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[
"How much commonality is there between 'human' medicines and medicines for use to treat animals?"
] |
[
false
] |
I expect that dosages will vary based on things like body weight or metabolism, but are the same medicines typically used for both humans and other animals, or not?
|
[
"There are a lot of different kinds of animals, so it is hard to answer with any specificity but generally a lot of medicines are able to be used interchangeably between mammals. Anesthetic agents, antibiotics and antiparisitic agents are just the examples I can think of off hand. Chemicals, however, can't always be used between different non human mammals, for example, permethrin is mostly harmless in residential qualities to humans and dogs, but fairly toxic to cats.",
"source: Nurse who grew up on a cattle farm."
] |
[
"There is significant commonality, but you are right in thinking that size and metabolism are variations determining what is used.",
"Metabolism (more specifically ",
"xenobiotic metabolism",
", that of breaking drugs not \"how much energy you use\" type metabolism) varies between species. We all have different enzymes and pathways to break down drugs. Virtually all of these processes happen in the liver (and can happen other places too, but this is a reason not to mess up your liver). There is oxidation, reduction, hydrolysis, you know usual organic chemistry stuff. These are grouped under Phase I reactions.",
"The ability to conjugate chemicals is another way to get rid of them: stick another molecule on it to make it more water soluble and then it can be excreted by the kidney or GI tract. These are Phase II reactions. The molecule stuck on varies and there are several pathways including methylation (adding a methyl group which is a carbon and some hydrogen atoms), sulfation (adding a sulfa group) and so on. ",
"Some species have certain types of conjugation while others have limited supplies or none at all. Cats, for example, have very limited ability to perform glucuronidation, so because of this they can't break down large quantities of drugs like acetaminophen or ibuprofen; this inability to break them down in large amounts makes them build up to toxic levels. In pigs, the ability to sulfate drugs is limited so some drugs need to be avoided in them (however cats are great at sulfation, hah!)\nDogs have limited aceytlation. Etc. Etc.",
"SO. This means that in many cases, yes we can use the same drugs just with more thought. ",
"Another issue to consider are receptors for the drug. A good example is the opioid group. Most vertebrate animals seem to have opioid receptors (mammals, birds, reptiles yadda yadda). These are receptors related to pain and pain relief (aka analgesia). There are several receptor types, named mu, kappa, and delta. These receptors vary between sites of the body, with more of some types in the brain and spinal cord and more of other types in the muscle and organs. Different animal species have different receptor expression as well, so selection of opiate drugs for analgesia must take that into account. For example, dogs and cats both will have good analgesia from morphine, a pure mu agonist. However, because of the various distribution of those receptors, dogs will tend to vomit when given the drug, and cats might vomit but will often become dysphoric (think: bad trip). Meanwhile if you give IV morphine to a horse rapidly, you might kill it from an acute allergic reaction!",
"So. There are many factors that go into whether animals and people get the same drugs. So many drugs made for people are safety tested using animals, so we have good data suggesting whether those drugs can be safely used in animals. (Funny thing in ",
" pharmaceutics in the USA, you don't have to prove the drug ",
", just that it isn't dangerous). The cost of developing drugs is HUGE, and for that reason many veterinary pharma companies are offshoot of human ones; there is limited money in veterinary pharma, so we get one or two new drugs a year compared to the handfuls of human drugs made or re-tooled. ",
"One more thing: off-label use. We veterinarians are given the ability to use drugs off-label. An example of this: Ivomec brand ivermectin, a dewormer labeled for cattle and swine, is often prescribed for dogs for demodectic mange. We can do this because #1 there is no evidence it is harmful #2 the veterinary community has agreed on its usage #3 there is nothing on the label specifically prohibiting its use in a dog. We can do this with human drugs too. In the chemotherapy realm, there are VERY few pet-labeled chemo drugs, but we can usually prescribe those medications for animals, still following all appropriate safety protocols for use. This is also true with some hormones and immune modulating drugs; there aren't enough pets that need the drug so no animal pharma company makes it, a vet won't carry the human version because of rare use and/or expense. But we can write a script to a human pharmacy or hospital to obtain the drug (as long as there is no official mandate the drug can't be used in that species).",
"I think I just wrote a framework for a book! Hope this helps :) \nCredentials: I'm a Veterinarian in the USA"
] |
[
"Hello Veterinarian in the USA,",
"If you like answering questions, you should consider ",
"applying for flair",
"!"
] |
[
"Moving to new laboratory! What do I need?"
] |
[
false
] |
Hey folks, I work in a biophysics/neuroscience lab, and we are moving to a new building. It is approaching last minute request time for furniture and hardware. What do you guys find particularly useful that is not standard issue?
|
[
"Things like safety glasses box near the entrance to the lab (preferably outside), glove dispenser might get forgotten.",
"Don't know what kind of stuff you would be doing but you can never have too many retort stands and clamps."
] |
[
"Label maker. This is key."
] |
[
"I like a buddha statue for this, it accepts donations and, after a few months, buys beer for the lab."
] |
[
"Do all organisms breathe, and if so, why? What is it about oxygen that makes it so important for life?"
] |
[
false
] | null |
[
"Oxygen is actually toxic to some organisms, due to it being highly reactive. These bacteria, called obligate anaerobes, usually live isolated underground.",
"However, all higher organisms require it to live. This is because, due to its reactivity, it can be used to extract 18 times as much energy from a sugar molecule than without it. Ultimately the role oxygen plays is that it is very electronegative (i.e. electron-hungry). In oxidative respiration, a high-energy electron is taken off a sugar, and passed along an electron transport chain where its energy is converted into energy the cell can use (ATP). Once it is a low-energy electron, it is accepted by an oxygen molecule, which splits, picks up a couple protons, and turns into water. It takes a very electron-hungry molecule to be able to accept such a low-energy electron. Interestingly, some underwater bacteria use sulfur instead of oxygen as a final electron acceptor."
] |
[
"Note: I've just finished highschool and am starting University this year, so please forgive if I make any silly mistakes.\nFirst of all, oxygen is used in respiration to release energy from stored energy (in the form of fats, proteins and other organic molecules (ie. Molecules based on chains of carbon atoms)). Cells use oxygen in respiration to increase the amount of energy they can obtain from the substrates (the stored energy molecules), this is because oxygen plays an important role in oxidative phosphorylation (a step in respiration within cells) 'disposing of' electrons and protons (produced in earlier steps of respiration) forming water as a by product. Without oxygen, respiring cells undergo anaerobic respiration (respiration without oxygen) and obtain significantly less energy and can produce potentially harmful waste products (E.G. Lactic acid in humans (at least, not sure about other organisms) when exercising). That said, many organisms are able to use other electron acceptors to dispose of the electrons and protons (see ",
"here",
" fore more info) and can function respire without oxygen. See ",
"here",
" for the steps involved in respiration.",
"The above was all from what I could remember form my highschool biology textbook without going too in-depth as for the second part of your question, I think oxygen is used so widely among organisms is because of photosynthesis. Since respiration produces CO2 as a by product and photosynthesis produces O2 as a byproduct, the two complement each other nicely and ensures that there is abundant amount of each for their respective uses? Someone else better qualified should answer though."
] |
[
"I can only answer part of your question.",
"Not every living thing breathes, but most do. Creatures that don't require oxygen are called ",
"anaerobic organisms",
", the most common example being yeast."
] |
[
"Why is it difficult to breathe when the wind is blowing in your face?"
] |
[
false
] |
Examples of when it happens include riding a bike at 30+ mph or sticking your head out the window of a moving car.
|
[
"I think it's because when fluids are in motion, they are at a lower pressure (Bernoulli's principle). Since you essentially decrease the pressure in your lungs to inhale, you can't get as much air if the pressure differential with the outside isn't as high.",
"This should also partially explain why it's harder to breathe at high altitudes."
] |
[
"From my experience (as a back-country skier) high altitude makes it harder to catch your breath, but not to breath mechanically. I have also noticed (as negativeK has) that when facing the wind it is harder to pull air into your lungs from a more physical standpoint and is not really similar to the effects of altitude.",
"Another question (cause i dont know much about fluid mechanics) how much does motion effect pressure? how much lower is the pressure of fluid moving at 30-60 mph?"
] |
[
"It would be decreased by d * v",
" /2, where v is the velocity of the fluid and d is the density.",
"\nThe whole effect could be simplified like this: normally, we decreased the lung pressure to \"inhale\". The breath stops when pressure inside and outside is balance. As the wind rarely blows straight into the nostril but rather passing by the nostril, it decreases outer pressure. Therefore the balance happens faster and you didn't inhale as much air, which the brain translates into harder to breathe."
] |
[
"How does being born blind or deaf influence the way you think?"
] |
[
false
] | null |
[
"DeafBlind people learn tactile sign language. So they think in that language. ",
"If you're interested in something more deeper, there have been studies that show hearing people are able to memorize 7 short bits of information (like a phone number) in only one direction, while Deaf people are able to memorize 5 more complex things (such as a family of five children, their ages and genders) forward and backward. This is due to the ability to use space to \"place\" things (such as on the fingers of the hand) in ASL."
] |
[
"Since there are areas of the brain specifically predisposed to process visual and auditory information, when someone is deaf or blind, they will often recruit these non-utilized regions of the brain for other functions. For example, when a blind person reads brail, the language regions of their brain will light up on an fMRI as expected, but in addition, their visual cortex will light up as well, even though they can't see, suggesting that their brain is utilizing this region to process the information as well. The same thing is observed with deaf people. Their auditory cortex is very active when they are communicating in sign language, even though they can't hear. It may go without saying that this extra activity is not observed in people without a sensory deficit. Interestingly though, people that can see, but are taught brail with a blindfold on, will actually recruit their visual cortex to process info in a similar manner to blind people, according to fMRI studies.",
"Essentially being born deaf or blind results in a region of the brain, that would normally be reserved for that particular sense, available for processing other information. Because the brain wastes no processing power, unused regions are quickly recruited by other functions, such as language or complicated motor control."
] |
[
"In addition, people with vision loss can utilize their hearing and sense of touch better, although that isn't something that \"naturally\" occurs. It happens because rehabilitation instructors teach them how to use that information. When using a white cane (I'm an instructor who teaches how to use a white cane), they practice using it and the tactile feedback gives them information about their surroundings.",
"One rare ability is echolocation. Some people claim that anyone can learn it, while others disagree. fMRI data also shows high activation in the visual cortex (",
"https://en.wikipedia.org/wiki/Human_echolocation",
"). While it shows up in movies often, it is extremely rare in real life (in 10 years of working as an O&M instructor, I've met maybe 5 people who can do it reasonably well). ",
"One other thing that I thought I should mention, because I noticed you had it tagged as psychology. Sometimes people ask me why some clients seem to have social issues or rude. That isn't directly because of their vision loss, but more often related to their situation growing up. Many blind children are sent to schools for their blind, which are well adapted for their education, but are poorly adapted for socialization. A good number of kids who come out of those schools have an assortment of social issues and can have trouble relating to others. "
] |
[
"Can you breath ozone?"
] |
[
false
] |
From what I know, we respirate by breathing oxygen (O ). But I am curious as to wether or not we can breath oxygen in other forms such as ozone (O ) or plain ol' O.
|
[
"Individual oxygen atoms can't exist as a free gas, they are far to reactive and will bond to literally whatever they hit first. The only place atomic oxygen can exist is in the near vacuum of outer space where they don't hit anything for a long time.",
"O3 is considered to be an environmental pollutant, and can irritate and damage tissues it touches by losing one O (extremely reactive, as explained before) and turning back into O2. I don't think it would go as far as setting you on fire, but a pure O3 atmosphere would be quite toxic, comparable (I think) to a Chlorine atmosphere."
] |
[
"Ozone is very unstable as far as molecules go. Yes, you can breath it. However, when you do, the O3 will give up an oxygen molecule, opting for the much more stable O2 molecule, with the free Oxygen, now known as a free radical defined by its high reactivity can now react with lung tissue or DNA. "
] |
[
"To expand on this, ozone is a far stronger oxidizing agent than O2 (diatomic oxygen.) As a result, it will react with compounds in the body, oxidizing (damaging) them and releasing O2."
] |
[
"What would the light-dark cycle be like on a tidally locked moon of a gas giant?"
] |
[
false
] | null |
[
"Depends on where you are.",
"The moon would experience a night and day cycle equal to it's orbital period around the moon. If you were on the side of the moon facing the gas giant, you would also have very bright nights whenever they are illuminated by the gas giant. The phase of the gas giant, and how it lights the moon throughout the night, would vary throughout the year.",
"If you were on the far side of the moon from the planet, you would have very dark nights like we have here on Earth away from cities. Judging by the number of moons around our gas giants, there would likely be other moons in the night sky that would provide modest illumination, and go through a very complicated series of phases and times of appearance."
] |
[
"Closer by life would not be possible. So it would have to be a moon like Titan. Not sure I think Titan is about 16 days? Maybe 500 hours is a bit on the long side.",
"THis kind of radiation doesn't blow away. It's charged particles. No isotopes. It just impacts once a revolution, when the planet is on the aft side and moves through the radiation trail. Remember Pandora? For Pandora to be free from radiation storms it needed a massive magnetic field. ",
"http://www.astrobio.net/news-exclusive/hiding-from-jupiters-radiation/",
"http://www.jpl.nasa.gov/releases/2001/belts.html",
"Radiation in the form of high-energy electrons and ions continuously bombard the top layers \nof Europa’s icy crust. This deadly dose is due to the fact that Europa—along with the three \nother Galilean moons (Io, Ganymede and Callisto)—orbits within Jupiter’s radiation belts.",
"These belts are much like Earth’s Van Allen belts but bigger, since Jupiter’s magnetic field is \nten times stronger than Earth’s. Electrons and ions from the solar wind become trapped in \nthe magnetic field and spiral down onto Jupiter’s poles to create impressive auroras.",
"The radiation in Jupiter’s belts is a million times more intense than in Earth’s belts. For this \nreason, spacecraft—such as the Galileo orbiter—have typically tried to spend as little time as \npossible inside the belts. Although the radiation is generally well-understood, no one has yet \nfigured out precisely what the effect is on Jupiter’s moons."
] |
[
"(Hemisphere Facing the gas giant)"
] |
[
"How does gravity work in Quantum Field Theory?"
] |
[
false
] |
I was watching this pretty cool video: and it contained a lot of interesting information about the nature of particles and how various fields interact with one another. My question is, given the best information available at the time, is there a theory on how gravity works within Quantum Field Theory (QFT)? I guess a secondary question would be, considering the interaction of say the Higgs field to add mass to an electron, how would one expect a gravity field to interact with a photon? I'm guessing such an interaction to exist given the ability of gravity to bend light; though I've a sneaking suspicion that something's wrong in my understanding. Thanks in advance for any information.
|
[
"QFT can describe gravity. But the theory, massless spin-2, is not renormalizable. That is, when we compute processes with several loops the theory gives infinities that we can't get rid of. "
] |
[
"Because photons are massless and travel at lightspeed. Electrons are massive (due to their interaction with the Higgs-field) and always travel at speed strictly lower than lightspeed."
] |
[
"In the language of quantum field theory, gravity is a spin-2 massless interaction. You can consider photon-graviton scattering with a lot of calculations that aren't always solvable, like ",
"here",
"."
] |
[
"How small can we go in terms of the sub-atomic structure?"
] |
[
false
] |
A lot of people I know don't realize that we've gone past the atomic level in science. My question is, what is the smallest particle that we've found so far?
|
[
"Our current \"standard model\" is 16 particles that are each fundamental, indivisible particles. ",
"Here's",
" one of our sciencefaqs that goes into a lot of detail about all the particles and forces."
] |
[
"In classical optics, the ",
"diffractive limit",
" gives you a maximum theoretical resolution that is on the same order of magnitude as the wavelength of the light. So with visible light, one cannot resolve objects or details much less than ~200 nm.",
"In particle physics, the wavelike nature of quantum particles enforces something similar to the classical diffraction limit. Typically, one resolves small details of systems by slamming particles into the system and seeing how the particles scatter. The higher the energy of the particle beam, the smaller the resolution. ",
"If you hit protons with a particle beam such that the energy of the collision (in the center of mass frame) is on the order of 100 MeV, the scatterings will appear as if you have been essentially hitting a infinitely small point particle. When the energy gets much above 1000 MeV (or 1 GeV), the scatterings are not compatible with the idea of a point particle, but rather a system of smaller particles, namely quarks and gluons, with a length scale on the order of 1 fm = 10",
" m. ",
"Now at the LHC, we can probe with energies up to 7000 GeV. This means that we can resolve the structure of compound particles as small as 10",
" or even 10",
" m. ",
"Even at these energies, particles like electrons still look like infinitely small point particles. So if electrons are made up of constituent particles, the whole system must be more than 1000 times smaller than a proton. So far, there is no real evidence of electron substructure.",
"So the smallest composite particles that one can roughly measure the \"size\" of are things like protons, neutrons, and pions. "
] |
[
"Seventeen, if you grant the Higgs honorary status. And eight of those go away if you consider the quark and lepton generations to be aspects of the same thing, which is not a totally unreasonable stance to take. Especially the neutrinos."
] |
[
"Why is the placebo Vitamin-C in this COVID-19 clinical trial?"
] |
[
false
] | null |
[
"But if the dangerous drug is no better than the harmless vitamin C, why would they want to use the harmful expensive drug, instead of the cheap harmless thing they can buy in bulk at a Costco? Surely if you’re going to introduce a new drug, you’d want it to be ",
" than something that’s already available? Isn’t this exactly what they’d want a trial to compare to?",
"(Vitamin C is of course useless in this context anyway, I’m not arguing it actually has any effect - just trying to figure out where they’re coming from. And of course I understand that they aren’t actually trying to make a reasoned argument, just expressing vague distrust and anxiety, and that you can’t reason people out of a stance that they didn’t reason themselves into.)"
] |
[
"Ok so I know mother jones is a pretty terrible source for this sort of this but it’s what I found the quickest. Put simply, the placebo chosen has to mimic the drug as closely as possible in aspects like after taste, color and consistency while being as physiologically inert as possible. Typically these studies will detail why they used what they used when the report is written so we’ll have to wait and see what the reasons were for choosing ascorbic acid. ",
"https://www.motherjones.com/politics/2010/10/placebo-ingredients-drug-trials/",
"Edit: something that just occurred to me was also the possibility that the researchers may be testing urine and so to maintain the anonymity of the samples in order to uphold the double blind aspect of the experiment it is possible they chose a vitamin placebo to darken urine samples of the subjects taking the placebo. Just a guess"
] |
[
"Are your friends claiming that vitamin C is ",
"? Because if their argument is that vitamin C is not a placebo because it’s good for you, then it’s harder for the vaccine to look good, because it has to be better than placebo to “pass” the clinical trial. Isn’t that what they’d want? ",
"I could understand it if the placebo was, I don’t know, strychnine or something, because then it would be easy for the vaccine to be better than placebo. But this seems like they haven’t thought it through."
] |
[
"Is everything in the milky way orbiting the supermassive black hole in the centre?"
] |
[
false
] | null |
[
"Sort of... The black hole in the centre only makes up a tiny percentage of the mass of the galaxy. We're really orbiting all the mass of gas and stars and dark matter inside the Sun's orbit around the Milky Way. We are orbiting the black hole because it happens to be in the middle of this mess, but if you removed the black hole it would have almost zero affect on the orbits of anything, except for the stars that are already really close to it."
] |
[
"Otherwise known as the galaxy's barycenter."
] |
[
"The black hole in the centre only makes up a tiny percentage of the mass of the galaxy.",
"To put some numbers on this: The mass of the central black hole is a few million solar masses, while the mass of the galaxy is about a trillion solar masses."
] |
[
"How do we know that the Milky Way is a spiral galaxy?"
] |
[
false
] |
Is it an educated guess? Or was it actually worked out? If so, how?
|
[
"Looking at the Milky Way galactic center we see a long thin strip which suggests a disc shape. The gas fraction, color, and dust content of our galaxy are spiral-like. Through studying the motions of the stars and nebula within our galaxy which are rotational and not random motions. As we began to take this information into account we made a map of our galaxy. "
] |
[
"There is a variety evidence that support this. Just one of the more simple and direct observations comes from just looking up at a really clear night sky like ",
"this",
". What you see here is some of the gas and dust in our Milky Way. It clearly has a very flat, disk-like structure which supports the idea that we live in a spiral galaxy opposed to an elliptical one."
] |
[
"Yes, in the same context as gravity, Newton's force laws and electromagnetism are theories. Don't confuse the word \"theory\" with \"random guess\". Like I said, there is a lot of evidence to support that we live in a spiral galaxy and likewise a lot of evidence to support that we don't live in an elliptical or irregular one. We can observe the flattened disk-like structure of our galaxy with the naked eye. We can measure the velocity of the stars and interstellar medium in our neighborhood and conclude that they're rotating. By looking towards the center of out galaxy in different wavelengths of the electromagnetic spectrum, we again see the disk-like structure and also the central bulge (",
"http://i.imgur.com/IbQyrvh.jpg",
"). I could continue like this, but you get the idea."
] |
[
"I believe I can feel EMF energy from cell phones. Help me design an experiment to test this."
] |
[
false
] |
I recently had a discussion in about EMF sensitivity. I believe that I am able to feel an active radio transmitter near my body. There is a physical discomfort I get from having a phone in my pocket for any length of time. Also, I get headaches from talking on a cell phone for too long. However, I am aware that the brain is capable of playing tricks on itself. I would like to test my EMF sensitivity in a blind experiment. My plan is to take two android phones, and have a friend randomly put one into airplane mode and set the other to transmit data over 3g. I will then hold the phones in either hand for a length of time until I can feel which one is transmitting. I will then repeat this procedure several times, with my friend randomly switching which phone is transmitting, until I get a statistically significant answer one way or the other. I will not activate the screens on the phones, and my friend will not tell me which phone is set to transmit, so there will be no way for me to determine which is transmitting, aside from my claimed EMF sensitivity. I have a few questions before I run the experiment: Is there any app that will make a phone continuously transmit data over 3g? I want to make the contrast between the inactive phone and the active phone as sharp as possible. How many times should I run the experiment to get a statistically significant answer? I do not have two identical phones. My phone is an LG Optimus Slider and my friend's is an HTC Wildfire S. Both are running android. If the transmitting phone is randomly switched enough times, will this be a problem? Is there anything else that I should alter about this experiment or add to make it more thorough and scientific? I will post the results of the experiment once it is completed, and I give my word not to lie or alter the outcome. If there is enough interest, I may even take a video of the procedure. While it is my belief that I am in fact EMF sensitive, I would not be embarrassed to publicly discover that it is all in my head. Note: This was originally posted in . I am posting it here as well because it is more relevant.
|
[
"additional things to do: ",
"Don't hold them in your hand. ",
"(1) Leave the room.",
"(2) Have friend select which is to be turned on based on random number generator.",
"(3) Have friend place phones in identical cardboard boxes. You may want to add some additional sound insulation, too. The point is to block any sound, light, heat, or other such signal that could be used to distinguish between the two phones.",
"(4) Have that friend leave the room, and have another friend (who claims to be insensitive to EMF) enter, and randomly switch around the order of boxes from 0 to several switches, based on another set of random numbers. Also, make sure she rotates the boxes around a bit, fiddles with the flaps, etc. ... just to make sure the first friend doesn't accidentally leave the 'on' phone's box a bit more open than the 'off' phone's or something like that.",
"(5) Have that friend leave room, and now you may enter. Make your choice of which box has an active phone.",
"You want to make sure that all information about location (except EMF) is removed. Also, have a few of the trials include both phones on and both phones off... you should be able to notice.",
"Statistical power can be tricky to work out, here. Ballpark estimate is a couple dozen-ish trials. It really depends on how sensitive you think you'll be. If you expect to be correct 60% of the time, you'll need more trials to rule out a chance result than if you expect to be correct 95% of the time. Off the top of my head, I think getting six out of six trials correct is all you need to reach the usual significance level with Fisher's exact test, but the sort of EMF sensitivity you're describing is so stupendously unlikely given ... well, everything... that the usual p<0.05 threshold is too generous."
] |
[
"This would be perfect for our ",
"Science Fair",
"."
] |
[
"youtube or a speedtest application. You can't set your phone to be a constantly-on emitter, that's against most regulations.",
"I don't know",
"most phones will transmit at roughly the same power at the same time. The output power of a phone is related to how crowded the network is, it's adaptive.",
"Get radio emitters that can send at other frequencies than the cellular ones. Would be curious to know if you are more sensitive to some frequencies or others.",
"Source: I design cellular products for a living."
] |
[
"How does a single nerve (like the vagus nerve) independently control several different functions?"
] |
[
false
] |
I mean without activating/deactivating all the functions at the same time.
|
[
"Basically because the nerve is not a \"single entity\" in the way that it's not a monofilament, but many individual \"strings\" grouped together. As a result, each string (in fact these are axons, each one belonging to a different neuron) starts in a specific place and end in another specific place, and responses can be mediated differently. ",
"But frequently the vagal response is generalized, acting on many organs at the same time."
] |
[
"Can a single neuron send (possibly different) outputs to different places depending on the input?"
] |
[
"I am tempted to say no, but as this is neuroscience I don't want to be absolutely positive it ",
" happens, unlikely as it sounds to me.",
"Basically the neuron, after activated, will send an electric current through all its terminations, affecting all subsequent cells. As the neuron usually carries a specialized function, I believe its direct output is the same to these cells. I can't exclude the possibility of the subsequent cells having different connections further down in the chain, so different ",
" results will happen as a consequence of the 1st neuron firing. Does this make any sense to you?"
] |
[
"Is there something that prevents you from getting do different colds/flu's at the same time, or does that happen?"
] |
[
false
] |
So if you get sick, your body builds up an immune response to fight it off. I'm wondering if this heightened immune response would make it more or less likely that you would get a second illness like that at once? So, does your immune response in its elevated state fight off a new bug more effectively - or is it so concentrated on the first illness that it's more likely to ignore the new bug? It's pretty hard to tell, when your sick, whether you just have one thing or more, but I've always assumed I just had "a cold" or "the flu". But maybe I've had more than one thing. Anyone know?
|
[
"Very well put, but this holds true only for the adaptive immune response and not for the innate immune response. Innate immune response is a more general fight anything type of immunity. This includes our phagocytic cells (which if called to an area of infection will eat just about anything there whether it's bacteria A, B or F). One other example of the innate immune response the production of interferons. Interferons are produced by some cells when they get infected by a virus, they stimulate the immune system and can actually protect/signal to other cells. These interferons could in theory protect your cells from virus B even if they were only infected by virus A. "
] |
[
"You can indeed be infected by two different viruses/bacteria at once. As for whether your heightened immune response will help fight the second one, I don't believe it would because of the way viruses and bacteria are fought using antigens specifically for each pathogen:\n",
"https://www.youtube.com/watch?v=zQGOcOUBi6s"
] |
[
"Thanks for the elaboration. I had a feeling that some parts of the immune response may target general foreign bodies but I had no specific examples. The immune system fascinates me more every time I learn something new about it!"
] |
[
"*Physics* Can someone explain what exactly is \"Einstein's biggest blunder\"?"
] |
[
false
] |
[deleted]
|
[
"It was a blunder because Einstein changed his physics to match up with a certain philosophical notion he had in mind - that the Universe was static and unchanging - rather than listen to what GR (without lambda) was telling him, which is that a (homogeneous and isotropic) universe necessarily expands or collapses.",
"We've since learned that even Einstein's static solution isn't very good, for two reasons. First, lambda needs to be incredibly fine-tuned to match up with the density of the Universe. If lambda has even a slightly different value, there's no static solution. Second (and related to the first), the solution is ",
" - give it a little push and it will either expand ad infinitum or collapse in a Big Crunch.",
"This isn't hard to visualize. Imagine a ball floating in the air, balanced perfectly between gravity pulling it down and some repulsive force pushing it up (assume that the repulsive force grows linearly with distance, like a spring). If you push the ball down a tiny bit, gravity is a bit stronger and the repulsive force is a bit weaker, and the ball will fall more and more. If you push it up a little, the repulsive force grows and gravity weakens, so the ball will be repelled away to infinity. This is ",
" to the static universe, just replace the position of the ball with the size (scale factor) of the universe.",
"One last note - introducing lambda wasn't ",
" terrible a move as Einstein would have thought, even from a purely theoretical level (i.e., before we discovered the acceleration 15 years ago). Let's say you want a theory of gravity which depends only on the metric and its derivatives (i.e., you don't introduce any other ingredients into gravity, like a scalar field) and whose field equations are only second-order in derivatives (so you avoid the problems with higher derivative theories). There's a theorem due to Lovelock that the ",
" (four-dimensional) theory which satisfies these is GR plus a cosmological constant. From that perspective, setting lambda to zero might even sound arbitrary! This theorem comes from the golden age of GR in the 60s and 70s, long after Einstein did his work in the field.",
"Lovelock's theorem is the reason why many modified gravity theories, like f(R) gravity (in which the action for gravity is a function of the Ricci scalar, rather than just R/16 pi G), have fourth-order equations of motion. The only way out is to either work in higher dimensions (where Lovelock's theorem gives you additional viable terms) or to add in extra fields (for example, f(R) gravity is actually safe from the problems of higher derivative theories because it turns out to be equivalent to a theory of GR plus a scalar field which ",
" second-order in those two fields)."
] |
[
"It only became apparent that we need the CC in the nineties (but with a different sign). So based on what was know at Einstein's time, its introduction was entirely baseless. It's bad science. He wanted to believe that the Universe is static so badly that he modified his equations to fit his ideal.",
"But in fact, since this is only an anecdote reported by George Gamow, it is not clear whether Einstein thought of this as his biggest blunder because he did bad science, or because he missed the chance of predicting the expansion of the Universe.",
"Edit: I guess just introducing the CC isn't bad science per se, but assigning it a specific value just because that's what you want to believe is."
] |
[
"It was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. Einstein abandoned the concept after the observation of the Hubble redshift indicated that the universe might not be stationary, as he had based his theory on the idea that the universe is unchanging",
"Simple enough, he was sure the universe was static and unchanging. So he modified his theory and included the Cosmological Constant to achieve that, however after Hubble redshift indicated the Universe isn't static, he abandoned it. \n",
"http://en.wikipedia.org/wiki/Cosmological_constant"
] |
[
"I always hear that \"a cure for cancer\" is misleading, because cancer consists of a variety of different disorders, with no single cure. That being the case, are there any individual cancers that have been effectively \"cured\"?"
] |
[
false
] | null |
[
"The most dramatic gains have been made in childhood cancers. This includes acute lymphoblastic leukemia, acute myeloid leukemia, testicular cancer, hodgkin's lymphoma, and many others. ",
"Here is a graph",
" demonstrating the gains in 5-year survival rates for lots of common childhood cancers.",
"More recently, chronic myelogenous leukemia (CML) is essentially cured in children and adults with imatnib (gleevec). ",
"wiki link",
". ",
"I'm sure there are many other success stories. I work in radiation therapy, and we tend to see the types of cancers that are poorly controlled through other means.",
"The effect of other cancers has been severely diminished through prevention. Stomach cancer was very common in 1950's US, but is fairly rare now because we identify and treat ",
" infection. Cervical cancer is on the decline in the US, mostly as a result of PAP smears and other types of screening. HPV vaccination should reduce this even further. (As an aside, we are only now starting to notice that HPV-induced mouth/throat cancer is going to be a major health impact. The number of HPV head and neck cancers is following the same trajectory as the number of HPV cervical cancers before the widespread use of PAPs)",
"Lung cancer is declining in American men, due to the dropoff in smoking rates. Lung cancer in American women is expected to show a similar decline this decade."
] |
[
"Getting a treatment option approved is an extremely long process. Most of the stuff you link is at the lab stage, so it needs at least four more main stages (working prototype, animal testing, small- and large-scale human testing) before it can start being used. That takes heaps of money and a lot of time, and every new stage has the potential for discovery of unintended side effects that render the option moot, either because it doesn't work, because the side effects are worse than what we currently have or because it just doesn't scale with current tech."
] |
[
"As a follow-up question:",
"It seems like every year there's a slew of new, novel treatments for cancer that get a big fanfare when they're first announced and then are never heard about again.",
"For example:",
"Gold nanoparticles",
"Cancer-targeting viruses",
"Carbon nanotubes as drug carriers",
"Cancer immunotherapy",
"Proton therapy",
"Yet the go-tos are still radiation, chemotherapy, and/or surgery. While I understand there is no proverbial \"golden gun\" that can treat all cancers, most of these approaches seem very versatile and potentially more effective and less damaging than what we have now, at least to a relative layman like myself.",
"Are these new treatments still being actively pursued? How aware are most oncologists of novel treatments like these? Can you postulate on when some of these might become more mainstream?"
] |
[
"Do the large lakes of North America have a common geological/geographical origin?"
] |
[
false
] |
When I was younger, me and my dad were looking at a map of North America, when he pointed out that a number of huge lakes - including Great Bear Lake, Great Slave Lake, Lake Athabasca, Lake Winnipeg and the Great Lakes - seem to cut an almost linear northwest-southeast slash across the continent. He wondered why that was. Now I do too. Is this just a coincidence, or is there a common link between them that causes them to do this? I know there was once a large glacial lake in the area, could that have something to do with it?
|
[
"Yes, the Great Lakes, Lake Winnipeg, Lake Manitoba, Lake Athabasca, Great Slave Lake, and Great Bear Lake are all remnants of far larger lakes that formed when the Laurentide Ice Sheet retreated after the last glacial maximum (colloquially \"the last ice age\" although calling it that really bothers geologists and other scientists who study that time period). The enormous number of smaller lakes covering most of Canada are also remnants of this as the glaciers left lots of gently undulating exposed bedrock. ",
"Hudson Bay was also created by the ice sheet. The weight was so great that the continental crust bent under it forming a big dent. With the ice gone it's very slowly rising back up.",
"This paper",
" has some maps showing the ice sheet retreating and the various huge ancient lakes."
] |
[
"Yes, continental glaciation for the Great Lakes. It was a place of heavy snowfall then, as it is now. The very thick ice gouged out the surface in some places (Great Lakes) and the debris it left in other places made a kind of dam that held back water. Other lakes, such as Minnesota's \"thousand lakes\", same thing, continental glaciation. The \"dams\" (moraine) caused a lot of lakes at the southern part of the glaciated area. I don't know for sure about all the other lakes you mention. ",
"Interesting fact: continental glaciation on the east coast of the USA went as far south as the NYC area. New England soils are more rocky than in the mid-Atlantic, because of this history.\nI will add, there are many people who know more than I do."
] |
[
"I’m by no means an expert but I know the Great Lakes were formed by a glacier so I would guess it’s possible the glacier was slowly moving in that direction and carving out the lakes along that same path. Again just an educated guess, I’d love for some one actually knowledgeable on the subject to also respond"
] |
[
"Why are Mexicans half as likely to develop/die from cancer than US/Canadian citizens?"
] |
[
false
] |
This question is based off 2012 statistics provided by the International Agency for the Research of Cancer It looks like the same is similar for other less-than-first-world countries. Is this reflective of reality or a product of dissimilar statistical sources?
|
[
"Part of the explanation may be that folks are dying of other things first. Also consider that available information can only include cancer that is ",
".",
"The rate, naturally, may very well be the same, they're just walking around oblivious to it. ",
"People need to see a doctor first for anyone else to know (and record) that they have cancer. There are many reasons a visit to a doctor may be unlikely. Price, distance, health, and general availability are primary factors in lessening the frequency of diagnosis. All of these thing are accentuated in 'less developed' countries.",
"Check out this ",
"life expectancy estimate put out by the CIA in 2012",
" and this ",
"chart from the WHO regarding cancer rates in 2015",
". ",
"This correlation is not unnoticed",
", although ",
"the disparity is shrinking",
" due to a lessening of the aforementioned causes. "
] |
[
"I don't think you understand. The surviving people are avoiding th cancer, BUT the people who didn't survive also avoided the cancer, by dying.",
"Cancer is measured as a percentage of total population. You could reduce the cancer rate to 0% if you just killed everyone before the age of two. That doesn't mean you cured cancer."
] |
[
"My understanding though is that Mexico has the distinction of being the only country with a higher obesity rate then America."
] |
[
"How do we know the laws of physics we observe are universal?"
] |
[
false
] | null |
[
"This is a really important question and it comes up with some regularity here. The answer seems to be that we haven't observed any variance of physics across our observed universe. Thus if they are non-universal they must change very slightly over ",
" long scales. ",
"But it's part of the philosophical inputs into how we do science. Until there's data to suggest otherwise, we assume that physics is universal, because for it to vary is a very complex problem. It's \"multiplying entities beyond necessity.\" Inventing a bunch of explanations to describe something we don't observe. "
] |
[
"what I'd expect to see is something truly unexplainable in the measurement of distant galaxies. I mean since they seem to behave with the same physics as local physics, then there's almost no test you could do locally to answer the question."
] |
[
"Well we observe dark energy pervasive through the whole universe... It's not something that behaves one way \"here\" and another \"there.\" It's just a new physical phenomenon. Another way of saying it is that the galaxies distant on our left behave the same as galaxies distant on our right, etc. It really seems to be a uniform energy distribution."
] |
[
"Why does the modern English language curiously lack diacritics compared to other languages that use the Latin alphabet?"
] |
[
false
] |
Why does it lack accent marks, umlauts, breves, etc. Or, are there other, lesser known languages with this alphabet that don't use diacritics?
|
[
"The most surface-level answer is because English uses digraphs extensively instead. Sounds like th, the other th, ph, gh (which used to be a specific sound), Sh, and vowel combinations like oo, ou, and x_e (where x is a vowel), take the place of what might otherwise be ç, š, ž, á, ö, etc.",
"English used to have four additional consonant letters to reflect sounds not in Latin but those were replaced with digraphs or w (th, th, gh, w).",
"An additional reason is because at the time that English spelling was starting to become entrenched (about 1450, invention of movable type), there were fewer vowels in the language, so there was no need (except to show stress, which English typists did not feel was necessary—even in Spanish it only became widespread/obligatory later on). Because of the great vowel shift and other sound changes, vowels in English got REALLY weird, but the spelling more or less stayed the same. (Not entirely, there were some shifts in spelling.)",
"There are certainly other languages that do not use diacritics, and yes they are not as well known."
] |
[
"All true. I don’t think you can overemphasize the importance of moveable type here. Printers made a lot of choices—many out of convenience for themselves—that became standard practice."
] |
[
"German uses many digraphs as well (ch, ph, eu, ng, ... ",
"Wikipedia has a long list",
"), but we still have umlauts and ß. The umlauts can be replaced by ae, oe, ue and ß can be replaced by ss, so we wouldn't need these four special letters, but they are used in German.",
"We even have a digraph using an umlaut! \"äu\""
] |
[
"Cutting someone in half and they still live for a few seconds?"
] |
[
false
] |
You see it in movies all the time. Someone gets a blade through their entire body (abdominal area) fairly quickly, cutting them in half and they manage to be alive long enough to look down at the destruction, say something, then die. Is that even possible? I mean, their heart and brain are still fine so I guess it can be possible, I just think its such a traumatic thing that you'd die almost instantly.
|
[
"There was a case of a cop somewhere in asia that got severed in half and survived. He does miss most of his lower half of the body. I'll try to locate the article and the video.",
"EDIT:\n",
" THE VIDEO OF THE COP THAT GOT CUT IN HALF BY A BUSS "
] |
[
"Yes, it is possible, and during the French Revolution, there were some doctors that were experimenting to see if the brain was still functional after decapitation by guillotine ",
"[1]"
] |
[
"Interesting question! Apparently the technical term for being chopped in half is ",
"traumatic hemicorporectomy",
". ",
"I did a cursory search on Google Scholar for references; pretty much everyone seems to classify it as \"obviously non-survivable\" but I found one report of a similar injury where ",
"the patient remained conscious and survived under emergency medical care for several hours before dying."
] |
[
"Is there a known maximum for the number of elements, or might we keep discovering new ones forever?"
] |
[
false
] |
[deleted]
|
[
"It's not known, but current models tend to point to an element with ",
"173 protons",
" as a hard limit."
] |
[
"Hey, I coincidentally asked the same question, and got more responses, ",
"check it out."
] |
[
"(For OP's interest)\nLook up nuclear shell models for more on this. Follow links on what you find, if you wonder why this is. I would recommend as a good textbook (easy to read and well-written) \"Modern Nuclear Chemistry by Loveland, Morrissey, and Seaborg."
] |
[
"If I had a steel tube, say 2\" in diameter, vacuum sealed and 30,000' high and dropped a marble down it, would that marble create a huge crater bursting through the bottom into the earth since terminal velocity has been removed?"
] |
[
false
] | null |
[
"No. A marble of mass 5 g at a height of 10 km has a potential energy of mgh = 0.005 kg * 10 m/s",
" * 10000 m = 500 J, which is equivalent to the explosive power of about a tenth of a gram of TNT, which is quite small. In order to create even a small crater you need thousands of times more energy. Note that the marble would be going about 450 m/s (about 1000 mph); meteors are typically travelling more than twenty times as fast, and the dangerous ones are at least a million times more massive. "
] |
[
"If we take OP's example to an extreme, then the highest speed achievable by something falling towards Earth is escape velocity ( 11.2 km/s ).",
"At that speed, the kinetic energy of the marble is going to be about 313,600 Joules or 75 grams of TNT (that is also close to what the kinetic energy of a 1 ton car traveling at 55 mph would be). ",
"wiki source on energies"
] |
[
"No, you had it right the first time. ",
"/u/HeraticXYZ",
" misinterpreted your comment. Then you misinterpreted his."
] |
[
"How sure are we that Type 1a supernovas are 'standard candles'?"
] |
[
false
] |
[deleted]
|
[
"I'm not saying it's way off, but is it possible that it's some off?",
"Yes it is, this is an area of active research as there are no really good models of what exactly happens during a supernova. There has also been some recent research showing that there may be trends between things such as the metallicity of the host star and 1a supernova luminosity that may be contribution to the tension if we assume (I'll dig out a link tomorrow). The supernova measurements are calibrated using something called the ",
"'distance ladder'",
". Broadly speaking, we use parallax to calibrate the luminosity of ",
"Cepheid variables",
", which are in turn used to calibrate type 1a supernovae. But systematics can propagate and magnify through this distance ladder, which is why having extra methods to determine the Hubble constant ",
"(such as the recent BNS merger by LIGO-Virgo)",
" are so awesome.",
"There is also new research being done (including by me) on the ",
"Lyman alpha forest",
" to measure the expansion rate at high redshift (z~4) which would act as an intermediary between supernovae measurements and the CMB and might help settle the debate, or at least provide some more insight into the point at which the tension becomes significant (very happy to go into more detail on this if you're interested).",
"edit: very recent paper on supernova variability ",
"https://arxiv.org/pdf/1706.07697.pdf"
] |
[
"I'm not saying it's way off, but is it possible that it's some off?",
"Yes it is, this is an area of active research as there are no really good models of what exactly happens during a supernova. There has also been some recent research showing that there may be trends between things such as the metallicity of the host star and 1a supernova luminosity that may be contribution to the tension if we assume (I'll dig out a link tomorrow). The supernova measurements are calibrated using something called the ",
"'distance ladder'",
". Broadly speaking, we use parallax to calibrate the luminosity of ",
"Cepheid variables",
", which are in turn used to calibrate type 1a supernovae. But systematics can propagate and magnify through this distance ladder, which is why having extra methods to determine the Hubble constant ",
"(such as the recent BNS merger by LIGO-Virgo)",
" are so awesome.",
"There is also new research being done (including by me) on the ",
"Lyman alpha forest",
" to measure the expansion rate at high redshift (z~4) which would act as an intermediary between supernovae measurements and the CMB and might help settle the debate, or at least provide some more insight into the point at which the tension becomes significant (very happy to go into more detail on this if you're interested).",
"edit: very recent paper on supernova variability ",
"https://arxiv.org/pdf/1706.07697.pdf"
] |
[
"First off, what you're referring to is chandrashekar ",
", not limit.",
"White dwarfs are responsible for 1a supernovae. They essentially leech off a star it's in orbit with until it gets heavy enough to go supernova. This means that the supernova always occurs at the chandrashekar mass, which means all 1a supernovae have roughly the same luminosity. ",
"Since they all have the same luminosity, if you have two 1a supernova at different distances, you can tell which is further away based on which appears to be dimmer. You don't have to worry that the dimmer appearing one is just a dimmer supernova because both supernovae have the same luminosity."
] |
[
"If someone had a tattoo covering their entire armpit, would they still sweat?"
] |
[
false
] |
[deleted]
|
[
"Oh man that sounds painful."
] |
[
"For science!"
] |
[
"What happens when tattoo ink is injected into a lymph node?"
] |
[
"Is asbestos really that toxic?"
] |
[
false
] |
[deleted]
|
[
"Some types of asbestos fibers (crocadilite or something like that if i remember correctly) are very strongly linked to mesothelioma, a cancer of the serous membranes (usually pleura, but possibly peritoneum), and also a type of cancer that is exceedingly rare without a history of asbestos exposure. So, yes, it is toxic and it leads to a form of cancer that has a poor prognosis. The danger IS in fact related to prolonged exposure, this is true, although I do not know the length and extent of exposure required to increase risk substantially.",
"Edit - via wikipedia, I had to go look this up after it nagged me for an hour:",
"\"Amosite and crocidolite are the most hazardous of the asbestos minerals because of their long persistence in the lungs of exposed people. Tremolite often contaminates chrysotile asbestos, thus creating an additional hazard. Chrysotile asbestos, like all other forms of asbestos, has produced tumors in animals. Mesotheliomas have been observed in people who were occupationally exposed to chrysotile, family members of the occupationally exposed, and residents who lived close to asbestos factories and mines.[30] According to the NCI, \"A history of asbestos exposure at work is reported in about 70 percent to 80 percent of all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos.\"[31] The most common diseases associated with chronic exposure to asbestos include: asbestosis and pleural abnormalities (mesothelioma, lung cancer).[32]\""
] |
[
"Everyone has a little asbestos in their lungs.",
"Interestingly, the toxicity comes from the structure, not the chemical reactivity."
] |
[
"Asbestos is associated with ",
" exposure. Anyone working with it has an increased risk of Mesothelioma. 90% of Mesothelioma patients reported previous asbestos exposure.",
"Asbestos exposure may also lead to pulmonary fibrosis and can predispose to bronchial adenocarcinoma.",
"According to my ",
"clinical handbook",
" the latent period between exposure and developing Mesothelioma may be up to 45 years.",
"To answer your question, a single exposure would not necessarily cause serious harm, ",
" the problem with finding asbestos in a building is that the people within that building are at an obvious risk due to prolonged exposure, as are the people who install/remove the asbestos."
] |
[
"Why is Guatemala green during the International Space Station flyover video (link in comments)."
] |
[
false
] |
Many of you have probably seen the . While watching it I noticed something strange at 1:26. I've looked into it and I believe it is the country of Guatemala. If you look as they fly over the country there is a green hue to ALL of the lights in the country except for the largest cluster which appears to be the capital, Guatemala City. EVERY other light in the whole country has this green tint to it that I haven't seen anywhere else on the planet in the video. Here is a of the part I'm talking about with what I believe to be Tapachula, Mexico and Guatemala City marked. It does not appear to be a large lighting effect that happens to be hitting Guatemala during the flyover because if you look closely it literally appears to follow the borders of the country almost exactly. It's especially obvious because of that little tip of Mexico that protrudes down into Guatemala. That little tip is the normal yellow tint that most of the world's other lights have. The flyover appears to come from the north so the little tip of Mexico comes before Guatemala in the video. The obvious explanation is that Guatemala has some sort of regulations that cause their lights to be of a different type. I have searched online and found no such regulations. Certainly nothing saying that the entire country right down to the little villages on the borders has adopted such a policy. Even worse, the capital city appears to be the only part of the country that does not have the green tint. So it would have to be a massive countrywide lighting program that didn't affect the largest city in the country and their capital.
|
[
"Architect here. Most street lighting in the world has always used high pressure sodium lamps. They were relatively efficient but cast an ugly yellow hue (you've seen these everywhere). Advances in LED technology mean that we can replace these with even more efficient LED lamps. Guatemala is ahead of other countries in converting all their streetlighting to LED. ",
"The hue of LED streetlights is white, so that would explain the sharp difference in appearance from one side of the border to the next. The fact that the white lighting looks greenish is probably just down to atmospheric effects or the camera. ",
"Here's something from 2009 on their efforts to implement the change. ",
"http://m.centralamericadata.com/en/article/home/Guatemala_18_Million_for_Street_Lightning",
"EDIT: This is my first post to ask science. I don't have proof that the world bank actually approved the loan or that work has started on the conversion. But the fact that the country was actively pursuing this 4 years ago, and had a cost savings incentive to do it, and this footage shows a distinct change in light color now, indicates to me that it's likely that they have begun the transition."
] |
[
"I don't know the answer to this, but since it appears that so far nobody else does either, I'll venture a hypothesis: ",
"volcanic ash of the right size can scatter red light out and let bluer wavelengths through",
", so if there were a relatively recent eruption in Guatemala it could potentially cause the lights from the ground to appear bluer than they otherwise would. The best candidate volcano I can find is ",
"Pacaya",
", which last erupted in May 2010. However, the ISS video appears to be from expeditions 28+29, the former of which began in May 2011. So Pacaya is probably not the cause of the green unless it had minor ejections that weren't counted as eruptions. It might also be another volcano in the region whose ash was blown over Guatemala (or the volcano idea might be totally wrong).",
"edit: it seems that Guatemala may have a nationwide program for LED street lighting, which would explain the color"
] |
[
"Just to add a bit:",
"The emission spectrum from low pressure sodium vapor looks like this: ",
"http://upload.wikimedia.org/wikipedia/commons/3/3f/SOX.png",
"It's a very narrow band and looks very yellow. ",
"A white LED isn't actually white. Generally, a white LED is a blue or UV LED with phosphors that cause it to emit a fairly broad spectrum. That spectrum has a big ol' spike in the blue because of the emitter, and then broad stroke of lower frequencies: ",
"http://i.imgur.com/v5S89Mn.png",
"Now, the trick with the phosphors is something we've been doing for decades with Fluorescent lamps, which is why the colors come off as so similar. Particularly the white LEDs have a lot of green in them -- green is 520-570nm on that graph. Fluorescent lamps and high color temperature LEDs have a lot of green in them.",
"Enough so that there are color correction filters called \"minus Green\": ",
"http://www.bhphotovideo.com/c/product/166304-REG/Gam_GC1583_1_4_Minus_Green_Cine.html",
"So, what I'm saying is: it's likely that if Guatemala has replaced their street lighting with LEDs to a large extent, we're seeing that effect in this photograph. ",
"However, there's an alternative: it's possible they're using high pressure sodium lamps. HPS has a much \"whiter\" spectrum, but it's also has a huge spike in green: ",
"http://upload.wikimedia.org/wikipedia/commons/c/cb/High_Pressure_Sodium_Lamp_Spectrum.jpg",
" -- so it could be they've just standardized on HPS instead of LPS and we're seeing that."
] |
[
"If I made a photomultiplier tube that was really long (imagine any length), would the cascade effect reach a point where a photocathode is forced to release all of its electrons? What would happen?"
] |
[
false
] |
I know the basic premise of PMTs..strike a photocathode with a photon, generate an electron, which then strikes another cathode that then releases two electrons, which then strike another cathode, releasing 4 electrons..and so on...If I continued this process for a really, really long time, would I eventually reach a point where so many electrons are striking a cathode that it basically gets all of its electrons knocked out? What would this do?
|
[
"I think the question is asking what the effects are of a very long dynode chain. I don't think it would affect the photocathode at all. The dynodes towards the anode and the anode itself might get damaged, depending on what they're made of."
] |
[
"The extra dynodes are the amplifier essentially. This particular PMT is very old with a 10cm aperture. The bandwidth is also very high, we are looking for around 10,000 pulses to appear in a total time window of a few hundred microseconds, with a pulse width of about 20ns. If we use a 1MOhm termination we get a lot more voltage, but it smears out over a long time window, so we use 50 Ohm termination. There was an attempt to use an RF amplifier to boost the signal initially, but we found that it skewed the shape of the waveform.",
"The PMT is near a very high energy EM discharge, so we wanted to minimize electronics near it. The scintillator and PMT live in a faraday cage with a 15m long coax cable leading back to a deep memory scope that is essentially inside the same faraday cage. We could have put the amplifier between the coax and the scope, but with the PMT we had available we were able to get signal into the scope just fine with about 2700V reverse bias. It is possible with a more modern PMT setup we could get signal with less dynode steps, but we got the larger older ones from a university for free essentially."
] |
[
"If you release too many electrons you will burn the photo-cathode. Those materials are set up to be very sensitive, to easily release electrons due to particle or photon impacts. If you release too many too fast, it is essentially having too high a current flow and will cause damage. This is exactly what happens to any PMT if you expose it to standard room lighting when fully reverse biased. I deal with many different types of PMT's at work for detecting particles via scintillation."
] |
[
"If we develop Artificial life and AI, what will they classify them as? Will they use the current biological system? Will they modify it? Will they invent a new one? What do you think is the best thing to do?"
] |
[
false
] | null |
[
"A good home for this question is ",
"/r/AskScienceDiscussion",
".",
"Please see our ",
"FAQ."
] |
[
"ok thanks. what exactly makes it more suited for that sub rather than this one?"
] |
[
"Discussion is for opened ended, speculative questions. This for example isn't something that can be answered concretely. We can speculate what we ",
" do in these situations, but we can't say for certain."
] |
[
"To achieve the Theory of Everything we need to unify all the fundamental forces, one of which being Gravity. But why is gravity even considered as a force if it is experienced due to the curvature of spacetime. Isn't it a fictitious force?"
] |
[
false
] | null |
[
"Oh, of course General Relativity is not a theory that explains gravity fully. It doesn't work when quantum effects become relevant. It must be an effective theory, just like Newtonian gravity is an even weaker one.",
"Can Quantum Foam be the answer for finding the interactions of spacetime to get a ",
" interaction between objects?",
"Find the answer, get a Nobel Prize."
] |
[
"It doesn't matter if you call it fictitious or not: It is an interaction, it should have some description. We have one already that works well in most situations - general relativity. But this is incompatible with the descriptions of the other interactions, and we would like to find a way to consider all of them together, unified or not. At low energies the description for gravity will keep looking different from the description of the other interactions, but that is nothing new."
] |
[
"It is way more abstract than that and has nothing to do with bending wires or anything. It is simply another mathematical description of the electromagnetic force. ",
"Wikipedia has a short entry on it."
] |
[
"IS it possible to have matter (like atoms or even galaxies) in this universe expanding and getting away nearly speed of light?"
] |
[
false
] |
Having in mind the universe expansion and the speed up velocities of the matter in the universe checked by Edwin Powell Hubble and Milton L. Humason whats the real chance of all universe speed up and all matter be swallowed into the dark of the (nearly) speed of light?
|
[
"Yes it's possible, because although nothing can travel faster than light, there's a loophole. It really means, nothing can travel fast than light ",
". The expansion of the universe however, is not matter flying away from other matter, it is space itself expanding. So the matter in space is travelling slower than light but space itself can expand at any speed it likes."
] |
[
"Serious question: Is there even a definition of speed outside space? When speed is measured by distance per time can it even exist if you are not in a space with measurable distances?"
] |
[
"Nope. If you can't measure something, even in principle, then it's a meaningless concept. This is why space, time and matter are all interdependent. you can only measure 'speed' and 'distance' if you have a ruler (light) and something different from the ruler (matter). If you can't measure where something is, the only sensible answer is 'its everywhere'. This (in my view) is what it was like before the big bang. No matter, so everything was everywhere all at the same time."
] |
[
"Does space-time have viscosity?"
] |
[
false
] |
it appears, to a layman like myself, that space-time acts exactly like a fluid.
|
[
"No; In the viscosity/fluid analogy, satellites would have to experience a net force at all times, slowing them down to some degree no matter which direction they travelled. Somewhat like the thoroughly debunked ",
"Luminiferous Aether",
".",
"A gravity-fluid flowing towards masses doesn't fit either, since acceleration under gravity is inconsistent with this model (no terminal velocity in a vacuum)."
] |
[
"There are some theories that model a local space as a kind of superfluid (meaning zero viscosity along with superconductivity) but its only really useful for understanding some of the properties of quantum systems."
] |
[
"But why does frame dragging happen at all?"
] |
[
"Is there marble on the moon?"
] |
[
false
] |
Are there metamorphic rocks on the moon? Does regolith have a metamorphic counterpoint the way some earth rocks turn into marble? Are there gemstones on the moon that do not exist on earth?
|
[
"Absolutely not. Marble is a metamorphic rock made from limestone - which is a sedimentary rock made from the hard shells of marine animals. so to get marble we need both oceans & life on the moon. "
] |
[
"This is the correct answer. I'd just like to point out that limestones are not ",
" made from the shells of marine animals (biogenic) but can also be directly precipitated from water if that water is saturated in calcium carbonate. Of course this doesn't change the answer with regards to the moon."
] |
[
"A smash of that intensity contains enough energy to entirely melt the rock, so it will re-crystalize as an igneous rock. "
] |
[
"How would astronauts navigate directions in open space?"
] |
[
false
] |
On Earth, navigation has always been relative to something (either the shores of the seas/rivers, or the magnetic poles). But in open space, how would you navigate? Relative to what we already know (stars, solar systems, galaxies etc.), or the need for new system of navigation would emerge?
|
[
"Allow me to introduce you to ",
"XNAV",
". It's like a GPS for space travel, using the regular signals emitted from pulsars instead of satellites. Incredibly, it's accurate to within 5km, which is an extremely small uncertainty given the vastness of space."
] |
[
"Assuming they aren't doing any near-light speed travelling it would be a simple matter of triangulation with known points of reference. Like their relative position in 3-space to the earth and sun etc. ",
"The on-board computers would be able to tally up distances and angles fairly well to give a good simulated approximation."
] |
[
"There's a lot of pulsars, that are quite easily identifiable based on frequency. ",
"You can also orient yourself relative to deep-space objects, such as other galaxies - unless you're going ",
" far, these will remain essentially fixed."
] |
[
"What happens when radio waves collide, or multiple sources broadcast on the same frequency?"
] |
[
false
] |
I know radio waves fall along the same spectrum as microwaves and visible light, and tuning into those frequencies with a device like a radio allows us to listen in on messages if you're within range of the source's broadcasting. What happens when a device is tuned into a frequency that more than one source is broadcasting in? Would it mash the sounds together, or just result in audio static? Does that mean that someone could play a bunch of noise on all available frequencies in order to drown out whoever is using those frequencies in broadcasting range? Please note, i'm not attempting anything like this, just wondered if it was possible or what would happen haha
|
[
"EM waves are additive, and hence so are the signals received.",
"The way this affects the final outcome will depend primarily on how the communication system is built. For instance, with AM or FM radio, the receiver outputs whatever signal is in the user-selected frequency band. Thus, in this case, both signals would be heard simultaneously as if two people are talking at once",
"In comparison, digital communication systems are more complex. If there is no ",
"coding",
" or relatively weak coding (e.g., Bluetooth), simultaneously broadcasting sources can result in unintelligible static. \nWhile with coding the output may instead be simply a message error.",
"There are also digital communication systems designed for multiple sources to be broadcasting on the same frequency. These operate using ",
"code division multiple access",
" with the principal being that sources can be separated by the underlying coding scheme (in opposition to them being separated by which frequency band they occur on). In fact, Ahlswede proved ",
"this technique is optimal (PDF)",
", although the model used has some profound differences from reality due to practical implementation issues. ",
"1 Note, there is also an equalization step where the output signal is normalized. This is done to make the end result more acceptable to the user, and not require them to adjust the volume as they change the distance from the source. Thus, a weaker signal can be effectively drowned out by a stronger one. Both are still present though."
] |
[
"What happens when a device is tuned into a frequency that more than one source is broadcasting in? Would it mash the sounds together, or just result in audio static?",
"Depends on the transmission encoding.",
"With AM it would just mix everything, with FM or QAM or similar it'll just make a mess of noise.",
"Does that mean that someone could play a bunch of noise on all available frequencies in order to drown out whoever is using those frequencies in broadcasting range?",
"This is called a \"signal jammer\" and they're illegal in most parts of the world for obvious reasons."
] |
[
"The energy is additive. So yes, if you had the equipment and knowledge, it might be possible to make it so that radio broadcasts are effectively blocked. All frequencies? That is going to take a bit of doing and a bit of power. And be prepared to be detected fairly quickly too since it isn't at all difficult to pinpoint the source of the signal. This makes it rather impractical - if you have the power, it wouldn't be mobile - ie easily caught. If it were mobile, it wouldn't have the power - limited impact and range."
] |
[
"What makes Hydrogen Peroxide/Iodine/Alcohol/etc kill germs?"
] |
[
false
] | null |
[
"There are different ways of killing cells. ",
"A very common one is to apply something called oxidants to them. Oxidants are basically just atoms or molecules that really strongly attract electrons. The oxidants then \"steal\" electrons from the compounds that make up the cell (membranes, proteins etc.) and destroy them that way. The ability to attract electrons (even steal them from others) is called electronegativity, and as you can see in ",
"this",
" table (upper right), Oxygen is really good at that, thus the name oxidants. ",
"Other good oxidants that you can see in the table are Iodine and Chlorine, which are also often used as disinfectants for that reason. Molecules can also be good at oxidating others, for example the hydrogen peroxide you mentioned.",
"Alcohols and some other disinfectants work by denaturating proteins and dissolving membranes as well, but have different mechanisms. Proteins are long chains of amino acids that have a very precise 3D shape. They get that shape from different interactions between the individual amino acids within the chain. Some of these interactions only really work in water, so when you get a high concentration of solvents that aren't water (like alcohols) the proteins can't retain their shape and become useless, thus leading to cell death. Denaturation just means that the protein loses it's shape and therefore its function. ",
"Here's",
" an illustration. ",
"Cell membranes also dissolve because the proteins that make up the membrane will start to react with alcohol rather than being held together by water.",
"There are other ways of killing microorganisms, but these are the most important ones I think."
] |
[
"Hydrogen peroxide works well if you cut yourself because every living cell has an enzyme catalase which is a catalyst of decomposition of H202. it breaks down like that 2H202 -> O* + O* + 2H20 -> O2 + 2H2O",
"before O* meets another O* to create O2 it's super oxidizing and bacteria suffer form a ricochet of that reaction.",
"This happens also without catalyst but takes longer time. That's why to decaffeinate hands people use ethanol not peroxide. "
] |
[
"Hydrogen peroxide is cool - the only reason it's safe to use around humans is that it's so hideously toxic, that most life evolved mechanisms to destroy it long ago. It's a potent oxidizing agent, and readily breaks down into free radicals. Iodine is similarly a good oxidizing agent. Both more or less wreck up the cellular machinery which enables life by oxidizing it in various ways.",
"Alcohol will denature proteins, disrupt the cell wall, and all sorts of fun stuff like that."
] |
[
"Why is there steam after a hot shower when the water wasn't over 100°C?"
] |
[
false
] | null |
[
"It's not the visibility that defines vapour, but the temperature at which it exists. Vapour is a substance in a gas phase at a temperature lower than its critical point. For water, any gaseous H2O at temperatures below 374˚C is water vapour."
] |
[
"Water vapor ",
" steam. If you can see it, it's called condensed water vapor or fog."
] |
[
"Out pedanted. Good job. :)"
] |
[
"How are doctors able to control the blood in this gif?"
] |
[
false
] |
[deleted]
|
[
"Blood isn't going everywhere because they avoid cutting large blood vessels. You only bleed where you cut into a blood vessel.",
"On top of that, they can use local vasoconstrictors to keep small blood vessel from bleeding, and they can clamp medium and large blood vessels that they have to cut.",
"Finally, yes, pericardium is lubricated."
] |
[
"Oddly enough, ",
"the pericardial fluid",
"."
] |
[
"Serous fluids, made by the serous gland cells. They make it from raw materials supplied by the blood. They are specialized for this purpose. The pleura does a similar job for the lungs, and the peritoneum does the same for most of the abdominal organs."
] |
[
"Why hasn't The Asteroid Belt formed a planet?"
] |
[
false
] |
[deleted]
|
[
"The total mass in the asteroid belt is quite small - much smaller than any planet, even much smaller than Pluto. That means a lower gravitational attraction between the objects, and a much longer timescale for the collisions of them (longer than the age of the solar system). In addition, Jupiter perturbs the orbits."
] |
[
"I'm not 100% sure, but I think it's because the Asteroid belt is hardly a belt. Asteroids in the belt are spread extremely far apart, about 2 million miles between each asteroid ",
"source",
"That's too far apart for the asteroids to attract one another and begin to collapse into anything considerable. Added with the fact that Jupiter's gravitational pull also affects the asteroids in the belt. It may not be allowing anything to form."
] |
[
"Size does not affect gravitational acceleration. Jupiter affects small asteroids the same as large ones."
] |
[
"What effects are responsible for the light shows of helicopter blades?"
] |
[
false
] |
This post was motivated by an post: My question: Is or static discharge? Or do both happen in different conditions? First hand accounts of the effect from the previous thread (in ) adamantly proclaim static discharge over pyrophoric effects which seems to contradict most of what I can find. A helicopter will charge due to the rotor blades flying through rain, snow, ice, or dust particles.
|
[
"Turns out this only happens in ",
"sandy environments",
". The blades kick up the sand, striking it, and causing the sparks you see. "
] |
[
"That's what I thought as well. People ",
"claming experence",
" have insisted otherwise. "
] |
[
"Here is the reason I don't negate the possibility of static discharge.",
"When you rub a piece of wool over a plastic rod to charge it there comes a point when you hear a bunch of tiny sparks as you rub the wool across the rod. At this point the rod is charged and there is a balance between adding charge and the charge jumping back to the wool (or your hand through the wool). If the blades of a helicopter were electrically isolated from the helicopter (I make this assumption for a few reasons) then they would gain charge as they whip through the air. Eventually they would gain enough charge so that there would be an equilibrium between charging the blade and coronal discharge of charge back into the air. The discharge would probably take place at the tips of the blade. I would still bet that this picture is one of dust striking the blade but I would also consider someone telling me that in some cases they see flickers of light at the tips of the blades through night vision goggles (",
"as was claimed here",
") when there was no dust. "
] |
[
"What does space consist of?"
] |
[
false
] |
I think this is basically a two part question. First, is what IS space? So you leave a planet, you're in the vaccuum of space. What's in it? Doesn't gas escape from planets? Where does it go? It must occupy this area so how can space be a perfect vaccuum? Second: What about space on earth? If you go down to the atomic level, what's in between the electrons / protons / neutrons? When you get down to the size of particles...what are they travelling through?
|
[
"Good question(s).",
"Space is rarely a true vacuum. Even in inter-galectic space there are some atoms floating around. In addition you have Quantum Fluctuations.",
"Quantum Mechanics posits a Euclidean Framework within which particles have position (Heisenberg uncertainty and Wave/particle duality apply). So from this view - the framework is what exists between particles.",
"Most of physics focuses on matter and its behaviour. The space between matter tends to be regarded as somewhat incidental. My personal opinion is that this is a mistake and that greater focus on why there is distance between things can prove enlightening."
] |
[
"The gases don't escape earth because gravity holds them down. That said, you get a better and better vacuum the further out you go."
] |
[
"No one's mentioned the one thing that's ",
" in space, which is the cosmic microwave background (as well as other backgrounds of decoupled species, like the neutrino background and gravity wave background, which are as yet undetected). At every point in space there are photons, about 2000 in every cubic centimeter, with an average temperature of 2.73 Kelvin left over from the earliest moments of the Universe. Gas and other forms of matter aren't guaranteed to be in any particular patch of empty space; the microwave background is."
] |
[
"Is there a reason or advantage that organisms are sensitive to light from ~ 380 - 740 nm, or is it just a coincidence of evolution?"
] |
[
false
] |
[deleted]
|
[
"In fact, there's a very good reason! On earth, we're sensitive to these wavelengths because those are the wavelengths at which the sun emits light most strongly.",
"This chart:\n",
"http://en.wikipedia.org/wiki/File:Solar_Spectrum.png",
" shows the distribution of the solar radiation by wavelength. You can see how the visible spectrum corresponds well to the peaks of the solar radiation spectrum.",
"Of course, there are some animals that can see ultraviolet light such as bees. After not too long though there's large diminishing returns, and the higher-energy particles have higher chances of causing damage as well."
] |
[
"I've always been skeptical of this explanation. The visible spectrum of light isn't just special in that it's the light emitted most strongly by the sun, it's also special in that it passes freely through our atmosphere, but is absorbed/reflected by most solid matter. Take radio waves, for example, which pass through pretty much everything (at least as far as life on Earth is concerned). If our sun emitted those most strongly, and our eyes evolved to pick up those wavelengths, what would it allow us to see? We couldn't see prey we wanted to eat or predators that were trying to kill us, because those waves would pass right through them. Also, to perceive radio waves, we'd have to evolve some type of cell that can absorb them, which I'm not sure is even possible with organic material. I'm just using radio waves as an example, it seems like this would be true of most of the wavelengths outside the visible spectrum, except for infrared and UV which are the closest to visible light on each side."
] |
[
"Another point to add: there's also animals sensitive to infrared radiation such as pit vipers. But infrared is harder to focus into an image and the photons are lower energy so harder to detect."
] |
[
"Are there any two species that are both a prey and predator of each other?"
] |
[
false
] |
Like a species that preys on its own predator. Edit: Or as said,
|
[
"This is quite common in fish, because most baby fish are tiny. For example, a bass is quite happy to eat green sunfish, but a green sunfish would eat a baby bass if it got the chance."
] |
[
"I'm not sure if this is exactly what you're talking about, but diving beetles regularly feed on tadpoles. When those tadpoles grow into frogs, however, they have no trouble eating the diving beetles. "
] |
[
"Many fish species are predators of juvenile members of their own and other species that were predators on themselves when they were juvenile.",
"We kill and sometimes eat crocodiles, and given opportunity crocodiles eat us. The same with some shark species."
] |
[
"Why is lead so effective at stopping radiation ?"
] |
[
false
] |
[deleted]
|
[
"Anything can absorb or scatter radiation. You just might need more of it than is practical in a given situation. Lead isn't exactly special, per se; it's just that heavier nuclei are better at absorbing electromagnetic radiation than lighter nuclei, and lead in its normal metallic state is quite dense, so there are a lot of heavy nuclei in a relatively small volume.",
"Depleted uranium is even better than lead at absorbing electromagnetic radiation, but of course depleted uranium is much more expensive than lead is, so lead is used instead."
] |
[
"Depleted uranium? It's less radioactive per unit mass than a handful of average dirt."
] |
[
"NOW ONE OF OUR NUMBER HAS GONE BLIND FROM RADIATION!",
"My God, does dirt have no mercy?"
] |
[
"If I eat food off the ground, never wash my hands...pretty much expose myself to germs, will my body be able to better fight off germs/disease?"
] |
[
false
] |
[deleted]
|
[
"It's better than water and soap for killing bacteria. But living in such hyper-hygienic circumstances eventually weakens the immune system."
] |
[
"It's better than water and soap for killing bacteria. But living in such hyper-hygienic circumstances eventually weakens the immune system."
] |
[
"Yes. But be wary. Some species of bacteria can cause illness with ingestion of less than 10 organisms. Also, ",
", which lives on your skin, can also cause digestive issues when ingested. Say no to hand sanitizer; wash hands with water and regular soap when necessary. "
] |
[
"Does temperature affect the experience of taste?"
] |
[
false
] |
My coffee tastes significantly better when it is warmer compared to when it is room temperature. Beer tastes better (to me) when it is cold. Is this just preference built over time or is something else at play?
|
[
"Do you have any source for this? I'm not really buying the \"emitting\" logic based on molecule speed."
] |
[
"Most flavor actually comes from smell. Hot food that has water vapor coming off it will carry a lot flavor in that vapor. ",
"Oils and fat also carry lots of flavor and need to be a minimal temperature to be in a liquid state that can readily impart flavor to your tongue and sinuses. Cold, solidified oils have a significantly reduced flavor.",
"In the case of coffee, you have both water vapor and oils at work carrying flavor. Coffee is also rapidly effected by oxidation so it gets funky and bitter if left to sit for too long. Many styles of beer have a fairly significant bitter content which gets subdued when it's cold while other, more desirable, flavors a less effected. That's also why some liquors are served ice-cold.",
"Low temperatures also numb your taste buds, making them less sensitive. So cold sweets like ice cream have an obscene amount of sugar in them to compensate for the whole numb-tongue bit."
] |
[
"Of course it does affect the taste. Molecules move faster when something is warm thus \"emitting\" more taste and smell. The only difference with your coffee and beer is that beer has more intense taste and is less pleasurable to most people at room temp. But i guess that part is purely subjective."
] |
[
"In Planck Units, why is the Coulomb constant set to 1 rather than the electric constant?"
] |
[
false
] |
I've been wondering this for a little while now, as in rationalized system (such as L-H units), the electric constant = 1. Setting the electric constant = 1 would simplify Maxwell's Equations. Therefore, why did Planck do this?
|
[
"If I'm understanding your question correctly you're asking why the coulomb constant, i.e. 1/(4 * pi* E0), is set equal to 1 instead of just setting E0 = 1 (here, E0 is the electric constant). I imagine people tend to opt for setting the coulomb constant to 1 because it makes the universal law of gravitation looks similar to coulomb's law. That is, if G = 1 and 1/(4 * pi * E0) = 1, then the universal law of gravitation looks like ",
"F = - m1 * m2 / r",
" ",
"and Coulomb's law looks like ",
"F = q1 * q2 / r",
"Also, setting 1/(4 * pi * E0) = 1 does simplify Maxwell's equations a little bit because 1/E0 is replaced with a 4*pi. But overall, I think people tend to go with setting the coulomb constant to 1 so the gravitational and electric forces look similar.",
"Another reason to do it this way is that it's easier to compare the strength of the gravitational force to the strength of the electric force. Using the natural units as defined above, it's clear that there is nothing special about gravity as a force that makes it weaker than electric forces, it's just that electric charges that occur for particles in nature tend to be much larger than their masses."
] |
[
"Sorry, I may be misunderstanding you again, but the universal law of gravitation was discovered by Newton long before Planck or Einstein were born. So, Coulomb's law and the universal law of gravitation were both well known when Planck came up with natural units."
] |
[
"You're right, I thought the question was why Planck made the choice he did. ",
"As you mentioned, even though GR is the currently accepted theory for gravity, it still reduces to Newton's law of gravitation to an exceedingly good approximation for problems involving smaller masses and longer distances. So, it might still be desirable to preserve the symmetry between electric and gravitational forces that we see in Planck's units. However, the more likely explanation is that we continue to use Planck's units for historical reasons, and that we don't stand to gain much, if anything, by switching things up."
] |
[
"Electrolysis of a saline solution...OMG why is it turning brown?"
] |
[
false
] |
Here's the deal. Cup of water + 2 salt (NaCl) packets + 9V battery. Electrolysis right? Should get the breakdown of H2 gas as well as O2 gas. And that I apparently saw as bubbles would rise in a 2 to 1 ratio from each of the battery terminals. BUT WAIT!...after a minute or so of intense bubbling, there started to be a yellowish...then greenish...then brownish tint to the water. Clearly more reactions were at play here. What could account for the color change? NaOH? HCl? CuCl2 (copper from the battery?) OCl2? Help me chemistry mavens....you're my only hope!
|
[
"Well, for starters is it brown and cloudy or brown but still seethrough? If its cloudy that means its not water soluble, see through means it is. Knowing that is a pretty good starting point.",
"If its cloudy I'd recommend grabbing some on a paper towel or something and drying it out, then seeing if its magnetic. If so then it's likely rust.",
"Now as far as I can google, your standard Alkaline battery is composed of Zinc and Manganese Dioxide.",
"Most zinc compounds are white as far as I know, and don't make much happen in solution.\nManganese likes to be purple I believe. Could potentially turn brown especially if mixed with something of a different color.",
"Its really been a while since my last chem class though so someone else around here could probably answer better than I."
] |
[
"What are your electrodes made out of? Copper would produce Green or Blue compounds in solution. Iron chloride is usually yellow or brown."
] |
[
"Well, it's pretty low tech. All I've done is drop your standard duracell 9 volt battery into a cup of water. There's a bit of precipitate that has settled to the bottom of the cup, but the overall color of the water is brown."
] |
[
"If I had an extremely strong container, filled it with completely with water, and chilled it to 20 Degrees (F), would the water be able to freeze?"
] |
[
false
] |
If there is no room for the water to expand and ice to form, will it simply not form? I'm assuming the pressure on the outside of the container would be enormous.
|
[
"Yes! This has actually been done before. The water molecules will align themselves in a different manner on a molecular level, resulting in different crystallographic phases (i.e. hexagonal, orthorhombic...). You can see the full phase diagram ",
"HERE",
". Disclaimer though, you'll need a ",
" of pressure to make this happen."
] |
[
"Ice can be packed in at least 15 different ways, depending on the temperature and pressure applied to it. The various packing methods are numbered with roman numerals. Ice we experience in our everyday lives is \"Ice I.\" ",
"To achieve all the other forms of ice, you need to tune the pressure and temperature of water appropriately. A full diagram of what pressure & temperature combination gives what result is found ",
"here",
". More information on the phases of ice can be found ",
"here",
". "
] |
[
"How/Because?"
] |
[
"How do stomach bacteria differ between vegetarians and those who eat meat?"
] |
[
false
] |
Are there any bacteria that are specific to meat?
|
[
"Current research seams to show yes!",
" The linked study is from ",
" (so paywalled, unfortunately, though there's good info in the abstract), and showed that even very short term changes to diet can change the kinds of gut bacteria (people's microbiome) can change quite a bit. ",
"Not sure if it's that the bacteria are specific to meat but that a higher fat/protein diet gives a different nutritional environment for your microbes, so the ones that can survive/thrive are different. ",
"There's a lot of current research about what influences human microbiomes - I went to a talk last week that included info from a study that showed people who have dogs compared to people without had significant differences in their gut bacteria! (Don't know the details of the study, but the talk was given by Ran Blekhman who's a new professor at U of M - this is his area of research). "
] |
[
"Actually what you might not realize is that the digestive tract is actually part of the environment, like a tunnel running through you. Not quite internal."
] |
[
"Yes, and I think a lot of caries are caused by bacteria from grain. Which helps to explain why the farther back in time you go in anthropological records the dentition becomes more intact.",
"When we switched away from meat toward grain as a staple we changed the bacteria in our mouths to accomidate strains that can eat our teeth."
] |
[
"Why does a water droplet on dry ice freeze into a teardrop shape?"
] |
[
false
] |
While dripping water onto a piece of dry ice, I noticed that the pattern it froze in wasn't spherical- more of a teardrop shape. The effect seemed to grow as I repeated the process. I think it might be because the "bowl" in the dry ice grew each time I froze some water in it. Basically, small bowl= mostly spherical ice, big bowl= teardrop. I have no idea why this happens. Could someone explain it?
|
[
"I second the shrinking radius of the hemispherical drop of water at the top. The scale is small enough that intermolecular force starts to matter. On normal ice, the water molecules' self-attraction would prevent this sort of shape, but a little droplet on some non-polar dry ice would probably be able to sit at the top of the growing crystal.",
"Another poster mentioned the sublimating CO2 rushing past the forming ice, but I'm skeptical that it would produce enough force or apply it so isotropically."
] |
[
"I second the shrinking radius of the hemispherical drop of water at the top. The scale is small enough that intermolecular force starts to matter. On normal ice, the water molecules' self-attraction would prevent this sort of shape, but a little droplet on some non-polar dry ice would probably be able to sit at the top of the growing crystal.",
"Another poster mentioned the sublimating CO2 rushing past the forming ice, but I'm skeptical that it would produce enough force or apply it so isotropically."
] |
[
"The very first part of the water droplet to freeze will be a ring, on the bottom of the drop where it's exposed to both cold air and the dry ice. So now you have a ring of ice holding a water droplet in place.",
"Well, it will start freezing inward from there. But as water freezes, it expands; so you'll have a small column of ice pushing the rest of the unfrozen water upward ever so slightly.",
"Repeat, and you end up with this little cone, built by freezing the bottom layer of a water droplet and working up."
] |
[
"Is there an effect the moon has on the atmosphere similar to the effect it has on the ocean by creating the tides?"
] |
[
false
] |
I imagine the effect of the moon may just be to create a bulge in the atmosphere close to the moon, but im not sure.... Does anyone know what the effect is and if it changes anything significantly, if so how?
|
[
"There is."
] |
[
"Interestingly the atmospheric tides caused by the moon are far smaller than that created by the sun",
"And for those that are interested, there are also ",
"Earth tides",
" (did I capitalise correctly?) as well."
] |
[
"According to ",
"google",
", 1 lunar cycle = 29.53059 days, and according to ",
"Wikipedia",
", the average menstrual cycle is 28 days long and anything between 21 and 35 days is normal. This means that it is highly likely that many women have menstrual cycles that follow the tides"
] |
[
"What makes Toxic Waste, War Heads, and other sour candies so sour?"
] |
[
false
] |
I love sour candy. I buy it all the time, it makes my eyes water, and I love it. Something that I've noticed is that a lot of it seems to be dusted in a fine white powder, which is the sour bit. Why is it so sour -- what is my tongue experiencing, and why does it make my eyes water?
|
[
"Neuroscience researcher here. What makes these candies so ridiculously sour is malic acid, which is more sour than the citric acid found in normal tart candies. There's one major cell in your mouth that lets you perceive sour and malic acid drives these cells batshit crazy. ",
"Warheads and Toxic Waste candies are so strong that they also wind up activating sensors for heat and cell damage (dead cells go sour) called TRP's, which are attached to a special pain nerve (facial nerve #5). Your eyeballs share the same nerve, so when a crazy strong signal travels down nerve #5, some of that pain actually travels ",
" into your eyeball, giving your eyeball the illusion that it's being hurt. And what does your eye do in response? Tear up. ",
"Eventually, the cells and nerves get so overdriven that they begin to die. It's called excitotoxicity. Then the acid starts dissolving away your mouth, which leads to actual pain. Hope this helps!",
": Your candies contain malic acid, which is so sour your face thinks its being attacked. Your eyes water as a defense mechanism."
] |
[
"Sour is one of the five primary tastes (think like primary colors on a color wheel). Sour is the taste of acid. The more acidic the food, the more sour it will taste. Lemons, vinegar, spoiled milk, vomit, all of these contain significant quantities of acid.",
"Sour candies like Warheads are dusted with a powder of acid (often citric acid) mixed with sugar. This is known as ",
"sour sanding",
".",
"The acid is also why your mouth gets super irritated after eating lots of sour candies or Salt & Vinegar chips. The skin of your mouth is being literally corroded away, and it needs time to heal."
] |
[
"excitotoxicity",
"Wait... that last bit was a joke, right? Or do some candies/foods actually have a strong enough effect to cause excitotoxicity?"
] |
[
"Are there stars that are dull enough to be seen as flaming balls instead of just intense light with the naked eye?"
] |
[
false
] |
Do we know of any right now? How big or small could they be?
|
[
"I think that part of the difference between \"flaming balls\" and \"intense light\" is the variation. There are certainly dull stars, and there are stars which are the various colors found in fire, but any star you can see is going to appear as a solid dot - whether that dot is solid fire-orange, ember-red, or blue.",
"You won't see a star undulating and flickering like a flame; it's simply too distant to see the chaos going on in the star's surface."
] |
[
"I think he means, that of we were in space and looked at the star from a relatively close distance, would we be able to look at it and just see a ball of fire rather than be blinded by the light. I'm guessing the question is are there stars at such a low magnitude of brightness that we can just simply stare at them and see the flames?"
] |
[
"This",
" is the dimmest true star. It is about 40 times smaller, 8,000 times dimmer and slightly less than half the effective temperature of our sun.",
"It should be about ",
"this color",
" based on the temperature. Iron would melt but tungsten lightbulb filaments and the sapphire lens in your smartphone camera would be fine.",
"You would only get a good view from nearby, but if you want to look at a star up close without ",
"fancy filters",
" then this would be a good place to go."
] |
[
"“In 1796, Edward Jenner, considered the founder of vaccinology in the West, successfully inoculated an eight-year-old boy against smallpox using vaccinia virus—from cowpox.” How?"
] |
[
false
] |
When first making a vaccine, how do scientists extract (harvest?) a virus and make it administrable to humans? After a vaccine is successfully made, can it just be made synthetically from then on?
|
[
"For the original cowpox inoculation it was literally just direct contact between the cow lesion and the boy. There was no vaccine per se just the concept of vaccination. Older vaccines used compromised virus by heat or chemical means - sometimes viable sometimes not. In the case of smallpox It worked because cowpox virus is capable of causing limited infection in humans but not well adapted enough to cause severe disease. Vaccinology has advanced much more as our molecular tools have advanced since then and instead of using “live” pathogens with altered tropisms, or that are inactivated or attentuated , we can now deliver pathogen components that are not capable of infection along with chemical adjuvants."
] |
[
"In simple terms, they took cowpox which was largely non-lethal to people and deliberately exposed people and children to it.",
"The clue lay in the fact that during bouts of smallpox, milkmaids usually survived with fewer and less serious symptoms. When it was observed they caught cowpox from handling cattle, the idea for inoculation through infection was formed. Albeit on a much larger scale than whomever was fortunate to be handling cow tits during a smallpox epidemic."
] |
[
"Pus from a cowpox lesion would be picked up on an implement like a small two tined fork with sharp points. Capillary action held a drop of pus which would wick into a scratch dug into the skin with the sharp points of the implement."
] |
[
"Properties of light scenario"
] |
[
false
] |
If one were able to create a box so that nothing could travel in or out (excluding neutrinos), and then install an LED inside this box, maintaining its seal, then turn it on, what would happen if the box is opened after the LED dies? Would a bright flash of light emerge? Would the box be empty, due to its constituent material absorbing the photons from the LED? Or would something else occur? Please excuse my ignorance, I am still in high school. Perhaps my understanding of the properties of light needs to be expanded. Edit: spelling
|
[
"A question almost EXACTLY like this played a big role in the development of quantum mechanics"
] |
[
"If you're allowing the box to absorb the light, then the box heats up and \"heat\" leaves the box breaking your initial premise. Therefore what we're imagining is a box that is perfectly reflective in which light is continuously being added. I'm inclined to say that in such a thought-experiment, yes the box would emit a burst of light upon opening."
] |
[
"If you're allowing the box to absorb the light, then the box heats up and \"heat\" leaves the box breaking your initial premise.",
"Not strictly true. You could have a box that absorbs the light, but is perfectly insulated to heat (as long as we're talking in hypotheticals). That still follows his premise."
] |
[
"Why do Human babies cry out loud? And why do they do it so much? Compared to other mammals"
] |
[
false
] | null |
[
"Using your google search, the only first page answer that actually answers the question asked is an un-sourced Yahoo Answers question. Other sites there include asking \"do other animals cry?\" \"when other animals scream, is it really out of fear?\" etc. "
] |
[
"Using your google search, the only first page answer that actually answers the question asked is an un-sourced Yahoo Answers question. Other sites there include asking \"do other animals cry?\" \"when other animals scream, is it really out of fear?\" etc. "
] |
[
"source?"
] |
[
"What's the largest diameter straw you could drink through?"
] |
[
false
] | null |
[
"Wait a minute, that's not true. The wider the straw, the more water it will contain at a given height. So for a normal straw, you have to apply a force equal to (density of water)*(pi*r",
" )*(height of straw)*(gravity) in order to get the water to the top of the straw; you need slightly more to actually have a flow of water if you are to overcome friction. The wider the straw, the larger r, so the larger the force you would need. After a certain point, your body would not be able to provide that force."
] |
[
"EDIT: Allright, while everything above was technically correct, I forgot to consider that the pressure is ultimately delivered by your lungs/mouth, and that doesn't change surface area with the volume of the straw."
] |
[
"Well, I just found a soda can, cut the top and bottom out and put it in a bucket of gatorade. Results: I pulled it through. Pretty sure the mouth diameter is the limiting factor here. I also coughed a lot and probably stained my white shirt."
] |
[
"I'm pretty interested in astronomy of late. What are some great books to start off with about learning and identifying constellations?"
] |
[
false
] |
.
|
[
"Get your real-time geo-specific sky maps and more at \"heavens-above.org\"",
" ",
"First link in the content lets you pick your location on earth from a google map. ",
"I believe there's a way to set up a cookie so that it remembers you..or sign in or something. Read. ",
"Anyway, once your coordinates are in, you can bring up a live real-time sky map for your exact position on earth. You can follow several other satellite events like ISS and Space Shuttle flyovers. ",
"Whenever there's something in the news about sky watching I go to this site to get coordinates, maps and info... Comet McNaught, bright satellites, eclipses etc... You can also fast forward to a time in the future to see if you will be able to observe particular eclipses etc...."
] |
[
"I have the Audobon field guide to the night sky, it's a very accessible introduction to amateur astronomy. It doesn't go much into the astrophysics side of things, but is a great guide to constellations, planets, nebula, meteor showers, and the like.",
"I'd also recommend getting a red flashlight for reading the book (or cover a normal flashlight with red cellophane), so your eyes can stay night adjusted while reading it. ",
"Also there are a lot of free night sky viewer/labeler software available. E.g., ",
"Celestia",
", ",
"stellarium",
", and ",
"google sky",
".",
"Note that scientific astronomers aren't necessarily knowledgeable about constellations and looking at the night sky (some are as amateur astronomy may be a hobby). Professional astronomers find a specific subfield and study that in depth (e.g., gamma ray bursters, magnetospheres, planetary surfaces/rings, extra solar planets, etc), and that never involves looking at the night sky visually with the unaided eye."
] |
[
"Not sure what someone who really knows about this would say, but I have ",
"this",
" guide book and it worked well for me."
] |
[
"What caused the jump in atmospheric oxygen levels in the Ediacaran Period (635 Million years ago)?"
] |
[
false
] |
The Great Oxidation Event (2.4 -2 billion years ago) gets a lot of attention and it seems like the leading hypothesis for what caused it was the proliferation of early photosynthetic life. However, (as far as I can tell) the levels of atmospheric oxygen were still relatively low until after the Cryogenian glaciations. So, in short, what caused this later rise in atmospheric oxygen ?
|
[
"The Great Oxidation Event (2.4 -2 billion years ago) gets a lot of attention and it seems like the leading hypothesis for what caused it was the proliferation of early photosynthetic life. However, (as far as I can tell) the levels of atmospheric oxygen were still relatively low until after the Cryogenian glaciations. ",
"So, in short, what caused this later rise in atmospheric oxygen ?",
"\"It is not clear what caused this rise in oxygen levels. Scientists have suggested cyanobacterial blooms, carbon and pyrite burial, or even the activity of the first animals themselves (",
"Lenton et al. 2014",
") as potential contributing factors. Regardless of the cause, one of the main consequences of increased oxygen would have been significantly more habitable areas of the planet into which organisms that required oxygen for their metabolism could radiate and evolve.\""
] |
[
"Thank you so much, it was bugging me. It's crazy to think that there was a time within the last billion years that you wouldn't be able to light a fire due to low oxygen, and that the evolution of animals might have changed that so quick."
] |
[
"r/paleontology",
" may be the best place to ask this. We have such a limited understanding of the Ediacaran as a whole, only recently proving that some creatures were in fact animals.",
"The thing is, very simple animals like sponges and jellyfish could have arose long before the ediacaran. There is a rare preservation during that period we don’t see much before or after. However, the preservation is largely imprints and does not give much info into their inner workings",
"Ediacaran life is incredibly cool and I love to see questions like this!"
] |
[
"Why does water drain around the circumference of a vertical pipe?"
] |
[
false
] | null |
[
"Is this just surface tension? Or something to do with the Coriolis effect?",
"It's neither of those, it's just conservation of angular momentum. When the fluid is poured into the sink, it will generally have nonzero angular momentum about the central point. What are the chances is has ",
" zero?",
"So as the water moves down the sink, its angular momentum is conserved. The angular momentum is proportional to the speed of the fluid in the azimuthal direction and the distance from the center, so as the distance decreases, the speed of rotation increases, and it circles the drain until it falls in."
] |
[
"So it keeps that angular momentum as it travels down what's called the fixture outlet pipe, straight down from a sink or toilet drain, this makes perfect sense. Then it travels through a P-trap, changing the direction of flow by 270 degrees, before travelling in a mostly horizontal pipe (usually 2% of fall) for up to 3m in the case of a toilet. Then it dumps into a main stack. Would that angular momentum be maintained during that horizontal slope? Or would the downward slope add momentum?"
] |
[
"The flow has some vorticity when it goes down the drain, so in general the flow will remain rotational."
] |
[
"From what I have learnt so far, refrigerators use chlorofluorocarbons for cooling. Do these chlorofluorocarbons run out after some time? If yes how are they replenished?"
] |
[
false
] | null |
[
"They are not “consumed” per se, although like any system where you trap a gas in a container there is potential for leaking.",
"AFAIK modern refrigerators are sealed systems. That means less likelihood of loosing coolant, but much greater difficulty in adding more back in.",
"Car and home (central) AC systems will have valves that allow you to measure the pressure of the coolant in the lines, and add more to spec."
] |
[
"A refrigerator takes advantage of the thermodynamic properties of these compounds and put them through a physical change. It is a 4-step vapor-compression cycle. Liquid refrigerant is passed through the refrigerator which removes heat and boilers the refrigerant, this is the \"cold sink\" in the process. A compressor increases the pressure of the vapor refrigerant so it can condense at ambient temperatures, the hodgepodge of piping on the back of the fridge (this is the hot sink). Once the refrigerant is liquid is moves to an expansion valve which decreases the pressure and then the cycle starts all over again. ",
"Basically the system takes advantage of the fact that compounds have different boiling temperatures at different pressures. I.e. most compounds will boil at a lower temperature at low pressure and a higher temperature at a high pressure. Most compounds have temperature pressure diagrams that explain this however for a more complete view on this phenomena you can look up the pressure v. enthalpy chart for specific compounds. ",
"Also it is important to note that because most chemical solutions are not 100% pure there could be possibility for interaction with the impurities over time which could deplete your chlorofluorocarbon, over time. Also there could be interaction with the refrigerant and the piping again this would be a long process that could take years. In addition as time passes seals become weaker and leaks and happen whether they be in the piping or the unit operation its self. "
] |
[
"As person who assisted with repairing of friges, mostly industrial but few domestic as well. There are valves too."
] |
[
"Just how far can signals from Earth go?"
] |
[
false
] |
Particularly how far until nothing can be recognized anymore due to interference.
|
[
"There is no fundamental limit. You just need larger receivers and more time for larger distances.",
"The Arecibo telescope could reasonably send text messages and even some images to equivalent telescopes on planets orbiting nearby stars, with decreasing transmission rate for larger distances. Make sender and receiver larger by a factor 10 (in radius) and you gain a factor 100 in distance. Increase the transmission power by a factor 100 and you gain another factor 10 in distance. Now you can reach a large fraction of the Milky Way."
] |
[
"Space is almost entirely empty space. Take a look at ",
"this",
" for some perspective. "
] |
[
"Voyager 1 was launched in 1977, and in 2012 became the first spacecraft to cross the heliopause and enter the interstellar medium. It's now more than 11.7 billion miles (18.8 billion kilometers) from Earth, and ",
"we're still in communication with it.",
". So we probably don't know yet what the limit is. The limiting factor seems to be just getting a powerful enough signal out, and detecting the very weak return signal."
] |
[
"Do snowflakes deaden sound?"
] |
[
false
] |
It always seems quieter outside when it snows (as long as there's no wind) .. is my logic correct that all those little particles could deflect (reflect?) sound?
|
[
"Snow also, if it is on the ground and the objects around you, acts like ",
"acoustic foam",
", thus deadening the noise."
] |
[
"There's probably more to this, but sound doesn't travel as fast or far through cold air than through warm air.",
"I would imagine that, and the dampening factor of the snow acts kind of like yelling at a blanket."
] |
[
"I hadn't even considered air temp! That makes a lot of sense."
] |
[
"If I were to point my telescope at a nebula, would it show up in colour?"
] |
[
false
] |
Do the images from HST have false colouring?
|
[
"Usually false-color. Images of nebulae typically include narrow-band filters which pick up only a specific emission line, such as H alpha or OIII. These filters are usually colored corresponding to where they are on the EM spectrum, so H alpha is usually colored pinkish or red because it's at 656 nm.",
"This site explains it very well and thoroughly",
"."
] |
[
"Depends what telescope and what nebula. With my 8\" SCT, I can can just about make out the faint colours of the Orion Nebula. However, orion is really the only nebula bright and large enough to appear colourful with an amateur scope."
] |
[
"Perhaps. I have a 14\" telescope and I can't see any colour in the Orion Nebula (naked eye). Some people looking through my scope can so perhaps it depends on the person to an extent, and of course, the nebula itself."
] |
[
"Is there any geographic evidence of the asteroid impact that wiped out the dinosaurs?"
] |
[
false
] | null |
[
"Yes.",
"\n",
"The Chicxulub crater",
" is off the Yucatán peninsular.",
"\nThe land around it is lower than the land surrounding it, just the entire thing is so large people didn't notice it at first.",
"\nWith satellites we've noticed a gravitational anomaly on the whole area.",
"\nWe've also noticed geological evidence that a huge tsunami radiated out from the area in places like Texas.",
"\nAlso there are sinkholes arrange in a ring on the edge of the crater called cenotes."
] |
[
"Yes there is. In addition to the huge crater in Mexico, there is a planet-wide layer of Iridium. This is called the K-T boundary. It's called this because it's located between the Cretaceous and Tertiary layers of strata. (K and not C because it was a German scientist who discovered it, they spell Cretaceous with a K). Iridium is common in ferrous asteroids. Iridium is also extremely rare on earth and the only explanation for this layer is because of a huge, cataclysmic asteroid impact which took place 66 million years ago. There are mountains of evidence supporting this claim and is by far the best explanation why dinosaurs (as we know them) went extinct."
] |
[
"That actually has to do with preservation conditions, not so much with the location of the impact which anyway caused a ",
" extinction event. ",
"The Mongolian Gobi Desert is the largest dinosaur fossil reservoir in the world",
" but it's very far from Yucatán."
] |
[
"Why is it that romaine lettuce healthier than iceberg lettuce?"
] |
[
false
] | null |
[
"Iceberg lettuce has been bred for crispness and size, while romaine has been bred for flavor.",
"In retrospect, breeding for crispness leads to a head of lettuce that is mostly cellulose and water. Romaine lettuce by contrast retains the vitamins and antioxidants common to green vegetables."
] |
[
"Looking at the raw data, it seems that romaine by weight is much higher in vitamin content. Now, whether vitamin content is sufficient to conclude that it is healthier or not I'll leave to the reader.",
"Sources: ",
"Romaine",
" v ",
"Iceberg"
] |
[
"This may help if you want to take a look: ",
"http://www.wolframalpha.com/input/?i=+compare+romaine+to+iceberg+lettuce"
] |
[
"When you take a drug (say caffeine) for a while and the receptors for that drug get 'down-regulated' what actually physically happens?"
] |
[
false
] |
[deleted]
|
[
"/u/Lee_the_scientist",
" gave a good answer. I'll elaborate on some of the points he made and add a few of my own.",
"The mechanism whereby tolerance is established varies depending on the particular drug. Long term administration of an activating ligand often results in downregulation of the receptor by enhanced endocytosis, post-translational modification (e.g., phosphorylation) of residues on its intracellular domains, and decreased transcription and/or translation of the receptor protein subunits. In neurons, downregulation of the opiate or GABA",
" receptor upon chronic narcotic administration or alcohol respectively, inhibits the interfering effects on nerve impulse transmission. This means increasingly higher concentrations of the drug are required to achieve the same effect and tolerance becomes established.",
"What's especially interesting is the diversity of endocytic mechanisms involved in downregulating receptors. Many, like the clathrin-dependent mechanism that downregulates μ opioid receptors in narcotic dependency, are fairly well-characterized. But many forms of clathrin-independent endocytosis exist (though not all are used to endocytose inhibitory receptors in neurons). Most, but not all, utilize the same downstream actin filament-modifying machinery to promote membrane invagination and enable budding, scission, and trafficking to the lysosome for degradation. In G protein-coupled receptor (GPCR) signaling the arrestin family of proteins are important for blocking activating phosphorylations of receptor intracellular domains and only after chronic activation does the receptor become internalized. Downstream of cytokine receptors, a protein similar to the arrestins called suppressor of cytokine signaling (SOCS) blocks transmission of activating signals in a different context. ",
"There is, however, a basal level of receptor expression, trafficking to the membrane, internalization, and recycling that occurs even in the absence of a ubiquitous activating ligand. Disentangling the signaling events that tip the balance in favor of increased or decreased surface expression of any one particular receptor is extremely complex as it involves the coordinated activity and mutual regulation of dozens to hundreds of other signaling proteins."
] |
[
"When a Ligand binds to a receptor many things can happen, first a confirmation change occurs which leads to receptor signaling. That receptor can then be destroyed via endocytosis of the membrane where the receptor is. That endosome can fuse with a lysosome and be destroyed. That's one way to down regulate a receptor. Also a receptor can be bond by a Ligand that leads to signalling that inhibits it's own transcription. so you have less transcription of the receptor coupled with normal receptor turnover, that leads to a net loss of receptors at the surface. Usually the activated state of a receptor signals for a specific function, but it can also signal for enzymes that lead to its destruction as part of a feedback mechanism. I can go into further detail about this signalling pathways for receptor turnover if you'd like. Just let me know."
] |
[
"How reversible it is? How long until tolerance drops?"
] |
[
"Why do stars appear to flicker but planets don't?"
] |
[
false
] |
[deleted]
|
[
"It has nothing to do with the distance the light travels, because all the twinkling we see happens in the last 50 km the light has to travel. The Earth's atmosphere is solely responsible for twinkling (and is a major advantage offered by telescopes in low Earth orbit, such as Hubble).",
"The reason stars twinkle and planets do not has to do with the apparent size of the object. If you look at most planets through even a small telescope, you'll see that they show a tiny disc. Almost any star in a telescope, though, will show a point, because it's well beyond the resolution limit of the telescope.",
"Now, picture our atmosphere as a roiling, turbulent fluid made of individual turbulence cells each moving around with their own slightly different densities/temperatures. Since stars are so small from our perspective that they can be treated as point sources, the light from a star is a pencil-thin beam that can only ever pass through one turbulence cell at a time. Whatever the temperature is of one turbulence cell along that path at any time, the light has to follow. Sometimes it refracts right, another cell quickly moves into place and it refracts left, etc. - and what you're left with is twinkling.",
"The light beam coming from a planet, on the other hand, is much wider, and will usually pass through multiple turbulence cells at a time. The light's direction is not completely determined by a single turbulence cell's temperature, and instead the light tends to follow the path determined by the average of all the cells' temperatures it passes through. That's much more steady, and doesn't produce twinkling.",
": From our perspective, stars are point sources, but planets are not. Light from stars can pass through only one turbulence cell in Earth's atmosphere at a time, while light from planets pass through multiple cells at a time, averaging out any individual variations."
] |
[
"Something else. ",
"The light of every object passes through the earth's atmosphere. Now all objects appear as tiny disks to an observer on the ground. The thing is, stars are so far away, that their disks appear extremely tiny, literally pointlike. When you have an atmospheric turbulence, it smears and shifts the incoming light. Since the source is pointlike, the objects seem to flicker. ",
"On the other hand, the planetary disks appear much bigger in the sky. Atmospheric turbulances are usually (but not always) not strong enough to entirely move the disk, so the planet appears more steady. Consequently planets usually don't flicker. ",
"Ths isn't universally correct. Planets can flicker, for example if they are close to horizon and/or when distant from earth, so their disks are comparatively small, or with strong winds. On the other hand, the flickering of stars constantly shrinks when you get to the zenith and with less turbulences, for example on various mountains. The most extreme case would be the vacuum of space, where you have no flickering whether for stars or planets. "
] |
[
"Actually they flicker, but because of their size you don't notice it, I do Astrophotography as a hobby, even the moon and the sun flicker, but you will see it if you use a telescope, that is why planetary astrophotographers don't use long exposures, rather they record video of the solar system object, lets say Jupiter, then they stack the best frames with less atmospheric turbulence in that video to increase the SNR (signal to noise ratio).\nNot all light wave lengths affected by atmospheric turbulence, for example when I autoguide my scope to do long exposures, I add near infrared filters to my guide camera, because the longer the wave length of the light, the less it will be affected by atmospheric turbulence.\n",
"Here",
" is a video of the moon through a telescope, notice the flickering."
] |
[
"Why is it that when we look at bright objects we see extra artifacts surrounding it, such as vertical lines of light?"
] |
[
false
] |
This was a little hard to explain, so I've attached an image It's particularly sunny today, and I noticed that most bright objects had these distinct, vertical lines. I'm a physicist by trade, but the best I can come up with is a lensing effect from our eyes (which makes sense). I'd love some more insight on why this occurs with humans and if there is any biological mechanism behind it as well.
|
[
"The bright lines in that particular picture look like ",
"CCD smear",
", an artifact caused by a certain type of image sensor.",
"For the vertical lines that you see with your own eyes, do they get more pronounced (brighter, longer, or larger) when you squint? If so, I think it may be ",
"the phenomenon described here",
". In short, it is caused by reflections off the edge of your eyelid and/or reflections from or refraction through the cylindrical layer of fluid (tears) that accumulates along that edge."
] |
[
"I agree with your first point; I chose that image because it most closely imitated the effect I was trying to describe, I understand that the causes of the two effects are different. ",
"As for the vertical lines I'm seeing, I was not squinting. The sources were just unusually bright (noon time, no clouds, reflective surfaces). That being said, I think your link accurately describes the same phenomenon I was observing or, at the very least, shares a similar mechanism. I had not considered the effects of fluid in the eye, only standard lensing effects. Thank you very much for your insight!"
] |
[
"I asked my optometrist this same question, as well as researching it on my own. What I have come up with matches everything the professional said, of course. The optometrist called them \"spokes,\" and I believe spokes of light is the most common search term on the internet concerning them. If there's enough to form a ring, then they're halos. Honestly I'm not sure quite where the distinction between the two is, or if they are synonyms.",
"As for the causes: Firstly, if you widen your eyes a little, and it goes away, it is mostly light reflecting off of your eyelashes. Much more likely, you may have astigmatism. If the shape of your eye is not what it should be, as compared to most people's, then light isn't received the same way, obviously. If you also see a sort of \"ghosting\" or double image of a bright or lit object, but only in one eye, it is almost certainly astigmatism (though possibly worse things, if it comes on suddenly). Of course, the symptoms of astigmatism depend on how sever it is, and may be just blurriness, and/or spokes, or so on. ",
" ",
" ",
"Although, I also have off-center pupils which I imagine adds a bit more for me. "
] |
[
"Are facial expressions instinctive or something that must be learned?"
] |
[
false
] |
For example, if there was a feral child who had NO human contact (that he/she can remember) in their entire life, would they know that smiling meant someone was happy? I imagine things like a wolf showing it's teeth would be instinctive, and even if you had never seen a wolf before you would know it is pissed.
|
[
"Also: blind children all over the world (blind from birth) make similar facial expressions."
] |
[
"They are instinctive. Though there are subtle cultural variations and specializations, we seem to have a small set of universally-recognized and utilized facial expressions. Infants make exaggerated facial expressions before they could reasonably be expected to have learned them.",
"In addition, I'll just point out that your feral child example is not necessarily applicable; it is possible to lose instinctive behaviors over the course of development through disuse, so a feral child who had normal facial expressions at age 0-3 may have lost them all by age 12 because they didn't serve any purpose."
] |
[
"You should check out research by ",
"Dr. Paul Ekman",
", a renowned psychologist who primarily does research on emotions and their facial expressions. He's done meticulous hours of coding to categories the countless faces' expressions from cultures all around the world, including indigenous ones. He also has trained CIA and FBI agents in programs designed to help them detect deception and to read people better.",
"But in short, yes, they are instinctive. darwin2500 makes a good point at looking at research on babies. "
] |
[
"Question about Electricity and Wind Farms (Help With My Son's Project)"
] |
[
false
] |
My son and I recently visted the with his Cub Scout Den, and his leader is asking each of the boys to make a poster with facts about the farm. We found plenty of information on the interwebs, but I want him to understand what he's putting on the poster. The Wind Farm is capable of producing 24 MW. Is this per hour? Per Year? What is the best way to explain (to 8 year olds) how much power this is? I did google this but couldn't find what I as looking for. Thank you in advance. EDIT: Thank you to everyone for the help! You've given me the info I was looking for!!
|
[
"MW (megawatts), is a measure of energy produced per second. Megawatts is a measure of power, so the maximum power is just 24 MW. So basically, the mill is capable of spitting out a maximum of 24 megajoules of energy per second"
] |
[
"The Wind Farm is capable of producing 24 MW. Is this per hour? Per Year?",
"No, it's just 24MW. A watt is defined as one joule per second.",
"According to ",
"Wolfram Apha",
", 24 megawatts is enough to power 4000 - 8000 US households."
] |
[
"Another way to picture 24MW is with kettles. Kettle is roughly 1KW I think, so 24000 kettles. "
] |
[
"Are artists really prone to mental illness and why?"
] |
[
false
] |
[deleted]
|
[
"About five years ago I took a master's level course called \"Creativity and Intelligence.\" I have also often wondered why it seems that so many creative individuals are often also mentally ill. The answer the course and the professor provided was along the line of, \"We're not really certain of the 'why' but there are some 'how's that we see, and frequently.\"",
"To illustrate this, please read the following passage that I have copied from the book, Handbook of Creativity, edited by Robert J Steinberg, 1999.",
"\"There is a long tradition of associating creativity with mental illness, or genius with insanity (Jacobson, 1912. Lombroso, 1891.) Recent surveys have added new credence to this tradition by demonstrating rather convincingly that the rate of various pathologies such as suicide, alcoholism, drug addiction, and institutionalization for nervous diseases is much higher than expected in certain \"creative\" domains such as drama, poetry, and music. ( Jablow and Lieb, 1988. Jamison, 1989. Martindale, 1989, Richards, 1990.) These results, however, demonstrate only that some fields, ones in our culture that get little support, are associated with pathology either because they attract persons who are exceptionally sensitive (Mitchell, 1972. Piechowski, 1991.) or because they can offer only depressing careers. They may have little or nothing to say about creativity itself.\"",
"So yeah, the psychologists recognize it is there and to me, seem to suggest that if an artist were able to receive validation and support (both monetary and social, among other forms) for their work (hence the \"depressing careers\") the mental illness that sometimes accompanies being creative may not be so pronounced as to result in suffering (suicide, alcoholism, etc.)",
"Again, I recognize that this does not answer your question of \"why\", but to know that even the experts in the field do not know why but do have some inkling of the \"how\", well, I hope that is some small consolation. I am sorry for your loss and I hope this brings you closer to peace. Take care."
] |
[
"Addiction is a mental illness. Also, drug use is not the same thing as addiction."
] |
[
"I don't have an answer for you, but I'd like to point out that the causal link you seem to be looking for could be reversed. An equally valid research question could be: Why is it that so many people who are prone to mental illness become amazing artists?",
"Ninjaedit: specificity."
] |
[
"Why does too much water kill my plants?"
] |
[
false
] |
[deleted]
|
[
"Roots need oxygen to survive, so too much water will literally drown a plant. In addition too much water can cause the growth of mold which can kill the plant."
] |
[
"They have adaptations that allow them to live underwater."
] |
[
"They have adaptations that allow them to live underwater."
] |
[
"Do bone conduction earphones protect hearing?"
] |
[
false
] |
[deleted]
|
[
"There's no reason to believe that they would. Hearing loss is usually caused by damage to the inner ear, which is still getting as much sound exposure with bone conduction as it would through the normal path of sound."
] |
[
"I would guess bone conduction earphones were provided due to being excellent at maintaining sound clarity in very noisy environments (as you said, it was windy). Most likely has nothing to do with protecting hearing."
] |
[
"Sort of a piggyback question: Could I have bone conduction earphones that are inside my ears, with no visible wires between/outside? That would be cool to \"play\" music from within my ears. Would I need a wire inside of me? Maybe a quick-release 3.5mm in my abdomen..."
] |
[
"Why hydrogen is placed on number one in modern periodic table?"
] |
[
false
] | null |
[
"Hi Bhootnathmainhoon thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"To check for previous similar posts, please use the subreddit search on the right, or Google site:reddit.com",
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" ",
"Also consider looking at ",
"our FAQ",
".",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"Because it has one proton",
"Helium, the second element, has two protons. The third element has three protons, and so on and so fourth. "
] |
[
"Why are oxidation reactions exothermic?"
] |
[
false
] |
A biochemistry professor of mine once posed this question: Why are oxidation reactions exothermic? According to my professor, it took a quantum chemist to answer it. If I remember right, it had something to do with the resulting electronic structure of the oxidation products, but I can't remember the details.
|
[
"You have a chemical that has electrons, but doesn't hold them that tightly (the reducing agent = fuel) and something that wants more electrons than it already has (oxidizing agent = oxidizer). The reducing agent gives up some electrons that were easy to give up and the oxidizer gains some electrons it wanted. The resulting bonds are stronger than the bonds that existed before and - boom! - heat comes out. It's exothermic. "
] |
[
"The answer is in molecular orbital theory. ",
"The slightly longer version of, \"the oxidizing agent wants electrons,\" is that the open energy levels of the oxidizer are lower-lying than the highest occupied orbitals in the reducing agent. The electrons get to fall to lower energy levels in the products from where they were in the reactants, which is accompanied by a release of energy equal to how far the electrons get to fall. "
] |
[
"A very unsatisfying answer coming up, but I hope it might be a starting point. It depends what you mean by \"oxidation\" and how deep you want to go.",
"At the shallowest level, exothermic reactions are ones where the products have lower enthalpy than the starting points. So I could give you the answer: \"Because the enthalpy of the products in lower.\" As enthalpy is just (energy + a small modification for hydrostatic pressure), we can say it's because the totalled-up energy of the bonds is lower in the product.",
"But an oxidation reaction is a tricky thing to define. :) Normally we say that one thing is being oxidised, while another is simultaneously reduced. It's to do with change in ",
"oxidation state",
", which is formally defined in the link.",
"I guess if you want to restrict the question to reaction of e.g. organic molecules with elemental oxygen, then we could think about ",
" the products tend to have lower enthalpy."
] |
[
"If a submarine loses it ability to function underwater, is it possible to “tow” it back to the surface?"
] |
[
false
] | null |
[
"Yes, there is emergency air to blow the water out of the ballast tanks. We used 4500psi air to blow the tanks.",
"My previous answer was in response to the question \"What if the mechanism for filling and depleting the ballast tanks fails?\"."
] |
[
"Submarines dive by filling ballast tanks with water. When the sub dives, air from the tanks is compressed into storage tanks, and replaced with seawater. In an emergency, the compressed air can be released back into the ballast tanks, blowing the seawater out and restoring positive buoyancy. Google \"submarine emergency blow\" to see the result. "
] |
[
"They would need a DSRV to rescue the crew in that case. There is no method for raising a submarine by hoisting it or \"towing\" it to the surface - they are simply too heavy. I served on a submarine - USS DRUM (SSN 677) - back in the day."
] |
[
"Is it possible to see the top of lightning?"
] |
[
false
] |
It has to start from somewhere, so does it have a top?
|
[
"There are such things as ",
"sprites",
"), which shoot off away from the top of the cloud when lightning strikes below it. Probably not precisely what you're looking for but very interesting nonetheless..."
] |
[
"When it comes to atmospheric electrical phenomena, lightning is only the beginning of the awesome.",
"http://en.wikipedia.org/wiki/File:Upperatmoslight1.jpg",
"Closest I've seen to a top:",
"http://en.wikipedia.org/wiki/File:Sprite_seen_from_space.jpg"
] |
[
"Well anything about lightning is cool, thanks. \nI'm just wondering if seeing the top of lightning is possible. It's always surrounded by clouds, and clouds aren't exactly solid (right?) so shouldn't the lightning go through it? Idk..."
] |
[
"What exactly is missing for the covid-19 vaccines to be full approved, and not only emergency approved?"
] |
[
false
] |
I trust the results that show that the vaccinea are safe and effective. I was talking to someone who is not an anti Vax, but didn't want to take any covid vaccine because he said it was rushed. I explained him that it did follow a thorough blind test, and did not skip any important step. And I also explained that it was possible to make this fast because it was a priority to everyone and because we had many subjects who allowed the trials to run faster, which usually doesn't happen normally. But then he questioned me about why were the vaccines not fully approved, by the FDA for example. I don't know the reason and I could not find an answer online. Can someone explain me what exactly is missing or was skipped to get a full approval?
|
[
"TL;DR - FDA approval is designed on purpose to be a ",
" to make sure a product is ",
" It's a process made hard on purpose. ",
"Meanwhile, an emergency use authorization slims down the red tape while still requiring a proven safety and efficacy record. ",
" If normal FDA approval is like a 300-guest wedding event, then emergency use authorization is a small courthouse wedding six months in advance of the main event so that they can file joint taxes and one spouse can technically be on the other's health insurance and dental. ",
"Right now the FDA has cleared just three of many vaccines (Pfizer, Moderna, J&J) for use via Emergency Use Authroization (EUA). To get there, they had to go through three phases, and at each stage demonstrate both a) effectiveness and b) safety. ",
"For an EUA to be issued for a vaccine, for which there is adequate manufacturing information to ensure quality and consistency, FDA must determine that the known and potential benefits outweigh the known and potential risks of the vaccine.",
"From a safety perspective, FDA expects an ",
" (meaning that at least half of vaccine recipients in phase 3 clinical trials have at least 2 months of follow-up) after completion of the full vaccination regimen. In addition, FDA expects that an EUA request will include a phase 3 safety database of well over 3,000 vaccine recipients, representing a high proportion of participants enrolled in the phase 3 study, who have been followed for serious adverse events and adverse events of special interest for at least one month after completion of the full vaccination regimen.",
"So far only 3 have made it to EUA. ",
" You have a vaccine, you proved it works, and you proved it's safe - you can produce it while you go through the rest of the slow-on-purpose process.",
"Now to have full approval, and under normal circumstances, the vaccine makers have to get full approval through a ",
" submitted to the Food and Drug Administration. This is a 3-stage process.",
"The BLA application itself includes:\n - Applicant information\n - Product/Manufacturing information\n - Pre-clinical studies\n - Clinical studies\n - Labeling",
"They schedule a bioresearch monitoring inspection. FDA comes out to inspect the production process and facilities.",
"Then they file a Form FDA 356th which includes:",
"Then we wait for the FDA review. This can take as much time as it needs to take.",
"Sources:",
"https://www.thefdagroup.com/blog/2014/07/test-the-biologics-license-application-bla-process/",
"https://www.fda.gov/vaccines-blood-biologics/vaccines/emergency-use-authorization-vaccines-explained",
" ",
"https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-initiate-rolling-submission-biologics"
] |
[
"wasn't it already made available for the EUA?",
"Yup. There's a duplication. The same information has to be submitted for both. ",
"The difference is like a courthouse wedding vs. a 300-guest wedding. They both ",
" require the same things (a bride, a groom, not related, not coerced, wanting to be married, witnesses, an officiant, etc etc.) but the 300-guest wedding comes with a lot of extra formality. ",
"In general the 300-guest wedding is preferred, but if a wedding needs to happen, and all the elements are there and verified, a courthouse elopement is fine.",
"Lack of hors d'oeuvres and a $5,000 gown doesn't make it not a wedding. ",
"In this case -- the couple is getting married immediately at the courthouse for health insurance purposes, then also having a massive church wedding for the families in six months.",
"Also about the scheduled inspection of the facilities - doesn't this happen for an EUA?",
"Manufacturing safety and consistency record is a pre-requisite. ",
"\"Part of FDA’s evaluation of an EUA request for a COVID-19 vaccine includes evaluation of the chemistry, manufacturing, and controls information for the vaccine. Sufficient data should be submitted to ensure the quality and consistency of the vaccine product. FDA will use all available tools and information, including records reviews, site visits, and previous compliance history, to assess compliance with current good manufacturing practices.\""
] |
[
"Thank you so much for the great answer.\nI think I was able to follow everything, but I still have a question.\nI understand that the EUA requires everything to say that a vaccine is safe, produced well, and effective.\nI understand that the BLA is a big amount of work and very formal procedure. But it seems to me that all that information that needs to go into the Form FDA 356th is essential to evaluate the safety of the vaccine, right? So, wasn't it already made available for the EUA? Or is it just that the information was handled, but that in this formal way?\nAlso about the scheduled inspection of the facilities - doesn't this happen for an EUA? I mean, it would be legit to be worried to get a vaccine from a company which facilities were not inspected? But maybe I'm interpreting this wrong (?)"
] |
[
"Why are antibodies ineffective against certain illnesses, or is that even the case?"
] |
[
false
] |
With infections like HIV and Lyme antibodies seem to exist but don't necessary completely defeat the illness. I'm sure there are others as well. If antibodies are ineffective, why is that? Through medical research could we make 'steroids' for antibodies to make them stronger/faster/whatever to perhaps make them effective?
|
[
"Some rare people develop antibodies that control HIV. One of the problem with antibodies is that pathogens can mutate themselves so that where the antibody would bind has changed, making the antibody ineffective. This is the major problem in HIV, because HIV has an extremely high mutation rate. Through natural selection, the viruses that are able to avoid the immune response become the dominant strains infecting someone. ",
"But as I said before, some people develop antibodies to an essential part of HIV that can't be mutated without losing its function. People are now working on making a vaccine that can induce these same effective antibodies in everyone. "
] |
[
"As other commenters have noted, there are many ways that pathogens can avoid detection by antibodies or resist or suppress the body's antibody-mediated reactions. I could go on for chapters describing all the known ways these evasions happen but I'll let what others have said suffice.",
"Since the methods of evasion are so diverse the means by which to make antibody \"steriods\" are equally diverse. The best antibodies are the ones that are already there from vaccines. Vaccination strategies are continually improving such that they leave you with much stronger/faster/whatever antibody defenses. Genomic medicine will eventually be applied to medical immunology as well - people with known variants of immune detection/signalling molecules will be given vaccines that are most appropriate for them, rather than the way it is done today where everyone gets the same thing."
] |
[
"Alot of diseases have methods to avoid antibodies. Antibodies float in the blood and if an infection is in a cell or surrounded by a coat that protects them from antibodies then they have no effect. There are currently no methods of improving antibodies function. With HIV the virus lives within cells for the majority if the time and it effects the cells ability to say that it is infected (this has something to do with the major histocompatibility factor i think) so it can stay in the body for a long time without being attached by antibodies."
] |
[
"On what basis is it decided that which medicine will be in form of capsule or tablet?"
] |
[
false
] |
I have opened many capsules and found a variety of type of medicines, like granules or powder but can't they be pressed into tablet form? Since most of the tablets are hard pressed powders (i might be wrong on this)
|
[
"Tablets are generally for medicine who you want to dissolve and absorb without regulating the speed of which they are absorbed or where they get absorbed ",
"Capsules, depending on the type of medicine, gives you control over that. Some capsules can tolerate stomach acid to protect the medicine and then dissolve in the small intestine to allow the medicine to bypass the stomach. ",
"Other capsules are just there to allow the medicine to be released faster than it would have if it was a tablet. These are fast dissolving capsules ",
"Capsules with little medicine tiny balls are usually extended release, where the main capsule would break in the early small bowel and then the small balls would actually have different dissolution rate, so some would dissolve quickly, others dissolve slower so you would get some medicine being absorbed for an extended period of time.",
"Tablets can also be modulated to control how they dissolve, but not as good, so it is really up for what the manufacturer think will work best."
] |
[
"Many different things can determine the composition of how a drug is delivered. Even what looks to be simple powdered/compressed drug can be mostly powdered cellulose (plant fibers) as a binding agent and to increase volume. Gels may help with rapid absorption. There might be a safety coating for your stomach. Sometimes a delayed release formulation is used that slowly breaks down in your stomach acid. Some drugs can't even be absorbed through your stomach and are limited to IVs; saline or water are pretty common for mixing IV drugs."
] |
[
"Definitely, although probably very small since there are many very cheap capsule. Advanced capsule that can time release probably is more expensive. ",
"In general, the difference between brand name and generic of any specific medicine lie in the quality of the carrier vehicle and how well it works"
] |
[
"Why do antibodies in Rhematoid Arthritis patients attack only joints?"
] |
[
false
] | null |
[
"They don’t.",
"RA can attack multiple organs and has a very variable expression. It is known for causing heart and lung problems. Including pericarditis, vasculitis, interstitial lung disease, pleural effusions. Also hematologic manifestations and neuropathies. It can certainly have a lupus-like picture.",
"As a physician, if I suspect that someone has an inflammatory arthritis, I’m doing a very broad immunological workup because there is a very large spectrum of diseases that could be at play. And if I do refer someone to rheumatology and they come back with a diagnosis, I do monitor new symptoms because occasionally, the extra-articular symptoms are the sentinel signs that their disease is no longer controlled."
] |
[
"Thank you physician, for caring and being an open minded critical thinker. I write this with sincere meaning."
] |
[
"The rheumatoid factor antibody does not attack joints. It actually attacks other antibodies (the Fc portion of IgG). These immune complexes (antibodies bound to each other) are found in people's joint synovium and joint fluid.",
"The joint damage in rheumatoid arthritis is actually caused by a complex interplay of many immune system cells fibroblasts and cytokines. ",
"Rheumatoid arthritis is not limited to joints but can also affect eyes, lungs, blood vessels etc.",
"But why does RA attack the joints in particular? We don't know."
] |
[
"How good are the ISS solar panels compared to currently available solar panels?"
] |
[
false
] |
Since there's been a lot of advancement in panel tech (I hope anyway) was curious to see if there was a big difference. I'm sure the ISS panels are state of the art when put in. Edit: I don't actually know what category this belongs in. Engineering sounds about right though.
|
[
"Their efficiency is quite a bit less than what's currently available.",
"ISS panels: 21 W/m",
" [",
"source",
"]",
"Commercially available, consumer panels: 143 W/m",
" [",
"source",
"]",
"Sounds considerably worse but the ISS panels and the commercial panels are prioritizing different things.",
"For the commercial panels:",
"Important:",
"High power density - people have a limited amount of space on their roofs",
"Low cost - competitive marketplace means that the lowest priced product will sell",
"Climate tolerance - they'll be used outdoors in all weather conditions",
"Not important:",
"Reliability - if one fails, the customer can get a new one. Not a big deal",
"Weight - they're sitting on houses and don't have to move. Weight doesn't matter",
"For the ISS panels:",
"Important:",
"Reliability - these are on a space station. They absolutely must not fail or people's lives could be at risk",
"Weight - every gram counts when you're launching a rocket",
"Longevity - they aren't getting replaced any time soon",
"Not important:",
"Energy density - there's plenty of space around the ISS",
"Climate tolerance - no climate in space",
"Cost - NASA can afford it",
"The panels are still quite advanced, they're just not the kind you'd put on a house"
] |
[
"Awesome, Thanks! That is a pretty big difference."
] |
[
"Energy density - there's plenty of space around the ISS",
"I wouldn't go that far. More area = more friction = ISS loses altitude faster and you need to raise the orbit. Not to mention constraints from the launch vehicle -> you need to fit the panels somewhere! Also there is a problem with large panels that part of the panel might get heated up by sun while the other side is still cold which causes panels to flex and thus influence spacecraft attitude. For ISS it's not such a big deal (unless something breaks) but was a huge issue for Hubble."
] |
[
"Has anyone ever been successfully cryogenically frozen/unfrozen?"
] |
[
false
] |
I know this might be silly as I've looked on the internet a bit but it just seems realistic and I Want to know how we've advanced on that if t all. And walt Disney?
|
[
"Well, all intentional cryogenic freezing must be done after the individual has died. Since we have no technology that can reverse death yet, no we haven't unfrozen someone and resuscitated them from ",
" cryogenic freezing.",
"However, \"unintentional cryogenic\" freezing happens in accidents in cold weather climates and such. Severe hypothermia can have symptoms that can closely simulate those of cardiac arrest/death. However, cold temperatures can also do wonders for preserving brain tissue from necrosis and brain damage. So some of these apparent (and medically \"dead\") have been brought back to life (using conventional medicine, such as cardiac resuscitation). I know that's probably not what you're asking, but I figured it might be interesting to you."
] |
[
"I can't find the story right now, but I recall reading about a successful freezing/unfreezing in Japan, where they used a rapidly oscillating magnetic field to prevent the cooling water from forming crystals (which is apparently the damaging part of the freezing process).",
"I realize this is not a scientific post, but it may spur other people to find that article, if it in fact has not yet been debunked. (I am not speaking as a panelist here, nor in any kind of knowledgeable manner. Do not take my above recollection as true until someone can confirm it.)"
] |
[
"No. And it won't happen for some time. The thing is, when you freeze a body, microscopic ice crystals form that perforate cells. When you thaw the body, almost all the cells are dead and so then is the whole. Cryogenics companies do replace much of the bodily fluid with a sort of \"anti-freeze\" that is supposed to help reduce this sort of cellular damage, but I really doubt it's effective enough to yield a living person after the thaw. Certainly not with enough intact brain cells to be the same person. ",
"There are some animals that have developed natural anti-freeze systems and so can be frozen and thawed safely, so perhaps there might be some avenues to explore. However the most complex animal I am aware of that does this is a toad. You would barely notice if a toad suffered a bit of brain damage from the process, assuming motor function was unaffected."
] |
[
"How can a new species be classified with only a partial fossil? What if that particular creature was just deformed?"
] |
[
false
] |
[deleted]
|
[
"The key to identifying something as a new species relies on isolating some unique feature - something that is found in no other species known. That's the fundamental goal of studying morphology (or genetics) of different species. By contrast, classification relies on finding shared similarities between species, ideally things that are uncommon and therefore likely to have been inherited from a common ancestor, rather than evolved independently.",
"As an example, you could choose something like the loose connection between the jaws to hypothesize that most snakes are closely related, because it's not something found outside snakes. But that wouldn't help you discriminate one snake from another. For that, you'd want to find something - even something small - that was unique to each snake.",
"For fossils, it's the same thing. To take your example, Spinosaurus is known from a lower jaw, several vertebrae, a femur, and some ribs. But those bones are different from the same bones in similar animals such as Baryonyx or Suchomimus. The differences might be minor, but they are the basis for naming a new species.",
"As others here have noted, a problem arises when you have only one individual to work from, because then it becomes difficult to know whether the differences are due to species differences or individual variations. The only solutions involve finding multiple individuals and measuring how much variation exists among them. But without that, scientists rely on comparisons with better-known species to estimate variation.",
"One final thing - most fossil dinosaurs species don't seem to have lasted more than a couple of million years, and most lived in only one area of one continent. So differences in time and space between fossils can also be useful in determining whether something might be a new species."
] |
[
"Modern paleontology uses morphological phylogenetics to determine the relationships of taxa. The gist is this: different groups have characters present on the skeleton (or in their soft tissue, but that rarely preserves) that are unique to that group. This is true for higher level taxonomic groups, like orders and families in Linnaean taxonomy, as well as for individual species. For a more specific diagnosis, we use the shape of the bone, various tubercles or condyles, or muscle attachment sites. Some bones are unique to a group. For instance, pterosaurs have the ",
"pteroid bone",
" in their wings. Some bones fuse together into an element unique to a group. Sometimes joints are present between bones that don't usually move relative to each other (a lot of reptiles have kinetic skulls).",
"You take these skeletal characters (often binary, so presence/absence) and \"code\" your new taxon alongside a bunch of existing taxa. You designate an ",
"outgroup",
" that has a lot of traits that are ancestral to the group you're studying. The placement of your new taxon will quantitatively support whether you have a new genus, new species, etc. Or it won't be able to distinguish it from existing taxa, in which case you can't officially designate a new species. If you're describing something new, you usually write up a ",
"species description",
", including your phylogenetic analysis. Here is a ",
"blog article",
" from a paleontologist that goes into this in lovely detail. ",
"Using highly incomplete material to describe a new species is something that paleontologists work to avoid, although in the past it was more common. Few specimens are ",
" complete, but they need to be complete enough to be able to check how that specimen is related to other species and to be able to referred to that species.",
"Species are (almost always) based on a single specimen known as a holotype. For another specimen to be referred to that species, it has to be identifiable using characters found on the holotype. ",
"While it's rare, there are certainly times when you can identify a species from a single fossil. For isolated bones it's not necessarily a good idea, so you may want to try and find more material. Sometimes things are so unique that they obviously represent a new species. Mammal teeth tend to be very specialized and often diagnostic for a taxon. However, isolated bones and teeth make referring material to a taxon extremely difficult. In fact, in instances where very incomplete material was used, species have be scrapped. They can also have a new type specimen (a neotype) designated. It depends on the circumstances.",
"We use ",
"open nomenclature",
" for things we can't definitively identify. For example, if we find something like an isolated crocodylian tooth or osteoderm, it doesn't have very much that sets it apart at the species level. If only one species is know from the area, a lot of times it will be \"referred\" to a taxon. Then the species name is written with a ",
"cf.",
" in front of it (e.g. ",
" cf. ",
"). I tend to think this is a bad idea, especially because a lot of databases that index fossil specimens will drop the cf., making it look like the identification isn't tentative. If no particular species has been described from there, we'll identify it as Crocodylia incertae sedis. More info on this is ",
"here",
".",
"The original ",
" material included a number of vertebrate from various parts of the spinal column and part of several bones in the jaw, but that material no longer exists. It was housed in a museum in Munich, Germany, and was destroyed in an Allied bombing in WWII. What we know about the material is based ",
"off of a few photos, drawings, and text descriptions",
" (PDF). In this instance, the drawings and later the photographs were used to refer material to the genus. It's not ideal, but it's the sort of thing we have to do in extraordinary circumstances."
] |
[
"Oftentimes you can get down to the family or order just because bones look characteristic. On my qualifying exam, one professor pulled 2 random fossils out of his briefcase for me to identify, and it wasn't that bad.",
"My labmate is currently publishing a statistical algorithm that will identify unidentified and disarticulated bones found in a fossil bed based on the characteristics of already identified bones in other fossil beds that are likely related. I'm not clear on all the details, but PM me if you want to ask her questions directly."
] |
[
"AskScience AMA Series: I’m Dr. Julia Shaw, a memory scientist and criminal psychologist. I study how we create complex false memories. AMA!"
] |
[
false
] |
** ** Hi Reddit! I study how we can create incredibly detailed memories of things that never actually happened. In particular, I implant rich false memories of committing crime with police contact and other highly emotional autobiographical events. I thought I’d share my work with the community, since I’m an avid Redditor. The technique I use in my research is essentially a combination of what's called “mis-information" (telling people convincingly that something happened that didn’t) and an imagination exercise which makes a participant picture the event happening. The goal is to get my participants to confuse their imagination with their memory. I find, as do many other scientists who study memory, that it is often surprisingly easy to implant memories. All of my participants are healthy young adults, and in my last study 70% of them were classified as having formed these full false memories of crime by the end of the study. I am currently working on further research and analysis to see whether I can replicate this, since this success rate was incredibly high. Last year some of this research, which I did with Stephen Porter at UBC, went viral. It was so amazing to see such a great reaction from the press and public. There really seems to be a thirst for wanting to understand our faulty memories. You can see my favourite write up of the research . In “ ,” a NOVA documentary airing tonight on PBS at 9pm Eastern time, you can actually see some real footage from the videos that I made during the interviews, which you can see . I actually have a whole book coming out this summer on memory hacking. It’s the first popular science book of it’s kind, and I’m super excited about it! If you find my research interesting you’ll definitely like the book. The book will be released in 8 languages (English, German, Dutch, Portuguese, Italian, Taiwanese, Chinese, and Japanese) and will be called “The Memory Illusion”. You can get preliminary information about it . If you want to know more about me and my science, and get free access to all the research I have published to date, go . Read my Scientific American contributions (almost all of which focus on memory errors) . Follow me on Twitter: @drjuliashaw I will be back at 1 pm EST (10 am PST, 6 pm UTC) and I will answer the most creative comments first! Julia
|
[
"Is there a way to reverse this? Or to somehow find out which is the \"true\" memory?"
] |
[
"Hello Dr. Shaw! Thanks for doing this AMA. My question is, are some people more susceptible to creating false memories than others? If so, what are some characteristics that contribute to this susceptibility? Thanks."
] |
[
"Great questions! ",
"There are two questions you seem to be asking. ",
"Q1: The first is whether not we can tell the difference between a true memory and a false memory, and the answer is “probably not”. ",
"When we show videos of false memories and true memories to participants in research studies, they generally cannot reliably tell the difference between them. This suggests that true and false memories of emotional events look the same to others. ",
"We also know that true and false memories can have multi-sensory components, which means that both can be incredibly detailed and have feelings, tastes, sounds, and sights all woven into them. This makes it likely that without independent corroborating evidence (such as photos or video footage) it is unlikely that we can reliably identify our own false memories.",
"Q2: Can we reverse a false memory? Essentially, yes. In the research I do participants seem to willingly revise their memories once I tell them what the research is actually about (in the debriefing). Essentially, this means that when confronted with compelling contradictory evidence, people are usually able to accept that they just dreamt up a scenario rather than actually experienced it. From that point the memory can either be forgotten OR they can become so-called “non-believed” memories, which are complex events that still feel like memories but we don’t actually believe happened. "
] |
[
"Why don't cars have frontal and rear magnetic fields to prevent collisions?"
] |
[
false
] |
Let me explain: If you could have two negative poled magnets at the back and front of every car, where the magnitude of the magnetic field increased the closer you approach the magnet, wouldn't this be an effective measure to help the deceleration of cars upon impact? This, in addition to the crumple zone, could increase the time for deceleration, and thus decrease the overall force, right? Concerning issues of parking in close spaces; the magnetic field could be electrically induced, and turned off when the car stops, meaning that it would not interfere with other cars when not in motion. (Perhaps, active when a set speed is achieved.) I am asking whether this could be a possibility, and if so, why is it not being marketed? Thanks.
|
[
"I just spent a funny two minutes imagining magnetic quadrupole cars driving around our streets. ",
"To get a force in the ballpark of being able to stop a car, you need very massive magnetic fields that require huge, heavy coils and tens of kW of electric power. A junkyard magnet has maybe a few Tesla and requires about 10 kW ",
"source",
"; since it lifts a car, we can estimate that this would be enough to decelerate a car at 10 m/s",
" which is about the same as braking. For an emergency system you probably want significantly larger decelerations. It also takes time to build up such a large field and associated current, although this can be counteracted by using a higher voltage. There are other problems, but the additional weight alone would probably make this impractical.",
"Why I was amused: a magnet like that wouldn't work like a brake, but more like a deflection shield. Both cars would be deflected towards the sides rather than being stopped. This would also create a torque on the car that would probably make it hard to control. Even if you carefully manage the fields to prevent this, any energy you store in the magnetic field would still need to be dissipated, so if deceleration occurs, the current would need to be dumped somewhere, probably as heat. 10 kW of heat energy is not so easy to get rid of. You need active cooling of the coils to avoid burning them out. If you didn't dissipate the energy, the cars would slow down, but once they are stopped, would be pushed away from each other again and end up going backwards with (nearly, due to friction) the same velocity as they were previously going forward.",
"The sides of your car would attract the fronts of other cars. To avoid this, you need to reverse polarity, but then another car coming from the front would be attracted to your front. It also doesn't sound very practical to have magnetic fields in the Tesla range around on the street. They would attract electric cables and any ferromagnetic metal objects (anything made of steel) in the vicinity. There would also be a pretty large danger to any electronic devices, including pacemakers."
] |
[
"Not to mention if you're going fast enough the magnetic field will do just as much damage to your car as a crash. A force is a force, it doesn't matter if it's the normal force of the car in front of you or magnet, its rapid deceleration of a portion of your car relative to the rest of it (and you for that matter) that causes damage."
] |
[
":) As with all things in engineering, it's a matter of the cost and benefit. If 50-60 years ago, somebody tried to compare the feasibility of trying to brake a car using quadrupole magnets vs. using a bank of computer processors that used radar/lidar ranging, advanced image processing/3D environment recomposition algorithms to automatically decelerate a car when it detects a hazard.... you'd be laughed out of the room for even suggesting the second. We just now have the infrastructure to make the second super cheap. If on the other hand, we developed the infrastructure to make the first cheaper, we'd have adopted that instead.",
"To wit, you don't need the magnets to be mounted on the cars themselves. As ",
"/u/nepharan",
" pointed out, the straightforward approach you suggested results in torques and energy dissipation issues. On the other hand, you were considering cars that were restricted to not drift out of their lanes (using magnets in the road), then you can use that to keep you on track. You can also consider using the same system that produces magnets along the lanes to somehow power your repulsion magnets and take and drain energy...",
"Or you can realize I'm just talking about maglev trains and that you don't need to brake against the previous train - you just need to detect that there is a train there (pretty trivial with our electronics) and then automatically apply magnetic braking, returning energy back into the circuit or powering flywheels or whatever."
] |
[
"What occupation has the longest life expectancy? Shortest? (x-post from AskReddit)"
] |
[
false
] | null |
[
"For shortest, my best guess is ",
"underwater welders",
". They generally only live 10 to 15 years, but they make a ton of money in hazard pay.",
"Most studies put the longest life expectancy with nuns (if you count that as a profession). Their average life expectancy is ",
"86",
" years. Low stress, healthy living, and depending on who you ask, maybe some help from the man upstairs."
] |
[
"Shortest? Occupy LA?"
] |
[
"Alaskan fishermen, elephant zookeepers and professional horse jockeys all have reputations of not lasting very long. Don't know the average lifespan though. Since most American zoos switched to protected contact (= keeper never goes in with elephants any more) the keepers are doing a bit better, but a bull still gets one of them now and then."
] |
[
"Why does the expansion of space only affect huge structures?"
] |
[
false
] |
Why aren't the sun and the earth pushed away from each other? Is gravity so strong that it easily cancels dark energy out on small scales? Is dark energy not distributed equally?
|
[
"Is gravity so strong that it easily cancels dark energy out on small scales?",
"I'd more think of it as \"Gravity between galaxies is so weak that it gets overwhelmed by the expansion.\""
] |
[
"Why Brooklyn is Not Expanding"
] |
[
"Some people have said that locally, gravity and other forces overwhelm the dark energy. This is partially true, but I think there's a more fundamental way to understand why the expansion of the universe is only apparent on cosmic scales, which would remain valid even if we ignored all other forces.",
"Imagine the universe as a sheet of graph paper with drawings on it. The paper is space, and the drawings are matter. At present the boxes are all, say, 1 unit wide. When we say that the universe is expanding, we mean that each box on the sheet of paper is getting bigger at the same time -- in this way, the universe expands without actually having a center. Now, let's say each box expands at 1 unit per second. So after 1 second, the boxes are 2 units wide, after 2 seconds they are 3 units wide, and so on.",
"Imagine an observer, Alice, at the origin looking through a telescope at Bob and Carol. Bob starts out 1 unit away from Alice, on the other side of a box. Carol starts out 10 units (10 boxes) away from Alice. After 10 seconds of cosmic expansion, Bob is now 11 units away, while Carol is 110 units away. Thus in the same amount of time, Bob has receded by 10 units, while Carol receded by 100. So the farther two observers are apart originally, the faster cosmic expansion pushes them apart, simply because each tiny interval between them expands by the same amount, so the more intervals between them, the more expansion.",
"So even if there were no other forces, the amount of expansion occurring at human scales would be negligible (and because the other forces actually exist, they block even that).",
"Now, all this ignores dark energy, which makes itself apparent in an ",
" of the cosmic expansion rate: in my example, perhaps dark energy would raise the box expansion rate to 2 units/second after 1000 seconds. If that acceleration continues indefinitely, there could come a time when cosmic expansion is apparent at human scales, such that it overwhelms all other forces and all objects, no matter how small, fly apart. This is known as the \"Big Rip\" scenario and it is one way the universe could end."
] |
[
"What exactly is the prevailing theory about how life began on earth?"
] |
[
false
] |
[deleted]
|
[
"There's the ",
"RNA world",
" hypothesis, recently, there had been a demonstration ",
"in the lab",
" of RNA replicating itself. ",
"There's no way to really know what happened 4 billion years ago, as this stage of life didn't leave anything behind, but it seems that this hypothesis is a pretty good one.",
"These RNA structures are pretty complicated in themselves, here's an ",
"article",
" dealing with the move from monomeres to polymers. Incidentally, at the end of that piece there's a nice summary of the state of our understanding regarding the origin of life:",
"it is widely believed (though by no means universally accepted) that at some point in history, an RNA-based world dominated the earth. But how it got there -- and whether there was a simpler system before it -- is still up for debate. Many argue that RNA is too complicated to have been the first self-replicating system on earth, and that something simpler preceded it.",
"Graham Cairns-Smith, for instance, has argued since the 1960s that the earliest gene-like structures were not based on nucleic acids, but on imperfect crystals that emerged from clay. The defects in the crystals, he believed, stored information that could be replicated and passed from one crystal to another. His idea, while intriguing, is not widely accepted today.",
"Others, taken more seriously, suspect that RNA may have emerged in concert with peptides -- an RNA-peptide world, in which the two worked together to build up complexity. Biochemical studies are also providing insight into simpler nucleic acid analogs that could have preceded the familiar bases that make up RNA today. It's also possible that the earliest self-replicating systems on earth have left no trace of themselves in our current biochemical systems. We may never know, and yet, the challenge of the search seems to be part of its appeal.",
"Recent research by Tkachenko and Maslov, published July 28, 2015 in The Journal of Chemical Physics, suggests that self-replicating molecules such as RNA may have arisen through a process called template-assisted ligation. That is, under certain environmental conditions, small polymers could be driven to bond to longer complementary polymer template strands, holding the short strands in close enough proximity to each other that they could fuse into longer strands. Through cyclic changes in environmental conditions that induce complementary strands to come together and then fall apart repeatedly, a self-sustaining collection of hybridized, self-replicating polymers able to encode the blueprints for life could emerge. "
] |
[
"To add to the nice explanation above on the 'RNA hypothesis' for origin of life, this recent (Oct, 2018) publication suggests a role for liquid crystals in formation of initial RNA strands that would be necessary for the transition of non living chemicals to form self-replicating structures.",
"American Chemical Society. \"Liquid crystals and the origin of life.\" ScienceDaily. ScienceDaily, 3 October 2018. ",
"www.sciencedaily.com/releases/2018/10/181003090350.htm",
" ",
"As discussed above, a variation of the RNA hypothesis has been suggested to link RNA and simple peptides, which together form a type of feedback loop, with the peptides forming enzymes that are necessary for RNA molecules to self-replicate. This RNA-Peptide hypothesis is discussed here...",
"https://www.genengnews.com/gen-news-highlights/ancient-enzymes-hint-at-alternative-origins-of-life-on-earth/81255120",
"See also this 2014 review publication on origin of life hypotheses being investigated:",
"https://www.liebertpub.com/doi/pdf/10.1089/ast.2013.1110"
] |
[
"I don't think there is a prevailing theory from what i am aware except several different hypothesis.",
"Many of the components of DNA exist freely in space, some have been identified in meteorites for example.",
"Its possible that lightning strikes on water could have caused some reaction/bonding but i'm not entirely sure."
] |
[
"If you could flip a coin in a vacuum with the exact same force and at the exact same angle each time, would it always land on the same side?"
] |
[
false
] | null |
[
"Yes. If all the variables are controlled, the outcome should be the same. ",
"Now, a perfect vacuum is experimentally impossible to achieve, but if we're talking about something as large as a penny, subatomic particles really won't make much of a difference on the penny."
] |
[
"If the air was carefully contained (IE no gusts) its effect on the motion of the coin would be the roughly the same every flip, so it would land on the same side. It's mainly the difficulty in maintaining a precise force and angle that causes the randomness in everyday coinflips."
] |
[
"Probability is a branch of mathematics. There's nothing debatable about that. It's the branch of mathematics that deals with the likelihood a random event will occur. ",
"True randomness does exist, but just at a quantum level. ",
"Have a read",
". ",
"When you get up to something as macroscopic as the physical world, there is definitely an argument that every particle has a calculable trajectory, and that there is no random chance, just predestined fate. I know absolutely nothing about this, and anything I say further would simply be speculation."
] |
[
"Is it possible for a solar flare to knock out the electrical grid for a long period of time?"
] |
[
false
] |
How likely is this to happen?
|
[
"Yes, it is without a doubt possible.",
" When we speak about solar flares we are generally referring to the ",
"emission of radiation",
" from a magnetic reconnection event in the Sun's higher atmosphere. These flares are not always but are often linked with an ejection of matter from the Sun called a ",
"Coronal Mass Ejection",
"(CME).",
"This ejection of matter travels through space and due to some consequence of plasma physics, called the frozen in flux condition, carries with it some magnetic field from the Sun.",
"If this CME reaches the Earth then the magnetic field carried with it will interact with our own magnetic field. The fields press on each other both reconnecting (cancelling out) and just squeezing. How much squeezing happens depends on the alignment (generally aligned is bad and anti-aligned is ok) and on the strength of the CME.",
" The pressure on the geomagnetic field changes it. We know from ",
"Maxwell",
" that a changing magnetic field induces an electric field. This electric field can induce currents in conducting material. These currents are called ",
"Geomagnetically Induced Currents (GIC)",
".",
"Now since an electric field we are talking about is tiny, even for large flares. Of the order of mV/m. However, if your conducting material is large the total voltage can be high (1mV/m * 50km = 50V). This means for oil and gas pipelines, metal telephone cables, or for high voltage electrical wires there can be a significant voltage.",
"The maximal voltage reached depends on the electrical grid configuration (long wires bad) and it depends on geology (the more resistive the ground underneath is the worse so granite is bad) as well as obviously the CME and magnetic fields themselves.",
"The failure point is essentially the transformers where these wires terminate. The voltage is small compared to the HV of the electrical grid itself but it is a DC offset on an AC voltage. This knocks the transformer out of phase and can cause a large amount of excess heat. This heat can overwhelm the transformers cooling system (oil) and rupture it's casing, this takes the transformer offline.",
"If one transformer fails it can cause a cascade of failures as redundancy is removed.",
" Well it has happened. ",
"March 1989",
" saw a storm following an extremely large X15 class flare. The GIC from this caused a cascade of failures on power transformers in Quebec.",
"In 2003 a geomagnetic storm",
" known as the halloween storm occured. Caused short term power outages. Power transformers in south africa have been destroyed by GIC.",
"The most exciting demonstration was in 1859 where the most massive ever recorded flare (and first), referred to as ",
"the Carrington event",
", caused a coronal mass ejection (CME) that produced very powerful geomagnetic storms.",
"In the case of Carrington, this potential drove such high currents in the telegram wires that some of them caught fire and some of them electrocuted operators.",
"If a CME as big as that associated with the Carrington flare were to happen it would almost certainly cause disruption to the electrical grid. We reckon Carrington is a once every 100-400 yr frequency event.",
" Away from the science a little, if transformers do fail then they can be hard to repair and they take years to manufacture. ",
"Not many companies make them and they don't exactly hold a stockpile",
". They are also made to measure a specific grid and location. If a significant number fail it could pose a long term problem.",
" We are becoming a lot better at predicting flares. By predicting I mean we can maybe look at an active region and say \"This region has a 70% change of an X-class flare in the next 24/48 hrs\".",
"We also have some kind of advanced warning, when a flare happens it can take 1-3 days for the CME to reach Earth (if it is even Earth directed). While we can not predict the GIC that accurately, mainly due to lacking data on the magnetic field strength and orientation until very late (once the CME reaches a satellite called ACE). This does allow some measure of reaction.",
"We are better at modelling the influence of GIC. Entire teams focus on forecasting what kind of field will cause what kind of GIC and where. Redesigning grids to minimize these voltages is possible.",
"Governments are aware of the risk. They know it can happen and they want to be prepared.",
"Electricity companies are aware. They know it can happen and they want to be prepared. There is liaison between solar science and electricity companies to understand the problem and how it can be helped.",
"Overall, I am not that worried."
] |
[
"So, given we find out that a Carrington type flare were to hit tomorrow, how would we prevent damage? Would turning off the power be sufficient, or would people have to go around physically disconnecting wires from the transformers?"
] |
[
"How far ahead can we reasonably predict flare activity? If the Mother Of All CME's were brewing, would we know a week ahead of time?",
"Like I said we have at least a 1-3 day warning from the flare to the CME arrival at earth, the time is less for bigger events but is never less than about a day.",
"It just being a big CME though isn't enough for us to know the danger. We need to know the magnetic field orientation which is barely beyond guesswork at the moment. You are at risk of a boy who cried wolf situation if you guess incorrectly and companies react.",
"As for the flare associated with the CME we have very little warning. We are working on models for estimating how much magnetic energy is stored in an active region as well as how likely a release is but they are infancy. Like I said before the best we can do is say there is likely going to be a big flare in the next 24 hours. ",
"Flares also come from active regions that take time to form. We won't really have a weeks notice of a flare because an active region will be either significantly smaller or non existent a week before a large event. We have no way of telling if a small region that has just formed will stay small or will become a monster region capable of X-class flares and large CMEs.",
"So we are getting there but there is inherent uncertainty. There isn't a direct correlation between a large active region and large flares, there isn't a direct correlation between a large flare and large CME, there isn't a direct correlation between a large CME and large GIC on Earth.",
"This means our predictive capabilities are always gonna hit these limits."
] |
[
"Can gamma rays break apart small nuclei?"
] |
[
false
] |
If fully ionized (electron free) nuclei of elements like hydrogen or helium or oxygen are hit with an extremely high-energy gamma ray, what happens? Would it cause the oxygen to undergo fission? Would it even interact with the hydrogen? Assuming it does interact, what happens?
|
[
"High energy gamma rays can cause particles to be knocked out of nuclei. They can even cause fission."
] |
[
"Fission generally refers to a nucleus splitting apart into two heavy ions. There's a whole spectrum starting at single nucleon emission, light ion emission, \"cluster\" emission, and spontaneous fission. Where exactly the lines are drawn is somewhat arbitrary, but there are some significant physical differences between nucleon emission decays and spontaneous fission decays."
] |
[
"Why is particle emission (protons, neutrons, alpha) not considered a type of fission?"
] |
[
"If our telescopes were powerful enough could we see the starting point of the big bang?"
] |
[
false
] |
It seems like the light from the big bang would have passed us by long ago.
|
[
"If we are looking at electromagnetic radiation, we can only see back to about 400,000 years after the big bang when the electrons in the universe became bound to the protons and it became transparent. This is the cosmic microwave background (CMB). We can look for signatures in the CMB from before that, such as the signature of gravitational wave polarization in the recent BICEP2 results.",
"We'd have to use other methods to see farther back than that. For example, a very powerful neutrino telescope could perhaps detect primordial neutrinos from the very early universe."
] |
[
"There is no center of the universe. The illustrations of the big bang shown in almost all TV shows, where it looks like a spherical explosion away from a point, are completely wrong.",
"The universe appears to be infinite, and has always been infinite for all times after the big bang. This means light from the early universe is coming from all points in space in all directions, so if you look far enough in any direction you'll see light which is just now getting here (the CMB).",
"/u/RelativisticMechanic",
" wrote this ",
"great illustration of what it means for an infinite universe to be expanding.",
"And honestly, \"Big Bang\" is not a very good term, because it leads to problems like this. It implies that there was an explosion at one point in time, when really the universe is still expanding and just used to expand faster."
] |
[
"This blows my mind. It's like an ant trying to figure out if the earth is round."
] |
[
"What specifically causes 'pins & needles', and why is it sometimes quite painless and tingly, but at other times very painful?"
] |
[
false
] | null |
[
"Parasthesia (the sensation of pins & needles) is most commonly caused by ischemia, pressure, stretch, or damage to peripheral nerves. When damaged or even under duress these nerves can send aberrant signals to the brain which may be interpreted as pain. Prolonged injury can cause numbness as well. Sensory neurons are generally more susceptible than motor neurons, which is why you're more likely to have parasthesia than paralysis. "
] |
[
"It might not be damage that's occurring, it could just be temporary stretch or ischemia. Once the insult to the nerve is relieved the normal function returns. Prolonged insult to the nerve can cause longer lasting effects. 'Saturday night palsy' is a term for when someone passes out awkwardly and compresses part of the brachial plexus. The prolonged compression overnight can lead to parasthesias and partial paralysis that lasts for days to weeks or even longer. It just depends on if there's lasting damage to the nerve or if it's a transient injury."
] |
[
"I assumed it was just lack of circulation, but you're saying I am doing damage to my nerves when I say, sit awkwardly and don't necessarily notice that I'm creating conditions for parasthesia? That damage must resolve quickly, if the feeling only lasts for some minutes?"
] |
[
"Why does your vision improve when you squint?"
] |
[
false
] | null |
[
"Not sure there is much to add beyond the canonical/Googleable answer:",
"Without really understanding why, many with vision problems find themselves squinting in order to focus. [...] By squinting, vision is able to improve slightly. But how does it work?",
"First, squinting decreases the amount of light that is able to pass through the lens. You’ll notice as you squint that the top and bottom eyelid come into view, obstructing part of your vision. This blocks a lot of the peripheral light that is entering your eye at an angle. These are the light rays that require your lens to straighten them and focus them on the retina – a mechanism that is flawed in people that require glasses. Only the rays coming straight into the center of the eye are unobstructed. They are already aligned and therefore don’t require focusing by the cornea or lens. ",
"Next, the shape of the eye is slightly changed, directly affecting how the light is filtered. Together, these two factors allow you to focus more clearly by limiting light allowed through the lens and then focusing it more precisely, near the center of the retina. While it may not drastically improve your eyesight, squinting can make just enough difference to allow you to read what’s on a page, see the TV, or receive a play-call from the sideline.",
"Source: ",
"http://www.eyespecialistsofla.com/blog/bid/324384/How-Does-Squinting-Improve-Vision",
"UPDATE: As ",
"u/djohn_14",
" ",
"u/Khashoggi",
" and many others have pointed out, there is a really very good Minute Physics video on this question: ",
"https://www.youtube.com/watch?v=OydqR_7_DjI",
" . Note that this video concentrates solely on the pinhole effect (less refraction required), and does not consider the change in lens-shaped caused by squinting (change in refractive power). I personally don't know which of these to factors is the more important for explaining the benefit of squinting, and their relative importance may vary from eye-to-eye."
] |
[
"This question has been asked many times before:",
"https://www.reddit.com/r/askscience/comments/11mmw3/why_is_it_that_people_sometimes_see_better_when/",
"\n",
"https://www.reddit.com/r/askscience/comments/vhas1/how_come_we_often_squint_our_eyes_in_order_to_see/",
"\n",
"https://www.reddit.com/r/askscience/comments/1hfw43/why_do_we_squint_when_we_try_to_get_a_better_look/",
"\n",
"https://www.reddit.com/r/askscience/comments/231a2b/why_does_you_vision_get_sharper_when_you_squint/",
"\n",
"https://www.reddit.com/r/askscience/comments/khu1t/why_do_we_slightly_close_or_squint_one_eye_when/",
"\n",
"https://www.reddit.com/r/askscience/comments/1miwju/when_i_squint_my_eyes_why_do_things_appear_sharper/",
"\n",
"https://www.reddit.com/r/askscience/comments/2lw8b6/why_do_blurry_objects_become_clearer_when_we/",
"\n",
"https://www.reddit.com/r/askscience/comments/i8dd9/why_does_squinting_improve_your_vision/",
"I found these simply by searching for \"squint\" in the ",
"/r/askscience",
" searchbar. Unfortunately, because of the high volume, a lot of really great questions and answers can get buried. Although a little finicky at times, the searchbar can be a great way of exploring ",
"/r/askscience",
"!"
] |
[
"Another thing to note is that often images will become clearer when viewed through a pinhole thanks to a similar effect. You can try this easily by making a very small hole between the ends of your two index fingers and a thumb and looking through it. This is a trick I use when I forget to take my glasses places."
] |
[
"Are there \"planes\" in the ocean? Like a desert, but in the ocean, so flat expanses of ocean floor where little to no life dares to dwell or live?"
] |
[
false
] |
Better explanation? Desert, but underwater.
|
[
"Most of the deep ocean floor is pretty barren of life. Never gets sunlight, so it subsists entirely on marine 'snow', rotting stuff falling from above. Areas where there's little surface life will only exacerbate that. And there's certainly vast abyssal plains where the ocean floor is pretty flat. I'm not aware if there's any correlation between these two, though. Any oceanographers to the rescue?"
] |
[
"I understand your question, but dont know too much about specific ecosystems in the ocean.",
"However, I do know a decent amount about deserts, having grown up in one (and listening/learning about my local environment).",
"A desert is classified by a lack of rain, not by a lack of life. There are a wealth of species who are specifically adapted to finding and conserving water who flourish in this type of environment. Jackrabbits, cacti, palo Verde trees, roadrunners, certain types of mice, scorpions, snakes, tarantulas, toads, etc. A desert is not classified by temperature either - the arctic is actually a desert because of a lack of precipitation. However, amazing ecosystems have also developed there.",
"So this leads me to my question about clarification. Are you looking for a hash local environment within the ocean where life needs to be highly specialized to survive? Or are you looking for an environment in the ocean with no life?",
"We have found life in some surprisingly harsh environments."
] |
[
"after watching the bbcs oceans documentary there's apparently plains near the corals of Australia, the clown fish from nemo live in coral thats poisonous to all but them there, and while there,s not as much life a in other parts there,s still stuff living there. It looked like there's basically life everywhere in the ocean to some degree, the documentary kept saying how surprising it was to keep finding life the deeper they went"
] |
[
"What determines how electrons return to the ground state after they are excited?"
] |
[
false
] |
[deleted]
|
[
"If the atom starts in a given excited state, it has some probability to transition to each lower energy level. It's probabilistic, but some are going to be much more likely than others.",
"What determines the probabilities for transitions to each final state is a few things.",
"Fermi's golden rule",
" states that the probability is proportional to a matrix element multiplied by a phase space factor (the \"density of final states\"). The density of final states ensures that energy is conserved, and depends on the energetics of the decay, and the final states available.",
"The more important factor for electromagnetic decays is the matrix element part. This represents a quantum-mechanical overlap between the wavefunctions of the initial and final states of the atom. The matrix element will be high for similar states, and low for very different states. There are some selection rules (angular momentum and parity) which will make the matrix elements for certain transitions ",
".",
"There are some general rules that can be stated about electromagnetic decays, without delving into the mathematical details. Transitions which carry away small amounts of angular momentum tend to be highly favored over transitions which carry away more angular momentum.",
"For a given angular momentum, \"electric\" transitions tend to dominate over \"magnetic\" transitions (whether a transition is electric of magnetic depends on the angular momentum and parity carried by the transition).",
"Transitions between states which are far apart in energy tend to be favored over transitions which are close in energy, but the angular momentum rule I mentioned above tends to overpower this.",
"So in your example with the n = 6 to n = 1, it depends on ",
" orbitals in the n = 6 and n = 1 shells you're talking about. Between two similar orbitals, you're more likely to get a direct transition. Between two states with very different structures, you're more likely to get a cascade of multiple photons before reaching the final state."
] |
[
"Is angular momentum at all related to the type of orbital?",
"Yes, there's the orbital angular momentum quantum number (ℓ) as well as the spin quantum number (1/2) for each electron.",
"These are summed over all electrons to give the total angular momentum (J) of the atom, in a given state.",
"Transitions between different atomic states in general change the J of the atom, and the difference in angular momentum must be carried away by the photon emitted during the decay."
] |
[
"Wow thanks for the great answer! Is angular momentum at all related to the type of orbital? As in, does changing between different orbitals relate to changing angular momentum like you were talking about? If not, what exactly does the angular momentum of an electron mean? Is that the same as electron spin? "
] |
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