Thursday, August 17, 2006

Anything Smaller Than A Gas Giant Is A Trivial Space Rock, Anyway.

So, Loyal Reader Magnus dropped a comment on the last post asking me what I thought of this article about the International Astronomical Union's proposed redefinition of the word "planet." I suspect I'm the last person with a blog and an interest in space science to talk about this issue, but I honestly can't seem to get especially worked up about it. It's a question of terminology rather than one of science... Ceres isn't going to change if we start calling it a planet instead of an asteroid, and Charon isn't going to suffer an identity crisis if it's suddenly reclassified as half of a double planet instead of as a moon. And, hey, the proposed definitions seem reasonable to me, in that they're trying to be as non-arbitrary as possible.

I get the impression that a lot of people are sort of bothered by the whole thing, or are viscerally resistant to the idea of reclassifying. And I do understand that. As kids, one of the first things we learn about the universe beyond Earth is that we're part of a solar system with nine planets orbiting the sun. It's learned so early and taught with such confidence that it feels like a fundamental fact, not like an artifact of language. And it seems to form part of our basic sense of identity as a planet, if there is such a thing. The plaques on the Voyager probes show a diagram of one large circle and nine smaller circles, with the probe flying away from the third one to show any randomly encountered aliens where it came from. And it's easy to imagine ourselves in some Star Trek-ish future, chatting with an alien, going, "My solar system? Yeah, we've got nine planets..." It just seems like part of what defines this place. I remember as a kid reading occasional SF novels in which a tenth planet was discovered, and that always seemed like some kind of symbol of expanding human knowledge, of our growth as a species out into the universe. "Look, we found another planet out there! There's more to our solar system than we thought! We're expanding our horizons, and our solar system literally gets bigger as our knowledge grows! Ain't that something? Humans rock!"

Reality, of course, is always much messier. Hey, look, there are rocks out beyond Pluto! But they're dinky, and somehow the thought of letting them into the planetary club triggers less of a "Whoo, we have more planets!" response and more of a "Well, if those guys count, the whole concept of a 'planet' seems diminished somehow." The truth is, we like things tidy. We like for things to fit into neat categories and we like for the categories we grew up with not to change. I think most people would like to be able to name nine objects and feel like, if they know those nine things, they've got a handle on the solar system. It's much less simple and satisfying to view it as a huge swarm of bodies ranging from a dust speck to a gas giant, made of rock or gas or ice or various combinations thereof, orbiting the sun, orbiting other bodies, orbiting one another, here, there and everywhere, with no clear cutoff point where you can say, "This rock is a place, but that one is just a rock."

Like I said, I think scientifically the terminology doesn't really matter all that much, and part of me find the idea that there's controversy over it just kind of silly. But, y'know, if the debate gets ordinary people to start thinking about this stuff, to shake themselves out of the oversimplified "nine planets and some rocks and snowballs" model we all learned in elementary school and to understand the solar system a bit better as the gloriously messy thing it is, that seems like a good thing to me.

So there ya go. My two cents on planetary classification. Sorry you asked, Magnus?

11 comments:

  1. For me, part of the "problem" is that we used to discover only one new planet a century, which is a nice, slow pace that allows everyone to get used to the new reality. (And it always strikes me as kind of weird to think that, up until a few hundred years ago, everybody lived in a universe that had no more than six planets -- or five, if they didn't count Earth.) Having three new planets dumped into the record books, so suddenly -- and one of them without a proper mythological name, even -- seems a little hasty, and could lead people to wonder if there is a whole flood of new planets in the wings. To put it another way, how often will we have to publish updated versions of our textbooks?

    Or as one friend of mine put it, he was upset enough when he found out the brontosaurus didn't exist any more. :)

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  2. Well, that's progress for ya. I mean, we could stop discovering things just so we could stop updating the textbooks (not that they're usually anything like accurate or up-to-date anyway), but I think that'd be kind of a drastic solution.

    Anyway, I think the fact that the state of our knowledge is still very much in flux is a good thing to learn. Probably a more important thing that which labels go with which astronomical bodies, to be honest.

    (Btw, speaking of "proper mythological names," I gotta say, I'm a bit tickled by the fact that people are still calling it "Xena." I kind of hope it sticks. :))

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  3. Did they name it for "the princess warrior?" Thats cool. I liked it when Pluto was named after the cartoon dog.

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  4. They did, yes, because astronomers are great big geeks. Needless to say, that's unlikely to be the official name... But I still hope it sticks.

    As for Pluto... *rolls eyes* :)

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  5. But it's only a few month since the Special Needs Department turned up with new, laminated mnemonics to include the asteroids (cos they're on the syllabus) and said these had to be displayed on the lab walls.

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  6. What, all the asteroids? That'sa lot to remember! :)

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  7. I hated Xena, wouldn't you prefer it if we started referring to it as Farscape instead? Or D'Argo, Chianna, Pilot, Stark...? And if we really wanted to kill a joke how about renaming Uranus to Zhann?
    As for being sorry I asked, no I am not. We do, indeed, tend to like things neat, tidy and convenient. Now if the nay sayers really hate them that much, they could just push for more funding, set up mining colonies and mine Ceres and the like out of existance.

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  8. Well, there's already a star named after Rygel, and a constellation after Scorpius... ;)

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  9. BTW, and off topic, I saw Genesis of the Daleks recently and think that The Simpsons could do a Davros and Nyder take off with Mr. Burns and Smithers. (It was the mention of Scorpius that reminded me)

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  10. Ha! They so could! And I would so watch it. :)

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  11. In fact, Davros' whole predicament at the end is such a Mr. Burns like situation.

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