title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"A question about Hepatitis C."
] | [
false
] | This is not asking for medical advice. I am pretty well educated in bloodborne pathogens, but can't find this answer anywhere. I know hep c normally takes 15-30 years for cirrhosis to develop, if it ever does. Have there ever been cases of extremly fast acting hep c, like cirrhosis in under 3 years? 5o follow that up, if it cannot progress that quickly, what are the other cost common causes of cirrhosis, other than alcohol? | [
"Studies have shown that the older you are when you acquire HCV, the more rapid your progression to liver injury.",
"Co-infection with HIV significantly speeds up the time to the development of fibrosis (cirrhosis).",
"Having a high BMI, or otherwise increased risk for hepatic steatosis (NAFLD) probably also in... | [
"Thanks for the info. Those are the factors I knew about except for the marijuana connection. That's really interesting and I will have to look into that study. Does it discuss the mechanism by which cannabis speeeds up formation of fibrosis? I never knew there was a connection. "
] | [
"I am a drug and alcohol counselor, and unfortuantely I don't have access to Pubmed or any other database at my work. I searched as much as I can on google and everything gave me the 15-30 year timeline. I am looking for cases of statistical outliers where hep c moves particularly fast and what coinfections or othe... |
[
"How can you tell if a solid ball of substance is uniformly dense?"
] | [
false
] | Supposing that any places of lesser density are exactly centered within it, like a perfectly spherical truffle with perfectly spherical chocolate filling, and assuming you don't know what material it is so you can't just try displacement. | [
"Measure its mass, radius, and moment of inertia. The moment of inertia about any axis passing through the center of mass should be 2MR",
"/5 for a uniform sphere."
] | [
"This is a good way to get some insight of the density distribution, but it is not a sufficient to ensure it is uniform:",
"For example an infinitely thin hollow sphere with the same mass as a uniform sphere has a higher inertia. But now you can increase the mass of the hollow sphere without changing its inertia ... | [
"Look at how it oscillates when struck - there are solutions for the free oscillations of a radially varying sphere.",
"Not great for a truffle since vibrations don't propagate very well in chocolate, but it works for the earth."
] |
[
"Gravity pulling a sphere around the planet?"
] | [
false
] | Imagine an indestructible sphere around our planet, hovering 60,000 feet above us. Would it stay stationary over the planet, or would it fall? If so, which direction? Since gravity pulls from all sides, would it stay where it is and move with us? Edit: The earth is inside the sphere. Edit : Thanks everyone. Just a thought experiment, but interesting | [
"It's like balancing a big steel rod on end.",
"It's theoretically stable, but in practice, as soon as there's a slight perturbation (gravity of the Moon, say), the thing goes out of equilibrium and the Earth and sphere will collide.",
"(60,000 feet is basically touching already, on the scale that you're talkin... | [
"Partly because they ",
" in orbit and your sphere is not. ",
"If you throw a ball up, it falls back down. That's what an orbit is, only bigger. ",
"If there's a big enough influence on something's orbit, it will definitely change the orbit or move the satellite or whatever we're talking about \"out of orbit\... | [
"Oh i see.",
"Answer: Inside the sphere you would feel no gravity at all. This is because inside a spherical shell, all the gravitational forces cancel out in every direction, ",
". So the earth and the shell would drift at whatever speed they started at. "
] |
[
"When I am trying extra hard to hear something quiet or far away, is my body doing anything different then normal, or am I just more focused on the sound?"
] | [
false
] | [deleted] | [
"When you're trying to listen to something quiet there are changes within your inner ear occurring. You have three little bones in your ear called ossicles, the malleus, incus and stapes which are flexed by sound waves coming into your ear. These sit against the oval window, which connects to a tube filled with flu... | [
"I don't know too much about that. but I would assume that it can help to transmit sound a little. I know that your mouth/nasal cavity, and ears are connected via the eustachian tube. So it may help to amplify the sound in a way since they're all in a sense, connected to each other. But that was not discussed in my... | [
"is there any truth to the notion that opening your mouth slightly improves the ability to hear?",
"i read this somewhere, and they claimed it was due to the way the jaw and ear bones function, and that sound waves entering the mouth can help transmit sound through bones."
] |
[
"How long does it take Curiosity to transmit images back to earth"
] | [
false
] | null | [
"Right now, Mars is about ",
"1.6 AU from Earth",
", so it takes light (and radio signals) 14 minutes to reach us from Mars."
] | [
"I believe I heard them say 14 minutes. So by the time it began the EDL sequence (the 7 minutes of terror) it had already been safely landed for about 7 minutes."
] | [
"Please post ",
"in the official thread",
" in order to consolidate information."
] |
[
"If gravity acts via gravitational waves, is it possible to create an anti-gravitational to cancel out gravity? Sort of like noise-cancelling headphones?"
] | [
false
] | null | [
"Gravity does not act via gravitational waves. One theory to explain how gravity could work suggests that there should be waves (as a biproduct). Scientists believe they may have detected these waves, which in turn adds weight to the validity of the theory."
] | [
"As far as I understand, gravitational waves are a result of two huge masses colliding and the result creates a rippling in space time called gravitational waves. No one knows what actually causes massive things to have gravity. "
] | [
"But gravity waves still don't cause gravity right?"
] |
[
"What is instinct? How does it guide an animal's behavior?"
] | [
false
] | I was thinking about animals and their natural-born instincts. As I understand animals, they are born with a drive towards certain behavior, and we call this "instinct." For example, they know what their diet should be. I'd assume that if a baby lion that had never had contact with other lions were given a choice, it would know to choose to eat meat over vegetables. Is that true? If so, how is that information "programmed" into an animal without outside forces guiding the animal? If it wouldn't know instinctually, would it eat the vegetable, get sick and learn that way? | [
"I would respectfully disagree with the current top response. Our current understanding of animal behavior is such that each observed action is guided by a variety of factors and can have varying amounts of influence from genetics or ontogeny (learning). The nature vs. nurture argument is effectively null as no b... | [
"You should read this article, if you can't get it free already, ask a librarian for help. ",
"http://www.nature.com/nature/journal/v434/n7030/full/nature03352.html"
] | [
"Sure, I generally agree with what you wrote, but I think the OP was asking if there are complex behaviors that are truly genetic in origin. Or, at the very least, (s)he was asking if there are any complex behaviors which are not learned. There are several well documented examples of complex behaviors which are not... |
[
"What is the absolute threshold for acceleration?"
] | [
false
] | Since we perceive acceleration rather than velocity, there must be a minimum amount of acceleration that our sensory mechanisms can pick up on. It's the same idea as the minimum number of photons/lumens to be able to see a light or a minimum number of decibels to hear a sound. | [
"Probably the best way to answer this question is to consult an aviation physiologist. They know a lot about this stuff.\nThere are small organs in our heads that amount to organic accelerometers. These are called otolithic organs. ",
"http://en.wikipedia.org/wiki/Otolithic_organs",
"\nI imagine that if one ... | [
"I was confused as well with donaldjohnston about the \"absolute\" part of your question. But we can at least throw up some numbers as a lower limit.",
"So far, no one feels queasy from the rotation of the earth, so we can probably be sure that this limit is bigger than the rotational acceleration of the earth",... | [
"I meant more of a minimum acceleration that we can sense as humans with (I believe) our vestibular system, not a limit on acceleration based on the laws of physics. More of a psychological question than those answers, but that thread does look interesting.",
"edit: I didn't mean a maximum that we can sense eithe... |
[
"What is on the ISS live stream right now?"
] | [
false
] | It looks like they have a drop of water between 2 sensors of some sort. The camera might change before anyone sees and has an answer. | [
"I don't have an answer, but I made a screenshot for posterity.",
"http://imgur.com/A2T1OJh"
] | [
"Thanks, The stream changed cameras so this is the best shot of what I was asking about. Its not possible to tell from a still but there seem to have been sediments floating around inside the ball of fluid."
] | [
"That must be it. The sediment floating around in the fluid did start to create structure before they switched cameras. Thanks!"
] |
[
"What is the biggest misconception about your field?"
] | [
false
] | Either the most commonly held incorrect belief, or your favorite example of an encounter where someone was so confused that you didn't even know how to begin to communicate with him... | [
"Neuroscience: So very, very many things. Just a few/the most common I hear: ",
"\nIn neuroscience literature, plasticity is generally used to refer to changes in size/activity/response of a particular synapse. These kinds of changes occur all the time in every single one of the (estimated) hundreds of trillions... | [
"That physics is just an opinion."
] | [
" There's not, and they don't. People who call themselves \"grammarians\" pass random judgments based on often-faulty reasoning and pretend they are explaining how language works. For linguists, language is what people say. We (synchronous linguists) essentially study how the brain processes language. So-call... |
[
"Why is boiling point of perfluoropentane les than pentane?"
] | [
false
] | null | [
"The boiling point of a substance depends on the strength of the interactions between molecules. There are several different types of interactions that can contribute, but for hydrocarbons like pentane, the only type that matters is called \"dispersion.\" Essentially, due to random fluctuations, the electron cloud ... | [
"C-F is poorly polarizable because fluorine is so electronegative. Electron density concentrates heavily around the fluorine, and because fluorine is also a very small atom, these electrons \"feel\" the fluorine nucleus quite strongly and are difficult to shift around ",
" polarize. Now, this effect would also cr... | [
"-fluorine bonds are much less polarizable than carbon-hydrogen bonds.",
"Why??? I mean, wasn't there a linear relationship for C-H, C-F, C-Br, C-I"
] |
[
"As time progresses, does the perimeter of the visible universe recede because photons (albeit redshifted ones) from distant stars finally reach us, or does it get closer because inflation pushes stars at the edge of the visible universe away faster than their light can get to us?"
] | [
false
] | I'm not asking about the absolute size of the visible universe; I'm asking if the number of stars inside the boundary line is increasing or decreasing (stellar lifecycles aside!) | [
"It does both.",
"It's best to think of this in terms of \"co-moving volume\". This is where you imagine a volume that expands naturally with the universe. If the density of the universe is basically constant, the amount of stuff within a \"co-moving volume\" is constant throughout the age of the universe.",
"T... | [
"The observable universe radius also increases in comoving coordinates. So I'm not sure what you mean when you say the amount of stuff in the observable universe has reached a peak. It seems you're actually talking about the event horizon. But I wouldn't really say the stuff inside the horizon has reached its peak.... | [
"The Hubble Sphere grows to a peak and then shrinks. The Event Horizon grows, but asymptotes towards a maximum.",
"You're mixing up two coordinate systems here. The Hubble sphere grows to a peak and then shrinks, ",
". The event horizon grows but asymptotes to a maximum, ",
".",
"That might be a better defi... |
[
"(anthropology/bio question) Allergies"
] | [
false
] | null | [
"That is probably the wrong way to look at it. You can't just look at an evolved trait and assume that it is beneficial. It might be there at random, or because it is hard to separate it from other, beneficial traits.",
"In the case of allergies, it is probably a case of tuning the activity of the immune system. ... | [
"That last bit, ELI5:",
"Imagine you are living with a friend. You do the shopping, he does the cooking. He likes quite spicy food, while you like the food less spicy. In order to get the food more like you like, you start buying milder chili. This works for a while, until your friend adapts, and starts to put mo... | [
"summon redditanalytics subreddit=askscience search=allergies"
] |
[
"If combustion/fire needs oxygen to keep going, then why would a strong wind (meaning one bringing a lot of oxygen toward you) tend to put a light out or make it hard to start one?"
] | [
false
] | null | [
"Think about when you light a candle, you hold a match to it to supply heat until it catches fire. This is essentially the same thing the flame does for itself to stay lit - transfer energy to the unburned fuel to get it hot enough to burn. When you blow the flame away from the candle, that is like moving the mat... | [
"In the case of a conventional flame, say, a camp fire or a candle, the breaking of bonds in the fuel (wood, wax, oil, etc.) releases more energy than the breaking consumes. This energy is released in the form of light and heat. Much of the heat escapes the system while some is absorbed by other molecules, breaki... | [
"The ratio of oxygen to nitrogen does not change with the speed of the air. So no, you're not changing the equilibrium, nor do you smother a fire by blowing on it. "
] |
[
"What is Neosporin actually doing when I apply it to a cut?"
] | [
false
] | [deleted] | [
"Neosporin works as an antibiotic and also claims that it speeds the healing process. A couple studies in the past have shown that Neosporin does not have any increased efficacy in wound healing than a basic petroleum jelly. So pretty much it just protects the wound from any outside bacteria by placing a gel 'shi... | [
"In particular, Neosporin contains bacitracin, polymixin B, and neomycin which are effective against a range of both Gram positive and negative organisms. "
] | [
"No. It prevents infection. Healing happens on its own through normal physiological processes. By preventing bacterial infection and the resulting inflammation,tissue damage etc., healing can proceed normally"
] |
[
"What causes light and heavy sleepers?"
] | [
false
] | I am a really heavy sleeper. It takes two regular alarm clocks and one alarm clocks on wheels to wake me up. Why is this different for different people? | [
"Differences in \"heavy\" versus \"light\" sleepers has to do with a type of brain activity called ",
"sleep spindles",
". Within the past ~2 years, research has started identifying genetic markers that influence sleep spindles."
] | [
"Are brain waves just a visual measurement for electric or chemical activity in the brain? For example, when someone sees a sleeper spindle show up on a readout, does that indicate that some chemical or electric process is happening? "
] | [
"Great questions, although I can only respond with current theories/hypotheses because we don't have clear definitive answers yet. Sleep spindles represent (thalamocortical) brain activity that we believe may be a signal of the brain \"managing\" information from the sensory systems during sleep. So if someone is... |
[
"Can a linear accelerator be re-configured and used as a 'decelerator'?"
] | [
false
] | Let's say one had a beam of charged particles moving at some speed, could they be slowed using a linear accelerator that is reconfigured to decelerate the particles? If it's simpler to think about this with defined 'packets' of charged particles, or particles that penetrate the 'decelerator' one at a time, then so be it. | [
"In principle, yes. But this is not the most efficient way to slow down a beam of particles. To ",
"slow down a charged particle beam",
", you just shoot it at some material. Charged particles lose energy and slow down as they interact with matter."
] | [
"Actually, yes! There are a few rf-cavity based linear accelerators that recirculate the beam back 180-degrees out of phase to decelerate the beam and recapture beam energy. This allows for extremely efficient operation with very high average beam currents.",
"For an example see the ",
"Jefferson Lab energy rec... | [
"I thought something like a linear decelerator was used for the cold antimatter experiments? "
] |
[
"Is light that is being \"pulled in\" by a black hole moving faster than regular light?"
] | [
false
] | If light can not move fast enough to escape a black hole, does it move faster towards it because it is "sucked" in? I doubt it is possible, but what really happens as light approaches it? Edit: Thanks guys! | [
"Light is still moving at light speed. It is space itself that is entering the black hole faster than light speed. Think of the light as a fish swimming against a stream. The fish might be moving at a regular pace but if the water flows too fast to anybody on the side of the rive the fish looks to be going backward... | [
"Light as ",
"/u/CatalyticDragon",
" said always moves as at the speed of light. But due to black holes' intense gravity they stretch out space time- meaning what you call 1 meter might be increased to 100 meter so apparently it wont seem to move at the speed of light. Light doesnt really get \"sucked in\" afte... | [
"If light can not move fast enough to escape a black hole",
"The reason, under general relativity, why light can't escape is because all directions inside a black hole point towards the singularity, due to the warped nature of space.",
"Once you are inside the event horizon, you could point yourself in any dire... |
[
"What do you get when you take multiple integrals? Derivatives? What is their application?"
] | [
false
] | Hey . So I just finished up a calculus 1 course and was left with a few questions about taking multiple derivatives/integrals. From the calculus course combined with the physics course i was taking i learned that differentiating a position function will give you velocity. Differentiating that gives you acceleration. Differentiating that gives you jerk. But what happens when you differentiate jerk? It's going to give you the fourth derivative of the function, but are there any practical applications at such high-order derivatives outside of constructing polynomial approximations of functions? (I only have a brief introduction to this subject so my knowledge of it is limited). Similarly, integrating a function gives you area under a curve. Integrating that will give you volume. But what do you get when you integrate volume? What is the applications of this? | [
"There are some physical models that use fourth order derivatives. Anything over that is extremely rare. Higher order derivatives are mostly useful in mathematics.",
"Actually, your brain is a highly specialised solver of second order differential equations. It has to be, to control your body in a universe where ... | [
"Derivative just represents how quickly something is changing. Velocity represents how quickly position is changing, and acceleration is how quickly velocity is changing. You can keep taking derivatives past that to see how quickly acceleration is changing, then again to see how quickly that is changing, etc. We ju... | [
"You can experiment with this by asking people to play a game where they control a vehicle by adjusting its nth order derivative. It will be very easy for n < 3 and extremely difficult for higher n.",
"Interesting idea!"
] |
[
"Why does our skin get numb when we're cold?"
] | [
false
] | null | [
"So your sensation comes from neurons that brings information from your skin to your brain. When it's cold, you can imagine that reactions needed to send that information slows down, and then when numb, most of that signal can't move out of that area towards your brain simply because the nerves can't fire effective... | [
"Blood flow to exterior arteries is restricted to keep the internal organs warm. "
] | [
"\"Veins carry oxygen-poor blood cells back to the heart and lungs to be re-oxygenated, so it is reduced blood flow in the arteries that can cause a drop in sensation in the legs, arms, hands, etc. Arteries contain freshly oxygenated blood and carry it throughout the body. As you mentioned, it is the capillaries th... |
[
"What is happening (physically and chemically) inside of an atomic bomb at its detonation?"
] | [
false
] | null | [
"The HowStuffWorks article is pretty good. If you have any questions after reading it feel free to ask.",
"http://science.howstuffworks.com/nuclear-bomb.htm"
] | [
"Colloquially speaking, an atomic bomb, as opposed to a hydrogen bomb, is a fission device. This means its energy depends on breaking atomic nuclei apart. A relatively easy way to do that is to start off with a slightly unstable, large nucleus and throw a neutron at it. The Plutonium isotope Pu-239 is large and eas... | [
"Yes. I've done plenty of my own research. In the end I just felt confused and mixed up between the myriad of facts thrown at me. I guess my reason for coming to reddit with this question was to have a more 'to the point' answer, rather than having to examine intricately written articles. "
] |
[
"What happens at the end of a mapping satellites lifecycle?"
] | [
false
] | I am using the following assumption, correct me if I am wrong: A Satellite that is mapping the Earth, as I understand, it would have to burn fuel in order to change its inclination in order to map the entire surface of the earth. What happens once the fuel is gone or near gone? Does ground control put the satellite into a parked orbit, leave it as it is, or de-orbit it? Is there any public data on mapping satellites and how much fuel they have left for orbital maneuvering? | [
"A Satellite that is mapping the Earth, as I understand, it would have to burn fuel in order to change its inclination in order to map the entire surface of the earth.",
"That doesn't really happen. Any satellite will have to use some amount of fuel to make small adjustments to its orbit, but making large changes... | [
"No, not really from further away. They're just at a higher inclination to begin with. A higher inclination means more latitudes are covered (in fact, the inclination also tells you the highest latitude achieved by the satellite - that's equal to the inclination or to 180 minus the inclination; e.g., a 51.6 degree ... | [
"So the inclination is not changed really after it is put in place",
"Correct. There might be a few tenths to one degree of change, but not anything drastic.",
"98° for the Earth's most intersting parts",
"98 degrees is useful for two reason. One, it allows coverage of almost all the Earth. If you look at a m... |
[
"If you have enough oxygen but too much carbon dioxide, Why would too much carbon dioxide kill anyone when carbon dioxide is nontoxic?"
] | [
false
] | I was watching Apollo 13 when they explain at one point in their voyage that they had enough oxygen but too much carbon dioxide. | [
"Too much carbon dioxide is called ",
"hypercapnia",
". If it gets bad enough that the acidity of the CO2 lowers the blood pH, the condition is called ",
"respiratory acidosis",
".",
"CO2 directly causes problems because it is a ",
"vasodilator",
", which means it causes blood vessels to expand. In se... | [
"Hemoglobin has an affinity for both O2 and CO2, though these affinities are not equal. ",
"When it's carrying CO2, it has less affinity for O2",
", so if there's a mixture of CO2 and O2, and there's too much CO2, you won't be able to get enough O2 onto the hemoglobin to transport to where it's needed in the bo... | [
"It acidifies the blood. C02 + H2O -> H2CO3, carbonic acid."
] |
[
"Where does a human's digestive acid come from?"
] | [
false
] | null | [
"Where does the creation of stomach acid occur? ",
"Do we naturally take in enough Hydrogen and Chlorine to keep creating HCl in our stomachs?",
"Could I produce less stomach acid if I simply stopped eating NaCl?"
] | [
"Cl- and Na+ ions are used in enough vital bodily functions that you would die long before stomach acid production was ever affected. ",
"Gastric acid is produced in the gastric glands lining your stomach. It's a bit of a complex process, but this video explains it nicely:\n",
"http://highered.mcgraw-hill.com... | [
"I understand the digestive system. What I was curious about was where the acid comes from. Does our digestive acid(meaning HCl) form within a certain section of our body like the gall bladder or the spleen. Also part of this question was to find out if we recycle our HCl or does it just exit as waste. I am sorry i... |
[
"Ununoctium is the largest element in the periodic table (#118). Is it theoretically possible that there could be elements with more electrons (that haven't yet been discovered), or is Ununoctium the theoretical \"largest\" element?"
] | [
false
] | As far as I'm aware, an element gets its number in the periodic table based on the number of electrons. Ununoctium has 118 electrons (with 8 electrons in the outermost "ring"). Is it possible that there may be elements with more than 8 electrons in this outermost ring, or even with more electrons in a new "ring" (pardon my lack of scientific language, I am but a mere layman)? For example, the structure of Ununoctium is 2, 8, 18, 32, 32, 18, 8, could a new element perhaps have a structure of 2, 8, 18, 32, 32, 18, 9, or even 2, 8, 18, 32, 32, 18, 8, 1? I imagine this will be ridiculously unstable, given how unstable the final few elements actually are, but is it a possibility? | [
"I imagine this will be ridiculously unstable",
"Actually, element 120 (unbinilium) is right in the middle of the ",
"island of stability",
", so, it might be more stable than you'd think.",
"Even unbihexium (element 126) ",
"\"is predicted to be near the centre of the hypothesized island of stability, a... | [
"Sure, the electronic structures have been calculated up to 172, ",
"by Pyykkö",
". There's no known definite limit to the number of electrons in an atom. It's the ",
" that's unstable."
] | [
"This is inaccurate. Basic chemistry teaches that elements are defined by the number of protons in it's respective atom. An element with more electrons could have a greater width, because it might have more shells, and therefore be \"larger\". The elements on teh periodic table, though, are not organized by physica... |
[
"Many of us would have anecdotes of pets attempting to comfort us when we're sad or sick, but are there any scientific studies on animals knowing when people are unhappy and showing empathy towards us?"
] | [
false
] | Obligatory edit: Oh cool, went to bed and this got front paged! Thanks for all the responses everyone. It'll take me a while to read through everything, but I'm sure there's a lot of good stuff here. | [
"A recent TED talk on the subject was just posted: ",
"TED",
"The talk is about the idea of empathy, morality, and fairness in various primates. The talk is very entertaining to watch, but here's the break-down.",
"Yes, the ability to empathize is an evolutionary trait that is not limited to humans. Being ... | [
"I don't disagree with anything you'd said, but I cannot find a source for:",
"Many animals have even shown to ability to comfort somebody and other animals when they are sad, hurt, or otherwise in need of comfort.",
"short of Washoe, who I linked to already. Do you have anymore? I find those stories heartwar... | [
"Animal Therapy",
" is becoming more accepted, and the wiki sources are more than valid. Some of the suggested animals (usually aquatic ones) are actually less suitable than most believe, and horses are often very good for this.",
"There are measureable personal benefits to having pets in our lives as well.",
... |
[
"Is there any factual basis to the phrase \"red sky at night, sailor's delight, red sky at morning, sailors take warning\"? What meteorological phenomena, if any, are responsible for this occurring?"
] | [
false
] | null | [
"The origin of the saying is unknown, although a form of it appears in the bible (Matthew 16:2-3). It has some basis in science and is a fairly good predictor of-though no guarantee-of weather at the mid latitudes in the Northern Hemisphere, where storm systems generally follow the jet stream from west to east. A r... | [
"http://www.reddit.com/r/askscience/comments/hwt8a/what_is_the_explanation_behind_pink_in_the_night/"
] | [
"I would say it's something to do with air pressure.",
"I would say..."
] |
[
"Can someone explain causal fermion systems and the Dirac Sea to me in \"smart layman's terms\"?"
] | [
false
] | Because Wikipedia's article on them are all grad student-level gobbledegook. I need something more on the level of A Brief History of Time or Cosmos. | [
"The Dirac sea was an attempt to make sense of the problems when one tries to relativistic quantum mechanics. These problems go away when you use quantum field theory instead and so the Dirac sea is not really relevant.",
"That said, it is an interesting idea. Basically the Dirac equation has positive and negativ... | [
"I understand that the Dirac Sea isn't needed in the Standard Model. However, causal fermion systems (an alternative to the SM) apparently use it."
] | [
"Sorry, I'd never heard of causal fermion systems and it seems like almost nobody has if you look at the number of citations the papers have. Good luck",
"Just a fun aside: beware of things which are called \"casual such and such\" the word causal is almost always attempting to make people think causality makes s... |
[
"I live in the midwest. Let's pretend it's just me, in my backyard, with a shovel, and nothing but time on my hands. How far can I dig before the shovel just can't go any deeper?"
] | [
false
] | For the sake of argument, let's say that I have a magical way of tossing the dirt I shovel out of the hole so it doesn't fill itself back up, but I can only dig with the shovel. I can take breaks, sleep, eat, and weather won't affect it. I'm just curious how deep I can go before the dirt is too compact, or I hit a huge layer of rock, or something like that. EDIT: I flagged this as earth science, but....that might not be right | [
"Geotechnical engineer here. Here is the scenario I think you are imagining: there is you, a shovel, and your backyard. You start digging a hole just wide enough for you to stand on the bottom and perform the \"digging\" motion and throw the dirt out of the whole (lets say 6 foot diameter). The way I see it ther... | [
"inverted cone, with about 45 degree slope",
"Just adding: use slope < soil's "
] | [
"Foundations for large structures can get pretty complicated but usually will involve piling into bedrock and some sort of pad or raft foundation anchoring the load bearing columns in the soil at a stable depth.",
"For a look into how complicated they can be here's the foundation system for the Grand Lisboa Hotel... |
[
"Why do some parts of a download take longer than others to download?"
] | [
false
] | null | [
"What kind of downloads? ",
"You wouldn't be talking about P2P ( torrents ) download per chance?"
] | [
"In what context? Without some more info I can say:",
"In general, some ISP give you a \"boost\" for the first part of each download.",
"If you are talking torrents/P2P file transfer, in this type of file sharing information is broken down in pieces and pieces that are more \"available\" (more people have them)... | [
"During the course of a download, your speed can vary. With a traditional direct download, you're sharing computer and network resources with other people around the world, so your download speeds will go down if there's network congestion.",
"In a peer-to-peer situation, other people are sending you the file. So... |
[
"How are astronomers able to take such clear images of celestial bodies?"
] | [
false
] | Our planet is constantly spinning and in orbit around the sun at extremely high speeds. And so is whatever they want to take an image of. How can they still come up with clear images of things so many light years away? | [
"Large telescopes will automatically track (i.e. rotate with) the position of interest in the sky while taking long-exposure photographs. Space telescopes do the same thing. Your handheld camera or phone has a very short exposure time of (at a guess) a few milliseconds. Space telescopes take exposures lasting ho... | [
"I don't think we have anything that tracks individual planets. The movements would be too small. We can track individual stars",
", and the differences we see between separate images of the same star enable us to infer something about the star and any planets that might be around it.",
"These things all cons... | [
"The adjustment of the telescope is to compensate for earth's movement and rotation, not the movement of what it's looking at. Unless it's something in our solar system, it's unlikely the photographed object would move even one pixel, even for long exposures. "
] |
[
"Are there any AI programs out there that have the ability to modify and recompile their own code?"
] | [
false
] | null | [
"Self modifying code exists, but it is not done by intelligent programs. Back in the 1950s and 60s, programmers had very little memory availiable, so they wrote programs, that rewrote parts of themselves to change functionality approriately (i.e. your disk driver was temporarily rewirtten to serve a different devic... | [
"You're talking about recent Jeff Dean and Andrew Ng work, article here",
"http://www.extremetech.com/extreme/131717-google-and-stanford-create-a-digital-brain-that-like-an-infant-learns-to-identify-a-human-face-from-scratch",
"If you read the paper their object recognition accuracy is 15.8%; hardly a solution ... | [
"How specific are you being with \"AI\"? If you mean programs in general, see ",
"Self-modifying code",
"."
] |
[
"If gravitational paths such as orbits are conic sections, what is the cone?"
] | [
false
] | I'm curious as to why a gravitationally determined trajectory, or any trajectory influenced by an inverse square law force, follows conic sections. How can I understand this? Bouncing off of that question, is there any known relation between Dandelin spheres and Kepler's first law? | [
"Conic sections are special because no matter where you are on the orbit, certain relationships and distances between you and the foci (or directrix) remain constant. This is precisely the behavior required for angular momentum to be preserved which makes sense as angular momentum by definition tells you about the ... | [
"Conic sections are special because no matter where you are on the orbit, certain relationships and distances between you and the foci (or directrix) remain constant. This is precisely the behavior required for angular momentum to be preserved which makes sense as angular momentum by definition tells you about the ... | [
"Sure, but angular momentum is constrained differently depending on the shape involved. Different shapes with angular momentum conservation let you produce different U(r). Essentially the ",
"Binet equation",
"."
] |
[
"As spacetime expansion accelerates, does this mean that the force due to dark energy is increasing?"
] | [
false
] | Or is it a constant force (if it even really is considered a "force")? And if so, will this force ever become big enough to overcome the force of gravity within galaxies, and pull their individual stars apart from each other? And eventually even individual molecules or atoms might be pulled apart? | [
"You can reason the first part of this out with basic mechanics: force=mass*acceleration; thus a constant force yields constant acceleration. AFAIK, we don't know enough to determine whether the force itself is increasing or remaining constant, and if it's not constant, what trajectory it will follow. If, for examp... | [
"I am glad you ask. Look, since we don't know, what exactly dark energy is, we characterize with the help of a bunch of numbers. One of those is the ratio of energy density and pressure, called w. For regular matter, dark or not, it is 0, for radiation, w is 1/3. We know w for dark energy must be smaller than -1/3 ... | [
"In interesting fact in that case is also that some advanced civilization similar to us in a couple billion years would not perceive anything else than their own galaxy, they would never be able to figure out the big bang theory.",
"I always wonder, and maybe this is more philosophical than scientific, if we aren... |
[
"Does a Tesla Coil affect your smartphone in any way?"
] | [
false
] | I was toying around with a little Tesla Coil and I was taking some pictures of it. I noticed that my phone was spasming out, as if someone pressed stuff randomly on the screen. This stopped as soon as I turned it off. Why does this happen? | [
"This is called EMI, electromagnetic interference. It is a common problem with electronics and subject to a lot of testing. Devices have to meet standards of resistance to this interference, But if you exceed the limits, it gets spazed.",
"https://en.wikipedia.org/wiki/Electromagnetic_interference",
"You just a... | [
"Thanks! Can this damage your phone or it just affects it during the high interference?"
] | [
"Depending on the field strength, it can just interfere, or at stronger field levels actually damage the electronics. I wouldn't risk my phone exploring this level."
] |
[
"My friend doesn't believe I have experienced rapid solidification in my house"
] | [
false
] | This is what happened: When I got home I put a few coronas in the freezer. Later in the evening I remember I had actually put them there. I open the freezer and take a bottle, it is cold but not frozen (all liquid), I take my bottle opener and open it, I took a big sip and it was pretty cool but not too cold to drink. At this point I still have the bottle in my hand and suddenly I see white flakes appearing inside the bottle, feeling confused I just stare at the bottle until many more flakes continue to appear and in less then 10 seconds the whole beer is frozen! Yes the same bottle I just opened and took a sip out of just froze while I had it in my hands! I keep telling my friends the story but they refuse to believe it actually happened, so tell me askscience, this CAN happen right? | [
"Yes"
] | [
"Congratulations, you ",
"supercooled",
" your beer. When you took the first drink you agitated the beer, resulting bubbles acted as sites of nucleation for crystal formation."
] | [
"It is possible, and it is called supercooling:\n",
"http://en.wikipedia.org/wiki/Supercooling",
"The basic premise is that you cool a liquid down below it's freezing temperature, without it freezing. It's easier to do when you cool a liquid rapidly: aka putting it in your freezer. Disturbing any of the liquid ... |
[
"I learned in my Geology class last week that all the galaxies regardless of direction around Earth are exhibiting blue shifts. Since they're all moving away, how exactly are we supposed to collide with Andromeda?"
] | [
false
] | null | [
"I see a few erroneous/ambiguous comments so just for clarity (with some basic sources) ...",
"In general, all galaxies regardless of direction or distance from Earth exhibit redshift, not blueshift. The amount of redshift is proportional to the distance from us. This is known as ",
"Hubble's law",
", and i... | [
"Actually most galaxies are redshifted as they move away from us.",
"Since Andromeda is moving towards us it is one of the few blueshifted galaxies."
] | [
"Actually most galaxies are redshifted as they move away from us.",
"Since Andromeda is moving towards us it is one of the few blueshifted galaxies."
] |
[
"What differs in the brain/body when moving, say a finger, compared to just thinking about moving it?"
] | [
false
] | null | [
"There isn’t actually a consensus on this. Everyone will agree that assuming that the action is voluntary, you’ve got some executive function stuff going on either way. Then there is something called motor programming, which can be thought of as a file cabinet of motor actions from which your brain draws. The selec... | [
"I once heard (watched a video) that imagining moving causes a really tiny subtle movement, and this is how ouija boards work. everyone's ",
" that the piece is moving, and since their hand is on it they imagine their hand moving which causes them to push it the way it seems to be going. since everyone is doing i... | [
"Something similar also happens",
" during internal monologue, with the muscles of the larynx and tongue executing tiny, usually imperceptible movements that match those that would occur to speak those thoughts out loud. This has lead to proposals that sensors to pick up this movement, combined with a cochlear im... |
[
"Is DID (or multiple personality disorder) recognised as genuine by the medical community? What do we know about it and its causes?"
] | [
false
] | A recent post had a brief conversation about whether it's 'real' or not - what's the scientific/medical community's consensus, if there is one? On a basic level is it just a matter of self-delusion, or does the brain literally close parts of itself off from itself? Is it possible for the other personalities to have distinct memories of a different childhood or anything like that? What's the best way of dealing with them? Any links to reputable studies or reports would be fascinating! Thanks! | [
"There was a recent Science Friday on this topic. They had a psychologist and psychiatrist that were on different sides of the debate. The discussion got rather heated, and was quite fascinating. The short answer is that it's very controversial.",
"http://www.sciencefriday.com/segment/10/21/2011/exploring-mult... | [
"Dissociative identity disorder is recognized by the DSM which is the holy bible of mental diagnostics. Like all mental disorders there is debates as to it's defining characteristics, so there's always controversy which way the debate seems to sway in terms of consensus is never to easy to gage. Anyway here's a rel... | [
"Don't think of multiple personality disorder as multiple people living inside of one brain.",
"Think about how you behave in front of your parents vs how you behave with your friends. Not the conscious choices you make, but the subconscious or unconscious differences in behavior. You might be more anxious in o... |
[
"New Intel Chip on Front Page: Does this differ quantum mechanically from other methods of storage?"
] | [
false
] | Front Page article: After learning about semiconductors and band gaps in quantum, I'm just wondering if there is any progress for physics with this announcement. | [
"I don't think, after looking at the paper in ieee, that they used QM at any step in the development (though its a trade secret so maybe...). At any rate the important part of this tech is the phase transition that occurs when you apply a current. Phase transitions do not require QM to understand, see ",
"landau ... | [
"It seems that it's intended to be a replacement for RAM and not disks."
] | [
"It says its flash, which is normally reserved for non-volatile memory which means it can be used for storage."
] |
[
"Are there any two stars that we know are extremely (or unusually) close to each other?"
] | [
false
] | If so, how close are they and how do we know that? I use the term "extremely" loosely. How far apart do stars need to be to form? Also, if this does happen, what sorts of problems does it present if any? | [
"There are two pulsars (neutron stars) that are 60,000 km from each other. That's much closer than the Earth is to the moon.",
"The system is called PSR J1744-3922."
] | [
"Both are a bit heavier than the sun, about 30% heavier. However, because they're so dense, they're only a few miles in diameter."
] | [
"As for what problems close stars cause, each star in a binary system has a region around it called a ",
"Roche lobe",
", inside which matter will remain bound to that star. If a star is larger than its own Roche lobe, it will gradually lose matter to the other star. This often happens in binary systems in whic... |
[
"Why is bare, non-insulated wires still the norm for electric transmission lines?"
] | [
false
] | Is it just cost? I live in an area that's fairly forested and there are fairly frequent power failures due to trees falling onto the power lines. I notice that some streets have insulated, twisted power lines instead - even the (edit: transmission/medium voltage), 3 conductor lines are insulted and the twisted cables seem really thick. Is seems that this has benefits for safety and for reliability in case something falls on the line. Is it just cost that makes this the exception and not the norm? | [
"Firstly, the voltage is really high - a simple layer of plastic isn't going to cut it. insulation to keep 10,000, 100,000 or 1 million volts is not trivial.",
"If a tree falls on a wire, the insulation and wires are likely to be damaged anyway.",
"The wires are out in the sun all day. Most plastics will last o... | [
"First, technically they are insulated since air is an insulator, but I'll assume you mean coated with an insulator material.",
"If memory serves, and I'm about half a decade removed from power systems studies, it's largely due to the added weight on the lines because of the required thickness to be effective, wh... | [
"The insulted wires in urban areas on overhead lines are almost always end user low voltage (<1000 V) or telecommunication wires/fibre. Not distribution medium voltage (1,000 - 50,000 V) or transmission high voltage (50,000 - 1,000,000 V). ",
"We do insulate distribution conductors in urban areas. This is almost ... |
[
"Newton's 1st Law"
] | [
false
] | [deleted] | [
"Your error is here:",
"That implies that there's a force keeping it in motion",
"No force is required to keep an object in motion if it already is. That's the point of the first law."
] | [
"\"",
"\"",
"No, there's no force keeping it moving. It is the object's momentum that is keeping it moving at a constant speed. In the absence of external forces (friction, etc.), it will keep moving at a constant speed and direction."
] | [
"Forces cause acceleration, not speed. You initially apply a force for a small amount of time, producing acceleration on the ball and changing its velocity from zero to something. Once you stop applying the force, the acceleration disappears too, and the ball keeps moving at constant velocity. "
] |
[
"Do \"higher thinking mammals\" like primates and dolphins have names, like we do, for each other?"
] | [
false
] | A few more (tangentially) related questions: Where does this sense of identity come from? Is it the same as sentience? How does the human brain almost seemingly hardwire recognizing our own names (which happens even in incredibly noisy situations)? Is it true that we can recognize our name much easier aurally than visually? (It seems harder to pick out one's own name in a lot of text) At what age do all the above begin to manifest in infants? | [
"Birds do:",
"http://blogs.discovermagazine.com/80beats/2011/07/13/baby-parrots-learn-their-names-from-their-parents/",
"... each bird has its own signature call that others use when addressing it and that the bird uses itself in avian “conversation.” Scientists have long wondered where these calls come from. N... | [
"Yes. Many other mammals have names for each other. (or at least distinct responses to individuals they recognise)",
"Most animals are sentient, sentience is just the ability to feel. I suspect you mean sapient, which means the ability to reason. Sapience is a bit of a tricky thing to categorise and it's too fuzz... | [
"I'm no expert on psychology (animal or otherwise), but it seems to me that assumes he is conditioned to hearing his name at both positive and negative things, which muddies up the idea that he is just reacting to a a sound that he thinks will be followed by a positive experience. He hears his name just as often af... |
[
"where does the energy for the movement of electrons around a nucleus come from?"
] | [
false
] | null | [
"The simple answer is that it does not require energy to move around the nucleus. The more complicated answer is that this is a major problem with the \"",
"orbital model",
"\" of the atom, as orbiting electrons would be accelerating and therefore give of electromagnetic energy.",
"It is actually one of the p... | [
"I'm not sure what you're asking here. Are you imagining a scenario where there is a constant input of energy required to maintain an orbit? Because that isn't the case.",
"Furthermore, thinking of the electrons as existing in a moving orbit analogous to that of planets is erroneous. The electron is described by ... | [
"To which the cop replies \"you were doing 56 miles per hour\". Heisenberg then cries \"fuck you! Now I'm lost!!!\""
] |
[
"What causes Cheerios (and other cereals) to link up into little rafts?"
] | [
false
] | When there are just a few cheerios left floating in milk, they don't float around independently from one another. They instead tend to link up into little groups. It doesn't feel like they're sticky. What gives? | [
"You may have noticed the effect that, if you fill up a glass of water, the water is not flat, but has a rim at the edge. This is because, due to the surface tension, water is 'sticky', so clings onto things. If you were to put a cork in said water, it would float to the side, as it is less dense than the water and... | [
"See ",
"Cheerios effect",
"."
] | [
"Think of the surface tension of water as a thin layer of saran wrap. The weight of the Cheerio depresses the surface of the water, creating a little dip in the surface. Gravity will cause adjacent Cheerios will slide along the side of the depression and they push up against each other, dipping the surface a bit mo... |
[
"What are the most advanced computers in the world being used for?"
] | [
false
] | null | [
"There are numerous applications of supercomputers. I'll describe my own usage as an example.",
"The Navier-Stokes equations are nonlinear partial differential equations that describe the motion of viscous fluids. Other than extremely simplified situations, they can not be solved analytically so we use numerical ... | [
"I can confirm this. We use Navier-Stokes for analysing fluids as well and one calculation on a very high end PC can take up to 20 days, and that is after reducing the number of tets in the model. I can easily imagine a run taking orders of magnitude longer."
] | [
"It depends on what you mean by \"advanced.\" There are lots of computer applications today with demanding constraints. Some computationally expensive problems might go to supercomputers, but programs that intelligently control cars and planes have demanding real-time and reliability constraints, while other appli... |
[
"When you play a chord on a guitar, do all the sound waves from the different strings lump into a single wave?"
] | [
false
] | I'm pretty sure mathematically they can be described as such but does this actually happen? Do the air molecule vibrations get added together perfectly? Does your brain interpret each wave individually or as a single sound wave? | [
"Sound is nothing but a variation in air pressure. When multiple sound waves combine all that is really happening is the pressure of the air in any one location becomes the average pressure of all the waves affecting that location. Any sound wave is just a plot of the air pressure at that specified point over tim... | [
"Yes, but you can separate them again with Fourier analysis, which is pretty much what the brain does with the signal, and is why we hear the chord as a chord and not a complete mess. In fact, the sound from a ",
" string is already a superposition of sin waves in a harmonic series. Typically (but depending on ho... | [
"Actually the \"Fourier analysis\" is done mechanically in the cochlea of the inner ear, rather than in the brain itself. The proximal portion is is stiff and resonates with high frequencies, and the distal portion is floppy and resonates with low frequencies. The neurons of the auditory nerve respond to the vibr... |
[
"How do ocean animals \"drink\"?"
] | [
false
] | null | [
"They filter out the salt. Saying they don’t drink is misleading, as lots of water is ingested while eating and just while going about their life. But they all have ways of filtering it that land animals just don’t need. So we don’t have."
] | [
"Not every sea creature, only mammals lack this ability to filter out the salt from sea water, saltwater fish filter out the impurities from the water and basically pee them out in highly concentrated yrine"
] | [
"But if every sea creature gets its water through eating other sea creatures, where does the original water come from? "
] |
[
"What would the crust of a neutron start look like?"
] | [
false
] | If two neutron stars collided, and a portion of ones crust was flung off, what would that crust look like? Given the huge decrease in pressure / temperature, how would it act (rapid expansion? Fragmentation? Stay intact?)? Edit: apologies for this misspelled word in the title. Start = star | [
"The crust is made up of iron bathed in a sea of free electrons. It's not made of \"neutronium\", i.e. pure neutrons, until below that. It's surface temperature will be of order one million Kelvin, so while it's still on the neutron star, I'm not sure it would look like anything except blinding (relativistically to... | [
"Without sufficient pressure, the ejecta would decay in an massive explosion, as the half life of free neutrons is only about 15 minutes or so. I have no idea what neutronium would look like to be honest, if it came from an ordinary hot neutron star it would probabely be brightly shining, like any other hot materia... | [
"Neutronium, assuming it didn't decay like the previous comment would suggest, would be impossibly spherical compared to anything we're used to. While we don't yet know what color it would be if the star was cold, it would be completely uniform due to there being little to no deviations in the structure of a neutro... |
[
"Would it be hypothetically possible to build a device that jams a single radio frequency so we'd always have a convenient \"dead station\" for our iPods in the car?"
] | [
false
] | And if so, how difficult would it be to make? | [
"Wouldn't that also jam the iPod radio transmitter?"
] | [
"No, jamming the station would also jam your iPod and I also believe that intentionally jamming a licensed frequency is a very illegal.",
"If you're in the USA, Wikipedia says:",
"Blocking radio communications in public can carry fines of up to $11,000 or imprisonment of up to one year."
] | [
"All you can do is transmit another signal. You can't grab a signal and pull it out of the air. "
] |
[
"moments after the big bang, if all matter was inside the swarzchild radius, why didn't gigantic black hole form?"
] | [
false
] | null | [
"The reason that a black hole normally forms is because there is a lot of matter in a small space that's all being pulled gravitationally toward the center of mass. This means that you need a mass differential: you need a very strong gravitational force pulling each particle in a single direction (i.e. toward the c... | [
"The big bang was not like an explosion outward from a point. It was more like an infinite sponge starting in a squeezed state and relaxing, causing an expansion similar to an inflation. Assuming the universe is infinite, then it was still infinite (and uniform) during the big bang. Even if the universe is finit... | [
"A simple way to think about it is that to form a black hole, you need mass-energy to be concentrated in a small area compared to space.",
"But the big bang happened everywhere, so immediately after the big bang the region where the mass-energy was concentrated was the same size as all of space."
] |
[
"Aerogel as a CPU cooler?"
] | [
false
] | Thinkgeek.com sells aerogel pieces for about 35 bucks. Would it be possible for me to use aerogel in a case mod, or put it on my CPU like a heatsink? This might not work at all, but it would be really cool if it could! | [
"It is really good at ",
" heat, meaning it will trap the heat on the cpu rather than moving it away. Kind of the opposite of what you want."
] | [
"diamonds, carbon nanotubes and graphene are the best conductors of heat. obviously none of them are even close to practical at the moment. the most practical heat conductor that you could use is pure silver, as it is around 45 times better at conducting heat than thermal paste. in general, pure metals like copper,... | [
"We have an aerogel detector in our experiment actually."
] |
[
"If I tried to \"swim\" through outer space, would I be able to?"
] | [
false
] | If so, what swim stroke would be the most effective? If not, why? | [
"No. Based on conservation of momentum, in a perfect vacuum, you wouldn't go anywhere because you'd need some momentum to go in the other direction. ",
"Space isn't a perfect vacuum but for the intents of this question, it's a pretty good approximaton."
] | [
"Plenty! Lot of people, myself included, study what's called the ",
"interstellar medium",
", the gas and dust and particles that exist out between stars. Space is actually really really active and dynamic and not a vacuum at all, it's just that relative to Earth, it is. A \"typical\" number density is about on... | [
"Basically, there is nothing to push against, so you would not move."
] |
[
"Optimal probability strategy for drawing numbers?"
] | [
false
] | Let's say that you and 9 other people have to draw numbers (1-10) from hat. The numbers drawn are random; however, you get to control when you draw a number from the hat. Is there an optimal strategy if you want a certain number? Or a number within a range? | [
"There is no difference when to draw. Lets replace numbers with colors and lets say there are 9 white and one blue ball, and you want blue ball.",
"If You draw first, probability to get blue ball is 1/10",
"If you draw second, probability is 9/10*1/9=1/10 (probability first did not get blue ball times probabili... | [
"Thanks, I understood what you found wrong in my proposed solution. I used this formula:",
"1 - P(A∪B)=1 - (P(A) + P(B) - P(A∩B))",
"When there is only one blue ball P(A∩B)=0, since both first and second cannot draw blue ball at same time (I probably should have added 0 earlier to avoid some confusion).",
"W... | [
"Oh my god, while it is correct, this formula isn't intended to be use with a lot of subset. ",
"It is totally right, but it gets so messy so quickly, it wouldn't have cross my mind to use it."
] |
[
"Does b-lactamase exist naturally? Did all enzymes and/or modifiers that provide antibiotic resistance exist in nature at one time?"
] | [
false
] | null | [
"In some ways - yes. Evolution can't produce anything ",
", it can only modify existing structures. For example, B-lactamase is a mutated version of normally occurring digestive enzyme. It could be even enzyme with a very restricted mode of action against antibiotic. But any resistance is better than none, and it... | [
"I wasn't able to find an exact reference for this, but I'm reasonably certain b-lactamases existed prior to the discovery of antibiotics by humans. Most antibiotics we have today are either based on or similar to the bactericidal compounds produced by other microbes which includes penicillin. These compounds wer... | [
"I was going to state that b-lactamases would certainly exist naturally because b-lactam containing antibiotics also exist naturally. You already had it covered.."
] |
[
"What is the context of the geometric mean when the 50 ohm compromise for impedance matching was determined?"
] | [
false
] | I had wished to understand why transmission lines and other electrical systems typically use 50ohm loads for impedance. Everywhere I look online, websites just repeat the facts that this is derived from taking the values that provide highest power transfer (30 ohms), lowest power loss (77 ohms), finding the arithmetic mean (53.5) and geometric mean (48), and 50 is a compromise between them. There’s a lot of other history and data on various other values, but I’m hung up on why geometric mean was considered. I understand the arithmetic mean more intuitively as a midway point between these two ideals, but I can’t wrap my head around the purpose of the latter. I have only seen the GM used in basic geometry for triangle side ratios or for certain statistical growth scenarios so I don’t have a good image of its use in this real world application; is there a connection with the trigonometry of RF waves and reactive components, or something simpler? | [
"Let's say you had two solutions of equal volume, one with a strong acid in it and a pH of 6, the other with a strong base and a pH of 8. Let's say you add these two solutions, what is the resulting pH?",
"If you took the arithmetic mean of the 6 and 8, then you correctly get a pH of 7. However, if you took the a... | [
"Just a small correction to your example: The arithmetic mean of 10",
" and 10",
" is 5.05x10",
", or pH of roughly 6.3. AM of two values will always lie between those values, in your calculation it didn't."
] | [
"50 is sort of in the middle between the two and is a nice round number, that is why it was chosen. I think some source just looked at both means and justified the choice as \"the average between both means\" and other sources you read copied them.",
"A standard is just that: a standard. As long as everyone agree... |
[
"Why do we expect Lake Vostok to show early earth life forms?"
] | [
false
] | It seems to me that something that has been isolated for so long would show us more about evolution in harsh climates and less about early earth bacteria. We have discovered relatively mild isolated systems before(I think of life on deep sea volcanoes, and in isolated underwater caves) but we learn more about how life adapts than what we learn about early life. So why should we expect different if we find life forms in Antarctica's deep lake "Vostok"? | [
"I have no definitive answers, mostly because I am a high school student, but I believe it is because of how ridiculously harsh conditions were on early earth. It is believed that before complex life evolved on earth, the planet went through many cycles of heating and cooling. The earth went from too hot to support... | [
"You would need a source of energy to have life, no matter how hardy. Since light obvious doesnt make it down there, there would have to be some source of geothermal energy to anything to live. "
] | [
"Not necessarily. Just look at the chemosynthetic bacteria that function as primary producers in deep-sea vent communities. While there is plenty of heat for them to use, their energy comes from chemical reactions within the bacteria, not the volcanic heat. While the lack of heat and light is not ideal for life, it... |
[
"How catastrophic is a supernova is terms relative to a nuclear explosion?"
] | [
false
] | null | [
"According to the NOAA, an average hurricane releases 1.5x10",
" Watts of energy from windspeed.",
"\n",
"http://www.aoml.noaa.gov/hrd/tcfaq/D7.html",
"\nAn ant is about 3mg, and a human is roughly 100kg. From ",
"http://www.reddit.com/r/AskReddit/comments/iphci/if_you_could_compress_a_lifetime_worth_of_... | [
"A small supernova will release more energy than the sun will produce in its entire life. Wikipedia suggests the sun releases the equivielnt of 9.192×10",
" megatons of TNT per second. The atomic bomb dropped on Hiroshima was about 15 kilotons. This means the sun is producing just over six trillion times the amou... | [
"This is why I love reddit."
] |
[
"Will the cores of the gas giants ever cool? If they will, what will become of the rest of the planet?"
] | [
false
] | They say that Mars lost most of it's atmosphere due to its core cooling, and no longer having a magnetic field to protect itself from solar radiation. Since planets like Jupiter and Saturn are pretty much entirely atmosphere, will they end up as small blocks of frozen hydrogen? | [
"The cores are balls of assorted ices ........ so they are already and have always been cold. ",
"This is completely wrong.",
"The core of Jupiter is believed to be a mixture of rock and ice somewhere around 24,000 Kelvin. We have an earthly observation bias that ice needs to be cold, but it does not. At the ex... | [
"The cores are balls of assorted ices ........ so they are already and have always been cold. ",
"This is completely wrong.",
"The core of Jupiter is believed to be a mixture of rock and ice somewhere around 24,000 Kelvin. We have an earthly observation bias that ice needs to be cold, but it does not. At the ex... | [
"First we need to understand the current structure of Jupiter. ",
"At the top we have the atmosphere, made mostly of cold hydrogen gas. As we dive deeper, the pressure and temperature starts rising. Eventually once hot and dense enough we hit a layer where hydrogen has transitioned to a \"supercritical fluid\", a... |
[
"What is a potential height for a tsunami generated by a large earthquake on the Cascadia Subduction Zone? How far would this wave travel and what regions would be underwater from it?"
] | [
false
] | null | [
"This is the type of thing that is the mandate of state and national geologic surveys and associated agencies. For WA state, the ",
"Department of Natural Resources",
" deals with producing hazard maps of this type. Specifically, they have produced ",
"tsunami inundation",
" maps for a variety of areas thro... | [
"This is generally true for a Cascadia earthquake (e.g. this ",
"tsunami simulation for a M9",
"), but there is still a risk for a tsunami for a rupture of the Seattle fault, e.g. ",
"this page, and specifically the Elliott Bay map",
"."
] | [
"While there are folks at UW studying a variety of things related to Cascadia, for most hazards related questions, you're usually going to be better off looking for what is on offer from state or local agencies (i.e. geologic surveys, department of natural resources, department of mineral resources, etc, every stat... |
[
"How did scientists (or geologists?) determine that the Earth was 4.5 billion years old?"
] | [
false
] | I know it has something to do with measuring the amount of uranium left in a lead rock, or vice versa maybe. I'm just having trouble understanding the methods and reasoning that lead (ha) to the conclusion! | [
"Most elements decay into other elements over time at a known rate. ",
"For example ",
"U has a half life of 4.5 billion years and decays through a chain of other isotopes into a stable isotope of lead.",
"http://en.wikipedia.org/wiki/Uranium-238#Radium_series_.28or_uranium_series.29",
"Because they have d... | [
"The age of the earth conclusion is indeed more complex and robust than that one measurement, but it's a basic start to understanding. Your hypothesis has reasonable merit, but isn't the case. Verifying evidence includes dating meteorites fallen to earth, moon rocks, and the sun itself.",
"I highly suggest readi... | [
"Floating in space doesn't stop elements from decaying, but it does stop (or at least impede) them ending up in the same place as their decay products. To use the uranium example, when uranium decays in space, prior to forming a planet, you get a planet with uranium deposits and lead deposits, for the same reasons ... |
[
"If some big disaster occured and wiped out almost all of humanity, how many people would be needed to keep our species alive and why?"
] | [
false
] | null | [
"According to the genetic bottleneck theory, between 50,000 and 100,000 years ago, human populations sharply decreased to 3,000–10,000 surviving individuals.",
"[31]",
"[32]",
" It is supported by some genetic evidence suggesting that today's humans are descended from a very small population of between 1,... | [
"To clarify, genetic bottlenecking refers to the loss of variety in a gene pool due to low population numbers, not an event specific to human history. Cheetahs have also gone through a genetic bottleneck which explains why they're all very genetically similar, and any currently endangered species which used to have... | [
"Basically you need 50 breeding individuals to avoid inbreeding depression and 500 in order to adapt,” he says. It’s a rule still used today – though it’s been upped to 500-5,000 to account for random losses when genes are passed from one generation to the next",
"https://www.bbc.com/future/article/20160113-could... |
[
"Where does the calcium come from during aortic calcification / stenosis?"
] | [
false
] | I only learned calcium ions playing a role in the nervous system, and since the cardiovascular nerves are independent (mostly) during heart beat (synapse from SA to AV node), and the cardiovascular nerves are not nearly as extensive as the muscles of the heart, where does the calcium physically come from during calcification of heart valves? Is there a small amount in our blood? Any journal or research references would be greatly appreciated! | [
"Without citing any research articles or journals, I can confidently say that calcium is present in the blood. It is simply impossible for calcium to get anywhere in the body without at least some being in the blood. Even in neurons, muscles etc, there will always be some calcium lost with every cycle of whatever... | [
"Thank you soo much. Great starting point into looking to journal articles. I am now going to try to find any information I can regarding the equilibrium/ calcium contraption in intestinal fluid and blood. "
] | [
"There is calcium in the blood. Most of it is bound to protein in the blood, mostly albumin, but some of it is as free ions. "
] |
[
"Why does mass bend space-time?"
] | [
false
] | null | [
"Because it has a rest energy E = m c",
" and energy-momentum curves spacetime.",
"As to why energy-momentum curves spacetime, and what exactly this means, that's quite a question.",
"Assuming the equivalence principle, we know that ",
" spacetime can be \"bent\" by something, it ",
" to be energy-momentu... | [
"im pretty sure E(rest)=mc",
" is only rest energy, since c is a constant and m is (rest)mass"
] | [
"I recommend Hobson's intro to GR as a first textbook, and then Carroll."
] |
[
"How was the island in the Manicouagan crater formed?"
] | [
false
] | [deleted] | [
"Above a certain size, the stress re-equilibration of a major impact has a rebound effect which produces a central uplift (see fig 10, here: ",
"http://www.lpi.usra.edu/publications/books/CB-954/chapter3.pdf",
").",
"However, in the case of Manic, since the impact is Triassic, the crater is FAR from fresh. In... | [
"Many ",
"impact craters",
" have a bump in the middle. These are know as ",
"Complex Craters",
". You can see numerous examples in those articles.",
"The reason for the formation is:",
"Above a certain threshold size, which varies with planetary gravity, the collapse and modification of the transient ... | [
"Vaguely recalling something I read once, I believe that the uplift in the centre of craters is due to the shockwaves from the impact rebounding off lower levels of rock - this will happen most powerfully at the centre of the crater, which is closest to the reflecting layers of rock. I've tried finding some informa... |
[
"If macromolecules are the building blocks of life, why do macro diets usually only focus on proteins, carbohydrates, and lipids (fats/oils), but exclude nucleic acids?"
] | [
false
] | null | [
"DNA is indeed one massive macromolecule. But DNA (aka a nucleic acid) cannot be metabolized in the way fats/sugars/proteins are. DNA is made up of nucleotides which can act as the skeleton for other things like healthy cholesterols and hormones, but eating DNA really doesn't provide any source of energy for our b... | [
"Thanks! I kind of understand this-but I was curious as to if we could be missing something. Many of the foods cited as being good for people for other reasons such as protein and oil also have high concentrations of nucleic acid: fish, spirulina, vegetables. I thought that maybe nucleic acids have a benefit, but w... | [
"its more of a correlation vs causation thing. Most healthy things are \"alive\" and thus have nucleic acids (plants, fish, turkey, fruits). "
] |
[
"Is there any practical use for laminar flow in liquids, or is it purely a neat aesthetic phenomenon?"
] | [
false
] | null | [
"In grease bearings and the like, you select a viscosity to avoid turbulence and make a set amount of friction to avoid over heating.",
"In pipe flow you avoid turbulence to avoid flow induced vibration fatigue in metal and excessive pressure drop along the line. ",
"In food prep, you apply chocolate or whateve... | [
"As far as medical stuff goes, anything that deals with blood (dialysis, heart lung machines, LVADs etc) pretty much needs to be laminar. Blood cells are not happy when things are turbulent, and if you start lysing (breaking) blood cells, things become a problem fast. ",
"In general I would say that laminar f... | [
"There are MANY applications for laminar flow."
] |
[
"Does neuroscience discount the whole discipline of psychology?"
] | [
false
] | null | [
"they are very tightly interwoven and cannot be separated, so it can't be that either one discounts the other.",
"at the margins, there are neuroscience studies that seem to have little to do with psychological science - e.g. a study of how exactly how a neurotransmitter binds to a receptor; or psychological stud... | [
"I do not think that external v. internal properties of a human is a helpful distinction between the two, as neuroscience is very interested in describing in terms of brain anatomy and function the mechanisms of identity synthesis, feelings and emotional states, the emergence of consciousness by means of synchrony ... | [
"I do not think that external v. internal properties of a human is a helpful distinction between the two, as neuroscience is very interested in describing in terms of brain anatomy and function the mechanisms of identity synthesis, feelings and emotional states, the emergence of consciousness by means of synchrony ... |
[
"Are there any studies showing how many Covid-19 cases are asymptomatic vs pre-symptomatic, and is there a difference in the infection rate or viral load?"
] | [
false
] | When the pandemic started, most of the attention was on "asymptomatic" infectees, but I've seen more people saying many of them may have instead been pre-symptomatic. What is the number of asymptomatic people that never get symptoms, and is there any differences between pre- and a- symptomatic people? | [
"This ",
"study in Indiana",
" found 44% of patients with an active infection were asymptomatic. I've seen estimates of 20-80% of cases being asymptomatic, our understanding of the prevelance of asymptomatic cases could definitely be improved. ",
"There was a ",
"very recent JAMA study",
" comparing vir... | [
"Not exactly what you're asking about, but Radiolab recently had a very interesting podcast episode about how a large percentage of homeless seem to be coming down with COVID-19 but remain asymptomatic, possible due to having higher Vitamin D than the average population. ",
"https://www.wnycstudios.org/podcasts/r... | [
"Thank you for sharing that, it makes me feel better. \nSincerely, someone with blood type A"
] |
[
"Out of all the spacecraft we have landed on planets, is it possible some may of contained bacteria that has stayed on that planet? And possibly even spread?"
] | [
false
] | [deleted] | [
"Concern about contamination is the reason why Cassini was thrown into Saturn. Originally the plan was to just let it keep going after it ran out of fuel, but discovery of geysers on Enceladus made scientists realize that if it crashed there, any microbes missed by the sanitation process could survive and multiply.... | [
"This is actually a huge concern for any space agency, since if there is any life on another planet and we bring our bacteria we risk killing that life. NASA has strict sanitation policies for spacecraft and personal, usually requiring them to spray down the aircraft with chemicals and having workers wear full body... | [
"For a long time, it was thought that this had actually happened with Moon probes. Parts of one of the early unmanned probes (Surveyor 3) were brought back by Apollo 12, and upon analysis they thought that there were some still-viable bacteria in it. However, as I understand it, they now think that the Surveyor par... |
[
"What is the evolutionary advantage of desensitization?"
] | [
false
] | By desensitization, I mean the down-regulation of receptors to repeated stimuli. Is there an advantage to such phenomenon? | [
"Our sensory systems are built to detect change in the environment. If there is some continuous signal that is irrelevant, we want to ignore it and prioritize processing on things that might affect us (e.g. threats, targets etc.). The classic example is that soon after putting on your clothes, you stop feeling them... | [
"To expand on that, the evolutionary advantage comes from the reduction of energy used to detect, send, and process the signals that are irrelevant."
] | [
"if you want a big theory, you could read about the ",
"free energy principle",
", the basic idea is that any living system, including a neural system, should always be striving to minimize its activity; reducing response to a constant stimulus is an instance demonstrating the principle."
] |
[
"If a container filled with gas was left alone for a very long time will the gas eventually run out of kinetic energy?"
] | [
false
] | Assuming the container was isolated from any form of external force and energy. | [
"There are two possibilities here.",
"If your container is perfectly insulated, then it is a closed system and no energy can leave or enter. In that case, the gas can't run out of kinetic energy because, basically, there is no other place for that energy to go.",
"If your container is not perfectly insulated, t... | [
"No. That is what \"perfectly insulated\" means (and this isn't something you can ever achieve in practice, of course)."
] | [
"So you are assuming that the container is pressurized, doesn't leak, and is completely isolated from outside sources of energy, such as heat.",
"Is this correct?",
"If so, your question is, if given enough time, the tank, with the pressurized gas, will \"loose\" its kinetic energy (which I think you mean the p... |
[
"Does quantum entanglement allow us to study some of the paradoxes associated with time travel?"
] | [
false
] | I recently came across this fascinating video of the where a single photon passes through a double-slitted barrier and is subsequently split by a prism into two entangled photons. The first photon always goes to the same detector, D0. The second photon goes on a different path to meet a number of possible detectors. D0 doesn't give any way to determine which slit the original photon went through. However, the other detectors may or may not give that information, depending on their position. Since the two particles are entangled, D0 will show either an interference pattern or a clumped pattern based on which detector the second photon hits. These results are always 100% correlated. Based on the detector the second photon hits, you will always know the pattern at D0. Also, based on the pattern at D0, you will know which of the possible detectors the second particle must have hit. If the path to D0 is shorter than the paths to the other detectors, doesn't that mean we can predict the future with 100% certainty? If we make the paths of the other detectors long, couldn't this give us time to attempt to change the results that we see at D0? In my mind this is analogous to the grandfather paradox - where the future is known, but somehow we are prevented from changing it. This experiment seems awfully simple to set up. And it would appear to be simple to change the results after seeing D0. Has this been done before or is there something I don't understand? Thanks!!!! | [
"I'm not going to address specifically your question about the delayed choice quantum eraser, because it's been a while since I've read up on it. I will tell you about another experiment that used quantum information to probe the grandfather paradox.",
"http://arxiv.org/abs/1005.2219",
"Basically, they said, if... | [
"Short answer is no. You can't predict where the other particle will land by observing D0 alone. The sum total of the interference patterns at D0 created by the other detectors is always a bell curve type probability pattern. They never actually see an interference pattern at D0. It is only after the measurements a... | [
"Thank you, I read the abstract and it sounds interesting. I like that term, \"retrodiction\" (versus \"prediction\")."
] |
[
"Is north pole shift really gonna happen?"
] | [
false
] | [deleted] | [
"I'll assume you're referring to a flip of the polarity of the Earth's geomagnetic field. Two points and then we'll get to the meat of your question.",
"(1) A pedantic point, but kind of important, it's not really meaningful to ask if the \"pole shift will happen\" as the geomagnetic pole is constantly shifting a... | [
"Great answer! What would be the reproductions of the reversal?"
] | [
"One thing to add:",
"\"the time that it takes for a reversal to complete is on average around 7000 years for the four most recent reversals.",
"\n Clement (2004) suggests that this duration is dependent on latitude,",
"\nwith shorter durations at low latitudes, and longer durations at mid and",
"\n high la... |
[
"Why do many various neurotransmitters exist if nerve signals are binary?"
] | [
false
] | As far as I know neurotransmitters are only released, bound to receptors and reuptaken in the synpatic cleft. I that is the case, then what's the point of multiple neurotransmitter types if chemical signal is going to only be translated into a binary electric signal that is 1 (excitation of the membrane), while none is 0 (resting membrane potential)? For me, in my limited knowledge, it appears as if their existance is useless since electrical signals alone or just a single neutrotransmitter type would suffice, unless neurotransmitters were released into the intracellural space and all neurons in an area of the brain with specific receptors would pick them up, which isn't a case in models I can find on the internet or in books. I know I am wrong but having asked many highschool teachers noone was able to answer this question to me years ago. Can anyone explain this to me in best detail possible? | [
"The first signal isn't binary. At the dendritic spine, neurotransmitters open different ion channels. Glutamate opens Ca-channels, GABA opens Cl-channels, etc. This creates graded membrane potentials called PSP (post-synaptic potential). All the PSP's from different dendrites travel to the soma, where summation oc... | [
"Neurons are relatively specialized for certain types of incoming signals. The presence of specific receptor proteins determines what type of chemical signal will cause a given response (excitatory, inhibitory, modulatory, etc).",
"The average number of synaptic inputs onto a given neuron is like TEN THOUSAND. Th... | [
"This. ",
"The analogy of a nerve impulse I would use would be an insanely complicated chain of analog bias circuits.",
"Not a whole lot in nature is binary"
] |
[
"I read that there are high concentrations of interstellar dust and gas near the center of the galaxy that make it difficult to resolve stars. If Earth were orbiting a planet very near to the galactic center, would space appear “hazy” instead of clear and black?"
] | [
false
] | Likewise, would the same apply to a planet within a nebula? If the affect wouldn’t be enough to make a difference visible to the naked eye, are we inside a nebula or some gas “cloud” ourselves? | [
"Some minor pedantery first: There are high concentrations of dust and gas towards the center of the galaxy. The actual galactic core is pretty devoid of dust and gas compared to the arms. When looking towards the galactic center, our view of the core is obscured by the nebulae in the arms between us and it.",
"O... | [
"Excellent answer. Thank you!"
] | [
"Well that's just untrue. Even in interstellar space there's quite a few atoms of hydrogen and helium in any given cubic meter, and I think hydrogen atoms count as 'anything'. (the amount is a few hundred thousand to millions of atoms)",
"In terms of more substantial stuff, there's an estimated number of about 0.... |
[
"Anyone have suggestions for darkening tungsten?"
] | [
false
] | I have some Tungsten that I want to make dark and, if possible, more rough. Does anyone have suggestions for doing this? It can be a reaction on the tungsten surface or some sort of coating. | [
"Yes, more information please. What kind of equipment do you have available? Is this in a lab or a garage or a kitchen?"
] | [
"You can oxidize the surface to a black oxide color"
] | [
"Does the surface have to remain tungsten? There are lots of ways of applying coatings or changing the surface of materials, but you'll need to be more specific for people to select some to share."
] |
[
"What are some of the simplified lies we are taught that doesn't accurately describe what's really happening?"
] | [
false
] | null | [
"This question is too broad, and not actually a question that can be answered by science since it's an argumentative premise (meaning that it is subject to debate, not that you are being argumentative.)",
"I'd like to let this question through, but in reality, it would likely turn in to an absolute shit-fest, wit... | [
"Very well. Thanks for the reply."
] | [
"We are considering this question as a \"Discussion\" thread put on by the Panelists, so it's a good question, we just really would need to be far more prepared."
] |
[
"What is the fastest form of space travel?"
] | [
false
] | Not warp drive, light speed, or anything like that. If we were to build a ship right now, what would be the fastest engine possible? Rockets? Solar sail? Ion boosters? Nuclear explosion for propulsion? | [
"Full link here",
" - need to backslash the brackets in order to include them."
] | [
"\"Fastest\" depends on how far you want to go. Chemical rockets are pretty good for getting you to the moon. They're probably not the best bet for getting you to alpha centauri. How far do you want to go?"
] | [
"let's say extra solar."
] |
[
"How did menstruation evolve in humans?"
] | [
false
] | null | [
"Hi pianopolo9 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the foll... | [
"Hi pianopolo9 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the foll... | [
"Hi pianopolo9 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the foll... |
[
"How do birds 'know' how to build their complex nests?"
] | [
false
] | I've seen a lot of bird nests, some of them somewhat complex. Humans build things much more complicated than bird nests but how do non-self-aware birds 'know' how to build their still somewhat complex nests? | [
"Here's an article",
" that discusses the neural aspect of programmed animal behavior. Serotonergic signaling (i.e. with the neurotransmitter serotonin) was found to play a major role in the maternal behaviors of mice, including nest building, pup retrieval, cleaning, and nursing. This is regulated through trans... | [
"The question is though, what mechanism is responsible for storing and conferring this information over generational gaps? Where in the DNA of a parent bird is it stored that they prefer stick type A over stick type B etc"
] | [
"Do you know if we find any programmed maternal behaviour with humans?"
] |
[
"What do we know about an individual's ratio of X sperm to Y sperm? Specifically, what things contribute to that ratio?"
] | [
false
] | What started as a philosophical discussion on the morality of gender selection turned into an argument in my house this evening. I made the statement that in the future, gender selection technology would likely advance to a point where a male could take a pill for a few weeks leading up to conception that would ensure his body only produced one type of sperm; X or Y. I suggested that this would theoretically be possible with some form of hormone or chemical that temporarily produces an environment that inhibits the creation of a certain type of sperm. I was told that this was "messing with nature" and shouldn't be done, and I made the mistake of saying that my theoretical pill was exactly the same as the contraceptive pill, in that it changes the conditions within the body and prevents or promotes a certain bodily behaviour through hormones. I guess this is ultimately a two part question: 1) How accurate was my understanding of how the contraceptive pill works, and 2) Is there any research on what factors contribute to sperm ratio? The only things I could find on google regarding #2 was a whole bunch of Yahoo answers that suggested if you conceive on the even days in a month, you will have a blah blah blah... I stopped reading. Any takers? | [
"Sperm can be sexed in a lab.",
"The ratio in humans is indistinguishable from unity.",
"Some animals alter the sex ratio of their gametes. Theoretically, a substance could be made that preferentially targets one sex of sperm. ",
"The oral contraceptive pill contains generally contains two hormones, estrogen ... | [
"Hormones aren't impacting if sperm have an X or Y chromosome, it is a completely random event during meiosis and has a pretty much equal chance of happening. Therefore, it would be very difficult to target that process by some sort of pill intervention. "
] | [
"I'm pretty certain that due to the fundamentals of ",
"meiosis",
", each parent cell will produce 2 Y sperm and 2 X sperm, so the ratio should be 50:50."
] |
[
"What \"generation\" star is our Sun?"
] | [
false
] | I understand that a certain number of elements are created when a star goes supernova. What is left over then becomes another star that goes supernova and creates the next level of elements, rinse and repeat. How many of these cycles have we been through to create the natural elements that exist on Earth? On reflection, I assume that some of the ancestors on the stars family tree will be from more recent generations at the same level of ancestry. Can we make any educated guesses as to how many ancestors our sun has? (Not just number of generations but actual number of stars.) How old is the oldest ancestor star on our tree? And when/if our sun goes supernova, which elements will it create that are not naturally occurring now? | [
"The Sun is a Population I star, meaning it contains metals from previous generations of stars. By measuring the spectral characteristics of stars, we can observe the ratios of metals to hydrogen or helium, and from this, we can determine how many generations of \"ancestors\" the star has had.",
"Stars may be cla... | [
"The sun would become a red giant and then a white dwarf. Red dwarf stars are small main sequence stars; class K or M."
] | [
"Our star the 'Sun' is composed of about; 70% Hydrogen; 28% Helium; 2% metals, and has a diameter of 1,390,000 kilometers making it one of the larger stars in the galaxy as it is larger than most stars in our galaxy.",
"As for our star's origins, the asteroids in our solar system are leftovers that originated fro... |
[
"Are tumors edible?"
] | [
false
] | IE, would anyone notice if a cow developed cancerous growths (in its muscles or I guess organs) before it was butchered? | [
"If you've ever eaten any sort of meat from a processing plant, chances are good you've eaten some tumor."
] | [
"And feces. Don't forget about the feces."
] | [
"Tumors are generally only harmful to the specific individual they came from (with a handful of ",
"notable exceptions",
") - if they enter the body of another individual (or another species), the immune system recognizes it as foreign and rejects it. This doesn't work if it's your own tumor, as said tumor disp... |
[
"If I apply a force to an object not through its center of gravity such that it accelerates both linearly and angularly, is its linear acceleration less than if I applied a force to it through its center of gravity so it only accelerated linearly?"
] | [
false
] | If so, how does that fit in with F=ma? If not, doesn't that violate conservation of energy? (I'm assuming something rotating has more energy than something equivalent not rotating). | [
"Be careful about trying to talk about F=ma when talking about a force at the end of a rod (or other object where you're not pushing through the center of mass) in a particular direction. It makes sense only for the first infinitesimal instant, after which the contact point has moved, and not in a simple linear way... | [
"It's linear acceleration is identical. ",
"/u/uh_no_",
" is wrong, or, more charitably, answering a question you didn't ask. And the reason is exactly what you say: F = ma. If the net force on the object is the same then the acceleration will be the same. ",
"Energy conservation looks like this: dE = W. The ... | [
"You are talking about motion of a rigid body. F=ma is strictly true for only a point source, where there is no rotation.",
"A complete description of motion is given by F=ma (where F and a are vectors) and M=dH/dt (where M and H are vectors). M is the moments and H is the angular momentum.",
"For simplicity, ... |
[
"How does the tension in a lift cable decrease as it accelerates downwards?"
] | [
false
] | Shouldn't the upward tension increase since mg and ma act along the same direction? | [
"You're thinking about it the wrong way. When the lift is stationary, the forces are balanced. The tension in the cable provides an upward force, equal and opposite to the force of the lift's weight. Mathematically, T - mg = 0",
"If the lift is accelerating downwards, that means the net force is in the downward d... | [
"Hmm I still don't get it. I did it mathematically and got what you got. But it doesn't make sense to me spatially (I hope that's the right word)."
] | [
"Imagine it's a tug rope instead, you against someone else, currently in equilibrium where both of you are pulling equally. If you want to win by accelerating the rope towards yourself, you have to pull harder than your opponent; if the elevator wants to move upwards, the tension force has to be greater than the gr... |
[
"Why did some social mammals evolve into patriarchal groups and others into matriarchal groups?"
] | [
false
] | Specifically looking for an answer outside of the context of human culture. For example, elephants, meerkats, lions, and killer whales all live in matriarchies - why did they evolve this way while many other mammals evolved in patriarchies? | [
"Excellent question! And not an easy one to answer.",
"Mark Van Vugt and Brian R. Spisak did research on this in human societies. Their findings showed a strong preference for female leaders during intragroup competition (fighting within your own group) and male leaders during intergroup (fighting with a rival gr... | [
"Food availability seems to work well with competition theory. No need for aggressive males running the show. The differences between the Common chimp and Bonobos are pretty incredible. The Max Planck Institute has a great chart ",
"here",
"."
] | [
"I'm not sure if Bonobos are a matriarchal species but I found it really interesting the contrast in their culture compared to chimpanzees. Isn't it due to more access to food with less competition with other large predators and apes? "
] |
[
"Since sound travels at different speeds depending on the medium, what's the fastest speed it could possibly reach?"
] | [
false
] | null | [
"In certain types of plasma and degenerate matter (like inside a neutron star) it can sizeable fractions of light speed. I believe the speed of sound through plasma is the speed of light divided by the square root of 3."
] | [
"Plasmas can be as dense or as rarefied as you like, given certain other conditions. To some approximation, metals can be thought of as plasmas. Likewise, the interstellar medium, with less than one particle per cubic metre, is also a plasma.",
"The speed of sound in a plasma goes like (ZT_e/m_i)",
" , where Z ... | [
"So is plasma extremely dense? I thought sound moved through denser material faster, but my impression of plasma is that it isn't very dense at all? ",
"Sorry for the stupid question. "
] |
[
"Is it possible to siphon energy from lightning?"
] | [
false
] | Its energy, right? | [
"Yes, it would be possible to harvest lightning energy, it just isn't terribly practical. You certainly could build devices that lightning would tend to strike (rather than the ground, buildings, or trees) and route that electrical power. But you'd also need to store the power, and distribute it to places where it ... | [
"Storage is really the problem. There's a lot of energy in a lightning bolt, but it comes in very quickly. You need a system that can absorb that much energy, then provide it back at a much slower rate. Such things exist (large capacitors), but it wouldn't be cheap to do. Putting in a system like that would proba... | [
"Ahh, makes sense, but what about a more home friendly use, like on the roof of your house to be stored somewhere. Could that ever become practical?"
] |
[
"Can light orbit a black hole?"
] | [
false
] | [deleted] | [
"It is physically possible. However, the orbit has extremely tight tolerances. Off slightly in one direction and the light’s trajectory will be merely bent instead of orbiting. Off the other direction and it spirals into the black hole. "
] | [
"The tolerance is zero. Every deviation from the perfect path will lead to the photon quickly escaping or falling in.",
"Every photon energy has the same orbit. They follow straight lines in spacetime and they don't depend on the photon energy."
] | [
"It's actually significantly outside the event horizon. Specifically, photons would orbit at 1.5 times the Swartzchild radius. At the event horizon, light can only escape the black hole if it is travelling directly away from the singularity."
] |
[
"How do homonyms form across languages? For example, \"Right\" means \"correct\", \"law\", and the direction. In Spanish \"derecho\" means the same three things. How do these parallels happen?"
] | [
false
] | I'm sure there are other examples, but Right/Derecho seems to stand out (three identical definitions!). I know English has a lot of Romance language roots, and so it shares plenty of words with Spanish (more than it shares with most languages). But... "Right" is Germanic in origin. So how did two independent languages form the same homonyms in parallel? I know it can't be a coincidence... | [
"You have to go further back than Latin. (PS: English is not a Romance language, although there are bits and pieces of Romance stolen and/or shoehorned into it) There is a ",
"Proto-Indo-European",
" language (PIE) that is the theoretical ancestor of many languages.",
"Many times, with languages, you have to ... | [
"This is interesting because even in Finnish, which descends from Proto-Uralic and not from Proto-Indo-European, the words for correct, right (direction) and right (legal) are the same* word:",
": correct, right (direction)",
"\n",
": justice, legal right",
"They are also related to \"oikoa\" (to straighten... | [
"To add another language related to English: In German \"rechts\" is the direction, \"Recht\" is law, and \"recht\" can be used for \"[done] in the correct way\" (although you'll rarely hear it, \"richtig\" is more common)."
] |
[
"Why would a bird repeat a whole scale of notes in succession?"
] | [
false
] | [deleted] | [
"Basically birds don't do vocal warmups, so what you heard was most likely the actual song(s). We'd have to hear a recording to know for sure what species you were listening to, but my guess is that you were hearing one of the species that (a) has a song that is a simple trill or whistle, and (b) has individual rep... | [
"Thanks for the response. I'm in Phoenix, and though I can't remember precisely what time of year it was, I believe it was a cold crisp morning, so early spring probably. ",
"What the bird sang was clearly a pattern of repeating one note four times, then moving on to the next note which he repeated the same num... | [
"bird songs are fairly plastic, they have been shown to shift frequencies to avoid traffic noise, for example. Birds are odd, lots of weird noises."
] |
[
"Question about Atomic Orbitals and Scale"
] | [
false
] | If there were an atom with an S orbital the size of the Earth, what would be the size of the subsequent P, D, and F orbitals? | [
"If you had an orbital the size of earth its physics would no longer be dictated by quantum mechanics, and its position would no longer be defined by a probability density. But, if you are willing to ignore reason, check out this ",
"picture",
". This is for n=3 shells. You would just take the max of the bigges... | [
"Interesting plot element! (pun intended)",
"f orbitals get pretty tricky -- they can do weird things sometimes in certain elements and compounds, depending on temperature, carrier density, and a bunch of other electronic structure properties. "
] | [
"Thank you, very interesting, I just wanted a rough idea of relative scales. I thought the P and D orbitals would extend outside the S orbital, but I suppose not. EDIT: And in case you were wondering why I would ask about such an unreasonable situation, I'm in the research phase for a science fiction story. It take... |
[
"What's happening when you crease or roll up paper? Why does it stay that way?"
] | [
false
] | null | [
"Got all this info from ",
"this",
" article. ",
"Paper is made up of vegetable fibres, which are felted together. They felt together because the fibres are somewhat rough, although other agents, such as size are often added to encourage the fibres to stick together. But the fibres are brittle and when you cr... | [
"This also explains why if you want to tear a piece of paper in a nice, even, straight line, it helps to crease it before you tear - the fibers that were fractured by the folding process represent a weak point in the chain, and so they break first, preventing the tear from proceeding irregularly."
] | [
"I'll explain it in a structural/materials sense. Have you ever taken a piece of metal and been able to bend it, and it comes back to its original position? When it can go back to its original position, we say that we are within the elastic (yield) limit of the material. ",
"When you apply enough strain to a c... |
[
"How is the reactivity of alkali metals with water measured and how do they compare?"
] | [
false
] | First, some background, I'm an art student making an animation installation about the groups of the periodic table. When making group 1, I thought of this video I'd seen on youtube So I showed caesium as an blowhard boasting about being the "emperor of the alkali's." He then gets corrected by the host, mendelevium. But as I was fact checking this, everything I found said that caesium IS the most reactive. Am I misunderstanding this video or is the video just wrong? But also, for a chart in my animation I do need to understand how the reactions of all of the alkalis are measured and how they compare. | [
"Sort of but you didn't address the issue raised in the video that I posted. Thunderfoot claims that when cesium reacts with water it actually releases less energy than lithium does."
] | [
"Sort of but you didn't address the issue raised in the video that I posted. Thunderfoot claims that when cesium reacts with water it actually releases less energy than lithium does."
] | [
"So for the purposes of my video, I shouldn't say that caesium is less reactive, but I could say that the reaction of caesium with water releases less energy?"
] |
[
"When two things are placed in the microwave, one gets hotter than the other. Why is this?"
] | [
false
] | Why is it that when two objects are put in a microwave, one of them comes out hotter or more properly cooked than the other? This happens in different microwaves, so I'm pretty sure it's not isolated. | [
"The microwaves aren't even across the entire bottom. That's why they have time rotisseries to help counteract the problem. "
] | [
"Water content is key. As well as metal (calcium in bones). The more of either of these the food has, the faster it heats relative to its mass. "
] | [
"What are these objects? Microwave oven doesn't heat all materials the same way. For example you can heat water in the microwave very well but it's not so good at melting ice. "
] |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away! | [
"hello to the medical doctors,",
"has any homeopathic remedy ever been proven to actually work? have any even been clinically trialed?"
] | [
"I'm assuming you're using homeopathy as a synonym for alternative medicine rather than referring specifically to homeopathic medicine which is a distinct subfield. Homeopathy is based on extreme dilution of the targeted \"toxin\" to be ingested. The dilutions commonly specified in homeopathy are well beyond concen... | [
"Not that I can think of -- it's not uncommon for elements to have both 2+ and 4+ states (manganese comes first to mind, but there are others too).",
"There is nothing special about the 8th period or the S-block in terms of properties either except as an \"isn't that neat\" factor.",
"Of course the chances of b... |
[
"How big or small was the universe at the time of the big bang?"
] | [
false
] | Compared to a common household object. | [
"We have no idea how big the whole Universe is or was at any time. The simplest assumption for calculations is that it is homogeneous and isotropic at all higher scales, that it is spatially flat, and simply connected; these assumptions imply it's infinite at all time.",
"What we know is: given a region of size R... | [
"Let's say a(t_0) is 1. It isn't necessarily, depending on conventions, but let's just say it is 1 today. It doesn't matter.",
"Now, consider the first combination of hydrogen, when the CMBR was emitted. This happened around t_r = 400 thousand years after the BB. I tell you that a(t_r) is around 1/1000.",
"Here... | [
"You might want to imagine a 2D universe that is mapped onto the surface of an inflating balloon. If you draw some galaxies on it, then for an observer standing on any one galaxy all the other galaxies appear to be moving away. The balloon is inflating at a fixed rate now, so using general relativity we can map wha... |
[
"If we had a convenient black hole available to observe, what questions could we answer about them that we can't already calculate?"
] | [
false
] | Like if we had a moon-mass black hole orbiting us at the distance of the moon, and could launch any space probe with our current technology, what sort of questions about black holes could we answer? (I'm not sure if a moon-mass black hole at moon-orbit is safe, if it isn't, just readjust the black hole to be a safe one at a safe distance) We seem to calculate out so much of their properties. I'm curious as to what we DON'T know but would love to directly observe. | [
"It's not about our ability to calculate their properties, but about our ability to verify those calculations. Strictly speaking, we can't say that a solution is physically valid, unless we observe the corresponding behaviour in nature.",
"p.s.: Am I the only one finding the idea of 0.11 mm big black hole orbitin... | [
"It would be so trolly. It would have taken people centuries or even millennia to find this massive and almost invisible mass that caused the tides. I guess gravitational lensing would show its location.",
"Plus it would actually take about 10",
" years to evaporate which is a lot longer than I was expecting."
... | [
"Well, for one, it would pretty much confirm that they exist in nature. As much as we love our black holes, just about all the observational evidence for them can probably be explained by other forms of exotic stars. So it would be nice to confirm they exist.",
"That being said, I'm not even SURE we could tell mu... |
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