----- Original Message ----- From: "Alberto Monteiro" <[EMAIL PROTECTED]> To: "Killer Bs Discussion" <[email protected]> Sent: Friday, August 25, 2006 9:02 AM Subject: RE: Planet No More
> Robert G. Seeberger wrote: >> >> If a body has enough mass to reform itself into (roughly) >> a sphere then it should be considered a planet. >> > Like the Moon or Ganimede? The orbit question is important! Not really. Both are planets in my estimation. That Ganymede is a sattelite and the Moon is part of a double planet system is really irrelevant to how you classify a body. Our moon wouldn't even be a minor planet. > >> Let me make a prediction: >> (and keep in mind how *I* would prefer to define a planet) >> At some point in the future a body that is multiples of earth's >> mass >> will be discovered that does not orbit any other body (excepting >> perhaps the galactic center and even then it will not be a regular >> orbit), it will resemble the terrestrial planets only colder. >> >> It will be called a planet. >> > No, it won't - it would be _wrong_ to call it a planet! It should > be called by something else, to stress the fact that it does > not orbit a star. That is exactly what I think is ridiculous. That orbits are more important to the definition of "planet" than the properties of the body itself are. It would only be wrong if one insists on defining what a planet is by it's position and motion relative to a star rather than the properties of the body itself. I don't see a problem with a term like "planetary orbit" or "sattelite orbit" since those are terms for orbits and not bodies. > "Rogue planet" is IIRC the science-fictional > term for those bodies [and "Rogue Star" is a star not bound > to a Galaxy]. I see such a statement of the inconsistancy I am arguing against. A star is a star no matter where you find it, but a planet is a planet only if it has a regular orbit around a star? That idea is what stikes me as silly. It is one of those exceptions one finds in science, which is ordinarily consistant in its terminology, that stands out to my mind. Electrons are always recognized as electrons. Stars are always stars. And no one denys that cosmic rays are atomic nuclei. > > Of course, maybe we should also re-work the definition of _moon_, > because there are moons that are bigger than planets, and moons > that are just pieces of rock. Some moons are "proper" moons, > and others are "asteroidal" moons. > True. I would just use terms like planetary moon and asteroidal moon for various satellites. xponent Planet Claire Maru rob _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
