Death's End

Time flowed by day after day like the smooth, placid water in that little brook.

Cheng Xin began to write her memoir so that she could record the history she knew. She named the book A Past Outside of Time.

Sometimes, they also tried to imagine life in the new universe. Sophon told them that according to cosmological theories, the new universe was certain to possess more than four macro dimensions, perhaps even more than ten macro dimensions. After the birth of the new universe, Universe 647 could automatically construct an entrance to it and examine the interior conditions. If the new universe possessed more than four dimensions, the mini-universe’s exit could be moved around until a suitable habitable location was found in the great universe. Simultaneously, their mini-universe could establish communications with the refugees of other Trisolaran mini-universes, or even with Galactic human migrants. In the new universe, all the migrants coming from the old universe would practically be one race, and should be able to work together to construct a new world. Sophon emphasized that one characteristic greatly increased the probability of survival in a high-dimensional universe: Out of the many macro dimensions, it was likely that more than one dimension would belong to time.

“Multi-dimensional time?” Cheng Xin couldn’t understand the concept at first.

“Even if time were only two-dimensional, it would be a plane instead of a line,” Yifan explained. “There would be an infinite number of directions, and we could simultaneously make countless choices.”

“And at least one of those choices would turn out to be right,” added Sophon.

—————

One night, after the second harvest, Cheng Xin woke up to find Yifan not beside her. She got up, went outside, and saw that the sun had already turned to the moon, and the little world was immersed in the watery, cool light. She saw Yifan sitting by the brook, his posture morose.

In this world of two, each of them had grown especially sensitive to the moods of the other. Cheng Xin had already known that something was troubling Yifan. Earlier, he had been sunny and upbeat. Until a few days ago, he had regularly shared his dream that, if they could find a peaceful life in the new great universe, perhaps their children could re-create the human race. But then he had abruptly changed, frequently going off by himself to ponder something, or to calculate something at a computer terminal.

Cheng Xin sat down next to Yifan, and he pulled her into his arms. The moonlit world was very quiet, and all they heard was the babbling brook. The moon revealed a field of ripe wheat; they’d have to start the harvest tomorrow.

“Loss of mass,” Yifan said.

Cheng Xin said nothing. She watched the moonlight dancing in the brook, knowing that Yifan was going to explain.

“I’ve been reading Trisolaran cosmology, and came across a proof for the elegance of the mathematics behind the great universe we all came from. The design of the total mass in the universe was precise and perfect. The Trisolarans had proved that the total mass of the universe was just enough to allow the big crunch. If the total mass were reduced even slightly, the universe would turn from being closed to open, and expand indefinitely.”

“But mass has been lost,” Cheng Xin said. She understood right away what he was getting at.

“Yes. The Trisolarans have already constructed several hundred mini-universes. How many more have been constructed by other civilizations in the universe to escape the big crunch, or for some other purpose? Each of these mini-universes took away some matter from the great universe.”

“We need to ask Sophon.”

“I have. She told me that at the time of Universe 647’s completion, the Trisolarans had not observed any influence from the loss of mass in the great universe. That universe was closed and was certain to eventually collapse.”

“What about after Universe 647 was constructed?”

“She had no idea, of course. She also mentioned that there was a group of intelligent beings in the universe that resembled the Zero-Homers, but they called themselves the Returners. They advocated against the construction of mini-universes, and called for the mass in completed mini-universes to be returned to the great universe…. But she didn’t know much else about them. All right, let’s forget all this. We’re not God.”

“But we’ve long been called on to think about matters that belonged to the province of God.”

They sat by the brook until the moon turned into the sun again.