Nature's Paintbrush

January Colorado Sunset

A few Moments Earlier

"Mother Nature has taken out her paintbrush again..." I said to the person driving the car, as I pointed to the sunset and reached for my camera. "And what a beautiful palette!" Mindlessly, I said these things to that slavish reader of Discover Magazine, memorizer of scientific factoids, analyzer of natural phenomena, rejecter of all things mystical and magical: my husband. Without even pausing to consider the inevitable scientific explanations.
He did not disappoint.
"Nonsense." He said. "Colorado sunsets over the prairie are beautiful because the physics of sunlight works well here."
Told you.
"Of course," I humored him. "And everyone knows that the skies are redder at sunset than at sunrise because…" Here he would normally complete the sentence for me. He disappointed.
"… because," I labored on.… "…because of that train whistle effect? Don’t they call it red-shifting?" It made sense to me. You know, as the earth spins towards the sun in the morning and away in the evening?
"You mean the doppler effect?" Now he did not disappoint, completing my thought. "That only works with sound. Applying it to sunlight would contradict Einstein’s theory of relativity, which requires that light travel at a universally constant speed without regard to the motion of the observer."
Quickly, before my eyes could glaze over, I snapped another picture.
I flashed him an indulgent little smile, then plodded on. "Of course. Everyone knows that sunsets are caused by all that stuff in the atmosphere, aerosols, pollution, particles…" even though I sensed his lack of conviction, still I soldiered on. "… and because the air is warmer, and more humid in the evenings than in the early morning." Did I also mention that he is a stoic? I saw his head nodding slightly forward in a kind of grim determination not to disagree with any of my continuing observations. So I gave him my summation: "I just wanted to see if you were paying attention."
"Think rainbows," He offered. His patient inner professor had found its voice. "Think how, after a rain, the water droplets in the air scatter and bend sunlight into its various wavelengths like a prism, which our eyes interpret as color. When the sun is on the horizon its light must travel through many more miles of Earth’s atmosphere than when it is overhead. It scatters the shorter blue frequencies, causing the sky to appear blue, and leaves only the red for us to see on the horizon. And since, on the Great Plains, clouds almost always form in the west in the evening, they provide a dense canvas for…?"
I refused to help him out. I just wanted to hear him say it. I continued snapping photos, capturing every swirl of Mother Nature’s hand.