Walter Maurice Elsasser

The American physicist Walter Maurice Elsasser (1904-1991) made original contributions to geophysics and to the discussion of the physical foundations of biology.

Walter Maurice Elsasser was born in Germany on March 20, 1904. After university studies at Heidelberg and Munich he gained a doctoral degree in physics at Göttingen in 1927. His subsequent employments were diverse, in many institutions and in three countries. He worked at the Technische Hochschule, Berlin (1928-1930) and at Frankfurt University (1930-1933). While research fellow and guest lecturer at the Sorbonne (1933-1936) in Paris, his main work was in atomic physics. He immigrated to the United States in 1936 and became a naturalized citizen in 1940. In 1937 he married Margaret Trahey, and they had a daughter and a son. After a divorce from his first wife, he married Suzanne Rosenfeld in 1964.

Elsasser's first appointments in the United States were in meteorology at the California Institute of Technology (1936-1941) and then at the Blue Hill Observatory, Harvard (1941-1942). During World War II he was employed at the Signal Corps Laboratories in New Jersey, where his research dealt with the atmospheric transmission of radio and radar waves. Following the war, he engaged in industrial research for a short time at the New Jersey Laboratories of the Radio Corporation of America. After that he held professorial posts at several universities, including Pennsylvania (1947-1950), Utah (1950-1956), California at La Jolla (1956-1962), New Mexico at Albuquerque (1960-1961), Princeton (1962-1968), and Maryland at College Park (1968-1974). In 1985 Elsasser became adjunct professor in the department of earth and planetary science at Johns Hopkins University, and was named Homewood Professor two years later. He retired from teaching in 1989.

In 1958 Elsasser published a book, The Physical Foundation of Biology, an important and highly original work concerned with broad philosophical, physical, and biological matters, strikingly different from his main researches. A sequel appeared in 1966, Atom and Organism. Other books by Elsasser include The Chief Abstractions of Biology (1975), Memoirs of a Physicist in the Atomic Age (1978), and Reflections on a Theory of Organisms (1987).

Calculations of wind systems led Elsasser by 1938 to consider the possibility that convection motion might exist within the earth's metallic core and might obey certain laws of cosmic magneto-hydrodynamics. He first studied the phenomenon of "secular variation" and demonstrated that his formulation of the magneto-hydrodynamics of a spherical conductor provided quantitative results in agreement with the observed phenomenon. Elsasser also explained how eddies with the circulation of the earth's core can account for the secular variation, whose distribution is regional and whose time scale, a few centuries, differs greatly from that of surface geological changes.

Being interested in the origin of the earth's permanent geomagnetic field, Elsasser first proposed a thermoelectric origin, but this did not account for the self-sustaining nature of the permanent field, and he abandoned it in favor of a dynamo theory. According to this model, the presence of a magnetic field in the core results in motion of matter perpendicular to the field, which in turn gives rise to a field producing motion, and so on in self-sustaining action.

Elsasser was elected to the National Academy of Sciences in 1957 and awarded the Bowie Medal of the American Geophysical Union (AGU) in 1959. He received the Fleming Medal of the AGU in 1971. Elsasser was also awarded the 1987 U.S. National Medal of Science. In his late research, Elsasser concentrated his efforts on the study of the earth's upper mantle. Elsasser died October 14, 1991.

Further Reading

• Elsasser's work in quantum physics is briefly discussed in William H. Cropper, The Quantum Physicists and an Introduction to Their Physics (1970). See also David Robert Bates, ed., The Planet Earth (1957; rev. ed. 1964).