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[
"Can non-human animals be allergic to other animals? E.g. can a cat be allergic to me?"
] |
[
false
] | null |
[
"Heres an article about cats which are allergic on humans. Sorry, the ",
"article",
" is in German. Can translate if you need. ",
"Edit: Found an ",
"English article"
] |
[
"Very, VERY good question! The thing is, animals tend to be far more resistant to allergens and a lot of bacteria than humans are (EDIT: because they have adapted to living in spaces that aren't as clean as ours), but, as pointed out ",
"below",
" animals can be allergic to humans, although it is much less common than humans being allergic to animals."
] |
[
"This isn't true. Animals can and do, frequently, have allergies (often, though, allergies are manifested in dermatologic problems such as pruritus). And also do get infections... they're not \"resistant\" to bacteria.",
"Edit: Since I'm apparently being downvoted, here is some more info, specifically about cat and dog allergies (since I'm in vet med) and bacterial infections. It is frustrating to see people say that animals do not suffer from the same ailments that people do, because this idea sometimes prevents people from bringing in their pets into a veterinary practice when they should.",
"Examples of commonly presenting allergies:",
"Atopic dermatitis is a commonly seen inflammatory and pruritic allergic skin lesion seen with clinical features associated with IgE antibodies. This is the closest thing to what most people think of as allergies, since antibodies are commonly directed against environmental allergies (such as pollen, dust, etc.) Lesions seen are typically on flexural surfaces, the face, paws, areas of friction, and skin folds.",
"Food allergy dermatitis is proposed to be caused by type-I, type-III, and/or type IV hypersensitivities. The allergen is the water soluble glycoprotein present on food such as beef, chicken, dairy, and wheat. We typically see pruritic otitis, anal furunculosis, and recurring pruritic pyoderma.",
"Flea allergy dermatitis, very commonly seen, is caused by type-I immediate, type-I late phase, and type-IV delayed hypersensitivies, and cutaneous basophil hypersensitivities. We typically see pruritic lesions in the tail base and inguinal areas.",
"Animals also don't really have immunity/resistance to bacterial infections. We see plenty of animals in the hospital with bacterial infections. The difference, which you may be thinking of, is that we are susceptible to different disease complexes and bacterial infections than animals. i.e. bartonella henselae which is not believed to be directly responsible to cause a disease complex in cats (although it is thought to be linked to plasma cell stomatitis), yet sometimes causes lymphadenopathy, immune dysfunction, and bacillary peliosis in people (usually are immunocompromised to begin with).",
"However, zoonotic and anthroponotic transmission of bacterial infections can and do occur. Furthermore, this is part of the basis of \"One Health\" initiative in which human and animal health specialists collaborate together to improve the health and quality of life of people, animals, and the environment."
] |
[
"Do computer simulations of the visible universe take into account the current position of stars considering the speed of light?"
] |
[
false
] |
[deleted]
|
[
"But \"where are they now\" is not a very deep scientific question. Science is more than mere stamp collecting. Yes, the real positions of stars and planets as compared to their observed positions could indeed indicate interesting interactions, IF we had the where-are-they-now data. But we don't. Any simulation of where-are-they-now would be based solely on our theories of gravity, hydrodynamics, and so on, as we currently know them, and therefore wouldn't ever reveal unknown physics."
] |
[
"But \"where are they now\" is not a very deep scientific question. Science is more than mere stamp collecting. Yes, the real positions of stars and planets as compared to their observed positions could indeed indicate interesting interactions, IF we had the where-are-they-now data. But we don't. Any simulation of where-are-they-now would be based solely on our theories of gravity, hydrodynamics, and so on, as we currently know them, and therefore wouldn't ever reveal unknown physics."
] |
[
"It would be possible to do that, but tedious and uninteresting. It's not the current positions of bodies that are important, but the nature of their interactions. ",
"Mapping \"current positions\" wouldn't do much to the cone structure caused by the zone of avoidance that you're talking about, because the distances involved are enormous and peculiar velocities are small. "
] |
[
"Does time have to exist?"
] |
[
false
] |
[deleted]
|
[
"Yes, special relativity has been experimentally tested. It's one of the most thoroughly tested scientific theories there is.",
"And yes, time exists."
] |
[
"I think it's worse here to improperly cite a quote than to not cite at all. ",
"-Wolfgang Pauli"
] |
[
"In that case, to avoid the conflict with memes, I'd just leave off the attribution in the future. I think it's worse here to improperly cite a quote than to not cite at all."
] |
[
"How much good would it do to have plants (that need high amounts of CO2) put on the roof of every skyscraper in every city?"
] |
[
false
] |
Right? Doesn't it seem like a somewhat simple solution to at least help a ? I know some plants require more CO2 than others, so why not use the ones that requier the most (or genetically modify ones to require excessive amounts) to put on the tops of skyscrapers and buildings to absord the absurd amounts emitted below...
|
[
"When a plant removes one ton of carbon from the atmosphere, it it puts the carbon ",
" - the plant's body is ",
" largely of carbon.",
"So what that means is: for a plant to absorb one ton of carbon, the plant must ",
" one ton of weight. Each time it absorbs another ton of carbon, the plant gets at least one ton heavier (in practice, quite a bit more, because the plant contains water too).",
"Many people think of plants as continuously consuming carbon from the atmosphere, but that's not exactly right - the plant is only consuming carbon when the plant is gaining weight. If for any reason the plant loses weight - say, a branch rots away - then the plant is releasing carbon while it's losing weight.",
"The number of tons of carbon you could realistically store on a roof is pretty limited.",
"If you want to take carbon out of the atmosphere, what you would do is grow plants, then seal them away forever, making sure they don't ever rot (which releases them back into the atmosphere). Then, grow more plants and seal them away too, and keep doing that until you've stored an awful lot of tons of plants."
] |
[
"a lot of people are not aware that a plant's mass comes from the air"
] |
[
"In the end, any attempt to remove carbon from the atmosphere is going to have to involve storing the carbon somewhere. But it certainly doesn't have to go into space. Just into long-term storage. By long-term, I mean long enough for us to come up with something better. Maybe 100 years, say. That's easy in small quantities, but there's no obvious way to remove and store the tons of carbon we need to without spending a fortune."
] |
[
"did dinosaurs roar?"
] |
[
false
] |
do their skeletons tell us anything about that? i know some lizards hiss loudly, but i dont know about roaring.
|
[
"Not sure why this is tagged as archaeology, since it's not human related. "
] |
[
"I'm guessing nothing like that has been.",
"\"Skippy\", but I don't know how well the throat was preserved",
"- Apparently \"somewhat\" -",
"Of the respiratory system little has been preserved. No traces of the lungs have survived, nor of any air sacks. The sole element still present consists of a seven millimetre long piece of the trachea of which about ten tracheal rings are visible, the most anterior of which are open at the top, giving them a C-shape.",
"http://en.wikipedia.org/wiki/Scipionyx",
" "
] |
[
"A better comparison would be bird sounds."
] |
[
"Why is it so much worse to get chicken pox as an adult than as a kid?"
] |
[
false
] |
I always assumed our immune systems got better as we got older (eventually declining with old age obviously)
|
[
"In adults, the varicella zoster virus (responsible for chicken pox in children and shingles in adults) wreaks havoc on the immune system. The virus is actually a latent type and is contracted as chicken pox as a child, recedes up into neural cells, only to descend back to the surface and show up as shingles (via the neural ganglia). It can also be newly contracted as an adult. Essentially it screws up a lot of neural pathways through damage of the neurons. The most severe complication can lead to vascular damage of the brain, leading to stroke, blindness, and/or permanent neurological damage. "
] |
[
"Maybe I'm reading this wrong but I don't feel this actually answered the question.",
"It explains it, sure, but I'm still unsure as to why it's worse to contract the disease as an adult.",
"In my personal (inexperienced) opinion, it's going to be something to do with how children are still growing therefore injuries are much easier to recover from and illnesses don't hit as hard? Can somebody please clarify this?"
] |
[
"I just read a couple of interesting articles about this. It sounds like a decrease in ",
"cell mediated immunity",
" towards the virus as we age is the culprit. During an infection, our body responds in two ways: a cell-mediated response (wikipedia has a better explanation that I could put here), or a ",
"humoral response",
" where we make antibodies to fight the current infection and stave off future infections.",
"Unlike many other diseases, when attacked by the chicken pox virus, or varicella zoster (VZV), the body's response by making antibodies is not very effective at clearing the disease though it is still effective at preventing future infections. This is why it can reactivate, causing shingles, in immunocompromised patients or in the elderly as their VSV cell mediated response declines.",
"I believe these articles are implying the lack of both of significant cell mediated response in an adult with no antibodies makes the disease much more difficult for the body to handle.",
"When you say our immune system gets better as we get older, I think you are referring the the fact we build up antibodies to more pathogens. Sadly, this only helps for the ones we have been exposed to, and if you weren't as a kid or were never immunized, your out of luck.",
"Couple of good articles, but a bit technical:",
"1",
" - Scroll down to the cell mediated immunity section",
"2",
" - Good overview of VSV. Figure 5 shows the decline of the cell mediated response to the virus with age. "
] |
[
"If a were shot in the head and killed, would he/she hear the gunshot before dying?"
] |
[
false
] |
[deleted]
|
[
"This would depend on the speed of the bullet and distance you are being shot from.",
"let [the speed of the bullet] = s. s∈R>0\nlet [the local speed of sound] = y. y∈R>0\nlet [the latency to 'hear'] = c. c∈R>0\nlet [the distance the bullet must travel] = d. d∈R>=0\nlet [you hear being shot] = b. b∈{true,false}\n\nIf (s >= y) then b = false.\nElse (if (d / s - c > 0) b = true).\n",
"Note, I do not account for extreme ranges where the sound might not be heard due to distance or for what ifs for how loud vs being able to hear it. I assume for simplicity that it ",
" be heard."
] |
[
"Be fair, a bullet traveling at 300 m/s will take about 0.5 ms (where a neuron's takes a full 5ms to fire at the maximum rate of 200hz) to pass through the entire brain. But yeah, since all but the very slowest bullets travel faster than nerve impulses, the bullet would get there before the message of \"ow\" did."
] |
[
"My brother got shot in the head a few years ago. The thing that saved his life was that he saw the muzzle flash and turned to look in that direction. He said he does not remember hearing the sound of the gun, but that may be because he just doesn't remember hearing it or was not paying attention to the sound. ",
"He was shot with a 9mm which is subsonic, so it wasn't that he was hit before the sound got to him. Based upon that, I would have to say, it would depend on how far away the shooter was, what was the velocity of the round, and where you were hit. "
] |
[
"How do epidurals work?"
] |
[
false
] |
I feel like I've heard a lot of differing answers on this, particularly in regard to child birth. From "the woman doesn't feel a thing" to "the woman feels everything but doesn't remember the pain." Well, what is the actual mechanism? Is the medicine blocking some function in the brain? Is it numbing? Just curious, thanks!
|
[
"It’s an injection of anesthesia into the spinal canal at a certain level which then “numbs” the nerves below that point. The idea being to numb to some extent those nerves most commonly agitated during labor. Not really anything to do with the brain other than signals coming from the nerves in a woman’s pelvis are hindered from reaching the brain to register as pain."
] |
[
"It feels like you are pushing a needle through an eraser when you’re going through the interspinous ligament, then there is an almost imperceptible grittiness as you go through the ligamentum flavum. You know when to stop when the needle tip reaches the epidural space and you get a loss of resistance to injection. You know you’ve gone too far when you take the syringe off the needle and there is CSF hosing out lol!"
] |
[
"Not a sciencey answer here, but first hand experience via child birth. Once the medicine is injected, you feel nothing while laboring. I took a nap. However, they turn the medicine off when you need to push so you regain feeling and can push. I felt every second of the actual birth. The epidural however enabled me to rest after 24 hours in labor until I had my son a few hours later. While it was in full effect, I watched my contractions on the monitor but could not feel them at all."
] |
[
"Are older/ elderly people's discs between their spine more flattened or dereriorated (on avg.) vs. a younger one?"
] |
[
false
] | null |
[
"In short, yes they are. ",
"Research suggests that over the age of 40 years old, 60% of people show degeneration in a least one of their discs. This shows the early onset of degenerations, and after, this then worsens.",
"Intervertebral discs have two principle parts to their structure. (1) A fibrous outer shell. This is a dense matrix of collagen which provides overall structure to the disc. (2) A soft central pulp. This softer core allows for the distribution of forces that act on the disc, hence forces are spread more evenly across the fibrous shell than they would be if the disc was ridged.",
"The problem is that once discs are formed they lose almost all of their blood supply and hence their ability to regenerate. The soft core has a considerable water content to keep it soft and malleable. Over time the water is lost and not replaced so that (1) the disc becomes smaller (2) the disc becomes overall more susceptible to damage (and too the spinal vertebrae, don’t forget).",
"The fibrous shell undergoes some degradation overtime as well then, and if it breaks open sufficient to allow the core to bulge out, we get the ‘slipped disc’.",
"So in conclusion, yes older peoples discs are more flat (smaller) and also physically deteriorated.",
"Hope that clears it up :)",
"Source: Medical Degree, BMSc. Statistic and some info taken from Wikipedia article, can get you a proper reference if required."
] |
[
"no thanks! that helps a lot.\nI kind of have a follow up question which I realized it what Im more going for. \nSo, if I play a bunch of sports or do a lot of lifting. So like Soccer, where theres a lot of sharp angle cutting and change of direction. And squats, well.. because of the compression. Will that make my back worse off that someone who just walks for exercise their whole life?\nI wonder if there stats of pro soccer players vs. normal spines. Or power lifters, if they have bad spines like the GoT mountain (worlds strongest man)"
] |
[
"Not necessarily. If you exercise, stretch, warm up properly and don’t push your body beyond its physical limits (like twisting a knee so much it strains, sprains, or tears a ligament for example) than you will be fine. If anything the exercise and sports more than likely help. The body grows stronger where it is needed. like the muscles that support your spine or the bones in your femurs if you are a runner. If it was as you suggested then neurosurgical and orthopedic spine surgeon offices would be inordinately filled with those patients disproportionately to the general population, which is not the case. ",
"In the case of power lifters think of it this way. People often say “don’t do deadlifts it can hurt your back.” Sure this is true, however, what should be said is “do not do deadlifts unless you use proper technique.” The proper technique actually strengthens the muscles that help support your spine, in essence shielding it from potential injury. Those who do not do exercises to strengthen their back and core muscles that support the spine and intervertebral discs are potentially at a greater risk of injury."
] |
[
"The connection between electrons and photons?"
] |
[
false
] |
So I'm confused about the nature of photons and electrons, and how they interact with each other. From what I understand, two photons can form an electron together, but photons are also used to transmit the electromagnetical force between charge carriers such as electrons. And they have the ability to knock electrons away from their cores in metals. So what are electrons? A bunch of photons together? Something completely else? Do they transmit photons or something? And why do they have mass when photons don't? Any insight in this subject is welcome.
|
[
"Not really. That's a commonly used analogy but it's not quite true. The electric field around electrons is modified by their presence, and those modifications behave like photons, but it's not the same as electrons emitting photons. ",
"link"
] |
[
"Also two photons cannot create an electron.",
"I was under the impression that since electrons and positrons do annihilate into two photons, it must be possible for two photons (of suitable spin and energy in respect to each other) to form an electron and a positron."
] |
[
"Electrons are massive charged spin-1/2 particles. Photons are massless neutral spin-1 particles, which are best viewed as quanta of electromagnetic radiation."
] |
[
"I can smell scents breathing in, why can't I smell the same scents breathing out?"
] |
[
false
] |
For example, sticking my nose in a scented candle jar, the smell is extremely strong, but I can't smell anything breathing it out.
|
[
"This is absolutely unacceptable behavior and will result in a permanent ban if repeated. "
] |
[
"This is absolutely unacceptable behavior and will result in a permanent ban if repeated. "
] |
[
"Your olfactory system is certainly active when you're breathing out - in fact retronasal olfaction (perception of the smell of food within the mouth) provides most of our sense of taste, and occurs mainly ",
"during exhalation",
".",
"I can't explain what you observe as not smelling anything while breathing out - I could offer informed speculation based on saturating olfactory receptor neurons while breathing in which are then essentially muted while you breathe out and the nasal fossa clears - but hopefully someone better qualified in this area can give you a definitive answer. "
] |
[
"Are face muscles controlled through the spine?"
] |
[
false
] |
[deleted]
|
[
"It depends on the causes of paralysis. Speech is a complex act and a lot of different nerves are used to make it happen. It is possible that some of them would be damaged while the rest would be intact resulting in partial loss of the ability to speak."
] |
[
"Just for completeness sake, there are also some muscles in the face (for chewing, primarily) that are controlled by branches of ",
"CN V, the Trigeminal Nerve.",
" But as ",
"/u/ReineBlanche",
" alluded, all cranial nerves attach to the brainstem rather than the spine. ",
"Edit: should read \"above the spine\"."
] |
[
"all cranial nerves attach to the brainstem ",
"CN I and II don't. "
] |
[
"Geologists: What forces caused these adjacent mountain formations to end up looking so different?"
] |
[
false
] |
I took this photo as I drove through the Mojave Desert near Barstow, CA. The coordinates from which I took it MIGHT be 34.766999,-115.472832 according to Google Maps (street view seems to match my photo), and I was shooting to the northwest.
|
[
"Looks like the darker mountains are cinder cones of volcanic origin. "
] |
[
"The darker ones look distinctly mafic to me, so I agree that they're probably igneous, maybe volcanic in origin.",
"General geomorphology though makes me think these things you're looking at aren't mountains, more like rotated fault blocks."
] |
[
"A fault block is just a geometric unit of rock that has been faulted. ",
"Sometimes the plane along which it has faulted is a bit curved (technical term for this is listric) and it causes the fault block to rotate as it progresses along the fault.",
"I realise I am doing a terrible job of explaining this and am hunting for something concise but informative that will hopefully do a much better job."
] |
[
"What causes Triboluminescence, where sparks appear when glass or hardened sugar for example is shattered?"
] |
[
false
] |
Edit: video example:
|
[
"All of this is from ",
"here",
"Triboluminescence is light produced while striking or rubbing two pieces of a special material together. It is basically light from friction, as the term comes from the Greek tribein, meaning \"to rub,\" and the Latin prefix lumin, meaning \"light\". In general, luminescence occurs when energy is input into atoms from heat, friction, electricity, or other sources. The electrons in the atom absorb this energy. When the electrons return to their usual state, the energy is released in the form of light.",
"The spectrum of the light produced from the triboluminescence of sugar (sucrose) is the same as the spectrum of lightning. Lightning originates from a flow of electrons passing through the air, exciting the electrons of nitrogen molecules (the primary component of air), which emit blue light as they release their energy. Triboluminescence of sugar can be thought of as lightning on a very small scale. When a sugar crystal is stressed, the positive and negative charges in the crystal are separated, generating an electric potential. When enough charge has accumulated, the electrons jump across a fracture in the crystal, colliding with exciting electrons in the nitrogen molecules. Most of the light emitted by the nitrogen in the air is ultraviolet, but a small fraction is in the visible region. To most people, the emission appears bluish-white, although some people discern a blue-green color (human color vision in the dark is not very good).",
"The emission from wintergreen candy is much brighter than that of sucrose alone because wintergreen flavor (methyl salicylate) is fluorescent. Methyl salicylate absorbs ultraviolet light in the same spectral region as the lightning emissions generated by the sugar. The methyl salicylate electrons become excited and emit blue light. Much more of the wintergreen emission than the original sugar emission is in the visible region of the spectrum, so wintergreen light seems brighter than sucrose light."
] |
[
"I did a science fair project in grade school in which I bit into each flavor of lifesavers to check whether I could see a spark (also a good excuse to eat a lot of candy). I saw sparks on each of the white minty ones (wintergreen, peppermint, etc.), but not on the sugary ones (five flavors, butter rum, etc.).",
"I then compared ingredients and found the one common to the white minty ones was Stearic Acid. I concluded that Stearic Acid is probably causing the light.",
"Thanks for the insight, now I understand what was going on better."
] |
[
"From what I can read, it is caused by electrical charges being separated in the breaking process(atoms being separated from some of its electrons). This causes potential build-ups which in turn causes the electrical arcing observed.",
"Basically it seems like \"static electrical buildups\" caused by the breaking of the crystals."
] |
[
"What is the proper way to break in an internal combustion engine?"
] |
[
false
] |
[deleted]
|
[
"You absolutely, without question, want to take it easy during break-in. The length of the break-in period is debatable, and it seems to be getting very short to non-existent on modern engines. But that's beside the point.",
"The reason you want to take it easy has a lot to do with friction. Everywhere in the engine that tolerances are too tight (where there is extra metal) is going to begin to wear via friction and abrasion processes. If done slowly, these processes are not detrimental, and any excess material is smoothly worn away until parts fit together and move against each other properly. If this wear occurs rapidly, a large amount of heat can build up, and cause all sorts of nasty problems. Heat treated components can loose their temper, really rapid wear may occur on bearing surfaces, and lots of scarring/pitting can occur in places you want smooth surfaces. All of these effects add up to poorer performance and shortened in-service life. ",
"Cheers."
] |
[
"Oh no, the feared vertical-text-super-rant.",
"The big thing here is the difference between a race engine and a everyday use engine. Race engines live short and violent lives, and are tuned to last just long enough. The article you linked is all about piston rings, and how a hard break-in gives you more power. I find the claim a bit dubious. If you take it easy (lower cylinder pressure) the normal forces on the rings will be less, and abrasion will occur more slowly. Go hard, and the wear happens faster. There is no reason or mechanism for a magical drop-off at 20 miles. But, I'm not a race tech, and I can't give much more than that.",
"The broader point is this: in your car's engine there are many bearing surfaces and wear points other than the piston rings. If you run hard during break-in, you accelerate wear on these parts and lower the lifespan of the engine. This isn't a big deal for a race engine (or race engine tuner) since the engine will be thrashed long before this problem comes into play. If you're not working with a high-performance race engine, the accelerated wear is a big problem however."
] |
[
"I think a machinist point of view would serve better. ",
"The new engine has lots of residuals from the machining. Metal dust, and metal burrs. If you run an engine for a little while, and then change the oil, you will see all this little metal crap in the oil. It is definitely going to accelerate engine wear. So you change the oil, and run it for another hour. Then change it again, and you should be pretty good to go. ",
"I have significant doubts that the range of normal engine usage will cause excess damage from tight fits causing too much friction. But more to the point, the \"crap in the oil\" explanation is empirically verifiable. And disgusting. "
] |
[
"How do neurons do math, (like adding, subtracting)?"
] |
[
false
] |
From my understanding, neurons are just wires that carry a signal, and have no means of computation like the logic gates in computers. How do they do it?
|
[
"The signal they carry affects the transmission of signals by other neurons, oftentimes by directly activating or inhibiting other neurons. Usually the activity of any given neuron is modulated by many other neurons. While we should be careful about taking this analogy too far, these activating and inhibiting interactions can be compared to the logic gates in computers."
] |
[
"I already think you're taking the analogy too far. Brains and computers share very little in the mechanics of how they function. The human brain doesn't really do math, it memorizes algorithms and certain equations (e.g. times tables) and applies them in combination with counting. Mental math is typically reliant more on this memorization and basic counting than on any particular algorithms, and when we do long-form math on paper it's as much the paper doing the computation as it is our brains."
] |
[
"I agree with your analysis. The brain doing math (specifically arithmetic) probably uses the same mechanisms it uses when we hit a tennis ball with a racket or drink water from a glass without spilling it. It repeats a practiced and remembered sequence of steps including math tables and how to write each number. When doing math, however, the brain does seem to present its operation more to the conscious part of the brain than it does for physical operations, perhaps because there are no inherent time constraints."
] |
[
"How do I ensure my body goes to science?"
] |
[
false
] |
Hoping this won't be relevant any time soon, but what are the logistics for donating my body after I die? (I'm Already an organ donor.)
|
[
"When you get older and are settled in one place you can approach a university and arrange through them. Medical schools for example need bodies and are very grateful if you decide to donate your body."
] |
[
"There are private companies that accept cadavers for testing medical devices (orthopaedic implants, etc), but generally they pay for all your funeral costs as their form of compensation. That does not mean they're not out there, ones that actually pay cash, but I'm not aware of any."
] |
[
"Where do you live? Maybe contacting your local health care whatever and ask.\nIn Sweden (where I live) we have a national database which you can sign up for different uses of your body when you die."
] |
[
"Why does testing for Ebola require venipuncture rather than capillary blood?"
] |
[
false
] |
Hi folks, With the current focus on Ebola, I've struggled to understand why healthcare workers are consistently exposed to needlestick injuries when evaluating patients with the disease. Per the CDC, the . This is consistent with other guidance from the WHO and MSF. This obviously requires the use of butterfly needles/vacutainers to obtain a sample which is more dangerous (in my opinion) than using a to obtain capillary blood. Is there a reason why we need (a) this quantity of blood and (b) why couldn't we use capillary blood using for testing? The reason why I get confused is for the following reasons: Thanks for any thoughts you might have!
|
[
"There is a higher possibility of surface contaminants from a finger stick/capillary blood sample. Venipuncture allows you to get a more pure sample from within the body with less chance of contaminants. "
] |
[
"is impervious to needles",
"Unfortunately, the gloves used by healthcare workers are not impervious to needles. ",
"The body can be pumped with antiviral drugs which quickly kills of the small amount that has entered the body. (the same treatment can be used for HIV and has ~80% success rate within 48 hours, I believe).",
"There is no approved post-exposure prophylaxis, such as anti-virals, for exposure to Ebola. "
] |
[
"is impervious to needles",
"Unfortunately, the gloves used by healthcare workers are not impervious to needles. ",
"The body can be pumped with antiviral drugs which quickly kills of the small amount that has entered the body. (the same treatment can be used for HIV and has ~80% success rate within 48 hours, I believe).",
"There is no approved post-exposure prophylaxis, such as anti-virals, for exposure to Ebola. "
] |
[
"Does DNA regulate its own susceptibility to mutation?"
] |
[
false
] |
Whenever I read about all the error-checking mechanisms and programmed cell death, I always think about whether a 0% error rate is even desirable. It's not difficult to think of situations wherein a small possibility of mutation a good thing. Or is the mutation rate always too high for the genes' own good?
|
[
"You raise a good point, without mutations there would be no evolution and such organisms would have long since died out. There's some discussion of it at this article here: ",
"https://en.wikipedia.org/wiki/Mutation_rate",
"It's also becoming increasingly common for scientists to look for the heterogeneity of genetic diversity of various species. A new record was recently set for the least genetically diverse species ever found -- I think it's still unpublished so I shouldn't say which -- but it might not surprise you to know that it lives in a rather pleasant environment.",
"I once read a fiction book... I forget which book, but it was in the future and there were people who were colonizing Mars, and they became were worried that they were going to have less sun exposure than humans on earth, which was nice because it meant less cancer but worrying because it also meant their rate of evolution would be slowed in comparison. So they decided that their civilization would give themselves mild doses of radiation to \"keep up\" with the earthlings. Or something like that. An interesting idea."
] |
[
"just to clarify though, the Sun's radiation does not contribute to heritable germ line mutations"
] |
[
"This paper",
" used 3gy of x-ray radiation on some mice, bred them, and then sequenced their offspring to determine rates of germ line mutation. They found increases in copy number variants and in indels - the number of single nucleotide polymorphisms was similar but the distribution more skewed in irradiated mice compared to controls. ",
"So ionizing radiation can in general probably influence mutation rates. But most germline mutations still probably originate through replication errors rather than radiation-induced breaks. ",
"I'm looking for a number of how much the background levels of IR are on Earth so I could do some back of the envelope calculation to figure out what proportion of CNV or Indels radiation it might be responsible for assuming a linear relationship - but am having difficulty finding the right number. ",
"That being said, I'd imagine bacteria might be more influenced by levels of background radiation than multicellular organisms, since any mutation they receive from it will definitely be passed on. "
] |
[
"Why is HIV the Vector of Choice for Gene Therapy Treatment?"
] |
[
false
] |
[deleted]
|
[
"Lentiviruses like HIV are popular backbones for gene therapy vectors for a few reasons.",
"The first is that they integrate into the host genome, permanently modifying target cells and enabling long-term correction of genetic defects. Most viruses do no do this, and are thus only capable of transient transgene expression. ",
"The second is that unlike many related retroviruses, lentiviruses are capable of transducing terminally differentiated cells (cells no longer actively dividing). This is particularly important if your target cells are neuronal in nature.",
"The third is that HIV is well characterized. We've spent a lot of money learning about this virus due to its relevance to human disease, and can modify and manipulate it with relative certainty.",
"There are multiple caveats to each of these points, but you asked for a simple explanation, so I won't go into those."
] |
[
"HIV is a member of the genus of viruses called Lentiviruses. Modified ",
"lentiviruses",
" are very useful in the lab because they can infect non-dividing cells (most retroviruses can only infect dividing cells), and once they integrate into DNA, all daughter cells will also express the gene (or whatever) of interest. TL;DR, you can get the DNA you want into the cells that you want. ",
"A major downside of the use of lentivirus in gene therapy is that because it integrates into DNA in a fairly random fashion, with low frequency it can integrate into important tumor suppressors, potentially causing cancer. "
] |
[
"Hey could you post some resources going into detail about transdusing non-dividing cells? That seems really interesting and I'd love to know more in depth about it."
] |
[
"Is any atom truly stable in terms of radioactive decay?"
] |
[
false
] |
Given there are atoms with half lives of billion of years, it it possible that all atoms decay, just over such large periods of time that they cannot be observed?
|
[
"This is something that theorists grapple with. There are limits to what we can observe, experimentally speaking. Some isotopes are predicted to be unstable with extremely large half-lives, such as ",
"iron-54",
" (with a half-life of ~10",
" years). Yet it is almost impossible to measure such a minuscule decay amount.",
"We can look at an isotope, and consider what the effects of every known decay path would be. If it is energetically favorable (e.g. if energy would be released from the decay) then we would predict that decay to occur at some point. So if there is an isotope where it is ",
" favorable to decay by any path, then we predict it to be stable. ",
"Here is a list of ",
"all observationally-stable isotopes",
". Of these, 90 have no predicted modes of decay, so theory would say that they are stable across all time. The other 164 have never been observed to decay, but we predict them to decay on extremely long timescales. "
] |
[
"I guess it's just a matter of semantics, but I tend not to include proton decay considering that there is no experimental evidence (despite decades of looking) and it is only even predicted to occur by some theories."
] |
[
"Of these, 90 have no predicted modes of decay, so theory would say that they are stable across all time.",
"They have no modes of decay which we have observed, but there are many theories that allow for ",
"protons to decay",
" in violation of ",
"baryon number conservation.",
" These could provide an additional decay mode for these nuclei."
] |
[
"Can fingers regrow their unique prints after having a chunk cut off?"
] |
[
false
] |
How similar would it be? What if there were previous prints taken?
|
[
"To add to that, you won't get new fingerprints. You'll destroy the fingerprints that you have, which will have a negative impact on your ability to grip things"
] |
[
"The structural information that determines the shape of your fingerprints is present in the dermis, which is the layer of skin just beneath your epidermis, which is the outer layer. Ridges/folds called dermal papillae exist at the boundary of these two layers and from these arise the prints. If you damage the dermis, you will have a scar that will change your fingerprint. If you cut a whole chunk of the dermis off, you're definitely going to have a scar."
] |
[
"Huh... never before have I thought of my fingerprint as a grippy pad, lol."
] |
[
"Is a planet with an eliptical orbit slowly adjusting to a circular orbit?"
] |
[
false
] |
Is a planet's orbit determined by its trajectory when getting caught by a gravitational pull? Does it slowly balance itself out like when you drop a marble in a sink?
|
[
"In a two-body problem like gravity, in bound orbits (circles and ellipses), the semimajor axis ",
" and the semiminor axis ",
" of the orbit are given by",
"a = -GMm/(2E)",
"b = L",
"/sqrt(-2uE)",
"where G = gravitational constant, M = mass of one body, m = mass of the other body, E = energy, L = angular momentum, and u = 1/(1/m+1/M) = reduced mass.",
"What this all means is that there are really two parameters that determine the motion of the two bodies: the energy E and the angular momentum L. Both are conserved quantities. So the only way to change from an elliptical orbit to a circular orbit is to change one or both of these parameters.",
"Your question about whether the orbits would sort of slowly balance themselves out is pretty much the same story. Suppose magically that you just suddenly appeared at some height above the Earth with some speed, not necessarily tangent to the Earth's surface directly below you. Other than probably dying, what would happen to you? Let's assume that only the Earth's gravity acts on you. So no atmospheric drag, no Moon gravity, no Sun gravity, nothing else. So your energy E and angular momentum L remain conserved. You will then just be taken into orbit about the Earth. (The point at which you appear is a point on your orbit.) The formulas I gave above for the semiaxes determine the shape of your orbit. I don't want to give the impression that it takes time for you to get into orbit. The point where you magically appear is already on the orbit, so you just continue on some elliptical path around the Earth, returning to your starting point once per orbit.",
"This technique is used in space travel methods like the ",
"Hohmann transfer",
", which is a basic method of transferring from one orbit to another. The principle is very simple. At some point on your current orbit, give yourself a boost of speed using rockets or whatever. This increases both L and E, creating an imbalance between the gravitational and centrifugal forces. So you move onto an elliptical transfer orbit which reaches farther out than your original orbit. (You can then boost again a bit later to move yourself onto an even farther circular orbit.) When you boost yourself, you don't quite have the right values of L and E to maintain your original orbit, hence why you move outward."
] |
[
"Ah, thanks. I corrected the language. I also changed the part about the velocity being initially tangential to the surface directly below you. That actually puts an extra constraint on the orbit, namely that where you magically appear is either apogee or perigee. I would rather just consider magically appearing anywhere along an orbit."
] |
[
"Some of this does not make sense. If you've got less than escape velocity, you are automatically in an elliptical or circular orbit. You don't have to fall before the orbiting starts - the \"falling\" is just part of your orbit. It could be a ground-intersecting orbit, but it's still an ellipse. Your starting point remains part of the orbit and you will keep going back there every time around, provided you don't hit atmosphere/ground."
] |
[
"How does one determine how much water can be absorbed by different compositions of the ground?"
] |
[
false
] |
Such as how much water can soil vs sand absorb, and how do we determine this? Say you have a patch of desert and water steadily dripping at a constant rate. How much of the ground would the water penetrate, get soaked up essentially, and at what radius? Additionally, how long would it take to convert the sand to soil?
|
[
"Those are some pretty broad questions. In a simple experimental set up, (i.e. dripping water at a set rate on some homogeneous material) you could probably get a reasonable answer to your question with ",
"Darcy's law",
", but generally the answer will depend on the porosity (how much of the material is void space), permeability (how much of the void space is connected), the viscosity of the fluid, and the pressure gradient (which will change through time as more fluid is added to the top and as fluid moves through the medium).",
"In nature, the same things will control the flow rates, etc, but because of variability in the material (e.g. the medium is going to be really heterogeneous, there will be layers with very different porosity and permeabilities, etc) and the variability from vegetation (roots provide pathways for water, but different plants will take up different amounts of water, etc) and climate (different spatial and temporal differences in delivery of precipitation, rates of evaporation, etc) things get quite complicated quite quickly. While we generally know these things will dramatically influence soil moisture content and have approximations of the basics of how they will do so, the details of how these different factors influence soil moisture and how their presence or absence (e.g. lots of plants vs few plants, types of plants, etc) influences changes in soil moisture over seasonal and single storm events is very much an open question. There are certainly lots of papers on the subject, just search for 'controls on soil moisture' and you'll find plenty. This is a pretty active (and important) line of research as the soil moisture and how it responds ultimately influences how much precipitation infiltrates the ground (important for thinking about things like ground water recharge) and how much becomes runoff (important for being able to model floods, etc).",
"As for the last bit, soil production is another exceedingly complicated process that is a mixture of physical (mechanically breaking down rocks into smaller bits) and chemical (chemically breaking down rocks and minerals into smaller or different components) weathering, much of it likely biologically mediated (e.g. vegetation again plays an important role in mechanically weathering rock through roots, providing water pathways, hosting microbic communities that may be important in some chemical weathering processes) and dependent on climate (e.g. moisture availability, potential importance of cycles of freezing and thawing in weathering material, etc). So the answer to the question, 'how long would it take to convert sand to soil?' has no single answer (and usually the question might be better posed as 'what is the rate at which soil is produced from bedrock?') as it will depend on the environment and starting material."
] |
[
"I'm going to read this again tomorrow to make sure it all sinks into the noggin.",
"I've been wanting to do an experiment where I basically have water drip for a period of time over a patch of ground.I figured I could test with 100% sand and then test it with different compositions of earth and maybe compost. Or even extract earth that has a well defined biota and see what happens.",
"Maybe make it a meter by a meter and encase it in glass to monitor.",
"Any thoughts?"
] |
[
"Permeability of the composition in question and how much room there is. Also to some degree the water itself, which is not likely pure in this scenario, as differences it it's composition can effect is surface tension among other things and might change the result. I could get all technical but that's the gist of it."
] |
[
"Got a question about mirrors...."
] |
[
false
] |
So, if there was a mirror placed one light year away facing earth could we see back in time two years later if we looked at the mirror? Also, if we some how projected the earth to the mirror for a year and then replaced this projector for another mirror, could we preserve that memory for eternity?
|
[
"I don't understand the second question, but the first is a \"yes... but\" kind of answer. The 'but' is ultimately engineering concerns like telescopes that could have infinite resolution to be able to perceive the earth in the mirror's image. Remember that if the mirror is a light year away from the earth, the earth in the mirror will appear to be two light years away from any telescope trying to observe it."
] |
[
"As to your first question: In principle yes, but in practice no. Light falls in intensity by the square of the distance traversed. We'd see nothing but a dim smudge.",
"As to your second question: There's no such thing as a perfect mirror. Light that's reflected is scattered and absorbed in various proportions depending on the properties of the reflective surface. So no. Light can't bounce forever between mirrors."
] |
[
"Light falls in intensity by the square of the distance traversed. ",
"This assumes that the light is diffusing outward in many directions. I'm not sure what OP meant with \"if we some how projected the earth to the mirror\", but a laser projector would not follow the inverse square law because all the light is moving in the same direction. "
] |
[
"Why are sulfonamides not considered antibiotics, but rather antibacterial agents?"
] |
[
false
] | null |
[
"Most infectious disease doctors are actually moving away from the term antibiotic due to its generic naming. ",
"Anti (against) bio (life), could in theory mean anything from anti-viral, anti-bacterial, anti-parasite, anti-human, anti-dog. ",
"You’re starting to see a conversion of terminology away from antibiotics and being replaced with antimicrobials or antibacterials."
] |
[
"\"Antibiotic\" in its strict medical definition refers to naturally-occurring things, or derivatives thereof. Macrolides like erythromycin came from Saccharopolyspora, penicillins from Penicillium, cephalosporins from Acremonium, etc.",
"Sulfonamides are totally synthetic, so often they are classed differently."
] |
[
"So without getting too deep, my understanding would be that all bacteria are microbes, but not all microbes are bacteria. ",
"So in the discussion of terminology, anti-microbial is less precise than anti-bacterial."
] |
[
"Does rinsing or just running water over my hands without soap after using the bathroom do anything?"
] |
[
false
] |
Does it add any germs or rinse any off without the soap to encapsulate the germs?
|
[
"I dont think that rubbing your hands together will kill bacteria. They are too small to unfluence that way. \nAbout the hot and cold water. You would need to put your hand in boiling water for an extended amount of time (hours) before it even remotely kills enough bacteria to be considered clean. And switching between hot and cold probably isnt gonna cut it either.",
"As already said the water makes it easier for bacteria to get loose from your hands. So that woulf only spread more. ",
"Best case scenario: wash with water and soap and dry using a (papr) towel and not those blowers"
] |
[
"Hypotheically, would quickly changing the water from very hot to very cold in a short amount of time possibly kill bacteria? Shearing aside. "
] |
[
"Hot water might kill some germs (but I wouldn't depend on water that hot not scalding you) and rubbing your hands together would break some of the bacterial cell walls through mechanical shearing. I would still use soap though"
] |
[
"Homemade light bulb"
] |
[
false
] |
Hi there askscience! Im working on a homemade lamp project, and have decided that what id really like to do is create a home made lightbulb using a spirit bottle as the glass. I've had a look on google, and found guides to making bulbs, but they all seem to be small scale science projects, in which the filament fizzles out really quickly, as a result of not being properly sealed. So i have a few questions, 1: what sort of gas would be best, i assume helium is easiest, but by its nature would escape the bottle easily. 2: would a tight rubber seal be enough to prevent the gas from escaping, or should i use something like an epoxy resin, which would of course mean the seal was pretty permanent (it'd) be nice to be able to open and close the bottle to replace the filament. 3: will i be able to break open another bulb and use its filament etc, or should i make my own with tungsten wire? I want the filament to be as crazy looking as possible (like a vintage bulb), but this will obviously require allot of trial and error Advice for any of these questions would be greatly appreciated!
|
[
"I thought about making a vacuum, but i figure that air pressure will eventually make its way through watever seal i use. Id like to get it to work for 1000+ hours"
] |
[
"I know that carbon filament bulbs were used back in the days that lightbubs were invented, they work quite well under poorly drawn vacuums. ",
"If you put the bulb in a bag and connect that with a vacuum cleaner, it should pull out enough to actually work. (Ofc this depends on your vacuum cleaner and the seal on the bag.) Once the bag has been pulled to a partial vacuum, you close the bulb and try it out :P",
"This would be more traditional but helium probably is a better alternative. "
] |
[
"If you seal it off correctly then it should stay good. Air can't leak in that easily. You can make partial vacuums with normal plastic bottles and keep them that way by screwing the lid shut. (The only problem is that they collapse under the pressure, glass bottles should do fine though.)",
"Bottom line, I suggest you try a few things and see what works best. "
] |
[
"Why did primates evolve to not internally manufacture an essential vitamin, vitamin C, whereas other herbivorous, carnivorous and omnivorous species did not lose this trait?"
] |
[
false
] |
I understand that we ( homo sapiens sapiens, and other primates) rely on consuming animals and plants that create this vitamin themselves, however, why has natural selection singled us out and (for all intents and purposes) caused us to not produce it ourselves? Why haven't herbivores, which eat flora that is vitamin C rich lose this trait? Same thing goes for carnivores, which eat other fauna (which contain vitamin C themselves from either flora or other fauna)? Since it is an essential vitamin, and can cause a myriad of problems if there aren't sufficient quantities of it in our body, why have we evolved to not produce it when other animals haven't? NOTE: I am presuming that the ability to produce this vitamin was present earlier on in our evolutionary timeline (hence why the vast majority of living things have the ability). If this is incorrect (ignore, otherwise), then a similar question: Why are we one of the very few species to not develop this trait, yet? Thanks guys! :-)
|
[
"The ancestors of old world primates lived in an environment that was abundantly rich in vitamin C in the form of citrus fruits. In this environment, being able to produce vitamin C didn't matter and genetic drift lead to it being removed from our genome. It only causes problem for human because the have spread out of this environment.",
"Source: The Selfish Gene by Richard Dawkins."
] |
[
"We didn't lose the genes. We still have them, in fact the first 3 out of 4 work but the last ",
"isn't active",
"."
] |
[
"There is no purpose to the evolution. The lack of biosynthesis of Vitamin C was caused by a genetic mutation on GLO gene which causes an enzyme not to be produced for the biosynthesis. What this tells us is that the mutation happened in the common ancestor of all extant anthropoids. It was not selected against because their diet is full of Vitamin C therefore no need in synthesizing it. ",
"Guinea Pigs also do not produce Vitamin C but the mutation happened much more recently. ~61MYA in anthropoids and 14MYA in guinea pigs. ",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145266/"
] |
[
"Leishmania is a parasite that targets immune cells. Why is it less dangerous than HIV?"
] |
[
false
] |
Leishmania is a protozan parasite that attacks immune cells and causes leishmaniasis. Since it also damages the ability of the immune system to protect against infection, why is leishmania less dangerous than HIV? Does it have something to do with the speed at which leishmania can reproduce? Why is there an AIDS pandemic but not a leishmaniasis pandemic? Since leishmania can infect vertebrates and be spread by insects (and HIV can only infect humans and can't be spread by insects), what makes leishmania less infectious than HIV? What makes leishmaniasis an easier disease to treat than AIDS? Does the immune system have any defenses against leishmania? If left untreated, what are the chances that someone infected with leishmania will recover?
|
[
"Leishmaniasis (called L- from here on out) prevalence largely depends on the prevalence of the sand flies that spread it. While technically it can be spread sexually [1], people with visceral L- are not generally in a condition to be having sex. Therefore, it doesn't spread too well as an STD. Meanwhile, HIV is an insidious disease where the host can survive for years and be active for much of it before succumbing. Additionally, there are often visible signs of L- sores and lesions- while HIV patients show no outward signs of the disease. In short, L- patients are generally clearly sick to both host and partners, while HIV patients are not.",
"In terms of treatment, you can wipe it out L- with antiparasitics. Treatment is unpleasant, but it is curable. In contrast, HIV is a very sneaky disease. It is a retrovirus, meaning that it can jam its genetic material into your cells' DNA and hide in that form. Even if every virus in the human body is wiped out, the HIV DNA in the host cells can activate, and then the patient is infected all over again. That's why HIV treatments are the way they are, where a patient can be basically normal, but not cured.",
"[1]: ",
"https://pubmed.ncbi.nlm.nih.gov/32943348/"
] |
[
"HIV is a retrovirus, meaning it inserts its genetic code into the host cells. So not only do those cells make the virus, but all their descendants will, as well. This makes HIV almost impossible to eradicate from the host. ",
"We have drug treatments for leishmaniasis which are extremely effective, and once it’s out of your body, it’s gone for good. With HIV, we have treatments that can inhibit the virus’s spread inside the body, but the infect cells and their progeny are still infected, and will remain so for decades. If the treatment is stopped, the infection will resume in full force.",
"So basically, leishmaniasis is easily curable in most cases, but HIV is not."
] |
[
"Awesome reply, thank you!"
] |
[
"How does reflection on the water surface work on the atomic level?"
] |
[
false
] |
If a photon hits a mirror, the angle of incidence is the angle of emergence. This alone is remarkable because if you think of the photon absorption and emission of atoms one would think that the photon is absorbed and then emitted in a random direction. One would also think that not all frequencies are allowed. However, we know that mirrors can reflect with almost 100% efficiency. It is usually argued that due to the high symmetry of the crystal in the mirror the photon actually couples to highly symmetric excitation and this leads to the fact that light is reflected according to Snell. If the symmetry of the surface is crucial then I wonder how the water/air surface can act as a mirror? In the limit of total reflection all the light is reflected and the angle is exactly the expected one. My conclusion is that this means that water at the water/air interface is highly structured like a crystal. Ideas?
|
[
"I'm not sure of the physics of reflection but scattering can occur when the electric component of light causes temporary polarization of the electrons orbiting an atom. ",
"The added energy promotes the electrons up to a virtual energy level which quickly returns to a lower, real energy level. The wavelength of the reemitted photon is typically the same as the exciting photon resulting in no net change in energy for the electrons but if the final energy level is higher or lower than the initial you can observe a difference in scattered wavelength from the incident light.",
"Again, I don't know how reflection works though I would imagine it works something like scattering but where some aspects of the photon's momentum are preserved allowing for the equal and opposite angles between incident and reflected light.",
"Raman Scattering",
"Reflection",
"edit: is to are"
] |
[
"Thanks for your reply.",
"I can understand the Huygens-Fresnel model which is also mentioned in the wiki link you gave. There, the emergent wave is built up from many small excitations at the surface. This however only work when the surface is highly isotropic, also on the atomic level.",
"Therefore my question: Can we conclude from this that liquid water is highly symmetric and structured at the surface? \nNaively one would expect rather diffusive reflection from a liquid, not?"
] |
[
"So you assume that water particles alone (without salt) do have this isotropy at the surface. My question is whether this is true. ",
"I think it is (based on the reflection argument) but have found no reference. ",
"Let me reformulate the question: How does water look like at the surface?"
] |
[
"Evolution Debate"
] |
[
false
] | null |
[
"Nothing in Biology Makes Sense Except in the Light of Evolution - Theodosius Dobzhansky"
] |
[
"Laboratory Observed Speciation",
"A starting point for objections to evolution",
"Nylon-eating bacteria",
" The latter being interesting in that it has apparently evolved enzymes only useful for digesting nylon products, which are not only different from its relatives, but also which would have also obviously been useless before humans invented nylon in the 30's.",
"Discussion on the misuse of the scientific terms fact and theory in the evolution debate"
] |
[
"Evidence of common descent",
"\n",
"20+ evidences for evolution",
"\n",
"A website with a load of links supporting evolution"
] |
[
"How do astronomers tell the difference between a cooler, red star blue shifting towards us, and a hotter blue star red shifted away?"
] |
[
false
] |
Is it based on the general shift of the local group the individual stars are a part of? Or do spectral lines become shifted as well?
|
[
"The doppler-shift is measured using spectral lines. Certain spectral lines show up in certain positions that are well known. Doppler-shifting shifts the position of the spectral lines. So by comparing the distance between the measured position of the spectral line and the position where it would be without the doppler shift we can find out the velocity of the star. Specifically we would know radial velocity, or how fast the star is moving towards/away from us. ",
"The temperature can be estimated in essentially two ways. Either you measure the ratio of blue and red light emitted by a star or you measure the whole spectrum and then numerically fit a computer generated spectrum to find the best possible fit."
] |
[
"First of all, a hot O star and yellow G star like the sun, and a cool M star have dramatically different spectra from one another. ",
"For example, the D lines of neutral sodium are very prominent in the spectra of cool M stars, but weaken quickly through the hotter K and G classes. The Hydrogen-alpha and beta absorbtion lines are weakly present in the solar (G2) spectrum but are much more prominent in hotter F and A stars. There would be little chance of mistaking a star's temperature given a good spectrogram. ",
"The radial velocity of stars relative to the observer is determined by precise measurement of the frequency shift of their spectral lines from their known rest frame laboratory values."
] |
[
"The spectral lines are shifted by relative motion and the expansion of the universe only. Their position does not depend on the temperature. You can shift that back to get the original spectrum, and then see how much infrared/red/blue/ultraviolet/... the star emits overall. That gives you the temperature."
] |
[
"Why Do Most People Root for the Underdog?"
] |
[
false
] |
Hundreds of movies and books, as well as personal observation, lead me to believe that most individuals root for the underdog when they don't have a vested interest in the outcome. Why? Has it been studied? If so, has there ever been a correlation between the tendency or lack thereof and normal vs. abnormal psychology?
|
[
"Researchers generally assert that we love to root for the underdog out of a general sense of fairness and justice for the disadvantaged, and that we perceive underdogs to be putting in more effort than the top-dogs, so we feel like they deserve to succeed.\nA recent study looking at who people tended to support in Olympics matches and in the Palestinian conflict found that people do indeed increase support for one side over the other when it is perceived as the underdog. In a follow-up looking at the associated mechanisms, they found that the underdogs were supported primarily because participants attributed increased effort to the underdogs.\nPeer-reviewed source: ",
"http://psp.sagepub.com/content/33/12/1603.abstract"
] |
[
"Thank you. For some reason this reminds me of the \"protestant ethic\": perception of spiritual salvation for those that deserve it by living a life of hard work and humility. "
] |
[
"It's worth noting that this is a cultural phenomenon as well. I suspect this has something to do with the number of underdog-based movies that the average Western-cultured person sees as a child.",
"There are some cultures -- notably in Korea and China -- where people tend to \"root\" for those that are actually the best, and not the underdogs. They are perceived as the best ",
" of their effort and hard work and are expected to win/be rewarded. When the #1 team plays the #50 team, many Koreans expect and still root for the #1 team to win because there is a high value placed on perfection and success."
] |
[
"Did an X20+ solar flare actually just happen?"
] |
[
false
] | null |
[
"No it appears there was an error on that table. It now correctly states: ",
"\n",
"\n"
] |
[
"I'm not super familiar with this stuff, but I'm not seeing anything of that magnitude on ",
"NOAA's SWPC",
"."
] |
[
"I'm not sure where you're seeing that, perhaps you're misreading the graph. The most powerful flare recently has been X3.2-class."
] |
[
"If humans(and other animals) have bilateral symmetry, how are certain organs (like the heart and liver) not symmetrical?"
] |
[
false
] |
I had this thought today. Obviously many things are symmetrical, such as two lobes of the brain, two kidneys, two lungs, but not everything. Why are the single organs not in the exact center of the body or not symmetrical side to side? I'd love any explanation, or some one two explain how I might be misunderstanding organ symmetry. edit: "are" not "our"
|
[
"The gist of the problem for asymmetrical organ development is left-right axis formation. We know a lot about antero-posterior and dorso-ventral axis formation, but left-right is less well understood. It is possible to deduce left and right if you already know which way is up and which way is forward. What we do know is this: In many model organisms (and humans), direction of extracellular fluid flow in the embryo influences asymmetry (some other org's use electrochemical gradients to accomplish basically the same result). The expression of left-ness appears to be related to Ca",
" concentrations which trigger cascades of other chemical messages (specifically we know of at least two chemical signals: ",
" and ",
" that indicate left-ness). ",
"Once the cells have a signal indicating left from right then it's all a matter of bending and stretching into their final shapes. The beginnings of left-right axis formation can be detected and influenced as early as the 8-cell stage in some embryos.",
"Here's a figure showing heart development. Each of the colors on the top series represents a specific cell lineage: ",
"http://i.imgur.com/nIH5gRO.jpg",
"source: Wolpert's Princ. of Dev."
] |
[
"am I correct to take the reading of that diagram to imply that the heart system starts development symmetrically, but through twisting and moving, finally forms asymmetrically?",
"yes.",
"I realize now that my explanation isn't that clear. The short answer is: ",
" which are chemicals being produced in regions of an embryo and diffusing throughout which alter gene expression. ",
"Morphogens establish axes through their concentration gradients. Why I focused on the L/R axis is because adding the 3rd dimension is ultimately what accounts for the asymmetry. "
] |
[
"very interesting diagram. I'll admit, I don't fully understand everything you're stating. Regardless, am I correct to take the reading of that diagram to imply that the heart system starts development symmetrically, but through twisting and moving, finally forms asymmetrically?"
] |
[
"At the most fundamental level, what stops me from falling through the floor?"
] |
[
false
] |
To my knowledge, it's only the electromagnetic force. But I don't understand that. If you could generate a strong electromagnetic field through some method - wouldn't it be impossible to walk through it? Would it feel like wall? How does this work? Edit:
|
[
"Actually, your second explanation is most likely right.",
"http://en.wikipedia.org/wiki/Pauli_exclusion_principle#Stability_of_matter",
"\"As described by FJ Dyson (J.Math.Phys. 8, 1538-1545 (1967) ), Ehrenfest made this suggestion in his address on the occasion of the award of the Lorentz Medal to Pauli.\""
] |
[
"I think the most common explanation is electromagnetic. My electrons repel the electrons in the wall/floor and thus we can't pass through them.",
"But I had a professor in undergrad that swore it was the Pauli exclusion principle at work. My electrons can't occupy the same space at the wall/floor's electrons. ",
": As other redditors point out, my professor is likely wrong. I just offered it because it was the only non-E&M explanation I'd ever heard. To respond to OP directly: Have you heard of ",
"solar sails",
"? Essentially as light bounces off of the sail, it exchanges momentum pushing the sail forward. Well, in a manner of speaking as your electrons get really close to the floor's electrons there's a lot of virtual photons being exchanged between them that pushes you away from the floor atoms and the floor atoms away from you. ",
" further down the thread some redditors justify the professor's response. Now I don't feel quite so bad about posting both. "
] |
[
"This question comes up a lot",
", and most people come up with the intuitive idea that the answer is the electromagnetic force, since the inverse square nature of the force means the force goes to infinity as the separation distance goes to zero. Except you'll also notice that no one even tries to offer an actual mathematical model to actually demonstrate this. And the reason for this is because it is not actually such an easy answer after all, and the appropriate resolution is that the electromagnetic force is not the correct answer. ",
"The correct answer is in fact, as unanin has pointed out, the Pauli exclusion principle, despite some of the responses in this thread. The electromagnetic force answer persists because it is simple and intuitive. It is also wrong, or at the very least, incomplete. The fact of the matter is, that if electrons were bosons, and not fermions, matter wouldn't act the way it does. ",
"Lieb, Rev. Mod. Phys., 48, p. 553 (1976)",
" explains the situation, but it is not an easy read.",
"Edit: ",
"Here's another interesting write-up on the issue."
] |
[
"Is there any advantage in our DNA being coiled into a double helix?"
] |
[
false
] |
Could also just be a side effect of the intrinsic DNA structure, but I suspect there might be some advantage to it? (rigidity? chemical protection?) Thankyou
|
[
"I think 'all the above' would work as an answer here. ",
"DNA bases (deoxyribonucleotides) are synthesized (by ",
"Ribonucleotide reductase",
") from ribonucleotides, those used as bases in RNA. Which is one of the reasons the dominant theory is that ",
"RNA evolved first",
". ",
"Unlike DNA, RNA is single-stranded. But it can still form a double helix, if part of the strand has a set of complimentary bases, it can loop back and form a helix with itself, which it does in ",
"tRNA",
" for example. I would say (or speculate) that this is mainly for structural and chemical stability there. But note that RNA that carry genetic information (mRNA) don't usually (or at least not necessarily) form helices as far as I know. ",
"Why bother with DNA in the first place? RNA can already carry genes (and e.g. ",
"some viruses",
" only have RNA), so it might seem redundant. It also costs energy to produce DNA bases from RNA ones. The apparent answer to this would be that DNA is more stable (both chemically and against mutations), which is something that's gets increasingly important as the amount of genetic material increases. From that perspective, it also makes sense why we'd still retain RNA for ",
"transcribing",
" genes, since they're just short fragments of genetic material - there's no need for the extra stability, so it's not worth the cost.",
"So, given that DNA is double-stranded (I'll get to that), it's sort-of a consequence of it's structure that it would be able to form helices like RNA does when it has a complementary strand. (However, there's a bit of difference in that RNA only forms 'A-type' helices, while DNA is usually 'B-type'. There are at least 3 types of DNA helices - ",
"A",
", ",
"B",
" and ",
"Z",
", so in order to not get bogged down in detail, I'll just leave it at 'forming a helix' here)",
"Now, the complementary strand, which is a key to helix-forming here, is a big difference to RNA. It does provide stability both against mutations and chemical reactions by having the bases inwards, facing each other, shielding them a bit from the environment. But there's more than just that, the redundancy allows for '",
"proofreading",
"' of the DNA, helping correct errors during replication.",
"So there are benefits to having a complementary strand, and having a helix likely helps with the aforementioned shielding of the bases. But in a way it's also side-effect of the structure. I don't think you could possibly 'flatten' it into a ladder-like structure without putting an implausible amount of strain on the chemical bonds. "
] |
[
"Excellent summary. I would only add that the regular double helix structure also provides simultaneous data density and data access. Long strands of RNA can be a horrible mess, with parts annealing to themselves and twisting into complicated 3D shapes, while DNA, with the ",
"2' hydroxyl",
" missing, will fold into more regular B-type form. "
] |
[
"A couple reasons: Size, chemical protection, and readability by proteins.",
"DNA is actually coiled multiple times",
". this supercoiling allows for space conservation inside cells. A fully uncoiled human genome in a cell would be a meter or two in length. This isn't directly associated with the double-helix nature, but helps nonetheless.",
"the double helix nature of DNA helps protect DNA from being damaged, while still being able to be unzipped by proteins who ",
" to access the DNA for some reason. Each (single) strand is built by covalent bonds, but the two strands in a helix use hydrogen bonds to keep eachother attached. H-bonds are weak alone, but a billion H-bonds acting at once are strong enough to keep a DNA strand intact. The twisting nature of the double helix also puts the hydrogen bonds on the \"inside\" of the helix, increasing its protection.",
"The spacing in the coils",
" are only a few angstroms in width, so there aren't many things that could get in there and mess around."
] |
[
"What is the best form of iron to take as a supplement for someone with iron deficiency anemia?"
] |
[
false
] |
[deleted]
|
[
"Heme iron (the iron in blood) is readily absorbed, so- red meat. Iron salts (such as the iron sulfate mentioned above) are poorly absorbed; the iron in breakfast cereals is frequently found as iron filings (!); it's a classic lab demonstration to put a beaker of water on a stir plate with a magnetic stir bar and add some \"Total\" breakfast cereal or whatever, and let it stir until the magnetic bar has fuzz on it from the iron filings.",
"Amino acid chelates",
" of iron are probably the best encapsulated or tableted form. I'd have to check the ingredients, but I ",
" this is ",
"one brand",
" that qualifies.",
"Note that wheat and ",
"other plant matter",
" inhibits the uptake of iron. Take it easy on the pasta (advice to the contrary notwithstanding)."
] |
[
"Yeah; SP is a very pricey line, with some sketchy distributors.",
"I would suggest you find a good source of organic beef liver, and try that. I can't stand the stuff, but smothered in mayo, it's tolerable."
] |
[
"Yeah; SP is a very pricey line, with some sketchy distributors.",
"I would suggest you find a good source of organic beef liver, and try that. I can't stand the stuff, but smothered in mayo, it's tolerable."
] |
[
"Since the rotation of the earth is slowing down, when will the day be twice as long as now?"
] |
[
false
] |
[deleted]
|
[
"Unfortunately, it's not a strictly linear figure that can be easily calculated out. There are, for instance, forces which accelerate the rotation of the earth, or slow it differently, than just the tidal interactions with the moon. For instance, the Indian Tsunami may have accelerated the rotation of the earth by as much as 3 microseconds, due to changes in the earth's moment of inertia. Similarly, the redistribution of significant mass caused by ice ages/end of ice ages also affects the earth's moment of inertia. ",
"If we were to ignore those significant factors, and just look at the last 100 years in average, we seem to have picked up 1.7 milliseconds. ",
"So it'd take around 50,823,529 more centuries to pick up an extra day, or 5 billion years, by which point the earth is potentially being destroyed by the sun, events calamitous enough that they will severely mess with our rate of rotation, assuming anything is left to rotate."
] |
[
"According to Wikipedia",
", one day is now longer by 1.7 miliseconds than it was about a hundred years ago. That is 0.0017 secs in 100 years. One day is 86 400 seconds.",
"86 400/0.0017 = ~50 823 529.411",
"50 823 529.411 * 100 = 5 082 352 941.1",
"That makes 5 billion years."
] |
[
"The sun doesn't have enough mass to die by supernova, but will go through a nova and shed its outer layers, leaving a white dwarf. This is after it expands near to the Earth's orbit, but not quite. It will absorb mercury and venus, however."
] |
[
"How do you grow \"seedless\" watermelons?"
] |
[
false
] | null |
[
"You use a chemical called colchicine, which prevents cells from dividing by only letting their nucleus divide, not the citoplasm. It's called karyokenisis without cytokenisis. This leads to a tetraploid, an organism with four sets of chromosomes.",
"Plants are quite a bit more flexible than animals. They can survive with two, three, four, or even eight sets of chromosomes and still be able to grow.",
"This tetraploid plant is then crossed with a diploid, which produces triploid. The total of two chromosomes from one parent plus one chromosome from the other makes 3 chromosomes for the offspring. ",
"However, because these plants don't have even pairs of chromosomes they cannot undergo successful meiosis because it requires chromosomes to be split into two even sets to create viable gamets. So they're infertile.",
"But plants have a different way of doing things to animals. Male gamets have 2 different nuclei, which do different things, even triggering the creation of fruit within a flower without the need for viable eggs. Even when two gamets fuse, many different kinds of nuclei are formed, all of which do different things such as create the endosperm, others are thought to tell the pant to know which way is up, etc. Since watermelon triploids produce flowers, they can be polinised by other plants, farmers allow them to be polinated by diploids. This triggers watermelons to grow, but since there are no viable eggs within the flower, seeds can't form.",
"This is also how many other seedless fruits are made. It's also important to note that polyploidy makes fruits bigger because cells have to accommodate more stuff. Strawberries are octoploids, and if i remember correctly apples are tetraploids. Furthermore, polyploidies in plants can also come about naturally or by selective pressures and even-numbered polyploidies often produce viable gamets."
] |
[
"This short article explains it pretty well.",
"Basically, you breed triploid plants so they are not so good at making seeds."
] |
[
"You use cultivars that have seeds that mature late in development. Using this method you get water melons that have seeds, just not big, hard black ones. Because you don't want big hard black ones in your mouth. "
] |
[
"What material and what speed would an asteroid-comet need to pierce a planet and exit the other side? xpost from /askreddit"
] |
[
false
] |
My gut says this isn't possible based on compression and densities deep within planets combined with the pulverization of the object crashing into the planet. But here's hoping... Let's keep our planet choices to ones in our solar system, Pluto and major moons also count. No made up minerals like adamantium or borg ablative armor. Real physics please. I'm merely interested, and certainly not working on any doomsday devices this week. Totally hypothetical scenario based on a CGI image It comes from this blog of other
|
[
"Consider the forces an asteroid would encounter when it smashes into solid rock. There will be inertial forces, i.e. forces required to physically accelerate rock, and mechanical forces (stiffness, pressure etc.) to deform the rock. The mechanical strength of both the Earth and the asteroid will be roughly constant, but the inertial forces get bigger for higher impact velocities.",
"For very fast impacts, the inertial forces are much bigger than mechanical forces and the rock will behave like something that has no mechanical strength, a fluid. Remember, this applies to both the Earth's crust and to the asteroid.",
"This means that the asteroid will splash rather than pierce."
] |
[
"You're confusing physics with minecraft again."
] |
[
"You're confusing physics with minecraft again."
] |
[
"What happens to competing virus variants in a given area?"
] |
[
false
] |
So I'm not sure exactly how to word the question, so sorry in advance. We keep hearing about new variants if the Covid virus (the UK, South Africa and Brazilian variants). They are all reportedly more transmissible and are becoming the dominant variant in the areas they were discivered. What happens if there is an equal prevalence of each variant in a given area? Do they mutate further to try and gain dominance? What governs that? Finally is there any benefits or negatives to the human population in those areas (having a virus compete for dominance)?
|
[
"Hey! Mutations are not something the virus can activly switch on to battle other viruses. Mutations are the result of errors during the virus replication. As far as i know they don't have the same proof reading mechanisms we have. So think of it like copying a long text by hand. You'll make errors. Youre cell machinery however would most likely find the error and correct it but a virus would not. The mutation can then make no difference or a positive/negative difference for the virus. So which virus variant will become dominat will be determined by its capability to infect new hosts (transmission) and its resiliance against our immune system. My guess is that the variants right now that are more easily spread will win short time and \"gain dominance\". As to the benefits for our immune system \"know your enemy\" (e.g. like by vaccinating) is an advantage. If a new variant comes along this could mean it's not recognized right away even if you have battled another variant before (you see this with influenze every year). Also for the negatives... i think i read something on the spanish flu that killed so many people that it has affected HLA heterogenity of the surviving population. This can have an effect on other diseases yet to come as they also rely on HLAs to bind and present peptides from the next pathogen. As for a benefit... better transmission doesnt mean that the virus causes more severe symptoms. If a variant is spread better but is less likely to cause severe symptoms and also primes the immune system for other variants then it could be protective for the worse variants.",
"[not an expert, so correct if anything in this post is bs :)]"
] |
[
"The brilliant evolutionary biologist Richard Dawkins put it like this: nothing really wants to mutate. Mutations are just something that happens and that you are forced to work with. Some viruses are better at mutating (i.e., worse at correcting errors) than others. Some are bad at this by design. In our bodies, mutations are rather unhelpful and can lead to cancer if they happen in critical genes that control the cell cycle and cell fate. We have evolved good error repairing mechanisms but many errors still slip through."
] |
[
"Hey, thank you for the detailed reply!"
] |
[
"What chemical is this? (PIC)"
] |
[
false
] |
While cleaning out the high school chemical storage, I found glass tubes. Before I pay someone to dispose of them, I wanted to know what they are. I would guess that it is either Bromine gas or Nitrogen Dioxide gas. And I don't know what the clear tube is. It's possible it's empty. I remember a demo that showed a decomposition of NO2 when heated. I could try to heat the tube up and see if it turns colorless, but would that be enough to know for sure that it's NO2? tl;dr What's in glass tubes?
|
[
"Why not do some spectroscopy to find out? "
] |
[
"It's pretty difficult to tell, but I'd lean strongly towards bromine, if only because that's a more common classroom example at that level. If the other one has gas in it, I'm guessing it'd be some noble gas. Perhaps Neon or Krypton since they're a bit more 'exotic'.",
"I wouldn't heat it though, too big a risk of the glass cracking or exploding. If you're really curious you could try and borrow a spectrometer somewhere. ",
"Too bad there's no iodine gas; it happens to have a fluorescent line which matches a lot of green laser pointers."
] |
[
"I was also afraid of the glass cracking, I would have done it in the fume hood though. I did not think that bromine was a more common classroom example, but then again, there is some old stuff in there so who knows. I found a glass jar(like a jam jar) with a chunk of sodium in it. Extremely oxidized.",
"I'll probably leave this to the disposal company, thanks."
] |
[
"What does a monogamous bird do when his partner die ?"
] |
[
false
] | null |
[
"It should first be noted that many birds exhibit \"serial monogamy\" in which the mating pair is faithful for one season, but may choose different partners the following season.",
"There are indeed long-lived birds that are described as mating for life, but in the two examples I can find explicit answers for, the mute swan and the bald eagle, a bird that loses its mate will eventually look for another.",
"http://digitalcommons.fiu.edu/cgi/viewcontent.cgi?article=3905&context=etd",
"\n",
"http://www.audubon.org/news/till-death-do-them-part-8-birds-mate-life"
] |
[
"I've seen similar rumors. There are certainly documented cases of female albatrosses, well old enough to be mating, joining a gathering during breeding season but then leaving without having ever mated. It is speculated that these females have lost their mate.",
"However, I could not find any solid scientific evidence that a widow(er) never looks for a new mate.",
"This is also, unfortunately, an area in which genetics doesn't help, since \"forced copulation\" is a thing that exists in birds. ",
"https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1474-919X.2006.00597.x",
"Overall, it's just very hard to make absolute statements about social behavior in an animal that can live to almost 70."
] |
[
"I've seen similar rumors. There are certainly documented cases of female albatrosses, well old enough to be mating, joining a gathering during breeding season but then leaving without having ever mated. It is speculated that these females have lost their mate.",
"However, I could not find any solid scientific evidence that a widow(er) never looks for a new mate.",
"This is also, unfortunately, an area in which genetics doesn't help, since \"forced copulation\" is a thing that exists in birds. ",
"https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1474-919X.2006.00597.x",
"Overall, it's just very hard to make absolute statements about social behavior in an animal that can live to almost 70."
] |
[
"How do archaeologists/anthropologists determine the sex of human remains (not limited just to skeletons)?"
] |
[
false
] |
Also, presuming there are different methods, how relatively reliable are different methods? Also, if there is a mismatch between the presumed sex of bodily remains and the presumed gender signaled by any burial goods found with the remains, how is this usually interpreted?
|
[
"That's a hard one to answer succinctly. There are lots of different physical characteristics that are unique to males and females, but they are variable dependent on race, environmental factors, age etc. (As an example it is near impossible to differentiate sex in child skeletons, and some races have more delicate, or robust skeletal structures than others so what may look like a European descent female could, instead, be an Asian descent male.)\nWith skeletal remains the pelvis and skull, and dentition (teeth) are the two best items for determining sex; in many races males have a notch that protrudes slightly at the back of the skull (an external occipital protuberance, to get technical ",
" that females often don't have . Also there is the thickness of certain parts of the skull, such as the suborbital ridges (above the eye), the mandibles (jaw areas), mastoid process (the bones behind the ear), occipital condyles (the bones at the back of your skull, near the vertebra) etc, which are usually more pronounced for males.\nWith the pelvis you're looking for things like the shape and size of various parts. The basic things you look at are the pelvic inlets and the sub-public angles. In females the inlets are wider than males, and the sub-public angles are larger, to make room for child-birth. There can also be marks on the insides of the bones, like pitting, that can indicate childbirth.",
"This is about the limit of my expertise; hopefully someone a little closer to their studies will be able to elaborate further. My knowledge is from my Biological Anthropology classes I took several years ago as part of my Anthropology degree at Otago University (NZ), and to be honest, it's a bit hazy since it wasn't my focus. The book we used as our main textbook was The Human Bone Manual by Tim White and Pieter Folkens, and I highly recommend it."
] |
[
"I wrote a blog post on this recently: ",
"https://namuhyou.wordpress.com/2016/06/18/sexism-when-sexing-your-skull-cultural-bias-when-sexing-the-skull/",
"The best way to interpret sex is by the pelvis. If this is not available then you have to use what is available. Some researchers argue to use post cranial rather than the skull, but there are also ways to sex the skull. Sexing is usually performed on a 5 point scale where something is deemed very female to very male. There can be slight dimorphism in teeth too. The larger the sample size means a better outcome of sexing individuals. Ancestry must also come into sexing and age. Ancestry can be tricky as some populations are more robust than others, whereas as hormones play a part in bone formation, so too does lifestyle. You cannot sex non-pubescent skeletons. ",
"Sex has in the past got confused because of burial goods. See the Red lady of Paviland for an example. ",
"Wasn't quite sure what you meant by \"not just limited to skeletons\" as if you have a warm body, then they have genitals...Hope that helped"
] |
[
"I would argue that all humans do have an external occipital protuberance as it is an attachment site, rather it is the robusticity that is in question. Walker (1994) instead uses the term nuchal crest to look at sex, which is a probably a better term to encompass occipital rugosity. ",
"The skull is arguable for sexing, and dentition (consider these separate), there has to be a sample size from a population, as with the skull...but teeth hmmm... ",
"I just wanted to point out that the mandible is only the lower jaw, and parts of this is considered e.g. mental eminence for sexing. ",
"The majority of papers advise against using occipital condyles as a sex determinate. "
] |
[
"Are rogue planets more spherical than planets that are orbiting a star?"
] |
[
false
] |
I was watching kurzgesagt's video about potential life on rogue planets (which is a great video: ), and it mentions the formation of these types of planets. However, it doesn't mention this essentially mundane question of mine. Could rogue planets be more spherical than planets that are in an orbit because they have a potentially less uniform rotation? I could understand that there's no way we could really accurately measure this and it's pretty useless information, but I was just curious if anyone had an idea. Thanks!
|
[
"The spericalness is mainly driven by the total mass of the object. The higher the mass the more spherical as surface gravity is highest. For this reason we see the largest mountain in the solar system on Mars and smaller bodies like moons or dwarf planets are even less spherical."
] |
[
"That makes a ton of sense. I didn’t think about that, thanks! Would having a higher mass of orbiting moons effect the sphericalness as well? Or if the planet has a hot core? "
] |
[
"A moon generates tidal forces and can massage a planet a bit ..in the end helping with smoothing it out. \nUnless they are fully tidal locked, meaning both bodies face each other with the same side. Then you will get two elongated bodies. Our moon for example is tidal locked to Earth this is why we see only one side all the time. And the moon is a bit elliptical.\nA hot core likely helps with flattening out as well, as rock material can easier subduct and move.\nUnless it happens to produces tons of vulcanism, which generates mountains on the surface, which are again flattened out over time."
] |
[
"Movies The Matrix and Cloud Atlas take place in a reality where the dead humans are liquidised to feed the living. How sustainable is this system?"
] |
[
false
] | null |
[
"Hi theshantanu thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
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", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScienceDiscussion",
"Please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"Okay thanks, I'll post it there."
] |
[
"Physically am I made up of the same atoms I was 7 years ago or am I essentially all new atoms, following the same chemistry structure of my DNA?"
] |
[
false
] |
Essentially What I am asking is, is the building blocks of who I am(atoms) in constant flux? How long on an average would a single atom be in my body before being lost to my environment. Physically am I made up of the same atoms I was 7 years ago or am I essentially all new atoms, following the same chemistry structure of my cells?
|
[
"However if you were to tag a certain bio molecule with a stable, but distinct isotope of one of the atoms in that molecule, the spirit of the question is if that molecules would move around or not.",
"The answer basically becomes \"depends.\" Some things are recycled continuously, others stored for long periods of time and still others enter and exit the body at quick intervals."
] |
[
"Wikipedia is a terrible source and the science on neurogenesis has been rapidly growing since the articles cited in that wiki were written. It is becoming a generally accepted idea in neuroscience that the brain is constantly replacing neurons through neurogenesis and there a many very well designed studies that either strongly suggest this or directly indicate it. "
] |
[
"Wikipedia is a terrible source and the science on neurogenesis has been rapidly growing since the articles cited in that wiki were written. It is becoming a generally accepted idea in neuroscience that the brain is constantly replacing neurons through neurogenesis and there a many very well designed studies that either strongly suggest this or directly indicate it. "
] |
[
"What happens when teleported particles/states collide?"
] |
[
false
] | null |
[
"No, because quantum teleportation is not taking a bit of matter and somehow getting it to a remote place.",
"In quantum teleportation, the process is that Bob manages to turn a particle in his possession into the state that one of Alice's particles previously was in. Bob cannot simultaneously turn his particles into two different states, so the issue you raise is moot."
] |
[
"I think you are misunderstanding the way that this 'teleportation' occurs. You can't 'send' quantum states to the other particle as that would violate the speed of light. Instead the way to look at it is that two people are observing the same event remotely. Collapsing one part of the entangled system collapses the whole thing."
] |
[
"you cant teleport 2 states to the same particle at the same time by definition of teleportation , since measurement is involved. the details are complicated thought, usually grad level physics "
] |
[
"Can the NeverWet superhydrophobic spray be applied to wood to seal in moisture and make it fire proof as a result of the Leidenfrost effect?"
] |
[
false
] | null |
[
"Nope, superhydrophobic doesn't mean air-tight, which means that water vapor can escape and will have its limits as an insulating layer. However, NeverWet is silicon-based and might confer some fire-resistance (though not much with something so thin)."
] |
[
"The Leidenfrost effect is when you dip your fingers in molten lead just for a second, and the heat from the lead instantly vaporizes the moisture in your finger thus creating insulation from the heat protecting your finger. ",
"Have it a little wrong here - you dip your finger in water ",
" The moisture is not coming out of your finger to provide the effect, the moisture is ",
" your finger. If the moisture is coming out of your finger to cause the Leidenfrost effect (which would require quick vaporization of water across a barrier that exists, at least in part, to prevent loss of liquid), you have already been burned. Quite severely, in all probability.",
"You were perhaps thinking of liquid nitrogen, for which the nitrogen provides the vaporization effect, protecting your hand.",
"This",
" gives specifics:",
"Before dipping one’s fingers in molten lead, the hand is dipped in a bowl of water.",
"The ",
"wikipedia article",
" actually italicizes ",
" in emphasis when talking about that demonstration.",
"It has also been used in some potentially dangerous demonstrations, such as dipping a ",
" finger in molten lead.",
"The Leidenfrost effect requires quick vaporization of a liquid (or a solid capable of sublimation - like dry ice) against a mass (liquid or solid) that is at a temperature much higher than the boiling point of that liquid. The resultant gas insulates the rest of the liquid - or acts as a barrier insulating your hand - due to how much lower the thermal conductivity of the gas is compared to the liquid.",
"So, assuming you have a situation where you keep a constant barrier of lower thermal conductivity gas or a substance between the hot surface and the thing you want to protect, you will indeed protect it. That has nothing to do with leidenfrost though, it is simply an application of the concept of insulation. You could get better insulation if you managed to create a vacuum in between your object and the hot surface, like a ",
"Thermos",
".",
"In regards to wood, then: no, although the NeverWet might be somewhat fire resistant itself.",
"In regards to your finger: Please don't burn them off, wet them first.",
" The Leidenfrost effect works via creating insulating vapor, and if you prevent the vapor, you prevent the effect. If you keep a layer of vapor in between a hot surface and the thing you want to protect (which seems to be what you are asking about, but is not technically the Leidenfrost effect), it will last longer, but low thermal conductivity does not mean ",
" thermal conductivity - there are limits to protection."
] |
[
"The thing is, the water dissipating is what keeps your hand from getting burnt in the first place. The phase change from liquid water to steam uses up the energy that would be denaturing the protein in your fingers.",
"If you did have some kind of glove to trap the steam in with your hand (A hydrophobic spray wouldn't work for the reasons milnerrad already explained), you would just be butting your hand into the equivalent a pressure cooker.",
"Same deal with a tree. It would be fireproof, but that's only because it would be in an airtight container, not because of the Leidenfrost effect. "
] |
[
"Infinite series question"
] |
[
false
] |
If you have an infinite series that has a term in it that divides by zero, does that make the series diverge? Ex.) If you have the infinite series cos(pi*n) / (sqrt(n) - 3)), starting from n = 1. When n = 9, you're adding a term that divides by 0, does this make the alternating series diverge, regardless of whether tests say it converges conditionally? tl;dr The definite of an infinite series is S = a_1 + a_2 + a_3 .... a_n. What happens when one of those terms in the infinite series divides by 0?
|
[
"It's not that the series is divergent - it's that it literally does not represent a value. A series as a concept is just a sum, right? But if part of that sum is something that does not have a value, then your sum is non-sensical, right? If I say \"what's 1 + 3 + purple + 5?\" there's not really an answer to that. That's why LoyalSol says the series is undefined, or the sum \"doesn't exist.\" One of the terms doesn't have a value."
] |
[
"The series is undefined for n=9 which usually implies there was an assumption in the derivation of that series that was not valid for n=9. How to handle this depends completely on what the series represents.",
"For instance if you were to develop a ",
"sin series",
" for sin(x)",
" you would end up with a series ",
"sin(x)",
" = a_1 sin(x) + a_2 sin(2x) + a_3 sin(3x)....",
"who's coefficient is given ",
"a_n = (6 sin(pi*n))/((n+1)(n-1)(n+3)(n-3))",
"For any value of n, sin(pi*n) = 0 and therefore a_n is 0, but in this expression we notice that if n=1 or n=3 you divide by 0. So the question becomes what happened at n=1 and n=3? As it turns out the way the sin series was generalized is invalid for 1 and 3 so you have to go back and re-evaluate the expression used to get these coefficients in the first place but instead of doing it generally for any n, we fix n to 1 and 3. If you do then you find out that",
"a_1 = 3/4\na_3 = -1/4",
"Which gives you the identity",
"sin(x)",
" = (3/4) sin(x) - (1/4) sin(3x)"
] |
[
"If the series has a term which divides by 0 then the series is undefined. Basically the series doesn't exist in the form you have given it. ",
"It can mean a lot of different things depending on where the series came from. You have to give the context of what the series is in order to derive any meaning from it. ",
"Although I might add that series would be divergent anyways. "
] |
[
"I am a resident of Miami, Florida and my mom is convinced the entire city will be underwater in 25 years. While I know this is false I don't have any evidence to back up my claim. Can someone knowledgeable on the subject tell me why this is false and at what time Miami will be underwater?"
] |
[
false
] | null |
[
"Current sealevel projections for the next 25 years forecast a rise in the order of 10 to 25 cm (see ",
"Horton ",
", 2008, figure 1",
"). The predicted rise over the next century is somewhere between 40 cm & 1 m.",
"On the other hand, maps of parts of Miami which are susceptible to flooding show that some parts of the city such as coastal islands, spits and sandbars are more vulnerable than others (",
"see Wweiss ",
", 2010, figure 3c",
") and lie at or beloe 1 m from current levels. But most of the city is in the 2 to 5 m above sea level range. So there is that. ",
"While the answer sort of dépends where you are looking, and over what time period, there is no reason to state that \"Miami will be under water in 25 years\". Some parts might be, slightly. Also worth noting these projections do not factor in accelerated erosion.",
"Which isn't to say sea level rise will be without consequence, but this might mostly be from increased vulnerability to storm surges and like that. The new Atlantis it ain't..."
] |
[
"I thought water was the only element that wouldn't expand with heat but with cold.",
"You are confusing 2 things:",
"Thermal expansion is a property of liquids, heat them and they expand slightly - over oceanic volumes, it is a measurable effect",
"What you are referring to is the density of ice (I THINK) - Water is indeed exceptional in being less dense when solid than liquid."
] |
[
"In a rise of a few inches will make storm surges and hurricane flooding worse. Never mind tides."
] |
[
"If I pour bleach in my toilet bowl, will it react to the ammonia in my urine and create chlorine gas?"
] |
[
false
] |
[deleted]
|
[
"If you were a fish or had kidney/liver problems and produced significant amounts of ammonia in your urine, yes. \nIf everything is working alright, your kidneys should be converting nitrogen to urea (",
"http://en.wikipedia.org/wiki/Urea_cycle",
") which shouldn't react with bleach fast enough to be noticeable."
] |
[
"Absolutely. I have at least one friend and several acquaintances who have been hospitalized for this.",
"http://en.wikipedia.org/wiki/Sodium_hypochlorite",
"Search for \"urine\" in the wikipedia article."
] |
[
"The reaction of bleach and ammonia isn't a simple one; a lot of different compounds are produced, and chlorine is one of them. You'll get some chloramine and hydrazine in the bargain, as well."
] |
[
"Would we be able to help the Helium gas depletion by using a lot of alpha emmiters to generate more helium?"
] |
[
false
] |
I know they don't have electrons but I assume the could be introduced somewhere in the production process. Also, I heard on Colbert that there is no natural source of Helium, wouldn't alpha emmiters create helium in the environment?
|
[
"This is where all our helium comes from. Alpha decay of uranium/thorium/etc in earth. "
] |
[
"If the ITER fusion reactor (or any other H-based fusion) ever gets running, that should give us a decent source of helium."
] |
[
"True, a 1 GW fusion reactor would only give you about ",
"75 kg of helium per year",
".",
"But my understanding of tokomaks is that you have to remove the helium to keep it from poisoning the fusion reaction, and that this is done with a diverter of some kind."
] |
[
"How does a computer know whether a number is negative or not?"
] |
[
false
] | null |
[
"To add to what ",
"/u/aecarol1",
" has posted, there are two ways the computer can keep track of this information:",
"1) The data type can be stored in the computer program.",
"2) The data type can be stored with the data.",
"Option (1) is the most common for low-level programming. Assembly instructions, C and C++, and so on all use this method. The only way the computer can tell if 1111 should be treated as -1 or as 15 is how it has been told to treat the data in its list of instructions.",
"As ",
"/u/aecarol1",
" mentioned, the upside to two's complement is that it uses the same add/subtract hardware as unsigned integers. One of the problems is dealing with overflow and greater than/less than determinations. Page 17 of ",
"this document",
" describes how the ARM instruction set deals with this issue. There is a bit (the carry bit) that signals overflow occurred for unsigned integers, and another bit (the overflow bit) that indicates overflow occurred for twos-complement integers. The user specifies in the instruction set which bits they care about.",
"Option (2) is more common for high-level programming (like in Python). In software such as Python, data is stored with extra header information that identifies the data type. This is how the software is able to detect type errors at run-time. However, storing and managing these headers takes extra memory and computation time (this is why vanilla Python is about 10-100 times slower than C++ code)."
] |
[
"Yes, subtraction is almost always used and the branch simply decides what kind of compare was meant. For many RISC machines, the compare and branch is often the same instruction as some architectures do not have condition codes. Assuming you have the typical flags of (C)arry, (Z)ero, o(V)erflow, and (N)egative, my cheat sheet is:",
"Do the subtract, then branch on the flags depending on what kind of compare was meant.",
"code test cond: unsigned signed\n0 C, ULT C <\n1 NC, UGE NC >=\n2 Z, EQ Z == ==\n3 NZ, NE NZ != !=\n4 UGT NC & NZ >\n5 ULE C | Z <=\n6 SGT S=V & NZ >\n7 SLE S!=V | Z <=\n8 SGE S=V >=\n9 SLT S!=V <\n"
] |
[
"Yes, subtraction is almost always used and the branch simply decides what kind of compare was meant. For many RISC machines, the compare and branch is often the same instruction as some architectures do not have condition codes. Assuming you have the typical flags of (C)arry, (Z)ero, o(V)erflow, and (N)egative, my cheat sheet is:",
"Do the subtract, then branch on the flags depending on what kind of compare was meant.",
"code test cond: unsigned signed\n0 C, ULT C <\n1 NC, UGE NC >=\n2 Z, EQ Z == ==\n3 NZ, NE NZ != !=\n4 UGT NC & NZ >\n5 ULE C | Z <=\n6 SGT S=V & NZ >\n7 SLE S!=V | Z <=\n8 SGE S=V >=\n9 SLT S!=V <\n"
] |
[
"What was the vital force in vital force theory of organic compounds ?"
] |
[
false
] | null |
[
"The vital-force idea was that there was \"something\" about living things that was necessary for the creation of organic substances, and that without that \"something\", it was not possible to create those substances. ",
"But no-one really knew what that \"something\" was -- it was more of a spiritual belief than an actual scientific theory. These were the very early days of organic chemistry.",
"The vital force idea basically died with Woehler's discovery that the major component of urine could be made in a test tube. But you still see traces of vital-force thinking in some places (the supplements industry, for example)"
] |
[
"If you don't get an answer here, you can also try ",
"/r/askhistorians",
", ",
"/r/historyofscience",
", ",
"/r/philosophyofscience",
", or ",
"/r/historyofideas",
"."
] |
[
"For more information on this and a fun read, check out Life's Edge by Carl Zimmer"
] |
[
"Could domestication be considered a miniature model of evolution?"
] |
[
false
] |
For example, we know dogs came out of wolves. Despite today having a ton of breeds of dogs, they used to breed for purpose rather than look and even then were much different looking.
|
[
"Essentially, artificial selection is still the same as natural selection, just with humans forming a very strange and dominant part of the creature's environment. It still follows the same rules as natural selection in that the organism has to survive long enough to produce viable offspring, but there are more factors involved which would be arbitrary in a more natural environment (if a breeder is breeding dogs for a certain look, then not having that look becomes \"unfit\" whether or not the animal would survive in the wild better). But the same genetic factors are at work."
] |
[
"Yup. Darwin spends a considerable amount of time speaking about domestic breeding programs. They prove that characteristics are hereditary and manipulable. I really recommend reading \"On the Origin of Species\". It can get a little dense, but the result is a pretty solid case for evolution."
] |
[
"The Dawkins narration of the audiobook is amazing and makes it much easier to digest, IMO. "
] |
[
"Multiple questions about Gamma-Ray Bursts. How dangerous are they to Earth?"
] |
[
false
] |
Would we be able to detect a Gamma-Ray burst heading towards Earth before it hit Earth? If so, how far in advance would we be able to detect it? What could we detect? Spread, size, amount of time it would hit Earth for, etc.? What is the maximum range for a gamma-ray burst to pose a threat to Earth? I've read 200 light years is a conservative estimate. What are the main threats to Earth? I've read so far that destruction of the Ozone, and Stratosphere would occur, which would lead to changes in the Earth's atmosphere, which would lead to increased cloud cover and permanent winter. For the side of Earth directly hit by the gamma-ray burst, would the people be killed immediately? Or would it be just enough radiation to make it a slow death, or just disfigured for life? Thanks, I am not a scientist, but I found some literature that talked about this, and found it incredibly fascinating. Unfortunately the information regarding my questions seemed very limited. And since I don't have the math or science skills necessary to do the equations myself I thought I'd ask for help here. If you can point me in the direction of any useful articles, books, or text on the matter I'd appreciate it as well. Thanks again!
|
[
"1. Would we be able to detect a Gamma-Ray burst heading towards Earth before it hit Earth?",
"No, but with a pretty big catch. ",
"They don't come from nowhere. It would be impossible to detect something coming at us at the speed of light, but we'd know it was coming thousands of years in advance from observing nearby large stars and seeing if any are even candidates for emitting a GRB in our general direction.",
"2. What is the maximum range for a gamma-ray burst to pose a threat to Earth? I've read 200 light years is a conservative estimate.",
"The power output and degree of focus of a gamma ray burst can vary quite a lot, but try ~8000 lightyears.",
"There is a candidate star 5,000 lightyears away, but ",
"it's pointed wrong",
" and will zorch a region of space which does not include Earth sometime in the next few hundred thousand years. Stars like that are incredibly rare, and other objects expected to produce GRBs (a pair of merging neutron stars for example) are even rarer.",
"3. What are the main threats to Earth?",
"4. For the side of Earth directly hit by the gamma-ray burst, would the people be killed immediately?",
"Air has a ",
"halving thickness",
" of 15 meters. That is, every 15 meters the intensity of ionizing radiation will drop by half.",
"There's a lot of meters of air above you.",
"A few ",
"kilowatts per meter squared",
" of gamma rays for a few seconds would be very fatal to astronauts and a little bad for people on jetliners, but on the ground you get no appreciable dose.",
"However, absorbing radiation would produce lots and lots of nitrogen oxides and destroy vast amounts of ozone. The paper I linked forecasts darker skies and a global ozone hole. This would sunburn plants and people and require you to wear sunglasses to reduce risk of blindness.",
"The nitrogen oxides will come down in rain eventually after a few months and the ozone reforms after a few years, but an environment where plants can't be grown except under a greenhouse due to cold and ultraviolet would be pretty apocalyptic.",
"And again just in case it got buried in my overly long post, this should never happen because of a lack of nearby objects capable of producing a GRB."
] |
[
"How long does a gamma ray burst last? Is it an instantaneous thing or does it last hours/days/months/years? "
] |
[
"Short GRBs are less than 2 seconds. These account from about 30% of GRBs we've detected. Ultra Long GRB's are over 10,000 seconds, and are exceptionally rare. The other 70% are called Long GRBs, and are inbetween the above two types, although they tend to the shorter end of that scale.",
"Basically, if a GRB was aimed right at the Earth we wouldn't do a full rotation on our axis getting the whole upper atmosphere cooked. It'll just be the side facing the GRB."
] |
[
"Is Dark Matter differently distributed than regular matter?"
] |
[
false
] |
For instance, do we have any examples of gravitational lensing or other phenomena that could be attributed to the presence of Dark matter that don't feature normal matter? Or does Dark Matter exist pretty much i parallel with where we observe regular matter? Or am I just interpreting it all wrong?
|
[
"On a very large scale (galaxy groups), you'll find dark matter where you also find normal matter, because one of the things we need dark matter for ",
" to explain the formation of galaxy groups. But if you zoom closer, you'll see that rather than forming complex structures like galaxies, and within them relatively speaking extremely dense clumps of matter (stars etc), dark matter tends to remain a vast diffuse network of blobs in which galaxies are embedded.",
"Normal baryonic matter tends to form clumps because it feels electromagnetic interaction. It can interact with itself, via what we call friction and other processes, converting kinetic energy to heat and radiating it away as photons. Mere gravitation can never cause initially diffuse particles to gather into clumps because it would violate the conservation of energy. But we need dark matter to stay diffuse, otherwise it couldn't explain the observations for which we invoked it in the first place, and thus it must be, well, ",
" as in not interact electromagnetically much or at all. It should also have negligible self-interaction except via gravity, so likely not something like exchanging \"dark photons\", quanta of some dark counterpart of the EM field."
] |
[
"For the most part, dark matter traces ‘normal’ or baryonic matter pretty well. Dark matter is what formed the gravitational potential wells which allowed for baryonic matter to collapse to form galaxies, stars, planets, etc. This is why we generally expect every galaxy to be embedded in a large dark matter halo.",
"However some dark matter deficient galaxies have been discovered, but I believe these are thought to be this way due to violent collisions and.or interactions with other galaxies."
] |
[
"I've seen graphics about some galaxies having dark matter being distributed differently from the visible matter. One example is the ",
"https://en.wikipedia.org/wiki/Bullet_Galaxy",
" , I don't remember the other names. Currently I do assume these data to be correct."
] |
[
"Do we actually only have 5 types of taste receptor?"
] |
[
false
] |
I've been thinking about the frequently mentioned idea that all flavours are made of the 5 basic tastes; salty, sweet, umami, bitter and sour. I can't accept this model the way I understand it. Here's a few reasons why: 1. It implies that every flavour is simply a combination of 5 aspects, and thus you could imitate the flavour of any food using just 5 ingredients 2. There are more identifiable tastes such as metallic, astringent, pungent, cooling, alcoholic, burnt 3. Those flavours come in more than one variety - chilli, ginger and spring onion are all pungent but all have a different pungency. Glucose, sucrose and honey all taste sweet but different. 4. Similar tastes come from chemically distinct molecules - even pure citric acid tastes different to pure acetic acid. How can there be just 5 flavour components if two chemically homologous acids tastes entirely different, despite the lack of any contaminants to add 'bitterness' or 'sweetness' to alter the flavour? Surely every chemical has it's own unique interaction with the taste buds?
|
[
"Our experience of taste is a combination of the activation of ",
"taste receptors",
" and many other kinds of chemo- and mechanical receptors, such as those responsive to temperature, hot and cool (e.g. menthol), texture, and smell (the general wiki article on ",
"taste",
" covers some of this). ",
"Receptors types (or dimers - combinations of receptors) do seem to correspond to particular perceptions of taste like umami, sweetness, sourness, bitterness, and saltiness. "
] |
[
"First it is important to distinguish between flavor and taste. Taste buds are not the only mechanism at work when perceiving \"flavor\". Typically, when we chew food, the odorant molecules from that food is pushed up into nasal cavity where they stimulate our smell receptors. The combination of the sensations from our taste buds as well as the olfactory sensations combine together to make flavor. This is why when you get a cold and you're nose is stuffed up, it is very difficult to taste anything, or when you were a kid and had to eat something gross, you pinched your nose. You're effectively blocking the olfactory sensation required for flavor. ",
"Considering the above, when you smell different things such has ginger, alcohol, honey, you can (usually) tell the difference between them. You may not be able to put a name to them but you could tell they are different from each other. Since our olfactory system is integrated with our perception of flavor, this explains why they taste different as well. \nAs for chili peppers, these contain the chemical capsaicin, which triggers the pain receptors on the tongue. "
] |
[
"Minor addition: Capsaicin triggers a receptor (",
"TRPV1",
") which is stimulated by both high heat and tearing / abrasion (and also a bunch of other things like acidity). The thermal property is why spicy food tastes hot. TRPV1 is a type of pain receptor (",
"nociceptor",
") and is also found in other parts of the body. "
] |
[
"How does an enlarged heart (congestive heart failure) make my dog cough?"
] |
[
false
] |
[deleted]
|
[
"Congestive heart failure causes an increase in pulmonary vein blood pressure, essentially due to failure of the heart to pump well. This increase in pressure increases the overall ",
"Starling forces",
" that push fluid out of lung capillaries into the alveoli and interstitial space (lung tissue). This fluid build-up is called pulmonary edema. Unlike a bronchitis, where there are large mucus collections in the upper airways that manifest as a productive cough, the fluid is at the level of air exchange, and can't really be coughed out."
] |
[
"Enalipril can cause a dry cough. ",
"Enalipril is an 'ACE-inhibitor' and a dry cough is a common side effect we always warn patients about. ",
"ACE (Angiotensin Converting Enzyme) is involved in regulating fluid/blood volume and is also seen in lungs. ",
"If the dog started coughing after starting the medication I would ask your vet if they think it may be due to the Enalipril. "
] |
[
"Medical management can optimize (but usually not cure) congestive heart failure and resultant pulmonary edema; I'm not sure to what extent human therapy is efficacious in animals."
] |
[
"What are the most promising technologies for storing electricity from a solar power plant for cloudy days?"
] |
[
false
] |
It is currently expensive to store electricity. The idea that I think shows a great deal of promise (with no basis in science) are flywheel batteries...Doesn't matter. My question is about storing power cheaply so that solar may someday be viable. What's going to be the way it gets done and why? Note: this question is not about producing electricity with solar tech but about storing that electricity given a sufficient means to supply it.
|
[
"Mechanical Engineer here.",
"Pumping water up into a lake for later hydroelectric use is fairly efficient. Solar panels are 15-30% (45% in the lab) and hydroelectric dams can get as much as 90% (depending on how you measure it, it's actually less than that.)",
"That's assuming you actually have water to pump.",
"You've probably heard that one before, but it's still the best as far as I know",
"EDIT: If you want to be possessive, it's EYE TEE apostrophe ESS. If you want to be contractive, it's just EYE TEE ESS. Scallywag!"
] |
[
"yeah you're right. Wrote that before I had coffee. Not going to change it out of shame :("
] |
[
"EDIT: If you want to be possessive, it's EYE TEE apostrophe ESS. If you want to be contractive, it's just EYE TEE ESS. Scallywag!",
"I believe you have backwards.",
". \"Its\" is possessive and \"It's\" is the contraction of \"it is\" or \"it has\"."
] |
[
"Is it possible to collapse a neutron star through impact rather than mass accretion."
] |
[
false
] |
From what I understand, neutron stars are held up against gravity only by neutron degeneracy. If a large impact (not necessarily by a very massive body) hit a neutron star, the area impacted should momentarily experience increased pressure and compression. Could this trigger a local collapse as the pressure overcomes the neutron degeneracy, leading to a chain reaction that collapses the entire star. Also, if this is true, this should be a fairly common occurrence since most impacts with neutron stars should be very large due to their strong gravitational pull.
|
[
"Any source of additional pressure will compress a neutron star a non-zero amount. However, unless the neutron star is right up against the ",
"mass limit",
", it will be \"stable\", meaning a small change in pressure will result in a small change in size. Thus a typical neutron star will be quite resilient against impacts.",
"Some Neutron stars have companion stars dumping vast quantities of mass onto them all the time. When enough of this material piles up on the surface it will undergo a ",
"thermonuclear explosion over the entire surface of the neutron star",
". There should not be significant compression of the star even from this.",
"Here is why your scenario is unlikely to ever happen:",
"The degeneracy pressure isn't suddenly gone if you manage to compress degenerate matter: it increases rapidly upon compression. Thus in order to continue collapsing degenerate matter, you have to continue adding energy at higher and higher rates as it collapses, or else it rebounds. This is why we only speak of gravitational collapses: as the star collapses more and more gravitational potential energy can be put into overpowering the degeneracy pressure. If the neutron star is above the aforelinked mass limit, the gravitational energy available will be sufficient to do this."
] |
[
"I'm not a compact object expert so I can't give detailed or rigorous answers about some of these points without spending a lot of time researching it. I suspect that in principle what you are proposing is allowed, but I'm quite confident though that the kind of impact which would be needed is beyond what is likely to be found in nature.",
"I'll also point out that at the beginning of a core-collapse supernova, something on the scale of a solar mass of material falls onto the proto-neutron star in a fraction of second and bounces off hard enough to begin the supernova explosion."
] |
[
"It would seem that such a large explosion should provide enough force to collapse the star if what I suggested is true.",
"It's unlikely that it would be possible to create a large enough explosion on the surface of a neutron star to collapse it just from the force of the explosion. Adding mass is the way to collapse it."
] |
[
"If you are in water right underneath the moon and the moon is at it's closest, do you float better than other places on earth?"
] |
[
false
] | null |
[
"Nope! The Moon is pulling both you and the water equally, so it makes no difference to how you float.",
"Tides work because gravity drops off with distance. The near-side of the Earth is pulled by the Moon more than the far side. So the water tends to be pulled away from the middle, and piles up on the near side, and falls away to the far side (edit: just to repeat, that's ",
" the far side, ie there are high tides on both opposite ends) - although the exact level of this and the timing of this depends a lot on the local geography. Over thousands of kilometres the difference in the Moon's gravity is big enough that there's a net difference in force, and that makes the water flow.",
"But if you're ",
" the water, you and the water are in pretty much the same place, feeling pretty much the same force. So you don't really experience any extra force relative to the water."
] |
[
"By a negligible amount, yes. Like the difference between inhaling and exhaling."
] |
[
"Wait a minute, do you weigh less if you're on the moon side?"
] |
[
"If an object traveling and half the speed of light emmits photons in transit and those photons hit you, did they hit you at 1.5 times the speed of light?"
] |
[
false
] | null |
[
"See the FAQ"
] |
[
"i did, how does this violate them. it's not a homework question, i'm a working adult and have a legit curiosity, if the speed of light is supposed to be the max speed, how can you have light come off something already moving towards you with relative speed of x. wouldn't the photon be going speed of light+x? ",
"To me this seems like the perfect place for this question. i'm not going to go buy physics books just to try and satisify my curiosty (nor spend the time to get up to speed to know how to answer it). I think asking people in a science forum would be ideal. this may be a stupid simple thing to physicists but i don't actually know the answer. "
] |
[
"Under the section for physics in the FAQ you can find at least two questions that are the same as this one. "
] |
[
"Are there any animals besides humans which have demonstrated 'thrill seeking' behavior?"
] |
[
false
] |
Is this behavior unique to us? I've seen some comments about turtles "liking the sensation of falling" but are there any studies that show this type of behavior or is it all speculation?
|
[
"Lots. Otters sliding down mud banks, wolverines, bears and badgers sliding down snowy hills, birds (especially corvids) suicidally teasing cats, cetaceans breaching, coyotes fucking around with dogs, parrots and other birds working branches like trapeze artists, etc."
] |
[
"What's the difference between \"having fun\" and \"thrill-seeking\"? And a crow attacking a cat, or a coyote messing up a farm dog, is always taking a risk of having their day ruined. "
] |
[
"Sledding crows:",
"http://youtu.be/mRnI4dhZZxQ"
] |
[
"Is salt a food?"
] |
[
false
] | null |
[
"Salt is a mineral..."
] |
[
"If you take ",
"this",
" definition from dictionary.com, yes."
] |
[
"Looking at various definitions of food, the phrases \"maintain life\" or \"sustain life\" seem to be integral. Salt, while certainly useful, does not maintain or sustain our life. You cannot survive on salt and water. I would say that a \"food\" must contain one or more of the major elements C, H, N, O, P, and S (in a form the body can utilize) to be called a food."
] |
[
"How is a galaxy formed?"
] |
[
false
] | null |
[
"There's a lot of research currently being done by astronomers and astrophysicists on more accurately answering that question. It's thought that when a galaxy first forms it takes a disk shape (which can later change), and theories about their formation tend to fall under the categories of either 'top-down' or 'bottom-up' as they are often called, though the former is considered to be a little out of date, and doesn't support certain observations.",
"This older ",
"'top-down' theory",
" proposes that huge areas of dark matter in the early universe clumped together and the resultant gravitational collapse began the formation of entire protogalaxies in the same action; with the mass gaining angular momentum in the process. Then over time this enormous mass contracted as it cooled, and as a result, it's rotation increased due to the conservation of angular momentum. This faster spin caused it to flatten out into a disk. With further cooling the gas within this new disk shape was no longer gravitationally stable, and so it broke up into countless small, denser clouds, which in turn collapsed to become the early stars that made up the galaxy.",
"The more recent ",
"'bottom-up' theory",
" proposes the opposite; that dark matter in the early universe formed smaller masses first, and that these masses, being in close proximity to one another would group together through their gravitational attraction to become larger masses on the scale of globular clusters. Multiple local larger masses would merge and become galaxies (which themselves, are drawn by gravity to form larger galaxy clusters like the Virgo Cluster, of which our Milky Way is a part). This still results in an overall disk shape, for the same reasons as the top-down theory.",
"In both cases, the majority of stars which make up (or made up, in the case of the short-lived Population III stars of the early universe) a galaxy are thought to have begun formation after the galaxy structure itself had already formed. As more time passed, longer-lived stars were born, as well as the supermassive black hole at the centre of the galaxy.",
"The shape of the overall galaxy can be dramatically changed by interactions with other galaxies as they move through space. Elliptical galaxies, for example, are generally thought to be formed through the merger of smaller galaxies."
] |
[
"How does dark matter clump together? I was under the impression that the only way for it to dissipate energy was through gravitational waves and that seems quite slow?"
] |
[
"There's a lot of research currently being done by astronomers and astrophysicists on more accurately answering that question. It's thought that when a galaxy first forms it takes a disk shape (which can later change), and theories about their formation tend to fall under the categories of either 'top-down' or 'bottom-up' as they are often called, though the former is considered to be a little out of date, and doesn't support certain observations. ",
"This older 'top-down' theory proposes that huge areas of dark matter in the early universe clumped together and the resultant gravitational collapse began the formation of entire protogalaxies in the same action; with the mass gaining angular momentum in the process. Then over time this enormous mass contracted as it cooled, and as a result, it's rotation increased due to the conservation of angular momentum. This faster spin caused it to flatten out into a disk. With further cooling the gas within this new disk shape was no longer gravitationally stable, and so it broke up into countless small, denser clouds, which in turn collapsed to become the early stars that made up the galaxy. ",
"The more recent 'bottom-up' theory proposes the opposite; that dark matter in the early universe formed smaller masses first, and that these masses, being in close proximity to one another would group together through their gravitational attraction to become larger masses on the scale of globular clusters. Multiple local larger masses would merge and become galaxies (which themselves, are drawn by gravity to form larger galaxy clusters like the Virgo Cluster, of which our Milky Way is a part). This still results in an overall disk shape, for the same reasons as the top-down theory. ",
"In both cases, the majority of stars which make up (or made up, in the case of the short-lived Population III stars of the early universe) a galaxy are thought to have begun formation after the galaxy structure itself had already formed. As more time passed, longer-lived stars were born, as well as the supermassive black hole at the centre of the galaxy. ",
"The shape of the overall galaxy can be dramatically changed by interactions with other galaxies as they move through space. Elliptical galaxies, for example, are generally thought to be formed through the merger of smaller galaxies.",
"thanks for that dude"
] |
[
"Why do bacteria not get crushed and die when objects millions if times their mass are placed on them?"
] |
[
false
] |
Bacteria are so tiny that even the lightest of objects would be extremely heavy in comparison. How is it that they are able to survive under the weight of things when they are so extremely small?
|
[
"This is a problem of perspective. ",
"Is that super heavy item perfectly smooth on a cellular scale? Is the object the bacteria is on also perfectly smooth? \nThink of it like steeping on a small bug, if the grooves in your shoe happen to land on the bug, it will appear to have survived the stomping. When in fact it wasn't stomped. "
] |
[
"Along the same lines, even if the object were totally smooth along with a smooth mat of bacteria you shouldn't think of all the force applied to one bacteria. You need to look at the pressure applied to a single bacteria. Since the area of that bacteria is so small, it's a really small force on any one bacteria. In addition if one bacteria poked its head up high it would take a lot force, but it would probably push its neighbors until they all took an even load."
] |
[
"Why don't your own cells get crushed by your body?",
"It's because the forces are tiny on tiny scales. 100 kg weighing down on, say, 100 cm",
" (part of a foot) can create a lot of pressure (nearly 100 kilopascals), but on the scale of a tiny cell, which may be only 100 microns x 100 microns in cross section for a big cell the total force is only about 1 millinewton."
] |
[
"Can a star cool down enough and become a giant planet?"
] |
[
false
] | null |
[
"When stars cool down(fusion in the core slows down), gravitational forces overcome outward heat pressures causing the star to shrink, this compression in turn causes the temperature to increase again until the star is hot enough to fuse heavier elements. ",
"For large stars the final shrink results in a supernova, for small stars the outer layers of the star swell up until they are no longer gravitationally bound and float off - becoming a planetary nebulae and leaving the core behind as a white dwarf. ",
"White dwarfs are the white-hot core remnants of a star that shed its outer layers at the end of its life. They theoretically cool down by radiative cooling over many billions of years, eventually becoming a black dwarf, although this process takes longer than the current age of the universe."
] |
[
"Brown dwarfs are just failed stars. Basically the temperature didn’t get hot enough at the beginning for nuclear fusion to begin so they’re just big balls of dust and gas."
] |
[
"So we only have to wait about 10,000,000,000,000,000 years (a bit less than a million times the current age of the universe) for a white dwarf to cool to a nice, reasonable 300 K so we can land and start mining for diamonds.",
"Of course, the surface gravity of that black dwarf will be about 300,000 G, but I'm sure by that time we'll have figured out some method of dealing with that. Some really good breathing techniques and a light breakfast maybe."
] |
[
"I assume most “cavemen” didn't actually live in caves. Where, then?"
] |
[
false
] |
I have an image in my mind of Neanderthals living communally in a cave. But I'm sure that's not really the case. What was their typical domestic situation?
|
[
"I don't think anyone knows for certain. Virtually all of their sites predate the last ice age and were in europe, so most were probably hopelessly destroyed or buried by glaciers. The cavemen thing arose because most of the earliest neanderthal remains we found were in caves. That probably has more to do with the stability of the environment there, though. There are a lot of species whose remains we know mainly from their presence in caves, probably for that reason. There was a neanderthal site found that wasn't a cave, and had buildings built from mammoth bones. So, yeah, the flintstones wasn't totally bullshitting us."
] |
[
"OK, several things to address here. Firstly, you have to realize that Paleolithic archaeology has an inherent bias in it towards Europe, especially the Perigord in France, simply because it's where the people who first started asking these questions lived, and that terrain is dominated by caves and rock shelters. It's just something you need to be aware of when talking about this time period.",
"Lots of Neanderthal/Mousterian sites are in caves and rock shelters, but by no means were all of them. Whether the open air sites can be shown as residences instead of kill and/or butchering sites is another matter though.",
"They are practicing an organization of technology known as residential mobility. Neanderthals were, for the most part, highly mobile hunter gathers that practiced a yearly round, moving from locale to locale as food sources moved. Tool stone was nominally collected from local sources (less than ~50 km away from residential sites). ",
"Evidence for structures has been found, as someone noted below there is the mammoth bone structure near Moldova, Ukraine. There have also been some suggestions of wooden structures scattered throughout Europe, but wood does not usually preserve for the length of time we are talking about, and researchers such as Clive Gamble have postulated that it was more likely simply areas of tree fall around which people gathered.",
"Semi-sedentary life styles became more common during periods of climatic amelioration, but by that time Neandethals were largely giving away to anatomically modern humans. True sedentimism with complex structures and residences appear after the transition to the Neolithic and the invention of agriculture. ",
"Edits: Added a bit more."
] |
[
"How about you just explain the part that he didn't catch, instead of being a dick."
] |
[
"What causes the onset of puberty specifically?"
] |
[
false
] | null |
[
"GNRH release is regulated by KNDY-neurons (Kisspeptide-neurokinine B -dynorphine)",
"The KDNY neurons get stimulated by progesteron, we get release of Kisspeptide which stimulates the GNRH neuron and releases GNRH",
"GnRH then binds on the gonadotropic cells which causes the release of FSH and LHLH and FSH stimulate the production of testosteron and estrogen then inhibits the KDNy-neurons (negative feedback loop) so we don't get too much of GNRH release",
"Edit: I don't exactly know what causes this release in the first place, but studies have shown that leptine, a hormone secreted by fat cells in the human body, stimulate the KNDY-neurones which could lead to the start of the GnRH release.",
"During puberty (10-12yo) the child starts having lots of lipid cells which thus means more leptin secretion. This also means the \"fatter\" childeren get a faster puberty. It's a process called the gonadarche.",
"",
"source: med student"
] |
[
"If I've learned to extrapolate anything from BioChem, there's probably a gonadotropin releasing hormone releasing hormone.",
"And also a gonadotropin releasing hormone releasing hormone releasing hormone.",
"It's releasing hormones all the way down."
] |
[
"Makes sense from evolutionary point of view. Oh there is enough food? Then we can go into this major growth, that requires a lot of energy. Oh there is not enough food? Let’s wait another year or two and hope that the situation is better then."
] |
[
"Can non-planetary celestial objects have ring systems?"
] |
[
false
] |
Would it be possible for a star, moon or black hole, for example, to have a ring system as prominent as the ones that planets can have? If so, how would the characteristics of these ring systems differ from the ones of planets?
|
[
"It was previously thought a fairly massive body was required to maintain a ring system, but the recent discovery of ",
"rings around asteroid 10199 Chariklo",
" disproved that idea. That said, they're nowhere near as massive as the rings found around the giant planets."
] |
[
"A black hole will develop an accretion disk if matter is falling towards it. But it's very different from a ring like Saturn's. The matter in the disk is shedding a heck of a lot of gravitational potential energy, so it gets extremely hot and radiates a lot of energy. Some of the brightest objects in the universe are black holes accreting matter, and that radiation comes from the accretion disk (the hole itself is black, of course)."
] |
[
"One example of a non planetary ring system is when you have 2 companion stars in a binary system, and one partner is at the end of its stellar evolution (e.g. white dwarf or a more exotic compact stellar object). It can pull mass from its companion. The mass coming from the companion can form an accretion disk around the smaller object as it falls toward the center of gravity of the object. There are some interesting videos made from computer models you can find online that illustrate what this might look like for a white dwarf/red giant pair."
] |
[
"Has the belief in homeopathy decreased within the past few years?"
] |
[
false
] |
It seems like I very rarely hear about homeopathic medicine treated as anything other than quackery anymore. A few years ago it seemed like the Next Big Thing in alternative medicine. What has caused this, or am I incorrect and it is still widely believed in? Disclaimer: I know homeopathy is objectively BS, just curious where belief in it is compared to 5-10 years ago.
|
[
"Chiropractic has only been shown to help with certain forms of lower back pain, and even then at relatively low significance. If chiropractic is helping people it's coincidence, as it is not an evidence-based practice.",
"Some chiropractors are also physical therapists or otherwise incorporate non-chiropractic methods into their therapies, which may be markedly more effective than chiropractic itself is."
] |
[
"Chiropractic has only been shown to help with certain forms of lower back pain, and even then at relatively low significance. If chiropractic is helping people it's coincidence, as it is not an evidence-based practice.",
"Some chiropractors are also physical therapists or otherwise incorporate non-chiropractic methods into their therapies, which may be markedly more effective than chiropractic itself is."
] |
[
"Herbal supplements in general are very different than homeopathy specifically, many have plenty of research to back them up."
] |
[
"CRT minus the vacuum?"
] |
[
false
] |
So, what would happen if a crt's beam was outside of vacuum, say you removed the phosphor wall from a monitor, or just removed the vacuum all together, would it operate, or would it just ionize the air all around it?
|
[
"The latter. CRT's emit beta rays, which, like you said, would ionize the air."
] |
[
"They're the same thing."
] |
[
"Do you mean beta particle, or are beta rays something different?"
] |
[
"When blind people \"see\" for the first time, do they see everything upside down?"
] |
[
false
] |
[deleted]
|
[
"Although it is true that the image on your retina is inverted (up-down and left-right), it is only inverted to an outside observer. That is, if I am looking at your eyeball, the bottom part is getting light from the upper part of the world (relative to my being upright). ",
"But your brain is not an observer. It does not have an extra set of eyes looking at your retinas and comparing that to the world. There is only one image (what's on your retina) that the brain has access to and there is nothing for it to be inverted relative to. There is no \"flipping\" that the brain has to do. "
] |
[
"People have done similar experiments to what you're talking about using prism googles. The prism bends the light in such a way that it makes everything look upside down. If you wear prism goggles like this for a long time, you will eventually get used to seeing the world upside down. You'll learn to account for the \"upside down-ness,\" for example, you'll reach down for a falling object, even thought it will look to you like it's moving upwards.",
"Now to your question. When you take these goggles off, you have to ",
" this correction. If you see a falling object, you'll tend to reach up, even though you see it falling down now that the goggles are off. ",
"This may be what you're getting at. The key is that these are all associations your brain learns between the images you're seeing, and the actions you take.",
"The prism goggles experiment is actually a very popular demo I've done many times when teaching kids about the visual system, and how the brain learns."
] |
[
"That's very similar to the ",
"Backwards Brain Bicycle"
] |
[
"Why is n-heptane such a commonly used fuel for fire in experimints?"
] |
[
false
] |
I have read many articles about experiments with fire, and they often use n-heptane. However, they never explain why they use this specific substance, and I couldn't find it via google.
|
[
"I would put my money on that it is a liquid that is cheaply available and burns quite nicely. "
] |
[
"This is correct. Additionally, it doesn't have a particularly low boiling point like pentanes (36 °C) and is significantly less toxic than hexanes (a neurotoxin). Pharmaceutical companies often use heptane over hexane for this reason, although academia generally does not as heptane is more expensive."
] |
[
"And it's a single compound so you can be sure it's the same every time, not like hexanes which is widley used as solvent, but can have slightly different properties depending on the composition."
] |
[
"What causes you to lose your voice?"
] |
[
false
] |
If your vocal cords are just muscles that force air to pass through it, then shouldn't it be more difficult to lose your voice from just yelling all night?
|
[
"They aren't muscles, really. They are more like soft mucous membranes that vibrate when air passes over them, rather that vibrating from direct muscle activation. ",
"Losing your voice has less to do with \"wearing the muscles out\" as it does damaging and inflaming the membranes, causing inefficient vibrations."
] |
[
"How does vocal training to reach pitches that you normally couldn't hit work?"
] |
[
"That's outside of my field of specialty. I'll defer to someone else before I speculate."
] |
[
"How do volcanologists determine that a volcano became dormant millions of years ago?"
] |
[
false
] |
How are they able to get estimates like that? How is it possible to tell that a volcano last erupted millions of years ago?
|
[
"In reality within volcanology we only ever talk about active and extinct - dormant is pretty meaningless. Even active and extinct are only ever really used colloquially.",
"The term extinct tends only to apply to systems that we believe have no active magma plumbing system. Now, we can look at local sediments to see if there's been any ash events in the last few hundred thousand years or so, but not all eruptions leave a record, so this is not a reliable method - particularly for volcanoes which have lots of small eruptions. The more general method is to look at where the volcano is situated relative to its source mechanism. So, for example, a hotspot volcano which is no longer near its hot spot can be classed as extinct, as there is no source mechanism anymore (e.g. the Hawaiian volcanoes older than Maui).",
"Dating when a volcano last erupted is simply a case of using ",
"radiometric dating system",
" on the most recent ash or lavas.",
"This is all complicated on a local scale by the fact that many different individual vents can have a common source. Separating what one might call parasitic vents from one another can seem quite arbitrary. Ultimately, the classification system is not as robust as high schol geography classes might have you believe. Hence volcanologists don't bother getting caught up in it; it's just not particularly useful."
] |
[
"Wow, thanks for the explanation! That's really interesting!"
] |
[
"How did you end up in volcanology and sedimentology? All volcanologists and sedimentologists I know can't stand eachother."
] |
[
"Did people have photosensitive epileptic seizures before TV's were invented?"
] |
[
false
] |
I've tried looking up info about it on Google but I wasn't able to find the answer to this question. Basically, would people have had flashing-light-based seizures before the technology to produce it was invented?
|
[
"ever tried to run next to a fence made out of vertical slats while the sun is shining through it? Same with trees essentially."
] |
[
"ever tried to run next to a fence made out of vertical slats while the sun is shining through it? Same with trees essentially."
] |
[
"Not an expert, but I do have epilepsy, though it is not the photosensitive kind. I doubt that the commonness of a stimulus correlates to sensitivity to that stimulus in epilepsy patients. In other words I think yes, people had photosensitive epilepsy before flashing lights were common. But I could be wrong; sensitivity could be triggered by exposure. But again, I doubt that. I would think the sensitivity must be there in the first place for it to initially be triggered. I have fatigue and stress induced seizures, but if I'd never been stressed or fatigued, I think theoretically I would still have those sensitivities, even though there would be no seizures to suggest it."
] |
[
"What’s the difference between the 2009 Swine Flu pandemic and COVID-19, and why weren’t masks/lockdowns encouraged in 2009?"
] |
[
false
] |
[deleted]
|
[
"The H1N1pdm09 influenza virus is less than half as transmissible as SARS-CoV-2 (R0 around 1.4 vs 3-4 for SCV2), and has less than 1/100 the mortality rate (0.001-0.01% vs 0.5-1%) (",
"CDC: 2009 H1N1 Pandemic (H1N1pdm09 virus)",
"), with a similarly lower rate of long-term complications. Of course there was less concern about this far milder and far more easily controlled virus. ",
"But of course your claim that “masks were not involved” is wrong too. Masks were widely used in many countries, though not so much in the US. However, followup analysis showed that face masks ",
" have been used in the US as well, in that they would have significantly reduced the burden of disease (",
"Economic Analysis of the Use of Facemasks During Pandemic (H1N1) 2009",
" and ",
"The Effect of Mask Use on the Spread of Influenza During a Pandemic",
", for example)."
] |
[
"Masks were widely used in many countries, though not so much in the US",
"It's worth noting that ",
" of masks was not high in the US. But the fact that our national PPE stockpile was depleted after 2009 is pretty good evidence that healthcare workers did use masks pretty extensively in the 2009 H1N1 pandemic."
] |
[
"The first paper makes a modelling assumption that I found the be ultra-wrong where I live. That masks are used \"always\". In october in Italy they mandated to have masks always on where you were outside your home. So you had to wear one while walking on the road, where the attack rate is like 10",
" And surveys found compliance level over 90%. But you could take it off in a social even (restaurant) where the attack rate is ~7%. Rt exploded to 2.2",
"So, I'm not sure that masks alone can do that much. Also, they assume a virus with Rt=1.25. So an extremely small reduction of it results in massive variations of the total number of infections.",
"But most of all, I'm genuinely scared of the concept of \"should\". COVID is a truly exceptional event. I hope that extreme limitations like we're seeing now aren't even remotely thought of to be ever applied again, unless it's the last resort"
] |
[
"What non-combustive means of propulsion are feasible for leaving earth orbit?"
] |
[
false
] |
Many are familiar with the more popular speculations concerning interstellar space travel: Ramjets, Solar Sails, Nuclear Bomb propulsion, etc.. What I'm asking is if there are proposals for leaving earth (other other bodies) orbits other than modern solid fuels like ammonium perchlorate and the like.
|
[
"Would these photons be able to overcome earths gravity and propel a craft out of our atmosphere? "
] |
[
"Would these photons be able to overcome earths gravity and propel a craft out of our atmosphere? "
] |
[
"The only issue I see arising from that method is earth's escape velocity.",
"The needed 11.2 Km/s would have to be achieved in a fraction of a second in a rail gun. The g-force upon contacting earth's atmosphere would crush any human and likely damage most cargo.",
"On the moon it might work, but I can't see it happening on earth where there's air."
] |
[
"(chem/phys) What kind of bond is created when I heat eggs in a frying pan and they \"stick\" to it's surface after? For the food that is really \"stuck on\", has this food diffused into the surface of the pan, or is their no atomic mixing at all? If not, then what accounts for the actual \"stickiness\"?"
] |
[
false
] | null |
[
"Usually when cleaning pans at the restaurant, we use sodium hydroxide mixed with water (it doesn't say on the label, but that's pretty much what it is). The highly basic or caustic solution pulls the burnt carbon off the cationic metal, and this reaction speeds up under heat. ",
"Along with this, if something has been previously frozen, it's even more likely to stick together. ",
"What's likely happening is the carbon is getting stuck to the metal, similar to what happens in an internal combustion engine. ",
"Carbon Build Up ",
"edit: Usually if there's not enough oil, then there will be carbon build-up. Metal tends to oxidize, and when this happens an oxidation layer forms. Once an oxidation layer forms its much more likely for a carbon build up to form. Oxidation tends to attract a lot of interesting chemicals, and is also what rust is. Rust is difficult to remove, and so has the same or similar properties to typical carbon build up(although they are not the same thing so we simply categorize the two into a very general class of what are called anionic compounds)."
] |
[
"The reaction between Sodium Hydroxide, and the Metal under heat, is proof that a bond is present. ",
"The metal essentially acts as a Cation for the Anionic Carbon. It however is not soluble in water, the Carbon essentially prefers Na to the Metal. "
] |
[
"Most importantly: If your eggs are sticking to your pan then you are over heating your pan when you cook your eggs.",
"They should stick initially (during which time you shouldn't move them) but then once they are cooked they should come off the pan easily. If they stick at the end then you're burning them.",
"The other answer is pretty good."
] |
[
"How are calories in food determined?"
] |
[
false
] | null |
[
"In the 19th and early 20th centuries they would burn food to determine how many calories it contained. This worked by placing the food in a “bomb calorimeter” filled with water at a measured temperature, and then burning the food via an electrical current that would be applied. Directly after the food was completely burned, they would measure the temperature of the water and determine how much the water was heated. This practice was largely found impractical after the FDA along with other similar administrations imposed the need for other nutritional information on food packaging, so then companies would use charts that show there are x amount of calories per x amounts of an ingredient."
] |
[
"I don't know how it is measured today, but calories can be determined (not with the most validity) by burning the substance in a calorimeter with water, and based on the specific heat capacity of water ( 4187 joules / litre degree celcius) and the amount of degrees the water increased it can be calulated what the energy output of the substance was, and based on the amount of the substance added, it can be worked out the energy output per unit of substance."
] |
[
"I don't see how the practice would be found impractical by the need to list nutritional information. It is still required to state the energy in the product, and that can't necessarily be done by measuring the energy content of a product's constituent ingredients.",
"What replaced the bomb calorimeter?"
] |
[
"How do we measure the height of mountains on planets with no sea level?"
] |
[
false
] |
Olympus Mons was recently compared to Mount Everest and I was wondering how comparable the survey methods were.
|
[
"I too saw this Reddit link. The Wikipedia page talks about this a bit; ",
"https://en.wikipedia.org/wiki/Olympus_Mons",
". This leads to a discussion of the Mars global datum, defined as (from ",
"https://en.wikipedia.org/wiki/Geography_of_Mars):",
"On Earth, the zero elevation datum is based on sea level. Since Mars has no oceans and hence no 'sea level', it is convenient to define an arbitrary zero-elevation level or \"datum\" for mapping the surface. The datum for Mars is arbitrarily defined in terms of a constant atmospheric pressure.",
"From the Mariner 9 mission up until 2001, this was chosen as 610.5 Pa (6.105 mbar), on the basis that below this pressure liquid water can never be stable (i.e., the triple point of water is at this pressure). This value is only 0.6% of the pressure at sea level on Earth. Note that the choice of this value does not mean that liquid water does exist below this elevation, just that it could were the temperature to exceed 273.16 K (0.01 degrees C, 32.018 degrees F).[4]",
"In 2001, Mars Orbiter Laser Altimeter data led to a new convention of zero elevation defined as the equipotential surface (gravitational plus rotational) whose average value at the equator is equal to the mean radius of the planet.[5] ",
"I hope others will comment and explain the last paragraph better for us all. Here is reference 5 from that article:",
"Smith, D.; Zuber, M.; Frey, H.; Garvin, J.; Head, J.; et al. (25 October 2001). \"Mars Orbiter Laser Altimeter: Experiment summary after the first year of global mapping of Mars\". Journal of Geophysical Research: Planets. 106 (E10): 23689–23722. ",
"A direct link.\n",
"https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2000JE001364"
] |
[
"So let's start on Earth. Sea level isn't really defined as the elevation of the ocean surface. The ocean's surface is variable due to how much water is coming in vs. going out, tides, weather, and other factors. Sea level is actually defined on Earth based on gravity measurements. Earth's gravity has been mapped for its entire surface. Earth's gravity actually changes a bit (the changes are very very small, but measurable with specialized instruments) based on variations in compositions in the Earth's crust and mantle. Using gravity, we can define a surface of the Earth where gravity is the same everywhere. Basically anywhere on that surface, you would weigh the same. This surface is an equipotential surface. There is equal gravitational potential energy everywhere on that surface. This surface is called the geoid. ",
"Now the geoid is really complicated. There area lots of bulges and depressions. It doesn't make for a really useful surface when you're making maps or trying to measure elevation. So in practice, scientists approximate the geoid using a set of equations. These equations are called the ellipsoid. Datums, or systems of latitude, longitude, and elevation, are based on the ellipsoid. Earth has lots of different datums and ellipsoids. NASA and others have done the same thing for Mars. On Earth, the equipotential surface (geoid) is set to approximate mean sea level. On Mars, the equipotential surface (Martian geoid?) is defined as Mars's gravity at the average radius of the planet. Elevations on Mars are measured relative to the Martian ellipsoid, which again, is based on the Martian geoid, which is defined as the gravitational potential energy at Mars's mean radius.",
"Edit to respond to some comments made below:",
"Yes, sea level is still measured directly today and we do keep track of mean global sea level. But we're not using that level to measure elevation. We're not necessarily going to change the height of Mount Everest due to climate change (I don't think...). ",
"Another thing that's come up a few times. There are geoid heights (elevation relative to the geoid) and ellipsoid heights (elevation relative to the ellipsoid). They are not the same, because the ellipsoid is only an approximation of the geoid. Others are right. We can and do measure geoid height. However, not all datasets are given in geoid heights. It depends on the application. Here's a decent resource for a lot of this stuff:",
"https://vdatum.noaa.gov/docs/datums.html",
"There's still a good chance I screwed something up. I am a geologist with some experience in geophysics and geodesy but those two specialties are not my current day job."
] |
[
"First you need to define a zero altitude. Height is a relative value instead of an absolute value.",
"If the planet has atomsphere, we can use the pressure deference between the mountain top and the defined zero altitude to find out the height of the mountain. You will also need to measure Temperature lapse rate, Standard temperature at zero altitude, Surface gravitational acceleration, Molar mass of dry air.",
"We can also send satellites to do the job, if there is no atmosphere. The cheapest way to do so is to send one satellite with laser distance measuring tool. The satellite sends a laser to two places I mentioned above and calculates the difference of the time of the laser traveled. The time times the speed of light(assume it’s vacuum), you get the height."
] |
[
"When a photon reflects off of a mirror and changes direction, does it decelerate, stop, then accelerate like objects with mass do?"
] |
[
false
] | null |
[
"Choose and want are not right words here. Photons can't choose or want something. It just happens randomly. Also particle never splits off. It is just a probability wave until it is observed. This wave collapses when it's observed. "
] |
[
"I never understood how this can be the scientific explanation.",
"To really understand it you need a lot of math, I fear."
] |
[
"Photons never stop in the sense you're speaking of, so no. A precise view of what happens is rather difficult since we're dealing with a quantum particle; in a sense it interacts with the mirror and takes all possible paths settling on one upon measurement (all the paths add to the quantum amplitude). Some photons get absorbed by the mirror, giving it energy, others are reflected and so on."
] |
[
"How do people recover from the Wuhan coronavirus?"
] |
[
false
] |
I was told that there is currently no cure for the Wuhan coronavirus and the death rate is 10%, so how are the other 90% surviving/recovering
|
[
"The same as how you recover from other viruses like the common cold, your body naturally fights it off using ",
"antibodies",
" and other parts of the ",
"immune system",
".",
"Cornaviruses cause respiratory problems such as pneumonia, an inflammatory condition of the lungs. Most people can survive these issues while their body fights off the infection, but the elderly, young, and those with various health issues may not be able to fight it off or may suffer more from the respiratory problems.",
"Last I heard, nCov-2019 was at 26 deaths and 870 cases, which puts the death rate closer to 3%. This doesn't take into account though that there will be many cases which haven't been reported as people stay at home, so the true death rate is likely much lower."
] |
[
"The human body is pretty good at fighting off viruses if a person has an intact immune system. Generally speaking, viruses are less robust than other pathogens like mycobacteria or bacteria in a spore form. Think about getting over a viral cold vs getting over tuberculosis (mycobacterium). ",
"Both your innate immune system (kill everything foreign!) and your adaptive immune system (kill this specific foreign thing we’ve seen before!) can play a role in clearing a viral infection, but it can take time. A lot of medical care for viral infections is aimed at mitigating the symptoms of the virus while your immune systems ramps up its activity. Symptoms like dehydration can go from uncomfortable to life threatening surprisingly quickly, especially in very young children, the elderly, and the immunocompromised. If you can treat the symptoms long enough and put a person in a favorable position for recovery (rest, humidified air, drink fluids, etc), the body will usually do a good job of taking care of a virus."
] |
[
"I'm conflicted on this because on one hand China has done that in the recent past and there are reports of hospitals in Wuhan not even taking peoples temperature before turning them away. On the other hand, the response is ",
" more robust than we've seen in the past and deserves recognition."
] |
[
"Why do most people who experience psychedelics come to a conclusion of wholeness and one with the universe?"
] |
[
false
] |
I'm an atheist, rational thought prevents me from believing in any sort of deity, however every psychedelic experience I've had so far makes me question such things since the experience is almost every time of strong spiritualism. I've tried reading journal articles about psychotropic effects on the brain, alas, I do not understand it. Anyone has an explanation for this in layman terms? Thank you.
|
[
"Hey people, I realize this question provokes a lot of questions about existence, reflection about life, and anecdotes about experiences you've had with drugs, but this is AskScience. We're looking for scientific answers that cite published works. Thanks!"
] |
[
"I'll split my answer up into a few bits to make it a bit clearer and I'll come back and add to it if I have some more time today.",
"It's a common side-effect of psychoactive drugs. There was a seminal study - Pahnke (1966)- explanation of this study taken from a ",
"follow up paper",
":",
"In a Boston chapel on Good Friday, drug-naive divinity students were given either a high dose of psilocybin or an active placebo in double-blind fashion. Most subjects in the psilocybin group reported profound spiritual insights with transformative effects that persisted for decades, according to a follow-up study by Doblin (1991).",
"and from their own results:",
"Regardless of culture of origin, users of psychedelic drugs scored significantly higher than users of other illegal drugs and nonusers on mystical beliefs, such as oneness with God and the universe, the illusory nature of physical existence, and the presence of a transcendental reality. Psychedelic users also scored higher on emotional empathy than the other groups, although only the comparison with nonusers was significant. The higher mean empathy score of psychedelic users was consistent with predictions based on the compassionate qualities attributed to those who have had enlightenment experiences according to the mystical traditions of Buddhism and Hinduism.",
"Drugs like ecstasy also seem to elevate empathic feelings but at the same time limit cognitive function so you have trouble assessing social situations (",
"here's one study",
").",
"An important thing to note is that there seems to be a difference between the types of people that use psychadelics vs other drugs. It can therefore be a bit difficult to tease out cause and effect in these cases as we can't ethically administer these types of drugs in a clinical setting any more and have to rely on people who decide to take it themselves. From ",
"this",
" paper:",
"On the SOC, a measure of belief in one's ability to cope with life stress, users of nonpsychedelic illegal drugs such as marijuana and amphetamines scored significantly lower than both users of psychedelics and nonusers of illegal drugs. This suggests that in contrast to psychedelic drug use, nonpsychedelic illegal drug use may more often reflect maladaptive attempts to cope with stress. Alternatively, use of such drugs may impair the subjective coping ability of some users. ",
"It's actually really hard to say because there was somewhat of a moratorium on research into these types of drugs on humans. We have to rely on using people who have already decided to take the drugs recreationally, and there are a lot of underlying behavioural factors that shape that decision. And gvien it's a little difficult to see if research animals are having mystical experiences, we're still a little stumped on the exact mechanisms."
] |
[
"Here's a ",
"video",
" of a neuroscientist explaining this very phenomenon, but it was induced by temporal lobe epilepsy rather than using drugs, but I think the explanation is valid for both."
] |
[
"How is blood tested for dopamine, serotonin, and/or norepinephrine? How are 'levels' determined; e.g. what is the actual mechanism of the test?"
] |
[
false
] |
I've been learning about different theories of human emotion and many of them focus on the three molecules listed in my title question. This lead me to wonder how these molecules are tested for. Since biology is one of my weaker areas of knowledge, I tried looking around on the web for how these substances are extracted and/or tested for; however, I found little information. Most of what I found focused on lay peoples' personal medical experiences–off topic for me. And, since I don't know what these tests are called in their professional context, I can't get my search on. What I'm curious about is how, in general, these substances are detected in the blood and how, from a technical perspective, the concentrations are determined. I was hoping that a basic description would lead me to a basic understanding the correct terminology so that I could study further on my own. Thanks. edit: Everyone, thanks for so many responses. It will take me a while to read through all of them but you all have given me a great start to my journey. Cheers!
|
[
"Not at all my area of expertise, but I found at least one potentially useful article that explains this stuff on a molecular level!",
"Serotonin Detection Method",
" \nJust looking at the abstract, it looks like the researchers used this \"hyperbranched viologen polymer\" as sort of a marker for the presence of serotonin. The idea is that the viologen polymer (which they call HB-1) has an affinity to bind with serotonin (and only serotonin) when they're in solution together. When the 2 molecules bind, they exchange electrons, and when HB-1 gains electrons, it ",
"emits blue light",
" ! So, the more serotonin present, the bluer the solution. The researchers could then use a device called a spectrophotometer, which detects how much light is transmitted through a solution relative to a standard, to quantify how much blue tint is in the solution, and therefore how high the concentration of serotonin is.",
"Hopefully that made sense? There are probably many other methods to detect the levels of these hormones, but this is at least one of them, and the principles behind it would probably be similar to other techniques! "
] |
[
"Many have mentioned antibody based strategies although I do not think they are standard for these specific molecules. These types of assays can take many forms (lateral flow, ELISA, suspension bead array). The way they typically work is you have a labeled antibody (your signal) that binds to the small molecule. The assay itself contains the same molecule you would like to detect but immobilized in some way. When your sample contains high levels of the molecule, the antibody will bind to that instead of the immobilized molecule and this lowers the signal output. If your sample has low levels of the molecule, the antibody will bind to the immobilized molecule and provide a higher signal. ",
"I believe the standard assay for detecting these specific molecules is actually electrochemical detection. In this type of set up they will isolate the small molecules from the sample and separate them by HPLC (a type of chromatography). As they are separated they are detected in a special sensor that performs a redox reaction on the molecule. The redox reaction generates electrical current, the more molecule, the more current. Quantification is done by comparing to standards."
] |
[
"Or you can use a monoclonal antibody for serotonin. That would work for an ELISA or western blot if you're working with blood samples"
] |
[
"How could a body decompose in a sterilized room completely clean with no bacteria to break down the flesh?"
] |
[
false
] |
I know we have bacteria all over us already but what if they body was cleaned?
|
[
"To add to the other commenter, [[edit: well now this is on top, so my comment is about ",
" to internal microbes leaving you with a only skeleton]] there are definitely different levels of decomposition that can happen. You won't always be left with a skeleton. Sometimes you may be left with a \"natural mummy\" that isn't very decomposed at all. Examples of conditions where you would find a natural mummy:",
"Icy mountains - the body is frozen, such as in the Alps. See: Otzi the iceman.",
"Also human sacrifices have been found in the Andes in even \"better\" condition. Here is a link but fair warning, it includes pictures of child mummies: ",
"https://www.penn.museum/sites/expedition/frozen-mummies-of-the-andes/",
"Dry sands - there were bodies buried in the ground in Egypt before the traditional mummification process was developed, I believe, and they were somewhat preserved by these conditions. This obviously dehydrates the body in a way that is different to ice mummies.",
"And, bogs - they may have high moisture, and not quite freezing temperatures, but importantly, they do have low oxygen and an acidic environment, which prevents the microbes from decomposing the skin.",
"Basically, various conditions can inhibit the decomposition process that microbes might otherwise cause. ",
"More reading here: \n",
"https://relay.nationalgeographic.com/proxy/distribution/public/amp/news/2016/01/160118-mummies-world-bog-egypt-science"
] |
[
"To add on to this, the Tarim basin in northwest China has produced large numbers of ",
"extremely well preserved mummies",
" due to the area having a perfect combination of saline soils, incredibly dry summers and freezing winters, with the bodies often buried in tombs or exposed coffins. Politically, the mummies can be very controversial, as they are neither Chinese or Uyghur and appear to be early Indo-Europeans."
] |
[
"Depends on the type of 'sterile' environment you're in. Depending on temperature, there are several ways for a body to decompose. Normally, your mucous glands all along your intestines keep your digestive bacteria in check, so once you dies, and those mucous glands stop protecting your gut, those bacteria start digesting you. This happens at a fairly predictable rate just based off of body temperature when the body passes, but extremes in temperatures can greatly affect this rate.",
"In a hot/humid 'sterile' environment, like a sealed room, a body will putrefy rapidly, turning into necrotic black soup. This is the fastest way to 'naturally' turn a body into a skeleton without outside factors like insects or foreign bacteria.",
"In a hot/dry sterile environment, a body can still putrefy, but high temperatures might kill off the gut bacteria before the bloat the body and turn it to ooze, so in this case, it's possible for a body to become a dry mummy at which point other factors like sand erosion might break down and disperse the biomass.",
"In tepid environments, humidity plays less of a factor, and a body will putrefy, bloat, and eventually turn to ooze on the inside, but the skin might remain recognizable for a fair amount of time. ",
"The interesting case, however, is in very cold environments. In particularly cold environments like the arctic and antarctic circles, as well as some mountain ranges, the low body temperature will cause a body to lose temperature at a rate fast enough that it can drop below the survivable threshold for bacteria long before putrefaction sets in too deeply. Once the bacteria are dead, the next thing that happens is that the moisture in the body will freeze, and ice has the odd ability to sublimate at low temperatures, so after a long enough period of time, the body will eventually dry out and leave a husk similar to a hot/dry decomposition."
] |
[
"Is it possible to transfer one’s organs into another body and become that person?"
] |
[
false
] | null |
[
"Personality, memories, etc. are stored in the brain, not the organs. At present, it is not possible to do a brain transplant."
] |
[
"So if a brain transplant is possible, then the transfer of memories and stuff is theoretically possible? "
] |
[
"In theory -- because that's where memories are stored. "
] |
[
"How do birds keep from running into each other when in large groups? Especially amazing to watch them take off simultaneously."
] |
[
false
] |
I have a bit of a hobby building small robots (using micro controllers and any available scrap electronics and so on) and my next project is going to be an attempt at a hive-mind thinking among multiple micro controllers. Just going about my day I noticed that even a large flock of birds when taking off simultaneously maintain an almost equal distance from each-other and mange to never interfere. Has anyone studied similar behavior and logic among birds or other animals or read any interesting articles or studies? Edit: Found some articles on blind fish and their organs, however i'm more interested in how they coordinate so well, not the organs they use, seeing how i'd like to implement it in my little robot swarm. Link:
|
[
"I don't know if this is how birds avoid collision, but schooling fish have an extra sense (I think it's called a horizontal line, but don't quote me) that even blind fish can swim in formation"
] |
[
"I'm not a biologist so take what I'm saying with the appropriate amount of salt.",
"Flocking behavior has been simulated since at least the 80's with Craig Reynolds' Boids algorithm. With a few simple rules like neighbor avoidance and alignment with local neighbor's directions, you can create very lifelike-looking flocks. Similar ideas have been used (including by myself) to control flocks of robots and UAV's. While this lends some weight to the idea that some variant of this local swarming control is used by real organisms, proving that is a bit different (and out of my area of expertise)."
] |
[
"I was listening to Richard Dawkins talk about this just the other day (in ",
"this podcast",
"). He referred specifically to 'local rules' as you mention. Although a maneuvering flock has the appearance of a hive mind, he says it is simply the result of each bird following the same set of rules, following or reacting to the birds closest to them."
] |
[
"How are modern transistors manufactured?"
] |
[
false
] |
With the current generation of GPU's and CPU's being released and talked about I keep seeing terms like 14nm and 7nm being thrown around. I sort of took this as an arbitrary number for a while and didn't think about it. However when I started doing some research, I realized that 14nm's is only ~7 silicon atoms wide. With that in mind, the NVIDIA 3080 is advertised as having 10's of billions of transistors. How is it possible to manufacture these on such scale to supply demand, and without error so that the chips actually work.
|
[
"Mostly due to advances in photolithography machines (e.g. ASML). The wavelength of the lasers used for patterning are being pushed lower, as this is one way to improve the resolution of printing the patterns to build up transistors and microchips. The latest machines are using 13nm Extreme Ultraviolet light. It is worth noting that nodes used by companies like Intel such as 14 nm, 10 nm etc are mostly marketing and normally don't relate to the actual critical dimensions of the chips"
] |
[
"Also in case it wasn't obvious to the asker: They don't make 10 billion little transistors and then put them on the chip. They make them all at once in different patterns, directly on the chip."
] |
[
"Mostly due to advances in photolithography machines (e.g. ASML)",
"Just to clarify: ASML is a leading manufacturer of photolithography machines."
] |
[
"Rupert Sheldrake - The Science Delusion @ TEDxWhitechapel | would love to see the community respond to/debunk/discuss some of these claims."
] |
[
false
] | null |
[
"At 4m 29s he talks about \"Dogma 9\"",
" about telepathic phenomena being impossible.",
"He seems to misunderstand the ",
"word dogma",
" ie an \"official system of belief or beliefs\". Science doesn't deal in beliefs and certainties, only in evidence and models and theories and probabilities.",
"Further, there have been repeated studies on telepathy, and it is ",
"regarded with extreme scepticism",
". However this is not a \"dogma\" as he uses the term. If there was good evidence then scientists would amend their view. As it stands there have been no good peer reviewed meta reviews showing clear evidence for telepathy. (As an aside - consequently it is regarded as a bit of a joke)."
] |
[
"This is the relevant TEDx video",
". He ",
"describes himself",
" as \"best known for his theory of morphic fields and morphic resonance, which leads to a vision of a living, developing universe with its own inherent memory.\" ",
"I have only just started watching his video, but I note he ",
"believes in telepathy",
", including telepathy in animals, which is a completely discredited idea. I don't want to do an ad homniem attack, but just by glancing at his website he seems to be using discredited ideas and making statements without good supporting evidence."
] |
[
"At 5m 10s he talks about Dogma 10",
" - a distinction between what he calls \"mechanistic medicine\" which scientists 'believe in' on the one hand and \"complementary and alternative medicine\" on the other.",
"I have not heard the term \"mechanistic medicine\" before, and do not think the term is widely used. There is a distinction between medicine for which there is evidence that it works; and on the other hand medicine without evidence.",
"The scientific and medical authorities tend to want to use evidence based medicine. They conduct trials and account for biases and other confounding variables and find out what works. Then they use what works. They call this ",
"\"evidence based medicine\"",
". This is because there is evidence that the treatment works.",
"The vast majority of treatments that are in the \"alternative or complimentary\" therapy group are not evidence-based in terms of their efficacy. However there are a few that are, and there is an excellent ",
"book called \"Trick or Treatment\" by Dr Simon Singh and Prof Edzard Ernst that shows which complemtary treatments are effective",
". ",
"His assertion about \"mechanistic medicine\" seems to be badly phrased and inaccurate."
] |
[
"Can we make sounds visible?"
] |
[
false
] |
Can we now or in the future film in such high definition that we could see materials vibrating due to sounds? For instance the wood of a table reverberating the sounds coming from headphones lying on top of it? I don't remember what movie it was but this supercomputer went rogue and trapped the characters inside a facility. The computer could hear their plans to escape through microphones. When they found this out, the disabled / destroyed the microphones. To be able to "hear" what they were planning, the computer reconstructed their voices through analyzing the vibrations in a cup of water. The closest example I can think of is .
|
[
"Yeah, it's pretty easy and we acousticians do it all the time for many reasons. There are a couple ways that we make sounds visible or use light to sense sound.",
"The first thing that comes to mind is high-speed video, like the one you showed of the drum. But we can actually do something similar that's visible to the naked eye using a strobe light! Dr. Dan Russell from Penn State posted a ",
"video showing the mode shapes on a drum head",
" (Warning: This video flashes) by illuminating it with a strobe light at a rate slightly different from the frequency of excitation for the drum. As I said, you can view this with the naked eye, making it a regular attraction at Science museums or science fairs.",
"Of course, those sorts of videos only show us the vibrating surface, and not the pressure waves moving through the air itself. For that, you need ",
"Schlieren Photography",
", which uses a setup with a parabolic mirror, a camera, and a razor blade to make tiny changes in refractive index visible. This is often used in fluid dynamics for things like turbulence, but here's a cool picture where you can clearly see the shockwave (a type of sound wave) ",
"coming off a gun as it's fired",
". Combining that with the aforementioned high-speed cameras gives you the ",
"same thing but in motion",
"!",
"On the more practical side is ",
"Laser Doppler Vibrometry",
". This directly uses light to measure sound waves, and is generally used when you would like to put a ",
"contact microphone",
" on something, but you either can't get at it or the presence of the mic would alter the sounds appreciably. The behavior is based on the doppler effect for light, where the frequency of the light is shifted very slightly when it reflects off a moving surface. Spy movies love this, because you can \"hear\" sounds on the other side of closed doors, walls, or even through sound-proof glass (assuming you can find something to reflect off of on the other side!)",
"Of course, the laser doppler vibrometer doesn't give you an image, but instead gives you sound. Unless, of course, you are using a ",
" laser doppler vibrometer. Here, you take vibrometry measurements at multiple points and use it to reconstruct the pressure field with a computer. Here's a really cool video ",
"showing this for a speaker",
". It's a cool video to watch all the way through, but a sidenote that I think is cool for someone who listens to music a lot is that I made a ",
"series of gifs",
" showing how high and low frequencies are distributed to the different drivers on a loudspeaker.",
"Of course, that's all to say nothing about ",
"sonoluminescence",
", which is where sound energy is actually converted into light energy! Acoustic waves repeatedly compressing a tiny air bubble in water can cause the air inside to become so hot that it releases light. The light is of a similar spectrum to Argon, which is a component of air, so this seems to be a related phenomenon to neon lights. Here's a cool ",
"minutephysics video about it",
", though I do think he makes this all sound more mysterious than it actually is. Here's a ",
"better video by an actual acoustician",
" that's at about the same conceptual level.",
"Hope you like this answer, and I'll be happy to address any follow-up questions you might have!"
] |
[
"Sorry for taking so long to reply, I wanted to find exactly the right video to show things off.",
"As for your first question, in the average living room, the vibrational modes of objects don't really matter. For the most part, sound either bounces off of objects or gets absorbed by them, so the most importance features are their shape an their material. In general, softer materials absorb more sound while harder materials reflect it. Try putting your ear next to the cushion of your couch and you'll notice that it is considerably quieter than when your head is a few inches a way. Likewise, put your ear next to a hard wall and you'll notice sounds get louder.",
"As for videos of sound moving through rooms, the best way to do that is through computational acoustics simulations. Here's a good video where someone ",
"shows off one such method",
", and there are a lot of visualizations of sounds and listening examples to show how it works."
] |
[
"This is seriously fascinating! Thank you for your answers. Now for the follow-up questions :-). ",
"We can see the mode shapes on the drum head, and vibrations of the tuning-fork in one of your videos. But how do objects, say in an average living room, vibrate and how does this influence the sound? Could it be that objects which resonate the sound create an echo? ",
"Also, more aimed at my first question, I would like to see (as in a visualization of) sound traversing a room and the effects it has on the objects within the room. Kind of like a blast from an explosion you might see in a movie. Like a combination of scanning laser doppler vibrometer with schlieren photography and high-speed video. Could we do that? Or simulate it in a CAD program? "
] |
[
"If light in a vacuum travels a Planck Distance every Planck Time, doesn't that mean that all slower objects would move less than a Planck Distance for every Planck time?"
] |
[
false
] | null |
[
"The idea of \"the universe is divided into Planck length pixels that update every Planck time\" simply isn't an aspect of modern physics. It's just a semi-common misconception."
] |
[
"They are useful because they are constructed from physical constants and not anything referenced to Earth or humans, like the SI units are. They also roughly set the scale of quantum gravity. See here: ",
"https://www.physicsforums.com/insights/hand-wavy-discussion-planck-length/"
] |
[
"So time and distance are ",
" quantized? ",
"If so, what's the meaning of the Planck Units? "
] |
[
"Do liquids float on themselves?"
] |
[
false
] |
What determines why a certain molecule of water, for example, is held above others? From my rudimentary physics knowledge, a free-body diagram of an individual molecule at the top of the container would include gravity, the force of the liquid wanting to spread out (don't know the technical term), the force of the container pushing back (creating equilibrium), and some force pushing up. What is that upward force?
|
[
"The upward force is the normal force of the molecule under it (just like how you're not falling through your chair because your chair provides a normal force that equalizes with gravity). However, water molecules are constantly moving if in a liquid.",
"Keep in mind that if you have a glass of pure water, the water molecules at the top of the glass will not be the same from one second to the next. They all move at a certain rate (depending on their temperature), and will thus move down into the glass, with other water molecules moving up to replace them. Some will even have enough energy to leave the liquid altogether (commonly known as evaporation)."
] |
[
"That's awesome! I suppose it makes sense that it would just be the molecule underneath it. Thank you very much, I really appreciate it!"
] |
[
"One more quick question: Is the density of a liquid therefore dependent on the size of the molecules themselves?"
] |
[
"Can anyone tell me why this small boulder looks like this?"
] |
[
false
] |
Found it along an old stone wall in the woods. It doesn't really look like the other rocks in the area. Has a nice wavy thing going on.
|
[
"Well, it is difficult to tell exactly from the pictures, but there would be a definite test you could do to tell exactly what it is. If you have access to some HCl or even a strong vinegar, you can drop some on a surface that you break off. If it fizzes, then it is most likely an algae mat or some biological organism that was calcified. If not, then you may be looking at some soft-sediment deformation (more likely in sands and silts). ",
"However, because of the complexity of the folding, and what may look like some other fossils within the matrix, you're looking at an algae mat. Such mats are things like ",
"stromatolites"
] |
[
"For that to be true, you'd need to have the whole rock unit folded, which is clearly isn't. "
] |
[
"the boulder is not in place. it's part of stone wall."
] |
[
"Titan squeezes and stretches as it goes along its elliptical orbit around Saturn, causing heating in its core. Is this unlimited energy, or if not, where does this energy come from?"
] |
[
false
] | null |
[
"Over time, it will break up and dissolve into a cloud of dust.",
"I would have thought that the orbit would simply decay, as that's the source of the tidal energy."
] |
[
"Physics bachelor here.",
"The answer to the question \"Is this unlimited energy\" is always no. Sometimes something looks unlimited, but that's just because we are small and live short.",
"The energy generated on Titan can be classified as \"tidal energy\". We have something like that on earth too, the tides of the ocean. We can generate energy from these tides - but it's not unlimited. In the specific case of titan, the squeezing and stretching deteriorates its structural integrity. Over time, it will break up and dissolve into a cloud of dust.",
"The energy that you can extract from titan now is basically potential energy that is slowly being converted into heat. There is a lot of potential energy in an orbiting moon, so it looks unlimited. But it's not."
] |
[
"In the specific case of titan, the squeezing and stretching deteriorates its structural integrity. Over time, it will break up and dissolve into a cloud of dust.",
"At the scale of a planet or large moon, all materials function as liquids. There is no large scale \"structural integrity\" to deteriorate.",
"The only reason it would break up would be if it lost enough energy that its orbit decayed to within the roche limit."
] |
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