title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Can higher animals experience surprise when their environment contradicts their expectations?"
] | [
false
] | null | [
"Absolutely yes. ",
"This is not exactly a peer-reviewed journal citation, but ",
"here's a series of cheap little videos of dogs surprised by their humans \"disappearing\" behind blankets.",
" ",
"Cats exhibit the same behavior, ",
"although maybe not so exuberantly.",
"And this parrot is pretty bedazz... | [
"dogs showed measurable signs of “surprise” (i.e., further searching for Target A) when they found Target B, which did not correspond to the odor of Target A from the trail. We conclude that dogs represent what they smell and search flexibly, which is independent from their educational background. "
] | [
"Good old object permanence. The classic magic trick for humans and other animals.",
"Here is a monkey"
] |
[
"Can I keep pet sharks in my salt water swimming pool?"
] | [
false
] | I'm thinking about building a salt water pool in my backyard...obviously I'm not planning on keeping great whites in there...but is it ridiculous to think that i could keep a couple small reef sharks or lemon sharks (or whatever small, non-threatening breed) in the pool the same way i would keep them in an aquarium? when i googled this question i didn't get too many reliable answers...but some say that the salinity of most salt water pools might not be high enough to support most sharks? are there any shark breeds that could thrive in a low-salinity environment (and that won't murder me when i swim)? if not sharks, are there other fish that might survive in the salinity-level of a typical salt water pool? also, if i feed a shark/fish that lives in the pool and if it's pooping in there, will a normal pool filter be enough to filter the water? thanks in advance for your advice and ridicule!! :) | [
"First, if salt produces chlorine, why hasn't the ocean killed all the fish?",
"My guess is that the oceans do not have massive electronic chlorinators attached to them. "
] | [
"I knew there was a reason that rap artists hadn't beaten me to this idea... :( oh well...thanks for the info!!"
] | [
"In a salt water pool, the salt is used to generate chlorine (via an electronic chlorinator), you need the chlorine to kill bacteria/algae so you can safely swim in it.",
"I doubt sharks or any fish could tolerate the chlorine.",
"A bit of googling reveals this effect of chlorine on fish.",
"\"damages gills,... |
[
"How does the universe expand?"
] | [
false
] | My understanding is that the universe expands by all the objects in the universe moving away from each other. If this is the case, why aren't the atoms in our body also expanding away from each other and ripping us apart? | [
"It seems that space itself is stretching, but it's speed only noticeable at very large distances. The Electromagnetic/Strongforces that hold together atoms overcome this expansion. However, with the advent of Dark Energy, it has been observed the Universe expansion is accelerating, which might indicate a Big Rip l... | [
"I would just like to point out, that a stretching of space-time of the universe will behave exactly like the shrinking of all matter in the universe. Both are an accurate representation of current theory."
] | [
"Just what I was looking for. Thanks."
] |
[
"If lightning starts at the ground how can people be \"struck\" by it?"
] | [
false
] | And a sub question is; Why does it seem to have different branches at the bottom, leading to one strong branch at the top? | [
"This might be helpful for explaining ",
"http://i.imgur.com/8qV7l.gif",
" \nYou can see that the lightning starts at the top. It then ionizes the air around and propagates in every direction (hence the branches). Once any of the branches touches the ground or anything conductive, the remaining charge in the cl... | [
"this is awesome, thanks for that!"
] | [
"Aside from the explanation ",
"/u/AvasyuB",
" provided, it might just be a language remnant from before we knew how lightning worked, exactly. The whole thing happens in well under half a second (not counting the sonic boom of course), so it might just be that people saw storm clouds, noticed that the ground a... |
[
"What if there was more anti matter than matter after the Big Bang? Would we be living in a similar world made of anti matter? Or would there be nothing"
] | [
false
] | null | [
"We don't know precisely when the matter/antimatter asymmetry emerged, but had the universe had an excess of what we call antimatter, then yes, we'd be living in a similar universe, but one made of antimatter. (Of course, probably in that universe, the terminology of what things we call matter and what we call ant... | [
"What do you mean intrinsic advantage? The most common theory is that there are CP violations in the weak force under very specific conditions-- so more matter was created than antimatter during beta decay. Not sure this really counts as an advantage. "
] | [
"Except that antimatter-matter collisions release enormous amounts of gamma radiation that are easily visible across vast distances, and if there were any significant volumes of antimatter in the universe, then gamma ray bursts would be much more common than they are."
] |
[
"Is kinetic energy relative?"
] | [
false
] | I hope this hasn't been asked before, I searched askscience to see if this question had been answered already, but I couldn't find a post that fit entirely to this. Let's say we have to particles p0 and p1. From our observing position, p0 is at rest and p1 is on a collision course with p0, moving at a speed close to the speed of light. If I remember my physics class correctly, this means that from our, and from its own, point of view, p0 has a kinetic energy of 0, while p1 has a non-zero kinetic energy. However, from the point of view of p1, is it the reverse? Is it p1 that has 0 kinetic energy and p0 that has the non-zero value? | [
"You are correct sir. Kinetic energy can be based on any frame of reference. ",
"Source"
] | [
"Kinetic energy is never negative, so the sum of kinetic energies can't be zero unless every single energy is zero, which is clearly not the case.",
"Also, comparing velocities over cosmological distances becomes problematic."
] | [
"Thank you! Does this also imply that the net (kinetic) energy in the universe is zero? Or do I misinterpret the consequences?"
] |
[
"How much \"younger\" than us on Earth did the crew on Apollo 11 get from their travel due to time dilation?"
] | [
false
] | Okay, younger may not be the correct word here, but how much more time passed by here on Earth than it did for them? | [
"The average speed of Apollo 11 was ",
"5500 km/hr",
" = 1528 m/s. At that speed, the effect of relativistic time dilation is 1:1.00000000001298521 s, which over the course of a 73 hour, 27 min flight would be 3.4e-6 seconds. This is a minimum estimate of the relativistic time dilation effect.",
"The maximum ... | [
"So in other words, if their 3 day mission resulted in 0.0000034 seconds of dilation... it would have to be a 2,417 YEAR mission to experience 1 second of time dilation. "
] | [
"So in other words, if their 3 day mission resulted in 0.0000034 seconds of dilation... it would have to be a 2,417 YEAR mission to experience 1 second of time dilation. "
] |
[
"What do sexes in fungus mean?"
] | [
false
] | From the Wikipedia entry on It has 23,328 distinct sexes; individuals of any sex are compatible for mating with all but their own sex. What does that mean? | [
"Just different ones. I doubt anybody took the time to name 23,000 sexes."
] | [
"Fungi \"sex\" is way different than genders like we think of in eukaryotes. The example you're thinking of is one of the most extreme - the vast majority of fungi have 2 or 4 sexes. It's different in that fungi just need a different mate - any of the sexes can \"get pregnant\", aka make a mushroom, and either can ... | [
"Just like with humans, you need different sexes to make offsping. Two men can't do it, two women can't do it. With the fungi, you still need two different sexes to make a baby, you just have more to choose from. a+ b = offspring, b + c = offspring, but a + a = nothing."
] |
[
"How does the Fourier Transform actually 'work'?"
] | [
false
] | I've covered the Fourier Transform in maths so I know the formula and what it does but its coming up again as part of my chemistry course (2nd year undergrad) when used in NMR and I'm having a hard time trying to figure out it converts from time space to frequency space. Has anyone got an explanation of how the integral 'picks out' which frequencies are present in the wave? | [
"The Fourier transform multiplies all values of a sine wave with a given frequency with your signal. If their values often correlate (your signal is above zero when the wave is above zero etc), you get a higher value / contribution for that frequency. If that frequency does not correlate well with your signal, it w... | [
"Here's a handwavey but very useful way to understand it. Let's take two sine waves with frequencies k1 and k2: sin(k1 t) and sin(k2 t). Each of them alternates between positive and negative, so when we multiply them",
"sin(k1 t ) * sin(k2 t)\n",
"the product is positive half the time (when the signs are both... | [
"The Fourier transform is just a ",
"cross-correlation",
" with every possible (complex) sine wave!",
"Say you want to know the magnitude of the 10Hz component of a signal. You can do this by finding the value of the Fourier transform at f=10Hz. What this is really doing is multiplying the signal by a 10Hz si... |
[
"What does defragmenting do to your hdd?"
] | [
false
] | Also what does trimming do to your ssd ? | [
"I will take a stab at defragging.",
"Imagine I have 10000 storage spots in a storage lot each in groups of 100. So basically 100 rows each labeled 1-100 in what ever row they are in. Those will be labeled 1-100 as well.",
"I need a way to help my customers store stuff as conveniently as possible. So ideally my... | [
"The purpose of SSD TRIM is to aid in wear levelling. Each cell in an SSD has a lifespan measured in rewrites. Every time you update something on a cell in an SSD, it has to rewrite that cell, which brings that cell closer to its death.",
"Every SSD out there does wear levelling. It knows how many times each cell... | [
"This helped greatly, thanks, I'm pretty sure I understand what your saying. "
] |
[
"Is the water at the bottom of the Mariana Trench just as salty as the water at the surface?"
] | [
false
] | null | [
"Luckily, someone has done a CTD (conductivity-temperature-depth) cast into the Marianas Trench down to 7 meters above the sea floor. ",
"http://link.springer.com/article/10.1007/s10872-005-0053-z",
"There is a paywall for this article but the abstract tells you what you'd like to know. Looks like salinity doe... | [
"Wouldn't saltier water be heavier, and therefore -in theory- sink to the bottom? Like a halocline. Of course in practice currents would change this but I can imagine a diffence of a few ppm?"
] | [
"Short answer: yes. \nThere is a concept in chemical oceanography called \"conservative elements\". Included in these are the majors salt ions that make the ocean \"salty\". The concentrations of these ions are practically the same everywhere in the ocean, given there is no freshwater input, etc. ",
"For more, se... |
[
"If a student is ill-prepared for a difficult memorization test, is it better to be awake all night and go over the material one more time or get a good night's sleep?"
] | [
false
] | null | [
"Sleep has been proven to help sort and remember information, so getting a good night's sleep is beneficial. Obviously, the student would have to know the information in the first place to perform well. Contrary to popular belief, knowledge osmosis does not occur when sleeping on an open text book.",
"article: ... | [
"Honestly, neither. Long term memory is not a function of just information acquisition, but more importantly reinforcement. This is why professors encourage their students to study over the course of the entire semester instead of just cramming at the last minute. With reinforcement your brain's normal neural pr... | [
"All night cram session for sure."
] |
[
"What form of radiation is given off by nuclear waste?"
] | [
false
] | I've been doing a bit of research on the subject, and all I've been able to find is that the radiation is extremely dangerous/potentially fatal, nothing about what form of energy the radiation actually is. I'm assuming that it is one or more of the higher-energy spectra, such as x-rays or gamma rays, but I'm not sure. Thanks in advance! | [
"Nuclear waste pretty much gives off all forms of radiation...alpha, beta, and gamma rays, neutrons, protons, and larger high energy nuclei.",
"It also gives off radioactive isotopes of iodine, strontium and cesium, that can accumulate in your body and give off radiation internally. "
] | [
"Alpha, beta, and gamma."
] | [
"Neutron as well. "
] |
[
"Biologically, how does pedophilia even make sense?"
] | [
false
] | [deleted] | [
"Although what causes pedophilia is not yet known, beginning in 2002, researchers began reporting a series of findings linking pedophilia with brain structure and function: Pedophilic (and hebephilic) men have lower IQs, poorer scores on memory tests, greater rates of non-right-handedness, greater rates of school g... | [
"All kinds of things don't make sense. Biological systems are cludged together from parts that were designed for something else. Add culture on top? And it's a quagmire of things that don't always have a purpose or function.",
"As an example, why do men have nipples? Answer: Because males and females are developm... | [
"Damn, so I'm probably stupid as well as fucked up. I'm one of the good ones though, so maybe the real stupidity is in acting on it. At least I have totally normal heterosexual desires on top of that to play with. I don't feel ",
" about it any more, that wouldn't make sense, but I did nearly kill myself when I w... |
[
"If matter is made of atoms, and atoms can be split into sub-atomic particles, what are sub-atomic particles if not matter?"
] | [
false
] | I have a pretty elementary knowledge of atomic structure and know that atoms can be broken apart into sub-atomic particles. I am working from the understanding that atom are the smallest particles of matter. So this is where I get lost, what are sub-atomic particles considered if not matter? | [
"I am working from the understanding that atom are the smallest particles of matter.",
"This is confusing you because it's not true. Your intuition that subatomic particles would also be considered matter is correct."
] | [
"Atoms are not actually \"atomic\" in the sense that they are the indivisible units of matter. Atoms are composed of hadrons (e.g. neutrons, protons) and leptons (e.g. electrons.) Leptons can be said to be \"atomic\" in the indivisible sense, but hadrons are not. Hadrons are composed of quarks, which to the best o... | [
"Perhaps I should have said \"could be considered matter.\" You're right, there is no universally accepted definition of \"matter,\" but, for one, fermions are often considered matter (as they have mass and are the basic building block of matter) despite the fact that they're subatomic.",
"It comes down to semant... |
[
"I'm watching Star Trek: First Contact and it got me thinking about FTL travel. Obviously we won't have FTL by the year 2063 but is there any legitimate research being done in the field, is it even considered a legitimate possibility?"
] | [
false
] | null | [
"Antimatter has positive mass. The charge is opposite what it would be for its counter particle though."
] | [
"Antimatter has positive mass. The charge is opposite what it would be for its counter particle though."
] | [
"Things like wormholes and wrap drives (alcubierre drive) are valid solutions to the Einstein field equations, but for them to exist requires the presence of some sort of exotic matter that has negative mass. We have no evidence to suggest that such a thing exists."
] |
[
"Is it possible for a neutron star to appear as a black hole?"
] | [
false
] | Hello. Similar questions might have been already asked, but I can't find the exact question I'm wondering about. So the theoretical max mass for a neutron star is around 3 suns, otherwise it "becomes a black hole". I also found that the escape velocity from a neutron star is typically 200 000 km/s. But is it possible for an object to be both a neutron star and a black hole? Let's imagine a neutron star with an escape velocity of c - 1 km/s. If slightly more matter was added, the escape velocity would be more than c, so it would appear as a black hole, right? However, would it be theoretically possible for it to still be a neutron star "inside" of that black hole, just with no way to escape? | [
"There's an interesting way to answer this and a less interesting way to answer this. I'm going to start with the more interesting one (to me), though. ",
"It actually can be ",
" to tell the difference, observationally, between a black hole and a neutron star that are eating things. And seeing them eat things ... | [
"The escape velocity isn't anything that is actually moving. It's just how fast something ",
" need to go to escape. If that number is above the speed of light, then yes it is impossible for something to reach that - so then nothing escapes. The \"event horizon\" is just the point where the escape velocity is equ... | [
"Thank you very much for this complete answer! It's very clear and absolutely fascinating."
] |
[
"What was the density, and the dimensions, of the cloud of dust & gas that our solar system formed from?"
] | [
false
] | null | [
"Hey, so I'm a PhD student who is studying star formation and this is right up my alley. ",
"So, stars form from roughly ellipsoidal clumps of gas and dust called cores. These cores are roughly spherical, their aspect ratio is low, A ~ 1 - 2. Here is a paper (",
"http://arxiv.org/pdf/1211.2663v2.pdf",
") whic... | [
"Thank you! About to board a flight and I'll look at the cited papers en route. Cool."
] | [
"Around, if I'm not mistaken, 10,000 miles x 20,000 miles, in a loop of course. Think of it like a great, impressive, smart doughnut, right. Constantly spinning, constantly evolving to meet the needs of gravity. Hope that helped :-) source: student in astrophysics doing a lab abt this "
] |
[
"The closest star system to the Sun is 4.3 lightyears away. Is that an anomaly, or are most star systems about 4 lightyears from their nearest neighbor in this neck of the woods?"
] | [
false
] | Or, to put it another way: On average, how close are stars to one another in this neighborhood of the Milky Way? | [
"In the solar neighborhood, the stellar density is about one star per cubic parsec (one parsec is 3.26 light-years.)"
] | [
"Nice! \"",
"Stellar density",
"\" That's the phrase I was looking for. ",
"Does that take into account multiple stars in a star system (ie - Alpha Centauri A, B and Proxima)? What's the typical variance in distance between stars (standard deviation)? ",
"Thanks!"
] | [
"I don't have numbers for you, but ",
"here",
" is a list of the distances to the nearest stars, and ",
"here",
" is a plot showing where you are so you can get a sense of the average distance between them. Looks like most of them have a closest star within 5 light years or so."
] |
[
"Why is gravity such a weak force?"
] | [
false
] | I mean compared to other forces of nature. | [
"This is just the mathematical formulation of that weakness, this doesn't show ",
" it's weak, just ",
" weak it is."
] | [
"This is just the mathematical formulation of that weakness, this doesn't show ",
" it's weak, just ",
" weak it is."
] | [
"The real answer to this is: no one knows. This is one of the biggest mysteries of physics today, something shown by the fact that the best accepted theory today about the workings of nature's forces, the Standard Model, doesn't include gravity",
"One of the explanations, although I don't remember which theory do... |
[
"This is a terrible question, but what happens if the penis is superglued so urine can't exit?"
] | [
false
] | I read this on twitter "BBC correspondent in Libya: Gadaffi tortured men by superglueing penises shut so they couldn't pee. Stuff of nightmares and I'm not a man." Ok I need real science, what really happens when they superglue your penis? Do the prisoner die of infection because he can't pee, or the bladder ruptures? How much time does it take? does the urine acidity disolves the superglue? | [
"This is called ",
"urethral stricture",
" or the related urethral blockage. No, the pee doesn't dissolve superglue.",
"Either way, it results in ",
"acute urinary retention",
", where the urine cannot exit the system. The bladder can be damaged and leak, but that usually isn't the CoD. It can rapidly cau... | [
"This actually happened to me less than an hour after giving birth to my son. I had a blockage due to swelling and \"debris\". On top of that, the nurses did not remove my epidural, but my catheter had been removed. So I had an IV drip, no pain, no sensation of having to pee. ",
"The epidural was removed and I re... | [
"Going to add on, from the human organ systems series, \"Renal an integrated approach to Disease\" by Schmitz.\n\"Acute obstruction at the level of the bladder, ureter, or urethra precipitates oliguria/anuria (low or no pee) and acute kidney injury\" (298)... \"Rapid relief of obstruction is crucial to prevent perm... |
[
"Is it possible that dark matter is a bunch of neutrino clusters?"
] | [
false
] | null | [
"It is not generally thought so, due to neutrino's that we know of being too \"hot\" or fast moving. If dark matter were neutrino's they would not reproduce the velocity curves around galaxies. No neutrino ever seen has less than the escape velocity of the galaxy, something that is required by dark matter.",
"D... | [
"This is pretty informative, but neutrino flavour change implies mass not because \"massless particles don't experience time\" but because it's required that the flavours states of neutrinos have different masses. (It's actually way more complicated than that but urgh. QFT.) "
] | [
"I'm assuming such neutrinos would be a 3K now, since that's the temperature of the microwave background radiation.",
"Googling tells me the average KE/mole of a gas is 3/2 RT. IIRC, that's for a diatomic gas, and I can't remember enough chemistry to be sure, so I'll just say the average KE for thes thermal neutr... |
[
"What are some of the controversies within the field of evolutionary biology?"
] | [
false
] | I understand the theory of evolution pretty well, however, I received a prompt in my drawing class about drawing something I dislike, but making it look appealing. As such, I decided to go the route of making a drawing about "teaching the controversy" but rather than the evolution vs. creationism thingy (not worthy of being called a debate cause evolution wins by a longshot) I want to make a drawing of some actual controversies within the field being taught. So would anyone care to enlighten me on these disagreements within the field? Edit: Thanks for all the input. That's what I came up with. This is some pretty interesting stuff, I am going to take up the challenge of actually trying to depict the controversial theories soon. | [
"The ",
"neutralist-selectionist debate",
" is a good example.",
"Group selection and multi level selection theory",
" are also extremely controversial at the moment. The majority of the field is sticking with the orthodox ",
"kin selection",
" as the only method via which apparent altruism may evolve. ... | [
"Id like to hear some of the theories for the cambrian explosion..."
] | [
"The Neutralist-selectionist debate blends into the ",
"adaptationism debate",
" (i.e. to what extent does evolution ",
" everything). This is one of the ",
" debates in evolutionary biology over the last 40 years or so.",
"Structuralism vs. Functionalism used to be huge in the 1980s, but seems to have di... |
[
"Does playing an instrument really transfer to other areas of cognitive performance? In other words, does it make you smarter in any way?"
] | [
false
] | null | [
"Follow-Up Question: If playing an instrument increases cognitive performance, does it increase cognitive performance on other tasks more than simply practicing that task?",
"This has been a point of contention between myself and my classmates/teachers for a while. Sure, maybe music makes you better at math, but ... | [
"Anecdotes are not answers!"
] | [
"But studying math won't teach you anything about music once you're past the middle school level."
] |
[
"What symptoms of the virus are the virus and what are the symptoms of the body defending against the virus?"
] | [
false
] | null | [
"The answer to that is as varied as viruses themselves, but some things are consistent.",
"Cough - is usually your body's response to foreign matter, like phlegm, in the throat or lungs",
"Sneezing - the same, but in the nose and upper throat",
"Inflammation - your body flushing an area with fresh blood to at... | [
"I don't think it is a misclassification at all.",
"I shoot you using a gun. Why did you die?",
"Well, you lost blood. How did you lose blood?",
"The gaping hole in your chest. What put the hole there?",
"The bullet that passed through it. What propelled the bullet?",
"Someone fired a gun. Who fired the g... | [
"Awesome answer, thank you!!!!"
] |
[
"A recent news article states that a plasma's temperature, for self-sustaining fusion, needs to be around 100 million C - but the core of the Sun is only around 15 million C. Why does a plasma's temperature need to be so high for fusion to work? And why not for the Sun?"
] | [
false
] | The article in question is here: . I get that the temperature must be high enough to generate a plasma, but to the best of my knowledge plasmas forming in the 10,000 C range. | [
"To get useful power out of it despite these two issues we need a higher temperature and we need a fuel that is much easier to fuse - deuterium plus tritium nuclei instead of protons."
] | [
"A fusion reaction occurs when two atoms collide with enough energy to overcome coulomb repulsion, allowing their nuclei to get close enough to fuse. To sustain a fusion reactor you need to have these reactions occur at a high enough rate. You can increase your reaction rate by increasing the density, so more colli... | [
"I don't really have any sources for general audiences on the subject. Biomedical plasmas weren't exactly my field of research, but it was close enough that a number of conferences I attended had a significant contribution from that field.",
"The most directly useful application is equipment sterilization. Applyi... |
[
"Wouldn't implanting young DNA compatible cells that replicate normally without being targeted by your immune system be the \"cure\" for old age?"
] | [
false
] | null | [
"This may be true if all cells in your body continually divide, but there are important cells (such as almost all your neurons in your nervous system) that are post-mitotic and will accumulate DNA damage over time."
] | [
"What about it are you not sure about? There are, without a shred of doubt, cells that stop dividing in your body. If this is what you're unsure about, just google \"postmitotic neuron\" and you'll see a huge list of published articles.",
"If it's about DNA damage in the postmitotic neuron with respect to aging, ... | [
"What about it are you not sure about? There are, without a shred of doubt, cells that stop dividing in your body. If this is what you're unsure about, just google \"postmitotic neuron\" and you'll see a huge list of published articles.",
"If it's about DNA damage in the postmitotic neuron with respect to aging, ... |
[
"If A and B are traveling in opposite directions at 0.51 c, does B appear to A as traveling faster than the speed of light?"
] | [
false
] | null | [
"No, velocities don't add trivially, they add such that the speed of light is the same in all reference frames, according to the ",
"velocity addition formula",
". In this case they appear to be going about 81% the speed of light."
] | [
"Interestingly enough, something like their speed -- their ",
" -- adds. Special relativity unifies the concepts of ",
" (through space) and ",
" (in spacetime). That is the hard part to grasp -- and about this time of year we get dozens of questions about special relativity as a new crop of students get ex... | [
"The laser would be fired from a zero velocity reference point, as without mass, it wouldn't have the momentum going the other way. The laser would travel at c, so would catch and hit 0.51c "
] |
[
"How do headphones actually work?"
] | [
false
] | I don't really understand how all the sound can be transferred through wires and played like you are at the concert, just through a tiny ear piece. Obviously there aren't tiny instruments playing inside the pieces, so how does the sound go through/play through such a tiny device? | [
"Sound is composed of a time-varying pressure in the air. Your eardrums transmit vibrations from the pressure changes into your inner ear, where it is sent to your brain to be interpreted as noise, or music, or whatever.",
"Most speakers replicate this change in pressure by driving a speaker cone with a magnet a... | [
"Inside the earphones are magnets and loops of wire. The magnet is attached to a thin membrane which can be pushed around. As an electrical signal passes through the loops of wire, the magnet gets pushed in and out, making the membrane move in and out. This causes pressure waves that we hear as music. This is t... | [
"Headphones have speakers in them, like any other stereo system; they're just small. Are you asking how speakers work?"
] |
[
"What causes lightning to strike in directions other than cloud to ground?"
] | [
false
] | [deleted] | [
"Electricity is always trying to find a path to an area with less resistance and less of a charge. A surprisingly large amount of lightning is Earth to sky/cloud."
] | [
"Charge can be positive or negative, so I can't see why lightning would only stick to one direction. The atmosphere can either have more or less charge than the Earth."
] | [
"Charge can be positive or negative, so I can't see why lightning would only stick to one direction. The atmosphere can either have more or less charge than the Earth."
] |
[
"Is it possible to have even a rough estimate of how long vaccine-induced immunity will last without prolonged testing to find the full lifecycle of the immunity?"
] | [
false
] | I'm excited for the recent COVID-19 vaccine news and what looks to be distribution of the vaccines in the immediate future. However, I'm wondering if there is any way to know how long immunity from the vaccines will last without having to actually wait out a continued testing period to find out when subjects are once again susceptible to COVID-19. Most talk about the number of available vaccines doesn't really take in to account if or when people will have to be re-vaccinated. Is there any way to know, right now, how long immunity may last? | [
"Nope. Until you wait and see and collect the data, it's all just guesses. ",
"Knowing how long natural immunity remains protective or knowing how long a similar vaccine to a similar virus provided protection might allow the guesses to be more educated, but they would still be just guesses.",
"Even when it co... | [
"Thank you for your reply!"
] | [
"Correction to the above post, I meant the flu vaccines when I mentioned vaccines and no the common cold does not have a vaccine because it is an umbrella term for a set of harmless symptoms that show up in numerous viral infections. Sorry for the confusion."
] |
[
"Is it better in the long term for a car to be \"warmed up\" in cold weather before using it?"
] | [
false
] | If not, at what temperature does warming it up become necessary? This question comes from a friend in Michigan. | [
"Michigan native, automotive engineer (mechanical) and general gearhead here. To expand on what botanist said:",
"Start the engine and give it 30 seconds of running to build oil pressure. It will build faster than that, but it's fine. If your car is covered in snow/ice, take the 5 minutes to get it all off.",
... | [
"For older cars (i.e. mid 1980s and older) it's definitely a good idea because the existing technology for engine ignition and fuel delivery worked best when warm. Nowadays, our cars have such advanced computer and fuel injection monitoring that the car can adapt to cold temperatures much, much better. Our modern... | [
"Yes and no, but I'll focus on newer cars. When you start up your car (after it has been sitting for a while), you'll notice the engine revs above idle and slowly comes down. The reason for this is to heat up your catalytic converters & O2 sensors as quick as possible (also know as a cold start cycle). The premise ... |
[
"Why don't professional athletes suffer from hearing damage due to constantly performing in extremely loud environments?"
] | [
false
] | Pro sporting events are very well documented as being so loud that they cause hearing loss among fans. It seems to me that, above all, the greatest danger would be to the athletes themselves, since they are at the center of attention for every match. Although it might not pose a big problem for sports with less frequent matches, such as NFL players or professional boxers, how is it that players in the NBA or NFL, with 82 game seasons, don't suffer hearing damage? | [
"They cause hearing loss among fans because a fan is standing next to other people being loud. The athletes are very far away in comparison, and the noise level is small in comparison.",
"You can understand this better if you realize that during a game you can stand just outside the venue and carry on a perfectly... | [
"That makes no sense. The reason you can stand outside and carry a normal conversation is because you are not in the direct path of the sound waves and the waves that reach you are weaker. You know all those Stadium loudness records? Those are recorded from the field. Additionally some stadiums (such as Seattle... | [
"That's not entirely true. There are times where players have complained about the noise being so loud they cannot hear each other, certain cities known to be more difficult to play in due to noise, etc. Depending on sport, the players aren't always very far away from the fans. ",
"I'm not sure if there's proper ... |
[
"Besides financing, What is stopping us from chucking the planets garbage into the sun?"
] | [
false
] | null | [
"i am amazed that no one has mentioned that we really don't want to throw stuff away after one use. Many things can be recycled, or composted, or used to produce methane for fuel. Making a program to recycle or reuse >99% of waste would cost far less than blasting in all into the sun. right now the cheapest to get ... | [
"The problem is almost entirely cost. We can shoot stuff into the sun, there's just no reason to. ",
"SpaceX, a commercial space corporation, believes they can get the cost of bringing one pound to orbit down to $500/lb, a ",
" reduction. The cost to send things into the sun would be about double (The delta-v b... | [
"That's the correct answer, really. With the possible exception of nuclear waste, things are ",
" dumped in landfills because no alternative means of disposal exist. A number of countries ban the practice to varying extents, not least for household trash. Things get dumped in landfills because it's a ",
" way o... |
[
"How do speakers produce more than one pitch at once?"
] | [
false
] | The concept of one thing vibrating yet creating multiple sounds makes no sense to me. | [
"The speaker's motion is controlled by the shape of the incoming signal. If ",
"this",
" is an excerpt from the music, then plotting the speaker's position over time should produce a nearly identical graph.",
"The principle in play here is superposition. According to superposition, playing a 1kHz sine wave an... | [
"It you pluck two strings on a guitar, they don't reach you as separate sounds. They reach you as one complex sound, and your brain then sifts through all that to identify the two sounds. ",
"Speakers work the same way: they don't produce two sounds, they produce a single complex sound, and your brain can take th... | [
"This ",
"graphic",
" shows the principle of superposition pretty well. If you want to play two distinct sounds like the first two waveforms, then the speaker will need to move in accordance with the third waveform."
] |
[
"Is it possible to cause water to boil/freeze using exo/endothermic chemical reactions?"
] | [
false
] | null | [
"Yup, in fact this can sometimes be a lab hazard. ",
"For example if you are trying to dissolve something that has a strong exothermic reaction with water (acids and bases being good examples of this) you can inadvertently heat up the water too fast causing it to boil and splatter all over the place. Which of co... | [
"The flameless ration heater, used in the military for its Meals, Ready-to-Eat, uses an exothermic reaction to boil water.",
"https://en.wikipedia.org/wiki/Flameless_ration_heater",
"The MRE heater contains magnesium metal, iron, and table salt. Upon addition of water, the magnesium is oxidized exothermically. ... | [
"Putting a pot of water on top of a fire will probably cause the water to boil, due to energy coming from an exothermic reaction."
] |
[
"How does antimatter work?"
] | [
false
] | [deleted] | [
"What is conserved is not strictly the mass but the total \"budget\" of mass and energy (since they are related).\nSo when matter and antimatter collide they annihilate into a cascade of photons and other pair of particles, created by the usually huge (on the subatomic scale) release of energy."
] | [
"How does antimatter work? Very well thank you very much.",
"But as you have deduced, mass is not conserved. Energy however very much is."
] | [
"Antiparticles",
" are simply particles that are just like normal ones but have certain properties, such as charge, reversed. Every particle has a corresponding antiparticle, but some neutral particles (eg. photons and possibly neutrinos) are their own antiparticles. That simply means that when you do the opera... |
[
"How would artificial gravity on something like a Stanford torus differ from regular gravity on a planet?"
] | [
false
] | You often see depictions of space stations in the future as , or , with gravity being simulated by centrifugal force. How would this differ from gravity on a planet? What would happen if you threw a ball up into the air, would it behave the same way as on Earth? | [
"The only difference I can think of is the gravitational acceleration. If you create a space habitat far smaller than Earth, the difference between the acceleration due to simulated gravity of two vertically-aligned points will be noticeable.",
"Here on Earth, two vertically-aligned points which are 10 meters apa... | [
"In other words, your feet will feel normal, but your head will feel a little bit lighter than usual. How much? It depends on the size of the ring. ",
"For a ring of diameter 1000m, your head would weigh 99.6% as much as normal",
"For diameter 400m, it would weigh 99.0% as much as normal",
"For diameter 100m,... | [
"There will also be Coriolis force effects, as described below. These will be very noticeable in such a small structure (relative to Earth)."
] |
[
"What will happen if a cell expresses proteins belonging to more than 1 cell type?"
] | [
false
] | For example - what if it expressed proteins belonging to both neurons and hepatic cells? Or any combination of cells in | [
"I think your asking about a phenomenon called ",
"ectopic gene expression",
", where a protein is active in a time or place that it normally isn't. Usually, this leads to pretty unhappy cells, but the unique affects it causes can give some insight into the function of a protein. ",
"Cell-types are defined by... | [
"Fun tidbit for you. Cells in the thymus (and elsewhere) have a transcription factor that lets them express proteins from different types of cells all over your body. It's called ",
"AIRE",
" and is crucial in preventing autoimmunity."
] | [
"I don't have a good understanding of how this would work, but i'm sure it does happen. ",
"If you understand that ATP (energy) is required to perform a significant number of the cell's functions, and that others rely on facilitated diffusion, gated channels, receptors, etc, then you can see that the cell might ... |
[
"If the cells in our bodies are only ~5-10 years old, why don't tattoos disappear in 5-10 years?"
] | [
false
] | I've heard bio folks tell me that the cells in our body are only ~5-10 years old because they die and are rejuvinated constantly. If this is the case, then why don't tattoos (which, from what I understand, are ink portraits on existing skin cells) disappear when those skin cells are replaced? | [
"Check out ",
"these past threads",
".",
"The short answer is that cells ",
" replaced every 5-10 years. There are many cells that don't replicate, thus are present since birth. Tattoo ink is injected below the basal layer of your epidermis - the layer that makes new skin - so it's not pushed out by skin tu... | [
"I just needed a cold sponge for my Scooby Doo tattoo."
] | [
"Are there tattooing methods that don't go below the basal layer of skin? "
] |
[
"My friend keeps saying that a teacher told him that the filament of a heat lamp is as hot as the surface of the sun. This is completely incorrect, right?"
] | [
false
] | null | [
"Sunspots can be as low as 3000 Kelvin which is similar to a light bulb.",
"http://en.wikipedia.org/wiki/Sunspot",
"Teach is correct in certain circumstances."
] | [
"The filament of a lamp may be extremely hot, but it seems not as hot as the surface of the sun.",
"Using numbers quickly grabbed from wikipedia, 'The upper temperature limit for the filament is the melting point of the metal. Tungsten is the metal with the highest melting point, 3,695 K (6,191 °F). A 50-hour-lif... | [
"Honestly, even the fact that a filament can reach some significant percentage of the sun's surface temperature is amazing (and \"half\" isn't a bad estimate - 2700K would be a reasonable temperature for a filament while the sun's surface falls just short of 6000K). Unlike most \"misconceptions\" this one is a matt... |
[
"How common is prion resistance/immunity in humans?"
] | [
false
] | I have general anxiety disorder, and recently I have been losing sleep over a prion phobia. So, how common is genetic resistance to prion disorders in humans? Specifically, my family is of southern Chinese background, and I would like to know if prion resistance would be common in a typical southern Chinese genotype. Thank you. | [
"Unless you're genetically related to a particularly small tribe of cannibals from Papua New Guinea, there's a very very low likelihood that you have any sort of immunity or even basic resistance to a prion disease. Not to mention there are multiple types of infectious prions and you would need an adaptation for ea... | [
"Prion disease is also very rare unless you are eating infected meat, fortunately.",
"Expanding on the immunity itself, prion disease immunity seems more conferred by a change in the amink avid structure of the prionogenic proteins themselves in your body which allow them to resist conversion. I don't think that... | [
"The incidence of CJD is about one per million people. It is a very rare disease.",
"And assuming you live in the modern world meat supplies are screened very aggressively for any cases of bovine spongiform encephalopathy.",
"CJD is more or less a disease of age! It's incidence in the young is much lower. Most ... |
[
"From where comes the power that make a magnet continuously levitate above a reversed magnet against the force of gravity?"
] | [
false
] | I mean, how could it fight gravity continuously without expend any energy? | [
"It takes energy to lift a magnet, but it takes no energy to keep it in place while floating. It's as if it were sitting on a table. The table is continuously fighting the gravity without expending any energy.",
"Formally, Energy = Force * Distance, and so even if the Force is great, if there is no Distance over ... | [
"It's useful that OP used the word \"power\" because power is literally the change in energy over time. For a static system, the energy stays the same so nothing has to exert any power."
] | [
"I thought about this and intentionally left it out at first since it does complicate things, even though this is where the confusion probably comes from in the first place. From a human perspective, it expends energy to hold still, but that's because our body isn't just an inanimate object. Muscle cells require en... |
[
"Do birds have different jobs when looking for food?"
] | [
false
] | maybe there’s a better board for this question but i couldn’t find one. today i was sitting outside and two tiny birds were walking around on the ground. the skinnier looking one was walking around looking for food. the other was continuously chirping, ruffling it’s feathers, and following the other bird after it got a certain distance away. it looked like the skinnier bird gave the food to the talking bird when it found food. what in the world was this dynamic?? | [
"It was the parent feeding a fledgling. Yes, the parent looked smaller, but that is what it was. The baby has been fed regularly, making it big. Although it can now fly, it is still relying on the parent to put the food in its mouth. I have often seen that myself. I saw it today actually. It is the time of year for... | [
"Correct, I would just add that fledglings sometimes look bigger than adults because they still have preliminary feathers that are \"fluffy\"."
] | [
"Keep in mind with birds that fluffiness can be different than size. Birds have different modes they can be in - fluffy and grooming is generally a relaxed/safe feeling bird. That same bird can look much skinnier when in ready-to-fly or stressed mode. So these two birds may have been much more similarly sized than ... |
[
"How High Can Bugs Fly?"
] | [
false
] | Can a Dragonfly fly 1km up in the air? Is there a maximum to how high they can go? If so, why? Does this change from mosquito to bee to dragonfly? | [
"On purpose? The air has to be warm enough for them to function, and dense enough for them to generate lift. For most insects this seems to top off at 5-6k feet. ",
"You do find insects much higher, though, but those buggers are usually kidnapped by wind. I read a paper saying some flies and butterflies were seen... | [
"some flies and butterflies were seen at nearly 20k feet",
"So nearly 4x their normal range? Sheesh.",
"Imagine jumping in the air and the wind picks you up an extra 10 feet."
] | [
"I’d imagine it’s more like hang gliding at 1000 feet and the wind one day takes you up to 4000 feet in one big gust."
] |
[
"Why does gravitational potential energy go up with distance in the equation U=mgh, but down with distance in the equation U=GMm/r?"
] | [
false
] | I understand the first equation is a "local approximation" in cases where the distance is small and the force of gravity can be taken as a constant. But I can't wrap my head around why, in one case an increase in distance makes it go up, but in the other case down. How does simplifying the equation turn something that was inversely proportional to something that is directly proportional?? | [
"U=-GMm/r :)"
] | [
"I believe you're missing a negative sign, U=-GMm/r where U=0 at r = inf. You can notice that as r increases the so will U (it gets less negative). "
] | [
"Ah! Oops! Good! That answers my original question!",
"New question: What does it mean for potential energy to be negative? Is that just the convention that was decided upon, or is there a fundamental reason it's defined as a negative?"
] |
[
"Does it make any difference in the children if a man were to impregnate a woman while he was in good shape, versus if he was overweight/obese?"
] | [
false
] | null | [
"The standard dogma would have been \"no\" just a few years ago, but epigenetics has upended that. Epigenetics is (roughly) a means of nongenetic inheritance in which there can be permanent activation or deactivation of certain genes in the sperm (or eggs) - so that, while all the DNA is technically still there, th... | [
"Yes. That's exactly why their effects last multiple generations. But I should have clarified that for mother -> offspring effects in mammals and in birds, there are other mechanisms of epigenetic effects that can occur w/o affecting gametes, or that occur later in fetal life. Via fetal environment or via egg-yolk ... | [
"Yes. That's exactly why their effects last multiple generations. But I should have clarified that for mother -> offspring effects in mammals and in birds, there are other mechanisms of epigenetic effects that can occur w/o affecting gametes, or that occur later in fetal life. Via fetal environment or via egg-yolk ... |
[
"Why can't a carcinogen that causes cancer on one site be assumed to cause cancer at another site?"
] | [
false
] | OK, so, for example, if we know TCDD causes cancer in lung epithelial cells or mammary epithelial cells, why can't we assume that it can cause cancer in epithelial cells in the stomach or salivary gland? Or can we? Is the limiting factor the ability of the carcinogen to GET to the site? Or is there something more (i.e. expression of different genes for similar cells in different locations? BONUS EPIDEMIOLOGY QUESTION: For a lot of the rarer cancers, is it very difficult to rely on research since subjects are so rare? I mean, can we rely on epidemiological studies with the very rare cancers, as the incidence is so low that it greatly diminishes available data? | [
"Carcinogens will usually cause cancer in any tissue they come in contact with so long as the carcinogen can enter or otherwise affect the cell. Usually carcinogens that only cause one type of cancer (like the various junk in cigarette smoke and lung cancer) do so because one type of tissue is exposed more than ano... | [
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3154583/",
" ",
"There is a fair amount of evidence that dioxins as a whole are kind of overblown as a health risk (at least for humans). There's some rather interesting history behind it, but a lot it boils down to the fact that the lab animals used were extremely ... | [
"OK, thank you!",
"Also TCDD is no longer believed to be a potent carcinogen, ",
"Wait, what? Do you have a source for this?!"
] |
[
"Is it possible to measure calories burned by heat output? (temperature of a room)"
] | [
false
] | I ask this question because i work out in a pretty small room, and just from doing an hour of cardio, the temperature of the room rises sometimes up to 8 degrees Fahrenheit. (maybe more, I've only actually tested this a few times) If it were possible to have a completely insulated room that lets no heat in or out, could you technically measure calories burned just by carefully monitoring the temperature of the room? | [
"Theoretically, yes. In practice I think it would be difficult to build a room that was well-insulated enough to get an accurate number."
] | [
"Theoretically, yes, you would essentially be in a giant ",
"calorimeter",
". Maybe not in the nutritional / food sense of calories, but you could measure the heat of the reactions occurring. You would just need a lot of time for equilibrium to happen. "
] | [
"so can I use the information I have to ballpark calories burned? Its colder outside than inside, and no heat in that room, so i think other factors are really not that important.",
"For example:\nThe room is 8ftx8ftx8ft\nThe temp is increased from 72 to 78 degrees.",
"Could i actually figure this out somehow?... |
[
"Why is the hair not growing anymore?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] | [
"Not sure if it is an isolated event. If you think it will invite unconstructive speculation, I am fine with it getting rejected. The question is genuine though. Thanks."
] | [
"Perhaps you can rephrase and post a more general question: \"Does hair growth rate change over the course of our lifespan, and, if so, why?\" "
] |
[
"A question regarding the event horizons of super massive black holes."
] | [
false
] | The news of the largest black hole yet discovered, NCG 1277, with an estimated diameter of 4 light days, reminded me of something I've wondered about for a long time. With SMBHs, I understand that the tidal forces at the event horizon can be quite low (negligible?). With a black hole the size of NCG 1277, would it be possible for a hypothetical space craft, orbiting at a "safe" distance from the event horizon, to deploy a probe at the end of a tether across the event horizon that would record data locally, and then reel it back across the horizon to the space craft? If so, would data captured by the probe be useful in any way? Is this a series of stupid questions? Why or why not? | [
"Ah, right. The mistake here is thinking in terms of escape velocity - if it were just a case of the escape velocity exceeding lightspeed, you could indeed escape via constant propulsion without every reaching that speed. However, this understanding of black holes is actually quite wrong, and the event horizon is t... | [
"So if I'm understanding you correctly, it's the geodesic of space time itself that prevents the probe from being tugged back across the event horizon? Jesus, I find this so hard to wrap my head around. I'm trying to imagine how these phenomena would physically manifest themselves... that is, how the components of ... | [
"It is very weird. Let me try to describe what would happen if you tried it (real scientists, please correct me if I get any of this wrong),",
"From your point of view on the spaceship, you press the button to lower the probe on its tether toward the event horizon. Say you've calculated that it will take 10 secon... |
[
"When photons become red-shifted because of the universe's expansion, where does the photon's energy go?"
] | [
false
] | null | [
"I love this question, it shows great physics-type reasoning. Even though it's covered in other places, I will give it a shot at a different take on it.",
"The answer is that you shouldn't expect conservation of energy to hold when you change reference frames. If you are holding a baseball in your hand, and I ask... | [
"Just a small correction in your formula: the kinetic energy of the baseball would be (mass of the baseball * speed of the car squared)/2, or 1/2 mv",
".",
"Cheers."
] | [
"So spatial expansion makes our universe an accelerating frame?"
] |
[
"Is it better to exercise before breakfast or after?"
] | [
false
] | Every study I read seems to contradict the other. So I'm turing to the Reddit Hive Mind. So, our livers produces glucose at night and stops when we have breakfast, right? So it makes senses to have eat as soon as we wake up. But exercise increases the permeability of our cells to glucose, so you have lower sugar in your blood for some time after exercising. What does this mean?!?! And then there's the The Journal of Physiology study that showed men who ate breakfast before exercising gained weight as they had become more insulin-resistant and were storing a greater amount of fat in their muscles. However, Deighton et al., seem to contradict this in their which suggested exercise is no effective when performed before or after breakfast. Reddit, please help. Do I have my Shreddies before or after the gym? | [
"Your liver stores glycogen mostly from fructose sugar, carries around a few hundred grams or so. Muscles store glycogen mostly from glucose sugar, and the amount they store depends on how much muscle mass you have.",
"So, our livers produces glucose at night and stops when we have breakfast, right?",
"Yes but ... | [
"If there is no definitive answer, maybe it doesn't actually matter."
] | [
"As you've noted, the answer is really \"there is no definitive answer.\" For what it's worth in reference to previous answers, you can't simply look at plasma glucose levels, since your skeletal muscle doesn't run exclusively on it. Skeletal muscle and hepatocyes (liver cells) are GREAT at storing glucose intracel... |
[
"How does Reynolds number correlate with the resistance coefficient?"
] | [
false
] | For example in a pipe bend. I can't seem to find any clear explanation on this matter. | [
"It's a nondimensional parameter that you can get in fluid equations from doing dimensional analysis or from the Buckingham Pi Theorem. There isn't an \"application\" for the number per say, but it has tremendous use in analyzing varying flow regimes in an elegant and descriptive way.",
"The advantage of it is th... | [
"Thank you so much for answering. "
] | [
"I'm wondering whether a high Reynolds number would generally correlate with a higher K value than a lower Reynolds number? "
] |
[
"Why does putting scotch tape on a frosted glass make it see through?"
] | [
false
] | [deleted] | [
"Layman's explanation - and a bad one - but I imagine that in some cases it acts the same as, say, covering paint with wax or a clearcoat. ",
"It fills in the \"scratches\" (or in this case, pits) and thereby produces transparency."
] | [
"Answered here: ",
"http://www.reddit.com/r/science/comments/93d3z/hey_reddit_i_noticed_at_work_today_putting_a/c0ba9zu"
] | [
"It depends on the glass. Some is frosted on both sides, some only on one."
] |
[
"If the average personal computer today is compared to a supercomputer from some time ago, at what year have their performance intersected?"
] | [
false
] | For example, purely hypothetical, does the average PC today even come close to supercomputers back in 1990s? | [
"Yes, but the details depend on your metric.",
"Supercomputers generally have hardware dedicated to a specific function, where PC's are more general purpose.",
"The first teraflop (trillion floating point operation per second)",
"Supercomputer: ASCI red, 1997",
"GPU: (3870x2), 2008",
"Desktop CPU: i9 what... | [
"agreed. FLOPS is one metric, but defining performance really depends on what problem you want to solve. One key to understanding this is ",
"https://en.wikipedia.org/wiki/Amdahl%27s_law",
". Some problems, like fluid dynamics, finite element analysis and similar simulations can be broken down into segments ... | [
"They haven't, in a single year.",
"It all depends on the application. By all metrics, all PCs today outperform systems for the same applications as 30 years ago.",
"There are also multiple metrics you can use. Pure processing power? Electricity consumption? Thermal output?"
] |
[
"When I am looking at the Milky Way, am I looking towards the black hole, or rather at the next outboard spiral arm?"
] | [
false
] | Been trying to get this answered for some time. | [
"Depends on where you're looking, Sagittarius is where the the galactic center is, while looking at Gemini is looking away from the center."
] | [
"It can be either, but the \"familiar image\" of the Milky Way (such as this: ",
"http://upload.wikimedia.org/wikipedia/commons/4/43/ESO-VLT-Laser-phot-33a-07.jpg",
" ) is towards the center of the galaxy. "
] | [
"Depends which direction you're looking. If you look in the direction of the constellation Sagittarius (slightly below the celestial equator, up in the northern hemisphere summer), you're looking toward the center of the galaxy, but you can't see it because of all the dust lanes in the disk of the galaxy.",
"If y... |
[
"Would it be physically possible to see the Apollo landing sites in recognizable detail with an Earth-based telescope? If so, what magnification would be required?"
] | [
false
] | I imagine the atmosphere would make it difficult to make out very small lunar surface objects, but would the atmopshere make it to see objects like the Apollo landing site? | [
"No, it's not possible. Under normal conditions, atmospheric turbulence means you can't resolve details with an angular size smaller than about 1 ",
"arcsecond",
", depending on conditions in the upper atmosphere. Sophisticated ",
"adaptive optics",
" can reduce this to around 0.05 arcseconds, comparable to... | [
"Whilst we cannot 'see' the Apollo landing sites on the moon from Earth, we can bounce laser light off corner reflectors positioned by Apollo astronauts on the lunar surface. By measuring the round trip time, we can accurately calculate the Earth-moon distance. For more info: ",
"http://science.nasa.gov/science-n... | [
"As ",
"/u/teraflop",
" said, it's impossible to resolve detail like that from Earth, but the Apollo landing sites have been repeatedly photographed by the ",
"Lunar Reconaissance Orbiter",
"."
] |
[
"Coriolis Force: Why don't we see its effects in hanging things?"
] | [
false
] | null | [
"The Coriolis force doesn’t govern the flow in toilets.",
"Anyway, the Coriolis force is proportional to the velocity of the object in the frame co-rotating with the Earth. If the object is not moving, the Coriolis force is zero. So objects which are hanging still don’t have any Coriolis force on them.",
"Hangi... | [
"=)",
"I thought that toilets flushing clockwise or anti clockwise had something to do with this force."
] | [
"Somebody else ",
"asked about this",
" a few days ago."
] |
[
"Are there Soviet Venera landers still intact, or even recognizable as Earth artifacts?"
] | [
false
] | Obviously we cannot send anyone to Venus' surface to check on their status. I was wondering if the good folks of this subreddit could put their minds together and try to extrapolate what the surface conditions of Venus have done to those landers in the decades since their respective missions. How long might it take for Venus' surface conditions to, for lack of a better term, degrade them out of existence? | [
"but the acid concentration is very small.",
"It's not just small, it's essentially zero. Repeating my comment further down:",
"The surface temperatures are much too high to allow droplets to stay in liquid form, resulting in ",
"virga",
", precipitation that evaporates well before ever hitting the ground. ... | [
"but the acid concentration is very small.",
"It's not just small, it's essentially zero. Repeating my comment further down:",
"The surface temperatures are much too high to allow droplets to stay in liquid form, resulting in ",
"virga",
", precipitation that evaporates well before ever hitting the ground. ... | [
"Wait, you don't need a magnetic field for a sustainable atmosphere?",
"Nope, and this is probably the most common planetary atmosphere myth I encounter.",
"After all, the atmosphere of Venus manages to survive just fine without the planet generating a magnetic field. (Yes, there is an incredibly weak magnetic ... |
[
"When there is an eclipse, why does the earth not become cold for that period?"
] | [
false
] | null | [
"I think you have a bad idea of what an eclipse looks like. The shadow of the moon only covers a small portion of the earth. That's why you can't see an eclipse from everywhere on Earth. ",
"Here is a representation of what it would look like from the international space station.",
"However there is in fact a l... | [
"Yes about the temperature drop.",
"It is pretty strange to have it get cold and all the birds start tweeting like it is dawn."
] | [
"Dogs start freaking out too and it does get noticeably colder in the shadow, it's basically like when a cloud hides the Sun."
] |
[
"What are two compounds that are surprisingly similar structurally but different reactively?"
] | [
false
] | I was thinking something crazy like sugar and cocaine. | [
"Thalidomide. Exact same chemical formula but it exists in two different \"geometries\" (chemistry term is enantiomers). One enantiomer helps alleviate morning sickness in pregnant women while the other causes birth defects in children. ",
"http://www.chem.yale.edu/~chem125/125/thalidomide/thalidomide.html",
... | [
"Ethanol and methanol. If you chop off a -CH3 you go from drunk to blind.",
"I was thinking something crazy like sugar and cocaine.",
"Was that intended as an example? The two aren't all that structurally similar."
] | [
"MTPT",
" and ",
"MPPP",
" (desmethylprodine) are two. Actually, MTPT is a potential byproduct and is the core of MPPP, which is an opiate like designer drug. The story behind the mixup is pretty tragic, an intrepid makers wanted to make the recreational drug and wound up making MTPT, which is processes to MT... |
[
"If you are unconscious/deeply asleep and wake up to a strong smell, are you already more accustomed to it? Or do you need to be awake to become accustomed to it?"
] | [
false
] | I understand that smell is one of the senses that is "hardwired" to the subconscious, but I have always wondered how this would relate to sleep. Can a smell wake you up the way another sense can? (Aside from the extremes like smelling salts.) Does the "getting used to" a smell happen at a sensory level or a conscious level? | [
"It is not true that humans \"cannot smell\" during sleep, but ",
"olfactory perception is greatly diminished during sleep",
". The result is that it is far more difficult (but not impossible) to wake someone up with a potent odor than, say, a loud alarm. However, some olfactory processing still exists during s... | [
"Your olfactory cilia (the cells that detect odour chemicals) fire in response to the binding of odourants, however this firing diminishes with time due to a process called desensitization which all other sensory modalities use (hence why you don't feel your clothes after you've put them on or see the blood vessels... | [
"That's exactly what I was looking for. Thanks!"
] |
[
"Do dogs eventually recognize themselves in mirrors, or do they just get used to having another \"dog\" around?"
] | [
false
] | When I first brought my dog home he went nuts barking at the mirror, but after a couple days he stopped barking and even looking at the mirror. I would try to get him to look, but he would turn away. edit: expanded my description | [
"With birds the usual test is to put something on the bird like a brightly colored sticker which the bird can't see unless it looks at itself in the mirror. If the bird tries to remove the sticker from itself after looking in the mirror, one can assume that the bird is aware that the image in the mirror is an refle... | [
"BA - Anthropology, UIUC [non-expert, but decent underlying knowledge anyway] Non-human primates have shown differing levels of ability to become aware of the self in a mirror reflection. Apes pick up on it rather quickly. Lemurs, on the other hand, show an (almost?) complete inability to recognize the self. Some d... | [
"BS - Cognitive Science here. Wikipedia does a decent job of covering the ",
"Mirror Test",
". So far the only known species to pass the mirror test, as far as we can tell, are Great Apes, Bottlenose Dolphins, Magpies (part of the family of birds known as Corvidae, which tend to have the same brain-to-body-ma... |
[
"What happened to El Nino/ La Nina weather events, and how are these affected by global warming?"
] | [
false
] | I used to recall discussions of El Nino or La Nina on the weather channel. But I haven't heard about them in a while. Our province is going through a 180 degree shift in weather pattern over last year. I'm curious if it's caused by one of those weather events. | [
"El Nino, often also called the \"El-Nino Southern Oscillation\", in short ENSO, is a phenomenon that occurs every few years. So it doesn't occur every year. It always occurs around Christmas, hence the name which can be translated as \"the christ child\". One way to characterize the strength of the ENSO is using t... | [
"TL;DR; La Nina is the opposite of El Nino. During El Nino events warm water from the western Pacific sloshes towards the eastern pacific, strongly warming the surface water there. During La Nina events there is strong upwelling of cold deep ocean water at the South American coast, reducing the surface waater tempe... | [
"Thank you! Is la Nina the same thing? Or is it a complimentary weather event?"
] |
[
"Does the discovery of gravitational waves mean that eventually we will be able to detect and map dark matter as gravity is the only evidence of its existance?"
] | [
false
] | [deleted] | [
"First, we can already use the paths of light and motions of objects in space to map out dark matter.",
"But will gravitational waves let us do more? From what we know of dark matter, it seems unlikely that this will help us, at least for some time. To be detectable, we need gravitational waves produced from so... | [
"Low energy is putting it mildly. The LIGO mirrors are 2.5 miles apart and the gravity waves detected changed that distance by approximately one ten thousandth the diameter of a proton."
] | [
"The measurement was so precise that the laser would only deviate from its intended path by the width of a human hair over three light years. What we detected, that insanely tiny perturbation, came from rotating / colliding black holes many tens of times more massive than our sun, that released more energy than the... |
[
"Questions about evolution and civilization"
] | [
false
] | This is a very very broad question, with a lot of variables, but I will try and be as succinct as possible. Regarding evolution, we as humans evolved in a physical sense from apes, and were able to populate and spread effectively enough that we set up civilization, in order to divide the necessary tasks to continue our survival amongst the most people possible. This single change, and the ramifications of it, I postulate led to a selective slowing of our physical evolution. Traits such as body size, ability to defeat predators or gather food became less important to our survival. I have heard some say that civilization has actually slowed or stopped evolution completely. I disagree fully. I believe at the point when societies began forming, our evolution itself . We began to evolve, not in a physical sense, but in a social sense. The traits that were more desirable were now social standing, money (an artificial construct made by society) and intellect (hopefully). This brings me to my question: our bodies evolved physically to be best able to handle our environment, but how did the shift to social evolution affect us? I believe that a majority of mental disorders can be attributed to this shift. Our brains were not physically made to handle the types of stress/ anxiety that is placed on it by a society. The rewiring of circuits (specifically the anxiety/emotional areas) to be able to handle the current stresses has led to them misfiring. So, yes, we are now seeing more mental health issues. I believe this is due to us being more aware of the possibilities of these diseases now than in the past, but it doesn't change the fact that there is such a high prevalence of mental disorders (specifically related to people interacting with society i.e. autism, GAD or depression) in our entire species. Is this due to this rewiring? This would attribute our mental issues to a lack of ability of our brain circuits to function properly in society. It could also provide a mechanism to understand the etiology of these diseases on a broader basis. If no two people's brain chemistry is the same, yet society demands them to conform to certain norms and inhibit their desires/actions in order to conform, wouldn't these disorders be able to traced? The best way to explain this would probably be an example: an introvert is forced to interact everyday with people, yet doesn't want to. This could explain an anxiety disorder that developed (social anxiety specifically). Finally, this opens up a final question. Are our actions now driven by this social evolution? I guess the central part to this would be are social activities tied into a "higher" reward system in our brain, or does it simply feed into the typical reward/addiction centers of our brain? My example is smoking: many otherwise intelligent people smoke, despite the enormous amount of evidence to the ill effects of it. While I understand nicotine is addictive, is the social effect smoking has more addictive? Think about it. When you smoke a cigarette at a noisy bar, you get to interact with a select group of people, and probably get to know them better (maybe through a relationship built on being in the "group"). Does this positive social feedback activate the reward centers more than the drug itself? (Also, I am aware that people do not always select mates based on social standing, choosing bigger or bustier mates as a remnant of the previous physical evolution, which fulfills more primal desires in us simply because those traits were deemed desirable earlier than social ones (sadly...see ). But if propagation of the genes is the true goal of evolution, it should be obvious that picking a mate now would be more focused on the financial and time burdens a child would place on it's parents, making a scrawny lawyer a better choice than a buff construction worker.) Fuck it, can't summarize that one. | [
"Normally I would have no problem doing this, especially for an interesting topic such as this. However, there are too many questions per paragraph, and you end up jumping around a lot, so it's a bit difficult to follow. If you want to get better responses limit each paragraph to one question and the elucidation of... | [
"This is a long, messy comment. ",
"spread effectively enough that we set up civilization, in order to divide the necessary tasks to continue our survival amongst the most people possible.",
"I'm not sure what you mean, but I don't think this is why we 'set up' civilization. I think civilization was the by-prod... | [
"What I'm saying is we've moved past the point where our society can be compared to any other species though. ",
"I don't believe this at all. We are primates. I've see the exact same behavior in wild primates that I've seen in humans. It is only our ego that disconnects us.",
"We have not been around for milli... |
[
"When I'm about to fall asleep and hear a noise in the dark, I can see a 'flash' even though my eyes are closed, as if I can see the sound. What causes this?"
] | [
false
] | null | [
"This is a fairly common experience, and falls under the category of a ",
"hypnagogic hallucination",
". Hypnogogia refers to the period when you're transitioning from being awake to being asleep, and experiencing auditory or visual hallucinations is fairly common. While less common, ",
"synesthetic experie... | [
"I don't usually make replies without content, but as the submitter I appreciate your knowledge and the time you took to make a comprehensive answer. Thank you."
] | [
"No problem! As an aside, I, for one, actually prefer when the OP responds/interacts to a post. It helps let me know that either the answer made sense and was what they were looking for, or if they need more information. Anyway, all the best!"
] |
[
"Is it possible for a planet to exist somewhere in our universe which experienced more time due to time-relativity?"
] | [
false
] | Forgive me for the title. I have a difficult time wording this question. My curiosity stems from our understanding that atomic clocks synced with clocks on Earth fall out of sync after being on spacecraft or fast flying aircraft for some time. I began to think how some galaxies may move at different speeds, and some locations in the galaxy may rotate at a faster velocity than other locations in the same galaxy (for example, a location closer to the galactic core might travel at a different relative velocity than a location closer to the galactic edge). This begged the question: could a hypothetical alien race have experienced hundreds or thousands of years more than us due to moving at a faster speed relative to us, or does some law of nature exist that prevents this from happening? | [
"Time dilation is caused by two things.",
"A moving clock appears to run slower than a stationary one\nHowever, if an alien planet was moving quickly relative to us, the same would be true for them; this is not so good for your comparison.",
"The more gravity that a clock experiences, the slower it appears to r... | [
"It all depends on your perspective. If you set your reference point to that hypothetical alien planet then WE are the ones that are thousands of years \"younger\" then them. For relativity to really make a major difference you have to be traveling pretty close to the speed of the light (relatively speaking) and th... | [
"Bear in mind that there are a bunch of caveats about how you would actually measure such a time difference, but essentially: yes, it's ",
", but highly unlikely. Planets just don't really move that fast relative to each other. So any time difference that would exist would probably be more on the order of fractio... |
[
"Universe expansion faster then light. How?"
] | [
false
] | [deleted] | [
"\"While special relativity constrains objects in the universe from moving faster than the speed of light with respect to each other, there is no such theoretical constraint when space itself is expanding. It is thus possible for two very distant objects to be moving away from each other at a speed greater than the... | [
"What do you mean by \"move\"?",
"If you mean \"increase the distance from you to the other point\", then yes. If you mean \"reduce the distance between you and a third point\", then no.",
"You can get further away, but you can never get closer."
] | [
"The main barrier to this is that we have no known way to squeeze spacetime like that. It's more of a 'the maths works!' solution.",
"(I think you probably are thinking of ",
"http://en.wikipedia.org/wiki/Alcubierre_drive",
" , or something very similar)."
] |
[
"Is it possible to change the ambient temperature range at which someone feels comfortable through any method other than acclimatization, such as with drugs or other therapies?"
] | [
false
] | null | [
"That isn't really the same thing, the jacket isolates a separate environment close to the skin that becomes a new ambient temperature."
] | [
"100% yes: put on a jacket"
] | [
"I would like to know the answer to this, as well. My \"thermo-neutral zone\" is tiny, and it would be interesting to try expanding it via internal means. Perhaps a less snarky answer?"
] |
[
"Time is just the 4th dimension used to identify a point in space. So what do people mean by \"space-time\" or \"curved space-time\"?"
] | [
false
] | I understand that they say the universe is 4-dimensional, because you need the x, y, and z coordinates as well as the time to identify a point in space. But what does "space-time" mean or "curved space-time"? | [
"The other answers here are good, but let me just add to them a little bit, because it's very easy to end up imagining the wrong things here.",
"The classic mental model of curved spacetime is a bowling ball on a trampoline. The bowling ball's weight pulls it down toward the ground, which causes the trampoline to... | [
"Mostly correct, except pseudo-Riemannian refers to the fact that spacetime is locally a Minkowski space (a Riemannian space is locally Euclidean)."
] | [
"And Minkowski space is indistinguishable from Euclidean space at low relative velocities. It's limits of approximation all the way down."
] |
[
"This guy in this video spins cups, blows on them, and then they launch up in the air. How does this work?"
] | [
false
] | null | [
"Here's my take: The cups stack quite tightly. Spinning them prevents them from getting jammed and let them slide in and out freely. In addition the spin adds stability when the cup is in the air.",
"The guy blows at the gap between the two cups. The sharp jet of air travels down between the two cups and increase... | [
"It should also be noted that by spinning the cups the friction between the cups is reduced. When objects are touching at rest there is static friction between the two surfaces. When they are touching but in motion with respect to one another there is kinetic friction between the surfaces. Static friction is quite ... | [
"http://thehappyscientist.com/science-video/floating-cups"
] |
[
"A question about action and reaction?"
] | [
false
] | null | [
"Newtons law applies to forces, not events in the sense you are thinking."
] | [
"So would you say that i would be correct in the sense of the decision making process? "
] | [
"Would you mind giving me an example of an action and reaction according to forces? "
] |
[
"How will time be designated once we become an intrasolar or extrasolar species?"
] | [
false
] | Has this been decided yet or are they still trying to figure it out? (since there is no obviously rush on it). For that matter, does anyone even care or think that the obvious obsolescence of this should even be addressed? I'd imagine that it would be in a metric form (10 base number system) and that a second would still be 192,631,770 periods of hyperfine radiation from a cesium-133 atom. However, a 24 hour day would kind of be obsolete, which would deprecate the hour and minute. OK enough speculation on my part :D | [
"My analyst could tell you some stories that would curl your hair."
] | [
"My analyst could tell you some stories that would curl your hair."
] | [
"There is no reason to redefine the second unless people decide to come up with a new system of units.",
"Our bodies are used to a 24 hour day so until that changes there is also no reason to consider it obsolete.",
"If you meant how we will keep track of time and be able to have a common reference, this part w... |
[
"Am I a supertaster or what?"
] | [
false
] | null | [
"You may be a supertaster (your preferences are certainly consistent with it). You can get tested. You can easily get some ",
"Phenylthiocarbamide",
" which tastes bad for supertasters and tastes bland to non-supertasters. Warning: As a supertaster who found out this with minimal warning in an intro psych class... | [
"any explanation as to why phenylthiocarbamide tastes so terrible to supertasters?"
] | [
"We had a speaker at my college about a year ago and I discovered I was a supertaster. The paper she handed out made me gag and I almost threw up while all the people around me looked and me and wondered what the hell is wrong with him....It sounds like you might be a supertaster especially given your preferences. ... |
[
"What is the definition of one second (in terms of time)?"
] | [
false
] | I know that for things like kilograms, there are places worldwide where the measurements are precisely kept, and there are units like the Ampere which is defined in terms of coulombs, and other units. Is there something similar for a second? How is it defined scientifically? | [
"The ",
"Wiki",
" page gives the definition:",
"\"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.\""
] | [
"Well, we had quite a definite notion of what a second was before we could do atomic spectroscopy, so people just took the measurement of the frequency as best they could, then calculated how many periods would fit in what they defined to be the second at that time and subsequently called this number the new defini... | [
"That number seems either extremely specific, or extremely arbitrary. "
] |
[
"Does the gravitational constant change over time?"
] | [
false
] | I was reading an article from the NASA site: The interesting part is here: (3) The universal force of gravity is very stable. Newton's gravitational constant G has changed less than 1 part in 100-billion since the laser experiments began. 1 part in 100-billion is well bellow the error in G. So what does this statement mean? And if G is changing, how did we measure it so accurately? Are any other constants we know of changing? If they are, how much of a change will be needed for someone to notice the change using only our physical senses? | [
"It's possible, but - as that site you linked to has said, in one form - there's no evidence for such a thing having happened. The change in G (or its first derivative) is a separate quantity to G itself, so there's nothing wrong with measuring that to a greater precision than we have (from separate experiments) in... | [
"This doesn't answer your question but it does clear up some confusion in this thread:",
"The attractive force that a particular quantity of matter exerts upon another particular quantity of matter, which is more or less constant regardless of location in the universe, is the universal gravitational constant and ... | [
"No, it's the actual gravitational constant. It's the guy that shows up everywhere from the universal force law F=GmM/r",
" to Einstein's gravitationalf field equations. You're thinking of little g, 9.81 m/s",
" ."
] |
[
"I've only been sexual active for nearly a year and have had 3 miscarriages, 2 natural. Should I be worried?"
] | [
false
] | null | [
"I have an appointment with my doctor next week to talk about the issue. I have also stopped having sex until the issue is resolved. "
] | [
"The issue with miscarriages. I am able to perform safe sex as I'm on the contraceptive pill, which works effectively without the need of a condom. "
] | [
"The issue with miscarriages. I am able to perform safe sex as I'm on the contraceptive pill, which works effectively without the need of a condom.",
"Then why do you keep having miscarriages? If you keep getting pregnant you are not practicing safe sex.",
"What exactly do you think a miscarriage is anyways?"
] |
[
"What genus has lasted on Earth for the longest span of time?"
] | [
false
] | So this is about as general a question as could be, but what genus of life has lasted the longest on Earth? I'm guessing the top record holder would be something microscopic that is found in the fossil record going way back, but I'm also wondering what larger plants or animals have been around the longest. Off the top of my head there are species of Ginko trees found in Cretaceous fossils. Wonder what animal lasted the longest, though. | [
"I'm expecting someone to correct me with something older but if you aren't counting single cellular organisms like cyanobacteria or Methanogens before that, animal wise Nautilus and Jellyfish go back 500 million years.",
"Sharks go back about 450 million years, which makes them older than trees.",
"The earlies... | [
"Most of the groups you mention are much larger than single genera though, and it's very uncommon for a genus to exist for the kind of timescales you mention. For example, it's true that Chondrichthyes first appeared over 400 million years (true sharks are not quite as old), but this group contains something like ... | [
"I'm not sure if it's a record-holder, per se, but the genus ",
" has been around since the Cambrian."
] |
[
"Is it true that 52 females are born for every 48 males?"
] | [
false
] | null | [
"No. Generally assumed to be around 105 males to 100 females live-birth.",
"Here are ",
"birth stats from Australia",
" which show the rate is between 105 and 105.7 between 2000 and 2011."
] | [
"Are you getting those numbers from the overall world population? That value does not correlate to the birth rate (at least partially) because women have a longer life expectancy than men."
] | [
"Not really. See:\n",
"http://en.wikipedia.org/wiki/Sex_ratio"
] |
[
"Why does the world bounce around when viewed through a camera while walking but stay steady when just using my eyes?"
] | [
false
] | If I hold a camera and walk, when I view it later it makes me nauseous. Running with a camera is even worse (obviously). How do our eyes filter out the bouncing? Do they somehow stay steady while our heads bounce or does the brain somehow filter it to make everything appear much more stable? | [
"The vestibular system corrects for motion and smooths it out.",
"You can \"bypass\" this by closing one eye, then taking your finger and repeatedly (but gently!) pushing your other eyeball to the side. You will see the world move around as you push, because your vestibular system isn't aware of the force that's ... | [
"Your eyes stay focused on the area your looking. Focus on your computer screen now move your head to the right while still focusing on the screen. Your eyes should have stayed in the exact same place just your head has moved. Its similar when you are walking you naturally allow for minor adjustments to maintain co... | [
"The eyes have some inertia and are in a well lubricated socket that make them want to stay in the same place so minor movement don't necessarily move the eye. It's like one of those plastic balls with a rubber ball in it surrounded by fluid. You roll the ball however the rubber ball on the inside stay in the same ... |
[
"As super massive black holes in the center of galaxies consumes more stars and other matter, does that increase the mass of the super massive black hole, also increasing it's gravitational pull, meaning it will be able to grow and pull in the entire galaxy eventually?"
] | [
false
] | I am watching How The Universe Works and they said we were too far away from the center of our galaxy for the super massive black hole to effect us. But if it keeps growing, wouldn't it eventually pull all the stars and matter into it? | [
"It can't ever have mass greater than what it consumes. Right now, we're orbiting the black hole plus the stars around it. If those stars become consumed by it, the total mass in the centre of the galaxy stays the same. Instead of a black hole and some stars, there's a slightly more massive black hole and no stars,... | [
"There is an area called the innermost stable orbit, the closest point to the event horizon where a body orbiting the black hole will just do that, orbit, nearly forever, due to the extreme orbital speeds of bodies that close to a supermassive black hole. The black hole at the center of the Milky Way is not \"eatin... | [
"There's a common misconception in your post about black holes and gravitational pull - if you shrunk the earth down until it became a black hole, all the satellites in orbit and the moon etc. would still keep going on as if nothing special had happened.",
"Realistically all of that stuff would be screwed, but no... |
[
"Are there any materials that exist at a Plasma Phase at the same Temp/Pressure that any other material is a Solid?"
] | [
false
] | I'm curious how any material can be at a Plasma state at the same temperature and pressure that any another material is at a Solid state. Are their any good examples where such 2 materials can co-exist in the same environment? | [
"There is a technique called ",
"plasma cleaning",
" where a plasma and a solid are allowed to interact, and it is very useful for removing impurities from the solid. If you ionize a gas, it takes a bit of time for the ions to recombine. So continuous ionization of a gas can produce a steady state plasma at rea... | [
"Na, this is great! I can now lookup Plasmonics as a keyword when searching. I also didn't know about that relationship between metals and plamas."
] | [
"Na, this is great! I can now lookup Plasmonics as a keyword when searching. I also didn't know about that relationship between metals and plamas."
] |
[
"If we hypothetically had a telescope powerful enough, could we be able to \"see\" the big bang?"
] | [
false
] | [deleted] | [
"Unfortunately that's not really how the universe works. Since the Universe isn't exactly a 3-dimensionally ball but more like 3d surface on a 4d object the big bang basically happened everywhere, there is no middle that the light of the big bang would be emanating from. What is visible to us is the Cosmic Microwav... | [
"No. Best we can do is look to the surface of last scattering. That is, the time when the universe went from too dense for light to move vast distances unobstructed, to less dense. This happened a few hundred thousand years after the Big Bang."
] | [
"The farthest back in time you can \"see\" is the cosmic microwave background or around 300,000-400,000 years after the big bang. It originated during a period when the universe was much hotter and denser than it is today. The background formed when the universe cool enough for hydrogen atoms to form, prior to this... |
[
"Do all birds lay eggs consistently like chickens do? And if so how do they know which ones are fertilized (and therefore should be protected)?"
] | [
false
] | null | [
"Chickens naturally don’t produce eggs consistently, this is due to humans forcing it, and the bodies of the hens are very weak. The hens in the egg industry usually have extremely weak bones and cannot walk because their calcium is totally depleted due to the amount of calcium required to form an egg shell."
] | [
"Some birds lay eggs to keep their nest at a constant amount. Take a robin, for example, which will almost always keep laying eggs until she has four in the nest, but only lay them once a day, to prevent them from hatching all at once and overwhelming her ability to feed them.",
"There are some really interesting... | [
"Chicken that Lay eggs every day are selectively bred to do so. A”chicken” in the wild will only lay 15-20 eggs a year. I originally herd this from a vegan group and this is why they think chickens laying an egg a day in cruel\nI also did later research In the future to find this is true"
] |
[
"What are some examples of animals exhibiting mental illnesses?"
] | [
false
] | I read earlier about police dogs exhibiting signs of PTSD, and a few others, but I was wondering if there were any studies done into more common mental illnesses shared with humans, such as anxiety or depression? | [
"Learned helplessness, a popular theory of human depression, was actually initially accidentally discovered in dogs. The learned helplessness model of depression states that depressive behavior may stem from learning to believe that you have no control over the outcomes in your life, so you instead resort to doing... | [
"Thanks for the good response, I will look more into this!"
] | [
"Animals that don't receive enough mental stimulation develop repetitive behaviors. You can see this in zoo animals that pace in endless circles: ",
"http://www.sciencedirect.com/science/article/pii/S0003347205806402",
"Birds that get bored or stressed will pull out their own feathers, which is similar to a com... |
[
"Can pulsars be use to determine your position in the universe in long distance space traveling?"
] | [
false
] | If you can find the direction and frequency of a few pulsars (with known positions) wouldn't you be able to make a gps-like system? | [
"Yes!",
"This is how the Voyager probe identified Earth's location on it's plaque.",
"http://www.newscientist.com/data/galleries/dn16980-messaging-et/apioneernasa.jpg",
"Those lines heading away from the central point are a binary representation of the spinning period of the pulsars, the line length correspon... | [
"You're right on that point. But clearly we're encoding some information about some specifically identifiable points in space. If humans received something like this showing two squid-people, I'd be willing to bet we eventually figured it out. I mean, it's an alien artifact. You throw your top people at that."
] | [
"Once you know that a pulsar is the thing being represented, it seems like most of the hard part is over."
] |
[
"Would it be possible to survive a jump from an airplane without a parachute and survive using only a pile of feathers to stop your fall?"
] | [
false
] | Say you jump from an airplane at an altitude of 30.000 feet, and below you is a pile of feathers in some container. If this is possible, how deep would this pile have to be, and how many feathers would you need in order to survive your fall? | [
"Partial answer:",
"Terminal velocity",
" for a human falling through air is about 195km/h. The largest acceleration that a normal human can reasonably be subjected to for a shortish time is around 20g. So, you'd have to have an amount of feathers which causes it to take you around ",
"0.28 seconds",
" to ... | [
"Well yes, that's the point. If I knew the effective 'spring constant' of feathers, I would have been able to work it out, but I couldn't find anything useable. "
] | [
"Sticking just with the first bit there have been instances of people falling from planes without parachutes and surviving you can see some examples ",
"here",
", not feathers but in one case ",
"the glass roof of a train station",
"."
] |
[
"Light speed limit - massive wheel question"
] | [
false
] | I thought about it from various points of view with time slow down perspective and can't understand why if you could theoretically build a massive wheel and rotate it very quickly the end of the spokes (or the rim) couldn't exceed the speed of light. Is this the relativity issue that if you were placed on the rim you wouldn't ever experience the speed of light? But if you were in the center could you observe and measure speed exceeding lightspeed? Could someone explain to me: would we be able to observe superluminal speed of the rim from the hub? If not what would stop us from observing that (or spinning the wheel a little bit more?) Thanks a lot - this has been bugging me now for years... | [
"This is the ",
"Ehrenfest paradox",
". It's quite a difficult one. The crux of the matter is that you will never have a wheel/disc that is perfectly rigid, so it will deform under the stresses acting upon it."
] | [
"Particles with mass cannot travel at the speed of light (C). As you accelerate to C, it requires more and more energy to keep accelerating to the point where it requires an infinite amount of energy to actually reach it.",
"As for the particles that do move at C, Electromagnetic Radiation (EMR) such as light, ra... | [
"Matter is not solid, it is a collection of points, held together by light.",
"Also the force required to accelerate past C would be infinite, therefore the stress on the structure would also be infinite. Nothing is that strong."
] |
[
"How do self-healing cork boards work?"
] | [
false
] | [deleted] | [
"I'm speculating a little, but I believe the \"healing\" in cork boards isn't some sort of actual resurfacing/relabeling on the surface, but rather just a function of the cork being elastic and having low density (air pores). If you stick something into cork, you basically are compressing some of the cells and when... | [
"Then what is it?"
] | [
"Then what is it?"
] |
[
"Why cant space craft's slow down before re-entering Earth's atmosphere to prevent burning up?"
] | [
false
] | If I'm not wrong, objects entering Earth's atmosphere burn up because they are travelling at enormous speeds and the air friction and pressure buildup is so much that their surface burns up. But then why don't space crafts like the shuttle slow down before re-entering? Wouldn't that save a lot of money and reduce risk? | [
"I just thought I'd point out a very common fallacy. It's not air ",
" that causes the heating, it's the rapid compression of the air, like in a piston...like how a bicycle pump heats up.",
"As expensive as heat shielding is, carrying extra fuel to lower the craft gently is impossibly expensive and problematic... | [
"The object is wicked fast. The air isn't given time to be nudged aside gently.",
"Terrible metaphor: a bus creeping through a crowd of people, vs a bus crashing through a crowd of people. Sorry, i cringe at how bad that metaphor is, but my point is that velocity is key here."
] | [
"It would reduce risk, but it would take an enormous source of thrust and fuel. Consider the ",
"space shuttle",
", which weighs some 2,000 tons. To get into orbit it must reach approximately 28,000 MPH, which it maintains while in orbit because of the lack of atmosphere to slow it down. When ready to come back... |
[
"Why do MRI machines require such extremely strong magnetic fields?"
] | [
false
] | null | [
"MRI (magnetic resonance imaging) operates on the principle of nuclear magnetic resonance (NMR). When a charged particle* with nonzero spin is placed into a magnetic field, the magnetic dipole moment of the particle can align either with the field or against the field. This creates two different energy states, ",
... | [
"In addition to field strength, field uniformity is also very important for a consistent signal.",
"To clarify this, as it might be misunderstood: Actually non-uniform (gradient) fields are used in MRI to select only one point in the patient to give a response upon excitation. In that sense it is also important f... | [
"When you put a hydrogen atom in a magnetic field, the nucleus starts wobbling like a top at a specific rate. This rate depends on a lot of things, but is pretty heavily dependent on the immediate environment of the nucleus (which is why you can use it differentiate different tissue types).",
"If you observe a la... |
[
"What are the current neurochemical explanations for psychiatric disorders?"
] | [
false
] | Kenneth Kendler (2005), co-editor-in-chief of Psychological Medicine, stated: “We have hunted for big simple neurochemical explanations for psychiatric disorders and have not found them.” What is the current state of neurochemical explanations for mental health problems? | [
"Depends on which disorder. For example, there is too much Dopamine activity in the misolimbic area of the brain and low dopamine activity in the misocortical area for schizophrenia. ",
"For Parkinson's, there is low dopamine activity in nigrostriatal area. For depression, there is low serotonin and norepinephrin... | [
"ADHD is very interesting in this respect. As far as psychiatric disorders go, it is fairly easy to treat with modern methods, but our understanding of its underlying mechanisms is still highly contested and rapidly changing."
] | [
"Hi rollen57, thanks for the reply. Sorry for the delay in this, but I don't get online much!",
"Do you have any citations for the explanations you've provided? Thanks! Much appreciated!"
] |
[
"Why don't fish have spines on their underside rather than the top?"
] | [
false
] | [deleted] | [
"You ask this question as if you're asking a designer about his flawed design. It's evolution, kyle. Flawed systems that 'mostly work' evolve because it's very hard for evolution to backtrack, as there's no selection pressure for a system to evolve 'again' if there's already a working version, or to lose an importa... | [
"spines evolved long before swim bladders"
] | [
"You are right, but I guess I was wondering what kind of evolutionary pressure would cause an animal to develop a dorsal spine but with an air bladder? Did fish develop as bottom dwellers into floating animals or was it jelly fish-style into more complex creatures?"
] |
[
"A question about potassium chloride [chemistry]"
] | [
false
] | It says in the that PC is used for bolus lethal injection, but that means eating it. And then it also says it can be used as a sodium-free substitute for sodium chloride, which suggested that potassium chloride can be eaten like a seasoning much like table salt. So who is right and who is wrong? It would appear that eating potassium chloride seems like an awful idea. | [
"They're both right. The role of potassium chloride in lethal injections is to raise the concentration of potassium in the blood, which can be readily done when a solution of KCl is directly injected into the blood and much much much more difficult by ingesting the substance, which is why potassium chloride is actu... | [
"I think the term bolus was confusing them since it also refers to the ball of food formed in mastication I believe."
] | [
"Alright. cool thanks!"
] |
[
"Skin cells constantly regenerate. So how/why is it possible to have scars?"
] | [
false
] | null | [
"The process of wound healing involves more than just the replication of epithelial (skin) cells. Skin is composed of both epithelial cells and an extracellular, collagen-containing, connective tissue that is laid down in a meshwork pattern when skin develops naturally. In a wound, both the cellular and connective ... | [
"To add to this (speaking as a researcher in epithelia), if you only wound the epithelium, there will not be a scar. However, since the epithelium is only a few tens to hundreds of micron thick, that would be a very superficial wound -- i.e. tiny little paper cuts."
] | [
"For a similar reason to why patching a hole in a piece of drywall looks like junk unless you cover it with something or replace the whole sheet. The repair/replacement process is not as efficient as the initial development. ",
"In scars, the laying down of collagen fibers that connect cells is done edge-in i... |
[
"Does everyone interpret different sound frequencies differently?"
] | [
false
] | If I tense my jaw in a certain way, or yawn whilst listening to music, the music will sound detuned until I'm relaxed again. Considering how this may be related to bone structure, does this mean that a frequency I hear may actually sound higher or lower to somebody else, when interpreted by the brain? | [
"Does everyone interpret different sound frequencies differently?",
"Ummm yeah. Everyone and all mediums are different and sound is a function of the material the pressure wave is traveling through so it will sound different.",
"If I tense my jaw in a certain way, or yawn whilst listening to music, the music w... | [
"Definitely possible. Interpretation is solely interpretation. Perception is a little different (e.g. I may be able to notice shades of IR while you may not) but as for what colour it shows up as in our brain it is solely interpretation and variable. Bats may very well see their 'echolocation' in 'colour' for ex... | [
"Well I do apologise if it seems obvious, you haven't misunderstood and I appreciate your answer. In the same way, are wavelengths of light (colours) also interpreted differently? For example, may my interpretation of red be closer to your orange?",
"EDIT: Just to clarify my original question, I'll reword. I supp... |
[
"If electrons are negitively charged and protons are positively charged why are they not \"attatched\"? Is it magnetism that attracts and repels at the quantum level?"
] | [
false
] | Am I wrong or "not even wrong" to think that if an electron carries a negitive charge while the proton a positive charge they would be attracted and "attatched" but though the electron is more like a cloud of probability the distance between the two seems to be repulsive instead of attractive? How wrong am I? | [
"You can think about it classically: the electrons have enough momentum that they keep spinning around the nucleus without falling in, similar to how the planets have enough momentum not to fall into the sun despite the pull of gravity. This obviously has some problems that require quantum mechanics to solve."
] | [
"Well, it was initially thought that electrons were little balls orbiting the nucleus, but when they calculated it, they found that the electron would have to be orbiting at a ridiculous speed to avoid falling in, and it would rapidly lose all of its energy (because accelerating charges radiate energy). ",
"So th... | [
"The right way of explaining this is invoking the uncertainty principle. The electron is attracted to the proton, but if it goes too close to the proton, the uncertainty in its position decreases and hence the uncertainty in its momentum increases. This will make the electron fly away. So the ground state of electr... |
[
"Why do humans, after hundreds of thousands of years of evolution, still have skin that is so sensitive to the elements? E.g. wind/sunburn"
] | [
false
] | null | [
"who is to say we are physicaly weak? yes a chimpansee could smash us to bits and can climb better, but I bet he couldn't run a marathon under 3 hours no matter how hard he trained. And even if he could he would use much more energy than a human. And yes a horse can run even better than a human, but can he climb a ... | [
"I've read somewhere that humans have the most endurance out of any animal, and humans can actually hunt animals by running them to the point of exhaustion",
"Ah here it is. Pretty awesome.",
"http://en.wikipedia.org/wiki/Persistence_hunting"
] | [
"Humans are actually not much slower than horses at long distances believe it or not, and sometimes faster:",
"http://news.bbc.co.uk/2/hi/uk_news/wales/mid_/3801177.stm"
] |
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