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Then why are sunsets red?
At sunset, light crosses far more air at a slant. The blue is scattered away on the way, and mostly red and orange light gets through. Physics 2.
The Duowenwen team · Updated
A blue sky and a red sunset are two ends of the same story. This is the second question in the middle school physics chain of the question map. The one before it was "Why is the sky blue?"
Then why are sunsets red?
In the evening the Sun sits close to the horizon, so its light has to pass at a slant through far more air before it reaches your eyes. Along the way the blue light has long since been scattered off in other directions, and what's left to come straight through is mostly red and orange light, which is why the Sun and the clouds around it look red. Where the blue is being scattered, the sky looks blue. Once the blue has all been scattered away, what remains looks red.
What if…?
What if you took the air away, with no atmosphere at all? What color would the sky be?
Next: open the next question, "What color is the sky without an atmosphere?", or ask your own.