Albert Einstein labored unsuccessfully for decades to create a theory that would merge relativity and quantum physics into one tidy mathematical package. But where Einstein failed, physicists may finally be on the verge of success, largely thanks to Edward Witten, generally considered the greatest theoretical physicist in the world. "Ed is unique," says John Schwarz, a theorist at Caltech, "the kind of person who comes along once a century."
The tall, thin, soft-spoken Witten, 52, didn't even set out to be a scientist. He majored in history at Brandeis and originally planned to be a journalist but ended up getting a Ph.D. in physics instead. By the mid-1980s, some of his colleagues had decided that the answer to Einstein's failed dream was to treat the building blocks of matter--quarks, photons, electrons and such--as minuscule, vibrating strings of energy rather than as particles. But superstring theory was considered no more than an esoteric and eccentric subspecialty until Witten (by this time a full professor at Princeton) turned his attention to it. Before long he was the dominant player in the field, and string theory was the hottest area of physics. Many of the big developments in string physics--the kind of ideas that break through theoretical logjams and bring everyone to a deeper level of understanding--can be traced to Witten. "Most other people have made one or two such contributions," says Juan Maldacena, who, like Witten, is at Einstein's old stomping ground, the Institute for Advanced Study in Princeton. "Ed has made 10 or 15."
What sort of contributions? Don't ask, unless twistor-space methods and Yang-Mills theories are your cup of tea. But if Witten's string theory is right, it means that the quest Einstein began to find the ultimate laws of the universe may nearly be over. The proof, however, may still be many years off. Witten once called string theory "a bit of 21st century physics that somehow dropped into the 20th century." If so, Witten clearly has the 21st century mind to handle it. --By Michael Lemonick