Ask Dr. Universe: Why is the sky blue?

Dr-Universe-230RICHLAND, Wash. – Just the other day I looked up and wondered the very same thing. The sky is certainly blue, I thought. But on second thought, it isn’t always blue. Sunsets burst in pink and orange. The night sky is black.

That’s when it hit me. If our sky gets dark when the Sun is out of sight, maybe the answer to your question had something to do with light.

I decided to visit my friend Cigdem Capan, a physicist at Washington State University Tri-Cities.

“When we look at the sky during daytime, the sky does not emit the light,” she said. “It receives it from the Sun and spreads it around. Only some of the rays will reach the surface of Earth, or our eyes.”

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