Was Pluto the 8th planet from 1969 to 2009 and Neptune the 9th?

Ahh, the Pluto wars, round 4384. It’s amazing how people can get so emotional about an iceball that’s 3 billion kilometers way. Especially when it’s a dog planet, not a real planet.

My take is that the IAU shoudn’t have tried to define the word planet. After all the geologists have not done the same for the word continent, as Mike Brown points out in his book. But since they did, they should have gone for a much simpler definition.

Pluto was discovered by Clyde Tombaugh. He died almost 10 years before Pluto was down classes. So, he had nothing to do with the change.

Well, fine. But my point was that the IAU (and other similar organizations) were responsible for choosing the name “Pluto”, a choice the rest of the world has been going along with ever since.

So if you accept their authority on this matter, why don’t you accept their definition of what a planet is — especially since the definition was chosen for scientific reasons?

Count me amongst the heartless Antiplutoists. The situation was becoming confusing and nobody could tell how many planets there were in the solar system any more. That’s a select club and we don’t want to let in any shmuck pretending to be a planet, or else we would be overwhelmed by a crowd of dirty iceballs. Next thing you know, the asteroids would want to join too.

What’s wrong with calling Ceres a planet?

Yeah! In with the asteroids! Down with the Cereal killers!

She doesn’t deserve it after the way she left mankind to starve while she was wandering around wailing for Proserpina. Minerva would never have done such a foolish, selfish thing.

Not so long as they still have liberty and justice for all.

Now, now, Skald, you can hardly criticize a goddess for being more foolish than Minerva. I mean, that’s rather praising with faint damnation, don’t you think? Everyone’s more foolish than Minerva.

I was describing, not criticizing. I don’t expect the lesser deities the rest of y’all worship to measure up to the standards of the True Sovereign.

I remember this (in 1979). We had just learned the planets in the other order and then the teacher says “Oh, now you need to reverse the two”.

Again, it’s much simpler if you order the planets by semimajor axis, instead of by instantaneous distance. Pluto’s semimajor axis is and always has been larger than Neptune’s.

Surely it’s more of a maximum radius than an average one?

The planet’s maximum distance from the Sun (at aphelion) will be longer than the semi-major axis, and its minimum distance (at perihelion) will be shorter. That’s because the Sun isn’t at the center of the elliptical orbit; it’s at one of the foci.

But I bet you knew that.

Oh, right. :smack: