It is amazing how little was known when we let the genie out of the bottle:

As Popular Mechanics reported, five men including Colonel Sidney Bruce, Lt. Col. Frank P. Ball, Major Norman “Bodie” Bodinger, Major John Hughes, and Don Lutrell volunteered to stand directly under the detonation point and stood their ground as the nuclear explosion went off 3.5 miles overhead. One additional man, George Yo****ake didn’t exactly “volunteer” but instead there to operate the camera and capture the moment for posterity.

Such actions may seem crazy today, but we should remember that based on the science of the time the men weren’t expected to experience any immediate harm from the explosion.
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