Top-notch teacher clarifies quantum physics for the layman

QED: The Strange Theory of Light and Matter, by Richard P. Feynman. Princeton, N.J.: Princeton University Press. 158 pp. $18.50. Richard Feynman, a professor of physics at the California Institute of Technology, is well known among scientists and engineers for his fresh approach to physics. ``The Feynman Lectures on Physics'' (three volumes) are modern classics. A collection of his adventures in physics (``Surely You're Joking, Mr. Feynman'') was a best seller last year and is now available in paperback. If you could choose, from all living physicists, just one to explain quantum electrodynamics (QED), you could do no better than Richard Feynman. For, in addition to his academic credits (including his 1966 Nobel Prize for fundamental progress in QED), Dr. Feynman is a superb teacher.

In ``QED,'' first given as the Alix G. Mautner Memorial lectures at the University of California at Los Angeles, Feynman describes with accuracy, insight, self-deprecating humor, and clarity the centerpiece of modern elementary particle theory -- quantum electrodynamics.

The first three of the four chapters are ``about a part of physics that is known, rather than a part that is unknown.'' Feynman states, ``My main purpose in these lectures is to describe as accurately as I can the strange theory of light and matter -- or more specifically, the interaction of light and electrons.'' To accomplish this is harder than it may seem at first. Quantum mechanics has never been easy to explain. Although it took a number of years to perfect, and a number of cherished preconceptions had to be abandoned along the way, quantum mechanics was eventually very successful in computing a number of effects observed on the atomic level.

As Feynman explains in ``QED,'' physicists do not have a mechanism for understanding the interaction of light with matter. Instead, they have a method for calculating very accurately the probabilities of events. And those probabilities depend on the experiments that are being performed. Throughout these lectures, many carefully explained examples convince the reader of the success of this new way of describing nature, giving one a sense of the triumph QED represents.

Deterministic models of the interaction of light with electrons cannot explain the many everyday phenomena -- like mirrors, oil slicks, or lenses -- and the more esoteric experiments now being performed. As wild as QED is, it is the most successful physical theory in existence today. By using QED, the probability of events happening can be calculated. All of biology, chemistry, and most of physics can be calculated this way.

Despite this emphasis on calculation in the theory, not a single equation is called on in these lectures to ``clarify'' the physics. Instead, Feynman aims to explain ``what physicists are doing when they are predicting how nature will behave.''

The last chapter is the best, if you have absorbed the first three. ``But now that we've come this far,'' says Feynman, ``being a professor -- which means having the habit of not being able to stop talking at the right time -- I cannot resist telling you something about the rest of physics.'' ``The rest'' includes protons and neutrons and all of the quarks you've heard about. In this last chapter the reader is invited to speculate about the nuclear phenomena that remain some of the science's most intriguing puzzles.

``QED'' will challenge the mind; it gives insight into everyday phenomena through extraordinary physics from one of the best teachers and practitioners of the science.

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