Quantum Mechanics, Computers, WIMPS.(BOOKS)(SCIENCE)

Article excerpt


Richard Feynman, the virtuoso physicist with an unmatched insight into the quantum world, once famously remarked that "Nobody understands quantum mechanics." Despite this disturbing situation, physicists were able to use the counterintuitive results of quantum mechanics to construct the panoply of devices, from nuclear bombs to lasers, MRI machines and electronic computers, that characterized the astonishing technological progress of the 20th century.

Barry Parker, for 30 years a physics professor at Idaho State University and author of a dozen popular science books, provides in Quantum Legacy: The Discovery that Changed our Universe (Prometheus Books, $29, 282 pages) a sprightly and intelligible account of quantum physics and what it has wrought.

The first part of Mr. Parker's book is a conventional historical account of the development of quantum theory, brought to life by numerous anecdotes. The theory began as a desperate mathematical maneuver by Max Planck to explain the spectrum of so-called "black-body" heat radiation. Defying the well-established principles of classical physics, Planck suggested that matter and radiation did not interact in a smooth and continuous way, but rather only via discontinuous finite packets, or "quanta," of energy. This idea was soon extended by Albert Einstein to explain several more otherwise incomprehensible phenomena, and later by Niels Bohr to provide a quantitative explanation of the spectrum of the hydrogen atom.

In the 1920s, this "old" quantum theory, a hybrid of classical ideas and ad-hoc rules, was superseded by the more sophisticated and far reaching quantum mechanics associated with the names of Schrodinger, Born, Heisenberg and Dirac. The new theory showed how matter and radiation possessed both particle-like and wave-like properties. This meant that in principle nature could only be described statistically, a dramatic departure from the classical view that the need sometimes to use statistics was simply a consequence of limitations on the human ability to calculate everything precisely.

This idea scandalized Einstein. In a long debate with Bohr, Einstein showed that assuming quantum mechanics was the ultimate description of reality showed that it implied that particles, no matter how far apart from each other, must be able to "communicate" instantaneously, contradicting a basic assumption of physics. In the 1980s, experiment showed that this scandalous situation was in fact true.

The second part of the book describes the practical consequences of the quantum revolution, including lasers, nuclear energy, DNA and molecular biology, and solid state devices like the microchips at the base of today's computers hardware. Mr. Parker stretches to include a long chapter on the history of computing, much of which has nothing to do with the quantum devices that make computers work so quickly. He might have done better to discuss some of the open problems of quantum mechanics with which today's researchers are struggling, rather than leaving the impression that the theory's paradoxical underpinnings were resolved back in the 1930s by Bohr's "Copenhagen Interpretation."

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Some of the different ideas being explored by current researchers are discussed in The Universe Next Door: The Making of Tomorrow's Science (Oxford University Press, $26, 191 pages) by Marcus Chown, a British astrophysicist turned bestselling science writer. One particularly unorthodox approach was put forth 45 years ago by Hugh Everett in his PhD thesis, and has gained more adherents in recent years. This "Many Worlds" interpretation differs from Bohr's approach in explaining the probabilistic nature of quantum mechanics.

According to Everett, the universe is continuously splitting into different universes, each of which is described by a different possible states. …