The German physicist Max Karl Ernst Ludwig Planck (1858-1947) discovered the quantum of action which provided the key concept for the development of quantum theory.

Max Planck was born on April 23, 1858, in Kiel. The son of a distinguished jurist and professor of law, he inherited and sustained the family tradition of idealism, trustworthiness, conservatism, and devotion to church and state. Planck studied at the University of Munich (1875-1877) and the University of Berlin (1877-1878). At Berlin he took courses from Hermann von Helmholz and Gustav Kirchhoff.

Returning to Munich, Planck completed his thesis for his doctorate in 1879. It was on the second law of thermodynamics, Planck's favorite theme throughout his long and productive life. However, his keen insight into the second law of thermodynamics gained him no professional recognition whatsoever. Displaying his characteristically indomitable will, Planck refused to become discouraged and to allow his researches to be interrupted...