“It’s the biggest mystery of my life,” said Jack, so stiff and serious that I couldn’t help smiling. He spoke rapidly. “I mean the fact that people aren’t more interested in what’s happening to the earth. Maybe they can’t take too much reality. No. It’s money, basically. The companies will rake in billions if the pipeline is built. But it’s our future—” He was in the middle of a you-and-me loop with his hand when he stopped. I could see him backtracking for a second, then deciding to go on. “For you and me, if we want a future, we have to leave fossil fuels in the ground. It’s that simple.”

He said some more things about the Anthropocene, the Faustian bargain, the two degrees Celsius. I could see he loved the science of it and the details and the words. Facts were facts, and I could read them and even try to let them become, as Miss Sedge said, part of my worldview. But Jack was wrong. It was not simple. Nothing was the least bit simple.

I could think about supereruptions and methane burps with calm curiosity during the day. But at night the images conjured up by the facts would wash over me until I was lying rigid in the dark, my whole body thumping with fear. What I couldn’t explain was the thrill it gave me to imagine it. Especially the tsunamis. As the ocean floor got shallower, the waves grew bigger and stronger until the shelf ran out and the waves were set loose. Then the buildings and the scattering people, dignified on their own scale, were just crumbs. Over and over the images ran through me in the dark. I felt each wave slowly gathering power into itself, like a creature thinking cruel and merciless thoughts, and on the other hand like a creature just doing what it couldn’t help doing, and what it would not stop doing until it was finished.

“So . . .” I could hardly admit any of this to Jack. “What are we going to do?”

“Have a look at this.”

He angled the laptop toward me and together we leaned in to the screen. I could have stayed there for a long time near the heat of his shoulder, scrolling through the site as he told me about the march students were planning from Georgetown to the White House. The point was to demand that the president follow through on his promise to reconsider the pipeline.

“It says here, ‘Participants must be at least eighteen years old.’ ”