ESOcast78 excerpt: Chemiluminescence

The Sun is constantly showering the Earth's atmosphere with ultraviolet light. During the daytime, this light destroys oxygen and nitrogen molecules, triggering a chain of complex chemical reactions and resulting in the creation of new molecules such as ozone.

When night falls, some of these molecules take part in further reactions and collisions, causing them to radiate light. This process is known as chemiluminescence, and it is shown in this animated video clip from ESOcast 78.