Re: Is the universe computable?

From: Georges Quenot <>
Date: Wed, 07 Jan 2004 10:44:59 +0100

Georges Quenot wrote:
> [...]
> I would be interested in reading the opinions of the participants
> about that point and about the sense that could be given to the
> question of what "happens" (in the simulated universe) in any non-
> synchronous simulation "when" the simulation diverges ?

Thanks for the replies. Until now I feel a bit confuse with them,
possibly because I do not have an appropriate idea of what is meant
exactly by "computable" and/or by what accounts for a simulation
of the universe. I probably have some naive intuition about them.
So maybe it would help to clarify some points:

By computable, is by default assumed something like physically
computable using current or future technologies or only formally
computable (possibly considering virtual computers containing very
much more memory locations than there are particles in the visible
universe and for computation times very much longer than the actual
age of the universe) ? In the latter case, does the memory of the
computer need to be finite or can it be considered as unlimited ?
Do the simulation has to end within a finite time or can the
simulated universe be something like an asymptotic state of its
description in a given formalism ? Alternatively or in other words,
could the simulated universe be in some way the limit of a series
of approximations computed with increasing available memories and
computation times ? Is "computable" relative to the universe as a
(spatio-temporal) whole or only to given supbarts of it ?

Also I feel some confusion between the questions "Is the universe
computable ?" and "Is the universe actually 'being' computed ?".
What links do the participants see between them ?

Finally, what link is there between the computability of the
universe and the possibility of its exact description in the
context of arithmetic ?

Maybe too many questions for a single post. I didn't go through
the whole archive and there might well be already answers to most
of these so I welcome any reference to appropriate previous posts.
By the way, are there some FAQs about these questions ?

Received on Wed Jan 07 2004 - 04:46:21 PST

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