Weather Whys: What determines the sunset’s color?

Weather Whys

The sunrise and sunset can paint beautiful shades of red and orange across the sky. What gives the sky its color, and what are the key ingredients to a vivid sunset?

It all starts with the sun! White light travels from the sun to Earth. The light splits into different wavelengths when it reaches the Earth when it hits molecules in the atmosphere. These different wavelengths have different colors. The shortest are blues and violets. The longest are reds and oranges.

During the daytime the sun’s rays have a more direct path to the Earth’s surface. There’s much less atmosphere to travel through at noon when the sun is most directly overhead. The shortest wavelengths are most visible at this time, creating a blue sky.

At sunset and sunrise, when the sun is at a low angle, the sun’s rays have a longer distance to travel. The short wavelengths scatter out first and are less visible. The longer wavelengths show up best and create a red and orange sky.

When there is a lot of pollution, dust and pollen in the air, the sun’s rays also hit these. They cause additional scattering and block some of this light. Clear atmospheres are best for vivid sunsets and sunrises since the most light will make it to your eyes. Clear skies are not always best, though! When we have clouds in the sky over us and clear sky in the direction the sun is traveling from, we have the most colorful sunrises and sunsets. The clouds act as a projection screen for the light that reaches us and reflect the colors back to us, creating our most picturesque sunrises and sunsets.

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