Why Does the Sky Change Color at Sunrise and Sunset? (2024)

Have you ever watched the sun rise or set? If so, the picture stays with you: Bright reds, pinks, and purples shoot across the sky as the sun rises or sinks on the horizon. Do you WONDER where those lovely shades come from? And where do they hide all day?

Those colors are always there! We just can't see them. How is that possible? When light enters our atmosphere, it's white. That white light contains all the colors of the rainbow. Gas molecules break the light into differently colored waves. Each color of light moves at different speeds. The colors we see depend on the light's path and the sensitivity of our eyes.

Molecules send the light waves off in different directions. We call this process scattering. Sunlight scatters many times before reaching our eyes. Blue light travels fast, so it scatters more often than most other colors. That's why we don't see the bright colors of the sunset during the day! So much blue light is scattered that it hides most other colors. Other colors peek through at sunrise and sunset because the light travels farther to reach us. That allows the other colors of light waves to scatter more often.

Would you believe the sky could actually be purple? Purple waves move faster than blue ones, so more purple light is scattered through the sky. Then why is the sky blue? The sensitivity of our eyes influences the colors we see. Human eyesight peaks in the middle of the rainbow. Because blue is closer to the center than purple, we see a blue sky instead of a purple one.

If you've seen more than one sunset, you know they're not always the same. Why is that? Many people say the most beautiful sunrises and sunsets occur in autumn and winter when the atmosphere is dry and allows light waves to travel more quickly. However, many events affect sunsets by adding new gas molecules to the air.

For example, volcanic eruptions send debris into the atmosphere. These particles cause light waves to scatter at a higher rate. Anyone who sees a sunset just after an eruption will see a glowing orange sky.

Pollution also changes the sunrise or sunset. In crowded cities, pollution from auto engines blocks many shades of light. The sunsets in highly polluted areas are just bright red instead of a pattern of colors.

Finally, clouds influence the appearance of a sunrise or sunset. You might worry that clouds would cover the event from view. However, a few clouds in the sky make the sunrise or sunset look even more breathtaking. Clouds catch the colorful rays as the sun rises or sets, resulting in colors rising higher into the sky.

Have you ever watched the sunrise over the ocean on a cloudy morning? How about the sunset on the horizon after a volcanic eruption? Many people believe these are the most beautiful sights in the world. What does the sunset look like from your home?