Dear George, to your series of questions I would like to add one as first: "What do you call universe?" as long as we do not make this identification, it is futile to speculate about "its" computability/computed sate. I see not too much value in assuming infinite memories and infinite time of computation, that may lead to a game of words, calling "computation" the object to be computed. Is 'Multiverse' part of your universe, or vice versa? Regards John Mikes

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----- Original Message ----- From: "Georges Quenot" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, January 07, 2004 4:44 AM Subject: Re: Is the universe computable? > 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 ? > > Georges.