Comment by cobbzilla
10 hours ago
It was fine and dandy until Eris came along.
Eris is bigger than Pluto, so if Pluto’s a planet then so is Eris. So you have 10 planets.
And then how many other Erises are still hiding? How many planets do we have then? It must be some very large unknown number!
Holding the true number of planets to be a large unknown number was anathema to many.
The demotion of Pluto was primarily motivated by a desire for the word “planet” to refer to a fixed, never-changing number of large bodies orbiting the sun.
> Eris is bigger than Pluto, so if Pluto’s a planet then so is Eris. So you have 10 planets.
Which is exactly how I remember learning it at the end of highschool (discovered during my junior year): Hey, did you know we just discovered a tenth planet?