Re: Finite time and infinite space

From: Russell Standish <>
Date: Wed, 16 Jan 2002 20:49:39 +1100 (EST)

I suspect that the answer to this lies in the concept of logical
depth, introduced by Charlie Bennett. The universe needs to be simple,
in a Kolmogorov sense, in order to get a high measure in the ensemble
of all descriptions. However, the flip side is that in order to
generate intelligent observers, it needs to be logically deep, ie run
a computation for a long time. This is the explanation for cosmic time
and space scales. In order to generate intelligent observers in a
small universe requires a more complicated description of the physics
generating it.

Of course, it would be nice to have a theory that gave order of
magnitude estimates on the amount of computation required to generate
intelligent observers, but at least the trends all point the right

                                        Cheers wrote:
> One of the things that strikes me as most peculiar and unexpected about
> the universe is this: that it is apparently finite and inhomogeneous in
> time, yet infinite and homogeneous in space.
> >From what we can tell, the universe began about 13 billion years ago
> and has gone through a series of phases or "ages" in which the dominant
> physical effects have been strikingly different. And current observations
> appear to indicate that the pattern will continue into the future, with
> our current era of matter and stars being destined to give way to low
> temperature and long-term effects.
> However at the large scale the universe shows no evidence of being finite
> in size. Some models predict that it should be finite, but these aren't
> very strong predictions given the struggles which cosmology is facing
> these days. And even if it is finite as inflation models predict, it
> is so huge that there is no real hope of distinguishing it from infinite
> in size. Likewise the universe appears to be roughly the same everywhere.
> Although there is clumpiness at many scales, there is no belief that the
> average density or other parameters of the universe will be different
> in widely separated regions.
> Is this something that might be predicted by a multiverse theory?
> It might be argued that the finiteness of (past) time is predicted by
> the theory, because it is questionable whether it is meaningful to
> have an infinite amount of computation in your past.
> The apparent infinitude of the spatial universe however does not fit
> too well, for the same reason. If the universe is infinite then it
> plausibly carries an infinite amount of information. This would require
> an infinite amount of computation. Of course most of it is outside of
> the "light cone" imposed by relativity, so perhaps this loophole in some
> ways could avoid the need for truly infinite computation.
> Even if the universe is finite, it does seem extravagantly large.
> It seems hard to justify such a size from anthropic arguments, especially
> the sizes predicted by cosmological inflation theories. Surely humans
> could have evolved in a much smaller universe, one which contains less
> information and requires less computation.
> The universe seems to contain a lot more information than is necessary
> for minds like ours to exist. Perhaps there are subtle reasons why such a
> large size is necessary (for example, perhaps inflation is a side effect
> of the simplest set of fundamental particles which would allow atoms to
> exist and hence life to form, so we get a big universe as a side effect
> of having simple physical laws at the microscale). But unless we can
> find such linkages, this appears to count against an ensemble theory.
> Put another way, the all-universe model should predict that our universe
> is little more complex than it needs to be for us to evolve. In effect
> it predicts that such linkages will be found.
> Hal

Dr. Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
Room 2075, Red Centre
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Received on Wed Jan 16 2002 - 02:03:03 PST

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