Notes of an Ex-Physics Student

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Notes of an Ex-Physics Student

More years ago than I care to admit -- although physicists will be able to date it -- my professor came running into the laboratory where I happened to be working, waving a copy of PHYSICAL REVIEW LETTERS. "They have found the neutrino," he yelled. "Can you imagine that?" Well, we could imagine it; but imagine it was all we could do.

Something of the same excitement returned as I sat through recent conferences on quantum physics and quantum measurement (SN: 1/11/86, pp. 26, 28; 2/1/86, p. 70; 2/8/86, p. 87), and I wondered how to convey it without being accused of biasing the news. It is worth quoting quantum physics specialist Anthony J. Leggett of the University of Illinois at Urbana-Champaign, as he puts the point on it: "The quantum measurement paradox is no longer a matter of 'theology.' It has become an experimental subject."

Theology is a subject in which one cannot do experiments. All one can hope is to be able to bring some experience to the contemplation of it. In our beginning physics courses we had discussed all these famous thought experiments that demonstrate the points and arguments of the new physics: Schrodinger's cat, Einstein's box, quantum interference, Einstein-Podolsky-Rosen paradox, single slit, double slit, etc., etc. Memories of their details began to surfaces as I listened to the talk in Cambridge and in New York.

Suddenly these experiments that nobody could ever do are on the agenda in serious laboratories. Nobody could do them because the "real" world with its multiple connections, its dissipation, its gritty frictional hardness, made them impossible. The cleverness of experimental physicists is now getting around these difficulties. Sam Werner of the University of Missouri at Columbia proposes to hang a neutron-diffraction apparatus upside--down from the ceiling--I'm not making this up--to test the effect of gravity on neutrons, particularly their wavelike behaviors.

Years ago the neutrino was a kind of ghost invoked by theory for its purposes. I doubt that my professor ever expected to see evidence of an actual one in his lifetime. Likewise I did not expect to see results of these quantum mechanical experiments in mine. The whole thing comes as a tremendous surprise. The leaders of the New York Academy of Sciences say that when they were asked to convene a meeting on quantum measurement, they hesitated. They were not sure there was really anything new to talk about. When they began to probe, they discovered this rich underground. Suddenly the relevant question is: "How many wave equations can collapse on the point of a pin? …