The Ground Beneath Us

Manhattan

Next to One World Trade Center, as part of the National September 11 Memorial, are the footprints where the two buildings stood, square depressions, water falling down the four sides and flowing into smaller squares. At ground level, the chest-high walls are etched with the names of those who died. Maybe most affecting are the names of the firefighters, those who rushed to help others, their names grouped together as they were in life. Next to the building footprints, a plaza holds some four hundred swamp white oaks and several rectangles of turfgrass. Small signs warn visitors off the grass, and when I ask a guard why, she replies, "It's not a park; it's a place to pay respects." So I will follow a biblical lead. "Remove the sandals from your feet," Moses is told before approaching the burning bush, "for the place on which you are standing is holy ground." I take a seat away from the crowds, remove my shoes, and place my bare feet on the concrete. Sometimes in the northern forest, I'll walk the loamy ground under Norway pines, salmon-colored needles cushioning my feet. But in day-to-day city and suburban life?

The experience of feeling our feet on natural ground, common throughout most of human history, has become increasingly rare. And for anyone in a city, rightly so—the hard and often filthy artificial surfaces beneath our feet call for some protection. The skin on the soles of our feet is our body's thickest and some of its most sensitive, covering a high concentration of nerve endings. Our feet, in fact, are as sensitive as our hands—imagine wearing gloves as much as we have our feet in shoes. And the prints of our toes? As unique as our fingers—some militaries keep inked footprints as backup IDs—and the ridges and curves on the soles of our feet are as unique as those on the palms of our hands.

Around the world we have footprints preserved, in wet sidewalk concrete and clay Mother's Day gifts, but ancient footprints, too. Most recently a 1.5-million-year-old set was found in northern Kenya, likely made by a human ancestor called Homo erectus. So similar to the prints of a modern human are the fossilized find that the archeologist who discovered them said they look "like something that you yourself could have made 20 minutes earlier in some kind of wet sediment just next to the site." Wherever you are, a footprint offers an invitation to imagine those who walked here before you.

We are made for walking; our bodies evolved to perform this skill. And walking is maybe our most elemental experience of the earth, our most direct contact with the planet on which we rely. Walking (or bipedal locomotion, as it's known in some scientific literature) propels us at the perfect speed to soak up our surroundings, to talk with a friend, to contemplate the impending decision between a slice of pizza or lunch of some other kind. If travel by airplane erases the history, diversity, and beauty of the land we fly over, and driving reduces the world's sensory buffet to a tasteless, scentless, soundless blur, walking is where we have a chance to make it all up.

Maybe that's why so many of us claim that our best thinking comes while walking. Charles Darwin had a "thinking path" outside his home, a circuit on which he knocked a small stone from a pile each time around. Virginia Woolf used walking to get out of her house and venture into an exhilarating evening where women weren't often allowed, to "walk all over London; and see people and imagine their lives." Thoreau thought walking four hours a day to be living well, and wrote an essay in which he extolled the virtues of sauntering, to which the secret of success was "having no particular home, but [being] equally at home everywhere." William Wordsworth is said to have walked some 180,000 miles in his lifetime, which averages to more than six miles a day beginning at age five. There are countless famous examples of how walking stirs the soul and makes us who we are.

These days, though, we don't walk much. In fact, we in the United States walk less than the inhabitants of any other industrialized country. That my immediate examples above all hail from the nineteenth century makes sense, as even the "civilized" world was still made for walking then, not yet rearranged for cars, trucks, and buses. To mourn the loss of walking isn't merely to pine for the good old days, but to call attention to something we have always enjoyed. In New York, Paris, and other walking-friendly cities, we humans take advantage; we walk. I think we understand, as Rebecca Solnit explains in Wanderlust, that with the loss of walking we lose "an ancient and profound relationship with the body, world, and imagination."

We are learning more all the time about the true costs of this loss. As one Slate writer says, "The decline of walking has become a full-blown public health nightmare." One new study after another confirms that walking promotes health and well-being. This is true whether said studies claim that walking will bring "substantial reduction in the incidence of cardiovascular events," or that in terms of improving health, walking is "the equivalent of popping a series of magic pills." In addition to cutting our risk of becoming diabetic, suffering a stroke, or developing cancer, walking reduces hypertension, helps prevent depression, and strengthens the circulatory system. While Amish men take about eighteen thousand steps per day and Amish women fourteen thousand, the average American takes four thousand. Perhaps as a result, only 4 percent of Amish are obese, compared with 30 percent of the general population. Declares the nation's leading newspaper, "To Age Well, Walk."

At the southern end of Manhattan the streets still generally follow the more natural routes adopted by the Dutch from the Indians and developed in a way that reflected the island's hilly topography (the native Lenape name translates as "island of many hills") and swampy ground. Though it runs only as far north as Wall Street (once an actual wall built to keep the English or Indians out), the street map of the Dutch city (New Amsterdam until 1664) remains largely intact. Beyond that boundary lay wilderness. Here, across Houston, I find a very small park, just twenty-five by forty feet, that Time Landscape created in 1978 to preserve (or, actually, to re-create) the forest that "once blanketed Manhattan island." The surrounding area, says the sign, was "once a marshland dotted with sandy hills," the "trout-filled Minetta Brook" making it a popular site for fishing and hunting ducks. I stand outside the park's short fence on flat, smooth, hard concrete. On the other side is dark soil holding living things. Once there was a woodland here of witch hazel, black cherry, and red cedar trunks. Oak, sassafras, sweetgum, and tulip trees, arrowwood and dogwood shrubs, bindweed and catbrier vines, and violets. The small park invites city dwellers "including insects, birds, people, and other animals" to experience "a bygone Manhattan."

Farther up the island, north on Fifth Avenue, the Empire State Building marks the horizon ahead, while behind me One World Trade Center marks the other. At Fourteenth Street I stop, for here begins a most remarkable story about the ground beneath this city.

In 1808, in an attempt to unravel the "evil of confused streets" and to facilitate the development of the island, city commissioners commissioned what would eventually become the street grid of horizontal and vertical lines that defines today's New York City. In doing so they turned to John Randel Jr., first for the grid's design—a survey that took two years to complete—and then for its execution. Turns out the survey was the easy part. To execute the plan, Randel had to mark the grid exactly (and this was a man of precision, in one case complaining that his measurements had set the grid off by 1.8 inches). For six years, the work took him through swamps and woods, farms and fields, over more than eleven thousand acres in total. He was pelted by landowners throwing artichokes and cabbages, chased off property by dogs, and arrested several times. Nonetheless, Randel and his employees placed more than a thousand bolts and monuments to mark future intersections. The development that would follow Randel's work took more than a hundred years to realize, but began almost immediately. Swamps were drained, woods were cleared, farmland and fields paved, the hilly island leveled—the bedrock just beneath the surface blown apart.

In fact, this drastic rearranging of surface life drew—even two hundred years ago—criticism for its brutish disregard of the island's natural topography. Walt Whitman and Frederick Law Olmsted criticized the plan, as did Alexis de Tocqueville, who claimed that it represented the imposition of "relentless monotony." Others criticized the chopping down of forests, burying of streams, and filling in of hollows to create a flat surface on which the commissioners could more easily lay out their grid. "The great principle which governs these plans," wrote one critic, "is to reduce the surface of the earth as nearly as possible to dead level." This is the reason Manhattan's streets are so flat and straight, its long rows of tall buildings creating canyons of stone that echo the sound of traffic, why twice a year the sun sets perfectly aligned along east-west streets, an event that's come to be called Manhattanhenge. Some ancient people's monuments to honor the sky and its gods? Or simply the unintentional result of what another contemporary critic called the "republican predilection for control and balance… (and) distrust of nature."

Though Randel and his men tromped through swamps, climbed hills, and crossed streams, almost none of those natural features figured in their final maps. In fact, even in their field notes the natural world was valuable only as a resource for human use. I think of historian Frederick W. Turner's description of European explorers discovering a New World filled with flowers and sea life and birds, a beauty worthy of inspiring song and poetry and praise—even "a new mythology"—and then his devastating line: "As it was, they took inventory."

Randel's maps take inventory as well, of ground that is portrayed as ready for the city's taking. In this way, Randel's hand-drawn and colored maps—which when connected together to show the entire island stretch nine feet long—reveal the challenge posed by maps in general, that they are abstractions of reality reflecting certain sets of values. It may be obvious that no map can include every tree or bee or birdsong, but the implications may not be so. While on our maps we often see a park as a block of green, for example, or a lake as a blob of blue, more often a field of wildflowers or a stretch of woods is simply left blank. Even today our road maps—think Google—show only blocks of color dissected by streets. These are maps of abstraction, of time schedules telling us when we will arrive, not maps of living things. Whether we use them to understand the route through a city or to make decisions about what to "develop" and why, we would do well to pause. "Caution," a corner of each map might read: "No map can hold the true richness of the world."

Given that the Earth is spinning in space as it spins around the sun, and the sun is spinning in a galaxy that itself is hurtling outward at a thousand kilometers per second, I sometimes wonder how we are able to walk this ground at all. But as with so much else on this close-to-perfect world, it turns out that our planet spins at just the right speed to keep us happily walking crowded sidewalks, pizza in hand. The concept is this: as in a subway car or an airplane in flight, we seem set in place—we can walk around, stand on one leg, perform daring feats of balance—even though the train or plane is rushing us from one locale to another. It's only when that vehicle begins to slow or accelerate that we feel the pull—our body no longer quite sharing the vehicle's speed. All the spinning through space of celestial bodies doesn't affect us here on Earth because all these various bodies are moving at a constant rate.

There's also the fact of gravity. Newton gave us a basic understanding, which Einstein then complicated. Early in the twenty-first century, gravity is still acknowledged as "the most puzzling and least understood of the four fundamental forces of nature." Any simple definition of the word hides the fact that scientists still have loads of questions. "A force pulling together all matter," says one definition; another reveals that gravity not only dictates the movement of the planets in orbit around the sun and the movement of our oceans' tides, but also "the adherence of humans to Earth." And that's not all. Besides bringing such benefits as holding our atmosphere in place, gravity actually shapes our bodies. To put it another way, we are physically shaped—our bones and muscles molded—by our body's resistance to gravity's constant pull.

The mysteries of gravity relate to us in other ways too. After spending 340 days in space, American astronaut Scott Kelly admitted that the hardest challenge wasn't the effect of weightlessness on his body but "being isolated from people on the ground who are important to you." That pull toward our loved ones is a feeling we all can understand. And there's more: Kelly also felt a pull to the planet ("The solid earth!") on which we all rely. After witnessing great spreads of pollution, storms the size of which we have never seen, and the fragility of the atmosphere, he said, "I feel more like an environmentalist since I've been up here." Like the size of the universe or time before your time, gravity, a force we only begin to understand though it shapes Earth's life, seems a mystery too big to hold, and to which the only worthy response is astonishment and thanks.

Walking past Rockefeller Center I think of the annual Christmas tree in the square, sawed at its base and delivered by semi, set atop a sea of concrete. Everywhere in this city you will find that juxtaposition of the natural world with the human-made: the rooftop garden, the small pine on a patio thirty floors up, the overgrown rail line turned park. It's a juxtaposition dramatically displayed on the cover of Eric Sanderson's book Mannahatta