Is Pluto truly a planet? A growing number of solar-system scientists assert that Pluto's minuteness and its membership in a swarm of like objects mean that it should be classified a "minor planet," as asteroids and comets are. Others are outraged by the idea, insisting that regardless of how its identity has changed, demoting Pluto would dishonor astronomical history and confuse the public. In the end, the debate boils down to this question: What compromises in precision should scientists make in the name of tradition, sentiment, and good public relations?

disrespectful to the public, Levy argues, and to children in particular. "Kids like Pluto," he says. The story of Ceres's [the largest of the asteroids in the asteroid belt] demotion isn't relevant, he claims, given that the public has never really thought of Ceres as a planet. Rather, he holds up the case of the brontosaurus. Early in the century paleontologists realized that the apatosaurus and the brontosaurus were actually the same creature; one of them had to go. Taxonomic convention dictates that the first- named species-in this case, the apatosaurus-subsume the second. And so it was that scientists dutifully declared the much-admired brontosaurus nonexistent. "Sure it's a rule, but every kid knows what a brontosaurus is," Levy says. "Why couldn't they have made an exception?" The brontosaurus has, of course, proved unsinkable in common usage. If astronomers ignore Pluto's place in popular culture, Levy warns, then popular culture could ignore them.