Revolution No. 9

Paul Jacob

8/27/2006 12:00:01 AM - Paul Jacob

What's the difference between science and politics?

Normally, I'd say science tends to add to the wealth of the world, while politics detracts. On Thursday, a quasi-quorum of the International Astronomical Union (IAU) gathered in the Czech Republic and demoted the ninth planet from its status as "planet." Pluto is now to be called, uh, a "dwarf planet."

We lost a planet (sorta). What did we gain?

Ever since Clyde Tombaugh discovered Pluto back in 1930, we've been calling the distant, roundish rock a "planet." Tombaugh had continued Percival Lowell's search for "Planet X," the planet suspected to exist beyond Neptune. By sheer trial and error, error and trial, Tombaugh found the itsby-bitsy planet, and the wealth of the solar system seemed to increase by one. Perhaps that's why it was called "Pluto," after the god of wealth. "Hades," that god's other name, means "hidden" or "unseen," also appropriate. But the name "Hades" is associated not with wealth but with that same god's status as the grim ruler of hell. Pluto sounded better.

I think we're all happy with Pluto. (No?)

Since then, a number of new discoveries of bodies in our solar system have cried out for inclusion under the same category. The IAU decided it was high time to have some sort of official definition of "planet" so some rational criteria could be applied to these new objects.

Prior to the conference, most observers were expecting a few new planets, not one less. An initial set of definitions would have upgraded Charon, Pluto's sidekick moon, to planet status, making the two a double planet. To distinguish the smaller icy orbs from gas giants and the Mercury-Mars series of round rocks, the two were to be called "plutons." And so would 2003 UB313, a planetoid slightly larger than Pluto that goes by the nickname "Xena."

But the Warrior Princess got nixed, as did Charon and Pluto itself. These are now categorized as "plutinos" instead of "plutons." A plutino is not, as near as I can make out, another name for "dwarf planet," alas. It means a "trans-Neptunian object" with a certain orbital relationship to the neighboring gas giant. We're left with "dwarf planet" as the more inclusive term for smaller-than-planet. Unfortunately, it begs the whole question: a dwarf planet sounds like a planet to me, just a small one — which means that, contrary to the voting astronomers, there are indeed at least eleven planets in our system. Some say that number could be 24. And it could grow, with more discoveries.

The core issue is not very "core": a planet is now defined as a roundish object orbiting the sun, not orbiting another non-stellar object, not itself a star, and having "cleared the neighborhood around its orbit" of debris and stuff and "small solar system bodies" (another new category).

Planets, it is said, clear their orbits.

Trouble is, Neptune, a huge gas giant (yes, I like saying "gas giant"), has not cleared its orbit of Pluto and Charon!

And Uranus (did you know that Uranus is a gas giant?) has not cleared its orbit of at least one plutino.

In a fascinating Space.com article, Alan Stern, head honcho at NASA's New Horizon mission to Pluto, was quoted calling the whole thing "absurd," noting that "Earth's zone is not cleared" and that Jupiter "has 50,000 trojan asteroids."

One suspects that something other than a quest for clarity is behind the whole thing. Is it size that really matters to astronomers?

What about Bodes Law? It was noticed back in the 18th century that the planets are spaced in a regular arithmetic relationship, with a gap between Mars and Jupiter. Then Uranus was discovered, and it fit the Bodes Law spacing, so the hunt was on for the missing planet. And Ceres was found in the asteroid belt, and the universe conformed to a simple arithmetic and everybody was happy. (It later got demoted to "asteroid" status, and with the new nomenclature is upgraded, now, to "dwarf planet." It was and remains the largest object in the asteroid belt.)

Then came Neptune, and it sort of fit, but not nearly so well, being far shy of the predicted Bodes placement. And then came Pluto, which didn't fit at all — intersecting, as it does, Neptune's unfortunately closer-than-Bodes orbit.

Do modern scientists still crave the stability of Bodes Law?

The whole thing does stink more of politics than science. It's a pity that only a handful of the world's astronomers were allowed to vote, but is there reason to believe that more voters would have led to a better outcome? This isn't democratic politics, which is about trying to get people to get along without warfare and revolution. This is science, which is supposed to be about real discoveries, real laws and regularities.

And yet, this nomenclature mess is what gets the news coverage.

Why? Well, to us non-scientists, it's the designations that matter because they seem certain. Even when they are (in truth) arbitrary.

There's a whole lot going on in our solar system. Maybe a huge boom in the number of planets would have been good for us, kicked us out of our sense of security. Maybe the scientists should have let well enough alone, letting the number of planets remain open to debate, giving us non-scientists a permanent reminder that science isn't just about answers, but about questions too.

Besides, agreeing to disagree about most things is the best lesson of democracy. Astronomers in the IAU should have learned that lesson rather than used voting techniques to "solve" a contentious issue not all that important.

How many planets are there? Well, there are four inner "terrestrial" planets, four outer gas giants, and . . . a whole lot of other objects that are a bit harder to categorize.

That answer passes scientific muster, probably better than the Prague vote. I bet that we mere Earthlings could've handled the lack of a simple answer on this subject.

As we can on many others.