The cameras shudder as blinding light flashes across the earth. Deformed white clouds balloon and mutate from the force of the nuclear test explosions.

These are some of the images captured in raw footage of bomb tests carried out by the United States between 1945 and 1962 in Nevada and the Marshall Islands. For the first time, the footage is available in an online archive after some of about 10,000 nuclear testing films were restored, scrutinised and declassified in a project by the Lawrence Livermore National Laboratory in California.

The bulk of the videos, some only seconds long and others just over seven minutes, had been stored at Los Alamos National Laboratory in New Mexico. But the experts in Livermore, southeast of San Francisco, have been working for years to retrieve and preserve the films, which over time had begun to turn brittle or curl, and then to create digital imprints.

So far, more than 60 films of the nuclear tests have been published by the Livermore lab's YouTube account, and more will be added. They offer an evolving glimpse of the closest that most people (one hopes) will ever get to a nuclear blast.

"It's just unbelievable how much energy is released," said Dr Gregory D. Spriggs, a weapons physicist in charge of the project at Livermore. 

"We hope that we would never have to use a nuclear weapon ever again," he said. "I think that if we capture the history of this and show what the force of these weapons are and how much devastation they can wreak, then maybe people will be reluctant to use them."

The films intersect with the history of the nuclear program. After the United States dropped atomic bombs on two cities in Japan in 1945, killing hundreds of thousands of people, it embarked on years of experimentation with its growing nuclear arsenal, conducting 210 atmospheric nuclear tests on Pacific islands and in the Nevada desert from 1946 to 1962.

Many thousands of soldiers and sailors – some estimates say as many as 400,000 – observed the explosions on the sea or in trenches a few miles from the sites.

"You feel the heat blast from it," said Frank Farmer, who witnessed 18 atomic detonations in 1958 while stationed on a ship in the Pacific, according to a New York Times report last year. "It's so bright, you actually see your bones in your hands."

After a 1963 treaty banned atmospheric tests, the United States started experimenting underground.

For each of the 210 tests conducted before the ban, multiple cameras were used. That means an estimated 10,000 films were created, Livermore's statement said. So far, the laboratory has located about 6,000 and scanned about 4,000 of them. The 64 films published on YouTube are among the 750 that have so far been declassified, it said.

There is still much work to be done.

The mission of the Livermore facility is to ensure that the safety, security and reliability of the U.S. nuclear deterrent is maintained. Its work falls under the National Nuclear Security Administration, which is part of the Energy Department.

In an interview, Spriggs said that the aim of the work on the films was to use modern imaging technology to verify data about shock waves produced by the explosions to a degree that was not possible in the 1950s.

Questions about shock waves, such as their intensity and speed, are a matter of life and death. It indicates where the damage from a nuclear bomb would be inflicted over a certain distance. As the force travels, it leaves a wake of destruction but gets weaker and weaker until it becomes a sound wave.

The laboratory is working with archivists, film restorers, software developers and other scientists on the project.

The United States no longer does nuclear testing, relying instead on experimental data from computer models, then comparing it with the data derived from the testing period of its history. The aim is to reduce the uncertainty between the two, and then use the latest data as a benchmark for scientists.

"So everything we are asked to calculate in terms of emergency preparedness, we are being asked 'what is going to happen if it is dropped downtown' or whatever," Spriggs said. "If we can't believe our computer codes, we can't give the government an accurate estimate of this and how many people will get hurt." Analysing the films will give them more confidence in the answers, he said.

In one detonation film, showing Operation Dominic-Housatonic over more than seven minutes, the fireball swells to several miles across, suspended in the sky.

"When people could realise how much energy is released and how much damage they can do, maybe they would think twice," Spriggs said. "It is a deterrent. We maintain the stockpile hoping that we never have to use it."

New York Times