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[
"Is mathematics a universal language? If so, how could we use it to communicate with another civilisation after initial contact?"
] |
[
false
] | null |
[
"This popular image",
" explains it far more quickly than I could. :)",
"In a nutshell, if you draw a right triangle with 3 dots on one side of the 90 degree angle, 4 dots on the other side, and 5 on the side connecting the two... you've just proven that you know A squared plus B squared = c squared. And the aliens will be like WHOA! The flesh creature does math!",
"Then you start mapping out a math system. From math, you can get the Periodic table. And once you have that, things get MUCH easier! A shared understanding of chemistry and physics is all you need to establish a baseline for scientific communication, and you can work out the details from there.",
"Edit: Bedtime here! Thanks for the interest. A final note to those wondering why we would need to impress them, wouldn't it be evident we're advanced, etc. That's not what this is about. It's about establishing a common language using math, not an interstellar beauty contest. Find basic concepts in common, share how they're written/drawn/expressed, establish a scientific language from there. Night!"
] |
[
"Out of curiosity, would it be possible for an alien civilization to have developed an understanding of mathematics which doesn't resemble Euclidean geometry? Could be a bit of an issue if so.",
"If you ask me, it might be best to first represent a line, square, and cube. That would probably give them a firmer grasp of where from we draw our mathematical concepts."
] |
[
"Originally Sagan intended for the humans holding hands, but soon realized that an extraterrestrial might perceive the figure as a single creature rather than two organisms.",
"This is actually pretty crazy; I don't think I would have ever caught such a small but important detail."
] |
[
"When you successfully fight off a mutated pathogen via antibodies from a previous infection/vaccination (that have reduced effectiveness, but still get the job done), does your body create updated antibodies for the mutated pathogen?"
] |
[
false
] |
This question is geared towards the Omicron Covid-19 outbreak, but really extends to the immune system in general. After receiving a booster of the Covid-19 vaccine, your body will produce antibodies targeting the original strain of the virus. Even though the potency of the antibodies against the Omicron variant is greatly diminished, this is still thought to improve your defenses against the disease. I'm particularly interested in the case where your body easily defeats an exposure to Omicron due to a large abundance of antibodies from a recent booster. Will the body bother creating updated antibodies in this case? Or will subsequent exposures still carry risk of infection, especially as the level of antibodies in your system wane over time since receiving the booster?
|
[
"Yes. This is a well-studied process called affinity maturation. Basically when you get reinfected, the white blood cells that responded to the initial infection or vaccine multiply, then each copy mutates itself slightly to produce slightly different antibodies. The antibodies with the tightest fit to the new infection are selected for and they get to multiply even more to fight the infection. ",
"https://en.m.wikipedia.org/wiki/Affinity_maturation"
] |
[
"If a mutation comes along that doesn't hospitalise people at a rate that overwhelms countries' healthcare systems then yes. Omicron is a step in that direction, but it's not there yet. If we let it circulate feely, immunuty in survivors will improve, but hundreds of thousands will die not just of the disease but because they couldn't get care for otherwise treatable problems due to hospitals being at capacity. Adapting the vaccine to the latest strain and getting good uptake is the best way out of the pandemic."
] |
[
"then get a booster a couple months later do your antibodies then revert back to how they were for the original strain?",
"They don't revert. You have a population of memory B cells (these go through affinity maturation) that recognise specific epitopes (specific parts of virus proteins), and when they get activated, they end up differentiating into antibody secreting cells. The antibodies they secrete will depend on the epitopes that lead to their activation, and epitopes will be shared between variants and the vaccine (even with omicron there are still shared epitopes)."
] |
[
"How much do our larger brains \"cost\" compared to our ancestors other closely related species?"
] |
[
false
] |
I want to get a sense of how high a "price" (in terms of additional calories required) human brains "cost" relative to those of other primates and close relatives. Do we have a sense on how much more food (if any) anatomically modern humans would have needed (beyond body size differences) relative to "Lucy" or other ancestors to grow and maintain our larger brain size. Natural history programs and articles frequently focus on changing brain size when examine human evolution. Is this as important as it is made out (i.e. modern humans have bigger brains than "Lucy" but their bodies are physically larger too.) Finally, non-scientific parenting books etc. seem to throw out statistics like "XX% of nutrition at this age is for brain growth" or "the brain uses YY% of our energy." These numbers are meaningless without context - dowe have a sense of how much energy other animals brains use? Googling this seems to unearth a wealth of useless "brain foods for babies!" type articles. Is there some google-fu for "brain-growth-nutrition-economics"? My wider curiosity (assuming humans have more "expensive" brains) is that the ever-increasing energy requirement must have represented a negative selection pressure and so some continuous benefit must have been provided as we evolved those bigger brains.
|
[
"According to ",
"this article",
" human brains use 20% of our total energy usage while our closest relatives use only 7-8%. I know its not a very good source but it's an interesting article. "
] |
[
"When you talk about the \"price\" or \"cost\" of the modern human brain, you're talking about a trade-off that relates to body size, so the two aren't really separable. Anatomically modern humans didn't evolve large brains because they were eating more food, necessarily, but food that was higher in quality and nutritionally dense. In fact, the shift to fruits and animal resources meant we didn't need to consume as much as we were when we subsisted on leaves and lower-quality vegetation. This new diet was also easier to digest and didn't require the specialized gut needed to process large amounts of leaves. The energy we saved by evolving smaller, simpler stomachs was now freed up, in a sense. This is a \"cost\" of a large brain. The increase in brain size and cognition also helped us acquire these new resources, which were harder to come by than leaves, and encouraged group sharing (e.g. hunted animals needed to be eaten before they spoiled). There are different theories about which came first, the selective force favoring increased cognition, etc. But to answer your question, yes, the large brain of anatomically modern humans is as important as it's made out to be."
] |
[
"I've seen charts/articles claiming that a house cats brain is actually more efficient in terms of power vs energy ratio, but it's totally anecdotal. "
] |
[
"[Biology] Question on Insulin Response"
] |
[
false
] |
My question is in regards to protein based insulin response. If this needs to be xposted somewhere, please let me know! I've read a bit, in my time researching more about ketosis, about how protein can also stimulate an insulin response. The only study I've been able to find is this one from 1966: It claims that it was able to generate an insulin response by INJECTING amino acids into the bloodstream. I've also read on random forum/blog posts that it'd be hard to produce the same response from physically consuming the proteins. I've been unable to find much on the subject except forum posts like this one: which have stated claims like this... "Note a complication: while dietary protein and carbs both trigger a major insulin response, protein (but not carbs) also triggers a rise in glucagon, which is antagonistic to insulin in several respects (for example, while insulin inhibits lipolysis, glucagon encourages lipolysis). For this reason (i.e., increased glucagon too), a rise in insulin due to dietary protein may have different overall effects than a rise due to dietary carbs." So I guess my targeted question(s) should be something like: Thanks in advance. Here is another SIMILAR type of thread but I was unable to find answers to the questions above:
|
[
"Insulin secretion happens when rises in blood sugar are detected; your body functions really well when it's maintained very close to 100. It isn't that consuming protein causes or doesn't cause this, but if you eat a protein-only meal, your body will need to compensate for the decrease in blood sugar in some fashion. The glucagon secreted when blood sugar drops does a lot of things, including stimulating a process called gluconeogenesis, basically the manufacture of glucose from other substances. Lipolysis is stimulated because something other than sugar may be needed to meet energy requirements, so fat starts going through beta-oxidation cycles.",
"Something to notice is what lipolysis is: the \"lysis\" part of that means destruction or cleavage, and the \"lipo\" means fat. Basically, stored fat is destroyed to produce energy. Insulin decreases lipolysis because there's enough sugar in the blood to provide energy so we've little need to waste fat energy, and increases lipogenesis, because that fat can be stored for energy uses in the future. The magnitude of insulin released seems to correlate with whether it triggers lipogenesis or not. High blood sugar-->high insulin happens in something called the \"Fed State\" (as opposed to the \"Fasting State\"), and here's a discussion of it: ",
"http://www.biochem.ucl.ac.uk/~dab/MSc%20clinbioc/MSc%20glucose%20homeostasis.pdf",
"Insulin and glucagon have mostly opposing purposes, but the effect of both is to regulate blood sugar, and when both are released, you'd see a net effect, in terms of blood sugar. Maintenance of blood sugar is interesting to look at in marathoners, because they're putting their bodies through both intense and endurance motion, and they often consume high glucose substances on their trek. ",
"http://www.medbio.info/horn/time%203-4/homeostasis_2.htm",
" This article is huge, but talks a lot about what you're asking."
] |
[
"I haven't seen an edit for sources, but are you talking about GLUT-4 in regards to the glucose being used for muscles? "
] |
[
"Does insulin release always lead to fat deposition?",
"No it does not. Insulin release is anabolic in nature in that it alerts cells that glucose is available in the bloodstream for absorption. This absorption can be done by fat cells or by muscle cells. Usually you don't get to choose which cells absorb the glucose, however you can give muscle cells a preference for the glucose absorption rather than fat cells through exercise. This is essentially the point of many nutrient timing fitness diets like carb backloading, or intermittent fasting if you want to do some further research.",
"Will edit post with links/sources soon."
] |
[
"Why don't people who've undergone major surgery wake up screaming in pain when the anesthetic has worn off?"
] |
[
false
] | null |
[
"Anaesthesia is distinct from analgesia (pain relief). Most general anaesthetic agents (with the exception of ketamine and nitrous oxide) have no analgesic properties.",
"If you are undergoing a painful procedure you will be administered analgesia before and during the procedure. This will usually be a combination of paracetamol (acetaminophen), non steroidal anti-inflammatory drugs and opiates.",
"This is not simply humanitarian (though it is that). While under an anaesthetic your body will still have a stress response to pain, and reducing this with pain relief improves surgical outcomes, and reduced other complications such as chest infections.",
"Your anaesthetist will aim to give you enough pain relief intra-operatively that you wake up comfortable or in minimal pain.",
"Use of regional anaesthetic techniques (local anaesthetic applied to nerves supplying the area of the body to be operated on) will achieve the same thing and means you can avoid the side effects associated with systemic opiates.",
"Source: Anaesthetist (or anesthesiologist if you prefer)"
] |
[
"It depends on the type of surgery as well. There are some parts of your body that don't have pain receptors and the pain you feel waking up would be due to the path the surgeon took to get there, dissecting tissues. This is why the recovery time for laparoscopic surgery is so quick.",
"Also, regional nerve blocks can be done, so that everything \"down stream\" of the nerve is numb for hours after the surgery. So, after you wake up and get pain medication and the general anesthetic wears off, the leg or shoulder that was worked on gradually regains feeling and then it hurts."
] |
[
"Much of the digestive system and supporting organs (kidneys, bladder) Discerning the exact location of an upset in your intestine is almost impossible, unlike your skin where you have a precise mental map for every centimetre of it. Of course you can have pains associated with them, but a surgical cut or stitch could not be discerned from general malaise or dysfunction."
] |
[
"How can timing of meals effect weight-loss or gain? If calories in < calories out, wouldn't you have to lose weight or violate the 1st law of thermodynamics?"
] |
[
false
] | null |
[
"Edit: wow I hate when I spend a long time writing an explanation to help someone, and they delete their question before I can post...",
"If it raises body temperature, it should increase calorie consumption. That energy must come from somewhere!",
"Trying my best to avoid jargon, and frankly things are more complicated than a Time Magazine article meant for general readership makes them out to be: ",
"The body needs to break down food into forms of energy it can use. This is generally a stepwise process. The energy transfers between the various steps are not lossless, and most of the energy that is lost dissipates as heat energy that is used to keep the body warm. The outside temperature is lower at night. When the body needs extra heat, it has a few mechanisms of ",
"thermogenesis",
". These mechanisms also use chemical energy (calories from food) to create heat used to keep the body warm. If you don't eat before bedtime, your body will use previously-stored calories to do this. If you eat right before bedtime, you will have plenty of heat (resulting from breaking down the calories you just ate) and you won't need to use your stored calories. ",
"So you and the article are both right: the energy for raising body temperature has to come from somewhere, and if you want it to come from burning fat stores at night instead of from the food you ate at 11PM, you shouldn't eat late at night. The same is true during the day, but the point the article is getting at is that sleeping is basically free fat-burning since you aren't taking in any calories while you sleep (with the exception of people who suffer from ",
"NSRED",
"). And also that eating during the day gives you a better chance of burning off any calories that you overate with your daily activities and exercise.",
"The other point the article makes is in regards to the hormonal regulations that are affecting your body's use of energy. Since the article didn't explain anything, I'll give some simplified cliffsnotes:",
"At night, levels of growth hormone normally rise in response to low blood sugar. If you've eaten late at night, your blood sugars won't be as low and growth hormone levels will be suppressed. Growth hormone promotes fat breakdown, protein buildup, and a lot of other things that humans generally want for themselves.",
"Thyroid releasing hormone levels increase when the hypothalamus is signaled that you are cold (and signaled about a lot of other things, too). This leads to TSH release, which leads to thyroid hormone release. Thyroid hormone leads to (among other things) increased fat breakdown, and increased energy-wasting in every cell due to upregulation of the sodium-potassium pump (which uses ATP energy to run) and extra loss of heat energy during the reactions of the electron transport chain.",
"Insulin and glucagon. Insulin opposes the actions of glucagon (and suppresses growth hormone). If you eat late at night, your insulin levels will be higher and your levels of both glucagon and growth hormone will be lower; if your insulin levels are higher, your body will try to store fat and protein instead of breaking them down to use as energy.",
"If you want all these hormones (and more that I don't have time to explain) to work in your favor all night long while you should normally be sleeping and not taking in any calories, all you have to do is not eat before falling asleep."
] |
[
"In technical terms, it is actually just as simple as that. The problem is that this is a completely useless bit of information in practical terms and can be very misleading when someone tries to apply it to weight loss.",
"The first law of thermodynamics only applies to closed systems. The human body is anything but a closed system - every time you eat, breathe in, breathe out, move, sweat, or simply exist, energy is moving in and out of your body.",
"Things such as meal timing, exercise, and the composition of what you are consuming (Protein, carbohydrates, and fat. But also vitamins in many ways) can have an effect on how your body uses the calories that it takes in. For example, consuming more protein might signal your body to create (or preserve, if losing weight) more muscle than fat. This muscle will generally consume more calories in the long run than the fat would, and these calories will leave your body as waste heat. The hormonal balance of your body plays an extremely large part in determining this, and that balance is affected by everything - calories consumed, the type of calories consumed, vitamins, exercise, your social status and mental state, how sunny it is, etc.",
"So in this way, calories in -> calories out is technically true. The part that is usually left out, and which makes the statement mostly useless, is that the type of calories taken in will affect the amount of calories that go out."
] |
[
"In our bodies, it is not as simple as calorie in, calorie out. The method we store it, are we metabolising all of it, the method of metabolism all control how efficiently we are making use of energy.",
"EDIT: I'm not talking about breaking thermo. I'm talking about about all calories we eat go the same way."
] |
[
"What is the feeling of an asleep body part? And why does there seem to be different stages? (Needles, Tickling, etc..)"
] |
[
false
] | null |
[
"There is a fatty lining surrounding your nerves called myelin that helps conduct and smooth messages (sensory feelings) as they pass to your brain. When you \"kink\" a nerve, or disrupt this lining, the signal passing along the nerve is garbled and your brain gets a signal or feeling of numbness or tingling. "
] |
[
"To expand on ",
"/u/StraydogJackson",
" 's response, we have 3 different \"types\" of nerve axons - AB [A-Beta], Ad [A-delta], and c. AB axons are able to pass signals the fastest, while c type axons are the slowest.\nAB-type axons are closely related to the sense touch;",
"Ad axons are closely related to temperature;",
"And c axons are closely related to pain.",
"So, when a part of our body begins to \"fall asleep\" aka we put pressure on a nerve, AB axons disappear first, then Ad, then c. When the pressure is removed, the reverse happens: aka c type axons activate first - this is the pins and needles feeling. Ad are next, which explains why the body part feels \"warm\" or \"cold\". Last are the AB type axons, which allows us to actually be able to \"feel\"/touch with that body part. Pretty quite interesting actually.",
"Also, the opposite is true when we put cocaine/lidocaine, -aine type products on our skin. C type axons \"disappear\" first (pain), followed by temperature, then finally touch. This is why at the dentist you may not feel pain 45 minutes into your procedure, but you can feel pressure and slowly start to feel temperature - warning signs that pain is coming next.",
"EDIT: added the cocaine part for extra fun."
] |
[
"Follow up question, does hitting the asleep limb or limps help at all?"
] |
[
"Diet coke freezes when opened"
] |
[
false
] | null |
[
"Sorry for the generic wiki link, but this process is called super cooling:",
"http://en.wikipedia.org/wiki/Supercooling",
"A similar thing can happen at the hotter end of the scale too:",
"http://en.wikipedia.org/wiki/Superheating"
] |
[
"This video",
" explains it a bit.",
"The same can happen with beer. If you cool a beer in the freezer and it feels too cold when you take it out, it might freeze when you open it or jostle it. Take it out of the freezer and gently put it on the counter til it warms up and you should avoid the flash freezing."
] |
[
"That's really cool, thanks for the info! I didn't realize you could supercool liquids."
] |
[
"Is biological uranium enrichment feasible?"
] |
[
false
] |
Modern uranium enrichment seems to be done almost entirely with centrifuges or the gaseous diffusion method (occasionally I've heard of laser-based methods as well). These all seem to use extreme amounts of power to run. Non-radioactive heavy water is known to kill eukaryotes in high concentrations, so there is obviously a cellular mechanism that behaves differently when subjected to different isotopes. So, would it be possible to engineer bacteria to do something like selectively reduce uranyl sulfate to uranium metal for only one isotope? I realize that the percent difference in weight is much smaller for U-235/U-238 vs. H-1/H-2, but if natural organisms can have a coincidental selective response to hydrogen isotopes, I wonder if intentional design could produce something even more selective that is more efficient than existing methods of uranium enrichment. (I'm not sure if this the flair for this should be biology or physics...)
|
[
"Plants are capable of fractionating copper",
", which is about 4 times heavier than oxygen, but uranium is about 4 times heavier than copper, and the change in relative abundance of ",
"Cu and ",
"Cu in plants was less than 1%. For light water reactors, the relative abundance of ",
"U is increased from about 0.7% to about 3%, so I guess it might be possible that several cycles of biological enriching could produce usable nuclear fuel, but I'm skeptical."
] |
[
"There is a project at Oak Ridge National Lab where they are working with bacteria that can bioaccumulate uranium, but I don't think they have any ability to discriminate isotopes. It is more of a bacterial toxic waste clesn-up kind of project."
] |
[
"Your chemistry teacher told you that different isotopes of the same element behave exactly the same. That is one of the many, many white lies in introductory chemistry; they're very close but not exact.",
"Boiling heavy water takes slightly more energy just because the water molecules are heavier, which is neat because it lets you do all kinds of isotope studies. The bonds heavy hydrogen forms are also very slightly harder to break, and many proteins rely on hydrogen bonds to hold them together and acquire the right shape. ",
"More here.",
"You will observe similar things with oxygen-16 vs oxygen-18, but less so because oxygen-18 is 1/8th heavier than its common twin while deuterium is twice as heavy as hydrogen. If you get to U-238 vs U-235 the difference is really, really small. "
] |
[
"Why do Warm/Hot showers still feel refreshing(cooling) even if you are really hot from the heat outside?"
] |
[
false
] |
[deleted]
|
[
"Thermometer time.",
"Maybe you just get high off of near-death experiences."
] |
[
"They don't. I can't stand them when I am physically hot."
] |
[
"It could be that your definition of a hot shower is still cooler than your body temperature. In this case, you could still radiate heat without immediate vasoconstriction. I am however just thinking out loud and a little wikipedia-ing tells me that water is often heated to temperatures upwards of 120 degrees Fahrenheit, so this theory could be completely wrong."
] |
[
"If time can warp and curve, does that mean that on different planets time is not the same as it is on Earth?"
] |
[
false
] |
[deleted]
|
[
"Apparently atomic clocks these days are good enough that the people at the national labs at Maryland and Colorado have to take into account the fact that one lab is in a basement, and the other on the second floor (because gravity gets weaker as you move away from the center of the Earth). Atomic clock times are also influenced by the gravitation form the huge mountains around the lab in Colorado.",
"So yea, there would be a very noticeable difference, by atomic clock standards, between places on say, Earth and Jupiter.",
"Discussed in Episode 4 of ",
"this series",
"."
] |
[
"Even if the difference was big enough, you wouldn't ever perceive the difference unless you had something to measure it relative to, though. "
] |
[
"by atomic clock standards",
"Though I feel compelled to clarify: That doesn't mean there'd be any sort of perceptible difference on human timescales."
] |
[
"Could TV signals be used as an Internet Connection?"
] |
[
false
] |
I was wondering earlier: could TV satellite signals be used as a connection to transfer data to your computer? The speed that a satellite signal must work at must be astounding, because it can stream HD signals in seconds. Couldn't that same technology be adapted to offer the same connection as a router or modem would? Can that satellite signal even do such a thing, and are they in anyway similar?
|
[
" But I am an IT Systems Admin.",
"I was wondering earlier: could TV satellite signals be used as a connection to transfer data to your computer?",
"Yes. ",
"http://www.wildblue.com/",
" But current technology in use requires that have dial-up in order to upload (e.g. tell the DNS server which website you want to see). Also latency is much higher 500–700 ms one way (the delay between requesting data and the response). It would totally suck if you like real time multiplayer games.",
"There are satellite dishes you can use to upload data, but they are very expensive. ",
"http://www.astra2connect.com/",
"The speed that a satellite signal must work at must be astounding, because it can stream HD signals in seconds.",
"It's impressive. But its heavily compressed with loss of data, so it isn't as amazing as we might like.",
"Couldn't that same technology be adapted to offer the same connection as a router or modem would?",
"I guess, but the high latency makes it impractical for such purposes unless you are on a boat, in rural areas and don't have access to cell towers or the Plain Old Telephone System (POTS).",
"Can that satellite signal even do such a thing, and are they in anyway similar?",
"Well the satellite is just redirecting your Internet requests so it has router functionality.",
"Oh & by the way, at one point they did offer broadband Internet over land based TV airwaves, but you still needed a dial up modem to upload your requests. It didn't work out because it wasn't cost competitive with DSL or cable Internet.",
"It looks like there are still attempts being made to make it work.",
"http://www.msnbc.msn.com/id/22728557/ns/technology_and_science-internet/t/fcc-will-test-internet-over-tv-airwaves/"
] |
[
"I might be wrong but I think satellites have a limited bandwidth. TV shows are all pushed out at once this is why you can not get on demand on satellite.The internet is on demand because you load a web page when you want. Satellite internet is available for places like Antarctica but its slow and crazily expensive and the ping is bad.\n",
"http://en.wikipedia.org/wiki/Satellite_Internet_access"
] |
[
"It's important to note the difference between broadcast and unicast. Broadcast means there is one source and many destinations, unicast means there is one source and one destination. Television signals (ignoring on-demand services) are broadcast, and because of this they are extremely efficient. The satellite signal only has to transmit one copy of each channel, which is received by anyone with a dish. TCP/IP and the internet in general is a unicast medium, which means that for example if 20 separate people visit a website, 20 separate connections must be established and that website's server must push out 20 separate copies of the page, even if it's the same for every visitor.",
"If a certain satellite band has, say, 50 megabits/s of bandwidth then that must be shared between all users of the service. If there are 10,000 subscribers then each will only have 5 kilobit/s of bandwidth. Things are not quite that grim because access tends to be bursty, which means that users aren't using their entire allotment constantly. For example, if each of those 10,000 subscribers only needed to actively receive data for one minute out of each hour then they'd each effectively have 300 kilobits/s during that period. But compare this to broadcast, where all 10,000 subscribers can receive the full 50 megabits/s all the time and you see how much more efficient broadcast is compared to unicast.",
"So, satellites are very well suited to broadcast media and very poorly suited to unicast media. Most implementations of satellite internet access are extremely slow. On top of the multiplex issue, satellite communications are unidirectional, i.e. you can only receive. In order to send you have to have some other channel such as a dial-up modem.",
"Satellite latency is also horrid, because the satellites must be in geosynchronous orbit which is approx. 36,000 km (22,000 miles) above Earth. And every signal has to make that trip twice, once up and once back, so even at the speed of light it takes a significant amount of time to send data 72,000 km (44,000 miles) -- about half a second."
] |
[
"Why can't particles have defined position/velocity before they are measured according to the Copenhagen interpretation?"
] |
[
false
] |
[deleted]
|
[
"You are talking about something called 'hidden variables'. Basically, this is the idea that particles ",
" have well defined properties like position and velocity, but that we just can't measure them for some reason.",
"There is something called \"",
"Bells theorem",
"\", which tells you that you can have ONE of the following be true, but not both:",
"1) Particles have well defined, yet hidden properties",
"\n2) Particle interactions propagate normally -- no instantaneous effects.",
"According to this theorem, if you want to invoke hidden variables, you also have to accept the fact that particles separated by an entire Universe can affect each other instantaneously -- \"spooky action at a distance\". "
] |
[
"I see you're trying to do the LaTeX – using 2 -'s. Tip: hold Alt and press - and you shall have a –"
] |
[
"Aah, thanks :) "
] |
[
"question about calories in protein"
] |
[
false
] |
protein has 4 calories per gram, however when we eat, for example, 30 grams of protein in one day (less than RDI), all of the protein is broken down to amino acids which are used by the cells to make more protein. does it still give 120 calories, even if the protein is broken down to be remade into new proteins? or does the body only reuse essential amino acids, and turn the rest into energy?
|
[
"A calorie is simply a unit of energy. 120 calories is always 120 calories. The way your body uses that energy and the amino acid substrates can be complex. Just because you eat less than the RDI of protein doesn't mean your body uses that protein to synthesize new protein. Amino acids are used for many functions in the body, including synthesis of glucose."
] |
[
"120 calories is always 120 calories.",
"Thermogenesis"
] |
[
"not sure about your main question but excess amino acids are converted into organic acids via the ornithine cycle in the liver.",
"also see ",
"this",
" on the calories in food phenomenon."
] |
[
"What determines how gases are transported?"
] |
[
false
] | null |
[
"Hi tubob 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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" 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.",
" ",
" "
] |
[
"'Chemistry'"
] |
[
"Chemistry"
] |
[
"Have we found a galaxy that doesn't have a black hole at the center?"
] |
[
false
] |
[deleted]
|
[
"I don't think we've found one in M33, and it's in the local group so it's close enough that we can get good measurements. For disc galaxies with black holes, the rotation speed of stars and gas goes up as you get closer to the black hole. We don't see that in M33.",
"Edit: Any particular reason for the curiosity? I'm down for follow-up questions :)"
] |
[
"nah, black holes have a lot of mass in a very small space. If all of the mass of the Milky Way was in a black hole, that black hole would be smaller than the distance between the Sun and the next closest star (I get about 0.1 light years). The central supermassive black hole is not going to be nearly that big (ours is actually not growing very fast at all), so it'll never get close to consuming a large portion of our galaxy."
] |
[
"It only deviates from classical gravity if you're close (like <10 Schwartzchild radii) or you're ",
" concerned with being precise down to large numbers of significant figures."
] |
[
"On a ventilator, you can increase the respiratory rate to decrease body CO2, but this doesn't increase oxygen since CO2 diffuses more readily in the lungs. Why does CO2 diffuse faster than oxygen?"
] |
[
false
] | null |
[
"CO2 diffuses out of lungs because the gradient of diffusion is high in blood, low in lungs. The diffusion constant for CO2 is much higher compared to O2. Henry’s law states that diffusion into /out a liquid depend on partial pressure and diff. constant. Thus CO2 goes out faster even at lower partial pressures. The amount of oxygen diffusing is limited by the relative lower concentration gradient.partial pressures for CO2 is 40 mm Hg in blood, 45 mm Hg in lungs. For oxygen it is 100 and 159 mm Hg. But again, CO2 has a much higher diffusion constant."
] |
[
"Most of the oxygen carried by the blood is bound to hemoglobin, found within the red blood cells. While carbon dioxide can also bind to hemoglobin, most (85%) is transported as part of the bicarbonate buffer system - an additional storage mechanism for CO2 that's not used for oxygen. So a red blood cell can both \"store\" more CO2 than O2, and take up the CO2 faster using the (fast) bicarbonate uptake pathway."
] |
[
"This is the answer. While everybody else is correct about diffusion constants and solubility and all that physics, the answer is physiological. In short, it’s due to the different proportions of each that bind to haemoglobin."
] |
[
"What is actually happening when you put metal in a microwave?"
] |
[
false
] |
It's pretty self explanatory really. I think it could be down to the particles gaining energy but I'm probably wrong. Any other interesting un-microwavable object science is welcome (I think tea lights make plasma).
|
[
"Microwaves are below the plasma frequency of metals (that's the resonant frequency above which the electrons cannot respond rapidly enough to the oscillating EM fields (radiation) so the metal simply becomes transparent) and so what is happening is that the electrons in the metal oscillate due to the incident radiation and essentially block the radiation from being transmitted into the metal.",
"As energy must be conserved this means that a large fraction of the radiation is reflected - metal is an excellent reflector of microwaves. This is why there is a metal grid in the glass - the holes in the grid may seem large but they are small with respect to the wavelength of microwaves and so the microwaves see it as one medium and are strongly reflected by the grid, however visible light can still pass through the holes allowing you to watch your food or tea lights or whatever the hell you are putting in your microwave :P",
"Obviously some of the incident radiation may be dissipated as heat but in general metals are very good reflectors in that regime.",
"(I'm pretty sure this is somewhat correct as I'm studying for an EM exam atm, so I hope it is, but it's quite late and I've been studying all day so I could be wrong and welcome any corrections)"
] |
[
"http://en.wikipedia.org/wiki/Microwave_oven#Metal_objects"
] |
[
"I understand that a certain fraction of the microwave energy is absorbed by metals, which accounts for the heating, but you haven't addressed why (some) metallic objects cause electrical arcs. Why is this?",
"I accidentally microwaved a plastic pot of rice pudding with some aluminium foil still on it, and it sparked brightly before setting fire to the pot whereupon I noticed and turned off the microwave.",
"However, another time I microwaved a dish of wet rice with a steel fork partway in it. No harm came of this. The rice cooked normally, and the fork along with its plastic handle was unharmed and not even hot to the touch. I assume this was because the tynes of the fork were stuck in the wet, salty rice which somehow conducted heat or current away from it and distributed it into the rice.",
"Why did the tiny speck of foil arc and heat up in the first accident, but the steel fork did not in the second?"
] |
[
"How is infrared radiation translated into vibrational energy in an atom?"
] |
[
false
] |
[deleted]
|
[
"I'll give this a shot.",
"The first thing you are missing is what is happening in the fundamental interaction between light and matter. Lets group everything into 2 categories: resonant interactions, non-resonant (scattering).",
"Nearly all of these interactions are subject to ",
"Fermi's golden rule",
" or ",
"this",
", where the hamiltonian H is going to the ",
"transition dipole operator",
". I am really skipping over some stuff here (I can go deeper if you like) but what this describes is effectively the probability that some light (E/M field) will interact with the electric or magnetic fields of a molecule and change it.",
"Non resonant interactions are a little special in that they do not exist in a bound state and can thus interact with all frequencies of light independently. However they do have a probilbity of interaction that is inversely proportional to the wavelength of light (shorter wavelengths are more likely to scatter), directly proportional to the polarizability of the object, and the scattering crossection.",
"Now inside of a molecule lets look at all of its degress of freedom. Translational, rotational(magnetic nuclear, and pure rotational), vibrational, and electronic.",
"\nTranslational can couple to light in a non resonant interaction as you infared earlier. Radiation pressure can exert a force on the electric field of the atom/molecule and physically move it (think optical tweezers).",
"General scattering is non resonant as well and can be broken down into elastic and non elastic events. Elastic is simply bounces off leaving the internal energy of a molecule the same. Inelastic events (raman, compton, mie, rayleigh....) leave some energy behind and allow for excitation of internal modes of an atom/molecule depending on the energy left. Scattering can excite any and all of the above degrees of freedom.",
"Here is the first thing you really have to remember. I mentioned fermis golden rule earlier. The frequency of light is going to need to be on the order of the timescale of the molecular motion in order to couple and interact.",
"NOTE: All higher order types (electronic > vibrational > rotational) can interact with all of the lower energy types of modes in their interactions due to selection rules. i.e. A vibrational mode (P/R branch) WILL change the rotational energies of a molecule as well.",
"Timescale: > picoseconds",
"Here molecules can rotate end over end in all 3 dimensions, or nuclear/electron spins can change their orientation in the lab axis in a magnetic field.",
"Individual atoms do not have pure rotational modes due to symmetry (all permutations in the internal axis and lab axis are indistinguishable outside of the nucleus).",
"Individual atoms DO allow for magnetic dipole interactions with nuclei (nuclear orientations are distinguishable in the lab axis). ",
"Molecules allow for pure rotational modes though it gets tricky as symmetric molecules are transition dipole forbidden.",
"Here atoms rapidly change their distance in relation to one another through intramolecular bending and stretching.",
"Timescale: < picoseconds to femtoseconds",
"Individual atoms do not have pure vibrational modes due to, well there is nothing to vibrate. Bulk condensed phase atoms DO have vibrations but they are no longer \"just atoms\"; instead we think of them more as a big molecule all made up of the same atom.",
"Molecules now have a vibrational spectrum both in internal modes and in the condensed phase.",
"Timescale: attoseconds",
"Anything that has an electron can work here, atoms or molecules.",
"l <1m",
"Most often will interact with nuclear spins, can also interact with very heavy molecular rotations.",
"1m < l <0.01cm ",
"Most often will interact with molecular rotations, can also interact with some nuclear spins, interacts with electron spins (EPR). Can interact with vibrations in the low THz. Phonon mode interaction as well.",
"0.01cm < l < 700nm",
"Primarily interacts with vibrational modes, phonon modes, and very low energy electronic states.",
"*",
"700nm < l < 400nm",
"Interacts almost solely through electronic interactions. High energy near IR transitions can be excited as well. Used often in Raman spectroscopy for vibrational scattering spectra.",
"** UV and up**",
"Exclusively electronic."
] |
[
"No, I'm not saying that. There are atomic transition lines in the infrared. The entire hydrogen ",
"Paschen series",
", for example."
] |
[
"No, I'm not saying that. There are atomic transition lines in the infrared. The entire hydrogen ",
"Paschen series",
", for example."
] |
[
"If we can discharge excess voltage into the Earth whenever we need to, why can't we draw a steady supply of electricity from the Earth in a similar way?"
] |
[
false
] | null |
[
"For the same reason that you can take a very hot (or very cold) object and put it in a large bath of water to bring it to room temperature, but that you can't take a room-temperature bath and use it to make something hot. You can, of course, draw a steady supply of charge from the Earth, it just costs energy to do so, just like it costs energy to pump heat outside of your refrigerator."
] |
[
"The earth is a infinite source of current, but in order to draw that current you need a potential difference which takes energy.",
"Imagine the earth as a huge reservoir at sea level, but you want to take the water to the top of a mountain so it can run down and run a turbine. That takes energy. ",
"Electricity is the same thing, but the mountain is a higher state of voltage. "
] |
[
"In the Earth there are a lot of charges moving around going nuts, some are formed from essentially friction so you get more free electrons in one region for example. How big that net positive number of electrons or any free charge I don't know the magnitude of so I'll make a slightly different argument which I think holds.",
"The earth is massive, so any slight fluctuation / excess in electric charge (due to an excess of charged particles somewhere) is so smeared out across the entirety of the earth - enough that the Earth can forever be considered neutral (quasineutral) - that any charge we might have - say in a charged up jumper, a van de graff generator, static build up etc, has a massive charge density comparatively. The large charge density therefore wants to equalise with the relatively negligible charge density of the earth, so the excess charge gets dissipated into the earth - electrons will flow either to or from the earth depending on the sign of the charge.",
"\nWe can't draw electricity from the Earth because then we would be drawing on a basically 0 charge density. To do so would probably require more energy than the amount stored as excess charge in the Earth. ",
"",
"Hope that made some sense!"
] |
[
"What stops black holes from collapsing in on themself?"
] |
[
false
] |
[deleted]
|
[
"Nothing stops it from collapsing. Time itself gets slowed down so much at the event horizon that it takes an infinite amount of time for it to finish collapsing, as observed by an distant, external, observer. But it still just keeps on collapsing. So it's not that there is a wall or anything. Time is just so slowed down near the event horizon that everything looks effectively frozen to an external observer."
] |
[
"The opposite, actually. The black hole will collapse and anybody who falls into it will experience time as they fall in, and reach the singularity in some finite amount of time. But anybody far away from the black hole will not observe this, from a distance the black hole looks frozen and light from anything falling into it is redshifted to the point of no longer being visible ",
" they fall in. So from outside it looks like whatever is falling in has slowed and stopped (but you can't see it frozen because the light it emits has been stretched to the point that it is not detectable) but falling in you don't feel anything particularly strange. (until the difference in gravity between your head and feet rips you apart at least)"
] |
[
"The opposite, actually. The black hole will collapse and anybody who falls into it will experience time as they fall in, and reach the singularity in some finite amount of time. But anybody far away from the black hole will not observe this, from a distance the black hole looks frozen and light from anything falling into it is redshifted to the point of no longer being visible ",
" they fall in. So from outside it looks like whatever is falling in has slowed and stopped (but you can't see it frozen because the light it emits has been stretched to the point that it is not detectable) but falling in you don't feel anything particularly strange. (until the difference in gravity between your head and feet rips you apart at least)"
] |
[
"Questions about the climate change debate between Bill Nye and Marsha Blackburn? Ask our panelists here!"
] |
[
false
] |
This Sunday, NBC's will be hosting Bill Nye and , the Vice Chair of the House Energy and Commerce Committee, for a . airs at 10am for most of the east coast of the US. or in your local listings. The show is also rebroadcast during the day. The segment is now . While this is a departure from our typical format, a few rules apply:
|
[
"For those that missed it, you can watch ",
"here",
" it's only 13mins and is less of a debate than two people making fairly random statements. There was no actual debate between the two",
"It was disappointing that the congresswoman was actively attempting to mislead viewers and that she was more or less allowed free-reign to do so and there was little chance to rebut these inaccurate or misleading statements.",
"My question then, is what rebuttals would ",
"/r/askscience",
" have given if they were allowed the opportunity?"
] |
[
"Why does one side of the debate get a scientist and the other a politician? Why couldn't they find one of the scientists that has an opposing view of climate change? Why am I asking reddit about this?"
] |
[
"In the USA, carbon monoxide pollution has been greatly reduced through the introduction of catalytic converters in automobiles which happened in the 1980s.",
"As to CO2, there simply aren't enough trees on the planet to absorb the amount of fossil-fuel carbon we are burning. If the trees and other vegetation could act as an effective 'sponge' they would already have been doing so and we wouldn't have had the large increase in atmospheric CO2 concentrations which has been observed. If we increased the number of trees on the planet by 10 or 20 times, maybe that would work but there isn't any place to plant those trees, nor the water to support their growth."
] |
[
"Are some people consistently more responsive to placebos than others?"
] |
[
false
] |
If I'm not mistaken, placebos generally work because we believe that the treatment we're receiving will have an effect, and so our minds are tricked into actually producing an effect in line with our expectations. So I'm wondering if people who tend to be more skeptical, especially in regards to medicine being effective, will more consistently have less of a response to placebos. Or if perhaps there could be other factors like genetics that affect how we respond to placebos.
|
[
"Humorously enough, hypochondriacs respond strongly to placebos acutely. Also in my experience elite athletes tend to respond very strongly to them, some aspect of their psyche makes them desire performance so much that they can get it from almost anywhere (a lot of athletes aren't especially bright either.) It's painful being an exercise physiologist and telling an athlete you're working with to keep wearing their power balance band because you know they'll probably perform better if they hear an expert tell them that they will."
] |
[
"Very true, but the magnitude of the effect can be increased by 'talking up' the substance or decreased by saying its a placebo or that you don't think it will work. Additionally placebo effects can sometimes be harmful, it has been called the 'nocebo' effect by some. For example a patient who is scared to death to take an antidepressant due to all the side effects they have heard about is more likely to experience those side effects."
] |
[
"Do you have any evidence for either A) placebo effect depends on intelligence B) Most athletes aren't that bright"
] |
[
"Can the earth's rotation generate electricity?"
] |
[
false
] |
This question touches upon physics and earth/planetary science... Since we know: - the earth has magnetic properties - the earth spins on its N/S axis Could a large piece of copper metal coil, perhaps connected to a space station, rotate the earth along the N/S plane and thus generate electricity passively?
|
[
"Technically yes, though it's an extremely small amount. Some cubesats use an attitude control system called a ",
"Magnetorquer",
", which uses Earth's magnetic field to reorient the craft. In that article they also mention:",
"Any spinning satellite made of a conductive material will lose rotational momentum in Earth's magnetic field due to generation of eddy currents in its body and the corresponding braking force proportional to its spin rate."
] |
[
"Also the period of rotation is a whole day. That kind of frequency doesn't play nice with AC power systems.",
"The kind of infrastructure you'd need to capture that power would consist of DC/DC converters, inverters, and high voltage series capacitors. The cost-benefit is upside down."
] |
[
"Sure. Easy! ",
"All you need is the patented Siemens Air Hook. ",
"Fix to any point above the earth's surface and connect a line to it, so that the line pulls on the axis of a generator and makes it turn. ",
"All the comments here talking about satellites are just as non-sensical: It is not the earth's movement, it is the movement of the satellites that provides the power, slowing it down in the process. ",
"Energy NEVER comes from nothing. You can only exchange one form of energy into another... or do the old E=mc2 trick and turn mass into energy. ",
"If you 'could' connect your rod to a space station, the energy would be taken from that very station. ",
"And of course, there already IS a way the earth's rotation provides us with ample power: in the form of wind. You could also harvest the temp difference between night and day, though that is less efficient."
] |
[
"Quasars and Radio Galaxies?"
] |
[
false
] |
I just want to know what is the difference between a quasar and radio galaxy. I know the formation of them but I also want the differences. Do Quasar also have radio jets/plumes coming out like radio galaxies? and since they are billion light years away, are they at a dying stage right now?
|
[
"These days, a radio galaxy and a quasar are pretty synonymous- the term \"radio galaxy\" is more from back in the day when they didn't quite know what these class of objects were, and if all radio galaxies were quasars.",
"Quasars are by this point also observable in non-radio frequencies, such as in the X-Ray and in the optical, so we now know they are not radio-exclusive objects. In fact, quasars with jets tend to be brighter in the X-ray! It's believed the strong radio emission from quasars/ radio galaxies come from jets, yes.",
"As for the dying stage, these days we know all decent-sized galaxies have a supermassive black hole in them, but all the ones nearest us are silent (ie not quasar-like), so people think most quasars run out of material compared to the early universe yes. You can spark/reignite a new quasar by giving it more material though- some have speculated that when the Milky Way and Andromeda collide in a few years later, material that falls onto the black holes at their centers will reignite the quasar."
] |
[
"Drat, sorry, wrong phrase- edited! Thanks for the catch!"
] |
[
"What would a quasar do to the habitability of our galaxy?"
] |
[
"What's the deal with poison ivy?"
] |
[
false
] |
And other similar topically-toxic plants. Is there any good adaptive expanation for this trait? How does being so awful help the poison ivy to survive? Do animals suffer its effects? And do animals show any behavioural evidence of "knowing of or "learning from" its effects?
|
[
"That's actually a good question. I had assumed that the urushiol in poison ivy (the substance that causes the itchiness) is irritating to other animals, and that it therefore acts as a deterrent to browsing, but that doesn't seem to be the case. Although there are apparently cases of dogs being affected by poison ivy, and ",
"mice can be affected experimentally",
", for many species it doesn't seem to be a big deal, and herbivores like deer are apparently very happy to eat poison ivy. Urushiol seems to be mainly toxic for primates, which doesn't seem like a very well targeted defense system.",
"So it seems likely that the irritant effect of urushiol is a coincidence. Why does poison ivy produce it, then? One possible explanation is that t's to protect the plants against bacterial infection. Urushiol has antimicrobial properties (for example, ",
"Antibacterial Effects of the Urushiol Component in the Sap of the Lacquer Tree (Rhus verniciflua Stokes) on Helicobacter pylori",
" and ",
"Antibacterial capacity of cavity disinfectants against Streptococcus mutans and their effects on shear bond strength of a self-etch adhesive.",
"), and that fits with the way it's used by the plants -- oozing out in large amounts after the plant is broken, which would reduce bacterial infection of the damaged area.",
"Is it an incredible coincidence that an antimicrobial plant compound causes irritation in humans? Humans can have irritations due to a similar mechanism from things like nickel (e.g. ",
"Systemic Contact Dermatitis to Foods: Nickel, BOP, and More",
") and no one would say that nickel has evolved for any particular toxic reason. The response to urushiol is an immune response, and immunity is constantly on the knife edge between over- and underreacting all the time, so this may just be a case where the immune hair trigger is a little too sensitive.",
"Purely speculation, but I wonder if the reactivity of urushiol that allows it to react with human skin proteins is part of its antimicrobial activity, so that the two effects go hand in hand. (On the other hand, apparently there's been some work making non-irritant versions of urushiol that still have antimicrobial effects (",
"Antimicrobial activity of the synthesized non-allergenic urushiol derivatives",
", so it's not an absolutely required function.)"
] |
[
"Good answer, immunological brother-in-arms! ",
"Urushiol is a very interesting molecule. There are many theories as to why some animals are reactive and why others aren't. To understand that a bit further we have to know how urushiol works.",
"Urushiol is a very small molecule called a hapten. Because of its size, it can pass freely through the outer coatings of our skin and enter the body. A hapten on its own is invisible to the immune system, for the most part. Generally, its too small to induce an immune response on its own. Many haptens, urushiol included, like to hijack our own proteins. This process, known as ",
", results in many hapten molecules binding to large molecules that we naturally have. Our immune system is incredible at knowing what proteins are a part of US, and which are FOREIGN. When our own molecules are hijacked by haptens they look foreign. This is where things get a little complicated. The process of haptenation causes the release of danger signals in our body. These signals essentially tell the immune system that a hapten is a bad thing- resulting in inflammation and a full blown immune response against the hapten, in our case urushiol. I really like ",
"this paper",
" which, while in a questionable journal, covers the topic quite well and cites all of the right work.",
"My supervisor would say that the fur that most animals in the wild have protect them from urushiol sensitivity. This is certainly speculative but there is a wealth of evidence in sensitizing mice and guinea pigs with urushiol that animals are sensitive to the molecule. "
] |
[
"That's really interesting! Thank you!"
] |
[
"Are there any other species that use tools to \"improve\" their environment?"
] |
[
false
] |
Adam Savage pointed out that humanity's ability to adapt to our environment (and adapt our environment to ourselves) has been a major evolutionary advantage. Clothing seems like the earliest example of this kind of adaptation. Unlike tool use for hunting/gathering, which definitely predated homo sapiens and shows up in other species, is use of tools for creating habitats unique to us? 1)
|
[
"Beavers essentially create habitat for themselves by building dams, and creating ponds. Those ponds provide a relatively safe watery environment to inhabit and build their lodges.",
"That said, beavers kind of do one thing really well, and they don't have the power to invent new tools and concepts like we do. No chance of a high tech beaver empire for now.",
"Still, they totally fit your question of using tools (dams, sticks, mud) to create habitats imo."
] |
[
"Well, one example is birds building nests. Check out ",
"Rufous Hornero",
", a little bird that gathers wet mud to build",
" a mud hut that it uses as its home",
". This isn't too different from humans creating huts out of mud ourselves, I think."
] |
[
"Related question: have you played Timberborn yet?"
] |
[
"How are deep ocean temperatures cold while pressure is high?"
] |
[
false
] |
I know pressure and temperature are correlated (i.e. increase in pressure = increase in temperature), so I was wondering why temperature continued to get colder as you got deeper. It seems strange that there's a (seemingly) inverse temperature-pressure relationship for deep ocean. Thanks in advance! Note: I do realize there are a lot of other variables like the sun warming up surface waters, ocean currents, cold seeps, hydrothremal vents, etc. Do these have that much of an effect though? Edit: Cool, thanks for the replies.
|
[
"There is a warming effect due to the pressure but it is small effect compared to other things going on. For typical ocean depth, 4000m, the warming due to pressure is only about 0.5°C. The exact numerical value depends on salinity and the water's initial temperature the surface. The relatively small effect is due to the near incompressibility of water. (If you took air, which is much more compressible than water, and increased the pressure by 400X it would compress and heat up much more.)",
"In the ocean, the pressure effect on temperature is relatively minor compared to geographic variations in sea surface temperature. Water in the deep ocean originates from sinking at high latitudes - around Antarctica, Greenland, Labrador and Norway. The cold winds at these locations chill the water to near it's freezing point creating a dense water which sinks to spread and fill the ocean's basins. Thus the vertical difference in temperatures in the ocean mostly reflects the difference between the polar seas (as cold as -1°C) and tropics (up to 30°C). Here's a ",
"cross-section image",
" which shows how the layering of temperatures in the deep ocean is connected to the locations of sinking. "
] |
[
"The process of pressurizing or compressing something increases it's temperature, but it will immediately begin to equilibrate it's temperature so it becomes the same as it's surroundings. You can make a fine chiller by compressing air or any other gas, letting it cool to ambient, then letting the gas expand. If it were not for the moisture in the air freezing this would make an economical air conditioner."
] |
[
"The relation of pressure to temperature only holds for closed systems. I.e. increasing pressure increases temperature if the energy can't escape. There's nothing stopping you from increasing pressure and applying cooling. So, it's not that high pressure means high temperatures, but increasing pressure will produce heat. The oceans have been at their current pressures for quite a while, so they've had enough time to cool."
] |
[
"If there is a normal matter periodic table, is it plausible that there is an anti-periodic table? (e.g. anti-protons and whatnot make anti-elements)"
] |
[
false
] | null |
[
"If you drank a glass of antiwater, you'd explode and take out several city blocks with you. Would not recommend 0/10."
] |
[
"There sure is! We've even made some of it,",
"\n",
"http://en.wikipedia.org/wiki/Antihydrogen"
] |
[
"I looked it up quickly and found the following:",
"\nAssuming a small glass of water is 200mL and 1 gram of antimatter annihilating being ",
"equal to 43kilotons of TNT",
" we get ",
"200*43=8.6 Megatons of TNT which is like 537 ",
"Little Boy",
"'s"
] |
[
"why hydrogen-4 is unstable ? what forces drive neutral neutrons away from atom core ?"
] |
[
false
] |
I know adding another electron is not possible because negative electron and positive proton has already neutralised each other and so another negatively charged electron wont stick to it. and adding another proton would make it a new element. but neutrons are neutral, so why wont they stick to hydrogen-3 ? what forces drive them away ?
|
[
"Neutrons are fermions, you can't have more than one in a given state. They fill up the available energy levels from the bottom up. The first two neutrons can get the lowest possible energy (one with spin up, one with spin down). The third one needs a much higher energy already. For hydrogen this energy is so high that the neutron is not bound to the nucleus. The same is true for helium. You need three protons until the third neutron can become bound (lithium-6)."
] |
[
"Hydrogen-4 is unbound. There’s still an attractive strong force between the hydrogen-3 core and the last neutron, but it’s not strong enough to form bound states."
] |
[
"H-4 has one neutron in a very high energy state while the other three nucleons are in low energy states. It makes sense to see this as H-3 with additional neutron. It is a resonance with a width of 3 MeV, it is not a proper bound state."
] |
[
"Q: what is blackbody radiation?"
] |
[
false
] |
I tried googling it but can't find a satisfactory explanation... could someone please try to explain what blackbody radiation is and what it has to do with Planck's constant? A link with a good explanation is also fine. thanks guys.
|
[
"Suppose you heat up a piece of metal. It glows when it's a certain heat. And the hotter it is, the peak of the light goes from red to yellow to blue (and beyond). It turns out that to some degree, the light is ",
" a function of the temperature, not the material. It could be a piece of iron in a forge, or the coals of that same fire, or the surface of the sun. Now there are some variations in the material or surface, so we create this hypothetical \"black body,\" an object that absorbs all frequencies of light equally so that the light you're seeing from it isn't affected by the light reflecting off of it. ",
"So for this \"black body,\" we can describe exactly how much light at which frequencies will be given off by it. We can even predict this from thermodynamic principles, looking at how much energy the object has, and predicting the energy of the light.",
" the theoretical prediction was wrong when we assumed that light could leave in a \"continuous\" manner. It said that for high temperatures, an infinite amount of energy would be released. This is the famous \"",
"ultraviolet catastrophe",
".\" The resolution, by Planck, was to not allow energy to be continuous, but to come in discrete packets or \"quanta\" of energy. This energy was equal to Planck's constant times the frequency of the light emitted. Future work would reveal that this \"quantization\" of energy was related to some rules about uncertainty in position and momentum and that formed the basic structure of \"quantum\" mechanics, mechanics of motion in which action is quantized."
] |
[
"From Simple English Wikipedia:\n\"Black-body radiation is radiation produced from heated objects, particularly from a kind of special object that is made so it will absorb all radiation (visible light, infrared light, ultraviolet light, etc.) that falls on it, and so that it will also radiate at all frequencies that heat energy produces in it.\"",
"It is related to Planck's Constant because it uses the constant in Planck's Law: ",
"http://en.wikipedia.org/wiki/Planck's_law",
"That's basically what it is, is there a certain aspect of it that you are interested in though? "
] |
[
"Blackbody radiation is energy emitted by an object based on its temperature. ",
"Blackbody radiation is how night vision goggles work (most objects around room temperature emit their radiation in the infrared spectrum)",
"It is why metal turns red when it starts to get hot, then white when it gets really hot, then blue when it gets extremely hot. It's also how incandescent bulbs work - they get the filament to several thousand Kelvin, which is hot enough to start emitting visible light in addition to infrared light. ",
"The output power per unit area of a blackbody radiator depends on the fourth power of the temperature, multiplied by the Stefan-Boltzmann constant. "
] |
[
"What kind of instruments directly measure space debris?"
] |
[
false
] |
I saw a statistic stating 29,000 objects over 10cm are tracked and was interested on how those object are tracked and how we use instruments to determine their location. Thanks!
|
[
"Space objects tracking is performed and disseminated by the ",
"United States Space Surveillance Network",
".",
"They mainly use a combination of ground-based radars and optical telescopes, but there have been experiments with using space-based instruments as well. You can see the different kinds of instruments they use on the link above."
] |
[
"This article has a pretty good overview.",
" The thing to know about space debris that's relatively nonintuitive is that orbits are extremely predictable. This means that you can have a lot of blind spots and go 90 minutes without getting an observation, and still know with a high degree of confidence that you're looking at the same thing the next time it comes around. Also, with some ",
"math techniques",
" you can improve the accuracy of your estimation beyond what the sensors would give you alone."
] |
[
"Radar seems the most likely way. Maybe just optical telescopes."
] |
[
"Why is it that people can't eat most raw meats without getting food poisoning, but carnivores can?"
] |
[
false
] |
For example, all carnivores survive by eating other animals raw. Why do we not have the ability to eat raw meat without getting food poisoning? Have we evolved since we first started cooking food?
|
[
"First humans (",
") speciated some 200,000 years ago. Evidence for fire and cooked food precedes this date, somewhere in our ",
" lineage. Physical evidence for fire dates back many hundreds of thousands of years, morphological evidence (changes within ourselves) go back further.",
": \"In Montreal, Canada in March 2004 stated that there is evidence for controlled fires in excavations in northern Israel from about 690,000 to 790,000 years ago. A site called Terra Amata, seems to have been occupied by H. erectus; it contains the earliest evidence of controlled fire, dated at around 300,000 years BC. Despite these examples, some scholars continue to assert that the controlled use of fire was not typical of ",
", but only of later species of ",
", such as ",
").\"",
": The ",
" lineage appeared about 2.4 mya with ",
". Before the control of fire - we weren't humans (",
"), we were another ",
" species. Some scientists argue that even the earliest members of the ",
" lineage used controlled fire to cook food, Homo erectus at around 1.8 mya. They justify this with changes in morphology resulting from this cooked diet - shorter guts and changes in dentition to name a few. ",
"Thus, anotomically modern humans have always had the ability to control fire, and cook food. As we progress through the Homo line - fire and cooking developed to be more complex/widespread leading to an even greater varied foraging and extracting diet. We do know that the diet was mostly cooked plants (tubers, fruits...) and that a smaller portion of the diet was made up of cooked meat. But that as hunting techniques and tools became more refined, meat increased in proportion. Thus fire having been used to modify our food also in turn effected our internal gut morphology. This probably affected our ability to deal with parasites - cooking food does that for us - so digestive system no longer had to \"solve\" that problem. It could direct energy elsewhere.",
"The next two articles discuss the origins of cooking food, its a highly debated topic. ",
"Human Adaptation to the Control of Fire by RICHARD WRANGHAM AND RACHEL CARMODY.Evolutionary Anthropology 19:187–199 (2010) ",
"The raw and the stolen: cooking and the ecology of human origins. Wrangam et al. 1999. Current anthropology. 40(5):567-594 ",
" - Hunting for meat with tools probable (6 MYA), Hunting for meat with tools (evidence - 4 mya), control of fire and cooking evidence: morphological (~ 1.8 mya), Controlling fire and cooking evidence: physical (400,000-700,000 years ago), arrival of humans (200,000 years ago).",
"Food poisoning is usually caused by viruses or bacteria - like E. Coli - and this is not restricted to raw meat. Often it can be infected raw veggies that cause food poisoning. Another problem with eating raw meat would be getting a parasite from it. Parasites are different from bacteria. Parasites tend to act over a longer time period and can cause long-term damage. Many people have parasites, usually in places where sanitation is poor but for the most part survive fine with them so long as they are healthy. If unhealthy individuals or malnourished individuals get parasites it can cause a lot of damage or death. If you got a parasite from eating raw meat there are ways to treat it. ",
"Carnivores and other animals do suffer from parasites and related diseases from eating bad food (meat and plants). Humans do suffer from the same problems if we eat bad food. Our internal gut morphology - for instance our stomach acid - cannot cope with every parasite or bacteria. Carnivores are better able to cope with these, because their digestive system is adapted to a carnivorous diet - however they are not 100% immune to the effects of bad meat or infected meat.",
"As mentioned by others, carnivores tend to eat freshly killed animals. Fresh animals don't tend to be infected with bacteria and viruses - parasites are another issue. Meat, in any stage can be infected with parasites - different parts of the body are targeted by different parasites. Moreover, animals that we eat are often kept in dense population levels (this increases the chance of disease) and after our animals are killed they are put through many processing and packaging steps. All of this handling and processing increases the chances of contamination and/or cross-contamination. That is why you should always cook meat, more often then not its safe but the consequences of eating bad food (meat and plants) can be very bad. Its important to exercise caution - but no need to go overboard either.",
"Even raw fish can contain parasites and other \"baddies\" - if you eat raw anything you are putting yourself at risk (although that risk may be very small)."
] |
[
"Ocean fish tend to have dramatically lower body temperatures than we do, while mammals tend to have very similar body temperatures. That means the bacteria that are adapted to grow in or on an ocean fish tend to have a really hard time growing in us, because it's too hot for them. ",
"Fish flesh also tends to be a lot easier to chew, I believe. One of the reasons to cook meat is so that it doesn't take you an hour to chew your meal, but fish are already squishy enough. "
] |
[
"Raw meat is usually served very ",
"finely sliced",
" or ",
"chopped up",
", because of the toughness issue. Finally, an AskScience question in which I know things!"
] |
[
"What is the diameter of a Carbon-12 atom?"
] |
[
false
] |
I have not been able to find anything about it online.
|
[
"less than a hundred!",
"Careful with this. The physical distance expressed in the name of technology nodes (i.e. 14 nm node, etc.) has absolutely no physical meaning. It's just made up marketing speak.",
"However, feature sizes tend to be about 50 nm, which is still ~400 atoms, which is still pretty impressive.",
"Also note that what you're quoting is the LATTICE CONSTANT of Si in a diamond lattice. That is by no means the diameter of the atom."
] |
[
"Atomic radius",
", while well-defined, isn't just one value. You will find both explanation for what you ask as well as measured and theoretical values across the periodic table in the ",
"links",
"."
] |
[
"I've looked into this for Silicon, in its crystalline form. Nearest neighbor in the lattice is 0.235nm. I was interested in this because I wanted to estimate how many atoms long a state of the art MOSFET channel is - less than a hundred!",
"https://www.princeton.edu/~maelabs/mae324/glos324/silicon.htm",
"Atomic radius of Carbon is 0.0914 nm, so smaller than Si, which makes sense.",
"https://www.princeton.edu/~maelabs/mae324/glos324/carbon.htm",
"I don't think the atomic mass would make a difference",
"I don't see a distance for diamond like I do for Silicon, but you should be able to calculate it geometrically."
] |
[
"With our new ability to measure changes in gravity, could information from within the event horizon of a black hole be communicated by creating gravitational waves within the black hole?"
] |
[
false
] |
[deleted]
|
[
"Gravitational waves ",
" escape a black hole.",
"On the subject of \"the gravity escaping the black hole\" ",
"read here"
] |
[
"I'd just like to point out that the LIGO experiment doesn't measure changes in gravity. We've been able to do that for a while (see ",
"gravimetry",
" and ",
"gravity gradiometry",
").",
"What the LIGO experiment can detect is gravity waves, which are not the same as gravity, and which manifest as distortions in space. Gravity is unchanged. An analogy with electromagnetism would be the electromagnetic field of a particle (say an electron) and the radiation emitted by the particle, which manifests as oscillations in the electromagnetic field."
] |
[
"the LIGO experiment doesn't measure changes in gravity",
"Small phrasing improvement: LIGO doesn't measure either gravity itself or ",
" in gravity. It does measure ",
" in gravity (as that is what a gravitational wave ",
" -- a propagating disturbance of the curvature of spacetime)."
] |
[
"How fast do our eyes move?"
] |
[
false
] |
It seems like my eyes go at a constant speed, I can't seem to make my eyes move any slower or faster, so how fast so they actually move?
|
[
"Your eyes don't actually move at a constant speed under most circumstances. They jump around from place to place, and your brain strings it all together into a smooth movement and makes it look constant. These movements are called saccadic movements, or saccades.",
"Here's a ",
"video",
" showing you what this actually looks like. It's a recording of someone's eye movements while watching a short clip of a movie. You can see that it jumps wildly from place to place and does not move at a constant rate.",
"You are actually doing this pretty much constantly. Sometimes, when following a moving object with your eyes, you ",
" move your eyes in a continuous, non-jerky movement (\"smooth pursuit\"), but when you are looking at most objects, your eye movements are saccadic.",
"You don't realize any of this, because your brain works very hard to smooth it all out and give you an easily digestible version of the world. But, in fact, your brain actually lies to you. A lot. For example, there's a spot in your visual field (your blind spot) where you can't see anything. Why don't you see a gaping hole in your visual field? Your brain fills the hole in with that it ",
" is there. ",
"Oh, and color. You can't actually see color very well, outside of the middle of your retina (your fovea). Here's an ",
"image",
" showing, on the left, the distribution of cones (color sensitive photoreceptors) in your retina. Outside of the middle, it drops off dramatically. So how come you don't see your peripheral vison in black & white? Your brain is keeping track of what color things are, and 'filling in' the color of objects that it currently isn't getting very good color information from."
] |
[
"Optrode answered the question well. Just to add onto it - the upper limit for \"smooth pursuit\" is 80-100 degrees/sec and the upper limit for saccades is 1000 degrees/sec. ",
"Sources -",
"Orban de Xivry, J., & Lefèvre, P. (2007). Saccades and pursuit: two outcomes of a single sensorimotor process. The Journal Of Physiology, 584(1), 11-23. doi:10.1113/jphysiol.2007.139881",
"Meyer CH, e. (2015). The upper limit of human smooth pursuit velocity. - PubMed - NCBI. Ncbi.nlm.nih.gov. Retrieved 26 June 2015, from ",
"http://www.ncbi.nlm.nih.gov/pubmed/4060608"
] |
[
"m/s is a linear velocity whereas degrees/second is an angular velocity. If you have an object rotating, as the eye does, every point at different cross sections centered on the axis of rotation will have a different linear velocity. ",
"Imagine a bicycle wheel turning. The tread is moving much more quickly than a point on a spoke near the center because it has to \"keep up\" with the rotation. "
] |
[
"Why can I listen to a certain radio station only when outside temperature is really low (-20 C/ -4 F)?"
] |
[
false
] |
It's the heart of winter here in Finland, temperatures around -20 C and stuff. I noticed that a certain radio station, which can not usually be heard where I live, has suddenly become available. So my question is: Do radio waves 'go further' in subzero temperatures and why does this happen? My friends speculated that the phenomenon has something to do with air humidity ('dry air') and thus electrical conductivity of air.
|
[
"The ionosphere has a different composition at night then during the day due to the sun's rays not hitting it at night. Finland is very far North, and being the winter time the ionosphere is hit by very limited sun rays. The Ionosphere reflects certain radio waves, thus allowing you to hear stations from much farther away in the night time; which happens to be pretty much all the time if you live in Finland in the winter."
] |
[
"Atmospheric conditions certainly have an impact on radio transmissions. The wikipedia article on ",
"radio propagation",
" lists many of the possible effects. Unfortunately my major was computer systems rather than communications, so I am not familiar with all of the mechanisms.",
"My educated guess would be that the denser surface air associated with the cold winter refracts the radio signals towards the ground more than during summer. This is similar to how an optical fibre \"traps\" a light beam in its centre by decreasing the refractive index of the glass as you move outwards radially.",
"Hopefully someone working in communications can step in and provide more detail!"
] |
[
"Receiver temperature does affect signal to noise ratio, but I believe atmospheric conditions are the primary factor in RF propagation.\n",
"http://en.wikipedia.org/wiki/Noise_temperature",
"At night, it is possible to receive stations over very large distances thanks to reflections off of the ionosphere. The wiki on radio propagation gives some info on ionosphere modes that might match up with what you are experiencing.\n",
"http://en.wikipedia.org/wiki/Radio_propagation",
"Some spacecraft use cryogenic ally cooled communications components to improve signal to noise ratio. ",
"From ",
"http://www.astrosurf.com/luxorion/qsl-mars-communication2.htm",
"\"The DSN [deep space network] consists of large antennas equipped with cryogenically cooled low-noise amplifiers (approx. 20 K noise temperature) that ensure communications between JPL and other scientist laboratories as well as with Mars Exploration spacecrafts placed on orbit or that landed on its surface. This network is of course used to contact most other spacecrafts from Ulysses to Voyagers. \""
] |
[
"My parents keep their batteries in a drawer of the refrigerator. They claim that this helps the battery last longer when not in use, as it retards the chemical processes within. Is there any truth to this?"
] |
[
false
] |
I never questioned the practice, as they have done it all my life, but a friend of mine gave me some very strange looks for doing the same. Does the method have any merit whatsoever? Or is it possibly even detrimental somehow? Or is it so ineffective as to seem ridiculous?
|
[
"For Duracell alkaline batteries, 70°F is definitely better than 100°F, but it isn't clear if refrigerator temperatures are any better than 70°F. The recommended storage conditions are from 50°F (10°C) to 77°F (25°C).",
"from: ",
"http://www.duracell.com/media/en-US/pdf/gtcl/Technical_Bulletins/Alkaline%20Technical%20Bulletin.pdf",
"Alkaline cells have long shelf storage life. After\none year of storage at room temperature, cells will provide 93 to 96 percent of initial capacity. When stored for\nfour years at 70°F (21°C), service of about 85 percent is\nstill attainable. Storage at high temperatures and high\nhumidity will accelerate degradation of chemical cells. At\nlow temperature storage, the chemical activity is retarded\nand capacity is not greatly affected. Recommended \nstorage conditions are 50°F (10°C) to 77°F (25°C) with\nno more than 65 percent relative humidity.",
"Figure 11 compares various DURACELL®\nzinc\nanode systems and the effect of temperature on capacity\nretention. At room temperature, the alkaline system loses\napproximately 5 percent capacity after one year of storage. Subsequent capacity loss is approximately 2 percent\nper year. By comparison, zinc-carbon cells lose nearly \n15 percent capacity per year at room temperature. As\nthe temperature elevates, capacity losses increase. At\ntemperatures above 113°F (45°C), the regular zinc-carbon cells will be completely discharged within one year,\nwhereas the alkaline system will still retain approximately\n80 percent of its original capacity."
] |
[
"Yes, storing batteries at a lower temperature will decrease their self-discharge rate. For most types of batteries, the higher the storage temperature, the higher the % capacity loss per year. Note that some batteries can be damaged when stored ",
" cold (from cells freezing), and that if the storage environment is humid, the terminals can corrode. Keeping batteries around 40 - 50 °F (5 - 10 °C) is best for most types of batteries.",
"See ",
"this page",
" for a graph of storage temperature vs. capacity loss for several types of batteries. It's exponential, so the losses aren't bad at room temperature, with a slight improvement at colder temperatures, and more drastic losses as the temperature warms up. For typical alkaline batteries, the annual loss is around 5%/year @56°F, 10% @72°F, 20% @88°F, 40% @ 104°F, 60% @ 113°F, etc..."
] |
[
"I would add that there is no good reason why storing batteries at refrigerator temperatures would be detrimental to their longevity."
] |
[
"Is there a way to freeze water in the same fashion that a microwave heats it up?"
] |
[
false
] |
[deleted]
|
[
"You just described a freezer. I don't think this is what they were asking for."
] |
[
"Somewhat serious followup question:",
"How can this be utilized to build a freeze ray?"
] |
[
"Somewhat serious followup question:",
"How can this be utilized to build a freeze ray?"
] |
[
"Does Computer Programming follow a set of laws?"
] |
[
false
] |
[deleted]
|
[
"The answer is yes, for any level at which you choose to look at the problem.",
"At a basic level, what I can program a computer to do is bounded by the same laws of physics that govern the universe -- I can rearrange electrons which can cause some fancy stuff to happen, but I am still bounded by the laws of physics in much the same way everything else is.",
"If that's too obvious for you and you prefer to look at it from a closer level then the answer is still yes. Machine language (which is the programming language that all other programming languages must in some form interact with at some point, although today we often have layer upon layer of abstraction between us and it) defines a certain set of operations. Things can be moved about in memory, have arithmetic performed on them, I can push and pop things onto the stack, change the memory address where code is currently being executed (conditionally or otherwise), etc.",
"Now to spare you having to look up a bunch of opcodes and understand machine architecture we could go up to assembly language, which closely maps machine language into a readable form. For example, ",
"here",
" is a reference of x86 assembly language. At the top of the page you will see 154 opcodes defined, each with a link explaining what it does. These define the laws of what is possible to program. Nothing that is not defined by those opcodes in some way can be programmed.",
"You can keep going higher and higher level (in terms of language), moving to C/C++, to something like Java/VB/C# to something like LISP or Scala, and the same rules apply both locally (the \"laws\" are defined by the programming language and you cannot do anything outside of them) and at the machine level (no matter how high level the language, it can never do anything that is not defined by those opcodes I showed you (for whatever machine architecture they're running on)."
] |
[
"At a basic level, what I can program a computer to do is bounded by the same laws of physics that govern the universe -- I can rearrange electrons which can cause some fancy stuff to happen, but I am still bounded by the laws of physics in much the same way everything else is.",
"There is a level even more basic than this - there are some limitations to what is even theoretically computable. For example, you cannot make a machine that checks if any program will or will not produce a result in finite time. These are the limitations imposed by logic and mathematics."
] |
[
"There's more examples like this, for example sorting. Whatever you do, you cannot sort an array without minimum nlogn comparisions (unless you impose certain limitations, as in counting sort)."
] |
[
"Are there \"colors\" in different parts of the EM spectrum like there are different colors of visible light?"
] |
[
false
] |
Every diagram of the EM spectrum shows everything other than visible light as a solid block, while visible ("white") light is broken up into ROYGBV, so it got me wondering as to whether other spectrums like radio have distinct divisions
|
[
"Color is just our brain's interpretation of various wavelengths of light. Color does not actually exist independent of our brain, so no there really isn't any \"color\" beyond visual light because its not a property of light. '"
] |
[
"This is true, and is also the reason not all animals see the same light. The rods in our eyes detect light as is, without interpreting it as a colour (hence why we see little to no colour in dark environments). The cones in our eyes (a lot fewer in number than the rods) detect a specific wavelength of light. ",
"We have three different types of cones. Red, blue, and green. Certain animals have less cones (dogs have blue/green IIRC), and some have more. Take the Mantis Shrimp for example (my favorite animal), which has 15(16?) different cones. They see infrared, ultra-violet, red, green, blue, and many more. "
] |
[
"As I recall it is 16, but funnily enough it is not R/G/B.",
"Mantis shrimp information presented in a light-hearted way:\n",
"http://theoatmeal.com/comics/mantis_shrimp"
] |
[
"Botulism, how does it work?"
] |
[
false
] |
My friend and I had a conversation the other day that surfaced a longstanding confusion of mine. We had roasted some potatoes wrapped in aluminum foil in a campfire, and a few were left over. The next day as we were packing up, she said that we probably shouldn't eat those as she had heard that someone died of botulism poisoning after eating a baked potato. I said that sounded a bit like an urban myth, but some Googling unearthed that this does seem to have happened at least once. My questions are mostly about the "anaerobic environment" part of the required conditions: 1) I had always understood this to mean that the food item needs to be cut off from the air completely. Will foil-wrapping really achieve this? Do other people foil wrap their potatoes that well? 2) As my friend mentions, would the inside of the potato be in an anaerobic environment since it's obviously not in contact with the air even if the potato isn't foil wrapped? Why aren't all potatoes dangerous then? Would a boiled potato be likely to harbor botulism? 3) I've heard of the dangers of botulism in sous vide chicken--is that because it's cooked vacuum sealed? But chicken isn't grown in the earth, so I'm not sure I understand how this works. Finally, I had heard the advice that raw garlic should not be stored in olive oil, but never heard that about cooked garlic. If cooked garlic is fine, then why aren't the potatoes?
|
[
"Checked ",
"wiki",
" to confirm that ",
" is in fact an obligate anaerobe and it says that ",
" \"tolerates traces of oxygen due to the enzyme superoxide dismutase (SOD).\" So that could explain why just foil wrap is sufficient for growth. "
] |
[
"Why the prescription to avoid foil-wrapped baked potatoes vs. unwrapped baked potatoes then, if the inside of the potato is also a great anaerobic environment? Wouldn't all potatoes be equally dangerous to eat then? "
] |
[
"Why the prescription to avoid foil-wrapped baked potatoes vs. unwrapped baked potatoes then, if the inside of the potato is also a great anaerobic environment? Wouldn't all potatoes be equally dangerous to eat then? "
] |
[
"Do the effects of dyslexia change depending on the native language of the affected person?"
] |
[
false
] |
I was wondering specifically about languages with logographic/syllabic alphabets like Chinese, Japanese, or Korean. The structure of Hangul in particular seems like it would be harder to misspell or misread a character since they are (sorta) like an instruction manual for how to pronounce each individual syllable. I don't speak any of those languages fluently though so I could be way off base here.
|
[
"Absolutely. It's been shown that different parts of the brain are used for learning/reading Chinese and English, and their forms of dyslexia, therefore, are dependent on the structure of those languages.\n",
"https://www.theguardian.com/education/2004/sep/23/research.highereducation2",
"Basically it boils down to that English is (mostly considered) phonetic and that certain letters determine what sound you will read, and English dyslexia is mostly about not knowing what sound to pair up what symbol on what order. Not the same in Chinese, so the problems interpreting the words/remembering the system changes in the brain entirely.",
"There's anecdotes of dyslexic English speakers having a much easier time reading Chinese/Japanese and vice versa, but I don't know of any official studies on it. Long time since my linguistics class!"
] |
[
"Somewhat but also not really. There are words in japanese like Yukata ゆかた and Yutaka ゆたか, so dyslexia can manifest in different and more varied ways compared to latin alphabet languages. It can be pictographic or syllabic. Like mixing up the order of certain radicals (small mini kanji within a compound kanji) / misplacing them/ misreading them, or misreading/writing mirrored kana or kanji さ、ち、く、人、入, ヨ vs E ",
"A similar example in the west would kind of be like how dyslexic people can have trouble with the letters, s, b, d, p,g and the numbers 2 and 5 , 9, 4 and 6 "
] |
[
"I actually have a dyslexic Japanese relative. I've never really asked him about it though."
] |
[
"How do cells recognize each other?"
] |
[
false
] |
In Immune by Philipp Dettmer, he describes your immune system as differentiating between your body and antigens with the analogy of checking if puzzle pieces fit together. In a bit more depth, what is happening when cells check to see if these protein "puzzle pieces" fit together?
|
[
"The major way the immune system distinguishes self from foreign is ",
"MHC I",
". These protein complexes work by taking random protein fragments from within the cell and presenting them on the cell surface. For this reason they play an important role in viral infections (when some proteins in the cell are viral) and in organ transplants where the MHC must be closely matched between donor and recipient (or else the immune system will destroy the new organ). Adaptive immune cells will only bind foreign protein fragments presented by MHC because they have been toleranced against all self proteins.",
"There are also other ways. The cellular components of the innate immune system use ",
"PAMPs",
", such as the peptidoglycan of bacteria cell walls that does not exist in human cells, among other things to identify pathogens/differentiate between them and self."
] |
[
"When white blood cells are created in your bone marrow, they are given a random assortment of genes that make MHC proteins. These proteins bind to pathogenic antigens, and because the genetic makeup is slightly different, the end product structure is slightly different. So each MHC molecule binds with a slightly different affinity to the target. The affinity of this binding is whats important.",
"Scenario 1: pathogen comes into your body and antigen presenting cells take the pathogen and present it to Tcells and Bcells. The MHC on the T and B cells bind weakly. No problem, the APC detaches and finds another one (after all theres millions of T cells and B cells, theres bound to be one that works)",
"Scenario 2: the MHC binds strongly (lots of thermodynamics and organic chemistry and electron stuff going on here). Other co-stimulatory molecules latch on and make this binding even stronger. Eventually the cells realize that this a \"good\" binding and everything gets activated.",
"Scernaio 3. If new maturing T and B cells end up binding to self-antigens when they are first \"tested\", then thats bad, it will lead to an autoimmune rxn. So this is a case where \"good\" binding actually leads to cell death. Loss of this mechanism is often implicated in autoimmune diseases.",
"These puzzle pieces exist to make sure your immune systems response is swift and direct. You want a good response but only to your target. You don't want a widespread good response nor do you want a weak response. The whole binding affinity stuff determines which cells get activated. Cytokines also play an important role in subsequent steps. The puzzle analogy, literally, is all about the stability of the intermolecular forces. If something is stable for some time, then the cells realize that it was a good match."
] |
[
"Not an expert, but I believe it is mostly due to ECM (extracellular matrix) that surrounds all cells and is the \"fluid\" that gets into and out of cells based upon their cellular membrane receptors. For example, where I am sorta of an expert in, is hyaluronic acid (aka hyaluronan, HA) that is \"the most important molecule in the body\" all based upon molecular weight of the molecule. For example, low molecular weight is inflammatory (thus increases immune response) whereas high molecular weight is anti-inflammatory (maintains joints, cellular metabolism and many other things). Thanks for your question! Happy Thanksgiving!"
] |
[
"why does a wick work in burning kerosene, but not methanol?"
] |
[
false
] | null |
[
"\"Kerosene is a thin, clear liquid formed from hydrocarbons obtained from the fractional distillation of petroleum between 150 °C and 275 °C, resulting in a mixture with a density of 0.78–0.81 g/cm3 composed of carbon chains that typically contain between 6 and 16 carbon atoms per molecule\"",
"Methanol is a chemical with the formula CH3OH ",
"The obvious differences (aside from the fact that kerosene is a mixture) is the length of the carbon chain. Methanol has only one Carbon in its Carbon \"chain\", whereas kerosene has between 6 and 16.",
"This affects the physical properties.",
"The flash point of methanol is around 11 to 12 °C, whereas the flash point of kerosene is between 37 and 65 °C. ",
"One might think therefore that methanol is easier to ignite that kerosene but the autoignition temperature of methanol is 470C and the autoignition temperature of kerosene is 220 °C.",
"The autoignition temperature or kindling point of a substance is the lowest temperature at which it spontaneously ignites in normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. ",
"One might think - whys is this relevant in this case? When burning a wick we are supplying an external source of energy, a lighter. ",
" Because burning methanol requires ",
" than burning kerosene and this is probably why you experienced a wick working in one situation and not the other. This is just a hypothesis though and would require further testing to prove it. ",
"Further, I'm not certain that your assertion that a wick works in burning kerosene, but not methanol is correct.",
"Another point to consider is the boiling point. The boiling point of methanol 64.7 °C whereas of kerosene is around 150 °C upwards.",
" Another hypothesis would be that the reason you didn't see a wick burning in methanol is that the methanol evaporated before it had a chance to become part of the wick. As u /PorchPhysics argues below \" It could be that kerosene has sufficient properties to be pulled up the wick by capillary action far enough before being burned/evaporated that it can sustain a flame and continue the reaction. If methanol doesn't work with a wick, its possible that it is not pulled upward at a rate great enough to keep the reaction going or to prevent significant evaporation by approaching the heat source.\"",
"So the scientific method ",
"involves",
" evaluation competing hypotheses through experiment. Of course if someone has done experiments before we can use this to decide what os correct. Does anyone have any links to relevant literature to confirm which of the two hypotheses is correct?",
"My gut instinct says hypotheses 2) is right but science is not based on gut instinct. Anyone want to help with relevant sources?"
] |
[
"I seem to remember little fist-sized flat-bottomed glass balls with screw-on metal lids containing methanol that used a wick. This was in chemistry class. The methanol would only have to \"wick\" a vertical distance of an inch, maybe 2\" max. I might be wrong, but that would be a first."
] |
[
"The physics of fluids has never been my strong suit, but when i read this question the first thing I thought of is ",
"capillary action",
". It could be that kerosene has sufficient properties to be pulled up the wick by capillary action far enough before being burned/evaporated that it can sustain a flame and continue the reaction. If methanol doesn't work with a wick, its possible that it is not pulled upward at a rate great enough to keep the reaction going or to prevent significant evaporation by approaching the heat source.",
"This is all just an inference, though. I don't know this for sure."
] |
[
"Where does the flu virus go when it's not flu season? What is the reservoir it uses to come back from each year?"
] |
[
false
] | null |
[
"Sick people. Flu season is just the time of year when the rate of infection by flu increases ~1,000%. But all year long it’s still steadily transmitting itself from person to person, there is no flu off-season unfortunately."
] |
[
"If we were able to quarantine people who were sick and those in contact with them, would it be possible to have the flu disappear entirely?"
] |
[
"Flu is global, so it's always influenza season somewhere. When it's summer in the Northern hemisphere, it's winter and flu season in the Southern hemisphere. In the brief periods between peak flu season in the Northern and Southern hemispheres, the virus is still circulating in tropical and semitropical regions."
] |
[
"Is there a scientific basis behind why my experiment showed the optimum pH for water photosynthesis to be 4.0?"
] |
[
false
] |
I'm carrying out an investigation into photosynthesis rates in pond weeds and the effects of changing different factors [I altered pH, temperature, light and CO2 concentration]. My data collection method wasn't the best [count bubbles coming off the freshly cut stems of 10cm strips of pond weed but I definitely saw a much much higher rate of bubble production in the pH 4.0 buffer solution, is there a scientific basis to why 4.0 would yield the highest rate or was it down to my poor choice of method to collect data? EDIT: I've noticed I said water photosynthesis instead of water plant photosynthesis Any help would be greatly appreciated, just need to make sure my results are correct. Thanks in advance!
|
[
"Have you realised that PH influences CO2 concentration inside the water because the pair C02+H20 // HCO3- is an acid/base pair ?",
"If you did do that (or if that isn't relevant for some other reason), please precise it in your post"
] |
[
"RuBisCo is also regulated by pH, if that's a factor in your experiment."
] |
[
"Ah I didn't take this into account, thanks very much for the information it was incredibly helpful."
] |
[
"What is the latest advancement/update that has been made on a 'Unified Field Theory' in physics? ie. The 'Exceptionally Simple Theory of Everything'?"
] |
[
false
] |
I just saw the episode of 'Through The Wormhole' where they discussed the prepints for a unified theory that could explain 'god' or 'creation' through pure universal science. ( or something like that! Please forgive me, I'm no physics major! haha) Is the 'An Exceptionally Simple Theory of Everything' still in its workings? What other great strides have been made in this area of a unified field theory? ...Oh how I regret becoming an Arts student!
|
[
"It didn't really pan out; there are certain irreconcilable differences between it and the standard model that it tries to extend. Ultimately this theory made very little noise in the high energy physics community but a disproportionately large noise among science journalists, who jumped on the story without concern for the underlying science.",
"In terms of \"theories of everything\" developed by single people, the most notable one in recent years is called Horava-Lifschitz gravity, which has made a big splash in the physics community but no journalist has ever written about it."
] |
[
"Wow that was fast! Thankyou so much!",
"I LOVE SCIENCE!"
] |
[
"You can read about what happened starting on page 12: ",
"http://arxiv.org/pdf/1112.0788v1.pdf"
] |
[
"How does our brain actually store information?"
] |
[
false
] |
From my understanding our brain is made up of tons of neurons that are all connected in a really complex network. How is it possible for us to remember images, words, or anything? Where does the chemistry interface with our conciousness? It can't simply be associating images with the firing of a specific branch of a neural network right? There has to be somewhere where that interaction is stored. For example: when you see a dog for the first time, a specific connection of many neurons fires, and you come to associate that firing with an image of a dog, but how do we associate that? How does our brain store the actual image of the dog that we can recall so vividly?
|
[
"This isn't completely understood but we know some things about how it works. We have 100 billion neurons that any one can connect to multiple others. Any sensory input we have can make many connections. But any single neural connection doesn't amount to anything mentally tangible and can be undone (short term memory). Repetition makes multiple connections that basically maps out some concept in your brain. Then, as you repeatedly traverse this mapped concept, or map whole other concepts together, the brain also processes these signals to form shortcuts for those \"mapped concepts\" with even more neural connections, so that accessing that stored information is faster. The brain is continuously reconfiguring these connections based on the input it receives (what you are doing) so whatever is repeated most could be retrieved the fastest. Trying to remember something is basically your brain looking for those shortcuts and if you were providing other sensory input, the reconfiguring to optimize whatever you were attentive would have used some of those neurons. Things you remember very easily, the connections were repeated enough to make so many connections that they'd never be completely undone again in your lifetime."
] |
[
"Memory recall besides where it is stored is not very well understood. The recognition you described it has to do with the part of the brain called the Fusiform Gyrus. It’s responsible for facial recognition and recall of facial features. Some people have the talent to recognize a famous person at any stage of their life due to it. It’s pretty interesting. This is where things like prosopagnosia and Capgras delusion come into play as well. "
] |
[
"That makes a lot of sense. Thank you!"
] |
[
"AskScience AMA Series: We're James Heathers and Maria Kowalczuk here to discuss peer review integrity and controversies for part 1 of Peer Review Week, ask us anything!"
] |
[
false
] |
James Heathers here. I study scientific error detection: if a study is incomplete, wrong ... or fake. AMA about scientific accuracy, research misconduct, retraction, etc. ( ) I am Maria Kowalczuk, part of the Springer Nature Research Integrity Group. We take a positive and proactive approach to preventing publication misconduct and encouraging sound and reliable research and publication practices. We assist our editors in resolving any integrity issues or publication ethics problems that may arise in our journals or books, and ensuring that we adhere to editorial best practice and best standards in peer review. I am also one of the Editors-in-Chief of Research Integrity and Peer Review journal. AMA about how publishers and journals ensure the integrity of the published record and investigate different types of allegations. ( ) Both James and Maria will be online from 9-11 am ET (13-15 UT), after that, James will check in periodically throughout the day and Maria will check in again Thursday morning from the UK. Ask them anything!
|
[
"Hi and thanks for joining us today on this great topic!",
"So many questions.",
"What do you think is the future for predatory journals? Should Beall's list make a comeback?",
"Do you think reviewers should be paid for their time?",
"Is there a better measure for a journal than impact factor?",
"Will scientific funding ever really allow for robust replication studies?"
] |
[
"What do you think is the future for predatory journals? Should Beall's list make a comeback?",
"Predatory journals are a symptoms of how we understand scientific reward - you publish something, and it counts towards your 'total aggregate output' or similar.",
"Any push to qualify the quality of that output will kill them stone dead. One of the things which obviously makes a difference is, when someone applies for a job, you - uh - check their resume. That can kill a lot of it.",
"Basically, academia moves slowly. Obviously predatory journals are several years old, but the full extent of the problem is only just recently being dealt with.",
"Beall's list had problems. It was the opinion of one guy, who made some mistakes, and annoyed some commercial publishers a great deal. It became this odd kind of gold standard, but at the end of the day, it was just the opinion of a single person.",
"But obviously the ability to retrieve information about any given journal and its ostensive value is hugely useful if you're encountering it for the first time. ",
"Do you think reviewers should be paid for their time?",
"You wouldn't believe the extent of the existing arguments about this. It's so hard to contain it all in one post with other things to answer. Relevant points:",
"tldr I lean towards \"yes\", but it's fiendishly difficult to have an omnibus opinion about something like this.",
"Is there a better measure for a journal than impact factor?",
"Impact factor is unscientific, easily manipulated (I'm writing a paper about this ",
"), borderline meaningless for any given paper, and has been subject to robust criticism since it was created. It is a terrible metric.",
"Everyone I know whose opinion I trust uses much more casual metrics. The one I've noticed most of all? ",
". I've often heard researchers who are really good say \"We'll send it to (mid-sized society journal or special interest journal) first because I want real, serious feedback.\" If only everyone thought like that.",
"Will scientific funding ever really allow for robust replication studies?",
"Yes."
] |
[
"**Alright, seadogs one and all, I'm spent. I've been checking in on this for about 8 hours now. But I'll still answer questions in perpetuity if you like, though: user tag me and I'll get to it.",
"One thing I'd draw your attention to in particular if you're interested in peer review - I'm working as part of a team who's adding a new aspect to peer review - trying to figure out quality assessment of a study in advance. Basically, post-publication review but for accuracy/reproducibility. Can you tell if a study is worthwhile just by reading it?",
"This is a big old project, so we can use the help. If you want to know more, I've set up a subreddit for it: ",
"www.reddit.com/r/repliCATS",
" - more info there.",
"Thanks for today, it's been a lot of work but damn it if I haven't had fun.**",
"Previous continues below:",
"Oi oi. The above looks a bit thin, so I've expanded.",
"I’m James Heathers - scientist, occasional author, and data thug. I'm a research scientist at Northeastern University in Boston.",
"(Data what? ",
"Data thug.",
" Silly name, but it kind of stuck.)",
"For the last five years, I’ve been involved in the meta-scientific research area of error detection. What is that? It’s using mathematical, analytical, and practical techniques to investigate if published research is accurate. Basically, it's post-publication peer review. With numbers.",
"Sometimes, we find serious problems. I’ve been involved in a ",
"few",
"\n",
"investigations",
" into these sorts of accuracy issues.",
"Doing this has made me something of a … let’s say “peer review and retraction connoisseur”. Most days, I get emails from people who’ve uncovered problems in peer review (both the normal kind and the post-publication kind) and need advice. There's not a lot of people to talk to about this sort of thing, and it's not a topic that many people are comfortable with.",
"Scientists as a whole don't talk about errors, misconduct, and fraud much. They should.",
"Where I am on the tubes:",
"https://twitter.com/jamesheathers",
" <- start here, probably",
"https://medium.com/@jamesheathers",
"https://jamesheathers.com",
"NOTE: if you have questions about the accuracy of a paper that you yourself have found, my advice is make yourself a burner account at ",
"www.protonmail.com",
" and email me.",
"Now: I was going to AMA at 9am, but there's already a dozen questions, so I'll start answering them.",
"Will be here throughout the day, most likely heavily caffeinated and muttering darkly.",
"EDIT: Still here. Keep 'em coming.",
"EDIT AGAIN: God I'm terrible at self-promotion. Totally forgot my podcast. Many episodes about this topic, and a lot of other things directly congruent to it. ",
"https://everythinghertz.com/"
] |
[
"How fast would I have to be moving before x-rays red shift into the visible spectrum?"
] |
[
false
] |
Is there a speed at which no light would be visible due to redshift? Could something else theoretically start to appear at the high end of the light spectrum that we're just not moving fast enough right now to detect?
|
[
"If you solve the relativistic Doppler shift equation for velocity, you get:",
"v = c (1-fo",
" /fs",
" )/(1+fo",
" /fs",
" )",
"Plug in a source frequency for low-frequency x-rays, fs = 3x10",
" Hz and an observed frequency for violet light, fo = 7x10",
" Hz and I get: ",
"v = 99.99997% c",
"As you can see, the relativistic Doppler shift only creates huge shifts of the source is traveling very close to the speed of light.",
"Is there a speed at which no light would be visible due to redshift?",
"The redshift does not destroy light, it just shifts it down in frequency. While its true that at very high speed, visible light will be shifts down into the infrared, but at the same time, ultraviolet rays, X-rays and gamma rays will the shifted into the visible region. There is no upper limit to the frequency of gamma rays, so no matter how fast you go, there will always be some gamma rays redshifted into the visible. It's true that there are less high-energy gamma rays than visible light, so the world will look darker to the human eye if you travel at very high speeds. Note that this is all hypothetical. The speeds required to shift gamma rays to visible light or even X-rays to violet are so high that humans can't presently go this speed. Even in interstellar space, if you really tried to go this speed , you smash into space dust so quickly that you would need enormous shielding."
] |
[
"Yes. "
] |
[
"... The speeds required to shift gamma rays to visible light or even X-rays to violet are so high that humans can't presently go this speed.",
"Although it would probably be easier, I don't think we have the technology to accelerate X-ray sources to those speeds either."
] |
[
"Why are *Hox* genes found in the genome organized by body location?"
] |
[
false
] |
TLDR: Why are genes physically ordered within the (fruit fly, and presumably human) genome in the physical order in which they are expressed in the body? Does it have something to do with recombination? I came across this curious fact in , having earlier heard it mentioned in . Both books mentioned the miraculous fact that genes, which control ultra basic developmental functions such as eye and limb formation, are found in the genome in the general order of the body. That is, developmental genes (in a fruit fly, but us too) influencing the head are in a cluster, then genes influencing the thorax, then genes influencing the abdomen. At least, this is what I they said. Both books mentioned it as a miraculous occurrence, but neither told it has to be that way. Why the heck should the physical order of genes in DNA matter, so long as the genes are on the proper chromosomes and are properly expressed? Might they be linked to reduce the likelihood that recombination messes things up? Even still, that wouldn't answer why the order is so precise. If all of the genes are linked, then you could reduce recombination by having "head, abdomen, thorax" just as well as "head, thorax, abdomen." Hopefully this is coherent, I don't really understand the subject well enough to phrase a proper question. Thanks!
|
[
"my background: PhD in molecular biology, postdoc studying Hox gene regulation in Drosophila.",
"This is actually a pretty active area of research, so it's a great question! poochwheels has already cited the Duboule lab, who are doing some neat work in mammalian Hox. Let me add a few things.",
"I have a few comments:",
"You ask, \"Why the heck should the physical order of genes in DNA matter, so long as the genes are on the proper chromosomes and are properly expressed?\" Which is a very sensible question indeed! So, if all animals do it this way, and this organization is conserved throughout the evolution of bilaterally symmetric animals, already you know that the answer must be that it works better this way. It makes the organism more fit and able to reproduce; other alternatives don't survive to pass on their genes. The dramatic conservation says so. But that doesn't really answer the \"why.\"",
"What directs each Hox gene to be expressed in the appropriate strength in the appropriate segment of the body (at least in Drosophila, what I know best and where these genes are best studied) is all the DNA between the Hox genes. In the Hox clusters, the Hox gene coding sequences are only a teeny tiny part of the real estate... the genes are something like a couple of kilobases long, but separated from each other by 50 or 100 kb DNA. All that \"extra\" DNA serves a regulatory function that keeps the Hox genes expressed in the right segments and repressed in the other ones. ",
"The hypothesis is that the DNA in the regulatory areas and the DNA in the Hox gene are organized in 3 dimensional space together with all the appropriate regulatory proteins to produce the correct pattern of expression in each segment. The extension of that hypothesis is that the physical arrangement of the regulatory sequences on the DNA strand relative to the genes is important for producing the correct 3D structure that regulates expression appropriately in the correct segment. Does that make sense? We're still learning a lot about how it works.",
"I can go on! This is something like the 30,000 foot view But I'll stop there for now and keep going if you have more questions.",
"edit: formatting"
] |
[
"Id just like to thank you all for bringing the level of discourse to an extraordinarily high level in this post. "
] |
[
"OK, sure. I need to back up a little bit first. This is all Drosophila research I'm talking about here, but it's probably (hopefully) similar in higher organisms.",
"The expression of the Hox genes has two phases: an initiation phase, where the pattern of expression and repression is established (smarmyknowitall commented on this \"elaborate cascade of transcriptional control\"), and a maintenance phase, where that initial pattern is maintained for the lifetime of the organism. The initiation phase involves proteins you might be familiar with from biology classes: sequence specific transcriptional activators. If the activator is expressed in the right segment, a Hox gene with the sequence targeted by that activator will get expressed in the right segment. The initiation of this pattern of Hox expression also involves repressors that operate in a similar way -- they will prevent expression of Hox genes that contain the sequence the repressors bind to.",
"But! these sequence specific transcriptional activators and repressors are only around for a few hours of embryonic development! Then they stop being expressed themselves. Now the maintenance phase of Hox expression takes over, for the rest of the life of the organism. Using a family of proteins called Trithorax group proteins, the Hox genes that were expressed in specific segments earlier in development can \"remember\" they are expressed. Genes that were repressed in those segments can \"remember\" they were repressed using some proteins called Polycomb group proteins. The Trithorax genes keep the correct Hox genes expressed in the correct places. The Polycomb genes keep the correct Hox genes repressed in the correct places. They all act on that regulatory DNA between the Hox genes.",
"What is this business about genes \"remembering\" previous expression levels? How does that work? What does that have to do with the co-linear organization of Hox genes? It's an active area of research! (I'm doing some of it myself!)",
"At the molecular level, it's still somewhat mysterious how this all happens. But one important observation is that in the Hox clusters, a lot of the repressed genes are all in contact with one another in 3D space in a way that depends on the activity of Polycomb group proteins. If the genes are repressed, they are close together; if one of those genes becomes active, it moves away from the repressed genes. So that's aspect of the 3 dimensional organization of the Hox clusters.",
"Another aspect of colinearity I didn't mention are pieces of regulatory DNA between the Hox genes that are called boundaries, or insulators. Boundary elements keep the repressive and activiting activities of the Polycomb and Trithorax proteins from spreading into neighboring Hox genes where they don't belong. It's not totally clear yet how the boundary gets its information about the expression of the neighboring Hox gene. You could imagine situations in which the gene to either side of the boundary is repressed, so the boundary doesn't need to function. But there could be other situations where the Hox gene to the left is repressed, but the gene to the right is expressed, and the boundary needs to set up a barrier to prevent the Polycomb and Trithorax proteins from spreading too far and setting up inappropriate regulation on the other gene. We don't really know how that happens, but it certainly is important that that boundary element is in that particular location on the DNA. ",
"edit: typos"
] |
[
"What stops the down quark in the proton from decaying into an up quark?"
] |
[
false
] |
I was reading up on quark flavors and stumbled upon image which shows what quarks can turn into when they emit W+ or W- bosons. And what immediately jumps out to me is that not only can the down quark decay into an up quark but it's one of the strongest decay paths too. So why do protons exist at all if the down quark can decay? If it decays and you have three up quarks they still have different colors so you don't run into Pauli's exclusion principle. Why isn't the uuu delta baryon the most stable thing there is? And, in fact, why is it so short-lived?
|
[
"Delta baryons have much higher masses than nucleons. A particle can only decay into things with lower masses. The proton is the lightest baryon, so it can’t possibly decay into another baryon."
] |
[
"For a uuu baryon, the Pauli exclusion principle puts constraints on the spin states that the quarks can have. The delta baryons have spin 3/2, while the nucleons have spin 1/2. And the strong force is strongly spin-dependent."
] |
[
"That makes things even stranger. I assume the extra mass of the delta comes from the quarks being in some excited state but why can't there be an uuu baryon that's lighter than the proton?"
] |
[
"How many derivatives can you take of a moving object before getting a value of zero?"
] |
[
false
] |
If the position of a theoretical object was defined by x^2, then the first derivative would be 2x, the second would be 2, and the third would be 0. How many derivatives can you take of, say, the position of a rocket ship launching into space or a person starting to run before getting a value of zero? Do some things in the universe never reach zero? Do all of them never reach zero?
|
[
"It depends on how it's moving, but you can easily come up with motions where arbitrarily high time derivatives of the position will not be identically zero. An example is a simple harmonic oscillator, where the motion is described by a sinusoidal function."
] |
[
"No, lots of motions are polynomials as a function of time. For example, objects moving with constant velocity, or with constant acceleration (non-relativistically)."
] |
[
"You can define functions where as you repeatedly take the derivative at a certain point, and that value goes up instead of down.",
"For instance, y = e",
" has the derivative y' = 2 * e",
". So y' = 2y. ",
"If you take the second derivative, you get y'' = 4 * e",
", so y'' = 4 y. That pattern continues, such that each successive derivative is twice that of the one before. So the y_n, the nth derivative of y, = 2",
" y.",
"Polynomials are just the beginning of calculus, and patterns on them don't always play out as you would expect."
] |
[
"Can we see close to the beginning of the universe?"
] |
[
false
] |
[deleted]
|
[
"For the first few hundred thousand years everything was so hot and dense that it was all a plasma. Basically, ",
" was opaque. It was so hot and dense that all photons were emitted and reabsorbed. ",
"This eventually lead to what we see today as cosmic microwave background radiation. ",
"Even if you could see infinitely far back, which we can't due to technical constraints currently, you'd be hard limited in the distance you could see due to this opaque plasma. "
] |
[
"The ",
"cosmic neutrino background",
" would be much older (probably decoupled around two seconds after the Big Bang), but we don't have equipment sensitive enough to detect it yet."
] |
[
"This eventually lead to what we see today as cosmic microwave background radiation.",
"So THAT is what that is! Thanks a lot! Can't you look outside the visible spectrum to \"look through\" the plasma though?"
] |
[
"Given that your teeth are pretty much fully formed does taking calcium actually promote strong teeth?"
] |
[
false
] | null |
[
"No, but it promotes the setting in the jaw bone. Strong, white teeth can loosen and fall out the same way rotten, brown teeth can, if you lack calcium."
] |
[
"Since teeth are living bone, they are being constantly remodelled and turned over by osteocytes.",
"This is super wrong. Teeth are not living bone and are not remodelled."
] |
[
"Since teeth are living bone, they are being constantly remodelled and turned over by osteocytes.",
"This is super wrong. Teeth are not living bone and are not remodelled."
] |
[
"Are electrons, protons and neutrons actually spherical?"
] |
[
false
] |
Do we have any proof they are spherical or do we just assume such due to their motion or reactions or some other observation?
|
[
"Well....in the case of the electron, the question is already a little dicey, as thinking of an electron like a tiny billiard ball really isn't quite right.",
"When you look at the wave particle duality aspect, ascribing a specific 'shape' to an electron doesn't make as much sense as you might think.",
"Then if you go deeper into quantum field theory, an electron is a localised probability density in a field that expands throughout all spacetime, and its movement is a perturbation of that field, so that gets even stranger.",
"However, that aside, they certainly appear as if they are spherical by the best observations to date.",
"There is some proof that they appear spherical, and you can read about it here.",
"Electrons appear to be spherical."
] |
[
"Electron tunneling microscopes don't show objects, or atoms in this case, as they appear in the physical world. In fact, tunneling microscopes can't observe an atom at all.",
"What you're referring to are called Atomic Force Microscopes. They use a probe which tapers down to a single atom; by placing this probe unbelievably close to the material intended to be observed, they measure the FORCE the material exerts on the probe.",
"This force is not physical any more than a magnetic field is physical, thus the physical shape of the atom is not revealed."
] |
[
"Just to add, they probably appear that way to us because of the limits of our measurements, which I know you were implying, but I wanted to state explicitly. "
] |
[
"Can general relativity explain the mechanism for quantum entanglement?"
] |
[
false
] | null |
[
"GR is a completely classical theory; it cannot explain any quantum phenomena."
] |
[
"GR does not contain any quantum mechanics. It is fundamentally a classical theory.",
"GR knows absolutely nothing about wavefunctions, or the Schrodinger equation, or anything else necessary to understand quantum entanglement."
] |
[
"GR does not contain any quantum mechanics. It is fundamentally a classical theory.",
"GR knows absolutely nothing about wavefunctions, or the Schrodinger equation, or anything else necessary to understand quantum entanglement."
] |
[
"Why is permeability represented as a complex number and what is the physical meaning of real and imaginary parts of it?"
] |
[
false
] | null |
[
"To add to this, imaginary exponent is really a mathematical convenience in solving time-dependent equations. You can do everything without using complex exponent, but algebra of dealing with sines and cosines becomes more cumbersome."
] |
[
"Permeability is only complex when you have an electromagnetic wave. It isn't when you consider static magnetic fields.",
"The real and the imaginary part refer to the in-phase and out-of-phase responses respectively."
] |
[
"(Regular) Permeability is the response of a material to an applied DC field, so it is a real number.",
"Generalised permeability is the (frequency-dependent) response of a material to an applied AC field. Now, our response has not only an amplitude but also a phase shift, so we need two real numbers to represent it. Complex numbers do the job, the real part is the reactive part and the imaginary part the dissipative part of the response. So the imaginary part corresponds to the part of the wave that is absorbed / converted to heat."
] |
[
"[Human Body] A gluten allergy has a cool name: celiac disease. Do other allergies have names as well? Or is a gluten allergy a special case?"
] |
[
false
] | null |
[
"This question doesn't make sense. \"Peanut allergy autoimmune disorder\" isn't a thing. Please take a look at the Wikipedia entries on allergies and Celiac disease.",
"Perhaps you are asking \"are there diseases primarily characterized by an allergic reaction or intolerance to some substance?\"",
"In which case the answer might be lactose intolerance.",
"Or perhaps you are asking \"are there any allergies / allergic reactions to which we have given special names?\"",
"To which the answer might be hay fever which is an allergic reaction to some pollens."
] |
[
"Celiac disease is not the same thing as a gluten allergy. It is an autoimmune disorder. It is possible to be allergic to gluten without having Celiac."
] |
[
"Okay then... Are there specific examples of peanut allergy autoimmune disorder names?"
] |
[
"How is meth different from ADHD meds?"
] |
[
false
] |
You know, other than the obvious, like how meth is made on the streets. I am just curious to know if it is basically the same as, lets say, adderal. But is more damaging because of how it is taken, or is meth different somehow? Edit: Thanks so much everyone for your replies. Really helps me to understand why meth fucks people right up while ADHD meds don’t(as much)
|
[
"Methamphetamine is actually prescribed sometimes for ADHD. Its drug name is Dexosyn. See: ",
"https://en.wikipedia.org/wiki/Methamphetamine#Medical",
"The only difference between Dexosyn and street meth is purity and formulation (although to be fair, formulation is pretty important for determining the effects of a drug, and as ",
"u/CanaryBean",
" pointed out the route of administration is also important)."
] |
[
"Ok so apparently I am the first medicinal chemist to discover this post! I have some things that I could shed some light on that nobody else has seemed to cover!",
"So, yes, amphetamine, the main ingredient in adderall, is extremely similar to methamphetamine. In fact, meth is simply amphetamine with an added methyl group at the N-position. The addition of this methyl group has two consequences that make methamphetamine a more powerful drug than amphetamine.",
"So yea, Meth is innately a stronger and more euphoric/addictive drug than amphetamine because of these medicinal chemistry properties, but I would argue that this isn't what makes street meth so much more dangerous than prescription meth, the other answers reflect this a lot better. The purity of the drug is a huge danger as you don't know exact ingredients like you would pharm grade drugs. The lack of accurately measured dosages is a big danger, especially since even 10mg of meth may be cut with 5mg or more of inactive or different ingredients with unknown effects. Also, people redose and redose for days on end because you can buy tons of meth in powder form, this is when amphetamine psychosis kicks in and people start doing stereotypical meth head shit. Amphetamine psychosis can happen to people on ADD meds too, I saw it happen to my GF in college as she picked bugs out of her face even when she knew they were not there.",
"And yea the worst thing about street meth/amphetamines vs ADD meds is route of administration. Just as I said the pharmacological differences of meth are enhanced by more direct method of administration such as smoking or injecting, these are the methods that most often are associated with the most danger. There isn't really a way to achieve the same type of rush from prepared ADHD medications, as one does from smoking or injecting straight crystalline forms of the drug. Now in the UK, speed is popular, which is a clandestine amphetamine preparation, and I am sure you see all of the same shit you see from meth in the US, despite the fact that amphetamine is the same chemical in adderall. Preparation and method of administration and dosage measurement are the main differences between street and Adhd stimulants."
] |
[
"Most of the good stuff has been covered, but what hasn't been covered is that both amphetamine and methamphetamine are analogues of a chemical that is already in your body called phenethylamine.",
"This is used by your body to regulate dopamine and a number of other neurotransmitters, and all that amphetamine and methamphetamine do are to replicate the action of this normal body chemical."
] |
[
"Linguists: since Vietnamese is a tonal language, and so is Chinese, could Chinese be written in an alphabet?"
] |
[
false
] |
I know some Chinese and I do understand that there's Pinyin, however, there are words which have the exact same pronunciation and different meanings, so Pinyin couldn't be used as spelling. I read some wiki and found that there were systems for Romanization, but none worked or were too complicated.
|
[
"however, there are words which have the exact same pronunciation and different meanings,",
"You do realize that happens in pretty much every language?",
"so Pinyin couldn't be used as spelling.",
"Why not? In English we can tell the difference between \"That's a pretty rose.\" and \"Jesus rose from the dead\"."
] |
[
"Pinyin could be used perfectly fine as spelling. In Chinese, as in English, we deal with homophones by context."
] |
[
"Linguist here. There's no reason why an alphabet couldn't be used for Chinese. Spoken Chinese has no visual aid to disambiguate between homophonous words, all you have is the linguistic context, and that's all you have in writing, too. It's an illusion of unfamiliarity that we would have a hard time disambiguating so many homophonous words. The truth is we don't have much of a hard time at all. You mention Vietnamese. Well, that makes the point even more so. Vietnamese is written purely alphabetically, it's tonal, and it has just as much homophony as Mandarin. Yet they have no trouble whatsoever. So yes, Chinese ",
" be written with an alphabet, and Pinyin is perfectly capable of fulfilling that role."
] |
[
"How close to the galactic center would I need to be to see orbiting systems moving with the naked eye?"
] |
[
false
] |
Sure I can see satellites moving across the sky, but how close to the center of the Galaxy would I need to be to see systems/stars moving across the sky with the naked eye?
|
[
"The actual ",
" of the orbits of stars doesn't really change much across the Milky Way - they all go at about 200 km/s. Stars take less time to orbit in the middle, but that's not because they're going faster - it's because they have less distance to travel. Even in the very centre of the galaxy, the fastest stars that directly orbit the central supermassive black hole are going something like 1000 km/s. At that speed, a star would still need to be well within your own solar system (like 10s of times the distance to the Moon) to really see the motion in real-time."
] |
[
"So I thought I'd actually try to run through the number. Apparently, angular resolution of the human eye is about 1 arcmin, or 0.3 mrad (from ",
"Wikipedia",
"). And let's say the star would have to traverse this arc in half a second.",
"That gives travel distance of 500 km (for the fastest system you mention). For small angles, sin(x) = x (in radians), so radial distance is 500 km / 3e-4, or about 1.7 million km. For reference, the Moon is about 400,000 km away from Earth, so the star would have to be just four times farther than the Moon. As ",
"/u/aescula",
" suggests, that may be too close for comfort.",
"I have to admit, this is surprising. My sense of scale was way off."
] |
[
"And at that distance it would be enormous, filling the sky, and probably blinding and cooking you, so that wouldn't help either."
] |
[
"How are trajectory adjustments made to far earth objects? How long does it take before these probes or rockets respond to commands from earth?"
] |
[
false
] | null |
[
"I know a little bit about commanding the mars rover, which is about 3 1/2 minutes away at lightspeed.",
"Basically, they schedule a set of commands with stop points for verification of status.",
"So the schedule will be like \"Move rover 200m due south, then stop and wait for confirmation, then turn 90deg west, wait for confirmation, then deploy arm\"",
"The confirmation points will be where the status of the vehicle is checked with sensors and cameras. Basically, they need to make sure they travelled due south for 200m, and didn't get stuck on a rock, or turned one way or the other by inconsistent terrain etc.",
"Communication with further objects like deep space vehicles takes a lot longer, but has the same basic principles. Most really far objects like deep space satellites etc. are largely one way transmitting their data, and don't really get many instructions or change course etc."
] |
[
"I don't know about every step, but they basically send a series of instructions in a batch to be executed, and then check how well they executed.",
"Yah, this is to prevent an unforeseen change in the outcome of step A from making step F impossible or damaging to the craft. ",
"If they were on a different angle on a hill than they predicted because the dirt slipped a little or something, this might mean that they smash their delicate sensor right into a rock rather than positioning it near the surface for a scan, that type of thing."
] |
[
"Most really far objects like deep space satellites etc. are largely one way transmitting their data",
"As an example, New Horizon's close fly-by at Pluto was so short the spacecraft couldn't get any feedback from Earth. After that it needed over one year to send back all the data."
] |
[
"If it gets continually harder for Voyager to transmit images back to Earth, can we send a series of other spacecrafts after it to \"leap frog\" the information back?"
] |
[
false
] | null |
[
"Voyager's cameras have been switched off since 1990 (straight after the ",
"pale blue dot",
" photo was taken) simply because they're not passing anything to take photos of.",
"If you mean data in general it looks like the ",
"deep space network",
" is sensitive enough to continue receiving data from the probes until their power runs out in 2025. As well as which as the power runs low more and more instruments have to be turned off, so there is less data being sent. I can't think of anything that would be gained from the expense of sending a relay probe to follow them."
] |
[
"Yeah, pretty much a vast sea of darkness. Space is a pretty damn aptly named place. Sure, the Oort Cloud is out there, but the bodies in the Oort Cloud, like bodies in the asteroid belt, are absurdly far apart. Maybe there could be some readings to take with other instruments, but a camera out there would be pretty useless."
] |
[
"Also, the Oort cloud would take 10 to 20 millennia to reach at Voyager's speed.",
"EDIT: ",
"Obligatory Carl Sagan Video"
] |
[
"Are the neural connections giving way to two images linked by an analogy similar physiologically in any way?"
] |
[
false
] | null |
[
"I don't understand your question. Could you try rephrasing it please."
] |
[
"Ideas aren't stored in individual neurons. However, it is the case that certain areas of the brain are organized \"semantically\" meaning that pictures of different kinds of animals, say, activate nearby regions of cortex. Pictures of tools activate another set of regions. Part of the proximity just comes from the fact that these are visual areas so all visual signals will stimulate them. But even within the small area, conceptually related images will activated small, adjacent regions."
] |
[
"Sorry for the confusion, my question probably stems from a misunderstanding/ignorance of the way neurons work in relation to ideas. I was wondering whether neural structures and connections physically mirror our thoughts. I initially wondered if an analogy between two seemingly unrelated ideas was reflected in the structure of our neurons (i.e. grossly simplified: neurons for idea 1 and idea 2 share some structural similarities). Is that clearer?"
] |
[
"If all of the matter and energy in the universe was uniformly distributed, would it eventually coalesce into planets, stars, galaxies, etc?"
] |
[
false
] | null |
[
"This is essentially what the Millennium Simulations did:",
"\n",
"http://www.mpa-garching.mpg.de/galform/virgo/millennium/",
"\n",
"http://www.mpa-garching.mpg.de/galform/millennium-II/",
"\nwhich simulated the formation of large scale structure in the universe. Here you can take a look at the collapse that occurs from an almost uniform start:",
"\n",
"https://youtu.be/74IsySs3RGU?t=1m48s"
] |
[
"If everything was perfectly distributed (not possible), no clumping would occur. Thankfully, the quantum fluctuations which naturally cause slight density giggles were blown up by the expanding universe and formed the seeds for our universe's large scale structure."
] |
[
"Thanks for those links. I found this on wikipedia regarding the Millenium simulation: ",
"each \"particle\" represents approximately a billion solar masses of dark matter",
". But I guess what I was really pondering as a starting point was a scenario in which there was only uniformly distributed atoms and molecules throughout the universe. For one thing, I don't know how dense the distribution would be, and whether or not there would be sufficient attraction to result in a universe not unlike the one we have."
] |
[
"Is it possible to use more natural gas in a vacant home than a home with 4 people living in it?"
] |
[
false
] |
the house is completely furnished with 5 gas appliances. Only 2 have a constant pilot lite. It is 3200 sq feet, The furnace is set at 62 degrees, and the out side temp average is 45 degrees, The gas company says it is"well known in the industry" that a vacant home will use more gas than a family of 4. How is this possible?
|
[
"Humans, on average put out 100W. They also use TV's, computers, radios, microwaves, etc. which use electricity and produce waste heat. Lets just assume that the people are home on average 12 hours per day. That is 17MJ/day contributed by the people inside the house. Since the house is at a higher temperature the heat transfer should also increase, assuming a 40% increase in energy lost due to the higher temperature. That brings body heat contributions to the house down to ~10MJ/day or about 3 therms per month. That's not a huge difference but that doesn't account for waste heat from all the devices people use, as well as differences in people's energy output can add up too. "
] |
[
"the only gas for a vacant house would be heating. ",
"so i suppose it is possible if the family take cold showers, eat cold food and sleep in the same bed."
] |
[
"It is completely furnished, window coverings and all, and is equipped with 5 appliances. it is set at 62 only because it has dipped in the 30's with high humidity and I want to protect the contents. It is a well insulated home and would not think a furnace set at 62 would have to turn on very often. According to the gas co. it is a bigger draw on the gas vacant then a family of 4. really? Keep in mind a family is going to pump up the temps to 68-70. I'm just not buying it."
] |
[
"What is the evolutionary benefit for a gap between the infundibulum of the Fallopian tube and the ovary itself?"
] |
[
false
] |
I was talking with some colleagues today about female reproductive anatomy and I could not think of any reason there should be a gap between these two structures. Maybe it has to do with embryological development, but if that is so, wouldn't we have evolved to remove this "shortcoming"? Usually any defect in the process of egg moving from ovary to Fallopian tube is fatal (to the embryo and mom). So you would think that this would be strongly selected against... Your thoughts?
|
[
"While I can't comment on that structure specifically, Evolution doesn't necessarily lead to the overall best outcome, just what is locally more competitive (eg, 3 hands might be better, but since we have two, two with fingers is better). This gap might not serve any purpose but could be a hang over from a pathway to a current facet of evolution. If you wanted to do some research on this particular one, I might suggest comparing it reproductive tracks of quad-petal animals or different bi-pedal animals and trying to spot something that might make sense there"
] |
[
"This video",
" shows fairly well how the infundibulum acts as a sort of \"gate keeper\" for the ovum. It moves closer in response to chemical signals from the follicle, then aids the ovum in moving into and down the Fallopian tube.",
"Because this process requires signalling from the follicle itself, this suggests to me that Wazwaz is right. The gap helps \"weed out\" defective eggs, because a damaged or mutant egg might have trouble releasing signal molecules, and would consequently remain far away from the Fallopian tubes. "
] |
[
"This is merely my informed speculation, but seems sensible to me.",
"There is no evolutionary benefit. Not all structures have an evolutionary benefit, some in fact have clear evolutionary detriment, but are retained none the less. The reason for this is the low probability of mutations that alter this structure to a new, more positive one, and/or the low selective pressure on a structure.",
"In the example of ovary/fallopian tubes, it is very hard to speculate on the evolutionary difficulty preventing correction of this, but it is entirely possible that any single mutations moving towards fixing this problem might be strongly negative, so a set of mutations would have to happen together to fix this. This makes the chance of it happening very low.",
"Secondly the evolutionary selection on this is actually very weak. Certainly it causes death when there is a intra-abdominal ectopic (without modern medicine), but the rate of ",
" ectopics is very low. Ectopics in the fallopian tube obviously have already over come this gap problem.",
"Edit: Actually after looking it up apparently most intra-abdominal ectopics are due to tubal rupture and re-implantation in the abdomen rather than a wayward egg, which means the selective pressure on this structure would be even lower. ",
"[1]"
] |
[
"Why does tetanus cause a red line to form on your arm?"
] |
[
false
] |
[deleted]
|
[
"You’re mostly correct, but the red streaking is more likely due to lymphatic spread of disease rather than hematologic. Also, this phenomenon is not unique or limited to tetanus. The tetanus booster given to the person in question was likely not to treat a tetanus infection, but instead prophylactic as tetanus is commonly found on rusty metal, as that is a favorable growth medium for the anaerobic microbe. "
] |
[
"Tetanus is a bacterial infection that enters the body at the site of injury. If left untreated, the bacteria can enter the bloodstream and travel to other parts of the body, where it causes muscle spasms, respiratory distress, fever, and a ton of other serious problems. That red line is the infection spreading up the blood vessels in his arm, heading towards his vital organs."
] |
[
"This is more Likely phlebitis caused by the local infection and Inflammation in the vein. You were smart to go the doctor, as this can lead to sepsis which can be fatal. The Tetanus shot is precautionary and not necessarily the “bug” that was causing the Infection."
] |
[
"Say we have the technology to create controlled black holes in nearby space. Could we theoretically use black holes and their gravitational bending of light like lenses in a giant telescope?"
] |
[
false
] |
[deleted]
|
[
"A black hole will bend light, but it will not act as a lens with a focal length. That is, one will not be able to form images.",
"A focusing lens bends light more the farther it passes from the center of the lens (the optic axis). A BH does the opposite, bending light more if it passes near the center."
] |
[
"Well in terms of gravitational lenses. Yes those do exist. Hubble has found a lot of galaxies that appear stretched and skewed due to large gravitational forces between it and other galaxies (dark matter). Some of these lenses are also just right to actually magnify the things behind it."
] |
[
"Assuming your ring is circularly symmetric then no light will be bent within the ring due to the ",
"shell theorem"
] |
[
"Is aquatic locomotion via jumping (e.g., dolphins) more efficient than travelling submerged?"
] |
[
false
] |
We see dolphins do this all of the time. People usually say it's for "fun", but that smells of anthropomorphism to me. I've seen large pods of dolphins off in the distance all jumping en masse as they cross large distances more-or-less in a straight path, as if they were trying to get to a key hunting area or something. Does temporarily leaving the water for a ~100x less viscous fluid (air) offset the energy lost by repeatedly deviating from a direct path parallel to the water surface?
|
[
"Perhaps I misused the term viscosity. I wasn't talking about the intermolecular forces that resist flow through a fluid, but rather the total amount of fluid friction a fluid can exert on an object. From what I understand, this is a very complex concept involving the shape of the object, the inertial forces of the fluid, flow turbulence, etc.",
"I lazily lumped it all together as 'viscosity'. What I meant is ",
"leaving the water for a ~100x less ",
" fluid (air)",
"with the 100 being simply an order-of-magnitude estimation. being off by an order isn't bad for a mental estimation, I guess."
] |
[
"Well, there are other reasons to do it besides just energy. Other cetaceans are known to come out of the water to get a better look at things. "
] |
[
"leaving the water for a ~100x less viscous fluid (air)",
"Just FYI, viscosity is rarely very important, and it isn't here. Water is more difficult to move through than air primarily due to the density difference (a factor of 830)."
] |
[
"How much does a 'tough mind' have to do in your immune system or fighting off a virus?"
] |
[
false
] |
So I was just in an argument with my brother over how he thinks his 'tough mindset' has helped him fight off sickness for like 6 years. He seems to think that he consciously controls his immune system by fighting off any sickness by himself. Is there any scientific basis for this or is he just talking poppycock?
|
[
"Or that stress weakens the immune system, doing badly causes stress, and if you're confident you'll do well you probably will."
] |
[
"Or that stress weakens the immune system, doing badly causes stress, and if you're confident you'll do well you probably will."
] |
[
"http://psychcentral.com/lib/2006/the-power-of-positive-thinking/",
"\"One recent study, for example, polled healthy first-year law students at the beginning of the school year to find out how optimistic they felt about the upcoming year. By the middle of the first semester, the students who had been confident that they would do well had more and better functioning immune cells than the worried students.\""
] |
[
"If we were to create a giant pie chart of human age, which age would have the biggest slice today?"
] |
[
false
] |
To clarify; which age is the most common right now in humanity? as in 11 years olds , 12 year olds, 50 year olds, etc etc.
|
[
"You're looking for a specific type of histogram called an age pyramid. These can be made for specific communities or populations, but here's one I found for the entire global population with previous records and estimated projections for the future:",
"http://populationpyramid.net/",
"The general trend for the whole world since the 1950s, which they project to continue into the future, is a more balanced \"tower\" instead of a pyramid. This demographic shift underlies a lot of the current policy considerations."
] |
[
"Unfortunately no, it's not my area of expertise at all."
] |
[
"I liked this ted talk (religion and babies) and it's relevent.",
"http://m.youtube.com/#/watch?v=ezVk1ahRF78&desktop_uri=%2Fwatch%3Fv%3DezVk1ahRF78"
] |
[
"Is the 10mg Phenylephrine dosage of Sudafed PE I just bought for my flu a waste of money?"
] |
[
false
] | null |
[
"Hi RedDyeNumber4 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"medical advice",
"/r/AskScience",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"Then you need to change your post/frame your question to fit within the guidelines that I've linked. We are very strict with people asking for medical advice, of which any answer to \"Is the 10mg Phenylephrine dosage of Sudafed PE I just bought for my flu a waste of money?\" is definitely advising you on medicine.",
"EDIT: If you need guidance with framing your question, feel free to send a message to the full list of moderators who may be able to help you out."
] |
[
"Where does the energy from this claimed \"perpetual motion\" machine come from?"
] |
[
false
] |
Let me begin by saying that I DO NOT believe this to be a perpetual motion machine, nor do I believe that they are even possible. I simply do not understand where the energy is coming from to overcome the friction, move the bar up, etc. It appears the overhead bar with a magnet is locked in place until the gear comes along, unlocks it and pushes it up so that the cylinder can rotate without the two attracting each other. Lets assume they are not using some hidden power source or motor. My knowledge of physics math is at a high school level but I understand the principles in effect. Please help me find the piece I am missing. Thanks!
|
[
"Thanks for sharing, it's a slick video. Sorry for being a downer, but I think that it's actually very appropriate to assume that a hidden power source is being used. The wheel appears to be taking several revolutions to accelerate to top speed. That means that energy is being added to the system well after the initial drop of the horizontal bar."
] |
[
"This is one of the better one of these I have seen At the end of the day though there cannot be more energy in the system than that introduced by initially dropping the bar, unless of course there is a hidden energy source.",
"My first thought was that the bar was dropped from an initial height higher than it gets raised by the cam, but it wouldn't be difficult to hide something inside the wheel.",
"I'm not sure but does it appear to slow before the hand touches it? It seems, just looking at it, that there is way too much friction in the system for it to work. Have you figured out what the device at the bottom is?",
"The thing to remember with all of these magnetic perpetual motion machines you see is that they produce very little torque. So you can forget hooking them up to a generator or a gearbox."
] |
[
"You can see the piece start to slow down towards the end, you're correct by stating that perpetual motion or \"free energy\" devices are not possible, the simplest laws of physics and thermodynamics will promise you that. Now lets explain how this little thing works!",
"The magnets arranged in opposite polarity, and you can see the rounded part of the white lever that pushes the stater magnets up and down is locked in place so that when the top bar starts to fall under gravity, it will force the white arm to slide forward, also the attraction of the first row of magnets to the top stater probably helps here, this starts the wheel spinning, and along with a probably poorly made in professional standards low friction axle, the alternate polarity on the magnets creates such an arrangement like a mag-lev train - pos, neg, pos, neg etc - which causes the magnets to push away, then attract, over and over, and because they are aligned in such a precise angle, it gives a preferential direction of rotation for the wheel.",
"The bottom stater magnet would server to further increases the lifespan of the system but it will always come to an end with no constant input of energy. Youre not being deceived or anything and I think you're over thinking it and perhaps didn't notice the top and bottom magnets, as well as the curve on the white lever giving rise to the starting motion. So I'd say the initial energy comes from gravity, the magnets help to prolong the spinning, but eventually it will just slowly grind to halt."
] |
[
"Are temperature screenings an effective method of detecting COVID-19 in public places?"
] |
[
false
] | null |
[
"Yes and no. Having a fever isn't specific to COVID, but is a fast and easy way to tell if someone has some kind of illness. It's also possible to be infectious for COVID without a fever. ",
"But it's quick, easy, and cheap, which are also important for a screening tool to be effective."
] |
[
"Follow up question. What's the purpose of temperature screeenings? Are they done to detect someone who has clear symptoms, and therefore should be self-quarantining anyway if honest? Or is there the possibility that someone with COVID might have a high fever without feeling any symptom (therefore you catch someone that otherwise wouldn't self-quarantine)"
] |
[
"One of the most common symptoms of COVID is having a fever. These temperature screenings are just a quick way to check if someone MAY have covid. Of course not everyone with a fever has covid, but for safety reasons it’s assumed if you’re running a fever it’s not worth the risk. Since people can be asymptomatic, they may display no signs of it, but could have a fever since that’s part of your bodies mechanism to fight off an infection."
] |
[
"Are humans a reservoir species for any known animal illnesses?"
] |
[
false
] | null |
[
"Yes. It's called reverse zoonotic disease transmission or zooanthroponosis. Examples include methicillin-resistant ",
", influenza A virus, ",
", and ",
". ",
"Here",
" is a paper on the subject."
] |
[
"Americans infected with measles infected dogs with canine distemper between 150 and 100 years ago. ",
"Panzera, Y., Sarute, N., Iraola, G., Hernández, M. and Pérez, R., 2015. Molecular phylogeography of canine distemper virus: Geographic origin and global spreading. Molecular phylogenetics and evolution, 92, pp.147-154."
] |
[
"Though they have similar names, foot-and-mouth and hand-foot-and-mouth disease are two different things. The former is a serious livestock disease while the latter is a painful but usually mild illness that affects mostly toddlers."
] |
[
"Why are solar panels typically blue and shiny?"
] |
[
false
] |
It seems counter-intuitive. In my mind they should be matt, black to absorb as much sunlight as possible.
|
[
"This is because silicon is best at absorbing light in the redder end of the spectrum, including infrared. Smaller wavelengths, on the blue end of the visible spectrum, are reflected more. So when the sunlight hits the solar cell, silicon likes to absorb the red and reflect the blue. This changes with different materials used to make solar cells. For instance, Spectrolab has triple junction solar cells that use Gallium indium phosphate, Gallium arsenide, and Germanium in order to cover a much wider bandwidth (it likes to absorb more \"colors\" of light), and by doing this they can reach around 30% efficiency but at extremely high cost.",
"Optical properties of Silicon",
"Spectrolab solar cells",
" I forgot to mention that Silicon solar cells are by far the most common at the present due to their low cost, hence my focus on Silicon. Most solar cells at some point try to target the red/infrared bandwidths since they are the most intense bandwidths coming from the sun, thus most solar cells have a blueish hue to them (though not always)."
] |
[
"Is this a surface effect, or does the light penetrate into the silicon before the interactions occur? ",
"This overview",
" suggests that it's a surface effect."
] |
[
"while there are surface effects to worry about, this is largely due to the bandgap energy. Silicon takes 1.12eV of energy to generate an electron. photons with less energy than this don't do anything, while photons with more energy waste the excess as heat. thus, it is best to absorb photons that have the same energy."
] |
[
"If measles was eradicated in 2000, then where did it come from when it made a resurgence in Minnesota recently?"
] |
[
false
] |
I am specifically referring to the US Here. Measles was declared eradicated in the US in 2000. Basically, if the virus was eradicated, then where did it come from to be be able to infect someone who was not vaccinated? Does it just evolve constantly and naturally? Are we basically surrounded by measles virus all the time? Did someone bring it back from another country and it infected one of the unvaccinated children in Minnesota?
|
[
"Measles was declared eradicated ",
" in 2000, thanks to decades of vaccination efforts. It's still a problem in some places elsewhere in the world, though.",
"The primary cause of measles outbreaks in the USA is travel. Someone brings back the virus, and infects someone who isn't vaccinated, and it spreads from there.",
"Lesson: Eradication is only possible if everyone who can get vaccinated does so. And if vaccination rates slip, a disease can come back."
] |
[
"Theoretically yes. That's why there is no smallpox anymore, we eradicated it worldwide.\nOne potential issue is if the Measles virus is also carried in animals which could infect humans, or if the virus is very stable (maybe frozen in tundra permafrost) in the environment and could get humans infected years down the road."
] |
[
"If a virus jumps the species barrier once, there is nothing stopping it from doing it again, but it wouldn't be the same disease, so it wouldn't be measles.",
"Although in this case, there is something stopping it - measles evolved from a cow virus called \"rinderpest\", which was finally eradicated in 2011 thanks to animal vaccination efforts."
] |
[
"Say a 1kg piece of steak takes 1 hour to cook in the oven, if you cut that piece of steak into 500 gram pieces will it take 30 minutes to cook?"
] |
[
false
] |
[deleted]
|
[
"Most likely not; it should take less time. Cooking in an oven is an outside-in process, where heat is transferred from the air in the oven to the surface of the steak, and then it moves from the surface to the inside parts of the steak. So the time to raise the interior to a specific temperature is more appropriately a function of the thickness of the steak. If you cut it in two heat transfer will be faster as you have more surface exposed and dimension(s) of the steak are reduced. As a logical extension imagine cutting it into 1mm cubes; heat needs only be transferred through 0.5mm to reach the center. "
] |
[
"This, the only thing you can conclude is that it would take less time. Three dimensional transient heat transfer would require sets of partial differential equations to model (which would be complicated further by the steak's weird geometry and somewhat non-homogenous nature) - definitely not linear. ",
"This is also why you can't do things like double the temperature and halve the cooking time, it's uncommon to see linear heat transfer in real life."
] |
[
"Agreed; heat transfer is generally modeled by the diffusion equation. Diffusion time scales as L",
" D",
" so I'd expect it to take a quarter the time."
] |
[
"Can you lungs remove small pieces of material (eg, plastic shavings, wood chips, metal filings)?"
] |
[
false
] |
I recently inhaled a small piece of plastic and was wondering if/how the body gets rid of pieces of foreign material?
|
[
"Large objects that are inhaled (e.g. a piece of food) are caught before the trachea divides into the right and left main bronchi. Things that get down further than that can become lodged in the main bronchi and have a greater tendency to end up on the right side because of its greater slope.",
"Smaller inhaled foreign matter will become trapped by the mucous membrane lining any part of the respiratory tract. Of those, larger sized particles are removed via the \"mucociliary elevator,\" which is a fancy way of saying little hairs the help push mucous back towards the trachea and pharynx (throat). From there, you cough up the goop. The smallest particles are removed via cells that \"eat\" or engulf the foreign matter. If anyone can elucidate the particle size, cell name, and fate of these cells, I think that would help answer the question better.",
": Airway and alveolar macrophages (aka phagocytes), which reside in either the part of the lung that conducts airflow or the part that exchanges gasses like oxygen and carbon dioxide, can engulf surface particles and are removed via the mucociliary elevator. Some particles make it beyond the surface layer of cells where they are phagocytosed by macrophages, and these cells remain in the lungs longer. \ncitation: ",
"http://www.ncbi.nlm.nih.gov/pubmed/12112434",
": This describes normal function and does not address disease or pathological states such as smoke or asbestos inhalation."
] |
[
"The answer is the same. The airways are lined with mucus that traps small suspended particles and moves them upward, where they are coughed out.",
"This system isn't perfect. Certain microscopic particles tend to get through and reach the deep parts of the lungs themselves, where they are hard to physically dislodge. If the particles are irritating to the fragile tissue there, long term damage can result. This is why asbestos fibers are dangerous, and it contributes to why smoking is so bad for you."
] |
[
"Cool thanks. I figured there was some kind of mucous elevator, but wasn't sure. Good info!"
] |
[
"If planes flying in a V formation, like geese, save fuel, would this also be true for cars ?"
] |
[
false
] |
C-17's flying in a V formation, like geese, is a current TIL saving 10% fuel = millions of dollars.
|
[
"No.",
"The reason a V formation lowers drag for aircraft is ",
"vortex shedding",
" off the wings. Basically, it's a result of flow going around the wingtips resulting in a swirling air current. If another plane, bird, etc, hits the upward part of the swirl, it gets free lift. (Not really free, but it was waste energy from the bird in front.)",
"So it works for flying things, but it's not as straightforward for cars. Cars can take advantage of drafting, riding inside the pocket of attached flow from a car directly in front, but there's no vortex to ride for cars."
] |
[
"This is vortex shedding: ",
"https://en.wikipedia.org/wiki/Vortex_shedding",
"You're referring to wingtip vortices, but otherwise your explanation is a good one."
] |
[
"Kind of. In ",
"car racing",
" it is a common technique to follow another car in close proximity to reduce air drag. It reduces fuel consumption and delays when you have to do your pit stop."
] |
[
"What part of science do you still find it hardest to wrap your head around?"
] |
[
false
] | null |
[
"The absence of time before the big bang."
] |
[
"Yeah that's another aspect of mine that's still mind-boggling. There wasn't anything sitting around empty forever before the Big Bang happened, there just wasn't a ",
" the Big Bang."
] |
[
"exactly. Higgs boson is another concept that I cannot fully understand. If the higgs field is responsible for providing mass to every other particle, what provides mass to the higgs boson? and why does every particle stop gaining mass at certain point?"
] |
[
"Can we have lenses for sound?"
] |
[
false
] |
So that we could derive information about our surroundings similar to what optical lenses provide.
|
[
"You could, but if it's a solid, the index of refraction will be huge, and almost all of the sound will be reflected. And if it's a gas, then it will just dissipate. You could use a heater to make sure the closer air is warmer, and therefore has a higher speed of sound, but any air currents will mess it up.",
"Although apparently the speed of sound in rubber is lower than in air, so it might be possible to build a solid lens that works well.",
"But it's much, much easier just to ",
"use a mirror",
"."
] |
[
"You are describing acoustic metamaterials, they are basically the acoustic version of an optical lens using periodic arrays of specific materials to manipulate sounds or other vibrations like phonons.",
"https://en.m.wikipedia.org/wiki/Acoustic_metamaterials"
] |
[
"Wow, that is very interesting! Could we place an array of microphones behind such a metamaterial lense, in order to take an acoustic \"picture\" of a scene?"
] |
[
"Does evaporation begin instantly and happen continuously?"
] |
[
false
] |
When I pour myself a glass of water, does it immediately begin evaporating and continue evaporating until it's all gone?
|
[
"Depends on the conditions surrounding the water. If the air around the water is \"saturated\" (i.e. 100% humidity), then there will not be evaporation*. If the air is not saturated (humidity less than 100%), then some water will be evaporating as soon as it leaves its closed container, whether that be a water pipe or a jug from the fridge."
] |
[
"So when it rains (or snows), does that mean that there is over 100% humidity where the clouds are? "
] |
[
"That's correct. Inside clouds made of liquid water droplets, the humidity is always 100% or greater, because otherwise the cloud droplets would very quickly evaporate.",
"The topic gets a lot more complicated when we take ice into account, because the humidity with respect to ice is different than humidity with respect to liquid water. But that would be a several-paragraph post in and of itself :)"
] |
[
"Are there any animal species where both sexes are sexual selectors?"
] |
[
false
] |
First off: sorry if I use any terminology wrong. As I understand it, pretty much every animal species has one sex (usually female) that is the sexual selector, so they're basically the "choosy" one. The other sex (usually the males) then has to sort of earn the right to mate through like fighting or just having the right body parts or dancing, etc. But I always get the impression that the males will pretty much just mate with any willing female. Anyway, I was just thinking: wouldn't it be advantageous if both sexes were selectors? Like if both sexes were choosy and therefore both had to be at the top of their game so to speak in order to mate, wouldn't the fitness of the species be better overall?
|
[
"Sure, lots of species work this way. It's called mutual mate choice.",
"First, why shouldn't an animal be \"choosy\" in the first place? The important thing to understand is that selection is driven by what's good for the ",
", what's good for the species as a whole is irrelevant. So think about it from the perspective of the individual animal. If mating now has no big negative impact on mating later, it makes sense to not be choosy. Consider a situation where an animal encounters a low quality mate who produces 2 successful offspring and later encounters a high quality mate who produces 4 offspring. The individual who mates with the low quality ",
" the high quality produces 6 offspring, and is more successful than the choosy individual who only mates with the latter and produces 4 offspring. So it often makes sense not to be choosy.",
"So why are species choosy? Well, often mating now ",
" reduce opportunity to mate later. In our scenario, if individuals can only mate once then a non choosy individual who mates at the first opportunity produces only 2 offspring, as opposed to the choosy one who produces 4. Female mating opportunities are often limited by the number of eggs they can produce, meaning they are often the choosy sex. Males, on the other hand, are often not limited by sperm production and so can afford to mate at any opportunity because it doesn't decrease mating opportunities in the future. But males can be choosy too. In situations where males engage in parental care, they are often limited in the number of offspring they can care for and so need to be choosy. For example, in red phalaropes (a type of shorebird) the females are brightly colored while the males care for the nest and eggs. But it doesn't necessarily have to be that dramatic. ",
"You often see this in species that pair bond to cooperatively raise offspring. When biparental care like this occurs, mating opportunities outside the pair are often (thought not always) lowered, so the reproductive success of each individual depends a lot on the quality of the other individual in the pair. The male's success depends on the quality of the female, and the female's success depends on the quality of the male. In these situations both males and females are often choosy and there's often less difference in appearance between sexes. This is true in some fish, lots of birds, and humans.",
"One species I studied a bit in college was is the convict cichlid, ",
". In this species, males and females form pairs and ferociously defend territories where they raise fry. The species ",
" sexually dimorphic, but both males and females are showy in their own ways. Males are larger than females (and females prefer big males) but females are more brightly colored and have a pink patch on the sides of their bodies when they are ready to breed. So both males and females are picky in this system."
] |
[
"Hmm, good question! I don't think so? At least when the two sexes are cleanly demarcated.",
"All extant animals inherited ",
"anisogamy",
" - that is, the binary compartmentalisation of sexes (male and female), with asymmetric investment in gametes; small (sperm) vs. large (eggs) - as a basal trait, and have therefore inherited the foundation on which intra- and inter-sexual competition is founded. Some, such as ",
"rotifers",
", have secondarily lost this, and become asexual, so sexual selection doesn't apply. Others, such as many molluscs, are hermaphroditic, which complicates things (see below). But otherwise, for the majority of animal species, the inherent asymmetry in parental investment (females bearing the brunt of this, in most cases) means there's inevitable asymmetry in mate-choice selection - the sex investing most into offspring being the 'choosier' one, and members of the opposite sex therefore competing amongst themselves to be 'chosen'. ",
"Sure, there's a whole load of meta-competition, conflict and strategy on top of that, which can include at least some degree of male mate-choice, but the same basic foundation is present in almost all species.",
"Hermaphrodites are different though - though previously thought to present little to no sexual selection, increasing evidence suggests that they too are indeed under it's influence, and perhaps it may be a bit more symmetric. For example, both common garden snails (",
") and greater pond snails (",
"), as in many slugs n' snails, engage in a cheeky bit of masochistic foreplay, engaging with one another with sharp ",
"'love darts'",
" before copulation. Previously thought to have some sort of stimulatory role, we now know they're used as a form of, I guess, 'forced sex-ing'.",
"Following research into these species, turns out, it's slightly more advantageous for a snail to make it's partner slightly 'more female' than itself, by using the darts to effectively shut down mechanisms that degrade sperm, thereby increasing the number of eggs fertilised by the other (and bearing that cost), thereby increasing the proportion of 'maternity' in the partner snail. As both snails are trying to pursue the same goal - wrestling to forcefully 'feminise' the other - on equal footing, perhaps this is an example that fits your question. At least, under the caveat they're hermaphroditic.",
"Otherwise, given eggs (and associated biology, e.g. being pregnant, if internally fertilised) are more costly than sperm, all species presenting anisogamy and separate sexes are by default going to go down an evolutionary trajectory where, in order to maximise investment, one sex has more reason to be 'choosy' than the other. Unless there's some niche set of animals which lost anisogamy but didn't become asexual or hermaphroditic, then I can't imagine a way in which evolution could make symmetric mate-choice selection possible.",
"Unless, y'know, they throw off the shackles of evolution, like humans supposedly have, so go us? But even then... *Opts not to open that can of worms*",
" Not really, no. Hermaphroditic animals do present sexual selection and, well, because all members of the species are sexually equivalent, then selection acts equally across them - which is the closest you'd get? Otherwise, wherever there are males and females with disproportionate parental investment (default in animals), one sex will always be more selective in mate-choice than the other.",
" ",
" ",
" ",
" Ooh, actually, after reading ",
"u/atomfullerene",
"'s ",
"comment",
", and some more ",
"recent literature",
" on mutual mate-choice, my \"",
"\" above was perhaps too ungenerous, and proportionally more symmetrical mate-selection strategy is more common than I thought.",
"Saying that, as above, often there are secondary and tertiary layers of sexual selection acting on mate pairings; in many birds, where primary mate-choice is indeed a more symmetrical affair, many of those same species engage in additional asymmetric mating strategies - for example, most 'monogamous' species are actually anything but, with both sexes engaging in affairs with external partners (known as ",
"'extra-pair copulation'",
"), a strategy that seemingly disproportionately benefits promiscuous males than females. Perhaps the closer to selective parity a sexual species gets, the more pressure there is for both sexes to outcompete the other via layers of alternative strategies, hence EPC and others, pushing 'choosiness' back outwards to some degree, until some stable dynamic equilibrium is reached. Hmm. Let's get m e t a, baby... !"
] |
[
"A couple of thoughts: ",
"Re: your last statement, I'm not sure that it would be advantageous because there are significant costs to trying to attract a mate, like increased risk of predation in animals with flashy colors or feathers, risk of getting hurt in fights, and so on. ",
"Also, there are lots of hermaphroditic animals, including simultaneous hermaphrodites, who have male and female gonads at the same time, and sequential hermaphrodites, who have different gonads at different times in their lifespan. To me, in a weird way, this is similar to what you're asking about, even though also kind of the opposite... interesting to think about"
] |
[
"How much of the deadliest toxin known to man, botulinum toxin, is present in Botox and how is it distributed uniformly in Botox in such small quantities?"
] |
[
false
] |
Botulinum toxin has an LD50 of 1.3–2.1 ng/kg. Billionths of a gram are deadly. A fraction of the lethal dose is used in Botox; how can such a small amount of proteins be measured and distributed uniformly? Their exact process is proprietary so i'm not expecting a definitive answer, but I would like to know more about how such a small quantity can be reliably measured and handled, and how much of the potent toxin is likely present in Botox.
|
[
"The answer is dilution and some very sensitive equipment.",
"There are 8 serotypes of the toxin (A-H). Botox and Xeomin use serotype A and Myobloc uses serotype B. Different strains of ",
" make different types. These types are typically differentiated through a ",
"mouse bioassay that uses monoclonal antibodies",
", although ELISA and real-time PCR can be used as well. This ",
"journal",
" states \" Each vial of Botox® contains 100 Units (U) of ",
" type A neurotoxin complex, 0.5 milligrams of Albumin (Human), and 0.9 milligrams of sodium chloride in a sterile, vacuum-dried form without a preservative.\" Each unit is roughly equivalent to ",
"5.0x10^-11 grams",
". Measuring this miniscule mass is possible but not practical.",
"I am not privy to their manufacturing standards, but I am familiar with Genentech's protein purification process which I would assume is similar. It begins with cell cultures in a giant vat of growth media. They harvest the fluid via centrifuge and run it through a cycle of affinity chromatography, charge chromatography, ion-exchange chromatography, and high-performance liquid chromatography. ",
"These processes essentially flow the fluid through a selective filter.",
" Different components of the fluid will interact with the filter, like hydrogen bonding, dipole interactions, such that they slow down or are trapped by the filter. After multiple iterations, you get an ultra-pure solution of your peptide. The solution can then be diluted to the order of magnitude you desire, and since they're usually using large volumes, it can actually be pretty easily measure, especially with robots. Constant mixing ensures a homogenous mixture. Finally, you can verify your concentration using a ",
"spectrophotometer",
"/Kinetics/Reaction_Rates/Experimental_Determination_of_Kinetcs/Spectrophotometry) which detects how much a compound absorbs light and determines the amount of sample in solution."
] |
[
"This is so interesting. I can’t even find a follow up question, I think you covered everything. Thank you"
] |
[
"Kevmomo gave a great answer. I'd like to add that all biologic products require a potency assay. The mouse LD50 assay is very accurate with low variability, and is used in addition to physiochemical methods for ensuring the final dosage is within specification. That being said, botulinum products are not considered interchangeable. That is, 100U of one product does not necessarily perform the same as 100U of another. But that is something the physician will have to consider during treatment."
] |
[
"Why does my runny nose clear up quickly when I get up and walk a short distance to blow my nose?"
] |
[
false
] | null |
[
"I'll piggyback. Why is it that when I have a stuffy nose, whenever I work out, through the duration of the workout I can breath just fine, but soon after I'm done, the stuffy Jose returns?"
] |
[
"To piggy back off that, human nasal cavities have a moderated amount of specialized tissue to control air flow. This tissue is very similar to erectile tissue found in human genitals (a venous plexus), and allows for tissues in the nasal cavity to expand. For example, have you ever noticed that you normally only breathe through one half of your nose? The obstructed half of your nasal cavity is due to an expansion of the tissue on that side. This occurs naturally about every 30min.",
"If you have a stuffy nose, both sides of your nasal cavity have expanded tissue, restricting air flow. When you start exercising, the blood is needed elsewhere in your body, which allows the tissue in your nasal cavity to relax.",
"Hope this helps.",
"source: I'm a medical student\nalso, ",
"http://en.wikipedia.org/wiki/Nasal_concha"
] |
[
"To piggy back off that, human nasal cavities have a moderated amount of specialized tissue to control air flow. This tissue is very similar to erectile tissue found in human genitals (a venous plexus), and allows for tissues in the nasal cavity to expand. For example, have you ever noticed that you normally only breathe through one half of your nose? The obstructed half of your nasal cavity is due to an expansion of the tissue on that side. This occurs naturally about every 30min.",
"If you have a stuffy nose, both sides of your nasal cavity have expanded tissue, restricting air flow. When you start exercising, the blood is needed elsewhere in your body, which allows the tissue in your nasal cavity to relax.",
"Hope this helps.",
"source: I'm a medical student\nalso, ",
"http://en.wikipedia.org/wiki/Nasal_concha"
] |
[
"At what point does a liquid become so viscous that it's considered a solid?"
] |
[
false
] |
Is there some sort of cut off point, or what?
|
[
"Is there some sort of cut off point, or what?",
"In short, no. If it has a measurable viscosity, it isn't a \"true\" solid. ",
"The popular definitions of \"liquid\" and \"solid\" don't rigorously exist in the science of rheology, which is the field that deals with how things flow (or don't flow). ",
"Some things are purely viscous, and they clearly ",
" like liquids. Other things are purely elastic, and they clearly ",
" like solids. But a wide range of things have both viscous and elastic components, so they don't fall entirely under either definition. Some materials, called ",
"complex fluids",
" can be a mixture of solids and liquids, and collectively behave much differently than the individual components."
] |
[
"Edit2: As someone pointed out, peanut butter and cement are bad examples because they're mixtures of both. There isn't really a cut off point because liquid v. solid are two different phases defined by things other than viscosity. Viscosity is the resistance to continuous shear deformation but it only really applies to fluids. It gets messy at large time frames and very low rates. ",
"There are big ranges of things that are not really solid or liquid, think of peanut butter or cement before it sets. One way to define it is by the mechanism of flow. Metal will flow at very long times because of diffusion and not viscous flow. The classic definition of a liquid is something that flows under its own weight so peanut butter would not be a liquid but it's not really solid either. ",
"Glass is interesting because it viscosity vs temperature curve is continuous and asymptotic. There is no phase transition, it only gets more viscous until it doesn't flow at all. There's no way to put a cut off because there's no point where you can say it's liquid but at -1 degree it's solid.",
"TLDR: liquid and solid are insufficient terms for defining the range of materials we have. ",
"Edit: \"Under it's own weight\" is maybe an insufficient way to say a fluid without a yield stress which means it will flow at an infinitesimally small shear stress. So the shear rate vs shear stress curve goes to the origin instead of hitting a minimum stress for shear deformation."
] |
[
"Lipsticks are a great example of this. When standing, it's a solid, but once you apply to it to the skin, the shear is enough for the surface to liquefy and spread on the skin. It's not just a matter of melting (melting points of lipstick are usually a bit above 50C and humans don't run that hot). To achieve that, you blend oils and waxes with different melting points together, sometimes with interesting interactions. Castor oil and beeswax, for instance, for an interesting gel matrix, but beeswax feels very draggy on the skin, and has a very dull look, so you add other waxes to improve slip and shine, such as carnauba and candelilla. There are many other ingredients, such as esters and polymers that add their own thing to a lipstick formulation. It's a pretty interesting exercise in rheology, but that's also why a good lipstick base is hard to formulate."
] |
[
"What causes testosterone to increase in men?"
] |
[
false
] |
Do you know of any activities, events, or circumstances that cause testosterone to increase - or remain high - in men? I wondered if there were any similarities with primates, whereby an alpha in a troop of primates may have the highest levels, and defeating rivals causes testosterone spikes. There's obviously quite a lot of outdated science (and broscience) surrounding this topic, hence me coming here first. Thanks for your help.
|
[
"ignore both of those other answers. Your body will adjust your testosterone level to always be the same (depending on age).",
"To raise that level noticeably, you have to add extra testosterone.",
"Since the steroid is illegal, the only way to do it is eat something that your liver turns into testosterone (a precursor). ",
"The precursor is androstenedione (\"andro\" to body builders), but it's illegal too.",
"However a prcursor of andro IS legal: DHEA. I take 800 mg/day to help me do my job. It will drive you insane with sexual desire if you take enough. I learned about it in college sex ed.",
"Safe at any dose; in the vitamin section at the grocery store."
] |
[
"It’s not illegal, it just has to be prescribed, and managed by a doctor. At least in the United States. Been on TRT a few years myself, and the improvement in quality of life can’t be understated from when I was low."
] |
[
"Do we know ",
" testosterone causes increased libido? If so how?"
] |
[
"What would a hypersphere \"flattened\" into three dimensions look like?"
] |
[
false
] |
This kept me up last night as I tried to imagine it. We can take a three dimensional sphere and flatten it to two dimensions like this So what would a 4 dimensional hypersphere that has been flattened into three dimensions look like?
|
[
"Well this depends on how you flatten it, like you can flatten an ordinary sphere into a flat plane lots of different ways. ",
"This wikipedia page",
" does a decent enough job of explaining a lot of how they look and behave in different dimensional projections."
] |
[
"I can't even imagine. This is as close as I can get. What do you get when a 3d sphere passes through a 2d plane? You get a circle that appears, expands and then contracts before disappearing. The circle is a 2d cross section of the sphere. Easy enough right? Now let's extrapolate. What do you get when a 4d hypersphere passes through a 3d space? You get a sphere that appears, expands and then contracts before disappearing. The sphere is a 3d cross section of the hypersphere. That is as close as my mind will get to imagining what a 4d object looks like."
] |
[
"You're presuming that the 4th dimension is time.",
"By convention, when referring to an n-dimensional shape, solid, or whatever the term is for higher-dimensional entities, all n dimensions are assumed to be spatial dimensions as opposed to temporal ones.",
"Certainly, it could be a temporal dimension, but when talking of hypercubes and hyperspheres, it's typically spatial. :)"
] |
[
"Water seeping in towels. How does it work?"
] |
[
false
] |
If I place a dry towel on top of a wet carpet, it will eventually draw water from the carpet and become damp, without any pressure or action on my part outside of placing it on top of the wet carpet. How does this occur? What force is at work? How does the water move upward against the pull of gravity? Is there a point in which the towel will become "filled" with water and no longer draw water from the carpet?
|
[
"It is due to capillary action. The force responsible for the capillary action is the intermolecular forces between the liquid and the surfaces of the towel. Basically, the water, a polar molecule, is attracted to any polar parts of the surface of the towel. Adding to the effect is the intermolecular force between water molecules themselves ( the reason water sits in droplets).",
"It moves upward against gravity b/c the intermolecular forces are actually greater than the force of gravity.",
"Eventually the mass of the liquid becomes so great that the force of gravity is greater than the force between the liquid and the towel. This could be considered when the towel is filled."
] |
[
"Great explanation. I will look up capillary action and learn more about it. thank you."
] |
[
"I think it is a little more complicated and subtle than this. Since the water starts off in the carpet, it is already in an environment with favorable intermolecular forces. It is even plausible that the water would be ",
" attracted to the carpet than the towel. For instance, some carpet is made of nylon which can hydrogen bond to water just like cotton fibers.",
"In the case where the intermolecular forces are neutral or even favorable to the water remaining in the carpet, the upward movement is driven exclusively by entropy. \"All water in the carpet and none in the towel\" is a much lower entropy state than \"some water in the carpet and some in the towel\"."
] |
[
"Is tidal locking between celestial objects in orbit only possible if there is liquid on/in them?"
] |
[
false
] |
for example liquid water or a molten core, even an atmosphere. I would have thought it'd be necessary to have some kind of dynamic behaviour for this phenomenon to take place. Thanks science-people, this has been bugging me for literally 2 minutes EDIT: fantastic answers, thankyou!
|
[
"Well, keep in mind that all solids also deform, to some extent. The earth's mantle, for instance, is very malleable (hence tectonic plate movement, and such).",
"So, no. Liquid is not necessary."
] |
[
"Liquid is not necessary, but it helps a lot.",
"The more the orbiting body can be deformed by gravity, the more rotational energy is lost due to tidal friction.",
"Solids deform, but liquids deform more. Gases deform a lot, but on most satellites, don't have enough mass to contribute. "
] |
[
"I always thought of it this way: If the moon were a perfect sphere and you stuck a bandaid to its surface, eventually that bandaid alone would tide lock the moon to the earth."
] |
[
"Is there way to determine, theoretically, the force produced by a magnet?"
] |
[
false
] |
I know it's a pretty poor question, but the stuff online is really hard to follow. Like, I'm talking about pure magnets - no electricity involved. I know electrostatic and magnetic forces are apparently the same thing but in just different frames of reference, but some equations I've found, , relate it to Volts and Amps which I am not dealing with. Essentially, I'm just looking for a way to determine the magnetic Force (in newtons) produced by a specific magnet. That is, a similar way that gravity is determined: a coefficient by the factors which are proportional and inversely-proportional i.e. F=G m2/d Any help would be appreciated. If not, I guess I could try ELI5 or something.
|
[
"It's a bit more complicated because magnets attract as dipoles. There's a Wiki article on the topic: ",
"http://en.wikipedia.org/wiki/Force_between_magnets"
] |
[
"Force is measured in Newtons or pounds. Gauss, along with Tesla, are the standard units for magnetic field."
] |
[
"Force is measured in Newtons or pounds. Gauss, along with Tesla, are the standard units for magnetic field."
] |
[
"Why are there lefties?"
] |
[
false
] |
[deleted]
|
[
"Short answer: we don't really know. But there's a lot that goes on between genes and \"deciding\".",
"First of all, in the literature they usually refer to \"right-handedness\" vs. \"non-right-handedness\", on the grounds that so-called lefties are actually just generally less lateralized and more or less randomly settled on the left side for some tasks (then there'd presumably be an equal number of righties who aren't very picky). Southpaws are not mirror images of wild-types, except in ",
"freaky cases",
".",
"The reigning hypothesis for a long time was that it involved ",
"prenatal testosterone",
". However, it's never really been conclusively tested, and now there's even contrary evidence."
] |
[
"While I'm not sure, I just want to share a link to the leftie-subreddit: ",
"r/Southpaws"
] |
[
"Partly because it's hard to find a left-handed mouse or right-handed baseball glove, and partly because left-handers aren't reversed, they're just less lateralized (in the literature they're usually just called \"non-right-handed\")."
] |
[
"How exactly does earth's moon affect the planet and how does the existence of multiple moons affect other planets?"
] |
[
false
] | null |
[
"Fascinating, thank you very much. Quick follow-up, is the moon still moving further from earth, so that in a few million years the days on earth would be even longer? Also interesting to know, that the sun's gravity is affecting the ocean as well."
] |
[
"Yes indeed it is! The moon is moving away from our planet at about 4cm (1.6\") every year which in turn means the Earth's rotation is also slowing. ",
"This will continue until the moon takes roughly 47 days to make one orbit around the Earth as compared to 27 days in the present."
] |
[
"Newton's law of universal gravitation is the best way I could possibly explain your question. This great equation states that every mass in the universe attracts every other mass because of the gravitational forces between the two. Taking the Earth and the moon as an example of this, the force of gravity is proportional to the product of the two masses and inversely proportional to the square of the distance between them (or their radius). So this can be written as: ",
"F (gravity) = m1 x m2 / radius",
"This equation will tell you the exact force that the moon exerts on the Earth. The gravitational force between Earth and its moon is F = (G x m1 x m2) / r",
" = 1.99 x 10",
" Keep in mind that the moon is roughly 1/4 the size of the Earth. This is relatively large when compared to other moons in the solar system especially the inner planets. ",
"The gravitation of the moon (and even less so the sun) affects the planet in a number of ways, most notably through the formation of tides in the Earth's oceans. The best way I can explain a tide is imagining it as a long wave in the ocean that's hundreds of miles / kilometers long. These 'tidal bulges' move as the Earth rotates and sometimes encounter shorelines. The crest of this wave represents high tide while the trough low tide. The difference between high and low tide is referred to as the tidal range and is more pronounced depending on your geographical location. Storm surges are also basically (albeit much smaller wavelength) bulges on the ocean's surface but these are formed through atmospheric pressure differentials. ",
"The sun's gravity also influences the Earth's oceans but at about 46% of the moon's gravitational pull. It is also important to point out that enclosed basins are not as influenced by the moon's gravity as Earth's oceans such as the Mediterranean sea where tides are basically non-existent except for 2 locations, the Gulf of Gabes in Tunisia and the Northern most part of the Adriatic sea in Italy. When the Earth, moon and sun are aligned (during a new moon), the gravitational pull of the sun is 'added' to that of the moon making high tides slightly higher and low tides slightly lower. This is called a spring tide. When the sun and moon are at right angles, the gravitational pull of the sun almost cancels out that of the moon forming neap tides meaning that high tides are a little lower and low tides are a little higher than average. ",
"The moon also influences the Earth in other ways. The gravitational pull of the moon reduces Earth's rotation. 1.4 billion years ago, a day on the Earth would have lasted 18 hours because the moon was much closer. The moon's gravity also stabilises the Earth's tilted axis, making the planet's rotation around the sun less 'wobbly'. Solar and lunar eclipses do not really affect the planet in any way but are very pretty to observe and relevant to mention. ",
"I do not imagine that Phobos and Deimos influence the red planet in any conceivable way. These natural satellites are basically captured asteroids that strayed too far from the asteroid belt and where captured by Mars's gravitational pull. They might result in short and dim solar eclipses but that's about as far as it goes. The outer planets in our solar system are not really influenced by their moons either as the size difference between these gas giants and their moons is substantial. Ganymede rotates around Jupiter and is the largest moon in our solar system but does not shape Jupiter in any way. The gravitational pull of Jupiter on the other hand, pulls and thugs on all of its natural satellites, heating them up in the process."
] |
[
"If the Earths magnetic field reversed tomorrow, what would the likely consequences be?"
] |
[
false
] |
would communications be knocked out? what effect (if any) does the reversal have on animals?
|
[
"Depends, if it simply reversed in a single day to it's original intensity but opposite polarity probably not much. I would think that that it would kind of interfere with our systems the same way a large solar flare would. ",
"I think the worry that geophysicsts have, is how long that transition actually takes. The record of dynamo shifts is preserver in the frozen polarity of iron in magma as it cooled in the spreading centres of the oceans. And they know from their size and the rate of contential drift that it happens every few hundred thousand years, but its not accurate enough to know how quickly they occur.",
"I think the worry would be a drawn out dimming, then flip, then strengthening of the field over a prolonged period could expose us to alot of stellar rays and particles that the magnetic field generally deflects of channels. As far as widespread extintions - animals which rely on magnetic navigation must have a way to cope, because a few hundred thousand years isn't really enough time to extinguish one species and evolve another. "
] |
[
"from the sidebar:",
"If you cannot clarify your answer in excruciating technical detail, don't answer at all. This is to reduce layman speculation, which is generally not helpful."
] |
[
"from the sidebar:",
"If you cannot clarify your answer in excruciating technical detail, don't answer at all. This is to reduce layman speculation, which is generally not helpful."
] |
[
"How is it stimulants make people feel energetic/awake?"
] |
[
false
] |
So I have been curious about this. I know a little bit about how the energy is made for humans(ATP), but how is it a stimulant like caffeine works on our body? is it all psychological? Is it a trick it plays on our body? Or some other thing that I am missing. Thanks!
|
[
"Feeling energetic or awake has little to do with the actual amount of the ATP floating around in your cells. Caffeine mainly does 2 things to cause the \"wakeful\" sensation that you feel:",
"Caffeine acts as a mimicker of another neurotransmitter called adenosine, which causes you to feel ",
" by slowing down neural functions. Caffeine can bind to adenosine receptors while not slowing down neural function (because it is not adenosine, after all), and prevents other adenosine from binding. Therefore, there is a overall decrease in drowsiness.",
"Caffeine acts on your adrenal glands and stimulates production of adrenaline, noradrenaline and other hormones produced when you are threatened. These hormones stimulates your body to prepare for a imminent threat by increasing your heart rate, initiating breakdown of glycogen (sugars) stored in your livers/other tissues.",
"With these two actions in mind, caffeine now basically not only made you feel ",
" tired, but also ",
" 'awake'",
"Other stimulants work differently, but basically differ only in what type of neurotransmitter they mimic, and which organs they effect."
] |
[
"No, it's a releasing agent. Very high doses also provide significant MAOI actitity. Reuptake inhibitors include cocaine and methylphindate(ritalin).",
"\"bath salts\" contain a mixture of 2 or more of both types of drugs, which is why they tend to cause psychosis at lower doses."
] |
[
"No, it's a releasing agent. Very high doses also provide significant MAOI actitity. Reuptake inhibitors include cocaine and methylphindate(ritalin).",
"\"bath salts\" contain a mixture of 2 or more of both types of drugs, which is why they tend to cause psychosis at lower doses."
] |
[
"What actually causes a coefficient of friction?"
] |
[
false
] |
From my understanding, coefficients of friction are different according to the surfaces. My physics teacher told me how some people get paid for determining what the exact values of these coefficients are through using equations with known masses and solving for μ (mu). However, I never understood what factors actually made a coefficient what it was. So, what actually causes a coefficient of friction?
|
[
"The most fundamental answer is the ",
"electromagnetic force",
". This force governs almost all of the physical interactions in the world, aside from gravity. In the case of two materials, say a wood block sliding down a metal table, each material's surface atoms interact with each other via the electromagnetic force to prevent these solid objects from passing through each other. Because these forces are interacting they have the effect of dissipating some of the energy the wooden block has, and we call this effect friction."
] |
[
"Well, the coefficient of friction is kind of an oversimplification. We're just relating the normal force to friction. In actuality, friction changes depending on other factors, not just the materials and their fundamental coefficients. Wheels, for example, can change things. The shape of what's making contact matters as well. Coefficients of friction, while useful for early-level physics courses, don't really apply in the real world. Yes, you can find the ratio of a particular situation's normal force to that situation's friction. But you can't really generalize and know a coefficient ahead of time. The real world of physics is simply too complicated."
] |
[
"The coefficient is dependent on many things. In addition to the other answers given, one of the major components is the roughness of the surfaces that are sliding past each other. If you look at ",
"a table of coefficients of friction",
" you will see that they have values listed for dry surfaces and greased surfaces. This even applies on the atomic level. The rougher the surface the more energy it will take to slide it on top of another one."
] |
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