What Causes the ‘Twilight’ of a Sunset?

When the sun is low on the horizon, its light has to travel through more of Earth's atmosphere. This makes the sky look like it's painted with colors. The blue and green light gets scattered away, leaving the reds and oranges, just like when you shine a flashlight through a glass of water and see different colors appear.

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Examples

A glass of water with food coloring looks different when you shine a flashlight through it, like the sky during sunrise or sunset.
When you’re on a beach at night and see the sky turn red, it's because the sun is just below the horizon, sending red light your way.
If you're in a city with lots of smoke or pollution, sunsets can look even more colorful.

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Categories: Physics · Optics,Light,Atmosphere