The first time the US tested an EMP weapon was a doozy

It was 1962 and only four days after Independence Day, but people living on the islands dotting the Pacific Ocean from Hawaii to New Zealand were about to see a light show brighter than any July Fourth fireworks display in history.

More ominously, many of those same people would get a taste of how a single nuclear weapon could wipe out a nation's electrical grid – and the U.S. military at the time had no clue how damaging the results would be.

Codenamed Starfish Prime, it was part of a series of nuclear tests conducted by the U.S. Atomic Energy Commission and the Pentagon. Some of those tests included launches from Johnston Island of the U.S. Air Force's PGM-17 Thor intermediate range ballistic missiles with live W49 thermonuclear warheads.

The purpose: rocket the warheads to the edge of space and detonate them to determine whether thermonuclear fireballs could be used to destroy incoming nuclear warheads from the Soviet Union.

Crazy? Perhaps – but keep in mind the events of the age.

In 1958, the Soviet Union called for a ban on atmospheric nuclear testing and abided by a self-imposed moratorium. Eventually, the United States followed suit. During 1959, neither superpower tested any nukes, but the brief lull in testing did not last. Soon, both nations were back at it.

In 1961, the Soviets detonated the humongous "Tsar Bomba." Though capable of a 100 megaton yield, scientists decided to dial back Tsar Bomba's destructive power to reduce the chance of fallout. At about 50 megatons, it still is the most powerful nuclear explosion in history. In fact, Tsar Bomba was so powerful, its heat caused third-degree burns on the exposed flesh of Soviet observers more than 60 miles away.

Starfish Prime was really the third launch attempt for the U.S. – the first missile was destroyed seconds into its flight and the second blew up on the launch pad. Both incidents rained nuclear contamination down on the Johnston Island test facility.

But on July 9, 1962, the third Thor missile performed flawlessly and lifted its payload into space.

The 1.4 megaton warhead detonated about 240 miles above the Pacific Ocean – and then all hell broke loose.

"Most fortunately, these tests took place over Johnston Island in the mid-Pacific rather than the Nevada Test Site, or the electromagnetic pulse would still be indelibly imprinted in the minds of the citizenry of the western U.S., as well as in the history books," Lowell Wood, a physicist and expert on EMP at Lawrence Livermore National Laboratory, told Congress in 2004. "As it was, significant damage was done to both civilian and military electrical systems throughout the Hawaiian Islands, over 800 miles away from ground zero."

In Hawaii, the effects were almost immediate: streetlights blew out, circuit breakers tripped, telephone service crashed, aircraft radios malfunctioned, burglar alarms sounded, and garage door openers mysteriously activated.

As the flash from the nuclear explosion dimmed, an aurora formed in the sky that could be seen for thousands of miles. One reporter in Hawaii wrote, "For three minutes after the blast, the moon was centered in a sky partly blood-red and partly pink. Clouds appeared as dark silhouettes against the lighted sky."

The high-energy radiation not only created a massive light show; it temporarily altered the shape of the Van Allen Belt – part of the magnetosphere surrounding the Earth that actually protects the planet from solar storms that could destroy life on the world's surface.

The Van Allen Belt had only been discovered four years earlier by University of Iowa physicist James A. Van Allen. The bands of high-energy particles held in place by strong magnetic fields were first seen as a threat to early space explorers – or a possible weapon to use against the Soviet Union.

In fact, there are historians of the Cold War who argue that there is compelling evidence indicating that both the United States and the Soviet Union contemplated exo-atmospheric nuclear explosions to blow up the Van Allen belt either to permit space travel or destroy their respective enemy.

Fortunately, there is no evidence that either the U.S. or Soviet nuclear testing in space permanently damaged the magnetosphere. As the weeks and months went by, however, there were other casualties from the Starfish Prime blast. At least six satellites – including Telstar, the world's first telecommunications satellite – were either damaged or destroyed by passing through the lingering radiation belt left by the detonation.

Scientists and the military were stunned by the results of Starfish Prime. They knew about EMP, but the effects of the blast far exceeded their expectations.

Despite the very public detonation of the weapon, the cause of the power failures and satellite malfunctions remained secret for years, as did a new discussion that began: how a single nuclear weapon might be used to cripple a nation in one blow.

It is a discussion that continues to this day as those in the national security community consider how a weapon like Starfish Prime detonated over or near the United States could plunge the country into darkness.