This is the popular name for the aurora borealis, the spectacular natural light display that occurs around the north pole. It is caused by highly charged electrons from the solar wind colliding with oxygen and nitrogen particles as they enter the earth’s atmosphere. As these react together, they create luminous flares that swirl across the sky. These can be green and reddish-brown where oxygen particles are struck, while nitrogen gives off rarer blue and red lights. During the seventeenth century, the aurora borealis was the wellspring of much superstition and was interpreted either as an ill omen or the result of aerial armies clashing with each other in the sky.
Watch an amazing time lapse video of the aurora borealis below.