Friday, August 25, 2006


A word on Pluto

Well, no, about Pluto; I'm not actually on Pluto, though when I was a boy I wished I were. I'm not alone in having been crazy about planets and stars and astronauts when I was a kid — those and dinosaurs; I had a set of those little plastic dinosaurs, which I used to play with all the time, and I was upset when they decided that the Brontosaurus was no more, having been subdivided into the Apatosaurus and the Diplodocus and so on. And now they're doing something similar to Pluto, changing something about it that I've known since I was barely out of the womb.

When I was a child, there were seven US astronauts. I knew all their names, and facts about them. John Glenn was a long way from being a senator them, and he and his colleagues, Gus Grissom and Alan Shepard, Scott Carpenter and Gordon Cooper, Walter Schirra and "Deke" Slayton, were my heroes. I wanted to be an astronaut. My parents wanted me to be a doctor — a surgeon, specifically. I ultimately followed neither of those callings, and look: now I blog.

I knew about the stars. There was a time when, as I could name The Seven, I could name the 88 then-recognized constellations (is that number the same now?), and I knew how to find many of them in the sky. I knew lots of stuff about the stars, the distance and magnitude of Sirius, the variability period of Algol, where to find the binary pair Mizar and Alcor, which one can see with the naked eye if one's naked eye be sharp.

And I knew about the planets and their moons. The solar system had 31 moons then, and I knew their names, from Phobos and Deimos around Mars, to Triton and Nereid around Neptune. We know of many more moons in our solar system now — Wikipedia tells me that there are 240 of them! (and that may grow even by the time I press the "publish" button) — but the number of planets, now that's always been nine.

Until now.

I'm not "upset", except in the silly way that I was about the Brontosaurus. Science learns new things all the time, and adapts. We no longer think of four elements, we've refined our measurements of the circumference of the Earth, and we have String Theory to explain more things in physics than we could before. And so we've decided that the Brontosaurus and Pluto were long misclassified. We should fix that. That's how science works.[1]

Pluto used to be bigger than Mercury. Pluto used to be alone in the sky, sans lune. Pluto used to be the most distant planet in the solar system. And then its eccentric orbit took it inside that of Neptune. We discovered a "moon", or a "companion", which we called Charon, matching Pluto mythologically. We found that Pluto was smaller than we thought. Lots smaller, smaller than Mercury. As Firesign Theatre said, everything you know is wrong.

But that's not really it. It's that we're always learning, and everything you know is constantly becoming better known. I love that!

Excuse me while I go listen to Gustav Holst; I love that too.

[1] The scientists, by the way are not the only ones who care. One astrologer has this to say:

No planet is capable of indicating absolutely [...explanation omitted here...]. But it isn't the planet that's preventing it, it's the person's own inclinations.
Oh, man, I can't tell you how relieved I am to be assured of that!

1 comment:

The Ridger said...

That same astrologer says "You should know that there are astrologers who experiment with all manner of orbiting bodies. Some people use comets, a minor body called Chiron that orbits between Uranus and Saturn is in widespread use. It's really a matter of whether astrologers feel they can get meaningful symbolism out of a thing rather than strictly speaking any kind of physical reality."