The German physicist Max Planck announced a startling result from his research into the foundations of thermodynamics, which is the study of energy and energy transfer. In a radical departure from classical ideas, Planck proposed that energy changes within systems occur in fixed discrete amounts called “quanta,” which can be thought of as “packets” of energy.

Planck proposed that light and radiant heat are absorbed or emitted from objects in form of these quanta, which have specific energy values according to the type of energy. This overturned the previously accepted view that energy transfer is a continuous process. Planck’s theory had far reaching implications.

Source: Popular Science: Science Year by Year. New York, NY: Scholastic, 2001.