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Pluto is Not a Planet
Despite a recommendation to the contrary by the planet definition committee, the International Astronomical Union has decided that Pluto isn’t a planet after all. The amused and confused news anchors, some of whom always thought of Disney when Pluto got mentioned, tried to explain it to a public that can’t name the planets in order. The whole thing was written off as a silly thing scientists get up to. In fact, the story is a lesson in political manipulation.
The International Astronomical Union’s XXVI General Assembly met in Prague for 10-days to talk about the kind of things astronomers discuss. On the list of things to do was establish just what criteria determined whether a celestial body is or is not a planet. Before telescopes, a planet was a “star” that moved in the sky (the word comes from the Greek meaning “wanderer.”). Then along came Galileo Galilei, and astronomers found Uranus, Neptune, Pluto, galaxies, super galaxies and quasars to name a few. The terminology was messy, and scientists don’t like messy – they believe that simplicity and elegance are preferable to complex sloppiness. E=MC2 is a good example of this.
So to clean this up, the IAU voted on planetary criteria deciding that a planet had to orbit a star without being a star itself, it must possess sufficient gravity to pull itself into a roughly spherical shape (but “roughly” is a rather messy word), and it must have “cleared the neighborhood around its orbit.” Pluto fails on the last score since it crosses Neptune’s orbit and since its “moon” Charon (which would have been counted as a planet under the original committee recommendation) is in a similar orbit. However, four different proposals were tabled before this one got the nod
The vote was held on the final day of the conference, with 424 voting scientists present out of 10,000 who attended earlier days of the meeting. Owen Gingerich, professor emeritus of Harvard, chaired the IAU's planet definition committee, told the BBC that he thought the vote had been “hijacked.” He also said, “In our initial proposal we took the definition of a planet that the planetary geologists would like. The dynamicists [astronomers who study the motion and gravitational effects of celestial objects] felt terribly insulted that we had not consulted with them to get their views. Somehow, there were enough of them to raise a big hue and cry. Their revolt raised enough of a fuss to destroy the scientific integrity and subtlety of the [earlier] resolution.” Professor Gingerich, having returned to the US before the balloting yesterday, didn’t get a chance to vote.
It is sad to think that the taxonomy of the solar system hinged on politics, but clearly, it did. The committee failed to get buy-in from the dynamicists, who then did what every threatened minority does in a legislature; they dragged their feet until the other side got tired. Then, they got changes through that, as Professor Gingerich noted, made the committee-approved resolution something much different than what it was meant to be. The bad news is that there are only 8 planets, but the good news is that the IAU will meet again in a Rio in 2009, and maybe, just maybe, a “Vote for Pluto” campaign could carry the day.
© Copyright 2006 by The Kensington Review, Jeff Myhre, PhD, Editor. No part of this publication may be reproduced without written consent. Produced using Fedora Linux.
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