(1917–1992) American physicist
Bohm's father, an Austrian immigrant, ran a successful furniture business. Born in Wilkes-Barre, Pennsylvania, Bohm attended Penn State University before moving to the University of California, Berkeley, where he gained his PhD in 1943. After a period working on the development of the atomic bomb under the supervision of Oppenheimer at the Radiation Laboratory, Berkeley, Bohm joined the Princeton physics faculty in 1947. Here he ran into political trouble; called to testify before the House Un-American Activities Committee he pleaded the Fifth Amendment and refused to give evidence against his colleagues. He was cited for contempt and threatened with prison.When his Princeton position expired in 1951, Bohm found himself unemployable in the USA. Oppenheimer advised him to leave the country and he worked in Brazil at São Paulo University (1951–55) and in Israel at Haifa (1955–57). He then settled in Britain, working first at Bristol University as a research fellow before being appointed professor of theoretical physics at Birkbeck College, London (1961), a post he held until his retirement in 1983.
In 1951 Bohm published a much respected textbook, Quantum Theory. He was, however, unhappy with the traditional account of quantum theory. His concern lay not with its lack of determinism, but with the fact that “it had no place in it for an adequate notion of an independent actuality.” Electrons could be both wave and particle and, because of Heisenberg's uncertainty principle, we can never simultaneously know an electron's position and momentum. One way around this difficulty is to suppose that quantum theory presents an imperfect view of nature, with a more complete and deterministic underlying reality. Such approaches, it was widely believed, had been shown by von Neumann in 1931 to be incompatible with quantum theory. Against this Bohm argued that von Neumann's proof was entirely mathematical and consequently based on axioms and presuppositions that were always open to question. In the 1950s he began to seek for the ‘hidden variables’, which would allow him better to understand quantum theory.
He proposed that the electron is a real particle with a definite position and momentum, but it is also connected with a ‘pilot wave’. Bohm regarded this new wave as real and known only by its effects on the electron. Electrons, of course, in Bohm's theory still display wave–particle duality because of the effect of the pilot wave. As the wave reacts with both the electron and the environment, the wave–particle complex responds accordingly to a particular type of measurement. It is a necessary consequence of this view that signals can be conveyed instantaneously from the pilot wave to the electron.
In a later work, Wholeness and the Implicate Order (1980), Bohm sought to establish a more general position. Bohm was inspired by an analogy with a device that he saw at a science exhibition. Two concentric glass cylinders have a layer of glycerine between them. If a localized spot of ink is placed in the glycerine and one cylinder is rotated with respect to the other, the ink is smeared out and the spot of ink disappears (in Bohm's terminology, it is ‘enfolded’ or ‘implicated’). Turning the cylinder in the opposite direction brings the ink back into a spot (it is ‘unfolded’ or ‘explicate’). Thus, while order may appear to have been lost in a system, it may in fact be enfolded in the system,and could be unfolded under the right conditions.