[ExI] Future and past was Many Worlds
jef at jefallbright.net
Fri Jan 11 00:46:48 UTC 2008
On 1/10/08, Rafal Smigrodzki <rafal.smigrodzki at gmail.com> wrote:
> On Jan 9, 2008 10:14 AM, Jef Allbright <jef at jefallbright.net> wrote:
> > On 1/9/08, hkhenson <hkhenson at rogers.com> wrote:
> > > At 09:22 PM 1/8/2008, Rafal wrote:
> > > >On Jan 8, 2008 10:41 PM, hkhenson <hkhenson at rogers.com> wrote:
> > > > >
> > > > > One of the things which falls out is that the past is as uncertain as
> > > > > the future. I.e., *many* pasts could have contributed to the current
> > > > > reality (whatever that happens to be).
> > > >
> > > >### I'd rather say, 1 << N(past) << N(future). The number of possible
> > > >futures is much larger than the number of possible pasts, and both are
> > > >unimaginably numerous.
> > >
> > > Time symmetry would argue for the number of past and future states to
> > > be the same. I don't think it is a good idea to go any further with
> > > this line of thinking.
> > I'm intrigued by Rafal's claim, but I come to the same symmetrical
> > result as does Keith.
> > I can imagine reasons why pursuing this topic might be demoralizing to
> > some, but I don't see it as a "bad idea" to try to increase
> > understanding of this. Rafal, can you provide a rational
> > justification for your claim?
> ### An increase of entropy in a system means that the description of
> the state of the system requires more bits. A perfect crystal can be
> described as multiple of its cell structure but the same matter
> vaporized requires enumeration of relative positions of every atom.
> The false vacuum which gave rise to all observable matter was a very
> low entropy system that at sizes below Planck scale could be described
> by just a small number of bits, and there were comparably few states
> that are compatible with our present - yet today the same part of the
> universe requires hundreds of orders of magnitude more information to
> be described to the same degree of precision. As entropy increases,
> the size of the universe grows, there will be even more possible
> states. Thus, the number of possible past states is very small
> (approaching 1 perhaps?) if you go close enough to the Big Bang, and
> the number of possible futures will keep on increasing, for a very
> long time if not indefinitely.
During our previous discussion, which appeared to go all Platonic and
shit ;-) -- I mean, it started out pure as crystal and then went
highly entropic -- I recommended to you the thinking of Hew Price and
his book Time's Arrow and Archimedes' Point . It seems appropriate
I don't necessarily disagree with your view here, but was hoping you
could offer an encompassing resolution to the question. I don't see
that in your response, and I suspect that any "solution" that doesn't
account for the inherently subjective nature of entropy will be found
Cosmology, Time's Arrow, and That Old Double Standard
It is widely accepted that temporal asymmetry is largely a
cosmological problem; the task of explaining temporal asymmetry
reduces in the main to that of explaining an aspect of the condition
of the early universe. However, cosmologists who discuss these issues
often make mistakes similar to those that plagued nineteenth century
discussions of the statistical foundations of thermodynamics. In
particular, they are often guilty of applying temporal "double
standards" of various kinds---e.g., in failing to recognise that
certain statistical arguments apply with equal force in either
temporal direction. This paper aims to clarify the issue as to what
would count as adequate explanation of cosmological time asymmetry. A
particular concern is the question whether it is possible to explain
why entropy is low near the Big Bang without showing that it must also
be low near a Big Crunch, in the event that the universe recollapses.
I criticise some of the objections raised to this possibility, showing
that these too often depend on a temporal double standard. I also
discuss briefly some issues that arise if we take the view seriously.
(Could we observe a time- reversing future, for example?)
On the Origins of the Arrow of Time: Why There is Still a Puzzle about
the Low Entropy Past
and a significant ongoing discussion at CosmicVariance.com where,
for instance, John Baez comments a little over a year ago: " Thanks
for putting in the energy to write a great post about one of the
trickiest and most controversial issues in physics! Shockingly, I
agree with almost all of it. Like you, I'm a big fan of Huw Price."
1. Time's Arrow and Archimedes' Point, Hew Price, 1996
2. cosmicvariance.com: Boltzmann's Anthropic Brain
3. John Baez: This Week's Finds in Mathematical Physics (Week 80)
4. "Thermodynamical entropy is no more objective than infomation
entropy. Both are as subjective as my opinion on that issue."
-- Pierre Dangauthier
5. "Glib, unqualified statements to the effect that "entropy measures
randomness" are in my opinion totally meaningless, and present a
serious barrier to any real understanding of these problems."
-- Edwin T Jaynes
6. "Entropy is an anthropomorphic concept."
-- Eugene Wigner
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