[MLUG - DISCUSSION] Debate Lingers Over Definition for a Planet

[Mike Miller <EMAIL:PROTECTED>]

It may be very difficult to get scientists to agree about the definition 
of a term when that definition involves arbitrary cutoffs.  I think they 
can do better than to vote at a conference in Prague without allowing 
absentee ballots!  --Mike

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http://www.nytimes.com/2006/09/01/science/space/01planet.html

N.Y. Times
September 1, 2006

Debate Lingers Over Definition for a Planet

By KENNETH CHANG

More than 300 scientists have signed a petition protesting the definition 
of "planet" decided by the International Astronomical Union last week. 
That definition demoted Pluto, leaving the solar system with eight 
planets.

The petition states: "We, as planetary scientists and astronomers, do not 
agree with the I.A.U.'s definition of a planet, nor will we use it. A 
better definition is needed."

Mark V. Sykes, director of the Planetary Science Institute in Tucson, 
Ariz., and S. Alan Stern, of the Space Science and Engineering Division of 
the Southwest Research Institute in Boulder, Colo., organized the 
petition. Many planetary scientists, they said, were dissatisfied with the 
new definition, some because of how it was decided, some because they did 
not find it sound.

The signers of the petition included NASA scientists, astronomers at major 
observatories, university professors and graduate students.

The astronomical union allowed only scientists attending a conference last 
week in Prague to vote.

The group's definition for a planet specifies three conditions: the object 
orbits the Sun, it is large enough for its gravity to pull it into a round 
shape, and it "has cleared the neighborhood around its orbit."

The last condition excludes Pluto because it is located among many other 
icy bodies in a ring of debris known as the Kuiper Belt. But it strikes 
some scientists as imprecise.

For example, Earth has not cleared out all of the asteroids that cross its 
path. Even Jupiter, the largest planet, has not entirely cleared out its 
neighborhood; asteroids known as the Trojans share its orbit.

"It's not functional," Dr. Sykes said of the definition, "and there are a 
lot of people that feel that way."

Dr. Stern and Dr. Sykes are organizing an international conference to 
revisit the question next year.

Dr. Sykes said: "I think the community at this point and time can organize 
itself to have this discussion and come up with its own consensus, and the 
I.A.U. can catch up later."


Copyright 2006 The New York Times Company

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