[Phys-L] entropy

[larry.smith at SNOW.EDU (Larry Smith)]

At 7:33 PM -0500 8/24/05, Jack Uretsky wrote:

> ps "The past is another country.  They do things differently there."
> I subscribe to the model that we and the observable universe, with all its
> contents and all our memories, were created last Tuesday at 1210 GMT.
> I defy anyone to prove me mistaken. (With thanks to Bertrand Russell).


Interesting in light of Brian Greene's discussion of the arrow of time and
entropy in his book "The Fabric of the Cosmos" in chapter 6 (especially
page 160, where he says "Since Newton's laws of physics have no built-in
temporal orientation, all of the reasoning we have used to argue that
systems will evolve from lower to higher entropy toward the future works
equally well when applied  toward the past."  "Thus, not only is there an
overwhelming probability that the entropy of a physical system will be
higher in what we call the future, but there is the same overwhelming
probability that it was higher in what we call the past.")

He argues that it is more probable that the universe was created last
Tuesday at 1210 GMT with us and all our memories intact than that the
universe had lower entropy in the past.

To produce a real arrow of time, then, requires that we come up with a good
explanation for why the universe started in such a low-entropy state.

Larry