Template:POTD/2011-10-10
A composite photo showing the development of a green flash, an optical phenomenon that occurs at sunset or sunrise, when a green spot or ray is visible above the sun. Green flashes occur because higher frequency light (green/blue) curves more than lower frequency light (red/orange), so green/blue rays from the upper rim of the sun remain visible after the red rays are obstructed by the earth.Photo: Mila Zinkova