Monday was the fiftieth anniversary of Starfish Prime, a high-altitude nuclear test the U.S. conducted over the Pacific Ocean. Via Phil Plait, a/k/a Bad Astronomer:

On July 9, 1962, the US launched a Thor missile from Johnston island, an atoll about 1500 kilometers (900 miles) southwest of Hawaii. The missile arced up to a height of over 1100 km (660 miles), then came back down. At the preprogrammed height of 400 km (240 miles), just seconds after 09:00 UTC, the 1.4 megaton nuclear warhead detonated.

And all hell broke loose.

It pretty much looks like what you would expect a nuclear explosion in low-earth orbit would look like. Nuclear explosions release huge amounts of radiation, obviously, plus electrons and heavy ions. The electrons basically crashed into the molecules of the atmosphere and created an aurora visible for thousands of miles. Then it got crazier: Continue reading →