Zog is introduced to Newton's basic laws of motion. By observing objects on earth and in space, Zog learns that nothing can start moving, speed up, slow down, change direction or stop unless a force is applied to it -- even if the force is hard to see. He learns that for every force there is an equal and opposite force and that is the principle behind jet propulsion. And he learns that, scientifically, work occurs only when a force moves an object some distance. [1:47]