What Causes a Sunset to Look Orange or Red?

The sun looks orange or red at sunset because the light has to travel further through the Earth's atmosphere. When the sun is low on the horizon, its light passes through more air than it does when it's high in the sky. This makes the blue and violet light scatter away, leaving behind the warm colors like orange and red. It’s like a filter being added to the sun’s light as it goes down.

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Examples

Imagine sunlight passing through a thick glass window, the blue gets scattered, leaving behind reds and oranges.
A sunset looks like a giant painting in your sky, with reds and oranges appearing because the blue has been taken away.
You can see this effect more clearly on clear days than on cloudy ones.

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Categories: Science · Optics,Atmosphere,Light