How many planets are there in the Solar System?
Nine is the answer today, but it might not be for long. 2500 astronomers are meeting right now to debate whether Pluto really is a planet, and if so, whether a larger ball of ice dubbed "Xena" by its discoverer is also a planet.
Xena? The warrior princess? Okay, Xena is acceptable, but let's just not go for her annoying sidekick, Gabrielle. . . .