Wednesday, August 23

Retreating from crazy, IAU proposal is now just bad

I should point out that my diatribe below about the crazy IAU proposal being debated this week is already obsolete, since an amendment to the original definition was adopted earlier today that would trim the number of planets from the proposed 53 (masquerading as 12) down to just 8. This decimation of the population was accomplished by adding one simple phrase, that the object must dominate its region of space. That immediately knocks out Ceres (part of the asteroid belt), and Pluto, Charon and 2004 UB313 (parts of the Kuiper Belt). So instead of gaining 44 planets, the solar system loses one, namely Pluto, and everybody who cares at all about this is just going to be very ticked off (except Neil Tyson of New York's Hayden Planetarium, who had already made the decision to go to just 8 planets).
It's an improvement over having 53 planets, which obviously nobody was going to take seriously, and eliminates the craziness of including Charon, and the weirdness of including Ceres. But really, what's the point?
Defining the "region" that must be dominated by a planet is intrinsically arbitrary. So why bother? If we're going to have an arbitrary definition, on a matter that affects culture far more than it does science, why not use the arbitrary decision that fits harmoniously with what culture has overwhelmingly agreed on, and is simpler and easier to rememeber to boot? Accept anything bigger than Pluto, or (virtually the same thing) bigger than the nice round 1,000 km radius, and everybody's happy. Kill off Pluto as a planet, and no scientific purpose is served, but lots and lots of people will be very angry. That's the choice that the astronomers in Prague now seem to be heading toward, like lemmings streaming toward a cliff.
Clark Chapman, an asteroid and comet specialist at the Southwest Research Institute in Boulder and someone who has spent a lot of time researching and thinking about the way astronomy is communicated to the public, agrees with the size-cutoff idea, as does Michael Brown, the discoverer of the "tenth planet." But almost nobody else has spoken up publicly for this simple, commonsense solution. Here's what Clark said about it in a recent email he sent me:
"Because the public is interested and involved, and because historical precedent is important, the solution I preferred (and sent last week to some of those involved in the Prague discussions) would have been to accept the nine planets we have had for most of a century, and add anything as big or bigger than Pluto to the list of planets."
Too bad he's not in Prague. I'm not sure if Brown is or not. We'll see what happens.

pluto comix

Cartoonists have been having a field day with the IAU planet debate. Many of them have used it as a foil for political satire about Bush being on another world. Here's a selection.
And here's one that's actually relevant to this discussion:

Astronomical lunacy

When is a moon not a moon? Well, apparently it's when a bunch of astronomers get together and get so far off in their little ivory tower that they lose all touch with common sense.
The proposal being considered this week at the International Astronomical Union's meeting in Prague has a lot of things wrong with it -- like the fact that it instantly expands the number of planets from 9 to about 53, and tries to conceal this fact from the public by claiming it's only an expansion to 12 (Michael Brown, discoverer of the "tenth planet" temporarily named Xena, explains this all very clearly HERE). This is a surefire way to guarantee that nobody will ever take this loony idea seriously. But the craziest part of the whole proposal is its attempt to reclassify Pluto's moon Charon as a planet.
The overall definition of a planet being offered, that it's anything round that orbits a star, is one of the four main proposals that have been out there, and which I have described elsewhere (HERE is my summary of the proposals, from an artucle I wrote in New Scientist last year. I think it's still about the clearest summary of the different ideas that I've seen anywhere, if I do say so.) The definition they chose is probably not the worst idea that's been floated, but it certainly isn't the best one.
But then, completely out of left field, unrelated to any of the discussion that's been going on relatively soberly for more than a year, the IAU committee just made up a whole new, incredibly esoteric and geeky criterion having to do with whether the center of mass of the system is inside or outside the planet's surface, and thus -- poof! A wave of the wand -- Charon is suddenly a planet, which nobody had ever suggested seriously before. There's simply no way a rational person in touch with the world could have made such an outrageous, nonsensical leap. Nobody wanted it, nobody understands it. There was no reason for it.
So, the upshot is that, as I said before, the whole fiasco is just going to end up being totally ignored by everybody, and rightly so. The astronomers can crawl back to their ivory towers, and the rest of us can go along as though nothing had happened -- except that millions of schoolkids around the world will be confused out of their minds, and many of them will figure out that astronomers are just fools.
What is a continent? It's not something geologists debate about. There is no rational definition. Why is Europe a continent? Because of history. Why is Australia the smallest continent, and Greenland the biggest island? Because we say so -- there is no pretense that there's a rational basis for putting the cutoff in size where we do, we just do. Nobody's going to try to change it, nor is anybody going to try to claim there's a rational basis for it. We just live with it.
The astronomers had a chance to provide a definition that would have made everybody happy -- and I do mean everybody, except perhaps the most pointy-headed of the astronomers themselves. Everybody understands that A) any definition is going to be at least somewhat arbitrary, and B) that astronomers themselves, in their actual work, don't give a hoot about such semantic distinctions, it's really only the public at large who are affected by any of this. So why not act accordingly, by adopting a basic philosophy of trying to screw things up as little as possible? And it turns out there's a very, very easy way to do that, provided as a gift by mother nature.
It so happens that Pluto is a bit more than 1,000 km. in radius (1,150), while the asteroid Ceres, Pluto's moon Charon, and most Kuiper Belt objects are well below this threshold (Ceres, which would be a planet under the IAU's silly scheme, is just 450). The new "tenth planet" discovered by Michael Brown last year, at about 1,500 km radius, is bigger than Pluto.
So since any definition is going to be arbitrary anyway, why not just accept the nice, convenient round number of 1,000 km radius, and declare that anything bigger is a planet, anything smaller is an asteroid or comet? Period, end of story. Simple definition, and very easy to remember, no confusion. And that means the solar system has just grown by one, from nine planets to ten. That's a result that anybody can accept -- we've added new planets several times before as new discoveries were made, most recently with the discovery of Pluto in 1930. It's a normal part of the process, and instead of turning people off about crazy astronomers, would actually make people excited and upbeat about astronomy. There's a new planet! There might be more still to be discovered! (Though not a huge number, at least not within our capacity to discover anytime soon.)
A rational answer, a simple definition that would make everybody happy. But nobody is even seriously considering it. I've loved astronomy all my life, I know and respect many, many astronomers and consider many of them my friends, including most of those involved in this stupid debate. But I think they've totally lost their minds, and if they go ahead with this nonsense they will lose public respect, big time. Too bad for them. I hope they come to their senses, but I think the chances of that are virtually nil.