In 1945, after the atomic destruction of two Japanese cities, J. Robert Oppenheimer expressed foreboding about the spread of nuclear arms.

“They are not too hard to make,” he told his colleagues on the Manhattan Project at Los Alamos, N.M. “They will be universal if people wish to make them universal.”

That sensibility, born where the atomic bomb itself was born, grew into a theory of technological inevitability. Because the laws of physics are universal, the theory went, it was just a matter of time before other bright minds and determined states joined the club. A corollary was that trying to stop proliferation was quite difficult if not futile.

But nothing, it seems, could be further from the truth. In the six decades since Oppenheimer’s warning, the nuclear club has grown to only nine members. What accounts for the slow spread? Can anything be done to reduce it further? Is there a chance for an atomic future that is brighter than the one Oppenheimer foresaw?