© The Clendening History of Medicine Library, University of Kansas Medical Center.

German physicist Max Planck (1848-1957) is widely regarded as one of the founders of quantum mechanics. He received the 1918 Nobel Prize in Physics for the work he began in an effort to calculate the spectrum of a blackbody from first principles. His seemingly preposterous postulate that energy of a harmonic oscillator could only change in discrete steps called quanta turned out to be a key concept in the new theory of quantum mechanics. (Unit: 5)