Discusses the use of units in measurement and scale. Segment 1, Weight: Describes the history of finding reliable standards of weight measurement, which started with the traders. Discusses the difference between mass and weight and the origin of the kilogram. Segment 2, Length: Looks at how standard units of length measurement were developed, which include hand, foot, inch, yard, and meter. Explains why measuring length is now based on the speed of light. Segment 3, Scale: Profiles an astronomer who uses scale to study our solar system. Sheldon Schafer has converted the city of Peoria into a scale model of the solar system to help understand the vastness of the scale of the universe. Includes suggested classroom activities after each segment.