Planck

A very short biography of Planck

The remarkably simple equation, E = h × f, tells us how photon size is related to frequency via Planck's constant. But who was Planck?

Max Planck was born in Kiel, Germany, in 1858. He came from a traditional intellectual family, his father being a professor of law. Planck developed an interest in physics at school and then went on to study physics at Munich University, starting in 1874 at the age of 16. In 1877 he went to Berlin for a year of study with physicists Hermann von Helmholtz and Gustav Kirchhoff, and in February 1879 he defended his dissertation, On the second law of thermodynamics.

In April 1885 the University of Kiel appointed Planck as associate professor of theoretical physics. He was subsequently named as successor to Kirchhoff at the University of Berlin and by 1892 he became a full professor. In 1900 Planck introduced his revolutionary idea, now known as the Planck postulate, that electromagnetic energy can be emitted only in quantised form or in chunks. In other words, the energy can only be a multiple of an elementary unit, E = h × f, where h is Planck's constant. At first he considered that quantisation was only a purely formal assumption… actually I did not think much about it. Nowadays this assumption, incompatible with classical physics, is regarded as the birth of quantum physics and the greatest intellectual accomplishment of Planck's career.

Planck retired from the University of Berlin in 1926, and was succeeded by Erwin Schrodinger. In January 1945, his second son Erwin, to whom he had been particularly close, was sentenced to death by the Nazi Volksgerichtshof because of his participation in the failed attempt to assassinate Hitler in July 1944. Planck died in 1947 at the age of 89.