THE NATURE OF REALITY

Physicist Pipes on the view from the atom.

When the atomic age burst into the world's consciousness during World War 11, people knew that life would never again be quite the same. This was, for many, the first glimpse at the revolutionary discoveries of atomic quantum physics. In demystifying the smallest details of the structure of the universe, quantum physics has implications of the greatest magnitude: it is challenging the very way we conceive of reality.

From birth we learn to deal with the world of everyday life in terms of two seemingly self-evident concepts. The first, "local objective reality," holds that an external reality exists independent of us, whether or not we choose to observe it. Although philosophers have argued the validity of this concept, it serves most of us quite well. The greenness of the grass or the blueness of the sky is there, waiting for us to see it, and it would be there even if we never noticed it.

The second concept is that a simple logic can be used to understand objective reality. In this logic some concepts are mutually exclusive while others are compatible. For example, a door can be either open or closed, but not both at the same time; however, the same door can be white and closed (or white and open) at the same time. Two particularly important concepts that are mutually exclusive are cause and effect. This is the logic that has been used to explain the physical world since the ancient Greeks. Formalized in the nineteenth century by George Boole and known as Boolean or classical logic, it is, among other things, the basis of digital computation.

Isaac Newton and those who followed him in the scientific revolution applied both local objective reality and classical logic to the world in ever-greater detail. They created classical physics, a set of theories of motion and forces that explain, to a very high degree of precision, the everyday world we live in from the flight of a baseball to the pointing of a compass needle or the flash of a bolt of lightning.

When physicists turned to the study of phenomena at the atomic level early in this century, they soon found that classical physics was insufficient to describe the results their experiments yielded. For example, when classical physics was used to predict the color of a red-hot coal, the answer always came out to be blue!

A break with classical physics occurred in 1925 when Werner Heisenberg and Erwin Schrodinger independently arrived at a novel explanation of atomic phenomena. Their theory dealt not with forces and motions but with probabilities and uncertainties. The physicists held that the determinism of classical physics is impossible in the atomic world. However, since quantum theory allows one to calculate the probabilities of outcomes for events at the atomic level, but not specific results for single events, problems of interpretation arose almost immediately, even though the predictions of the new quantum theory were in precise agreement with experimental results.

Einstein, Boris Podolsky and Nathan Rosen were among the critics. They pointed out in 1935 that some of the predictions of quantum theory apparently violated the notions of local objective reality and classical logic. They described a thought experiment, completely consistent with the new quantum theory, in which a measurement at one point seemed to cause instantaneously an effect at another point far away a clear violation of Einstein's Special Theory of Relativity.

Neils Bohr, one of the architects of quantum theory, countered that Einstein, Podolsky and Rosen were unnecessarily restricting themselves by trying to retain elements of classical physics that were not demanded by quantum theory. Bohr contended that a complete description of atomic phenomena required utilizing complementary concepts concepts that were incompatible in classical physics. It was as if the complete description of a door now required the door to be open and closed at the same time. The so-called wave-particle duality is a case in point: in classical physics a phenomenon could be described as a particle or a wave, but not as both simultaneously; quantum theory required both concepts to be used at the same time.

Laser technology has made it possible to perform laboratory experiments similar to the thought experiment proposed by Einstein, Podolsky, and Rosen. The results are precisely as predicted by the quantum theory. Bohr's interpretation was vindicated; Einstein, Podolsky and Rosen were wrong.

But the debate about reality is far from over. It has become clear that quantum theory does not allow one to hold on to both local objective reality and classical logic one or the other must go. But the theory gives no guidance about which concept should remain. The reading list below will allow readers at various levels of mathematical and scientific sophistication to join the debate.

I was a science geek," Physics Professor Bruce Pipes declares, recalling his high school days in Texas during the late fifties, right before Sputnik opened the realm of space. "I wanted to study rockets and aeronautic engineering," he says. "In Texas at that time Rice University was considered the place to go. Unfortunately it didn't offer aeronautics, so I was advised to do physics as an undergraduate and then go on to aeronautics in graduate school." He never made it to aeronautics. Physics claimed him along the way. "I had great courses in physics and math at Rice University. My professors had a tremendous influence on the direction I took," Pipes says, adding, "There was an intellectual involvement, and a competition and camaraderie among the 12 physics majors —we all went on to grad school." (As an aside, Pipes notes that about a third of Dartmouth physics majors Continue with graduate studies in physics.)

Pipes arrived at Dartmouth in 1972 after doctoral work at Stanford and jresearch positions at Leiden in the Netherlands and Louisiana State University. He specializes in very low-temperature physics including using low-temperature technology to corroborate Einstein's theory of relativity and to study magnetic fields generated by the human body.

Pipes's approach to teaching bears the influence of his Rice mentors. "Like my freshman professor, I strive to make everything seem logical," he says. Matching his care in teaching undergraduates is Pipes's devotion to working with Dartmouth's physics graduate students. He notes that he would not have come to Dartmouth to teach had there not been a graduate program in physics. "I wanted to guide the next generation of physicists," he explains. Pipes points out, however, that "it's unique to Dartmouth to conduct a graduate program without de-emphasizing undergraduate teaching."

As associate dean of the faculty for the sciences for the last five years, Pipes has striven to attract top faculty to the College and to upgrade the science facilities. In addition, he frequently lectures at alumni-club meetings and alumni seminars. "I think it's critical for scientists to communicate with people outside the sciences," he contends. "A public that lives with and votes on science and technology issues has to understand the science behind them."

Bruce Pipes making waves.