And eventually, you got to this long stretch where there seemed to be a very nice, meaningful number of planets. It changed with the discoveries of Uranus, Neptune, and Pluto, but it was still workable.
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Replying to @mssilverstein @arthur_affect
Then it broke down, and they just tried to save it by including orbital parameters, which isn't at all what it's really about in any kind of public or even scientific imagination.
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Replying to @mssilverstein
The guy who invented the concept of "clearing the neighborhood" they used was one of the people opposed to the new definition, saying it wasn't actually an objectively defined quality but one made up for convenience
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Replying to @arthur_affect @mssilverstein
Earth hasn't actually "cleared its neighborhood" in any absolute sense, and thanks to the fact that we live here we have quite an exhaustive list of all the trash still in our neighborhood, even if an astronomer on Ganymede wouldn't find it notable
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Replying to @arthur_affect @mssilverstein
Well that's a can of Discourse to open up The current definition of being a "planet" or not depends the idea of a scientific, objective difference between a "clean room" and a "cluttered room"
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Replying to @arthur_affect @mssilverstein
"It's just a pair of socks, I'll get it in the morning"
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Replying to @arthur_affect
Yeah - and I mean, the problem is that if we're looking for "objects that really feel like worlds of their own," which I *think* we are, then Ganymede and other large moons would be great fits.
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Replying to @mssilverstein @arthur_affect
Honestly I don't know why astronomers don't just go for the middle and say fine "Pluto is a planet but the gas giants and terrestrials are the *big* planets that are most important."
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I mean they sort of did with the "dwarf planet" label but then many of them will get pedantic and say "actually a dwarf planet isn't a planet."
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I feel like it's a good reminder that scientists like regular people often want categories to be neat, tidy, and elegant even if nature doesn't really work that way. (A lot of astronomers will also stubbornly insist rogue planets aren't planets either.)
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Hilariously this is just another iteration of discourse we had before, where Ceres used to be one of the planets but then became just the biggest of the "minor planets" or "planetoids" (which we ended up most commonly calling "asteroids" just to avoid confusion)
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The invention of "dwarf planets" led to a further demotion, Ceres is a dwarf planet but the rest of the asteroid belt are just SSSBs (small solar system bodies)
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And it's worse than you say, the ONLY official planets are the eight that orbit Sol All the other ones orbiting all the other stars in the universe are "exoplanets"
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