There’s truly nothing like a pretty sunset. As the sun sets, the heavens above are like cotton candy: lighting up with a beautiful display of deep reds, vibrant oranges, and intense pinks. Simply put, the sky seems to be on fire.

The reason we see different colors at different times has to do with the physics of light.

Visible light travels in electromagnetic waves, which we see as the colors of the rainbow.

Different colors have different wavelengths of light. Violet and blue have the shortest wavelengths, whereas red and orange have the longest. Gas molecules in the atmosphere are even smaller than the wavelengths of light. When light enters the atmosphere, it gets scattered by molecules like nitrogen and oxygen. And because blue wavelengths are the shortest, they get scattered more, resulting in a blue sky.

During a sunset, however, light scattering works differently. The sun’s light has a lot further to travel. Blue wavelengths are filtered out, and so the red and orange wavelengths peer through the atmosphere. In fact, everyone who is in the same latitude is looking at the same rays of light, it just appears like different colors because of the atmospheric scattering.

And while some believe that extremely bright and beautiful sunsets are a result of dust and pollution, that isn’t the case. If that were true, cities with high levels of pollution like New York and Los Angeles would constantly have colorful sunsets. Dust and pollution could potentially influence a sunset’s vibrancy, but most of the scattering happens at the middle and upper levels of the atmosphere.

That being said, there are some reasons why a sunset might be brighter than others. Temperature is one major factor at play, as winter sunsets tend to be more vibrant. Cold air has less water vapor, which can cling to particles in the air like dust and pollen, causing them to block sunlight. Not to mention, colder air typically comes from areas like the Arctic, where there are fewer trees and less pollution to create the particles that would block light.

Clouds also affect what a sunset will look like. If the sky is full of clouds and overcast, from the ground you won’t see that pretty of a sunset. But if you hopped on a plane, crossing the boundary layer of the atmosphere, you would probably get to see a more colorful display.

Not all clouds block sunset light though. The wispy and feathery cirrus clouds are high enough that they reflect the last red orange rays of a setting sun back to the ground.

Finally, weather can also influence the sunset. The contiguous United States is situated under a jet stream, or a band of air that flows from west to east. Certain weather patterns, such as rain showers or blizzards, affect that jet stream. If the disturbances happen in the east, the cooler air will worsen weather conditions. But on the western side, the air will clear and dry, allowing for a nice sunset. This is why there is often a beautiful sunset after a storm.

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