December 2008

Sarah Burke

features

Look Books: A Natural History of Seeing and How to Use Your Eyes

“What you look at hard seems to look hard at you.”
-- Gerard Manley Hopkins, journal entry, 1871

What seems solid isn’t, right? We learn this in high school and it sticks with us even after we forget the difference between atomic number and atomic mass. Electrons swarm around nuclei in clouds that, like real clouds, are mostly space. Atoms align themselves in ways mysterious to most of us into the substances of our world, and we rely on them to stay in the places where they started, or to follow prescribed patterns when we subject them to our influence. This is just to say: how little we think about the things in our world and the reasons they act and look the way they do.

Humans see because of light. Light enters an eye via the cornea, passes through the pupil, hits the lens, which flips and projects the light onto the retina, where a net of rods and cones turns the light into electricity. The electricity jumps to the brain to become a picture. This happens millions of times per day, as our eyes move about, taking into account the hundreds of objects, moving and unmoving, that reflect light towards us at a given moment. A picture show.

The eye has many beautifully-named parts that reflect the long history of optics: aqueous humor, vitreous body. Different creatures have different sorts of eye. Shrimp have eyes composed of many reflective boxes that, in aggregate, resemble disco balls. A cat’s eye appears to glow at night, but the reality is in fact much weirder and has to do with small mirror-like layer of tissue (the tapetum lucidum) behind the retina. We still don’t entirely understand how the human eye evolved, and its mystery remains part of the limited arsenal employed by those who argue for intelligent design.

Back when visionary literature was the rage, wandering mystics and anorexic nuns would communicate their experiences with terms such as blinding light, consuming fire, exceptional brilliance. They climbed sparkling ladders in their dreams to walk through a series of veils in order the see angels, God, and other beings of light. They would be given things to eat that looked one way but tasted another, a cognitive disconnect demonstrative of God’s power: this scroll tastes like honey. They saw. They were enlightened. We knew before we knew that vision came from light.

Simon Ings has a new book called A Natural History of Seeing. James Elkins has a not-particularly-new book called How to Use Your Eyes. They are both very good and they go well together. Ings wants us to know how our eyes work. He begins the book with the image of his daughter as fetus, blind and one-eyed before the molecules followed their cues and shifted apart from one another to create two eyes, an arrangement preferable for many evolutionary reasons. He explains rods, cones, and the funny house-of-mirrors apparatus that allows us to see. He also walks us through the history of ophthalmology, which is more exciting than it sounds. In the eleventh century, for example, Ibn al-Haytham lived for twelve years in a dark house, pretending to be crazy so he would be free to study the geometrical behavior of light. Ings makes you think about seeing:

When we read, our eyes fixate on between just twenty and seventy percent of the words. Who or what tells our eyes which words to choose? Where does that knowledge reside? How is it made, where is it stored, and how is it accessed?… The eyes stay one step ahead of the body, dealing with the next view, the next task, the next set of predictions and calculations, while the body relies on the "buffer." This raises the odd but compelling idea that the "present moment," as we experience it, has a measurable duration. We operate in the world, not as it is, but as it existed half a second ago.

I often became aware of my eyes receiving information from the pages of Ings’s book. Ings provides a photograph of the face of a young girl and a diagram of how our eyes are likely to process it. I felt my own eyes tracing the lines programmatically, saccading like “an insect’s antennae, or a mouse’s whiskers” to and fro from areas of extreme light and dark. I couldn’t help but take in the information precisely as the diagram suggested I would. That was peculiar, but also wonderful: how often are we so aware that we are looking at a book when we read it? Also, Ings includes optical illusions at the head of each chapter that require you to go cross-eyed to make the lines cohere into a three-dimensional cube, cylinder, whatever. What fun!

James Elkins’s book is also fun, in the way of a nineteenth-century encyclopedia or a child’s book of suggested activities for a rainy afternoon. Minerals, maps, constellations, secret codes, fingerprints! How to Use Your Eyes is divided into two parts -- “Things Made by Man” and “Things Made by Nature” -- both beautifully illustrated, about 30 chapters in total. Elkins begins his book by counting the days remaining in his life in which he will have the time to pay attention to grass. He comes up with only 600, noting that “they can easily slip away.” Elkins wants us to notice our terrain. Ice halos, for example, are bright circles and arcs that form around the sun in the winter-time. They are not uncommon but, perhaps due to a reasonable aversion to looking at the sun, we miss them. Also, physicists still don’t entirely understand them. Elkins has a 1551 German woodcut in facsimile that shows several mysterious halos:

That is the real beauty of halos, as far as I am concerned -- some of them are so fabulously rare that no one knows how they are formed. Even in five centuries of observing, only a few people in Wittenberg ever saw the arcs that are recorded in that woodcut.

Elkins provides you with many details that will make you more interesting on road trips. Did you know that bamboo is a kind of grass? That the light of the moon obscures the light of the stars, so a moonless night is best for star-gazing? That the human eye can be tricked in many ways, but that a mirage is not one of them? Mirages are real. They are created by the way light bends through the air at particular temperatures. They can be photographed. Elkins joyfully explains the different types of cracks that appear in old oil paint (craquelure) and gives photographic examples of curved cracks, jagged cracks, and “cracks in islands.” Don’t just look at the image in the frame, he says, but at the object. Figure out how it works. Test it with your eyes.

The other day I emerged from hours of working at my computer in a shadowy room. I went to the last farmers’ market of the season and began the walk home carrying altogether too many winter squash. It was windy and had recently rained. As I paused to shift the weight of the produce I happened to see a rainbow spread emphatically from one end of the sky to the other. A rainbow as an idea is not spectacular -- just some colors -- but as an experience it is energizing, because it is always a surprise. I stared for several minutes while people moved around me. (Why are people so disinclined to pause to look at what a stranger is looking at?) An abundance of riches: just moments later the trajectory of a red-tailed hawk caught my eye and for some time I watched this bird hover, hunting, over the handkerchief lawns of my neighborhood. The hawk landed and took off again. It went behind a tree but I was prepared and knew where it would emerge. I felt my eyes bounce around charting the shapes and movements of my world and was grateful to be aware of these things.

Thanks to Katie Peterson by way of Alex Rothman for the Hopkins quotation.