Program 39 discusses James Clerk Maxwell's discovery of displacement current and how this discovery was used to produce electromagnetic waves called light. Program 40 discusses the properties of waves, including reflection, refraction, and diffraction. Explains that the properties of light are really just properties of waves. Program 41 deals with the Michelson-Morley experiment of 1887 which was designed to measure the motion of the earth through the ether. Explains why this experiment is considered the most brilliant failure in scientific history. Program 42 examines the hypothesis that if the speed of light is the same for all inertial observers, as indicated by the Michelson-Morley experiment, then measurements will depend upon who does the measuring. Uses computer animation sequences, historical reenactments, and close-up photography of experiments.