WE’RE CAMPING on the shortest night of the year in northern Wyoming, our tent pitched in a spot that must have lain beneath snow no more than a week ago. A few yards away, a meltwater freshet chatters and rushes toward pussy willows that haven’t even begun to leaf out, though they’re fat with soft-furred potential. A Wilson’s warbler works the branches, flitting about and feeding.

Five miles southeast is Medicine Mountain and the Big Horn Medicine Wheel, our destination for the solstice sunrise. A monument of rocks laid thinly on the landscape, the medicine wheel lacks the vertical reach of the great standing stones of Stonehenge; exposed to the sky at an elevation of 9,642 feet, it is accessible and visible only during the brevity of snow-free months in summer, so lacks the history of architectural inhabitation one admires in the great houses and towers of the Ancestral Puebloans. But according to solar astronomer John Eddy, the wheel calibrates the summer horizon in a variety of ways, lining up with the solstice sunrise and sunset in June and, at different times throughout the weeks of summer, at least three different star risings in the predawn dark, just before they’re lost in the sun’s glare (“heliacal risings” is the term for these). Like most other scholars, Eddy remarks on how well preserved the medicine wheel is, and how monumental in its dimensions, which are attractions enough to make me want to see it with the sunrise washing across the pattern of its cairns and spokes.

There’s one other party arriving in the campground, two men and a little boy. They park their camper near our tent and step outside to stretch. The boy hurries back inside, then re-emerges having traded his shorts for long pants; soon, all three are lobbing snowballs at one another while the boy shrieks with enthusiasm. I watch them, then watch Dave following the warbler with his camera, trying to get a good shot. Wilson’s warblers are impressive migrants; most spend the winter in Mexico or Central America, then hustle northward to their breeding grounds — the Yellowstone area on up to Alaska, or across the Canadian Shield to Labrador — before the snow has melted. Their bodies carry records of these great migrations: each feather holds an isotopic signature of the latitude at which it grew. That signature is a kind of watermark, since, as Dave explains — he researches this process in prairie birds — rainwater varies in its isotopic composition, or the proportion of deuterium present. And what determines that variation is time (the season) and place (the distance from the Earth’s equator); the heaviest vapor falls first, as you might expect, while the lightest travels the sky’s currents toward the poles. If you drink melted snow above the Arctic Circle, you’re drinking some of the lightest water on Earth, and its specific identity is laid down in your hair, inscribing on your person where you’ve been. And if you are a prairie dweller in the rain shadow of the Rockies, your hair will record the changing seasons, as moist warm air swirls upward from the Gulf all summer, with its greater molecular weight mottling the thunderheads, while the sleet or snow or plain old chilling rain of midwinter has likely swept down from somewhere farther north.

In the Wilson’s warbler all this is recorded in black and yellow plumage. This one probably wintered somewhere in northern Mexico. Warbler feathers show that the individuals who winter farthest south also travel farthest north come springtime: the symmetry of their migrational arc is more important, it seems, than any equivalence of distance. And what sets those tiny travelers out on their seasonal journey is the sun — photoperiodicity, the length of daylight, as gathered in the bright round eye that, morning to evening, turns its perky attention outward to the world. The inner workings of the avian body-clock announce that it’s time, and hormonal changes shift the bird into breeding season: his plumage, his behavior, his defense of whatever handsome patch of landscape will become his territory until that summer’s young are fledged and ready for the long trip south. Sitting in the evening’s cooling air, drinking beer from the cooler packed with snow, I marvel at their receptivity to the season’s signals, as the year turns and turns again.

THE WHEEL LIES on the northwest shoulder of Medicine Mountain, at the southern end of a bone-shaped, treeless meadow. It’s draped like an enormous tatted doily of white stones above a high saddle overlooking the dry basin lands below. Today a visitor can reach it by hiking a mile and a half of broad dirt road up a gentle incline from a parking lot, as we intend to do in the morning, to see the sun begin to cast its longest day of clear, mountain light across the landscape.

In the early years of the twentieth century, when some scholars sought contemporary interpretations of the monument among the local tribes, the symbolic nature of the wheel was explained as a Medicine Lodge or a traditional Sun Dance Lodge. Naturalist George Bird Grinnell relates that a Cheyenne man named Elk River, who was born early in the 1800s, told him: “The outer circle of stones . . . represented the wall of the Medicine Lodge; the lines leading toward the center, the rafters — or, as he called them, the lodge poles — of the Medicine Lodge.” In the mid-twentieth century, Chief Robert Yellowtail presented a different explanation of the wheel’s symbolism with no uncertainty: “It is very plain to me that the Medicine Wheel is a large replica of the Sun Dance as it existed among the Plains Indians of this area.”

But excavations in 1958 and 1973 revealed that the impressive wheel-like pattern on the ground today doesn’t represent the monument’s form as it was first built. The structure is a composite, with a large central cairn and some additional cairns at various positions around the outer rim laid down far earlier than the spokes or rim itself. Exactly how far earlier remains undetermined. There are interesting possibilities, though, beneath that record of sequential renovation and addition. Archaeological remnants indicate that the immediate area was seasonally inhabited for millennia: along Crystal Creek on the mountain’s southwest flank, a Paleo-Indian point dating to ninety-five hundred years ago was found, and other artifacts, including pottery shards, indicate the site was used as an intermittent campsite for more than four thousand years.

So there’s a lithic scatter of continuity that drapes the landscape of Medicine Mountain. Try to imagine the gathered pool of time that has not yet been drained into the linear flow of the “historic period,” as well as the people who followed the seasons from low elevations to high, from grasslands through the wind-tossed aspen shade and into the aromatic cover of evergreens and back down again. In a stationary culture (the agriculturists, say, who measure the unfolding pattern of time as it plays out on familiar land), time perhaps comes to one. Place remains the known constant, while the mutability of week or season casts a variable light on the known terrain. In a migratory culture (the hunter-gatherers who must arrive in a particular ecosystem when the bounty is best and be ready to move on for the next destination), the emotional value of greeting the landscape — taking one’s leave and making one’s return — enters, and time and place both vary, though in a close association. Or, more surprisingly, perhaps both time and place are the constants, and in a shifted sense of planetary perspective, it’s the people who are variable, who arrive and depart, always in the continuous present, while the sweet specificities of fruit or game resolve themselves in their expected confluences. Of course, this is conjecture, my own attempts to glimpse other ways of locating the self, and the self’s social world, in the conceptual territory that one might call geochronicity — adopting a term from the realms of Earth sciences, and adapting it for more philosophical contexts.

But even if we were to stand atop Medicine Mountain well before dawn, we wouldn’t see Aldebaran rise as observers might have once. Epochs ago, it would have risen early in a still-dark sky; then, ages later, it would have lifted only briefly, like a sudden signal, into the northeast sky before disappearing in the glow of dawn. It is the Earth’s own motion, torqued between the competing pulls of sun and moon as it spins on its axis, that leads to these slow changes. That wobble in the planet’s rotational axis is often described as “like a top’s,” but for the Earth, this precession, as it’s called, is top-dwarfingly slow, taking nearly twenty-six thousand years to complete a single wobble. So discussions of these sky-markers of another age are all in the subjunctive mood, almost as if the past is some alternative universe, a hypothetical possibility whose point of intersection with actuality’s sweep is anchored here in a pale stone pattern in shortgrass and the brief flares of wildflowers. But speculation, possibility, those are the rays along which we can train our gaze, to see whether they connect us with anything greater than ourselves.

WHEN THE SUN FIRST SLIDES above the horizon I see the alignment, as if the spoke were a narrow cobbled pathway leading into the crescent of light. Then the glare becomes far too intense to continue close scrutiny, and as the sun lifts, already inscribing its arc toward the southeast before it’s fully cleared the ridge, the spokes of the wheel stand out in exaggerated relief. The visitors — about twenty of us — look at one another, some smiling.

A couple dressed like ranchers, wrapped in a western blanket, is silent. A Northern Cheyenne man talks quietly with a younger white man, who seems to be a sort of student under his guidance. The young women who work for the Forest Service as interpreters all stand together, beaming.

There’s no practical purpose for our presence here: none of us will hold today’s solstice against our personal tally sheets to correct our sense of time. None will now be better able to plan when to plant, or harvest, or pursue any portion of our daily business; even if any among us are farmers or hunters or, like me, zealous seekers of springtime morels, the certainty we gain that today is the standstill of the sun, the very midpoint in the annual cycle we understand to be a year, won’t figure in our material well-being. I have no idea whether there’s a religious motivation behind anyone else’s presence here, but the private air that seems to hold sway over us all doesn’t imply the sense of group cohesion that lies behind so much of religious ritual.

“Right relation” is the term that comes to mind for what we’re after. It’s a handy pair of words that can be called on variously to help identify the hinge function of the knee or the Christian’s personal connection to God through Christ or the metaphysical realist’s observation of the world unfolding. “Alignment” is central to this concept, though I know it’s partial since few of us will be around in the coming months to watch the sun reverse its northward course. For us, this is just a single point in time, abstracted from the full cycle.

Still, we’ve glimpsed the wheel in its best light, before full daylight can begin to shrink the suggestive shadows. From the Buddhist mandala to the archetype of the Jungian self to the Native American sacred hoop, a circle suggests the elegance of wholeness, of complementarity. And with its center point marked, it maps a possibility of belonging: one could place one’s self there, in the direct center of completion’s curve, time circling the body with certainty and light.

TWO DECADES AGO Bill McKibben described what he called the aesthetic response of his sadness at our brave new world with carbon-flooded skies. We have since crossed the threshold into the new millennium and begun to see signs of greater unpredictability in the weather as well as what biologists call phenological mistiming: birds whose migrations no longer calibrate precisely to the seasonal availability of food sources, for example. Some now arrive too late to feed on their accustomed caterpillars, and their young go hungry. And we all talk about the changes in our local experiences of weather. Back home in Kansas, the rains seem to have shifted slightly from their accustomed arrival in early summer toward something more like the monsoons of the Southwest, in late July or August. But I’m not sure we have discovered what McKibben called “the irrelevancy of the past.” I’m not talking about particular forecast models that will no longer work, but rather the larger sense that haunted McKibben — that the great sea change is how we understand the world. “The end of nature” meant that sublimity no longer pertains, that the daily phenomena of the weather itself, and the global climate that drives it, are now within the sphere of human activity rather than outside. This insight is still perceptive, sobering, and saddening, but there may be an additional truth here, in the shadows of our understanding.

For most of the time the various species of Homo have lived on this Earth, climatic change has been the order. The brief stability we’ve called the Holocene has been a geologic oddball, although it’s been within this period that Homo sapiens has domesticated the world, from corn to cows to combustion engines, and that we’ve reproduced so successfully as to colonize the planet. Change often takes the form of that nineteenth-century geologic theory, catastrophism, in which rupture shakes the sleeping landscape from its bed and leaves the dream of uniformitarianism — slow, elegantly steady alterations to the landscape’s features — scattered across the uplifted hillside. But what happens in the aftermath is still change: adaptation or extinction.

Rick Potts, of the National Museum of Natural History, seems cautiously optimistic about the coming decades under climate change. Discussing what he calls “the evolution of adaptability” — that is, what circumstances led to Homo sapiens’ development of enormous flexibility, our astonishing adaptability that allowed the species to spread across all continents except Antarctica, and make them home — he notes that periods of rapid climate change throughout the past few million years tend to coincide with some of our ancestors’ major evolutionary changes: upright posture, tool use, migration out of Africa itself.

To call what may befall us “change” will be no comfort to the people whose villages or cities are destroyed by flood or rising seas, nor to those who die from malaria or drought or famine. It will not lessen the despair should the grimmest predictions come to pass and stark extinction shroud each hilltop. And my comments should not be construed as neoconservative denial of the data, nor smug assurance that in our technological cleverness we’ll invent our way free of our own responsibility, build an exclusive little ark, say, in which we’ll float above the sea change of our own making.

But perhaps it can be useful to understand the changes from a different philosophical or psychological perspective: this is the resurgence of the sublime and its honest shiver of fear, not its disappearance from our lives. It’s a return to an even older past, one in which abrupt, disruptive change trumps stasis. None of today’s cultures are shaped by that world, but it is the one in which our bodies and brains evolved. We don’t have any idea, yet, what will be demanded of us or how we’ll respond. But it’s worth remembering that the current world — modernity — is not the only one our kind has thrived in.

We may have come full circle. Even now we’re standing at the threshold of our own, or our next, beginnings. O