The Usual Colors of the Sky

Why is the sky blue? Why are sunsets red? The answers and explanations to these questions can be found fairly easily on the internet. But there are many subtle “Wait a minute…”-type questions in between the cracks that seem to necessitate subtle answers and more “difficult” searching around the internet to find those answers.

So, why is the sky blue?

No, but first, what color is sunlight?

Sunlight spectrum1, from http://wtamu.edu/~cbaird/sq/2013/07/03/what-is-the-color-of-the-sun/

Visible light generally is from 390 nm (violet) to 720 nm (red). Visible sunlight is a mix of these colors at the intensities we see in the figure above.

, with maximum eye sensitivity at 555 nm (green).


1. http://wtamu.edu/~cbaird/sq/images/sunlight_wavelength.png

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