Many physicists will take exception to such harsh judgments (three sympathetic treatments of superstrings were reviewed here in April). But neither of these books can be dismissed as a diatribe. Both Smolin and Woit acknowledge that some important mathematics has come from contemplating superstrings. But with no proper theory in sight, they assert, it is time to move on. "The one thing everyone who cares about fundamental physics seems to agree on is that new ideas are needed," Smolin writes. "We are missing something big."
The story of how a backwater of theoretical physics became not just the rage but the establishment has all the booms and busts of an Old West mining town. Unable to fit the four forces of nature under the same roof, a few theorists in the 1970s began adding extra rooms--the seven dimensions of additional closet space that unification seemed to demand. With some mathematical sleight of hand, these unseen dimensions could be curled up ("compactified") and hidden inside the cracks of the theory, but there were an infinite number of ways to do this. One of the arrangements might describe this universe, but which?
The despair turned to excitement when the possibilities were reduced to five and to exhilaration when, in the mid-1990s, the five were funneled into something called M Theory, which promised to be the one true way. There were even hopes of experimental verification. A piece I wrote around that time carried this now embarrassing headline: "Physicists Finally Find a Way to Test Superstring Theory."
That was six years ago, and to hear Smolin and Woit tell it, the field is back to square one: recent research suggests that there are, in fact, some 10500 perfectly good M theories, each describing a different physics. The theory of everything, as Smolin puts it, has become a theory of anything.
Faced with this free-for-all, some string theorists have concluded that there is no unique theory, that the universe is not elegant but accidental. If so, trying to explain the value of the cosmological constant would make as much sense as seeking a deep mathematical reason for why stop signs are octagonal or why there are 33 human vertebrae.
Most theorists reject this postmodern fatalism, hoping for the breakthrough that points the way to the mountaintop. Gathering in Beijing this summer for the Strings 2006 conference, they packed the Great Hall of the People to hear Stephen Hawking declare: "We are close to answering an age-old question. Why are we here? Where did we come from?"
This article was originally published with the title The Inelegant Universe.