[X] My Assistant

[mars loon]

Dear Friends,

Today I am extremely dissapointed that the Pluto Demoters have triumphed.

I respect their opinion, but disagree with it.

I strongly agree with Alan Stern's statement calling it "absurd" that only 424 astronomers were allowed to vote, out of some 10,000 professional astronomers around the globe.

This tiny group is clearly not at all representative by mathematics alone.

I believe we should formulate a plan to overturn this unjust decision and return Pluto to full planetary status, and as the first member of a third catagory of planets, Xena being number two. Thus a total of 10 Planets in our Solar System

Please respond if you agree that Pluto should be restored as a planet.

ken

Ken Kremer
Amateur Astronomers Association of Princeton
Program Chairman

[Superstring]

Heider: Mars in orbit around Jupiter. Titan in orbit around Saturn. Huya a Planet. Equal rights for equal mass? Perhaps the definition either needs to be ALL inclusive or dynamically exclusive!

I agree with this. My original definition made any non-fusing gravitationally-rounded object a planet (including moons)...with sets of sub-categories based on orbit and physical traits. Although I still maintain this is the most scientific scheme...it lacks cultural acceptance. Do you really think people will start calling the moon a "secondary planet" as opposed to "a moon"? That won't fly. Since we have to make a separation between moon and planet...two categories for the same physical kind of object...why not further distinguish spheroids that are orbitally dominant and those that are part of a swarm? Ceres, Pluto, Eris, Quaoar, etc are all planetoids...that is, they are large enough to be a planet, but they are not dynamically significant bodies and thus do not quite meet the requirement for planethood.

I think this concept is easy to explain. There are 3 types of large objects in any given solar system: Planet=orbits star, controls its own orbit. Planetoid=orbits star in a region of other objects and planetoids. Moon=orbits planet or planetoid and (IMO) also has to be round. The remaining small objects can be divided into asteroids, comets, and moonlets. All of the above classes can still have sub-classes.

I think this is a scientifically good scheme. It enables us to teach the 8 planets, plus the Main Belt (which contains many asteroids and one planetoid) and also the Kuiper Belt (which is larger and contains asteroids, comets, and planetoids).

[JRehling]

To one and (almost) all:

This planet definition issue isn't a scientific matter, really, but it wouldn't hurt to discuss it on a high level.

In a debate, the two (or more) sides advance arguments. The arguments, unless truly ludicrous, merit some rebuttal, and some kinds of appeal are more persuasive than others. I see a little of that in this thread. A little. But what I haven't seen anyone TOUCH is to seriously address this:

Why define planet at all?

There is a "countermove" which goes something like:

"Because as scientists, we must provide order to an otherwise chaotic universe. It allows us to agree upon terms when we discuss them, which is a basis of all discussion."

OK, counter-counter-move is:

"This only makes sense when the categories themselves make sense. "Prime number" and "composite number" truly are all-encompassing and mutually exclusive for the natural numbers greater than 1. But "planet", we are learning, is not such a category! And scientists deal with many such categories already. "River" is a great example. Serious journal articles are written on serious research on the hydrodynamics and biomes of rivers without any rigid definition discriminating between rivers and streams. We once thought "planet" was amenable to a rigid formal definition but the facts have consistently led us to the opposite conclusion, that it is like "river", a you-know-it-when-you-see-it category."

And I've found it VERY frustrating that no one has a counter-counter-counter-move to this, no one attempts one, but just goes on assuming that they can tinker with the definition with one hack or another and of course there has to be such a definition.

I think the definition itself (not any one specific definition, but the idea of having one) has become like a toy that every child in the room wants in his or her own hand, and the idea of there being no formal definition threatens each person's personal ambition to have influence on the definition, so it is being waved off without a shred of rational consideration.

If someone has a counter-counter-counter-move along these lines, I would love to have some serious discussion with them. If simply ignoring this line, or repeating step #2 endlessly (we've moved past it... it's time for step #4) is all anyone has, I think they've stopped being a serious discussant of this topic, regardless of credentials.