Schrödinger, Erwin (1887–1961)

views updated

SCHRÖDINGER, ERWIN
(1887–1961)

Erwin Schrödinger was born in Vienna, Austria. After his years at the Gymnasium, where he was given a strong education in classics and in science, he studied physics and mathematics at the university of Vienna from 1906. His major teachers were the successors of Ludwig Boltzmann: Franz Exner and Fritz Hasenöhrl. Schrödinger's early interest for philosophy is evident in several manuscripts of this period, which contain reflections about Greek and Indian thought and British empiricism. He was then awarded the D. Phil. Degree in 1910 and became assistant experimental physicist in Exner's laboratory in 1911. From this date until 1922, he worked on several subjects, including atmospheric radioactivity, statistical physics, psycho-physics of sensations, general relativity, and atomic physics.

At the end of World War I, in which Schrödinger served as an artillery officer in the Austrian army, he devoted one year to studying philosophy. He wrote down his philosophical reflections later, during the summer of 1925, in an essay that became part one of his book My View of the World. After brief appointments in various German universities, he became full professor of theoretical physics at the university of Zurich in 1922. In the autumn of 1925, he formulated wave mechanics, construed as a development and alteration of Louis de Broglie's ideas. In 1926 Schrödinger published classic papers in which he formulated and solved the "Schrödinger equation" and demonstrated the empirical equivalence between wave mechanics and Werner Heisenberg's matrix mechanics.

Schrödinger then succeeded Max Planck at the prestigious chair of theoretical physics of Berlin in 1927. But he left Berlin to go to Oxford in mid-1933, a few months after Hitler's rise to power. The same year, he shared the Nobel Prize for physics with Paul Dirac. During his two years at Oxford, he wrote several important papers about the interpretation of quantum mechanics, presenting for the first time the concept of "entanglement" of states and the "cat paradox." Schrödinger then accepted an appointment at the University of Graz in Austria in 1936. But with the advent of the "Anschluss" in 1938, Schrödinger had to flee once more from the Nazis. After spending some time in Vatican and in Belgium, he received an appointment in 1940 at the Dublin Institute for Advanced Studies. The Institute was founded mainly for him by Eamon de Valera, then prime minister of the Irish Republic. During his stay in Ireland, Schrödinger devoted his work to unified field theories (in Einstein's spirit), to renewed reflections on the interpretation of quantum mechanics, and also to conferences for a broader audience. His well-known books What Is Life?, Nature and the Greeks, and Mind and Matter arose from these conferences. In 1956, Schrödinger returned to Austria, where he retired in 1958. He died in Vienna in January 1961.

Philosophy of Physics

The key to Schrödinger's philosophy of physics (especially quantum mechanics) is contained in a letter to Arthur Eddington of March 22, 1940. There, Schrödinger insists that Ernst Mach's radical empiricism and Ludwig Boltzmann's taste for rational "pictures" are not mutually exclusive strategies. He regarded Mach's empiricism as a good guide to tabula rasa whenever unwarranted old intellectual constructs hinder a proper understanding of new physical phenomena. But this is only the first step of research. Boltzmann's urge to picture must be the second step. Indeed, "forming absolutely clear, almost naively clear and detailed "pictures" allows one "to be quite sure of avoiding contradictory assumptions." (The Interpretation of Quantum Mechanics, 1995, p. 121).

Schrödinger used both methods. He was clearly inspired by Mach's method when he criticized vehemently the old-fashioned concept of "particle" construed as a small permanent material body. He formulated his criticism as early as 1913, when he first heard of Bohr's model of the atom, and then refined it throughout his career. According to Schrödinger, the concept of an object is constructed out of actual observations complemented with appropriately selected virtual observations. But if the interpolation of arbitrarily numerous virtual observations is not allowed by the most advanced predictive theory, then the very process of construction collapses, and the corresponding object cannot be said to exist. For elementary particles, "Observations are to be regarded as discrete, disconnected events. Between them there are gaps which we cannot fill in" (Science and Humanism, p. 27). We cannot fill them in according to a trajector pattern, because of Heisenberg's uncertainty relations. But if there is no trajectory, the discrete events cannot be tied up into a spatio-temporal continuant. Therefore, the idea that these scattered events reveal some permanent being is a sort of kinetic illusion : particles do not exist.

After this Machian preliminary move, however, Schrödinger activated the Boltzmannian side of his philosophy of physics. To him, without a precise picture, scientific thought is threatened with ambiguity. Yet the picture must not be taken as mere mimicry of "things out there." It is nothing more than the most efficient mental tool we have, with no ontological implications. This is the status Schrödinger ascribed to his wave function in the 1950s, after having apparently held a naively realist belief in the existence of ψ-waves in 1926. His mature view of wave functions was expressed in Science and Humanism (p. 40): "We do give a complete description, continuous in space and time … a description of something. But we do not claim that this 'something' is the observed or observable facts; and still less do we claim that we thus describe what nature … really is." Yet the description, or picture, must be taken seriously in view of its epistemological value. Its continuous evolution according to the Schrödinger equation and the entanglement between wave functions must be allowed to develop throughout without any sudden "reduction of the state." The only constraint to be exerted on this picture is that it must have some connection with experimentally observable events. But to secure this connection, it is sufficient to use either a rule about expectation values of observables or Born's probabilistic rule: no reduction, no "quantum jump," no collapse of the wave packet, is needed. This is Schrödinger's "solution" (or rather "dissolution") of the measurement problem of quantum mechanics.

Metaphysics

Schrödinger was usually careful to separate his metaphysics from his scientific work. He held that Western science arose from the act of "objectivation"—the act of withdrawing oneself from the domain under study. By this objectivation, we push aside color, pain, esthetic judgment, and ethical values, and restrict our interest to that which is common to all: numbers and structures. But, Schrödinger argues, there is no real duality between ourselves and the objects we have thus posited. Furthermore, our personal selves are identical with the one all-comprehending universal self. Whereas science is only concerned with the relations between objectified entities, metaphysics ventures to say something about the one that comes before any objectification has taken place. This nondualist conception (which Schrödinger called the "identity theory") was overtly borrowed from the Indian Advaita Vedânta and was remarkably similar to Schopenhauer's earlier views. The arguments Schrödinger presents in favor of this view are as follows: (i) The truth of the "identity theory" is somehow directly experienced; (ii) The "identity theory" provides us with a coherent picture of the world as a whole, including the vexing mind-body problem; and (iii) The "identity theory" has a potentially high ethical value, because it cuts egocentrism at its root. The only point of contact between Schrödinger's metaphysics and philosophy of physics is negative. In Mind and Matter, Schrödinger sharply criticized Heisenberg's suggestion that quantum mechanics had weakened the Cartesian dichotomy between res cogitans and res extensa. After all, Schrödinger wrote, "Subject and object are only one. The barrier between them cannot be said to have broken down as a result of recent experience in the physical sciences, for this barrier does not exist."