title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"How have scientists been able to \"store' anti-matter?"
] | [
false
] | [deleted] | [
"Using electromagnetic fields to keep the atoms suspended and not touching the walls of the chamber they're in. An example is a ",
"Penning trap",
"."
] | [
"It's the most energetic reaction in the universe, but antimatter is produced in such vanishingly small quantities that it's not the primary issue. They use the traps mostly so they can keep it around for use in experiments, which you can't do if it's constantly vanishing into thin air."
] | [
"Extremely energetic. I am not sure if all of the matter is converted to energy, but if it is, a 500 gram apple would react with 500 g if normal matter to produce around 9x 10",
" joules, or about the same amount of energy as a 40 megaton nuclear bomb."
] |
[
"What is the difference between these equations involving Strangeness Conservation that makes one permissible and one not?"
] | [
false
] | Why is Λ -> p + π permissible, but K + p -> n + π not? uds -> uud + d and s + uud -> udd + u Both involve a change of quark flavour - the s quark of the Λ and K both becoming down quarks - implying the Weak Interaction and hence Strangeness not necessarily being conserved. So what is different between the two interactions that means the second is a no-no? The two interactions have been pulled from different sources. The first is from Hyperphysics and the second is from a CGP textbook which claims it is not allowed. Admittedly the textbook does not even approach the idea that Strangeness is not always conserved... EDIT: got the sources mixed up. | [
"The channel by which a strange quark decays into a down quark has additional byproducts, which show up in the decay channel of Λ",
" that you mentioned, but not in the second reaction.",
"The second section on this ",
"hyperphysics page",
" shows the channels in which the various quarks can decay. There ar... | [
"There is no way for the second reaction to occur without additional particles in the initial or final state. There is no known process in the Standard Model that can turn a strange quark into a down quark with no other byproducts. Even hypothetical flavor-changing neutral currents above tree level would at least p... | [
"Yeah you're right. I was so focused on how an individual quark can decay, I completely overlooked the fact that we have interacting particles here. So yeah, as you said, it's not impossible, but we're unlikely to ever observe it. ",
"In that case, the textbook saying that \"it's not allowed\" is either an oversi... |
[
"Is there a foolproof way of drawing angles with relative precision without a protractor or compass?"
] | [
false
] | I've always wondered this. Protractors are lovely, but sometimes you need to draw that 65° angle and you don't have one on you. It seems logical to me that using a ruler there should be some way that I am missing to be able to do this. | [
"Folding paper can be handy. Fold a piece of paper diagonally from one corner for a 45º angle. Fold it in thirds for a 30º angle. Fold in half twice for a 22.5º angle. Fold in thirds, then in half for 15º, and so on. I use this to make reference angles for drawing from time to time.",
"edit: If you do thirds, ... | [
"If you've got a table of trigonometry values...",
"Or a calculator?"
] | [
"If you've got a table of trigonometry values and a very accurately marked ruler, it's possible. Just find from a lookup that tan(65) is about 2.1445, draw a line segment of length one and a perpendicular one with length 2.1445. Connect the dots.",
"If you'll allow a compass to be used as well, there's quite a bi... |
[
"How does the quantum tunneling effect limit development of micro processors and how do we overcome that?"
] | [
false
] | null | [
"The issue is not that the material is thin but rather that the distance between parts of different voltages (base and collector for example) is small enough that tunneling can occur through otherwise nonconductive material. The energy of the electrons is not the problem its the voltage gradient. Copper transistor... | [
"When transistors get to a certain size, they can’t always hold electrons back, which can cause false signals and errors in computations. As far as I know, we can’t directly overcome tunneling, we can only work around it."
] | [
"As technology miniaturized within transistors, the materials became so thin that the energy of electrons flowing through them was enough to cause the electrons to tunnel through to the substrate to other transistors or be lost to the substrate of the processor.",
"As a professor of mine described it, back in 200... |
[
"Is there a succinct unit name for liters per meter squared per hour?"
] | [
false
] | Question above. The hypothetical situation would be in relation to absorption / dispersion of fluids. Example how much one individual sweats out of a particular area of their body. | [
"Well liters are a measure of volume, in fact 1L is 0.001m",
" so",
"1 L / m^2 . hour\n= 0.001m^3/m^2 . h\n= 0.001m / h\n"
] | [
"In case someone is similarly weirded out by this unit of measurement:",
"This is how rainfall can be stated. Length per time unit."
] | [
"Another weird/fun unit is using square metres for fuel consumption of cars.",
"For example, 6 litres per 100km is 0.006 m",
" / 100000 m = 6x10",
" m",
" = 0.06mm",
"This area is actually the cross-section of a very thin pipe or noodle of fuel, that when laid on the road would let you drive without a fue... |
[
"Apparently the sun's magnetic field is about to \"flip.\" What causes this to occur and why does it do so every 11 years?"
] | [
false
] | Why 11? Does it have something to do with the way the sun spins? The Solar System? Some type of Galactic process? | [
"I'd like to elaborate in that we know a lot more than noott's post gives credit for.",
"It is very hard to pin down exactly what we know though, with physics as complex as plasma physics in a body the size of a star we will never fully be able to recreate it and it is unlikely we will every analytically be able ... | [
"We do not know!",
"That's basically all. ",
"It's an active field of research within solar physics.",
" We do not understand the details of the generation of the sun's magnetic field, let alone what causes the flips and 11-year cycles. ",
"I can say with certainty that it is not a galactic process, thoug... | [
"Meant to reply but made a top-level post by mistake, I think you are bang on that we don't know what is going on with the Sun's magnetic field but the things you highlight ",
" mostly understood, we do know what causes the dipole field as well as roughly what causes the flips, we also definitely know a lot about... |
[
"How do trains carrying liquid freight not have their cargo freeze in the winter?"
] | [
false
] | I have to imagine they don't want whatever is in those tanks to freeze, but I can't figure out how they might prevent it... | [
"Sometimes trains actually let the liquids freeze when transporting. Here's a fun fact:",
"Liquid Na metal that is refined from the ",
"Downs process",
" is directly put into ordinary railroad tank cars. That liquid sodium then freezes while it is inside the tank. When the car arrives at the destination, the ... | [
"Well, we don't transport water on trains. Hydrocarbons and oils typically freeze at a lot lower. Remember that water is also unusual in that it expands on freezing; most substances contract, so there's no risk of damaging the container. So there's relatively little need for heating unless it's a substance that wou... | [
"Insulation."
] |
[
"How does aging/curing meats avoid contamination from harmful bacteria such as c-botulinum?"
] | [
false
] | null | [
"Depends on the method. Dry aging for instance is usually done at colder temps, which halts bacterial growth. Most “curing” relies on salt to prevent the growth of harmful bacteria, meanwhile fermentation relies on either salt or lactic acid, or a combination of both.",
"In all of these situations though it all... | [
"To add, pH plays a role, too. Especially in fermented sausages like salami, where lactic acid fermentation shifts the pH out of the viable range of C. botulinum. Also, addition of nitrite in non-fermented sausages."
] | [
"Drying makes it harder for most bacteria to grow. Smoked meat uses the chemicals in wood smoke to kill/inhibit a lot of microorganisms. Biltong uses the acid from vinegar to make the meat inhospitable to pathogens. Spices like mustard, garlic, and pepper have antimicrobial properties.",
"Humans have figured out ... |
[
"What are the benefits of copper or aluminium layers in pans and pots?"
] | [
false
] | What I think I understand are some copper clad frying pans I've seen that have sort of half cylinders of copper on their bottom transferring heat to a larger surface area of steel on the curve of the half cylinder of copper. What I don't understand are the very popular 3 ply steel pans that just seem to have a layer of aluminium sandwiched between steel. Is it textured at all? It seems like if it was flat there would be no surface area benefit, so the transfer would not improve. | [
"Al and Cu have much higher thermal conductivities than steel, meaning they transfer heat faster than steel. However, they are not suitable for the daily abuse pots and pans see. They scratch easily, dent, oxidize, etc. So, the manufacturer compromises by using them in the core of the pot to do the bulk of the heat... | [
"If you are asking why they just don't make really thin steel pans, to maximize heat transfer, the reason is because fast heat transfer isn't the only goal of good cookware. The goal is also ",
" heat distribution across the surface of the pan. The thicker the pan, the more uniform the temperature on the surface... | [
"Yes, but the heat still has to be conducted through the aluminium. Does a simple flat sheet improve the conductivity at all? While copper is more conductive, what's even more conductive than copper is nothing at all, because copper doesn't conduct heat perfectly. So isn't it just a layer of inefficiency?",
"I... |
[
"How does it happen that an entire volume of data can become corrupt when the writing of only a small portion of it is interrupted?"
] | [
false
] | The other day, the electricity went out while I was saving a folder of word documents to a flash drive. When I powered it back up again, Windows told me that the drive was corrupt and needed a reformat. The flash drive is 16GB, and my documents were only a few megs. What happened that the entire drive became corrupt? | [
"In your case it seems was damaged the File Allocation Table (FAT). This file system can be read and written by a wide range of devices, but it is very fragile because of how data is arranged logically. In most cases you can fix the problem with a specialized application, like chkdsk under Windows.",
"If you are ... | [
"NTFS does not write 'less logically' but certainly it is more robust than FAT. ",
"You have journaling features in NTFS that can keep 'records'/journals of changes to the filesystem before being committed to writing which can make data-recovery far more likely, as well as less likely loss of data due to corrupti... | [
"Ah, cool! So the NTFS file system arranges data...less logically, but also in a less fragile manner? "
] |
[
"Do our eyeballs grow after we are born?"
] | [
false
] | null | [
"I love how the guy asked his question on reddit, reddit searched google, google found a yahoo answers post, reddit copied and pasted it back on reddit and ended up wasting a lot more time than needed. But with that being said, I find a lot of interesting posts on reddit that I would have never thought about in a m... | [
"I love how the guy asked his question on reddit, reddit searched google, google found a yahoo answers post, reddit copied and pasted it back on reddit and ended up wasting a lot more time than needed. But with that being said, I find a lot of interesting posts on reddit that I would have never thought about in a m... | [
"Short-sightedness (myopia) is usually a result of the eyeballs growing too long along the horizontal axis. So, yes, they do grow for some time after birth."
] |
[
"If a quantum wave function has 3 state would making a measurement on only 1 state collapse it?"
] | [
false
] | for example if a particle is superpose in position A B and C with an amplitude of sqr(1/3) each, would testing if the particle is at C collapse the wave function assuming we find nothing or change it to 50% for A and B keeping it superposed. | [
"Excellent question. I'm going to imagine this as a ",
"triple slit experiment.",
"So basically the wave function is as predicted by QM.",
"Now we put a detector beside one of the slits say the left slit, \"collapsing\" electrons that pass through this slit.",
"These results are the same as a double slit th... | [
"It would remain in a superposition between the A and B states.",
"An analogue of this measurement is to have a particle with three states A, B, C. Now, suppose states A and B are degenerate (same energy). We proceed to measure the energy of the particle. If we measure the particle to be at that shared energy, th... | [
"It's not necessarily a single eigenstate. A measurement will collapse the wavefunction into a subspace of the original eigenspace."
] |
[
"Why didn't natural selection eliminate poor eyesight before glasses were invented?"
] | [
false
] | My train of thought with this is that poor eyesight seems like it would've been a big enough hindrance to things like hunting and gathering and generally not running into stuff and dying back in those times that eventually people with poor eyesight wouldn't have been able to reproduce. Am I just confused on how poor eyesight works? | [
"Most \"poor eyesight\" is heavily influenced by environment, not solely genetics. That is, you may inherit the tendency to become myopic, but you don't actually develop myopia unless you add in the environmental triggers:",
"Even though the tendency to develop myopia may be inherited, its actual development may... | [
"Of those, only tool-making seems like it's really comparable to the modern environmental triggers. Watching TV or reading can easily leave your eyes focused on the same spot for hours at a time, day after day; whereas starting fires might take a few minutes or a half hour; cutting wood with a stone axe better not... | [
"For something like poor eyesight to be weeded out of a population, it would have to kill a portion of that population before that portion had a chance to reproduce. Since a lot of young creatures have parents to look after them, they have a fairly good chance of living to a sexually mature age. And since you don't... |
[
"Just as \"red\" in hundred meant \"count\", does the \"ter\" in close relatives (like father, mother, brother, sister) mean anything in Old(er) English?"
] | [
false
] | null | [
"Yes! Father, mother, and brother are derived almost unchanged from proto-Indo-European (PIE), where -ter is a kinship suffix. Sister is from PIE *swesor, probably from PIE roots *swe- \"one's own\" + *ser- \"woman.\"",
"If you like this sort of thing, etymonline.com is fantastic. "
] | [
"There are four r-stem kinship terms in proto-Indo-European (pronounce h₂ like the sound you make in the back of your throat when you blow on your glasses to fog them up):",
"*-tḗr does seem to be an agentive suffix elsewhere in the PIE corpus (e.g. *h₂eh₁s- (burn) + -tḗr (-er) > *h₂stḗr (burner) > \"star\"), but... | [
"I'm curious why we don't have this in other relatives like son, uncle, aunt, nephew, and niece.\nIt seems that they had multiple words that meant \"man\" and \"woman\" to be able to just add \"ter\" or \"ther\" to mean a specific relative.\nI haven't been to etymonline, thanks for mentioning it."
] |
[
"Can the Stern–Gerlach experiment measure spin direction?"
] | [
false
] | [deleted] | [
"it can also measure the spin of individual particles, but not the direction of them",
"What do you mean by this? How do you define measuring the spin vs measuring the direction of spin?",
"The apparatus measures the direction of spin along any arbitrary axis. "
] | [
"In the SG experiment, each of the final two beams are uniquely polarized along the axis of the inhomogeneous magnetic field. In a sense, you can use a series of inhomogenous magnets in the same way you can use a series of polarizers for light beams. However you've only isolated the ",
" of spin along a certain a... | [
"a further note the SG experiment actually hasn't been done for electrons or positrons",
"I came across this a while ago, not sure if it has been repeated, but claims to do just that:",
"https://www.researchgate.net/publication/292985810_Picture_and_Result_of_Experiment_-_Stern-Gerlach_experiment_by_free_electr... |
[
"Watching things at the speed of light"
] | [
false
] | I read that the Pillars of Creation were destroyed about 6000 years ago, but due to the light speed limits we will not see the event for another 1000 years. If I travel towards the pillars at, let's say, 99% velocity of speed will I see the events fast-forwarded? And if away - slow-mo? Is it that simple or is there a catch to it? Does that mean that there's a natural fast-forward/ slow-mo limit? | [
"If I travel towards the pillars at, let's say, 99% velocity of speed will I see the events fast-forwarded? And if away - slow-mo? Is it that simple or is there a catch to it? Does that mean that there's a natural fast-forward/ slow-mo limit?",
"There is a distinction that can be very subtle here and many people ... | [
"Then there is also the relativity of simultaneity, which means that after you boost, the destruction of the pillars now happened way longer than 7000 years ago, and what is currently happening for the pillars is an event that was in the (spacelike) future is now in the present.",
"The only good way that I have f... | [
"You will see it faster. You just discovered relativity, and are travelling forward in time. ",
"I'd read up on it. RobotRollCall likely has a relating post."
] |
[
"If a billiard ball was fired into someone at close to the speed of light, would it vaporize him or leave a clean circular hole?"
] | [
false
] | null | [
"There is a fantastic explanation by an MIT professor depicting of the kinds of effects you might encounter with fractional C projectiles hitting another mass (in this case, a can of ravioli hitting a starship): ",
"http://www.mit.edu/people/daveg/Humor/ravioli_as_gas",
"actually, let me just post the entire te... | [
"Assuming that the billiard ball survives reaching the guy, the guy would be vaporized by the huge fireball accompanying the billiard ball.",
"Already movement at high Mach numbers heats the atmosphere around the object up ",
". ",
"http://www.youtube.com/watch?v=RChlt5wdqBs",
"Now if you look to meteorites... | [
"Anatoli Bugorsk",
" put his head in an accelerator beam accidentally. About the only thing close to that speed and body interaction."
] |
[
"Do animals ever think of \"why\" something happens? If they can only think visually, do they ever reach that level of asking \"why\"?"
] | [
false
] | I always wonder what my cat thinks me and a friend are doing when we're sitting on the couch talking. I wonder he thinks we're making sounds and looking at each other. But a recent discussion about animal thinking talked about how, without language, you can only think visually. People that didn't get taught language until they were well into their teens describe that period as very fuzzy and emotional, akin to what it was like being a baby. So, do they ever even to that level of questioning? | [
"People that didn't get taught language until they were well into their teens describe that period as very fuzzy and emotional, akin to what it was like being a baby.",
"What's your source on that? My impression is that the number of cases of this sort of thing happening that have been well documented is so smal... | [
"Hahaha reproduction deviates from your field."
] | [
"That deviates too far from my field for me to say anything even remotely authoritative about it. ",
"I would speculate (as a layman) that no, they don't understand the connection between mating and birth the way they understand the connection between rolling over and getting a treat. That's something they woul... |
[
"How does the flash from a camera \"ruin\" a painting?"
] | [
false
] | In some museum galleries, they have signs that say "no flash photography" because it'll supposedly mess up the paintings over time. However, in other galleries flash is completely fine. Does it have to do with the type of paint or the age of the painting? What exactly happens? | [
"It's not a single flash, I don't think, but the prospect of hundreds of strobing flashes every day---if they were exposed to sunlight, they would bleach and fade, and I'm positive the same would happen under enough flashes. "
] | [
"Wikipedia is your friend",
"."
] | [
"Not in this case. The photobleaching being discussed in the Wiki article is ",
" about the photochemical destruction of a fluorophore - a fluorescing molecule. Sadly, photobleaching is a more general term than that and can be used within the context of this discussion - the loss of color agents (dyes and/or pigm... |
[
"What is the relationship (if any) of the electric field in EM radiation to the Force (perpendicual)/ Force (centripetal) and the electric field of a point charge?"
] | [
false
] | In lecture today, I was told that E(rad) = kqa/(c r). Playing around with the equation I found another way to write this equation, however my professor quickly brushed this off as just a coincidence. I would like a second opinion. Here is what I found: given E(point charge) = kq/r , F(perpendicular) = ma(perpendicular), and when v=c F(centripetal) = mc /r, I saw that E(rad) = kqa/(c r) = E(point charge)F(perpendicular)/F(centripetal). Is there some reason behind this, or is it just like my professor said, a coincidence? | [
"I'm not sure I understand your notation.",
"An electromagnetic wave incident on a surface exerts a pressure that is equation to the average Poynting vector divided by c. The Poynting vector is proportional to the square of the electric field.",
"Also, no charged object moves at the speed of light."
] | [
"My understanding in this area is fairly limited, as I'm sure you could tell from the question, however hearing that no charged particle moves at the speed of light makes my relation void. Thank you for your response."
] | [
"What you're talking about sounds sort of like the ",
"classical electron radius",
" which is the radius at which the electrical potential energy equals the rest energy (mc",
" )."
] |
[
"Is there a way to tell if a product is made from BPA plastics over say, another plastic like ABS, if there are no recycling symbols given?"
] | [
false
] | Asking because I have fake nails I glue onto my fingers, which means I’m in skin contact with plastic for weeks and through hot showers. I’ve heard BPA is a big issue in both these situations so I’m a bit concerned. Is there any way to test this at home? For example, through their reaction with alcohol or through testing their melting point? | [
"You can’t tell on products like that unless the manufacturer tells you the material. You can ask them usually. I will say, the main way we’re exposed to these chemicals is through ingestion. I personally don’t think absorption through the nail would be very large. As a person who studies microplastics for my PhD, ... | [
"BPA isn’t a type of plastic, it is a plastic additive which makes plastic more flexible, clear, and durable. ",
"It is generally safe to say that unless a plastic product specifically indicates that it is BPA free, then it contains BPA."
] | [
"Ingesting foods with fat that are packed in plastic, scented products (some microplastics stabilize fragrances and are labeled as “parfum”), and then receipt paper. But honestly we need a systemic change, where countries fully ban these products for you to fully avoid them. Most of these microplastic chemicals hav... |
[
"How much of the water we drink stays in the body?"
] | [
false
] | [deleted] | [
"None of it. The water you drink passes ",
" your body. Along the way, your body uses it to transport various water-soluable chemicals around in useful ways, until finally the last thing your body does with it is use it to carry water-soluble waste products ",
" of your body as urine.",
"Assuming you're a gen... | [
"What is the cause of the times in which the body discharges the fluids..",
"Some days its normal ever few hours others you may not go for extended periods threw out the day. While odd days it seems like every 40m. Referring to urination and considering roughly same amount of water is taken in daily. Health... | [
"It depends on different factors. The following are notes from my Anatomy and Physiology class. You'll see that water output SHOULD equal water input, but perhaps if you spend a hot and dry day outside, you'll expel more through diffusion or sweat and less through urination. In your question's case though, perhaps ... |
[
"What kind of unethical/illegal/immoral experiments would advance your field?"
] | [
false
] | null | [
"Being allowed to try any cancer treatment we can come up with (with plausible reason to think it would work) \"just to see\".",
"but that's an easy/obvious one."
] | [
"Can't you already do this with rats?"
] | [
"You think everything happens identically in rats as it does in humans? you would be sorely mistaken."
] |
[
"I heard that after sex, men have a biological impulse to get away from the woman and women have the impulse to keep the man close. Is this true?"
] | [
false
] | null | [
"The real, honest answer, that you won't actually see much on reddit: Nobody knows.",
" ",
"We don't know much about our behaviour and evolution and \"Why do humans..\".",
"We can make guesses based on neurotransmitter levels. (Oxytocin especially in this case would be relevant).",
"The statement \"Humans h... | [
"This (and a myriad of other gender-related behavior explanations) are very popular in evolutionary psychology. However, there is hardly any supporting research to back-up these claims. Take it with a grain of salt."
] | [
"I'm an evolutionary psychologist, and this is gibberish. It assumes that there are tons of women just waiting for a man to come along and have sex with them, so that the guy could just go find another mate immediately, which is just ridiculous. Furthermore, if this were true, then presumably some other male would ... |
[
"What is quantum tunneling? Under what conditions does it occur?"
] | [
false
] | If we model an electron as a particle in a box, I understand that the box represents an orbital, its opaqueness models uncertainty, and the length of the box models the idea of different orbitals having discrete energy levels, sort of like standing waves of a string. How does quantum tunneling fit into this picture? BONUS: How do scanning tunneling electron microscopes work? How about atomic force microscopes? EDIT:Thanks for all the replies so far...I actually posted before searching the subreddit and your replies combined with some past questions about quantum tunneling have helped my understanding of the phenomenon. In particular, has been extremely insightful. Now I'm more curious as to why this is so. Mathematically or experimentally, how do we know that the probability distributions overlap at higher energy levels? | [
"I only have a moment now, so let me answer what tunneling is, and leave the microscopy for another person or another time:",
"In classical physics, we know that kinetic energy is always positive, and as a consequence, the total energy is always greater than the potential energy. That means it is impossible for ... | [
"Lol, I think we both are a little confused. Wikipedia article on Schrodinger's equation:",
"The time-dependent Schrödinger equation predicts that wavefunctions can form standing waves, called stationary states (also called \"orbitals\", as in atomic orbitals or molecular orbitals).",
"I thought only electrons ... | [
"Lol, I think we both are a little confused. Wikipedia article on Schrodinger's equation:",
"The time-dependent Schrödinger equation predicts that wavefunctions can form standing waves, called stationary states (also called \"orbitals\", as in atomic orbitals or molecular orbitals).",
"I thought only electrons ... |
[
"Why does U-Pb dating have a limit of 500,000 years ago?"
] | [
false
] | [deleted] | [
"You got the direction wrong. It is largely useless for samples newer than 500,000 years because the amount of lead that accumulated in that time is small. Uranium-lead dating is better for older samples. The absolute uncertainty is still large, but \"635 +- 1 million years\" is a good measurement while \"0 +- 500,... | [
"Thanks a lot for this response. I think my book contradicts what you're saying, it states that this dating method is only usable for 500-500,000 years BP. But you say that it's useless at short time scales, I think that your explanation is way more logical but I'm not sure what I have to remember now."
] | [
"Thanks a lot for this response. I think my book contradicts what you're saying, it states that this dating method is only usable for 500-500,000 years BP. But you say that it's useless at short time scales, I think that your explanation is way more logical but I'm not sure what I have to remember now."
] |
[
"Why does sound travel farther on water?"
] | [
false
] | For example, when I go fishing. I can hear a couple on a kayak at least 100 yards or so away, and still be able to make out what they're saying. While another person is only 20-30 feet down shore and I can't make out a word they're saying. | [
"Two reasons: First, on the water there are much fewer objects to get in the way of the sound. Other than a few waves (and if you're fishing, I'm assuming there aren't many of those) there is nothing to block the sound getting to you, so you can hear it from further away. On the shore, you have rocks, trees, and ... | [
"This is correct, but there's more to it. Sound also reflects off of water when the water is calm. "
] | [
"You're right, that's what I meant when I mentioned the surroundings (I.E. water) not absorbing much sound, but I should have made that clearer."
] |
[
"Would a plant housed in darkness with mirrors directing light at the leaves photosynthesise at the same rate as if it were outside?"
] | [
false
] | Are the light waves reflected from a mirror identical to those hitting the mirror or is the mirror absorbing some of the energy? Does it depend on the mirror material (eg glass vs polished metal)? If so would this significantly impact a plant's capacity to grow under these conditions? | [
"There is no such thing as a perfect mirror, so in some ways the answer is no. All mirrors transmit some percentage of light (transmit being the opposite of reflect), and it varies across the spectrum. That said a typical silver mirror reflects about 85-90% of visible spectrum light that hits it. Some specialized m... | [
"that does help thanks"
] | [
"Reflected light isn't precisely identical to the incident light, as mirrors only imperfectly reflect light, doing so in a frequency-dependent way (meaning that different colors of light are absorbed slightly differently by the mirror). Also, light reflected from mirrors is ",
"polarized",
", whereas the incide... |
[
"What exactly happens when we \"startle\"?"
] | [
false
] | Kind of curious about this. What happens physiologically when we startle or jump from for example a sudden sound? | [
"What do you mean by \"psychologically\"? Do you mean \"physiologically\"?"
] | [
"That could very well be. I was thinking in regard to why we react as we do. Jumping, screaming, etc. Are there any benefits from such a reaction, both chemical and physiological?"
] | [
"Thank you for a detailed and informative response! "
] |
[
"How does putting more metal stuff around it correct a ship's compass?"
] | [
false
] | I visited a maritime museum over the weekend, and there was a part of the exhibit explaining that when ships started to be made of metal, it was found that it caused inaccuracies in the compasses when travelling east-west. This is corrected by a steel bar called a Flinders Bar, and maybe Kelvin's Balls - which are unmagnetised iron, all of which pretty much surround the compass. But how does this all work? Surely adding a lot more metal around a compass means it will be more attracted to that than to the earth's magnetic field? | [
"The earth's magnetic field induces a magnetic field in the ship's metal, which alters the magnetic field seen by the compass. The point of the Flinders Bar is to exactly cancel the field generated in the ship's metal so that the total field seen by the compass is again the earth's field."
] | [
"Interesting related fact, realizing that the metal hulls of ships took on magnetic properties, the Germans actually developed mines to be triggered by magnetic fields, so they would go off when any ship came near them. If I recall correctly, they started wrapping metal cables around the hull to demagnetize the ent... | [
"Sounds like a pain to set up, but in a pinch it is clever. Of course, GPS is becoming a little more common; my tank in the military didn't seem to have any such thing to keep its hull demagnetized, my compass didn't work, but the GPS sure did."
] |
[
"Did Baumgartner ever actually break the speed of sound, measured at ambient air density, at any point in his descent?"
] | [
false
] | null | [
"The speed of sound in a gas depends on the composition of the gas and the ambient temperature. This relationship is c=sqrt(gamma * R * T) where c is the speed of sound, gamma is a thermodynamic property known as the ratio of specific heats, R is the gas constant for the gas, and T is the temperature. Gamma and R w... | [
"No problem.",
"As an interesting side note, if CNN's reporting is accurate, and Baumgartner reached Mach 1.24 and 834 MPH (372 m/s), that corresponds to an outside temperature of 224 Kelvin, or 50 degrees Celsius below zero. ",
" this temperature matched the Standard Atmosphere model (big if), that means Baumg... | [
"The speed of sound is dependent on temperature, but not altitude (in the context of pressure). And the speed of sound is lower at low temperatures than high ones, so he did break the sound barrier of the air in which he was travelling."
] |
[
"Is this a reasonable simulation of tension across a hanging rope?"
] | [
false
] | Hi! I was debugging some game physics/kinematics and noticed something I found interesting: the tension across my hanging rope was equal across its entirety, which goes against one of the few things I remember from my physics classes a decade ago. However, the simulation seems to match most of the rope characteristics that I can think of having observed in real life (it's actually uncanny; I hate it), so I'm reexamining my understanding of physics. Attached is a screen grab; the red circles represent the tension at each point (the radius of each circle is equal to "tension", which is a variable in the engine with a magnitude and no real units). Is reasonably representative of what I would expect to see if I were to measure across a real rope with a... tension...ometer? Note: I haven't seen any posts like this, before, so I'm not sure if I'm allowed to do this; I notice that media posts are disabled, but I'm not sure if that means that they're not allowed, or if they're disabled to weed out low-effort spam. I'm assuming the latter (and also assuming that this isn't a low-effort question); please let me know if I'm wrong! Edit: suggested that the tension should be equal across the horizontal component, but I didn't even write code to that, let alone have it . So I wrote a little script to draw components of vectors (and to pass the direction component of the tension vector to the script) and !! Aaaaaahhhhhhhh I am BESIDE MYSELF RIGHT NOW HOW DOES CODE I WROTE KNOW MORE PHYSICS THAN I DO THIS IS AMAZING!!! I love all of you. | [
"Tension is a vector. It has a magnitude and direction.",
"The horizontal component of the tension should be equal everywhere.",
"The vertical component will be max at the highest point and zero at the minimum point.",
"This is assuming you have gravity.",
"So, you probably have it right, but it would be ea... | [
"That is ",
"a beautiful catenary",
". That is exactly what it looks like.",
"In intro physics, you dealt with ",
" ropes, which are massless. Try changing the density of the rope to zero to see what happens to the tension."
] | [
"Well, now I'm curious. I'm going to separate out the components; this'll be fun.",
"Edit: Wait, I forgot that I already updated the sim to (try to) replicate rigid motion, instead (which is somehow ",
" harder than stretchy motion, go figure). I'm totally going to do this ",
", though!",
"More edit: Well... |
[
"\"An implication of Albert Einstein's theory of general relativity is that physical space itself is not Euclidean, and Euclidean space is a good approximation for it only where the gravitational field is weak.\" What does this mean?"
] | [
false
] | null | [
"Euclidean space is space described the Euclidean geometry, which is derived from a set of postulates originally published by the Greek mathematician Euclid. Euclidean geometry is geometry as you expect it in our every day life. Where the sum of the angles in a triangle is always 180 degrees, where two parallel lin... | [
"Euclidean geometry only works on a flat plane",
"Err, no - Euclidean geometry works perfectly well in 3 dimensions. In fact it's applicable to any number of dimensions, but is most often associated with 3 for obvious reasons.",
"where real world measurements have the Z of X,Y,Z axis to complicate the math beca... | [
"Euclidean geometry only works on a flat plane",
"Err, no - Euclidean geometry works perfectly well in 3 dimensions. In fact it's applicable to any number of dimensions, but is most often associated with 3 for obvious reasons.",
"where real world measurements have the Z of X,Y,Z axis to complicate the math beca... |
[
"Can typical consumer Hydrogen Peroxide solution (3%) be turned into safe drinking water?"
] | [
false
] | null | [
"Heating water doesn't release oxygen from the oxygen atoms in H₂O. All it does is release any dissolved oxygen. This process does not involve the breaking of any chemical bonds.",
"Hydrogen peroxide ",
"naturally decomposes into water and oxygen",
", and heat will increase the rate of decomposition."
] | [
"Yea, I meant O2 molecules in solution with the water.",
"OK, but how do you know when the Hydrogen Peroxide solution has decomposed enough to be safe drinking water?",
"Is there a way to accelerate it besides heating it?"
] | [
"I don't think it is in the place of anyone on an internet forum to provide procedures on making commercial hydrogen peroxide solutions safe to drink. It's the reason I provided the relevant information about decomposition, and that's it."
] |
[
"Which berry and fruit was the first in the world?"
] | [
false
] | How did berries evolve? And where did they grow? I would like to learn all about this! (Posted this in , but mods told me to try instead, so here I am) | [
"Fruits in the strictest botanical sense are produced by Flowering Plants, only. ",
"Fruits of flowering plants as we recognize them today, probably originated in the late cretaceous or the early paleocene, possibly after the K-T extinction event that killed most of the dinosaurs as well a large amounts of other ... | [
"True fruits in the botanical sense grow from the ovary of a flower. True flowers are found on angiosperm plants, which are about 130 million years old depending on who you ask and how old your botany textbook is.",
"The murky origins of angiosperms make it hard to speculate what the very first fruit would have t... | [
"Thanks!"
] |
[
"Total Energy in the Universe?"
] | [
false
] | Has anyone ever attempted to determine the sum of all the energy in the universe? Would it be expressible as a number of Joules? Is this even a meaningful question, considering that dark matter counterbalances the energy of matter (maybe my question is about the sum of the absolute values of all energy in the universe)? | [
"Depends on what kind of energy you are talking about.",
"\nIn general, cosmologists talk about the energy density of the universe (the ammount of energy per unit volume), because this is what actually matters in the evolution of the universe, not the actual total, this is because the total volume of the universe... | [
"What? Your link has absolutely nothing to that effect (only a throwaway line about how large the energy contained in a uranium nucleus is), and \"power of a uranium packed nucleus\" is nonsense anyway! Not to mention that all uranium nuclei are contained within the universe meaning that the energy of the universe... | [
"What? Your link has absolutely nothing to that effect (only a throwaway line about how large the energy contained in a uranium nucleus is), and \"power of a uranium packed nucleus\" is nonsense anyway! Not to mention that all uranium nuclei are contained within the universe meaning that the energy of the universe... |
[
"Is it true that my wife can't get pregnant when not in her fertile tone of the month?"
] | [
false
] | I just got married last week. Someone in another thread mentioned natural family planning and the idea that it is impossible for a woman to get pregnant if she's not ovulating. Is this true? | [
"Close. You can learn enough about her cycle to ensure she doesn't get pregnant, but the window is wider than just her partial week of ovulation. Sperm can fertilize an egg for about 3-5 days after it has been deposited. So pre ovulation sex can cause pregnancy. ",
"If you are serious about avoiding pregnancy thr... | [
"This is known as 'the rhythm method'.",
"It is well known for producing parents.",
"The underlying reasoning is sound - if you avoid sperm finding an ovulated egg, yes it is impossible to become pregnant - but unfortunately as with all things human, it is very hard to be that precise and any number of events c... | [
"no this is not known as the Rhythm method. It is known as Natural Family Planning/ Fertility Awareness Method, of which Rhythm is the oldest (developed in 1930). Rhythm corrected the medical advise doctors were giving couples. Prior to that, it was believed a woman was least fertile in the middle of her cycle (... |
[
"Am I losing hearing in my left ear?"
] | [
false
] | null | [
"We can't comment on personal anecdotes / isolated incidents without resorting to speculation which we try to avoid."
] | [
"Ah im sorry. This is an area of concern for me and this sub was the first to enter my mind when I started asking questions about it"
] | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"medical or safety advice",
"/r/AskScience",
"guidelines",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"If earth's core suddenly stopped being nuclear and would drop to surface temperature, would earth's surface get any colder?"
] | [
false
] | null | [
"Other than what the other comment said, the earth's core is definitely not nuclear. "
] | [
"Absolutely. It would turn into mars. Without a heat gradient, the electromagnetic rotation in the core would cease, removing the magne field around the earth. The solar wind, which the earth fends off with its magnetic field, would then carry away our atmosphere, and without the greenhouse effect, the temperature ... | [
"Also thought so. While earth still being fully liquid, the heavier elemts (which most radioactive are) sunk toward the core, leaving them as heat source."
] |
[
"What IS the placebo effect?"
] | [
false
] | I don't understand it at all, any help? | [
"Basically, sometimes people get better when you give them a fake treatment ",
"Its thought to be caused by a variety of reasons, the \"power of positive thinking\" , the relief of anxiety in knowing that youre now on a tablet for your condition, self delusion etc",
"In testing drugs , you always divide up the ... | [
"Something not mentioned yet, is that the placebo effect can work even if people know that they are getting a placebo.",
"http://www.guardian.co.uk/science/2010/dec/22/placebo-effect-patients-sham-drug"
] | [
"It's when there's an improvement that's not attributable to the pharmacological effect of the treatment. In a classical example, when sugar pills are given to treat pain or anxiety - small amounts of sugar don't affect either - but for many people, taking pills for pain does affect pain and taking pills for anxiet... |
[
"If the solar system travels thru a nebula or a big dense cloud of matter, can our solar system grow? Can Jupiter or the sun grow in size?"
] | [
false
] | null | [
"No. The solar wind creates a \"bubble\" of plasma that prevents gas and dust in the interstellar medium from touching planets or the sun. And that plasma doesn't touch most planets since it is deflected by their magnetic field. In the few cases when it does, like Mars, it actually takes away more atmospheric matte... | [
"Every year, Earth gains about the weight of two aircraft carriers landing on it – two HMS Ark Royals, or about 40,000 tonnes-worth of debris, which lands on Earth from space. You can demonstrate this for yourself. If you put a big plastic sheet or a white sheet on your grass in the garden on a nice day, leave it f... | [
"That's interesting, forgot about the bubble the sun creates... So are we leaving a trail of matter as we travel? Like footprints"
] |
[
"How do nations communicate with each other?"
] | [
false
] | null | [
"Formal day to day communication happens between embassies and (typically) state departement of the host country. They send very official hand delivered letters to each other (called Diplomatic Notes). They can also have meetings with government officials and ambassadors. ",
"Highest form of diplomatic contact... | [
"There is also both Track 1 and Track 2 means of communication with countries. Track 2 is what you don't hear about, i.e informal talks between academics on both sides. Track one is as listed already, state departments communicating through embassies, and even phone conversations set up between executives."
] | [
"This may not be a popular or even legal response in this subreddit, but I recommend referring to the West Wing. Despite having a political science degree, it gave me some understanding of the different methods.",
"As far as translation goes, most treaties are formed in multiple languages and verbal communication... |
[
"Can you trap light in a vacuum?"
] | [
false
] | [deleted] | [
"I'm an electrical engineer, though there's really not much of a distinction between us and physicists these days, especially when dealing with nanoscale devices and effects.",
"If you take a slightly leaky 'light-trapping box' and replace the vacuum inside it with a material that can amplify light (given some so... | [
"I'm an electrical engineer, though there's really not much of a distinction between us and physicists these days, especially when dealing with nanoscale devices and effects.",
"If you take a slightly leaky 'light-trapping box' and replace the vacuum inside it with a material that can amplify light (given some so... | [
"Total internal reflection happens at an interface between materials; in this case, it would be vacuum and some non-vacuum material. The resulting device would be functionally equivalent to a vacuum-filled box with mirrored walls, in which case light can most certainly be trapped inside the box, just like it could ... |
[
"How exactly does cutting things work at the molecular/atomic level?"
] | [
false
] | Sharp object cut things. I understand that. How does that work at the molecular/atomic level? Does it interfere with the covalent, ionic, metallic, or whatever other types of bonds the object being cut has? Can someone explain? | [
"Check out ",
"this big thread",
" on this topic.",
"In short, it depends on what you're cutting. At the end of the day, you are disrupting intermolecular and/or chemical bonds when you physically separate something with a knife."
] | [
"It has a higher hardness than the things you're cutting usually. "
] | [
"It does a bit - which is how a knife gets chipped or dulled.",
"But the knife's bonds are mostly stronger than the bonds it's mostly cutting."
] |
[
"Do large impacts cause nuclear reactions?"
] | [
false
] | For example, in the impact that wiped out the dinosaurs, or the impact that created the moon, are the conditions during impact sufficient to cause nuclear reactions within the impact material? | [
"I'm going to go ahead and say that I think it's not possible. ",
"The Chicxulub impactor (the one that we think killed the dinosaurs) was 10 km across, and going 20 km/s. A little Googling tells me people have done lots of simulations of ",
"what this might look like,",
" and seem to believe that 10,000 K so... | [
"To get nuclear reactions with ordinary material you need to focus the energy ",
". There are current experiments trying to do it with very powerful laser bursts being focused to very small points. Even though there's a lot of total energy in the impact, it won't be concentrated enough to get any atoms to fuse."
... | [
"I don't think that is necessarily true. There are a lot of nuclear reactions that occur at lower energies (photoexcitation and inelastic scattering). The impact releases large amounts of energy over a wide area. There will be hot spots. Especially from the plasma formation. The lowest nuclear excitation is 7.... |
[
"In movies/tv they say there are always a percentage of people who are naturally immune to new diseases, is this true and are there people naturally immune to COVID-19 specifically?"
] | [
false
] | I'm watching The Last Ship right now (lol), and i realized while they're discussing the Immune, we've not really heard anything about any people being naturally immune to COVID-19. why? is that not a real thing? | [
"Very few people are going to be spontaneously immune, in the formal sense of \"immunity\", to a novel pathogen.",
"What can happen is that people can be genetically resistant to infection or disease caused by a new pathogen, due to random or not-so-random mutations and variations. The classic example is CCR5 del... | [
"A few months ago I read about this man: John Hollis didn’t realise he’d been infected with Covid-19. But he later discovered he’s one of the rare people who has developed “super antibodies”. The research claims that you could dilute the antibody in his blood 1 to 10,000 times and it would still kill 90% of the vir... | [
"Scientists have found \"super antibodies\" (e.g. broadly cross-reacting, very high affinity antibodies) against several diseases in a handful of individuals, including to HIV and influenza. In some cases (HIV especially -- the very few people who have these antibodies seem to be extremely resistant to HIV infectio... |
[
"Why is it possible to ground an electrical device by connecting it to the Éarth?"
] | [
false
] | Where does the electrical energy and charge go? Is it possible for the Earth to become saturated at some point in the future? | [
"Remember that net charge is always conserved so to charge the earth you would have to either remove a lot of its electrons and shoot them off into space, or get a whole bunch from space and shoot them into the ground.",
"In addition to this, even if you did manage to change the net charge of the Earth, there is ... | [
"An object with charge has an excess (or lack) of electrons. These electrons repel each other and so will flow as far away from each other as possible. ",
"By connecting a charged object to the ground, you give a path for these electrons to flow so they are even further from each other. The earth is really big an... | [
"Total charge is conserved. If an object gets an excess charge, this charge came from the Earth before - it just returns when the object is grounded. Earth is huge, it doesn't care about the temporary motion of a little bit of charge on its surface. It is only relevant for electronic devices if they build up too mu... |
[
"What would the proposed DC-AC-DC converters do for the U.S. national power grid?"
] | [
false
] | If they're there to regulate flow from one side of the country to the other, why use these converters and not something else? Thanks! | [
"They aren't there so much to regulate power flow as they are to allow for different chunks of the grid to run asynchronously. Each colored block you see there is a proposed region with a constant phase and frequency. Technically, this means that if you plot a voltage somewhere in one section the transmission syste... | [
"It's more about balancing power flow between many different loads, while keeping the frequency at roughly 60 Hz. The power output of a coal plant takes hours to change, and a nuke plant is even longer. Hydro and gas plants can change output relatively quickly, so they are used as 'topping' reserve that keeps eve... | [
"You're misunderstanding the nature of a grid intertie. This isn't a transmission line subject to DC or AC line losses, it's a facility. Addition of a DC interconnect will always make the network less efficient because it's not replacing any line, it's just a node in the network. "
] |
[
"Are film clips still \"moving pictures\" when recorded and stored digitally, or does the recording of a digital video work differently from analogue recording?"
] | [
false
] | I put computing as flair, but I'm honestly not sure in which category this belongs. Feel free to mark it with more appropriate flair, admins. | [
"The basis of digital video formats is still a sequence of still images, just like analogue film.",
"However, for efficiency purposes, various optimizations are made, because storing a full resolution still image for every single frame would require a large amount of storage space (and a large amount of bandwidth... | [
"Yes. If you look at ",
"http://wp.xin.at/archives/3465",
" which compare two different ways of encoding a video, more precisely these screenshots : ",
"http://wp.xin.at/wp-content/uploads/2016/02/H.264-AVC-1mbit-00000006-proc.png",
"http://wp.xin.at/wp-content/uploads/2016/02/H.265-HEVC-1mbit-00000006-proc... | [
"So would a video of constantly changing static take more storage than a typical movie of the same resolution?"
] |
[
"Do plants ever feel \"full\" if they absorb enough sunlight?"
] | [
false
] | For humans, we have hormones that tell us we feel full when we eat enough food. Do plants have a similar system that tells them when they absorb enough sunlight? What do they do with the excess energy they absorb? | [
"Roughly speaking, photosynthesis turns carbon dioxide + water + light into sugar + oxygen. The sugar production is not evenly distributed through the plant, so the plant must transport sugar from where it is produced to where it is consumed. It has things called phloems (like blood vessels) to do this.",
"There ... | [
" is (as far as we know) a concept limited to organisms with a nervous system. However, the sensations we experience serve biological functions, as you alluded to, and these biological needs can be met in ways other than with a nervous system. Therefore, plants of course don't actually ",
" anything the way we co... | [
"Disclaimer, I'm not basing this off of anything I've read, but logically I doubt this would be needed. ",
"Hunger and fullness exist in some animals because locomotive species have to go acquire food when we need to eat. We need intrinsic motivation not to starve to death. Don't think of fullness so much as prev... |
[
"How do computers know which wireless signals are meant for them?"
] | [
false
] | Additionally, how do they know which signals the individual signal fragments belong to? With all the information being sent wirelessly across the globe, it seems like it'd be extremely difficult to know what constitutes any individual signal as opposed to fragments of other messages. How on earth do our computers manage to know exactly what messages are meant for them and the exact content of those messages with all the "noise" they're surrounded by? | [
"Messages which are carried through networks contain meta data as well as payload. The payload might be part of a web page or image. The meta data would be addressing information (sending and receiving IP addresses), and sequence numbers which identify that message (or packet) as a part of a stream. The reieving n... | [
"Extending the scope of the question and answer, I'd also like to add to this that because the packets don't have any extra encryption that is only readable by the target computer as opposed to another (just like snail mail has a TO: address, but isn't locked; you just hope it goes unopened to its proper destinatio... | [
"Anybody else also connected to a secured network can also see the \"plaintext\" packets. \nEven somebody not attached to that network can capture them and later decode them."
] |
[
"Realistically, what would motivate humanity to colonize our moon or other planets?"
] | [
false
] | [deleted] | [
"There is probably no non-scientific reason to colonize the moon because it can't be terraformed, has no magnetic field and lacks a number of other qualities you'd want. If we found a planet that could support our life reasons to colonize would include ",
"It's like saying \"why would we colonize land if there's ... | [
"Commerce."
] | [
"Simply, a lack of natural resources, the inefficiency of creating artificial resources, and the rise of pollution to the point of no return. "
] |
[
"What is the relation between photons and electromagnetic fields?"
] | [
false
] | null | [
"Photons are the ",
" of the electromagnetic field. This means that electromagnetic fields come in discrete 'chunks' called photons. But this is a quantum-mechanical description, not a classical one, so you shouldn't think of photons as particles with definite properties--the photons act like waves, too, just as ... | [
"Yes. Well, QED is specifically the theory of photons and electrons, but it includes photons. (And you also generally want something around that can interact with the photons.)"
] | [
"Thank you for your answer.",
"Yes, but not in terms of a classical field--you need a quantum field theory to describe photons.",
"Are you having specifically quantum electrodynamics in mind here? If so, I'll look into that. Will I perhaps get all of these questions explained to me in QED?"
] |
[
"What mental illness needs the most recognition in 2018, and why?"
] | [
false
] | null | [
"Hello,",
"Open-ended questions are more appropriate for ",
"/r/AskScienceDiscussion",
".",
"Cheers."
] | [
"Hello,",
"Will this be allowed then? Or removed?"
] | [
"It is removed, but you are encouraged to post it to ",
"/r/AskScienceDiscussion",
" instead."
] |
[
"Does water have a limit to how much soluble matter it can dissolve? If so, how is this measured?"
] | [
false
] | null | [
"Fellow coffee lover here! But definitely not sophisticated enough to be a snob- I just consume large quantities of it. :3",
"This is actually a very complex question because coffee is not a uniform substance. It contains thousands of different chemical compounds, each with its own unique properties and varying s... | [
"The limit to how much solute can be dissolved in a solvent is dependent on a lot of different factors, such as the properties of the solute and solvent, temperature, pressure, and pH. We don't assign a \"maximum solute dissolving ability\" to the solvents, like water in this case. We measure the concentration of a... | [
"It's actually a tremendously complicated question. You're not so much \"dissolving\" the coffee as doing an extraction. The various compounds in the coffee beans (and there are quite a few of them) are trapped inside the matrix of the bean. Some of them leave that matrix (are extracted) more or less easily unde... |
[
"Apart from AIDS, is there any other syndrome/disease the HIV causes? Or is it only AIDS?"
] | [
false
] | null | [
"A short time after initial infection, many people experience a brief flu-like illness. After this subsides the virus becomes latent for a period of up to a number of years before causing immune deficiency.",
"The virus also can cause neurocognitive changes independently of opportunistic infection, ranging from m... | [
"In addition, though these are not ",
" by HIV, there are a number of infections/symptoms that are indicative of HIV due to the immune suppression:",
"• Candidiasis (esophagus)\n• Cytomegalovirus of retina, brain, spinal cord, gastrointestinal tract\n• Lymphoma, brain or non-Hodgkin's (B-cell or immunoblastic)\... | [
"HIV-Associated Neurodegenerative Disorder (HAND) is actually believed to be caused by the virus itself, or at least indirectly through proteins it encodes. HIV is believed to activate the infected macrophages, as well as microglia and astrocytes, which then damage their surrounding neurons.",
"An article on HAND... |
[
"I've read that living an inactive lifestyle is on par with being a smoker. Is one particularly worse than the other?"
] | [
false
] | null | [
"It could just mean many more people are inactive than smokers."
] | [
"It could just mean many more people are inactive than smokers."
] | [
"I would think that if one made a Venn Diagram with two circles representing both groups, there would be considerable overlap."
] |
[
"If i let a bottle of let's say vodka sit for a while, will the alcohol rise to the top of the bottle?"
] | [
false
] | Since alcohol has a lower density than water? Additionally, if i freeze the liquid, could i then cut a piece of the top, which would then contain more alcohol than the average of the overall bottle at a specific abs.vol (40%)? | [
"Ethanol has a lower density than water, so if the two didn't mix, you'd have ethanol on the top. Ethanol and water are fully miscible however, so you don't get a concentration of ethanol on the top. The two liquids act as one and don't retain the density properties of the original liquids.",
"Vodka also doesn't ... | [
"I was wondering how these mixtures evaporated. If you left a 50/50 EtOH/H₂O container uncorked at 25°C for a week, would more EtOH evaporate by virtue of its higher vapor pressure? I think yes.",
"So I went off to read about the behavior of vapor pressures of miscible liquids and discovered ",
". Cool stuff... | [
"Funnily enough if you slowly lower the temperature of an an alcohol water mixture, the exact opposite happens. The water actually freezes first and the liquid you leave behind is enriched in alcohol, this is because alcohol water mixtures have a lower freezing point than either pure water or pure alcohol and the c... |
[
"So our brains release dopamine when we listen to moving music, but why?"
] | [
false
] | What's the point of that? how did it come about? | [
"The first step in answering the \"why\" questions is to look at any evolutionary benefits it might have had - if any activity is evolutionarily beneficial, the body will want to promote it, and one way to do so is to have it be pleasurable so that the individual and eventually the species at large engages in said ... | [
"Great answer! I've always liked to think human's affinity for music also stems from the sheer mathematics of the music. Is there any science behind that, or just my wishful thinking?"
] | [
"It is entirely possible that it is the math. I study the relationship between various mathematical aspects of music and how we behave when we listen to them. There's something called fractal structure which is present in nature, art, your body's rhythms, etc... This is also found in music (distribution of pitches... |
[
"How much is too much coffee?"
] | [
false
] | null | [
"TIL I'd have to drink about 174 cups of coffee in short succession to die.",
"Thank goodness my 5ish cups a day comes no where near that number!"
] | [
"There have been tons of studies based on coffee and it seems that every week the verdict is out whether it is good for you/bad for you. For the most part though, most of the effects of coffee are tied to the caffeine content of it.",
"Everybody has a different tolerance for caffeine based on their weight, height... | [
"Your complement, the 5 pot/day guy, checking in. I don't have any studies to back myself up, but I feel fine. It definitely varies from person to person."
] |
[
"How are you supposed to picture complex wave functions?"
] | [
false
] | intro quantum mechanics. | [
"It's not easy when you have a wavefunction that depends on three spatial coordinates and time, and it's complex-valued. But there are little tricks you can use. For example you can often decouple the radial and angular parts of the energy eigenstates. The angular parts are usually just given by the spherical harmo... | [
"There are some ",
"cool applets here",
" (the quantum mechanics section) that let you visualize wave functions. The main idea is to use the color wheel as a stand in for the phase of the wavefunction. Then a wavefunction like e",
" that has constantly varying phase will have a rainbow color pattern where the... | [
"Physically, and not mathematically, what does the radial part represent? Many thanks for your answer,"
] |
[
"Is it possible to have red lightning?"
] | [
false
] | if so how or why does this work? | [
"Might be a camera artifact, color-balance issues. Perhaps it shows up in a photo, but nobody saw any red color during the lightning strike. Odd colors are associated with ",
"lightning inside ash clouds."
] | [
"I suspected this to be a time lapse because the clouds move quickly, and tin eye says I was correct.",
"http://bocaberta.org/2009/09/tempestade-em-timelapse.html",
"The third image there is the same location and cloud formation, and has the red lightning's shape shown in white. The video shows more of the same... | [
"I believe what ",
"this website",
" tells me on what causes lightning to have color"
] |
[
"Why are certain people able to eat and digest spicier foods better than others?"
] | [
false
] | [deleted] | [
"TRPV1",
" is a receptor that responds to capsaicin. People who lack this or are deficient in this would theoretically have little or no response to spicy foods. So yes, technically, by mutation, you can avoid the spicy sensation.",
"On the other hand, what you are probably referring to is why Indians can eat... | [
"FWIK, digestion is irrelevant. Capsacin only affects the mouth and anus, it does absolutely nothing to the digestive system. i still dont understand why some people fly to the toilet after spicy food."
] | [
"It is a mixture of both genetics and environment, with a larger proportion of it being environment. When one is exposed to certain spices and ingredients in their diet from a very young age, his/her digestive and immune systems adapt to digesting and metabolizing those substances very well. That being said, there ... |
[
"Would you still be able to donate your organs if you've gone though chemo therapy?"
] | [
false
] | null | [
"In practice, the answer is no - but it's not because of the chemo, it's because of the cancer you presumably had which the chemo was treating. If you for some reason received chemotherapy but did not have cancer, I'm not sure if the chemo on its own would preclude organ donation."
] | [
"Thank you! Thats what I was trying to figure out as well. "
] | [
"In my country, depending on the cancer and the treatments and so on people might still be able to donate organs. Obviously not during therapy, but if somebody had a potentially curable cancer, received the adequate therapy and remains cancer free after X years, they may be able to donate certain organs. Usually, t... |
[
"A time travel/astronomy question: could I look at the stars and tell the date at any time in the past?"
] | [
false
] | Let's say my time machine has malfunctioned and I know where I am, but not when. What can I do to determine my location within time? | [
"With careful measurements of the positions of the stars and moons you could work out a range of time in which you found yourself. ",
"You could narrow it down further by quizzing locals about comet sightings (assuming after building a time machine you also built a cochlear implant to translate language to unders... | [
"If your time machine had a computer you could indeed analyze the position and drift of the constellations and stars to tell when you are, It would be very difficult to do this manually though. "
] | [
"How would that help the traveller? The location of the constellations would not necessarily have been recorded, or even necessarily in a uniquely different location, and it would be so difficult to calculate any of this, even with the aid of a computer, that it would be practically impossible. "
] |
[
"Does lightning make a sound when it strikes small bodies of water?"
] | [
false
] | such as lakes, or Tampa Bay? | [
"Yes. Pretty much all of the sound comes from the air the lightning goes through, not from the target itself. By far most lightning goes only through the storm cloud itself and we can hear these aswell. Only reason they do not seem as loud is because they are further away than if lightning strikes near you."
] | [
"The sound comes from the expansion of the super heated gas where the lightning travels through the air, making a pressure wave from the expanding gas (thus sound). So where the lightning connects to the earth does not matter."
] | [
"The sound lightning makes comes from the air expanding. Air has a huge electrical resistance, so when current passes through it, energy is deposited in the form of heat according to the formula E = t * R * I",
" where E is energy, t is time, R is the resistance, and I is electrical current. When gasses are heate... |
[
"Why is it when i dry clothes in a dryer they're soft and fluffy, but air dried in a heated bathroom they come out crispy?"
] | [
false
] | My dryer is broken so I've been hanging up some clothes and it's been bugging me. | [
"The answer for this is simpler than you'd expect. When you dry them on a rack inside your house, they stay in virtually the same position for the entire drying period. The clothes kind of 'set' in the position that they're in. When using a dryer, clothes are tumbled around throughout the cycle and don't have a cha... | [
"there's also a waxy softening agent that makes things feel softer. Counter-intuitively though, this stuff makes towels slightly LESS absorbent."
] | [
"So should i patent the tumbling outdoor solar clothes dryer?"
] |
[
"Has an industrial accident ever caused volcanic lightning?"
] | [
false
] | If not, what would it require? Would it be possible? | [
"Volcanic eruptions typically involve quantities of energy and matter that are very large by human standards. (It would have to be a ",
" of an industrial accident to be in the same ballpark.)",
"But something that might be of interest are pyrocumulonimbus (pyroCb) clouds that can result from forest fires, and... | [
"as ",
"/u/charlaron",
" said - its unlikely that an ",
" has ever led to a pyrocumulonimbus-like cloud or lightning. However, it is well ",
"studied",
" that nuclear bomb tests have induced lightning, as can be seen ",
"here."
] | [
"ah thanks",
"I actually had no idea that forest fires could produce them."
] |
[
"Eye color relating to sight perspective question"
] | [
false
] | I've wondered this for a long time, and I hope one of you can answer this for me. Is it possible for people with different eye colors or any other reason to see colors different? We've all been taught to call blue blue, but what if I see blue as your green? Reasoning(in my head) that this could be: different eye colors/the way its communicated to the brain in different people. | [
"the color of your iris isn't going to affect your photoreceptors. "
] | [
"Eye colors do not effect vision whatsoever. Light does not pass through the iris to reach the retina.",
"It is nonsense to ask what we perceive colors as.",
"I perceive it as a set of electrical impulses passing chemical gaps.",
"So do you.",
"To try to tell if they're the \"same\" is meaningless. Percepti... | [
"Very informative, thank you for your time. "
] |
[
"How to classify and differentiate of sub-species and breeds."
] | [
false
] | Hi simple question How do we classify and differentiate if its a sub-species or a breed of something? There are times when a subspecies look alot like the other, but breeds can appear to look very different. (e.g Borneo Pygmy Elephant to Asiatic Elephants = subspecies, Toy poodle to Huskies = Dog Breed) Please provide academic link, google is only giving me forum links. Thanks | [
"A major distinction is that the term \"breed\" is really only used in animal husbandry and not in taxonomy (classification of species) or in biology. The problem with breeds is that they are often based on shifting sets of physical characteristics both in time and in space. One kennel club may describe a breed a c... | [
"Thanks a lot :D"
] | [
"So you're asking \"when do we say 'x' and 'y' varieties of a living being are breeds vs being subspecies?\"?"
] |
[
"Is photosynthesis more efficient than combustion of oil?"
] | [
false
] | Hey askscience, could you guys help me determine if plant photosynthesis is more efficient at energy production than other forms we are using for energy (combusting oil, moving water, decaying radioactive elements)? What does photosynthesis do, that we can't mimic or utilize the process? Thanks! Edit: grammar | [
"I'll let somebody else tackle the comparison to petroleum-- but compared to currently-available ",
"photovoltaics",
" (6-40% efficiency, with common panels around 15%), photosynthesis is ",
"not very efficient at all.",
" (0.1%-8%, with most plants around 0.1% and most crops around 1.5%).",
"Put another ... | [
"But the way that the efficiency are being calculated here doesn't lend itself to a fair comparison. For photovoltaics you are looking at the amount of electricity generated to calculate the efficiency, and for photosynthesis you are looking at the amount of biomass. Looking at biomass to calculate efficiency is li... | [
"You can, however, compare the quantum efficiency of photosynthesis to the quantum efficiency of a solar cell.",
"When comparing the efficiency of two things, it is crucial to know what we're comparing-- but that doesn't make comparing the useful energy obtained with both systems an \"unfair comparison.\" ",
... |
[
"Do black holes really have infinite density? (And other questions about black holes)"
] | [
false
] | : I've heard black holes described as having infinite density a bunch of times. Density=Mass/Volume, and black holes definitely have a non-infinite mass (otherwise its gravity would be infinitely attractive). If density is infinite and mass is not, the volume of the black hole would have to be infinitely small, right? : Now, to my understanding, black holes can be formed when a big enough star runs out of fuel. (Are there any other ways to form black holes?). Stars need to have some sort of fusion reaction going on in its center in order to counteract the massive force of gravity, and when fuel for this reaction runs out, the force of gravity overcomes the (pauli exclusion forces? is there some kind of name for this force?). The star then collapses in on itself. But how does this make for a black hole with infinite density? Wouldn't all the matter in the star occupy the space of a single neutron? How can the black hole get smaller than that? Thanks :D | [
"neutron degeneracy pressure is actually only minimally responsible in supporting a neutron star from collapse. At densities greater than the nuclear saturation density (~ density of an atomic nucleus), the strong force actually becomes ",
" trying to restore the nucleons back to a nuclear equilibrium. In fact, i... | [
"question 1... it depends. The most conventional understanding is a point mass. It's kind of improper to specifically call it infinite density, but yeah the mass divided by zero volume is \"infinite\". More contemporary interpretations that aren't really necessarily a part of science proper skirt this definition.",... | [
"I've heard black holes described as having infinite density a bunch of times. ",
"I'm not an astrophysicist so someone correct me if I'm wrong, but my understanding is that there are two conflicting schools of thought. Based on just General Relativity, there should be a true singularity, which would have \"infi... |
[
"Did the early universe have an event horizon and behave as a black hole?"
] | [
false
] | I was watching a lecture about calculating the Schwarzschild radius/event horizon for a black hole, and I wondered what the Schwarzschild radius of something with the mass of the observable universe would be so I ran the numbers on it using an estimate for the mass of the universe from . Where r = 2GM/c r = [(2)(6.67E-11)(3E+52)]/8.99E+16 r = 4.45E+25m = 4.7 billion light years If all of the observable matter in the universe existed within a radius of less than 4.7 billion light years, which it must have during the inflation of space-time, would that not mean that it would have qualified as a black hole? Would it only have appeared as one to an outside observer, but because the density inside the radius would have been so much lower, would it not have appeared as one to a contained observer? And what would have happened after inflation drove the matter outside of its own Schwarzschild radius? Or have I just gone horribly wrong in my math somewhere? | [
"The equation r = 2GM/c",
" is really only valid for a system that can be reasonably approximated by a point mass at the center of the coordinate system and very little mass outside. When you have such a setup of a large concentrated mass one can solve the Einstein Field Equations to get the ",
"Schwarzschild m... | [
"Very cool. Thanks for the reply"
] | [
"The Schwarzschild metric and associated equations are roughly valid as long as the mass is all inside some finite radius R, it is spherically symmetric, it isn't spinning too fast, and it doesn't have much charge. ",
"For example, I can treat the sun like a black hole with all of its mass at the center, and the ... |
[
"Have there been any unbiased studies on the long-term effects of cannabis use and what are the effects on lung capacity, memory intelligence, ect."
] | [
false
] | [deleted] | [
"I just went through a bunch of MJ stuff on a ",
"bestof",
" thread and on another thread ",
"here",
".",
"There haven't been great studies on MJ and lung function. There are some earlier studies from New Zealand, including ",
"this one",
". Then there was a recent paper published in JAMA ",
"here",... | [
"You're welcome to read the citations in the wiki if you don't think they're good sources... ",
"http://www.cmaj.ca/content/166/7/887.long"
] | [
"I read the ",
"wiki",
" section on the long term use of marijuana's effect on memory and intelligence and I find it pretty accurate... that moderate use has little or no effect, but heavy use does."
] |
[
"How do you calculate the limits of functions using the exponential one?"
] | [
false
] | Something has been bugging me for a while. Let's say there's a function such as . How would you get the limits when x reaches infinity? It sounds impossible to me. Moreover, how did we find out about the way to solve this problem (if we ever did)? | [
"You can use ",
"L'Hopital's Rule",
". If you write g(x)=x and h(x)=e",
", then f(x)=g(x)/h(x) and the limit of g(x) at infinity is infinity, and the limit of h(x) at infinity is also infinity. It then looks like the limit of f(x) at infinity should be infinity/infinity, but since this is undefined, we can't ... | [
"L'Hopital's rule is super cool and essentially tells you which infinity is growing or shrinking faster.",
"So, you can intuitively determine that e",
" approaches 0 much much faster than x approaches infinity and will win out in the end."
] | [
"L'hopitals is usually the answer. Sometimes you need repeated applications for it to resolve things. Another under utilized tool you can use though is the logarithmic derivative, which can be used to determine convergence. (If you're actually interested hit me up and I can elaborate) ",
"The example I use is 2",... |
[
"I think randomness doesn't actually exist, but is only used to fill in gaps of understanding. My colleagues think I'm being ridiculous. What are your thoughts?"
] | [
false
] | Let me explain what I mean first. I am a scientist and always come across statistics used to explain phenomena as best we can, but are ultimately deemed "random" usually because they have far too many nonlinear factors involved in any possible explanation. An example would be quantum physics where we cannot determine where an electron might be at any one time. However, I find randomness to be a stopgap only. While events may "randomly" occur in the view of current scientific understanding, this does not mean the system follows laws of randomness, whatever those might be. Instead, there are laws governing why that electron might be in one location versus another, but we lack the necessary tools to prove that scientifically. Overall, I believe that there is only a "perceived randomness" that we use as a tool to approximate the behavior of the system, no different than when we use finite difference methods to solve numerical simulations. We know that the output of a simulation is only approximate, but we can gain insight from using the output. I feel we should use the same approach towards "randomness" where it is only a tool of understanding and not necessarily a final classification of the behavior of a system since statistics is only a tool we use to gain insight into complex systems, and not a definitive solution. Does any one else think along these same lines? If not, please feel free to explain why. I'm always open to learning new things that I have not considered when it comes to what I believe. Edit: Thanks everyone for responding. I'm glad there are still places on Reddit to have logical, serious discussions, instead of just mindless bashing. I'm learning a lot from each of you! Thank you! | [
"The first thing that came to my mind to address your question was something that I learned from some of the physics panelists' posts: ",
"Bell's theorem",
", which seems to refute what you've suggested."
] | [
"It's been a little while since I got my physics degree, but what you're suggesting is a well-known but physically refuted set of notions about quantum randomness, termed ",
"hidden variable theories",
".",
"Basically, the idea behind hidden variable theories are exactly what you suggest, ie, that seemingly-r... | [
"I wouldn't call that proof, more like a lack of evidence for determinism. We can apply statistics to highly chaotic systems like human behaviour and our brains (without getting into QM, although some scientists are trying to bring QM into neuroscience); that doesn't make us inherently random. Tossing dice or a coi... |
[
"What science related podcasts do you recommend?"
] | [
false
] | I like listening to general science based podcasts on my commute, but can't seem to find any more good ones on iTunes. I really like Skeptiod, but have listened to the entire back catalog. I also like Science Fantastic with Micheo Kaku, but they are only clips on iTunes. Any recommendations? | [
"Radiolab"
] | [
"Neil deGrasse Tyson's StarTalk Radio Show is interesting and often humorous as his guest hosts are usually comedians."
] | [
"This Week in Virology",
". It's a podcast by a virology professor with a few other co-hosts, including a science writer, other professors, and special guests. The discussion is much more in depth then a Radiolab-type podcast and might be initially daunting for a layperson, but they make a real effort to make t... |
[
"When marine mammals have open cuts or wounds does the salt water sting for them?"
] | [
false
] | I asked this in last night and got no answers so I decided to put it up here; I don't think I broke any rules... | [
"Yes, almost certainly. But they are to a degree desensitised to it after a life of living and getting injured in salt water. It’s difficult to measure long term discomfort from a wound in marine mammals because, as with most animals, they ignore the pain and just get on with things.",
"But yes, there is no reaso... | [
"That is wrong, since the salts are dissolved, right? I'm pretty sure the pain is due to osmotic stress."
] | [
"That is wrong, since the salts are dissolved, right? I'm pretty sure the pain is due to osmotic stress."
] |
[
"How does the stomach let through food and water, but not the acid?"
] | [
false
] | null | [
"The stomach doesn’t hold the acid back. First, the stomach makes a small amount of acid when you aren’t eating. When you do eat the acid production increases. However, it gets diluted buy the food/liquids you ingest along with your saliva and mucus. Second, your body neutralizes the acid as fast as possible on... | [
"Abundant Brunner glands in the duodenum also secrete bicarbonate to buffer the acid. There’s plenty of checks to prevent acidic damage. The GI tract is truly remarkable for its Neuroendocrine regulation. "
] | [
"Abundant Brunner glands in the duodenum also secrete bicarbonate to buffer the acid. There’s plenty of checks to prevent acidic damage. The GI tract is truly remarkable for its Neuroendocrine regulation. "
] |
[
"Is it possible to not \"see\" a tangible object?"
] | [
false
] | Hallucinations are defined as "an experience involving the perception of something not present", so I was wondering if it were possible for a human to not "register" something that is physically present? | [
"It is absolutely possible. Attention gates our consciousness of visual phenomena - if our attention is directed elsewhere, our conscious mind often misses things. For demonstrations, check out this ",
"selective attention experiment",
" and this ",
"change blindness experiment",
"."
] | [
"A local scotoma or hemianopia perhaps? Blindsight and spatial neglect are another two possibilities."
] | [
"My pleasure! Many of the problems with eyewitness testimony are caused by memory issues induced by ",
"misinformation",
", but a weak initial memory trace due to inattention would certain compound them."
] |
[
"What does string theory does differently that current theories do not when dealing with singularities?"
] | [
false
] | From what I gather, in string theory we naturally unify QFT and GR, so does it solve the problems that we encounter at a singularity? If so, what explanation does it offer when particles are broken down to their fundamental bits inside a black hole. Please shed light on how our understanding of black holes, and singularities would further if string theory is indeed true? | [
"In string theory, black holes are actually p-branes. Normal particles are instead strings. When the strings are very close to the brane, it becomes possible for them to interact in a way that leads to no infinities. The interaction is the result of the contribution of all possible histories (as it's normal in a qu... | [
"So can you expand on it a little bit maybe? Like in QFT, you have quarks as fundamental particles, so what exactly would happen to the vibrating strings of a quark once it gets sucked into the black hole (or p-branes as you say)",
"They would join the brane and could generate one or more quanta living on the bra... | [
"To give an intuition, the \"regulator\" that prevents the singularity from being truly singular is the finite size of strings which cuts the divergences short - intuitively the string cannot see things smaller than the string length.",
"So can you expand on it a little bit maybe? Like in QFT, you have quarks as ... |
[
"When I'm scuba-diving, I'm breathing pressurized air. Why don't breaths last longer when I'm deeper ? Don't they contain more oxygen ?"
] | [
false
] | null | [
"The urge to breathe is controlled by rising levels of carbon dioxide, not falling levels of oxygen. This is why you can pass out if you hyperventilate - you're lowering the CO2 levels to such a low level that you can run out of oxygen before you feel the need to breathe.",
"So while it's true that more oxygen m... | [
"The urge to breathe is regulated by both CO2 and O2 levels. The body responds much more rapidly to high CO2 levels than to low O2 levels.",
"Otherwise, you are right on the money. The CO2 builds up, which can cause a big problem. This is the principle behind ",
"rebreathers",
", which 'scrub' CO2 from the... | [
"http://en.wikipedia.org/wiki/Hypoxic_drive"
] |
[
"Why doesn’t diesel have different grade levels at gas stations like gasoline?"
] | [
false
] | null | [
"Gasoline engines compress a mixture of vaporized gasoline and air, and ignite that mixture with a spark plug in an explosion that pushes the piston back down. Now, compressing a gas heats it. That can lead to the mixture detonating prematurely, before the piston has reached the top, in which case explosion will tr... | [
"By way of explanation: diesels spray a precise amount of fuel directly into the cylinder at very high pressures. In modern electronic controlled diesels there may be as many as 20 injections in one combustion cycle. They don't use a spark for ignition, instead, rely on having a much higher compression ratio to pr... | [
"Thank you for explaining this!"
] |
[
"Why is ADD and ADHD so common now?"
] | [
false
] | I have read it affects somewhere from 5-9% of the population. I myself have ADHD, and have been prescribed Ritalin. However, my diagnosis wasn't based on cognitive ability/other factors, but rather on questions such as "Do you feel so and so when you do so and so?". Is it just overdiagnosed, it is because of television and the internet, or what? Also, is there any way to cure AD(H)D? Edit: Wow, this question got more attention than I thought it would O__O. Don't bother answering the second question if you're going to contribute. Also, could anyone explain the causes behind ADD/ADHD? | [
"[Master's in Clinical Psychology, working towards Doctorate]",
"Go, go, EBSCOHost!",
"QUESTION 1",
"Sciutto, M. J., & Eisenberg, M. (2007). Evaluating the evidence for and against the overdiagnosis of ADHD. Journal of Attention Disorders, 11(2), 106-113. doi:10.1177/1087054707300094",
"LeFever, G. B., Arco... | [
"Don't forget about the chance of misdiagnosis as ADD/ADHD when the child is actually intellectually gifted/talented. The ",
"list of characteristics for each",
" has a lot of overlap. Also, sorry I don't have a better link than that - most of my knowledge comes from books like ",
"Webb's",
" on Misdiagnosi... | [
"From an epidemiological perspective, one of three things could be going on... ",
"The actual incidence of true ADD/ADHD may be increasing. If this is the case, it would be helpful to identify what causes ADD/ADHD. Unfortunately, there is probably no one cause, nor is the exposure to one of those 'causes' guarant... |
[
"Why aren't quadricopters more common in full-scale?"
] | [
false
] | As common as quadricopters seem to be for drones, why haven't we seen a larger adoption of that format in full-scale? The advantages of the platform (easy to fly, stable, maneuverability) would seem to be applicable to some roles that helicopters or airplanes serve now. Is there an inherit disadvantage to the 4 rotor setup in large scale, or do the advantages just not outweigh the drawbacks for most usage? | [
"Quadcopters are great in the hobby scale since they are incredibly maneuverable and can be relatively inexpensive.",
"The maneuverability does not scale up. Just as the surface area to volume ratio of a cube will drop as the cube gets bigger, the ratio of rolling/pitching/yawing power to moment of inertia goes ... | [
"Single rotor aircraft can already lift incredibly heavily loads and for even heavier loads we have dual rotor craft such as the Chinook. There are few needs for an aircraft with 4 rotors. The extra weight and extra fuel makes such a large aircraft less efficient. If you research the history of the V-22 you'll find... | [
"Koooooj got the answer right here, but I'd like to say something regarding your assumptions. Quadcopters are most certainly NOT easy to fly, nor stable. They only seem that way due to a generous amount of gyro's and stabilization software. Aircraft in contrast can be (and usually are, except for fighter jets and t... |
[
"What are physicists' best ideas for solving the proton radius puzzle?"
] | [
false
] | When you measure the proton radius by firing electrons at it, you get a different value than if by firing muons. Currently, this is unexplained by the standard model and there is no widely accepted explanation as to why this should happen. Despite this, what believable interpretations have physicists postulated since? | [
"Yes, I beleive its about 5%, but the quoted ucertainties from the relevant measurements are ~1%, perhaps less. In otherwards the discrepancy of about 5% is significantly larger than the variation one would normally expect to see given the stated precision of the measurements. "
] | [
"Of course you are completely correct that protons are not classical hard balls of matter, but that doesn't really address the issue that OP is asking about.",
"As far as I understand the proton radius puzzle comes from disagreements about the charge radius, specifically measurements which are used to infer the r... | [
"Of course you are completely correct that protons are not classical hard balls of matter, but that doesn't really address the issue that OP is asking about.",
"As far as I understand the proton radius puzzle comes from disagreements about the charge radius, specifically measurements which are used to infer the r... |
[
"Why do sockeye salmon rot, while still alive, during their trip upriver to spawn?"
] | [
false
] | I'm watching an episode of Monster Fish, and they briefly touched on it, but didn't really give any explanation for it. Just that the salmon "undergo a dramatic change" during their trip upriver, and the flesh literally rots off of them by the time they're done. Why does this happen? And does it provide some kind of an evolutionary advantage? | [
"Pacific Salmon go on a one way trip to spawn. Once they start upstream they stop eating, but still need large amounts of energy to get up those turbulent cataracts. That energy has to come from somewhere, so their bodies strip off the body fat and starts to eat itself from within to supply the body with nutrients ... | [
"Nature tends to take the most economic path in the end. If you have problem which requires a fish to spend immense effort to swim up a difficult stream as quickly as possible and spawn, after which the fish has no further purpose, then this is a quite efficient way of doing it.",
"Initially they all survived, bu... | [
"Is this different from fasting?"
] |
[
"How can we experience such seemingly long dream sequences if REM Sleep cycles only last 10-15 minutes?"
] | [
false
] | I may be wrong, but it's my understanding that there is REM sleep during which dreaming occurs which lasts about 10-15 minutes, then we go through Stages 1-4 then 4-1 of the sleep cycle before we get back to REM sleep. Furthermore, we very rarely can recall our dreams unless we are woken up during REM sleep. I'm perhaps incorrectly presupposing that dream sequences are not continuous and related from one period of REM sleep to another because of the long period of time separating them. So, my question then is how can we experience "events" during dreams that we perceive to elapse over a significantly longer period of time than actually passes in the real world? Thanks in advance for anyone who takes the time to read and respond. | [
"There seem to be a few potential misconceptions here, so let me add some thoughts.",
"1) As has been pointed out, REM sleep bouts are short early in the night but become longer towards the end of the night.",
"2) It is not usually true that \"we go through Stages 1-4 then 4-1 of the sleep cycle before we get b... | [
"Sorry for not originally posting sources, most of that was based on memories of college courses. I should have looked this up before posting, now I feel silly. For the real-time aspect of dreams, Daniel Erlacher & Michael Schredl conduct a study in which they state: ",
"Nowadays, the hypothesis is widely accepte... | [
"Your view of the sleep cycle is pretty close, here's a ",
"handy little chart",
" showing a breakdown of the different cycles over six hours. The first REM cycle lasts about ten minutes, with each successive REM cycle lasting longer. The longest REM cycles are close to an hour in length. ",
"To answer your q... |
[
"Just read about denaturation. Question about fevers"
] | [
false
] | So I'm taking Biol 190 and just read about how proteins can undergo denaturation. As I have understood it, this is basically the proteins losing their shape and becoming useless. the book then mentions that high fevers are fatal because the proteins in the blood become denatured at the high temperatures. I know that ice packs are usually put on a person's body to help cool them off. I was wondering if injecting a cooled saline solution into the blood stream would also work or work quicker? Or if that would cause more damage? | [
"Perfusion would be the act of pumping blood into the organs. Vasoconstriction can lead to multitudes of issues - by definition, it would mean the \"tightening\" or \"narrowing\" of blood vessels. ",
"You have it right - if we vasoconstrict someone's vessels by using vasopressors, we pharmacologically increase ... | [
"Thank you. I didn't think the body would react well to basically cold water being injected into. But there was some gray area in my head. Thank you for clearing that up. ",
"Follow up question. What is perfusion? Also I can gather what vasoconstriction means, but why exactly is it bad? I think its bad because ... | [
"Thank you. I didn't think the body would react well to basically cold water being injected into. But there was some gray area in my head. Thank you for clearing that up. ",
"Follow up question. What is perfusion? Also I can gather what vasoconstriction means, but why exactly is it bad? I think its bad because ... |
[
"Does turning a box of icecream on its side with the top off make it melt faster?"
] | [
false
] | I have been pondering this with my grandpa. He usually does this to make it melt faster. It does seem logical; given that cold air is heavier than warm air, it would presumably "spill" out, or the air that has been cooled in the heat exchange will fall down and allow new warm air to exchange heat. But maybe the thermodynamics are more complicated than that. | [
"It's more likely just about contact area. Ice cream cartons sit on a ridge so the only contact between the cold ice cream and the countertop is a thin ridge of material and so heat is not transmitted into the ice cream very quickly. . When your grandpa turns it on its side then the cold carton is touching the coun... | [
"I agree with the argument saying that the contact with countertop increases temperature. ",
"Another reason could be that you’d increase the pressure applied on the ice cream towards the side of the box, since that side would be supporting more of the weight. As pressure decreases the melting point, this might a... | [
"I’d guess the convection properties of the cold air spilling over the edge and being replaced with ambient air probably make it a wash",
"Perhaps.",
"But ",
"this video",
" from Technology Connections makes a pretty good argument for why chest freezers are so efficient. In short: dense, cold air easily spi... |
[
"[Earth sciences] I have some trinitite. How would I check if it's legit?"
] | [
false
] | null | [
"Use a geiger counter. Or put it in a very dark room with no light and look at it with your cell phone camera. If you see little distinct white dots in the picture it is emitting beta/gamma radiation that can be picked up by the camera's CCD."
] | [
"Thank you! I'll check this out!"
] | [
"/r/whatsthisrock",
" is probably a good place to ask about identifying rocks."
] |
[
"Why isn't CO2 visible?"
] | [
false
] | I happened across a of CO2 which included the very end of the visible spectrum. It seems to show CO2 absorbs light in the 630-700 nm wavelength, at least somewhat. I'm curious why, if CO2 seems to absorb some visible light, high concentrations of it are not visible as bluish/cyan gas (white light removing the deep reds). Is there something I am missing here? What led me to this was an interest in replicating the sort of things shown or . These all seem to use mid wave IR and a narrow bandpass filter. I would imagine that if a narrow bandpass filter around 650 nm on a regular camera would let you see CO2, they would have done that instead. But I don't see why it wouldn't work. : As Shookfoot notes below, the units on the graph are wavenumber, not nanometers wavelength. As such, the absorption isn't in the visible spectrum at all. | [
"Hi there! The answer to this question is about the units of the absorbance spectrum you have shown us. The units are in wavenumbers, not nanometers. 600 wavenumbers is approximately 17,000 nm. Hope that clears things up!",
"Source: aspiring chemist. "
] | [
"That makes perfect sense, thanks! The simplest answer is I just misread the units."
] | [
"The unit cm",
" is commonly pronounced as \"wavenumber\", so it's not unreasonable for someone to write it out that way."
] |
[
"2 'prompt critical' reactions were caused by accident during experiments on the 'demon core' in 1945-1946."
] | [
false
] | [deleted] | [
"Nuclear chain reactions are full of negative feedback mechanisms. This is what makes building a nuclear bomb so difficult. In the case of the ",
"demon core",
" accidents, the system is very rapidly increasing its rate of energy release (doubling on a sub-millisecond timescale). All this heat and energy ten... | [
"if I have a huge mound of gunpowder, and I light a little bit of it, only a small fraction of the gunpowder will detonate - the rest will be scattered by the energy release and not explode. ",
"As someone who's lit a pile of gunpowder, I can tell you from first hand experience that the gunpowder will all go up i... | [
"Yeah, not the best analogy. I'll leave it to other people to think of something better."
] |
[
"In double-blind studies measuring effectiveness of birth control, does the control group receiving the placebo have affected pregnancy rates?"
] | [
false
] | null | [
"Depends what you mean by placebo affect. Medically it means all the non-specific effects of a trial. For example participants might be having regular check ups with doctors as part of trial, or be told not to drink during a trial, which would all be part of the 'placebo effect'. A lot of people use the term to jus... | [
"Affected compared to what? If compared to the general population than it would typically be different since the study participants aren't a perfect sampling of the population. If compared to the pregnancy rate of the participants prior to starting the trial than it would also typically be affected since the behavi... | [
"To be fair the placebo effect seems theoretically unlikely also, and yet there it is."
] |
[
"Are drops of liquid (say water) limited in possible size, or can they grow very large, depending on circumstances?"
] | [
false
] | [deleted] | [
"As drops grow there volume/mass increases by a cubed factor as the surface area increases by a squared factor. drops are held together by a combination of surface tension and adhesion to the surface they are fixed. As drops get bigger the stress per surface are increases until the tension is no longer supported by... | [
"Although there would still be a limit to the size of a liquid planet. At some point the middle of it would be compressed into a crystalline structure."
] | [
"Do you mean their?"
] |
[
"Stumped by my 1st grader's potato battery. Am I using the right kind of voltmeter?"
] | [
false
] | [deleted] | [
"if you can't get a battery to read (assuming it's not dead) then you're not using it properly. Can't get far without this, so break out the instructions, try a few things and get that reading. "
] | [
"if you can't get a battery to read (assuming it's not dead) then you're not using it properly. Can't get far without this, so break out the instructions, try a few things and get that reading. "
] | [
"Did you test the voltmeter against a battery to make sure it's working?"
] |
[
"Why are old buildings so good at blocking phone signals?"
] | [
false
] | null | [
"This is labeled a physics question, but I think it's just as much a structural engineering question. ",
"Ignoring ancient Roman buildings, modern concrete construction really began in the late nineteenth and early twentieth centuries. However, construction isn't a fixed thing. Like every kind of technology, it i... | [
"Depending on how old we're talking, it could also be lead paint in the building."
] | [
"What about brick? Does the iron oxide in brick have any effect?"
] |
[
"How do we know that Polio has been eradicated from North Korea? From uncontacted groups in the Amazon?"
] | [
false
] | , Polio was eradicated from Brazil around 1990 and North Korea in the mid-1990s. But how do we know this? Does North Korea allow disease surveillance by international organizations? And what about in the Amazon? How do we know that they don't harbor Polio? | [
"You can find a high-level overview of what is involved in polio-free certification for a region (it's region-based, not country-based) on ",
"this WHO page",
". The short answer is that, yes, North Korea does cooperate with the WHO, and the extent of that cooperation is documented in cooperation briefs also ",... | [
"They're uncontacted by Europeans directly, but presumably they're in contact with other tribes that have been contacted."
] | [
"I would think that uncontacted groups in the Amazon never were exposed to the polio virus in the first place."
] |
[
"Why is Dexamethasone used for severe covid patients if it has immunosuppressant effects?"
] | [
false
] | [deleted] | [
"It's not counterintuitive when you think about what corticosteroids actually do. They don't directly immunosuppress you. They dampen your immune response by preventing inflammatory mediator release, including cytokines. Your body responds to COVID by producing these inflammatory mediators - that's what's causing a... | [
"To build on your comment, think about the long term effects of inflammation on highly vascular tissue, such as the lungs. When inflammation becomes sustained, eventually scar tissue builds up over time.",
"Dexamethasone is a powerful tool to help fight inflammation and it's downstream adverse effects."
] | [
"I dont know about the nitric oxide, but COVID-19!is characterised by two phases: the viral phase and the hyper inflammation phase. The people who become severely ill usually fall into the latter. The immune system has become dysregulated. Cytokine storm is an extreme form of that and not all people get it. However... |
[
"Did inflation of the early universe stop or did it just slow down?"
] | [
false
] | Is the current expansion of the universe a remnant of initial inflation phase or is dark energy a different mechanism? If they are the same mechanism does that mean that the rate of inflation is decreasing? If inflation stopped ... why? | [
"In the most accepted models, Inflation was caused by an excited exponential scalar field , and stopped when it rolled down to its ground state."
] | [
"Like the Higgs field, or is there a different scalar field?"
] | [
"A different field:",
"http://en.wikipedia.org/wiki/Inflaton"
] |
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