Last word on Pluto

As of this week, Pluto is no longer listed as a planet.

But Pluto was never a planet. We thought Pluto was a planet. We also thought it was bigger than it's turned out to be. We thought Charon orbited Pluto, instead of both objects whirling around an empty spot between them. We thought Pluto was the biggest object at its general distance from the Sun. All those thoughts led us to consider Pluto to be like the previously spotted planets, and all those thoughts turned out to be wrong. Astronomers have developed more knowledge of Pluto and similar objects, and a better understanding of what sets planets off from other objects in the solar system; Pluto doesn't match those criteria.

So we discard the errors and think more accurately. That's how science works. No one's arguing that we still have to study the cosmic aether or the spike-nosed Iguanodon or the disease of nostalgia because people once believed in them, too.