Guess what ! I know something you don't know !   What's that ?   How many planets are there in the solar system ?   That's easy . Everyone knows that there are nice .   Not anymore ! Can you believe it ? They've decided that Pluto is not a planet anymore !   Nice try . I wasn't born yesterday , you know .   I'm dead serious . They've decided that it's too small to be a planet , but actually they haven't yet agreed on how big something has to be in order to be a planet anymore .   That sounds crazy . They can't just change their mind about things like that . 