Pringsheim, Ernst (1859–1917)

German physicist whose experimental work on the nature of thermal radiation led directly to the quantum theory. In 1881 he developed a spectrometer that made the first accurate measurements of wavelengths in the infrared region.

Pringsheim was born in Breslau (now Wrocław, Poland) and studied at several German universities. He was professor at Berlin 1896–1905 and at Breslau from 1905.

Pringsheim began in 1896 to collaborate with Otto Lummer on a study of black-body radiation (see black body). This led to a verification of the Stefan–Boltzmann law that relates the energy radiated by a body to its absolute temperature, but in 1899 they found anomalies in laws that had been devised to express the energy of the radiation in terms of its frequency and temperature. The results encouraged Max Planck to find a new radiation law that would account for the experimental results and in 1900, Planck arrived at such a law by assuming that the energy of the radiation consists of indivisible units that he called quanta. This marked the founding of the quantum theory.