Sixty-two newly declassified videos have just been released by the US government showing footage of atmospheric nuclear tests from the first half of the 20th century. The videos, never before seen by the general public, have been uploaded to YouTube, offering scientists and historians a fascinating new look at a time of extreme nuclear experimentation.

Between 1945 and 1962, the United States conducted over 200 atmospheric nuclear tests and it's estimated there are around 10,000 films chronicling these experiments. Many of the films sit unseen and unpreserved, deteriorating rapidly.

"We've received a lot of demand for these videos and the public has a right to see this footage," says nuclear weapon physicist Gregg Spriggs, from the Lawrence Livermore National Laboratory (LLNL). "Not only are we preserving history, but we're getting much more consistent answers with our calculations."

Film preservation expert Jim Moye was set the task of digitizing the old prints, which involved scanning each film twice to capture as much optical data as possible. As well as preserving important historical records, this exercise is proving important for scientists in gathering more data to improve computer simulations.

"It's been 25 years since the last nuclear test, and computer simulations have become our virtual test ground," explains Spriggs. "But those simulations are only as good as the data they're based on. Accurate data is what enables us to ensure the stockpile remains safe, secure and effective without having to return to testing."

The team uses these nuclear detonation films to calculate the yield (amount of energy released) of each test. The old measurements used to calculate yield came from analysts in the 1950s and 1960s eyeballing images projected onto grids. While these measurements were "pretty accurate" according to Spriggs, they often weren't exact enough.

The team at LLNL developed a computer program that can automate this measurement process by analyzing each frame of these test films to generate the most accurate yield calculations ever made.

For the layperson these newly released videos offer a stark perspective on humanity's most frighteningly powerful weapon. These 62 videos, available here on YouTube, are a reminder of the horrific destruction nuclear weapons can unleash. LLNL promises to publish more videos as they are processed and approved.

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