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[
"Does food temperature affects the nutritional absorption?"
] |
[
false
] | null |
[
"Not really, everything quickly becomes the same temperature as your insides, making the starting temperature a moot point."
] |
[
"I can see why that would be true eventually, but would temperature noticeably affect the rate?",
"For example: I drink milkshakes fairly frequently, and I'm a fan of blending blueberries into it. I just switched to frozen blueberries so I could buy them in bulk. Assuming nothing is lost by freezing them, how much would it affect uptake in the first hour?"
] |
[
"Everything is back to body temperature in a couple of minutes, the time it takes for the stomach to grind things up is longer. "
] |
[
"Did all winged insects evolve from a common winged insect, or did wings evolve multiple times in insects?"
] |
[
false
] | null |
[
"Theories on how wings evolved in insects come and go as more fossil evidence is found, but the current theories all point to a single evolutionary tree for flying insects. (It's slightly complicated because some lineages have lost and regained wings.) ",
"There are still competing theories on which body parts evolved into wings and what the intermediate benefits were, possibly including assisted jumping and better heat absorption. ",
"More details are online, including ",
"https://www.sciencedirect.com/science/article/pii/S0960982216314610"
] |
[
"The vast majority of ant species have members of the colony with wings. Drones (males) and maiden queens will have wings, once a queen begins mating and starts building a nest she tears her wings off. Just like in bee colonies, the drones do no work, and exist seemingly to fertilize new generations of ants when appropriate.",
"There are a few exceptions, but this is the general rule."
] |
[
"Would ants be a subset of that tree that lost the winged trait? Or do all ant species have a type of flight in their colony?"
] |
[
"Do prescription SSRIs affect brain development during childhood and adolescence?"
] |
[
false
] | null |
[
"this is kind of a double edged sword. ",
"On one hand, many drugs during the developmental process can have an effect on brain development. on the other, does the benefit outweigh the risk of taking said drug. (in this case SSRIs and SNRIs)",
"lets take an example, \nduring pregnancy, stress levels of the mother can effect gene expression of her unborn child and can alter dentate gyrus granular neurons spines, length, and complexity. thus, having an impact on here child. they are not sure of the exact role (as far as i can tell but i don't have a lot of time to do the research) of these drugs on the offspring, but reducing the stress/depression of the mother with a SSRI or SNRI may be more beneficial for the offspring than leaving her untreated. ",
"as far as childhood and adolescence go, I'm not sure. but since, at this stage of development, untreated stress/depression can have a long term effect on the way our body handles stress (i.e. the coping/response to stress results in long term changes in gene expression and our future stress events are coped with according to these long term changes.) I would say, either way you are altering something but it is probably more beneficial for people to take these than not. It might be a way to avoid negative alterations. ",
"as far as receptor damage or anything like that, these are just reuptake inhibitors so it just allows noradrenaline and serotonin (for SNRIs) to act longer in the synapse and i'm not sure but i don't think it would cause damage, especially since these levels would be lower than normal anyways. ",
"I hope that at least answers a little of your question! "
] |
[
"it also important to not that these drugs are based on the monoamine deficiency theory (which is the deficiency of these neurotransmitters). there is another theory based on a BDNF (brain derived neurotrophic factor) deficiency. BDNF is important for neuronal plasticity, dendrite growth, stability of synapses etc. with a low level, these neurons are not able to sustain normal function. so, a BDNF supplement in the developmental stages of these patients might be able to help develop these neurons and, in response, may be able to revert the negative side effects long term. i'm not sure about the long term part if the patient quits taking the supplement, but it would be worth a shot. There are probably articles on this but I would have to look into that another time. "
] |
[
"Thank you! I got put on Prozac in 4th grade (not sure how/why) and 15 years later I'm wondering if I can ever stop, or if SSRIs caused my brain to develop in such a way that it would be more disturbing than normal to wean off them.\n ",
" "
] |
[
"What is happening in your body when you get the chills from reading a scary story?"
] |
[
false
] | null |
[
"An intense emotion activates the sympathetic nervous system, which triggers the contraction of muscles called ",
", attached to hair follicles. This contraction causes the hair to erect, causing goose bumps. Generally speaking, the sympathetic nervous system is activated by stress and prepares the body to a fight-or-flight behavioral response. Goose bumps allow hairy mammals to look bigger (so more dangerous) than they appear. A scary story triggers a hint of this fight-or-flight response."
] |
[
"I know a bird isn't a mammal, but when my canaries feathers are fluffing up, is he trying to make himself look bigger to scare off other birds/animals?"
] |
[
"Awh. Poor baby. He'll always be alone. But if he had a female with him, he'd stop singing."
] |
[
"What actually gives elderly folk that \"old person smell\"?"
] |
[
false
] | null |
[
"The smell that we attribute to the elderly is largely attributed to one particular compound, ",
"2-nonenal",
". This particular compound appears to be a type of degradation product that increases with ageing. More specifically, certain lipids (fats) are oxidized on the skin, forming 2-nonenal, which occurs at a faster rate in the elderly (they tend to have more oxidation damage, and are less able to fix this damage as well as younger people)."
] |
[
"Would that compound \"collect\" in their houses? Personally, I've never noticed a body odor type old-people-smell... I've always associated it with their houses."
] |
[
"Since the compound is a result of oxidation, maybe the use of an antioxidant would help, such as vitamin E. Maybe also limiting the intake of any of the fats that could potentially be oxidized to this compound."
] |
[
"When running a statistical test, why do you have to make all of your decisions before testing or looking at the data?"
] |
[
false
] |
I just finished a stats class, and the professor was adamant that once you've decided on your hypotheses and the test you'll run, you can't change any of it after you've seen your data. For example, you can't make your initial alternative hypothesis "Group 2 has a lower mean that Group 1", then after testing realize that Group 2's mean is significantly higher and change your hypothesis to the opposite. Or you can't realize after you've finished testing that the subjects aren't as random as you'd like (Maybe the control group, through pure luck, is full of older people and the treatment group just happened to be full of young fit people) and alter your hypothesis or re-randomize the groups. But why is this? The data isn't going to change just because I decided to test one hypothesis or the other. If I had chosen to test the second hypothesis in the first place, it would have been a perfectly valid test. Why does this validity disappear just because I had temporarily chosen the first hypothesis originally?
|
[
"When running a statistical test, why do you have to make all of your decisions before testing or looking at the data?",
"Because if you don't do this, you might inadvertently design your test based on the results you ",
" to see, or what you ",
" you've see when you peeked at the data. Instead you should \"blind\" yourself by defining the test ahead of time, and then carrying it out. If you don't you could introduce bias to your analysis."
] |
[
"Presumably, there must have been initial evidence to show that your hypothesis would have been the correct expectation. This would at least show that it made sense prior to the test to have made the hypothesis.",
"Not only that, the test results aren't invalidated because your hypothesis was wrong. It just suggests that the hypothesis is wrong. In science, that's perfectly acceptable if the procedure is legitimate, genuine, and founded.",
"In your example, it might be an inherent flaw in your control group because of a deviation of age. Your test wouldn't be invalidated because your hypothesis was wrong, but it may be invalidated because of the inconsistency of your source of data."
] |
[
"Because after you've looked at the data you can always come up with a hypothesis supported by that data. It's the same as having an answer (data) and the picking a question (hypothesis) that gives you that answer."
] |
[
"Do vehicles painted black have a greater tendency to overheat versus those painted white?"
] |
[
false
] |
I'm no expert in auto engineering, but while shopping for a new car, I pondered this.
|
[
"While not the most credible of scientific sources, ",
"Mythbusters seems to suggest that black cars do heat up more"
] |
[
"That was the interior of the car, I'm sure he's talking about engine overheating."
] |
[
"I would think that in terms of the engine overheating, no. Cooling systems are quite advanced and incorporate not just the aqueous liquid circulating through the radiator and engine block, but also taken into account is the amount of cool air being drawn in on the intake stroke, the engine oil and the ability of the engine chassis to act as a heat-sink. I guess, in a way, that black paint may absorb some of the infra-red radiation of the surrounding (hot) air and help wick away latent heat. A black-painted car might not help cabin temps on a hot sunny day, but then the windows do a pretty good job of helping the cabin heat up too!"
] |
[
"How do retroviruses become endogenous?"
] |
[
false
] |
I am really confused by the final paragraph of : Villarreal predicts that, without an effective AIDS vaccine, nearly the entire population of Africa will eventually perish. “We can also expect at least a few humans to survive,’’ he wrote. They would be people who have been infected with H.I.V. yet, for some reason, do not get sick. “These survivors would thus be left to repopulate the continent. However, the resulting human population would be distinct” from those whom H.I.V. makes sick. These people would have acquired some combination of genes that confers resistance to H.I.V. There are already examples of specific mutations that seem to protect people against the virus. (For H.I.V. to infect immune cells, for example, it must normally dock with a receptor that sits on the surface of those cells. There are people, though, whose genes instruct them to build defective receptors. Those with two copies of that defect, one from each parent, are resistant to H.I.V. infection no matter how often they are exposed to the virus.) The process might take tens, or even hundreds, of thousands of years, but Darwinian selection would ultimately favor such mutations, and provide the opportunity for the evolution of a fitter human population. So I don't see the jump between defective genes for cell receptors and "newly acquired endogenous viruses". What am I missing? Are these defective genes caused by endogenous viruses? Would HIV become endogenous if it couldn't penetrate our cells?
|
[
"Wow the author is jumping around on this subject. In general, one method of resistance is if the individual develops mutations in the receptor that the virus docks on to the point that the virus cannot dock on the host's cells. The virus needs to dock in order to be incorporated into the hosts cells. In this scenario, there will be a selection to resistance. This often happens over many many many generations. Unfortunately the virus can also adapt to the host and it is like a war of mutation with the virus often winning due to the higher mutation rate. This is the case with the flu virus and is why you need yearly flu shots. ",
"Another method of resistance can come about when the population develops mutations in an endogenous proteins that the virus needs to replicate. In this scenario, the population will have the virus but the virus will not be able to propagate throughout the population of resistant individuals. Again, there would be mutations in the virus that would favor the the mutated individuals proteins and due to the higher mutation rate may lead to no advantage. Also, the population may have lower fitness due to the mutated proteins. A good example of this is sickle cell anemia. Heterozygotes for the gene are resistant to Malaria but with two copies of the defective gene results in Sickle cell Anemia resulting in the gene being kept in the population for resistance at the cost of Homozygotes being ill. Remember, if one individual has the genetic magic bullet it would not result in the population having it unless everyone is infected and dies suddenly and you have an island effect. ",
"Basically, it will not be endogenous if it cannot infect you via the mutated receptor. But can be endogenous if it infects and cannot replicate and is incorporated into the genome (and it helps if it can convey some sort of advantage with the incorporated population). "
] |
[
"That's what I was thinking. People with HIV immunity generally have a defective CD4 receptor, so the virus can't ever get into the T-cells, right? It's possible to get endogenous retroviral DNA if the virus gets into the cells, inserts its DNA, but then can't do anything after that, but it still needs to get in.",
"These HIV viri can't even enter the cells of people with the immunity, so I don't see it ever being possible unless a completely new mutation occurs that gives HIV immunity in some other way that allows the viri to enter the genome."
] |
[
"OK, so I'm not crazy/stupid. That paragraph still doesn't seem to make any sense though. He jumps from people having defective receptors to them incorporating HIV into their DNA, and I ",
" can't figure out why. "
] |
[
"How can does gene therapy work? More so, how can it help people with cystic fibrosis?"
] |
[
false
] |
I am researching gene therapy for a class I'm taking. I understand that doctors remove a cell that is affected by the disease, alter it so it can't spread, and then replace the cell back into the body via a virus. If I am understanding it correctly. It seems very simple, however I don't understand it. Specifically, how it can help treat cystic fibrosis in a patient.
|
[
"The gene would be incorporated into the target cells (targeted in a number of ways, but that's beyond the scope of this...), and then it would function just like any other gene, including replication with cell division. It's the same phenomena as a virus incorporating viral DNA into a cell, causing the cell to express the viral proteins and by doing so generate more viruses. In fact, the main way of delivering these genes to cells is through the use of... viruses! Scientists remove the genes from the virus that it needs to reproduce (thus making it harmless), and insert the genes they desire to give the patient. Then the virus is injected, and delivers the disease-fix genes just like it would normally deliver its own malicious genes. After all, viruses are really just gene delivery machines. That is all they do; they infiltrate a cell, deliver their viral genes, and then the cell replicates those genes and packages them with proteins also encoded by the viral genes, producing hundreds-thousands of viral capsules that eventually cause the cell to burst and be released to surrounding cells or circulated in the body.",
"The diseases for which gene therapy is a possible \"cure\" occurs because the wrong proteins are being created by the cell, or some proteins are not being created at all (or some proteins are being created too much/too little, but scientists are still fairly far from being able to deliver a regulatory sequence so well that it cures this issue). In the case of CF, as explained in the wikipedia link, a deletion of three base pairs from a gene causes a certain protein residue to be missing from a protein in CF patients when the protein is assembled, resulting in the symptoms of the disease. By giving them the gene for the correct protein, the body will synthesize both the faulty and correct proteins, and thus \"cure\" the disease (since the disease only manifests if BOTH patient's chromosomes possess the gene mutation, and not just one; if only one possesses the mutation, then there's a mix of faulty/correct proteins--just as there would be in a CF patient after gene therapy--and the presence of the correctly functioning proteins prevents the mucosal buildup symptomatic of CF).",
"As another example, \"Green Fluorescent Protein\" (GFP) is a protein found in jellyfish that is extremely useful for science since it fluoresces green, just like its name would imply. If you deliver this gene to a mouse, for example, cells infected with the GFP-encoding gene will produce the protein, and thus fluoresce green. If an organism has a gene, and there's no regulatory interference, it will produce the protein for which the gene codes. We mass-produce the protein insulin, for example, by utilizing bacteria that are infused with the insulin gene. We feed them sugar, they create insulin, and then we gather it. In the same way, if we introduce the fixed gene for CF in a patient, they will make the correct protein, and the disease will be \"cured.\"",
"The issues with gene therapy is that actually delivering it in an effective way that is safe for the cell is difficult. It's difficult to control where it is incorporated (it might disrupt other genes), how much it is incorporated, and how it is regulated. For example, gene therapy has produced cancers in some patients as a result of unintended effects of incorporating this gene.",
"I'm trying to keep this as straightforward and simple as possible, but if you'd like more in-depth explanation, let me know. I took a graduate-level class on methods for gene delivery just a semester ago, and I also know several grad students doing PhD work on this topic."
] |
[
"Gene therapy is a means of delivering a useful gene (DNA sequence) that may be transcribed and translated into proteins in the patient's cells in the same way all other genes are. For example, patients with hemophilia lack a gene that codes for a signalling molecule that's essential for thrombosis (blood clotting). In hemophilic rats, scientists have delivered the gene required to produce this signalling molecule, and the rats showed a newfound ability to clot their wounds.",
"The cause of cystic fibrosis is a gene mutation (explained fairly well ",
"here",
"), and thus gene therapy for this disease would be accomplished by delivering a copy of the unmutated gene."
] |
[
"Wow thank you so so much. That really cleared it up for me. I'm repeating this just to make sure I get it. They place a replicating good gene into a virus, and inject it into the patient. This would in turn replicate the good gene, which would in a sense cure the disease. The problem with this method is that the correct cells cannot be easily targeted, and can thus cause side-effects which can inevitably be worse. Very interesting, I guess not all the stuff we learn in school is as boring as I had thought. "
] |
[
"Why does turning on an electric blender in the kitchen cause my HD antenna signal to go out in a different room?"
] |
[
false
] | null |
[
"Cheaper blenders have non-brushless motors in which electrical contacts are repeatedly connected/disconnected during rotation, causing sparks and thus some radio-frequency radiation emission (basically the fourier frequency content of a square wave), some of which is probably overlapping with the frequency bands used by your antenna. "
] |
[
"The rf noise produced by the blender is not going to be a constant frequency. It's noisy both in frequency and amplitude space, because sparks themselves have stochastic properties (basically the reason lightening is all jagged)."
] |
[
"Wouldn't that only affect a signal encoded by amplitude modulation, which I'm assuming modern TV signals are not? ",
"If a TV signal is encoded as an FM or phase shift modulation, wouldn't that signal be immune to the RF signals emitted by the blender?",
"(Btw, my last telecom class was over 10 years ago so I may be a bit rusty!)"
] |
[
"Are deep water currents affected by the coriolis effect?"
] |
[
false
] |
Hello. I was wondering if deep water currents are affected by the coriolis effect. I have read about Ekman transport and how the coriolis effect plays a role in surface currents, but I was wondering if a similar process could occur in deep water currents? When I look at a map of the ocean currents, all I see for deep water currents is a relatively straight path from the Northern hemisphere to the Southern hemisphere, and then around Antarctica and up into the Pacific. I know they are density-driven, but shouldn't they deflect a little due to the coriolis effect as they move? Thanks!
|
[
"Yes absolutely. My PhD dissertation is studying exactly this effect. While the structure of the surface Ekman layer is determined by friction by atmospheric winds, the structure of the bottom layer is determined by a combination of bottom drag (the fact that the velocity has to go to zero at the boundary with solid earth) and turbulent mixing. Those maps you see of deep ocean currents are just cartoons depicting the flow we determine must exist to give the observed tracer distributions in the ocean - they do not represent what the flows actually look like. Ask me again in 2 years and I'll tell you more but the Ekman layers at the bottom are really important for shaping the deep ocean currents!",
"A first attempt at determined the effect of Earth's rotation on deep ocean currents is Henry Stommel's classic paper on the \"Abyssal Circulation\" from 1958, which predicted deep ocean currents that look like this ",
"http://slideplayer.com/slide/10047809/32/images/57/Schematic+Abyssal+Circulation.jpg",
", where the interior flows are all there due to rotation."
] |
[
"Wow, that sounds really interesting. Thank you for your answer. Good luck with your research! "
] |
[
"Conservation of vorticity (how much a parcel of water rotates) is a super important concept in physical oceanography. The reason it is useful is because parcels of water rotate for two reasons: because they’re actually spinning around in a vortex (like an ocean version of a weather system) AND because they rotate along with the whole planet. The combination of the two has to remain constant (conserved) but the amount that goes into fluid velocity versus Planetary spinning can change. As a result, currents become more or less spinny as they go from a low latitude (earth rotates really quickly at the equator in absolute speed) to high latitudes (earth doesn’t rotate at all at the north and south poles. The cool patterns in the link I showed above are due to this conservation of vorticity concept!"
] |
[
"What happens if you flip a bullet mid-flight?"
] |
[
false
] | null |
[
"Either one you'd like. You're describing something impossible and asking what would happen if you did it, but once you've assumed that you ",
" do impossible things most questions lose meaning.",
"But say you shot a \"smart\" bullet that could somehow flip itself around in flight: ",
". The bullet isn't propelling itself, it's just moving through the air at a near constant velocity (though slowing down over time due to air resistance); all the velocity of the bullet was gained in the short fraction of a second while it was in the barrel, being propelled by the gunpowder or whatever propellant it was using. While the aerodynamics of the bullet might cause it to start tumbling and fall (since obviously bullets are designed to fly forward), it's not going to suddenly reverse its direction just because it changed its orientation."
] |
[
"I guess I'm thinking of the situation more along the lines of, I guess, the momentum that is pushing the bullet forwards.",
"\nWhen the orientation of the bullet is reversed, is the momentum also reversed with it?",
"\nOr does it remain pushing the bullet in the original direction, from point A to B?"
] |
[
"Momentum doesn't \"push\" the bullet, the bullet was accelerated by the explosion in the gun. After it leaves the gun, there's no pushing (except for a tiny bit of air resistance pushing back on the bullet). ",
"Momentum is a quantity that the bullet has, equal to the mass times the velocity. The momentum can only be changed by applying a force to the bullet. That's ",
"Newton's First and Second Laws of Motion",
": an object with no forces acting on it will maintain the same velocity, and the change in momentum over time is equal to the force acting on the object. With no force, the momentum remains the same."
] |
[
"Is the weakening of the arctic jet steam and collapsing of the arctic vortex early signals of a impending ice age?"
] |
[
false
] | null |
[
"No. \n",
"https://www.theguardian.com/us-news/2019/jan/30/polar-vortex-2019-usa-what-is-it-temperatures-cold-weather-climate-change-explained",
"The opposite, if anything. A warming planet disrupts or weakens the jet stream, so cold air will blow down from time to time. But it's part of an overall warming trend, not an ice age. "
] |
[
"Let's get the terminology correct first: technically we are in an ice age right now, since there are permanent polar ice caps. We have been in this ice age for the past 2.5 million years...but we are currently in an interglacial period. I believe what you are asking is when we enter the next glacial period.",
"Glacial periods are triggered by a combination of different orbital cycles lining up to produce a minimum of sunlight hitting 65 degrees north latitude. Specifically, those cycles are the extent of our axial tilt (a 41,000 year cycle), the amount of orbital eccentricity (a 413,000 year cycle), the direction of perihelion (a 112,000 year cycle), and the direction of axial tilt (a 26,000 year cycle). Read up on ",
"Milankovitch cycles",
" if you want to know more.",
"To answer you question: left to its own devices, Earth will not enter another glacial period for 50,000 years due to a current minimum in our orbital eccentricity. Source: ",
"Berger & Loutre, 2002",
".",
"However, if you include the influence of human activity on the climate, we may not see another glacial period for the next 500,000 years. That assumes we end up releasing 5000 gigatons of CO",
"; we've released 1500 gigatons in the past 100 years, and roughly 3500 remains in our oil reserves, with unknown amounts in methane clathrates that could be liberated by increasing temperatures. Source: ",
"Archer & Ganopolski, 2005",
"."
] |
[
"Well, about 32 million years, since it is still the Late Cenezoic Ice Age, due to Antarctica being where it is. Semantics, though.",
"If we released ",
" sequestered carbon reserves, we would induce a situation where more carbon is in the atmosphere then there ever has been at one time, so I presume we would end up warmer than the Carboniferous."
] |
[
"Emotions in animals"
] |
[
false
] |
Me and a friend were talking about intelligence in animals, when I said that some animals, if not all, have emotions too. He disagreed with me saying that they only have the basic instincts but are incapable of emotions. He gave an example saying that humans are the only species where the members use sex for recreation rather than procreation. Wikipedia says that scientists haven't reached a conclusion yet on the whole thing but i wanted your opinion. It just seems very far fetched to me that Humans can be the only species to have emotions. IMHO, it might be difficult to measure emotion in animals but it does definitely not mean it is absent. P.S. Talking about non-human animals
|
[
"Well I can't provide you with specific studies and I doubt any such studies exist. How would you perform such a study anyways when we can't even specifically nail down where all our own emotions come from? ",
"I can tell you that it is my ",
" that animals absolutely have emotions. You don't have to own an animal for long to learn when they're happy, sad, mischievous, and so forth. I've seen animals mourn for lost owners and for lost 'siblings'. I've seen my dog 'laugh' at me when I do something stupid. Take out a leash around most animals and they go from bored to elated in seconds flat. ",
"Many people think it's anthropomorphizing but I don't think so. "
] |
[
"Well at least, we ARE NOT the only animals that have sex for recreation. I've seen documentaries where monkeys do it every morning just for the heck of it. If you see planet earth, they show how Chimpanzees rape and cannibalize nearby groups when there really is no need to. I'd take that as emotions at work.",
"If I'm not wrong Dolphins also do \"it\" for fun. And I read long ago that some species of dolphins also kill other animals just for fun. A dolphin can actually get quite excited when you keep a mirror, they'll even try to groom themselves (as some recent front-page reddit videos have shown). They also follow ships' wakes purely for fun, if I'm not wrong.",
"So depending on how you define emotions, at least two other clades of animals have lots of similarities."
] |
[
"You get home from work one day and your dog has torn up the trash and has spread it all over the kitchen. When you chastise him he puts his tail between his legs, whimpers, and holds his head low (granted not all dogs do this). We as humans would interpret this as shame, but we have no evidence that they can feel shame. ",
"This is actually a huge problem in training. People are so sure that the animal is feeling remorse for their actions, but it's much more likely (almost certain) that the animal has no idea what you're chastising for. They don't plan for the future nor associate things with the past. Can they learn a wire is electrified? Sure, after touching it, but they generally tend to extrapolate that information to ALL wires from that point on, not that specific wire. Or rather, it's not an extrapolation, but a failure of differentiation between a wire here and a wire there. ",
"Additionally you may not even be correcting the thing you think you're correcting. Instead the animal could learn to fear:",
"\n1) You.",
"\n2) You and garbage in the room at the same time. (but not necessarily itself and garbage in the room at the same time)",
"\n3) Garbage in general, no matter the location (including litter on walks).",
"\n4) You coming home.",
"\n5) The room itself.",
"\n6) The carpet on which the trash is scattered. ",
"And so on. It is absolutely destructive to chastise a dog for something they did hours ago. They simply don't make the connection. You ",
" to catch them in the act or within close proximity to it (within 3 seconds or so) so they can know specifically what they did wrong. "
] |
[
"Why does it feel good when someone scratches you on the back?"
] |
[
false
] |
Just hit me, what is that makes it feel so good and relaxing when someone is scratching my back? Is it because the intimacy of another human being?
|
[
"what is the evolutionary benefit of bees",
"Pretty tired of people overextending the applicability of the theory of evolution."
] |
[
"you've got part of it, but you're missing the initial impetus...which (as I've posted below) has deep evolutionary roots, linked to parasite defense in social animals."
] |
[
"Point being?"
] |
[
"Are we, as human being, able to absorb water from moisture in the air via breathing ?"
] |
[
false
] |
If yes, are we able to absorb more water in a humid environment than a dry one ? If no, is there any living thing that does this ?
|
[
"Every time you breath the air is combined with water droplets which changes the partial pressure of oxygen. Based off that I think in higher humidity environments the partial pressure of water you breathe in would be increased and possibly decrease the partial pressure of oxygen. Maybe that’s why it’s harder to catch your breath when it’s humid.",
"If someone has a better answer please jump in. That’s just my thought process",
"ETA: humidity also affects sweating which is a factor when exercising in higher humidity but that’s a whole other story"
] |
[
"Thanks, that would makes sense. \nBut as you \"breathe\" water droplet, are we able to absorb them in your body resulting in a better hydratation as opposed to a dryer environment ?"
] |
[
"opposed to a dryer environment ?",
"It is mostly a matter of the equilibrium of water vapor loss. Your normal metabolism of carbohydrates produces water, which you exhale. In a wet environment, you would lose less water than in a dry environment, but still losing water.",
"https://www.ncbi.nlm.nih.gov/pubmed/22714078"
] |
[
"How can a particle Travel through Time?"
] |
[
false
] | null |
[
"I have always wanted to know about Space Time but even the books I was recommended have gone over my head.",
"Is there something anyone can recommend that will help me understand?",
"I have read \"Murray Gell-Mann and the Revolution in Twentieth-Century Physics\" by George Johnson, \"The Fabric of the Cosmos\" by Brian Greene, \"The Strange Theory of Light and Matter\" by Richard P. Feynman"
] |
[
"Mostly it's due to the uncertainty principle, below a certain threshold energy conservation can be violated."
] |
[
"An anti particle moving forward in time behaves the same way as a particle moving backwards in time.",
"Edit: I forgot about parity, but when a particle anti particle pair is created they have opposite parity, so in this case what I said is true."
] |
[
"What would happen if we \"equalized\" the Panama Canal?"
] |
[
false
] |
[deleted]
|
[
"I'm having some difficulty understanding what you mean. Are you referring to a situation where the panama canal was a simple horizontal slot joining the two oceans, with no lock gates between?",
"If so, there is a lot of speculation involved - particularly in terms of the biology part of the question. As far as currents go, you would have a tidal current running through the canal - strong enough that shipping would likely not be able to use the canal. Nothing of note would happen to sea levels anywhere."
] |
[
"The canal would not be big enough to support a counter-current. Frictional effects would be too large. The canal is only 12 m deep by ~20 m wide. In comparison the Bosphorus is ~65 m deep by 1 km wide."
] |
[
"You'd get an increase in invasive species passing between the west and east. The freshwater segment prevents fish and other things from simply swimming through or riding through stuck on ship hulls, so the only organisms that can pass through are ones that can survive in ballast water. Cut a sea level passage and you would get all kinds of stuff dispersing between the two sides.",
"Sea level is a bit lower on the Carribean side than the Pacific, and tidal variation is ",
" higher on the Pacific side. This would likely cause a current through a simply designed canal, though the canal makers would probably work to minimize this. The amount of water passing through the canal would be far too minuscule to change the depth of the oceans...equivalent to a smallish river flowing in impact."
] |
[
"What is the role of NMDA receptors?"
] |
[
false
] |
Why are they present on the membrane? I hear that they are important for learning and memory, but what differentiates them from AMPA receptors/ when is an NMDA receptor activated against an AMPA?
|
[
"This is an awesome question! NMDA receptors differ from AMPA receptors because they require glutamate binding and membrane depolarization (usually the postsynaptic membrane) in order to open. This essentially allows NMDA receptors to act as coincidence detectors - i.e. they detect activation of the presynaptic membrane (which releases glutamate) and activation of the postsynaptic membrane (which causes depolarization). AMPA receptors, in contrast, do not require membrane depolarization to open.",
"Furthermore, NMDA receptors allow for Ca",
" entry into the cell and since Ca",
" activates a whole bunch of secondary messenger processes into the cell, it can contribute to the transcription/translation of genes/proteins that promote learning and memory. AMPA receptors, on the other hand, generally allow for only Na",
" and K",
" entry. ",
"If you like, I can go into much more detail! Alternatively, here is a comprehensive paper that summarizes our current models of learning and memory. ",
"http://www.nature.com/nature/journal/v361/n6407/abs/361031a0.html"
] |
[
"Just going off of this, NMDA receptors can be considered to be on a longer time scale. They require glutamate binding, glycine binding, and membrane depolarization to activate. AMPA only requires glutamate. The reason NMDA receptors require membrane depolarization is because NMDA is nonspecific to cations, so any cation can go through this receptor when it is opened. One of the he ions that can do this is Mg2+. The issue is that Mg2+ is inhibitory of the NMDA receptor. Basically as soon as glutamate and glycine bind the NMDA receptor, Mg2+ is going to go through and inhibit it. However, if the membrane was depolarized, there would be less if an electrical gradient pulling Mg2+ across the membrane, so the receptor can stay open longer. ",
"Essentially when glutamate is released into the synapse, it will first open AMPA receptors which will depolarize the post synaptic cell membrane. This will allow NMDA Receptors to stay open as well."
] |
[
"Oh I totally didn't mention the whole Mg",
" blockade. It's presence is what confers the NMDA receptor its coincidence detection abilities. Thanks!"
] |
[
"Are galaxies moving in circles relative to one another, like solar system do inside galaxies?"
] |
[
false
] | null |
[
"As a point of information, no orbit is ever a true circle.",
"This will help explain this and about how objects similar in mass orbit one another. ",
"https://en.wikipedia.org/wiki/Kepler_orbit",
"In direct answer to your question, it depends on whether they are gravitationally bound to one another. Galaxies that are close enough to one another and moving below the escape velocity of the gravity wells of any other near it will be bound. Several things can happen. They may orbit one another like two balls on the end of a string around a common center of gravity somewhere in between them. If one happens to be much larger, it may capture several satellite galaxies that would rotate around it. They may collide and merge with one another. If one is large enough and moving fast enough compared to another it is passing it may disrupt it without capturing it. There are many possible permutations.",
"Since these clusters can be enormous. It might be hard to tell how they appear on a grand scale. That being said, given our own galaxy has several satellites galaxies, it is not hard to imagine a massively larger galaxy collecting many more around it. This might appear on such a scale to resemble itself a galaxy. It most certainly would be caused by the same forces. Sort of Russian doll form."
] |
[
"Thank you for responding!",
"Just to clarify, I'm asking not what galaxies do when clashing, but rather \"do the black holes at the center of each galaxy in the universe move on an orbit(like suns in a single galaxy) or remain stationary in space?"
] |
[
"On the largest scales, most galaxies are moving away from most other galaxies, not orbiting some common universal center.",
"That's not to say they're moving away from a central point, they're moving away from every point, as all space is expanding.",
"If they're close enough, a collection of galaxies might orbit one another, and in that case the Supermassive black holes would also take part in that orbit.",
"But since space itself is expanding, on the scale of the universe there is no such reference frame where all, or even most galaxies are stationary."
] |
[
"How accurate a reconstruction/projection of a human's facial characteristics could be made just from using a skull?"
] |
[
false
] |
Sorry my question isn't the clearest, basically if you had a skull and the sufficient technology and know-how, could you make a facial reconstruction and how accurate could it be?
|
[
"Two articles in Swedish but I guess you can google translate them:",
"http://www.svd.se/kultur/birger-jarl-rekonstruerad_4534225.svd",
"http://www.popularhistoria.se/artiklar/historiens-ansikte-tar-form/",
"They basically build up the face from the cranium up, by adding layers of muscles and everything else (in clay). The thickness of these layers is apperantly well known. So they end up with a very good reconstruction of the general apperance of the face, but shape and colour of things like hair, nose, ears and eyes is a guess. They get close enough that people who know the guy who was reconstructed should recongnise him."
] |
[
"From the little knowledge I learned in an intro to Forensic Science class, they can determine approximate age, race, and gender based on certain class characteristics of bones. There are also individual characteristics like bone-wearing that can narrow things down. There's not much accuracy in these methods, but combining it with other sources of info (like DNA analysis) can provide some useful reconstructions. "
] |
[
"There is an element of art to facial reconstruction based on a skull, but you can get pretty darn close using good science. I've toured a few forensic labs and talked to the reconstruction artists and I've seen a reconstruction that was used to help identify a skeleton alongside the picture of the woman before she died that was on display at one of them. It was amazingly close.",
"Using structural features of the cranium as well as knowledge of the age, gender, and ethnicity of the individual (which are easy to determine based on a skull) it is possible to create a fairly accurate reconstruction of the person's face. Each craniofacial muscle attaches to specific points on the skull and by measuring the size and angle of each point it is possible to recreate the muscle. Once the muscles are in place it's possible to estimate the amount and location of adipose deposits (easier with a full skeleton) once those are placed and cartilaginous features (the ears and nose) are created based on ethnicity, age, and gender they can put a skin over the whole thing.",
"Then comes the art portion where they have to base skin-tone, eye color, and hair color/style on statistical probabilities based on age, gender, and ethnicity as well as probable culture. The recreation that I saw was of an African American female in her early 30s who lived in the southeastern U.S. and died during the mid-1990s. Based on those facts and the features of people in a similar demographic in the region the artist estimated her probable skin-tone, eye color, and hair color/style.",
"Turns out he was spot-on. So there is a bit of art involved in forensic facial reconstruction, but the majority is science."
] |
[
"Do octopuses have a dominant right or left side?"
] |
[
false
] |
I'm drawing an octopus right now, and I'd really like to know.
|
[
"From \"The Soul of an Octopus\" by Sy Montgomery: \"University of Vienna researcher Ruth Byrne reported that her captive octopuses always choose a favorite arm to explore new objects or mazes... Tank-bound octopuses, at least, are known to have a dominant eye, and Byrne thinks this dominance might be transferred to the front limb nearest the favored eye.\" However, as others have stated in the thread, all eight limbs act somewhat autonomously. The author in this section actually refers to the possibility of \"bold\" and \"shy\" arms, describing how some arms will display curiosity when presented with a new object while others retreat."
] |
[
"I'm amazed you found a cited response to such an obscure question. Bravo!"
] |
[
"Each tentacle has its own nerve center independent of the other 7. So one tentacle may know how to open a jar while the ones either side would not. Some tentacles are probably preferentially used over others I don't know if there is a side bias, but if there is it would not be 4 on one side dominate to 4 on the other. "
] |
[
"Stupid question. What does it mean when somebody says \"a photon gets absorbed\" or \"a photon gets emited\"?"
] |
[
false
] |
So, the photon helps an electron to get in a higher orbit. How? And then the electron drops the orbit and emits it again. Why? What causes it to drop the energy level again? Is it a spontaneous process? Im sorry if the question is badly phrased, but english is not my native language. Im trying to get beter :_-)
|
[
"When an electron absorbs a photon, because of conservation of energy, it has to move to a higher energy state. ",
"As for the emission, yes, it can be spontaneous. Though it can also be stimulated, as in laser emission.",
"http://en.wikipedia.org/wiki/Spontaneous_emission",
"http://en.wikipedia.org/wiki/Stimulated_emission"
] |
[
"Thank you. That was very helpfull.\nWiki:\"Imagine trying to hold a pencil upright on the end of your finger. It will stay there if your hand is perfectly stable and nothing perturbs the equilibrium. But the slightest perturbation will make the pencil fall into a more stable equilibrium position. Similarly, vacuum fluctuations cause an excited atom to fall into its ground state.\""
] |
[
"Photons and electrons are both particles, but you can think of them as waves, too.",
"A photon is a perturbation (a vibration or wave) in the \"electromagnetic\" field. An electron is a perturbation in the 'electron' field. They're both 3-d fields everywhere in space, so the following analogy isn't exactly right, but imagine them as two piano strings very close to each other. If you pluck one, the other one will start vibrating, and they'll transfer energy to each other when that happens. That's another way to think of photons being absorbed and emitted by electrons, just waves in fields transferring energy to each other. "
] |
[
"Why is it that cocoa powder is almost impossible to emulsify with a large amount of liquid, but will emulsify easily when just a little bit of liquid is used?"
] |
[
false
] |
If you dump a large amount of water, milk, or other liquid into a cup filled with cocoa powder or if you dump the cocoa powder into a cup of liquid, the cocoa powder will float to the top and no amount of stirring will cause it to completely emulsify. However, if you start with the cocoa powder and add just a little bit of water, it will emulsify easily and completely and it then becomes a simple matter of adding more liquid until the desired ratio is achieved.
|
[
"My informed but non-expert explanation: The problem is that cocoa powder as a substance has its own surface tension when in contiguous and sufficient quantities.",
"I found a link with ",
"some elaboration",
".",
"Wetting properties of cocoa powder",
"\nWetting by water is closely related to whether something is hydrophilic or hydrophobic. If it's hydrophilic, it loves water and wetting occurs easily; water spreads out on the surface. If it's hydrophobic, the opposite occurs, such as on Gore-Tex. Wetting is not limited to water, and other solvents also possess wetting properties. These properties are in turn closely related to the surface energy. A general rule is that media/material with similar surface energies will possess similar wetting properties.",
"Galet et al. reported that the surface energy of cocoa powder is considerably lower than surface tension of water. Result: water and cocoa powder don't mix very well (surprise...). The bad dispersion behaviour of cocoa is caused by a number of phenomena, and one is the hydrophobic nature of cocoa, the fat content being 10–12% in cocoa powder. The mean particle size of cocoa is commonly around 16 micrometres (0.016 mm), but the size distribution is wide. The smaller the grains, the more difficult is the dispersion. Granulating the powder (making grains of 0.02 mm - 2 mm) resulted in enhanced wetting properties.",
"Partly, the bad dispersion properties is because of the bad flowability and the cohesive forces of the powder. The cohesion results in solid agglomerates, and the shear forces are not sufficient to break the cohesive forces between the grains. In plain words: cocoa powder lumps up in water, simply floating on top (another surprise...).",
"I wouldn't consider this peer reviewed, but it's a good start."
] |
[
"While you consider the hydrophobic nature of cocoa powder, you also have to consider the physical action of stirring vs mashing/grinding that OP doesn't state happens, but will actually happen when mixing various ratios of cocoa to liquid. When you take a little bit of cocoa and dump it into a large volume of water, the default action is stirring which will not have the force required to overcome the \"cohesive forces of the powder\". However, if you take the same volume of powder and add a few drops of water, initially the water will ball up (like it would on gore-tex) until you begin to knead it into the powder (stirring would not be the default action in this case). This action forces the water in between the grains of cocoa powder and allows for more mixing."
] |
[
"I think it comes down to wetting of the individual cocoa powder grains. I think a typical scoop traps a lot of air in it. The 1:1 slurry is really just a rule of thumb that makes it easier to wet the non-soluble bits of cocoa powder. When you finally mix it into the rest of the ingredients it will disperse easier."
] |
[
"Doesn't the Earths crust just keep recycling?"
] |
[
false
] |
My understanding of techtonic plates is that one slides under another. So wouldn't this completely recycle all the rock on Earth eventually? How can we know we haven't lost information over time?
|
[
"Yes, we lose a lot of information over time, though not exactly in the way you describe. Only the oceanic crust is really recycled through subduction(well, the vast majority of it anyway - some can get preserved). Continental crust is too light to subduct back into the mantle in the same way. ",
"Continental crust is still recycled through the mantle , mostly through the processes of erosion and eclogite delamination (which results in material loss on the bottom of parts of continents). Also, in a sense continental rocks can be recycled right here above the mantle too - through metamorphism at depth. So a rock can be buried a number of kilometers and then have most useful information lost as a result.",
"But the amount of continental crust out there is absolutely incredible, so even with constant erosion there will be plenty of old rocks left behind. We have found rocks over four billion years old, though no native Earth rocks as old as the planet yet. We have found individual crystal grains as old (or nearly as old) as the planet however. Also, not every part of the continent is equally prone to these recycling processes. Continental Shields/Cratons are very stable and old parts of continents that lack large mountain ranges. That drastically reduces the rates at which things are eroded and buried, so all of the above recycling mechanisms are slowed down a lot.",
"Also, a large part of getting information from the past is finding rocks that were buried and protected, but have since been uplifted. This is effectively a requirement for preservation of the past. Luckily, rocks get buried all the time, and may remain buried and protected for just about any length of time.",
"But yes, our \"resolution\" of the past, if you will, drops pretty quickly once you start going back many hundreds of millions to billions of years. You have to look harder and harder just to find an outcrop of rock from the time you want.",
"EDIT: To further address your question, yes, in theory plate tectonics could result in recycling of all continental crust. Rocks will be eroded away, that sediment will eventually find itself in the ocean, where some of it will be pulled under through oceanic crust subduction. However, realistically, plate tectonics will slow down and stop ",
" before we lose all the information out there. It might slowly get harder to find rocks older than four billion years, but most periods in the planet's history will be represented in the rock record for the rest of this planet's lifetime. At least represented well enough to study and draw many meaningful conclusions from."
] |
[
"The minerals making up continental crust are less dense than oceanic crust. If two tectonic plates collide where one's continental and the other's oceanic, the continental crust stays on top. If both plates have continental crust at the plate boundary, neither one subducts and they just smash into one another, piling up a mountain range like the Himalayas.",
"Not only does this keep the continental rocks from being recycled, but it's thought to be the main process by which the early Earth gradually assembled larger and larger continents---volcanoes deposited scraps and pieces of lower-density minerals on the surface, and once there, they couldn't sink back down but were just slid around by plate tectonics until they smashed together and stuck (more or less)."
] |
[
"No rocks have been dated to the age of Earth, unless you count meteorites. The oldest rocks we have dated are somewhere around 4.2 billion years old or so.",
"Now we have dated certain ",
", such as tiny grains of Zircon, to the age of Earth (of very close to it). But there is a distinction there."
] |
[
"If humans were never taught about sex, would our animal instincts kick-in or would we all die out?"
] |
[
false
] |
[deleted]
|
[
"As I understand, a woman's first time is not pleasant at all and actually quite painful, they know pain is like the bodies way of telling you \"Oi. Stop that\" and as the ladies have no knowledge of intercourse they'd go with the stronger pain feeling than their deep down need to have children?",
"For many women, it doesn't hurt at all (mine didn't). No, ladies don't want to get their bone on because of a \"deep down need to have children\"; we want to because ",
". Come on, it's 2011: do we really need to remind people that women have sexual urges too?"
] |
[
"I'm pretty sure we'd figure it out. We're not pandas..."
] |
[
"They really don't. Getting animals to breed in captivity can be a real nightmare."
] |
[
"If electricity can create a magnetic field, can collapsing a magnetic field create electricity?"
] |
[
false
] | null |
[
"Yes, changing magnetic fields can be used to produce electricity. This is how generators work."
] |
[
"Thank you for your response! So let's say you could make a flexible, ring shaped magnet, like the shape of a washer. Since it's flexible, if you stretched it out, the shape of the magnetic field would change, correct? And if so, would this changing shape of the magnetic field produce electricity? "
] |
[
"You could use the field to produce electricity, yes. If you put a wire loop nearby as you change the shape of the ring, the changing magnetic flux through the wire loop would generate an electric current in it."
] |
[
"Are rapid SARS-COV-2 tests still as reliable with the new lineages BA.4 and BA.5?"
] |
[
false
] |
And how come the rapid test kits can still detect the antigen even though these new variants shows such affinity for immune evasion? Will we have to test for another antigen in the near future? Or is the antigen somehow better "protected" against mutations?
|
[
"The tests have already not been very reliable at all for Omicron strains: while a positive result is almost definitely true, a negative result has a very good chance of being false, especially early in the infection. I've seen doctors and public health officials estimating a 40% false negative rate based on clinical experience, but I haven't found a published study to confirm that. Research lag time is likely a factor here. ",
"This is a news article from January that covered the subject well, explaining a variety of factors that could lead to the apparent lower reliability of the tests. It's not just differences in the antigens themselves, but also how many surface antigens the virus produces, and what tissues the virus accumulates on VS what tissues we swab for the test. ",
"https://www.npr.org/sections/health-shots/2022/01/23/1074978193/rapid-covid-tests-omicron#:~:text=A%20week%20later%2C%20a%20small,of%20the%20authors%20of%20that"
] |
[
"This is partly why kits come with two tests and you’re supposed to take both 24 hours apart. The odds of one false negative were fairly high even before the new variants (something like 1 in 4), but two false negatives would be much more unlikely (~1 in 16)."
] |
[
"The vaccines targeted the spike protein on the outside of the virus which is evolving rapidly, but the antigen tests look for an internal structural protein of the virus which is evolving much more slowly. So yes, they’re still very reliable at detecting large amounts of viral antigen."
] |
[
"Are there any chemicals so deadly a mere drop on skin could kill?"
] |
[
false
] |
My grandpa (a known story stretcher) told me he used to haul tankers full of this chemical. It was supposed to absorb really fast and that it was so deadly a drop on your skin would kill you in a minute or two. It was used in the production of tires. He said it was phenol but phenol doesn't match up with his description. He's told me this story since I was a kid but now at 23 I'm curious as to if there are any chemicals that deadly and what they would possibly be used for.
|
[
"There certainly do exist some chemicals where just a few drops on your skin can kill you. The chemical in question needs to have two properties:",
"the median lethal dose or LD50",
"A very famous example of a chemical that fits both criteria is ",
"dimethylmercury",
". This is a powerful neurotoxin that is frankly terrifying. To quote the Wiki article:",
"The toxicity of dimethylmercury was highlighted with the death of Karen Wetterhahn, a professor of chemistry at Dartmouth College, in 1997. Professor Wetterhahn specialized in heavy metal poisoning. After spilling a few drops of this compound on her latex glove, the barrier was compromised and within minutes it was absorbed into her skin. It circulated through her body and accumulated in her brain, resulting in her death ten months later.",
"In other words, even when wearing safety attire, just spilling a few drops on a glove was enough to send the researcher to an early grave. "
] |
[
"Last I heard, no one really works with or puts dimethylmercury to use, largely because it's so dangerous. Probably not something being transported in trucks. "
] |
[
"Last I heard, no one really works with or puts dimethylmercury to use, largely because it's so dangerous. Probably not something being transported in trucks. "
] |
[
"Is a third vaccine justified by sinovac vaccines?"
] |
[
false
] |
[deleted]
|
[
"Sinovac is the company that manufactures the \"Coronavac\" vaccine. Coronavac is an inactivated SARS-CoV-2 vaccine adjuvanted with AlOH, a common and well-studied adjuvant. ",
"There's relatively limited data available on Coronavac, especially compared to several other vaccines that have been fairly open about the details of their clinical trials and ongoing findings. That said, there are ",
"several dozen peer-reviewed papers",
" on the vaccine, generally showing good safety and moderate efficacy.",
"The ",
" problem is that the long-term effectiveness of Coronavac may not hold up. I believe this mainly comes from a preprint (not yet peer-reviewed):",
"neutralizing antibody titers induced by the first two doses declined after 6-8 months to below the seropositive cutoff ",
"--",
"Immunogenicity and safety of a third dose, and immune persistence of CoronaVac vaccine in healthy adults aged 18-59 years: interim results from a double-blind, randomized, placebo-controlled phase 2 clinical trial",
"Antibody titers may or may not correlate with protection, so this isn't necessarily bad news; but given the very stable antibody titers following vaccination with some of the other COVID vaccines, it does raise eyebrows. ",
"It also fits with the apparent findings of several countries that are apparently unhappy with Coronavac's long-term efficacy. For example:",
"Thailand leaked memo raises concerns over Sinovac vaccine’s efficacy",
"Coronavirus: Singapore excludes China’s Sinovac jabs from national vaccination tally; South Korea cases surge",
"Covid: Is China's vaccine success waning in Asia?",
"If the vaccines are indeed losing efficacy (and again, there's not much more than gossip and rumor at this point) then the obvious solution is to give a booster. That's apparently being considered (",
"Report: China Considering Foreign Booster Shot to Improve Efficacy of Its Vaccines",
"), and the preprint mentioned above shows that a booster does work:",
"When a third dose was given 6-8 months after a second dose, GMTs assessed 14 days later increased to 137.9 [95%CI 99.9-190.4] for Schedule 2, and 143.1 [95%CI 110.8-184.7] for Schedule 4, approximately 3-fold above Schedule 1 and Schedule 3 GMTs after third doses. ... A third dose of CoronaVac administered 6 or more months after a second dose effectively recalled specific immune response to SARS-CoV-2, resulting in a remarkable increase in antibody levels, and indicating that a two-dose schedule generates good immune memory. ",
"--",
"Immunogenicity and safety of a third dose, and immune persistence of CoronaVac vaccine in healthy adults aged 18-59 years: interim results from a double-blind, randomized, placebo-controlled phase 2 clinical trial",
"Other possibilities obviously include boosting with different vaccines. There are of course literally hundreds of different possible combinations and permutations of the different COVID vaccines at this point, and of course not all (and as far as I know, none with Coronavac -- there's an ongoing trial in the Philippines that won't have answers for a year or so) have been looked at. Those combinations that have been looked at all seem safe and effective, and there's no theoretical reason to expect anything else:",
"Mixing COVID-19 vaccines is emerging as a good way to get people the protection they need when faced with safety concerns and unpredictable supplies. Most vaccines against SARS-CoV-2 must be given in two doses, but multiple studies now back up the idea that mixing the Oxford–AstraZeneca jab and the Pfizer–BioNTech vaccine triggers an immune response similar to — or even stronger than — two doses of either vaccine.",
"--",
"Mix-and-match COVID vaccines: the case is growing, but questions remain",
"In particular, there’s virtually no safety concern (that is, there’s no obvious reason any combination of the COVID vaccines would be less safety than the individual vaccines themselves), and there’s no reason that the booster effect wouldn’t kick in, so the only real question is how much booster effect there would be - will it be good, better, or best with combination X, Y, and Z. ",
"No mix-and-match trials have yet reported severe side effects. In the Com-COV study, mixing vaccines elicited more side effects than did administering two doses of the same vaccine, according to preliminary data released in May5. But this wasn’t the case in the Charité and Saarland studies or CombiVacS, where side effects were no worse than for two shots of the same vaccine.",
"--",
"Mix-and-match COVID vaccines: the case is growing, but questions remain",
"Once again: There's very little information on this, and what there is includes unreliable media reports and un-peer-reviewed preprints. It's likely that just waiting a few weeks will see a lot more information, so a wait-and-see approach is probably the way to go."
] |
[
"Probably for the sake of resources and an overabundance of caution.",
"We give different formulations of vaccines all the time. The tetanus shot you got when you were a kid is probably not the same you got most recently, for example. I don't even live in the same country I got most of my childhood vaccines in."
] |
[
"https://www.bbc.com/news/health-57636356",
"https://www.npr.org/sections/health-shots/2021/05/05/993882203/giving-2-doses-of-different-covid-19-vaccine-could-boost-immune-response",
"You wanted an opinion on mix and match boosters from a scientist, well, you're talking to one. My opinion is that it will improve the response and poses no risk. The WHO wants more people to get ",
" shot before we start giving boosters to those who are already considered fully vaccinated, regardless what individual scientists think."
] |
[
"How do shockwaves affect small organisms on the cellular scale?"
] |
[
false
] |
I.e. shockwaves from explosives affecting things like amoebas, bacteria, etc
|
[
"I can answer this question from the microbe side, not so much from the physics perspective. You can rupture cells with sound waves in a process called \"sonication\", but it works by creating very tiny bubbles which collapse and release energy that destroys the outer part of the cell. If a shockwave were strong enough to do this, then we might expect it to cause cells to lyse and, ultimately, die. Their contents would be released into the environment.",
"I don't know if shockwaves from bombs are intense or sustained enough to do this.",
"Another effect could be changes in gene expression. Recently, a class of acoustic reporter genes was discovered and characterized in E coli. These respond to sound waves to cause genes to be expressed. I don't think we have a clear idea as to why they exist, but it might have something to do with natural environmental processes that generate a lot of sound waves, such as natural shockwaves from earthquakes, volcanoes, and tsunamis. "
] |
[
"I can answer from the physics side but not the microbe side. Shock waves from explosives start out much stronger than anything than any ultrasound that could be made in the lab, including from collapsing bubbles--in air, it's a pressure change of potentially thousands of atmospheres in about a nanosecond (corresponding to about 10",
" meters between the shocked pressure and the ambient pressure). It depends on distance though: shock waves decay rapidly and are much weaker at, say, 1 m than right up against the explosive. But there's typically just one big pressure jump in the signal (the leading shock) although depending on the situation there may be significant secondary shocks, echoes, or even powerful rarefactions (which would be much more gradual pressure changes than the shocks--strong instantaneous rarefactions decrease entropy so they can't exist). ",
"Given what you said, I'd imagine that a strong pressure change over such a short distance would be able to lyse a microbe cell if it was close enough to the explosion.",
"Interesting what you said about gene expression and sound. Do you remember what frequencies the gene expression depended on? Most geophysical sounds (crashing waves, volcanoes, thunder, etc) are concentrated in the low audible and infrasound bands."
] |
[
"Thanks for this!"
] |
[
"Do all electromagnetic waves bend in the same way light does when it changes media?"
] |
[
false
] |
Hey, so today in physics class we were going over some problems from the homework and then it hit me: If light waves are just electromagnetic waves, then does that mean they can be bent in the same way light waves are bent when they go through different mediums (i.e. can radio waves also be bent by changing mediums)? I assume that the answer is yes, but the teacher wasn't exactly sure and told me to go figure out and tell the class tomorrow, so could any of the physicists on reddit help me out? Thanks.
|
[
"You can see this phenomenon with other electromagnetic waves -- ",
"here",
" for example is a material with an index of refraction of 38.6 for waves of around 10",
" Hz. As another example, radio waves undergo refraction when they travel into the ",
"ionosphere",
".",
"And it's not just electromagnetic waves. You can see refraction with ",
"sound waves",
", for example."
] |
[
"Different frequencies of radiation behave differently in materials. That's why white light is spread into different colours when it goes through a prism: each colour has a slightly different speed, because the index of refraction is different for each frequency.",
"For high energy radiation like x rays there isn't much that can be done to slow it down: it's very hard to experimentally verify that the index of refraction isn't 1.0. For radio waves it only becomes an issue if the medium is large compared to the wavelength, which isn't relevant for materials like glass, but for air it is."
] |
[
"Yes, absolutely. Radio waves and microwaves all refract when changing propagation media. However, for the most part the effects are not nearly as apparent at the lower frequencies, and for terrestrial communications, the effects are negligible. One place where we do model atmospheric refraction though, is for GPS signals. I'd link a paper, but I'm on my phone - Google \"GPS atmospheric refraction\" - there are a few non-walled papers available."
] |
[
"How is heat death of the universe possible if energy cannot be destroyed?"
] |
[
false
] |
Does this mean all heat and light would be emitted into infinite emptiness?
|
[
"Laws of thermodynamics predict that work can only occur when there is a temperature difference. When the entire universe is the same temperature, no work will be possible. The laws of thermodynamics have been very successful predictors of experimental results."
] |
[
"Right now energy is unevenly distributed. Picture it like a large basin with a divider in the middle. One side of the basin is filled to the top with water and the other side is empty. Now punch a hole at the bottom of the divider and the water from the full side will move the empty side, but only until both sides have the same amount of water. If there is absolutely no input from outside of this system you will see motion happen in the water while it is transferring but after it is balanced out it'll start to go still and then not move anymore."
] |
[
"It's the same reason why Engines can't have a 100% efficiency. While energy is conserved, it's converted into a form where it can't be used. Before that, lets talk about the heat death.",
"It’s one of the theories on how the universe will end: the ‘Heat Death’ – also known as the ‘Big Freeze’ or the ‘Big Chill’ – has been suggested as one of the ways in which the cosmos could come to an end, especially since it’s ever expanding.",
"You might think that Heat Death implies some astronomically high temperature that snubs everything out. However British physicist Kelvin, who proposed the idea in the 1850s, referred to the loss of mechanical energy as the theory of heat. In fact, it has been suggest that the more the Universe expands, the cooler it gets.",
"The idea of heat death actually originates from the second law of thermodynamics – that’s that idea that entropy(randomness) increases in an isolated system (this system being the universe). Entropy, which is the number of ways in which a system can be arranged should never decrease, evolving to a state of maximum disorder (or thermodynamic equilibrium). When this happens, all energy will be evenly distributed throughout the cosmos, leaving no room for any reusable energy or heat to burst into existence. Processes that consume energy, which includes our very living on Earth, would cease and everything everywhere will be the same temperature. That means nothing interesting will ever happen again. Every star will die, nearly all matter will decay, and eventually all that will be left is a sparse soup of particles and radiation.",
""
] |
[
"How do we know that what we interpret as quantum indeterminacy isn't just blank spaces that haven't been filled yet?"
] |
[
false
] |
To clarify/expand: My current understanding of our deterministic universe is that, on a macro level, every physical process can be predicted with the right tools and can only have one possible outcome. However, on the quantum level, a number of things can happen that are not predictable at all, or are only predictable in terms of probabilities, but there are no certain outcomes from given configurations of matter and energy. It makes more sense to me, as a layman, to see these probabilities and the lack of certainty, and assume that there are deterministic processes at work producing these probabilistic outcomes that we simply have yet to identify, rather than making the claim that the universe simply is not deterministic at the quantum level. Most people who seem to know more about this disagree with me, but they have not explained why in a way that has made sense to me. I feel like there is something I am not understanding about this.
|
[
"It sounds like you're suggesting the existence of \"hidden variables\".",
"https://en.wikipedia.org/wiki/Hidden_variable_theory",
"Basically, quantum mechanics and hidden variable theory make slightly different predictions for certain experiments. We can rule out the existence of local hidden variables (local meaning that the \"hidden variables\" near you aren't communicating with \"hidden variables\" further away faster than the speed of light\"),",
"https://en.wikipedia.org/wiki/Bell%27s_theorem",
"however a non-local hidden variable theory is (as far as I'm aware) still possible."
] |
[
"This isn't a solved problem in physics. I suggest searching ",
"/r/AskScience",
" for posts dealing with determinism and interpretations of quantum mechanics for discussions on this."
] |
[
"How do we know that what we interpret as quantum indeterminacy isn't just blank spaces that haven't been filled yet?",
"We don't know that. There may be a majority of physicists who think that, but it's certainly not a consensus. While it's ",
" crude, there's a nice overview of interpretations of quantum mechanics on wikipedia where you can clearly see several of them are deterministic. Some of them are very fringe ideas, but others are pretty mainstream,",
"https://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics#Tabular_comparison"
] |
[
"As a follow-up to a question that was asked about bringing back the woolly mammoth - if elephants were also extinct, would that completely eliminate the possibility of bringing back the mammoth?"
] |
[
false
] | null |
[
"Nope, it's fine. We hold things in the spam filter to check them first, so this just wasn't released. ",
"If you respond to a panelist in a relevant portion of the thread, they should respond to you. However, they often ignore repeat questions, which is one of the reasons we avoid them."
] |
[
"No problem, although I'm not a sir. Let us know if you have any more questions!"
] |
[
"Have you asked this question to the panelists in that thread? We don't really allow multiple threads on the same topic at the same time."
] |
[
"Is there any substantial environmental damage from acquiring the materials necessary to make solar panels, wind turbines, or hydroelectric dams?"
] |
[
false
] | null |
[
"They take quite a lot of energy and raw materials to make. They aren't cheap.",
"With the case of hydroelectric, the \"substantial environmental damage\" isn't so much the result of acquiring the materials but the negative effects of the dam itself. The worst of these is a build up of sediment that would otherwise be flushed downstream, which then decomposes to release methane, which is a major greenhouse gas. A lot of hydroelectric projects have ended up causing more environmental damage than they prevent."
] |
[
"Speaking very generally, any mining or earthworks projects will cause environmental disruption and damage to the existing conditions. Of the three you listed one, hydroelectric is what I would consider the most different. But first I want to address solar panels and wind turbines. Just supposing that the materials are extracted from the ground in a manner that produces no harmful by-products the steel to make the turbines and the silicon to make the solar panels will need to be dug up from deposits in the ground. Often refining mined materials results in large amounts of overburden (useless soil and rock above the material) and tailings (rock extracted with and then separated from ore/minerals on the surface). That alone constitutes a significant amount of damage as often the material is just left in waste piles and the ground can subside due to extensive excavations. Modern mining techniques, are meant to mitigate a lot of these problems, by reducing polluted rainwater through the waste rock and advanced geological analysis to prevent structural issues. ",
"Hydroelectric dams, I would say stand alone, even though they tend to be a major investment of materials such as concrete (a major source of CO2 emissions) an extracted minerals, it tends to pale in comparison to the direct local effects of water retention. Hydroelectric power is generated due to the weight of water under gravity and by exploiting that by forcing water to move through an electric turbine. In general it means that we're stealing a bit of the water's potential energy as it flows toward the ocean, but the problem is that we convert it to kinetic energy to extract it. So what happens when you install a dam is not only that the upstream side is flooded, destroying the ecosystems for an area determined by the elevation of the water (To appreciate this better I suggest looking at ",
"FEMA flood maps",
" ) But also a potential washout of the downstream where the flow rates can be at the mercy of the elements as much as during natural flows. The difference is that if there is a huge flood wave heading towards a full reservoir for the most part the water they are releasing from the dam will be fast and furious due to the static water level from the top. Just look a the damage caused at the ",
"Oroville spillway",
" last year. ",
"A properly designed, operated, and maintained hydroelectric dam should never cause catastrophic damage to humans, their property, or the environment in that order so sometimes the environment can take the short end of the stick. The flip side is that in North America, hydroelectric power is developed enough to a point that we are taking a good look at what is necessary to operate these facilities in the optimal way and so that the environment is able to thrive. This is through things such as fish lifts and controlling flows timed with historical seasonal flows. There is a lot more to this, not to sound tired but ",
" so it tends to be a very nuanced issue with problems ever cropping up. What I know I neglected to mention are issues with agricultural needs balanced with population needs and the every marginalized environment but there is sure to be more to discuss. If it wasn't already obvious I am most knowledgeable about water resources, so I'll stand behind those details the most."
] |
[
"Just to illustrate the impact one particular hydroelectric dam project can have on the environment, consider the Three Gorges Dam in China:",
"https://www.businessinsider.com/three-gorges-dam-south-to-north-water-diverson-project-china-2010-7#the-three-gorges-dam-cost-37-billion-to-build-1",
"The adverse impact of other hydroelectric dam projects differ only in the matter of scale and degree."
] |
[
"What chemically happens to water to create the \"old\" or \"stale\" taste?"
] |
[
false
] |
I am just wondering. When we diagnose water as stale, be it from it sitting out for several days, or just unfinished in a water bottle. What chemically causes us to recognize it is old. (I don't believe dust is the answer because bottled water, despite it being in plastic, metal, or glass, can still become stale.)
|
[
"As you probably know, the air you breathe is composed of Nitrogen, Oxygen, Carbon, and other gasses. Now, when you leave water sitting around, some of these gasses will get into the water. Most of the gasses don't do much, but the Carbon dioxide in the air gets into the water as well, and if you know your chemistry, you know that water is a very good solvent, and any acid that gets into it will dissociate. So, when the CO2 gets into the water, it becomes carbonic acid, which decreases the pH of the water by adding H+ ions (hydrogen ions). This makes the water more acidic, and changes the flavor of the water. What ",
"/u/somethingpretentious",
" said about bacteria might not be incorrect, but this is the actual reason as to why water changes taste."
] |
[
"So with atmospheric CO2 going up from ~310ppm in 1960 to 400ppm today, our stale water is actually tasting more stale today than 50 years ago?"
] |
[
"All of the chlorine in chlorinated tap water will evaporate over the course of a day or so, so that will also contribute to the change in flavor and smell. "
] |
[
"How is magnetized plasma created and what kind of gasses produce them?"
] |
[
false
] |
Curious about magnetized plasma. How is it created in a laboratory? Is there special equipment needed to create/store it? What gasses will produce them? The more info the better.
|
[
"The gases can be most anything. Hydrogen (including its fusion-fuel isotopes deuterium and/or tritium) or helium are common choices. Storage generally requires some sort of magnetic confinement. A toroidal magnetic field geometry such as in a ",
"tokamak",
" is a common choice, though there are other geometries, such as ",
"stellarators",
". ",
"In tokamaks, plasma is often made by pumping the chamber full of neutral gas and then sending current through a central coil, discharging in the medium. This acts to heat the medium (through Ohmic heating) as well as generates a toroidal magnetic field in the plasma. Alternatively, plasma can be heated by propagating energetic neutral beams into the medium or using some sort of radio-frequency or microwave heating. ",
"Alternatively, you can also make magnetized plasma in the laboratory by zapping matter with an intense laser beam. One way of generating magnetic fields in such plasma is to produce misaligned gradients in electron density and electron temperature, causing a thermoelectric magnetic field to grow in the medium. These magnetic fields can be quite large, up to ~10",
" Gauss in the case of the highest intensity lasers interacting with solid-density matter. ",
"Edit: added some links"
] |
[
"Thanks a tonne. That answers a lot. If I may bother you for one last question. If I had, say, a Neon tube laying around could, hypothetically, I use it to generate a magnetized plasma at home or is this something I'd need a physics lab for?"
] |
[
"You could certainly generate a plasma at home--there are plenty of YouTube videos and amateur scientist magazines that will tell you how to do so. ",
"Make magazine",
" published plans for making a Farnsworth Fusor, for instance.",
"I'd caution you to be very careful if you do opt to start tinkering with plasmas, particularly if you start using high voltages. It's surprisingly easy to make a deadly mistake. (This happened to a student of mine, who electrocuted himself and died while playing around with high voltages in his house without supervision or proper training and safety precautions.) "
] |
[
"is \"life\" possible without oxygen or water?"
] |
[
false
] |
Say a planet somewhere in the universe had an atmosphere of say pure nitrogen. Could something evolve into life on this planet? Life as we know it needs oxygen, but that's just as we know it. If you believe in evolution than don't you have to believe that it could be possible?
|
[
"There are plenty of solvents besides water. For example, Saturn's moon Titan has seas of liquid methane (it also has an atmosphere of mostly nitrogen - is this what you were thinking of?). There's no reason Titan organisms couldn't exist in these seas, eating acetylene and excreting ethane or benzene. They would be very different from life on earth (extremely flammable, for one) but if they reproduce they would still be quite identifiable as life. "
] |
[
"Water has certain advantages - it is a good solvent for a broad class of compounds, it is very stable, and it is common in the universe. And we certainly have no examples of non-water-based life. But in principle, no, water is not necessary, and there is probably life without it out there somewhere. The cosmos is a big, weird place. "
] |
[
"Yes - and a means of self-defense if there did happen to be life. I've actually considered writing this as a short science fiction story. "
] |
[
"What is the most efficient way to keep a home freezer: completely jammed full or with space for air to flow?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"/r/AskScienceDiscussion",
"Please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"What makes my question speculative? Someone who knows something about thermodynamics should be able to tell me about my freezer! "
] |
[
"Maybe not speculative, but it is a discussion oriented question that would be better suited for ",
"/r/AskScienceDiscussion"
] |
[
"What does the ISS do during meteor showers?"
] |
[
false
] |
I was watching the Perseids the other day and was blown away. Some of the meteors streaked across as much as 20-30% of the sky and some left long visible trails, which I imagine means they were probably quite big. How does the ISS avoid disaster when we move through these debris fields?
|
[
"Space is big, VERY, VERY, VERY, BIG. Debris for a meteor shower is small, like grain of sand size small and spread out tremendously. The chances of a single grain of sand hitting a single football field sized object is near 0. Even when it does we have ",
"high tech solutions",
" using astronaut fingers to plug the holes while some other guy gets some gauze and epoxy together."
] |
[
"\"You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long ways down the road to the Chemist's, but that's just Peanuts to space.\"",
"-Douglas Adams"
] |
[
"Though in the case you cited, I thought it ended up being an assembly flub on the part of the Russians? Ie some technician at Energia accidentally drilled a hole through the pressure hull and rather than tell his superiors, figured that he’d hide it under a glob off epoxy. As it was on the orbital module, he figured that burning up on reentry would hide it."
] |
[
"Why are land animals so much smaller now than they were millions of years ago?"
] |
[
false
] |
When you see the bones of dinosaurs and even gigantic mammals they are MUCH larger than any land animals we see today. I am sure the answer is easy, however, I do not know it. Thanks, AskScience!
|
[
"Because humans killed them.",
"Mass extinction of megafauna have been shown to have happened in the Americas and Australia shortly after the arrival of humans.",
"Interestingly, the surviving megafauna are from Africa and Asia (think big cats, elephants, giraffe), where they did coevolve with humans. But when we did arrive in a new environment where the local megafauna was not used to us it was exterminated in a very short while.",
"See also ",
"here",
"."
] |
[
"While I also think that humans played a significant role in the extinction of large megafauna, I think it's only fair to mention that many paleontologists today still don't buy into that story, at least not completely. It's perfectly possible that a combination of multiple factors resulted in these extinctions, of which humans were only one (a necessary but not sufficient condition)."
] |
[
"You'll also notice that today, most of the large animals that exist are seriously endangered. Tigers, elephants, apes, rhinos, whales, polar bears, (for a while there) buffalo, etc. It's apparently in our nature to kill large animals to the point of extinction or endangerment. "
] |
[
"European Bat Lysavirus 1-2 less pathogenic than Classical rabies (RABV) ?"
] |
[
false
] |
How come they are less pathogenic than classical rabies ? Does it mean that humans immune system fights better these viruses ?
|
[
"They are closely related viruses. Couldn't comparing them to see why they act differently be useful?"
] |
[
"There are literally millions of pairs of closely-related viruses, including more than a dozen lyssaviruses, all with different pathogenicity profiles. The European lyssaviruses are only moderately closely related to the rabies viruses, with the better-studied Australian viruses being considerably closer. ",
"In other words, if your question is “why don’t scientists compare related viruses”, the answer is that of course they do (though they tend to be less informative than you’d think). If your question is “why don’t scientists compare these particular viruses”, the answer is that again they do, but there is only so much time and so many virologists and there are more interesting pairs to look at."
] |
[
"They’re different viruses. There’s no reason to expect them to be the same."
] |
[
"Question on cardiac muscle cells"
] |
[
false
] |
I read that The aerobic energy systems take longer to produce the ATP and reach peak efficiency, and requires many more biochemical steps, but produces significantly more ATP than anaerobic glycolysis. Cardiac muscle on the other hand, can readily consume any of the three macronutrients (protein, glucose and fat) aerobically without a 'warm up' period and always extracts the maximum ATP yield from any molecule involved. ..and was just wondering how this happens. Any insight is appreciated.
|
[
"How it happens is based off of metabolic processes - look up Carbohydrate catalysis, lipid catalysis, and protein catalysis (I'd linksauce it up but there's so many sources, just find what you think is most easily understood as some is overly simplistic and some is overcomplicated). I'll outline the basics if what you're wondering is how exactly anaerobic metabolism works vs. aerobic metabolism, but in short, with anaerobic metabolism you can only undergo glycolysis, but when oxygen is present, mitochondria can function in oxidative metabolism, and burn off the byproducts of glycolysis to create even more ATP.",
"\"Efficiency\" is based off of reaction conditions, mostly substrate concentrations (O2, CO2, molecule being catabolized) and things like pH, amount of water present in the cell, etc. and different cells ",
"Since your heart is always beating, it's always producing the proteins needed for these catalyzation reactions,and given that it's by and large the most important organ in your body, it's evolved to consume just about anything to keep on going",
"Does this answer your question? I can't tell what exactly you are wondering how what happens (I know what I've said is a little simplistic, but I will elaborate based on what you ask)."
] |
[
"I don't think it has much to do with mitochondrial protein synthesis."
] |
[
"Did you read the post?"
] |
[
"Does/would a person in zero g slowly start to spin due to blood circulation?"
] |
[
false
] | null |
[
"Purely internal forces cannot cause you to rotate overall",
"This is incorrect - see ",
"https://en.wikipedia.org/wiki/Reaction_wheel",
". This is how many spacecraft orient themselves.",
"As far as ",
"/u/Telewyn",
"'s question, no, for several reasons. If your circulatory system were more like a torque converter and less like a distributed network of veins, arteries, capillaries and such, then it might be possible, but even then, your blood would have to accelerate and decelerate in flow rate, instead of flowing uniformly.",
"So conceptually, the physics supports OPs question, but the geometry of blood vessels and the fact that flow doesn't change much over time prevent the spinning OP is asking about."
] |
[
"If you read the question and then that answer, it sounds like \"rotate overall\" is talking about the body rotating. Otherwise, the answer doesn't address the question."
] |
[
"You're right, but I'm not exactly incorrect either (not if \"overall rotation\" means \"total angular momentum of your body\"). Reaction wheels don't violate angular momentum conservation, obviously, they must take on whatever angular momentum you're trying to give to your object with them. It's pretty clear (as you said) that unless your circulatory system were very contrived, this would not happen.",
"EDIT: But \"total angular momentum\" of your body is probably not what OP was asking about, so you're right of course. :)"
] |
[
"What is the relation between the Higgs field and chirality?"
] |
[
false
] | null |
[
"The question is almost certainly about the chirality of elementary particles, same as is posted on SE. (In case not: the Higgs field has nothing whatsoever to do with the chirality of amino acids.)"
] |
[
"Did you just post this on stackexchange as well? There's a highly technical answer with symbols and stuff that goes way over my head, but it seems to fit this exact question: ",
"http://physics.stackexchange.com/questions/45450/what-is-the-relation-between-the-higgs-field-and-chirality",
"Or perhaps you meant the chirality of amino acids, in which case the following article outlines some possible explanations: ",
"http://scienceandreason.blogspot.com/2009/04/amino-acid-chirality.html"
] |
[
"Not all mass in the Universe is due to the Higgs. In particular, composite particles like protons and neutrons (which are each composed of three quarks) get most of their mass not from the quarks making them up, but from the strong nuclear forces binding those quarks together. That binding contains a ",
" of energy, the equivalent mass of which (think E=mc",
" ) is significantly greater than the mass of the quarks (which do get their masses from the Higgs). Those strong nuclear forces in turn owe a lot of the mass they generate to something called chiral symmetry breaking, but that's a pretty technical topic and not one I'm best qualified to answer."
] |
[
"where is the magnetic field of the earth generated?"
] |
[
false
] | null |
[
"There's a lot we still don't know about how the earth's magnetic field forms. But we have a pretty good idea and it has to do with the earth's core.",
"The inner core of the earth is solid iron/nickel and the outer core is liquid iron/nickel. The outer core is slowly crystallizing on the contact between the outer and inner core. This crystallization releases heat which drive convection cells in the outer core. Small electric currents in the outer core are generated from this convection of molten metal. This is all part of something known as the ",
"geodynamo theory.",
" Electric current generates magnetic fields and on their own, they are pretty small. The coriolis effect from the earth rotating creates helical columns within the earth's outer core that align the magnetic field in the direction of the earth's rotation. The small magnetic fields add together and generate an overall magnetic field around the earth. All of this generates a magnetic field about 100 times weaker than a refrigerator magnet."
] |
[
"*at the surface of the earth. Take a fridge magnet 6,000km away and it'll be a lot weaker."
] |
[
"The heat is not coming from friction. When a material goes from liquid to solid it has to release a small amount of heat in the process. Your air conditioner is based off the same principle just the other way around. It takes a liquid and turns it into a gas which consumes heat and makes the immediate area a bit colder.",
"The earth's heat comes from three main mechanisms: radioactive decay, heat from the formation of the earth, and friction from when the iron was sinking to the core. Pretty much all the heat is attributed to radioactive decay and the heat left over from when the earth formed."
] |
[
"Why do styrofoam coolers squeak so horribly?"
] |
[
false
] |
What makes them squeak and why do some forms squeak less than others? For example, I have a styrofoam coffee cup here that doesn't squeak. Yet, things like coolers and the kind that's used as cushioning/packing material is awful. ··· (Also, , "In the United States and Canada, the word styrofoam is often incorrectly used as a generic term for expanded (not extruded) polystyrene foam." So, what do English-speaking people call a styrofoam cooler outside outside of North America?)
|
[
"Styrofoam is mostly air, and is otherwise walls of the polymer polystyrene. The reason that it is so squeaky is that when something rubs against it, on the microscopic level, there is a \"stick-slip\" interaction between the surface of the box and, say, your finger. When you \"stick,\" friction compresses the small bubbles (walls) of the polymer, and when you \"slip,\" your finger moves to a new spot. In this time, your finger is off of the surface, and the bubbles that you compressed now expand, contract, expand, contract, and do this at the frequency (-ies) that you hear the squeak. It is loud because the entire box effectively acts like a resonator- the energy dissipated from the scene of the \"stick-slip\" causes secondary oscillations from neighboring bubbles. ",
"Dip your finger in grease, which will cause less of the \"stick\" when trying to recreate the squeak. No sound, right? ",
"This is all based on friction between the \"sticky\" polystyrene and (using a musician word here), a mallet.",
"One can make the analogy that polystyrene is an ensemble of very small ",
"friction drums",
".",
"edit: typo"
] |
[
"To better clarify, the microscopic surface of the polystyrene, combined with its mostly-air composition, both help to create a squeak. If there is another polymer which does not exhibit sqeaks, it is due to its surface morphology and/or its volumetric composition. I'd imagine that if the polystyrene was extruded using a much heavier gas (say, krypton versus regular air), or if the bubbles were made larger, the oscillations would be slower, and the frequency of the squeak would decrease. ",
" \nAgain, you need two things- a surface that vibrates when rubbed and a cavity for the vibrations to resonate. Polystyrene has both of those. "
] |
[
"In Flemish its called \"piepschuim\" literaly translated \"squeaking foam\""
] |
[
"Is there a reason why denser planets are closer to the sun and gas giants are further out?"
] |
[
false
] | null |
[
"What's important here is a concept known as the \"snow line\".",
"Water can only exist in two states out in space - as a gas, or as ice. Since the pressure is essentially zero in space, water's phase will only depends on temperature. In our solar system, this threshold is somewhere around 5 AU (where 1 AU = the average distance between the Sun and Earth), known as the snow line. For space inside of 5 AU, water is generally found as a gas, while for space outside of 5 AU, it's generally found as ice.",
"This threshold is very important for solar system formation. If you imagine proto-planets slowly building up from dust grain sizes up to planetary sizes, you can build a lot faster with rock and ice rather than rock alone. This is especially important if you want hydrogen gas to be a significant percentage of your planet - the general rule of thumb is that a proto-planet needs to be about 5 Earth-masses or greater before it has enough gravitational force to hold on to hydrogen.",
"Also remember that as the Sun ignites, it also starts blowing all that gas out of the system over relatively short timescales, so the places where the proto-planets can grow to 5 Earth-masses the quickest are the places that are eventually going to have planets with lots of gas. Again, reaching this 5 Earth-mass threshold will happen the fastest for planetary cores made of both rock and ice rather than just rock alone...but that can only happen outside the snow line.",
"It's no surprise, then, that Jupiter is at 5.2 AU, just outside the snow line, while the remaining giant planets are out beyond that. Inside the snow line, meanwhile, nothing got massive enough to hold on to hydrogen gas, so we just see rocky planets there.",
": Out past 5 AU, water in space becomes ice. This is important because the proto-planets beyond that distance could be built from both rock and ice, allowing them to more easily reach the 5 Earth-mass threshold required to hold on to hydrogen gas."
] |
[
"It all has to do with mass and velocity. ",
"In a cloud of gas where collisions are frequent (e.g. an atmosphere), the molecules are all moving with a range of different speeds, but the most probable velocity of a molecule will be:",
"v = sqrt(2kT/m)",
"...where ",
" is just a constant, ",
" is the temperature, and ",
" is the mass of the molecule. ",
"So what is this equation telling us? Well, consider a mixture of oxygen and hydrogen all at the same temperature. The atomic weight of molecular oxygen, O2, is 32. On the other hand, the atomic weight of molecular hydrogen, H2, is just 2.",
"Since the hydrogen is 16 times lighter than oxygen, on average it's going to be moving sqrt16) = 4 times faster than oxygen. That means it's much, much easier for hydrogen to reach the escape velocity of a planet. Being much heavier and therefore slower, oxygen is much more likely to get trapped in the gravitational well."
] |
[
"It all has to do with mass and velocity. ",
"In a cloud of gas where collisions are frequent (e.g. an atmosphere), the molecules are all moving with a range of different speeds, but the most probable velocity of a molecule will be:",
"v = sqrt(2kT/m)",
"...where ",
" is just a constant, ",
" is the temperature, and ",
" is the mass of the molecule. ",
"So what is this equation telling us? Well, consider a mixture of oxygen and hydrogen all at the same temperature. The atomic weight of molecular oxygen, O2, is 32. On the other hand, the atomic weight of molecular hydrogen, H2, is just 2.",
"Since the hydrogen is 16 times lighter than oxygen, on average it's going to be moving sqrt16) = 4 times faster than oxygen. That means it's much, much easier for hydrogen to reach the escape velocity of a planet. Being much heavier and therefore slower, oxygen is much more likely to get trapped in the gravitational well."
] |
[
"What do you call a water molecule that is made of 1 deuterium atom and 1 protium atom?"
] |
[
false
] |
On the quest to determine if all slow flakes are truly unique, I stumbled upon an argument based on the idea that some of the water molecules would contain a deuterium atom. My curiosity struck and I realized I don't know much about this niche of chemistry. I am wondering if the following configurations of water can exist, and if so, what do we call them? How rare are they relative to each other? Also I would like to know of any neat facts, such as certain ones being poisonous or explosive! H O H - Water - Dihydrogen Oxide - H O H - Heavy Water? - Deuterium Oxide? - H O H - ??? - ??? H O H - Super Heavy Water - Tritium Oxide - H O H - ??? H O H - ??? For arguments sake, if 1% of all water molecules were H O H, would it make sense to say that 1% of 1% of water molecules are H O H?
|
[
"HDO is ostensibly \"semiheavy water\" but I don't really recall many people calling it by this name. It's usually just HOD or HDO. I am not aware of any common names for those other isotopomers you mention. Also, you missed out on the stable isotopes of oxygen that are possible. ",
"Tritium is radioactive, as you likely saw on Wikipedia. While I can culture my bacteria in deuterium oxide-containing broth, multicellular eukaryotic organisms are generally not so happy - of course, it requires exclusive intake of deuterium oxide for some time before ill effects are observed. You can grow certain yeast strains in highly deuterated broths for biochemical and biophysical studies. "
] |
[
"Oxygen has three stable isotopes: 16, 17, and 18. However, 16 is the most common. According to wikipedia, if you include the unstable isotopes, 14 radioisotopes have been characterized."
] |
[
"In addition to the other reply to you question, it is important to note that all elments have multiple isotopes. The only thing that is limited in number is the amount of stable isotopes. An element is considered radioactive, like U or Tc, when it has no stable isotopes."
] |
[
"Why does sudden and rapid regressive autism only occur following vaccination?"
] |
[
false
] | null |
[
"You can find plenty of examples simply by searching for something like \"regressive autism\" in Google scholar which indexes scientific articles. ",
"Here",
" is a random one I found."
] |
[
"I was hoping to find more anecdotal stories or case studies. ",
"Studies can often be flawed in one way or another and this can be difficult to detect. ",
"It just seems strange that I can literally find thousands of stories of a sudden and rapid regression into autism following a vaccination, but I can't find a single story of this just occurring out of the blue in the same way that these other parents are describing. "
] |
[
"This isn't the right sub to ask for stories. They have no meaningful scientific value. However, the article I linked was based on parental report which sounds kind of like what you're looking for."
] |
[
"Could anyone try to explain to me whole photon-electron relationship?"
] |
[
false
] | null |
[
"Can you be more specific?"
] |
[
"The ways they interact with each other. I don't think I can be very specific. I just want to understand anything a little better. "
] |
[
"The way that photon interact with charged particles is described by quantum electrodynamics. QED is too much to explain in a comment, but I'd start with the Wikipedia article on it to get some background about it."
] |
[
"What is that \"freezer taste?\""
] |
[
false
] |
What is that sort of metallic taste that gets on food when you put it in the freezer for a while? This taste is especially prevalent in ice cubes. Where does that odd taste come from?
|
[
"Because you have a frost-free freezer",
"Sublimation of ice cubes is normal, which causes them to shrink and therefore concentrate any mineral components of your water. The longer the ice cubes sit in the freezer, the more metallic they will taste. Particles from other foods in your freezer will also accumulate on ice cubes and will be concentrated in the same manner by sublimation.",
"EDIT: This is especially noticeable in areas with a lot of minerals disolved in the water, such as Florida (calcium, iron) and Texas (calcium). A good filtration system and water softener will help prevent the odd taste, but your ice cubes will still shrink."
] |
[
"As the solid water (ice) sublimates (changes directly to gas; bypassing the liquid stage) only the H2O in the \"ice cube\" will evaporate. The other elements suspended in the ice remain there. The longer the ice stays in the freezer the more water evaporates leaving more mineral and less water leading to a stronger metallic taste. "
] |
[
"... so if you did this repeatedly you could theoretically accumulate ice-cube trays full of whatever minerals are in your water..."
] |
[
"If two frequencies, one or both of which is by itself OUT of the audible range, have a beat frequency that is IN the audible range, might someone perceive the beat frequency?"
] |
[
false
] |
Suppose there are two pure sine waves with frequencies created by separate function generators, playing aloud through separate (theoretically perfect quality, mind you) speakers. f is a high but audible frequency, and f' is just beyond the largest audible sound for a given person, who is standing in a room. Suppose f-f' = 4000 (a very, very audible frequency) Notes to all: 1)My strong feeling is YES, so if you answer no, I will almost certainly attack your stance until you satisfy my doubts. Do not take it personally, or think I lead you into a trap by asking. I'm telling you now. I think the answer is absolutely 2)I am working under the true premise that so though they are not in the Fourier decomposition of a sum of sines, they are heard. 3)I know that everyone has a different "highest audible frequency,", the question transcends this matter because the frequencies are arbitrary. 4) This is probably not a question of physics or only signal processing. When arguing with said engineer on the matter, it came down to a question of the manner in which the ear and brain process sound.
|
[
"You might hear a ",
"difference tone",
" that simply arises from the nonlinearity of the ear or of the air (",
"sound from ultrasound",
"). In this case, there is literally some physical object vibrating at f-f', and that's what you hear. No mysterious perceptual effects involved.",
"The difference frequency is the same as the beat frequency. But you're not hearing the actual beats in the high-frequency tone in anything like the way that you hear beats in audible tones, so it's somewhat misleading to claim that you \"perceive the beat frequency\"."
] |
[
"This is correct. The confusion arises from a common error regarding beat frequencies vs. the heterodyne effect. ",
"When you simply add to frequencies, you get sin(xt)+sin(yt). When x and y are close, you can graph this, and you get what appears to be sin(xt) with a slowly varying amplitude (varying with frequency x-y). But there is no ",
" at that difference frequency.",
"If your detector is non-linear, then the shit hits the fan. now you've got signal=(sin(xt)+sin(yt))",
" which will give you a sin(xt).sin(yt) term, which ",
" gives you a (sin[(x-y)t]-sin[(x+y)t] term. So now there ",
" power at that frequency.",
"If you're familiar with fourier transforms, that's the way to think about it. "
] |
[
"Yes, an ideal sound recording system would not suffer from such problems.",
"If you're hearing it, it's in audible frequency. If it is being generated by non-linearities inside your ear, it's ",
" - you're hearing what's not there. If it's being generated further down (by spontaneous nerve impulses, for example, like in tinnitus), it's hallucination.",
"There's nothing special about high-frequency sounds. You can also cause sound to be generated inside your ear by other mechanisms. For example, focused radio waves have been known to heat up the inner ear and cause sound sensations. Would you insist on having a microphone system that can pick up those as well?",
"The bottom line to all of this is that the Nyquist theorem still holds. Sampling sound at double the highest audible frequency can reproduce the audible portions ",
"."
] |
[
"Do black holes show any promise in the hunt for dark matter/energy?"
] |
[
false
] |
Wouldn't we have a greater chance of finding an example of dark matter/energy near a black hole? If they suck in everything including light, wouldn't they suck in dark matter/energy, therefor resulting in more dark matter near the black hole?
|
[
"Black holes don't really \"suck\", they have the same force of gravity that everything else does. The main difference is that black holes are denser so you can get closer to the center without diluting the mass. If we replaced the sun with a black hole of the same mass, the Earth's orbit wouldn't change a bit. As you move towards the black hole sun, it remains the same as the old sun until you get to where the surface of the sun used to be. The Sun has a radius of 700,000 km, so if you are 400,000 km from the center, you've now got quite a bit of matter above you, so the gravitational pull is less than it would be if all the matter were still below you at the same radius. With a denser object of the same mass, all the mass is still below you, pulling you down. At the center of an object like the Sun or the Earth, the gravitational force pulling on you is zero (though the pressure from all of the stuff above you being pulled on is incredible). A black hole, though lets the parabolic increase in acceleration due to gravity with diminishing radius continue to much smaller radii.",
"For a little while, people thought maybe dark matter ",
" black holes. They called them \"Massive Compact Halo Objects\", or \"MaCHOs\" for short. In the late 80s, people set up projects to look for gravitational lensing around these black holes, which, if they existed, should be numerous. They pretty quickly proved that there was no secret population of black holes in the galactic halo responsible for dark matter, though. Now, the favorite candidate for dark matter is Weakly Interacting Massive Particles, or \"WIMPS\" - you know, instead of \"MaCHOs\". Particle physicists at Fermi Lab and CERN are looking for these in their colliders, but haven't found any dark matter candidate particles yet. "
] |
[
"A black hole is just a region of spacetime within which the energy density is above a certain critical value such that light cannot escape; it doesn't matter (sorry) whether this is dark matter, normal matter or some other form of energy.",
"Is your question about using black holes to study these things in closer detail, as they are areas where there should be lots of dark matter and dark energy to examine?",
"If so - people have come up with lots of clever ways to study and map the distribution of dark matter, producing maps such as ",
"this",
", where the spikes are the galaxies and the smoother curve shows where the dark matter is, and ",
"this",
", which shows the dark matter distribution on much larger scales (where a galaxy is now a single pixel basically). Generally black holes compared to these scales are really incredibly tiny, so I'm not sure that there is much to be gained by specifically looking for dark matter effects in the region of black holes, though it is an interesting idea.",
"As for dark energy, that is a slightly different phenomenon. Dark energy is a name given to the observed accelerating expansion of the universe, which can be explained by attributing a uniform, constant energy density throughout the universe. Since this stays constant and can be thought of more as a fundamental property of spacetime itself, it doesn't clump around black holes the way 'normal' energy and matter does."
] |
[
"Black holes host some of the most extreme physics known in the universe. They will be used to test theories in the quantum gravity regime.",
"For example any time a signal passes by a black hole that can then make its way to Earth, for example if a pulsar (an incredibly accurate astrophysical clock) is eclipsed by a black hole, you end up with a test of (some properties of) quantum gravity.",
"Edit: You can read about the galactic centre excess of gamma rays ",
"here",
" for example, which could be due to dark matter annihilation. There is also a super massive black hole at the centre of the galaxy, but for your question, as others have explained, this is a case of \"correlation is not causation.\" I.e. the same process of gravitational collapse has put an excess of dark matter and a supermassive black hole at the galactic centre, but one didn't really cause the other."
] |
[
"When the sun goes red giant, will any planets or their moons be in the habitable zone? Will Titan?"
] |
[
false
] |
In 5 billion years will we have any home in this solar system?
|
[
"While Saturn will be in the habitable zone and Titan along with it you have to think of how these worlds will be affected by the increase in temperature. The average density of Titan suggests it is a good mix of rock and ice, so with an increase in radiation from the sun, most of the methane will be lost to space and the ice might melt, but that much ice may mean a water world (covered in ocean). Titan is tidally locked to Saturn and orbits ~16days, so its days are ~16 Earth days. This would mean wild temperature variations between day/night sides. Also, Titan does not have its own magnetic field so maintaining an atmosphere is not promising. It does get some protection from Saturn’s mag field, but it also ventures outside of it and gets blasted by the solar wind."
] |
[
"Yep. Both in the bombardment by cosmic rays and general increase in radiation. Saturn is more than 90% hydrogen and the increase in radiation (i.e. temperature at Saturn) would give that hydrogen enough kinetic energy to escape the grasp of Saturn’s weak gravity. As it loses hydrogen it loses mass and gravity weakens even more, before you know it Saturn would be nothing more than a rocky planet.",
"Edit: changed “tiny planetoid” to “rocky planet”. I meant tiny compared to current day Saturn."
] |
[
"Wouldn’t Saturn lose a bunch of its atmosphere (and therefore mass) as the sun goes red giant? Would the increase in radiation from the sun strip it away?"
] |
[
"What makes jackscrews so capable at lifting heavy loads?"
] |
[
false
] |
I've been reading about the that was carried out in the 19th century to enable the construction of a modern sewerage system. I find it hard to believe something as mundane-looking as a can lift buildings. From the article, bolded emphasis mine: In January 1858, the first masonry building in Chicago to be thus raised—a four story, 70-foot (21 m) long, brick structure situated at the north-east corner of Randolph Street and Dearborn Street—was lifted on to its new grade, which was 6 feet 2 inches (1.88 m) higher than the old one, “without the slightest injury to the building.”
|
[
"IMHO, There is two aspects to the usefulness of a jack screw. ",
"The first one is lever. For one full rotation of the lead screw, you move up only pitch of the screw. As you make a reasonably fine pitched jack, it means you can apply reasonable amounts of torque on the jack screw to move an enormous mass. ",
"Let's say your pitch is 1cm. If you move your lead screw 5 degrees, you are moving up 1cm x 5/360 = 13 microns up. So if you are lifting 10 tons, that's 10,000kg x 9.81 x 13e-6 = 13.62 Joules worth of work. Now, that means you had to apply a torque of (13.62/ deltaAngleinRadians) = 156.13 Nxm. Assuming you are using a bar of 1m length to run the lead screw (your \"tire-iron\"), you had to apply 156 Newton of force. Or about 16kg....so clearly, the lead screw acts as a lever with a huge differential ratio (about 500 in this exemple, moving a 10 ton weight with about 16kg of lead screw \"force\"). You can move immense masses a very short distance using very small forces applied a much longer distance, but unlike the conventional lever, the mechanism is very compact, being wrapped around a screw. Very, very convenient. ",
"The second is the large area of contact between the screw itself and its base. In mechanics, a screw is often described as an inclined plane wrapped helically around an axis, and the exercise that typically follows is to calculate the area of contact between the screw and its mating piece. The result is a surprisingly large area, that depends on the pitch, the lower the pitch, the longer the area. This area serves as a transfer mechanism for the force/weight the jack bears. Because it is a large area, the pressure on the teeth of the screw is lowered, and therefore doesn't reach the mechanical limit of the material used to build it. Heck, if you have a problem with that, just make the female part of your jack slightly longer, and further increase the area of contact, decrease the pressure. Or lower your pitch further....",
"As an aside, the often used rule of thumb is often that if a bolt is threaded in an effective length deeper than the small diameter of its shaft between its teeth, it is actually the shaft of the bolt that will break long before the threads rip as you increase stress on it. So for a jack, you can always make the lead screw fatter, and the female section holding it longer to decrease the stress on the teeth....",
"In summary, a jack has a huge leverage combined with a flexibility of design (length of female piece and size/pitch of thread) that allows to lower material stress to acceptable levels for incredible weight loads. "
] |
[
"Very well explained. ",
"For OP's example, the building weighs 750 tons, and was lifted using 200 screws. That means that the shaft of each jack (excluding the threads) must be large enough to support 750/200 = 3.75 tons without failing. Standard ",
"A36 structural steel",
" is specified as having a minimum yield strength of 36,000 psi (18 tons per square inch), so we need a shaft with a cross-sectional area of at least 3.75 / 18 = 0.208 square inches. That's really not very much- a half-inch diameter shaft is about right (pi*r",
" = (0.25 in)",
" * pi =0.196 in",
") . Make it an inch thick to have some margin of safety. ",
"We also need to consider ",
"buckling",
". If I assume the column effective length factor is 1, given a 3.75 ton load our inch-thick rod can be 61 inches tall before buckling becomes an issue. That's a bit lower than OP's value of 74 inches, plus we'd want some extra for safety factor. If we instead use a pipe with an outer radius of 2 inches and an inner radius of 1.875 inches (0.125 inch wall thickness), we find that it can now be up to 467 inches long before buckling becomes an issue. Much better. Cross-sectional area is pi*(r",
" - r",
") = 1.52 in",
", about twice that of the 1-inch diameter rod (pi*r",
" = 0.785 in",
"). ",
"Buckling is often much more of a limit than outright material failure due to excessive load for slender shapes under compression, as observed here. This is why tubing is useful as a strong, lightweight structural member- it resists buckling far more effectively than a thin rod of equal cross-sectional area, due to its much higher ",
"area moment of inertia",
". "
] |
[
"Crap. These are thought out explanations.",
"To summarize: Jackscrews are a combination of mechanical advantage through screws and leverage by simple levers through the jack. They're setup in a symmetrical arrangement that spreads load and allows for scaling. With hundreds of screws its possible to raise things without pushing the hard bits first."
] |
[
"Why do I get light-headed when I start eating?"
] |
[
false
] | null |
[
"Hi dephress thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"'Human Body'"
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"We do not offer ",
"medical advice",
" on ",
"/r/AskScience",
". Please see our ",
"guidelines.",
" If you have concerns about your or someone else's health, you need to speak to a medical professional.",
"Questions based on personal anecdotes or isolated events tend to invite speculation and more anecdotes, which are not allowed on ",
"/r/AskScience",
".",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"How good a sword could you make with current technology?"
] |
[
false
] |
Improving swords has essentially stopped a few centuries ago, what with them no longer being up to modern combat. Yet you occasionally see super swords pop up in science fiction, like vibro blades and nanoswords. I've been wondering if significant improvement of swords, over the generally assumed peak in swordforging, a well made katana, is possible with today's technology.
|
[
"A very similar question was asked a ",
"couple months ago",
" with a pretty good discussion of why it probably wouldn't be dramatically better than swords made a few hundred years ago."
] |
[
"Thanks!"
] |
[
"One of the problems that I think you overlooked (thanks to the meme that knowledge is ever-increasing, and never lost) is that we presently ",
" replicate some of the best historical swords, due to their maker's disappearance & general lack of interest in making decent swords anymore.",
"As a side note, I remember reading an article on old Katanas, where the carbon \"spontaneously\" formed nano-carbon agregates ... of course, they didn't have a theory for this, only experimental (and lost) knowledge."
] |
[
"Why do the planets nearer a star become rocky and those farther out become gas giants"
] |
[
false
] |
Or is this not always a general make up of a system? It it's "generally but not always" true, have there been system discoveries of the opposite, with the gas giants in close and the rocky ones farther out?
|
[
"We discover a lot of close-to-star gas giants because they're easiest to see. I don't know if they are more prevalent.",
"From the number of hot gas giants we've detected, it appears that they're pretty rare. Something like 1% of stars have such planets. As you said, they're just much easier to detect.",
"During the Nebula stage of our solar system being formed, heavy elements sank closer to the center of gravity (the sun).",
"It's actually more that the light elements got blown out of the inner solar system. Water, for example, is a gas close to the star and gets pushed out to the point where the temperature is low enough that it freezes into ice and accumulates at the \"snow line\". All this extra matter at the snow line allows a massive planet to form very quickly and begin pulling in hydrogen and helium from the solar nebula. This is, we think, why Jupiter is so much larger than the other planets.",
"Outside of the radius where Jupiter formed, there was enough ice to allow the other giant planets to form fairly quickly and gather some light gases as well. Inside of that radius, there was only rocky material, so only small dry planets were able to form. Some water was added to those planets by comets, but only Mars and Earth were able to retain much of it.",
"If our model of the formation of the solar system is accurate, I think we'll find that configurations similar to our system with small rocky planets close to the star and gas giants farther out are pretty common."
] |
[
"The actual reason for this is the frost line ",
"http://en.wikipedia.org/wiki/Frost_line_(astrophysics)",
"The theory goes that inside the frost line, most light elements are fluid gasses, and thus tend to dissipate rather than coalesce (the thing required to start planetary formation). Because of this there is less planetary formation and much of it is rocky. ",
"Outside of the frost line, however, light elements are often found as solids and can coalesce, thus more material is available for planetary formation. This means that an object can quickly run away in its formation grabbing more and more material at a more rapid rate than it would inside the frost line (because it is more accessible). ",
"Inside the frost line most planetary objects will end up around earth's mass, and thus will not be able to suck in many gasses. Outside of it, however, they will rapidly pass the threshold of 5 earth masses and begin to suck in gasses, running away to gas giants, though they may already have been made mostly of frozen gasses to begin with. "
] |
[
"I would repost your answers as a new top level comment, as the one you're replying to is pretty wrong."
] |
[
"Why are the reproductive systems of so many animals tied to their waste-disposal system?"
] |
[
false
] |
Is there an evolutionary advantage to this? Wouldn't the increased risk of infection slowly migrate the reproductive organs elsewhere. Is there some example of an animal that has evolved multi-personal copulation, but also has their reproductive organs as completely separate from their waste disposal? (Ie; not sharing the same tubes). Wouldn't placing it in a far more accessible place, such as the face or head (as comedic as that may seem) be a far more viable reproductive strategy?
|
[
"I can speak to the development of vertebrate urogenital systems, and particularly that of humans. The urinary and genital systems are tied developmentally. They both develop largely from a specific part of the mesoderm (the middle layer of cells in an embryo). You can't decouple them to move the reproductive system elsewhere. Here is a brief run-through to get you started:",
"As an embryo develops, it elongates and folds from a hollow ball of cells to something more recognizable as an organism. This is called embryonic folding, and it creates what's called a ",
"urogenital ridge",
" out of mesoderm. You have a urogenital ridge on the right and left sides of the embryo. The urogenital ridge is going to differentiate into different aspects of the urinary and genital systems.",
"Within the urogenital ridge you have a clump of cells called the ",
"nephrogenic cord",
". It develops into different excretory organs during kidney development: the ",
"pronephros, mesonephros, and metanephros",
". ",
"amniotes",
"Meanwhile, just below the nephrogenic cord on the urogenital ridge you have another clump of cells called the gonadal ridge. Different hormonal cascades will cause these to develop into ovaries or testes. ",
"One structure that is incorporated into the genital system from the mesonephros is called the ",
"mesonephric or Wolffian duct",
". ",
"The mesonephric and paramesonephric ducts open into a pouch at the very end of the hindgut called the ",
"cloaca",
".",
"The cloaca ",
"partitions off",
" in placental mammals to form the rectum and urogenital sinus. The urogenital sinus further separates into the urethra and lower portion of the vagina in female placental mammals, and the prostate and part of the urethra in males. It forms much of the bladder in both sexes.",
"So both systems are completely intertwined. This means you can't merely move the reproductive system regardless of whether there are options that seem \"better\". You'd have to completely re-evolve it from entirely different structures in a way that is heritable and still allows an organism to reproduce. The fact that this is so complicated is evidenced by the different types of reproductive systems we see across all vertebrates (external fertilization, internal fertilization, hard-shelled eggs, live birth, etc.) that all come from these same embryonic structures. They're not re-inventing the wheel, they're just tweaking what already existed.",
"Here",
" is a brief source on the urogenital development of various vertebrates, while ",
"here",
" is a source that is more in-depth and has better illustrations."
] |
[
"Reproductive systems do not have to function for an organism to live. They have to function for an organism to reproduce. This is an important distinction when talking about evolution, because reproductive success is what is central to evolution by natural selection. ",
"Also, there are equally fundamental aspects of organisms that have nothing to do with the urogenital system. The reason they are coupled in living vertebrates is that they literally arise from the same chunk of cells in the embryo. They're completely intertwined. The de novo structures that would allow them to separate have no arisen in any group of vertebrates that I know of. ",
"There are other structures that are highly constrained by development, covered briefly in an excerpt from a developmental biology text ",
"here",
". Tetrapod limbs are an example. There is a reason why tetrapod limb morphology is so incredibly conservative, and it has to do with developmental constraints. Even in disparately adapted limbs there are identifiable common components. So limbs would certainly be an example of a structure that can only change up to a certain extent without impacting an organism's reproductive success (or else some mutation isn't heritable)."
] |
[
"Another way to look at this: Energy intake (and hence also waste disposal) as well as reproductive systems are absolutely fundamental to any organism (if it doesn't just self-replicate). How many arms a being has, whether it has an endo- or exo-skeleton, how many eyes it has (If any.), etc., that's all arbitrary in regards to being able to live at all. Since these systems are so fundamental, they are also extremely old and hence build on the same \"subroutines\" (which is a nice metaphor because Evolution happens to massively reuse stuff). That's not the sole reason they stuck together, but it's a good one.",
" ",
" ",
" "
] |
[
"Do flames have mass or any weight at all?"
] |
[
false
] | null |
[
"If, by flame, you mean the glowing part of the fire, then yes it has mass, because t is hot gas. It rises because its density is less than that of the surrounding air - it \"floats\"."
] |
[
"The relation ",
"c",
" only holds for massive objects at rest. The general relationship in special relativity is ",
" ",
"c",
")",
"+(",
"c)",
", where ",
" is the object's momentum. Light has no mass, so its relationship between energy and momentum is ",
"c. ",
"TL;DR: Light is never at rest, so ",
"c",
" is never valid for light."
] |
[
"Well, it depends if OP has in mind the gas that is emitting the light or the light itself. It's not obvious to me which. ",
"One could probably put mass on energy as follows: m=E/c2",
"This is not correct, or at least very misleading. Light has energy, but no mass."
] |
[
"Does liquid iron continue to be shiny (like liquid mercury) or does it stop being shiny after it starts emitting light?"
] |
[
false
] |
[deleted]
|
[
"Here",
" is an example of molten copper being shiny when under a bright light."
] |
[
"Metals are shiny because they are conductive (mostly). I would expect it with iron as it's still conductive when molten. My googling says its true for aluminum and mercury.",
"With that said, I can't find any pictures, to see the shinyness you really need a bright flash to drown out the glow of the molten iron."
] |
[
"Why are conductive materials shiny? What is their property that makes them interact with light in a certain way?"
] |
[
"How do male animals know that offspring is theirs?"
] |
[
false
] |
I was watching a documentary on zebras, and in it, the narrator mentioned that the stallion will kill any offspring that is not his. I have also heard of this behavior in hippopotamuses. Are animals aware that insemination causes pregnancy? Or is it some chemical in the offspring's body that gives off an odor that signals the behavior in the adults?
|
[
"Usually infanticide (the killing of babies) occurs when a new male takes over a polygynous group (one male mating with multiple females). Because the new male hasn't mated with these females, he can assume the infants aren't his. He won't kill the infants sired during his tenure as the male in charge of the group, just for probability's sake, if dominant males usually sire most of the offspring in the group. Common species with observed infanticide include lions, many primate species (some baboons, gorillas, patas monkeys, etc), among many others."
] |
[
"You aren't giving enough credit to innate behavior. It can be quite complex, like a spider weaving a web. It doesn't have to mean that there is conscious thought. "
] |
[
"Zebras and hippos are both species that tend to live in small groups known as harems. These harems consist of one breeding male and several females that the one male alone breeds with. The killing of offspring generally happens when a new male challenges the current owner of the harem for ownership of said harem and the new male succeeds. Given that he has not bred with any of the females in the harem, any offspring already present are necessarily not his and he will kill them. ",
"I don't not know if there are other mechanisms in place for a male to recognize the a female may be pregnant already and to kill the offspring once it's born. I know that in elephant seals there are often \"sneaky\" males that will attempt to breed with females in another's harem because he has not won his own and as far as I know, the offspring are from the sneaky male are not recognized as foreign or killed by the harem's owner so I would assume that any offspring born after taking a harem are assumed to be the current owner's and left alone. I am not 100% sure on that however."
] |
[
"Since dinosaurs were discovered far below the earths surface covered in dirt, how does the earth gradually pile dirt on itself, forming layers covering up history over the past few centuries?"
] |
[
false
] | null |
[
"Okay, a lot of these are wrong. I'm an archaeologist so let me try to clear some of these misconceptions up. ",
"You are generally going to find fossils within sedimentary rock, and there are a few types of sedimentary deposition. The most common is by water, where tiny pieces of sediment (not dirt, sediment is weathered/eroded pieces of other rock) are placed either by tides, or simply by falling through water. ",
"The other major type of sedimentary deposition is aeolian, or Loess deposition. Instead if the sediment being carried by water, it's carried by the wind. China has a gigantic Loess plateau, which is interesting because if you examine the types of sediment you can get a complete record of that areas climatic conditions. ",
"As far as fossilization goes, fossils will preserve best when they are deposited quickly, so in an area with a high rate of sedimentation. Many aquatic environments will do this, or landslides, or areas that have sediment windblown quickly. But remember this is generally a very SLOW process, but it happens over enormous timescales. ",
"Sorry for writing a book but I hope this helps. ",
"EDIT: Upon rereading the title I noticed you said \"dinosaurs\" and \"centuries\" at the same time. Some archaeology is done from centuries old, these you can find by digging down. Dinosaurs haven't been around since 65 Ma (millions of years ago), typically these sites are found via exposure due to weathering, which is how people know where to look for dinosaur sites. ",
"Also, if anyone is curious I deal with paleolithic archaeology, a nice happy medium between historic arch and paleontology. "
] |
[
"Tar pit, or at the bottom of a shallow sea, quickly covered by a landslide to create an anaerobic environment. "
] |
[
"I think the root of your question is: the whole earth getting bigger? Where does that extra material come from?",
"And I think the answer is no, it doesn't happen everywhere, just locally. Some spots get more material, some get worn away. We only find fossils where it's been net built up over the time since the fossilized creature died."
] |
[
"Does the deep ocean have seasons?"
] |
[
false
] |
Times of the year where there are pronounced temperature differences?
|
[
"No. The seasonal ",
"thermocline",
" only extends down to ",
"a few hundred meters",
" below the ocean surface."
] |
[
"Maybe temperature will be constant but the flow of 'snow' - the stuff that constantly rains down on the ocean floor is likely to change with changing conditions on the surface. A lot of the bottom feeders rely on this."
] |
[
"Okay, thank you!"
] |
[
"Why is methane plumes in the arctic significant?"
] |
[
false
] |
[deleted]
|
[
"I believe that the methane is stored in frozen methane hydrates on the seashore. It is speculated that a warm tendril of water destabilised the methane on the arctic slope and so it is rising. Regardless of the cause they are measuring around 10 times the concentration of methane compared to normal ocean conditions. There are a lot of news organisations referencing what i believe is ",
"this",
" document so you can read more about that there and i'm sure some expert will be happy to elaborate for you (not me unfortunately)",
"Now on to the more complicated question of what will happen. \nThe atmosphere is made up of many different molecules and all of these absorb different wavelengths of radiation. The degree to which they do that is a function of their concentration and they each have their own absorption spectra. There is a decreasing return in the amount of radiation absorbed as you add more and more of each molecule as the 'window' through which each wavelength of light attempts to travel is filled up. If you have an almost full window then adding a little more absorbing material does not make a large difference to how much radiation is absorbed but if you have a relatively empty one then an increase there will result in significantly more radiation being absorbed. ",
"The type of radiation we are interested in is the terrestrial radiation which is in the infrared part of the spectrum. Absorption of this radiation by the gases in the atmosphere results in the trapping of energy on the Earth which leads to a rise in temperature. That's a gross simplification but it will do.",
"Many different molecules absorb this terrestrial radiation chief of which is water. Also among these are carbon dioxide, methane and other greenhouse gases. The direct effect of methane on the climate is that it has a relatively empty window and so an increase in concentration of methane results in more radiation being absorbed compared to a similar increase in concentration of carbon dioxide for example. So for our purposes methane is around 20 times more effective a greenhouse gas than carbon dioxide.",
"This isn't the only effect that methane can have however. It also is an important component of tropspheric and stratospheric chemistry and could affect different absorbers and have some indirect impact. I don't know anything about that but i found a ",
"paper",
" from 2000 on atmospheric methane, there is probably something more recent out there. ",
"Some news websites have reported an association between this methane and the methane trapped in permafrost. There is no connection specifically between methane as a greenhouse gas and the release of further methane. Any temperature rise can cause this feedback loop. It has always and will remain a potentially very serious problem. I should mention that the climate system consists of multitudes of coupled feedback processes and as such it is hard to predict the exact nature one forcing will have on the system as a whole. ",
"You might want to look at Jason Box's ",
"blog post",
" about this particular event and his interpretation of it. Also this ",
"tweet",
" probably sums up his feelings about where this might all be going. Unfortunately it is hard for scientists to communicate directly with the public in a meaningful way as discussed in ",
"this",
". Sometimes the only thing you can do to raise what you think is warranted alarm is to be “alarmist”."
] |
[
"Is this related to the recent permafrost 'explosions' in Siberia?"
] |
[
"The two events wouldn't have a direct causal relationship even accounting for the most extreme case of the butterfly effect. This is simply because the oceans act on Timescales that are much longer than the atmosphere due to higher inertia both to motor and thermal changes. The release of methane from the ocean was way below the mixed layer of the ocean so we can say that whatever caused the oceanic event was already on the pipeline before the Siberian methane explosions occurred.",
"The events are linked due to their similarity and what we can guess as being a common cause. Both events are episodic events that have resulted in the release of methane into the air that has normally been stored in a frozen state. In the case of the Siberian event it is theorised that the local warming of the permafrost in the summer of 2012 contributed significantly to the cause. (I believe it was on the order of 5 degrees, will check when off mobile). As stated elsewhere the oceanic event was also speculated to be caused by a local intrusion of warmer water the key being the local nature of the warming. ",
"This is important because while it may be easier to predict the global temperature change, predicting.the local change is much more difficult. It is certainly possible.that while the global warming could be small, if it is localised in places such as these then there will be powerful feedback mechanisms that could skyrocket temperatures. We won't precisely see the effect of these events but they will contribute and if such events become more frequent then these sorts of events will be very significant."
] |
[
"Does the chlorine used to disinfect drinking water in cities all over the country actually cause severe and chronic problems with our gut microbiome over time?"
] |
[
false
] |
When you google it, the first answer is: 'No studies have confirmed this is a problem, but you should take pro-biotics just in case.' 'No studies have confirmed it... yet, if you've ever had a betta fish and lived in the city where I live- the tap water kills the fish within 5 minutes (if you don't let it rest, or use drops). A 1987 Toxicology study found that consumption of water with even fairly low levels of monochloramine, a commonly used disinfectant that persists in drinking water longer than chlorine, disrupted the immune systems of rats—a finding that's notable given the strong link between the human immune system and gut microbes. What are the actual implications of this? With all of this recent research linking gut bacteria to our health and mental well-being?
|
[
"No. The amount of chlorine in the water is too small, and it will be destroyed completely - to basically salt - by stomach acids.",
"'Probiotics' mess up your natural internal biome, and are only of use if you are already messed up. Even if you have just taken a course of antibiotics, your microbiome recovers sooner if left alone."
] |
[
"I think this quote from the article is telling (emphasis is mine):",
"Leach suspects that several factors may impede bacterial diversity in Americans, among them the profligate use of antibiotics, overconsumption of processed foods, and, at least to some extent, consumption of chlorine in tap water. “It’s something I’ve discussed with a number of other microbiologists,” he replied when I asked about the possibility. ",
"So, there is no actual evidence, but they are certain of the result..."
] |
[
"One of the most egregious sins that mainstream journalism persists in making is drawing a straight line from the results of animal studies to consequences for human beings. If this were reasonable, we wouldn't need to do human trials at all and go straight from animal studies to commercial sale of drugs. These google results should always be taken with a grain of salt, ESPECIALLY if they say things like \"... you should take pro-biotics just in case.\""
] |
[
"How does gene therapy actually work?"
] |
[
false
] |
[deleted]
|
[
"These viruses you speak of are modified to have no pathology, and are used to spread genetic material through a host the way a virus normally would. Viruses have this ability, because it's the manner in which they reproduce. The modified viruses inject this new genetic material into all of the target cells it comes in contact with, changing the genetic makeup of each of these cells."
] |
[
"To expound upon the best general answer:",
"Viruses are not structured the same as what living things are made of, cells. Cells have complicated membranes and internal organelles and are generally much larger. Viruses are thousands of times smaller and pretty much just a strand of DNA or RNA in a protein coat with an injector protein.",
"Now, the idea behind gene therapy is that you make a virus and in the viral DNA/RNA include the code for the protein that is bad in the patient. You also have to make sure that your body does not recognize the virus as a target of immune cells. The virus injects the DNA or RNA payload, and now the patient's cells are making the proper protein using viral DNA (or in the case of retroviruses, their RNA payload gets turned into DNA and inserted in the patient's genome itself)."
] |
[
"Right, and the delivery mechanism is varied, but typically they will either take cells from the patient, engineer them, and stick them back, or inject the virus directly into a tumor (the virus would be carrying p53 or something else which is anti-cancer). You can not take cell lines and transplant them into patients because of graft vs host disease, the body will kill those cells off. So it has to be either a virus which can evade the immune system or the patients own cells."
] |
[
"Why do things \"produce\" light when they get very hot?"
] |
[
false
] |
[deleted]
|
[
"This is called ",
"black-body radiation",
". The cause is because all warm object will emit some of their heat. The way they emit heat is via photons (light particles). The hotter something is, the more heat it emits, thus the more energy it will release. The energy of a photon his given by the equation E = hf, where h is some constant called \"plank's constant\" and f is the frequency of the light. You and I are not very hot, so the light we emit is a very small frequency (long wave length) so the light we emit is in the infrared spectrum (if you've ever seen a heat camera, that's all they are, cameras that see in the infrared). When things get hotter, they emit photons will a high enough frequency that the light enters into the visible spectrum. This is how a normal incandescent light bulb works- the filament is heated up to the point that it emits photons in the visible spectrum. "
] |
[
"We often see red, orange and yellow when a light is warming up(or on a heating element).",
"Why don't we generally see metals go green and blue? We do see UV lights as violet... and it would seem that if lights are giving off white light then they must have passed the blue / green wavelengths... so just curious why we never see that."
] |
[
"why we never see that.",
"The colour of the total light emitted is different from the peak light, it is the peak emission that increases in frequency as the temperature increases. When the peak is in near infra red there is a lot of red light and still but not much blue so the thing glows red. When the peak is in green there is a lot of both red and blue light so the whole thing glows white. When you go very very hot the peak is in UV and there is a lot more blue light than red, the thing looks blue."
] |
[
"What's the best way to approximate the square root of ANY number precisely?"
] |
[
false
] | null |
[
"Example: 76\nIs between 64 and 81, so the whole number will be 8. The rest: 76-64=12, 81-64=17. So an approx. is 8 12/17 or 8.705882, actual root is 8.717798"
] |
[
"You can find the denominator easily because it's 2N+1 where N is the whole number."
] |
[
"Your number is A. To find the square root of A:",
"Pick a number X that is kinda close to the square root of A.",
"calculate (X + A/X)/2. Replace your current X with this new number.",
"Do step 2 a few times until X is good enough. That's it.",
"From the ",
"wiki page",
" for computing square roots. It makes sense because X and A/X will always be on opposite sides of the root of A, so averaging them always gets you closer. And even better, only a handful of repetitions gives you many decimal places of accuracy.",
"Example: sqrt(1000):",
"\nguess 50->35->31.79->31.62 which is pretty much the answer 31.6227766. "
] |
[
"How do coupled reactions ensure that the entropy of an organism is always increasing?"
] |
[
false
] |
I know that life doesn't violate the 2nd law of thermodynamics because organisms aren't closed systems, but apparently that answer isn't good enough. My professor gave me the hint of coupled reactions, but I'm not seeing how coupled reactions answer the question.
|
[
"The entropy of an organism is not always increasing, the entropy of the universe is always increasing. Living things tend to decrease entropy, for example a tree sucks up CO2 gas and locks carbon into cellulose molecules where it has less entropy, but it is only able to do so by absorbing light from the sun, and the nuclear reactions that are the source of that light cause an increase in entropy, so overall the entropy of the universe is increasing. "
] |
[
"It's hard to know what your professor is getting at, but I can think of an example that might be relevant.",
"Let's say you're concentrating a type of molecule inside a cell, pumping it inside. Moving up a concentration gradient like that increases entropy, so it's not going to occur spontaneously.",
"What biological system often do is couple reactions to make the net result energetically favorable so the reaction proceeds. One way to do this is with e.g. ABC transporters that couple transport with hydrolysis of ATP. The hydrolysis releases energy which can be used to pump the molecule. Or, you can have a transporter powered by proton gradients, where the 'pressure' of the protons drives the transport of another molecule."
] |
[
"Thank you, this is exactly what I was looking for. I actually had a huge sudden understanding of how coupled reactions answer the question before you even responded, but thanks for the answer all the same!"
] |
[
"Has the average IQ of people in North America increased or decreased in the last 100 years?"
] |
[
false
] | null |
[
"This is an odd question because by definition the average IQ is 100 -- the test is standardized. So every few years, test-takers take a new test and it's standardized so that the average score is 100. However, if these same test-takers take the old test (standardized on a different set of subjects a while ago), the average of the new test takers is typically higher than 100. This is called the ",
"Flynn effect",
" and you can find more information with a simple google search."
] |
[
"That's surprising to me. I may just be a pessimistic, nihilistic cynic with a superiority complex, but it would seem to me that a large portion of people seem to lack the ability to think and process information intelligently, along with having little to no common sense. Shooting yourself in the testicles with a pistol (on purpose) is a prime example. Then there is gang culture and gang violence, which, in my opinion, is NOT \"the only way\" for the underprivileged to survive. Gang culture seemed to have risen sharply when prohibition was first introduced, so maybe that was a catalyst. Do you think that the same percentage of people are, for lack of a more effective term, morons today than last century? Or has the average intelligence of the human species as a whole increased over the years?"
] |
[
"Among people who take IQ tests, performance has improved relative to previous years. It is questionable whether IQ tests measure anything beyond ability to take IQ tests. An argument could be made that a certain portion of the population that takes these tests is simply being better trained to be test takers of a certain kind. ",
"\"Intelligence\" is a difficult term to operationalize in general. ",
"Everything else you write about is speculative."
] |
[
"Why do bugs fly into lights?"
] |
[
false
] |
[deleted]
|
[
"Because they use the moon to navigate. The moon is far enough away that all the light rays coming from it are (effectively) parallel. When a bug sees a light on the Earth, it uses it to navigate like it would the moon. The rays coming from a light on the Earth, however, are not parallel. Following them leads the bug, who thinks its going in a straight line, on a spiral path leading to the source of the light."
] |
[
"And the cases where it doesn't spiral inwards would be much less likely to be noticed by us, because the insect would not get close enough to the light for us to see it."
] |
[
"I understand how keeping the lamp at a constant bearing would fly you in a circle. However it does not explain why it spirals towards the light. Why does it not spiral away, or orbit at a constant distance?"
] |
[
"What would code for a quantum computer program look like?"
] |
[
false
] |
I can't even begin to wrap my head around it.
|
[
"The way we describe quantum algorithms is not via a programming language as you're used to seeing them. Instead, we describe a sequence of quantum processes that embody the calculation. Each step involves what's called a unitary transformation; it means there is a step in which the quantum state is made to evolve in time in some specific way. Eventually, there will be a step in which a quantum measurement is made, from which the answer can (or, at least, with high probability can) be extracted.",
"These processes are often represented by ",
" which are a representation of the algorithm, with each step implemented by a ",
", i.e., something which implements the particular step."
] |
[
"I think the 'nearest-neighbour' of current programming languages to a future quantum-code-language is either VHDL or Verilog (used to \"program\" transistor circuitry). In these, you clearly define input signals (analogy:qubits), the logic gates they interact with (quantum gates/processes), and the output signals (qubits, real signals from measurement). I have NO idea how many years it will be until we can make a quantum-processing-device analogous to an FPGA, but when we do I think that these languages will be the starting point to developing architecture descriptions for context-specific use."
] |
[
"Well, but if you think about it in this way, the quantum computer programming language would not look too dissimilar from assembler code at first. And then it's easy to imagine a higher level code around that.",
"For example: in assembler, you can deal with gates directly, e.g. you have two bytes in a register and you do an 'AND' operation on them. In a quantum computer, you have a quantum register, and you operate on them via quantum gates like 'CNOT'.",
"The higher level code would be stuff like \"Do a quantum Fourier Transform on qubits 1 to 10\".",
"But yeah, I think the real problem is that the algorithms we know are incredibly specific, so there is no real advantage in having code which allows you to do QFT on qubits 1-10, because we don't know what to do with the output anyway. ",
"On the other hand, a punch card 'computer' would have had little use for concepts like objects and pointers."
] |
[
"Can a microwave oven be repurposed as a Wi-Fi and Bluetooth signal jammer since they're both 2.4GHz?"
] |
[
false
] | null |
[
"Yes. In fact, microwave ovens with defective or very poor radiation shielding (usually very old models) already disrupt Wi-Fi connections.",
"However, Wi-Fi isn't exclusively 2.4 GHz, a lot of devices these days use the 5 GHz band which would not be affected."
] |
[
"I feel it should be noted that broadcasting a signal strong enough to jam is illegal in most places. In the US, the FCC ",
" find such devices if left online or used frequently, and the fines are significant."
] |
[
"You can reduce the effective range or fry the radio's. 200-500 Watts is a big hammer. Also dangerous to mess with.",
"It's not the most efficient way to do it those because usually a microwave produces RF at a single frequency. Wi-Fi uses spread spectrum. The effect of that is from the Wi-Fi receivers point of view the microwave oven's RF gets spread over the band reducing it's effective amplitude. Bluetooth is a frequency hopper so will spend most of it's time on a different channel than the microwave.",
"That said if you have enough power you can just over-drive a radio's input amplifier."
] |
[
"do bugs have brains? if so are there any animals without brains?"
] |
[
false
] | null |
[
"Bugs have brains, yes. ",
"There was just a front-page post in /r/science about the evolution of insect brains.",
"Sponges are animals with no nervous systems. They don't have digestive or circulatory systems, either. They just sit around and let water go through them, delivering nutrients."
] |
[
"Bugs have brains, naturally they are small, Little more than a bundle of nerve cells.\nMany animals do not have brains, invertebrates like jelly fish do not have brains or even nervous systems as far as we can tell."
] |
[
"Jellyfish have a nervous system",
" but not \"central nervous system\" or brain."
] |
[
"[Physics] Water's boiling point - the temperature at which it becomes a gas - is 100°c, so why is there water vapour - gas - in the air at lower temperatures?"
] |
[
false
] |
Please explain in layman's terms if possible :)
|
[
"Because some of the molecules in the water can have sufficient energy to escape the fluid and become vapor, even though not all of the molecules have enough energy. Temperature is a bulk property, and the energy of individual molecules can deviate from average.",
"http://www.reddit.com/r/askscience/comments/1cyxrc/how_does_water_naturally_evaporate_it_doesnt_boil/"
] |
[
"The boiling point of a substance is the point at which it begins to be more energetically favorable for the liquid to exist in a gas phase instead. But this is usually referring to the 'bulk' of the material. That means the boiling point describes the conditions at which a chunk of water surrounded by a bunch of water will transform to the gas phase. It is actually easier for water at the surface of the water to 'boil' away and can thus happen at a lower temperature. It is easier because the water at the surface has fewer neighboring water molecules attracting it. ",
"(Water molecules attract eachother because water is a highly polar molecule)",
"hope that helps"
] |
[
"Water molecules attract each other because water is a highly polar molecule",
"It's important to remember that attractions can arise from other intermolecular forces than polarity"
] |
[
"Where does the sand in deserts come from?"
] |
[
false
] |
My son asked me this today and I realized that I never even thought about it before. How did a desert like the Sahara get filled with sand? Did it come from somewhere else or did it get left behind when the other soil, plants, etc. got removed?
|
[
"I'm studying for my finals, so I think I can answer this roughly. Apologies for occasional grammar mistakes, German here.",
"When we are talking about 'hot', 'dry' deserts, like the Sahara, Gobi or Atacama, about 80% of the desert are made of rocks, stones and other bigger grains. (Those kind of deserts are called Hamada, Serir or Reg.) The basic mechanism is as follows: Because of the absence of water, physical erosion is dominant in these regions; mostly aeolian erosion (by wind). The wind carries the smallest, lightest grains of those deserts and those particles land somewhere else on the ground - forming sand deserts (Erg).",
"The sand is formed by other types of erosion, e.g. by splitting bigger stones with the huge temperature differences between day and night. (Yes, you can die of hypothermia in a desert)",
"Hope that I could help you!",
"Edit: Accidentally some words"
] |
[
"Some deserts are ancient seas and the sand formed from the tides back when there was water. But sand is only 20% of the surface area of deserts; mostly there are exposed, rocky plains. It's also important to remember that there are mountain deserts, cold deserts, rain shadow deserts, and more, not just the stereotypical sandy and arid desert. "
] |
[
"Not all deserts were oceans, although there are some which were, for example the \"Whale Valley\", or Wadi al-Hitan in Egypt. 40 million years ago, there used to be the Tethys Ocean. It dried up gradually, leaving a huge amount of skeletons of sea dwellers, including whales. But basically, every area with a tiny amount of precipitation can become a desert.",
"Erosion is not the main reason why deserts are formed; the process is just a consequence of wind, temperature and other exogenetic factors. ",
"Climate is more important, e.g. when an area only gets hit by offshore, dry winds. Or when the area is right behind a high mountain chain, which causes aridity (the humid winds have to reach a higher altitude because of the natural barrier, air pressure and temperature change and excess water is removed, causing rainfall; the wind becomes dry and passes the mountains - no precipitation for the area behind it; e.g. Gobi behind the Himalaya). Or when the area is in a high pressure area which effects the dissolving of clouds, also leading to a lack of precipitation (Sahara). Or when the cold ocean currents make the humid winds dry so that no humidity can reach the coast regions (Atacama). And so on...",
"The Sahara desert used to be a savanna thousands of years ago, allowing vegetation, civilisation and fruitful soil to exist. (Proved by archaeologists who found various man-made tools, bones of mammals and fish, dried up rivers and even ancient drawings.) But a sudden change in climate, leading to mutation in the wind systems, gradually dried out the forest. (Maybe someone else can explain it further, I only know that it is assumed that the melting of glaciers in Europe led to a change in atmospheric pressure, moving the Sahara to the drier subtropical high pressure area.) Ironically, the Sahara seems to have one of the biggest subterranean water capacities. And it is also fertilizing the Amazonas! (Winds carry the minerals in sand grains to the Amazonas, crossing the huge ocean between those two continents)",
"Man-made deserts are also known, e.g. the Aral Sea nowadays. It used to be one of the cleanest, biggest seas. In the mid '60s, the Russian government began to use the water to plant cotton (yes, COTTON in Russia) to become less dependent on other countries. Also, a lot of industry was done there. Now, the sea shrunk by 85% (leaving only 15% of its original size) and consists of an unknown toxic broth.",
"Our planet is fascinating!"
] |
[
"Why does it feel so good to pee?"
] |
[
false
] |
For most guys, at least, peeing is like having a miniature orgasm. But it's just water running down from the bladder through the urethra. So why does it feel so damn good?
|
[
"I don't actually know anything about the mechanism of why it feels good, but I would imagine that it's evolutionarily adaptive for urinating to feel good for the same reason that it's adaptive for eating and drinking water and pooping to feel good - because it's bad for the body if you don't do these things. Conversely, it feels bad to starve yourself or to 'hold it in' and not got to the bathroom for a long time."
] |
[
"My general impression is that things with an evolutionary imperative are generally associated with pleasurable feelings. Since peeing is important for survival, you are compelled to do it by positive reinforcement which has evolved over millenia to make sure you don't hold it in too long and hurt yourself."
] |
[
"A full bladder puts pressure on the intestines around it and it's uncomfortable. Same for a full colon."
] |
[
"Why are some men's facial hair a different color from their hair?"
] |
[
false
] |
I was never able to understand how that works. Any ideas?
|
[
"Hair color is one of those things used as an examples in simple genetics problems but is not understood well. Pigmentation is polygenic and we see the production of several different protein products. I suspect that in different tissues (ie scalp, chest, chin) expression of the genes are different and the differential expression causes different colors."
] |
[
"Because secondary sex characteristics in males (like facial hair) develop in response to pubertal rises in androgens (namely testosterone), it is possible that those follicles are more responsive to this hormone. Testosterone may be regulating some of the genes responsible for pigment production by either promoting or repressing their transcription. (This is just a theory based on background knowledge.)"
] |
[
"Not to hijack the thread, but I was also wondering why I have a few stray red hairs on my face. I'm dark-haired all over, and I never had any that color until about 3-4 years ago (I'm 29 if that helps)",
"Only in my stubble, not down there, or in my eyebrows or head. "
] |
[
"From the perspective of an outside observer, when does the Schwarzschild radius of a black hole grows?"
] |
[
false
] |
As I understand, from the perspective of an outside observer, an object falling into a black hole approaches its event horizon asymptotically and takes infinite time to actually reach it. So, when would the observer be able to register the Schwarzschild radius of the black hole increase, if, as far as they’re concerned, the object never crosses the horizon? Would it be the moment when the object gets close enough to the “old” horizon to be encompassed by a “new” horizon that accounts for the objects mass?
|
[
"The infalling object has a gravitational field way before it merges with the black hole. The event horizon is a global thing and will grow accordingly. You can see this animation for two black holes ",
"https://youtu.be/Tr1zDVbSjTM",
" . So all the time dilation business is never an issue."
] |
[
"From the perspective of an outside observer, she sees a \"last photon\" from an in-falling object. For a stellar-mass BH, this last photon comes within milliseconds of the object falling in. So there's no need to worry about the asymptotic behavior, since the discrete photon behavior is so different.",
"As for registering the Schwarzschild radius, I don't know what that means in this context. We can see only the photons from near the BH. And gravity waves, if there are significant dynamics. (Non-rotating isolated BHs don't have gravity waves.) The BH radius is inferred from behavior of the photons we see, which come from OUTSIDE the photon sphere.",
"The inner-most light we see from near a BH is observed to come from a radius of 2.6 Rs (plus small corrections for a spinning BH). So we see the light, measure the apparent radius, figure Rs, and thus the BH mass. Any object that has fallen pass the photon sphere is, for all practical purposes, part of the BH.",
"[Edit: yeah, the \"last photon\" might come years after the object falls in. But how would the outside observer catch it? I would bet the photon rate seen by the observer falls off super fast; whatever the intensity is at 1 second before \"crossing\", it is a million times less at 0.010 seconds before the crossing, and then another factor of a billion times less at 0.0001 seconds, etc. The result is that the observer might, if she is lucky, see a photon at time T, the next at T + milliseconds, then T + 10 days, then T + millions of years.]"
] |
[
"I think you're suggesting that gravity wave measurements and optical (infrared) measurements might give conflicting results. That would be a fantastic finding! But it isn't going to happen, because you need really really huge masses falling into the BH, in order to detect gravity waves. I'm thinking at least Jupiter-mass. And objects that massive have complex structure, which will result in a lot of fine-grained complexity in the gravity & light measurements. Since we don't know the structure details of the falling object, we can't compute what to expect from those fine details in the gravity waves and optical measurements. For all practical purposes, the details look just like noise.",
"We might measure and track every mountain and hill on something 300 times bigger than Earth, but I don't see going down to level of individual rocks. But individual photons come from atoms and molecules, which are billions / trillions of times smaller. Besides, real BHs have a LOT of dust and gas falling into them all the time, so you would have to track that also."
] |
[
"Could you still see through an eye that's knocked out of its socket?"
] |
[
false
] |
Imagining something like the scene here: (NSFL, fake movie violence) where the eye is forced out of the socket and hanging by a thread. Would it still be functional?
|
[
"Yes and no. Your eyes does manny sudden movements and fixations every second, since the nerves in the retina are not at all even distributed (highly focussed in fovea). You would still be receiving information, but without being able to saccade you would only have detailed information about a very small part of your visual area (the centre of your visual field). You wouldn't be able to 'see' in the traditional sense - you'd be pretty much useless at it."
] |
[
"For the sake of argument, let's accept that an eye could be removed from the orbit without damaging it so badly that intrinsic function was compromised. Possible, but quite the trick shot to accomplish, as the extraocular muscles and orbital tissue are quite strong (muscles are about 10x the strength needed to move the eye).",
"Now, you have an eye that is no longer constrained in its movements, as it was in the orbit, where it made well known rotations about three axes (slight offset between angle of rotation and optical center, but that's not too big an issue). In addition to this, we also have to account for movement (head and body) through six degrees of freedom (three rotational and three translational dimensions). And all of these disparate movements must be accounted for by the ocular motor system (and some associated portions of the brain such as vestibular circuitry) to allow us to maintain a clear and stable image of the world as we go about our daily routine.",
"All of these signals are kept track of, through a mechanism known as \"efference copy\" that essentially models the effects of the signals on a virtual representation of the eye and its muscles, to allow the motor system to anticipate the results of the command and prepare the next one without needing visual feedback (which is much slower).",
"Now let the eye move freely, so that the commands that move it no longer correspond to what it does. You are going to have a terrible sense of disorientation, and very likely extraordinary nausea as what you see is unrelated to what your balance (vestibular) organs sense.",
"I wouldn't go so far as to say \"useless\" for your vision out of that eye. You will have a normal view of the world, in terms of acuity, for the central degree of wherever your eye is pointing. That acuity falls off very sharply as you get more than a few degrees away. But your motion sensitivity and peripheral vision are still going to give you a sense of what is going on around you. (If you're lucky it'll be someone coming over to stabilize your eye in saline gauze and a clean cup.)"
] |
[
"It's been a couple of years since I was certified in first aid, but for some reason we actually covered this topic. IIRC, you should immediately attempt to place the eye in a styrofoam cup or similar container. And by that I mean putting the cup over and around your eye socket with the eye. This has the double benefit of removing confusing sensory input (which apparently almost always causes nausea), and preventing contact with the eye and related tissues(for infection prevention). I also remember that one should place a damp paper towel in a ring between the cup rim and the face, but I don't remember the reason given. I think something having to do with relieving pressure, but that's an educated guess."
] |
[
"Why is electricity transmitted at high voltage? Confused about interaction with Ohm's Law."
] |
[
false
] |
So I get the money saving part with lighter wires (If you did high current low voltage you'd need bigger wires to handle the current), but I don't get the I loss and transmitting at high voltage low current. It seems like when you subsitiute with Ohm's Law if you raise voltage resistance goes up since R=V/I. Conceptually High current low voltage would mean more electrons bumping into side which creates resistance, but high voltage low current would mean less electrons bumping into side, but since they have more electric potential energy associated with them they would create more resitance upon bumping into side like quality over quanity. Sorry if this doesn't make sense, I'm really confused.
|
[
"To clear things up: You want to transfer power over long distance.\nThis Power is P=VxI (Lets use DC current for simplifying stuff)\nNow you want to minimize losses and/or material cost. With high voltage for the same Power P you have less current. This smaller current need smaller diameter in the transmission lines and you have less restive losses because P_loss=I",
" x R_line. You notice losses scale with the square of current for a given length and diameter line. So for a given line and same Power to transfer, higher voltage means less current, means less losses.\nOR for a given line (same lenght and diameter), you can transfer more power if you use higher voltage (needs better insulation / air gaps) since P_new=V_new x I, with the same losses P_loss=I",
" x R_line (current and line resistance remain the same)."
] |
[
"In most situations, including this one, resistance is just a function of the material the wire is made out of. So the resistance will not go up; R = V/I means that if voltage rises, current also hast to rise."
] |
[
"P_loss=I",
" x R_line.",
"Isn't P_loss also equal to V",
"/R_line? And when you raise the voltage/current ratio, isn't that the same thing as adding resistance?"
] |
[
"Domesticated animals are known to be a source of many diseases in humans. Historically, are there any pandemics that have been caused by canine diseases? If not, why do dogs not carry plague-worthy illnesses, or why are humans immune?"
] |
[
false
] |
When Europeans migrated to the New World, they brought with them many diseases that ravaged the native human populations, which had no immunity due to a lack of domesticated animals. However, both populations already had domesticated dogs. Were there any major infections caused by a canine disease? Or did human proximity to dogs since prehistory give us immunity, and so no potential for more recent pandemics, or are our immune systems too dissimilar for transmission?
|
[
"Our immune systems and cell biology are certainly similar enough for the potential of zoonotic transmission of disease from dogs to people; rabies is one example. The lack of major disease outbreaks related to dogs may be related to the conditions in which humans keep dogs versus other domesticated animals associated with those major diseases. For example, measles is one of the diseases that ravaged Native American populations and ",
"evolved from rinderpest",
", a cattle virus. The nature in which humans keep cattle (i.e. large herds) enables a virus like rinderpest to spread amongst cattle until it evolves the capability to jump to humans and evolve into measles. Humans typically haven’t kept dogs in large groups the way they have for domesticated food animals, which may have limited the ability of canine viruses to be passed from dog to dog while being in close proximity to humans for a spillover event.",
"Edit: added link"
] |
[
"Another thought is that dogs have lived with humans for ~ 35,000 years and mutual immunity is helping. (",
"https://www.boehringer-ingelheim.com/our-responsibility/animal-health-news/human-dog-relationship-historical-perspective",
")."
] |
[
"Plus, taking something like BSE (Mad cow disease) as example, most societies do not eat their dogs.",
"*1 Another aspect worth mentioning: Thanks to extensive research on Covid as a virus group, we know that there are thousands, potentially tens of thousands Covid variations per year that do cross over to humans, but don't spread far. And that's just in China.",
"I don't know of any research that tries to explore the reasons for this, but it does show that crossover events are far more common that we previously thought and that the vast, vast majority of these viruses just can't spread efficiently, if at all."
] |
[
"Does Gravity travel at different speeds in different mediums?"
] |
[
false
] |
Light travels at different speeds in different mediums. Gravity is said to travel at the speed of light, so is this also true for gravity?
|
[
"No, it always propagates at the same speed. If its path was warped by another gravitational field, it might appear to travel slower because it's taking a longer route.",
"edit: see ",
"here",
" for a very small effect due to absorption of gravitational waves in different media."
] |
[
"Sorry, ",
"/u/iorgfeflkd",
", but this is not correct. See for example Sec. 2.4.3 of Kip Thorne's lectures at Les Houches (1982) where he works out the absorption and dispersion of GWs in media (I put up a scan ",
"here",
"). Of course this leads to a dispersion relationship and hence a different phase and group velocity, which depends on the background density. This effect is ridiculously tiny but it's there.",
"A simple way to think about it is that a GW goes by and stretches and squeezes some medium, which then responds and re-radiates slightly out of phase. This is the same as photons being absorbed and re-emitted in medium."
] |
[
"So let's say we had an ideal gas of black holes..."
] |
[
"Magnetic fields as propulsion in space?"
] |
[
false
] |
I was just thinking about that Train in Japan that set the speed record, and it made me think aren't there magnetic fields in space, and can we use those as way of propulsion of a space craft?
|
[
"Kind of. Maglev trains are propelled by magnetic fields, but they are applying a reaction force on the tracks. In space, with no matter around, this wouldn't be so easy.",
"Fortunately the solar wind exists, it's very weak but present. In theory it would be possible to use a magnetic field to deflect those charged particles, absorbing their momentum and transferring it to the spacecraft.",
"https://en.wikipedia.org/wiki/Magnetic_sail",
"It could also be used in the proximity of a planet with a meaningful magnetosphere, e.g. Earth or Jupiter. But for now, it's only futuristic technology."
] |
[
"on a similar vein why is nuclear power not talked about much in regards to space travel\nas it allows submarines to be at sea for a very long time before returning home\nand of course keeps nuclear plants going indefinitely and nuclear bars would be a lot easier than gallons of fuel "
] |
[
"While it might be useful when near planets as the above comment points out I guess It wouldn't be of much help in trying to cross our milky way with huge gaps between large bodies but I do like that question and have wondered could we not use magnetism to push a space craft of the earth? thus riding ourselves of the weight of fuel now needed. "
] |
[
"Do any chemical reactions occur in the plasma phase?"
] |
[
false
] |
Or are all interatomic bonds broken in a plasma? If so, is it possible to control how the atoms recombine into molecules when you cool the plasma back down into a gas?
|
[
"Plasma",
", the so called fourth state of matter is when \"the gas phase is heated until atomic electrons are no longer associated with any particular atomic nucleus. Plasma s are made up of positively charged ions and unbound electrons.\"",
"Chemistry is concerned ",
"with",
" \"atoms and their interactions with other atoms, with particular focus on the properties of the chemical bonds formed between species. \"",
"The plasma state in stars - if it is of sufficient energy - can prodcue nuclear fusion which produced all chemical elements, and in a sense could be described as the foundation of the production of elements, and elements are necessary for chemistry.",
"But in terms of actual chemistry in the plasma state, there is too much energy for long term chemical bonds to form, and the electrons have too much kinetic energy to stay bonded to any given nucleus."
] |
[
"They certainly won't coalesce into anything orderly on their own. Any hot gas has an enormous amount of entropy, and a plasma has even more. To control which atoms go where, could probably induce some ordering with strong gravitational or magnetic field to separate the high/low mass/charge particles.",
"Keep in mind that as the plasma cools down and turns into a gas, there is usually little to no actual molecular order going on, just a bunch of lone atoms, some Di-Halogen pairs, and perhaps some triplets such as CO2 or what have you. That's still highly disordered. So if you have a bunch of C, H, N, O, P and Ca in a plasma and you want organic molecules or cells, you'll need to cool the whole thing down way below a homogenous gas phase (~1,000K?) before anything that's mildly interesting is even stable (~400K?), and the mixture will need to approach that temperature from a highly disordered state. So the simple answer to your question is no, other than electric/gravitational separation."
] |
[
"Ok, so what about the part of the question I posted in the text box? Can you control how the atoms bond to each other when you cool the plasma back down into a gas?"
] |
[
"Why can't you see your own eyes move in a mirror?"
] |
[
false
] | null |
[
"Your visual processing system of your brain-eye system (they’re very closely integrated) filters out anything that happens during saccades (movements of the eye to fixate on something else), because it would just be a confusing blur. In fact, it replaces that time interval with something else, either “stretching” the last thing you saw a bit longer or post facto projecting the first thing you see after the saccade back into the past, or some mixture of both. That’s why the seconds hand on a clock can seem to stand still for a lot longer than one second after you focus on it: your brain stretches the image you saw after your saccade ",
" to fill the time of the saccade. ",
"TL;DR: your own head is screwing with you, put on some tinfoil."
] |
[
"Just like the brain uses photoshop-like skills to cover up that permanent blind spot where your optical nerve cable plugs into your vision-screen. Reality is a lie, can't even trust your own brain nowadays."
] |
[
"I think that’s pretty much the same mechanism. The brain always creates an internal “movie” from fragments it catches with the eyes. That input is always incomplete and most of that movie is actually interpolated from moment to moment. The blind spot is one such thing causing incompleteness, but the difference between central and peripheral vision alone causes a lot of interpolation between the two. That’s why your eyes are constantly darting around, trying to fill in the complete picture as well as possible. Actually, as well as ",
", until it thinks it has seen enough to help you with whatever your current objective is. A ton of information gets filtered out every second, you’re never actually seeing the “complete” world around you in all detail."
] |
[
"How are diamonds attached to saw blades that they can manage to stay on while cutting through steel and diamonds?"
] |
[
false
] | null |
[
"There are three common ways to hold the diamonds.",
"2 (a) Resin bonding",
"\nDiamond grit is mixed in a resin, which is then cured (chemically and/or heat and pressure)",
"2 (b) Metal bonding\nDiamond grit and fine metal powder are mixed with a temporary binder then pressed into shape. The assembly is put into a furnace to remove the binder then sinter the metal powder. This requires a controlled atmosphere because diamonds are carbon and will oxidise in air."
] |
[
"Corrosion resistance. Diamond saws and grinding wheels are usually water cooled."
] |
[
"Thank you. Do you also know what is special about nickel that makes them such metal of choice for attaching diamonds? "
] |
[
"If everyone stayed indoors/isolated for 2-4 weeks, could we kill off the common cold and/or flu forever? And would we want to if we could?"
] |
[
false
] | null |
[
"Unfortunately, influenza can also spread through many animals, such as pigs, so no, the flu would survive."
] |
[
"Being that no-one has touched on it yet, I thought I'd add a bit about the second part of your question when you ask \"would we want to?\" ",
"Removal of any organism from an environment is likely to have an effect. Take smallpox as an example (which as far as I knew is fully eradicated), there is starting to be a link with its eradication and the emergence of monkey pox in humans. When people were being vaccinated for smallpox they received cross-protection against monkey pox. Since vaccination stopped there has been an increase in the number of monkey pox cases as it is able to fill the niche left by the smallpox virus. If we were to eradicate rhinovirus and influenza (as you suggest) then it's highly possible that other viruses/diseases could fill the niche. Eradication isn't a bad thing, I think we are doing the right thing targeting polio and presumably measles afterwards but there is a potential for some consequences. ",
"Here's an article about smallpox/monkey pox",
" by Ed Yong"
] |
[
"This is the most important point, IMO. Any disease that has any \"reservoir host\" or a carrier will not be eradicated. At least not with the technology we currently have."
] |
[
"Can bugs sneeze?"
] |
[
false
] |
I was talking with my brother about animals sneezing and this came up... Can they?
|
[
"Many insects are thought to passively exchange air through these tubes without any muscular involvement.",
"While many others ",
"actively breath",
": "
] |
[
"No, not in the way that you are thinking. Insects unlike reptiles, birds and mammals don't breathe through their mouths. ",
"Insects have tubes, called spiracles that exit on their abdomen and allow for air to exchange with their internal structures. Many insects are thought to passively exchange air through these tubes without any muscular involvement. ",
"Here's a picture of the respiratory system of a grasshopper",
"Edit: added unlike"
] |
[
"Interestingly, while insects can't necessarily sneeze ",
", they can (and frequently do) vomit! ",
"In fact, this is the ",
"mechanism",
" by which ",
" (the bacterium that causes the bubonic plague) gets into the blood of humans and other mammals: the bacterium infects a flea and begins growing in the insects' midgut. As the infection progresses, ",
" blocks off more and more of the flea's esophagus, so that the flea has to throw up some of the bacteria before it can swallow a blood meal. ",
"Mosquitos",
" also puke up anticoagulants to make your blood flow easier when they bite you. "
] |
[
"How easily is nicotine absorbed through the skin? Does different skin have different absorption rates? & does nicotine act differently when absorbed through your skin compared to inhaling it?"
] |
[
false
] | null |
[
"Due to the permeability barrier of the skin (in particular, the outermost layer, called the ",
"), there are very few drugs that can be absorbed through intact skin. Nicotine is one of the few that can be delivered transdermally. It is able to diffuse through the stratum corneum in part because it is a small molecule (162 Da) that is lipophilic (oil-soluble). ",
"How easily is nicotine absorbed through the skin?",
"What type of answer (value) are you looking for? Nicotine patches can deliver approximately 20 mg nicotine over the course of a day. Other measures that might answer your question are the permeability coefficient, the diffusion coefficient, and/or the partition coefficient. If you are interested in any of these, I (or others here) can help you find values.",
"Source: ",
"Prausnitz et al., (2004)"
] |
[
"I have spoken with people that hand harvested tobacco, usually as children or teenagers. They all talked about getting nauseous and \"wired\" from the physical contact with the plants. It essentially rubbed off on their exposed skin and sickened them. They do not recall it fondly."
] |
[
"They may be looking for the transdermal bioavailability, which according to ",
"this paper",
" and ",
"wiki",
" is around 68%."
] |
[
"How is LSD made?"
] |
[
false
] |
I am not looking to make it, but from what I understand it is one of the most difficult drugs to make. Using dark rooms, perfectly sterile labs and only putting enough of a dose to get someone to the level they want. Seeing as such a minute amount is used to get someone there. What is the process to make it and synthesize it. Also, why does lsd effect the mind like it does? Edit: I found out how to make it. Jw, for any chemist out there, could you make it? If you can or can't please state your education level.
|
[
"He's changed the question since I answered it. ",
"LSD is hardly one of the most difficult drugs to make, it's not even on most total synthesis people's list of remarkable challenges.",
"Compare ",
"Brevetoxin",
" to ",
"LSD",
", or even ",
"Stychnine",
"LSD is the type of thing you do for a problem set in grad school, interesting, but not even close to the most difficult things. Heck, here's the link to buy it from ",
"Aldrich",
", and Aldrich doesn't really sell things that are difficult to make.",
"Also, ",
"Discodermolide",
" took a ",
"Novartis team",
" 20 months to make 60 g. "
] |
[
"http://learn.genetics.utah.edu/content/addiction/drugs/mouse.html",
"This will answer your second question."
] |
[
"A few additional comments:",
"The total synthesis would be quite a task. But of course, starting from lysergic acid, making the amide would not take that much effort. As far as the OP's comments about dark/sterile rooms, much of this has to do with retaining LSD's psychoactivity. LSD will isomerize in base and also grow significantly more reactive towards species like water when exposed to light. Because of this—and furthermore, because the active dose is so minute—special care must be taken to avoid contamination of the final product."
] |
[
"Granted that humans walked to the different inhabited continents, how did we wind up on tiny polynesian islands?"
] |
[
false
] |
Aboriginal tribes, Hawaiians, and especially the really tiny islands nobody really talks about like Wallis et Futuna, all seem by my recollection to have had native tribes upon being discovered and mapped. How did they get there to begin with? Is it as anthropologically easy as "people went sailing and got lost"?
|
[
"The ",
"Kon-Tiki",
" experiment certainly provided some scientific validity to this theory."
] |
[
"US airmen Louis Zamperini and Russel Phillips survived 47 days and drifted about 2000 miles on a life raft in the South Pacific after being shot down in WWII. And that was with the occasional strafing. So it is certainly quite possible."
] |
[
"Or a small family or group of families to get lost and manage to survive on a fertile island."
] |
[
"Would keeping an \"injured\" body part at higher temperatures make it heal faster?"
] |
[
false
] |
I recently worked out my calves and walking kind of hurts. That got me think. If ice makes things numb and generally slows down bodily functions, would keeping a body part at a higher than normal temperature make it heal faster?
|
[
"While being cold could slow down bodily functions, the reason you ice injuries, or sore muscles, is that it reduces the swelling which reduces the pain. I don't think heating up a limb would help very much because your body is pretty good at knowing what temperature to be. A lot of the metabolic pathways in your body work best at your normal body temperature. Many enzyme have work better with increased temperature to a point there is a threshold after which the enzyme begins to lose function."
] |
[
"Ice and heat are often used interchangeably during sports injuries. Ice is used to reduce pain and swelling as when damage occurs you have vasodilation in the area which leads to edema, ice helps prevent this and therefore prevents swelling.",
"Heat on the other hand should be used if the injury lasts for more than a week or so, its used to reduce muscle spasms and therefore again reduce pain.",
"Either way you're simply reducing pain by using ice or heat on an injury, they wont significantly help speed up or slow down the healing process."
] |
[
"Either way you're simply reducing pain by using ice or heat on an injury, they wont significantly help speed up or slow down the healing process.",
"This is false. Cold can be used throughout the injury and recovery stages, but heat should not be applied until after the acute inflammation period (~3-4 days). \"If heat is applied too soon in the injury response process, the increased cell metabolism causes an increase in the number of cells injured or destroyed because of hypoxia. Increasing the inflammatory rate could possibly extend the acute or subacute inflammatory phases.\" [Therapeutic Modalities, 2nd edition, C. Starkey p124]",
"The correct use of heat and ice can and will shorten recovery time, while improper applications could extend the healing time required. "
] |
[
"If it wasn't for air resistance would balloons rise with the same acceleration as gravity?"
] |
[
false
] |
I realize that there needs to be air for the balloon to rise
|
[
"Ignoring air resistance, the forces on the balloon are gravity and buoyancy.",
"F = rho_air * V_balloon * g - m_balloon * g\n",
"where rho is a density, and g is the gravitational acceleration. We can also write",
" V_balloon = m_balloon / rho_balloon\n",
"so",
"F = m_balloon*g*(rho_air/rho_balloon - 1)\n",
"Newton II says F = ma so",
"a_balloon = g*(rho_air/rho_balloon - 1)\n",
"in other words, the balloon acceleration upwards depends on the ratio of densities of the surrounding air to the balloon contents. It will have an acceleration upwards equal to g if and only if rho_air/rho_balloon = 2 -- if the balloon is half as dense as the surrounding air.",
"This is also ignoring any expansion or compression of the balloon as the outside pressure changes."
] |
[
"Imagine a tennis ball in a swimming pool. If you let go of it from the bottom of the pool, it travels upward. Both the water and the tennis ball are pulled toward the earth by gravity. But since the water is more dense than the tennis ball that has air in it, the water is pulled underneath the tennis ball, causing it to rise. ",
"So, a balloon isn't really travelling upwards against gravity in as much as the heavier air around it is travelling under the balloon, causing the balloon to rise.",
"In a vaccuum, the balloon wouldn't rise at all, because there would be no heavier air for the balloon to sit on top of. In a vaccuum, it would be like the tennis ball sitting on the bottom of an empty swimming pool. There has to be water in the pool for it to float."
] |
[
"The same situation arises with an imbalanced counterweight.",
"Say you have a 10 kg mass you want to spring upward. You attach a string to it, make the string go around a pulley, and attach a 20 kg counterweight to the other side.",
"The initial answer many will jump to would be that it accelerates upwards at twice the acceleration of gravity, but of course that's wrong. ",
"The total system has an interial mass of 30kg, but gravity asserts a ",
" force of only the 10kg difference. The acceleration will be one-third of gravity."
] |
[
"When I am all alone, and there is no noise in the room, and it is all still and quiet, there is a sound in my ears/head that is similar to a ringing of the ears, but it's not quite the same. What causes that?"
] |
[
false
] | null |
[
"Tinnitus",
": \"the perception of sound within the human ear in the absence of corresponding external sound\". ",
"Causes are varied, so check the ",
" link for more on that. "
] |
[
"It's a fairly sly reference to the ",
"Legend of Zelda",
" video game series where the protagonist, a boy called Link, is often referred to as Zelda, actually the princess that Link is trying to save, by players who haven't followed the story and dialogue. You obviously don't spend much time 'round ",
"r/gaming",
"!"
] |
[
"Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes ",
"I think he is talking about a sound of blood running through veins near to his ears. You can hear it clearly if you are in a silent room and shut off your ears with your fingers."
] |
[
"Does anyone still bother to read papers by the giants of theoretical physics?"
] |
[
false
] |
Their most highly-cited papers (of people like Yang, Oppenheimer, Teller, Feynman, etc.) are surprisingly readable. And they're deep. They're highly cited for both of those reasons, after all. But no one seems to touch them anymore. - Teller's "On the Change of Physical Constants" - Feynman's most highly cited paper - the famous Yang-Lee paper - Parity Conservation in Beta Decay - Dirac's Quantum Theory of the electron
|
[
"TBH, it seems to me that papers are the invention of an idea, but textbooks are more expansive/better explanations of said idea. Most of us have learned these things through classes on the ideas I guess."
] |
[
"Yeah, that seems to be the standard assumption. But I do wonder if some ideas are lost in the textbook's explanation. By reading papers, you sort of do get a better idea of what inconsistency prompted the invention of a new theory (or technique) to correct that inconsistency. And this helps with formulating further hypotheses."
] |
[
"What's lost in a text will be picked up by a person's interactions with their peers. Often, I think, reading older papers will give a person insight into where a certain style of thought comes from; but unless you were actively reading a paper to really fight with the claims being made, I'm not sure how much insight you'd get into the subject itself. ",
"It's much more fun to read recent papers anyway, you have the chance to interact with the author and really pick apart their ideas. "
] |
[
"Not sure how to classify neuron on their properties of excitatory vs inhibitory effects(very stupid question too)"
] |
[
false
] |
Before I go on, I want to make sure that everyone knows I don't know ANYTHING about neurons or biology. So please forgive this stupid question ahead time. At It talks about groups of neurons and how they are excitatory or inhibitory, but I would like to understand what that means and how this works exactly. My question is this - "Does each group(serotonin neurons, glutamate neurons, Gaba neurons etc) have a seperate excitatory neuron vs inhibitory(excitatory-glutamate vs inhibitory-glutamate) or are their different neurons groups for the inhibitory function(glutamate = excitatory function vs GABA = inhibitory function type that would be classified as a "group")
|
[
"Glutamate is typically excitatory and GABA is typically inhibitory, but there are situations in which ",
"GABA has an excitatory effect",
", and ",
"inhibitory glutamate receptors",
" are known. So it cannot be said that each neurotransmitter can only be either excitatory or inhibitory, since this depends on the type of receptor that is receiving the neurotransmitter. "
] |
[
"tl;dr To see if a neuron is grouped as excitatory or inhibitory, look at the change in voltage in the downstream neuron. (Cheater method that mostly works: look at the neurotransmitter released.)",
"The voltage on the \"in cell\" side of a neuron is lower than on the \"out of cell\" side of the membrane. Raising the voltage inside above a threshold triggers a series of events that releases neurotransmitters into the \"gap junction\" between this neuron and the downstream neuron, which affects the downstream neuron.",
"The neurotransmitter binds to an ion channel protein in the membrane of the downstream neuron, which allows a certain type of ion (sodium, potassium, or chloride most often) to pass through the membrane. Letting in sodium (Na+) increases the voltage inside the downstream neuron, shifting the voltage closer to the threshold: excitatory. Letting in chloride (Cl-) or letting out (K+) has the opposite effect: inhibitory. ",
"Different neurotransmitters unlock different ion channels. ",
"Glutamate binds to the NMDA channel allows Na+, K+ and Ca++ (calcium) ions to move across the membrane (since more",
" Na+ and Ca++ ions to enter the cell than K+ ions to leave the cell), which increases the voltage inside the cell (depolarization). The increase in voltage from ion flow is called an excitatory post-synaptic current (EPSC): ",
" because the voltage inside the cell is closer to the threshold, ",
" because this happened in the downstream neuron \"after\" the gap junction, ",
" because this happened through ions flowing (current = charged things moving in a direction). So an upstream neuron that releases glutamate is excitatory. ",
"GABA is a bit more annoying because there are excitatory and inhibitory GABA receptors, but most people speak of the latter (because they are more common). When GABA binds to the GABA receptor, chloride Cl- enters the cell, which decreases the voltage. The decrease in voltage from ion flow is an inhibitory post-synaptic current (IPSC). So an upstream neuron that releases GABA is most often inhibitory. ",
" Depending on other conditions, like the current voltage detected by the NMDA receptor and the presence of Mg++ and other ligands. "
] |
[
"It's nice to finally have an answer. Much appreciated"
] |
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