Re: Is the universe computable?

From: Frank <>
Date: Tue, 6 Jan 2004 07:40:58 -0800

Indeed, I've always thought there was a dubious assumption there.
There isn't a universal time to pace the clock tics of a simulation.
Relativity forbids it.
Anyway, time is a subjective illusion.

Back to the question:
So what happens when the simulation "diverges" from regularity?
Some possibilities:
a) The universe ends
b) Pink elephants pop up everywhere
c) It's already happening

I like (c)

----- Original Message -----
From: "Georges Quenot" <>
To: <>
Sent: Tuesday, January 06, 2004 8:32 AM
Subject: Is the universe computable?

> I start from a part of this post from David Barrett-Lennard (Mon,
> 3 Nov 2003 19:48:49) but I could probably hev selected several
> similar other ones:
> > Given the "source code" for the simulation of our universe, it would
> > seem to be possible to add some extra instructions that test for a
> > certain condition to be met in order to tamper with the simulation.
> > It would seem likely that there will exist simulations that match our
> > own up to a certain point in time, but then diverge. Eg it is
> > possible for a simulation to have a rule that an object will suddenly
> > manifestitself at a particular time and place. The simulated conscious
> > beings in such a universe would be surprised to find that induction
> > fails at the moment the simulation diverges.
> It seems to me that there is a very strong assupmtion here which
> is that there should be some synchronicity between the "time" in the
> postulated computer into which the universe would be simulated and
> the time inside that simulated universe (as this is typically the
> case when an electronic device is simulated).
> But such an assumption not only does not seem necessary in any way
> but it also does not seem possibly consistent (or it would be very
> arbitrary at least) with a universe like ours for what we know of
> the implications of general relativity (it does not seem possible
> to define any global time in any consistent way in our universe).
> Many other way of simulating the universe could be considered like
> for instance a 4D mesh (if we simplify by considering only general
> relativity; there is no reason for the approach not being possible in
> an even more general way) representing a universe taken as a whole
> in its spatio-temporal aspect. The mesh would be refined at each
> iteration. The relation between the time in the computer and the time
> in the universe would not be a synchrony but a refinement of the
> resolution of the time (and space) in the simulated universe as the
> time in the computer increases.
> Alternatively (though both views are not necessarily exclusive), one
> could use a variational formulation instead of a partial derivative
> formulation in order to describe/build the universe leading again to
> a construction in which the time in the computer is not related at
> all to the time in the simulated universe.
> It seems to me finally that the simulations in which there is a
> synchrony between the time in this universe and the time in the
> computer simulating it are very specific (if even existing) among
> all other possible simulations of the same universe (at least
> for the kind of relativistic universe we live in). I would even
> conjecture that the measure of the set of synchronous simulations
> is null within the set of all possible simulations of a given (not
> so trivial) universe (if one can give a sound sense to this).
> 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 ?
> Georges.
Received on Tue Jan 06 2004 - 12:34:22 PST

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