Last year, hundreds of films of the nuclear test from the 1950s and 1960s were released to the public, and both researchers and lay people have been looking at them, studying them, and (for our convenience) uploading them online.

In the last few days, people have been sharing a particularly shocking one, the Castle Bravo test, that took place on Bikini Atoll on March 1, 1954. The bomb was the most powerful nuclear device ever detonated by the US and it has a yield of 15 megatons of TNT. That’s about 1,000 times more powerful than the Hiroshima and Nagasaki bombs. The yield was actually surprising because it was predicted to be six megatons. It was increased due to an unexpected reaction of one of the lithium isotopes in the reaction.

The explosion created a fireball 7.2 kilometers (4.5 miles) across, leaving in its wake a crater 2 kilometers (1.2 miles) wide and 70 meters (230 feet) deep, and a mushroom cloud that reached 14 kilometers (8.7 miles) in altitude in about a minute. The explosion was so powerful that it not only destroyed all nearby the instruments designed to record information about the test, but it also damaged buildings on the other side of the island.

This detonation released a cloud that contaminated 18,000 square kilometers (7,000 square miles) of the Pacific Ocean. The danger of such fallout was ignored by authorities. Residents of the Rongelap and Utirik atolls were not evacuated until three days later and suffered radiation sickness. The crew of the nearby Japanese fishing vessel Daigo Fukuryū Maru were also hospitalized because of acute radiation syndrome. This strengthened the strong anti-nuclear weapon commitment of Japan, and some consider the creation of Godzilla directly related to the Daigo Fukuryu incident.

Thousands of people were affected and the US paid compensation to many who subsequently developed cancer and other illnesses due to the fallout exposure. The test created a global outcry and ultimately it led to the ban on atmospheric testing of nuclear weapons. It would take almost a decade for the US to move its testing underground. Since 1992, all the newly developed nuclear weapons in the States are tested using computer simulations.

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