BIRTH OF MODERN QUANTUM MECHANICS

HEISENBERG, WERNER

Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen.

Berlin, Julius Springer, 1925. 8vo. Bound in full cloth with library label to lower part of spine and library stamps to front free end paper. In "Zeitschrift für Physik, 33. Band, 1925". Front boards very loose and spine almost detached. Internally fine and clean. [Heisenberg) Pp. 879-893. [Entire issue: VII, (1), 950 pp.].

First printing of Heiseberg's seminal and groundbreaking paper which laid the foundation for matrix mechanics and thereby giving birth to modern quantum mechanics; a theory that states quantum mechanics should be based "exclusively on relationship between quantities which in principle are observable" (From the abstract).

"The alternative, which he [Heisenberg] chose in his historic paper [the present] and which led to the development of matrix machanics, the earliest formulation of modern quantum mechanics, abandoned Bohr's description of motion in terms of classical physics altogether and replaced it by a description in terms of what Heisenberg regarded as observable magnitudes" (Jammer, The Conceptual Development of Quantum Mechanics, P. 197).

"After nearly two weeks on Helgoland, Heisenberg returned to Göttingen, where he drafted his fundamental paper "Über die quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen," which he completed in July. In this paper Heisenberg proclaimed that the quantum mechanics of atoms should contain only relations between experimentally observable quantities. Theresulting formalism served as the starting point for the new quantum mechanics, based, as Heisenberg's multiplication rule implied, on the manipulation of ordered sets of data forming a mathematical matrix." (DSB)

Before Heisenberg's discovery the Bohr-Sommerfeld quantum theory was the leading theory. By the early 1920's most physicists agreed that the Bohr-Sommerfeld theory had problems and that there was a need to replace it with a new quantum theory. Heisenberg's main achievement was to replace the idea of orbital path with what could be observed, namely the light emitted and absorbed by the atoms. Because of the unfamiliar mathematics which Heisenberg's new theory used, several physicists had doubts about its consistency. But Max Born soon realized that the laws, which the theory relied on, were the same as the laws, which apply to matrix algebra. In 1925 Born and his student Pascual Jordan published "Zur Quantenmechanik" which reformulated Heisenbergs theory in terms of matrices, in the special case of one degree of freedom. With "Zur Quantenmechanik II" (or the "Three Man Paper") published 1926, Heisenberg, Born and Jordan described the new theory in the general case of arbitrarely many freedom degrees.

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