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[
"Is there a place on earth where meteors hit fairly regularly?"
] |
[
false
] |
Is there a place on earth where meteors hit fairly regularly? I know we get approximately 17 meteors hitting the earth a day but I want to know if anyone would know if there’s a place that they commonly hit.
|
[
"There are places where meteor strikes are more and less apparent- Antarctica, with its lack of vegetation and snowy ground cover is near ideal for spotting meteorites. The ocean basins are places where they are least apparent, due to the lack of ability to closely observe much of the bottom and the nature of the water surface (i.e., no persistent crater or evidence of impact)."
] |
[
"The simplest answer is no, they are random."
] |
[
"Correct, they are random. So the place that gets hit the most is the Pacific Ocean, simply because it's the largest place on Earth."
] |
[
"Why does video shown at 50-60fps look so unnatural?"
] |
[
false
] | null |
[
"Are you talking about \"High Frame Rate Movies\", or just anything at 60 fps? A game, for example, shouldn't look unnatural, it should usually look more natural at 60 frames per second than something like 30, but motion in a game is going to be generated differently.",
"Movies might look unnatural, and at a high level this is simply because this is not what you are used to seeing. You are used to seeing the \"24\" to \"30\" fps (it's not always an integer) in most other current technologies. Up to a certain point your brain is filling in the gaps. It is interpolating the \"frames\" that aren't there from the current frame and the previous frame, to create blurred motion that lacks detail but still looks natural, less discrete or jerky. ",
"At 24 frames per second, for example, your brain is receiving (distinct/unique) images faster than it can process them. It holds onto an image for a certain amount of time and if gets another image within that time, they are going to get blended together by your brain in an attempt to connect the two images and create fluid motion.",
"When you have something like 48 or 60 frames per second, you are seeing much more detail/information. You aren't just seeing more frames in the same amount of time, but you are able to see more of their contents. The missing frames your brain created before couldn't have detail that wasn't from other frames, and so that made up detail ends up being an average of the adjacent frames. So in the case of \"High Frame Rate Movies\" those frames are actually there, with all their detail. Your brain still fills in the missing information, but there is less of it. That information you aren't used to seeing now makes it look unnatural since your brain isn't used to processing it. If you watched them long enough you would get used to it just like any other frame rate within a certain range.",
"So if you look at it as having to do with the difference between any two frames or distinct images, there is usually going to be more of a difference in a lower frame rate and your brain fills in more information to allow the images to be continuous. As the frame rate increases there is a less of a difference between the two (or more) images and your brain has to fill in less. Whereas before a detail might have been absent from one frame and present the next, or the one after that, etc. and your brain spends time processing the composite image in a certain amount of time, now it is more likely that that detail will be in more of the images and it won't get blurred/averaged out in the composite image, making it stand out more, especially when you aren't used to it.",
"Something similar happens in photography with still images. If the camera picks up detail that your eye doesn't, then it can make it look unnatural. An example might be that an airbrushed image of a woman might look more natural because its closer to what you are used to seeing. You might not see every freckle or wrinkle in her skin. But when you see that unaltered image it can look unnatural because details/information you aren't used to processing stand out.",
"Hopefully a vision expert can come along and give a better explanation than that (and correct me if I got anything wrong), but hopefully this is a starting point."
] |
[
"It's just because you are used to 24fps video."
] |
[
"First, let me point out that I am not vision, video or TV expert...",
"Are you asking when does a frame rate become unnecessarily high? Well, there are technologies that go as high as 300 fps... Those would probably get scaled down to be viewed. So it's difficult to say what is unnecessary.",
"(Looking up the time), your brain holds onto an image for about 1/15th of a second. So as it receives images within that time, they get composited to form a continuous image. At 60 frames per second, your eye is receiving an image every 1/60th of a second, so 3 or 4 within that 1/15th of a second.",
"As the number of images within that 1/15th of a second goes up, the closer they are going to be until eventually they are virtually the same, meaning only so much can change in a certain amount of time that your brain could even process. I think it is probably hard to say at what point that happens. It depends on the image, and its content and the details it may or may not contain. A low detailed image isn't going to need as many frames per second to display it faithfully as a highly detailed image.",
"You'll see technologies that involve 300 frames per second. Those are most likely going to get down-converted when they are broadcast, especially on TV. But that allows for a certain amount of detail to be preserved, even if it isn't meant to get to the viewer in that state. For example, to down-convert it to 50 or 60 fps, frames could be dropped or interpolated for normal speed. But if there is a part that is meant to be slowed down, for example, in a sports replay, then the frames wouldn't be dropped or interpolated; instead they might be displayed multiple times to slow down the image while maintaining the detail included. So for normal speed footage, every 5 or 6 frames might be turned into one by dropping or interpolating. For slowed down footage, each frame might be displayed 5 or 6 times.",
"So I think it would be hard to say when it is unnecessary (if that is what you were asking) because it depends on what is being presented and how it is being presented.",
"As for the \"bonus question\", yes it should be able to physically do that as far as refresh rate, but as far as that image being \"twice as smooth\" as 60hz, that would depend on how the image is being delivered. For example, your cable probably isn't going to look any better. A computer game that can run at 120 fps probably will, although because of the way games are displayed, I'm not sure you would notice as much of a difference."
] |
[
"Is it true every atom in our bodies came from a star that exploded?"
] |
[
false
] | null |
[
"Except some hydrogen, helium ",
" atoms , whom have existed since the Big Bang, all elements comes from dead stars, since it's the only place, where it is hot and dense enough, for larger atoms to form.",
"Edit: Thanks ",
" and ",
" for letting me know about the lithium."
] |
[
"Not a silly question, when a supernova scattered the heavier elements through the galaxy the shockwave runs into pre-existing clouds of hydrogen/helium. This disturbance can cause the cloud to begin to collapse, forming a star. It is ",
" sensible that this could have happened with our star meaning a lot of the H and He gas came from this cloud and not the supernova. This doesn't mean the gas has never been in a star but it allows us a decent possibility."
] |
[
"Is it likely that these hydrogen and helium atoms have all gone though a star? (this feels like a silly question)"
] |
[
"Would gravity be possible as we have it on Earth on a flat surface?"
] |
[
false
] |
As I understand gravity, objects are drawn towards the center of mass of an object. Since Earth is relatively spherical, the center of mass is in the center of mass is in the center, and gravity works like . (with the red square being the center of mass, the red arrows being the direction of gravity, and the green dot being the Earth) On a flat surface (like previously thought by many who-knows-when), gravity would work like , where people near the outer edges of the surface would essentially be standing on walls. Is gravity like shown in the sphere possible on a flat surface?
|
[
"On a flat infinite surface, the gravitational field is constant and pointing in the direction of the surface. "
] |
[
"You're beginning with an incorrect assumption. Gravity doesn't attract towards the center of mass. What happens, though, is that a spherical body of even mass distribution acts (mathematically) like a point mass when you calculate its gravitational field. In other words, the \"center of mass\" assumption conveniently works for spherical objects, but not necessarily for others.",
"Anyway, your guess for how the gravity would look on a flat Earth with finite size is at least qualitatively correct. I'm not particularly interested in doing the math to calculate the gravitational field, but it's clear from just an intuitive look at the situation that if you're not in the exact center, there's going to be a gravitational pull trying to bring you back to it.",
"If you want to make a \"flat\" surface that acts like a sphere, it's mathematically possible. If you assume that the surface is infinite, the field at any point near the surface is normal to it; in other words, gravity is pointing straight down.",
"Now, obviously, an infinitely large surface is physically impossible. However, if the surface is large enough, you can use an infinite sheet as a reasonable enough approximation. For example, if the earth was flat, but billions and billions of miles across and everyone just happened to live near the center (maybe the rest is oceans, idk), it would be very hard to tell just from gravity whether you're on a sphere or a very large flat surface."
] |
[
"This problem is mostly worked out in terms of electric fields rather than gravitational, but they behave the same. You can treat a capacitor as an infinite surface with constant charge density, and use either Coulomb's or Gauss' law to figure out that the electric field is constant."
] |
[
"Do bugs sleep? Plain and simple."
] |
[
false
] |
Do bugs sleep? (insects, spiders, moths,flies, the colloquial application of the word bugs is implied)
|
[
"Yes. The only living organisms that ",
" sleep (in some form) are the ones who don't live long enough to incorporate the day/night cycle into their lifespans, ",
". Plants sleep. Slime molds sleep. Single-celled organisms sleep. The common misconception that \"sharks don't sleep\" comes from the observation that sharks never close their eyes, but as it turns out, sharks don't have ",
"."
] |
[
"Mayflies live for a significant amount of time as nymphs. Would they not sleep during that period?"
] |
[
"Also sleep is not always linked with the day/night cycle. Apparently ants sleep about 200 times a day. For one minute each time."
] |
[
"Why is the Prandtl number for the Earth's mantle so high?"
] |
[
false
] |
On Wikipedia's entry for the , it states that the earth's mantle's Pr is around 10 . Does plate tectonic activity contribute to a high kinetic viscosity (∴ high viscous diffusivity) relative to a very low thermal diffusivity, or is the latter just extremely low relative to a low viscous diffusivity?
|
[
"It's not actually correct to describe the mantle as magma because it's not predominantly melt. In fact there's practically no melt there at all. It's crystalline but able to plastically deform. "
] |
[
"This is really because magma has an incredibly large viscosity.",
"It's pretty common to picture magma in the mantle as similar to liquid lava pouring out of a volcano, but the material properties are ",
" different. For all intents and purposes, if you had a piece of magma sitting on your kitchen table, you'd think it was just a solid piece of rock. Technically speaking, it's a ",
"rheid",
".",
"Magma's viscosity is somewhere around 10",
" centipoise, about 10-100 times more viscous than granite at room temperature and pressure (and by comparison, water's viscosity is about 1 centipoise). When you divide that by thermal diffusivities that are typical for minerals, about 10",
", you can easily reach a Prandtl number of of 10",
"."
] |
[
"Right, this is true - I probably should have just said \"mantle material\". It's also important to point out that those deformation rates are much, ",
" slower than a lot of folks think.",
"On average, a piece of the mantle is going to move about one inch per year."
] |
[
"What is the chemical progress that happens when you freeze something and then shatter it?"
] |
[
false
] |
I assume it has something to do with the atoms, but I might be wrong.
|
[
"Objects smash when you freeze them because the water inside them turns to ice, and ice is very brittle. This liquid to solid phase transition is a physical change rather than a chemical one, so the chemical structure of your arbitrary object remains essentially the same. There are very likely a large number of weak intramolecular bonds which are broken when this occurs (hydrogen bonds, for example), but that would depend on exactly what your object is."
] |
[
"also if the OP is talking about the freezing flower (apple, broccoli, etc.) in liquid nitrogen; rapid freezing ruptures cell walls, so even if you let it melt instead of shattering it you'd be left with something that's more like broccoli soup than the original broccoli."
] |
[
"This is a difficult question to answer as phrased. Matter can exist in 4 phases, solid, liquid, gas, and plasma. \"Freezing\" something colloquially involves a conversion from its liquid state into a solid one. Not all solids are brittle, and therefore don't shatter (think of steel, or rubber for example). ",
"When you freeze something with a non-arbitrary structure, like say water, all the water molecules line up in a pattern so that the (relatively) negative charge of the oxygen and (relatively) positive charge of the hydrogen are as close as possible to each other (the lowest energy state possible). If this 3D grid of molecules is altered, same charges come in close contact, and they push apart, causing the crystal to \"shatter\". ",
"If you are asking why things 'shatter' when you cool them with something like liquid nitrogen, that also has many answers. For some things, it is the water content which is freezing, and subjecting the whole object to the issue described above. For something like a metal, which tends to become brittle at low temperatures, the effect is caused by a decrease in the metal atoms to 'flow'. Metals are cations bathed in a sea of electrons, where the metal ions move around within the material relatively freely. When metals get extremely cold, these ions stick close to each other, and have a decreased ability to move, causing the metals to break under stress as opposed to bend. "
] |
[
"Gene-swapping vaccines spawn lethal poultry virus - Could this happen with human vaccines?"
] |
[
false
] |
[deleted]
|
[
"It's possible, but we are much more careful about vaccines we use in humans. First off, majority of human vaccines these days are not full, live, attenuated viruses as was the case in these chickens. Instead they are specific epitopes (i..e. a small part of the virus that acts as a recognition sequence for the immune system). That means it's not just a few mutations from becoming a full. replication-competent virus again; rather it's just a small section of the virus that needs a lot more information to become whole again. ",
"In the cases where live attenuated viruses are used in humans, we know the full sequence of the virus (i.e. how many mutations it would require to become virulent again), and are (hopefully) careful not to inoculate a patient with another virus that already contains the \"solutions\" to the mutations. In the chickens' case, the sequence of the vaccines was not fully known (but it appears they were attenuated via different mechanisms) and (probably) someone got sloppy by giving one chicken both vaccines. Once in this chicken they recombined and made a virulent virus again.",
"So the short answer is ",
", but much more unlikely given the vaccines and additional care we use for humans. It's also something we'll definitely think about in future vaccine design."
] |
[
"Yes, Polio itself or vaccine associated paralytic poliomyelitis (VAPP) can be caused by vaccine derived poliovirus (VDPV) from OPV (live attenuated oral polio vaccine). ",
"Either there is reversion to wild-type by mutation, divergence of vaccine strain into two distinct strains which recombine ('gene swap'), or there is inter-typic recombination due to coinfection with wild-type and vaccine poliovirus strains. There is evidence for all of these. ",
"Point is, VDPVs have been found to cause outbreaks in Egypt, Haiti, Philippines, Russia, Congo (again just recently, even after WHO declared it Polio free once), and many other countries. The persistence of these vaccine derived strains poses a major problem for eradicating polio. "
] |
[
"[–]Surf_ScienceGenetics|Systems Biology|",
"I'm guessing that would be Yellow Fever. Maybe Polio is runner-up?"
] |
[
"When you leave a carbonated drink to sit for a while after being shaken to avoid it fizzing over, what is actually happening here?"
] |
[
false
] | null |
[
"A carbonated drink means theres dissolved co2 in the liquid. The concentration of dissolved co2 depends on several factors but the main one in this case is the co2 concentration in the air above the liquid's surface. If you've noticed, all carbonated drink bottles are somewhat pressurised, even if they havent been shaken for some time. That pressure is the equilibrium pressure where the amount of co2 fizzing out of the liquid is equal to the amount of co2 being dissolved back in the liquid. When you shake the bottle you are artificialy increasing the rate at which the co2 comes out of the liquid and this creates a higher presure inside the bottle, which will no longer be at equilibrium and the co2 in the air inside the bottle will begin slowly dissolving back into the liquid until the pressure decreases and it reaches equilibrium again. That is why, if you leave it to sit for a while, it will not fizz."
] |
[
"The paper I cited shows that pressure actually ",
"drops",
" (marginally) upon shaking. I haven't observed that a shaken bottle is more difficult to compress.",
"\nBasically what's happening is that shaking introduces more nucleation sites for CO2(g), allowing CO2 to form nanosized bubbles. Bubble formation (nucleation) is a results of imperfections on the can surface (and impurities in the liquid). When you agitate the mixture, bubbles become distributed in the liquid colloidally for a period of time (i.e. not dissolved). Then when you open the bottle, the CO2 suddenly has millions of nucleation sites within the liquid in which to vaporize. Since you move from a closed system to open system, pressure is greatly reduced and vapor pressure does not apply. CO2 gas is free to form as a function of surface area which is now elevated due to dispersed bubbles, resulting in an explosive foam. In contrast, if those sites were not distributed within the liquid, nucleation would occur only at the original nucleation sites, i.e. sides of can. ",
"/u/agate_",
" said exactly this and I just didn't see it. It's a phenomenon that can't be explained in context of ideal gas which is why I think it's confusing"
] |
[
"Thanks for the mention. The slight pressure drop makes sense to me: the equilibrium between gas and dissolved species depends on having a ",
" gas/liquid interface, so a gas molecule at the interface is just as likely to enter the liquid as the gas. If the surface is a curved bubble, there's slightly more liquid nearby than gas, so the dissolved species will be slightly more likely, and the gas pressure should drop.",
"... but I don't have access to the paper you cited, is that their explanation?"
] |
[
"Can the gut microbiome restore itself to healthy levels after antibiotics and if so, how long does this take?"
] |
[
false
] | null |
[
"PhD in Gut Microbiome here - yes they can restore - as for time it’s very dependent on the situation pre abx exposure- infants with a naive microbiome can take years to return to a pre-antibiotic treated state. \nAlso of course you’ll have opportunistic pathogens trying to gain detrimental colonisation. Someone says use probiotics with abx - I’d wait a few days and get your probiotics in - also use only properly researched and licensed strains of probiotics - don’t go pay a fortune for nonsense :)"
] |
[
"In general - if you just check the box/bottle and if there’s some Bifidobacterium that’s always a good sign - they’re a great commensal - strains of bif longum and bif infantis, bif bifidum have been shown to be positive probiotics for various issues - specifically good for infants. Lactobacillus also another great one for stress and immune health :)"
] |
[
"What are some properly researched and licensed strains please?"
] |
[
"Why does intense pain make me nauseous?"
] |
[
false
] | null |
[
"I suspect a few possibilities. For one, injury causes not only pain but also activates the sympathetic nervous system. This is a protective response to minimize damage while also keeping you alert because injury makes you incredibly vulnerable in the wild. Sympathetic activation decreases blood flow to the skin in order to staunch bleeding from bites or scratches but also decreases blood flow to the digestive organs. This can cause nausea as the movement of contents in the stomach and intestines slows. It's like being unable to eat before a big presentation--your body is in fight or flight mode, and doesn't want to deal with digesting food at the moment. Many animals will even void their bowels and/or vomit in response to fight or flight mechanisms. Anything to make you lighter, and possibly make you less appetizing to a predator. ",
"Secondly, pain has three components: sensory, affective, and motivational. Sensory tells you the difference between types of pain sensation (burning, aching, dull, sharp, throbbing), motivational is related to taking action to stop the pain by removing or escaping the source of pain, and affective is the specific emotional response associated with pain sensation. It's the quality of pain that makes it so unpleasant that we are willing to do anything to make it stop. For really intense pain, the emotional response can be equally intense, because your body needs you to do something about it. ",
"Finally, pain triggers an inhibitory feedback system via the periaqueductal grey (PAG) utilizing the inhibitory actions of opioids. This release of endogenous opioids helps to counter the intense signals from the spinal cord, but unfortunatley opiates are also reallly good at activating your brain's vomiting center (area postrema). You have one because it normally responds to the ingestion of poison or pathogens that need to be evacuated ASAP. Morphine is one of the best painkillers, but damn if it doesn't cause you to puke like crazy. So, I suspect that opioid activation of the vomiting center induces nausea in response to the opioid release associated with pain. ",
"It's probably a combination of all three. "
] |
[
"Wow, thank you for such an indepth answer. I remember feeling so sick to my stomach and I was focusing instead on not throwing up that I forgot the pain for a bit.",
"I appreciate your time in answering!"
] |
[
"Thanks! I study pain for a living, so whenever I see a question I can give a decent explanation for I try to do it. "
] |
[
"Do cells have specific sizes or can they be incredibly large or incredibly small?"
] |
[
false
] |
As an adult I've discovered an interest in the AP bio classes I largely and regretfully ignored. So I'm learning from scratch now how my body works. I just watched a video about T cells, viruses, and b cells and it seems like they all come in different shapes and sizes. What are the similarities that make a cell a cell? Can they be as small as, say mRNA or a protein? Why isn't a protein a cell? Thanks for your patience.
|
[
"Great questions and welcome back to biology!! ",
"A cell is defined by its boundaries. Each cell is an individually competent unit of life, I.e it carries out the functions it needs to survive within itself (intracellularly) or gets what it needs from its environment (extracellularly). Human cells, as well as all of the animal kingdom, have cells bound with a semi-permiable lipid bilayer. Each of those cells contains a set of organelles, the cellular machinery. All cells have a nucleus (stores DNA), ribosomes (make protein), mitochondria (generate energy), and a few others. Some cells specialize by including or excluding organelles. Red blood cells, for example, lose their nucleus in exchange for being more efficient carriers of oxygen. In exchange, they can no longer divide.",
"Cell sizes also vary highly among animals and bacteria, but as a general rule the more complex an organism, the bigger the cell. Humans have comparatively pretty big cells, but as you’ve discovered, cell size can vary based on the organ and system it belongs to.",
"Protein isn’t a cell because protein on its own isn’t self sufficient, it cant generate energy, it isn’t enclosed by a membrane, it cant self replicate, etc.",
"I’d also be careful about describing viruses as cells. Viruses technically are not living, and are not composed of cell. Viruses are just nucleic acid wrapped in a protein shell, which has to invade living cells to take advantage of their properties to live."
] |
[
"Upper limit is set by surface area to volume ratio. Volume increases by cubes, but surface area by square so you start hitting limits of transport and diffusion. Lower limits are reached because there just us to be enough room to get things done. Some bacteria are probably near the lower limit."
] |
[
"That is true for all 3 dimensional shapes, not only bacteria. ",
"It is cause by geometry and not anything biological."
] |
[
"Why is it no matter how hard you blow underwater there are bubbles and not one big bubble?"
] |
[
false
] |
I was swimming and just wondered. No matter how hard I blew, a bunch of bubbles came out. I was underwater on my back, same thing. Why is it that you have a bunch of bubbles as opposed to a long bubble, like a balloon then? Stupid question, maybe, but thought I'd ask.
|
[
"It's not a stupid question at all. I thought about this question for about 10 minutes now and could not think of a reason that I feel at all comfortable posting! Great question."
] |
[
"The behavior of water, or any substance, at temperatures below every day experience and at varying pressures is difficult, if not impossible to describe in words. There are many interesting predictable effects at low T and many more that are yet unexplained. It's an exciting field!",
"tl:dr - I have no idea. It depends on the exact point in (p,T) space!"
] |
[
"what if we were swimming in really low temperature water under absurd pressure to keep it from freezing?!"
] |
[
"Are humans red or white meat?"
] |
[
false
] | null |
[
"I seriously doubt we differ so much that our muscle fibres would be another class. "
] |
[
"Red meat. White meat is reserved for fast twitch muscle like fish, which we have little of (maybe black people have more white meat)."
] |
[
"That's racist!"
] |
[
"Where did the electricity for telegraphs come from during the American Civil War?"
] |
[
false
] |
Looking at Wikipedia, it mentions electromagnets and voltaic piles, but I don’t understand how such a small amount of electricity would be able to travel the hundreds of miles needed. I can notice a reduction of power in my leaf-blower when using multiple extension cords, so how would wires from the mid 1800s be able to carry a signal from an early electrochemical battery over a meaningful distance? Edit: Thanks for the explanations and analogies, they’ve really helped! It makes a bit more sense now.
|
[
"In addition to the other answers: they ",
" have ",
"repeaters",
". But, these were not like modern repeaters -- they were human beings. The human operator would hear the (weak) signal coming in and, by hand, send it on down the line, now at full strength again. ",
"At some point this was automated but I don't know when."
] |
[
"They also had electromechanical repeaters from around 1840ish. It makes sense, considering that telegraph sounders basically WERE relays to begin with."
] |
[
"The signal in early Morse telegraphy was very simple -- \"voltage on\" or \"voltage off\".",
"As long as there was enough voltage left at the receiving end to activate an electromagnet (creating the clicks, or marks on paper, etc.) the message could be copied. With enough voltage in the system and sufficiently thick cables, it wouldn't have been a problem."
] |
[
"What makes a tumor inoperable?"
] |
[
false
] |
[deleted]
|
[
"Location, location, location. In ",
" general, it's because the tumor cannot be cut out entirely. Remember that even a single cancer cell can bring about a whole new tumor, so surgeons must be very sure they can get it all or else they cannot cure surgically. Another reason is that if the tumor has already spread to other parts of the body, removing the primary tumor will not cure the disease. Additionally, there are also occasions where the tumor is in a place that anatomically prohibits removal - this is seen with brain tumors, where an attempt at removal could cause severe brain damage. It can also have to do with being wrapped around important blood supply and surgical removal could result in severe bleeding. ",
"In short, no tumor is \"inoperable\" - it's just that a surgeon deems it inoperable when they look at what it is, where it is, and how far along it is and say \"I cannot cure this disease by removing the tumor.\" "
] |
[
"To add to this, physicians also take into account the specifics of a person's history to determine if it's worth operating on. It's all about cost vs. benefit. If you have an 90 year old man with a pancreatic tumor, the risks associated with getting to it, or even operating and anesthesia for that matter, are almost certainly not worth the the risk. Physicians really do try and weigh quality of life in their decisions. "
] |
[
"Almost every tumour is \"operable\". In the least the surgeon can do a debulking procedure, that is, cut out a chunk of the tumour to reduce the size, the idea being that a smaller tumour is more tolerable to the patient, and there are other palliative (and non-curative) surgeries that can be done to improve quality of life. ",
"Off the top of my head the factors that limit a curative procedure are:"
] |
[
"Why do large animals with bigger hearts have a lower resting heart rate compared to tiny animals who with smaller bodies and thus smaller hearts who have much higher resting heart rates? (Think whale vs mouse)"
] |
[
false
] |
I am curious as to why small animals, such as the mouse I found in my kitchen, with it's tiny body and small amount of blood to pump around, has such a high resting heart rate, even if it's just sitting there doing nothing. By comparison, a whale or elephant, with their massive hearts in proportion to their massive bodies, have a much lower resting heart rate, yet have so much more liquid to pump around.Is it just that as the heart gets physically larger it also gets stronger out of proportion to it's size e.g increase size tenfold it gets a hundred times stronger, thus less heartbeats required?
|
[
"Total metabolic rate ",
" with body size. Metabolic rate per unit of mass generally decreases as the surface area to volume ratio decreases. ",
"An elephant burns more kcals per hour than a mouse because there is much more cellular activity in the elephant than the mouse because there are many, many more cells in the elephant. However, each of the mouse's cells must work harder than the elephant's cells at maintaining equilibrium because of its higher surface area to volume ratio. It loses or gains heat much more easily than the elephant, and must compensate for that. ",
"I would also like to point out that this isn't a perfect relationship. Poikilotherms have a lower metabolic rate when compared to homeotherms of equal mass. "
] |
[
"I remember reading that because small animals are small they have high metabolic rates. They need more energy to keep maintain their temperature. So with a higher metabolic rate the cells need more fuel, therefore more heartbeats to transport the fuel via the blood. Also what the other guy said probably has something to do with it.",
"\nedit: I have a source! ",
"biology textbook notes",
" look in the section titled \"Concept 40.3 Animals use the chemical energy in food to sustain form and function\" ands in bold it should say \"body size influences metabolic rates\" IF you don't want to read it. it says that a a gram of a mouse will consume 20 times more calories than a gram of an elephant. Then, it says that since small animals are small they have a larger surface area to volume ratio so they lose or gain more heat so it takes more energy to maintain homeostasis. This is from an biology class I took last year."
] |
[
"I've been trying to find an answer to this all day, and the body temperature explanation has come up a few times, but doesn't explain why the same relationship (metabolic rate increases with increasing body size) holds true for all other taxa from bacteria to reptiles ",
"(Image)",
"If anyone can elaborate further or suggest more alternatives I'd love to hear them!",
"EDIT: Edited because I can't read a graph properly. Doh!"
] |
[
"Why do I unconsciously emulate the accent of those around me?"
] |
[
false
] |
I have to constantly remind myself not to adopt the speech patterns of people I'm holding a conversation with, particularly accents. Am I just some kind of jerk, or is there an explanation for this?
|
[
"This phenomenon is known as \"phonetic convergence\" within linguistics. While there are ton of studies discussing the phenomenon, (it seems to me as though the exact reason \"why\" is still uncertain) I thought this study was the most useful in answering your question: ",
"Phonetic convergence in spontaneous conversations as a function of interlocutor language distance - PDF",
"We interpret this pattern as suggesting that phonetic convergence between talker pairs that vary in the degree of their initial language alignment may be dynamically mediated by two parallel mechanisms: the need for intelligibility and the extra demands of nonnative speech production and perception.",
"EDIT: This is a study assessing phonetic convergence and proving that it happens: ",
"On phonetic convergence during conversational interaction",
"These results suggest that talkers in conversational settings are susceptible to phonetic convergence, which can mark nonlinguistic functions in social discourse and can form the basis for phenomena such as accent change and dialect formation.",
"EDIT2: Sadly, I can't find the final paper ",
"this study produced - PDF",
", but this work seems to suggest that there are social factors that include social desirability and the social status of the accent that influence the degree to which phonetic convergence will occur. ",
"In the end, all of these studies seem to affirm the basic point that imitation is an essential part of communication and its facilitation. You've probably been unconsciously imitating a lot more than their accent...it's just the most consciously noticeable thing."
] |
[
"Please everyone: This is not asking if you do the same thing, it's asking for an explanation. Please no more \"me too\" posts. "
] |
[
"http://en.wikipedia.org/wiki/Style_shifting",
"It's more prevalent in Asia with tonal languages, and at least in Malaysia where people speak 2/3 languages, multiple dialects and accents, it's considered necessary to change your speech patterns unless you don't look like a local."
] |
[
"Are there invasive species that benefit the local ecosystem?"
] |
[
false
] | null |
[
"Yes! In varying degrees, of course. ",
"First, there are invasive species that fix what human activity (including the introduction of other, destructive invasive species) already disrupted.",
"It provides habitat for young invertebrates and fish in places like the southeastern United States",
"re-populating over-farmed land with native plant and animal species",
"Then there are invasive species that help ",
" parts of the native ecosystem, but hurt others.",
"creating healthier salmon",
"they forced out a lot of the native marsh crabs",
"There are invasive species that \"help\", but only by fixing the same problem they caused in the first place.",
"But now the California clapper rail has begun nesting in—you guessed it—invasive Spartina grass",
"And lastly, there appear to be a very few cases of \"win/win/win\", where invasive species help themselves, and others, without causing any real problems for anybody.",
"But they are also encouraging those bird species to feed on—and spread the seeds of—native species of fruits, too"
] |
[
"Usually a species becomes invasive because it has no real predators and fills a gap in an ecosystem more effectively than the native species, whether that be plant or animal.",
"Most of the time they become destructive by out competing rival species and exhausting prey species."
] |
[
" the Western honey bee. Its native to Europe/Africa/Asia not the Americas or Australia and was introduced to the Americas in the 1600s and later to Australia. It quickly spread across all the continents and by modern standards would be considered invasive as it likely out competed native bee species. However the size of ",
" hives means it does a lot more pollination of local plants than the solitary native species so many native plants probably benefited even if ",
" wasn't as specialized in pollinating those plants as the native species."
] |
[
"Introducing /r/AskElectronics: a new subreddit along the lines of this one, for all your circuits/electronics questions"
] |
[
false
] |
All technical questions are welcome, at any level of expertise.
|
[
"Do you honestly think that ",
"/r/askscience",
" wants questions like:",
"Do I need a GFCI in this circuit?",
"How does one calculate the power gain as well as power dissipated through a transistor?",
"what is the symbol to represent a boost converter in a circuit diagram? ",
"Looking for a good VCO IC for audio circuit.",
"etc.",
"Personally I don't."
] |
[
"Do you honestly think that ",
"/r/askscience",
" wants questions like:",
"Do I need a GFCI in this circuit?",
"How does one calculate the power gain as well as power dissipated through a transistor?",
"what is the symbol to represent a boost converter in a circuit diagram? ",
"Looking for a good VCO IC for audio circuit.",
"etc.",
"Personally I don't."
] |
[
"StackOverflow is probably better, but ",
"here you go",
"."
] |
[
"Using another liquid for steam-powered engines?"
] |
[
false
] |
This post is inspired by this image: My question is: would it be feasible to collect the water vapor and use it to heat another liquid with a lower boiling point? Would this increase the efficiency of a steam-powered engine, or would heat loss/something else be too great a barrier?
|
[
"Yes you can use other working fluids. IIRC pentane is sometimes used in geothermal power plants.",
"Lower boiling point means lower thermodynamic efficiency for rankine cycle engines.",
"http://www.douglas-self.com/MUSEUM/POWER/oddfluid/oddfluid.htm"
] |
[
"No materials lose mass when converting to steam. Perhaps you're thinking about density? Mass is always conserved.",
"You can compress any vapor back into a liquid, but doing so requires that you put back in all the energy you got out, so it doesn't benefit you."
] |
[
"Compound Steam Engines",
" featuring multiple expansion stages were very popular precisely because of the potential to increase efficiency. Extending the concept further with the use of another working fluid is technically plausible, but the gains that could be realized are generally not worth the extra complexity."
] |
[
"How does smoke function in a zero-g environment?"
] |
[
false
] | null |
[
"We are used to seeing smoke rise up, because it is carried by convection currents. In microgravity, there would still be air currents but no set direction for the smoke to go. If the air is very still it might make a spherical cloud around the source, just like ",
"flames on the ISS",
"."
] |
[
"It'd behave a lot like any other fluid that has been in a 0 gravity envirionment. It would simply move in the direction that force has been applied to it or remain motionless if no force has been applied. With no gravity present no bouyant forces are exerted on the smoke from the surrounding fluid (ie. no sinking/rising). ",
"https://en.wikipedia.org/wiki/Buoyancy"
] |
[
"I'm wondering if a zero-G, still-air environment would cause a fire to smother itself out fairly easy. Without convection to expel waste gases and bring in oxygen, a fire would have to physically spread in order to get fresh oxygen.",
"At the same time, they would retain all heat generated to facilitate burning the surrounding environment easier."
] |
[
"How do seeds know not to germinate when inside a piece of fruit? Like a tomato or pineapple?"
] |
[
false
] |
[deleted]
|
[
"I skimmed the Wikipedia article ",
"http://en.m.wikipedia.org/wiki/Germination",
"Oxygen, light, and other factors present in the outside environment, but not present inside the fruit, all contribute to the chances a seed will germinate.",
"In your example of the pineapple seed you said no light was required. But didn't the seed get exposed to some light before it was wrapped in the towel? It was exposed to oxygen and light the moment it leaves the pineapple. Add water and the little bugger knows it's time to do its thing."
] |
[
"If you just bury a tomato, a cherry tomato in particular, or even leave it on the ground it will germinate next season, so it doesn't have to out of the fruit.",
"Some fruit won't germinate until after the fruit has gone through an animal's digestive tract. In Australia there are seeds that won't or can't germinate until they've been in a fire."
] |
[
"I have a soil mix that has old tomato seeds in it. These seeds only germinate and sprout when they get close enough to the surface, like when I've just filled a new pot. In a clear container with no lid, no seeds germinated, but in pots suddenly they started growing.",
"Some seeds, like lettuce, will use specific wavelengths of light. Different wavelengths penetrate the soil to different depths. This allows them to germinate only when they are within the best range of the surface for survival."
] |
[
"Is fat burned during or after exercise?"
] |
[
false
] |
I know excersizing burns fat, but does it occur while you're excersizing or does it take place afterwards?
|
[
"Both. Mostly during heavy breathing exercising like cardio. Keep in mind that most of your fat is actually breathed out. When fat is burned it converts to about 20 percent water and 80 percent CO2 which you then breathe out. "
] |
[
"The simplest answer, both. But the time that your body burns the most fat is after exercise. This is because fat loss has a lot to do with your metabolism. During exercise, your body uses carbohydrates as energy to fuel your body's movements. When your body is depleted of carbohydrates, your body switches to fat to use as energy. Exercising itself burns about 15-30% of the fat you are trying to lose. The rest of the fat burning process has nothing to do with physical movement whatsoever, but rather your metabolism. Exercise is merely a means to increase your capacity to burn fat. The more muscle you gain, the less room for fat there will be, and the more metabolically active your body will become. This means that when you exercise, after you have stopped, your body is internally revved up and is using all of its processes to keep you energized. It is this process that sheds the fat. The more you exercise, the harder you will be able to push yourself, which will increase your metabolism, thereby making it easier to digest foods and not store them as easily as fat storages. "
] |
[
"http://andrewskurka.com/2015/metabolic-efficiency-test-results-hiking-running/",
"The above blog post gives the results of hiker and ultrarunner Andrew Skurka's ratios of fat and carbohydrate burned at a range of paces."
] |
[
"Does bacteria become resistant to dish soap?"
] |
[
false
] |
Dish soap and similar products always claim that they kill 99% of bacteria. If we have antibiotic-resistant bacteria, why don't we get dish soap-resistant bacteria?
|
[
"I'm a little puzzled by gfpumpkins comment, as a) I can't find any dishwashing liquids that use triclosan (hand soaps, yes, but not any dish soaps. Disinfectants appear to be more common in dish soap), and b) studies have found little evidence that bacteria can become resistant to triclosan (",
"source",
"). ",
"However, triclosan is used in hospitals to control ",
"MRSA",
"00002-8/fulltext), so resistance would be rather bad, since it'd be one less tool to treat antibiotic resistant bacteria."
] |
[
"Does dish soap have a similar effect on skin? If not what is the difference between skin and bacteria?"
] |
[
"Does dish soap have a similar effect on skin? If not what is the difference between skin and bacteria?"
] |
[
"If you had ALL the data from seconds after the big bang, knew all the laws that dictate time and space, and were able to process it, could you predict the entire history of the universe?"
] |
[
false
] |
I know that the few moments after the big bang were essentially chaos, but chaos as I understand it just means too many tiny variables to ever accurately calculate. If you knew where every bit of matter/antimatter in the universe was, it's speed and mass and energy, and knew all the laws of nature, including things like what goes on inside a black hole, couldn't you extrapolate that out to predict the entire history of the universe if you had some insanely powerful supercomputer? I suppose this question gets at free will as well, could you predict human events and even thoughts? Am I destined to be sitting here on reddit at this exact time typing this exact question? Is anything truly random?
|
[
"That's a very interesting question, and I thought about it a lot.\nAssuming there is no God or other influence, the answer would be that that we can't predict what is going to happen with great accuracy.\nNot every process in nature is deterministic. For example, radioactive decay is not deterministic (you don't know when an atom is going to decay). A lot of quantum stuff is also non deterministic (particles can exist in multiple states at a time).",
"But even if everything was totally deterministic, you wouldn't be able to use a supercomputer to predict stuff, unless if you can move that computer outside of the universe. Because if you can't move it outside, the computer would have to emulate itself too, and this is not going to work.",
"So we could probably predict the shape of the universe, but not finely predict stuff like you posting this on reddit."
] |
[
"This is more a philosophical than a scientific question. The Universe contains irreducible (chaotic) systems, such as turbulent eddies, brains, and, well, computers simulating discrete irreducible problems. Such systems are not subject to modeling under any approximation, because small errors between the actual and modeled system diverge exponentially, dredging micro-scale approximations up to macro-scale differences in behavior. It is thus not possible to exactly model the Universe as a whole without, in some deep sense, creating it -- i.e. you'd have to set up a computational system whose working parts interacted ",
" as do the working parts of the actual Universe. This has been covered a lot in philosophical literature, but a nice popular level treatment is in Hofstadter's still-fresh-although-written-35-years-ago \"Godel, Escher, Bach: An Eternal Golden Braid\". That is a very interesting line of thought -- for example, it places very strict limits on the omniscience of any hypothetical God: there can't be any useful difference between such a God ",
" about the Universe, versus ",
" the Universe.",
"A corollary is that you couldn't create such a simulation inside the Universe -- for an absurdist proof, see Umberto Eco's essay \"On the Impossibility of a 1:1 Scale Map\". ",
"Another corollary is that human-like patterns present in your simulation could not know the difference between the simulation and an actual Universe exactly like our own."
] |
[
"If the current understanding of quantum mechanics is accurate, then it is impossible to know those things, regardless of technological advancements. Read this: ",
"http://en.wikipedia.org/wiki/Hidden_variable_theory"
] |
[
"What is the evolutionary reason(s) behind dogs having dichromatic vision?"
] |
[
false
] |
I've always wondered about this. Dogs can see violet/blue, yellow, and shades of grey. Why? Blue isn't common in nature and yellow doesn't seem that important. Wouldn't red/green be a lot more beneficial for a dog?
|
[
"all mammals except for \"old world\" primates have dichromatic vision (or even less - i think that cetaceans only have a single cone pigment - can't look it up now but I think they lost the short-wavelength pigment long ago).",
"primates developed a mutation that produces a variation on the longer-wavelength cone pigment - in \"new world\" primates this mutation never quite caught on, and so trichromacy exists only at very low rates (similar to the low rates of dichromacy in humans and other old-world primates).",
"in the old world primates (including apes, macaques, baboons etc) the mutation took hold, and so we all (or like 97% of us) are trichromats.",
"anyways, having receptors tuned to different wavelengths (like the mammal-standard \"long/short\" arrangement) gives you the ability to distinguish colors. in all animals with color vision (which is virtually all of them) the receptor pigments are spaced to cover most of the visible spectrum. it's not about \"what colors are beneficial to see\" - it's about seeing what light there is to detect. then, you make the most of what you get.",
"dogs etc can see lots of colors! it's just that having the third pigment lets you make finer distinctions.",
"there's still a lot of debate over \"why\" primates have the third pigment. lots of birds and insects are also trichromats (some are even tetrachromats), but they got there on different evolutionary paths. it's not really about seeing specific colors - it's about being able to distinguish more differences. personally I think the best explanation is just that 1) the extra pigment lets you see a little more detail, and 2) there's virtually no cost to implementing it. The reason most mammals don't have it isn't because it wouldn't be useful, it's because they never hit on the right mutation, and photopigments are famously stable evolutionary creations (i.e. evolution only hits on a new photopigment every hundred million years or so).",
"\nOne theory for \"why\" primates are trichromats is that it helped some ancestor to find 'red' fruit in 'green' foliage, something like that. But this is a very vague and hand-wavy just-so story and i think it's mostly fallen out of favor. for one thing, it's been shown that trichromat monkeys that eat fruit tend to eat it before it's become ripe enough to become significantly differentiated in its shade (i.e. while still green). But for another thing, like i mentioned above, it's not like we can just evolve new photopigments \"on demand\". It's not like \"oh it would be useful to see color X, i will evolve the appropriate pigment\" - no, instead photopigments are extremely conserved, and change extremely slowly in evolutionary time. Plus, you're as likely to just get a ",
" pigment, as you are to get a ",
" changed pigment, i.e. getting a new pigment and keeping the \"old\" one. And look at what we old-world primates got: our third photopigment is just barely different from the \"standard\" mammal long-wave pigment. Just that tiny change turns out to be useful in making visual distinctions, but it can hardly be claimed to have been done ",
". It was a happy accident and we've made the most of it."
] |
[
"True but I think these are very very minor differences, getting that extra ability to distinguish spectral differences apparently more than makes up for the very slight loss in sensitivity.",
"In our case, the L and M cones have such overlapping spectra that they ",
" encode the same light - but it's the differences that matter. But yes, shifting half of your cones to a slightly different wavelength means you lost a little bit of sensitivity to the original range.",
", I think it's not a coincidence that Old World monkeys (& apes) are almost all diurnal, spending most of their waking hours in daylight. In daylight, cones are rarely going to be working near threshold - there's way more light than they need to signal, so a little loss of sensitivity isn't going to have much practical consequence.",
"As to the rods/cones comparison: rods and cones work in almost totally separate light regimes, only overlapping in a very narrow range of luminance. So it's hard to think about tradeoffs in varying the ratio of rods and cones (more cones: better spatial resolution in daylight? more rods: better absolute sensitivity at night?), kind of apples-to-oranges.."
] |
[
"there's virtually no cost to implementing it.",
"Wouldn't they be losing sensitivity at their original range of frequencies if they had replace some of their receptors with the new '3rd color' receptors? ",
"Similar to how we humans have better overall light sensitivity at the pheriphery of our eyes than at it's center. That's because the center has a large amount of color receptors (cones) but proportionally fewer light receptors (rods). A common way of checking this is looking at very faint stars, you'll probably find that you won't be able to see them when looking at them dead-on but will when looking slighlty away."
] |
[
"What is mass? What do scientists mean when they say a particle has no mass?"
] |
[
false
] | null |
[
"Mass is what makes objects resist changes in velocity. Particles without mass always go at the fastest possible velocity."
] |
[
"Mass is what makes objects resist changes in velocity.",
"For some reason that sort of opened my eyes, mass is just simply the property that resists changes in velocity. Thats it."
] |
[
"Neutrinos may be commonly treated as massless where it is convenient, but it is not believed that they are actually massless. Like quarks and electrons, neutrinos come in three varieties of different mass. The only way they can have three different masses is if their mass is not 0."
] |
[
"Is There a 100% Reflective Surface?"
] |
[
false
] |
Mirrors don't reflect 100% light. Is there any surface that does? I think it'd be impossible for such a thing to exist though. Prove me wrong! (or not)
|
[
"It is of course impossible to get 100%, but you can get pretty good. There are superconducting microwave cavities that are used in particle accelerators and/or quantum experiments with quality factors approaching the billions. Basically two mirrors facing each other; inject a photon and it bounces off each mirror hundreds of millions of times before it is likely to be absorbed (or scattered). I don't have as much experience with optical cavities but the same principle applies."
] |
[
"TIR is a perfect 100% reflection, but it requires going through a medium that has some absorption."
] |
[
"The photons would need to be scattered for you to see it was actually on. "
] |
[
"Why are is blood delivered so slowly during a transfusion?"
] |
[
false
] |
200 ml/hr seems ridiculously slow.
|
[
"I agree that a slower infusion might limit harm from a transfusion reaction. ",
"The second part of your answer is incorrect though. As blood is (by definition) isotonic, giving a single blood transfusion slowly is very unlikely to cause changes to plasma osmolarity and gross fluid shifts (unlike unbalanced crystalloids). Fluid shifts can occur, however, in processes such as TACO - transfusion associated circulatory overload - due to gratuitous infusion of blood."
] |
[
"I agree that a slower infusion might limit harm from a transfusion reaction. ",
"The second part of your answer is incorrect though. As blood is (by definition) isotonic, giving a single blood transfusion slowly is very unlikely to cause changes to plasma osmolarity and gross fluid shifts (unlike unbalanced crystalloids). Fluid shifts can occur, however, in processes such as TACO - transfusion associated circulatory overload - due to gratuitous infusion of blood."
] |
[
"So RBC are concentrated and hypertonic during the transfusion",
"No! This is also flat out wrong. PRBC are isotonic. The cells are separated out physically, by centrifuge, but that doesn't change the tonicity of the fluid they're suspended in."
] |
[
"How do Parallel SEM Avoid Interference Between Parallel Electron Beams?"
] |
[
false
] |
Today I learned that companies like Zeiss have electron microscopes that have parallel electron beams, to increase scanning rate. However, given that electrons are negatively charged, how/why do the parallel electrons path's not become distorted? Do computers do the math to correct for distortion caused by electrostatic repulsion?
|
[
"You could look up beam currents, typical separation of the beams and calculate the effect size based on that, but there is a much simpler approach: Compare it to the effect of the beam on itself. The electrons in a beam repel each other. They are ",
" closer together so their repulsion is much stronger. That is something to keep in mind with larger beam currents, but it doesn't stop electron microscopes from working. Beams separated by far larger than the beam width will have a much smaller influence."
] |
[
"The statement is true for any beam currents, the self-interaction will always be stronger. ",
"This paper",
" discusses how stronger beam currents can lead to notable electron-electron interactions within a beam."
] |
[
"Aren't beam currents In a SEM sufficiently small that the electrons don't interfere with each other? At least that's what I remember being taught. Should be easy to calculate given the current, velocity and travel distance are known"
] |
[
"If we found a meteorite on Earth that originated outside the solar system, how would we be able to determine its age?"
] |
[
false
] | null |
[
"With every applicable method that can be used for meteorites in our solar system within a margin of error. The application of a dating technique is not limited by the origin of the object but by its history, mineral and therefore element content, etc. If I take a basalt from Earth or from Marsfor example, I can still date them; I only have to pay attention for any processes that might have influenced the isotropic pattern of the sample. ",
"For our example that means specifically: if we assume that the partition coefficient of a specific element in a mineral/substance at a given condition is different from outside our solar system to samples in our solar system (and why should it be different?), you can date this thing, I would speculate. ",
"Edit: I got a notification concerning an answer to my post where - if I read that right - I was asked to formulate it a bit easier. Unfortunately I cannot read that reply, it doesn't show up. \nTherefore, I cannot answer everything that was asked in this reply, but here we go: \nEvery element has a specific partition coefficient for each mineral. As an analogue, think about mixing salt into water. There exists a given value which determines how much salt can be solved in water at a specific temperature, right? Same with mineral partition coefficient. Although I don't think that meteorites are typically dated with that, let's take U-Pb dating of zircon crystals. Uranium does not appear in the mineral formula of zircon, but it has a partition coefficient >1 for zircon, meaning if the zircon is crystallising from a melt, Uranium (U) is more likely to be incorporated in the crystal than to stay in the melt. Now over time this U will decay to Lead (Pb). Since we know into which isotope (isotope = same number of protons but different number of neutrons for one element) of Pb the radiogenic U will eventually decay and we also know the time of decay rate, we can then calculate the age of this specific zircon crystal. Now; meteorites are more commonly dated with Rb-Sr (which allows for awesome isochrone dating) or Sm-Nd as ratios, but the principle is more or less the same; if we assume similar partition coefficients (and why should they be different in another place of the universe?), then dating an extra-solar (is that the right word? I don't know) meteorite shouldn't be different from dating one from our solar system. ",
"I hope that this explanation helps - and is mostly correct. 😅"
] |
[
"if we assume similar partition coefficients (and why should they be different in another place of the universe?)",
"They wouldn't, but the absolute abundances of the elements do vary widely across the galaxy. I would have thought that makes it harder to translate an isotope ratio to an age."
] |
[
"This is true, but this comes mostly down to measurement accuracy then. The methods themselves would not differ, only perhaps the instruments used would differ. So instead of e.g. an ICP-MS (I know, not commonly used in dating) you would use...the frick do I know; maybe an AMS?"
] |
[
"Why did humans evolve to be mostly hairless?"
] |
[
false
] |
Seeing as humans evolved on the plains of Africa, where most other examples i can think of animals living in that habitat have fur. What benefit did losing most of our hair (or at least it's becoming so fine that we are effectively hairless) have for our species?
|
[
"Sweat.",
"Relevant TED. (Important part starts at 5:00. Answer is at 9:30)",
"Humans are weak. We aren't fast, we aren't strong, we can't camouflage, and we don't have claws of big teeth. But we can run forever. Which led to an interesting method of hunting. Persistence hunting, where you chase one animal until it gets too tired and just gives up. And they get tired before humans because humans can cool themselves by sweating because they don't have fur."
] |
[
"It could be simply a mutation that ",
" beneficial, but propagated anyhow. People need to realize that evolution isn't always about ",
" - it's about a mutation that carried on through a successful ancestry. ",
"As an example, a three horned goat with fingers might propagate because it has fingers, but the third horn is useless - always was. Here we are, 500k years later going \"what's the advantage of that third horn?\" -- when there was none. Evolution is just \"mutations that survive\" - they don't ",
" to be beneficial to that survivability -- some other trait of that creature may be what is carrying it through generations, while this other mutation piggybacks for the ride.",
"For all we know, the hairless mutation was just a carry-over mutation with no advantage at all (or more comically, all our knuckle-dragging ancestor females thought that hairless mutation was \"exotic\" and mated him left and right). The point being is that it doesn't have to have an evolutionary ",
" to be with us here and now."
] |
[
"how about why humans have hair in their armpits and groin, yet other apes have the opposite. Related but just as strange. "
] |
[
"If one had an infinite amount of carbon and hydrogen, and let them react, which hydrocarbon would be formed?"
] |
[
false
] |
There are an incredible amount of different hydrocarbons that exist. A lot of these hydrocarbons are more stable than elemental carbon and hydrogen, which means that if carbon and hydrogen are put together, a reaction would occur. How is it "decided" which one is formed?
|
[
"What makes you think a single molecular species would be formed?"
] |
[
"under what pressures and temperatures? If you're at absolute zero, nothing will happen. You need to define boundary conditions for this question. "
] |
[
"Infinite amount of what graphite? double bonds? Organic reactions (or most for that matter) aren't as simple as putting two elements together/ Saying an infinite amount of carbon and hydrogen is like asking how fast you could go with an infinite amount of fuel and wheels"
] |
[
"[Chemistry] If Hydrogen bonds to Chlorine, is there any way this can be ionic?"
] |
[
false
] |
I know HCl is covalently bonded but is there the possibility it can be ionically bonded?
|
[
"Every bond can be described as having some degree of covalent and ionic character. That 1.7 difference in electronegativity cutoff is just something we tell freshman students because they need something to memorize and regurgitate on exams. The greater the difference in electronegativity, the greater the percentage of ionic character in the bond. ",
"HCl has a large degree of covalency to its interaction, but there is a significant amount of ionic character in there, too."
] |
[
"As an aside, bare protons are too unstable to exist in aqueous solutions. A \"hydrogen ion\" is actually a hydronium ion, or H3O+"
] |
[
"Upvote for more complete answer. But I don't think anyone would call HCl ionic. "
] |
[
"Dating amber and the fossils within. How do they do it?"
] |
[
false
] |
... because you see these fantastic fossils congealed in amber, but since amber is a thing that oscillates between solid and liquid, and since carbon-dating is more complicated for really old stuff ... and so on and so forth, I just got this hunch that when they say this lizard is 65million years old, it seems just remotely possible that sometimes they might be far far off. How is it done? Example stupid situation: some tree sap drips into a little rock pocket that is kept freekishly warm for eons because hey, why not ... and a lizard creeps in last thursday (give or take a few decades) and suddenly the environment of the ambr changes and it solidifies. That afternoon it is spotted and transported with great enthusiasm to a place that estimates the surrounding rocks as being multimillions of years old. But that lizard knew a world with wifi. Hyperbolic, I know, but it's to make my doubts easier to understand.
|
[
"Dating Amber is complicated, as you must use an indirect approach (… aaaaaand, in just one sentence, here I am in ",
"/r/outofcontext",
" territory…).",
"So … Amber, it’s complicated…",
"Amber is a carbon-based compound, the only radio-elements it contains which might be usable are carbon isotopes … and C",
" dating can’t reach beyond a few tens of thousands of years … most amber deposits are waaaay older than that, so C",
" is useless.",
"So, we use indirect methods. The simplest is ",
"faunal correlation",
"; it’s a method which has been in widespread use for decades. In its simplest form, you note down the list of species present in what you are trying to date (whether it be limestone, mudstone or even amber), and find other places with a similar assemblage of species where the age might have been determined from other methods (by dating local associated volcanic rocks by the ",
"U-Pb method",
", for instance). Preferably you focus on species which were geographycally widespread, but existed for relatively brief time periods, these are termed index fossils.",
"For instance, ",
"these guys",
" looked at the pollen assemblages in the sedimentary rocks containing their amber deposits and found a pollen/spore assemblage which was consistent with the specific flora of a given time period (Aptian to late Albian).",
"These other guys",
" used a different approach, since their amber deposits contain small amounts of volcanic pebbles, and that these are datable by direct methods, they used U-Pb datation on the pebbles and more specifically the zircons they contain. However, they first had to establish that there was only one possible source for these volcanic fragments (apparently, in their area, it is so). You will also note that this method only provides a maximum age … the amber cannot be older than the pebbles it contains. Technically, this data could be further bracketed by using another method to provide a minimum age. However, the authors consider that for preservation reasons (see their discussion), the age of the amber is probably about the same as that of the zircon-bearing volcanic material."
] |
[
"Another lovely answer. Thank you very much. Is it fair to say, going by your last paragraph example, that in the case of a lizard in some amber, and latching on to the \"only determines a maximum age\" thing, it is difficult to affirm that the lizard got stuck in the Amber at the same time that the volcanic pebbles got stuck there .... and therefore, end of sentence approaching, the age of the lizard would be a wild guess and might be off by a sizable amount?",
"\nActually, a defining factor in all this would be how long tree resin can can remain viscous. Because if it could stay liquid for enough thousands of years, the volcanic pebbles would be less significant."
] |
[
"on to the \"only determines a maximum age\" thing, it is difficult to affirm that the lizard got stuck in the Amber at the same time that the volcanic pebbles got stuck there",
"That's not quite the nature of the problem - there is no doubt the lizard and pebbles (if there are pebbles with the gecko - I do not know if that's the case) got there at the same time (geologically speaking). What matters is the gap in age between the material the pebbles are made of, and the trapping of the gecko in tree sap. In the case of the Burmese deposits, analysis of the particulars suggests they are penecontemporaneous.",
"Allow me a different example. I live next to the Grenvillian orogen of the canadian shield. Those rocks are on average 1 billion years old. And those rocks are eroding and feeding sand, and zircons, into the catchment basins of the local rivers. If a salamander (we don't have lizards) got trapped in pine sap there, today, with a few grains of sand containing datable zircons, future geochronologists using the same method would conclude that the salamander-containing amber is at most of Grenvillian age (1 billion years and counting). They wouldn't eb wrong, bu that age would not be very usefull. Te method must take into accont the local particulars of each case."
] |
[
"Using spectrophotometry to estimate biomass?"
] |
[
false
] |
I was doing some work in a lab over the summer, including recording in vivo (blue) chlorophyll of some plankton samples. I've recently been sent the data (I'd given it to a lab technician to put into excel), and 'chl in vivo blue' is recorded in fluorescence (RPU). What is this unit? And is there a way I can use this to estimate biomass? Other data I have are abundances and biovolumes, but without cell density, I don't know how I can calculate biomass. Does anyone have any suggestions?
|
[
"Fluorescence is often measured in arbitrary units, I've always seen them called \"RFU\" or relative fluorescence units. You need a standard curve of known concentrations of plankton in order to convert the fluorescence into a cell density or biomass sort of measurement."
] |
[
"I have these ",
"growth curves",
". ",
"I also have the corresponding fluorescences, so could I combine these to create a biomass curve?"
] |
[
"Yes, if you have the fluorescence values for a bunch of known concentrations of cells, then you can graph them against each other (that is, graph RPU on the x-axis and the corresponding cell densities on the y-axis) and use excel to generate an equation like y = mx + b, where x is the RPU and y is the corresponding cell density. Then for any fluorescence value in RPU, you just plug it into that equation to get the corresponding cell density in cells/ml or whatever. ",
"Make sure your standard curve actually looks linear before trusting a linear approximation, and beware of extrapolating outside the range of your standard curve. Let me know if you'd like any more details."
] |
[
"Why are potato chip bags made with aluminum? What special property does it have that makes it preferable to 100% plastic?"
] |
[
false
] |
Bonus question: If the bag is made with aluminum, how come you can see light through the bag?
|
[
"Because metallized films are more expensive, and if the product isn't sensitive to oxygen it's not an economical choice to use them. Packaged ready-to-eat cereals are usually low in their unsaturated oil content and so rancidity isn't an issue with them. Plastic films do a good job of providing a moisture barrier, though, and high humidity is the biggest threat to quality in dry cereal products."
] |
[
"The metal content of the film provides a superior barrier to oxygen over pure plastic; which allows the product to maintain quality longer."
] |
[
"It's known as Modified Atmosphere Packaging, and it shows up in other places as well. In oxygen-sensitive foods (potato chips are a great example, as the oil content makes them susceptible to rancidity) the in-package atmosphere usually decreases the oxygen and increases the nitrogen content. For fresh vegetable products such as bagged salads, the lowered oxygen is replaced by carbon dioxide to prolong cellular respiration and extend shelf life. ",
"Meats are more complicated. Simply purging the oxygen from a package of meat will help retard spoilage, but a lack of oxygen will also result in myoglobin converting to an unappetizing brown form, metmyoglobin. High concentrations of oxygen will shift this to oxymyoglobin, which is bright red - in this case, high concentrations of carbon dioxide are also required to prevent bacterial growth, so the modified atmosphere has a low nitrogen content. Carbon monoxide can be used, but it will force such a strong red color in the meat that it actually conceals evidence of spoilage and leads to a false impression of freshness, so its use is considered unethical and potentially illegal if done deliberately to cover up tainted meat.",
"Usually the simplest way to establish a modified atmosphere is by packaging the food under those conditions. On occasion, chemical scavengers are used to scrub the in-package atmosphere of one particular component, but they tend to have a higher cost and thus see less use."
] |
[
"Why some people passed out when they saw Michael Jackson and some don't?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"Where do I ask then? I seriously searched everywhere I could and I can't sleep properly. Can you send me on track? Help is much appreciated."
] |
[
"Not quite sure to be honest."
] |
[
"Do other mammals get headaches too?"
] |
[
false
] |
I’m specifically wondering about dogs, but do all mammals get headaches? If so, how can we tell that they have a headache? Do they also get migraines?
|
[
"Glaucoma (increased intraocular pressure) can cause something akin to a migraine in dogs due to the acute increase in pressure on the optic nerve. If the retina is already non-visual and enucleation (surgical removal of the globe) is performed, you can see near immediate relief in some dogs based on their demeanor before and after the surgery. ",
"For example, my own dog developed severe glaucoma over the course of three days, IOPs in the upper 80s mmHg. She had very dull mentation, quit eating, and overall was just not herself. The affected eye was enucleated and upon recovering from anesthesia later that day she was bright, alert, and back to her normal personality despite having a surgical wound on her face.",
"In contrast, cats tend to develop glaucoma more slowly and can go years before IOPs become high enough to cause discomfort.",
"Source: am vet with glaucoma research experience",
"Edit: See the \"Early to Midstage Clinical Signs\" subheading for more details.\n",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4862370/"
] |
[
"I've heard about elephants getting something called Musth which causes them to become highly aggressive. The temporal glands swell up and press on the elephant's eyes and cause pain. It's believed to be comparable to a severe root abscess toothache. It could be similar to, or cause, a headache.",
"https://en.upali.ch/musth/"
] |
[
"There was a 2013 paper published about a dog with migraines.",
"The dog in the 2013 study occasionally experienced episodes of apparent fear, which were followed by the dog emitting vocalizations. These episodes were observed throughout the dog’s life, beginning when she was about 6 months of age.",
"The episodes would typically begin with the dog hiding under furniture and withdrawing from her family. A few hours later, the pain appeared to set in, and she would cry out relatively continuously.",
"She often suffered from both photophobia and phonophobia (sensitivity to loud noises) during these episodes, and she’d sometimes refuse to eat and drink. Many times, she also displayed symptoms of extreme nausea, such as drooling and frequent swallowing.",
"These symptoms are all consistent with a migraine, but there was one more piece of important evidence: The pooch would usually act lethargic and exhausted for a few days following the episodes.",
"As you can imagine, the poor pup’s owner took the dog to several different vets, who searched far and wide for a cause. The spaniel’s results all came back normal, so a variety of different medications were administered to try to treat the symptoms. Most – including opioid painkillers – failed to produce any results.",
"However, as the vets continued to rule out one condition and medication after another, they considered migraines. This led them to prescribe Topiramate, an anti-epileptic medication commonly prescribed for humans who suffer migraines. Thankfully, this appeared to have a noticeable effect, and although it didn’t eliminate the episodes altogether, it significantly reduced her symptoms and the duration of the episodes."
] |
[
"Could a nut and a bolt made of perfectly rigid materials be tightened together?"
] |
[
false
] |
Lets say we have mathematically perfect, rigid material and you make a nut and a bolt out of it - could the two be tightened together? Im asking because I noticed that good quality nuts and bolts screw into each other with little to no resistance and only become tight once maxed out - what exactly happens at the last bit and why it gets tight? Im assuming the materials get ever so slightly bent, deformed and thats what makes it tight?
|
[
"I’ll give it a shot. The screw doesnt become tight before maxing out since all the grooves slide against each other. When the screw is completely in, the sliding is no longer possible and further twisting will press the surfaces tight against each other and the friction holds it in place. In practice some elastic transformation takes place (temporary bending which happens because of the stress but springs back when tension is removed). Elastic transformation happens always when there is stress, but in theory is not required for friction exactly, though if the materials were ’perfectly rigid’ then the screw would loosen quite easily since there wouldnt be any force holding the screw in place since it is this ”spring force” that is applying constant force that enables the friction so you would have to hold the tension in the screw manually in place as I see it. F = uN where F is static friction force, u is friction coefficient of the material pair and N is the force’s perpendicular (relative to the surface) component subjected to the surface by the elastic transformation.",
"Bonus: In some high temperature applications this can cause some effects because the tension is changed by heat expansion of the objects and screws, because they are often not exactly the same material. So the tension might be increased (breaking the bolt or the component) or loosen (not enough tension for a tight joint and lets the pieces slide around the bolt). And some theorizing has been done whether stress relaxation (i.e. elastic transformation becoming plastic i.e. permanent) could cause leaks in some cases but I’ve not studied that too much so far."
] |
[
"further twisting will press the surfaces tight against each other and the friction holds it in place",
"With nonsticky materials, friction arises predominantly from deformation of surface asperities. This wouldn’t happen with perfectly rigid materials. It would be like sliding wet ice on wet ice; the nut would loosen and unwind upon application of any force (again, assuming the materials aren’t sticky)."
] |
[
"We can look at it the other way: such a nut&bolt would tighten but infinitesimal amount of force would open it."
] |
[
"If something is 41degF hotter than another thing, is the difference 5degC or 23degC?"
] |
[
false
] | null |
[
"The conversion from F to C is",
"F = (9/5)*C + 32\n",
"so any difference in F, F2-F1, can be written",
"F2-F1 = (9/5)*C2 + 32 - ((9/5)*C1 + 32)\nF2-F1 = (9/5)*C2 - (9/5)*C1\nF2-F1 = (9/5)*(C2-C1)\n",
"So if the difference in temperature is 41 F then the C equivalent is ~22.8C"
] |
[
"Thanks. The internet here is really slow and I have a hangover. ",
"I don't know how linear the scales are.. but I arrived at 22.77...9C with: (100/180)*degF\n..those numbers being the change in degrees from freezing to boiling in each scale."
] |
[
"I'm not sure what you mean by from freezing to boiling. ",
"In C the difference is 100C (0 to 100), which translates to (9*100/5) = 180 degree difference in F (from 32 F to 212 F).",
"In the case where the temperature difference is 41F then yes, 22.77...9C is the right answer (I rounded up in my original post). ",
"edit - I'm still confused but I see where 100 and 180 come from now... this gives you the 9/5 ratio (180/100 = 9/5)."
] |
[
"Why do some animals lay brightly-colored eggs?"
] |
[
false
] |
confused me. Wouldn't brightly-colored eggs be easier for predators to see? I understand that evolution doesn't act with intention, but I'd think those animals with more naturally-camouflaged eggs would find theirs eaten less often.
|
[
"Great question. The short answer is we are not sure. Here is one potential explanation: Eggs need to be distiguishable, because otherwise another bird could infiltrate their own eggs into other birds's nests. Some Cuckoo birds do this (it's called brood parasitsm if you want to learn more). If all eggs were all camoflauged they would be fairly indistinguishable and such parasitic birds would florish."
] |
[
"College class prof used robin's blue eggs as an example of measured directional selection. Studies (nope, don't have sources handy as class was taken years ago) found that bluer eggs were found in areas with higher incidences of brood parasites (like cowbirds or cuckoos). My fuzzy memory even says that robins were documented quickly shoving the easily distinguished cowbird's eggs out of the nest soon after their appearance.",
"Edit: couldn't leave it be and had to look up at least one reference. N. American robins do reliably reject the eggs of brown-headed cowbirds (bright blue, unspotted eggs vs white and brown spotted eggs).\n ",
"http://web.stanford.edu/group/stanfordbirds/text/uessays/uBrood_Parasitism.html",
" "
] |
[
"Interesting question. I did a bit of digging and found ",
"this",
" write up which cites some research indicating that the blue color provides protection from UV radiation, which can damage embryos.",
"This ",
"article",
" cites research showing that male robins take better care of offspring from bright blue eggs...essentially saying that the color is a signal from the female indicating her offspring are high quality and worth investing time into. ",
"Note that both of these explanations could well be true.",
"In a broader sense, camouflage is usually stronger in ground nesting bird eggs, such as the eggs of plover. Robin eggs are in nests usually located well off the ground. Visual camouflage on the eggs is less important because the eggs themselves are fairly well hidden by the nest and the leaves around it. "
] |
[
"Would scientists be able to synthesize photosynthesis? If not, why not?"
] |
[
false
] |
I mean, could they take 6 carbon dioxide molecules and six water molecules and make glucose and oxygen?
|
[
"Yep. ",
"http://en.wikipedia.org/wiki/Artificial_photosynthesis"
] |
[
"You're far more lenient than I am. ",
"Here's the Google search results for ",
"\"scientists make photosynthesis\"",
". You might be right basing your opinion on how OP phrased things but I won't cut an adult slack when they can't think of then word \"artificial\" ",
"The point remains that there are MDs and PhDs here willing to contribute to legitimate questions but this is a disrespectful waste of time as it was very easy to google and find responses a lay person could readily understand. "
] |
[
"When the top, only, and most concise answer is a direct link to the wikipedia page that directly answers OP's question, then yes, google your question first. ",
"Then maybe ask follow up question not covered in wikipedia. "
] |
[
"How would a scientific lab break Doritos down into its component parts?"
] |
[
false
] |
[deleted]
|
[
"You can first do a physical separation, as you proposed.",
"I think I would use a suitable solvent - or a group of suitable solvents, and blend the chips to a mush. Then one can do separation on the compounds via a number of chromatography techniques before throwing it into a mass spectrometer.",
"However, this can give you information on what's in it, but not really how it is prepared. That's really the most difficult part."
] |
[
"As rupert1920 said your best bet would be to grind up some chips and then separate the Dorito into components that are soluble in solvents of different polarities (i.e. water soluble vs soluble in ethanol vs soluble in heptane etc).",
"Then you could use chromatography techniques like ",
"HPLC",
" or ",
"TLC",
" to separate the mixture into individual components and then try to identify each individual component via something like ",
"mass spec",
" or ",
"IR spectroscopy",
"."
] |
[
"You can bet Pepsi has a scientific lab that's any chemist's wet dream trying to crack Coca Cola's secret. And vice versa."
] |
[
"Steven Hawking's, in In To The Universe, just claimed that 10 minutes after the big bang the cosmos was already thousands of light-years in diameter; how can this be possible?"
] |
[
false
] |
Obviously this is so far faster than the the traditional speed limit of 1 light-year in 1 year, I can't thing of an explination other than the show misquoted Hawking.
|
[
"Expansion isn't measured in speed. The distances between two galaxies may increase due to expansion at such a rate that from Galaxy A's perspective, Galaxy B recedes at a \"velocity\" greater than the speed of light, but the key here is that it's not a real velocity. Nothing is actually moving. It's just the distance between them increasing, and therefore there is no limitation on the rate of expansion.",
"As for the video, it's probably talking about only the observable universe (the portion of the overall universe that we can directly observe) when it mentions \"the cosmos.\" A good portion of the scientific community believes the universe is likely spatially infinite, and so it would have no finite diameter (and never would have). "
] |
[
"I asked a very similar question ",
"here",
". Basically the big bang was not really a central point. More like a giant plasma spanning great distances when it cooled things were already far apart from each other"
] |
[
"Space-time itself is not subject to the light speed limit. Thus space-time can expand faster than the speed of light, which we see today. During early time, inflation caused massive expansive which accounts for the universe becoming thousands of light-years in diameter in 10 minutes. The observable and possibly size of the universe is much larger then 13.7 billion lightyears. Much much larger."
] |
[
"Why do some parts of the world generally experience more vivid/'better' sunsets?"
] |
[
false
] | null |
[
"The fluctuation in sunsets by location is to largely due to the particulate matter in the air. Since every particle has a different size, and refractive index, they cause light to refract, reflect or even diffract differently. Basically, these particles in the air, can cause light to bend/change direction and or polarise the light. This is what accounts for the different light intensity range you see across a sunset sky. The colours are mostly result of the refraction of light through different air particles/molecules."
] |
[
"And in many places the particular particulate matter (heh!) is man-made pollution."
] |
[
"Although some of the prettiest sunsets I've seen have been in rural country during crop harvesting season or in desert countrysides."
] |
[
"Why does the light spectrum have bands instead of continual fading from color to the next?"
] |
[
false
] | null |
[
"They do fade into each other:",
"http://en.wikipedia.org/wiki/File:Linear_visible_spectrum.svg"
] |
[
"Why do they appear as bands? A rainbow seem to have discrete bands"
] |
[
"They fade into each other too. How's your eyesight?"
] |
[
"Why doesn't the suction power behind a fan feel as strong as the wind coming out of the front?"
] |
[
false
] | null |
[
"Because it's diffuse. The air coming out of the fan is in a very narrow path - the fan's energy is pointing in one direction. The air going into the fan might be coming from anywhere behind it, not from any particular angle, so the moving air is harder to feel at any one spot."
] |
[
"This is how I imagine vacuum machines work. Maybe something similar but more complicated"
] |
[
"So theoretically, if you put a cone on the back of a fan that was wider on the fan side and tapered down, the force of the air being sucked into the fan through that tiny opening in the cone would be greater because it is more concentrated?"
] |
[
"Do animals ever forget their own kids after a while?"
] |
[
false
] |
My dog just had puppies about 8 weeks ago and we are in the process of giving them away. I was wondering if the mother dog will ever recognize her children if she would ever come across them again?
|
[
"Agreeing with this. Dogs certainly can recognize their own family members and ",
"studies",
" have shown that reunited siblings do show kin recognition, and display behavioral differences, even after an extended absence and early separation from littermates. And while anecdotes are not science, I'd just like to add as a brief side note that both my family and the other breeders we know have observed this to an extent when briefly re-uniting littermates with each other or with their dams.",
"EDIT: grammar"
] |
[
"Agreeing with this. Dogs certainly can recognize their own family members and ",
"studies",
" have shown that reunited siblings do show kin recognition, and display behavioral differences, even after an extended absence and early separation from littermates. And while anecdotes are not science, I'd just like to add as a brief side note that both my family and the other breeders we know have observed this to an extent when briefly re-uniting littermates with each other or with their dams.",
"EDIT: grammar"
] |
[
"If this were a common practice, don't you think it would be a little bit at odds with the biological imperative to reproduce? Animals are known to eat their offspring in certain cases, but not simply as a matter of course."
] |
[
"Why can eggs/sperm be frozen for future use, but the same is not true for humans?"
] |
[
false
] |
[deleted]
|
[
"Alot of it has to do with speed of freezing/thawing. Slower freezing means big pointy ice crystals which rupture cell membranes. Faster freezing means smaller crystals. Big things freeze slower so bodies freeze more slowly and get bigger crystals. This could be overcome with really, really rapid freezing.",
"You have a different problem being thawed. Your body needs to come out of being frozen close to natural body temperature in a matter of seconds without frying you. If your brain thaws before your heart, you die. If your heart thaws before you can breathe, you die. And so on.",
"But assuming you can freeze us really quickly and thaw us out instantly to exactly the right temperature, there is still one big problem. Things just spread out when they freeze, resulting in tiny tiny cracks. For a round ball, these can more easily heal, but for neurons, this can be a real problem. ",
"Brain freezing is really the critical step remaining. Scientists have done it for individual mammalian organs (heart and liver) but not for whole creature. Brains are still the critical step."
] |
[
"When you freeze an egg or a sperm, you are freezing cells that do not depend on one another for survival. Humans, however, are made of trillions of interconnected cell systems. Freezing a body would take too long and the change in temperature would not be evenly distributed. For example, if you freeze the heart before other organs, the organs would die before freezing due to oxygen/energy starvation and waste build up. However, as technology gets better, there is no telling what may happen in a few decades."
] |
[
"The crux of the problem lies in not being able to freeze a complex multicellular organism instantly-at once. But also in terms of thawing, we cannot unfreeze the complex organism instantly. Instead the process occurs slowly from the outside in and then when thawing from the inside out. This of course causes major tissue damage.",
"If we could solve this major problem, then there is no reason as to why we wouldn't be able to freeze living organisms without doing harm."
] |
[
"Do voltaic piles lose charge over time? Why?"
] |
[
false
] |
My friends and I are concerned that if we were to spontaneously wind up back in time, we wouldn't know how to reconstruct modern technologies. In the interest of gaining that knowledge, we intend to make an electric motor from scratch, powering it with simple voltaic piles. In the course of our investigation, we came across the question of whether and how it is that voltaic piles lose charge. So, do voltaic piles lose charge, why do they, and how do we recharge them? Also, any other advice about whether this will work or how else we might go about this project would be much appreciated.
|
[
"batteries run out. You should check out why there's a current in the first place."
] |
[
"A voltaic pile is based on a chemical reaction, typically where a metal reacts with hydrogen ions in an acid, resulting in a metal compound and hydrogen gas.",
"Eventually, you run out of metal or you run out of acid. Since it is not a closed system, with hydrogen escaping to the air, recharging consists of getting more of whatever ran out."
] |
[
"I am not sure what the exact reaction with the saline solution would be, but Volta's original pile was quickly improved to use an acid electrolyte.",
"The key is for the less electronegative metal to give up electrons to H+ ions and form H2. Even pure water will have H+ ions (pH 7 doesn't mean neutral, instead pH 7 ~= 10",
" mole H+ per mole of solution)...acids are just going to have a lot more. ",
"In theory, any two metals and any water based solution will form a voltaic pile. To make a good one, you want one metal to have a low electronegativity (Zn, Al, Mg) and one to have high EN (Fe, Ni, Cu, Ag, Au), and a strong acid that won't react directly with either electrode alone. Both lemon juice and vinegar should fit the bill just fine.",
"And remember that pennies are mostly nickel these days...but you should have no problem finding copper washers if you want to be a purist...try plumbing supply if you can't find them in your local hardware store."
] |
[
"What FPS (Frames Per Second) Would real life be in? And additionally, what resolution do our Eyes see?"
] |
[
false
] | null |
[
"See the FAQ"
] |
[
"Which section? I can't find my question under physics?"
] |
[
"Neuroscience for some reason"
] |
[
"Do we know of a \"gas-moon\"?"
] |
[
false
] |
Is there any moon, orbiting a planet, which is made out of gas, instead of rock, that we know of?
|
[
"No, we haven't detected any exoplanets with moons and none of our solar systems moons are gaseous (mostly rock, one that's mostly ice/water).",
"It is also difficult to believe that such an object would be possible. The reason why the outer planets have such thick atmospheres is a result of their size. By the time you are massive enough to be a Gaseous body you are likely just a planet."
] |
[
"There isn't one yet. People have suggested that Earth and the Moon are a double planet, and back in '06 people tried to make Pluto and Charon a double planet instead of Pluto being a dwarf.",
"One proposal relates to the center of mass. Right now, the center of mass (the barycenter) of the Earth-Moon system is within the Earth's surface. The Earth does wobble though. In this proposal, the Earth is not a double planet. However, in a few million years, as the Moon moves further and further away, it will be. On the other hand, this creates a problem: many of the exoplanets we've found (and our own buddy Jupiter) pull on their star so strongly that the barycenter is outside of the star.",
"Asimov had a formula ( m1/m2*(d1/d2)",
" ) wherein m1 was the mass of the larger of the two planets/moons, m2 the mass of the star, d1 the distance between the smaller body and the sun, and d2 the distance between the two planets/moons. If the result is fractional, then it's a binary planetary system. Earth and the Moon come out to 0.46 (that is, the sun pulls on the moon more strongly than the Earth), so to Asimov, we were a binary."
] |
[
"we haven't detected any exoplanets with moons",
"This is \"we don't have the means to detect whether or not they have moons\" not \"we have confirmed that none of them have moons\", right?"
] |
[
"Is there a way to protect the JWST from damage from space debris or are we taking a chance that nothing will hit it?"
] |
[
false
] | null |
[
"There really isn’t much debris in space, especially not in places that are gravitationally unstable like where JWST is. That said, JWST is designed to withstand considerably more than the predicted amount of debris strike over its lifetime without degrading the optical performance unacceptably. Mostly it can achieve this by being big - each strike on the primary mirror only damages a small area."
] |
[
"Adding to this, it has ",
"already been hit",
", but is still performing above the expected levels. There is a small be detectable signature of the strike in observations, but the data processing has been updated to account for this."
] |
[
"To add a bit of trivia: The Harlan J Smith telescope in Texas (of course…) has several bullet holes in its main mirror. It still works."
] |
[
"Flying above clouds, I noticed a shadow of our helicopter on the top of a cloud, with a rainbow encircling it. What is this phenomena called, and what causes it?"
] |
[
false
] | null |
[
"It is called a Glory.",
"https://en.wikipedia.org/wiki/Glory_(optical_phenomenon)",
"A glory is an optical phenomenon that resembles an iconic saint's halo about the shadow of the observer's head, caused by light of the Sun or (more rarely) the Moon interacting with the tiny water droplets that make up mist or clouds."
] |
[
"Rainbows are caused by light refracting off water droplets when you are between the sun and said droplets. Clouds are, obviously, filled with water droplets.",
"All rainbows would like to be full-circle rainbows, but, because people are so close the horizon and rainbows take up a large field of view perpendicular to your viewing angle, the bottom half gets hidden by the ground (light ",
" refracting there; we just don't see it).",
"When you are in an aircraft with the sun high in the sky above you, your position causes the rainbow's plane to be almost parallel to the ground, so there is nothing to cut it off, and you are far enough away from that plane for it to take up a smaller field of view. "
] |
[
"A rainbow always has the same angular size. It only depends on the index of refraction of water. Other rainbow-like optical phenomena have different mechanisms and different names, this particular example is called a glory."
] |
[
"When someone is about to die, why are they told to not fall asleep? Why does that increase survival?"
] |
[
false
] |
My thought is that staying awake would boost circulating catecholamines?
|
[
"<- EMT. Having a constantly re evaluated assessment of a persons level of consciousness (LOC) is one of the best indicators of shock. Shock is defined has the lack of perfusion in the body, in other words the exchange of carbon dioxide made in the cell that is exchanged at the capillary level for oxygen brought in by red blood cells. No perfusion, cells starve and die. First effected organ is the brain because it requires a late supply of oxygen. Earliest signs of hypoperfusion are altered LOCs like agitation, tiredness, and confusion.\nAlso the measuring scale for things like triage and Glascow Coma Scales are effected by the LOC. Diminished LOC for most any reason outside of normal raises priority and can effect treatment. So by assessment standards, you are considered more likely to survive and less critical if you are capable of staying awake and alert. ",
"Hope that helps. Other than this practical reason, it's a lot more dramatic and cool. Also try slapping them in the face for Oscar worthiness. (But not in real life please.)",
"EDIT: quick example of of altered LOC that doesn't alter patient assessment would be diabetic issues where behavior changes would be the norm so other checks are made like glucose levels, vitals, and oral intakes over the past several hours. Family members usually can tell what is normal issues and what is severe issues. Other examples would be mentally challenged or dementia patients."
] |
[
"In the movies, it's for drama. In real life, it's for diagnostic purposes. A patient's level of consciousness helps us see how well their brain is oxygenated. ",
"If they can stay awake and respond to questions, that's a positive thing. If they're awake but confused and can't tell me their name or where they are, we know there's a problem. And if they can't stay conscious without constant uncomfortable stimulus, it's not a good sign. "
] |
[
"There's an indirect effect: staying awake gives more useful feedback to medical personnel about your current state, which may improve their performance and therefore give you a higher chance of living."
] |
[
"I just started learning quantum physics, and of course, I'm confused. I tried a thought experiment for determining the mass of a particle produced by a standing wave, I got that it would have imaginary mass. Is that possible?"
] |
[
false
] |
I asked my professor if sound waves or a waves traveling across strings have particles associated with them, and he told me they do, and they're called phonons. So I thought "why not examine a stationary arrangement of something like a string (arranged in a wave pattern - like a wave frozen in time, I suppose), and see if that produces a stationary particle?" Here is what I did: using de Broglie's equation for wavelength: lambda = (h) / (p) solving for momentum and putting it into the relativistic relation of energy, momentum, and mass [ ( E ) = ( pc ) + ( mc ) ] and setting E equal to h f (that is, planck's constant times the frequency, which would be 0) I got this relation: 0 = ( h*c/lambda ) + ( mc ) and solving for m I got the mass equal to i( ( h )/( lambda*c ) ) where i is the square root of -1. Did I make an incorrect assumption somewhere? EDIT: By the way, I know I'm wrong, I'm just wondering why I'm wrong.
|
[
"De Broglie frequency is defined as f = E/h so for a stationary particle (p=0) it's mc",
"/h not zero.",
"The de Broglie wavelength for a particle with no momentum is undefined since you're dividing by zero",
"Stationary particles exist in time, too, so there's no reason to stop time",
"I'm not really sure what you're trying to do"
] |
[
"The de Broglie wavelength is defined how it's defined. At zero momentum it's numerically undefined (or infinite if you take dividing by zero to equal infinity.)",
"Waves oscillate. If you arrange a string in a sinusoidal pattern, but it's not moving, there is no wave."
] |
[
"I'm confused. ",
"Is the de Broglie relation wavelength for a momentum-less particle wrong, then?",
"What if I have a string arranged in a wave-like pattern, giving the wave (that doesn't oscillate with time) a wavelength?",
"Then I don't think I'd be dividing by zero, would I?"
] |
[
"Chemistry Titration problem"
] |
[
false
] | null |
[
"OK, fair enough. I did not check your math, but what you wrote is correct.",
"I then reasoned that the number of moles used to neutralize is the same number of moles of the H+ in the acid.",
"This is true because 1 mole of NaOH reacts with 1 mole of CH",
"COOH -- they happen to react in a 1:1 mole ratio."
] |
[
"Many of these acid-base problems have extra information that are irrelevant to the problem. It's just how these questions are designed."
] |
[
"Try ",
"/r/homeworkhelp",
"."
] |
[
"Enzyme Question"
] |
[
false
] |
I have a question regarding enzymes. Asian people have a different version of alcohol-dehydrogenase which causes them to get drunker quicker. While on one hand it is true to say that they have a different version of the same enzyme. Wouldn't also be true to say that those two enzymes are technically different enzymes, although they are functionally (in terms of their purpose not effeciency) the same? That they have a different enzyme for alcohol metabolism than do caucasians?
|
[
"No, it wouldn't be true. Enzymes are classified by function, not sequence. It's not a different enzyme, it's a different ",
"isozyme",
"."
] |
[
"So its like isotopes for enzymes?"
] |
[
"I suppose it could be classified as an isotope for enzymes, but generally protein chemists use the word \"isoform\" to distinguish between two enzymes that catalyze the same reaction but they have slight variations in their amino acid sequence and their kinetic parameters. "
] |
[
"I am standing in front of an airlock in outerspace..."
] |
[
false
] |
Assuming my feet were bolted to the deck (so I don't get sucked out), and I had plenty of air behind me (so I never run out of air to vent), what pressure would I feel if I cycled the airlock open and closed- the pressure of the spaceship, vacuum, or something in between? Would there be enough pressure from the escaping air to allow me to survive the cycling of the airlock (like in the movies) or would I die from decompression? How about freezing to death (either temp of space or the temp of the rushing air expanding into a vacuum)? Let's assume a 60 second cycle time. Would I be able to breathe while the air is escaping, or will I end up suffocating? If the air pressure is high enough, but the air is too cold, will my lungs freeze? As for the size of the airlock door- we can go with something large enough to pass a human being through. A pinhole sized airlock doesn't count. How different will the effects be with a larger airlock, vice a smaller one?
|
[
"Because of ",
"Bernoulli's principle",
" the air rushing out of the airlock door will have a lower pressure than it had at rest inside the spacecraft, so you may not be able to effectively breathe when the door is open."
] |
[
"I think much of this would depend on the size of the ship and how much air is stored in the ship. I am assuming the air pressure in the ship is at earth sea level of 14.696 psi. The psi around you would immediately drop and this low pressure would spread to the rest of the ship. How rapidly it would spread would depend on the size of the air lock and the size of the ship and dimensions of the ship. The way this would effect you depends on where you are standing and how the ship is designed around where you are standing. For example, a narrow hallway might have a lot of air rushing through it while a large room might have very little. Saying something like, if the air pressure is high enough but the air is too cold doesn't make sense because temperature always goes up as pressure rises or vice versa. "
] |
[
"And the closer you are to the door from the air source, the less pressure you will see. If you have a hose or a pipe, the pressure drops from the source pressure (about 45 psia for most houses) to the outlet (14.7 psia right outside the hose) So if you stand halfway down the hose, you will feel pressure halfway between the two. In the space station example, you seem determined to stand near the door, so you will feel almost a pure vacuum. ",
"For the other stuff, read this: ",
"http://en.wikipedia.org/wiki/Space_exposure"
] |
[
"How exactly do prion diseases work?"
] |
[
false
] |
i'm especially curious about Human Spongiform Encephalopathy and how it starts/spreads.
|
[
"Take a protein in human body. This protein has to be folded in space a specific way in order to perform its biological function, and it is folded in that way when it's synthesized by a cell.",
"If it is not folded correctly, it doesn't work and is degraded by the cell. This happens all the time in normal cells.",
"A prion is a protein which is folded incorrectly, but it also disrupts folding of other proteins in exactly the same way that its own folding is disrupted. So, it basically spreads an incorrect folding through nearby proteins, which in turn spread it to other nearby proteins, etc.",
"If this incorrect folding spreads faster than the cell degrades incorrectly folded proteins, then they build up inside the cell and disrupt its functioning, and you have prion disease."
] |
[
"Does that mean you could cure a prion disease by introducing a protein that would \"re-fold\" the damaged proteins to their correct shape? A first-aid prion?"
] |
[
"Theoretically, yes; I am not aware of any such having been discovered or synthesized thus far."
] |
[
"What is the smallest diameter/mass a black hole can be?"
] |
[
false
] |
[deleted]
|
[
"I don't see how that's the case. Can you elaborate?"
] |
[
"Sorry, should have elaborated:",
"Planck length is the square root of Newton's constant. It's the \"coupling constant\" for gravity. When talking about micro black-holes (like the smallest you can have), there is no geometric picture, there is no notion of horizon and they behave more like bound states. Keep in mind that the Schwarschild solution is a classical one, it's a property of eternal black-holes that are composed of infinitely many degrees of freedom. ",
"Now, if you scatter two particles at high energies, you can characterize everything by the typical wave-lengths measured at the center of mass frame. Until you get to the Planck scale there is no way you can create black-holes, namely because the typical wave-lengths will be much bigger than the Scharzschild radius for the process. Or in other words, gravity is weakly coupled and it makes sense to talk about gravitons, as they are perfectly well described in the quantum theory, despite all the \"we have no theory of QG\" nonsense)",
"Once you get to the Planck scale, now gravity becomes strongly coupled, which is the statement that the gravitons that you were exchanging now interact a lot more within themselves, and now they cannot be described as the actual degrees of freedom of the theory. So either there are new weakly coupled degrees of freedom (which doesn't make sense for gravity), or there are bound states that need an appropriate description (that actually doesn't exist in standard qft, but that's another story and it's more related to whether or not elephants decouple from low energy experiments). It's like quarks and gluons when you lower the energy: they become strongly interacting and you have bound states appearing.",
"Now, if everything we know about gravity is at least ok-ish, then these bound states are really black-holes. And their size is just at the order of the Schwarschild radius for something with Planckinan mass, which is just the Planck length. ",
"Now take this with a grain of salt, because no one really knows where the strong coupling scale is (but it for sure cannot be bigger than Planck scale). Or in other words, by looking at the coupling constant, one would immediately guess that the strong coupling scale for gravity is at the planck scale, but of course that this may not be true if there are some strange mechanisms acting for gravity: for instance, if there are large extra dimensions, then the strong coupling scale can be lowered to the TeV, and then you can have black-holes already at the LHC. ",
"(edit: quantum black-holes are my day-job)"
] |
[
"To clear up misconception:\nPlank length is not supposed to be the smallest meaningful length. It is (supposedly) the length at which both general relativity and quantum mechanics have significant effects. The problem at this point is that we don't have an adequate theory to describe what's going on"
] |
[
"After the K-T extinction, how did the survivors live while the Earth was recovering?"
] |
[
false
] |
Clearly not ALL plant and animal life died out with the dinosaurs. How did the ones that clung to life in the post-Chixculub dark era do so?
|
[
"There's been a fair bit of back and forth about a lot of these points, but this ",
"https://onlinelibrary.wiley.com/doi/10.1111/brv.12128",
" seems to sum up the current consensus. In short: there was some loss of diversity in certain groups in the very late Cretaceous that may have made the ecosystem more fragile, but no long-term decline, and no particular reason to think dinosaurs couldn't have recovered diversity as they had before; any large group will regularly experience disruptions and recoveries like this. And while the Deccan traps couldn't have been particularly healthy, the timing and pace of the extinction still seems best explained by the impact."
] |
[
"My question still stands. 75% of all life on Earth vanished in that perfect storm. What was life like for those that remained? How was food found in that nuclear winter? What sorts of species thrived in that environment?",
"I ask because my worldbuilding project is ",
" that sort of environment. It's been long enough so that particular planet has ",
" recovered (as in, the sky's cleared up, etc.), but biodiversity hasn't had a chance to return; at the time that planet was struck, it was the year AD 184 on Earth."
] |
[
"There is alot of myth about that impact. ",
"The thing is, dinosaurs were already on the way out. Diversity had plummeted by the late cretacious. The dekkan traps had been going off for like a million years causing major ocean acidification and climate change. ",
"The meteor was just the final straw. Pop science doesn't talk about the volcanic angle much at all, I'm guessing cause it's not satisfying like an impact?"
] |
[
"Is there any correlation between the direction that your eyes are looking and your mood? Example: Sadness = Looking downward"
] |
[
false
] |
Or if you we're angry you might be staring straight ahead. Is there any relation between the two or not?
|
[
"Generally this type of action is done as a social que/body language, either habitually learnt from society or as to let others around us know how we feel. In the sense of sadness we will tend to try to divert from interaction with others and an easy way of doing this is avoiding eye contact by looking down or away. "
] |
[
"To elaborate on this, one might be able to categorize shifting one's gaze as an emotion regulation strategy, specifically \"attentional deployment\". Here's an example for clarification: Say you're watching a sad movie. This movie is eliciting a sad emotion from you. To downregulate or dampen this sadness you're feeling, you avert your eyes. That is, you have deployed your attention away from the movie in order to reduce how sad it's making you feel. You can probably imagine how this would extend to other emotions; e.g., if a stimulus made you happy, you'd continue to deploy your gaze to that stimulus in order to continue feeling happy.",
"Hope this helps!"
] |
[
"Yes. Google body language and eye/gaze direction."
] |
[
"When taking a shower, whats the difference between water pressure and water velocity? Low flow shower heads don't restrict pressure, do they?"
] |
[
false
] |
When people say the shower doesn't have any pressure because the water isn't shooting out of the faucet, don't they mean that the shower doesn't have any velocity? Does pressure even affect the shower quality?
|
[
"P = v"
] |
[
"In the US , a low flow head has to be below 2.5 gallons per minute and 80 psi. Some aerate the water to reduce flow. These suck. Look for non-aerating heads. "
] |
[
"You ",
" can take the aerator out if it is right at the thinger where you screw it on."
] |
[
"In devices that require multiple batteries (like say, an xbox controller) do both batteries lose same amount of charge over time? What would the battery-life expectancy be if I changed only one battery, when both old ones are dead?"
] |
[
false
] | null |
[
"In most cases you use multiple batteries to increase the total voltage to a level needed to get the needed work out of it. So for example, if you need a voltage of 4V you can stack up four 1V batteries in your circuit. For example, that's the main reason why the orientation of battery generally alternates, ",
"as shown in this image",
" to make the wiring easier. Now because the batteries are operating in series, this means (by definition) that the same current must flow through each battery. If each battery has an identical voltage (I) and has the same current, then the power that each battery will produce will be equal to P= IV. As a result, all batteries will discharge at about the same rate."
] |
[
"No, that's not how it works. The simplest answer is that the setup will only work as intended until you drain the old battery. When you put things in series the weakest link breaks the chain so to speak. What this means in practice is that once the old battery drains is that it will stop acting as an EMF source at its initial voltage (V in my example), so the total voltage of the setup will drop below 4V. ",
"In fact, once the electrochemical processes that made the battery run in the first place run out, the other batteries will be shoving electrons into it in a configuration it may not have been designed for. This is the reason why replacing just one battery will not make your remote start working. In fact, it's also why they warn you not to mix old and new batteries, since the new batteries will try to push charges through the dead battery in an active circuit, which can cause unwanted chemical processes (including those that lead to chemical leaks) to happen, which in turn can damage not just the old battery and the entire device."
] |
[
"This is a great answer.",
"A decent analogy you can use is to imagine the electrical circuit to be replaced with four pumps one after the other trying to pump water somewhere. When all pumps are running they help each other push the water, and as a result you get more water through. If you shut off one of them, not only do you lose the pushing power it provided but the water still runs through it, so the three other pumps also have to spend energy on making the last one turn."
] |
[
"How do computer alarms/alerts work?"
] |
[
false
] |
Is there a process in the background sitting there polling the time every microsecond and comparing it to the value of the alarm time? It seems like that would be a dumb way to do things but I can't think of how else it might be done.
|
[
"To elaborate a little. Most processors allow for interruptions. An interruption is either an internally or externally generated signal that tells the processor that something happened. This could be an alarm from a timer, a key press from a keyboard, or data connection. When a processor receives an interrupt request, it can either ignore it, because it's doing something more important, or it can stop running the code it is currently running, and switch to the code meant to treat that specific interrupt request.\nSo in the case of an alarm, you have a counter that is incremented with a certain frequency, for example 32.768kHz. After the counter reaches a certain value, an interruption may be generated to inform the processor that a certain amount of time has passed. For example, after 32768 increments, exactly one second has passed. The processor can then run the appropriate code. If an alarm has to be generated at that particular, time, then it is. Otherwise nothing is done. And in both cases the processor goes back to what it was doing. This way, a separate piece of hardware is responsible for time keeping and the processor only has to run a very small piece of extra code once a second, which isn't much for a powerful processor."
] |
[
"Well there are a few different ways. Operating systems having something called a scheduler which decides when various processes run and how much time they get. If you put an alarm program on your cell phone or laptop it will receive minimal time from the scheduler and only get a minimal slice of the processors time per second. Most modern schedulers also have event based scheduling where the program can basically say \"wake me up when X is true.\" ",
"Embedded devices, like your clock radio, often will not have an operating system so no scheduler. These devices have very few tasks and they don't vary so it makes sense to just hard code the program to spend a certain amount of time each second doing various things (listening for a button press, displaying the display, ect). These devices generally don't run more than a few million instructions per second, they also use small architectures that require far less power than the stuff your computer has. Alternatively you can have a 555 timer (or something similar) send interrupts to the processor and have it run the given tasks every half second."
] |
[
"I've dont some programming, not a ton, but that's basically correct.",
"You computer has a built in clock that even runs while it is off (maintained by a battery on the motherboard). ",
"The simplest 10 second alarm clock (one that would not update it's time on the screen) would do:",
"ask user: how long to wait?",
"user enters: 10 seconds",
"program then: wait(10,000 milliseconds)",
"(the wait command will then hold the program until the 10,000 ms has passed)",
"print message: \"ALARM\"",
"\n(or play a sound or whatever)."
] |
[
"How is polyethene different from an arbitrarily long alkane?"
] |
[
false
] |
If you draw a structural diagram of polyethene, it seems exactly like a really long alkane to me... but long alkanes do not exhibit the same properties as polyethene, so how is it wrong to see polyethene as a really long alkane?
|
[
"long alkanes do not exhibit the same properties as polyethene",
"Sure they do, since they're the same. But polyethylene can have different properties depending on how branched it is (HDPE vs LDPE), and the average molecular weight of the chains in it, and the distribution of chain-lengths. "
] |
[
"I get that, but the monomer in polyethene has no double bonds."
] |
[
"The monomer of polyethylene has a double bond. The monomer is ethene (C2H4). During polymerization, the electrons from the double bond go to making a new bond with another monomer, so the polymer does not have any double bonds.\nI don't think there really is any difference between an arbitrarily long alkane and polyethylene. Paraffin wax is an alkane with ~20-40 carbons in its chain. It is often considered an extremely low molecular weight polyethylene chain. The reason \"long alkanes\" exhibit different behavior from polyethylene is probably because of your definition of long. Polyethylene often has a molecular weight in the hundreds of thousands and ultra high molecular weight polyethylene even has a molecular weight into the millions. So I think polyethylene really is just an extremely long alkane."
] |
[
"If the force of gravity is determined by the mass of an object then how does a star, that is constantly losing mass in the form of energy, collapse into a black hole with a gravitational force many times that of the star's original state?"
] |
[
false
] |
Is there some other method of producing gravity? Or does the stars mass somehow suddenly increase to the point of collapsing into a black hole? If so, where does this mass come from?
|
[
"One thing your probably are not aware of is that, if you take a spherical shell of matter, the gravitational force will only be felt outside of that shell. Inside, there would be no gravitational force at all. Now, picture a star as a collection of concentric shells (a bit like the layers of an onion). The maximum gravitational force is felt just outside the star, due to the contribution of all those concentric shells. If, for some reason, the start collapse, the force at a given point outside would not change ... but you could get much closer to the \"center\" of the star and thus start feeling a greater and greater force."
] |
[
"Not completely. First you get heavier elements fusing untill iron, sometimes the core of those heavier elements just becomes too dense and make a black hole. ",
"So once you start fusing helium the core is actually helium not hydrogen with non fusing helium surrounding it than fusing hydrogen followed by nonfusing hydrogen. That core keeps increasing in size untill next element fuses and the cycle continues. Untill at some point the core is dense enough to create black hole. The death of a star starts when it's elements start fusing into iron. ",
"The black hole is created when the energy through fusion is not strong enough to keep the core from collapsing into a black hole. With lighter elements that's not hard but the further down thr list you go the more energy is required"
] |
[
"The gravity doesn't increase in the way you are assuming. Rather the forces inside the star push against gravity, when the reactions causing the force inside the star run their course and finish the star can collapse. By collapsing it creates a point of space with a high enough density that even light cannot escape it but that only happens in a very small area compared to the original star. In fact the \"total\" gravity of the new black hole will likely be less than its original star until it has time to absorb new matter. ",
"https://en.m.wikipedia.org/wiki/Black_hole"
] |
[
"Why does the Moderna vaccine include two 100 micrograms doses of mRNA, while that for Pfizer is two doses of 30 micrograms each?"
] |
[
false
] |
Considering the overall efficacy rate is comparable.
|
[
"Just a note, using \"MRNA\" to mean Moderna is pretty confusing in this context. I had to read it a few times to figure out what you were talking about."
] |
[
"Basically, just in case. There's no other reason. Moderna could set their dose at 30ug (probably even lower) and it would work - they just didn't know that at the time so they wanted to play it safe instead of flopping."
] |
[
"MRNA chose 100ug based on an early study. Later results showed their lower doses worked fine but the phase 3 was already designed.",
"MRNA vaccine had more adverse effects than PFE- Id guess because of the higher dose. But apparently there’s a non linear relationship between your immune response and the initial bolus- at some point it capped out.",
"Moderna early reports: ",
"https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-positive-interim-phase-1-data-its-mrna-vaccine",
"Edit: interesting pre print ",
"https://www.medrxiv.org/content/10.1101/2021.03.06.21253058v2.full.pdf",
"Even 1ug dose x2 of pfe had comparable lab markers of immunity to a single 30ug.. and 10ug x2 was comparable."
] |
[
"Solids precipitate out of solution, but what do gasses do?"
] |
[
false
] |
To be precise, what's the word for a gas going from an aqueous state to a gas state?
|
[
"Outgassing",
".",
"@",
"/u/mavric91",
", ",
"/u/DrJesusHChrist",
": Evaporation is the process where the solvent goes into gas state, not the things dissolved in it."
] |
[
"As Wikipedia says, outgassing includes evaporation. I had assumed that OP was referring to a chemical reaction (intramolecularly) rather than a state change. It seems I misunderstood, and focused just on one part of the whole."
] |
[
"Nah, that’s still not it. Outgassing means coming out of solution ",
". Just coming out of solution would be exsolving, or perhaps vesiculation. "
] |
[
"How does one country export usable electricity to another country? especially at great distances?"
] |
[
false
] |
If a country has generated electricity to excess and wants to sell it what is the scientific (or technical) method that this is accomplished? Especially over oceans, mountains across different continents? Are there any other challenges or obstacles with this task? I would appreciate any other interesting facts about global electricity or energy trade (especially having to do with renewable sources)
|
[
"If a country has generated electricity to excess and wants to sell it what is the scientific (or technical) method that this is accomplished? ",
"No different than how power within a country's grid is distributed between consumers and the various generators. A transmission line is built two connect the two regions, power flows down it, and you stick an power/energy meter on to see how much is being transferred. The amount of power you can transfer is limited by the interconnecting line's capacity, which is governed by how much current it can take before the conductors (or transformers on the ends) overheat. ",
"If our lines were simple DC lines, power flows down a line simply by one end having a higher voltage. The side of the line where the power is being produced would be higher voltage, and the current and power would flow to the other end at a lower voltage where it is being consumed. The power grid is a little bit more complex being AC, with factors like power factor, reactive power, and frequency all butting their head in, but it works the same way. At any given time, power is generated and it is being transported and consumed somewhere at that instant. In real time power flow, power generation, and energy economics are managed within grids and between them. ",
"Especially over oceans, mountains across different continents? ",
"They don't, not unless the gap between the grids is small enough to feasibly build a transmission line over. Asia and Europe have interconnected grids. France and England have transmission lines buried across the sea. North America and Africa are not connected and don't exchange electric power. Mainland American and Hawaii do not have an interconnected grid. ",
"Are there any other challenges or obstacles with this task? ",
"In order to connect two grids, they have to have the same frequency and phase. Frequency is the rate at which the alternating current swaps direction, and phase is how delayed the alternating is between two grids (a grid 180 degrees out of phase would be swapping the opposite direction). Basically, if the two waveforms don't match, the grids can't be connected. ",
"Europe and North America could not be simply connected by a standard transmission line because Europe uses 50 Hz and NA uses 60 Hz. ",
"North America also has several different grids within itself, all in different phases. Most of the west (BC, Alberta, Oregon, California, Nevada, etc) is in one grid. Most of the east is in another (Ontario, New York, Carolina, Florida, etc.) is in another. Quebec and Texas have their own grids (shocking it would be those two, I know). These grids cannot be interconnected by a simple transmission line as they are out of phase. ",
"To connect grids of different frequencies or phases, you need special DC transmission lines (or a couple other tricks). One ends\n converts their power to DC, it travels across the line, and then it is transformed back into AC to match the other grid. "
] |
[
"Maybe not in the USA, but in Europe most countries have cross-border connections. Norway has a few ocean going DC links to Netherlands, UK and Denmark, and also grid links to Sweden.",
"Other countries also have transmission lines to it's neighbours."
] |
[
"What's the reasoning behind keeping the grids out of phase? Did they just start independently and the work required to bring them in phase is just too great at this point?"
] |
[
"Are there examples where differences in quantum states have macroscopic consequences?"
] |
[
false
] |
The quantum world is, as we know, teeming with a fundamental uncertainties that are, in the language of several interpretations of quantum mechanics, resolved only when the wave-function collapses, when the quantum property is observed, etc. So an individual electron has a uncertain spin until we observe it, at which point we see it has spin up or spin down, yes? Are there any such quantum states where the outcome of this has classical, macroscopic consequences? (Other than the fact that you can measure them in a laboratory.) Or does it all average out? A dumb example of what I mean: if every electron in the Sun had the opposite spin than it does right now, would it matter at all? In most cases the answer seems obviously "no," and indeed it seems part of the Correspondence Principle is to say that this would be the case (that is, all of those quantum options, even where they might matter, just wash out to be essentially classical). I can think of very artificial ways to make it happen (e.g. Schrödinger's cat, where a quantum measurement device is attached to some kind of macroscopic consequence) but having no luck in imagining a situation where this would occur without clever human intervention. The closest I can come to is maybe thinking that in the case of cancer as a result of nuclear decay — the timing of decay seems related to a wave-function collapse (right?) and if the decay releases a gamma ray that happens to ionize the right piece of DNA it can result in a cancer. Even with this it seems like a bad way to think about it because the odds of any single radioactive decay giving someone cancer is infinitesimally low. Any and all thoughts, corrections, etc. would be appreciated. I am just a dabbler here, not a physicist, obviously.
|
[
"Well there's giant magnetoresistance. If electrons try to flow through a magnetic layer, they can readily do so if their spin is aligned with the magnet they are flowing through. If the spin is in the opposite direction, then it has to 'flip' to match the spin of the magnet.",
"On the macroscale this leads to a resistance that can differ by a few orders of magnitude depending on whether the flowing electrons are spin up or spin down."
] |
[
"Thanks — it's not that I am looking for situations that illustrate the validity of quantum mechanics (I don't doubt that), it's more that I'm curious if there are situations where the ",
" in possible quantum states results in ",
" that matter on a macroscopic level. So, again, something like where an electron's spin being up or down results in a different outcome on classical physics level."
] |
[
"If you want something that is not predicted classically that happens on the macroscale one need not look further than a superconductor.\nThey differ from classical ideal conductors in that they have no internal magnetic flux. It gets expelled out, is observable on the macroscale (I imagine you've seen \"quantum levitation\" [the meissner effect] by now- it's all over the internet).",
"Superfluidity is a good one as well. There are plenty of youtube videos of liquid helium acting as a superfluid- showing zero viscosity, flowing uphill, lots of crazy stuff! Check it out!"
] |
[
"How do you remove indium metal from a metal surface?"
] |
[
false
] |
We got indium on a copper surface and want to remove the indium without damaging the copper surface. Is ther anyway to do this with a solvent or anything from than mechanically peeling/scratching it off?
|
[
"You can oxidize it off in a dilute acid solution. I'd use 0.1M Sulfuric acid, with include 0.1M Copper Sulfate. Volume of solution needs to be calculated based on the amount of In you need to remove. Don't let the Indium exceed 0.05M or so.",
"Use alegator clips to connect your In coated piece to a sheet or snarl of Cu wire that's been well cleaned and has at least twice the surface area of the one you're trying to save. The Indium should dissolve off leaving the Cu exposed below.",
"The Cu underneath might look a little dull but light polishing will restore the shine."
] |
[
"I spent several months doing an experiment where I melted indium on top of copper to use as a thermal contact material for silicon wafers.",
"If your copper was dirty, you're in luck. The indium will peel right off.",
"If your copper was clean, you're screwed. You will have to scrape it off with a razor blade."
] |
[
"You will most likely need to scrap or treat it with acid. If memory serves me correctly, Indium reacts with hydrochloric acid while copper does not. You might be able to dissolve it off if you are able to use acid. ",
"Though as always don't use acid without doing your safety and regulation homework first. Don't use it in a closed area, wear proper protection, and make sure anything around the metal is not going to be damaged by the acid. "
] |
[
"How to understand that Godel's Incompleteness theorems and his Completeness theorem don't contradict each other?"
] |
[
false
] |
As a layman, it seems that his Incompleteness theorems and completeness theorem seem to contradict each other, but it turns out they are both true. The completeness theorem seems to say "anything true is provable." But the Incompleteness theorems seem to show that there are "limits to provability in formal axiomatic theories." I feel like I'm misinterpreting what these theorems say, and it turns out they don't contradict each other. Can someone help me understand why?
|
[
"The completeness theorem says that any logical consequence of the axioms is provable. This means that we're not missing any logical rules, the ones we have are \"complete\". They suffice to prove everything you could hope to prove.",
"The incompleteness theorem says that any set of axioms is either self-contradictory, or cannot prove some true statement about numbers. You can still prove every logical consequence of the axioms you have, but you can never get enough axioms to ensure that every true statement about numbers is a logical consequence of them.",
"In a word: completeness says that every logical consequence of your axioms is provable, incompleteness says that there will always be true facts that are not a logical consequence of your axioms. (There are some qualifications you have to make when stating the incompleteness theorem precisely; the axioms are assumed to be computably listable, and so on.)"
] |
[
"This is very good thinking. This is ruled out in the premises of a \"workable set of axioms\" as the set of axioms needs to be recursively enumerable. If this premise is dropped, Gödel's incompleteness theorem would not be true for precisely this reason."
] |
[
"But what if my set of axioms is an exhaustive list of every true statement about numbers?"
] |
[
"What's the difference between a negative pressure and a vacuum?"
] |
[
false
] | null |
[
"It's a semantic difference. You are creating a pressure gradient which drives a flow."
] |
[
"Can you explain this to me like I’m 5? "
] |
[
"If there's a difference in pressure between two positions, there is a force acting on the fluid in the direction of the lower pressure."
] |
[
"When people are suffering from a severe, and sometimes fatal illness (such as cancer), does \"fighting for your life\" actually do anything? Does a person's level of resolve to fight and survive actually play any role in their recovery?"
] |
[
false
] | null |
[
"An optimistic attitude is associated with better health outcomes. ",
"Research seems to show this is because optimistic people participate more actively in their own care, and seek opportunities to improve their health. That is, it's probably not the attitude itself, but the way optimism makes you behave. ",
"Here's an example article on the topic.",
"It's also hypothesized that a negative attitude makes the body produce more stress hormones, and those hormones worsen the chance of things like stroke or heart attack. But I haven't yet seen any good research to support that."
] |
[
"Super interesting. I understand that having a positive outlook will lead you to make better choices (such as quitting smoking or changing your diet) in illnesses like hypertension and diabetes which can be directly caused by lifestyle. I was really curious if the power of optimism and hope like the authors of the paper described, or the patient being a \"fighter\" as commonly described with an illness that can not be erased by lifestyle changes actually had any quantifiable effects. Thanks for enlightening me!"
] |
[
"There's a specific study on this that found it doesn't have an impact. I'm not across the literature enough to know how this fits in to the overall science though;",
"https://www.webmd.com/cancer/news/20040209/attitude-doesnt-affect-cancer-survival"
] |
[
"If our star system was near (relatively) a dense nebula, would we see blue skies during the day, but amazing swathes of color at night?"
] |
[
false
] |
And if it was sufficiently dense, would it be obviously very far away? i.e. could we look at the moon & think 'yeah, that's the moon & it's a very long way away, but that nebula is REALLY far away'? I would imagine that sort of view at night would give us a completely different perspective of the universe. the scale would be immense. of course, we don't really think of the stars as far away, they're just dots of light in the dome of night. at least, that's the way I see them, unless I think about it. maybe we'd perceive a nebula in the same way.
|
[
"Amateur astronomer here. Not actually a scientist, I just looking at cool stuff through a telescope.",
"No. Nebulae are too dim. Being closer to a nebula wouldn't make it brighter, just larger, and making it larger wouldn't the cone cells in your eyes detect color in them. There are plenty of nebula in the sky that are quite large but so dim you don't see them. The moon is about 30 arcmin wide. The Orion nebula is one of the brightest nebula in the sky, and it's 60 arcmin wide. At best, it's a dim splotch in the sky, and unless you are looking for it you probably don't notice; despite the fact that it's twice as wide as the full moon, with four times the area. Even with a telescope, it's too dim to see color, even though it's actually quite color saturated; only the rods in our eyes are sensitive enough to detect it, and the rods cannot discern color.",
"Being extremely close to a nebula like that would block the light from the stars behind them. There would be a large, dim, featureless gray area with a few ",
" bright stars in it and little else. We would probably be able to make out a few ",
"bok globules",
" within it.",
"I don't know how such a feature in the night sky would affect our perceptions."
] |
[
"Let's talk about what \"brightness\" means, because it can mean multiple thing depending on context. It is not really a very useful scientific term because of how loaded it is. I apologize for that; I should have been more rigorous.",
"Objects appear \"brighter\" when they get closer because they appear larger. If you reduce the distance you are from a lightbulb by half, the lightbulb will appear to be four times larger. Since it appears four times larger, four times as much light will reach you: its ",
"irradiance",
" will increase four-fold.",
"So it is with nebula; when it gets half as far away, (twice as close) it will appear four times larger, and will be four times as irradiant. But it will take up four times as much space in the sky: that irradiance doesn't come from the same small spot in the sky, it is spread out. So the ",
"radiant intensity",
" will stay the same.",
"When I said confusingly said brightness, that's what I meant, its radiant intensity. It is a very dark grey now, and if it were a few lightyears away instead of 1350 lightyears, it would still be a very dark grey. It would just be much larger."
] |
[
"The closer you are to a source of light the brighter it gets so it would in fact make it brighter. "
] |
[
"Could concentrated injections of B lymphocytes be a solution to cure cancer?"
] |
[
false
] | null |
[
"There is plenty of research looking at using the bodies own immune cells to combat cancer, you suggest. B cells are not the main cell of interest for this however. B lymphocytes tend to be more associated with combating humeral diseases, small things in the blood. ",
"The cell we generally want to kick into action is the T Lymphocyte. These cells are designed to attack and kill body cells that have gone awry, due to either mutation or virus attack. ",
"B and T cells do have many interactions, so a B cell response can result in tumour regression, but generally the T cells are far more useful for this. ",
"Now you could inject a bunch of T cells into a person, but first you have two main problems. Firstly, where do you get the T cells from? You could mass grown them cheaply in a lab, but then the patient would probably recognise them as foreign, and would be destroyed by the hosts immune system. ",
"Secondly, you need to educate and activate T cells, to make sure they attack only the tumour. If you don't train them to recognise a specific \"tumour antigen\" then they are worse than useless. ",
"Now, this is the important bit. ",
"T cells are effector cells, they have to be activated and then they go out to cause an effect. You therefore need just a small number of specific activating cells to stimulate a large T cell response. There is a lot of interest in using these activating cells (primarily Dentritic Cells) to kick the T cells, and rest of the immune system into action.",
"There is already a company out there doing this with a drug called Provenge. They take host Dendritic Cells out of the body, activate them in a lab and train them to respond to a specific tumour antigen. The cells are then introduced back into the patient, where they can go on to stimulate the desired T cell response. ",
"A point to keep in mind however is that the immune system is a fantastically complicated machine, with multitudes of interactions and cross links. We still are a long way away from a complete understanding of it. Most treatments using just one approach, activating just one cell type, are fairly lackluster. It's about shifting the entire immune system to attack the cancer, not just a specific cell compartment. "
] |
[
"Is this specific to CD8+ T cells, or are there other T cells who partake in killing cancer cells, except for activation?"
] |
[
"CD8+ are the main cells that mediate specific cell killing, which is generally what we want in cancer or viral infections.",
"If possible we also want CD4+ Th2 helper cells activated, as they promote CD8+ killing, but don't attack the cancer cells directly themselves.",
"There are a number of T cell types that we don't want activated though. Suppressor T cells and CD4+ Th2 cells for example will both dampen the sort of immune response we want.",
"There is another type of cell called a Natural Killer (NK cell) which is also used to attack non-normal cells. These however are not T cells, but could still have a role in attacking cancer. NK cells aren't specific to exact antigens (As T cells are) however. "
] |
[
"Why is oxygen paramagnetic while iron is ferromagnetic?"
] |
[
false
] |
Ogygen and iron atoms both have unpaired electrons. Why can these unpaired electrons keep existing in iron (making it magnetic) while they can't do this in oxygen?
|
[
"Because the atoms of iron exist within a periodic lattice. And the unpaired electrons on adjacent iron atoms align with one another due to the exchange interaction. The oxygen molecules in the gaseous or liquid state take essentially random orientations with respects to each other.",
"Exchange interaction: essentially, it costs less energy to align the unpaired electrons in the iron lattice because by being in the same spin state the electrons can exist further from one another (Pauli exclusion). So there is less coulombic repulsion. This 'saved' energy is the exchange energy."
] |
[
"While your second paragraph is absolutely correct I disagree with the first one a bit. Yes, a lattice is important for ferromagnetism but it does not guarantee it. Vanadium has 3 d electrons, yet it's a paramagnet in bulk. So is manganese. In Fact, the only ferromagnetic (at room temp) bulk materials are Iron, nickel and cobalt."
] |
[
"Below its curie temperature, each Material will be ferromagnetic and above it, ferromagnetic",
"Good answer, but should that read \"and above it, ",
"\"?"
] |
[
"Would it be (theoretically) possible to use the heat in the air to generate electricity effectively enough that it would cool the air significantly?"
] |
[
false
] |
The reason I'm asking is because if it was possible you could create an air conditioner that would generate electricity.
|
[
"No, it's only possible to generate electricity through heat differences. Thermoelectric devices work by producing a voltage across a material that has a different temperature on both sides of them. In space satellites, this is achieved with radioactive pellets.",
"Essentially, in your example, you would need to allow heat to flow into your house after cooling it down in order to produce (less) electricity. Thermoelectric devices are very inefficient, to boot. "
] |
[
"You're laboring under a misapprehension, that \"heat in the air\" is a form of energy that can be harnessed.",
"First of all there's no such thing as \"heat in the air\". There's the ",
" of the air, and there's thermal energy in the air, but heat is a transfer of thermal energy (of any kind) from one thermodynamic system to another. I don't want to go any further about that because it's being unnecessarily pedantic, bitching at you for using the wrong terms. It's clear what your question's about, harnessing the thermal energy in the air. The only reason I'm bringing this up at all is that I'm about to give you the thermodynamic answer to this question, and these terms, ",
", ",
", and ",
" have specific meanings in that context.",
"The true reason you can't just transfer thermal energy from the warm room and ",
" from the exchange, generating heat, is that it would violate the second law of thermodynamics, which tells us that in all conditions, the entropy of a system will either remain unchanged or increase. If you have a warm room and an equally warm exterior (outside), those two systems are in thermodynamic equilibrium, and they are also at a maximum amount of entropy. Two systems at the same temperature have a higher entropy than one system ten degrees cooler and one system ten degrees hotter. (At least if both those systems have the same thermal mass - clearly your bedroom and the ",
" do not. :) ) So nature abhors when two thermodynamic systems in thermal contact do not equalize, and it transfers heat from the warmer one to the cooler one.",
"I go into the details of heat transfer & temperature ",
"here",
" but it's way beyond the scope of answering this question. Suffice to say entropy will always increase. ",
" You might ask. ",
"You're right. But the air conditioner ",
" to accomplish that. While it's removing entropy from the two systems by creating the temperature difference, it's also ",
" the overall entropy by adding energy to ",
" systems, which actually increases the entropy even more! And how does it do that? By consuming energy from an external source, consuming electrical energy. ",
" in the physics sense. And note, if we actually include the source of the electricity, be it mains power or a battery or whatever, the ",
" system actually ",
" increase in entropy! The additional entropy of consuming electricity and the inefficiencies of the refrigeration cycle injects ",
" thermal energy into both the outside and inside systems. If we include the entire system of the Earth, entropy ",
" increases.",
"Point is while your air conditioner reduces the entropy of the system consisting of your bedroom, and the air immediately outside your house, it does so only by increasing the overall entropy of the Earth. And even then it has to do work, (and thus, consume electricity) to accomplish even that much. In the real world, there is no such thing as an \"external source\"; that's just a convenient abstraction. After all, where does electricity come from? One answer, a thermodynamic answer, would be \"the sun.\" Be it oil, coal, gas, nuclear, or solar, it all really originates from the sun, right? Maybe nuclear is from a ",
" sun that went supernova, but all the fossil fuel starts out as solar radiation feeding plants feeding stuff that eats plants and dies and becomes oil/coal/gas. And solar ",
" comes from the sun. You'd better believe that the fusion the sun undergoes increases entropy.",
"The entropy of ",
" only ever increases, full stop. In this house, ",
"we obey the laws of thermodynamics",
"!"
] |
[
"Every heat engine operates off of a temperature difference. (I.e., the Stirling engine is not particularly special in this way.) No heat engine can remove thermal energy from a system except by sending at least some of it to a lower-temperature system. "
] |
[
"At an altitude of 1470km, how fast is Dawn traveling, orbiting Ceres?"
] |
[
false
] | null |
[
"TL;DR answer: an average of 179.6 m/s, relative to Ceres, ignoring Ceres' rotation.",
"Orbital parameters aren't immediately obvious on JPL's web site, so I'll assume we're talking about a uniform circular orbit. As outlined at ",
"physicsclassroom.com",
", this can be modeled with the simplified satellite equation: v=√(G*M/R), where:",
"G is always 6.673 x 10-11 N*m",
" / kg",
" . The mass of Ceres is approximately 9.393 x 10",
" kg, and its mean radius is 473 km. If we add the altitude of 1470 km to this and convert to meters, we get an orbital radius of 1,943,000 m.",
"From there, it's a matter of crunching the numbers."
] |
[
"Thank you for the details! 180m/s is not that fast, I'm surprised."
] |
[
"No worries. Its gravity is a measly .03g, so it doesn't take much to orbit. :)"
] |
[
"#eng Why are I6 engines considered so highly balanced but a V8 isn't?"
] |
[
false
] |
There are 4 strokes in a complete cycle, so shouldn't an engine like a V8, which is an even multiple of four, be able to cancel out the forces generated by each piston by virtue of the fact that another piston must also be doing the exact opposite motion?
|
[
"reciprocating mass connected via two links have something called shaking force (think of a motor in your phone allowing it to vibrate). With even number of cylinders the force can be balanced. However, this doesn't account for the moment caused by the shaking force. Two pistons opposing the shaking force is at different location on the crankshaft, and thus will result in unbalanced moment. Moment must also be balanced for stability. Moment is analogous to torque. Perhaps the layout limits the balance that can be achieved. The moment caused by V8 will be 60 degrees apart, with 2 planes and 4 pistons per plane. Whereas, I6 will have 1 plane, 1 moment and 6 cylinders. Each cylinders can be aligned to minimize the shaking force and crankshaft have counter weight to balance the moment caused by the shaking force. That is the limitation of my expertise.",
"So... I hope you could decipher what I was trying to convey. The concept you're missing is the ",
"moment",
"). For an object to be balanced, the moment must also be balanced. Perhaps the I6 arrangement is able to accommodate it better. Some designs, by the nature of the design itself, makes some aspect of it impossible to change.",
"P.S. something to add... the location and the mass of counter weight on a crankshaft is limited. The shaking force I mentioned MUST be balanced. If this isn't achieved, we have an engine that has a significant vibration. This is a major limitation when it comes to balancing multiple reciprocating mass on a common shaft. ",
"So I guess this isn't a very good answer to your question. Though I believe if you do understand my answer, you would be able to fully appreciate the distinction between inline and v- configurations. "
] |
[
"Why ",
" a I6 engine naturally balanced but I4 and I8 engines are not?"
] |
[
"An inline engine has all cylinders in the same line (like this: | | | | | |), so the up-down motion of the pistons can be balanced. A V engine has cylinders at an angle to each other (like this: \\ /). V8 has two banks of 4 cylinders on each side of the V. The motion of the pistons is partially up-down and partially sideways, at weird angles to each other. Basically the only way it can be balanced is if the angle between the cylinders is 180 degrees, which would make it a horizontally-opposed, a.k.a. boxer, engine. An engine that is not naturally balanced requires counterweights and heavier flywheel. ",
"A better question would be why, according to wiki, an I6 engine is naturally balanced but I4 and I8 are not."
] |
[
"If the dinosaurs hadn't been wiped out, what would the world look like today?"
] |
[
false
] |
Would we still have evolved to be the dominant species or would they have eventually developed intelligence and became dominant?
|
[
"Intelligence isn't necessarily an advantageous trait to develop, and certainly isn't the end goal of evolution. There's no reason to think that they'd develop it given enough time."
] |
[
"More dinosaurs, mostly.",
"Dinosaurs were around for 160 million years, and died out around 65 million years ago. That isn't such a huge gap considering their long evolutionary lifetime. In contrast, we've been around for 50,000 or so.",
"Edit: Fixed for correct time."
] |
[
"Don't you mean 65 million years ago?"
] |
[
"How did people before modern times deal with torn acls?"
] |
[
false
] |
In addition, there was a story about in nba player Dejaun Blair who was able to sustain a career for a period of time without an ACL. How is this possible? He is also not the only one.
|
[
"When I tore mine, the physio said that I can get surgery, or I can do a lot of work to strengthen up all the muscles from my ass to my calves to prevent my knee going backwards again. There's no guarantee though. I'd say if people are already elite athletes, they're in a great position for strengthening already. Other than that, perhaps that dude just got lucky."
] |
[
"Depends what you mean by modern times I would think, for example if you think back to the 1800’s I’m sure there were less acl injuries due to less intensive sports I would imagine, but in terms of more recently, I believe treatments for torn ACLs was developed in the 1970s at some point. Before these treatments I would imagine they would’ve just suggested rest and maybe a cast of some sort"
] |
[
"Full ACL tears cannot be healed without surgery. A pre-surgery-option person would be injured for life. ",
"However, very minor tears can heal on their own over time (months-> years). Ligament tissue heals really slowly. An injured person will be limited to activities that don't involve pivoting on the knee. For instance, running in a straight line is fine.",
"An injured person would naturally avoid activities that involve pivoting the knee. The muscles surrounding the knee will also start to strengthen to support the knee to compensate for injured ACL. Usually the person knows their limits before it starts to hurt.",
"Used to be there were certain athletes famous for being unable to pivot in one direction. Naturally talented in other areas to compensate, but opponents would know to attack on the weak side."
] |
[
"Is solar wind energy at all possible?"
] |
[
false
] |
I remember reading something around Reddit some time ago about the theoretical possibility of harnessing solar wind in order to create energy for practical human uses, like we do with wind turbines or solar panels. Is there any reality behind this idea? I've had little luck finding much of anything on this, as it seems to be more of a proposed idea. Any idea where I could find more information/research? Cheers.
|
[
"Its possible, but I suspect that the solar wind is too diffuse to make harnessing its energy a viable option. I also suspect that there is a much higher density of solar energy from light than there is from the solar wind."
] |
[
"I don't think that solar wind will ever be a terrestrial power supply. I don't think solar winds even get through the magnetosphere. ",
"It might be used one day as a way to get around the solar system. You don't have to carry fuel with you."
] |
[
"Not quite solar ",
" but somewhat relevant: ",
"Dyson Spheres",
"."
] |
[
"If I leave my phone in the sun it gets pretty hot very quickly. Would this happen more slowly if the screen stayed on a white screen?"
] |
[
false
] | null |
[
"No.",
"You're right that white things stay relatively cool under intense sunlight, but that's because they ",
" light and avoid absorbing it. A phone's screen is ",
" light instead, so colors are irrelevant for controlling the temperature. Rather, you should cover your phone with a white reflective surface (e.g. paper or white clothes)."
] |
[
"Not really. The pixels aren't 'colored white'. There are actually 3 different pixels (red, green and blue) that are all lit up to trick your brain into seeing white. So all in all, you still have the exact same non-white pixels absorbing not only the Sun's energy, but also the backlight."
] |
[
"What's the difference between ",
" and ",
"? Isn't it just colored pixels with a backlight, instead of reflected light?"
] |
[
"What has a greater effect on melatonin levels, light intensity, or the tint of the light itself?"
] |
[
false
] |
It seems common knowledge that light in the blue spectrum has a significant impact on our melatonin levels, which can lead to decreased sleep quality. But would a bright light in the red spectrum have a similar impact?
|
[
"A common model is that what matters most is the amount of light in the blue-green range, most strongly in the 400 nm to 500 nm range, and tailing off somewhat gradually beyond there. However, some recent work indicates that the relative spectral power does matter, and it's not that simple. [1] has some plots and discussion of those different models, and then looks at design of light sources to try to get visual effectiveness with minimal effect on melatonin. For any of the models, if you have light that is just red, that will have little effect, even if it's bright. But it's not only blue that has an effect: green, depending on the particular spectral distribution, can have a substantial effect as well.",
"[1] Qi Dai, Wenjing Cai, Wen Shi, Luoxi Hao, Minchen Wei,\nA proposed lighting-design space: circadian effect versus visual illuminance,\nBuilding and Environment,\nVolume 122,\n2017,\nPages 287-293,\nISSN 0360-1323,\n",
"https://doi.org/10.1016/j.buildenv.2017.06.025",
".\n(",
"http://www.sciencedirect.com/science/article/pii/S0360132317302603",
")"
] |
[
"if you have light that is just red, that will have little effect, even if it's bright. But it's not only blue that has an effect: green, depending on the particular spectral distribution, can have a substantial effect as well. ",
"OP, just to follow up on this good answer with some of the biological details as to why it's primarily blue light: ",
"The entrainment of our circadian rhythm to light is primarily due to special neurons located in our retinas that detect light. These aren't the traditional Rod and Cone photoreceptors you might have heard about, but rather they're a specialized class of ganglion cells. Instead of projecting into the image-formation pathway (think Visual Cortex), they project to the hypothalamus to a nucleus important for setting the circadian clock (to which melatonin production is heavily inversely tied to). These special cells in the retina use ",
" (nicely named) as their light-sensitive photopigment. Melanopsin's sensitivity spectrum is highest to blue light, with very little sensitivity to red light. There's some overlap with the longer green wavelengths, so that's why depending on the intensity, green light should activate these neurons as well. ",
"This website is public-access and is a great source of information for anything involving vision:",
"\n",
"https://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/melanopsin-expressing-intrinsically-photosensitive-retinal-ganglion-cells/"
] |
[
"Awesome, that's really interesting. Thanks for the great response!"
] |
[
"If a solar panel isn't connected to a power grid, what happens to the electricity generated?"
] |
[
false
] | null |
[
"If a solar panel is in the sun but not connected to anything, it will maintain its normal voltage but no current will flow (because there's no complete circuit for it to flow through).",
"It's exactly analogous to having a battery with nothing connected. Same voltage as normal but no current flowing.",
"Using the water analogy to electricity (where water height is like voltage and water flow is like current), this is like water held behind a high dam with the outflow blocked. "
] |
[
"Absolutely not true. Most of the world's solar capacity is connected to the grid, not batteries. (And yes, grid-scale backup batteries do exist but they're kind of fringe, and the connection between them and solar panels is not at all direct.)",
"You only need a battery if you're off the grid, or otherwise need to be entirely self sufficient with solar only."
] |
[
"As ",
"/u/cuicocha",
" points out, no current will flow. ",
"Interestingly, this means that if you were to leave a connected panel and a disconnected panel out in the sun, the disconnected panel will get warmer since none of the energy hitting it is leaving via the wires."
] |
[
"who would win a zipline race - a heavier or lighter person?"
] |
[
false
] |
[deleted]
|
[
"The heavier person would. If they have the same drag, it would affect the lighter person proportionally more than the heavier person."
] |
[
"so if you dropped two balls with the same coefficient of drag but different masses, the heavier one would always hit the ground first?"
] |
[
"Yes as it has more mass the drag force has less of an effect on it due to F/m=a."
] |
[
"Sarcopterygii, Myxini, Cephalaspidomorphii, Chondrichthyes, Sarcopterygii - why all the \"fish\"?"
] |
[
false
] |
[deleted]
|
[
"The unsatisfying answer is that \"fish\" is not really a technical term as far as taxonomic classification goes. I've heard conodonts and even protoconodonts referred to as fish by people who are into taxonomic hairsplitting with the fire of a thousand suns. Same with whales.",
"If you've been introduced to the groupings you mentioned, you probably know the characteristics each one is associated with... bony or not, what kind of jaw, ray/skate like, and so on. They're all separate and worth paying attention to at least in part because the have different first appearance dates and that presumably tells us something about evolutionary history. It's also interesting because fish are essentially the oldest vertebrates and crown group species still exist... it makes understanding their taxa all that more emotionally salient if nothing else."
] |
[
"Taxonomy is such a mess. I learned three different classification structures, just during my grade1->b.Eng. But what's beautiful about that is we can easily permute the trees depending on the most currently accepted lineage. I think of it like some gigantic program that can be patched whenever 'bugs' around found. ",
"We just don't want to teach taxonomy as a 'complete science' because it is almost surely incomplete and will see major changes as we identify more and more early life forms."
] |
[
"You repeated Sarcopterygii, you probably meant Actinopterygii for one of them ;)",
"There isn't really a one-sentence way to distinguish them other than that they are different branches on the vertebrate tree of life. ",
"And why do frogs, reptiles, birds and mammals only get one class each?",
"This has to do with how our classification (the Linnean system) predated our understanding of branching in the tree of life. Technically birds are nested within \"reptiles\" (birds are dinosaurs, which are archosaurs, which are sauropsids). Amphibia, much like \"reptiles\" and \"fish\", is also ",
"paraphyletic",
". Modern ",
"cladistics",
" attempts to create a more evolutionary based classification scheme. As a result you end up with seemingly paradoxical, but true, statements like \"humans are more closely related to salmons than salmons are to sharks\" - humans are within Sarcopterygii, which has a sister group relationship with Actinopterygii (where salmons belong), and both of these groups share a common ancestor with Chondrichthyes (where sharks reside)."
] |
[
"Why do we shake when we flex a muscle and hold it still?"
] |
[
false
] |
I often find that whenever I flex and hold a part of my body still (such as my leg) it tends to shake/vibrate. Why does this happen?
|
[
"When you are holding your leg out, your muscles will become fatigued. When our muscles are flexing, the muscle fibers sort of take turns holding up the weight, switching on or off - this is called a 'twitch.' When we start to become fatigued, these muscles do not have time to fully relax between each twitch causing the twitches to build up and results in a summation of ",
"Muscle Contractions",
" called a ",
". ",
"IMAGE",
"Not to be confused with ",
"Fasciculations",
" which are muscle twitches when resting. ",
"I hope this simplified answer satisfies your question. There are a lot of panelists who have a greater understanding of this and can provide a more detailed answer."
] |
[
"When you first start strength training for weight lifting it is common to see very fast increases in the amount of weight that can be lifted. These increases are faster then muscle can be built. These increases come from neural adaptation. Essentially you are training your neural system to synchronize the firing of more muscle fibers.",
"For more info, see this link: ",
"http://skinnybulkup.com/neural-adaptations-during-strength-training/"
] |
[
"I am happy to provide!",
"Zatsiorsky, V., Kraemer, W. Science and Practice of Strength Training. Champagne: Human Kinetics, 2006.",
"Walker, A. \"The Strength of Great Apes and the Speed of Humans.\" Current Anthropology. 1 Apr. 2009, Volume 50, Number 2: 229-234.",
"\"There is also the upstream control of motor neurons to consider. There are well‐known cases of “hysterical strength,” where people suffering seizures exhibit considerably more muscle power than normal. There are also many anecdotes about people in very stressful situations being able to do things that would normally be considered impossible—lifting cars off trapped people, for instance. Add to this the effect of severe electric shock, where people are often thrown violently by their own extreme muscle contraction, and it is clear that we do not contract all our muscle fibers at once. So there might be a degree of cerebral inhibition in people that prevents them from damaging their muscular system that is not present, or not present to the same degree, in great apes. I do not know of any experimental evidence to support or refute this idea, although cortical inhibition of motor impulses has been experimentally demonstrated in animal models and with magnetic inhibition in people.\" ",
"Hysterical Strength",
"\"Hysterical strength can result in torn muscles and damaged joints. This is why, in addition to high lactic acid production, the body limits the number of muscle fibers the human body uses\""
] |
[
"Did they need glasses?"
] |
[
false
] |
Dear Reddit, I now need glasses to see things up close, like reading this post. I hate that! Anyway, it led me to ponder if the eyesight of man has evolved over time. Given Neanderthal people did not have the need to read, did they have eyesight that enabled them to see fine detail up close, like we can? Or was their eyesight only developed to a point that enabled them to see large detail? Just pondering. Edit. Many thanks for all the input. Very interesting.
|
[
"lack of selective pressure",
"IIRC not at all that. There were comparative studies between Jewish children in Israel. They compared those growing up in a Kibbutz and were outside a lot, and those who attended religious schools to reading the Torah a lot.",
"They found that the latter suffered more from myopia, i.e. couldn't focus things which were far away. As the genetic background of these kids was similar, it was probably the way they grew up.",
"There was also an experiment with chicken; if they placed a lens in front of their eyes while the eyes were still growing up the eye would become too large (myopia also).",
"It seems that the growth of the eye is not just pure genetics but seems to depend on environmental factors. As myopia is obviously no advantage evolution probably just attached to a certain phenomenon that was usually present when you focused things further away which happened to be present for most of the evolutionary history.",
"So the stereotype of the bespectacled intellectual seems to be true!"
] |
[
"I do not think that reading has been a factor in the evolution of our eyes to be able to focus at short distances. I would think most creatures with eyes can focus well at arm, claw or tentacle length. Compound eyes exempted perhaps.",
"That poor eye sight is common among humans probably has more to do with increasing age and lack of selective pressure that kills you if your eyes do not function optimally."
] |
[
"Their eyesight was probably similar to ours. However:"
] |
[
"If the Beta(1,4) bond in cellulose is hard to break, does that mean it was hard for the plant to make it as well?"
] |
[
false
] | null |
[
"AFAIK, the beta(1,4) isn't actually a stronger bond than the alpha(1,4) linkage of amylose (normal starch). Rather, we just don't have an enzyme that can do the reaction (and such enzymes are apparently relatively uncommon in nature, maybe it's a hard shape for enzymes). I don't actually know the energy expenditure in cellulose synthesis vs. amylose synthesis, but I suspect that it isn't significantly higher."
] |
[
"Not necessarily. The strength of a chemical bond is not equal to the work it requires to cause the bond to form. Some bonds, like between two individual hydrogen atoms, form spontaneously without any real external effort but are incredibly resistant to breaking. "
] |
[
"Apart from the fact that very few organisms have an enzyme to break down the beta (1,4) glycosidic bond, cellulose is relatively difficult to break apart. The glycosidic bond itself is actually relatively easy to cleave with acid in either cellulose or amylose. The big problem with cellulose is that it forms a crystalline structure where the individual cellulose strands are closely packed and linked by hydrogen bonds. This makes it very difficult for an enzyme (or a proton from an acid) to actually access the bond that needs to be cleaved. Due to the geometry around an alpha(1,4) bond, amylose and other alpha (1,4) linked polymers form a different and more easily accessible structure. "
] |
[
"What causes arthritis?"
] |
[
false
] |
So I've been digging through the Ask Science sub-reddit, and I've seen a lot of "does cracking your knuckles cause arthritis?", "why not?", etc. But I haven't seen a "What causes arthritis?" so I'm asking. Is it a virus? Genetic defect? Wear and tear? Bacteria? Symptoms of injury? Diet? I've heard about the various types, but never a solid cause.
|
[
"There are quite a few different causes for arthritis. The two most prominent that come to mind are rheumatoid and osteoarthritis. Rheumatoid is an autoimmune disease where the immune system, which normally should not be sensitized to the joint capsule, gains immunity against it and attacks joints. Rheumatoid arthritis is devastating, and I wouldn't wish it on my worst enemy. Joints and ligaments are completely destroyed by the immune system, eventually leaving nothing behind.",
"The most common arthritis is osteoarthritis and it is more or less wear and tear. We see it on XRAY as joint space narrowing; the cartilage on the ends of bones degenerates and thins, causing bone on bone contact. This causes pain. Eventually this degrades to the point where these articular surfaces may need to be replaced in a total joint arthroplasty, which I had the pleasure of doing all last month.",
"Bacterial arthritis is far less common, but can happen. The joint need only be inoculated with a few bacterial colonies to facilitate joint infection. In my experience, orthopedic surgeons are way more concerned with sterile technique in the OR than other surgeons for this reason. Bones do not seem to have very good immune response capability (despite largely being responsible for the production of the immune system in bone marrow), and osteomyelitis (bone infection) is difficult to cure.",
"Gout and pseudogout are crystalline forms of arthritis. Basically what happens is that something in the joint fluid precipitates into crystals which are sharp and make you very unhappy. There are some ok treatments for this one.",
"As with many things in medicine, arthritis actually has a ton of different causes. Diseases in medicine tend to be grouped together by symptom instead of etiology, probably because we didn't used to know what caused problems."
] |
[
"To add to the OA discussion the spine works a little differently than most other joints due to the presence of discs. In spinal osteoarthritis the first phase is damage of the cartilage end plates of the disc/vertebra, this produces a decreased nutrient flow to the nucleus pulposus of the disc (it gives the disc its height and mobility) which decreases its ability to produce chemicals to attract water and eventually can lead to cell death. Although nutrient flow can still be kept up by making sure imbibition occurs though proper joint motion and decompression. Once the NP of a disc is dead the process really accelerates with Wolfe's law causing bone spur formation along the rim of the vertebral body. If there is variance from normal weight bearing postures (anterior head carriage or hypolordosis) this process is accelerated. Other factors such as muscle spasm or scoliosis will complicate the issue.",
"Also OA does not necessarily cause pain but it certainly predisposes one to joint based discomfort.",
"But the model described above for OA does apply to the facet joints of the spine quite well.",
"There are other conditions fitting the above descriptions but I preferto use the classic category descriptions: degenerative (OA), inflammatory (RA/JCA), metabolic (gout/CPPD), and infection (bacterial)."
] |
[
"There is no one set cause of arthritis. There are only risk factors, and all of the things you listed plus things you can find on the arthritis ",
"wiki",
" can predispose you to getting arthritis. There are also over 100 types of arthritis. This is such a complicated area that there is an entire field dedicated to joint/connective tissue disease called ",
"Rheumatology",
". A comprehensive answer to your question would need more room than provided in this answer's character constraints."
] |
[
"Will a piece of wet laundry dry faster if I throw it in the dryer alone, or together with other, already dry textiles?"
] |
[
false
] |
Sometimes I need a certain piece of cloth to dry as soon as possible. I assume having towels in the dryer could work as they absorb the humidity and distribute it, whereas the additional load may also block the airflow.
|
[
"It will change the dynamic - it will get partially dry faster, as the other textiles absorb moisture from it, but it will take longer to get completely dry, as they block airflow around it. Finding the optimal amount to include is an extremely complicated and idiosyncratic problem that depends on the materials involved, beginning and desired ending wetness, heat and motion of the dryer, and other factors. I'm not sure there's a universally optimal solution, but you could do some simple experiments with your own dryer and clothes to get a partial solution for your own case."
] |
[
"If I just have one garment to dry, I always dry it with an already clean and dry towel. I have found that it is typically much faster this way. The reason is that there are usually a few lips/humps inside the dryer to help the clothes mix when drying an entire load. If you just throw one garment in, these will sometimes cause it to crumple into a ball and not actually dry. "
] |
[
"In my particular case, I often want to dry a piece of cloth, several meters long, made from woven cotton. The already dried fabric that I would add consists of several pads made from microfiber terry cloth."
] |
[
"Could someone actually use a smart meter to spy on one's computer?"
] |
[
false
] |
Okay, hear me out: I just read Neal Stephenson's and there was a part in there with something called "Phreaking." As I was reading cyberpunk, I was unsure as to whether this was hypothetical or an actual technique. Anyway, I read about smart meters, and it just tracks usage and reports the data through an RF transmitter. I was wondering if someone sneaky wanted to, could they intercept the data and translate the changes in power usage into the rastering of a monitor, effectively capturing the screen output? Edit: I just realized that I not only gave an anecdote, but also commited the crime of speculating as a layman. I appreciate the fact that I haven't been deleted.
|
[
"It is possible. The general technique of determining what is displayed on a monitor from its EM emission is called Van Eck phreaking [1]. The general technique of attacking 'secure' systems through indirect means is called side-channel attack [2]. Another example of a side-channel attack is using microphones to determine the password as a user enters it on their keyboard.",
"[1] ",
"http://en.wikipedia.org/wiki/Van_Eck_phreaking",
"\n[2] ",
"http://en.wikipedia.org/wiki/Side_channel_attack"
] |
[
"I'm kind of geeking out right now. Thanks!"
] |
[
"how does the meter capture a wide band of EM radiation?"
] |
[
"Why are asteroids all different shapes, but planets and moons are mostly round?"
] |
[
false
] | null |
[
"Planets, some moons, and dwarf planets are big enough for gravity to be strong enough to pull them together. Systems tend toward their most stable state over time and that is one where potential energy is minimized- ideally, a sphere. Rotation can bulge mass around the equator creating an oblate spheroid. ",
"It's one of the criteria to be a planet- to be big enough to roundify yourself"
] |
[
"This.^",
"The reason why planets amd moons are round is that the higher gravity from all their mass pulls them into a sphere. The reason it turns into a sphere is that any high points tend to fall/shift towards the center of mass. This keeps happening and gets you a sphere instead of a cube, disk, or otherwise.",
"Asteroids just don't have enough mass to shift the irregularities out."
] |
[
"This.^",
"The reason why planets amd moons are round is that the higher gravity from all their mass pulls them into a sphere. The reason it turns into a sphere is that any high points tend to fall/shift towards the center of mass. This keeps happening and gets you a sphere instead of a cube, disk, or otherwise.",
"Asteroids just don't have enough mass to shift the irregularities out."
] |
[
"How do hydraulic systems amplify force?"
] |
[
false
] | null |
[
"Hi ThePreaux 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",
"There are more restrictions on what kind of questions are suitable for ",
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", the above are just some of the most common. While you wait, check out the forum \n",
" 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.",
" ",
" "
] |
[
"‘Engineering’, ‘Physics’"
] |
[
"Engineering, Physics"
] |
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