It's eschatology in motion: 62 tests carried out between 1945 and 1962, of detonations filmed from up to 50 angles. A total of 210 tests were carried out and this tranche is a good slice of them.
The videos released this week include footage of the "Harlem Event," a 1.2 megaton atmospheric detonation above Christmas Island in 1962. The video below shows how nuclear explosions can result in two distinct flashes of light. The first flash happens when the shockwave is formed, but quickly the superheated air around the blast epicenter "shields the light from inside the fireball," according to LLNL. "As the shockwave cools to below 3,300 Kelvin, the air becomes transparent and the hot gases begin to show through, creating the second pulse." Measuring the time between these two flashes, as well as the darkest frame between the two flashes, can help calculate the blast's yield.
More haunting declassified scans of nuclear weapons test videos released [Megan Geuss/Ars Technica]