Why the sky is blue
(and sunsets are red)

Sunlight is white — every color mixed together. Air scatters the blue part of it far more than the red. So when you look up, the blue light bouncing around the sky is what reaches your eyes.

Drag the sun toward the horizon. Its light now has to plow through much more air to reach you — and watch what colour is left.

Sun position Overhead (noon)

Air the light crosses: least Colour reaching you: blue sky

At noon, light takes a short path through the air; plenty of blue scatters across the whole sky. Near the horizon, the path is far longer — so much blue gets scattered away before it reaches you that mostly orange and red survive the trip. Same sunlight, same air. Only the distance changed.

Why does the sky turn red at sunset?

This same scattering is why the Sun looks yellowish rather than white, and why Mars has blue sunsets. Curious how rainbows or why clouds are white fit in? Ask me in the chat.

Primary source · NASA Space Place — Why Is the Sky Blue?

Why the sky is blue(and sunsets are red)

Why does the sky turn red at sunset?

Why the sky is blue
(and sunsets are red)