As someone who obtained a minor in Astronomy in college, and one of the only people I know who can consistently name the planets in order without having to resort to mnemonics, I’d like to take a moment out from the whole W3C thing to comment on the de-planetization of Pluto.
It’s about time.
Its classification as a planet was never really justifiable, and recent discoveries like 2003 UB313 (Xena) have only served to underscore that fact.
Now, that said, I’m no fan of the “dwarf planet” compromise. That just smells of committee-think, and it’s got to go. For that matter, the newly adopted definition for “planet” is pretty terrible. If it were up to me, I’d go with a definition that was based on orbital characteristics and a minimum surface gravitational acceleration threshold—maybe size and density, too. But none of this “cleared its orbital path” crap.
Furthermore, I think all this a great illustration of how science works. Although it’s quite the fashion to talk about “scientific dogma”, what this shows is exactly how science works. There is no inflexible dogma. As new evidence emerges and is incorporated into the general body of knowledge, the “orthodoxy” changes. There are no absolute truths in science—only the best available information. Once we thought meat transformed directly into maggots; now we know otherwise. Today we think that no physical object can move faster than the speed of light in a vacuum, but tomorrow (or a hundred years from now, or a thousand) we may find we were wrong. It doesn’t mean anyone was wrong in their previous understanding. It means simply that their previous understanding was incomplete.
And that’s fine. In fact, it’s better than fine: it’s expected and, by and large, welcomed. I often wonder if the real conflict between religion and science isn’t that science stands in opposition to religion, which it does not, but that science embodies a way of approaching the world that could not be more different than that taught by most religions. There are no absolutes in science, no final immutable truths, nothing that cannot be supplanted by some new understanding. Change may happen slowly, and it always happens after there is clear and convincing evidence, but it does happen.
As with Pluto. At one time, it seemed like it could qualify as a planet. Now it does not. As we understand more about the universe, we will be able to formulate better definitions of what is a planet and what is not. Maybe that will mean one day re-planetizing Pluto, and if so, then fine. It’s all part of the process—excuse me, the method.
Maybe that’s a lot to hang on a change of classification for a tiny, frozen pile of rock, but it’s true nonetheless. Or at least it will remain true until someone can convincingly show otherwise.