Reaping the Triumphs of Modern Physics

Article excerpt

The theoretical physicist Lee Smolin examines the role of time in the universe.

Time Reborn. From the Crisis in Physics to the Future of the Universe. By Lee Smolin. Illustrated. 319 pages. Houghton Mifflin Harcourt, $28; Allen Lane, Pounds 20.

In one of the more fanciful conceptions of nature, the British physicist and philosopher Julian Barbour proposed that the world is just a "heap of moments," each an instant of frozen time. There is no order to the moments, no sequence, no cause-and-effect relationship. We exist only from moment to moment. If we experience time passing, it's because this particular moment has memories of another moment woven into it. Some moments are interesting: They contain complexity, stars and planets, life. Others are boring: They contain only energy, or perhaps nothing at all.

In "Time Reborn," Lee Smolin, a physicist and author of "The Life of the Cosmos" (1997) and "The Trouble With Physics" (2006), recounts Mr. Barbour's cosmology with some admiration and then goes on to offer even more radical ideas of his own. Mr. Smolin argues that the Now has been taken out of physics, and it is time to put it back in.

For example, he says that Newtonian physics expresses the notion that the future is determined by the past and so, in a sense, the future already exists. He rightly remarks that Einsteinian physics frames time as a relative concept in which the line between past and future varies with the observer. To remedy these perceived problems, he suggests major structural revisions to the two fundamental pillars of modern physics, relativity and quantum mechanics. His book, a mix of science, philosophy and science fiction, is at once entertaining, thought-provoking, fabulously ambitious and fabulously speculative. Although full of wonderful metaphors and analogies, it may prove heavy sledding for many readers.

Twentieth-century physics has brought us two kinds of strangeness: strange things we more or less understand, and strange things we do not understand. The first category includes relativity and quantum mechanics. Relativity reveals that time is not absolute. Clocks in relative motion to each other tick at different rates. We don't notice relativity in daily life because the relative speed must be close to the speed of light before the effects are significant. Quantum mechanics presents a probabilistic picture of reality; subatomic particles act as if they occupy many places at once, and their locations can be described only in terms of probabilities. Although we can make accurate predictions about the average behavior of a large number of subatomic particles, we cannot predict the behavior of a single subatomic particle, or even a single atom. We don't feel quantum mechanics because its effects are significant only in the tiny realm of the atom.

The category of strange things we do not understand includes the origin of the universe and the nature of the "dark energy" that pervades the cosmos. Over the past 40 years, physicists have realized that various universal parameters, like the mass of the electron (a type of subatomic particle) and the strength of the nuclear force (the force that holds the subatomic particles together within the centers of atoms), appear to be precisely calibrated. That is, if these parameters were a little larger or a little smaller than they actually are, the complex molecules needed for life could never have formed. Presumably, the values of these parameters were set at the origin of the universe. Fifteen years ago, astronomers discovered a previously unknown and still unexplained cosmic energy that fills the universe and acts as an antigravity-like force, pushing the galaxies apart. The density of this dark energy also appears to be extraordinarily fine-tuned. A little smaller or a little larger, and the life-giving stars would never have formed. …