title
list | over_18
list | post_content
stringlengths 0
9.37k
⌀ | C1
list | C2
list | C3
list |
|---|---|---|---|---|---|
[
"Why does our skin feel warm/hot while sunburnt?"
] |
[
false
] | null |
[
"A sunburn is usually a first degree burn, and the body's natural reaction is to increase bloodflow to the place that hurts. There's also one (or two) less layers of epidermis on a burn area, so you're feeling more of your own body heat directly."
] |
[
"correct, the blood vessels dilate, increasing blood flow near the surface. This is why the skin looks red. "
] |
[
"So it's actually physically warmer, not just a psychological thing?"
] |
[
"If we are travelling in a train along the equator at half speed of light, what would a live broadcast of events inside the train look like outside?"
] |
[
false
] |
Consider a railway track around earth's equator and a train at say ½ speed of light or 2/3 speed of light. Now suppose we are broadcasting events on the train live to the people on ground, so what will the broadcast look like to stationary people on ground.
|
[
"You would get a crappy signal. As the distance between the station and the train increases, it would take more time for the signals from the train to reach the station (or broadcast tower) which would a varying signal.",
"If the TV crew inside the train were taping a clock, it would run at a slower rate than a clock that a person, who is watching the tv, is looking at. ",
"Observers moving will always experience time passing slower relative to a stationary, or slower moving, observer. "
] |
[
"Well the most basic principle about General Relativity is that, where ever you are. Regardless of your speed, ",
"\nIf you use a mirror in that Train, the Light would have to bounce from the mirror and reach to your eyes in the speed of light. But from the outsiders perspective if someone would measure the speed of the bounced light.",
"\nThey would think that the speed of light is 1.5 times, why? because the Light has to travel at the speed of light + the speed of the train, to reach your eyes.",
"\nObviously we know that this isnt true, because the speed of the mirrors Light ",
" be the speed of Light.",
"\nSo how do can we fix this? Well at that speeds the effects of ",
" are starting to play a bigger and bigger role.",
"\nYou can even ",
"calculate this easily yourself",
", by putting the right numbers in it.",
"\n(for e.g. half the speed of light is 150.000.000 m/s and 150.000 km/s) with this you get a relatistic change factor of 1.15 .",
"\nNow we are left with the Question what this Factor actually means, it simply gives you the Factor of how much your Train ",
" at that speed. This means a 100 metric Ton Train is going to be ",
" at that speed.",
"\nBut what about your live broadcast? As is already said, its the basic principle of general relativity that whichever speed or perspective you are looking at something ",
" ",
"Edit: Also for further reference a relativistic factor change of 1.15 not only means an increase of mass of that Factor, but also that your length will be contracted by this factor and your time feeling would change (1.15 Years on that train equals 1 Year on Earth)"
] |
[
"But from the outsiders perspective if someone would measure the speed of the bounced light.\nThey would think that the speed of light is 1.5 times, why",
"No, they would measure it as light speed exactly. It's the same in all frames of reference, regardless of origin."
] |
[
"How does language develop differently in deaf children who are taught sign language?"
] |
[
false
] |
Young children often have difficulty speaking concise and coherent sentences, adding in filler words and making frequent tangents. How does this differ in children who are deaf from birth and taught sign language from a young age? Are they able to communicate their thoughts more clearly?
|
[
"https://pubmed.ncbi.nlm.nih.gov/9712135/",
"In the present longitudinal study, 20 deaf and 20 hearing children were observed during free play with their hearing mothers when the children were 22 months and 3 years of age. Compared to hearing children, deaf children were severely language delayed, with deaf 3-year-olds using less language (speech or sign) than hearing 22-month-olds. Deaf children communicated primarily through nonlinguistic vocalizations, with increasing use of gesture from 22 months to 3 years of age. Although mothers of deaf children used more visual communication than mothers of hearing children, they still primarily communicated through speech. In addition, deaf children did not visually attend to much of their mothers' communication. Therefore, deaf children received much less communication than hearing children. These results suggest that intervention efforts should be focused on increasing the quantity of perceived linguistic input by the child."
] |
[
"Pretty big limitation there in studying only deaf children of hearing parents. Language development of deaf children in homes where sign language is the primary language could be rather different."
] |
[
"I am giving an example from the NIH. There are many different ways to study children."
] |
[
"Could humans become nocturnal?"
] |
[
false
] |
I understand that under natural conditions attempting to be nocturnal can cause health problems, but would it be possible to use modern technology to do so with little risk?
|
[
"Well, a certain proportion of people are nocturnal. Read , nightshift workers. I have spent a not unreasonable amount of time in nocturnal mode. If you can work during the night there is a certain feeling of peace, not hearing the daily hustle and bustle , cars etc that comes from being awake during early hours. It can be a rather schizoid existence though."
] |
[
"What do you mean by nocturnal? That is, would someone who merely stays awake all night qualify as nocturnal or do they require a built in mechanism that encourages them to stay awake at night?",
"It is quite possible for someone to sleep during the day and stay awake all night. Plenty of people do just that for their jobs.",
"Edit: grammar"
] |
[
"This actually arose from a conversation with a night shift worker. He mentioned that although he is able to stay awake at night it doesn't quite feel right for him and that there is some evidence that it may be detrimental to his long term health. My question then, is if it is possible to adjust the bodies rhythms such that staying awake at night comes naturally without any lingering side effects."
] |
[
"Is it possible for Big Bang theory to be false .Like Universe to expand only in our neighbourhood and staying constant or contracting elsewhere?"
] |
[
false
] |
[deleted]
|
[
"That wouldn't explain the cosmic background radiation (the discovery of which pretty much ruled out most other cosmological models at the time) and the abundance of elements in the universe (which can be explained with big bang nucleosynthesis). ",
"One could probably create additions to your hypothesis which explain these things, but they can most likely be discarded by Occam's razor (until some other evidence submerges). "
] |
[
"Why were you downvoted at all?"
] |
[
"Nope, the universe is definitely expanding. We can determine the distances of faraway galaxies by using the brightness of a particular kind of supernova, and their velocities by using the redshift of their emission spectra, and the distance correlates pretty well with the velocity for every distant galaxy we've observed.",
"Now, is it possible for the big bang theory to be false? That's a different question, because the big bang theory is an explanation of why the universe is expanding, not just the observation that it is expanding. Sure, it's possible, but there are a bunch of observations that are neatly explained by the big bang theory and not by any other theory anyone's managed to come up with. So the theory seems quite likely to be true."
] |
[
"Atomic Orbital Theory, Molecular Orbital Theory, Valence Bond Theory."
] |
[
false
] |
What are the differences between these three theories?
|
[
"\"A scientific theory should be as simple as possible, but no simpler.\"",
"The standard model is our current understanding of particle physics and all interactions besides gravity. Everything is a field. Fields interact to produce the artifacts that we see. Everything is relativistically sound.",
"Quantum electrodynamics is a simplification of this model where we don't really consider anything other than electrical forces. In fact, most common treatments involve just light (the EM field) and electrons/positrons (the electron field). This theory is still too notoriously hard to for anything other than, say, predicting scattering of light from subatomic particles etc. It takes everything from light quantization to light polarization into account. It correctly produces fermionic and bosonic statistics for electrons and light.",
"Dirac's theory is a simplification of this that does not involve the creation/destruction of electrons. It is simply a model that relativistically describes how electrons would interact with light or external potentials assuming that there somehow already was an electron in this potential field. It was the first one to realize that positrons are real things if we properly relativistically treat quantum mechanics. It takes electron spin into account.",
"Schrodinger's wave theory is a simplification of the Dirac equation. It is not relativistically correct. It assumes slow moving electrons stuck in a potential field. You can't use this to describe electrons zipping towards you at high speeds. You can't use it to describe light or its behavior (light doesn't have a Schrodinger wavefunction like electrons). It doesn't describe electron spin at all - you need to jam it in as a separate rule called Pauli's exclusion principle. But it's a useful simplification. It's still exactly one electron. The orbital pictures you see from atomic orbital theory are pictures of the probability density of a ",
" electron in a particular shell around an approximated nucleus (the nucleus is modeled as an unchanging electric potential field). If you throw a second or third electron into the mix, the orbitals actually look nothing like that. So this theory is useful for more general descriptions of spectral lines, but not subtle issues like line splitting.",
"VSEPR theory takes this single electron model and tries to produce a multi-electron model from it. It works roughly to explain certain shapes and symmetries of systems (under the assumption that one can look at just the outer most electrons and how they might \"interact\" or \"combine\" into new orbitals). Since the basic underpinning are still a single atom model, it doesn't get get good energetic/quantitative results for multi-atomic systems like big molecules. It can be used for simple molecules like CO2 or whatever to describe their symmetries. I lie a bit.. you can patch things up a little... but try hard enough and you'll just get MO theory.",
"MO theory tries to make that a little better. It actually tries to model multiple atoms and their interacting potentials. Notice how you, in intro course, aren't actually taught ",
" to produce and calculate the exact energy levels involved. That's because that shit's hard. A lot of the equations involved are intractable to solve without computers and many admit no closed form solutions. You can still get some qualitative understanding about how various bonding/anti-bonding orbitals create differences in energy levels, but the actual energies are calculated by little minions in some lab somewhere. The most important assumption behind this theory (that makes it useful) is that the important effects we care about can be described by simply linearly combining the atomic orbitals produced in the single atom cases (LCAO). This discounts second order effects and hence makes the theory not very useful when describing the dynamics of a much more complicated system such modeling the movement of electrons in molecules being blasted by nuclear radiation that causes the molecule to split up, but that's not the goal in using this theory anyway. If you want to blow shit up, go back and use the QFT equations and crunch numbers with super computers at a particle accelerator.",
"If you are masochistic enough to volunteer to be one of those minions that calculate energies, you then come up with density functional theory which is a set of underlying strategies and models to help numerically compute behavior of electrons in a molecule. When you've gotten here, you have really gone far from the abstract single electron models. You are trying to simulate a bucky-ball or how codons work in DNA or something way way more detailed and specific. In the process, you can introduce assumptions like the fact that electrons in your DNA have a mass and are not zooming around at the speed of light or that your DNA is radioactive or producing anti-matter. They all come from the same place but have different uses.",
"Zoom out in a slightly different way and you can use crystal and lattice theory to work with highly ordered systems like ionically bonded solids. Now you get to pretend that lattice vibrations are little waves of their own called phonons. There's no such fundamental physical thing, but the math is there. ",
"Go one level higher and you get statistical mechanics. Now you're dealing with ensembles of tiny units. Now you've zoomed so far back that you can pretend that molecules are identical blobs that interact in certain fixed ways. You ",
" pull out the concepts of temperature (which by the way, involves a derivative - you can't really take derivatives unless you have enough states to make things look continuous). You now have entropy.",
"Zoom further back. Now you have solids, liquids, gases. You have your standard laws of motion. You have macroscopic electrical properties like capacitance/inductance of objects. You have fluid mechanics. You have bulk properties like shear stress and plasticity. You start looking up stuff in engineering tables. Your assumptions start getting bigger and bigger. But it's a complicated system and you aren't going to sit there solving for the spring constant of a spring by solving the QFT equations for the atoms in a spiral metal lattice.",
"Now we run into a problem. At this scale gravity becomes hard to ignore - so you throw in Newtonian gravity. ",
" is where you actually add something new to your equations. This isn't just a simplification of the old stuff. This is an actual new behavior that you can't work out from all your previous equations. It works well enough for bodies that are travelling slowly and aren't too big.",
"Zoom out more and you run into problems with space and time itself. All of a sudden all those nicely local, well crafted coordinate frames that measure length and time don't make much sense any more. Then you get GR. What we don't have is a quantum theory of GR."
] |
[
"All three are models of the wave-particle duality of electrons in an atom, and are essentially related to one another. Atomic orbital theory is used to describe the energetic nature of electrons in a single atom; molecular orbital theory (related to VB theory) qualifies these wave interactions between multiple atoms in a molecule with mathematical equations (the shapes assumed by the orbitals) and quantifies them in terms of energy (in the form of an energy diagram).",
"Source: student in inorganic chemistry. :)"
] |
[
"I just finished up a group theory class that really tackled MO and VB theories. The major difference between MO and VB theories is that the electrons are delocalized through the molecule in MO theory, and confined to directly bonds in VB theory.",
"MOs can be found using group theory easily by ",
"1) determining the symmetry of the molecule by ",
"findings its point group",
"2) choosing a basis set of orbitals. If you are looking at the pi system in benzene, you would use the pz orbitals, if you want the full MOs you would use the 2s and 2p orbitals on each carbon.",
"3) Find and reduce a reducible representation.",
"4) once you have irreducible representations, which give you the symmetry of your orbitals, you can use a very simple projection formula to find the symmetry-adapted-linear-combinations, or SALCs.",
"5) these SALCs aren't exactly your MO, but they are just a few steps away.",
"Why is this important? Well if you use the matrix representation of your SALCs, where you have (s)=(SALC)(phi). Where (s) is the symmetries of each SALC, (SALC) is the coefficient of each orbital, and (phi) is the orbital vector you can easily find your VB theory bonds. All you do is left multiply by the inverse of the SALC matrix to get (SALC)",
" (s)=(phi). This is neat because it gives you exact solutions very quickly and easily by hand."
] |
[
"What happens in my brain and/or body to make me feel drowsy?"
] |
[
false
] |
Are there any specific chemical or physical changes that occur in me that cause me to feel drowsy? This is especially interesting to me because it seems like the drowsiness kicks in all at once, like a bag of bricks hitting me in the face.
|
[
"While you are awake, adenosine levels increase in your brain, and past a certain level, adenosine receptor stimulation will make you feel drowsy. When you sleep, adenosine is broken down, reducing the drowsy feeling. Caffeine makes you feel less awake because it \"tricks\" your brain into thinking that there are lower levels of adenosine in the brain by blocking adenosine receptors. Thus, when the caffeine is eliminated from your system, you experience a \"crash,\" because your brain quickly goes from experiencing a low level of adenosine receptor stimulation to a much higher level of adenosine receptor stimulation.\nNeuroscience Undergrad."
] |
[
"So will drinking more coffee over a long period of time make me less sleepy in the evening? Funny enough I just wondered about that before seeing this thread. Would you mind having a look at ",
"this",
" please ?"
] |
[
"See the post you linked for an explanation!"
] |
[
"What is happening to the reception of a Wi-Fi signal on my laptop when near an operating microwave?"
] |
[
false
] |
Hello askscience! This community has been very knowledgeable and easy to understand in the past (even to someone with only a layman's knowledge of many branches of science like myself), so I hope this answer to this question is painfully obvious. I noticed that my laptop's internet connection (to a wireless network) cuts out every I'm waiting for my lunch to heat up in a standard microwave. I assume that the microwave is radiating something to interfere with the wifi, but I can't imagine what. If it were actually "micro waves", wouldn't that kind of electromagnetic radiation be dangerous to people and thus be strictly contained inside the microwave? I'm hoping that some people can shed some light on this without super complicated jargon (I only have two 1st year physics courses under my belt). Thanks!
|
[
"Microwaves are only dangerous in sufficiently high amplitudes that they'll cause significant skin heating and thus burns. There's no physical difference between the microwaves emitted by your wifi and those emitted inside your microwave oven, it's just the energy level is orders of magnitude different. As KaneHau says, the oven itself is shielded and shouldn't itself cause interference."
] |
[
"Microwaves generated by microwave ovens are generally around 2.45 gigahertz which is smack dab in the middle of the WiFi spectrum. To reduce this from happening, try changing to other channels to find one that is least bothered by the interference."
] |
[
"Yes, they interfere with each other.",
"It isn't microwaves escaping the oven per say - rather, the electronics driving the microwave horn is oscillating at that frequency and generating radio interference.",
"Similar to how we used to debug computers in the old days (when computers were much slower). Back then the CPU was slow enough that it was oscillating in the AM radio spectrum. We could set an AM radio near the computer and tune it to the right frequency and hear loops and conditionals in the CPU. More than one enterprising programmer wrote special 'do-nothing' software to play music this way."
] |
[
"Does at least one person in the world have to have Ebola (or any other virus) at any given time to make it continue on?"
] |
[
false
] | null |
[
"If a virus has a ",
"natural reservoir",
" (some plant or animal it can exist in), then it is not necessary to have a human infected at any given time in order for that disease to persist. This is especially pertinent to the ",
"Ebola virus",
" since natural reservoirs are being actively sought after to explain its pattern of recurrence. ",
"Alternatively, any virus that could survive for extended periods of time in the natural environment outside of a host could also \"continue on\" in the absence of actively infecting someone."
] |
[
"Yes they are immune. And what you suggested has been tried and is the basis for the mouse antibody serum you've read about in the news. Unfortunately this serum while theoretically (and possibly really) is helpful in ramping up an infected individual's imm be system, it's not curative. "
] |
[
"No, even if, and as is usually the case, no humans were presently infected with Ebola, the virus would continue to live on in its host animal(s). The Ebola family of viruses exist naturally without human involvement in the wildlife of Africa, originating with a species of fruit bat, I think. It's only when the virus jumps species to humans (through bodily fluid contact) that the Ebola you're hearing about in the news comes to surface.",
"\nConversely, there are human viruses that have been eradicated by exactly the method you're suggesting. Smallpox, the scourge of humankind for millennia, was finally wiped out in the '70's through a system of containment and immunization. Since it had no natural host other than humans, when the last case was cleared, smallpox was declared eradicated."
] |
[
"What is the difference between the magnetic pole and the geomagnetic pole?"
] |
[
false
] |
Wikipedia has too many fancy words that make no sense to me.
|
[
"The magnetic poles, or the magnetic dip poles, are the two points where the magnetic field lines are vertical, i.e., if you had a compass that allowed its needle to move in 3 dimensions, the compass needle would point straight down (or up, depending on which magnetic pole we're considering) when you were standing on the magnetic pole. The magnetic poles move a lot as part of ",
"geomagnetic secular variation",
" (e.g., the ",
"path of the north magnetic pole for the last few hundred years",
") and the two magnetic poles are generally not antipodal. Meaning that if you drew a line that passed through the north magnetic pole and the center of the Earth, it would not intersect the south magnetic pole and vice versa. This is in part because the magnetic field is not a true dipole, i.e., in reality it's not like a simple bar magnet.",
"The above being said (and true), at the surface of the Earth, the magnetic field and poles are ",
" to being like a dipole field. So, the geomagnetic poles are the locations of two antipodal points that best approximate the current location of the two magnetic poles as if they were generated by a simple dipole field (e.g., if the Earth's magnetic field was generated by a bar magnet at its center). The geomagnetic poles are a construct, or a fit to the true magnetic field (kind of like a fancy version of a linear regression, where you fit a line through a cloud of points that have a linear relationship but don't define a single line on their own). This means that if you went to the current location of the geomagnetic poles, chances are that if you had your 3 dimensional compass again, the field lines would not be completely vertical at the geomagnetic poles, but they'd be close. Just like the linear regression example, where it's easier to deal with the fit as opposed to the cloud of points in many cases because all we need to know is the slope and y-intercept to define the relationship, for many purposes, it's much easier to deal with geomagnetic poles (i.e., a set of antipodal points) than the true magnetic dip poles. For most purposes, the small amount of inaccuracy that comes from dealing with the approximation of the geomagnetic poles is outweighed by the benefit of not having to deal with the much more messy true locations of the magnetic poles (and their short term movements).",
" Please note, that in this context the word \"secular\" has nothing to do with religion. ",
"Secular variation",
", of which geomagnetic secular variation is a type, is a common term in time series analysis to refer to non-periodic variations in a time series."
] |
[
"Really neither and there is a lot of nuance. The ",
"first chapter",
" from this book on paleomagnetism provides a (somewhat) approachable perspective. Specifically, in terms of the observed magnetic field (and thus the resultant location of the magnetic poles), a decent mathematical representation (but not necessarily good physical representation in terms of ",
" these complications exist) can be produced by considering a main dipole field that is perturbed by a series of lesser magnitude and variably oriented radial dipole fields (to account for the so-called \"nondipole components\" of the field) where the location of the magnetic poles essentially represent the result of interference of multiple different dipoles. As discussed here, in terms of approximations (i.e., the geomagnetic pole), we can actually get a slightly better fit typically if we relax the embedded geocentric assumption (i.e., that the line between the two geomagnetic pole goes through the center of the Earth). The resulting \"eccentric dipole\" does a slightly better job of explaining the observed field."
] |
[
"Does that mean there are two monopoles that make up the magnetic field or is it just like a bent dipole?"
] |
[
"What are the implications of the existence of the graviton - the force-carrying particle of gravity?"
] |
[
false
] |
The graviton is a hypothetical particle, probably massless, which carries the force of gravity and is responsible for its effects. in another thread is very illuminating. But what are the implications of this particle? In GR, sitting in a gravity field is equivalent to acceleration, relative to the reference frame of the massive object, correct? So the particle also plays an integral part of all the crazy time-dilation, space-warping craziness, right? And what about black holes? Clearly gravity can escape it, but not light? So gravitons are not subject to the effect of other gravitons, I take it? Then they wouldn't necessarily follow the same topology of the rest of the universe at the largest of scales, it seems to me - if the Universe is closed due to the effects of gravity, the gravitons would escape if they are unaffected by gravity... I just don't understand it at all! Finally, the most important question of all: if gravity is just another fundamental force, like light, for instance, do you think the possibility exists to someday construct a gravity laser? One which shoots gravitons in a collimated beam of synchronized gravity-insanity? What would it ? p.s. I suggest a name for this device: gravity-laser => gazer. Hah!
|
[
"Gravitons are just the quantized versions of gravitational waves, which we're pretty sure exist (based on the Hulse-Taylor binary). Gravitons are to gravitational waves as photons are to electromagnetic waves. The problem is that there isn't a working quantum theory of gravity, so gravitons don't work mathematically yet. So if gravitons exist, it implies some form of quantum gravity, which is cool."
] |
[
"I started writing one, but I realized I'm not fully qualified to answer so I stopped. So take this with a grain of salt.",
"Lasers are based on a transition between two electromagnetic states. Usually this involves an electron jumping from one orbital to another, which releases a photon. The gravitational equivalent would be a gravitationally bound rotating system, changing orbital modes. Classically, there is only one equilibrium orbit for each two-body system, but in GR I believe there are two (only one is stable), so I suppose there could be a jump from one to the other releasing a graviton. However, in practice you would basically have to have two massive and dense bodies like black holes orbiting each other, which needless to say is difficult in practice. Perhaps if micro-black holes can be created, have two of them near each other and see what happens. Keep in mind that gravity is about 10",
" times as strong as the EM force, so the gazer would produce a much weaker field then the laser.",
"Gravitational waves are a quadrupole wave, which means if they shoot through a circle of particles, ",
"it turns into a wobbling ellipse",
". So basically, you could do that at will."
] |
[
"Is it possible to make any comments on gazers without a mathematical model for gravitons?"
] |
[
"Can you trick a plant into growing faster by changing the duration of the day - night cycle?"
] |
[
false
] |
In the simplest terms: if I have a plant who has 6 hours of light and darkness rather than 12, so experiences two shorter days for every 24 hour period, would its growth be any faster?
|
[
"Maybe. It depends on what you mean by “growth”",
"If you mean “net uptake of carbon dioxide fixed into carbohydrates”, then probably not. Net uptake is a product of temperature, water, light, and CO2 limitation, and that won’t change by changing day length.",
"But day length is a critical component of hormone and chemical cycling in plants. It can control transpiration, phloem translocation, flowering timing and fruit development, among other things. You can’t really control how much a plant will take up carbon, but you CAN control where it puts its resources when it gets them. Includes in this is the initiation/suppression of dormancy. All of this heavily depends on what plant we’re talking about though - many plants won’t change behavior at all with the treatment you’re describing."
] |
[
"You can ",
" when day and night are, so your plant gets light when the environment is night.",
"Environmental CO2 levels peak at night, and noticeably so."
] |
[
"If I have a plant who has 6 hours of light and darkness rather than 12, so experiences two shorter days for every 24 hour period, would its growth be any faster?",
"The plant wouldn't enjoy this at all. Most plants and animals are specifically adapted to Earth's 24-hour daylight cycle through a biological circadian clock, that synchronizes all the stuff that happens in the body over the course of a day with the natural day/night cycle. Experiments tend to show that the more closely the experienced day/night cycle matches the internal rhythm of the organism (which can vary by an hour or so; that's why it's called \"circa-dian\", not \"precisely-dian\"), the better the organism performs. ",
"Here's a nice example in bacteria",
".",
"But what you ",
" do (as other commenters have touched on, and as plant growers will actually do) is keep the day/night cycle 24 hours long, but ",
", as would happen naturally across the year (long days in summer; short days in winter). Depending on what time of the year a given plant species normally exhibits certain behaviors (growing fast; growing more slowly; storing nutrients; making flowers; shedding its leaves; etc.), you can potentially trick it into exhibiting those behaviors by providing a particular daylength.",
"It is of course also true that having more light in a day provides at least the potential for more growth, as the plant can photosynthesize during more of the day. Whether or not this translates into more growth will depend on to what extent this particular plant is limited by photosynthetic rate (it might not be), and what its response to a long light phase is (many species use up their resources to produce flowers and then die when they experience long summer days, so it might be counterproductive).",
"Either way, this would mean something like providing 20 hours of light and 4 hours of darkness; providing twice-as-fast days isn't going to help anyone. The plant would be getting 12 hours of light per actual day either way, and its circadian clock would be stressed the hell out by the weird non-standard photoperiod."
] |
[
"Are there any countable continuous sets?"
] |
[
false
] | null |
[
"Depends what you mean by a 'continuous set'. The notion of continuity is usually tied to topology and is used to describe mappings, not sets.",
"In topology, we make a classification of some subsets as 'open', and from this classification we can derive concepts like continuity (of mappings, not sets), closed sets, compact sets, connected sets, topological dimension and so on. So if we can rephrase the question in topological terms it can be answered.",
"I'm assuming the intuitive notion of a continuous set is something like interval in R: it's open, or at least it has an open subset, and it's connected. If so then yes, you can create a topological space where there are countable, even finite subsets that have this property. In fact I can't immediately think of any topological property that can't be satisfied by a finite set so long as you make the right choices.",
"Now, the topology of the real numbers ensures that open sets must be uncountable. So in that interpretation, it's impossible."
] |
[
"Same story there though, it's absolutely possible, in carefully chosen topologies, to have finite dense sets. Just not in the topology of R."
] |
[
"What's wrong with Q? That is dense."
] |
[
"Why is my paintball bruise a ring with an undamaged center?"
] |
[
false
] |
image:
|
[
"Just as an off-the-cuff direction to go with your thinking:",
"You know how when you squeeze a paintball between your thumb and index finger it bends (Unless you are using marbleizers...things may have changed since I've last played, but seriously, fuck those things)?",
"Well, you can imagine with the force of a few grams traveling 300fps, when it hits your arm the pressure inward is a lot more than your squeezing -- the middle bends in to absorb the impulse, directing the paint to the edges radially outward. By the time it bursts, the ring around the middle of the paintball has built up a substantial pressure, and 'gives' a lot less than the center. This means that the edges feel more 'solid' and so when it collides with your arm it is more rigid than the middle, and therefore transmits the force of the paintball itself disproportionately onto the area of your skin where the bruise is.",
"edit: clarity"
] |
[
"Ultra slow motion Video demonstrating how the edges of projectiles impact radially outward (cool vid to watch just on it's own) ",
"http://www.youtube.com/watch?v=QfDoQwIAaXg",
"Edit: After watching the vid again it's almost like seeing fluid dynamics demonstrations when dealing with such extreme speeds and forces, cool stuff. "
] |
[
"Makes sense. I would also guess that it has to do with the fact that the center only experiences a compressive force, while the ring around the center gets more stretching/shear forces, which may be better at tearing capillaries. "
] |
[
"Is a sonic boom most intense at Mach 1?"
] |
[
false
] |
[deleted]
|
[
"A boat on a lake at constant speed leaves a V wake. A faster boat leaves a narrower wake. The speed of the ripple is like the speed of sound. That is your cone! Sound at Mach 1 spreading out as the plane rips past."
] |
[
"Let me know if I'm wrong, but by how you proposed this \"addition of sound waves\" I'm guessing that you are thinking as the sound waves as the way the actual (audible) sound is propagated through space. That is totally correct but it's not actually sound what fluid dynamicist are referring to when talking about the speed of sound and its relation with the object's velocity.",
"The speed of sound is treated in aerodynamics as the speed at which perturbations in the fluid (as in change of direction, change in pressure...) are transmitted. That means that ",
"the Mach cone that you talk about and so many books use it to explain supersonic flight",
" actually refers to the domain in space where the perturbation generated in one point is transmitted downstream (in the direction of flow movement). This means that points outside of this cone wont realise that flow has changed.",
"You can see in that picture that in the subsonic regime, flow before the point can receive the information of the perturbation but in the supersonic regime the information is only transmitted downstream. The fact that the flow right before the body (the body as a cause for perturbations because flow has to move around it) won't realise its presence, forces the fluid to suddenly change its properties, creating a discontinuity in the flow. This discontinuity means that flow suddenly realises that it has to change its properties and abruptly does so (creating a jump in pressure, density, velocity...) instead of a continuous change as it happens in subsonic. As you may have guessed by now this discontinuity is a shock wave. It is easy to understand that the faster (the higher the Mach) the flow moves, the faster the flow has to adapt and so the jump in properties becomes more extreme. That explains why the higher the Mach the more intense the shock wave is. The sonic boom is actually how you perceive this changes in pressure generated by these discontinuities. The differences in pressure that you perceive as sound generated from the aerodynamics of the plane (vortices for example) are really small compared to these jumps in pressure for a supersonic jet.",
"Finally, in order to explain what a shock cone is you need to know that there are 2 types of shock waves:",
"Normal shock waves: the discontinuity is perpendicular to the flow. More intense and produced when the flow doesn't have to change direction. Flow after is subsonic.",
"Oblique shock waves: the discontinuity makes an angle with the object (and the incoming flow). Less intense and typically to change the direction of flow by a certain amount. Flow after is still supersonic.",
"This picture shows the type of shock waves you can get. Detached are a mix between oblique and normal",
". Once you know what oblique shock waves are you can imagine that when people talk about shock cones what they are really referring is to a bunch of oblique shock waves (actually to a really complex structure of shockwaves) that when observed in 3D looks like a cone. ",
"This would be an example.",
"However, do not confuse the shock cone with ",
"the vapour cone",
". This is a different phenomenon, caused by increased speeds around the object that reduces the local pressure condensating the ambient's water vapour. The shock wave is actually after the visible cone when the pressure suddenly rises and water droplets disappear.",
"Sorry for the long explanation but I think the topic requires it."
] |
[
"Ignoring for a second that your hypothetical wave would only have constructive interference directly in front of the aircraft and not for any observers of the craft, no because that’s not really how supersonic works. ",
"Supersonic aerodynamics is much more complex than most physics teachers have lead people to believe. There are two cones on a the front of a simple supersonic object: a Mach cone and a shock cone. The Mach cone is as you’ve described with an angle corresponding to hypothetical sound waves coming off of the object. The shock cone is the actual extreme discontinuity in pressure and other flow properties which occurs at a different angle because that’s how the thermodynamics works out. The flow discontinuities are stronger for higher Mach numbers with Mach 1 actually corresponding to zero discontinuity at the theoretical shock angle. In real life, you can hear sonic booms before Mach 1 due to flow speeding up and slowing down around various parts of the aircraft. Plus, all sonic booms that we observe in real life are propagated from the aircraft to the ground which always muddies things. ",
"Mach cones are used to calculate boom carpets because they will always be bounding of the sonic boom. Because of the way fluids work, it is impossible for a fluid within the Mach cone to have any effect on the fluid outside of the cone. So the Mach cone will necessarily always be larger than the shock cone no matter what subtleties you throw at the problem."
] |
[
"How does the DNA replication machinery know when it has already replicated a chromosome?"
] |
[
false
] |
Before mitosis, cells undergo DNA replication to generate two copies of each chromosome. How is the DNA replication machinery controlled such that it knows when a chromosome has been replicated. In other words, what stops it from over-replicating a chromosome?
|
[
"Cyclins are a type of protein closely related to telling our cell when to start the DNA synthesis phase of the cell cycle and regulating it. More specifically Cyclin E promotes/initiates the assembly of protein complexes that actually do the replicating. Then another type of Cyclin called Cyclin A comes in, and serves two purposes. First, it tells the protein complex to begin replication, and secondly it inhibits other protein complexes from forming. With only the one complex, the DNA won't be able to replicate more than once.",
"Source: ",
"http://www.nature.com/ncb/journal/v4/n7/abs/ncb813.html",
"So basically, the \"machinery\" doesn't know when DNA has been replicated already. It is simply prevented, by Cyclin A, from accessing DNA."
] |
[
"The crux of preventing re-replication in eukaryotes works through the helicase, the enzyme which separates the two strands of DNA for the replication machinery. In a nutshell, the way this works is that the helicase is only capable of being loaded onto DNA during G1 phase. Once you've entered S-phase the necessary loading factors are either degraded or moved out of the nucleus, preventing the helicase from being reloaded on replicated chromosomes. ",
"In detail: (note, I study DNA replication in yeast, but the core processes I'm describing are highly conserved). So in eukaryotes, the replicative helicase is this 6-protein complex called Mcm2-7. These proteins make a donut-like structure, where the DNA goes in the middle. To be loaded onto DNA, it needs help from several other factors. Some factors bind to origins of replication first, and other factors recruit Mcm2-7 to those origins. One of those factors appears to pop the Mcm ",
"ring open like a lockwasher",
", at least it does ",
". This open ring is thought to be important for loading the Mcms. ",
"So the Mcms are loaded in G1 phase, associated with these other protein factors in a ",
". At this point, the helicase is biochemically inactive. There it it sits, doing nothing, until the pre-RC is activated by regulatory kinases (Cyclin-dependent kinases, and their neglated stepcousin DBF4-dependent kinase). Once this happens, we're committed to entering S-phase, no going back. The critical result of the phosphorylation by this kinases are the recruitment of some replication specific scaffolding proteins and some conformational changes of the Mcm complex (we assume from ",
" studies). This brief period is called the ",
", and a lot of the molecular details at this point are poorly understood. Somehow we get 'initation, DNA unwinding occurs and polymerases, single stranded binding proteins, and all that other good stuff is recruited.",
"Now we have fully competent ",
". The Mcm2-7 complex, now bound to 5 other proteins, forms the CMG-Complex, and is a DNA unwinding juggernaut (it's kinda like an S-phase Voltron). At those point, all those other proteins that were in the Pre-Replication context are gone, in particular, that protein that holds Mcm2-7 in an \"open ring\" form has been degraded, and the helicase now forms a tight, closed ring circling ",
"a single strand of DNA",
". Since those other factors are gone, and the Mcms are in a different conformational shape, no reloading of the helicase can occur until the next time the cell enters G1 phase."
] |
[
"Got it. Thanks!"
] |
[
"Why are smaller atoms generally more electronegative?"
] |
[
false
] |
[deleted]
|
[
"Less electrons on the outside shielding the protons, thus attracts more electrons more effectively."
] |
[
"Electronegativity is the tendency for an atom to attract a disproportionate number of electrons in a covalent bond. As such, it is obviously affected by charges. The nuclear charge of the nucleus in small atoms is obviously smaller than in larger atoms, but they tend to have higher electronegativities on the whole, especially in nonmetals. The cause of this is that inner orbital electrons are able to shield outer orbital (valence!) electrons from the nuclear attraction. This is why cesium is so unstable: the lone electron that is so far and shielded from the nucleus is quite easy for another atom to incorporate in a reaction. Fluorine has the highest electronegativity because it has the highest atomic number in its period and thus the most valence electrons. Its period has very high electronegativity on the whole because it only has one inner energy level to provide shielding, and that level only has 2 electrons anyway."
] |
[
"Right. As Jeebs says. ",
"Imagine yourself as an electron in an atom in two situations:",
"1) with a nice attractive nucleus close to you; \n2) a nice attractive nucleus further away with a cloud of unattractive electrons in the way. ",
"In which situation are you more attracted to the nucleus? The first one, where the atom is smaller."
] |
[
"Can dogs (or other animals) go crazy if left alone in a small room for an extended period of time with no social interaction?"
] |
[
false
] | null |
[
"That's not 100% true. Most of the time dogs destroy things when left alone at home it's due to anxiety and stress caused by under stimulation. It has nothing to do with \"social interaction\"; an appropriate set of toys would serve the same purpose as having a person or another dog in the house.",
"tl;dr - Dogs don't destroy things because of lack of social interaction, they destroy because they are bored."
] |
[
"This is actually a major reason why dogs destroy things at home while their owners are at work. It's not full on insanity, but it's an extremely negative behavior brought on by being left alone."
] |
[
"Social interaction is a type of stimulation though, yes? Sure if you leave your dog at home with stuff to do he will likely be entertained. my dog usually sleeps when I'm not home and he's never been destructive from boredom, so it certainly is not a hard and fast rule.."
] |
[
"Why can't we simulate gravity?"
] |
[
false
] |
So, I'm aware that NASA uses it's so-called "weightless wonders" aircraft (among other things) to train astronauts in near-zero gravity for the purposes of space travel, but can someone give me a (hopefully) layman-understandable explanation of why the artificial gravity found in almost all sci-fi is or is not possible, or information on research into it?
|
[
"In addition to using centrifugal force to simulate gravity you can also use linear acceleration. If your spacecraft can sustain accelerating at 9.8 m/s",
" for a long period of time the occupants inside the spacecraft would experience a force equivalent to gravity in the opposite direction to the acceleration. ",
"This is one of my favorite parts of the show \"The Expanse\". Often when they are travelling in space they have gravity and it was established early in the series that this is achieved by constantly accelerating toward the destination. Then when the spacecraft is halfway to its destination there is a warning followed by a brief moment of weightlessness as the craft flips around to point in the opposite direction. Then the deceleration burn begins and the simulated gravity is restored. That is a super neat detail in that show. "
] |
[
"Observed from the spaceship, accelerating at 1g would reach 0.77c after 1 year.\nObserved from Earth, it would take 1.19 years, and would have travelled 0.56 light years.",
"After two years on the ship at 1g, you would reach 0.97c, however 3.75 years would have elapsed on Earth and you would have covered 2.90 light years. Viewed from the Earth, your mass would have increased 4x, and you would be a quarter of your size!",
"After five years on the ship, you would reach 0.99993c. 83.7 years would have elapsed on Earth, and you would have covered 82.7 lightyears. You would stand about an inch high, and have a mass of about 6 tons as seen from Earth, though you would not notice any difference.",
"After 8 years, you would reach 0.9999998c. 1,840 years would have elapsed on Earth. Great, you are far from what was your home. 400 US presidents came and went. What is more, you are now 1mm high and have a mass of 140 tons.",
"Nothing to lose now, lets go on, still at 1g...",
"After 12 years, you would be travelling 0.99999999996 c. By now you would have crossed the galaxy and be 113,000 light years from home. Time is now running 117,000 times more slowly for you than on Earth. You stand 15 microns tall, and your mass is about 9000 tons.",
"So, in fact you have travelled \"faster than light\" by covering 113,000 light years in 12 of your years, but well and truly burnt your bridges in doing so.\nYou have also become a very significant problem for any destination, and would require 12 years too to slow down at 1g, assuming you have survived the deadly blueshifted light and cosmic radiation."
] |
[
"Just to be clear, the aircraft NASA use to simulate weightlessness are not in any way \"generating\" zero-g or removing the force of gravity. They are simply free-falling toward the Earth. Gravity is pulling them down, but there is nothing stopping them from accelerating so they experience the sensation of weightlessness.",
"This is similar to why astronauts on the ISS feel weightless. They are moving so fast horizontally that they are in free-fall around the Earth. They are still under the force of gravity, but they don't feel it."
] |
[
"How does brain control heart rhythm in people that are from neck down paralyzed?"
] |
[
false
] |
If a person is paralyzed due to serious injury to their spinal cord around neck, how does the brain still control the heart or even simple breathing is possible?
|
[
"It doesn't, at least not directly. The heart has its own internal pacing system that takes over. This is actually a real problem around the time of the injury, as the patient may be in shock from their trauma but the body can't manage to mount a high heart rate because the nerves have been severed. The brain can influence certain hormones that affect heart rate and blood pressure, though. Also, breathing is also affected by high spinal cord injuries. The phrenic nerve, which controls most of breathing, receives input from below the C4 area of the spinal cord (roughly speaking). An injury higher than that results in an inability to breathe, and the person will be ventilator-dependent."
] |
[
"C4 is only a couple inches from the bottom of the skull.",
"The brain doesn't just receive information in nerve form, it also has chemical, hormone, and pressure receptors."
] |
[
"The Vertebra are named based on the region of the spinal column they're located in and their place from top to bottom within that region. For example, there are seven cervical vertebrae designated C1 through C7. The eight cervical spinal nerves are similarly named. ",
"Here's a schematic showing all of them, and their global motoric fuction.",
" "
] |
[
"Why isn't fiberglass as dangerous as asbestos seeing as they are both fairly similar fibers?"
] |
[
false
] | null |
[
"fiberglass is man made, we melt and make glass into thin strands (1-10 micron usually).",
"Asbestos naturally forms extremely tiny crystals which are a lot smaller than fiberglass.",
"Fiberglass is still really dangerous and you shouldn't abrade it without proper ventilation and PPE. We have a carbon fiber shop at work that does carbon and fiberglass, and we treat both of them pretty much like asbestos. lots of containment, PPE etc.",
"you can't breathe in fiberglass unless is it abraded, since the fibers are usually really long. Some silicate powder is used for filler in resin to lay up fiberglass as well, and that stuff is just about as bad as asbestos.",
"really any form of solid material that can be respirated (diameter and length < 5µm) is bad for you to inhale."
] |
[
"As I recall, the real issue with some forms of Asbestos is that it can cleave down to atomic scale fibers. This is what allows it to do the DNA damage, and cause cancer. Fiberglass (and other silicate materials will cause issues (silicosis), but afaik, won't have the cancer issues that Asbestos can have."
] |
[
"In addition, I read somewhere that one of the problems with asbestos fibers is that when macrophages try to engulf and digest them, they are unsuccessful and they end up just impaling themselves on the fibers and then dying. The punctured macrophages then spill their cell contents which include reactive oxygen species, which can then damage neighboring cells.",
"See ",
"http://www.sciencephoto.com/media/249880/view",
"and ",
"https://www.youtube.com/watch?v=tZFQ3mEOIVw"
] |
[
"How did humans figure out that the ocean tides had anything to do with the moon?"
] |
[
false
] |
Early humans certainly realized that tides occurs with predictable regularity. And they knew that the moon had a predictable, regular cycle. But it's not nearly as obvious to the naked eye that there is a causal relationship between the tides and the celestial body hanging out in the sky. When did we figure out that the moon causes the tides, and what proved it?
|
[
"The tides tend to get stronger and weaker in about a two-week cycle, exactly half the cycle length of the Moon. You can follow that pattern over years or even decades, and it's always linked to the Moon. Full/new Moon: Large tides. Half moon: Small tides. Pretty obvious that they are connected somehow."
] |
[
"There will always be a high tide within a few hours of the moon reaching its highest point. Depending on the lead or lag caused by the local geography.",
"Coupling this with the observable king tides when the moon is new or full, coastal communities rightly assumed there was a connection.",
"So as others have said, humans have learned this independently all over the world many time over thousands of years."
] |
[
"A little tidal history!",
" ",
"The earliest evidence for at least a practical understanding of the tides dates back to 2500-1500 BC in the form of a tidal dock at ",
"Kathiawar",
".",
" ",
"There is evidence, of a controversial nature, for humanity's understanding of the relationship between the tides and the lunar cycle that dates back to at least 2000 BC through ancient megaliths in western Europe.",
" ",
"It took a long time before any progress was made, some of the most important contributions were:",
"William Gilbert",
") (1544-1603): proposed the tides were of a magnetic nature (he was responsible for the discovery of the Earth's magnetic field)",
"Galileo Galilei",
" (1564-1642): proposed the tides were a direct result of accelerations due to orbital motion of the Earth around the Sun (largely he used this as evidence\nfor the Copernican model of the solar system) ",
"Johannes Kepler",
" (1571-1630): actually made the correct prediction (based on documented observations), that some attractive force between the Earth and Moon was responsible, although it met with fierce resistance from Galileo ",
"Rene Descartes",
" (1596-1650): introduced a quite creative Theory of Vortices which was regarded as the correct answer for many decades (despite not only completely ignoring Kepler's laws but also making no reference to any previous tidal theory!).",
" ",
"It was Newton's pioneering work in Philosophiae Naturalis Principia Mathematica that provided the correct description for the cause of the tides, which came as a consequence of his Universal Law of Gravitation (which Kepler was close to). However, Newton's ideas were not accepted over the Theory of Vortices until 1740 with the help of giants such as Daniel Bernoulli, Leonhard Euler, Colin Maclaurin, and others. ",
" ",
"This (1940) is really when we actually knew, not before as other posters have suggested (it was hypothesised but the mechanism was not understood). The reason we did not know prior to this is because the cycle of the Moon did not universally explain observations which is why other theories were proposed. However, I would say Newton gets an unfair amount of credit for his discovery of the mechanism behind the tides, he actually did little work on tides. It is the work of ",
"Pierre-Simon Laplace",
" (1776) that is the basis of modern tidal theory.",
" ",
"For a more complete review of tidal history see ",
"Cartwright D. E., 2000, Tides: a scientific history",
".",
" ",
"TLDR ~1740"
] |
[
"Microscope to look at pond life?"
] |
[
false
] | null |
[
"Biology"
] |
[
"Biology"
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"Do you think consciousness could be quantum mechanical?"
] |
[
false
] | null |
[
"Hi Fxck_its_demii thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"I've been asked to add flair to this post, I tried to leave my question an minimal as possible so as to not look like a moron. I was just wondering as I had watched a video recently on YouTube about this person asserting that consciousness is quantum mechanical, I wrote it off as they provided no evidence. But just as a fun hypothesis let dig into it, is there anyone here that has an opinion, for or against the possibility & why. "
] |
[
"Such questions are better suited for our sister-sub ",
"/r/asksciencediscussion",
". Please post there instead."
] |
[
"What is the current limit of CRISPR/Cas9 technology in human gene-modification?"
] |
[
false
] |
How far can we go with the current tech and the current understanding of human genome in terms of human modification? Without concerning ourselves with legal and moral issues, how much can we change a human embryo? What is the strongest positive change we can make with the current tech?
|
[
"The main challenge with using CRISPR to make the sorts of changes that people are imagining is that you need to deliver it to relevant cells, which is far from easy. The CRISPR cassette is fairly large, too large to fit comfortably in most AAV or lentiviral vectors. Adenoviral vectors are immunogenic issues, and even in all these cases, it is a tall order to suggest you could deliver to a majority of cells in a particular tissue of interest. People are actively working on this delivery issue.",
"How far can we go with the current tech and the current understanding of human genome in terms of human modification?",
"Well, we can modify pretty much any part of the genome, and typically can add genes into the genome, although integration into signaling/expression networks is still a bit more difficult. ",
"Without concerning ourselves with legal and moral issues, how much can we change a human embryo?",
"An embryo? Pretty much not at all. The ",
" of CRISPR is probably the main current challenge, and while that is hard enough in a regular human being, it has added difficulty in embryos since they are 1. small, 2. fragile, and 3. still inside the mother, and are therefore hard to get to.",
"What is the strongest positive change we can make with the current tech?",
"Probably ",
" modification of immune cells, stem cells, islet cells, etc. Fixing/changing a small number of cells in a petri dish that we can reintroduce into the body to have a larger effect is the most reliable thing we could do with current tech."
] |
[
"What if you are doing an alteration to a zygote? As I understand there are just few cells there, which should make altering all of them easy. At this stage is it possible to make alterations to a zygote with CRISPR?",
"Yeah, zygotes would work, if you didn't mind accidentally killing some of them during the process. Delivery isn't a painless process, which is why most CRISPR work is applied to a large number of cells, with the expectation that some die and others never receive the plasmid in the first place.",
"I was curious if we could, for example, alter the eye color, height, life expectansy etc.. By using CRISPR to alter human zygote, and have the said zygote develop into a healthy baby.",
"If you had a several zygotes that survived the delivery process, most of them would have whatever modification you were trying to do (provided it is a single† indel‡ modification). If that modification doesn't really affect viability, then you'd have about the same chance that IVF has of producing a viable baby. The examples you give are largely polygenic, so you'd need to change several genes (sometimes in pretty specific ways) to try to get the change you want, and there isn't a way to know if the zygote got all the changes in the specific way you wanted them until you can sample some of its DNA -- after it is a fetus.",
"† Trying to make multiple changes at once is harder to do, since you need to ensure that the several guide RNAs are all delivered to the relevant cells -- something that is pretty hard to check on. Including multiple guide RNAs on a single plasmid can work, but you start to have really big plasmids the more changes you're trying to make.",
"‡ Trying to disable a gene is more efficient than trying to introduce a specific change (replace one nucleotide with another) or insert an entirely new gene. Not only does delivery get more complicated (more DNA needed), but the process of homology directed repair has a lower success rate than NHEJ repair does.",
"I'm also curious about our current understanding of genes that affect intelligence. Can we alter the genes in a zygote in a way that would make the resulting baby smarter? (I know there is a debate on what intelligence is, Let's say, instead of intelligence, higher IQ score)",
"There is some work that has tried to find loci correlated to higher intelligence, with some mild success. Most of the changes are from one nucleotide to another, which would generally require HDR, and creating indels in those genes would probably end up being fatal. It would be hard to do, that's for sure."
] |
[
"So the only thing that's stopping us are legal boundaries.",
"And time and money. Sperm might be a dime a dozen, but human ova are time-consuming and expensive to acquire. ",
"Although, as far as I know some countries permit human gene editing in embryos (correct me if I'm wrong)",
"IIRC, the only people who have tried on human zygotes was a research team in China, and they were using zygotes that were irregular and couldn't be used in IVF.",
"What's stopping companies from experimenting with designer babies using CRISPR?",
"The time and money part.",
"Out of 2 methods (CRISPR and Pre-implantation genetic diagnosis) Which one is more technologically and commercially viable for mass producing designer babies?",
"They are both going to probably use a lot of cells before you find the ones you want. I guess with CRISPR, you can at least ",
" to make changes that you wouldn't really get no matter how many times you mix sperm from person A with ova from person B.",
"If you're trying to use CRISPR to just break a gene, you can get somewhere from 60-100% efficiency. If you're using CRISPR to ",
" a gene from one allele to another, now you're talking about 0.5-20% efficiency. For traits where there are 3 genes you need to change to see the trait you want, that is a 0.0000125-.8% chance of getting all three changes in a cell. So out of 125 cells (assuming 100% delivery), you'd have at best 1 that had all the changes you want. And three genes is not very much for a polygenic trait, let alone traits that we don't understand as well that could have dozens of associated loci.",
"So for IVF, where you typically implant several zygotes, you'd need 3-6 bona fide altered zygotes. If you're trying to make this designer baby for someone that wants to pick eye color, hair color, approximate height, some genes to help them have a good metabolism, etc, we're talking about maybe a dozen genes that you'd want to change. To get a few of those zygotes, with all of those changes, you'd probably need to CRISPR something around a billion cells. ",
"I guess, if we're getting more 'out there' with it, you could try to do all this CRISPR stuff on cheaper cells, like some stem cells or something, and then try to do SCNT to 'clone' the CRISPR'd cell nucleus into a zygote. Now, no one has successfully done that with human cells, so someone would probably have to figure that out first, and that would undoubtedly have its own success rate issues."
] |
[
"I'm wondering what the brief history of cleaning and sanitation products is. Is there any sort advances coming soon?"
] |
[
false
] |
I assume surfactants have been known about for a long time (how long, I'm not sure). But other cleaning and sanitation products, I'm not sure about. And is there any discoveries or anything like that which will be coming to us soon? I don't really know chemistry or compounds, so a layman explanation might be best :)
|
[
"Mr. Clean Magic Eraser",
" is a pretty recent and awesome cleaning development."
] |
[
"In terms of history a recent invention has been the application of enzymes in laundry detergent. The enzymes digest protein, organics and other stains. Now it may seem trivial to add these but they were a significant development. They required isolation, purification and a lot of modification to work in the washing machine. It's a pretty hostile environment with high temperatures, diverse ph and surfactants. They have also begun engineering the enzymes to work at cold temperatures so there is no need for hot water. "
] |
[
"There's this research project with 3 sea shells that looks promising...",
"=)\nThe new nanomaterials are the next big advance. Nanoparticle siliver is already being used as a way of preventing microorganism growth. Hopefully the next big thing will be \"lotus effect\" surfaces, super hydrophobic surfaces that the dirt just rolls off.",
"Not really my area though."
] |
[
"Why do whales plunge out of the water?"
] |
[
false
] |
Most of us have seen the iconic hop of whales out and back into the water, causing the ships of many fictional characters to become surfboards. Why do they need to do this--is it simply to breathe, or is it tied to a hunting strategy or a mating call?
|
[
"Interesting theory, but dolphins also jump in and out of water, and for them it would not produce enough sound to travel long distances. An often neglected hypothesis for animal behaviours is just that the animals are having fun, but its nearly impossible to prove that is the reason for any animal behaviour. I wonder if this could be the case for dolphin acrobatics and maybe even whale breaching? "
] |
[
"Interesting theory, but dolphins also jump in and out of water, and for them it would not produce enough sound to travel long distances. An often neglected hypothesis for animal behaviours is just that the animals are having fun, but its nearly impossible to prove that is the reason for any animal behaviour. I wonder if this could be the case for dolphin acrobatics and maybe even whale breaching? "
] |
[
"Dolphins also use this for hunting. If you look into large baitballs, you can see dolphins on the ends of their hunting lines jumping out to signal where the end of the baitball is so that the rest of the hunters can work together easier."
] |
[
"With the current world birth rate at about 1 every 8 seconds, when was the last time we could say there was \"one born every minute\"?"
] |
[
false
] |
Try as I might, I have not been able to find a historical record of this. Source: EDIT: One every 8 seconds for the US, the world is about one every 2.5.
|
[
"Are you refering to the idiom of \"A sucker born every minute\"?",
"If so we need to define the percentage of newborns that would be considered suckers.",
"Borrowing snusmumrikan's data of current birth rates and required births per year and making the (hugh) assumption that birth rates have been relatively constant and are linear with population. My best estimate would be when the world population was roughly 50,000,000 and according to my research this equates to about 1000BC"
] |
[
"At birth, it is difficult to distinguish, so everyone must be considered a potential sucker."
] |
[
"Where are you getting the one every 8 seconds data? ",
"The data from the UN I've just looked up seems to suggest 2.5 births per second.",
"I tried to do some quick rough maths to answer your question but it means finding a year with half a million births, which will be so long ago there won't be any reliable records. "
] |
[
"Why cant we just cure dental caries/tooth decay?"
] |
[
false
] |
Given that tooth decay is due to bacteria ( and ), why can't we just get rid of those using something like antibacterial tooth paste? We're almost rid of several bacterial diseases in the west, for instance leprosy, cholera or typhoid infections, so why isn't anything done about tooth decay? Sure, it's bad for dentists, but there has to be someone out there willing to do something about it.
|
[
"I notice this source doesn't link to any peer-reviewed journal articles on the matter. Is this a result published in a reputable journal of medicine, or just a blogger making an unsubstantiated claim?"
] |
[
"You mean like a ",
"vaccine",
"?"
] |
[
"The oral microflora contains many of the disease causing bacteria normally. Example: what we call in dentistry as the red complex: p. ging, t. Forsynth, and p. Dent are found together in most cases of gingivitis, periodontitis etc. but a normal person might have one, two or all three of the bacteria and be fine. Just because you have the bacteria doesn't it will cause disease. Also constantly using abx in toothpaste will cause abx resistance so that's not a feasible method to control bacteria population. We use fluoride in toothpaste, water, mouth wash because it has been proven as a good antibacterial agent. Dental caries wouldn't be a huge problems if people follow ada guidelines but its because people don't listen to suggestion of dentists is when it becomes a problem."
] |
[
"Is voter apathy a relatively new phenomenon and does it exist and/or have repercussions in countries with compulsory voting?"
] |
[
false
] | null |
[
"Voter apathy is as old as democracy. In Athens, they used to send out slaves carrying a ",
" rope dipped in red ochre to round up voters from the agora. Anyone who tried to avoid attending the assembly (ekklesia) would have their clothes marked with the red paint, and could later be fined for failing to do their civic duty.",
"Edit: typed 'robe' when I meant 'rope'. The keys are, like, right next to each other. If you have really fat fingers."
] |
[
"OK, so I'm preparing for my comprehensive exams in political science, so I'll take this opportunity to address the question in terms of the literature that has been done on it (mostly relating to rational choice theory). ",
"In regards to 'apathetic voters' Downs (1957) would argue that it is quite irrational to vote in the first place, as the costs (taking the time to inform oneself, time spent going to polling place, etc.) is not worth the benefits (influencing the election) because the probability of doing so is infinitely small. Further, even if you have a preference between the two candidates, your preferred outcome is just as likely to occur whether you bother participating or not, thus creating a free-rider problem (Olson 1965). ",
"So the question shifts from: why do so few people vote? – to why do people vote at all? Well, Downs added a 'D' term to this equation, which basically indicates a perceived value in 'saving democracy' - people realize that if everyone voted abstained from voting, democracy would fall apart. In addition, individuals and groups with a larger stake in the outcomes of elections or perceive a higher value in ‘being informed’ will take the extra lengths to do so, but many won’t. ",
"A number of subsequent researchers have been unsatisfied with Downs’ conception of the ‘D’ term, and thus have augmented it, making it independent of the probability of actually influencing the election. For instance, Riker and Ordershook (1968) argue that part of the ‘benefit’ of voting is being able to ‘express’ oneself, and thus individuals are willing to ‘pay’ the costs of doing so. For Riker and Ordershook, the utility function in rational choice theory can include non-material benefits, such as the ‘good feeling’ you get from voting for the candidate who more closely aligns with your views or for ‘fulfilling your civic duty’. However, this civic duty benefit is not valued as high for everyone, as some are socialized at an early age to be part of the political process, and thus these individuals are likely to minimize the costs associated with informing themselves and getting to the polls, as the benefit is worth paying for. Others who never experienced this socialization process do not value the sense of ‘civic duty’ as highly, and thus consider the costs not worth the benefits of voting. Berry (1970) criticized rational choice theory, and Riker and Ordershook in particular, for failing to explain variances in turnout at the individual level, as ostensibly one’s ‘civic duty’ is unlikely to wax or wane from election to election – as was explained before, one’s predilection for valuing civic duty and thus voting is generally instilled at a young age and unlikely to be altered significantly through his or her lifetime. ",
"In come to terms with Berry’s concern, political scientists have examined the psychological aspects regarding the calculus of voting, most notably with the ‘minimax regret’ model (Ferejohn and Fiorina 1974). Essentially, minimax regret refers to the feeling of an outcome occurring in which you ‘regret’ (your candidate didn’t win), and thus if you abstained from voting, you feel partly responsible for your least preferred candidate in winning (even if irrational, since obviously your own vote didn’t make the difference) – and thus are more likely to vote next time to correct the wrong. On the flip side of this, if your preferred outcome occurred (your candidate won), but you abstained from voting, you are just as likely to abstain again next time. These arguments have been supported by subsequent scholars, as Sutton and Barto (1998) found that individuals ‘learn’ from their past actions, and the outcome reinforces their behavior because people tend to be retrospective, as opposed to forward looking. ",
"Part II forthcoming "
] |
[
"Part II:",
"In terms of the probability of influencing the election and its effect on one’s propensity to vote, researchers have reached diverging explanations on the matter. For instance, back to Riker and Ordershook, they found that primary elections in the previously Democratic-dominated South experienced higher turnout than the general election in many instances, making the case that a ‘competitive’ encourages individuals to vote. Electoral systems scholars (Lijphart 1997; Powell 1986) generally support the notion that the ‘closeness’ of an election increases turnout, as the single-member-district/plurality system in the US has been found to have lower levels of turnout, relative to other democracies, because so many votes are ‘wasted’ (more on this below in the institutions discussion). However, substantial work has been done to analyze how being part of a group can alter the calculus of voting in this regard (Uhlaner (1989), as being part of a ‘collection of voters’ not only increases the probability of influencing the election, but the presence of ‘group norms’ and ‘social sanctions’ for abstaining can increase the costs of staying home on election day (and increase the benefits). Thus, Uhlaner explains the decision to vote by including ‘selective incentives’ (Olson 1965) that are provided at the group level (solidarity, policy preferences more likely to be adhered to by candidates), thus increasing the value of the benefits of voting.",
"In regards to the institutional effect alluded to above, a number of scholars have argued that the costs and benefits of voting are significantly influenced by the electoral arrangement of a given country – from the ballot structure to the rigidity of registration laws. For instance, Rosentone and Wolfinger (1980) found that decreasing barriers to registration and allowing same-day voting increases turnout, particularly for certain demographic groups that are typically the least likely to turn out (more on that below). Moreover, Lijphart (1997) makes the case that proportional representation encourages individuals to vote because fewer votes are wasted, you avoid the ‘spoiler effect’, and one need not vote for ‘the lesser of two evils’, but can instead vote for a candidate more proximate to his or her ‘ideal point’ (Blais and Carty 1990). He argues that many people in the US fail to turnout because they find both candidates unacceptable, and under plurality rules, minor parties have little chance of winning the election (Duverger 1954). ",
"Moreover, under multi-party systems, campaigns tend to be less negative, as candidates and parties are encouraged to emphasize their positive qualities, rather than tear down opponents. Alternative vote, for instance, allows for ranking your preference among candidates, and thus parties have an incentive to appeal to be the second or third choice among voters, which would be harmed by being too negative. Moreover, the frequency of our elections also discourages turnout (Boyd 1989), as individuals experience ‘voter fatigue’ by being asked to turnout to the polls more often than in other democracies (House two-year terms are by far the shortest duration; we also have offset local/national elections in many cases). Additionally, having elections on a weekend or making it a holiday tends to encourage voting, as forcing wage laborers to leave work early further exacerbates the cost/benefit analysis. This is why most democracies have already made this reform, while politicians in the US who benefit from low turnout have blocked this proposal every time it has come up (Senator Hillary Clinton actually proposed this back in 2006). Finally, our separation of powers system creates a situation in which the majority party often struggles to enact the legislation they were voted in for in the first place (which is exacerbated by the filibuster rule, which creates a super majority requirement in the Senate). Thus, gridlock makes elections less consequential because the status quo bias is much stronger in the US than in other democracies (Baumgartner et al. 2009). ",
"These institutional arguments are quite compelling, as comparative studies have found Americans to be just as ‘civically engaged’ as their European counterparts in many aspects (talking about politics, being involved in a campaign, etc.) (Putnam 1994), yet we vote in lower numbers. This discrepancy, it seems, can be explained by how our electoral system increases the costs (registration, frequency elections), while decreasing the benefits (fewer choices, wasted votes, status quo bias). ",
"Finally, from a more qualitative perspective, Schlozman et al. (2012) examine the socioeconomic disparity of participation, dating back to the 1950s (when survey data first became available). They find that stratification among advantaged and disadvantaged groups has actually grown over time, as the poor are less likely to participate in politics than they were in the past, while the wealthy are more likely to do so (participation includes not only voting, but also donating to a campaign, attending meetings, etc.). They attribute this growing disparity to both individual and group dynamics, as affluent parents are more likely to instill a civic duty in their kids, not to mention provide them with a better educational background that provided them the cognitive capability required to sort through relevant policy issues of the day. As individuals grow up, they tend to associate with like-minded people who have also been socialized this way and thus the propensity to participate in politics is reinforced through group norms (Campell 2013). For instance, Schlozman et al. found that individuals who are involved in recruiting for campaigns tend to target their friends (or strangers) who are in similar socioeconomic groups as themselves, while largely ignoring disadvantaged groups. These trends have even been found online, as social networks that discuss politics tend to bypass demographic groups that were never engaged in the political process in the first place (Schlozman 2008). ",
"To address the compulsory voting issue - unsurprisingly, a number of scholars have examined the effect, finding increase turnout (Hirczy 1994). Lijphart argues that compulsory voting improves democracy by encouraging individuals to become more involved and informed about politics – if you are forced to vote, you might as well learn about the candidates and the issues so you’re not just standing there checking off boxes in the booth. Essentially, making voting compulsory helps alleviate the collective action issues discussed early, and thus making it more ‘rational’ to vote and inform oneself, rather than free-ride off those who participate for the ‘fun of it’. Even small sanctions, as they have in Australia ($20), are quite effective at encouraging individuals to turnout on Election Day. ",
"To conclude, voters are not more apathetic than they have been in the past – turnout has been pretty stable over time (McDonald and Popkin 2001), with fluctuations for ‘important’ elections. Some have argued that the media environment has increased the gap between the ‘politically motivated’ and the rest of society (Prior 2007), and perhaps he is correct. However, turnout numbers have been pretty stable in the US, as we haven’t really undergone any substantial institutional reforms that would decrease the costs or increase the benefits of voting. The reason for this is probably rational choice based in itself – any benefit received from increasing turnout would be a collective good, and thus no individual is incentivized to prioritize it as an issue (although I would argue that Democrats collectively gain from it, so they should make it more of an issue). Anyway, that’s my spiel – I hope you learned something. "
] |
[
"What are the physiological mechanisms involved in the expression of complex mammalian coat patterns?"
] |
[
false
] |
As far as I understand, some patterns are influenced by temperature (siamese cat), while others (female, calico cat) result from the random inactivation of one or the other X chromosome which each contain one of two different alleles of a gene that determines color. Unless this is entirely incorrect, I think I have a good understanding of these mechanisms as they are frequently used examples, so I'm not looking for more information on these patterns. What I am interested in knowing, however, is how more complex patterns occur consistently throughout a species. One example would be in which seem to have circular clusters of spots around slightly larger, lighter spots, especially on their backs. I'd also be interested in learning how expression of complex patterns of spots might be similar or different to expression of stripes, such as those found on a . Thanks!
|
[
"I'm having trouble figuring out exactly what you're asking. Are you just wondering about the how the gene expression and physiology work to create the patterns? Here's some of my knowledge on the subject:",
"As far as pigment goes, there are genetic pathways that convert one pigment into another. But the patterning would be caused by induction/inhibition (and differentiation) of the pigment expression in the hair producing cells during development. I don't think it gets much more complex than that. The different particular patterns that we see in animal coats come from environment dependent selection.",
"Edit: The pattern is apparently called a rosette,a term which seems to apply to any part of the coat that is abnormal to the rest. I found a paper from the 1930s from a ",
"study with guinea pigs",
" that may satisfy some of your curiosity, they mention some genes and their phenotypes but the actual ",
" are kind of left out."
] |
[
"I guess I'm asking what signals are involved in turning on genes coding for one color or another, and how they are precisely localized to form patterns. I understand how gene regulation works in general and how these patterns might evolve over time, but I'm curious as to how these genes are turned on and off in such a specific and consistent way so as to get spots or stripes. "
] |
[
"If you're familiar with developmental gene regulation I think you have all the answers you need. You might be thinking it's more complex than it really is, which it does seem like it could be something interesting. Think about the gradient mechanisms that ensure that hox genes (and others, of course) are activating at the right time in development. It's just cycling of inhibition and expression, the genes of the particular animal dictate the manner in which this happens. Personally I can imagine a model of inhibitory and inducing patterns that would lead to the spots of a jaguar, but I can't say exactly how that would all translate into genetic code or what the signals responsible for those pathways are. Sorry I couldn't be of more help, I can't really find research on this subject but it's got to be out there somewhere :/"
] |
[
"What is a Tachyon?"
] |
[
false
] |
What exactly is this particle?
|
[
"\"Tachyon\" is a catch-all term for any particle which travels faster than c. Nobody has ever observed one, and most physicists probably don't believe they exist."
] |
[
"It's worse than that. In quantum field theory the presence of a tachyon corresponds to an unstable equilibrium. The mass squared of a particle corresponds to the coefficient in front of the harmonic potential in the field theory description, positive mass squared means you're at the bottom of a valley but negative mass squared means you're at the top of a hill, which is thermodynamically unstable. High energy theoretical physicists consider a tachyon to be a sign that either a) your theory is just broken or b) you're expanding perturbatively around the wrong point in field space. A good example of this is the Higgs potential. At phi=0 there is an unstable equilibrium and a 'tachyonic mode' but that doesn't mean that we observe tachyonic Higgs bosons, rather the field decays into some true vacuum where the masses are all real.",
"So in order for tachyons to exist semiclassically (even aside from the relativistic causality issues) we would have to be entirely wrong in our understanding of quantum field theory."
] |
[
"Although a group in Italy thought they did for a few months in 2011!",
"(turned out to be the result of a loose cable)"
] |
[
"Would it be feasible to have an electric car that was charged via solar panels built into it's frame?"
] |
[
false
] | null |
[
"The maximum solar energy available in any given area is limited to a maximum of around 1kW/m",
" In space it can get up to 1.4kW/m",
" but the atmosphere attenuates it a lot. The average energy available due to cloud cover and day/night cycles is 140W/m",
" The average car engine can produce around 100hp (76kW) or , but on average uses closer to 20-50hp (15-38kW). ",
"So, in order to power a car steady state, perfectly efficient solar panels in the best possible light conditions would need to cover 15-38 m",
" which is somewhere between the exposed area of a Ford Focus and a Suburban. Unfortunately, solar panels are between 12-20% efficient, and average lighting conditions are 6x dimmer than the best case scenario. These factors add up to require about 35x the area of the car to be covered in solar panels, which turns it from a nimble compact craft into a sailboat."
] |
[
"And, sadly such a big solar panel system would be heavier and larger than your average car so it would need more power to move, and even more area for solar panels. So put on some more, but then your car is larger and heavier...damn."
] |
[
"In addition to the other replies, concentrators save you the cost of the solar cells themselves but you still need a large collection area. If you're collecting energy from the same area and concentrating it onto a small cell, then you still need some sort of lens covering your car. This would again cause issues due to the weight of the lens material."
] |
[
"Has a non-native species of animal or plant ever been introduce into a habitat and it actually have a positive effect?"
] |
[
false
] |
Recently read about non-native ants in hawaii and how they’re threatening native Hawaiian butterfly species. It got me wondering if a non-native species of animal or plant has had a positive effect on a certain habitat.
|
[
"It’s almost unilaterally an awful outcome. ",
"Australia had a rich history of f*#king their ecosystems up with this! ",
"Cane toads are the prime example, rabbits, cats and foxes have done absolutely incalculable damage. Possums we’re taken to NZ from Australian, they have no native mammals so the possums have decimated bird species. Australia now has the largest wild population of dromedary camels in the world despite them being native to the Sahara!",
"Overall it unfortunately comes back to human interference and the inevitable damage it does. ",
"I don’t have any references to give but having studied animal science and been in the conservation industry for over a decade I can’t think of a single positive example."
] |
[
"Relaunching the everglade (florida) panther was interesting. They brought in 8 panthers from texas to restart the population. ",
"NPR Florida Panther",
"Another one is the moose of newfoundland. They originated from 4 released over 100 years ago. Moose is now a staple of newfoundland population and culture. ",
"Reddit Moose Post"
] |
[
"Moose have had negative impacts on Newfoundland forests, as well as putting pressure on native caribou populations, both by competing for resources and by providing more food for coyote populations.",
"Degradation of Boreal Forests by Nonnative Herbivores in Newfoundland's National Parks: Recommendations for Ecosystem Restoration",
"Impact of Non-Native Terrestrial Mammals on the Structure of the Terrestrial Mammal Food Web of Newfoundland, Canada",
"Reintroduction of the Florida panther is just that: reintroduction. Not a non-native species being introduced to a new ecosystem."
] |
[
"Is the leaf-like structure of the Leaf Katydids actually leaves or the material that leaves are made out of?"
] |
[
false
] |
Upon observation of Leaf Katydids, it appears that the leaves on their bodies resemble actual leaves of a tree, to the point where they look brown, have holes in them, and other things that commonly happen to leaves. Is the cellular structure of the leaves on their bodies the same as the leaves from the trees they hide in? If it is, does that mean they can use chlorophyll to synthesize sunlight and water into a sustainable food source?
|
[
"The katydid's wings are made out of the same material as the rest of the insect's exoskeleton, which is chitin. That's an animal protein that makes up the exoskeletons of all of the insects and other arthropods. That protein is also found in mollusks, in the radulae of the gastropods and the beaks of the cephalopods. ",
"The leaves on the tree are primarily made out of the same woody stuff as the branches; and that's cellulose. Cellulose is a long chain of glucose molecules that has a very high tensile strength and gives plants their structure. It's the primary component of the cell walls in plants. ",
"So the answer to your question is Nope.",
"\nThe katydid isn't made out of the stuff as the tree it lives in but it has certainly evolved an excellent ability to ",
"mimic",
" those trees!",
"\n(Just not good enough to actually photosynthesize.) ",
"Interestingly animals don't have cell walls. We only have the cell membrane which means our individual cells aren't as structurally strong as plants. But fungi do have cell walls like plants except their cell walls are not of cellulose because they aren't actually as closely related to plants. Instead, their cell walls are made out of chitin. That hints toward the fact that fungi are actually more closely related to animals than they are to the plants! "
] |
[
"Very interesting. Thank you for your response! "
] |
[
"I was of the impression that there are very strong differences between animal and plant cells.",
"Like this: ",
"http://img.sparknotes.com/figures/9/93c5cab1f150fcaaa9f2533d0a0b45c2/plantanimal.gif",
"Is it possible for any organism to have both?"
] |
[
"What changes when you break the sound barrier?"
] |
[
false
] |
Do things feel different, act different, sound different, etc? Or is everything similar to traveling at subsonic speeds?
|
[
"Nope nothing changes. There are many pilots who have talked about this online, but from the cockpit nothing feels different (other than a small shudder when initially break it). Some have described it as quite disappointing actually."
] |
[
"Nothing really changes from the views of a pilot however there are some really cool changes that occur within the machinery. If you look at any jet engine you notice the cone shape of the engine output. The jet engine pushes gases into an hourglass shaped funnel. As the funnel contracts the velocity increases. The gases then enter the expansion portion of the \"hourglass\". Under normal circumstances this causes the velocity to decrease BUT if you are at Mach 1 or above then it does the opposite! This is what propels the space shuttle and super sonic jets. "
] |
[
"Not the answer i was expecting but still good to know. Thanks!"
] |
[
"Does the water in clouds cause drag on aircraft?"
] |
[
false
] |
Obviously there’s quite a bit of water in clouds in any size from vapor to rain drops, as aircraft go through this does it have any effect on power requirements due to increased drag?
|
[
"In short, not really. The liquid water content in a cloud is rarely more than a few grams per cubic metre. Compared to the density of air (~1.2 kg/m",
" ), the water has little influence. And since clouds consist of tiny droplets, most of the water will just flow with the air, and only a small fraction ends up actually hitting and depositing on the plane.",
"The water that does deposit on your wings will increase drag slightly, but most aircraft that aren't high performance gliders won't notice the difference. A bigger risk is flying through a cloud at freezing temperatures. Then the water that deposits on your wings turns to ice, which will grow into thick ugly structures on your leading edge and can really ruin your day. Which is why many larger aircraft have de-icing systems installed, allowing them to safely pass through regions of light or moderate icing."
] |
[
"Clouds have the same average density as the surrounding air at the same altitude. They have to, otherwise they would go up or down."
] |
[
"The presence of water can cause icing on the aircraft, which can indeed increase drag and in addition cause premature stalling as the ice can cause flow separation to occur sooner (the texture of the ice is rougher than that of the aircraft skin)."
] |
[
"Wish I'd gotten a pic of the bottom which is bony and has horn like protuberances. What the heck is this?"
] |
[
false
] |
It was found in a coastal region so I'm guessing it's some sort of marine animal... It's been identified as Black Drum Pharyngeal Teeth. Thanks, 30000.
|
[
"I have a buddy who found something similar in the water on the Gulf Coast. So I asked reddit about it here:",
"http://www.reddit.com/r/animalid/comments/jqyhh/can_anyone_identify_this_thing_that_came_out_of/",
"The best answer that I got (and still not sure if it's correct, btw) is that they are pharyngeal teeth. There seem to be many kinds, but a google search will find some that look like yours. Namely:",
"http://media.photobucket.com/image/recent/ewestmnw/pharteeth.jpg",
"\n",
"http://baitfinger.qondio.com/what-the",
"http://en.wikipedia.org/wiki/Pharyngeal_teeth",
" for some information. Not sure, but that's my best guess. Hope it helps.",
"Edit: I'm no marine scientist or ichthyologist, just thought I could help."
] |
[
"I agree. Do we have one handy? Is there an ichthyologist in the house?"
] |
[
"I've seen these before while in a marine biology class on the shore (not an icthyologist) - it functions as a grinding plate for fish. betta fish have them - you can see and hear it working when they grab a 'kibble', and their head moves up and down"
] |
[
"Does the moon have tectonic plates like the earth does?"
] |
[
false
] | null |
[
"No. The Earth is largely unique in the Solar System with the presence of plate tectonics, although Mars may have briefly had it in its past.",
"Plate tectonics requires that the body remain hot long enough for the interior to convect and keep the crust moving. The moon, being relatively small, was not endowed with much heat to begin with, and it cooled relatively quickly.",
"Instead of forming plates, it formed a solid shell of anorthosite (a rock primarily composed of calcium feldspars). This crust would later be broken up by massive impacts, and in places, some of the large impact basins flooded with basalt. These are simple volcanic processes, though, and not a sign of plate tectonics."
] |
[
"Mars may have briefly had it in the past.",
"What happened? Did they fuse together? Could that happen to Earth's?"
] |
[
"As the planet's core cools, the molten rock gradually solidifies so in essence, yes, if Mars has plates then when the core cooled they stopped moving and became a solid mass.",
"That will eventually happen to Earth as well, but we have a looooooong way to go before the core cools sufficiently. Estimates vary because it's impossible to take measurements of exactly what's going on down there, but it's safe to say it's in the many billions of years range. With that kind of time line, I think the sun is due to go red giant first."
] |
[
"Besides C-14 and other forms of radiometric dating, which other techniques are used to determine the age of fossils and bones?"
] |
[
false
] |
C-14 dating can be used to date animal and plants remains that are less than 62000 years old and other forms of radiometric dating require the presence of igneous (volcanic) rocks. Which methods are used for dating when these techniques are out of the question? EDIT: is the reason for my question. "To everyone's surprise, the bone was part of a remarkably complete skull and upper body of a child that died 108,000 years ago, "
|
[
"Most are dated using ",
"relative dating",
" and then tied to an absolute age using methods of radiometric dating (dating igneous rocks within a sedimentary sequence, for example).",
"Using fossil succession is a very powerful method commonly used. This is done by observing the entire fossil assemblage, i.e., all the fossils found in a rock layer. Paleontologists have worked out the sequence of fossils in rocks and how long they have persisted. Thus, by looking at the overlaps it is possible to pin down the time interval in which a group of fossils will occur (",
"example figure",
").",
"Edits: typos and added example figure."
] |
[
"Now that I see your particular interest, I suspect they used U-Th disequilibrium isotope dating, paleomagnetism, or thermoluminescence. I can find no references other than the fluff piece you link, so it is impossible to say. In future, I'd appreciate knowing the specific question up front."
] |
[
"One somewhat obscure technique is thermoluminescent dosimetry. It is rather complex to describe, but a university library might have a decent book (McKeever wrote a decent one a while back).",
"Edit: Quick description... radiation causes certain materials over time to have electrons move to relatively stable higher energy states. If the material is heated, those electrons will settle and release the energy as photons. More photons (i.e. more light) means more bumped up electrons and more radiation. If the radiation was based on accumulation of background behavior then it can be an indicator of age. It is limited to materials that have the pseudo-stable states and haven't been thermally reset but there are a few out there."
] |
[
"Is there a link between unemployment and death?"
] |
[
false
] | null |
[
"There have been multiple studies over the years that have found some significant relationship between unemployment and suicide rates, but there are also a lot of variables that can impact those results, since life is a rather complex and multilayered thing in modern society. ",
"Here are a few studies I've found with a casual google search (I don't expect everyday people to know how to translate all the various sciencey terms and stats, so it's okay to read the Abstract at the beginning and then skip to the Conclusions/Discussion section near the end:",
"\n",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5451921/",
"https://jech.bmj.com/content/57/8/594",
"https://www.sciencedirect.com/science/article/abs/pii/S1344622306001349",
" ",
"As far as the \"40,000 people die\" quote, I haven't been able to find a specific source that states that specific number, but that doesn't mean there isn't a legit source out there somewhere (and I really only spent about 3 minutes looking for one)"
] |
[
"There are a lot more factors than just suicide. Unemployment can be an indicator of an economies overall health and declines in the economy can impact many aspects of life. On an individual level, less $ means reduced access to healthcare, unhealthy food, increases in mental health disorders etc. On a societal level less $ means worse infrastructure, less funding for medicine, less aid/public programs etc. ",
"For example take a common problem here in the US, food deserts. If you live in a food desert and don’t have the $ for a car or adequate transportation, you have no choice but to eat unhealthy food. As a result you have a higher chance of being overweight and getting diabetes and/or heart disease. In this case you might not be able to afford sufficient doses of insulin to maintain your blood sugar (insulin is practically worth its weight in gold rn) and this will have an impact on your health. ",
"I’m not sure where that statistic is from but I wouldn’t be surprised if it was true. There is likely a relationship between unemployment and increased mortality.",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4577549/#!po=12.5000",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5961388/",
"https://scopeblog.stanford.edu/2018/11/26/with-rising-demand-for-insulin-half-of-those-in-need-will-lack-access-in-2030-new-study-suggests/"
] |
[
"This is a very important question right now as the world balances the decision of when to return back to work. If we wait too long or return to early the consequences could be enormous. With almost 17,000,000 applying for unemployment in the last three weeks, or about 10% of the workforce, the answer to this question could have 600% more effect on our lives than the virus itself is projected to have.",
"40,000 per 1%...that means 440,000 in the current scenario (Week ending April 4 @ 11%)",
"440,000 is 380,000 more than the 60,000 projected...or about 600% more.",
"From CNN:",
"\"Over the last three weeks, more than 16 million Americans have filed jobless claims with the Department of Labor.",
"Here's the breakdown of the last three weeks:",
"Those add up to ",
" claims.",
"The US labor force had ",
"155.8 million people",
" in it as of March, so 16.8 million is roughly 11% of that.\"",
"EDIT:",
"Here's some grim stuff. Suicide is can be attributed to unemployment about 25% of the time. ( ",
"https://www.weforum.org/agenda/2015/02/the-link-between-unemployment-and-suicide/",
" ) ",
"There were about 50,000 suicides in USA in 2018. ",
"https://afsp.org/about-suicide/suicide-statistics/",
" ",
"Therefore about 12,000 of them were from unemployment. Unemployment was approximately 4% in 2018. Since we're closing in on triple that percentage, we should have about triple the suicides...or an extra 25,000 deaths. Yuck."
] |
[
"Can someone explain the concept of quantum computing?"
] |
[
false
] |
From what I know, classical computing uses two states, 1 and 0, true and false. Quantum computing is not limited by two states and thus can process values much faster. My question is, how would this even work (not practically, but I want an explanation behind the theory)?
|
[
"There are lots of really bad explanations of quantum computing floating around. (For instance, it's often claimed that a quantum computer can let you \"try all possible solutions at once\" which is almost entirely wrong.) ",
"Here's a layman's explanation by complexity theorist Scott Aaronson."
] |
[
"Check out the ",
"Bloch Sphere",
".\nIt is essentially a single qubit which has an absolute, whole, existing value. But the constituent parts of it are in probabilistic terms. That is, what defines the digital quantum information in a single qubit is from observations and measurements of changes at a quantum scale. ",
"With standard bits (1's and 0's) you can only really ask, \"Is this a 1 or 0?\" and that's what provides us with digital information. However, since qubits aren't quite as discrete, we can ask more questions based on the probabilistic states of the qubit yet yield the same responses. The fact that we can ask a qubit, 'more questions' means greater potential for efficiency in processing data."
] |
[
"Correct me if I'm wrong.",
"Rather than classical computing's use of square waves in order to have a set of 2 states, quantum computers use a full sinusoidal probability wave which, through some means (the computing itself), constructively interferes with the correct answer. Likewise, incorrect values are destructively interfered, if not fully cancelled out. With a range of amplitudes, rather than a solid true, or false, the computer can have a probability of any answer being correct. The one with the largest amplitude is mostly likely correct.",
"This is my understanding so far. Is that correct? "
] |
[
"If I submerge a jar under water, will the water flow constantly in and out of the jar?"
] |
[
false
] |
Or would the water that's in the jar be stagnant? I'm hoping the answer is that yes water would be slowly moving in and out of the jar. What about water that's closer to the bottom of the jar? There is current in the main pool of water flowing slowly over the jar and the jar is about 2-3 inches below the surface. Its a tall coffee jar.
|
[
"The jar will shield most of the movement from its contents, but you will get some slight exchange in and out. If you want to see it happen, pull some water with food coloring into a straw (to the top of the straw), put your finger on the top of the straw, insert the straw to the bottom of jar while submerged and let go the top. Don't take the straw back out, as it will move things. You can let it go though and observe."
] |
[
"If there's a current flowing over the open part of the jar itself, then there certainly will be some exchange - the open mouth of the jar will create some turbulence. How much and on what time scale, though, is not easy to predict, because turbulent flow of liquids is one of the hardest things to model. It could well depend very strongly on just what the current is, how wide the mouth of the jar is, what angle it sits relative to the current, and so on."
] |
[
"make sure there's no air in the jar....like none....as the air will cause turbulent mixing"
] |
[
"What exactly happens to an atom as we increase the strength of a hypothetical magnetic field?"
] |
[
false
] |
Do the quarks all experience forces in different directions due to their velocity and the atoms are either crushed together or ripped apart?
|
[
"The most exciting thing that happens to an atom in the presence of a (static) magnetic field is the Zeeman effect, where some of the energy levels for a given electron shell are split. ",
"This turns out to be an extremely useful effect for a lot of applications, but unfortunately it's not nearly exciting enough to use words like \"crushed\" or \"ripped\" to describe it. "
] |
[
"The effect applies to nuclear energy levels too!"
] |
[
"No. Will edit with answer when I get to a computer at work.\nEDIT:\n\"In particle physics, the strong interaction (also called the strong force, strong nuclear force, or color force) is one of the four fundamental interactions of nature, the others being electromagnetism, the weak interaction and gravitation. At atomic scale, it is about 100 times stronger than electromagnetism, which in turn is orders of magnitude stronger than the weak force interaction and gravitation.\" -Wikipedia: Strong Interaction\nIn short, the attraction between nucleons in an atom (protons and neutrons) is so powerful that it takes massive amounts of energy to rip them apart. The reason that nuclear reactions are so powerful (individual atoms giving off millions of electron-Volts) is precisely because the nucleus is so tightly bound."
] |
[
"What are some good TV shows on science?"
] |
[
false
] |
I'm not sure this is the right subreddit. Sorry, if this subreddit was not intended for these types of questions. I was watching the following, but they're either canceled or on break: I didn't add Nova ScienceNOW, because I just simply can't find the episodes for download. :( Anyone know any similar TV shows? EDIT: To keep the list going, here's what you've recommended so far:
|
[
"Not really a tv show but if you haven't watched it yet I suggest you watch\n",
"Richard Feynman's Fun to Imagine",
". Really interesting stuff about physics. "
] |
[
"Cosmos by Carl Segan was good"
] |
[
"\"Segan\" ",
"ಠ_ಠ"
] |
[
"What is the brightest light on Earth?"
] |
[
false
] |
Hello reddit, I just saw another space post by someone on the ISS. Some areas on earth at night are obviously brighter than others due to being clusters of lights in cities. I now wonder, what light on Earth is the most noticeable from space. It's almost like looking for the North star, except on Earth.
|
[
"Well, the north star is not particularly bright in the scheme of visible stars in the night sky. It ranks somewhere near 50th for brightness. ",
"But for the question if the brightest \"light\" on Earth, it depends on your scale. The brightest city is most likely LA. The brightest city section is reported to be the ",
"Las Vegas strip",
". But the brightest individual light? That goes to the ",
"Luxor Sky Beam",
" atop the iconic pyramid. "
] |
[
"Follow the citation: ",
"http://www.lasvegasnow.com/news/the-story-behind-the-luxor-light/79163434",
"The first thing you learn at the top is that there is no giant light bulb. Instead, 39 individual lamps, housed in dark, sturdy reflectors sprout from the floor like a forest. They combine to create the light.",
"You won't find these on sale at Walmart. Each Xenon lamp costs about $1,200 and will last 2,000 hours, working more like a welder's arc than a light bulb. ",
"39 lamps * ($1,200 / lamp) / (2,000 hours / lamp) = $23.40 / hour, so only $7.60 / hour of the cost is unexplained.",
"I'll speculate that cooling would be a big cost as well, even if it's just a bunch of fans."
] |
[
"When at full power, the system costs $51 an hour to operate, with $20 per hour of that just for its 315,000 watts of electricity.",
"...Where does the other $31/hr go? Human salary?"
] |
[
"Is there any significance at all to Earth's position in the universe? Anything at all unusual? Or are we situated in a completely unremarkable neighborhood?"
] |
[
false
] | null |
[
"There is one significant feature of our position in the galaxy: we're in the Local Bubble. ",
"http://en.wikipedia.org/wiki/Local_Bubble",
"\nThis is an area of interstellar space that is relatively free of gas and dust, and allows us to see farther into the Universe than would otherwise be possible. It was caused by one or more supernovae long ago. If we weren't in this bubble we'd probably be a bit farther behind in astronomy and physics than we are now."
] |
[
"The only thing remarkable about the earth (aside from its life) is how unremarkable it is.",
"It is a medium sized planet. Orbiting a medium, unremarkable star. In a medium, unremarkable system. Orbiting in an unremarkable part of an unremarkable galaxy which is in an unremarkable cluster of galaxies...",
"But it's also those very mediocrities that have lead to our being here to talk about it.",
"Our solar system has a star that isn't temperamental and won't burn out too quickly. And it is still powerful enough to have rocky planets, and a planet with liquid water.",
"Our system also has a couple very standard gas giants that clean up or expel many of the things that would look to destroy us.",
"Further, our system is far away from any other temperamental stars or groups of stars. We're not too close to the center of the galaxy and all the hustle and bustle that goes on there.",
"Our galaxy hasn't gone through any traumatic events that would damage it (turn it from a virgin spiral galaxy to a blob galaxy). There's nothing crazy like a gamma ray jet or anything coming from our central black hole or any near by.",
"While it's true we're at the center of the observable universe, it's no more important than the fact that if you were on a boat in the middle of the ocean, that you would seem to be at the center of the observable ocean. Each observer is at the center of his own observable universe.",
"Our planet is the normal of the medium of the commonplace. And that's fantastic. It opens up the possibility that we're not a fluke. That life and intelligent life may be as an inevitable result of liquid water, heat and time as a star is the inevitable result of clouds of hydrogen.",
"The things that are remarkable about our planet, our position in space, and our position in time...",
"Our moon is at a distance that means solar eclipses can be total (though its elliptical orbit will make some eclipses be more than total - moon is too big - or less than total - moon is too small... And in time it will continue to drift away until all eclipses are partial).",
"Our planet is in the Goldilocks zone of our sun. But much like the 'observable universe' issue, this is no more interesting than it's interesting that a basketball has a spherical shape. Any other shape would render it useless and the basketball wouldn't exist. Intelligent life can only come into being where conditions are right that intelligent life can come into being. If we had been beings that live in space, need no sustenance and could bend laws of physics, then we could claim to be remarkable.",
"Our moon contains a lot of the 'lighter' elements from earth's crust. The impact that created it seems to have taken a lot of material with it. But not the heavier material, only the lighter elements that floated to the surface. This could mean our planet has a thinner crust than might be typical for a planet of our size.",
"Our moon is relatively large. It doesn't just drive tides of water, which helped mix the primordial soup, but it also drives tides of earth itself, causing earthquakes and help keep the tectonic plate system flowing. And helps eject or absorb meteor impacts.",
"The universe itself is after a time when the sky would have been completely bright in all directions, and before a time when the sky seems completely dark in all directions. This helped drive our curiosity about our place in the universe. If there were no stars to see, nobody would have asked what they were. It would have been far easier to assume the universe was tailor made for us."
] |
[
"I remember a couple neat things about our solar system that are fairly unusual... If I remember correctly, the fact that our solar system is a single star, and not a binary star system, is actually relatively uncommon.",
"Also, the fact that the moon happens to be the correct distance away from us to make a total solar eclipse is pretty special. It will eventually drift, and total solar eclipses won't happen anymore. That's gonna be awhile before that happens though.",
"From wikipedia: ",
"https://en.wikipedia.org/wiki/Solar_eclipse",
"Total solar eclipses are seen on Earth because of a fortuitous combination of circumstances. Even on Earth, eclipses of the type familiar to people today are a temporary (on a geological time scale) phenomenon. Hundreds of millions of years in the past, the Moon was too close to the Earth to precisely occlude the Sun as it does during eclipses today; and over a billion years in the future, it will be too far away to do so.[36]",
"Due to tidal acceleration, the orbit of the Moon around Earth becomes approximately 2.2 cm more distant each year. It is estimated that in slightly less than 1.4 billion years, the distance from Earth to the Moon will have increased by 30,400 km. During that period, the angular diameter of Moon will decrease in size, meaning that it will no longer be able to completely cover the Sun's disk as seen from Earth. This will be true even when the Moon is at perigee, and Earth at aphelion. The sun is also increasing in diameter by about 5% per billion years.[37] Therefore, the last total solar eclipse on Earth will occur about six hundred million years from now.[36]",
"Edit: source on the solar eclipse thing",
"Edit 2: I remember where I learned the fact about the solar eclipse! It was on a podcast called Astronomy Cast, in this specific episode, put out years ago. I love this podcast, lots of really neat information about astronomy.",
"http://www.astronomycast.com/2007/01/episode-17-where-does-the-moon-come-from/",
"Edit 3: Grammar, for the Grammar God."
] |
[
"Why is U–Pb dating so effective in measuring the age of the Earth? Wouldn't there be decaying uranium floating around the early Solar System, or even *before* the formation of the Sun during the nebula stage?"
] |
[
false
] | null |
[
"Yes, there would. Then it all gets melted into a homogenous mess during planetary accretion. With the uranium locked in place, and the Pb unable to escape, we can measure their ratios to tell how long they've been locked in place.",
"Radiogenic dating tells you when the substance was last melted, not anything else."
] |
[
"A small addition to say that we mainly date zircons in the rock when using uranium-lead dating. Not only is zircon particularly long lived and resistant (even for a mineral), but it incorporates U into its crystal lattice ",
". So any Pb must have come from the decay of certain U isotopes. ",
"There is also the fact that two decay chains of different U isotopes result in two different Pb isotopes, so we have a two-for-one deal with U-Pb. We can exploit this by cross checking the data to make sure both of these decay clocks have given ‘concordant’ results ie. in agreement with eachother. "
] |
[
"Radiogenic dating tells you when the substance was last melted, not anything else.",
"This isn't really accurate. Radiogenic dating tells you the time at which the system (here meaning both the mineral you're targeting and the parent and daughter isotopes you're measuring in that mineral) became closed, i.e. when the mineral cooled below the ",
"closure temperature",
". For U-Pb, in most minerals the closure temperature is similar to the crystallization temperature (thus the U-Pb age can be interpreted as the time of last crystallization), but this is not true for all minerals, e.g. ",
"the closure temperature of U-Pb in the mineral apatite is relatively low",
", and definitely not true for all radiogenic systems."
] |
[
"How do magnets lose their strength and can they be strengthened or remagnetized remotely?"
] |
[
false
] |
This is my first time asking on because I feel my questions will not be adequate enough. I apologize ahead of time for the potato question. When I say remotely, imagine a cylindrical magnet suspended magnetically in a tube lined with opposing magnets.
|
[
"I don' t understand exactly what you are getting at. Regardless of its environment, it is always possible to heat something up with enough power. Spinning a magnet in atmosphere would generate friction on the surface and heat the magnet up. Spinning a magnet in a vacuum will generate a small amount of heat due to the 1 hydrogen atom per cm",
" but this will be rather insignificant as you mentioned. The magnet will have radiative heat transfer with the space around, which will cool the magnet. I don't know what other way spinning the magnet would heat it up. If it was in the presence of a conductive material, spinning the magnet could induce a current in the conductor if they are aligned properly, and the heat would radiate back to the magnet. This would be a really tough way to heat the magnet to its curie temperature, but possible.",
"Did you have a specific situation in mind?"
] |
[
"A permanent magnet looses field when it is heated above the Curie temperature, or is impacted. A sufficient field can also force a change in the direction of the field in the magnet.",
"Permanent magnets are produced by heating the magnet above the Curie temperature and applying an external magnetic field using an electromagnet."
] |
[
"In a vacuum which would be a frictionless environment, could the magnet reach that temperature while spinning?"
] |
[
"Why do some allergies only affect certain parts of the body?"
] |
[
false
] |
Many allergies seem to only affect the respiratory system or the digestive tract. Why can the same allergen be rubbed on skin in some cases and no reaction occurs, or post stomach not cause reactions throughout the rest of the digestive systems? I am assuming there is no reaction after leaving the stomach due to the acid denaturing the protein responsible, but why is this the case for other parts of the skin/body?
|
[
"The antigens have to be bound to IgE and then end up activating immune cells (mast cells especially). That's just much easier to accomplish in the respiratory and digestive tract. Unbroken skin is an excellent barrier for entry, and the respiratory and gastrointestinal tract make up most of the rest of the barrier between \"outside\" and \"inside\" of the body (the gut lumen etc. is topologically outside the body)."
] |
[
"Humans are donuts. The inside is also outside. (Same with most animals.)"
] |
[
"True allergies are related to mast cell activation where histamine is release as a response to the allergen. The sequence of bodily reaction to the allergen is related to the release of histamine. Example: peanut allergies and swelling of your tongue etc",
"In sensitivities, other immune factors are released so a different reaction is produced. Example: gluten sensitivity (not celiac's disease- which is an autoimmune response). ",
"Source: I am a dietitian "
] |
[
"If the bodies of rodents spasm when shot in the head, wouldn't that mean that a human's body would also spasm if shot in the head?"
] |
[
false
] | null |
[
"depends on what part of the brain is hit. ",
"and yes people can twitch when shot.. sometimes for quite some time as random firings of a broken brain make their way to muscles. "
] |
[
"You seem to be awfully familiar with the death-twitch of rodents... That's pretty creepy.",
"But it depends on which part of the brain is hit."
] |
[
"Yeah, I wouldn't take too much of reality from what you see in video games.",
"I've killed lots of things, and shot quite a few deer in the head. They kick and spasm and do all kinds of things. Its unsettling: death is not pretty.",
"Even when you shoot through the heart and/or lungs a deer might run a hundred yards or more. ",
"People may be different from deer, but I would be surprised if many people who get shot 'just drop dead' - no twitching, spasms, screaming, etc.."
] |
[
"Why do celestial bodies spin? What keeps them spinning? Have we discovered any that don't spin?"
] |
[
false
] |
Celestial bodies meaning planets and stars.
|
[
"Because of conservation of angular momentum. Objects form from smaller stuff colliding and sticking together. ",
"If you have two or more objects, unless they collide head on, the final object has angular momentum and will be spinning. It's incredibly unlikely that anything in space was formed from objects colliding head on with each other. "
] |
[
"It does spin. It's rotation roughly matches it's orbital period around the earth"
] |
[
"Just remembered what tidally locked actually means, thanks "
] |
[
"Is there a name for sine-like waves that are generated from shapes other than a circle?"
] |
[
false
] | null |
[
"I don't know of any special name for these functions, but the creator (",
"/u/lucasvb",
") of the .gif you have linked tends to call them \"polygonal trigonometric functions\". It's a bit of a misnomer since trigonometric already means \"having to do with a right triangle\", but in the absence of a better term, it will do for the sake of brevity. You can see more on ",
"his tumblr",
", where you can ",
"play around with the waves yourself",
". He also has contributed many of my favorite animations to Wikipedia, which can be viewed ",
"here",
". (I am fairly certain I have used his animations to explain some elementary concepts of geometry, waves, and pendulum motion on this very sub.)",
"Here are some more animations like the one you posted: ",
"triangle, square, hexagon",
", ",
"star",
", and a ",
"heart",
".",
"All that's really going on in these animations is that a line segment from the origin to the boundary of the enclosed region is drawn and swept around the origin at a constant angular speed. The graphs show either the x- or y-coordinate of the point on the boundary. It's nothing too difficult to work out explicitly, but the animations make for some very striking and beautiful images. For instance, for the stationary square (the animation you linked), you can easily show that the wave consists of 4 parts: a piece of the graph of the tangent function and its left-right reflection, and two horizontal line segments."
] |
[
"I particularly like that the region corresponding with the top-middle of the heart is smooth, but the one corresponding with the bottom-middle is sharp. Thanks for sharing."
] |
[
"Polygonometic functions?"
] |
[
"What happens to one siamese twin when the other die?"
] |
[
false
] |
I read the case of Chang and Eng Bunker ( ) that when one died, the other one passed away few hours later. What caused the death of the second one? What happens in other cases of siamese twins?
|
[
"Hmm, I'm going to speculate...I'm willing to wager that not much is known about this phenomenon, since conjoined twins are extremely rare to begin with.",
"First off, I'm going to begin with the assumption that the twin's vascular system (blood supply) is joined. Now, if their hearts were separate, I would imagine that each heart was designed to work in concert with the other (i.e. each heart did half the work). I'm going to wager that other body preserving organs, such as kidneys and lungs work the same way.",
"If that's the case, the shutdown of the lungs from the first dead brother would quickly kill his heart as well. The heart gets its oxygen supply directly from the lungs via the pulmonary veins, and is extremely sensitive to oxygen fluctuations. After this, the living brother's heart and lungs would have to work twice as hard, which would strain his system and would give him a slow death.",
"This is what I'm thinking at least, but it doesnt seem to quite make sense. If the living brother's heart and lungs were pumping double time and keeping the living brother alive, the same circulatory system should have kept the dead brother's brain alive. ",
"I am quite stumped. I will think about a possible mechanism for this strange death, and repost if no one else comes up with something."
] |
[
"Eng survived some hours [... i]t is more likely that he bled to death into his brother through communicating vessels; during the embalming of their bodies it was found that Chang was suffused with blood while Eng was greathy depleted (Tempelton, 1993).",
"GoogleBooks wouldn't show me the references page, but I think the Tempelton 1993 is ",
"this",
".",
"I'll offer my own speculation based on this:\nYou need to maintain blood pressure to ensure delivery of nutrients throughout you body, else you die. Normally, your blood vessels are constricted a bit - using a process that consumes a bit of energy - and so to space in your circulatory system that may be occupied by blood is matched by the amount of blood you actually have. ",
"Were one's blood vessels dilate all at once, the available space is greater than it should be given your total blood volume, and you can't maintain blood pressure. This would cause death (it's one of the components of ",
"septic shock",
" (CTRL+F \"systemic vasodilation\")). On the other side of the equation, losing too much blood causes death because, total blood volume decreases to the point that the available space is not occupied (and, actually, your blood vessels will constrict to try and match the available space to the remaining blood volume, but can only do so much) and you can't maintain pressure.",
"For conjoined twins with connected circulatory systems (even if the connection seems fairly minor), when the first one dies:\n(1) His heart stops pumping blood ",
" to the living twin, but the living twin continues pumping blood to the dead twin. This is the explanation giving for Chang and Eng... like as though Eng just bled through an open wound. And,\n(2) His blood vessels dilate, creating a lot of potential space for blood. This makes it impossible for the living twin to maintain blood pressure, causing death. Thinking of a normal (non-twin) person for a moment: If all the vessels on only her right side fully dilated (never mind how that could be possible) she'll probably die.",
"In a sense these are two sides of the same coin: There's too much space for a fixed blood volume, and too much of the blood volume ends up where it shouldn't be. Depending on how shared the circulatory systems are, though, one explanation might be better than the other. For twins with heavily connected circulatory systems, #2 might be a better explanation. For Chang and Eng, #1 is better explanation for a reason I didn't cover above:",
"Consider that the heart is positioned to take care of two circuits of blood at once... blood is sent to the lungs at high pressure, and returns with low pressure, then blood is sent to the rest of the body at high pressure and returns with low pressure. \nWhen Eng pumps blood to Chang through a shared vessel, it starts through one circuit at high pressure and ends with low pressure. But now that Chang's heart isn't pumping, the second circuit can't be started with the high pressure needed to complete it (unless the blood vessels dilate enough, but now we're at #2 above) and return blood to Eng at a reasonable rate."
] |
[
"Do you think possibly when the first brother died, cell necrosis released toxins that killed the second? Thats the only thing I can think of; kind of like when you have severe frost bite, you have to remove the dying or dead flesh before it kills you..."
] |
[
"Why are Moths nocturnal if they are drawn to sources of light?"
] |
[
false
] |
I know that Moths wouldn't necessarily be drawn to a light source such as the Sun, and that during the day lamps and the likes aren't likely to be switched on, So I guess what i'm asking here really is, a) Why do Moths come out during the night? b) What is the difference between Nocturnal moths and those who appear during daylight hours? and c) what is it that attracts them to light sources? Is it for Heat?, or is that a misconception that I have? Thanks.
|
[
"Moths use light waves to navigate in the dark. Obviously before humans, the only source of light at night were the moon (within reason)\nNow,throw in artificial light and those motherfuckers get confused. Im sure some lovely redditor has the science behind it."
] |
[
"That's pretty much it."
] |
[
"Thanks man."
] |
[
"Why do lupus and fibromyalgia mainly affect women?"
] |
[
false
] |
I was reading up on both this morning (mother has fibro) and found out that in both about 90% of patients with either condition are women mainly in the childbearing age range. Is there any reason for this? Thanks.
|
[
"hormones have significant immune effects. Lupus and fibro (to an extent) are seen as autoimmune diseases. Estrogens are seen as immune-stimulating. Women in childbearing age have higher levels of estrogens. This is a really active area of research but there are far more unknowns than knowns since the immune system is ",
" ",
"The other response in this thread is speculation. Or less charitably, they are talking out of their butt"
] |
[
"If there are sex-linked genes involved then perhaps on the X chromosome are dominant genes that contributes to the disease. Females would have a much higher chance of expressing a dominant gene on the X chromosome since they have 2. If something happens during childbearing it’s likely a gene that is expressed in other processes that involve reproduction or just a coincidence. There’s probably many mutations that are possible since many things can cause the body to attack itself."
] |
[
"Isn't it known that in general women suffer more from auto-immune diseases while men suffer more from immune deficiencies?"
] |
[
"Were massive slabs of similar materials that make up the Earth, rock quarries for example, formed recently or at the beginning?"
] |
[
false
] | null |
[
"Entropy only increases in a system that doesn't have external energy. Luckily, we have the sun, which provides energy for the erosion and subsequent deposition of sediments, and we have radioactive energy coming from the mantle/core that provide upwelling currents in the Mantle.",
"Lets take your example of limestone: Limestone is formed in shallow warm seas from mainly biological influences. When you say 'erode into water', we have to realize that water can't just hold sediments, they will fall out of suspension as soon as the raleigh number falls to a certain threshold for that particular size and weight of particle. ",
"There are some rocks that are about 3.6 billion years old, and these are granites. One example is from Finland and western Russia. ",
"There have been some cataclysmic events over time, but they are more localized and other than the K-T boundary, there isn't really a traceable world-wide marker. ",
"All rocks that we see now were formed after the solidification of the Earths crust, about 3.8 billion years ago. ",
"If you are interested, you can check out the ",
"Wilson Cycle",
", or the wiki page on ",
"sedimentary rocks",
" is also pretty good. ",
"Let me know if you have any other questions, I love geology stuff!"
] |
[
"To add to what GoeManCam has already posted, rocks have been formed continuously through Earth history. Right now in rivers, lakes, deserts, deep water, and all sorts of other environments you have sediments being deposited which can - over time - be buried, and eventually lithified (turned from loose sediment to rock). We have active volcanoes so that means we have active igneous activity crystallising new rocks like granite within the crust. Plate tectonics pulls our ocean basins apart, meaning new basaltic oceanic crust is continously being formed at mid ocean ridges.",
"These rocks are then effected by tectonic activity such as mountain building, faulting and folding which can bury them or expose them back up at the surface. If you go to parts of Australia or South Africa or Canada you can go and look at rocks that are almost as old as the Earth itself (around 4 billion year old rocks). Alternatively, head to southern England and you'll see stuff that's only a few tens of millions of years old. At different places you can find rocks exposed of all the ages in between.",
"As suggested - have a look up about the Wilson Cycle, but also plate tectonics and the rock cycle more generally might be of interest."
] |
[
"There are some rocks that are about 3.6 billion years old, and these are granites. One example is from Finland and western Russia. ",
"What about Isua? 3.7-3.8 Ga sediments and volcanics."
] |
[
"Does a herniated disc still show up on an MRI weeks or a month after the rupture?"
] |
[
false
] |
I would think a herniated disc, after a week or so when it's healing, would start failing to show up on an MRI because the nucleus would be mostly gone. EDIT: Didn't mean to start a religious medical imaging war :) but it is interesting for a layman like me to learn about the nuances. I think the answer to my question is "yes" based on the what was said. Thanks to all that replied.
|
[
"A herniated disc is simply one which has “pooched out” from the margins of the vertebrae into the surrounding tissue. In doing so it often impinges on nerves emerging from the vertebrae, causing pain. Main point though, a herniated disc is not necessarily ruptured. Yes herniated discs show up on mri. However they also show up on much less expensive CT scans too. The mri would be used for looking at the soft tissues to see exactly what the herniated disc is pressing against. It might also be used if surgery is planned so the surgeon would know where the nerves are to avoid cutting them"
] |
[
"MRI is the correct modality for imaging herniation, effacement, stenosis and more. CT is better for imaging bone related issues, conventional radiography will show disc foreshortening, subluxation, scoliosis and more, that's one reason why they usually do standing obliques before they get to the scans. Most (think it's around 80%) of herniated discs will recede by themselves and as such will not require surgical correction, it's only when said herniation remains on the nerve root that degradation such as muscle mass loss, unyielding pain, numbness, dropfoot and other complications usually occur. Additionally, compromised discs are capable of emitting chemical irritants which hurt even more. Radiologists may also add Gadolinium as a contrast agent, depending on what they see, After a surgery contrasted exams are always what they order going forward."
] |
[
"Not all herniated discs will show up on a CT. The MRI is best suited for water containing soft tissues such as discs and will be more effective for diagnosing hernias. CT scans are better at more calcified structures such as viewing bones and fractures. The CT is not as popular as it used to be, but still used frequently because insurance companies would push for CT over MRI. It also depends on the patient, pregnant women are not recommended to undergo CT scans due to possible effects of radiation, while people with metal in their bodies or with older models of pacemakers are not permitted in MRIs. Instead, CT myelography might be used as an alternative."
] |
[
"If we attempt to land a space craft on say Europa, aside from hauling large amounts of fuel with the craft, is there another practical way to slow down, such as Aerobraking in Jupiter?"
] |
[
false
] |
Considering the speed the craft would need to get there in a reasonable time and in the case of Europa, carrying a large heat drill and submersible, the probe would have a very large amount of inertia, are there any other ways to slow down? Edit: I should have clarified, I mean any distant body without an atmosphere.
|
[
"We can use ",
"gravity assist",
" to both speed up and slow down a craft:",
"Due to the reversibility of orbits, gravitational slingshots can also be used to decelerate a spacecraft. Both Mariner 10 and MESSENGER performed this maneuver to reach Mercury."
] |
[
"Cool, so something like passing (relatively) close the planet in a very elongated orbit and breaking orbit at the apoapsis?"
] |
[
"Yep, pretty much. I'm sure that the orbital mechanics are slightly more complicated than that, but the main idea is that the craft must appear as having the same momentum both coming and going from the reference frame of the planet (conservation of momentum and all that jazz). This means that, from a different reference frame (either ours or the destination's), the amount of momentum will appear to change.",
"The end result is that the orbital velocity of the planet that is used to gravitationally assist the craft is either increased or decreased by an imperceptible amount, and that momentum is either subtracted from or added to the craft's."
] |
[
"How does a Whammy Pedal work?"
] |
[
false
] |
From what I understand, to change the frequency of an input signal requires multiplying it with a different signal. So on a Whammy pedal, if you’re pressing the pedal and the pitch slowly raises up to an octave above the input, are more and more signals being multiplied together the more you press down? Where are these generated from? Is there a digital shortcut to recreate this effect that I’m unaware of?
|
[
"You're talking about frequency shifting, or Single Sideband Modulation (SSB). It shifts the entire spectrum up or down by a fixed interval, in Hz. This is not what pitch shifters do, it's more similar to a ring shifter. ",
"The reason is that frequency shifting doesn't preserve harmonics, because it shifts everything by the same interval (harmonic relationships are based on integer multiples of frequencies, not intervals between them). ",
"Almost all pitch shifting is digital. The way it works is by over/undersampling and then time stretching. If you think of it like a tape machine, they play back faster while stretching out the tape to increase pitch, or playback slower while cutting the tape short to playback at a lower pitch. It's a little more nuanced when dealing with samples, but the concept is the same. "
] |
[
"I understand that a wah pedal is a BPF, but for a Whammy? I know signals are a combination of frequencies and harmonics but are guitar input signals always complex enough that you can isolate a component up to two octaves above the prominent pitch?"
] |
[
"Now that you mention it, I was talking about wahs and not whammies! Doh!",
"Whammy pedals are pitch shifters renamed by marketing people. They're all digital now, so they work by math. The exact algorithms are trade secrets. But basically, they must do a Fast Fourier Transform (see wikipedia), copy the signal 1 or more times, pick pitches to manipulate (optionally), then multiply or divide the numbers and mix some percentage of this modified signal back into the dry signal.",
"Hendrix and others in his era used analog pitch shifters like the Octavia. Those things were powered by germanium diodes, unicorn bones and magic."
] |
[
"The asteroid belt...is it a sphere?"
] |
[
false
] |
I was thinking this morning that the solar system isnt flat, and if the asteroid belt which is commonly quoted (no reference) as one of the reasons earth hasnt been hit by any planet killing meteors, wouldnt it have to be a sphere, or is it on the same vector as Earth? (and even then, meteors can come out of anywhere (i think).
|
[
"The asteroid belt is pretty flat, you can imagine it like one of the rings of Saturn in shape. The reason for this is that all the planets/asteroids etc in the solar system formed inside a spinning ring of matter (an accretion disc) around the very young Sun, so are all orbiting roughly the same way (interactions between bodies since then has scattered some out, hence the rogue asteroids we worry about hitting the Earth, but the majority of stuff is still merrily spinning on round the Sun in the same plane we are)."
] |
[
"The belt isn't as flat as Saturn's rings , but the bulk of orbits are within 15 degrees of the ecliptic plane. More of a flattened bagel starting just outside the orbit of Mars and extending about halfway out to the orbit of Jupiter."
] |
[
"No, actually the solar system ",
" pretty much flat and the belt is in a plane with the planets. It protects us from asteroids which are pieces of left over failed planets (in very simple terms, they're more complex than that). However, the Oort cloud (at the edge of the Solar system) is pretty spherical and objects that get bumped out of that can approach on pretty much any angle. Meaning that we have to worry about killer comets.",
"Good question! And one that I haven't seen before on Askscience, which is turning into a rarity recently..."
] |
[
"My Crabapple tree is blooming in the fall and we live in Alberta, Canada. This has never happened before and we've lived here for 10 years. What is happening? [pic]"
] |
[
false
] | null |
[
"That is odd. Apple trees flower in the spring. Has there been some odd weather there? Apple trees may flower after 50-90 days of growing days without a frost in the spring, but that would be weird in the fall. It appears that your tree has apples too.",
"Has your tree been grafted with some other cultivar? That's all I could think of."
] |
[
"The weather has been pretty dry, but we have been watering very consistently. The Crabapple tree is located on our front lawn, which has been green all season.",
"No grafting has been done.",
"The article you linked in the comment below was very interesting. Although, there was no mention of Crabapple trees blooming twice in one season.",
"After doing a bit of research, the tree is either a 'Royalty Flowering Crabapple' or a 'Thunderchild Crabapple.' Hope that helps! Thanks for the answers so far!"
] |
[
"Alberta can get some weird climate activity, with unseasonal weather for weeks on end. What's the summer been like, there? It's possible that a period of cooler than average weather followed by warmer than average could have tricked the tree into behaving as if it were spring."
] |
[
"Are there any problems in Computer Science that *can't* be solved with classical computers but *can* be solved with quantum computers?"
] |
[
false
] |
It's already pretty well-known that certain classes of problems may have more efficient solutions (e.x. factoring primes) when using a quantum computer vs. a traditional one, but I was wondering whether there are any "unsolvable" problems that become "solvable" when using quantum computers?
|
[
"Actually, we've proven that there are no problems that a quantum computer can solve that a classical computer cannot. A classical computer can simulate a quantum computer so a classical computer can solve any problem that a quantum computer can, just slowly. ",
"Its still an open question if there are models of computation more powerful than Turing Machines (that don't rely on magic oracles) but pretty much everybody believes that Turing Machines are as good as we are going to get in terms of computability. "
] |
[
"Not that we know of. Computational Complexity problems are all solvable with different kinds of resources. For example, problems in EXP take exponential space and time to solve, but are still 'solvable' in the sense that you are describing.",
"The class of problems that are 'unsolvable' are known as 'undecidable'. And no, quantum computers are not known or believed to be able to solve undecidable problems."
] |
[
"Just out of curiosity how is it possible that another model of computation more powerful than a Turing Machine would exist? Wouldn't that be self-evident?"
] |
[
"Since light is an Electro-Magnetic radiation, are photons as a light particles deflected when passing through strong Electric or Magnetic field?"
] |
[
false
] | null |
[
"Nope. Photons ",
" the electromagnetic field. The thing that measures ",
" with the electromagnetic field is a particle's charge, and photons don't have any. Photons don't directly interact with themselves (i.e. the electromagnetic field)."
] |
[
"To be pedantic, at low energies they don't interact with one another, but at gamma ray energies and higher I believe, two photons colliding can produce a electron-positron pair. This is the time reverse of the electron-positron annihilation that produces energy."
] |
[
"I just wanted to add that in a sense photons can interact with each other, through virtual electrons. While the existence of electrons (or other charged particles) is needed for this to happen, no actual (i.e. real, on-shell) electrons are necessarily involved in the process."
] |
[
"What helps Californium-252 become such a good neutron emitter?"
] |
[
false
] |
I read that Californium - 252 decays by alpha decay and spontaneous fission. But which of these contributes to Californium producing neutrons?
|
[
"Alpha decay is the emission of one helium nuclei ( 2 protons and 2 neutrons bound together) from the original nuclei.Ppontaneous fission usually produces 2 (or more in very rare cases) lighter nuclei than the original one plus 2-3 free neutrons. ",
"Cf-252 decays to 96.908% over alpha decay and to 3.092% over spontaneous fission with a half life of 2.645 years. So the reason why it is such a good neutron emitter is its short half life and a comparatively large amount of spontaneous fission."
] |
[
"Spontaneous fission. Every fission emits on average 3.7 neutrons. It has a reasonably high SF rate of around 3%. "
] |
[
"This was very helpful. Thank you "
] |
[
"How can a speaker produce multiple noises at once?"
] |
[
false
] | null |
[
"Speakers work by the ",
"principle of superposition",
". If you want to hear two tones at once, just add their vibrations together.",
"When you compare the voice box the a reverse eardrum, you've got it exactly right. The voice box, in a given configuration, can only resonate at one frequency (and higher harmonics). The same is true of wind and brass instruments. A speaker doesn't use resonance to produce sound, it uses power--amplification, basically. Likewise, you ear doesn't use resonance to hear certain sounds, although one could make a device that is only sensitive to certain sounds using resonance."
] |
[
"Vibrations 'add' together. What we normally think of as sound waves, are really pressure/displacement waves in air. The information in the wave is completely encoded in how much each air molecule has been displaced from where it was an instant ago. When you listen to, say, a Queen tribute band live in concert, you are actually hearing the sum of these displacements. A speaker reproduces this 'sum'. The technical term for this adding of waves is 'superposition'. "
] |
[
"I made a pretty successful answer to this same question about a month ago:",
"http://www.reddit.com/r/askscience/comments/m2v0f/how_can_a_speaker_produce_more_than_one_sound_at/c2xmyx4"
] |
[
"Does the binocular effect apply to dimensional projection?"
] |
[
false
] |
I've read a small amount on dimensional projection, as far as I can tell it takes rules that apply to the dimensions we understand and telescopes them out to explain each successive dimension. For instance, according to dimensional projection, a 3-dimensional object casts a 2-dimensional shadow. Therefore, a 4-dimensional object would cast a 3-dimensional shadow. So, kind of along this line, we can simulate a 3-dimensional object by layering 2 2-dimensional objects over one another. Could two 3-dimensional objects be layered over each other to create a 4-dimensional image?
|
[
"I see; so mathematically speaking, layering 2 (or maybe more) slightly varied 3d images over one another could \"fool\" the optic sensors of a 4-dimensional being, but as 3-dimensional beings these images would just be confusing. Thanks for your input"
] |
[
"Kinda; It's possible to reconstruct 4-d information based on the 3-d projections of an object, mathematically speaking. But we don't have sensory input capable of handing 3-d objects. So we just end up with pictures like ",
"this",
"; The reason the binocular effect works with your brain is that your brain is quite used to inferring 3 dimensional properties based on two dimensional slices."
] |
[
"Apropos, there are computer graphics that are meant to represent a ",
"projection in 3D of a 4D tesseract",
"."
] |
[
"If allergies are caused by an over active immune system, does that mean someone with bad allergies is more likely to get sick as their immune system is constantly \"preoccupied\"?"
] |
[
false
] | null |
[
"Saying that allergies are an \"overactive\" immune system is the result of an oversimplified explanation. It's not really overactive, it's dysregulated.",
"Imagine you are traveling in a car driven by a trusted friend at 50mph down a road in California. Everything is good and you are on your way to an intended destination; this is analogous to a properly regulated immune system. ",
"Now imagine you are traveling down that same road at the same speed in a car without a driver. You now have a problem. This is analogous to an unregulated immune system.",
"Now imagine that you are in that same car traveling down the same road in California, but the driver is from England and is convinced that he is currently driving in England no matter how much you try to persuade him to get back on the correct side of the road. You are in for a world of hurt, and this is analogous to a dysregulated immune system.",
"But in no case is anything \"overactive\", it's just that in the last scenario the action is inappropriate for the circumstances. In allergy, your body reacts to pollen (or whatever) like it would a pathogen. If it were a pathogen, this would be the proper response, but it's not a pathogen so we say it's dysregulated. "
] |
[
"So expanding on MolecularBio's question, in the dysregulated situation, does this inappropriate reaction mean that the body's immune system, specifically the functions which are part of the allergy response, leave the body less able to respond to other pathogens? For example (and even this might be confusion on my part): Does having an allergic reaction during pollen season leave the body less able to \"fight off\" a cold virus?"
] |
[
"Does having an allergic reaction during pollen season leave the body less able to \"fight off\" a cold virus?",
"I don't know of any studies that have looked at this directly, but my initial (and somewhat speculative) response would be to say that it may increase your ability to fend off a cold virus, or at least a flu virus.",
"Mucus has the ability to kind of \"soak up\" viruses that get into the lung. For example, one lab here studies flu viruses by infecting bronchial epithelial cell culture with them. If the cultures have a lot of mucus on top of them they are harder to infect (titer must be higher to get an infection). But this is speculation based on a lab result. It may or may not be relevant.",
"As for the general concept...no, I don't think it would have much of an effect. Your immune system doesn't function on a zero-sum game; you can crank out a ",
" inflammatory response in a short period of time. And if you have allergies, your body has days to adjust to the new level."
] |
[
"Would a child naturally learn bipedal ambulation?"
] |
[
false
] |
If a typical child were somehow raised by robots (assume they have wheels or levitate), would that child naturally learn to walk on two feet with an upright stature without having an example?
|
[
"This has been asked before. Last time I tried to argue that children would continue crawling, and I used some reports from feral children to make my case.",
"Long story short, there's no evidence that children would continue to crawl."
] |
[
"There are central pattern generators in the spinal cord which are 'pre-programmed' with the alternating gait of bipedal locomotion. I have not seen evidence that the same thing exists for our arms (though a lack of evidence is not evidence for a lack of something), which would be indicative of an inborn propensity for prolonged locomotion via crawling. Additionally, the adult body would not be able to sustain crawling for very long because of the biomechanics of locomotion (body designed for loads parallel to all leg bones, weakness of kneecap to repeated blows, etc)",
"/college student who does stuff to neurons"
] |
[
"Much of this is hypothetical... but that may be the best you get for this answer, as to my knowledge there is no definite answer to this question.",
"One component towards reaching a plausible hypothesis to your question is the fact that (to a certain extent) walking is a spinal cord reflex. ",
"As in, at a ",
", it's not a complicated ",
" motor program stored in your frontal cortex, which is then played out through your spinal cord to your muscles, with its output constantly adjusted based on proprioceptive and visual input sent from your body and inner ear to your cerebellum.",
"At a basic level, all of the calculations your body needs to walk are anatomically and developmentally ",
" into your spinal cord. IOW, the neural circuits needed to walk ",
" - they are programmed into you (in your spinal cord).",
"That being said though, when you are actually walking in real life, you're not relying only upon this base program that you were born with - you're constantly modifying it so that it's more efficient, or to adapt it to specific situations. IOW, when ",
" walking, you are using motor programs in your frontal cortex and modulating them based on information sent from your body... and all of these signals are then processed in your cerebellum and the motor output is adjusted appropriately.",
"As a tangent - the fact that humans have a built in walking reflex (at a basic level - pressure on your foot leads to you lifting that leg up and moving it forwards slightly, followed by reciprocal movements in the opposite leg - imagine if you step on something sharp what happens - you jerk that leg up and shift your wait to the other leg - take that movement and make it bilateral, and alternating, and modify it slightly, and you get a basic walking reflex) is a more recently appreciated fact, and an exciting one. The fact the reflex is encoded at the spinal cord level means that there is hope for people with spinal cord injuries to walk again... provided we can learn how to hack the spinal cord through proprioceptive signals to efficiently trigger the walking reflex to allow someone to actually walk in a useful manner.",
"All of this aside... what this means is that humans are anatomically hard-wired for the ability to walk on two legs.",
"The other important component to your question is whether this is enough to learn how to walk. If you never learned form watching others that bipedal movement was possible... would think to do it? Just because you have the anatomical means doesn't mean you'll do it. There have been studies showing that people can be trained (relatively quickly) to follow scent trails. This is obviously not a skill most of us have at the moment... or most people will ever learn. But apparently we are hard-wired for this skill to some extent.",
"If we assume that there is no social stimulus (no example) to walk on two legs... the only other two possible ways that someone would learn to use the built in walking ability we have would be because of environmental motivation (gee, that grass is tall - if I stand up I can actually see over it... oh hey! I can move using only two legs! it makes much more sense for me to walk than crawl!)... or if there existed some anatomical circuit in your brain which, once it matures, makes your prefer bipedal locomotion. Ie: an intrinsic motivation towards bipedal locomotion - something like how once you hit puberty, everyone develops this intrinsic motivation to have sex - it's programmed into us.",
"So that leaves us with the conclusion that, yes, people would still walk provided:",
"There was an environmental (non-social) stimulus/benefit to bipedal motion (even something as simple as the fact that in humans, bipedal motion is more efficient and faster than crawling would probably be enough... but that's another hypothesis).",
"We are hard-wired to be motivated to walk after a certain age. The existence of this is purely hypothetical and I am aware of no evidence for the existence of something like that.",
"At the end, I would wager that people would still end up walking, based on the fact we have a built in ability to walk, and likely at least because of the first point just mentioned.",
"But there are a lot of variables there which I don't have the exact answer to."
] |
[
"Obviously, I'm not a golfer..."
] |
[
false
] |
A couple years ago I was having an online discussion with someone about man's responsibility in Global Warming and I came across a bit of a pickle. Now, I'm a complete layman, so I tried my best to explain the greenhouse effect and whatnot, but eventually this guy pulled out something I wasn't expecting. He told me it was all a cycle - something I had already heard before -- but one that could be explained by water currents. was something I wasn't sure how to respond to. Here's what I have saved from back then: Here's why we shouldn't fear Global Warming: The ice caps melt. The ice caps release freshwater into the ocean. The freshwater slows down the ocean currents due to its density. Less warm water reaches the poles from the tropics. Over time, and with enough fresh water released, the poles freeze over due to the lack of warm water from the tropics. This is how an ice age naturally happens! (This is what happened during the Little Ice Age.) The tropics heat up and eventually melt all the ice. Water currents aren't really my forte. So, did this guy go wrong in his logic? If so, please enlighten me. Made an error. He wasn't saying that's how Global Warming happened, he was trying to convince me that we shouldn't fear it.
|
[
"Does it being a cycle make it any less deleterious?",
"And if humans are really rapidly increasing the rate of the ice caps melting, how is that an excuse to say it's okay?",
"Tell your friend that you heard he was going to fall asleep tonight and then tell him not to be mad at you when you drug him and he passes out and sleeps through work all day. Why would he be mad? Falling asleep and waking up is just a cycle, and you just helped speed it up a little bit!"
] |
[
"The problem with things like that are you aren't quantifying any of the results, you don't know how much the currents are being affected, or how this affects refreezing, or any of the other stages.",
"It's kind of like saying that I walk around all day and get hot. If I attach a turbine that is moved by my walking motion, I can generate power. I can attach a fan to the turbine, to blow air, and cool me down. Since I am cooler, I can walk faster, which will in turn produce more energy and cool me down further.",
"That sounds good, but in reality you would not get anywhere near enough energy to power the fan.",
"If the currents are not slowed enough, the ice caps will melt too much anyway. They could refreeze eventually, but what if that is in 200 years? By then a huge amount of the earth could have been flooded."
] |
[
"No, water currents do not control global climate. They do redistribute a huge amount of heat, though, and have big effects on local weather and climates around the world. They also have various feedback effects on the climate system, which I don't know enough to tell you about off the top of my head (and which aren't fully understood at this point anyway). Check out ",
"thermohaline circulation",
" and the ",
"shutdown therof",
" on Wikipedia for more. The most immediate effect of melting the Arctic ice cap is that reflective ice is replaced with dark water, which absorbs ",
" more solar radiation than ice. This is one of the big positive feedback loops tending to accelerate global warming.",
"Global climate has been roughly cyclical over the past few hundred thousand years. There is evidence that this periodicity is linked to ",
"kinks in the earth's orbit and rotation",
", altering the amount of solar radiation we receive by a small amount. This small change is not enough to alter climate on its own, but gets amplified by various ",
"feedback loops",
". The most important involve increased concentrations of greenhouse gases (methane, CO2, water vapor) in the atmosphere. Our human civilization, by burning fossil fuels and releasing CO2 and methane in to the atmosphere, is giving the system a huge, unidirectional kick in the ass.",
"The bottom line: ocean currents cannot control climate in an ultimate, global sense. The only way that can happen is to change the earth's energy balance with outer space, via changes in solar radiation or, as is happening now, by holding more heat in the lower atmosphere with greenhouse gases."
] |
[
"Do non-human primates have dominant handedness like humans do?"
] |
[
false
] | null |
[
"Findings on the subject are inconsistent. Some studies have found no evidence of handedness while others have found clear hand preferences. Often individuals favor one hand strongly but the choice seems random. Most likely there is no strong species level lateralization like with humans but rather individual learned behaviors. "
] |
[
"I know your question was about primates, but I thought this might be of interest. Rats and mice also tend to have a dominant \"hand\" and it tends to be the right one more than chance",
"https://www.sciencedirect.com/science/article/pii/S0166432801003308",
"https://www.sciencedirect.com/science/article/abs/pii/030439409190138J",
"However, they are dextrous and flexible creatures, and it isn't as obvious in them as it is in us, so you actually have to do a fairly specific test (like make a cage where they can only reach food with one paw and rigorously count which paw they use) in order to see this."
] |
[
"We haven't noticed any with monkeys, and we've worked with many species. ",
"I have no experience with nonhuman Apes in research."
] |
[
"Is it true that as we get older, our brains will lose it's capacity to learn new skills?"
] |
[
false
] |
....Or could it be just due to the lifestle changes as we grow? Job/responsibilities/having no spare time/ etc ... ? Particularly i don't feel i like my capacity is affected on a neurological level, rather it feels like more as if my attention was focused on other things that being the reason for learning impairment on a later age. Anyways, curious about it. Thanks
|
[
"Age does affect our overall brain plasticity, so basicly how well our brain forms new synapses. You dont lose the capacity to learn new skills as you age, rather it can be more challanging for you to make those special connections which are associated with learning new things.",
"To my understanding, being cognitively engaged, and challanged is a good way to combat this."
] |
[
"One of the best practical things you can do to encourage lifelong neurogenesis is to learn to play a musical instrument. Larry Sherman (a neuroscientist at OHSU) has a fabulous talk he delivers on the topic, though I'm coming up short on an online reference to it aside from one of the event links where he delivered it: ",
"https://viaproductions.org/events/alberta_sept_4_music/",
" ",
"With any luck that'll make the ",
"podcast",
" eventually. But anyway: pick an instrument and be diligent."
] |
[
"How else does one maintain/improve brain plasticity?"
] |
[
"If humans have evolved to have hair on their head, then why do we get bald? And why does this occur mostly to men, and don't we lose the rest of our hair over time, such as our eyebrows?"
] |
[
false
] | null |
[
"Edit: My answer below covers the mechanistic reasons for baldness (because I'm biochemist and that's the portion I know about) and why it occurs mostly to men. I'm not aware of definitive research on the evolutionary reasons for baldness so I've stayed away from speculating on that and tried to stick to what biochemistry/physiology does know. You are free to speculate about the why as much as you'd like, hopefully someone with a good understanding of hominin anthropology can likely fill in such details. Note that not all traits are positively selected so Male Patterned Baldness may just be a non-deleterious side-effect of sexual maturation. ",
"Hair follicles are mostly switched on by the presence of androgens (i.e. testosterone and dihydrotestosterone) and the follicles have two important reaction parameters; a testosterone sensitivity threshold and a kind of response strength. The sensitivity threshold level sets how much testosterone must be circulating before a follicle switches over to producing mature hairs. Head and eyebrow hairs are examples of follicles with exceptionally high sensitivity. Very, very, very little testosterone/DHT is required for the follicle to switch on, mature and start producing hair. And this is why male and female infants quickly start producing mature head hairs. On the other hand pubic, underarm and beards hairs have low androgen sensitivity and this is why they do not switch on until the increases in testosterone/DHT levels seen at puberty.",
"Alongside this follicles have a response strength that dictates how vigorously the follicle produces hair once they are activated. Beards hairs have high response levels, eyebrow and arms hairs not so much. So beard hairs come in fast and thick. Scalp follicles also have a very strong testosterone/DHT response but they don't undergo significant changes at puberty as they are already fully mature when puberty arrives.",
"If just so happens that there is a loose correlation between this response strength and testosterone/DHT toxicity. Essentially the more strongly a follicle reacts to testosterone the more likely it is to die off after chronic DHT exposure. I guess you could think of it like the follicle being \"overworked\" but it is a little more sophisticated than that (see first link). As men produce the most testosterone their most sensitive and strongly reacting follicles are at higher risk of this toxicity, and these happen to be the ones on the scalp. And this appears to be the driver for Male Pattern Baldnss. The mechanism for this are not completely understood but this is a nice easy to read summary",
"http://www.medicalnewstoday.com/articles/68082.php",
"As I recall this is also a great review of the effects of androgens on hair development and it covers a lot of detail on the biochemical science of follicle maturation.\n",
"http://onlinelibrary.wiley.com/doi/10.1111/j.1529-8019.2008.00214.x/full"
] |
[
"Mma fighters who a use testosterone replacement therapy such as Dan Henderson, randy couture, or the commentator Joe Rogan all go bald and get big fat heads. They look weirdly similar after they do that. ",
"Why is it? "
] |
[
"The patterned baldness I guess might be a result of the ",
" added testosterone. It would be hard to say with a sample of just 3 people.",
"wrt their body and facial structure I don't really know enough about testosterone's other systemic effects to comment."
] |
[
"Do VHS tapes expire or just lose data over time?"
] |
[
false
] |
My question is a bit more complex, i'm wondering if i store a VHS in a cool dry enviroment over time (decades) would the quality of the movie ever decrease? If I video tape over that old VHS would it be at a good quality again?
|
[
"The magnetic layer of the tape will eventually come off. When you play an old tape you will find brown dirt on the head which comes from the dissolving tape. The lifetime of a tape is around 10 years.",
"Another effect is that the magnetic information will be copied to the next layer on the reel. Therefore cassettes should be rewound once a year.",
"If you want to preserve them you should digitize them."
] |
[
"Try it. Make sure to read the tape only once to minimize mechanical wear."
] |
[
"Couldn't agree more. \nDigitise them and store them in at least two locations.",
"I'd recommend at least one be an online service like Glacier or Carbonite. ",
"Also my last manager told me his family lost some home movies on VHS tapes because a mould or fungus grew on the tape itself. I don't know how common that is though. "
] |
[
"How can nuclear fusion happen in a star when hydrogen doesn't have neutron?"
] |
[
false
] |
[deleted]
|
[
"Protons and neutrons can turn into each other by emitting/absorbing electrons/positrons and neutrinos/antineutrinos.",
"In the case of fusion, two hydrogen atoms combine to make a deuteron (which is Hydrogen-2, which is a nucleus with one proton and one neutron), and conserve charge and lepton number by emitting a positron (which is a positively charged antimatter electron) and a neutrino. ",
"Here's a typical fusion chain."
] |
[
"For those on mobile, this image might appear as just a bunch of circles with the 2 keys at the bottom. Just open it in a non-night mode browser, it'll actually show everything that way."
] |
[
"It might need to be noted that this reaction isn't actually the dominant source of energy in stars slightly larger than our sun, the CNO cycle is",
"http://en.wikipedia.org/wiki/CNO_cycle"
] |
[
"I left a bag of skim milk out by accident. When I found it, the bag was full of air and about to burst. The milk was gunk floating in clear fluid. What happened?"
] |
[
false
] | null |
[
"When the milk warmed up, some acid and gas producing bacteria had a feast. Some bacteria produced the gas that filled up the bag with 'air' and other bacteria produced some acids that caused the fats and stuff (gunk) in the milk to separate from the whey (clear fluid). The same thing happens when you make ricotta cheese by adding vinegar to the milk."
] |
[
"The likeliest culprit here is fermentation carried out by bacteria present in the milk. These bacteria, when breakup(ferment) the milk give off gases. e.g fermentation of a sugar, a glucose, releases carbon dioxide (a gas)."
] |
[
"It depends on exactly what bacteria took up residence. How does it smell?"
] |
[
"Everyone says to get a colonoscopy at 50 but what other tests should be mandatory throughout your life?"
] |
[
false
] |
Something I'm generally curious about. I mean, how many lives could be saved from certain cardiovascular diseases if a Magnetic Resonance Angiogram (MRA) was talked about as often as a colonoscopy?
|
[
"There's even doubt about some of the obvious screening tests listed about; mainly because of a fifth criteria: 5) early intervention as a result of screening should improve outcomes over intervention that does not come as a result of screening (i.e., if you hadn't been screened, but just waited until symptoms appeared, would you actually be any worse off).",
"Mammograms have come ",
"under fire",
" recently because the early detection provided does not tend to result in any better outcomes.",
"Prostate cancer screening, is also ",
"studied",
" because in many cases, the disease is non-lethal. Thus a man with prostate cancer might die late in life of something else, having never known he had cancer. However, had he been screened, a series of expensive (but ultimately unnecessary) procedures would be performed.",
"Source: My work required me to follow epidemiology and health outcomes, but am not an epidemiologist. Please provide counter-argument if you disagree."
] |
[
"There are a few screening modalities that have some proven evidence of benefit - i.e. mammographies for breast cancer, colonoscopies/fecal occult blood tests for colorectal cancer, pap smears for cervical cancer, +/- PSAs for prostate cancer and low dose CTs for lung cancer in high risk individuals (depending on where you fall on those particular debates). By definition, the goal of this sort of screening is to help catch cancers in asymptomatic individuals. Typically when this is brought up there're a lot of questions as to why we don't screen for everything. For a screening test to be useful, it must be 1) ",
"accurate",
" at detecting 2) relatively high-prevalence diseases with 3) potentially serious consequences that 4) can be treated effectively. Most of the time when people ask 'why aren't we doing this test on everybody?', one of the above conditions is not met. In other words, it is not worthwhile to apply population level screening with a bad test, for a very rare disease or a disease with little morbidity/mortality, or for a disease that once diagnosed cannot be treated. ",
"More on some of the statistics behind screening tests here.",
" ",
"You can follow current USPSTF recommendations here",
"."
] |
[
"This is a good point that I just sort of conflated into my #4 above. A common criticism of studies on these screening modalities is the issue of ",
"lead time bias",
", where screening may lead to earlier diagnosis of disease and thus 'longer' survival post-diagnosis, without actually affecting overall outcomes. ",
"Screening is an ongoing area of research and controversy because of the cost, the potential for significant benefit ",
" harm, and the fact that it is often very difficult to study. I'll also add here that another consideration needs to be the effects of the screening test itself - many of them involve radiation or other invasive procedures, and in many case a false positive will only detected after a more invasive testing step (often surgery). There are a lot of factors in determining whether a population wide screening test should actually be implemented."
] |
[
"If gravity is the bending of space-time, then how can there be a graviton - a single particle of gravity?"
] |
[
false
] |
I just don't get that part. The presence of matter causes space-time to warp, and it is this warped space-time which we experience as gravity - at least that's how I've heard it explained many times. If this is the case, then how can there be an exchange particle for gravity? (The graviton, as I understand it). The two things don't add up for me - is it a wave/particle duality thing? Does anyone have a vaguely decent which can help me wrap my head around this?
|
[
"Consider the electric field around a charged object. When the object accelerates, the electric field changes and information that this changes has occurred propagates outward at the speed of light. This is electromagnetic radiation. If the change in the source of the field is discrete (like an electron changing energy levels in an atom) then the propagation of the field is also discrete: we call this a photon.",
"When a bound gravitational system changes, the gravitational field around it changes and this propagates as gravitational radiation. Gravitational radiation has been indirectly observed by monitoring the orbital decay of pulsars. If there were to be a discrete change in the source of the gravitational field, that discrete quantum of gravitational radiation would be a graviton."
] |
[
"Particles are an antiquated notion. A flock of particles don't determine the underlying shape of the gravitational field. The gravitational field is a flowing four dimensional surface of waves. ",
"The existence of matter at one point causes ripples to propagate on the surface of the gravitational field and communicate the warping behavior. ",
"We call the \"particles\" gravitons because when we see quantum effects of fields (such as the gravitational field), these effects are discrete and in bundles of specific size instead of a completely smooth flowing continuum. So when we model things mathematically, instead of saying a \"discrete bundle of gravitational field\" interacted with a \"discrete bundle of fermion field\" we instead say a graviton interacted with a fermion.",
"Take note, however, that the \"graviton\" is speculative so far. We have no working theory of a graviton, but we expect there to be one. So it's more of a placeholder for the name of the theory that actually ends up working. "
] |
[
"You are talking about two different ways to understand gravity.",
"According to general relativity, it's spacetime being warped.",
"According to quantum theory, it's an exchange of carrier \"particles\" (although \"particle\" is not entirely appropriate).",
"However, we do not have yet a full understanding of gravity from a quantum perspective. When that theory will be finished (or if), then it should hopefully provide a new point of view, which will reconcile the \"spacetime warp\" and the \"exchange of particles\" into a better, more comprehensive model.",
"TLDR: Our current theories are incomplete."
] |
[
"Do creatures with short life span perceive time differently?"
] |
[
false
] |
[deleted]
|
[
"I believe there are many studies that seem to insinuate that our perception of time is largely based on memory processing. When asked to try and guess after 60 seconds has passed, younger individuals typically guessed too soon (they felt that time was passing faster than it actually did) and older individuals typically guessed too late (they felt that time was passing slower than it actually did). This is why time seems to \"fly by\" and move faster the older you get.",
"This is also why they think that time seems to \"slow down\" when in a state of emergency. All of a sudden, your brain isn't throwing out all of the wasted information it normally does. It realizes that it needs to process much more information and so you memorize and pay attention to more things going on. So in essence, I would guess that every living being experiences time differently (and some guess it is a result of memory processing).",
"Edit: I can't remember the exact studies I was reading, but I do know they were done by David Eagleman, and here is a pretty extensive list of his publications. ",
"http://eaglemanlab.net/publications"
] |
[
"We don't know how animals perceive the world. We don't even know which animals feel pain, or how much.",
"EDIT: We are confident that some animals, such as mammals feel pain. But we don't know the answer to this question regarding many other species. "
] |
[
"Older people guessed too late. They thought only 60 seconds passed, but it was really 80 seconds. Therefore, 80 seconds must pass for them to feel a minute.",
"Thus, time flies by as one ages."
] |
[
"What comprises speech?"
] |
[
false
] |
What Comprises Speech? Is it a series of overlapping frequencies? What makes an A sound different from an O? What about glottal stops?
|
[
"This is a pretty involved question. At the most basic level, speech is just a bunch of sounds. Sounds are of course vibrations, and these are produced in a variety of ways in the vocal tract.",
"First of, we need to understand that spelling isn't the same thing as sounds. It's easy to confuse these, but it can lead us into real problems. Ask most people how many vowels English has, and they'll say \"five\". If you actually look at how many vowels English has, in American and Canadian English, it ranges from 13 to 16 vowels. To determine this, by the way, we look at which sounds give a meaningful contrast in peoples' speech. Just like ",
" and ",
" don't mean the same thing because a different consonant is used at the beginning of the word, ",
" and ",
" mean different things because a different vowel is used. How we write English here isn't always helpful, because ",
" seems to end in a vowel in the written language, but it rhymes with ",
", which doesn't have a written vowel at the end. In any case, just by listening to the sounds, it's clear both end in a consonant, /k/, so the difference between, say, ",
" and ",
" is only the vowel (or here, the diphthong /ei/).",
"I'll start with vowels because they're fairly simple. To produce a vowel like /i/ (as in English ",
", ",
", or ",
"), you push air out the vocal tract with your lungs. It passes over the vocal folds in the larynx, which vibrate at a fundamental frequency. However, we hear more than just one pitch, and more than just differences in frequencies in speech. The vibration creates lots of harmonics (integer multiples of the fundamental frequency). These frequencies can be further \"shaped\" by the rest of the vocal tract. With vowels, your vocal tract remains essentially completely open, with the tongue moving towards some other part of the throat and mouth to shape the sound. For /i/ specifically, it moves upwards and towards the front of the mouth. Different vowels (excluding nasalized vowels like in French, or voiceless vowels like in Cheyenne) are made by having the tongue in different positions, creating a different set of frequencies. Nowadays, linguists generally analyze vowels by measuring the frequencies directly. For instance, Labov et al. (2013) found that the /i/ in Philadelphia English had an F1 (first formant above the fundamental frequency, or F0) of around 530 Hz, and an F2 (second formant above F0) of around 2000 Hz. For most vowels, F1 and F2 are adequate, but sometimes F3 is needed as well.",
"Also note that in some languages vowels are not just steady frequencies. In classical terms, we're talking about diphthongs, where more than one vowel can serve as the \"core\" of a syllable (called the nucleus). Examples of this in English include ",
" and ",
". The frequencies of the vowels change across the syllable nucleus. ",
"Here's a nicely labelled spectrogram of both monophthongs--single vowels in the nucleus--and diphthongs--two vowels in the nucleus.",
"Consonants add a layer of complexity on to this. Like with vowels, consonants are articulated at a certain place in the vocal tract (called a ",
"place of articulation",
"), anywhere from the larynx/glottis all the way to the lips. In addition to this, however, consonants differ from one another in how they constrict airflow (called a ",
"manner of articulation",
"). Consonants always constrict airflow in some manner (which separates them from vowels). One sort of consonant, then, is a plosive stop. This is where you use your tongue (or some other articulatory) to completely stop airflow momentarily. The glottal stop /ʔ/ (in the middle of English ",
" or in Hawaiian ",
" 'to roll'), as well as consonants like the alveolar stop /d/ (in English ",
"), where the tip of the tongue touches the ",
"alveolar ridge",
".",
"To give a little more detail about the glottal stop specifically, it's an interesting sound because many plosive stops can actually be voiced (like the contrast between voiced /d/, as in ",
", and voiceless /t/, as in ",
"). But because the vocal folds are the active articulator here (they're blocking airflow completely for a brief period), they can't vibrate, so there can never be a voiced counterpart to the glottal stop.",
"Generally, because consonants involve some sort of blockage or restriction of airflow, it isn't very useful to look at the different frequencies of sounds they produce (though we do sometimes), and it's instead much more useful to figure out exactly how they are produced. We can do that by looking at things like ",
"palatograms",
"."
] |
[
"Not really sure what you're asking. Words are comprised of phonemes, a language's basic unit of sound, used to form clusters (words) that export meaning. In short, it's the arrangement of sounds to impart a message to a listener. This subreddit is notorious for poor linguistics answers (*cough* ",
"What's the oldest language?",
" *cough*) so you should ask this in ",
"/r/linguistics",
" if you want more information."
] |
[
"I think he means \"what are sounds made of\""
] |
[
"Why do some very expensive CPUs use lots of slow cores vs. fewer very fast cores?"
] |
[
false
] |
Basically my question as an amateur computer builder and IT curious person with not a ton of in depth knowledge of computer engineering is this: Server grade processors, which have MSRPs that at the highest price point are $20,000+US, seem to utilize tons of cores running in the mid 2.5 GHz range per core. High end enthusiast processors run significantly less in the $500 - $1000 range and have core speeds that are now pushing past the 5 GHz range per core. What are the limitations or engineering reasons why you don't see at this moment, Intel or AMD releasing CPUs with massive core counts and also massive clock speeds? Wouldn't it theoretically be an advantage to have a ton of super fast cores? Are the reasons economic or due to engineering or technological limitation? A more minor follow up would be is this something that the future of CPU design has in store or is it less practical as high core counts and programs meant to utilize multi-core systems become more common and standard?
|
[
"Speaking for the supercomputers my lab uses, we are actually not terribly interested in the cpu's processing power for many of our calculations - a 5 year old Xeon doesn't matter when you have a Titan V. We get much better performance from gpus so that's where the money ends up going (think the ",
"Nvidia DGX-2",
" ). That said, one consideration for clusters that are CPU heavy is that running a lot of cores at a higher clock speed will lead to a lot of heat generation and a room full of clusters takes a LOT to keep cool. If you can leverage all 64 cores of a node at 2.5Ghz it will obviously outperform an 8 core consumer chip at 5Ghz so it's ok to be running lower clock chips with more cores. A final consideration is many clusters will have 20+ nodes in a single stack and so this heat problem really gets compounded quickly."
] |
[
"It's simply different optimization for different tasks. Faster cores require more power, and power is a major limiting factor in CPUs, due to the motherboard supply limits or the cooling fan dissipation limits.",
"",
"Home users with enthusiast processors tend to do things like gaming or light media editing that only utilize a few threads*. Home users also tend to do one or two things at a time, so one core is likely to stay on the same job for a while. Because home users only benefit from a few cores, these cores are run at very high power, squeezing every bit of performance out of each one.",
"",
"Servers are often handling many more simultaneous tasks, or single tasks that are designed to be split into multiple threads, and can therefore make use of many cores. Each of these cores can be run at the power levels that optimize performance per watt. e.g. you might get 70% of the performance with 50% of the power usage. More cores running more efficiently give better overall performance to the end user. ",
"",
"I suspect that if you look hard enough you'll also find some processors with higher clock speeds meant for server sockets.",
"",
"*-A thread is a string of instructions to be run sequentially on the same processor core."
] |
[
"The gpu is so strong because it takes that same scaling to a higher level, right? Only 800mhz or 1000 but something like 200 cores, or logical threads or something like that?"
] |
[
"What would the pressure be like in a body of water in free fall?"
] |
[
false
] |
I was thinking about the giant free "ponds" in Larry Niven's Integral Trees. On a planet, pressure as a function of depth is fairly straightforward. But if the water is held together only by cohesive forces, how does it change with "depth"? In the book they were free floating and various sized Water is less dense as a solid so pressure causes it to melt, so I'm not thinking there could be a solid core by pressure. I'm wondering, if there was a drop of water 14 miles across (so the center is as far from the surface s the Challenger Deep), what would the pressure be at the center? Could we scuba all the way through? Maybe it would help to imagine a spherical "drop" of water of radius (depth) x, in free fall, with enough of a "balloon" around it to prevent heat loss and evaporation but not add and "squeeze pressure." How would pressure change through the pond? How big would it have to be to noticeably influence itself by gravitational effects?
|
[
"Free fall is equivalent to being in a region of space without gravity. Let's also assume a vacuum around it such that we can neglect external air pressure etc.",
"There is one force left, namely cohesion. It will attempt to minimize the droplet surface, morphing the it into a spherical shape. The pressure at the center is given by ",
"P= 4 gamma/R",
" with R being the droplet radius. It is tiny for any sizeable droplet. It also gets smaller for larger droplets. until the droplet becomes massive enough to generate its own sizeable gravity."
] |
[
"That's a combined curve I'd like to see graphed. I hear excel calling me now!"
] |
[
"The blob of water is just floating in space (probably surrounded by some shell to avoid evaporation)? You would only get some pressure from gravity of the water. With a surface gravity of 4 mm/s",
" we get a pressure difference of 28 kPa or 0.28 Earth's atmospheric pressure between surface and center (equivalent to 2.8 m of water on Earth). You need some pressure at the surface to keep water liquid, going to the center won't change the total pressure much."
] |
[
"How can two black holes merge instead of orbiting each other endlessly?"
] |
[
false
] |
I was recently reading about the LIGO experiment and its famous 2016 detection of a gravitational wave signal consistent with the merging of two stellar mass black holes. A truly remarkable observation, but it left me stuck wondering how the orbit of something like two black holes could ever decay. I imagine bodies orbiting in space somewhat like a pendulum oscillating in a perfectly frictionless environment; unless something significant intervenes they would seem inclined to orbit each other nearly perpetually. It seems especially unlikely when you consider there can’t be tidal forces on what are essentially points (or can there?), and when it is difficult to imagine anything with more inertia than a black hole. What is the “friction” that could provide damping of the orbits of two black holes? Does this occur with other orbiting bodies, like planets around a star or are there mechanisms unique to such extreme objects?
|
[
"What is the “friction” that could provide damping of the orbits of two black holes?",
"Gravitational radiation. They emit gravitational waves, and lose energy. They spiral towards each other and eventually coalesce.",
"It's not unique to black holes; orbiting objects emit gravitational radiation, but the rate at which energy is lost may be extremely small."
] |
[
"E.g. the earth radiates away ~",
"200 Watts",
" through gravitational waves due to its orbit around the sun."
] |
[
"Time depends on the location, but that's not relevant here."
] |
[
"So recently I’ve been told that Earth is the only planet in our solar system, where water can be liquid, gas and solid. This is interesting as it is but I was wondering why it isn’t like this on the other planets?"
] |
[
false
] | null |
[
"The statement isn't quite accurate- it's probably the case that Earth is not the only place where water can be in all three states at once. The rarest state of water in the solar system is definitely liquid water, while gaseous and solid water are probably present everywhere in at least trace quantities. Thus, the real key to your question is whether or not Earth is the only body in the solar system that has liquid water.",
"There are three other planets that might harbor liquid water: Mars, Neptune, and Uranus (with Mars having the strongest evidence-based claim, and if liquid water exists on Neptune or Uranus it is probably not accessible or useful). There are also four additional moons that may hold liquid water: Europa, Enceladus, Ganymede, and Ceres.",
"This question happens to be at the center of another major question in astronomy: \"Is there life on any of the other planets in our solar system?\" The reason is that liquid water is considered an essential ingredient for all forms of life as we know them, so much time and thought has been put into where liquid water might exist outside of Earth:",
"https://en.wikipedia.org/wiki/Extraterrestrial_liquid_water",
"But first, why exactly is liquid water so rare? When studying how chemicals change between the different states of matter (solid, liquid, gas) we use a phase diagram. You can see the phase diagram of water here:",
"http://www1.lsbu.ac.uk/water/water_phase_diagram.html",
"This diagram tells you what state water will be (solid, liquid, or gas) based on two variables- temperature along the horizontal axis and pressure along the vertical axis. For example, if you locate the \"E\" near the center of the graph this tells you the average pressure on Earth. If you go left and right from this point you vary the temperature, and as you go left the temperature goes down and eventually water freezes. As you go right the temperature goes up and eventually water boils. ",
"The intersection line between the liquid water and the solid water regions is called the freezing point, and the intersection line between the liquid water and the gaseous water regions is called the boiling point. You'll notice that this varies with pressure- perhaps this is not surprising to you, as you may have heard that water boils at a lower temperature at high altitudes. It's also true that the freezing point varies with pressure as well.",
"Now, the key observation that answers the question \"Why is liquid water so rare in the solar system?\" is this: look at the end-behavior of water all around the edges of the graph. Along the left and top edges which correspond to low temperature or high pressure water is always solid. Along the bottom and the right edges which correspond to high temperature or low pressure water is always gaseous. The conclusion is that the conditions for water to be liquid are somewhat rare, and when you go to extremes of temperature or pressure you always end up with a solid or a gas otherwise. ",
"Of particular concern for us is that once you get below a certain pressure, you'll see that the liquid water region disappears and there is only one line that joins the solid and gaseous regions. Most bodies in our solar system have very little atmosphere. They're in a total vacuum or very close to it. For all of these bodies there can be no liquid water because the pressure is too low. Instead of water melting or boiling when it warms up it's converted directly from solid water to gaseous water (called sublimation). Instead of water freezing or condensing when it cools down it's converted directly from gaseous water to solid water (called deposition).",
"Thus, we can use our phase diagram and analyze each of the major planets in turn:",
"Mercury has no atmosphere, so it cannot have liquid water. The dark side of Mercury is actually quite cold, and there are parts of Mercury at the poles that receive very little sunlight. It is suspected that Mercury could have some solid water stuck at the bottom of craters in these cold regions that are rarely or never exposed to sunlight. However, Mercury is so close to the sun that anything that is exposed to sunlight is superheated. ",
"Venus has a very thick atmosphere- so thick in fact that it never cools down, even at night. The greenhouse effect has run to the extremes, so it is never cold enough to support solid or liquid water.",
"Earth is right in the middle. We have liquid water most of the time in most of the places, but our polar caps are cold enough to support solid water all of the time. Gaseous water exists as water vapor in the atmosphere.",
"Mars is right on the border of the liquid water region: the average atmospheric pressure is a little too low to support liquid water, but seasonal and temperature differences cause big enough variations in the surface pressure that liquid water could be supported under the right conditions. Importantly, apparent \"flows\" of material have been identified in the warm season on Mars that definitely suggest some kind of liquid exists, but spectroscopic attempts to conclusively identify these flows as water have not been successful.",
"Uranus and Neptune are very cold ice giants, and are thought to be largely composed of water. While their surfaces are cold, the temperature of their cores is quite high due to the tremendous gravitational pressure. The story here gets a little weird, because at very high temperatures and pressures water is no longer just liquid or gaseous, but actually enters a state called ",
"supercritical water",
" and takes on some properties of both liquid and gaseous water. There are probably large underground oceans of supercritical water on both of these worlds, but whether or not you consider that to be liquid water that satisfies your question is up to you. "
] |
[
"Thank you for the thorough explanation!!"
] |
[
"If we're really limiting the inquiry to planets here, and water in the familiar forms on earth (ice, flowing water, vapor) I think it might be a somewhat overly specific question; our sample size is just to small. ",
"You have eight planets; of them, four don't have solid surfaces at all, which would rule out surface water by definition. There may be exotic liquid-like forms of water, but not the kind of thing you're thinking of or looking for.",
"Then you can rule out Mercury, which is too small to have an atmosphere, guaranteeing that there would be no appreciable amount of vapor to detect, and that any liquid water would boil away into the vacuum.",
"Further Mercury - and Venus - are too close to the sun for ice to exist, and it would melt away.",
"So, just like that, we've shrunk our sample size to two planets, and even if we say that only Earth fits the bill, we're just talking about a coin flip.",
"But does it? Mars very clearly has water ice at its poles, so that's one. There are also visible cirrus clouds with a water component, and water in the atmosphere, so that's two. ",
"Liquid water doesn't exist there very long. It's almost always too cold, and when it's not, the low pressure causes water to boil almost immediately (important note for Martian bakers!) However, there is abundant evidence that Mars used to have water on its surface - even lakes or oceans, plus some intriguing possibilities for at least short-term water flows, or persistent groundwater. ",
"If confirmed, that would mean that all three states of water are present on all planets where it's even plausible!"
] |
[
"Does a Fermionic condensate violate the Pauli exclusion principle?"
] |
[
false
] |
Does a Fermionic condensate violate the Pauli exclusion principle?
|
[
"This is from Wikipedia:",
"\"It is far more difficult to produce a fermionic superfluid than a bosonic one, because the Pauli exclusion principle prohibits fermions from occupying the same quantum state. However, there is a well-known mechanism by which a superfluid may be formed from fermions. This is the BCS transition, discovered in 1957 by John Bardeen, Leon Cooper and Robert Schrieffer for describing superconductivity. These authors showed that, below a certain temperature, electrons (which are fermions) can pair up to form bound pairs now known as Cooper pairs. As long as collisions with the ionic lattice of the solid do not supply enough energy to break the Cooper pairs, the electron fluid will be able to flow without dissipation. As a result, it becomes a superfluid, and the material through which it flows a superconductor.\"",
"In other words, pairs of fermions can become coupled to form boson pairs. These pairs can then form a condensate."
] |
[
"I'm not sure you're asking so I'll cover the bases:",
"A cooper pair might consist of one electron with momentum +p and another electron with momentum -p, so these electrons do not occupy the same state. However, the coupled pair has a total momentum quantum number of zero (p-p=0). If you have many such pairs, with individual electrons with momentums p1, p2, p3 and -p1, -p2, and -p3, then you can have a lot of electrons that do not have the same quantum states (all different momentums), but cooper pairs that do (all momentum zero).",
"So the pair acts like a boson, but the individual electrons are fermions.",
"This is oversimplifying, but does it kind of answer your question?"
] |
[
"But aren't these coupled pairs occupying the same quantum states?"
] |
[
"Lake Baikal growth: how is it measured?"
] |
[
false
] |
Hi guys, I was watching a video of SciShow about lake Baikal ( ). At the very beginning of the video (min 1:07) they mention that the lake gets wider about 2cm annually. I have no doubt about the tectonic fact, however, I was wondering how can it be measure with such precision. Of course, my first thought was "well... using satellite you can compare one image to the other, yadah yadah", but talking about such large distances, and satellite images, measuring a difference of cm sound like a long shot. Maybe I'm wrong and is possible. Anyway, this is just a curiosity, I would appreciate your answers. Cheers!!
|
[
"First off, I don't know where they got 2 cm/year, at least if they're actually talking about the lake widening from rifting, because the rate of extension is significantly lower than that at ~4 mm/yr. This measured rate of extension does involve satellites, but not images. It's measured using permanent/continuous (high precision GPS receiver attached to a pole and cemented into the ground that measures its position continuously) or campaign (a permanent monument cemented into the ground that is \"occupied\" by a high precision GPS for a few days each year) station measurements of the movement of the Earth's surface. The commonly cited modern extension rate for the Baikal rift comes from ",
"Calais et al, 1998",
" and was measured using 3 years of GPS data (which was good for the time, though a short time series compared to what we use now) and found to be 4.5 +/- 1.2 mm/yr. Looking at updated GPS data in this region (e.g., ",
"Calais et al, 2006",
" or ",
"Vergnolle et al, 2007",
"), the extension rate and uncertainty stayed about the same (and in detail, the uncertainty for most stations in this dataset are around 0.5 to 1 mm/yr). ",
"More generally, GPS is the primary method by which we measure modern plate motions and especially with continuous stations operating for multiple years, can reach sub-mm precision in terms of average motion rates (e.g., ",
"this video",
" from UNAVCO explaining a little about how this works). There are remote sensing techniques like what you envisioned, i.e., time series of satellite images to derive displacements (e.g., COSI-Corr - ",
"Leprince et al, 2007",
", ",
"Ayoub et al, 2009",
") but the magnitude of displacements that can be resolved is limited both by the pixel size of the images and your ability to co-register the images, so in practice these are more appropriate when the target is something with meters of displacement over short periods of time (e.g., faults that moved during an earthquake, sand dunes, landslides, etc). Alternatively, techniques like ",
"InSAR",
" (which also really shine for measuring large displacements after earthquakes, etc) can be used to measure relatively small (cm scale) gradual movements under ideal circumstances and with long time series (e.g., ",
"Grandin et al, 2012",
"). All told, there are a few other ",
"geodetic techniques",
", e.g., ",
"VLBI",
", or time series of LiDAR (e.g., ",
"Okyay et al, 2019",
") or photogrammetry (e.g., ",
"Nagle-McNaughton & Cox, 2020",
") which can be used to measure displacements. The latter two, like InSAR and COSI-Corr are very well suited for relatively sudden movements, but can theoretically be used to measure average rates, but will depend on the resolution of the underlying data (individual point spacing) and the ability to co-register scans/datasets."
] |
[
"Wooooow. Thank you! This is a great explanation. You have not only enlighten me but now I’m super curious about these measurements. Gonna have some interesting reading to do. \nIf only I had coins to award you. But be sure you have my forever appreciation."
] |
[
"These are some good options -- thank you!"
] |
[
"What is happening in the brain when someone is unconscious?"
] |
[
false
] | null |
[
"Unconsciousness is defined as a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. When you are asleep you are still fairly responsive to your environment. You would respond to noise, movement, your eyelids being opened, and painful stimuli. So, no sleep doesn't count. It's considered an altered state of consciousness. "
] |
[
"We don't know exactly what is happening but here is the best guess. Anytime someone is unconscious (that is not medically induced) they have either sustained a traumatic head injury or are seizing. We know that the brain stem is usually spared because they are breathing and the heart continues to contract. The exception to this of course is when a seizure affects the midbrain and thus the occulomotor control goes out the window. We also know that the \"working memory\" which is in the prefrontal cortex, is damaged, as well as the hippocampus. This accounts for the memory loss of up to a minute before the incident. Other than that there is cell death. "
] |
[
"Anytime someone is unconscious (that is not medically induced) they have either sustained a traumatic head injury or are seizing",
"Does sleep not count?"
] |
[
"If you melt a magnet, what happens to the magnetism? Does the liquid metal retain the magnetism or does it go away?"
] |
[
false
] | null |
[
"Sometime before it melts, the ",
"Curie temperature",
" will be exceeded and it'll lose its ability to retain a magnetization in the absence of an external field."
] |
[
"I'm an amateur blacksmith, and I've seen people use magnets to check the temperature of steel they're working on. If the magnet doesn't stick, you know it's past the Curie temperature"
] |
[
"And ready to be quenched! This is because the crystalline structure inside has realigned. This causes loss of magnetism and is good for strength. That's why we freeze it it by quenching"
] |
[
"Can x, y, and i be graphed on the same graph?"
] |
[
false
] |
This question came up in my high school Algebra II class today. We were learning about graphing complex numbers using the complex plane, and someone asked if you could just add the imaginary axis to a graph that already has x and y axes. My teacher said he had never really thought about it, and therefore could not provide a good answer. If you can graph all three (x, y, and i) on the same graph, what would it look like? If you can't, why not?
|
[
"While I prefer teachers to admit when they don't know something rather than dissemble or deflect, I hope this is no indication of the general state of your teacher's education in mathematics.",
"I'm not quite sure what the question is about, but in general, the answer is yes. There are three possibilities:",
"You want to graph a real-valued function of complex numbers (a function f that takes complex arguments but outputs real numbers). Example: the magnitude |z| of a complex number",
"You want to graph a complex-valued function of real numbers (real argument, complex value). Example: a complex exponential exp(I t) with real t",
"You want to graph a complex-valued function of complex numbers (complex argument and complex value)",
"The first two options are easy. You create something like a 3D ",
"isometric plot",
". For option 1, we typically choose the horizontal plane as the complex plane and plot the function value on the vertical. For option 2, you usually choose one of the horizontal axes as the time (real) axis and the other two as the complex plane.",
"The third option is more tricky because we cannot imagine what a 4D plot would look like. Usually, you will use several 3D plots over the complex plane to visualize the function. For instance, you could create two separate plots of the real and imaginary values respectively, or the argument (angle) and magnitude, or all four of them. "
] |
[
"Lots of good answers here, but let me try my own shot at explaining things in a way that's very very simple and directed straight at what's useful for the OP.",
"• Right at the outset, it's important to distinguish between x & y, which are variables in this context, and i, which isn't. The simplest way to think of it is as the imaginary unit: the real number line goes 1, 2, 3...; the imaginary number line goes i, 2i, 3i... and so forth. ",
"• If I want to graph the number 4, I don't need a sheet of graph paper — I just need a one-dimensional number line; I can then put a dot at 4. On a sheet of two-dimensional graph paper, each point represents a pair of numbers — for example (3, 4). ",
"This is often useful when graphing equations, because if I establish a relationship between two variables (y = x+1, for example), I can then graph all the pairs of numbers (such as (3, 4)) which satisfy that equation. (In this instance, that set of points forms a line.)",
"• On the other hand, if I treat my sheet of two-dimensional paper as the 'complex plane' which you learned about in school today, each point represents a SINGLE complex number. So, for example, the point (3, 4) on your page is actually the number 3+4i. ",
"• So what this really means is that when we use a sheet of 2D graph paper to plot points in the complex plane, it's analogous to using a 1D number line to graph points among the real numbers. ",
"• Of course, we can have equations in which we think of the variables as representing complex numbers. So, for example, consider the equation y = x",
" + 4. One possible solution to this equation is (0, 4). But another possible solution is (2i, 0).",
"• It's easy to graph a function y = f(x) on a 2D sheet of graph paper if x and y are both real numbers. But what if we allow either or x or y to be complex? Well, if one or the other of them is complex, we would need to build a three-D graph. And if they BOTH are complex, we'd need 4D graphing, which isn't really possible!",
"Is this a helpful start, OP?",
": minor fixes."
] |
[
"I believe that you misunderstood the question. The question is about the graphical representation of a complex number such as Argand diagrams and if there exists a representation in which there are 3 axes. Unless I also misunderstood the question, but if I'm right I don't understand why his teacher did not know the answer.",
"The answer the OP's question is no, since complex numbers are 2-dimensional. For example, let x+yi be a complex number. To graph this on a plot with x-, y-, and i-axes would be nonsensical. i is not a variable."
] |
[
"Help resolve a roommate argument. Would plastic blinds that are closed over a large window have any insulative properties?"
] |
[
false
] |
Two roommates have a two day long argument over whether or not the plastic blinds they have hanging in front of a large window in the living room would help, even if only a little, to keep cold air out. Not saying that the window is open. Any science to end this civil war?
|
[
"This is exactly what I was looking for, thank you. I can't wait to show this to them and walk around the house with a well-deserved smug look on my face. "
] |
[
"This is exactly what I was looking for, thank you. I can't wait to show this to them and walk around the house with a well-deserved smug look on my face. "
] |
[
"The blinds help, ",
"I think you're doing some disservice by not including what I assume was roommate's argument -- That the sun through the windows is helping heat things up.",
"During the winter, any windows you have facing the south (Or north if you're in southern-hemisphere winter) should have the blinds up ",
". South will catch sun during most of the day. (That the sun's path across is so skewed south is the (oversimplified) reason for winter, after all). At night, lower the blinds.",
"Any windows that aren't facing south aren't going to catch much sun over the course of the day, and then the convection-breaking of the blinds will win out. "
] |
[
"Why is there less oxygen in the atmosphere than is believed to be present in prehistoric times?"
] |
[
false
] |
As I understand it, in prehistoric times there was a lot more oxygen in the atmosphere, and now we have less. Where did it go? Thanks!
|
[
"It binds with other elements, limestone CaCO3 traps quite a bit "
] |
[
"Photo-autotrophic organisms such as plants and phytoplankton 'sink' carbon dioxide in order to utilize the sun's energy, and have a net release of oxygen.",
"It is thought that these photo-autotrophs were so good at sinking the CO2, that they flourished excessively. They eventually poisoned themselves by releasing too much oxygen into the atmosphere. This is thought to have caused a massive bottleneck event in natural selection, killing a large amount of photo-autotrophs, and allowing the emergence of the first aerobic bacteria. (those that use oxygen) After this point, oxygen began to have a net usage by organisms, slowly going down.",
"Similarly, heterotrophs (including humans) have to eat these other organisms in order to obtain energy. In doing so, we expel carbon dioxide while having a net intake of oxygen.",
"But, it depends when you're talking about. Oxygen in the earths atmosphere has gone up and down repeatedly over time, often due to different causes.",
"There are also a series of geological rationalisations, most of which I am not familiar with."
] |
[
"Originally oxygen was just a waste product, created by cyanobacteria via photosynthesis about 300 million years ago. Oxygen was toxic to most forms of life at the time. As forms of life adapted to use oxygen, we saw a gradual reduction in oxygen levels. The oxygen didn't actually \"go\" anywhere, its just not in the atmosphere, Its now just being used by a large number of animals(and some plants) and constantly being cycled.",
"The high level of oxygen is also why we saw such huge insects back then. Insects respirate through their skin, and the higher oxygen levels allowed them to grow larger. The lowering oxygen level over time is also one of the reasons the lungs may have evolved the way it did as well."
] |
[
"Why don't stretch marks bleed when formed?"
] |
[
false
] |
So i've got a bunch from both weight lifting and letting myself go for a while there and as they appear, it always surprises me because there is no real signs that it's happening, they just seem to show up all of a sudden. Why is it that if your skin is basically ripping, why do those areas not bleed when it happens and why is there no pain involved?
|
[
"Not really. You can try cocoa butter to get them to fade, but there is no real cure for stretch marks...if there was a cure, believe me, Oprah would not have them."
] |
[
"your skin has three layers. The dermis, the epidermis and the subcutaneous layer. Your blood vessels are in the dermis layer. You can damage part of your skin without damaging the blood vessels (which would cause you to bleed).",
"Your skin can stretch and feel strain. It will compensate by laying down new material to repair the damage. This new material is different from the old material and is less flexible and more rigid. This is the same reason you get a scar. But you dont bleed because only the skin cells and not the blood cells are damaged"
] |
[
"Think of your skin as a rubber band that can stretch and stretch and stretch without breaking, however your skin will as a rubber band does when you stretch it get a stretch mark, same thing happens to your skin."
] |
[
"When metal wears down, like a coin wearing smooth over time, where do the atoms/matter go?"
] |
[
false
] |
[deleted]
|
[
"All over the place. On your hands, the table, your pocket and other coins, etc."
] |
[
"Could be absorbed into your skin (in the coin example) or just becomes part of the dust in the environment. Whether that's outside, in your pocket, or on your floor."
] |
[
"So I could have a single molecule of steel just hanging out on my skin?"
] |
[
"What does a spider’s field of view look like?"
] |
[
false
] |
I’ve seen pictures of spiders having eyes on parts of their heads where it looks as if a fluid and connected image would not be possible. Do they see similar to say, a security set up where there are different points of view? Or does the image present itself like one very wide angled picture? Thanks!
|
[
"The answer will depend somewhat on which type of spider you're considering. While almost all spiders do have eight eyes, their specific structures and arrangements are ",
"impressively variable",
". Tarantulas, for example, have pretty poor visual acuity overall (and only one type of light-sensitive pigment; ",
"Dahl and Granda 1989",
"), and their ",
"tiny eyes are all clustered together",
" on top of their heads. Actually, some spiders have no eyes whatsoever like ",
"this ",
", so their field of view is just... non-existent.",
"The ",
"four pairs of eyes",
" in most spiders are named according to their most common positions (figure from ",
"Morehouse et al. 2017",
"). The anterior median eyes are usually the largest and are called \"principal\" eyes, while the other three pairs have their retina arranged the other way around and are generally called secondary eyes (even though they are actually larger in some species, such as ",
"this ",
"). There is surprisingly little actual study of fields of view in spiders, but this has been looked at in a few species. In the ",
"chapter on eyes",
" from Barth's 1985 book on arachnid neurobiology, Michael Land presents ",
"this figure",
" which maps the fields of view from each pair of eyes onto a globe for four different spiders. The Morehouse et al. paper I already cited above has a ",
"slightly easier to interpret version",
" of this with some nice colour-coding too (but for only two species). As you can see, the different pairs of eyes only overlap a little bit, but mostly are spread out to allow for a more complete overall field of vision.",
"Unlike in vertebrates, where our single pair of eyes must be able to carry out all visual functions across a wide range of focal lengths, spiders can afford to diversify their eyes and optimize different pairs for different functions. ",
"Jumping spiders",
" in particular are widely thought to have the best vision among spiders (and indeed, some of the best among invertebrates as a whole), and so they tend to be the most well-studied for this kind of thing. Their anterior median eyes, in addition to being quite large, are also ",
"tubular and elongated",
", which gives them a very narrow but focused field of view (basically equivalent to our fovea). Meanwhile, the other pairs have lower visual acuity but broader fields of view, and function ",
"more like peripheral vision",
". Though as that image shows, the anterior lateral eyes do actually overlap a bit, giving partial binocular vision. ",
"Here's another figure",
" which demonstrates this nicely; the anterior median eyes have a tiny field of view that almost looks like a pair of yellow lasers, but they can actually ",
"move this pair of eyes",
" (as indicated by the dotted lines), which compensates for this somewhat. I also came across ",
"this neat video",
" of some visual research on jumping spiders which you might find interesting."
] |
[
"Spiders on average have roughly a 300 degree field of view.",
"We humans on the other hand have 120 degrees of field of view.",
"So basically a spider can see its front , sides and ,in its peripheral view, some of its rear"
] |
[
"If imagine it’s probably stitched together just like our vision is, but we can’t really tell. It’s not like we can just ask spiders what they see. We would need to completely reverse engineer their nervous system to find out."
] |
[
"Why do guns kill people so quickly (or are movies lying to me?)"
] |
[
false
] |
[deleted]
|
[
"Movies are lying to you. As you suspected, gunshot wounds are very rarely instantly fatal. A shot to the abdomen or chest is often not even incapacitating for some time. ",
"Anecdotal, but relevant: my grandfather was shot through the throat by a high powered military rifle round, and wasn't at all sure what happened at first. Apparently it took him a good several minutes before he fell over and several more before he passed out, which gave him enough time to crawl back into cover. "
] |
[
"First question: does getting shot kill you as quickly as it does in the movies?",
"I don't think that most of the time movies are lying to you. They are just simplifying things for you to help the flow of the movie. In reality a lot of the people shot would probably be writhing in agony and slowly dying and so on, but that might distract from the plot/action. Most of the time you don't see where people really got shot, they just \"die\", and I guess you should assume it is the head or chest.",
"In a movie most of the time incapacitated/neutralized is just as good as dead. They aren't going to show you that this person is still alive but bleeding to death or this person is in shock and this one is twitching around on the ground or the other guy over there is probably going to be okay but is in no state to stay in the action. They are usually \"killed\" if they are just taken out of the action, especially if they are a frivolous character.",
"Some of the people who get \"killed instantly\" in a movie could possibly still have brain activity and their heart may still be working, etc. But if that doesn't contribute to the plot then they probably aren't going to show you that.",
"Second question: Biologically - why? I can understand getting shot in the head, but anything in your torso isn't immediately necessary for life in the next few seconds. I can understand dying from damaging major organs, but it seems like getting shot anywhere other than the head should take you anywhere from a minute to maybe ten to bleed out, etc.",
"A bullet doesn't just punch a nice clean hole in you (if it does, then you are probably lucky, aside from the fact you just got shot). Lower velocity ball rounds are designed to deform on impact and/or fragment and this can cause a lot of extra damage. Higher velocity rounds are often designed to tumble on impact which also causes additional damage and is designed to prevent the round from passing through the target, which means a large portion of the energy it carried is transferred to the target and used to cause damage.",
"Bullets carry a lot of energy (relatively speaking) and most of that energy is transferred to you when you are hit. Many bullets are designed to have \"stopping power\" which doesn't mean that they kill you instantly, just that they put you in a state where you are not likely to be a threat, the most ideal usually being dead.",
"In a movie when you see somebody get shot and keep moving that is probably because they just got winged by the bullet. Often you might hear them or another person talk about it being \"through and through\" or something similar. That means the bullet went through them (hopefully just muscle), which means it probably didn't have time to tumble or deform and did minimal damage. This person surviving is part of the plot.",
"But when you see somebody go down that is because they weren't meant to survive and so the gunshot was fatal. Would they really die that quickly in real life? Who knows? Could they? Probably, yes.",
"When you see a death scene for a specific character you usually get more information about the character's injury. They might take longer to die than the nameless cannon fodder of the movie but still die pretty quickly from blood loss and so on. Again that might just be a simplification. This character is important enough to see die, but the movie isn't about the 10 minutes they stayed conscious while they bled out and so on (another factor is that you don't always know how much time is being skipped). Also, when people are severely injured, especially if they are bleeding or in pain, they might pass out/lose consciousness. The movie isn't going to sit there while the other characters stare at the shot character for the next 5 minutes between \"movie death\" and clincal death where all brain activity has ceased.",
"So are movies \"lying\" about the time between getting shot and the complete cessation of brain activity? Maybe. Are they lying about how effective guns are at incapacitating targets? Not really. That's what guns are for."
] |
[
"99% of military rounds are FMJ they are designed to pass through. hunting rounds are soft and designed to deliver their energy into the target. that is why when cleaning a game animal you find the heart/lungs have been obliterated, and a massive exit wound.",
"watch this ",
"video",
" he starts shooting at around 1 minute. notice how when he shoots the gel with the hollow point it jumps off the table. that is the energy of the round being delivered into the target.",
"TL:DR your grandpa was lucky his neck was not blown apart because he was shot with an FMJ."
] |
[
"If I'm 21 with a receding hairline, what are the chances that I'm not going to go entirely bald?"
] |
[
false
] |
I realise this is a desperate and ultimately futile question, but one can dream.....
|
[
"you have no idea how reassuring that is"
] |
[
"my hairline started receding about that time, the progress stopped a couple years later and now i'm 39 years old with the same head of hair, quite full, albeit a couple inches higher up."
] |
[
"I think it goes by your maternal grandfather, at least mine does."
] |
[
"I know 0 Kelvin is the lowest temperature achievable in the universe. Is there a maximum on the other side of the scale? If so, is it possible for scientists to reach it?"
] |
[
false
] |
We are learning about low temperatures in science class and I was wondering how things were at the other side of the spectrum. Is there a Bose-Einstein condensate type effect that happens at high temperatures? Also, I'm in 8th grade so simple terminology would be appreciated.
|
[
"Scientists actually aren't sure if there is a maximum temperature or not. A good theoretical bound is Plank's Temperature but that is only because current models break down above that temperature. Within other theories there are other maximum temperatures by different mechanisms."
] |
[
"Just for kicks, I will point out that technically, there is such a thing as a negative temperature on the Kelvin scale. Although these are generally odd states that can be created under very strict circumstances."
] |
[
"No, its not that if has negative energy. Its that it gains entropy by losing energy. (Typically object lose entropy as they lise energy). So if this negative temp object transfers energy to a normal object, both gain entropy. The net entropy increasing means the process happe.s "
] |
[
"Why must chocolate be tempered?"
] |
[
false
] |
I've seen it done on cooking shows and how-they-do-it type things before but I'm not entirely sure why it's done.
|
[
"Cocoa butter can form at least 6 different crystal structures. Only one - the so called beta form - is what you want. The different crystal forms have different temperatures at which they melt, in addition to the other properties (shine, snap...)",
"The trick in tempering is to get a liquid substance with enough beta crystals mixed in that when it does crystallize fully it all follows the pattern of the beta crystals already present and it will all make the good kind of crystals. Since the crystals will melt over a range of temperatures it is possible to have a mostly liquid batch of chocolate at the low end of the melting range that can hold a sufficient portion of the correct crystal type.",
"It's a troublesome issue with chocolate making, but it's great when you get it to work. My preferred method (that doesn't use a machine) is to melt chopped up chocolate in the microwave in 30 sec bursts. When you can stir it up after letting it sit for a minute or two and there's still a little bit of unmelted chocolate left, you're in the right spot. ",
"A dab of chocolate on your lower lip should feel just barely cool when it's at the right temperature. Stir well and work quickly - tempered chocolate is supposed to set up fast. When done right it should look smooth, set up quickly, and not have any streaks or lines."
] |
[
"There are three ways to do it, and one of them is melting and remelting. In that way you heat the chocolate up to 120 deg or so. This melts all of the crystals of every form. Then you cool it quickly down to 82-85 deg while working the chocolate in a bowl or on a slab. This forms a whole lot of very small beta and beta prime crystals. Then heat it back up to 92 deg (for dark chocolate, others are lower) to melt away the less-stable and unwanted beta prime crystals, leaving just beta crystals. Best with the right equipment and plenty of practice, but is the only way to temper untempered chocolate without seed crystals.",
"The second way is to slowly raise the temperature of tempered chocolate until you get to 92 deg. That way you have melted a large number of the crystals, but not all of them. The ones that are left are beta crystals from the previously tempered chocolate. Gotta heat slowly (if you overshoot you have to go to option 3) and start with tempered chocolate.",
"With the seed method, you heat up to 120 deg or so, let it cool to 100 deg or so, then add tempered chocolate with stirring to bring the temp down and add seed crystals. Chopped up pieces work faster, but a big lump is easier to remove once the liquid chocolate is tempered. ",
"In all the final goal is to have mostly melted cocoa butter (the important part with regards to tempering) in the chocolate, but not totally melted, and what isn't totally melted is in the right crystal form. "
] |
[
"I can personally attest to this man's chocolate tempering skills. I had no idea how involved it was."
] |
[
"This may be a dumb question, but would it be possible to change what “type” of cell a cell is?"
] |
[
false
] |
So I’m currently taking highschool biology, and we’re covering cells. The notes mentioned that cells such as blood cells, muscle cells, and nerve cells have the same DNA, they just have different genes activated by chemical signals. Assuming that this is correct, could purposefully giving the cells a certain chemical signal to make them into a different cell work? As an example of what I mean, perhaps sending chemical signals to a stem cell to create new nerve cells to repair nervous system damage. And if it is possible, why aren’t we currently doing it?
|
[
"Yes, there are many examples already:",
"https://scitechdaily.com/neurons-can-be-changed-from-one-type-into-another-from-within-the-brain/",
"http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/moaction/change.html",
"https://www.sciencealert.com/scientists-discover-an-enzyme-that-can-change-a-person-s-blood-type"
] |
[
"One of the strategies for stem cell research involves taking differentiated cells (eg skin cells) and turning them into stem cells with chemical signals. These stem cells can then be differentiated into other target cells. ",
"In such a system one would collect your cells, produce stem cells, then populate a structure with them and cause them to form something else- convenient things include bladder, esophagus- all sorts of stuff that is hard to get transplants working correctly for it. This would give you a rejection-free transplantation option."
] |
[
"Like everyone else said, it is possible, but there are limits.",
"Red blood cells, for instance, can't be changed because their DNA is destroyed as a part of the process of becoming blood cells.",
"If a cell is highly specialized, it may have already implemented changes which would be hard to reverse. A nerve cell, for instance, would be difficult to change to anything other than a different type of nerve cell, simply because of the drastic changes that have already been made to it's structure in order to change it into a nerve cell.",
"The more specialized a cell is, the less likely it is to be able to change it into something else.",
"That's why stem cells are great for this. Stem cells are unspecialized. They haven't already been changed into nerve cells or muscle cells or skin cells, so they are a blank slate and can be changed into any specialized cell.",
"There's been a lot of research, ",
"and some success",
", in changing in changing certain cells (especially skin cells) back into stem cells. But mostly it's been only partially successful."
] |
[
"Layman proof of an old earth"
] |
[
false
] | null |
[
"There's not really any such thing, no. That's a big part of why young-earth creationism is so popular; if you're willing to believe that every scientist in the field is lying, you won't run across any reason to change your mind. If you try to deny relativity or something, you still have to explain why all the scientists are lying, but you ",
" have to explain why all the things that rely on relativity work."
] |
[
"If there were, we wouldn't have had to wait until after several thousand years of human history to figure it out; the old Earth would have been in Plato and Aristotle and that would be that.",
"Also, there's no such thing as \"proof\" in science - all we can do is gather more and more evidence for or against something. But proof, real 100% proof, only exists in the world of mathematics. Which isn't to say there's any realistic doubt that the Earth is billions of years old, but that doesn't mean it's proven. Understanding what we do and don't know in science, and how well we know them, is a pretty important step that unfortunately most creationists never take."
] |
[
"How about the fact that it is very unlikely for such a complexity to develop from an evolutionary system in a lot less time? Oh, wait..."
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.