Gravity Is A Mystery (Let'S-Read-And-Find-Out Science 2)Read and find out about gravity in this colorfully illustrated nonfiction picture book. What goes up must come down. Everybody knows that. But what is it that pulls everything from rocks to rockets toward the center of the earth? Its gravity. Nobody can say exactly what it is, but gravity is there, pulling on everything, all the time. With the help of an adventurous scientist and his fun loving dog, you can read and find out about this mysterious