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[
"Vacuum pull to Space"
] |
[
false
] |
Imagine a tube, located on land, from sea level to low earth orbit or just short of it. Would it be possible for the vacuum of space to suction up the contents of the tube? Would it be possible to construct a tube capable of sustaining that type of suction down to the base of the tube without collapsing, giving us the ability to use the vacuum of space as a force to exit the planet? I don't know how to begin estimating calculations to think this could be structurally possible. This could be a very efficient way to launch people into space towards space stations and even used as a phase one launch to other celestial bodies. I just thought it sounded cool and was looking for other input about it.
|
[
"The point thetripp was trying to make was that the atmosphere is also 'open' to space.",
"Vacuum does not actually suck. The pressure in the pressurized part presses. And in the direction of space, it does press. But gravity pulls in the other direction.",
"This would be just as true in your straw. The gravity would keep the atmosphere in the straw (although just like in the atmosphere, the pressure would gradually decrease till it is almost zero at the space end...)"
] |
[
"This question gets asked a lot, and the answer is no - the vacuum of space cannot be used in the way you are thinking. To help you understand why, I would ask that you consider what, if anything, is different between the scenario you describe (a straw from the surface of earth to space) and the actual scenario of earth and its atmosphere sitting in the vacuum of space. "
] |
[
"Why doesn't all the air on Earth escape into space? What's holding it in, and would that also affect your tube?*",
"*Gravity, and yes."
] |
[
"How do biologists divide asexually reproducing organisms into species?"
] |
[
false
] |
I remember one working definition of "species" that went somethin like: Individuals who can produce fertile offspring belong to the same species. Of course this does not apply to organisms that reproduce asexually. How do biologists determine the borders among species for, say, bacteria?
|
[
"Poorly.",
"Taxonomy of procaryotes is messy and convoluted and is currently undergoing radical overhaul (and there are all sorts of competing ideas --all over the place in biology, but it's the most extreme in procaryotes-- and debates about how to better organize taxons). Over the past couple decades there have been major discoveries made in genomics; in terms of procaryotes one of the major issues is gene swapping, making it impossible to create pure monophyletic clades (this even happens in complex life forms, for instance placental mammals have placentas which are built using viral protiens that were introduced to an ancient organism through infection, so placentals in some sense are partialy descendants of ancient viruses. The effect is simply more extreme in many procaryote groups).",
"Ultimately the answer to your question has to do with history. In the late 19th, and 20th centuries researchers were busy discovering, identifying and organizing bacteria and they followed Lineaus' model to do so. It's important to note here these microbiologists were not being dumb, they simply didn't have all the information we have now, they did the best they could with what they had. Now though we we are stuck in a situation where procaryote classification is archaic and messy, and arguably more importantly there is no clearcut way to fix it because the decent and ancestory of procaryotes is messy, not to mention trying to impose a classification system built for sexually reproducing eukaryotes runs into all sorts of problems when applied to asexual procaryotes that swap genes all willy nilly.",
"So tldr; you are correct that the concept of species doesn't work very well for bacteria, but we use it because of historical precedent, and it's still really the only system we have."
] |
[
"Excellent question.",
"Under the biological species concept (BSC), you really can't. This is because the BSC is biased towards sexually reproducing organisms.",
"A better definition of a species (to me) is the unified species concept (USC). Recall that populations evolve; to the USC, a species is defined as a separately evolving metapopulation lineage (or segment thereof). If some genetic lineage in a metapopulation becomes separate (e.g. no gene flow, etc) it is classified as a new species. This means speciation is rather easy and quick, as opposed to waiting for reproductive isolation under the BSC.",
"A good paper on the USC can be found ",
"here (free!)",
".",
"This definition has its pros and cons. A con is diagnosing what exactly is a separately evolving metapopulation lineage. Typically used is Bayesian Inference, where species are assigned a probability. But this isn't a cure-all.",
"The pros are that this definition agrees with basically every other species concept (e.g. ecological, phylogenetic, BSC, etc). It actually allows the other species concepts to stop in-fighting. The ecological species concept and the BSC (as an example) aren't in contention, because they both merely help diagnose a species (see Fig. 1 in the provided link).",
"phungus420 is correct in noting that lateral gene transfer greatly obscures evolutionary relationships in bacteria. Our models of phylogeny make several assumptions (with regards to incomplete lineage sorting, etc), and violating the assumption of vertical gene transmission is very problematic.",
"Hope this helps."
] |
[
"You're quoting one species definition, the biological species concept. There are many different species concepts: John Wilkins described ",
"A list of 26 Species “Concepts”",
" and those aren't all-encompassing. ",
"More important, all of these are just definitions. That means they have ",
" to do with biology as such, they're just conveniences for the way people talk about biology. The whole concept of ",
" is a human thing; in reality, biologists know that there's no such thing, that there are fuzzy edges and ambiguous cases and so on, and it doesn't matter, because there's nothing ",
" interesting about coming up with a terse summary of \"species\". That's what advertising jingles are for, not science. "
] |
[
"Why is the Inflation Theory so important in understanding the Big Bang?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"/r/askscience",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"This is a common question covered in the ",
"AskScience FAQ",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"Thank you for the message, ",
"I've actually been doing that for the last couple of days. I'll research more then.",
"Have a great day, ",
"-MAD623"
] |
[
"AskScience has a bunch of past threads on it, but the Wiki article",
"\n",
"https://en.wikipedia.org/wiki/Inflation_%28cosmology%29#Motivations",
"\nsums it nicely, without inflation you have, ",
"The horizon problem - why our universe in thermal equilibrium",
"The flatness problem - why our universe's spatial curvature is near zero ",
"Without inflation, the LambdaCDM model of cosmology is broken and doesn't work. You can have a big bang without inflation, but it's have to be a very different big bang theory than LambdaCDM."
] |
[
"What would happen to me if I stood in the path of the Large Hadron Collider?"
] |
[
false
] | null |
[
"A similar thing ",
"happened to a Russian scientist in 1978.",
" The short of it is this guy survived even though he received a \"lethal dose\" of radiation because he got lucky where the beam struck. ",
"The LHC has far higher beam energies (~13 TeV max)* than this old synchrotron (~76 GeV max) and thus it would be dramatically worse. You would succumb to acute radiation syndrome. ",
"*~13 TeV for colliding beams. "
] |
[
"Just thought I would add ",
"some pictures",
"."
] |
[
"No, but it did pass through him, causing damage along the way. "
] |
[
"If R=V/I, how come power lines have such low resistance?"
] |
[
false
] |
[deleted]
|
[
"The quantity you care about is the ",
" dissipated as heat in the wire. It turns out that the resistive power loss is equal to ",
"P_l = I",
" * R",
"Now the power transmitted over the wire is equal simply to ",
"P = I * V",
"So by increasing the voltage and decreasing the current, the transmitted power can be kept constant. And by decreasing the current, the resistive losses are drastically decreased."
] |
[
"Well, remember, resistance is more a property of the material than what you do to the material (except heating it). It's a measure of how much current will flow across the material given some potential difference, I=V/R.",
"Anyway, in a power line, it's not that it changes the ",
" of the line, it's that it changes the ",
" of energy ",
". So if Power (lost) = I",
" R, raising the voltage lowers the current (Because you pass it through a ",
"Transformer",
" that allows you to trade either voltage for current or current for voltage)",
"So essentially, there's very little overall electron ",
" through the wire, so the resistive losses are low, but the ",
" of their motion is rather high, so they transmit the energy down the line better."
] |
[
"You aren't understanding the circuit well if this is your question.",
"V is the power drop ",
". In this case, the single wire is the resistive element. The resistance in the wire is very small. However, the voltage drop between the ",
" (the +ve and the -ve, to use the DC terminology) of the electrical grid is large to overcome transmission issues, and it is reduced to 120V through transformers when it enters your home.",
"You have to consider the full circuit to understand what is going on, not just one wire in a circuit."
] |
[
"Why are musical notes in an octave?"
] |
[
false
] |
Is there any reason behind them being their specific frequencies or is it just a system that we invented long ago that still pretty much works?
|
[
"Let's say you have two notes, f1 and f2 (f is for frequency).",
"When f1 = 2*f2, they are one octave apart. If you have an instrument like a violin, playing an open string then stopping it at the midway point (half the string length = double the frequency) will result in the second note being an octave up.",
"If you were to press the string at the 1/3 point, you get a perfect fifth, which corresponds to a frequency ratio of f1=(2/3)*f2. This is considered the next most harmonious interval after the octave, as it's next simplest integer division of the string.",
"If you were to start on any note, take the perfect 5th interval, then take the perfect fifth interval of that, then again... after 12 notes you end up back to your original note. This is why we have 12 notes in an octave. ",
"However, the spacing between notes tuned this way is not even, so while things sound fine in keys related to the base frequency you tuned from, as you go into other keys some notes will sound a bit sharp or flat. Therefore, for instruments like pianos which need to be able to handle playing a variety of keys without retuning, we use a system called even tempered tuning, which splits the octave into 12 equal tones. The ratio between notes is 2",
" ~= 1.059... To a keen ear basic intervals like a perfect 4th or 5th won't resonate as cleanly, but this allows for more key changes in a given piece of music while averaging out the intonation discrepancies that you'd normally get from doing so."
] |
[
"Octaves themselves exist since doubled/halved frequencies are perceived as the same note, just higher or lower, respectively. The divisions of an octave into other notes that comprise it is mostly arbitrary - there are in fact alternative systems, e.g. dividing an octave into 15 semitones rather than 12."
] |
[
"Got a good source about mathematics of music? I'm a physicist who would like to learn all about this stuff during my free time."
] |
[
"Why doesn’t light bounce against cladding in single mode optical fibre?"
] |
[
false
] |
I can’t seem to find anything explaining how light waves can possibly travel straight through the middle without bouncing inside an optical fibre and I really wan’t to know how it works.
|
[
"Basically the core in single mode fiber (SMF) is so narrow that you can no longer accurately model it with ray optics. You need to consider the full electromagnetic wave equation to understand how SMF works. ",
"You can see a similar effect when a water wave moves in a narrow canal, ",
"for example, here",
". (This is actually a bit more specialized phenomenon, called a soliton wave. This can be reproduced in optical fiber, but is somewhat more tricky than the general waveguiding in SMF) The main thing is that the physics of the situation (mathematically described by the differential equations and boundary conditions at work) only allow one \"kind\" of wave to move along the waveguide (canal or fiber), so you get very little change in the wave shape as it travels."
] |
[
"If you look at the electric field pattern, it does touch the sides, and even extends into the cladding a bit. It just touches it equally all around, rather than sometimes one side and other times the other side like a ray optics model might make you expect."
] |
[
"Have you ever seen a mirage on a hot road? That is a reflection due to a difference in refractive index between warmer(lower index) and cooler(higher index) air. The reflection only happens when the light hits the boundary at a shallow angle. There is a difference in refractive index between the core(higher index) and cladding(lower index). As long as you don't bend the fiber too much, the light reflects off the sides of the core. This is a simplified description, but is basically correct. "
] |
[
"How does one photon have more / less energy than another photon ?"
] |
[
false
] | null |
[
"Their energy is proportional to their frequency. It is kinetic energy, of course the Newtonian expression for kinetic energy won’t work because something travelling at the speed of light is as far from the Newtonian regime as possible"
] |
[
"Why can any given thing have energy and have it in different amounts, and why do you think photons don’t meet this criteria? I might be able to better answer if you can talk a bit around the question"
] |
[
"That’s ok. That’s helpful in formulating a hopefully useful answer, so thank you.",
"So the problem is that the wave-particle duality thing is a little misleading. Photons (or any “particle”) aren’t either waves or particles nor are they both. Photons in particular are specific configurations of the electromagnetic field, which obeys quantum mechanics.",
"These can be, in some cases, well approximated by classical particle behaviour and in others by classical wave behaviour but they aren’t either.",
"In fact all of these “particle” states are defined as having a given wavevector, so frequency is baked into the definition of all of them."
] |
[
"Has the string theory been validated by any experimental evidence like from the LHC?"
] |
[
false
] |
Are there better contenders for the theory of everything? I know just the basics of what the string theory is, that is using vibrating strings and extra dimensions to explain all the different forces and particles. I come from a medical background, so please excuse any gross misunderstandings of the concept.
|
[
"Some required aspects of string theory have been constrained by the LHC. ",
"String theory requires more than the 4 dimensions of space time. The size of the proposed dimensions has been constrained as if they were larger we would have seen things that disagreed with the standard model.",
"Super String Theory requires super symmetry. Low energy or \"Natural\" Super-symmetry was not found. String theory is compatible with any energy of super symmetry below the plank scale however. So lots of proposed models of string theory were shown to be incorrect, but not the general model of the universe.",
"This has caused some worry in physics as it now appears that string theory will not have any interaction with experiment for the foreseeable future. That may change with gravitation wave astronomy, but so far there is zero experimental disagreement with General Relativity."
] |
[
"No, I may have worded it badly. Models that are within Super String Theory made incorrect predictions about low energy super symmetry. Those models have failed, not string theory itself. Super String Theory in general does not make any generic predictions about \"low energy\" physics, so there is no current predictions for string theory as a whole."
] |
[
"The biggest factor is that we don't see more than 4 spacetime dimensions. This means they have to be hidden someway. There are so many of these you can get almost any low-energy physics you want."
] |
[
"Why can't our eyes move smoothly as we scan across our field of view, but can move smoothly when focusing and tracking a moving object across our field of view?"
] |
[
false
] |
Try this experiment: film your face with your phone as you look to the side and try to move your eyes smoothly across the screen. You can't. All you'll see is eye movement (rapid little darts in eye position). Next, hold your finger behind your phone and focus on it while you move your finger from one side to the other. You'll see that your eyes move perfectly smooth while they track your finger. Why is this the case? I can already imagine evolutionary motivations for it: when we look out into our environment, we are performing so rapid, darting eye movements are good for snapping from one area of interest to another. But, when tracking a moving object of interest (such as prey) it is important to be able to smoothly fixate on it. But my question is, do we know the involve in this? Is there some sort of reflex involved?
|
[
"When you fixate on a target you do what’s called a pursuit eye movement as you track it. These are smooth almost involuntarily extra ocular muscle movements to maintain binocular fixation of the retinal image on the fovea (area with the most dense photo receptors)\nWhen you try to voluntarily do the same thing you have no retinal image to tell the brain to fixate on. So it jumps around and cannot track it. \nThese eye movements are more jumpy as you try to find an object to fixate one this is a saccade. The initiation of both come from different areas in the brain. The Frontal eye field initiates both saccades (jumpy eye movement) and smooth pursuit tracking I believe. Could be wrong about that part. It’s been a while since I got out of optometry school.\nHere’s something else that’s interesting. You have involuntary eye muscle movements of a stationary object when your in motion. Look at your phone camera and start turning your head up down left and right. Your eyes will be turning smoothly to track a stationary object without any input from you to move the eyes. This comes from the input from a combination of cranial nerves and is called the vestibulo ocular reflex. It’s like a natural image stabilization for our eyes"
] |
[
"This makes a lot of sense, thank you!"
] |
[
"This comes from the input from a combination of cranial nerves and is called the vestibulo ocular reflex.",
"My favourite fact about that is that it's controlled by just three neurons."
] |
[
"How do we decide where a mountain begins?"
] |
[
false
] |
At what point are you “on the mountain” as opposed to being on the countryside around a mountain, or on a neighbouring mountain? I’m curious if there’s a specific point where someone would be considered standing on the mountain as opposed to under/beside the mountain or on the next mountain. Edit: my question was spurned by this post about the “base” of Olympus Mons on Mars:
|
[
"Speaking as a geologist. ",
"As with everything in science one needs to define terms. 'A mountain is...According to this particular definition it's starts...' ",
"An aside, nobody gets that caught up what a mountain is. It has a bit of relevance in volcanology but otherwise not too much. More relevant is the height of a particular structure above sea level, etc."
] |
[
"Thanks for that, mate. Always appreciate hearing info from someone in specific fields. :)"
] |
[
"Not a geographer but my guess would be you would take the average elevation difference of the surrounding terrain and draw the line where the elevation shift is not lining up with the differential average(ex: when the terrain starts to really become mountain instead of just a hilly patch of land)"
] |
[
"Does pollination between different plant species occur? If so, does it cause issues in the gene pool?"
] |
[
false
] | null |
[
"While this is the norm, its not at all the full story.",
"Very often, the hybrid plant is more fit than either parent species. This is known as hybrid vigor and, while it can happen in animals its far more common in plants.",
"Hybrid sterility can still be a problem but , plants have a trick for this called whole genome duplication.",
"The reason hybrids are often sterile is because of differing genome counts in the parents. If one has 10 chromosomes and the other has 12 then a hybrid offspring between them will have 11. Since thats an odd number, this plant will have a hard time producing gametes.",
"So the plant simply doubles its entire genome. This results in 22 chromosomes that pair properly so meiosis occurs normally.",
"Additionally, the new plant will often be unable to breed with either parent species. Meaning its reproductively isolated and can be considered a new species. Its estimated that about 3% of flowering plant species alive today, and 7% of fern species, began in this way."
] |
[
"While this is the norm, its not at all the full story.",
"Very often, the hybrid plant is more fit than either parent species. This is known as hybrid vigor and, while it can happen in animals its far more common in plants.",
"Hybrid sterility can still be a problem but , plants have a trick for this called whole genome duplication.",
"The reason hybrids are often sterile is because of differing genome counts in the parents. If one has 10 chromosomes and the other has 12 then a hybrid offspring between them will have 11. Since thats an odd number, this plant will have a hard time producing gametes.",
"So the plant simply doubles its entire genome. This results in 22 chromosomes that pair properly so meiosis occurs normally.",
"Additionally, the new plant will often be unable to breed with either parent species. Meaning its reproductively isolated and can be considered a new species. Its estimated that about 3% of flowering plant species alive today, and 7% of fern species, began in this way."
] |
[
"While I imagine you're actually referring to fertilization, it's worth pointing out that pollination only means that some pollen is deposited on the surface of the stigma. Pollen from another species can end up on a flower's stigma really easily, especially in plants that are pollinated by generalist pollinators or by wind pollination. It happens all the time, but in most cases this pollen will not even be able to form a pollen tube since that process depends on species-specific chemical signaling between the flower and pollen. If it does form a pollen tube, it probably won't reach the the ovary. If it does reach the ovary, the sperm probably won't be able to actually fertilize the egg. The few remaining cases are the hybrids other comments have discussed."
] |
[
"Vaccine study (including thimerosol) with rhesus macaque infants showed significant neurological changes. Does it have ANY relevance to humans in 2012?"
] |
[
false
] |
In , researchers tested the effects of 90s-style vaccines (includes thimerosal) on rhesus macaque infants. Neuroimaging detected significant differences in the vaccinated group versus the control group. From the Discussion: "Volumetric analyses identified significantly greater total brain volume in exposed compared with unexposed animals at both measured time points." And then... "Interestingly, a rapid increase in total brain volume between 6 and 14 months is generally considered to be a consistent finding for many children with an Autism Spectrum Disorder" Of course, since thimerosal is no longer in use, the information in this study already seems pretty irrelevant to whether you would have a kid vaccinated in 2012. HOWEVER, when you have crazy relatives that say things like, "well if they'd put this drug in a vaccine without knowing how harmful it is, who knows what kinds of other harmful things could be in it now?" Then you need a little more ammo to fire back with. So, in the opinion of askscience, is this study legit, and does it have any relevance to humans in 2012? By the way, if I am posting this in the wrong place, please tell me so that I can correct my mistake. Thank you!
|
[
"It's part of the monkey studies led by several researchers who have performed some rather shoddy studies in the past. ",
"It's an interesting story"
] |
[
"I'm not a neurologist, but reading through the study I find it very difficult to believe the results imply much about the effects of thimerosol on humans.",
"They did a very small study of only 16 macaque monkeys split into two groups. Any statistical difference among such a tiny group had to be a very large change between the two groups. But yet when we take thousands or hundreds of thousands of children vaccines containing thimerosol and compare them to children not exposed, we can't find any behavioural differences in large epidemiology studies. These guys found brain size differences in monkeys with 2 groups of 8. Now, they did imaging studies, and I'm talking about behaviour, but the implication of the imaging studies is there's behavioural differences that result from it. ",
"Essentially it just seems rather odd to me that this relatively large effect they found in macques with only 16 monkeys isn't just blindingly obvious to us, after millions of kids have taken thimerosol containing vaccines. ",
"In short, I wouldn't make any conclusions based on one study of 16 monkeys. ",
"As far as convincing crazy relatives, well arguing science isn't really going to convince them of anything, since they're just following fear. I'd emphasise the very REAL and known risks of not vaccinating children. Children can still die from even measles. These diseases aren't just minor inconveniences. Then bring up herd immunity, and how their choice of not vaccinating has health implications for everyone. ",
"Arguing difficult scientific principles to people with little or no scientific knowledge or training is pointless. Use the same (but scientifically valid) techniques the anti-vaxers use. Fear."
] |
[
"Holy cow, that definitely puts the study into perspective. I had no idea. Thanks for the history lesson."
] |
[
"Why is brain-to-body size often used as an indicator of intelligence (looking at you, koalas) instead of raw brain size?"
] |
[
false
] |
Wouldn't animals with similar brain sizes be similarly intelligent irrespective of body size? In other words, does a bigger body require a bigger brain for the same functionality?
|
[
"Because a large portion of the brain is used to control the body, homeostasis and similar thing, so you can't expect a large animal with an extremelly small brain to be able to both conduct all of it's bodilly functions and have a high intelligence. All functions in the brain need some space, because neurons have to fit there with all of their branches. So if an animal is small, has less muscle fibers that have to be innervated, has less cells regulated by the CNS in general, but has a relativelly large brain, you could potentially expect a higher intelligence, because that means that there are more neurons that aren't directly involved with basic functions. Of course that isn't a direct causation, because many other factors play a huge role - neuron density, brain organisation (if it's all olfactory bulb, what can you expect), synapse density, lobe distribution, and others, but since generally motoric and regulatory functions come first, in a small brain they will definitelly be there, and intelligence will be pushed aside.",
"Hope this made at least a little bit of sense :D"
] |
[
"It does contribute by transmitting the signal to the muscles (the neurons that connect to the muscle are different), and controlling involuntary actions - partially visceral actions in specific nuclei, but a lot of information for them is also sent from above, and controlling reflexes. And mammals do have a well developed spinal cord. Since evolutionarilly the spinal cord is much older, there are animals that have a spinal cord, but don't really have what we would call a brain."
] |
[
"It s probably more of a rough correlation of observations with one variable beeing very empiric: what is intelligence ?\nA good part of the brain in human mammals is used to process vision, in dogs would be smell etc..."
] |
[
"For as long as I can remember I have had frequent episodes of lucid dreaming, sleep paralysis, and what an online search called \"hypnopompic hallucinations.\" Is this combination or frequency special enough that I should be volunteering for sleep studies?"
] |
[
false
] | null |
[
"This falls under our rule against giving ",
"medical advice",
". If you have medical questions please go ask them to a medical professional."
] |
[
"I am not asking for medical advice. From my perspective this is not a problem, medical or otherwise. I adjusted to this before I was even a teenager and very much enjoy lucid dreaming. ",
"I am asking strictly for research purposes. I thought maybe there was a neuroscientist out there that was interested in studying lucid dreaming or sleep paralysis, but was unable to because of the inability to find a subject who could lucid dream on command. Or perhaps it is rare for a person to have all three so it may be interesting enough that I should volunteer for some psychology studies about dreaming or something. "
] |
[
"This still falls under the medical advice rules within ",
"/r/askscience",
". You are asking about a particular medical condition concerning yourself.",
"If you don't agree with that you can try reaching for higher level mods through the modmail (link in the sidebar). ",
"I advise you to try other subreddits like ",
"/r/biology",
" or ",
"/r/psychology",
", ",
"/r/neuroscience",
" or ",
"/r/Neuropsychology",
". They may have more lax rules on this kind of topic."
] |
[
"Can you lose part of your brain with no noticeable difference to your personality or brain functionality?"
] |
[
false
] |
[deleted]
|
[
"well, your concious may not notcie it because i lost the ability to notice it",
"it is possible of course, there have been cases were peoples brains received a bullet",
"but it turned them into monsters for the rest of their lifes",
"i had a tbi as a kid was knocked out at least 5 to 10 minutes",
"amtough i had adhd before it made especially the social functioning worse",
"it made the excentric guy i am today",
"i am at the end of my major recovery process and plan to resocialize in university now that ive studied psychology, neurology enough to do so and secured my intellectual future",
"but it was hard, years of deppression",
"a person will deffinitelly change a lot, but after a decade there may be no significant difference depending on what the person is doing"
] |
[
"the brain is incredibly resilient and adaptable, altough complex and fragile",
"litterally anything could happen"
] |
[
"the brain is incredibly resilient and adaptable, altough complex and fragile",
"litterally anything could happen"
] |
[
"Do any viruses other than Chickenpox reemerge after the primary infection and cause a second disease like the varicella-zoster virus causes Shingles?"
] |
[
false
] |
I know that Shingles is a reactivation of the virus that causes Chickenpox, and if you haven't had Chickenpox, you can't get Shingles (although you can get Chickenpox from someone who has Shingles). Are there any other viruses that lay dormant and cause a future infection? Is SARS-CoV-2 a type that could reactivate later?
|
[
"HIV causes an acute disease of flu-like symptoms when you first get infected. Then it goes dormant, sometimes for years. And then, slowly slowly, it erodes away your immune system, until you start getting chronically sick with opportunistic infections."
] |
[
"In addition to herpesviruses which ",
"/u/vbwrg",
" mentioned, some polyomaviruses can reactivate if the immune system is weakened. These include things like ",
"BK virus",
" and ",
"JC virus",
" which can cause severe disease (brain damage, kidney damage, etc.) in transplant recipients taking immunosuppressants.",
"Is SARS-CoV-2 a type that could reactivate later?",
"No, coronaviruses do not establish latency. However, there can be long-term damage that's not as a result of viral reactivation."
] |
[
"The only viruses that can go dormant and reactivate later are those capable of causing chronic infections. Herpesviruses like the varicella-zoster virus that causes chickenpox and shingles are the masters of this. All herpesviruses are capable of latency and later reactivation, including the herpes simplex viruses that cause cold sores and genital herpes, and the Epstein Barr virus and cytomegalovirus that cause infectious mononucleosis. ",
"To reactivate, a virus needs to have both the ability to go dormant and the ability to reverse that dormant state. Herpesviruses have special genes that allow them to do this. Coronaviruses do not. The only viruses that can exist in a latent state are those whose reproductive cycles include DNA: either DNA viruses or retroviruses. ",
"RNA viruses like coronavirus cannot establish latent infections."
] |
[
"Why does it take so long for common CFL bulbs to achieve full brightness?"
] |
[
false
] |
I've noticed for years that compact fluorescent light bulbs will turn on quickly, but their brightness will continue to increase a little over the course of the next few minutes. I am curious about the electrical/chemical/other mechanisms behind that lagging intensity.
|
[
"AFAIK, Flourescent bulbs function sub-optimally at colder temperatures. Once the bulb reaches an optimal temperature, they achieve full brightness.",
"Source: I work for an electrical distributor as an events manager and attended the same Lighting seminar 6 times."
] |
[
"Cool. Helpful! "
] |
[
"To add to this, why do they have paler light?"
] |
[
"Perhaps a silly question; why is space so cold?"
] |
[
false
] | null |
[
"Temperature is a measure of the average kinetic energy of the particles in your medium. In a vacuum, there are ",
" few particles (atoms, molecules, etc) present, and although those that are present may have a great deal of energy, there simply aren't enough for the word \"temperature\" to have much meaning.",
"If a person (or anything wet) goes out into space without a suit, they will freeze (eventually), not because space is inherently \"cold\", but because the pressure is so low. This results in boiling/evaporation of the water the body. Heat from the body goes into the vaporization of water, which, given time, will freeze the body solid as the temperature drops far enough."
] |
[
"Loss of heat by radiation is hilariously slow and inefficient."
] |
[
"I was bored, so here's a solution to the differential equation that would describe the temperature of a iron ball with a radius of 1m, cooling only through black-body radiation starting at 533 Kelvin. This is a plot of the first seven days.",
"http://www.wolframalpha.com/input/?i=Plot[%28%28533%29+^%28-3%29+%2B+3*%28t*3600*24%29*%284.81164*10^-14%29%29^%28-1%2F3%29+%2C+{t+%2C+0%2C+7}]+\n",
"Sorry for the code text, Reddit wasn't liking the url",
"Edit: Lol, whoops; said seven, entered 100: fixed",
"Seems pretty fast though"
] |
[
"Looking at WWI/II fighter aircrafts, isn't it dangerous having the aircraft's propellers within the machine gun's line of fire?"
] |
[
false
] | null |
[
"Yes, it would be, and manufacturers came up with different solutions to this. Some mounted the guns completely above the propeller, others ",
"synchronized the firing rate to the propeller's rotation."
] |
[
"Thank you, I came to the thread to say this.",
"The synchronized machine gun was at the time a great feat of technology. These days synchronizing a mechanism even lower than .1 second is easy peasy. A couple 3 volt relays and a $.25 controller chip. ",
"But in 1916 tensioning a chain without slippage to those tolerances? Machining the gears and sprockets? Just working out the math of the timing with pencil and paper!"
] |
[
"And in the first world war, there was at least one aircraft where the gun barrel went through the center of the rotary engine (not to be confused with a radial engine)."
] |
[
"What does it mean for worker bees to be \"female\"?"
] |
[
false
] |
Worker bees are "designed" in a way it is absolutely not possible for them to bear children. In fact they lack necessary organs, for example their egg laying apparatus was modified in a way that it now functions as a stinger. They don't produce eggs and are not able to do so. This seems to me to be in odds with the very definition of being a female. For example according to Wikipedia "female (♀) is the sex of an organism, or a part of an organism, which produces non-mobile ova (egg cells)", and Webster defines is as "of or relating to the sex that can produce young or lay eggs". Obviously this may not be true on an level - there exist individuals belonging to the sex, who (for one reason or another) are born sterile or are rendered sterile later in life. We obviously still consider them female. However, the case of worker bees seems to be quantitatively different. They seem to be a separate of an individual, and their sterility is certainly not a fluke on an individual level. Most sexually reproducing species have two basic of individuals - those that produce eggs (females) and those that fertilize them (males). Worker bees doesn't seem to belong to either one of them. So my question is: I suspect the answer may be: they share chromosomal layout with fertile females of their species, but not fertile males. Also, they had potential to become fertile females during initial development, depending on environmental variables. This answer would be only partially satisfying. There are many species with no difference between sexes on a genetic level. There are many species where sex is determined based on an environment, and even species whose members can change sex later in their lives. We still consider those individuals male or female purely based on a they fulfill. So I suspect there is a better answer when it comes to worker bees than the one I was able to come up with.
|
[
"I had never heard about \"laying worker bees\" but ",
"here's a wiki:",
"Even in a normal hive, about 1% of workers have ovaries developed enough to lay eggs. However the usual number of the laid eggs is very small. Only eight eggs (seven moderately and one fully developed) were found after examining of 10,634 worker bees (strong colony contains about 100,000). Workers eventually lay significant numbers of eggs only in queenless colonies."
] |
[
"They are female, because even the workers can lay eggs, but just male eggs, because the sperm is missing.\nEvery female bee is the same (So every worker is a queen), the workers are just \"castrated\" throught the queens pheromones and the diet in the larva-stadium."
] |
[
"But they can built them up and lay eggs -male eggs, if the Queen dies, then they will... not all -because if likely 5 start, the others think there would be a queen, but ..they will .)",
"Just for the ressource, I'm a beekeeper for 4 years now.",
"So it just needs time, but normally every female bee could lay eggs. If she doesn't die before "
] |
[
"Why does human brain tissue start to die after only 4-6 minutes without oxygen when other body tissues can survive for hours without oxygen?"
] |
[
false
] |
Are there any other mammals with brains that can survive longer without oxygen? If so, why?
|
[
"Briefly, one of the reasons is that the glycolytic capacity of the brain is low. Consequentially, ATP depletion and lactate production is dramatic in the brain.",
"This paper",
" should answer your question quite comprehensively. If you can't access it, send me a PM and we'll get you the pdf."
] |
[
"If you don't really want to wade through the paper that was posted, the tl;dr of it is that neurons, in particular, rely heavily on maintaining ionic homeostasis across the cell membrane, and this is mostly upheld by the Na+/K+ exchange pump, an ATPase (meaning it cleaves ATP to provide the energy to undergo what would otherwise be an unfavorable process) that pushes Na+ out of the cell and brings K+ back in. You need oxygen for the production of ATP, and so if you don't get oxygen to the cells, you can't power the pump. The result of this is an accumulation of Na+ in the neuron, which depolarizes the cell membrane and activates more Na+ conduits, and also induces the release of glutamate, an excitatory neurotransmitter. The glutamate binds to NMDA (n-methyl-d-aspartate) receptors in the postsynaptic terminals of other cells and induces greater depolarization there, too. The whole thing is a positive-feedback loop and is referred to as excitotoxicity. It eventually leads to all sorts of things, like the release of Ca++ from the mitochondria and initiation of necrotic and apoptic processes (the two forms of cell death).",
"Not so surprisingly, glia (the brain cells that aren't neurons) are less susceptible to hypoxic injury because they maintain different permeability to various ions (they're more permeable to K+ than neurons and less permeable to Na+, so their resting potential is close to EK).",
"Interestingly (and very annoyingly if you're doing experiments with this sort of thing), neurons in culture don't die nearly as easily. It can take up to a few hours in hypoxic conditions to kill a substantial portion of neurons in culture. Even 15-30 minutes in high concentrations (even up to 10 mM) of NaCN (which does the same thing as hypoxia, in essence: it inhibits the functioning of complex IV in the mitochondrial matrix and thus prohibits production of ATP) won't kill that many cells. "
] |
[
"I think that it does. When you are not moving, your muscles use very little oxygen. There isn't really an analogous state for the brain. Additionally, if you kill some muscle cells, they will grow back. Your brain will not. ergo, you notice it more.",
"I suppose the other part of the question is \"can other mammals do better?\" The answer is yes, but they have strategies. One way is to carry more oxygen with you, and the other is to reduce your metabolic needs so carried oxygen lasts longer. These can be practiced (e.g. david blain really did hold his breath for much longer than this) and are also subject to genetics (e.g. whales and peoples at high altitudes)."
] |
[
"I tried boiling water in the microwave and it didn't work, until I took it out and it spontaneously erupted for 5 seconds and stopped as suddenly as it started. Why?"
] |
[
false
] |
It wasn't even when I set it on the counter. I was making jello and getting frustrated that the water wouldn't boil. I decided it was hot enough and took it out. After sitting on the counter for a few seconds it exploded bubbling boiling water all over the counter. Then it stopped boiling completely. This at least makes sense since it shot all its energy out. But how did it store that heat without boiling??? Was my Pyrex measuring cup too smooth and boiling requires a point for the bubble to form? Setting it on the counter disturbed it and suddenly the water realized it was well past its boiling point? There was no lid involved and it was regular tap water.
|
[
"Your guess was right. Pyrex is very smooth. If there are no irregularities, it's possible that no bubbles form. The water just basically becomes superheated. Once it's disturbed, causing irregularity, it'll boil in a flash. When I microwave water in Pyrex, I always put a wooden skewer in there to give the bubbles a place to start forming."
] |
[
"At least there is a scientific answer. I can see someone thinking this was straight up magic. "
] |
[
"Yeah, put a wooden toothpick in water you are heating in the microwave to create nucleation sites. Superheating can burn the crap out of your hand."
] |
[
"If you to stand at the base of a space elevator, and look up on a clear and cloudless day (or night), would you be able to see the counterweight on its end?"
] |
[
false
] |
The counterweight would have to be above an altitude of 35,800 km (22245.1 miles... which, to help visualize that length, is 89.33% of the circumference of the earth). Obviously, this would depend on how big the counterweight is. As such, perhaps a more precise (and therefore perhaps more answerable) question would be this: what size would the counterweight have to be, so as to be visible from the base of a space elevator? And what about for someone like me, with 20/10 vision, what size would it then have to be? EDIT: Not sure of the right flair for this. I went with Biology, because it's about a person's eyes. However, I think perhaps physics would be applicable, too.
|
[
"If that's the case, then how are stars visible? or the ISS? Or the Moon?"
] |
[
"Humans can resolve things at an angular resolution of .07 degrees",
" That means to see something 35800 km away, it'd need to have a diameter of about 44km. "
] |
[
"For what size object? We can see the moon quite clearly (granted, that object is huge), and it's far further than 100 miles. ",
"Therefore, there must be some size at which an object is visible at the distance of the counterweight. What size would the counterweight need to be, to be seen from that distance?"
] |
[
"Are there flying insects out in the middle of the Pacific Ocean?"
] |
[
false
] |
Say you're on a boat in the middle of the Pacific, miles from any island. Would there be anything like flying above water, like gnats or smaller?
|
[
"Insects aren't noted for being marine (relatively few species live in or near saltwater), but they've been dispersed to many Pacific islands (the Hawaiian islands being some of the most remote landmasses). Air and water currents are frequently invoked as colonization mechanisms. So while you might find some flies buzzing around kelp off shore, I would expect the abundance and diversity to decline tremendously with distance from shore.",
"After some googling, apparently the only truly pelagic (open ocean) insects are 5 species of ",
", a type of water-strider, and they are wingless.\n",
"Learn more!"
] |
[
"i go fishing off the coast of mexico all the time and ive seen butterflies as far as 5 miles out flying around pretty regularly. i think they just get lost and fly as far as they can until exhaustion. strong winds probably play a big role as well."
] |
[
"Some, at least:",
"Every year, millions of dragonflies fly thousands of kilometres across the sea from southern India to Africa.",
"http://news.bbc.co.uk/earth/hi/earth_news/newsid_8149000/8149714.stm",
"That article also discusses butterflies."
] |
[
"Are there any negative environmental impacts from collecting and using solar and wind energy?"
] |
[
false
] | null |
[
"Lots of drawbacks to both solar and wind. As a couple of people have mentioned wind power can be pretty disastrous for birds and bats. ",
"Altamont Pass",
" is well known for slaughtering birds of prey. Though keep in mind that Altamont Pass is pretty old in both design and placement. The problem is basically that ridges tend to have good wind generation. That is good for both energy production as well as hawk/eagle migration and dispersal. New sites have to go through more intensive siting processes to assess use by birds of prey and sometimes bats - however wind power is quite dangerous for birds.",
"Putting large solar fields in the desert builds on sensitive habitat for a number of threatened species. Some of those species don't like the disturbance that big solar fields will need.",
"Another factor not often mentioned is that the power production has to get from where ever it is being produced to your home. That requires transmission lines. Sure, they're kinda ugly - but they are pretty bad environmentally. In the sagebrush country transmission lines act as perches for hawks/eagles/ravens/crows/etc that can then go about and hurt other wildlife populations (e.g., sagegrouse). In more forested habitats, we cut down trees to make way for the transmission lines, creating habitat edge that many interior woodland species don't like and giving some invasive species access into the forest (e.g., starlings and brown-headed cowbirds - yes, I know BHCB are not technically invasive, but people have allowed them to spread well beyond their historic range). Finally the roads associated with transmission lines are used frequently by people - often people using off-road vehicles. The disturbance can be too much for some species, but the access allows more disturbance (and often habitat destruction) along the road for increased use. "
] |
[
"This ",
"article",
" might be of some interest."
] |
[
"That is an interesting article, I didn't know bats were such an important aspect when it comes to pest control. "
] |
[
"How are scientists able to determine which chemicals in the brain correspond to certain emotions and actions?"
] |
[
false
] |
[deleted]
|
[
"First of all, the human brain is extremely, insanely, absurdly, complex. Almost anything you read in the popular press about the links between neurotransmitters and behaviours is undoubtedly simplified, ",
" if it's about \"higher-order\" cognitive processes like emotions, beliefs, etc.",
"That being said, there are a few different ways neuroscientists can answer these kind of questions. Here's a (not exhaustive) list. Keep in mind that some of these techniques can be combined, and many of them answer different kinds of questions.",
"We know the areas of the brain that produce certain neurotransmitters like dopamine and serotonin. If you go into an animal's brain and cut out that area, they won't produce that chemical any more. You can then test them versus animals without the operation and see how they behave differently under certain circumstances.",
"We can stick some very thin electrodes into the brain of an animal so that they're measuring the activity of neurons we know are involved in producing or transmitting certain neurotransmitters. We can measure how these neurons fire based on the animal's behaviour.",
"We can actually breed animals that are lacking the genes to produce certain neurotransmitters or their receptors in the brain. You can compare the behaviour of the genetically modified animals to the \"normal\" ones in a variety of situations.",
"We know a lot of the genes that control these in humans as well. We can do correlations where we look at how people with different versions of the gene for, say, the serotonin receptor, behave in different situations or how likely they are to get things like depression.",
"(this one is my favorite!) Our body has to synthesize these neurotransmitters out of the foods that we eat. We know the chemical processes that form them in the body, so we know what nutrients people need to form specific ones. By giving people diets with very low levels of these nutrients, we can modify the levels of the neurotransmitters in their brain and then see how they behave differently.",
"We know that certain drugs act to increase or decrease the levels of certain brain chemicals. For example, prozac and other related SSRI antidepressants increase the amount of serotonin in the brain. You can note how the behaviors, thoughts, etc. of people or animals change when they've been given these drugs. If people tend to get less depressed when given a drug that increases serotonin levels, it's reasonable to assume that serotonin has something to do with mood regulation.",
"We can measure the amount of some neurotransmitters in the cerebrospinal fluid or the blood. You can then correlate how much of these neurotransmitters people have with their mood, behaviour, etc.",
"We have technology (fMRI) that can see when certain brain regions brain are \"active\" by telling when more blood is flowing to that area. If we know that brain region produces a certain neurotransmitter, we can make assumptions about that neurotransmitter being involved in whatever process is happening when the person does things. ",
"We can give people doses of little radioactive molecules that attach to a neurotransmitter or its receptor. Using a special device that can see radioactivity, we can see whether (and when) these are released in certain circumstances and emotional states."
] |
[
"Excellent reply! Another (very common) way to study the role of different brain chemicals in behavior is to inject those chemicals into an animal's brain. Scientists inject neurotransmitter analogs, or the neurotransmitter itself, into the brain. We can also inject drugs that block the activity of certain neurotransmitters. This is done systemically (affects the whole body, and the brain if the compound crosses the blood-brain-barrier), into the cerebral ventricles (affects the whole brain, in theory), or into specific brain regions (like the hippocampus or amygdala). We can then have the animal perform tasks that model human behaviors.",
"We may not be able to study \"emotions\" in a mouse, but we can model those emotions with certain behaviors. This process can be very creative! For example, we can model anxiety-like behavior in mice by observing whether they bury marbles with bedding in their home cages, whether they emerge from a safe, dark place into a bright, open place to explore, and whether they display a disproportionate amount of fear behaviors, like ",
"freezing",
". We can model depression-like behaviors by measuring how much an animal will prefer sugar water to plain water (similar to anhedonia in depressed humans) or how much an animal will continue to swim before \"giving up\" and just floating there in a tank of water. Note in that last case, the test periods are only about 5-10 minutes and the animals just float; they don't drown. ",
"We can also model processes like learning and memory by teaching an animal to navigate a maze, perform a task to obtain a reward, or to avoid/fear a certain place or cue (like a tone or light). By blocking or activating different brain chemicals or their receptors, we can determine whether they are required for learning a task or remembering how to perform the task later on. "
] |
[
"Also, the studying a person who has a sustained a certain injury to a select part of the brain offers a slightly more ethical way of understanding what areas of the brain are involved in what behaviours or function."
] |
[
"How does the velocity of planets affect the time dilation for objects on it?"
] |
[
false
] |
[deleted]
|
[
"Technically the speed of the planet ",
" have an effect on the time dilation but it would be relatively tiny; planets and stars move too slowly to notice the effects of Special Relativity (i.e. time dilation due to speed) or such effects are vastly outshined by those of General Relativity (i.e. time dilation due to gravity).",
"To notice time dilation due to speed you have to get much closer to the speed of light than any planetary body we know of does."
] |
[
"Yes, slightly. Time dilation actually effects the precision of GPS satellites and must be corrected for."
] |
[
"Satellites are affected in two ways.",
"There is a special relativistic time dilation due to their speed relative to an observer on the ground. That is, to an observer on the ground, the clock of the satellite appears to run slow.",
"There is also a general relativistic time dilation due to the satellite being in a weaker gravitational field (really, being further from a massive object, or being in a space of lower curvature) than an observer on the ground. To an observer on the ground, the satellite's clock appears to run fast.",
"The strength of the effects is not the same. That is, while a clock appears to run fast due to being in a different gravitational potential, this effect is far outweighed by the special relativistic effect. So, overall, the clock appears to run slow, but not as slow as if you had only taken special relativity into account."
] |
[
"A quick question about relativity"
] |
[
false
] |
I was reading about how when you reach the speed of light, time essentially stops. Wouldn't this mean that light is actually moving than the assumed speed limit? IIRC it takes light from the sun 8 minutes to reach earth, if at this speed time stopped, then the trip would be instant from our perspective. It would make sense if light was actually moving slightly slower than this "speed limit" but not at the absolute maximum. Since i'm pretty sure i'm just not properly understanding something, can anyone explain it to me a little better?
|
[
"The whole basis of relativity is that there is no measurement in an inertial frame that will measure light in a vacuum at any other speed."
] |
[
"Also remember that when talking about this nonsensical photon reference frame, not only is it experiencing no time, but it's traveling no distance as well."
] |
[
"Ok, first, the whole idea about time stopping at speed of light is bollocks. You cannot reach the speed of light. While time does slow down relative to others as you speed up towards the speed of light, it never stops.",
"Only energy / massless particles move at the speed of light, and they cannot \"experience\" time. While time does not exist when moving at the speed of light, this equally makes no sense to us as humans because we could never reach the speed of light.",
"Regarding your question, time stopping is only for the light, not the observers (us).",
"So while the trip might appear instantaneous from lights perspective, it still takes 8 minutes from our frame.",
"Light can not move faster from the sun to us than 8 minutes, because doing so would break causality and all of the known physics of our universe. There is no \"faster speed\".",
"Light doesn't move at c because of a limit, it moves at c because ",
", this has to do with the relationship between time, space and velocity. "
] |
[
"can any solids melt in a vacuum?"
] |
[
false
] |
(Specifically an ultra hard vacuum like in interstellar space.) I've seen answers to the related question, "Can any liquids *exist* in a vacuum?", to which the answer seems to be "From a practical standpoint, yes, from a technical standpoint no." All liquids have some finite vapor pressure, so in a perfect vacuum they won't technically be stable and will continue evaporating, but if their vapor pressure is low enough then this will happen very slowly, and they can remain liquid for timescales of years or more. Apparently some 'ionic liquids' are quite good for this, with vapor pressures so small they often can't be measured. My question, however, is about the phase change itself. Could you start with a frozen solid sample of a low vapor pressure liquid, and then heat it up in a vacuum until it melts into a liquid? Or in that case would it go directly from solid to liquid?
|
[
"There are definitely at least ",
" solids that will happily melt in a vacuum. Let's agree that we only count it as \"melting\" if the amount of liquid is macroscopic and lasts for at least a few minutes.",
"Even so, probably most ionic liquids, and other low-vapor-pressure liquids like glycerol, will work, but I have the greatest confidence in gallium, which has an unmeasurably low vapor pressure at its melting point. Let's say, just to be on the safe size, that it's 10",
" Pa, though it is actually much lower. For a moderate size lump of gallium (let's say a 10-cm radius sphere), that vapor pressure is a million times lower than the internal pressure resulting from surface tension, which is 14 Pa (gallium has a high surface tension of 0.7 N/m).",
"Thus, the sphere will not boil, and can only evaporate from the surface. The kinetics of surface evaporation will not be significantly different from those under atomspheric pressure with ventilation. Melting, then, will occur much faster. Yes, the resulting spherical drop will be unstable, but equilibrium can be achieved arbitrarily slowly."
] |
[
"I think this question has already been answered on another reddit post from aways back:",
"",
"https://www.reddit.com/r/askscience/comments/1km5qg/can_a_strong_enough_vacuum_convert_a_solid_to_a/"
] |
[
"The sticking point here is fundamentally just about vapor pressure. A true vacuum provides almost no stabilising vapor pressure, so traditional liquids are a no-go.",
"However;",
"Could you start with a frozen solid sample of a low vapor pressure liquid, and then heat it up in a vacuum until it melts into a liquid?",
"My overwhelming reaction is yes, this is probably possible. A lot of ionic liquids do not have strong lattice collapses. Something like BMIM-PF6 might fit this. Basically anything where the cation has low symmetry would probably be a candidate, although I'm not sure on any details."
] |
[
"If chimps were to be breeded selectively based on their intelligence, how many generations would it take before we could describe them as \"human-like\" in terms of intelligence?"
] |
[
false
] | null |
[
"It wouldn't work that way. Even if there were selectively bred for intelligence there are simply too many differences between the human and chimpanzee brain for them to reach the potential of being \"human-like.\" Additionally, if you look at the ratio of brain mass to body size, chimpanzees have a much smaller brain (although debate exists regarding brain size in relation to intelligence.)",
"Humans and chimpanzees last shared a common ancestor 6-8 million years ago. Modern Homo sapiens have only been in existence ~100-200 thousand years. The biological differences I alluded to above could take a really, really long time."
] |
[
"Evolution has a couple genetic tools at its disposal...genetic potential, and mutation.",
"Genetic potential works with genes already in the gene pool...you breed big dogs together until all the \"big\" genes are all in one place, and you wind up with a Great Dane. This can happen within a few dozen generations, but once you find all the \"big\" genes, you hit the ceiling and have nowhere else to go. That's why big dogs (and cats and horses) haven't gotten significantly bigger in the past few centuries.",
"Change through mutation takes time and luck. Dogs just don't have the genetic potential to get horse sized...very large dogs already at the limit...and pay a huge price, having about half the lifespan of smaller breeds. To get bigger, dogs would need new genes...several in fact. Selective breeding might identify and proliferate a beneficial mutation should one arise, but it won't make them occur more quickly.",
"So if we were to breed chimps for intelligence, we would problem get very, very smart chimps relatively quickly...then wait around thousand of years looking for elusive mutations. "
] |
[
"Slowly but certain pegasus_527 gazed upon his username"
] |
[
"Why are food allergies on the rise?"
] |
[
false
] | null |
[
"There are several theories on this out there right now, but none of these have been proven. It is important to realize that what your body is doing with an allergic reaction is similar to an immune response run amok.",
"The first one is that the types of foods we are exposed to right now is much broader than it has ever been in history. Ever. So we just be uncovering underlying allergies. Like peanuts are essentially a new food to most people's genes. Maybe we are just uncovering this problem by feeding everyone peanuts.",
"Another idea is that there are \"sensitive\" periods of development where your body is getting a feel for it's an environment. Again the peanut butter. There have been studies which have shown that giving peanut butter too early can cause allergies to form, but not giving it at all can cause allergies to form even worse. The ideal time seems to be between 6-12 months of age for several of these foods as a first exposure. It may be that reacting to and avoiding certain \"allergenic substances\" may cause allergies to form.",
"A third idea is the hygiene hypothesis which essentially says that we are so clean now that bad things are happening to our bodies. This could be from two mechanisms. The first is that our bodies are always on the lookout for something, essentially waiting to get sick, and that because we get sick much less often, our bodies end up fighting things that they shouldn't i.e. food allergies. The second potential mechanism is that we now have a different flora (bacterial or otherwise) in our bodies than we used to. There is some evidence that parasites such as hook worms may be effective in alleviating allergies, even food allergies, but the studies I have seen were all small.",
"Finally, there may be a genetic component. The exact mechanism of food allergy development is unknown, but it is known that allergic tendencies are quite heritable, and vary from population to population. What may be happening is that there are some fairly common genetic mutations which keep happening and instead of selecting against those by letting people die, the genes are passed on to the next generation and the allelic frequency is rising because of accumulated genetic mutations. ",
"Finally, some people think it's from processed foods. Specifically soy, wheat, milk, and eggs which are in everything.",
"TL:DR No one knows for sure but there are lots of ideas."
] |
[
"Thanks for this detailed response. Interesting to think that our bodies are always looking for something to fight and that might be it. "
] |
[
"So could you develop an allergy if you stop eating something for awhile? I started to eliminate grains from my diet. Once in a while I'll have grains, bread or wheat - and I'd feel lethargic. "
] |
[
"If speed can only be measured relatively, then is it correct to say the moon on the horizon orbits my head faster than the speed of light whenever I spin in a circle?"
] |
[
false
] |
[deleted]
|
[
"An inertial reference frame is one in which you don't accelerate, a non inertial reference frame is one where you do. Speed is relative when you're travelling at a constant velocity (speed and direction). If you and I pass each other at a constant speed neither of us can say that I'm moving and you're standing still, vice versa, or we're both moving. However acceleration, i.e. change in velocity (so change in speed or direction), is non inertial. When you're in a car you know that the car is speeding up because you can feel the car seat 'push' you. So in your example you're spinning and thus accelerating (changing direction) and thus you're not in an inertial reference frame so the same special relativity rules don't apply, we then apply general relativity. "
] |
[
"An inertial reference frame is one in which you don't accelerate, a non inertial reference frame is one where you do. Speed is relative when you're travelling at a constant velocity (speed and direction). If you and I pass each other at a constant speed neither of us can say that I'm moving and you're standing still, vice versa, or we're both moving. However acceleration, i.e. change in velocity (so change in speed or direction), is non inertial. When you're in a car you know that the car is speeding up because you can feel the car seat 'push' you. So in your example you're spinning and thus accelerating (changing direction) and thus you're not in an inertial reference frame so the same special relativity rules don't apply, we then apply general relativity. "
] |
[
"inertial reference frame so the same special relativity rules don't apply, we then apply general relativity.",
"Special relativity does handle acceleration, it just requires a more thoughtful and careful application.",
"\n",
"http://math.ucr.edu/home/baez/physics/Relativity/SR/acceleration.html"
] |
[
"How is the phenomenon of natural instinct passed on at a genetic level"
] |
[
false
] | null |
[
"Wish I could answer the OP's question, but I know that reflexes are a product of nerve stimulation that produces muscle contractions without the need for your brain to consciously react. In this case, it's passed on at a genetic level simply by the nature of how your nerves are connected to each other.",
"Sorry for the layman answer - real biologists, feel free to clarify & expand and correct me if I'm wrong!"
] |
[
"Pretty much spot on. Reflexes are the result of (relatively) simple neuronal circuits that bypass higher cortical processing - which is why they are so quick. The most basic form like the Patellar reflex (",
"http://en.wikipedia.org/wiki/Patellar_reflex",
") can be pretty well explained by 'two neurons connected to each other'. 'Higher' reflexes involving vision and audition can be a bit more complex, but the principle is similar. ",
"So in essence if you're asking 'how are reflexes passed on' you're asking 'how is the human body assembled in a relatively homogeneous manner throughout embryo-genesis and development'. "
] |
[
"I do hope you were referring to the edit. The idea of a meme refers to the spread of ",
" in populations, and that it undergoes \"selection\" like genes. While I'd be the first to argue that our development of culture is \"natural,\" this has ",
" NOTHING to do with how an instinct would be genetically provided to an organism's offspring. However the above poster did mention this is the edit, and this part does hint at how this is very interesting in either case, and could be something that would seem to simply make sense, even if complex, if we were able to identify genes that would lead to the expression of a certain phenotypic instinct."
] |
[
"Dental practices with Fluoride?"
] |
[
false
] |
So from what I've learned in school is that fluorine chemically "eats" calcium, and teeth are exactly that. So why is it that dentists would use fluoride gel or foam or what-have-you, on teeth?
|
[
"Here's a paper from the conspiracy nuts at the Harvard School of Public Health: ",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491930/",
"\nThey try to evaluate the threshold at which negative effects from water fluoridation might be seen, and more or less end up suggesting that public water supplies should only be fluoridated up to about 0.7mg/liter, and not higher (previous recommended limit was 1.2mg/liter). It's worth remembering that the dose makes the poison; pure sodium fluoride is really pretty toxic. You want an ",
" dose to protect your dental health, and no more."
] |
[
"There are two key minerals in tooth enamel; hydroxlapatite and fluoroapetite. Fluoride treatment helps \"remineralize\" fluoroapatite which slows down cavity formation. "
] |
[
"What do you mean 'fluorine eats calcium'? Calcium is an element, and fluorine certainly doesn't change that. Also, ",
" and ",
" refer to very different compounds."
] |
[
"How do scientists determine the origin of a pandemic so specifically?"
] |
[
false
] |
[deleted]
|
[
"Phylogenetic analysis you sequence the virus and measure how much they have evolved. So they had bat Coronavirus sequences since we found SARS in bats. Once you sequence an unknown virus you use similarity to other sequences to find similar things, generally using BLAST. Then you use phylogenetics to do a more specific analysis of how the virus evolved from other sequences to validate that it's similar in the way we expect."
] |
[
"Basically identifying the RNA sequence of this virus and matching it against other known viruses that lve within these animal species.",
"All RNA has a code made of 4 building blocks, so whatever is the closest match is the most likely candidate."
] |
[
"Usually diseases that are common enough to manage to mutate are common enough there is a ton of it around. Like it wouldn't be all bats, but the disease that mutates is really likely to be the super common version in the animal it came from. You need an awful lot of copies of a virus for one to happen to change so dramatically."
] |
[
"How can I visualize the propagation of an electromagnetic wave through 3D space?"
] |
[
false
] |
I've seen tons of diagrams of waves in textbooks, but they seem to always be from a "sideways" or "top" perspective - either propagating in circles from a central source or as a sin wave horizontally from their source. But what would a wave look like if, say, we could see 3D models of them? I ask because I was standing in my kitchen with a friend and, when she moved, she disturbed the radio reception. This got me thinking about these waves' physical manifestation and what they might look like if we could see them. I imagined her standing at either the peak or trough of one of the waves I've seen in textbooks. I understand that we can see light and that this might be a good analog for "seeing" micro, gamma or radio waves, but I'm more interested in understanding how accurate (or inaccurate) the diagrams we see in highschool and college intro courses textbooks are.
|
[
"An EM wave can take on many wave-front shapes, waveforms, and polarizations, so it takes a lot of practice to visualize EM waves in general. The simplest form to visualize is a vertically-polarized monochromatic plane wave. To a good a approximation, the waves created by a linear radio antenna pointing up are vertically-polarized monochromatic plane waves (when you are reasonably far away from the antenna). ",
"A vertically-polarized plane monochromatic EM wave can be thought of as a uniform wall of little, strong, up arrows approaching you; followed by a wall of little, weak, up arrows; followed by a wall with no arrows; followed by a wall with little, weak, down arrows; followed by a wall with little, strong down arrows, and so on in a cycle. The arrows represent the electric field and their directionality has physical meaning. An electric charge at rest feels a force from an electromagnetic field and moves in the direction of the electric field. So as the wall of little up arrows in the radio wave passes your body, those arrows are the direction that the electrons in your body (or your phone, etc.) are getting nudged."
] |
[
"would it be safe to visualize them as a sphere expanding from their origin?",
"Yes, if the radiation source is small compared to the distance to the observer, the source acts like a point source and therefore emits wavefronts that are expanding spheres (somewhat like the expanding ripples on a pond caused by throwing a rock in). Note that the spherical wavefront shape does not imply that the intensity of the waves is the same in all directions. Wavefront shape and intensity pattern are different things. But not that the wavefront spheres are generally smooth in the transverse directions (that is in fact what defines a wavefront). The waving happens in the radial direction and not along the surface of the spherical wavefront. In this way, the radiation pattern is not like a Hoberman sphere. ",
"Does the directionality of an EM field orient itself to Earth's gravity like I do, or is down an arbitrary direction?",
"I am sorry to have confused you. The directionality of the electric field in an EM wave in is completely determined by the source, and not by earth. For a simple linear wire antenna, the direction of the electric field in the waves is aligned with direction of the long dimension of the antenna. A wire antenna that has its long dimension oriented up relative to the earth will create waves with \"walls\" of electric fields that oscillate generally up and down relative to the earth. The earth is doing nothing special in this process. I just used the earth as a fixed coordinate system to describe the process. A wire antenna that has its long axis oriented sideways relative to the earth will create waves with an electric field that oscillate side to side relative to the earth. The exact same thing happens in space, but its just harder to describe in words because there is no convenient reference coordinate system. ",
"And are the up and down arrows you're describing part of what an EM field would look like, or are they simply a representation of its directionality?",
"It depends on what you mean by \"look like\". Humans can't see radio waves, so they don't literally look like anything to humans. But we can visualize its effects. The directional of the electric field is physical. If you have a little radio receiver with an antenna, you will get good reception when you align your receiving antenna with the electric field and poor to no reception when the receiving antenna is oriented in a different direction. You can therefore \"see\" a radio wave with the appropriate detector.",
"As for the rest, I assume that these \"walls\" follow each other closely and correspond to the sin waves that laymen like me see in our college textbooks...",
"Yes, each \"wall\" is a peak or trough in the sine wave. A peak in the sine wave would be a wall with the electric field pointing in one direction tangential to the wall and a trough in the sine wave is a wall with the electric field pointing in the opposite direction. Because the sine wave cycles positive, negative, positive, negative, etc. you get a wall of up-pointing (for instance) Electric field; and a half-wavelength behind it, a wall of down-pointing electric field; and a half-wavelength behind that, a wall of up-pointing Electric field; etc.",
"Perhaps this will help;",
"http://en.wikipedia.org/wiki/File:Plane_Wave_3D_Animation_300x216_255Colors.gif"
] |
[
"A wave in water isn't technically a physical thing; it's a perturbation of the water's surface that carries with it certain information like frequency and amplitude. Sounds waves are perturbations of the density of air. Electromagnetic waves (photons) are similarly perturbations of the EM field. It's been a long time since physics for me, but I think the analogy holds. It's a bit difficult to visualize, since most people have a hard time conceptualizing what exactly a field is. ",
"That's about the limit of how helpful I can be. I'm hoping someone with the appropriate background can help explain fully. Hope this helps."
] |
[
"Why are wind turbines the height they are?"
] |
[
false
] |
[deleted]
|
[
"Also as you have a longer blade, you are going to have more weight and stress on the joints. You are ultimately limited by the strength of the material. Nobody wants their blades snapping off. Same goes for the height. Too high and the torque from winds could blow it over. In this case, you could use tougher materials and a larger base, but cost increase vs power gain probably makes this prohibitively expensive."
] |
[
"As the wind blows across the surface of the earth, something called a boundary layer is formed, and wind speed within the boundary layer is lower than outside of it. Depending on the terrain, that layer can be 100 meters or more thick, but it is usually less thick. Wind turbines need to get out of the boundary layer in order to operate in clean air stream, so they need to go higher. \nBut the higher you go, structural loads on the column increase, and so does the weight and cost of the apparatus. As for the blade length, if they are too short, their surface area is too small, so is their Reynolds number so it isn't efficient. Go too long for the blades, and they need to be heavier so it takes stronger wind to turn them, and also you start getting aeroelastic phenomena which means you have to strengthen them even more, thereby making them heavier. \nAnd size isn't really an industry standard, it depends on location, usual wind speed, etc."
] |
[
"Increasing the size of the blades also increases the weight and could make it take stronger winds to push the blades. They probably did a lot of studies on the aerodynamics of the blades to find the ideal blade size to try to maximize the efficiency. The height is also likely determined by a similar process to determine the ideal general height needed to put the blades into some stronger wind currents while also being able to keep the costs of the supports down to a level that makes the technology more affordable for use."
] |
[
"What exactly causes the skin to itch?"
] |
[
false
] | null |
[
"unmyelinated tactile C fibers under your epidermis that are sensitive to mechanical stimuli and histamine."
] |
[
"sorry. There are different types sensory nerve fibers in and under your skin that are in charge of letting you brain feel touch, heat, pain, itch...etc. The type that conveys itch are the slowest (type C) type of fibers, so you feel an itch a lot slower than say, when something touches you. ",
"The reason that an itch can be \"persistent\" even after the cause has been removed is because they respond to the release of a cytokine call histamine, which is something your tissues gives off when it becomes irritated. A cytokine would stay in the general vicinity a lot longer than tactile stimuli, causing the itch to last a long time.",
"Also, C fibers have a larger receptive field when they travel to the brain, and histamine, like all cytokines would diffuse to the surrounding area, which means it may be harder to pinpoint the exact location of an itch, instead of just scratching in the general area."
] |
[
"I should maybe take this question to ",
"/r/explainlikeimfive"
] |
[
"Why are Saturn's rings nearly planar? Are all planetary rings planar for the same reason?"
] |
[
false
] | null |
[
"An interesting question, say you start with a moon (which is what saturn's rings started as) and you break it up into lots of pieces, either by a big collision or by tidal forces. These pieces will all be orbiting Saturn in a big thick ring made up of particles with some bulk motion (the same as the old moon had) and a random distribution of momenta. Now what flattened out the rings was collisions between these particles, take two particles:",
"http://i.imgur.com/vc4yM.png",
"Collisions will happen between two particles one coming from below the disk plane and the other from above, after the collision momentum is conserved and the \"out of plane\" components in general will reduce whilst the the momentum in the bulk direction will remain. Over millions of years eventually the \"out of plane\" momentum all but dissapears and the particles are left in a very very very very thin disk.",
"Remember, this all relies on the \"out of plane\" momentum starting off 0 which is the case for a moon that broke up into the ring debris. This moon had it's orbit in the same plane that the rings take now.",
"As for do all planets with rings have very planar rings? If they came from a moon and they have had enough time then yes. ",
"As an aside, the beautiful patterns come from tidal forces and resonances from all of Saturn's other moons."
] |
[
"So the fact that it is planar suggests all of the inner rings were formed by one body? Are there any bodies with two intersecting ring formations?"
] |
[
"We have 8 planets, 4 of them have rings, none of them have 2 intersecting sets of rings. As for a general rule, there is something stopping this. Remember that the two rings constantly orbit so the intersection point would have collisions between the two rings that would scatter the ring debris in pretty much any direction."
] |
[
"What was the Amazon like when the Sahara was still green?"
] |
[
false
] |
The sandstorms from the Sahara are cited as a contributing factor to how big the Amazon is because of all the mineral nutrients that are carried in the sand to Amazon soil (and North American soil as well). Well what was the region like a few thousand years ago when those sandstorms weren't happening? Was it it's own dessert? Or did the Amazon river support a river plain like the Mississippi River basin in the US and Canada?
|
[
"I think you are misunderstanding what people mean when they say that nutrients are in short supply in Amazonian soils (or other rainforest soils, for that matter).",
"It is not that the rainforest happens to emerge in a nutrient poor region and needs an external inflow of nutrients in order to survive.",
"Rather, because water and sunlight are so abundant, mineral nutrients become the limiting factor on how much life can grow. As a result, the rainforest grows until it hits that limit - which is when the nutrients in the soil are basically all absorbed and all meaningful nutrients are in the bodies of living plants. At this stage, new plants cannot grow until an existing plant dies and decomposes, releasing its nutrients back into the soil.",
"This dynamic would still hold true if the amount of nutrients were much higher, and it would also hold true if the amount were much lower. The thing that changes is how tall and dense the forest can grow before it hits that limit. ",
"If the nutrients from the Sahara were not present (which is a massive amount), the Amazon would probably not be as tall or as dense, but it would still be a massive rain-forest. "
] |
[
"The \"Green Sahara\" has to be taken with a grain of salt. It was never a climax forest but has varied between extreme desert that it is today and open savannah grassland in different climate periods. The Amazon forest has also grown and shrunk. ",
"This diagram",
" shows some of the variations between both of them over the past 20,000 years. This was taken from the following science article page\n",
"https://wileyearthpages.wordpress.com/2017/01/13/amazonian-forest-through-the-last-glacial-maximum/"
] |
[
"I am pretty sure if you took the 27 million tonnes of nutrients that come directly from the Sahara away, the rainforest would not survive. In fact, nutrients are in short supply in amazonian soils, thus the forest depends on the nutrients brought in by the wind to survive. NASA released an entire study on it: ",
"https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL063040",
" "
] |
[
"Why does it take some people longer to achieve an orgasm?"
] |
[
false
] |
To elaborate, what are the differentiating factors (physical vs. mental) that determine how long it takes for a male or female to achieve an orgasms? Like, if there was a scientific formula, what would it look like?
|
[
"Premature ejaculation in men is thought to be related to increased number/increased firing of sensory/excitation cells on penis. One of experimental approaches for plastic surgeons to deal with that problem was to surgically scrape the shaft for some of them. I cant really quote you the success rate though.",
"Orgasms are an insanely complicated manner, with factors like is para- og sympathetic nerve system, hormones, transmitters, emotional state, stress, anatomy, age, life experience, included. Plus any number of yet unknown factors. Our research on brain and functions like orgasms is rather at its beginning. We are not even yet sure why females evolved to have orgasms, as bad as it sounds (there are many theories but no consensus) "
] |
[
"Yeah, let's get down to the obvious practical things. There are so many little things:\nHow turned on are you?\nHow much lubricant?\nRhythm, pressure, position",
"Many medicines affect orgasm: Anticholinergics, antidepressants are very common. \nMedical conditions themselves also cause issues, whether it's decreased blood flow from small vessel disease (sickle cell, atherosclerosis) or damaged nerves (diabetes, trauma). "
] |
[
"Yeah, let's get down to the obvious practical things. There are so many little things:\nHow turned on are you?\nHow much lubricant?\nRhythm, pressure, position",
"Many medicines affect orgasm: Anticholinergics, antidepressants are very common. \nMedical conditions themselves also cause issues, whether it's decreased blood flow from small vessel disease (sickle cell, atherosclerosis) or damaged nerves (diabetes, trauma). "
] |
[
"Does anyone have info about this infrared image, as seen on Google Sky?"
] |
[
false
] |
To the left, the large purple and black image that only appears in the infared view?
|
[
"I think the black is just indicating that that region of pixels is brighter than the dynamic range of the sensor."
] |
[
"This is correct. The sensor is over saturated just as a digital camera would be in the visual spectrum if the sun was in the photo. The IR colorings are false so black in that photo equates to a heat that is at the peak or higher than the sensor can handle."
] |
[
"I think what you are seeing is an effect known as blooming. The area of over saturated sensors is larger than the actual area emitting the offending heat. So sensors near the offending ones are also over saturated and thus you are missing what is in that transition area. This can happen both in the electronics as well as due to lenses, etc."
] |
[
"How do we get vitamin D from sunlight?"
] |
[
false
] |
There are no particles or molecules coming from the Sun, unless you take the photons into account.
|
[
"It's really pretty straightforward conceptually. Vitamin D is a breakdown product of cholesterol (basically, it's a modified cholesterol molecule with a couple of its carbon ring structures broken open). These changes happen to cholesterol molecules in the skin when they get exposed to sunlight, or, more specifically, to some of the more energetic UV wavelengths present in sunlight at ground level.",
"While teleological explanations of biochemical processes can be dangerous, I'll share one of my speculations here: I've always thought it was a clever adaptation that the signaling molecule that tells the body to recruit calcium from the gut/diet for use in bone-building and maintenance is generated when we are active in the sunlight (i.e. during parts of the year when we are both in need of stronger bones and likely to be consuming a nutrient-rich diet)."
] |
[
"I wanted to ask this question for a long time. ",
"Glass blocks UVB right? So If I'm driving my car with the windows up and the sun on me, there is no Vitamin D produced out of the UVA?"
] |
[
"I wanted to ask this question for a long time. ",
"Glass blocks UVB right? So If I'm driving my car with the windows up and the sun on me, there is no Vitamin D produced out of the UVA?"
] |
[
"Why does neutron capture by nitrogen-14 in the atmosphere lead to carbon-14 instead of nitrogen-15?"
] |
[
false
] |
says "Carbon-14 is produced in the upper layers of the troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms", the reaction being: n + N14 -> C14 + p. Why doesn't this produce N15?
|
[
"That’s not a capture reaction, it’s an (n,p) reaction (transfer or charge exchange). Neutron capture would be (n,γ). ",
"N(n,γ) would produce ",
"N.",
"Carbon-14 could be produced by the capture reaction ",
"C(n,γ)."
] |
[
"In that notation, the thing after the comma is what comes ",
". \"14N(n,γ)15N\" means \"14N plus neutron in, 15N + gamma out. ",
"The actual reaction has a neutron coming in, proton going out. That means the mass stays the same, but the atomic number goes down by one due to the lost charge."
] |
[
"(n,γ) means a neutron is captured and a gamma ray is emitted. You asked why ",
"N(n,p) “capture” doesn’t result in ",
"N. The answer is that (n,p) is not capture, and ",
"N(n,p) produces ",
"C, not ",
"N. In other words, “Why is a blue car not red?”. Because it’s blue."
] |
[
"Does a black hole grow as it absorbs more mass?"
] |
[
false
] | null |
[
"There is a direct correlation between the radius of a black hole's event horizon, and the amount of mass that is contained in the black hole. This is known as the ",
"Schwarzschild Radius",
". As it obtains more and more mass, the radius of the event horizon will continue to grow."
] |
[
"yes, it means the black hole will not consume the universe anymoe than the star from which it originated. It will \"consume\" everything that collides with it though."
] |
[
"No, because the universe is a very sparse place, tons of room between most objects, and is expanding. But they can get VERY big, like 10million times more massive than our Sun, usually in the centers of galaxies. [source: am a PhD Astronomer]"
] |
[
"If CO is called carbon monoxide to differentiate it from CO2, why isn't NO most commonly called nitrogen monoxide, rather than nitric oxide, to differentiate it from NO2?"
] |
[
false
] |
On that note, why is NO most commonly called oxide, rather than oxide? Why isn't NO2 called nitric dioxide instead? Are these all just the result of naming conventions, or do they serve a specific purpose?
|
[
"They are basically naming conventions. Endings like ",
" and ",
" give a clue to the oxidation state of the element in question -- the ",
" ending implies that the central atom is in the higher of two common oxidation states, while the ",
" ending implies that it is in the lower. ",
" and ",
" nomenclature is more systematic but still subject to confusion.",
"Oxides of nitrogen are complicated, and their nomenclature is a mixture of the ",
" and ",
" systems. The three compounds NO, NO2, and N2O are all stable at room temperature. We refer to them colloquially as ",
", ",
", and ",
" respectively. They have very different properties. ",
"You can see how using the name \"nitrogen monoxide\" would be confusing, as it could reasonably describe both NO and N2O. Over time the chemistry community has settled on the current nomenclature for the common nitrogen oxides but largely uses the ",
" etc. system for the less common ones."
] |
[
"The answer is slightly incorrect.",
"Nitrogen monoxide can ",
" refer to NO, as N2O would be referred to as dinitrogen monoxide. The mono- prefix is not explicitly stated for the leading element in these types of compounds. ",
"The explanation on the -ic and -ous endings is correct. This is also used in metals: Copper(I) Oxide is called cuprous oxide while Copper(II) Oxide is called cupric oxide. However, in almost all cases, including with nitrogen, the -ic and -ous endings are NOT the IUPAC preferred names. They are less clear and harder to learn/memorize; the whole point of a name is to communicate what the thing is. ",
"That said, the -ic and -ous endings are used extensively, and it's easy to see why. Saying nitrous oxide is so much easier than dinitrogen monoxide. ",
"(Side note: IUPAC is the official naming organization for all things chemistry. I believe it also does other stuff, but I primarily know them for the naming conventions. Almost everything has a clear and systematic convention which allows for almost any element, compound, or molecule to be named in such a way that you can know the exact thing the person is talking about. This is especially important for organic chemistry where nearly infinite possibilities exist.)"
] |
[
"I see. Thanks for your answer!"
] |
[
"Why does reception change with my TV antenna when I stand close to it?"
] |
[
false
] |
I thought maybe I was just imagining the difference in reception when I move around a room, or touch the antenna with my hand, but I think there really is some sore of effect there. Is my body conducting a signal or something?
|
[
"I don't think the body is a great antenna. It is conductive but has a lot of resistance compared to metals. The wavelength of the radio signal matches the physical length of an antenna rod, (or some multiple of the length). The radio wave resonates only with the matching element length, creating an electrical signal in the antenna, down to the tv. So if you take a rooftop antenna and take off all but one of the rods (elements), the antenna can only receive one frequency (channel), kind of. ",
"Most antennas are receiving a radio signal from multiple directions due to the fact that the original signal has bounced around and hits the antenna from several directions, some delayed, giving you 2 signals that don't exactly match up. When you touch the antenna or move around the room, you may be blocking one of those stray reflections of radio waves in the room, and allowing only one signal to hit the antenna. ",
"If you are talking about a more complicated antenna than just bunny ears; rooftop units or some of those table top units that look like they have wings, are actually designed to reflect the signal from the back to the front elements, creating a stronger signal. Your body may be interrupting, or helping that reflection loop."
] |
[
"Your body acts as an antenna. It's actually one of the best antennas available. "
] |
[
"The antennas are designed to catch radiowaves at some wavelengths. In order to work correctly, they have different elements (conductor rods) that amplify, concentrate or bounce radiowaves, and a conductor that catches the radiowave and sends it to the TV through the cable. But you are made (mostly) of salty water, which is a decent conductor. Therefore you interfere with radiowaves. Also, when you are near an antenna, your body acts as a capacitor near the antenna's elements. That throws off the designed parameters of the antenna, and makes it works in a non-expected way, sometimes better, sometimes worse."
] |
[
"If humans could build an incredibly powerful telescope from earth and view galaxies, stars, and planets up close would you be seeing millions of years in the past?"
] |
[
false
] | null |
[
"Yes; light from 200 light years away left the source 200 years ago."
] |
[
"Only inference. For example, we can now see the ",
"pillars of creation",
", but they may no longer be there because of a possible supernova that was closer to us that we can already detect."
] |
[
"Thanks. So would there be no way of telling what it would be like in the present of the celestial mass?"
] |
[
"If you spun a helicopter rotor that was one-tenth the size, but spun ten times as fast, could you still achieve lift?"
] |
[
false
] | null |
[
"And that is how you clearly answer a question. Thank you."
] |
[
"And that is how you clearly answer a question. Thank you."
] |
[
"Wow that's amazing! Thank you! Really cleared a lot of things up. :)"
] |
[
"What is the loudest sound in the known universe?"
] |
[
false
] | null |
[
"Soundwaves require a medium to propagate, so we can't really \"hear\" interstellar objects.",
"The loudest sound recorded on Earth was \"The Bloop\"."
] |
[
"I would actually argue that the August 27th 1883 eruption of Krackatoa was the loudest recorded (on paper) sound. ",
"It was so loud that even 3000(!) miles away, on the island of Rodrigues, people thought that there was nearby cannon fire. Loud to the point that even 5 days after the explosion air pressure meters (barometers) all over the world were still registering pressure spikes.",
"Source",
"Edit: ",
"Mount Tambora",
" may have been louder, with 4x the energy of Krackatoa. However there seems to be a lack of measurement information about it given that it took place in 1815. This was before the large British presence in the area and much more advanced scientific equipment and record keeping."
] |
[
"Saw ",
"this",
" on Reddit very recently and although there is no mention as to the auditory volume of the black hole's sound waves, the energy that created them is mind boggling and they are the lowest sound ever heard in nature. ",
"In musical terms, the pitch of the sound generated by the black hole translates into the note of B flat. But, a human would have no chance of hearing this cosmic performance because the note is 57 octaves lower than middle-C. For comparison, a typical piano contains only about seven octaves. At a frequency over a million billion times deeper than the limits of human hearing, this is the deepest note ever detected from an object in the Universe.",
"Edit:typos"
] |
[
"If you could travel adjacent to a plane generating sonic booms at mach >= 1, would you hear a deafening roar that is a continuous sonic boom?"
] |
[
false
] | null |
[
"The shock wave that causes the sonic boom is very nearly a physical discontinuity in the air - it's only a few hundred nanometers in length. What we perceive as a sonic boom is the result of this extremely rapid change in pressure across the shock wave. If you are stationary relative to the shock wave, you will not hear it. It must travel over you for you to perceive it as a noise."
] |
[
"It would be like riding a jet ski right on top of a boat wave. That's what a sonic boom is. It's a \"splash\" in the air like a boat making in waves. The single boom you hear as a stationary view is just the wave hitting you and moving on "
] |
[
"You wouldn't hear anything if your were next to the plane because you'd be traveling faster than or as fast as the the sound wave that trails the other plane. If you were a bit back say in the pressure wave wake of the plane, I suspect it would be very turbulent, deafening and more than a little dangerous."
] |
[
"Why aren't there uuu and ddd nucleons?"
] |
[
false
] |
[deleted]
|
[
"I will never achieve a level of education high enough to convince me that what you just said isn't gibberish"
] |
[
"I will never achieve a level of education high enough to convince me that what you just said isn't gibberish"
] |
[
"Ground state spin-1/2 uuu and ddd baryons are forbidden by the Pauli exclusion principle"
] |
[
"How does medicine cure depression?"
] |
[
false
] | null |
[
"Disclaimer, I'm on mobile so I won't include any sources. ",
"Depression is a really crazy disease that can have a lot of different symptoms. You can have deficits in cognition, motivation, motor activity, eating, sleeping, but then also the guilt, feelings of worthlessness, and on and on. This points to depression being a state where a lot (or at least multiple) of systems in the brain aren't working properly, because no one area or circuit controls each of these things. Moreover, we're beginning to link non-brain-centered pieces to depression, like the immune system, or the microbiome in the gut. Depression is insanely complex because of the huge number of factors (both internal and external) that can play a role in propagating the symptoms. ",
"That said, we don't really know how medications or treatments work to alleviate the symptoms, if at all (around one-third of patients don't respond to SSRIs, the typical first line of treatment). We know that SSRIs are active in the brain immediately, but their therapeutic effect isn't felt for weeks after taking it - this doesn't make sense, and points to some downstream target beyond of the inhibition of serotonin uptake. We also know that non-standard, more experimental treatments like ketamine, or psilocybin mushrooms, or deep-brain stimulation can help treat depression. How? - there are a lot of theories, but no one's totally sure. Part of the trouble in nailing down a common mechanism is how diverse the symptoms of depression can be, like I said earlier. There's some thought that depressed patients should be broken into groups based on their symptoms so as to identify what makes one group different from another, and if (and how) a certain med is better for one of them. ",
"This is really rambly, sorry."
] |
[
"The truth is, we don't really know. Some compounds are known to help through \"interactions\" with certain brain receptors, and that's about it. I say that in quote marks because the pharmacokinetics are not well understood. Some drugs seem to work for one person, but not for another. And for the people in which they are effective, the results are varied, with some seeing vast improvements and, essentially, a cure; while in others the effect may be very mild even at the highest doses (e.g. suicidal thoughts stop, but the general depression persists). ",
"It's an incredibly tricky and difficult topic, because it is thought that depression is a disorder that doesn't just affect a particular molecule or system, but affects the entire brain. This makes investigating it very slow and painstaking, as each proposed part of the brain circuitry must be analysed with different parameters of each of the other parts. Again, this varies person to person. ",
"Much like cancer, it is not unheard of for depression to be considered a collection of disorders, all with different characteristics but leading to similar symptoms. ",
"Not much is known about antidepressants, even from the basics. For example, it is not known why some antidepressants take multiple weeks to begin working correctly, and why initially they may cause deterioration in the condition (although, some decent theories are currently being tested)."
] |
[
"Please read this : ",
"https://www.theguardian.com/society/2019/jun/03/mental-illness-is-there-really-a-global-epidemic",
" ",
"and this : ",
"https://www.theguardian.com/science/2018/apr/26/gene-map-for-depression-sparks-hopes-of-new-generation-of-treatments"
] |
[
"Will occur refraction if there's a change in the overall luminosity?"
] |
[
false
] |
[deleted]
|
[
"Can you provide the link to the site? Is it a physical demonstration or just a description of something?"
] |
[
"Here",
" is the link, completely in portuguese. ",
"It's a site focused on science fairs projects, some have a complete description, this one is brief and say",
"\"Observe agora a caixa preta e verá que o orifício é mais negro que a própria caixa, destacadamente. Leituras a respeito do ",
" resolvem o porque da questão.\"",
"translating to english",
"Now look at the black box and you'll see that the hole is blacker than the rest of the box, outstandingly. Readings about ",
" will solve the question\"",
"I could understand if the light was absorbed, but since it changes direction, I got really confused. And if you let the laser-bean touch edge of the hole, you'll see it at the back of the box, in an almost straight line. "
] |
[
"Where does it describe the behaviour of the laser like you mentioned in your post? Or did you conduct the experiment yourself and make those observations?",
"The experiment in the link you provided is just an experiment showing how a blackbody can be modeled as a cavity in a box. "
] |
[
"Why are there no computer simulated drug trials?"
] |
[
false
] |
We have computer simulations for car crash tests, atomic explosions, black holes, even the whole universe. Why can't we just create a model of the human body and use it to research the effects of new drugs?
|
[
"Modeling an entire organism, even a bacterium, is orders of magnitude more complicated than our most advanced computer simulations of biological systems. Today, we can model in explicit detail the dynamics of a large protein for a few microseconds, and even a simulation of that scale requires an enormous amount of time on a supercomputing cluster. The results of the simulation itself are in doubt, too, since any computational model at that level is an approximation of the true chemistry. Developing accurate models is a busy and complicated field of research when it comes to biochemical simulation, and some scientists still don't trust any results of computer simulations for this reason. ",
"As far as drug trials, we can still have a hard time accurately simulating the interaction of a single molecule of a drug with its target protein when we already know what the result is, let alone trying an unknown drug on a model of a complete organism."
] |
[
"We do, sort of. Complex proteins interactions are simulated with computers, but it's not really worth it to simulate the rest of the human body because...",
"-It takes a massive amount of computing power",
"\n-It's unlikely any simulation would be accurate enough to verify the actual effects of the drug on the human body",
"\n-The people they use in drug trials are suffering from the disease it's meant to cure. For some people, the trials are the only chance they have of successful treatment.",
"As for those other things you mentioned, simulations are the best available data we have. We can't just create a black hole in a lab to study it directly."
] |
[
"It's unlikely any simulation would be accurate enough to verify the actual effects of the drug on the human body",
"There's the crux. GIGO. Garbage in, garbage out. We just can't accurately construct a model of what's going on inside the body. We have simplistic models that help predict, but the real thing is so complex we can't accurately tell a computer all the details, since we don't know."
] |
[
"In E=MC2 - how does it work that you can multiply meters per second by kilograms and come out with joules?"
] |
[
false
] |
I was just watching a BBC show about "Beautiful Equations" and this is one of the famous equations that it discussed. However, this question still lingers in my mind. In most everyday mathematics that one does over the course of a normal life, the units are the same throughout the equation. What makes the kilogram, the meter, the clock second, and the joule special - so that you can convert from one to the other in this manner?
|
[
"Joules are defined as a kilogram * meter",
" /second",
"A meter is defined as the distance that light covers in 1/299,792,458 of a second. A second is defined as the amount of time it takes for a cesium atom to oscillate 9,192,631,770 times. A kilogram is defined as the amount of mass in a silicon cylinder in France.",
"Basically, theres nothing special about the joule, the second, or the kilogram. They're all defined in some way."
] |
[
"This. Even from the start, the units of energy are Work = Force * distance\nSo, J = N * m. But F = m",
" m/s",
" Put it all together and J = N * m = kg * m",
" /s"
] |
[
"In fact, the equation can be elegant and simple, because the newton itself was invented in the process of drawing up equations such as this one, right?",
"The relationship between the masses of objects and their gravitation wasn't created by Newton; the inverse-square relation exists whether we knew it or not.",
"Newton's equation includes Big G, the universal gravitational constant. This constant accounts for units such that you can construct Newton's equation in any applicable units and only have to modify the constant with the appropriate conversion as well. It's basically a system-dependent unit conversion factor.",
"The equation has the same inverse-square form no matter what unit system you use, much like most laws of physics. There's nothing special about the meter or the second except that we've calculated constants using them; giving the illusion that the meter and the second are somehow privileged units."
] |
[
"What increases fluid intelligence?"
] |
[
false
] | null |
[
"This is actually a question the field struggles with. TL;DR: Practicing helps, but only for what you practice.",
"There are plenty of studies out there showing enhancement but the consensus seems to be that one cannot increase overall general fluid intelligence (what's sometimes referred to as \"Gf\") but one can train to get better at specific tasks (think about practicing/playing any sort of game - over time you get better); that improvement, however, does not appear to transfer to novel things (e.g. getting good at poker doesn't mean I'll be good at blackjack). ",
"The first few google scholar hits: ",
"link 1",
"link 2",
"link 3"
] |
[
"Not entirely true, There are multiple studies showing positive results using Dual-n-Back 20 sessions, 4 or 5 times per week."
] |
[
"Interesting - I'd love to read them. Do you know if it's improvement on n-back tasks, or does it generalize to other things as well (and if so what?)"
] |
[
"How can we imagine two (or more) temporal dimensions?"
] |
[
false
] |
I know that we live in three spacial dimensions and one temporal, but we are able to imagine how a four dimensional cube looks like, so can we also imagine how two temporal dimensions would work?
|
[
"I'm not an expert here, but ",
"physicists have considered cases with this possibility.",
"Also, if anyone posts the \"imagining the 10 dimensions\" video, that is simply not based on science. It's a fiction. A popular internet fiction."
] |
[
"Typically, when we talk about physics and equations of motion, we mean equations that allow us to predict a particles location at a later time if we know it's location, velocity, etc. at some earlier time.",
"But if we have two temporal coordinates, say t and u, on top of spatial coordinates x,y,z, well then it doesn't make sense to ask where a particle will be at time t=7, say, because maybe it never experiences time t=7. Maybe that particle only exists on the circle t",
"+u",
"=25. So instead we would have to use another parameter, not a dimension but a measure of time as experienced by the particle. Call it arc length, call it proper time, but whatever you call it, let's label it s. Now we say, starting from point (x1,y1,z1,t1,u1), where and when will our particle be after it experiences 1 second of proper time? And then we just look at the values of those 5 variables after 1 second of arc length / proper time. ",
"This is not terribly helpful for understanding multiple temporal dimensions.",
"Up to bat next is relativity. As it turns out, almost the entire structure of special relativity - the various effects of travelling near light speed, the constancy of the speed of light, etc. - arise from something called Lorentz transformations, which in turn comes from the metric of space-time. ",
"A metric is a fancy word for \"version of the Pythagorean theorem.\" You're familiar with the Pythagorean theorem - the hypotenuse of a triangle, squared, is the sum of the square of it's other two sides. We can use this to get a distance formula for two-dimensional space. If you have two points, and the distance between them is ds, and the difference of their x-coordinates is dx, and the difference of their y coordinates is dy, then their distance can be found with ds",
"=dx",
"+dy",
".",
"It turns out this works in three dimensions. If you set up three mutually perpendicular axes, the distance between two points is ds",
"=dx",
"+dy",
"+dz",
".",
"When we talk about four dimensions, where one is time, we stop looking at distance and start caring about \"space-time interval.\" The formula for this is ds",
"=dx",
"+dy",
"+dz",
"-dt",
". First of all, note that for two events that happen at the same time from your point of view, the space-time interval is just the distance in space between those two events. But if they happen at different times from your point of view, then the space-time interval starts to get smaller. In fact, if dt",
"=dx",
"+dy",
"+dz",
", then the space time interval between them will be 0, even though they're different events! ",
"To construct a space-time with TWO timelike dimensions, we simply invent a 5-D construct and add another temporal coordinate u. Now the metric looks like ds",
"=dx",
"+dy",
"+dz",
"-dt",
"-du",
".",
"Let's take a moment and go back and examine a funny expression I used earlier, Lorentz transformations. What are those? Well, to answer that I'm going to step back again and talk about 3D space, without any time component. When we rotate this space, a single point traces out a circle - try and picture that in your head. What's more, if we stretch and rotate at the same time, a single point traces out a sort of stretched circle, called an ellipse. For this reason, the kinds of transforms you can have of this space, and hence the equations you can have that describe the motion of a particle as the space rotates and stuff, are called ",
".",
"Now, when we add that time dimension, with it's negative value in the metric, the things we can do to the space aren't necessarily elliptic any more. Some \"rotatons\" actually end up tracing out hyperbolas - the kind of curve you see when you plug 1/x into your graphing calculator. For this reason, the equations of motion here are called ",
"Now, when we add a SECOND time dimension, the kinds of rotations we can do are called \"ultrahyperbolic.\" That doesn't mean they trace out funny-looking ultrahyperbolas, it's just a name. The fact is, it's not possible to say what a particle will trace out; ultrahyperbolic equations are not predictable in a single variable. ",
"So remember earlier when I said we could just trace along some parametric descriptions for a certain amount of proper time to get the location of a particle after 1 second of proper time? It turns out there really isn't any nice way to figure out what those parametric equations are. And if you managed it anyways, it wouldn't really matter, because the particle you are observing will probably have a different proper time than yourself, so knowing where and when it will be after it's experienced one second doesn't tell you anything about where and when it will be after YOU'VE experienced one second.",
"There's an interesting exception to the point that multiple time dimensions lead to unpredictability. Suppose we lived in a universe with three time dimensions, but only one spatial dimension. As it turns out, it would be perfectly predictable, but you'd use space as the independent variable and the time coordinates as the dependents. Everything would be flipped - you could never travel slower than light speed. "
] |
[
"God, I hate that video so much. People become genuinely interested, go search to learn about higher dimensions, and instead they get that nonsense. ",
"For laymen, I generally post ",
"this video",
" from Cosmos in response to that video."
] |
[
"Has long term vegetarianism led to any discernible genetic differences in South Asian populations?"
] |
[
false
] | null |
[
"(layman here)",
"I would imagine there's not really enough data.",
"First of all, \"long term\" vegetarianism isn't that long of a term in a biological sense. I mean, King Ashoka was 270BCE?",
"Second, even in societies where the main religion has vegetarianism as a tenet, not everyone is vegetarian. I would say it's pretty rare for even a majority of the population to be 100% vegetarian, with most (by number) of them at least eating goat or fish.",
"I'm vegetarian myself. Vegetarianism is a luxury afforded by civilization. It requires the logistics that are only found in a society with a large amount of agriculture and trade. Mainly soy or lentils and legumes. When people get hungry, and I mean ",
", the principles go out the window and people eat what they must."
] |
[
"Without the current system of global infrastructure and technology it would be night impossible to locally obtain everything that you need for a vegetarian diet.",
"In addition, any civilization without agriculture would likely be unable to grow or thrive because of the immense amount of time they would need to spend gathering and foraging for food. Our brain uses a ton of energy (25% of our total calories?) and meat is the only realistic way to efficiently maintain the caloric intake we need. It is theorized that the ability to cook meat contributed greatly to our brain evolution, since the net calories from cooked meat are much greater than that of raw meat.",
"There is probably genetic change over thousands of years, but it will be coupled with all the other hosts of genetic changes that happened at the same time, and so may be hard to separate. Humans are also really good at overcoming selective pressures. For instance, over time evolution may cause certain humans to digest fiber for added calories from plants, but before that happens, humans will overcome the general lack of calories through social changes (e.g. eating different foods such as nuts/soy vs grasses and greens), and so any selective pressure for that mutation will likely be lessened, which leads to less genetic change."
] |
[
"I absolutely agree. I'll add to that by saying that vegetarianism would have negative health consequences for some people if it weren't for things like iron supplementation, etc. That said, in the modern world enmass meat eating has its problems in terms of the environment and logistics because of things like the volume of grazing land required for cattle. There are prominent groups who argue that a diet that includes insects would solve a lot of problems and be the best of both worlds (",
"http://www.the-scientist.com/?articles.view/articleNo/34172/title/Why-Insects-Should-Be-in-Your-Diet/",
").",
"There was a program here in the UK that examined an animal's herbivore diet (basically raw veg) in humans and they literally had to eat all day to get enough calories and by the end of the day, their jaws hurt, etc so it could be said that a 100% vegetarian diet is unnatural for humans."
] |
[
"Why does water have no taste or lack thereof?"
] |
[
false
] |
I asked my Geosystems teacher this question and he didn't have answer so I thought could help me :)
|
[
"Because you don't have taste receptors for it. There wouldn't be much point in having them, since your mouth is nearly always full of water. ",
"However, there are animals who can smell water, and they use that sense as a method to find sources of water in dry climates. Though I can't find a good source for it, it is said that elephants can smell water from several kilometers away."
] |
[
"Spitballing here, but probably by wind direction? How else would anything locate the source of an odor?"
] |
[
"Spitballing here, but probably by wind direction? How else would anything locate the source of an odor?"
] |
[
"Why can't we handle division by zero the same way we handle the square root of -1?"
] |
[
false
] |
Define 1/0=m Three dimensional space with axes Real, Imaginary, m Using m whenever division by zero occurs may allow carrying through proofs until m cancels. Identities: If m = 1/0, 0*m=1 1/m = 0
|
[
"Because allowing division by zero results in ",
"completely broken mathematics",
". Let's just do some simple algebra with what you've proposed:",
"m = 1/0\n1/m = 0/1 Take the inverse of both sides\n2 * 1/m = 0/1 * 2 Multiply both sides by 2\n2 * 1/m = 0 * 2/1 Rearrange the right side\n2 * 1/m = 0 Anything times zero is zero, so eliminate the 2/1\n2/m = 0 2 times 1 equals 2\n1/(2/m) = 1/0 Take the inverse of both sides again\n1/(2/m) = m We already defined 1/0 as \"m\"\n1/2 * m = m 1/(1/x) = x for any x\n1 * m = 2 * m multiply both sides by 2\n1 = 2 Therefore, 1 equals 2.\n",
"You can modify that proof to prove that any number is equal to any other number. Which makes mathematics which allow division by zero completely pointless.",
"On the other hand, introducing complex numbers (numbers with an \"imaginary\" component, which is a terrible name, but we're stuck with it) results in consistent mathematics, without contradictions or paradoxes. ",
", there are some problems which ",
" have solutions, but are not solvable using just \"real\" numbers. I ",
" recommend watching ",
"this video series",
" which introduces complex numbers in a very easy-to-understand way, in the context of algebra and history. I personally learned a lot from these videos.",
"Edit: added comments to make the math easier to follow",
"Edit 2: Come on people, let's ease up on the downvotes for follow-up questions and comments. This is a subreddit for learning and teaching."
] |
[
"Yes, you can make it say 0 = 0, but you can move terms around to make it say ",
". That's the heart of the problem: by using completely valid algebraic operations, I came to a contradiction when I allowed division by zero. Allowing division by zero makes all of algebra break down."
] |
[
"Let's go from your 1/m = 0 identity. Adding 1/m to both sides, we have 1/m + 1/m = 1/m. Now, multiplying both sides by m, we have 1 + 1 = 1. So you can see how such a system yields inconsistent results pretty quickly.",
"To dig a bit further more into where the problem lies, recall the definition of division: k = a/b if k is the ",
" number such that kb = a. So, setting b to 0, we get that whatever a/0 is, it is the unique solution to 0*k = a. Now there are two possibilities: either a=0 or a≠0. If a≠0 then there can be no k that satisfies this equation—it is easy to show that in any ",
"sensible number system",
", 0*anything=0. On the other hand, if a=0, then ",
" k solves this equation. Either way, by defining a number a/0, you're asserting that there is a ",
" solution to 0*k=a, which is impossible. Assigning a number to be equal to a/0 is inherently contradictory by the definition of division.",
"As a comment on the difference your idea and defining i = √(-1), it's a little different. The fundamental properties of number systems",
" imply that the equation 0*k=0 holds for any k in any number system. But it turns out (and it took us awhile to be sure about this) they do not preclude a solution to x",
" = -1. In the real numbers there is no solution to that equation, but it turns out that introducing a solution is completely consistent with all the rules about what we call numbers systems. There's nothing in the definition of squaring which forces a number squared to be positive, whereas it is the very definition of division itself which prevents division by 0.",
" ",
"rings."
] |
[
"Flair:'Maths' If the limit of ratio A(N+1)/A(N) in the Fibonacci sequence approaches the golden ratio, how is it an irrational number?"
] |
[
false
] |
If the ratio of two aleph-null sized numbers is still irrational then my question is trivial. However it still seems that there exists a concept of a number whose rational can be expressed as an irrational number but that might be common knowledge. Edit: sorry for the screwed up title I thought the flair: 'maths' would be the mathematics flair.
|
[
"The limit of a sequence of rational numbers isn't necessarily (or even most times) a rational number, since the set of rational numbers isn't ",
"complete",
". Another example of a sequence with that property is the one indicated in that page, that converges to sqrt(2)."
] |
[
"The sequence {A(n+1)/A(n)}, as n goes from 1 to infinity, may approach an irrational number. ",
"Just because a sequence of values is composed entirely of rationals, that does not mean that the limit is rational.",
"In fact, one of the ways to define the real numbers (ie, the rationals and irrationals together) is as sequences of rationals numbers. (Actually, it's equivalence classes of such sequences - two sequences can converge to the same limit and hence we say the class which contains them both is the real number).",
"Now, I'm not sure what you're talking about with this aleph business. If you're asking whether we are ever dividing infinite numbers by each other, no, we never are. One would never write (aleph-null)/(aleph-null), that's not how these symbols are used. ",
" For any tiny value you care to give me, I can find an n such that A(n+1)/A(n) is that close to the golden ratio. For example, you say, \"I bet you can't get it to within 1/1000000 of phi!\" and I'll say, \"Oh, yes I can!\" and I'll do some math and come back to you with an n value - maybe a trillion or something, who knows - such that A(n+1)/A(n) is within 1/1000000 of phi. And what's more, for every higher number m>n, A(m+1)/A(m) is even closer to phi than that!",
"That is what we mean by limit.",
"I think the confusion stems from thinking of aleph-null as a number. It's not. The cardinality of rational numbers is aleph-null - countable infinity. But it isn't a number itself, it's a measure of the size of a set of numbers. The cardinality of all real numbers (rational and irrational together) is a \"higher\" infinity, 2",
". The continuum hypothesis states that this is in fact the NEXT highest cardinal, aleph-one. The continuum hypothesis is neither required nor forbidden by the standard rules of mathematics as they are used today."
] |
[
"A rational number is a number that can be represented as a ratio of integers. Each element in the sequence A(N+1)/A(N) is a rational number, but the golden ratio is not any element of the series, it is only the limit of the series.",
"You seem to be trying to say \"well, A(Infinty) is an integer, and A(Infinity+1) is also an integer, so A(Infinity+1)/A(Infinity) is a rational number\". This does not make mathematical sense: There is no integer that corresponds to A(Infinity), and there is not even a limit of the sequence A(N).",
"This is actually not that strange. In fact, all irrational numbers can be expressed as the limit of a sequence of rational numbers (this is one way that you can define the set of real numbers, as the limits of all sequences of rational numbers)."
] |
[
"How do cruise ships prevent almost all the rocking from the sea?"
] |
[
false
] |
The only time I felt it was during a storm, and it was much less than I expected.
|
[
"Size",
"Design - specifically metacentric height",
"Roll stabilizers - special fins that help counter-act roll forces as the ship is underway",
"Active ballast control - computer control ballast system that moves mass around to reduce the effect of roll"
] |
[
"The ship has in some ways a resonance frequency about how quick it can rock back and forth. If the waves are small enough, their frequency is not right and the ship will simply ignore it. Its too slow to respond to those quick variations in forces. They require slower stronger forces created by bigger waves."
] |
[
"Used to work on a cruise ship. The boats are very large, so they take a decent amount of time to rock and back forth. The other part of the equation is that the further you get from the center of the ship, the more pronounced the motion is. You'll notice the promenade deck is on deck 7 and most of the things are nearer to the center. My cabin was almost all the way to the bow of the ship, and you noticed the movement of the ship very much. Also, I worked on the top deck nightclub at the very back of the ship, and in rough seas it was difficult to walk."
] |
[
"How do our eyes see the stars much better than a camera?"
] |
[
false
] | null |
[
"They dont, if you could remove an eye and plug it into a printer, open the shutter for a tiny fraction of a second the picture you would get would be more or less jack. ",
"Now take a camera, have the shutter open and close about once a second for minutes, have a powerful computer that stabilises the image, adjusts light sensitivity, and plugs in gaps by recreating complete parts out of imagination/expectation and you would probably get a much better image than our eye. ",
"Its obviously not the hardware, its the software."
] |
[
"take a camera, have the shutter open and close about once a second for minutes, have a powerful computer that stabilises the image ",
"Your description of camera + software explains how a camera can capture very dim light sources (potentially better than the human eye), but it does not explain how the eye without long exposure time and without image stabilization can detect sources that are more dim than a (consumer level) camera in the same circumstances (no long exposure time and no image stabilization). ",
"Its obviously not the hardware, its the software. ",
"Clearly cameras can benefit from software (and from long exposure time), but the eye does not do long exposure time nor does the brain have an equivalent of the required image stabilization software (it only does relatively short duration stabilization). ",
"I don't know how sensitive the sensor of an average digital camera is, but it may well need more than minimum 5 to 14 photons entering the lens in order to be detected by the sensor (a few photo receptors each being hit by 1 or 2 photons), as the human eye does. ",
"https://en.wikipedia.org/wiki/Absolute_threshold#Vision",
" ",
"So the difference wrt sensitivity between eye and camera (with same exposure time) probably is in the hardware and not in the software. "
] |
[
"The sensor in a camera might be bigger than the sensor in your retina, but it’s trying to capture a whole scene. Hold your thumb up at arm’s length - that’s about the size of the image your macula captures in any given instant. The macula is the part of your retina that is densely packed with cone cells, which are the cells that give you high resolution colour vision.",
"The rest of your retina is largely rod cells, and those cells are what allow you to see the stars at night. They don’t discern colour - most of the colour you perceive at night is just you remembering or inferring - but you have a ",
" of them. Over 100,000,000. That’s a lot more than the number of sensing pixels in any camera.",
"But hang on - more pixels doesn’t make better cameras. We all know that. The more information you try to suck out of a camera’s sensor in less and less time - in other words, the higher the ISO setting - the noisier the image gets. Why don’t our eyes have that problem? At very very low levels, they actually do! In a pitch black room, the random noise from misfiring of come and rod cells actually becomes sort of visible. You can vaguely perceive colours and shapes. But mostly, we don’t experience the same levels of noise as a CCD because our eyes are biochemical, not electrical. The noise on a CCD is almost entirely due to its mechanism of operation, not a physical characteristic of the light entering through the lens.",
"But hang on! What about film cameras? Those are entirely chemical, and they’re even worse than digital for low light! Yes, but think about what they have to ",
". The film is a camera has to undergo a chemical reaction significant enough to change its colour (or its crystal structure) from ",
". There’s no external source of power priming the film to be ready to change, it has to do all the work on its own. The activation energy for film has to be low enough that it can be triggered by visible light, but high enough that it can’t be triggered by heat or movement. (Remember how you used to store film in the fridge?) Meanwhile, all your cone and rod cells have to do is leak some neurotransmitter to the optic nerve, which will happily amplify and clean up that signal before it gets sent off to the brain.",
"I hope this all makes sense, it’s 3:30am and insomnia is writing this post a bit. Check ",
"this PetaPixel article",
" for some more info on cameras versus eyes."
] |
[
"Is it possible to set something on fire by pouring boiling water on it?"
] |
[
false
] | null |
[
"yes, if it is a water reactive substance like calcium carbide water will react exothermically and ignite the gases produced"
] |
[
"To expand on this, there are a myriad of materials we call Pyrophoric which spontaneously combust when treated with air. Typically the reason they do combust is moisture in the air. The most common example is sodium metal."
] |
[
"Besides a chemical reaction with water itself, anything that has an ",
"autoignition temperature",
" below 100 C could theoretically be ignited by heating it with boiling water. However, if the material did not react with water and you poured the water on top of it you might simply smother any flames that would be normally produced."
] |
[
"Do mitochondria undergo secondary endosymbiosis?"
] |
[
false
] |
I've frequently read about chloroplasts undergoing secondary endosymbiosis, but not mitochondria. I've tried looking it up but I couldn't really find anything explaining why this would be the case. Is it just because mitochondria were incorporated so early into the eukaryotic lineage, that pretty much every eukaryote has one? And so there isn't a need to grab one from another eukaryotic species?
|
[
"Are you asking if there are two or more lines of mitochondria, or if mitochondria were taken from one eukaryote by another, making their phylogeny not match their host?",
"If the former: as far as I know, ",
" mitochondria derive from the same primary endosymbiosis event. The phylogeny of all eukaryotes and all mitochondria are the same until that event, barring odd cases like where male mitochondria are not destroyed or such, though that would hardly be a blip in a phylogenic tree. ",
"If the latter: I'm unaware of this happening but it would certainly be ",
", though I cannot imagine why it would be advantageous."
] |
[
"Yeah, since extant eukaryotes had mitochondria ancestrally, there wouldn't be a strong selective benefit to picking up a secondary one. Whereas picking up a secondary plastid allows you to do photosynthesis. ",
"Some eukaryotes, particularly parasites and anaerobes, have greatly reduced or in one known case entirely lost the mitochondrion. In principle they might act as hosts for a secondary mitochondrion, though AFAIK they lost their original mitochondrion for a reason, i.e. they are living in an environment where having oxidative phosphorylation wouldn't be much use."
] |
[
"I assume “secondary mitochondria” refers to cases where a eukaryote established an endosymbiotic relationship with another eukaryote and integrated the symbiotic eukaryotes mitochondrion (i.e., a case similar to secondary plastids)",
"I can’t think of any potential examples. It would be hard to establish using purely phylogenetic criteria given the small size of most mitogenomes - this would limit the power of any analyses. Moreover, the extreme base composition and the shifts in base composition over time could lead to strong biases in phylogenetic estimation.",
"However, I cannot think of any examples of mitochondria with additional membranes (like secondary plastids). Since the common ancestor of extant eukaryotes is likely to have had mitochondria there would be no case where a truly amitochondriate eukaryote (as in a primitively amitochondriate eukaryote) could integrate a secondary mitochondrion. I assume that it why you say there would not be a selective advantage - is that right? If so, I agree."
] |
[
"Why is radioactivity measured in half-lives?"
] |
[
false
] | null |
[
"Because it is a fundamentally random process. A uranium 235 atom created a micro second ago, and one created 50 million years ago have identical chances to survive the next 10 seconds."
] |
[
"The half-life of a radioactive isotope is how long it takes for half a large sample of that isotope to undergo radioactive decay, or conversely how long it would take for a 50% chance that any single atom of that particular isotope to undergo decay. The half-life is constant over time, so describing the decay of a particular isotope with a half-life is a convenient way to quantitate the decay with a single, simple number.",
"This works because atoms aren't distinguishable. That is, all the atoms of a particular isotope have identical properties. As a consequence of this, we cannot tell how old any single atom is, as if atoms underwent an age process of some kind, we could tell them apart. So, for an atom that undergoes a decay of some sort, it must have the same probability of decaying during a given amount of time no matter when that time is. A radioactive atom has the same probability of decaying in the next year as it does between one million years from now and one million and one years from now (assuming it hasn't decayed prior to that, of course!)",
"For example, an atom of Carbon-14, commonly used for radioisotope dating of recently-deceased (<50,000 years or so) biological matter, has a ~0.012% chance of decaying between now and a year from now. It has the same probability, ~0.012%, of decaying in the year after that, and so on.",
"After one half-life, half of the atoms of a given radioisotope will have decayed through this random process. As the likelihood of the remaining atoms decaying is the same as it was for the initial sample, half the remaining atoms will have decayed after the same amount time as the first half decayed, etc.",
"To put some numbers to this, if a particular fraction of the atoms, p, decays in some time t, then the likelihood that an atom won't have decayed in that time is 1-p. After twice the time, 2t, the likelihood that an atom hasn't decayed is (1-p)*(1-p), as the probability of decay is the same in the first time period as the second. In general, after n time periods the likelihood of not having decayed is (1-p)",
" .",
"A half-life is the time (t_0.5) in which there is a 50% probability that a particular atom has decayed, or p = 0.5. Thus, the probability that an atom hasn't decayed after n half-lives is (1/2)",
" . Macroscopically, this translates to (1/2)",
" of an original sample of these atoms remaining after n half-lives.",
"We can re-cast n as",
"n = t/t_0.5, ",
"where t_0.5 is our half-life, and t is the elapsed time. In this way, you can calculate how much of bunch of a radioactive isotope will be left after some arbitrary time t, p(t), or conversely what the probability one atom of said isotope will not have decayed in the same time, and so:",
"p(t) = (1/2)"
] |
[
"I think that's the best explanation I've seen yet"
] |
[
"Why can't we film a TV or computer screen clearly?"
] |
[
false
] |
Whenever someone takes a photo or takes a video of a screen it usually comes out distorted in one way or another depending on whether it is video or a photo. Why is this?
|
[
"This is the result of aliasing - a difference between a frequency inherent to the observed phenomenon and the sampling frequency used to record it. This is why you sometimes see wheels appearing to rotate backwards on vehicles in film. The frame rate is such that each successive frame happens to catch a spoke in a position slightly behind the previous frame, even though it rotated forwards to get there. Video displays are similar. They have refresh rates typically between 50 and 80 Hz, while the video is recorded at 30, resulting in flicker that you wouldn't otherwise see."
] |
[
"This phenomenon is caused by How TV displays an image on the screen. The TV will change the image by changing each individual pixel from the top left moving right, and work it's way down. The rate at which it does this is so high that we don't notice the change and appears to be a smooth moving image. When we see a TV on another TV the two refresh rates clash and we can see the change in between two images. This is very much like why you can see the rotor blades on a helicopter on TV and not in real life."
] |
[
"Thanks a lot guys. I knew you could help me out."
] |
[
"Why does rate of reaction not change when you add product?"
] |
[
false
] |
According to Le Chatelier, wouldn't the rate of the forward reaction slow down if product was added?
|
[
"The rate of a reaction is only dependent on the educts. That makes intuitive sense, because why would the educts care if there is product around? The reaction in the forward direction only depends on the interactions of the educts, after all. If you add product, the rate of the reverse reaction increases, again, because that only depends on the concentration of the product. Because that rate increases, the equilibrium shifts according to Le Chatelier."
] |
[
"I would like to add a side note, a minor exception. If the reaction is surface mediated then the products may reside on the surface to some degree and therefore poison the surface. With less surface area available for the reactants the reaction will start to slow. A good chemist wouldn't select such a surface/ catalyst that has a high affinity for products though in the first place, hopefully."
] |
[
"That's not exactly correct. Take a unimolecular reaction A -> P as the simplest example. The reaction rate depends on the concentration of A and the rate constant k, d[A]/dt=k[A]. That's a consequence of the fact that only those molecules of A that have a certain energy follow the reaction path and the amount of those is proportional to the total amount of A."
] |
[
"Could humans ever evolve to a point where certain races of people could'nt reproduce with each other?"
] |
[
false
] |
[deleted]
|
[
"I don't know, maybe the boat will return in the form of interplanetary colonisation. I mean suppose that space travel remains a difficult challenge, for all the reasons we have to suspect it may. Maybe we build a few colonies, but they remain largely independent, biologically isolated groups. Now you have new selection pressures and isolation from the \"main\" branch of the species. I think that would probably well lead toward speciation. But it may not be along the lines of \"race\" as we know it now. I mean unless different ethnic populations specifically choose to populate different colonies. "
] |
[
"That boat has pretty much sailed. Due to the transport options and freedom of travel we have now, there is more mixing of racial genes right now than at any other point in our history."
] |
[
"That doesn't seem to be a good argument because adaptation by natural selection does not occur at a constant rate.",
"Your example does not mean at all that speciation could not happen within 40000 years."
] |
[
"Do veins have the same pattern for all humans?"
] |
[
false
] |
I suspect major arteries might have the same layout in all of us, but what about smaller ones?
|
[
"Even some major arteries vary a lot from one person to another, so veins, especially smaller ones, vary a lot too. There are of course veins, that are in the same place in the majority of people, but a majority is still not much. Smaller veins (arteries too) vary so much, that nobody even puts them in anatomy textbooks. But that's not surprising, because the large and supposedly important blood vessels are very diiferent among humans. I mean there are people who are alive and well without one of carotic arteries, and there are people who don't have veinous dorsal arches on their hands, that are relativelly large. In general vascularisation is not constant, and the anatomy of arteries and veins is more or less just a guideline rather than a concrete thing.",
"Fun fact - only ~25% of people are anatomically correct."
] |
[
"I feel like with that statistic, anatomically correct is not a firm definition"
] |
[
"Yes I kinda wanted to put quotes on that, but was afraid to end up in ",
"r/suspiciousquotes",
" :D what I meant was, that only that amount of people have the most common, I guess textbook common, variation of everything - no more or less of anything and the most common blood vessel pattern."
] |
[
"Why do people make definitive statements about the R0 of a virus? Is it not a relative term?"
] |
[
false
] |
I see people say that covid's R0 is 'x', or the flu has an R0 of 'y', but is the R0 not a variable that can change depending on how people, governments, etc treat the spread of a virus?
|
[
"Strictly speaking when you hear reports of the R of the current Coronavirus being this figure or that figure in different locations or at different times the number being reported is the ",
" reproduction number, Re, i.e. the average number of people an infected person will infect ",
"The R0 is something different, being the average number of people an infected person will infect in a completely naive population where there is no immunity, no social distancing, no special measures in place.",
"See ",
"this article",
" for a deeper explanation."
] |
[
"",
"Yes, it can vary depending on circumstances, as noted in a recent NY Times article. A quote and the URL below. See the sentence in bold for a direct answer to your question.",
"\"When the virus first emerged in China, epidemiologists scrambled to understand how it spread from person to person. One of their first tasks was to estimate the average number of people each sick person infected, or what epidemiologists call the reproductive number.",
"\"The new coronavirus turned out to have a reproductive number somewhere between two and three. ",
" ",
" ",
" ",
"\"This averaged figure can also be misleading because it masks the variability of spread from one person to the next. If nine out of 10 people don’t pass on a virus at all, while the 10th passes it to 20 people, the average would still be two.\"",
"From: ",
"https://www.nytimes.com/2020/06/30/science/how-coronavirus-spreads.html?searchResultPosition=3",
"",
"From:"
] |
[
"It looks like R0 still depends on typical behavior in a place though, and therefore cannot be constant. For example, a town populated mainly by meatpacking workers (who are constantly in close quarters with each other) will have higher R0 than a town populated mainly by loggers because their ordinary day-to-day behaviors are different. A country filled with mainly small farmers working their own land would have lower R0 than a country filled with mainly office workers spending their days in meetings. This is independent of immunity, social distancing, etc."
] |
[
"Harmful effects of Cola drinks: What are they? And provide links to actual studies"
] |
[
false
] |
I've always heard of the harmful effects of Cola drinks in many a conversation and newspaper/magazine article. Besides the obvious obesity issue, I've heard about liver and even stomach damage, among other crazy theories. I'd like to know how much of it is real science. Any doctors care to chime in here? Linking to actual studies supporting your claims is not absolutely necessary but it's a huge plus! I really want to see some literature on this matter.
|
[
"http://www.youtube.com/watch?v=dBnniua6-oM",
"This video talks about the metabolic processing of fructose being the same as that for alcohol and having the same effect on the liver. "
] |
[
"Great reply. This is exactly the kind of stuff I'm looking for.",
"Can anyone poke some holes into the video? It's important to know where he's reaching too."
] |
[
"Consider this as a scaffolding for the real answers from scientists: drinking what is essentially pure sugar plus a number of non-nourishing chemicals is quite unhealthy. "
] |
[
"What can we deduce from 3D renderings of protein?"
] |
[
false
] |
[deleted]
|
[
"To determine things like how the protein changes as it works people do things like crystallize the same protein with no ATP, with ATP (nonhydrolyzable analog), and with ADP (or ADP analog). Then you can compare the structure before/after/during an ATP hydrolysis structure.",
"If you know which domains of a protein are important for an interaction, you can look at a structure and predict (based on which amino acids have exposed side chain) which individual amino acids are important for the interaction. You can then make mutations in those amino acids and test the interaction with purified proteins and, if there's a change in affinity, see if the mutation changes function in a cell. You may be able to predict or design a small molecule that can fit into that interaction surface/pocket and interfere with the interaction.",
"You can compare the structure to known structures which can be useful for predicting what novel domains do.",
"In yeast we use analog sensitive kinases as a research tool. You can mutate the ATP binding pocket of a kinase (and you can use the structure to predict which amino acids you should mutate) so that it can be specifically inhibited with an ATP analog but otherwise works essentially normally."
] |
[
"That's awesome! Thanks!"
] |
[
"Just once concept I've been doing lately in frontier molecular biology, that one of the best understanding for how you get post-translational modifications such as glycosylation or phosphorylation of the serine and threonine amino acids on proteins is purely through the 3D shape of the protein around those amino acids. It appears there are hundred of different enzymes which guide and glycosylate proteins, the only limiting factor seems to be which enzyme can actually fit into the pocket.",
"The special property of the serine and threonine residues (amino acids, it's a habit you pick up calling them after a while) is that they have an -OH group on their side chains (part of an amino acid which differentiates between them). These -OH groups allow for a condensation reaction where the -OH group of a monosaccharide (i.e. the 3' carbon of glucose) will react with the -OH group of the serine or threonine, producing water and having an ether bonding. ",
"It appears that there is no special feature about it that would classify it as a substrate to an enzyme - so it appears that whichever enzyme can get into the socket will condense its monosaccharide to the protein."
] |
[
"How far could a modern telescope see if it was the diameter of the earth?"
] |
[
false
] |
First of all i understand that modern telescopes actually absorb energy wavelengths and the way we interpret the data through computers isn't really the same thing as how a human eyeball "sees". -If, hypothetically, a satellite was built that was around the diameter of the earth; how far could it see? I guess i realize that by "far", I mean , "how far back in time" as the light was emitted long ago. With the size of our universe is it feasible we would actually be able to see anything in any detail; is our technology limited by the size of the receiver or by the number of pixels/ method the data is recorded?
|
[
"I have no answer to your question.",
"With the size of our universe is it feasible we would actually be able to see anything in any detail",
"Even though Space might be infinite, the radius of the visible universe is calculated to be about 46 billion light years (",
"source",
"). That's where we then see the background radiation which was emitted shortly after the beginning of time. In the far future, we would be able to see farther, but the max distance (Again, radius.) might be 62 billion light years (",
"source",
") because the Metric Expansion is practically stealing the cosmos from us. And the current cosmic \"event horizon\" is at a distance of about 16 billion light years: A radiation event that happens in a galaxy with that or a shorter distance could be observed by us in the far future, but current events further away would never reach us. This is untouched by the fact that the distance of that \"event horizon\" is changing."
] |
[
"This is not an answer to your question, but we already do have telescopes the diameter of the Earth. This is achieved by pointing a telescope in the same direction into space 12 hours apart, that is, when the telescope is on opposite sides of the planet."
] |
[
"The ability to see back in time is referred to as sensitivity in instrumentation terms, that is things further away (in space/time) are dimmer. So less energy reaches us.",
"The bigger the aperture of your instrument the more energy you gather from the source, with a few assumptions. To go much furhter though requires making a lot of decisions about the optics of the instrument and quality of your detector to make numbers a bit of a guessing game. "
] |
[
"I would post this to /r/neuroscience, but it has a rather low readership so my question is:"
] |
[
false
] |
Can anyone tell what permanent medium-to-severe suppression of CNS Acetylcholine can have in effects? The medication in question is Biperiden (Akineton(R) as brand name where I live). I feel constantly depressed ever since taking it, at points even to the point of suicidal ideation, and I'm worrying it's because of the mentioned meds. Thank you all and sorry in case this is inappropriate in AskScience. (I tried googling up something conclusive but wasn't able to.)
|
[
"Not my specialty (ignore the badge), but you should talk to a (specialist) doctor about this not necessarily a scientist/researcher. ",
"I'm not saying this is inappropriate thing to ask, but scientific researchers aren't the most knowledgeable about side-effects of drugs (or consequences of abruptly stopping drugs). A drug designed to suppress a neurotransmitter likely does other stuff as well and drugs often react very differently to different people. Or it could be a coincidence or a negative placebo effect or a result of some underlying disease. (Again not an expert; have no knowledge of your drug or in treating depression. I recommend talking to a doctor about it if you can).",
"Best of luck with finding better treatment."
] |
[
"I'm a neuropsychologist, not a medical doctor, so please take everyone else's advice and go see your medical doctor. ",
"But yes, Akineton side effects can include depression - and it would be considered a \"rare but serious\" side effect (more common emotional side effects would include anxiety/agitation/confusion). ",
"Here's a link",
" if you want one. Of course, the condition that Akineton is usually prescribed for is also very highly associated with depression. ",
"Either way, you should talk to your prescriber right away. "
] |
[
"To OP:",
"While there are some doctors on askscience, the majority of us are scientists who don't know anything about clinical drugs and don't know enough are your specific question (due to our extremely high degree of specialization) to give exact answers. You may be better off posting in somewhere like ",
"/r/health",
".",
"I posted some of what I know below, and will add this: drugs that affect your nervous system will always have huge side effects. Anti-Parkinsonian medication is known to be heavy in side-effects, and if you are taking any drugs effecting the dopamine system, know that the dopamine system is important in modulating reward and emotion. It may be caused by your drugs, it may be something else. You should bring it up to your doctor rather than trust anonymous online people, because if you are having suicidal thoughts it is becoming a serious issue, whether it is caused by your (Parkinson's?) disease or the medication. However, do not immediately dismiss your medication, because in spite of the side effects it will help your health more. Ask a doctor, and try to find a way to deal with the depressive side effects."
] |
[
"I saw a post about bill sharks that were stranded in a golf course lake and thriving. If left alone with a sufficient food supply, how long would it take to see evolutionary changes?"
] |
[
false
] |
Here is the original link.
|
[
"Are bill sharks similar to loan sharks? Anyway they would probably die off pretty quickly, not enough DNA for a healthy new population to form "
] |
[
"Just as a note, evolution is a constant process. Changes occur in every generation; you contain several mutations in addition to your parent's DNA. So we could see evolutionary changes in the first offspring, and the only question is how dramatic a change we want for us to decide to draw a line."
] |
[
"are you taking about micro evolution or macro evolution"
] |
[
"What would be the best way for me to learn Matlab outside of class?"
] |
[
false
] |
I was wondering if any of you knew any good resources or books that would help me quickly pick up Matlab. I have experience using basic Python, so I'm sure that would help. I'd rather not take a class since I'm trying to learn this as quickly as I can, although I know the guidance and practice from a class would greatly help.
|
[
"Project Euler."
] |
[
"Working through Project Euler problems is my favourite way to introduce myself to the syntax of any new language. Nice suggestion.",
"Edit: I should say that when doing these problems you should investigate solutions that use matrix operations instead of for loops and things like that. The real power of MATLAB comes from the what you can do with matricies. Otherwise you might as well just use python."
] |
[
"when doing these problems you should investigate solutions that use matrix operations instead of for loops and things like that. The real power of MATLAB comes from the what you can do with matricies. ",
"This is the best advice here. You should very very rarely ever use FOR loops in matlab. If you can learn to run all your code with matrix multiplication and a few related functions (cumsum, cumprod, ones, etc) you will be a much better Matlab'er.",
"As far as getting the syntax right, there are so many people using Matlab that a google search on your error message usually works pretty well. Also the built-in help in Matlab is great (just type \"help <function name>\")."
] |
[
"why don't gas giants solidify?"
] |
[
false
] |
So, I can only come up with two potential energy sources that can keep them gassy: - centrifugal force - internal heating (similar to a sun) both of those don't really make sense to me, since 1. as far as I know they are (at least some of them) very cold, and while they rotate quicker than earth relative to their size, they don't even nearly rotate quick enough to keep all their matter in the form of a gas. So how come they don't collapse ?
|
[
"At the temperature they're at, they're gasses.",
"There's not a lot of ways to loose heat, besides radiating in space. If you're orbiting a sun there's an influx of heat. These usually balance each other. So temperature should remain constant."
] |
[
"Pretty much everything will solidify under a state curve with a low enough temp and a high enough pressure. What amstan is saying is that the equilibrium of energy in & out on these planets is such that the temperature doesn't get low enough to condense the gas. The gas itself is an insulator in some cases, reflecting radiated heat back into itself rather than letting it escape. On a planet without an atmosphere, there's nothing to retain the heat so they are cold by definition. ",
"Someone a bit more educated in the field will have to explain why a planet ends up with or without an atmosphere (often it has to do with the magnetic field or lack thereof). "
] |
[
"So they are nearly entirely composed of gases that solidify under very high pressures with very low temperatures? I mean other planets with less mass have frozen gases on them (methance, co2)"
] |
[
"If some elements have such a short half-life, why are they still here?"
] |
[
false
] |
[deleted]
|
[
"An ",
" doesn't have a half-life, each individual ",
" of every element has its own half-life.",
"There are some radionuclides on Earth whose half-lives are much smaller than the age of the Earth, for example carbon-14.",
"It just means that these nuclides are being produced by some processes that happened after the birth of the solar system, and could still be ongoing."
] |
[
"That's precisely why carbon-14 is such a good tool for dating organic artifacts. As organisms absorb carbon from the environment to build their bodies while alive, the ratio of radioactive carbon will remain more or less constant. But when they die, they're no longer \"repaired\" with new materials, which allows us to use that ratio to date them."
] |
[
"They eat food with carbon in it, thereby renewing the supply of carbon-14.",
"edit: a word."
] |
[
"What physically stops two like poles of a magnet from touching?"
] |
[
false
] |
I get that the magnets each form a magnetic field, but what fundamentally causes this repulsion between like charges?
|
[
"but what fundamentally causes this repulsion between like charges?",
"The electromagnetic field is fundamental. The four fundamental interactions are gravity, electromagnetism, the weak nuclear force and the strong nuclear force. Static magnetic fields, such as created by permanent magnets, are just particular forms of the electromagnetic field. ",
"Some people say that a magnetic field is just what an electric field looks like from a certain reference frame. While this is partially true, it is misleading. Every reference frame is equally valid. Therefore a magnetic field is equally as real and as fundamental as an electric field. More accurately, if you actually mathematically apply reference frame transformations to electric and magnetic fields using Special Relativity, you find that they actually can't be neatly separated. There is just one unified field: the electromagnetic field. Depending on your frame of reference, a certain electromagnetic field may look more magnetic and less electric, or vice versa, but there is really just one unified, fundamental, electromagnetic field. "
] |
[
"I think you should first watch ",
"this",
" and then ask follow up questions :)"
] |
[
"Some people say that a magnetic field is just what an electric field looks like from a certain reference frame. While this is partially true, it is misleading. ",
"Would like to second that. I see people using the example of calculating the force on a ",
"charge near a wire in different reference frames",
" quite a bit. Don't get me wrong, it is a great example of the deep connection between magnetism and electrical forces. But it doesn't mean I can always find a reference frame where the magnetic forces vanish, and you aren't going to get Maxwell's equations by switching reference frames in clever ways."
] |
[
"Mathematically speaking, if a given game of Sudoku, in its initial state, has only one possible outcome, will it always solvable without having to resort to guessing a cell's value?"
] |
[
false
] |
I have long felt this must be the case, but my limited mathematical skills prevent me from proving this
|
[
"The issue is that 'trying out' a particular solution and then following the logical consequences of that solution is one of the fundamental techniques for solving a sudoku puzzle. Often, following the logical consequences of a solution can be done without writing anything down, but that depends on the limitations of the solver. ",
"For example, consider the puzzle that begins 1/4 of the way down this page: ",
"http://www.sudoku-space.com/sudoku.php",
" and look at the top rightmost 3x3 square. One possible way to solve this square is to see that there are only three numbers left: 3,5 and 9, and to see that 3 cannot go in either of the open squares in the middle row. In some sense, this solution is the same as trying to put 3 in the middle row, and seeing that it leads to a contradiction.",
"The technique your colleague describes is similar to this process, except that the implications of the \"guess\" are more complicated, so it is helpful to write in the guess, with the understanding that it may be erased later."
] |
[
"Unless the person who made the puzzle made a mistake a sudoku puzzle has only one correct solution and enough information from the start to solve it without guessing."
] |
[
"A puzzle with only three or four numbers can have multiple answers and would require making guesses but this is not a proper sudoku puzzle."
] |
[
"Would someone please explain how operators like multiply/divide and XOR work in computing and simulations?"
] |
[
false
] |
I'm trying to freshen up my knowledge of particle and fluid simulations for visual effects and I still don't fully understand what's going on when I use these operators. For instance what is happening when I use a divide operation to divide the age of a simulation using a gradient ramp texture that has grey scale values 0-1, or values greater than 1 that is connected to a color/diffuse channel. Same Question but using procedural fractal map instead? And what is happening when you use the XOR operation.
|
[
"Exclusive OR: One or the other are true, but not both (or neither for that matter).",
"A XOR B | Result\n----------------\n0 | 0 | 0\n1 | 0 | 1\n0 | 1 | 1\n1 | 1 | 0\n"
] |
[
"The quickest way to remember XOR:",
"Are A and B different? yes=true, no=false"
] |
[
"Wikipedia has articles that describe digital division and multiplication.",
"Division",
"multiplication"
] |
[
"The first reports of Mad Cow Disease (BSE) were filed nearly 30 years ago in Britain. Have we seen the worst of its effects by now?"
] |
[
false
] |
Growing up in Europe, the late 80s all through the 90s, we were constantly bombarded about BSE and its potential effects on the population. Those born in the 90s or after may not remember or know too much about that whole saga. As I recall, in France, we heard about how a huge chunk of the population would be developing Creutzfeldt-Jakob Disease in the next 20 to 30 years. Here is a brief of the spread of BSE. I am sure it is incomplete but at least gives an overview of how things happened. January 1993 - The BSE epidemic in Britain reaches its peak with almost 1,000 new cases being reported per week. 1996 - The first case of variant Creutzfeldt-Jakob Disease is reported. I can't seem to find any data that suggests a sudden upswing as one might expect if the predictions of the experts at the time were correct. Are we in for a sudden burst of Creutzfeldt-Jakob Disease for Europeans? Should we be worried?
|
[
"Probably we don't need to be worried that a huge chunk of the population will develop the disease, but there are still things we don't know about how the disease develops. You can see a chart ",
"here",
" of diagnosed cases in the UK. Although the total deaths from CJD are increasing, the green line is the one to watch. That tracks the variant Creutzfeldt-Jakob Disease (vCJD), or the version that is linked to mad cow disease. The trend line was disturbing up to the year 2000, but after that year the numbers began to drop instead.",
"In the 90's and early 2000's, we knew prion diseases could be transmitted between species ",
"in controlled studies of mice",
", but there was no good way to know how effective transmission to humans was. Current estimates suggest ",
"about 500 people per million have the prion associated with vCJD",
" in the UK, but there are a much smaller number of cases of the disease (177). This seems to be connected to what type of protein people have naturally, and whether it has a valine or a methionine at a key position (prion diseases are thought to spread when one mis-folded protein introduced to your body starts to convert your own proteins into the mis-folded state, so if your target protein has a different sequence it could strongly affect how the disease develops).",
"So what does it mean that many people have the prion but fewer have the disease? It looks like some people were more susceptible to the disease than others, but a large number have been exposed. Those people who are carriers of the prion but don't have the disease (numbering in the thousands in the UK) might be completely resistant, or it might just take longer for the disease to develop. These prion carriers could infect others who are more susceptible to the disease through blood transfusions as well. ",
"The early estimates you remember had huge error bars on them, and the media is bad at communicating these uncertainties. We also were lucky that a large chunk of the population seems to be less susceptible to the disease. We still might be looking at thousands more cases of vCJD in the UK over time, but we should be able to prevent new transmissions to humans through farming practices and the screening blood donors."
] |
[
"A virus self-replicates, using the contents of a cell as building blocks.",
"A prion is a more stable form of a protein; if you've ever seen ",
"supercooled water",
" freezing, that's similar in a way: the molecule itself doesn't change chemically. Proteins are structurally much more complicated than water, of course, but it's similar in that the molecule is going to a lower energy state.",
"Kurt Vonnegut's fiction piece ",
"Ice Nine",
" is built on a similar principle causing the end of the world."
] |
[
"This report",
" suggests it might just be increased diagnosis because the disease has been in the news. Apparently the trend is the same in many countries."
] |
[
"How can I find the amount of Energy contained in a system by measuring the temperature?"
] |
[
false
] | null |
[
"It’s not necessarily possible to calculate the total energy of a system given only its temperature. For a classical ideal gas, the relationship is E = 3NkT/2. So you are required to know both the temperature and the number of gas molecules. For more complicated systems, there are more complicated relationships between E and T, that will in general require you to know more about the specific system."
] |
[
"So of I knew the number of particles withing the system I would know the energy from the definition of temperature being \"the average kinetic energy of the particles of a system\"?"
] |
[
"For a classical ideal gas, all of that is true."
] |
[
"What exactly is happening when you mix sugar into Sulfuric acid?"
] |
[
false
] |
It turns black, and I think the acid somehow strips the Oxygens and Hydrogens off of the C6H12O6 molecule, but how does that happen and what products are left? Also I noticed that if you add Nitric acid into the solution of carbon black sugar residue, the carbon black residue seems to disappear, what exactly is happening there on the molecular scale?
|
[
"Sulfuric acid is a strong dehydrating agent. The sugar undergoes a dehydration reaction, leaving water and elemental carbon behind.",
"Nitric acid is an oxidizing agent, and will oxidize your elemental carbon into carbon dioxide."
] |
[
"When you say elemental carbon, surely it can't just be C sitting there unconnected to any other carbons. Do you know what structure the carbon would form?"
] |
[
"It'll be ",
"amorphous carbon",
", similar to soot. It'll be connected to other carbons, as well as having dangling bonds and bonded to other atmospheric elements."
] |
[
"If a spider builds its web in a bad spot, will it be smart enough to give up after a day or two and move elsewhere, or will it just starve to death because it can't realize it made a bad decision?"
] |
[
false
] |
[deleted]
|
[
"Orb Weaver spiders, the most common group of spiders that build spiral wheel-shaped webs, generally build a new web each day. They'll eat the old web in the evening, rest for an hour or so, and then spin a new web."
] |
[
"Spiders are known to relocate if they have a low prey capture rate",
".",
"The research citations are from ",
"here",
" but are behind a paywall."
] |
[
"That doesn't speak to whether or not they relocate at any point though.",
"The ones I've observed (also orb weavers) often retain the same location over extended periods."
] |
[
"If you made a range of paints that were x-ray, microwave, or radiowave 'coloured', would they appear black to us?"
] |
[
false
] |
Also, it seems that many of our paints/colours were originally created from naturally occurring pigments in plants etc. Do substance occur in nature that would only reflect far outside the visible spectrum of light?
|
[
"The way in which they interact with x rays or infrared etc would be irrelevant to how they appear to us, the only thing we can see is which parts of the visible spectrum they reflect. So if you had 2 red paints, one reflects x ray and one absorbs it, they would both just look like red paint to us."
] |
[
"Honestly not really sure, x-rays and radio waves have vastly different wavelengths to visible light, so they start to interact with matter differently to how we are used to with normal light. The wavelength of x-rays is similar to the spacing between atoms, so the specific atomic geometry and orientation of whatever material you're looking at becomes important when you want to consider how a material will interact with x-rays. Radio waves have the opposite property, and the wavelengths are so big that the macroscopic geometry, size and orientation of the object is as important as the material itself."
] |
[
"I understand what you're saying. But what I'm getting at is if it would be conceivable to have a paint which only reflected x rays or radio waves?"
] |
[
"Why does solar wind speeds up when moving away from the Sun?"
] |
[
false
] |
The initial velocity of the solar wind is subsonic. As it moves away from the Sun in a radial direction, it is expanding in area and thus should be slowing down instead of speeding up. My compressible fluid professor mentionned that the Suns gravity has the effect to speed up the flow but didn't elaborate. Is someone here able to explain me more in detail what is happening?
|
[
"Thanks for your answer. My other question is now: If the gravity gradient is indeed acting like a converging nozzle, how does the flow pass the sound barrier to reach velocities over Mach 1? In the case of a strictly converging nozzle, the flow would simply choke at the throat of the nozzle and it wont be able to speed up to supersonic without the addition of a diverging nozzle after the converging section.",
"EDIT: Actually when I think about it, I guess at a very long distance from the Sun the effect of gravity becomes too small to counterbalance the fact that the flow is expanding, but since the flow there is already at Mach 1, it can expand to supersonic values. I don't know if I'm explaining it well but I think it makes sense. Anyway, thanks a lot for your explanation!"
] |
[
"Thanks for your answer. My other question is now: If the gravity gradient is indeed acting like a converging nozzle, how does the flow pass the sound barrier to reach velocities over Mach 1? In the case of a strictly converging nozzle, the flow would simply choke at the throat of the nozzle and it wont be able to speed up to supersonic without the addition of a diverging nozzle after the converging section.",
"EDIT: Actually when I think about it, I guess at a very long distance from the Sun the effect of gravity becomes too small to counterbalance the fact that the flow is expanding, but since the flow there is already at Mach 1, it can expand to supersonic values. I don't know if I'm explaining it well but I think it makes sense. Anyway, thanks a lot for your explanation!"
] |
[
"I don't know what was in the deleted comment, but your reply is making me rather nervous. My understanding is that firstly the mechanism behaind the solar wind aren't well understood. The acceleration is likely due to interaction between the charged particles that make up the wind, and the sun's magnetic field. Photon pressure will have a small effect, but not nearly enough to overcome gravity. This talk of nozzles has me very puzzled."
] |
[
"Why does a faster moving boat create smaller waves?"
] |
[
false
] |
With two boats of the same size and hull shape, why does it seem as though if one were moving faster it would create smaller waves compared to a slower moving one?
|
[
"Hydroplaning. Generally, the faster a boat goes, the less of it’s hull actually touches the water. Different hull shapes and designs will produce different results based on the use of the boat. Less contact with the surface of the water will produce less wave action.",
"Also, keep in mind that this only really applies to smaller boats. You can’t really get a cruise ship or an aircraft carrier moving fast enough for the effect to happen. The physics of ship and hull design can get really complicated."
] |
[
"You probably could hydroplane a cruise ship but it would be lightly impractical."
] |
[
"Now I’m imagining hydrofoils on a cruise ship to help and have to believe there’s a downward pressure wave causing chaos undersea to generate enough lift to get a 200k ton cruise ship aloft"
] |
[
"This is getting tossed around as debunking climate change."
] |
[
false
] |
Found claiming that this study debunks climate change. I'm slowly working my way through it now, but, well, I'm not a climatologist. Can someone help break down for me?
|
[
"No, it certainly doesn't. This ",
"realclimate article",
" has a good explanation of what's going on in the new study, and what its implications are.",
"Some excerpts:",
"The most exciting–and in our view important–development is that they seem to have greatly ameliorated the “divergence problem” that has plagued some surface temperature reconstructions based on these types of data.",
"Interestingly, this is left out in most of these \"global warming debunked\" articles which have popped up like mushrooms in the climate \"skeptics\" blogosphere. The \"divergence\", also sometimes known as \"decline\" (as in \"hide the decline\") is a phenomenon where high-northern latitude treerings stop mirroring actual temperatures in the mid 20th century.",
"Another interesting finding is that N-Scan exhibits a substantially larger pre-industrial (pre 1900) millennial cooling trend (around -0.31C/1000yr) than a tree ring width (TRW) based summer temperature reconstruction from the same trees. This seems a plausible conclusion,... Yet the article extrapolates quite a bit, in terms of its conclusions regarding proxy-based temperature reconstructions more generally... They argue that TRW data which fail to record this forced long-term cooling might therefore underestimate variability on millennial timescales more generally, and potentially underestimate the warmth of past warm periods (e.g. medieval and Roman periods).",
"Orbital forcing is indeed substantial on the millennial timescale for high-latitudes during the summer season, and the theoretically expected cooling trend is seen in proxy reconstructions of Arctic summer temperature trends (Kaufman et al, 2009). ",
".",
"In other words, the authors extrapolate from their localized sample to global temperatures, but other, non-treering proxy reconstructions from more southern regions do not actually show the phenomena they found. ",
"And finally, Schmidt and the others at realclimate point out that non-treering proxies actually show lower cooling than treering proxies, which—in direct contradiction to the new study—allows the conclusion that treerings ",
"estimate cooling trends:",
"There are a few rather interesting observations here. One is that the Moberg et al (2006) reconstruction, which–unlike all of the other reconstructions listed above–uses no tree-ring proxy data at all to estimate centennial and longer-timescale temperature variations, shows the smallest cooling trend of all. That is in contrast to Esper et al’s hypothesis that including tree-ring data leads to reduced long-term cooling trends."
] |
[
"Yes. It's hard to see how a cooling of 0.3º per millenium could be seen as negating the recent warming of 0.3º ",
" (one hundred times bigger!) or the patently obvious ",
"observed effects",
" of recent climate change.",
"I guess some people just aren't very bright."
] |
[
"From a quick skim through, it seems that they are claiming that global temperatures are on a general decline. This may well be true, but global warming as we generally consider it is caused by man-made greenhouse gasses, which have only been produced in significant quantities in the past hundred or so years.",
"If you look at ",
"this",
" graph that they produced, the temperature has been on a fairly rapid increase over the past hundred years, so the claim that this study will completely debunk global warming is total bollocks."
] |
[
"Can children eat rare or med rare steak?"
] |
[
false
] | null |
[
"None that I can think of. The inside of a piece of uncut meat(beef) is sterile. Make sure that the meat isn't mechanically tenderized or injected with a brine solution. ",
"The problem arises when meat is ground because then the potentially contaminated outside becomes the same as the previously sterile inside.",
"Other meats are different. As long as pork isn't injected, you can probably serve it slightly pink but do so with care. Don't do it with chicken."
] |
[
"Chickens are able to have salmonella within their tissue. This occurs in around 1/100000 chickens. This is a low number, but we eat a lot of chicken. Also, the majority of supermarket chicken has been injected with a brine solution to help maintain moisture and tenderness since they are so low in fat. If you grow your own chickens, then by all means have at it. If you don't, it's probably a bad idea."
] |
[
"other than taste, is there a reason why having slightly under-cooked chicken breast is a bad idea? i know that salmonella is considered a potential worry, but wouldn't that require the meat to have been infected with salmonella in the first place (ie. an uncommon occurrence)?"
] |
[
"Why can methane that is built up in landfills not be used as energy in some way?"
] |
[
false
] |
I recently learned that landfills have columns in various spots to relieve methane that builds up from decomposing waste. If this wasn't done, there is a possibility of a fire burning the throughout the landfill for a long time and posing a serious hazard to people. So as opposed to letting the methane just rise into the atmosphere, why isn't anyone trying to collect it for energy purposes? Or is this not even practical?
|
[
"We do. The EPA has a program to add incentives to this - ",
"link",
". As always, the issue with a potential energy source isn't \"can we do this?\" It is \"can we do this ",
"?\""
] |
[
"No. The limit is how much it costs to collect and use the gas.",
"The amount of money the government puts in to start the project, however, determines how well the options to extract it are examined and developed. "
] |
[
"One of the larger problems for doing this cost-effectively is that the landfills do not simply emmit methane. The gas mixture varies depending on the microbacterial flora (which is usually not controlled) and the ingredients (which vary and are likewise usually not controlled). Even within one landfill the mixture can vary wildly. Apart from the methane content varying you also have variations in toxic and corrosive gases. ",
"If you want to use the gas industrially, you usually want a (more or less) constant methane concentration and the absence of corrosive gases which damage the consumer (as in the apparatus being fed with the gas). So a lot of work is going into how to \"clean\" the gases and how to influence the gas production."
] |
[
"Question about drafting.."
] |
[
false
] |
Say if Vehicle B was driving behind Vehicle A close enough to be inside of Vehicle A's slipstream.. It would obviously improve Vehicle B's fuel efficiency. But my question is: would it decrease Vehicle A's fuel efficiency as if Vehicle A was having to "pull" Vehicle B? Also, would this be similar in water? I am a swimmer and there has been some debate about whether drafting on someone hinders the performance of the person who is doing the "pulling" (the person who would represent Vehicle A in the above scenario)
|
[
"It is justified and commonly used in Nascar."
] |
[
"I don't have an answer for you, but I wanted to add another possibility (and piggyback the question I guess): I've heard that in some cases it's possible for the presence of the drafting person to actually ",
" the person in front by improving the slipstream (like putting a better tail on an aerodynamic geometry). But the spacing would have to be really close and it's probably not terribly practical. Is this justified?"
] |
[
"If vehicle B is close enough, it will actually help vehicle A by reducing induced drag, in this case the suction behind the vehicle. There is no penalty to vehicle A because it is not actually pulling vehicle B. Vehicle B is just enjoying less friction in the air that Vehicle A pushed (and pulled).",
"The density of the water and slow speeds of the swimmers make the induced drag reduction on the lead swimmer essentially nil. But the trailing swimmer can get a decent benefit by drafting."
] |
[
"Why doesn't the west coast get any hurricanes or tropical storms?"
] |
[
false
] |
I've been living on the west coast for 18 years and had never had a problem with hurricane, but every fall the east coast always gets a storm.
|
[
"We do get hurricanes, but they are farther south. If you are in Southern California, a lot of the tropical weather we get here in the late summer/early fall is the \"left overs\" of the hurricanes that peter out over land in Baja or the colder northern waters off the Californian coast. ",
"Hurricanes get their energy from warm waters. The reasons why hurricanes can reach so far North on the East Coast has to do the with the direction the oceanic currents run. ",
"As a (huge) generalization, the Northern hemispheric currents run clockwise due to the Coriolis force/effect due to Earth's Rotation. This means that warm water from the equator will run north on the \"west side\" of an ocean and south on the \"east side\" of the ocean. Ex: In the Pacific, the warm water currents run north from the equator up to Japan and the Korean penninsula up into the artic, where it cools down, then runs south passed Alaska and down the West Coast of the US where it then mixes with the warmer southern waters off the cost of Southern California and the Baja Peninsula. ",
"This is why you hear about typhoons hitting the SEA area and Japan which mimics the hurricanes that hit the Caribbean, Gulf of Mexico, and the East Coast. ",
"In short, hurricanes and typhoons thrive on warm water. Warm water is near the equator, and currents run clockwise patterns. This means that you will have more warm water on the \"left side\" of an ocean and colder water from the Arctic on the \"right side\" of an ocean. This is opposite in the Southern Hemisphere due to the Coriolis force switching directions(Currents run counter clockwise). "
] |
[
"Yes, there are anti-clockwise currents in the Southern Hemisphere. And yes, there are associated hurricanes (in this context just called tropical cyclones) that can hit the east coast of Africa below the equator as well as northern and western Australia and across Indonesia. But yes, it is a messy picture with many factors. There are virtually no cyclones in the South Atlantic, for example, because there is a lot more wind shear - and ironically, stronger winds in general, but the sort that break up any incipient cyclone that would form. Cyclones are defined by their pattern around low pressure zones, rather than sheer wind strength - so perhaps ironically, moderately strong wind can prevent the super strong winds that come with cyclones. ",
"Why that asymmetry between hemispheres, though? This last point is the case in turn because the Southern Hemisphere has more ocean than the Northern Hemisphere (since it has only a fraction as much land), since water takes much longer to warm up than land and the colder average currents lead to more of this wind sheer. But also (complicated again) because a large chunk of the land it does have is around the South Pole, i.e. Antarctica, which is under an ice sheet regardless. Though land itself allows far more flow of heat (one property), it also allows much more of a physical “solid platform” for the ice to cling to and propagate (another property working in another direction), which is why Antarctica has more ice than the Arctic, helping to make the Southern Hemisphere even colder.",
"There’s far more to it and I don’t understand all of it myself, but hope that goes some way towards an answer. "
] |
[
"I found this a decent visualization of the hurricane path patterns. ",
"https://en.wikipedia.org/wiki/Humboldt_Current#/media/File:Tropical_cyclones_1945_2006.png",
""
] |
[
"Did the impact that created the moon have a substantial effect on Earth's orbit?"
] |
[
false
] |
I've read that the existence of the moon itself stabilizes Earth's orbit and makes the planet more hospitable to life, but I was wondering more about the impact itself. Do we know if there was a meaningful change to Earth's orbit after the collision?
|
[
"Yes it would have definitely changed the rotation rate of the Earth. That is the best we can say though as we do not know if the collision was more direct or more of a glancing blow. What makes this problem even harder is that the outward migration of the Moon and hence the spin down of the Earth is not constant in time. There are a number of reasons for this but the main one is that dissipation of tidal energy which is responsible for the energy transfer is a function of a great many variables. This masks the ability to integrate backwards in time from where we are to get a good prediction of the impact conditions."
] |
[
"What dukesdj is saying (I think) with the last sentence is that scientists are not entirely sure about what exactly happened; theories range from two objects coming from the same source material, never having colided, to total vaporization of both celestial bodies in a frontal crash - some fitting better into models than others. Angle, velocity, the masses of the two objects, all the details of the collision are still being discussed. Somewhere in the process of finding that out is also the potential change in orbit."
] |
[
"What makes this problem even harder is that the outward migration of the Moon and hence the spin down of the Earth is not constant in time. There are a number of reasons",
"Just because I'm super-biased to start talking about atmospheres, here's another really interesting reason: Earth's rotation period can lock into a resonance with its own atmospheric ",
"thermal tide",
".",
"There is reasonably good evidence (",
"Bartlett & Stevenson, 2016",
") that Earth got ",
"stuck at a 21-hour day",
" for about a billion years. The authors further speculate that Earth only broke free of the resonance due to rising global temperatures coming out of the last \"Snowball Earth\" phase some 600 million years ago."
] |
[
"What are the anatomical differences between a left handed person and a right handed person? Especially internal differences?"
] |
[
false
] |
I didn't see anything asked here before
|
[
"Nurse here. None that I know of. "
] |
[
"Tom, the male nurse, is correct. :P",
"Apart from the differences one might expect to find between two normal and right handed people. ",
"There are some expected differences in brain function, but as far as I know this is simply because the other hand is dominant same goes for the brain. There are some studies that have been done on differences in thought, speech, and and language processing, that suggest there is a difference between righties and lefties, I do not know how well proven such studies are, or if such differences are significant.",
"edit: you (OP) might be interested though in kartageners, in which people have their heart on the right side of their body... but those people aren't necessarily right handed or left handed."
] |
[
"Yep, murse here!",
"You make good points as far as brain hemispheric functions go between lefties and righties. ",
"I would add to your point that people with transpositions of organs generally have a lot of other issues do well. Many of them fair poorly. "
] |
[
"So two part question, is absolute zero the lowest temp possible? And is there an upper limit of temperature?"
] |
[
false
] | null |
[
"I just realized I don't think I'm smart enough to be asking questions here. ELI5?"
] |
[
"Absolute zero is not the lowest possible temperature, because temperatures can be negative. However when a system is as cold as it can possibly be, its temperature is absolute zero. There is no maximum temperature, but if your system has a maximum possible energy, then in that state, its temperature is zero."
] |
[
"When a thermodynamic system has its lowest or highest possible energy (if there is a highest possible), it has a temperature of absolute zero. Absolute temperatures ",
"can be negative",
", but that doesn't mean that the system is colder than absolute zero; in fact it's hotter than it would be at infinite temperature.",
"In order of increasing \"hotness\", absolute temperatures go between",
"0",
" (as cold as possible), positive (typical situations), +∞, -∞ (wraps around to negative), negative (thermodynamically unstable; wants to give away energy), 0",
" (as hot as possible).",
"Because of the weirdness of this progression, some people prefer to use thermodynamic beta, which is defined by β = (kT)",
". This has more natural units, and progresses continuously from +∞ to -∞ rather than wrapping around like T does.",
"Here",
" is a more in-depth explanation of negative absolute temperatures."
] |
[
"Why are your ears, nose and throat all connected?"
] |
[
false
] | null |
[
"Because once upon a time your ancestors were fishes.",
"I'll do this one organ at a time.",
"Your throat is derived from a structure called the ",
". The pharynx in fishes is essentially the tube between the mouth and the entrance to the esophagus. This tube, in fishes, has holes in the side. These holes are called ",
" In most fishes, there are thin, highly vascularized filaments inside these slits, and the pharynx is used to pump water over these filaments. We call this sort of structure a \"gill.\" In humans, the pharynx is the back part of the throat up to the epiglottis.",
"The nose develops initially from a pocket that forms in the anterior head of an embryo called the ",
". This capsule contains all the sensory receptors of the nose and is tightly integrated with the anterior brain via the olfactory nerve.",
"In early fishes, the nasal capsule is just a pocket in the side of the snout. Later fishes have a flow-through system, with an anterior and a posterior nostril. When you get to the lineage that leads to tetrapods, the posterior nostril slips inside the mouth, and the flow-through nasal capsule not only becomes a means of smelling things, but a means of getting water into the mouth, where it could then pass over the gills. We call this internal nostril a ",
". The choana later becomes a means of getting air into the pharynx for passage into the lungs as our ancestors start moving onto land. In most reptiles and amphibians, the choana is perforates the bony palate right behind where your canine tooth is.",
"Now, in mammals, what we see is that there is what's called a \"secondary palate\" which is a plate of bone that forms between the oral cavity and the choana to create an actual nasal cavity, which is what we have. You still have a passageway between the nasal cavity and the pharynx, but it's further back now. This, among other things, allows you to breathe while chewing and to avoid getting food wedged up your nose all the time.",
"There are three parts to your ear: the inner ear, the middle ear, and the outer ear. The inner ear includes a series of canals associated with balance (",
") and a series of tubes and membranes that transduce sound waves into firing of nerves. The outer ear includes the rubbery flap of ear on the outside of your head (the ",
") as well as the ear canal. The middle ear contains a series of bones (",
") that connect the eardrum to the inner ear. Of these, the middle ear is the only part of the ear directly connected to the throat.",
"Now, there are three bones in the middle ear; the ",
", the ",
", and the ",
". You may know these as the hammer, anvil, and stirrup. Fishes have these same bones, but they don't use them for hearing. They're part of their jaws. The malleus is a bone from the lower jaw called the ",
". The incus is a bone from the upper jaw called the ",
". The stapes is a bone that braces the upper jaw against the skull, called the ",
". The upper and lower jaws occurs between the quadrate and articular. There is a passage that runs past the hyomandibula called the ",
", which is essentially a specialized pharyngeal slit. It was used to modulate water flow across the gills.",
"Now, as our ancestors crawled out of water, they started using these bones in their jaws to carry sound to the inner ear. The articulation between the quadrate and the articular is still the primary jaw joint in most amphibians and reptiles, for example. In mammals, though, a second jaw joint forms called the ",
" (TMJ) and the quadrate/incus and articular/malleus completely separate from the lower jaw. The spiracle slit never opens, leaving a thin membrane across the surface of the spiracular opening. This membrane is the eardrum or ",
". What's left of the spiracle now is the middle ear and the tube that connects the middle ear to the throat, called the ",
".",
"So, in other words, the reason these organs are all connected is because of a combination of how these organs develop and the evolutionary history of these organs in our distant fishy ancestors.",
"Hope this helps."
] |
[
"Thanks. That really helps. "
] |
[
"No problem!"
] |
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