Text 737, 53 rader
Skriven 2006-03-18 12:21:02 av Paul Rogers (1:105/360.0)
     Kommentar till en text av Herman Trivilino
Ärende: Is Pluto a planet?
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 HT> There is no accepted definition of the term "planet".

Isn't that self-referential?  How would definitions become
accepted if scientists didn't make judgements?

 HT> And there is no consensus among the experts!

"Experts", you mean like the 19th Century geologists that
rejected Wegener's "Continental Drift" hypothesis?  Perhaps
even physicists out of their field of special study who
rejected the Copenhagen Model of Quantum Mechanics? ;-)

 HT> So, I don't know if Pluto is a planet or not.

You have to be told?  That's an appeal to authority, not
Science.  How do YOU define a planet?

 HT> It was a planet when I went to grade school in the 1960's.
 HT> A lot has changed since then.

And when I was in grade school the shorelines of Africa and
South America were just a coincidence, or so I remember being
told.

I define "planet" as a body which evolved within the primordial
disk of and orbiting its primary within definite limits of plane
and eccentricity (captures need not apply), of sufficient mass
to reorganize itself into sphericity.  I'd be more disposed to
consider Ceres than Pluto.

A corollary of the first criterion would be that it shares
isotopic proportions consistent with the origin of its primary
and siblings.  The second criterion could allow situations where
resonance perturbations might fling an orderly planet into
unusual orbital parameters--though I'd be prepared to accept an
argument that's impossible if it truly evolved from the
primordial disk.  It eliminates all moons.  The second & third
criteria eliminate comets and the like.

There are three areas of stable orbits around a binary system.
One for each primary, and one around the pair.  Would a body in
that third area qualify as a "planet"?  Possibly, but the point
is moot at present.

Paul Rogers, paulgrogers@yahoo.com                       -o)
http://www.angelfire.com/or/paulrogers                   /\\
Rogers' Second Law: Everything you do communicates.     _\_V

... Is infinity odd or even?
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