title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Two bowling balls are at rest 5 Megaparsecs apart, and connected with a cable. Is there any tension in the cable caused by universal expansion?"
] | [
false
] | According to Hubble's Law, at 5 Mpcs distance each bowling ball would see the other receding at 351.5 km/s, but the cable prevents that from happening. Does that mean there's a "cosmological stress" in the cable induced by the expansion? | [
"Here's an actual paper written on the subject: ",
"https://ui.adsabs.harvard.edu/abs/1995ApJ...446...63H/abstract",
". The abstract:",
"\"In principle, the expansion of the universe can be harnessed to provide energy. In a gedankenexperiment, energy is gained by connecting together widely separated bodies wi... | [
"But if the bowling balls are far enough apart that space between them is expanding faster than the speed of light, the bowling balls can't be moving toward each other at the speed of light. So wouldn't the cable be stretched and ultimately break?"
] | [
"Apparently, the tethered-body experiment delivers 'nascent' energy that previously did not exist in any identifiable and quantifiable form.",
"Except, wouldn't that correlate to dark energy? We have no idea what it really is, and we may not be able to measure it directly, but we have managed to measure the impac... |
[
"How do trees living in temperatures under -50 centigrade for more than a month at a time keep from freezing to the core?"
] | [
false
] | I mean, it's not like they have much insulation, and they can't do much actively to keep warm. What allows them not to just completely freeze and die when it's very cold? | [
"Cool! Something I can actually contribute to. Freezing tolerance in plants is not based on resisting the freezing, but on surviving the thaw. The freezing doesn't do anything but halt the biology of the plant until it warms back up. ",
"When a plant is frozen, the fluid outside individual cells becomes low in li... | [
"The effects of freezing are pretty universal on plant tissue. The visible differences between woody and non woody tissue may vary, but all the tissues die for the same basic reason. The plasma membranes burst. The advantage that woodier cells have is the fact that the cell damage does not usually disrupt the ligni... | [
"I used to work up North, and when we would get prolonged periods of extreme cold we used to hear trees \"explode\" around us. So, sometimes the trees DO freeze!",
"http://en.wikipedia.org/wiki/Exploding_tree"
] |
[
"Do animals develop regional \"dialects\"?"
] | [
false
] | null | [
"The book ",
" covers this. Yes, birds have accents in their calls, even down to specific 'neighborhoods'.",
"More here.",
"There has been a lot written these past few years about how animals learn from each other. ",
"https://www.smithsonianmag.com/smart-news/fish-may-have-regional-accents-make-it-hard-the... | [
"In addition to what ",
"u/shillyshally",
" said, whales and dolphins have also exhibited dialects based on regions. In fact species of dolphins are believe to actually develop cultures. The calls among different groups are audibly different but, when two groups meet, they can change their calls to communicate ... | [
"yes here in the uk we did an experiment, we all had our dogs bark down the phone it turned out dogs do have regional accents ",
"",
"having a Scouse accent myself the thought of my dog barking scouse is hilarious"
] |
[
"Why do some people learn more effectively through different means of stimulation (auditory vs. visual) than others? Is the portion of the brain that mediates processing of the preferred stimulus more effective than other portions?"
] | [
false
] | [deleted] | [
"The \"auditory\" / \"visual\" learner distinction is a myth. ",
"Here",
" is a little NPR story about it, ",
"here",
" is another pop-sci piece.",
"Pashler et al. (2009)",
" is a review of (lack of) evidence for learning styles and discusses what would constitute acceptable evidence."
] | [
"We don't. Learning effectively has little to do with the medium and more to do with timing, active mental interaction with the material, and how much you train recall (described in more detail ",
"here",
" )"
] | [
"Awesome! Thanks for the link."
] |
[
"Are there enzymes that can resume normal activity after denaturation by heat?"
] | [
false
] | I had previously assumed that when enzymes are denatured by heat, the denaturation is permanent. However, I have recently come across a book that says 'Denaturation is frequently temporary, as in many instances the intra-molecular bonds will re-establish when the temperature returns to a suitable level'. Is this true? | [
"There are proteins in cells called Heat Shock Proteins, some of which can ",
"help re-nature or re-fold denatured proteins",
", which is very pertinent to diseases that involve protein misfolding such as ",
"Alzheimer's Disease"
] | [
"Hi sorry I just stumbled to this post. Yes denaturation may be temporary depending on the type of denaturation. Denaturation by heat disrupts the non-covalent bond, a small un-complex protein has the highest chance to refold back to its functional state after denaturation. ",
"One example that I know of is RNAse... | [
"It ",
"depends",
" on the degree of denaturation. Minor changes, such as bond angle alterations due to heat stress or disulfide bridges disconnecting, could be reversed. ",
"If covalent bonding starts to occur, as it does with higher temperatures and longer times, the process rapidly shifts towards irreversi... |
[
"Why did humans evolve to be one hand dominant?"
] | [
false
] | null | [
"You're asking about laterality and lateral dominance. I'm not aware that there is a definitive answer to this question.",
"Lateral dominance is present in many species. Even in invertebrates and fish, which suggest that it is either an ancient feature of brains in general or that it can commonly/easily evolve in... | [
"Its a super common assumption that everything in biology is absolutely optimized by selection. But evolution isn't survival of the fittest, it is the survival of the fit enough. Sometimes a bug isn't a feature. ",
"I think handedness could easily fall into this category. The selective advantage of handed motor s... | [
"We likely have evolved to be one hand dominant due to tool use. If we look at other monkeys and apes they have no hand preference when on all fours. However when they use tools they actually have more of a preference.",
"Do you have a citation for that. Many animals which don't use tools display some kind of lat... |
[
"Is time expanding too much like space is? Is there evidence that it is or that it isn't?"
] | [
false
] | null | [
"Earlier thread:",
"http://www.reddit.com/r/askscience/comments/g2skw/does_metric_expansion_of_the_universe_apply_to/"
] | [
"I think he's asking since the universe is expanding, and the universe consists of spacetime, and space is expanding when the universe expands, does time as well?"
] | [
"I think he's asking since the universe is expanding, and the universe consists of spacetime, and space is expanding when the universe expands, does time as well?"
] |
[
"When a limb is lost, what happens to the brain cells that are assigned to control it?"
] | [
false
] | null | [
"Eventually, neural plasticity will allow the space previously held to control that limb to be somewhat repurposed for other functions. But the connections for the limb cease, and, if I’m not mistaken, they are pruned."
] | [
"Yep. What the other comment said. Neuroplasticity allows surrounding neurons in the brain to use that space. That’s how you get phantom limb syndrome. For example, some people who lost their arm can still feel the arm. Tickling someone’s face can also stimulate the lost arm since the face neurons are so close to t... | [
"They're reprogrammed. The brain is very very programmable and people have done studies of this where they see that after a limb is amputated, the area of the motor cortex that was responsible for controlling that area before is reprogrammed to control other body parts."
] |
[
"Why do advances in animal models rarely translate to equally functional & effective therapies?"
] | [
false
] | I understand that there are fundamental differences in biology between animal models and humans. However, I don’t think I have a clear answer as to what broad categories of issues might be responsible for the aforementioned failure of successes in animal models to translate to human therapeutics and I was hoping someon... | [
"A few of the \"broad categories\" that come to mind:",
"There are more factors, to be sure. ",
"I don't think that anyone using animal models of disease in their research expects the models to be perfect analogues of human physiology / biochemistry, but the idea is that the animal models are far closer to the ... | [
"I absolutely hate this argument. The vast majority of people doing research on disease in the setting we are talking about are working in a University or Research Center (non profit) capacity.",
"This incentive that is talked about among manufacturers to prolong disease might exist in terms of treatment develop... | [
"I think there is also a large historical enertia associated with model organisms. It seems that researchers lose sight of curing diseases after decades of working on the murine model. I work on histocompatability between species, and it seems like every week there is something amazing in mouse immunology that does... |
[
"How, exactly, does dissipating the proton gradient across the inner mitochondrial membrane (e.g. during brown adipose tissue thermogenesis) produce heat?"
] | [
false
] | It is well known that cells of brown adipose tissue, used for thermogenesis, express uncoupling proteins which dissipate the proton gradient across the inner mitochondrial membrane, generating heat. There are also medications (2,4-dinitrophenol) that do the same thing, leading to higher energy usage but uncontrolled he... | [
"Because the cell wants to keep the proton gradient intact, it will increase the rate at which it pumps protons across the membrane in order to balance the increase in protons diffusing in the opposite direction. The increase in proton pump activity is facilitated by an increase in ATP hydrolysis to provide the nec... | [
"The FoF1 ATP synthase can run in reverse, hydrolysing ATP to pump protons across the membrane."
] | [
"Yeah my bad on the ATP hydrolysis comment. I've been out of practice for a little bit. I forgot that NADH is mostly responsible for pumping electrons in the ETC. The basis of my answer should still be true though. Whatever process in the cell that is responsible for producing NADH (Citric Acid cycle, etc.) for the... |
[
"Whats the relationship between intensity of photon and their absorbing in our atmosphere when traveling a know distance?"
] | [
false
] | Reworded this as i'm not sure if was clear. What i'm want to know is the atmosphere's effect on a laser beam of a set frequency and constant intensity or brightness being generated, when we know the composition of gases it passes through and the intensity at some point along its path. Using this too work out the intens... | [
"The intensity of an electromagnetic wave through a lossy or absorbing medium falls off exponentially. How long it takes to decay has to do with the imaginary part of the index of refraction of the medium. ",
"It's simpler to treat this as electromagnetic waves rather than photos, unless you're dealing with gamma... | [
"I=I(0)e"
] | [
"What is the equation that describes this phenonmenon?"
] |
[
"Why did penicillin replace sulfa drugs that were used prior to its discovery? What was so great about penicillin in comparison to them?"
] | [
false
] | null | [
"Efficacy and toxicity.",
"Penicillin actually kills bacteria in addition to inhibiting their growth by interfering with their ongoing activity of remodeling their cells walls. Sulfa drugs do not kill bacteria, they only inhibit bacterial growth by inhibiting cell division by inhibiting folate synthesis - folate... | [
"\"Sulfur\" are still in use such as trimethoprim and sulfamethoxazole. There are many non antibacterial drugs that are in common use that contain a sulfur moiety. For example, the diuretics (including frusemide/furosemide and the thiazides), the diabetic medications (gliclazide and similiar) and others. Despite t... | [
"How prevalent is antibiotic resistance in staph infections in the third world? It seems like it wouldn't be as prevalent there with less exposure to antibiotics, but on the other hand in our interconnected world I don't want to make that assumption. If penicillin was taken off the table I imagine that would make t... |
[
"What is transition energy?"
] | [
false
] | So what is transition energy? I am specifically interested in transition metals. | [
"In chemistry, transition energy is the amount of energy it takes to cause an electron to transition from one energy level to another. Typically you'll only see this for hydrogen because it only has one electron, and anything beyond that gets complicated really quickly.",
"The name \"transition metal\" actually h... | [
"In the gas phase there is no d to d transition energy. However in solid phase compound and compounds in solution will in general have a d to d transition energy.",
"This splitting of the d orbitals is down to the ligand field ( different groups will be arranged around the metal in a specific way eg the H2O molec... | [
"Will I be able to find something if I run them through a spectrophotometer? Could I for example calculate the transition energy?"
] |
[
"Hydrogen bonds of ADP + Inorganic Phosphate, stronger than Bonds between Phosphate groups in ATP?"
] | [
false
] | I just read in my Biology textbook that I'm confused at the hydrogen bonds between ADP and phosphate and water. Do the water molecules in a system surround both ADP and Phosphate separately, forming hydrogen bonds between ADP and Water and Phosphate and Water? I understand that the strength of the hydrogen bonds betwee... | [
"That does appear to be a weird statement. (No slam on biology in general, but the textbooks often seem to get details of chemical thermodynamics wrong a lot). ",
"These are two different things. A) The bonding energy of the phosphate-ADP covalent bond, and B) The ",
" energy of the dissociation products (ADP +... | [
"It does require energy to break chemical bonds, but making bonds releases energy. In the reaction ATP + H20 -> ADP + Pi the energy required to break the bonds is almost exactly replenished when the new bonds form. You need to break 2x O-H bonds to hydrolyse the water and 1x P-O bond to split the ATP. Then 2 new O-... | [
"In water, breaking a chemical bond can both require energy or liberate energy, in total. But breaking a bond (or any chemical reaction) typically requires that the molecule has a certain 'activation energy' for it to occur. It needs to gain energy before it can lose energy. ",
"You can view it as walking over a ... |
[
"Changing \"baseline happiness\""
] | [
false
] | I read in many pop-psy articles that people have a baseline happiness, and that major life events like weddings, promotions, divorces and sudden unemployment don't change a persons happiness very much. Is there any way to change a persons baseline happiness? | [
"There is evidence mediation can improve happiness. ",
"Buddhist monk is the world's happiest man",
"Tibetan monk and molecular geneticist Matthieu Ricard is the happiest man in the world according to researchers at the University of Wisconsin. The 66-year-old’s brain produces a level of gamma waves - those lin... | [
"Dropping this off here. \n",
"Journal of happiness studies",
"I haven't looked at it, but seems like a good place to start looking. It appears to be sort of open access as well. ",
"I was brought to this while googling for a project I heard about long time ago. I recall some professor(MIT, Carnegie Mellon?)... | [
"Seligman, who is one of the few academically sound/respected self-help writer-psychiatrists, has written two books, 'Learned Optimism' and 'Authentic Happiness', which I expect (having read some of his other books) are heavy in citations and references to other sources."
] |
[
"A question about treeline elivations in the Western US."
] | [
false
] | I was part of a discussion in about the treeline on Mt Hood in Oregon and why it is so low as compared to the treeline in the Rocky Mountains at the same latitude (5k feet vs 10k feet respectively). One redditor suggested that it was due to costal winds but I pointed out that the treeline in Southern California, which ... | [
"Treeline is affected by a wide variety of factors, any number of which could influence this. The trees will grow until they can't, which is determined by how \"hard\" it is for them. The main ones we focus on are:\n-Temperature: generally colder is worse, its colder higher up. Frozen soil is bad.\n-Humidity: it... | [
"I understand that there are a wide variety of reasons why trees stop growing at specific elevations but what I see in the PNW specifically Mt Hood, though you can add Mt Shasta, and Mt Rainier to that list, is a dramatically lower treeline than what is reflected by the gradual drop due to latitude. For instance; M... | [
"Mt. Hood is actually in Oregon. Hood, Shasta, Rainier, Adams, Jefferson, etc. are all volcanos. There's not much fertile soil beyond a certain elevation."
] |
[
"Artificial eyes and the brain"
] | [
false
] | Imagine an artificial eye that had the same capabilities of a mantis shrimp's (12 color cones, perception of polarized light and hyperspectral color). Would the human brain be able to process information from an implant like this? | [
"If human would be born with those kind of eyes, or would get them at young age, I don't see why not. It's possible that some humans are ",
"Tetrachromats",
" (4 color cones). "
] | [
"So someone who was born with a normal set of eyes would not be able to handle replacements? "
] | [
"I don't know. I think it's in realm of possibility, but there should be some rearrangement in the brain areas that deal with color perception. If adult brain already interprets all color signals from optic nerve certain way, having different coding would be mighty confusing. "
] |
[
"What would happen if a battery pack with 2200mAh battery capacity that called for a charger to input charge at a rate of 800mA was charged with a charger that charged at a rate of 1A? Would it damage the battery pack or would the battery just charge quicker/slower?"
] | [
false
] | I'm wondering because this has always confused me. | [
"The current is determined by the drain (the battery), not the source (the charger). When you see a battery needs a 800 mA charger, that means a charger capable of ",
" 800 mA. A 1 or 2 or 500 A charger will work, but the battery will only draw 800 mA. ",
"If you use a charger not capable of 800 mA, then the vo... | [
"Safety of battery charging is limited by heat dissipation. A good rule of thumb is that you should not charge your battery with a current numerically larger than 0.1C with C being capacity expressed in Ah, i.e. if it has a capacity of 2.2Ah, you shouldn't charge it with a current higher than 220mA. However this de... | [
"Nothing bad will happen, if anything, it's bad to use a charger with a lower Amperage than what is recommended to use by the device that is being charged. It will most likely charge faster, since the charger is what dictates the max \"energy flow\"\n.\" I have a 6000mA Powerad battery pack and I use a 2.1A Anker c... |
[
"Why does gravitational potential energy increase with distance from the centre of mass?"
] | [
false
] | null | [
"Yes, the potential energy is negative. The point of zero potential energy is arbitrary, because only ",
" in potential energy have physical meaning. So it's defined in a way that the potential energy is zero at r = infinity. Since gravity is an attractive force, that means that the potential energy everything at... | [
"I get it now! Thanks so much for your help."
] | [
"It's -GMm/r. The negative sign means that it ",
" (gets closer to zero) as r increases."
] |
[
"How did the United States so greatly lower the occurrence of tuberculosis?"
] | [
false
] | I hope this is a good place to ask this. Some antivaxxer started arguing recently about how the US isn't discussing how many tuberculosis kills a year. I know the numbers they quoted were skewed, but I got curious about how the US brought the disease to a near-stop. It's not common for infants without risk factors to b... | [
"Growing up in the 60’s and 70’s, it was commonplace even in private schools for students to get screened for TB every other year or so. I remember well waiting in line at the nurse’s office to get my arm pricked, and then returning a few days later so the nurse could check for signs of a reaction. So they had a ... | [
"So previously positive TB person just want to point out that there is not a vaccine for TB that is widely used in the U.S.",
"\nFor me there was only treatment. If you get it you have to take one of two pills for 6 months and get screened every month to see if your lungs show signs of TB. There is a danger from ... | [
"We never had to wear masks - Covid is the first time in my life masks were commonplace. Vaccinations were a big deal, though, with Polio being one of the big diseases of the day, and I’m sure there were others. Hell, my entire generation has a scar on the back of our left shoulder where we received some sort of ... |
[
"How much computing power would it take to simulate all the molecules and interactions in a human body?"
] | [
false
] | when might we get there according to Moore's law? does quantum computing help in any way? Would it be possible to obtain an "image" of a human while still alive? | [
"There are about 10",
" atoms in a typical human cell, which is coincidentally about the same number as there are cells in a human body. So with around 10",
" atoms to simulate, you now would need to define at what level you were going to simulate each molecule and how rapidly you need to update that to get an ... | [
"You cannot simulate ",
" the interactions. Period. Thus far we can only achieve analytical solutions for a number of specific situations (e.g., hydrogenic atoms). Modern calculation methods (for example, density functional theory) use basis sets that are approximations to provide \"close enough\" answers. Even t... | [
"Yes, I was being quite conservative."
] |
[
"Assuming the universe is infinite, would that mean the universe was already infinite immediately after the big bang?"
] | [
false
] | As I understand it, space isn't really a thing at the point of the big bang. So let's say, at a single unit of Planck time following the big bang, was the universe already infinitely large? | [
"Most of the answers in the thread are somewhere between wrong and confused.",
"In the standard model of cosmology (LambdaCDM), the universe is spatially flat (k=0). Think of it a bit like an infinite 3D dimensional space, like you might encounter in a video game like Minecraft- going really far doesn't get you b... | [
"This answer is the closest to 'right' you're gonna get in two sentences, and I'll just object to the 'to start with' sentence in the middle since we really don't know why the universe exists, but this is definitely right enough for OPs purposes."
] | [
"This answer is the closest to 'right' you're gonna get in two sentences, and I'll just object to the 'to start with' sentence in the middle since we really don't know why the universe exists, but this is definitely right enough for OPs purposes."
] |
[
"What are the likely origins of singing?"
] | [
false
] | null | [
"I'm going to try to keep this really short since the origins of music/singing are heavily debated. I'll give you one really popular theory that is mulling around the music psychology circles--",
". Essentially, some theorists believe that something like music arose from mother(or caretaker) interactions with a n... | [
"Bird singing or human singing? I would assume bird singing evolved as communication and to persuade others to mate."
] | [
"And in humans?"
] |
[
"Why does pulling on the skin at the corners of your eyes blur your vision even though nothing is obstructing your field of vision?"
] | [
false
] | Does it have to do with thingies behind your eyes? | [
"I'm not 100% sure how you're pulling at the corners of your eyes so I can't say for certain. My suspicion is that your putting tension on your eyelids which are in turn pushing on your eyeballs and changing their shape.",
"In optics it isn't just if you can see the light it's also how the light is focused. Your ... | [
"You're distorting your eyeball. If you have astigmatism, like I do, you can do the same thing to ",
" your vision, because you can ",
"distort your eyeball. Even with my contact lenses in I can get a bit of extra sharpness by gently pulling on the skin at the corner of my eye."
] | [
"Awesome answer thanks! That makes a lot of sense."
] |
[
"How exactly does a short-circuit damage a device?"
] | [
false
] | I accidentally left my iphone turned on in my pants when I was washing them a few weeks ago. Suffice to say it was dead as dead afterwards. It got me curious. How is it that a short circuit damages the device? I feel intuitively that just because electricity is taking a different path it shouldn't damage the device, bu... | [
"First it is important to understand how electricity works. The rate at which electricity flows through a circuit is determined by its resistance. In fact, resistors are extremely important in circuits for this very reason, because they place limits on how much electricity can travel through a given part of the cir... | [
"It is not necessarily the case that a short circuit is what killed your phone. There are numerous metal contacts and connections in the device which are simple 'contact' points which would be disrupted by even a small amount of corrosion. Similarly, many ICs are inside protective packages, but those packages are n... | [
"Does the increased volume from the water provide any diffusion? That is, would a singular path of water be worse than complete submersion, keeping in kind that submersion seems to still be detrimental enough. "
] |
[
"Is there anything (disease, condition, poison, etc) that can prevent hemoglobin from unloading its oxygen?"
] | [
false
] | [deleted] | [
"Methemoglobinemia.",
" Oxygen is bound but cannot unbind from the damaged protein. ",
"You turn blue",
".",
"EDIT: Medline Plus was slightly wrong. See below."
] | [
"Not sure if this technically counts in answer to your question, but carbon monoxide will bind to hemoglobin, blocking oxygen uptake in your lungs. This is one of the reasons smokers have less energy than non-smokers."
] | [
"Everyone's blood has a small amount of their hemoglobin (Hgb) in as methemoglobin (met-Hgb). In deoxyhemoglobin (no oxygen bound), iron is in the ferrous form (Fe",
" When oxygen binds (oxyhemoglobin), the iron becomes ferric iron (Fe",
" When oxygen is released to the tissues, the the reverse reaction occurs,... |
[
"Why are the biggest animals almost never predators?"
] | [
false
] | Throughout the history of the world, the largest species have usually eaten plants or very small animals such as plankton. Why aren't the largest animals always predators? | [
"Great Question",
"I think the best answer to your question was provided by Max Kleiber, a Swiss biologist who published a paper in 1932 that describes the relationship you eluded to in your question. Kleiber found that an interesting relationship existed between the size of a predator and the size of their prey... | [
"Larger animals require more food to sustain their body mass. For example, a leopard is estimated to need to eat 100 lb's of meat to gain one pound of body mass. You can also see that size and all of that would potentially slow an animal like an elephant or hippo (who also have a very large bone structure) because ... | [
"Surface area to volume ratios are important whenever you think about an animal's body size. With increasing total size, surface area increases at a slower rate than volume does ( length",
" vs length",
" ). Surface area leads to heat loss, which is wasted energy. A big animal requires fewer nutrients per unit ... |
[
"What do swordfish use their sword for?"
] | [
false
] | null | [
"There is some debate over how the sword is used to hunt. In a study on swordfish in 1981:",
"... swordfish rise beneath a school of fish, striking to the right and left with their swords until they have killed a number of fish, which they then proceed to devour",
"Swordfish are also different from other fish w... | [
"A more recent study focussing on sailfish: ",
"https://royalsocietypublishing.org/doi/full/10.1098/rspb.2014.0444",
"One thing to note though:"
] | [
"They will swing it through groups of smaller fish injuring or disabling some to create easier to catch prey. It's ",
"also speculated",
" though never observed that they use their bill to disturb bottom sediments, releasing deepwater crustaceans & other bottom dwelling creatures for food. "
] |
[
"Why do lower frequencies seem to travel through materials easier?"
] | [
false
] | You can hear the bass in a song throughout an entire house basically. Why is it that the higher frequencies seem to get lost? | [
"When sound, or any wave, travels through a medium, it loses energy by transferring it to the medium. For sound, this usually means kinetic energy - the medium vibrates with the sound, which robs the sound wave of energy. Each time the wave cycles through the medium, some of that energy is lost. Since lower frequen... | [
"Audio Engineer in training here.\nFor this case you can compare audio to waves in the ocean, because sound waves are pressure waves in the air. \nYou know how it is way harder to make a large wave, say, using your entire arm, then it is to make a small wave with using only your hand. Same goes for sound with low f... | [
"You appear to be conflating waveform amplitude with its frequency."
] |
[
"How do we know what comprises the insides of the Sun?"
] | [
false
] | so was watching this recent Kurzgesagt vid ... which got me thinking, how can we possibly know how the Sun is layered? obviously no human has gone to the Sun, much less bored thru to the center. no machine is capable of doing that either for obvious reasons. so what sort of a super xray telescope (if theres such a thin... | [
"There are some direct ways, like looking at specific types of electromagnetic waves (that lets us see some of it).",
"There are indirect ways too, like looking at the composition of the exterior, seeing how much energy is radiated away, then comparing that to the model of hydrogen fusion and the mass of the sun.... | [
"Stellar structure is how we square what we know about the Sun and other stars, and what we know about what they're made of. Since we can't examine the interiors of stars directly, we use a physical model to understand what is going on inside them. We then examine the predictions of this model and see if it account... | [
"By \"layered\", I assume you mean the fact that the interior of the Sun has two distinct regions by which the transport of energy differs.",
"This is an amazing topic. I purchased a few years ago a book by I. S. Shklovskii called \"Stars\" which delves very deeply into this.",
"One of the most powerful tools "... |
[
"What is the escape velocity for leaving the Milky Way?"
] | [
false
] | The Milky Way is held together by gravity, just like the Earth, therefore it exerts a force on any body that is within it and pulls it back. So what is the minimum required velocity required for a body (take for example a regular spacecraft) to escape that force? Please correct me if I am on the wrong line of thought h... | [
"Wikipedia says ",
">525 km/s",
". Most stars within the Milky Way Galaxy travel with velocities of a few hundred km/s or less. ",
"Stars that are unbound from a galaxy's gravity",
" travel with velocities of thousands of km/s.",
"The Voyager 1 is traveling at 12 km/s. "
] | [
"thanks"
] | [
"What?"
] |
[
"Can a strong enough electric field penetrate Faraday cage?"
] | [
false
] | [deleted] | [
"Let's check.",
"We can do a rough calculation for the electric field between two plates.",
"I am going to pretend that my two plates are made of 1cm",
" of iron between them (just so I have the size in my head) and I have taken all the electrons from 1 plate onto the other. This is deliberately a tiny tiny a... | [
"A Faraday cage works because the electrons in the cage respond to an external electric field and re-arrange themselves naturally to create an equal and opposite field.",
"Hypothetically, if you had a large enough externally applied field that all the free electrons moving from one side to the other does not prod... | [
"If cars work as Faraday cages, why can you get cell phone reception inside a car?",
"It is to do with the frequency, lightning is basically DC, i.e. 0 frequency, whereas your phone is high frequency and so is small enough to be able to penetrate the gaps in the cage (the windows).",
"edit: this is the same rea... |
[
"According to evidence, how much benefit does eating enough fiber have? What benefits does it have?"
] | [
false
] | I see a lot of benefits of eating enough fiber thrown around on internet articles, and they seem to change drastically with only a few consistent ones. Obviously, it helps with digestion and probably nutrient uptake, but anything else ? , is Fiber One Honey Clusters just as good of a source for fiber as fruits/vegetabl... | [
"Fiber does help with nutrient uptake, as it essentially 'fluffs up' the stool, allowing it to be pressed against the insides of your intestines better, allowing for greater nutrient absorption.",
"By increasing the size of stool, it becomes easier for the intestinal muscles to squeeze on it, and thus improves th... | [
"Fiber that comes from grain may reduce your risk from ",
"colorectal cancer",
". The classic benefit is reduced risk of diverticular disease as mentioned already. "
] | [
"http://en.wikipedia.org/wiki/Dietary_fiber#Effects_of_fiber_intake"
] |
[
"Is there \"anything\" in our current math or physics that dictates that time MUST move forward?"
] | [
false
] | I've heard that there's nothing stopping time from moving in reverse if you look squarely at the math/equations. But since we can't reverse entropy, there must be "something" that dictates that in our current understanding of time, it cannot move backwards. Right? | [
"In physics, there's really only two major concepts that are not time reversible: ",
"Entropy in thermodynamics, or why vases don't unshatter themselves. ",
"Charge-Parity violations with weak nuclear interactions are, if CPT hold, establish a preferred direction of time. ",
"The second is much too weak to... | [
"This really is an open question, no? Unitarity may indeed still be preserved for all quantum processes. Outside that, regardless whether or not the measurement problem is truly solved, we do have a giant hint on how classical behavior emerges from environmental decoherence. When a system entangles with both a dete... | [
"I'd add to your comment that wave function collapse in QM is ",
" time symmetric. A wave function can be collapsed, but we never see wave functions un-collapse."
] |
[
"If I hovered over a button with a 39-and-a-half million light-year long pole, would the button be pressed as soon as I moved the pole forward, or would there be a delay?"
] | [
false
] | null | [
"Check out the FAQ",
".",
"tl;dr: When you press on an object, that force travels through the object at the object's speed of sound."
] | [
"Oh that's embarrassing that this exact question is answered in the wiki. Should I remove it?",
"edit: Followup question concerning this answer: ",
"\"If I were to push on one end of the rod, I'm pushing on atoms on the surface, which will in turn push on the next layer of atom, and the next layer, etc. There i... | [
"No, it is not possible. The electromagnetic force is transmitted by photons which travel at the speed of light, so this is the absolute limit of speed at which an impulse can travel in an object. In reality though, the practical limit is ",
" lower."
] |
[
"Given that atoms are mostly empty space, what make matter opaque?"
] | [
false
] | Are photons too big to pass through the space? | [
"If you have a big crystal of diamond, then it is transparent, but if you have lots of small crystals the light scatters and it becomes opaque. Light scatters if there any changes in ordering, hence small crystals cause scattering, as do most powders. Diamond does not have electrons that can absorb photons of energ... | [
"Scattering of light is probably the main cause of opaqueness in the sense you're thinking of. Opaqueness is caused by scattering, reflection and absorption. Absorption is what makes materials coloured or black, and reflection is fairly self explanatory. ",
"Scattering",
" is what it sounds like, with light hit... | [
"For the absorption part of opacity, the photons typically excite the electrons to higher energies.",
"EDIT: Whether compounds absorb is based on their electron energy levels and imparts colour if we absorb in the visible range."
] |
[
"Why is the sky brighter on cloudy nights than on clear nights?"
] | [
false
] | I suspect the clouds disperse the light coming from the moon [reflected, I know], causing that to happen. | [
"You're correct! Unless it's a really thick cloud layer, the clouds will scatter extraterrestrial light and act as a diffuser. Don't forget that clouds will also reflect light coming from the earth (from cities and towns)."
] | [
"Ah yes, I forgot that our cities can generate an enormous amount of light. And now that I think about it, the brighter nights are the ones when the clouds are that very homogeneous, white layer. I also think the color is very interesting, 'cause at least around here, the sky is of a brown/orangeish color, which is... | [
"Clouds are essentially a thick clusterfuck of aerosols (water droplets and random particles). They aren't very good at absorbing visible light, so instead it bounces off a cloud's surface and back to Earth. This causes the sky to \"glow\" more so than usual. Technically speaking, thick clouds also bounce light fro... |
[
"Practicality way aside, could a non electrical computer exist?"
] | [
false
] | Monitor is electric and space is no issue. Obviously don't just create a generater and don't worry about online capabilities. Could simple programs be run through mechanics only? | [
"Yes, that is possible. The ",
"first computers were mechanical",
", in fact. They were mostly built to perform calculations, but nothing prevents you from stringing together addition, subtraction, and register shifts (i.e. recreate the basic commands of the assembly language) to make a computer that runs any k... | [
"There have also been surprisingly effective attempts to harness the computing powers of slime molds.",
"see:\n ",
"http://www.sciencedirect.com/science/article/pii/S136970211400025X",
"and",
"http://www.phychip.eu/",
"and",
"http://gigaom.com/2014/04/04/how-slime-mold-can-design-transportation-networks... | [
"Redstone works by transferring a current from a power source, which is similar enough to electricity to not count in a purely mechanical computer in my opinion at least. ",
"EDIT: deleted extra word"
] |
[
"how does mars' lower gravity effect Curiosity? Is the rover more efficient in terms of energy used to move the vehicle?"
] | [
false
] | null | [
"Depends on the terrain really. Lower gravity will generally give reduced traction for the same terrain type."
] | [
"True, but going uphill should be immensely easier in a lower gravity environment so long as the vehicle is able to maintain traction."
] | [
"it is not ''more efficient'' on mars, it was designed to work on mars. "
] |
[
"A Bunch of Questions Regarding Light, Light Bulbs, and How We Perceive Man-Made Light vs. Natural"
] | [
false
] | The first question is - Does man-made light travel at the same speed as natural light? Would the light produced by a light bulb still travel at the same speed as light from say, the sun? Or does some of the man-made properties of bulb (The glass, the filament, fixtures, amount of voltage/wattage, etc.) affect the speed... | [
"All light travels at the same speed, it's a fundamental property of light. Traveling through a medium can effect the speed, but that is the same regardless of its source. ",
"Light takes an amount of time to travel a given distance, so once a lightbulb burns out it does take some very short period of time for yo... | [
"Light always propagates at the same speed (give or take a minuscule amount given the refractive index of the material it's travelling through). Bulbs are Constructed so that an incoming amount of electricity heats or excites some material (i.e. the filament for an old incandescent bulb) and the material emits ligh... | [
"Interestingly, incandescence is basically the same process the sun uses to give of heat. Of course, it's hotter, so it emits the light in a bluer part of the spectrum. Fluorescence, on the other hand, is an entirely different process, that emits light of an entirely different kind of spectrum, and there actually h... |
[
"In medicine can 400mg vs. 600mg of some medicine actually mean they are stronger, not just quantity ?"
] | [
false
] | Probably a stupid question - seems obvious. The only reason I ask this is because where I'm from you can buy 400mg of a drug, but if you want to buy the 600mg version, you need a prescription. Obviously if instead of going to the doctor and getting a prescription you can just take more pills. Was just wondering if t... | [
"The activity of the drug molecule is unchanged.",
"I think the biggest concern is accidental overdose - doubling up on a 600 mg pill has a bigger impact than doubling up on a 400 mg pill.",
"On the flip side of things, I can see 3x 400 mg pills dissolving much faster than 2x 600 mg pill, even though the total ... | [
"The dose level that gives a therapeutic effect and the dose level that may start creating toxicities can be very very close. That's the point of measuring therapeutic drug levels, we like to make sure the dose is actually above therapeutic level, but below toxic levels in drugs where the margin for error between t... | [
"where did I give medical advice?"
] |
[
"What conditions lead to a deciduous forest, instead of evergreens?"
] | [
false
] | For example, why is the eastern US covered in hardwoods (oak, sycamore, basswood) while the west is primarily pine varieties? | [
"Frequency of wildfires can be a major decider as full grown evergreen trees (long needle pine for example) that are full grown often do not have branches very low in a wildfire's reach, where hardwood and deciduous trees will often be burned up entirely. This keeps a balance to many forested areas; the piedmont of... | [
"Based on many visits to Yellowstone and more than a few ranger-guided hikes therein, the lodgepole pines that constitute much of the forests there are especially adapted to fire. Under normal conditions, the trees respond to being burned by opening their cones and raining seeds all over the surrounding area. Thi... | [
"I don't dispute the notion that the most dire predictions proved wrong. However, my intent was to suggest \"very slow\" in comparison to how a totally natural pine forest would recover from a wildfire. There the saplings spring to life in a matter of weeks, and it only takes a few years for proper trees to start... |
[
"What failure modes on the Webb Telescope are the “electric heater strips” meant to avoid as it cools?"
] | [
false
] | NASA’s webb.nasa.gov site mentions that as the telescope cools, “[it] will be carefully controlled with strategically-placed electric heater strips.” I can imagine various warpings of the frame othat might happen if the scope cools unevenly, but I’m sure that’s too crude or just wrong. What are the specific failures fo... | [
"I suspect that these would have less to do with structural deformation and more to do with the operating temperature of the command and data handling subsystems. The optics need to be very cold, but the brains have to be warm enough to send and recieve commands, so an active thermal control subsystem is necessary.... | [
"The frames for space flight hardware can be made out of carbon fiber layups that maintain geometric stability over the temperature swings between the light and shady sides of the planet. Titanium joints have almost the same coefficient of thermal expansion as carbon fiber. Warping of such frameworks has been avoid... | [
"\"so that everything shrinks carefully and so that water trapped inside",
"\nparts of the observatory can escape as gas to the vacuum of space and",
"\nnot freeze as ice onto mirrors or detectors, which would degrade",
"\nscientific performance.\""
] |
[
"AskScience AMA Series: Hi Reddit - we are group of 250 engineers, scientists, innovators, technologists, digital experts, and designers with a collected 45 PhDs / Professors and 35 members representing national science or engineering institutions. AUA!"
] | [
false
] | A year ago, we did an answering science or technology questions on any topic from Reddit. We had a blast and so we're back again! So please ask us any questions any of you have to do with science or technology and how they affect your life. There are no silly questions - ask us anything and we will try to give an easy-... | [
"Professor Humber says that over the past 70 years plastics have revolutionised our every day and we now know that micro and nano plastic particles are everywhere and are increasingly contaminating every conceivable habitat. ",
"However, while there is evidence that large pieces of plastic can physically harm a... | [
"Time travel is absolutely possible but we have only worked out how to travel one way which is ‘forward in time’.",
"We call it time dilation and it doesn't quite work like in Hollywood or in Dr Who unfortunately. The way to explain this (simply) would be if you were travel in a space ship very quickly, time for ... | [
"What are some of the most game changing technologies available to homeowners today who want to be green, cut cost or just have a smarter home? Is there anything upcoming to keep an eye on?"
] |
[
"Why is there more matter than antimatter?"
] | [
false
] | null | [
"We don't know.",
"This question, often referred to as the \"baryon asymmetry problem\", is one of the major open questions in elementary physics.",
"It's natural to assume that matter and antimatter would've been created in equal quantities in the big bang, but the fact that there seems to be a very large imba... | [
"Symmetry. All processes we know produce and destroy matter and antimatter in equal amounts - with deviations so small that they don't explain the asymmetry we see today. At the time matter and antimatter formed some process must have formed more matter than antimatter."
] | [
"Why is it natural to assume that matter and antimatter were created in equal quantities?"
] |
[
"Is gravity 3D? Would it be possible to establish an orbit from Earth's north pole to south pole, with no lateral movement relative to the poles?"
] | [
false
] | So the way I've always seen gravity represented is that spacetime is distorted around mass. However, the fact that planetary orbits and even human satellites all orbit along a rough plane confuses me. For example, is former due to just how the sun distorts spacetime into a gravity well? Or is it possible, assuming temp... | [
"The \"distorted rubber sheet\" view of gravity is misleading because it's only trying to show you how strong gravity is in a single plane of space cut horizontally though the earth. The dip then represents the strength of the gravitational field (the \"distortion\" of spacetime) but the dip doesn't at all represe... | [
"So the way I've always seen gravity represented is that spacetime is distorted around mass. However, the fact that planetary orbits and even human satellites all orbit along a rough plane confuses me. ",
"Planetary orbits are roughly all on the same plane because of how the solar system form. It started as a rot... | [
"GPS satellites are not in geostationary orbit, their orbits are considerably lower. ",
"https://en.wikipedia.org/wiki/Global_Positioning_System#Structure"
] |
[
"How much heat does the earth lose to space?"
] | [
false
] | I hear a lot about global warming and it got me thinking that the earth must naturally lose a lot of heat out into space over any given period, so how much are we losing? | [
"The rate of heat lost by Earth is given by the Stefan-Boltzmann law. It states that the rate is proportional to the fourth power of temperature of Earth’s surface, multiplied by a constant and a physical quantity called emissivity, which is the ratio of energy radiated compared to a “perfect” object. With an avera... | [
"First, the amount of heat we are losing is nearly exactly the same as the amount that the sun puts in. There is actually slightly more output, because of the internal heat of the Earth leaking out (meaning the heat contained in the core and mantle that only ",
" comes out as volcanoes.) This energy balance is ... | [
"There is actually slightly more output, because of the internal heat of the Earth leaking out (meaning the heat contained in the core and mantle that only visibly comes out as volcanoes.)",
"Currently, Earth's yearly output is actually slightly less than it's yearly input! You're right that over long periods of ... |
[
"How is it that a projector can make something look bright white on a tan wall?"
] | [
false
] | We use a projector on tan/off white walls at work, and they look like they're brilliant white. How does this work? My guess is that it has something to do with the light absorption rate of the paint/wall surface. | [
"Your eyes actually can adjust or \"white balance\" quite dramatically without you even noticing. For example, the outdoor light is much, much bluer than indoor light, but when you look at your clothes in both environments they don't seem to change color. Hope that makes sense."
] | [
"The green and blue \"arms\" are actually the same color. Exactly the same."
] | [
"Our perception of \"color\" isn't the same as the scientific description of \"what frequencies of light are absorbed/emitted?\" They overlap in a lot of ways, true, but they aren't exactly the same.",
"Consider the many optical illusions where you perceive a color other than what the real spectrum of light actua... |
[
"How much energy could the US save by raising the average temperature of air conditions by 2 Fahrenheit degrees / 1 Celcius degree?"
] | [
false
] | I was wondering how much energy could be saved just by not cooling down houses, malls, office buildings etc by a few degrees. To my understanding 1 degree Celcius equals around 1.8 degrees Fahrenheit. Average recommended temperature for apartments is around 20-22 degrees Celcius (around 68-72 degree Fahrenheit) in Cent... | [
"Interesting. So that means around 150.000 MWh could be saved assuming an average price of $0.30 per kWh.\nAny idea about commercial buildings such as office buildings, malls, stores and so on."
] | [
"Interesting. So that means around 150.000 MWh could be saved assuming an average price of $0.30 per kWh.\nAny idea about commercial buildings such as office buildings, malls, stores and so on."
] | [
"It'd require some recalculation for the U.S., but ",
"here's a piece",
"about Japan trying to do the same thing."
] |
[
"How do insects heal? I think we've all accidentally pulled a leg off a grasshopper at one point."
] | [
false
] | Also curious about arachnids, especially spiders, since they're effectively hydraulic. | [
"Many insects have a life cycle of egg > larva > pupa > adult. Basically, once it hits the pupa stage, there isn't much that can be done to heal any damage. The cuticle (or exoskeleton) cannot be repaired as molting only happens during the egg/larval stages, so any damage to that lasts the rest of the insect's li... | [
"Grasshoppers (and all other insects) cannot regrow limbs once they are completely mature, as they stop replacing their exoskeleton once they are mature.",
"\nHowever, in the case of grasshoppers, mantids, cicadas, cockroaches, and mayflies, their immature forms look very similar to their mature forms, and it is ... | [
"So the adults feed from the larvae, yet what do the larvae eat?"
] |
[
"So do we consider spacetime flat or curved after all? And could dark matter just be the result of curved spacetime?"
] | [
false
] | I know that Dark Matter is responsible for 85% of the gravitational force in the universe. I also know that the universe shows to be having critical density indicating that spacetime is flat. However according to Einstein's Theory of General Relativity he claims that spacetime is curved and Gravity isn't really a force... | [
"Spacetime is certainly curved. The critical density means that, on average, ",
" is flat, but because it's expanding, space",
" is curved (it's just curved \"in the time direction,\" in a manner of speaking). And that's only on average, i.e., if you smooth things out over scales bigger than a few hundred milli... | [
"It does have a local presence, in most models, but because it only interacts very weakly, its effect is quite small. It's most noticeable on very large scales because that's where gravity is most important, when electric charges balance out to zero and only the gravitational force is left. This is not unusual; neu... | [
"What's the current explanation of why there is so much dark matter but it has no local presence ? also do you think eventually we'll eventually whittle away the need for dark matter as more sources of classical matter are discovered?"
] |
[
"Time dilation question."
] | [
false
] | If velocity can augment time relative to another slower point, would a planet revolving around a star faster than ours and having that star orbit faster around its galaxy produce a noticeable dilation effect? | [
"Depends on the gravitational fields around the two planets, too. There is gravitational time dilation."
] | [
"Well, the earth orbits the sun at around 18.6 miles/second.",
"Mercury, the fastest planet in terms of orbital speed around the sun, moves at about 30 miles/second.",
"Light speed is 186,282 miles/second.",
"So, earth is moving at 0.009% of the speed of light.",
"Mercury is moving at 0.016% of the speed of... | [
"Define \"noticeable\".",
"Scientists can measure a difference with our satellites or even flying super accurate clocks on a plane.",
"That said the dilation effect is miniscule.",
"The effect becomes greater faster the closer you get to light speed. The really noticeable effects (to humans without equipment... |
[
"Does the vast amount of air-conditioning units running year round have an affect on global warming? They seem like they produce more heat than cool air overall and with temperatures rising globaly they are more and more common."
] | [
false
] | null | [
"Air conditioning units always produce more hot air than cool air overall, this is a basic thermodynamic principle. Compare this to your fridge, which gets hot outside (on the back), but cools its inside. This is why if you would leave your fridge open on a hot day, the fridge would ",
" up your house overall.",
... | [
"There are some people who legitimately believe that it will help cool down their house"
] | [
"They definitely have a localized effect that can be seen in and around cities. But this is also due to reduced greenery and paved roads. You want to look up Heat Islands. As a worldwide contribution air conditioner direct heat output is tiny in the scheme of things. It's more important to look at what fuels are bu... |
[
"How do brute-force decryption programs know when they are successful? If I encrypted gibberish or a made-up language would it be able to pick it out?"
] | [
false
] | I guess you could look at letter frequency and bayesian methods to discern gibberish from cleartext? Alternatively, suppose I encrypted my message, then encrypted it again with a different key. Would a brute-force program be able to notice the difference between guessing the correct and incorrect keys for the second le... | [
"Data to be encrypted generally has some order that can be discerned. Many file types have a header that allows programs to identify it given nothing more than the first few bytes. If the attacker knows that the encrypted contents is such a file then they can look for known headers and identify a correctly-decryp... | [
"Typically, the assumption is that a brute force attacker has some idea of how you're doing the encryption, so that there's a way for them to work out whether they've guessed right.",
"For example, one of the common scenarios is where the attacker knows some plaintext, the corresponding cyphertext, and is trying ... | [
"This question has actually already been answered quite recently. Please refer to ",
"this thread",
".",
"I guess you could look at letter frequency and bayesian methods to discern gibberish from cleartext?",
"Yes you could, if you are quite certain the cleartext will be plain text. Additionally, without kn... |
[
"How close to the sun would I have to keep my cup of coffee for it to remain the same temperature indefinitely?"
] | [
false
] | null | [
"I'll assume your coffee enclosed in a sphere situated somewhere in space.\nThe coffee will lose energy by (black body) radiation - the Stefan-Boltzmann T",
" law: ",
"https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law",
"\nAlso your coffee will receive energy from the Sun.",
"So, your coffee temper... | [
"Well... If wel assume the sun to radiate evenly in time, so no spikes in heat radiation and such, any place will do. The temperature of your coffee will depend on the distance to the sun, but it will stabilise at a certain temperature. "
] | [
"OP is correct. The surface area of a sphere is 4 times the area of a circle with the same radius. That is the area that catches the suns radiation. A hemisphere is actually illuminated, but almost all of that hemisphere is not directly facing the sun so it is not receiving full sunlight.",
"However the OP is ass... |
[
"Is the current number of human beings alive higher or lower than the number of humans that have died?"
] | [
false
] | I don't know how to properly phrase this question so bare with me. In an exercise about problem solving techniques this question arose. Is the number of current human beings alive higher or lower than the total number of humans that have died since the human race exist (or some early point in history)? It's hard to def... | [
"If you define the current species as having emerged 50,000 years ago, then there have been about 100 billion people who have been born.\nSince there are 7-8 billion people alive now, that means that there are about 8% of all people who have ever lived are alive now. Which quite frankly is a huge proportion.",
"T... | [
"It doesn't really matter, to be honest. The estimated number of humans 200,000 years ago is between 10,000 and 30,000, dipping as low as potentially 1,000 humans at one point. Counting all the way back to 200,000 years ago would only bump the data up by half a billion or so at most, so 0.5% increase."
] | [
"Why are the religious estimates even relevant to a clearly scientifically charged question?"
] |
[
"How and why did they detonate the little boy 580 meters above Hiroshima?"
] | [
false
] | null | [
"When you set off a large explosion, if you have an idea of how big it is, you can set it off in a way that will cause the blast wave to reflect off of the ground. This reflected wave moves faster than the initial blast wave, and can catch up to it. When it catches up to it, it creates an even more powerful effect.... | [
"Detonating above the earth ensures that the majority of the energy is expended to the surface rather than below the surface. They did so using a 3-stage interlocked fuse system that relied on a combination of timing, barometric pressure, and radar altimeters to detect the correct height."
] | [
"Altimeter trigger. There were a couple of radar altimeters included in the case which detect the distance to t he ground. When they showed the bombs had reached the right altitude the bomb detonated. ",
"Course this was 40s technology and they wanted redundancy so they had to use a whole bunch of components to ... |
[
"Is there a scientific explanation to why, when I'm passing a scooter outside the city with my car, there's almost every time another car in the incoming lane, and the three vehicles always meet at the same place, in a line?"
] | [
false
] | null | [
"http://www.reddit.com/r/askscience/wiki/index#wiki_avoid_questions_about_personal_or_isolated_events"
] | [
"I don't see how you can expect a ",
" answer to this ",
".",
"I've removed the question for the cited reason."
] | [
"I don't see how you can expect a ",
" answer to this ",
".",
"I've removed the question for the cited reason."
] |
[
"How did the MESSENGER space probe use Mercury's gravity to slow itself down?"
] | [
false
] | [deleted] | [
"The technique is called ",
"Gravity assist",
".\nIt's been used a lot in space missions that take place beyond Earth and rarely even in Earth satellite missions. For example, its been used by both Voyager missions or even the current New Horizons mission to boost velocity. On the Messenger mission it was used ... | [
"Adding to this, due to restrictions on shuttle payloads, Galileo used three gravity assists: one with Venus and two with Earth, instead of directly boosting to Jupiter as originally planned. "
] | [
"The probe is effectively 'giving' it's momentum to Mercury and the result is that it slows down. Gravity helps transfer the momentum. ",
"Imagine two people are skateboarding on parallel paths. Also imagine one person behind the other but moving slightly faster. Now as the person in back approaches the person in... |
[
"Are there any animal/plant species that are considered native to every continent?"
] | [
false
] | Except Antarctica, of course. My friend and I were arguing about this earlier and I'm really curious to know if it is possible at all. | [
"The Barn Owl (",
") is the most ",
"widely distributed",
" species of owl, and one of the most widespread of all birds. ",
" is found almost anywhere in the world except polar and desert regions, Asia north of the Alpide belt, most of Indonesia, and the Pacific islands.",
"http://en.wikipedia.org/wiki/Ba... | [
"The peregrine falcon is even more widely distributed. It is only absent in polar caps, deserts and rainforests."
] | [
"tardagrades, water bears, are semi-microscopic organisms that are native to every continent... defining species for microorganisms is a bit tricky though, so its not exactly the same as saying like a lion verse a tiger.",
"Also Diatoms (small snowflake looking algae like organism) have been found all over the wo... |
[
"Does voluntary exposure to germs increase your immunity against them?"
] | [
false
] | null | [
"Yes, but there is a catch. While controlled exposure to bacteria and viruses, such as immunity from vaccines, either kill or modify the bug in a way to render it (mostly) harmless, exposure by natural means can make you sick, or even be deadly because the bugs are not modified in a way to render them harmless, or ... | [
"How about a garden variety (heh) tactic of “voluntary” exposure like letting a pet dog lick your face?",
"Stopping short of eating dirt.",
"The question read to me like exposure being voluntary could potentially “brace” your immune system or let it somehow be known you’re willingly going into probably not leth... | [
"You immune system doesn't know what your intentions are. Nor do you always know (outside controlled things like vaccines) what you're exposing your immune system to."
] |
[
"How far will lightning change course to follow the path of least resistance?"
] | [
false
] | Exactly as the question states, how much will lightning change it's course to follow the path of least resistance? | [
"but not going to go 1000 miles to the right because it's less resistant. ",
"Yes it would, if it actually ",
" less resistive. It probably won't be, though."
] | [
"Well if you watch lightning in slow motion, it doesn't follow a single path. There are \"feelers\" that grow up from the ground as well as descend from above. These feelers fan out trying to find a path to eliminate the potential energy. Once a feelers leg finds the leg of another, you now have a direct short to g... | [
"To expand upon this, here is a Gif of a lightning strike in very slow motion. ",
"http://julianware.com/main/wp-content/uploads/2011/03/slow-motion-lightning.gif",
"Charge starts building up in the lower part of the clouds. The amount of charge become so great that the air undergoes \"dielectric breakdown\",... |
[
"What would happen if two hurricanes merged?Hurricanes Leslie and Michael are getting pretty close to each other in the mid-Atlantic."
] | [
false
] | The NHC at NOAA has the storms' tropical storm wind speed maps partially merging: What would happen if both storms merged into one? Would the wind speeds compound? Would they most likely counteract each other and fizzle out? Would it just be a giant, otherwise normal, hurricane? I'm not a meteorologist, just a curious ... | [
"Note that those maps are probabilities of a given wind speed from ",
" storm, and Leslie and Michael are not expected to merge at this time.",
"However, there is nothing which would prevent two storms from merging (this actually happens quite often with non-tropical storms). By the nature of what is known as t... | [
"There is no simple formula. The atmosphere is an extremely chaotic system. Any of these scenarios are possible, but the most likely is that if two substantial systems formed, the merged system would start out weaker, since the strength of a hurricane depends greatly on the fine structure. This is why hurricanes ar... | [
"There is no simple formula. The atmosphere is an extremely chaotic system. Any of these scenarios are possible, but the most likely is that if two substantial systems formed, the merged system would start out weaker, since the strength of a hurricane depends greatly on the fine structure. This is why hurricanes ar... |
[
"Double Slit Experiment, how does it work?"
] | [
false
] | I saw this animation but I don't understand what the heck is going on. Waves create interference patterns. Marbles do not. When you shoot matter, electrons, it creates the interference pattern result but if you put a camera up close it goes back to the same thing as the marble??? | [
"Disclaimer: I did not watch the video, though I have a decent grasp of quantum and the double slit experiment.",
"One of the big problems that people have with quantum is that they can't accept the idea that before we measure where the electron is, the electron ",
". The electron's \"location\" (not very well ... | [
"OP ignore this; it's nonsense."
] | [
"OP ignore this; it's nonsense."
] |
[
"Is there actually a correlation between high intelligence / IQ and poor social skills?"
] | [
false
] | Is there any truth about the general interpretation or portrayal of those with high iq's or those with a good knowledge of academics, as they are often portrayed as socially inept, behave in wierd and anti-social/asocial ways, having poor social skills and have troubled minds, both emotionally and psychologically, and ... | [
"Edit: Just realized I misunderstood your question. The correlation exists but in the other direction; high IQ correlates with more social skills not the other way around "
] | [
"The traditional and most commonly used test to measure IQ (WAIS) includes many sub tests. Some of them measure things that one may think as social skills. For instance, one portion measures whether the person knows common sense information about the world. Also part of the IQ test is a clinical and behavioral inte... | [
"that's funny. I thought I always assumed the opposite, just like plenty of people state",
"even Nikola Tesla once mentioned 'anti social behaviour is a sign of intellgence in a world full of conformists'",
"or another quote from the bible, 'thou increase in knowledge, increase in sorrow' (if I remember it corr... |
[
"What is the antiseptic mechanism behind basic molecules like Hypochlorite, Sulfite, Hydrogen peroxide ?"
] | [
false
] | null | [
"I found an answer to your question. The antiseptic mechanism is complicated, and each chemical contributes in a unique way.",
"For example, Hydrogen peroxide releases a ROS (oxygen) that kills cells in a variety of ways: \"In addition to direct damage of cell membranes and structural proteins of the extracelluar... | [
"Excellent answer. ROS = Reactive oxygen specie. This is basically oxygen molecule that lacks only one electron to be stable so it will rip an electron from the closest molecule. This tends to create other free radicals (molecule lacking only one electron to be stable) and can create chain reaction of cellular dama... | [
"ROS does harm your cells, but normally they are neutralised before too much damage can be caused, or they are generated in the \"right place\". There are several mechanisms involved in \"mopping up\" ROS, including several forms of the enzyme superoxide dismutase, and reduced glutathione, which is able to be oxid... |
[
"Why did evolution favored woman not to have facial hair?"
] | [
false
] | I was wondering if there are facts or theories to as why woman don't have facial hair compared to men. Thanx! | [
"I remember learning about the sexual differentiations between males and females in psych class (taught by Steve Pinker, about 10 years ago). As I remember it, it stems from males seeking young females, which would be best equipped to have many years ahead of bearing potential offspring. Generally, more body and fa... | [
"I would be interested to know the answer to this, besides the obvious layman answer \"because no one would tap that bearded woman\".",
"As a secondary question:\nWhy is body hair more prominent in certain races more than others? Is this linked to OP's question? "
] | [
"besides the obvious layman answer \"because no one would tap that bearded woman\" ",
"That might actually be the answer. Sexual selection is one of the driving forces behind evolution. If males started to prefer females with less hair at some point (for whatever reason), hairy females would've become less likel... |
[
"When we breath in and out, why does the oxygen we just breathed in go to our lungs rather than just coming back out again and what stops the carbon dioxide from going back to our lungs?"
] | [
false
] | [deleted] | [
"Cells throughout your body consume oxygen (which they take out of the bloodstream) and produce carbon dioxide as a waste product (which they dump back out into the bloodstream). This blood then returns to the right side of the heart which will pump it to the lungs. In the lungs the blood moves into smaller and sma... | [
"Not really. The surface area of the air-blood interface in the lung is enormous (",
"Wikipedia",
" says 50-75 square meters, or about half the size of a tennis court) and thus will equalize in less time than the duration of an average breath. Remember, during exercise your breath rate increases and you are sti... | [
"Does the oxygen intake percentage increase if you hold the air in your lungs for a couple seconds or if you rapidly exhale into and inhale from your closed mouth a few times before taking a real external breath?"
] |
[
"How does a GPS device synchronise its internal clock?"
] | [
false
] | [deleted] | [
"The basic measurement in GPS is the pseudorange: receive time minus transmit time. The ",
" is because of the clock errors. Both the receiver and satellites have clock errors, but the satellite clock errors are precisely known, and provided in the broadcast satellite data. The receiver clock offset is computed a... | [
"The receiver doesn't need to \"know\" the time at its location beforehand. It calculates the point on the globe where the multiple signals can be received with their differing times. I think you are assuming that the receiver subtracts its local time from each of the received signals to calculate the time of flig... | [
"With FOUR satellites, you can get four equations for the four unknowns x, y, z, and t. So you don't need to know the time in advance: you can solve for it. "
] |
[
"Why are some pharmaceuticals bounded to an hydrochloride and some to an hydrobromide?"
] | [
false
] | Dextromethorphan is typically solubilized with HBr while morphine is often made into a salt with HCl. Why not always HCl? Is there such a difference between the solubilities? | [
"There is a difference in how well the crystals form. Larger ions like larger counter-ions, typically, to make stable crystals. When making the drug you want stable crystals to recover the most product cleanly at the end of the manufacturing process."
] | [
"But to your question, there is a difference in solubilities, too. To get the right dosage at the right timing you often can change up the counter ions to have a quicker release or a more delayed dosage, depending on the desired effect. The latter is an effect of the solubility kinetics, while the solubility is a t... | [
"Hadn't thought of that. It makes a lot of sense."
] |
[
"Can photons red-shift due to gravity wave losses?"
] | [
false
] | I have heard photons have momentum, and with it an effect on gravity. If large masses slowly lose speed due to radiating gravity waves, could photons be affected similarly over long enough distances? Would it change our estimates of galaxy speeds? Edits: For more clarification, I am asking about the red-shift due to ... | [
"Gravity waves are things like water waves. You mean gravitational waves.",
"Things moving at a constant velocity don't emit gravitational waves. Consider the paradox this would produce for massive objects: They move in some reference frames, but they don't move e.g. relative to itself. If they would slow down in... | [
"Gravitational waves are only produced by objects that are accelerating. Since acceleration is a vector quantity, this applies not only to changing linear velocity, but also to changing direction, which is why rotating/orbiting objects can create waves (for a single rotating object, there must be some asymmetry to ... | [
"As others said photons cannot themselves emit gravitational waves. However, it is possible to generate gravitational waves by emitting photons in an asymmetric way, e.g., by radiating more in one direction than in the others. This effect is sometimes called the gravitational wave (linear) memory effect. ",
"That... |
[
"How important are sextants in modern oceanography?"
] | [
false
] | I’ve had this question stuck in my head for a few weeks now because I just had a physical oceanography class where we just learned how to use sextants. I was just wondering if sextants are even used in the modern world anymore since of GPS. Any help is highly appreciated! | [
"They're the analog backup to any failure in electronic methods. Every sailor should still be comfortable using one. NASA is sending one to the space station soon to test its possible usefulness in space navigation. "
] | [
"Disclaimer: As my flair should indicate I am not an oceanographer, but a broader version of this question is 'How important are traditional skills for locating oneself in the Earth Sciences?' and that's something I feel (VERY) passionately about so I'm going to provide an answer while we wait for a more 'oceanogra... | [
"I'll offer this anecdote to explain my feelings (at least as far as being able to read topographic maps are concerned). I am a field geologist, location of observations are primary data for me. I work in foreign countries. It is expensive to travel to and conduct field work in these places (a single standard field... |
[
"Why is the sound of someone grinding their teeth in their sleep so dramatic and \"cracky?\""
] | [
false
] | My 5 year old son grinds his teeth at night but the sound makes it seem like he's cracking them into pieces! It reminds me of cracking open walnuts or how ice cracks when you pour room temperature liquid over it. We are going to the dentist this week to talk about it and perhaps having him wear a mouth guard at night.... | [
"Not a very satisfying answer but its really just a result of the physical and acoustic properties of bone. It's denser that the rest of your body and therefore sound travels more easily. I imagine the sound is also boosted as it reverberates through the nose and sinus cavities"
] | [
"While I agree that this isn't a satisfying answer, it does make sense ;-) Thanks all the same. "
] | [
"My 5 year old son does the same thing. It is frightening. I'm sorry you are experiencing this also!"
] |
[
"Question on the validity of Superposition"
] | [
false
] | The Law of Superposition states: "In any undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below." (Lutgens, Frederick, and Edward Tarbuck. Ed. . 9th ed. Prentice Hall, 2005. Print.) I recall hearing, in a scientific argument for Noah's flood and against the certain... | [
"Please don't let this turn into a religious discussion. I bet there are a bunch of geologists here who could give highly informative answers if we avoid turning this thread into one that belongs in ",
"/r/atheism",
"."
] | [
"no such undisturbed sequence has actually been found, meaning that our fossil records are inaccurately formed. Can somebody disprove this?",
"That's absolutely incorrect. There are such a fantastically large number of counter-examples that I don't know where to start. Modern lake beds, ocean beds, rivers, alluvi... | [
"If you would only accept layers of sediment laid down as neatly as the parts of a pristine BLT sandwich, then you are probably never going to be satisfied with the applications of the law of superposition to geological time. ",
"However, the whole point of geology is to interpret stratigraphy when those layers ... |
[
"what is the fourth dimension?"
] | [
false
] | I was taught that the first dimension was a point, the second was a flat line, and the third was a box. I have never known what the fourth dimension was though. I have searched it online and came up with conflicting results. | [
"It depends on the context. In mathematics, a dimension is just a coordinate. So (x,y,z,t) for example could be the length, width, height, and time. Or the temperature, pressure, volume, and number of molecules. Or anything measureable. So the \"fourth dimension\" could be anything relevant.",
"In physics, we usu... | [
"The fourth dimension is time when you are referring to a concept called ",
"Minkowski space",
", which is one of the easier ways to describe spacetime when you're going to do calculations involving relativity.",
"It's important to note that Minkowski space is ",
" shaped in a way that you could imagine as ... | [
"this was also helpful to see the mathematical side too."
] |
[
"Which type of light do solar panels run on? Thus can you run a solar calculator from room lights or does it need to be from the sun?"
] | [
false
] | null | [
"Solar panels use the visual light spectrum, so you could run it off of a lightbulb if you wanted to.",
"But why? You'll never get back as much energy from the solar panel as you will spend powering the light bulb because even if your solar panels were literally the best they could ever be you'll still have to lo... | [
"He asked about a calculator and you went to perpetual motion machine?"
] | [
"No. You won't get even a 2% charge. The phone will not charge at all unless there is enough voltage and current. Calculators can run on room lighting because they need a tiny fraction of the power a phone needs. The cost to charge a phone from AC is about 55 cents/year. Electricity is incredibly cheap unless you u... |
[
"In-grown hairs: Why can't the body differentiate b/t foreign contaminants and objects native to the body?"
] | [
false
] | In this specific case, I get a large amount of ingrown hairs on my face. While this is a nusiance, my main question is why does the body treat a hair, something the body produces itself, and a foreign object, like a splinter, the same way? Pus, inflamation, pain, etc. Shouldn't I be able to break down that hair under m... | [
"Inflammation is a general response to danger. Most often, it occurs because the immune system directly senses the presence of a potentially pathogenic organism (virus/bacteria etc). However, we also have mechanisms to detect things that might be correlated with danger, even in the absence of those specific signals... | [
"Hair is mainly composed of keratin, not collagen.",
"The main reason I can think of as to why ingrown hairs cause inflammation is that once a newly synthesized hair is exposed to the outside world, it starts to pick up bacteria. It probably even picks up bacteria from your normal skin microbiome on its way out. ... | [
"You should take that \"I'm guessing\" off... Because your answer is correct (or at least part of what is going on) and people tend to downvote you if you \"guess\" even if your answer is correct."
] |
[
"Why does the boiling point of water rise when you put salt in it?"
] | [
false
] | [deleted] | [
"The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. ",
"Salt is non-volatile. A non-volatile solute has a vapor pressure of zero, so the vapor pressure of the solution (salt and water) is les... | [
"Simply put, think of it this way:",
"Would it be faster to boil one cup of water or three cups of water? More number of particles does not mean it's faster in gaining heat, in fact, it's the opposite.",
"I think you may be confused about the definition of boiling point. It is a temperature. Your understanding ... | [
"Adding salt in water only marginaly elevates the boiling point, unless you use a lot of salt. 10g of salt in 1L of water makes the mix boil at 100.2°C instead of 100°C for pure water. You would have to put over 20% salt to the water (so over 200g per liter) to have a significant effect."
] |
[
"How Does Sound Combine to be Louder?"
] | [
false
] | Example: One person yelling at the top of their lungs is loud when close-up, but take 10000 people yelling at the same volume and it becomes deafening and audible from a long distance. What is the science of sound combining and becoming more powerful? Update: Thank you for the great responses! Constructive interfe... | [
"Sound deposits energy into the air by exciting vibrations. More people means more energy density equals more sound. You can carefully construct sound to interfere and even cancel out -- if you take two speakers playing a monotone and separate them by some distance, there will be points at which there is no sound d... | [
"If you're looking for zones where there is exact cancellation, they don't have a range of distance. Exact dead zones are actually just certain points at which the difference in distances travelled (path difference) by the two waves from the two speakers is a certain value, which does depend on the wavelength."
] | [
"Sound is physically just pressure waves in the air. When two waves overlap, they add together, because if you pressurize something that is already pressurized, it gets more pressurized. Obviously there's a limit to which air can be pressurized, but in practice that limit is much much higher than most sounds are."
... |
[
"Is there a standard distance for measuring decibels?"
] | [
false
] | We've all heard supposed decibel levels for different things. A jet plane might be 130-140 dB. But where is this measured from? I would imagine for certain things, like a chainsaw, it's measured from an assumed distance (from the engine to your ears). What would it be for a jet engine, though? Is there a different ... | [
"Out in the field, the measurement is often taken where the sound is going to be commonly perceived. Distance plays a big factor in sound, see the ",
"inverse square law",
". ",
"But, a lot of equipment is measured in anechoic chambers which allows us to know how many decibels the actual piece of equipment ge... | [
"While ",
"/u/Westicle",
" is right about decibel being a unit of comparison, he did not actually answer the OP's question.\nI have a quote from wikipedia article on ",
"Decibel",
" which actually confirms to what i've been taught in school:",
"The decibel is commonly used in acoustics as a unit of sound ... | [
"Actually, I wouldn't consider it valid at all. Purely because the question in itself is ",
" nonsensical. Like most measurements, we absolutely need a ",
" to our data. The distance isn't predefined, nor does it need to be. Because instead of defining it, it's considered during analysis. An example of this, is... |
[
"(X-post from r/science) If this stuff is lighter than air, why doesn't it float?"
] | [
false
] | Here is a link to the article: I've checked out the densities and, indeed, aerographite is less dense than air (sources: , ). So what's the deal here? Why doesn't this stuff float in air? | [
"This is outside my area of expertise, but my understanding is that aerographite has such a low density because it's sort of like a mesh; the volume is larger than just the carbon bits out of which it's composed, which reduces the overall density of the structure. For a totally exaggerated analogy, imagine that you... | [
"So they actually got the density wrong, because they got the volume wrong.\nI always use the 'throw it in a bathtub and see how much volume gets displaced' analogy. This way, if a material is porous, the density goes up, because the voids dont count as volume."
] | [
"This. The cube analogy is a bit confusing, but aerographite itself is less dense than air, but with air in it's void space, it's more dense than air.",
"If you were to somehow evacuate the \"pores,\" aerographite would float away. Likewise, the above iron cube would do the same if the air inside were evacuated."... |
[
"How did umbilical cords work before modern surgery, lets say the stoneage? Did they just fall off? Did humans just have pieces of gut dangling for a while?"
] | [
false
] | Like bruh what did their belly buttons look like | [
"Same way it works for all mammals. The umbilical connects the belly to the placenta, which is also ejected at birth.",
"So the baby keeps getting nourishment from the placenta until blood stops flowing, at which point the cord begins to wither, eventually falling off just like the clipped ones do.",
"[edit] A... | [
"Should have kept it preserved so you could take it out to gross-out/embarrass her/friends/future-significant-other in later years."
] | [
"Typically, nonhuman mammal mothers cut the cord with their teeth and eat it, along with the placenta.",
"https://www.reddit.com/r/askscience/comments/rybip/how_do_nonhuman_primates_remove_the_umbilical/"
] |
[
"Why do we launch space-bound shuttles straight up?"
] | [
false
] | Why do we launch spaceships straight up? Wouldn't it take less force to take off like a plane then climb as opposed to fighting gravity so head on? | [
"It's like in Mario Kart where if you drive off the side into the mud, the drag slows you down. If you drive back to the road in a perpendicular fashion, you minimize your time in the mud, but you've built up no momentum once you get to the road. If you drive parallel and angle yourself gradually toward the road, y... | [
"Also, launching them straight down has had statistically less successful results."
] | [
"Getting to orbit isn't about altitude nearly as much as it's about velocity.",
"With the exception of the very beginning of launch, the major component of the shuttle's velocity actually ",
" parallel to the surface of the Earth; you can see this clearly in ",
"photographs like this one.",
"As the shuttle ... |
[
"Why do vulcanoes create lightning when they explode?"
] | [
false
] | [deleted] | [
"When a volcano erupts it ejects hot ash into the atmosphere, which can become electrically charged. These ash particles interact with each other, creating static electricity. There can also be ice formation in the plume, which helps to drive an electric charge. The ice forms, at least sometimes, as vapor inside th... | [
"I've always found it very unsatisfactory how people just say \"rubbing creates charges\" and then move on. But how it actually works has interestingly been a conundrum for thousands of years. I found a very recent paper on the issue that offers an attractive explanation (link to it in the article): ",
"https://w... | [
"If I were trying to explain why friction aids in generating a charge then I'd agree. However the question was why do volcanoes create lightning and not why does friction aid in generating a charge. ",
"Given the scope of the question I feel that likening the charge to an accessible experience most have had (stat... |
[
"Why do onions turn clear when fried?"
] | [
false
] | Your onion bits start off really opaque and then turn noticeably more translucent as they cook. What sort of reaction is happening to turn them clear as they cook? | [
"Cooking the onion breaks down some of the chemicals in the onion (including the chemical irritant known as syn-propanethial-S-oxide -- the one that makes you cry), as well as causing some of the water to evaporate out of the onion. These chemicals (including the water) give the onion its opaque white color. Cookin... | [
"I know this is part of your side note, but if the pigment from a red onion is released when being cooked, can that pigment stain other foods? Say if it were red onion and white rice (maybe some recipe calls for it), would the rice turn a slight pinkish tone?"
] | [
"Please provide a source. Tissue transparency is a function of light scattering at visible wavelengths."
] |
[
"What collapses a wave function?"
] | [
false
] | [deleted] | [
"He said that a conscious observation was needed to collapse the wave function.",
"This is complete and utter bullshit that is propagated by people who are entirely talking out of their ass. It is simply an interaction between particles that causes the WF to collapse. ",
"Does it really matter whether the obser... | [
"Then he says that they had the observing machine on, but did not collect any data and the wave function did not collapse (@ 2:30). He said that a conscious observation was needed to collapse the wave function. Everything I think I know about the universe goes against that line of reasoning.",
"That's because thi... | [
"It is simply an interaction between particles that causes the WF to collapse.",
"No it's not. Particle interactions are described by unitary time evolution exactly the same as freely propagating particles are. Particle interactions are roughly time-reversal invariant but wavefunction collapse definitely isn't.",... |
[
"Pigeons Head Bobbing?"
] | [
false
] | Is the way pigeons' head bob when they walk psychological (like swinging our arms when we walk)? Or is it physical (ie. they can't walk if their head doesn't move)? | [
"Firstly, I'm not sure if arm swinging is merely \"psychological\" - it increases stability and efficiency of our movements. (",
"http://en.wikipedia.org/wiki/Arm_swing_in_human_locomotion",
")",
"Secondly, as ",
"/u/seriousSeb",
" mentioned, the head bob is to do with eyes working best when they are stil... | [
"I don't know if pigeons must headbob in order to walk correctly ",
", but that isn't why they evolved to bob their heads in the first place",
"When a bird's head bobs, it is motionless relative to the environment it's walking in",
"A still head means their eyes are steadier, thus can see their environment in... | [
"I always though there were 3 types of \"walking\" birds do. The pigeon bob, the parrot waddle and the sparrow hop... Oh and I guess emu and ostriches etc walk 'normally'.",
"Do they all technically bob their heads as well to compensate like you said?"
] |
[
"If a mother has a blood-born disease like HIV/AIDS, what are the chances she will transfer it to the fetus?"
] | [
true
] | [deleted] | [
"For HIV, if the mother doesn't have some kind of treatment to reduce viral load, about 1 in 4. ",
"Transmission is usually perinatal, though; that is, it happens during birth. Sometimes nursing, too, IIRC. (",
"source",
")",
"But AFAIK, HIV and most bloodborne disease is not transmissible across the placen... | [
"How come it can't cross the placenta?"
] | [
"With modern medicine, vertical transmission (mother to child) of HIV can be prevented nearly 100% of the time. Even with no treatment the infection rate is about 20-25%. Basically if the mother is on her anti retroviral drugs, is given an IV of anti retrovirals during delivery, and then the baby is put on anti ret... |
[
"Randomly spotted this lake on Google Earth. Can someone shed a little light on it?"
] | [
false
] | Is this a massive freshwater lake bounded from the Antarctic on the East side by a tini-tiny sandbar? Sea ice? The wikipedia stub says the lake is only 1m above sea level. I don't think I've ever seen anything quite like this. Also, is the channel running from the lake to the sea a natural formation? | [
"Yes its a fairly typical lake. You can see the highland to the west, the water will flow towards the sea to the east. The sandbar is common in most ocean outflows - you can think of it as a compromise between outflowing water, and inflowing sea water. Most rivers systems have terminal sandbars. This is where the r... | [
"One assignment I wrote something along the lines of \"This relatively rare floodplain...\" The marker circled it and wrote 'not rare'. And deducted 30% of the marks. ",
"West coast USA is pretty desert dominated, so river flows are typically low volume and non-seasonal. You get all the same features, just make s... | [
"Huh. Very interesting, thanks for the thorough reply. I'm surprised it's so common.",
"I've lived most of my life in the western united states. I've been up and down the west coast many times, and never encountered a lake like this one, so close to the ocean (the flat floodplain obviously just even weirder). "
] |
[
"Why do fusing nuclei lose mass?"
] | [
false
] | null | [
"The total mass of the particles has not changed",
"Actually, it has. The mass of a bound system of particles is not equal to the sum of the masses of its individual parts; it's a little bit ",
". So if you take two free particles and bring them together, forming a bound state, you gain a little bit of energy. ... | [
"But why is it less?"
] | [
"Because the interaction energy contributes negatively to the total mass of the system, if the interactions are attractive (which they must be for a bound state)."
] |
[
"Hypothetically, what would happen if a black hole suddenly reverted back into normal matter?"
] | [
false
] | I.e. imagine we have a line that represents the density a black hole forms at a given mass. What if by magic you could tip it back befor this line. I know this isn't possible but what if by some phenomenon we are yet to understand this is what were to happen eventually as hawking radiation eats away at the black hole. ... | [
"It's not possible. There are some impossible stuff that you can imagine hypothetically (like stuff regarding the speed of light) by extrapolating current equations, and there's stuff like this where it's just plain impossible without coming up with baseless arguments. "
] | [
"Even though the exact question the OP asked is impossible, there is something to be discussed here.",
"As a black hole is evaporating, it's evaporation rate is increasing. By the time it gets to be about 230 metric tons in mass, it has about 1 second left (if I did my math correctly). That means in the last 1 se... | [
"I can't find a reliable source for this, but I read some time ago that at the moment of a black hole's extinction, a very violent gamma ray burst is emitted, which would be consistent with your calculations."
] |
[
"What's actually happening when I lose or gain weight?"
] | [
false
] | Is all food stored as fat/muscle and then our body uses current stores for energy or will it tap it directly from food. What happens if I ate 5000kcals today and only burned 3000. How long til the others are now fat?? | [
"Aerobic glycolysis uses oxygen in a series of chemical reactions to essentially 'burn' the carbohydrates stored in your muscles and cells into carbon dioxide and water along with energy we need to move, live etc.",
"The same happens to fat in a process called lipolysis also using oxygen.",
"The calories you us... | [
"If you were to lie down in bed all day, your body would burn a certain amount of calories simply by pumping blood, breathing, and doing all the other involuntary bodily functions. This is called your basal metabolic rate. Disregarding any sort of exercise and what was consumed to receive the calories (i.e. was it ... | [
"Hi,",
"Thanks for the response, I understand the basics of the basic rate of burning calories etc. ",
"I mean whats actually happening on a deeper level?"
] |
[
"Can skin ever grow together?"
] | [
false
] | I phrased this kinda weird in the title. What I'm wondering is if, for example, you kept your arm on your stomach for huge amounts of time, never moving it, would the skin that touched grow together? If not, what would actually happen? Maybe a better example is rolls of fat: what happens to the skin that is folded t... | [
"The serious injury part: If the blood supply was worked out, it would grow together. That's how they repair or reduce people's earlobes that have been stretched to accept large gauge earrings. They pretty much cut the excess off and sew the rest together."
] | [
"...which is why I don't think I will ever gauge my ears. Thanks!"
] | [
"When we were learning about burns in nursing school, there was a case of a little girl who had a serious electrical burn on/in her hand. The problem with electrical burns is that there is very serious injury through the body or body part along nerves and blood vessels. They ended up grafting her hand to her abdo... |
[
"How does radiation make other objects radioactive?"
] | [
false
] | And is it always happen regardless of dosage? | [
"The primary way that ionizing radiation makes things radioactive is by inducing nuclear reactions in the material, and transmuting its nuclei into different, radioactive species.",
"This is primarily only a concern with neutron radiation, although very high-intensity, high-energy charged particles or gamma rays ... | [
"Thank you for your comment tho :D"
] | [
"Ionizing radiation can displace atoms from their lattice sites, and over time with a large dose, it can cause degradation of the material."
] |
[
"Why do wild cat species have different scientific names but all domesticated cats are Felis Catus?"
] | [
false
] | Is this done out of convenience or do all domesticated cats share the same genome? | [
"What do you mean by 'share a genome'? Individuals of the species ",
" do have unique point mutations within their genome."
] | [
"Reproductive isolation is only one criterion used to determine species identity, and it is not a universal one. Domestic cats can and do produce fertile hybrids with other wild cats, e.g. Servals. ",
"What matters is that wild cat populations and domestic cat populations both have significant gene flow within ... | [
"It comes down to the definition of species. This dictates that if they can and do interbreed and produce fertile offspring then they are a species, and would fall under the same taxonomic name.\nMore: ",
"http://en.wikipedia.org/wiki/Species"
] |
[
"In The Roman Warm period the climate was 2 degrees Celsius warmer than today and is partly credited with Rome success and abundance. Why is returning to a warmer climate considered so dangerous now?"
] | [
false
] | I am not asking this question in bad faith or in an attempt to start a political debate. I was just listening to a Blinkist on the Roman Warm Period and got curious. | [
"A first thing to clarify is that the \"2 degree C warmer than today\" for the Roman Warm Period (or Roman Climatic Optimum as it is also called) is that this is for reconstructed sea surface temperatures (SST) for the Mediterranean, not the temperature on land (e.g., ",
"Margaritelli et al, 2020",
"). Generall... | [
"Well that’s terrifying, but thank you for the answer."
] | [
"In other words: you can't pick up and move farms to better locations when the climate changes"
] |
[
"Question about and image of NGC 7027"
] | [
false
] | In , there are irregular orange smears in the image, are they seperate galaxies or star clusters? | [
"Most likely stars. They are probably smeared due to the exposure time of the photo. They are definitely separate from NGC 7027 since it is a relatively recently formed planetary nebula. ",
"Edit: Also, Hubble has limits - anything fainter than 25 magnitude can become halo-shaped or smeared."
] | [
"disagree, if that was the case they would probably have smeared in the same direction, and everything on the picture would be affected. in ",
"this version",
" of the picture we can see how much noise was in the picture, so if I had to guess I'd say there are artifacts from a very high noise picture, IE the s... | [
"Tough to tell. It could be stars but if that were the case I would imagine all of the stars would smear and there are a lot of pinpoint stars in the picture. It could be an imperfection on a filter or lens but since it is from Hubble I would expect to see it in other pictures. ",
"If I had to hazard a guess many... |
[
"Why do all the planets orbit in the same direction?"
] | [
false
] | null | [
"Play with this",
"http://www.nowykurier.com/toys/gravity/gravity.html",
"It will give you some idea (and pass a few hours...)"
] | [
"All the planets, and the sun, formed from the same accretion disc."
] | [
"Thank you for this. Sincerely."
] |
[
"Why can insulated containers, such as a thermos, keep a liquid cold for longer than it can keep a liquid hot?"
] | [
false
] | null | [
"Heat transfer rates are generally proportional to temperature differences, and drinks tend not to be as cold as they are hot. What I mean by that is a cold drink might be 20 degrees C below room temperature, but a hot drink might be 70 degrees C above room temperature, so it would transfer heat more quickly."
] | [
"Also: hot drinks tend not to contains significant amounts of water vapor, while cold drinks often contain ice. The ice requires significant additional energy to melt."
] | [
"Yep, this! The drink that is at 70' C (typical hot coffee) vs. room temperature of 24' C is at a much greater temperature differential than the chilled drink that is at 5' C. More than double, actually (46' instead of 19')."
] |
[
"Are people with latex allergies allergic to latex house paint?"
] | [
false
] | Do they need to avoid touching walls, for example? | [
"Typically, no. Latex paint is usually made with a synthetic latex that tends to not cause an allergic reaction like natural latex does. There can be other chemicals in latex paint that may cause a reaction though. Consult your physician for more information."
] | [
"The technical definition of latex is is suspension of small particles of polymer in liquid. Natural latex is the sap of the rubber tree plant that has rubber particles in it that coalesce into latex rubber when the liquid evaporates. Latex paint has particles of acrylic or vinyl, so it is a different material enti... | [
"I am 43 years old and I have lived my whole life believing that \"Latex\" refered to the substance itself and not the suspension part. \n🤯",
"So when people say they have latex allergy the correct term would be latex rubber allergy?"
] |
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