> There are people who feel that it's worth classifying all the objects in our solar system and that doing so is useful. Up to a point. Part of my point is tha

> There are people who feel that it's worth classifying all the objects in our solar system and that doing so is useful. Up to a point. Part of my point is that the specificity of the new definition of "planet" is a bit silly. It's completely arbitrary. It's certainly not uniquely correct in any sense. It's also a kind of post-hoc definition which assumes our specific Solar System. For example, let's say you had a rocky body, around the size of Mercury, that had a very eccentric orbit that only reached the Kuiper Belt every few hundred years, at its apoapsis. Would this object "clear its orbit"? Hard to say - the IAU definition isn't precise enough to answer this. The IAU definition is basically the answer to the question: how do we label the closest eight planets to the Sun as planets without saying that's what we're doing, because we don't want to have to add a whole bunch of KBOs to the list of planets? None of what the IAU did here constitutes anything resembling real science.