The rainbow has a closely-guarded secret known to only a few. During my first flight on a commercial aircraft in 1961, at the age of 21, it was revealed to me in all its glory.
I was on a 400-mile trip from San Francisco to Long Beach, California, and the plane was nearly empty (something that was possible in those days). Despite the brevity of the flight, which didn’t last much more than an hour, it was punctuated by two memorable events. In the first of these the passengers were served drinks, which they proceeded to imbibe. Mine was in my hand at one moment, and at the next I found myself spilling it all over my clothes. For a few seconds I didn’t know why this had happened, and then I realized (partly with the help of a message from the captain) that we had hit an air pocket and the plane had suddenly fallen several hundred feet. My drink had separated from the cup that held it, and then it followed gravity downward to my lap.
Spectacular as an encounter with an air pocket can be in a commercial flight, the second event was far more dramatic. There probably were fewer than fifty passengers in an aircraft capable of seating over 200. As a result, I was able to move about rather freely from my assigned seat, and I took advantage of this to look out the windows of the plane, first on one side and then the other. I don’t recall how long this was going on before in the early evening I saw something that totally startled and absorbed me outside the landward side of the plane as we flew south. At a distance of perhaps 100 yards (it may have been considerably further, but distances were not easy to estimate under the circumstances) what appeared to be a circular rainbow was moving through the clouds, appearing to jump from one cloud to the other. Most remarkably, in the middle of this circle was a perfect silhouette of the plane, shadowing us like a UFO as we flew. It was otherworldly. I had to blink to believe what I was seeing, but it continued like this for some minutes, and there was no denying what my eyes were reporting to me.
I had no idea what was causing this rare and beautiful spectacle, and I naturally had no name for it. It was only years later that a chemist friend who worked in spectroscopy told me it is an optical phenomenon that has been known, but not well understood, for many years. He called it the ‘glory effect’, but subsequent research has taught me that it is commonly known simply as ‘the glory’.
Since that first magical experience I have seen the glory twice while in flight, once in a long flight from Holland to Indonesia, where it appeared somewhere over the skies of Southeast Asia, and most recently in a flight from Baltimore to Honolulu, where it appeared near Phoenix, Arizona in a different form. This time, instead of following us a hundred yards or more off our right wingtip, it appeared in a ‘here again gone again’ pattern on the tops of the clouds below us. All of this naturally depends on the position of the sun relative to the plane, and on the necessary ice crystals or water droplets in the air to act as miniature prisms for the sun to shine through. There is no need to enter into details regarding the complex physical conditions needed for the glory to appear, but a few general remarks should not be out of order.
The most important point for the physicist is perhaps that the conditions necessary to produce a rainbow, are somewhat different from those needed to produce a glory. For anyone else what probably matters most is that a rainbow can be seen from almost any location, while a glory usually requires an elevated sighting position:
Although it offers a display hardly less impressive than the rainbow, the glory has remained a considerably more recondite phenomenon, ever since its first reported observation in 1735. Its sighting ... requires locating the antisolar point, usually through the shadow of some object on the clouds (most often an airplane) (Nussenzveig 1979:1073).
The last part of this quotation may suggest that the glory could not possibly have any connection with beliefs about the rainbow and related phenomena by preliterate humans, since they could never have been in a position to view it. However, the fact that the glory was first reported in 1735 indicates otherwise. As noted by Sassen, Arnott, Barnett, and Aulenbach (1998:1428) “The unique backscattering response of small (relative to visible wavelengths) cloud droplets to create the glory was rarely appreciated, and mostly by early mountain climbers, until the advent of frequent air transportation.”
Regardless of how the physics of the rainbow and the glory may differ in producing the visible effect of a prismatic ring, to the layman what the glory appears to be is a circular rainbow, and this is visible from any elevated location. Quite apart from seeing the combination rainbow plus silhouette while in flight I have since seen the glory without an enclosed silhouette from the seventeenth floor of an apartment building in Honolulu, where during a light rain shower one hovered below me over the asphalt backdrop of a parking lot in front of an adjacent church.
What does this have to do with dragons? While most dragons appear uncoiled, serpents that form a circle by swallowing their own tail are found in several cultural traditions, including the following:
In Europe the dragon swallowing its own tail appears as a symbol of unity or totality within the medieval tradition of alchemy (Jung 1970:223).
According to Allen and Griffiths (1979:66), “The alchemical dragon was often expressed as the Ouroboros, the circular serpent-dragon which bites its own tail, a symbol of unity and of the prima materia of the universe which is far older than alchemy and which may have had its origins in Egypt as Apophis, the encircler of the earth.”
A similar theme appears in the Midgard Serpent, described in the Icelandic sagas as a colossal dragon that encircled the planet in one enormous coil, much of which was under water and consequently unseen, although its movements were said to cause tidal waves and other violent events at sea.
2 Ancient Near East
With regard to ancient Egyptian mythology, we are told that “Another creature … is the divine serpent Sito, reputed to encircle the world with its immense coils and also represented in several other mythologies. Sito is often merely depicted in the form of a circle, holding its tail in its mouth” (Hogarth and Cleary 1979:19).
It is hard to know how much traditional peoples knew about the glory. They would certainly have seen lunar, and sometimes solar halos which resemble a circular rainbow. However, whether they would have been associated with dragons in the same way that ordinary rainbows are is an open question. In addition, the ouroboros appears to have been a concept of the priestly class in Egypt, and the Midgard Serpent appears to have been more a creation of the literati who composed the Icelandic Eddas than of the common people, so the idea of a supernatural serpent biting its own tail to form a circle may not have been readily available to the common people anywhere on the planet, especially among tribal people. The distribution of this idea is also relatively restricted, being limited so far as is currently known to ancient Egypt, the Icelandic sagas and medieval alchemy, hence to Egypt and Europe, with no known cases in India, the Far East, the Americas, New Guinea, Australia, the Pacific Islands or sub-Saharan Africa.
Nonetheless, since rainbows were Rainbow Serpents, and therefore dragons to most preliterate peoples, what appeared to them to be a circular rainbow might well have been viewed as a dragon swallowing its own tail. Moreover, seeing it encircling heavenly bodies such as the sun or moon would have provided a model for mythological dragons that encircle the Earth. At least provisionally, then, we can suggest that the concept of the ouroboros, no less than the dragon idea itself, could have arisen from observations of the natural world.