Sunsets can be spectacular in Tucson, Arizona. Bright colors predominate, such as the red one above. Sometimes, they’re dark red, sometimes orangish-red like on this night.
Why are these sunsets red? Because of particulates in the air. The colors of a sunset are caused by the scattering of light’s wavelengths. Stuff in the air like dust, smoke, pollution, and water change the intensity of the light, i.e. scatter the light. However, the wavelengths don’t scatter equally. The short wavelengths, blue and violet, scatter away easily, so we can’t see them. The other colors of red, orange and yellow are able to make it through.
The dust from the Sonoran desert monsoons can enhance the red color. It’s good to know that the dust has a positive purpose.
Even though our sunsets result merely from light scattering, their brilliance can be quite enjoyable.
The same scattering effect happens at sunrise. The light at sunrise has even farther to travel through the air because the sun is low on the horizon.
It’s nice to know why the sky can be so colorful. Understanding the science doesn’t diminish our enjoyment of the bright colors at all, does it?