Entropy question

I remember reading an account of the fact that when a gas expands
in a container entropy goes up, but when gas and dust clouds in
space do the opposite and condense, entropy increases as well. (I
think it was in a Roger Penrose book.)

Why exactly is this? From a statistical POV, I don't see how N
number of particles know which kind of system they are participating
in or if they are behaving in the most likely way.

--
Craig Franck
craig.franck@xxxxxxxxxxx
Cortland, NY


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