Walter Maurice Elsasser (March 20, 1904 – October 14, 1991) was a
German-born
American physicist considered a "father" of the presently accepted
dynamo theory as an explanation of the
Earth's
magnetism. He proposed that this
magnetic field resulted from electric currents induced in the fluid outer core of the Earth. He revealed the history of the Earth's magnetic field through pioneering the study of the magnetic orientation of
minerals in rocks.