Naturalist rainbow

A Rainbow in the Eye of the Beholder

There has to be a rainbow around here somewhere.
I was thinking this while I was driving along Route 9 late one afternoon in mid-August, on my way home.
The sky ahead of me was dark with blue-black summer clouds, and raindrops were hitting the windshield. The sun behind me was throwing clean, gorgeous light over everything.
Low sunlight beaming through rain means there's a blue, yellow and red arc of colored light somewhere, if my eye could only pick it up. Meaning, if I was positioned at the right angle to catch reflections from the drops.
It's hard to know exactly why, but rainbows have made hearts leap at least since Noah's time, if scripture and poetry are any evidence of that unseen feeling. A peculiar sense, which has never faded from human perception, that some kind of grace is being imposed on the world. Or so it seems.
Scientifically speaking, of course, there is no earthly reason to believe a rainbow is anything but a product of mindless physics. Rays of light from a setting or rising sun strike raindrops, which are not tear-shaped, but spherical. The light is refracted inside the drop, which means the light's path is deflected when the light hits the back wall of the drop and reflects toward the sun. A person with his back to the sun catches that refracted light in his eye.
The colors arise from light reflecting out of each drop at different angles. White light is made up of all the colors, and the drop refracts out the spectrum. The angle of the light's reflection determines the color your eye picks up - blue, yellow, red and everything in between - depending on where you're standing.
No two people see the same rainbow. It has no location in space. The rays refracted in and reflected out of the drops form a cone of light, with the tip at each person's eye. If you're high up you can see almost a whole rainbow circle, or really, disk. Each person sees his own cone, although the colors sort out the same way for everyone. In the bright primary bow, blue is the innermost band and red the outermost because of the angle of reflection for each wavelength of light. The "rainbow angle" for deep red light is 137.5 degrees, a number some readers might recall from observations made here some months ago about spiral galaxies and flowers. To me this feels like a lot more than mere coincidence, but what do I know? Beauty's in the eye of the beholder.
When the sunlight is refracted twice inside each drop, a fainter secondary bow develops. Its colors mirror the primary: red on the inside, blue outside. Beyond the secondary bow, sometimes third and fourth bows appear when the light reflects three or four times inside the drops. There's a darkness between the primary and secondary bows because the drops along the angles of sight between the two can't send light into your eye. That darkness is called "Alexander's Dark Band" because it was observed in ancient Greece by Alexander of Aphrodisias.
While I was driving, the rainbow was revealed to me. It arced up over the trees of Ward Hill in Troy, gorgeous and hopeful in the distance, whatever distance it was. I recollected an enormous, vivid rainbow I stared at over Warden's Hill in Northumberland one summer evening 20 years before. Attached to that cone of light pouring into my eye was the woman back across the ocean in Waldo County who eventually would become my wife, and if you think that rainbow was merely a mindless hallucination of sun and rain, you're wrong. My English friends were astonished by it too, though they had their own reasons why.
That afternoon on Route 9, the two rainbows were bound each to each. One when life began, the other, thankfully, now I'm growing old. A joy forever, and increasing, or so it seems.

© Dana Wilde 2011

Naturalist home
The Mind Errant home