The Three-Body Problem

Compared with the general state of the field, my progress could be said to be a breakthrough. Some years ago, Richard Montgomery of UCSC and Alain Chenciner of Université Paris Diderot discovered another stable, periodic solution to the three-body problem.30 Under appropriate initial conditions, the three bodies will chase each other around a fixed figure-eight curve. After that, everyone was keen to find such special stable configurations, and every discovery was greeted with joy. Only three or four such configurations have been found so far.

But my evolutionary algorithm has already discovered more than a hundred stable configurations. Drawings of their orbits would fill a gallery with postmodern art, but that’s not my goal. The real solution to the three-body problem is to build a mathematical model so that, given any initial configuration with known vectors, the model can predict all subsequent motion of the three-body system. This is also what Shen Yufei craves.

But my peaceful life ended yesterday.

*   *   *

“This is the crime you’re reporting?” Shi Qiang asked.

“Yes. A man called yesterday and told me that if I didn’t cease my research, I would be killed.”

“Who was he?”

“I don’t know.”

“Phone number?”

“Don’t know. Caller ID showed nothing.”

“Anything related to report?”

“Don’t know.”

Da Shi laughed and tossed his cigarette butt into an ashtray. “You went on and on forever, and in the end all you have to report is one line and a few ‘I don’t know’s?”

“If I hadn’t gone on like that, would you have understood the import of that call? Also, if that were all, I wouldn’t have come here. I’m lazy, remember? But there was another thing: It was the middle of the night—I don’t know if it was today or yesterday—and I was in bed. As I was drifting halfway between sleep and wakefulness, I felt something cold moving on my face. I opened my eyes and saw Shen Yufei, and I almost died of fright.”

“What’s so frightening about seeing your wife in the middle of the night?”

“She stared at me in a way that I had never seen. The light from outside fell on her face, and she looked like a ghost. She held something in her hand: a gun! Moving the barrel over my face, she told me that I had to continue working on the three-body problem. Otherwise she’d kill me.”

“Oh, now this is getting interesting.” Da Shi gave a satisfied nod. He lit another cigarette.

“Interesting? Look, I’ve nowhere to go. That’s why I came to you.”

“Tell us exactly what she said.”

“She said: ‘If you succeed in solving the three-body problem, you will be the savior of the world. If you stop now, you’ll be a sinner. If someone were to save or destroy the human race, then your possible contribution or sin would be exactly twice as much as his.’”

Da Shi blew out a thick cloud of smoke and stared at Wei Cheng until he squirmed. He pulled a notepad out of the mess on his desk and picked up a pen. “You wanted us to take notes, right? Repeat what you just said.”

Wei did.

Wang said, “What she said is indeed strange. What does she mean by exactly twice as much?”

Wei blinked. “This seems pretty serious. When I came, the officer on duty immediately sent me to see you. It looks like you’ve already been paying attention to Shen and me.”

Da Shi nodded. “Let me ask you something else: Do you think the gun your wife held was real?” He saw that Wei didn’t know how to answer. “Could you smell gun oil?”

“Yes, there was definitely an oily smell.”

“Good.” Da Shi, who had been sitting on his desk, jumped off. “Finally we have an opening. Suspected illegal possession of firearms is enough to justify a search. I’ll leave the paperwork until tomorrow, because we have to move right away.”

He turned to Wang. “No rest for the weary. I have to ask you to come and advise me some more.” Then he turned to Xu Bingbing, who’d been silent the whole time. “Bingbing, right now I have only two men on duty, and that’s not enough. I know the Information Security Division isn’t used to fieldwork, but I need you to come along.”