In its quest for Cold War military superiority, the United States detonated more than 1,000 nuclear weapons.
Government researchers blew up many of the bombs on the ground and others in ocean atolls. Yet as threats moved into space and concerns increased about fallout — soil and other material that's sucked into a blast and becomes radioactive — the US exploded 210 of the terrifying devices high in the atmosphere.
Thousands of films of such blasts, made from 1945 through 1962, were analyzed and locked away in high-security vaults. It's likely no one has seen the footage for decades.
But on March 14, after more than 55 years of collecting dust, the US declassified 750 of the high-speed films — and released dozens of the digital scans on YouTube. We first heard about the movies from the writer Sarah Zhang on Twitter.