HEISENBERG, WERNER (KARL)

born Dec. 5, 1901, Wrzburg, Ger. died Feb. 1, 1976, Munich German physicist and philosopher who discovered a way to formulate quantum mechanics in terms of matrices (1925). For that discovery, he was awarded the Nobel Prize for Physics for 1932. In 1927 he published his indeterminacy, or uncertainty, principle, upon which he built his philosophy and for which he is best known. Heisenberg studied theoretical physics at the University of Munich under Arnold Sommerfeld and obtained his doctor's degree in 1923. In the same year he became assistant to Max Born at Gttingen; he was appointed lecturer there in 1924. He then worked for three years with Niels Bohr at Copenhagen, and from 1927 to 1941 he was professor of theoretical physics at Leipzig. From 1942 to 1945 he was director of the Max Planck Institute for Physics at Berlin and from 1946 was director of the Max Planck Institute for Physics at Gttingen. In the 1920s Heisenberg proposed a radical reinterpretation of the basic concepts of mechanics as applied to atomic particles. He sacrificed the existing model of discrete particles moving in prescribed paths for an approach in which such phenomena merely represented observable, or measurable, quantities that could be expressed by arrays of numbers obeying the rules of matrix algebra. Heisenberg and other scientists found that with the application of matrix theory, they could specify the set of possible values for physical variables on the particle level and could provide mathematically expressed probabilities for the occurrence of distinctive energy states and transitions among those states. Heisenberg's work on the quantum theory profoundly influenced the development of atomic and nuclear physics. He wrote Die physikalischen Prinzipien der Quantentheorie (1930; The Physical Principles of the Quantum Theory) and many other books and papers on quantum mechanics, atomic physics, and cosmic rays.