Casanova of the Mind : GENIUS: The Life and Science of Richard Feynman, <i> By James Gleick (Pantheon Books: $27.50; 530 pp.)</i>

Save for the beatified Einstein, few physicists have become famous. Robert Oppenheimer or Werner Heisenberg might be exceptions. But how many other physicists can we pick out of the serried ranks?

Maybe one other--Richard Feynman, who won the requisite Nobel Prize and taught for many years at Cal Tech before becoming famous, first as a popular author and then as a member of the panel examining the Challenger space shuttle disaster in 1986.

Feynman was famous, but perhaps for the wrong reasons, as James Gleick asserts in his new biography of the scientist. Before his death of cancer in 1988, Feynman’s fame had become the mask of a carefully cultivated persona, argues Gleick, a persona that actually obscured the man’s real accomplishments.

It is Gleick’s aspiration to use Feynman’s life as a window into the history of modern physics, our “modern secular religion,” as Gleick calls it. He has performed a monumental task of sifting through Feynman’s papers and interviewing many of the important figures in his life. The book is ambitious and thorough, but Gleick has a tough assignment when he follows Feynman in retelling stories that the scientist himself had already narrated. Feynman--or actually Feynman and his collaborators, since he never really wrote any of the books that bear his name--did a brilliant job of bringing his raucous Broadway patter to the page.

The Feynman myth began expanding outward to become part of our national heritage in 1985, when he published a collection of autobiographical squibs called “Surely You’re Joking, Mr. Feynman!” Assembled by the son of one of his colleagues, this as-told-to book became a bestseller. It was followed after Feynman’s death by another grab bag of stories titled “What Do You Care What Other People Think?,” which also became a bestseller.

Not since James Watson’s “Double Helix”--a book greatly admired by Feynman--had a scientist exposed himself so brazenly to the public. While Watson admitted that scientists have egos, Feynman confessed that they also have ids. This “noetic Casanova,” as Gleick calls him, put science next to sex, where it belongs in alphabetical order. His books are full of brainy pranks and skirt-chasing honed to a science of its own.

The Feynman myth charts the following trajectory: A gifted Jewish kid from Far Rockaway--a genius, some might say--after a meteoric ascent through MIT and Princeton, arrives at Los Alamos as one of the youngest in a select group of bomb builders. In an age before machines could do this kind of work, he was the fastest computer in the West.

He learned how to break into safes, pick up showgirls in Las Vegas and play the conga drums in Brazil, while computing his way to the forefront of theoretical physics, where his intuitive, informal style, and the course of studies gathered by his friends into “The Feynman Lectures,” became the model for younger physicists to emulate.

“Most physicists are nerds,” says a practicing friend of mine, “but Feynman was not a nerd. He was articulate, charismatic, funny, heroic. He was the person we all wanted to be.”

Aside from his books, it was television that made Feynman a national folk hero. When President Reagan appointed a NASA-friendly panel of experts to examine the Challenger disaster, the only uncompromised member of the group was Richard Feynman. He would become famous as the man who demonstrated the cause for the disaster, and in the process revealed the back-scratching chain of command and mess of old-boy contracts that made the shuttle a technological kludge ripe for disaster.

Feynman’s experiment was replayed for weeks on the nightly news: The professor pries a rubber gasket out of a model of the shuttle, squeezes it with a C clamp, and dunks the apparatus into a glass of ice water. In a few seconds he has found the “rat” the nation was looking for, an inelastic O-ring with no tolerance for cold temperatures. On prime-time TV, 250 million people were being instructed on what physics is good for: tinkering up the solution to a problem; reproducing with known variables a previously unexplained event.

“I have tried not to lean on them too heavily,” Gleick says of these and other stories narrated in Feynman’s books--stories that Gleick claims are “mostly accurate, but strongly filtered.” So what did Feynman leave out in the telling? Behind the safecracker, conga drummer and practitioner of what he called “aggressive dopiness” lay a scientist troubled by his engagement in building the atomic bomb and someone whose life had more shadows and conflict than he ever let on.

The most poignant example of this darker Feynman is a letter he wrote to his first wife two years after she died of tuberculosis. “You, dead, are so much better than anyone else alive,” he wrote to his beloved childhood companion, before ending with, “P.S. Please excuse my not mailing this--but I don’t know your new address.”

“That he had written such a letter to a woman he loved, two years after her death, could never become part of the iconography of Feynman, the collection of stories and images that was already beginning to follow him about,” writes Gleick. “The Feynman who could be wracked by strong emotion, the man stung by shyness, insecurity, anger, worry, or grief--no one got close enough anymore to see him.” Instead, his life got transposed into stories “in which Feynman was an inadvertent boy hero” mastering the world “by virtue of his naivete . . . commonsense cleverness . . . and emperor’s-new-clothes honesty.”

Feynman is the perfect subject, and Gleick’s biography succeeds in opening a grand perspective onto the history of quantum mechanics and particle physics during the half-century in which they came to dominate science in the United States. As the bomb builders gathered at Los Alamos, writes Gleick, “a final valedictory was being written to the Protestant, gentlemanly, leisure class structure of American science,” which would come to be dominated in the postwar years by increasingly expensive accelerators and other experimental toys.

Today the big-ticket items are harder to finance, and many of the best graduate students, including Feynman’s son, have gone into computers or molecular biology or new areas in physics, such as chaos theory, which was the subject of Gleick’s last book. In this context--and in spite of his biographer’s claims--Feynman was more a marker at the end of an era than a signpost leading into the next.

He got “the Swedish prize,” as his colleague and arch-rival Murray Gell-Mann puckishly calls it, for independently inventing in the 1940s, with Schwinger and Tomonaga, the theory of quantum electrodynamics. This was the last big development in the field, a grand finale to 20 years of discoveries in quantum physics. But perhaps the final word on the subject is Gell-Mann’s, whose quarks are the last subatomic particles--or metaphors--to be squeezed into the model.

As its title indicates, “Genius” spends a lot of time discussing the subject of genius and speculating on the reasons for our current shortfall in producing geniuses. One suspects the problem lies not in the diminished capacity of our age, but in the fact that this 19th-Century concept doesn’t quite fit the specialized, speedy, cooperative nature or science today.

Feynman himself debunked any claims to genius. He barely squeaked into graduate school at Princeton with some of the lowest GREs in English that the school had ever admitted. His second wife thought she was married to “an uncultured man with a Ph.D.” “We are not that much smarter than each other,” was his own evaluation of the subject.

After Feynman, the next modern scientist to grasp fame’s golden ring is Stephen Hawking. But where Hawking’s ideas partake of a kind of Church of England domesticity, Feynman’s are infused with tonic doubt. “We may now be near the end of the search for the ultimate laws of nature,” intones Hawking. Feynman’s rejoinder (borrowed from another occasion): “I’ve had a lifetime of people who believe that the answer is just around the corner.”

“I don’t have to know an answer,” said the prophet from Pasadena. “I don’t feel frightened by not knowing things, by being lost in a mysterious universe without any purpose, which is the way it really is as far as I can tell.”

“Feynman was a larger-than-life character, a mixture of hero and pain-in-the-ass,” said one of his colleagues. I found myself moved by the final pages of Gleick’s book, sorry to see this vital life flicker out in a bon mot. “I’d hate to die twice,” were Feynman’s last words. “It’s so boring.” For all Feynman’s flaws--no, because of his flaws and time-bound thoughts--this is a life worth reading.