h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Sedna is inside the solar system but I think that soon enough so many new 'planets' will have been discovered everybody will only class planets with an atmosphere as proper planets.

But how do you define atmosphere? All bodies have hazes of gas attracted to them because of their gravity. I'm sure you could find background haze on our moon which is said to not have an atmosphere. Is it, the more molecules of gas the more atmosphere? If so, when does haze of gas become actual atmosphere?

i definately think sedna is a planet
i mean hello!! it could have life, it isnt a star, it may well be an asteroid but that would also make our 9 planets go down to 8!!
i mean we have no way of changing, why shouldnt we go up in the world. have a positive look on life

An atmosphere is a body of gases that is somehow capable of producing weather and storms of some kind.

Another thing; forget Sedna, Pluto is a bit of a joke as it is.

I don't really see what all this curfuffle is about really. Who cares if we call it a planet or not? Surely this is all semantics?

Also. Whats wrong with an asteroid with life? If we had some lump of rock with some bacteria on it and short it out into space, then watched as it began to orbit the sun, does that make it a planet, just because it has life? I think not.

My opinion:

Planets are of some size or other orbiting a sun.
Moons are a smaller but similarly defined size, and orbit planets.
Asteroids are too small to be a planet but orbit the sun.
Rocks are too small to be a moon but orbit a planet or moon.

Some suggested diameters:

Planet: Greater than 3500 miles
Moon: 3500 miles - 1 mile
Asteroid: Less than 3500 miles
Rocks: Less than 1 mile

This has some interesting implications, most notably that Mercury becomes classified as a large asteroid, let alone pluto and all the other little ones out there. People who cant cope with having 7 planets in our solar system are too traditional for their own good. 1000 years ago they thought the world was flat, why should we accept all thier conceptions of what they think about planets, now we have more knowledge?

Andúril