2 - De Broglie's pilot-wave theory

Summary

Background

At a time when no single known fact supported this theory, Louis de Broglie asserted that a stream of electrons which passed through a very small hole in an opaque screen must exhibit the same phenomena as a light ray under the same conditions.

(Prof. C. W. Oseen, Chairman of the Nobel Committee for Physics, presentation speech, 12 December 1929 (Oseen 1999))

In September 1923, Prince Louis de Brogliea made one of the most astonishing predictions in the history of theoretical physics: that material bodies would exhibit the wave-like phenomena of diffraction and interference upon passing through sufficiently narrow slits. Like Einstein's prediction of the deflection of light by the sun, which was based on a reinterpretation of gravitational force in terms of geometry, de Broglie's prediction of the deflection of electron paths by narrow slits was made on the basis of a fundamental reappraisal of the nature of forces and of dynamics. De Broglie had proposed that Newton's first law of motion be abandoned, and replaced by a new postulate, according to which a freely moving body follows a trajectory that is orthogonal to the surfaces of equal phase of an associated guiding wave. The resulting ‘de Broglian dynamics’ – or pilot-wave theory as de Broglie later called it – was a new approach to the theory of motion, as radical as Einstein's interpretation of the trajectories of falling bodies as geodesics of a curved spacetime, and as far-reaching in its implications. In 1929 de Broglie received the Nobel Prize ‘for his discovery of the wave nature of electrons’.