Regarding the demotion of Pluto as a planet, an astronomer once tweeted:
So, hey, Pluto is still not a planet. Actually, never was. We just misunderstood it for 50 years. Now, we know better. Nostalgia for Pluto is not a very good planet argument, but that's basically all there is. Now, let's get on with reality.
I'm sure this guy thought he pwned the folks defying Pluto's demotion. There's a nastiness in his tweet, isn't there? Not surprising, considering his handle is @plutokiller.
He's wrong, in any event.
"Planet" is not a designation like "baryon" or "lepton." There is nothing in the design of the universe that relies on some profound distinction between, say, a "planet" and a "dwarf planet." Sorry, but Pluto was
a planet for 50 years. We said
it was. We did not learn anything new about Pluto that would make it not a planet.