The Fabric of the Cosmos: Space, Time, and the Texture of Reality by Brian Greene. Alfred A. Knopf, $28.95, 569 pages.

The News & Observer

February 15, 2004

It’s About time, It’s About Space

By Phillip Manning

Brian Greene’s mother read only a few pages in his previous book, the bestseller “The Elegant Universe” before putting it down, saying “it gave her a headache.” That book introduced string theory, a complex mathematical construct that may solve one of physics’ deepest problems: the unification of Einstein’s theory of relativity — which specifies a cosmos composed of smooth spacetime — with quantum mechanics, which deals with the discontinuous, jittery, uncertain universe built of subatomic particles. In “The Fabric of the Cosmos,” Greene revisits some of the ground he plowed in “The Elegant Universe,” but he digs deeper into the fine structure of space and time. This book may give his mother a migraine.

Greene and the thousand or so other theoretical physicists who are
probing the universe’s big questions live in a world that is different from the one the rest of us inhabit. It is a world of strings that vibrate in nine or ten spatial dimensions, a world of black holes and wormholes, of quantum entanglement and multiple universes, a place where gravity repulses rather than attracts. It is a world of very large numbers (one number used in calculations is so big it takes up an entire page) and unimaginably small ones (Planck time, for instance, is 0.0 … 01 second, where the … represents 41 zeros). It is also a world that no one has ever seen and may not exist. No test has ever been devised to prove or disprove string theory or the presence of multiple universes or the host of other hypotheses and possibilities that Greene offers.

Why then, one might ask, should you read this book? First, it introduces the reader to the mind-boggling landscape of cutting-edge theoretical physics, where mathematics rules supreme. But a more important reason is to better understand the universe we live in, even if the nature of that universe is counterintuitive to our everyday experience. Aristotle wrote that “All men by nature desire knowledge.” Aristotle was right, but the world is rife with people who are uninterested in knowledge unless it benefits them directly — to get a better job, make more money, relieve stress, and so forth. However, some people want more. They are curious about how the universe works at the most fundamental level. And those readers will love this book.

“The Fabric of the Cosmos” is literate, wide ranging, well written, lavishly illustrated, and packed with analogies featuring everything from ultrafast skateboards to a movie star working her way through the paparazzi. The early chapters educate readers on the basics of relativity, quantum mechanics, entropy, and cosmology. The last half of the book concerns string theory and other speculative science.

String theory posits that all matter and energy in the universe is
composed of tiny vibrating strings. Although much remains to be worked out, string theory appears to resolve the conflict between relativity and quantum mechanics. This is exciting stuff, and it explains why many physicists are devoting their careers to a untested theory that may prove to be a dead end.

But string theory is just the starting point for Greene. He dips his toe into M-theory, a recent development that attempts to merge five variants of string theory into one. M-theory leads the reader into a new universe that may contain membranes (“branes” to physicists). Branes come in several varieties, including the delightfully named p-branes. Toward the end of the book, Greene becomes even more speculative, devoting a chapter to far-fetched concepts of time travel and teleportation. Surprisingly, a common thread runs through all these theories and
speculations. Greene is not just manufacturing ideas. All of these
worlds and possibilities spring from mathematics, and the physicists are going wherever the math leads them. If there is a universal language, a code of revelation, it is mathematics — that system that springs from mankind’s brain and yet seems able to unlock the to the mysteries of the universe (or universes!). The reliance of theoretical physics on mathematics leads to a problem.

Because “The Fabric of the Cosmos” is aimed at a popular audience, it comes with nary an equation in the text. Trying to write a book about mathematical topics without any math is a tough undertaking, but Greene does an admirable job in explaining the disparate theories with well-chosen words and analogies. Still, the highly mathematical nature of these theories may leave readers wondering why they should care about theoretical physics at all. Does the math ever connect to reality?

Indeed, it does; one theoretical study, for example, has led to an exciting confirmation of the quantum nature of the early universe. About 40 years ago, scientists discovered that space was suffused with microwave radiation, a remnant of the big bang. Back when television sets had antennas, some of the snow that interfered with “Gunsmoke” came from this radiation, a blurry gift from the big bang itself.

The temperature of the radiation was uniform throughout space and measured only a few degrees above absolute zero, about -455 degrees Fahrenheit. This finding was predicted by theoretical cosmologists and was a dramatic confirmation of the big bang theory. But even better news was in store for the theoreticians. One of cosmology’s biggest puzzles concerned the uniform distribution of matter and energy shortly after the big bang. What caused matter to clump into the stars and galaxies that we see today?

Inflation theory,another mathematical construct with no evidence to support it, answered that question. If space expanded enormously for a very short period just after the big bang, quantum jitters arising from the uncertainty principle would produce nonuniformities that would grow into today’s lumpy universe. However, inflation theory also predicted that the temperature of the microwave background radiation should vary slightly. And, in 1992, precise temperature measurements by a satellite showed that the predicted temperature fluctuations did exist and were identical to those predicted by theory. This was a stunning triumph for theoretical physics, and dramatic testimony of the quantum nature of our universe. “The more than 100 billion galaxies, sparkling throughout space like heavenly diamonds, are nothing but quantum mechanics writ large across the sky,” writes Greene. Much as inflation theory helped explain the cosmos, string theory and its alternatives may one day give us even deeper insights into our universe and its origins.
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