Marnen Laibow-Koser wrote:
This was not a "mistake". The term "planet" was not given an official definition by the IAU until 2006 (see http://astro.cas.cz/nuncius/nsiii_09.pdf , page 8, resolution 5A; this is apparently the final text of the resolution that passed). Before that, there was no reason to say Pluto wasn't a planet.
Dictionaries had no problem defining it before 2006. And there was a reason Ceres was de-planetted back in the mid-19th century. It didn't need a resolution by the IAU. People just realised that it was not really different than the other asteroids, and since they couldn't all be called planets none of them should be. Exactly the same thing has now happened to the Kuiper belt. Pluto is no different than all the other Kuiper belt bodies ("plutinos") and either they're all planets or none of them are. Ceres was considered a planet for almost as long as Pluto, too, so it's not as if tenure in the textbooks is that important. -- Zev Sero Something has gone seriously awry with this Court's zev@xxxxxxxxx interpretation of the Constitution. - Clarence Thomas