This dog won't hunt
Well, Pluto is apparently no longer considered a planet. That's why "that dog won't hunt" - we all remember Pluto, the Disney cartoon character, or at least I hope we do. The International Astronomical Union has redefined just what constitutes a planet. First of all, a planet must be large enough so that its gravity pulls it into a round shape as it orbits the sun - and it must orbit the sun (as opposed to some other body, such as another planet). Secondly, a planet, to be considered a planet,... Sign in to see full entry.