Re: [asa] Thermodynamics & Eternal Universe - A Question

Yes, the article talks at length about the possibility that we've reached our present state via contraction of an earlier universe.

I took my cue from the magazine cover, which states, "Quantum gravity theory predicts the universe will never die," and shows a cartoon of a multiply bouncing universe. The cover set the frame of reference within which I read the article; but it's possible the editors didn't bother to get Bojowald's approval. And of course lots of atheists--which I take the editors to be--would like to believe the universe is eternal, so they have a motive for taking Bojowald's idea possibly further than he intended.

Perhaps I should have said (at a minimum) that the SciAm interpretation of Bojowald is that the universe is eternal. : ) But my reading wasn't that analytical.

Don

  ----- Original Message -----
  From: gmurphy10@neo.rr.com<mailto:gmurphy10@neo.rr.com>
  To: Don Winterstein<mailto:dfwinterstein@msn.com>
  Cc: asa<mailto:asa@calvin.edu> ; Christine Smith<mailto:christine_mb_smith@yahoo.com>
  Sent: Sunday, October 05, 2008 8:14 AM
  Subject: Re: [asa] Thermodynamics & Eternal Universe - A Question

  Actually Bojowald doesn't speak of an of a universe that alternately contracts & expands _over & over_ - i.e., an oscillating universe. He just says (at least in Sci.Am. - unless I skipped something) that our expanding phase could have been preceded by a contracting one. Gamow did that - without any reference to quantum gravity &c - long ago. Einstein's equations allow an infinite space of negative curvature that starts at t = - infinity at zero density (of course as a limit) & contracts to a big crunch. If you can get it to bounce (which is where quantum gravity comes in) it could then expand forever toward a state of zero density as t goes to + infinity.

  Shalom,
  George

  - Don Winterstein <dfwinterstein@msn.com<mailto:dfwinterstein@msn.com>> wrote:
> Getting back to Christine's question, "...If the universe is argued to be eternal, does the 2nd law of thermodynamics even make sense to begin with?" Fred Hoyle's steady state universe and Martin Bojowald's alternately expanding and contracting universe (SciAm 10/08) are both models of eternal universes. Hoyle no doubt got around implied 2nd Law dissipation via continuous creation of new matter (although I don't recall having seen this problem addressed), while Bojowald's universe would reset itself at each bounce. A third option is the multiple universe idea. So eternal universes are not out of the question despite the 2nd Law. A steady state universe has largely been ruled out by empirical evidence, and multiple universes IMO are unlikely ever to be scientifically compelling. Further, as George pointed out, if a bouncing universe is intrinsically dissipative, it is fundamentally unstable and will eventually die.
>
> Don
>
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Received on Sun Oct 5 23:52:52 2008