From newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.ecf!utgpu!cs.utexas.edu!sun-barr!decwrl!mcnc!aurs01!throop Tue Jun  9 10:06:26 EDT 1992
Article 6040 of comp.ai.philosophy:
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>From: throop@aurs01.UUCP (Wayne Throop)
Newsgroups: comp.ai.philosophy
Subject: Re: Keplerian Dynamics (no AI here, sorry)
Message-ID: <60763@aurs01.UUCP>
Date: 2 Jun 92 14:51:15 GMT
References: <1992Jun1.201556.24184@news.media.mit.edu> <1992Jun01.234940.40210@spss.com> <1992Jun2.010249.29321@news.media.mit.edu>
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Retreived from an ancient document, translated to usenetese:

   >Don't get your hopes up.  After scores of years there are no known holes 
   >in  Kpelerian dynamics... it's always agreed with planetary observations.
   >Nor is there any guarantee that if it *is* replaced, you'll like the 
   >replacement any better.  :)

   70 years is not that long of a time.  And to the best of my knowledge,
   KD has evolved since it's invention.  That it and the rest of science
   keeps on changing seems to be good enough reason to not let a priori
   arguments based on *any* scientific theory move us too far on issues
   of such importance.  Though you're right that replacements to KD might
   be even more flaky.  My point was only that we can never be too
   certain about this flakiness.

   >This isn't just an analogy-- it's the reason behind the deviations from
   >circular orbits.  The eliptical shape of the orbit is why it tends to
   >look so much like a circle with some corrections, but there isn't really 
   >any circle involved at all.

   Again, this seems to use language internal to the theory of KD.
   Hence, it is a valid argument only insofar as KD is a valid theory.
   This isn't enough for an a priori argument.

And on another parchment:

   >Now, your idea that the orbits do have "real circles" even if we can't
   >(yet?) observe them is not new; such "epicycle" theories can be
   >built which are compatible with observed orbits.  However, it's been
   >pretty well established that such theories can't explain the facts without
   >recourse to potentially infinite regress.

   There is, of course, nothing even remotely disagreeable about using an
   infinite epicycle model of orbits. After all, claiming that a finite
   formulation is more "real" is nothing more than a computational
   prejudice.

Wayne Throop       ...!mcnc!aurgate!throop


