We were learning about the solar system the other day, from the best teacher in the world (the Cat in the Hat, naturally), when we noticed something strange on the cover of the book. "Revised Edition", it said. Why, we wondered.
"There are eight of these planets that circle the sun"... Oh yeah, that.
So peculiar, isn't it? During our entire childhood we had the nine planets drilled into us, and now, when we try to pass the knowledge to our children, we have to be oh so careful to drop Pluto, that poor unfortunate Pluto. And why?
Blame Michael Brown, Chad Trujillo, and David Rabinowitz. The trio discovered the space object Eris that lies beyond Pluto, circles the sun, and is larger than Pluto. So if Pluto is a planet, what does that make Eris... and what's there beyond? Where does it all end?
After much debate, the International Astronomical Union downgraded Pluto, classifying it, as well as Eris (and a bunch of others) as dwarf planets. And, as a result, we now live in a world where the Cat in the Hat needs to teach our children new mnemonics and poor old Pluto is just an afterthought.
So what are we going to learn about next? Well, the Cat also has a book about the human body. It's not like they are gonna discover the eleventh toe any time soon, right?