Walter Maurice Elsasser | |
|---|---|
 | |
| Born | 20 March 1904 |
| Died | 14 October 1991 (1991-10-15) (aged 87) |
| Known for | Dynamo theory Complex system biology |
| Awards | National Medal of Science(1987) William Bowie Medal(1959) Arthur L. Day Medal(1979) |
| Scientific career | |
| Fields | Physics Theoretical biology |
| Doctoral advisor | Max Born |
Walter Maurice Elsasser (March 20, 1904 – October 14, 1991) was aGerman-bornAmericanphysicist, a developer of the presently accepteddynamo theory as an explanation of theEarth'smagnetism. He proposed that thismagnetic 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of the Earth's magnetic field by the study of the magnetic orientation ofminerals in rocks.[1] He is also noted for his unpublished proposal of the wave-like diffraction of electron particles by a crystal. The subsequentDavisson–Germer experiment showing this effect led to aNobel Prize in Physics.[2]
Between 1962 and 1968 he was a Professor of Geophysics atPrinceton University. Between 1975 and 1991 he was an adjunct Professor of Geophysics at Johns Hopkins UniversityThe Olin Hall at theJohns Hopkins University has a Walter Elsasser Memorial in the lobby.
Elsasser was born in 1904 to a Jewish family[3] inMannheim,Germany. Before he became known for hisgeodynamo theory, while inGöttingen during the 1920s, he had suggested the experiment to test the wave aspect ofelectrons.[2] This suggestion of Elsasser was later communicated by his senior colleague from Göttingen (Nobel Prize recipientMax Born) to physicists inEngland. This explained the results of theDavisson-Germer andThomson experiments later awarded with theNobel Prize in Physics. In 1935, while working in Paris, Elsasser calculated the binding energies of protons and neutrons in heavy radioactive nuclei.Eugene Wigner,J. Hans D. Jensen andMaria 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 theEarth's magnetic field. He conjectured that it could be a self-sustainingdynamo, powered by convection in the liquidouter 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 theU.S. Army Signal Corps.[4]
During his later years, Elsasser became interested in what is now calledsystems biology and contributed a series of articles toJournal of Theoretical Biology.[5][6][7][8][9][10][11] The final version of his thoughts on this subject can be found in his bookReflections on a Theory of Organisms, published in 1987 and again posthumously with a new foreword by Harry Rubin in 1998.
Elsasser died in 1991 inBaltimore,Maryland, US.
Abiotonic law, a phrase invented by Elsasser, is a principle of nature which is not contained in the principles of physics.[12]
Biotonic laws may also be considered as local instances of global organismic or organismal principles,[13][14] such as the Organismic Principle of Natural Selection.[15][16]
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 currentsystems 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 exceptionis an important part of Elsasser's legacy to bothComplex systems biology andRelational Biology.[17]
Elsasser was elected to theNational Academy of Sciences in 1957. From theAmerican Geophysical Union he received theWilliam Bowie Medal, its highest honor, in 1959; and theJohn Adam Fleming Medal (for contributions to geomagnetism) in 1971.[18][19] He received thePenrose Medal from theGeological Society of America in 1979 and the Gauss Medal from Germany in 1977.[4][20] In 1987, he was awarded the USA'sNational 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."[21]
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