in physics, in reference to the work of German physicist Max Planck (1858-1947); e.g. Planck's constant, attested in English from 1901.
German physicist who in 1900 formulated quantum theory, which explained and predicted certain phenomena that could not be accounted for in classical physics. Planck's theory was essential to the work of Albert Einstein, Niels Bohr, and many other modern physicists. In 1918 he won the Nobel Prize for physics.