Re: 2nd Law violation and Time

From: Paul Draper (pdraper_at_yahoo.com)
Date: 10/06/04 

Date: 6 Oct 2004 08:07:30 -0700

jhelfand@umd.edu (Joe) wrote in message news:<e62610ea.0410052309.2b14b2cf@posting.google.com>...
> Suppose I put an ice cube in a glass of water. I look at it, I see it
> doesn't violate the second law. Now someone comes into the room and
> looks at it. He says, what the hell, what's an ice cube doing in
> water?! I say what, I put it there. But he goes on to say that this
> violates the second law of thermodynamics, and starts talking about
> phase space and entropies, and the "macrostate of largest microstates"
> and all these things. But I just tell him look, I just put it in
> there! He says, oh, it could have been there for a while, like a
> year, and I was surprised. For some reason, my physicist friend
> needed to know that the ice cube was only just put there to not
> violate his precious laws. Why is that? Why can't he figure that out
> for himself?

The ice cube's appearance is possible, even with the 2nd law, just
exceedingly unlikely. So your friend is faced with two choices: either
the system (the glass of water) is not closed, or an exceedingly
unlikely event just occured. It's not a priori obvious what the
correct choice is in all situations.

PD

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