Shadows

Shadows of clouds falling on slightly hazy air can create unusual scenes. Even nearby objects can produce some interesting perspective effects and are always worth watching out for.
A low sun produces crepuscular rays.			A high sun can give unusual cloud shadows.
Earth shadow can be seen at sun rise or set.			Your own shadow in fog can make a spectre.
See Atmospheric Optics for a more detailed description of cloud shadowing and perspective effects.