3 ms·

What is problematic about that? In what way does it violate the second law of thermodynamics? If anything, it seems like a great example of the natural tendency

What is problematic about that? In what way does it violate the second law of thermodynamics? If anything, it seems like a great example of the natural tendency towards disorder. Also, it’s not possible to infer macroscopic prior states even with an infinitely powerful computer. When you mix water at different temperatures, entropy is irreversibly increased. It’s not possible to tell the initial temperatures just from the final state.

jfengel 5y ago
It's a subtle point. Several key theorems of thermodynamics rely on the ability to count unique states. If you could evolve the exact same state in two different ways, the proofs would fail. That's how thermodynamics derives indistinguishable macro states from distinguishable micro states. Throw that off and thermodynamics stops working. Since it has worked well so far they're reluctant to throw it out. Something has to go, and since they already know there's something funny going on where black holes meet quantum mechanics, that's the lowest hanging fruit.
- SnowHill9902 5y ago
  So you are saying that if I solve the Schrödinger's equation for all the particles that make up her I could know where my wife wants to go out for dinner?
wanda 5y ago
> In what way does it violate the second law of thermodynamics? If you read my comment, you will find no mention of the second law of thermodynamics or any violation of said law. In fact, black holes need to evaporate in this way in order to comply with said law of thermodynamics. > When you mix water at different temperatures, entropy is irreversibly increased. It's not possible to tell the initial temperatures just from the final state. It is still water, however. You may not be able to say what temperatures W(a) and W(b) were from W(c), but you could at least say that W(c) may actually be W(ab) i.e. may be the mixture of two bodies of water W(a) and W(b). Bring the same water to a black hole and you have: W(a) went into a black hole and x came out, where x is some random heat. If you detect the heat x, what could you say about anything that may have been before? If W(a), W(b), Chair(a), Xylophone(g), Stone(f), Person(z) or anything went into the black hole, only heat x comes out in the end.
- SnowHill9902 5y ago
  Perhaps I’m missing some advanced theories or contradictions, but it seems to me quite intuitive or at least reasonable that there exists some very efficient generators of entropy, i.e. black holes. Even if not having fallen into a black hole, such water would have decayed to heat and fundamental particles eventually. Why is it contradicting that it happens much faster in some places in the universe? It may be surprising but what does it contradict? I’m asking sincerely. Regarding the water thought, if you recite a poem inside a chamber, it turns into heat. If you are outside and can only measure that the room slightly increases its temperature you also can’t recover the poem.
  - marcosdumay 5y ago
    That's because something may fall on the black-hole with larger entropy than the usual "black-hole matter", and it would decay into the lower entropy particles. But whether something with higher entropy than "black-hole matter" exists is a more refined question than if black-holes erase the entropy of what fallen into it. And Quantum Mechanics has a problem with erasing entropy, even if it's into a larger amount.

jfengel 5y ago

It's a subtle point. Several key theorems of thermodynamics rely on the ability to count unique states. If you could evolve the exact same state in two different ways, the proofs would fail. That's how thermodynamics derives indistinguishable macro states from distinguishable micro states. Throw that off and thermodynamics stops working. Since it has worked well so far they're reluctant to throw it out. Something has to go, and since they already know there's something funny going on where black holes meet quantum mechanics, that's the lowest hanging fruit.

SnowHill9902 5y ago
So you are saying that if I solve the Schrödinger's equation for all the particles that make up her I could know where my wife wants to go out for dinner?

wanda 5y ago

> In what way does it violate the second law of thermodynamics? If you read my comment, you will find no mention of the second law of thermodynamics or any violation of said law. In fact, black holes need to evaporate in this way in order to comply with said law of thermodynamics. > When you mix water at different temperatures, entropy is irreversibly increased. It's not possible to tell the initial temperatures just from the final state. It is still water, however. You may not be able to say what temperatures W(a) and W(b) were from W(c), but you could at least say that W(c) may actually be W(ab) i.e. may be the mixture of two bodies of water W(a) and W(b). Bring the same water to a black hole and you have: W(a) went into a black hole and x came out, where x is some random heat. If you detect the heat x, what could you say about anything that may have been before? If W(a), W(b), Chair(a), Xylophone(g), Stone(f), Person(z) or anything went into the black hole, only heat x comes out in the end.

SnowHill9902 5y ago
Perhaps I’m missing some advanced theories or contradictions, but it seems to me quite intuitive or at least reasonable that there exists some very efficient generators of entropy, i.e. black holes. Even if not having fallen into a black hole, such water would have decayed to heat and fundamental particles eventually. Why is it contradicting that it happens much faster in some places in the universe? It may be surprising but what does it contradict? I’m asking sincerely. Regarding the water thought, if you recite a poem inside a chamber, it turns into heat. If you are outside and can only measure that the room slightly increases its temperature you also can’t recover the poem.
- marcosdumay 5y ago
  That's because something may fall on the black-hole with larger entropy than the usual "black-hole matter", and it would decay into the lower entropy particles. But whether something with higher entropy than "black-hole matter" exists is a more refined question than if black-holes erase the entropy of what fallen into it. And Quantum Mechanics has a problem with erasing entropy, even if it's into a larger amount.