Today one of the great men of history died. Even to write down his accomplishment sends chills along the back of the neck: He was the first man to walk on the moon. The idea still fills people with childlike disbelief and wonder. Once upon a time, a man walked on the moon. With Armstrong's death, we're mourning, not so much a man, as a conception of the world in which human beings believed themselves to be capable of anything.

He was a scientist. He was an explorer. But what Armstrong provided was a new way of thinking about our place in the universe. He changed what it meant to be a person. His very existence promised a new possibility of the human, something verging on a new evolutionary state. After his journey, the moon was no longer an unattainable ideal. The moon was something we could stand on. People could do that. Extraordinary people certainly, but still people.

There will never be another achievement like Armstrong's. That statement isn't nostalgia or pessimism. It's evident that we are currently living in a great era of scientific triumph, and as I write this, Curiosity is rolling over the surface of Mars, a victory worthy of the profound celebration it inspired. And yet Curiosity is just a machine. The future of our exploration will be through technology and its literally superhuman capacities, which is a disappointing, if sensible and inevitable, retreat from the space exploration of a former era.

The machines don't need us anymore. We no longer need fighter pilots; we have drones instead. We no longer need astronauts; we have rovers. That's a profound loss to our sense of humanity. The astronaut had to endure unfathomable G forces, to float in strange new gravities, in order to stand outside the earth. Armstrong was the ultimate expression of the fusion of man with machine, the smooth avatar of a future of speed and limitless potential, one in which our changed nature promised an ever-expanding future of human possibility. We are neither so grand nor so naïve in our relationship to technology anymore. The overwhelming tendency of the moment is to fear technology and what it can do to us. Partly the new resistance is because our technologies promise us so much less than they used to: "You can play Angry Birds any time you like" rather than "you can stand on different planets." But also, we've grown up, left behind our unrealistic optimism. The real question of our moment is whether the amazing power of engineers will destroy the planet we have rather than whether they will bring us to new ones. We have come to understand that human beings are bound to the earth. Forever. This terrestrial understanding isn't wrong. It's just smaller than the hope that motivated Armstrong.

Our awe at his achievement remains. His meaning survives his death. Human beings can go to the moon. Armstrong proved it: We are capable of anything.

PLUS: Charles P. Pierce on What Neil Armstrong Knew, American Legends on Their First Words on the Moon and What Buzz Aldrin's Learned

Stephen Marche Stephen Marche is a novelist who writes a monthly column for Esquire magazine about culture.

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