Walter Gerlach (1.08.1889-10.08.1979) was a German experimental physicist and a member of the Göttingen Academy of Sciences (1947). He was born in Wiesbaden. He graduated from the University of Tübingen (1911). In 1916—21 he worked at the universities of Tübingen and Göttingen, in 1921—25 he was professor at the University of Frankfurt, and in 1929—57 at the University of Munich.
His research concerned atomic and nuclear physics, spectroscopy, quantum theory, magnetism and the history of physics. He carried out precision experiments to determine the constant in the Stefan — Boltzmann law and the magnitude of radiation pressure. In 1922, together with O. Stern, he performed the experiment that proved that an atom has a magnetic moment — spatial quantisation (the Stern — Gerlach experiment). In 1931—32 he derived empirical relations between the electrical resistivity and the magnetisation of ferromagnets in an external magnetic field (the Gerlach formulas). He initiated (1926) quantitative spectral analysis. He studied the anisotropy of single crystals of iron. He was the author of books on J. Kepler, M. Faraday and O. Hahn. A member of a number of academies of sciences.