Re: seti@home is SORTA WORKING

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On Mon, 12 Jul 1999 13:45:20 +0100 Rob Harris Cen-IT <Rob.Harris@bournemouth.gov.uk> writes:
> My understanding is that gravitational systems are not
> predictable in the long term (this is called the N-body
>problem
> in astronomy). As the SI has perhaps a 600-billion-body
>problem
> to solve at least 100 billion years into the future, where
>some
> of the bodies may not follow "natural laws" (i.e. they are SIs
> that decide to change course for independent reasons), this
> could very well take a significant amount of computation.
>
>A system with a load of variables that we can't track at this tech
>level is
>not "unpredictable", it is "very hard to predict", if you want to be
>correct.
>
>
>
>

I think N-body systems are 'chaotic', meaning that extremely small differences in initial conditions can result in immense differences in outcomes, over sufficient time. While the computation may be impractical, I suppose that in principle the motions of an N-body gravitational system may be predictable from a classical perspective. But that does not take into account quantum fluctuations, which I suppose are in principle unpredictable. So the motions of an N-body system would seem to be in principle unpredictable, and in practice approximately predictable for a limited time.

Ron Kean

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• [ Next ][ Previous ] In reply to: Rob Harris Cen-IT