title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"If Alien scientists from 10 billion years ago made their own picture of the Cosmic Microwave Background, how different would it look from ours?"
] | [
false
] | Edit: Or earlier? Could anything be learned from it that we don't already know? | [
"The microwave background would have been hotter, by about 6 kelvin. (Fantastically, people have actually ",
"measured",
" the CMB temperature over time and shown it evolves as we expect.)",
"However, the ",
"picture",
" we usually see of the CMB doesn't contain the CMB's temperature but its temperature "... | [
"Picture an infinite ruler with 1 cm between the marks. Now, stretch it until there's 3 cm between the marks. It's still infinitely long, and all distances are tripled.",
"Edit: words."
] | [
"It did, though the problem may lie in the choice of words \"tripled in size\". It might be more accurate to say that distances tripled. This applies to both the Universe and the ruler."
] |
[
"What happens to you during a panic attack?"
] | [
false
] | I have always wondered what happens to a person biologically during a panic attack brought on by an intense phobia or anxiety. Also to take that one step further but how those biological effects change your perception and senses to produce what ever the attack may feel like? | [
"Panic attacks are a very interesting example of the effect of our thought process in our bodies. It can be triggered by a small stimuli. Like brief dizziness or chest pain that by itself is nothing of importance. But the patient gives this event an importance much greater than what it really is. This creates a... | [
"From what I understand, a panic attack is a body's 'fight or flight' response. This results in increased heart rate, shallow breathing, adrenaline, rapid thoughts, etc. Your body is prepping you to run away (e.g. as in from a lion in the savannah), but the response can be triggered in circumstances where this is n... | [
"Really the person starts to think they are dying that is much worse than i could have imagined."
] |
[
"Ask Anything Wednesday - Engineering, Mathematics, Computer Science"
] | [
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! ... | [
"Short answer is yes. The block chain is really big and unwieldy. So far they've been able to get away with it, but in the future they will probably have to allow people to participate in the network without the full history of the blockchain. Their are also bandwidth limitations on the bitcoin network in terms of ... | [
"AI is not lacking a roadmap, its just that the things we are working on have nothing to do with the sort of sci-fi AIs you see in movies. ",
" strides have been made in the last five or so years in tons of AI subfields. Just no progress in the sort of inference engines that people in the 70s and 80s said would l... | [
"The Bitcoin network uses additional nodes to increase the security of the network, ",
". That means that the transaction throughput is limited to the throughput of the median node, ",
".",
"See my comment ",
"here",
"."
] |
[
"What is the maximum theoretical size for a sunspot?"
] | [
false
] | Edit: our sun, not other stars | [
"Do you mean a single sunspot or a complex cluster? Sunspots tend to break up into complexes as they grow.",
"Observationally, single sunspots get up to about 60Mm according to this comprehensive summary of the science from 2002: ",
"http://www2.mps.mpg.de/dokumente/publikationen/solanki/r45.pdf",
"\"Why do s... | [
"Generally depends on the star and its magnetic field, but for the purpose of this answer I'm sticking with Sol.",
"First, to understand what a sunspot is and the underlying mechanisms.",
"A sunspot is a region of the sun where its sub-surface magnetic field has become twisted and knotted, then forced through t... | [
"Yes we have, but due to the size of the object we're trying to pick out directly on another solar surface, its generally only the really big ones we can see directly (up to 100x larger than on Sol's surface). Others require various techniques to detect the spots. Naturally, such sunspots also generate x-ray activi... |
[
"Can you transplant organs across genders?"
] | [
false
] | For example can a man receive a woman's heart? Vice versa? What about transgendered? | [
"Gender is not a relevant criterium to judge possible organ donors. I only know about live organ donation, for example kidneys, but I assume that it is very similar with recently deceased donors. Your blood is tested for the amount of reactive antibodies, indicating how many of your white blood cells will recognize... | [
"I remember seeing something recently about men being at higher risk of death after blood donations from ever-pregnant females, hypothesized to be as a result of immune system changes pregnant woman have to help protect the baby. A slight risk, but the study showed it to be statistically significant. Do you know of... | [
"To provide some anecdotal evidence to Opthalmic's explanation, my mum gave a kidney to a long time friend of the family who is a dude. I think it's been 10 years now and he's still going strong.:-)"
] |
[
"If the world is slowing down (ie. Spinning slower each year), would it have been noticeably faster millions of years ago?"
] | [
false
] | I say noticeably, I mean would a human being alive at that time (hypothetically) feel any different than they do in the present day? | [
"620 million years ago: the day was 21.9±0.4 hours"
] | [
"It's slowing at a miniscule rate. Basically it's syncing up to the moons orbital speed. As the earth slows the moon moves farther away, about an inch a year. They'll never sync up though because before that can happen the sun will come to the end of it's life, grow to a red giant and engulf them both.",
"Edit: s... | [
"So it is neither speeding up or slowing down? Or is it slowing at a miniscule rate?"
] |
[
"What would happen if a healthy person took the highly active antiretroviral therapy?"
] | [
false
] | [deleted] | [
"It would definitely reduce HIV transmission risk, if that's what you're asking. I don't think anyone knows how much it would reduce it, though. Most of the trials for this have been conducted in Africa with only single drugs or pairwise combinations, usually the cheapest ones available. I'm guessing that a full-... | [
"it can make people with compromised immune systems live about as long as people with healthy immune systems",
"This is a wildly inaccurate description of HAART intervention. There are many, many reasons for immune deficiency beyond HIV infection, and obviously antiretrovirals do not affect these. It decreases th... | [
"it can make people with compromised immune systems live about as long as people with healthy immune systems",
"This is a wildly inaccurate description of HAART intervention. There are many, many reasons for immune deficiency beyond HIV infection, and obviously antiretrovirals do not affect these. It decreases th... |
[
"How do solar flares and other types of activity of a star influence its movement through space?"
] | [
false
] | null | [
"Stellar activity will not influence an ordinary star's movement significantly at all. The total mass ejected by the Sun is around 10",
" solar masses per year. If you assume the ejected mass was travelling 50% of the speed of light in a single direction (it's actually traveling much less fast) it would change th... | [
"Thank you, in short: it has effect but for most thing it will be negligible, because the effect is very small?"
] | [
"Exactly."
] |
[
"Why is the Higgs needed for atoms and stars to exist?"
] | [
false
] | "This symmetry breaking is required for atoms and other structures to form, as well as for nuclear reactions in stars, such as our Sun." on the Higgs wiki page. From what I understand the Higgs is the reason that Electromagnetism and the Weak force are two separate forces rather than one Electroweak force. And atoms ca... | [
"This blog post by Matt Strassler",
" discusses what the universe would be like if the Higgs field had a mean value of zero. That's a slightly different question than the one you're asking, but it's close enough to be interesting, I think.",
"Some highlights (edited slighty for brevity):"
] | [
"Why is the Higgs needed for atoms and stars to exist?",
"Because there is no mathematical reason why particles such as the W and Z boson have mass -- they should be massless without a reason to have a mass. The Higgs mechanism provides a way to give the W and Z bosons (and other particles such as electrons) a m... | [
"Both are dependent on the universe's temperature. The electroweak merging temperature is around 10",
" K; the energy scale for proton and electron recombination is on the order of 10",
" K. So there are 11 orders of magnitude difference."
] |
[
"Why do lightbulbs need so much \"free space\" between the filament and the glass?"
] | [
false
] | [deleted] | [
"The bulb is filled with an inert gas (usually argon) that does not react with the filament. Throughout the bulb's life time, oxygen slowly seeps into the bulb, and once it passes some threshold, there is enough oxygen for the filament to oxidize and break, which causes the light to go out.",
"Therefore, with a l... | [
"I seriously doubt that this has anything to do with it at all. More likely it's simply heat-transfer limitations. Incandescent bulbs operate with the filament basically as hot as it can get without destroying itself, and the transfer of heat out of the bulb will be limited by its surface area. If you make the b... | [
"I'm not sure if slow continuous evaporation is the dominant failure mechanism either. Most of the tungsten deposits on surfaces of a blown bulb probably occur during the last few seconds prior to failure, during which time a defect has created a localized region of high resistance, localized heating, and accelerat... |
[
"Reddit, are you ready for my glass challange, I need your help!"
] | [
false
] | *repost from askreddit where they directed me to here. Hi Reddit, So, I have been lurking for some time, but I have no where else to turn. I have been trying to melt glass without bubbles for some time, and I just can't figure it out!!!!!! I have spent over a year and thousands of dollars. I am trying to make a small b... | [
"I might be able to help. I worked in glass formulation, raw material batching, and melting for over 8 years.",
"First thing first, what type of glass are you melting? Technically what you're doing at 1150C is softening the glass, not a true melt. If you're starting with a raw batch, that temperature won't cut... | [
"Vacuuming the bubbles will not help. In industry the techniques are actually the opposite. You add things like water or bubble oxygen through the glass. Because those make large bubble and pass (usually) quite easily through the molten glass, they collect the tiny bubbles from carbonate and sulfate sources as w... | [
"Hi THere AlchemistPrime!! thank you so much for your reply, first off. ",
"What you said at first was extremely frustrating. I am melting Borsilicate 33 and soda lime glass. They are small chunkds of glass, right now I am using scrap glass for those two types, as I am not in production now..",
"your 2nd bubble... |
[
"Does air enter the vascular system after traumatic amputations?"
] | [
false
] | After an event that causes a traumatic amputation a tourniquet is usually applied to prevent exsanguination. Before the tourniquet is applied can/does air enter the vascular system or do the veins retract far enough proximally to prevent an embolism from developing? | [
"No, air embolism is not generally a concern in that situation. Even though veins are under less pressure than arteries, they are still at higher pressure than the surrounding atmosphere. Any open wound results in blood flowing outward, not air being sucked in."
] | [
"Thanks for the answer, I was worrying about this the other day."
] | [
"No. The circulatory system doesn't work on suction. It works on positive pressure, forcing blood forward through the system. All blood vessels are under greater pressure than the air outside, so puncturing a vessel will always cause flow from the inside out, not the other way around.",
"Air by itself will never ... |
[
"How does the fusion within stars work? Is it similar to a fusion reactor, and could we pull energy from it to power things?"
] | [
false
] | I have a basic understanding of how stars work (hydrogen bounces into each other to form helium which forms lithium which forms yaddah yaddah on and on until it's heavier and heavier). With this basic understanding, it makes sense in my head that one could harness this natural reactor to use it as a giant engine. Does ... | [
"Hi, ",
"your idea is not very realistic. Inside stars, you have temperatures of millions of degrees and pressures of billions of bars. Anything would just squished and ionized simultaneously in these conditions. Even if you ignore this, harnessing the produced energy would be difficult, because it is hard gamm... | [
"Yeah, the core of a fusion reaction is probably the last place you want to be. Having a small artificial star at the core of your space station would make more sense."
] | [
"As Schublade points out, there is no ",
" way to do this, but you're writing science fiction, so lets look at it from that perspective. If you've ever seen the movie ",
", the characters pilot a ship into the liquid outter core of the Earth. It is able to survive the intense pressure and temperatures because... |
[
"How has life affected what the Earth looks like?"
] | [
false
] | How has biological life affected what the Earth looks like? If that's too broad a question I've got some specific ones below, and I'd love answers to any of them. Thanks for any interest in answering. Thanks again! | [
"Life has strong influences on many aspects of Earth processes",
". ",
"Some notable points include:",
" Life is largely responsible for ",
"atmospheric and oceanic oxygen",
", and influences the ",
"nitrogen cycle",
" and the ",
"carbon cycle",
".",
" Life alters ",
"erosion patterns",
" b... | [
"The most obvious life-related features are probably carbonate formations (limestone, chalk), formed mostly of the skeletons of dead plankton. These can be kilometers deep and cover large regions, so they certainly have an effect on coastlines, though only to an extent: Tectonic activity forms the general shapes of... | [
"...the oxygenation of the Earths atmosphere ~2 billion years ago still hasn't been figured out...",
"I was under the impression that this (the Great Oxidation Event) was fairly well understood to be as a result of cyanobacteria as oxygen sinks filled up (evident from banded iron formations)?"
] |
[
"How does schizophrenia effect people who lack a sense of sight and/or sound? Are visual and/or auditory hallucinations still experienced?"
] | [
false
] | Would these effects be different between those who were born without one or more of these senses, and those who lost these senses later in life? | [
"We haven't seen any blind schizophrenics yet (Sanders et al. 2003).",
"Deaf schizophrenics seem to have many visual and tactile hallucinations, with auditory hallucinations not usually attested (Schonauer et al. 1998).",
"References:",
"Sanders,Glenn S., Platek, Steven M., and Gallup, Gordon G. (2003). No bl... | [
"One of the hallmark features of schizophrenia is the noticing of connections between things that really have no connection. It takes learning to get to this point, which requires NMDA receptors. What I'm describing here is acquiring the information to support a delusion. ",
"An example would be, they go groce... | [
"Interesting. I wonder why that would be when schizophrenia can simply include delusions, e.g. paranoia. So it would stand to reason (to me) that a blind person could simply have delusions but no visual hallucinations, or delusions that are accompanied by auditory hallucinations.",
"Could somebody explain in laym... |
[
"How can a black hole created by a collapsed star have a stronger gravitational pull than the star it came from?"
] | [
false
] | Black holes can swallow up light particles, but stars don't have nearly that strong a gravitational pull. Is the area of effect of the gravitational pull simply smaller, but more powerful? | [
"It doesn't. The reason is that the same mass is compactified into a smaller region, so you can get closer to the black hole while still feeling the same amount of mass. If you're outside a star, you'll feel the same gravity as you would the same distance from a black hole of the same mass. But if you're inside tha... | [
"If you continue this train of thought, you realise that anything can be turned into a black if you would be able to squeeze it hard enough. If you were to compact the earth to something the size of 8.8 mm (which, incidentally is app. the size of a red ant), it would become a black hole. This size is called the Sch... | [
"In most gravitating bodies, their radius is larger than their ",
"Schwarzchild radius",
". This means that if you go inside the star or planet, the gravity doesn't keep increasing because the mass further out than you doesn't have a net effect. For example, at the very center of Earth, there is basically no ne... |
[
"How often do animals known for their quickness or agility (like a deer or cheetah) tear ligaments or pull muscles?"
] | [
false
] | null | [
"Pulled muscles again do not occur very often. They have evolved to run and jump withstanding the associated stresses",
"It is also notable that many fast animals are significantly lighter than your average human being. Less weight means less torque on acceleration, so it takes a cheetah less 'power' to suddenly ... | [
"Pulled muscles again do not occur very often. They have evolved to run and jump withstanding the associated stresses",
"It is also notable that many fast animals are significantly lighter than your average human being. Less weight means less torque on acceleration, so it takes a cheetah less 'power' to suddenly ... | [
"Here's one next to a person- ",
"https://i.ytimg.com/vi/CEid3OzxE8U/maxresdefault.jpg",
"They are smaller than I thought, too."
] |
[
"How do we differentiate the Earth's magnetic field weakening due to a pending reversal instead of a complete shutdown like is suspected to have happened to Mars?"
] | [
false
] | From my understanding, it is suspected that Mars once had a magnetic field like ours, but because of its smaller size, the core eventually cooled and stopped its movement, causing the field to "turn off". How do we know the current weakening of Earth's field is not a similar process, but instead just a reversal? | [
"Loss of magnetic field is a gradual process which results from the cooling and solidification of the liquid outer core. We know from seismic studies we are nowhere near that point - it is still large and molten. Turning off of the magnetic field is ",
" a rapid on-off process.",
"The reason we're so far from ... | [
"No, there is no fission. There is simple decay. Fission is driven by neutron bombardment, whereas decay is a natural process with a relatively much lower energy yield than fission. Fission ",
" occur in some very rare cases, but it is not considered a heat source within the earth.",
"The main elements responsi... | [
"No, there is no fission. There is simple decay. Fission is driven by neutron bombardment, whereas decay is a natural process with a relatively much lower energy yield than fission. Fission ",
" occur in some very rare cases, but it is not considered a heat source within the earth.",
"The main elements responsi... |
[
"What is this radiation device at my school?"
] | [
false
] | [deleted] | [
"That's a ",
"Crookes tube",
". (Plücker version)"
] | [
"looks like a ",
"cathode ray tube demonstrator",
"."
] | [
"What do the warning tags say? even if they dont have names they might have numbers which could help figuire out what it is."
] |
[
"Reddit, here's a video of a powerful water cutter. If it can cut steel, what keeps the nozzle from being destroyed?"
] | [
false
] | null | [
"You're close here: the water is travelling parallel to the nozzle, so the nozzle does not wear much. The water strikes the steel, however, all of that energy is imparted into the steel, breaking it apart. "
] | [
"Yes. And appearently, they use a jewel - like ruby or a diamond - to narrow the jet stream and thereby increasing the pressure:",
"http://en.wikipedia.org/wiki/Water_jet_cutter"
] | [
"I would think that since you basically have a pipe flow within the nozzle (fluid moving more or less parallel to walls), then you would get a boundary layer of much slower fluid interacting with the nozzle walls."
] |
[
"What are the odds that any viruses or bacteria survived any missions to the moon and would they be able to do anything with the moon \"dirt\" to continue living or more?"
] | [
false
] | null | [
"That's not even remotely true, and you are in fact entirely wrong... there are plenty of bacteria that use anaerobic respiration, or are chemotrophisms to do survive in areas without oxygen. Absolutely nothing says all life on earth needs oxygen to survive. NASA in fact uses an equation to predict living cells on ... | [
"That's not even remotely true, and you are in fact entirely wrong... there are plenty of bacteria that use anaerobic respiration, or are chemotrophisms to do survive in areas without oxygen. Absolutely nothing says all life on earth needs oxygen to survive. NASA in fact uses an equation to predict living cells on ... | [
"Correct viruses are not alive. They are only broken pieces of DNA in a protein coat. They don't even have the basics of a simple cell. They are only tiny bags of DNA or RNA whose only purpose is to attach to the correct organism's cell and reprogram it"
] |
[
"Why does human hair grow so long? I've noticed that other apes and monkeys don't seem to have really long hair. Humans on the other hand can grow out the hair on their heads and get it pretty long."
] | [
false
] | null | [
"Why does human hair grow so long? The anagen phase tends to last several years on scalps. Other apes have far shorter anagen phases. ",
"Humans have thinner shorter hair over much of their bodies because we evolved to be long distant runners and sweating allows for very quick cooling. ",
"Obviously this isn't ... | [
"Which would, essentially, cause an increase in sex, therefore sexual selection, right?"
] | [
"sexual selection is a popular idea, but there's also the hypothesis (e.g. ",
"here",
") that long head and pubic hair are for increasing surface area for pheromone distribution."
] |
[
"Texas hold'em probability question?"
] | [
false
] | null | [
"You're succumbing to a way of thinking that's very common and that intuitively makes sense, but incorrect: the Gambler's Fallacy (apt, in this case), also known as the Monte Carlo fallacy. Essentially, if two events occur independently, then it doesn't matter which order the two events occur in; the probabilities ... | [
"Overall, my question is this: Say when you are playing 1 on 1, and you get dealt the losing hand 4 times. So that means that the chances of your opponent getting dealt the winning hand for a 5th time in a row is 1/(25)=1/32=3% right? So should that affect the percentages pre-flop? ",
"If you've already won four ... | [
"So that means that the chances of your opponent getting dealt the winning hand for a 5th time in a row is 1/(25)=1/32=3% right? So should that affect the percentages pre-flop?",
"Not really because the hand gets reshuffled after each hand, so your chances of getting the winning hand are the same for each hand, r... |
[
"How much of the moon's original mass has been lost to impact damage?"
] | [
false
] | null | [
"None, in general it gains mass from impacts while dust and other debris is lifted from the surface the gravity from the moon is enough to recapture most of the debris and it will eventually settle back down on the surface."
] | [
"A tiny amount. Most impacts only add mass to the moon - whatever is kicked up by the impact just falls back. A very few very large impacts have hit with enough force to send a few particles into space, but none in recorded history."
] | [
"Thanks"
] |
[
"Does breathing salty air dehydrate you more than inland air?"
] | [
false
] | I'm wondering if the salty air when near the ocean, or on a boat can dehydrate the human body faster than if you were away from the ocean. Also, what amount of concentration of salt is in the air that you're breathing. Many times I have found piles of salt in my bags, when on a long voyage on a boat. Thanks for the inf... | [
"Salt air is a real thing. As wind blowing over the ocean lifts sea water and vaporizes it, fine salt particles, ie salt dust, remain in the air. This salty air can be carried for some distance inland, but air that is closest to the sea has the highest salt concentrations. High humidity, fog, and rain can captur... | [
"If you can smell something, it's physically in your nose. ",
"So I'd say that smelling saltwater spray does indeed dehydrate you a tad bit more than regular air."
] | [
"If you can smell something, it's physically in your nose. ",
"So I'd say that smelling saltwater spray does indeed dehydrate you a tad bit more than regular air."
] |
[
"A few questions about the origin of life."
] | [
false
] | 1-What is the most up to date theory on the origins of life? 2-In the Blind watch maker, Richard Dawkins talks about clay crystals acting as a building frame or something. can you please explain that to me. 3-What evidence do we have that all life originated from a common ancestor? 4-is it possible that there are mu... | [
"So there are many different conjectures as to how ",
"abiogenesis",
" occured. There is no general theory of Most of them are basically imagined scenarios that are bound by the laws of physics, the chemical environment at the time, and the requirements of life. \nNo one has recapitulated abiogenesis ",
" an... | [
"A note regarding the speculation at the end: in early protolife, it is possible that multiple \"start\" events happened, including some mixing of early genetic materials. However, ",
"phylogenetic tests of all existing life",
" strongly support the idea that there is one universal common ancestor, making mult... | [
"thanks. That is exactly what I was trying to say. There would be a period of \"trial and error\" just to create a cell, but once it succeeded one time. ",
"AKA, multiple start ups, one success."
] |
[
"Why boil water for (instant) coffee?"
] | [
false
] | I understand that coffee will dissolve faster in hotter water but I don't understand why people heat water to a scalding temperature, only to let it cool down again. Not only does it seem to be a waste of energy but a waste of time too. I turn my kettle off before the water boils so I use hot water with my coffee. This... | [
"I don't think this is so much of a science question, but anyway :) ",
"You should never really use boiling hot water for even normal coffee, as it scalds it and can give coffee a burnt flavour. Instant Coffee, is really just coffee which has already been steeped and dehydrated. There really is no need to use boi... | [
"More to the point, how else are you supposed to know when the kettle's ready? Sure you could build a super-fancy kettle with internal thermometers and some kind of blasted ",
" stuck to it that will scream at you when the water reaches the right temperature … or you could just wait for the whistle."
] | [
"We have no problem with our drinking water, but I have been to some countries where I would definately not drink any tap water without boiling it first! Also when i've been camping/tramping, taking water from a stream you ",
" boil the water even though you only have instant coffee :)"
] |
[
"Can bird flu spread through eating infected chicken?"
] | [
false
] | Just curious how the transmission of this disease works. | [
"No human bird flu infections have been reported from proper handling of poultry meat or from eating properly cooked poultry or poultry products.",
"—",
"CDC: Avian flu transmission",
". Can I get avian influenza from eating poultry or eggs?",
". No. Poultry and eggs that are properly prepared and cooked ar... | [
"Idk man, campylobacter food poisoning is like a week of bloody diarrhea and vomiting, but at the same time people mostly recover on their own (or with antibiotics if it’s really bad) and the chance of death is incredibly low (.03%). Meanwhile, the current H5N1 strain of avian flu that’s going around in flocks has ... | [
"Also think it is worth pointing out that bird flu wouldn't even be the worst thing you can catch from improperly cooked chicken meat or eggs. Dying a painful bloody diarrhea death is probably worse than bird flu"
] |
[
"Why are modern birds dinosaurs and not fish?"
] | [
false
] | I've seen it said many times (eg ) that modern birds are dinosaurs. But couldn't the same be said that all vertebrates with lungs are fish? What are the rules about whether descendant groups get excluded from a classification? Is this what's meant by "paraphyly"? | [
"This is a good question, and something that I very often see confusion about. The main issue here stems from the disconnect between technical, scientific names for groups of organisms and general English words. Pretty much all modern taxonomists agree that scientific naming conventions should reflect evolutionar... | [
"Technically birds and all tetrapods ",
" fish in the cladistic sense. Incidentally, apes are in fact monkeys for this same reason, so the next time someone gets pedantic with you about this, you can get even more pedantic back at them",
"But \"fish\" is often used as a term for what's called a \"grade\". Thi... | [
"The main disconnect is between Linnaean Classification and modern cladistics.",
"From my own experience, even ~10 years ago the Linnaean system was the only one taught in my country's equivalent of High School. Cladistics weren't even mentioned once, even though they are of crucial importance to our modern under... |
[
"How far apart are raindrops vertically?"
] | [
false
] | On average, how long before 2 raindrops hit roughly the same spot one after another? I guess what I'm asking is, what is the average rate at which raindrops fall? If I place a raindrop sized object under a raincloud, how many raindrops will land on that object in 1 second? | [
"Using Google",
", let's estimate a raindrop is 0.2 cm in diameter, giving a volume of 0.034 cm",
" Rain is going to fall on some area of land. For now, say the area is a container 1 cm x 1 cm. Thus one raindrop landing in the container will raise the height by 0.034 cm. If the container filled up 1 cm in 1 hr,... | [
"Exactly the answer the question deserves - thanks for working it out for us!"
] | [
"Double checked ",
"/u/I_hate_usernamez",
" and they're on the money. He's my estimate with slight different numbers. A medium rain gives about 5mm per hour. Let's use a drop size of 2mm and a drop speed of 10m/s.",
"Dividing the volume of water per second by the volume of air and the volume of a drop gives a... |
[
"How do we forget?"
] | [
false
] | Warning, stupid question inbound. Does the human brain actually completely erase a memory when we forget something? Or does the thought/memory just go to a part in our brain where we cant access it? Sorry if this makes no sense, I am not a smart man. | [
"Great question, not stupid at all.",
"When I first read the question, my first thought was \"Well you tell me how we remember things, and I'll tell you how we forget them\". Meaning that it's hard to explain how a process is reversed if we don't really know what it is to begin with. I really should have my girlf... | [
"There is no evidence for this.",
"Well, obviously, I would disagree,. I would say there is a vast amount of ",
" for this. Is there ",
" of this? No. But evidence: there is truckloads. Most tellingly, there stuff coming out of Tonegawa's lab in the last 2 or 3 years. And of course the work by Nabavi et al.,... | [
"It would be, if that was the only evidence. However, we also know that if you damage areas of the brain the are believed to code for the perception of a sense (i.e. the same areas that are activated when the perception is had) then the person can no longer perceive the sense. Likewise, if we activated the area art... |
[
"How are the digits of PI actually calculated?"
] | [
false
] | How do we know that what we've calculated is correct? This Wikipedia page states that so-and-so of years past has calculated X digits of PI, but only Y are correct. Is there a formula for calculating the digits of PI? If so, is it something I can sit down and do on paper? This is the Wikipedia article I'm referencing a... | [
"Is there a formula for calculating the digits of PI? If so, is it something I can sit down and do on paper?",
"Yes and yes. There are a few formulas for calculating π actually. One of the simplest is really simple, called the ",
"Leibniz Formula for π",
":",
"π = 4/1 - 4/3 + 4/5 - 4/7 + 4/9 ...\n",
"This... | [
"Someone else has said ",
" we calculate digits, so I'll focus on how we CONFIRM such digits. I have actually worked on methods of calculating Pi in the past using computers, so if anyone is interested in different methods I can elaborate! ",
"When they say they calculated X digits and Y are correct, they're u... | [
"You can watch someone doing it by hand here:",
"https://www.youtube.com/watch?v=HrRMnzANHHs",
"Matt Parker (The Standup Mathematician) is worth a watch, his channel tends to show serious mathematics with a humourous (and usually understandable to the novice) slant."
] |
[
"What will happen to the cores of planets during the \"heat death\" of the universe?"
] | [
false
] | I have a rudimentary understanding of entropy; heat transfers from a hotter object to a less hot object, eventually there will be an equilibrium temperature between the objects. The universe will reach that equilibrium in the future as well. So here's the question, with all the heat created by pressure at the core of a... | [
"There wont be any planets left when heat death finally occurs. There are several stages of metamorphosis, including the ",
" which ends with near complete nucleon decay (no more atoms), the ",
" which ends with all matter being bound to black holes and the ",
" where all black holes have evaporated and the u... | [
"Would it be fair, at that end point, to assume the universe has reverted to its state when the big bang occurred? Granted this assumption would imply that time did in fact exist prior to the big bang, even if in an infinitesimally small scale. ",
"This ultimately sounds like the potential playing grounds of a ne... | [
"Our entire idea of time revolves around two main concepts, which are the \"arrow\" of time (past and future within a reference frame), and the idea that time is actually another dimension of the universe which we can measure events against. ",
"In our mathematical model, we have no idea what the \"universe\" lo... |
[
"If light always travels at the speed of light (perfect certainty in momentum), then how can it have a position?"
] | [
false
] | Light obeys the position-momentum uncertainty principle. Light always travels at the speed of light. Therefore, light never has a well defined position. But it's sunnier outside than inside. This seems like a contradiction. Where did I go wrong? Does it have to do with interference between various modes (each infinite ... | [
"perfect certainty in momentum",
"This is incorrect. The momentum of a photon is",
"p = E/c = hf/c",
"i.e. the momentum is proportional to the frequency. A lower uncertainty in frequency means a higher certainty in position, and vice versa.",
"Technically, the distribution of the photon's wavefunction in po... | [
"Photons don't have positions. It's entirely reasonable to say that until a photon is absorbed (or scattered, same thing in this context) it doesn't exist at all, except as a little bit of non-localized momentum. At the instant a photon is absorbed, it ceases to exist entirely. So it never has a position where it "... | [
"Not at all, no.",
"You're probably thinking of gravity as if it were the same as electromagnetism. It isn't. Gravity isn't an interaction. It's geometry. Light (and here by \"light\" I mean a large number of photons considered together) propagates through spacetime. As such, the trajectories it follows are funct... |
[
"Confused about basic physics: So photons are the electromagnetic force carriers. How exactly do they mediate the influence that a negatively charged particle exerts on a positively charged particle?"
] | [
false
] | [deleted] | [
"Confused about basic physics: ",
"So photons are the electromagnetic force carriers.",
"That is not basic physics! That is very advanced physics.",
"If you want an analogy, imagine two people on skates on ice, and one of them is holding a pillow, and the other person grabs the pillow and takes it, and they r... | [
"Are you asking how the 'virtual photon exchange' picture can explain attractive forces? The simplistic picture of little hard spheres emitting other little hard sphere breaks down in that situation. There was a ",
"previous thread",
" about this. There are a variety of ways of thinking about it, each with thei... | [
"charged particles are basically spewing photons and absorbing them all the time",
"This is another thing which is only a kind of loose analogy. What actually happens is that charged particles do what the maths says they do, and a good way of looking at this maths is to say that there are 'virtual particles' bein... |
[
"Geoengineering's Affect on Ocean Habitats?"
] | [
false
] | I read the article on what would happen if Geoengineers released aerosol particles into the atmosphere to reduce global warming. I noticed that they mentioned the Rainforest, but they left out any other habitat. So, AskScience, what would happen to the coral reef and deep sea waters if this was to happen? Original arti... | [
"In short, increasing CO2 levels in the atmosphere would still be terrible for Coral reefs. Ocean acidification will increasingly make it more difficult for marine organisms to precipitate their skeletons, and corals will be most affected. As far as the more diffuse light goes, I think this is bad for corals but am... | [
"The direct effect of increased aerosol particles would be small - slightly less sunlight reaching the surface of the ocean. The indirect effect would be huge because this would allow ever greater amounts of fossil-fuel carbon to be burned. The radiative effects of the increased greenhouse gases might be balanced b... | [
"It's often repeated uncritically that aerosol geoengineering will \"do nothing\" to prevent ocean acidification, but the reality is more complex.",
"We know from past volcanic eruptions that the diffuse light created by stratospheric aerosol injections can potentially promote productivity in the terrestrial bios... |
[
"When a newborn is flailing its limbs and moving around, is it consciously moving them or is it some sort of automatic function of a new human being?"
] | [
false
] | null | [
"It sounds like you're asking about some of the ",
"primitive reflexes",
". While they occur when an infant is conscious, they're involuntary. ",
"These reflexes disappear with age. They're understood to be inhibited as the brain develops (specifically the frontal lobe). Adults with disorders that affect the ... | [
"Here is something every new parent should lookout for as it is so neat.",
"At around 3 or 4 months of age a newborn will discover that it has conscious control of its arms and can make them move at will. To do this it will lie on its back and stare at the arm while moving it around. ",
"It is a fascinating pro... | [
"We also tend to exhibit them in the last stages before death, they manifest as sheet pulling or grasping motions. It can be quite disturbing to watch even after you realise the movements are reflexive. "
] |
[
"Why does plaque build up on teeth, but not on oral piercings, such as lip rings/labrets or tongue piercings?"
] | [
false
] | [deleted] | [
"Plaque can and does build up on oral piercings, especially tongue jewelry. All jewelry, regardless of piercing location, should be cleaned regularly. Tongue jewelry can easily be cleaned while brushing your teeth. "
] | [
"Teeth are porous and have uneven surfaces which it's easier for bacteria to adhere to (plaque is actually bacteria and their secretions) and harder to remove them from. If you look carefully you'll sometimes see plaque in the crevice formed where the ball attaches to the bar on oral jewellery, or if you want to gr... | [
"No problem. "
] |
[
"Where is the electrical energy generated from power plants stored? Do they have like very big batteries of sorts?"
] | [
false
] | null | [
"Very little energy storage tech has been developed for city grid applications. Any electricity we generate, we must use immediately. Powerplants have been designed so that they are able to match as closely as possible the generation of electricity with the demand for electricity, reducing excess as much as possibl... | [
"I just want to correct you on one point. Hydroelectric is the fastest way to balance loads. Typically coal and natural gas respond in minutes, hydroelectric in seconds."
] | [
"In the vast majority of the cases it is not stored. It is injected directly into the grid."
] |
[
"Is there a way to tell the difference between two atoms of the same element?"
] | [
false
] | Is there a way that a scientist could look at an atom, and then be able to tell that atom from any other atom of the same element? If so how? If not, why not? | [
"No. There is no difference. We know this because of quantum physics. Under quantum physics if you get the same state two different ways, you get interference. For example, if a photon goes through a slit on the right vs a slit on the left and ends up in the same place either way, it creates an interference pattern... | [
"The only way to distinguish two atoms of the same element is, if they are not build in the same ways.",
"1.) if they are different isotopes (i.e. one of the atoms has more neutrons than the other, like in ",
"radiocarbon dating",
")\n2.) if they have a different amount of electrons (i.e. one of the atoms is ... | [
"You're basically right. The only differences I can see is if there one is an isotope of another, for example U-235 and U-238.",
"Other than that, the only other differences would be differences in position or velocity or temperature, which aren't really differences than one couldn't change.",
"But for two atom... |
[
"Do scientists need to know the amount of an isotope present initially when doing radiometric dating? If so, how do they know?"
] | [
false
] | Hi everyone, this may be a dumb question, but I'm curious as to how we know what the amount of Carbon-14 was thousands of years ago? I've never considered this before, but I was speaking to a friend who is a YEC, and he gave me this analogy - "Radiocarbon dating is like coming in a room, finding a burning candle, and m... | [
"Yes, we have to, and we do that by measuring the amounts of stable daughter isotopes present. ",
"I use U-Pb a lot, because C",
" is useless for materials in the age range I study. So, what I look for is zircon crystals, which are a very tough and stable geological material. When zircon forms, it is a natural ... | [
"Radioactive elements decay through a specific chain of isotopes, until they reach a stable isotope which does not decay. There is a specific chain for ",
"U",
" , there is another for ",
"U",
" - the former ends at Pb",
" & the latter at Pb",
" , all of which can be dosed with extreme accuracy and prec... | [
"Your friend is right in thinking C-14 levels have varied enormously through. As I wrote previously, there are several factors that are responsible for that, and all the known ones are taken into account when using radioactive dating. That's (one of the reasons) why C-14 dating has gotten more and more accurate. Le... |
[
"Where do elements heavier than iron come from?"
] | [
false
] | Since when a star begins fusing iron it dies, where do the heavier elements, i.e. copper, nickel, and so on up the table, come from? | [
"There are other nucleosynthetic processes that happen in nature. For example, the ",
"s-process",
", the ",
"r-process",
", the ",
"p-process",
", and the ",
"rp-process",
".",
"The s- and r-processes are responsible for producing most of the nuclides above the iron peak.",
"The rp-process happ... | [
"Technetium just happens to be the lightest element with no stable isotopes. It is produced naturally, it just decays quickly."
] | [
"Is technetium a gap?"
] |
[
"Why are rainstorms frequently accompanied with lighting, but snowstorms/blizzards rarely (never?) have lightning?"
] | [
false
] | null | [
"Lightning requires energy. Lots of static electricity and heat to generate the charge differential that leads to lightning. Temperature difference between ground and air can do it, too.",
"Snow storms happen when it is cold. Meaning not as much energy source for lightning. When it does happen, it is called thund... | [
"Former meteorology major here. Lightning requires high cloud tops for a greater electric potential. These higher clouds typically occur with more potential buoyancy, meaning warmer temps down below and colder temps at higher altitudes. More water vapor also increases the buouyancy of air, and allows clouds to grow... | [
"I was snowboarding a week ago in minnesota during our record blizzard. The lightning lit up the snow so brightly."
] |
[
"A question about lab goggles, need help with comfort and sizing"
] | [
false
] | I'm currently working with an Arduino board and I have a project that requires some sort of goggles to fit certain expectations. Ideally the goggles need to be comfortable as they will be worn for long periods of time I would prefer goggles with a flat front Do they sell large goggles? i have things that need to attach... | [
"You can indeed find large goggles. I'd advise going to the nearest lab, trying on their goggles, and ask where they got the pair you like best.",
"On a side note, unless you are doing something really odd, Arduino work shouldn't require eye protection. Just don't jam the soldering iron in your eye."
] | [
"Ah I should have clarified, the goggles arent for protection.",
"They are going to have Arduino components attached to them!"
] | [
"In that case, I wouldn't go for lab goggles, but some \"fashion\" goggles. I see a lot of teenagers with bug-eye goggles on their heads, and I assume they're coming from somewhere. Probably the same place as steampunk goggles.",
"And just what are these goggles going to ",
"? "
] |
[
"Do dark surfaces contribute to climate change?"
] | [
false
] | Dark surfaces meaning asphalt-paved roads, dark roofs, &c. | [
"Yes. They absorb visible light and re-emit the energy as infrared light, which is absorbed by greenhouse gasses. Lightly-colored surfaces, on the other hand, reflect more of the incoming visible light back into space, so that energy doesn't have to find its way through the greenhouse gasses (as they are transparen... | [
"Yep. They would basically act like ice patches that don't melt. In a compounding effect, white roofs in hot environments also mean less electricity is used for cooling, meaning less heat is generated ",
" less greenhouse effect generally."
] | [
"Would it make a signifiant difference to the earth's energy balance if all roads and roofs in the world were somehow made white? "
] |
[
"Why aren't men and women the same size?"
] | [
false
] | Largely, I mean. | [
"\"Why\" is always a difficult question to answer - is it \"what mechanisms causes this phenomenon\" or is it more \"what is the benefit of this phenomenon\"?",
"In nature we can see that there are examples of vast differences between sexes (for instance male polar bears and gorillas can be 3 times as large as th... | [
"While it is true that most societies have an approximately equal sex ratio, this is not because it provides a balance between optimal protection and resource allocation. It simply boils down to the fact that when there are more women in a society, it is evolutionarily advantageous to produce male offspring (more p... | [
"\"what mechanisms causes this phenomenon\"",
"This would be \"how\" would it not?"
] |
[
"What if there is no quantum description of gravity?"
] | [
false
] | null | [
"Then things are extremely weird, because every other force of nature is described quantum-mechanically, but gravity isn't. I don't think any serious physicist considers this a possibility."
] | [
"Right but physics in itself is extremely weird at the quantum level anyway, and physicists haven't found 95% of the universe, so clearly we are very early in our understanding.",
"",
"Is there any way to at least confirm gravity has quantum mechanical properties?"
] | [
"Quantum mechanics is unintuitive to someone who's only experienced classical phenomena, but there's nothing illogical about it.",
"A universe where almost everything is quantum, \"stapled to\" classical gravity just doesn't make any sense.",
"Is there any way to at least confirm gravity has quantum mechanical ... |
[
"Why does running water freeze at lower temps?"
] | [
false
] | Is there a temperature at which water will freeze no matter how fast it's moving? | [
"Flowing water has enough internal energy to resist crystallization. The water molecules are flying past each other, and so they are gaining energy from the jostling against the riverbed, each other, or their container. This gives them enough energy to remain above freezing temperatures."
] | [
"The energy he's talking about is kinetic energy (the energy of motion). When you say that they are moving past each other too quickly to form intermolecular hydrogen bonds, you are saying that their kinetic energy is too high for the system to exist as a solid.",
"You're saying/thinking the same thing, just with... | [
"It is due to the lack of nucleation sites for ice crystals. Same reason you can slowly chill a beer and then smack it on the counter and watch it all freeze over."
] |
[
"How does a genetic mutation propagate through the generations?"
] | [
false
] | I saw an article a while back about a Chinese kid who was born with weird eyes that let him see in almost complete darkness. I assume this is a mutation of some gene or genes that make the eye. How would that trait be passed down to his offspring? I figure that he would meet a woman with normal eyes and the baby wou... | [
"Genes don't get watered down, traits might.",
"\nThe genes are either passed on or not"
] | [
"Genes are specific, discrete things. They're composed of discrete nucleotides.",
"A trait is often the combination of many, many genes.",
"When DNA is crossed through reproduction, genes are (more or less) chosen from each parent. Every gene in your body is more-or-less traceable to one of your parents (though... | [
"That makes a lot of sense. Thank you. I think I'll read some more information\nAbout it. "
] |
[
"Why is it that when I close my eyes tightly I hear a rumbling sound in my ears?"
] | [
false
] | Is there a name for it? What causes it? | [
"Pretty sure you're talking about ",
"Tensor tympani muscles",
", specifically voluntary control of."
] | [
"Almost definitely right, but I think it's possible for it to be any muscles in the general area. If you hold your arm or fist up to your ear, you can even hear the rumbling noise from those when you tense up the muscles."
] | [
"OH, YES. I have been wondering about this for so long, but I've had no idea how to ask the question without sounding crazy, just in case I'm alone. I can do it on the fly, so I had no way to ask. Thanks for answering, and thanks OP for asking."
] |
[
"Why do magnetic field lines leave at ninety degrees from an object?"
] | [
false
] | Apologies if this isn't worded too well. I'm taking physics in my final year of high school and we recently learned that in a magnetic field the magnetic field lines will enter and leave an object at ninety degrees. The only explanation I'm hearing is that 'it does because it does'. Is there any better explanation for ... | [
"There are really two distinct cases to bear in mind:",
"In a magnetic material, like a bar magnet, the magnetic field is created by the material itself. The magnetic field lines don't leave it at always ninety degrees, it rather just acts as a dipole. ",
"The more important case is that of an electromagnet. Ma... | [
"Yes that's true. You can either derive the magnetic field from classical electrodynamics or do a lorentz transformation between the intertial systems of a point charge or a nearby current. Both yield the same answer.",
"As to why the field is perpendicular I can't really tell you. The is seldom a 'why' in physic... | [
"Why is the field perpendicular to the current? ",
"My understanding is magnetism is explained as \"normal\" electricity operating under Lorentz transform from special relativity. Do the maths and see currents behave as if there is a thing such as a magnetic field, so we just say there's one."
] |
[
"What is the most efficient way to learn? Can you teach yourself?"
] | [
false
] | null | [
"That's what I've ",
", but I'm thinking there just might be some science to it. "
] | [
"I would also like to know this. I've got a hunch it has to do with dopamine and other related neurotransmitters during the learning process.",
"Like, if you enjoy music, and the process involves melody or rhythm, then you would be more responsive than just reading from a book.",
"Any studies on this avenue of ... | [
"Learning is different for everyone, and some people learn with better methods than others. Some people can listen to a professor give a lecture on a subject and retain all the information. Some other people are better at learning with diagrams and visual aids, and may be better if they read about a subject. Others... |
[
"Why is it that animals, such as gorillas, can gain large amounts of muscle mass naturally. Whereas humans need to physically make an effort to \"get bigger\"?"
] | [
false
] | null | [
"Because humans and gorillas aren't the same species. Their muscles are adapted for force where ours are adapted for fine, precise control. "
] | [
"I think he was refusing humans vs gorilla musclemass, not including the use of cars.",
"Even with cars it is a decent question, and here's why.",
"Gorillas live a VERY sedate lifestyle compared to humans. Very much like pandas if they were fiercely territorial. They find a nesting area do nothing but eat a... | [
"I think he was refusing humans vs gorilla musclemass, not including the use of cars.",
"Even with cars it is a decent question, and here's why.",
"Gorillas live a VERY sedate lifestyle compared to humans. Very much like pandas if they were fiercely territorial. They find a nesting area do nothing but eat a... |
[
"What is this object in space?"
] | [
false
] | I'm currently on which allows you to see the milky way and local universe. I just randomly zoomed all the way in some where and saw What is it? It only shows up under visible light, at coordinates (-117.25,-11.55) | [
"Yep, that is an artifact from the optics. Maybe some combination of ",
"diffraction spikes",
" caused by the support beams holding up the secondary mirror and some ghosting effects. Could also be from improper flat field division. Look at the 3 images at the bottom of ",
"this page",
". A lot of calibr... | [
"It looks very much like an image of a telescope mirror, which I ",
" could be caused by dust particles."
] | [
"It's almost certainly an artefact from the telescope they used. Like how you see \"rays\" coming out of stars in some images."
] |
[
"How does centripetal force act to make the globe of death motorcycle stunt work?"
] | [
false
] | null | [
"For a motorcyclist riding inside the globe, the centripetal force is the normal force of the globe, pushing inwards."
] | [
"What I don't understand is how a force that, from my understanding, pulls object inwards, seems to work to push objects outwards, like keeping the motorcycle glued to the outside of the ball, or a hammer throw. From the language used I would think that the force would be pulling the rider off the cage of the ball ... | [
"What I don't understand is how a force that, from my understanding, pulls object inwards, seems to work to push objects outwards",
"It's just uniform circular motion. Working in an inertial reference frame, there is no outward force. The force points inwards, so the acceleration points inwards. That's why the mo... |
[
"Why does it seem like the Hubble Space Telescope can image distant galaxies with much better clarity than our own neighboring planets?"
] | [
false
] | It seems like HST photos of planets, when they exist, are incredibly blurry, grainy, or pixelated. Is it a focus thing? Is it just how incredibly massive those distant structures are, that they have a larger apparent size despite the vast distances? Or to put this another way, why don't or can't we use the Hubble for p... | [
"I don't quite understand what you mean why you say that HST planetary photos are blurry. The photos of our solar system objects are outstanding, see ",
"this",
" as an example. Exposure times for Jupiter for example are about 10secs or so, so you are never going to spend orbits looking at a solor system plan... | [
"For the same reason you can see a mountain from 10 miles away much more clearly than a grain of sand 50 feet away. The mountain is larger."
] | [
"It seems like HST photos of planets, when they exist, are incredibly blurry, grainy, or pixelated. ",
"They are.",
"Is it a focus thing? ",
"Not for the most part. ",
"Is it just how incredibly massive those distant structures are, that they have a larger apparent size despite the vast distances?",
"Yes,... |
[
"Is there a size limit to molecules? Could you theoretically have a hydrocarbon hundred of carbons long, for example? Thousands?"
] | [
false
] | [deleted] | [
"So some hundred or thousands is no problem. For example look at ",
"polyethylene",
", tehse are just straight hydrocarbon chains. The longest ones have a molecular weight of 5million which means about half a million carbon atoms.",
"So these molecules get unstable if they get longer. Right now I'm not sure a... | [
"So these molecules get unstable if they get longer. Right now I'm not sure about the right answer to why. IIRC (I have to find this in a book/lecture slides but I cannot remember where I learned it) it's because two orbitals in the same molecule aren't allowed to have the exact same energy. So with big molecules a... | [
"Billions of a.a.s? Really?! The ones I've worked with are all just a few hundred.",
"But the DNA sequences encoding for these proteins will always be longer, given that each aa is encoded by a sequence of 3 nucleotides"
] |
[
"If helium balloons float upwards because it's less dense than air, shouldn't a container under vacuum also be lighter than air? Could you make an airship float using vacuum if you had a material light, yet strong enough to not collapse on itself?"
] | [
false
] | null | [
"Yes - and it's ",
"not a new idea",
".",
"The practical issue is that there's a big pressure differential between the atmosphere and the vacuum, and it's to support a balloon against that pressure, it has to be made of a very rigid strong material, which will be constantly under stress like a submarine. This... | [
"Yes, but you don't gain that much.",
"For fixed pressure and temperature, the density of an ideal gas is proportional to its molecular weight.",
"For air, this is around 29 g /mol on average, for helium it's 4 g/mol, and for hydrogen it's 2 g/mol. A perfect vacuum has a density of 0 g/mol.",
"Buoyancy comes ... | [
"If we put this “vacuum balloon” in our atmosphere, the air pressure, which is 1 atm, converted to SI unit, would be 101kPa. So how much is 101kPa? 1 Pa (pascal) is a unit for pressure, by dividing force (in N, Newton) by area (in m",
" ), so 1 Pa = 1 N per m",
" . Then 101kPa should be 1.01 * 10",
" N per m"... |
[
"Do I need to be a scientist too read The Origin Of Species?"
] | [
false
] | null | [
"Oh thanks for telling me."
] | [
"Oh thanks for telling me."
] | [
"Not the right sub for such questions, but the answer is no, it is very accessible."
] |
[
"Is base 10 the right system to use?"
] | [
false
] | First off, I'm not much of a mathlete. By the time I got to 4th year (undergrad) differential calculus my brain had decided that was about all it could take and left the building. But a few nights ago I was reading a comic ( ) which has a scientist use a base of PHI ( ). The idea had never occurred to me that an irra... | [
"does changing the base number system significantly alter any higher level math out there?",
"Absolutely not. Whatever your system, it just changes what you write, not what you mean. It is akin to asking if writing it in French changes the story of a book."
] | [
"We routinely alter the number base to make certain types of math easier. For instance, Boolean is Base-2 (logic math), Hexadecimal is Base-16 (computer addresses), Radian Math Base-Pi (circular math), Duodecimal is Base-12 (time and lots of British Units), Babylonians used Base-60. ",
"So to answer your questio... | [
"Is base 10 the right system to use? ",
"There's no ",
" right base. ",
"Just convenient bases for particular things.",
"Aside from how you write numbers and a little convenience with things like fractions, changing bases changes almost nothing of any importance.",
"(Write it as 'base ten', to save the 'e... |
[
"Why do some materials like iron, gold and other bend, while other like coal or rocks break?"
] | [
false
] | null | [
"It all depends on what kind of bond and structures the atoms form. when talking about metals and rocks, crystal structures become very important. The crystal structure of a compound it decides by its composition and its preparation. Some crystal structures are very rigid and won't bend easily, other materials are ... | [
"The answer lies in the difference in bonding between metals (iron and gold) and ceramics (coal and rocks).",
"\"In ceramics, however, dislocations are not common (though they are not nonexistent), and they are difficult to move to a new position. The reasons for this lie in the nature of the bonds holding the cr... | [
"There's one major phenomenon behind this difference: dislocations. Dislocations are a type of defect in a crystal. If you imagine a crystal as a lattice, a large array of evenly stacked atoms, a dislocation is a missing half plane of atoms. When you look at dislocations under an electron microscope, they look l... |
[
"Do sociopaths yawn after others?"
] | [
false
] | I remember reading that the reason people yawn is a empathetic reaction from back in our pack hunting days. Since sociopaths don't have empathy, do they not yawn after others? (Assuming they don't fake yawn to conceal themselves.) Or is yawning beyond a traditional definition of empathy that is primarily concerned with... | [
"\nWe require that all top level answers ",
" include at least ",
" sources to support their statements. If an answer does not have a source attached for support, the post will be removed.",
"\n",
"\nA source should be external corroboration that independently verifies your statements. These include, but ar... | [
"Disclaimer: I'm an engineering student, not a psychology/neuroscience student.",
"This question interested me, so I've been researching around. I found an interesting article ",
"here",
". The article addresses the absence of contagious yawning in children with autism spectrum disorder, which isn't a direct ... | [
"why this thread in particular"
] |
[
"Why and how is it that a given batch of tea leaves of even moderate quality can be used to brew more than one successive batches of flavorfull tea, while coffee grounds cannot."
] | [
false
] | You can normally re-use tea bags and leaves at least 2, and even 3 times and brew good tea, while coffee brewed from previously used grounds is flavorless. But both drinks are normally caffeinated and infused from plant material - why does one release all of it's caffeine and flavor in one shot and not the other? | [
"Thank you for a detailed and illuminating response. It will be interesting to compare the info you get from your tea guy with the coffee data; my informal intuitive opinion would be that there is even less soluble material in the tea leaves, and yet they keep on brewing...",
"Also, anybody which can boast of hav... | [
"Thank you for a detailed and illuminating response. It will be interesting to compare the info you get from your tea guy with the coffee data; my informal intuitive opinion would be that there is even less soluble material in the tea leaves, and yet they keep on brewing...",
"Also, anybody which can boast of hav... | [
"Mostly because they are two entirely different parts (coffee seeds vs. tea leaves) of two entirely different plants, containing different chemicals, used in two entirely different ways - \"soaking in hot water\" is a wild generalization on preparation of both beverages.",
"Also, tea can release all of it's flavo... |
[
"Concerning DNA and the origin of life"
] | [
false
] | [deleted] | [
"Until someone invents a time machine I don't think we'll ever know for sure, but the most prominent theory is probably ",
"abiogenesis",
", the idea that individual molecules came together to eventually form more complex ",
"biomolecules",
", perhaps ",
"forming RNA",
" which could replicate itself and... | [
"This is not my field of study but, I think I read on here that the so called information contained in DNA you talked about is mostly used in the evolutionary debates and are insignificant. The information is counted by assigning bits to the DNA code. I say this because it is usually used in common discussions in t... | [
"This is not my field of study but, I think I read on here that the so called information contained in DNA you talked about is mostly used in the evolutionary debates and are insignificant. The information is counted by assigning bits to the DNA code. I say this because it is usually used in common discussions in t... |
[
"Before we understood how light waves work, what was the historical understanding of refraction?"
] | [
false
] | I was taking a bath earlier and if I didn't know any better, I totally could have been convinced that my hand was physically shrinking when I dipped it in the water. Did people believe anything to that effect before we understood that it was refraction of light waves? Or did people generally understand it was some kind... | [
"I remember Bernoulli solved the Brachistochrone problem in the 1600s using light refraction. So by then the behavior of light was well understood. They didn't understand that it's both a particle and a wave, they didn't understand that it carries the electromagnetic field, and so on, but the basic behavior was wel... | [
"I actually have some time to write up an answer myself =) Most of this comes from ",
" by A. Mark Smith.",
"Accounts of refraction exist as early as Euclid's ",
" (4th-3rd century BCE). There are a bunch of ancient Greek works (and subsequent ones) called either ",
" or ",
". Roughly, optics was usually ... | [
"If you don't get an answer here, you can also try ",
"/r/askhistorians",
", ",
"/r/historyofscience",
", or ",
"/r/philosophyofscience"
] |
[
"How do plants cells and animal cells remove waste from their systems?"
] | [
false
] | null | [
"This depends on the nature of the waste. For small molecules, simple diffusion across the membrane allows the waste to be eliminated. This, by the way is why cells have a low ",
"surface-to-volume ratio",
" with regards to their size. A larger cell would take longer to rid itself of waste material (and also al... | [
"Do you know of a site talking about the mechanisms of the lysosome like organelle in plants?"
] | [
"I often use this reference from Miller and Levine ",
"http://www.millerandlevine.com/ques/lysosomes.html",
", mostly because of Miller's reputation as a cell biologist. There aren't a lot of articles in the popular science articles about plant lysosomes, but if you do a search on Google Scholar (for example) f... |
[
"Has popping joints been proven to affect local residents of other systems when popping the neck/shoulders/back?"
] | [
false
] | Lymbic/endocrine, etc | [
"It doesn't cause arthritis. Also, some info about the mechanics of knuckle cracking. - ",
"Johns Hopkins"
] | [
"Please remember that this is not the place for anecdotes and everything needs to be sourced. Please no more laymen speculation. "
] | [
"Popping the joints has some local effects. It causes a release of nitric-oxide, a very short lived vasodilator. It also has a temporary pain relieving effect and this is primarily why a person feels better after seeing a chiropractor. However, no effect outside the joint and immediate surroundings have been demons... |
[
"Is earth relatively to other planets, considered 'small'?"
] | [
false
] | [deleted] | [
"It is bigger than three planets in this solar system and smaller than four. It is smaller than pretty much every one of the thousands of known extrasolar planets (might be some exceptions), but that is mainly due to our detection techniques."
] | [
"But! Earth is the largest of the rocky ",
"\"terrestial planets\"",
"."
] | [
"In our Solar System it is, but compared to all known rocky planets it's in the middle."
] |
[
"A ziploc bag is airtight, yet scents from inside the bag will still permeate the plastic over time. How do scent molecules do this without the exchange of air?"
] | [
false
] | null | [
"Small, nonpolar molecules can still diffuse through plastic. They basically dissolve in on one side and un-dissolve on the other side. ",
"If you want a more impermeable food containment strategy, use aluminum foil. "
] | [
"That is sort of a unique case, because Helium gas is one of the smallest molecules that exists. As a result, it is notoriously difficult to contain and store."
] | [
"True. But even a balloon filled with regular air shrivels after a few days."
] |
[
"Do the elements of supernovae stay within the range of the previous solar system? Is a solar system with a star of sufficient mass just recycling elements within that range?"
] | [
false
] | I get that nebulae can be many AU’s in diameter, but isn’t the distance between solar systems much larger to the point where there would be very little cross pollination between solar systems? Also what happens to planets that aren’t destroyed by supernovae? Are there gas giant sized planets drifting around within gala... | [
"Nah supernova remnants spread out really quickly, and mix into the general mess of low density gas called the \"interstellar medium\". The interstellar medium is the thin gas that fills most of the volume of the galaxy, and it's very turbulent - it gets stirred up by supernova and winds, and by the rotation of the... | [
"No. Supernova remnants expand far beyond the range of their original systems. For example, the Crab Nebula, the remnant of a supernova observed in 1054, has already expanded to a diameter of about 10-12 lightyears, and is still expanding at a rate of ~1500 km/s."
] | [
"Not so much, there are \"planetary nebulae\" that are the end stage of stellar systems too small to go supernova & the radial velocity of these is near to the escape velocity of the system.",
"",
"Supernova remnants though can expand at up to 10% the speed of light & as they expand the shockfront sweeps up in... |
[
"What are the long term effects of anti-depressants?"
] | [
false
] | [deleted] | [
"As others mentioned in this thread, there are many different types of anti-depressants. Your use of the words \"long term effects\" could refer to any number of things such as mechanisms of action or side effects. Because I have the time, I will try to cover both of these in as easy-to-understand language as possi... | [
"My apologies. I was simply recalling information that I had previously learned. Here are a couple articles you might be interested in:",
"http://www.sciencemag.org/content/210/4465/88.short",
"\nThis explores the possibility of decreased number of neuroreceptors due to extensive use of antidepressants",
"htt... | [
"Any comment on Tetracyclics and how they fit into this picture? Great post, btw!"
] |
[
"Does obesity exist in wild animals?"
] | [
false
] | I googled it but all I could find was half thought-out or misinformed opinions. Obviously, there are animals that purposely but on weight for hibernation or when giving birth, but I assume that well within the weight that a particular animal can handle doesn't hinder their life expectancy or abilities. Maybe I need a b... | [
"If a wild animal's survival is affected by its eating habits and weight then it tends to die. If it doesn't it is easy to conclude that the gorging doesn't hinder it's survival. In other words it seems we have defined away the ability to have an \"overweight\" animal; either it is successfully managing its weight ... | [
"Some animals come from environments where food is scarce, so they will eat pretty much anything that you put in front of them. There's never been any evolutionary pressure to put an upper limit on what they'll eat because starvation has always been the bigger problem.",
"However if the environment is changed the... | [
"Foxes don't just think \"Hey, food is a bit scarce this year, I better not have a few more babies.\" They have as many as they can every year. It's just that when there's more food available, more of the offspring survives. ",
"As a result, when there's plenty of food, the fox population quickly increases. If fo... |
[
"If we can't predict the weather a week in advance accurately how can we predict the doomsday scenarios of Global Warming?"
] | [
false
] | null | [
"Weather and climate are not the same thing. I recommend starting with a simple google search for some background reading on the topic and coming back with a more specific question."
] | [
"Ooo shots fired ;)"
] | [
"My question is still valid why do I need a more specific question?"
] |
[
"When someone gets a transplant, if you wait long enough, do all the organ's donor cells get replaced by the recipients cells?"
] | [
false
] | [deleted] | [
"This would depend slightly on the organ, but in general I would say no. First of all, the \"all our cells get replaced in x years\" factoid is not true. Second, replacement of cells within an organ, if it happens at all, falls to the resident ",
"adult stem cells",
", which are likely to have been transplanted... | [
"If they got replaced it would be from the donor's stem or just normal cells contained in the organ. As far as I know you have no cells in your body that retain the ability to turn into say a liver cell. They have all progressed past that point and are no longer totipotent (able to become any cell). The reason i... | [
"Part of the organ recipient procedure is being on immune suppressant drugs for the rest of your life. That wouldn't be necessary if your body replaced the donor organ. Cells in the donor organ live and reproduce just like your own cells."
] |
[
"Why is a screening test recommended every year for breast cancer but not for any other types of cancers?"
] | [
false
] | For breast cancer, a screening exam like a mammogram is done every year for women around a particular age. However for other types of cancers, screening annually is not recommended in the healthy population. So the question is: Why is breast cancer screened every year, but other cancer's are not screened at such a high... | [
"The tests for different cancers vary a lot in terms of how expensive, how reliable and how invasive they are. For breast cancer, it just happen there is something relatively useful that can be done every year for little money. For bladder cancer, they do unpleasant things to you that I wouldn’t want to repeat ever... | [
"I think cervical cancer is screened more than breast cancer women. ",
"Other cancers are screened too e.g. prostate cancer in men.",
"This is done where the benefits of screening (early detection) outweigh the risks (mainly false negatives), and where the health system can afford it."
] | [
"There are other screening tests that are cost effective for the general public or select populations, such as colon cancer screening, lung cancer screening, prostate cancer screening.",
"These are not necessarily every year, though. For example, usually colon cancer goes through a pretty clear pathway from norma... |
[
"[physics] When looking at pictures of atoms, what am I really seeing?"
] | [
false
] | Am I seeing the nucleus or something else? | [
"You are basically seeing how much the apparatus you are using interacts with that atoms at each position along the surface being examined. You can read about the various methods ",
"here",
"."
] | [
"thanks! precisely what I was looking for."
] | [
"Just a little addition here, all the methods listed here are generally used to survey the ELECTRONIC degrees of freedom. If you want to image the NUCLEI (like you suggest) the best way to image them is through XRD provided they're in a regular lattice (x-ray diffraction) or gain other information (which unfortuna... |
[
"Why is it apparently impossible to create a velocity profile for fluids with turbulent flow, but not laminar?"
] | [
false
] | null | [
"Turbulent water is incredibly chaotic, but laminar flow is smooth and easily predictable.",
"To add a little bit to this: laminar flow can be accurately represented with many different \"models\" of water behavior. Turbulent flow is nearly impossible to model correctly. For turbulent water, you need to track the... | [
"When U try to determine the average conditions and write down the equations you get second-order statistical terms involving the cross-correlations between the velocity terms. When U derive the equation for the second-order terms it contains third-order statistical moments, etc. This is the turbulence closure prob... | [
"The problem is that in fluid dynamics, you can't really smooth over small scale fluctuations without introducing an error. When you try to make a smooth large-scale average, the terms don't cancel out, and you end up with extra bits that you have to create some model for. Turbulence is a cascade of eddies that goe... |
[
"Is antimatter related to energy in the same way that regular matter is related to energy?"
] | [
false
] | The matter that surrounds us is related to energy through the equation E=mc I know that when comparing matter and antimatter, for each property with an opposite (for example electric charge), a particle and it's antiparticle are opposite, but for properties without an opposite, they are the same. So are matter and anti... | [
"Yes, they are related to energy the same way. An electron and a positron have equal rest mass, and thus equal rest energy (",
"); if both are moving at speed ",
", their kinetic energy non-relativistically will be ",
", and relativistically their combined rest and kinetic energy will by ",
"."
] | [
"Got it. Thanks for the answer!"
] | [
"You're welcome."
] |
[
"A question about memory"
] | [
false
] | [deleted] | [
"Although there are a lot of different ways to categorize memory subsystems in the brain, you are asking about the difference between ",
"recognition memory",
" and ",
"recall memory",
" ). ",
"Everyone can better ",
" things that they have heard/seen/learned/smelled etc than they can independently ",
... | [
"There is a difference between these two \"memory items\":",
"One, GOURANGA, is a very specific -and rather unique- thing. I only played GTA1, so I only remember it as the message you got when you mowed down the whole C-company at once, but anyway; you used the code as a means to a special end. It is, bluntly sai... | [
"i thought those guys were joggers at first, but it turns out they're ",
"hare krishnas"
] |
[
"Does the earth's core (everything under the crust) move or flow?"
] | [
false
] | [deleted] | [
"Solid flow isn't the same thing as liquid flow. Solid flow occurs when a solid is heated close to its melting point. Ice is a very good example of a hot solid - glaciers flow at speeds that are easily measurable in time periods comprehensible to humans but it's still hardly comparable to a lazy river!"
] | [
"Because there's a temperature gradient between the hot core and the cool crust, ",
"convection currents",
" will form in any material capable of flowing. The outer core is liquid metal, and flows quite readily. It's more viscous than liquid metal at atmospheric pressures, but not much moreso. The currents in t... | [
"So hypothetically if I could survive being thrown into the mantle, I could float around like it was the lazy river?"
] |
[
"What does it mean to say that \"Electromagnetism is a more powerful force than gravity\"?"
] | [
false
] | null | [
"The electrostatic attraction between a proton and an electron is about 10",
" times as strong as the gravitational attraction between them."
] | [
"Not that this really matters, but to nitpick, your number is the ratio of the two forces when two electrons interact. For a proton and an electron, the ratio is on the order of 10"
] | [
"Yeah you're right."
] |
[
"Astronomers, et. al. is it really possible to see detail like in this picture from earth?"
] | [
false
] | I live in an urban area, but I've spent long nights in deserts,forests, etc. without population for miles and miles, and I've seen detail like in in the night sky. So, in addition to basically asking 'Is this photo shopped?' I am also wondering, if it is possible, under what circumstances? Have I just not been stargazi... | [
"Its probably taken with a long exposure. By leaving the camera aperture open long, it lets in significantly more light, making for a more detailed picture."
] | [
"Wouldn't the stars move and leave streaks in that long exposure? ",
"Here is the same arch, as far as I can tell, but with stars moving",
". ",
"If the camera were on an equatorial mount, I'd expect to see the arch move. ",
"Like the trees in this photo",
"."
] | [
"In that first photo it looks like stars have rotated through about 90 degrees, so that would be an approximately 6 hour exposure. With a full frame sensor DSLR I'd imagine that you could get pretty good data from an exposure of even just 30s - 1m which would have minimal trails. It could also be a composite of t... |
[
"Why don't protons and electrons attract each other to form a electrostatic lattice?"
] | [
false
] | I was wondering why electrons orbit protons as opposed to joining with them to form almost a lattice structure between the positive proton and negative electrons. The protons and electrons do have a difference in size but not charge so I don't understand why they just orbit, and also why do protons with +1 charge join ... | [
"I was wondering why electrons orbit protons",
"They don't, really. That's just a metaphor.",
"almost a lattice structure between the positive proton and negative electrons.",
"These are called atoms.",
"and also why do protons with +1 charge join with neutrons?",
"The strong interaction causes this."
] | [
"Atoms aren't lattice structures? I think his use of lattice implies like a salt crystal, which electrons and protons decidedly don't do."
] | [
"He said \"almost.\""
] |
[
"Can one attain a PhD in physics nowadays doing research in Newtonian physics?"
] | [
false
] | Just curious. | [
"Turbulence is still pretty much wide open."
] | [
"Of course. You could do nonlinear dynamics or, as its also called, chaos."
] | [
"Yep.",
"My galaxy simulations use newtonian gravity, because the corrections for GR on those scales are basically nothing. And nothing generally goes above a thousand km/s, so special relativistic corrections aren't important either. I've been doing isolated galaxy simulations, so I don't need to look at the exp... |
[
"Is it more beneficial to lay on your left side, right side, or back when you have a stomach ache?"
] | [
false
] | [deleted] | [
"If the stomach ache you're referring too is caused by a buildup of stomach acids, then lying on your left side might be beneficial. This is purely due to the normal orientation of the stomach (preventing acid reflux due to gravity). The best position would be to lay with your head elevated."
] | [
"There isn't any benefits for lying on any side...if there's a problem with your stomach, it will be there no matter how you lie down...but your stomach is on your left side, if that helps..."
] | [
"Beneficial in what way? More comfortable? And what kind of stomach ache. If you have appendicitis you'll have a stomach ache, but you'll also get one if you just at a bad chimichanga. "
] |
[
"Why do Tau & muon particles not produce currents like Electrons?"
] | [
false
] | As I learnt, Electron, Muon & Tau particles come into the category of leptons. Electron, on its motion produces electric current. Then, why does Muon not produce Muonic Current (imaginary naming) & Tau -- Tauonic Current? From a few reads I got that these have many similar properties --motion, rotation, electric charac... | [
"Any time charge moves — either negative ",
" positive — we call it \"current.\" Muons and tauons are charged, so when one moves, you get a current … very briefly. On the order of a millionth of a second for muons, a ten-trillionth of a second for tauons."
] | [
"Every charged particle produces current if its moving. So they do as well."
] | [
"Unless they're very very fast, and that extends their lifetime somewhat from our perspective."
] |
[
"If the minimum shutter speed of my phone camera is at 1/6000 of a second why can't I shoot slow mow videos with 6000 fps?"
] | [
false
] | null | [
"There are multiple reasons.",
"One is related to the way data is read from camera-sensors. With most sensors (especially in phone cameras), the entire sensor is not read in one go, but rather row by row. With a shutter speed of 1/6000, each row only collects 1/6000 of a second of light, but not all rows capture ... | [
"A simple analogy: how long does it take you to crack open a can of soda? Maybe one second? If that's the case, why can't you drink 60 cans of soda in a minute?"
] | [
"Wow, thank you for this detailed answer 👍"
] |
[
"Whats the difference between liquid and gas?"
] | [
false
] | I know this many sound like an extremely simple question, but on a molecular level, what's the difference between a liquid and a gas? From a young age we're shown a collection of diagrams showing how the structure of molecules in solids, liquids and gases differ. In diagram of the solid, they're touching, in the liquid... | [
"The molecules/atoms in solids aren't really \"touching,\" they are just held tightly together by weak intermolecular forces. There is an energy level at which the molecules/atoms are able to slide past one another despite the intermolecular forces, but are still held together: thus the liquid state. In a gas, howe... | [
"Briefly, condensed matter (i.e., solids and liquids) has a positive surface tension; gases do not. ",
"Put another way, it costs energy to form a condensed matter surface because such a surface is associated with unsatisfied bonds. There's no such implication with gases."
] | [
"that difference between a solid and a liquid is the molecules 'touching', there molecular bonds",
"This is not true. Molecules in liquid are also \"touching.\" The difference is that bonds in a liquid can freely shift from one to another, while the bonds in a solid are fixed.",
"Equally, there is a definite po... |
[
"I've started studying quantum physics but have come across a problem I simply can't get my head around..."
] | [
false
] | From my understanding, in beta decay, a down quark in the neutron emits a W- boson, which then decays into a B- particle and an electron antineutrino, and then changes into an up quark. I know that a down quark weighs more than an up quark, but a W- boson weighs much more than the difference between them so where is th... | [
"These are two very good questions.",
"Starting with the B- decay: The issue here is that the W- that decays is actually not a real particle, but a virtual particle. A virtual W- does not necessarily have the same mass as a real W- boson, and exists solely to transmit the weak force. Where does the energy come... | [
"Thank you, the textbook made it seem as though a single proton simply changed into a neutron for no other reason than because. Even reading it again doesn't provide any better insight. ",
"As for the B- decay, are you saying that technically energy can be created, then, as long as the energy is then destroyed in... | [
"What does quantum foam mean? It sounds like gobbledygook to me! :)"
] |
[
"question about the old saying \"its like riding a bike, you never forget\", what is it about riding a bike that makes it so difficult to forget it?"
] | [
false
] | null | [
"Close. Motor skills. And rusty.",
"Good English for a non-native speaker! ...actually just straight up good English in general."
] | [
"Riding a bike is, mostly, not something requiring \"training\", but rather just holding your arms straight and moving your feet. Most people can learn that in, like, less than 10 minutes, depending on their age. It's more about having the confidence in ",
" you can ride a bike, and not fall over. That might take... | [
"It's to do with the part of your brain that you use wilst controlling / learning this skill. The motoric skills in general are relatively important to our human race, so we remember them for a long time as long as we do them from time to time. Imagine a primitive human in the savannah of Africa suddenly having the... |
[
"Why don't ICBMs require a launch window?"
] | [
false
] | I've been following SpaceX's recent launches and there is always talk of launch windows and weather delays. At the same time conversations about ICBMs being launched at a "push of the button" are happening at the highest levels. My understanding is an ICBM is very similar to a multi-stage rocket used to launch a satel... | [
"A couple reasons.",
"Firstly, there is the fact that the launch is surface to surface not surface to orbit. The Earth rotates and thus the relationship between the position and momentum of a specific point on the Earth's surface (a launch site) and a specific orbit (inclination, phasing, etc.) of Earth or a spec... | [
"If you are launching ICBMs, it is hoped that this is an absolutely desperate last-resort measure. If you have time to think about the weather you should not be launching nuclear weapons at people. Also, the plan has always been to launch a lot of them at once, in order to overwhelm any defences, so you expect to l... | [
"Most space missions have a launch window because of the relative motions of the launch center and the mission target. For example, when SpaceX tries to rezvendous with the International Space Station they need to launch at a time that allows the rocket to intercept the space station. If this is not timed correctly... |
[
"How could we travel faster than the speed of light?"
] | [
false
] | null | [
"We can't."
] | [
"You're right. No, we can't currently because the amount of energy required to move an object that has mass approaches infinity as the object approaches the speed of light, as I understand it. But what theoretical ways could we get around this?"
] | [
"None.",
"If you could, you could build a time machine, which makes physics inconsistent."
] |
[
"Is this a meteorite?"
] | [
false
] | I found stuck in my shoe today, it looks like shiny metal in a few spots where it was worn, the rest of it looks like a volcanic rock with lots of tiny bubbles. It is attracted to a magnet and is roughly 1.5cm long. Sorry for the poor picture I can take a better one tonight. | [
"Looks more like a chunk of slag to me. Any blast furnaces in the neighborhood?"
] | [
"Sould slag be magnetic?"
] | [
"If it's got enough metal in it. Depends on the slag, but the kind that looks like this often does."
] |
[
"What magnification is required to view DNA during mitosis??"
] | [
false
] | I remember back in highschool Biology class I had the opportunity to look at plant cells undergoing various stages of mitosis. I remember being fascinated by how clearly visible each cell wall was and how clearly I could see the strands of DNA and the cells duplicating during anaphase. I always wondered how much more m... | [
"You can't see individual strands of DNA without an electron microscope (very high magnification). What you saw under the microscope were ",
", which is DNA packaged together so tightly that makes the strands negatively supercoiled and will break without the help of various proteins inside the cell. These chromos... | [
"I always wondered how much more magnification it would take to actually be able to see the nucleobases.",
"Bases are so small you have to move away from \"regular\" (light, electrons) magnification based microscopy and towards other technologies. Scanning tunneling microscopy and atomic force microscopy give you... | [
"when you look at cells during mitosis what you see is actually chromosomes. These are tightly coiled wound and spooled double stranded DNA/protein complexes. To actually \"see\" a nucleotide with any clarity, you would need the use of x-ray crystallography or similar method such as NMR. You can begin to see the DN... |
[
"Do octopuses have specific limbs that would be arms and legs or are they all the same?"
] | [
false
] | [deleted] | [
"Your question also made me wonder about a follow up; do octopodes exhibit handedness?",
"I found this cool article: ",
"http://www.nature.com/news/2004/040615/full/news040614-1.html",
"In it it also says: ",
"Favourite arms are usually at the front of the animal, the team found. Meanwhile an octopus's rear... | [
"It’s interesting and colorful… maybe even pretty… but you and I must have very different definitions of “cute”.",
"(I can’t even tell where front and back are in that picture.)"
] | [
"It’s interesting and colorful… maybe even pretty… but you and I must have very different definitions of “cute”.",
"(I can’t even tell where front and back are in that picture.)"
] |
[
"Sodium lauryl sulphoacetate - what's the deal?"
] | [
false
] | A friend of mine has bought some rather nice liquid hand soap that proudly boasts amongst other things that is has no parabens (good) and no sodium lauryl sulphate (apparently good). But I read the ingredients: it might not have sodium lauryl , but it does contain sodium lauryl . Now, as a non-chemist that looks like a... | [
"Here are some references.",
"http://en.wikipedia.org/wiki/Sodium_dodecyl_sulfate",
"http://chemicaloftheday.squarespace.com/todays-chemical/2010/9/14/sodium-lauryl-sulfoacetate.html",
"They appear to be very similar compounds, both chemically and in some of the symptoms/side-effects. Apparently SLSA is newe... | [
"Sodium Lauryl Sulphate (SLS)- \"It is a known skin irritant and is absorbed through the skin and retained in the heart, liver and brain for long periods of time.\"",
"I would look at this with extreme skepticism. There is no way they could put this in every shampoo, toothpaste, etc. known to man, if that was tr... | [
"I'll be buggered. I spent ages searching for info and turned up very little.",
"I'd like to see some stuff from chemists and a bit more detail, but that's a fantastic start. Thank you!"
] |
[
"If a camera focuses on a mirror will all the things in the mirror be in focus too?"
] | [
false
] | null | [
"Yep. Your eyeball also has a lens just like a camera that needs to focus. ",
"You can do a simple experiment by taping a picture on your mirror and focusing alternatively on the picture or on your reflection. You can feel your focus changing and can see that only one of the images is in focus at a time."
] | [
"No. Focal distance for objects seen in a mirror is sensor to mirror + mirror to object. You can focus on the surface of the mirror or on the reflect you see in it. "
] | [
"What is sensor to mirror and what is mirror to object?"
] |
[
"Will there ever be a point in time on Earth when we won't be able to look at the entirety of the geologic record?"
] | [
false
] | Another phrasing: will there ever be a point in time where the beginnings of the geologic record will be wiped away by geologic forces? | [
"We are already missing large portions of the geologic record. While we have some material preserved from early portions of the Earth, e.g., ",
"the ~4.4 billion old zircon grains from the Jack Hills",
" which can provide a variety of clues about processes going on at the time of their formation (e.g., ",
"Us... | [
"This completely satisfied my curiosity while also giving it something else to crave. Thank you!"
] | [
"This is categorically untrue. ",
"I'm familiar with the video you're referring to and I have to say it is ",
" bad. I was a fan of Kurzgesagt, there's a place for pop-science as a tool to spark interest in a topic and no one can argue with the Kurzgesagt's production value. While I had noticed an instance or t... |
[
"How fast would the planet have to decelerate to a halt in its orbit to cause objects to overcome gravity and fly off the planet?"
] | [
false
] | null | [
"9.8 m/s",
" That's the acceleration due to gravity at the surface of the Earth, so as long as the planet decelerates faster than that everything on the leading edge will overcome gravity. Everything on the trailing edge, of course, will experience up to 2g. "
] | [
"Yes, humans can withstand 2g for a long time according to NASA research ",
"http://history.nasa.gov/conghand/mannedev.htm",
" figure 5. Remember this is only true for grown adults, small children with comparable weak bones would suffer from disformation of their skeleton."
] | [
"Ignoring air resistance and earth's rotation because they make things hard,\nto leave the surface of the earth, 9.8m/s",
" However, this will really just toss everything a little bit in the air, while earth's gravity pulls it back down. So the earth is accelerating away from you at 9.8m/s",
" but you're fall... |
[
"Does hearing bat squeaks indicate we are in their field of view? Do bats produce a focused enough echolocation sound that whatever can hear the sound is being observed by the bat?"
] | [
false
] | null | [
"Humans are not capable of hearing most bat squeaks (they're mostly ultrasonic), but bats are capable of producing remarkably focused sounds as well as adjusting the level of precision by altering the frequency and loudness of the sound they're using. A study published in nature found that on average, a bat call ha... | [
"Well, if you are behind something the bat cannot \"see\" you. Echolocation does not form a 3d map, but rather a picture that looks like it came from an eye. You can strand behind a tree and hear the bat just fine, but the bat will only \"see\" the tree,as that is the only thing that will bounce directly back to it... | [
"The audible sounds you are hearing are mostly for communication purposes, not echolocation."
] |
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