Liouville & Entropy: Solving the Controversy

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SUMMARY

The discussion addresses the perceived controversy between the second law of thermodynamics and Liouville's theorem, particularly in conservative systems like gases. Participants assert that while Liouville's theorem suggests all states can be reached, the second law remains a statistical result applicable primarily to infinite particle systems, where fluctuations are negligible. They emphasize that real systems experience fluctuations, making extreme deviations from the second law possible, albeit with very low probability over extended timeframes. References to the fluctuation theorem and related experiments further support the argument that the second law is not an absolute law.

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Gerenuk
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Next to all recent Entropy thread I'd also like to have a question solved.

What's the solution to the controversy between the second law of thermodynamics, and Liouville's theorem that for conservative systems (as a gas should be?!) every state should be reached at some point? So eventually after an extraordinary long time all molecules would also gather in the corner.
 
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I don't think there is a controversy. The strict "thermodynamic" result is
only valid for an infinite number of particles (thus, no fluctuations). Real
systems do fluctuate though; all particles gathering in one place would be
a BIG fluctuation, thus very low probability, thus something that would only
happen after a very, very long time.
 
OK, that's also my favourite interpretation.

So the second law is rather a statistical result and in an extremely long period of time the second law could be arbitrarily violated?!

Any objections from someone else?
 
Gerenuk said:
OK, that's also my favourite interpretation.

So the second law is rather a statistical result and in an extremely long period of time the second law could be arbitrarily violated?!

Any objections from someone else?

You're right. I've posted a few questions of the same kind. For instance, see https://www.physicsforums.com/showthread.php?t=319633.
See the fluctuation theorem. There was a paper about an experiment that showed entropy decreases macroscopically for a few seconds... The paper was accessible from wikipedia. The Second Law is not a "fundamental law".
I just found something related to the article: http://www.newscientist.com/article/dn2572-second-law-of-thermodynamics-broken.html.
 
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