String theory used to get everyone all tied up in knots. Even its practitioners fretted about how complicated it was, while other physicists mocked its lack of experimental predictions. The rest of the world was largely oblivious. Scientists could scarcely communicate just why string theory was so exciting--why it could fulfill Albert Einstein's dream of the ultimate unified theory, how it could give insight into such deep questions as why the universe exists at all. But in the mid-1990s the theory started to click together conceptually. It made some testable, if qualified, predictions. The outside world began to pay attention. Woody Allen satirized the theory in a New Yorker column this past July--probably the first time anyone has used Calabi-Yau spaces to make a point about interoffice romance.

Few people can take more credit for demystifying string theory than Brian Greene, a Columbia University physics professor and a major contributor to the theory. His 1999 book The Elegant Universe reached number four on the New York Times best-seller list and was a finalist for the Pulitzer Prize. Greene is now host of a three-part Nova series on PBS and has just completed a book on the nature of space and time. SCIENTIFIC AMERICAN staff editor George Musser recently spoke with him over a plate of stringy spaghetti. Here is an abridged, edited version of that conversation.

   
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