na+, Ca++, Cl- out, K+ in). For most neurons, this will be \"not at all\", but doubtless some have an underlying rhythmic pace a la pacemaker cells in the heart. ",
"A fair proxy for the farthest... | [
"There was a russian experiment where a guy hooked up a severed dog's head to a pump. The head responded to several different stimuli: light, sound, tactile. ",
"Footage from the experiment"
] |
[
"Why exactly does E=MC^2 ?"
] | [
false
] | null | [
"Ah. That's actually pretty interesting. He came up with his theory for how electromagnetism works when the source is moving (what we now call special relativity) and looked at what happens when the object emits radiation. He realized that his theory implied that as radiation with energy E is emitted, the mass must... | [
"I was thinking more along the lines of a derivation/explanation of how Einstein came about forming this equation."
] | [
"You should really really read this book: ",
"Why Does E=MC",
" (And Why Should We Care?)",
"http://www.amazon.com/Why-Does-mc2-Should-Care/dp/B004LQ0ICE/ref=sr_1_1?ie=UTF8&qid=1302835764&sr=8-1"
] |
[
"Does the effectiveness of Positive/negative reinforcement change if the receiver is aware that they are being used? Why/why not?"
] | [
false
] | null | [
"Motivation is a really interesting subject, and one with a ton of nuance between a number of different factors that all interact with one another. Largely, reinforcement models are used for things like behavior modification, for aspects that tend to be very deeply seated within the psyche (like hoarding), or physi... | [
"Hey, thanks! I learned probably as much from this post as I did from all of my \"Intro to Psychology\" Class last semester..."
] | [
"Board certified behavior analyst here. The answer to this question is no, not if you have a true reinforcer (or aversive stimulus, for negative reinforcement). Often times we think we are using positive reinforcement when we say \"good job\" or the like, but that isn't necessarily reinforcing for everyone. ",
"P... |
[
"What would be the \"evolutionary\" reason for us wanting to be completely covered by blankets (can't be exposed, can't have arm dangling over)?"
] | [
false
] | null | [
"I think the question is flawed. There has not been any evidence that indicates what you're claiming is true for all people. "
] | [
"What I mean is that there is no evidence to indicate that an evolutionary reason exists."
] | [
"Just because it's not true for all people doesn't mean the question flawed. Not everyone is light skinned and not everyone practices rape, but you can still ask about evolutionary reasons for those things."
] |
[
"How do we determine how many stars are in The Milky Way?"
] | [
false
] | I've tried to look this up, but every site that I go to either goes into detail explaning how we estimate the number of stars in galaxies, but never much for the Milky Way. So how do we do it? | [
"Stellar counts are always a guesstimate from an assumed distribution of stellar masses and overall stellar mass of the galaxy. To work out the mass distribution, we can literally just count up stars, using differences in their spectra to work out what their masses are. To get the total mass in stars, we can look ... | [
"It's because we can get an outside view of the other galaxies, but we can't get a full view of our Galaxy, since it's well... Really big, and we are inside it. Imagine if you were on a cruise ship and so another, you can't see your ship but you can see the other one in it's full size."
] | [
"thank you for that, but that isn't the question I asked. The question was (essentially) how did we come up with the estimate for how many stars are in the Milky Way."
] |
[
"If alpha centauri went supernova, how long until the effects reached Earth?"
] | [
false
] | I mean all of the stars in the alpha centauri system. | [
"Alpha Centauri A and B are each about the size of the Sun. The third, proxima centauri is much smaller. All are too small for a supernova. At the end of their lives A,B, and the Sun will grow into red giants eventually blowing off most of their mass leaving a white dwarf.",
"(It won't happen) but if a supernov... | [
"How far away is the nearest large enough star?"
] | [
"150 light years, but it'll be a few million years before it will have a chance of going supernova."
] |
[
"Particle accelerators - is bigger always better?"
] | [
false
] | Let say we are able to build a particle accelerator the size of earth's orbit around the sun and are able to harvest 1% of the sun's output as energy source. What types of experiment would we be able to perform that we cannot now? Would the size of Mars' orbit and 2% of the sun's energy be much better, a little better, or about the same? | [
"So it's kind of a combination of things. First it matters what particle species you wish to collide. Light particles like electrons and positrons generally are accelerated linearly, to reduce syncrotron radiation. Protons and the like get the advantage of circular accelarators (you can keep passing the particles t... | [
"so the size doesn't really matter here exactly (I'll presume that the engineering challenge of providing the acceleration within some length is solved by the same magical engineers that let us harvest 1% of the sun's energy). But let's say after all the energy losses 1% of the sun's energy (let's say in 1 second),... | [
"ah, so let me put it this way, there's one remaining test of high energy particle physics. At a certain energy scale, we expect that the strong force will behave an awful lot like the electroweak force ",
"about 10",
" eV",
", so we'd be able to probe that scale along the way (we have about 10",
" more ene... |
[
"How large would an asteroid need to be to have enough gravitational pull so that a human could walk along it without needing to \"hold on\"?"
] | [
false
] | For clarification by "hold on" I mean being able to walk in a standard space suit and not need and special foot clamps or the like. | [
"hop around like a kangaroo",
"A lot of people would approach this question in terms of escape velocity but that's not a good way to look at it because even if you cannot reach such velocity, it'll still be quite uncomfortable to be able to launch yourself up several hundred meters by a mere jump, even if this ju... | [
"I won't use the bean, because that's both irregularly shaped, difficult to pack, and meaningless to anyone who isn't familiar with the silver bean in Chicago. Hopefully these other calculations will give you a sense of the scale.",
"A sphere with a radius of 5.6km has a circumference of around 21.9 miles, meanin... | [
"In order to walk on a body, the escape velocity would have to be greater than the speed of the movements a human makes whilst walking. My best guess is ~5m/s.",
"The best way to get a relationship between mass and escape velocity is via conservation of energy.",
"GMm/r",
" = 1/2mv",
"You can eliminate the ... |
[
"Is it possible to learn physics concepts on your own?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"A good home for this question is our sister subreddit ",
"/r/AskScienceDiscussion",
" because of its open-ended or speculative nature. Please feel free to repost there!",
"Please see our ",
"gui... | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"A good home for this question is our sister subreddit ",
"/r/AskScienceDiscussion",
" because of its open-ended or speculative nature. Please feel free to repost there!",
"Please see our ",
"gui... | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"A good home for this question is our sister subreddit ",
"/r/AskScienceDiscussion",
" because of its open-ended or speculative nature. Please feel free to repost there!",
"Please see our ",
"gui... |
[
"How were the photographs of Betelgeuse taken?"
] | [
false
] | In astronomy 101 I learned that stars are point sources of light. Even the most powerful optical telescope cannot resolve a star into a disk. If this is still true, how were the recent photographs of Betelgeuse taken? Are these photographs at all or are they digital representations of spectrographic data? (with apologies to the moderators for second pass at this) | [
"If this is still true",
"It's not. That phrase has been taught in Astronomy 101 for decades but technology has moved on. We now have telescopes powerful enough, and optical processing techniques sophisticated enough, to generate a true disc image of a star. We can get true optical images, not just digital simula... | [
"Betelgeuse is actually the third largest star by angular diameter in the sky after the Sun and R Doradus. With 50 milliarcseconds (mas), it appears almost as large as Pluto (60 to 110 mas, depending on its distance).",
"With current, modern telescope, that is large enough to simply point the telescope at it and ... | [
"In terms of raw resolution, seeing a planet as isolated dot can be easier than resolving features on a star. The orbits are usually larger than the stars (trivially true within a specific star system, but also if we look at different systems). The contrast needs to be much better, however.",
"Resolving features ... |
[
"Why don't we pass down our vaccinations to our offspring?"
] | [
false
] | null | [
"In the adult body there is only a select population of cells whose DNA will be used to create the offspring. These cells are called germ cells and arise from the precursors in the germline cells. In other words, only sperm and egg cells will be used to make the offspring, and so if the offspring is to inherit any ... | [
"There is a certain amount of inherent immune system that we ARE born with. These are immune cells such as macrophages that will attack bacteria on sight, or kill virus-infected cells. This kind of general immunity IS passed down, but that's not what vaccines do. ",
"Acquired immunity (the kind you get from vacci... | [
"This isn't true. IgG Antibodies do cross the placenta, but their lifespans are finite (the last maternal antibodies tend to fade around six months of age). The real reason immunity isn't permanently transferred is because the actual WBCs which produce the antibodies indeed don't get passed, so once the antibodie... |
[
"Why do sneezes typically come in two's?"
] | [
false
] | A student asked me this the other day... I was about to dismiss the question as coincidental, but I thought about it. Sneezes do come in two's or multiples of two's a lot of times. Coincidence? Or is there a biological purpose? EDIT: Since no one agrees with my original premise... How about why sneezes are always more than one? | [
"Confirmation bias."
] | [
"I always have a minimum of 3."
] | [
"I usually have one, sometimes two, never three or more. I know people who have three or more.",
"And yes, I'm talking about sneezes and not other things."
] |
[
"If you drop an electric appliance into water and then remove the appliance, does thew water stay charged?"
] | [
false
] | I feel like this is such a dumb question, but I honestly don't know the answer. Say there is a bath tub full of water and I drop my hairdryer into the water while it is turned on. If I unplug the hairdryer and pull it out of the tub, will the water still be charged? | [
"No. To put it in non-scientific terms, the water makes it easier for the electricity to jump from the appliance to your body and then to ground, but does not itself retain electricity. ",
"That's academic, however, as modern bathrooms are required by electrical code to have a ground-fault circuit-interrupting ou... | [
"Gfci's can react as fast as 1/30 of a second, and will trip with an imbalance as low as 4 miliamps"
] | [
"Keep in mind that water doesn't conduct electricity, the impurities in it do."
] |
[
"Why was expansion of space greater than 10 times lightspeed 12.85 billion years ago, but has since slowed down and is now accelerating?"
] | [
false
] | Given that we can see galaxies as they were approximately 900 million years after the Big Bang And further given that those above mentioned galaxies were at least 20 billion light years apart from far edge to far edge at 900 million years after the Big Bang. Then we can deduce that at that time these galaxies were flying away from each other at an average speed of, or at least, the expansion of space was proceeding at an average speed of, over 10 times the speed of light. We can calculate that by assuming that, in the most conservative case, we are at the center of the Big Bang, and the most distant galaxies were at least 10 billion light years distant from our location at that time. If these galaxies show a red shift of z=8 or less , and that equates to a speed of significantly less than a relative speed of 10 times the speed of light. And further, if space is currently expanding at an accelerating rate Then the above considerations mean that the expansion of space was faster than it is now, and so at some time slowed down. Yet now the expansion of space is accelerating, so the expansion of space has speeded up after it previously slowed down. So my question is this: What possible mechanisms can possibly explain why the expansion of space was greater than 10 times the speed of light 12.85 billion years ago*, but has since slowed down and is now accelerating? *(Date of the "Big Bang" = approx. 13.75 billion years ago, minus 900 million years = about 12.85 billion years ago). | [
"When the universe was dominated by dark matter in the past, the expansion rate was slowing down. This is because normal matter acts normally... its gravity attracts things, and thus slows down the expansion.",
"Recently, the expansion rate has been speeding up. This is because dark energy now dominates the uni... | [
"An ignorant and naive non-scientist such as myself might conclude that the addition of \"dark energy\" and \"dark matter\" and the \"expansion of space\" are simply ad hoc additions to prop up the flawed big bang theory and other shortfalls of current scientific theory.",
"You might conclude that, but you'd be w... | [
"This is a really intriguing question! And for someone (like me) who has no possibility of answering it, I look forward to the equations and lingo surrounding a possible theory / answer!"
] |
[
"Got questions about archaeology, shipwrecks, or the archaeology of shipwrecks? Ask them here!"
] | [
false
] | Ask away! This isn't really an AMA, as I'm not keen to talk about myself too much, but I'm happy to answer questions about the field! | [
"It would be irresponsible for me to put that on the internet.",
"Let me clarify: professional ethics that let me stay in the scientific community (publishing, presenting etc) don't let me help artifacts enter the private trade. Telling people \"here are three rich wrecks\" on the internet falls too close that u... | [
"Have you read Throckmorton's \"The World's Worst Investment: The Economics of Treasure Hunting with Real Life Comparisons\"? It lays out the case pretty nicely for the unprofitability of most treasure hunting projects.",
"I have no problem with private archaeologists. I do have a problem with treasure hunters.... | [
"Sidenote: One weird but interesting application has been to use lead from",
" shipwrecks to line neutrino detectors",
". "
] |
[
"In thermochemistry is ΔH=q, or is ΔH=-q?"
] | [
false
] | null | [
"I understand that q can be negative (exothermic) or positive (endothermic). From what you are saying, the signs of ΔH and q are always the same. When enthalpy is increasing (positive ΔH), then heat of the system is also increasing (positive a). Then vice versa for enthalpy decreasing and heat leaving?"
] | [
"I understand that q can be negative (exothermic) or positive (endothermic). From what you are saying, the signs of ΔH and q are always the same. When enthalpy is increasing (positive ΔH), then heat of the system is also increasing (positive a). Then vice versa for enthalpy decreasing and heat leaving?"
] | [
"Thank you."
] |
[
"Does a star oscillate between ignition and non-ignition at the beginning?"
] | [
false
] | So the gas cloud collapses and finally reaches the pressure and temperature to ignite as a star. But then I am thinking, the fusion explosion of the ignition pushed gases outwards, reducing the pressure. Does it happen that the pressure get reduces so much, that ignition stops again? Then we have to wait until the gravity pulls everything back in again, igniting a second time. Then third, forth... and so on. Like a pendulum. Until the star reached it's equilibrium between gravity-pressure and ignition-pressure. Or does it ignite once and burns until the end, because the equilibrium is reached the first time? And as a bonus: Does it happen that a star ignites, but then pushes too much gas away as solar wind, so that it kills itself of 'shortly' after and now no longer has the gravity to ignite a second time? | [
"So the gas cloud collapses and finally reaches the pressure and temperature to ignite as a star. But then I am thinking, the fusion explosion of the ignition pushed gases outwards, reducing the pressure. Does it happen that the pressure get reduces so much, that ignition stops again?",
"First off, fusion ignitio... | [
"Not just ",
" more gradual, but definitely more gradual. Different species (e.g. lithium, deuterium) start fusing at different temperatures, and their energy generation rates have different temperature dependencies.",
"YSOs (young stellar objects) are often variable. The prototype, T Tauri, expels blobs of gas... | [
"Your teacher is correct-- the hydrogen \"burning\" which fuels stars is a nuclear fusion reaction, like what happens in a hydrogen bomb, not a chemical reaction like when we burn methane or some other chemical by oxidizing it.",
"Astronomers frequently refer to the nuclear fusion which powers stars as \"hydrogen... |
[
"Avogadro's number is the accepted number of molecules in one mole of a substance. How was this number derived and what experimental evidence proves it to be the correct number?"
] | [
false
] | I understand that it was Loschmidt who truly determined this quantity, and I have read that his calculations involve the average velocity of molecules in a gas and their respective diameter, but this just raises further questions in my mind. How does one measure the average velocity of individual molecules? How does one measure the diameter of a molecule? | [
"Here is an easy experiment that gives you a rough approximation. It may give you an idea about how you can measure it:",
"Have a cylinder of a certain material lets say monocrystalline silicon. You know the mass, you can measure the volume. This means you can calculate the density of your cylinder.",
"You know... | [
"No, ",
"Loschmidt's number",
" is a different one. I'd credit ",
"Perrin",
" with the most accurate determinations of his day, recounted in his book ",
"Atoms",
" (",
"). (Or just ",
"skip to the results",
" on page 206) They were sufficiently accurate and done in so many different ways, for it t... | [
"http://en.wikipedia.org/wiki/Avogadro_constant#Measurement"
] |
[
"Why is there this weird pattern of frost on my airplane window?"
] | [
false
] | null | [
"What hole?"
] | [
"The pressure-regulating cylindrical tunnel that's more visible in the second picture. It seems to connect the gaps of two panes of window."
] | [
"http://www.quora.com/Why-does-a-frost-ring-form-in-a-circle-around-the-inner-hole-in-airplane-windows"
] |
[
"Whats sulfuric acid for? Other than dissolving dead bodies?"
] | [
false
] | null | [
"Generally you don't use sulfuric acid as a solvent, though it can be useful in certain circumstances where nothing else can dissolve your organic compound as it can protonate and solvate nearly anything.",
"In the lab it is mostly used in diluted form as a versatile strong acid for a wide range of tasks, as well... | [
"So can you buy straight sulfuric acid at a store or just like in diluted forms? "
] | [
"I think concentrated sulfuric acid is restricted but you should be able to buy less concentrated grades. "
] |
[
"If forced to spin, whether for a game or as a contest, what is the most effective way to avoid sever dizziness?"
] | [
false
] | null | [
"According to my daughter who used to dance, you just get used to it. Spotting just gives you a way to maintain orientation while your inner ears are going crazy.",
"Also, my sifu once gave us a one day bagua seminar, where part of the the practice was spinning. You don't get over being dizzy, you just learn how ... | [
"Do what ballerinas do. Keep your head in one position and turn it fast and stop, fast and stop, fast and stop. This is precisely why they do this - to not get dizzy."
] | [
"It is an orientation thing. Keep a reference point.",
"from ",
"wikipedia:",
"The goal of spotting is to attain a constant orientation of the dancer's head and eyes, to the extent possible, in order to enhance the dancer's control and prevent dizziness."
] |
[
"What part of the \"stink bug\" actually smells?"
] | [
false
] | null | [
"The adult pentatomoid odours are due to light yellow oily materials produced by paired tubular glands and accessory glands. Their secretions are accumulated in a single reservoir (occasionally in paired reservoirs) situated ventrally in the metathorax. This reservoir opens to the exterior at each side between the ... | [
"Could you perchance tell me which of those chemicals is also present in cilantro (as I find it to smell/taste just like stink bugs)."
] | [
"Stink bug chemicals and cilantro taste are indeed similar chemicals (aldehydes)!!!",
"http://chenected.aiche.org/chemicals/stink-bug-breakdown/",
"Spectrometry to determine at least two of the compounds present in the stink bug \nodor: the aldehydes trans-2-decenal and trans-2-octenal",
"Cilantro taste is r... |
[
"Watched Hawking's 'Curiosity' last night, question: if there was no time before the Big Bang, why at a specific instant did the universe spontaneously come into existence?"
] | [
false
] | I thought the program was great for the layman and although I wish they had gone into how some parts of the universe are into more detail, it would have taken too long and not been relevant to the question. Related (same, reworded) question: If the conditions of the pre-bang singularity (is that what you'd call it?) were unchanging because there was no time, then there was no internal change to cause the Big Bang. And there's no external change because there is no anything. This is sort of similar to paradox (which isn't really a paradox, it has a fundamentally flawed assumption, right? That there are universal, discrete instants in time.) Perhaps there is no answer. Hence the term "spontaneously". I suppose to someone not versed in quantum physics and the beginning of the universe, "spontaneously" means "magic", with some underlying cause. We have to dispel that connotation/assumption. Thanks in advance. | [
"Imagine that you want to make a long trip and decide to always go north.\nIt's easy: you know how to use a compass, you just have to follow this direction. But then you reach the North Pole. Some people have warned you that the concept of \"north\" is a bit singular there. Your compass isn't indicating anything us... | [
"I think what he is asking is what was before time?",
"What is north of the North Pole?",
"If change requires time then how could the universe change to suddenly have time?",
"I don't have an answer because I don't have any words to describe it. \"Suddenly\" is time-related so isn't relevant in this context. ... | [
"I think what he is asking is what was before time?",
"What is north of the North Pole?",
"If change requires time then how could the universe change to suddenly have time?",
"I don't have an answer because I don't have any words to describe it. \"Suddenly\" is time-related so isn't relevant in this context. ... |
[
"How exactly does chronic high blood sugar cause damage to the body?"
] | [
false
] | I know high blood sugar can cause organ damage, eye damage and can lead to people needing amputations, but why is this exactly? Whats going on in the body? Edits: Thank you all so much for your responses, I'm reading through all of them. | [
"Glucose is a surprisingly reactive molecule. When it's carried in the blood, it reacts with both hemoglobin (creating Hb1Ac, which is monitored in diabetics) and the vessel walls. This can make vessel walls rigid and leaky.",
"The effects are first seen in the microvasculature, which due to their size are more v... | [
"The damage is always occurring, it's just that at lower levels of blood sugar it occurs at a rate that the body can deal with and repair.",
"If you want to know more, look up AGE (advanced glycosolation endproducts) and RAGE (receptors for advanced glycosolation endproducts) - a mechanism that mediates some of t... | [
"But we always have glucose in our blood. why is 125 mg/dL the cross-over point for when it starts doing damage versus not?"
] |
[
"Do we know how close we are to the center of the universe?"
] | [
false
] | null | [
"We are at the center of the observable universe. Beyond that it is thought to be unbounded with no center."
] | [
"That makes sense. I didn't know if we had any idea about the size of the universe outside what is observable"
] | [
"This should answer your question:",
"http://youtu.be/5NU2t5zlxQQ"
] |
[
"If water boils at 100 degrees Celsius and turns to steam (water vapour), how is it that we can see water vapour in our breath when it is cold?"
] | [
false
] | null | [
"Steam is actually invisible, if you boil a kettle and look at the spout you will notice that the air is invisible for about an inch or so, than you see the vapour. What you see is when the air starts to cool down and the water vapour becomes visible (condenses). The higher the temperature, the more water vapour th... | [
"We see ",
" water vapour after it is exhaled. This happens because the air we exhale expands and cools as it leaves our body. Cool air holds less vapour than warm air so some of the vapour in our breath turns to small droplets of water."
] | [
"Dry steam is invisible, it is hot enough to be water ",
", wet steam is what we're familiar with, it contains water gas and saturated water droplets. ",
"http://www.corrosionpedia.com/definition/420/dry-steam"
] |
[
"Could quantum entanglement be used to transmit information almost instantaneously over large distances?"
] | [
false
] | null | [
"No",
".",
"[...] no-one knows the state of the particle until it has been observed, but you still cannot affect the state of the particle [...]"
] | [
"No. You ",
" use quantum entanglement to transmit information, but doing so requires some other information which would have to be transmitted at the speed of light."
] | [
"You can't influence the outcome of a measurement on that entangled system in such a way that someone on the other end could tell if you'd influenced it or not. So you'd have to tell them something classically anyway."
] |
[
"How can GPS co-ordinates have poor precision?"
] | [
false
] | As I (hand-wavily and probably incorrectly) understand it, GPS co-ordinates are calculated from the round-trip distance to 3-or-more known-position satellites. The intersection of the ensuing spheres gives the location. But GPS-enabled apps always provide a "confidence radius", which they're "pretty certain" that the user is in, rather than an exact location. How is that the case? The only imprecisions I could think of are the signal speed of the satellite signal, or the processing time of the satellite itself, and I would guess that both of those would have a tiny variance (in the latter case, the satellite could return the processing time along with its response to take that out of the equation). | [
"http://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System",
"The sensitivity of the GPS signal is quite high. The following is to give you some perspective:",
"Light travels around 30 cm in a nanosecond.",
"The height GPS of satellites is listed as 20,200 km. Light travels that distance i... | [
"Keep in mind that the gps you are using is not the best technology available. The government/military restricts the use of the best available to stop people from making mischief/missiles. See SPS vs PPS for more information."
] | [
"Understood - thank you!"
] |
[
"What is the default state of the muscles that are responsible for closing your eyes?"
] | [
false
] | If you were to turn 'off' the muscles that open/close your eyelids, would your eyes stay open or closed? I know that the majority of the time when people die, their eyes stay open, but it is possible to close the eyes and have them remain closed. When we go to sleep, we almost feel like our eyes are wanting to naturally close, but when we're awake, it's very easy to keep them open, so would that mean that we're using our eyelid muscles constantly when we are awake? Edit: grammar | [
"If your eyelid muscles were off, your eyelids would generally be droopy/mostly closed.",
"We have muscles to open AND to close the eyes. If they're paralyzed, then the eyelid will do whatever friction+elasticity dictates. ",
"If someone does have a paralysis of their eyelid muscles, a patch is often applied t... | [
"\"There are multiple muscles that control reflexes of blinking. The main muscles, in the upper eyelid, that control the opening and closing are the orbicularis oculi and levator palpebrae superioris muscle. The orbicularis oculi closes the eye, while the contraction of the levator palpebrae muscle opens the eye. T... | [
"Ah so there are muscles dedicated to independently opening and closing, meaning that having relaxed eyelid muscles would result in the eyelid remaining how it is?"
] |
[
"How does non-ionizing radiation such as gamma rays actually cause damage to our bodies?"
] | [
false
] | null | [
"Gamma rays are ionizing. Non-ionizing radiation starts in the UV range.",
"At any rate, even non-ionizing radiation can break some of the weaker chemical bonds or hydrogen bonds (UV to visible light) or cause heating (infrared and microwaves can directly heat body fluids). "
] | [
"Ultraviolet with wavelengths less than 125nm, extreme and vacuum ultraviolet, has energies of more than 10 eV and would be ionizing. "
] | [
"Where is the transition from ionizing to non-ionization radiation? I thought that UV (or at least some UV) could ionize."
] |
[
"What'd happen if water was frozen inside a sealed, rigid, unbreakable container? Would it not turn into solid ice? Would it require lower temp to freeze it?"
] | [
false
] | I know if typical material would break under stress from the expansion. But what if the material is so strong...could anything possible contain the frozen water? | [
"If it was rigid enough, it would form a different form of ice that forms under greater pressure. ",
"Ice VI",
".",
"And no, Ice-Nine isn't like in the book."
] | [
"I'd say it like \"The ice has enough of an energy deficit to bring an entire glass of room-temperature water below its freezing point.\""
] | [
"\"The types are differentiated by their crystalline structure, ordering and density.\"",
"-Wikipedia"
] |
[
"Are phonons a type of electromagnetic wave?"
] | [
false
] | [deleted] | [
"Phonons are not electromagnetic waves, they’re mechanical oscillations (or at least the quantum version of them)."
] | [
"Although this is, I suppose true, it's quite a bit of semantic gymnastics. When light \"travels\" through a medium it does so as a dressed wave of electrical polarization. The quantum version of this, when appropriate, is the POLARITON. Polaritons are excitations of polarization just as plasmons are excitations... | [
"Phonons are in now way EM waves. If one did want to assign a quantized excitation to the polarization waves that are truly meant when people haphazardly talk about \"light in a medium\", it would be something like a polariton.",
"That being said, you sure you didn't mishear \"optical phonons\" and misunderstood... |
[
"Is it possible for a dormant virus to lyse an entire human body?"
] | [
false
] | So ever since high school bio I've always wondered something stupid. If a virus were somehow able to infect a zygotic cell, inserting viral DNA and entering a dormant life-cycle, would it be possible for the DNA to remain dormant into an adult's life where all the cells in that person's body contained the DNA at which point whatever cue would turn on expression of the viral DNA causing a mass lysing event? Essentially, Melting Man. Couple of legitimate reasons why this couldn't occur that I tossed around: -Virus Specification- given that viruses are highly specified and incredibly small, it may not be possible for a single virus to have the capacity to both infect zygotic cells and upon lysing in any number of somatic cells, infect or interact with all those cell types as well -Differential Expression of genes- the virus would need mechanisms to allow any or all somatic cells to express its genes given that the cells will have long since specialized in function and gene expression. So guys, humor me. Any ideas; is Melting Man a possibility? | [
"Usually one virus only infects a single locus, at random. Loci are \"locked away\" as chromatin topography changes during specification and then differentiation. However, there are many genes that must be on for almost all cells. Lamin A/C, Histones, ion channels, basic metabolic transport proteins, enzymes, etc. ... | [
"This process is essentially a way to systematically and conditionally cause an organism to decompose. Doing so in a multi-cellular organism would appear to have few uses, but in the biofuels industry it may have promise.",
"Consider an algae which you can program to 'pop' in such a way that it releases its cont... | [
"Not a very good idea, It is difficult to predict the effects of a virus like this leeching out into the environment.",
"I opine that there are easier, cheaper, and safer ways to approach any example you mentioned above.",
"Even still, I find it awesome and amusing that we are talking about something like this.... |
[
"A question regarding hangovers"
] | [
false
] | Possibly the wrong subreddit but in the interests of my poor head I want to approach this scientifically. So, hangovers are mainly caused by dehydration right? Does this mean if I was for example to drink lots of Vodka and orange, the orange juice would act as hydration? I'll possibly get destroyed by all the scientific minds here but it seems plausible. Please help me and my poor head. Edit: Ok so thanks scientific chaps. It appears my dastardly plan of drinking OJ with vodka is futile. I appears that I either need to A: Reduce the ratio of vodka to OJ which isn't conducive to my tastes. B: Hydrate said liquor is consumed or C: discover a decent source of vitamin B12 I think I'll go for a mix of option B and C. Thanks guys, | [
"Coconut juice is supposedly naturally isotonic. ",
"Replying here as well so both OP and Dimpl get an orange-red."
] | [
"Alcohol is diuretic, meaning that it causes the body to lose more water than it takes in. Therefore, if you consume many non-alcoholic fluids while alcohol is present in your system you will simply pass them. Instead, it's critical to wait until the alcohol has started to work its way out of your bloodstream (ty... | [
"I have a hangover cure I wrote many years ago that I reverse engineered. Here it is for your listening pleasure.",
"This discovery came from trying to see what supplements would help the osteoarthritis in my spine. Incidentally, I observed that many of the supplements that I was taking noticeably decreased the ... |
[
"Can you tell from a persons blood work, what kind of diet this person eats and/or if someone engages in physical activity?"
] | [
false
] | Maybe a stupid question, I don't know, but can you tell in general (illnesses and extremes like malnutrition aside) for example if someone is eating more or less meat or no meat at all, or a lot of vegetables and/or fruit or not? How does physical activity show up in a blood work? Can you tell how much physical activity someone engages in and -maybe as a bonus question- what kind of sport someone does (for example swimming vs running or both of them vs weight lifting)? | [
"I see both responses so far have mentioned blood glucose tests and their limited timeframe, which is true, but ",
"hemoglobin A1c tests can tell you a patient's average blood sugar levels over the past few months.",
" It's used to identify how diabetic patients have been managing their diet. "
] | [
"Not likely, mostly because blood tests really only give a very limited snapshot of what's going on at a point in time. You might be able to make some very limited inferences as to what the person does from the blood test alone, but I'll get to the point in a moment. ",
"For instance, if I eat a candy bar right b... | [
"Given the wide availability of supplements, it's very difficult to tell the difference from an omnivore and a well-supplemented vegetarian/vegan.",
"Taking that aside, only animals are sources of vitamin B12. Thus, presence of vitamin B12 in the blood suggests sufficient animal (meat, eggs, etc.) intake. If ther... |
[
"How does one particle \"know\" the charge of another through photon exchange?"
] | [
false
] | Particle A exchanges a photon with particle B. Maybe if they are oppositely charged, the exchange causes them to move a little closer together. What is it about the photon itself that "tells" one particle to move either toward or away from the other? | [
"Forces don't really work by particles shooting force carriers at each other. So it's definitely not as if two charged particles interact because they're shooting lasers at each other! Virtual particles that we say mediate forces are like ripples in the underlying ",
". It's the field which tells charged particle... | [
"Don't think of the photon as a particle, think of it as a fluctuation of the electromagnetic field. The fluctuations propagate through the field and \"tell\" each particle what to do."
] | [
"Thanks, that was a great a read!"
] |
[
"In math, is the order of operations arbitrary? Meaning is there a real reason x and / comes before + and -, or is that just the order we decided and as long as the operations are consistent and that's what really matters?"
] | [
false
] | null | [
"That article contains a rare sighting of anyone remembering or even knowing about Forth."
] | [
"That article contains a rare sighting of anyone remembering or even knowing about Forth."
] | [
"It's possible to change the order of operations and rewriting all notation accordingly so all equations continue to have the same meaning, as we have a parentheses system (and fractional notation) that manually overrides the order of operations.",
"Notation and the order of operations within it isn't so much arb... |
[
"Can Neutrons decay into an anti-proton and a positron?"
] | [
false
] | I've never heard anything about it and can't find anything on the subject. I know that regularly free floating neutrons decay into protons and electrons, but could they decay into a positron and anti-proton? Changing into an anti-proton and a positron would still conserve both charge and mass. The only law it would seem to disobey is the law of conservation of Baryon number, but I know that that law has been proven to be only approximately conserved. I'm not concerned so much about how likely it is as much as the possibility. | [
"No. It would violate conservation of ",
"baryon number.",
" Protons and neutrons have a positive baryon number, while anti-protons and anti-neutrons have a negative baryon number. ",
"Beta decay, which allows a neutron to turn into a proton by spitting out an electron and an anti-neutrino does conserve baryo... | [
"But couldn't an anti-neutron do this? That should be no problem."
] | [
"Correct"
] |
[
"Could a laser be made from sound as it is from light?"
] | [
false
] | Civilizations from other times and places used sound to move heavy objects, bore tunnels and power engines, according to the Seth Materials. If this were true, could we do this in our civilization? I'm guessing that to start we'd have to control and amplify the sound energy. So, my question: Could a laser be made from sound? | [
"Yes, there are ",
"SASERs",
".",
"Here",
" is an article from ",
" about the first such device."
] | [
"I was just walking in to explain why I thought it would not be possible. That's unbelievable!"
] | [
"I'm not sure I believe that this was a SASER. Audible frequencies have a very long wavelength. If I understand SASERs correctly, then the coherency of the produced beam is still related to the size of the aperture, in wavelengths.",
"It is far more likely that the shopping mall demo was an application of phase... |
[
"Electrons aren't really particles, however, they have a velocity. To me, this seems incongruous. What am I misunderstanding?"
] | [
false
] | [deleted] | [
"Electrons are particles and 'physical entities' as far as anything is. In fact, they're elementary particles, so more particle-ish than most particles. What I mean by 'elementary particle' here is that they have no known constituent parts, no observed internal structure. Electrons interact with things as if they w... | [
"They 'look' quite different. Free, moving electrons have a net momentum for starters, and their probability distribution (which is thus moving through space) can have an almost-arbitrary shape. Except that the shape of the probability distribution (regardless of situation) is related to the kinetic energy (again p... | [
"They 'look' quite different. Free, moving electrons have a net momentum for starters, and their probability distribution (which is thus moving through space) can have an almost-arbitrary shape. Except that the shape of the probability distribution (regardless of situation) is related to the kinetic energy (again p... |
[
"Do identical twins develop at exactly the same rate?"
] | [
false
] | Assuming a near identical diet and environment will identical twins develop at exactly the same rate? Ie teething, growth spurts and general development | [
"In theory? But the genes x environment interaction is so complex and it’s nearly impossible to hold all environmental factors constant for individuals so I don’t think this could actually happen in real life. Maybe in a laboratory setting but that’s beyond unethical "
] | [
"Nope. Even before birth that ship has sailed. There is a competition for resources during gestation that usually puts one twin developmentally ahead for life. Not hugely...not even significantly to most...but the differentiation already begun. "
] | [
"Twin studies have shown that even monozygotic twins with maximum genotype overlap still have genetic variations between them which then manifests in phenotype.",
"In other words, no, even identical twins will not develop at \"exactly the same rate\", they will have variation, even if it is only slight."
] |
[
"What is the driving force behind the expansion of our universe?"
] | [
false
] | null | [
"In a sense, it's pressure.",
"Imagine a box of air, sealed up tight. Subject that box to heat of some kind, say by lighting a fire under it. What happens inside the box? Well, the pressure goes up, of course.",
"But now imagine it's a ",
" box, one that can grow and shrink freely. If you heat up ",
" box, ... | [
"Well, RRC is probably just human, and he/she gets irritated or frustrated at things like anyone else."
] | [
"Don't think RRC needs me to be a white knight here but in my opinion if someone is really, completely wrong about something you shouldn't be afraid to tell them so, and you shouldn't have to sugarcoat it, especially not on the internet. People that are actually knowledgeable on the topic shouldn't have to feign hu... |
[
"Can we tell whether an object is in front or behind us based solely on hearing?"
] | [
false
] | [deleted] | [
"Yes we can because sound reflections on ears, shoulders etc. depend on the direction of the sound source. Stuff like that never ceases to amaze me.",
"From Wiki:",
"\"Sound localization in the median plane (front, above, back, below)",
"The human outer ear, i.e. the structures of the pinna and the external e... | [
"That wiki page may need editing. First of all, let's assume you want a really specific test. So, you fix the position of a sound in the horizontal plane, and makes its fore-aft mirror position the other test. In other words, we will test localization of sound in front of, and behind, but with the same interaural t... | [
"It's worth pointing out that our lateral perception works more consistently than our median perception."
] |
[
"Can electrons be polarised like photons?"
] | [
false
] | null | [
"In short, yes.",
"At a fundamental level, the polarization of light waves is an artifact of the spin of the photons, so a beam of photons in the same spin state will be a beam with a specific polarization. Thus, if we take a collection of electrons and get them all in the same spin state will be polarized."
] | [
"Not only does it have applications, they are well-known and really important too",
"."
] | [
"Many thanks, does this electron polarisation have any current real world applications? "
] |
[
"Hubble Telescope has been producing the best space images for decades, and is still going. Is it about to become obsolete or should we make another/better version to spread the workload?"
] | [
false
] | null | [
"It is great, and we want it to keep running as long as possible, but we are building new instruments to improve things.",
"On the ground, adaptive optics technology mean that we can get ",
" the same resolution as Hubble within the atmosphere. The next generation of 30-metre size telescopes are underway, and w... | [
"Well said! Some definitions for anyone wondering:",
"Adaptive optics is a really cool process. The observatory shoots out a laser into the sky and is able to see a reflection coming from the atmosphere. The laser went straight out, but coming back it's a bit wobbly from all the atmospheric interference (clouds a... | [
"There are two projects - the Extremely Large Telescope in Chile, and the Thirty Metre Telescope which is supposed to be on Mauna Kea in Hawaii, but may or may not end up there.",
"There is also the ",
"Giant Magellan Telescope",
". Smaller than ELT and TMT but still much larger than any existing telescope."
... |
[
"So i tried applying super glue with a Qtip, moments later got a cloud of awful smelling smoke and the glue was almost instantly dried. Wtf?"
] | [
false
] | null | [
"Cyanoacrylate (crazy glue) ",
"reacts",
" strongly with cotton."
] | [
"What were you applying the glue to?"
] | [
"plastic, but I never got that far. It started smoking momentarily after glue hit qtip"
] |
[
"How do bee-eater birds bee-proof themselves?"
] | [
false
] | null | [
"Many animals create an antivenom for certain venoms they come into contact with often. I don't know if this is the case with bee eater birds.",
"Venom is not dangerous if ingested. I could swallow an entire vile of rattlesnake venom and be fine. So when a bird eats the bee, it doesn't have to do anything special... | [
"What about for the physical damage of the stinger making a puncture? Is it negligible or would they have an extra tough stomach?"
] | [
"I'm honestly just guessing. But I would say they try not to eat the stinger, but if they do, it would probably be negligible damage. Most bees have a venom sac, they have to choose to squirt the venom through the stinger. So if it's already dead, it won't be squirting venom. That's what causes the problems The ven... |
[
"What is the most \"painless\" way to prepare a lobster?"
] | [
false
] | In my country (Belgium) there is currently a huge discussion going on about how to prepare a lobster as a meal. This was sparked by a chef who, on national television, cut a living lobster in half (lengthwise), ripped out it's legs and arms and put it on the barbeque. His argument was that the taste of the lobster is the best if it is done this way. Regarding alternative methods, there are people saying that putting the lobster in a kettle of boiling water for approximately a minute is a better way. Both these methods seem pretty painful to me, however I'm not certain if crustaceans experience pain the same way humans do. I know for a fact that decapitation of humans will result in a painless and immediate death, so could this be considered an acceptable way of "killing" lobsters, based on scientific grounds? If not, what would be a better way? | [
"I work next door to a lobster lab and they brought a guest speaker in last year whose specialty is crustacean pain. Though it is impossible to know for sure what the subjective experience of an animal is (or for that matter, from a philosophical point of view, ",
"), there has been a rough consensus that if an a... | [
"Alton Brown recommends that you put them in your refrigerator for a little while. Supposedly, that will knock them out. Then, you split the head in half, bisecting the brain and killing them as ",
"/u/icomrade",
" describes."
] | [
"OTOH we ",
" be fairly certain that destroying the brain first will eliminate any possible consciousness that may or may not exist to experience pain/suffering. I believe once we take that into account it's clear that ",
"/u/icomrade",
" is correct."
] |
[
"if electrons flip poles when rotated, why don't magnets?"
] | [
false
] | null | [
"Are you referring to the phase that you get when applying a rotation by 360 degrees to the state vector of an electron? That doesn’t mean that its spin has flipped, it just means that the state vector acquired an overall phase of e",
" when you apply a 360 degree rotation."
] | [
"i think so, is it only the complex phase that changes? I would have assumed the real probability of finding a particle in either state would change as well under a 360° rotation"
] | [
"D(θ = 2π)|Ψ> = -|Ψ>, where D is the unitary rotation operator (Wigner D matrix), and |Ψ> is an arbitrary state vector for a spin-1/2 particle."
] |
[
"How would seasons work on a tidally locked pair like Pluto and Charon if they had atmospheres and proximity to a star akin to Earth's?"
] | [
false
] | If you had a dwarf planet and moon of similar size, mutually tidally locked, roughly 1 AU from a star similar to the Sun, both with atmospheres similar to the Earth's (regardless of how plausible that is), how would the seasons work? Also, would they necessarily have an erratic orbit like Pluto and Charon? | [
"Tidal locks tend to be focused on equators, don't they? How does a two-way tidal lock affect the axial tilt of the two bodies?"
] | [
"One thing you must know to answer this is why Earth has seasons. The seasons on Earth are a result of the tilt of Earth's axis and actually has nothing to do with how the moon orbits Earth. ",
"The earth has a 23.4 degree tilt from the normal (perpendicular line to plane of orbit around sun). If we start in the ... | [
"It doesn't, that's just the angle between the pole and it's orbital plane. Its not affected by Charon's tidal lock."
] |
[
"A question on how things fall when on a moving vehicle."
] | [
false
] | Say I am on a train and I drop a sack of pennies. This bag falls straight down in a straight line. It doesn't fall several feet away from me. Why is this? It is because me, the train and the sack of pennies are all moving at the same speed? Thanks! | [
"Objects in motion tend to remain in motion unless acted upon by an outside force.",
"The pennies are moving at 100 km/h with the train. You drop them. They continue to move in the same direction at 100 km/h."
] | [
"Relative motion is sometimes pretty hard to get a good intuition for. At the beginning, you, the train, and the bag of pennies are moving at the same horizontal speed. When you let go of the bag, you let gravity pull it down; the key is that gravity only pulls down, not in any other direction. There is no hori... | [
"You're right. It's called inertia.",
"It's the same reason why, if you were standing on the train holding a particular heavy bag of pennies, you'd feel them pulling forward as the train slows down. That's the pennies decelerating. "
] |
[
"When I hit my hand against a wall, what exactly is stopping my hand from going through the wall?"
] | [
false
] | I know it sounds like a stupid question. When you're looking at it on an atomic level, what makes atoms (or nuclei) unable to intersect with one another? Why are some subatomic particles able to intersect, but not atomic particles? | [
"It's the force of the electrons in your hand repelling the electrons in the wall. The closer your hand gets, the larger that force gets; due to the inverse square dependence of electrostatic forces, you don't notice it until you're pressed right up against it."
] | [
"Well it explains why an electron of one carbon can't spontaneously enter the orbital of a nearby carbon atom if it is already occupied, so there is repulsion as a result of that as well."
] | [
"It's not just electrostatic repulsion.",
"There is what is known as \"pauli repulsion\" between atoms. This happens because two electrons cannot be identical (have the same energy and spin).",
"When two surfaces come together, if they are uncharged then quantum fluctuations will cause them to stick together by... |
[
"Electron diffraction - how did they know that graphite had the atom spacing of the wavelength of an electron if they didn't know the wavelength of an electron before doing the experiment?"
] | [
false
] | In the electron diffraction experiment, electrons were passed through a graphite crystal (the atom spacing was similar to the wavelength of the electrons) to prove that electrons produced a diffraction pattern and so also existed as waves. So how did they know that graphite had the atom spacing of the wavelength of an electron if they didn't know the wavelength of an electron before doing the experiment. Trial and error? | [
"Thomson observed",
" the ring patterns and saw that their radius depend on the electrons energy. He even related that to the already known ",
"de Broglie hypothesis",
" (λ = h/p), but is not sure what the diffracting systems are (atoms or molecules)."
] | [
"Thanks for the answer,\nSo the rings related to the electron energy because of the equation E=hc/λ. Where the spacing between rings is λ?",
"And so the λ of an electron could be calculated before its existence as a wave had been proved? "
] | [
"X-ray diffraction predated electron diffraction by a few decades. They could ",
"compare the electron diffraction to x-ray diffraction",
" at known wavelengths.",
"As other commenters observed, de Broglie had also worked out the theory of particle wavelengths before the experiments were performed."
] |
[
"Learning a foreign language with radio and TV."
] | [
false
] | When learning a foreign language, why does have a radio station/TV program in the target language playing as background noise help your listening skills? I'm at a language institute and people do it all the time with successful results, I just want to know why. | [
"Listening to your language of study passively helps your brain learn to attribute the sounds of that language as being important. ",
"When your brain is listening it is actively filtering out sounds as unimportant or important. (When speaking about languages and other sounds too.) It is also learning the new com... | [
"Thanks for the response, it sounds legitimate to me. I ask because I'm learning a language to become a Linguist and I always wondered how this works. I had my theories but I didn't know how accurate any of them were."
] | [
"If you don't know about it already, there's ",
"/r/languagelearning",
" as well as ",
"/r/learnanewlanguage",
" which might help you find other resources. "
] |
[
"When the Apollo astronauts prepared to leave the surface of the moon, they discarded their EVA life support backpacks by tossing them out of the LM. How did they do this without exposing themselves to the Moon's vacuum?"
] | [
false
] | With the LM's hatch open, its interior held no atmosphere, so the astronauts had to enter with their EVA backpacks attached and operative. Were they able to disconnect them, toss them out, close the hatch, and repressurize using only the residual oxygen in their suits, or did the LM have the necessary hardware to provide their suits with oxygen until the backpacks were discarded and the LM repressurized? | [
"They only tossed the backpacks out, not the whole suit. the PLSS backpack was exactly that, a backpack that connected to the space suit via hoses and electrical connections. When inside the LM, the astronauts simply connected their suits to the LM’s life support system, negating the need for the backpack."
] | [
"I never thought they tossed the entire suit out; the missing part for me was how the suits connected into the LM's life support system, and whether that connection could be made under vacuum, or if they needed to repressurize the LM, disconnect the backpack, connect the LM life support system, depressurize the LM,... | [
"The Apollo spacesuit had dual connectors for the life support gases (two inlets and two outlets), along with single connectors for cooling water and for electricity. On early models these are prominent on the chest (they were moved around a bit on suits used on later Apollo missions and Skylab).",
"This means th... |
[
"Why does 16 Psyche have such a low density?"
] | [
false
] | I read that asteroid 16 Psyche was composed mostly of pure iron and nickel. However, it only has a density of around 3.3 grams per cubic centimeter. How is this possible? If it's really pure iron/nickel shouldn't its density be WAY higher, like at least double? | [
"It is very porous. It was probably never completely molten, and its gravitational attraction is not strong enough to get rid of those empty spaces inside either.",
"\"macroporosity of 30-40%\"",
" - meaning 30-40% is empty space."
] | [
"More like a bag of marbles.",
"30-40% empty space (edited above, took the wrong number) and 50% metal content are consistent with the density estimate."
] | [
"So is it like a bag of marbles? Or is it like a sponge?"
] |
[
"What is the difference between me flexing my muscles hard vs lifting weights. I feel like if I flex my arm is just as stressed as if it were lifting a weight."
] | [
false
] | null | [
"Isometric (tensed , not moving) versus concentric (moving against resistance) contractions are different in that in an isometric contraction, no 'work' (in the physics sense) is done. Mass isn't moved or displaced.",
"From an exercise point of view, it's nearly the same amount of energy required, however studies... | [
"http://en.wikipedia.org/wiki/Isometric_exercise#Comparison_with_dynamic_exercises",
"Plenty of additional support for the effect out there."
] | [
"threegigs is correct about only strengthening in that range of motion. While it is the same muscle fibers acting on the forearm and arm to pivot your elbow you have to realize that muscle force isn't constrained to a single plane. There are X and Y components to the force itself on top of the \"line of pull\". Als... |
[
"Does heating water requires the same amount of energy during the entire process?"
] | [
false
] | I was making coffee and was wondering, is the amount of energy needed to raise the temperature of water from 20 to 30 degrees, is the same amount of energy required to raise it from 90 to 100? Yes? No? And why? | [
"Almost but not quite. Here is a chart ",
"https://syeilendrapramuditya.files.wordpress.com/2011/08/water_specific_heat_capacity_vs_temperature.gif?w=500&h=300",
"Note the numbers on the left. There is only about 0.5% difference between highest and lowest point."
] | [
"Almost got it, it's not because the water has more energy, but because it actually changes. Water changes its material properties a bit when it heats up so that it has a higher (sorry if this is the wrong term) heat capacity, or resistance to change in temperature. If water was perfect and nothing changed in it be... | [
"In everyday practice, no. The water will lose more heat to its surroundings if it has a higher temperature. Thus you'll need to add more heat than it's losing. At lower temperatures it will lose less heat, so you won't need to add as much. Assuming the surroundings are around room temperature.",
"In a situation ... |
[
"Why do we forget our dreams?"
] | [
false
] | Even the interesting ones, I can never hang on to for more than a few hours... I can wake up thinking "That was awesome!" or "That was absolutely terrifying. Turn the lights on.", or "That was the wierdest windmill made of kangaroos I've ever seen," etc. but no matter what, a short time later I can only remember the haziest outlines of what that dream was. Is there a reason for this? | [
"Here are a few other posts that may be useful:\nHas some useful answers:\n",
"http://www.reddit.com/r/askscience/comments/h5oyt/why_does_your_memory_of_a_dream_fade_so_quickly/",
"Not overly useful:\n",
"http://www.reddit.com/r/askscience/comments/g1e2z/why_is_it_so_hard_to_remember_dreams/",
"Empty at the... | [
"Yeah, no problem. I did the same as you, but only looked deeper because I knew I saw one before."
] | [
"Yep, try that search function! ",
"As pineapplol mentioned ",
"this",
" thread from a while back will be helpful to you."
] |
[
"An escalator moves at the same speed whether it's empty or has a lot of people on it. How does the motor \"know\" to change its power output?"
] | [
false
] | [deleted] | [
"Here's an excellent article about constant-speed motors. I really recommend you read it to get a good overview of how they work.",
"To answer your specific question, escalators and chairlifts and other constant-speed motors are designed to provide enough torque for a maximum load. For something like an escalato... | [
"As most applications use squirrel cage motors, the speed is probably not identical in no load and loaded conditions. But the difference is negligible. Typically a squirrel cage motor on 50Hz can go from 1500 to 1475 rpm on full load. "
] | [
"Simply put, they don't. They operate like a servo. A VFD drive spins a 3 phase motor with a tach on the back. The VFD reads the tach signal and adjust the frequency to the drive to adjust it's output speed, resulting in a constant speed regardless of load. ",
"That being said, I'm sure older units may have a con... |
[
"So I have a relativistic rock and a flashlight..."
] | [
false
] | Let's pretend I have a perfect vacuum, an idealized rock moving at relativistic speeds, and an idealized beam of light. The rock is moving from point A (At relativistic speeds, say .5c), towards the source of the light, which is at rest relative to point A. The light is exerting a pressure on the rock, which deaccelerates it. At some point, the rock reaches rest relative to A, and begins accelerating the other direction. The question is, what speed will the rock be moving when it passes A again? The reason I'm not sure is because of the red/blue shift. As the rock moves toward the light, the light is blue shifted. As such, it has more energy, and exerts a higher pressure that it would at rest. However, when the rock is moving away, the light is red shifted, with less energy, and so exerts a lower pressure. Wouldn't this mean that the rock is actually moving slower when it passes A the second time? | [
"I just solved it numerically in Mathematica for a 1kg rock moving at c/2 at t=0 decelerated by a 1000W 500nm light source with zero beam divergence (maybe in one dimensional space?).\nThis ",
"Plot",
" shows position in blue and velocity in red. (There is no scale for the velocity, I couldn't figure out how to... | [
"There is nothing wrong with your analysis.",
"In fact, you can use this doppler shift with lasers to ",
"cool atoms",
" down (though it also relies on the absorption of the photons changing with the doppler shift).",
"Also, I don't think relativity affects this question."
] | [
"In physics, \"idealized\" doesn't mean \"doesn't obey the laws of physics\". In fact it typically means almost the opposite: assume that the equations being used apply precisely, ignoring effects that are secondary to the problem, like friction, or in this case, the effect of the interstellar medium on the veloci... |
[
"is it possible to graft a fruit tree onto a non fruit tree?"
] | [
false
] | Is it possible to grow a maple apple tree? | [
"Persimmon trees and ebony are both in the diospyros genus and can be grafted.",
"What the OP is talking about though is just not done, we don't graft lumber and fruit trees together because it's pointless. For example, persimmon trees have the same wood as ebony, if you grow a persimmon for 50+ years and harvest... | [
"Persimmon trees and ebony are both in the diospyros genus and can be grafted.",
"What the OP is talking about though is just not done, we don't graft lumber and fruit trees together because it's pointless. For example, persimmon trees have the same wood as ebony, if you grow a persimmon for 50+ years and harvest... | [
"If you grow it out to full size, yes, it's certainly possible to train the tree to keep things balanced, but those kind of trees are more novelties than something you'd grow for commercial fruit production. If you've got a backyard fruit tree, you can go full Elden Rings with your grafting, I've seen a few greenho... |
[
"Are dinosaurs more closely related to modern-day birds or reptiles?"
] | [
false
] | [deleted] | [
"Birds (aves) evolved from theropod dinosaurs. Dinosaurs evolved from basal archosaurs, which were closely related to reptiles. So, it's kind of like this: \"reptiles\" would be your aunt, \"dinosaurs\" would be your dad, and \"birds\" would be you. That's really simplified, but explains the relationship."
] | [
"Think of it like this: Birds are to dinosaurs as bats are to other mammals. "
] | [
"Birds are dinosaurs. The following statement is true for dinosaurs and birds:",
"All dinosaurs share more recent common ancestors than any dinosaur and any reptile. ",
"I realize yahoo answers is not science",
"It's bad science. It is awful. There is not smooth transition between animal classes, nor is there... |
[
"If life originated on Earth more than once, and the descendants of each still exist and are easily found, would we know it?"
] | [
false
] | If life originated on Earth more than once, and the descendants of each still exist and are easily found, would we know it? | [
"Probably.",
"It is somewhat likely that life ",
" in fact originated multiple times on Earth, but the prevailing theories are that only one lineage has survived to this day...which then diversified into life as we know it. We suspect this because despite the huge differences seen between the 3 domains of life... | [
"Viruses are an interesting case since they are so incredibly simple forms of \"life\". However, they still use similar means to store genetic information (as either DNA, or RNA) as the other forms of life, so while it is difficult to speculate about their origins and how they came about, it is unlikely that they ... | [
"How would viruses fit into this?"
] |
[
"How do we communicate with and control satellites that are millions of miles away? (Like the Rosetta Lander)"
] | [
false
] | I have always wondered how we send and receive data to and from satellites that are really far away. What kind of technology is used to do this? | [
"/u/katinla",
" mentioned parabolic antennas with a large area for collecting and concentrating signals. Here is how large these antennas can get (notice the cars for scale!):",
"http://mars.jpl.nasa.gov/msl/images/goldstone.jpg",
".",
"This is part of NASA's Deep Space Network, which can still communicate ... | [
"Very interesting. Thank you for sharing!"
] | [
"It is true that big distances like millions of miles have a strong influence on our communication capabilities due to free-space loss. To be precise this has an influence on the received power, which decreases with the square of the distance.",
"Basically we have two ways of mitigating the issue. First is using ... |
[
"Electrons have mass and therefor curve spacetime. Why can't we measure that curvature to find position or speed without collapsing the wave function?"
] | [
false
] | [deleted] | [
"Measurement in quantum mechanics doesn't really have anything to do with our ability to measure things. It's referring more to what information is physically possible to obtain and what happens when that information is obtained.",
"In other words it doesn't refer to any specific means of obtaining the position o... | [
"No, you couldn't. You can't perform any measurement without an interaction occuring.",
"To register a measurement, something in your measuring apparatus must be changed by the presence of the object you're measuring, which means there's an exchange of energy between the object and measuring device.",
"For exam... | [
"An interaction can occur without the wavefunction collapsing. For example, in an atom, the electron and proton are interacting, but the wavefunction doesn't collapse. This can work because you don't need the position of an electron to know how its electromagnetic field behaves: the wavefunction itself has a spatia... |
[
"Hey, this is more of a mental health question. I'm coming here because I couldn't find anything on Google."
] | [
false
] | null | [
"It could be many different things. I would suggest talking to a psychologist about it as any advice given here would be medical advice and therefore inappropriate. "
] | [
"This post has been removed. Please observe the rules on the sidebar - Free of medical advice (see reddit's user agreement). If you have any medical questions (including your mental health), please consult a qualified professional."
] | [
"If your doctor can't personally help with your problem, he or she should refer you to specialist in the field. I would suggest consulting with a psychologist for your problems. It may be costly, but it surely beats consulting the Internet for diagnosis.",
"Hope this helps, good luck."
] |
[
"Why does friction create heat?"
] | [
false
] | Friction is the result of microscopic ridges on an object's surface and acting against frictional force generates heat. But if you were a giant, trees would be microscopic, meaning that microscopic is subjective and,thus, the size of the ridges isn't what is creating the heat. So what's going on when I rub my hands together. | [
"But if you were a giant, trees would be microscopic, meaning that microscopic is subjective and,thus, the size of the ridges isn't what is creating the heat.",
"This isn't quite true. Ultimately, the interaction between the giant's hands and the trees are due to the interactions between the atoms in each. Regard... | [
"Beyond the \"bounce back\" point, heat can be thought of as incoherent higher energy states in the system.",
"From that point of view the giant does increase the \"heat\" of the forest by breaking trees apart. The broken bonds raise the internal energy of the system and because it is done in a somewhat random ma... | [
"Friction and temperature are not related and that is not what a mercury thermometer does.",
"A mercury thermometer gives you the temperature based on the change in density of the mercury as a function of temperature. Friction has nothing to do with the density of the mercury; it is an intrinsic property of the m... |
[
"Why do we get itchy?"
] | [
false
] | null | [
"it evolved as an evolutionary adaptation. People who feel compelled to rub their body where something lightly touched it happened to be more likely to live because they brushed off bugs that could carry disease,poison,ect"
] | [
"I am interested on this sensation on a cellular level. Can anyone describe the relationship with irritants and dendrites or other involved cells?"
] | [
"I was recently wondering about why itching causes a compulsive desire to scratch (after a recent bout of poison oak). It seems there is generally no benefit to scratching as it causes further skin damage and does not relieve the itching at all. There has to be a reason we have a desire to scratch at things that it... |
[
"How is earth oriented in relation to the Milky Way?"
] | [
false
] | When we look up into the night sky and gaze upon the Milky Way, are we looking towards the center of the galaxy? Does our orientation stay consistent over time? | [
"The direction of the galactic center is at a specific point in the celestial sphere, near the constellation Sagittarius. ",
"In this circle",
"."
] | [
"does that mean the earth spins at a 90 degree angle to the center plane of the galaxy?"
] | [
"So is the orbital plane of the earth aligned with the plane of the galaxy, or offset by a significant angle? Intuitively, I would expect solar system discs to form on average in the same plane as the galactic disk, but maybe it's more or less random...",
"edit: never mind, quick google answered my own question: ... |
[
"Is there a way to reverse a chip from being stale?"
] | [
false
] | It would be magical | [
"Silica gel. It's a moisture absorber. You know, those little packets labelled DO NOT EAT that come in the box with expensive electronics. A fairly large one can be sealed in a bag full of stale Doritos and they will \"magically\" return to crispness in about 24 hours. OK, not magically, it's science. Staleness is ... | [
"This type of sarcastic answer does not help make ",
"/r/askscience",
" a better subreddit."
] | [
"Staleness is often caused by absorbing moisture. A short (10 min) bake in a very low (200F) oven will undo it. Source: personal experimentation."
] |
[
"Why don't scabs form on cuts to your palms and palm side of your fingers?"
] | [
false
] | [deleted] | [
"They absolutely do.\nAbout 5 weeks ago I had a thin dog leash gash about a cm into my middle finger and a little into my ring finger (palm side), it scabbed up pretty bad.\n",
"Possibly NSFW",
"\nThat was taken ~5 minutes after it happened, it was more of a rope burn than a slice, so it didnt bleed very much a... | [
"Why is this being down voted when it is the most correct answer? henfeathers asked why scabs form everywhere on your body except your hands when \"they're not needed to stop the bleeding or to keep the wound clean?\"",
"I'm not sure what he is talking about in terms of scabs forming elsewhere when they are not u... | [
"I think he was talking about small wounds such as a paper cut, these tend not to form a scab over the wound on the palms and can remain open for days before healing."
] |
[
"What’s your favourite element and why?"
] | [
false
] | null | [
"Chemistry"
] | [
"Chemistry"
] | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"guidelines",
"/r/AskScience",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"Wouldn't a starvation diet pull lipids, fats and calcium from all sources in the body and therefore also from the unwanted arterial blockages this lessening them - If not why not?"
] | [
false
] | null | [
"By starvation i mean pure fast with water only.",
"I would think that when the body was pulling from fat reserves that it might pull from some constituents of the blockages.",
"Then as body fat reserves were depleted it might pull from more constitients of the arterial blockages.",
"Additionally since the ... | [
"The problem is that the lipoprotein lipase needed for hydrolyzing the triglycerides in lipoproteins to free up fatty acids are located on the luminal surface of the endothelium. Atherosclerotic plaques are located in the tunica intima between the endothelium lining and the vascular smooth muscle cells of the tunic... | [
"But wouldnt there be a break in the endothelium somewhere above the plaque? Didnt some lesion need to start the plaque?"
] |
[
"How many fully grown lions would we need to send into the sun at once to extinguish it?"
] | [
false
] | null | [
"This question has little didactic value."
] | [
"Where should I ask this to get a serious answer then? I'm mostly trying to get an actual answer from someone much smarter than my friends and I, who started debating the troll question \"Who would win in a fight, 100 trillion lions or the sun?\"",
"We did a whole bunch of mass calculations but don't know enough... | [
"Try ",
"/r/estimation",
" or ",
"/r/theydidthemath"
] |
[
"Do objects have inertia through time?"
] | [
false
] | null | [
"Objects always travel through the time dimension. How do you think the second hand on your wristwatch moves?"
] | [
"Yes but what about two 3 dimensional objects colliding in the 4th dimension while stationary in the 3rd?"
] | [
"For two objects to collide, they must come into immediate proximity in all 4 dimensions. Objects that would collide in the 3 spacial dimensions, but are separated by time do not collide. Objects that would collide in time and two spacial dimensions but are separated by the third spacial dimension do not collide."... |
[
"What is the highest velocity an object in space can travel at before relativistic effects take place (or become a problem?)"
] | [
false
] | Say I had a fast spaceship and I wanted to zoom around the solar system. How fast relative to the speed of light could I go before the I (or an observer) would experience noticeable shortening, increase in mass, or time dilation? I understand that this may be akin to asking exactly when our distant ancestors became human, in that you can't really pin down one iteration that changes everything, but it's something that I've been thinking about for a while. What is the fastest I could go so that, upon my return, the people on Earth and I have a time discrepancy of only a few minutes or so? So what would you guys say? .01c? .001c? Less? More? Thanks! If my question is stupid or improperly thought-out, tell me and I'll try to rephrase it. | [
"The main relation you'll need is the Lorentz factor. This, essentially, describes how big the relativistic effects will be for a given speed. It is:",
"where ",
" is your velocity, and ",
" is the speed of light. This is equal to the ratio of the dilated time (what you observe a clock on a spaceship to do if... | [
"It depends what you mean by noticeable. In order to experience a 1% change in elapsed time or distance, you'd have to be going 14% the speed of light."
] | [
"I guess I meant where the effects would be a problem, particularly time dilation, where I would leave and come back and everyone I cared about would be dead. In my hypothetical ship, energy wouldn't a problem until infinite energy is required.",
"So, if my ship was 100 meters long and if I were to travel at .14c... |
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