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[
"How do atoms convert to energy?"
] |
[
false
] |
If matter and energy and interchangeable, how do atoms convert to photons?
|
[
"Take the simplest atom - a hydrogen atom, which is composed of one proton and one electron bound together. There is a certain amount of energy that you would need to 'pry' these two particles apart, i.e. to drag the electron away from the proton, which results from the fact that they have opposite charges and so they attract each other. This energy is called the 'binding energy'.",
"Now, if you take the mass of a proton and an electron and add them together, this total mass is actually a little bit ",
" than the mass of a hydrogen atom. But what's going on here, if a hydrogen atom is just an electron and a proton, the masses should be the same? The mass difference is actually given by the binding energy multiplied by c",
" , and is an example of the mass energy equivalence. As the proton and electron are brought into a bound state, they actually lose a bit of their combined mass, equivalent to the binding energy, and this is given off as radiation.",
"The same thing happens in nuclear reactions, as atoms undergo transitions between states of different binding energies, the difference between these binding energies is either radiated or absorbed. So its not so much that an atom is converting into a photon, its more that a reshuffling of protons, neutrons and electrons inside an atom results in a change of energy state and a change in total binding energy, and therefore a very slight change in the total mass of the atom. This change in mass is given off as energy. Hope this helps, if not please let me know!"
] |
[
"If matter and energy and interchangeable, how do atoms convert to photons? ",
"you are equation energy to photons and matter to atoms which isn't very correct. ",
"E = mc² means that mass is one form of energy. in a reaction in principle if the energies involved are high enough, the mass can change into a different form of energy. say in a nuclear reaction the sum of the masses can be more or less before the reaction than after and some of that energy might go into kinetic energy of the products for instance. a nuclear reaction may also produce additional particles which carry energy. that may be neutrinos or photons (gamma rays) for instance. ",
"E = mc² doesn't mean that matter can be converted to \"pure energy = photons\" as is often misleadingly summarised, it means that there's more usable energy in atoms if we can rearrange is constituents (on the level of the strong force mostly, chemical reactions also do that but on a much lower scale, as the energies involved are a lot smaller) . if the energies are small the mass is (at least approximately) conserved so a lot of energy is locked away for such processes. "
] |
[
"Thanks for the reply!"
] |
[
"Why do bruises adopt different colors, such as red, yellow, green and black?"
] |
[
false
] | null |
[
"Bruises are collections of blood in the tissue. They start out red/purple because that is the color of ",
"hemoglobin",
", a major component of the red blood cells that are leaking out of ruptured vessels. These red bloods cells get stuck in the tissue are are slowly degraded. The first substance that hemoglobin is degraded to is ",
"biliverdin",
", which is green. Biliverdin is degraded into ",
"bilirubin",
", which is yellow (Bonus fact: this is the substance that makes your urine yellow). Bilirubin is degraded to ",
"homosiderin",
", which is a yellowy-brown."
] |
[
"Bonus bonus: in ",
" (the book), Lecter amuses himself by telling the FBI that the killer's name is William Rubin, which it wasn't. Bilirubin is part of what gives poop its color so the clue was bullshit."
] |
[
"\n",
"\n",
"\n",
"\n",
"\n"
] |
[
"Is there a correlation between skin cancer in people's arms and on which side of the road they drive?"
] |
[
false
] |
For example, is there a higher rate of skin cancer in the left arm of right-side drivers? Conversely, is there a higher rate of skin cancer in the right arm of left-side drivers? I think about this after taking long trips in the car. My left arm is always slightly darker than my right. There is a man at my church who had melanoma in his left arm after driving a Lance delivery truck for 35 years, but his right arm was fine.
|
[
"Ooh! Oooh! I'm a random idiot undergrad with no qualifications whatsoever but I know something tangentially related to this! Specifically, ",
"here is a case study",
" of a truck driver with unilateral skin damage due to sun exposure through his window.",
"According to the study,",
"Ultraviolet A (UVA) rays transmit through window glass, penetrating the epidermis and upper layers of dermis. Chronic UVA exposure can result in thickening of the epidermis and stratum corneum, as well as destruction of elastic fibers. This photoaging effect of UVA is contrasted with photocarcinogenesis. Although exposure to ultraviolet B (UVB) rays is linked to a higher rate of photocarcinogenesis, UVA has also been shown to induce substantial DNA mutations and direct toxicity, leading to the formation of skin cancer."
] |
[
"Truck drivers get some serious damage from the sun.",
"Here is a picture of an old retired truck driver ",
"http://i.huffpost.com/gen/634768/thumbs/o-BILL-MCELLIGOTT-SUN-DAMAGE-570.jpg?4"
] |
[
"That study is one of the few/only studies done on the 'unilateral' side of things, specifically caused by something like truck driving. A wide-spread epidemiological study of this could be interesting, comparing say, Australia, where we sit on the right side of our cars, with the US, where you sit on the left, and seeing whether melanoma is more prevalent on either side of the body for a given country.",
"Also, for more general information on dermatoheliosis, check out ",
"this paper"
] |
[
"Is there a meaningful variance in the maximum/minimum wavelength the human eye registers?"
] |
[
false
] |
To put it in another way, are there people who can see a bit into the part of the spectrum what the general population would regard as infrared or ultraviolet, or can't see certain pure reds or purples at the ends of the visible spectrum?
|
[
"There are individual differences that are measurable and significant. Depending on what population you study (normals, deutoronopes, or protonopes), which cone type you are looking at, and depending on what methods you use, you get slightly different results. Overall, the standard deviation of shift in spectral sensitivity functions ranges from 1-16 nm, which is quite a lot. In normals, it appears to be closer to 1-3 nm for M and L cones. This is the standard deviation of the shift of the peak of the function, so it assumes that all functions have the same shape / tails I believe. For a very thorough review, see ",
"Stockman, MacLeod, and Johnson (1993)",
"."
] |
[
"I was watching a show the other day that noted a man who had cataracts, and had gotten surgery to repair the problem. After the process he was able to see uv wavelengths. ",
"An article about him and seeing uv: ",
"http://www.extremetech.com/computing/118557-the-eyes-have-it-seeing-ultraviolet-exploring-color",
"And now today i learned its called Aphakia: ",
"https://en.m.wikipedia.org/wiki/Aphakia"
] |
[
"Follow up question for someone in the field:\nWhich retinal cells transduce this information?"
] |
[
"Multiple basic questions about the Hubble photos"
] |
[
false
] |
The most pressing one: are these all (except when explicitly stated otherwise, e.g. "Saturn in Infrared") a representation of what a normal human eye would see if they were standing right next to the end of the telescope? Are the colors really like that? On to the more basic ones:
|
[
"1) It's made up of basically the same stuff as everything else - 3/4 hydrogen and 1/4 helium, then a small amount of heavier elements. The Pillars of Creation are made of dense (\"molecular\") gas that's getting blown away by some bright young star cluster. The gas isn't uniform, so there are some dense knots that take longer to blow away. These dense clumps also shield the area behind them from the radiation and winds too. So You have these long columns of \"protected\" matter appearing.",
"2) Typically everything in space moves at tens to hundreds of kilometres per second. Supernovae are a bit faster. For example, the crab nebula is a supernova remnant, and it's still expanding at 1500 km/s.",
"3) They don't really. I think what you're seeing there is the diffraction spikes, which are a telescope effect.",
"4) Nope. Light comes from everywhere. At the very least you can't escape the cosmic microwave background.",
"5) So one of the big things of general relativity is that gravity is not a force - it actually bends space-time instead. So that means that gravity affects everything, even things that don't have mass. This means that light rays will bend as they go around massive objects. In the case of very strong lensing, this can stretch distance galaxies into long arcs.",
"6) Image light as a longitudinal wave, like a vibrating string. Unpolarised light is when the string is vibrating in all sorts of different directions. Polarised light is when the string is vibrating in just one direction, such as directly up and down. Sometimes it's somewhere in between - it's vibrating in several directions, but more \"up and down\" than \"left and right\". Examining the polarisation can tell us some details about where the light came from - in particular it can tell us about magnetic fields.",
"7) This would be particular to how they do things at Hubble. Probably the press team make something up.",
"8) Honestly, planets are not something I know much about. I ",
" that the bands are because if you don't have irregularly shaped continents, the only thing that sets your climate is your latitude, so you get bands of similar weather. I don't know about the core.",
"9) Yeah, that's just a nice example of very strong gravitational lensing."
] |
[
"Thank you very much!"
] |
[
"Thank you very much!"
] |
[
"Why does a laser spot look grainy?"
] |
[
false
] | null |
[
"To understand this, you have to first understand that light is a wave, and like other waves, sometimes the wave pulls up, and other times it pulls down. The brightness at a given point doesn't matter whether the wave is pulling up or down, just on how hard it's pulling. ",
"A laser produces coherent light, so what that means is if you \"cut\" a laser beam perpendicular to its direction (think of a cross section), it would all be pulling the same way.",
"The rough pattern you see is called speckle. What happens is that a rough surface caused the light to bounce, and its scattered everywhere. As the light travels, it's phase (whether its pulling up or down) is a dependent on how far it travels. If the distance between two point happens to be one full wavelength, then the two points of light \"pull\" in the same direction, and end up being twice as bright. If the two points are a half-wavelength, then they pull in opposite directions and there's no light. ",
"The significance of the coherence is that normal light is so random that all these patterns cancel each other out. With lasers, since the light is all the same to start out with, the depth of the scattering really matters.",
"http://en.wikipedia.org/wiki/Speckle_pattern",
"edit: Interestingly enough, people used to think that the speckle pattern was random and useless. Later it was discovered that the pattern is related to the surface of the material, and so laser light can be used to image the structure of surfaces.",
"editagain: To be clear; speckle is subjective, which means that the observed pattern is dependent on from where it is viewed. Its not necessarily that the surface itself is illuminated in a speckle pattern, but that the light scattered off of the rough surface differs in phase, depending on where its scattered from. The light will then form an image on your retina that has an interference pattern. If you want to figure out whether a given point on your retina will be bright or dark, you have to consider the contribution of the scattered light off of every point illuminated by the laser. So the \"distance between two points\" is a bit of a simplification, but still correct."
] |
[
"They're called ",
"speckle patterns",
", and it's due to interference."
] |
[
"No. This is an artifact of rapidly turning on and off the LEDs for each digit & segment in sequence to allow fewer pins to control more LED's. Likewise, if you wave your hand in your field of view quickly at night under non-incandescent illumination (particularly sodium vapor) you will see it appear to fade in and out due to mains frequency modulating the intensity of the light. "
] |
[
"Why is the softness of ice cream sometimes different?"
] |
[
false
] |
Why is it that sometimes when I take ice cream out of the freezer, it is extremely hard, while other times it is relatively soft? When hard, even a spoon soaked in hot water doesn't scoop it well. When soft, a normal spoon with minimal effort works perfectly fine. The temperature of the freezer isn't changed and I keep the ice cream in the same place. Is there a way to prevent this minor inconvenience?
|
[
"Just because your freezer is set to the same temperature, doesn't mean that it is the same temperature all the time.",
"Every time you open the door, the cold air falls out and is replaced with warmer room air. The freezer needs to turn on to cool it back down to the desired temperature. In doing so, it will actually overshoot the low temperature and go cooler than it's set, so that it can stop cooling and warm up to the temperature. It will then overshoot again and be a bit warmer, turning the chiller back on, and so on. Your freezer temperature can fluctuate quite a bit. The location you've put your ice cream can make a big difference too, depending on if the cool air from the chiller is being actively blown on it, or if there is adequate air movement to get the cool air near it.",
"This was just a quick answer as I've got a place to be, but if you have more follow up questions, don't hesitate to ask. I'll get back to you in time."
] |
[
"The softness of ice cream depends largely of the particle size of the frozen water crystals, which in turn depends on how the ice is mixed and frozen. The air content also have a say, as mpranav explained, but you have very little control over that unless you make your own ice cream.",
"Smaller crystals lead to a softer consistency, and this can be achieved by freezing the ice in a specific manner. When the ice is allowed to thaw, the small ice crystals melt and when refreezing, they freeze together as larger crystals.",
"As to how you avoid the change in softness... Assuming store-bought ice cream, don't allow it to heat up. Easy in principle, but as walexj explained, freezers can be tricky."
] |
[
"The softness of ice cream depends mostly on the air content in the ice cream as well. Soft serve ice cream, for example, is very easy to dig into because of the microscopic air bubbles included in freezing. When you put ice cream in your freezer, its just the slight variations in air content that tell how it will be once you take it out."
] |
[
"Did a Lockheed SR-71 “Blackbird” fly above a Space Shuttle orbiter?"
] |
[
false
] | null |
[
"That not possible, the max altitude the SR-71 could achieve was well below any orbit the Shuttle was flying at.",
"There was several inspection methods for the heatshield. Some included taking pictures from ISS, some involved a camera mounted on the robotic arm."
] |
[
"Thank you so much for the reply! That is what I thought. I wonder where the rumor started. Is it theoretically possibly for an SR-71 to zoom climb or pull up to reach space? I do not think so, but I would love to know a professional’s thoughts on this."
] |
[
"One other fun note. According to Wikipedia, “On 28 July 1976, SR-71 serial number 61-7962, piloted by then Captain Robert Helt, broke the world record: an \"absolute altitude record\" of 85,069 feet (25,929 m). Several aircraft have exceeded this altitude in zoom climbs, but not in sustained flight.”\nI wonder what the lowest orbit of the Space Shuttle orbiter was. Yeah I know, 85,069 feet is much lower than the FAI definition of the Kármán line of 330,000 feet (100 km) above Earth’s mean sea level, or even lower definitions. But I would like to spark a discussion on the SR-71’s zoom climb abilities. I doubt it ever went to space."
] |
[
"Why when you are cooking and you lower or turn off the heat does the pot steam noticeably more?"
] |
[
false
] |
Why when you are cooking and you lower or turn off the heat does the pot steam noticeably more?
|
[
"I've never noticed than, I'll try it out next time I boil something!",
"The reason though, I believe, is the decrease in temperature. Water vapour is colourless and invisible to the human eye. What you call ",
" is the water condensing into tiny micro-droplets as the vapour cools down.",
"With the heat on you produce very hot steam that takes a while to cool down to condense and become visible, however as you turn off the heat suddenly the steam escaping your water pot is much less energetic, condensing much faster. This sudden drop in temperature leads to an observable (as you say) increase in visible ",
"."
] |
[
"Are you using a gas stove? Sometimes when adjusting the valves on a gas stove (that is, turning the knobs to change the amount of gas burning below your pot) you pass through positions you don't expect. If you are talking about a gas stove, then when you pass from the \"low\" position to the \"off\" position, you likely pass through a \"light\" position where a lot of gas is passed to the burner for initial lighting. This sudden burst of gas burns and heats up the pan, and then a second or two later you'll see the water boil more vigorously because this energy has finally made it from the bottom of the pan, through the metal, to the pan/water interface, and then into the water. More heat into the water means more water converted to vapor, and thus more steam!"
] |
[
"I have noticed it on both gass stoves as well as electric and also even on campfires when i pull a pot off of it completely. It spears to definitely be from a reduction of heat, not an increase or burst of heat. "
] |
[
"What happens when microwaving a lit match?"
] |
[
false
] |
When you microwave a lit match which is contained inside a glass cup you can create plasma as seen in this video: When I attempted this I got a similar result and the glass eventually shattered, so my question is what causes the plasma and the shattering of the glass?
|
[
"Fire produces ions and free electrons as chemical intermediaries. Plasma is conductive, microwave induces currents in plasma, creates more plasma. Now you have a cup of plasma. Fairly clever really.",
"Heat makes objects expand. In the case of rigid, brittle objects like glass, uneven heating often causes enormous buildup of stress and cracking. That blue-white ball is at thousands of degrees."
] |
[
"Ionizing radiation(X-ray, Gamma rays) can ionize the air, because the frequency is high, it can hit atoms and take out small particles.",
"The lower-frequency radiation can ionize air too, but this is because of heating effects(If I'm not mistaken).",
"Why doesn't a microwave cause a plasma by itself? The energy required to ignite a plasma in normal circumstances(Room temp, atmospheric pressure) is ",
". It is easier, however, if you take a soft vacuum and try to ionize the trace gasses in there. This is how ",
"Plasma cleaning",
" works, which is basically an antenna transmitting 2.4GHz(Microwaves) into a low-pressure environment. That being said, if you build a microwave with an immense power output(I have no idea how much exactly) you ",
" ionize air.",
"A preignited plasma, however, is much easier to sustain and add energy to. Fire is a plasma. The microwave radiation adds more energy to the plasma, thus sustaining it and raising the energy until the power is turned off. Remember, a microwave can put hundreds of watts out in microwave radiation.",
"As you might or might not know, plasma is the state of matter with the highest enthalpy(Barring some of the more complex states). It contains a ",
" of energy and is therefore very hot. The glass you used couldn't handle the intense heat change from a match flame to a bigger plasma and cracked.",
"tl;dr: Making a plasma is hard. Sustaining a plasma is easy. Fire is a plasma and the microwave adds energy to it. Glass cracks because of heat.",
"If you have more questions, don't be afraid to ask."
] |
[
"Not sure if the new pyrex (tempered glass) can handle that. I'm sure the old pyrex(borosilicate glass can), though."
] |
[
"Engineers and Scientists of Reddit, what are the difficulties from having a person skydive from the ISS? What kind of suit would be required?"
] |
[
false
] |
Is it realistic to beat the record the Felix Baumgartner made with his jump in the next couple of years?
|
[
"if you jump off the ISS you are in orbit.. for a very very long time.. you don't fall from things in orbit, you find yourself in your own orbit. ",
"if you were to jump from a stationary hovering platform in space and were to fall you would incinerate in the atmosphere. "
] |
[
"you burn up in the atmosphere like any other piece of debris that falls to earth. ",
"you would need to be in some sort of capsule or a suit that was extremely rigid and protected from heat.. falling to earth at 17,000 MPH is dangerous shit. "
] |
[
"all the thermal insulators i have ever heard of (the kind which can withstand reentry heat) are ceramic based. Those tend to be brittle. ",
"Hopefully someone else chimes in on this post and can give you a better materials answer. "
] |
[
"What is the difference between quantum uncertainty and ordinary uncertainty?"
] |
[
false
] |
In an electron diffraction experiment, we can shoot electrons one at a time through a grating, and they will make a diffraction pattern, showing that the electrons are really waves. This diffraction pattern is a statistical distribution of the electron wavefront at the detector, and the grating helps to illustrate the connection between uncertainty in position and momentum. If i make macroscale experiments, i will also get statistically distributed results. If i make different experiments on the same sample, the order of experiments is usually important. With better methods i can reduce the interaction between the experiments. Is the Heisenberg uncertainty just the theoretical lower bound on this interaction, or are there other differences as well?
|
[
"The short answer is that the difference is one between true, intrinsic uncertainty in the quantum case, and a simple lack of information in the classical case. A concise way of stating the distinction is to say that it is one of \"quantum uncertainty\" vs. \"classical ignorance.\"",
"To look at this idea more closely, the key difference between quantum mechanics and classical physics in terms of uncertainty is that only quantum mechanics allows for the possibility of ",
"interference",
" between physical states. To use your electron-diffraction experiment, realize that this result is ",
" predicted by classical physics. In a classical experiment the path of the electron would have been fully deterministic. You could have treated the electron as a ball and the grating as a pinball machine and then you could have exactly predicted the electron's trajectory. The only reason there would have been a spread in its final distribution of the electron's position would have been due to experimental limitations, which might be called \"classical ignorance\". This result is qualitatively different from the quantum mechanical picture, where you simply can no longer trace such a sharply defined zig-zag path for the electron. Instead, now the most you can say about the electron's effective movement is that the final position will be a properly weighted sum of the different paths the electron can take and ",
"the interference pattern these would create",
". ",
"So to reiterate, it is interference that is what sets true \"quantum uncertainty\" apart from what can be called \"classical ignorance.\" In the quantum case, the wavelike nature of ",
" particles means that the interaction between particles and even the time evolution of individual particles will show interference effects. Importantly, these interference effects are possible when there is a well-maintained phase relationship in the system. The reason you need to keep the phase stable is ",
"shown in this cartoon",
". If the phase varies wildly, then the phase information will be effectively washed out and the wave-like interference can be ignored. Such a situation can occur if you allow your system to interact with some large external \"environment,\" where this process of washing out the phase is called ",
"decoherence",
". In the limit of complete decoherence you lose the possibility to have any interference, and as you may expect you recover the classical limit."
] |
[
"It's the difference between \"we don't know because we haven't checked yet\" and \"we don't know because it hasn't actually been decided yet\". In QM, the universe genuinely ",
" where the electron is until it matters to something outside of the isolated quantum state because the electron would interact with it.",
"As ",
"u/crnaruka",
" points out, this is what allows a single particle like an electron to interfere ",
" as it goes through the grating. If we were in a hidden-variable universe where the electron really only went through one hole or another, and we were dealing with the \"we don't know\" kind of uncertainty rather than the \"it was never decided\" QM uncertainty, then single particles couldn't interfere with themselves.",
"The exact mechanism that supports quantum uncertainty is a matter of interpretation. In the Copenhagen interpretation, the particle's wave-function interferes with itself in the way waves do. In the many-worlds interpretation, the distinct possibilities exist together in a coherent superposition, and interfere with each other as a result. The math is the same, it's just how you picture it.",
"So the uncertainty principle is not expressing a limit on our experimental methods. It is expressing what we currently understand to be a fundamental limit in how our universe is built. It's not that infinite precision in the electron's position and momentum is there somewhere, but we just can't get at it. It's that electrons can only be blobs of a certain total volume in position/momentum space, so pinning them down along one of those dimensions will just spread them out along another."
] |
[
"In the classical case, the uncertainty is just due to you not knowing what the exact position and velocity of each particle is, but we can still talk about each particle having a hidden value for both momentum and position. In quantum mechanics, these hidden variables can't exist locally. Here is what I mean:",
"If you had a machine that launched baseballs at a wall and they hit the wall at random with a gaussian spread in position, you could attach a camera halfway between and measure the position and velocity of each ball accurately. Then you could understand that the different velocities and positions of the different balls at the halfway point is what caused them to make the pattern.",
"When you shoot electrons through a slit, the electrons are actually much smaller than the slit is. So, like the baseballs you can measure the positions of each electron right before it went through the slit. You can't measure this position perfectly, but you could be much less uncertain than the width of the slit without changing the velocity much. The thing is, that measurement has to spoil the coherence of the electrons that might have passed through the left side of the slit and the electrons that might have passed through the right side of the slit. The diffraction pattern you measure has to change.",
"So, classical uncertainty is just due to local hidden variables that still have a real value for each particle. Quantum uncertainty can't be due to local hidden variables. Einstein really hoped local hidden variables could eventually explain quantum uncertainty in some way, but Bell's inequality has ruled that out."
] |
[
"On aircraft that crash in water why are their black boxes kept in water after found?"
] |
[
false
] |
Yo know, the typical cooler filled with water to transport the black box for further analysis
|
[
"If you take the electronics out of salt water, exposing them to air can cause corrosion and potentially damage data. They leave them in the salt water and only take them out when they're in a position to clean everything properly. It can take 3 days to clean and then dry the electronics so data can be extracted."
] |
[
"The earlier models of flight recorders were based on \"wire loops\". In the early days of sound recording thin wire was used as a recording medium, as the plastic tape/iron oxide tapes we are/were familiar with had not been perfected yet. When it was decided to make flight recorders standard equipment one of the requirements was a recording medium able to withstand possible fires/high heat situations so they went back to old reliable wire recorders. Wire could withstand heat better than plastic tapes, and you could record an endless loop of it without physical degradation like tape. Early protocols assumed wire recorders and rust was a killer. Submerged recorders were pulled and covered in distilled water preferably, and taken to a lab and recovered."
] |
[
"The newer units store data on solid state drives, the older ones and they're still in use store data scored onto strips of metal. The metal strips would be the ones liable to corrode in ways to make it difficult to read. The solid state ones could well be done that way, not sure that it'd be freely available at some of the crash or handover sites though; although they could bring it with them... but then there's weight restrictions to think of with the aircraft..."
] |
[
"If heat rises, why are the mountains frozen?"
] |
[
false
] | null |
[
"The temperature rises in the stratosphere because that is where much of the UV energy from the sun is absorbed."
] |
[
"The temperature rises in the stratosphere because that is where much of the UV energy from the sun is absorbed."
] |
[
"That doesn't have anything to do with why mountains are cold though. Mt. Everest is firmly in the troposphere, though may sometimes be in the tropopause (the gray area between the troposphere and the stratosphere).",
"EDIT: And then I read Jeffy_Weffy's last sentence. I'm not changing it though, I was wrong to assume and I'll admit it."
] |
[
"If your bladder is full do you dehydrate slower?"
] |
[
false
] |
Is there a mechanism that senses the bladder is full and stops/slows pulling water from your body? Or is water just pulled from your body automatically without regard to your bladder?
|
[
"This is a fairly basic and simplistic overview of kidney physiology, but essentially there are three things that govern how much fluid they excrete.",
"First is the pressure gradient driving the filtration of blood at the beginning of the kidney (glomerular capsule).",
"Second is the excretion/reabsorption of various solutes.",
"And third is how much your kidneys allow osmosis to occur to concentrate the urine and prevent dehydration.",
"The bladder does not have any hormonal or neural signalling that affects kidney physiology. The only thing a pathologically full bladder might affect is the pressure gradient. This does occur in patients that have an anatomic problem with their bladder or outflow tract including things like stones, a large obstructing prostate, or cancer (think of a tumor growing into a tube blocking it). This results in \"hydronephrosis\" which is a medical diagnosis for a fluid filled kidney caused by outflow obstruction. Hydronephrosis can cause severe kidney damage if not relieved and is typically treated as an emergency. If the obstruction is severe enough, these patients can become fluid overloaded, but typically at that point they've already reached kidney failure and can't/won't produce much urine anymore unless they get a transplant."
] |
[
"There are several mechanisms by which kidney function can be controlled. Unfortunately, the bladder is not involved in any of those (as far as we know today). Evolution would not favor such a mechanism. In nature, we dont really have to hold our pee for hours. Also interesting: even if you dont drink anything your kidneys are going to produce about 200ml of pee every day. If a certain point is reached, they shut down. And then you are screwed."
] |
[
"Technically yes, as you can just drink the urine to rehydrate yourself briefly."
] |
[
"How Many People Can the Earth Hold?"
] |
[
false
] | null |
[
"correction:",
"surface of a sphere: 4",
"r",
"0.5 * 0.25 = 0.125 m",
" area per person.",
"((4 * 3.14 * (12 756 200",
" )) * 0.2889) / 0.125 = 4.72356404 × 10",
" people"
] |
[
"You've corrected some of his errors - namely the \"footprint\" calculation and lack of conversion from square kilometers to square meters when dividing the areas - but you seem to have introduced your own.",
"You've correctly stated that the surface area of a sphere is 4 pi r",
" - however, note that he was using the ",
" of the earth -so his original surface area calculation is the correct one. (4 pi r",
" = pi d",
"So finally, the correct answer should be:",
"((3.14 * (12 756 200",
" )) * 0.2889) / 0.125 = 1.18089101022633792 × 10",
"An adjustment by a factor of 4."
] |
[
"I suppose I meant sustain, I don't really see the benefits in putting 118,148,997,600 shoulder to shoulder. I do however, find it interesting that about 6% of this shoulder space is already occupied. "
] |
[
"Are two lottery tickets always the optimal number of tickets to buy?"
] |
[
false
] | null |
[
"All that matters is \"X\". If it is less than 100 then the maximum expected value is always at 0 tickets. If X>100 (can happen in charity raffles if the prizes are donated and worth more than the total price of all the tickets) then more tickets is always better. If X=100 the EV doesn't change between any number of tickets, if you're risk averse the best options in this are to buy 0 or all tickets."
] |
[
"Lotteries are always designed so they pay out less than the total put in. The optimal amount is always 0."
] |
[
"I don't really play the lottery, and I don't have delusions of winning and I get how hard it is to win. Just wanted to see how the math works for this as a thought experiment. "
] |
[
"Why do shower curtains attack?"
] |
[
false
] |
Every morning my wife and I take a shower together. When one of us leaves the shower, the shower curtain starts to aggressively encroach on the personal space of the person still in the shower. Why does this happen?
|
[
"There's a wiki",
". Surprised? I was."
] |
[
"Until I looked at the URL I thought you meant an actual whole wiki about this one effect, and was ",
" surprised..."
] |
[
"I'm going to take a stab and say that the egress of one person starts a circulation airflow and the warm shower air is flowing upward and drawing cool air from the rest of the bathroom in under the shower curtain."
] |
[
"Has there been any research on mathematical thought and the brain?"
] |
[
false
] | null |
[
"Yes. There have been many studies. You can get a sampling just by searching for something as simple as \"math fMRI\" in google scholar. Do you have a more specific question?"
] |
[
"In general, most of your brain is active no matter what task you're doing: solving a math problem, for example, involves seeing the problem, reading, understanding, doing math, making decisions, accessing memories etc. ",
"At best, we can ask \"are there regions of the brain that are necessary for solving math problems or which are more active when solving math problems relative to other tasks\". The answer is yes. See for example ",
"Lee (2000)",
" which reviews some early findings on acalculia. Interestingly, they suggest that different math operations might have different cortical loci. In general, arithmetic-related activity has been found in prefrontal, posterior parietal, and anterior temporal cortices among others. However, those areas are involved in many other processes. There is no single \"math\" part of the brain, as is the case for most functions. "
] |
[
"Are there any areas of the brain that are known to show activity when one answers an equation? If so what are they and how do they work?\nIs there a basic structure behind such a process?"
] |
[
"Top down versus bottom up models of ecology: Why not syncretic/hybrid views of ecology?"
] |
[
false
] |
In my undergrad ecology courses, my professors explained how ecologists view ecosystems either using top-down models (apex predators influencing the ecosystem the most) versus bottom-up (detritis feeders and producers influencing the ecosystem the most). I was taught that most ecologists subscribe to either view of ecosystems. What I never understood is why having that model is even useful or important, because it seemed to me that both sides had valid ways of understanding ecology, but also didn't understand why going one way or the other would be more useful way of understanding the environment. It seemed to me from reading the debate about top down versus bottom up that it would make just as much sense to view different dynamics in different ecosystems and throw out both models and just try to understand ecosystems as they are as they come. I would like to hear opinions and thoughts about top down versus bottom up and would love to be pointed out to supplemental readings as well.
|
[
"Are you familiar with Robert Ulanowicz's work? He is a strong proponent that ecosystem organization results from both bottom up (i.e., traditional reductionalist) and top-down influences. (Disclaimer: I'm not an ecologist, but I've been reading Ulanowicz's papers on information theory.)"
] |
[
"Can you link one of his papers?"
] |
[
"Here's",
" an overview I like. His stuff can be a tough read depending on your background. I found his book ",
" to be a gentler, albeit much longer, introduction."
] |
[
"How to solve this Combination problem?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"/r/HomeworkHelp",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"But it's not for my homework, my dad was asked this question by his friend, and my dad couldn't think of the answer so he asked me.",
"And neither could I think of anything so decided to ask reddit. ",
"/r/askscience",
" is the largest sub for these kind of question/doubt so I decided to ask there. If it doesn't belong here, please point me towards somewhere else.",
"/r/HomeworkHelp",
" isn't the right place imo because it requires me to put in which \"level\"(of maths I presume) the question belongs to, which I don't know."
] |
[
"/r/LearnMath",
", ",
"/r/AskMath",
", ",
"/r/cheatatmathhomework",
", ",
"/r/HomeworkHelp",
". The kind of math is \"combinatorics\"."
] |
[
"With normal usage, are teflon pans actually bad for you?"
] |
[
false
] |
If one avoids scratching teflon (or other non-stick) pans, are there any negative health effects to worry about, short or long-term? I can't seem to get a good science-based answer (probably partially because I can't access the actual papers, and don't have the expertise to interpret them properly).
|
[
"Your definition of \"normal usage\" may differ from other people's, so I can't say exactly whether it's safe in the manner that you're using it. However, here's a ",
"pretty easy to read summary of several studies",
".",
"Summary of the papers:",
"In peer-reviewed research, the lowest temperature known to kill birds is 396 degrees. Anecdotal evidence suggests that birds may die at temperatures as low as 325 degrees, but again... that's anecdotal.",
"Rats begin to die off at higher temperatures.",
"Note that if you cook stuff at a high temperature, it's quite possible that your pans will get into the \"bird killing\" range under what you might call normal usage. And if you heat an empty pan over a burner for awhile, it might get to high enough temperatures to make you feel sick. Fortunately, humans are large and resilient enough that a common Teflon pan won't kill them.",
"The best way to avoid overheating a Teflon pan is to ",
". If a recipe calls for preheating your pan, put a little cooking oil in there. If the oil begins to smoke, you're getting pretty hot and should immediately put food in or take it off the heat. Once food is in the pan, it's harder to overheat the pan unless you have absolutely on idea what you're doing and are looking to obliterate your food :)"
] |
[
"The \"scratching the pan\" thing is a red herring. The important thing is how much perfluoro material, perfluorocarboxylic and sulfonic acids, are released. ",
"Studies at NOAA where I work have shown increasing levels of these contaminants in water and marine organisms. They are known endocrine disruptors. Also, they are fat-soluble and are known to bioaccumulate. I think people who say \"just don't overheat the pan\" are being a little bit over-optimistic: heating just oil in the pan sounds to me like a recipe for preparing a solution of fluorinated compounds in cooking oil.",
"The short version: there may be slowly accumulating effects of teflon pan use, which is not covered in the link elchip provided. I personally steer clear of teflon AMAP, only using it once a month or so. Offgassing is not the real danger, it's accumulation of fluorinated compounds that get into your food. "
] |
[
"If you have birds, the best thing to do is to simply give or throw away your teflon.",
"Is a single meal, or a single pan, worth the life of a companion?",
"We switched to cast iron after getting our birds and learning about teflon.",
"Turns out, they're way better anyway... :D"
] |
[
"Do men and women utilise peripheral vision in different ways?"
] |
[
false
] |
I can't remember now what it was, but something today made me wonder about this. We all have a certain degree of it, and surely we're all attuned to respond to different things in different ways, but has research been done into how people make use of it? Humans having been hunter gatherers for a long time, with gender-based division of labour... Women staying back in the family group lookin after the young while men go off to hunt... Could it be that women notice faces more easily in their peripheral vision, while men notice shapes and cues better... I'm not trying to convey a sexist agenda here, I'm just curious if there's been any research about this. I know there are hardwired differences between the genders such as how women see more colours than men, amongst other things like this.
|
[
"Women staying back in the family group lookin after the young while men go off to hunt",
"On the contraire! Women in simplified hunter-gatherer societies, due to the society having a low division of labor, are very busy. The society as a large ",
" hunters/gatherers, and everybody pulls their weight regardless of gender. As women in these societies are primarily gatherers, they would also need an acute sense of peripheral vision for identifying edible and/or useful plants."
] |
[
"Males and females use their brain differently because there is a difference in brain connectivity. When they are both performing the same task, different areas in the brain are activated.",
"The typical male brain has connections that mostly run back and forth of the same brain hemisphere, which can account for better spatial skills and muscle control. In females, neural connections go side to side across the left and right hemispheres of the brain, which can account for the better verbal skills and intuitive abilities. ",
"In perceptual speed test, such as saying words like (limp, livery, lug, liquid, lift, liver) women are generally faster, and in verbal fluency tests, women perform better. ",
"In regards to peripheral vision, I am sure men and women view and analyze visual stimuli differently but I question if there is enough difference that only women or men can see certain things or in different ways, as both genders possess the same type of photoreceptors and the same nerves that carry information to the brain. How each gender process the information is different, however."
] |
[
"I've read that in Hunter/Gatherer society, men would go out on the day(s) long hunts while women reared the children and foraged close to the tribe's camp among many other likely duties. ",
"For this, men required better focal distance and hand/eye coordination and relied on the 'pack' to provide security in the flanks reducing the need for individual acute peripheral vision.",
"Women however foraged, which meant paying close attention to what's in front of them. But it also meant requiring a situational awareness to their flanks as they wouldn't have been able to provide the same level of attention and security in groups without their ability to forage efficiently being affected.(",
") Thus they would have developed a more acute peripheral vision but not so much for detail but movement and possibly color, both beneficial to detecting threats as well as gatherables not in their direct line of sight.",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
"I would say the differences individually aren't very noticeable but on a large population being tested I would wager men come out better for tracking, long sightedness and higher resolution at a distance. Women would come out on top for shortsightedness, color perception and movement detection/contrast perception.",
"It seems logical and they both complement the weakness of the other but again this is just theoretical last I read.",
"The same can be said though for the angle of out-turned-ness of the arms of men and women.",
"Men's arms are angled outwards more so than women's, which provides a more fluid extension of the arm while throwing a spear, rocks or thrusting with a spear.",
"Women's arms seem to angled inwards more so than men's which conveniently is more suitable for carrying things better as well as providing minor protection to the vital circulatory system that is more exposed on the inner arm than outer such as when moving through precarious undergrowth or defending against predators that may use biting or slashing as an offensive strategy.",
"Just my 2c, if I'm wrong or inaccurate I'd be very interested in being corrected as this topic, the biological and evolutionary difference between men and women, is one I find thoroughly interesting."
] |
[
"If microwaves have a longer wavelength than visible light why can they harmful?"
] |
[
false
] | null |
[
"They’re harmful at high intensities. And that’s not due to ionization, just just burning."
] |
[
"Then why is visible light harmless to our skin"
] |
[
"It’s not harmless at high enough intensities to cause burns."
] |
[
"Plenty of animals produce highly acidid fluids (e.g. stomach acid). Do any animals produce highly basic fluids?"
] |
[
false
] | null |
[
"I know that unlike mammals, the gut of many (if not all?) insects is very basic (around pH 10). I believe this is the primary reason why BT toxin (a common pesticide) kills insects, but doesn't hurt mammals."
] |
[
"The human duodenum produces a fairly alkaline solution to combat the acidic nutrients leaking out of the stomach into the intestine. Human males produce a slightly alkaline solution to add to semen in order to counteract the acidic environment of the female vagina.",
"A lot of insects have alkaline guts.",
"I'm sure there are many other examples."
] |
[
"Oh, neat. Searching for insect gut pH is returning some nice results. ",
"Physicochemical Conditions and Microbial Activities in the Highly Alkaline Gut of the Humus-Feeding Larva of Pachnoda ephippiata",
" ",
"pH profiles of the extremely alkaline hindguts of soil-feeding termites (Isoptera: Termitidae) determined with microelectrodes"
] |
[
"Why are fingerprints an individually unique feature of the human race? Are there other species that exhibit features like this?"
] |
[
false
] | null |
[
"Cow's noses have a unique pattern, and the nose-prints can be used for identification, similarily to our fingerprints ",
"link"
] |
[
"Koalas are generally law abiding. Drop bears on the other hand are notorious for pinning their crimes on humans."
] |
[
"Gorillas and chimps also have them. Koalas have fingerprints that are almost indistinguishable from humans.",
"www.odec.ca/projects/2004/fren4j0/public.../animal_fingerprints.htm",
"EDIT- ",
"http://www.odec.ca/projects/2004/fren4j0/public_html/animal_fingerprints.htm",
"Thanks sharoz"
] |
[
"Every computer program is compiled (or interpreted) by another program, called the compiler or interpreter. This includes compilers themselves. Is there a \"common ancestor\" compiler of all high-level programs today, and if so what is it?"
] |
[
false
] |
I assume the first compilers were written by hand in machine code. Then subsequent compilers can be written in the language implemented by that first compiler, etc. Is there a single hand-written program that basically "birthed" all high-level code we use today?
|
[
"No, not really. The methodology of programming is similar, but there is no single ancestor. You need to understand how the CPU works at the very low level. It fetches data from a memory location. That data contains a bunch of bits that represent an instruction. That instruction can be an add, multiply, jump to a memory location, etc. - a very simple operation. A CPU is really an ISA - an instruction set architecture. An ISA defines what all the different bits mean - what operation they represent. An x86 ISA is different from an ARM ISA - the different bits mean different things. (A CPU is a HW implementation of an ISA to be precise)",
"So, when you have a CPU, in order to get a program, you need to string a bunch of these data together. At first, sure, people would \"write\" them by hand. Then people realized that it's convenient to write small chunks of these instructions together into \"procedures\", which use multiple instructions to perform more complex tasks. At some point you create enough of these to create a compiler - a program that takes a text file (assembly or C), and emits the instructions for you. Then you can start writing a new compiler using the old compiler, etc. etc. Just a note that assembly is simply a more readable binary, and there is a 1:1 ratio of assembly to binary instructions. C needs to be parsed and broken down into simpler operations, but it's surprisingly close to assembly, to the point that some people call it a \"more elegant way of writing assembly\". This may be a stretch, but it's not a huge stretch.",
"Anyway, that's what would have to happen if you had the first CPU, but it's not what would happen today if you created a new ISA. If you create a new ISA and you want to write a compiler for it, you'd take an existing compiler on your PC, say, GCC, and you'd write the emitter portion for your ISA. The parts that parse the C/C++ text files are just fine - they don't need to change. The only part that needs to be implemented is the \"back end\" the very \"last\" portion that actually emits the instructions for the ISA. You'd have yourself a \"cross compiler\", because you'd run it on your PC, and use that CPU to generate the binary instructions for the new CPU. Once that's done, you could compile the compiler itself for your new ISA using the very same compiler on your PC, and run it on the new CPU! Fun, eh? These days, only very small ISA-specific bits are written using assembly - and it takes a very simple compiler to translate the mnemonics of the instructions into binary.",
"HTH "
] |
[
"There's still ",
" ancestry. It's mostly a sea of unrelated points, with no lineage, but there is ",
". At the risk of trusting StackOverflow, the original C compiler was based on, and written in B. The first B compiler was written in TMG, and the TMG compiler was written in assembly. So there's actually some lineage in the B -> C compiler.",
"https://stackoverflow.com/questions/1653649/how-was-the-first-compiler-written",
"I'm not particularly knowledgable about B, but it doesn't look like it's too different from C. This is probably why there is the connection, much easier to just adapt the B compiler to include C's features."
] |
[
"Note that people have written C compilers in Assembly as well. While you can trace ancestry of the ",
" compilers, those weren't necessarily the most influential. The first ",
" C compiler was written in... surprisingly... C.",
"The first B compiler was written in TMG, but B itself was a simplified version of the BCPL language. TMG was literally... a language/compiler that was written/designed to... compile compilers.... which BCPL was also designed for.",
"But, it's difficult if not meaningless to trace ancestry like this. Not everyone worked off of the 'first compiler'. If we are just tracing the 'C' line, then until you hit C, it's meaningless as it is fairly linear but branches based on what tools they used. B doesn't incorporate TMG functionality or concepts, it's just that TMG was used to write the compiler as TMG was literally the 'compiler compiler'. B itself was mainly an evolution of BCPL, itself an evolution of CPL, which was an expanded concept based upon ALGOL 60, and going back from there you end up in FORTRAN and, surprisingly, Plankalkül - Konrad Zuse's language which was itself based upon ",
" - 'Concept Script' that defined a formal system of logic in 1879 by Frege...",
"So, language-wise, C has its furthest ancestry in:",
"So, you have a shared language ancestry based around the actual CPU and writing for it and from formal logic systems... which makes sense, since that is all a programming language is. This spreads to daughter languages like C++, which are originally expansions of C -\n C++ originating with Stroustrup's \"C with Classes\", and originally was compiled using CPre, which was a preprocessor for C. CPre was used to compile CFront, which was the first C++ compiler, itself ",
" being a fancy preprocessor for C.",
"Nobody uses these 'first compilers' anymore. The most common C and C++ compilers in used presently are ",
", ",
", and Visual C++. I'm not sure what ",
" was originally compiled with - probably another C compiler. ",
" was originally compiled with ",
". Visual C++ was originally compiled using Microsoft C. Microsoft C was based on Lattice C. I do not know what Lattice C was originally compiled with - probably, like ",
", another C compiler.",
"But the basis is that if you have a language like C where you want to write a new, 'good' compiler in, perhaps a standardized one... you usually will still write it in that language, but perhaps a simplified version of it. You can then bootstrap it - you can use either an older compiler, or just write a simple compiler in assembly, which isn't particularly hard for a language like C or B. So, there are likely plenty of points where the 'compiler ancestry' breaks or is just meaningless."
] |
[
"In the northern hemisphere, why does the sky lighten in the north early in the morning?"
] |
[
false
] |
I live at 47 degrees north. The northern sky lightens significantly earlier in the morning and stays light significantly later in the evening. Why is this? It seems at odds with the fact that the sun appears in the southern part of the sky. Shouldn't the southern part of the sky get light earlier, since that's where the sun actually shows up?
|
[
"The further north you go, the more the Sun appears to circle around the sky rather than go up and back down. You're far enough north that as it goes around, it's not too far below the northern horizon, so you see it's light there. But by the time it rises it's gone around more to the east. If you go far enough north (I was there just a week ago!) you won't see it set at all right now, it'll just be high in the south during the day and low in the north during 'night'. Check out ",
"this image",
" for an illustration."
] |
[
"Great! I felt like I needed to visualize something like that image, but I wasn't quite able to wrap my head around it. And I didn't have a globe handy. Thanks!"
] |
[
"If you watch closely around the summer solstice, you'll see the sun rise around 55 degrees east of north. So it actually does rise in the northern half of the sky. Scattering in the atmosphere causes even parts of the sky far from the sun to light up."
] |
[
"Why does buoyancy depend on the weight of the displaced fluid?"
] |
[
false
] | null |
[
"Well nature is not obligated to be “obvious” to us. But when you wrote down an expression for the pressure gradient force on the submerged object, you find that it just equals the weight of the displaced fluid."
] |
[
"Alright, I thought that maybe someone else in the last hundreds of years would have pondered over that question and found an answer. It is such a striking \"coincidence\" that those forces are equal."
] |
[
"and found an answer",
"We have found an answer. But answers in physics come from math, rather than what \"seems right\"."
] |
[
"which would get warmer?"
] |
[
false
] |
If you had a sealed clear plastic container with air in it, and a sealed clear plastic container with co2 in it, and you left them both in the sun... would the container with co2 get warmer faster? edit// +faster
|
[
"hang on, something's backwards.",
"Heat capacity is a property that determines how much energy it takes to heat an amount of the material. Low heat capacity means it takes very little energy - high heat capacity means it takes more energy.",
"CO2 has other properties that sets it apart, of course, but there's still something wrong with this specific answer. Are you quite sure that CO2 doesn't have a ",
" heat capacity?"
] |
[
"Yes you are quite right, I have it backwards. CO2 would heat slower"
] |
[
"The key is that the container containing carbon dioxide would cool more slowly, this is the problem with global warming. There is a very simple practical you can do to see this; all you need is plastic milk bottles, alkaseltser, data-loggers and a lamp."
] |
[
"Is there some sort of \"flower controversy?\""
] |
[
false
] |
I recently was talking to a friend who made a comment along the lines of "we don't understand how the first flowers developed, they came out of nowhere." Is this true? I have a hard time believing this one. edit: mystery, not controversy.
|
[
"I apologize\n",
"http://www.nytimes.com/2009/09/08/science/08flower.html?pagewanted=all"
] |
[
"I apologize\n",
"http://www.nytimes.com/2009/09/08/science/08flower.html?pagewanted=all"
] |
[
"ha, I was staring at a map of wales wondering what I was supposed to think."
] |
[
"How does one \"acquire\" taste?"
] |
[
false
] |
Does eating or drinking something enough actually alter your taste buds in some way?
|
[
"Things many claim are acquired tastes tend to have a bitter component (e.g. coffee, beer). Our tongue has only one receptor (actually a dimer thereof) for all \"tastes\" - sweet, salty, sour, umami - except bitter, for which we have somewhere in the 50's i think (correct me if i'm wrong). This is because we've evolved to find potentially harmful compounds as bitter (we could have 50 different sensations for them but the brain likes economy). And indeed, many commonly found toxic compounds are bitter - e.g. mold.",
"However, many harmless foodstuffs are bitter, as mentioned above, especially today. Thus, when we first drink beer or coffee, we usually don't like it, because our brain is telling us that it's probably harmful. However, if our experience ends up being positive for whatever reason (social context, effect of caffeine or alcohol), the brain learns to dissociate that particular taste from the aversion reflex. "
] |
[
"With taste it's the same as with other senses -- most of it happens in the brain, not in the sensory organs (the taste buds in this case). Think of optical illusion, as a comparison. ",
"How something tastes to you depends on:",
"So most of the factors that influence subjectively perceived taste have really nothing to do with tastebuds. Especially item #2, expectations, obviously varies as you get more used to a food or drink."
] |
[
"Thanks! I'm learning all sorts of stuff today."
] |
[
"If an asteroid hit our moon, with the impact being large enough to be visible by the naked eye, what effect would it have on our planet? [xpost from /r/Askreddit. I didn't know /r/askscience existed]"
] |
[
false
] |
I'm not talking about the moon being obliterated, as that would obviously have an enormous effect. I'm thinking more of the smallest possible impact that could clearly be viewed by the naked eye. I started thinking about this when I was walking home in the early hours of this morning and (as always) was completely mesmerised by its beauty.
|
[
"I find this mildly hilarious. Think of all the shit we'd have to adjust"
] |
[
"I doubt it would have any effect. If the moon became heavier or lighter then the tides would change in amplitude, and if its orbit changed then the length of the month would change, but I don't think an impact that size would be big enough to do either of those things."
] |
[
"The moon moves about a kilometer per second. The biggest asteroid is about 1% the mass of the moon. If it slammed into the moon at opposite speed, and momentum was conserved, it would slow down the moon by about 3% and a lunar month would be about 31 days."
] |
[
"Does Acupuncture work?"
] |
[
false
] |
Basically what the title says: Does acupuncture work in the treatment of any medical condition (as more than a placebo)? I'm not thinking about undergoing it or anything, just curious. Note: It's not likely I'll value your input if you believe in homeopathy.
|
[
"There is no evidence",
" supporting acupuncture. It doesn't work and any reason people think it may work is the placebo. There is a small chance that any sort of pressure can help with back pain so it may slightly alleviate that but so would a massage for less hassle. ",
"It definitely doesn't cure or did any disease or other ailments. There is no way as we understand the body that it even could. It was created way before we had any understanding of the human body and was essentially a guess based off fake assumptions about chi lines, and confirmation bias mixed with the placebo affect. "
] |
[
"I'm an M.D., but I apologize in advance, because this will be somewhat anecdotal. (I will preface this by saying I've never had acupuncture performed on me and I certainly don't have any financial interest in referring people to an acupuncturist.) ",
"Of all the \"alternative\" medicines, this is the modality I'm most in favor of, simply because it does have a strong placebo effect. People seem to think \"placebo\" is a bad thing, but, and I know this sounds trite, for short term non-pharmacological treatment of minor conditions, I think placebo is wonderful and shouldn't be dismissed. ",
"One place I've seen acupuncture used fairly regularly in a well-established hospital was in preoperative patients. It wasn't used for anesthesia, or to take the place of \"real\" medicine, but was used to calm and relax the patient prior to surgery. People would be asked if they were anxious, nauseated, etc., and the acupuncturist would tailor the technique to what the patient said. I'd be lying if I said it didn't help or completely relieve the symptoms of nearly all the patients. I'd much rather the patient find some relief that way, then by giving anxiolytics, antiemetics, etc. ",
"So, even if acupuncture doesn't necessarily \"cure\" a condition, it can be a powerful placebo that is an important outcome in its own right."
] |
[
"Thanks for all your responses guys - the general consensus I'm getting is that it doesn't really work as an effective medical treatment and any affect it does have is negligible to the point of uselessness and can mostly be explained by placebo."
] |
[
"Why are we colder when wet?"
] |
[
false
] | null |
[
"Our sensation of being cold (or hot) is strongly affected by the rate at which we exchange heat with the environment. When we're wet, the water is almost always colder than the 37 C of our body. That means that heat flows from our body into the water on our skin. And since water has a considerably higher heat conductivity than air, the body loses heat more rapidly when it's covered in water.",
"Next, the water will evaporate, which lowers the average temperature of the water that remains, causing further heat flow from the body to the water on the skin. Essentially, this is the same as sweating, except that sweating is a beneficial process that the body initiates when it is too hot.",
"So when we're wet, we lose heat more rapidly than when we're dry. This causes a stronger sensation of feeling cold, even though the water on our skin may be warmer than the air."
] |
[
"this reminds of an experiment we did in middle school. you touch a metal table and it feels cool to the touch. you touch a wooden chair and not so much. but when you touch a thermometer to them both, they are the same temperature. the metal, being a better heat conductor, causes your skin to lose heat faster, so it feels cooler than the air around it, even though it's not. that blew my mind in the sixth grade haha"
] |
[
"this reminds of an experiment we did in middle school. you touch a metal table and it feels cool to the touch. you touch a wooden chair and not so much. but when you touch a thermometer to them both, they are the same temperature. the metal, being a better heat conductor, causes your skin to lose heat faster, so it feels cooler than the air around it, even though it's not. that blew my mind in the sixth grade haha"
] |
[
"Photoelectric effect and electrons explanation?"
] |
[
false
] |
From what I understand, solar panels are made of materials that can be used with the photoelectric effect. Light reaches the object, and eventually the atoms receive so much energy that electrons break-off the atom and start moving freely. An example of these materials is silicon, a semiconductor. My question is, don't the silicon atoms eventually "ran out" of electrons to release, or where do they get new electrons from? I feel like I am lacking knowledge about this area nd would like someone to explain this to me, if the silicon atoms are constantly losing electrons which we are using for our electricity, wouldn't the silicon eventually "wear out"? Lose all its electrons?
|
[
"So silicon doesn't have free electrons. You dope it with something like phosphorus called N-type doping to add electrons and boron that adds an electron-hole in the silicon lattice called P-type doping.",
"If you stick these different types of doped silicon back to back, then you have a diode. Which is basically what a solar cell is, just lots of diodes with electrons at the edge, a.k.a the depletion region.",
"So usually you'd shine light at silicon, and it absorbs enough energy that electronics become excited and move around, but now they can only flow in one direction. And you're right, and the electrons have nowhere to go, thus cannot flow.",
"So what you do is attach one side of the cell to the other side, so the electrons flow back into the other side, round and round. Seems a bit silly until you realise you can attach something like a transformer to the circuit as a means of extracting the electronic flow, a.k.a energy.",
"And that's basically how solar cells work, you string them together in series and connect it to an inverter as a means of generating AC power.",
"I've spent the last couple of weeks working on a solar farm testing their kit.",
"TL;DR, they don't escape. It's a closed circuit and they flow back into themselves."
] |
[
"From what I understand, solar panels are made of materials that can be used with the photoelectric effect.",
"Actually, the mechanism underlying solar panel operation is called the ",
"photo",
" effect",
", not the photoelectric effect. The photo",
" effect is when electrons are ejected from a material by light. The photo",
" effect is when electrical currents are induced in the material by light. Although they are related, there's a big difference between the two effects!",
"An example of these materials is silicon, a semiconductor. My question is, don't the silicon atoms eventually \"ran out\" of electrons to release, or where do they get new electrons from?",
"Well, no, silicon is used in things like solar cells because it is amenable to the photo",
" effect, which does not eject electrons from the material. So they do not lose any electrons over time.",
"I feel like I am lacking knowledge about this area nd would like someone to explain this to me, if the silicon atoms are constantly losing electrons which we are using for our electricity, wouldn't the silicon eventually \"wear out\"? Lose all its electrons?",
"It would, if that were how electricity works ... but electricity doesn't work that way. Electricity isn't some kind of \"consumption of electrons.\" When you use electricity, all of the electrons mostly stay in place; their motion is usually measurable only in the millimeters per second or so. The motion of electrons is what transfers useful energy, but the energy is passed along from electron to electron; it isn't ",
" made out of electrons, it's in the forces and potentials ",
" electrons. That's why electrical signals and power can be transferred very quickly (around half to two-thirds the speed of light) even though individual electrons are barely moving at all. Think of it as a sort of ",
"mechanical wave",
" (in the linked animation, energy is being transferred from the bottom right to the top left even though there is no net motion of any circle).",
"Hope that helps,"
] |
[
"u/ZeroBullshitMan",
" covered it pretty well. If you have an electrically-isolated solar cell then the excited electrons will just move toward one side of your solar cell and sit there. But if you're connected to a circuit then you've got, say, metal wires that have electrons and other things in the circuit. What's really happening is the electrons coming out of your solar cell end up pushing the electrons in the wire all the way around such that an equal number of electrons flow into the solar cell from the other side.",
"\nYou can think of \"conservation of charge\" here - draw a box around any segment of your circuit and the number of electrons leaving the box will equal the number of electrons entering the box. You could draw this box around a segment of wire, around your solar cell, or around the entire circuit (no electrons enter or leave, 0 = 0)."
] |
[
"Is soap required to \"foam\" in order to work properly?"
] |
[
false
] | null |
[
"Nope! Two soaps that don't foam are laundry detergent and the type of soap that goes in dishwashers. If you put a foaming type of soap in either of those machines, it will cause a huge mess. However, those soaps still clean dishes and clothes just fine.",
"Lots of cosmetics companies actually add things (like sodium dodecyl sulfate or ammonium lauryl sulfate), to soaps to make them foam more, because many people associate foam with cleanliness."
] |
[
"No...that sounds like the definition of an old wives tale.",
"More foam nearly always means more foaming agents, nothing more. Some soaps foam more or less than others at baseline depending on the oil they were created from (coconut soaps foam more than castor soaps), but almost all of the foam you see in modern soaps comes from foaming agents such as Lauryl Sulfates."
] |
[
"Foam is not needed for soap to work. In fact, the less foam you have, the more soap is activly at work in the water. \nFoam is a by-product of soap, created by the fact that soap lowers the surface tension of water, allowing it to form bubbles. So lots of foam on the water means less active soap in the water. "
] |
[
"Why doesn’t our moon rotate, and what would happen if it started rotating suddenly?"
] |
[
false
] | null |
[
"It does rotate, but the time it takes to rotate around its axis is exactly equal to the time it takes to orbit the Earth. And as a consequence, we always see the same side of the Moon.",
"Now you might say: \"That seems a bit too neat to be a coincidence!\"",
"And you would be right, because it's not a coincidence. The tidal force (the same thing that makes the tide come and go out) causes the rotation of an object to sync up with its orbit. In this case, the tidal force of the Earth on the Moon has constantly pulled at the Moon until the rotation and orbit were synced up. This state is called a \"tidal lock\".",
"If something were to give the Moon a nudge that would alter either its orbit or its rotation, the same tidal force would gradually pull it back in sync again. It would just take a long time.",
"It also happens the other way around: The tidal force from the Moon isn't just making the seas and oceans move around, it also pulls at the solid bits of the Earth, ever so slightly slowing down the rotation of the Earth. If the Sun wouldn't gobble up the Earth when it expands in 4-5 billion years, than some 50 billions years from now the Earth would be tidally locked to the Moon at which point the same side of the Earth would always be facing the Moon and the length of a day would be much longer than the 24 hours it is now."
] |
[
"The force of gravity falls of with the square of the distance. Despite this, the Sun is so massive that even though it's much further away than the Moon, it is still the gravitationally dominant body for our planet.",
"However, while the tidal force on our planet is a consequence of gravity, it is a function of the difference in gravity between the point on our planet nearest to the other object and the point on our planet the furthest away. So if the distance from the center of the Earth to the object is ",
" and the radius of the Earth is ",
", the tidal force is proportional to:",
"1 / (r - R)",
" - 1 / (r + R)",
"If you do some algebra on that expression, you'll find that the tidal force falls off like 1 / r",
", so with the cube of the distance to the other object, instead of the square of the distance for regular gravity. And because of how strongly the tidal force scales with the inverse of distance, the relatively lightweight Moon is the dominant player because it is so much closer than the much heavier Sun."
] |
[
"Silly question but why doesn't the earth sync in the same way? A planet much closer to the sun would sync?"
] |
[
"Could a neutrino interact with a water molecule in my eye and release a photon that I could \"see\"?"
] |
[
false
] | null |
[
"Yes, there is an incredibly small probability of a neutrino interacting with something in your eye and you seeing it. It would most likely be a neutrino-electron elastic scattering, which can accelerate the electron to a velocity faster than the speed of light in that medium resulting in ",
"Cherenkov radiation",
"."
] |
[
"I thought this was a super cool question so instead of working on calibration for my experiment I wanted to do a quick back of the envelope calculation.",
"so the cross section for inelastic scattering on a neutrino... okay thats way to complicated :P lets look at a well know neutrino experiment Super-K and compare to the human eye and make a terrible assumption that they are equally sensitive. Super-K has 50,000 metric tons of water and observes roughly 4000 solar neutrinos a year.",
"[1]",
" The mass of the human eye is ~ 7.5 g ",
"[2]",
".",
"So if we do a simple ratio ",
"7.5g / 50,000 metric tons = x/4000 neutrinos/year",
"1.5*10",
" = x/4000 neutrinos/year",
"x = 6*10",
" neutrinos per year in an eye ",
"so we can expect 1.2*10",
" neutrinos to be detected in a pair of eyeball sized Super-Ks. As far as the efficiency of the super-k photomultiplier tubes compared to the human eye I am not so sure on so lets call it Ɛ. I would guess that Ɛ is a pretty small number. (I might try to come back to this and give a order of magnitude estimation for Ɛ.)",
"[1]",
"http://hep.bu.edu/~superk/about.html",
"\n[2]",
"http://kirschner.med.harvard.edu/files/bionumbers/Density%20and%20mass%20of%20each%20organ-tissue.pdf"
] |
[
"Roger that ",
"/u/EventHorizon511",
" Thanks so much. I always thought that it might be possible in theory!"
] |
[
"Physical significance of S(q) structure factor against scattering vector q?"
] |
[
false
] |
In diffraction experiments it is common to graph the structure factor against the scattering vector q. My question is what exactly do the peaks in the resultant plot from x-ray diffraction of neutron diffraction physically correspond to? Also, I think it would help to frame the answer in the case of a non periodic structure (or perfect crystal scenarios). Any help would be appreciated.
|
[
"Scattering is essentially a momentum transfer. The scattering vector is essentially just the difference in momentum of in the incoming beam with the detected beam. So that for diffraction you can have detectors either moving through different angles or set up at multiple angles, and at that specific angle if a particle is detected it has transferred an amount of momentum directly proportional to the scattering vector. ",
"The structure factor is how the specific positions of atoms in the sample influence the amount of signal that will be detected with a specific scattering vector. If you look at the autocorrelation of atom positions, you essentially have the radial distribution function. If you take the Fourier transform not only is it easier to calculate the the correlation because of the convolution theorem, but you're in momentum space as the Fourier transform of the momentum operator is the position operator. The function is thus the the momenta associated with the difference in atomic positions of the atoms, and is proportional to the amount of particles scattered through an angle described by that much momentum transfer. Having measured the structure factor you can take the Fourier transform back into position space, if you have phase information of the scattering (say by using a coherent beam source) you can recreate the positions in detail, if you don't have phase information you can get an RDF, but not the true positions of atoms. ",
"So the structure factor is just how easy certain changes in momentum are in the sample. "
] |
[
"So that basically means peaks in the structure factor have no direct physical significance other than the fact that they can be transformed back into position space and given known phases can calculate the RDF? Meaning that peaks are just |intensity|",
" maximums corresponding to little resultant impact that the atomic structure has on the incident q vector. Please correct me if I am wrong."
] |
[
"Its not as though momentum isn't physically significant. Diffraction techniques are generally use crystallographically so the position-space is what you're looking to get information on from momentum-space. The structure factor is however a direct reflection of the likelihood of transition between momentum states, which is physically significant even if not always the desired direct physical significance of the experiment. "
] |
[
"How Does Cherenkov Radiation work?"
] |
[
false
] |
How does Cherenkov Radiation work? Are you getting Energy from nothing, or is the particle slowing down?
|
[
"The particles are slowing down. It requires particles going faster than the speed of light in the medium (this is still slower than speed of light in vacuum). When the particles are slowed down to the speed of light in the medium the Cherenkov Radiation stops."
] |
[
"To add to this, Cherenkov radiation is the electromagnetic equivalent of a sonic boom."
] |
[
"Cherenkov radiation occurs when a charge particle goes though a medium at a speed superior of the speed of light in that medium.",
"Passing by, the charge particle interact with the atoms of the medium by changing their polarisation (imagine the atoms like little magnet, the charge particle make the magnet move).",
"To go to the previous state (or calm down = deexcitation in physic term) the atoms emit a photon (particle of light). The photon are also waves that interact between themselves along the path of the particle, making a cone of light."
] |
[
"Can you get \"hit\" by the Earth?"
] |
[
false
] |
[deleted]
|
[
"Yes this is perfectly possible. The earth spins at a rate of 1 revolution per 24 hours on its axis (solar day) and revolves around the sun on an elliptical orbit at a rate of 1 revolution per 365 days(sidereal year). The earth travels at a speed of 108000 km/hr and the total distance covered over the period of the year on its orbit is roughly 150000000 km. ",
"For example if you were 24 hours ahead on the earths orbit you would be roughly 0.0027% around the distance of the orbit or 405000 km away from the oncoming earth. From a human point of view you would most likely looking at a small dot because if you look at pictures taken from the International Space Station they appear to see roughly half of the earth from a distance of 386 km. But yes, the Earth would \"run into you\" technically and by that I mean you would be incinerated by the atmosphere."
] |
[
"Complete stop relative to...?",
"If you mean relative to say, The Sun, then yes, you would see The Earth hurtling towards you and smacking right into you with tremendous force."
] |
[
"Yes, but note that there is not really such a thing as a \"complete stop\". You are always moving relative to someone. Staying stationary with respect to the Sun and \"waiting for\" the Earth to hit you at 30 km/s is exactly the same as considering the Earth to be stationary and you're crashing towards it at 30 km/s,"
] |
[
"What is the origin of human sexual fetishes? Why can some be so particular and even self-harming?"
] |
[
false
] |
I can understand why humans would find things sexually attractive from an evolutionary standpoint, but some fetishes do seem out there and confusing. Some even self-harming. Like, cannibalism, BDSM, scat, castration, etc. What led the human species to originally develop such fetishes?
|
[
"There are several theories regarding atypical sexual behavior, so I'll give a quick summary of those that I know of. ",
"First is the courtship theory. This is based on the idea that normal sexual interactions involve a series of steps (courtship), and that somehow an exaggeration or distortion occurs at one of the steps. This isn't the best model overall because it doesn't account for many paraphilias, but works for things like exhibitionism, frotteurism, and voyeurism. ",
"Next is the behavioral theory, which is based on the idea that a non-sexual stimuli is paired with sexual arousal (classical conditioning). In this model, aversive experiences could be paired to sexual arousal, causing to paraphilias that can involve self harm. This pairing may be more potent during puberty, so it is possible that the atypical interests will arise during this period in development. ",
"The biological theory bases paraphilias on brain organization. It states that neural networks for arousal and the neural systems for pain and punishment overlap and become associated. This is only really used to explain BDSM, and is not really widely supported. ",
"The last theory I'll talk about is the Lovemap theory. This suggests that children develop a template for sexual relationships as they grow older, and disruptions to this template somehow result in paraphilias. For example, a child raised in a safe, sex-positive household that receives good sexual education and has a well functioning family could grow up to have more typical sexual interests. On the other hand, a child raised in a house where sex is paired with shame/anxiety/guilt may experience a disruption to the template, and see paraphilias arise as a result. ",
"The brain is extremely complicated, so as far as I know it's still uncertain as to where exactly these interests come from. I don't think that paraphilias would have necessarily developed in humans as a part of evolution through natural selection, as I can't think of any advantage they would have conferred. I would guess that they are more likely a behavioral byproduct of evolution, and just come to be through the complexities of neural functioning and how that affects behavior. ",
"Sources: Undergraduate psychology and biology; I took a course specifically on sexual psychology."
] |
[
"Doesn't all of this ignore the societal aspects - some societies find exposed breasts to be unbearably sexual, while others do not, and obviously a great deal of breast-focused fetishism would be more prevalent among a group where they are heavily sexualized, no?",
"I've always found it made sense to consider it like any other things we enjoy, to a degree. A lot of people like chocolate, I think it's mediocre at best, unless paired with something. Why do some people like huge tits and some people like slapping their nuts with a paddle? Unless they are doing lasting damage it's hardly that different from choking ourselves half to death deep-throating, save that it's culturally \"abnormal\" to a point.. Yet oral sex of that nature is extremely unremarkable, and I do have to imagine the cultural angle is significant in normalcy and fetishism."
] |
[
"Wow, very interesting! Thank you!"
] |
[
"Is Saltation what causes ripples in both sand and clouds?"
] |
[
false
] |
I've done some cursory googling. It seems rippling in sand is called saltation. But I can't find anything that connects saltation to the phenomenon of ripples underwater and also ripples in clouds. To me they all seem connected, and saltation does define itself as a fluid moving over a substance (such as sand) so presumably that definition also applies for underwater and in the clouds. Just curious if anyone has seen these various appearances of rippling connected in any way? pictures:
|
[
"It seems rippling in sand is called saltation. ...and saltation does define itself as a fluid moving over a substance (such as sand)...",
"This is incorrect, ",
"saltation",
", at least in terms of its use in relation to bedforms (i.e. ripples, dunes) that form from sediment transport by a fluid, is a mechanism of sediment transport that can be simply thought of as \"hopping\" of sediment grains, i.e. grains are periodically suspended in the flow, but unlike suspended sediment impact the bed and unlike bed load are not rolling/creeping along the bed (though this gets squishy as some grains may both saltate and roll intermittently depending on their size, shape, and flow conditions).",
"But I can't find anything that connects saltation to the phenomenon of ripples underwater and also ripples in clouds. ",
"The formation of bedforms is exceedingly complicated, largely because they are a reflection of fluid dynamics, which is exceedingly complicated. For ripples, dunes, antidunes, etc formed by both fluvial (i.e. water) and aeolian (i.e. wind) transport, saltation is a key part of sediment transport and thus plays a role in bedform formation, e.g. these review papers on either fluvial bedforms (",
"Seminara, 2010",
") or aeolian bedforms (",
"Anderson, 1990",
"), but to say that saltation directly causes ripples or other bedforms is not correct. Without going into a lot of pretty ugly math and theory (check out the Seminara paper if you want some of that, or for a slightly more approachable source, ",
"these lecture notes",
"), the formation of bedforms are a reflection of instabilities in the boundary layer between two mediums with different physical properties (i.e. sediment and fluid). The formation of individual bedforms is quite complicated, but things get even messier (or interesting, depending on your perspective) when you consider systems of bedforms migrating and interacting within a river / dune field (e.g. ",
"Kocurek et al, 2009",
").",
"Just curious if anyone has seen these various appearances of rippling connected in any way?",
"This is pretty far out of my depth, so maybe another panelist with more experience in clouds and/or fluid mechanics more generally can help, but at least in part, some forms of these, e.g. ",
"gravity waves",
" reflect a somewhat similar process, i.e. formation and propagation of instabilities at the interface between two fluid media with different properties. For these, I can't really imagine that there is a cloud equivalent of particle saltation, but I'll happily be corrected if someone has more information."
] |
[
"/u/CrustalTrudger",
" 's got the sand grain ripples side of this question, so I'll tackle the clouds.",
"Ripple patterns in clouds are typically caused by ",
"Kelvin-Helmholtz instability",
". This occurs whenever two fluid layers move past one another at different speeds. Any slight disturbance in the flow interface between layers leads to pressure fluctuations, and those pressure fluctuations are carried by the flow in a way that causes them to get bigger: the disturbance amplifies itself. The math for this is complicated, but the phenomenon is similar to how a flag flaps in the breeze -- but without the flag.",
"The key point is this: ",
"."
] |
[
"Fixed link for saltation:",
"https://en.wikipedia.org/wiki/Saltation_(geology)",
"For the purposes of this discussion, the key point is that saltation (Latin for \"leaping\") refers specifically to the way sediment grains can \"skip\" into the air after bouncing off the sediment surface. This is just one of several ways sediment can be mobilized by a fluid."
] |
[
"Does every layer of the atmosphere have the same angular velocity as earth's surface?"
] |
[
false
] |
By going higher in the atmosphere, gravity decreases but how does that effect atmosphere's angular velocity?
|
[
"No. The convective currents cause the atmosphere to circulate, and drive weather patterns. Angular velocity varies as a result.",
"Space does not impart significant rotational drag on the atmosphere counter to the rotation of the earth. The atmosphere doesn't \"lose angular velocity\" at altitude, if that's what you're getting at."
] |
[
"Yep, that's what I was asking. Thanks :D"
] |
[
"are you cheating on a test right now?"
] |
[
"The coldest temperature recorded on earth is 183.8 kelvin, carbondioxide solidifies at 194.5 kelvin. Does this mean that the carbondioxide in the air turned solid and snowed down?"
] |
[
false
] | null |
[
"The vapour pressure of CO2 at -90°C is roughly 300 mmHg or 400 mbar (estimated from the graph on Wikipedia’s ",
"CO2 data page",
")). This is way higher than the partial pressure of CO2 in the earth’s atmosphere (410 ppm or 0.4 mbar), or even in exhaled breath (4% or 40 mbar). According to ",
"this Wikipedia page",
" even exhaust gases from internal combustion engines do not have a sufficiently high CO2 concentration to reach saturation (14% or 140 mbar). And in the best case scenario where you burnt pure carbon in the atmosphere, you’d only get as much CO2 as there was oxygen in the first place, which at 21% would correspond to a partial pressure of 210 mbar.",
"So essentially, there’s no situation you could reasonably encounter where CO2 would start snowing on Earth."
] |
[
"doesn't matter if it's h2o or co2, air can contain a certain amount even below their freezing points. you won't get co2 crystals forming in the air unless there's more of it in the air to begin with than the air can contain when the temperature drops to 183.8k."
] |
[
"When we say something is at its \"freezing point\", we mean solid and gas can exist together. But that point depends on the pressure of the gas. 194.5 Kelvin is the temperature at which solid CO2 is in equilibrium with ",
" of CO2. But since CO2 makes up a small fraction of the air, its \"partial pressure\" is about 0.04% of a full atmosphere. At this pressure, the freezing point would be much lower, so no solid CO2 forms.",
"https://www.researchgate.net/figure/Carbon-dioxide-pressure-temperature-phase-diagram-for-liquefaction-using-heat-exchanger_fig1_44188603"
] |
[
"How did it hail in my country eventhough I'm at the equator?"
] |
[
false
] |
Not sure why I just remembered it, but a few years ago (2007/8 I think) it got really really hazy for about a month, it was so hazy we had to cover our mouths and noses with masks. I remember I was just sitting in my house having some lunch, then it started to hail?? The hail was circular and they looked like this in video. I think this is exactly the same hail storm I witnessed. If I'm not mistaken, it happened last year too. I live in Malaysia, temperatures range from 26c on good nights with rain and 40c on horrible afternoons. We also have monsoon season around Nov-Dec. Can someone explain how this happened?
|
[
"Hail happens when the temperature near the ground is above freezing, the temperature farther up is below freezing, and there are strong updrafts. Small ice particles fall down, and are coated in a thin coat of water. Then they are blown back upwards to where it is colder, and the water freezes, making the ball of ice slightly larger. This happens several more times until the ball is too heavy for the updrafts to lift, then it falls as hail.",
"That's why you don't see any hail when it's below freezing, because it's too cold for hail to form."
] |
[
"Okay so, let me try to understand this.",
"There were really strong winds blowing upwards as it was raining ice particles right? Then they get blown up again and it refreezes, then it falls again and this keeps repeating until it gets too heavy and falls to the ground.",
"So, hail can occur anywhere if there are strong enough updrafts? Right?"
] |
[
"Large hailstones, usually golf-ball or larger, are typically a sign of impending tornado in areas prone to that sort of thing."
] |
[
"Is there a minimum wavelength in the EM spectrum?"
] |
[
false
] | null |
[
"There is no minimum."
] |
[
"The energy approchaes infinity."
] |
[
"Does anything special happen as the wavelength approaches 0 or does the energy just increase?"
] |
[
"Al Gore's AMA prompted me to ask a question, that I've thought about for a long time, about the global warming theory.."
] |
[
false
] | null |
[
"We haven't been ",
" climate data over the millions of years, but we have a decent idea of what the climate has been like using scientific methods. For example, we know that there have been several ",
"ice ages",
" in Earth's history."
] |
[
"To elaborate on what cssher said. Based on many paleogeological studies, we've managed to paint a fairly accurate picture of what earth's temperature variance looked like over the last few hundred million years.",
"What we found that the temperature was largely cyclic. It had periods of high temperature that gave rise to hot humid climates and explosions of oceanic life, and it had periods of low temperatures that resulted in ice ages. Most importantly, we found that they had a regular pattern to them.",
"What concerns us now is that the pattern is being broken. The rate of increase of temperature we have now is completely unnatural. Our pattern suggests climate change only changes the average temperature by a few degrees every tens of millions of years, whereas we've almost had a degree increase in temperature since 1980.",
"That is thousands of orders of MAGINITUDES higher than what we expected, and that is what is so concerning."
] |
[
"so, all in all, the evidence of human activity on global warming is apparent and large. but there is a small, small, chance of hope that we didn't fuck everything up if it ends up being cyclic once more. just something i wanted to know :("
] |
[
"Can a rocky planet be Jupiter sized?"
] |
[
false
] |
In terms of mass, could such a world exist? Is there no way there would ever be that amount of mass available around a star? Are we just assuming all large planets detected are gas giants?
|
[
"Our prediction is no. According to Seagar et al 2007, for all common compositions, once a planet gets to a few hundred Earth masses adding more mass just compresses the interior more and the radius actually starts ",
".",
"https://www.planetary.org/space-images/mass-radius-diagram-wide-seager",
"Edit: Earthlike compositions top out at about 3 Earth radii."
] |
[
"Wow, \"goldilocks\" indeed, that is way narrower of a margin than I realized."
] |
[
"https://postureinfohub.com/can-you-stand-on-jupiter/",
"Tl;Dr sort of. ",
"We don't know if Jupiter has a solid core, but states of matter don't really work the same way at these pressures regardless. There's not a \"surface,\" but rather a transition from gas to liquid to solid very slowly. You'd get crushed in any attempt to \"land.\""
] |
[
"Does using a laptop regularly while it is on your lap do any damage?"
] |
[
false
] |
I always remember the speculation that keeping a laptop over your testicles/genital region often does damage. Is there any legitimacy to this statement?
|
[
"do you have any links for further information? specifically on the wi-fi being linked to DNA damage in sperm."
] |
[
"First of all, this is not a place for speculation. Since you're not an expert and you gave a fairly vague answer, you're just speculating. The correct action in this case would not be to speculate on what could be the answer and let an expert correct you later, because the expert's answer would have been the same whether you submitted your speculation or not. The correct action would be to wait for an expert to submit an answer that is certainly correct, at least to their knowledge. Adding speculation could also confuse people who are looking for answers from experts, because your speculation may not match up with an expert answer. Saying that you're not an expert does not make it okay to post speculation, because you ",
"Second, your answer is vague and useless. Laptops don't even create an electrostatic field, by the way, they emit radiation. They're two different things, with two different properties. Anyway, it's quite evident that the effects would depend on the characteristics of the radiation. That doesn't need to be said, and it doesn't add anything to your answer either. The asker is looking for ",
" of radiation is emitted, and what the effects of that specific radiation is.",
"You didn't have to say that entropy is always at play, either. ",
" entropy is always at play. It's a ",
", for heaven's sake. You didn't write anything about the consequences of entropy in this context, you just stated that it exists. That's doesn't add anything to the answer, either.",
" You posted useless information with a layman's perspective, showing exactly why this sub prohibits it in the first place."
] |
[
"http://en.wikipedia.org/wiki/Erythema_ab_igne",
"I don't know about damage to genitalia/sperm/etc, but according to the Wikipedia article and it's cited sources, prolonged exposure to warm temperatures can cause a rash. ",
"Here's the portion on laptops:",
"Resting a laptop computer on the thigh (laptop computer-induced erythema ab igne). In a 2012 review, Riahi and Cohen describe the characteristics of laptop computer-induced erythema ab igne.[5] Temperatures between 43-47°C can cause this skin condition; modern laptops can generate temperatures in this range. Indeed, laptops with powerful processors can reach temperatures of 50°C and be associated with burns. Positioning of the laptop on the thighs can allow for direct exposure to the heating elements of the laptop, which include the central processing unit (CPU) and the graphics processing unit (GPU).[5] At least 15 cases have been reported by 2012 with the condition usually affecting the left anterior thigh.[5] In these reports, 9 of the 15 patients were women (60%) with an average age of 25 years at diagnosis."
] |
[
"AskScience AMA Special: We’re Carolyn Porco, imaging scientist on the New Horizons mission, and Miles O’Brien, veteran aerospace journalist. Ask us anything about New Horizons, Pluto, and beyond!"
] |
[
false
] |
Hi reddit! We are Carolyn Porco and Miles O’Brien, and we’re here to answer your questions about the New Horizons mission to Pluto and beyond. Thanks to and the for organizing this AMA. Carolyn Porco is the leader of the imaging science team on the Cassini mission presently in orbit around Saturn, and a veteran imaging scientist of the Voyager mission to the outer solar system in the 1980s. Miles O’Brien ( ) is a veteran freelance broadcast and web journalist who focuses on science, technology, and aerospace. He is a producer for NOVA and the science correspondent for PBS Newshour.
|
[
"Are you the Miles O'Brien from Star Trek? How often are you asked that? If you lived on a spaceship in the 24th century and got stuck back in time in the 21st, is this not the job you'd apply for?"
] |
[
"first time! You are amazing."
] |
[
"Are the images of pluto's smaller moons going to improve or are they just too small and/or far away from NH during the flyby? "
] |
[
"In the event of an heart attack why is it an either or decision between thrombolysis and angioplasty? Why can't both be done at the same time or successively?"
] |
[
false
] |
Non-native English speaker here. From what I understand, in the event of an ongoing heart attack the doctors must choose between thrombolysis or an angioplasty with stenting/PCI (PCI and Angioplasty are the same thing right?). But both cannot be done. So suppose someone is very far away from a hospital with angioplasty facilities. Why can't they be given thrombolysis first to save heart muscle and then when they reach the hospital after an hour they are treated with angioplasty with stents? Why does it have to be an either or decision?
|
[
"Mostly bleeding risk. Once you take those thrombolysis meds, your risk from complications from any intravenous activity shoots through the roof. Also, thrombolysis meds only work in a short window during the onset of a heart attack.\nSo it's more of a what's the best too for the job, not really an either or. "
] |
[
"CAN be done, but not really done typically. The emergent period/damage to the heart tissue has already been done by the time the thrombolysis typically wears off. Usually the patient is then in a totally different care process that the doctor will manage. ",
"That being said, if the patient is deteriorating, many doctors will still choose to cath a patient post thrombolysis, typically that is a patient who is actively deteriorating and they are trying to do everything they can.",
"Unfortunately, the biggest issue with your question is lack of background knowledge. I am not trying to shame you, because understanding your healthcare is extremely important. However, each patient presents with an enormous amount of variables unique to their situation. If you find yourself in that situation, trust the doctors. The saying in the field is \"time is muscle\". The doctors will try to do everything they can to give the right action plan given their tools available to them. One of which is timely access to a cath center. Unfortunately, rural areas don't have that quick access to a cath lab, so other alternatives may be a better choice!"
] |
[
"Also, thrombolysis meds only work in a short window during the onset of a heart attack. ",
"So thrombolysis meds can be given first and then angioplasty done if the time needed to reach the hospital is about an hour?"
] |
[
"How are discoveries in psychology measured?"
] |
[
false
] | null |
[
"The general rule for psychology experiments is you need a p value of <0.05 which basically means that there's less than a 5% chance the found effects are the result of chance. Beyond that, effect size is also important. There are tonnes of different types of tests that show effect size or the level of relationship between the variables that largely depend on the type of study being done but almost all use a p value of 0.05 (and will report 0.01 if their report reaches that significancE). Is there a particular type of study or an example you have? I could run you through the basics of how you'd analyse it (It's good practice for me considering I'm studying for a research methods i psychology subject as we speak)."
] |
[
"It depends on the type of study you're doing. There's basically two different types; experimental and non-experimental (I'll leave out quasi-experimental but it's basically halfway between the two). ",
"In an experimental design, you're doing everything you can to eliminate all confounding (variables that you're not trying to measure that will change the result) variables. It always involves a a manipulation, a control group and trying to eliminate outside variables. For example, three groups come in for a quiz, theyr'e randomly assigned to groups where one is told that the quiz is really easy, the other is told it's really hard and the last group is told nothing (control group). You then measure the scores of different groups and compare them to see the effect of the independent variable (how hard you told them the test was) on the dependant variable (test score). ",
"In a non-experimental design, there are variables you can't control because it's impossible or unethical. For example, I want to see the effect of trait introversion on IQ tests. I get in all of my participants and give them a personality test to see their levels of introversion and then make them do an IQ test (see how there's no manipulation?). All I do then is compare the scores of each person's IQ test and their personality test. As you pointed out, there's a lot I'm not controlling for which is why experimental designs are always used when possible. At best, I could say there's a ",
" between IQ and trait introversion whereas in the first one I can show that the manipulation ",
" the effect (assuming all my results reached statistical significance). "
] |
[
"It depends on the type of study you're doing. There's basically two different types; experimental and non-experimental (I'll leave out quasi-experimental but it's basically halfway between the two). ",
"In an experimental design, you're doing everything you can to eliminate all confounding (variables that you're not trying to measure that will change the result) variables. It always involves a a manipulation, a control group and trying to eliminate outside variables. For example, three groups come in for a quiz, theyr'e randomly assigned to groups where one is told that the quiz is really easy, the other is told it's really hard and the last group is told nothing (control group). You then measure the scores of different groups and compare them to see the effect of the independent variable (how hard you told them the test was) on the dependant variable (test score). ",
"In a non-experimental design, there are variables you can't control because it's impossible or unethical. For example, I want to see the effect of trait introversion on IQ tests. I get in all of my participants and give them a personality test to see their levels of introversion and then make them do an IQ test (see how there's no manipulation?). All I do then is compare the scores of each person's IQ test and their personality test. As you pointed out, there's a lot I'm not controlling for which is why experimental designs are always used when possible. At best, I could say there's a ",
" between IQ and trait introversion whereas in the first one I can show that the manipulation ",
" the effect (assuming all my results reached statistical significance). "
] |
[
"Does a permanent magnet have permanent net angular momentum while at rest?"
] |
[
false
] |
Since ferromagnetism is due to electron spin alignment, and since there is angular momentum associated with spin (in addition to the magnetic field), does that mean a kitchen magnet has a net angular momentum while at rest? If so, is it measurable with existing lab techniques (and further, has anyone done so?) It's odd to think there might be a slight gyroscopic effect to an object that is not moving....
|
[
"Yes this is all true, you should read about the ",
"einstein-de haaas effect",
". You need a high sensitivity experiment though!"
] |
[
"Thanks! Hadn't come across that one before... Very interesting. Somehow it's a little easier to wrap my mind around the idea of a coil inducing motion in a magnetic material (I guess I'm spoiled by induction motors, etc) than the concept of an inert stationary mass acting like a gyroscope (if only slightly). It certainly proves the point though!"
] |
[
"I always like it when a question which I have wondered before comes up."
] |
[
"Does the age at which a species typically reproduces (relatively to the maximum age it can live) have any substantial effect at the rate it can evolve?"
] |
[
false
] |
Say a species lives in average for 10 years. Would it experiment any signs of evolution at a faster rate if it reproduced when it reached 2 years of age, as opposed to say 6? This is of course with the assumption that it has adapted for optimal conditions to reproduce at the ages mentioned, and with very little changes on its environment. To put it in another way, Group A reproduces at 2, while Group B reproduces at 6. Both live in the same environment, but can only reproduce with those of their group. Would one group evolve significantly faster (or slower) than the other just based on the time in their lifecycle they happen to reproduce?
|
[
"Absolutely. \nRemember that the rate of genetic change is not dependent on time but on number of generations. This is because the genetic drift occurs only at the next offspring, not the reproducing adult.",
"Thus, organisms that reproduce quicker (younger) are able to have many more generations, then adapt and respond to environment stresses much more rapidly. ",
"This is the primary reason that pesticide resistance and anti-bacterial resistance are a big deal. "
] |
[
"If we assume all else is equal and there is heritable segregating genetic variation for the trait under selection, yes. More generations means more opportunities for selection to sample among the segregating variants. However if species (populations) differ in the amount of segregating variation, mutation rate, effective population size, recombination rates, etc then it depends. "
] |
[
"This is part of why everyone is always scared of antibiotic resistance. Under the right conditions, bacteria can go through a generation every ten minutes. It takes years to develop a new antibiotic and a year is like eons for them."
] |
[
"Are there particle annihilations that result in other Bosons besides photons?"
] |
[
false
] |
When reading about particle collisions and annihilations, the most common example given is a collision with an electron and a positron, resulting in two high-energy photons. Are there other collisions which result in annihilations with different force-carrying particles? If so, does this imply that there is more to duality besides particle charge?
|
[
"Quarks can annihilate to gluons, and at high energies, particles can annihilate to Z bosons."
] |
[
"Thank you for the in-depth explanation! I really appreciated the level you provided and the Feynman Diagrams to explain.",
"If I may ask,"
] |
[
"Thank you for the in-depth explanation! I really appreciated the level you provided and the Feynman Diagrams to explain.",
"If I may ask,"
] |
[
"How can we know if an astronomical object is moving relative to us if Doppler effect is measured based in the proper wavelength emitted by the source?"
] |
[
false
] |
For example: how can we determine the blueshift of Andromeda galaxy if we never observed it standing still in our reference frame to know its proper emitted light wavelength?
|
[
"Because Andromeda is made of the same materials as we are, and we know how those things act in the lab. For example, hydrogen atoms have electrons that only can occupy specific energies, and when they transition between those energies, they emit or absorb photons of specific wavelengths. So we look at stars in Andromeda and see that they look just like stars in the Milky Way, with hydrogen and helium and oxygen and calcium, but all shifted bluewards by the same amount, which is caused by Doppler shift. ",
"Even if we don't observe Andromeda at rest, we know what the elements look like at rest, and Andromeda is made of the same stuff we are."
] |
[
"We can look at the sun which is not moving much relative to us and see the absorption lines, then look at Andromeda and see how shifted those lines are"
] |
[
"The spectrum of a light source contains patterns of bright and dark bands specific to the materials of which the light source is made. Those patterns shift towards blue or red depending on the amount of Doppler effect.",
"\n",
"https://en.wikipedia.org/wiki/Spectral_line"
] |
[
"Please help us, please, please, please help!"
] |
[
false
] | null |
[
"Go see a doctor, we're not letting this thread out. "
] |
[
"I understand that, but we don't exactly have money to spare."
] |
[
"we are obliged to follow the Reddit TOS which directly says we cannot give any kind of medical advice. There's nothing we can do on this forum. Sorry. "
] |
[
"Do arthropods experience emotions and/or pain, and how can we know that?"
] |
[
false
] |
Is there any new research on insects or other arthropods on this topic? Can they feel emotions and suffering in a similar way to mammals, even if their nervous systems are much simpler?
|
[
"As far as I'm aware, we don't have a good way of objectively describing, measuring, or comparing a subjective \"experience\". We know that they can detect a nociceptive (painful) stimulus and change their behavior to avoid the stimulus. We can even accurately simulate the entire nervous system of some simple arthropods in a computer program and completely understand how they process information and \"think\". Despite this, I don't think we can know if they suffer."
] |
[
"Look up \"OpenWorm\". We're still at a primitive stage but we're doing amazing things."
] |
[
"I'm sorry, I only remember reading about a complete C. elegans simulation with 302 neurons several years ago and assumed that more advanced simulations have since been run. I actually don't know for sure and haven't looked into it since. I apologize if that was misleading."
] |
[
"How long does it take for tourniquets to start causing tissue damage?"
] |
[
false
] |
I know that applying a tourniquet leads to tissue damage by way of hypoxia, but I'm having difficulty finding an answer to this particular question. Also, can applying the tourniquet to an extremity also cause tissue damage in other parts of the body?
|
[
"I don't know of any good data on the issue, but for orthopedic surgery we will use a tourniquet for up to 2 hours at a time, which is generally considered low risk. We also try to keep tourniquet pressure to a minimum. After a recovery period, it is also considered safe to reapply the tourniquet, but there is not good data that I know of to guide the length of recovery and subsequent tourniquet application.",
"Here's a random paper I found on physiologic changes following tourniquet release: ",
"http://www.eymj.org/Synapse/Data/PDFData/0069YMJ/ymj-33-153.pdf"
] |
[
"8 hours seems pretty long. It's always a balance between risk and benefit, so if the risk is certain death by rapid exsanguination, exceeding 2 hours may be justified. However, ischemia (ie. lack of blood flow and everything that involves, including hypoxia) to the limb will cause large buildup of metabolites like lactic acid, and tissue injury will also increase potassium levels (and acidosis worsens this). In a severe case following a longer tourniquet time, the rapid infusion of potassium from tourniquet release could rapidly induce a fatal arrhythmia."
] |
[
"I had heard in my EMT class (I think that was where I heard it, hence the reason for posting here as I wanted to try to find clarification) that the risk of major tissue damage due to tourniquets is relatively low in general, despite the general perception. I had heard that you can be relatively safe about using one for up to something like 8 hours I think? As a Basic, I'd never use one unless there was extreme, uncontrollable bleeding, but I did sort of want to know a bit more about the time window involved. Never hurts to know more. ",
"Does 8 hours seem a bit too long? Also, what toxins are released and why? Is it simply due to hypoxia?"
] |
[
"If I was on a planet who's sun emitted only light waves in non-visible frequencies to me, what would I see around me?"
] |
[
false
] |
Would it be black, white, or hazy? Would I be able to see some things around me or would seem to be in empty space? Cheers.
|
[
"It would be black, except if there are things on the planet that absorb that light and convert it to a visible frequency. Certain chemicals do this. You might see bioluminescence if any creatures exist. You might be able to see a little bit do to the starlight of other, normal stars."
] |
[
"http://en.wikipedia.org/wiki/Nonlinear_optics",
"Frequency doubling, BAM! ;-)",
"Other than that, there really is no star emitting no visible radiation. Even brown dwarfs which can barely sustain any kind of fusion emit visible light (even if its only a little) so for the question we should suspend disbelief for a bit."
] |
[
"Absorb that light and convert it to a visible frequency",
"I don't know about this. From my limited (very limited) knowledge of how stars work, they emit a blackbody spectrum. (They can reach a certain energy of photon, then emit all photons [that don't get absorbed by the sun's atmosphere] of lower energy) From my slightly-less limited knowledge of fluorescence and phosphorescence, all conversions and re-emissions are though a step-down mechanism ",
"As shown in this picture.",
"What is my point? If something can emit visible light, it needs to have absorbed visible light or higher energy photons. If the source is from a star, these higher energy photons would also be accompanied by visible light photons."
] |
[
"How do accents develop?"
] |
[
false
] |
[deleted]
|
[
"Naturally, as we are raised, our mouths begin to form so that we communicate comfortably with the vowels and sounds we’re used to. But when we’re confronted with a different environment with a different language and set of linguistics, our mouths struggle to perfectly imitate the sounds, thus, the accent is created "
] |
[
"Why though do children say with parents that have a different accent to the natives develop the accent of the natives and not the parents? When for the first few years almost all the child's interaction is with the parents. "
] |
[
"A study I heard about some years ago -- forget the details now, I'm sorry -- determined that accents are mainly socially influenced, and that certain kinds of people have more influence than others. Near or at the top were people who invited others into their homes to spend time with them and their families. An example given was certain mothers in some neighbourhoods who routinely hosted other people's school children after school. But it could be anyone who provides a sense of safety and stability for the child, which encourages imitation.",
"Separately, when different groups meet and mix, they inherently influence each other's speech. The Australian dialect, for example, is mainly a blend of the social groups that went to Australia in large numbers."
] |
[
"What percentage of the atoms in our bodies were in us a year ago? Ten years ago?"
] |
[
false
] | null |
[
"While most of your cells are constantly replaced, and even those that aren't will have a portion of their atoms exchanged through normal biological activity, some parts undergo exchange very slowly. For cells that don't divide and never get replaced, the DNA doesn't incorporate new, or lose old, atoms, unless they're damaged."
] |
[
"Makes sense. Are you willing to tackle the percentage questions?"
] |
[
"The way you would study this empirically is by putting uncommon isotopes into people's bodies and measuring the level of that isotope over time. For instance, ",
"99.8% of oxygen is oxygen-16",
", so what you could do is have them drink water with oxygen-17 in it and measure its concentration in their body at different times (before administering the water, days after, months after, etc.. Do this for each element, weigh the results by ",
"elemental composition (percent of atoms)",
", and you're done.",
"There's a few problems, though. It's hard to get an unbiased sample of the inside of a human body without putting the body through a blender first, for one. You can take blood samples, but if your fancy isotope ends up concentrating in, say, liver or bone tissue, you're not going to see it in the sample. And speaking of bone tissue, the replacement speeds for different elements probably change with age and behavior, as different tissues develop and atrophy. Also, while all of the elements that mostly make up the human body do have several stable isotopes, hydrogen is almost two thirds of the atoms in you, and its only other stable isotope, deuterium, is twice as heavy as normal - so it's ",
"not at all obvious that it behaves the same biochemically as normal hydrogen does",
". Well, actually, it is obvious that it is different - replacing all of your water intake with heavy water ",
" eventually kill you - so you know you can't really use deuterium to reliably study the rate of hydrogen replacement."
] |
[
"Why are human reaction times so slow compared to other animals?"
] |
[
false
] | null |
[
"we aren't significantly slower in general. our reaction time from stimulus to action is similar to other animals of similar size. some pure carnivore predators are quicker reacting in specific ways, but we're faster in others.",
"size plays a big factor. a sparrow is going to have faster reflexes than an eagle, and it will have faster ones than a bear. we're much quicker than the huge critters. a rhino can run faster than a human, but its reaction time is nearly double ours (iirc)",
"it boils down to the speed a signal can travel from sensory input (the eyes for example) to the brain, then generate a response, and travel back out to the body. (about .25 seconds for vision in humans) \nalso, the modern age means we don't have to rely on reflexes for basic survival, so our bodies and minds aren't geared for maximum response. good training can reduce the times pretty significantly."
] |
[
"In what task?"
] |
[
"Thanks! Couldn't ask for a better answer."
] |
[
"If I were to sit neck-deep in a tub full of whiskey, would I feel inebriated at all?"
] |
[
false
] |
For science!
|
[
"I believe alcohols will evaporate and you will be breathing it in. So yes?"
] |
[
"This study in the BMJ",
" demonstrated that sitting with just your feet in a bath of vodka will not get you drunk. Extrapolating from that, I would go with no, assuming that all your orifices were plugged up. "
] |
[
"I believe it would.",
"Diffusion",
" causes particles in high concentration to pass through a membrane to areas of low concentration. That's the manner by which your lungs absorb oxygen (and expel carbon dioxide), and also the manner in which the alcohol in an inebriated persons bloodstream makes its way into the air in the lungs, to be detected by a breathalyser.",
"If you sit for a long time in an ordinary bath, you can see the results of ",
"osmosis",
" on the cells in your fingertips, which absorb water from the bath and cause your skin to become wrinkly (\"prune fingers\").",
"If you were sitting in a bathtub full of whiskey, which is roughly 40% alcohol, the alcohol would pass through the membrane (your skin) from the area of high concentration (the bath) to the area of low concentration (your body), and thus you would begin to get drunk. In fact, if you sat in there for long enough I think you'd probably absorb enough alcohol to eventually poison yourself and die."
] |
[
"Wouldn't it take a tremendous amount of fuel to mine an asteroid and transport that mineral back to earth?"
] |
[
false
] | null |
[
"Yes, and unless they happen to find an asteroid with an astounding amount of precious metals (gold, platinum, palladium, etc.) it is unlikely to be cost effective near-term to return the material to Earth. ",
"However, the (potentially) really exciting bit about this announcement is not bringing the material back to Earth. It currently costs somewhere in the neighborhood of $10,000 per kilogram to place something into orbit. If most of the raw materials are already up there, space exploration costs could drop by an order of magnitude or better. ",
"Imagine if they can capture an iron, chromium, and nickel rich asteroid, about 95% of the materials for a stainless steel is already in orbit. Bring up the balance of trace elements from Earth and ships, space stations, and satellites could mostly be produced in orbit. A foundry would not be all that difficult to run in orbit, using centrifugal force to stand in for gravity and solar collectors to capture all the energy needed to melt the metal. Also, high quality 3D printing of metals is only a couple years away and is steadily gaining traction in many industries. "
] |
[
"I'm having trouble finding hard numbers, so I'm about to make several assumptions. They should all be reasonable though. ",
"Taking ",
"Zarya",
" as an example, which was the very first module of the International Space Station. It weighs about 20,000 kg which corresponds to a launch price of $200 million. That is just counting the price of the launch vehicle and the fuel to get it up there, not development costs. ",
"Now, approximately 80% of that weight is structure, fuel tanks, thrusters, etc; all of which could have been built from orbit. As you said, just steel is pointless. Once that is finished, we would have to bring up the other 20% of materials to finish it out. Now, instead of launching 20,000kg worth of materials, we would only need to launch 4,000kg. Correspondingly, the price of putting that module into orbit drops from $200 million to $40 million. "
] |
[
"There are two ideas to asteroid mining:",
"A) the one the wikipedia article explains quite well and that is you go there, get material, and bring it back. This can't be cost effect unless the price of say platinum goes up by an order of magnitude (at least)",
"B) You grab a 1000kg asteroid and place it in the L2 lagrange point of the Earth-Moon System and then use it as a space ship for future voyages. The advantages to this would be that you don't need to bring up a lot of the material for a space ship since it's already in orbit. This would make excellent radiation shielding for example for future long term human missions",
"It isn't entirely sure what's meant by asteroid mining in this case but if it's option A then it's not feasible and if it's option B then that would be really really cool."
] |
[
"Why does sticking your fingers back your throat trigger your gag reflex, but swallowing food doesn't?"
] |
[
false
] | null |
[
"https://www.reddit.com/r/askscience/comments/171mp2/why_doesnt_eating_stimulate_our_gag_reflex/",
"Quote : \" I believe that swallowing is what's called a \"prepotent reflex.\" This means that it is essential for survival or avoiding harm, and is therefore given the ability to override other competing reflexes, in this case the gag reflex. Gagging is also the result of receptors mainly located in the posterior 1/3 of your mouth, behind the palatoglossal folds therefore in the oropharynx. The boundaries of the pharynx itself are usually only breached upon the actual act of swallowing, so you are at a lower risk of gagging. Note that you will still gag if you accidentally try to swallow something without chewing it, as the area is not prepared and in the act of swallowing. \"",
"-genuflect_before_zod, 4 years ago, slightly edited for better reading."
] |
[
"This answer is fine, but one could guess that it's because swallowing is important. I wouldn't mind reading more about the mechanism of the \"override\" if someone has those details! "
] |
[
"Yeah, as is it doesn't really answer the question.",
"\"Why doesn't swallowing trigger the gag reflex?\"",
"\"Because the gag reflex doesn't trigger while swallowing.\"",
"Cool, thanks! "
] |
[
"How much more radiation was on earth when life first formed?"
] |
[
false
] |
Of various radioactive isotopes created from supernova(e), assuming additional elements did not become radioactive until the earth was formed or otherwise collided with the earth, how much more radioactive was the earth's atmosphere when life first started than there is today?
|
[
"This is getting off topic so I'm going to message you."
] |
[
"Well we think that life started ~4 billion years ago and we don't have a lot of information about Earth's atmosphere at that time. So unfortunately there is no answer to your question. However, I expect just off the top of my head that it would be fairly similar if not a little lower because solar activity was a bit lower."
] |
[
"But would there would be more radioactive isotopes on earth that have now since decayed?"
] |
[
"What is the point of Variance?"
] |
[
false
] |
I understand that it is the Standard deviation squared, but what is it actually used for?
|
[
"Variation is much easier to compute directly in many situations, and has a more 'natural' definition when building up from discrete probability. They both measure distribution, and while standard deviation is commonly used as a quick measure of distribution for experimental data, variance is (at lease when I've seen it) much more useful for theoretical work. ",
"Note, I am not a statistician, but I often use variance in probabilistic proofs. I have never seen standard deviation used in mathematical research."
] |
[
"This",
" is a great place to start. \nI can't possibly pretend to be familiar with a variety of math research, but it arises fairly naturally from the expectation in combinatorics and probability and is simple to compute using moment generating functions. Standard deviation may be nice for getting an idea of a cluster of experimental data, but variance is used for just about everything else."
] |
[
"Thanks! You mentioned that variance is more useful for theoretical work. Why exactly is that?"
] |
[
"I want to clarify the nature of Planck's constant and its relation to wave functions in light..."
] |
[
false
] |
There is a fundamental misunderstanding on my part about Planck's constant. I cannot wrap my head around the origins of why it exists... I've looked at the Wiki, I have seen diagrams of Photons bouncing against each other when a limited amount of space, I have considered the relationship of specific particles and what parts of the light spectrum those particles emit...but Im lost. In the simplest terms, can someone explain what the primary observations are/were that defined Planck's constant?
|
[
"In the simplest terms, can someone explain what the primary observations are/were that defined Planck's constant?",
"This is a truly excellent question.",
"Planck's constant was invented to explain exactly how hot objects give off radiation, like a glowing filament in a light bulb. I will use this example to explain Planck's constant but I won't explain it the same way it was historically discovered.",
"You can think of every physical thing as a \"degree of freedom.\" By degree of freedom we mean a thing that can change and interact with other degrees of freedom. For example, the position and speed of a baseball are degrees of freedom. They can interact with the degrees of freedom of surrounding air molecules.",
"When you say an object is at a certain temperature you're loosely saying that all of the degrees of freedom in that object are equally sharing energy. For example, a cup of water at a certain temperature involves vibrational and rotational degrees of freedom of the water molecules and vibrational degrees of freedom of the atoms in the cup. These things are all in contact because atoms in the cup push on atoms in the water. It's because of this contact that they all come to the same temperature.",
"Electromagnetic radiation can also be though of as degrees of freedom. Instead of position and speed of atoms we have strength of the electric and magnetic fields at all points in space. These can interact with eg. the atoms in the cup: the electric field can push on electrons in the cup's atoms and incite the atoms to vibrate. In this way the electromagnetic field can come into thermal equilibrium with the cup and the water. This is a weird idea for some people but yes, the electromagnetic field has a temperature[1]. Just always remember that electromagnetic fields and regular matter can ",
" and then it's pretty natural to see that they can exchange energy and come into thermal equilibrium.",
"When you heat up a block of material it glows. This is roughly because you're making the atoms in the block vibrate more, so the electrons wiggle around more. Since electrons are charged their motion causes emission of electromagnetic radiation. This is why light bulbs glow, roughly.",
"If you try to explain exactly how the amount and color of radiated energy depend on the object's temperature you get into the business of figuring out the details of the electromagnetic degrees of freedom in a block of material. To actually do the calculation you need to know two things",
"When Planck started trying to figure this out he assumed there were a continuum of possible degrees of freedom in the electromagnetic field. This turned out to not work, he couldn't explain experimental observation. At some point he tried assuming the electromagnet degrees of freedom were discrete. When he did this the calculation worked if he assumed that the energy of each degree of freedom was related to the frequency of that degree of freedom's frequency via",
"Energy = h x frequency",
"where h is value now called Planck's Constant.",
"So, one answer to your question is that Planck's constant is a conversion factor from frequency to energy that is needed to understand how objects radiate energy. More generally it connects energy to frequency. For example let's say we want to build a photo-detector that detects photons with frequency at or above f. One way to do this is to go find a metal whose electrons have a binding energy equal to h x f. This way when a photon smacks into the metal it will have enough energy to kick off an electron which can then be detected as an electric current. If a photon of lower frequency hits the metal it doesn't have enough energy to eject an electron and is therefore not detected.",
"[1] You may have heard of the \"Cosmic Microwave Background\" which is at temperature of ",
" 2.7 Kelvin. What this essentially means is that if you put a block of material in space at 4K energy would radiate ",
" the block at the same rate that energy would be absorbed ",
" the block from the ambient electromagnetic field."
] |
[
"...So, does this (with Planck's constant) explain how you can use spectroscopy to identify the elements present in a light source?",
"Not really. If you get a jar full of some element, say hydrogen, and stimulate it by driving electrical current through it you will see that it ",
"emits light at specific wavelengths",
". Each element has it's specific set of wavelengths that it emits. We catalog these sets of wavelengths here on earth and then point a telescope at stars and measure the wavelengths coming from them. By comparing to our catalog made here we can find out what elements are up there.",
"This would work even if you didn't ",
" anything about quantum mechanics or Planck's constant. That said, if you want to understand why each element emits the spectrum that it does you'd have to do a quantum mechanics calculation and Planck's constant comes in. ",
"Here's a summary of the results of that calculation for hydrogen",
". Note the presense of Planck's constant.",
"There's a difference between the thermal radiation I mentioned in my first post and the spectral lines were discussing now. If you have a material [1] in thermal equilibrium with the surrounding electromagnetic field you find that the power at each frequency (or wavelength) it emits follows what's called the ",
"black body spectrum",
". Calculation of this spectrum is what lead Planck to postulate the discreteness of energy levels and his so-called constant. Stellar matter emits discrete spectral lines is not in thermal equilibrium with the ambient electromagnetic field [2].",
"[1] The material has to be a good absorber/emitter of radiation to actually follow the black body spectrum. Things like metals emit a different spectrum, but this is a detail to be saved for later.",
"[2] I don't feel that I've explained this quite well enough so someone else please jump in."
] |
[
"/u/DanielSank",
" already wrote about Planck's constant in the relationship between energy and frequency, but it has another role: the fundamental amount of angular momentum in the universe is half of Planck's (reduced) constant. That means particles can only have 0, h/2, h, 3/2 h, 2h etc angular momentum but nothing in between.",
"A photon has one h of angular momentum. The kinetic energy due to angular momentum is E=h",
" /I where I is some moment of inertia. Another way of writing the angular momentum is h=fI where f is some angular frequency (normally the notation is the Greek omega, but I don't have a Greek keyboard). If you isolate the angular momentum from the second expression and use it to cancel the angular momentum in the first expression, you get the familiar E=hf. "
] |
[
"With light produced in the Sun's core, does it move slower than the light that's present at the surface? Or is it all mostly the same speed?"
] |
[
false
] | null |
[
"Light does travel slower in a medium. Note that when we say things like \"in special relativity, the speed of light is the same for all observers\", we are talking about the speed of light ",
", i.e. under idealised circumstances. The speed that a pulse of light moves at will depend on the medium it's going through. Light does travel slower in glass, for instance.",
"The Sun is actually a bit more complex than that, because the majority of the Sun is actually opaque. The plasma is so hot that it emits lots of photons everywhere, but those photons very quickly get absorbed by nearby electrons and nuclei, which then emit new photons and so on. This means that energy doesn't travel outwards at the speed of light - instead, it slowly diffuses outwards from particle to particle. This comes out to be very slow. The effective speed can be slower than 1 cm/s, which means it can take thousands of years for light to diffuse out to the surface."
] |
[
"A medium contains atoms / molecules. A vacuum (in this case) doesn't have anything.",
"When you look at what the light does in the medium, i.e how it's transmitted and how it actually travels, it gets super technical. But if you don't worry about how it's traveling, it's a ton more simple. ",
"When light travels through ",
" it's slowed compared to when it travels through nothing (aka a vacuum)"
] |
[
"That's the trouble lol, it's complicated, mostly because the mathmatical models that describe the hypothesis don't work for all cases. ",
"You could say that the molecules absorb and then emit the light, like a game of telephone, but that model says the light should slow down further than it does, and that it should warp the wavelength/energy, which doesn't happen. ",
"Or you couls say the light bounces like a pinball, but then light should scatter more than it does. ",
"The youtube channel SixtySymboles did a video with a physics professor about why glass was transparent, and his answer is nobody really knows. The competing theories are right in some places, but wrong in others. That's where I'm getting my knowledge of the subject from.... and that was in like 2012ish, so maybe there's been a breakthrough since then?"
] |
[
"Evolution: What findings, if they would be discovered, would completely disprove Evolution, or at least significantly disturb the existing model?"
] |
[
false
] |
[deleted]
|
[
"Well evolution is about more than just chronology. It's also about heredity and genetics. There were any number of creatures dreamed up in ancient mythology that would be seriously disturb our understanding of evolution if found. For example, if in some remote jungle, tomorrow they discovered a living, breathing griffin, that would be quite the find. ",
"It's pretty hard to explain something with the body of a lion and the head and wings of an eagle. None of the ancestors of lions have anything like feathers, a beak, or even wings. So some mutant can't have somehow dredged up some of its own ancient, dormant genes. Lions and eagles are so far apart genetically and morphologically to make interbreeding comical at best. ",
"So yeah, most of these creatures, if found, would go a long way to disproving evolution:",
"http://en.wikipedia.org/wiki/Category:Mythological_hybrids",
"Cultures all over the world have imagined these evolution-defying hybrids. It's telling that as we have scoured the globe and attempted to discover all of its species, none of them have ever been found."
] |
[
"Fossils of dinosaurs with arrowheads stuck in them?",
"A fossil of a triceratops holding an autographed photo of Kirk Cameron?"
] |
[
"God/aliens coming down from the sky and creating a new species and stating that previous species were created by them. (And not through some middle-man prophet or ancient book.)"
] |
[
"What's going on in your throat/voice box when you lose your voice?"
] |
[
false
] |
I am losing my voice from a cough. Why and how does this happen? What's going on in there?
|
[
"Doctorate in voice here.... regarding laryngitis from overuse of the voice: the cords vibrate against each other to create sound, much like if you tried to make a trumpet sound with your lips. The cords are essentially rubbing against each other several hundred times per second; that is the basis of phonation. Overuse can mean one of several things. It can mean using the voice relatively well but for too long (like talking to someone at a party for a long time) or using it poorly (yelling, screaming like you might at a sporting event). The vocal cords begin to swell and become irritated in the same way your hands would become irritated if you rubbed them together vigorously for a long time. Keeping the same hand rubbing analogy, doing this repeatedly without giving adequate time for the cords to heal in between leads to callouses on the cords, the same as would happen to your hands.",
"Vocal hygiene issues can compound the problem: acid reflux, alcohol, smoking and even certain medications to predispose the larynx and the cords themselves to irritation, swelling, and eventually laryngitis.",
"Irritation of the vocal cords themselves is one cause of laryngitis. The other contributong factor is the irritation of the throat in general. The muscles that control the fine movements of the cords retract and tighten when the throat is orritated, much the same way your lower back muscles tighten of you had lower back pain. Ot is an instinctive response. Because those muscles have tightened, they have a smaller range of movement. So, even if the vocal cords might be in relatively good condition, they still womt vibrate efficiently because the muscles that bring the vocal cords together have a limited range of movement.",
"(Written on my android pad at opera rehearsal. Please excuse the many misspellings) "
] |
[
"im pretty sure its from inflamation from overuse, causing it to not be able to vibrate and produce sounds."
] |
[
"The relevant ",
"wiki article",
" agrees with you. The \"Causes\" section has several sources supporting that inflammation from overuse will cause laryngitis, but a very cursory examination doesn't explain the mechanism behind this, which I feel would be much more interesting. Do you (or anyone else) have insight into the mechanism by which over-use of the vocal chords leads to an inability to produce sound?"
] |
[
"How did the early solar system sort itself out?"
] |
[
false
] |
Why did the lightest gas, hydrogen, migrate to the center of the “dust cloud?” Why are the rocky planets and the asteroids next, then more gases to form the gas giant planets? It seems the original disc/cloud was complex, so how did it sort? Was it homogeneous initially?
|
[
"Yes, you start with basically a homogeneous cloud, which is mostly hydrogen, followed by helium, and then a sprinkling of everything else. ",
"This composition is what you then get for the Sun, in the center. This composition is also what you start with everywhere else in the cloud.",
"The cloud has heated up as it has collapsed into a disk, and the center will collapse all the way into making a star, so that will become very hot indeed, but the farther out you look from the center, the more things will be cooling down. Heavier more refractory substances (rocks and metals) will be the first things to be able to coalesce and freeze out--if you're in the inner solar system, the temperature will drop below the vaporization point of, say, iron oxide, while still being above the vaporization point of, say, ice, so you can get solid particles of rocky stuff forming, but not of ices.",
"At any given point of time, you can draw a line in the disk and say \"inside this line, it is too hot for anything solid to form, but outside this line, it is cold enough for rocks and metals to solidify,\" and call this the rock/metal line. Similarly, you can draw another line farther out and say \"inside this line it is too hot for ices to form, but outside this line, they can,\" and call this the frost line. Between these two lines, solid planets can form. Outside this line, not only can solid planets form, they will be much bigger, because they can form from not only the rarer rocks but the much more plentiful ices.",
"Now, at all of these places, you still have the full mix of elements--about 75% hydrogen by mass, 25% helium by mass, a sprinkling of heavier atoms--but in the very center they're all gases, in the middle zone, the rocks are solid, and in the outer zone the rocks and ices are solid while hydrogen and helium are still gases. The planets grab onto atmospheres made of whatever gases are nearby; the bigger they are, the more atmosphere, so the outer ones grab much bigger atmospheres.",
"Now the Sun kicks in with an early phase of intense solar wind and blasts all the loose gases out of the solar system. The inner rocky planets are too small to hold on to anything and are stripped down to bare rock. The outer rock+ice planets are big enough and far away enough that they hold on to their atmospheres, which are huge, so that rocks and ice are hidden deep away inside and all we see are those atmospheres. Jupiter is still basically the same mix of elements as the Sun and the original cloud, but Earth is now very different."
] |
[
"As a tack on to this answer the initial perturbation that causes the homogeneous gas cloud to have a locally dense pocket, which acts as the \"star seed\" for the rest of the cloud to be drawn towards, is thought to often be the result of gravitational disturbances from passing celestial bodies or the explosive death of nearby suns! However, observing star formation is pretty tricky due to the long time periods it's possible some other mechanism is at work, causing locally dense gas pockets for stars to form around."
] |
[
"The way I understand it, the extra piece is ",
"planetary migration",
", which is part of the ",
"Nice model",
", the most popular model for the formation and evolution of the Solar System. That doesn't invalidate anything ",
"u/HappyFailure",
" said, though."
] |
[
"Is brown rice really a more \"healthy\" choice than white rice?"
] |
[
false
] | null |
[
"Brown rice naturally has more nutrients like vitamin B and iron, but when making \"enriched\" white rice they usually add them back in. Still, white rice usually doesn't have any magnesium. Also, there's twice as much fiber in brown rice, which is a significant amount considering its health benefits. Also, brown rice contains bran oil not present in white rice, which has been shown to help lower cholesterol. "
] |
[
"brown rice impairs magnesium retention",
"Cullumbine H, et al. Mineral Metabolism on Rice Diets. British Journal of Nutrition, 1950;"
] |
[
"No. People often believe it is as it is less processed but this is an appeal to nature fallacy. In actuality it has worse nutrient bioavailability, more anti nutrients, and more arsenic.",
"Cullumbine H, et al. Mineral Metabolism on Rice Diets. British Journal of Nutrition, 1950;",
"Rama Rao G, et al. The Effect of the Degree Of Polishing of Rice on Nitrogen and Mineral Metabolism in Human Subjects. Cereal Chemistry, Jan-Feb, 1960;",
"[Miyoshi H, et al. Effects of brown rice on apparent digestibility and balance of nutrients in young men on low protein diets. Journal of Nutritional Science and Vitaminology, 1987;](",
"http://www.ncbi.nlm.nih.gov/pubmed/2822877",
"]",
"Meharg AA, et al. Speciation and localization of arsenic in white and brown rice grains. Environmental Science & Technology, Feb 15, 2008; 42(4): 1051-1057.",
"Zavala YJ, Duxbury JM. Arsenic in rice: I. Estimating normal levels of total arsenic in rice grain. Environmental Science & Technology, May 15, 2008; 42 (10): 3856-3860.",
"Sun GX, et al. Inorganic Arsenic in Rice Bran and Its Products Are an Order of Magnitude Higher than in Bulk Grain. Environmental Science & Technology, 2008; 42 (19): 7542–7546.",
"EDIT: my citations are all messed up but you get the idea"
] |
[
"What is \"herd immunity\"? Is this term being thrown around correctly? Is this a viable solution to Covid19?"
] |
[
false
] | null |
[
"Herd immunity is when there are so many people that are immune to a disease that infectious people aren't able to spread the disease further. If you are infected but everyone around you is already immune to the disease you can't infect anyone else. ",
"It is not a solution to Covid-19. It is a desired endstate. The question is how do we get there? Do we get there by infecting everyone with Covid-19 or do we get there by vaccination? If we get there by infecting everyone millions of people might die. If we wait for vaccines, we might have to live with social distancing for quite a while longer. It is also important to note that it doesn't erradicate the disease. It will just stop it from infecting everyone that is without immunity. Furthermore it is unclear how long the immunity even lasts. ",
"Last but not least it is important to note that it is not entirely clear when herd immunity is reached. It depends on the properties of the disease. For more infectious diseases you need a higher percentage of the population to be immune than for a less infectious disease.",
"Some visualization of herd immunity. ",
"https://imgur.com/gallery/8M7q8#J7LANQ4"
] |
[
"What is \"herd immunity\"?",
"When most people are immune so it becomes unlikely for a pathogen to come into contact with people who aren't, because it can't simply jump through the population in general.",
"Is this term being thrown around correctly?",
"Doesn't look like it, much of the current discourse seems tantamount to sitting back and just letting everyone die, then hoping the survivors don't get it again; whereas a proper herd immunity approach usually hinges on widespread vaccinations including people with a very low risk of catching relevant pathogens - it's worked quite well for mumps, measles, rubella, polio, etc, but there's no vaccination for covid-19 yet.",
"Pox parties",
" used to be a thing supposed to help build herd immunity with pathogens that affect children less than adults, but it turns out they're rather more problematic than helpful so their popularity has dropped significantly.",
"Is this a viable solution to Covid19?",
"Until a viable vaccine is widely available, only if you're ok with millions of people dying on the way there, and we can actually form long-term immunity to it - which hasn't been demonstrated, and there's ",
"at least some indication that it may never be a thing",
" like influenza and the common cold."
] |
[
"Good explaination but I think that it is important to expand on the \"we don't know how long the immunity lasts\" point.",
"If the immunization lasts, Say 5 year, with a vaccine we can just re-do the the vaccination every 5 years, no big deal.",
"If we reach herd immunity \"naturally\" every 5 years we are back at the \"people dying\" step.",
"(Ok, It would not ",
" be like that since the virus would still be spreading and selection Will kick-in, etc, but you get the point)"
] |
[
"Is there a practical application of the fact that there are distinct degrees of infinity?"
] |
[
false
] |
I recently learned that there are different degrees of infinity -- e.g., countably infinite sets vs. unaccountably infinite sets. This is certainly interesting from a "curiosity" point of view, but is there a practical application of this knowledge? Can you explain to me whether this fact is an inconsequential mathematical technicality, or if it there are conceivable engineering applications that could be affected by it?
|
[
"Yes and no. For example: in science and engineering, one of the most important mathematical tools we have is calculus. Calculus relies on certain properties of the real/complex numbers, for example you cannot define a derivative as a limit if you are using the integers (which are countably infinite) because the epsilon-delta formalism completely fails. Functions also behave strangely on the integers, and continuity is not very meaningful. In short, using a countably infinite number system to do physics is very difficult."
] |
[
"From a computer science point of view, countable sets are really the only thing we can deal with. Because computers are digital, the number of different values they can represent are always countable - even if we assume that we have unbounded resources (e.g. time and memory).",
"So for example, given enough resources, a digital computer can represent and calculate with any possible integer. However it can't, for example, represent all real numbers."
] |
[
"Outside of computer science, it is not directly important. I don't think any structure has been built using the consequences of countability. But countability and uncountability are so important in the mathematics that were put into building the structure that they are very relevant."
] |
[
"Thanks, r/askscience"
] |
[
false
] | null |
[
"Understood, however meant it more in terms of everyone who comments and has input in general"
] |
[
"We appreciate the comment :) But \"message the moderators\" on the right side-bar is the way to contact us."
] |
[
"Well, as commenter/inputter, thank you again :P"
] |
[
"If a woman has an irregular period, let's say once every five months, does she extend her birthing years?"
] |
[
false
] |
[deleted]
|
[
"You have this a little backward. You're correct in that the they are born with their set amount and they do get older.",
"There isn't a hormonal change that triggers menopause. What happens -- through mechanisms we don't totally understand yet -- is that when you are younger the eggs initially released were the ones most sensitive to FSH and LH. When you're older you have the eggs left that for whatever reason haven't been able to mature because they were not sensitive enough to FSH and/or LH.",
"When you finally go into menopause it is because the only eggs left aren't very responsive, and their follicles don't mature and don't create the estrogen and progesterone. Your body really ramps up the FSH and LH trying to get those last eggs to mature and then ovulate. But alas they are only left with the insensitive eggs. The high FSH is what we think causes hot flashes.",
"edit: grammar"
] |
[
"You have this a little backward. You're correct in that the they are born with their set amount and they do get older.",
"There isn't a hormonal change that triggers menopause. What happens -- through mechanisms we don't totally understand yet -- is that when you are younger the eggs initially released were the ones most sensitive to FSH and LH. When you're older you have the eggs left that for whatever reason haven't been able to mature because they were not sensitive enough to FSH and/or LH.",
"When you finally go into menopause it is because the only eggs left aren't very responsive, and their follicles don't mature and don't create the estrogen and progesterone. Your body really ramps up the FSH and LH trying to get those last eggs to mature and then ovulate. But alas they are only left with the insensitive eggs. The high FSH is what we think causes hot flashes.",
"edit: grammar"
] |
[
"I disagree with the idea that women don't \"run out of eggs\" during their lives, as the other commenter suggests.",
"The current consensus is that the hormonal irregularity of menopause is a kind of retrospective marker of the depletion of ovarian follicles. The age of ovarian follicle depletion is based on the number of oocytes (\"eggs\") that a woman has at birth, and the rate of depletion of oocytes, which is determined by a host of factors. One thing that controls oocyte depletion is their maturation, which is under control of cyclical hormones (which control follicle growth, ovulation, and periods).",
"There was a debate about whether or not oral contraceptive use could extend fertility by suppressing FSH, a hormone responsible for causing follicles to grow. Based on retrospective studies, oral contraceptives are not believed to extend fertility. However, some epidemiological studies have shown a correlation between low FSH and later menopause.",
"So, my answer would be a tentative \"not likely.\" I think the major determinant of follicle depletion is simply the rate of cell death (\"atresia\"), rather than follicles maturing. Women are estimated to be born with 10,000x more oocytes than the number of times they ovulate. Most eggs simply never get the chance to mature.",
"Additionally, this answer depends strongly on the cause of a woman's irregular period, as a period is not necessarily a marker of ovulation.",
"Here",
" is a free article, where the authors discuss some of these issues and conduct a study of oral contraceptive use and age of menopause."
] |
[
"How accepted is the quantum theory?"
] |
[
false
] | null |
[
"What do you mean by \"the quantum theory\"? Quantum mechanics is accepted by every serious physicist on the planet."
] |
[
"doesnt quantum mechanics imply that us looking at something impacts it? with the double slit experiment making it seem as though nothing really \"exists\" until we see it. i know eintsein said something like \"i believe the moon is there even when im not looking\" I am kind of trying to make sense of the implications of quantum mechanics"
] |
[
"QM has many counterintuitive implications (many of which get exaggerated or misrepresented in popular science media). But it is very well supported by experimental evidence. It is definitely a more accurate model of reality than classical mechanics, any physicist will agree with that."
] |
[
"What's the real-life use of solubility product constant?"
] |
[
false
] |
I searched and searched but I could not find a real-life use of solubility product constant. I saw that water filtration requires solubility, however, it does not need the Ksp value, whose real-life application I am looking for. Thanks in advance.
|
[
"Ksp helps you determine the strength of the common-ion effect for any given substance. The common-ion effect is important in all kinds of industrial processes involving purification by precipitation. Ksp is also useful in explaining the formation of particular minerals. "
] |
[
"Imagine you have a mixed solution of the nitrates of Sr",
" and Ba",
" and want to separate the two ions. Both of their sulfates are pretty much insoluble in pure water, so as you add a sodium sulfate solution, the sulfates precipitate. You can use the Ksp values to determine the composition of the precipitate (BaSO4 vs. SrSO4) at any given solution concentration of sulfate. In this way you can find the ideal set of conditions to ensure complete precipitation of BaSO4 with minimal contamination by SrSO4.",
"Another application is in the production of photographic emulsions, which are usually mixtures of AgBr and AgI, created by reacting a mixture of silver nitrate with sources of Br",
" and I",
". You use their solubility products to calculate how much of each component to add to get the desired ratio of AgBr to AgI in the precipitate."
] |
[
"Why would one require Ksp value for purification?"
] |
[
"Can anterograde amnesia be used as an anesthetic?"
] |
[
false
] |
I was reading on Wikipedia that a variety of drugs can induce anterograde amnesia, and it occurred to me: has anyone ever used this as an anesthetic? For example, if a patient was given an amnesia-inducing drug before surgery, would that person fail to remember the pain, therefore making it not actually matter if that person were sedated?
|
[
"As a sole anesthetic, never. Amnestics are part of the balanced anesthesia care model and can help when the anesthetic has to be light because the person is physiologically unstable. However, there are other factors to be concerned about than just recall of the surgery. Painful stimuli produces a huge surge of catecholamines which can increase heart rate and blood pressure, increase the risk of arrhythmias, and also increase the risk of intraoperative heart attacks. So pain control is obviously pretty important as well."
] |
[
"I assume the fact that the patient would be squirming about would also be a factor?"
] |
[
"It really depends on the surgery. Not all surgeries require neuromuscular blockers (paralytics), but you're right in that benzodiazepines don't give adequate surgical muscle relaxation. So if it were a surgery that required relaxation, that's another reason that amnestics only wouldn't be enough."
] |
[
"How come gases are so cold in their pressurised cans?"
] |
[
false
] | null |
[
"The gas in a can like spray paint isn't actually cold. Its the same temperature as the can or the air around it. Its when the gas is rapidly expanded that the temperature drop happens. The opposite is also true. When you compress a gas it heats up. Its what makes most air conditioning systems possible. "
] |
[
"It's not simply compression and expansion. It is the phase change from liquid to vapour that causes the biggest change in temperature. This is true for refrigeration system as well."
] |
[
"Chemist here. I actually did a lab experiment analyzing the Joule-Thomson effect (the exact effect you are describing.) This is sometimes known as the \"throttling process\", and as mentioned in another comment, is frequently utilized in refrigerants and other cooling processes.",
"As a gas expands in this manner, it is an adiabatic process (meaning no heat flow). As total energy is changed by heat and work, and the heat flow is 0, only work can change the energy of the system. However, as the gas is expanding into a (relatively) open space (the air), no work is done. So the total energy of the system is conserved, without taking or giving anything to the surroundings.",
"Here's where it gets neat. The gas has so much extra room, the potential energy the system has increased dramatically. Normally, this extra energy would relate to the heat absorbed by or work done to the system. Since both of these are 0, and we can't magically create energy in a non-nuclear process, it comes from the kinetic energy of the particles. As that kinetic energy decreases, the particles slow down. The bump into each other and their surrounding less often, which is how we define \" temperature.\"",
"So the gas starts out at normal room temperature, and is not cold inside the can. Instead, the sudden depressurization causes the kinetic energy to drop, which in turn lowers the temperature of the gas, all without any heat exchanged. The cold gas then matches the temperature of its surroundings by absorbing heat, leaving the can, the air, and your hands feeling cold.",
"Some interesting extra info: Different gases have different changes in temperature, even when exposing the same amount of gas to the same pressure change. This difference is called the Joule-Thomson coefficient, and explains why some gases are \"better\" than others for refrigeration or cooling. Also, hydrogen, helium, and neon are the only gases that do not exhibit this process while at room temperature.",
"Sorry if the formatting is odd, or I left out a word. Currently on my phone, I'll update and edit as needed once I'm home! "
] |
[
"If the earth's atmosphere was compressed into a liquid, how would it compare in volume to the oceans?"
] |
[
false
] | null |
[
"Perhaps a bit surprisingly, it's really not that much. The total mass of all gases in the atmosphere comes out to 5.15*10",
" kg. Since most of this gas (~80%) consists of nitrogen, let's use the density of liquid nitrogen, which is 0.807 kg/L. Dividing the two numbers we get, 6.4*10",
" L. This may sound like an insanely large volume, but it doesn't seem that much when you find out that all water on Earth comes out to a volume of 1.4*10",
" L. ",
"To give you a better visual of what that would look like, if all the water on Earth were bunched into a sphere, it would look ",
"like the larger sphere in this picture",
". If all the Earth's gases were compressed down to a similar liquid sphere, you would only get a small drop, more than 100 times smaller in volume, just smaller than the middle drop in that image.",
"edit: clarified the comparison a bit"
] |
[
"For another way of looking at it, if you spread that throughout the earth it would be about 12.5 meters deep."
] |
[
"The atmosphere as a liquid would be less dense than water so it takes more depth to exert the same force."
] |
[
"could life be created and sustained without a planet?"
] |
[
false
] |
I was reading an article on cracked . It says that there's a huge water cloud. My question is Could life be created in this water cloud or another water cloud in space. If life could be created, could it even be sustained?
|
[
"Life as we know it, (carbon based) could not, now that being said, that doesn't mean that life couldn't be based on something like silicon (",
": Silicon based life would be possible at extremely low temperatures, ( lower than -100ºF). Problem being is that water wouldn't be liquid in a cloud in space, in order for life to start, you need a liquid for the proteins to coalesce (this is also assuming you have some sort of energy source (static discharge, or some steady source of radiation as energy is needed for the chemicals to combine) IF you have something like a huge raindrop of X liquid in space, it would need to be something like liquid methane to be the solvent. Then and this would be an extremely long shot, maybe you could get a few amino acids going. My final thought on this would be, 1. yes, probably only extremely basic bacteria. 2. Not very long assuming it did happen. ",
"Notable cites: ",
"http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Methane"
] |
[
"Really appreciate the detailed response. Thanks again!"
] |
[
"No problem glad to help!"
] |
[
"Why do knots seem to form \"easily\"?"
] |
[
false
] |
[deleted]
|
[
"Basically it is much more likely for a string to fall in a knotted positing than a un-knotted one. Also, once a string is knotted it resists being untied (which is the basically the definition of a knot) so it'll remain knotted until someone unties it.",
"Here's a study about it ",
"http://physics.ucsd.edu/~des/DSmithKnotting.pdf"
] |
[
"I think the US army did a study on this at one time. Tried to calculate the likelihood of knots forming and difficulty in untangling them. To me this may have been futile as the variables are too great.",
"Ultimately I think it comes down to this. For any cord, there are many combinations for a knot/knots to form but only one combination for that cord to not have a knot."
] |
[
"That is exactly it: topologically speaking there are a huge number of configurations we call knots, and only 1 possible configuration that is not a knot."
] |
[
"Why do mitochondria need their own DNA?"
] |
[
false
] | null |
[
"As has been said, endosymbiotic theory which is pretty widely accepted states that both chloroplasts and mitochondria were once bacteria of their own right. We believe the modern day equivalents are cyanobacteria and proteobacteria respectively.",
"Some nice sets of evidence:",
"Circular genomes as seen in bacteria",
"No nucleus of their own and no chromatin packaging (prokaryotic features)",
"No introns as in eukaroytic systems",
"Double membrane akin to the inner and outer membranes of gram-negative bacteria.",
"Encode their own tRNAs",
"Replicate at a different point in the cell cycle to other organelles",
"But do they \"need their own DNA\". No they don't. But it's the system that works and nature is good at keeping systems that work, even if they're not the optimal system. A considerable amount of mtDNA and chDNA has migrated to the nucleus such that mtDNA no longer fully encodes for a functioning mitochondrion. Why doesn't all the DNA migrate to the nucleus? Because this system works :)",
"See quantum_lotus' comparison of eukaryotic and prokaryotic mitochondria including chimera activity recovery"
] |
[
"Complete mitochondria (like those found in humans, plants and most eukaryotes) do seem to need mitochondrial DNA (mtDNA) to keep their distinctive shape. Yeast cells that lack mtDNA (known as rho0 cells) have abnormal mitochondrial morphology. But the number of mitochondria do not differ between rho0 and rho+ cells. So the researchers conclude that mtDNA is necessary for the proper morphology/shape of mitochondria, but not their generation. Evidence for this comes from: ",
"Holmuhamedov ",
". Deletion of mtDNA disrupts mitochondrial function and structure, but not biogenesis. ",
". 2003 Aug;3(1):13-9.",
"And if you're unconvinced that the shape of a mitochondrion is important, remember that the enzymes that make up the respiratory chain are clustered together in the cristae of the inner membrane, allowing for increased rates of respiration. Furthermore, it is speculated that the morophology of the inner membrane facilitates necessary interactions between the complexes of the respiratory chain.",
"*Edit: clarified that I am not talking about mitosomes, unlike ",
"/u/PsiWavefunction",
" (who has very good points)"
] |
[
"Certainly. Lynn Margulis gave the theory the boost it needed back in the 60s. She didn't really help her cause in the 80s when she tried to attribute most organelles to endosymbiotic theory in addition to her (later) views on HIV. Unfortunately it's often the case that when a perfectly good idea is proposed by someone who is viewed badly by the community, it takes a while to catch on.."
] |
[
"If Jupiter is a gas planet made up of Hydrogen and Helium, could it turn into a star if parts of it were heated enough to start nuclear fusion?"
] |
[
false
] |
I just wondered
|
[
"Jupiter needs to be about 80 times as big as it currently is for that to happen. It only needs to be about ~13 times as big to start burning deuterium."
] |
[
"I believe that the issue is not heating, but compression. Thus you would need to add mass, not energy to make it a star."
] |
[
"Jupiter lacks the required numbers of atoms to start a proper nuclear reaction. With more atoms, Jupiter would gain more gravity; then, \nit could begin to contract under its own gravity, setting off the process which will convert it into a star (or, to be precise, a Protostar, which is not a real star).",
"So, when Jupiter will be a Protostar, the atoms will start to collide towards the centre, thus augmenting the density of the planet and diminishing the size. After a good million years, if everything goes right and all the atoms start to collide (going towards the centre is a crowded way), the Protostar will reach 10",
" Celsius degrees. This is the temperature where the nuclear fusion will start and our star will be born!"
] |
[
"If I am paragliding through dark clouds, would I be able to fill up an empty waterbottle?"
] |
[
false
] |
Say I glide through storm clouds and was able to to keep altitude until I got out of it. Would I be able to catch water? Would I be wet when I got out? Is the water safe to drink?
|
[
"Well I do sailplane gliding quite regularly on top of having a pilot's licence(on top of what seems to be the prerequisite of being in this sub; a physics major), and yes, it does get the windscreen wet if you pass through cloud. As a matter of fact the water droplets adversely affect glide performance so as a glider pilot we tend to stay out of clouds and rain. I assume fabric and skin would be the same as glossy paint so I don't see why you wouldn't get wet. Probably wouldn't get ",
"As for catching water, it might require some apparatus, such as a sieve to collect water particles. Or a cloud collector, one of whose designs may be found ",
"here",
".",
"The typical cloud droplet's size is on the order of 0.02mm, so it would be best if the sieve's holes are approximately in that region as well. I am, of course, assuming several things at this point, such as laminar air flow through the sieve and no water tension; in practice either of these wold result in collection of water much lower than usual.",
"By storm clouds i presume you mean cumulonimbus? You'd be crazy to touch those, even the big boys in the airlines steer clear. But for the sake of this thought experiment, I assume you are. Wikipedia states that the water content of a CB cloud is 1-3 g/m",
" The equation you want, therefore, is",
"W=pSvt,",
"where p is the density, S is the surface area of your sieve, t is the time of flight in cloud, and v is the velocity you're flying at; probably at around 60km/h, give or take. Due to weight and drag limitations, say your sieve is about 0.1 m",
" So, in theory, you'd be able to collect 600-1800g per hour flight time, or 0.6-1.8 L/h. Theory, of course, tends to deviate pretty far from practice. Depending on your collector design, efficiency rate, and a hundred other factors, it would be somewhat significantly less. However, cloud collection as a viable source of drinking water has in fact been deployed in ",
"africa",
".",
"And that article answers your last question; yes, it is extremely pure, and therefore drinkable; more so than tap water. Pretty much the equivalent of rain collection before it becomes rain, really."
] |
[
"By storm clouds i presume you mean cumulonimbus? You'd be crazy to touch those, even the big boys in the airlines steer clear. But for the sake of this thought experiment, I assume you are.",
"Why's that, stronger winds/electrical charges lead to an unsafe environment?"
] |
[
"The purity would be related to air quality, but even dirty air would be ok to drink. You might not want to do it regularly though. It depends on the contaminants that make it into the water. If it's just low pH as a result of SOx and NOx (acid rain), then you'll be fine as people drink things that are way more acidic (lemon juice, soda) on a regular basis. There could be other compounds (mercury, lead, etc) that were originally particulates that could cause long term problems if you kept drinking the water. More info on acid rain here:",
"http://www.safewater.org/PDFS/resourcesknowthefacts/Acid_Rain.pdf"
] |
[
"Why is it more difficult to breathe warm air?"
] |
[
false
] |
When I get into my car when the sun has been baking it all day, I feel like I can barely fill my lungs. In cool air, though, breathing is much more comfortable. Why is body-temperature air stifling vs cooler air?
|
[
"It’s not harder to breath, but there is less oxygen per volume of hot air compared to cold air. Cold gases are denser, meaning more oxygen per volume, your body feels this lack of oxygen in the air and tells you to breath harder to make sure you continue to get the requisite amount of oxygen that your body needs to survive."
] |
[
"I’m no expert but warm air has higher temperature so your lungs don’t feel much change in temperature because it is already warm. But if it is cold then you can notice the difference more and thus feel like you have indeed received air. Also the warm air is sometime more humid so it may be thicker and thus more difficult to breathe."
] |
[
"Warm air moves the oxygen dissociation curve the wrong direction also and makes it harder for your lungs to release CO2 and absorb O2"
] |
[
"Why does hair turn grey / white when mammals get older?"
] |
[
false
] |
Beyond just the obvious reasons (lack of melanin), what triggers in the body make this occur and why?
|
[
"I'd be interested to here from someone who actually works closer to this than I,but here is the ",
"Wiki",
" article on the subject. ",
"\" The change in hair color occurs when melanin ceases to be produced in the hair root and new hairs grow in without pigment. The stem cells at the base of hair follicles produce melanocytes, the cells that produce and store pigment in hair and skin. The death of the melanocyte stem cells causes the onset of graying.\""
] |
[
"So it is a matter of the lack of melanocytes? Are all melanocyte stem cells used up at a certain point? ",
"I'm less interested on how this happens and more in why it occurs."
] |
[
"It's probably related to ",
"Telomeres",
", but that more of the \"How\" then the \"Why.\" ",
"The \"Why\" falls under the evolutionary biology heading more, and there is always the general \"because it allows offspring to better survive.\" That's hardly a real explanation however. ",
"This is the same sort of thing as baldness in men, it may be a social cue of age which enables better social ordering and hence a more efficient society, or it could be a circumstantial effect of a larger factor (like the coloration of dogs as they are domesticated.) "
] |
[
"Is there anyway to take heat and turn it into electricity?"
] |
[
false
] | null |
[
"In principle, yes. A heat engine is a device that takes heat from a hot object and moves it to a colder object. In the process we can extract some work from it, usually by expanding and contracting gases appropriately and making the gas move something mechanical. If you want electricity, you then have to turn the mechanical work into electrical energy by moving conducting wires around in strong magnetic fields. ",
"Note that you can't just turn \"heat\" into \"work\" with no waste heat left over! That violates the second law of thermodynamics as you're essentially removing entropy from the hotter object as you suck the heat out of it and you're not increasing the entropy of anything else. There always has to be some waste heat to balance the entropy equation!",
"So, what about in practice? For the moment, let's put aside the (many) practical considerations of building a mini-powerplant on your desk. Let's assume your hot laptop is running at about 70C (~340 K), and room temperature is a nice, comfortable 25C (300K). The theoretical efficiency of our hypothetical heat engine is thus (1 - 300/340) = 0.117 ~= just under 12%. Keep in mind that this doesn't take into account ",
" inefficiencies in design - this is the maximum amount of recoverable energy!",
"Now, in reality it's obviously not worth it to build a complex, destined-to-be-inefficient desk-sized powerplant. There are materials that will convert heat to electricity with no moving parts! These are called thermoelectric materials, and they rely on the Seebeck effect, named after the guy who discovered that you can induce a voltage difference by heating part of a wire loop made out of two different materials. ",
"Keep in mind that these materials aren't \"magic\" - they have exactly the same laws-of-physics restrictions on recovering energy as before, and are actually pretty bad at it. A quick googling of thermoelectric energy recovery reveals that the current available technology can return about 8% of the available energy. So, using our figure for available energy from before, we arrive at 12% * 8% ~= 1% total energy efficiency.",
"Of course, with 99% of the waste heat remaining, your entire thermoelectric device will quickly heat up and destroy the internal temperature differential without adequate cooling, rendering the whole setup useless. "
] |
[
"Look up thermionic generators. Several ways of doing it. Basically a junction that is cold on one side and hot on the other creates a potential and moves current if a complete circuit is available. Have you seen those picnic coolers that have a little fan on one side and plug into your car's 12 volt system? When you apply a voltage to it, one side gets hot and the other cool. If you unplug it and apply cool to one side and hot to the other it will create voltage and current, about 65 watts worth if I remember right."
] |
[
"A Stirling engine can operate on as little as a 0.5 K temperature difference, can use practically anything as a heat source, and can approach efficiencies as high as 30%. You would need to gear one to a generator somehow, and I don't know as much about those. ",
"http://en.wikipedia.org/wiki/Stirling_engine"
] |
[
"Why are burns more prone to infection than lacerations or abrasions?"
] |
[
false
] |
I was under the impression that the biggest threat with a burn is infection, why is that?
|
[
"Depending on how serious the burn is, it can destroy the skin to various depths. Thus opening the barrier that was there to keep infections away (notice how permeable your skin becomes at the burn site, it usually becomes shiny and wet as your plasma leaks out). Burns tend to have a bigger surface area than the other two wounds, and also harder to close through blood clotting and sabbing.",
"I think if you have a large and serious abrasion wound, it'd be similar to a burn wound in terms of the effect."
] |
[
"Actually, a lot of the bacteria that are considered \"normal flora\" that inhabit the surface of your skin can cause quite serious complications if they get into areas that they're not supposed to. For example, staphylococcus aureus likes to colonize the nose and throat and doesn't cause problems (usually). But if it gets to places it's not supposed to, like the blood stream, it can cause toxic shock syndrome and other serious illnesses.",
"So to answer your question, yes - anytime you disrupt the normal flora of an ecosystem, it can allow opportunistic organisms to invade. But a much more likely explanation is that things already on your skin are getting into places where they're not supposed to be."
] |
[
"Burns have two major problems relating to infection 1) typically the local immune response is destroyed, compromising the ability of the body to keep out foreign invaders since the skin is the major defense 2) Burns do not clean themselves out. The body is made to react to cuts, a very intricate system starts occurring the moment one happens, and irrigation is the number one factor in reducing infection. Wounds that bleed profusely are more or less self irrigating. Burns typically do not bleed, and in fact can hold infectious material in place. "
] |
[
"What does the Schrodinger's equation give me exactly?"
] |
[
false
] | null |
[
"Hi yousif777 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
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" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"i am new to reddit, what is a flair"
] |
[
"It is the category that we assign in this subreddit to each question, like \"Chemistry\" or \"Biology\". This helps users and panelists sort questions by category. Please see the auto-generated comment above about instructions for adding flair."
] |
[
"Is blood letting an effective form of reducing blood pressure?"
] |
[
false
] | null |
[
"Yes and no. In the acute sense, it's very effective in the sense that removing blood from an otherwise closed system will by definition drop the pressure. It, however, in no way tackles any underlying chronic cause of high BP. "
] |
[
"I'm not a medic, just a humble biochemist, but my understanding is this. You restore blood volume, and therefore pressure, very quickly - just osmotic movement restoring plasma volume. But restoring the non-aqueous content (both cellular and other components like platelets) takes longer. ",
"So I suspect you (hypothetically!) would remove blood each morning, your pressure would fall, it would rise during the proceeding 24 hrs and you'd do it again. You'd end up diluting your cellular count (especially your white cell count) drastically. When you take into account all the clotting factors you'd be diluting as well - it would be mayhem. In any case, even if this isn't the reason why it's a bad idea, it's definitely a bad idea :P"
] |
[
"This. You'd end up pancytopenic very quickly. "
] |
[
"Can we ever expect to see the inner layers of Earth?"
] |
[
false
] |
I'm guessing it's very doubtful, but I'm curious to know if there are any technologies in development that could make it plausible in the future.
|
[
"I'm not sure what you mean by \"see\" here, could you please elaborate?"
] |
[
"I'm pretty sure that he/she means ",
"this",
".",
"I'm sure that we'll find a way to drill into the mantle and see it (using cameras or bringing up samples for testing), but humankind will never be able to reach the inner core or outer core. The pressure and heat at those depths is just too great for drills to work."
] |
[
"There are some environments, such as mountain belts, where broad cross sections several km wide of the earth crust are exposed. These sections are thouroughly deformed and fractured, but we can make sense of them. In some cases, such as ophiolitic complexes, the section goes all the way down to the upper mantle. For deeper rocks, you don't have much other options than mantle xenoliths and the like..."
] |
[
"Can a star be so hot it is invisible to the naked eye?"
] |
[
false
] |
The hotter a star is the higher the frequency at which it glows. So can it be so hot that it is 'glowing' at x-ray frequency and is invisible to normal light?
|
[
"No. As temperature increases, the intensity of every wavelength always and only increases. Different wavelengths increase more than others, causing the peak to shift, but still the intensity everywhere increases. If it's glowing at X-ray frequencies, it also glowing quite brightly in the visible as well."
] |
[
"The tail end of the blackbody spectrum would still be strong enough in the blue for a person to see. This is similar to Cerenkov radiation: most of it is in invisible wavelengths, but we still see it as blue."
] |
[
"Exactly. It's just that it's also glowing even more in the blue range, too."
] |
[
"Are their any risks to life expectancy for patients who receive donor organs that are older than their age?"
] |
[
false
] |
So I have a question. Does putting an older person’s organs in a younger patient have any risks? Like, would someone who was say 12 years old have the same average life expectancy if they were to have the heart of someone who gave their organ at say 35 years old+?
|
[
"Getting a transplant shortens your lifespan significantly, regardless of the donor (except, perhaps, from an identical twin, but even then it may)",
"The thing is, it shortens your lifespan much less than the disease which was killing you would have. So on balance, it adds to you lifespan, but not nearly as much as if you hadn't needed one in the first place. So, if you get a kidney from a 50 year old while you're in your 20s, your body will probably reject it before it gets too old to work."
] |
[
"The average heart transplant lasts ten years and may last twenty. Transplants do not repair people or make them healthy again. Transplant recipients are constantly fighting rejection -- their body attacks the foreign organ. The medicines they have to take to slow rejection cause a lot of side-effects and often injure the kidney or liver, requiring transplants of those also. Children who receive transplants of any organ will need multiple transplants to live a long life."
] |
[
"Another thing to consider is the fact that anti-rejection medications increase the risk of various cancers. This is because medications given to organ recipients are immunosuppressive - they keep the body’s immune system from attacking foreign tissue. However, it is this same immune system that protects us from cancer, so disabling it carries a risk. Obviously an increased risk of cancer or organ rejection is better than dying from organ failure, but it is an unfortunate consequence."
] |
[
"On the Wikipedia page for \"Koch's postulates\" it is stated that HIV causing AIDS doesn't follow from them. How so?"
] |
[
false
] |
Under .
|
[
"Koch's Postulates mainly apply to bacteria, fungi, and protozoans. The Postulates require that you are able to take samples from an infected individual, isolate them in culture, reintroduce them to a healthy individual, and recreate the disease. This breaks down for viruses at the \"culture\" stage. Unlike living things, viruses are incapable of being grown on a medium and isolated. They can only replicate in living cells. If you can't isolate them in culture, you can't be sure that you're reintroducing the correct thing into the healthy individual, so the whole process gains a scientifically unacceptable margin of error. Also, unlike pathogenic life forms, viruses tend to be extremely species-specific, so there comes ethical questions about introducing HIV or other dangerous diseases into healthy humans simply to validate a hypothesis. There are far more effective and ethical means of determining the cause of disease and infection in modern medicine."
] |
[
"When ever you read something on Wikipedia it is important to look at the source and verify. The statement you quoted is cited as coming from a Nature article published in 1990. It discusses the Duesberg hypothesis, that argues for an alternate cause of AIDS. Either recreational drugs or the potent anti-viral drugs in an iatrogenic effect, and that HIV was merely a non-disease causing passenger virus.",
"The scientific consensus is the Duesberg hypothesis is incorrect. If you are interested in reading a one page review of the arguement put forth, you can find it here: ",
"http://www.sciencemag.org/site/feature/data/cohen/266-5191-1647a.pdf",
"Basically it boils down to referencing a claim from two and a half decades ago that was proven false. Wikipedia should probably edit the statement to reflect that."
] |
[
"As it states earlier, his postulates are mostly obsolete as the field of virology formed and made more sense of things. HIV causing aids doesn't follow his postulates, which is an example of why they're mostly obsolete."
] |
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