Walter M. Elsasser

Walter Maurice Elsasser (March 20, 1904 – October 14, 1991) was a German-born American physicist, a developer 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 by the study of the magnetic orientation of minerals in rocks. He is also noted for his unpublished proposal of the wave-like diffraction of electron particles by a crystal. 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.

Biography
Elsasser was born in 1904 to a Jewish family in Mannheim, Germany. Before he became known for his geodynamo theory, while in Göttingen during the 1920s, he had suggested the experiment to test the wave aspect of electrons. This suggestion of Elsasser was later communicated by his senior colleague from Göttingen (Nobel Prize recipient Max Born) to physicists in England. This explained the results of the Davisson-Germer and Thomson experiments later awarded with the Nobel Prize in Physics. In 1935, while working in Paris, Elsasser calculated the binding energies of protons and neutrons in heavy radioactive nuclei. Wigner, Jensen and Goeppert-Mayer received the Nobel in 1963 for work developing out of Elsasser's initial formulation. Elsasser therefore came quite close to a Nobel prize on two occasions.

During 1946–47, Elsasser published papers describing the first mathematical model for the origin of the Earth's magnetic field. He conjectured that it could be a self-sustaining dynamo, powered by convection in the liquid outer core, and described a possible feedback mechanism between flows having two different geometries, toroidal and poloidal (indeed, inventing the terms). This had been developed from about 1941 onwards, partly in his spare time during his scientific war service with the U.S. Army Signal Corps.

During his later years, Elsasser became interested in what is now called systems biology and contributed a series of articles to Journal of Theoretical Biology. The final version of his thoughts on this subject can be found in his book Reflections on a Theory of Organisms, published in 1987 and again posthumously with a new foreword by Harry Rubin in 1998.

Elsasser died in 1991 in Baltimore, Maryland, US.

Biotonic laws
A biotonic law, a phrase invented by Elsasser, is a principle of nature which is not contained in the principles of physics.

Biotonic laws may also be considered as local instances of global organismic or organismal principles, such as the Organismic Principle of Natural Selection.

Some, but not all, of Elsasser's theoretical biology work is still quite controversial, and in fact may disagree with several of the basic tenets of current systems biology that he may have helped to develop. Basic to Elsasser's biological thought is the notion of the great complexity of the cell. Elsasser deduced from this that any investigation of a causative chain of events in a biological system will reach a "terminal point", where the number of possible inputs into the chain will overwhelm the capacity of the scientist to make predictions, even with the most powerful computers. This might seem like a counsel of despair, but in fact Elsasser was not suggesting the abandonment of biology as a worthwhile research topic, but rather for a different kind of biology such that molecular causal chains are no longer the main focus of study. Correlation between supra-molecular events would become the main data source. Moreover, the heterogeneity of logical classes encompassed by all biological organisms without exception is an important part of Elsasser's legacy to both Complex systems biology and Relational Biology.

Awards
Elsasser was elected to the National Academy of Sciences in 1957. From the American Geophysical Union he received the William Bowie Medal, its highest honor, in 1959; and the John Adam Fleming Medal (for contributions to geomagnetism) in 1971. He received the Penrose Medal from the Geological Society of America in 1979 and the Gauss Medal from Germany in 1977. In 1987, he was awarded the USA's National Medal of Science "for his fundamental and lasting contributions to physics, meteorology, and geophysics in establishing quantum mechanics, atmospheric radiation transfer, planetary magnetism and plate tectonics."