Dark lighting is a largely-invisible burst of energy that floods the sky with gamma rays and hurls antimatter into space, says NASA.
It sticks around for just a few a few microseconds, but if you do happen to see it, dark lighting shines with a faint purple glow, says Discovery News. The bursts of gamma rays affect the region often occupied by cruising airliners, but the radiation dose is pretty low: “similar to going to the doctor’s office and getting a CT scan.” So, not particularly dangerous.
Dark lightning was first discovered in 1994, and is just one of many odd and usual forms of lightning that have puzzled researchers in the past few decades.
Regular lightning, which you’ll find arcing down from a thundercloud, is dazzling enough, especially when watched at high speed.