Last month, we launched a new feature on TheAtlantic.com called the "Iran War Clock." We based it explicitly on the "Doomsday Clock," an iconic image that the Bulletin of the Atomic Scientists has variously deployed since 1947 to represent its view of how close humanity is at a given moment to complete ruin. It wouldn't be especially modest of us to say that our project is comparatively modest in scope, though we took it to be similar in spirit: "... the purpose is to gauge the chances of conflict with Iran in the hope of producing a more informed debate in the U.S. and abroad."
The original Doomsday Clock has typically been set somewhere between 11:45 p.m. and 12:00 a.m. Its "latest" setting was at 11:58 p.m., after the United States and the Soviet Union tested thermonuclear devices within nine months of each another in 1953; its "earliest" was 11:43 a.m., after the U.S. and the Soviets signed the Strategic Arms Reduction Treaty in 1991.
Midnight signals, in the Bulletin's formulation—with what might be the most tellingly gratuitous use of an adjective ever—our "catastrophic destruction." That used to mean our annihilation by global nuclear war. But in recent years the Bulletin has expanded its definition of "doom" to encompass "climate-changing technologies and new developments in the life sciences that could inflict irrevocable harm." Or rather, since humanity is presumably risking these different kinds of self-destruction on different timelines, the Bulletin hasn't expanded its definition so much as multiplied its definitions of "doom"—to categories beyond the traditional competencies of atomic scientists—while somehow still representing the world's proximity to an overall state of destruction with a single indicator. The Bulletin has specified little over the decades about its process for deciding to move the minute hand—and less about its methodology.