What this means is that if you could shrink the Earth to the size of a billiard ball, if you could take planet Earth, with all its mountain tops and caves and rainforests, astronauts and uncontacted tribes and chimpanzees, voodoo dolls, fireflies, chocolate, sea creatures making love in the deep blue sea, you just shrink that to the size of a billiard ball, it would be as smooth as a billiard ball, presumably a billiard ball with a slight bulge around the middle.