Nan Rendong: twenty-two years in the mountains, casting a giant ear on the sky

In 1994, an astronomer proposed something that sounded like science fiction: build the largest radio telescope on earth, five hundred meters across, a vast dish set into the ground, listening for sound from the far side of the universe.

The idea was beautiful and it had nowhere to land. The technology, the money, the site — each one was a wall. Most people heard it, admired it, and put it down. Nan Rendong did not put it down. He carried it on his back for twenty-two years.

Choosing the site alone took twelve. A telescope like this cannot stand on flat ground; it needs a natural depression, with stable rock beneath, drainage for the rain, and a radio environment quiet enough to hear a whisper from space. Nan took more than three hundred satellite images and walked, with his team and a bamboo stick for support, through nearly a hundred of the great karst hollows scattered across the mountains of Guizhou. There were no roads. Underfoot was stone and mud. He coughed as he walked; the lung cancer would be diagnosed later.

The villagers remember "the city man with the shining eyes." A scientist in his fifties who ate instant noodles with them and asked the most detailed questions about the geology under their fields.

The project was approved in 2007. In September 2016, FAST — the Five-hundred-meter Aperture Spherical Telescope — began operating in a karst basin in Pingtang, Guizhou. Five hundred meters across, the largest single-dish radio telescope in the world, more than twice as sensitive as the biggest one before it.

By the opening ceremony Nan was gaunt, changed past recognition. The workers remember what he looked like on site: hard hat on, climbing the towers, going down into the foundation pits, turning bolts alongside them. "He didn't come to inspect. He came to work." He said a thing to his colleagues that they have repeated ever since: "If FAST has one flaw, we have failed the country."

In September 2017, a few days short of FAST's first anniversary, Nan Rendong died. He was seventy-two. He was posthumously named a Model of the Times, and two years later received the national title People's Scientist.

He spent twenty-two years answering one question: how deep can a person's obsession with the sky go. Deep enough to pour an entire life into the drawings of a single enormous dish.

The telescope did not let him down. Since it opened it has found pulsars by the hundred and become the most sensitive radio telescope in the world. Signals from deep space keep revising what humanity knows about the sky. And the name FAST has taken on a second life in the field, because in English the word means quick. People say that was the shape of the man: once he was sure of a thing, he did it at once, and then he did it for the rest of his life.

His last public appearance was at the FAST opening. In the video he is holding a railing, taking the steps slowly, one at a time. Facing the camera, he does not list achievements. He says: "The beautiful universe, with its mystery and its splendor, calls us to step past mediocrity."

Step past mediocrity. Four words, and he did them.

The villagers of Dawa township became his old acquaintances. During the site survey years he often ate at their tables, and a bowl of fresh tofu would be finished down to the last drop. At the peak of construction, thousands of workers were camped in the mountains, and he worried about their food and their safety. He put it bluntly: "We do everything we can to feed them well and let them rest well. Every screw they turn is part of this telescope." When he was already weak from illness in the last stage of the work, he insisted on coming to the site anyway. The workers told him to rest. He waved them off. "If I'm here, everyone feels steadier."