I’ve always heard that the more beautiful the sunset, the worse the smog. But I’ve seen gorgeous sunsets on days that seem clear.

We can, of course, have a beautiful sunset on a clear day, but if it’s murky outside, the sunset can be even better. Particles in the air—from smoke, dust, and yes, tailpipe emissions—scatter light as it travels through the atmosphere, says NASA-JPL scientist Michael Gunson. “That enhances the warm red glow.”
Photograph courtesy flickr/feverblue