After a long while, the vehicle stopped. We passed from this relatively wide tunnel into a considerably thinner and smaller spur, and if not for my helmet, I would have knocked a few lumps in my head. Our headlamps created small patches of light but we couldn’t see anything clearly. Students shouted that they were scared.

After a while, the space opened up in front of us. Here the ceiling was supported by lots of columns. Opposite us, there were many points of light shining from lamps like the ones on our helmets. As we drew closer, I saw lots of people were at work, some of them making holes in the cave wall with a long-bore drill. The drills were powered by some sort of engine whose sound made my skin crawl. Other people with metal shovels were shoveling some sort of black material into railcars and leather satchels. Clouds of dust occasionally blocked them, and lanterns cast shafts of light through the dust.

“Students, we’re now in what’s called the ore zone. What you see is a scene of early mining work.”

A few miners came toward us. I knew they were holograms, so I didn’t move out of the way. Some of them passed through me, so I could see them very clearly, and I was astonished.

“Did China hire black people to mine coal?”

“To answer that question,” the teacher said, “we’ll have a real experience of the air of the ore zone. Please take out your breathing masks from your bags.”

We put on our masks, and heard the teacher say, “Please remember that this is real, not a hologram.”

A cloud of black dust came toward us. In the beams from our headlamps I was shocked to see the thick cloud of particles sparkling. Then someone started to scream, and like a chorus, a lot of other kids screamed as well. I turned to laugh at them, but I, too, yelped when I got a look: Everyone was completely black, apart from the portion the masks covered. Then I heard another shout that turned my hair on end: It was the teacher’s voice!

“My god, Seya! You don’t have your mask on!”

Seya hadn’t put on his mask, and now he was as completely black as the holographic miners. “You said over and over in history class that the key goal was to get a feel for the past. I wanted a real feel!” he said, his teeth flashing white on his black face.

An alarm sounded somewhere, and within a minute, a teardrop-shaped micro-hovercar stopped soundlessly in front of us, an unpleasant intrusion of something modern. Two doctors got out. By now, all of the real coal dust had been sucked away, leaving only the holographic dust floating around us, so their white coats stayed spotless as they passed through it. They pulled Seya off to the car.