Elsasser, Walter Maurice

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(b. Mannheim, Germany, 20 March 1904;

d. Baltimore, Maryland, 14 October 1991), physics, geophysics, biophysics.

Elsasser trained originally in physics (especially quantum mechanics), but worked for most of his career in atmospheric dynamics, geomagnetism, seismology, and theoretical biology. His development of early dynamo theories of Earth’s main magnetic field ultimately gained him wide recognition and several important awards. More than once in his career, however, Elsasser produced theoretical aperçus that were received with skepticism; subsequent theoretical elaboration and experimental work demonstrated the value of his insights, but the development was made by others. In the words of Victor Weisskopf, Elsasser generated “great flashes of ideas; and it was not Elsasser’s style to elaborate details” (1979, p. 759). The wide-ranging character of his fields of activity was paralleled, not coincidentally, by a rather peripatetic career. Elsasser’s memoirs frankly portray these aspects of his scientific work and reflect on the psychological underpinnings of scientific creativity.

Early Years . Both sides of Elsasser’s family ran prosperous businesses: burlap manufacturing for the family of his mother, Johanna Masius, and fruit brandy distilling for that of his father, Moritz. Moritz Elsasser obtained a law degree, entered the civil service, and was eventually appointed a judge in Mannheim—where Walter and his sister Maria were born—then later Pforzheim and Heidelberg, along with a period of military duty in Konstanz during World War I. Walter attended a humanistic-classical Gymnasium, but his mathematics teacher encouraged him to pursue science professionally. A brief stint in his grandfather’s firm convinced him that science—specifically, physics—was a better career choice than business, and he entered the University of Heidelberg in 1922.

Elsasser’s parents were both Protestant converts, though not very religious; heretofore he had been conscious of his Jewish family background only in an abstract, philosophical sense. At the university, however, Elsasser witnessed students’ enthusiasm for the anti-Semitic, ultra-nationalist sentiments of the physicist Philipp Lenard, and he was warned that he would face extreme antagonism in Lenard’s laboratory. Elsasser therefore transferred to Munich, where he studied with Wilhelm Wien and Arnold Sommerfeld. But once again he sensed strong undercurrents of anti-Semitism and took advice to go to Göttingen, which had a more congenial reputation.

Interests in Physics . Elsasser arrived in 1925, just as Göttingen was becoming a center of the new quantum mechanics, and he became a student of the experimental-ist James Franck. In Max Born’s seminar on atomic structure, Elsasser learned of an experiment by Clinton Davis-son and Charles Henry Kunsman at Bell Laboratories in which the angular distribution of electrons scattered from a platinum plate showed maxima and minima. Contemporaneously, Franck, Born, and their students were discussing Albert Einstein’s notion of gas degeneracy as a wave phenomenon, which referred in turn to Louis de Broglie’s thesis on electron orbital wavelengths. Juxtaposing these results, Elsasser suggested that the electron scattering patterns, as well as the Ramsauer effect, might be interference phenomena. Franck and Born encouraged Elsasser to publish a note in Naturwissenschaften. Most readers—including Einstein, who refereed the brief article—were apparently intrigued but not entirely convinced; Davisson himself regarded this explanation of his experiment skeptically. Elsasser’s own experiments to confirm the result were unsuccessful and convinced his mentors that his talents lay primarily in theory. The theorist Born therefore took over as the Doktorvater of a 1927 thesis on the quantum mechanics of electron-hydrogen atom collisions. Meanwhile, Davisson returned to the scattering problem with methodological innovations that produced definitive results, and with the benefit of Erwin Schrödinger’s widely noted adoption of de Broglie’s thesis. For this work, Davisson received the Nobel Prize in 1937.

After receiving his doctorate Elsasser became an assistant to Paul Ehrenfest in Leiden, apparently through the recommendation of Robert Oppenheimer, who had become acquainted with Elsasser in Göttingen and who had previously been Ehrenfest’s assistant. Ehrenfest and Elsasser, both sensitive personalities, found it impossible to get along with each other, and after several weeks of escalating tension, Elsasser departed in a state of depression for Berlin, where his parents now lived. After another postdoctoral semester, this time with Wolfgang Pauli in Zürich, Elsasser took up an adjunct research assistantship with Fritz Houtermans at the Technische Hochschule Berlin. In summer 1930, Elsasser became a technical specialist at the new Physico-Technical Institute in Kharkiv, Ukraine; ill health compelled his return to Berlin after only six months, but Elsasser was profoundly affected by his experience in the Soviet Union. The following summer, he was appointed to an assistantship with Erwin Madelung in Frankfurt. There Elsasser also began an extended psychoanalysis with Karl Landauer. His interest in psychology also led, subsequently, to extensive reading in the works of Carl Jung.

With an apparently stable job and a fresh psychological perspective, Elsasser started his time in Frankfurt promisingly. However, the National Socialists’ rise to power in 1933 presaged even more virulent anti-Semitism. At Landauer’s urging, Elsasser departed in April for Zürich. Soon after his arrival, Pauli matched him with an opening for a theorist in Frédéric Joliot-Curie’s laboratory.

In Paris, Elsasser’s attention turned to nuclear structure. Rejecting a then widespread idea that alpha particles constituted a kind of primary building block for heavier nuclei, Elsasser instead picked up a suggestion by James Holley Bartlett and theorized, based on Pauli’s exclusion principle, that nucleons resided in shells analogous to the electron shells. Elsasser found evidence for this in patterns in the number of stable isotopes for a given atomic number, in the relative abundance of isotopes, and in nuclear binding energies. However, the theory remained suggestive rather than comprehensive. A much greater accumulation of data on nuclear reactions enabled Maria Goeppert-Mayer and Hans Jensen to develop a more thorough theory of nuclear shell structure in the 1940s— once again, Nobel Prize–winning work.

Elsasser felt welcome in Joliot’s laboratory but was daunted by the prospect of a permanent accommodation to French culture and nationality; moreover, he remained concerned by the European political situation, particularly for the sake of his parents. On a 1935 trip exploring options for emigration to the United States he met several useful contacts—as well as a young American woman, Margaret Trahey, whom he married in 1937—but he did not land a job. On a return trip in 1936, Elsasser took up California Institute of Technology (Caltech) president Robert Millikan’s suggestion that he move into meteorology, a field that Millikan was seeking to bolster at Caltech. Elsasser surmised that the next fruitful arena for physics after the breakthroughs of quantum theory would be an attempt to apply physical principles to complex systems, and he saw in meteorology a chance to try out this conjecture. Specifically, he decided to study the process of heat transfer in the atmosphere via infrared radiation, a topic still relatively unfamiliar to meteorologists.

Meteorology . Meteorology at Caltech was officially under the purview of the fluid dynamicist Theodore von Kármán. In 1941 the head of research of the U.S. Weather Bureau attempted to persuade Caltech to make Elsasser head of the department, and Kármán took this perceived outside interference as a reason to dismiss Elsasser. After a brief period at Harvard’s Blue Hill Meteorological Observatory, where he published a widely noted monograph on his infrared radiation studies, Elsasser joined the Army Signal Corps as a civilian expert, working first on electronics (at Fort Monmouth) and then on meteorological effects in the use of radar (in New York). After the war there followed short stints at RCA’s Princeton laboratories and at the University of Pennsylvania. With some relief, in 1950 he accepted an invitation to develop a physics graduate program at the University of Utah.

When Elsasser arrived in Utah, his main attention became focused on a research field he had been cultivating almost as a diversion alongside his official duties since the late 1930s: geomagnetism. Discounting a hypothesis popularized by Einstein and Patrick Maynard Stuart Blackett that Earth’s magnetic field is a property of its rotation per se, he thought instead of a self-sustaining dynamo in the molten metallic core. A key clue for Elsasser in his approach to the problem was a similarity between maps of the long-term variations in Earth’s magnetic field and the maps of atmospheric flows familiar from his work in meteorology. Elsasser theorized that Coriolis forces and convection currents in the conductive liquid combined to produce poloidal magnetic and toroidal electric fields (the former extending beyond Earth’s surface, the latter interior to it) that had a feedback effect on each other. Though some details were unclear, he argued that the dynamo theory gave the right order of magnitude for the magnetic field’s strength and potentially accounted for its secular variations. By the mid-1950s, Elsasser’s junior colleague at Utah, Eugene Newman Parker, and the British physicists Edward Crisp Bullard and the Australian-born George Keith Batchelor had explored alternative dynamo models and elaborated the mathematics showing that the field was self-sustaining. The dynamo theory ultimately received wide acceptance. It subsequently also became a key element of Hannes Alfvén’s Nobel Prize–winning work on plasma electrodynamics. In the 1960s, Elsasser’s geophysical interests moved into modeling seismic deformation in the context of the burgeoning theory of plate tectonics.

Largely in recognition of this breakthrough in the theory of terrestrial magnetism, but also in acknowledgment of his earlier work in quantum physics and meteorology, Elsasser was elected to the National Academy of Sciences (1957), later receiving the Bowie and Fleming medals of the American Geophysical Union (in 1959 and 1971, respectively), the Gauss Medal in Germany (1977), the Penrose Medal of the Geological Society of America (1979), and the U.S. National Medal of Science (1987).

Theoretical Biology . While at Utah, Elsasser also began publishing in yet another field, theoretical biology. His earlier experiences and reading in psychology were great influences on his work in this direction, giving him an intuition that the workings of the mind, and therefore by implication biological systems in general, were in some way “irrational.” Another major influence was his former colleague in Paris, the physiologist Theophile Kahn, who emphasized the uniqueness of individual organisms and the difficulty in treating them as homogeneous classes, something that Elsasser felt was consonant with his own first-hand experiences of the attempt to forge a collectivist society in the Soviet Union.

Elsasser’s central concern as a theoretical biologist thus became the complexity and individuality of living systems, which he contrasted with the simplicity and reproducibility of those systems studied in the physico-chemical laboratory. He became convinced that it was not possible simply to extrapolate the methods of physics and chemistry to the study of biology, except in certain limited circumstances. The laws of quantum physics arose precisely out of the identity of its objects—all electrons, for example, were mutually indistinguishable. Living organisms, by contrast, represented unique individuals within a range of hypothetically possible molecular arrangements that was immensely large. Elsasser expressed this formally in “the principle of finite classes”—the fact that biological entities such as proteins or pathways have an astronomical number of potential states, far more than can possibly be instantiated in the real world—and he used the term “generalized complementarity,” adopted from the Copenhagen Interpretation founder Niels Bohr, to describe the impossibility of a full, quantum-level, description of a living system. In short, for Elsasser reductionist approaches to, and mechanistic or deterministic explanations of, biology were inadequate for a complete understanding of organisms. For example, he suggested the likelihood of indeterminate behavior in protein molecules, on the basis of the fact that John von Neumann’s quantum mechanical proof of determinism at the macroscopic level was invalid when applied to finite classes. Later experimental evidence suggests that this is untrue (possibly as a result of quantum decoherence within individual proteins), but a formal demonstration of exactly why Elsasser was wrong about this had not yet been obtained by the early twenty-first century.

In the light of the principle of finite classes, therefore, it was the task of biology to account for the extant organisms functionally and holistically. Toward this end, Elsasser advocated attention to several key concepts: “variostability,” the tendency for regularity to appear in macroscopic structure despite irregularity in the finite class of the underlying molecular structure; “creativity,” the process whereby an organism navigates the states of a finite class; and “operative symbolism,” the use of control structures, for example, genetic switches, to release creativity. Memory, for example, when analyzed from an information-theoretic viewpoint was more than a problem of chemical storage, but had to be understood as a manifestation of these concepts. Likewise, after some early skepticism that DNA could be the carrier of hereditary information in the organism, he produced the subtler modified argument that, while DNA was the molecule of heredity, it did not completely specify the organism but rather acted as a trigger for its holistic morphological development. Elsasser thus proposed that biology should be treated as an essentially inductive science where the “irrational” organism is the central focus of experimentation rather than the suborganismic components such as molecules.

Whereas Elsasser’s contributions to atomic physics and geophysics are of acknowledged importance, his theoretical biology remains controversial. Many of his critics were dismissive, seeing his efforts as an attempt to reintroduce vitalism into biological discourse, something that Elsasser always denied. By the late 1960s Elsasser had decided that his early theoretical biology was impaired by his reluctance to offend the biological “establishment,” many of whom were indeed evidently offended, and this is reflected in the more speculative character of his subsequent writings. As a result, he was rather marginalized from the scientific mainstream during the last fifteen years of his life.

Nevertheless, with the expansion of systems biology since the late 1990s, Elsasser has once again begun to be discussed by biologists, for whom the problems of extremely complex systems have continuing relevance. Many of the specifics of Elsasser’s biological work have come to be considered obsolete—for instance, his early skepticism concerning the role of DNA in information storage and his prediction of indeterminate behavior by proteins on the basis of the principle of finite classes. Rather it is the questions that Elsasser asked, questions neglected in the first fifty years of molecular biology, that are his legacy in that field.

Alongside successes and challenges in his professional life, Elsasser experienced a hard personal loss with the death of his wife Margaret in 1954. He married his second wife Susanne Rosenfeld, a childhood friend (and relative), a decade later. The peripatetic pattern of his career continued, with moves to physics, later oceanography, at the University of California, San Diego (1956), to geology at Princeton (1962), to a research professorship at the Institute for Fluid Dynamics and Applied Mathematics at Maryland (1967) and, finally, to an adjunct professorship of earth and planetary science at Johns Hopkins (1974). This last post—after his formal retirement—proved to be the longest lasting of his multifarious career.


Correspondence and manuscripts, primarily from the 1950s onward, are available from the Walter M. Elsasser Papers, Special Collections, Milton S. Eisenhower Library, Johns Hopkins University, Baltimore, Maryland. Elsasser’s narrative response to a survey on the history of geophysics and the responses by several of Elsasser’s colleagues to it are available from the Niels Bohr Library, American Center for Physics (NBL-ACP), College Park, Maryland. Oral history interviews with Elsasser and several of his teachers and colleagues are available from the Archives for the History of Quantum Physics (AHQP), at NBLACP and several other deposit libraries.


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“Interferenzerscheinigungen bei Korpuskularstrahlen.” Naturwissenschaften 16 (1928): 720–725.

“Sur le principe de Pauli dans les noyaux.” Pts. 1 and 2. Journal de physique et le radium, 7th ser., 4 (1933): 549–556; 5 (1934): 389–397, 635–639.

“On the Origin of the Earth’s Magnetic Field.” Physical Review 55 (1939): 489–498.

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Richard H. Beyler

Derek Gatherer

Walter Maurice Elsasser

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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 researches 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). □

Elsasser, Walter Maurice

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Elsasser, Walter Maurice (1904–91) A German-born physicist, Elsasser became a US citizen in 1940. He worked on the structure of the nucleus and on terrestrial magnetism. In 1946, he proposed that a ‘self-exciting dynamo’ in the Earth's outer core might be the cause of the magnetic field.

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