On 11/6/2014 4:08 PM, Bruce Kellett wrote:
meekerdb wrote:
On 11/6/2014 3:15 PM, LizR wrote:
On 7 November 2014 09:56, meekerdb <[email protected]
<mailto:[email protected]>> wrote:
I'd say that expansion of the universe is almost necessary, not
contingent. The AoT has to point in the direction of entropy
increase and in almost all models that's correlated to the
expansion of the universe. If it is bigger at one time than at
another then the AoT will point toward the bigger end. 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, at least until the total entropy equals the Bekenstein
bound. Or on the other possibility, L.S. Schulmann has written a
nice little book about his investigation of universes in which the
AoT reverses so it always points to the biggest phase of the universe.
Yes, that is indeed exactly the position I have long argued for on this very
forum.
To summarise my argument, which has at times been vigorously opposed, I think by you
amongst others,
Not me. I helped edit Vic Stenger's books that presented exactly that view.
but not yet actually shot down (kaon decay comes closest, but doesn't appear to be
very important in generating the AOT, although it's possible it actually had/has a
pivotal role we're unaware of).
a) the universe is expanding for some reason, possibly necessary in the sense of being
built into the laws of physics (e.g. as a result of eternal inflation ... perhaps?) -
or perhaps contingent, that is to say not mandated by the laws of physics, but maybe
the result of some symmetry breaking etc.
You seem to overlook that the "expansion" is very likely just tautological, i.e. it is
nomologically necessary that the AoT points in the direction of bigger.
No, it points in the direction of higher entropy.
Sure, but the physics is such that entropy must increase in the direction of expansion -
the two are linked (that's what I meant by "nomologically necessary").
As I recall it, Vic later recanted his earlier idea that the AoT reversed if the
universe began to re-contract.
I don't remember him ever asserting that the AoT would reverse, but he liked the idea of
"the biverse" which "contracted" relative to our time coordinate and also had a reversed
AoT. Schulmann does study the case in which is entropy and the AoT reverse. He ran Monte
Carlo simulations and then selected those that satisfied the reversal.
Brent
Anyway, that is purely academic. With with known magnitude of dark energy, the universe
will expand for ever, even if it is technically closed (k = +1).
Bruce
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