During daytime
During daytime
Earth’s atmosphere scatters a greater proportion of blue light than of red light.
Civil, nautical, and astronomical twilight. Dusk is the end of evening twilight.[6]
Dawn is the beginning of morning twilight.
See also: Atmospheric optics and Diffuse sky radiation
Sky during day time
Except for direct sunlight, most of the light in the daytime sky is caused by scattering, which is dominated by a small-particle limit called Rayleigh scattering. The scattering due to molecule-sized particles (as in air) is greater in the directions both toward and away from the source of light than it is in directions perpendicular to the incident path.[7] Scattering is significant for light at all visible wavelengths, but is stronger at the shorter (bluer) end of the visible spectrum, meaning that the scattered light is bluer than its source: the Sun. The remaining direct sunlight, having lost some of its shorter-wavelength components, appears slightly less blue.[5]
Scattering also occurs even more strongly in clouds. Individual water droplets refract white light into a set of colored rings. If a cloud is thick enough, scattering from multiple water droplets will wash out the set of colored rings and create a washed-out white color.[clarification needed][8]
The sky can turn a multitude of colors such as red, orange, purple, and yellow (especially near sunset or sunrise) when the light must travel a much longer path (or optical depth) through the atmosphere. Scattering effects also partially polarize light from the sky and are most pronounced at an angle 90° from the Sun. Scattered light from the horizon travels through as much as 38 times the air mass as does light from the zenith, causing a blue gradient looking vivid at the zenith and pale near the horizon.[9] Red light is also scattered if there is enough air between the source and the observer, causing parts of the sky to change color as the Sun rises or sets. As the air mass nears infinity, scattered daylight appears whiter and whiter.[10]
