Back at the dawn of the atomic age, many Americans were rightfully worried about the effects of nuclear fallout. So, in a (failed) attempt to reassure people that atomic weapons were nothing to get in a huff about, the U.S. Air Force recruited five volunteers (plus one photographer who didn't have much of a say in the matter) to stand directly beneath a 2-kiloton nuclear detonation. The result is a video that you won't soon forget.

The video was commissioned by Col. Arthur B. Oldfield, the public information officer for the Continental Air Defense Command in Colorado Springs. It was through the video, and its (unintentionally comical) commentary, that he hoped to show the relative safety of a low-grade nuclear exchange in the atmosphere.

The exercise happened on July 19, 1957 in a deserted area about 65 miles northwest of Las Vegas. In the video, the soldiers can been seen standing approximately 18,500 feet directly beneath the atomic blast (the video claims that it's at 10,000 feet, but that's incorrect). And in what appears to be a rather macabre gesture, they stand next to a sign declaring, "Ground Zero: Population 5".

Writing in NPR, Robert Krulwich (who many of you might know from the popular Radiolab show), offers his perspective:

Watch as these five soldiers stand directly beneath an atomic blastS

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.

Perhaps the best quote comes from Col. Bruce, who seconds after the explosion declared, "My only regrets right now are...that everybody couldn't have been out here at ground zero with us."

Check out Krulwich's entire article, which features a second video demonstrating what an actual nuclear explosion sounds like.

Inset image via NPR/Atom Central/YouTube.