Presents science experiments based on a yo-yo, wind wagon, cork sailboat, inverted tumbler, Cartesian diver, and hang glider which the experimenter makes himself and then changes as he tests scientific data.
When the Aldens help a friend of their grandfather's to build the world's largest yo-yo, they soon discover that more than one person is trying to prevent them from finishing the job--and for more than one reason.
Presents the history of the yo-yo with tips on care and technique and instructions, accompanied by step-by-step photographs, for basic, intermediate, and advanced tricks.