Like all of northern China, Lanzhou has central heating — the heat turns on for everyone on November 1, no matter the temperature. It’s October 28. The students wear their winter coats in the classroom.

Waiting for my turn, they call out numbers in a random order.

Lanzhou is dusty. A car left for a few hours will look like it’s been off-roading. There’s the sand, coming from the mountains and desert…