I read this morning that in a meeting of the International Astronomical Union, Pluto has been demoted to the new status of “pluton,” or dwarf planet, while the objects Ceres, Xena, and Charon have been promoted to dwarf planet status for their roughly spherical shape. So now we have eight major planets and four dwarf planets for a total of twelve planets in our solar system. Other objects — Sedna, Quaoar, Vesta and Pallas — may join the list as plutons.
In other news, I have named my left pinky Matilda. Say hello to the world, Matilda! Matilda? Oh dear, she doesn’t have a voice — she only powers the shift key. But I tell you she is there, and her name is Matilda. And, like the reclassification of Pluto, Ceres, Xena, Charon, Sedna, Quaoar, Vesta, and Pallas, it matters next to nothing. The reclassification of Pluto has bloggers agog — apparently it “makes life more interesting”, it’s “very interesting”, it’s “sparking controversy”, and it “will change the dynamics of our understanding of the solar system”. Oh, wow! Except, no, no, no, and no it won’t. This does not reflect an actual change in the state of the solar system, and it will not result in a change in scientific understanding of what objects like Ceres, Sedna and Pluto are — it’s a change in their name.
This reminds me of Shakespeare — “What’s in a name? That which we call a rose by any other name would smell as sweet” in objective terms. It is only in the understanding of the Montagues and Capulets that the contrary is true. This social understanding, not the underlying reality of the pair’s unity, has real consequences for Romeo and Juliet. Another memory: when I was in grade school, my teacher once became incredibly upset that her students continued to say the word “Rep-TIE-le” rather than her preferred “Rep-TILL.” She turned off the lights and announced that nobody would be headed for the lunchroom until everybody said “Rep-TILL” three times. How could we hope to become scientists, she wailed, if we could not even pronounce words like them? But variation in the pronounciation of the word “reptile” doesn’t lead or follow from variation in the character or behavior of reptiles. It’s just a bit of associated noise, a human creation.
The fuss, dear Brutus, is not in our stars, but in ourselves.
Proper categorization is one of the fundamental necessities in science. Until things are properly categorized it is difficult to fully understand their properties, origins, and nature. The naming system for biological organisms devised by Linneaus in the 18th century enabled us to make huge advances in the description and understanding of biology. Likewise, the categorization of chemical elements provided a crucial understanding of the nature of chemistry.
Categorization of astronomical objects is key to understanding their properties and origins. The processes that created the planets are different than the processes that created other objects in the solar system. By classifying Pluto and Charon as plutons we are recognizing that the processes that created them are different from the processes that created planets. Their characteristics are also quite different.
One clarification: the IAU hasn’t approved the new rules yet. They’ve been hammered out by a committee, but the IAU membership still has to vote on it at their meeting this month. According to what I heard on NPR this morning, there’s enough controversy to make that uncertain.
And, yeah, changing the definitions doesn’t really mean anything for science. However, it may mean something for scientists: with objective rules about what a planet is, they can avoid future arguments over whether X is a planet.
Mind you, I don’t think the proposed rule is objective enough. It says a planet “has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape”. So now astronomers are going to have to argue about X is nearly round? Or what if X is too small to be round, except that it’s so close to the sun that it’s permanently molten? (A liquid body would flow into a sphere more easily.) Does that qualify? What if it’s got a highly elliptical orbit, so that it melts for part of its orbit and then refreezes?
There’s just too much wiggle room. They might be better off banning the word “planet” altogether, the way the French scientific community of the 19th century banned discussions of human origins because they were too contentious.
The IAU press release.
I’d go with you Mark, but only so far: after all, the process that created Jupiter and its system is different from the process that created the Earth-Moon system, too. But you’re right about classification and its place in science. I’m just leery of the hubbub about what is really a romantic idea that started outside of science — the “wanderer” planets — and the notion that changing what fits on the list somehow changes the nature of outside reality.
And thanks for the note about the nonfinality of this decision, John. The Earth doesn’t have a spherical shape, either — it’s a bit squashed — but is certainly a planet.
Fortunate that the 19th century Darwin didn’t live in France!
Mmm, not necessarily—the same process, on slightly different original states, can yield vastly different outcomes. (That’s what chaos means.) Jupiter and the Earth may have formed around the same time, but the Earth was so close to the Sun that most of its hydrogen boiled off. The commonalities are probably larger than they appear.This raises an interesting point, though. Since what’s most interesting is how the Solar System was formed, maybe the IAU should define its categories in terms of formation, not in terms of end result. Otherwise, they’ll wind up prejudging their data.
Oh, I have no doubt French scientists worked on human origins; they just couldn’t do it in the…French Academy?(Unfortunately, I don’t have a reference for this claim; and, now that I think about it again, it might have been a geographical society, and the origins of the Earth.)
I was thinking of the current theory that the Moon-Earth system is the product of the collision of a Mars-sized object with the early Earth.
Ah, right. Yeah, it would take quite a collision to knock a solid body off of Jupiter.
If you’re going to demote an object from planetary status, then don’t call it a planet anymore! I don’t care if it’s a “midget planet” or a “micro planet” or a “monkey planet”, if the word “planet” is the noun, no matter what adjective precedes it, IT’S STILL A PLANET.
I would rather have my sense of tradition skewered by calling it an “asteroid” than having my logic flawed by demoting it but still calling it a “planet”.
Bravo dhinge.