Very interesting and insightful opinion piece from an astrophysicist. I'm really curious why it's on the forbes.com website though; the "Forbes" name doesn't make me think "This is a science or astronomy website", in fact I thought it was originally about finance, which is what the old Forbes magazine was all about.
Anyway, I totally agree with him. Call anything round a "planet" and suddenly it loses all meaning, because thousands of objects in our system alone qualify for that. Maybe we could call the Big 8 the "major planets", and normally omit the "major" qualifier.
I don't think "anything round and orbiting the Sun" equates to thousands of objects[1]. Maybe we can project that it will in theory, given how many there might be in the outer solar system, but it's not thousands yet. Furthermore, instead of dividing things into arbitrary categories of "major" and "minor", we could just as well divide things into near by and far away, since all the additional large objects are going to be very distant.
Well it's already in the hundreds. Do you want to try to memorize them all? I certainly don't. Near and far isn't that helpful, because people seem to care more about Uranus and Neptune and Saturn than they do Vesta and Ceres, and they seem to care a lot more about Pluto than they do Makemake, Eris, and a bunch of others that I don't recall the names of that are in the same general area.
Why do you think it's in the hundreds? I count less than 20 objects on the Wikipedia page I linked to that are Ceres size or larger and orbiting the Sun, excluding Haumea because it isn't really round.
So hydrostatic equilibrium is your filter? You realize that the size of the object can vary dramatically there, depending on what it's made of, right? (One made of ice will be round with far less mass than one made of rock.)
Anyway, I totally agree with him. Call anything round a "planet" and suddenly it loses all meaning, because thousands of objects in our system alone qualify for that. Maybe we could call the Big 8 the "major planets", and normally omit the "major" qualifier.