Erwin Schrödinger

The Austrian physicist Erwin Schrödinger (1887-1961) was the founder of wave mechanics and described the quantum behavior of electrons.

For nearly 5 decades, Erwin Schrödinger, one of the most creative theoretical physicists of the 20th century, contributed papers to the scientific literature. Yet, from the start, his intellectual life was broadly based. He illustrated the breadth of his interests when he described how he intended to fulfill the duties of a professorship he expected to receive in 1918 at Czernowitz, Austria: "I was prepared to do a good job lecturing on theoretical physics … but for the rest, to devote myself to philosophy, being deeply imbued at the time with the writings of Spinoza, Schopenhauer, Mach, Richard Semon and Richard Avenarius." This professorship did not materialize. Nevertheless, throughout his life his philosophical concerns came to the surface, principally because he recognized that physics alone cannot provide an answer to Plotinus's ancient question, "And we, who are we, anyway?" Schrödinger's life was unified by his search for an answer to that simple but profound question.

Schrödinger was born on Aug. 12, 1887, in Vienna, the son of a successful and cultured businessman. In 1906 he entered the University of Vienna, where he was most stimulated by the experimental physicist Franz Exner and the theoretical physicist Fritz Hasenöhrl. After Schrödinger completed his doctoral degree in 1910, he remained as an assistant to Exner. In that capacity he explored various problems, many in solid-state physics.

In 1914 Schrödinger became privatdozent at Vienna but almost immediately found himself serving as an artillery officer in Italy. Shortly after he married Annamaria Bertel in 1920, he went to the University of Jena as an assistant to Max Wien. Within the next year he was called, first as associate professor to the Technische Hochschule in Stuttgart, then as full professor to the University of Breslau, and finally as full professor to the University of Zurich. His years at Zurich (1921-1927) were, scientifically speaking, the most productive in his career.


Discovery of Wave Mechanics

In the immediate post-World War I years, Schrödinger worked on a variety of problems in different areas of physics: general relativity, statistical mechanics, radiation theory, the theory of colors, solid-state physics, and atomic spectroscopy. Some of his results are of great historical interest but have been superseded by new insights; others have remained of permanent interest. All of this work was but a prelude to those famous 2 months in 1925/1926, when, in an outburst of genius, he discovered wave mechanics.

When Schrödinger learned of Louis de Broglie's "matter-wave" hypothesis, he immediately tried to use it to explain the bright line spectrum emitted by the hydrogen atom; that is, he tried to apply it to the case of a single electron electrically "bound" to a proton. The results of his investigations—the wave equation he postulated and to which he applied the appropriate "boundary conditions"— were not in agreement with experiment. Discouraged, he put the work aside for some months—until one day in late 1925 the thought struck him that perhaps he should go against his instincts and not take account of the relativistic mass increase of the electron. The results were in striking agreement with experiment! Interestingly, it is now known that even Schrödinger's first, relativistic treatment of the problem is essentially correct—earlier, he had simply not taken account of the "spin" of the electron, a concept unknown to him at the time.

The nonrelativistic wave equation that Schrödinger assumed to govern the behavior of the electron in the hydrogen atom was of course the equation now universally known as the Schrödinger wave equation, the fundamental equation of wave mechanics. In less than 2 months he discovered his equation and began applying his elegant and beautiful theory to enough physical situations to carry complete conviction of its correctness. The capstone of his achievements was his proof of the logical equivalence of wave mechanics and "matrix mechanics," the latter discovered almost simultaneously by Werner Heisenberg in 1926.


Later Scientific Work

In 1927 Schrödinger became Max Planck's successor at the University of Berlin, where he remained until the political events of 1933 and the accompanying anti-Semitic attacks on many of his colleagues forced him, as a matter of conscience, to resign his position. That year he received the Nobel Prize in physics, sharing it with Paul Dirac.

Schrödinger was a fellow at Oxford University from 1933 to 1936, when he accepted a professorship at the University of Graz. After Hitler annexed Austria in 1938, Schrödinger's outspoken anti-Nazism forced him to flee to Italy. As a member of the Pontifical Academy in Rome, he was reasonably safe and began to explore an idea communicated to him earlier by Eamon De Valera, a mathematician who at the time was also president of the Irish Republic, to establish a research institute in Dublin modeled after the Institute for Advanced Study in Princeton. Schrödinger went to Dublin in 1939 as director of the institute's School of Theoretical Physics. By the time he left Dublin in 1956 for Vienna (where a special chair in theoretical physics was created for him), his health was badly damaged and his productive life in physics was over.

During the preceding 3 decades, however, Schrödinger had continued to contribute to the development of quantum theory. He explored the theory of the Compton effect and potential barrier-penetration problems, and he developed the elegant factorization ("ladder operator") technique for generating solutions to the Schrödinger equation for some particular problems. In 1930 he demonstrated that a Dirac electron traveling in free space has superimposed on its motion a very small oscillatory motion, or Zitterbewegung, an insight which was subsequently of considerable theoretical importance for certain studies. Schrödinger carried out studies on relativity, cosmology, the unified field theory, meson physics, counter (detector) statistics, and statistical mechanics. He rarely worked with a colleague or student. Like Albert Einstein, he was a "horse for single harness" whose influence was disseminated and perpetuated not by a band of devoted followers but, rather, by his extensive writings.


Humanistic Concerns

Schrödinger was always deeply concerned with philosophical questions—not only those that pertain to scientific issues but also those that pertain to essentially humanistic issues. The fundamental reason for his concern with these issues was his full recognition of the limitations of science. He was convinced, for example, that Heisenberg's uncertainty principle has nothing whatsoever to do with the ageold question of human free will. He believed that to illuminate questions such as these—to obtain a complete world picture—one requires the union of all knowledge, the insights achieved in all disciplines.

Schrödinger's quest to understand the nature of science and self led him to the study of history, particularly ancient history. He regarded Thales of Miletus as the first scientist because of Thales's profound insight that nature is understandable or comprehensible and not characterized by a capricious interplay of superstitions and uncontrollable forces. A century later Heraclitus concluded that this comprehensibility is possible only if the world is so constructed as to appear the same to all sane, waking, persons—only if there exists a "world in common."

According to Schrödinger, this world in common is discovered through observation in combination with insights of a metaphysical nature—hunches, spontaneous creative thought, and the like—that guide the interpretation of the observations. He believed that this world in common, to be comprehensible, had to be to a large degree a deterministic, causal world. Chance elements could enter only through the "intersection of causal chains"; these chance elements are precisely the sort of events that scientists prefer not to talk about, but that theologians and philosophers are profoundly interested in. Thus, once again, Schrödinger was led to conclude that the only way to achieve a complete world picture is to take account of nonscientific as well as scientific knowledge. He felt this to be particularly true when discussing questions like the origin and nature of life, as well as the profoundly interesting role that chance played in Darwinian evolution.

Schrödinger died in Vienna on Jan. 4, 1961.


Further Reading on Erwin Schrödinger

Schrödinger discussed his work in his Nobel lecture, reprinted in Nobel Lectures in Physics, vol. 2 (1965). A collection of letters exchanged by Schrödinger, Einstein, Planck, and Hendrik Lorentz is Letters on Wave Mechanics, edited by K. Przibram and translated by M. J. Klein (1967). The most complete source of information on Schrödinger and his work is William T. Scott, Erwin Schrödinger: An Introduction to His Writings (1967), which includes a bibliography. An obituary by Walter Heitler is in the Biographical Memoirs of Fellows of the Royal Society of London, vol. 7 (1961). For the historical significance of Schrödinger's work see Max Jammer, The Conceptual Development of Quantum Mechanics (1966).

Additional Biography Sources

Mehra, Jagdish, Erwin Schrödinger and the rise of wave mechanics, New York: Springer-Verlag, 1987.

Moore, Walter John, A life of Erwin Schrödinger, Cambridge;

New York: Cambridge University Press, 1994. Moore, Walter John, Schrödinger, life and thought, Cambridge;New York: Cambridge University Press, 1989.

Schrödinger, Erwin, What is life?: the physical aspect of the living cell; with, Mind and matter; & Autobiographical sketches, Cambridge; New York: Cambridge University Press, 1992.