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Subject: Blue Sky

Why is the sky blue?

    The sky is blue due to a phenomenon known as Rayleigh scattering of light. This process occurs when white light from the Sun interacts with molecules of oxygen and nitrogen in the atmosphere. It turns out that blue light wavelengths have the proper energy to be very effectively scattered (disrupted) as they pass through our atmosphere, causing the sky to appear blue to those on the Earth's surface.

Ken Rubin, Assistant Professor
Department of Geology and Geophysics
University of Hawaii, Honolulu HI 96822


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