String theory

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THE COSMIC LANDSCAPE: STRING THEORY AND THE ILLUSION OF INTELLIGENT DESIGN

By Leonard Susskind

Little, Brown, $24.95, 403 pages

REVIEWED BY JEFFREY MARSH

The greatest triumphs of 20th century physics were the revolutionary theories of quantum mechanics and relativity. The former brought unparalleled accuracy to the description of matter on the smallest scale, while the latter provided an explanation of the behavior of the universe on the largest scales of space and time. The greatest disappointment for physicists during most of the century, from Albert Einstein down, was their inability to unify the two theories. In the 1980s, though, a new approach called string theory seemed to offer a way to overcome the obstacles and provide a unified picture of nature.

In "The Cosmic Landscape," Leonard Susskind, a physics professor at Stanford who was one of the originators of string theory, presents as comprehensible an account as a layman can imagine of this mathematically complex subject, and explains why he is willing to accept the bizarre picture it presents of the universe.

Mr. Susskind is a very entertaining writer, and further enlivens his breezy presentation of seriously challenging topics with many personal asides describing both his own history and his lively debates with other physicists, including numerous Nobel laureates and world-famous figures.

He begins with an account of the so-called standard model of elementary particles, which deals with the three forces that describe the behavior of atoms and nuclei. The first force is electromagnetism, which binds electrons to atomic nuclei and underlies chemistry and biology. Electromagnetism was tidied up in the 1940s by a theory called quantum electrodynamics (QED).

In the 1960s and 1970s, the protons and neutrons that inhabit the nucleus were dissected by a theory called quantum chromodynamics (QCD) into smaller building blocks called quarks. Unlike protons and neutrons, quarks cannot be examined individually, because the force that holds them together, called the strong force, binds them ever more tightly as attempts are made to pull them apart.