Friday, November 21, 2008

Spectacular Spectrums

I can't see rainbows, but I think most people would agree with William Wordsworth: "My heart leaps up when I behold, a rainbow in the sky." I hear that it isn't difficult to be dazzled by this evanescant visual phenomenon, which the Old Testament describes as a sign of God's covenant with Noah after the flood. The fascination fo this offspring of sunlight and raindrops never dims: the hipsters of British rock group Radiohead titled their 2007 album In Rainbows.

I wish I had seen a rainbow, but since I havent, I have to write about what I have heard of them. I have heard that the rainbow has the power to thrill. Let's skip the poetry and move to the prosiac: What is it, exactly, that you are beholding when your heart makes that familiar leap? Rainbows are only the most common form of a number of fascinating visual phenomena that adorn the planet, some so fragile that they simply cannot be photographed.

Rainbows are formed by the interplay between water and light. When white sunlight moves through a water droplet, it is refracted, or bent, and splits into the seven visible colors that compose it: red, orange, yellow, green, blue, indigo, and violet (Roy G. Biv). Why? Because each of those colors operate on its own distinct wavelength. In this case, raindrops are acting like the prisms through which Isaac Newton passed light and seperated it in his pioneering work on the science of optics.

There is more to rainbows than meets the eye; the light spectrum usually forms a round rainbow in the sky, but our view is limited by the horizon, so it appears as a semi-circle. From an aiplace, it is possible to see Mr. Biv as a complete circle.

Rainbows are elusive phenomena, but if you have seen a moonbow, congratulations. This much less common optical phenomenon occurs when moonlight passes through raindrops or water vapor and forms a circular spectrum. Moonbows are generally only seen on clear nights when the moon is full. Certain waterfalls, like Africa's Victoria Falls and Lower Yosemite Falls in Cali, are noted for the frequency in which moonbows appear.

Sundogs are another of nature's fascinating optical phenomena. Scientists call them parhelions; they most often form when the sun is low in a sky filled with ice crystals within cirrus clouds. The effect varies: sometimes two false suns appear of either side of the star, at other times a full halo is visible, sometimes the visual effect more resembles a stained smudge of light with a tail than it does a falso sun. In all cases, your eye's are playing tricks on you; nature is.


Allanna said...

I'm sorry that you can't see rainbows ... but you can see sundogs, right?

Brooke said...

I am not sure....I probably could, but I never have that I can remember...Are they common?