[meteorite-list] Pluto May Get Demoted After All

From: Larry Lebofsky <lebofsky_at_meteoritecentral.com>
Date: Fri Aug 18 14:14:46 2006
Message-ID: <1155924879.44e6038f2856a_at_hindmost.LPL.Arizona.EDU>

Hi Doug:

I am not an expert on dynamics, but the center of mass is the center of mass.

If you have two objects in orbit (revolve, not rotate) around the center of
mass, if one were larger, its orbit would have to be elliptical in order for
the center of mass to go outside to inside of it.
We are not talking about multiple systems with liquid planets, that is going a
little too far. One body cannot go into and out of another.

I do not understand your first P.D. That is a slap in the face of the people on
the committee as well as the organizations that recommended and picked them.
Are you more qualified to have chosen the committee?

To answer your P.D.D., it would help to actually check your facts. The name of
the planet predates the dog by nearly a year. The kid is still alive and was
interviewed earlier this year, why not ask her?

Larry

Quoting MexicoDoug <MexicoDoug_at_aim.com>:

> "> and the Charon aspect specifically for going too far in essentially
> > recasting too many small round objects as full-fledged planets.
> Eventually,
> > with new discoveries, there would likely be hundreds."
>
> Hello Again, The Charon and the "rotating around center of mass outside the
> larger body (Pluto in this case)" criterion aspect is very unwieldy for me.
> If a soccer ball, or other object which could have melted and rounded itself
> (or even rubble-pile modeled asteroids) gets into a meta stable orbit around
> the center of mass of the multi-body system in the appropriate conditions,
> it will become a planet for the moments it rotates outside the other members
> crust. And more interestingly, if the orbit is of high enough eccentricity,
> the center of mass will vary inside and outside the major body. I guess the
> simple solution would be to refine the definition for convenience to say
> that all bodies are compared as if they orbited the major body of the system
> at "X" distance, etc. But this innocent corollary is a needless
> complication and goes against the grain of the intention: to make it a
> fairly independent set of criteria based on a priori physics. There is
> "based on physics" and "making reference to physics". Anyone can make
> reference to physics - the IAU committees still hasn't understood that
> though they've come a good way along. Ganymede and our Luna moons are
> excluded based on what boils down to an arbitrary criterion. Time to cut to
> the Gordian chase and toss out this criterion. Anything else will smack of
> arbitrariness. How scientific can an issue be when you have near 50%-50%
> acceptance/rejection after so many years of debate? I won't get going on
> "dwarf" status. With stars it has real meaning. However, it is arbitrary
> in its proposed use with the planets and again a cheap shot to put
> pseudoscience masquerading as real science (unethically) by experts in
> something who seems to feel that their diplomas make them experts in
> applying well defined astronomical terms to an amorphous limbo. If you want
> to call it a dwarf planet - a double planet - any icy planet - a terrestrial
> planet - that's fine and highly context dependent. Thus the adjective of
> choice is in the domain of the speaker, not in the quaint streets of Prague
> in meetings as astronomers eat up the travel and entertainment bill.
> Best wishes, Doug


> P.D. The IAU Committee has utterly failed by not including a committee
> member of the class and stature of Saul Kripke. Historians and
> Astronomers...but how about including someone with real experience and
> credentials in aprioricity who has danced with the likes of Kant (and
> usually held his own). I trust they will remedy this, as good scientists
> not concerned about who shares their turf...
> P.P.D. Pluto was actually named after the Disney Dog character by a British
> child, but was endorsed by astronomers under the auspices we generally
> consider when explaining the logic of planetary nomenclature.
>
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-- 
Dr. Larry A. Lebofsky
Senior Research Scientist
Co-editor, Meteorite                      "If you give a man a fish,   
Lunar and Planetary Laboratory               you feed him for a day.
1541 East University                       If you teach a man to fish,
University of Arizona                        you feed him for a lifetime."
Tucson, AZ 85721-0063                                     ~Chinese Proverb
Phone:  520-621-6947
FAX:    520-621-8364
e-mail: lebofsky_at_lpl.arizona.edu

Received on Fri 18 Aug 2006 02:14:39 PM PDT