Science questions not worth a thread I: I'm a moron!
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hobbsyoyo
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Kind of what I was figuring but I wasn't sure.
Naw, aren't those basically thermometers?
madviking
north american scum
Bluemofia
F=ma
(Thermopiles)
They are fundamentally limited to the thermodynamic efficiencies (Carnot efficiency) inherent in temperature gradients doing work. Basically, ignoring the properties of the material, your thermodynamic efficiencies are limited to:
(T_hot - T_cold)/T_hot
This is also why you would want to run a power plant at as high of a temperature as you can without causing materials problems like carbon becoming soluble in iron or your machine melting or whatever.
So if you use a thermopile to harvest energy from, say, a high pressure water boiler at 1000 degrees C hooked up to a steam engine with proper cooling to room temperature (20 C), you have an efficiency of ~77% efficiency initially. This drops to a 71% efficiency when not properly cooling off the waste heat to 20 C, and instead hooking that up to a thermopile with an efficiency of 21%.
So 1000 J of energy input will get you 770 Joules of work in the first proposal, while in the second, you get 710 J from your steam engine, and 60 J from your thermopile, which is exactly the same as if you had just the steam engine.
In reality however, there are other factors other than the theoretical maximum efficiency, such as thermal properties of the material in question, which then reduces the efficiency even more. So it would be better off to keep the original proposal of boiler/steam engine.
Does anyone have a layman's understanding of whether or why dark matter is sucked into black holes and destroyed?
Things which are sucked into black holes are not destroyed, you just can't see them any more. (And if your car is sucked into a black hole, it will be torn to pieces obviously, but an electron that is sucked into a black hole is still an electron.
Since we don't really know what dark matter is, I'm not sure if I can answer the rest of your question.
Since we don't really know what dark matter is, I'm not sure if I can answer the rest of your question.
Bluemofia
F=ma
It's not "destroyed" per say, but its energy is absorbed into the black hole and becomes indistinguishable from anything else (because the black hole only can be described by its charge, spin, momentum, position, and mass) that falls into it.
A 1kg bar of iron falling in will become indistinguishable from a 1kg bar of gold, a 1kg bunny, or a 1kg blob of dark matter.
The only thing currently known for sure about dark matter is that it reacts with luminous matter gravitationally. I think we can say with a very high degree of certainty that it doesn't react with luminous matter electromagnetically, or via the weak or strong force*. Which is why it's called dark.
So anything that experiences gravity will be subjected to the effects of a black hole in the same way as 'normal' matter.
*More accurately, it's safe to say dark matter doesn't interact via electromagnetism. I don't know if the others have been positively ruled out. Weakly Interacting Massive Particles were ruled out as a candidate for DM a few years ago, if I recall correctly.
Bluemofia
F=ma
No, Dark Matter cannot interact via the strong force or electromagnetically because it implies it has either color charge or EM charge. Color charge is easier to detect than EM charge because it has much higher interaction probabilities, and EM charge would be easily observed because it would interact with photons by its messenger particle.
The weak force however, is a possibility that they can interact with, because it is so weak and short ranged. However, it is not observed to, otherwise we would have had headlines with a direct detection report already. They are currently trying to do so with a variety of experiments.
WIMPs on the contrary are the only "realistic" candidate left for DM, unless if I am mistaken (source?). The only things ruled out are MaCHOs (Massive Compact Halo Objects), Neutrinos*, and MOND (Modified Newtonian Gravity).
MaCHOs can be detected via gravitational lensing events of passing stars over background galaxies/other stars. These are not observed nearly statistically enough to have evidence of it as Dark Matter.
Neutrinos are ruled out* because they are too light to account for the DM fraction, as well as being too relativistic to account for the observed galaxy simulations.
MOND is ruled out because they need to be fine tuned to specific galaxies, and no individual MOND theory can adequately describe the observed phenomenon over all observed galaxies, so it is highly unlikely considering how many additions need to be done in order to make it sorta work.
*Sterile Neutrinos, which is a 4th generation neutrino which does not interact at all except for gravitationally is not quite ruled out, but it is a rather hideous addition to the model. Using Z boson decay resonances, we have ruled that only 3 generations of matter exist, assuming the lightest lepton is less than half the mass of the Z boson, or 91 GeV. It is possible that the 4th generation neutrino is greater than 45.5 GeV in mass, but such a jump from ~ 1 eV with differences of 0.1 eV of the other neutrinos to suddenly >45.5 GeV is unreasonable.
Thank you for the deep correction, Blue Mofia!
I'm under the impression that the mass becomes compressed into a new state completely dissimilar to the original matter, and then is slowly evaporated away as Hawking radiation?
Bluemofia
F=ma
That is the "Black Hole has no hair" theorem, which means that it does not care what originally fell in, a black hole can be described with the earlier mentioned quantum numbers. It's not really destroyed, it's just converted into mass-energy which then evaporates away. Saying it is destroyed tends to imply violation of conservation of energy, and Physicists don't like that implication.
However, this appears to violate the conservation of information, which is supposed to be a big deal (I'm just parroting things now without any real knowledge of why), so supposedly the information is preserved and is slowly re-radiated back, mixed with everything else that fell in during the lifetime of the black hole.
Well, we don't really know what the inside of a black hole looks like, or if that's even a relevant question.
Hawking radiation, of course. Which can be anything, but is mostly photons and lighter particles (electrons, positrons, maybe muons and pions).
madviking
north american scum
There are these things called quantum fluctuations which allow for a particle/antiparticle to be formed. Since the particle has energy E and the antiparticle has energy -E, energy is conserved during these fluctuations.
Now these fluctuations are happening everywhere all the time; they are just too small and ineffectual for us to notice. However, on the event horizon, you can have a quantum fluctuation that causes one of the particles to fall into the black hole and the other one escapes away from the black hole. Hence, energy is slowly evaporated from the black hole and since energy is mass (E = mc^2) this causes the black hole to lose mass every so slowly, which is called Hawking radiation.
Mise
isle of lucy
Why is it always the particle that escapes and the anti-particle that falls in? If the antiparticle escapes and the particle falls in, then the black hole gains mass, no? Surely this balances out?
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