This topic has been discussed on this list a number of times, under
the heading "White Rabbit paradox".

My personally preferred solution to this problem is described in my
paper "Why Occam's Razor". Alternative approaches exist - for example
that of Schmidhuber's second paper (it's referenced in Occam), whereby
any ensemble generated by a resource bounded machine will
automatically have a prior that solves the white rabbit problem - the
so called "speed prior".

I don't quite follow why noncomputability of the universe would
help. If anything, I would have thought it would make the problem
worse (random strings are noncomputable).


David Barrett-Lennard wrote:
> >But what would, exactly, constitute "strange behavior" on the part of
> the universe? 
> >One could argue that the universe can't go completely wacko because we
> would 
> >cease to exist, and that would violate, the anthropic principle.
> It is true that in the ensemble of all possible programs (that are all
> equally valid by Tegmark’s premise), the ones that go completely wacho
> (and we cease to exist) exist but no one is there to observe it.
> However it would seem there will be an enormous number in which we
> indeed witness bizarre events like “popping up pink elephants”.    The
> options seem to be either
> 1.  Programs with a special rule that is waiting to fire at a given
> time/place in order to cause a bizarre event are mathematically
> impossible
> 2.  Programs with such special rules hardly ever occur (in terms of the
> ensemble); or
> 3.  Programs with such special rules are common but we have been
> extraordinarily lucky
> None of these options appear reasonable.   It seems that the simplistic
> notion of a simulation on a computer is not tamper proof.  In the
> ensemble of all possible programs we must accept arbitrarily complex
> programs - we have no right to limit ourselves to programs that maintain
> consistent "physical law" over time.  The invariants in physics all
> point to a "program" for our universe that is tamper proof.  One
> potential solution is that awareness only emerges in the totality of an
> infinite computation.  This could be tamper proof because of a holistic
> relationship between "virtual time" and "simulation time".  Another
> solution is that our universe is not computable in any sense.
> -  David
> -----Original Message-----
> From: Frank [mailto:[EMAIL PROTECTED] 
> Sent: Tuesday, 4 November 2003 5:54 PM
> Subject: Re: Is the universe computable?
> Hi, this is my second post. My name is Frank Cizmic and I'm a
> computer Engineer from Uruguay.
> David Barrett, I'd like to comment on one aspect of your reasoning with
> which I have some doubts.
> If I understand correctly, you are saying that *if* the universe is the
> result of a "program", then it is very strange that at any one point in
> time this program doesn't "go nuts", making strange things occur,
> like popping pink elephants out of nowhere, or resisting prediction
> by us sentient beings by violating its previous "good behavior".
> But what would, exactly, constitute "strange behavior" on the part of
> the universe? One could argue that the universe can't go completely
> wacko because we would cease to exist, and that would
> violate, the anthropic principle.
> So what would constitute "strange" behavior? Isn't life strange enough?
> Aren't we facing new facts every day? If by strange you mean "twilight
> zone" kind of events, wouldn't we eventually adjust to this and end by
> considering it normal behavior. Isn't this, in a sense, what we
> experience since birth? A wacky universe, that is always surprising us ,
> but never to the point where we lose sanity. One could posit that we, in
> a sense, would cease to be, if we lost our mental health. This might be
> formulated like a variant of the anthropic principle. We always live in
> a Universe that makes a minimum of "sense", otherwise, our psyque would
> eventually break down, and we would, essentially, cease to be.
> cheers
> ----- Original Message ----- 
> From: David Barrett-Lennard 
> Sent: Monday, November 03, 2003 7:45 PM
> Subject: Is the universe computable?
>  How can a past which has been well behaved prevent strange things from
> happening in the future?

A/Prof Russell Standish                  Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile)
UNSW SYDNEY 2052                         Fax   9385 6965, 0425 253119 (")
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