The Good and Bad of String Theory

The most celebrated theory in modern physics faces increasing attacks from skeptics who fear it has lured a generation of researchers down an intellectual dead end.

In its original, simplified form, circa the mid-1980s, string theory held that reality consists of infinitesimally small, wiggling objects called strings, which vibrate in ways that yield the different subatomic particles that comprise the cosmos.

Advocates claimed that string theory would smooth out the conflicts between Einsteinian relativity and quantum mechanics and the result would be a unifying "theory of everything," which could explain everything from the nature of matter to the Big Bang to the fate of the cosmos.

Over the years, string theory has simultaneously become more frustrating and fabulous. On the one hand, the original theory has become very complex, one that posits an 11-dimensional universe, far more than the four-dimensional universe of Einstein. The modified theory is so mathematically dense that many Ph.D.-bearing physicists haven’t a clue what their string-theorist colleagues are talking about.

On the other hand, new versions of the theory suggest our universe is just one of zillions of alternate, invisible universes where the laws of physics are radically different. String buffs claim this bizarre hypothesis might help to explain various cosmic mysteries.

But skeptics suggest it’s the latest sign of how string theorists, sometimes called "superstringers," try to colorfully camouflage the theory’s flaws, like "a 50-year-old woman wearing way too much lipstick," jokes Robert B. Laughlin, a Nobel Prize-winning physicist at Stanford. "People have been changing string theory in wild ways because it has never worked."

Already, the split over string theory has caused tensions at some of the nation’s university physics departments. "The physics department at Stanford effectively fissioned over this issue," said Laughlin, now on sabbatical in South Korea. "I think string theory is textbook ‘post-modernism’ (and) fueled by irresponsible expenditures of money."

The dispute could become explosive this year, with the publication of contrarily minded books by two of the best-known and most eloquent scientific popularizers of physics, string theorist Michio Kaku of City University of New York and astro-physicist- particle theorist Lawrence Krauss of Case Western Reserve University in Cleveland.

Skeptics have long mocked string theory as untestable, because experimental studies of it would require machines of huge scale, perhaps even as big as the solar system.

In his new book "Parallel Worlds", Kaku disagrees and argues that the first experimental evidence for string theory might begin to emerge within several years from experiments with scientific instruments such as a new particle accelerator, the Large Hadron Collider, which opens for business near Geneva in 2007.

Kaku, whose previous books include the acclaimed "Hyperspace" and equation-packed textbooks on string theory, also suggests that humans might eventually travel to those alternate universes, perhaps via hypothetical portals in space called wormholes.

Such claims dismay Krauss, a leading expert on cosmic dark matter and dark energy.

The dispute has split partly along subdisciplinary lines, and mirrors a timeless squabble in the philosophy of science: Which is more important for scientific innovation — theoretical daring or empirical observations and experiments?