Our eyes track a fly ball till it drops into a glove. They pick out differences among snowflakes. From a dozen store racks, they find just the pants to match a new yellow shirt.
But human eyes aren’t the only eyes around. There is more to this world than what our eyes can see. As we look at the animals around us, we might wonder, Do you see what I see?
Imagine that you are an owl perched in a tall tree, watching with an owl’s saucer eyes. It’s sunset, but sky and field are grayish. You don’t see the flaming colors that humans do. As night falls, you search the ground below for food. In a tenth of a second, your head swivels more than a half circle in each direction.
At night, humans see only fuzzy shadows. But night for you is never really dark. Your view is as clear as a black-and-white photo snapped on a cloudy day. When a garter snake slips through grass far below, you track it easily. You dive on soundless wings through a night a hundred times brighter than the one that humans see.
Next, imagine that you are a bee. Each of your compound eyes is made up of thousands of single eyes crowded together. It is a cloudy summer morning. Near the entrance to your hive, another bee dances a fast, complicated dance, telling you where she has found nectar. Your eyes are quicker than human eyes, which would see her many movements as a blur. Your bee eyes would see a movie as a series of still pictures.
You find your direction by the sun. Even though the sky is cloudy, a light and dark pattern, which human eyes can’t see, shows you just where the sun is. As you fly, each surface of your eye shows a dot of color, light, or shadow. Your world is a pattern of dots. It looks like a newspaper photo seen through a magnifying glass. You especially notice things that move, like flowers swaying in the wind.
Humans can distinguish thousands of different objects, whereas you notice only two kinds of objects—flower-shaped things and formless blobs. But you see different flower shapes—triangular, six-petaled, daisylike. Your garden is brightly colored, but it’s a different rainbow, with colors human eyes never see.
Finally you reach the patch of primroses the dancer told you about. As you come in for a landing, a colored pattern on the flower guides you to the nectar. You use this “honey guide” the way a pilot uses lights on an airport runway. But the primrose landing guide is ultraviolet, a kind of light human eyes can’t see. Only photos taken through yellow or ultraviolet filters reveal it.
Now imagine that you have no eyes. Instead, you have eyelike organs all over your body. You live in the soil, and tunnel endlessly. You are an earthworm. In your underground world, you don’t need to see. You find your way by touch. Your skin is moist and delicate. Beneath it, instead of bones, there is a layer of liquid. Your liquid skeleton can make your body long and thin or short and fat, or make it ripple like a wave. These movements help you tunnel through the ground. You love the cool underground darkness. Too long in the burning sun, and your body would sizzle and shrink, like a drop of water on a hot grill.
One day as you tunnel through the dirt, you come too near the surface. Your back pops out into the sunlight. Tiny cells in your skin detect the light, as eyes do. But they don’t see it, as human eyes would. Instead, they send a message to your muscles, as human skin does when it touches a sharp knife. “Pain!” they say. “Danger! Go away from the light! Dig down into the dark!” Your muscles obey. You burrow down, and the cells send a new message: “Now it’s cool and dark. You’re safe again.”
The next time you look at an animal, think about how different a world its eyes may see.