Thursday, April 21, 2005

Oppenheimer centenary

2004 was the 100th anniversary of J. Robert Oppenheimer's birth. See here for a partial list of recent biographies, and here for a Times review of two of them.

I can think of few figures as complex as Oppenheimer. "American Prometheus" (the title of one of the biographies) is a suitable characterization. From the Times review: "American Prometheus" is a work of voluminous scholarship and lucid insight, unifying its multifaceted portrait with a keen grasp of Oppenheimer's essential nature. What did he do upon finding himself in a Capitol Hill elevator with Senator Joseph McCarthy, the embodiment of Oppenheimer's comeuppance? "We looked at each other," the physicist told a friend, "and I winked."

"American Prometheus" sees the full implications of such a gesture: charm and bravado on the surface, Dostoyevskian darkness underneath. It traces Oppenheimer's arrogance to the kind of upbringing that would give him his own sloop at age 16 (he named it for a chemical compound) and lead one of the oral examiners of his doctoral thesis to say: "I got out of there just in time. He was beginning to ask me questions."

Many of the stories from his time at Berkeley, Caltech, Los Alamos and the IAS concern his role in the Manhattan project, or his communist sympathies and fall from grace during the McCarthy era. His contributions as the founder of what was at the time the leading school of American theoretical physics are often overlooked.

Perhaps most important was his work in the 1930's on the endpoint of stellar evolution, with his students Volkoff and Snyder at Berkeley. They explored many of the properties of black holes long before the term "black hole" was coined by Wheeler. Oppenheimer and company were interested in neutron star stability, and gave the first general-relativistic treatment of this complicated problem. In so doing, they deduced the inevitability of black hole formation for sufficiently massive progenitors. They also were the first to note that an infalling object hits the horizon after a finite proper time (in its own frame), whereas an observer orbiting the hole never actually sees the object hit the horizon. The work received amazingly little attention during Oppenheimer's life. But, had Oppenheimer lived another few decades, it might have won him a Nobel prize.

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