In the 21st century, humanity will see many technological developments, but also increased risks of confrontation. And the place where this confrontation is likely to be exacerbated will be in space, probably during the conquest of the Moon or Mars. On July 9, 1962, the night sky above the Pacific Ocean, from Hawaii to New Zealand, suddenly became illuminated by brilliant light, as if it were the middle of the day. A stunning artificial aurora appeared, creating a glow of green, yellow, and red, which lingered for less than an hour. Then came the blackouts. The streets of Hawaii became unlit, telephone service was disrupted, burglar alarms went off. What looked like a beautiful light show from Earth was the result of the biggest nuclear bomb ever detonated in space.

From a tiny island in the middle of the North Pacific Ocean, the U.S. had launched a 1.4-megaton nuclear warhead, a weapon test and a display of power during a particularly tense period of the Cold War. The experiment, dubbed Starfish Prime, generated an electromagnetic pulse, releasing a massive burst of energy 250 miles above the ground, which fried about one third of all active satellites at that point and turned out to be more destructive than anyone expected.

Then, on October 22 of the same year, the U.S.S.R. conducted its own high-altitude experiments, including the Project K nuclear tests. The Soviets launched and detonated a 300-kiloton warhead some 180 miles above central Kazakhstan. The smaller yet lower and therefore more destructive blast also affected infrastructure on the ground, frying overhead telephone lines and causing the fuses to blow on their overvoltage protectors, shutting off underground power cables and knocking out a power plant. Nukes in the sky don’t stay only in the sky: With their electromagnetic radiation, they’re a threat to any technology or device that can carry a charge, and they can destroy satellites, immediately disrupting key functions that those spacecraft provide.

Read more on April 1st, 2025.