Here's a great little video from C.G.P. Grey. In it, Grey -- in his trademark fasted paced and informative manner -- explains the basic history of Pluto, some of the reasons why it was reclassified and the precedent for reclassifying planets.
What I really like about this video though is the fact that Grey doesn't just address the history of Pluto but also explains why there are problems classifying planets to begin with, as well as a very basic etymology of the word 'planet'.
Rusty is the co-founder of How To Survive Alien Invasion Novels, and gets up to all kinds of shenanigans planning for any and all kinds of apocalypse when he's not busy reading, writing, or yo-yoing. Keep up with him and Rachel on Facebook and Twitter to get cool, space related news or click here to read more of his thoughts on the terror of alien invasion novels.