Magazine article Science News

A Midrash upon Quantum Mechanics

Magazine article Science News

A Midrash upon Quantum Mechanics

Article excerpt

A Midrash Upon Quantum Mechanics

The Copenhagen Interpretation ofquantum mechanics has become the standard way of explaining the physical and 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, and he didn't escape all controversy over it (although the quote above is a bit of an exaggeration). Bohr did die before the experimental and theoretical developments that have transposed the debate over the appropriateness and adequacy of the Copenhagen Interpretation into a new key, and he may well have been lucky to have escaped when he did.

"There is no authoritative codificationof CI [the Copenhagen Interpretation],' write T. Gornitz and C. F. von Weizsacker of the Max Planck Institute in Starnberg, West Germany, in their formal presentation to the recent Loyola Conference on Mathematical and 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 and [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 becalled a Copenhagen attitude. It concentrates on observable phenomena, makes statistics and probability central to its understanding, considers quantum mechanics primarily a theory of knowledge or information and becomes a kind of physica negative (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.

From the beginning, critics have saidthat CI is unrealistic and too positivistic, and gives too little information to be a complete physical theory. Einstein and Louis de Broglie put forward alternatives that they believed were more realistic or more complete. In the opinion of many physicists, recent experiments have finally blown both of those suggestions out of the water, but the same experiments bring quantum mechanics out of the realm of the unseen and untouchable (atoms, unclei, elementary particles) and into the realm of macroscopic objects we can handle--up to and including the whole universe itself.

In consequence, the need for viableinterpretations of quantum mechanics that will come to grips with underlying reality and will try to deal with the problems of applying a basically statistical mathematics to the fate of single objects is even more strongly felt. Several new interpretations have arisen in recent years, and one of the purposes of the Loyola conference was to discuss the adequacy and relation to CI of some of them, particulary the Transactional Interpretation of John G. Cramer of the University of Washington in Seattle.

Interpretational problems are not newin physics, but quantum mechanics raises them to new levels of complexity. How one translates mathematics into physics and the semantic problems involved with the words chosen to effect the translation are questions that accompany any physical theory. Gramer, Gornitz and Weizsacker use Newton's second law as an example. "[We] define the physical meaning of the mathematical quantities t, x, F, m by means of words which are available in the English vernacular: time, body, force, etc.,' Gornitz and Weizsacker write. "But are we sure what these words mean? Every student of the empirical foundations of classical mechanics becomes aware of the difficulty of defining them unambiguously. …

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