From: Ron Kean (ronkean@juno.com)
Date: Mon Jul 12 1999 - 10:03:58 MDT
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
.
.
.
.
.
.
___________________________________________________________________
Get the Internet just the way you want it.
Free software, free e-mail, and free Internet access for a month!
Try Juno Web: http://dl.www.juno.com/dynoget/tagj.
This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 15:04:28 MST