"The surface of the Earth is the shore of the cosmic ocean... Recently, we've managed to wade a little way out, and the water seems inviting." - Carl Sagan
Airglow over Mono lake
It’s not just auroras that fill our sky with eerie light. A weaker phenomenon called airglow also exists, and unlike the aurora, which are focused towards the poles by Earth’s magnetic field, it can be seen from anywhere on Earth with luck and a dark sky or long exposure photo. Both phenomena arise from excited atmospheric atoms, but with different solar sources for the excitation energy. Like aurorae, airglow can be patchy and shift on a scale of minutes across the night sky. It is also present during the day but hidden in the glare.
Image credit: Matt Granz