What is a planet?

[Meleager]

With that logic, we're in a "similar orbit" with Jupiter.

ummm... no. The logic is that lots of astroids have similar orbits (i.e. they sligshot around the sun)
besides astroids simply arn't big enough to be "sepherical due to their own gravity", a point which you continue to ignor.

 

[Gogf]

ummm... no. The logic is that lots of astroids have similar orbits (i.e. they sligshot around the sun)
besides astroids simply arn't big enough to be "sepherical due to their own gravity", a point which you continue to ignor.

There are a number of "moons" around the sun, as well as the asteroid Ceres. I didn't believe that you needed me to note this, as Perfection did a good job of it. True, not ever comet and asteroid would be a planet, but a sizable number.

"Slingshot around the sun"? That's a similar orbit? The orbits of asteroids and comets outside of the Main Belt, Kuiper Belt and Oort Cloud are highly irregular, and are not very similar. Again, our orbit is more similar to that of Jupiter than most of these small bodies' orbits are to eachother.

 

[Gogf]

Any celestial body that contains a molten core and orbits a star is a planet. Remove the molten core, it becomes a rock, and therefore is an asteroid. A chunk of ice is a comet.

I believe Mars has a solid core. Is Mars an asteroid?

 

[Meleager]

There are a number of "moons" around the sun, as well as the asteroid Ceres. I didn't believe that you needed me to note this, as Perfection did a good job of it. True, not ever comet and asteroid would be a planet, but a sizable number.

"Slingshot around the sun"? That's a similar orbit? The orbits of asteroids and comets outside of the Main Belt, Kuiper Belt and Oort Cloud are highly irregular, and are not very similar. Again, our orbit is more similar to that of Jupiter than most of these small bodies' orbits are to eachother.

1. Moons would obviously fall under a different category
2. Ceres does NOT have greater mass then the sum total of all the other asteroids
3. Very few asteroids are circular (even less (perhaps none?) due to their own gravety)
4. Ofcourse not all asteroids would be in a "similar" orbit but I would say that some are
5. Your still ignoring the circular under their own gravity part


I suggest you re-read my definition as you clearly do not seem to understand it.

 

[Meleager]

I believe Mars has a solid core. Is Mars an asteroid?

So does earth and jupiter and so on... I believe he was refering to magma.

 

[Gogf]

1. Moons would obviously fall under a different category
2. Ceres does NOT have greater mass then the sum total of all the other asteroids
3. Very few asteroids are circular (even less (perhaps none?) due to their own gravety)
4. Ofcourse not all asteroids would be in a "similar" orbit but I would say that some are
5. Your still ignoring the circular under their own gravity part


I suggest you re-read my definition as you clearly do not seem to understand it.

You don't seem to be paying any atention to what I'm saying.

1. There are planetoids that orbit the sun directly that, I believe, are classified as moons. Under your definition, they are planets.
2. My point was that you said no asteroid was big enough to be spherical due to its own gravity. Ceres if spherical. How can this be, if it's not a planet, as it doesn't have a great mass than the sum of the mass of the rest of the asteroid belt, and is therefore not a planet? Is Ceres a comet? Is it a meteor?
3. Again, Ceres.
4. Yes, most are. There are also a good number that are not.
5. No, that's just not what I was talking about in the point you were responding to. I was talking about your "similar orbit" definition.

 

[Gogf]

So does earth and jupiter and so on... I believe he was refering to magma.

I always thought Jupiter had a liquid core.

 

[Ultima Dragoon]

I always thought Jupiter had a liquid core.

Jupiter is supposed to have a solid core. Not sure of what though.

 

[Perfection]

Jupiter is supposed to have a solid core. Not sure of what though.

Iron Nickel and trace heavy metals like earth's. This would be sorrounded by less dense heavy elements.

 

[Ultima Dragoon]

I thought of that, but I didn't want to post it just in case I was wrong.

 

[Meleager]

You don't seem to be paying any atention to what I'm saying.

1. There are planetoids that orbit the sun directly that, I believe, are classified as moons. Under your definition, they are planets.
2. My point was that you said no asteroid was big enough to be spherical due to its own gravity. Ceres if spherical. How can this be, if it's not a planet, as it doesn't have a great mass than the sum of the mass of the rest of the asteroid belt, and is therefore not a planet? Is Ceres a comet? Is it a meteor?
3. Again, Ceres.
4. Yes, most are. There are also a good number that are not.
5. No, that's just not what I was talking about in the point you were responding to. I was talking about your "similar orbit" definition.

Rather then go through this again could you please give an example of something that would be a planet but isn't with my definition. My definition even excludes pluto (mass greater then bla bla)

 

[Gogf]

Rather then go through this again could you please give an example of something that would be a planet but isn't with my definition. My definition even excludes pluto (mass greater then bla bla)

Something that would be a planet under what circumstances? I don't understand what you're asking. Could you please clarify ?

Also, I don't see how your definition excludes Pluto. Charon is orbiting Pluto, not the sun, and therefore does not have a "similar orbit." Even if it did, Pluto's mass is greater than that of charon. Or, are you including the enter Kuiber Belt in the objects that have a similar orbit to Pluto? Again, the similar orbits thing is very confusing. Could you please provide a specific definition of what you mean?

 

[Perfection]

Gogf, his (quite good definition) is here http://forums.civfanatics.com/showpost.php?p=3140160&postcount=34

Rather then go through this again could you please give an example of something that would be a planet but isn't with my definition. My definition even excludes pluto (mass greater then bla bla)

Here's a fun one:

Theia
http://en.wikipedia.org/wiki/Theia_(planet)

This mars sized terrestrial body wouldn't be considered a planet because proto-Earth would've been much bigger than it.

 

[Meleager]

Something that would be a planet under what circumstances? I don't understand what you're asking. Could you please clarify ?

Also, I don't see how your definition excludes Pluto. Charon is orbiting Pluto, not the sun, and therefore does not have a "similar orbit." Even if it did, Pluto's mass is greater than that of charon. Or, are you including the enter Kuiber Belt in the objects that have a similar orbit to Pluto? Again, the similar orbits thing is very confusing. Could you please provide a specific definition of what you mean?

Yeah, I was going to say its part of the Kuiber Belt. I kinda stole my definition from parts of wiki talking about the real proposed definitions so i suppose if they do go with that then they going to have to define it. I can make up an exact definition but I would say that the asteroids in the astroid belt have a similar orbit.

Mike Brown of Caltech has suggested that a "planet" should be redefined as "any body in the solar system that is more massive than the total mass of all of the other bodies in a similar orbit"

Blame him not me! He seems to think it works.

 

[Meleager]

Rather then go through this again could you please give an example of something that would be a planet but isn't with my definition. My definition even excludes pluto (mass greater then bla bla)

Darn! I mean "is a planet but shouldn't be".

 

[Gogf]

The thing is, I liked Meleager's idea, it's just I'm unclear about some parts of it. For example, I think you should change "similar orbit" to something that is a bit more clear.

I'm also confused about how that excludes Pluto.

 

[Meleager]

The thing is, I liked Meleager's idea, it's just I'm unclear about some parts of it. For example, I think you should change "similar orbit" to something that is a bit more clear.

I'm also confused about how that excludes Pluto.

Do you have an idea about "similar orbit"?

 

[Perfection]

Blame him not me! He seems to think it works.

Not anymore. Check this out.
http://www.gps.caltech.edu/~mbrown/planetlila/index.html#name
Rater interesting arguement.

 

[Gogf]

Darn! I mean "is a planet but shouldn't be".

No . Of course, "shouldn't be" is an opinion.

The point was that I was primarily arguing with others points you made, not the actual definition.

But, on another note, should the definition involve a magnetic field at all? Do all known planets (potentially exclusing Pluto and 2003 UB313) have a magnetic field?

 

[Gogf]

Do you have an idea about "similar orbit"?

It's unclear. Does similar orbit mean the same orbit? Does similar orbit mean nearly the same orbit within a certain distance? Does similar orbit include a scaled-down version of another orbit? Does similar orbit include the same orbit on another angle?

It's a good way to phrase it, and keeps the definition simple, but "similar orbit" should be definied somewhere . Unless, of course, it already is, but I don't think it is .