Why was the Doomsday Clock created?

A magazine of worried scientists

The Bulletin of the Atomic Scientists began in Chicago in December 1945, four months after Hiroshima, as a newsletter for scientists of the Manhattan Project, the wartime program that built the bomb. Its founders, Eugene Rabinowitch and Hyman Goldsmith, and many of its writers had worked at the University of Chicago, where the first controlled nuclear chain reaction was achieved in December 1942. They wanted the public to understand the new weapon and to press for international control of it before an arms race began. For the cover of the June 1947 issue, the editors turned to an artist.

Why seven minutes to midnight?

The artist was Martyl Langsdorf, a painter married to the physicist Alexander Langsdorf, who had worked on the Manhattan Project. She drew only the upper left quarter of a clock face, with the minute hand at seven minutes to midnight. Midnight stood for catastrophe, the nearness of the hand for urgency. Why seven? Langsdorf said the time simply suited her eye: there was no calculation behind it. The design worked so well that the Bulletin kept it, and the image became known as the Doomsday Clock.

The first move, 1949

For two years the hand stayed where Langsdorf had put it. Then, on August 29, 1949, the Soviet Union tested its first atomic bomb on the steppe near Semipalatinsk, in Soviet Kazakhstan, sooner than American intelligence had predicted. On September 23 Truman announced it: “We have evidence that within recent weeks an atomic explosion occurred in the U.S.S.R.” For Moscow, which had read the American bomb as a message aimed at the Soviet Union, the test ended the American monopoly. The editor, Eugene Rabinowitch, moved the hand to three minutes to midnight. From then on the clock was a judgment made by people, not just a picture.

Up and down through the Cold War

In 1953, after the United States and the Soviet Union had both tested hydrogen weapons, the hand moved to two minutes. In 1960 it went back to seven. It did not move during the Cuban Missile Crisis of October 1962 (the crisis), and in 1963, after the treaty banning nuclear tests in the atmosphere, it went back to twelve. In 1991, after the Cold War ended and Washington and Moscow signed a treaty cutting their long-range weapons, it was set at seventeen minutes to midnight, its furthest setting ever. The logic behind those moves, that a war between nuclear powers could destroy both, came to be called mutually assured destruction (what MAD means).

Who sets it today

After Rabinowitch’s death in 1973 the decision passed to a board. Today the Bulletin’s Science and Security Board sets the clock, in consultation with its Board of Sponsors, which includes Nobel laureates. The board announces its decision every January, and since 2007 it has also weighed climate change alongside nuclear weapons. The clock is a warning, not an instrument: the minutes are a panel’s judgment of danger, drawn in the image a painter chose in 1947 (Trinity and the first bomb).