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[
"Is it possible to say that the pulse from a neutron star is directed as shown in this gif http://www.astro.umd.edu/~miller/Images/pulsarSmall2.gif or could it be a pulse over the full surface of the star?"
] |
[
false
] |
Given the magnitude of the angular momentum of a neutron star, it's poles should remain in the same orientation. This means that a radiating beam from the poles of the star as it is either pointed at or away from the observer. So if it was from the pole, it should not blink. So is it possible that the hole star is blinking and this is seen in every direction from the star at the same time or that the beam does not come from pole.
|
[
"If I understand correctly, if the beam was in the same direction as the rotation axis (along the poles) AND it was pointed directly at you, then yes, it should not be seen to pulse, at least to first order. More on this in a moment. But, in nearly all cases, the beam does not come from the poles. The beam is ",
"offset from the rotation axis",
", which is what gives the lighthouse effect that causes us to observe pulses.",
"Pulse profiles have a wide variety of shapes. Many of them look something like in the gif you supplied, but many do not, especially for millisecond pulsars. ",
"Here",
" is an example of one \"famous\" millisecond pulsar, PSR J1713+0747, from ",
"Gentile et al. 2018",
". Ignore the top panel. The middle panel shows the pulse profile, and I would just focus on the black. The bottom panel shows a blow up of the baseline of the middle panel, and what you see is that there is actually very low-level emission (\"microcomponents\") across nearly all of the rotation of the pulsar as we see it. This was obsered only because of the very high sensitivity of the Arecibo Observatory. So in the middle panel, what you would see as \"on\" and then \"off\" a a standard pulsar, you actually see as \"on\" and then \"dim\". You can imagine then that this makes the naive picture of a single beam as in that gif very wrong.",
"Another extreme of this is the milliseconnd pulsar PSR J0218+4232. ",
"Here",
" is a picture of the pulsar emission at different wavelengths of light, with the radio at the top (panels a,b), and then down to X-ray and gamma ray at the bottom. You can see this figure in ",
"Kuiper et al. 2000",
". Keep in mind that phase goes from 0 to 2 here, meaning you're seeing two rotations of the pulsar on the x axis, not one. You'll notice that in the radio, instead of microcomponents, you just have these very broad emission components. This is very common in the X-ray/gamma ray but less so for radio, yet there it is. So that itself has weird implications for the beam geometry as well. One possibility, to go back to the very first point, is that the beam is largely oriented along the pole and that the pole is pointed towards us. However, beams are thought to be \"patchy\", so that within the beam, there are brighter patches and dimmer patches. So even if in the scenario you give that the beam is oriented along the pole, which is pointed towards you, if the beam is not uniform, then you will still see brightness variations that give rise to what look like pulses."
] |
[
"Thank you for the time you've spent and an excellent explanation. I was going to ask more questions, but I should first digest all you've sent me and try to wrap my head around it. I find the offset of the magnetic field from the axis of rotation counter intuitive, suggesting that there must be some other physics (force) that prevents such a symmetry. I realize earth's magnetic pole also does not align with the axis of rotation. I wonder if there is some relation that is just a bit weaker on earth. Do you know if pulsars ever reverse poles? Sorry don't answer that. I need to do some work myself.",
"Thanks again."
] |
[
"Absolutely, feel free to ask away when you'd like!"
] |
[
"What is the plastic wrap on dishwasher detergent capsules and where does it go?"
] |
[
false
] |
Obviously it dissolves, but I couldn't find out what it is made of or how this happens. An example of what I'm referring to would be Cascade 2-in-1 Action Pacs.
|
[
"Gelatin is a good guess, but They're actually ",
"Polyvinyl Alcohol",
".",
"Source: Used to work for the company that makes the material that cascade makes its pouches out of."
] |
[
"I work for a company that makes polyvinyl alcohol. The alcohol group allows it to dissolve in water. In a lot of manufacturing circle it is know as PVOH. It is also know as PVA. ",
"In 3D printing they use it for support of another plastic. Then you can soak the part in warm water and dissolve the PVA. Allows for more complex parts that would collapse without the support.",
"It is also one of the plastic films used in LCD screens. That is why you don't wash TV screens with water or glass cleaner. If it works around the first layer it will dissolve the PVOH layer. ",
"After it dissolves it is in solution with the water just like the soap is and just gets flushed down the drain.",
"Typing on my tablet. Punctuation isn't perfect. "
] |
[
"It could be a variety of different materials, but the general principle is this: You have a polymer film (i.e. plastic) composed of water soluble monomers forming a backbone that is readily hydrolyzed",
"Think of dissolving the capsule as breaking down the chains into smaller and smaller building blocks. Although the polymer is not water soluble, its monomer subunits are. Once you have broken the chain, it is easily rinsed away and exposes the contents of the gel pack."
] |
[
"If a black hole initially contains the mass of the star that collapsed to form it, then why was the gravity of the star not enough to prevent light from escaping its pull?"
] |
[
false
] | null |
[
"Simply put, because all of this mass is now in one point and the gravity is not \"condensed\" ",
"This is very important, because gravity is a 1/r",
" force, which means that it weakens with the square of the distance you are away from the mass. So if you stand on the surface of a star (theoretically), you don't feel the pull of every particle to it's full extent, while you do in a black hole (or at-least very close to the full pull)"
] |
[
"This is only a ",
" simplified view of the matter, disregarding all general relativistic effects (which are actually essential for that phenomenon, but are kind of over my head to explain).",
"I think this might give you an idea, though, how the gravitational force behaves differently, even though the mass is the same:",
"The gravitational force is given by F_gravity = G * m * M / r",
" (G being the gravitational constant, m&M the two masses and r the distance between them)",
"When dealing with a sphere, we can approximate the star as a point-mass in the center of the body when calculating the gravitational pull.",
": when you reach the surface of the star, and enter the sphere, the parts of the sun that are further away from the center than you are will not contribute to the gravitational force. Thus, the greatest force of gravity is applied on the surface of a celestial body. ",
"But, if all the mass *",
" a point mass (again: over simplified), the gravitational force will keep increasing, the nearer you get.",
"Now, if you consider the proportionality of 1/r",
" the force will increase towards infinity as r approaches zero. "
] |
[
"Actually, you can consider bodies like this a point mass by using center of mass. While it is true that the far end masses don't contribute much individually, there are far more of them than up close. When you add all of these individual vectors up, the force is directed towards the center of mass, with magnitude as if all of the mass was there."
] |
[
"Why do we use steam to spin turbines and not high molar mass gases?"
] |
[
false
] | null |
[
"No you would not get more work. Remember the combustion gas is at greater than 1000C. - you want to add the heat at as high a temperature as you can. The turbine inlet temperature is the restriction - currently it's less than about 650C. So if we want to add heat isothermally ( phase change) at as high a temperature as possible we need materials which boil at as high a t and p as possible. Water fits the bill - it's critical pt is about 374C and 220 bar."
] |
[
"The mechanical work does not derive from the phase change, it derives from converting enthalpy of the working fluid to mechanical work output. The more change in enthalpy you can get between the heat source and heat sink the more work you can get out of the heat engine. Heat capacity is proportional to how much internal energy/enthalpy rises for a change in temperature. A lower heat capacity fluid will result in a lower change in enthalpy for a constant change in temperature. Because of this the enthalpy that can be converted to work is less for a lower Cv fluid.",
"Similarly, the efficiency of a a Carnot cycle (ideal heat engine) is a function of source and sink temperatures. To produce more work and to maximize efficiency you want the source as high as practicable and the sink as low as possible. To achieve the same source temperature for a fluid that boils at lower temperature will require heating of the vapor form of the fluid, which typically is much more insulative than the liquid form (greatly lowering the heat transfer rate). "
] |
[
"Would it make sense to use a liquid with a higher boiling temperature? Adding a noncorrosive ion might be a cheap way to give water a higher boiling temperature."
] |
[
"Is it known how many times has life spontaneously appeared in earth?"
] |
[
false
] |
Pretty much the title … are all life forms on earth descendant of one single ancestor? Or has life appeared multiple times?
|
[
"The question doesn't really admit of an answer -- we simply don't have any usable record of the earliest days of life and life-like processes. What we can see is that every life form we have encountered on earth has a large set of similarities, using the same genetic communication medium, decoded in the same way, into the same library of amino acids. Some proteins and functional RNAs can be traced back to common ancestors between ",
" and human beings. This very strongly implies that all extant life is derived from a single origin event.",
"However, other forms of life may have existed contemporaneously with this \"eve organism\" and gone extinct during the course of evolutionary time, or retreated to particularly strange or inhospitable environments where we do not have access to them. Because most microorganisms are not preserved as fossils, and even if preserved, alternate life forms might not be recognized as such, we will probably never have a definitive answer to this question."
] |
[
"Every lifeform we have ever studied shares the same ancestor.",
"Ultimately this makes sense, since after life happened once it filled every niche and any emerging proto-life would just be easy food for existing life that has already adapted to the same environment.",
"This is one of the reasons why discovering extraterrestial life would be so exciting. We'd go from one studiable event of life emerging to a whopping TWO EVENTS. That's DOUBLE the number of points on this scale! Would make theorizing about how life happens much more solid to have more than one event to study."
] |
[
"What about them? I don't understand the question. Tardgrades are animals and related to all other animals and trough some common ancestor to plants, fungi, bacteria and archaea too."
] |
[
"How is a bacteria immune to a virus without its corresponding spacer?"
] |
[
false
] |
[deleted]
|
[
"That is definitely a drastic oversimplification of what happens and I don't blame her given time restrictions.",
"CRISPR adaptation (aka acquisition of a new spacer) has distinct mechanisms that makes it so that the acquisition is biased towards foreign DNA. It is not in fact random.",
"For example, CRISPR acquisition proteins can be unregulated as a stress response, e.g. envelope disruption response (PspA). In E. coli, the type I CRISPR system also is biased towards foreign DNA for acquisition. This is related to the density of chi sites and the stalling of the recBCD complex on chi sites. The density of chi sites on chromosomal DNA is spaced relatively evenly. This prevents extensive chew back of double stranded breaks because recBCD will stall periodically on the chi sites. Acquisition is biased towards single stranded DNA, so a phage which has linear DNA that is being processed by recBCD, with less chi sites, will generate longer strands of ssDNA. This allows the biased acquisition of foreign DNA. Similarly, the more replication forks that exist, the higher chance that a spacer will be acquired from that piece of DNA. High copy plasmids are also thus biased for spacer acquisition.",
"In type III systems, the bias is based off of highly transcribed genes. Because phages oftentimes hijack and overwhelm the cell machinery, any transcript that is highly transcribed is recognised by the type III acquisition method. Obviously there will be self immunity issues but these are pruned from the population."
] |
[
"However, they never explained how those surviving bacteria survived in the first place without the spacer already in place. Was it just chance? And if so, what was the random element?",
"I actually was at a talk by ",
"Emmanuelle Charpentier",
" a few weeks ago, and someone asked this question. She said it was basically random chance (one example would be if the bacteriophage had a mutation that meant it could enter the cell but not replicate). Lots of things can go wrong for a virus during infection. Other bacterial immune strategies (for example, restriction enzymes) could also play a role."
] |
[
"Cas1/Cas2 forms a heterotetrameric complex that \"searches\" foreign DNA in the cytoplasm for a target sequence (PAM sequence) and then binds, excises the protospacer, and incorporates it into the CRISPR locus. This sequence is then available to whatever Cas protein the bacteria uses after some processing. ",
"One important evolutionary pressure for this type of foreign DNA integration is that bacteria are more than happy to take DNA in from their environment, unlike eukaryotes (think horizontal gene transfer, mobilomes, etc). Because of this, a robust integrase is crucial for a defense system like CRISPR/Cas."
] |
[
"Is observation of proton decay the cheapest experiment for ruling out potential unified field theories?"
] |
[
false
] |
I mean, you basically just stare at a giant inert mass and wait for something to happen, rule out interaction with neutrinos and cosmic radiation, and see if anything decays, right? Isn't the lack of observation of proton decay a big problem for the theories that say it must happen?
|
[
"That's how they ruled out Georgi-Glashow theory."
] |
[
"Current lower bounds on the proton half life are around 10",
" years. In order to see one decay per year, you would need to be looking at a ball of protons with about ",
"the same mass as the titanic",
". Picking one decay event out per year would be extremely challenging, considering all the other interactions that could take place, and all the other protons that would make it difficult to observe the decay.",
"As a side note, it is weird to find a problem that Wolfram Alpha can't calculate correctly. 1-e",
" for small x is easy to approximate as x based on Taylor series, but WA blows up if I give it really small values. Anyway, based on my calculations you need ",
"~10",
" g",
" of protons to observe one decay per second"
] |
[
"I don't know if it's the cheapest one, but the current bounds are pretty strict. Usually, if a model predicts proton decay faster than the current bounds, model builders will try to add on extra symmetries that forbid proton decay and see what they imply for the model.",
"For example, in supersymmetric models, the danger of proton decay can be ameliorated by imposing R-parity.",
"Another easy way to rule out potential theories is to look for flavor-changing neutral currents (FCNCs). We have very tight bounds on those from experimental data - FCNCs are very very very weak, just like proton decay. Model builders are also continually trying to find ways to control the FCNCs in their models."
] |
[
"If you struck a tuning fork in deep space, would it ring forever*? If it entered the atmosphere could you eventually hear it?"
] |
[
false
] |
[deleted]
|
[
"No, as the 'tines' flex they do work which heats up the metal, this is then lost to space irreversibly, so the fork would stop ringing eventually."
] |
[
"A tuning fork loses energy through a mixture of heating itself up by expanding and contracting, and via having to move the air out of the way. Ok, you could eliminate the latter by removing the air, but you'd still have the energy dissipating through heat. So the tuning fork would ring for ",
", but not forever. The dominant mechanism of energy loss here would be heat, so it won't even ring for much longer.",
"Say the tuning fork slowly approaches a planet with an atmosphere similar to ours. Would it become audible?",
"In the vacuum of space, the tuning fork would be inaudible because sound is oscillations of a medium. It would indeed become audible as it approaches an atmosphere. ",
"Would it sound the same at high atmosphere (dilute gas) than at ground-level atmosphere? ",
"Sound waves are pressure waves. Pressure waves propagate poorly in a low density medium (such as the upper atmosphere), so the sound will be quieter. The extreme example of this is when the density is so low that it's actually a vacuum, then the sound has no loudness at all."
] |
[
"Metals like steel or aluminium are the most efficient conductors of sound (think how much louder banging on a steel railing would sound if you were to put your ear on it). I'm not sure what you mean by the density of a substance becoming too great. All materials have a certain compressibility, this is all you need for sound propagation. ",
"Why do the sound waves not transfer from the water to the air?",
"This is a good question, I don't have an answer right now that I can \"clarifying excruciating technical detail\", but I hope someone else does."
] |
[
"Stellar Parallax - why are the background stars nescessary?"
] |
[
false
] |
If I want to know how far away a nearby star is, I can measure its angle in the sky, wait six months and then measure its angle again from the other-side of the sun, and use trig to compute its distance. What I dont understand is the purpose of the background stars in all this. In some of the videos I've watched they talk about the star being measured moving in relation to more distant background stars. Is that simply for illustration, or are the background stars necessary? I've grok'd how parallax works, but I cant see any reason why the background stars are necessary. Are they?
|
[
"They are used because they are the most reliable and convenient reference. Just imagine trying to measure the positions of stars in respect to the orientation of the earth, moon, sun or planets, while they swoop and wobble around in annoying patterns."
] |
[
"A minor addition to what Redshift64 says - you also don't just measure it once every six months - you measure it continually, so you see the star go in a little loop over the course of a year."
] |
[
"What are you going to measure the angle against?",
"On a rotating planet revolving around the sun, with air currents and thermal expansion and structural fatigue, how difficult do you think it would be to return a telescope to the ",
" same angle after several months?",
"Much easier and more accurate to calibrate the telescope against a background star."
] |
[
"What would happen to the standard model if the Higg's boson isn't discovered?"
] |
[
false
] | null |
[
"Then the theorists will finally have something to do."
] |
[
"Damn near anything can fit into string theory, because there's something stupid like 10",
" possible ways to describe it."
] |
[
"What specific problems would it cause for the standard model? ",
"Have there been any possible patches?"
] |
[
"Hurricane Sandy is tracking Northeast, and all of the models show it make a hard western turn towards New York. Can someone explain to me, like a child, how this happens?"
] |
[
false
] |
I have heard people discuss the jetstream, but not graphics with both hurricane models and jet stream. Can someone help me understand this prediction? How is it going to turn, what causes it, and what is the jet stream doing now that helps this action?
|
[
"The paths of hurricanes are largely steered by the surrounding winds. In this case, a strong low-pressure system is expected to be crossing across the eastern US just as the hurricane transits north. If/when they combine, the eye of the hurricane is expected to be pulled west. Its not exactly ELI5, but more info is available ",
"here",
"."
] |
[
"Not really either. There's a strong ridge of high pressure to the north. What this means is that there's basically air to the north that is more dense and is generally sinking. Well, the storm will hit this mass of relatively denser air and almost bounce off a wall. On the contrast out to the west you have an area of rising air which leaves acts in the opposite way.",
"The storm is basically just following the path of least resistance. Its not really being \"sucked\" in as much as its the easiest direction for it to move. Think of it as a doorway to the west while in each other direction there is a wall."
] |
[
"I think it's a combination of two things. (1) Sandy comes in close contact with another cyclonic system that gets wrapped into it from the southwest, inducing a ",
"Fujiwhara Effect",
" like steering of Sandy to the west while the trough is wrapped around Sandy. (2) Strong precipitation on the west side of Sandy could be causing the system to ",
" westward rather than being pushed westward, through low-level vorticity being constantly produced west of the storm's current location. It would be interesting to see a vorticity budget for this event and look at where the non-advective contribution to Sandy's evolution is, and the relative size of that contribution."
] |
[
"What is the end product of photosynthesis?"
] |
[
false
] |
[deleted]
|
[
"The end product could be many things, but the Calvin cycle portion of the light independent reactions of photosynthesis generate simple, 3-carbon sugars that then go on to be used in creating glucose, sucrose, and cellulose, among other things."
] |
[
"You could say basically it's \"organic matter\" or \"Carbonated chains\" (it means the same thing)",
"Glucose, sucrose and any other form of sugar are basically variations of carbonated chains. That's justthe name we give to organic energy stocks. ",
"In reality, each plant will produce the one chain it needs at a given point, and it can produce several different at the same time, each chlorophyl cell working individually."
] |
[
"Its really glucose first, which is then condensed with fructose to give sucrose (sucrose is just glucose bound to fructose). The fructose can come from isomerization of glucose. Fun fact, fructose is named fructose because its from fruit! (ie plants make it, an isomer of glucose)."
] |
[
"CD Track problem, Lens and laser"
] |
[
false
] | null |
[
"Huh? I think you'd get a better response if you were more clear and your picture was good quality. What do you mean \"as soon as I put a lense in between\" and \"move along with the laser\"?",
"All I can see in your \"pic of the pattern\" is, what looks like to me, a faint interference pattern, a bit like ",
"this",
", which is what you'd expect to get..."
] |
[
"I don't know because I still don't understand your setup. What do you mean \"dot without a lens\"? Also what do you mean \"big\"? You can have as great a distance between minima/maxima as you want if you project it onto a screen far enough away."
] |
[
"Oh that is an interference pattern? That is how it looks in the 0th order, how exactly does that form? as its just a dot without the lens. \nAnd what exactly is it an interference pattern of? As its really small, so it has to be something with a quite large d?"
] |
[
"how much energy would it take to vaporize the earth?"
] |
[
false
] |
I am building a giant death ray and need to get the specs right!
|
[
"Roughly, we can use the gravitational binding energy of the Earth. There are chemical bonds in there too, but this is a rough estimate and we can ignore them here.",
"The magnitude of the binding energy of a uniform sphere is (3/5)GM",
"/R, which is another approximation because the Earth is not uniform. Plugging in the Earth's mass and radius, we get about 10",
" J.",
"For a sense of scale, if you built a Dyson sphere around the Sun and absorbed all the Sun's radiation, it would take about 10 days to build up this much energy.",
"Interestingly, the ",
" energy of the Earth is actually ten times larger than its binding energy. This means that it's easier to blow up the Earth than to move it. If you wanted to smash a a single asteroid into the Earth to cause the Earth to fall into the Sun, it turns out that's not possible - you would actually smash the Earth to pieces rather than cause it to fall directly into the Sun. Keep this in mind when designing your doomsday devices."
] |
[
"So from E=pc, you have about 10",
" kgm/s of momentum to deal with. This won't push the Earth much - a total of about 0.1 m/s - but yeah, how much it pushes your death ray back will depend on how massive it is. This does start to depend on the details of the technology, so we're kinda getting into science fiction speculation rather than actual answerable science.",
"But if you're firing this from a large asteroid with the mass of Ceres, and distributing the momentum across the whole asteroid (e.g. by firing slowly or by having a series of small lasers across the asteroid etc), then the total kick is about .7 km/s, which is significant, but not nearly enough to knock you out of the solar system.",
"For an asteroid or space-station 10 times smaller you'd get a kick 10 times bigger (7 km/s) and so on."
] |
[
"So from E=pc, you have about 10",
" kgm/s of momentum to deal with. This won't push the Earth much - a total of about 0.1 m/s - but yeah, how much it pushes your death ray back will depend on how massive it is. This does start to depend on the details of the technology, so we're kinda getting into science fiction speculation rather than actual answerable science.",
"But if you're firing this from a large asteroid with the mass of Ceres, and distributing the momentum across the whole asteroid (e.g. by firing slowly or by having a series of small lasers across the asteroid etc), then the total kick is about .7 km/s, which is significant, but not nearly enough to knock you out of the solar system.",
"For an asteroid or space-station 10 times smaller you'd get a kick 10 times bigger (7 km/s) and so on."
] |
[
"Why does a vortex mix things in liquid, but separate things in air."
] |
[
false
] |
When I make a beverage from a powder like kool aid, I swirl the water with a spoon to mix the powder in the water, but inside my vacuum cleaner, the same type of phenomenon, a vortex, is used to separate the dirt from the air. Why are these different if both air and water are fluids? Is it just a matter of the kool aid powder being so small?
|
[
"The kool powder dissolving in water is one reason, the other has to do with density. The density of ",
"sucrose crystals",
" is only about 50% higher than the density of water. Therefore the turbulence that you introduce while stirring tends to disperse them through the water more strongly than they are forced to the outside by the vortex.",
"On the other hand, the density of sugar crystals is about 1200 times that of air. The vortex in your vacuum cleaner tends to force the heavy crystals to the outside much more strongly than the turbulence introduced tends to mix them."
] |
[
"Kool powder is dissolving in water. The water molecules break it down and surround it dispersing it evenly throughout the volume. It is now a ",
"solution",
" of koolwater. In contrast, if you put a bunch of different massed things in water that were not soluble (ie. plastic pellets of different density), they would separate just like those over-priced vacuums claim to separate different sized pieces of dirt.."
] |
[
"I'm not even sure what you're talking about."
] |
[
"Why isn't space a perfect insulator? Where does planetary heat \"go?\""
] |
[
false
] |
Outer space is mostly empty, right? Then how do planets diffuse heat if there is nothing nearby to transfer to? Is there enough space debris to take away the kinetic energy, or are there heat sinks on every planetary body? If we launch a ball of, say, iron into space at 100 degrees celsius and could somehow keep track of its temperature, what would it do? Would it remain 100 degrees celsius indefinitely? If not, do we have a timeframe or model for when it would start to cool? I've also read that empty space has a temperature due to background radiation from the Big Bang, so does this mean that a perfect vacuum (absolutely NOTHING AT ALL in it) doesn't exist in our world?
|
[
"One of the main mechanisms of heat transfer is through the emission of ",
"thermal radiation",
". All macroscopic objects above 0K will emit electromagnetic radiation simply by virtue of being at a non-zero temperature. The spectral profile of such this radiation is that of a so-called ",
"black-body",
" and depends on the temperature ",
"as shown here",
". For the sun, which acts as an effective black-body at 5800K, the thermal radiation peaks in the visible range, which is why it produces so much visible light. The Earth on the other hand, acts as a black-body with an effective temperature of about 250K, and so most of its radiation occurs well into the infrared as ",
"shown here",
". As a side-note, the difference in the two spectral profiles is critical to understanding the ",
"greenhouse effect",
". While most sunlight can pass through the atmosphere, a large fraction of the thermal radiation from the Earth is reflected back by gases in the atmosphere (such as CO2), ",
"as shown here",
", resulting in far higher surface temperatures than would exist in the absence of an atmosphere. ",
"Exactly the same would happen to your ball of iron. Whether it is in space or on Earth, it would be continuously emitting thermal radiation and cooling in the process, until it reached an equilibrium temperature."
] |
[
"That's pretty much exactly what it is. The temperature indicated on lighting sources is the so-called ",
"correlated color temperature",
", which is simply the effective temperature of a black-body emitter having a color profile that most closely resembles that of the light source in question."
] |
[
"Just in case it wasn't clear from crnaruka's post, I would like to point out that the LEDs themselves are not actually operating at these temperatures (e.g. 5800 K). They are room-temperature devices which emit a spectrum which somewhat resembles a high-temperature blackbody spectrum. Well, high-power LEDs may get up to around 100 C or so, but that's still well below their correlated color temperature.",
"Further reading:",
"https://en.wikipedia.org/wiki/Thermal_management_of_high-power_LEDs",
"http://ca.mouser.com/applications/lighting-derating/",
"http://www.digikey.ca/en/articles/techzone/2011/jun/calculating-led-junction-temperature-in-lighting-applications"
] |
[
"Could someone explain why we only recently found out neutrinos are possibly faster than light when years ago it was already theorized and observed neutrinos from a supernova arrived hours before the visible supernova?"
] |
[
false
] |
I found this passage reading The Long Tail by Chris Anderson regarding Supernova 1987A: Astrophysicists had long theorized that when a star explodes, most of its energy is released as neutrinos—low-mass, subatomic particles that fly through planets like bullets through tissue paper. Part of the theory is that in the early phase of this type of explosion, the only ob- servable evidence is a shower of such particles; it then takes another few hours for the inferno to emerge as visible light. As a result, scien- tists predicted that when a star went supernova near us, we’d detect the neutrinos about three hours before we’d see the burst in the visible spectrum. (p58) If the neutrinos arrived hours before the light of the supernova, it seems like that should be a clear indicator of neutrinos possibly traveling faster than light. Could somebody explain the (possible) flaw in this reasoning? I'm probably missing some key theories which could explain the phenomenon, but I would like to know which. Edit: Wow! Thanks for all the great responses! As I browsed similar threads I noticed shavera already the discrepancies between the OPERA findings and the observations made regarding supernova 1987A, which is quite interesting. Again, thanks everyone for a great discussion! Learned a lot!
|
[
"The neutrinos got a head start. ",
"When a supernova happens, neutrinos and photons are created at the core of the star. They start trying to travel outward immediately, but the outer layers of the star are still in the way. ",
"Photons are rather easily blocked, even by the gaseous stellar material getting blown away from a supernova. It takes a few hours for the photons to \"work their way through\" those outer layers of the star and get on their way through empty space. But neutrinos barely interact with any kind of material at all, so they reach empty space almost immediately. It's that difference that gives neutrinos a head start.",
"If supernova neutrinos did travel faster than light, we would expect to have seen a much greater difference in the arrival time. SN 1987a happened more than 150,000 light years away, so neutrinos had an awful lot of time to outrace the light if they were going to. If the CERN measurement was accurate, then the neutrinos should have arrived about ",
" earlier than the photons. ",
"This all means that if our supernova measurements are correct, then either CERN's measurement is wrong, or else something else more complicated is happening."
] |
[
"Can I highlight here that no one has yet proved neutrinos are travelling faster than light. "
] |
[
"Wow! Interesting stuff! I wanted to ask the additional question of wether the scenario for 'faster-than-light' travel by neutrinos would occur during a supernova, but it appears you already answered that question. Thanks a bunch!"
] |
[
"Viewing light as a particle, is there a theoretical maximum resolution achievable by a classic lens telescope?"
] |
[
false
] |
[deleted]
|
[
"Hi thetgi thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"If I understand what you're getting at, your question could be rephrased as:",
"Can the intensity of incident light affect the resolution of a lens?",
"Surely yes. There are materials that have a non-linear response to high intensity light (see ",
"non-linear optics",
") and that means the refractive index is affected. So the lens will not resolve an image as it did for lower intensity light."
] |
[
"Right, if we make the pixels of the camera sensor smaller and smaller, less photons will strike each one, so the randomness of exactly how many hit it will matter more. The net effect is as if you added some random noise (like television static) to the image.",
"This is called \"shot noise\", unlike other noise sources it's unavoidable (you can't make the light continuous), and it's actually ",
"one of the biggest contributors",
" to noise on modern cameras.",
"So the effect is that adding \"more megapixels\" to the sensor doesn't necessarily help, because the smaller pixels are too inaccurate (so you can only get an acceptably denoised image by scaling it down, so the errors average out). The solution is to make the sensor larger, e.g. ",
"this one",
" for a telescope in Hawaii is 25cm x 25cm."
] |
[
"The Oberth Effect (domonstrated in KSP) - Where does the energy come from?"
] |
[
false
] |
We are demonstrating and explaining 'The Oberth Effect' and the extra efficiencies you can gain from doing some of your burns at the highest possible velocity. It may seem that the rocket is getting energy for free, which would violate conservation of energy laws. Where does the energy come from? Why does the same amount of velocity increase give you more kinetic energy at higher relative velocities? Would love feedback!
|
[
"In addition to what ",
"/u/DCarrier",
" said, the Oberth effect can be understood in terms of what happens to the fuel after you eject it.",
"Assuming you are in orbit around some central body (such as a planet) the fuel will remain gravitationally bound to that object. Depending on the speed after ejection, it might remain in orbit or it might fall down into the planet (or it could be blown away by solar wind). But whatever happens to it later, it is effectively part of the planet system now as far as our spaceship is concerned.",
"By burning that fuel deeper in the gravity well the ejected fuel has less potential energy. By burning closer to the planet you are taking energy away from the planet/ejected fuel system and giving to your spaceship."
] |
[
"It comes from the reaction mass. If you're not moving, then the reaction mass gets kinetic energy. If you're moving faster than you can shoot out the reaction mass, you're slowing it down so it loses energy. Since kinetic energy is proportional to the square of speed, the faster you're going the more a certain loss of speed makes the reaction mass lose energy."
] |
[
"Adding to this, we can reason about it in even simpler terms and get to the same result.",
"The increase of kinetic energy in a moving body is equal to the work applied on it. Work is the product of a force and a displacement (let's call them F and Δx).",
"The increase in speed is the product of acceleration and time.",
"Let's consider what happens in a small enough time interval so that we can neglect that the mass of the rocket decreases over time. If you burn in a high orbit for a time Δt, applying a force on the rocket along a path Δx, the quotient Δx/Δt will be small, since this is equal to speed and the rocket is moving slowly.",
"If you burn in a lower orbit, Δx/Δt will be larger, as the rocket is moving faster. Since Δt stays the same, the rocket has moved along a bigger Δx. And since F times Δx equals work, more kinetic energy has been applied to the rocket."
] |
[
"A question about natural selection."
] |
[
false
] |
I've heard, and seen people say that doing something stupid, and dying as a result is "natural selection." I'm not sure, but I'm pretty sure that they are wrong. I read that natural selection is when something has a genetic mutation, that allows it to survive better than the others. They will reproduce and have more offspring with that mutation. Or is it both? I'm not sure, so If you could tell me where I've gone wrong I would appreciate it!
|
[
"There are two parts to the process of evolution.",
"1) Random mutation - this is the part where random defects in DNA are introduced. These defects can manifest themselves as a changed trait in the organism. For example a single bacterium may acquire drug resistance. Note: these mutations need not necessarily have a positive effect on the organism's survival. ",
"2) Natural selection - this is a non-random process that selects those individuals with mutations that favour their own survival. In the bacterium example, this could be the application of an antibiotic (one that the mutant bacterium is resistant to). After the application of the antibiotic, all the other bacteria have died out except the mutant one. The mutant one remains and breeds. After a few divisions, all the individuals are now drug resistant. The bacterium has essentially evolved drug-resistance.",
"These two processes are separate from each other. Natural selection has nothing to do with mutations or genes. It simply selects those individuals who are more fit for survival. In fact the theory of natural selection was long before we knew about genes and DNA.",
"Now if someone does something stupid and ends up being unable to reproduce, they have essentially been selected themselves out of the genepool. Hence it is a case of selection."
] |
[
"IF people killing themselves is a result (even partially) of genetics, then those genes/alleles are themselves, at some level, the result of mutations (at some point).",
"Which means it is perfectly correct to say that the people who kill themselves doing stupid things are being acted upon by 'natural selection'. Unless you want to argue the mistakes that lead to the Darwin Awards (and etc.) are unrelated even slightly to genetics (good luck)."
] |
[
"Not necessarily. If such behaviour is on average beneficial it may still prevail in the long run. Risk taking is a good example. While it can put you in dangerous situations, it can also lead to rewards when the gamble pays off. ",
"Thus over many generations of a large number of individuals, \"stupid\" behaviour may well be the result of genetic influences that also cause creativity, risk taking, adventurism and similar, which can have very positive effects. ",
"Trying to analyse evolution is HARD, and most naive predictions turn out to be very wrong."
] |
[
"Are pets and other domesticated animals at all affected by human language?"
] |
[
false
] | null |
[
"I don't understand your question. Can you try rephrasing it?"
] |
[
"Do pets and/or other domesticated animals perceive different human languages? To word the example better, would a dog who grew up with and was trained by an English-speaking owner understand the same commands (e.g. \"Sit\") in another language (e.g. Chinese)?",
"Does that make any more sense? Apologies if I can't explain it well enough."
] |
[
"No. Dogs don't understand meaning of words in the same sense. They learn to associate a particular sound or gesture with a command / action that they should take. If you teach a dog to sit using the English word, you would then have to teach them to also sit when you use the Spanish word, say. But you could just as easily teach them to sit whenever you say \"elbow\" in whatever language you choose."
] |
[
"What is the next Viable source of energy?"
] |
[
false
] | null |
[
"Geothermal is viable in places which have alot of geothermal. Iceland for example uses quite a bit of geothermal power.",
"According to this wiki article 26.2% for electricity and more used directly for heating energy. \n",
"http://en.wikipedia.org/wiki/Geothermal_power_in_Iceland"
] |
[
"Geothermal is viable in places which have alot of geothermal. Iceland for example uses quite a bit of geothermal power.",
"According to this wiki article 26.2% for electricity and more used directly for heating energy. \n",
"http://en.wikipedia.org/wiki/Geothermal_power_in_Iceland"
] |
[
"Good point. In Iceland's case, the problems with geothermal are slightly mitigated because they don't have to go nearly as deep to get the same levels of heat as we do elsewhere. Additionally, oil and gas need to be refined elsewhere and shipped, so are comparatively more expensive.",
"There are corollaries for most forms of alternative energy--solar is almost competitive in Arizona, wind is almost competitive on coastlines, etc."
] |
[
"Do tectonic plates change direction and if so why?"
] |
[
false
] |
I just saw this gif: And it looks like the plates converge around North America hundreds of millions of years ago and then completely change direction and they all move away from North America. Is this an issue of map accuracy, or are there reasons why tectonic plates change direction so completely?
|
[
"Just to add to the nice answer by ",
"/u/fastparticles",
" (TLDR: yes, but we're not sure why)...",
"A nice piece of evidence showing that tectonic plates not only move, but also change directions, is the Hawaiian island chain. The Hawaiian islands are the surface expression of a ",
"hotspot",
", of hot material rising to the surface (likely due to a mantle plume). Since the tectonic plates effectively slide over the mantle and this hot spot, this results in linear chains of volcanic islands, where the ages of the volcanoes increase as you move down the chain from the currently active volcano. ",
"This is shown schematically in this figure",
".",
"Okay, so if the tectonic plate moves steadily, in one direction, for a long period of time, we expect linear chains of volcanic islands. What happens if the plates change direction? ",
" In fact, ",
"if you look back far enough in the Hawaiian chain, we see a kink",
". The Hawaiian island chain ",
"transitions into the Emperor chain",
". By ",
"dating each of these previously active volcanoes",
", we can work out the timing of this shift in plate velocity, and start to understand something about plate kinematics..."
] |
[
"The short answer is: Yes they change direction and we don't know why",
"The long answer: Yes they change direction but we can't agree on what is actually driving plate tectonics so it's tough to really say why. There are two current ideas that are popular: The first is slab pull and the second is strong plate/mantle coupling",
"Slab pull: The idea that subducting slabs pull on the plate they are attached to and this drives plate tectonics. So if this is the case then there is some change in a subduction zone, perhaps a slab breaks off and this changes the forces that are expressed at the surface",
"Strong mantle/plate coupling: In this scenario the plates move on top because the mantle is convecting due to being heated from below (and cooled on top). This requires strong friction coupling between the plate and mantle (in the slab pull case there is very weak coupling). In this case perhaps changes in local heat flow or other factors caused the plates to change direction."
] |
[
"Very interesting, thanks for the links!"
] |
[
"To what extent are cancer cells still body cells?"
] |
[
false
] |
I was wondering, if you have for example cancerous lung cells, can the body still use those cells to perform the function of the lungs, or do they lose their function?
|
[
"You have hit on an important concept in cancer biology. 'Differentiation' is a measure of how similar a 'cancerous' cell is to it's 'normal' parent cell. Many tumours are made up of well differentiated cells, which means they closely resemble their parent cell, and typically mean they retain at least some functional properties. Very fast growing, invasive cancers often consist of poorly differentiated cells which are largely functionless. To sum up, cancer cells show a complete spectrum of differentiation, and as a result can range from being completely devoid of function to being well differentiated, functioning cells. "
] |
[
"This is an excellent answer. I hope you won't mind me expanding on it a little bit.",
"The pathology lab usually uses the terms high, intermediate, and low grade to describe the level of differentiation. Depending on the situation there are different scales, some will have an additional fourth grade (anaplastic) while some omit intermediate grade. In any case, grading is performed by a pathologist based on the physical appearance of the cells under a microscope. Tumors that are said to be low grade are closer in form (and presumably function) than intermediate grade tumors, and so on and so forth. High grade (or anaplastic, depending on the scale) tumors are the least differentiated- you might think of them as more generic. Tumor grade provides a measure of aggressiveness- high grade tumors tend to be dividing more rapidly and generally more aggressive. Tumor grade is used to some extent to determine treatment and prognosis but it is not the same as staging, which measures physical spread of the cancer within the body."
] |
[
"Cancer cells are almost entirely the same as \"normal\" body cells, but the control mechanisms that govern cell growth and division have failed. Consequently, those cells grow out of control, and form tumors.",
"If you had a lung cell become cancerous, it would probably function just fine--until it started dividing uncontrollably. The structure of the alveoli in lungs has a huge effect on how gasses pass between the blood and the atmosphere, so the affected part of the lung would start to function poorly once the cells reproduce enough that the alveoli structure is compromised."
] |
[
"The earth developed slowly and progressively - yet we call it 4.5 billion years old. What was the turning point that marks the beginning of \"the earth?\""
] |
[
false
] | null |
[
"Essentially, the solidification of the surface. This is when the clock starts for the age of the oldest rocks, the ones scientists use to estimate the age of the planet."
] |
[
"Not exactly.",
"The 4.54 billion year figure is for meteorites. That is, the age of the oldest rocks in the solar system. These rocks later fell to the surface of the earth.",
"The solidification of the Earth was in the 4-4.2 billion year range if I'm recalling this right."
] |
[
"I still think this statement deserves a footnote: These areas are the oldest known areas. To say that they have never solidified/liquified is probably a bridge too far. Especially with collision ejection theory."
] |
[
"Is there any evidence that Kinesio tape actually does anything?"
] |
[
false
] |
[deleted]
|
[
"Not as of yet. Scientists have found little support to the claims that Kinesio tape assists muscle and joint support. ",
"Recent article."
] |
[
"Never underestimate the power of the placebo effect. Especially in sports."
] |
[
"So far the scientific evidence is leaning towards the idea that the taping provides some short term pain relief but not long term pain relief. There are also recent studies that indicate muscle changes, but it is unknown if those muscle changes result in better performance.",
"http://www.ncbi.nlm.nih.gov/pubmed/22613238",
"http://www.ncbi.nlm.nih.gov/pubmed/22771110",
"http://www.ncbi.nlm.nih.gov/pubmed/22032998",
"http://www.ncbi.nlm.nih.gov/pubmed/22645478",
"http://www.ncbi.nlm.nih.gov/pubmed/22274976",
"There's plenty more if you do a search on pubmed.org"
] |
[
"Normally, I have shaky hands when I extend them outwards. When I take adderall, they don't shake anymore...why is this?"
] |
[
false
] | null |
[
"My guess is that part of it relates to dopamine levels in the nigrostriatal and maybe corticostriatal pathways - one of adderrall's mechanism is to bind the dopamine transporter, preventing uptake into cells and increasing the amount of free dopamine. Decreased amounts of dopamine have been correlated with movement disorders (i.e. Parkinson's) - so if you have low dopamine then creating more would alleviate the tremors. "
] |
[
"Ha! Or eat a lot of chocolate :p If only that could be the solution...!"
] |
[
"Interesting, thank you...so as far as a drug-free treatment goes, all I would have to do is fall in love? :p"
] |
[
"Is it possible to create a drug that increases a persons rate of perception allowing them to see in slow motion?"
] |
[
false
] |
I've always been interested with the idea for military applications, Soldiers would have heighten reflexes and would be able to aim quicker. Does anyone know of any drugs that may have this effect, and what chemicals in the human brain could be altered to increased perception.
|
[
"People keep suggesting amphetamines, and yes, those do increase alertness, but they don't make it seem as though events are occurring in slow motion.",
"There is however a way for this effect to be achieved, sort of. While this is based on anecdotal evidence from patients I've had, the simple fact that soooo many patients have experienced similar feelings makes me assume the anecdote is a good enough source for the purpose of this discussion. ",
"The drug(s) I am referring to are sevoflurane administered with nitrous oxide which are anesthetic gases often used for the induction phase of anesthesia, as well as maintenance of anesthesia. Patients tend to report that as they are losing consciousness, the people around them seem to move slower, sounds are heard in a way similar to if you watch a video with audio in slow motion, and as they are nearly unconscious, some report that the sound of the machines monitoring their vitals, the voices of the medical team, and other noises sound just like a CD that skips, and then they're unconscious. ",
"Now, this is the opposite of what you want, which is faster reflexes, and a general boost in physical performance. Anesthetics don't do that, obviously, and the reason they seem to slow things down, is because well, in a way, they are! "
] |
[
"you just described the whole point of an \"upper\"\ne.g. amphetamines, cocaine, some designer drugs"
] |
[
"No, such drugs do not exist. People often associate adrenaline surges with time slowing down, however it is just an illusion. What actually happens is we store more memories during that period.",
"Source: ",
"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001295",
"Seriously, you are down voting the ONLY post with sources to back up its assertions?"
] |
[
"Why does this spodumene specimen have such a funky shape? (mindat link in post)"
] |
[
false
] | null |
[
"We can't comment on personal anecdotes / isolated events without resorting to speculation which we always try to avoid."
] |
[
"Hi there,",
"Maybe I should rephrase my question? I’m trying to ask what mechanisms could have made this crystal form this way. I’m asking for possibilities, not an absolute answer."
] |
[
"Yes perhaps there is a more general phrasing like \"how do X crystals grow into Y shapes\" or something like that. We try to avoid posts where the answers will necessarily be speculative like when asking about what happened in some specific instance."
] |
[
"Would a near light speed electron that collided with a potential barrier have a higher chance of quantum tunneling due to the barrier being thinner in the electrons frame?"
] |
[
false
] |
Im only 3 weeks into my special relativity module so I am still very confused on alot of the concepts. I asked my lecturer about this and he answered to the best of his knowledge. He also told me if I wanted to know more i should have a look at quantum field theory. I also understand that special relativity and quantum dont like to get along with each other.
|
[
"The tunneling probability increases with the energy - this has nothing to do with length contraction, it is a result that is true even for very low energies. As you get closer to the energy of the potential barrier the tunneling probability increases. You can always consider the situation in the rest frame of the barrier where there is no length contraction even at high speeds - and that is the easiest case anyway."
] |
[
"A complete answer would involve more rigorous treatment with quantum field theory. But if you stick to standard QM, the wavefunction (and tunneling probability) for a particle with energy ",
" approaching a barrier with potential ",
" falls off as ",
", where ",
". So it depends on how large the potential barrier is. ",
"This page",
" has a nice calculator for tunneling probabilities using this treatment."
] |
[
"Standard QM completely fails in this case. The probability for the electron to tunnel through the barrier can not be higher in one frame due to length contraction than in the rest frame of the barrier. But the probability ",
" to be different, because the wavefunction formula you gave is made from non lorentz-invariant quantities (unsurprisingly, as it is derived from the non relativistic Schrödinger equation)."
] |
[
"Do kites require a string to stay aloft?"
] |
[
false
] |
[deleted]
|
[
"why would negative stability be a good thing? so if the computer breaks or malfunctions, it cant fly? "
] |
[
"Unstable planes are more manoeuvrable, better in a dog fight "
] |
[
"One can also say that stability is required for flight. For example, many fighter jets are designed to have ",
", so without constant correction by computers, they couldn't fly at all."
] |
[
"What is the \"limit\" for how many pixels a screen can have before the human eye stops noticing any difference?"
] |
[
false
] |
With the new 4K resolution, you can sometimes see a slight improvement from full HD (1080p), but I can't imagine there being any point of making higher resolutions than that. Is there?
|
[
"That depends on how large the screen is and how far away you are from it. It also depends on your visual acuity (i.e. 20/20 or 20/15 or 20/40). ",
"Here is a graph showing at what distance/size a higher resolution tv becomes worthwhile. ",
"http://www.rtings.com/images/optimal-viewing-distance-television-graph-size.png",
"So if you sit 2 feet away from your monitor, your monitor has to be larger than 32 inches in order for you to need a higher resolution than 4k.",
"And you don't need a 1080 television in the bedroom since that 32\" is 8-10 feet from your head."
] |
[
"The resolution limit for a good human eye is about 1 arcminute (1 60th of a degree). Assuming your screen is about 75 cm (30 inches) from your face, that makes the resolution limit 220 microns (9 thousandths of an inch). So having pixels smaller than that size won't be noticable.",
"For a 23\" diagonal monitor, that reflects a resolution of about 1300x2300"
] |
[
"I'll think about that when I'm gonna get my new 100\" Super Ultra HD TV for my room. hah "
] |
[
"Why do objects become harder to break the smaller they get?"
] |
[
false
] | null |
[
"Someone correct me if I am wrong.",
"Say you have a long stick. At first it's pretty easy to snap. With each half you create it gets increasingly harder to snap. But why? It's mostly due to leverage. ",
"To put it simply, the thickness of the stick is relatively the same, it's material properties does not magically change, hence it's breaking point stays the same as it gets shorter.",
"As the object gets smaller (shorter in this case) it is physically harder to be able to induce tension on the object and the possible leverage due to the shortening of the object is also reduced. ",
"Edit: numbers wise, the bending of a beam is typically related to the square or cube of the length (this depends on how you are holding the stick and how you break it) so that if the length of the stick is halved then the deflection is 1/4 or 1/8 respectively of the deflection at full length with the same force . So a greater force is needed for a greater deflection that will cause the breaking stress. "
] |
[
"The torque on a lever is the exerted force times the distance from the fulcrum (in many cases the center of the object).",
"The higher the torque, the higher the total force on the object. Try pushing a door closer to its hinge and it is much harder.",
"In the case of an object (say, a coin) you would create a fulcrum by putting one finger behind it in the middle while two other fingers or whatever else try to push both sides forward. The coin won't break since the lever is so small. ",
"In contrast, if you had something like a coin but just larger, it would be much easier to bend or break, relatively speaking. It would require more force, but that force is now more easily achieved."
] |
[
"Thanks for the great explanation!"
] |
[
"On an Earth like planet that was tidally locked, how much of the land surface area would be habitable?"
] |
[
false
] |
I've been looking into exoplanets that are in the habitable zone and came across Gliese 667 Cc, and although this planet was thought to be habitable it has apparently been discovered to be tidally locked. My question is if a planet IS tidally locked, how much of the surface could support life? Is there a very small sliver of land that humans could live on, or is it in fact quite thick? Do we know by how much the temperature would increase as you walked round the planet? I'm asking as it's very difficult to conceptualise a tidally locked planet give we live on one that is spinning! I presume for example the Sun would be un-moving in the Sky from any one point. Mny thks for any thoughts
|
[
"There is a pretty decent body of literature out there considering this question for exoplanets (e.g., ",
"Kite et al., 2011",
", ",
"Hu & Yang, 2013",
", ",
"Koll & Abbot, 2016",
", ",
"Lewis et al., 2018",
", ",
"Sergeev et al., 2020",
", ",
"Kane, 2022",
"). If you browse through some of these, you'll find that there's not a single answer because it depends a lot on the details (e.g., what type of star is it orbiting? is there an ocean? what's the configuration of continents and oceans and thus possible ocean currents? etc)."
] |
[
"The idea that a tidal-locked planet would necessarily only have a thin habitable strip is something of a persistent myth. That sort of climate might occur in some cases, and like CrustalTrudger says, the particulars will depend on a lot of factors, but there are numerous models (like ",
"this one",
", see figure 7 in particular) showing climates for tidal-locked planets with temperatures between 0 and 30 C across nearly the entire day side of the planet. They also usually suggest that the hottest part of the planet will usually be the wettest, contrary to the common perception that it would be a desert."
] |
[
"Yeah the seemingly pervasive idea of a narrow strip of \"habitable\" temperatures between permanent day and night has to effectively assume no atmosphere and/or ocean. Once you have a semi-global fluid involved, there's really no way a planet is going to maintain crazy stark temperature contrasts."
] |
[
"If two different substances form a solution, is the sum of their initial volumes the volume of the solution?"
] |
[
false
] |
This is a legitimate question that has confused me many times while mixing ingredients... Intuitively, it would make sense that when you mix them their volume would be the sum of the two substance's volumes. However, something tells me that density would change, resulting in a smaller/larger volume.
|
[
"Definitely a legitimate question - ",
"check out this curve for ethanol and water.",
" Ethanol and water mix to produce less volume than the sums of the initial pure solutions."
] |
[
"Volume is not conserved in a manner similar to mass, so the summation of two volumes is not guaranteed to yield the correct total volume. It can go both ways, with the product being either larger or smaller volume. Total volume may be affected by smaller particles fitting in the gaps between larger particles, and this works at macroscopic (sand in between gravel) and molecular levels (salt dissociating into ions, in between water molecules). When estimating total volumes, you may have to throw in attractive or repulsive parameters to account for intermolecular forces between molecules. Each solution you make will have differing interactions between particles/molecules and which will affect your total volume."
] |
[
"That's a pretty interesting visual. I assume the variances are a result of both density and the way that solutions form?"
] |
[
"How/why do jumper cables work?"
] |
[
false
] | null |
[
"Are you asking how the cables themselves work, or how jumping a car works? The cables are just pieces of wire that allow electric current to flow through them. Jumping a car works by using a live battery from a different car to start the car with the dead battery."
] |
[
"Like why is there positive and “ground”? And how does a dead battery restart?"
] |
[
"Like why is there positive and “ground”?",
"That's true of most electrical circuits. You either need a closed circuit, or you need a ground for the current to flow to/from.",
"And how does a dead battery restart?",
"Well it's possible to use a live battery to charge a dead battery. But in this case, the live battery is mainly just being used to start the engine of the car with the dead battery. Once the engine is started, the alternator charges the battery."
] |
[
"Questions RE: An infinite universe"
] |
[
false
] |
Some people on here have stated that the universe is infinite. Not unknowably large, but infinite. If the universe was infinite though, several things don't make sense to me. First, the universe would have to have infinite mass (though not infinite density, since it would be spread out over an infinite about of space). There is no way to have an infinate universe with a finate amount of mass, at least without having vast tracks with space with nothing (not close to nothing, literally no matter at all). Second, and this part bugs me more, our expansion rate would have had to been infinite. If the universe has not existed forever, but only 13.7 billion years (unless we are wrong about a ton of stuff which I find unlikely), then there is no way to have a truly infinite universe. No finite rate of expansion would allow it. Maybe I'm really missing something here and if I am, please let me know, but I don't see how we can hit those values of infinite mass and infinite expansion. ASKSCIENCE - teach me what I'm missing, please!
|
[
"That's not what the theory says at all. Space has ",
" infinite."
] |
[
"Yes, it's wrong.",
"No.",
"N/A."
] |
[
"This is correct.",
"Just because two things are infinite doesn't mean that one isn't bigger. "
] |
[
"If we were able to leave the solar system, how would we find out way home again?"
] |
[
false
] |
I've been thinking about space travel a bit, and I'm wondering how we would be able to find earth, once we leave the solar system. Say we were able to reach Alpha Century as an example, how would we then locate and return to earth?
|
[
"actually traveling to Alpha Centuri, the appearence of most of the visible stars would not change too much. As rfengineer said,you would be able to use basic trig and star observation to navigate back."
] |
[
"The same way we reached Alpha Centauri in the first place. You know where the Sun is (it's that first magnitude star between Cassiopeia and Perseus, as seen from Alpha Centauri), you know its relative speed, you know the performance of your spacecraft, so plot a course that will have you intercept the Solar system."
] |
[
"Have we reached Alpha Centauri?"
] |
[
"If a person has sleepwalked multiple times in there childhood/early teens will they continue to sleepwalk as an adult or does it go away?"
] |
[
false
] | null |
[
"Thank you!"
] |
[
"Thank you!"
] |
[
"https://en.wikipedia.org/wiki/Homicidal_sleepwalking",
"People have even sleep killed. But it's really rare, obviously."
] |
[
"How does lemon, bleach, and alcohol brighten hair?"
] |
[
false
] | null |
[
"Hair color is due to melanin pigments which absorb light, destroying those pigments will make the hair absorb less light and appear lighter. Bleach and the acid in lemon juice can destroy pigments, alcohol can dissolve some of the pigments and have a similar effect. Interestingly UV light also destroys pigments which is often what people are trying to replicate chemically."
] |
[
"So I have black hair, if I spent enough time in the sun my hair would become brown?"
] |
[
"yes. I have dark brown hair that, when long, turns almost orange at the tips under the heavy sun of Cyprus."
] |
[
"making use of highway right of ways for industrial crops (useless -?- included here)"
] |
[
false
] | null |
[
"(useless -?- included here)",
"If you do this again, you'll be banned. We have this rule for a reason. Our experts spend hours every day reading through posts, and they shouldn't have to open them up to know what someone is asking about. ",
"I see this as a way to bring good crop land back to food production and reduce government expenditures on maintenance of these areas. it could in fact be leased for a profit to help maintain the road system itself.",
"Your post isn't a question, it's a personal theory, and it's not appropriate for the forum."
] |
[
"Nobody critiqued your writing; you were simply told to repost with a question included in the title. You opted not to do so, and made a post where a decent chunk of text is dedicated to complaining about the rule and insulting the mods. This really isn't up for debate, because it's a rule we made out of consideration for the professionals who volunteer their time here to answering questions. Without them, we don't have an AskScience, and we're not going to waste their time with nondescript titles. ",
"We don't allow personal theories to be posted here. We can't vet your idea and tell you whether it's good idea or not. You could try posting on ",
"/r/AskScienceDiscussion",
" if you'd like."
] |
[
"and where else would you suggest asking about it then?",
"Because I am asking about it. I had an idea and I want to know what the people with bigger brains think about it.",
"I wasn't asking to be critiqued on the way I write. or harassed about it. This isn't Jeopardy. It's very frustrating to keep having your questions refused because an arbitrary set of rules. And then having to keep waiting to repost it because of the spam protection( the one thing that I understand, yet, does not make it any less frustrating when you are trying to ask about something. The single question mark has nothing to do with a person ability to understand a sentence. I have brain damage due to a hit in the head in Iraq and have trouble understanding things, what is your excuse?",
"I think my inquiry is perfectly valid."
] |
[
"Is it possible to arrange a series of squares with side lengths 1, 2, 3, ..., n into a rectangle without gaps or overlaps?"
] |
[
false
] | null |
[
"If you look at the simplest cases, you can't arrange two squares with the sides 1 and 2 into a rectangle, nor three (1,2,3) squares. Clearly this doesn't hold for any/every ",
", so I'm not sure what you're asking?"
] |
[
"It's a fascinating question: is there an n such that the set of all squares with side lengths 1 => n can be arranged into a rectangle of an arbitrary size?"
] |
[
"Start by looking at the possible factorizations of the total area.",
"The area of the first n squares is 1",
" + 2",
" ... n",
" = n*(n+1)*(2*n+1)/6.",
"for n = 46, the total area is 33,511 = 23 * 31 * 47. The possible integer rectangles would be 23 X 1457, 31 X 1081, 0r 47 X 713. You can't fit a 46X46 square in the first two choices. The third choice leaves a 46 X 1 rectangle that can't be filled. I can't see how to get to a general proof from this. There may be some n that would work."
] |
[
"Does a empty freezer use less electricity than a full freezer?"
] |
[
false
] |
Re post from Assuming - 1. The freezer is full of ice blocks or 2. The freezer is empty Which one would use less electricity? Initially more electricity would be used to freeze the ice, but once frozen the ice would cause it's own cooling effect so less external input (or electricity) would be needed to maintain the temperature. If the freezer is empty there is nowhere for the cold to be stored so it would leach out faster. Am I right or full of crap?
|
[
"if any object that is warmer than the freezer is put inside it, then the freezer has to work to maintain it's temperature. Work costs energy. So it takes energy for a full freezer, but once everything is in equilibrium with the freezer, than its just the same amount of energy put in as an empty freezer. "
] |
[
"And a full freezer will tend to lose its \"cold\" more slowerly than an emptier freezer, at least when it's opened to remove articles, since air conducts heat faster than most freezer contents do. (I'm not sure if this is true when it's closed or not.) From that perspective, a fuller freezer will tend to use less energy than an emptier one."
] |
[
"http://www.consumerenergycenter.org/home/appliances/refrigerators.html",
" ",
"\"As your food budget permits, keep your freezer and refrigerator full-but not so full that air can't circulate. The mass of cold items inside will help your refrigerator recover each time the door is opened. Here's a hint: If your refrigerator is nearly empty, store water-filled containers inside.\"",
"A nearly full freezer will keep it's temperature down better when opened ."
] |
[
"How did hunters and gatherers really eat?"
] |
[
false
] |
I know today we have the paleo diet and it claims it's how hunters and gatherers ate, but I don't think it's accurate. I'd like to know a few things: I've been looking at multiple sources from native american history to various historic evidence such as stool findings.
|
[
"When we call people hunter-gatherers, all we're really saying is that they don't farm or keep domestic animals, and rely solely on wild foods. In fact a much better word for the way of life is simply \"foraging\": because some \"hunter-gatherers\" wouldn't necessarily hunt ",
" gather.",
"People didn't start farming until around 8,000 BCE. Which means from that point to as far back as humans have existed—2 to 6 million years depending on where you want to draw that line—every human being in the world was a forager. Foragers have lived in every environment on Earth through millions of years of environmental change, technological development and the evolution of the species itself. Some ate mostly meat, some mostly carbohydrate-rich plants, some fish, some fruit... there isn't a wild food out there that people haven't eaten and most foragers would have tried to eat the widest variety of foods they could. In some places and times they had plenty, and only had to forage for a few hours a day (or less) to eat enough. Undoubtedly in others they struggled and starved. And over the course of our evolution we went from eating food raw, to discovering fire and cooking, to learning complex ways of processing, combining and cooking ingredients. So I'm afraid if you want specific answers to your questions you're going to have to narrow down them down a lot!",
"That's why the paleo diet is so ridiculous. How can you possibly claim to know even the \"typical\" diet of the entire world's population for millions of years? The only common feature is that they didn't feature domesticated species, and that's nigh on impossible to replicate today."
] |
[
"/r/brigantus",
" has provided a totally solid answer.",
"To supplement their answer we largely don't have access to enough archaeological evidence to provide definitive answers to most of your questions. What we do have is access to a large number of current pre-agricultural groups of humans. This gives a good idea of what people eat in different environments without access to farming or domesticated animals and plants. By extension we might use this to estimate what prehistoric, pre-agricultural societies ate. What you see is that what people eat is wildly varied and totally dependent on the environment. It ranges from nearly completely plant based to nearly entirely animal based. This paper summarises the macronutrient intakes of 229 extant hunter-gatherer and non-agricultural groups.",
"http://www.direct-ms.org/sites/default/files/E10965-Cordain.pdf",
"There is a preference to meet energy needs via animal products if they are available. This is in part likely due to all of an animal being consumed and organ meats tend to be fattier and more energy dense. Other broad trends include a moderately high but not excessive protein intake (20-35% of energy), lower carbohydrate intake (due to wild grains not providing as much), greatly increased fibre intake.",
"With regards fire there is good evidence that use of fire and cooking predates the emergence of homo sapiens, with homo erectus circa 400,000 years ago. There is possibly increasing support for an earlier date but a date around the existence of homo erectus has fairly good agreement.",
"in summary:",
"What were their macro nutrient ratios?",
"Possibly similar to the ratios listed in the paper I linked above but utterly dependent on the immediate environment",
"How often did they eat? Did they fast for days or weeks?",
"Most extant hunter-gatherer groups eat daily regular meals/food. We don't really have any reason to believe this wasn't common in the past.",
"How much did they process or cook their foods?",
"Cooking was definitely performed and all archeological evidence points that way. Processing would depend on what you mean. There would have been no leavened breads, no cheese or dairy, no tofu and nothing we regard as refined like white bread flour or white sugar. But they might have made porridges, seed cakes and similar.",
"Did they cook over fire or did they have other cooking tools and methods? (e.g. forest natives cooked with fire, inuits boiled their fish)",
"I'm not sure we know a great deal about this. With fire both roasting and steaming are all easily possible as is making flatbread type things. It's hard to regularly boil water without some kind of containers I'm not sure what was commonly available until the invention of pottery though. You can boil water inside the larger bamboo stems but that isn't universally availble everywhere",
"Did they only eat berries or all fruits?",
"Almost certainly not."
] |
[
"Flavour changes do tend to be variations on a theme but wild and domesticated fruit and veg can be quite different, at least for the ones I've tried.",
"Einkorn, emmer and spelt wheats are quite distinct from modern wheats in flavour. They also have a lot more fibre. As einkorn and spelt contain little gluten they make especially dense breads (leavened or otherwise) and that impacts the flavour quite a lot.",
"Wild brassica is a scrubby, bitter cabbage flavoured leaf where brocolli, cauliflower and kohlrabi are quite distinctly flavoured. It always blows my mind that they are all cultivated form the same ancestor.",
"Whatever the wild citrus was it was likely something akin to the pomelo or citron and would have been somewhat sour like a grapefruit. Modern citrus fruits can be intensely sweet and makrut limes are perfumed in a way none of the other citrus fruit are.",
"With regards meat. Most likely domesticated livestock are less intensely flavoured and significantly softer and easier to chew. The most obvious difference most people could try out themselves would be the differnce between wild boar and pork. Where the wild meat will be more intense and gamey. It's a shame there are no Aurochs around to compare to contemporary cattle.",
"But yeah mostly variations on a theme than radically different flavours"
] |
[
"At equilibrium, does the equilibrium constant always equal 1?"
] |
[
false
] |
I recently took a chemistry midterm and the following multiple choice question was asked: "At equilibrium, the equilibrium constant is...?". The correct response was: "is equal to 1". Now, by my understanding, a reaction is at equilibrium when the equilibrium constant (K) = the reaction quotient (Q). So if K and Q are both 50 for example, then the reaction is at equilibrium, no? Am I wrong to say that at equilibrium, K does NOT always equal 1? My prof says im wrong, but I really dont think I am. Can someone explain this to me?
|
[
"I would completely agree with you. The equilibrium constant is dependant on the reaction, and it definitely does not always equal 1. A simple proof of this is that the solubility of salts differ, or that acids have varying strengths. Maybe what he meant was that when a reaction reaches equilibrium, the ratio between the equilibrium constant and the reaction quotient is 1?"
] |
[
"Hey, thanks for your reply.\"Maybe what he meant was that when a reaction reaches equilibrium, the ratio between the equilibrium constant and the reaction quotient is 1?\"\nI thought the exact same thing at first because nothing else makes sense. After talking to him though, he made it clear that this isn't the case. I have gone to him twice and both times he is adamant that k=1 at equilibrium. Ive made so many different arguments, but he wont budge. This class has screwed me for so much stupid stuff already, im pretty fed up."
] |
[
"You should find the relevant chapter in your textbook and discuss it with him."
] |
[
"People have different accents depending on where they're from. Do animals also have \"accents\"?"
] |
[
false
] |
Do animal noises differ somewhat from the same species that lives in another part of the world?
|
[
"Not exactly answering your question but still interesting: As you probably know, bees have different \"dance moves\" to communicate with each other. But bees from different countries or regions will not be able to interpret each others dances correctly. I'm not quite sure if bees from different tribes in the same area understand each other, though."
] |
[
"Many bird species have accents, especially those found across wide geographic areas. Interestingly, depending on the species, their accent can be genetic or learned. They also have variable levels of mutual intelligibility. Your common Black-capped Chickadee is a great example - they are found widely in North America and generally have the same accent except for Chickadees in the Pacific Northwest. In the PNW they have a learned accent that individuals from other regions can't understand. A related sub-species in the PNW, the Chrestnut-backed Chickadee also has a regional accent that the local Black-caps can understand. There are many more examples among birds at the very least. "
] |
[
"Yup:",
"http://www.livescience.com/14197-sperm-whale-language-accents.html"
] |
[
"A question about velocity in space"
] |
[
false
] |
[deleted]
|
[
"In principle, no, there's nothing stopping a spacecraft from doing this. In practice, yes there are things.",
"If you have a rocket, the problem is the ",
"rocket equation",
". The amount of propellant that you require grows exponentially with your desired final velocity (or ",
"rapidity",
", actually, if you're talking ",
"relativistic rockets",
"). The only way that building a different rocket helps you is if you can build one with a higher exhaust velocity, and even then there is a maximum (speed of light).",
"Bussard ramjets",
" were a proposal for harvesting fuel from the interstellar medium while en route, but they appear to be impossible.",
"If you don't have a rocket, then you must be relying on some external source of propulsion (the sun, a laser on Earth). The laser on Earth will spread out over distance, so it will grow less effective the further you go. And I suspect light sails would be pretty useless far from the sun.",
"(disclaimer: I am a computer scientist, not anything rocket-related.)",
"(edit: relativistic rocket note)"
] |
[
"It certainly doesn't work in atmosphere, but it works quite well for station-keeping and minor orbital adjustments. To actually develop a large velocity, yeah, it would have to get away from planetary masses first."
] |
[
"Only if you can build a really, really bright laser. I don't know exactly how bright and big your laser would have to be in order to produce a beam both powerful and tight enough to do better than the sun over the course of your trip."
] |
[
"I am very confused about the sensory transducer channels called Piezo, TRP, and Pickpocket1. Is there any way that someone can explain what they are and how they function? the more details the better."
] |
[
false
] |
My understanding is that they are ion channels that all differ in in function and process different neurotransmitter signals.
|
[
"Piezo is a mechanosensitive ion channel - that is, changes in pressure alter the way it conducts ions. Therefore, it is thought that this channel may play a role in the conversion of mechanical forces into currents, potentially generating an action potential. As far as how the channel actually accomplishes this is still an active area of research not only for Piezo, but other mechanosensitive channels as well. It is thought that altering the curvature of the membrane (e.g., through pressure) changes the conformation of the channel into a conductive state, but the responsible elements of the protein have only been identified for a few channels (e.g., the COOH-terminal domain of a K",
" channel called TREK-1)",
"TRP channels are a broad class of cation-selective channels that can also exhibit mechanosensitivity. For example, the hair cells in your ear express several TRP channels, and it is thought these channels play a role in converting the mechanical forces from sound waves into currents. Additionally, many TRP channels are affected by the \"flavorful\" elements in food. Capsaicin, the compound that gives chili peppers their \"hotness,\" activates the TRP channel TRPV1, which functions primarily as a heat-sensing channel...thus the sensation of heat when you're exposed to capsaicin.",
"I'm not familiar with Pickpocket1, but I did a quick literature search and found that it's a Drosophila (not surprising, considering the colorful name) homologue of human acid-sensing ion channels. As the name suggests, the activity of these channels is sensitive to pH. As far as a physiological function, it appears that these channels can play a role in pain sensing and have been implicated in neurodegenerative diseases, but I can't tell you much more about them."
] |
[
"Ok I have a better Idea now of what these are. Is there any way that I could find the homologs between drosphila and humans? So basically all three are fundamentally Ion channels that sense different forms of stimuli? "
] |
[
"To find homologues between human and D.m. you can use the ",
"Ensembl biomart tool",
". Just use the drop down menus and the options on the sidebar (look at 'Attributes > Homologs and then pick the species in which you want to find orthologs) to find the related gene. Hope this helps.",
"And yes, these ion channels can all contribute to the ability to perceive the classical \"senses.\" "
] |
[
"Would a process that converts chemical potential energy into mechanical energy be subject to Carnot effeciency?"
] |
[
false
] |
Let's suppose we construct a synthetic muscle tissue type molelcule, that when exposed to a particular chemical, reacted by mechanical contraction or expansion with a particular force. Because this process does not invlove heat transfer, is the Carnot effeciency irrelevant?
|
[
"Carnot efficiency only governs systems that derive work by operating between a cold and hot reservoir. So no."
] |
[
"Does such a molecule/device exist?"
] |
[
"Well chemical batteries use chemical reactions to generate electricity. There may be something like what you are suggesting, but the only one I know of is actual muscle."
] |
[
"Why do both birds and bats have wings?"
] |
[
false
] |
Birds are thought to have evolved from theropods long before mammals came about. Birds parted ways with mammals long before rodents existed. How then did bats develop wings? I realize that bugs have wings as well, but bats have a similar skeletal structure, flexibility, size, wing layout, and flight mechanics to birds. Is it a coincidence or is there some way the information could have been passed?
|
[
"... but bats have a similar skeletal structure, flexibility, size, wing layout, and flight mechanics to birds.",
"Not really. The wings on a bat are formed from the phalanges (the analogous structure being fingers on humans), while the wings of birds are formed from the humerus and the radius/ulnar (upper and lower arm in humans).",
"This phenomenon is called ",
"convergent evolution",
"."
] |
[
"It is an example of convergent evolution. That is, two unrelated species develop similar characteristics/traits that often perform very similar functions. It is most likely a coincidence, and ",
" unlikely any genetic information was passed between the two (I say this hesitantly because biology is full of many exceptions, and who am I to say what did and didn't happen anyway, without any solid, outstanding proof?).",
"Bird wings have feathers which extend from their body. Bat wings are made primarily by sheets of skin. Insect wings are formed by extensions of their exoskeleton. Despite the similar functions of the wings between these different types of animals, they would have arose separately.",
"Wing development often starts with a \"gliding\" functionality. Before \"bats\" learnt to fly, they probably stuck to gliding from tree to tree to catch small insects. They most likely started off quite similar to the \"",
"flying squirrel",
"\".",
"Scientists are currently speculating that wing development occurred in birds because it helped them to jump and \"float\" a little in the air, which helped them to catch low-flying insects easier. Eventually their primitive wings evolved to give them the capacity to fly.",
"Basically, no \"information\" was transferred between the two species. The development of wings just helped them to adjust and take advantage of their environments better. And although the wings are similar in function, they are actually quite different if you look at them in detail. Bird feathers are very similar to the scales on a lizard (though they perform different functions), and bat wings are very similar to the skin found in people with webbed digits."
] |
[
"I would also point out that the OP is incorrect in birds being older than mammals. The first true mammals appeared roughly 220 Ma. The first discernable Aves separated from Therapods roughly 150 Ma.",
"Even then, even older ancestors of Mammals, the Synapsids (of which the Mammals are a part of) were around roughly 300 Ma (including the ",
"Dimetrodon",
", which much media seems to pretend is some kind of dinosaur, ignoring the fact that it existed and went extinct ",
" before dinosaurs existed).",
"Mammals have a very interesting evolutionary history, taking us from being the dominant land animals (our ancestors, the Synapsids and Therapsids) to being out-competed by Theropods and being limited to niche environments as proto-Rodents, to becoming the dominant land-forms as the descendant taxon Mammalia."
] |
[
"Is a neutron star a perfect electrical insulator?"
] |
[
false
] |
Neutron stars don't contain any electrons, right? Does that mean that they have precisely zero electrical conductivity? Or is it more complicated than that?
|
[
"On the contrary, they are very very good conductors.",
"Neutron stars are in 'beta equilibrium.' This means that there are a small number of protons and electrons. If you have too many neutrons, it is energetically favorable for some of them to beta decay and become protons and electrons. It's somewhere between a 10 to 1 or 20 to 1 ratio of neutrons to protons. ",
"The protons in the core are under such enormous pressure that they form Cooper pairs. This basically means that protons pair by spin, like electrons filling atomic orbitals. This produces a 'superconductor,' a conducting medium which supports enormous electric currents and magnetic fields."
] |
[
"It's somewhere between a 10 to 1 or 20 to 1 ratio of neutrons to protons.",
"This is absolutely fascinating and I had no idea until now. Do these protons, neutrons, and electrons organize into \"atoms\" of some kind, basically superheavy isotopes of some element? Or is the entire star one big soup of particles?"
] |
[
"It is much more soup like, especially in the part of the star we believe is superconducting. No atoms of any kind, electrons are mostly free"
] |
[
"Historically speaking, how was breathing/respiration explained?"
] |
[
false
] |
People must have been aware that you need to breathe in order to stay alive. How did they try to explain this before the modern explanation was established?
|
[
"From what I understand, the process of breathing was not well understood for the longest time, but Aristotle first thought it to be a mechanism for cooling the heart, as it was understood that the heart produces significant amounts of heat as a byproduct of it's functioning. \nAfter some time, a Greek physician in the Roman empire named Galen provided a semi accurate description of a heart and lungs model, but was not entirely correct as it didn't account for the two types of blood vessels, arteries and veins. \nIt wasn't until the discovery of oxygen gas that the process of pulmonary circulation and gas exchange was understood, which was originally not know to be a passive diffusion process, as opposed to active transport."
] |
[
"Aristóteles explained this as the body connecting with the outside world. Obviously with much more fancy thinking behind it. ",
"https://en.wikipedia.org/wiki/On_Breath",
"Google skills",
"https://pubmed.ncbi.nlm.nih.gov/25532022/",
"The purpose of breathing remained an enigma for a long time. The Hippocratic school described breathing patterns but did not associate breathing with the lungs. Empedocles and Plato postulated that breathing was linked to the passage of air through pores of the skin. This was refuted by Aristotle who believed that the role of breathing was to cool the heart. In Alexandria, breakthroughs were accomplished in the anatomy and physiology of the respiratory system. Later, Galen proposed an accurate description of the respiratory muscles and the mechanics of breathing. However, his heart-lung model was hampered by the traditional view of two non-communicating vascular systems - veins and arteries. After a period of stagnation in the Middle Ages, knowledge progressed with the discovery of pulmonary circulation. The comprehension of the purpose of breathing progressed by steps thanks to Boyle and Mayow among others, and culminated with the contribution of Priestley and the discovery of oxygen by Lavoisier. Only then was breathing recognized as fulfilling the purpose of respiration, or gas exchange. A century later, a controversy emerged concerning the active or passive transfer of oxygen from alveoli to the blood. August and Marie Krogh settled the dispute, showing that passive diffusion was sufficient to meet the oxygen needs."
] |
[
"Death by cold heart. That is, until the first ever person drowned in warm water.",
"Edit: my sincerest apologies."
] |
[
"Does the dna contains the genes for building a mitochondria?"
] |
[
false
] |
I know that the mitochondria has it's own dna but if we remove a mitochondria from the cell, will the cell know to build a new one using code in it's nuclear dna? And now that I am thinking, I have a similar question about the ribosomes. If ribosomes build everything how was the first ribosome built?
|
[
"mitochondria has its own dna and required proteins to duplicate it.\nduring a cell division like mitosis, cell's mitochondrias are spread in the 2 daughter cells and so dont require a synchronous division mechanism in both cell and mitochondria.",
"about the first ribosom, it seems (the real answer and associated evidences will be a golden path to Nobel prize about life beginning) it was a spontaneous association that may have lead (in coordination with information storage into dna/rna) to build up the first auto replicant organism (hi grand grand grand grand grand Pa)"
] |
[
"Over the course of our evolution, mtDNA slowly began to integrate into nuclear DNA. It still does and will continue to do so. So at some point in the future all mtDNA will be part of the nuclear DNA.",
"https://www.nature.com/articles/s41586-022-05288-7"
] |
[
"The cell does not have the information needed to to make mitochondria, and thus would not be able to make more if more was needed.",
"The first ribosome question is really interesting. I don’t know when the first ribosome was created, but it probably took an unfathomable number of tries to get it right. Even after something like a ribosome was created, it probably to another unfathomable number of tries to get it to what we consider to be a ribosome today."
] |
[
"Why do breaks in the bone (such as fractures) cause massive swelling?"
] |
[
false
] |
I've had two bone breaks in my body. One was a hairline fracture in my wrist (the the fracture was in the radius), when i was 7. The other was a complete fracture of my Tibia (which I needed surgery for), at age 14. For both these incidents, the area surrounding the break completely swelled up. For my broken leg, I can understand the swelling, as a piece of my tibia came off and probably irritated the muscle. However, for the broken arm, it was just a small hairline fracture. If it wasn't for the fact that it was swollen and was in some pain, I wouldn't have noticed the break. What is the purpose of swelling? We try to bring swelling down as much as possible in injuries, so how did swelling come to be (from an evolutionary standpoint)? How could my body tell that the hairline fracture was there, and make my wrist swell up?
|
[
"In general, inflammation is the response of capillary beds to the various chemicals (cytokines, interleukins) released by damaged cells.",
"The response is to dilate the capillaries, leading to the leaking of blood plasma (not red blood cells) and white blood cells into the affected area. This allows your body to create a temporary \"workshop\", for lack of a better term, for you to feed material and various helper/killer/cleanup cells into the area.",
"For more minor injuries, this is self-regulating; after the damaged cells are cleaned up and healing has started, the \"alert\" chemicals are gradually either broken down or washed out of the area, allowing the capillaries to contract back to a normal size. The remainder of the material that was leaked into the area is removed via your lymphatic system.",
"Problem is, the body doesn't know when to stop. Your inflammatory system is kind of a \"do or die\" response; it either gets the job done or just keeps on going indefinitely. At times, this can actually cause more problems than it solves - too much swelling in an area can crush other tissues, called \"compartment syndrome\" in limbs, or too much fluid is leaked out into an area, causing an unsafe drop in blood volume/blood pressure. That's called \"septic shock\", generally.",
"So, when a patient has a significant amount of swelling, we treat it to prevent over-loss of fluid or over-accumulation in an area. If it's not problematic and we're addressing the underlying issue, we may well leave it alone and allow the body to go about its business.",
"That make sense?"
] |
[
"Swelling is part of your body's inflammatory response. Your bones are made of cells, fed with nerves, arteries, and veins just like everything else in your body. Swelling is the build up of fluid as your body tries to repair the break"
] |
[
"If it's part of the body's natural response, is there a reason for it, that is, does it contribute to the healing process or is it some genetic leftover? If it does have a purpose, why do we generally try to reduce swelling? Is it only for the comfort or mobility of the patient, or is there a medical reason as well?"
] |
[
"I am allergic to cows while around them, though when I eat beef there is no reaction. Why is this?"
] |
[
false
] | null |
[
"Short answer is that you are likely allergic to animal dander and saliva. The \"meat\" muscle tissue you consume does not contain the same antigenic proteins to which your allergic reaction is specific. "
] |
[
"The answer I was searching for. Thank you."
] |
[
"Most likely I would say you are allergic to the fur of the cow, which would explain why you would be able to consume the beef."
] |
[
"Is our solar system considered normal? What other variations are there? Stars with rings? Stars as planets? Special orbits?"
] |
[
false
] |
[deleted]
|
[
"Our detection methods don't work well for systems that look like our solar system. We don't know yet. What we know for sure: There are many systems that look completely different. Planets much closer to the star, much more distant, inner gas planets and outer rocky planets, planets in double star systems, planets as hot as some stars, ..."
] |
[
"Stars with rings:",
"The Sun does have a number of \"rings\", such as the asteroid belt, but of course this belt is ",
" empty - you are unlikely to see any large object whilst passing through. It is necessary for any ring in orbit around a body to be low density, since any ring which had a high density of matter will slowly coalesce into a planet given time. Ring systems can be found around young stars that are still forming their planets, or ",
" in systems that recently experienced some sort of major event, such as a collision between two planets. Not a star but with regards to rings: the rings of Saturn are something of a curiosity- they shouldn't be stable over long periods. One theory suggested that Saturn's rings were formed relatively recently due to the breakup of a moon.",
"Stars as planets:",
"This sounds like a ",
"binary star,",
" a system with two stars orbiting each other. Whenever you have multiple bodies in space, they will orbit around their mutual centre of mass. If one object is significantly larger than the other, the centre of mass of the two will be very close to the larger one, so the larger object will barely move, and the smaller object will circle it. Amazingly, about half of all star systems contain two ",
" stars- there is no real upper limit to how many stars can form together.",
"Some of our most famous stars are actually systems: ",
"Sirius",
", our brightest star, is one example of a binary system with a large star (Sirius A) being circled by a much smaller one (Sirius B). ",
"Alpha Centurai,",
" our closest neighbour is a three-star system. There are huge systems like ",
"Castor,",
" -6 stars- which ",
"is arranged",
" so that there is a pair of stars, orbiting another pair, the four of which are being orbited by a third pair. The possible joint record holders are believed to be ",
"AR Cassiopeiae",
" and ",
"Nu Scorpii",
" with seven.",
"Special orbits:",
"What we have -elliptical orbits, with low eccentricity so that the orbits appear circular- is a very stable configuration. It's possible to contrive strange orbits like ",
"this figure 8 orbit",
", but these are unlikely to exist naturally: they require very precise starting conditions to form, and minor perturbations are prone to causing the orbits to fall apart. "
] |
[
"Since binary stars actually orbit each other, trying to do some sort of figure 8 around them wouldn't really work. It could probably happen under the most perfect of circumstances, but would still probably be unstable enough that the planet would either be ejected from the system or settle into a normal elliptical orbit eventually.",
"Most likely, the planets in question would either orbit one star or another (with some tugging by the other one) or the planets would orbit the barycenter of ",
", especially if the two stars are really close together.",
"Also, bear in mind that many binaries have a more massive primary and a smaller dwarf companion. They can be the same size, but many, may of them differ in mass. That means that a binary system could look much like our own, just with a smaller star out on the fringes of our solar system, basically in orbit around the Sun like we are. "
] |
[
"I took a long exposure picture of the stars and there are blue and red stars. What does that mean?"
] |
[
false
] | null |
[
"Nice shot! The red stars are cooler, the blue stars are hotter."
] |
[
"could you explain how hot = blue and cold = red stars? wouldnt it normally be the other way around?"
] |
[
"It's like how the blue part of a flame is hotter than the orange part. Hotter things emit radiation with a higher average frequency, and blue light has a higher frequency than red light."
] |
[
"Is there a mutually agreed upon definition of \"cognition\"?"
] |
[
false
] | null |
[
"Sort of. It means \"thought\" or \"thinking\"... But we don't really have a good definition of what it means to think (see for example, Turing's paper where he introduces what we now call the Turing test). That doesn't stop us from teaching cognitive psych courses that include topics like perception, attention, judgment and decision making, reasoning and problem solving, language, memory, learning, consciousness, mental imagery, etc. So all of those fall under topic of cognition... That's about as good as it gets."
] |
[
"Amoeba and humans"
] |
[
"Thanks. I know, as you said, there are no clear boundaries, but could you give me an example of an organism which pretty clearly isn't cognitive, and one which pretty clearly is?"
] |
[
"The Australian Cricket Scandal: How does rubbing tape against the ball make it move unpredictably?"
] |
[
false
] |
So lately there has been this huge controversy in Cricket where the Australian team was caught ball tampering. The bowler apparently rubbed the ball with yellow tape and "roughed up the ball on one side," making it more challenging for the batsmen to hit. How does A). Rubbing a ball with tape rough it up? Is tape really that damaging to the surface of a cricket ball What does tape do to the surface of cricket ball. B). How much of a difference does that actually make? How does the trajectory of the ball change when one side is more rough? How uneven does the surface of the ball have to be to make a noticeable difference?
|
[
"A cricket ball is made of leather, and generally has a smooth surface ",
"when it's new",
", which gets ",
"progressively rougher",
" during the game, due to natural abrasion as the ball comes into contact with the bat, the ground, etc.",
"When a cricket ball is bowled to the batsman (think of it as throwing a pitch at the batter, in baseball terms), it's beneficial to get the ball to 'swing' (i.e. curve in the air). The trajectory of a swinging ball is very difficult for the batsman to predict, so this naturally gives the bowler a huge advantage. ",
"One way to achieve swing is to keep one half of the cricket ball shiny and smooth, while making the other side as rough as possible. When such a ball travels through the air when it's bowled, the surrounding air flows smoothly on one side of the ball, and turbulently on the other side. This causes an air pressure differential between the two sides of the ball, causing the ball to be pushed to one side by the air around it, in an attempt to equalize the pressure. In other words, the air flow is laminar on one side of the ball, and turbulent on the other side.",
"Here's a more detailed ",
"explanation",
":",
"As the ball is flying through the air, a thin layer of air called the \n\"boundary layer\" forms along the ball's surface. The boundary layer cannot stay attached\nto the ball's surface all the way around the ball and it tends to leave or \n\"separate\" from the surface at some point. The location of this separation point\ndetermines the pressure, and a relatively late separation results in lower pressure on that side.\nA side force or swing will only be generated if there is a pressure difference between the two sides of the ball.",
"This is why you'll often see cricketers rubbing the game ball on their pants or other parts of their clothing (which happens to be legal) - they're trying to roughen one side of it. You might also see cricketers rub their saliva on the other side of the ball (yeah, I know, gross) - this is to clean it, and keep it smooth and shiny. ",
"Here's an example",
" of a ball that will probably swing well - notice how shiny it is one one side and not on the other. ",
"(Note: 'inswing' and 'outswing' in the above image refer to the direction in which the ball will swing, which can be controlled by the orientation in which the bowler chooses to hold the ball.)",
"Here are ",
"some examples",
" of the kind of swing a skilled bowler can generate with such a ball, and why it's so effective. Notice how the ball moves in a curved trajectory in the air - this makes it extremely difficult for the batsman to pick where it's going to land.",
"Now, why were the actions of the Australian team controversial? It wasn't the tape itself that caused the controversy - in this incident, an Australian cricketer used a piece of tape to pick up dirt from the field, effectively turning the tape into an abrasive, sandpaper-like object. This object was then used (or was intended to be used) to roughen one side of the ball. This is technically illegal in cricket, since it's using a foreign object to alter the state of the ball, rather than using 'natural' means like normal wear and tear due to play, or rubbing the ball with your hands or on your clothing. Some people also feel that the premeditated nature of the action makes it much worse, since it contravenes the spirit of fair play that the game endorses. Hopefully this explains why the scandal grew as large as it did."
] |
[
"This is why you'll often see cricketers rubbing the game ball on their pants or other parts of their clothing (which happens to be legal) - they're trying to roughen one side of it.",
"Don't they rub it to smooth that side, not roughen it?"
] |
[
"The Magnus effect doesn't come into play with cricket, when talking about a ball that swings as the ball doesn't really spin. ",
"It is due to the pressure differential between the smooth and rough sides of the ball as discussed here: \n",
"https://pdfs.semanticscholar.org/2634/64417e3e708055a658f10b4f256f0607f053.pdf"
] |
[
"A colleague of mine suspects he is being recorded in meetings. Is there any way for him to disrupt/scramble the recording?"
] |
[
false
] | null |
[
"Google",
" - 5 seconds"
] |
[
"He has looked at a few of those, he is just looking for an expecting."
] |
[
"He could try having the meeting in a noisier environment."
] |
[
"How are commercial amounts of Citric Acid produced?"
] |
[
false
] |
Are there groves of Citrus Trees dedicated for this purpose, or are there other means of production?
|
[
"It's not cost-effective to prepare citric acid by extraction from fruit.",
"Instead, it is produced in bioreactors by the action of ",
" type molds on various sugar sources. By engineering the conditions just right, most of the sugars are turned into citric acid, which can then be isolated from the \"broth\", purified, and packaged for distribution."
] |
[
"Pfizer was the first company to employ this method of production in 1929. They were very rich before this, and worth even more afterwards."
] |
[
"Was there a time when this method was not known but citric acid was still in demand? What I mean is, did someone at some point in history get very rich on citric acid?"
] |
[
"Why does light travel so fast?"
] |
[
false
] |
[deleted]
|
[
"Simple dirty answer: It has no mass, so it has no inertia. It happens that the speed of light is also the speed of all the massless things."
] |
[
"That's all gravity is: things moving in a straight line at a constant speed through curved spacetime."
] |
[
"John Archibald Wheeler put it this way: \"Matter tells space how to curve, and space tells matter how to move.\"",
"Objects that are not accelerating move along geodesic paths, which is the technical term for \"straight line at constant speed.\" Photons are not exempt from this."
] |
[
"I can find info on how bumblebees fly. But nothing mentions how they can be so nimble. Without a tail, what mechanism allows them to manage such quick changes of direction?"
] |
[
false
] |
I've seen them float stationary, then take off, then do a complete 180 with no discernable slowdown. How do they do it?
|
[
"Most insects (bumblebees included) don't simply flap their wings up and down. Each stroke (and both the up and down strokes) can be angled and turned depending on what they are trying to accomplish. Additionally they flap very fast. This combination of speed and variety of wing strokes allow many insects to change direction rapidly.",
"How fast are their wings? Synchronous flight muscles beat at 5 to 200 hertz (Hz), in those with asynchronous flight muscles, wing beat frequency may exceed 1000 Hz."
] |
[
"This is great stuff, but also many bees (all if I remember correctly, though I am not sure), have two sets of wings. 2 opposing fore-wings, and 2 hind wings. This ",
" lends itself to the bee's agility."
] |
[
"Aerodynamicist here.",
"tl dr: It's really complicated. Insects use a very different mechanism to fly compared with a plane. It's like comparing ability to turn when running and driving in a car. Their wings and body all act as rudder, motor and lifting device...",
"As others have hinted, the aerodynamics of insect flight is incredibly complex. Much of the information from others is correct although I think it is important to realise that flight for an insect is very different from an aircraft. Insect are small, for them air is much thicker and this is very important because insects generate most of their flight from unsteady mechanisms (watch the first video below for an explaination of what I mean by \"unsteady mechanisms\").",
"To give you some idea of how different insects are from planes, the principle mechanism that many insects use to fly is very similar to the stall process in an aircraft. For those that might not know, stall is very bad for planes. It is explained here:",
"http://www.youtube.com/watch?v=cInwuPmxobM",
"And this is just for hovering flight. There are many additional tricks that can be used. For instance in this video at 31 seconds:",
"http://www.youtube.com/watch?v=4uePMwDf9Io",
"All the blue stuff that comes off the wings represent vortices. Insects are very good at stitching together jets and vortices when they fly, which has the end result of generating strong airflow pushing them in what ever direction they want to go.",
"Essentially they rely on beating their wings which is not a continuous motion it has to be repeated. Further they can position their wings where ever they want. A plane flies using a continuous force (the engine) and it's wings are fixed. ",
"It's sort of analogous to how as a human you sprint, moving your legs back and fourth over and over, your feet can be placed anywhere not just immediately in front of you allowing you to push left or right or jump... dodging is easy...",
"In a car, which constantly just turns its wheels, the wheels must go immediately in front of where they just were, your force is always applied in the same place and turning is done at only 2 wheels and not by the whole car at once...",
"This is why cars turn slowly but people can dodge... ",
"And it's why insects dance around and planes turn slowly. If anything an aircraft is just a bad excuse for a bird...forever stuck in a gliding position...",
"Hope this helps..."
] |
[
"Would it be possible to read and comprehend while entering a black hole?"
] |
[
false
] | null |
[
"You'd be able to read just fine as you cross the event horizon, provided the black hole is massive enough. You would experience a stretching and blue-shifting effect as you approached and passed through the event horizon, but, for sufficiently massive black holes, this shouldn't interfere with reading."
] |
[
"\nWhy? The forces near the event horizon of such black holes are so extreme that you would be ",
"spaghettified",
" (yes, this is a real technical term) immediately, probably much before you \"entered\" the black hole. And even if you survived the entire trip you wouldn't have enough time to see and process even a single word before you became part of the singularity.",
"\nIf you're free falling into a super-massive black hole like ",
"Sagittarius A*",
" then your local frame of reference would be nearly flat and tidal forces would be barely noticeable (at first, that is). Still, you wouldn't get very far into your book since even for an enormous black hole it wouldn't take you more than a few seconds to reach the singularity."
] |
[
"Here's a sort-of simple way to put it:",
"Your field of view changes because black holes alter light itself, with an amount varying on the black hole's size. ",
"So, for a large black hole, it would really impact the text being read, while not so much for a smaller one (which I do realize many have mentioned :P)"
] |
[
"Does all matter give off heat?"
] |
[
false
] |
[deleted]
|
[
"All objects above 0K radiate. You are confusing radiation and NET heat transfer (or NET radiation). The object at 0.01K radiates according to Stefan-Botzman Law proportional to T",
" where T is 0.01K. It also receives radiation from the object at 1000K proportional to (1000K)",
" so the NET radiation the object at 0.01K receives is proportional to (0.01K",
" which is a negative number (or, in this case, net heat gain) so the object at 0.01K heats up."
] |
[
"You may want to read about ",
"black body radiation",
"."
] |
[
"All matter that is not at 0K has kinetic energy that comes from molecules vibrating. This can be seen as \"giving off heat\" if the environment that he object is in has a lower temperature than the object.",
"So yes I'm going to say everything can give off heat"
] |
[
"If I'm in New York and I send a text message to someone in Japan, how does my phone know on which local and undersea cables to send the information through for it to get to the recipient?"
] |
[
false
] | null |
[
"This is decided by each router your message passes by, individually, for each message you send. The question at hand (\"where should I send this piece of information?\") is answered by some quick maths that the computers do relating to whichever ",
"routing protocol",
" they're running. ",
"There are ",
"many different",
" routing protocols to choose from, and each make their decisions on where to send data differently. Of course, the routers can also be manually configured by an admin to say \"hey if this needs to go to Japan I'm for sure sending it down this exact cable every time.\"",
"This played a role in Facebook/Meta's big offline-ining earlier this year, as part of the issue was related to a command sent out that said \"hey, this data is going to Facebook? Facebook doesn't exist anymore.\" Here's a ",
"lay explanation",
"."
] |
[
"Since no answer so far has explicitly said it: your phone doesn't know how the message is sent. It simply sends the message to your phone service provider via the nearest station and that's it, job done for your phone. As already explained in the other answers, the provider then takes care of routing it to the provider of the recipient, who will then push the message to the receiving phone."
] |
[
"Fort phones specifically, your phone is always talking with the nearest tower, so your carrier does know what tower to use to reach you when it needs to send data. When someone sends you a message, it first routes to your carrier (your IP address belongs to a block they own), and then the carrier knows how to physically route it to your device because of its check-ins."
] |
[
"Another CISPA bill is being introduced to \"prevent or mitigate a cyber 9/11.\" How credible is the threat of this kind of attack?"
] |
[
false
] |
Article here: What could a sophisticated attack with the intent of disrupting our economy really do? What would that look like? What exactly are Napolitano and Panetta proposing, how much would it help, and are there alternative ways to protect against these threats without giving the government this kind of power?
|
[
"The most sophisticated cyber attack on infrastructure every carried out (that is public knowledge), was the Stuxnet worm, which was used to attack Iran's nuclear refineries. Stuxnet was a targeted attack, and seems to be deliberately engineered to only activate once inside a control system with certain technical characteristics (presumably those of Iranian centrifuge control systems). However, it also ended up infecting a whole bunch of other systems, and it could have caused a lot more damage if it were programmed to. ",
"Is this a likely kind of terrorist attack? Probably not. Keep in mind that Stuxnet was also likely to be the costliest malware in history, and could really only have been developed by a sophisticated cyber-weapons program in a country like the US or Israel. So in terms of terrorism risk, something like this is probably like the risk of a biological or nuclear attack--potentially very dangerous, but also very unlikely."
] |
[
"What's more is you have to ask the question: is there such a thing as \"cyber terrorism\"? Consider what terrorism is: deliberate attacks which instill fear into the people through mass casualties and destruction; that's hard to do with the tools of the cyber realm. An attack of that scale, say targeting infrastructure systems, is politically (as in direct change of power/coup, which in the US is quite slim) and/or economically motivated, not to bring about fear and chaos. Let alone the cost of manpower and equipment. That is only sustainable by a nation/state (an enormous risk if discovered). Cyber attacks are a means to an end for access, usually not the end of an attack itself.",
"Stuxnet is a complicated tool, and as outlined above the only other cyber attack which follows those political/economic guidelines was the recent ",
"Red October",
" attack within the former Soviet Union.",
"In the US, its all about Anonymous. State actors coming into our networks is common, but don't surpass too great a security threshold.",
"And when it comes to government action, keep in mind there is a lot of difficulty in keeping the laws and justice in line with the pace of the technology. Introducing legislation and policy is a part of that"
] |
[
"In terms of the power grid, it would probably be possible (with good planning and some good luck) to trigger a cascading failure like the one that struck the northeast in 2003. Probably a bit less dramatic since there have been improvements made since that event. Physical damage to the grid would be minimal, since there are many safety devices, many of which aren't networked. However, a number of other systems, such as water and transportation, would be affected by such a large outage. ",
"The ",
"wikipedia article on the blackout",
" discusses some of the effects of the blackout on other major systems, such as water and transportation. ",
"By itself it wouldn't be a particularly effective terrorist attack. Very few (if any) people would die, there would be little lasting damage to the grid itself. However, such an attack could make it possible for a more harmful conventional attack to be carried out. I don't work for the CIA, so I can't tell you how likely something like this would be. "
] |
[
"If all forms of cancer were completely eliminated would it raise our average life expectancy and how much?"
] |
[
false
] |
If not cancer, is there one thing we could cure that would add a huge amount of years to our lives?
|
[
"I think you are right that there is something wrong with using the person-years statistic. According to David Schottenfeld (an epidemiologist at the University of Michigan):",
"Total eradication of cancer by curative and preventive interventions would ultimately result in a gain of about 2.5 years in the average life expectancy in the general population, but for the one in four Americans who would have died from cancer, the gain in life expectancy would range from 10 to 15 years.",
"edit: I think the number you came up with is so far off because cancer mostly affects older people. As you get older, your expected life span gets longer and longer. If you check out ",
"this actuarial table",
", you can see that the average 50 year old man makes it to 79, and the average 70 year old man makes it to 84. Because anyone over 60 has a significantly higher expected life span than a newborn does, it doesn't make sense to use the latter's number as the baseline for the former. Another strange thing about the statistic is that if cancer kills a 75+ year old man or 81+ year old woman, that does not affect the final outcome at all. So the baseline that should really be used is, for the given individual, the expected life span of someone their own age who ends up dying of something other than cancer."
] |
[
"any facts to back this up? e.g in the U.S. it seems around 1/2 a million people die each year from cancer. Supposing this didn't happen, they would die later from other causes. Even if they lived another 20 years, this would add something in the order of 10 million people to the US population, i.e. 5%ish. I doubt this would cause \"massive food and water shortages and serious sanitation issues\". ",
"To consider OP's question, it would definitely increase life expectancy, but in developed countries where mean life expectancy is already around 80, it's hard to see this increasing by much. "
] |
[
"any facts to back this up? e.g in the U.S. it seems around 1/2 a million people die each year from cancer. Supposing this didn't happen, they would die later from other causes. Even if they lived another 20 years, this would add something in the order of 10 million people to the US population, i.e. 5%ish. I doubt this would cause \"massive food and water shortages and serious sanitation issues\". ",
"To consider OP's question, it would definitely increase life expectancy, but in developed countries where mean life expectancy is already around 80, it's hard to see this increasing by much. "
] |
[
"What does human DNA tell us about the evolution of humans?"
] |
[
false
] |
In relation to the fact that it is composed of the same four chemicals, repeated.
|
[
"Is this a homework question?",
"Firstly, DNA isn't composed of four chemicals repeatedly. DNA is a polymer, meaning it is comprised of lots of repeatable monomers. In DNA, the monomer is a nucleotide. ",
"A nucleotide is comprised of an organic base, a sugar, and a phosphate group. In DeoxyriboNucleic Acid, the sugar is deoxyribose. This and the phosphate group make up the backbone of DNA, and the organic bases attached bind via hydrogen bonding to form the alpha helix between two strands. There are four possible bases in DNA: Guanine, Cytosine, Adenine, and Thymine. It is the order of these in each strand that codes for all your genes. ",
"The relationship between these 4 bases and human evolution is that all known life on earth (and some non-living agents like viruses), all use DNA, or its related RNA, to code for proteins. This means it's extremely likely that all life on earth has a single common ancestor. "
] |
[
"There's lots of things about DNA that tell us about the evolution of humans, but wrt being composed of strings of the same 4 nucleotides as everything else, that means that our genetic code is made of the same stuff as various other primates, mammals, chordates, animals, eukaryotes, and finally, all living things, and therefore we can compare how similar our DNA sequences are to all of those different branches on the tree of life and sketch a map of how we came to be what we are."
] |
[
"To be concise, that we are most closely related to chimps and bonobos. Owing to the fact that DNA stores information, by using combinations of these \"four chemicals,\" and our information is most like chimp and bonobo information. "
] |
[
"How are surgical pins inserted through bones?"
] |
[
false
] |
A couple years ago I had surgery performed on my ring finger. It was surgically broken and then set in place with a couple pins, one of which went through the center of the bones in the upper two segments of my finger, to let the bone grow back straight. How do surgeons get those pins in?
|
[
"This may not apply to your finger, but my doctor friend did once describe orthopedic surgery to me as carpentry as much as anything else. In many cases the answer to \"how did they get that pin/screw/strap in there\" is \"with a lot of force, and perhaps a hammer or two\"."
] |
[
"The procedure is called an ORIF, which stands for \"Open Reduction and Internal Fixation.\" An incision is made in the skin, muscles and other tissues are incised or moved out of the way, and the bone is exposed. Then, as other commenters said, screws and pins are (carefully!) driven into the bones with power tools.",
"Here's an animation that shows the procedure. It's on a leg, rather than a finger, but the principles are the same:",
"\n",
"http://www.youtube.com/watch?v=qKeJd0j2J4E"
] |
[
"Dont know about the ones you are talking about, but sometimes they just drill a hole, ",
"grab some giant titanium lag bolts and crank those suckers in there with a wrench",
". "
] |
[
"I hold an empty 12oz glass under an American kitchen sink faucet and turn on the \"cold\" water. The glass fills and I turn off the tap, none drips into the sink itself. If I drink this glass of water, typically how many more bacteria am I consuming as opposed to a factory-sealed 12oz bottle of water?"
] |
[
false
] |
Bonus points: What factors determine the level of bacteria and other undesirables in American tap water? Examples are: facility temperature, time between faucet flows, jurisdiction you live in, elevation, time of day/year, etc.
|
[
"This is an older paper but still has a great deal of info.",
"http://www.mwra.state.ma.us/01news/2008/waterpapertext/textpaperii.htm",
"TL:DR In essence, bottled water is unregulated, untested and has enough human fecal coliform present that it should be. DPW water is consistently tested, regulated and mostly devoid of bacterial contaminants in the US."
] |
[
"Here is a snippet:",
"The relationship between tap and bottle waters was summarized as follows (17):",
"Tap water was purer than 15 samples of bottled water",
"\n3 samples of bottled water were basically as pure as the tap water",
"\n39 samples of bottled water were purer than tap water",
"\n8 bottled waters contained at least 10 times the bacteria of tap water and",
"\n6 bottled waters contained at least 1000 times the bacteria of tap water",
"Edit: formatting on my phone..."
] |
[
"Tap water is much purer than you think. I grow fungi for a living and the particle washing procedure for soil I follow to remove fungal spores has you sieve the soil samples by running tap water over the sample, and I've never noticed anything that I could directly attribute to as coming from the tap. I've also rinsed insects in this way before putting on agar plates to grow fungi from them. Sometimes you'll just get nothing growing and that wouldn't be the case if fungal spores or mycelia were present in any significant amount in the water. Bacteria will have a similar extremely low level of contamination if the water is for human consumption in the US."
] |
[
"What prevents two pieces of metal from bonding together simply by touching?"
] |
[
false
] |
Ignoring metals which form an oxide on their surface, what's to stop me pushing two pieces of metal together to produce one piece?
|
[
"Nothing prevents it, in fact this is what cold-welding is and does.",
"However cold welding only works with flat surfaces.",
"Before you say you have two flat pieces of metal... you don't. You would NOT get consumer level metal that would have properties to allow cold welding to occur.",
"Cold welding occurs at different levels, the flatter the surface the better. Micro and nano level cold welding manufacturing processes exist now.",
"Why does your two pieces of metal not adhere? They aren't flat, are probably coated, have some level of oxide layer, and many many many other factors. You also need much much more pressure to get these pieces to adhere/bond, push with a couple tons of force if your pieces are not flat/clean enough and they will most likely cold weld together.",
"http://en.wikipedia.org/wiki/Cold_welding"
] |
[
"I guess a follow up question to that then is: why does it have to be so incredibly flat to work? It's still just the same two materials being pushed together."
] |
[
"Simple answer: The more flat the object, the easier it is for both objects to get closer with less force applied.",
"I also did not mention, but cold welding really only happened in a vacuum, you can make it occur in a non-vacuum but it requires more energy or force to get the cold weld to occur.",
"In fact macro cold welding requires extreme pressures and rather good vacuums, that being said nanoscale gold wire are found to cold weld together under mechanical connection within seconds."
] |
[
"Why are some parts of the planet rich in gold while other parts are rich in lithium, iron, uranium, or even nothing at all and what determines the planetary distribution of such minerals?"
] |
[
false
] |
Hope this isn't too broad a question as I'm guessing there are many factors at play here (eg. volcanic activity, environmental chemistry).
|
[
"Your guess is correct; many factors come into play and it largely depends on the deposit type. Typically, upper-undergraduate courses in ore geology only scratch the surface on each model of genesis. Broadly - and by broadly I ",
" broadly - ores can be classified into two types: primary or secondary.",
"I would define primary ores as those that developed during the formation of their host-rock. Examples in ore (host-rock) form include porphyry copper and gold (porphyritic granitoid), chromium (layered mafic intrusions), iron (banded iron formations) and potassium (evaporites). Since they are tied to a specific rock, their distribution is controlled by processes that formed such rock.",
"By contrast, 'secondary' ores form by some kind of sorting, winnowing, precipitation, etc. Examples include gold (quartz veins in mylonites), tantalum (pegmatites), aluminium (laterites), and lead-zinc (carbonates). Sometimes this will happen more than once in the case of, say, an epithermal gold deposits being eroded, transported, and sorted into a placer gold deposit. In many cases their occurrence is controlled by a fluid percolating through the rocks (H2O and CO2), but in others it may be magmatic (e.g. diamonds transported from mantle source and deposited in crustal kimberlites). Again, what occurs where depends on a number of factors. Additionally, their distribution often relies on local structures as a consequence of larger tectonics.",
"There is often overlap; a copper porphyry deposit may exhibit an alteration halo with some other ore, or it made intrude a carbonate to form a secondary skarn. Other examples may include a nickel-bearing ultramafic rock (primary) getting sheared so that the nickel is concentrated in pressure shadows (secondary).",
"In many cases, a single element or ore mineral can have many different deposit models. A geologist experienced in Archean lode gold may struggle with Proterozoic VMS, or Phanerozoic Carlin and epithermal deposits.",
"Good topic, tho."
] |
[
"How much of this clumping is chemical in origin, i.e. due to crystallization? Even given the random variation in element abundances, you still wouldn't expect to see overabundances like gold or silver veins unless there were something more than random blending that was driving the process."
] |
[
"When the Earth formed, it accreted from the leftover heavier elements of previous stars. Even if we assume all these elements were placed in varying amounts in a blender and spun to form the Earth (equal distribution in the earth's crust, its is 4.5 billion years of plate tectonics, volcanic activity, continental drift etc that pushed this distribution into \"clumps\". "
] |
[
"Can we determine the orientation of a magnet without using another mainly magnetic instrument?"
] |
[
false
] |
When I was thinking about it I was thinking can we look at a magnet and determine its orientation, but I realized the scale of what is going on with a magnet was probably beyond the visible spectrum. However if we had 2 separate chunks of aligned magnetic material in a place with no other magnetic fields which would influence them, could we determine which end was positive and which end was negative without bringing them together? apologies if a repost, everything is though :(
|
[
"First, magnets are north and south, not positive and negative. We make this distinction because magnetism is not like charge, where you can have positively charged particles and negatively charged particles. To our best knowledge you can only have things with a north and south \"pole\" rather than charge. ",
"But yes, you can measure the current through a loop of wire and \"poke\" the loop with one end of the magnet. If you're looking at the loop from the same side as the magnet, and you're poking the magnet into the loop, if the current goes counterclockwise around the loop then it's the north pole that you're poking into the loop. If the current goes clockwise, then it's the south pole."
] |
[
"You can place a ",
"kind of material",
" above a magnet, and then shine polarized light through the material and see how the polarization rotates?"
] |
[
"Do you consider a Hall probe to be a magnetic instrument?"
] |
[
"How do animals eyes cope with wind resistance at such high speeds. Eg. Falcons or Cheetahs"
] |
[
false
] |
I would imagine their eyes water heavily, since when I ride a roller coaster for example I have a hard time just keeping my eyes open. Do they have a protective layer that we don't?
|
[
"They have a ",
"nictitating membrane.",
" I've been reading up on birds ever since klenow introduced me to their respiratory system a few weeks ago.",
"This is probably not ",
" of the relevant information, but it's what I'm able to contribute."
] |
[
"It really amazes me that there are people out there that study Falcon eyes. Thank you for an informative post."
] |
[
"It really amazes me that there are people out there that study Falcon eyes. Thank you for an informative post."
] |
[
"Is vaccination always recommended after infection regardless of the type of pathogen?"
] |
[
false
] |
Is it my understanding that vaccination for COVID-19 is recommended even if you have previously tested positive for the virus. Is this also the case for other types of pathogens with (relatively) new vaccines such as chickenpox? Why or why not?
|
[
"No, not all vaccines are recommended after infection. This is something that varies according to each pathogen and the evidence base behind vaccination. ",
"I'm sure there are more counterexamples, but two that come to mind are:"
] |
[
"Measles is another example. It provides very durable immunity, so vaccines are not recommended for those who have already had it."
] |
[
"The #1 thing a measles vaccine provides is immunity against measles, which is a serious illness with a roughly 1 in 1000 death rate and other potential complications. It also has the charming feature of occasionally hiding out in a child's brain and reappearing and slowly killing them years later. And it's incredibly contagious. So it's most certainly a disease you want to avoid!"
] |
[
"What's the trick to those \"drop the coin through the plastic reservoir of water and into the tiny cup to win a prize\" games you see at fast food chains?"
] |
[
false
] |
I wish I could find a picture of the game/competition/charity I'm looking for, but I can't. If there isn't a trick to it, what's the science behind it and why is it so hard to make the quarter drop straight down?
|
[
"None of the other answers sound like they know what they're talking about, but I'll assume that's because they haven't taken fluid dynamics. I didn't even know the answer until I took that course.",
"It has to do with vortex shedding (you know, the same thing that makes flags flap in the wind). The angle of the flat body in relation to the force of gravity makes the streamlines around the object change. Doing so creates local pressure differences which creates a torque on the coin and makes it rotate around.",
"tl;dr Fluid dynamics, conservation of momentum/mass/energy"
] |
[
"There is a similar game at my local Taco Bell. Instead of it being filled with water, they have a ",
"cylindrical spiral staircase of plastic steps",
" that gets rotated by a handle on top by you. If you reach the bottom without falling off you win free food. My buddy found a trick where you tap the handle quickly and the coin starts moving down the stair case. He won 3 hard shell tacos, an order of cinnamon twist, and a burrito with the change i received from my meal."
] |
[
"Thank you for that. I was pretty skeptical of the other answers, hence my follow-up questions or lack of replying.",
"This seems like it might be related the reason why windows in my car vibrate like crazy if they are partially rolled down. It kind of reminds me of wind eddies."
] |
[
"Do all non-plant life forms have pleasure responses to induce them to eat/mate? Is this true for bacteria/microbes?"
] |
[
false
] |
People and animals like eating. Are smaller and more simple life forms motivated the same way?
|
[
"This is a pretty existential question. As we don't know what the actual physical correlates of pleasure (or level of consciousness, or any internal percepts) are in any organism it's impossible to look at a given organism and infer it's internal experience.",
"My best guess would be that organisms which can form simple associational memories, probably via a nervous system, and show stereotyped appetitive and aversive behaviors to \"pleasurable\" vs \"noxious\" stimuli will have some level of experience like this. It's definitely possible it exists in the absence of memory, but between not knowing what a conscious experience is and not knowing what benefit it confers, it's very hard to draw a line between \"simple mechanical behavior\" and \"simple conscious behavior with emotions\". On the other hand, I STRONGLY doubt any single-celled organism has any experience that can be likened to \"pleasure\" or anything we experience. The question is more along on the lines of whether simple insects and small multicellular life has some very rudimentary \"emotional\" experience akin to ours in any way."
] |
[
"I’m not sure if you’ve taken a course (or two) in biology, but when you learn taxonomy and evolutionary history, it gets very weird because there’s an entire spectrum of organisms between us and bacteria, and it’s extremely difficult to draw lines. You always see things “start to appear,” but nothing ever just abruptly appears. So when you talk about something like pleasure, there’s a question of how you should define it. In a way, all organisms are just input/output automatons, some more complex than others. Humans can be viewed as a bunch of sensors with a central processing unit that is capable of responding to stimuli using chemicals for regulation. The only reason we can say humans are conscious is that the self can declare itself conscious (and even then, if you wanna get philosophical about it, we can’t prove that anyone else other than the self is conscious)"
] |
[
"Something I've often wondered is if insects/spiders approach rudimentary actual consciousness or are simple input=output mechanical responses to situations. This seems tied into that. Pleasure seeking seems to be a very conscious thing."
] |
[
"Is there a significant variance in the composition of a person's muscle \"type\"?"
] |
[
false
] |
In reading post on the excerpt in question asserts that people have differing muscle "types" (e.g. Muscle that consumes and recovers energy quickly but becomes fatigued quickly, vs slower, weaker muscle that lasts longer). It also asserts that people have a particular composition of muscle made up of more of one or another type of muscle, the athlete mentioned in question being "unique". Is there any science to back up or discredit this "typology" of muscle in people mentioned?
|
[
"I think what that post meant was muscle fibre types:",
"Type I fibres are slow twitch, and are red in colour because they contain a lot of myglobin (binds one molecule of O2 while hemoglobin in the blood binds 4). These muscle cells have a lot of mitochondria as well so they are efficient at using oxygen during aerobic respiration. They are slow to split ATP - this means they are slow to fatigue, but also slow to contract.",
"Both type II fibres are considered fast twitch. Type IIA muscle fibres are red (due to high myoglobin content) but split ATP faster than Type I muscles. They can use both aerobic and anearobic respiration to generate energy. Type IIB muscle fibres are white in colour (due to low myoglobin content). They contract the fastest out of the three and are therefore easier to fatigue. These use glycolysis (anaerobic respiration) to generate ATP, which doesn't require oxygen.",
"Different athletes will have different compositions of these muscle types resulting from different types of training. For example, marathon runners will have more slow oxidative fibers (long duration of aerobic exercise requires muscle fibers that don't fatigue too quickly). On the other hand, athletes that need quick, powerful bursts of energy (say, a boxer?) may have more fast glycolytic fibers - which is what that article seems to claim Messi has.",
"Hope this helps!",
"Edit: formatting + ",
"this",
" may be interesting to you :)",
"Also, according to ",
"this article",
", people are typically born with 50/50 slow/fast twitch muscle types, and switching muscle types with training is still being debated even though ",
"this peer-reviewed article from the Journal of Strength and Conditioning Research",
" says that muscle fibres can switch within their types (IIA <--> IIB).",
": ",
"/u/enragedbee",
" has pointed out that athletes won't drastically change muscle fibre types from training to the extent that they have one muscle fibre type dominating. Plus other cool facts that merits more than a tl;dr ",
"(ﾉ⊙ヮ⊙)ﾉ～『✧~",
"~✧』"
] |
[
"I thought that training only allowed Type II fibres to transform, i.e. a lot of low intensity aerobic work would change Type IIB fibres to Type IIA and a lot of sprinting would cause Type IIA fibres to become Type IIBs. Also, if this was his problem wouldn't it make him one of the fastest players in the world? (I know his quick, but I mean elite-level speed).",
"EDIT: CLARITY"
] |
[
"Under carefully controlled experimental conditions (i.e. with animals), there are observable fiber type changes. For example, under endurance training type conditions, a change in characteristics from fast to slow fiber types can be observed, as well as other changes (qualitative appearance, i.e. how the muscle \"looks,\" vascularization, enzyme concentrations, whole-muscle and individual fiber cross-sectional area, and others) occur as well. Fiber remodeling takes a while, though, because the protein isoforms are different for different fiber types. Also, these animals are either rigorously trained on a daily basis, or electrodes are implanted in their muscles to give a steady supply of motor stimulation (e.g., an electrode in the right Tibialis Anterior muscle of rats, with stimulation of 1Hz for a certain number of hours per day), and these models aren't entirely comparable to what we'd see in an average person.",
"In humans, under normal circumstances (though I'm unfamiliar with the research involving world-class athletes) you're not going to see a drastic change in overall fiber types due to exercise. That is, you're not going to see a runner's calf muscle transition from mostly fast to mostly slow. The reason you see performance increases is due to a number of factors--in the case of sprinters (vs. distance runners), there's increased whole-muscle cross sectional area, increased IIx (fast, fatiguable) fiber cross-sectional area, and increased glycolytic enzymes. Endurance training would cause changes that focus on efficiency rather than power and strength, such as increased oxidative enzymes, increased vascularization in the muscle itself (increasing blood flow -> increasing oxygen delivery), and reduced cross-sectional area to maximize efficiency of oxygen transport. In either case, there's likely some fiber type change (slow-to-fast or fast-to-slow), but not on a drastic level, where someone's body would be dominated by one vs. the other.",
"(side note: interestingly enough, individual muscles have fiber type percentages that are roughly predictable. For example, in humans, postural muscles in the back are primarily slow-fiber muscles, while muscles like the quads and the gastroc are primarily fast-fiber muscles. I specify humans because occasionally different muscles will have different dominant fiber types in different species.)",
"However, changes we CAN readily observe in humans come after disuse/atrophy. A slow-to-fast transition can be observed in affected muscles. In a rehab setting, one of the first aspects of regaining muscle function is regaining the \"endurance\" of affected muscles, as it's among the first things to go with disuse. It's quite literally a case of \"use it or lose it.\"",
"If you want to know more about that specifically, look up research involving immobilization and casting, especially in cases of rehab in which a therapist tries to regain normal muscle function. ",
"Source: Undergrad Muscle Phys class, PT school, and specifically a abook called ",
" by Richard Lieber. ",
"EDIT: And to add what others have said, your fiber types are basically determined before you're even born. That isn't to say, though, that everyone has a predisposition to only be able to perform certain sports. There was an example someone used of \"a marathon runner would never be a defensive lineman in the NFL.\" Well, yes, but that's also a lot to do with overall body type, not just percentages of one fiber type vs. the other. That isn't to say that a predetermined dominance of slow fibers wouldn't help your running career, though--that would absolutely give someone an advantage, in theory."
] |
[
"What benefits does training at higher altitude, if any, confer upon someone when competing closer to sea level?"
] |
[
false
] |
Originally posted this in but thought that you all might have more input into the physiology of it. It's always a topic of discussion during Denver's home games that the opponent's offense/defense seem to look 'gassed' or more tired than usual when playing in Denver. I'm curious though if those benefits would also translate over into away games at regular elevation. I'm afraid I don't know much of the physiology behind it besides there being less oxygen at higher altitude, so are there tangible benefits to playing in Denver versus other places? How large a role could living/playing/training in Denver factor into the conditioning of the players on the team at or near sea level?
|
[
"About to jump in bed, but I thought I'd quickly go over this as I actually just went over this in one of my physiology lectures recently. So, when you go to increased altitude, there is less atmospheric pressure (think of why planes are pressurized, etc). The fall in atmospheric pressure at higher altitude decreases the partial pressure of inspired oxygen and thus there is less oxygen for our blood to carry and this state starts a reaction where production of erythropoietin by the kidneys increases. Erythropoietin is a biomolecular molecule that produces red blood cells and hemoglobin, so therefore we have a net increase in both. Since we have now more blood cells with hemoglobin in our blood, our blood can carry more oxygen to our muscles, brains, etc and it is more efficient.So training in high altitude makes your body adapt to poorer conditions, such that when you compete in low altitude, you have almost \"extra\" blood oxygen carrying capacity.",
"This is a good paper summarizing the effects of altitude on human physiology",
"Fun fact, fetal hemoglobin actually has a greater carrying capacity, so fetuses need less oxygen than their mother while in the womb!"
] |
[
"It's important to note that erythroproietin is not the on regulational increase in high altitude. 2,3 DPG (or BPG) is increased as well which strongly influences the oxygen binding curve allows greater offloading of oxygen in tissue as well as less oxygen binding in the lungs. "
] |
[
"About fetal hemoglobin: it's not that fetuses need less oxygen than their mother, it's that they are more efficient at transporting it from their lungs to their peripheral tissue. "
] |
[
"How long would it take to reach light speed safely?"
] |
[
false
] |
Assuming a craft capable of reaching light speed were built, how long would it take to do so with out injuring the occupants? (Not accounting for time dilation.)
|
[
"Ignoring relativity issues (which is what the question asks), it's a straightforward issue of G forces on the occupants of the spacecraft. There is a limit to how fast you can accelerate/decelerate before G forces will kill or seriously injure a human. With proper training and a gsuit a human body can continuously endure up to 9G (The average unacclimated human with no suit can sustain 5G), this is equivalent to accelerating linearly at 88m/s (gets more complex if we are looking at G forces through a turn).",
"So from here it's pretty straightforward. You want to get to 95% of c, which is 2.85 x 10",
" m/s. So (2.85 x 10",
" m/s) / 88 m/s",
" = 3.24 x 10",
" seconds, which comes out to around 37.5 days.",
"So, if through space magic you fixed all the relativistic issues with going this fast, and your only limit was the endurance of the human body, the fastest you could get up to 95% of lightspeed from rest would be 37 and a half days."
] |
[
"I think you're missing the point of the hypothetical question.",
"We're not trying to bust your chops here. You're asking for a numerical answer based on the rate of acceleration yes? Well, the mathematics literally are working against you here and does not allow what you asking to ",
" occur. It's not even just some principle written in English, it's literally the equation being used.",
"You know the equation for a parabola, right? y = x",
" . Alright, if you draw this parabola, you'll notice that it never crosses into the negatives, you're equivalently asking when does the parabola y=x",
" cross y=-3 on the real number line. Just attaching the word \"hypothetically\" doesn't help at all because there's no logic you can even follow. The answer to your question doesn't exist."
] |
[
"No massive objects can ever travel at the speed of light.",
"...sorry for the unexciting answer."
] |
[
"Where does a star's angular momentum go as its spin slows down?"
] |
[
false
] |
So we know that stars slow down as they age. But total angular momentum must be conserved. Where does that angular momentum go? The dissipation of Earth's tides transfers Earth's angular momentum to the moon (as shown in my answer at ). But where does a star's dissipation go?
|
[
"Layman here.",
"The dissipation of Earth's tides somehow transfers Earth's angular momentum to the moon",
"This energy is transferred to the moon via ",
"tidal acceleration.",
" The way I picture it is that Earth's tides are two waves that travel around the Earth; every 24 hours they make one complete rotation. The Earth's rotation is slowed down by the friction between the surface and the water.",
"Because of the friction, the waves aren't able to be exactly where they want to be; ideally, one wave would be pointing exactly towards the moon, and the opposite wave would be pointing exactly away from the moon. But instead, it's slightly off center. Since each of the waves has its own mass and its own gravity, the near wave pulls the moon in the direction the earth is rotating, and the far wave pulls the moon in the opposite direction the Earth is rotating. Since the near wave is closer, it exerts a stronger force, and the net effect is that the near wave is pulling the moon in the direction that the Earth is rotating.",
"Since no solid is perfectly rigid, this happens even in solid bodies with no oceans. But this effect is much weaker for solid bodies.",
"So we know that stars slow down as they age. [...] But where does a star's dissipation go?",
"When a star burns, it replaces low-density hydrogen with high-density helium. (well, relatively high density) As the density in the star's core increases, the rate at which it burns hydrogen increases. Since it burns faster, it heats up. This increase in temperature makes the outer layers expand. This expansion of the star causes its rotation to slow down."
] |
[
"If the star expands in radius during this process, the angular momentum can be conserved.That's the only \"conventional\" behavior I can imagine that explains the behavior, but the creation and subsequent radiation of energy in the star may also play a role."
] |
[
"wikipedia says that some angular momentum from a neutron star is lost through its own magnetic field",
". I suppose that if it were a neutron star, there may be stellar remnants surrounding that star. Some rotational energy could be transferred to those stellar remnants."
] |
[
"How do proteins work on a atomic scale?"
] |
[
false
] |
I know how proteins are build up, what they do and how they are created, but it is still is a mystery for me how they exactly work. For example alpha-amylase, how does it break down starch into maltose? Does the structure of the protein create electromagnetic forces, that break down the bonds between the sugar molecules?
|
[
"In general enzymes create a micro-environment that stabilizes a transition intermediate in a reaction. This lowers the activation energy of the reaction and allows it to proceed much faster then it would in a regular environment."
] |
[
"This isn't alpha-amylase, but these videos of ",
"atp synthase",
" show how enzymes work by undergoing conformational changes when molecules attach to their binding sites. ",
"This clip shows a simple, fictional enzyme",
", and how it acts as a substrate to two fictional molecules. As soon as they're both bound to their binding sites, the enzyme undergoes a conformational change, bringing the two molecules into a position where they can easily bind to each other. Once bound, the enzyme bounces back and releases the new combined molecule."
] |
[
"Thanks vor the videos, they are great. Together with the post above, I'm finally able to understand it :)"
] |
[
"Inspired by a (very) recent post: what's the best way to maintain a cool temperature in my dorm?"
] |
[
false
] | null |
[
"Get a fan pushing air in from the window and try to seal the window as well as possible so the new air doesn't get pushed back out.",
"Get a buddy to do the same thing but with his fan pointed out and then leave both your doors open to establish airflow through the building."
] |
[
"Create a draft. Your fridge puts out a fuck ton of heat, though. Put it near the side of the room where the air is escaping. A west facing wall isn't all that bad. Put up a reflective screen in the evening. You can get one of the ones made for car windshields at walmart. "
] |
[
"There's no magic answer, man. Just buy an air conditioner. If it's running at full blast and you're not getting cooler, then you need to improve the insulation of your room. Blocking the crack under the door and covering the walls with cloth wall-hangings might help some, but you're fighting an uphill battle. ",
"If AC is off limits, your best bet is to put something with a giant thermal mass in your room (if you're feeling especially DIY capable, you should consider getting a phase change material that melts ~23 C from an industrial supplier) and get it as cold as possible at night. Then, during the day do as much as you can to prevent light and heat from outside from getting in so the thermal mass can do its job."
] |
[
"Is it possible to re-enter the earths atmosphere with out (I don't know what to call it) the burn up stage?."
] |
[
false
] | null |
[
"There is an answer for a very similar question ",
"here.",
". I suggest you have a look at it first."
] |
[
"Thank you!. "
] |
[
"Hi Twiggy199 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Do women who opt to skip their periods via birth control experience menopause at a later age?"
] |
[
false
] |
As I understand it, women are born with a set number of eggs, and (this is where I might be wrong) menopause occurs when those eggs run out. Some women choose to have their period once every three months (or longer), and can do so via birth control pill. If the eggs aren't "wasted", is there a delay in the start of menopause?
|
[
"So you're not far off the mark - the human body is born with a set number of eggs. During fetal development, a couple thousand germ cells start multiplying like crazy - at a fetal age of roughly five months, they've formed into 5 to 7 million egg cells. Numbers wise, it's all downhill from here. At birth, 1 million or so egg cells remain; at the onset of menstruation, it's down to half a million.",
"In the late 30's, oocytes (egg cells) number around 25,000. Around here the decline accelerates even faster. As the numbers decline, menstrual irregularities start to develop over a period of roughly a year, with menopause ultimately occurring within a year or two of turning 50.",
"Here's where a slight correction is in order. The oocytes aren't declining in number solely because they're being flushed out every month during menstrual cycles, or becoming fertilized and contributing to a pregnancy. Oocytes decline and die off as a function of ovarian aging. Part of this is protective effect. As the oocytes age, the risk of genetic aberrations such as Down's syndrome becomes progressively higher. ",
"As far as birth control's specific effect on menopause timing, I'm just going to quote my source text directly:",
"\"The average age of menopause has remained constant throughout recorded history. It does not appear to be related significantly to race, parity, height, weight, socioeconomic status, or age at menarche. Evidence suggests that genetic and environmental factors influence the age of menopause, although the specific nature of these relationships is characterized poorly. Given the strong association between age at menopause between mothers and daughters, this is likely a genetically determined trait. Environmental factors may not have a significant effect in themselves, but the interplay among environmental factors such as smoking (known to accelerate the age of menopause by 1.5 to 2.0 years), body mass index (BMI), alcohol use, and socioeconomic status and genetic risk may be important.\"",
"Source: Danforth's Obstetrics and Gynecology"
] |
[
"Thanks for the great reply. Wikipedia gave me the vague idea that birth control pills didn't have an effect, but I didn't have access to Danforth. ",
"Learned a lot. Cheers. "
] |
[
"I'm not qualified to comment on the idea that women are born with a set number of eggs but i'm aware their is some recent dissent on that topic\nconsider ",
"http://news.nationalgeographic.com.au/news/2012/02/120229-women-health-ovaries-eggs-reproduction-science/",
"and ",
"http://www.wired.com/medtech/health/news/2004/03/62609"
] |
[
"Is there a limit to how deep ocean trenches can be?"
] |
[
false
] |
I remember a question a while back about the limits of how high mountains can be, and it made me wonder about the opposite. The Mariana's trench is the deepest in the ocean, and (I believe) some points of the arctic ocean are the closest to the center of the Earth (due to Earth not being perfectly spherical). Is there some way to figure out what the hypothetical lowest point of an ocean can possibly be? Or how close to the center of the Earth it can be?
|
[
"The Mariana Trench is a special case and still under investigation; however there is a central point to be made regarding your question. The depth of a trench is likely to be controlled by the ",
"style of subduction",
" which is controlled, in general, by the age of the slab and the rate of subduction. Oceanic subduction zones can be classified into normal-to-steep (high-angle) and flat (low-angle) subduction styles. Steep (normal) subduction ",
" has a dip angle of ≥ 30°, although some areas are > 70° at the top of the upper mantle, whereas flat subduction is characterized by ",
"shallow dip angle and a high degree of coupling between the converging plates",
" less than 30°. ",
"Slab roll back",
" occurs as the slab sinks into the mantle, and the trench propagates towards the subducting slab (this is how back-arc basins form such as the one between ",
"Japan and North Korea / Russia",
"). \nThe following is an excellent paper on the bathymetry of the Mariana Trench and the complexities that are considered: \n",
". \nSo, yes there is a limit to how deep ocean trenches can be because there are limits to the driving forces that control their formation such as subduction (maximum age of the oceanic crust as it reaches negative buoyancy is ~200Myr) its related forces (ridge push, slab pull, etc.) and the rheology of the slab in question. Currently the steepest dipping slab is located in the Mariana Trench where, not coincidentally, the oldest oceanic crust is also located. \nI'm unaware of any calculations based on lose hypotheticals but given a maximum oceanic crustal age, subduction rate and slab roll back, I would postulate that the Mariana Trench is a likely candidate for an end-member on possible trench depths under Earth's current geological configuration. ",
"Somewhat unrelated, but interesting: The thickness of the oceanic lithosphere can be estimated using the following formula: L = 11 x the square root of its age at that location ",
"Depth of the ocean can be estimated using the following formula: \nD = 2.5 + 0.35 x the square root of the age of the oceanic crust at that location (generally it will be slightly shallower than the estimated value calculated due to volcanics and accumulated sediment)"
] |
[
"That would be pretty cool, getting so deep that the heat of the earth boils the water, but the pressure above instantly compresses it back into a liquid creating a bubble of gas at the bottom of the ocean.",
"Is that even possible?"
] |
[
"There is water in the mantle! It just is in molecular form in minerals. See work by Marc Hischmann from Univ Minnesota if you want to nerd out about it. Interestingly there is more water in the mantle than on the surface."
] |
[
"My 8 yo Daughter just asked me what the slowest creature in the ocean is? Can you help me Reddit?"
] |
[
false
] |
[deleted]
|
[
"There are plenty of bacteria in the ocean that move at a maximum speed of only tens of microns per second. I'd say they're probably the slowest creatures in the ocean. If you want the slowest macroscopic animal, I'd go with some sort of jellyfish."
] |
[
"The ones that don't move. By creature I assume she means animals not plants. There are animals like corals and oysters that once they reach adulthood are fixed in place much like plants. \nThen there are innumerable creatures in the ocean who are free floating, but not really capable of independent movement. They move only at the whim of currents. These types of creatures range from microscopic plankton to much larger jellyfish. "
] |
[
"I might go with adult coral, which are animals but sedentary; they don't move. Most people think they are plants. "
] |
[
"Why is Technetium radioactive?"
] |
[
false
] |
It's in the middle of the periodic table with stable elements far along on both sides. What is so special about 43 protons?
|
[
"The stability of an atom is determined not just by the atom in question, but the atoms that it could decay into as well. If an atom is heavier than another one plus the mass of any emitted radiation needed to get there, then it will be radioactive. This is because mass is energy (E=mc",
") so extra mass means energy available to emit.",
"So the basic answer is \"because every Tc atom is heavier than an Mo or Ru atom of the same mass number plus and electron and neutrino\".",
"Why that the case? A major part of it is that nuclei are lighter and therefore more stable when they have (separately) even numbers of protons and neutrons, because they like to pair up. Tc has 43 protons, so it's partially screwed on that count. Furthermore, Tc-98 is smack on the line of stability, but has 45 neutrons, and is screwed on both counts (and Ru-98 is even-even of course, so that exacerbates the difference in mass). Its neighbors Tc-97 and 99 would have a good shot at being stable having even numbers of neutrons, but nuclear physics just happens to work out to make them barely able to decay to Mo-97 and Ru-99 (both are over the threshold by only about 300 keV, which is around 60% the mass of an electron).",
"Why did the masses happen to work out this way for Tc when it doesn't for most other odd-proton elements (Promethium is another example)? I'm a nuclear physicist that specializes in measuring nuclear masses, and I have long ago given up trying to understand how nuclear masses work. Nuclear theory is so complicated that it is basically unsolvable, so I can't point to any one effect that caused this. For now we just go out and measure the masses.",
"I know that's unsatisfying, but so is nuclear physics in the end."
] |
[
"Why is it that adjacent isobars can't be stable?"
] |
[
"Basically it is just a bad number. Normally, atoms with even atomic numbers are more stable than those with odd atomic numbers. This makes sense because in the odd number situation you always have that one man out. Elements with an odd number of protons can sometimes fix this with the correct number of neutrons giving them at least 1 stable isotope. This is not true of Technetium. There are no known numbers of neutrons that can stabilize technetium. If you do the math, you'd find likely stable isotopes of technetium\nBetween 95 and 102. Elements 42 and 44 already have stable nuclides in this region. Since adjacent isobars cannot both be stable, this eliminates the possibility of a stable\nTechnetium isotope. ",
"I left out a few finer details, but this is the basic idea. "
] |
[
"So what would happen if a thimble full of Neutron Star were to suddenly transport itself instantly into empty space?"
] |
[
false
] |
Number 6 on this link: In case you don't click the link: 6. Just a thimbleful of a neutron star would weigh over 100 million tons. So what would happen if this little thimbleful of star were to pop in empty space? Would it explode? Expand? Or would it be like "naa, i'm just gonna stay a thimble size, try and pick me up foo!" I'm curiously confused...
|
[
"It would expand phenomenally fast (might as well define it as an explosion), as the force compressing it would be gone. It would be at a very high temperature, but more than that the structure of a neutron star is extremely unstable and only held in place by the massive gravitational field of the star, so most of the force of the expansion would, I would say, come from the nucleons returning to lower energy states.",
"Basically though, big big explosion."
] |
[
"volume and mass are not directly related, and while it would likely \"explode\", it's own gravity would immediately become a factor in what happens next."
] |
[
"cool thanks, but dare I ask, how big? "
] |
[
"What regions are presently the most prone to large scale geological events?"
] |
[
false
] |
[deleted]
|
[
"The regions that in general terms are most prone to geological events are located at plate boundaries, that means regions were two or more tectonic plates collide (subduction zones), diverge (divergent) or 'slide' alongside of each other (transform boundaries). See here for a map: ",
"http://en.wikipedia.org/wiki/File:Plates_tect2_en.svg",
"Of those three boundaries the subduction zones (arrows pointing towards each other) and the transform boundaries (arrows pointing in opposite directions NEXT to each other) are the most prone, and, if you so will, the most dangerous regions. Those regions are, amongst others, US Westcoast, Japan and Mediterranean Sea. "
] |
[
"On a smaller scale, there are for the example New Zealand and its North-South running fault system, Southern Italy and the eastern Mediterranean Sea, also the Andes Mountain Range.",
"If you are looking for danger areas in the US, I cannot help you further since I am not from that continent. ;)"
] |
[
"What about on a smaller scale? What are some regions that would follow along the lines of the New Madrid Fault or the Yellowstone Caldera?"
] |
[
"Stoner friend keeps trying to convince me that smoking pot doesn't cause cancer. How can this be true? Is marijuana smoke really that different from cigarette smoke?"
] |
[
false
] | null |
[
"From a recent review:\n\"Cannabis smoke is carcinogenic in rodents and mutagenic in the Ames test. Cannabis smoke contains several of the same carcinogens as tobacco smoke at up to 50% higher concentrations and with three times the tar per cigarette.\" However, \"it has been difficult to strongly correlate cannabis use and the development of human cancers.\"",
"The studies that the review looked at gave mixed results, with some studies showing correlation between marijuana use and cancer rates, and other studies showing no effect of marijuana on cancer rates. So, currently there is no strong consensus one way or another in terms of the carcinogenic effects of marijuana smoking.",
"The review can be found here:\n",
"http://www.ncbi.nlm.nih.gov/pubmed/22019199"
] |
[
"IIRC, isn't the issue that even the heaviest stoner smokes less than a chain tobacco smoker? Or is that sort of thing irrelevant given how these various studies measure/use their statistical magic and what not? "
] |
[
"While \"tar\" usually refers to wood tar made from pine or birch, almost any plant matter, when heated, will release the fluids inside as a tar-like substance. In the case of cannabis and tobacco, the smoke you inhale is composed of droplets and fine particles of this substance. The tar is actually the delivery mechanism - the THC or nicotine present in the plant is carried into your lungs by the tar, where it sticks and transfers the chemicals to your bloodstream. "
] |
[
"If light travels faster than anything in the universe, but still has enough mass to be pulled in by a black hole, how does it not destroy everything in its path?"
] |
[
false
] | null |
[
"Light does not have mass."
] |
[
"How does it get pulled in by the black hole? "
] |
[
"Every kind of particle interacts with gravity, even if it has no mass."
] |
[
"Why does my pur carbon filtered water actually has a higher total dissolved solids then my tap?"
] |
[
false
] |
The filter is the faucet mointed basic design. It was flushed and it has about a week worth of use. My tds meter has automatic temperature compensation. I tested phoenix tap water. Tap was 425 ppm Filtered was 450 ppm
|
[
"Consumer water filters use materials called ion exchange resins to remove metals like calcium or lead from water. They essentially work by swapping out an ion that had been preloaded onto the resin for the one in the water. Ions like calcium or magnesium have a +2 charge. Sodium has a +1 charge. Because you have to maintain charge balance in solution, you end up adding in two sodium ions for every calcium that gets removed. This would register as a greater ion concentration in your detector. ",
"There are exchange resins that produce water after the ion swap instead of other ions, but you wouldn't want to pay for a system like that unless you really needed pure water."
] |
[
"No, the activated carbon will remove the non-ionic impurities that can give water an unpleasant smell or taste. I suspect that your tds meter is actually just a conductivity probe, and it would only detect ions anyway."
] |
[
"This is very interesting!",
"Do activated carbon filters add anything to the water as well?"
] |
[
"Why do people grind their teeth when they are asleep? Aren't all the muscles supposed to be in sleep paralysis?"
] |
[
false
] | null |
[
"Muscles aren't ",
" paralyzed ",
" the time during sleep. Muscle tone is usually reduced during sleep (hypotonia) and is sometimes nearly absent during REM sleep and other times (atonia). But during hypotonia, and even atonia, there are exceptions.",
"For one, the atonia is not anatomically uniform. Some cranial nerve motor branches escape this atonia (eg. eye movements or jaw twitches during REM). In addition, atonia and hypertonia are punctuated by various arousal episodes, including jaw and mouth movements. It's during these arousals that motor events, like jaw clenching or grinding, can occur.",
"Everyone has these arouals, but people with sleep apnea or, in this case, bruxism (teeth grinding during sleep) experience many ",
"more arousals",
", during which individuals with bruxism grind their teeth. ",
" people with bruxism have more arousals is an open question."
] |
[
"I can attest that because I clench my teeth at night(not grind) and multiple times I have caught myself clenching while conscious due to being stressed or tense. It's something I do unconsciously, and I assume that it would be the same for those that grind. "
] |
[
"I can attest that because I clench my teeth at night(not grind) and multiple times I have caught myself clenching while conscious due to being stressed or tense. It's something I do unconsciously, and I assume that it would be the same for those that grind. "
] |
[
"What would this stuff do to bike tires in the rain?"
] |
[
false
] |
it was posted in videos and the question was asked would your traction be better or would it completely screw you up and make you hydroplane?
|
[
"I've worked with hydrophobic materials in pharmaceutical development (making sure aqueous proteins do not adhere to the reaction vessel), but not necessarily with the physics of the material. I would think that the tire and the road would both have to be hydrophobic for traction to improve, and that with only one surface being treated, there would be a reduction in friction between the two materials because one would be wet, and the other would be repelling the wet surface."
] |
[
"In practice bicycles ",
"can't hydroplane",
"."
] |
[
"Having raced bicycles, allow me to report that while they may not hydroplane, per se, bicycles are still definitely at increased risk of loosing traction on wet roads. Road paint and steel sections are especially hazardous."
] |
[
"Why does the light of a star seem to flicker, while that of a planet does not?"
] |
[
false
] |
I would assume it's because of the huge difference in distance from our eyes, buy there are probably other factors, like the fact that there aren't constant explosions on planets. I was looking at Venus last night, at least I think it was, and it didn't flicker while the stars around it did. Even then, some stars flickered and others didn't.
|
[
"To add onto that, the amount of light received from an object varies with the inverse square of the distance. So, for objects that \"transmit\" the same amount of light, the closer one will be much brighter. If I put a light bulb a foot away from my eye, and then another one ten feet away, the light bulb that's a foot away will be a hundred times brighter to me."
] |
[
"The other answer is incorrect; here's the real scoop:",
"Stars are ",
" far away; so far away that they are essentially points of light. Due to movement of the air, along with the fact that air of different density/temperature has a slightly different refractive index, causes light to be ever so slightly bent as it travels through the atmosphere. Turbulence means that the bending is constantly changing, resulting in the \"twinkling\" of stars that we're familiar with.",
"Even the closest stars are tens to hundreds of thousands of times further away than the planets; so even though the planets are smaller than stars, and might appear to just be points of light like the stars, ",
"they are actually much bigger in the sky",
" than the stars. ",
"Reference this handy XKCD chart on angular sizes",
"; the \"largest\" stars in the sky are hundreds of times smaller in apparent size than most significant objects in the solar system. ",
"The amount of movement of the \"twinkling\" of star light is usually smaller than the angular size of the planets, so you don't notice it."
] |
[
"Image",
" Angular Size",
" If the celestial sphere were mapped to the Earth's surface, astronomy would get a LOT easier; you'd just need a magnifying glass.",
"Comic Explanation",
" This comic has been referenced 7 time(s), representing 0.065% of referenced xkcds.",
"Questions/Problems",
" ",
" ",
"Website"
] |
[
"How dangerous is bleach?"
] |
[
false
] |
Hi AskScience So my dad has once again decided that the clinker bricks around our house aren't white enough, and is spraying them with bleach. There is now a very strong smell in the entire house, including my bedroom. Is there any danger in me breathing the vapors for several days?
|
[
"Bleach is a powerful oxidizer.",
"\n",
"http://en.wikipedia.org/wiki/Oxidative_stress",
" ",
"Bleach is sodium hypochlorite, the sodium salt of hypochlorous acid. Oxidizers destroy cell tissues, shred DNA and create tons of free radicals and other secondary products that are very toxic. These things are definitely correlated with cancer and DNA mutation during cell replication and a host of other diseases listed in the wikipedia article.",
"Essentially, whatever bleach will do to destroy bacteria, it will do similar things to your cells too. Is there hype about how bad it is? maybe, there are groups trying to get bleach banned or regulated. Are they overhyping? maybe, but it is a strongly reactive chemical, like lye, it should be used with caution and definitely not inhaled. The lungs are delicate organs.",
"I appreciate metalmoe posting the MSDS, that is a good place to go too, but they often primarily state the immediate acute health effects and not longer term exposure."
] |
[
"Here is an MSDS",
" for bleach. It says that exposure to vapours may irritate skin, eyes, nose, throat, and lungs, and may aggravate chronic respiratory conditions such as asthma.",
"It doesn't sound like anything too serious, but you should still be careful. Get yourself out of the house as often as possible to get fresh air, open windows and use fans to try to get rid of the vapours, get medical attention if you think you have any serious symptoms, and call your dad an idiot for doing such a stupid thing."
] |
[
"Open a window."
] |
[
"Reddit! Do you have ideas for science labs/projects for blind youth?"
] |
[
false
] | null |
[
"Have them smell a variety of Jolly Ranchers (sour apple, cherry, grape, etc.). Let them taste a few. Then have them taste the Jolly Ranchers while holding their nose shut. Most people can't distinguish between the flavors at that point.",
"Afterwards, you can discuss the link between scent and taste."
] |
[
"Here",
" is \"The Earth as a Peppercorn,\" a great activity for getting a sense of the scale of the solar system on the National Optical Astronomy Observatory website. The nice part is that the distances and sizes are already worked out for you at this website. It is straightforward to appreciate the planetary sizes tactilely, and getting a sense of scale by walking is also a non-visual experience."
] |
[
"This helps out a lot because I was already trying to figure out how to do a scale of the solar system for them! Much appreciated! "
] |
[
"New Horizons is going to go at a distance of 12000k from Pluto from the Charon facing side. Considering that Pluto to Charon is ~18000km, doesn't that make NH closer to Charon than Pluto?"
] |
[
false
] |
[deleted]
|
[
"The countdown clock indicates the actual time closest approach is happening, not adjusted for light travel time.",
"We won't be getting signal back for quite a while after closest approach anyway. The spacecraft doesn't have any moving parts, so the radio dish can't always be pointed at Earth when instruments are pointing at Pluto or the moons. The spacecraft will send us a 'phone home' signal to indicate it is still healthy, which we will receive Tuesday (July 14) at ~9pm EDT. The data will start being transmitted to us on Wednesday (July 15)."
] |
[
"When New Horizons passes through the plane of the Pluto system it will be at Charon's distance, on the side of Pluto opposite Charon. This is the place least likely to have debris floating around. Closest approach to Pluto will actually happen about 20 minutes after New Horizons passes through the plane of the system, since New Horizons is travelling at a bit of an angle relative to the plane of the Pluto system. Check out ",
"this graphic",
" and the graphics on the ",
"webpage showing the current location New Horizons",
" to get an idea of the flyby geometry."
] |
[
"Is the New Horizons time of closest approach given as the actual time that it's happening, or is it adjusted for the travel time of light from where it's happening?",
"I mean, the countdown clock right now says 15 hours 37 minutes, so does that mean that we wouldn't be getting any signals back from it until over 20 hours from now?"
] |
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