Why is the sky blue?

September 25, 2008 9:20:23 AM PDT
The sky is blue because that is the only color in the light spectrum that the air molecules reflect.

Erica's Answer:

Our sun's rays enter the atmosphere as almost pure white light. Visible light contains all the colors in the spectrum, from the brightest red to the deepest violet. The air molecules in our sky reflect the blue-violet rays of the sun, while the rest of the sun's light rays pass right through the air molecules, where they can reflect off everything else we see. Our eyes see the color that an object reflects, which is why our eyes interpret our sky as being blue.

When pollutants enter the atmosphere, they change the molecular composition of the atmosphere, which alters the sky color a bit. That's why on hazy days, the sky takes on a bit of a brown or yellow cast- what you see is the sun's light reflecting off the pollutant molecules, which reflect different colors of light other than our usual, clear blue.

- Erica


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