It is rare in science that one can point to the work of a single individual as being truly revolutionary, marking the turning point between two very different eras in science. Isaac Newton and Albert Einstein are two such individuals. Max Planck is yet another. In fact, scientists now tend to refer to the centuries before Planck's discovery of the quantum as classical physics and to the years since as modern, or quantum physics.

Planck was born in Kiel, Germany, on April 23, 1858, into a famous family that included scholars, lawyers, and public servants. He obtained his early education at the Maximilan Gymnasium in Munich, where his family had moved when Max was nine. He entered the University of Munich in 1874, but transferred to the University of Berlin three years later. At Berlin, he studied under Hermann von Helmholtz and Gustav Kirchhoff. He received his doctorate in physics from...