The long-distance scientific recordings of the blast wave from the first hydrogen bomb test have been rediscovered in a formerly classified safe at Columbia University.

On November 1, 1952, physicists created the second fusion explosion the solar system has ever known. The first occurred around 4.5 billion years ago and ignited the ongoing fusion reaction in the sun. The second, the Ivy Mike experiment, was shorter lived and detonated on an atoll in the South Pacific. This 10-megaton blast was five times more powerful than all the explosives used in World War II combined, including the nuclear-fission bombs dropped on Hiroshima and Nagasaki.

The blast set off a low-frequency sound wave beneath the human hearing range, which was recorded halfway around the world at special listening stations designed by the Lamont Geological Observatory in Palisades, New York, for monitoring just such an event. The microbarographs measured changes in atmospheric pressure, and were particularly well-suited to detecting a nuclear explosion. As the wave passed, the ink-filled needles of the instruments scribbled on paper rolling around a drum.

It was the first time a nuclear explosion had been detected from such a long distance and it marked the beginning of international test monitoring, a key element of nuclear non-proliferation plans. The recordings were swiftly marked "classified" and stuffed in a vault at Lamont. And there they sat for more than 50 years.

Then, in preparation for retirement in 2008, Lamont's former security director Ray Long began cleaning out the safe. Recognizing there might be something to the recordings, he contacted Paul Richards, a seismologist and specialist in nuclear-test tracking. Richards immediately knew the measurements "were of historic importance."

If they couldn't be declassified, they would have to be sent to the U.S. Air Force, which originally classified them, or destroyed. So, Richards tracked down the right people in the Air Force and asked them to declassify the documents so that they could by preserved for posterity.

"They had the bureaucratic problem that there was no obvious indication on how to do it," Richards said. "They were very helpful, but it took a while."

Now, finally, more than 57 years after the ink was first laid on the paper, the recordings can be seen by all.

At first, the Lamont scientists working on the problem of remote nuclear-detonation detection thought they might need to get measurements from high in the atmosphere. So they sent balloons up with recording equipment. As an odd historical footnote, this research program may have launched the long-standing rumors of something strange going on near Roswell, New Mexico, when one of its stations crashed in the area.

"The program was called Project Mogul, and its goal, set by a postwar America wary of losing its atomic monopoly, was to search high in the atmosphere for weak reverberations from nuclear-test blasts half a world away," journalist William Broad explained in a 1994 New York Times article. "The debris, found near Roswell, New Mexico, was a smashed part of the program's balloons, sensors and, of most consequence to the growth of spaceship theories, radar reflectors made of thin metal foil. At the time, the Air Force said the wreckage was that of a weather balloon, a white lie."

Over the years, scientists realized that they could use ground-based stations and didn't need high-flying balloons. For years, microbarographs were used to measure nuclear weapons tests as they grew ever bigger, up to the largest test ever by the Soviet Union, which topped 50 megatons, a thousand times more powerful than the bombs dropped on Hiroshima and Nagasaki.

Satellites largely took over weapons-test monitoring in the 1960s within the United States and Soviet Union. However, with the signing of the Comprehensive Nuclear Test Ban Treaty in 1994, cheap, easy-to-deploy microbarograph stations were deployed at dozens of locations across the world from Piñon Flats in California to Antananarivo, Madagascar.

Image: 1. Lamont-Doherty Earth Observatory/Kim Martine. 2. Video of Ivy Mike experiment.

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