A Natural History of the Senses

  Throughout time and place, people have been obsessed with the many moods of the sky. Not just because their crops and journeys depended on the weather, but because the sky is such a powerful symbol. The sky that gods inhabit, the sky whose permanence we depend on and take for granted, as if it really were a solid, vaulted ceiling on which stars were painted, as our ancestors thought. The sky that can fall in nursery rhymes. In the nuclear disarmament marches of the sixties, some people wore signs that read: CHICKEN LITTLE WAS RIGHT. We picture the sky as the final resting place of those we love, as if their souls were perfumed aerosol. We bury them among pine needles and worms, but in our imaginations we give them a lighter-than-air journey into some recess of the sky from which they will watch over us. “High” is where lofty sentiments dwell, where the “high and mighty” live, where choirs of angels sing. I don’t know why the sky symbolizes our finest ideals and motives, unless, lacking in self-confidence, we think our acts of mercy, generosity, and heroism are not intrinsic qualities, not characteristics human beings alone can muster, but temporary gifts from some otherworldly power situated in the sky. Stymied by events, or appalled by human nature, we sometimes roll our eyes upward, to where we believe our fate is dished out in the mansions of the stars.

  Driving four hours south, along spectacular cliffs and a wild and dramatic ocean where sea otters bob in the kelp beds, sea lions bark, harbor seals clump together like small mountain ranges, and pelagic cormorants, sanderlings, murres, and other seabirds busily nest, I pause on a wind-ripped slope of Big Sur. A Monterey pine leans out over the Pacific, making a ledge for the sunset. The pummeling gales have strangled its twigs and branches on the upwind side, and it looks like a shaggy black finger pointing out to sea. People pull up in cars, get out, stand and stare. Nothing need be said. We all understand the visual nourishment we share. We nod to one another. The cottony blue sky and dark-blue sea meet at a line sharp as a razor’s edge. Why is it so thrilling to see a tree hold pieces of sky in its branches, and hear waves crash against a rocky shore, blowing spray high into the air, as the seagulls creak? Of the many ways to watch the sky, one of the most familiar is through the filigree limbs of a tree, or around and above trees; this has much to do with how we actually see and observe the sky. Trees conduct the eye from the ground up to the heavens, link the detailed temporariness of life with the bulging blue abstraction overhead. In Norse legend, the huge ash tree Yggdrasil, with its great arching limbs and three swarming roots, stretched high into the sky, holding the universe together, connecting earth to both heaven and hell. Mythical animals and demons dwelt in the tree; at one of its roots lay the well of Mimir, the source of all wisdom, from which the god Odin drank in order to become wise, even though it cost him the loss of an eye. We find trees offering us knowledge in many of the ancient stories and legends, perhaps because they alone seem to unite the earth and the sky—the known, invadable world with everything that is beyond our grasp and our power.

  Today the ocean pours darkly, with a white surf pounding over and over. Close to the shore, the thick white wave-spume looks applied by a palette knife. The damp, salty wind rustles like taffeta petticoats. One gull finds a shellfish and begins picking it apart, while the others fly after it and try to snatch the food away, all of them squeaking like badly oiled machinery.

  When I was in Istanbul many years ago, I marveled at the way the onion-shaped mosques carved the sky between them. Instead of seeing a skyline, as one would in New York or San Francisco, one saw only the negative space between the swirling, swooping, spiraling minarets and bulbous domes. But here one sees the silhouette of distinctive trees against the sky: Scotch pine, which has a long stem with a roundish top resembling a child’s rattle; tall, even, rice-grain-shaped cypress and spruce. Farther north stand the sequoias, the heaviest living things to inhabit the planet. The talcy-leaved eucalyptus, nonnative trees that are so hardy and fast-growing they’ve taken over whole forests in California, look like bedraggled heads of freshly shampooed hair. In the fall and winter, one can find among their branches long garlands of monarch butterflies, hanging on by their feet, which have prongs like grappling hooks. Each year, a hundred million migrate as much as four thousand miles from the northern United States and Canada to overwinter on the California coast. They cluster to keep warm. Butterflies seem to prefer the oily mentholated groves, the fumes of which keep away most insects and birds. Blue jays occasionally attack the monarchs when they leave their garland to sip nectar or sit out in the open and spread their wings wide as solar collectors. Monarch larvae eat the leaves of milkweed, a poisonous, digitalislike plant, to which they are immune, but which makes them poisonous; and birds quickly learn that eating monarchs will make them sick. If you see a monarch flying around with a wedge-shaped piece of wing missing, you are most likely looking at a veteran of an uninformed bird’s attack. When I was helping to tag monarchs, I saw just such a female trembling on the porch floor outside my motel-room window. A huge blue jay in a nasty temper perched on the porch rail, screeching and flapping, and getting ready to dive at the monarch again. Though I usually know better than to intrude in nature’s doings, my instincts took over and I rushed outside, lunged at the blue jay to punch it in the chest, just as it leapt up with a great squawk and flap, truly terrified by my sudden attack. The butterfly stood her ground and shook, and I picked her up carefully, checked to see if she were pregnant by pressing her abdomen gently between my thumb and forefinger, feeling for a hard pellet. She wasn’t, and the missing wedge of wing didn’t look too bad, so I carried her to the base of a tree, at the top of which swayed a long orange string of monarchs. Then I held her above my open mouth and breathed warm air over her body, to help heat her flying muscles since it was a chilly morning, and tossed her into the air. She fluttered right up to her cluster, and, as I walked back to my room, I saluted her. The blue jay was still shrieking bloody murder, and then I saw it fly out of the yard with strong, confident beats.

  At Big Sur, the hawks are working the thermals like barnstormers, swooping and banking as they ride invisible towers of warm, rising air above the sun-heated ground. Birds are so nimble and adroit. Each species has its own architecture, flight habits, and talents to make the most of the sky, which they sometimes reveal in their silhouettes. On some owls, for instance, the leading edge of the primary feathers is softly fringed to muffle the sound of their approach. Finches flap hard a few beats, then close their wings and rest a little. Turtledoves flap continuously when they’re flying. Peregrine falcons fold in their wings when they dive. Swifts, which average about twenty-five mph, have very pointy wings that make them sleeker by cutting down on drag as they dart and glide. At the Grand Canyon, you can see them working the canyon walls like small aerobats.

  Our sky is also filled with “passive flyers.” Female ash trees loose their winged “keys,” and aspens and others produce long catkins that drop and blizzard across the ground. Maples launch tadpole-shaped seeds that fall whirlygig down, all blade, all propeller, like small autogyros. Thanks to the wind, the sex lives of many plants have changed. Dandelions, milkweed, thistles, cottonwoods, and others have evolved wind-riders in the shape of parachutes or sails. Pine, spruce, hemlock, maple, oak, and ragweed don’t have flamboyant flowers, but they don’t need them to divert a bird or bee. The wind is go-between enough. Plants can’t court, or run away from a threat, so they’ve devised ingenious ways to exploit their environment and animals. Pollen grains may be as small as one ten-thousandth of an inch in diameter, yet they must travel uncertain winds and strike home. Using a wind tunnel, Karl Niklas, a Cornell scientist, recently discovered that plants aren’t just hobos, hoping their pollen will catch a passing breeze and get off at the right stop. Niklas found that the pine cone has evolved an architecture perfect for capturing wind from any direction: a turbine shape, with petal-blades that spin the air all around it. Like a planet, the pine cone wraps itself in an atmosphere of rapidly moving air, with, just below the upper, swirling lay
er, a still and vacant layer. When pollen falls from the rapid layer to the still layer, it cascades right down into the cone. Niklas also tested the air-flow dynamics of the jojoba plant, which uses two rabbit-ear-shaped leaves to direct air, with results that show similar finesse.

  In allergy season, pollen makes me (and millions of others) sneeze a little, and my eyes sometimes itch so that I can’t wear my contact lenses. But I like knowing that all this mischief happens just because of shape. Tiny Sputniks traveling through the lower sky, some pollen looks like balls covered with spikes. Others are as football-shaped as the pupils of alligators. Pine pollen is round, with what looks like a pair of ears attached to each side. Their shapes make them move or fly at different speeds and in different patterns, and there’s little danger of the wrong pollen swamping the wrong plant. It’s odd to think of the sky having niches, but it does; even the wind has niches.

  As night falls on Big Sur, all the soot of the world seems to pour down into the sunset. A swollen yellow doubloon drops slowly into the ocean, shimmer by shimmer, as if swallowed whole. Then, at the horizon, a tiny green ingot hovers for a second, and vanishes. The “green flash” people call it, with mystical solemnity. But it is the briefest flash of green, and this is the first time in all my sunset-watching that I’ve seen it. Green, azure, purple, red: How lucky we are to live on a planet with colored skies. Why is the sky blue? The sun’s white light is really a bouquet of colored rays, which we classify into a spectrum of six colors. When white light collides with atoms of gases that make up the atmosphere—primarily oxygen and nitrogen—as well as with dust particles and moisture in the air, blue light, the most energetic light of the visible spectrum, is scattered. The sky seems to be full of blue. This is particularly true when the sun is overhead, because the light rays have a shorter distance to travel. The red rays are longer, and penetrate the atmosphere better. By the time the sun sets, one side of the Earth is turning away from the sun; the light has to travel farther, at an angle, through even more dust, water vapor, and air molecules; the blue rays scatter even more and the red rays remain, still traveling. The sun may appear magnified into a swollen ghost, or slightly elliptical, or even above the horizon when it’s really below it, thanks to refraction, the bending of light waves. What we see is a glorious red sunset, especially if prowling clouds reflect the changing colors. The last color that plows through the atmosphere without being scattered is green, so sometimes we see a green flash right after the sun disappears. In space, the air appears to be black because there is no dust to scatter the blue light.

  At Big Sur lighthouse, perched on a distant promontory, a beacon flashes to warn ships away from the coast and sandbanks, its light zooming out to them at 186,000 miles per second. The searchlight of the sun takes about eight minutes to reach Earth. And the light we see from the North Star set sail in the days of Shakespeare. Just think how straight the path of light is. Pass sunlight through a prism, though, and the light bends. Because each ray bends a different amount, the colors separate into a band. Many things catch the light prismatically—fish scales, the mother-of-pearl inside a limpet shell, oil on a slippery road, a dragonfly’s wings, opals, soap bubbles, peacock feathers, the grooves in gramophone records, metal that’s lightly tarnished, the neck of a hummingbird, the wing cases of beetles, spiders’ webs smeared with dew—but perhaps the best known is water vapor. When it’s raining but the sun is shining, or at a misty waterfall, sunlight hits the prismlike drops of water and is split into what we call a “rainbow.” On such a day, rainbows are always about, hidden somewhere behind the skirts of the rain; but to see one best, you have to be positioned just right, with the sun behind you and low in the sky.

  It is nighttime on the planet Earth. But that is only a whim of nature, a result of our planet rolling in space at 1,000 miles per minute. What we call “night” is the time we spend facing the secret reaches of space, where other solar systems and, perhaps, other planetarians dwell. Don’t think of night as the absence of day; think of it as a kind of freedom. Turned away from our sun, we see the dawning of far-flung galaxies. We are no longer sun-blind to the star-coated universe we inhabit. The endless black, which seems to stretch forever between the stars and even backwards in time to the Big Bang, we call “infinity,” from the French in-fini, meaning unfinished or incomplete. Night is a shadow world. The only shadows we see at night are cast by the moonlight, or by artificial light, but night itself is a shadow.

  In the country, you can see more stars, and the night looks like an upside-down well that deepens forever. If you’re patient and wait until your eyes adjust to the darkness, you can see the Milky Way as a creamy smudge across the sky. Just as different cultures have connected the stars into different constellations, they’ve seen their own private dramas in the Milky Way. The “backbone of night” the Bushmen of the Kalahari call it. To the Swedes, it is the “winter street” leading to heaven. To the Hebridean islanders, the “pathway of the secret people.” To the Norse, the “path of ghosts.” To the Patagonians, obsessed with their flightless birds, “the White pampas where ghosts hunt rheas.” But in the city you can see the major constellations more easily because there are fewer stars visible to distract you.

  Wherever you are, the best way to watch stars is lying on your back. Tonight the half-moon has a Mayan profile. It looks luminous and shimmery, a true beacon in the night, and yet I know its brilliance is all borrowed light. By day, if I held a mirror and bounced a spot of sunlight around the trees, I would be mimicking how the moon reflects light, having none of its own to give. Above me, between Sagittarius and Aquarius, the constellation Capricorn ambles across the sky. The Aztecs pictured it as a whale (cipactli), the East Indians saw an antelope (makaram), the Greeks labeled it “the gate of the gods,” and to the Assyrians it was a goat-fish (munaxa). Perhaps the best-known star in the world is the North Star, or Polaris, though of course it has many other names; to the Navaho, it is “The Star That Does Not Move,” to the Chinese, the “Great Imperial Ruler of Heaven.”

  Throughout time, people have looked up at the sky to figure out where they were. When I was a girl, I used to take an empty can, stretch a piece of tinfoil over one end and pierce pinholes in it in the outline of a constellation; then I’d shine a flashlight in the other end, and have my own private planetarium. How many wanderers, lost on land or sea, have waited till night to try and chart their way home with help from the North Star. Locating it as they did connects us across time to those early nomads. First you find the Big Dipper and extend a line through the outer two stars of its ladle. Then you’ll see that the North Star looks like a dollop of cream fallen from the upside-down Dipper. If the Big Dipper isn’t visible, you can find the North Star by looking for Cassiopeia, a constellation just below Polaris that’s shaped like a W or an M, depending on the time you see it. To me, it usually looks like a butterfly. Because the Earth revolves, the stars seem to drift from east to west across the sky, so another way to tell direction is to keep your eye on one bright star in particular; if it appears to rise, then you’re facing east. If it seems to be falling, you’re facing west. When I was a Girl Scout, we found our direction during the day by putting a straight stick in the ground. Then we’d go about our business for a few hours and return when the stick cast a shadow about six inches long. The sun would have moved west, and the shadow would be pointing east. Sometimes we used a wristwatch as a compass: Place the watch face up, with the hour hand pointing toward the sun. Pick up a pine needle or twig and hold it upright at the edge of the dial so that it casts a shadow along the hour hand. South will be halfway between the hour hand and twelve o’clock. There are many other ways to tell direction, of course, since roaming is one of the things human beings love to do best—but only if they can count on getting home safely. If you see a tree standing out in the open, with heavy moss on one side, that side is probably north, since moss grows heaviest on the shadiest side of a tree. If you see a tree stump, its rings will probably be thick
er on the sunny side, or south. You can also look up at the tops of pine trees, which mainly point east. Or, if you happen to know where the prevailing wind is coming from, you can read direction from the wind-bent grasses.