The blue sky, like many other things around us, scatters polarized light. Light consists of an electromagnetic wave with a certain orientation, the polarization. The polarization is always perpendicular to the light path itself. If just a single polarization direction is present in the light, the light is said to be linearly polarized. The blue sky for example, polarizes the light tangentially with respect to the sun, and causes a linear polarization which is largest about 90 degrees away from the sun. Polarization filters show this polarization really well. If the sun is low in the sky, the zenith may be polarized as much as 90% or more!

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