1915-1950

**Werner Heisenberg** []

German physicist and Nobel laureate, who developed a system of quantum mechanics called matrix mechanics, and whose indeterminacy, or uncertainty, principle had a profound influence on 20th-century physics and philosophy. In 1923 he became an assistant to the German-British physicist Max Born at the University of Goettingen. **Under Neils Bohr, he was chosen Lecturer in Theorectical Physics at the University of Copenhagen in 1926. **In 1927 Heisenberg was appointed professor of theoretical physics at the University of Leipzig. Subsequently he served as professor at the universities of Berlin (1941-45), Goettingen (1946-58), and Munich (1958-76). In 1941 he became director of the Kaiser Wilhelm Institute for Physics (renamed in 1946 the Max Planck Institute of Physics). Heisenberg was in charge of scientific research in connection with the atomic-bomb project in Germany during World War II. Under his leadership, attempts were made to construct a pile in which the chain reaction would proceed so rapidly that it would produce an explosion, but these attempts were never realized. He was interned in England for a time after the war. Heisenberg, one of the world's foremost theoretical physicists, made his major contributions in the theory of atomic structure. Starting in 1925 he developed a theory of quantum mechanics, called matrix mechanics, in which the mathematical formulation is based on the frequencies and amplitudes of the radiations absorbed and emitted by the atom, and on the energy levels of the atomic system. Heisenberg's uncertainty principle (q.v.) played an important role in the development of quantum mechanics and also in the trend of modern philosophical thinking. Heisenberg was awarded the 1932 Nobel Prize in physics. He died on Feb. 1, 1976, in Munich. Among his many writings are The Physical Principles of the Quantum Theory (1930), Cosmic Radiation (1946), Physics and Philosophy (1958), and Introduction to the Unified Theory of Elementary Particles (1967). “HEISENBERG, Werner” __Funk and Wagnall’s Encyclopedia__ 1992-1995 ed.
 * -Born in Würzberg, Germany on December 5, 1901. **
 * -Died in Munich, W. Germany on February 1, 1976. **

**Erwin Schrodinger** []

Austrian physicist and Nobel laureate, best known for his mathematical studies of the wave mechanics of orbiting electrons. Schrodinger was born in Vienna and educated at the University of Vienna. He taught physics successively at the universities of Stuttgart, Breslau, Zurich, Berlin, Oxford, and Graz. He was director of the school of theoretical physics of the Institute of Advanced Study in Dublin from 1940 until his retirement in 1955. Schrodinger's most important contribution to understanding the atom was in developing an elegant and rigorous mathematical description of the discrete standing waves that electrons must follow in their orbits around atomic nuclei. “SCHROeDINGER, Erwin” __Funk and Wagnall’s Encyclopedia__ 1992-1995 ed.
 * -Born on August 12, 1887 in Vienna, Austria **
 * -Died in Alpbach, Austria on Jan. 4, 1961 **
 * In 1926, Erwin Schrödinger developed a mathematical equation to describe the movement of electrons in atoms or the behavior of the electron in a hydrogen atom. His work leads to the electron cloud model. The current explanation of electrons in atoms, the quantum mechanical model, comes from the mathematical solutions to his equation. This model determines the allowed energies an electron can have and how prone it is to find the electron in diverse locations around the nucleus. **