starfish prime

As part of a series of nuclear armaments testing called Project Fishbowl, begun in response to the USSR’s announcement that it would be withdrawing from a mutual moratorium on test launches, the above high-altitude explosion took place on this day in 1962 about four hundred kilometres above Johnston Atoll in the Pacific.
Though nearly fifteen hundred kilometres away, the afterglow and aurora was visible in Honolulu and the electromagnetic pulse it generated (part of the stated goals of the tests were to have a better understanding the disabling effects of the weapon’s fallout)—even in an era when electronics were not so pervasive and indispensable—knocked hundreds of streetlamps and cut off telephone communications. The radiation belt of high-energy electrons lingered in the atmosphere (see also) and caused at least six communications satellites to fail, including the UK’s first satellite, Ariel 1, put in orbit just in April of that year.