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> 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
>
> ----- Original Message -----
> From: Christine Smith<mailto:christine_mb_smith@yahoo.com>
> To: asa@calvin.edu<mailto:asa@calvin.edu>
> Sent: Wednesday, October 01, 2008 9:37 AM
> Subject: [asa] Thermodynamics & Eternal Universe - A Question
>
>
> Hi all,
>
> A quick question to all the physicists out there...I was reading one of the articles on the ASA faith-science new blog, and came across the following:
>
> "Materialistic explanations of the universe have to rely on one of two explanations for where the universe came from. The first is that the universe is eternal. This idea runs into problems almost immediately because of the second law of thermodynamics. This law states that the useable energy in a closed system is constantly decreasing, which means that an eternally old universe would have run out of useful energy by now. To solve this problem, some physicists argue that the universe can reset itself periodically by collapsing and re-forming in what is known as an oscillating universe. While there are logical problems with this idea (see William Lane Craig’s The Kalam Cosmological Argument), it still leaves us with our current universe having a starting point."
>
> My question is...if the universe is argued to be eternal, does the 2nd law of thermodynamics even make sense to begin with? I'm having a hard time conceptualizing the argument without a reference to time, as in "why should we assume the energy would have run out by now?...what if we're close to the beginning of eternity?"
>
> Thanks ahead of time for your responses :)
> In Christ,
> Christine (ASA member, who's definitely not a physicist)
>
>
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Received on Sun Oct 5 12:15:44 2008