This little book is a good explanation as to why Pluto is a dwarf planet and not a full planet anymore. Pluto doesn't care if we call it a planet or a mouse. Really. Why would a ice ball care at all? I love that so many people made Pluto out to be a person who's going to be brokenhearted that we've demoted him. The reasons given were logical, while the reasons not to do so were all based on emotion and sentiment rather than facts. You can still have Pluto as your favorite planet, it's just a dwarf planet now. No big deal.
Although I was very upset at the time I learned this (2006). It was sad, but that's emotion rather than facts and logic. And I'm much more logical than I was then, more obsessed with it than I was. And now I feel like a Vulcan. I'm such a Trekkie.