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Processes by which particles of similar size and
electrical characteristics separate or disperse different wavelengths (read
colors) of light. First described by Gustav Mie in 1808. Since the sun's visible
spectrum contains a mixture of (traditionally ordered) red, orange, yellow,
green, blue, indigo, and violet colors, these wavelengths are differentially
scattered by particles as they travel through the atmosphere. Red--longer
wavelength--light is scattered not much and blue--shorted wavelength--light is
scattered much more. This is why the sky appears blue: the sun's blue light is
scattered back towards your eyes from atmospheric particles so when you look
up--that is, away from the sun, the light you see is light scattered to your eye
from atmospheric particles. (You might ask yourself why the sky--viewed at an
off angle from the sun--isn't black instead of blue.) Mie scattering is also the
reason why sunsets appear red: the sun's red light is NOT scattered as much as
blue light by atmospheric partricles and so solar blue light is scattered away
from your eyes on its way from the sun and red light is scattered less. The
result is that more solar red light hits your eyes than blue and sunsets appear
red. Notice also that the redness of sunsets increases at the amount of
atmospheric particles between you and the sun increase, that is as the sun "goes
down" mie scattering increases as the amount of particles between you and the
sun increases.
[Webster's New World Dictionary; Third Edition: page 265; 1994.]
[Scientific American; v265: pages 80-85; 1991.]
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