I seem to be stuck on light, as inspired by the shift to the growing amount of light this time of year. What I realized is that it isn’t just the amount of light in the day but its quality. This is particularly noticeable after spending too many hours indoors under artificial lights while staring at screens that glow with even more artificial light. I wonder why my eyes feel tired until I walk outside and stare up at the sky and they suddenly relax. I’m no ophthalmologist, so I can’t explain the intricacies of what happens to the human eyeball under certain light conditions. I do know that it seems more natural under natural light, like when I walk outside on a sunny day and squint or put a hand up to shade my face. If I looked in the mirror, I would see that my pupils had shrunk in an effort to let less light into my eyes in a sort of built-in-sunglasses effect. I’ve been trying to get better about wearing actual sunglasses, but part of me enjoys the unfiltered light and as much of it as I can get in the winter in Maine, even as sensitive as I am to bright light.

It made me think about what the differences are in types of light and why natural light seems so different. Of course, there is firelight and candlelight, both of which have warm tones, and there are even some types of artificial light that are impressively soft and warm in the glow they give off. But none of these are the same as the ever-varied natural light that fills the sky and water, particularly when you live along the coast and every moment is just a little, if not a lot, different than the one before — like when a dark and brooding day shifts to be bright and clear, as if the entire season suddenly changed.

What seems so pure as crystalline sunlight is, of course, the combination of many different colors that, when combined together, cancel each other out — only to be broken apart by a prism, or maybe a droplet of moisture, into a rainbow. This is known as refraction. How these colors are freed when light enters into and under the water is a whole other magic. Basically, when light enters the water, it gets bent and that bending splits the colors apart. That’s why light looks different under the water. Water is also much more dense than air, so light is absorbed more quickly, making everything look kind of blue or gray and fuzzy. In addition, certain colors get absorbed at different depths and therefore disappear from what you see. Red happens first, then orange, yellow, green, blue, indigo and violet — same as the colors in the order of the rainbow, leaving everything looking blue at around 100 feet unless you shine a bright light on it and then it again becomes a rainbow of color.

The oddities of light underwater also partly explains why fish have very different eyeballs than humans. If you ever have a chance to look at a fish eye closely, you’ll find a little hard ball hidden inside that is the lens. In a human, this is shaped like a concave disk, but in a fish, it is a sphere. This is so that a fish eye can gather the light that is coming into it from all directions since light is much more scattered underwater than in the air. If you’ve heard someone refer to a fish-eye lens, it isn’t a lens that is round like this but rather refers to the phenomenon that results from the refraction, or bending of light, when it enters the water from the air. Because of this, it makes things seem artificially magnified — thus the creation of a “fish-eye” lens often used in underwater photography that has a curvature that corrects for that refraction.

One of the neat reasons that the light bends when it enters the water is that it slows down since water is more dense than air. It’s a seeming metaphor for how our eye slows down when it looks out at the water, even when it is not looking underneath (although it may slow down even more underneath the water given how poorly the human eye sees there). Regardless, it is yet another reminder of how amazingly well-adapted sea creatures are to see amidst what light there is underwater and whatever color and form it takes. Perhaps that’s the true slowing down: in that appreciation for simplicity as well as specificity in nature.

Susan Olcott is the director of operations at Maine Coast Fishermen’s Association.

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