Physics in the Making in Bohr's Copenhagen

A. Pais

Slobodan Perović

Dietrick E. Thomsen

The Copenhagen Interpretation of quantum mechanics has become the standard way of explaining the physical philosophical meaning of the mathematics of microscopic behavior. It developed from the thought of people who attended the Institute for Theoretical Physics of the University of Copenhagen during the 40 years that Niels Bohr directed it, from 1920 to 1962. Bohr took a large part in developing the Copenhagen Interpretation, he didn't escape all controversy over it (although the quote above is a bit of an exaggeration). Bohr did die before the experimental theoretical developments that have transposed the debate over the appropriateness adequacy of the Copenhagen Interpretation into a new key, he may well have been lucky to have escaped when he did. There is no authoritative codification of CI [the Copenhagen Interpretation], write T Gornitz C. E von Weizsacker of the Max Planck Institute in Starnberg, West Germany in' their formal presentation to the recent Loyola Conference on Mathematical Interpretational Problems in Relativistic Quantum Theory, and under the conditions of its origin there probably could not be one.... All prominent authors of the time who wrote on these questions, like Bohr, [Werner] Heisenberg, [Wolfgang] Pauli, J[ohn] v[on] Neumann on one side, [Albert] Einstein [Erwin] Schrodinger on the other, fell, so we feel, into some stammering when they tried to express their own positions. Nevertheless there is what might be called a Copenhagen attitude. It concentrates on observable phenomena, makes statistics probability central to its understanding, considers quantum mechanics primarily a theory of knowledge or information becomes a kind of physica negativa (analogous to a theologia negativa) in trying not to say too much about things that can't be seen or felt. For example, it doesn't much care whether the orbits of electrons in atoms are real or not and, in fact, tends to regard them as unreal. It appears in most textbooks as the standard way of looking at things.

Ig. Tamm

Jim Baggott

Abstract The confrontation between Einstein and Bohr over the interpretation of quantum theory has been painted in the past as a direct conflict between realism and positivism. However, more recent attempts to uncover the philosophical positions of both Einstein and Bohr have revealed that these were not so black and white. Einstein’s realism was conditioned by the strong empiricist influence in his own early experiences as a theorist and the growing wariness that led him eventually to reject Machian positivism. His was a realism born of a sense of necessity: a belief that a realist stance is the only one that leads to productive theorizing about the physical world. Bohr’s philosophy went through some quite marked changes, principally in response to Einstein’s challenges. The father of modem atomic theory could hardly subscribe to an uncompromising positivist position that rejected the reality of atoms. But the reality of the inner workings of those atoms was, Bohr contended, beyond the reach of a knowledge founded on complementary classical concepts of waves and particles. As Einstein’s challenges became deeper and more subtle, so Bohr’s position shifted to that of a distinctive anti-realism. Add to this a rhetoric in Bohr’s speeches and published writings that insisted on the logical inevitability of the Copenhagen interpretation, that insisted on its status as the only feasible interpretation, and that countenanced no other alternative, and you have dogma in the making. Heisenberg called it ‘Kopen hagener Geist der Quantentheorie’, the Copenhagen spirit of quantum theory which, he declared in 1930, ‘has directed the entire development of modem atomic physics’. Einstein frequently referred to the Copenhagen doctrine as ‘Talmudic’.