On Thu, Nov 6, 2014 at 3:56 PM, meekerdb <[email protected]> wrote:
> I'd say that expansion of the universe is almost necessary, not > contingent. > I'd say that by about 1850 when people started to have a understanding of what Entropy was physicists had all they needed to have known that the universe must have started out in a very very low entropy state, that is to say they could have predicted the Big Bang in the early to mid 19th century; and they wouldn't have needed to go near a telescope to do so. But unfortunately they didn't, it's one of the great failures of nerve or imagination in the history of science. > The AoT has to point in the direction of entropy increase > But the question is WHY does time point in the direction of entropy increase. The answer is because in the first instant of time the universe was in a extraordinarily low entropy state, probably as low as it could get, and because there are vastly more disordered (high entropy) states than ordered (low entropy) states. So regardless of what the laws of physics were by the second instant of time the chances are overwhelming that entropy will be higher than it was at the first instant. If instead in the first instant of time the universe was in a very high entropy state then in the second instant Entropy could have been smaller or larger with about equal probability and there would be no second law of thermodynamics and time would have no arrow. > I say "almost" because there are some ways around it. If the universe > recontracts the AoT will probably continue to point toward the Big Crunch > Even if that were true time would still have a arrow, it would just be pointing in the opposite direction we are accustomed to. But why should time have a preferred direction at all? The laws of physics alone can not explain it nor is there any reason to expect that they should. Even if you know all the laws of physics there is to know you still can't predict what a system is going to do tomorrow unless you know what state it is in today; you've got to know the initial conditions. The laws of physics can explain why Entropy will be higher tomorrow than today, but it can't explain why it was lower yesterday than today, for that you need initial conditions. John K Clark -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
