Watch: The Brave Six Who Stood Beneath An Exploding Nuclear Bomb

The world has made a lot of progress in developing nuclear power in the past few decades. It all started with the Second World War, and since then, the world has crossed many milestones, making nuclear weapons more potent.

When nuclear bombs were dropped on Hiroshima and Nagasaki, the world witnessed the commencement of the atomic age. Subsequently, extensive research and development efforts have been dedicated to advancing these formidable capabilities. To assess the impact of nuclear weapons on humans, the US undertook an exceptionally audacious experiment.

According to NPR, on July 19, 1957, five Air Force officers and one photographer stood together on a patch of ground about 65 miles northwest of Las Vegas. They'd marked the spot "Ground Zero, Population 5" on a hand-lettered sign hammered into the soft ground right next to them. In a video from that time, two F-89 jets roar into view, and one of them shoots off a nuclear missile carrying an atomic warhead.

The soldiers wait. There is a countdown; 18,500 feet above them, the missile is detonated and blows up. Which means these men intentionally stood directly underneath an exploding 2-kiloton nuclear bomb. One of them, at the key moment (he's wearing sunglasses), looks up.

Watch the video here:

According to Smithsonian Magazine, "Those five guys were Colonel Sidney Bruce, Lieutenant Colonel Frank P Ball, Major Norman "Bodie" Bodinger, Major John Hughes, Don Lutrel, and George Yoshitake (the cameraman, not seen)."

According to Vice News, after World War II, the UK, USSR, and US detonated more than 2,000 atomic bombs. In Britain, 20,000 soldiers witnessed atomic blasts conducted by their own government. Only a few of them are still alive today, and the nuclear glow of the mushroom cloud they witnessed still haunts them. "Nuclear detonations-that was the defining point in my life," Douglas Hern, a British soldier who experienced five nuclear bomb tests, told Motherboard.

"When the flash hit you, you could see the x-rays of your hands through your closed eyes," he said. "Then the heat hit you, and that was as if someone my size had caught fire and walked through me. It was an experience that was unearthing. It was so strange. There were guys with bruises and broken legs. We couldn't believe it. To say it was frightening is an understatement. I think it all shocked us into silence."