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Entropy. What is it?

by Homesick345
Tags: entropy
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Dec14-12, 10:24 AM
P: 887
In Penrose's book the Road to Reality, he sort of asserted without proof that when gravity pulls things together, this increases the entropy. It seems that if this is to be the case, gravity must somehow increase the degrees of freedom of the system, but this wasn't explained.
Dec14-12, 10:52 AM
P: 5,462
In Penrose's book the Road to Reality
Page reference please?

In quantum statistical mechanics (and hence in thermodynamics, which is derived from statistical mechanics),
I think this claim will not stand up to detailed examination.

There is not complete overlap between the domains of applicability of thermodynamics and statistical mechanics. They both deal with areas not covered by the other.
Dec14-12, 10:55 AM
P: 166
My understanding is that as gravity pulls disorganized masses together into objects like stars and planets, the entropy of that particular system decreases, but that this is offset by the rise in entropy over a wider scale / bigger system. As with most of these things, I suppose it depends on how wide you want to cast your net when defining the boundaries of the system.

A house of cards on its own is a low entropy arrangement, but the entropy of the system has increased overall if you include the energy used by the person building it.
Dec31-12, 12:37 AM
P: 2
Quote Quote by Drakkith View Post
Either elaborate or provide a reference for this please.
I think the famous article by Eric Verlinde " on the origin of gravity and the laws of newton "

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