Well, it’s happening again. People asking what the hell Pluto is, in the light of new evidence. And, yes, “what the hell” was a joke. About Pluto. Not a good joke, necessarily. I guess this subject doesn’t leave me with much of a sense of humor.
Like that boor that nobody wanted to invite to the party, let me reiterate how dumb the IAU’s decision was to (allegedly) demote Pluto out of planethood.
First, if they felt that calling it a “dwarf planet” demoted Pluto from planethood, they failed grammatically. “Dwarf” is a modifier. Calling something a “dwarf planet” does not make it no longer a planet. It makes it a type of planet. A dwarf elephant is a type of elephant, for example. That’s how modifiers work.
More importantly, science is about universal rules, which is why the IAU’s rule about a planet having a cleared orbit is utterly unscientific. A thing doesn’t become something else based on where it is or what’s around it. Scientific definitions have to stand in spite of local conditions.
The IAU’s definition of planet makes as much sense as calling a can of beans something different based on whether it’s alone on your kitchen counter or among other cans in your cabinet. A gray wolf is Canis lupus whether in a pack or on its own. Ice doesn’t become water because it’s not surrounded by other solids. Ice is ice based on its own characteristics.
Most obnoxious are the attempts to blame complaints about Pluto’s “demotion” on sentimentalism. This is completely backward. It was a sentimental attachment to a simpler Solar System, reeling from the discovery of many trans-Neptunian planets, that drove the IAU’s silly plan. The IAU has even tried (and failed) to rewrite the history of astronomy by redefining the term “classical planets” to mean something other than what classical thinkers meant. Their scheme is entirely dishonest, unscientific, and craven. And it should be abandoned.
Distinguishing big, mostly fluid object like Saturn and Neptune from small, mostly solid ones like Earth and Pluto would make sense. But separating Pluto from Earth and Mars (and Titan) based on what’s nearby is just dumb. We should just accept a definition for planet that has nothing to do with where it is, even if it means that we have to explode the number of planets in our Solar System from seven to dozens or even scores.
I’m not against revising the old system. For example, I’m full-on enthusiastic about renaming that embarrassingly monikered seventh planet. But, scientific revisions should make scientific sense. The effort to demote Pluto was never about science, and it should be stricken from the scientific record as an act of irrational fear.