New "planet" definition

I don't understand why people are still arguing over this. Almost everyone I know thinks this is an appropriate solution:


Pluto is not a planet by definition, but will be considered a planet because it'll be grandfathered-in, therefore all new Kuiper-Belt objects, some of which may even be bigger than Pluto, will not be considered planets.


Pluto: planet by tradition, not by strict definition.


Makes sense?

"Well, since we're not 'smart' enough to reach Pluto, let's just sit here on Earth and argue semantics."

Quote:

Original post by Mithrandir I don't understand why people are still arguing over this. Almost everyone I know thinks this is an appropriate solution: Pluto is not a planet by definition, but will be considered a planet because it'll be grandfathered-in, therefore all new Kuiper-Belt objects, some of which may even be bigger than Pluto, will not be considered planets. Pluto: planet by tradition, not by strict definition.

I agree, but what definition of planet are you using? I'm trying to think what would be a good definition. The best I can come up with are:
A) Big and not something else (e.g. asteroid, Kuiper belt, moon, star)
B) I know it when I see it
But, I'm not the sharpest tool in the shed when it comes to such things. [smile]

Quote:

Original post by Way Walker Quote: Original post by Mithrandir I don't understand why people are still arguing over this. Almost everyone I know thinks this is an appropriate solution: Pluto is not a planet by definition, but will be considered a planet because it'll be grandfathered-in, therefore all new Kuiper-Belt objects, some of which may even be bigger than Pluto, will not be considered planets. Pluto: planet by tradition, not by strict definition. I agree, but what definition of planet are you using? I'm trying to think what would be a good definition. The best I can come up with are: A) Big and not something else (e.g. asteroid, Kuiper belt, moon, star) B) I know it when I see it But, I'm not the sharpest tool in the shed when it comes to such things. [smile]

* orbits a star directly
* Mercury-size or larger (pluto fails)
* Reasonably close to the eliptical plane (pluto fails)
* Reasonably circular orbit (pluto fails)



Though to be honest, the whole term "planet" is an ancient term which really shouldn't be used for scientific discussions anyway.

If we consider Earth a planet and Jupiter a planet, that means the term "planet" has a very broad definition, since those two objects are nothing alike. Hell, Pluto is closer to earth in classification than Jupiter, so why is Earth a planet and Pluto not?

So you can see, "Planet" is a misleading term that should be applied to the 9 existing bodies that we consider planets, in regular parlance. Anyone who actually works with celestial sciences uses more specific terms for the "planets".

ie, mercury, venus, earth, and mars are all "terrestrial planets", and Jupiter, Saturn, Neptune, and Uranus are all "gas giants".

They really do deserve differing classifications.


In my opinion, if you want to be strictly technical, then only Mercury, Venus, Mars, and Earth should be planets. Everything else will have its own classification. Asteroids, KBO's, Comets, etc.

Why would Charon be a planet instead of a satellite of Pluto? Are they arguing that Charon is sufficiently big that it and Pluto orbit each other (as opposed to Charon orbitting Pluto)? Is there a cutoff for the mass ratio?

Quote:

Original post by Anon Mike Why would Charon be a planet instead of a satellite of Pluto? Are they arguing that Charon is sufficiently big that it and Pluto orbit each other (as opposed to Charon orbitting Pluto)? Is there a cutoff for the mass ratio?

That is indeed the case: the center of mass (and the point around which they orbit) of the pluto/charon system is outside both of their volumes, so they are effectively a 'double' planet/pluton/oversized snowball/whatever else you want to label them as.

Quote:

Original post by Mithrandir Quote: Original post by Way Walker Quote: Original post by Mithrandir I don't understand why people are still arguing over this. Almost everyone I know thinks this is an appropriate solution: Pluto is not a planet by definition, but will be considered a planet because it'll be grandfathered-in, therefore all new Kuiper-Belt objects, some of which may even be bigger than Pluto, will not be considered planets. Pluto: planet by tradition, not by strict definition. I agree, but what definition of planet are you using? I'm trying to think what would be a good definition. The best I can come up with are: A) Big and not something else (e.g. asteroid, Kuiper belt, moon, star) B) I know it when I see it But, I'm not the sharpest tool in the shed when it comes to such things. [smile] * orbits a star directly * Mercury-size or larger (pluto fails) * Reasonably close to the eliptical plane (pluto fails) * Reasonably circular orbit (pluto fails) Though to be honest, the whole term "planet" is an ancient term which really shouldn't be used for scientific discussions anyway. If we consider Earth a planet and Jupiter a planet, that means the term "planet" has a very broad definition, since those two objects are nothing alike. Hell, Pluto is closer to earth in classification than Jupiter, so why is Earth a planet and Pluto not? So you can see, "Planet" is a misleading term that should be applied to the 9 existing bodies that we consider planets, in regular parlance. Anyone who actually works with celestial sciences uses more specific terms for the "planets". ie, mercury, venus, earth, and mars are all "terrestrial planets", and Jupiter, Saturn, Neptune, and Uranus are all "gas giants". They really do deserve differing classifications. In my opinion, if you want to be strictly technical, then only Mercury, Venus, Mars, and Earth should be planets. Everything else will have its own classification. Asteroids, KBO's, Comets, etc.

that's like complaining that "animal" is too broad of a word because it includes voles and whales.

Quote:

Original post by Mithrandir Though to be honest, the whole term "planet" is an ancient term which really shouldn't be used for scientific discussions anyway.

More or less what I was thinking. The strict definition you provided is too arbitrary (What's "reasonably"? And, even more, why "Mercury-sized"?). However, since there seems to be little confusion about what is meant by "planet", it seems there must be some definition.

Quote:

Original post by capn_midnight that's like complaining that "animal" is too broad of a word because it includes voles and whales.

No, you didn't read the post.

No one claims that voles and whales are not animals.

People, however, claim that Jupiter and Earth are planets, yet Pluto is not, despite the fact that Earth is far more similar to Pluto than Jupiter.


This is further aggravated by the fact that many other objects are not considered planets either, such as asteroids, etc.

So what is a planet? Conclusion: the term is too broad for meaningful scientific dialogue.

Quote:

Original post by Mithrandir So what is a planet? Conclusion: the term is too broad for meaningful scientific dialogue.

Like a cow and much everything else let us assume it is a sphere of uniform density :). Its just a word which we may define as we please, context will dictate and in practice we approximate it as if it was a cow. It will serve however, to remove ambiguities, regardless of outcome.

Here's my take. Pluto is not a planet but making that announcement would lead the news media to create a stir that would lead the traditionalists to launching a public pressure campaign to have it reinstated as one - and scientists don't want to have to deal with that kind of crap so they seek to avoid it by retooling the definition of what constitutes a planet so that Pluto can remain on the list. To remain consistent with this new definition they have to include Ceres, Charon and Xena on the list and maintain the possibility that additional bodies will be added later.

I think it would have been "cleaner" for them to introduce the new concept of "pluton", declare Pluto to be the object that exemplifies plutons (hence the name) and that Charon and Xena are also plutons. And then delcare that this reclassification means that there are only 8 planets in the solar system, the last being Neptune.

A lot of this could be circumvented by stating a planet has the following attributes:

1) Spherical shape (as previously stated) and sufficient mass
2) Elliptical/spherical orbit of a star
3) Within a certain distance of a star at its furthest point from orbit.

Or, simply, a plant is a big lump of rock contained within a given solar system (whatever the hell a solar system is classified as)

no matter the definition of planet I still call pluto a dog

I don't know enough about this so I'm just throwing it out there but would Earth not be a planet any more if fell out of the sun's orbit?

Quote:

Original post by GameCreator I don't know enough about this so I'm just throwing it out there but would Earth not be a planet any more if fell out of the sun's orbit?

That would make it an asteroid, yes? A very big asteroid.

Quote:

Original post by GameCreator I don't know enough about this so I'm just throwing it out there but would Earth not be a planet any more if fell out of the sun's orbit?

If something happened to this planet that would knock us out of the suns orbit, I think we'd have bigger problems to worry about...

Quote:

Original post by Mithrandir Quote: Original post by GameCreator I don't know enough about this so I'm just throwing it out there but would Earth not be a planet any more if fell out of the sun's orbit? If something happened to this planet that would knock us out of the suns orbit, I think we'd have bigger problems to worry about...

Nah.. forget all our current problems, like AIDS and cancer, we're going to devote our scientists to deciding if Pluto is a planet or not. I don't see that changing if earth went out of the sun's orbit (except maybe soldiers needing snow shoes and mittens in iraq..)

Quote:

Original post by GameCreator I don't know enough about this so I'm just throwing it out there but would Earth not be a planet any more if fell out of the sun's orbit?

Good question. Are there not free floating planets bigger than earth without a set orbit in the galaxy that we are aware of? I known there are lone stars, but aren't there lone planets also?

They're all part of the same continuum. A black hole is a star that was too big for its own good. Jupiter is a star that is too small to fuse hydrogen atoms at a reasonable rate. Mercury lost its atmosphere and is a barren rock. Astroids are much smaller rocks.