What Causes the Sky to Change Colors at Sunset?

At sunset, the sky changes colors because sunlight has to travel farther through Earth's atmosphere. This makes the light scatter more and show off its hidden colors, like when you shine a flashlight through a glass of water and see different colors pop out!

Sunlight is white, but it’s made up of many colors. When sunlight travels through the air, the blue part scatters more easily, which is why we usually see blue skies during the day. But at sunset, light has to go all the way around Earth, so the red and orange parts get scattered more, making the sky look like it’s on fire!

You might notice that sunsets are especially vivid when the air is clear, like after a storm or in the mountains. That's because there's less stuff in the air to mess with the light!