Seen outside of Elgin, Oregon on the Hell's Canyon Scenic Byway, spanning the sky, this rare horizontal rainbow.
Here's a close up.
Seeing this appear in the sky stopped the day. On the other hand, it didn't exactly appear. It was there before it was pointed out. Still, it was an amazing moment; one of those instants in which what you see is so beyond what you know that you sense you are in the presence of the miraculous. Along the road under this rarest of the rainbows, people were pulling their cars and trucks to the side and getting out with whatever photo equipment they had and aiming it at the sky.
Of course, you cannot capture anything that fills the large western sky in a small digital box, but you can, in essence, take note -- in all senses of the word. But still you try. Here's a few of the many pictures I took.
As with most things miraculous, there is a current scientific explanation for the phenomenon. In this case, it is a rare seldom seen rainbow that occurs when conditions are just right. Wikipedia gives it the name "Circumhorizontal Arc:"
"A circumhorizontal arc or circumhorizon arc (CHA), also known as a fire rainbow, is a halo or an optical phenomenon similar in appearance to a horizontal rainbow, but in contrast caused by the refraction of light through the ice crystals in cirrus clouds.Another reference notes: "The arc is a very large halo and is close to, and parallel to the horizon. Usually only fragments are visible where there happen to be cirrus clouds." In other words a rainbow so big that it rolls right on out of the sky.
It occurs only when the sun is high in the sky, at least 58° above the horizon, and can only occur in the presences of cirrus clouds. It can thus not be observed at locations north of 55°N, except occasionally from mountains.
The phenomenon is quite rare because the ice crystals must be aligned horizontally to reflect the high sun. The arc is formed as light rays enter the horizontally-oriented flat hexagonal crystals through a vertical side face and exit through the horizontal bottom face. It is the 90° inclination that produces the well-separated rainbow-like colours and, if the crystal alignment is just right, make the entire cirrus cloud shine like a flaming rainbow.
Still another sighting via National Geographic News adds:
"The arc isn't a rainbow in the traditional sense -- it is caused by light passing through wispy, high-altitude cirrus clouds. The sight occurs only when the sun is very high in the sky (more than 58° above the horizon). What's more, the hexagonal ice crystals that make up cirrus clouds must be shaped like thick plates with their faces parallel to the ground."
All perfectly explained and easily understood. In retrospect. The actual sighting held, and still holds, in my mind as a close contact with the continuing miracle of the world and universe as it unfolds around us. Reflecting on it now it brings to mind a small poem I read long ago by the greatest living poet of the American land, Gary Snyder:
almost at the equator
almost at the equinox
exactly at midnight
from a ship
in the center of the sky.
"Once only." Every moment in life is delivered to us "once only," filled with the enduring mystery and miracle of creation. We know this deep inside us always. But sometimes it takes a rainbow roof painted on the sky to remind us.Posted by Vanderleun at July 3, 2007 9:48 PM | TrackBack