Why Is The Sky Blue?

Why is the sky blue?

• Anywhere in the world we see the sky blue, has it always been blue? Is there something in the atmosphere that absorbs other wavelenghts? Form space we also see the earth blue (at least a portion of it), does this has something to do with the sky being blue too?

• Answer:

  The sky is blue due to a phenomenon known as diffuse sky radiation. Diffuse sky radiation is solar radiation reaching the earth's surface after having been scattered from the direct solar beam by molecules or suspensoids in the atmosphere. The blue portions of the earth seen from space are of course water. Water exhibits a similar characteristic, where red light wavelengths are absorbed. This effect is only visible with large quanities of water though (like a pool or ocean), however. Water in small quantities (like a glass of water) appears clear.