On 1/7/2014 2:14 PM, LizR wrote:
On 8 January 2014 11:06, meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>>
wrote:
If the universe reached a maximum and started to contract (which now seems
unlikely)
the maximum possible entropy would still be much higher than the actual
entropy so
entropy would continue to increase until the contracted enough to reduce
the maximum
to near the actual. If it were the reverse of the Big Bang it would be a
very
sudden contraction, aka "deflation". Of course it might actually be symmetric.
Lawrence Schulman has a nice book about this "Times Arrow and Quantum Measurement".
He did some computer simulations by just considering randomized initial conditions
and then post-selecting the ones that satisfied the final conditions.
We actually don't know what would happen in a "bouncing universe", or even if such a
thing is physically possible. Certainly my mental image is that entropy would continue
to increase, at least until it was approaching the Big Crunch, which would itself look
something like a Big Bang in reverse (but with black holes thrown in). But if the BC
acts as a boundary condition on the universe, as the BB appears to do, then that /could/
constrain matter to follow an opposite arrow of time, no matter how anti-intuitive that
seems - or there could be a gradual switch over from one arrow to another.
The global switch over would have to reverse the radiation arrow-of-time. This might be
possible without creating anomalies if the expansion made the universe so dilute that
there was no difference between expanding and contracting, i.e. nothing to "measure" the
difference. So an ancient signal from the expansion phase would converge upon an antenna
in the contracting phase, but the beings there would see it as being broadcast, not received.
Brent
Actually I once tried to write a story to this effect, with dark stars sucking in light
and time-reversed aliens trying to flip their entropy gradient so they could avoid their
BC, aka our BB. But I couldn't make it work very well, and gave up...
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