“Sensors transmit burn and production conditions of all combustible gases at every point in the seam to the surface by ultrasound. These signals are aggregated by a computer to build a model of the coal-seam furnace, enabling us to control, through the holes, the scale and depth of the subterranean fire as well as the burn rate. Specifically, we can inject water into the holes to arrest the burn, or pressurized air or steam to intensify it. All of this proceeds automatically in response to changes in the computer’s burn model so that the fire is kept at an optimum state of incompletely combusted water and coal, to ensure maximum production. You’d be most concerned, of course, with controlling the fire’s range. We can drill a series of holes ahead of its advance and inject pressurized water to form a fire barrier. Where the burning is fierce, we can also employ a pressurized cement curtain, the kind used in dam building, to block the fire.” He trailed off. “Are you listening to me?”

A noise outside had attracted the director’s attention. Liu Xin knew that the image his plan evoked in the director’s mind was different from his own vision. The director surely knew what igniting subterranean coal meant: right now, coal mines were burning all over the world, including several in China.

The previous year, Liu Xin had seen ground fire for the first time in Xinjiang. Not a stitch of grass on the ground or hillsides as far as the eye could see, and the air churned in hot waves of sulfur, shimmering his vision as if he were underwater or as if the entire world were roasting on a spit. At night, Liu Xin saw ribbons of ghostly red where light seeped through countless cracks in the earth. He had approached one to peer inside, and immediately gulped a nervous breath. It was like the entrance to hell. The light shone dimly from deep within, but he could still sense its ferocious heat. Looking out at the glowing lines beneath the night sky, he’d felt as if the Earth were a burning ember wrapped in a thin layer of crust. Aygul, the brawny Uighur man who had accompanied him, was the leader of China’s sole coal-seam fire brigade, and Liu Xin’s aim in making the trip there had been to recruit him for his lab.

“It’ll be hard to pull myself away,” Aygul had said in accented Chinese. “I grew up watching these ground fires, so to me they’re an integral part of the world, like the sun or the stars.”

“You mean the fire started burning when you were born?”

“No, Dr. Liu. This fire has been burning since the Qing Dynasty.”

Liu Xin stood rooted in place and shivered as the heat waves rolled over him in the night.