I held plutonium in my hands only once in my life. It was on the afternoon of Aug. 31, 1957. At daybreak that morning I had witnessed the explosion of an atomic bomb in Nevada. It was part of the “plumbbob” series of tests. This one—named Smoky—had double the explosive power of the bomb used on Nagasaki, also a plutonium device.
That afternoon Carson Mark, who was the head of the theoretical division at Los Alamos, where I was a summer intern, took me and a colleague on a tour of the site. We climbed a tower where the device…

