You may have seen a popular trend of sunset pictures recently, captioned with people calling themselves, ‘look at the sky’ kind of people, but what is behind these pretty skies?

The pretty colors we see in a sunset come from a scientific phenomenon called light scattering, when light rays hit particles in the air, changing the direction of light. It is determined by the different wavelengths of light. 

If you remember learning about ROYGBIV in science class, it refers to the colors of the rainbow from top to bottom, but also the visible light spectrum. According to NASA for example, violet has the shortest wavelength while red has the longest wavelength.

When we see red sunsets, it indicates the atmosphere is full of moisture and dust particles. We see the color because it has the longest wavelength in the spectrum. The shorter wavelengths, like blue, are not visible because they are broken up. These same principles also explain why the sky is blue during the day.

Not only do the moisture and dust particles in the air affect sunsets, but also the clouds. Typically, the best sunsets seen in skies are with mid-level clouds like altocumulus and cirrus clouds, and the opposite of which is low-lying clouds like stratus and stratocumulus clouds. 

Time of year is another contributing factor, as you may see more beautiful sunset pictures being posted in the late fall and winter months. This is due to the normal weather patterns in this area, which result in a clean and clear lower atmosphere.