Colors Of Dawn, Dusk Decoded

(via Times of India) Scattering happens when light collides against molecules in the atmosphere, causing it to scatter. The study, by researchers at the University of Wisconsin at Madison, shows how scattering determines the colours you see in the sky at sunset or sunrise.

According to Steven Ackerman, who led the study, the colour blue, being of shorter wavelength, is scattered more than other colours by the molecules. This, he says, is why blue light reaches our eyes from all directions on a clear day and the sky appears blue. At sunrise or sunset, explains Ackerman, as the Sun is low on the horizon, sunlight passes through more of the atmosphere - and hence encounters more molecules. “When the path is long enough, all of the blue and violet light scatters out of your line of sight. The other colours continue to your eyes. This is why sunsets are often yellow, orange, and red.” As red has the longest wavelength of any visible light, the sun seems red when it’s on the horizon, where its extremely long path through the atmosphere scatters all other colours away.

Useful link:
http://timesofindia.indiatimes.com/Colours_of_dawn_dusk_decoded/articleshow/2544426.cms

Insightful and educational.