The Three-Body Problem

“The sun is the result of the large hole in the outer sphere being projected onto the inner one. The projection is so bright that it penetrates the inner sphere like the shell of an egg, and that is how we see the sun. Around the spot of light, the scattered light rays are also very bright, and can be seen through the inner shell. That is why we can see a clear sky during the day.”

“What is the force that propels the two spheres in their irregular motion?”

“It’s the force of the sea of fire outside the two spheres.”

“But the sun’s brightness and size change over time. In your double-shell model, the sun’s size and brightness ought to be fixed. Even if the brightness of the flames in the sea of fire is inconstant, the size of the hole would not be.”

“Your conception of this model is too simplistic. As conditions in the sea of fire shift and change, the two shells will expand and shrink. This leads to changes in the size and brightness of the sun.”

“What about the flying stars?”

“Flying stars? Why do you care about them? They’re not important. Maybe just some random dust flying about the inside of the universal spheres.”

“No, I think the flying stars are extremely important. Otherwise, how does your model explain the sudden extinguishing of the sun during the time of Confucius?”

“That’s a rare exception. Maybe it was because a dark spot or cloud in the sea of fire just happened to pass over the big hole in the outer shell.”

Wang pointed to the large copper sphere. “This must be your model, then?”

“Yes. I built a machine to replicate the universe. The complex gears that move the sphere simulate the forces from the sea of fire. The laws governing such motion are based on the distribution of flames in the sea of fire and the currents within it. I deduced them from hundreds of years of observations.”

“Can this sphere contract and expand?”

“Of course. Right now it’s slowly contracting.”

Wang used the handrail at the edge of the platform as a fixed visual reference. He found Mozi’s assertion to be true.

“And there’s an inner shell inside this sphere?”

“Of course. The inner shell moves within the outer shell through another complex set of mechanisms.”

“Truly a skillfully designed machine!” Wang’s praise was heartfelt. “But I don’t see a large hole in the outer shell to cast the sun’s light onto the inner shell.”

“There is no hole. On the inner surface of the outer shell I have installed a source of light to simulate the hole. The light source is made of the luminescent material gathered from hundreds of thousands of fireflies. I used a cool light because the inner shell is made of translucent plaster, which is not a good heat conductor. This way, I can avoid the problem of too much heat accumulating inside the sphere that we would have with a regular source of light. The observer can then stay inside for a long time.”

“There’s a person inside the sphere?”

“Yes. A clerk stands on top of a shelf with a wheeled base that is kept at the center of the sphere. After we set up the model universe to correspond to the current state of the real universe, the motion of the model thereafter should be an accurate simulation of the future, including the motion of the sun. After the clerk records the movements of the sun, we will have a precise calendar. This is the dream of hundreds of civilizations before us.

“And it looks like you have come at an opportune time. According to the model universe, a four-year-long Stable Era is about to begin. Emperor Wu of Han has just issued the order to rehydrate based on my prediction. Let’s wait for sunrise!”

Mozi brought up the game’s interface and slightly increased the rate of passage of game time. A red sun rose above the horizon, and the numerous frozen lakes and ponds scattered over the plain began to melt. These lakes had been covered by dust and had merged into the dun ground, but now they turned into numerous mirrors, as though the earth had opened many eyes. From up so high, Wang couldn’t see the details of rehydration, but he could see more and more people gathered on the shores of the lakes like swarms of ants coming out of their nests in spring. The world had once again been revived.

“Do you not want to join this wonderful life?” Mozi asked, pointing to the ground below. “When women are first revived, they crave love. There is no reason for you to stay here any longer. The game is over. I am the winner.”

“As a piece of machinery, your model universe is indeed incomparable. But as for its predictions.… May I use your telescope to observe something?”

“Please.” Mozi gestured at the large telescope.

Wang walked up to the instrument and paused. “How can I use it to observe the sun?”

Mozi retrieved a black, circular piece of glass. “Use this smoked glass filter.” He inserted it in front of the eyepiece.