What Causes a Sunset to Change Color?

The sky changes color at sunset because the sunlight has to travel through more of Earth's atmosphere. Imagine the sun as a big, bright ball in the sky. When it’s high up during the day, its light goes straight down and hits us quickly. But when the sun is low on the horizon at sunset, its light has to go through much more air. As it passes through this extra air, most of the blue light gets scattered away, leaving the warmer colors like red and orange to shine through.

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Examples

  1. When the sun is low on the horizon, it's like looking through a long tunnel of air that makes blue light disappear.
  2. If you look at a sunset from a mountain top with clean air, the colors are bright and clear.
  3. A cloudy day can make sunsets appear more pink or purple because the clouds catch some of the scattered light.

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Categories: Physics · optics· light· scattering· sunsets