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From 1945 until such tests were banned in 1963, the US conducted 210 atmospheric nuclear tests. The explosions were filmed with multiple cameras capturing each event at around 2,400 frames per second.

Those films had been left to quite literally rot—scattered around the country in vaults and safes—until physicist Greg Spriggs at the Lawrence Livermore National Laboratory began tracking them down five years ago. He estimates about 10,000 explosion films were made and so far his team has located around 6,500 and scanned about two-thirds of them into a digital archive.

Since the US hasn’t exploded a nuclear weapon in the atmosphere since 1962, scientists use data from these past explosions to help certify that the aging U.S. nuclear deterrent remains safe, secure and effective. Reanalyzing the films with modern techniques, Spriggs discovered that much of the data embedded in computer codes on things like explosion size and shock wave were wrong—by as much as a 30% margin.  ”That’s a big number for doing code validation,” Spriggs said. “When you go to validate your computer codes, you want to use the best data possible.”

He’s working his way through the films to update the data. Spriggs doesn’t want nuclear weapons to be used. Ensuring that nuclear weapons are safe and effective—and making that known—provides an effective nuclear deterrent and keeps the US safe, he argues.

You can watch all the videos declassified so far, below.