Crimson Sunsets

The sun's face blushes crimson at sunset and at sunrise. Why?

In order to understand why, one must first realize that the air absorbs sunlight. And when the sun is low in the sky, absorption increases because the rays pass through the atmosphere sideways. But the important thing is that the blue and yellow rays are heavily blocked while the red rays come through relatively unimpaired. That's why looking through a red filter makes things appear clearer; red light cuts through haze.

Getting back to the sun, we now can understand why at sunset the sun looks red. It's simply because the atmosphere acts as an optical filter allowing the red sun rays to pass through easily. If there are clouds along the horizon then the clouds will be lit by the sun's red rays and we have a pretty sunset.

This theory of light passing through the atmosphere was first explained by the British scientist, Lord Rayleigh, a century ago. But long before that, people were enjoying beautiful, red sunsets.