12/30/2004: Green flash at sunset

[Undertoad]

Credit and copyright Tony Cook and used with his permission. This was the Earth Sci pic of the Day a week ago. Taken on Tenerife in the Canary Islands, it's a great photo and also shows an interesting phenomenon - at the top of the sun, a green flash appears. This green is not on the sun itself, but a product of how the atmosphere affects the light. From the ESPoD explanation:

Green flashes are created by variations in refraction near the horizon. The refractive layer causes sunlight to be weakly dispersed into the constituent colours of red, yellow, green, blue and violet. Violet and blue light are normally scattered in the Earth's atmosphere, with the result that the last portion of the dispersed light to be observed as the Sun sets is green.