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Fight for Pluto !, A Campaign to Reverse the Unjust Demotion
Greg Hullender
post Feb 6 2007, 10:22 PM
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Alan: Sorry about that. I guess I identified you too closely with the original IAU 12-planet proposal. Declaring the Moon to be a planet is apt to be controversial, but it doesn't bother me from a scientific perspective. (Assuming a computer guy is entitled to have a scientific perspective.) :-)

My whole reason for wanting to use "planetoid" for the root term was the belief that it just won't be possible to get people to call the moon a "planet."

Thinking about your comment on planet types, it occurs to me that there's another issue with using "dwarf planet" to identify a round body that never got big enough to finish sucking down its bit of the accretion disk: since we haven't studied any of them closely yet, we don't really know if that's an important difference.

Contrast that with the other three obvious (to me) planet types: Gas Giant, Rocky, and Icy. Will Ceres really be different enough from the Moon or Pluto different enough from (say) Europa that we should give them their own type? I'd be surprised if they had much similarity to each other, that's for sure.

I suppose this argument has already been raised (that it's premature to define "dwarf planet"), but I don't remember having seen it.

On the bright side, it does seem we'll be getting a good look at both Ceres and Pluto in the next decade -- and unless I miss my guess, we'll still be arguing about it. :-)

--Greg
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JRehling
post Feb 7 2007, 06:46 PM
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QUOTE (Greg Hullender @ Feb 6 2007, 02:22 PM) *
My whole reason for wanting to use "planetoid" for the root term was the belief that it just won't be possible to get people to call the moon a "planet."


Therein lies the 800-lb-gorilla: These terms are not scientific.

The Moon is an extreme case to be sure in terms of its salience in the popular consciousness, but it is not an extreme case in terms of superordinate classification. The average citizen wouldn't care what group the Moon were placed in for scientific purposes -- aside from the certainty that any reclassification thereof would earn and by now deserve a snort of public derision since the scientists have ceded any gravitas in these matters.

The Moon stands in relation to planets much as the thumb does to fingers. In English, Spanish, German, and I'm certain other languages, the issue of whether or not the thumb is a finger is often baubled about. In Spanish, they actually have one word for toe and finger, but a different word for thumb. Obviously, there's no medical sense in the issue. No orthopedic surgeon would pause before a diagnosis to consider the philosophical matter of whether or not the thumb is a finger. How a language chooses to classify that digit is entirely arbitrary. Doctors could have a panel discussion on the matter and bring it to a vote, but there's simply no medical need. Amateur ontologists age 3-83 still "debate" the "issue".

The question in my mind is when astronomers will reach the level of wisdom regarding "planet" that doctors have regarding "finger" and "thumb" and hydrologists have regarding "stream" and "river". The word is simply not in their territory, nor need it be.

That there are no small icy bodies very near stars is simply obvious. That only very large bodies can retain hydrogen is simply obvious. That tiny bodies do not deflect other ones from their orbits is simply obvious. There is no meat here for the basis of a science of classification. We have a couple of defining scales regarding the nature of bodies, with mass being one of the most important and temperature being somewhat less important. These are attributes we measure on scales, and the attributes have consequences on scales, but only generally speaking. That's not a scientific system of classification.

Planet is a folk concept for folk ideas. Originally, a starlike dot of light that moved over time. Then a nonluminous body of considerable size in our solar system. Now with our discoveries of recent years, we know it is ready to be retired permanently from any notion of scientific use and left to the public, who have some affection for it. Let it go, along with thumb and stream and meadow. When a legitimate need for a scientific category arises (white dwarf versus neutron star versus black hole, for example), know the difference.
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nprev
post Feb 8 2007, 02:14 AM
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Very, very well said, JR, and for me that was the capstone post of this debate...well done! smile.gif


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A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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