Illustration by Scott Bakal

Not long ago, I was asked to stand before a camera at Niagara Falls and speculate about what might happen there if humans suddenly vanished from the earth. The occasion was the History Channel show called Life After People, which uses spectacular computer graphics to show how the world would go to pieces -- awesomely -- if we up and disappeared. I hadn't seen the show, but when the producer called I got the point at once.

"Oh, yeah, the post-human sublime," I told him. "That meme is everywhere."

I didn't know the half of it. Life After People, I was told, is one of the most popular shows on the History Channel, along with Ice Road Truckers and Modern Marvels. Our roads and bridges and dams fascinate us, whether serving our needs or succumbing to ruin. The producer directed me to online clips, and I spent an afternoon gripped by footage of buildings caving in, bridges falling down, highways eroding to dust. Some episodes showed our pernicious influence outlasting us: landfills leaking toxic goo, untended nuclear reactors irradiating wildlife. But mostly the program implied that eventually, in a world without people, the earth would regain its balance.

I wasn't sure I could get on board. Yes, the post-human world is popular. Alan Weisman's The World Without Us was a best-seller; Alexis Rockman's post-apocalyptic cityscapes are hit paintings. And people flock to film's post-human landscapes, from the drowned Statue of Liberty in Artificial Intelligence to the blasted highways of Cormac McCarthy's The Road.

There's a word for all this: sublime. The artistic term describes the awe we feel for things larger than ourselves. In the past, the natural world was sublime: mountains, waterfalls, the ocean, and the stars gave people a sense of insignificance in relation to the vasty universe. But we have lost the faculty to be so diminished. We move mountains and harness rivers. We have unleashed the power of the atom, unraveled the secrets of our genome, and unbalanced the planet's climate. What on this puny rock could be bigger than we are? Yet our seeming omnipotence does not satisfy us. We still yearn to see the natural world as supreme, but to do it we have to exterminate ourselves.

I think the sublime also accounts for the current vogue for ruins, especially the decaying industrial wreckage of the Rust Belt. The inevitable hand-wringing about "ruin porn" misses the point: ruins are an age-old route to the sublime. "Everything dissolves, everything perishes, everything passes, only time goes on," wrote Diderot.

But if the ruin is a memento mori, how is it changed when it evokes the fleetingness of not just one human life or empire but the whole human race? Is this the greatest imaginable humility in the face of the implacable march of time? Or is it an easy out for a species unwilling to face up to its own ruinous reach? This is what bugged me about the post-human meme. It seemed to yield a kind of hopelessness I associate with extremists -- Earth First! and biblical literalists -- who preach that the world will one day be cleansed of mere mankind. For both, the extirpation of earthly humanity is a consummation devoutly to be wished. Neither worldview gives us much reason to improve our special connection to this planet. We are, after all, only passing through.

Considered in that light, the "life after people" fantasy seemed despair-inducing, an excuse for turning away just as we should be focusing in. But I was overthinking things.

"Are there any well-known monuments above Niagara that could get swept over the Falls?" one of the show's writers called to ask. And then I saw it: fun was the factor I had forgotten. Imagining the monster in the closet makes us appreciate the cozy bed.

I did the show. Big freighters crashed over the brink, power plants collapsed, and the Falls eroded into a series of piddling rapids. I stood in a light rain, trying to sound as if I knew something about geology. The show -- though it scared my nephews -- was not despairing. Look at the world, it urged us. Human things are not all that matters. Grass matters. Falling water matters. They would matter if we were gone. In forcing us to imagine our own absence, it was calling out for presence, goading us to take up once more a right relationship to a world that must remain, for the foreseeable future, saddled with us.