Walter Maurice Elsasser | |
|---|---|
 | |
| Born | 20 March 1904 |
| Died | 14 October 1991(1991-10-14) (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 who developed the presently accepteddynamo theory to explainEarth'smagnetic 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of Earth's magnetic field is revealed by the magnetic orientation ofminerals in rocks.[1] He is also noted for his unpublished proposal that the diffraction of electrons sent through a crystal would demonstrate their wavelike nature. 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. As a physics student inGöttingen during the 1920s, well before hisgeodynamo theory, he suggested an experiment to test the wave aspect ofelectrons.[2] Though the experiment was tried inEngland and failed, his suggestion was later communicated by his professor at Göttingen,Nobel Prize recipientMax Born, to a physicist at Bell Labs in the United States.[4] TheDavisson-Germer andThomson experiments verified electron diffraction and eventually netted aNobel 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.[5]
During his later years, Elsasser became interested in what is now calledsystems biology and contributed a series of articles toJournal of Theoretical Biology.[6][7][8][9][10][11][12] 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.[13]
Biotonic laws may also be considered as local instances of global organismic or organismal principles,[14][15] such as the Organismic Principle of Natural Selection.[16][17]
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.[18]
Given that an analysis of the organism on the basis of classical mechanics fails in the face of "unfathomable complexity," Elsasser made use of his familiarity withquantum mechanics to arrive at a viable approach.[19] With reference toNiels Bohr's framework ofcomplementarity, he noted that an exact specification of the "particle" aspect of a quantum system precludes a description of the system in its "wave" aspect. By generalizing complementarity to include any system that involves irreducible individuality, Bohr extended his framework to include organisms. Elsasser argued that generalized complementarity in biology would mean that the overall understanding of the organism is incompatible with a complete analysis of its physico-chemical properties. Biology, he wrote, must "restrain its preoccupation with too many empirical details in favor of some holistic understanding."[20]
Elsasser reasoned that the failure of deterministic physico-chemical processes to explain biological order necessitates "creative selection" on the part of the organism. Since many possible patterns of internal activity conform withphysical law, the organism must select one pattern above all others. The central question is then the criterion by which the organism makes its selection. Elsasser's answer was "holistic memory." Non-deterministic internal activity "results from a selection, among the immense numbers of patterns available, of a pattern that resembles some earlier pattern of the same organism or of preceding (parental) organisms."[21] Alongside the hereditary information stored in genes, which constitutes a "mechanistic" form of memory, life exhibits holistic memory on the basis of a "primary phenomenon of nature": the conservation of information. Just as physical processes reveal the conservation of mass, momentum and energy, "the conservative property of organisms is their similarity to preceding states without intermediate information storage."[22]
Elsasser dismissedvitalism, which he defined as laws that apply solely to matter that constitutes complex systems such as organisms.[23] Though evident only in the context of biology, the conservation of information is nevertheless a general feature of nature and therefore biotonic, not vitalist.
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.[24][25] He received thePenrose Medal from theGeological Society of America in 1979 and the Gauss Medal from Germany in 1977.[5][26] 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."[27]
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