Think this is good criteria for a planet?

Question

1. Has to spin on its axis

2. Has to have liquid (not neccesarily H2O water)

3. Has to have a magnetic field to protect from radiation

4. Has to have geological features (Volcanoes, mountains, valleys ect.)

5 Has to have weather (Tornadoes,Hurricanes,earthqua...

6. Has vegatation

7. Has some kind of internal plumbing

8. Size of planet is irrelavent.



Good criteria? Or did I exclude something from this list? And why or why not is this a good list to accurately know what a planet is?

Answer 1

By your criteria, Mercury, Venus, Mars, Saturn, Jupiter, Neptune, and Uranus are not planets.

Mercury has no atmosphere and therefore no weather or vegetation.
Venus has no vegetation. It's 900 degrees on the surface!
Mars has no vegetation, no liquid, and no magnetic field.
Saturn & Jupiter are gas giants and have no vegetation.
Neptune and Uranus are mostly gas and do not have vegetation.

Thus, by your criteria, Earth is the only planet.

I did not consider "internal plumbing" because the term is too vague.

Answer 2

Surely you're not trying to come up with a new definition for the word "planet", as only Earth has vegetation.

Are you specifying criteria for a planet we could live on? Then we would need an oxygen-rich atmosphere complete with an ozone layer. And lots of water.

Are you specifying criteria for a planet with intelligent animals we can communicate with (a.k.a. aliens)? Then I would argue that the size of the planet is relevant, because the size determines the strength of gravity. One limit to how large an animal can become is how heavy it is (for example, an animal with legs must have strong enough legs to support the rest of its body). If the planet is too massive, than only very tiny lifeforms will be able to evolve, making it impossible for lifeforms with large brains to evolve. If the planet doesn't have enough mass, it will never retain a significant atmosphere, and its interior will cool down too quickly (so no magnetic field, "internal plumbing", volcanoes, etc.)

Answer 3

sorry, i can't agree with any of this. i was going to agree to #8, but size is relevant. unless it is a certain size it is not to be considered a planet.

additionally, not all planets spin. nor do they all have a liquid. if it does spin there will be a magnetic field, but , ... . could be smooth as a marble. "weather" is dependent on other factors. vegetation? no. i really don't understand what you mean by "internal plumbing."

Answer 4

Hi. This describes a planet with life on it. Not all real planets support life.

Answer 5

it doen't need liqiud, vegatation, internal plumblng system,

Answer 6

no then we would be the only planet