The German physicist Max Planck was the discoverer of the quantum of action, also called Planck's constant. Born in Kiel, he studied physics and mathematics at the University of Munich under Philipp von Jolly and at the University of Berlin under Hermann von Helmholtz and Gustav Kirchhoff. After receiving his Ph.D. at Munich (1879), he taught theoretical physics, first in Kiel, then (starting in 1889) in Berlin, as Kirchhoff's successor. "In those days," he wrote later, "I was the only theoretician, a physicist sui generis, as it were, and this circumstance did not make my début so easy." At this time Planck made important, and indeed quite fundamental, contributions to the understanding of the phenomena of heat, but he received hardly any attention from the scientific community: "Helmholtz probably did not read my paper at all. Kirchhoff expressly disapproved of its contents." The spotlight...