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[
"NPR's Science Friday wants you to \"Ask a Quantum Mechanic\""
] |
[
false
] |
Hey Reddit! Today at 3:10 Eastern Time, is talking quantum mechanics with MIT physicist and "Quantum Mechanic" Dr. Seth Lloyd. We'll open up the phone lines to hear from listeners, but we also want to hear from you. Ever wondered about a quantum internet teleporting data? Counterfeit-proof quantum cash? Or the welfare of Schrodinger's Cat (and kittens)? Now's your chance to ask those quantum questions. We'll pick a few of the best questions and ask them on the air. And please later today to hear the answers! I'll post a link to the live audio once the show is live.
|
[
"First of all, let me welcome Science Friday and Dr. Seth Lloyd to reddit!",
"I'd also like to clarify to the redditors here, the questions will be answered on the air. This is not an \"AMA-style\" session, so don't be upset if you don't get a response in this thread. Science Friday is just collecting questions to answer on the show :)",
"To get things rolling, I have a couple of questions about quantum entanglement.",
"It's often said that quantum entanglement is \"spooky action at a distance\", and \"instantaneous\". However, it is still impossible to transmit information faster than the speed of light. So:",
"What is meant by \"instantaneous\" in this sense? ",
"What is being \"transmitted\" between entangled particles?"
] |
[
"(I doubt this will get asked, as it's probably too critical, specific and technical, but it's an honest question, so here goes..) ",
"Dr Lloyd, you're fond of talking about quantum effects within biochemistry, and what you call \"quantum hanky-panky\" - implying that these effects are unexpected or not 'supposed' to happen. ",
"As a quantum chemist who does study these things, I don't quite understand this. As I'm sure you know, chemistry is ",
" quantum-mechanical. There has never existed a 'classical' theory of how atoms work or why chemical bonds are formed, much less a classical theory of how electrons move between or within molecules, how molecules interact with light and electromagnetic fields, how energy is transferred, and so forth. ",
"So the question is, where do you draw the line between quantum-mechanical effects on chemistry that are to be expected and the \"hanky-panky\" ones where you wouldn't? You cite things like photosynthesis as examples of \"hanky-panky\", but how could such a thing - involving the absorption of photons and transfer of electrons - ever have a non-quantum-mechanical explanation? Isn't the involvement of quantum mechanics rather unsurprising?",
"While 'conventional wisdom' (and explicit calculations) holds that decoherence means that quantum effects don't occur in such systems at large scales or in the 'noisy' environment of the cell, I don't see how that carries over to descriptions of what's going on ",
" a protein - which is after all just a single molecule, albeit a large one, and relatively isolated from the surrounding cellular environment. Isn't the relevant distinction in quantum behavior between whether you're talking about the molecular or cellular ",
", rather than whether a molecule/reaction exhibiting quantum effects happens to be in a cell rather than a test tube? Because as far as I know, nobody ever held that chemical reactions in biomolecules were fundamentally distinct from how it works elsewhere. "
] |
[
"I know this, I want him to explain this on the radio so I can stop having to explain it so much!"
] |
[
"Everything in space orbits something, right?"
] |
[
false
] | null |
[
"No, not everything orbits something else. The largest orbits in the universe are those of galaxies within galaxy clusters, but those take such a long time (billions of years) that they aren't consistent or stable. At the supercluster scale, things stop being gravitationally bound to each other. We're not bound to the Virgo Supercluster, and we aren't orbiting it. On very large scales, the universe is ",
" rotating, and the peculiar motion of galaxies is insignificant compared to the spreading out of the universe, which precludes large-scale orbits.",
"Most astronomers think it's quite likely that there is other life in the universe. One of the fundamental ideas underlying modern astronomy is the Copernican Principle, which could be summarized as \"We are not special\". The last half millennium of astronomy has been a continuous fight against the idea that we occupy a privileged place in the universe. The discovery over the past several years that planets are extremely commonplace only further supports the idea that life probably exists other places besides Earth."
] |
[
"If you want to get technical nothing is orbiting \"something\" but instead each of those things is orbiting a point in space between them. ",
"For example, Jupiter doesnt orbit around the Sun. Both Jupiter and the Sun orbit around the location of their combined center of mass. I use this example because that point is actually ",
"outside of the sun itself",
", albeit very close to the surface. The Earth and the Sun both orbit a similar point, but in this case the point is inside the Sun and close to the center. So most people and applications will ignore this and say that the Earth is orbiting the Sun, which is pretty accurate. ",
"The only reason I point this out to people is because it can lead to misconceptions and questions like can a star orbit another star. No, they orbit a point between them that is determined by the ratio of their masses. Same goes for everything. ",
"For the non-pedantic answer that actually answers what you were asking see Das_mines answer."
] |
[
"That's a good point, and clearly there is significant internal motion of the universe (galaxies colliding, stars exploding etc.), but as I understand it (and I understand very little), it is very hard to describe the whole universe as \"going\" somewhere, like our galaxy is. That is, the universe is expanding, but not in any particular direction, just out. I guess this could be a function of not having reference outside the universe to base the universe's motion on."
] |
[
"why does number of protons affect chemical and physical properties of an element?"
] |
[
false
] |
How can an atom change from Nitrogen to Carbon each with completely different physical and chemical properties, by changing one particle in the atomic structure?
|
[
"The electron structure of an atom determines most of its chemical and physical properties.",
"The number of protons determines how many electrons you'll find in a neutral atom."
] |
[
"The nucleus of an atom determines the number of electrons of the atom. The electrons are found in orbits around the nucleus in the s orbital, p orbital, d orbital and f orbital, with increasing energy levels and complexity. ",
"It is the bonds that form from the electrons in these orbits along with the weight and spin characteristics of the nucleus that determine the chemical properties of the atom. ",
"Simply going from Hydrogen (1 proton, 1 electron) to helium (1 proton, 1 neutron, 2 electrons) makes a huge difference. Why? The one electron of hydrogen is very unstable and therefore reactive because the 1s orbit needs 2 electrons to be stable. That's why hydrogen only exists in nature as a stable molecule as H2. Helium has 2 electrons filling 1 s orbit and is a nonreactive and stable element. So it is the properties of these orbits that determine the properties of the atoms. The rest of the elements down the periodic table follow this fundamental principle . "
] |
[
"Typo? He has 2 protons."
] |
[
"If a drop of some liquid was extremely hot (really really hot) could dropping it in say.. a large pool of cold water - theoretically,heat up the entire pool?"
] |
[
false
] | null |
[
"It depends how hot you want the pool to get (and how big the pool). Theoretically if there was a magic substance that could be extremely hot and yet remain in the liquid phase, then you could bring any size pool from 0 degrees C to 100 degrees C from a single drop of this substance. But in practice this would be impossible because there just aren't any substances (that I am aware of) that remain in liquid (or even solid) phase above a few thousand degrees. And, depending on the size of your pool, you would want your drop of liquid well above a billion degrees. ",
": relevant ",
"youtube video",
" of a red hot nickel ball in water. "
] |
[
"Well I can't answer this for sure, but I'd venture to say it would need to be at such a high temperature that it would be plasma at that point, and disregarding the pitfalls trying to contain plasma to place it in a cold body of water, my mathematical instincts tell me that the net temperature change would be local, without any substantial change to the entire body.",
"Edit: To explain a little further, given water's high heat capacity, and that the object inserted is not a solid, therefore dissipates heat much more quickly, the net temperature change assuming brownian motion in the dimensions of the body may taper off in a logarithmic fashion. Layperson here, so somebody please step in and correct me if I'm wrong."
] |
[
"you would then also have the inconvenience of having to re-organize the rubble that is now the your hmisphere after a billion degree substance enters the atmosphere"
] |
[
"If I am malnourished and typically consume less than 800 calories on average a day, and then suddenly eat 7,000+ calories worth of food in one sitting, what negative effects could come from it?"
] |
[
false
] | null |
[
"You should rephrase the question to not make it about any individual. Note that the thread the poster linked to ",
" states what is and isn't medical advice. Not only are you asking \"what would happen to ",
" if...\", you are asking \"Why haven't I pooped it out\". So you are asking for a diagnosis, ",
" asking for the prognosis.",
"Medical advice isn't limited to \"what should I do.\" Asking \"what is happening to ",
"\" is as well. The kicker is that in your edit, you tried to say you're not soliciting medical advice, ",
"!",
"If you have a concern about your body, please consult your primary care physician."
] |
[
"You need to go see a doctor, right fucking now. Reddit's not gonna have good enough medical advice for you. Seriously. See a doctor."
] |
[
"I'd suggest getting yourself to a doctor as soon as possible. \nYou're right about the holocaust survivors dying from suddenly eating way too much food for them to handle."
] |
[
"How exactly does the immune system ward off external parasites?"
] |
[
false
] |
My curiosity was piqued by reading about mange in dogs, specifically quotes from this page about how a healthy immune system keeps mites under control: Demodectic mange most often occurs when a dog has an immature immune system, allowing the number of skin mites to increase rapidly. Source: Since mites are outside of the body and presumably too large for white blood cells or the typical immune system defense against e.g. bacteria anyway, by what mechanism exactly would it be affecting their reproduction?
|
[
"I will write this in the context of Demodex mites infecting the skin since that is your interest, but these defense mechanisms broadly apply to other lung or intestinal parasites as well. I will go over a typical barrier response in the skin and then describe how defective or immature immune system could cause mange.",
"First, a \"fun\" fact. Everyone has Demodex mites living on/in them right now. ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3884930/",
"Here is a review on the immune response against canine Demodex: ",
"https://www.ncbi.nlm.nih.gov/pubmed/24910252",
"To begin, Demodex colonizes the hair follicles and glands in the skin. It is thought that this colonization of mammals has occurred for millions of years. Normally, the host immune system tolerates the mites since they really don't harm mammals in any way. However, even tolerated organisms are detected by the immune system. In the case of Demodex, it is specifically keratinocytes in the skin that sense Demodex. The keratinocytes bear special receptors called Toll-like receptors (TLRs). There are many TLRs that detect conserved molecules present on foreign organisms like bacteria, fungi, and parasites. For Demodex, the TLRs detect chitin which is not found on mammalian cells. Though they are detected, the immune system doesn't usually respond against the Demodex. Immune responses themselves can lead to tissue damage and since the Demodex is normally on the \"outside\" of the body it is seen as harmless and ignored. ",
"Cue tissue damage. At some point of the colonization a mite might damage the epithelial barrier of the skin while living in the hair follicle or gland. Tissue damage is a great stimulator of the immune system. The damaged epithelial cells in the skin begin relaying to the immune system that they are damaged. This is done via signaling molecules called cytokines chemokines. Innate immune cells, which are some of the white blood cells, are recruited first. These include neutrophils, eosinophils, and basophils. Other cells, like mast cells, were already present in the tissues and act as surveyors against infection. Some of these cells (mast cells, eosinophils and basophils) are specialized for fighting against large external parasites. The cytokine signals produced by the epithelial cells direct the immune system to what type of organisms is causing the infection. The TLRs mentioned above are what drive the distinction. Different receptors trigger different signals. For external parasites a Type 2 inflammatory response is produced. This is the same response that causes allergies and asthma. Once recruited the immune cells perform their function as directed by the cytokines and chemokines. For mast cells, eosinophils, and basophils they essentially come in ",
"and dump packages of highly toxic compounds",
" onto the mites. These compounds are meant to kill the mites. Macrophages come by and clean up the dead stuff.",
"At the same time the innate cells are doing their job, special cells called dendritic cells are picking up bits of the mites (mostly protein) and hauling them back to the lymph nodes. In the lymph nodes, special cells called lymphocytes are activated (these are the other component of white blood cells). Specifically T cells and B cells. These cells were previously generated by the immune system and are waiting to be activated by recognizing the small bit of material the dedritic cell brought back. This is very generalized explanation on this process. Essentially what happens next is you get expansion of the T cells and B cells that recognize the mite bits. The end result that is important in this case is production of antibodies by the B cells that are specific against some part of the mite. These antibodies are dumped into the blood, diffuse into the tissue where the mites are, and bind to them causing them to be further recognized by the immune system. The antibodies can get into the tissue due to leaky blood vessels and fluid build up caused by the cytokines mentioned previously. Specifically, the antibodies in this case will largely be IgE and IgG antibodies. The IgE antibodies happen to also bind to the mast cells I mentioned previously and act as a trigger mechanism. So if a mast cell encounters a mite that has damaged the skin it will cause the mast cell to activate via the bound antibody.",
"In this way, cellular and antibody mechanisms will keep the colonization of Demodex mites in check by periodically eliminating some of the mites infesting the hair follicles and glands.",
"So now on to the defective immune system. The immune response is a complex process that involves a lot of cell types, a lot of receptors, and a lot of signaling molecules. You could imagine how loss of a specific part I described above could lead to an absent immune response against the mites. This is essentially what happens. Dogs with defective immune systems are lacking a specific part of the immune system normally used to keep the mite colonization in check. Without a strong immune response the mites are able to reproduce to much greater numbers. The large increase in mites causes more tissue damage and the disease. ",
"Say for instance the dog has a mutant TLR receptor that can't detect chitin. The keratinocytes will be less effective at sensing the mites. Or if the dog has lymphocyte deficiencies. They cannot make T and/or B cells which ultimately lead to antibody production. The dogs no longer produce antibodies against the mites which normally bind to the mites or arm mast cells to be triggered by mites. "
] |
[
"I’d love to give a short simple answer. But there really isn’t one. It’s a lot of different processes and a very long and complex answer. ",
"The best I can do is provide you a link. While it’s about itch mites and humans, it’s a good overview to what’s in play with how the body and the skin combat that type of attack. ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5553898/"
] |
[
"Extracellular parasites get marked by Immunoglobuline E which recruits and activates mast cells (these are a type of white blood cells). Mast cells bind on the IgE on the surface of the parasite and induce inflammatory response.\nAll this is mediated by T helper 2 cells."
] |
[
"How do lungs clean themselves?"
] |
[
false
] | null |
[
"Most of the larger particles are caught by nasal hairs, then the smaller particles that evade the hair are caught in the mucus produced in the respiratory passages (up till bronchi). Further ahead in the respiratory bronchioles and alveoli (the part where actual gaseous exchange takes place) there are no mucus producing cells, and the even more smaller particles such as bacteria that do manage to reach there are eaten up by alveolar macrophages, which are basically your germ eating cells."
] |
[
"Adding to this, bronchi and bronchioles have smaller hair-like structures called cilia which moves the mucus up and out the airway in a process called mucociliary clearance."
] |
[
"There's mucociliary clearance which are tiny ciliary cells (they look like beating hair strands) that help move larger particles up to the larynx where they can be swallowed and macrophages in the far reaches of the lungs to get the small debris that makes it that far."
] |
[
"For an extinction event-sized meteorite (e.g. the one that caused the Chicxulub crater, ~10km), how long would the object be visible in the sky before impact?"
] |
[
false
] | null |
[
"It depends a bit on the composition of the asteroid (it's only a \"meteorite\" after it's survived landing on Earth). Some materials are more reflective than others. We call the proportion of light reflected away the ",
". Earth's albedo is about 0.3, for example. Icy objects like comets have higher albedos, while rocky ones have lower albedos. Asteroids typically have albedos ~0.1, though it varies. ",
"It also depends on where the asteroid is coming from relative to the Earth-Sun system. If they are crossing Earth's orbit from within Earth's orbit going outside, there may not be much of its lit face towards us (like a crescent, or even new, moon). ",
"Lastly, it's going to depend on its shape and how much surface area is visible, and how it's rotating. If it's cigar shaped and we're looking down the long axis, we'll see relatively little reflected light. If it's oriented or rotating so that we can see the long face, we'll see more. If it's closer to spherical, of course, the orientation doesn't matter so much.",
"There's a chart ",
"here",
" of absolute magnitudes of different sizes of asteroids assuming a range of albedos from 0.25-0.05. Magnitudes are a logarithmic system, where 5 magnitudes is a factor of 100 in brightness. Higher magnitudes are fainter. The usually accepted limit of human vision in a dark sky is 6 magnitudes (in a city, it's much worse - the brightest stars are around magnitude 0, and in the middle of a city like NYC, I don't know if even they are visible). Using that chart, a 10km object at phase angle 0 and at 1 AU from both the Sun and the Earth is at magnitude 13, well below the threshhold of human vision (not hard for even a small telescope, though). To be detectable at even a dark site by eye, it needs to be >7 magnitudes brighter, which is about a factor of 1000. Since brightness goes as 1/d",
" if we keep the distance between it and the sun the same, that means it needs to be ~30 times closer to Earth than 1 AU, which is about 5 million km. To start being really noticeable to people in suburbs or people who weren't really looking for it, it would take until it was about 1 million km away (which is when, ",
", you might start to notice a new star in a constellation). Assuming a relative Earth/object velocity of 25 km/s (a typical meteor speed, can't be too much more than a factor of 2-3 different), that would give you a time of about 11 hours from when it was getting noticeable to a lot of people, or a bit over 2 days from when it was at the threshhold of human vision. ",
"Again, I want to stress how much that could vary with viewing angle of the asteroid, the angle at which the asteroid approaches Earth relative to the Sun, the particular asteroid's speed relative to the Earth, and how reflective that particular asteroid is. It could easily not become very visible until a couple hours before impact, or it could be noticeable in the sky for a couple of days.",
"This exercise demonstrates the importance of early detection systems with telescopes, so we can detect Near Earth Objects and map their orbits decades before a potential collision with Earth. About 95% of NEOs have been found, going by the rate of new discoveries. Orbits can change, though, as they interact with the Earth-Moon system or other planets, and new objects can be launched towards Earth from Jupiter and it's moons or from the Kuiper belt. Comets, in particular, can change their orbit with every pass as ice evaporates as it passes the sun and makes little jet engines of outgassing. If you want to do anything about a collision, like have a ",
"tow truck",
" or engineering its orbit by ",
"changing the albedo",
", it's vital to have telescopes dedicated to early detection and orbit mapping."
] |
[
"There, the question isn't \"is it detectable?\", it's \"is anyone actually pointed at it and going to recognize it?\". Something 10 km in size is going to be visible to us with a variety of ground based telescopes, from very far away (anywhere inside of the asteroid belt, certainly) without much difficulty. The problem then is that the sky is big and most astronomers imaging the sky at any given time aren't ",
" for asteroids. Some people are, with smaller telescopes dedicated to the task. It's a question of how automated the detections can get and how much human involvement is needed to notice something moving against the background of stars, make the necessary astrometric measurements, and figure out if it's a possible future danger. It's more likely than not that if a new one was imaged several times by someone who wasn't looking for it, it would go unreported. And imaging it more than once is critical; with just 1 image and no measured proper motion, there's no way to tell what it is: a dwarf nova, classical nova, supernova if it's near another galaxy, an AGN flare, or any other of several possibilities that are probably each more likely than a new NEO. Someone needs to be thinking about finding them in the data they take, which really means a permanent project to do it (which exist)."
] |
[
"Thank you! Great response. It is scary to think of the consequences of this kind of event even 50 years ago. With such a small window of notice, I can only imagine the chaos that would ensue after people realized what they were looking at in the sky. "
] |
[
"What units are color charges measured in?"
] |
[
false
] |
Also, what is the formula for the force exerted between charges in the strong force, assuming it's small enough to write type in a comment?
|
[
"The color charge of the strong force is quantized, and you generally work in units where the color charge of each particle is 1. Unlike in electromagnetism (gravity), you never have macroscopic charges or currents (masses) where you might want to define a unit where the elementary charge is not equal to 1. ",
"At low energies, the strong force between two particles actually increases with distance F=-k d. That means that the potential energy increases as particles move apart. If you keep pushing them apart, they eventually get enough energy to form a particle-antiparticle pair that neutralizes the color charge of the two particles. Therefore, the strong force effectively acts only over short distances (otherwise it basically neutralizes itself through particle creation), and exhibits confinement which prevents particles with net color from existing on their own."
] |
[
"So color charge is unitless?",
"I know that weak isospin can be added to electric charge to get weak hypercharge so I assumed those are measured in coulombs. Is this why strong and electroweak haven't been unified yet?"
] |
[
"In calculations where you might add isospin to electric charge, I very much doubt that you ever use charge in Coulombs - instead you would use units in which the elementary electrical charge is 1. I wouldn't say that color charge is unitless like a true dimensionless number, it's just that there are no calculations where you might wish to invent a unit other than the \"natural\" one where the charge is 1. My statement had nothing to do with unification of forces."
] |
[
"When two particles get too close together why don't they launch themselves due to their gravity?"
] |
[
false
] | null |
[
"Your example gif violates conservation of energy. Very likely, your simulation is running into problems due to the diverging forces as the particles approach one another.",
"In reality, if two particles with only an attractive gravitational force were to go straight into one another, they would become faster as they approached one another due to the increasing force of attraction. Their velocities would become ",
" (which any numerical simulation will struggle with) as they passed through one another. They would then slow down as they moved away from one another, such that the video would look identical going forwards or backwards.",
"In reality, there are other forces at work, e.g., the electromagnetic force."
] |
[
"How would I fix such a thing then?"
] |
[
"It would depend what you are trying to simulate. You could model some type of elastic or inelastic collision once the particles come within a certain distance of one another."
] |
[
"Why do we not see deadly mutations of 'standard' illnesses like the flu despite them spreading and infecting for decades?"
] |
[
false
] |
This is written like it's coming from an anti-vaxxer or Covid denialist but I assure you that I am asking this in good faith, lol.
|
[
"We do. The flu has been around so long though that most of us acquire immunity from our mothers to specific strains and have partial immunity from that to help fight against other variants. There are now many, many strains of the flu, some more dangerous than others. An example; ",
"\"The 1918 influenza pandemic was the most severe pandemic in recent history. It was caused by an H1N1 virus with genes of avian origin. Although there is not universal consensus regarding where the virus originated, it spread worldwide during 1918-1919. In the United States, it was first identified in military personnel in spring 1918. It is estimated that about 500 million people or one-third of the world’s population became infected with this virus. The number of deaths was estimated to be at least 50 million worldwide with about 675,000 occurring in the United States.\"",
"https://www.cdc.gov/flu/pandemic-resources/1918-pandemic-h1n1.html",
"Many strains are fairly weak against an immune system that even has partial immunity, but when one pops up and has everything just right it can do some serious damage. Even today, although not as common, people can be hospitalized and/or die from the flu",
"Edit: honestly what I found most shocking about that is how much the world population has increased in 100 years..."
] |
[
"\"We do.\" is definitely the answer and it makes me sad that this isn't more common knowledge.",
"This is precisely why you need to get a different flu shot every year, because it is changing constantly.",
"The big difference between it and COVID is that COVID started out more dangerous, so its mutations are also more dangerous.",
"We see fewer mutations in some of the really, really deadly (but rarer diseases) like Ebola simply because they are so deadly, they kill their host off too fast to spread far and wide.",
"COVID is so dangerous in part because it has hit this sweet spot of being crazy contagious and not instantly killing all of its hosts, giving it lots of chances to spread, and lots of chances to mutate."
] |
[
"Also Ebola is spread by bodily fluids, much easier to barrier than an airborne or respiratory virus. Imagine if Ebola was airborne.."
] |
[
"Why does the movement of carbon molecules in carbonated liquid cause an increase in pressure?"
] |
[
false
] |
[deleted]
|
[
"The carbon dioxide is a little bit stuck in the fluid and can only come out very slowly. Shaking allows the gas to come out much much faster. With or without shaking the pressure will eventually reach the same level in the container, the only difference is speed."
] |
[
"Thank you!"
] |
[
"Pressure is often defined as the collisions of molecules against the walls of a closed container. ",
"With that being said, when a container is closed and the molecules are shaken up, kinetic energy increases, and the number of collisions to the walls in the closed container become more frequent, therefore increasing the pressure.",
"When a can is open, the molecules are given an opportunity to move down the pressure gradient (as they most always will) out of the can."
] |
[
"Do \"dihydrogen monoxide\" and \"dihydrogen oxide\" refer to the same thing?"
] |
[
false
] |
[deleted]
|
[
"The two names make different assumptions about the nature of the chemical bonds in water. If we assume that water has covalent bonds, the naming rules say that its name should be dihydrogen monoxide. If we, instead, treat it as an ionic compound, then its name would be (di)hydrogen oxide. In the latter case, the \"di\" is superfluous, but not necessarily wrong."
] |
[
"Water has covalent bonds."
] |
[
"I guess the natural follow up from the layman is, \"Does water have covalent bonds, or is it an ionic compound? (Or is science just not sure)\"",
"P.S. If this really should be an ELI5, I can ask it there. "
] |
[
"How fast do shooting stars go?"
] |
[
false
] | null |
[
"Typically tens of kilometers per second. The minimum is 11 km/s (Earth's escape velocity) and while there is no hard maximum something faster than ~70 km/s is extremely uncommon."
] |
[
"The speed of the debris burning up in the atmosphere would be unique depending on the event that caused it to move in the first place. I wonder what the speed restrictions on solid matter moving through space are?"
] |
[
"Not actually stars flying around, they are typically small objects burning up in our atmosphere which appear like stars against a backdrop of similar sized twinkles. The distance between the stars you see in the sky is phenomenal and more so the distance from our planet to the stars you see is mind boggling, so to actually imagine something the size of a sun flying across those unimaginable distances is absolutely implausible."
] |
[
"How does human brain differentiate timbres of sounds?"
] |
[
false
] |
Consider a speaker, all they do is produce waves that correspond to whatever you are listening to. Our brain is the thing that decomposes this complex wave into different parts and enable us to percieve multiple timbres. Do we know how this works? I guess we have a biological Fourier transformator inside ourselves.
|
[
"The cochlea is a long bone in our inner ear. Different sections of the cochlea respond to different sound frequencies. These are then interpreted by the auditory nerve. ",
"So, in essence, you’re right as one could consider the cochlea a physical implementation of a frequency transform."
] |
[
"Yes, we know how it works. Sound is vibrations in the air. The vibrations in the air hit your ear drum, also called the tympanic membrane. The tympanic membrane is like a drum petal, when sound vibrations hit the side on your ear canal, the tympanic membrane kicks the cochlea causing it to vibrate to the frequency of the sound wave. (So we've converted sound into mechanical movement.) The cochlea vibrates like a long thin, flat piece of metal would. It's thicker on the front so that part picks up low vibrations, and thinner at the end for high vibrating. It's just rolled up like a snail to fit in your head better. Little cilia run underneath the cochlea, so when it raises and lowers in vibration, neurotransmitters are released. Depending on where along the cochlea those neurotransmitters release is how your brain records its pitch. Which can often be multiple pitches at once. The frequency of the vibration of the cochlea(also the air) determines pitch. Then your brain decomposes the patterns in the sound to seperate them into instruments so that it isn't just a blaze of complex noise."
] |
[
"Didn't know that the location of neurotransmitters affected the percieved pitch. Thank you."
] |
[
"If hydrogen cars took off, what would the implications be on dry environments?"
] |
[
false
] |
Suppose everyone in arizona drove hydrogen cars....all of those cars are releasing vapor. Would all this vapor condense and start creating abnormal amounts of rain for the area? If so, would it not affect the ecosystem that is specifically adapted for dry climates?
|
[
"The internal combustion engine widely used in most vehicles already produces water vapour as part of combustion."
] |
[
"hydrogen has to come from somewhere, and typically water is used in that process. that water has to be harvested--most likely near ground level*, same level as the hydrogen car exhaust. it's a rather closed system. ",
"the big problem i personally see with hydrogen cars is the storage. hydrogen, like helium (which i use almost on a daily basis), cannot be liquefied at room temperature. the best you can do is compressed gas cylinders, which is significantly less energy dense. perfect sealing is also difficult with the small molecule size. ",
"edit: typo."
] |
[
"Yes, but would hydrogen not produce more vapor than a combustion? "
] |
[
"Do dogs get any benefit from fans?"
] |
[
false
] |
I've always been told that dogs do not have sweat glands. It is also my understanding that fans do not cool you down, but remove perspiration and that is what gives fans a cooling effect. None or all of this may be true, just wondering if pointing a fan at my dog while the A/C is out is doing her any favors.
|
[
"I also want to add that you can simulate the effect of sweating for your dog by periodically spraying a fine mist of water on its fur.",
"(Also, dogs do have sweat glands, but only in the nose and paw pads. Humans, on the other hand, have sweat glands all over their body. Thus, sweating is a primary mechanism of temperature regulation for humans, but not so for dogs. It's not that dogs don't sweat at all, it's just that they don't sweat enough. Panting and blood vessel dilation are primary mechanisms for a dog.)"
] |
[
"It's true that they don't have sweat glands, but when they're hot, the air around their fur is also a little warmer. A fan would blow the hot air away and cool them off a bit, although not to the same extent as if they had been sweating. ",
"Think about how a fan feels cooler to you even if you aren't sweating"
] |
[
"That is a great idea, thank you very much! I appreciate the information on dog temperature regulation, I'm gonna sound so smart next time this comes up."
] |
[
"Why neuroimaging is not used for mental disorder diagnosis?"
] |
[
false
] |
Why do we still use questionnaires rather than brain imaging to detect mental disorders? Questionnaires seem likely to be affected by biases one has, whereas brain imaging would be more objective measure of the disorder, as I understand. For example in ADHD, as I understand, there are well-documentated differences in the prefrontal cortex, for which diagnosis could be made. I imagine that with neuroimaging we could help people before their life starts to fall apart before they have to come to the realization that something is truly wrong. We could also decrease misdiagnosis. Whenever I have filled a questionnaire, often recent events would create a huge variety in how I would respond to a question. Sometimes I would have extremely positive outlook, sometimes not. Sometimes the question can be interpreted in multiple ways, and then you have to figure which answer to answer. It seems to me that undiagnosed or misdiagnosed mental disorders impact one's life much more than likely costs of the better precision of diagnosis. So why neuroimaging is not the first step in disorder diagnosis? Is it less reliable than I believe it is? Is it expensive, if so, how much more expensive is it? Is it still unproven?
|
[
"There isn't always a one to one relationship between brain and behaviour. It's a lot messier than it seems. Yes, a certain set of behaviours may present a characteristic pattern of brain activity that may be significantly different from 'normal' activity. For example, there have been reports about hyperactivity of the basolateral amygdala in people with anxiety disorders compared to the general population. However, dysregulation within the amygdala have also been related to numerous other psychological disorders including OCD, PTSD, borderline personality disorder, depression, etc. In a sense, at this stage, it's not entirely a precise method as it doesn't really tell us much until the individual (or relatives) reports that they are indeed experiencing the specific symptoms of the hypothesized disorder. That is, the psychological and behavioural manifestations to the individual is more informative and significant when diagnosing and treating mental disorders, beyond brain activity/anatomy representations.",
"I understand that self-report questionnaires will always have some bias involved. Whether it's about how it is interpreted, the current mood of the individual during reporting, or overall how they perceive their own experience. That's why heavy reliance on self-reports would be a mistake on the practitioners end. Other assessments are often involved if they are considered relevant including interviewing and cognitive tasks which tap into constructs such as concentration, processing speed, language, and reasoning capabilities."
] |
[
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3052989/",
"2011: \"Unlike many neurological disorders, psychiatric disorders do not cause changes visible to the naked eye in the neuroimaging study of the individual patient.\"",
"I read an article that compared advancements in neuroimaging to advancements in satellite imaging. Decades ago, we could use satellite images to make maps, but the images weren't good enough to, say, read a license plate from space. Until neuroimaging gets to a higher level of detail, we don't even know what we're looking for. The articles I found indicate that neuroimaging is currently used to rule out things like brain damage and tumors, but cannot visualize anxiety or depression, yet."
] |
[
"Neuroimaging is being used pretty intensively to ",
" psychiatric disorders, and is ",
"beginning",
" to show ",
"functional",
" and structural ",
"changes",
" between healthy and affected individuals. However, at this point results across studies are ",
"not consistent enough",
" to justify using this expensive technique ($500-$2600 per scan, due to the delightful vagaries of the American healthcare system), which is often distressing for the person, as a diagnostic tool. ",
"The machines themselves are also very expensive to purchase: the newer ones that have sufficiently high resolution to pick up changes in psychiatric disorders (especially in the early stages) can cost $500,000 to $3 million depending on resolution, so very few hospitals have one. Most hospitals have lower-resolution machines that are totally sufficient for their normal needs, but not adequate as diagnostic equipment for psychiatric disorders."
] |
[
"How does science funding work? How do scientists get money for their studies? Can you briefly explain please?"
] |
[
false
] |
[deleted]
|
[
"This is an interesting question, and has a lot of potential answers. The answer to your question, starting with the most common:",
"1) National governments realize that scientific (and by extension) technological advancement is a driving force in the economy (and by extension) the general wellbeing of the citizens. Thus agencies like the US National Science Foundation (NSF) awards funding to research proposals. Depending on the area of research about 10-15% of proposals are funded.",
"2) The military is always looking for a better way to kill the bad guy and keep the good guys safe. Modern warfare historians will tell you that the army with the most advanced technology wins the war. Thus DARPA, Air Force Labs, Office of Naval Research, Defense Intel Agency, and countless other military agencies all offer LOTS of money to researchers who can convince then that their research will (i) kill the bad guy and/or (ii) keep the good guys safe.",
"3) National labs have researchers on staff working on fundamental and applied research questions. These scientists are typically not affiliated with a university and do not have to write grants, they just get paid a salary by the government to do their research.",
"4) Large companies especially like to perform research in order to develop new products. Because most of the \"in house\" research is product oriented, some of the more theoretical or foundational research is done in collaboration with university researchers. ",
"5) Small companies, especially in the technology industry, are funded by venture capital firms. These venture capital investments are typically used for R&D work in the first few years while the major products are being refined. Lots of researchers start spin off companies with their research in this way.",
"6) Universities frequently have a collection of money that is used to support new faculty members who have yet earned their own grant money, and for small projects. ",
"I think this about covers all the bases, can anyone think of any that I missed?"
] |
[
"I can assure you that many grants are applied for on national labs. They are typically owned by the Department of Energy but actually run by a university and/or private company (Stony Brook runs Brookhaven, UChicago runs Argonne and Fermi, etc). They get paid a salary but the funds for the research come from the DoE, NIH, or whoever else. It is comparable to how research is funded at universities.",
"I've had two internships on national labs, and my mom is the person you go to if you need help applying for a grant at BNL."
] |
[
"Researchers submit grant proposals to some of the different agencies that tyrial pointed out.",
"I would like to point out that independent researchers can also apply for grants and get them."
] |
[
"How do we really know what our own galaxy looks like?"
] |
[
false
] |
So?
|
[
"We can use wavelengths other than visible to peer through gas clouds and the like and then find distances using ",
" parallax and other techniques to create density maps of the stars in our galaxy based on these we can make a map of what our galaxy looks like",
"Edit: ",
"/u/OverlordQuasar",
" pointed out redshift is useless this close to use and parallax is a much more effective means of measurement"
] |
[
"In our galaxy, redshift is next to useless, only helpful in a few cases. Parallax is much more useful."
] |
[
"I'm sorry. I will change that, I am not well versed in measuring astronomical distance"
] |
[
"If a brown dwarf is as hot as a cup of tea, what would prevent us from going right up to it and scooping out a bit of \"star stuff\"?"
] |
[
false
] |
Relevant link:
|
[
"I'm going to assume you have some way of getting to your brown dwarf and back. There are two obvious approaches for collecting a sample from something like a brown dwarf. The first is to treat it like landing on a planet: fly down, hover, collect your sample and fly back up. The problem is that stars have very, very high surface gravity, so you'd need extremely powerful rockets and lots of fuel to pull this off. I don't know anything about brown dwarfs in particular, but ",
"this paper",
" suggests they have surface gravity on the order of 30 g's.",
"The other option is to do a hyperbolic fly-by and skim your sample off the star's atmosphere. In principle this doesn't require any extra fuel because the star's gravity does all the work for you. The problem with this idea is that at apoapsis, you'll necessarily be traveling at or above the star's escape velocity. Assume a surface gravity of 30g and the same radius as Jupiter. Then the escape velocity is about 300 kilometers per second. To a first approximation, air resistance is proportional to the square of your velocity, so the probe would have to withstand incredibly high temperatures from frictional heating."
] |
[
"That makes no sense... Assuming you could get there and back it would certainly be possible to fly a satellite low enough to grab some of the material... For example the Genesis spacecraft sat in orbit and collected the solar wind for a year (",
"http://en.wikipedia.org/wiki/Genesis_%28spacecraft%29",
"). I'm imagining a similar spacecraft on maybe a hyperbolic orbit going near said star and then using a rocket/fuel to get away from the gravity well. None of it is fundamentally impossible it is just incredibly expensive. And with the distance we would all be dead when the results came back..."
] |
[
"Thanks for the great answer. Not just yours, but everyone else’s too. I guess I didn’t realize that there wasn’t a clear boundary between what is star and what isn’t star… that a star is just a big ball of gas that gets denser as you get deeper in. I mean, conceptually I knew that stars are big balls of gas… but I didn’t think through what that meant from a practical standpoint.",
"What might have misled me are all the pictures of our Sun, which from what I can tell looks like a big orange ball of fire. It’s appears that there’s a surface to this ball of fire, and that one of the main things preventing me from standing on the surface of our sun or any other star (travel time and gravitational pull not withstanding) was the extreme temperature. So when I read that there are stars out there like this brown dwarf that are not very hot, a part of me thought, oh… so maybe I can walk on this thing without getting incinerated?"
] |
[
"When power-cycling a device, does keeping it off for 30 seconds actually make a difference?"
] |
[
false
] |
I've always been told to reset devices like modems and routers by switching off and waiting 30 seconds before switching back on. Does it really matter? Does something actually happen during those 30 seconds?
|
[
"Rarely, it can. It allows time for capacitors to discharge and for SRAM to lose its contents. These days, pretty much all devices have good power-on reset circuits (usually built into the microcontrollers or processor supervisors) so no more than a second or two is necessary."
] |
[
"It also gives the server on the other end time to notice that the connection has been broken. Whether or not this is necessary depends on how the server is programmed and what caused the disconnect."
] |
[
"This is the explanation that I have always been given from an ISP when power cycling the hardware. If I'm on the phone with them at the time, they will tell me when it's no longer visible at the other end, which can sometimes be a few minutes, before powering back up."
] |
[
"How does gravity slow time?"
] |
[
false
] | null |
[
"This explanation bothers me. It doesn't actually explain anything.",
"I know it is a standard physics introduction to GR explanation. It is what is taught. It is, however, junk.",
"Special Relativity Twin Paradox - fine.",
"Then we pack the vague stuff into acceleration at the end and pretend we've understood something.",
"So... The returning twin has barely aged because 'acceleration', while the at home twin has aged 8 years.",
"What if the round trip was sixteen years (by stay at home clock)? The acceleration phases would be the same - so where does the 8 year difference (from the previous thought experiment) come from?",
"What if the trip out was 30,000 years - 60,000 round trip (by home clock)? It still takes the two identical sets of acceleration/deceleration (start, mid point stop and start back, end). How can the same acceleration/deceleration cycle on each of these trips account for the different ages of the twins (8, 16, 60,000 years)?",
"The true problem has been swept under the carpet. There is no genuine explanation or understanding being provided. "
] |
[
"There are a number of ways to think about this, but here's one. This is basically a variant of the twin paradox. Suppose there are two twins and one gets in a spaceship and travels to Alpha Centauri at very close to the speed of light. The other stays home. Due to time dilation, the one that stays home will have normally aged ~8 years whereas the one that went to Alpha Centauri will have hardly aged at all. This is just your standard special relativity time dilation.",
"But remember that everything is relative, so according to the twin in the spaceship, the twin on Earth was the one that was traveling close to the speed of light. In the reference frame of the twin in the spaceship, he was standing still! So he should have aged ~8 years and the twin on Earth should hardly have aged at all. ",
"Why does this not happen? Well, the twin in the spaceship had to turn around when he got to Alpha Centauri. When he does this, he is subjected to enormous accelerations. These accelerations basically forced the time of the twin on Earth to \"catch up\" relative to the twin on the spaceship. In other words, just prior to turning around, the twin on the spaceship would have thought that the twin on the Earth had hardly aged, but in order for the twin on Earth to have aged ~8 years by the time he got back, all this time had to \"catch up\" during the acceleration phase. So the twin on the spaceship would notice that time was moving much more rapidly for the Earth twin during this acceleration phase. ",
"But according to the general theory of relativity, you cannot distinguish between an acceleration and a gravitational field. So, for all the twin in the spaceship knew, someone just turned on a really strong gravitational field. But if time for the Earth twin moved more quickly during the acceleration phase, then time for the Earth twin would also have to move more quickly if he was outside of the gravitational field. Hence, time must move more slowly for someone inside a gravitational field."
] |
[
"This is always how I've seen it. Basically we're always moving at the speed of light (c) through space time. All we can do is change our vector. i.e. move faster through space and slower through time. This is also why it's impossible to move faster than light. Also, the vector is relative to everyone else's. There's no absolute reference. "
] |
[
"How does my TV know which pixel to light up?"
] |
[
false
] |
It seems the internet is filled with explanations as to how a pixel works but no explanation regarding how the TV knows which to light up. I imagine new TVs have an easier explanation than the old cathode tube TVs. I would like an explanation of both please. Edit: Thanks for the replies...regarding the CRT, how can two magnets control 100,000 of electron at a time. If you have an animation i think that would be very helpful.
|
[
"These explanations are simplified, but should help.",
"A CRT has an electron gun in the back. Somewhere between the electron gun and the screen, there are two electromagnets. The electromagnets should be perpendicular to each other. Since the electrons that are fired at the screen are charged and moving, it will be affected by magnetic fields. By altering the strength of the two magnetic fields, you can steer the electrons to the correct spot on the screen.",
"For an LCD/LED TV, there's usually an active-matrix style (formerly, passive-matrix) addressing scheme. The TV has a certain resolution - and hence, a certain number of rows and columns. Each pixel exists at the intersection of a row and a column. You can picture these as a grid where the rows are on top and the columns are on the bottom, with the pixels in between. In order to have current flow, you need an electrical path - so to have current flow through a particular pixel, its row has to be activated, and its column has to be activated simultaneously. Only one row and one column can be on at a time, corresponding to a single pixel. The other pixels in that row don't have active columns, and can't turn on. The other pixels in that column don't have active rows, and also can't turn on."
] |
[
"Cathodes ray tubes use either precisely controlled magnets or electrostatic plates to deflect electrons shot out of a gun to precisely the right location on the screen, where each electron excites a phosphor on the screen, which then emits visible light. ",
"Projection-based displays use optical lens to focus light to the right spot on a white screen.",
"Flat-panel screens (LCD, LED, plasma) have essentially a grid of pixels built into the screen and hardwired. Note that each pixel does not have its own wire. Rather, each row (or column) of pixels has its own wire, and a row's worth of information is sent in sequence through a single wire across the whole row, and then made to excite the right pixel through proper timing. But ignoring this complication, you can think of each pixel in a flat-panel screen as connected to its own wire supplying it information."
] |
[
"When an image is recorded, it is broken down into information for a certain resolution. It basically includes what each pixel of a tv will need to display (red/green/blue of various shades) to reproduce each frame. This happens several times per second (24 frames per second for film). This information is then codefied and sent to your tv, where it is decoded and reproduced by your set. Think of it as a very quick slideshow.",
"If you took a photo and laid a grid over it you'll divide it into several squares. Copy each one of these squares and arrange them properly on a blank piece of paper, and you'll have a copy of the image. Tvs and recording devices do the same thing, but with much smaller squares."
] |
[
"Do gases have surface tension?"
] |
[
false
] |
For example there are two gases in a container and one of them is heavier/more dense and will therefore collect on the ground, is there some kind of surface tension where the gases meet? If yes does this have any relevance?
|
[
"Not really, and spontaneous stratification of gases is not as common as you might think. At least, not at normal gravity.",
"Essentially, if it's a gas, it's doesn't have surface tension. Surface tension derives from the persistent attractive forces between molecules. Gases are defined by their complete lack of intermolecular forces, at least in the ideal case. Even under non-ideal conditions, the attractive forces present are not long-lived, and wouldn't give rise to anything resembling surface tension.",
"In your example, if you did have two truly stratified gases, the only barrier to them mixing is the need to lift the heavier gas to a higher elevation to make room for the lighter gas. "
] |
[
"I think this answers it. Thank you. "
] |
[
"To continue off of this, I'm fairly certain that even in stratified gasses there is not a true \"phase separation\" in the same sense you would observe in a liquid. ",
"Because the intermolecular forces in a gas are weak, thermal energy should be more than enough to allow for diffusion between the two gases. Even if one gas is relatively more concentrated near the bottom, they will not remain completely separated. The rapid elimination of any sort of phase boundary would make it difficult to actually create an interface from which to observe a surface tension."
] |
[
"How do we know how long Jupiter's storm has been going?"
] |
[
false
] | null |
[
"We don't really, we just know for sure that it's been observed since 1830. There are observations of a spot from the 17th and 18th centuries but those may have been a separate storm, since there's a gap of about 100 years between those observations and what we know to be the modern great red spot. If it's the same storm it's been going for more than 300 years! If it's not, it's been about 190."
] |
[
"We actually don't know.",
"If you go back in the historical observation record, the Great Red Spot was first observed in 1685 by Cassini, then after the late 1600s it seemed to just disappear for a century or two as the entire latitude band clouded over - literally no observations of it were made for 175 years, in spite of plenty of telescopes that could easily have seen it. It was only first re-observed in 1869 by Joseph Gledhill, at the time referred to as \"Gledhill's Ellipse\". Reference from 1898 ",
"here",
". (I'm yet to see any references that actually verify the earlier 1830 re-discovery date that's sometimes claimed, and the original source material linked above actually contradicts that.)",
"Point being, it could have just clouded over for almost two centuries...or maybe it did disappear entirely, and the potential vorticity gradient at that latitude that just makes a giant vortex want to form there."
] |
[
"Is it because Galileo saw the storm",
"There's no indication that Galileo ever observed the Great Red Spot when he was observing in the early 1600's, and it's very likely his telescope wasn't actually good enough to see it. It wasn't until some 80 years later that Giovanni Cassini recorded the first observation of the Great Red Spot in 1685."
] |
[
"Was the Sahara ever underwater?"
] |
[
false
] |
Was what we now call Sahara underwater/part of an ancient sea/ocean?
|
[
"Yes and no, but ",
". The Sahara is a massive region and parts of it have not always been on the same continent. It is roughly composed of the ",
"West African Craton",
" and the ",
"Saharan Metacraton",
" along with smaller later uplift and convergence zones such as the ",
"Atlas Mountains",
" and the ",
"Mountains of the Eastern Desert",
". These smaller uplift regions at the edges of the African plate are relatively recent and are among the most complex systems on the planet. They contain a mishmash of oceanic crust remnants from the ",
"Tethys Ocean",
", volcanic formations and a host of deformed strata from various origins. The main part of the bedrock of the Sahara consists of the two cratons. The cratons are very old very stable parts of the lithosphere and have not been under any form of ocean possibly since their differentiation from oceanic crust at the start of plate tectonics. The West African craton came together some 2Ga ago (2 billion years). The Saharan Metacraton is even older. The Saharan Metacraton may have been partly and temporarily covered by the ",
"Pharusian Ocean",
" some 700Ma ago, although most certainly most of that ocean will have consisted of oceanic crust created during rifting. So while yes, you can find ancient sea/ocean floors in the Sahara, nearly all of the Sahara consists of stable continental crust and volcanic formations.",
"If we include inland seas and lakes the story gets considerably more complicated. The Sahara's climate has varied greatly over the course of geological time. A detailed answer is impossible (it would fill several volumes). Yet very recently geologically speaking the Sahara was indeed much wetter than it is today, during the ",
"African Humid Period",
" between 16,000 and 6,000 years ago, see ",
"this map",
". During that time vast areas of the Sahara were submerged beneath the ",
"Mega Chad",
" paleolake which reached all the way to the ",
"Bodele Depression",
". Additionally large lakes or lake existed in what are today the Algerian-Tunisian chotss Melrhrir, Gharsa, Djerid, and Fejej (west to east). Whether the Qattara Depression was flooded at that time is unknown but given the literature available to me it does not seem likely. The river Nile also seems to have created mega lakes in the region earlier during the Pleistocene (see ",
"here",
")."
] |
[
"Ah a very interesting case! Geologically Egypt is a very versatile country. Within its borders the rocks vary greatly in age containing some of the newest formations in the Nile Valley and Delta which are sometimes mere thousands of years old as well as some of the oldest formations in the Tibesti and Eastern mountains dating back to the Precambrian many hundreds of millions of years to even billions of years ago.",
"I looked up the coordinates of the Wadi El Hitan (29° 20′ 0″ N, 30° 11′ 0″ E) and it is part of the ",
"Qasr el Sagha formation",
" dating back to the Eocene. You can find it on the most detailed geological map of Egypt I could find by looking west of Faiyum, east of 30 degrees east, marked as the \"Te\" formation. ",
"See here",
". This part of the region was under water some 56 to 33.9 million years ago and was later uplifted.",
"Egypt in general forms the edge of the Saharan Metacraton. ",
"See this map",
". This can be seen most clearly on ",
"this map of Egypt",
" (simplified for readability). Generally everything south-west of the line Siwa-Aswan is part of the Craton and has been stable for exceedingly long periods. To the north and east of this line things get considerably more interesting. Although some areas on the craton are still being covered by newer sediments. Namely wind blown sediments (the Great Sand Sea as well as many smaller dunes), a large portion of which were blown in from the Qattara Depression. The region along the Red Sea coast dates to the Precambrian and the region to the north of the Siwa-Aswan line are generally Eocene and Miocene formations.",
"So basically everything north-east of the Siwa-Aswan line has at one point been ocean floor as long as it is not part of the Red Sea-Sinai mountain ranges."
] |
[
"Thank you for the extensive answer! I've been told about Wadi El Hitan in Egypt which apparently contains a lot of (early) whale fossils. Would that mean that particular area was underwater?"
] |
[
"Does anyone know how solar panels handle applied pressure?"
] |
[
false
] |
I'm working on an underwater glider and am researching various types of solar panels as a potential option for power. One of my concerns is with semi-flexible solar panels. I'm having a hard time finding data on whether those solar panels can handle pressure up to 300 meters below sea level. Thanks in advance for any help/answers!
|
[
"Your best bet is to design the panels to be inside a transparent hull. Also, there is very little light below 200m, so solar panels would be mostly worthless. May be even higher depending on the absorption spectra of water and the spectra used by the solar cells. "
] |
[
"This is the idea."
] |
[
"My best guess is that isotropic pressure would not have a big effect on the optical properties. You might get interconnect failure due to strain on the vessel."
] |
[
"How fast could a rock planet spin before centrifugal force started doing strange things to it?"
] |
[
false
] |
Assuming similar mass and composition to Earth. Edit: strange things like becoming noticeably oblate, or becoming unstable. I assume if a rock planet was spinning fast enough if would fling itself apart. Edit 2: Maybe a better question: what would happen to the Earth if its rotation was gradually sped up.
|
[
"Well, as you might know, centrifugal force is already acting upon our own Earth. It causes the earth to 'flatten', causing more mass to be prevalent around the equator. In the study of the Earth's gravity field (or any planet's gravity field, for that matter) a first approximation of this gravity field would be a 3D sphere. Where the intensity of the gravitational pull decreases as the radius of this sphere increases. However, in real life we notice that due to the flattening of the earth (known as the J2 effect, extremely detailed explanation of one of the representations of the Earth's gravity field ",
"here.",
" ) the mass density is larger around the equator, distorting the gravity field. Please note that the gravity field is also disturbed by other things, like mountains, large bodies of water etc.",
"This effect is very important in spaceflight. When a satellite you're designing is supposed to go over a certain point close to the equator, it will receive an extra acceleration in the north direction is it is approaching the equator from the southern pole. Logically, it would also receive a southward acceleration when the satellite has passed the equator.",
"You can imagine that when a celestial body that has a large enough mass to form an approximately spherical body, and you would increase its angular velocity, the planet would flatten out even more, until the planet is turning at such a large angular velocity that gravity and molecular attractional forces cannot hold the matter together. However, increasing the angular velocity the size and mass of a planet is going to require a large amount of energy. I do not have enough knowledge of atmospheric behavior to tell what would happen to the atmosphere at these large numbers of angular velocity.",
"But: Most planets in the universe are formed by condensing gasses/particles held together by gravity. These particles are much more likely to 'fly away' when the angular velocity is too high than solid matter. These particles 'flying away' reduce the junior planet's angular momentum (when the particles that have flown away are not being considered anymore), if the junior planet expands again to its original radius, the velocity is smaller (due to conservation of angular momentum) and might be small enough for the gravitational forces to start forming a rocky-type planet. And thus it is quite unlikely that you will find solid rock-type planets being formed while turning at immense rotational velocities. ",
"Per illustration of the earth's rotational velocity: Consider the earth rotating and a person of 100kg standing at sea-level: This person would experience a force of 3.39 newtons, or an acceleration of 0.0339 m/s. This is much larger than the standard 9.81 m/s of acceleration you experience from gravity itself. A mere 0.35 percent of the gravitational acceleration. For anything 'strange' to happen, it would need to spin at a much larger rate"
] |
[
"Obligatory xkcd post",
"Edit: ",
"Some context",
"tl;dr: \"Centrifugal force\" crops up only in a 'non-inertial' reference frame. This is why it has been loosely labeled a \"fictitious force\". ",
"Imagine yourself in a centrifuge, revolving around an axis. Your frame of reference is 'non-inertial' in this case (meaning your frame of reference is actually accelerating, i.e. changing its velocity). From your perspective, there will be a sort of 'gravity' pulling you to the outer radius of the circle you're moving in. You can treat it as an actual force from your frame of reference, and it will make a number of kinematic calculations easier.",
"However, zooming out from your perspective into the \"lab frame\" of reference (one that recognizes your personal frame of reference as moving and changing constantly), you will recognize the phenomenon as simply your inertia."
] |
[
"Fg=Gm1m2/r",
"Fc=mv",
" /r",
"'Strange' things would happen when you these to forces become relatively equal to one another. So for a back of the envelope calculation lets set them equal. ",
"Gm1m2/r",
" =mv",
" /r",
"GM/R=v",
" , where G is grav constant, M is mass of the Earth, R is the radius of the Earth",
"=> v = 7.9 km/s ",
"the radius of the Earth is 6368 km, that means it takes 5060 seconds or 1 hour and 24 mins for one day at that rate. ",
"Granted up until that point gravity would have less and less of an influence as Earth speeds up. This is just the break even point. As for material stresses I'm not so sure what will happen as you exceed this point. I'm more experienced with rapid rotation of stars."
] |
[
"Do contact with the virus work as booster shots for vaccinated/recovered people?"
] |
[
false
] | null |
[
"Kind of. The shot results in a predictable dose of antigen exposure, response, and zero risk of actual infection.",
"An exposure to the virus will absolutely provoke a response that will have a “booster” effect, but how much of a response will vary tremendously based on the nature of the exposure, and there’s obviously a risk of infection. Even asymptomatic infections cause tissue damage in lungs, so one would want to avoid that, if possible.",
"The booster effect exists in both cases, but they are not equivalent in safety, magnitude, or consistency."
] |
[
"I just want to point out that this article is pre-print. While the authors may be credible, it has not been peer-reviewed. Please take it with a healthy dose of salt."
] |
[
"Yes, to about the same extent as a 3rd vaccine dose (“booster”) does. ",
"Vaccinated individuals who tested positive for SARS-CoV-2 demonstrated substantially higher antibody responses than vaccinated individuals who tested negative for SARS-CoV-2, including 28-fold higher binding antibody titers and 34-fold higher neutralizing antibody titers against the SARS-CoV-2 delta variant. Vaccinated individuals who tested positive also showed 4.4-fold higher Spike-specific CD8+ T cell responses against the SARS-CoV-2 delta variant than vaccinated individuals who tested negative.",
"—",
"Immune Responses in Fully Vaccinated Individuals Following Breakthrough Infection with the SARS-CoV-2 Delta Variant in Provincetown, Massachusetts"
] |
[
"Superfluid vs Hydrophobic material."
] |
[
false
] |
What would happen if you had a container (say a fishbowl) made of a hydrophobic material and then filled the container with a superfluid? No specific kind of superfluid. Would the superfluid still seep through or would it maintain the shape of the container?
|
[
"It's important to note that the behaviours we commonly associate with hydrophobicity apply mainly to water. A hydrophobic surface is generally nonpolar and creates a large surface area without hydrogen bonds, so it's entropically favourable for water to avoid wetting the surface and bead up instead. Superfluid liquid helium, for instance, doesn't form hydrogen bonds and therefore wouldn't interact with a hydrophobic surface like water in any case.",
"A superfluid's ability to \"seep\" through a container relies on the existence of (even small) pores in that container. If there are no openings for the atoms to pass through, the fluid won't seep."
] |
[
"Interesting! Thank you! :)"
] |
[
"Is it possible for any type of solid to have no \"openings\"?"
] |
[
"Why do we become physically tired after a day of mental or emotional exertion?"
] |
[
false
] |
It makes sense to me that a body would become tired after a day full of physically demanding tasks, like hiking or swimming. But what is the science behind us becoming tired after a day of emotional trials? For instance, if I receive bad news during the day or have a very up-and-down experience hearing about a family member's condition in the hospital, at the end of the day I feel as tired as I would if I had run for a long distance or something. Does worry or panic or just a lot of thinking lead to a fluctuation of hormones that make me tired or something?
|
[
"Pretty close. It's the third stage of the General Adaption Model. ",
"Here's a nice graphic if anyone's interested",
"1) Alarm - adrenaline is released eliciting a fight-or-flight response due to some stressor. This is when cortisol is first released. ",
"2) Resistance - body tries to adapt to stressor, and more cortisol is released. If the stressor persists (like a looming important test), the body starts to deplete its resources. ",
"3) Exhaustion - exactly what it sounds like. This is probably what OP is referring to. All of the body's resources are depleted. Because of this, the body's functions can't return to normal until resources are replenished. If it persists, this can lead to immune suppression, ulcers (as a result of immune suppression), and increased risk of cardiovascular disease and diabetes. This is due to high levels of cortisol, a glucocorticoid produced by the adrenal glands that sit just above the kidneys. One of the functions of cortisol is to keep blood sugar levels up so that the body has the resources to adapt to the stressor, but if these remain elevated for too long, it causes problems like insulin resistance and increases chances of type 2 diabetes developing. Long term exposure to high cortisol can also suppress reproductive functions because if someone is in a stressful environment, it probably isn't the best situation to have offspring. This is why some women can skip cycles when under severe stress. ",
"During my undergraduate physiology lab, we actually took spit samples throughout the semester so we could do a lab practicing using an Enzyme-Linked Immunosorbent Assay (ELISA), which was completely new equipment for our lab and was awesome to be the first to use it. You could actually measure cortisol spikes before rounds of tests. The only not fun part was actually transferring the saliva from the small tubes into the tray the ELISA used (guess who has two thumbs and pulled that shitty job, that's right, this guy). Hope that elaborated enough and answered questions. ",
"TL;DR It's the third stage of General Adaption Syndrome called the Exhaustion Phase. "
] |
[
"Pretty close. It's the third stage of the General Adaption Model. ",
"Here's a nice graphic if anyone's interested",
"1) Alarm - adrenaline is released eliciting a fight-or-flight response due to some stressor. This is when cortisol is first released. ",
"2) Resistance - body tries to adapt to stressor, and more cortisol is released. If the stressor persists (like a looming important test), the body starts to deplete its resources. ",
"3) Exhaustion - exactly what it sounds like. This is probably what OP is referring to. All of the body's resources are depleted. Because of this, the body's functions can't return to normal until resources are replenished. If it persists, this can lead to immune suppression, ulcers (as a result of immune suppression), and increased risk of cardiovascular disease and diabetes. This is due to high levels of cortisol, a glucocorticoid produced by the adrenal glands that sit just above the kidneys. One of the functions of cortisol is to keep blood sugar levels up so that the body has the resources to adapt to the stressor, but if these remain elevated for too long, it causes problems like insulin resistance and increases chances of type 2 diabetes developing. Long term exposure to high cortisol can also suppress reproductive functions because if someone is in a stressful environment, it probably isn't the best situation to have offspring. This is why some women can skip cycles when under severe stress. ",
"During my undergraduate physiology lab, we actually took spit samples throughout the semester so we could do a lab practicing using an Enzyme-Linked Immunosorbent Assay (ELISA), which was completely new equipment for our lab and was awesome to be the first to use it. You could actually measure cortisol spikes before rounds of tests. The only not fun part was actually transferring the saliva from the small tubes into the tray the ELISA used (guess who has two thumbs and pulled that shitty job, that's right, this guy). Hope that elaborated enough and answered questions. ",
"TL;DR It's the third stage of General Adaption Syndrome called the Exhaustion Phase. "
] |
[
"Psychological coping mechanisms can help, like meditation. Ketoconazole inhibits glucocorticoid synthesis and Mifepristone is a progesterone and glucocorticoid receptor antagonists, but Mifepristone is also an abortifacient (a substance that induces an abortion). IIRC dark chocolate and black tea can be part of diets to reduce cortisol levels. "
] |
[
"How does \"burning fat\" physically work?"
] |
[
false
] |
[deleted]
|
[
"When fat or sugar are burned, the result is CO2 and H2O. The CO2 exits your body when you breathe. The H2O hangs around in the blood, but will leave the body through various means.",
"An average 140 lb person will lose about 1 kg of CO2 per day from basal metabolism. That takes about 270 grams of carbon out of your body. Fat is mostly chains of CH2, so about 85% carbon, and the rest mostly hydrogen.",
"The conversion of fat to CO2 and H2O happens during cell respiration. Cells prefer to use sugar for energy, but of course our bodies have processes to pull out and break down fat into molecules that can be used for energy in cells. These two usages happen at the same time, along with breaking down and burning proteins, but they happen at different rates.",
"We don't have control over the rate most of our cells work, but we do have control over our muscles. That's why we have to work out if we want to lose more weight than our basal metabolism will burn. When you're working out hard, you can lose 8-10 times as much CO2 as when being a couch potato. "
] |
[
"Cells prefer to use sugar for energy",
"There's no evidence for this. The metabolic path from adipose tissue to utilising ketone bodies is longer and more complex than utilising circulating carbohydrates. However at point of use your cells are almost completely agnostic to whether they are burning ketone bodies or sugars.",
"When your insulin levels cycle upwards (prior to and after meals, prior to waking etc...) your body preferentially stores fats and the tissues preferentially take up circulating carbohydrates. This is how your body makes immediate use of the food you've just eaten and stores a little away to use during periods you're not eating (during the night while you're asleep)"
] |
[
"That's true, from your text this is the more accurate way to describe what I was trying to say \"your body preferentially stores fats and the tissues preferentially take up circulating carbohydrates\"."
] |
[
"Are there any materials that like ice are less dense when solid than when liquid?"
] |
[
false
] |
I'm generally thinking human comfortable temperature and pressure ranges, but any info on this would be much appreciated, thank you!
|
[
"The words you're looking for are elements vs compounds (chemicals made with more than one element). A molecule is just two or more atoms joined and without charge. An element is a group of the same \"type\" of atom.",
"For example: Nitrogen gas (N2) is a molecule consisting of two atoms of nitrogen. It's an element (because it only has nitrogen). Nitrous oxide (N2O) is a molecule consisting of two atoms of nitrogen and one atom of oxygen. It's a compound because it's two different elements.",
"As to answering your question: I suspect that there are numerous compounds that have this property. However, it's easy to look up the density and properties of elements at various phases as they're well documented in reference tables."
] |
[
"Gallium - 5.91 (solid) vs 6.095 (liquid)",
"Bismuth - 9.78 (solid) vs 10.05 (liquid)",
"Germanium - 5.323 (solid) vs 5.60 (liquid)",
"Silicon - 2.3290 (solid) vs 2.57 (liquid)"
] |
[
"Water's unique hydrogen bonding and molecular geometry allow it to be less dense in solid form, what makes these materials have that property?"
] |
[
"What is the name of the physics law that deals with this phenomenon: \"burning a piece of wood will produce less energy than the wood contains\"?"
] |
[
false
] |
Likewise, using the heat to produce steam that drives a turbine will produce less energy than the heat contains.
|
[
"Law of conservation of energy?"
] |
[
"Second law of thermodynamics"
] |
[
"Yes."
] |
[
"Why is the smell of smoke strongest right after a candle has been extinguished?"
] |
[
false
] |
Whenever I put out a candle it produces a strong smokey smell. Why is this present/strongest immediately after a candle has been extinguished. Edit: Thanks for all the responses. I had a lot of fun showing people the relighting candle.
|
[
"You mean like this? ",
"http://i.imgur.com/RGO6i.gif"
] |
[
"Smoke is often a by-product of incomplete combustion. As you begin to smother the flame, smoke emits. After you smother the flame, it no longer has enough heat energy to continue complete combustion. It does however have enough energy to continue smoking and oxidizing until that heat is used up in the exothermic reaction of combustion. "
] |
[
"Which, as I recently learned, can be re-lit with a fire source from a distance. It suffices to approach a lit match or lighter to the 'smokey trail' at a maximum vertical distance from the recently-put-out wick of .5 inches. A neat experiment to show kids (and adults)."
] |
[
"Are there any major concerns of Maslow's Hierarchy of Need's? Is it still a good model?"
] |
[
false
] |
This idea was published within Maslow's theory of motivation in the 1940's. 75 years later, does it still hold water, and is there a better well supported idea that is relevant to how motivation of humans along this same vein?
|
[
"It is important to note that Maslow's (1943, 1954) five stage model has been expanded to include cognitive and aesthetic needs (Maslow, 1970a) and later transcendence needs (Maslow, 1970b).",
"Psychologists now conceptualize motivation as a pluralistic behavior, whereby needs can operate on many levels simultaneously. A person may be motivated by higher growth needs at the same time as lower level deficiency needs.",
"Contemporary research by Tay & Diener (2011) has tested Maslow’s theory by analyzing the data of 60,865 participants from 123 countries, representing every major region of the world. The survey was conducted from 2005 to 2010.",
"Respondents answered questions about six needs that closely resemble those in Maslow's model: basic needs (food, shelter); safety; social needs (love, support); respect; mastery; and autonomy. They also rated their well-being across three discrete measures: life evaluation (a person's view of his or her life as a whole), positive feelings (day-to-day instances of joy or pleasure), and negative feelings (everyday experiences of sorrow, anger, or stress).",
"The results of the study support the view that universal human needs appear to exist regardless of cultural differences. However, the ordering of the needs within the hierarchy was not correct.",
"https://www.simplypsychology.org/maslow.html"
] |
[
"The big problem or rather underlying limitation of all such 'basic need' studies is its devlishly hard to provide evidence for the theory. For example how do you show that love/relationships is an intrinsic human need and not a learned or culturally mediated deal?",
"Also how do you show that there is a hierarchy. I mean you can't really chuck participants out on the street and see if they only pursue shelter, and only pursue connections once shelter is achieved!",
"It's a person bugbear of mine that many people just take Maslow's work and assume its correct, when we don't even have solid evidence that human's have intrinsic psychological needs (in the sense of 'basic drives' obviously we need to eat and we know what contexts lead to good psychological health) "
] |
[
"Interesting perspective. Thank you."
] |
[
"Imaginary numbers are visualised as being on a number line perpendicular to real numbers. Does another type of number exist on a number line perpendicular to both (z-axis)?"
] |
[
false
] |
I remember seeing years ago in maths class. My question is, does another class of numbers exist on the number line in the 3rd dimension? Extending this idea, how about four, fifth, and nth dimensional number lines? I hope I'm making some sense!
|
[
"Well, R",
" is a pretty well-defined and commonly used three dimensional number system.",
"In general, you can define a vector space (over the reals) that has as many dimensions as you want/need, and these are all going to be isomorphic to R",
" (mathematically this means that, in all important senses, they are identical). If you're primarily interested in ",
" properties this is usually the kind of structure you work with.",
"The nice thing about complex numbers, quaternions and octonions (vector spaces of dimension 2, 4, and 8 over the reals) is that they have a nice ",
" (multiplication) structure as well; there is a consistent way of multiplying two, say, quaternions together and getting another quaternion. This is mostly missing from the other vector spaces; in R",
" you still have the cross-product, but it has some undesirable algebraic properties like sometimes ",
" x ",
" = ",
" even if neither ",
" nor ",
" were zero. (We would say that R",
" with the cross-product \"has zero divisors\" which is bad from an algebraic standpoint.)",
"The problem with zero divisors is that you can no longer divide! For instance, in my example above, I know that ",
" and ",
" are both non-zero, but if I try and divide the expression",
" x ",
" = ",
"by ",
", then I get",
" = ",
" / ",
" = ",
"which I know isn't true.",
"Complex numbers, quaternions and octonions all allow division though; this is why dimensions 2, 4, and 8 are in some sense \"more special\" vector spaces than dimensions 3, 5, etc."
] |
[
"Actually there is no well defined \"three dimensional\" number. You have to go straight from complex numbers to quaternions to octernians."
] |
[
"These number-lines are just a construct for visualisation. You can define any amount of new numbers in higher dimensions.\nAn example are ",
"quaternions",
". These consist of another two imaginary axis orthogonal to a real number and the first imaginary axis. "
] |
[
"Is there any scientific reason to be worried about the calcification of the pineal gland?"
] |
[
false
] |
I hear a lot of pseudo-science people claiming that the calcification of our pineal glands is responsible for a myriad of problems. At first I didn't even believe that the pineal gland calcified, but apparently it often does, seen in x-rays: . I'm really curious what/if there are any consequences to this. Does this inhibit pineal gland function? Is this why we tend to produce less melatonin as we age? ( .)
|
[
"Even though the reasons behind calcification of the pineal gland seem not to be completely understood at this point, it is widely accepted that this does, in fact, happen.",
"This paper",
" from 2004 links decreased melatonin production in the pineal gland with the onset and progression of Alzheimer's disease. It suggests that not only does melatonin deficit strongly affect the ability of AD patients to maintain normal circadian rhythms, it also suggests that a deficiency in melatonin's antioxidant properties may speed the progression of AD. ",
"To address the link between the decrease in melatonin with calcification of the pineal gland, ",
"this 2007 study",
" correlated increased nighttime calcium levels with decreased nighttime melatonin content.",
"An even more recent study from 2008",
" found that Alzheimer's patients have a smaller ratio of uncalcified pineal tissue to calcified than patients with other forms of dementia, with depression, or control subjects. Alzheimer's patients also had a higher degree of calcification in the pineal than did other subjects. Degree of calcification was correlated with the individual's ability to produce melatonin. Alzheimer's patients notoriously have decreased melatonin production, and thus, disrupted sleep cycles. ",
"Anyway, yes, it appears that there is a link between calcification of the pineal gland over the life span, decreased melatonin production with increased calcification, and pathologies associated with decreased melatonin. "
] |
[
"Unfortunately, I haven't been able to find any scholarly papers that explain this with any reasonable certainty. Like you said, there is a ton of psuedoscience. There are many websites claiming that a calcified pineal gland needs to be \"detoxed\", and that it's something that happens when you're doing something wrong. Nothing substantiates any of that with actual science, as far as I can tell. It seems to be a natural function of aging. It happens in rats and gerbils too. "
] |
[
"I see a lot of CT head scans and it's very common to have pineal gland calcification over the age of 30. It's so common radiologists don't even mention it in their reports. While it is probably linked to melatonin production and Alzheimer's there is literally nothing you can do about it, everyone gets it to some degree. "
] |
[
"Is it actually worth donating my spare CPU cycles to distributed computing projects such as Rosetta@home?"
] |
[
false
] | null |
[
"New hardware has significantly better idle power consumption."
] |
[
"New hardware has significantly better idle power consumption."
] |
[
"Both those parts are 2 years old, approaching 3 which in tech time is quite old. The GPU is certainly using most of the power on idle though."
] |
[
"Is there a maximum size or volume of a single bubble under water?"
] |
[
false
] |
How does type of gas or fluid affect bubble size? What about other environment variables, like depth or temperature?
|
[
"A large enough bubble won't be stable because drag force isn't distributed evenly across it's surface. A small bubble withstands that deformation with surface tension, but once a bubble gets large enough then drag will rip the bubble apart into smaller bubbles. A similar phenomenon happens with drops of water falling through the air. You can't have one giant drop, it'll break up because of drag forces."
] |
[
"Given enough space there wouldn't be a theoretical limit. Assuming the bubble was continually moving upward without breaking the surface it would grow as the water pressure caused by the column of water above it decreased.",
"If it reached a ceiling (of a cave say) and you kept adding gas it would displace the water below it until either it filled the cave or (if it was trapped) the pressure became so high that the gas in the bubble turned liquid. "
] |
[
"Doesn't that violate the ",
"Laplace bubble equation?",
" There will be an equilibrium bubble size depending on the hydrostatic pressure generated by the liquid on the bubble, and other bubbles will gradually collapse or grow to this size (via ostwald ripening.) If you look at that link it has bubble size for an infinite solution there and says it only depends on the hydrostatic pressure. although I think surface tension is bundled in there too. Suggest you read that link, it provides a much more rigorous mathematical explanation than I can since I last studied Laplace bubbles in 2005. "
] |
[
"How does a hurricane affect life underwater?"
] |
[
false
] |
Obviously, hurricanes are big news for life on land, but what kinds of things go on underwater? Do animals retreat? Do coral reefs just hope that they don't break apart? Or is life below the surface oblivious?
|
[
"There was a post yesterday asking this question with regard to marine life.",
"The conclusion was that some marine life can sense fluctuations in the pressure of the water (which alerts them that there is a storm). Sharks do this and since they want to swim in a certain pressure, the reduced pressure under a hurricane, causes them to swim deeper.",
"http://www.telegraph.co.uk/earth/earthnews/3337163/Sharks-could-warn-of-storms-claims-research.html",
"It seems likely that other organisms of similar complexity would also have there share of evolutionary tricks."
] |
[
"very interesting, and thanks for the link!"
] |
[
"Winds can create big waves, but wave action doesn't really extend as far under the water as you might think. Coastal structures might be damaged by the increased wave action, but overall the ocean critters are just fine."
] |
[
"Given what we know about the origins of life, is it possible to estimate the earliest possible occurrence of life in the universe?"
] |
[
false
] |
[deleted]
|
[
"Current scientific consensus is that the Earth was formed around 4.5 billion years ago, and life evolved between 3.5 and 3.9 billion years ago.",
"Source: ",
"http://en.wikipedia.org/wiki/Abiogenesis#Early_conditions"
] |
[
"Anything is possible. I think the answer to this question (besides being somewhat related to 42) would be purely speculation (obviously). I don't know if there's a way to estimate this since anything is possible. ",
"I would say, depending on the conditions, after the first habitable planet was formed. Said planet could hold any type of life-form (either carbon-based, arsenic-based, etc)."
] |
[
"Assumption 1: life on Earth is typical.",
"Life on Earth evolved about a billion years after the formation of the planet (maybe earlier, but whatever).",
"Assumption 2: Earthlike planets only form around type 1 stars.",
"Type one stars have high metallicity (aka, any element heavier than helium). Type 1 stars formed as much as 10 billion years ago according to some random webpage on the internet.",
"Combine those two things and you get life showing up 9.5 billion years ago. ",
"EDIT: I apparently can't subtract 1 from 10. Make that 9 billion years ago."
] |
[
"If Gravity Keeps Large Objects Spherical, What Keeps Things On The Atomic Scale Spherical?"
] |
[
false
] |
Pretty much as the title says. I'd guess electromagnetic forces, but then I thought about neutrons...So I'm confused.
|
[
"The nuclear strong force pulls neutrons and protons together to form an atom's nucleus. Just as with gravity on the macro scale, the force binds them tightly together. A sphere is the most efficient/tightest configuration to pull them all together, so that is what shape is formed."
] |
[
"Strong force does it on small scales, this is the force that lets protons pull at electrons. Its incredibly powerful but only over very short distances. Like the space between a proton and an electron. the electromagnetic force works on for the most part our Scale. (human)"
] |
[
"Strong force binds protons and neutrons to each other in the nucleus, overcoming electrical repulsion between positively charged protons. The attraction between electrons and the nucleus is based on electromagnetic force, not strong force."
] |
[
"How does soap work? And why is it seemingly so effective against essentially everything?"
] |
[
false
] |
Soap. What is it made of? What is the cleaning element? Why does it cut through oil so well but it needs to be added to water? etc...
|
[
"Soap is an amphipathic material, otherwise known as a surfactant. That is to say, it is composed of molecules that have an ionized and unionized end. The uncharged portion of the molecule will \"stick to\" other uncharged, or hydrophobic materials, primarily dirt and oils in the case of soap - the result of a statistical force favoring a more disordered state. ",
"The charged, hydrophilic ends then are attracted to water. As water runs over an area lathered with soap, water pulls on the surfactant, which is \"sticky\" to the oils and dirt, taking them with it. So the soap being pulled away by water pulls the dirt away as well. ",
"Soap is produced by subjecting fats to potassium hydroxide or sodium hydroxide - this ionizes the glycerol end of the fatty acid chain, and leaves the rest of the chain unaffected. The latter is hydrophobic, the former hydrophilic."
] |
[
"Their functional unit is essentially the same - an amphipathic molecule. This time, hydrophobic ends surround the insoluble material, exposing the other end of the surfactant, the hydrophilic end, to water. This way the previously insoluble substance becomes soluble. "
] |
[
"Because marketers and scientists define things differently. It still contains a surfactant, maybe even the same one as other brands. However, the marketers make a distinction between soap (meaning a bar of surfactant soap and all its ingredients) and their beauty bar (a bar of surfactant soap with different additives to help it rinse clear and moisturize skin). So what allows them? Easy: no one's stopped them."
] |
[
"What is the possible scientific theory behind this gadget working?"
] |
[
false
] | null |
[
"There isn't any."
] |
[
"I smell a scam."
] |
[
"Placebo and confirmation bias"
] |
[
"Is there a direct correlation between star size and average planet size?"
] |
[
false
] |
I know that there is a maximum size of a planet, due to the fact it will collapse under its own weight. But does a stars size/gravity have an affect on it's planet formation?
|
[
"I don't have a whole lot of time right now, so maybe someone will come fill in the gaps here.",
"But yes, given the information we have right now, it seems like bigger stars can make bigger planets. Jupiter-mass planets are much rarer around smaller stars than they are around solar mass stars. And stars bigger than the sun seem to host more and bigger giant planets.",
"The general reasoning behind this is that small stars have smaller proto-planetary disks. There's just less stuff around to make planets out of, so it's tough to get enough of it together to form Jupiter-type planets. Neptunes and Earths are much more common around the small stars, and that generally seems to be as big as it gets. Meanwhile the bigger stars have bigger disks with more material, so gas giants (and lots of them) can form pretty easily.",
"This ",
"wiki page",
" summarizes bits of it. Just reading the introduction to ",
"this paper",
" (it's only 1 page) gives a decent summary too."
] |
[
"A planet won't collapse under its own weight. If Jupiter merged with like 70 other gas giants of the same mass, it would turn into a star (specifically a red dwarf) because the interior would be dense and hot enough for fusion to occur. If a bunch of rocky planets did the same, they'd also turn into a red dwarf, but with really high metallicity. Keep adding mass and the red dwarf would turn into a bigger, brighter star. To make gravitational collapse happen, you'd need a really massive star."
] |
[
"Exoplanet.eu shws this: ",
"http://www.exoplanet.eu/diagrams/diagram.png?t=&f=&x=star.mass&xmin=min&xmax=max&y=mass&ymin=min&ymax=max&ylog=on",
"Which is a really biased sample but is the up to date ''official'' record of planets discovered so far...",
"You can plot a lot more from their web interface."
] |
[
"If there are an infinite number of prime numbers, why can it not be proven that there are an infinite number of twin prime numbers?"
] |
[
false
] |
I was just watching a video about primes and twin primes, and it was said that there is no proof that there are an infinite number of twin primes. Why is that the case? If there are an infinite number of prime numbers, then shouldn't each prime number have a twin being the next prime number above it, with the chain going on infinitely? Sort of like a weird inductive proof?
|
[
"Twin primes are not a prime and the next prime above it.",
"Twin primes are prime numbers that differ by 2. So, for example, 11 and 13 are twin primes, 17 and 19 are twin primes, but 37 and 41 are not.",
"We do know that primes get, on average, sparser as one gets to larger and larger numbers. As you say, whether there are still an infinite number of cases where the next prime is just 2 greater than the previous prime remains an open question, but recent progress has shown that there are infinitely many primes separated by 246 or less."
] |
[
"If there are an infinite number of prime numbers, then shouldn't each prime number have a twin being the next prime number above it, with the chain going on infinitely?",
"Twin primes are primes whose difference is 2. So 3 and 5 are twin primes, but 7 and 11, although adjacent primes, are not twin primes."
] |
[
"Take your list of primes below N, multiply them to get x, and then x+1 and x-1 will have prime factors that are not include on your original list. However, there is nothing to ensure that x+1 and x-1 are themselves prime.",
"Example: 2 x 3 x 5 x 7=210",
"209=11 x 19",
"211 is prime",
"Edit: Fixed formatting."
] |
[
"Do people who live in the desert have less oxygen to breathe than people who live in the woods?"
] |
[
false
] |
I understand that plant life converts carbon dioxide to oxygen, but I wonder if the extreme locations can create a measurable difference. Furthermore, I wonder if this difference can have any effect on humans like differences in altitude can.
|
[
"Air on Earth is fairly well circulated. There's about the same amount of oxygen in most places.",
"However, if you live at altitude, the lower air pressure and density means that less oxygen makes it into the body. People who live at altitude for many generations (such as in Nepal or Peru) have adaptations like more hemoglobin in the blood to help compensate."
] |
[
"The concentration, as a percent, of Oxygen higher in the atmosphere will be slightly lower due to it being heavier than Nitrogen, but the dominant effect is just that there's less air overall. Less air, less oxygen, and it's harder for the body to absorb it."
] |
[
"Nothing.",
"The air pressure is lower, so there is more empty space on average between air molecules."
] |
[
"Why haven't species developed more eyes?"
] |
[
false
] |
It may sound like a stupid question but it seems odd to me that so many animals have only two eyes. I know a lot of herbivores have developed eyes on the side of their head to allow them to see predators from behind them, why haven't they just developed eyes on the back of their heads, so as not to have decreased visibility in front of them?
|
[
"Species don't develop new traits specifically to accommodate some need. Mutations are entirely random and only \"stick\" if it increases survivability long enough to become homogeneous among the population."
] |
[
"The more (complex) eyes, the more cerebral power is required to utilize their input."
] |
[
"That doesn't answer the question though, just asks the person to rephrase it to be more scientific. The question as asked isn't a bad layman's version of:",
"\"Why does having multiple eyes not increase fitness enough to become dominant in the population, or alternatively, why are mutations allowing extra eyes so vanishingly rare that animals never had the chance to evolve two\"",
"These are good questions, worth investigating.",
"Also, there's an unstated assumption in this question that \"animals\" here means vertebrates, since invertebrates do indeed regularly have more eyes.",
"My guess is that the vertebrate body plan is too genetically \"set\" for a mutation allowing multiple eyes to result in viable offspring. You don't tend to see duplications of complex structures occurring over evolutionary time in vertebrates, certainly not as much as losses. Any mutation severe enough to produce multiple eyes would inevitably result in a head so deformed as to be inviable. You need a developmental geneticist to confirm that."
] |
[
"AskScience AMA Series: We are geoscientists, emergency managers and communication specialists working on the ShakeAlert earthquake early warning system in CA, OR and WA. Ask us anything!"
] |
[
false
] |
We are geoscientists, emergency managers and communication specialists working on the Pacific Northwest ShakeAlert earthquake early warning system in CA, OR and WA. We're here to raise awareness and answer questions about the new early earthquake warning system, earthquakes and Pacific Northwest hazards in general. We'll be on at 11-2 PST (2-5 ET, 19-22 UT), ask us anything! Usernames: , ,
|
[
"The public alerts via WEA (",
"Wireless Emergency Alert Systems)",
" are not including a countdown to when shaking is expected to arrive. There are a variety of reasons for this including uncertainty in in the travel time of earthquake waves through the rock between you and the earthquake and the fact that even the early \"P\" wave that triggers the system can be damaging when close in to a large earthquake.",
"Technical users and licenced app developers can incorporate countdowns that are calculated assuming a average travel time for the \"S\" waves that are usually the first arriving damaging waves and your distance from the origin or \"hypocenter\" of the earthquake. The ",
"\"quake alert usa app\"",
" does provide a countdown to subscribers.",
"Bill Steele ,University of Washington, PNSN"
] |
[
"Are you planning to provide the users how much warning time they will have?? Also, how you calculate the lead time in EWS??"
] |
[
"How soon do you think you'll be able to roll out service tied to the EAS and WEA systems so people just get alerts on their cell phones? Is that system capable of delivery alerts fast enough to matter, or do you think it'll have to stay app-based forever to give you finer control over the delivery speed and mechanism of alerts?",
"Is there any way to crowdsource seismic data, e.g. by listening to the accelerometer data on millions of smartphones to pick up earthquakes in areas that are underserved by traditional seismometers? Similarly, is there any sort of low-cost seismo installation hobbyists/volunteers could install in their backyard to bolster the sensor network?"
] |
[
"Why can't they just stop diverting the rivers so as to replenish the Aral sea?"
] |
[
false
] |
This is something that has bugged me about the Aral sea since I learned of what the soviets did to it. I understand the water is still being used for agriculture in Kazakstan and Uzbekistan, but the devastation of losing the 4th largest lake in the world would seem to me to outweigh that. Am I missing something here? They just had a "Global Disruptive Tech Challenge 2021: Restoring Landscapes in the Aral Sea Region" in April, but none of them discussed even partially returning the rivers.
|
[
"In short, because the economies of Kazakhstan, Uzbekistan, Turkmenistan, and Tadjikistan are all heavily dependent on the agriculture made possible by the irrigation projects, inefficient as they are/were. This discussed in virtually any paper proposing solutions to refilling the Aral Sea, i.e., that the economic and societal fallout of ending all of this agriculture are not offset by the ecological or economic benefits of refilling the Aral via this route. For complete discussions check out ",
"Badescu & Schuiling, 2010",
", ",
"Micklin, 2014",
", or ",
"Micklin, 2016",
". In the published literature (including some of the above), there are certainly solutions which involve modifying the irrigation and agriculture (e.g., trying to make the irrigation more efficient so less water is lost, switching to less water intensive crops than rice or cotton so less water is needed) with the goal of delivering more water to the Aral through its original sources. However as discussed in the linked papers (and others), it's not a viable solution now, ~60 years after these projects started, to simply upend the economies of 4 countries by stopping the diversion completely."
] |
[
"Thank you that answers my question! It seems that I misunderstood how much of an effect losing the water for agriculture would be on the countries."
] |
[
"isnt the Aral sea beginning to grow again because they have built a damn to hold the outflow back, ",
"https://www.cntraveler.com/story/the-aral-sea-is-refilling-for-the-first-time-in-decades"
] |
[
"Does probability still exist if the results are already determined?"
] |
[
false
] | null |
[
"One way to consider this is that probability is a measure of the uncertainty that a person has in the outcome. From your point of view, you have no information and the chance is 50%, but from the point of view of someone who knows where the price is, there's no uncertainty.",
"Or rather, the entropy of the results you expect is related to your uncertainty. You have 1 bit of uncertainty and the person who knows the answer has 0 bits."
] |
[
"There are numerous interpretations of the concept of probability. This is the ",
"Bayesian",
" interpretation, which contrasts with the ",
"frequency",
" or ",
"propensity",
" interpretations.",
"Each is useful and meaningful in a different context."
] |
[
"For the observer, there was a 50-50 shot of you picking the right box.",
"For you, there was a 50-50 shot of you picking the right box.",
"Your scenario exists in the moment of time where the observer's outcome was already revealed, but your outcome was not. Still same odds for everyone involved."
] |
[
"What causes different materials to expand or contract at different rates?"
] |
[
false
] |
Recently finished the thermodynamics unit in physics, and wanted to know what causes different materials to expand or contract at different rates? Does it have anything to do with the heat capacity, or are they two separate things? (I am aware that it is called the "coefficient of linear expansion" btw)
|
[
"Intermolecular bonding energy. Heat is atomic kinetic energy, right? Well, if a material is bonded to itself really strongly (tungsten), it will take a lot of energy (heat) to force them to spread out. If they are weak (plastic), they will spread out a lot further with application of the same amount of energy."
] |
[
"Usually thermal expansion/contraction refers to reversible changes, maintaining crystal structure if such exists. Your permanently shrunk plastic bowl is probably due to the polymer structure permanently rearranging itself. Plastic items are often shaped by forcing them to stretch/mold, which lines up the long molecules in the stretched direction. When cool the strands lock in place, but heated again they have enough energy to jostle out of their orderly arrangement back into a tangles, and the item shrinks.",
"http://pslc.ws/macrog/work/shrink.htm"
] |
[
"Usually thermal expansion/contraction refers to reversible changes, maintaining crystal structure if such exists. Your permanently shrunk plastic bowl is probably due to the polymer structure permanently rearranging itself. Plastic items are often shaped by forcing them to stretch/mold, which lines up the long molecules in the stretched direction. When cool the strands lock in place, but heated again they have enough energy to jostle out of their orderly arrangement back into a tangles, and the item shrinks.",
"http://pslc.ws/macrog/work/shrink.htm"
] |
[
"How can a torus or Klein bottle-shaped universe retain flat global curvature?"
] |
[
false
] |
So we know that the universe is globally flat with a (i.e. geometrically flat - triangles add up to 180 degrees, parallel lines won't meet or diverge, etc). From Wikipedia: 'Flat universes that are finite in extent include the torus and Klein bottle. Moreover, in three dimensions, there are 10 finite closed flat 3-manifolds, of which 6 are orientable and 4 are non-orientable. The most familiar is the aforementioned 3-Torus universe.' I don't understand why a universe of shape would retain flat curvature any better than a spherical universe would. If you draw a triangle on the outside of a Torus the angles will exceed 180 degrees (positive curvature). The opposite is true on the inside. Most areas of the shape clearly have non-neutral curvature. I've looked into it but I can't get my head around it. How is this meant to work?
|
[
"Yes, I misunderstood the question and answered the easier one."
] |
[
"Yes, I misunderstood the question and answered the easier one."
] |
[
"So hypothetical universes with positive or negative curvature are ",
" locally flat?"
] |
[
"Is there a difference between \"strong\" and \"tireless\" muscle fibre on a biochemical level?"
] |
[
false
] |
In other words: Is there a difference between the muscle fibre you would find in a marathon runner's calves and the one in a weigthlifter's biceps/triceps? If not, what determines these two attributes? Relatedly, how would "pumping" 0.5 kg weights for long periods of time affect one's ability to do pull ups (i.e. straining the same muscle group with forces of wildly different magnitude).
|
[
"Muscles consist of several types of muscle fibers. The ratio of different types varies with exercise and function of the muscle. Two main types of muscle fibers are glycolytic (aka fast twitch), which are not very efficient, but are very fast to respond; and phosphorylative (aka slow twitch), which are very efficient, but not very fast to respond.",
"Generally speaking, muscles that are exerted over extended periods of time (for example, your back muscles, which work all day and night) will preferentially use glycolytic fibers, because efficiency is paramount for muscles with long periods of utilization; meanwhile, muscles that are exerted in short and fast bursts will preferential use phosphorylative fibers, because speed is more important than efficiency for those muscles."
] |
[
"Entire textbooks are written on the topic, but you can get some good info by looking up ",
" on google or wikipedia.",
"In general, there are ",
" (strong, easily faituged, high-threshold) and ",
" (less strong, resistant to fatigue, low-threshold) muscle fibers. There are many differences between them, mostly they are metabolic differences. This means that the FT fibers can produce lots of force by processing lots of energy very quickly, but this means they accumulate metabolic byproducts quickly and fatigue. ST fibers have a lower max strength, but they deal with byproducts much better and can operate at a high % of effort for long periods of time (or indefinitely).",
"As for the second part of your question: look up ",
" and the ",
". Each muscle has lots of fibers (~100 - ~500 for most skeletal muscles), and in general they are always activated in the same order. What this means is: if your biceps have 200 muscle fibers, and lifting a 0.5kg weight requires only 20 fibers to be active, you will always be using the same 20 fibers, and the remaining 180 inactive fibers will be mostly unused and untrained.",
"On top of that, for the most part it is the slow fibers that turn on first, and the fast ones that turn on last. So, if you want to do an activity that requires lots of strength, you will want to train your FT fibers. If you lift a 0.5kg weight, you are not training your FT at all. For the same reason, walking won't help your high-jump.",
"In training, specificity is king. If you want to get better at pull ups, then you should do pull ups."
] |
[
"Perfect, thanks a lot for taking the time to explain all this. "
] |
[
"Why do liquids boil in a vacuum?"
] |
[
false
] |
[deleted]
|
[
"Not all liquids boil in a vacuum, liquid nitrogen turns into a solid.",
"Not quite; both liquids (all liquids) boil in a vacuum until the loss of thermal energy from the phase change causes them to freeze. Then they sublimate until the solid phase is gone."
] |
[
"Not all liquids boil in a vacuum, liquid nitrogen turns into a solid. Liquid water boils because the boiling point of a liquid is the temperature at which the vapour pressure of the liquid is equal to the environmental pressure surrounding the liquid. Basically, there is no air pressure keeping the water in liquid form so it boils into steam, but maintains it temperature. This is why water boils at a lower temperature at higher elevations, less atmospheric pressure."
] |
[
"So if my layman understand of what your saying is correct, the only thing keep liquids as a liquid is the air pressure around them. Remove that and they vaporize. Is that correct?",
"Strange to think about the world that way. Water seems like a pretty stable substance, not something just waiting to explode into vapor given the right circumstances."
] |
[
"It seems like a tail would be a useful appendage. Why did humans lose theirs?"
] |
[
false
] | null |
[
"I understand that it originally helped with balance and mobility, and I'm guessing that those tasks were taken over by higher brain function and leg muscles, but wouldn't I be even more balanced and mobile with a tail? Seems like it'd be an evolutionary advantage to have one."
] |
[
"Evolution is blind, and doesn´t consider what is going to be useful or not. If we lost the genes for having a tail and it didn´t have enough of a negative effect to be selected against, that´s it, the tail stays gone.",
"Since our immediate ancestors were rather big and ground-based, there was probably little use for the tail anyway by this time and perhaps losing the tail was even selected for, eg. using the energy on making the brain bigger instead (this last part is speculation only, as so much is when one tries to figure out why evolution \"did what it did\")."
] |
[
"Because there was no selective pressure for it, or selective pressure against it. ",
"http://en.wikipedia.org/wiki/Human_vestigiality#Coccyx",
"The tailbone, located at the end of the spine, has lost its original function in assisting balance and mobility, though it still serves some secondary functions, such as being an attachment point for muscles, which explains why it has not degraded further."
] |
[
"Why is Tritium so ridiculously expensive?"
] |
[
false
] |
I am a huge fan of self-powered radioluminescent light sources powered by tritium like keychains. For a long time I have been wondering why isn't there anything more powerful (like a flashlight) since such keychains output is something like couple hundred microlumens. After a quick web search I found out that tritium price is in the range of 30.000 USD per gram making it one of the most expensive substances on Earth. I would like to learn why is that so. From what I understand tritium is produced as a waste product in heavy water moderated reactors in quantities exceeding commercial demand and that it can also be made from lithium (which is a common and cheap metal) by neutron capture. Is it so difficult and expensive to separate tritium from deuterium in reactors moderator? Is it so difficult to insert a lithium rod into an ordinary nuclear reactor in order to irradiate it with neutrons and then extract resulting tritium? I wish to understand difficulties behind tritium production and where does the high cost come from.
|
[
"a.) It's got an expiration date. You've got a half-life of about 12 years, which means that you constantly need a new supply of it, and that any light is going to die, and any manufacturer is going to need to anticipate a continuing production line, not just buy up a lot at once.",
"b.) It's not naturally occurring - all tritium comes from nuclear reactions, so there's no source of it out there to be cheaply exploited, you need to contract with a nuclear plant.",
"c.) It's radioactive - on its own, it's not especially dangerous, but if it's inhaled or consumed, it can hurt people, which means that the costs of storing it, shipping it, and working with it are much higher.",
"d.) No economies of scale - since the entire marketplace of tritium is pretty small, and the process to create it is pretty specialized, you don't get to spread the fixed costs over a lot of products. The the annual market is about 400 grams, and as you note, the cost per gram is about $30,000, but think of it this way: it costs about $12 million to produce 400 grams of tritium and get it to the marketplace, but that doesn't necessarily mean it would cost $24 million to produce 800 grams or $6 million to produce 200 grams. It might cost $11 million just to get ",
" tritium out there, and after it's set up, then maybe each additional gram is fairly cheap. But you gotta start somewhere. ",
"So it might be that all the tasks involved are scalable, and tritium could get much cheaper if there was demand. But getting started is so expensive, and demand is pretty small, so it's a niche product."
] |
[
"It makes up a very, very small fraction of natural hydrogen."
] |
[
"It does occur in water as a result of mentioned production by cosmic rays, however concentrations are far too low to make any exctraction reasonable."
] |
[
"Will a person burn more calories a day by living in a colder environment?"
] |
[
false
] | null |
[
"Yes. Your body uses more energy to generate heat and so you lose more calories. This is why when people go to the arctic and antarctic they have pretty extreme diets which include things like eating whole sticks of butter."
] |
[
"The answer is yes. "
] |
[
"From what I understand, you can burn more calories in colder environments because the body uses more glucose (along with some other stuff) to produce heat. ",
"But, it also takes effort to cool the body, so living in very warm climates could also cause you to burn more calories. "
] |
[
"Why do flu vaccines need to be adapted to the latest variation but not others such as MMR or chickenpox?"
] |
[
false
] |
In other words, why do you need a new vaccine each year for Flu but for many you get it early on and are set? If it is a matter of flu viruses mutating, why isn't that the same case for other diseases? Does flu mutate faster?
|
[
"The influenza virus (an orthomyxovirus) is indeed more likely to mutate, due to its segmented genome. These segments are far more likely to undergo reassortment through high-frequency recombination, resulting in genetic shifts (which are responsible for pandemics). At the same time, there are also genetic drifts (which occur through genome mutations that also occur in other viruses) due to the error-prone viral polymerase.",
"some more info here, but unfortunately in Spanish only."
] |
[
"So is there a relationship between virulence and complexity? ",
"Not that I am aware. However, there is a relationship between severity of disease and the age of the pathogen and this may speak more to your second observation. Before I explain that let me just correct one possible misconception for you. Because the flu is so hypermutable, it is not really correct to think of it as a single thing but rather a collection of things, a \"quasi-species\". The severity of flu is thus also fairly random from year to year. The deadliest disease in history (by some estimates) was the strain of flu floating around in 1918 for instance. Granted, they did not have flu vaccines back then (and wouldn't until 1940 or so), but the point still holds.",
"But back to the severity/age correlation. The very worst pathogens kill thier hosts, which severely limits the number of new hosts the pathogen can come in contact with. Even debilitating diseases that make people bed-ridden do this. The best pathogens will cause no apparent disease symptoms at all in thier host, thus enabling that host to interact with as many other individuals (new hosts) as they normally would through their day (or lifetime). This then leads to selective pressure on diseases to become less harmful over time. For flu, this algorithm also holds but because it is so mutable, it often bounces back to a more harmful form."
] |
[
"Sounds like the answer to my question. Thanks! ",
"This makes me thing that vacines themselves are an evolutionary force that will tend to favor such segmented genomes. "
] |
[
"Why can't we see the Pacific Garbage Patch on satellite pictures?"
] |
[
false
] |
We've all seen pictures of the patch like and of the Great Pacific Garbage Patch. We've also been told it covers an area twice the size of Texas. Something isn't adding up though because if an area twice the size of Texas were as dense with trash as those pictures, it would be blatantly obvious on satellite pictures of the earth. When you look at said pictures of the ocean, there is clearly no brown patch twice the size of Texas in the middle of the ocean. What is going on here? Are the pictures of the patches just particularly dense, and relatively small, sections?
|
[
"The overwhelming majority of plastic in the ocean garbage patches are broken apart to millimeters in size from friction and sun weathering. You will not see this plastic from a boat, much less from space as it's essentially a transparent density. The pictures you are linking to are generally from ",
" debris which can easily get that dense if near a large population center. Out in the ocean, things are different.",
"88% were less than 10 mm in largest dimension, and most had characteristics suggesting physical deterioration such as brittleness, rough edges, or cracks. It is likely that plastic pieces ultimately become small enough to pass through the 335-μm mesh net used in this study - (Law, et al.)",
"The plastic from say a milk jug is still there, but now in smaller bits. In the North Pacific central gyre, there is about 5 kg of plastic for every square kilometer of open ocean, this was measured to be six times more plastic by mass than plankton in the same region. The plastic can stick around for awhile because of the ocean's currents. ",
"The dominant clockwise gyral currents also serve as a retention mechanism that inhibits plastics from moving toward mainland coasts. A recent surface current modeling study simulated that most of the particles from our sampling area should be retained there for at least 12 years - (Moore, et al.)",
"Moore, et al. ",
"A Comparison of Plastic and Plankton in the North Pacific Central Gyre",
". ",
". 2001.",
"Law, et al. ",
"Plastic Accumulation in the North Atlantic Subtropical Gyre",
". ",
". 2010."
] |
[
"Those pictures are not of an oceanic garbage patch. Those are pictures of contaminated costal waterways. ",
"The density of plastic in the Pacific Ocean northern gyre garbage patch is given as 5.1 kilograms per square kilometer of ocean area, or 5.1 mg/m",
" ",
"The article cited in Wikipedia",
" says:",
"The abundance and mass of neustonic plastic was the largest recorded anywhere in the Pacific Ocean at 334 271 pieces km2 and , respectively. Plankton abundance was approximately five times higher than that of plastic, but the mass of plastic was approximately six times that of plankton. ",
"For comparison, a typical single-use plastic grocery bag given freely in US supermarkets weighs about 6 grams, of a material (0.5 mil HDPE plastic) that weighs about 12 grams per square meter. 5mg of material per square meter then runs about 4 square centimeters of grocery bag plastic per square meter. ",
"It's ecologically significant, but nowhere what those images of costal garbage accumulation might lead you to believe. "
] |
[
"Building on this, the plastic bits are consumed by lower levels of the food chain and concentrations are magnified in successive levels. It's a real issue, much in the same way that Eagles were affected by DDT. "
] |
[
"Ethics aside, would it be technically possible for scientists to clone a dinosaur (or other extinct species) in this decade?"
] |
[
false
] |
[deleted]
|
[
"http://www.reddit.com/r/askscience/comments/fx6sx/in_all_seriousness_what_obstacles_currently/"
] |
[
"Not a dinosaur, but perhaps an aurochs."
] |
[
"Nah, the Heck Cattle are a joke. That's not breeding aurochs, that's breeding big weird cows that look a little like what aurochs looked like."
] |
[
"Has all the \"easy\" stuff already been discovered?"
] |
[
false
] |
For example, it is easier to "get" classical mechanics vs. string theory. I would surmise this is due to classical mechanics being concrete and directly observable and the level of math involved. As physics becomes more abstract, does it require greater genius to solve today's unsolved problems than one's of the past?
|
[
"We dont know yet :)"
] |
[
"The relevant expression is \"the low hanging fruit have been picked.\"",
"There are some classical problems, such as the three body problem, that can't be solved mathematically even though the physics is simple. Another classical problem, the motion of fluids, is so complicated that some mathematicians (not physicists) devote their careers to examining it.",
"One of the reasons you \"get\" classical mechanics but not more advanced stuff is because classical mechanics is often taught through the Newtonian formalism (in terms of force), whereas once you learn the Lagrangian and Hamiltonian formalisms, it's easier to see how you go from one theory to the next.",
"As for whether the people today need to be smarter to solve problems, I don't know how to answer that. Can anyone say if Einstein was smarter than Newton?"
] |
[
"In chemistry, the answer is most likely \"yes,\" especially compared to the golden age of chemistry when you couldn't help but make discoveries. Instead, whole fields of traditional chemistry are kind of going away, they are being replaced by new fields, but they are much more complicated. ",
"Chemistry is a mature science, our models work, and we can do just about anything we want, the trick is figuring out what we want."
] |
[
"Why is there suddenly static on my car's radio when I'm close to a bus?"
] |
[
false
] |
I've noticed this happening, when city buses get closer my radio fritzes out and turns to static.
|
[
"Think about the radio signal your car is receiving. When next to a bus, the signal reflects off the bus and instead of having f(t), you now have f(t) + α f(t-δ). With a bus, the coefficient α should be close to -1, because a bus (presumably metal) is much more dense than air. So what you end up getting is something that looks like f(t) - f(t-δ), which in essence cancels out your signal and you get static."
] |
[
"Thanks!"
] |
[
"If the noise is only heard when the bus is moving and it is a hybrid electric bus, the motor drive electronics could be emitting radio frequency interference. More likely, the bus is blocking the radio waves from your antenna. Have you ever noticed how the radio gets static at a stoplight, but if you move forward a few inches the signal returns? Radio waves are bouncing around all the vehicles and buildings creating multipath distortion. "
] |
[
"Would taking cooked meat out of the fridge, warming it, and then putting it immediately back in the fridge make it go bad?"
] |
[
false
] |
My mom has always told me not to do this, but I'm not sure if it's true. If it, what's the reason behind it? I have a bowl of ground meat that I just warmed and I decided I didn't need it now. I'm not sure whether i can just stick it back into the fridge while it's hot or if I should wait!
|
[
"Meat in your fridge contains pathogenic microorganisms. They divide very slowly (if at all) in the cold fridge, but much more rapidly at room temperature. Air in your kitchen also contains pathogenic microorganisms, some of which would grow rapidly on nutrients they can extract from meat. ",
"These pathogenic microorganisms can hard you in two different ways. Some of them, when ingested, will divide in your body and make you sick. These are typically killed by proper cooking. Some of them secrete toxins that make you sick, and those toxins can persist long after the microorganisms stop dividing or die. These toxins may or may not be destroyed by cooking.",
"So, every time you warm meat up, you give the pathogens in it — as well as any that might land on it — a bigger opportunity to grow and secrete toxins that might harm you or kill you. ",
"On the other hand, most of the risk of those pathogens and toxins is mitigated by properly preparing the meat. ",
"So if you re-heat the meat to a proper meat cooking temperature later, you will probably be OK. But if you just re-thaw it and eat it, you are putting yourself at higher risk of food poisoning. How high that risk depends on a variety of things, including whether the meat was properly prepared to start with, how long it was left out before being initially refrigerated, as well as how long it was out before being subsequently refrigerated. ",
"In short: you mom isn't wrong, but you might be OK. I definitely wouldn't make a habit of it."
] |
[
"One thing to note that there isn't anything special about meat in this context. This applies to all foods capable of sustaining bacterial growth. "
] |
[
"Actually, there is; for example, if the food is still contaminated with pathogens that came with it (which depends on the type of food and the method of preparation), then the kinds of things you will find growing on it are going to be substantially different depending on type of food. For example, you are more likely to find lethal E Coli on meat, and you are more likely to find Salmonella on fruit and vegetables."
] |
[
"Interesting math problem that's driving me crazy"
] |
[
false
] |
There is a random whole number of indeterminate length in front of you. You can only see the ones column (last digit) of it. How can you determine what this number is? You can perform any mathematical manipulation to it, but you will always only be able to see the ones column (even if it becomes a decimal, you will only see the ones column). Apparently the solution is relatively simple and uses basic operators (+, -, *, /, %, etc.) but I haven't figured it out yet.
|
[
"Count the number of times you have to subtract 1 until 0 in the visible column is followed by 1 rather than 9? Works only if the starting number is positive, so doesn't fit everyone's definition of \"whole number\".\nI am not a mathematician."
] |
[
"Would still technically work on a negative number, as the digit would increase as you subtracted 1, so you would know it was negative and start adding 1 until you get to a point where 0 becomes 1 instead of 9."
] |
[
"Wow, now I feel like a tool for not getting it sooner. Well done."
] |
[
"Could Earths atmosphere become Venus-like?"
] |
[
false
] |
Is it a real threat?
|
[
"Yes. We think that Venus got the way it is because the temperature increase due to being closer to the Sun is just enough to drive the carbonate-silicate cycle in the other direction to what it is on Earth, and preferentially create carbon dioxide over carbonate rocks. ",
"Earth has an enormous amount of carbon trapped in carbonates and if the temperature of ",
" planet increase enough, it's possible that the same thing could happen - those rocks would be weathered and the formation of carbonates would not happen as readily, leading to the release of carbon dioxide, which acts as a greenhouse and increases the temperature more. ",
"If you get into this kind of effect it is called a positive feedback, and the raise in temperature will only serve to raise the temperature more. At some point you would get the oceans boiling off, and since water vapour is also a greenhouse gas, this would make things even worse.",
"So yes, it's possible, but would take hundreds of millions of years and would most likely be quite a gentle increase in temperature until some 'inversion' point was reached where the positive feedback took over.",
"Some people think the warming we see at the moment will eventually give way to a cooling period and potentially even an ice age (with these kind of cycles definitely happening in the past) but in truth we don't know enough about climate forcing to predict which way we'll go. There's a lot of comparative planetologists that look at current Venus and Mars as potential end-states of Earth's future climate."
] |
[
"References or credentials?"
] |
[
"Was it not the formation of water vapour that caused the increase in CO2 production, not the other way around as you suggest? Let me piece together an informal timeline to explain my position:",
" ",
"I always thought of it as the removal of water first from Venus resulted in the loss of major carbon sinks and high temperatures, causing high atmospheric CO2. Particularly as a reversal in the carbonate-silicate cycle as you suggest would requires mean temperatures in excess of 300C, at which temperature it would be reasonable to expect you've already lost any surface water as water vapour. I would be interested to hear any different theories as although I'm a geologist by trade, my knowledge of carbonate geology and planetary atmospherics is only cursory, tectonic processes and hard rock geology are more my area. "
] |
[
"What spesific mechanism stops one lump of matter from occupying the same space as another?"
] |
[
false
] |
Looking at different pictures made by electron microscopes got me thinking, matter looks solid enough but physics tells us its 99% nothing. So then, what stops my glass when put on the table, from ever so slightly occupying the same space as the table? Thanks in advance. G
|
[
"The facile answer is \"electrostatic repulsion\" between the electrons in matter - but that isn't really the case, since most atoms and molecules are, on the whole, electrically neutral - as would be a mix of nuclei and electrons all crammed into the volume of a normal molecule.",
"Really it's the fact that electrons are a special kind of quantum particle called a \"fermion\" (after Enrico Fermi). Fermions have a weird symmetric property that prevents any two of them from occupying the same quantum state. The weird property that it takes 720° of rotation to bring a fermion back to its original pre-rotation state. That is weird because we're used to the idea that after only 360° of rotation any system looks just like it did before the rotation. ",
"Here's how that works: Rotating a single fermion (like an electron) by 360° has the effect of multiplying its wave function by -1 everywhere. Bizarre but true -- it takes 720° (two full rotations) to see the fermion exactly the same way. I won't get into why in this post, it just is.",
"A system of ",
" fermions has the opposite symmetry of a single fermion - rotating the two fermions together by 360° has the effect of multiplying the total wave function by 1 everywhere, since you get a factor of -1 for each of the two particles, and (-1)*(-1) is just 1. ",
"But two particles in ",
" have the same wave function as a single particle in that state, multiplied by 2. So if you start with two electrons in exactly the same state, and rotate the system by 360°, one method of reasoning gives you a factor of -1 and the other a factor of 1 in front of the wave function. The only way they can both be right is if the total wavefunction is 0, since (-1)*(0) and (1)*(0) have the same value. That means the wavefunction ",
" to be 0 everywhere, which means the probability of ever finding two fermions in the exact same quantum state is always 0.",
"That in turn means putting two electrons into the same location in space requires exciting one to a higher energy state to make their two wave functions slightly different. Exciting one of them costs energy, which acts like a repulsion -- if it costs a lot of energy to put two molecules in exactly the same place, then you have to supply that energy by pushing hard if you try to compress them together.",
"Fermions are counterintuitive and bizarre, but without them there would be no solid matter - bosons, the other main kind of quantum particle, are more gregarious and matter would tend to condense into very dense blobs rather than remaining relatively spread out. The Universe would be very different, and probably wouldn't contain people.",
": You can't put two electrons into the same place without exciting one by giving it more energy. That effect, not electrostatic repulsion, is what keeps electrically neutral atoms from occupying the same space."
] |
[
"I think this is a great answer but why didn't you reference the actual principles you are referring to? ",
"In specific the principle that two fermions cannot occupy the same quantum state at the same time is Pauli's Exclusion Principle:",
"http://en.wikipedia.org/wiki/Pauli_exclusion_principle",
"Personally, I think the coolest aspect of these understandings is their implications for neutron stars and black holes. The Chandrasekhar limit and Schwarzschild radius both set up mathematical bounds for when and how Pauli's exclusion principle breaks down."
] |
[
"Heh :-) I didn't name the PEP specifically, because so many, many people just point to it as a magical property. But understanding the symmetric origins of the PEP makes it, well, simple.",
"Cheers!"
] |
[
"A meta-science question. Wherever you are in your career, has your H.S. education been predictive your career in science (e.g., your ability or interest in science)? Specifically, what role have your H.S. math & science classes played in your career in science?"
] |
[
false
] |
I'm especially interested in this after seeing , which I highly recommend.
|
[
"I'm an un-natural example, I graduated from a Technology magnet high school with a concentration in chemistry, I was the first declared major in my college class, majoring in chemistry, then went to grad school in chemistry, and I now work as a chemist. ",
"So yeah...I've known I wanted to be a chemist since early on in high school.",
"A good friend of mine graduated from a Waldorf High School, pretty much the opposite of me, in which science class was \"let's go look and the flowers, how about writing a poem about the flowers.\" ",
"He's now a chemistry professor at one of the best liberal arts schools in the country. ",
"So draw your own conclusions."
] |
[
"I was interested in science from a young age. During high school I read books on relativity for fun. I found it all fascinating.",
"I ended up getting a B.Sc. in Physics, but that process completely soured me on Physics. I never felt like I actually learned much science, just math, math and more math. I like math, but endless lectures on proofs with no practical application just sucked.",
"So after graduation I spent a summer re-thinking things and ended up going back for a degree in my other love: computer science. I've worked as a software developer ever since (20 years now).",
"But to answer the question, my HS education 100% predicted my career. I always knew I'd end up doing something \"science-y\"."
] |
[
"Yes. I excelled in high school math, and got a 5 on the AP Biology exam. But I can go back to about 3rd grade and see that I was destined a scientist. ",
"I'd like to think when you know, you know, but I do come across the random student who has come back to school after managing a store for 15 years or working in finance or in the Army, and they have a knack for molecular biology that they never knew about. That's always intriguing and impressive to me."
] |
[
"Questions about the phylogeny of Echinoderms... re-evolution of radial symmetry? Homologous structure to Chordates?"
] |
[
false
] |
Wikipedia doesn't really clarify their phylogeny too well. Looking at a tree of life of the phyla of Animalia, it would imply that Echinoderms like starfish branched from Chordates relatively recently compared with the advent of bilateral symmetry, which is common to most Animalia phyla. However, Echinoderms for the most part have 5-point radial symmetry whereas Chordates are bilateral. I have two questions in this: first, are echinoderms indeed descended from a bilateral common ancestor of most of the bilateral phyla, and if so why and how was it evolutionarily advantageous to redevelop radial symmetry or by what mechanism was it redeveloped? Second, somewhat unrelated: chordates mostly have 5 appendages: two front legs/arms/fins, two hind arms/legs/fins, and a head; is this a homologous arrangement to the 5-point symmetry of many echinoderms or was it a separate development? Thanks for any and all clarification!
|
[
"Hi,",
"Developmentally, echinoderms start as bilateral organisms; check out these ",
"echinoid larvae.",
"\n The pentameral symmetry shows up as they grow up. Keep in mind that pentameral symmetry also is fundamentally bilateral - the bilateral symmetry group is within the pentameral one.",
"There are also tri-radial early echinoderms. Some echinoderms can also rarely have more than 5 limbs, suggesting that the pattern of developmental repeats is a matter of having the right amount of a chemical (I can give a reference if you want to read about some crinoids that demonstrate this).",
"There are of course plenty of echiconderms that have secondary bilatteral symmetry; holothurians, irregular echinoids.",
"Why was it developed? I don't think there is a good known answer to that. Why is it beneficial? Because it is omni-directional.",
"5-limbness in chordates is neither homolgous or similar beyond the superficial to that in echinoderms."
] |
[
"Sea urchins actually have a very pronounced pentameral symmetry; they have 5 teeth on their mouth parts, they have 5 pairs of ambularcal grooves moving from the center. Next time you see an echinoid test, look through it into a light source; you'll see the 5 paired rows of holes where the tube feet would be when alive."
] |
[
"You say:",
"the bilateral symmetry group is within the pentameral one.",
"Does this mean that a pentameral echinoderm is, anatomically speaking, almost like 5 bilateral organisms arranged around a hub?",
"I know you said that it's unknown how it developed, but could it be that the original n-mer was simply ",
" conjoined organisms, or some genetic mutation caused a bilateral organisms to n-tuple and that form was capable of surviving and reproducing?"
] |
[
"How does the body eliminates fat tissue?"
] |
[
false
] |
I have been changing my life style, eating habits and exercising more. And it made me wonder, how does my body eliminates the fat issue previously stored?
|
[
"It depends on what you mean by fat tissue.",
"Your fat, like the fat in your belly, is made up of huge adipocytes 100x+ more voluminous than fibroblast cells. These adipocytes are tethered together and packed densely with capillaries and larger vessels wending through. When you lose weight due to exercise or eating habits these adipocytes shrink in size (they're undergoing lypolysis). Basically, the lipid they've been storing is being burned up, so they shrink.",
"If you continually run a calorie deficit then eventually, and here the research is incomplete, your fat cells will decrease in number as well. The thought is that there is a certain turnover rate of fat cells, atomic labeling studies show ~10% of adipocytes turn over every year. So, unless they are replaced at the same rate, you will eventually decrease the number of adipocytes you have. Eating certain foods, and having a calorie excess, can lead to more pre-adipocyte stem cells to decide to differentiate into adipocytes. Just so, if you're running a deficit fewer pre-adipocyte stem cells will differentiate into adipocytes. So, over time, you'll lose cells naturally and they won't be replaced if you are restricting your calorie intake. ",
"So you lose fat by the cells shrinking, and by the cells dying. "
] |
[
"That is not correct. The tissues stays, it just gets smaller. The fat they contain is comsumed. After the energy is used up the remains are actually exhaled at carbon dioxide and water. ."
] |
[
"That is not correct. The tissues stays, it just gets smaller. The fat they contain is comsumed. After the energy is used up the remains are actually exhaled at carbon dioxide and water. ."
] |
[
"How rigorous is the science behind programs like p90x and Insanity?"
] |
[
false
] |
I'm trying to start a new workout plan, and I'm wondering if programs like p90x and Insanity were conceived through real scientific method, or if they are just using guys in lab coats to sell a product.
|
[
"You should probably be aware that the state of exercise science is pretty crappy. It's easy to blame scientists for this (and, to be sure, in many ways they ",
" to blame), but a great deal of the crappiness also comes from the difficulty in securing funding, finding willing subjects who will conform to the demands of the study, and control for a large number of confounding variables.",
"Factors like this are why coaches often don't take peer-reviewed exercise science literature seriously. Essentially no workout program is designed by \"science\", unless by \"science\" you mean decades of trial-and-error combined with anecdotal evidence and folklore from hundreds or thousands of coaches and athletes, often with some attempt to tie it to theory or an understanding of anatomy and adaptation. This is often termed \"bro-science\". In some cases it is far superior to the real science in the field.",
"Circuit training programs like p90x and Insanity are not magic. If you're completely unadapted strength-wise, you'll get stronger. Your metabolic conditioning will improve. You'll probably shed body fat. The basic principle underlying short, intense workouts (and their superior utility relative to long, low-intensity cardio-fests) is well attested both in the scientific literature and in bro-science. Beyond that, it's hard to say what'll work for you. Exercise programming, by its very nature, is something very individual. Pick something you like and stick with it."
] |
[
"I always wanted to know if muscle confusion was a real term that discribed a method that improved muscle definition. "
] |
[
"It doesn't. Muscles do not have brains; they cannot get \"confused\". The term is used to refer to two phenomena:",
"a) during a training program, dropping one exercise (like the barbell bench press) in favor of a similar, related exercise (like the dumbbell bench press). This is done in the belief that muscles \"get used to\" a particular type of stimulus and stop growing or progressing unless the stimulus is changed. In reality, dropping one exercise in favor of another may facilitate recovery (since the stress induced by the new exercise, to which you are not yet as well adapted, cannot be as severe), and it may emphasize slightly different muscles, but there is no aspect of \"confusion\" involved. Muscles do not \"catch on\" to your exercise program, and switching exercises does not magically \"trick\" them into adapting.",
"b) circuit training, or switching from one type of movement to another during a workout. This is simply done so that muscular fatigue doesn't limit your ability to continue operating at a high level of intensity.",
"In the context of circuit-training routines like p90x, the term seems to be used to refer to both. It's bogus, no matter what. There is a simple explanation that does not rely on the mystical ability of muscles to get \"confused\"."
] |
[
"How does a buried seed know where \"up\" is?"
] |
[
false
] | null |
[
"First of all, a seed has a plumule (plant shoot) and a radicle (roots). They grow due to a hormone called auxin.",
"High concentration of auxin in the plumule increases the plasticity of the cell wall and leads to an increased cell elongation.\nFor example, if the plumule were to grow horizontally, gravity pushes down the auxin to the lower cell wall. This causes the lower cell wall to increase in plasticity and increases elongation of the cell walls while the upper cell walls grow with a normal elongation.\nBecause the lower cell walls have a higher elongation, this causes the plumule to bend and grow upwards.",
"In the radicle, the same thing occurs. However, in the radicle, a high concentration of auxin decreases the cell plasticity and cell elongation. This causes the the top cell walls to grow with normal cell elongation while the bottom cell walls grow with decreased cell elongation, making the radicle bend and grow downwards into the ground ",
"Heres a diagram which makes it easier to understand"
] |
[
"There’s a book called “What a plant knows,” I can’t remember the authors name off the top of my head. \nYou may enjoy that. It explains all kinds of things like that in layman’s terms, but was written by a man with a PhD in biology (if I remember correctly) and had good cited resources. "
] |
[
"Shoots and roots respond to gravity in different ways. When shoots and roots develop from the seed, auxins gather on the underside. This results in negative geotropism in the shoots [",
"], and positive geotropism in the roots [",
"]. "
] |
[
"Why do so many people need vision correction, while animals seemingly don’t?"
] |
[
false
] | null |
[
"There is currently a myopia epidemic.",
"Here's a general article with some stats: ",
"https://www.aao.org/eyenet/article/facing-the-myopia-epidemic",
"And here is an older Nature piece:\n",
"https://www.nature.com/articles/519276a",
"You can find many more by googling myopia epidemic or by searching this sub for myopia.",
"We don't really know why it is happening. There is some evidence that being exposed to sunlight when young is a factor (in preventing onset), but nothing conclusive."
] |
[
"Such a sweeping generalization is short sighted (ha, get it?).",
"Shanidar 1 is just one example. A Neanderthal from around 40,000 years ago, likely blind but definitely disabled/featuring paralysis, lived to old age with community support. Prehistoric Homo species definitely cared for each other (with some exceptions). ",
"https://humanorigins.si.edu/evidence/human-fossils/fossils/shanidar-1"
] |
[
"Such a sweeping generalization is short sighted (ha, get it?).",
"Shanidar 1 is just one example. A Neanderthal from around 40,000 years ago, likely blind but definitely disabled/featuring paralysis, lived to old age with community support. Prehistoric Homo species definitely cared for each other (with some exceptions). ",
"https://humanorigins.si.edu/evidence/human-fossils/fossils/shanidar-1"
] |
[
"Why do a lot of the Earth's peninsulas seem to point the same direction?"
] |
[
false
] | null |
[
"The broader point is that there is no geologic reason for peninsulas pointing a particular way. That there happens to be more pointing one way (which is again, actually arguable and also gets into how big a landform allowed to be while still calling it a \"peninsula\" which does not have a formal definition in terms of size) is random."
] |
[
"One could ask the same question with a different direction. E.g., why do so many large peninsulas like Norway/Sweden, Aleutian, Kamchatka, etc point southwest? It's random and you've selected a particular direction to see as more prominent, i.e., the best answer to your question is confirmation bias."
] |
[
"But there aren't many other major peninsulas that point southwest though. Other than those you mentioned one could cite Iberia (and Europe in general) and maybe the southern tip of South America if that counts at all, but that's pretty much it."
] |
[
"First Aid: Burns should be kept dry?"
] |
[
false
] |
My 8yo nephew was badly scalded by shower water resulting in second degree burns. My first instinct was to cool the affected area with water. I got water from the ref, raised its temperature a bit with water from the tap and splashed him with it. We did this for 15-20 minutes, taking care to wrap him up in a towel so that he didn't get too cold. After this, we dressed him up and his parents took him to the emergency room. The doctor who attended him said Is this true? The medical book (it's an old Britannica medical encyclopedia) and first aid book we have at home recommended cooling the area with running water. Is there some new standard for treating burns? edit: We kept the water on him because he said it provided relief. I made sure that ice was never applied on his skin, despite my mother's insistence that it should be done.
|
[
"I am an intensive care specialist working in a burns centre. \nYou did nothing wrong."
] |
[
"I teach first aid. You should flush the area with cool water, but then wrap in a dry dressing (no burn creams or anything like that). By dressing, I mean gauss or something similar.",
"The exact quote from the ",
"Canadian Life Saving Society",
"'s first aid manual is:",
"Flush the burned area with cool, clean water.",
"Cover the affected area with a sterile, dry dressing.",
"Do not break blisters, but if they break on their own, cover with a dry sterile dressing and bandage."
] |
[
"It is my understanding that you did the right thing. I'm not aware of any other efficient and convenient cooling methods besides running water (you were also correct not to use ice).",
"It is kind of ridiculous that the doctor didn't offer any future suggestions or an explanation."
] |
[
"are black holes super cold?"
] |
[
false
] |
My thought was black holes are so powerful that nothing escapes so they must be very cold. Secondly if some heat escapes does escape does that mean the area around a black hole is Super hot? Thank you for your answers.
|
[
"The temperature of a black hole (due to Hawking radiation) depends on its mass: the more massive it is, the colder it appears to be. Astrophysical black holes are quite cold; a black hole with 5 times the mass of the Sun is about 10",
" K, meaning that radiation is entirely undetectable. Tiny black holes that could conceivably be created by high energy cosmic ray collisions would be much hotter and evaporate very quickly."
] |
[
"Does temperature have a meaning inside the event horizon?"
] |
[
"Physics still works inside the event horizon (albeit differently compared to outside) but everything is still operating under the same laws of physics up until the inevitable singularity point.",
"We typically think of the singularity as the point of infinite spacetime distortion at the middle of a black hole, but on the interior of the event horizon spacetime still exists, it's just that all possible timelines (light paths) end at the inevitable future that is the singularity."
] |
[
"What process does a Quantum computer undergo, at an atomic level, to \"read\" Qubits, and how do the Qubits collapse into the state which solves the task?"
] |
[
false
] |
I'm doing a project on Quantum Computing and I've hit a bit of a wall when it comes to Qubits being in the "right" state as it were. As an example, if a Quantum computer were asked to find the two prime factors of a number (like in decryption/encryption), how would the Quantum computer read the selection of Qubits to give the correct solution? The only way I can think of this happening is to have a selection of logic gates that somehow collapse the Qubit into the correct state when observed; however, I'm not too sure how this actually would work with Qubits. Any overview/condensed answers would be as much appreciated as those which go into a more atomic/chemical depth about how it would all physically function. Cheers!
|
[
"I am not entirely qualified to answer this, so please correct me if I'm wrong and I hope someone answers you more in depth.",
"You need to keep in mind that collapsing a quantum state is done with respect to a basis, but that doesn't mean that you create the state out of nowhere, the system already is in a given state, which will be the result of whatever calculation/gates you've done, and that is the \"correct\" state, the task is solved through the interaction of quantum states, no collapsing involved! So what you need to do is read out the final state the system is at after all calculations have been done.",
"As to how that's done, it depends on the system and what is used as qubits, there's spin qubits, qubits made of pollarized light etc.",
"Usually you just need to use the tools and measurements available to you in the experimental set-up to try to find out information about the state of the system.",
"For example, when it comes to using electrons spins as qubits, ",
"Loss & Divicenzo",
" proposed getting the electrons into a quantum dot with a given set of magnetic properties so that it would be influenced by the electron spin, and then you would measure the magnetization of the whole dot. Similarly, you can measure the current that flows through the system which is usually heavily affected by the spin state of the electrons, or the charge distribution, and figure out what state the system must be in for that to happen.",
"So, generally from what I know, you don't just simply collapse the system by measuring it directly, you just create an experimental set-up where by measuring properties of the system, you can reverse engineer the quantum state it is in.",
"Again, the in depth explanation about how that's done would depend on what is being used as qubits, how the computer is designed etc, there's tons of papers that focus on understanding how different qubit states affect physical measurable properties of the systems just to help create different trustworthy read-out options."
] |
[
"I too am not really qualified to answer, but I have some experience with atoms in optical cavities which is essentially qubits interacting which each other.",
"Reading out qubits is not really different from reading out normal bits but instad of 1 and 0, qubits contain a linear superposition a|0> + b|1> which essentially means, if you read out a bit with that state, you will read a \"0\" with a probability |a²| and a 1 with a probability |\"b²\"|",
"There's not more to it than that.",
"I don't know anything anything about quantum algorithms, but in general they will probably deliver a result with cubits in states that are 1|0> + 0|1> (or 0|0> + 1|1> )\nWhich means you have a 100% probability of reading \"0\" (or 1 for the case in brackets).",
"If for some reason a quantum algorithm results in a specific qubit superposition with specific a and b values, then to obtain those a an b values, you literally have to repeat your algorithm and use some statistics.\nThere are some complications with that because a and b are complex numbers. So you can know the magnitude but not the phase."
] |
[
"you just create an experimental set-up where by measuring properties of the system, you can reverse engineer the quantum state it is in.",
"This is called quantum state tomography. It is not possible to create a single set of measurements to re-create a given quantum state (see ",
"Holevo bound",
"). This is the foundation for all quantum based encryption / security. In a quantum computer you don't want to do state tomography as the number of needed measurements scales with the size of the Hilbert space, that is, exponentially in the number of quits."
] |
[
"Why does adding an iron core to a coil increase the flux density?"
] |
[
false
] |
So the current in the coil generates a magnetic field. Why does adding an iron core to the centre increase the flux density? I know it's something to do with the generated magnetic field reinforcing the domains that reinforce the field, and shrinking those that oppose it. But I don't exactly know what that means. What is a domain?
|
[
"A domain is a chunk of matter inside a body whose component atoms have their electrical spin aligned in the same direction. Meaning, if you were to rip out that chunk of, say, iron from the whole, it would act as a magnet.",
"Normally, any given piece of iron has many domains, all going in different directions, not one strong enough to expand and magnetize the whole. But when you expose the iron to a strong magnetic field, individually each atom moves to align its spin with the field. On a higher level, this causes the domains to shift, align, and merge into one, giving you a temporary magnet.",
"Since this new magnet has its own magnetic field, the result inside the coil is an increase in the intensity of the magnetic field at each point, or an increased flux density on the whole."
] |
[
"Thank you! I understand now."
] |
[
"Magnetic domains exist also in monocrystalline materials, but grain boundaries can also affect how the domains form.\nSo you don't ",
" the grains to form domains, but they will have an effect on them, if they are present."
] |
[
"For the vast majority of Earth's history, there was no life on the surface. What did the landscape of the Earth look like before plant life, or land animals?"
] |
[
false
] |
This is a strange question, but it's bothering me. I don't think I've ever seen an artists impression/depiction of what Earth's surface has looked like for most of its lifetime. I remember in Walking with Monsters they depicted it as a dry, desert, arid landscape. What would it have looked like? If the Earth was stripped bare, would the rocks be grey? Yellow? Brown? Would it be dusty, muddy, or sandy?
|
[
"It's actually a really fascinating question and gets at the myriad of ways plant and animal life (and especially plants) influence the processes active at the surface of the Earth. ",
"This is a pretty cool review (but short) article",
" on this subject, which touches not only what we (generally) think landscapes looked like before land plants, but also how the evolution of different broad categories of organisms changed processes and thus landscapes. ",
"The view of an arid landscape isn't quite right (at least not everywhere), but things would have looked quite different. Without plants to stabilize river banks, most river networks were big, broad networks of streams, the closest analogues being ",
"'braided rivers'",
" we see in the modern in areas with high sediment loads. In some places, the view of arid landscapes aren't too far off as 'aeolian' deposits (e.g. large dune fields, etc) are also quite common in rocks of the age from before land plants. For me, one of the most interesting tidbits is that generally before plants and significant terrestrial microbial activity, chemical weathering was thus extremely minimal, which meant that you see almost no fine grained material (i.e. muds) or clay minerals. ",
"The disclaimer here being that I study much younger landscapes (well, younger geologically speaking, 5 Ma is damn young on a 4.6 billion year timescale), so someone more familiar with the Archean and Precambrian rock record might have more things to add."
] |
[
"There are some fascinating examples of long-lasting weathering surfaces (soils) that developed in the Precambrian. ",
"A seminal paper from 1982",
" found evidence of soils as mature as modern tropical soils to have formed long before any land plants existed (near modern Michigan, but it would have been equatorial in the past). Here's another, more ",
"updated example",
" hailing from below the ",
"Great Unconformity",
" in Wisconsin. ",
"In the modern Baltics, there is a ",
"paleosol",
" preserved in the bedrock that was so intensely weathered it likely formed for at least many hundreds of thousands of years. That's pretty nuts, considering there weren't plants to physically stabilize the landscape and facilitate chemical weathering. It is likely, though, that bacteria and perhaps fungus had inhabited the soil, but a lot of that weathering is just straight chemical decomposition of mineral grains under hot, wet climatic conditions."
] |
[
"Awesome!"
] |
[
"Would shooting a grenade actually cause it to detonate?"
] |
[
false
] |
Sorry in advance if this is the wrong sub, but it's something you always see in movies or video games, but how accurate is that? I know some explosives, like C4, will only detonate if the right detonator is used, is the same true for grenades?
|
[
"This is not 100% correct, it is possible to detonate a Grenade but one would have to hit the grenade in one of two places. The primer under the cock striker which is under the spoon, or with a strong enough bullet to hit the lead azide or Mercury fulminate in the blasting cap in the center of the main explosive. May take a few shots but it works. This technique is called Smud. But to in crease the chances we used high explosive incendiary rounds that detonate on impact. I used this multiple times on IED's when I suspected a set up to kill the operator. And it is fun "
] |
[
"This is not 100% correct, it is possible to detonate a Grenade but one would have to hit the grenade in one of two places. The primer under the cock striker which is under the spoon, or with a strong enough bullet to hit the lead azide or Mercury fulminate in the blasting cap in the center of the main explosive. May take a few shots but it works. This technique is called Smud. But to in crease the chances we used high explosive incendiary rounds that detonate on impact. I used this multiple times on IED's when I suspected a set up to kill the operator. And it is fun "
] |
[
"I don't know why nobody has cited it yet, but the answer is:",
"(Yes) Plausible",
". ",
"Small-arms and shotguns both actually rendered the grenades inert (separating the blasting cap from the grenade), but a .308 rifle round imparted enough force to cause detonation of the grenade without aid of the blasting cap."
] |
[
"Do the large numbers of holiday lights this time of year have a measurable impact on the brightness of the US at night as seen from space?"
] |
[
false
] | null |
[
"I think this is hard to judge because most of the images where you see a map of \"lights\" of the US or world or other country are usually done in upwards of 200 passes of the satellite. this means that it'll more than likely take longer than the christmas season to complete. if it could be done in a night I believe there would be a difference in the light maps.",
"P.S. sorry everyone hijacked your question with power consumption facts. WTF mate."
] |
[
"better yet, do they have a measurable impact on the average electric bill?"
] |
[
"Now you are in my wheelhouse. Time for some imperial data. I have been running ",
"this",
" display for the last 6 years. Measurable impact; the first year my electric bill went up ~$15 for the month of December. The best reasoning I can find is that unlike a normal light display, mine is programmed so it is always only on from 5pm to 10pm. On average, at any given time, only about 25% of the lights are on. The lights that are on are usually fading some direction, so they are not consuming a the full rated power. None of the cost savings was done intentionally, it was just the best way to make it look good with the music. My show consists of about 15,000 LEDS and 30,000 mini-incandescent bulbs. Surprisingly, the LEDs were not a good investment because $6 a string, they will never yield enough cost savings to pay off the electricity difference vs. the purchasing cost. On the flip side, there is less manual labor because they don't burn out and I don't have to hunt for the one bulb in 15,000.\nTLDR; ",
"This",
" show costs me about $15 in electricity."
] |
[
"Why is it dangerous to stare right into the sun?"
] |
[
false
] |
[deleted]
|
[
"It is dangerous because the sun is really bright and your eye works like a lens, focusing the light onto the back of your eye.",
"We all know of the kids lighting leafs and ants with magnifying glasses, thats what your doing to your eye :P",
"I strongly suggest you not to do it ever again, you eye can take some rough handling, but once you've scorched the nerves your blind. "
] |
[
"Though I do like the fact that you question things and want to experiment yourself, it is always good to check how dangerous something can be before exposing yourself to it. :P"
] |
[
"Though I do like the fact that you question things and want to experiment yourself, it is always good to check how dangerous something can be before exposing yourself to it. :P"
] |
[
"Could humans train themselves to evolve to the point of needing only an hour or two of sleep?"
] |
[
false
] | null |
[
"see ",
"Uberman Sleep Schedule",
". 6x20 min naps = 2 hours"
] |
[
"I've heard of this before, but there a quite a few professions out there that this would be impossible with, and not something that could be done by humans as a whole."
] |
[
"It's the closest thing to your question that has been proven to work."
] |
[
"Are there any harmful effects of drinking vitamin B12 energy shots?"
] |
[
false
] |
Today I was ID'ed for buying one of those vitamin B12 energy shots (like the "5-Hour Energy" drinks). This really caught me off guard as I've never been ID'ed for purchasing energy shots before. (Mind you, I can count the number I drink in one year on one hand) I assume the motivation to keep energy away from minors is to protect them from potentially harmful effects of ingesting too much caffiene, amongst other stimulants. But AFAIK the main component of energy is a massive dose of vitamin B12 (~8000% the recommended daily dosage); energy otherwise lack the stimulants that drinks like Red Bull or Monster contain. My limited knowledge of biology tells me that my body will discard any excess vitamins in urine after my body has "used up" what it needs, so there is no harm done in drinking "too much". Am I seriously off here? Seems to me the abuse of energy shots don't pose any serious risks the way energy drinks do. Is there some sort of legitimate reason to control the distribution of energy shots to minors?
|
[
"I believe the distinction is that vitamin B12 is water-soluble, so it makes its way out of the body easily in the form of urine. Whereas something like vitamin A is fat-soluble, so the body cannot discard it as easily.",
"I'm no expert though, my knowledge is limited to first-year biology."
] |
[
"I believe the distinction is that vitamin B12 is water-soluble, so it makes its way out of the body easily in the form of urine. Whereas something like vitamin A is fat-soluble, so the body cannot discard it as easily.",
"I'm no expert though, my knowledge is limited to first-year biology."
] |
[
"You ",
" OD on water soluble vitamins, such as B12, but you'd have to work really hard at it. Wikipedia even states that there is no known tolerable upper limit for B12 (and before anyone jumps on me for using Wikipedia, the source for this information IS a reputable source). But you can OD on fat soluble vitamins (like A and D) a bit easier. ",
"In this case, your body will simply eliminate any B12 you didn't make use of. If you've ever taken a general B vitamin supplement, then you might already be acquainted with the neon yellow urine it gives many people.",
"That said, I have no idea why someone would card you for buying an energy drink."
] |
[
"Before things like electric drills, welder machines, forklifts, excavators etc. became widespread, how were major factories and ships etc were built?"
] |
[
false
] |
Even at the pictures of factories from 1890s, there seem to be very big moving metal machinery, and I just wonder how they made it and put it there.
|
[
"They had hand powered drills, steam powered drill presses, and sometimes just poked holes in red hot iron on the forges. ",
"They could hammer red hot pieces of metal together to weld, or as in ships, riveted them together. ",
"They had ramps and hoists to do the work of forklifts. ",
"They had little excavators (",
"tumblebugs",
") to drag behind horses, or even had thousands of men hauling off buckets of dirt to replace excavators."
] |
[
"This a a pretty good summary. The history of machinery is pretty fascinating when you consider that, for example, if you wanted to make something like a milling machine, you'd first think to make the parts using a milling machine. The need for better machines in order to make better machines is part of why modern technology took a while to develop."
] |
[
"You might enjoy the book, \"Foundations of Mechanical Accuracy\" which talks about how technological advances required a new standard set for mechanical precision and accuracy. It is very interesting and has a lot of cool photos of the process.",
"http://mooretool.com/publications.html"
] |
[
"What does askscience think of the e-cat?"
] |
[
false
] |
The e-cat (Energy Catalyzer) is supposedly a Low-Energy Nuclear Reaction build by an Italian inventor, Rossi. It has gained some credibility this week by running three hours sustaining it self and generating an even amount of heat with no signs of decrease. Description from : The Energy Catalyzer (sometimes shortened to E-Cat) is an apparatus built by inventor[1] Andrea Rossi,[2] with support from his scientific consultant, physicist and emeritus professor[3] Sergio Focardi. The 2009 patent application[4] claims "a method and apparatus for carrying out nickel and hydrogen exothermal reactions," with production of copper.[5] Although the patent cites previous works on cold fusion,[6] one statement by Rossi asserted that it is not cold fusion, but rather LENR, Low-Energy Nuclear Reaction.[7][8] Claims of a similar system, but yielding considerably less power, had previously been advanced by Focardi et al.[9] According to Focardi, "the hydrogen is heated at a given temperature with a simple resistor. When the ignition temperature is reached, the energy production process starts: the hydrogen atoms penetrate into the nickel and transform it into copper.”[10] The device has been demonstrated to an invited audience several times, and has been commented on positively by Bologna physics professor Giuseppe Levi, and by the Swedish technology magazine Ny Teknik, together with the online publication New Energy Times. However, Ny Teknik and the New Energy Times, together with other sources, have since published less favourable reports - with Ny Teknik pointing out apparent flaws in the science involved in testing, and the New Energy Times going as far as to assert that Rossi's claims may be fraudulent. According to Rossi, commercial application of the device will begin in October of 2011. Snake oil? What would it mean if it is real? Here is a link to Here is a
|
[
"I know we've discussed it a million times, but I'm having trouble finding old discussions on the matter, so I'll just go ahead and summarize my usual arguments here.",
"They don't have open-box demonstrations, so who the hell knows what they're doing. Without reproducibility it's not science in the classical sense. I understand their perceived need for protection for their idea, but until the effect can be independently verified and reproduced, it's not a part of public physics knowledge. Which then leads into a discussion of whether science is a public vs. private concept, and a particularly interesting argument someone gave me about secret cryptoanalysis studies and whether that counts as science even if it isn't publicly disclosed and peer-reviewed.",
"They don't have a good proposal of what's physically happening. Fusion requires two nuclei to overcome their mutual repulsion to then form a lower-energy bound state. Without a good explanation of how this happens, I remain skeptical at best. To date, they've only self-published an explanation, and haven't published in a peer-reviewed source. Again, without open-box knowledge who the hell knows what's going on.",
"I would be skeptical, extremely skeptical. If they can make more energy than it costs to produce the energy, even if it's not fusion, then they'll make money, and that's fine. But I doubt it highly. Right now it's a magic trick (\"an illusion, Michael\"). It's a black box where they claim magic happens and energy is produced. "
] |
[
"I don't know the answer to that. Only they do apparently."
] |
[
"Thank you for your reply shavera. I feel that your summary seems fairly accurate of what the general consensus is. ",
"However, actually they opened some parts of the \"reactor\" this last test.",
"Furthermore, the casing enclosing the reactor was opened after completion of the test, and the invited guests was thus able to see what was inside – basically a heat exchanger with metal flanges; within it, according to Rossi, was a shielded flat reactor unit with three reactor chambers, only one of which was operating during the test.",
"However the inner workings are still hidden, but it still makes me wonder, what it would take generate \"between two and three kilowatts\" for three hours with something concealed. Would a small battery be sufficient?"
] |
[
"Does light lose speed after reflecting of objects?"
] |
[
false
] | null |
[
"It doesn't lose speed, light always travels at the same speed, but, even for a perfectly reflecting mirror, it does lose energy. When a photon reflects off a mirror it undergoes a change in momentum (momentum is directional so the photon leaves with a momentum of opposite sign). Due to conservation of momentum, the mirror must gain equal and opposite momentum. If the mirror does not have infinite mass then this change in momentum must result in a corresponding energy change. From conservation of energy, this manifests itself as a drop in the photon energy and thus an increase in its wavelength. In other words, a red-shift.",
"I discussed exactly how the mirror gains energy in this post",
", including a rough calculation of how big the effect is, for those that are interested.",
"I have also had about a half dozen comments asking how something with no mass can have momentum so my reply is:",
"Momentum being a property unique to things with mass is only true in newtonian physics. ",
"In special relativity everything with energy has momentum.",
"A photons momentum, since it's rest mass is 0, can be calculated from the simple expression p = E/c, in the direction of propagation."
] |
[
"What would happen if you trapped light between two mirrors? The energy of the photon would go down every time it bounces off one of the mirrors but what happens if the energy reaches 0?",
"It would continually lose energy yes but mathematically it is more like the energy asymptotically approaches 0 rather than actually becomes 0. Physically this would be interpreted as the frequency asymptoptically approaching 0 as well.",
"In reality it is probably more complex, as the wavelength approaches a size comparable to the separation between the mirrors then you would have to begin to consider the wave nature of the photon rather than just treat it as a tennis ball bouncing off a wall. It is probably, at least as a thought experiment, possible to set up a standing wave between the two mirrors, which could theoretically stop any further loss of energy."
] |
[
"Definitely impossible to construct."
] |
[
"How can exoplanets in systems whose planes do not allow transits visible to earth be detected?"
] |
[
false
] |
Wikipedia lists astrometry and thermal imaging as being the two methods that don't require earth to be within the system's plane, but they are very limited in comparison to transits. Are there any promising methods that may eventually allow reliable detection of exoplanets in systems whose planes don't align nicely with earth? I imagine only a very small percentage of systems' planes allow allow transits observable from our system. If all systems were aligned such that their exoplanets were observable by transit, what's an estimate of the increase in detectable planets that would occur? That is, what percentage of exoplanets that would otherwise be detectable are expected to exist but are undetectable because of the angles of their planes?
|
[
"There's a lot more methods to detect exoplanets. I'll summarize them : ",
"For further reading see : ",
"https://exoplanets.nasa.gov/alien-worlds/ways-to-find-a-planet/",
" (you can see exact detection statistics here) and ",
"http://www.mpia.de/homes/ppvi/chapter/fischer.pdf"
] |
[
"Astronomy"
] |
[
"Astronomy"
] |
[
"Mutation in a Multicellular Organism"
] |
[
false
] |
Hi team, I've asked . So I likely have some misinterpretations which confuse both. I'll try to be clear. I'll probably get a lot of the technical terms wrong; I've only studied biology to grade 11 and some armchair reading. By all means use the correct technical terms, but please be patient with me. My understanding is that there is a process (Mitosis?) by which a multicellular organism (MCO) replaces cells in its body with other cells in its body. So... while the cells that make up your stomach lining or brain (for example) have the same genome as the cells in your stomach lining or brain did ten years ago (unless you're 8), they are physically different cells. It seems that many errors (mutation) during mitosis are either killed off (usually by apoptosis?) or become cancer. But surely there must be some mutations that slip through and are either benign or - rarely I would guess? - favourable to the organism. So... what happens if the mutated neutral or beneficial daughter cell then becomes a parent cell? Is it possible for two (or more!?) slightly different genomes to exist within the same 'organism'? What would prevent such a being from being classified as symbiotic? Maybe I have it all wrong... But I tried to find this online and I could not.
|
[
"I would guess that everyone does have subsets of cells with a slightly different genome due to mutation. Every mole probably has a slightly different genome. The genetic term for this is 'mosaic.' ",
"Probably what separates them from being called a different organism is the inability of the cells to replicate outside of the host, as well as perhaps the similarity between the genomes of the cells. ",
"You could even further ask whether cancer could be considered a parasite. It wouldn't surprise me if there was a large difference between a cancer cell's genome and the host genomes, larger than the difference between some species. But again, the cancer can't replicate outside of the host or spread between people, which is what I think limits whether it is considered a separate life form. Some cancers are transmissible though, among Tasmanian devils. Normally you can't catch someone else's cancer because you recognize the cells as foreign, like an infection. But there are so few Tasmanian devils that they are all very immunologically related so they can catch each other's cancer. ",
"Some people have proposed that a human cancer cell line (HeLa) that can be propagated in lab culture constitute a new species. However the scientific community has generally not been very accepting of this train of thought. "
] |
[
"As grateful as I am for your help, I wish that I'd been the first to think of it... It's a whole thing!"
] |
[
"As grateful as I am for your help, I wish that I'd been the first to think of it... It's a whole thing!"
] |
[
"According to Relativity, how fast would I need to travel before my mass was sufficient to collapse into a black hole?"
] |
[
false
] |
According to relativity, your mass at speed is higher than your rest mass, and as you approach the speed of light, this mass increases exponentially. Assuming I'm 70kg and was able to move without a craft or anything of the sort, how would I work out how fast I would need to travel before the Schwarzchild Radius of my body increased to beyond myself, collapsing me into a black hole? My apologies if I'm spouting utter nonsense- Just an idea that occurred to me, and I wanted to know if it was (hypothetically) possible.
|
[
"This is one of the reasons people don't use this outdated increasing mass idea anymore. Your mass is your mass; it doesn't change or increase as you get to higher speeds. And good thing, too, because one of the fundamental tenets of relativity is that as long as you're moving at a constant speed, you might as well be at rest. You're always moving at near the speed of light with respect to ",
" reference frame, so it would be very odd indeed if you spontaneously turned into a black hole!"
] |
[
"This",
" gives a good explanation of why that's not possible."
] |
[
"Your mass doesn't increase in your own reference frame because you are always at rest to yourself. So, in your reference frame, you never form a black hole. Therefore, you don't form a black hole in ",
" reference frame.",
"The idea of \"certain amount of mass in a certain volume\" forming a black hole is slightly misleading, because in general relativity there isn't a clear value that corresponds to mass."
] |
[
"How much of a disadvantage was Russia's high latitude for the USSR's space program?"
] |
[
false
] |
As I understand it, there is a benefit to launching spacecraft from a location near Earth's equator. Russia, however, is no where close to the equator. Would this have made it significantly more difficult for the Russians to make it to the moon? or would the difference be negligible?
|
[
"Baikonur is 46N. Canaveral is 28.4N.",
"That means that Canaveral is whipping around at (cos(28.4)-cos(46)*40,000km/24hr faster, or about 335km/hour faster.",
"Low Earth Orbit is about 28,000km/h.",
"There is a difficulty that you tend to get a more tilted orbit which changes the places you might land."
] |
[
"It must have been quite a lot. ",
"Since october 2011, Russian are using Kourou in French Guyana. According\nto the ",
"wikipedia article",
", this increases the payload of the same Soyus rocket from 1.7 tonnes to 2.8 tonnes\nwhen launching to geostationary orbit. "
] |
[
"That's cool, I didn't know the math worked out that easy. Thanks :)"
] |
[
"Is more energy used in running a distance rather than walking the same distance?"
] |
[
false
] |
I'm not really sure about this. But I thought since the same mass is transported the same distance, than the same of work is done.
|
[
"It depends on the speed you are travelling. At around 5 or 6mph I think it is more efficient to run than walk. This is why speed walkers burn so much more energy than runners. ",
"http://sprott.physics.wisc.edu/technote/walkrun.htm"
] |
[
"Note that this is if you are comparing runners and walkers moving at the same speed. Also the calculations you link too are fairly simple- I'm not sure if the linear relationship between power and running speed is borne out in more complicated work. Also note that Figure 1 compares power (i.e. energy/time) used walking and running. Thus if you use the graph to compare two different speeds, you must take into account the time used in each activity."
] |
[
"I have remember seeing the curve of measurements of energy used for running and walking at different speeds. At least qualitatively, the curves are remarkably similar to the ones in the link, so I don't think the approximations are too harsh. I think the running curve seemed to have a small non-zero intercept, but apart from that, it was quite linear. Sorry, no source, I just remember the shape of the two curves, and how the measurements were positioned."
] |
[
"Considering its solid core, why is Saturn referred to as a gas giant rather than a rocky planet with immensely thick atmosphere? Can you \"fly through\" a gas giant?"
] |
[
false
] |
Than you for your time and answers.
|
[
"Our gas giants are referred to as gas planets because the vast majority of their mass is composed of materials found as gas on Earth.",
"In reality all four have large non-gaseous regions in the center. ",
"Jupiter and Saturn are large enough that the pressure increases steadily until the hydrogen enters a supercritical state and behaves more like a molten metal than a gas.",
"Uranus and Neptune are smaller and colder and likely have pressurized water-ammonia \"seas\" deep beneath the clouds.",
"So no, you could not fly through them.",
"In our solar system there's a clear difference between rocky planets and gas planets since there's a huge mass jump from Earth to Uranus. We've never observed a planet in the 5-10 Earth mass range to see how it behaves."
] |
[
"I have a related question, Given the fact that these Gas Giants have undoubtedly absorbed millions of tons of rock and metal in the form of asteroids and probably a few dwarf planets, could they have a rocky core if all this material settled to the center?"
] |
[
"They will have started off with some 'rocky' elements anyway, so yes, there are probably some present in somewhere in their interiors."
] |
[
"How do wifi signals work?"
] |
[
false
] |
I know the router emits the signal. How does this signal travel? It's it affected by mediums such as solids and liquids?
|
[
"The physics of Wi-Fi relies on the same principles as any other radio device. When an electrical current is passed through a long wire, such as an aerial, and this current is reversed in direction very quickly, it produces electromagnetic waves that propagate away from the aerial with the same frequency. These waves are just like visible light but of a much lower frequency. The range of frequencies that we label as microwave and radio have properties that make them ideal for broadcasting data, be it TV signals or Wi-Fi. Some materials that would be opaque to visible light frequencies are near transparent to these frequencies, while the larger wavelength allows the signal to diffract around larger objects.\nSo in short, yes they are affected by objects and materials but one of the many motivating factors in the choice of the Wi-Fi frequency is how transparent the walls of your house will be to the signal, for example. ",
"The signal is received in a similar way to how it is broadcast. The same kind of antenna used to produce the signal will also be sensitive to receiving such a signal. The electromagnetic waves will oscillate the electrons in it, in the reverse process of generating a wireless signal by oscillating the electrons with an alternating current. "
] |
[
"On a related note, ",
"this blog post",
" explores solving the Helmholtz equation to visualize how the signal propagates through a house. ",
"Pretty neat",
", imo."
] |
[
"The signals are electromagnetic radiation, other examples of which are visible light, gamma rays and x-rays, although these all have different wavelengths. It shares many properties with the visible light that we're used to.",
"Electromagnetic radiation is not completely understood - we do know that they are a result of an electric field and a magnetic field oscillating perpendicularly against one another.",
"It is indeed affected by the medium through which it travels, similarly to how a cucumber reflects green light, while a tomato instead absorbs green light. How it's affected depends on the materials' abilities to support electric and magnetic fields for that frequency. Does this answer your question?"
] |
[
"How small can an object be in space and still support an atmosphere?"
] |
[
false
] |
I'm assuming it would not only require enough mass but maybe a magnetic field too. Could a large asteroid potentially have a very thin atmosphere? Thanks.
|
[
"For gases to stay over geological timescales the escape velocity must be a large multiple of the typical thermal speed of particles.",
"For the lower size limit you want a slow thermal speed - cold and with heavy gases like xenon. If you are fine with very thin atmospheres then asteroids could have atmospheres if far away from a star. At 100 K, xenon typically moves at ~100 m/s, an escape velocity of 500 m/s (Ceres) would give it some survival time but with significant losses. A bit more mass or a bit lower temperature and you can keep it over geological timescales. The vapor pressure of xenon at 100 K is very low, however."
] |
[
"When the Pioneer and Voyager probes passed Jupiter and imaged the sulfur volcanoes on Io, their instruments also detected a torus of gas surrounding Jupiter in which Io orbits. It is very low pressure, hardly more than the local interplanetary vacuum surrounding jupiter, but it has a consistently higher density all the way around the planet. After some pretty extensive modelingl the scientists determined that it was held there by the combination of the constant outgassing from Io and the steep gravity gradient that close to Jupiter. I've never see the math, but it was shown to Sci-Fi author Larry Niven. He took the equations a tried to find a scenario where you could have a breathable atmosphere in a zero-g environment in space. The scenario he came up with was supernova remanent neutron star orbited by the blasted remanent of a neptune class gas giant outgassing its atmopshere. The result is a near earth normal pressure \"ring\" or torus around the neutron star with the planet embedded in it. It's not quite your scenario of an atmosphere around a small body, but is instead an atmosphere in complete zero g. Niven wrote a couple of sci-fi novels, the \"integral trees\" and \"the smoke ring\" and short stories in this setting. The environment is ",
"diagramed",
" a few places on the web. The link just posted says there is similar ring around Saturn and Enceladus, which is also constantly outgassing"
] |
[
"You need to define what atmosphere means for you. The moon technically has an \"atmosphere\" as does Mercury. Pluto as well has a thin hazy layering of gases. An asteroid like Ceres may hold on to some trace amounts of gases. That all being said if a body hasn't reached hydrostatic equilibrium then it's not going to have an atmosphere, that I can be sure of. Please remember all of the atmospheres I mentioned would be very very good vacuums here on Earth. Everything is relative.."
] |
[
"In a closed energy system with a set amount of energy, are there only a finite number of ways it can reach a state of total entropy?"
] |
[
false
] |
[deleted]
|
[
"Please correct me if my interpretation of the question is wrong. It seems like this system has fixed N,V, and E, so we are working with the microcanonical ensemble. Each microstate that the system can take on is equally probable, with probability 1/(total number of microstates). (NOTE: In my interpretation of the question, the starting microstate is one of these equally probable microstates.) Since each microstate is equally likely we can infer that the total number of microstates must be fixed. This means that the entropy of the system will not evolve and that there is no \"end\" point."
] |
[
"That would imply there can be no loops in the path, which is not a given."
] |
[
"This is also a question I wanted to ask, which I should probably have a separate post for. But how concrete is the second law of thermodynamics? Is there any reason why it absolutely always must apply to a system? Or does it just happen to always apply in the universe that we live in?"
] |
[
"What happens when I skip a meal? Why some people appear to be unfazed, while others feel bad almost instantly?"
] |
[
false
] | null |
[
"Thank you, it seems I was missing something during my reading, and now it all makes sense!\nBrain not having enough energy takes care of the headache part of your explanation, but where does the physical weakness come from? Muscles should still be able to use fat for energy, as they have nothing to do with ketogenesis, right?",
"One post below, you mentioned glycogen levels. Can the amount of stored glycogen vary greatly (say 1.5x or more) between people? (Assuming all of them are getting their carbs, of course.)",
"And to clarify further: I'm not talking about the sensation of hunger. If I'm engrossed in something, it's quite possible for me to skip a meal and only notice it by the secondary symptoms that I should be hungry."
] |
[
"Thank you, it seems I was missing something during my reading, and now it all makes sense!\nBrain not having enough energy takes care of the headache part of your explanation, but where does the physical weakness come from? Muscles should still be able to use fat for energy, as they have nothing to do with ketogenesis, right?",
"One post below, you mentioned glycogen levels. Can the amount of stored glycogen vary greatly (say 1.5x or more) between people? (Assuming all of them are getting their carbs, of course.)",
"And to clarify further: I'm not talking about the sensation of hunger. If I'm engrossed in something, it's quite possible for me to skip a meal and only notice it by the secondary symptoms that I should be hungry."
] |
[
"You're right, I completely misread the comment at the top of this tree; I thought it said \"carb-rich,\" not \"less carb-rich.\" Thanks for that."
] |
[
"Is it possible for radio waves to be created by red shift and gamma rays with blue shift?"
] |
[
false
] |
Some context on how I came to think of this, I was learning some stuff about emission and line spectra and how they can be used to determine the elements in a star. Later on in the lesson it was explained red shift effects the colours seen and red shift needs to be taken into account. That got me wondering surely red shift (and blue shift) can be so extream that the waves can be radio or gamma waves. Is it even possible for the wavelengths to be larger than radio waves or smaller than gamma waves.
|
[
"all EM is the same stuff, really. if you're in a spaceship cruising at relativistic speeds toward a radio source, the waves are blueshifted. how much it shifts depends on relative motion. also photos exiting a gravity well redshift, and blueshift when they \"fall\" toward a massive object. wavelength is variable beyond what you study in class, but you'd need longer and longer antennae to detect infraradio."
] |
[
"Is it even possible for the wavelengths to be larger than radio waves or smaller than gamma waves.",
"Radio and gamma radation are just defined as radiation above or below a certain frequency or wavelength or energy, so no, any very long wave would just be a low-frequency radio wave and any very short wave would just be a high-energy gamma ray.",
"The Cosmic Microwave Background started out as primarily infrared and optical radiation, and has been redshifted all the way to the microwave regime (and some of it is in the radio). That's the highest cosmological redshift for any object. ",
"If you were in a spacecraft traveling very close to light speed, you would observe light ahead of and behind you getting strongly blueshifted and redshifted, respectively, and in principle you could go fast enough that an optical photon would appear like a gamma ray or radio wave to you. But in practice it's unlikely that such a situation would be achievable."
] |
[
"from quora:",
"I don't think there are absolute limits on the electromagnetic spectrum but I can come up with two limits:",
"The longest wavelength for a photon would be on the order of the distance to the CMB radiation that started when the universe was only 379,000 years old. Since the big bang started 13.8 billion years ago, the wavelength would be: \\lambda = 13.7 billion light years. The energy of the photon would be:",
"E \\approx 10",
" eV \n(see (plancks constant) * (speed of light)/(13.8 billion light years))",
"The highest energy gamma ray would be on the order of the Planck Energy:",
"E \\approx 10",
" eV \n(see planck energy)",
"The reason this could be on the order of the maximum energy is that the wavelength of that photon would be a Planck Length and if you confine a Planck Energy to a Planck Length a black hole would form.",
"So the ratio of the minimum to the maximum possible energy or wavelengths or frequencies of photons would be 60 orders of magnitude. For comparison, the Wikipedia article on the Electromagnetic spectrum only lists only about 20 orders of magnitude for named ranges of the electromagnetic spectrum. These range from Gamma rays at 1 picometer (1.2 MeV) to Extremely Low Frequencies waves at 100 million meters (1 femto eV). The energies I list for the maximum and minimum photon shown above are all about 20 orders of magnitude larger or smaller than the named limits.",
"http://www.quora.com/Physics/Is-there-a-limit-to-the-electromagnetic-spectrum"
] |
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