July 23, 2006
Many Worlds in One: The Search for Other Universes by Alex Vilenkin. Farrar Strauss and Giroux, 235 pages, $24.
God’s Universe by Owen Gingerich. Harvard University Press, 144 pages, $16.95.
by George Scialabba
The universe keeps getting stranger. First Einstein informed us that an object in motion is shorter than the same object at rest and that a moving clock keeps time differently from an identical clock at rest. That was special relativity. To improve matters, he then declared that there is no such thing as a straight line: ie, that space (or rather spacetime, since it seems the two are fundamentally equivalent) is curved, which also, he added, turns out to be the definition of gravity. That was general relativity.
Relativity, however, was simplicity itself compared with the next great leap forward: quantum theory. We already knew that things get a bit exotic at the atomic level. But as you get even smaller, there stop being things altogether. At the quantum (roughly, subatomic) level, there are no longer entities, or even well-defined events; there are only ranges of specified probabilities. Moreover, some subatomic events (I know I just said there aren’t any events at that level, but we – or at any rate, I – can’t do without the word) happen without a cause. Particles appear or disappear, or move across barriers, for no reason. It’s not just that we don’t yet know the cause, or even that we’ll never know the cause – there is no cause.
Lately, physicists have become convinced that the fundamental units of spacetime are strings, infinitely thin filaments that form tiny (approximately 10-25 cm.) vibrating loops, which are in fact the elementary particles, as well as curling up into nine extra but undetectable spacetime dimensions. On paper, string theory unifies relativity and quantum theory – a staggering achievement. In practice, it has proven hard to carry out, or even imagine, experiments that would test it.
You might think all these utterly counterintuitive results would have discouraged physicists and astronomers from venturing forth to construct an all-embracing explanation of the cosmos. Not a bit. As Alex Vilenkin, director of the Tufts Institute of Cosmology, relates in his wryly mind-stretching Many Worlds in One, the twentieth century was a golden age of cosmological theorizing, and the scientific community is hoping excitedly that the twenty-first century will yield the scientific Holy Grail: the Theory of Everything.
Surprisingly, Einstein was not an adventurous cosmological thinker. He made largely commonsense assumptions about the universe, including the crucial one that it was static. One of his Russian followers, Alexander Friedmann, disagreed. Discarding the static assumption, he found that the universe was expanding; and working backward, he deduced that it had all started with an explosion – a “big bang.” Most physicists agreed, but as the data and calculations piled up over the decades, it appeared that the chances of the Bang’s initial conditions being within the range necessary to produce the universe as we know it were fantastically small. If the density of matter, for example, had been 0.00000000000001 percent different, the universe either would have collapsed immediately or would now contain nothing but very thin gas.
For decades, cosmologists were bemused by the Bang. Everyone believed it had happened, but no one could say how or why. Meanwhile, astronomy and particle physics were evolving new conceptual tools: false vacuums, repulsive gravity, scalar fields, quantum tunneling, density perturbations, spacetime foam. In 1980 Alan Guth, now at MIT, proposed that a tiny chunk of superdense matter could generate repulsive gravity of sufficient strength to blow itself up, or “inflate,” at a nearly incredible rate, ending in a fireball, or shower of elementary particles. That was the big bang.
Here Vilenkin’s own discoveries enter the story. Vilenkin determined that inflation continues indefinitely, generating an infinite number of big bangs and separate, non-communicating “island universes.” He calls this “eternal inflation.” And not only are there infinitely many universes, but each one is infinitely large. Quantum mechanics, however, sets a limit on how many events can occur in a universe. It follows that “every single occurrence [is] repeated an infinite number of times.”
While you’re digesting that, I’ll just mention that Vilenkin also claims universes are “quantum fluctuations,” i.e., they emerge out of nothing and have no cause. Many Worlds in One is quite a trip to take in a little over two hundred pages. Fortunately, Vilenkin is an ideal guide, droll, plain-spoken, and literate, supplying amusing illustrations and wonderfully apposite epigrams for each chapter and section.
The eminent Harvard astronomer Owen Gingerich also covers a lot of ground in comparatively few pages, but God’s Universe is an argument rather than a history. Gingerich is a theist and a believer in intelligent design, though not in Intelligent Design, which poses as an alternative to Darwinism. Gingerich accepts Darwinism. But he denies that either Darwinism or modern cosmology makes the existence of God less likely. On the contrary, by demonstrating the extreme improbability, the sheer fortuitousness, of cosmic and biological evolution, both Darwinism and cosmology make the existence of a Creator more plausible. The likelihood that a complex protein, for example, will form by accident, by hit-or-miss evolution, is, according to one calculation, 1 in 10321. Science has revealed an astoundingly “finely textured tapestry of connections.” It might all be chance, he concedes, but mightn’t there be a smidgen of purpose, an occasional shaping touch?
Gingerich pleads for separating physics from metaphysics, efficient causes from final causes, how from why. He is more earnest, less jaunty, than Vilenkin, but just as likeable and as knowledgeable. In the end, he persuaded even a hardened skeptic like me that there might, possibly, be more to the cosmos than is dreamt of in my philosophy.
George Scialabba, a regular contributor to the Book Section, has just published Divided Mind (Arrowsmith Books).