Linking Quantum Mechanics to Freshman Physics

Ivan B. Djordjević

M. L. Horner, Alfred S. Goldhaber

Quantum mechanics is known to forbid charged, spinless particles from entering an infinitely thin tube of magnetic flux, though particles which do possess spin may even be bound inside. For spin 1/2 the particles may be ‘‘quasibound,’’ so that some penetration from outside to inside is allowed. We use freshman physics and plane geometry to explore such charge-flux systems in classical electrodynamics, finding remarkable similarities to the quantum case, along with characteristic differences. Both aspects illuminate the relationship between classical and quantum physics.

Michael J. Gerver

Although I was present at a talk David Mermin gave at MIT in the 1980s, I do not recall the exchange with Victor Weisskopf over the quote from Aage Petersen. I do recall that Weisskopf was sitting in the front row of the audience. After the talk, he said something to the effect that Bell’s theorem is not so surprising, since it only says that quantum mechanics is inconsistent with a local hidden variable theory and that quantum mechanics is intrinsically nonlocal. Much of what people consider the weirdness or paradoxical nature of quantum mechanics, he said, was really due to its nonlocality; people thought that it ought to be local.What I remember most, however, is not Weisskopf’s comment, but a story told by Stephan Berko, my freshman physics professor in 1966–67, who was also in the audience at that talk. After listening to the rather inconclusive discussion among Mermin, Weisskopf, and others, Berko recalled something that Bohr said to him—in fact, the only thing Bohr ever said to him directly. Berko had been visiting the Institute for Theoretical Physics in Copenhagen in 1958 and attended a holiday party, which featured a magic show. After watching some particularly baffling magic tricks, Bohr turned to him and said, “It’s all done with smoke and mirrors!”© 2004 American Institute of Physics.

Ivan B. Djordjević

Kenji Watanabe

David Wick

reprinted in the British trade journal Physics World in 1990, three separate and 5 lengthy replies from establishment physicists were printed in subsequent issues. For outsiders, especially scientists who rely on physicist's theories in their own fields, this situation is disquieting. Moreover, many recall their introduction to quantum mechanics as a startling, if not shocking, experience. A molecular biologist related how he had started in theoretical physics but, after hearing the ideology of quantum mechanics, marched straight to the Reg­ istrar's office and switched fields. A colleague recalled how her undergraduate chemistry professor religiously entertained queries from the class - until one day he began with the words: "No questions will be permitted on today's lecture." The topic, of course, was quantum mechanics. My father, an organic chemist at a Midwestern university, also had to give that dreaded annual lecture. Around age 16, I picked up a little book he used to prepare and was perplexed by the author's tone, which seemed apologetic to the point of pleading. It was my first brush with the quantum theory. 6 Eventually, I went to graduate school in physics. By then I had acquired an historical bent, which developed out of an episode in my freshman year in college. To relieve the tedium of the introductory physics course, I set out to understand Einstein's theory of relativity (the so-called Special Theory of 1905, not the later and more difficult General Theory of 1915). This went badly at first.