January 09, 1998|By Douglas M. Birch | Douglas M. Birch,SUN STAFF

Edward Witten was back in his home town of Baltimore this week, gently fretting over the lack of recent progress in his effort to draw a basic blueprint of the universe.

No one seems to be better suited for this task than the 46-year-old physicist, considered by some of his colleagues to be the smartest of them all. And no one has generated more brilliant insights into what he calls "the foundation of everything that's known."

Not only is his work cited by other physicists more often than anyone else's, he has already won a Fields Medal, the mathematics world's equivalent of a Nobel prize. Now based at the Institute for Advanced Study at Princeton, Witten was in Baltimore Wednesday for the American Mathematical Society's annual meeting, and delivered the 71st annual Gibbs lecture. He one of a few non-mathematicians to be so honored. Another was Albert Einstein, who delivered the 11th Gibbs lecture in 1934.

The current lull in discoveries in Witten's field follows three years of conceptual leap-frogging. So perhaps it is understandable that Witten, during an interview at the Renaissance Harborplace Hotel, seemed preoccupied.

The trim, 6-foot-2 scientist sat, back straight and shoulders squared, and poured himself a glass of water from a sweating aluminum pitcher.

"There are some signs that the field is starting to get stuck again, progress is slowing down," he lamented, speaking in his soft, almost childlike voice. "We might be entering a period like the late '80s and early '90s, where you start filling in more details."

Witten is the leading proponent of string theory, more formally known as superstring theory, which holds that while molecules are made of atoms and atoms are made of tinier objects called quarks, quarks are constructed of even smaller bits called strings.

Strings, which are billions of times smaller than the atom, have been described as mathematical curves, tiny threads of energy or rips in the fabric of space-time. These objects, far too small to be seen by even the most powerful microscopes, are thought to be either open-ended, like lengths of rope, or looped, like rubber bands.

As they fly around the subatomic world, these strands vibrate like violin strings. But instead of producing musical sounds, their complex harmonics create the whole wild and woolly menagerie of fundamental particles -- from electrons and protons to positrons and neutrinos -- that are the construction materials for the universe, from sunbeams to silly putty.

When they were first dreamed up in the late 1960s, strings quickly became popular. They instantly solved a nagging problem. They reconciled the two theories that dominate modern physics.

One is Einstein's theory of general relativity, the notion that gravity results from the way matter bends space. The other is quantum mechanics, which accurately predicts the behavior of matter at very tiny scales.

The main problem, Witten said, is that quantum mechanics is not compatible with general relativity. Specifically, quantum theory makes gravity impossible, while relativity makes it inevitable.

String theory bridges this gap, allowing the quantum world to produce gravity.

Superstrings seemed like a candidate for the long-sought "Theory of Everything," a small number of equations that would vastly simplify human understanding of the physical world. Witten was smitten. But there were several big problems.

Early on, it was clear that superstrings only exist in 10 dimensions, six more than the four dimensions we humans experience -- up and down, left and right, forward and back and the fourth dimension, time. And there seemed to be an infinite number of potential string theories, which, to say the least, complicated the search for the one true theory.

String theorists quickly disposed of the surplus dimensions. They were, they said, probably rolled up tightly like little sleeping bags and stowed in the sub-quark realm. In the human-scale world we live in, they remain invisible.

But the hunt for a consistent string theory among all the possible ones proceeded slowly, and fueled the skepticism of many anti-string physicists, who rebelled at the notion of curled-up dimensions.

"It was difficult to show that there were consistent quantum string theories," Witten said. "A huge amount of work went into that in the 1970s and early 1980s." Finally, by the mid-1980s, five rugged and equally plausible theories emerged. Interest in string theory revived.

Five theories is fewer than an infinity, but it's still troubling.

"If one of them describes our world," Witten asked, "who lives in the other worlds?"

So Witten and others began searching for links between these theories. Then, in 1995, Witten made a breakthrough. He realized that, by changing the superstring picture, all five of the theories could be viewed as instances of a single, more fundamental theory.