Physicists mobilize to reduce the nuclear threat. Again.

We live in an increasingly dangerous nuclear world, a time at least as perilous as the worst years of the Cold War. The Bulletin of Atomic Scientists’ Doomsday Clock offers a clear representation of existential risk. In 1953, when first the United States and then the Soviet Union began testing thermonuclear weapons, the Bulletin Science and Security Board set the clock at two minutes to midnight. Over the intervening six decades the nuclear threat fell and rose, and fell again, but few would dispute that in recent years the alarm has been sounding for those who would hear it. Today, the Science and Security Board set the Doomsday Clock at 100 seconds to midnight—closer than it has ever been to catastrophe—warning that “any belief that the threat of nuclear war has been vanquished is a mirage.”