1. Youth Return to main menu(1901-1920) 2. Student and Postdoctoral Years (1920-1925) 3. The Development of Quantum Mechanics (1925-1927) 4. Professor in Leipzig (1927-1942) 5. The War Years (1939-1945) 6. The period of Reconstruction and Renewal (1946-1958) 7. The Munich Years (1958-1976) Return to: Heisenberg-Society |
The early 1920s witnessed fundamental difficulties in atomic physics. The quantum theory of atomic structure, founded by Bohr and largely developed by Bohr and Sommerfeld, did not describe the properties of complicated atoms and molecules. Moreover, the discovery of the Compton effect at the end of 1922 focussed attention on the problem of the nature of radiation. Its interpretation in the light-quantum hypothesis contradicted classical radiation theory, and the radical attempt by Bohr, Kramers and Slater in early 1924 to resolve the difficulty by assuming only statistical conservation of energy and momentum was refuted by the experiment of Walter Bothe and Hans Geiger in April 1925. Heisenberg was growing ever more concerned with these and other difficulties in atomic theory. His works on the anomalous Zeeman effect, only successful in part, and his unsuccessful calculation of the helium states with Born had sensitized him by early 1925 to the “crisis” of current theory. Nevertheless, his latest calculations in Copenhagen on dispersion theory and on complex spectra, especially the principle of “sharpened” correspondence applied in these works, seemed to point toward a future satisfactory theory. With characteristic optimism the Göttingen
After Born and Jordan managed in August and September
1925 to develop the mathematical content of Heisenberg’s work into a consistent
theory with the help of infinite Hermitian matrices (Z.Phys. 34, 858, 1925), Heisenberg participated, starting
in September 1925, in the completion and application of the new “matrix
mechanics”, culminating in the long “three-man-paper”, by Born, Heisenberg and
Jordan, submitted on 16 November 1925. Further developments followed rapidly:
Pauli calculated the stationary states of the hydrogen atom in October 1925;
Cornelius Lanczos in Frankfurt and Born and Norbert
Wiener in the USA extended the method of operator mechanics to describe
continuous motions (December 1925); and Paul Adrien
Maurice Dirac in Cambridge developed independently of the Göttingen
school a different scheme based upon Heisenberg’s July paper, the method of In May 1926 Niels Bohr
offered Heisenberg a position at his institute in Copenhagen as Lector and
successor to his assistant Kramers. There Heisenberg
delivered lectures at the university (in Danish) on contemporary physicsl theories, directed beginning students, helped
guests researchers with their problems, and discussed with Bohr the most
important results of quantum mechanics, the quantum atomic theory that Erwin
Schrödinger began introducing in January 1926. The complete mathematical
equivalence between Göttingen’s matrix mechanics or
Dirac’s Born’s statistical interpretation of Schrödinger’s wave function, Heisenberg’s uncertainty relations, and Bohr’s complementarity principle formed the basis of the physical interpretation of the new quantum mechanics, as explicated by Bohr in his lectures at the Volta Conference in Como (September 1927) and at the Solvay Congress in Brussels (24-29 October 1927). This “Copenhagen Interpretation” of quantum mechanics, as it was later called, found acceptance by most physicists, but not by all: Albert Einstein in particular raised serious objections to it at the 1927 and 1930 Solvay conferences and later, for example, in his paper with Boris Podolsky and Nathan Rosen (Phys.Rev. 47, 777, 1935). David C. Cassidy and Helmut Rechenberg |