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[
"How would someone derive a roll equivalent of a D20 using D6?"
] |
[
false
] |
Just a little math problem I've been trying to figure out in my head for a bit that I'm having trouble with. How would you get the closest to a D20 roll outcome using multiple D6 rolls? Is it painfully simple?
|
[
"If you're just looking for a convenient way to enact d20 rolls when you don't have an actual d20 around, the way I did it was this:",
"Roll the d6 once. Reroll it if it comes up 6. Multiply this number by 4. You now have 0, 4 ,8, 12, or 16.",
"Roll the d6 again. Reroll it if it comes up 5 or 6. Add this roll to your previous number.",
"You now have a number from 1 to 20. Great success!",
"If you're looking for a more rigorous algorithm, sorry, I've got nothing."
] |
[
"If you want to be rigorous about it, you could use a Markov chain to verify that the probability of each outcome works out to be equal to 1/20."
] |
[
"Why would we do math when we have matlab?",
"rolls = zeros(1,20);\nfor i=1:1e7\n d1 = randi(6,1,1);\n while d1 == 6\n d1 = randi(6,1,1);\n end\n d2 = randi(6,1,1);\n while d2 >= 5\n d2 = randi(6,1,1);\n end\n d20 = 4*(d1-1) + d2;\n rolls(d20) = rolls(d20) + 1;\nend\nplot(rolls/1e7); axis([1 20 .049 .051]);\nxlabel('Equivalent d20 roll');\nylabel('Frequency');\n",
"Result: ",
"http://i.imgur.com/u4z9c.png",
"Looks about right. Note that Das_Mime had an omission in his explanation: You need to subtract 1 from the first d6 roll before multiplying.",
"Edit: Also, matlab needs do-while, please and thank you."
] |
[
"Since all emotion is in the brain, why do different feelings seem focused in different places?"
] |
[
false
] | null |
[
"I think the simple answer to this is that the body and brain release different hormones (in different proportions) in response to stimulus. These hormones act on body systems in different ways, which may be \"felt\". For example, stress is associated with cortisol, which acts on a vast array of body systems. ",
"http://en.wikipedia.org/wiki/Cortisol"
] |
[
"Both of those seem...unscientific. How can \"the body\" possibly \"feel\" independently of the brain when everything we know about feeling traces back to neurons? "
] |
[
"This makes more sense to me. So it's just that different hormones are processes by different organs, thereby making different sensations? Cool. "
] |
[
"Does cooling really account for 30% of all CO2 production by humanity?"
] |
[
false
] |
Today, my professor for thermodynamics claimed that 'it is estimated that cooling (i.e. airconditioners, refrigerators and other cooling devices) account for 30% of humanity's CO2 production. It sounded like quite a bold statement to me, so I wonder: is there any truth to this claim?
|
[
"Ask him to provide a source for that statistic next time you see him. ",
"The number seems high, but not outside the realm of possibility considering ",
"this",
" site claims 40% of energy consumption is from buildings. He should be able to provide sources for his claim, or at least explain where he came up with the number and in my experience professors typically think more highly of the student who actively expresses interest in the topic at hand."
] |
[
"It seems slightly high, but the figure is well within the realm of possibility, especially if one includes heating as well. As an architectural rule of thumb, HVAC (Heating, Ventilation, Air Conditioning) systems account for roughly 40% of energy use in commercial buildings, and around 50% in residential buildings. This varies by country and region, depending on local climate and building codes, but is a good estimate for much of the built environment."
] |
[
"Agreed. It's not unfathomable, particularly in regions of the world where it's always warm, such as Saudi Arabia. Air conditioners and other cooling apparatus use more power than all other common devices... even computers spend a large portion of their power on internal cooling.",
"I'd ask your prof for his sources, however. He's likely cutting a few corners on his math."
] |
[
"Is it possible for an insect to become obese?"
] |
[
false
] | null |
[
"Absolutely! \nThere has been many studies in flies involving feeding and obesity. I used to work with Drosophila Melanogaster (the fruit fly), and was studying the effect of octopamine. A study published in the Proceedings of the National Academy of Sciences of the United States of America (Long and Murdock, 1983), demonstrates that blowfly feeding can be increased after octopaminergic drug treatment. This is not just about feeding more and having a big belly with food, but the insect actually would gain more fat in their abdomen. Similarly, in the fruit flies, you can dissect well-fed fruit flies and easily observe significantly more fat in their abdomen. "
] |
[
"Dissection of fruit flies? That's something that sounds like you need very steady hands for"
] |
[
"Sadly, adult insect's cuticle cannot expand... The fat insect would indeed try to pack more fat underneath, but the cuticle would do its best to stop it. As a result, the inner pressure increases by a lot. Imagine yourself eating 3 pizzas but having a very tight belt wrapped around your belly, not allowing your stomach to expand... At some point, the insect has to stop getting fatter, or the pressure would probably harm/kill itself... In fact, fat fruit flies do suffer diabetic-like symptoms, and live significantly shorter than a regular-fed fruit fly. When we cut open a starved fly, not very much happens. But when we cut open a fat fly, the moment when the cuticle is cracked open, fat would burst out from the abdomen..."
] |
[
"Are animals in nature capable of counting?"
] |
[
false
] |
This is a question I have been wondering about for quite some time and it continues to stump me. Its a fairly simple question and I'm sure(or at least I hope) that someone has an answer. But due to lack of any research and laziness to do so, I just decided to ask someone. Basically, I'm asking if animals in nature, such as apes or other complex species of animals are capable of counting things like how many of the same species live within their group, how much food they have gathered, etc. I am also wondering if they are capable of simple math like addition and subtraction. The reason why this stumps me is because animals as far as I know have not developed names for numbers. Is this actually necessary for simple calculations though? I've imagined that apes can simply compare things like "this many apes is looks like this many fingers", and such. Although, like I said before, I have no real evidence. If anyone could please take the time answer this then I would be grateful. Thanks.
|
[
"It would appear that the answer is yes, but it depends what you mean by count. Few animals actually have a symbolic expressions for abstractions like numbers, but many species do seem to have the ability to perform some mathematical operations. For example:",
"This study",
" involved researchers placing a chimpanzee in front of two sets of two bowls both of which held different numbers of treats. The chimps had to pick the group with the greatest number of treats (summing the number in different bowls). They made the right choice 90 percent of the time.",
"In another study, if scientists took mealworms gathered by wild robins, the birds would realize some of the worms were missing and would look for them. ",
"Chickens, generally not known for their keen minds, but when chicks placed in front of two screens and saw one ball go behind the first screen and several behind the fourth, ",
"the chick approached the one with more balls up to 80 percent of the time",
". ",
"The desert ant Cataglyphis fortis seems to ",
"count the number of steps it takes to get home",
" and are fooled into thinking they have returned to their nest if their count is disrupted. "
] |
[
"There have been quite a few studies of this. Here's one ",
"Quantity discrimination in jungle crows, Corvus macrorhynchos",
" and here's a journalistic ",
"overview of some others",
". It seems like there is evidence that various species have some sense of / ability with numbers although stating \"they can count\" would probably not be scientific. I'm just a layman though so I'm sure this sub will have more expert input."
] |
[
"There's a huge literature on this - ",
"here's a great review",
" (pdf). ",
"The first thing to know is that defining \"counting\" is harder than you'd think. There are actually quite a lot of different ways that humans, and animals, assess quantities and amounts. For example:",
"\"more/less\". Can you look at two trees, one with twenty apples and one with sixty ,and just see which one has MORE apples? Pretty much all species tested can do this.",
"\"subitizing\". (quick recognition of small numbers, based on the Latin for \"sudden\"). This one is fascinating. It's the near-instantaneous recognition of numbers up to (usually) 4. When you look at three eggs you just know instantly it's three eggs - you don't have to count \"one, two, three\"). Humans can subitize up to about 4, ",
" no matter whether it's 1, 2, 3, or 4; then get worse at 5 and 6 and after that we have to abandon subitizing and start doing real counting (see below). What's fascinating is that a huge number of other species can also subitize up to about 4, just like humans. Chimps subitize up to 4, horses subitize up to 4, lots of birds subitize up to 4, etc. It's such a widespread skill that the theory is now that subitizing may actually be coded in to our visual processing system (e.g. the visual system may be able to automatically pick out contours of up to 4 objects at once, processing cases of 1, 2, 3, or 4 \"contours-detected\" differently than each other). It appears not to involve higher brain centers.",
"true \"counting\", i.e. sitting there and patiently working through sequential numbers in your mind as you look at each object one at a time: \"one, two, three, four, five, six, seven, eight eggs! There are eight eggs.\" Counting can be recognized in humans because the response time gets progressively longer for each additional item added, indicating the people are taking an additional moment of thought for each additional item. There's been a lot of debate about whether chimps or African grey parrots can be trained to do true counting, and also debate about whether true counting requires language.",
"The last is \"estimation\" - this occurs for very large numbers of objects where you cannot keep track of them by true counting. (\"looks like about fifty or sixty apples on the tree... I'm not sure\").",
"tl;dr - sudden recognition of numbers up to 4 is widespread in vertebrates and may be a built-in feature of our visual system. \"True counting\" beyond 4 is much rarer."
] |
[
"Is Mars more like a \"baby/early\" Earth, or a dead Earth?"
] |
[
false
] |
[deleted]
|
[
"There are a couple differences. Earth has large amounts of liquid water. Mars has some water, but it's mostly frozen at the polar caps. Also, Mars has no magnetosphere to protect it from solar wind which caused most of its atmosphere to be stripped away. It's less than %1 as dense as our atmosphere on Earth.",
"There is evidence that Mars did at one time have a thicker atmosphere lots of liquid water, and a magnetosphere. For some as yet unknown reason, the liquid metallic core of mars stopped turning and this lack of a dynamo effect caused the magnetosphere to decay and mostly disappear.",
"If we knew what happened to Mars we'd be able say if the same fate awaits Earth. It's possible that whatever stopped the dynamo of Mars's core could also happen here. After billions of years of no magnetosphere for protection Earth could end up looking just as barren as Mars."
] |
[
"\"We make our world significant by the courage of our questions, and by the depth of our answers.\" ~Carl Sagan",
"I actually thought that you asked an interesting question. Made me want to know the answer. :D"
] |
[
"Thanks. After some thought I did think of it more as a dead Earth. Sorry If my question was a little ",
", I was watching Into the Universe and the question popped into my head."
] |
[
"Why do people sound different when they're reading out loud compared to when they simply speak?"
] |
[
false
] |
[deleted]
|
[
"Not everyone does -- people who read (silently) sufficiently fast and have sufficient interest in the subject matter (or just good acting skills) can make reading aloud sound perfectly natural.",
"It boils down to just how much of the text you're processing at once. People who read with a flat tone of voice are reading individual words, uttering each one in sequence, because they haven't processed the entire statement through to know the cadence of the whole phrase. People who read the whole phrase before speaking aloud will sound much more natural.",
"Meanwhile, when you're just talking, you generally already know what you're going to say -- or at least you know how you feel about what you're going to say and have a rough idea of its structure -- so it comes out naturally by default."
] |
[
"Many (most?) people, when reading text aloud, will have flat inflection and slower words."
] |
[
"Different in what way? "
] |
[
"Is it possible for a bullet to cause enough force to knock someone back?"
] |
[
false
] |
Movies/video games have exaggerated in the past. But is it possible or just a complete myth? Even not possible/noticeable at low velocity/high caliber rounds? What if you had a vest on and the bullet did not penetrate completely through your body?
|
[
"Since momentum is conserved, the bullet can't impart more momentum to its target than it initially has. Since the recoil in a gun isn't enough to throw the shooter back, the bullet doesn't have enough momentum to throw a person forward. Mythbusters did a segment on this, and they showed that before special effects got more commonplace, actors just fell down when their characters got shot."
] |
[
"This is mostly true, however, there exist shoulder-fired weapons that ",
" generate enough force to throw a shooter back, or knock a shooter over. Examples are rifles chambered in the ",
"20mm X 102mm Vulcan",
" round or home-built \"big bore\" loads like the ",
".700 Nitro Express",
". These sort of loads are beyond what the mythbusters tested, and are extremely uncommon, but they do exist.",
"Rifles in these calibers are commonly made to be heavy, with bipods and muzzle-brakes, and shot from prone and supported positions, to avoid knocking the shooter back or over. If a projectile was made that imparted a large percentage of its momentum to a target, these sort of loads could knock someone down without too much trouble. ",
"Note, of course, that most bullets are not 65g chunks of metal at 600 m/s. And that even these loads will not throw someone off of the ground, movie style."
] |
[
"It should also be considered that once a bullet achieves these energies, it is more likely that the bullet will go straight through or dismember the target. If the velocity is extremely high, it will go straight through like a high velocity rifle round. If the mass is increased like a connonball, it will just dismember the person.",
"It is possible to impart this energy to a person, but it would have to be by something fluid and probably compressible. I am thinking something like a shock wave from an explosive. The problem with a solid object is that it will never be able to disperse the impact over enough area so that the object will transfer all the energy without passing through.",
"As mentioned above, maybe with an extremely high power round, and extremely heavy armor, this could happen as it will spread the impact over a larger area. However, the armor required to do this would just be ridiculous for a person to wear. "
] |
[
"Why does friction generate heat?"
] |
[
false
] |
I saw a post a while ago asking where the energy to move something under the force of gravity comes from, and it got me thinking. I was running my hand against a wall as I walked and noticed the heat generated by the friction, and started to wonder something similar; where does that heat come from?
|
[
"This is actually a really good question, so I'll do my best to answer it as thoroughly as it deserves:",
"Heat is, essentially, just a measure of the average kinetic energy of particles, in terms of their motion relative to each other (i.e. you wouldn't call us insanely hot because we're all on the earth moving at extreme velocities)",
"When you go to move, you convert chemical energy in your body into kinetic energy of the system of your arm and hand. As you rub something, the molecules in your hand interact with the particles in the wall. This ultimately results in * the system * of your hand losing energy to the ",
" in your wall and in your hand, in the form of random motion - i.e. heat."
] |
[
"All particles emit electromagnetic radiation as an approximation of a blackbody curve.\nMore energetic particles will emit EMR of a shorter wavelength, i.e. tending towards visible and/or ultraviolet light. Longer wavelengths are the result of cooler objects.",
"The amount of energy emitted is a function of the total energy of the object - i.e. a cool object emits little energy, while a hot object emits a lot of energy, thus two objects will tend towards equilibrium."
] |
[
"this is solid, but I was confused in a couple of places. ",
"Correct me if I'm wrong:",
"when particles become \"energized\" they radiate that energy outward towards equilibrium. For some particles this radiation is visible as light, for others this radiation is felt as heat. Friction transfers energy from one object to another, thus \"energizing\" particles that were previously at equilibrium.",
"I think I'm wrong in there somewhere, but I don't know where. "
] |
[
"If the comet that is not going to hit Mars actually hit it, would it noticeably effect the orbit of Mars around the sun?"
] |
[
false
] |
I read about it on worldnews.
|
[
"No.",
"Even though the comet is quite big, it is a lightweight compared to Mars.",
"We do not know the mass of the comet but it might have a diameter of up to 50 km and is going at 55km/s.",
"Mars has a diameter of roughly 6500km going at roughly 25km/s.",
"At constant density the mass of an object is proportional to the third power of its diameter. This means that, if both objects have the same density, Mars is at least 2 million times heavier than the comet.",
"Given that Mars is rocky and the comet is mostly ice and also might be significantly smaller it is unlikely that an impact would have a significant impact on the orbit."
] |
[
"But would it kill Curiosity?"
] |
[
"The 55 km/s is relative to Mars and it's that high mostly because the comet is going to collide (or rather not collide) almost head-on with Mars. From ",
"the orbital parameters",
" I get a Sun relative speed of 35.6 km/s which is pretty much exactly the escape velocity at that distance from the Sun. In other words the comet is almost certainly from the Oort cloud."
] |
[
"Why is the speed of light 299 792 458 m/s in a vacuum? Why not faster or slower?"
] |
[
false
] |
[deleted]
|
[
"The numerical value of the speed of light is totally arbitrary, and not a directly measurable thing. The only reason that we think of the speed of light as a dimensionful constant with a particular value is because historically humans have insisted on measuring time and space with different units. In light of relativity, time and space should be seen to be the same sort of thing, so it really only makes sense to measure them using the same units. ",
"If you measure time and space with the same units, the speed of light is just \"1\", a dimensionless constant, and all slower speeds are just fractions of the speed of light. This is analogous to if you had a topographical map of a place and insisted on measuring distances along the north/south axis in kilometers but distances along the east/west axis in miles. This would be a bit of a weird thing to do, although there's nothing ",
" with it. However, suppose your friend had their own map of the same area, but their axes were tiled with respect to yours, and they also insisted on measuring up/down on their map in kilometers while they measured left/right in miles. Now, if you tried to transform coordinates of things on your map to their coordinates on your friends map, you would end up with a transformation law that had conversion factors hanging all over the place to account for the fact that your \"kilometers\" direction is tilted with respect to your friends \"kilometers\" direction. This is what the speed of light is, it's just the conversion factor between the units of space and the units of time. If we don't insist on doing a funny thing by using different units, the need for the conversion factor goes away.",
"However, all that being said, it does make sense to say that the speed of light is ",
". It seems that clearly if the speed of light were much slower, we would see all kinds of crazy relativistic effects in regular life. But I just spent the last two paragraphs arguing that the value of the speed of light is totally meaningless and arbitrary. How can we reconcile these statements?",
"The point is that humans are slow. We care about time scales like seconds, but we care about length scales like meters. These values of distances and times are \"typical human scales\". But, if we express the length of one second in meters (I know, seems weird, but relativity is weird), we get that 1 second = 299 792 458 meters. So a typical human time scale is ",
" compared to a typical human length scale, i.e. we are very slow. So, you can phrase the question \"why is the speed of light a big number\" as \"why are human so slow compared to their size. The answer to that question has much to do with the complicated fundamental and emergent physics that describe our biology and the environments in which we've evolved, and I'm certainly not aware of a simple explanation. "
] |
[
"Does light travel one 'plankt meter' in one 'plankt second' ?",
"First it is \"Planck\". Second they are DEFINED that way, i.e. t_p = c*l_p by definition. Third the Planck units aren't necessarily absolute maxima or minima for anything. They are simply (related to) a curvature scale above which we can't do anything with GR. Saying anything further is purely speculation."
] |
[
"You're basically asking why 1 is 1, and not a little more or less than 1. The speed of light is a nature constant, that happens to be a certain way in vacuum, and there are no hidden factors that change the speed of light in vacuum.",
"The number seems super arbitrary, simply because it's expressed in units we arbitrarily 'made up' a long time ago, at a time there was no concept like \"the speed of light\". We chose later to express the speed of light in meters per second, and using the meter we had defined long ago it yielded that rather arbitrary number for the speed of light. "
] |
[
"Atoms, Gravity, and Time"
] |
[
false
] |
[deleted]
|
[
"Does every object with mass have a gravitational pull? Do atoms have a gravitational pull? Does any object with mass alter the time around it (I'm thinking like a black hole)?",
"Yes, and by extension yes and yes (although not to the same extent as a black hole - which warps spacetime ",
" light can't escape - does).",
"Finally, if an atom does have mass, and does slightly alter the time around it, does that every object in space is in a slightly different time?",
"What do you mean? Whether two things are occuring at the same time depends on one's frame of reference to begin with, so saying two objects are at \"the same time\" or \"a slightly different time\" is somewhat meaningless."
] |
[
"Atoms have a very, very slight gravitational pull (far outweighed by things like electromagnetic forces they carry) and a gravitational pull will cause time dilation. This effect is negligible to the point of ridiculousness."
] |
[
"Isn't it true that even electromagnetic radiation has gravity?"
] |
[
"Are there stars that orbit perpendicular to the galactic plane?"
] |
[
false
] |
In spiral galaxies, there is commonly a ‘galactic bulge’ of light. As most of us know, stars usually orbit around the plane, but is it possible for a large number of stars to orbit at (at least close to) a 90 degree angle relative to this? If so, how would that formation process have occurred? Or am I overthinking it and the bulge is simply a result of the massive light output from the high density of stars? Edit: just to clarify, I know that there are irregular galaxies that are composed of stars in a ‘cloud’ of sorts, like the Magellanic Clouds. I am referring to conventional spiral galaxies for this post. Edit 2: by ‘large number’, I’m referring to a significant portion of the total number of stars. Maybe 0.1-1% of total stellar count or mass. Something along the lines of 0.1-10 million stars at least.
|
[
"Sure, in the bulge or the stellar halo of spiral galaxies, the orbits are ",
" random, so you get orbits in every direction (some bulges resemble elliptical galaxies in some ways). Whether it counts as \"a large number\" is up to you."
] |
[
"You could take a whole course in galaxy morphology and evolution. It's a pretty deep subject.",
"If you haven't played Galaxy Zoo, that might be a good activity: ",
"https://www.zooniverse.org/projects/zookeeper/galaxy-zoo/",
"Here's a free textbook about it: ",
"http://astro.utoronto.ca/~bovy/AST1420/notes/index.html",
"Here's a talk on the formation of the Milky-Way bulge in particular: ",
"https://www.youtube.com/watch?v=OM7WXOYMuZc"
] |
[
"Your problem is that you've defined away the entire population of galaxies. \"Conventional spiral\" ",
" there aren't any weird out-of-plane features. If you just want to consider galaxies broadly, there are very many examples: ",
"https://talk.galaxyzoo.org/boards/BGZ0000004/discussions/DGZ1006810/"
] |
[
"What kind of field is the Higgs Field?"
] |
[
false
] |
Is the Higgs field a field describing the strength of a force at a point in space, like the Electromagnetic or Gravitational fields? If not, what kind of "field" is it? If so, which of the fundamental forces does it describe? EDIT: to another thread about the Higgs field and the Higgs Boson. In the discussion, someone mentions that there are 17 fields in the standard model. How are these fields related to the four fundamental fources of nature? Why do we have 17 instead of 4? Are the four comprised of the 17 acting together in different ways? Are they the same "type" of field (by that I mean equations giving the magnitude of some vector at some point in space)?
|
[
"Is the Higgs field a field describing the strength of a force at a point in space, like the Electromagnetic or Gravitational fields?",
"Not quite. It differs by being a scalar field (mass is not a vector quantity) and it has a non-zero vacuum expectation value.",
"I'm not sure the number 17 is quite correct. There are 4 electroweak fields, not 3, for example. (B",
" W",
" W",
" W",
" which mix to give γ Z",
" W",
" W",
")",
"Anyway, the different fields correspond to different elementary particles: quarks, leptons, gauge bosons and the Higgs. So only some (i.e. the gauge bosons) correspond to the fundamental forces."
] |
[
"It seems to me that you are a bit confused about what a field is. Therefore I'll start from there and hopefully someone who knows more will post something about Higgs field.",
"Let's try to define a field.\nFirst we introduce an object called a manifold. It is nothing more than the place where your fields will live and you can picture it as a collection of points that behaves locally as if it was flat (not unlike the surface of earth), in absence af a more proper mathematical definition.\nThe reason for this request is to preserve some properties of the usual euclidean spaces.",
"Pick now a point of this manifold. You can choose there a real number (a scalar), let's say 3. But you can choose other numbers in other points on the manifold until it's all covered. ",
"You can also induce a set of coordinates on your manifold through what is callled an atlas of charts (this one is simply a set of rules to assign coordinates like latitude and longitude on earth). Thus for every point you have a real number as a function of some coordinates. This is indeed a real valued function on your manifold or a scalar field.",
"Now we want to build some more.\nIntroduce a curve on your manifold. I'll skip a bit of math and ask you to think of this as a road on earth surface. For every mile you make, you'll have different values of latitude and longitude; so this is actually a set of your coordinates expressed as a function of a single parameter (the miles you make).",
"To each curve you define, you can associate a direction. The direction does not lay on earth's surface but it is defined in the tangent plane to each point. That's beacuse it is a local object and locally your manifold is flat. So you need something that lives in the tangent plane.",
"This is a vector. If you again define the elements of the tangent planes (that more properly are called tangent spaces) for every point, you build a tangent bundle (the union of all these tangent spaces). A vector field lives there (again I skip the math) and is, exactly as you might think, an object with a value and a direction associated to each point of your manifold.",
"Vectors are usually defined with regards to the transformation laws of their components but this might be misleading. All you need to know is that you can stack together your tangent planes in order to obtain more complicated objects called tensors. Still you can associate one of them to each point to build a tensor field.",
"So far we said nothing about physics properly. Fields are indeed a mathematical object that you can use in physics the way you use integrals ore derivatives.",
"In classical physics you often deal with vector fields. Why? Because they are exactly what you need to express the effect that something (let's say a point electric charge in the origin of your coordinates) has on every point of your space. You usually talk of electric field in x as the force a unit charge would experience if placed in x. It seems clear why you should use a vector field for that (given that force is itself a vector). But you can also use scalar fields (for instance the temperature or the concentration of some substance) or tensor fields (takes a bit longer to find a trivial example).",
"Classical physics is not the only one where you can use fields. Turns out that you can build a theory where you can quantize fields; as you did quantize position and impulse in quantum theory. I will avoid details but feel free to ask.",
"If you do so, you have to put in place some rules for the commutator of your fields (because this is how you quantize stuff - if you make the wrong rule you won't get anything that make sense so you need to choose wisely). From these rules you find that you can associate to your quantized fields quantities such as energy, spin, impulse and so on. You can carefully check that these are legitimate properties of particles (the traditional fermions and bosons at first, but also - and this is a bit harder - photons and so on) and so your fields, that have almost nothing to do with the classical ones except for the fact that they are the same mathematical object, are now no longer forces but somehow particles.",
"For Higgs boson you need to take the math to the next level but I hope you understand why you can use fields to describe lots of different things."
] |
[
"First, as explained by others, a field is not necessarily something describing strength of a force, it can describe anything. Temperature is a nice example of a field: it takes some value at every point in space, and the value is a number (a scalar), so we call it a scalar field. ",
"The fields of the standard model is associated to the different kinds of particles, so you have an electron field, a bunch of different quark fields, some different neutrino fields and so on. The field associated to the photon is the normal electromagnetic field. These fields are of different types for the different particles, depending on their properties. And the Higgs is just one of these fields, which is what we call a scalar field (meaning that it takes just numbers as values, just like the temperature field). The special thing of the Higgs, which is why it gives masses, is that the Higgs field has a non-zero value in empty space. All other fields vanish in empty space. ",
"(Of course all this is a bit simplified and ignoring the very important quantum part of the story and so on)"
] |
[
"Why do we feel nauseous when we spin?"
] |
[
false
] |
For example when you spin really fast in an office chair and begin to feel sick. What causes this? Does it or did it serve a purpose?
|
[
"How Stuff Works has a pretty good article on this:\n",
"http://science.howstuffworks.com/science-vs-myth/everyday-myths/question483.htm"
] |
[
"If you spin in just the right way, you don't even need a real conflict",
"For most people that's a very slow spin and even then there are limits to how long you can spin even at a slower speed."
] |
[
"If you spin in just the right way, you don't even need a real conflict",
"For most people that's a very slow spin and even then there are limits to how long you can spin even at a slower speed."
] |
[
"Potential energy and the conservation of energy"
] |
[
false
] |
This question has bothered me since I took physics in high school. The law of "Conservation of energy" states that energy in a closed system remains constant. So if you apply energy to lift a rock up twenty feet with a crane, where has that energy gone? Tt has now become "potential energy." My question is, isn't this circular reasoning? Of course there will be conservation of energy if you define potential energy as the difference in energy states between the two states of the system.
|
[
"Think of potential energy as an energy storage, like in a ",
"weight-driven clock",
". If you give some mechanical energy to an object by moving it up, it'll store that energy (as potential energy), and give it back when it's allowed to go back to its original position. ",
"The law of conservation of energy thus becomes: the amount of energy the object consumes going up is the same as the amount of energy it gives back going down + the thermal energy due to friction."
] |
[
"The beauty of it is that the definition of potential energy does not have to have anything to do with the circular part of your definition. ",
"You can start by dropping rocks and measuring how much work they can do. Use them to drive in nails or turn a wheel and grind flour, or whatever you like. You will always find that the net total energy expended is exactly equal to the energy used to lift the rock. "
] |
[
"Nope. You're thinking too literally.\nLet's assume you take your rock and move it a metre into a vacuum. Two things will happen.",
"Assuming a 100% efficient system (no drag, no heat losses) what will occur is the following:",
"The gravitational potential energy gained by the rock will be equivalent to the work done lifting the rock. This is literally work done against gravity - if there was no gravity, you would not be lifting the rock, you would be propelling it and after you let go it would continue off at a constant velocity until otherwise perturbed.",
"The force required to lift the rock must be equal or greater than the force exerted upon the rock by gravity AT ALL TIMES.",
"The moment the force keeping the rock aloft is removed, the gravitational force begins to exert acceleration on the rock. This then transfers the gravitational potential energy back into kinetic energy which means the rock then begins to accelerate. It descends into the gravitational well, thus losing GPE and gaining kinetic energy until it comes to a stop when it hits the ground, thus losing its kinetic energy into the ground in whatever way you see fit.",
"In conservation of energy, all you ever have to consider is that the energy goes somewhere within said system and that it is accounted for. In other words:",
"Energy in = energy out",
"In our theoretical vacuumless system, this follows the following process:",
"Kinetic energy of rock (rising) = GPE energy of rock = Kinetic energy of rock (falling) = Kinetic energy of impact surface",
"In a real situation, you will have thermal losses such as drag and friction, molecular losses such as stress fractures in the rock, multibody dynamics such as n body interactions with sand, air and so on.",
"All that is important is that the energy within the system goes somewhere and it is not just lost. It doesn't matter where it goes. It just doesn't have to get lost. When we say \"lost\", we mean, we can't explain where it goes."
] |
[
"How does shooting down a nuclear missile work?"
] |
[
false
] |
I've always wondered how this works? With all the tension going on with North Korea and the threats of a nuclear attack on the US, if a missile were to be on its way to the United States surely it would be shot down before it reached, (I would hope) But how? and would whatever was underneath the blast, land or Ocean, be screwed?
|
[
"The idea behind missile defence systems is that you smash it with an interceptor missile before it reaches its target. There's no danger of a nuclear explosion being triggered if you destroy an incoming nuclear missile in this way - causing the nuclear explosion itself requires a fairly precise orchestration of events. If you literally smash the missile into pieces, those events can't happen and you're left with, at worst, a uranium or plutonium core falling to Earth somewhere. It'd need professional cleanup, but it's way better than having it go critical overhead!"
] |
[
"ICBMs do, yes. They typically boost up to about 300km on their engine, and coast the rest of the way. During this flight phase they can reach around 1000km altitude, depending on how far they have to travel. They then re-enter the atmosphere over their target and, depending on the nature of the missile, make minor course adjustments to maximise accuracy."
] |
[
"Do these nuclear missiles actually go in to outer space then fall back down?"
] |
[
"Does exercise burn more calories at different parts of the day? What time of day is the body most efficient at fat burning?"
] |
[
false
] |
To specify cardio would be jogging/running for about 30 mins These articles are contradicting each other and both source valid papers. One says that the morning is best, the other says that the late afternoon is best. Please help me my poor brain is quite confused.
|
[
"You'll burn more fat at times when less carbohydrates are available for energy, it's that simple, and the first article says exactly that. Second article is not about cardio, it's about resistance training, so I don't know why you are trying to apply its facts to cardio."
] |
[
"\"According to a February 2009 \"Flex\" magazine article by Jim Stoppani, a study conducted in 2005 at the University of Southern Mississippi followed 16 males for 10 weeks. Half of the participants trained in the morning before 10 a.m. and half trained in the evening after 6 p.m.. The evening group decreased body fat by 4 percent.\" ",
"The paper in this article considers training to consist of 45 minutes of cardio and 45 of lifting. ",
"EDIT also the second article is arguing that if you rev up your metabolism (via cardio) in the late afternoon a time when it normally starts to slow down, you would note an increase in the rate of lipolysis/decrease in glycogen stores. "
] |
[
"Can you link to the \"study conducted in 2005 at the University of Southern Mississippi\" ? The link in the references isn't producing anything for me."
] |
[
"why can't we use capillary pressure for free energy"
] |
[
false
] |
[deleted]
|
[
"The water rising up from capillary action is actually ",
" - that is, the water rises so it has more intermolecular interactions with the walls of the container and itself, because it's a stable configuration.",
"That means whatever way you try to ",
" water from that configuration, you're ",
"."
] |
[
"It's necessarily more, since you're moving the tube as well as overcoming the adhesion between water and the container. It's just not noticeable because the adhesive force of water is weak - so weak that it can only overcome gravity in a narrow tube, where the surface area versus volume of water is favourable."
] |
[
"The increased gravitation potential is offset by the intermolecular forces between the water and the brick. One way to see it is that the enthalpy change in the formation of the water/brick bond is used to raise the water.",
"A clearer example would be the freezing of water into ice - forming the bonds and forcing the molecules into a rigid lattice structure is what provides the energy to expand the water (and raise it) when it freezes."
] |
[
"Confusion about what is considered a gene."
] |
[
false
] |
I'm learning genetics right now and it's a bit confusing, mainly genes and alleles. Lets say a plant has green leaves and it's crossed with a yellow leaf plant, it will produce some green leaf plants and some yellow leaf plants. Would that mean there are two genes involved or two alleles?
|
[
"The ",
" is the unit of genetic material (DNA) that encodes a trait - in this instance, leaf color.\nAn ",
", on the other hand, is a variation of a gene. G and g, for example, would be the two alleles belonging to the color gene.",
"This is, of course, a very simple example, and assumes that there is only one gene involved in the example you provided. "
] |
[
"Actually, genes are getting more difficult to define, not easier. Remember in the past, all we could do is experiments like those described in your question. However, when we discovered, characterized and started sequencing DNA we started to understand the molecular basis for genes and alleles. Sometimes the nomenclature of the field can get confusing, because sometimes even senior scientists mix the terms. ",
"On a molecular level, genes are generally regions of the genome that are (regularly) transcribed into RNA. Many genes are translated into proteins but not all, including micro RNAs, ribosomal RNAs and others.",
"Alleles are typically a genetic variant or a group of genetic variants that give rise to different traits. On the DNA level these are genetic differences in the population that give rise to different DNA sequences (polymorphic)."
] |
[
"A good analogy would be a piece of clothing. You have many different genes, like you have many different pieces of clothing. Plants have a gene for leaf color and you have a glove. ",
"Gloves and genes can come in many different varieties. These are alleles. A plant has two sets of chromosomes and thus two alleles (one relating to each set of chromosomes) as you can have two varieties of gloves. One allele for the plant could be G (for green) and one could be g (for yellow) while one glove of yours could be colored green and one could be colored yellow.",
"The genotype could be Gg and the related \"genotype\" for gloves could be Green glove - Yellow glove.",
"Then next, the phenotype would be \"green leafed\" and the related \"phenotype\" would be.......ok this is where the analogy breaks down, but hopefully you get it by now :P"
] |
[
"Is there a way to \"emergency-charge\" a battery?"
] |
[
false
] |
To clarify, what would have to be different, either on the battery's end or whatever you are using to charge it, in order to greatly increase the speed at which the battery charges? Also, if a battery was designed that could be charged regularly and "emergency charged" (even if the latter comes at a permanent cost to the battery), what would it feature to be able to accomplish this? Sometime back my cousin plugged her phone in to charge when it was almost dead and dropped it. The battery bar immediately jumped to fully charged. I told her it was most likely an error in the phone gathering information about the battery but it's always made me very curious. Thank you.
|
[
"To fully charge a battery, you have to deliver a certain amount of energy to it. Power = Energy/Time, so to decrease the charge time, you have to increase the power. Since most batteries have a relatively fixed internal resistance, this would be done by increasing the current through the battery. This will work, but it's risky. High currents can be deadly (it's the current, not the voltage, that kills you). Also, circuits with high currents running through them can build up a lot of heat. Not only is this dangerous (both to you and to the circuit components), but it also decreases the effeciency of the process."
] |
[
"Is it not bad for the overall longevity of the battery to charge it too quickly? ",
"Is that a myth, or is it something to do with the higher temperatures involved? Or something else? "
] |
[
"IANA electrical engineer, so I don't know. It very well may be."
] |
[
"Do we see diffraction in gravitational lenses?"
] |
[
false
] |
The lens-angle formula, as Wikipedia gives it, doesn't account for photon energy. I know newtonian objects all fall at the same speed regardless of mass, but can we say the same about photons? I guess the question comes down to: Does the equivalence principle hold for light?
|
[
"I think you're mixing up a few terms here. I think you're asking about dispersion of photons, like how light passing through a prism breaks up into components because each frequency is bent by a different amount. In that case... no, gravitational lensing does not have a frequency dependence in how it bends light. ",
"I don't know what you mean by the \"equivalence principle hold for light.\" "
] |
[
"It's the standard explanation for objects falling at the same rate even though the gravitational force on an object is proportional to the object's mass. \nSince more massive objects experience more grav-force, you might intuitively expect them to fall faster, but inertia (resistance to that force) is also proportional to mass in exactly the same way. This is the equivalence principle. If this weren't true for photons, you would see a diffraction-like effect around massive bodies as higher-energy photons are bent more/less depending on whether their inertial or gravitational mass is greater. This strikes me as a handy astronomical proof of the E.P. for photons, unless we see peaks at one or a narrow band of wavelengths from lensed objects."
] |
[
"ah yes, I usually think of it in terms of the weak equivalence principle, I guess. That acceleration is indistinguishable from gravitation. I didn't see how you were applying it for light then above.",
"That being said, yeah tests of energy-dispersion are broadly conducted for a couple of reasons, one of which is what you mention, placing limits on the mass of a photon. Similarly you might also not slight differences in arrival times for a burst of photons some very far distance away. To date we've seen no evidence for such relationships."
] |
[
"Why did scientists in the '60's think that Mars was covered in vegetation?"
] |
[
false
] |
Text from an article in Science Digest in 1963 Mars has pronounced seasonal variations, with the seasons about twice as long as those on earth, during which the surface temperature ranges from -120 to +30 degrees Celsius. When the northern hemisphere is in the "winter" season the dark green areas change to brownish gray. Based on this, we speculate that some simple form of life - lichens and mosses - is likely to exist on Mars. The reddish-orange areas show little color change with the seasons. And then later in the article: Most of the surface is desert consisting of granulated or powered iron oxide. A thin layer of vegetation covers about one-quarter of the surface, and a thin ice cap forms at the poles, the sides of both these regions changing with the seasons.... Full article here: What changed in our knowledge of Mars over the years that these scientists were wrong about?
|
[
"I had to dig a bit for that bit of historical trivia!",
"This is what I found:",
"Sinton, W. M. (1959). Further evidence of vegetation on Mars. Lowell Observatory Bulletin, 4, 252-258.",
"Sinton, W. M. (1957). Spectroscopic Evidence for Vegetation on Mars. The Astrophysical Journal, 126, 231.",
"Schlumberger, R., & Antoniadi, E. M. (1929). Changement Remarquable sur Mars. L'Astronomie, 43, 38-41.",
"In short: optical observations of Mars were coming in, and seasonal variations in color when regions within one or other hemisphere were getting darker or lighter, were being interpreted as resulting from seasonal vegetation cover. Furthermore, observations of absorption spectra of the martian atmosphere showing absorption bands around the 3.46 μ wavelength were also coming in. These were interpreted by Sinton as indicative of vibrations from C-H bonds, but this interpretation was later dismissed as inconsistent with spectral signature of the atmosphere as a whole. The conspicuous absence of spectroscopic evidence for oxygen or water vapor, as well as the thinness of the atmosphere, made such an interpretation nonsensical; it was suggested instead that these spectra were the result of the oxydation of nitrogen in the atmosphere. The color changes were (rightly) ascribed to dust storms. (See: ",
"Kiess, C. C., Karrer, S., & Kiess, H. K. (1960). A new interpretation of Martian phenomena. Publications of the Astronomical Society of the Pacific, 72(427), 256-267",
")."
] |
[
"Isn't it mind blowing to compare space science then and now? I wonder what we will achieve in the next century if science can keep this progress rate!"
] |
[
"It's particularly interesting to me that we went from thinking there was abundant life to determining there was no evidence for it with such depth that now if we did actually find life it would be amazing news."
] |
[
"Why is it that superficial wounds don't heal 100% sometimes? (details inside)"
] |
[
false
] |
I'm not sure if this is a generic anatomy question, or something specific to my (somewhat dysfunctional) body but here it goes: I rollerblade. I fall often. My hands take the brunt of the damage, but sometimes I land on other body parts. Some wounds heal 100%, you could never tell they were there. But I have a few that while they have healed, the skin where the wound originally was stays pink, even though the wounds where superficial and too much time has passed for it to heal completely (more than 6 months). Is there a particular reason for this?
|
[
"It can be difficult to determine whether you have damaged the epidermis (where the tanning takes place), as it does not necessarily affect the healing process as such.",
"One of my friends fell and hit his shin on a small piece of rubble, it did not break his skin (it barely bruised) and yet, to this day he has a pink spot there."
] |
[
"Well, my limbs are the ones getting hurt most of the time. I'd say it's mostly random, and I haven't really had that many wounds to be able to pinpoint a pattern. I have small ones in both of my legs, some a little bit more than a month old, others more recent, but left colored patches. I have one in my thumb's knuckle more than an year old, one in my elbow like that, and that's about it. I've hurt my hands' palms plenty but they always heal 100%. "
] |
[
"I have Raynaud's but I never have problems with areas of poor circulation healing. Even the most superficial scrapes on my legs can leave a scar and deeper cuts leave nothing. I think you're normal! "
] |
[
"When we say that the faster an object travels through space, the more mass it gains, is it because it interacts more and more with the Higgs field?"
] |
[
false
] | null |
[
"This is a common misconception. The faster an object moves, the higher its inertia is with respect to you. The rest frame mass of the object remains the same. Some people call this increased inertia \"relativistic mass,\" but it's a concept that leads to all sorts of confusion, so we don't use it anymore. Less useful is that this increased inertia is unique to your reference frame, similar observers will see different values. The same concept crops up with kinetic energy, a train is moving with a lot of energy until you're riding the train and suddenly it's just stationary as far as you're concerned.",
"Now the Higgs field, firstly, it is only one mechanism which accounts for mass in physics. Protons for instance gain their mass via the binding energy-momentum of the quarks, the masses of the quarks are something like 1% of the proton mass. The Higgs mechanism specifically refers to generating the masses of the vector bosons, though you can extend the concept to give the other fundamental particles mass as well.",
"The Higgs mechanism lives in the land of quantum field theory. Quantum field theory explicitly obeys special relativity, so the laws of physics in it are manifestly covariant. This means the higgs mechanism doesn't bother you based on your speed, because the physics doesn't change when you change inertial reference frames."
] |
[
"What a wonderful question! Accelerated frames in QFT ",
"are really weird!",
" I have never read any elucidations on this, but to be fair I haven't looked around too much yet. One immediate consequence pops into my head, in accelerated frames, you no longer are able to have an invariant vacuum expectation value. The most dramatic example is that of Unruh and Hawking radiation where accelerated observers see a thermal radiation being emitted from spacetime horizons. A black hole is one such horizon.",
"So the Higgs mechanism works because wherever say a Z boson goes, it experiences the same nonzero Higgs field. Since vacuum fields are no longer invariant under acceleration, this would naively correspond to a stronger or weaker Higgs mechanism--this would mean the masses of the fundamental particles would be different under acceleration.",
"I'd love to read a paper about this specifically, I've never really thought about it before."
] |
[
"This means the higgs mechanism doesn't bother you based on your speed, because the physics doesn't change when you change inertial reference frames.",
"Does the mechanism change when you are in an accelerating frame?"
] |
[
"How quickly does a SCRAM happen?"
] |
[
false
] |
I don't know the situations for when a nuclear reactor needs an immediate shutdown (or how often that comes up) but I do know that once a reactor is packed up with control rods, the next step is to cool the reactor down. How quickly are control rods inserted into the reactor, and does the speed or method vary with reactor configuration? Like, are they just lowered by actuators, do they fall, do they slam down? What is the urgency of a SCRAM?
|
[
"Fast.",
"The control rods are held out of the reactor by an active mechanism. When the button is pushed, or when the power fails, that mechanism lets go and the rods are let loose into the core. ",
"The exact setup does vary a bit by reactor design. In some reactors the rods are suspended out of the core by electromagnets, with a compressed spring at the top. When the magnet shuts off, the rods fall downward into thier places by gravity, with the released spring just giving a kick to make them move faster.",
"In other types, the rods are underneath the core, and a pressurized hydraulic system applies a constant upward force pushing them toward the reactor. An electric motor constantly holds them back as long as the power is on. When the power stops, the motor turns off, and the rods get shoved in by the hydraulic pressure. ",
"The physical movement of the rods takes maybe a couple of seconds for full insertion. As they're inserted, they're already absorbing the neutrons that are needed to sustain a chain reaction, and so the reactor power drops off almost instantaneously. By the time the rods are in all the way, the reactor power will have gone down by something like 95%.",
"The power doesn't instantly go to zero. There are always secondary decay processes that don't rely on those neutrons, such as from radioactive wastes that are left over when the fuel is consumed. As those wastes decay into inert material the power continues to decrease. It drops off rapidly at first, and within a couple of hours should be down to around 1% of the power before SCRAM.",
"Of course these numbers are only ballparks and examples. There's wide variation based on reactor design and fuel type. But I hope this is helpful."
] |
[
"As they're inserted, they're already absorbing the neutrons that are needed to sustain a chain reaction, and so the reactor power drops off almost instantaneously. By the time the rods are in all the way, the reactor power will have gone down by something like 95%.",
"Just a quick note: While this is how it should be, it may not always be true. One of the contributing factors (and criticism of the ",
"RBMK",
" reactor design used) in ",
"Chernobyl No. 4",
" was the control rods. They took some 20 seconds to insert and had a design with a neutron moderator rod at the end of the control rod. The idea was that you could pull out the control rod and use this neutron moderator to displace water to improve the performance of the reactor. ",
"So, when running the reactor you had the control rod pulled out until the neutron-moderating graphite was in the core, and the graphite part hanging above, with water in between (and under the the core). When, during the SCRAM, they pushed the rods downward, they also pushed out the neutron-absorbing water from the lower part of the core, replacing it with neutron-moderating graphite. This caused the lower part of the core to spike during the SCRAM, overheating, fracturing the fuel and bending the control rods... and about 3 seconds later you had the explosion. "
] |
[
"Than again chernobyl bypassed a lot of its safeties and was a really old design, they also boosted the performance quite a bit this together with the missing safety protocol, unfinished maintenance and human error made it meltdown.",
"Modern generation gen2 3 and 4 shouldn't do this. "
] |
[
"How is energy used for sudden actions stored in the human body?"
] |
[
false
] |
I'm assuming that the energy produced through digestion is stored somewhere, which allows it to be used at a very short notice, e.g. suddenly sprinting. How is it stored, and what allows it to be ready for use so quickly when the body's power requirement is drastically increased?
|
[
"The main source of cellular energy in humans is ",
"adenosine triphosphate",
" (ATP). ATP can be produced via a number of metabolic processes, such as ",
"glycolysis",
", ",
"citric acid cycle",
" and ",
"oxidative phosphorylation",
". The basic principal of these interconnected metabolic pathways is the utilization of glucose to produce ATP. Note that the other biomolecules such as fats and proteins we ingest can be converted to glucose, or to intermediates of glycolysis, the citric acid cycle, or oxidative phosphorylation. ",
"With that bit of technical explanation over lets get more into your question. To simplify things I will focus only on the path of glucose from digestion to action. When you eat a meal rich in glucose, this glucose is absorbed by your digestive track, and sent into the blood. From the blood, this glucose enters cells where is can either be used immediately if needed, or converted to ",
"glycogen",
". When the cells recognize an increased need for energy, such as when you start running, glycogen is broken down so as to allow more glucose to enter into glycolysis. This will lead to more ATP production, which is ultimately used to power most cellular activities, such as ",
"muscle contraction",
".",
"I hope this all made sense and wasn't too jargon laden. If you have questions let me know."
] |
[
"What ",
"/u/Jazzeater",
" explained in his ",
"comment",
" is correct. However, there is another mechanism that is very relevant to your question, and that is the very fast regeneration of ATP through phosphocreatine.",
"http://en.wikipedia.org/wiki/Phosphocreatine",
"Phosphocreatine can anaerobically donate a phosphate group to ADP to form ATP during the first 2 to 7 seconds following an intense muscular or neuronal effort. Conversely, excess ATP can be used during a period of low effort to convert creatine to phosphocreatine.",
"Basically, there isn't too much ATP just sitting in the muscle, ready to be used. Instead there is a pool of phosphocreatine, effectively acting as a \"buffer\". Of course this buffer has to be replenished through glycolysis and/or oxidative phosphorylation, but to bridge the immediate gap between the huge spike in ATP use in the muscle and the activation of these metabolic pathways, this mechanism exists. It keeps the level of ATP constant so you don't just fall over after the first step in your sprint. It also allows a level of performance for a short time that couldn't be sustained long term (but there are many reasons why muscles get tired, this is just an example).",
"http://en.wikipedia.org/wiki/Creatine",
"The concentration of ATP in skeletal muscle is usually 2-5 mM, which would result in a muscle contraction of only a few seconds.[10] Fortunately, during times of increased energy demands, the phosphagen (or ATP/PCr) system rapidly resynthesizes ATP from ADP with the use of phosphocreatine (PCr) through a reversible reaction with the enzyme creatine kinase (CK). In skeletal muscle, PCr concentrations may reach 20-35 mM or more.",
"You see, the difference in concentration can be quite dramatical at 4-10+ times more phosphocreatine than ATP."
] |
[
"Exactly. This is the answer that OP was looking for. The order of substrate use for muscle action is: ATP > Phosphocreatine > Glucose/Glycogen in Glycolysis, and then it gets fairly complicated and depends on duration of exercise, intensity of exercise, and nutrition status (substrate availability). Basically burst movements are powered for a brief time by the ATP pool, which is quickly exhausted and then is replenished by phosphocreatine, which gives the muscle cells time to upregulate glycolysis, which then becomes the primary source of ATP."
] |
[
"What does it mean to say this universe is \"flat?\""
] |
[
false
] |
[deleted]
|
[
"Well, there is no outside. At least, we don't expect there to be an outside. Moreover, there are no words to describe what it would \"look like\" because our languages developed to describe the sorts of things we can see, and our vision evolved to interpret 2-dimension images of uncurved 3-dimensional objects (which sometimes have curved ",
" but are never themselves curved). As such, the question of what \"shape\" an infinite 3-dimensional possibly curved universe would have doesn't have an answer."
] |
[
"That it isn't curved. Specifically, that initially parallel lines (marked by light-rays, perhaps) remain parallel indefinitely.",
"Consider the surface of a sphere. Imagine you start two paths on the equator, both heading due north. They are thus parallel to begin. But they immediately ",
" to be parallel and cross at the north pole. On the other hand, imagine drawing two lines on a Pringles chip that are parallel right at the middle. However you do it, they'll start to diverge from one another as you move away from that point. These are ",
" spaces. But if you draw two lines that are parallel at one point on a flat surface, like a table top, they will remain parallel forever.",
"When we talk about the universe, the three basic overall shapes we consider are closed (a 3-d version of Earth's surface), open (a 3-d version of the Pringles chip), or flat (a 3-d version of the table top)."
] |
[
"To add just an intuitive point to RM's post, the important message is that this thing we call \"curvature\" (or its absence, \"flatness\"), which is familiar in the 2-dimensional case, also exists for all higher dimensions.",
"To really \"feel\" the curvature of a 2-dimensional object, we need to be able to visualize in 3 dimensions. This is no problem, since we are used to living in 3D space. But, our brains poop out when it comes to visualizing 4+ dimensions, and so there is no simple intuitive picture of curvature of higher-dimensional objects.",
"Luckily, differential geometry provides us all the tools we need to mathematically manipulate things like curvature, etc., in higher-dimensinal manifolds."
] |
[
"A question for /u/AsaChemicalEngineer"
] |
[
false
] | null |
[
"One of my roommates... who? Are you sure you heard right? ",
"I don't know what AVATAR is though. Sorry I can't be of any help."
] |
[
"No problems, just surprising on my end. Sorry I can't be of any help. I don't do any cyber security work. If you have a general computing question (that isn't nessisarily about a single system) feel free to rephase and ask that on the ",
"/r/AskScience",
" forum."
] |
[
"Sorry. I believe I have the wrong mod then. AVATAR is an advanced system that can detect eye movement, passport authenticity, pupil dilation, etc. It was displayed at an Arizona GenCyber camp at University of Arizona. Sorry for wasting your time."
] |
[
"Is it possible that blowing your nose to relieve sinus congestion could have more drawbacks than benefits?"
] |
[
false
] |
I've read a few articles linking blowing your nose to higher possibility of a stroke due to a brain hemorrhage. I was just curious if anyone had any knowledge on the subject. Obviously it is commonplace to blow your nose when you are sick, but I sometimes wonder if it is counter-intuitive to the body's reaction to swallow mucus.
|
[
"Daily mail health articles are less medically accurate than a nice cheese sandwich.",
"If this is all you've got to go on I wouldn't worry about it. I don't know anything about the specifics of this article though. "
] |
[
"Well, based on the description in the daily mail",
" it's only a short term risk induced every time you blow your nose, and they're not looking at long term complications. ",
"I did have quick search on google scholar for the original article, but I can't find it."
] |
[
"Found ",
"this link",
" in the related ",
"science daily",
" article."
] |
[
"Why is it that some substances are metabolized according to half-life (caffeine) and others by set amounts (alcohol)?"
] |
[
false
] |
Is either more accurate, or are these just rules-of-thumb for lay people to use so they don't get too drunk or caffeinated?
|
[
"The difference is essentially first-order vs. Michaelis-Menten kinetics.",
"First-order reactions occur at a rate proportional to the concentration of the reactant. This tends to be true for the elimination of caffeine. This means that the elimination rate of caffeine is directly proportional to its concentration in the blood plasma. This leads to exponential decay of the concentration and therefore a half-life.",
"The elimination of alcohol on the other hand, follows Michaelis-Menten kinetics. For small concentrations of alcohol in the blood, it is eliminated at a rate approximately proportional to its concentration in the blood plasma. However, once the concentration becomes too high, the rate of elimination saturates to some maximum value. The body cannot metabolize the alcohol any faster than this, even if the concentration of alcohol in the blood continues to get higher. This leads to the rule of thumb of approximately one standard drink per hour, since the body typically cannot metabolize alcohol faster than this.",
"Michaelis-Menten kinetics",
" occur because an enzyme has to first bond with the reactant to break it down. During this time, the enzyme cannot be bonded with any other molecule of reactant. This causes a bottleneck -- if there is too much reactant, the enzymes cannot service them all at once."
] |
[
"The answer does address a fundamental limitation of enzymes though, which is simple saturation (overwhelming the enzyme with substrate, while the catalytic rate is maximized. Enzymes can only work so fast). "
] |
[
"The answer does address a fundamental limitation of enzymes though, which is simple saturation (overwhelming the enzyme with substrate, while the catalytic rate is maximized. Enzymes can only work so fast). "
] |
[
"My biology teacher told me that our eyes generate a new frame every 1/16th of a second. So 16 FPS? Is that true?"
] |
[
false
] |
That seems unbelievable! If that's true, why can I tell the difference in video games between 60 FPS (eg. Call of Duty) and 30 FPS? (eg. BF: Bad Company 2)
|
[
"That's not really true. Human eye's don't have frames or frames per second the way that video recordings or video games do. When enough light hits a photoreceptor in the eye, triggers and sends a signal to the brain, but then the photoreceptor needs to refresh before it can be triggered again. The limiting factor is how long it takes photoreceptors in the eye to reload. Human eyes are much more sensitive to big changes, especially in the more light direction. In ",
"one study",
" subjects were able to identify images flashed for 1/200th of a second. So by this measure humans have >200fps vision. ",
"But on the other hand, If you are in a dark room, and someone takes a picture of you with a flash. You are blinded for many seconds, up to minutes, because your photoreceptor cells were so overloaded. So by this measure humans have <0.1 fps.",
"So it depends on how you measure it. "
] |
[
"your eyes don't exactly see in \"frames per second\". the closest thing to anything regarding FPS is that images usually persists for roughly 1/25th of a second on the retina. it is really wrong to assign an FPS value to the human eye, but if i were to do it because there was a gun to my head, i would say 25-30 FPS. ",
"\"but i can tell the difference between 30 and 60 fps!\" you might say, and that is because, while images usually last 1/25th of a second on your retina, this still doesn't mean your eye sees things at 25 FPS. ",
"tl;dr: your eye is not a camera and frames per second doesn't really apply to it."
] |
[
"As I understand it, the main point is that your eyes don't take snapshots synchronized with a clock (not the thing on the wall, just an on-off oscillator). Rather, lots of different places on your retina send lots of different non-synchronized messages to your brain.",
"Think of it like this: you have a bike in front of you in a dark room and its wheel is spinning at a constant rate. Turn on strobe light #1 at time=0 sec (the strobe pulses once every second). With just one strobe light, all you see is\n snap snap snap snap",
"Now let's try it again, with one difference: turn on strobe #2 at time=0.5 sec. Guess what you see?\n snap snap snap snap\n snap snap snap snap",
"Imagine this effect multiplied by a very large number (the number of light-receiving areas on your retina) and you have something closer to the way that your brain asynchronously receives images."
] |
[
"Theoretically, would it be possible to create an atmosphere on the moon?"
] |
[
false
] |
Would it be possible to create and sustain a breathable atmosphere on the moon? Of course, this is just asking if it is theoretically possible, because that would require a very large amount of oxygen. But would it even be possible to create an earth-like atmosphere, if we had the resources?
|
[
"This is sort of simplistic.",
"Titan, one of Saturn's moons, has a surface gravity less than that of our moon. Yet it has an atmosphere 1.5 times as dense as Earth's. Clearly, it is not gravity alone that is the problem. Objects with less gravity than the moon can hold massive atmospheres. We have an example in our own solar system.",
"The problem is heat. Titan is far from the Sun, and gets very little heat. On the other hand, our moon gets very hot (on the side facing the Sun at the time). Heat gives the molecules more energy and therefore faster velocities, so the number of molecules that can reach escape velocity in the upper atmosphere is higher. This might cause the topmost layers to eventually \"boil off\".",
"However, this could take a very long time span. Since the question is \"can we create an atmosphere on the moon\", I assume he is asking this in relation to human efforts to colonize the moon. In this context, the time that an atmosphere could last would probably be long enough. It would be in the order of hundreds of millions of years, which seems sufficient. Humans won't be around that long, and if they are, they are probably not going to care as much about the moon.",
"However, there are more wrinkles to this problem. An atmosphere is a great distributor of energy - for example, on Earth, the atmosphere helps distribute the heat over the surface of the Earth through winds. The same thing would happen if there were an atmosphere on the moon (remember, while the \"day\" side can get heated to about 110 C, the \"night side\" can be as cold as -150 C). So an atmosphere on the moon would distribute this heat, so the difference between the two is decreased. This would tend to negate the previously mentioned concern about the atmosphere boiling off, allowing it to stick around for much longer.",
"Fact is, I don't think anyone can answer the question \"how long would it last\" just off the top of their heads. You would need to run a computer simulation, with all these factors (and a few more) to get an idea. But just as a rough ballpark figure, an atmosphere would probably not last as long as the lifetime of planets (the Earth's atmosphere has lasted 4.5 billion years and will last billions more until the Sun expands and burns Earth up). But it will probably last in the order of hundreds of millions of years.",
"The real problem, of course, is how to create an atmosphere in the first place."
] |
[
"This question was asked before, and I answered it in some detail ",
"here",
".",
"I also answered a related question about how much gas would be needed to create an earth-normal type atmosphere on the moon ",
"here",
"."
] |
[
"(LAYMAN)",
"Presumably also important: Titan lies within the ",
"magnetosphere of Saturn",
", but the Moon is about 4 times farther out than ",
"Earth's magnetosphere",
"."
] |
[
"Is the solar system in equilibrium, or is it unstable?"
] |
[
false
] |
Have we modeled how the planet's orbits will change as the solar system ages? Are planets gradually going to collide with one another, float off into space, or just remain* in their current orbits? *until the sun goes nova
|
[
"Any gravitational system involving more than two objects is unstable. But often, this instability will only manifest over very long timespan. Moreover, it's usually chaotic - which means that absolutely tiny changes to the initial conditions (like moving Mercury 1m to the left) can have significant changes on the final outcome. ",
"But like I said, this sort of gravitational instability usually only comes into play over very long time scales. Mercury stands a non-neglibale chance of getting thrown out of its current orbit before the Sun dies of old age, but the rest of the planets will probably not undergo anything dramatic before then.",
"Also, for the record, the Sun will never go nova. A nova is what happens when a pile of accreted matter on the surface of a white dwarf undergoes runaway fusion. Nor will the Sun go supernova; only massive stars die that way (or white dwarfs that accrete way too much matter). Rather, the Sun die by shedding its outer layers in a heightened stellar wind, producing a beautiful, short-lived planetary nebula, and leaving behind a white dwarf."
] |
[
"When you say long timespans, how long are we talking?\nAnd I'm also assuming that as far as you know there isn't a time accelerated model of our solar system that could show possible changes?"
] |
[
"For the planets in the solar system, billions or tens of billions of years.",
"The problem is that it's not possible to accurately predict the effects of gravitational instability on the solar system over long time-scales; that's what we mean when we say it's a \"chaotic\" system.",
"For example, a solar system where Venus is located a few centimetres closer to the Earth would likely have a dramatically different outcome than a solar system where Venus was a few centimetres further away from the Earth. This is a problem, as we just don't ",
" the position of Venus to that sort of precision. So we can't accurately predict where the planets will be in billions of years time.",
"A cool application of this is the Juno spacecraft, currently en route to Jupiter. When the mission ends, they plan to crash Juno into Jupiter. The reason for this is that they don't want to risk it accidental crashing into Europa and contaminating any native life there. Because of the chaotic nature of the gravitational interactions of Jupiter's many many moons, it's not possible to predict where a probe in orbit of Jupiter would end up after a few decades. So if they just leave Juno parked in orbit when the mission ends, there's a risk it may one day crash into Europa. Therefore, they're slamming it into Jupiter when they're done with it."
] |
[
"If our lungs are in our chest why does our stomach expand when we breathe in and not our chest?"
] |
[
false
] | null |
[
"If your chest doesn't expand, you are doing it wrong. The diaphragm does push down on the belly and pushes out the contents, but your abdominal muscles are auxillary (secondary) muscles of respiration. Your belly will passively outpouch, but you shouldn't be breathing primarily with your belly.",
"Think of the ribs like bucket handles, angled downwards during expiration. The diaphragm contracts, moving downward into the abdomen and flattening. The flattening pushes out the ribs more horizontally. Moving downwards is more of a piston-like motion. All of these actions act to increase the thoracic cavity volume. Since the lungs are held to the chest wall and the diaphragm by negative pressure in the pleural space, the lungs expand with the thoracic cavity. There are a number of ways to demonstrate it, but a simple way is to place your hands flat on the back of someone, one on each side of the spine. Your hands will rotate and move apart as the ribs become more horizontal during inspiration.",
"There are a number of different things that can go wrong with the chest wall, lungs, and diaphragms, and I spend my life dealing with them. Anything altering the mechanical efficiency of the system leads to recruitment of more muscle groups to help alter that thoracic cavity size -- including the belly muscles, the shoulder muscles, the muscles between the ribs, and the neck muscles."
] |
[
"Your chest should expand somewhat when you breathe (at least mine does). However, your abdomen also moves outward because of your ",
"diaphragm",
". This muscle sits below your lungs and contracts, pushing into your abdominal cavity, to \"pull\" air into the lungs. In case the wiki isn't clear, I found this ",
"youtube video",
" showing the mechanics behind it's function.",
"Edit: Accidentally a comma."
] |
[
"It's fine to use accessory muscles when exercising or singing. But you should have to depend on those for normal passive breathing."
] |
[
"Is there a point where too much muscle is bad for your body?"
] |
[
false
] |
Correct me if I am wrong, but the heart works extremely hard in cases of obesity, which is a bad thing. Would there be a point that the heart would work equally as hard to sustain a certain level of muscle in the body?
|
[
"Everyone seems to be missing the point of the question, so I will rephrase in hopes have we can get an answer. I am also curious about this question. ",
"While maintaining a healthy body fat percentage, can a person build so much muscle it can effect their health? Why?"
] |
[
"I believe the simplified answer would be no. Unless you are a mutant or intentionally mess with its function, ",
"myostatin",
" works to limit the total amount of muscle a person can have. Getting there is a different story, but even in the few cases of natural mutations having up to 40% more muscle mass doesn't seem to be detrimental. "
] |
[
"You could still have a high muscle mass and a high enough body fat ratio as well."
] |
[
"The liver breaks down alcohol, but what does it break it down into?"
] |
[
false
] |
Basically the title
|
[
"Ethanol (drinking alcohol) is metabolized by the enzyme alcohol dehydrogenase into acetaldehyde. The same enzyme then further metabolizes acetaldehyde into acetate. ",
"Methanol (moonshine runoff) is metabolized into formaldehyde and then formic acid, by the same enzyme",
"Isopropyl alcohol (rubbing alcohol) is metabolized into acetone, again by alcohol dehydrogenase. ",
"All of these metabolites are toxic. Acetaldehyde is partially responsible for hangovers, formic acid is responsible for blindness. ",
"Edit: my mistake, the second step is by the enzyme aldehyde dehydrogenase. I'm a bit busy today but I'll answer what I can on mobile "
] |
[
"Mostly correct.",
"Alcohol dehydrogenase (ADH) converts alcohol to acetaldehyde. Then acetaldehyde dehydrogenase (ALDH) converts acetaldehyde to Acetate.",
"The reason people have different alcohol tolerances is due to different levels of ALDH expression. Asians have really low levels, hence Asian Flush Syndrome. The acetaldehyde is what is responsible for the hangover (as well as dehydration).",
"Fun fact, the treatment for methanol poisoning is actually alcohol. So those tequila shots could save your life (under very specific situations)."
] |
[
"It should be said the treatment for methanol poisoning is ethanol, but only because if your body is flooded with ethanol it dilutes the methanol enough so the methanol is converting the formic acid more slowly because it needs to convert the ethanol as well, so it doesnt build up quickly enough to hurt you."
] |
[
"I'm looking for a scientific study showing a difference between how right and left wings brain works, could anybody help me?"
] |
[
false
] |
I'm not quite sure about the specifics, but anything on the matter would be appreciated. Thanks.
|
[
"http://www.ted.com/talks/lang/eng/jonathan_haidt_on_the_moral_mind.html"
] |
[
"That's exactly what I thought of, nice work. "
] |
[
"Not sure anything like that has been done. The best you can do are things like this:",
"http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W4M-4TKXD92-1&_user=10&_coverDate=12/31/2008&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1308047166&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=f0b00f8541302917b926d446ea9b0281",
"It was free from google scholar."
] |
[
"How do scientists know how many elements there are?"
] |
[
false
] |
I've always been a huge fan of science fiction and space travel in particular. My most recent science fiction obsession is the Mass Effect series in which an imaginary element named element zero is used to generate dark energy and allow extreme faster-than-light speeds. I've always heard that scientists know what every element in the universe is or at least know the amount of elements that exist. How can they be sure? Do they speculate based on the information available that there is only 118? How do they know that somewhere, somehow, there is no other elements or substances that we don't know about?
|
[
"Each element in the periodic table represents a nucleus with a unique number of protons. 1 proton is hydrogen, 2 is helium etc etc, most people know this about the elements, so I say this just to demonstrate what differentiates one element from another. ",
"Now, there is a key reason why you can't just keep adding protons to a nucleus. The important thing to know about elements is that there are two opposing forces that exist inside the nucleus. The electromagnetic force, and the nuclear strong force. The electromagnetic force is always working to push nucleons (Protons+neutrons) apart. This is natural and easy to understand as we know that protons are positively charged, and like charges repel. The strong force is obviously quite strong at ",
" as it manages to overcome the electromagnetic force and push the Protons into a very tight ball. ",
"However, as you start packing more and more neutrons and protons into a nucleus, naturally its size increases, which means that the electromagnetic force becomes more powerful, and the nuclear strong force holding the nucleus together gets weaker, as the nuclear strong force is only strong at very close distances. You can see where this is going I hope, as the more protons you pack in a nucleus, the stronger the electromagnetic force becomes relative to the nuclear force, and eventually, it overcomes it, preventing the creation of a new element with more protons in the nucleus. ",
"All of the recent additions to the periodic table are not known to occur in nature, and likely none of the future additions will either, as most these new elements have only been able to maintain a stable nucleus for a very short period of time, under very strict laboratory conditions, before the electromagnetic force blows them apart."
] |
[
"Each element has a unique number of protons(and electrons), starting with hydrogen at 1 going up to uranium with 92. Beyond uranium the elements become unstable and are usually man made, if they were to somehow be created naturally they decay rapidly into other elements, usually in fractions of a second."
] |
[
"You're question isn't stupid, xieish is just an ass. There most likely are no planets made of elements we don't know about because we know of all the elements up to 118 and only up to lead-208 are stable ones.",
"There could possibly be an island of stability up in the really high z numbers, but we have no evidence to support that notion. The Earth is mostly made from the most common star produced elements and it'd be unlikely and probably impossible to find exotic planets made of z>118 elements."
] |
[
"Why do the significant majority of Southeast Asians have light skin and black hair?"
] |
[
false
] | null |
[
"Is it not true then that the black skin tribe in Africa became the dominant group because their black skin gave them a reproductive/survivability advantage? "
] |
[
"Is it not true then that the black skin tribe in Africa became the dominant group because their black skin gave them a reproductive/survivability advantage? "
] |
[
"Technically, Japan is generally considered to be East Asia. Southeast Asians are countries like Malaysia and Thailand, and they're generally darker. Japan's about at the same latitude as Spain, so there's no particular reason they should be much darker than that. Japanese popular culture also skews towards preferring pale skin, so if you're getting your perception of Japanese average skin color from their pop culture, you should be aware that their models and actors tend to have much fairer skin on average. "
] |
[
"How fast does rain fall?"
] |
[
false
] |
How fast does rain fall from the sky. I do not think that rain would be falling extremely fast because raindrops have low mass, and they do not hurt or sting when they hit you. Is there any kind of radar gun that could be used to measure this? Thanks for reading.
|
[
"What you are looking for is the drop's ",
"terminal velocity",
" and it should be fairly easy to estimate with the formula on wikipedia. You'll have to look up some constants and chose the size/shape of your drop. The ",
"drag coefficient",
" is probably the most annoying thing to pick, but I think it'd be fair to pick the \"streamline body\" from the table (the drop might not have that shape when it starts to form, but it should be forced into it as it falls)"
] |
[
"Thanks for that. I’m not any good at physics so I am not going to try to find the answer."
] |
[
"This is an old post, but I wanted to point out that raindrops are not streamlined. They are typically spherical, but large drops grow more oblate rather than streamlined. ",
"source"
] |
[
"What is the Moshinsky atom?"
] |
[
false
] | null |
[
"Do you have some more context? Where did you hear about this?"
] |
[
"Thank you for your reply!",
"The specific context is this ",
"paper",
".",
"I am familiar with some of the math behind open quantum systems i.e., Quantum Markov Semigroups. ",
"I would like to understand what is the \"Moshinsky atom\" in the sense of:\nWhat does it describe? (ELI5)",
"Is it a model for a \"real\" phenomenon or an ideal one ? \nIf it's an ideal one, in which sense is ideal?",
"Thnx !"
] |
[
"Just from looking at the Hamiltonian given in the paper, it looks like an \"atom\" where the two constituent particles interact via a harmonic-oscillator-like interaction. It looks like you have two particles placed in some external HO potential, which also interact with ",
" via a different HO potential.",
"But for more detailed explanations, I'd recommend a more specialized sub like ",
"/r/AskPhysics",
", or the weekly questions thread on ",
"/r/Physics",
"."
] |
[
"How did multicellular life appear?"
] |
[
false
] | null |
[
"This is a big question in biology with no definitive answer. Paleomicrobiology (i.e. the study of ancient microscopic life) is a tricky field because microbes don't fossilize the way macroscopic life does, and Precambrian rocks are relatively hard to come by. Paleontology is not my specialty, but to my understanding, studying the evolution of microbial life relies primarily on 1) chemical residues left in rocks by ancient microbes, and 2) comparisons of modern microbes.",
"Based on the simplest multicellular organisms alive today, I would dispute the insinuation of the other answer here that cell specialization necessarily followed growth in size. There are macroscropic organisms (e.g. ",
" edit: apparently not sponges - maybe \"macroscopic\" is reaching too far) that do not have any specialized cell types and yet behave more or less as cohesive units, and there are specialized cells that live in groups of just four or five cells. A classic example of the latter would be certain types of cyanobacteria that form small clusters in which some cells exclusively perform photosynthesis, while others exclusively fix nitrogen (i.e. turn atmospheric nitrogen gas into usable ammonia). This strategy is advantageous because oxygen is necessary for nitrogen fixation but inhibits photosynthesis - thus the nitrogen-fixers can flush themselves with oxygen while the photosynthesizers can exclude oxygen.",
"I think the cyanobacteria example provides a good illustration of how multicellular life probably emerged - though this doesn't mean that cyanobacteria ",
" the first multicellular life forms. Just like the cells in your body, the cyanobacteria which play different roles have the same genome but express different genes. This doesn't clarify the entire process though, because sexual reproduction and deterministic growth (i.e. growing specific, recognizable structures) represent two further evolutionary jumps towards modern multicellular life. I think there are some good theories out there about the emergence of sexual reproduction, though I not familiar enough with them to comment on that."
] |
[
"It didn't just appear, multicellular life started out as small colonies of simple cells called protists. This tactic proved very useful through natural selection, and so multicellular creatures started growing in size, in complexity, and their cells started to specialise.",
"However, the exact reason or the turning point of one cell suddenly wanting to cooperate with others of its kind is not yet known."
] |
[
"You're right, I totally misinterpreted that in my reply. Thanks for the correction!"
] |
[
"How do you calculate the radius of a large explosion?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/estimation",
"/r/theydidthemath",
"guidelines",
"/r/askscience",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"The question involves performing a calculation.",
"No, the question asks for the formula so I can do the calculation."
] |
[
"Which is similarly off-topic, for the same reason, and ",
"more",
". Specifically, asking ",
"/r/askscience",
" to do your research is not something we allow.",
"Cheers."
] |
[
"Where can I go to find reliable sources for global warming?"
] |
[
false
] | null |
[
"Reputable governmental science organizations and professional science associations relevant to climate change include:",
"The ",
"National Oceanographic and Atmospheric Association",
"NASA's climate change page",
"The ",
"Environmental Protection Agency",
" ",
"The ",
"Royal Society",
"The ",
"Geological Society of America",
"The ",
"American Physical Society",
"The ",
"Max Planck Institute for Meteorology",
"You'll find that all of them agree that climate change is real, that it's primarily due to human activity, especially the burning of fossil fuels, and that it poses a real danger."
] |
[
"Awesome, This is exactly what I needed! Thank you!"
] |
[
"I also recommend searching through ",
"/r/AskScienceDiscussion",
". We've had a few really great climate change posts there. "
] |
[
"How do directions work in space?"
] |
[
false
] |
Say I'm standing on the moon and want to go Mars. How is it calculated? I'm imagining that you calculate the movements and time needed and then you get a vector that points you in the right direction. How does this vector work? What does it relate to? Is there a standard way to get from one (moving) point to another in space? I'm not so much interested in the exact calculations, just a basic overview if possible.
|
[
"There's nothing special about directions in space as such (maybe if you get into general relativity but I don't suppose you meant that). Mars is right in the direction where it seems to be. What I think you're asking is how the orbits work. That is, if you are on the Moon and want to go to Mars, with a spaceship that's at least somewhat realistic, then you of course don't point your ship towards Mars and just go.",
"You might be thinking that things in space go in a straight line so to get from A to B, you just point to B and go. And that's true if there's nothing else in space but everything in the solar system is in a big gravity field. So things don't go at all in straight lines, they go in what are called ",
"conic sections",
". There are three kinds of conic sections, ellipse (the circle is a special case of this), hyperbola and parabola. An object that's escaping the system is either on a parabolic (if exactly at the escape velocity) or a hyperbolic trajectory (if greater than the escape velocity). Everything else is in an elliptic orbit and we'll focus mostly on them now. An important thing to keep in mind is that if you don't use your engines or get close to another planet or moon or get inside the atmosphere of something, then you will stay in the same orbit forever. It doesn't spiral down to the object you're orbiting. It doesn't circularise itself. After a full orbit you return to the same spot you left from and at the same speed.",
"Orbits have a couple important properties. First the ",
"eccentricity",
". This means how circular the orbit is. Eccentricity 0 means that the orbit is perfectly circular, values between 0 and 1 mean more and more elliptic orbits as the eccentricity gets closer to 1. Eccentricity 1 is a parabolic orbit and values higher than 1 are hyperbolic. ",
"The other important thing is altitude, or radius. If the orbit is perfectly circular then altitude is clear. If it's an ellipse then the altitude will vary at different points of the orbit and it's better to use something else. One way is to specify the radius at the lowest and highest point, called the ",
"periapsis and apoapsis",
", respectively. Or names such as apogee and perigee are used if you're on Earth orbit, or aphelion and perihelion on Solar orbit or a whole lot of other stuff for other planets but they all mean the same thing. Another way to specify the same thing is to use the ",
"semi-major axis",
". It is the \"radius\" of the ellipse at the most elongated point. Note that it's measured to the middle of the ellipse, not to the central body you're orbiting. In essence this is a number that roughly describes the radius of an elliptic orbit. For a circular orbit it is the actual radius.",
"There are other things too that relate to how the orbit is aligned three-dimensionally. Like is it an orbit that goes over the poles or one that goes along the equator and such things. But we best keep things two dimensional for now so we don't need them.",
"And when thinking of moving around in the solar system, or just between the Earth and the Moon, or even just between different Earth orbits, don't think at all about going in a straight line or maintaining your velocity or in what direction the gravity is and how it'll affect your velocity. Just think what your orbit is, that is the eccentricity (how elliptic it is) and what the altitude is. And of course, where on the ellipse you are now. Your velocity, both direction and magnitude, are fully determined by your orbit and your location in it. An object on a specific orbit always has the same velocity at the same point regardless of the mass of the object or anything else (it does depend on the mass of the central body though). Or when you intend to change orbits think of it the other way round, how your changed velocity will determine your future orbit.",
"So let's start with a circular orbit around the Earth. You make some kind of a change in your velocity by using your engines. The orbit you get to will be one that goes through the point where you used your engines. That should be intuitive since your current location must of course be a point of the orbit. So if you want to get to an orbit that doesn't intersect your current orbit, then you will necessarily have to do at least two engine burns. First to get to a temporary orbit that intersects your current orbit and the target orbit, this is called a transfer orbit. And then a second engine burn at the intersection of the transfer orbit and the target orbit to get to the target orbit.",
"So let's say we want to get from a low Earth orbit to a geostationary orbit which is a much higher orbit. They are both circular and of course do not intersect. In general circular orbits of different radius can naturally never intersect. First we want to turn our low circular orbit into an elliptic orbit that will intersect the higher geostationary orbit. To do this we accelerate along our orbital motion. That means tangential to the circle. Or parallel to the surface of Earth. You'll get a long way by just accelerating along the motion (prograde) or opposite the motion (retrograde) and never accelerating in any other direction. Accelerating prograde will always increase the altitude at the opposite side of the planet. In other words it increases the semi-major axis and in this case it also increases the eccentricity, that is makes the orbit more elliptic. We should burn the engines until the altitude of the orbit at the opposite side is just at the height of geostationary orbit, anything that intersects the geostationary orbit would get us there but any more is a waste of fuel. After that we just wait until we move along the orbit to that point, that is the point where our transfer orbit and the geostationary orbit intersect. There we'll do another engine burn to turn our transfer orbit into the desired geostationary orbit. This will again be prograde (along the orbital motion) increasing our speed and again raising the altitude at the opposite side of the planet. Again the semi-major axis is increasing but now the eccentricity is decreasing and our orbit is becoming more circular. When the altitude at the opposite side is also at the geostationary orbit altitude, we will be done and are on a circular geostationary orbit.",
"What we just did is a ",
"Hohmann transfer",
" and it's the basic building block of all orbital transfers. You can drop your orbit by doing the opposite, first burn retrograde (against the motion to deccelerate) and then again retrograde at the opposite side. To get to the Moon you do pretty much the same thing but raise the orbital altitude all the way to the orbit of the Moon and just time it so that the Moon is there when you get close to its orbit. Only thing that'll be a bit different is that the gravity of the Moon will become significant at some point and you need to start thinking in terms of orbiting the Moon and not the Earth. Or to get to the Mars it's again the same thing but now we're orbiting the Sun and not the Earth. So you have to accelerate along the orbit around the Sun to raise your solar orbital altitude. You should try to do this when your orbit around the Earth goes the same direction to take advantages of your orbital speed around the Earth. ",
"If you want to get an intuition about orbits in a fun way, I highly recommend trying the ",
"Kerbal space program",
" game."
] |
[
"15 people beat you to the ",
" reference. No need to post it again; it only makes more work for the mods. Thanks."
] |
[
"If you want to get an intuition about orbits in a fun way, I highly recommend trying the Kerbal space program game.",
"Along those same lines, ",
"Orbiter",
" is another good space simulator, it has a steeper learning curve but also has ",
"a lot more depth",
"."
] |
[
"What enviromental conditions existed that allowed for Megafauna to exist, like Mammoths and Giant Sloths?"
] |
[
false
] |
Specifically I am talking about Pleistocene Megafauna, which includes: and many others. I make this distinction as I am aware that Megafauna exists today, however I am interested in the larger ancestors to many types of animals that are around today. I would like to know what conditions were original around to allow mammals to grow to such large sizes, and I would also like to know why they are no longer around today. (My guess is that they are no longer around today because they were hunted by neolithic humans, but I was wondering if the recent ice ages also had anything to do with their extinction. However I have no idea how these creatures got to be so big, and I was wondering if there was an environmental change (make up of the atmosphere, temperature or something similar) that contributed to their appearance and disappearance.
|
[
"The evidence is strong that humans caused the decline of megafauna. These species had already endured many glacial-interglacial cycles, but in each case the arrival of humans preceeds the extinction of nearly all large mammals. Importantly, humans arrived in Australia, Madagascar, and the Americas at different times, and in each case megafauna went extinct soon after. Recall also that a glacier covered a large fraction of North America, so the land area at the time was not remotely as large as today. The large predators are thought to have gone extinct in the absence of their prey. What has not been explained is why the megafauna persisted in Africa and tropical Asia, but I think it's fairly obvious that humans were never able to reach high levels of abundance in these regions because of the high pathogen load. Humans and their pathogens evolved in Africa. These pathogens can act like a predator maintaining human populations at low density."
] |
[
"The only animals for which oxygen has been conclusively correlated with size are invertebrates."
] |
[
"The only evidence I can find that suggests there is a relationship between mammalian megafauna size and environmental conditions is ",
"Bergmann's rule",
" but that doesn't necessarily provide insight into why Pleistocene megafauna died out. I've read some arguments suggesting that the increasing heat post-ice age selected in favour of smaller mammals, but critics of this view point to Australian megafauna which were very well adapted to dry and arid environments. ",
"Basically - I could not find any evidence to support the sort of relationship you seem to be describing. I think you're looking for something like the relationship between oxygen, heat and arthropod size which helps explain why insects are much larger in hotter countries, and why larger cold-blooded animals are no longer common. Like I said, I could not find evidence of a comparable relationship for the Pleistocene Megafauna. ",
"Not an expert in this area, but I hope it helps!"
] |
[
"Can you measure the local curvature of space by measuring the size/shape of the cone of reflections between parallel mirrors?"
] |
[
false
] |
I guess what I'm asking is, would the decay in the size of the reflections between parallel flat mirrors fixed together at an arbitrary distance change measurably in differently curved space? All other things being constant, the value of pi would change as the horizon would advance or recede? The distance between reflections could also be measured with a radar or laser? Would the sides of the cone also become more concave/convex, and would that cone bend or lose isotropy? Would that variance be measurable? Would that value be inversely proportional to the local rate of expansion (lambda? omegasublambda?)? Sorry if I'm fundamentally misunderstanding mirrors and/or basic physics/optics, just something I've been wondering and it's most assuredly waaay out of my depth haha... Thanks! :)
|
[
"I think it would. You'd effectively be looking at gravitational lensing, made easier to see by multiple passes through the space between the mirrors. (Assuming you're in our universe where curved space is because of GR; in a hypothetical other curved space that happens to have mirrors in it, you'd be measuring the local curvature of space.)",
"the value of pi would change",
"Just to be nitpicky here: the ",
" would change, but pi is a constant and stays the same (equal to that ratio in flat space).",
"A related concept is the deficit angle: if you walk all the way around a point and return to your starting position, how much of an angle have you turned through? In flat space, you've always turned 360°. In curved space, it depends on the curvature and the area of the region enclosed by your path."
] |
[
"Yes, this is a way to measure curvature. More generally, two objects dropped together in free fall (=under no force other than gravity) will not remain parallel as they move through a gravitational field. The distance between them will change, and that distance is given by the ",
"geodesic deviation equation",
", which explicitly involves the Riemann curvature tensor. This tensor contains all information about curvature, so these sorts of experiments are sufficient to find all info about local curvature. (Though of course the measurements are very difficult to make since changes in gravity are weak over small distances)."
] |
[
"That's effin cool, thanks! :D"
] |
[
"What happens when a sperm and an egg of two different species come in contact with each other? Does the egg not even let the sperm in, or does it let it in but then the zygote DNA doesn't fuse? What happens with the conception of hybrid species like ligers?"
] |
[
false
] | null |
[
"So, several things probably prevent this from happening. One, there are certain cell-surface proteins required for the sperm and egg to fuse correctly, that result in proper recognition. If these differ, the two cells are unlikely to meet correctly or induce the acrosome reaction, where the sperm basically burns its way through the outer layer of the egg.",
"Once this happens, the other barrier is going to be that the fused cell immediately undergoes mitosis. This is pretty much right away; both nuclei duplicate their DNA and dissolve, preparing for metaphase. This will mean the cell has to get past the mitotic checkpoint; this means every chromosome has to be correctly paired. I.e., there have to be two copies of each chromosome in order for mitosis to proceed. If the species are fairly diverged, this is unlikely to work out well, and the zygote will never get past its first mitosis.",
"Obviously, though, the mitotic checkpoint doesn't always work (otherwise you wouldn't ever have aneuploidy in adults, like with Down syndrome). In that case, the barrier to successful offspring is going to involve genetic incompatibilities (gene dosing is wrong, this species is missing a key transcription factor, etc.) Sometimes there aren't that many genetic incompatibilities, the zygote is viable, and you get a liger.",
"EDIT: Hey folks, major error in this comment, which ",
"/u/control_freek",
" correctly points out below (read their comment!); since the sperm and egg are both duplicating their DNA before division, the mitotic checkpoint won't come into play, unless there are protein incompatibilities and the like. This means the major barriers to successful fertilization and growth of the embryo are going to be the inability of the sperm and egg to recognize each other and the inability of the genome to produce a viable organism. The aberrant count WILL come into play during meiosis, where homologous (not identical) chromosomes need to be paired up, at which point the mis-match will trigger the checkpoint and sterility will result (as with mules, etc.)."
] |
[
"If you don't mind a little off topic (not really animals) but plants actually manage this all the time, They have an amazing cross-breeding history due to a duplication of chromosomes called polyploidy, which means that instead of say, 6 chromosomes you have 12. If you have that mutation (can occur during meiosis/formation of sex cells) and manage to get your baby pollen in another plant with 12 chromosomes then you can start dividing and become a beautiful mutant plant abomination. Here's the rub: You're sterile. HOWEVER if two of these mutant plant children (each with 24 chromosomes at this point) somehow at meiosis (where the chromosome number divides in half) they BOTH wind up with all 24 chromosomes in one daughter cell and form a zygote (embryo) then that will grow into a fully viable plant. An example of this is the hexaploid derivative of wild maize known as corn."
] |
[
"Mitosis is generally not the limiting step in species isolation post fertilization events - meiosis is. If the sperm and egg somehow merge from two different species the resulting embryo is capable of undergoing mitosis because the chromosomes are not required to pair up along the cell axis for division. Each chromosome will duplicate into two copies called chromatids, and the sister chromatids (identical DNA strands) are what is pulled apart during mitosis. Because of this it doesn't matter if the sperm had 10 chromosome and the egg had 13. So if fertilization occurs one of two things will happen:",
"The cell will begin to divide but will biologically break down because the proteins are incompatible. Think of trying to build a car with Toyota and motorcycle parts, you are given a components from each vehicle and that's it, you cant modify anything, they either fit together or they don't ......chances are the \"car\" is going to die before you even star the engine. The inner working of the cell is the same - all the proteins, hormones, and sugars in a cell must work together, but if they are different models the cell won't be able to preform necessary functions of live and will likely die in early embryonic development. ",
"The two species are compatible enough (usually closely related) that the cell is capable of performing all necessary biological functions to develop and survive. The next barrier occurs in the ovaries or testis of the hybrid. Unlike mitosis, in meiosis 1 the pairs of ",
" do line up on the cell axis and are then separate. However because these chromosomes do not have pairs, they cant line up properly and become mismatched. So when division occurs the chromosomes will be unevenly divided between the two cells - to keep with the car analogy, one cell will get two engines, and no cooling system while the other cell has no engine and 7 wheels. These gametes are missing critical genes for basic function and will not produce viable gametes. There are example of hybrid animals (mule is a classic) that produce healthy animals that are sterile because of this. ",
"Note: I have made the assumption that the species are genetically incompatible and are reproductively isolated biological species. Not all ",
" are reproductivly isolated; species can be isolated for a variety of reasons and would change the outcome of this question. Plus plants are excluded. They're weird, break all the rules."
] |
[
"Big Bang temperature and density."
] |
[
false
] |
[deleted]
|
[
"There are no such things as \"pure\" energy, much like there are no such thing as \"pure\" mass. ",
"Particles can have properties such as mass or energy, and a bulk of particles with high (thermal) energy has a high temperature."
] |
[
"To piggy-back on Ampersand55's correct answer ...",
"But at the same time they say that no matter existed but only energy.",
"They are, unfortunately, wrong, as far as we can tell. The matter that existed may not have existed ",
", but \"something\" was certainly there.",
"Energy doesn't have a material existance; it only exists as a property of particles and of systems of particles. If there are no particles or systems, then there is no energy to speak of."
] |
[
"There was a good post around here a while ago about just this, energy is just a number that helps us keep things in order. So far, theory and observation tells us that no matter what, this number is conserved."
] |
[
"Why does our vision blur?"
] |
[
false
] | null |
[
"Because you are drunk. Really though perhaps a little more info? "
] |
[
"I think what Gamefox24 means is please provide more information about the question. When, for instance."
] |
[
"I think what Gamefox24 means is please provide more information about the question. When, for instance."
] |
[
"If someone's receiving cancer treatment and given the all-clear, is it inevitable that they'll get it again at some point if they live long enough?"
] |
[
false
] |
I've always had the notion that once you get cancer, it's not a question of it'll come back, but when. I'd be interested in how right or wrong my assumption is. Is there any data on the percentage of cancer survivors who remain cancer-free for the rest of their natural lives? I assume it would vary depending on the type of cancer.
|
[
"There are cancers we can cure and some that we can't. It depends on the cancer, and for some cancers we can cure some stages and not others. The data for long term cancer-free survival is really dependent on the cancer and stage. For one example, ~85% of standard risk childhood leukemias can be cured. That means they won't get that cancer again. Some treatments raise your risk of getting another new cancer later, but that is different than a relapse. "
] |
[
"Relevent XKCD:\n",
"http://xkcd.com/931/",
"Alt text has explanation of the final frame."
] |
[
"Cancer isn't really a single condition, you have to think of it as a grouping of conditions, and it would depend on what type of cancer. "
] |
[
"Has anything actually reached 0 Kelvin? And if not, is it thermodynamically possible?"
] |
[
false
] |
And I don't mean 0.0028 Kelvin, I mean 0.0000000000 to infinite significant figures. Thanks :]
|
[
"It is not possible. But you can get arbitrarily close. The record I believe is several hundred trillionths of a kelvin."
] |
[
"To add to what's been said, it's not possible because a state in zero temperature is a state whose particles all have exactly zero energy. However, quantum fluctuations will ",
" cause there to be a slight amount of energy, even in a vacuum, and so there will always be a corresponding non-zero temperature"
] |
[
"Another way of putting it would be the Uncertainty Principle, right? Zero temperature means 0 energy, which means being able to know both position and momentum to arbitrary precision."
] |
[
"What is intrinsic curvature?"
] |
[
false
] |
[deleted]
|
[
"We call it \"curvature\" really only by analogy.",
"Consider some two-dimensional surface in three-dimensional space. Like the surface of a sphere, say, or a hyperbolic paraboloid, or whatever.",
"Every point on that surface can be described in terms of ",
" coordinates. If you imagine a sphere hanging in space, you can see how it's possible to fix a set of three-dimensional Cartesian coordinates on that space — ",
" — and assign each point on the surface a set of coordinates against that basis, yeah? For instance, we might say that the center of the coordinate basis is at the center of the sphere, and that the unit in this basis is such that the radius of the sphere is ",
", and then the surface of the sphere becomes all the points ",
" where ",
" + ",
" + ",
" = ",
" right?",
"But ",
" is not three-dimensional. It's ",
"dimensional. And that means — by the definition of \"two-dimensional\" — that we only ",
" two numbers to uniquely identify any point on that surface. So we can, if we choose, discard the ",
" coordinate frame we just established and instead choose a set of coordinates ",
" We traditionally call these coordinates ",
" and ",
" just to be generic. For any two-dimensional surface ",
" you need only a pair of real numbers ",
" to uniquely identify any point on that surface.",
"In the case of a sphere, the most natural choice for ",
" and ",
" is longitude and colatitude, where longitude works exactly the same way it does on the globe and colatitude is almost exactly like latitude except we define it as being zero at the pole and going up to ",
" at the other pole rather than being zero at the equator and going from –",
" to ",
" This gives us a set of ",
" coordinates that we can use to uniquely identify any point on the surface of the sphere.",
"But when we do this, we find something interesting. Yes, we're dealing with ordinary, mundane rectilinear coordinates. But we find that within this system of coordinates, ",
" from the way it works on the Euclidean plane also described in terms of ordinary, mundane rectilinear coordinates. For example, on the Euclidean plane in ",
" the distance between any two points is just given by the Pythagorean theorem: ",
" = ",
" + ",
" right? Not so on the sphere in ",
" On the sphere, the distance between any two points is … well, more complex. I don't remember it off the top of my head, and I don't feel like doing the Christoffel symbols, and I ",
" don't feel like trying to typeset it. So suffice to say, the Pythagorean theorem does ",
" on a sphere.",
"However, we can ",
" just exactly ",
" the geometry of ",
" differs from the geometry of ",
" by examining an object called the ",
" I don't want to go into the details of that right now, but suffice to say that for any space there exists a rank-two tensor field that fully describes the geometry of that space at all points within that space. For the plane, the metric tensor is just the Kronecker delta, and for the two-sphere it's one-zero-zero-sin",
" ",
" (Deriving that is left as an exercise blah blah blah.)",
"Once we have a ",
" of our sphere — that's the ",
" bit — and a ",
" guess what? ",
" Seriously. We don't need it any more. We now have everything we need to do geometry. As long as we understand how to generalize our formulae to work in any geometry — things like knowing how to use the components of the metric tensor as coefficients and such — we can forget the fact that we ever had an embedding in ",
" at all, and just do pure abstract differential geometry. Which is ",
" because the biggest application of abstract differential geometry has to do with ",
" and visualizing a four-surface is absolutely impossible on its own even before you contemplate the living hell of trying to visualize a four-surface ",
"So what does all this have to do with curvature? Like I said, we call it curvature by analogy. If the metric tensor of a space differs from the metric tensor of ",
" space of equal dimension — the Kronecker delta, in other words — we say that the geometry of the space is curved, because the geometry of that space is the same as it would be if we embedded our ",
"-dimensional space in some ",
"-dimensional space where ",
" is greater than ",
" and let it be … well, "
] |
[
"Intrinsic curvature means two things. One is that space doesn't have to curve into anything, which you seem to understand pretty well. So I'll gloss over that, even though it's usually the question.",
"Intrinsic curvature also means that the distances between points are affected by the curvature though. You can see, for instance, that a cylinder is curved, but the curvature does not affect the metric so its ",
" curvature is zero. Now consider Asteroids. The length of any line segment on the map, regardless of where it is, is just length of its projection onto a sheet of paper or something. This means that, like a cylinder, the Asteroids map must have ",
" intrinsic curvature.",
"But how can this be, since the Asteroids map is clearly a torus? Well, it turns out that you can in fact have a flat torus. There's no way to embed such a thing in anything lower than 4 dimensional space; any torus in 3 dimensions will have some intrinsic curvature. Think on that; the structure of the Asteroids map actually cannot be represented in 3D space."
] |
[
"Very very simply, yes. It's a bit more complex than that, for reasons that you can see clearly with just a little examination. For example, in the case of the metric of the cylinder, you can map it to a plane, but you must ",
" two edges of the plane. That is, you must say that the curve of constant longitudinal coordinate zero and the curve of constant longitudinal coordinate 2",
" (in the case of a unit cylinder) ",
"This is especially meddlesome in the case of the torus, because you have to identify curves of constant longitude ",
" curves of constant colatitude in that fashion. Which breaks the \"wrap it in up in wrapping paper\" mental model.",
"But yes, in the most simplistic terms, a good rule of thumb is that if you can wrap a surface in a piece of paper without crinkling that paper, the surface is geometrically flat. In general. Sort of. Not really, but it's a start."
] |
[
"Is a water soluble calcium salt less likely to be ionized in stomach acid than a poorly soluble calcium salt?"
] |
[
false
] |
[deleted]
|
[
"Aah I see\nIm wasn't familiar with the product you're talking about, so yeah... xD",
"But I get it now.",
"The Ca form would likely indeed ionize inside the stomach, but then it would need to be hydrolised by stomach acid into a organic compound to get absorbed into the body. \nOsmosis into the body will likely reject the substance otherwise.\nSo the Ca form will likely still work just fine, if ingested after a meal.",
"So the difference between both is not a scam but that de FA form will be absorbed into the body much quicker, because this is already hydrolysed and thus absorbable in the body.",
"Edit: Why is the Ca form cheaper, the substance in the form of a salt is more stable than the acidic form."
] |
[
"You answered my question. No, I was speaking of HMB-CA specifically, a calcium salt of hydroxymethyl butyrate, which also has another form, Free Acid HMB sold at a much higher price. I needed to know if the HMB-CA, which is water soluble, loses all the calcium through ionization, leaving behind HMB-FA, what this states to me is that yes, as long as HMB its self doesn't break down (doesn't break apart), the calcium, most to all of it, should be ionized correct? ",
"Basically this proves HMB-FA is a scam, and that HMB-CA goes into FA form in the stomach due to calcium ionization. Trying to figure out if a supplement is a scam, which the marketed HMB-FA is just a money grab. ",
"EDIT: Everyone keeps talking about calcium carbonate and I want to slap them so hard, I want to slap you with a wet pool noodle."
] |
[
"You answered my question. No, I was speaking of HMB-CA specifically, a calcium salt of hydroxymethyl butyrate, which also has another form, Free Acid HMB sold at a much higher price. I needed to know if the HMB-CA, which is water soluble, loses all the calcium through ionization, leaving behind HMB-FA, what this states to me is that yes, as long as HMB its self doesn't break down (doesn't break apart), the calcium, most to all of it, should be ionized correct? ",
"Basically this proves HMB-FA is a scam, and that HMB-CA goes into FA form in the stomach due to calcium ionization. Trying to figure out if a supplement is a scam, which the marketed HMB-FA is just a money grab. ",
"EDIT: Everyone keeps talking about calcium carbonate and I want to slap them so hard, I want to slap you with a wet pool noodle."
] |
[
"Why does rubbing alcohol feel slightly warm to the touch when I pour it over my skin?"
] |
[
false
] | null |
[
"It does? Without testing this right now I would say it should feel slightly cold due to rapid evaporation. Compare it with water and report back."
] |
[
"This was my understanding, and I just tried it out with some IPA I had lying around. This is common with other alcohols as well, such as ethanol, and what happens is that the alcohol draws heat away from your skin in order to give it energy to evaporate. This is the reason why they evaporate much quicker than water, for example. Because it draws heat away from your skin it therefore cools you skin down giving you the cold sensation."
] |
[
"Yup, it does. Every single time I've used it my entire life."
] |
[
"Why are trans-unsaturated fats viewed as more dangerous than saturated fats?"
] |
[
false
] |
[deleted]
|
[
"I used to teach organic chemistry, and am studying medicine now. As a principle, the body can be either incredibly selective, with enzymes only binding one skeletal structure but not a similar one. Alternately, they can be absurdly nonselective. It's messy. ",
"In this case, it remains somewhat unclear exactly what the problem is, although it's quite clear that there is a problem. (This is usually what happens in medicine--if you can prove good or bad results, the actual reason why it happens takes a back seat. People took aspirin for almost a century before anyone figured out how it worked.) What we do know: Industrially produced trans fats do increase LDL and decrease HDL, increasing risk of coronary artery disease, and probably other bad things.",
"The main pathway does seem to involve screwing up fatty acid metabolism, leading to arterial plaque formation and thus predisposing to heart attacks and such. Other proposed mechanisms include various ways of messing with chemical messenging between cells, mucking up the lining of blood vessels, and doing something bad to cell membranes.",
"http://onlinelibrary.wiley.com/doi/10.1002/mnfr.201100700/epdf"
] |
[
"In a biochemistry class last year I seem to remember that trans-unsaturated fats are not made in biological systems. So when unsaturated fatty acids are made by the body they're always cis, which makes me think the trans variety won't be metabolised very well in the body and therefore cause a greater increase in cholestrol and therefore arterial plaque etc.",
"In regards to trans-unsaturated fats looking like saturated fats, this is just on paper but in reality (in 3D) they're different too."
] |
[
"If I might hazard some educated guesses at mechanism (biochem PhD here), then I might guess that the trans compounds slip through the cracks. While fatty acids with a double bond in nature are cis, they would be easily excluded by shape from enzymes designed to handle only saturated fatty acids. Some of these enzymes might still be okay incorporating a trans fatty acid. Once there, the trans compound could be \"stuck\" because the next enzyme would need to handle only saturated molecules, and the result would be inhibition of the next enzymes in line. And inhibiting metabolic enzymes can have all kinds of nasty downstream effects.",
"/wild speculation"
] |
[
"Why do I feel better after I cry?"
] |
[
false
] |
I've been all fucked up about things lately and I just had a good ole cry about things and I really feel like a different person. What does crying do to make me feel at peace?
|
[
"All I have to go on is ",
"Wikipedia",
" but what it has to say is definitely intriguing.",
"Tears produced during emotional crying have a chemical composition which differs from other types of tears. They contain significantly greater quantities of the hormones prolactin, adrenocorticotropic hormone, Leu-enkephalin[4] and the elements potassium and manganese.[2]",
"William H. Frey II, a biochemist at the University of Minnesota, proposed that people feel \"better\" after crying, due to the elimination of hormones associated with stress, specifically adrenocorticotropic hormone.[7] This, paired with increased mucosal secretion during crying, could lead to a theory that crying is a mechanism developed in humans to dispose of this stress hormone when levels grow too high.",
"If this theory is correct, crying makes you feel better because it lowers the levels of stress hormones in your body.",
"Unfortunately there doesn't seem to be much evidence to support the claim, which is odd since you can test cortisol levels fairly easily."
] |
[
"There is no way you would get IRB authorization for an experiment where one step is:",
"Now we make fragile people cry.\n"
] |
[
"Unfortunately there doesn't seem to be much evidence to support the claim, which is odd since you can test cortisol levels fairly easily.",
"How would one go about setting up such an experiment? I mean, you'd have to induce situations that would make people cry, wouldn't you?"
] |
[
"Are there any speech impediments only found in specific languages?"
] |
[
false
] |
Or can they all appear in any language containing the "impeded" sounds?
|
[
"This is not really answer, but a clarifying comment regarding your question as your question, at least to me, is a bit vague.",
"Edit: Mods, feel free to delete if you do not find this adequate.",
"It's important to understand that speech impediments can vary in cause. It can be a physical defect in the speech production organs (i.e., clef palate, lack of necessary motor control over specific speech production organs). It can also be psychological.",
"Languages have phonetic inventories. Many languages around the world have overlapping sounds. There is a [p] in English and German for example. It would stand to reason that a speech impediment in the production of [p] caused by a defect in a speaker's lips would exist in both English and German. In contrast, German has a velar/uvular fricative (fricatives are sounds created by air over a surface) which is not present in English. So a speech impediment caused by a defect in the speaker's speech production organs resulting in a non-standard production of the velar/uvular fricative for a German speaker would, in this case, not exist in the English speaker as English does not have this phone.",
"I have not come across any body of research that has documented a specific speech impediment (assuming we are, again, referring to just the sound structure and not syntax) that exists across all languages where all languages has the one shared sound that can be \"impeded\"; for example, all human languages have [p] and therefore an \"impeded\" [p] would exist universally vs. only one language in the world has a voiced glottal fricative [ɦ] and therefore this is the only language that can have an \"impeded\" [ɦ]."
] |
[
"Thanks, your clarifcations got at the question I was really trying to ask. Would it be ",
" for a speech impediment to only affect one language or language family? E.g. A person replaces [s] with [θ] when speaking English, but not when speaking Japanese. My instinct is that it couldn't happen, but I'm wondering if a psychologically-based speech impediment could be tied to only one language in the brain."
] |
[
"You may or may not have access to the full-text, but ",
"this article",
" on congenital amusia (tone-deafness) suggests that those who are tone deaf and speak tonal languages can produce contrasting tone phonemes just fine, but have marked impairments in their discrimination and perception of lexical tones. The study was limited to mandarin speakers and suggests that tone-deafness is a general disorder and not specific to cultural or language."
] |
[
"With sunglasses on, one of my computer monitors is almost unaffected, only slightly darker, and the other one turns entirely black. What about monitors or sunglasses makes them react differently?"
] |
[
false
] | null |
[
"Most monitors have a polarization layer on the screen that helps to greatly reduce any glare on the monitor. The effect is that light emitted by the screen itself is also polarized in a certain direction. If you then pass this light through another polarizer, such as polarized sunglasses, then depending on the orientation it may cause the light to be blocked (almost) completely.",
"The reason the other monitor doesn't have this effect is either because it has no polarization layer or because the direction of its polarization lines up with that of the sunglasses.",
"You can play with this by rotating your sunglasses (or the monitor, but that's less practical). If both the sunglasses and monitor have a polarization filter, then depending on their respective orientation the light from the monitor will be blocked or let through or anything in between."
] |
[
"Correction to ",
"/u/Rannasha",
" 's answer....",
"Most monitors have a polarization layer on the screen that helps to greatly reduce any glare on the monitor.",
"Most flatscreen monitors have ",
" polarization layers that are ",
". Glare reduction is not the purpose.",
"LCD monitors work by having two polarizing filters, one that blocks light waves that wiggle horizontally, one that blocks light waves that wiggle vertically. Normally that means that ",
" light is blocked, and the screen is dark, but if you apply electricity to a special liquid layer between them, the liquid rotates the direction of wiggling so the light can pass through.",
"Net result, LCD monitors emit light that's polarized. Your sunglasses are also polarized, so they block the light depending on their orientation.",
"HOWEVER, this is annoying. So some LCD screens add ",
" layer, which changes the light so it \"wiggles\" equally in both directions. But this layer adds cost, so it's mainly found on more expensive screens."
] |
[
"More fun: If you put a second pair of polarized sunglasses between the first pair and the monitor when the monitor looks black, you can find a rotation for the second pair where some of the monitor's light is visible again."
] |
[
"How could viruses with high mutation rate like HIV maintain their functions? Isn't it like reshuffling pages in a book without changing its meaning?"
] |
[
false
] |
A genome of a virus is surely more complicated than an average book, and its mutation is like removing or reshuffling some of its pages. And somehow the entire book still makes sense (aka maintains its functions)?
|
[
"I would suggest that a mutation is more like changing a single letter on a page in a book. These mutations typically do not have positive impacts, most are deleterious, and more effective organisms (virus, bacteria, cells, etc.) out compete the now less-effective mutated organism. If the mutation is serious enough that the book is illegible (continuing your analogy) than the organism will die out and we'll never hear of it."
] |
[
"The majority of HIV virions produced are not infectious. HIV's strategy relies, in part, on integration into the genome such that a single provirus (i.e. the DNA genome) can produce innumerable progeny. ",
"In short, you only need one successful infection event with HIV, theoretically, to get near limitless tries at propagation. Some viruses are similar in that they produce gobs of uninfectious virus (e.g. HCV). A lot of DNA viruses, in contrast, produce mostly infectious virus particles. "
] |
[
"To extend your book analogy, the better way to understand it is to imagine you have a stack of millions of books, and you occasionally randomly substitute one word in each book. In one the random substitution turns a 'hello' into a 'goodbye' and now the sentence no longer makes sense, so you throw that book out. In another the substitution replaces 'hello' with 'howdy' which still makes sense so the book is kept. This results in a variation of these books which all make sense but have their own quirks. This is where the analogy gets tricky because viruses replicate while books dont. Lets say though that the books that sell the most are printed more, and those that don't aren't printed at all. This results in a book that changes with peoples changing tastes, or going back to the virus, it changes to adapt to the immune system of the host."
] |
[
"Does hair growth add weight?"
] |
[
false
] |
Okay say I shaved my head. Would I, as a whole, get heavier as my hair grew back?
|
[
"You would get heavier as you consumed food. Hair, in this analogy, can be seen like sweat. The only difference is that it's an excretion you retain, instead of one that evaporates. "
] |
[
"No, because it's just moving mass around your body. Hair gets its mass from foods that you consume."
] |
[
"Of course. All other things being equal, there is more of you than there was before, so you will weigh more. It's not that hair growth uses up another part of your body."
] |
[
"How does anything other than a head shot kill you instantly?"
] |
[
false
] |
So I was watching a crime show, and the coroner said the victim died instantly after being shot in the heart. Wouldn't the brain continue to function for a few minutes until it ran out of oxygen?
|
[
"Being shot in the heart would likely result in hypovolemic shock. ",
"I'm not of what exactly would happen to a heart when being shot, but lots of blood would be lost. This rapid loss of blood would cause hypovolemia, or a state of decreased blood volume. This would likely cause the victim to lose consciousness. The speed at which this would happen, I'm not sure. I don't want to speculate. "
] |
[
"\"Died instantly\" really has two meanings, the literal and (what I'll call) the perceived. If something shreds your brain to pulp, it really is instantly. If you got hit on the head hard enough to lose consciousness, and then shortly there after a bleed stops brain function some people still call it instant. "
] |
[
"I agree with Sunny. Literally, the only way to lose consciousness immediately would to have your brain pulverized instantaneously. We've all heard speculation about how long a person who has been beheaded stays conscious. In my mind, this is the ultimate trauma besides instantaneous brain injury, and even then the creep of death is staved off for a few extra moments, potentially, at least. "
] |
[
"How much energy does it take a bird to flap its wings during flight? Is it equivalent to humans walking/running?"
] |
[
false
] |
Oh wow. Thanks for all the amazing answers and follow up questions. For science!
|
[
"It varies by the type of flight and the species of bird. Most flight is energetically expensive, at least on a calorie per second basis. ",
"Gliding is very efficient, especially with favorable thermals. Some birds can fly for hours without a single flap. This is roughly analogous to you standing on a bicycle while rolling down a hill. You could probably do it all day, but it's going to be tiring and make you sore.",
"From there, you have migratory birds which can fly large distances at high speeds. That is roughly equivalent to a brisk walk or light jog for you.",
"After that, it's a sliding scale of flight becoming more and more energy intensive. As a good rule of thumb the more agile a bird is, the more energy it needs to spend to stay airborne. This peaks with the hummingbird, which burns a staggering amount of calories staying airborne.",
"It's also worth noting that taking off is generally the most taxing part of flight for any bird."
] |
[
"How does the energy expenditure of a hummingbird compare to a bee?"
] |
[
"What seems like aimless flying around to you is probably serving a purpose for the bird. They have to fly around to forage for food, look for potential mates, look around their nesting area for predators/rivals, collect nesting supplies and that sort of thing."
] |
[
"How Rats and Mice developed symbiosis with humans?"
] |
[
false
] | null |
[
"Cats, dogs, pigeons, crows, etc. Anything living in cities basically. There are wild mice and rats that do not live in cities like field mice."
] |
[
"Cats, dogs, etc. were domesticated by man. This is not what I was asking."
] |
[
"What does it mean to domesticate? How different is it from pigeons, possums, skunks, seals, fish, bears etc. coming to places or living where they learn that food can be found?"
] |
[
"I turn my iPod on \"shuffle.\" Had I clicked the same button earlier, or ten seconds later, would the result have been any different?"
] |
[
false
] |
[deleted]
|
[
"Difficult to say, unless somebody knows the seed of the random function in the shuffle. It is quite common to use system time in milliseconds or similar as a seed for low security randomisation, so if that is the case in the source code of the ipod music player, then yes, it would be different. Most other sources for a random seed would also give a different result at a different time. So the answer is \"probably yes\"."
] |
[
"Yup, even if we were to go to something more secure liking using a seed generated from noise on the CPU, we would still likely generate a different song choice."
] |
[
"Think of the code saying:",
"play random\nrandom = number\nsong = number\nplay number\n",
"the programing just takes a random number generated the instant the code is run (so yes it will be different every time you ",
")"
] |
[
"Can levels of calcium in ancient bones tell us anything of interest?"
] |
[
false
] |
Or is there jut too much contamination etc to analyse the Ca levels?
|
[
"Calcium isn't radioactive, so it wouldn't be useful in determining age. Diet maybe?"
] |
[
"Why would analyzing Ca be of any value? Ca is one of the major elements in bone, which is made largely of hydroxyapatite (Ca10(PO4)6(OH)2). Because of this, Ca would be less subject to contamination than many other elements."
] |
[
"It's most useful for making deductions about diet. ",
"Here's",
" one case where calcium levels in the bones of Roman gladiators tell us that they actually took calcium supplements, in the form of small amounts of wood and bone ash, because their regular diet didn't contain enough calcium. It's not ",
" about detecting how much dairy products people ate, though, because you find similar calcium levels in very early bones (prior to the development of animal-based milk production) and in relatively recent bones. The reasons why are still unclear.",
"This Oxford archaeologist",
" does a fair amount of work with calcium; if you're feeling daring you could take a look at her articles to see the kinds of things that people are trying."
] |
[
"The real culprit of 90's violence was lead? Does this theory have any truth in it?"
] |
[
false
] |
[deleted]
|
[
"Lead is bad for neural development, like the parts of the brain that deal with impulse control."
] |
[
"Boom: ",
"http://en.wikipedia.org/wiki/Lead_poisoning#Nervous_system"
] |
[
" check the wiki."
] |
[
"Could a dog survive on the exact same diet as its owner? (no chocolate)"
] |
[
false
] | null |
[
"The phrase \"",
"eating your own dog food",
"\" is believed to have originated with the president of the Kal Kan pet food company. He claimed that their pet food was good enough to eat (by humans) and put his money where his mouth is by eating a can at a shareholders meeting."
] |
[
"It was my impression that it was the theobromine in chocolate that was toxic to dogs. White chocolate should indeed then be very safe -- it's not really chocolate at all, and contains minimal theobromine. On the other hand dark chocolate should be incredibly dangerous, even more so than milk chocolate, which has been slightly diluted by the milk."
] |
[
"The main active ingredient in chocolate, especially dark chocolate is Theobromine. It is similar to caffeine and is what gives humans the 'kick' from chocolate you would usually get from coffee or pop.",
"That being said, theobromine is very toxic to dogs, as they are unable to metabolize it fast enough to over come a build up which leads to theobromine poisoning, which can lead to death.",
"So if your dog sneaks a Hersey's kiss it probably isnt a big deal, but don't go feeding your dog chocolate, especially the dark variety.",
"Wikipedia - Theobromine"
] |
[
"What determines where the poles are on a ball magnet? Or a bar magnet?"
] |
[
false
] |
On a bar magnet, one end is north and the other is south. What exactly determines which end is which? What about a sphere magnet? They would be on opposite sides obviously but what determines where the north and south are on something that doesn't have ends? Couldn't really find an answer from google but I probably don't know what to search for. Thanks a lot in advance. In a debate with a flat earther and I need some ammo from smarter people. EDIT: Thanks guys, I learnt a lot of interesting stuff about magnets from this. Unfortunately, the flat earther I was debating called me a sheep and scuttled off into the internet undergrowth when I asked how a flat, stationary earth generates a magnetic field. All he did was link a video of Eric Dubay blithering incoherently before crawling away.
|
[
"Its defined by how it was magnetized, the direction of the field that was applied when making it. The internal magnetic domains align according to that.",
"There is no particular reason that a bar magnet has to have the poles at each end either. It would be perfectly feasible to make one with one long side north and the opposite one south."
] |
[
"There is no particular reason that a bar magnet has to have the poles at each end either",
"Yes, there is! For an elongated shape, shape anisotropy (caused by the demagnetising field) favours magnetisation along the long axis."
] |
[
"True, but you can still make one that has its poles along the long side, couldn't you? It just wouldn't be as strong as one with its poles on the short side"
] |
[
"AskScience, What is your take on \"Torus Vortex Mathematics\"? [video inside]"
] |
[
false
] |
[deleted]
|
[
"In short that sounds like a quite typical pile of crackpot nonsense to me. I don't actually see any real physics or math here. as far as pseudoscience goes, it's below average in the pseudo- ('appearance of') department. Looks and sounds more like a New Age book than actual physics or mathematics.",
"It's not actually a TED talk in the usual sense but a talk from an \"independently organized TED event\". I suspect their independent organizers aren't quite as good at checking up whether the ideas they're promoting really live up to their slogan of \"Ideas worth spreading\"."
] |
[
"Apparently he's a student of ",
"this dude",
", and from a cursory reading, it looks like typical crackpot science.",
"Edit : holy timecube on a popsicle, its nonsensical. Also ",
"refer here",
" for some insight. This guy had better be trolling and I quote ",
".",
"TEDx is not the same as TED. Its organised by students at a university or something of the sort, who in this case seem to have been particularly naive."
] |
[
"So I watched one of his \"advance math\" videos on youtube. I feel like this is a perfect example of taking a little bit of knowledge/ seeing an underlying pattern and just going \"off the reservation\" with it. From what I saw he was working with what is known by real mathematicians as modular arithmetic. Its nothing new. I am not entirely sure why he picked to work in mod 9, didn't really care to know, but you can do this sort of thing with any number. Wiki has a decent ",
"write up",
".",
"Sort of reminds me of the awt guy that comes around every now and then. "
] |
[
"How do scientists describe where something is in the universe?"
] |
[
false
] |
To locate a place on earth, we use Longitude and Latitude, and everything works because it's in 2 dimensions and the continents are not constantly moving. But in space, there are 3 dimensions and everything is constantly in motion. So how do scientists describe the coordinates of various stars or planets in the universe?
|
[
"There are two coordinates used to describe where something is in the sky: declination, which is how high the object is relative to the celestial equator (the ring of the sky above Earth's equator; Polaris has almost degrees declination), and right ascension, which it's how far \"East-West\" something is in the sky. The zero-point of right ascension is arbitrarily defined as the point in the sky where the sun crosses the equator on the March equinox. These two coordinates unambiguously point to a location in the sky.",
"Then there is distance. For close things, the distance is typically given in parsecs or kiloparsecs. A parsec is about three lightyears, and is the distance something has to be at which it will appear to move by one arc-second if you measure it relative to more distant stars, six months apart.",
"For things beyond the galaxy, the unit of distance is typically called \"z\" which is a measure of redshift. Something at z=1 is 1/(1+1)=0.5 the age of the universe away in light travel time, so about 7 billion lightyears. At z=2, it's 2/3 the 2/(2+1)=2/3 the age of the universe away. This is a bit confusing because distance doesn't increase linearly with redshift."
] |
[
"This ^",
"I was also taught to use different fundamental planes (although this is something I rarely come across these days), so, if I remember correctly, you could locate celestial bodies using the Horizontal, Equatorial, Ecliptic, Galactic or Supergalactic coordinate system. ",
"So, for example, I believe Herschel's Supergalactic coordinate system has its equator lined up with galaxy clusters, whereas the Galactic plane \nhas its equator lined up with the mass of the Milky Way (or whichever galaxy the coordinates correspond to).",
"As this was at university and has since partially leaked out of my brain, I'm not sure if this is entirely the best answer, or entirely correct, but thought it worth mentioning."
] |
[
"Never knew there was a sort of equator for various galaxies! Awesome stuff to read about, thank you both for your answers!"
] |
[
"With antibiotic resistance becoming more prevalent, what are some possible effective antibacterial alternatives for the future?"
] |
[
false
] | null |
[
"In the body: immunotherapy, vaccination, GMO counter-pathogens.",
"Out of the body: UV sterilization, copper plating, protein denaturing chemicals.",
"I'm sure there are other things coming, but that's just what's off the top of my head."
] |
[
"In my opinion the only way we will ever \"overcome\" resistance in bacteria (or viruses/fungi for that matter) will be using other organisms instead of drugs. My hope is that someday we will be able to use bacteriophages (viruses that specifically target bacteria) for this. Since the virus can evolve as quickly (or faster) than the bacteria they will be able to out-think them and always have an answer to the resistance the bacteria have. The other possibility would be super strength immune cells (genetically modified white blood cells) that could be taken or harvested from people with stronger immune systems, but that would open the possibility of leukemias because it would be very hard to control their growth."
] |
[
"I foresee the future of bacteria fighting beimg in bacteriophages. These are viruses \"programmed\" to attack specific bacteria. The interesting thing about these bacteriophages is that they can leave all the good bacteria untouched. If your interested a quick Google search can give you a plethora of information on bacteriophages."
] |
[
"Is it possible to temporarily shut down the corpus callosum (with an injected local neuroleptic or something) to create a transient split brain state?"
] |
[
false
] |
I'm very interested in the possibility there might be more than one "consciousness" in a brain. Like all questions regarding "consciousness", this is a hard subject to tackle. I'm familiar with the state of research with patients who have undergone corpus callosotomy. In these cases, the non-speaking hemisphere collects experience/data while separated from the speaking one, but can't report it because it never regains speech. So I wonder if a non-surgical, temporary deactivation of the corpus callosum could help us get access to the experience/data of this other hemisphere. But I don't know if partial temporary deactivation of specific regions of the brain is possible, or at what cost. So, is it possible? If possible, how? Has it been done? edit: The selectively deactivates a hemisphere by injecting a barbiturate into an artery that only supplies one hemisphere. Is there an artery that only supplies the corpus callosum?
|
[
"The brain is divided into 2 hemispheres, that are connected by several fiber tracts, the largest of which is called the corpus callosum (CC). In people with certain types of epilepsy, we can surgically disconnect the two hemispheres by cutting/removing the CC (this can help reduce the frequency and severity of their seizures). This produces a state often called \"split-brain\", where there are essentially two brain halves that don't communicate with each other the way they used to (they DO still communicate through other fiber tracts, they are not literally completely separate... also the CC is not usually completely cut/removed). In patients who have had this procedure, we've learned a lot about the brain and how it functions. One of the issues that has been raised but not well studied is whether split-brain patients have two separate \"souls/consciousnesses\" or whatever. My professional opinion having worked closely with these patients and studying the brain is that no, they don't, especially as it's clear that the hemispheres DO still communicate with one another, just not with the same ease as before. ",
"So, OP is asking whether we could recreate this split brain state without doing permanent surgery. My answer is that it would be possible if you used a magnetic coil to send pulses that can temporarily stop a brain area from working the way it's supposed to. However, because of the location of the CC, it would be hard to do without doing brain surgery. OP also suggested the idea of using a technique where we feed a tube up from the femoral artery in the thigh into the brain, and then release a chemical that shuts down one side of the brain at a time. My answer is that it would be too hard to do this because of how many different blood vessels give blood to the CC. ",
"Does that help, or were you just trying to be funny?"
] |
[
"In theory, rTMS could be used to temporarily disrupt callosal activity, but it would be difficult to focus the pulse only on the CC without a craniotomy. As for using the Wada technique, the CC has vascular input from both the anterior and posterior cerebral arteries... it would be essentially impossible to pull off that selective of a catheter feed, as you'd need multiple catheters fed into several different unpredictable branches. It would be incredibly dangerous, and I doubt you'd find a radiologist ballsy enough to do it."
] |
[
"Eh, I figured other people would benefit from it too."
] |
[
"Meteor? Space Junk? Radioactive debris and I'm going to die?"
] |
[
false
] |
So I heard a clunk on my roof and then this landed on the gravel path in front of me. Can't say it was hot but it certainly is like nothing I've seen before. All I really know is its dimensions, and its weight (5 grams). What is this? Oh, and it appears to be ferrous but according to my fridge magnets it's not that strong.. any clues from you guys? Also I should add, I live rurally, between my roof and the sky there is only air.. . also I'm worried about the radiation thing =/
|
[
"You should probably go over ",
"this site",
" before doing anything further. Most people don't find meteorites, but a rare few do."
] |
[
"If your concerned about radioactivity, you could give your local university physics department a call. They should have a Geiger counter around and are likely interested in a potential meteorite. ",
"PS: I know on earth its exceedingly rare to find anything natural with dangerous levels of radiation. In space? I have no clue."
] |
[
"Doesn't look like ",
"this one"
] |
[
"What was the average lifespan of pre-historic man?"
] |
[
false
] |
Or what is a reasonable estimate. How long did early Homo Sapiens live? How often did he die of natural causes, as opposed to surprise mountain lion? I'm doing some research and I realized I'm making some assumptions about the early lifespan of man that I have no basis for.
|
[
"Why are you people guessing? Stop guessing! Provide some sources!",
"First, we need to figure out what you mean by \"pre-historic\". You say early ",
", so I'm assuming you mean paleolithic/neolithic. The term \"prehistoric\" is a big one, and it includes things like pre-contact American Indians. This is also a field with small sample sizes and a lot of variation. I'm also not an expert in early humans, but this might get you started:",
"Caleb Finch (2007:402) argues that by the Upper Paleolithic in Europe - 30,000 Years Before Present (YBP) - people were living significantly longer than the great apes do (15-20 years).",
"A study done on two populations of neolithic skeletons (15,000 - 12,000 YBP and 12,000 - 8,000 YBP) lists life expectancy at birth as about 25, and the adult mean age at death as 32. The ratio between adult mean age at death for females and males was swapped between the two cultures, which is a little odd. In any case, the two had the same mean (Hershkowitz and Gopher 2008:445).",
"There was a Bronze Age (~4000 YBP) site in Thailand where the scientists argue a life expectancy at birth of just around 28 years. The mean adult age at death there was about 36. The authors note that that's at the high end of the prehistoric Japanese societies (~29-35 years) (Pietrusewsky and Douglas 2002:196)",
"References:",
"Finch, Caleb E.",
"2007 ",
". Elsevier, San Diego, CA.",
"Herskowitz, I. and A. Gopher",
"2008 \"Demographic, Biological and Cultural Aspects of the Neolithic Revolution\". In ",
". Jean-Pierre Bocquet-Appel and Ofer Bar-Yosef, editors. Springer, New York, NY.",
"Pietrusewsky, Michael and Michele Toomay Douglas",
"2002 ",
". UPenn Museum of Archaeology, Philadelphia, PA.",
"Edit: Added the Neolithic bit."
] |
[
"That's what the \"mean adult age at death\" means."
] |
[
"\"Mean adult age at death\" means the average age of death for an adult. Life expectancy is usually given at Ex0, which is the mean life expectancy for an infant. In the case of the Neolithic populations, the Ex0 was about 25. The average age at which the adults they studied died was 32.",
"Also, please provide a reputable source for your claim about \"people have always lived about 70-85 years on average\"."
] |
[
"Assuming the human eye has a resolution of 1 arcminute - why did HDTV ever take off?"
] |
[
false
] |
[deleted]
|
[
"I usually point out the chart that willbir mentioned.",
"I think your constraints are atypical, and maybe that's why you don't understand. If you can't do anything to decrease the 3m viewing distance, and if you simply don't have room for a bigger television, then all you can do is find your place on that chart and pick the best resolution. At 9m and 82cm, you have no reason to upgrade.",
"But do realize that ",
", it ",
" make sense to upgrade. You seem stuck on the idea that the important thing is avoiding pixelation... If you can see pixels (for a set distance and screen size), it definitely means you need a higher resolution. But you seem to be forgetting the fact that more pixels means more detail.",
"Let's imagine that you ",
" have room for a bigger television. If we increase your screen's diagonal size from 82cm to 102cm (32\" to 40\"), suddenly you are in the green region on the chart. This ",
" mean that you need 720p resolution to avoid pixelation. But it also means that ",
"! All of a sudden, you will be able to see things on your television that you literally couldn't see before (both on the 32\" SDTV or for a 40\" SDTV). ",
"Consider the sizes you listed. I didn't check the math, but we'll assume it's right.",
"SDTV, 720 pixels wide: 72cm",
"HD 720p, 1280 pixels wide: 127cm",
"HD 1080p, 1920 pixels wide: 191cm",
"HD 4k, 3840 pixels wide: 335cm",
"You have calculated the maximum screen size for each resolution (at a 3m distance) beyond which pixelation is visible. So, for a 3m distance, these are the optimal screen sizes. But that doesn't mean a 72cm SDTV will give you the same results as a 127cm 720p TV. The 720p television offers 2.7x as much detail, the 1080p offers 6x as much detail, and 4k offers 24x as much detail, compared to SDTV. Higher resolution doesn't just offer a bigger screen without pixelation- it enables your television to show details that you wouldn't be able to make out otherwise. By making your screen bigger (for a set distance) you're able to fit more things on it with higher resolutions. By sitting closer (for a set screen size) you're able to see more things on it with higher resolutions."
] |
[
"I fail to see how this implies no real world benefit. I mean i've never seen anyone have their tv more than 10-12 feet away from whatever furniture they use to sit and watch tv, so according to this chart even 1440p would be a distinguishable improvement from lower res, let alone 1080p. And given the same screen size the different resolution are distinguishable as well, even if the differences arent drastic for small screen sizes. "
] |
[
"No, you've got it exactly right. It's why the entry-level 4K TVs that are only 140cm (55 inches) are only really useful as computer monitors, since you have to sit so close to them to benefit over a traditional 1080p display.",
"Just one clarification -- the sizes that you give are the actually at the top of the useful ranges, not the bottom. This means that a TV of 192cm would still benefit from being higher than 1080p resolution (since 1080p gets its maximum benefit at 191cm), just you wouldn't get the full benefit of 4K until you reach 335cm, going by the numbers you calculated. So a 4K TV of, say, 200cm would still look better than a 1080p TV of the same size."
] |
[
"What is the mechanism of Uncanny Valley?"
] |
[
false
] |
Have people before the advent of AI experienced this phenomenon? Are we likely to feel this way about our closest relatives-apes?
|
[
"Have people before the advent of AI experienced the Uncanny Valley? Absolutely. The Uncanny Valley isn't new by any means.",
"To elaborate, what we refer to as the Uncanny Valley is something like a scale of \"realism.\" Most often, in the sense of how human-like something is. It can be more broadly applied, but this is the easiest sense to explain.",
"A ragdoll or a cartoon person are both ",
" of humans, but they're so far off from what a real person looks like that there's no real concern. More elaborate dolls, mannequins, and clowns are all on the edge of the Uncanny Valley, which is part of the reason they're all such common fears. A human corpse, on the other hand, is smack dab in the middle.",
"Generally, the Uncanny Valley is seen as the manifestation of the instinct to avoid corpses and the very ill, but in a more modern sense, you could say that it's an aversion to things that are \"close, but ",
"\""
] |
[
"Ah, “close but wrong” is exactly what describes my sentiments. Thanks for this phrase!"
] |
[
"Here's an article that digs into it:\n",
"https://www.jneurosci.org/content/jneuro/39/33/6555.full.pdf"
] |
[
"In the way that gravity is based on mass, and electromagnetism is based on charge, are there analogous properties for the weak/strong nuclear forces?"
] |
[
false
] |
Gravity and electromagnetism seem quite similar in that they are forces based on the mass and charge, respectively, of the objects involved. Do the strong and weak nuclear forces have similar properties that the interactions are based around?
|
[
"The strong force property is ",
"color charge",
", of which there there are 3 types and three anti-types.",
"For the weak interaction there is ",
"weak isospin",
" and ",
"weak hypercharge",
", but these act a lot less straight forward, and also depend in part on the electric charge (or the electric charge depends partly on them)."
] |
[
"I recently had to teach basic particle physics in a high school setting. Is there a simple explanation for color charge? I've read the wiki and I still don't understand:"
] |
[
"Yes, and the rule that all free particles must be colorless “explains” why we see baryons (bound states of 3 quarks) and mesons (bound states of quark anti-quark pairs), but we don’t see individual free quarks, or bound states of 4 quarks, for example. ",
"Gluons, which are the bosons that mediate the strong force, are even more complex. The carry a color charge and an anti-color charge."
] |
[
"How to determine the age of a person medically? eg: to validate a guinness record for oldest person in the world as the written records can be forged"
] |
[
false
] | null |
[
"How to determine the age of a person medically?",
"You can't. Guiness goes by written records. People have been excluded from the book when they didn't have records. You print up your own birth certificate, but you can't print one up that's 120 years old and was registered by a government agency 120 years ago."
] |
[
"Not sure if this is a procedure that can be done while the person is alive under medical grounds (I guess you can take a tooth from them?) but I think an accurate way is to radiocarbon date teeth. It's been done to archeological remains to estimate the age of the deceased individual. The principle relies on the carbon-14 that is present in an individual's teeth enamel. Since enamel doesn't turn over, the carbon-14 found in the enamel reflects the levels in the atmosphere found during the time it was formed (ie. a person's birth year).",
"Here are some articles that explain the technical parts better than I can (might need a university log in for access):",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2957015/",
"https://www.sciencedirect.com/science/article/abs/pii/S1752928X18305183"
] |
[
"The NCBI article is claiming +/- 1.5 years for bomb radiation dating in your teeth as long as you’re born post mid-1940’s, 10 years for other carbon dating methods."
] |
[
"So human babies are woefully underdeveloped at birth compared to other mammals. How would, theoretically, a much longer pregnancy affect human development?"
] |
[
false
] |
So our pelvis is now made for walking on two legs and our craniums are large, explaining this is necessary. However, would this be possible, and what would the implications be? Would a longer pregnancy have any positive effects whatsoever? What would be the effect of the deprivation of sensory input? Any other implications? Would things such as in utero sound stimuli have a greater effect after, say, 12 months or longer?
|
[
"I think the premise of the question kind of implies that things like this would be adjusted as well."
] |
[
"Well ignore my panelist bar here, but baby horses can walk in a few seconds after birth; many animals can do at least something when born. But its true that its highly dependent on the niche the occupy. ",
"However, my Documentary-based knowledge is that we have underdeveloped babies on birth because our head sizes are too big after this stage of growth to pass easily through the pelvis. We are already in the borderline and thats why childbirths in humans require assistance to at least some extent while almost no other animal needs so. We only survived this onslaught on our program because we actually had already evolved the intelligence to help out each other without instinct.."
] |
[
"Because it says ",
" and human babies can't climb right? Judging by the upvotes that's been a convincing thought, but sperm can swim. Are they more developed than human babies who can't? Of course it's a contradiction to even ask whether sperm are \"more developed\" than what they develop into, obviously they're not.",
"Look a little closer at hullabazhu's example:",
"Human babies:",
"born with open eyes, immediately begins to learn about the world around it",
"born with fully formed limbs, hands, feet, fingers, and toes. Weak muscles but it's all there.",
"fine body hair and a full head of thicker hair",
"born with basic ability to communicate with it's family",
"at birth can be more than ",
" of mother's height",
"at birth weighs more than 5% of the mother's adult weight",
"Kangaroo baby:",
"completely blind at birth",
"hind legs are undeveloped stumps",
"hairless",
"at birth is only 1% of the mother's height",
"at birth weighs ",
" of the mother's weight (less than a gram!)",
"Bears and other mammals have \"woefully underdeveloped\" babies compared to humans too so the exact wording of the original question is a little inaccurate, but it's an interesting question all the same."
] |
[
"In regards to sunscreen and its effectiveness over time. How is it \"used up\"?"
] |
[
false
] |
They say that you need to reapply sunscreen every two hours but is that duration dependent on how much the sun's photons reacts with the sunscreen on your skin or is it simply that the sunscreen loses its effectiveness the longer it is on your skin?
|
[
"Humans sweat and rub their skin. Over time the sun screen is either absorbed or rubs off.",
"Aside from that, it doesn’t fully block UV light; only enough so that the skin can repair any damage inflicted. Over time, the damage due to exposure increases past the point your skin can safely handle."
] |
[
"What do you mean by absorbed?"
] |
[
"See what I'm wondering is if we put the sweating and rubbing off aside, would we have to reapply?"
] |
[
"Does a saline IV dilute hormones your body produces during childbirth?"
] |
[
false
] |
I've been reading through the Bradley Method of childbirth with my wife and, while the exercises and relaxation techniques are great, there seems to be some bad pseudo-science in the final chapters. The BM (heh) says 2 things about IVs drips. One is the above, that a saline/glucose IV dilutes hormones your body naturally produces to combat the pain and stress of childbirth, thus making it more difficult. The second is that a lower glucose level is actually beneficial to the baby during childbirth, letting it handle the stress of being in the birth canal better. Is there any truth to this?
|
[
"It would take a pretty significant amount of fluid to appreciably dilute hormones in the bloodstream. I don't have much experience with routine delivery of babies in the hospital setting, but I can't imagine that women in labor are generally given huge fluid boluses (especially since one of the primary pregnancy complications (eclampsia) is associated with high blood pressure).",
"According to various sources around the internet, an average woman, at full term in her pregnancy, has ~10 liters of blood. A few hundred cc's (which is a generous amount if it's just being used to deliver medication) isn't gonna make a big dent in that.",
"As far as the second point goes, it sounds equally suspect to me, but I don't know enough about the topic to say so definitively."
] |
[
"Here's ",
" study that seems to indicate that more fluids (250mL/hr vs 125mL/hr) led to 'easier' deliveries:",
"http://journals.lww.com/obgynsurvey/Abstract/2006/10000/Increased_Intravenous_Fluid_Intake_and_the_Course.5.aspx"
] |
[
"As mentioned, no fathomable amount if an IV drip will dilute your blood that much.\nBut the second part of your question is slightly correct. Estrogen causes the uterus to release glucose, which is the fermented by Lactobacillus bacteria naturally found in the uterus. This fermentation process is does decrease the pH of the uterus. Now I am not a doctor, only a microbiologist. But I believe the baby is covered in a protecting layer that would neutralize this acidity."
] |
[
"Why do I dream more vividly when stressed?"
] |
[
false
] | null |
[
"Are you sleeping the same number of hours? Are you waking more often during the night?",
"I ask this because many people have a lot of dreams that they simply don't remember, unless they awoke during the dream."
] |
[
"I am sleeping the same number of hours. I don't think I am waking up more during the night, but the sleep is less restful. Perhaps I am waking up during the night but not remembering it in the morning. "
] |
[
"Are they just regular dreams or are they nightmares?"
] |
[
"Are humans unique in their ability to consciously act against their best interests?"
] |
[
false
] |
In other words, I've never seen an animal knowingly commit suicide or eat something poisonous, or engage in hazardous acts with the intent to harm themselves. Sure animals get themselves trapped or hit by cars, but is there any case of an animal intentionally harming itself for the sake of harming itself? EDIT: The question whether animals are aware of the out come and not just acting irrationally. Example: A man walks across the street blindfolded and gets hit by a truck. He may have been acting recklessly, which lead to his death, but his intent wasn't necessarily suicide.
|
[
"I can't say for sure, since that falls outside my realm of experience (evolutionary dynamics) and starts to become a question for an animal behaviour specialist.",
"I suspect not though. Given the challenges we are having defining what consciousness and free will are in humans, I doubt anyone has done even minimal research in animals. At a certain level you would expect an animal to be aware of it's actions, and certainly in some cases of altruism (such as the adoption of orphans in primates species) you could hypothesise that the atriusts make a reasoned decision. as the species become more primitive it becomes harder to say though.",
"You could probably study it using examples of altruism where the altruistic behaviour was not exhibited 100% of the time (and these do exist, I just can't remember which species they are in right now, sorry). Where you have individuals who may or may not make an altruistic action when the situation calls for it you have the implication of a cost-benefit analysis being made; or it could be completely random. Past a point you are trying to work out the emotional motives of cats and dogs, and that's not the world's biggest field of research."
] |
[
"No, we're not, and understanding the evolutionary significance and implications of this type of behaviour (",
"altruism",
") is a major field of current research in evolutionary theory.",
"The classic example are prairie dogs, when the group is out of the warren if an individual spots a predator it will make noises to warn the others, lowering the chances of it's own survival but increasing the survival odds for the rest of the group. In this sense it is definitely acting against it's own best interest.",
"If you are interested in reading further, you could look at the wikipedia pages on ",
"altruism in animals",
" and ",
"kin selection",
" No, other animals do this too."
] |
[
"Intresting. I'm browsing from my phone now, so I think I'll wait to take a look. Thanks for the info!"
] |
[
"What would happen to a dead body if it was just dumped in space?"
] |
[
false
] | null |
[
"It depends on where it was dumped, ie close to the sun it would be damaged more than out around Pluto. It would definitely dry out though. Some of the liquid would freeze initially as the air pressure dropped. Some water would evaporate away. Anywhere inside the orbit of Earth (roughly) the body would dry out entirely, eventually."
] |
[
"Provided that it doesn't collide with an object and/or go spinning into someone's atmosphere first."
] |
[
"What happens to a human body in vacuum//How determines the temperature of objects in space?"
] |
[
"What are the differences between waves?"
] |
[
false
] |
[deleted]
|
[
"Light waves and microwaves are the same, just at different wavelengths. They are both examples of electromagnetic waves.",
"Sound waves are just the motions of compressed air. A vibrating object will cause the air around it to compress and then decompress as it moves towards the air and then away.",
"We call things \"waves\" if they obay the mathematical \"wave equation\" which you can google. It is a partial differential equation that relates how quickly things are changing in space are connected to how quickly things are changing in time.",
"It turns out the intensity of light and how light moves follows the same rules as the volume of sound and how sound moves. Just with a different underlying thing changing (air pressure or strength of electric fields) and different speeds. But the math for both work the same so we call them both waves."
] |
[
"First I just want to say, they are ",
" parabolas. They are sin (or cos) functions. Which do look like parabolas near the top or bottom of a wave but not quite the same.",
"The rate of change of a wave, is governed by that waves frequency or wavelength (they are linked, high frequency means shorter wavelength.)",
"Different colors of light are due to how quickly the light is changing.",
"Different pitches of sound are due to how quickly the pressure wave is changing.",
"We can only hear sounds if they are changing somewhere between 20 times per second up to 20,000 times per second. Each different frequency is a different pitch.",
"For light we can only see it if it is between 430,000,000,000,000 times per second to 770,000,000,000,000 times. Each different one is a different color."
] |
[
"First I just want to say, they are ",
" parabolas. They are sin (or cos) functions. Which do look like parabolas near the top or bottom of a wave but not quite the same.",
"The rate of change of a wave, is governed by that waves frequency or wavelength (they are linked, high frequency means shorter wavelength.)",
"Different colors of light are due to how quickly the light is changing.",
"Different pitches of sound are due to how quickly the pressure wave is changing.",
"We can only hear sounds if they are changing somewhere between 20 times per second up to 20,000 times per second. Each different frequency is a different pitch.",
"For light we can only see it if it is between 430,000,000,000,000 times per second to 770,000,000,000,000 times. Each different one is a different color."
] |
[
"Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"The body would be subject to the same laws of physics as anything else. Assuming an airtight seal, it would experience minor degradation as it would allow microorganisms present to decompose it for a time before death. A non-airtight seal allows particles to escape, and assuming all microorganisms present die, the body would remain in a preserved state. There would be nothing left to continue the process of decomposition. ",
"Biggest obstacle for leaving the solar system is time. We have the technology to travel across space. We just won't get anywhere in the same lifetime. This is why most science fiction solves this problem with warp drives to teleport across vast distances, cryostasis to wait it out, or use generational ships (where the crew's grandchildren are the ones who arrive at the destination). We currently do not have viable versions of those sci-fi solutions. So the biggest obstacle is overcoming the long trip duration."
] |
[
"No, those are all obstacles we've already overcome with space probes. Biggest obstacle is just time.",
"Also I didn't realize your question was about sending a dead body out of the solar system lol",
"We've sent probes outside of the solar system already. Wouldn't be hard to send an inert coffin the same way."
] |
[
"The mathematical solutions are points, but the practically useful regions are huge. JWST and Gaia orbit the Earth/Sun L2 point at distances of a few hundred thousand kilometers. Compare this to the 1.5 million kilometers between Earth and L2."
] |
[
"As someone gets more obese, do their actual skin cells stretch or do they replicate fast enough to keep up with the increasing surface area?"
] |
[
false
] |
A follow up question would be: If the cells stretch more than they replicate, does this mean that there is a lower concentration of nerve endings? Would stretched skin around large fat deposits be less sensitive to touch?
|
[
"Their skin cells divide to increase surface area. Individual cells have limited elasticity and if they simply stretched to cover the increased fat tissue underneath, it would be like blowing up a balloon (e.g. getting thinner). In fact, more than just the skin cells help cover the area. Blood vessels, connective tissue, the fat cells themselves all have to accommodate the increased tissue volume. As a corollary, when someone has massive weight loss, you can see the large amount of loose and excess skin. The signals from the body to make the skin cells divide to cover the larger area can't just reverse instantaneously (you also have issues with looser connective tissue, loss of elasticity of various components, etc.) so now you have large folds of skin hanging around. ",
"EDIT: Forgot to respond to your follow-up. You can have issues with less touch sensitivity but it's hard to say that it's just because of less nerve endings (your nerves can make new connections so you still have touch sensations). More often, losing feeling in really any part of your body (bodybuilders with massive skeletal muscles, areas of fat deposits) is a combination of factors like poor blood flow to the cells rather than just not enough nerve endings."
] |
[
"To add to this, they can only replicate so fast, so if you gain weight (fat cells, which grow more quickly) faster than your skin can keep up, you’ll get stretch marks, which are permanent weakenings in the connective tissue layer below the thin outer skin layer. ",
"Edit: I’d like to clarify that stretch marks are a normal process that almost everyone goes through, whether during puberty or muscle growth or even losing weight. Your cells do not all replicate at the same rate, so there is bound to be some mismatch between tissue types. Everyone’s got stretch marks, don’t worry about yours!"
] |
[
"You'd be amazed at what the human body can adapt to. There was once a guy in Scotland I want to say, he got his car stuck in the snow in some remote area, and was stranded. He basically hibernated in his car and lived for like a month without food just eating snow to stay barely hydrated.",
"Edit: ",
"Here's the story",
" after all."
] |
[
"Ketchup as a non-Newtonian Fluid ?"
] |
[
false
] |
How has it been proven that ketcup is a non-Newtonian fluid, and how does it rank against other fluids? Wherever i look about this they mention the ketchup effect, however that is an analogy and that in itself is not proof (analogy's can be missleading in that way). I was reasoning that if ketchup is a non-Newtonian fluid shouldent the bottle be drained of ketchup once it getts going, and not stopp as it actually does whit only a small amount coming out off the bottle compared to whats in the bottle. But then that assumes that the ketchup is uniform with no internal defects like airbubbles and such, it also assumes that there are no degrees of non-Newtonian fluids, that all non-Newtonian fluids are perfect fluids. So to repeat my question, how has it been scientific proven that ketchup is a non-Newtonian fluid, and is there a list where fluids are ranked from Newtonian fluids to non-Newtonian fluids and where does ketchup rank in such a list. Maybe ketchup is a non-Newtonian fluid but behaves closer to water then for example a polymerbased fluid. Thank You
|
[
"According to ",
"Viscosity functions data\nshowed that all ketchups under examination were non-Newtonian\nfluids, since the values for flow behaviour\nindices, n, were below 1, which was indicative of the\npseudoplastic (shear thinning) nature of tomato ketchups\n(Singh Gujral et al., 2002; Sahin & Ozdemir, 2004;\nBayoda et al., 2008).",
"pdf"
] |
[
"I think there is a misunderstanding going on here as to what a Newtonian fluid actually is. A Newtonian fluid is simply any fluid that obeys Newton's law of viscosity. Simply put Newton's law of viscosity is that there is a proportional response between applied (shear) stress and the velocity profile of the fluid. You simply put the fluid between two plates and move the top plate with a constant shear stress. You can then examine the velocity profile within the fluid. You can do this at a number of different shear rates and compare it to the following chart to determine what type of fluid it is.\n",
"http://www.msubbu.in/ln/fm/Unit-I/Rheology.gif",
"The chart shows what the relationship between shear stress (y axis) and the velocity gradient (x axis) is for varying fluids.",
"There are loads of non-Newtonian fluids. Ketchup and mayonnaise are often used as examples of bingham fluids. Note how they refuse to flow at 0 shear stress and instead require some initial shear to get going. This is why they are slow to pour out of a bottle for example and sometimes you've got to whack it to get them going. ",
"Note that there is a lot more to rheology than this, especially when you start to consider polymers, polymer melts, composites etc. Let me know if you want to know about anything else or need clarification."
] |
[
"Because fluid dynamics are complicated. There is a lot to learn when dealing with the relatively simple Newtonian fluids. Frankly, not many physicists ever even specifically learn much about non-Newtonian fluids in a classroom because it's just not really a core component that most physicists need to know a lot about. ",
"It makes sense to break it down into Newtonian fluids, which behave nicely and as you would normally expect, and non-Newtonian fluids which behave oddly in some way or another (and which tend to be more complex in their behavior and in the physics that describe it)."
] |
[
"Are there any bacteria or viruses which are resistant/immune to antibodies?"
] |
[
false
] |
I am aware that it is possible for bacteria to become resistant to antibiotics and for some viruses to gain resistance to anti-viral meds. But is it also possible for them to become resistant to antibodies produced by the immune system?
|
[
"Yes, and it's much more interesting than the obvious antigenic drift that we see with influenza viruses (and probably coronaviruses as well).",
"As background ",
" has an arsenal of ways to avoid the immune system; every virus today is the outcome of millions of generations of viruses that successfully avoided immunity long enough to replicate and transmit to new hosts. Different viruses use different types of immune evasion, but generalizing wildly, the smaller RNA viruses tend to target inflammation and innate immunity, and also might undergo antigenic drift; the larger DNA viruses, which are more mutationally stable and have more spare room in their genome, target both innate immunity (inflammation) and adaptive immunity (T and B cells).",
"\"Larger DNA viruses* of vertebrates includes ,mainly herpesviruses, poxviruses, and adenoviruses, and indeed some herpes- and poxviruses do include genes that actively target antibodies. For example:",
"Many herpesviruses encode immune evasion molecules that interfere with activities mediated by antibody and complement, suggesting the importance of antibody and complement in host defense against herpes infections. ... Herpesviruses encode glycoproteins that bind the Fc domain of IgG, referred to as viral IgG Fc receptors (vFcγR). Table 63.1 lists the human herpesviruses that encode vFcγRs and the genes involved. Non-human herpesviruses, pseudorabies virus (PRV) and murine cytomegalovirus (MCMV), also express vFcγRs, suggesting that vFcγRs fulfill important roles in pathogenesis. FcγRs are detected on many micro-organisms, including staphylococci (protein A), streptococci (protein G), schistosomes, trypanosomes, hepatitis C virus (core protein), and coronaviruses (S peplomer protein). ",
"--",
"Subversion of innate and adaptive immunity: immune evasion from antibody and complement",
"(I believe the mention of coronaviruses here might be a red herring; I am not aware of any work showing that there's any functional effect of this form of antibody evasion in coronaviruses, and especially not in SARS-CoV or SARS-CoV-2.)",
"Poxviruses tend to target complement rather than antibodies -- complement is a set of proteins that respond to antibodies to destroy pathogens and pathogen-infected cells, and poxviruses often have a panel of complement-binding proteins:",
"Large DNA viruses defend against hostile assault executed by the host immune system by producing an array of gene products that systematically sabotage key components of the inflammatory response. Poxviruses target many of the primary mediators of innate immunity including interferons, tumor necrosis factors, interleukins, complement, and chemokines. ",
"--",
"Poxviruses and Immune Evasion",
"It's worth pointing out that none of these immune evasion effects seems to be spectacularly effective; herpesviruses, poxviruses, and adenoviruses are all effectively controlled by antibodies and by T cells. The viruses are looking for a bit of a boost, not an overwhelming advantage."
] |
[
"Yes, it happens all the time. Antibodies bind specific locations on pathogens, if the pathogen slightly alters those locations the antibodies don’t bind as well. Now irl your body produces many antibodies against many epitopes (specific locations) on pathogens so they are still recognized, just not as well.",
"Edit: For example, the Omicron COVID variant has mutations to spike protein which reduce the binding of antibodies. The antibodies still work, just not as well as they did on previous variants."
] |
[
"But is it also possible for them to become resistant to antibodies produced by the immune system?",
"You can go further, there are viruses that go beyond and actively use the antibodies your body produces to attack you further. It's called antibody dependant enhancement, or ADE. Dengue fever is one such example. There are 4 main strains of it. The first infection is milder, your body learns to fight it and creates antibodies against that strain. And your body will produce those same antobodies for subsequent infections, the other strains included. The problem is that they the antibodies for one strain aren't neutralizing for the others, they just hook on and actually help the virus enter and infect your cells. And so when you get the other 3 strains it will be far nastier. A large dengue vaccine trial ran into this problem late in phase III of their trial, it was beginning to cause ADE in a subset of children. Similar issues in cats and coronoviruses."
] |
[
"What evidence lead to the comination of two of the universal forces, electromagnetism and weak force?"
] |
[
false
] |
From the previous force weak, electromagnetic, gravitational, and strong( now known as colorful force?)
|
[
"What evidence lead to the comination of two of the universal forces, electromagnetism and weak force?",
"Perhaps most primarily, the nonzero mass of the W and Z bosons.",
"After quantum electrodynamics proved to be a very successful theory, the same framework (quantum gauge field theory) was used to model the weak force. It was clear from this model that there needed to be two W bosons and also a Z boson. Meanwhile, it was clear from experiments with the weak force that the force was very, very short-ranged.",
"In the mathematical framework, the W and Z could only be massless. However, that would lead to a force with infinite range; the only way to have a limited range would be for these particles to have a very high mass. The question remained as to how masses could be given within the frameworks we were using, or how to modify the frameworks to incorporate masses.",
"The question was more or less resolved with the proposal of the ",
"Higgs mechanism",
", which can give the W and Z bosons masses, but only if there also exists an additional scalar field with certain very unique properties -- the Higgs field. The particle corresponding to this field, the Higgs boson, would need to be even more massive than the W and Z.",
"When it became possible to perform experiments that could detect the W and Z, we went looking, and sure enough, we found them right around the expected masses. This more or less confirmed the accuracy of the theory, but we would have to wait another 30 years before we could build colliders that could detect the Higgs boson. For most of that time period, it was accepted that some form of the Higgs mechanism was realized in nature, but the exact details were not accessible to us. There were proposals for other possibilities that resembled the Higgs mechanism in spirit but did not necessarily require the Higgs field as it was originally proposed.",
"As you probably already know, recently the LHC collected very strong evidence for the existence of a particle that almost ",
" matches the predicted properties of the Higgs boson. The closeness of the match is uncanny; as I understand it, ",
" evidence is consistent with the predictions, to the point where we can now say that the discovered particle is at least ",
" Higgs boson, if not quite ",
" Higgs boson. Research is ongoing as to whether or not there is actually any difference from prediction at all.",
"The fact that there appears to be no differences yet has many scientists disappointed -- if there were differences, we would have some clues as to how to further improve our models of nature. But if it turns out there are no differences at all, then we have fewer clues to guide us in modelling parts of nature that aren't explained by the standard model of physics.",
"Hope that helps!"
] |
[
"I have no quarrel with you",
"Sure -- sorry, I don't mean to start an argument, I'm just disagreeing. :)",
"I think that your original post is informative about the Higgs mechanism, but that it does not elucidate why people were interested in unifying the electromagnetic and the weak forces. And it's not that the weak force is short-ranged, but that, despite it being short-ranged, it had similar properties as the electromagnetic gauge field.",
"Okay, I understand your point, it just seems like only the first part of the story, and having similar properties to electromagnetism alone does not seem particularly key to unification, to me. It seems like a starting point, not a critical point.",
"At first, there wasn't much interest in ",
" the forces, rather there was interest in modelling the weak force using the same frameworks that were used to model the electromagnetic force, because of the successes of electromagnetic models.",
"In trying to build such models for the weak force, it became clear that unification of the two forces would be necessary, but it was not clear exactly ",
" to go about doing that correctly, ",
" the framework could not incorporate masses for the weak bosons even with naive attempts at unification. The naive attempts to unify failed to give an accurate description of the weak force.",
"The OP asked what ",
" led to the successful unification. The Higgs mechanism was ",
" most major development that allowed unification to be done successfully, and the main need for the mechanism came from the significant mass of the weak bosons, which is why I focused on that in my answer. The fact that trying to model the weak force using the same framework implied a need for unification seems to me to be more of a useful coincidence and not so much \"evidence\" that drove us toward the ultimate successful unification.",
"I guess we're just looking at it from two different perspectives."
] |
[
"Hey, thanks for the post"
] |
[
"Is it possible for particles to briefly or temporarily exceed lightspeed?"
] |
[
false
] |
1) I heard from a professor or TA once that particles have some nonzero probability of exceeding lightspeed, and that that probability decays very quickly outside of the particle's lightcone. Is this true? Is this possible? How does it work? 2) Second question. Suppose an electron is flying along, and then somewhere up ahead of it, the quantum foam coughs up an identical electron and its anti-electron partner. The anti-electron travels backward and annhilates the original electron, while the new electron travels forward. Is the new electron indistinguishable from the original electron? And if so, is this a mechanism for exceeding lightspeed randomly? Thanks!
|
[
"(I have to say I think it's funny that nobody seems to have identified yet what the questioner is talking about, even though ",
" do, and I'm in a branch of physics that makes almost no use of QFT whatsoever)",
"I'm pretty sure what your teacher in 1) is talking about is the Feynman propagator, which indeed is nonzero but with exponential decay outside the light-cone. This might seem like it violates causality, but it doesn't because the commutator is zero there. The ",
"wiki article",
" on propagators explains it pretty well.",
"2) This question hinges on the controversial assumption that virtual particles actually exist, rather than just being a way of looking at the mathematics of perturbation theory. And however you stand on that, I think you might be putting the cart ahead of the horse here. You want to calculate the amplitude for an electron at A ending up at B, and the way you do that in perturbation theory is to sum over the contributing ",
" states, one of which is the creation-annihilation process you describe. ",
"This doesn't violate causality. And the 'virtual' intermediate state which contributes cannot be observed. (for which reason it's dubious whether it should be considered a description of any real process) If it ",
" real and detectable, then ",
" would violate special relativity though, since virtual particles are off-shell."
] |
[
"Mathematically they are allowed to exceed the speed of light, but the physical implications are damning."
] |
[
"I am sorry, RRC, but this is the correct answer to question 1. Peskin and Schroeder chapter 2, discussions on the causality of the Feynman propagator. ",
"Edit: some of the text of the chapter, which contains an important nuance:",
"\"So again we find that outside the light-cone, the propagation amplitude is exponentially vanishing but nonzero.",
"To really discuss causality, however, we should ask not whether particles can propagate over spacelike intervals, but whether a ",
" performed at one point can affect a measurement at another point whose sparation from the first is spacelike.\"",
"Peskin goes on to show that it does not."
] |
[
"What effect does the seawater brought inland by a tsunami have on local plants? Does it make the land infertile for a while?"
] |
[
false
] | null |
[
"In Holland we don’t have tsunami’s, but the results of salt water floods have been studied pretty well. For instance, after the 1953 north sea flood.",
"For the Dutch soil, all salt from flooding is washed away within 1-4 years. This depends on sveral factors, such as duration of flood, dept of the groundwater level, amount of moisture in de ground above groundwater level, precipitation etc",
"For some recovery nature needs some help. The (NaCl) salt water also worsens the mineral structure of older clay. Even if the salt itself is already washed away. Naturally the clay could take up to 8 years to recover. Fertilizing with gypsum is enough to repair this and this pays for itself in the first year.",
"A sweet water flood costs 1 year of production, a salt water flood generally 2-3 years.With gypsum that 3 years can be reduced to 2 years of loss. The second year some salt-resistant crops can be grown, so the economic damage could be a bit less. In fact, for weaker fields the silt from the inundation increases fertility in the long term."
] |
[
"It seems likely that tsunamis impact local plants / soil through the addition of clay and silt with a high salt content. Land is inundated by a tsunami for a relatively short period of time and the salt is usually washed away by precipitation anyway meaning that the saturation of soil by saltwater is not the leading cause of salt contamination. ",
"While it is true that salt impacts plants through salt (",
") toxicity, water stress and a reduced nutrient uptake (especially of ",
"), the main problem when it comes to tsunamis is the introduction of clay and silt from the seabed which has a high salt content. Salt in the soil is best washed away by fresh water, but because this clay / silt layer is relatively impermeable, the filtration process, called ",
", is slow. The duration of salt contamination will depend on the level of drainage and precipitation rates for that particular area so difficult to generalise."
] |
[
"Evaporation in the Netherlands is probably not a big issue (We’re further north than Newfoundland).",
"But in Holland much of our land is below sealevel, so if a flood happens the land is inundated for weeks before it is pumped away. ",
"However, we’re basically living in a swamp, so all the ground is already very wet. It’s hard to say what the impact is from a much much briefer salt water inundation in a very dry and porous area."
] |
[
"How does a computer determine if a given number is larger than another number?"
] |
[
false
] | null |
[
"Typically, a computer will represent binary numbers in a slightly more complicated way than you may have been taught in school.",
"Positive binary numbers are simple enough. They work like regular numbers, except you only use ones and zeros, i.e. counting up from zero is 0 -> 1 -> 10 -> 11 -> 100 -> 101 etc.",
"Negative numbers are represented a little differently though. Basically minus one is \"11111\", with as many ones as the size of the register. That means that an 8 bit storage will represent negative one as 11111111 while a 4 bit storage will represent it as 1111. Negative two is 1110, three is 1101 and so on. It sort of \"counts down\" (this standard of binary negative numbers is called Two's Complement numbers, and is the most common because of their versatility).",
"This means that you can also tell if a number is negative simply by looking at the first binary digit (bit). If the first bit is 1, it is negative.",
"This is useful for many reasons. First of all, you can add negative numbers to other numbers correctly. If you add three to negative one with four bit registers, that is, 0011 + 1111, for example, you get 10010. As a computer does not add more bits if the number is bigger, you get something called an \"overflow\", and the computer basically ignores the extra bit at the end, so the answer is still 4 bits. The answer the computer comes up with is, in other words, 0010, which is two. The computer added negative one to three correctly!",
"You can also subtract easily. Simply by inverting the number you want to subtract and adding one you can add it and get your answer. Let's try to subtract positive 1 from 3. Three is 0011, and one is 0001.",
"Inverting one means you switch all bits to the opposite, so 0001 becomes 1110. You then add 1 and get 1111 (which you may remember is -1, inverting a binary number and adding one is always the same as multiplying it by -1). You can then add this to 0011 and get 0010 once you get rid of the overflow. It worked!",
"So what does this have to do with size comparison?",
"Well, a computer can easily subtract one binary number from another, and that number will be either positive, zero, or negative. Positive binary numbers and zero always have their first digit as 0, and negative numbers always start with 1, as I've already explained. This means that the computer can subtract one number from the other and immediately look at one single bit (called the sign bit, always the first/most significant one in the memory register) and tell wether this number is zero or greater, or less than zero."
] |
[
"Here is an example of how 2 numbers in binary can be added with the use of logic gates: ",
"https://cdn.instructables.com/FP1/ZI2I/GHX77248/FP1ZI2IGHX77248.LARGE.jpg",
"there you have one number (A) that can be 1 or 0, and another number (B) that can be 1 or 0, and the sum can be 00=0, or 01=1, or 10=2.",
"The 0 or 1 can represent low current/high current in the wire.",
"And the logic gates work this way: ",
"https://www.youtube.com/watch?v=7ukDKVHnac4",
"You could also make a mecánica \"transistor\"/logic gate: ",
"https://twitter.com/page_eco/status/1188749430020698112",
" ",
"From them you can have two numbers 00101001, 10010111, and subtract them or whatever to get another number, or find which number has the first non zero digit, etc. All with lógica gates (AND, OR, NOT)."
] |
[
"Unless you want to vary the clock cycle speed depending on the instruction",
"This is exactly what I'm doing - there is no global clock signal. This is how most redstone computers work, because the game itself provides a predictable clock in the form of every component having a known delay. Redstone is essentially just a beefed up cellular automaton like conway's game of life or powdertoy.",
"So in my case, different instructions take different amounts of time to execute. ",
"noop",
" takes 0.4 seconds to read, decode, and execute, while an instruction like ",
"add",
" takes 0.7 seconds to read, decode, and execute.",
"One thing that's important to my decision is that I'm using a mod that lets you condense a bunch of combinational logic into a single block that takes a flat 1/10th of a second to update, no matter how many gates are used. So my ripple-carry adder is already extremely fast, since it fits into two ICs (one handling the MSBs and one handling the LSBs, with a carry signal going from one to the other) it can return a valid result within 2/10ths of a second.",
"So my worry with going through all the effort to make a comparator is that it won't actually fit within two ICs, so it very well could end up being slower. Making a dedicated comparator seems like a task more suited to real world silicon (or completely vanilla unmodded Minecraft redstone), where circuit depth—the actual number of transistors as well as wire length a signal has to propagate through—is the real performance concern."
] |
[
"AskScience: What are you best science brain teasers?"
] |
[
false
] |
I'll start with what should be a well known thought experiment: Can a airplane on a treadmill take off? (Feel free to give an answer!) Who else has some good teasers? Ever fooled your supervisor? Ever been fooled by a really good one? Let's hear them!
|
[
"Your pee is already warm. Urinating will remove the mass of body-temperature pee and hence your total energy goes down, but you were in thermal equilibrium already (give or take)."
] |
[
"Here's one that got me in back in high school. It's actually a math brain teaser. ",
"x",
" = x*x",
"x*x = x plus itself x times = x+x+x+x+...x (x times)",
"d/dx [x+x+x+x+...x (x times)] = [1+1+1+1...+1 (x times)] = x",
"BUT d/dx (x",
" = 2*x",
"2*x = x ??!?!?!?",
"The answer is actually extremely obvious once you've had a little bit of physics and understand the derivative a little better. But this sure stumped me back in high school calculus."
] |
[
"right but you are using energy to keep it warm."
] |
[
"If you move a wild bug far from its home but the same environment will it go back home or make a new life there?"
] |
[
false
] |
Like if you took a grasshopper from one side of a lake to the other, one mile away, could it make the trek home? Would it stay there and find a new cluster of grasshoppers like it? Would it starve and die?
|
[
"It really depends on the insect.",
"Many insects, I believe including grasshoppers, typically do not have one nest or other type of \"home\" they can return to. Most insects also do not rely on being part of one society or group. They live where they happen to be at the moment, and if they can't find what they need in an area, they keep moving until they find it.",
"Other insects, notably the ants, wasps, and bees, are \"central place foragers.\" They have a nest or hive or other \"home\" where they hang out, and if you displaced them they would fly up to ",
"miles away",
" to get home as long as they have memorized enough landmarks and directional cues (and they are very good at that.) Some of these insects are social, and have a strong drive to return to their own social group, which they are typically related to."
] |
[
"IIRC bees attack other bees who don’t smell like the rest of the hive. IIRC beekeepers who want to introduce a new queen to a hive protect her with a small cage with a wax/honey plug. By the time she’s eaten through the wax plug she smells like the rest of the hive and is accepted by the worker bees."
] |
[
"If they could not locate original home , could they become part of another colony? "
] |
[
"Why does the north get more snow than the south?"
] |
[
false
] |
From that image it really seems like there is more snow in the northern hemisphere. Why is that?
|
[
"Check this out:",
"(crappy but does the trick) ",
"map with tropics delineated",
"Southern hemisphere has very little land outside of the tropics, besides Antarctica. I didn't realize how lopsided the land distribution was. "
] |
[
"Somewhat related tangent: Another indicator that the land distribution is lopsided is how the atmospheric CO2 concentration varies based on seasons. When the northern hemisphere is in summer the huge increase in photosynthesis decreases CO2. As I understand, most of that variation comes from forests in Asia; Siberia. ",
"http://earthsci.org/processes/weather/airpolute/co2-concentration.gif"
] |
[
"You do notice the biggish chunk of snow in the south, called the Antarctic?",
"I think the rest can be explained by the lack of large land masses around 40 latitude, and maybe the sea currents are distributed differently."
] |
[
"Why are there multiple stop codons (UAA, UGA, UAG) but only one start codon (AUG)?"
] |
[
false
] | null |
[
"There's a scientific paper on it: ",
"https://www.sciencedirect.com/science/article/pii/S0022519312001580?via%3Dihub",
"Its an evolutionary advantage to reduce useless translation and save energy. Here's the short summary: ",
"► We assume that the synchronization shift of length 3 in DNA or RNA is violated. ► Then the probability of reading a shifted stop codon is quite high. ► Thus the synthesis of undesired proteins will soon terminate. ► In this way cells save energy."
] |
[
"There ",
"actually are other start codons",
"; they're just very uncommon in eukaryotes (everything other than bacteria and archaea). They're slightly more common in RNA than DNA, and they are a lot more common in mitochondrial DNA, which makes sense because they are a lot more common in prokaryokes such as bacteria and mitochondria are probably descended captured prokaryotes."
] |
[
"I can speculate that it's for the same reason: frame shifts will be less likely to initiate inappropriate transcription, thereby reducing the number of improper proteins."
] |
[
"Do the Voyager spacecraft experience time dilation and has it been recorded?"
] |
[
false
] |
Seems to me that since the Voyager spacecraft are the fastest vehicles ever built by mankind, they would be experiencing the most profound time dilation ever recorded by humans. So, has the time dilation that they are undoubtedly experiencing been recorded?
|
[
"I wouldn't say it's negligible. GPS satellites orbiting the Earth experience time dilation and have to synchronize their clocks with those on the ground to provide accurate readings."
] |
[
"Exactly. For voyager 1, .05 seconds per year would translate into 28,050 meters difference in it's position over its 33 year life so far. Imagine trying to send a laser signal and being off by more than 28km."
] |
[
"Voyager I is moving at 17000 m/s, which results in a negligible amount of time dilation. You're looking at a difference of ~.05 seconds per year in length of time experienced."
] |
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