Re: slightly OT, but still connected

Ο "Chris L Peterson" <clp@xxxxxxxxxxxxxxxxxx> έγραψε στο μήνυμα
news:1b3a715hn3mpph649fvvojea76a8s5829g@xxxxxxxxxx
>
> On Sun, 1 May 2005 19:56:52 +0300, "Ioannis" <morpheus@xxxxxxxxxxxx>
> wrote:
>
> >About 10 years ago, when Pascal was the more popular programming
language, I
> >came upon an n-body simulation algorithm, which had n celestial bodies
> >placed on a 2-dimentional grid, with varying masses and the user launched
a
> >projectile using the mouse trying to put it into orbit around the main
more
> >massive body. I was able to put the projectile in orbit in something like
> >1-2% of the cases by trial and error. The rest of the times the
projectile
> >would either immediatelly crash on one of the bodies or would
*eventually*
> >crash, after a number of revolutions, sometimes going into what seemed
like
> >a good orbit, but eventually failing. And even when the projectile would
go
> >into what seemed a "stable" orbit, I had no way to tell if the orbit was
> >*eventually* stable, as it could well fail after I interrupted the
program.
>
> If it was a good enough program, the object would have never been
> stable. There is no such thing as a stable orbit except on paper.

That was the case with that program. In the few times I was able to
successfully put the projectile into what seemed like a "stable" orbit, the
program had the option to let the projectile leave a visual trace, and the
trace itself indicated what you mention. The new traces were always slightly
different from the older ones.

> In the
> real Universe, which _is_ in fact chaotic, all orbits are (at best)
> metastable in the short run and unstable in the long run.

My point was actually to point out that if you let someone with insufficient
knowledge of the underlying mechanics trying to set up a couple of orbiting
bodies with trial and error, the probability the orbits will be unstable *in
the short run* is close to 98%.


> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
--
I. N. Galidakis
http://users.forthnet.gr/ath/jgal/
Eventually, _everything_ is understandable

.

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