A vague presence crept into my peripheral awareness in a nearly imperceptible way– I couldn't quite grasp its nature or content. An uneasy flutter danced in my solar plexus as when you feel someone watches you from some hidden vantage.
Now on alert, I listened intently, but the afternoon air was unusually quiet– even dead-quiet. I slightly clenched my teeth as I scanned the area of our yard before and beside me, but all seemed familiar and normal. A large black beetle briefly broke the silence as she buzzed by. Her erratic flight path both surprised and annoyed me as it took her inches from my nose. I wildly waved my hands and sputtered– "Aaaaaa!– git outta my face!"– as if she could understand my command. As my distraction dissipated my attention gradually drifted upward.
With the clear autumn sky coming into the edge of my view, I notice a distinct, thin white line tracing through the intense blue. Though I have witnessed hundreds of jet-plane contrails, this is a remarkable sight. The line is exceedingly thin, indicating the unseen plane must be very far away– at extremely high altitude. Moreover, the line appears exactly the same width along its entire length. There are no discontinuities or inconsistencies to be seen in it. When condensation trails are laid down as an airplane passes through the atmosphere, the varying wind velocities and directions invariably move segments of the white plume in a more or less random manner. What starts out a straight, white line will typically shift, slash and shuffle into a bent and jaggy path. On occasion, these paths remain more or less uniform, but the one I see above me appears scary-perfect. With my eyelids parting even wider, my lips follow their lead.
My eyes continue tracing the trail's path through the blue and I see now it isn't taut-string straight. The white thread forms a very slightly curved arc across the heavens– the arc looks the segment of a perfect circle. What, in the heavens, am I looking at?
Puzzled by the heavenly scene of perfection above me, I scan more of the sky. The white trail is not alone, as I detect more than one companion to the first. Flexing my neck fully back, my view now extends all the way to the zenith. With my upward gaze full of the azure atmosphere and the pin-prick brilliance of the sun, my puzzlement explodes into profound wonder as I observe arc upon arc, and multiple complete circles of perfect geometry. If these traces resulted from the passage of airplanes, the required synchronization and precision of their flight paths twist my mind into a frenzy. What I see is an impossibility.
The geometric perfection overhead surely had its source in some kind of optical phenomena. The nature of physical optics excels in producing geometric effects of all sorts. The simple fact that light travels in a straight path, and that it radiates equally in all directions from a single point, makes it imminently suitable as a mechanism for the construction of perfect geometry– the straight-edge and compass of nature. But this alone wasn't moving me to a final understanding of what I witnessed.
I stood on the porch, stunned by the great mystery, not so much because my knowledge of optics was small, but the mystery actually deepened for me because my understanding was considerable. At one time or another I worked through the physics of our perception of the colored bow before or after a rainshower. I also convinced myself, from first principles, how and why the daylight sky appears to us blue. And the unsettling color of a "moon turned blood" during total lunar eclipse was an easily reasoned (and calculated) result of the dispersion of refraction and scattering in the earth's atmosphere. But the whole of my previous reasoning concerning atmospheric optics did not prepare me for what I witnessed. I could partially explain some of the arcs and complete circles, extrapolating from my solving of the rainbow's geometry. But others of the arcs and circles baffled me. My mind raced from one mental filing cabinet to another, in a desperate search for a plausible explanation. I simply could not fit them into my geometric model of the behavior of light.
I rushed back inside the house to retrieve a large sketch pad and a pencil. If I could not understand what I witnessed, at least I could attempt a faithful record of the observation. I spent quite a while on the porch, intently sweeping out arcs and circles by hand, filling the sheet with what would likely appear an intricate, but mad, design to anyone not privy to the phenomenon at hand. Having done all I could to congeal the image into black and white, I returned the sketchbook to its origin, and finally went about my nearly forgotten business.
Once or twice a decade, in search of some bit of old information, I ran into my drawing of the sky full of arcs. Seeing it always bubbled up as a fresh experience, once again awakening the stark nature of the mysterious, awesome sight.
A few years back, a colleague, who also thrilled in the unexpected, loaned me his copy of Minnaert's Light and Colour in the Open Air. The work, written in Dutch, is a copious compilation of a host of optical effects and phenomena observed in nature. The author explains in extensive, but accessible, detail how these sights are generated. Many of the described phenomena are unusual, even rare. As I read through the work, I searched with eager hope to find mention of my perplexing arcs. The book did not disappoint.
In the chapter "Rainbows, Haloes, and Coronae," Minnaert wades through a deep pool of various arc-like specters in the sky. He relates in detail the physical, geometric reasons underlying a half-dozen or so "haloes" produced by unusual configurations of ice crystals, and known by various names. Some of these arcs, because of their placement and angular extent, surely populated my singular moment on the porch. But some of the clear, thin wisps I observed were not directly mentioned by Minnaert. Perhaps, my yet unexplained arcs fit into the section he titled "Very Rare and Doubtful Halo Phenomena." Should something "doubtful" be labeled a "phenomenon?"
While some of the sights Minnaert works through are truly rare, many only seem rare to us because no one ever told us to look for them. Once we know where and when and why to look for such sights, we see them almost daily– while the uninitiated might close their eyes in death, never having observed such wonders.
Recently, I thrilled to discover a computer program written for the sole purpose of calculating the paths of light rays as they interact with various configurations of the hexagonal crystals of frozen water. The aim of this software (Halopoint 2.0) is the generation of all possible arc-like optical phenomena of ice crystals suspended in the atmosphere. So far, the program has verified nearly all of the extremely rare optical haloes mentioned in the records of centuries past. Before such computational power was available, many of these phenomena seemed, in the words of Minnaert, "doubtful."
I eagerly downloaded a simulation of the sky that the program generated: twenty-seven arcs littered the image. Nearly all of my hand-drawn arcs appeared in the synthetic sky scene. I felt gratified– my drawing proved faithful, and my arcs were now named. But in my drawing one holdout remains. Perhaps my record waxed more eloquent than accurate. Or is there a deeper mystery, not yet revealed?
The details of this universe bulge with mystery. Some mysteries have their root in our ignorance. We see but don't understand enough to explain them away. Yet the more powerful mystery follows on the heels of deep understanding. Though we know much, the greater weight of reality thumbs its nose at us, defying any exhaustive explanation.
As Job comes to the end of himself, attempting to understand the dark mysteries of his own life, he is compelled to utter: "Therefore I have declared that which I did not understand, things too wonderful for me, which I did not know." Such things are only seen– experienced– and cannot be explained nor fully understood. "I have heard of You by the hearing of the ear; but now my eye sees You..."
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>>> Unless otherwise attributed, all text and images are Copyright, Bill Brockmeier, 2015. All rights reserved.
Note: image is from: http://vjac.free.fr/skyshows/icehalos.html
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