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[
"Does placebo effect occur when there is no physical placebo (eg. pill)?"
] |
[
false
] |
For example, if a cancer sufferer prayed everyday instead of getting chemo? PLEASE NO SPECULATION I'M JUST USING PRAYER AS AN EXAMPLE!!!!!!
|
[
"Of course that can be a placebo. Anything that you think is having some sort of impact can act as one."
] |
[
"I believe your interpretation of effect from placebos is incorrect. While it is likely true that there isn't a direct physiological action from the placebo itself (say the sugar in the pill); there is a multitude of support showing physiological effects from the belief in the treatment. Neurological changes, as demonstrated here: ",
"The Functional Neuroanatomy of the Placebo Effect \n",
", are a prime example. ",
"This statement is patently false: ",
"Relying on placebos to get better is the equivalent of being in denial and willing away the disease. "
] |
[
"Just to clarify, what mightberight means by \"patently false\" is \"is not consistent with experimental evidence\". It's not a logical falsehood, but an empirical one."
] |
[
"Why can't we utilize the crushing forces of ocean depths to generate green energy?"
] |
[
false
] | null |
[
"Ignorance is not stupidity.",
"\nIgnorance is not knowing.",
"\nStupidity is not knowing and never asking."
] |
[
"this isn't actually something that can work ",
"This one, there's no mechanism to harness energy from that. You can't run a turbine off water that isn't moving, you can't harness the pressure deep under the ocean any more than we could harness the weight of a brick to generate electricity. Now if you have a stream of water that is ",
", then it's easy to put a turbine in it's path and spin a generator. "
] |
[
"I appreciate how you cropped out the part about my being stupid. Upvote for sparing my feelings."
] |
[
"Why is the Number Needed to Invite (NNI) so frequently reported and considered in clinical studies?"
] |
[
false
] |
How is it reconciled with the Number Needed to Screen/Treat when trying to look at the quality of a screening test or treatment?
|
[
"Intention-to-treat, rather than strict randomized control trials, are often used in assessing screening efficacy for various reasons. I'd hope outcomes other than NNI would be reported for treatment efficacy, but I suppose it could be done. ",
"Here's a decent review of the subject."
] |
[
"Thanks! That review was really helpful. I guess if you have the NNI and the NNS then you essentially get bounds for your test with the former more conservative and lateral more liberal. "
] |
[
"Agreed. NNI is conflated with many other factors, such as prioritizing that particular treatment, ability to attend scheduled appointments, interest in participation in a trial rather than standard clinical care, etc. It can still provide important information, but as you point out, it should be considered in context along with NNT, etc."
] |
[
"Why do only some wounds cause scars when healed? And why do scars appear different from the rest of the skin?"
] |
[
false
] | null |
[
"generally scar tissue is produced by the body as a last resort, because it isnt as good as replacing the skin. Scar tissue is different from the skin because it is not made up of the same materials. If the wound is big enough that the body cannot heal the wound with its normal repair mechanisms it resorts to scar tissue instead. This tends to happen on deep cuts, wide cuts, or massive cuts/scrapes that the body cannot repair quickly enough"
] |
[
"I would add in that scar tissue also forms from other types of damage i.e. binge drinking will cause liver damage and scar tissue there as well, scar tissue is not limited to just skin.",
"Also for OP appearance of scar tissue is different from normal tissue because it is not normal tissue, less porous, less stretchy etc."
] |
[
"Generally speaking, in the case of skin, the different appearance of the scar tissue is for the most part due to an overexpression of collagen fibers along with other matrix proteins. Wound healing is a complex process and the skin will heal itself completely if possible, however in the cases where it is not, instead most commonly a keloid scar tissue is formed. This scar tissue is both functionally and structurally differentiated from skin. What causes the greatest difference is the proliferation of fibroblasts (primary cells of the connective tissue) just below the epithelial cells and the collagen deposits synthesized by these fibroblasts. The accumulation of collagen type III fibers that turn into collagen type I fibers, which are normally a part of the extracellular matrix of the cells of the skin, gives the scar tissue its specific appearance. It should also be noted that the arrangement of collagen fibers differ from the arrangement of fibers in skin's normal extracellular matrix."
] |
[
"Are there ocean deserts? Are there parts of the ocean that never or rarely receive rain?"
] |
[
false
] | null |
[
"I appreciate the clear explanation made easy to understand, slut_4_cum. So could you say gyres and ocean deserts are interchangeable terms?"
] |
[
"I appreciate the clear explanation made easy to understand, slut_4_cum. So could you say gyres and ocean deserts are interchangeable terms?"
] |
[
"Yes. If you look at a map of annual precipitation, a few of the recognisable land deserts look like they stretch well out to sea. Mainly off the western edge of continents, eg. off Western and Southern Africa (Sahara and Namib deserts)."
] |
[
"So, sperm live about 5 days, and an unfertilized egg lives about 1 day. But if the egg gets fertilized it lives on its own another 3-4 days before it implants. Why/how does a fertilized egg live longer than an unfertilized one?"
] |
[
false
] |
I'm using for my numbers. I would think after fertilization it would be busy doing more stuff and burning more resources. Unless maybe it was super tiring for it to crank out the chemical signals to attract the sperm? Does the fertilized egg get to use some of the extra energy stores the sperm was carrying with it? Edit: maybe more to the point, why doesn't the unfertilized egg live longer? If it's got enough mojo to keep rollin' that many more days after it's been fertilized, why not stay alive longer and increase the window in which it could get fertilized? I hear you guys saying the unfertilized egg has a cell death programmed, but why would it program a death so soon? Unless for some reason while it's unfertilized it's busy doing stuff that damages itself such that it wouldn't produce viable offspring if it were fertilized?
|
[
"Ok, so you're driving in your car, with your girlfriend trying to decide if you want to go to the next town over to see a band. It takes a half tank of gas to get there and back, so if she says yes before a half tank, it's all a good time. If not your just yell that you didn't want to go anyways go home and sleep on the couch. ",
"It's not that you suddenly had more gas to get to the next town over, it's that you decided to just kill the trip as soon as it wasn't possible anymore. "
] |
[
"Once the sperm fertilizes the egg chemical signaling begins to happen and the egg goes into a sort of \"survival mode\" where the molecular machinery to survive and begin dividing is turned on and the molecular machinery for programmed cell death is turned off. "
] |
[
"At some point, the egg doesn't have enough energy to start dividing. One you reach that point, staying alive waiting to be fertilized is pointless."
] |
[
"Are there any actual scientific theories regarding the creation of the universe?"
] |
[
false
] | null |
[
"The Big Bang",
" is the most widely-accepted, though it's pretty widely known.",
"Some steady-state hypotheses have been put forth as well",
", though they have considerably less support these days, given the preponderance of evidence for the Big Bang."
] |
[
"Ah, so you're looking for more of a \"what caused the big bang\" sort of thing? That's a bit harder, as physics gets pretty weird back at the beginning of the big bang, and so asking what came before is even more challenging. In fact, if time is a dimension of the universe itself, asking what came before the big bang may be tantamount to asking \"what is north of the north pole\". That's not necessarily true, and ",
"there are other ideas about what came before, if that has meaning at all.",
"But right now none are beyond the level of hypothesis at best, to my knowledge."
] |
[
"Ah, so you're looking for more of a \"what caused the big bang\" sort of thing? That's a bit harder, as physics gets pretty weird back at the beginning of the big bang, and so asking what came before is even more challenging. In fact, if time is a dimension of the universe itself, asking what came before the big bang may be tantamount to asking \"what is north of the north pole\". That's not necessarily true, and ",
"there are other ideas about what came before, if that has meaning at all.",
"But right now none are beyond the level of hypothesis at best, to my knowledge."
] |
[
"Can babies really pick their parents out?"
] |
[
false
] |
My wife and I had a baby girl and she spent some the time in the NICU and the nurses said talking to her in her isolet(sp?) Would help her. Can babies really pick their parents voice out that early? And they said our daughter could smell my wife and gave us a little blankie to get my wife's scent on. Can babies really do that too?
|
[
"They've been hearing her voice in-utero for a while, so yes, she's able to recognize her mother's smell and voice because he's lived with it for months already. If you talked to the bump she knows your voice too!"
] |
[
"Yes, especially the mother. The moment the ear to brain connection starts functioning it can hear the mother's voice. Anyone else too if they're loud enough and spend enough time around the mother. Outside of the heartbeat and breathing, the voice is the most common sound in it's little world, and once they're out, it jumps straight to number one."
] |
[
"How do we know they can still recognize from outside the womb? It's got to sound very different coming through the air instead of through the mother's body."
] |
[
"If phone lines (but not necessarily modems) transmitted perfectly, how fast could dial-up modems transfer data?"
] |
[
false
] |
Since the transfer rate of the modem depends on how fast it can modulate (and demodulate) bits into an interrupted tone, phone line noise would cause high speed modems to lose data in transmission, but if a phone line were to be perfect (i.e no noise and all transmissions came through the other end of the line exactly as they were input), how fast could we potentially build a modem?
|
[
"Infinite. The easy explanation is simply a proof. If I have no noise, for any message, such as 01010100001, I can find a voltage level between 0 and 1 whose greedy binary expansion is that message. I can then send that value, and on the other end (since no noise) read that value and determine my message. No noise means infinite data rate.",
"And if that answer is all you care about you can stop there, case closed, life is good, have a great weekend. If you want to know a little bit more we can continue on. ",
"Data rate (bits/second) is actually a function of two important quantities, the bandwidth and the statistical characterization of the channel (which is commonly called \"noise\"). One of the most commonly touted theorems in this regards is the Shannon Hartley theorem, which gives an upper bound on this value for an ",
" (AWGN) channel of",
"B log( 1 + SNR )\n",
"where B is the bandwidth and SNR is the signal to noise ratio. Often times, you will hear this bound stated as gospel for all channels. It is in fact a ",
" on the ",
" amount of information that one pass through a memoryless channel where the noise has a known variance. For linear time invariant channels though, we may always write the maximum data as ",
"2BC,\n",
"where C stands for the ",
"Channel capacity",
". ",
"Before discussing channel capacity, lets get an overview of why 2B. The value of 2B is the maximum number of ",
" that can be transmitted using a bandwidth of B, and not causing intersymbol interference (ISI). Without diving into the fourier transform definitions, think of it like this, for every 0 I send 0 volts, for every 1 I send 5 volts. If my signal goes 0101010010101 I am rapidly changing between 0 and 5 volts, at a frequency defined by the number of symbols I send per second. On the other hand I may have to send a signal 1111111111, which is just always a 5 volts signal, in other words it is a dc signal. So to accommodate both 0101010101 and 11111111, and everything in between, I need to use all of the bandwidth between 0 Hz (dc), and the frequency associated with the number of symbols/second I am sending. The difference of these two terms is what we call the bandwidth, B. We get to 2B by using not only the positive frequencies, but the negatives ones as well. In communications there are called the ",
" (I) channel and the ",
" (q) channel. What they come down to though, is one channel is sent using sine, the other cosine. ",
"With that out of the way, we move to the channel capacity C. The channel capacity is the maximum bits/",
" that can be transmitted over a given channel, and is basically a sacred concept in information theory. For memoryless point to point channels, the channel capacity is simply the maximum possible ",
"mutual information",
" between the transmitter and the receiver. Mutual information, as you will note, is a function over probability distributions. So how can we ever even talk about it in relationship to this scenario? Lets walk through an example.",
"Suppose that we limit the input power of our signal (because infinite power is not a thing). To do this, we can view our input signal by a random variable X, and then say E[X",
"] < S where S is the signal input power. We will transmit X across an AWGN channel which will add noise where E[noise",
"] = N. If we assume our signal X has a Gaussian (or normal) distribution then we know the received signal (Y = X + noise) will also be gaussian with a second moment of S+N since",
"The first equality depends on the noise and the signal being uncorrelated. Now we can apply the mutual information. In fact we can write the mutual information between our transmitter X, and receiver Y as ",
"where h is the ",
"differential entropy function",
". Both terms our gaussian, Y was discussed earlier, and Y given X (how the second term is read) is simply just the noise. The entropy of a normal distribution is then 2",
" log( 2 π e σ",
" ) where σ",
" is the variance. So now we just plug in our values of variance for Y, which is S+N, and for Y given X which is just N.",
"Multiplying the above by 2B from earlier we arrive at the Shannon Hartley theorem of B log (1 + S/N).",
"So with your case, the maximum amount of information you can send per symbol is infinite, which means infinite data rate. "
] |
[
"To make it simple there are two factors: noise and channel. Any channel is limited in capacity and always makes a distortion to a signal. Most like it introduces an echo which affects a receiver side and can't be evaded from a signal completely, as information was already lost. Another problem is a noise and again a receiver has no idea how to distillate origin signal and a noise. In your case there is no noise and a channel capacity is unlimited, so no information loss at transmission, then you can reach unlimited bandwidth."
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/estimation",
"/r/theydidthemath",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"Mercury is an ingredient in some skin whiteners. How toxic is exposure to 30 000 ppm of Mercury?"
] |
[
false
] | null |
[
"Here",
" is an MSDS I found. This will give you government regulations on skin and vapor exposure. I would assume that 30,000 ppm mercury is extremely dangerous based on the IDLH number. IDLH stands for \"Immediately Dangerous to Life and Health\" and represents the maximum suggested exposure for a \"one-time\" exposure.",
"Other values include TWA which stands for \"Time-Weighted Average\" and that specifies a suggested amount for continuous exposure for workers in mercury environments. (I believe the TWA is for 8-hour work days and 1,000 work-hours per year.)"
] |
[
"I assume there are different values because ones I'm aware of are for presence in marine sediments. In water, animals will be ingesting it, but in this case people are rubbing in on their face.",
"But NOAA guidelines show an ERM (effects range median) of 0.71 ppm, and ERL (effects range low) of 0.15 ppm. Those are ranges where effects are known to occur.",
"That said, 30,000 ppm is ridiculously high. I wouldn't go anywhere near those."
] |
[
"I almost forgot. Keep in mind that my link is for pure, liquid mercury. Mercury inside of a cream will have different properties. Now, I'm only speaking for the United States, but every manufacturer of chemicals (whether pure or mixture) must put out an MSDS for the public concerning each product's health hazards. Or at least they're supposed to.",
"There is probably an MSDS out there for those specific creams if they were manufactured in the United States."
] |
[
"Is it possible for humans to learn new reflex actions?"
] |
[
false
] |
For a example if a boxer dodges enough punches, could they eventually train their nervous system to skip the brain completely and just dodge involuntary without thinking about it? So something like a learned extension to the . I know training makes people better and faster at responding to stimuli but I'm specifically asking about developing new reflex arcs (or at least I hope I am, I just now googled all these terms).
|
[
"On short, no. The action of dodging a punch would require input that suggests a punch is coming and where it is going to land (left vs right), which will most likely be visual (or possibly auditory stimuli if someone threatens you, but it would be difficult to dodge based only on sound), so the action will always be processed in the brain and the reaction descending from the brain. It is way more complex. In the withdrawal reflex, the reflex is mediated locally in the spine and does not require brain input to work."
] |
[
"As has been pointed out here, a reflex doesn’t involve the brain. Stimulus sends a signal to the spinal cord which sends back a signal for the proper response. No thinking needed, it is very fast. In order for a boxer to dodge a punch, he has to know the punch is coming. That information comes from the eyes and must be processed by the brain. ",
"There is something else that looks and feels a lot like reflex that can be developed through repetition, practice, training, etc. People here are calling it muscle memory, but that’s a misleading term as it implies the memory resides in the muscles. It happens when a response or activity becomes so familiar that it is stored in a part of the unconscious brain. Many of the daily tasks we do are executed in this way: tying your shoes, driving home from work, typing on your keyboard. You’re barely aware of doing them and you would be hard pressed to explain exactly how you do them.",
"It would be impossible to hit a fastball if you had to think about it; it would be in the catcher’s mitt before you formulated any thought or initiated any action. But practice trying to hit a ball 1000 times, or 10,000 times, and then you’re ready to bypass, not the brain, but the conscious thought process. And, if you’re good, you will be able to hit that fastball one time out of every three or four. But it’s not a reflex, the information needed to do it is still in your brain, but in a part of your brain that works much faster that conscious thought.",
"Sources: ",
": Daniel Kahneman, ",
": Steven Pinker."
] |
[
"A morbid thought: If someone's head were chopped off, a reflex mediated in the spine would suggest the reflex would still trigger? So a headless body would react to their hand being placed on a hot surface?"
] |
[
"Is there any credible research that cell phone 'shields' aka ‘EMF protection devices’ are effective?"
] |
[
false
] |
[deleted]
|
[
"They should still buy one of my tiger repellent amulets just to be on the safe side."
] |
[
"Okay, but protection from what? What's the mechanism by which harm comes? These are the specific details that get overlooked, and the basis by which these products make money. To prevent something from happening you need to disrupt the mechanism by which it happens. The only way to properly disrupt electromagnetic waves from your head would be to wear a faraday cage all the time. If that sounds impractical, then we need the next step of that mechanism, how exactly does the electromagnetic radiation affect the body in a harmful manner. Because maybe ",
" step can be mitigated.",
"Are we talking about dielectric heating? Because then it's just a matter of asking if our brain cools well enough to handle the additional heat the phone generates. Even ",
" the little device does somehow decrease the power of the signal (usually a bad thing when you're trying to make a call, but whatever) it wouldn't protect you from all the stray radio radiation that you encounter on a day-to-day basis."
] |
[
"Okay, but protection from what? What's the mechanism by which harm comes? These are the specific details that get overlooked, and the basis by which these products make money. To prevent something from happening you need to disrupt the mechanism by which it happens. The only way to properly disrupt electromagnetic waves from your head would be to wear a faraday cage all the time. If that sounds impractical, then we need the next step of that mechanism, how exactly does the electromagnetic radiation affect the body in a harmful manner. Because maybe ",
" step can be mitigated.",
"Are we talking about dielectric heating? Because then it's just a matter of asking if our brain cools well enough to handle the additional heat the phone generates. Even ",
" the little device does somehow decrease the power of the signal (usually a bad thing when you're trying to make a call, but whatever) it wouldn't protect you from all the stray radio radiation that you encounter on a day-to-day basis."
] |
[
"What is it that prevents scientists from developing an HIV vaccine?"
] |
[
false
] | null |
[
"Because HIV is an exceedingly difficult virus to vaccinate against; covid is an exceptionally easy one.",
"The strategy proving so successful with covid vaccines (generate antibodies to the envelope's proteins) was tried ",
" with HIV (for covid, the envelope protein is spike; for HIV, it's gp120/gp41). It failed. So have dozens of more complex vaccination strategies.",
"The challenges with HIV are the following:",
"(1) We do not know the correlates of protective immunity - whereas most people's immune systems are able ",
" covid, almost nobody's immune system is able to beat HIV (and the few who come close to beating HIV are not making immune responses that are easy to simulate in others). Most vaccines are just inducing a similar immune response as natural infection: you get measles, you produce anti-measles antibodies, you don't get measles again. So we give a vaccine that allows you to produce anti-measles antibodies without getting sick. That doesn't work with HIV - people get HIV, produce an immune response, and it neither defeats HIV nor prevents them from getting infected with new strains.",
"(2) Envelope proteins are sparsely scattered on HIV. Whereas coronavirus has dozens of spike proteins per viral particle and influenza has hundreds, HIV has only about 10 or 12. When envelope proteins are closely spaced, a single antibody molecule can bind to two at a time. This increases the bond strength and efficacy of the antibody more than 100-fold. But HIV's surface proteins are so sparse and spread out that antibodies can only bind ",
" at a time. This greatly reduces their neutralizing and opsonizing efficacy. Antibody responses are generally so ineffective at controlling HIV that the virus doesn't even have to mutate to escape them (as it generally does with cell-mediated responses)",
"(3) HIV hides its important antigens under glycan shields - stringy bits of sugar that prevent the relevant immune cells from \"seeing\" them or binding them.",
"(4) Rapid mutation rate. This isn't the biggest part of the challenge, but HIV's immunodominant antigens are capable of rapidly mutating to escape any effective immune responses the person makes. At this point, HIV has so many different strains and quasispecies that makes it more difficult (not impossible, but more difficult) to create a single vaccine that covers them all.",
"(5) Possibility of making infection worse. Again, not the biggest challenge. But there were previous ad-vectored HIV vaccines that increased the risk of infection in some groups. HIV's target cells are the CD4+ T-helper cells. A vaccine that increases the number of T-helper cells in the genital tract ",
" can increase infection risk by increasing the number of target cells for the virus."
] |
[
"The problem with HIV: it has literally ",
" to evade the adaptive immune system. HIV reproduces by injecting its genetic information into the nuclear genome of the cell. But HIV is an RNA virus whereas the genome is written in DNA. So it comes with the reverse transcriptase - a molecular machine that transcribes RNA into DNA, oppositely to the central dogma of molecular biology, hence 'reverse' transcriptase.",
"Why is this relevant? Well, as the reverse transcriptase works, it generates a huge amount of errors in the genetic code. This, in effect, means that HIV mutates wildly.",
"So the vaccine has to be vert robust to account for the mutations that occur in the virus while it is inside the body. Natural selection takes place inside the individual and only the viruses mutated enough to avoid being destroyed by the adaptive immune response survive and reproduce.",
"Reference:",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2572109/#:~:text=The%20extraordinary%20diversity%20of%20HIV,represent%20unprecedented%20challenges%20for%20vaccine"
] |
[
"I would hope that the latter half of what I wrote made it clear to anyone remotely familiar with central dogma. It’s the latter."
] |
[
"Once a black hole decays from Hawking radiation what is left behind?"
] |
[
false
] |
Once the hole is completely decayed what happens to everything that was "sucked up". Is it just a mishmash of everything from light to stars and planets? Or once it decays does it re collapse into a new black hole or a star? I'm so confused on what happens to black holes that die.
|
[
"Hawking radiation is insignificant for massive black holes. It only becomes very important when a black hole is very small and has little mass or energy left, and it causes the black hole to lose mass and energy very quickly. We're not really very sure what is released in the last few milliseconds of the black hole decay, because the mass of the black hole is approaching the Planck mass and a quantum theory of gravity is needed to figure out exactly what happens. There is ",
"recent work",
" that indicates that the final energy release contains information about everything that fell in in the first place. But once the black hole has decayed, nothing remains."
] |
[
"Nothing but the radiation that was emitted, which is probably far away from the black hole by then."
] |
[
"Or once it decays does it re collapse into a new black hole or a star?",
"By the time it gets really small it is most likely billions of years after it initially formed and it has been radiating away energy over those billions of years, so it isn't in any danger of just re-collapsing. ",
"I'm so confused on what happens to black holes that die.",
"As others have said no one knows for sure because we don't have a theory of quantum gravity, but presumably the black hole radiates energy away until it is just a heavy unstable particle like a top quark, which then decays through known decay channels like any other unstable particle. "
] |
[
"Why are 10 dimensions needed in string- theory ?"
] |
[
false
] |
please explain why "superstring" needs 10, M-Theory 11 and bosonic even 26 dimensions, equations and everything else is very much appreciated.
|
[
"Basically, and someone can correct me if I misrepresent things, there's a mathematical procedure you do in quantum field theory called renormalization, which takes equations that would normally give an infinite answer and makes them finite. You can do this with a variable D in your equation that represents an arbitrary dimension, and then set D=3 (for example) when you're done.",
"When you try to do this for superstring theory, you get an infinite result unless D=11. For bosonic string theory, it's D=26."
] |
[
"This is exactly what I was looking for. Thanks.",
"And I'm not OP. "
] |
[
"Very few, if any, will be able to explain it very concisely.",
"If you're really interested, I'd recommend a book \"The Elegant Universe\" as a starting point. ",
"Edit: and it looks like iorgfeflkd is one of those. I'd still recommend the book"
] |
[
"How cold, and for how long, does the earth have to be in order for all bodies of water to completely freeze solid?"
] |
[
false
] | null |
[
"You wouldn't necessarily have to be that cold. The phase diagram of water (",
"http://ergodic.ugr.es/termo/lecciones/water1.html",
") shows that even at the bottom of the Marianas Trench (pressure of ~100 MPa), water will still freeze at ~0ºC. Granted, the oceans aren't pure water, so the freezing point drops due to the dissolved minerals (\"sea salt\"). ",
"So if you could cool the entire surface to, say, -10ºC and waited maybe a few hundreds or thousands of years, the oceans could freeze solid. This neglects the heat from inside the earth, which is released into the oceans as superheated water and lava from undersea vents and volcanoes. In reality, even if the surface of the earth were to cool to -300ºF, there would be a crust of ice on top of a liquid ocean (or at least pockets of liquid water), kept above freezing by the earth's heat. And the Earth's internal heat won't peter out for probably another couple billion years, meaning you could never totally freeze all the oceans.",
"In the same way, the ",
" of Europa is -260ºF, but the hypothesized liquid water ocean below the solid crust is presumably warmer. In that case, the warming heat comes from tidal forces induced by Jupiter's gravity \"warping\" the moon. Kind of like how when you bend a coat hanger back and forth it warms up.",
"In short, you couldn't keep all the water completely frozen in perpetuity until the sun stops shining and the internal temperature of Earth drops to at least close to freezing. If both of those things happened instantaneously, it might take from a few years to a few thousand years for all the water to freeze, depending on how far below freezing you make things."
] |
[
"Assuming that the coldness was coming from some direct source, you would have to have a very cold temperature. The first to freeze would be lakes, ponds, etc. The oceans would be very difficult to freeze, because of enormous size and freezing point depression due to dissolved salt in the oceans. One of Jupiter's moons, Europa, has water. The temperature of Europa is -260 degrees Fahrenheit, and we have discovered that it contains liquid water beneath the surface. Seeing as these bodies of water are smaller than Earth's and they still contain liquid water, you would have to reach a very low temperature to freeze all of Earth's water."
] |
[
"When you say 'water' do you actually mean water, or just a liquid of similar properties? "
] |
[
"If stars convert mass directly into energy via fusion, is there a \"natural\" way to convert energy back into mass?"
] |
[
false
] |
I just saw video explaining how stars convert mass into energy. Is there a way that does the opposite? And if not, will there come a time in the universe where all mass will be eventually pure energy running around forever?
|
[
"where all mass will be eventually pure energy running around forever? ",
"Technically there are no such things as \"pure\" energy nor mass. Mass and energy are properties, ability to resist acceleration (inertia) and ability to do work respectively. They are also conserved quantities which means that they can't change within a closed system.",
"Matter though, is a real non-abstract \"thing\" which can have properties such as mass and energy, and it can be converted into non-massive particles with energy, such as photons.",
"The Large Hadron Collider creates particles mostly from the kinetic energy of accelerated hadrons. ",
"The Higgs particle was ",
"~67 times",
" heavier than the protons that fused it.",
"EDIT: Added some clarification of matter, mass and energy. Also, accidentally a word."
] |
[
"This is wrong.",
"Nope. It just is something that isn't taught as often in chemistry because the effect is so small. ",
"If you add up the masses of 6 protons and 6 neutrons, you will find that the result doesn't equal the mass of a carbon nucleus. That's because the binding energy of the nucleus plays a role. Similarly, if you add up the mass of 1 proton and 1 electron, the result isn't the same as the mass of a hydrogen atom. ",
"In chemistry, the changes in energy of bonds is very small compared to the mass energy of the atoms themselves. So if you wanted to measure the change in mass as a result of energy release, it would be very difficult. Coal has an energy content of around 24 MJ/kg. Converting this to mass-energy (E=mc",
" ) tells us that the relative mass change would be ",
"less than one billionth",
". "
] |
[
"Isn't Hawking radiation at the boundary layer of a black hole creating matter from energy?"
] |
[
"What is actually happening in my face when the left side of my nose is more congested than the other, then I lay on my right side and the congestion migrates to that side?"
] |
[
false
] |
I understand gravity is pulling mucus through to the other side, but I cant seem to visualize how that's actually happening -- is there no membrane? what consistency is the mucous for it to do what it does? It seems like even the most porous membrane would stop that. Boogers arent exactly flowing, and it doesnt feel runny either. Almost like a spongey slug walking back and forth between nasal cavities as I toss and turn.
|
[
"http://en.wikipedia.org/wiki/Nasal_cycle"
] |
[
"There is actually a lot of communication between the paranasal sinuses, and they are actually divisions of a larger cavity. ",
"http://www.webmd.com/allergies/picture-of-the-sinuses",
"So the sensation you have the the mucus passes from one side to the other is true. The mucus is viscous, but it flows a lot better when it is a warm (body temperature) and 100% humidity environment. When it eventually get to your nose it is a lot more viscous because it is a lot colder and less humid."
] |
[
"https://www.youtube.com/watch?v=eiAx2kqmUpQ&feature=youtube_gdata_player",
"\nSauce explains it brilliantly"
] |
[
"Does the 4.54 billion year age of Earth mean the planet has orbited the Sun 4.54 billion times?"
] |
[
false
] |
Or is it just that old based on how many times it would have to orbit at our current yearly rate? We add leap seconds ever couple years, so I'm just wondering how much of an affect that would have over 4+ billion years.
|
[
"http://en.wikipedia.org/wiki/Year#Variation_in_the_length_of_the_year_and_the_day",
"Sun loses mass, year gets longer by 1.25 micro-seconds a year. This leads to the earth orbiting the Sun ~4.5405 billion times in 4.54 billion years."
] |
[
"I've heard the days are slowing down because of tidal interactions with the moon. I hadn't heard the year was getting longer. Any links/arguments as to why this is the case? "
] |
[
"Pb-Pb dates of comparably old materials (in meteorites) typically have errors of 1-2 Ma, well in excess of the 0.5 Ma noted above."
] |
[
"Where do you find the best and most informative coverage about the US and Stem Cell Industry?"
] |
[
false
] | null |
[
"Wired. Hands down. Their innovation blog is spot on."
] |
[
"Regardless, very few publications (particularly of the major news corporations) have taken time to give perspective on what many of the tenets of stem cells.",
"Take pluripotency for example, it wasn't until I found his article through Forbes that I learned there was a discretion between full and partial pluripotency."
] |
[
"I have found Forbes does a good job of breaking down mid-high level science while incorporating excellent sources. John Farrell is one of my favorites."
] |
[
"Why do humans and most other animals have a soft \"underbelly?\" Why doesn't our rib cage protect our digestive organs as well?"
] |
[
false
] | null |
[
"The rib cage isn't just for protection. The rib cage's most important purpose is to inflate and deflate the lungs. The muscles between the ribs help them to expand and retract which brings air into and pushes the air out of the lungs. The diaphragm, which attaches to the inferior border of the rib cage, also helps this purpose. There is no functional need for ribs below the diaphragm."
] |
[
"Also if we had an abdominal section of the rib cage mobility would be greatly reduced. "
] |
[
"There is no functional need for ribs below the diaphragm.",
"Exactly this. If the rib cage extended to cover our digestive system, we wouldn't be able flex our trunk, or bend at the hip. It is simply not bio-mechanically sound. It would affect our ability to bend over, squat down, sit up, have babies grow in the womb, etc. "
] |
[
"Does this image of a bacteriophage comes from an electron microscope or is it CGI?"
] |
[
false
] | null |
[
"It looks like a real SEM, but it does not look like a real virus. ",
"EDIT: Yup. DLC FIB on Si substrate. Real image, fake virus. ",
"http://geometrymatters.tumblr.com/post/55950708193/artificial-nano-t4-bacteriophage-t4",
" "
] |
[
"Thanks! that make sense, cause it did look like a SEM image, but the other bacteriophage I saw where less shaped. ",
"So it's like a model? I found these words: \"diamondlike carbon (DLC) resonator by focused-ion-beam\". No idea what that means though :P"
] |
[
"A focused ion beam is like a nanoscopic 3d printer. Except it can both add and subtract material. DLC is just the material that particular FIB machine uses to print with. "
] |
[
"When condoms are listed as 99% effective, is that per use? How is that number determined?"
] |
[
false
] |
If a condom is 99% effective every time you use it, eventually, the odds are pretty bad. If you and your partner have sex 100 times, the condom's effectiveness would be .99 or 37% effective. Or is the use of condoms 99% effective regardless of the number of times you have sex? That number seems to be arbitrary.
|
[
"besides the actual statistics (the 100 couples for 1 year thing) this number is likely made by lawyers, not scientists. even if they were 100% effective, no company would ever market something as 100% effective when the consequence of failure is having a kid."
] |
[
"This questions comes from a misinterpretation of that statistic. It isn't that there is a 1 in 100 chance each time you use a condom that it might fail. Instead, it's something much weirder than that, but eventually I'll explain why it's really the only way we can measure this.",
"That 2/100 number (actually not 1/100) refers to \"number of couples, out of 100 couples regularly using condoms, who got pregnant in the first year of perfect use.\" This literally tells you nothing about how much risk a single condom has, or how many times you can use a condom before you're likely to get pregnant. A given couple could have had sex ten times or hundreds of times in a year. This literally only tells you how often it happens to couples annually. (In fact the rate for typical--imperfect or inconsistent--use is 18 out of 100 couples in a given year getting pregnant.)",
"How this measurement works--hundreds of couples are asked:",
"Now, the simplest real world example: Researchers collect the data for every couple who used only condoms all year and did it perfectly, and see that 2 out of every 100 couples still got pregnant. Then they look at people who only used condoms and did so with typical consistency, and found that 18 out of every hundred couples got pregnant.",
"That is useful data. You can look at rates for other methods and compare their effectiveness.",
"But you may still want to know the chances that ",
" will not work. Unfortunately, a study to determine that would need hundreds of couples to write down, after every sexual encounter during a long period: when it happened, whether a condom was used, if it was used correctly, what the nature of the encounter was (was there ejaculation, did it happen inside the woman, did it happen outside the woman, was it inside a condom whether it was inside or outside the woman, was a new condom used after ejaculation to continue having sex, etc.) when the event occurred in relation to the woman's menstrual cycle, and if a pregnancy occurred, identify when it happened if more than one encounter could have caused it. You're not getting that kind of journal out of very many people for very long, and dealing with the many potentially confounding factors will take a lot of work.",
"Further, that data couldn't be gathered for other methods which confer long-term protection, and for those, even imperfect use isn't a one-off event.",
"So, it doesn't mean that there is 2/100 chance this particular condom won't work. I couldn't tell you that chance if I wanted to, and it might not actually be the most useful data anyway. But above is what the number actually means."
] |
[
"Condoms come along with a small information package that tells you what the failure rates are. Here is an example: \"Pregnancy rates for birth control methods. (For one year of use in the United States)\"",
"For \"Male latex condom\" it states 2% for \"Lowest Expected Rate of Pregnancy\" - so it means that if users do everything right for the full year of regular intercourse, 2% of the time the product will fail and lead to pregnancy.",
"So the 98% figure isn't \"per use\" - it is \"per typical year of correct use for every act of intercourse\".",
"Unfortunately in this sample packet, the definition of \"one year of use in the United States\" is not given, but is a common method of reporting failure rates (e.g., like this ",
"CDC site",
")."
] |
[
"Do veins grow in the same configuration in most/all people? That is, will my neighbor's veins branch in the same places/same way as mine?"
] |
[
false
] |
Obviously human bodies have variation, but most people are born with two eyes, two hands, ten fingers, etc. which are all in the same places. Does this apply to veins, too, or do they vary in the number of places they branch/particular places they branch? I guess this question can apply to other parts of the body, too, like the nervous system...
|
[
"The major vessels have a pretty much identical branching pattern in terms of where and how often, which is a pain in the arse to learn in anatomy courses, believe me. Same holds for nerves. If you look at the small vessels supplying the tissue directly, things get more random, again for innervation."
] |
[
"Consider them much like hands and eyes: at a large enough scale, they are very similar, but when you get to finer scales (fingerprints, the structures in the iris, fine veins and capillaries), they become much more unique. A forensic anthropologist in the UK has performed research on the individuality of vein patterns in the forearm for the purpose of using as evidence in court cases, since those patterns will show up on IR cameras."
] |
[
"I’d just like to add that there are areas in the body that are prone to more variation than others, the forearm for example has a few different vein patterns which are quite common, but as the others said, most of the important vessels don’t variate much"
] |
[
"In Layman's terms, how do the new RTX graphics cards calculate the path of light rays?"
] |
[
false
] | null |
[
"The maths behind raytracing isn't too complex. You work out where a beam of light hits a surface, and then you work what direction it bounces to etc. The problem is that you have a ",
" of rays of light to deal with, and that gets computationally expensive.",
"So what you do is you run the calculations in ",
". That is, instead of having one processor chip doing one ray at a time, you have several chips running one ray each at the same time, and that speeds things a up a lot.",
"Now, this is where you have a choice. You can either use a small number of expensive but fast chips with lots of features, or you can use a large number of cheap but slower chips with minimal features. Which is better depends on a lot of things, but mostly on how complex your problem is, and how easy it is to split up your problem into small chunks. If the chips have to do a lot of communication with each after to solve the equations, then it's usually better to have a small number of fast chips. But if the chips can solve the equations independently of each other, then it's usually better to have a large number of cheap chips.",
"Raytracing is one the best examples of the second type. The maths for the rays can all be done independently, and the equations are actually pretty simple. So what you want is a large number of cheap chips. ",
". Your computer might have 2-16 expensive \"CPU\" processor chips, but a GPU (a graphics card) might have hundreds or thousands of cheap \"GPU\" processor chips. So, for these particular problems, the GPU solves them much much faster.",
"Additionally, because people use GPUs for problems like raytracing so often, they can actually hard-code some of the maths onto the chip to make it extra fast. So if you're doing something like matrix multiplication, which involves several steps of additional and multiplication, you'd normally have to do each of those steps one at a time, sending the results back and forth each time, storing things in memory along the way etc. A GPU might have a special section dedicated to matrix multiplication, so you send in a chunk of data and it spits out the result extremely fast without having to go through the intermediate steps.",
"But the key thing is that a GPU is a big pile of cheap processors, and that's often a lot faster than a small pile of expensive processors."
] |
[
"i'd like to add that following ray bounces from light source to camera still is not cheap so instead they follow rays from camera to light source"
] |
[
"Indeed. This is primarily done so the GPU doesn’t have to worry about rays that end up out of sight of the camera."
] |
[
"Why are African Americans usually lighter skinned than Africans?"
] |
[
false
] |
[deleted]
|
[
"My thought is that it is a result of interbreeding with light skinned people",
"Yup.",
"(",
"ref",
")"
] |
[
"What makes you think that this is actually true? I'm not saying it isn't, but has this been approached scientifically?",
"Also, it is possible and likely that the genetic diversity throughout the African dark-skinned races is much much larger than in America. It would make sense that the slave trade \"imported/kidnapped\" people only from a few specific locations in Africa. That means you can't really make a general statement about the skin color of all Africans."
] |
[
"Sounds right. I just wanted to make sure I've considered the whole picture (or at least a bit more than just the focal point) and clarified that there isn't just one skin color throughout Africa before jumping the gun."
] |
[
"What are the molecular differences between milk, creme, butter, and cheese?"
] |
[
false
] |
What are the molecular differences between milk, creme, butter, and cheese? Are there chemical differences too?
|
[
"Milk is a colloid composed mostly of water and fats and also calcium and protein. Cream is an oil in water emulsion, meaning more water than oil. It's basically just the milk fat clumping together. Butter is the opposite, a water in oil emulsion. Take most of the water out of milk and leave the fat, that's butter. Cheese is a huge grouping, it's mainly milk fats and proteins acidified to induce curdling and treated with bacteria or mold. "
] |
[
"I apologize for not making my question more detailed, but I am curious more about specifics. I understand the general differences between the four. I understand the processes of production for all of them as well as their basic fat/water/protein relationships. That much i've learned from my own reading and working with the materials.",
"CarbonWeAre says \"Take most of the water out of milk and the fat, that's butter\", but isn't that cream? Cream is the fat from milk in ultra-concentrated form, but if you just leave cream out it doesn't turn into butter, it turns into sour cream. What changes are occurring during cream's transformation from concentrated milk fat into butter fat? All it takes is a good whipping for about 20 minutes and your cream is butter, but it's a radically different thing. What is happening in that shift?",
"I'm more interested in why/how (on a scientific level, not just \"churning cream makes butter\" or \"bacteria in milk makes cheese\") the changes occur between the different states, and most importantly what changes are occurring on a deeper level, such as variations in fatty acid chain lengths, triglyceride concentrations, protein structures, etc. These foods are vastly different from each other, and I want to really understand those differences.",
"Again, sorry for not including all that in the subject. I just assumed if I \"asked science\" that I would get some crazy-ass detailed answers. Thanks CarbonWeAre and LULBASAUR for your prompt responses!"
] |
[
"I believe most of the calcium is contained in the proteins. Not that it makes much difference in then end though."
] |
[
"How do electrical storms affect cell phone reception?"
] |
[
false
] |
Today I was having trouble with cell phone reception over the course of several hours, and postulated that it was due to a large storm passing by. Would a storm block cell phone reception and if so how?
|
[
"The electrical storms generate a lot of random radio waves, which decrease dramatically the ",
"signal_to_noise ration",
". An example of it would be whispering in a silent room vs whispering on high way, you can hear it perfectly in the room but not on high way."
] |
[
"How are the radio waves generated? Buildup of EM-spectrum energy that's discharged via lightning, right?"
] |
[
"When a large diffrence in the electrical charge of the ground and the cloud (or cloud to cloud) builds up, large amounts of charged particles can break through the atmospheric barrier and flow between the air and ground. This mass transfer of charge radiates much like an antenna would."
] |
[
"How can things with no mass make up everything that has mass?"
] |
[
false
] |
Basically, how can elementary particles with no mass, electrons and quarks for example, make up everything that has mass, such as protons and neutrons?
|
[
"Quarks",
" and ",
"electrons",
" ",
" have mass. However, the mass of the individual constituent quarks is ",
" than the total mass of the particles they make. The reason for this has to do with binding energy, but this delves into quantum chromodynamics which I don't really know anything about; I hope someone with more expertise will chime in."
] |
[
"This is a good YouTube video by Veritasium called \"",
"Your Mass is NOT From the Higgs Boson",
"\" which gives a nice heuristic explanation of how baryons get their mass."
] |
[
"Interesting fact: the top quark weighs about as much as a tungsten atom. It is by far the most massive elementary particle."
] |
[
"What happens to the debris we inhale on a daily basis? do we absorb nutrients from the air?"
] |
[
false
] |
[deleted]
|
[
"Dust and other irritants are not absorbed into the bloodstream nor otherwise broken down in one's respiratory system. They are captured by small hairs and mucus and expelled out the way they came through coughing, sneezing, and picking. With the lungs some may also be swallowed and dealt with by the digestive tract.",
"As for the whole nutrient rich dust, you need to understand how molecules can cross a mucus membrane. There are two primary mechanisms known as para-cellular (where they go through cells) and intercellular (where they go inbetween cells). Although some gases can cross as they are, dust is solid particles which would first need to dissolve into solution. There is just no way you would be able to transfer the required amount of water and calories to sustain life."
] |
[
"You're right that we don't have that dust in your lungs, as the gas exchange areas of the lungs (alveoli in particular) are very, very delicate and prone to infection. We don't want any debris in there. ",
"What happens instead is that, as you say, any debris we inhale is caught in mucus. We then have what is termed the mucociliary escalator which is just the name for the process carried out by specialised cells in the respiratory system that have all those finger like projections called cillia, and they\"beat\" in a cranial direction (towards the head). ",
"This removes particulates from the bronchi in the lungs and the trachea (windpipe). The mucus is moved via this mechanism to the oropharynx where it can then be swallowed. This means that any dust, debris or bacteria we inhale is destroyed in the stomach by the acid. Basically, the mucocilliary escalator is just the body making us swallow our own snot and phlegm. ",
"As such, no, it wouldn't be possible to gain any nutrients from dust because particulates don't make it to the blood stream (because the mucus catches it and we swallow it so it can't get to the blood via the lungs) and anything we swallow gets broken down in the stomach. And it's not just nutrients we need to live, we need energy as supplied by fats, sugars etc...",
"Edit 1 - just needed to make my final paragraph clearer"
] |
[
"Your respiratory cilia ",
"move mucous toward the throat",
" where it is swallowed."
] |
[
"Why does a camera measure luminance in a scene and not illuminance?"
] |
[
false
] |
I always thought that a CCD or CMOS sensor measured how many photons had hit a pixel within a given time frame. This seems to suggest that illuminance is being measured, if the pixel has a certain area its value will be proportional to the illuminance hitting it. However i understand that a camera is sensitive to Luminance, and is demonstrably so by moving it further away from a light source, where the light source looks smaller but has the same "brightness". How is this?
|
[
"The key here is to note that the camera is measuring the light coming from the scene it is taking a picture of. It thus measures the amount of light being reflected off the object from a light source; this is luminance. Measuring the total amount of light hitting the object, reflected or otherwise, would be illuminance. You are correct in thinking that measuring the amount of light hitting the camera lens would be illuminance, but note the luminance being referred to is that of the scene the camera is taking a picture of, not the camera lens."
] |
[
"The amount of light passing through the lens and aperture should be directly proportional to the luminance of the scene, so theoretically yes the illuminance on the CCD should be proportional to the luminance of the scene. If you have no lens or aperture but simply a CCD it is directly measuring how much light is incident upon it coming from the scene, so again the illuminance on the CCD will be directly proportional to the luminance of the scene, just by a different proportional constant than if you had a lens/aperture."
] |
[
"So the CCD sensor is a measure of the illumination hitting it. However the illumination hitting it comes from the lens and not the scene, so is the illumination hitting the CCD proportional to the luminance of the scene when there is a lens/aperture? ",
"If instead of a camera i has a ccd with no lens and no aperture that would measure the illumination of the ccd from the scene , and not the illumination of the ccd from a lens/aperture?"
] |
[
"Why don't freight trains use turbine engines?"
] |
[
false
] |
Freight trains in the US use diesel-electric drive trains where the engines act as a generator that then drives electric motors. These trains are supposedly extremely efficient, with a commonly-cited figure of 400 mpg per ton. However, I'm operating under the assumption that turbines are the most efficient way to produce electricity as they're used to produce electricity for the grid. If this is the case, then why aren't trains using turbines, since they're trying to turn fossil fuel into electricity at peak efficiency? If it's not, then why do power plants not use diesel?
|
[
"Because trains do a lot of idling as well. Turbines are ungodly inefficient at low speed (power)",
"There are several examples of turbine locomotives though. The opitomy of which were Union Pacific's General Electric turbine locomotives (GTEl's). Flooring 8500hp (and by some accounts capable of up to 10k.)",
"The main disadvantages comes in their size, and the massive amount of fuel.",
"The GTELs used a 3 unit consist for each motive into. By today's standards it would be underpowered (8500 vs 13k in flagship locomotives), they also used more fuel. The reason that UP's GTELs were economic for the time was that bunker C fuel had no other use (This was a time before advanced refining techniques) and it was first cheap.",
"They are/were also exceptionally loud."
] |
[
"This is super interesting, thanks! Btw, the word you're looking for is epitome, not opitomy."
] |
[
"Power plants work differently. They use heat to generate high-pressure steam, and send that through a series of turbines to extract work from it. That process is very efficient. For a gas turbine engine, it's the expanding gases from the combustion itself that turns the turbine. While capable of generating high power, it's not as efficient in terms of % of the original thermal energy that is converted to electrical energy.",
"The reason they don't do heat->steam->turbine->generator setup on locomotives is that it's much too bulky. The steam turbines scale up very well and can be made more efficient as they make them large. If you tried to scale it down to a locomotive size, it would be much heavier and less efficient than the diesel electric setup they currently use."
] |
[
"Will we be able to feel or notice when the andromeda galaxy collides with ours?"
] |
[
false
] | null |
[
"Assuming you're anthropomorphizing The Milky Way, we will feel it. The individual solar systems not so much. The space between the stars is so vast, that the stars will just glide through each others neighbourhoods.",
"\nOn astronomical time scales, there will be stars thrown about all over the place, but on civilization time scales, absolutely nothing will be happening, except the night sky will change slightly."
] |
[
"The andromeda galaxy will collide with ours in about 4.5 billion years (4.5 billion years is also the age of the Sun. Coincidence? yes). By then, it seems unlikely that any humans will still be around. Even if we spread across the galaxy somehow, presumably we'll have evolved into something we wouldn't recognise as human.",
"But if we ignore that and imagine what would happen if we are around... I don't think we'd feel anything. Astronomers would be having a great time, there'd be so much going on. Astrologers would be panicking as all the constellations fall apart. ",
"But the thing is that it would all be pretty slow on human timescales, and it's unlikely that any stars will be colliding with other stars. The Sun might get thrown out of the new galaxy forming from the collision, but that's not necessarily a bad thing for anyone living around it, apart from disrupting our plans for galactic domination.",
"By the way, if you want to see what it would look like, the game Universe Sandbox has a simulation of it, it's pretty cool to watch"
] |
[
"We won’t be here. And likely, neither will any other species alive today. 4 billion years of evolution molded us to the species that we are today, and 4 billion more is going to do the same. ",
"As for your question, maybe someone like ",
"u/astrowiki",
" could comment about gravitational effects or whatever. I suspect we wouldn’t feel anything though, except for the absolute briefest moments in cosmological time,"
] |
[
"What are these lights that shine on the astronauts when they get interviewed?"
] |
[
false
] |
Every time I watch one of Commander Scott Kelly's interviews, I see a bunch of laser looking lights on him. They don't appear to have a pattern and they seem to be shining around the room as well; you can see them on the cameras too in the following pictures. Apologies for the low quality images, but you should be able to see the lasers in any interview with Commander Scott Kelly. Without circles: With circles: Thanks in advance!
|
[
"Cosmic radiation damaging the CCD sensor in the camera in certain spots where it hits."
] |
[
"A paper describes this exact problem: ",
"Influence of Terrestrial Cosmic Rays on the Reliability of CCD Image Sensors ",
". ",
"Or you can read this ",
"astronomer's web page about general imaging nonsense",
"."
] |
[
"Not so much \"explosions\" as they are \"photonic booms\", the light equivalent of a sonic boom. ",
"Sonic booms happen when an object creates sound waves while traveling faster than the speed of sound in the medium it's traveling in. ",
"Likewise, light travels different speeds in different mediums. The only \"absolute speed limit\" is the speed of light ",
". It is perfectly possible to have something travel faster than light in a medium. Cosmic rays do just that when they pass through a dense medium - such as the liquid in your eyeball. So they create a sonic-boom-like pressure wave of light that astronauts see as a flash. ",
"That's also how cosmic ray detectors on Earth work - they're just a big pool of water with a bunch of light detectors around them, looking for the \"photonic boom\" of a passing cosmic ray. "
] |
[
"Will a planet(s) eventually form in the Kuiper/Oort Cloud?"
] |
[
false
] |
[deleted]
|
[
"Yes, the asteroid belt is also very low density. The whole thing has only a few percent of the mass of the Moon, and that's spread out over a gigantic area. ",
"Also yes, Jupiter prevents asteroids from doing very much accumulating."
] |
[
"Yes, the asteroid belt is also very low density. The whole thing has only a few percent of the mass of the Moon, and that's spread out over a gigantic area. ",
"Also yes, Jupiter prevents asteroids from doing very much accumulating."
] |
[
"No, there's very little matter out there and it's ",
" low density, and the Kuiper Belt can't really create large accumulations of bodies because the gravitational influence of Neptune will perturb orbits too much.",
"The Kuiper Belt has really low density, but it's ultra-crowded compared to the vast empty expanse that is the Oort Cloud. It's never actually been directly observed, but its presence is inferred from the presence of long-period comets. These all have highly elliptical orbits, which prohibits them from ever clumping together. It's possible that there are objects out there with circular orbits, but probably not because there's nothing to circularize the orbits and thus any perturbations would not be easily corrected."
] |
[
"If we turned off every electrical light in the whole world, would light pollution go away instantly, or take time?"
] |
[
false
] | null |
[
"Light would dissipate at the speed of light - so it would appear instantaneous to humans to the extent that photons would stop bouncing off of the air and traveling back to eyeballs in a fraction of a fraction of a second. ",
"You probably wouldn't immediately see a wonderful dark sky, though, because human night vision takes time to acclimate to dark. The rods in your eye contain a protein which is destroyed by energetic light (not by low energy red light, importantly). When that protein in your rods is destroyed by a photon, it sends a signal to your brain, allowing you to construct a gray-scale image (night-vision is color blind!). Rods are much more efficient in detecting photons than are the color-sensitive cells in your eye, the cones. In bright light, all of the light-sensitive proteins are destroyed and they take about half an hour to build back up completely. So in half an hour or so, the effects of light pollution on your sight of the night sky would be gone."
] |
[
"In the big East coast blackout of 2003, I hope people took the opportunity to look up at night. Truly dark skies are absolutely mind blowing. It's safe to think that a significant portion of the population has never seen the milky way with the naked eye."
] |
[
"I remember the 2003 blackout. It was too cloudy where I was to see the milkyway. What a waste"
] |
[
"Is it possible to refine iron out of Hemoglobin?"
] |
[
false
] |
I've done some snooping around the net, and I found that there is about 5.5 liters of blood per person. Take all the red blood cells in 5.5 liters, times 280 million hemoglobins in 1 cell, times 4 hemes per hemoglobin, and you get ~2.7 grams of iron in a person. Is there any way to refine the iron out of blood? I don't care if it's feasible or even sensible, only if it's possible. If so, how would it be done? Thanks! PS:Not a serial killer! I just had an idea for a character with a vendetta. This is all for theory.
|
[
"Most definitely. Part of it has already been done in alchemical history, though extracting iron was not the goal.",
"Prussian blue",
" is a paint pigment that's first synthesized in the 18th century. It is an iron compound complexed with cyanide ligands. It was accidentally discovered when a paint maker used materials contaminated with animal blood, which was the source of the iron in the compound.",
"Now of course, the paint pigment isn't pure iron, but without the baggage of complexing with heme the resultant reduction to elemental iron is considerably easier.",
"So, to this day, you can repeat this very experiment - though using very caustic and harsh ingredients - to extract iron from heme to complex with cyanide. A documentary series called ",
"Chemistry: A Volatile History",
" has a segment specifically on the synthesis of Prussian Blue, and I highly recommend the series."
] |
[
"Interesting question. Possible? Yes. Easy? Nooooooo. ",
"If you could purify all the iron ions from the heme, the problem you'd still have to deal with is a very energy-intensive chemical reduction reaction to convert the Fe",
" to Fe",
" This is basically un-rusting the metal and takes a lot of energy, though it is possible with electrochemical techniques. "
] |
[
"There would be many ways of doing that. The most straightforward method, although not likely to be anywhere near the most efficient, would be mass spectroscopy (something like ",
"ICP-MS",
". Which, in simple terms, entails blasting the molecules apart completely into atoms and then sorting the atoms according to mass. ",
"A method that'd be more efficient would be to use traditional 'wet chemistry' methods. I.e. something like dissolving it all in a strong acid or oxidizer to destroy the organic matter, and leave free Fe-ions, which could be separated out. e.g. maybe start with raising the pH, which would cause Fe and other insoluble metal hydroxides to precipitate out, wash the crystals, re-dissolve them and then use reagents specific to iron to precipitate it out alone (or alternately get rid of the others). ",
"I wouldn't be surprised if the biochemists hadn't already found specific methods for getting the iron out of hemoglobin though."
] |
[
"How much harder would it be to get to another planet if the destination planet was orbiting in a plane perpendicular to ours?"
] |
[
false
] | null |
[
"You play KSP, don't you?"
] |
[
"It would depend on a lot of things -- ",
"how fast the planet is moving (relative to the star)",
"how strong the planet's gravity is",
"what other planets are available for ",
"gravity assist maneuvers",
"In some gravity-assist scenarios, you could match a polar orbit quite cheaply. The ",
" spacecraft was tilted into an orbit perpendicular to earth's, using a single flyby of Jupiter. (It studied the polar regions of the sun, so it needed this kind of orbit). Using a giant planet for several such gravity assists, you might be able to closely match a target object's orbit, and insert into it with not much propulsion.",
"https://en.wikipedia.org/?title=Ulysses_(spacecraft)#Jupiter_swing-by",
" gravity assists, it could be extremely expensive, given how fast planets move around their stars. Earth orbits at 30 km/s, for instance. A massive planet would be somewhat easier to capture into to, given the ",
"Oberth effect",
". With a less massive planet, you'd have to match the orbit speed using propulsion. ",
"I graphed a range of numbers for a simple case -- the propulsive delta-v cost needed to match a target's orbit, starting from an intercepting trajectory. The upper figure is for coplanar orbits; the lower one is for perpendicular ones. The range of target planet sizes includes earth-size ones (11 km/s escape velocity) and gas giants (~40 km/s). The star's mass is 1 solar mass, and the intercept trajectory is a Hohmann transfer ellipse from 1 AU (= earth orbit).",
"https://imgur.com/a/lpNw4",
"\n(source equations included)",
"It looks really impractical in most cases -- all except a massive planet in a very slow, distant orbit. For other cases, you'd need either some kind of gravity assist, or very efficient, unconventional propulsion like ion engines."
] |
[
"Not significantly. The added delta-V cost would be on the order of planetary orbital velocities, tens of kilometres per second. But to achieve interstellar travel in a reasonable timescale, you would already want to be doing at least hundreds and preferably thousands of kilometres per second."
] |
[
"Can pathogens actively target wounds, or are infections totally random?"
] |
[
false
] |
Can pathogens detect open wounds and attack them, or are the infections we receive totally random happenings?
|
[
"There are also the bacteria which are part of your natural flora to consider. Staphylococcus aureus is a nonpathogenic bacteria until it is given the opportunity to multiply more rapidly (in a wound) than it normally does on your skin where it is not exposed to as much sensitive tissue. "
] |
[
"Not really. Bacteria on fairly dry surfaces don't move fast, and there's also the skin's natural flora to contend with. Usually, bacteria are carried in by another, faster moving object like a hand or paw fiddling with the wound or contaminated materials getting into the wound. Viruses aren't motile. I really can't speak to protozoa, but I'd wager they don't seek out wounds, either.",
"In principle, there could be chemotaxs - movement seeking out certain chemicals, but I can think of no evidence suggesting this. Additionally, the worst of the wound infections tend to be bacterial in nature, and those bacteria tend to be ones which are better adapted to soil conditions than infection conditions."
] |
[
"Yes, that's true. I overlooked that; thanks for the correction. "
] |
[
"Is it possible to become addicted to a substance when unaware of taking it?"
] |
[
false
] |
Say I have Addicting Substance A (known to cause both physical addictions and mental dependency). It's effects are euphoria, peaceful feelings, and a strong antidepressant. I secretly administer this substance to Subject A through a variety of ways; in his food, powder on his clothes, piped in through vents, etc (so he doesn't get attached to a single carrier, ie from a cigarette). Will Sub A become addicted? Additionally, he give AddSub B to Subject B. It is also physically and mentally addicting. However, it's single effect is that is slowly lowers cholesteral, no other side effects. It is administered in a similar fashion. Will Sub B become addicted as well, even though there's no feelings, good or bad, present? Lastly, AddSub C and Sub C. Addicting, anonymous delivery. This drugs effects are minor nausea, dizziness, and a depressant. Would Sub C become an addict even though it's a complete downer?
|
[
"Physical addition is different from concious addiction.",
"A human body will certainly become \"addicted\" to substances whether they are aware that they are taking them or not. This \"addiction\" is more of an acclimatisation, simply becuase the body gets used to having the substance, so it will go through any and all withdrawls as per normal. The kicker is that the person will not understand the reason for the withdrawl symptoms.",
"A concious addiction however is where the user is mentally aware of what it is that they crave. Yes, they go through the physical withdrawls, but the mental and concious withdrawl may actually make it much harder.",
"I used to smoke, and when I quit, it was quite difficult, but in retrospect, it wasn't the actual physical withdrawl that made it painful or difficult, but rather the constant thought \"Hey, take five, smoke em if you got em...\". If I was to right now suffer through the exact same physical symptoms, I would probably be mildly annoyed for about two weeks, then get totally over it. (That certainly wasn't the case when I did quit smoking however)."
] |
[
"in his food, powder on his clothes, piped in through vents, etc ",
"Through the umbilical cord is the usual method for this experiment."
] |
[
"At first I was like \"WTF, who would approve that experiment?\" Then I realized what you were saying and got depressed. "
] |
[
"I've heard that if you kno k out a tooth, it's possible for a dentist to put it back. Could you transplant teeth from one person to another? "
] |
[
false
] | null |
[
"The process is called ",
"dental avulsion",
", which is the immediate replacement of a knocked out tooth. However, like reattaching limbs or other organs, time matters, and how the tooth is stored really matters.",
"Placing another person's tooth might be possible (I couldn't find anything that supported that type of use), but you'd have all the same problems as with any other transplant. Rejection. Infections. Etc. Moreover, the article seems to indicate that there needs to be a close fit between the tooth and the ligaments that held the tooth in place. Someone else's tooth may not fit precisely."
] |
[
"Placing a knocked out tooth back into its owners body is difficult enough, you've got about 5 minutes to wash it off with tap water, get it into a glass of milk and rush to see a dentist, after about an hour we will generally not try reinserting a tooth due to necrosis of the periodontal ligament cells. Given all that, what LeftCoastMan says about transplants. Rejection etc. No way it would work even with an exact fit, your body would certainly reject it. Besides we can do plenty of other good things to replace it that wouldn't mess you up."
] |
[
"I thought you that referred to implanting false teeth? "
] |
[
"Why is there glycine in Western Transfer Buffer?"
] |
[
false
] |
Grad student here that does western blots everyday. But I don't know why every protocol which I can find calls for the addition of glycine in the Western Transfer Buffer. Before I get inundated with people mentioning the process of SDS-PAGE and glycine's role in stacking; Western blotting is different, and I don't know why we use glycine when there is no change in pH.
|
[
"Post-Doc in biochemistry here. I looked up the section on protein blotting and immunodetection in \"Methods in Enzymology\" Vol 182 pp 681-682.",
"\"",
" The choice of buffer composition depends on the types of gel and membrane selected. The procedure of ",
"Towbin",
" as modified by ",
"Anderson",
" specifies a Tris-glycine pH 8.3 buffer containing SDS. The recirculating, ice-cooled, high ionic strength buffer used helps prevent the gel from swelling in the absence of methanol during transfer, which can cause poor resolution of proteins on the membrane. However, 10 mM 3-[cyclohexylamino]-1-propanesulfonic acid (pH 9.0 or 11.0) plus 10 % methanol is suggested by ",
"Matsudaira",
" for transfers for SDS-PAGE mini-gels to PVDF membrane.",
"Although many variations of electrophoretic transfer of protein to nitrocellulose have been described, we have found that the procedure that omits alcohol from transfer solutions is generally optimal. Because SDS is not rapidly removed from the protein in the absence of alcohol, the detergent-bound proteins are all initially negatively charged and a more quantitative transfer of proteins is achieved. Furthermore, alcohols or other reagents can alter or modify molecules andmay therefore destroy some antigenic determinants.\"",
"TL;DR glycine helps to keep the gel from swelling during the transfer step and making your protein bands crap-tastic"
] |
[
"Honestly, probably just for buffering since as you said, there's no pH change. It's not doing what it does in the sds-page, that's for sure."
] |
[
"Hmm wow, thanks. I had given a literature search a college try but didn't find anything this satisfying, thanks. ",
"We currently use MeOH in our buffer, I may try excluding it."
] |
[
"Chickens are encouraged to eat as much as possible. Why wouldn't the excess calories just turn into fat? Especially since the goal is to build more muscle."
] |
[
false
] |
It sparked my curiosity several weeks ago when watching a mention of this on the Colbert Report. And today it was turned into a front page post on . The issue is that chickens are fed caffeine amongst other methods of stimulation. All of it contributes to the chickens eating more than they would normally. The idea is to get chickens to grow and mature faster. All the eating in humans just causes us to accumulate fat; why isn't this mirrored in the chickens?
|
[
"True, but the antibiotics they use promote growth."
] |
[
"No, I have a BS in (micro)Biology, so I am familiar with what you're saying. ",
"The question that I am asking is why are the chickens building larger muscles vs fat deposits. The larger food intake is causing them to mature to be fully grown faster. In mammals, we just get fatter. The former just seems like such a foreign concept."
] |
[
"(I did not downvote you)",
"The USDA (can't say the same about other nations) does not allow hormones to be used in poultry. Go to your local grocery store and look at their chicken. A lot of them will boast about how it is all natural and does not contain hormones (added). Well that is because it would be illegal to do so, but they still like to use it as a selling point. "
] |
[
"How do spacecraft get rid of excess heat?"
] |
[
false
] |
I've read the but finding visuals would also be nice. Are there also hypothetical methods of venting heat in space that we currently don't have the technology for?
|
[
"The only way to get rid of heat in space is through radiation. In addition, temperatures across a spacecraft can vary tremendously and can range from +70C to -40C just from one side of the spacecraft to another. So there are a few different things that we can do to mitigate temperature variation and keep our components at optimal temperatures.",
"First off, our on board computers are always generating heat and are at a huge risk of overheating if we don't dump the heat somewhere. So we build heat sinks with materials that love to accept heat such as copper and we route it to the outside. On the outside we will paint panels various colors from white to black depending on our thermal analysis. Different colors have different values for absorption and emission so they can alter the average temperature in the satellite. We also throw insulation in places where we want to keep heat or keep heat away depending on the design. ",
"Essentially though, thermal management in terms of the whole spacecraft falls onto painting panels that are facing space a certain color in order to keep us at the temperature we want."
] |
[
"The only way to get rid of heat in space is through radiation.",
"You ",
" heat something up and chuck it out an airlock, but of course that's not very sustainable."
] |
[
"In ",
"this picture of the ISS",
", the large white panels pointing down from the main fuselage of the station are radiators. Ammonia coolant is circulated through the station and then pumped to the radiator panels, where the heat is rejected into space.",
"Since there's no air in space, there's no medium for conductive or convective heat transfer to occur, so the only method of reject heat into space is via radiation. We may come up with increasingly effective radiators using exotic materials or coolants, but any method of cooling a spacecraft will have to rely on radiation in some form."
] |
[
"Can a supernova remnant coalesce back into a star?"
] |
[
false
] |
If you take something like the crab nebula, could the expanding gas cloud start to collapse back in on itself and form a new star? Or would the shock wave and/or neutron star there prevent that from happening?
|
[
"From the Remains, New Stars Arise\nThe dust and debris left behind by novae and supernovae eventually blend with the surrounding interstellar gas and dust, enriching it with the heavy elements and chemical compounds produced during stellar death. Eventually, those materials are recycled, providing the building blocks for a new generation of stars and accompanying planetary systems.",
"http://science.nasa.gov/astrophysics/focus-areas/how-do-stars-form-and-evolve/",
"So yes and no to your question. The remnants of supernova do go on to form new stars, but they wouldn't 'collapse back in on itself' creating a new star in the same spot. ",
"edit: fixed typo"
] |
[
"So the final 'form'of a supernova is basically a tiny nebula, capable of forming several new, smaller stars and brown giants?",
"Nope. The supernova particles move outward and can't coalesce together as they thin out. What ",
" happen is, that these particles hit other gas clouds in the vicinity and cause new star formation there. Since the particles may be heavy elements produced in the supernova progenitor, the newly formed star will contain these elements as well. "
] |
[
"The short answer is no, not really. The expanding remnant is moving much too fast for that to happen. However, there is a case for a certain range of high-mass stars where some of the supernova ejecta does fall back on to the left-over neutron star a short time after the explosion and cause it to collapse into a black hole."
] |
[
"Do objects actually have a defined color? Is it defined on what color the light source is?"
] |
[
false
] |
For example, my bed sheets are white. I can see that they are white under normal sunlight. However, if I were to take a red light bulb and illuminate my room in red light, the sheets become red; they changed color. I believe you could do that with any other color, like my blue shirt under the red light would look different, my yellow pencil will be different. Are we so used to the color of things under natural sunlight that we consider those colors to be true, or is the color of an object simply based on what color the light source is? I hope this makes sense and I believe I am thinking too much about this, but I'd like to hear the explanation anyways.
|
[
"Your bed sheet is white. What does that mean? Simply, your bedsheet reflects all colors back at you. When you shine white, it reflects all the white back and you see white. What if you shine red? Well there's only red light now, and it reflects the red light back, so it appears red to you.",
"Now let's think of your blue shirt. A blue shirt reflects blue and absorbs other colors; that's why it appears blue to us. Now, if you shine a red light onto it, there isn't much blue light to reflect back to us; the red light mostly gets absorbed into the shirt, so it will appear much darker than usual.",
"Objects do have a defined \"color\" - to be more specific, objects have properties which allow them to absorb certain wavelengths of light and reflect others. So yes, they have an inherent color, but the light that is reflected off also depends on the light you shine on them, because blue shirts cannot reflect blue light when blue light is not there. So the light you shine on objects makes a difference too.",
"Unfortunately the answer to your question is \"both.\" The interaction of the object's properties with the light that's shined on it will form the color you see. :)"
] |
[
"The problem with that, though, is to then wrongly assume that because wavelengths are real, the color we see matches wavelengths linked to that color. When you see \"orange\" on a computer screen, it's not light which is ~630nm, it's an interpretation of 3(ish) wavelengths combined to simulate \"the color orange.\" ",
"That's why I don't like to equate spectral reflectance with color; our subjective experience of color does not necessarily line up with the actual truths in a reflectance spectrum. "
] |
[
"Colour is a property of your perception. It is not a physical property inherent to an object. What ",
" inherent to the object is its absorption spectrum - the object absorbs specific wavelengths of light more than others - or other scattering phenomena."
] |
[
"How precise are large astronomical telescopes (e.g., Mauna Kea)? Does the surface have to be precise within a fraction of the wavelength, or is there more margin for error?"
] |
[
false
] | null |
[
"They have to be precise within a fraction of a wavelength - to get the full resolution and light collection, you want light from the whole mirror to add constructively.",
"ELT with its (segmented) primary mirror of 39 m diameter gets mirrors ",
"smoother than 10 nm",
" or 0.25 ppb - supported ",
"at 20,000 points",
" to keep the overall mirror segments in the right place.",
"It gets worse for shorter wavelengths. The X-ray telescope Chandra had mirrors ",
"significantly smoother than 1 nm",
" - at a level where individual atoms can \"stick out\"!"
] |
[
"Yes, for a reflecting telescope a good mirror is figured (shaped) to within a fraction of a wavelength.",
"The shape of the mirror can be tested optically using very simple equipment. The Foucault knife-edge test requires a lightbulb, a pinhole, and a razor blade. Modern large telescopes are tested with much more sophisticated equipment but the general principle is the same, check the shape of the mirror by checking how it reflects light.",
"The high points identified by the test are then polished down. Historically by hand (a craft amateur astronomers keep alive), in modern practice with either a polishing machine or an ion beam.",
"https://www.opteg.com/ion-beam-figuring/",
"For mirrors larger than about 5 metres figuring the mirror precisely isn't enough, because the mirror's own weight will distort it as the telescope moves around. Today's large telescopes therefore use ",
", where the mirror is supported by actuators that can be adjusted to bend the mirror into shape.",
"https://en.wikipedia.org/wiki/Active_optics"
] |
[
"Typical optical mirrors are already at a fraction of the wavelength in surface flatness (1/4 to 1/10). They are probably at least in those orders of surface roughness, because they not only need to be large to collect more light but also to be precise in order to identify details. The exact precision will depend on the instruments you are using and your goals. There are also tools to compensate for the distortion of the light passing through the inhomogeneous atmosphere in near-real time."
] |
[
"Why does water form these tiny air bubbles on the side of a glass bottle if it is allowed to sit still for a while?"
] |
[
false
] | null |
[
"Most water has various gases dissolved in it, like oxygen or carbon dioxide. The warmer the water is, the less gas it is able to hold--that's why your soda foams up so much more when it's hot than when cold. Also, the less pressure the water is under, the less gas it's able to hold--that's why your soda foams up when you open the can and release the pressure.",
"Water comes out of the tap, where it was cold and under pressure, and starts to warm up. These gases come out of solution, forming bubbles. The bubbles formed at the wall of the glass tend to stick there until they get big enough to break away, which sometimes never happens."
] |
[
"And to supplement this post even more: they form at the side of the wall because the gas adsorbs there for energetical reasons. It \"costs\" less energy for a nucleus (here a tiny bubble, elsewhere a tiny crystal) to grow at a surface. This is called heterogeneous nucleation. In case they would form in water it is called homogeneous nucleation and needs more energy."
] |
[
"And to supplement this post even more: they form at the side of the wall because the gas adsorbs there for energetical reasons. It \"costs\" less energy for a nucleus (here a tiny bubble, elsewhere a tiny crystal) to grow at a surface. This is called heterogeneous nucleation. In case they would form in water it is called homogeneous nucleation and needs more energy."
] |
[
"Could someone recommend a good video tutorial on the chemistry of molecules? I'm taking general biology and might fall behind here."
] |
[
false
] |
[deleted]
|
[
"http://www.khanacademy.org/#chemistry"
] |
[
"And you could also go check out ",
"the biology section",
" if you have trouble at any point in your class. I haven't watched any of those ones (or the chemistry section for that matter), but I did use the probability and statistics sections for brush-up not too long ago, and they are overall, quite good."
] |
[
"Can't upvote this enough."
] |
[
"What percentage of sea level rise is from the thermal expansion of water vs. melting polar ice?"
] |
[
false
] | null |
[
"that's a rise of about 4 m",
"This seems high, so I redid the calculation myself. Yes, recent research has given more refinement to how climactic change has affected water at various depths, and the distribution is far from uniform, so that caveat still stands, but using some basic assumptions:",
"Thermal expansion coefficient for water at 10°C",
": 0.000088 /°C",
"Volume of oceans",
": 1.3 x 10",
" km³ ",
"Average temperature increase of oceans due to global warming over past century",
": 0.1°C",
"Surface area of Earth's oceans",
": 360,000,000 km²",
"If 1.3E18 m³ of water at 10°C heats up by .1°C, it expands by 1.1E13 m³. Dividing this by the surface area of ocean, we end up with ",
" increase.",
"edit: used the right number, but put the wrong one here for ocean volume (10",
" not 10",
" )."
] |
[
"Let's say the average seawater temperature is 15 degrees. If it warms by 1 degree C you get about 0.1% expansion. So for a water column that is about 4km deep (average ocean depth) that's a rise of about 4 m. By comparison, if the icecaps completely melt you're looking at something in the order of about 60 - 65 m of water depth.",
"So the expansion is significant (remember that's about 4m per degree of total ocean warming) but actually very difficult to calculate in reality; different layers of ocean water warm more or less for example."
] |
[
"Yep, thanks. I dropped a zero on my expansion coefficient"
] |
[
"What is the mechanism that causes my heart rate to increase with physical exertion?"
] |
[
false
] | null |
[
"It's a brain signal, you have the SA and the VA node that control the rate at which the heart pumps. Your brain simply detects it is exercising and needs more oxygen and less waste products. When you're exercising, you need more oxygen and you are also generating more waste, but you already know this. Heart beat is a subconscious activity and your brain simply tells your heart to beat faster because it basically feels it's being deprived of oxygen during intense exercise."
] |
[
"You have a number of receptors in blood vessels (aorta and carotid) and in the brain itself which send signals to the cardiac control centre in the brain stem. These receptors monitor the pH of the blood (high carbon dioxide levels = low pH) and pressure of the heart beat. Your heart will beat faster if there is more CO2 dissolved in the blood or if the heart is pumping at a lower pressure. \nThe cardiac control centre in the brain stem then sends messages down the sympathetic or parasympathetic nervous system to the heart increasing or decreasing the heart rate respectively. "
] |
[
"That's what I was looking for. Thanks!"
] |
[
"If a balloon filled with air goes deep enough in the ocean, will it not float up?"
] |
[
false
] |
To further explain this, from my understanding of buoyancy, what creates the buoyancy is the fact that the less dense material displaces more of whatever the surrounding material so much so that displaced material weighs more than the material doing the displacing. So my question is, lets say I have a normal balloon filled with normal air. And I were to bring this balloon to the bottom of the ocean, or to a depth that the pressure of the ocean is so much so that the air inside the balloon is compressed to a size where the amount of water displaced, weighs less than the balloon. What would happen then? Would it just sit at that depth? Would it sink? or would it for some reason I dont know of, float back up to the surface?
|
[
"You would need to be approx. 4.85 miles under water for the density of air to equal the density of water. Any higher and the balloon floats, any lower and the balloon sinks. ",
"I did this calc. quick using this ",
"http://www.calctool.org/CALC/other/games/depth_press",
"\nand this:\n",
"http://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html"
] |
[
"The air would rapidly dissolve into the surrounding water and diffuse outward. ",
"Depending on what type of rubber the balloon was made of, the fragments would likely slowly float upwards."
] |
[
"The air would rapidly dissolve into the surrounding water and diffuse outward. ",
"Depending on what type of rubber the balloon was made of, the fragments would likely slowly float upwards."
] |
[
"Is it true that science knows only a fraction of the molecules present in, say, a grapefruit?"
] |
[
false
] |
How is this recognized and dealt with by the scientific community? Is it important? Is it only necessary where notable side effects have been observed?
|
[
"In order to know they are there you must measure them or prove beyond a reasonable doubt that it has to be there for something to occur. Even then, some are transient, others are just indistinguishable or no one has cared enough to make a reasonable effort of measuring it. Companies spend inordinate amounts of money just trying to figure these things out so they can replicate the taste or smell of something. My business wouldn't exist currently if this was not true.",
"There is a large difference between well understood and complete. For example, organic chemistry is well understood from an empirical sense but we as physical chemists still struggle to accurately model simple interactions. ",
"There is literally no way an intelligent person can currently sit down and give a list of \"these are the the molecules in X object and the only molecules in X object.\" To do so, with any knowledge of how the measurements work is at best myopic and at worst scientific misconduct. Just by the sheer number of permutations of plants and fruit, saying we know the exact molecular make up of one because \"molecular biology is well understood\" is an exercise in ignorance."
] |
[
"This isn't true. There are very few biological molecules that aren't well known, most of them are only trace amounts, especially in something relatively simple, like a fruit."
] |
[
"Partially correct. We more than likely know of the molecules that are in a grapefruit but it doesn't mean we actually know if they are there.",
"As a guy who is building a business designing instruments to help detect these things it is somewhat of a big problem. These kind of systems are incredibly complex and have a very very large number of species big and small. There is no one instrument that can measure all of them even with good separations and even then a lot of the instruments are shaky at best in their identifications.",
"The standard way of measuring these things is instead (for now) \"chemometrics\" where a system produces a fingerprint and all that can be said is that fingerprint is different than system b.",
"P.S. as a pet peeve if we knew all the biologically relevant molecules a lot of scientists like me would be without a job. Don't assume we know everything; assume you know nothing until you have reliable experience otherwise."
] |
[
"Are GMOs generally unsafe?"
] |
[
false
] |
Here in Germany (actually a lot of places in Europe) we have movements that want to completely ban GMOs. They claim that GMOs are generally unsafe because the undestanding of how genes work etc. isn't developed enough and we can't foresee any side effects, even after testing the crops/plants/whatever. They fear that the (probably harmful) organisms will spread uncontrollably. Now, how much of that is true? Are they just technophobic? Also, when will I be able to combine pigs and spiders so that I can get 8 legs per pig? (You don't have to answer that ;-)) I'm not talking about patents, about big business and so on, I'm really just interested in the scientific aspect of the issue.
|
[
"First off, GMO is a broad category. It is often (wrongly) used interchangeably with transgenic, which is different. A GMO, or genetically-modified organism, is any organism that has had its DNA modified directly without using breeding. Transgenic organisms are GMOs where the new DNA in the transgenic organism is from a different species.",
"So, are they dangerous? Unfortunately, this is a question that has to be asked about every specific case individually. So to answer one of your questions, fearing all GMOs is silly. Europe is going overboard on this. ",
"Here are a few specific concerns to have:",
"When we create a GMO, we (not me, I've never done it) do it by inserting the gene we want in our organism into shitloads of eggs/embryos/whatever. The gene gets inserted at a random spot in the DNA - we can't target specific insertion sites yet. This is the reason we have to start with so many - most of the organisms with the extra DNA will be fucked up because the gene will get inserted somewhere necessary for function. Some of the organisms won't have their necessary functions screwed with, but the inserted gene won't be activated like we want it to be. And then finally, by the cosmic lottery, a few of the GMOs will develop normally ",
" have the inserted gene work as desired. When this happens we use some fun techniques that are irrelevant to this discussion to make sure we can get reliable GMO seed.",
"So that is the process. One concern from that process is that even though the GMOs might appear to be acting normal, its possible the new DNA got inserted in a place that fucks with, for example, nutritional quality of the crop (we can basically assume this is all crop-based for awhile).",
"Then come specific problems. First lets talk about corn. GMO corn has a few issues, some \"scientific,\" some social. The main \"scientific\" issue is that while you can control where you plant the GMO seed, you can't easily control where its pollen flies off to. This results in the possibility of the new DNA getting into non-GMO corn, or (possibly but unprobably) hybridizing with wild grasses. ",
"This is directly tied to a social problem with GMO corn: Monsanto owns it. If you are found with it, but didn't buy it ",
", you will get sued/fined up the ass. Aside from the problems this causes in places where people traditionally kept their seed for future years, if GMO pollen gets into your field and Monsanto tests your corn and it comes up positive ",
", you can still get screwed. This is a major problem.",
"Another thing that scares people about GMO corn is that the kind that we talk about that makes the news is really transgenic corn with a gene from the ",
" bacteria. This scares people for two reasons: first, its a frankenstein. I think that is just a social fear, lacking in logic. The second is that the bacteria makes a toxin, which sounds scary.",
"But the truth is that toxin, the Bt toxin, can only harm Lepidoptera (moths and butterflies, which are the biggest pests in larval form). We are pretty sure it is benign to us and most other animals (including many other orders of insects). A caveat to this is that greenpeace-funded study trollingisfun alluded to. It is possible that Bt is bad for us, but clearly it is not bad enough for us to cause us to become sick. If there is a problem with it, it is slow and subtle. ",
"This is kind of an aside, but one hilarious thing about the fear of Bt is that ",
". ",
"One agricultural problem with Bt corn, which isn't related to the transgenic itself, is that it didn't solve all of our problems. For example, Bt is used in cotton these days, also (yep, lots of transgenic cotton throughout NA). The Bt did kill the lepidopteran pests, but then the natural enemies (predators and parasites) of those pests went away, and other pests moved in, requiring in many cases as much pesticide application as prior to Bt. So in these cases clearly the Bt didn't help, but you couldn't call it unsafe. ",
"Yikes this is getting ridiculously long.",
"Before going overboard, I'll just conclude and say that GMOs in theory are not unsafe, but we have not perfected their use by any means, and each specific case should be scrutinized for safety and health concerns independently.",
"To give you a taste of the other side, here are some possibilities GM/trangenics could do for us: ",
"nutritionally complete rice (already in the works)",
"crops that synthesize expensive drugs",
"crops that make energy molecules that are more simply used",
"hardier crops that can deal with climate change, including droughts",
"etc.",
"I think its a bright future. Which may mean you should take my explanation with a grain of salt, because I guess I'm one of the \"bad guys\".",
"Hope this helped! Also, if you have more specific questions, I'll do my best to answer them."
] |
[
"Still testing, no proof of safety hazards.",
"Warning: transgenic plants may contain alllergens. There are brazil nut proteins that are moved into other organisms for purposes of pest-resistance and/or herbicide-resistance. Test for allergens in whatever way you know how before consumption of suspected GMO.",
"Warning 2: If you are a caterpillar, you may be effected by the Bt toxin. Do not eat North American corn -- the toxin may put holes in your abdomen, triggering a state of sepsis on infection. Sepsis hurts. A lot.",
"Warning 3: There is a Greenpeace funded study that says that GMO's (Bt toxin linked GMO's) may be harmful. While Greenpeace is as respectable as PETA, you should be on the lookout for more literature on the issue.",
"Warning 4: The people who are \"afraid\" of transgenics are usually not knowledgeable about transgenics. GATTACA is not a valid source for knowledge of transgenics. Consult your nearby academic teaching unit (ATU/\"professor\") for further information.",
"Warning 5: You may be subjected to bullshit when browsing the internet. Reddit is not an exception to the internet. Please treat any advice you get on the internet as if it came from SomethingAwful or 4chan, and scrutinize information you gain on the internet before you do something silly."
] |
[
"As I said, I'm only interested in the scientific aspect, not legal issues like DRM or patents. That's a political problem.",
"Can you elaborate on your first three sentences though? If they're poorly tested why have there not been any health problems etc.? Have there been any that I'm not aware of? Why are they unnecessary, are there not massive problems with malnutrition in the 3rd world? Why are they irreversible? Are GMOs that have been altered to have the maximum worth for humans even able to compete with the natural flora and fauna?"
] |
[
"Can we inherit intelligence?"
] |
[
false
] |
I mean as if 2 parents with IQ around 120 have a child will the child have an IQ of 120 or More?
|
[
"Heritability of intelligence has been measured, but the outcome is strange and I actually think that's because of a fundamental problem in equating IQ to intelligence. It would really be far more accurate to say that the heritability of IQ has been measured. ",
"Nonetheless, ",
"this study from last year",
" measured a number of aspects of intelligence as a behavioral trait. I think the most interesting finding here for me personally is that assortative mating for intelligence is greater than any other behavioral trait and also greater than the measured physical traits! Which implies that intelligence is more attractive than attractiveness. And from an evolutionary perspective that's extremely interesting. ",
"The strange outcome in the measured heritability of intelligence (IQ) is that it appears to increase throughout life. They found a heritability of around .2 in infancy which increases to about .8 later in adulthood, which is a strange result to say the least. ",
"I'll ",
" that that result actually just highlights the difficulty inherent in measuring intelligence and it may not actually represent a very accurate finding. "
] |
[
"See my responses in this recent thread:",
"https://www.reddit.com/r/askscience/comments/3g4mtq/do_humans_with_bigger_brains_have_more/"
] |
[
"Nonetheless, this study from last year measured a number of aspects of intelligence as a behavioral trait. I think the most interesting finding here for me personally is that assortative mating for intelligence is greater than any other behavioral trait and also greater than the measured physical traits! Which implies that intelligence is more attractive than attractiveness. And from an evolutionary perspective that's extremely interesting.",
"That sounds incredibly fascinating. Does this only apply to people we consider \"mating material\" (long term partners) or also to people we consider hook ups only?"
] |
[
"Pretend for a moment we are mining resources from other worlds and bringing them to Earth. How would this additional mass affect our orbit?"
] |
[
false
] |
At what point would we have brought so much extra mass to the Earth that the planet's orbit around the sun or in relation to the moon/other bodies is fatally affected? These are the things that keep me up at night.
|
[
"It would not affect the orbit around the sun. It probably wouldn't affect the moon either, unless we brought a shitload of mass back. All the asteroids in the solar system weigh less than a percent the mass of the Earth, so that would be difficult."
] |
[
"Is that a metric or standard shitload? (I'm breaking the rules but this was nearly irresistible.)"
] |
[
"The earth already gains between 40,000 and 80,000 tons of mass each year from cosmic dust and meteors, and that has no measurable effect on our orbit. And it has been doing this for billions of years. In other words, more extra mass than is even worth considering. "
] |
[
"When people say \"I can see for miles,\" how would this actually translate?"
] |
[
false
] |
[deleted]
|
[
"The equation to find out, depending on how high your eyes are off the ground, is this. ",
"Distance(miles) = 1.323 * Sqrt(eye height ft)",
"Distance(kilometers) = 3.57 * Sqrt(eye height m)",
"so if your eyes are at 6 feet you can see a horizon line at about 3.24 miles. ",
"Source",
"Btw this only works for Earth, the equation depends on the size of the world. "
] |
[
"The distance to the horizon is based mainly on the height of the viewpoint.",
"For an unobstructed view to the horizon, go to the ocean, for a 5'7\" person standing at sea level, the horizon is 3.1 miles away.",
"For a bunch more explanation and math, check out the ",
"Wikipedia article on the Horizon",
"Edit: Sycosys beat me to it while I was typing."
] |
[
"Others have answered quantitatively so I won't bother, but just for interest, you don't even need a theoretical smooth Earth to imagine this, it's a very visible effect on the ocean. If you look at a distant sailboat for instance, there is a point where you can see the sails but the hull of the ship lies below the horizon. This effect is part of what led ancient people to realize that the earth was a sphere."
] |
[
"On average, do you lose more weight through respiration or pooing/peeing?"
] |
[
false
] | null |
[
"So the primary part of respiration that would be \"losing weight\" is co2 from respiration.",
"1 mol of co2 is gonna take up about 25L and weight about 50g. At normal tidal volume of 500 mL and 12 breaths per minute, you are expelling about 300 mL of carbon dioxide per minute, or 18L per hour. Let's call it 400L per day. So that's 800g of co2 expelled per day.",
"Urine weighs about 1g per mL. A normal person produces around 1600 mL of urine per day, or 1600g.",
"1600 > 800.",
"Of course there are factors like a lot of the co2 you respire being created from inspired O2 and things like that, but the basic math still holds."
] |
[
"Thanks!!"
] |
[
"Not my field, but I was under the impression that you exhale a lot of water vapor as well. That should be fairly heavy, right?"
] |
[
"What would large quantities of protons, neutrons, and/or electrons look like?"
] |
[
false
] |
For example, the inside of Neutron stars is essentially just neutrons correct? What would it look like if we were able to take a knife and cut that star open and let the neutrons spill out?
|
[
"For example, the inside of Neutron stars is essentially just neutrons correct?",
"It's actually a bit more complicated than that - see the cross-section diagram ",
"here",
". But sure, neutron stars have a lot of neutrons inside them.",
"What would it look like if we were able to take a knife and cut that star open and let the neutrons spill out?",
"The answer depends on specifically what you want to know. What defines the color of a neutron star is essentially its temperature - being so dense, it is also extremely hot. Surface temperatures can be hundreds of thousands of degrees, and as a result they radiate X-rays as well as visible light. ",
"According to ",
"this article",
", one neutron star has been observed to emit \"dim blue light\". But in that case, the color is due to photons being emitted due to enormous energy, so this is not exactly the color of neutrons, depending on what is meant by that.",
"If you \"cut open\" a neutron star, you'd still be dealing with the same basic situation. What you'd see is not the color of free neutrons but rather the color of the energy radiated by hot neutrons. ",
"To observe a mass of cool neutrons, you'd have to remove them from the neutron star environment, in which case the superdense material will explode once the star's enormous gravitation is no longer holding it together. But, along with that neutron-star-cutting knife you have, let's assume you have a containment mechanism in place that can keep the neutrons at a reasonable density. Not a physical container, because neutrons would just migrate into the walls - they're neutral so will slip right through the electron barrier that normally keeps atoms apart. Instead, you'd need a giant version of something like this ",
"magnetic trap",
". ",
"You now have a mass of neutrons - realistically, it would be a gas, but let's assume you've somehow managed to condense it to the density of a solid. Now you can finally look at it. What do you see? Nothing. Neutrons are too small to interact with visible light, and won't reflect it. Our neutron mass would be transparent. ",
"But wait! [Free] neutrons decay with a half life of 14 minutes, so in our sample which would need to contain quadrillions of neutrons to have had a hope of being visible to us, neutrons will be decaying all the time. And that decay occasionally produces photons, some of which are in the visible spectrum - see ",
"What light from yonder neutron breaks?",
" This means that our mass of neutrons should ",
" radiate in the X-ray and low end gamma ray part of spectrum, so still not visible to the naked eye. You could take an X-ray picture by standing in front of it for a while, though, although I wouldn't recommend it!",
"[Edit: the decay of neutrons also presents a problem for our neutron mass, because neutron decay produces protons and electrons (and neutrinos), and they would immediately start to form atoms, as the protons attract the electrons. After about 15 minutes, half your neutron mass would consist mostly of isotopes of hydrogen.]",
"[Edit 2: I misinterpreted \"relatively low energy\" in the article about radiative neutron decay. Turns out the photons they radiate are in the X-ray to low-end gamma ray range.]"
] |
[
"That short decay time only applies to free neutrons, i.e. neutrons that are not bound inside a nucleus. (I've edited my previous comment to clarify.) ",
"Also, neutrons are produced in various atomic reactions, so the supply of neutrons is not fixed. Such reactions commonly occur in stars, and along with production, atoms ",
"capture neutrons",
", so that the neutrons stick around. Which is lucky, otherwise the universe would consist only of hydrogen."
] |
[
"You just made me realise, if neutrons have a half life of 14 minutes, how do they continue to exist after being formed? It seems to me they should decay away within hours. "
] |
[
"Why are men's testicles so sensitive?"
] |
[
false
] | null |
[
"Doesn't getting punched/touched in any organ feel sensitive? Like your kidneys? We just don't notice other organs being sensitive because they are not exposed. Just a guess but seems possible. "
] |
[
"There's always an exception to things so why can't skin be in this case? And skin is relatively sensitive in some places like being ticklish and sensing heat? Like I said, I literally know nothing about this I'm just taking shots in the dark. "
] |
[
"You're saying you shoot blanks?"
] |
[
"In unltrasonics an increase of 6Db will double your signal. How are the two correlated?"
] |
[
false
] |
[deleted]
|
[
"In general, dB is a ratio between two power levels. In general, the formula is Ratio(dB)=10 log(P1/P2). However, it is often possible to use voltage instead of power. In this case (considering that P=(V",
" / R), the ratio in terms of voltage = 20log(V1/V2). ",
"As a result, an increase of 6dB for voltage (which I believe ultrasonic signal is measured) means that the new power is double of the original power(10",
" = 2)."
] |
[
"Since the decibel scale is logarithmic, and the ratio between two sources (in your case ultrasound) is equal to 10",
" , where x is the number of decibels you increase, you can see when you increase the output by 6dB, the amplitude of the ultrasonic wave approximately doubles."
] |
[
"See my comment below. If power increases by 3 dB, then power doubles (voltage increases by square root 2). If power increases by 6 dB, then voltage doubles (power increases by 4x). Both are equivalent, you just have to be clear what formula you are using. OP is using voltage (20 dB change in power is 10x change in voltage)"
] |
[
"Is there a way to obtain a perfectly random natural number between 1 and ∞? If so, if you take the average of 10.000 purely random numbers, what result do you get?"
] |
[
false
] |
[deleted]
|
[
"No. There is no uniform probability distribution on a countably infinite set. Such a distribution would have to satisfy p(x) = p for each ",
". Hence p+p+p+... = 1, which is impossible."
] |
[
"Nope. If you get rid of the logical framework surrounding how we count/analyze numbers, you can't cherry-pick some rules just to make your nonsensical result sound reasonable. ",
"Well, you ",
", but it would give arbitrary results. You decide your first principles, and that determines your result. It's pseudomathematics!"
] |
[
"Nope. If you get rid of the logical framework surrounding how we count/analyze numbers, you can't cherry-pick some rules just to make your nonsensical result sound reasonable. ",
"Well, you ",
", but it would give arbitrary results. You decide your first principles, and that determines your result. It's pseudomathematics!"
] |
[
"What color does the human eye track the best?"
] |
[
false
] |
So say you had a dot moving around, what color dot would the human eye be able to follow and react to the fastest and most accurately? EDIT: MERRY CHRISTMAS
|
[
"a dark dot on a bright background or a bright dot on a dark background; the part of the visual system that senses achromatic contrasts is faster than the part that senses chromatic contrasts.",
"ultimately the bright dot would be easier to follow if you wanted to go to the limit of \"dot\" - an infinitesimally small black dot on a bright background would be invisible while an infinitesimally small bright dot on a dark background would still be visible (if bright enough - think stars).",
"To get a little more specific since people are reading this: what i was referring to in this comment (\"sensing achromatic contrasts is faster\") is the general distinction in the early visual system between the ",
" and ",
" pathways. The magnocellular pathway mainly transmits information about brightness contrast and motion, while the parvocellular pathway mainly transmits information about color contrast and spatial pattern. Of course nothing is ",
" that simple in the visual system, but it's a useful way of talking about certain functional/physiological distinctions in the brain.",
"The root of the magno system is in retinal cells that pool inputs over all types of cones (mostly L+M cones); the root of the parvo system is in retinal cells that pool over specific types of cones antagonistically (e.g. L vs M or [L+M] vs S). Because the former (magno cells) are pooling broadly they are very sensitive to slight changes in stimulus (i.e. motion cues), but they are not great at picking up fine detail or distinguishing one type of cone from another.",
"So, motion perception relies mostly on brightness contrast, i.e. edges or features that are distinguished by variance in their luminance intensity across space and time. ",
" ('color' contrast) is a very very poor input to the motion perception system - if you remove all brightness cues from a video, you will have enormous difficulty making sense of what little motion you can see.",
"Usually, in nature, chromatic and brightness contrasts are strongly correlated, i.e. where you find one you find the other, but with unnatural stimuli (i.e. experimental conditions) these powerful differences can be brought out."
] |
[
"The human eye response is most sensitive in the green, peaking around 555nm. If these hypothetical colored dots were all of the same intensity, a green dot would appear the brightest. Not sure how perceived brightness affects tracking, hopefully somebody with knowledge in that area can weigh in."
] |
[
"The color is called chartreuse; and yes, I believe that's why they go with that color.",
"Fun side note, Washington State Patrol had a bunch of ford tauruses one year that were a god awful shade of purple. And they are goddamn invisible if you aren't looking for them, they are the exact opposite of chartreuse."
] |
[
"Can mRNA vaccines like those made for covid 19 be made for bacteria as well?"
] |
[
false
] | null |
[
"If I’m not mistaken, mRNA vaccines for covid 19 is for the body to produce antibodies against the pathogen. So it shouldn’t matter whether or not the pathogen is bacteria or a virus. Someone correct me please?"
] |
[
"If I’m not mistaken, mRNA vaccines for covid 19 is for the body to produce antibodies against the pathogen. So it shouldn’t matter whether or not the pathogen is bacteria or a virus. Someone correct me please?"
] |
[
"not necessarily, some of the immunogenic portions of bacteria are not proteins, they are sugars. mrna vaccines tell the human body to make an immunogenic protein. but they can't tell the human body to make a uniquely bacterial sugar.",
"https://www.breakthroughs.com/impacts-innovation/vaccines-fight-sugar-coated-bacteria#:~:text=A%20polysaccharide%20vaccine%20builds%20immunity,the%20pathogen%20upon%20future%20exposure",
"."
] |
[
"Why does camphor sublimate? What property of it enables it to go from solid to gas?"
] |
[
false
] |
Are there any other solids like camphor?
|
[
"The liquid phase is basically when something becomes amorphous and mobile. Meaning the molecules are moving about and aren't in any fixed crystal structure any more, but at the same time they're still attracted to each other to the extent that their thermal kinetic energy isn't enough to cause them to fly apart completely and become a gas. ",
"A substance sublimates when it doesn't have a liquid phase (at that temperature/pressure). In other words, it has structural and intermolecular binding properties that are such that, once it gets hot enough to break the bonds holding it together as a crystal, the remaining forces between the now-disorganized molecules aren't enough to keep them together, given their thermal energy. So they go straight to a gas.",
"Substances that sublimate are like chemical plugs and sockets, they'll only stick together when arranged in a specific way. While substances that form liquids are more like chemical velcro strips. They still stick together even if they're not perfectly lined up."
] |
[
"Here",
" is a simple phase diagram. The X axis is temperature, and the Y axis is the pressure of the system. It shows you what phase the substance is at at your temperature and pressure. Some substances at certain low pressures do not become liquids. Likewise, at very high pressures most substances will never become a gas. It turns out that at 1 atm (normal pressure), camphor does not have a liquid phase.",
"I can't explain the mechanics of it though, sorry."
] |
[
"Anything can sublimate. All that is necessary is for its vapor pressure to exceed the applied pressure ",
" for the temperature to be below its melting point. This is a weird requirement, because vapor pressure goes down with the strength of the intermolecular forces through which the molecules are interacting, but melting point goes up.",
"Practically speaking, many of the things that sublimate are like your example, medium-sized organic molecules where the forces that hold the molecules in a solid crystal are primarily composed of London dispersion forces. Other good examples are naphthalene, ferrocene, and p-benzoquinone. Iodine is another one, although not organic. In other words, it seems like sublimation is favored by a lack of extremely strong intermolecular forces such as hydrogen bonding holding the material in the solid phase. The best subliming compounds are ones where the interactions between molecules are primarily mediated by polarizability. "
] |
[
"If you didn't know about nuclear fusion, how would you attempt to explain why the sun is hot?"
] |
[
false
] |
Methinks it a mystery!
|
[
"erroneously"
] |
[
"Reciting from memory here but here it goes:\nIndeed before we did know about nuclear fusion, why the sun is hot was a pretty big mystery. At the time the best theory was that it was still releasing energy from it's formation (energy from gravitational potential), but this would only be able to power the sun for up to ~ 7 million years. Anything chemical powering the sun was out of the question because this would only be able to power the sun for a few thousand years."
] |
[
"Historically speaking they ",
" assumed a chemical source for powering the sun, and used those few thousand year figure as the age of the universe, further reinforcing the bible version of events. A bit of circular reasoning perhaps, but it must have seemed viable at the time."
] |
[
"Is there a theoretical 'maximum' to how loud a sound that room temperature / sea level air can reproduce without distortion?"
] |
[
false
] |
It would seem to me that since sound is a mechanical wave and rarefactions can't get any 'stronger' than a vacuum, there would be a limit. But I can't figure out how to compute it in SPL. Also, I'm curious about the heat that would produce, though I suppose that would be highly frequency dependent.
|
[
"Eventually you get something called nonlinear propagation where the air is squished so much that it changes the squishiness."
] |
[
"There certainly is, you can't produce anything you'd call \"sound\" after 194.094dB due to the waveform being clipped at 0 pressure, after this you just get shockwaves. "
] |
[
"Sound waves are pressure waves. When we pressurize air we effect temperature. So I think your question is flawed since it sounds like you want to know the answer to you question given a fixed temperature and pressure. If you relax those constraints, then we can start thinking about extreme examples of sound propagation ... Sonic boom of aircraft, hyper velocity of plasma escaping from Atomic Blast ... Solar outbursts .. they seem to me at least to be all related. ",
"You state \"without Distortion\". Hmm, what do you mean? If I take that literally by my way of thinking, I'd generate an acoustic sine wave (a pure tone) at a specific frequency. Then I'd set up a microphone with an Acoustic (or Audio) Spectrum Analyzer at the some listening location. Then I would turn up the \"loudness\" of the source until the spectrum analyzer started to show harmonics and overtones beyond the pure tone of the sine wave. Of course you would have to place the microphone far away enough so as to not overdrive it, since then you would be also measuring it's own distortion. Oh, and by the way you would have to be sure that your source (sound generator) also was not the source of the distortion. ... And all this would answer your question only at a specific frequency (or tone).",
"Do you have a specific example you are thinking of that leads to your question? "
] |
[
"How do strong acids \"eat through\" things?"
] |
[
false
] |
Just wondering what the chemistry is here. I know that acids are compounds that either donate protons or accepts electrons, but I'm not sure how that results in the effect of eating through stuff. Why is it almost a universal effect for strong acids to eat through things? Can bases do the same thing, and if so how do they do it?
|
[
"\"Eat through\" is a misnomer. Nothing is destroyed. Just changed. Acids chemically change materials into weaker substances. Take steel (iron) and HCl (arguably not the best acid for this, but it's easy). The reaction alters the metallic iron to iron chloride (ferrous chloride, FeCl2). Unlike hard, metallic iron, ferrous chloride is VERY water soluble, so it washes away. And even when dry it's a powder, not a hard metal. Acids generally chemically change stable molecules into weaker ones.",
"Bases can and do alter things similarly. Two sides of the same thermodynamic coin."
] |
[
"Yeah. In various ways. For example, the proteins in your body need a specific pH range to properly function. Acid changes that and denatures proteins, rendering them nonfunctional. Many acids are also strong oxidizers, like sulfuric or nitric acid, so you also get oxidation damage. Others are outright toxic, so you can add the toxicity to the mix. Ultimately, the damage kills cells at the point of contact, giving you the acid burn."
] |
[
"Ah, ok, that makes sense. So say you get an acid on your hand. The reason it is harming you is because it's essentially reacting with you?"
] |
[
"Where exactly does the heat from fusion reactions come from?"
] |
[
false
] | null |
[
"The fission and fusion reactions used for power generation and bombs are exothermic. "
] |
[
"Yes, that much I know. But what creates this heat when the elements fuse? Like electrons, breaking of some force, etc? For fission it is clearly stated because of the release of high energy photons in the form of gamma radiation. Does fusion release photons or something else?"
] |
[
"Most of the energy released by exothermic fission reactions is not in the form of gamma rays. And anyway even if that were the case, that doesn’t mean that the gamma rays are what cause the reaction to release energy.",
"You have the cause and effect backwards. The reaction is exothermic because it has a positive Q-value. The way that energy is released is a combination of recoil kinetic energy, prompt radiation, and delayed radiation.",
"In exothermic fusion reactions, it’s the same thing. The Q-value is positive. Energy is released in the kinetic energy of the fusion residue, and whatever radiation it gives off."
] |
[
"How moving parts are lubricated in curiosity rover on Mars over these years? If not what technology is used to ensure longer life?"
] |
[
false
] | null |
[
"Finally my time to shine! (ME, been doing my PhD and been working ever since in aerospace tribology)",
"As was said earlier, lubrication is a BIG issue in space as similar metals will cold well if pressured into contact as soon as any existing coating (oil/grease, chrome protective layer, etc.) is removed. ",
"But you can't just use any lubricant and call it a day. In low pressure/vacuum environments, your typical lubricant will simply boil off the surface. ",
"Moreover, when exposed to extremely low temperatures (be it in the vacuum of space or in a cryogenic engine), your typical oil/grease will become a solid.",
"Fortunately, we have ways around that. Some materials are self-lubricating, meaning they're able to wear off very nicely and evenly, leaving a nice, low friction coating on the contracting surface. So you've got ball bearing cages made of PTFE or PTFE-coated composites, rotating seals made of graphite and the like to procure some lubrication, for instance.",
"We also use greases and oils, we just have to select them so that they don't boil off too fast in low pressure. Look up PFPE oils for instance, they're probably the most used along with PAO oils."
] |
[
"With opportunity and spirit they main missions was only planned for 90 martian solar days. Spirit's missions were extended until from 2004 to 2010 and opportunity kept going until 2018. In 2009 spirit got stuck in the sand so the retasked to station science platform. Opportunity's right front wheel drew more current than other wheels. So opportunity was often driven backwards to extend the life of that wheel. There was one time we thought opportunity would die because it's panels were so dusty it barely got any power. Well during a huge dust storm all the dust was blown off and opportunity was renewed!",
"So basically the rovers worked for what they were planned for, and when problems showed up NASA figured out solutions to work around them."
] |
[
"Certain materials such as nylon and composite-impregnated metals are self-lubricating, so they don't require the direct application of a separate lubricant to function smoothly. Not sure if any of the Mars rovers actually use self lubricating components but that's my guess"
] |
[
"Can you trap a mosquito by flexing the muscle it's drinking from?"
] |
[
false
] |
A friend of mine said that if you were to wait until the mosquito is drawing blood and you clench your muscle then the mosquitos proboscis (sic) wouldn't be able to retract and that you could make it die from too much blood. I was skeptical, but I don't know insects so... what have you guys got for me?
|
[
"Short answer: It's unlikely.",
"Longer answer: If you look at a ",
"mosquito's proboscis",
", it's essentially a very thin, sheathed needle; it lacks the barbs or spurs you might see in other types of blood-feeding arthropods (ticks, for instance). Given this construct, you would have to apply quite a bit of pressure for it to get stuck.",
"If you wanted to see a mosquito burst, you would probably have to disrupt their abdominal nerves or modify their gut in some way."
] |
[
"Unless you have video, the sidebar says:",
"Personal anecdotes and layman answers are not acceptable posts."
] |
[
"Former Winnipeger here. Here's what actually happens: If you let the mosquito bite you and just watch it, it will use its legs to extract its proboscis and fly away. If you try to trap it by flexing a muscle or pinching the skin around it or whatever, the mosquito will do the exact same thing except it will flap its wings to get away (if it is unable to do so merely by floundering about a bit more). I have tried this dozens if not hundreds of times and have yet to get a mosquito to burst. This includes preventing it from flying away and attempting to squeeze blood into it. ",
"I hate the things and have been bitten a bazillion times, so trying to engineer an interesting demise for them once they've gotten their greedy snout in me was somewhat of a hobby."
] |
[
"Would the accretion disc produced by two neutron stars merging into a black hole be composed entirely of neutrons?"
] |
[
false
] |
[deleted]
|
[
"Not entirely - neutron stars aren't ",
" neutrons, and may have a \"crust\" that contains some protons & electrons too. When you're ripping them apart, they're going to go through some interesting nuclear reactions and some of the neutrons will turn into a proton plus electron through a process called beta decay. These might capture neutrons and form heavier elements etc. Basically, you're in a very different environment from a neutron star core, so you'll expect some changes to happen."
] |
[
"To elaborate - free neutrons have a half-life of about 10 minutes, decaying to a proton, electron and electron neutrino (and occasionally an additional gamma ray). Once the neutrons are released from the intense pressures at the core of the neutron star, they will tend to undergo this process, and after a very short time (astronomically speaking) there will be no free neutrons left."
] |
[
"In general, the matter in the accretion disk will be too hot to form into atoms. The protons and neutrons should pair up into the occasional deuterium or tritium nucleus, though. This should be more common than in the early Universe, as there is a higher density of unbound neutrons (initially) relative to protons."
] |
[
"How do elevators (and elevator banks) figure out which floor to go to?"
] |
[
false
] |
Multiple people on various floors, up, down... How does an elevator system keep wait times to a minimum?
|
[
"I actually had an interview question once about how you would model an elevator. The interviewer wanted to know what classes to create, the functions in the classes, and how the elevator would determine what floor to go to. ",
"The simplest ",
"elevator algorithm",
" is just for the elevator to continue moving in its current travel direction until empty, then to reverse direction.",
"There's a more complicated approach where the rider enters the floor he wants to go to and a computer assigns the rider to a specific elevator. This is called ",
"destination dispatch",
". ",
"Here's",
" a paper that describes the algorithm in depth. ",
"Here",
" is another paper which analyzes the performance of destination dispatch systems."
] |
[
"It's an interesting problem and there is no optimal solution (because there is no single parameter that everyone agrees should be optimized). Here is a story of someone who designs elevator algorithms: ",
"http://online.wsj.com/article/SB10001424127887324469304578143200385871618.html"
] |
[
"Thank you. I imagine a crude parameter to be average wait time. A more sophisticated metric could be money generated by rent, which would be a bear to analyze."
] |
[
"In the honor of the upcoming mole day, is it possible to calculate the molar mass of an avocado?"
] |
[
false
] | null |
[
"A very simple approximation. ",
"12 grams of a sample of carbon-12 isotope contains one mole of substances as defined by Avogadro's constant. The mass of the avocado in grams divided by 12 gives us a ratio value, giving us the number of moles.",
"The ratio of the mass of the avocado to the amounts of substance gives us the \"molar mass\" of that ",
" avocado. Not all avocados \"are made equal\", but all element isotopes are equal more or less. ",
"Edit:\nThe avocado is not an element, you're absolutely right. But this can still be approximated as its total mass corresponds to its own amounts of the substance, which is what we need, that's all. ",
"I suggest starting with a dried avocado, for example, evaporation is a potential phenomenon that might not make the most \"perfect\" approximation.",
"Also, what defines a fruit anyway? Some people would include a property of water content. In biology, \"dried mass\" is an interesting concept."
] |
[
"That wouldn't be correct though; An avocado is not 100% carbon. Is it possible to find the ratios of the elements that comprise the avocado and then use the molar mass of those elements to find the average molar mass of an average avocado. Yes, dehydrating the fruit would be a great place to start, but there are still other substances in the avocado like fats and minerals. Thank you so much for your response, if I'm misunderstanding anything here please let me know."
] |
[
"Sure, that would be quite easy. How much does an avocado weigh, something like 100 grams? Multiply that with Avogadro's number, 6.02*10",
" and you'll get the molar mass of avocados. This puts us at right around 1% of ",
"the weight of the Earth",
"."
] |
[
"Do we know how pangea formed or why it broke up?"
] |
[
false
] |
[deleted]
|
[
"Plate tectonics.",
" Pangea is the most recent supercontinent but it isn't the first.",
"The Earth is still molten in the interior, there's only a very (relatively speaking) thin layer of solid rock \"floating\" on the liquid mantle.",
"The layer of solid is fragmented into different plates and these are constantly pushed around by motion in the mantle. Sometimes the raised sections (continents) are jammed together (pangea) and sometimes they drift apart (right now)."
] |
[
"http://en.wikipedia.org/wiki/List_of_supercontinents",
"Rodinia and the older ones had no life, and were just barren rock surrounded by ocean. ",
"http://upload.wikimedia.org/wikipedia/commons/2/27/Oceanic_spreading.svg",
"Plates form as the surface cools, and the picture above shows how mantle convection sort of rates chunks. This process has slowed over time, and initially it was very fast, and the fact that we were still in the bombardment phase meant that our surface was constantly becoming molten. "
] |
[
"http://en.wikipedia.org/wiki/List_of_supercontinents",
"Rodinia and the older ones had no life, and were just barren rock surrounded by ocean. ",
"http://upload.wikimedia.org/wikipedia/commons/2/27/Oceanic_spreading.svg",
"Plates form as the surface cools, and the picture above shows how mantle convection sort of rates chunks. This process has slowed over time, and initially it was very fast, and the fact that we were still in the bombardment phase meant that our surface was constantly becoming molten. "
] |
[
"Can dark matter form planet like objects?"
] |
[
false
] |
From my understanding dark matter is a substance that we think must exist because the way galaxies behave doesn't make sense without a lot of extra mass out there. Assuming I have that more or less correct, does the behavior only work if the mass dark matter represents is spread thin throughout space, or is it possible that dark matter may have come together from its own gravity into planets or planet like structures and still explain the movement of the galaxies? Edit: Thank you everyone for your answers, I have learned more about dark matter today than I have in my entire life. :)
|
[
"So you're actually asking a two part question:",
"Can Dark matter collapse from its own self-gravity into planet-sized bodies?",
"Could a lot of planet-sized bodies produce the same gravitational effects on galactic scales for which we believe dark matter is responsible?",
"To answer the second question first: yes, a very large number of planet-sized objects distributed around the galaxy and halo will produce the same large-scale gravitational effects that we observe. Some 20 years ago, one of the leading theories about the source of dark matter was ",
"MACHOs",
" (MAssive Compact Halo Objects). Essentially these would be a large number of rogue planets and brown dwarfs wandering through the galaxy, generating extra mass but being relatively dark. ",
"The MACHO hypothesis has since fallen out of favor. If there were such a huge population of planet-like objects, they should produce a large number of individual lensing events, when a more distant star would be subject to a sudden brightening as a MACHO passed in front of it from our point of view. Large surveys were taken to find this effect, and there are much fewer lensing events than would be necessary if MACHOs were the source of dark matter. Note that this would happen even if dark matter weren't made out of ordinary planets and brown dwarfs, but some exotic material in planet-sized objects.",
"Getting to your first question, the current hypothesis holds that the source of dark matter is a diffuse cloud of exotic particles that interact with gravitational forces, but not electromagnetism - in other words, it feels and exerts gravity, can neither absorb nor emit photons. If you know a little bit about how star/planet formation works, a diffuse gas cloud begins to collapse and form compact bodies when it has cooled to the point that the molecular motions from heat can no longer maintain equilibrium with the cloud's self-gravity - this is known as ",
"Jeans instability",
". For your average star-forming region, it needs to cool a fair amount before star/planet formation can occur - from the typical 10,000 Kelvin diffuse interstellar medium, down to a 50-100 Kelvin large molecular cloud.",
"Here's the thing, though - in order to cool in space, you need to radiate your energy away through photons. If dark matter's source is a non-electromagnetically interacting particle, that means it can't emit photons...which in turn means it can't radiatively cool! So, these diffuse clouds stay warm, which means they can't collapse down to planet-sized object in the first place.",
": A large number of planet-sized bodies would produce dark matter's gravitational effects...but we currently don't think that dark matter can cool in the first place to form planet-sized bodies."
] |
[
"Yeah, there is something supremely psychologically dissatisfying about proposing the existence of an invisible 90% of the the universe's mass to explain the 10% you can actually see.",
"I actually used to side with you on this. Gravity is not well-understood - as of yet, we have never directly observed gravitational waves, and no one has any idea what a graviton looks like. Maybe there is no missing mass, and we just don't get gravity? This class of theories - which is definitely a minority opinion, but still not considered completely bunk - falls into a category known as \"",
"Modified Newtonian Dynamics",
"\" (MOND). That is, Newtonian gravity works at small scales, but takes a different form at large scales.",
"What changed my mind to accept the existence of dark matter were observations made of the ",
"Bullet Cluster",
". This is the active merging of two galaxy clusters that we're seeing at just the right time. The two clusters have made their initial pass through each other.",
"The first thing to know about galaxy clusters is that, in terms of ordinary matter, the galaxies themselves are only a fraction of the cluster's mass. There's a surrounding bubble of hot gas that contains the majority of the cluster's ordinary matter. ",
"When two galaxy clusters merge, the galaxies themselves pass through relatively unaffected. The gas, on the other hand, is subject to ram shock pressure, and forms a pancake of mass at the middle.",
"So, in the case of the Bullet cluster, we actually see that the galaxies have passed through one another, and are now on opposite sides. The gas, meanwhile, has piled up in a pancake in the center.",
"Now, here's the trick: if there is no dark matter, then most of the mass of the system will be in the gas pancake in the center. On the other hand, if dark matter does exist, then it too will have passed through unaffected, and will be at the same location as the galaxies on opposite sides of the central pancake.",
"So what do observations tell us? If you do a gravitational lensing survey of the Bullet Cluster, which shows where the bulk to the mass is, it's ",
"concentrated in the galaxy regions",
", not the gas pancake. So, more matter is near the galaxies, which means the gas is not the primary source of mass, which means ordinary matter is not the primary source of mass."
] |
[
"I'm sorry if it isn't appropriate to add on a question that isn't exactly related, but there is something that has always bothered me about dark matter and you sound like you might be able to help.",
"Basically we assume dark matter must exist because galaxies spin faster than the visible mass would lead us to believe. Isn't it just as possible (maybe more so) that we're just ",
" about how fast a galaxy should spin? Inventing massive-yet-invisible matter seems like more of a stretch than the possibility that gravity works differently than we currently believe at large scales. Is there any reason this shouldn't be considered? ",
"Dark matter/energy just seem like we're trying too hard to prop up a theory that doesn't fit the evidence with weird excuses. Sort of like towards the end of the Ptolemaic theory when the \"odd\" motions of certain bodies were explained by more and more convoluted oscillations."
] |
[
"As an enthusiast of astrophysics, and one who is out of the loop, I would love to know about quantum fluctuations."
] |
[
false
] |
Let's keep this in laymen's terms, but I can follow along pretty easily if it is explained with detail. I would love to know the math behind the big bang theory. I have watched a few lectures on how quantum fluctuations of energy can build up and potentially cause such an event, but how do these occur, and what is their natural starting phase.
|
[
"How do you know you have a \"true\" vacuum? You measure the energy of a region. But uncertainty in energy measurement forms a Heisenberg pair with uncertainty in time measurement. So if you want, you can kind of think about quantum fluctuations as imprecision in knowledge of energy over very small time scales. You can't be ",
" sure you have nothing. "
] |
[
" states have ground states. In principle, a free particle has no such restriction. A massive particle in its rest frame has no kinetic energy. "
] |
[
"well we are pretty sure that space doesn't have edges, and even if it did, then we'd have to understand the physics of the edge of the universe to be sure (one of the reasons why we don't posit the existence of an edge). In reality, sure. Almost everything is a bound particle, even if the binding is exceedingly small. And if the binding is exceedingly small, the ground state energy is functionally negligible. ",
"But anyways, quantum fluctuations aren't the same as the ground-state energy of a particle. Quantum fluctuations, as most people mean it, are about virtual particles or pair-production annihilation in a vacuum."
] |
[
"When in evolutionary history did private parts become private?"
] |
[
false
] | null |
[
"This isn't an evolutionary matter, its a cultural one. There are societies right now where people do not share western values of modesty.",
"EDIT: Point of clarification, I am not claiming that modesty is unique to Western society. Quite the opposite, the great spectrum of beliefs surrounding the concept of modesty lies at the heart of my argument. There are plenty of historical and contemporary societies that include individuals who would feel no degree of self-consciousness exposing parts of their bodies which individuals in the West would feel self-conscious about. Likewise there are societies which view the degree to which Westerners expose their bodies to be be immodest and embarrassing. Humans do not possess a universally shared definition of modesty nor do they all cover themselves or their genitalia in the same manner if at all. Such acts are cultural, not something that has been hard-wired into our nature. This isn't of course to suggest that human sexuality and other biological mechanisms do not play into our creation of our own conceptions of modesty, rather it is to emphasize the extent to which those conceptions are created."
] |
[
"Sexual modesty",
" has been observed in every human culture on Earth. That is quite a hefty coincidence to have nothing to do with either evolution or the widespread (in Western and non-Western cultures) practice of covering external sex characteristics.",
"None of us are any closer to actually answering OP's question. I worry we're veering towards a Margaret Mead-esque \"everything is relative and Western culture is bad\" social science circlejerk. ",
"Edit: The fact that ",
"this comment",
" is sitting at negative 22 despite being a perfectly valid point is unsettling. AskScience should not be the place to downvote points because they are not hivemind-friendly."
] |
[
"Yes. Culture, not evolution: Anthropologists to the front!"
] |
[
"How lethal is acute radiation sickness today, compared to 1986 ? Has anything changed?"
] |
[
false
] |
Yeah yeah I'm watching the HBO show about the Chernobyl disaster. It made me wonder how ARS could affect us today compared to Chernobyl. Has there been any advances in medicine which could help mitigate the symptoms of ARS, and thus increasing survaivability? Are there better methods to treat patients today? I know the symptoms vary depending on the dose, but in general terms, has anything changed?
|
[
"There are basicly three things you can do for someone who has been severly exposed:",
"Decontaminate. Externally through the removal of clothes and washing the patient. Internally through some drugs that bind heavy metals like plutonium and allow them to be excreted and giving the patient potassium iodine so their thyroid will stockpile less radioactive iodine.",
"Treat bone marrow damage. The main problem with radiation sickness is the damage to the immune system causing subsequent infections and death. You can give some proteins that stimulate the immune system, this is relatively new, as in not available in the 80's.",
"Treat symptoms & complications like infections trough antibiotics. Here medical science has made some progress.",
"All in all I think with the progress made patients that receive a dose of ~6 Gray will have a much better chance of survivel than a patiënt that receives non.",
"Edit: 80s not 50s"
] |
[
"Filgrastim (recombinant G-CSF) was FDA approved in 1991, so it should have been in clinical trials or available experimentally in 1986, although I don't know when the idea to use it for radiation sickness was conceived, over 15 years ago I believe but I don't know exactly."
] |
[
"FYI Chernobyl was in the 80s, not 50s. Are protein treatments newer than that?"
] |
[
"Can children or adolescents develop Alzheimer's ??"
] |
[
false
] |
My old neighbour texted me to catch up, he's a lot younger (15 or 16 years old) but then he said he was diagnosed with alzheimers since moving back to germany. I tried googling it but cant seem to find any legit cases of children with alzheimers.. does anyone have any input?
|
[
"If he has a family history, he might have gotten a genetic test. Mutations in the PSEN1, PSEN2 and APP genes predispose for early onset Alzheimer's. But even the early onset inheritable form generally only presents with symptoms in the 30s to 40s."
] |
[
"it's possible, though \"unlikely\" (rare). there are genes (mutations) that predispose people to have early onset Alzheimer's (hereditary) but most cases affected folks in their 30's to 40's. the earliest/youngest known patient with dementia (Alzheimer's) is 23 at the moment"
] |
[
"Not that I know of, specifically. I'm not an Alzheimer's guy, I just worked with prions and read up occasionally on other aggregation diseases. Plaque formation might be a stochastic process that takes its time until it really can take off. It id similar to inherited prion diseased - they also strike in the middle of your life and rarely earlier."
] |
[
"What would happen if a window from an airplane would break at high altitude during mid-flight?"
] |
[
false
] |
Let's say the airplane is going approximately 1000 km/h. At an altitude of 10 km above the ground. What would happen in the airplane if a window suddenly for some reason broke? Would people freeze due to the low temperature for example? Or would people actually get sucked outside or something?
|
[
"See ",
"this British Airways incident",
"."
] |
[
"what a great thread to read as im sitting at DFW on a layover"
] |
[
"D:",
"Note: that was the FRONT window, and it was fitted wrong. But still, D:"
] |
[
"Why are we not looking for life on Venus?"
] |
[
false
] |
I think the notion of "it's too hot for anything to survive" I was taught in school no longer applies since the discovery of extremophiles. I know it's a hard place to explore, but is that the only reason we're not doing it, or is there some other reason to believe there's nothing there?
|
[
"I was taught in school no longer applies since the discovery of extremophiles.",
"Thermophiles have been found in the range of 70C to 120C. The surface temperature of Venus is 460C. Venus isn't just hot, it's hot enough to melt lead.",
"In addition to being hot, it's dry. There's no water, ammonia or anything else that life could use for a solvent. There's sulfuric acid, but at such high temperatures it would destroy everything organic."
] |
[
"Venus missions",
"\n",
"from the Planetary Society",
"\nand to update where it lets off ",
"AKATSUKI (PLANET-C) The AKATSUKI is expected to usher in a new era of Venusian exploration. It was launched aboard an H-IIA Launch Vehicle No. 17 in May 2010 (JST.) It smoothly flew and spurted out jets from its orbit control engine on Dec. 7, 2010. Unfortunately, the AKATSUKI failed to inject itself into the orbit of Venus. JAXA set up an investigation team not only to examine and study the causes of the failure and countermeasures, but also to see if it is possible to insert the AKATSUKI again into the orbit when it comes closer to Venus in about six years. ",
" "
] |
[
"Venus isn't just too hostile for life, it's too hostile for our machines."
] |
[
"How does a fractal pattern camouflage on Jets work? I understand how Army camos work by blending with the environment but in an open space like the sky,how does it benefit by the use of such pattern? Example image inside."
] |
[
false
] | null |
[
"1: This isn't a common pattern of camouflage and may be experimental- in other words it might not work that well.",
"2: In general, the blocky/pixely/fractal patterns on many new camouflage designs works by breaking up straight lines as much as possible. If you aren't really close, like in that picture, the human eye would see the dark/light interface as a fuzzy blur. Just like how pixels blend together on a computer monitor. Military camo is designed to break up the outline of whatever you might be looking at so your brain doesn't separate the camouflaged object from its background. "
] |
[
"What you're seeing here is not standard. Every year, NATO hosts a training mission, called tiger meet. Each year, countries paint one of their jets as with a \"tiger\" theme. This may incorporate stripe, fangs, claws or other items. This seems to be a tiger meet flagship. ",
"Here is another, more obvious jet:\n",
"http://www.airshows.org.uk/news/riat_tiger11.jpg",
"Edit: here is a post about tiger meet. Note the Panavia tornado in one of the pictures appears to be the same as in OPs picture. \n",
"http://www.fightercontrol.co.uk/forum/viewtopic.php?f=16&t=34061",
"Tl;dr: it doesn't. This is for show. "
] |
[
"I'm not sure about this camouflage, but on concept cars put to production for extended road testing they will often wrap the car in a similar pattern to keep anyone who sees it from being able to clearly identify body lines. Volkswagen is one manufacturer I can think of that does this routinely. "
] |
[
"How is it that you can get energy both by splitting atoms (fission) and combining atoms (fusion)?"
] |
[
false
] |
[deleted]
|
[
"In fusion, the binding of two light nuclei, such as Hydrogen, forms a heavier nucleus, which has less mass than the sum of the hydrogen nuclei by themselves. This difference in mass is due to the different binding energies present in the nuclei. ",
"However, if you use two heavy nuclei, such as iron, the resultant nucleus becomes heavier, because it requires extra binding energy in order to remain stable. This means that the fusion of iron uses up energy.",
"In fission, the opposite of the above occurs. The extra binding energy in the larger nucleus is 'used up', and the mass of the products is less than the mass of the input. The binding energy in this case is released, and translated into kinetic energy of the products.",
"2.My guess is that with Iron, the configuration of it's nucleus means that the force of electrostatic repulsion between the nucleons is just too great, and this will use up a lot of energy. Usually, in smaller atoms, supplying heat is enough to get the two nuclei to fuse, and the energy released is higher than the heat put in. However, with Iron, the energy released is probably less than the energy put in. That's just my guess, however, I'm not too sure about this.",
"3.This graph may be of use to you: ",
"http://www.scienceinschool.org/repository/images/issue5fusion3_large.jpg"
] |
[
"Look into ",
"liquid drop model of the nucleus",
", which describes why fission/fusion happens. I also posted significantly about stability of nuclei yesterday in askscience in the thread on ",
"the instability of Be-8",
". ",
"Oversimplifying a little (see above link), there's two counteracting forces at work in the nucleus. The attractive ",
"strong nuclear force",
" that binds nucleons (protons/neutrons) together, but only operates on a very short range. There's also the standard electromagnetic force, which due to the positive charge of protons is repulsive (e.g., like charges repel), and tends to cause the nucleus to want to break apart. ",
"The best explanation I could find was that any element lighter than iron would give off energy under fusion, and anything heavier would give off energy under fission.",
"Yup.",
"What about iron makes it the dividing point?",
"Iron just happens to be at the sweet spot. Larger nuclei than iron tend to be less stable because of excessive Coulombic repulsion (which is a long range force) while the strong force binds less (as it is only a short range force). Smaller nuclei are less stable because each nucleon isn't in contact with enough other nucleons on average so it isn't as strongly bound by the strong force.",
"Is there a direct correspondence between energy given off and the atomic number? ",
"No. There's an exact correspondence from the energy given off and the difference in mass of the initial products and the end products, from E(given off) = (M(initial) - M(final) ) c",
" When fusion happens you have to pay attention to what its given. There's a weak correspondence as atomic number is related to the mass of the nuclei, but you have to pay attention to what the decay products are as well."
] |
[
"The ",
"silicon burning",
" Wikipedia article actually has a very nice, simple explanation:",
"At the end of the day-long silicon-burning sequence, the star can no longer release energy via nuclear fusion because a nucleus with 56 nucleons has the lowest mass per nucleon (proton and neutron) of all the elements in the alpha process sequence. Although iron–58 and nickel–62 have slightly less mass per nucleon than iron–56,[2] the next step up in the alpha process would be zinc–60, which has slightly more mass per nucleon and thus, would actually consume energy in its production rather than release any. The star has run out of nuclear fuel and within minutes begins to contract.",
"I think it has more to do with the nature of quarks than anything else...but I could be very, very wrong. Things get very weird when you start talking at the border between QCD and nuclear physics."
] |
[
"Can some things burn without oxygen? If so, how?"
] |
[
false
] |
Saw something in askreddit that said it can happen. With oxygen being part of the "fire triangle" I always thought it was impossible to burn anything without there being oxygen involved.
|
[
"One of the more commonplace fires that doesn't use oxygen (O2), are metal fires. Some metals, such as magnesium, will burn when heated in the presence of ",
"carbon dioxide",
", which is why a lot of welders will have specific ",
"fire extinguishers",
" at their job site than the common CO2 extinguishers."
] |
[
"Yes things can burn without oxygen. You just need a very strong oxidizer. Fluorine or chlorine trifluoride and two very strong oxidizers and they will react very readily and a flame will be produced.",
"https://www.youtube.com/watch?v=vtWp45Eewtw",
"http://en.wikipedia.org/wiki/Chlorine_trifluoride"
] |
[
"Oxygen is merely the most common oxidizer, but it's not the only one. ",
"Related: the reason why lithium batteries are dangerous is that lithium fires do not require oxygen, and so once a lithium fire starts (for example, by overheating, overcharging, puncturing, or shorting out a lithium battery), it can sustain itself even if deprived of oxygen."
] |
[
"How does Shazam and other apps like Shazam work?"
] |
[
false
] |
Even when there is plenty of background noise Shazam can still find the song. I was just curious on how these apps work
|
[
"The algorithm on how shazam works was published back in 2003. ",
"You can find it here",
". Of course shazam doesn't simply record music that you listen to and compare it with songs from it's database. Instead shazam doesn't simply have every single song in it's entirety in it's database but rather it generates a much smaller \"fingerprint\" which is saved. ",
"How is this fingerprint generated?",
"\nI hope you have some basic understanding of how sound works. Sound is composed of many different frequencies. In a spectogram you can see which frequencies contribute how much to the sound you hear. ",
"Here is an example of a spectogram",
". For the fingerprint you just need to segment the song and find the frequency with the most contributions for each segment. You don't even need the amplitude. ",
"This would look like this",
". This ",
" compresses the storage needed for each song. This method works particularly well for noisy recordings, because you only look at the peaks in the frequency spectrum. Now, generally the noise is going to be lower than the song, so all the peaks in the spectrum are due to the music and not the noise. So the noise has little impact on the fingerprint. Therefore it is fine if there is a lot of background noise, as long as it's mostly less loud than the music. ",
"For example music is usually recorded with a 44kHz sampling rate. That means for each second there are 44 thousand data points. But the fingerprint might only use one data point every second. That means the data reperesenting the song was compressed by a factor of 44000. Of course in reality it is not quite that simple, but that is the basic principle of the fingerpint technique. ",
"The fingerprint is generated for every song in the shazam database. Then when you listen to some song, shazam calculates it's fingerprint on the fly and compares it with all the songs in it's database. The comparison uses pairs of points rather than single points. This speeds up the search for the match in the database. But I don't really know why this works and if I keep talking I might say something completely wrong.",
"edit: small correction at the end"
] |
[
"Shazam built the fingerprints themselves. Probably from a number of different sources- ",
"according to this, they got a large number of songs by digitizing Entertainment UK's collection",
". When Shazam launched with the App Store, they included tons of links to the iTunes store, so maybe they got a deal there too. ",
"Note that this paper came out years after Shazam launched. Everyone had their own unique solution to this problem and their own database with the songs they could manage to gather. The general method for any app is gonna be very similar, but Shazam's works very well and they probably had a music library advantage on top of that."
] |
[
"And how is this database made? Is it a copy of some existing database on the internet or it was made for Shazam and similar apps?"
] |
[
"are we really overpopulated/moving towards overpopulation?"
] |
[
false
] |
I keep hearing Internet misanthropes decrying overpopulation, and sometimes arguing for eugenic solutions to that, but is the view that our world is overpopulated by humans based on reality?
|
[
"What you're asking is a difficult question to answer, it depends a lot of future growth rates, increases in longevity, distribution of resources, and future undiscovered technologies. But you can get some hard facts from numbers, and since this is askscience, and you want some data, let's get some. I'm going to be quoting results a lot from the excellent resource: ",
"http://www.google.com/publicdata/directory",
"First we'll look at energy.\nEnergy use per capita in the US is about 7200 kgoe per year = 300TJ, or continuous usage of 9.5kW. If you extrapolate this to the entire world population, you get a value of about 66TW of power. Total solar fluence on the earth is approximately 174 petawatts, and this should be viewed as the sustainable energy amount. We haven't surpassed this yet, so from a strict energy budget standpoint, we aren't yet over the value. (nevermind that most of the world doesn't use the same amount of energy as the US)",
"Arable land:\nCurrent use is roughly 0.2 hectares per person in the world and about 0.55 hectares per person for the US. It's hard to find a minimum value, but I found ",
"this estimate",
" which says 0.07 is the minimum value to live on. It assumes an almost entirely vegetarian diet, so keep that in mind. So we have roughly a factor of 2 with current arable land. Additional arable land can be found, but most of the new arable land comes at the expense of the Amazon rainforest. Also there can still be increases in crop density, so the minimum value per hectare could go down. However, looking at the curves for arable land shows a steady decline in hectares per person, and you probably don't want to be pushing up against the 0.07 limit, because a famine would be pretty devastating. There is not enough arable land for everyone to eat like the US does. Nevertheless, we are technically not overpopulated in our ability to feed the world's populace.",
"Lastly on arable land. This is going to change a lot in the next 50 years due to global warming. There will be increased arable land in canada and siberia, but decreased arable land in low-lying areas like vietnam and bangladesh. In the US, planting seasons will be longer in Wisconsin but Arizona may not be able to support any agriculture at all.",
"Fisheries:\nIn addition to arable land, there's the additional source of food for fisheries. These are much harder to catalog. Total aquaculture for OECD countires has remained relatively stable. However, total fish landings has been going down steadily dropping by over a factor of 2 for OECD countries in the last 15 years. Nevertheless, aquaculture does allow us to support a larger population than agriculture alone. (I could not find data for non OECD countries, like thailand where we get a lot of our fish from in the US.)",
"So from a basic analysis, it looks like arable land will be the limiting factor to support the worlds population. If you're willing to have everyone go vegetarian and farm nearly everything that you can, then you can probably double or triple the world's population with current technologies. If you want people to live like the US currently does, you need better technologies or a smaller population."
] |
[
"hydroponic agriculture falls under future technologies. ",
"As for what you can conclude, all I've given are raw quantities, and a zeroth order estimate. I'm not going to draw conclusions from them. As I said in the first paragraph, there are a ",
" of factors that can skew things by large margins.",
"For example. I mentioned that there's more than enough solar energy to support the earths population. But right now, we've only managed to generate about 20% of our energy needs through solar or nuclear (I'm assuming other renewables = solar in this case). That hasn't changed since 1980! This is just one example of a confounding factor. Is the fact that 80% of our energy derived from fossil fuels a sign that we're screwed when they start running out, or will we be able to switch to more renewables smoothly? No one knows the answer to this, but the question of whether the world is overpopulated depends somewhat on the result."
] |
[
"but hasn't Malthus been completely discredited? in the end, technological progress and production ISN'T linear"
] |
[
"If light is massless, how is a black hole able to prevent it from escaping?"
] |
[
false
] | null |
[
"Light is massless, but it is affected by gravity.",
"Two ways to understand this:",
"Light has energy, and gravity acts on energy.",
"OR",
"Gravity is the curvature of spacetime, and so the paths that light can travel are determined by gravitational effects."
] |
[
"I know the model, but a new question just popped up for me. ",
"Gravity is the curvature of spacetime, so the photon, for it's own point of reference, it's travelling through spacetime in a straight line. If it keeps going in a straight line, but the curvature of spacetime is directing it into a black hole, we must be able to theorize where this photon is popping out of the black hole again, right? Or is a black hole really like a bottomless well for all energy that's getting 'sucked' into it?"
] |
[
"Gravity is the curvature of spacetime. Spacetime becomes curved, or warped, by the presence of mass. The more mass, the more warping, which means stronger gravitational attraction. "
] |
[
"If we received a photograph from a random place in the universe, could we tell where it was from by looking at the stars?"
] |
[
false
] |
Hi AskScience, I was wondering this: if we received a photograph from a random place in the universe, could we analyze the stars in the photo and determine roughly where it was taken? We can assume the photo is clear and we have a good look at the stars and their relative brightness. The photo is just a simple RGB photo like . There is no crazy deep spectrum data or whatever else our super-powerful satellites use to look into the furthest reaches of space. I think this would be hard because the star field would look completely different to us from a random perspective. Additionally, the brightness of the stars would also be different. Would it require an impossible amount of calculation to determine where the photo was taken from? BONUS QUESTION: What if we took two photographs, with the camera being rotated 45 degrees between each photo? Would that make it easier?
|
[
"No, because the vast, vast majority of such images would have no discernible stars in them at all. ",
"There are stars in our sky but that is because we are embedded in the disk of a galaxy. A random place in the ",
" is overwhelmingly likely to not be in a galaxy at all. ",
"And even if it were, we do not map anything but the stars in our own galaxy and the brightest stars in nearby galaxies. If you did end up landing in a random galaxy and did have stars in the image, we would have nothing to compare them to, unless by astounding luck you found yourself in the Milky Way. "
] |
[
"I think this would be hard because the star field would look completely different to us from a random perspective. Additionally, the brightness of the stars would also be different.",
"In a static Universe, you could have a perfect cartography, at even the most insane levels of zoom. A gigantic computer may even track and project movement over time.",
"BUT! Stars are born, change in luminosity over and over again at different stages in their existence, then they die, and light takes time to reach us and let us know the status of things at any point in time. From one spot in the Universe, we might detect a \"new star\", even as that star has already become a white dwarf in \"real time\".",
"In the dynamic Universe that we have, the answer to your thought-provoking question is a definitive \"no\"."
] |
[
"Then, supposing you had all the IRAF star catalogs and a lot of time, patience, and puzzle-solving ability, you might be able to locate yourself if you were within the Sun's quadrant of the disk. You might get incredibly lucky and recognize a nebula. You also might by chance have captured one (or if yore incredibly lucky, more than one, which would essentially give you an immediate approximate location in the Galaxy) of the more distant but still photographically capturable objects like the Megallanic Clouds, the recognizable globular clusters, or M31/M101 which would assist in triangulation. Allowing the use of spectroscopy would let you find your local Oort Constants, and thus allow you to deduce your galactic radius. It might also allow you to confirm the identity of certain known peculiar stars if you were nearby to our neighborhood enough. But a single image would likely have none of these things in it and leave you pretty stranded, even if you were pretty close to the sun."
] |
[
"Why do most medicinal pills have \"-HCl\" added to the end?"
] |
[
false
] | null |
[
"This means the medicine is formulated as the hydrochloride salt. Many drugs are organic amines, which would otherwise be basic, so neutralizing them with hydrochloric acid to form the corresponding salt is part of formulating them into a neutral form patients can take. This also makes them more water soluble for better bioavailability, and more crystalline for better stability and compounding.",
"Tetracycline, for instance, ",
"is only very slightly soluble in water and has an amine group",
" that makes it a base, with a pKa corresponding to a pH of 8.3. But hydrochloric acid neutralizes this, and the hydrochloride salt is crystalline (good for making into a pill) and \"freely soluble\" in water.",
"Similarly, the beta-blocker, ",
"propranolol",
", has an amine group and is formulated as the hydrochloride in ",
"Inderol",
"; the anti-depressant, ",
"buproprion",
", has an amine group and is formulated as the hydrochloride in ",
"Wellbutrin",
"; etc.",
"A lot of science goes into properly formulating drugs, including the ",
"salt selection",
". Some things you may target for are:",
"Aqueous solubility measured at various pH values, depending upon the intended pharmaceutical profile",
"High degree of crystallinity",
"Low hygroscopicity (i.e., water absorption versus relative humidity), which gives consistent performance",
"Optimal chemical and solid-state stability under accelerated conditions (i.e., minimal chemical degradation or solid-state changes when stored at 40 °C and 75% relative humidity)",
"Not all drugs are basic, some are an acid and must be neutralized with a base instead of an acid."
] |
[
"It depends on the specific chemical and how strongly basic it is: it could irritate your throat on the way down, and not being as water soluble as the salt, it might not wash down off the throat lining as well, either. In addition, a lot of ",
"alkaloids",
" (morphine, quinine, etc) tend to be bitter as the free base, so the hydrochloride is just more palatable.",
"But once you've swallowed it, the hydrochloric acid in your stomach would get you right back to the neutralized form anyway, so your system would treat it the same after that."
] |
[
"What would happen if one were to take the non hydrochloride form? When you say basic, you mean they will hurt our insides?"
] |
[
"Is there an equation for how much water expands when turning from liquid to solid?"
] |
[
false
] | null |
[
"Yes, to be more precise, there is a property of water and ice that will tell you how much the water will expand. It's called ",
" and it's defined as the mass of the material per unit of volume. So a unit of density is the gram per cubic centimetre (g/cm",
" ). Water has a density of 1 g/cm",
" and ice has a density of about 0.93 g/cm",
" , i.e. a cubic centimetre of water contains 1 gram but a cubic centimetre of ice (the same volume) weighs less at 0.93 grams.",
"Now since the total mass does not change when water freezes, but the density decreases (since ice is less dense) you can work out how the volume will change.\nSay you have one litre (1000 cm",
" ) of water - this weighs 1000 g (1 kg). If you freeze it, it still weighs a kilogram but now has a lower density. Since density = mass/volume, rearranging the formula gives you volume = mass/density. The new volume is therefore (1000 g)/(0.93 g/cm",
" ) = 1075.3 cm",
" , or 1.0753 litres. So you can indeed work out the expansion.",
"Note: the densities of water and ice vary slightly with temperature, but this can be ignored for most applications.",
"Edit: formatting"
] |
[
"Crystals and amorphous solids exhibit varying density depending on temperature, hence thermal expansion."
] |
[
"While density can be used to determine the volume change in a material, that's kind of the back door approach. There are entire tables of a material property called an expansion coefficient. It's a typically linear value that can be used in a formula to determine the volume of an object at any given temperature. It's used in a lot of construction, even if it's not what they call it. Ever wonder why they put cracks in concrete? Expansion. It heat and expands, and the larger the slab, the more stress you put into it. Brick can expand up to 1 inch for every 60 feet. Like any material, wood expands and contracts, which is why you hear your house creak as the temps cool from the day. "
] |
[
"Is there a limit on the amount of things that a brain can retain?"
] |
[
false
] | null |
[
"There's a physical limit a to how much information can be stored in a certain volume. This has been asked before and I think the number I calculated was around 10",
" bits for the size of the brain. The actual number is certainly much smaller, but at least it's an upper bound"
] |
[
"That's if you consider the brain to be similar to a computer's hard drive. It isn't so the comparison is not very valid. In \"The Shallows: What the Internet Is Doing to Our Brains\" by Nicholas Carr he argues that there's no actual limit of the brain's capacity to store memories but only in recalling those said memories."
] |
[
"No, I consider it bound by the laws of physics. "
] |
[
"Why don't humans ever have yellow eyes?"
] |
[
false
] | null |
[
"\"there are many types of birds, Homo Sapiens is just one\"",
"Just clarifying meaning/intent, since this makes it sound like you're saying humans are birds- I think your intention is to say that Homo Sapiens is a single species whilst \"birds\" are an entire (class? subclass?) so there's a wider variety there. Please don't take this the wrong way, it's just a little ambiguous from a language standpoint!"
] |
[
"As far as I know, ",
" land vertebrates are unable to produce colors other than brown, black, or red through the use of pigments. Most bright colors are produced by refracting light."
] |
[
"As far as I know, ",
" land vertebrates are unable to produce colors other than brown, black, or red through the use of pigments. Most bright colors are produced by refracting light."
] |
[
"Why is it that I suddenly get a ringing in my ears when staying sitting down?"
] |
[
false
] | null |
[
"Medical advice would violate the ToS of reddit.",
"If you were wondering what could cause occasional ringing in the ears, a potential answer could be ",
"tinnitus",
". However, I'm sure there are other possibilities."
] |
[
"Tinnitus is not a cause, just the fancy name for \"ringing in the ears\"."
] |
[
"Yeah, the rules forbid this type of posting, and also forbid answering it!"
] |
[
"Do insects get old in a manner that mammals do?"
] |
[
false
] |
Losing their endurance, speed, durability, brainpower etc.? Or do they remain same during all of their life?
|
[
"Interesting question. Some species have no mouth parts in their adult versions. They just breed and die. On the other hand Queen termites can live for 30 years. It takes monarch butterflies 5 generations to migrate north each season but the fifth generation migrates all the way to Mexico in the fall and partway back north in the spring."
] |
[
"Honey bees wear out as they age both physically and in the pheromones they produce. Since they can not repair damaged parts the wear eventually adds up to limiting the bees lifespan.",
"Once worker emerge as adults they spend time progressing through various jobs in the hive slowly progressing to forager. Foraging is the last job a worker will do and it will die as one. In spring/summer after an average of about 45 days. The main issue is wings becoming shredded and worn making it harder to fly. Wings can not be repaired so once they are torn enough flight becomes impossible the bee is effectively dead. There are some ",
"internal chemical issues",
" (go to the section \"Foragers have a short warranty\") tied to wing use which also limits life span.",
"Queens demonstrate this damage to wings (likely caused by workers grooming her) also but since they only fly when young for mating and when old for swarming the wings and flight muscles are not as much of an issue. More of an issue to queens is when they run out of sperm. A queen will only mate once in her life. She will leave the hive a few days after emerging from the pupal stage and mate with a number (up to 35, average of 12) drones. The sperm she collects at his time must last her whole life, once she runs out she lays only unfertilized eggs which develop into drones not workers or queens. ",
"Queens also lose pheromone production as they age. Queens produce a number of pheromones which do things like inhibit the workers from laying eggs. Older queens tend to produce less and less and this is one of the causes workers replace queens, often in the 2nd year of their life. "
] |
[
"I have no idea for house flys but its likely similar to bees, wing damage and chemical issues with muscles powering them. Predation is also a large factor. ",
"Honey bee workers work themselves to death as described they continue to fly until they are physically not able to. Foraging an area 3 miles in circumference makes predation a major cause of death. Queens however live longer 3-4 years is not unusual. They are often killed by the workers themselves as part of supercedure, replacing her with a younger more virile queen."
] |
[
"If we had a telescope 100 light years away from earth would we be seeing into the past? (And follow on questions)"
] |
[
false
] |
[deleted]
|
[
"A telescope at 100 ly would indeed see light that departed the Earth 100 years ago.",
"While I haven't done the math, I'm going to assume that it would be impossible to achieve sufficient resolution to see individual people as mentioned in your followup question.",
"And if there was a way to bounce back light and have enough of it make to Earth to register as a signal, we would be looking at signals that left our planet 200 years ago. In that sense it would be like \"looking into the past\". However, in order to be able to see such signals, we would have to deliberately send powerful signals out into space, ideally pointed directly at where this reflector is (or a recorder that simply rebroadcasts what it receives, that might be better even). You won't be able to slap a mirror at 100 ly distance, point a big telescope at it and get the ability to peek into the backyard of the neighbors 200 years ago. There's not even remotely enough light coming from our planet (or the neighbors backyard) to be able to do that."
] |
[
"Gravitational lensing and space dust would be a huge barrier to that kind of resolution, also. In theory, with enough computing power, you could model that in, but we are talking about solutions far beyond what our current technology could even begin to grapple with."
] |
[
"I'm not doing the math either, but I think in theory, you could resolve the image of a person standing on earth from 100 light years away, but the size of the telescope would have to be really big. Like a perfectly shaped mirror the size of a solar system kinda big. ",
"As for photon reflection, the properties of mirrors are kind of amazing when you think about it. Technically, the wall in front of you is reflecting a lot of the light that you are reflecting, right back at you. But, for an object to reflect a meaningful image back at something it has to have some pretty specific properties. Most things in our universe behave more like walls than mirrors."
] |
[
"How can modern humans and Neanderthal be seperate species if they interred?"
] |
[
false
] |
I have always been told that one of the things that define the cut off to a new species is losing the ability to interpreted. Since we all carry Neanderthal DNA how are they considered seperate species?
|
[
"This is covered in ",
"Why can two different species sometimes hybridize and produce viable offspring? Shouldn't they be the same species?",
". Interbreeding between different species is not unusual; there are many unambiguous examples. Even horses and donkeys, the classic example of sterile hybrids, occasionally have fertile offspring.",
"Successful Neandertal/sapiens hybrids were probably very rare. Neandertal/sapiens hybrids were almost certainly very sub-fertile. Male hybrids were probably sterile altogether. That's what we often see today with interspecies hybrids.",
"We find that observed low levels of Neanderthal ancestry in Eurasians are compatible with a very low rate of interbreeding (<2%), potentially attributable to a very strong avoidance of interspecific matings, a low fitness of hybrids, or both. These results suggesting the presence of very effective barriers to gene flow between the two species are robust to uncertainties about the exact demography of the Paleolithic populations, and they are also found to be compatible with the observed lack of mtDNA introgression.",
"--",
"Strong reproductive isolation between humans and Neanderthals inferred from observed patterns of introgression.",
"Our results indicate that the amount of Neanderthal DNA in living non-Africans can be explained with maximum probability by the exchange of a single pair of individuals between the subpopulations at each 77 generations, but larger exchange frequencies are also allowed with sizeable probability. ",
"--",
"Extremely Rare Interbreeding Events Can Explain Neanderthal DNA in Living Humans. ",
"Our integrated demographic analysis of multiple archaic and present-day human genomes suggests a scenario of long-term decline in the populations of Neanderthals and Denisovans, with the consistently small Altai Neanderthal population perhaps reflecting a long period of isolation in the Altai Mountains. In addition, we provide evidence for modern human introgression into the ancestors of this population of Neanderthals, and no such evidence in the European Neanderthals. ",
"--",
"Ancient gene flow from early modern humans into Eastern Neanderthals",
"Genes that are more highly expressed in testes than in any other tissue are especially reduced in Neanderthal ancestry, and there is an approximately fivefold reduction of Neanderthal ancestry on the X chromosome, which is known from studies of diverse species to be especially dense in male hybrid sterility genes. These results suggest that part of the explanation for genomic regions of reduced Neanderthal ancestry is Neanderthal alleles that caused decreased fertility in males when moved to a modern human genetic background.",
"--",
"The landscape of Neandertal ancestry in present-day humans",
"Finally, the reduction of both archaic ancestries is especially pronounced on chromosome X and near genes more highly expressed in testes than other tissues (p = 1.2 × 10(-7) to 3.2 × 10(-7) for Denisovan and 2.2 × 10(-3) to 2.9 × 10(-3) for Neanderthal ancestry even after controlling for differences in level of selective constraint across gene classes). This suggests that reduced male fertility may be a general feature of mixtures of human populations diverged by >500,000 years.",
"--",
"The Combined Landscape of Denisovan and Neanderthal Ancestry in Present-Day Humans."
] |
[
"Interbreed, not interpret. Anyway, there is no one perfect definition of species because you may always have a continuum across which organisms that are different enough to be considered different species, yet can interbreed to produce fertile offspring. You have to draw the line somewhere, but if every sexually-reproducing organism that ever existed were alive today, you should be able to find pairs of species for every organism to produce fertile offspring. Neanderthals are considered different species perhaps because there are likely a species or species (plural) that Neanderthals can produce fertile offspring with but we can’t. Also not every Homo sapiens has Neanderthal DNA (DNA that had evolved in Neanderthals but not Homo sapiens prior to interbreeding)."
] |
[
"A chimp's DNA is not 99.8% identical to a human's DNA, that is a misunderstanding of the research. There are considerable differences between the two genomes."
] |
[
"If symptoms of a virus (like a cold) are indicative of the body's fighting off the bug, then do medicines that suppress the symptoms prolong the illness?"
] |
[
false
] |
I've always been taught that a runny nose, a cough, sneezing etc are all different ways of the body expelling the virus, wouldn't something that stops all of those then make it harder for the body to fight the illness?
|
[
"Not a doctor, but I can specifically say that one of the most notable examples of the body behaving in the way the OP describes is the fever response.",
"Infectious bacterial bugs (like most living things) have a preferred temperature range that they like to live and reproduce at. Temperatures too far above or below that range cause them to die off or not reproduce as quickly, which is why most animals that are capable of producing a fever will do so naturally in response to infection--this evolutionary response allows the body to more readily fight disease. ",
"As a result, some infectious disease specialists will choose not to treat a fever response unless it reaches dangerous temperatures--though they can be uncomfortable, fevers actually do significantly reduce the time spent with symptoms of infection.",
"Source: ",
"Dr. Mark Crislip's Infectious Disease Podcast",
"Sidenote: I am not sure how much a fever helps stave off a viral infection, can anyone expand?"
] |
[
"Not necessarily, it depends on what we're dealing with.",
"The body releases a lot of mediators when you're sick, chiefly histamines and cytokines if we want to be specific about the symptoms you're referring to. These alert the immune system, and draw more blood flow to the area where the fight is going down. They also cause all the undesirable side effects, and a lot of the time, our body over-reacts. It's not perfect, basically.",
"Removing the undesirable side effects can be helpful sometimes, it all depends on what condition one has, and what one is taking to manage it.",
"This article",
" says combining OTC's with antibiotics can prolong ear infection. This is possible for reasons of drug interaction, or because the antihistamine is preventing some healing process from occuring. I'm going with the former. It's not even really that it prolonged the infection, simply that more fluid remained, and outcomes were identical, so as much as it might happen, it's irrelevant.",
"However, in the event of an infection that's preventing you from clearing mucus, a drug like acetlycysteine or guafanesin can actually help to clear the mucus, and result in faster healing. ",
"Here",
" (Yeah, it's ehow, but the reasoning and science is solid and I can't find a journal at the moment.)",
"Long story short, as tends to be the case in medicine, it depends."
] |
[
"Great answers above, upvoted both.",
"Noone mentioned a specific class of drugs - corticosteroids. Corticosteroids are drugs that purpously SUPPRESS your immune system. They are based on, and in fact include, a natural hormone your body makes, cortisone/cortisol. This hormone and the drugs based on it naturally depress your immune system. We generally give in cases of severe allergic reactions/aggressive autoimmune diseases that are out of control, or sometimes even to symptomatically just reduce localized inflamation that is NOT of infectious origin.",
"Does it work great to combat the specific disease we are treating, which is your immune system gone haywire? Sure. Can it make an arthritic knee or a pinched nerve in your back symptomatically better for the short to mid term, without really fixing the problem? Sure. But it comes at a cost, it makes you much MORE susceptible to infectious forms of diseases, over the long term.",
"Disease is a complicated concept - you seem to be talking about just infectious diseases, but there are many other classifications of disease besides infections."
] |
[
"Saturated Fat: what are the facts?"
] |
[
false
] |
I keep hearing on reddit that saturated fat is fine, and okay for you. This statement is usually introduced with citations from "Gary Taubs". Just because nearly everyone on reddit states that saturated fat is fine, I cannot get myself to believe it. The following departments and professional organizations recommend to stay away from saturated fat, as much as possible: The USDA The World Health Organization the International College of Nutrition the United States Department of Health and Human Services the American Dietetic Association The American Heart Association The British National Health Service the Dietitions of Canada The American College of Physicians the Cleveland Clinic the American Academy of Family Physicians The scientific consensus is obviously in support of the theory that saturated fat is bad for your health. Could they possibly be wrong? Is there extraordinary evidence to show that saturated fat is "okay" for you? If so, why have these organizations saying otherwise? On reddit, if you say that saturated fat is bad for you, then you get downvoted. Reddit doesn't seem to be "science denying", so what gives? My Sources: - PDF - PDF
|
[
"I'm kind of tired/hungry right now but I'll try and get this down as quickly as possible and then edit in relevant stuff later.",
"Saturated fats are ",
". Saturated fats ",
" are bad for you (same as anything else). ",
"Some saturated fats (such as Medium Chain Triglycerides, found in high amounts in both coconut and palm oil) are ",
" healthy for you and substantially raise your HDL cholesterol. Some sources of dietary saturated fat are also ",
" healthy for you and have a ",
" of benefit for various markers of health. Oily Fish and Coconut Oil both contain a substantial amount of saturated fat but are ",
" healthy for you. ",
"Here's a study regarding coconut oil and people",
"(pdf) and ",
"here's one regarding fish oil",
". The coconut oil part might have to do in part with coconut oil containing ",
" amount of medium chain triglycerides relative to most other sources of food.",
"Fish also often contains a substantial amount of Omega 3 DHA+EPA (polyunsaturated fatty acids) which have a great deal of health benefits, and are often not present in our diets in nearly large enough quantities; especially relative to Omega 6 fatty acids.",
"Excess consumption of carbohydrates ",
" bad for you, and a much more common problem in North American society than excess consumption of saturated fats. ",
"Here's a study showing as much",
". ",
"In regards to saturated fats, carbohydrates, and LDL cholesterol: consumption of saturated fats raise levels of light and fluffy LDL cholesterol, consumption of carbohydrates raises levels of small and dense LDL cholesterol, and triglycerides (which both serve as a better marker of health than unoxidized light/fluffy LDL cholesterol). ",
"Here's the wiki on LDL cholesterol",
". ",
"Newer research is suggesting that saturated fats are ",
" nearly as large a causative factor in the development of heart disease as several other things (excess consumption of carbohydrates). ",
"Here's a recent meta-analysis showing that saturated fats do not significantly contribute to heart disease",
". Also, ",
"here's a study discussing as much saying that excess carbohydrates are worse for you than excess saturated fats",
".",
"A lot of the older research regarding saturated fats carried out predominantly by a man named ",
"Ancel Keys",
" had a lot of problems. ",
"This is silverhydra's comment with some cited sources explaining some of the problems with the research",
". Silverhydra would be ",
" better suited to answering this question than me, but some of the attitudes of ",
"r/askscience",
" have mostly kept him out of here (\"citation or it didn't happen!\").",
"In reality, it's excess consumption of calories ",
" that is worse for you than consuming a slightly large amount of one macronutrient while eating an isocaloric or hypocaloric amount (in fact, this might actually be ",
" if it's protein and you are otherwise healthy). Too many saturated fats are bad for you the same way too much of anything is bad for you, that's why it's ",
".",
"Also hopefully many of the larger nutritional bodies will amend some of their views in light of new scientific research stating some of their original conclusions are wrong. Most people don't exactly need 300g of carbohydrates a day, but it's the opinion of many of these organizations that we do. (When I'm not injured) I run 15-30 miles a week and lift heavy for 3-4 hours a week and do just fine on around ~250g a day. Many of these larger organizations are wrong about other nutritional requirements too (the average adult needs ",
" than 400IU of Vitamin D everyday in the absence of sunlight, ",
"source",
"), but hopefully their minds will be slowly changed when they can no longer disagree with the mounting evidence in front of them. Sometimes I think of larger scientific bodies more as a group of politicians, and much less like scientists.",
": I'm not a huge fan of Dr. Lustig or Gary Taubes either, but they're mostly right about a lot of this stuff, if a little bit sensationalist. When they say you should avoid consuming certain types of fruit like grapes because of excess fructose relative to glucose I very much disagree. Screw that shit, I love grapes."
] |
[
"I get that, but sometimes there is no citations or they're very hard to find and often just 'common knowledge' among anyone who's ever read a physiology textbook or something to that effect. Sometimes they don't even ",
" because clinical trials have never been conducted or can't be conducted within reason. Look at someone like ",
"John Broz",
" who trains world class resistance athletes, but you can't exactly put his training method under the scientific knife because the studies would be observational. But then again, no one would ever really invest in the studies either.",
"Sometimes citations are ",
" or the data is ",
" to come to a conclusion (inherent biases coming through). Just look at the Ancel Keys fiasco. ",
"Here's a relevant video",
" about his research (from the movie Fat Head).",
"Then there's also the Princeton study which was carried out on rats and is the ",
" study ever (that I know of) to show that consumption of HFCS causes more weight gain than Sucrose. Of course the study has been ",
" ripped apart (in fact that's what happens when most scientific journals cite the study) because the rats were under ",
" and allowed to consume as much as they wanted to. ",
"The paper was still circlejerked all over the news though. It occasionally gets used here to answer questions regarding HFCS and the answer skyrockets to the top because people see \"oh, citations, UPVOTE!\" and they fail to think critically about it.",
"Also, just take a look at the plethora of information by ",
" and their nutritional guidelines ",
" vilifying saturated fats. Now people are jumping on the \"fructose is evil\" bandwagon and it's even some of the same people who say saturated fats aren't evil, they've jumped away from one villain they knew to another. The reality is somewhere in the middle, but scientific evidence exists across the board (low fructose is great, moderate fructose is better, high fructose is terrible, high saturated fats are terrible, saturated fats are fine, low-saturated fats is bad).",
"Then there's meta-analysis which again often ",
" out of data to come to their intended conclusion. The Institute of Medicine recently changed their guidelines for Vitamin D's DRI; it went from 200IU -> 400-800IU (infants-seniors) in the states and 400IU -> 400-800IU (infants-seniors) in Canada I, the UL went to 2000IU for America and went from 2000IU to 4000IU in Canada. ",
"But they ",
" the findings of several of the ",
" in Vitamin D research. They failed to address that the NOAEL in the all the literature is 10,000IU/d; except on ",
" when it was 2,000IU/d. The original upper limit was established because they discovered supplementing ",
" with 2,000IU/d retarded growth. If I'm not mistaken the current guidelines in the US state that infants require 400IU/d, and fully grown adults require 600IU/d, but lactating and pregnant mothers ",
" require 600IU/d... does this make sense to you? The ",
" DRI was established in the early ",
"20th century when they found that Vitamin D helped cure rickets and they based the recommendation off of how much Vitamin D was in a teaspoon of cod liver oil (200IU, enough to prevent rickets), I believe.",
"This is a paper",
" that is ",
" regarding the safety of supplementation of Vitamin D. Even in the paper (which again is 12 year's old) they recommend switching the Vitamin DRI to at least 1000IU/d. The Institute of Medicine of course decided to ignore the paper. Most experts agree the DRI in the complete absence of sunlight is probably around 5000IU/d (",
"here's a paper on Vitamin D regarding lactation",
"). ",
"This",
" is the page I'm working on, a recent study showed that men supplementing with 3332IU/d Vitamin D say improved many markers of health (many cardiovascular) during weight loss and also had their serum Testosterone levels rise from the lower end of average to the higher end of average. The Institute of Medicine is yet to see or analyze these findings, but the take home point is there was no observed adverse effect taking 1.5x the current UL and in fact only ",
" markers of health. Okay... I'm going to end the Vitamin D crusade now.",
": Sometimes there is a difference between reality/facts and science (but ideally there shouldn't be). Sometimes scientific evidence doesn't exist for things, sometimes citations ",
" because of the flawed methods/analysis. People also often fail to think critically. ",
"This is a discussion on some of the practices of r/askscience",
" (albeit in a circlejerk subreddit so there's a lot of joking, but it's my favourite subreddit and there's quite a few very knowledgeable people in it). Even take a look at ",
"this post",
" which isn't going to drop a whole lot of citations but hopefully manages to impart a great degree of knowledge on people asking questions."
] |
[
"Is there extraordinary evidence to show that saturated fat is \"okay\"\nfor you? ",
"AFAIK nobody claims that short-chain saturated fats are bad, and medium-chain saturated fats are not usually disparaged either, so I'll assume we're discussing long-chain saturated fats (C14+).",
"If you eat more protein or carbohydrate that necessary to maintain your tissues and fill your glycogen stores, the body will convert the excess food energy to long-chain saturated fat (palmitic acid I believe) for storage. We can not assume without evidence that we have evolved to store excess energy in a toxic form, so the null hypothesis should be that long-chain saturated fats are harmless.",
"The question should be: Is there extraordinary evidence to show that long-chain saturated fats are harmful?"
] |
[
"Does squeezing a plastic milk bottle after pouring some milk, to reduce the amount of air in the bottle, before putting the cap back on, keep it fresh longer?"
] |
[
false
] |
This is something I've done sometimes and I wondered if the amount of air in the bottle has a meaningful effect on the life of the milk. Type of bottle in case there is any confusion: I suppose what I'm asking is, whether a reduction in interaction with air slows down the process of lactose being converted into lactic acid? Or any other part of the process?
|
[
"Temperature and light have more of an effect on milk than air content. Store your milk as far away from the door as possible and try to keep it around 39 degrees f. Don’t let it sit out longer than it takes to pour or transport it. You want to keep the cap on tight so the milk doesn’t absorb other flavors in the fridge air."
] |
[
"onsider getting organic milk or specifically UHT",
"Organic and \"UHT\" are quite different things.",
"If where you live all organic milk is also UHT then that's really crap. That's not the case everywhere.",
"Organic milk won't last any longer than regular milk.",
"The Scientific American article is misleading: where I live organic milk has exactly the same shelf life as non-organic milk \"despite\" not having any antibiotics in it. If their assertions were correct then that wouldn't be true.",
"It's pasteurisation, not the presence of antibiotics, that preserves fresh milk."
] |
[
"onsider getting organic milk or specifically UHT",
"Organic and \"UHT\" are quite different things.",
"If where you live all organic milk is also UHT then that's really crap. That's not the case everywhere.",
"Organic milk won't last any longer than regular milk.",
"The Scientific American article is misleading: where I live organic milk has exactly the same shelf life as non-organic milk \"despite\" not having any antibiotics in it. If their assertions were correct then that wouldn't be true.",
"It's pasteurisation, not the presence of antibiotics, that preserves fresh milk."
] |
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