Max Planck
Max Plank (1858-1947) was one of great German physicists. He advanced the subject of thermodynamics, thermoelectricity, the theory of dilute solutions, and was one of the founders of quantum mechanics.
Planck's revolutionary discovery, one of the most influential in all of science, was that energy emitted by a resonator could on have discrete values or quanta. The energy for a resonator of frequency v is hv, where "h" is a universal constant that is now called Planck's constant. This theory explained discrepancies between theory and observations, and became known as quantum theory. This helped lay a foundation for the future discovery of quantum mechanics.
Planck's son was executed for attempting unsuccessfully to assassinate Hitler in 1944.