https://phys.org/news/2018-09-pluto-reclassified-planet.html
I posted this reply,
The fact that researchers a few hundred years ago don't use the clearing of the path definition of a planet is not a logical deduction.
I was struck that Philip Metzger pointed out "what defined a planet from an asteroid?" I this is the right question. And the answer is partly that of sphericity. But, I've been arguing that what distinguishes a planet from an asteroid is that of element differentiation. The heavy elements diffuse to the core, surrounding the spherical surface of lighter elements.
I wrote a blog entry about it awhile ago. I've shared it with Mike Brown. He pointed out some rather obscure asteroid, which didn't really disprove my definition. i forget which, and that twitter account got shut down(I have a bad habit of getting twitter accounts closed. I really don't believe they were justified in shutting them down.)
