On October 24, 1962, an American nuclear chemist, Harrison Brown, began writing a guest editorial for the Bulletin of the Atomic Scientists just as the Cuban Missile Crisis was reaching its climax.

“I’m writing on a plane en route from Los Angeles to Washington and as far as I know this op-ed…may never be published,” Brown said. “Never in history have peoples and nations been so close to death and destruction on such a large scale. Midnight is upon us.

With this dire warning, he was referring to the Apocalyptic clock, which has been the Bulletin’s signature motif since its inception 75 years ago by Albert Einstein and some of the University of Chicago’s Manhattan Project scientists. Their work had contributed to the making of the atomic bomb, but many of them were outraged when the United States used it against Japanese cities.

The image of the clock ticking away to midnight was meant to convey the sense of urgent danger Brown felt so viscerally on that 1962 flight to Washington.

“He thought the world might end while he was on that flight,” said Rachel Bronson, the Bulletin’s current president.

On Thursday, the Doomsday Clock will be unveiled for the 75th time, and we’ll find out how the Bulletin’s panel of scientists and security experts move the minute hand. For the past two years, it’s been stuck at 100 to midnight. With Russia poised to attack Ukraine, it’s hard to imagine the clock being turned back, and that means experts believe that we are more in danger than ever.

The nearest clock at the height of the Cold War was two minutes to midnight in 1953 after the first detonation of a thermonuclear warhead, a hydrogen bomb.

At the time of the Cuban Missile Crisis, only seven minutes remained, but despite Brown’s doomsday editorial, the Bulletin decided not to advance them because the shock of a near-disaster had given Washington and in Moscow a new incentive to work on risk reduction and arms control.

The furthest hour from midnight the clock has ever moved was 17 minutes, just at the end of the Cold War. Since then, it has fallen back to extinction. This is partly due to the increasing volatility of geopolitics, the proliferation of nuclear weapons and the new existential threat of climate change, which was officially factored into the calculation in 2007.

The Doomsday Clock image was originally the work of Martyl Langsdorf, a famous abstract landscape artist of the time, whose husband, Alexander, was a physicist on the Manhattan Project. When in 1947 he and his anxious colleagues decided to turn their mimeographed in-house diary into a magazine, they turned to her to design the cover for the new Bulletin. She felt she was “the only artist they knew”.

The design was originally to be based on a U for Uranium, but increasingly alarming table discussions between scientists in the couple’s social circle pushed Langsdorf toward more urgent images.

“She took the imagery of the countdowns and the rocket launches and put it into a clock,” Bronson said. She added that the original time on the clock, seven minutes to midnight, “translated the urgency, but also the hope, the feeling that we can do something about it. We can put it back. And all this in an image that does not depend on the language.

It’s an image designed to cut through the dense nature of the underlying science to engage the audience with the issues. He has since appeared in Cold War novels, Doctor Who episodes, songs from The Who and Iron Maiden. Boris Johnson referenced the Doomsday Clock in his speech at the COP26 summit in Glasgow in November, although he incorrectly said it was set for one minute to midnight.

“He got the time wrong, but he used it and we’re okay with that part,” Bronson said. “At the Bulletin, we believe that public engagement is crucial in this regard. In the United States, we are about to spend $1.8 billion on a new nuclear arsenal. The public must engage because it’s their money.

“It’s really hard to stay engaged on an urgent issue that’s 75 years old,” she added. “But it’s still urgent, and through politics, and through art, and through journalism, we must be able to avert the worst.”