As soon as he opened the door to Ding Yi’s brand-new three-bedroom apartment, Wang smelled alcohol. Ding was lying on the sofa with the TV on, staring at the ceiling. The apartment was unfinished, with only a few pieces of furniture and little decoration, and the huge living room seemed very empty. The most eye-catching object was the pool table in the corner.

Ding didn’t seem annoyed by Wang’s unannounced visit. He was clearly in the mood to talk to someone.

“I bought the apartment about three months ago,” Ding said. “Why did I buy it? Did I really think she was going to become interested in starting a family?” His laugh sounded drunk.

“You two…” Wang wanted to know the details of Yang Dong’s life, but didn’t know how to ask the questions.

“She was like a star, always so distant. Even the light she shone on me was always cold.” Ding walked to one of the windows and looked up at the night sky.

Wang said nothing. All he wanted now was to hear her voice. But a year ago, as the sun sank in the west, when she and he had locked eyes for a moment, they had not spoken to each other. He had never heard her voice.

Ding waved his hand as though trying to flick something away. “Professor Wang, you were right. Don’t get involved with the police or the military. They’re all idiots. The deaths of those physicists had nothing to do with the Frontiers of Science. I’ve explained it to them many times, but I can’t get them to understand.”

“They seem to have conducted some independent investigation.” “Yes, and the investigation’s scope was global. They should already

know that two of the dead never had any contact with the Frontiers of Science, including … Yang Dong.” Ding seemed to have trouble saying her name.

“Ding Yi, you know that I am already involved. So … as far as why Yang made the choice that … she did, I’d like to know. I think you must know some of it.” Wang thought he must sound very foolish as he tried hard to disguise his real intent.

“If you know more, you’ll only get pulled in deeper. Right now you’re just superficially involved, but with more knowledge your spirit will be drawn in as well, and then it will mean real trouble.”

“I work in applied research. I’m not as sensitive as you theoreticians.”

“All right, then. Do you play pool?” Ding walked to the pool table. “I used to play a little in college.”

“She and I loved to play. It reminded us of particles colliding in the accelerator.” Ding picked up two balls: one black and one white. He set the black ball next to one of the pockets, and placed the white ball about ten centimeters from the black ball. “Can you pocket the black ball?”

“This close? Anyone can do it.” “Try.”

Wang picked up the cue, struck the white ball lightly, and drove the black ball into the pocket.

“Good. Come, now let’s move the table to a different location.” Ding directed the confused Wang to pick up the heavy table. Together they moved it to another corner of the living room, next to a window. Then Ding scooped out the black ball, set it next to the pocket, and again

picked up the white ball and set it down about ten centimeters away. “Think you can do it again?”

“Of course.” “Go for it.”

Again, Wang easily made the shot.

Ding waved his hands. “Let’s move it again.” They lifted the table and set it down in a third corner of the living room. Ding set up the two balls as before. “Go.”

“Listen, we—”

“Go!”

Wang shrugged helplessly. He managed to pocket the black ball a third time.

They moved the table two more times: once next to the door of the living room, and finally back to the original location. Ding set up the two balls twice more, and Wang twice more made his shot. By now both were slightly winded.

“Good, that’s the conclusion of the experiment. Let’s analyze the results.” Ding lit a cigarette before continuing, “We ran the same experiment five times. Four of the experiments differed in both location and time. Two of the experiments were at the same location but different times. Aren’t you shocked by the results?” He opened his arms exaggeratedly. “Five times! Every colliding experiment yielded the exact same result!”

“What are you trying to say?” Wang asked, gasping.

“Can you explain this incredible result? Please use the language of physics.”

“All right … During these five experiments, the mass of the two balls never changed. In terms of their locations, as long as we’re using the frame of reference of the tabletop, there was also no change. The velocity of the white ball striking the black ball also remained basically the same throughout. Thus, the transfer of momentum between the two balls didn’t change. Therefore, in all five experiments, the result was the black ball being driven into the pocket.”

Ding picked up a bottle of brandy and two dirty glasses from the floor. He filled both and handed one to Wang. Wang declined.

“Come on, let’s celebrate. We’ve discovered a great principle of nature: The laws of physics are invariant across space and time. All the physical laws of human history, from Archimedes’ principle to string theory, and all the scientific discoveries and intellectual fruits of our species are the by-products of this great law. Compared to us two theoreticians, Einstein and Hawking are mere applied engineers.”

“I still don’t understand what you’re getting at.”

“Imagine another set of results. The first time, the white ball drove the black ball into the pocket. The second time, the black ball bounced away. The third time, the black ball flew onto the ceiling. The fourth time, the black ball shot around the room like a frightened sparrow, finally taking refuge in your jacket pocket. The fifth time, the black ball flew away at nearly the speed of light, breaking the edge of the pool table, shooting through the wall, and leaving the Earth and the Solar System, just like Asimov once described.13 What would you think then?”

Ding watched Wang. After a long silence, Wang finally said, “This actually happened. Am I right?”

Ding drained both glasses in his hands. He stared at the pool table as though looking at a demon. “Yes. It happened. In the last few years, we finally obtained the necessary equipment for experimentally testing fundamental theories. Three expensive ‘pool tables’ have been constructed: one in North America, another in Europe, and the third you are familiar with, in Liangxiang. Your Nanotechnology Research Center earned a lot of money from it.

“These high-energy particle accelerators raised the amount of energy available for colliding particles by an order of magnitude, to a level never before achieved by the human race. Yet, with the new equipment, the same particles, the same energy levels, and the same experimental parameters would yield different results. Not only would the results vary if different accelerators were used, but even with the same accelerator, experiments performed at different times would give different results.

Physicists panicked. They repeated the ultra-high-energy collision experiments again and again using the same conditions, but every time the result was different, and there seemed to be no pattern.”

“What does this mean?” Wang asked. When he saw Ding staring at him without speaking, he added, “Oh, I’m in nanotech, and I also work with microscale structures. But that’s orders of magnitude larger than the scale at which you do your work. Please educate me.”

“It means that the laws of physics are not invariant across time and space.”

“What does that mean?”

“I think you can deduce the rest. Even General Chang figured it out.

He’s really a smart man.”

Wang looked outside the window thoughtfully. The lights of the city were so bright that the stars of the night sky were drowned out.

“It means that laws of physics that could be applied anywhere in the universe do not exist, which means that physics … also does not exist.” Wang turned back from the window.

“‘I know what I’m doing is irresponsible. But I have no choice,’” Ding said. “That was the second half of her note. You just stumbled on the first half. Now can you understand her? At least a little?”

Wang picked up the white ball. He caressed it for a bit and put it back down. “For someone exploring the forefront of theory, that would indeed be a catastrophe.”

“To accomplish something in theoretical physics requires one to have almost religious faith. It’s easy to be led to the abyss.”

As they said their farewells, Ding gave Wang an address. “If you have the time, please visit Yang Dong’s mother. She and her mother always lived together, and she was the entirety of her mother’s life. Now the old woman is all alone.”

“Ding, you clearly know a lot more than I do. Can you tell me more? You really believe that the laws of physics are not invariant across time and space?”

“I don’t know anything.” Ding stared into Wang’s eyes for a long time. Finally, he said, “But that is the question.”

Wang knew that he was only finishing what the British colonel had begun to say: To be, or not to be: that is the question.