There is no ordinary light here; no ordinary marking of time. You feel it most acutely at dawn and dusk, when in midsummer the sun rises as late as it sets early. The horizons in this place are outlined by granite walls thousands of feet tall. You must look way up to see the sky.

The last morning star had been washed from the east two hours before I began my climb to Yosemite’s Vernal and Nevada falls. The sun was up, but something was blocking it from view, something standing 4,800 feet above the valley floor: the fortress of granite called Half Dome, its sheer face still stained with the blue-grey of twilight.

The stillness was eerie. Most of the hikers, climbers, campers and tourists that crowded the valley’s 7 square miles were still asleep. The scavenging bears had retreated from parking lots and campsites and were headed for the sanctuary of Tenaya Canyon and the trees below Ribbon Fall, far from the distressing two-legged creatures.

As I hoisted myself up the trail skirting the Merced River’s perpetual thunder, I was struck by how Yosemite puts large matters into perspective. The scale of this place is measured not only in space – in the loft and mass of its walls of stone and daring plummet of its waterfalls. It’s measured not only in the canyon-carving force of its rivers. The scale of this place is measured in time: 15 million years ago the Merced was a mere creek zigzagging through a shallow valley half its present elevation. As 10 million years passed, the Sierra’s granite backbone drove upward and the Merced engraved a V-shaped valley. Half Dome rose to 5,000 of its present 8,800-foot mark.

In the chill of dawn, as the shadow of the valley’s south walls rappelled down the north walls across a mile of space, I tried to picture the next chapter of Yosemite’s tale. A million and a half years ago, a river of ice filled this valley to the brim. As the millennia unfolded and the glacier retreated, it sculpted the battleship prow and pilothouse of Washington Column and North Dome, chiseled a slit beside Yosemite Point that would become the spout of the tallest waterfall on the continent.

I closed my eyes and fast-forwarded to 12,000 B.C., to a Yosemite I would still not recognize. Half Dome had grinded skyward to its present level, but the valley was deep underwater. And I was standing on the residue of the silt that filled the bottom of that lake: the valley floor of A.D. 2011.

My existence had been put in perspective, but so had Yosemite’s. Sure, I’d lived a paltry 61 of the valley’s 15 million years on earth. A wisp. But wasn’t Yosemite’s paltry 15 million of earth’s 4½ billion a wisp? I came to the Vernal Bridge and watched the river, like time, race beneath my feet – like time, inch beneath my feet.

But earth was rotating beneath sun; day was in relentless ascent. Pressed for time, I hadn’t the luxury of meditating on the nature of Time. If you target Yosemite’s Mist Trail between Memorial Day and Labor Day – vacation time, tourist time – you start early.

I struck upward and eastward, where the solar fountain was spraying an aura of palest gold behind the silhouette of redwoods on the fall’s rim. Only a handful of hikers, some bound for Half Dome’s famed perch, joined in the ascent.

When I reached the trail’s first granite stair, it was clear that the winter and spring of 2010-11 had created a snarling beast. Heavy snow had become heavy water in these high places of the world. Droplets had converged with trickles; trickles with rivulets; rivulets with streams; streams with creeks; creeks with rivers in a crescendo of mass and momentum. The Merced was set on full boil.

It was my fourth trip up the Mist Trail, a mile and a quarter of tall, steep and slippery granite steps to Vernal Fall; a further 2 miles to Nevada Fall. Now, in 2011, I watched in awe as the Sierra’s winter melt rocketed down the riverbed, ricocheted off boulders like sparks in a foundry, fumed like steam off a kettle. The Mist Trail had morphed into the Suffocating Torrential Downpour Trail. I donned my poncho. This climb was idiotic enough to be really appealing.

Like a kid in a splash park I giggled and groaned my way up to the sun-dried sanctuary of the top. Along the way, rainbows exploded through sheets of wind-whipped spray. Just below Vernal’s broad launching ramp, up close and personal, the fall was barely visible through the monsoon of moisture; my thoughts barely audible through the barrage of water – tons per second – slamming onto the rocks below.

It wasn’t till later that day atop Glacier Point, as I gazed far down across Illilouette Gorge to the falls I’d climbed, that I came full circle. From stillness to stillness. The noise of Vernal and Nevada failed to carry up here; the voice of the river of time had fallen silent. I sat on the warm granite 3,200 feet above the valley floor and closed my eyes; felt the past and future fall off me like a garment. I existed in the naked now, the now of rock and water and the consciousness to know them.

I opened my eyes and time flooded back into the cosmos. Another world was calling, a world of obligations, deadlines, the tick of clocks. But a world of memories – good ones. I gave the valley, spread beneath me like a banquet table, one last taste.