Max Planck

It’s the birthday of Max Planck, who was born in 1858 in Kiel, Germany. As a student at the University of Munich, Planck was a keen musician. He decided, however, to become a physicist. By 1892 he was a full professor at the University of Berlin. Two years later he took up the challenge of explaining how the intensity of the electromagnetic radiation emitted by a black body depends on the frequency of the radiation and the temperature of the body. His breakthrough came in 1900, when he postulated that radiation was emitted in discrete packets whose energy is proportional to frequency. Planck’s theoretical spectrum not only accurately explained experimental data, it also provided impetus to the new quantum theory. Planck struggled to interpret the quanta behind his theory, yet unlike other classical physicists, he didn’t try to explain them away. The image next to Planck’s photograph shows the polarization of the biggest black body in the universe, the cosmic microwave background. The map was derived from data gathered by an ESA spacecraft named after Planck.

Date in History: 23 April 1858