How did 20th-century physics change long-held notions of light’s makeup and behavior? This group of 12 concise computer-animated videos illustrates Einstein’s monumental contributions to the study of light. Showing how rudimentary ideas of material wave motion yielded to more advanced concepts of electromagnetic waves, the program details Einstein’s conclusions about the speed of light and his conception of time—which, given his findings on mass and energy, proceeds according to variable frames of reference. Relativistic thought experiments, conveyed through helpful animation, demonstrate simultaneity, time dilation, length contraction, and relativistic mass. (63 minutes)