#Also this isn't coming from a place of nostalgic intransigence

[assyriangoatfaerie]

No, these are not the same, and yes I'm mad about it! AFAIK basically all paleontologists/taxonomists agree birds are dinosaurs, but the scientific community is split over whether Pluto is a planet or not. Major astronomers, such as Alan Stern of the New Horizon's mission and Mike Brown who discovered Eris, argue that Pluto should be considered a planet - as should Eris, Ceres, and arguably others.

The 2007 IAU decision to demote Pluto was made by a small group of astronomers, and many astronomers have made (to my mind) compelling criticisms of their reasoning. The IAU's first criterion for a planet is that a it must orbit the sun, which unnecessarily excludes exoplanets around other stars and rogue planets adrift between stars. The second is that it must have enough mass to make itself roughly spherical, which everyone agrees is important. The third is that it has to have cleared it's orbit of other objects, which is the one most people take issue with, because it was made up specifically to exclude Pluto and other Kuiper Belt objects.

Like, why do other things in a planet's orbit have any bearing on whether it's a planet or not? The most compelling argument I've heard is "Well then we'd have to call like a dozen other things planets and that's a lot for people to remember." So what! So what if most of the planets in our solar system are in the Kuiper Belt, poorly understood, and only discovered in the last twenty years? That's not a problem, that's awesome! Just because you've never heard of Huamea, Quaoar, Makemake, Sedna, Orcus, or Gonggong doesn't mean they aren't planets.

The guy who coined the term "Dwarf Planet" meant it to be a subcategory of "Planet" - not a different thing from them - along with "Classical Planet" and "Satellite Planet" - the former referring to the major eight, and the latter to moons large enough to be spherical such as Charon, Europa, Titan, Calisto, and more including our own moon, Luna.

And honestly, Mercury, Venus, Earth, and Mars have way more in common with the Satellite and Dwarf Planets than they do with Jupiter, Saturn, Uranus, and Neptune, so some have argued we should split "Classical Planets" into "Terrestrial Planets" and "Gas Planets", as that division more accurately reflects the nature of the bodies in our solar system.

Eschewing the IAU's first and third criteria also means we're only relying on intrinsic characteristics of the object to define what a planet is: a star is a body massive enough that its gravity causes fusion, and a planet is a body too small to cause fusion but massive enough to make itself spherical. What happens if a rogue blackhole caused Earth to be ejected from the solar system? According to the IAU it wouldn't be a planet anymore, which is just dumb. Of course rogue planets are planets, as are dwarf planets! They literally have "planet" in the name!

"pluto isn't a planet" 🤝 "birds are dinosaurs"

being very well documented scientific facts that are completely inconsequential in everyday life, yet manage to immensely piss people off as if they are being directly attacked