Thursday, August 31, 2006

Moving the Planets

I seem to be stuck on planets, don't I? Bear with me, I'll be done soon.

In my last post, I suggested a classification system. The focus of that system was the objects themselves -- how to look at an object and know what it is.

The IAU has complicated the issue by adding 'how it moves' as part of its classification system. I believe that is a seperate issue, and once removed from the 'what kind of an object' question is fairly easily resolved. The object either is gravitationally bound to something else, or it isn't. That something else can be named.

So Luna is a planetoid bound to Earth (a satellite) but at some time in the future, it'll likely be bound to the sun. But it will still be Luna.

This issue is important to me as a science fiction writer because I move things. In my Terraforming Project stories, I move Ceres and Vesta into orbit around the Earth. The objects don't change their basic nature, unless 'how they move' is part of that nature. Asteroids become satellites. I also move gas giant moons into orbit around the sun. Satellites promoted to 'planets'.

From this perspective, it's plain that 'how it moves' is not part of the nature of the beast. Yes, it's part of an object's history. And yes, it makes a difference in how to predict where you can find it in the sky. But a moon doesn't morph into a planet. It is moved into a planetary orbit. Picking up a salt shaker from the table and putting in a cabinet doesn't change a salt shaker into a different kind of object.

It's important to get this clear, and quickly. We're discovering extra-solar, non-star objects every day. Are they planets? The IAU's definition says we can't know because we don't know how they move.

I rather like the practicality of the Stargate shows. They don't care. They call them 'P-numbers' planets, but its obvious by the gas giants seen in alien skies that many of them are moons. Hey, if you can walk around on it and breathe, it must be a planet.

The human race is on the verge of a flood of new planet-like objects, and its time to cut loose a lot of old baggage. Let's have a soft spot in our hearts for the 'Classic Planets', but don't let past restrictions color what we need to do.

No comments: