The U.S. Air Force recruited five volunteers and one photographer, to stand directly beneath a 2 kiloton nuclear detonation. And this was back in the day. It's one video we'll never forget.
The video was commissioned by Col. Arthur B. Oldfield, the public information officer for the Continental Air Defense Command in Colorado Springs. In the video, he hoped to show the relative safety of a low grade nuclear exchange in the atmosphere. Check it out below:
The experiment took place on July 19, 1957, in a deserted area 65 miles northwest of Las Vegas. The soldiers in the video can be seen standing 18,500 feet directly beneath the atomic blast and they were in the video carrying a sign declaring, "Ground Zero: Population 5". Robert Krulwich writes in NPR:
Watching this film, there are many things to wonder (and worry) about, but one of the stranger moments is how the bomb bursts in complete silence. We see a sudden white flash. It makes the soldiers flinch. Then there's a pause, a pregnant quiet that lasts for a beat, then another and then - there's a roar. ("There it is! The ground wave!"), after which the sky above seems to go black and the air turns to fire.
Basic physics explains the pause. Because light travels quicker than sound, you see light first, you hear sound later. In most movies (even in government-released atomic bomb blast films), the sound is artificially time shifted to make the flash and the sound appear simultaneous.