Walter M. Elsasser

Walter Maurice Elsasser (March 20, 1904 – October 14, 1991) was a German-born American physicist who developed the presently accepted dynamo theory to explain Earth's magnetic field. He proposed that this field results from electric currents induced in the fluid outer core. He demonstrated that the history of Earth's magnetic field is revealed by the magnetic orientation of minerals in rocks. He is also noted for his unpublished proposal that the diffraction of electrons sent through a crystal would demonstrate their wavelike nature. The subsequent Davisson–Germer experiment showing this effect led to a Nobel Prize in Physics.

Between 1962 and 1968 he was a Professor of Geophysics at Princeton University. Between 1975 and 1991 he was an adjunct Professor of Geophysics at Johns Hopkins University The Olin Hall at the Johns Hopkins University has a Walter Elsasser Memorial in the lobby.