Effects of Polarization and Scattering of Light
The Earth appears as a pale blue dot because of the effects of polarization and scattering of the light reflected from Earth. The polarization effect of planet Earth depends on various factors such as cloud cover, exposed areas of oceans, forests, deserts and snow fields, etc. The contribution of each surface type is a combination of Rayleigh scattering above the surface and reflection at the surface. The integrated effect causing Earth to appear as a pale blue dot depends on wavelength, scattering angle and cloud cover. The degree of polarization is particularly strong in the blue region of the visible spectrum due to Rayleigh scattering in the atmosphere. The degree of polarization for Earth to appear as a pale blue dot at 443 nanometers and 90° scattering angle, as calculated using polarization observations of Earth made from the POLDER satellite radiometer, is 23% for 55% (average) cloud cover and up to 40% for 10% (minimal) cloud cover.
Read more about this topic: Pale Blue Dot
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