The softly glowing night sky

There's a lot more going on over your head than you know. For example, the atmosphere of the Earth thins out gradually the higher you go, and when you get to about 100 kilometers (60 miles) up, different physical processes become important. One of them is called chemiluminescence -- light produced by chemical processes. This can make the upper atmosphere glow in different colors. It's faint, and best seen from space... where we conveniently keep several astronauts. Neuroscientist and amateur video maker Alex Rivest has collected pictures of this airglow taken by astronauts and made this eerie and beautiful time lapse video: