Thursday, August 24, 2006

Astronomers Lied

Pluto died. There never were nine planets. We were sold a phony solar system based on false readings of the available information. We paid for it with thousands of wasted hours memorizing nine planets when there are only eight. I believed it. I was wrong.

Hey, teachers. Just in time for the start of school, here's a new chore: Climb up on a chair and snip a string off that solar system mobile. And we all now carry one more bit of outdated and useless trivia in our skulls, lodged there since elementary school.

It's hard not to detect size-bias in this decision. Pluto's big and round and it goes around the sun, but it doesn't get to be a planet? If inhabitants of Jupiter, the solar system's big dog, were deciding the cut-off point for planets, little poodle Earth likely wouldn't make the cut.

Here's the quandry: People use words and categories that are ill-defined but convenient for a shorthand understanding of the world around us. We divide food into groups, paintings into art or illustration, people into races that have no genetic reality. We invent political labels like "liberal" and "conservative."

Scientists need to make empirical and precise statements about the world. But they're stuck with the same squishy words we all use. It never quite works. Biologists continue to talk about "species" without being able to agree on what one is, or whether dogs and wolves are one or two.

For the solar system, they're stuck with "planet," originally an ancient Greek word for any kind of heavenly body that wasn't in the same relative place in the sky all the time, including the sun and the moon.

Along came Copernicus at the end of the Middle Ages, and the whole universe changed. But the word stayed. Then telescopes came along and we realized there were a gazillion things strewn through our space, from dust motes to gas giants. Then we found Pluto. Then we realized there were a lot of them.

And here we are. Pluto woke up Thursday morning as a "dwarf planet," a category that seems to please no one. Planetariums had to cancel their shows. NASA was despondent. Just this year it launched a $700 million mission to what turns out to be a non-planet.

"Dwarf planet" as a subcategory is temporary, the astronomers assure us. They narrowly rejected calling them "plutonian objects" and also nixed "plutons." The scientists say they will solicit the public for a permanent name.

Here's a suggestion: Potters. For Potter Stewart, the Supreme Court justice who, groping for a definition of pornography, decided he couldn't say exactly what it was or wasn't, but he knew it when he saw it.