Sister, Sister, Why Don’t Things Fall Up?

Little Brother’s inquisitive mind is always full of questions for Big Sister. He knows Big Sister has all the answers, because she is always reading one big fat book or another. In this book, Little Brother wonders why things don’t ‘fall up’? At least Mother wouldn’t grumble about the mess he was always making on the floor! Of course, Big Sister has the right answer in the end, but before you start reading this fun book to find out, tell us: why do YOU think things fall down?