Cixin Liu - Death's End

The purple continents took up most of the view from the monitoring system. They were able to confirm that the purple was due to the color of the vegetation. The change in the sun’s radiation had probably caused the plants on Planet Blue to change from blue to purple as they evolved to adapt to the new light.

As a matter of fact, the very existence of the sun puzzled Cheng Xin and Guan Yifan. Since E = mc2, reduced-lightspeed nuclear fusion could produce only small amounts of energy. Perhaps the interior of the sun maintained normal lightspeed?

The shuttle’s landing coordinates were set to the same spot from which it had taken off and left Halo . As they approached the surface, they saw a dense purple forest at the landing spot. Just when the shuttle was about to lift off again in search of a more open spot, the trees dashed away to escape the flames from the shuttle’s thrusters. The shuttle then gently set itself down in the open space vacated by the fleeing trees.

The screen showed that the outside air was breathable. Compared to the last time they had been here, the oxygen content in the atmosphere was substantially higher. Moreover, the atmosphere was denser, and the atmospheric pressure was one and a half times higher than at the last landing.

Cheng Xin and Guan Yifan exited the shuttle and once again stepped onto the surface of Planet Blue. Warm, moist air welcomed them, and a layer of soft, bouncy humus covered the ground. The soil around them was filled with numerous holes left by the roots of the trees that had gotten out of the way. Those trees now huddled around the clearing, their broad leaves rustling in the breeze, like a crowd of whispering giants gathered around them. The clearing was completely covered by their shade. Such dense vegetation made Planet Blue a completely different world than the one they had seen before.

Cheng Xin didn’t like purple. She’d always thought of it as a sick, depressing color that reminded her of the lips of invalids whose hearts did not supply them with sufficient oxygen. Yet now she was surrounded by purple everywhere she looked, and she would have to spend the rest of her life in this purple world.

There was no sign of Halo, no sign of Yun Tianming’s ship, no sign of any human presence.

Guan Yifan and Cheng Xin surveyed the landscape around them and realized that the geographical features were completely different from the last time. They clearly remembered that there had been rolling mountains nearby, but now the forest was growing over a plain. They went back to the shuttle to confirm that the coordinates were really correct—they were. Then they looked even more carefully all around them, but still found no trace of any prior human visit. The site resembled virgin land—it was as though their last visit had occurred on another planet in another space-time that had nothing to do with here.

Yifan returned to the shuttle and established a link with Hunter, which was still in near-ground orbit. Hunter ’s neural computer was very powerful, and its AI was capable of direct natural language communications. Under reduced-lightspeed conditions, the conversation from ground to space suffered a transmission delay of over ten seconds. After dropping out of lightspeed along with the shuttle, Hunter had been scanning the surface of the planet from low orbit. By now, it had completed a survey of most of the land on Planet Blue, and it had discovered no trace of humans or signs of any other intelligent life.

Next, Cheng Xin and Guan Yifan had to turn to a task that terrified them but was absolutely necessary: determining how much time had elapsed in this frame of reference. There was a special technique for radiometric dating under reduced-lightspeed conditions: Some elements that did not decay under normal lightspeed decayed at different rates under reduced lightspeed, which could be used to precisely tell the passage of time. Given its scientific mission, the shuttle was equipped with a device for measuring atomic decay, but the instrument required a computer for processing. Yifan had to go to some trouble to connect the instrument to the neural computer on the shuttle. They directed the instrument to test the ten rock samples taken from different parts of the planet one after another so that the results could be compared. The assay required half an hour.

While waiting for the test results, Cheng Xin and Guan Yifan left the shuttle and waited in the clearing. Sunlight illuminated the clearing through gaps in the canopy. Many strange, small creatures flitted through: Some were insects with spinning rotors on top like helicopters; others were like tiny, transparent balloons that drifted through the air, giving off a rainbow sheen as they passed through shafts of sunlight; but none of them had wings.

“Maybe several tens of thousands of years have passed,” Cheng Xin muttered.

“Or even longer,” said Guan Yifan, looking deep into the woods. “In our current state, tens of thousands of years aren’t very different from hundreds of thousands of years.”

Then they said no more, but sat on the stairs outside the shuttle, leaning against each other and taking comfort in their heartbeats.

Half an hour later, they climbed back into the shuttle to face facts. The screen on the control panel showed the test results from the ten samples. Many elements had been tested and the charts were complicated. All the samples yielded similar results. Underneath, the average of the results was listed simply:

Average atomic decay dating results (error range: 0.4%): Stellar time periods lapsed: 6,177,906; Earth years lapsed: 18,903,729.

Cheng Xin counted the digits in the last number three times, turned around, and quietly exited the shuttle. She descended the stairs and returned to this purple world. Tall purple trees surrounded her, a beam of sunlight cast a tiny circle of brightness next to her feet, moist wind lifted her hair, living balloons drifted overhead, and almost nineteen million years followed her.

Yifan came to her. They locked gazes, and their souls embraced.

“Cheng Xin, we missed them.”

More than eighteen million years after the DX3906 system turned into a reduced-lightspeed black hole, seventeen billion years after the birth of the universe, a man and a woman held each other tightly.

Cheng Xin sobbed her heart out over Yifan’s shoulder. In her memories, she had cried like this only once before, when Tianming’s brain had been taken out of his body. That was… 18,903,729 years plus six centuries ago, and those six centuries were but a rounding error at such geologic timescales. This time, she cried not only for Tianming. She cried out of a sense of surrender. She finally understood how she was but a mote of dust in a grand wind, a small leaf drifting over a broad river. She surrendered completely and allowed the wind to pass through her, allowed the sunlight to pierce her soul.

Letting the past go, she allowed her growing esteem for Guan Yifan to take over her heart.

They sat on the yielding humus and continued to hold each other, letting time flow by. The dappled sunlight gently shifted around them as the planet continued to rotate. Sometimes Cheng Xin asked herself, Has another ten million years passed by? A small, rational part of her mind strangely whispered to her that such a thing was possible: There really were worlds where one could step through a thousand years at will. Consider the death lines: If they ruptured and expanded just a bit, the speed of light within would rise from zero to an extremely small number, like the rate at which continents drifted over the ocean: a centimeter for every ten thousand years. In such a world, if you got up from your lover and walked a few steps away, you would be separated from him by ten million years.