The String Snaps Back

Theoretical physics is perhaps the most abstruse field in science. Its most rarefied subfield is called string theory, a mathematical framework based on the notion that matter is made not of individual particles but rather of tiny, vibrating string-like loops.

The scientists now constructing string theories, like Columbia University professor Brian Greene, are clearly more capable of abstraction than most of us; by age 5, Greene was multiplying 30-digit numbers. Nevertheless, recent developments in string theory show that at bottom, the field is a familiar human quest to find an elegant order underlying the seeming hurly-burly of life. Like medieval knights seeking the Holy Grail, many string theorists are motivated by a quest to find a powerful talisman: a “grand unified field theory” that shows the still elusive links between the four fundamental forces of nature: gravity, the electromagnetic force and the strong and weak nuclear forces.

In the early 1980s top physicists flocked to string theory because its ideas seemed at once more elegant and sophisticated than the then-leading school of theoretical physics, called quantum field theory.

Since the early 20th century, physicists have been unable to use quantum theory to unite the fundamental forces of nature. They suspected their progress was being blocked by quantum theory’s notion of particles as zero-dimensional points in space. While wonderfully convenient for doing math, that notion was too simplistic to fully capture nature’s subtler behavior.

In the mid-1970s, Caltech’s John Schwartz envisioned particles instead as having tiny strings extending along one axis and found to his amazement that calculations based on his model showed new links between the fundamental forces.

String theory’s stardom faded in the mid-1980s when its math became increasingly complex and its approaches, like one envisioning 26 dimensions, increasingly fantastical. In 1986, Harvard physicists Paul Ginsparg and Sheldon Glashow worried that the field was becoming a kind of “medieval theology” that would undermine science itself. “For the first time since the Dark Ages,” they wrote in 1986, “we can see how our noble search may end with faith replacing science once again.”

String theorists led by Caltech’s Schwartz, however, persevered, and in the last three years their faith has been validated with string theories that have satisfied doubters like Ginsparg and Glashow by fulfilling the sine qua non of physics: predicting the behavior of matter.

For example, recent research by Harvard’s Andrew Strominger shows how string theories help explain the behavior of black holes, and not-yet-published research by Stanford’s Raman Sundrum and Princeton’s Lisa Randall advances Schwartz’s research by suggesting how the latest atom smashers can be used to measure nature’s most physically obvious and yet theoretically baffling force, gravity.

Schwartz has explained that he never gave up on string theory largely because “it is too beautiful a mathematical structure to be completely irrelevant to nature.” This could be construed as a theological quest, but hardly one for Ginsparg and Glashow to worry about. As string theory’s recent successes in elucidating the forces of nature show, science is usually helped, not hindered, by the faith of scientists like Schwartz.