Light, like sound, travels in waves and is measured from crest to crest in wavelengths. The spectrum of light visible to the human eye is in wavelengths of 400-700 nanometers (a nanometer = a billionth of a meter; micrometer = a millionth of a meter; 1 millimeter = a thousandth of a meter; and 1 cm = a hundredth of a meter). Humans can no longer see with their naked eye wavelengths larger than 700 nanometers or smaller than 400 nanometers. Longer than 700 nanometers, these electromagnetic waves are: infrared (wavelengths of 700 nanometers to .1 millimeter), heat from which can be detected by the human body directly and by instruments that help us "see in the dark"; microwave ( .1 millimeter to 1 cm.), which is the range of signals to and from satellites, very useful for telecommunications and yes, for cooking inside out as the microwave oven does; and radiowaves (1 cm. and larger), extensively used for broadcasts and before satellites, in communications. Shorter than 400 nanometers, there are ultraviolet rays (400 to 10 nanometers), whose energy is very high that they are used to kill bacteria in medical equipment and if it were not for the ozone layer protecting us from it, life as we know it now on Earth would not be; x-rays (.1 to 10 nanometers) that can penetrate not just clothing but living tissues for medical diagnosis; and gamma rays (less than .1 nanometer) used in cancer treatments. (Source: Rose Space Center, American Museum of Natural History, NY and Trefil, James. The Nature of Science. Houghton Mifflin Company, Boston and New York, 2003)
Now, the colors of the rainbow are precisely the colors in the spectrum visible to the unaided human eye. Prisms have facets or cuts that bend the white light, splitting it into its many component colors, to an extent depending on its wavelength. Thus, when light travels from one medium such as from air, to a glass or crystal prism, it would be revealing the colors to my unaided eye with wavelengths between 400 and 700 nanometers, red, orange, yellow, green, blue, violet, with red having the longest wavelength and violet the shortest. It must have been delightful for Sir Isaac Newton in 1666 when he made this experiment with prisms and observed white light being split into many colors and came up with the first correct explanation on the nature of light and color. In his treatise on Light and Color, he wrote: "These things being so it can no longer be disputed whether there be colours in the dark, nor whether they be the qualities of the objects we see, no, nor perhaps whether light be a body… since colours are the qualities of light" (Microsoft Encarta 2000).
But what about those who cannot see? What relevance do color definitions or measurements have to their perception? Helen Keller was blind from birth, yet wrote with supreme imagination that surpassed colors. Cynthia Ozick, writer for the New Yorker, lights Keller’s prism for us: "While red may denote an explicit and measurable wavelength in the visible spectrum, in the mind, it varies from the bluster of rage to the reticence of a blush; physics cannot cage metaphor." I think I can understand that. When I hear or read prose, tale or poetry, it is layered on to my mind in color. Sometimes, the humdrum rhetoric of politicians would register in my mind as a tedious march of dark, gray-hooded members of some drab Fellowship of the Ordinary. Other times, the inspiring rendition of the moment’s reality by a poet-friend travels in my mind as a blue-violet wave of wild peace with magenta frills. And when with children, their spoken or written insights are lodged on to the basket of my brain nestled in refreshing sheaths of green and yellow, behooving me to think fresh and to re-examine browning, aging ideas about life and living. I also think though I have to look into this further, that women can differentiate colors better than men, prompting men to complain: "But isn’t ‘peach’ a fruit?!"
Of course, it is because I can look at things using my eyes that I recognize these color metaphors in the way I think and digest things mentally. But I also think that "looking" is not all there is to "seeing." A prism I think is also a good metaphor for really seeing and understanding. It is the facets, the way we are "cut," first biologically through evolution, then melding our passions with the choices we make in our lives, that we are able to "break" something we experience into aspects, and recognize the range – physical, emotional or intellectual – that live in us so we can understand it, even if not wholly, and make it help us make the most out of experiences we choose or find ourselves in. Animals have differing sensitivity and perceptual abilities. They are able to sense some things that are totally out of the reach of human senses. We lose them and we also lose our chance to truly know our world, and we would be slaves to our own limited human perception as just one creature among at least 10 million (in terms of species). With my human friends who like to examine and think about stuff, we sometimes look at a scene, physical or mental, and each, in his/her turn, says what he/she sees. Museums are also elegant and inexpensive adventures for the minds of visitors where the seemingly simple, familiar things become life-changing entries to the extraordinary!
What gratitude I feel that I have on my desk, a prism fashioned into the shape of bottled ink-and-quill, to help me think and write about an aspect of the nature of light and color. I can still hear in my head the younger girl, 8, who handed the crystal ink-and-quill to me, uttering these words with a faux British accent: "To escort words to eternity." Wow, and I am the writer?
(For comments, e-mail at dererumnatura@mydestiny.net)