by Cixin Liu
The light belt on the other side of the ship was thinner but brighter, and its surface showed no details. Unlike Planet Blue, this belt’s length cycled rapidly between a bright line that connected the red and blue clusters, and a bright circle. The belt’s periodic circular state told Cheng Xin that she was looking at the star DX3906.
“We’re orbiting Planet Blue at lightspeed,” said Guan Yifan. “Except the speed of light is now very slow.”
The shuttle had been moving far faster, but as the speed of light was an absolute speed limit, the shuttle’s velocity had been cut down to that.
“The death lines ruptured?”
“Yes. They spread out to cover the entire solar system. We’re trapped here.”
“Was it due to the disturbance from Tianming’s ship?”
“Perhaps. He didn’t know the death lines were here.”
Cheng Xin didn’t want to ask what their next step was, knowing that nothing more could be done. No computer could operate when the speed of light was below twenty kilometers per second. The shuttle’s AI and control systems were all dead. Under such conditions, not even a light inside the spacecraft could be turned on—it was just a metal can with no electricity or power. Hunter was the same, also dead. Before falling into reduced lightspeed, the shuttle had not yet began decelerating, and so the small spaceship should be nearby—but it might as well be on the other side of the planet. Without the control systems, neither the shuttle nor Hunter could open their doors.
Cheng Xin thought about Yun Tianming and 艾 AA. They were both on the ground, and should be safe. But now there was no way for the two sides to communicate. She never even got to say hello to him.
Something light gently struck the visor of her helmet: the metal bottle. Cheng Xin looked at the ancient pressure gauge on it again, and touched her own space suit. Hope, once extinguished, lit up again like a firefly.
“You’ve been preparing for situations like this?” she asked.
“Yes.” Yifan’s voice sounded distorted in Cheng Xin’s earpiece due to the use of ancient analog signals. “Not for ruptured death lines, of course, but we were prepared for accidentally drifting into the trails of lightspeed ships. The situations are similar: The reduced lightspeed stops everything.... Next, we need to start the neurons.”
“What?”
“Neural computers. Computers that can operate under reduced lightspeed. The shuttle and Hunter both have two control systems, one of which is based on neural computers.”
Cheng Xin was amazed that such machines existed.
“The key isn’t the speed of light, but the system design. The transmission of chemical signals in the brain is even slower, only two or three meters per second—not much faster than us walking. Neural computers can still work because they imitate the highly parallel processing found in the brains of higher animals. All the chips are designed specifically to function under reduced-lightspeed conditions.”
Yifan opened a metal bulkhead decorated with many dots connected in a complex web like the tentacles of an octopus. Inside was a small control panel with a flat display, as well as several switches and indicator lights. The whole assembly was built from components deemed obsolete by the end of the Crisis Era. He toggled a red switch and the screen lit up: text scrolling by. Cheng Xin could tell it was the boot sequence of some operating system.
“The parallel neural mode hasn’t been started yet, so we have to load the operating system serially. You’ll probably have a hard time believing how slow serial data transmission is under reduced lightspeed: look, the data rate is a few hundred bytes per second. Not even a kilobyte.”
“Then the boot sequence will take a long time.”
“That’s right. But as the parallel mode gradually builds up, the loading will speed up. Still, it really will take a long time to complete the sequence.” Yifan pointed to the progress indicator, a line of text on the bottom of the screen.
Remaining load time for boot module: 68 hours 43 minutes [flickering] seconds. Total remaining system load time: 297 hours 52 minutes [flickering] seconds.
“Twelve days!” Cheng Xin exclaimed. “What about Hunter?”
“Its systems will detect the reduced-lightspeed condition and automatically boot the neural computer. But it will take about as long to complete.”
Twelve days. They could only get to the survival resources in the shuttle and on Hunter after twelve days. Until then, they had to rely on their primitive space suits. If the space suits were powered by nuclear batteries, the electricity should last long enough, but they didn’t have enough oxygen.
“We have to hibernate,” said Yifan.
“Do we have the equipment for hibernation on the shuttle?” As soon as she asked the question, Cheng Xin realized her error. Even if the shuttle had such equipment, it would be controlled by the computer, which was out of commission right now.
Yifan opened the storage unit from which he had taken the oxygen bottle earlier and took out a small box. He opened it to show Cheng Xin a few capsules. “These are drugs for short-term hibernation. Unlike regular hibernation, you won’t need an external life-support system. Once you are in hibernation, your respiration will slow down to the point where you consume very little oxygen. One capsule is enough for fifteen days of hibernation.”
Cheng Xin opened her visor and swallowed one of the pills. She watched as Yifan also took one. Then she looked outside the portholes.
Patches of color now moved so fast over Planet Blue—the broad belt that connected the blue and red ends of the lightspeed universe on one side of the ship—that they turned into a blur.
“Can you see the patterns on the belt repeating periodically?” Yifan wasn’t looking outside at all. His eyes were half-closed as he strapped himself into the hypergravity seat.
“They’re moving too fast.”
“Try to follow the motion with your eyes.”
Cheng Xin tried to match her moving gaze with the patterns flowing across the belt. For a moment, she could see the blue, white, and yellow patches, but they blurred almost immediately. “I can’t,” she said.
“That’s all right. They’re moving too fast. The pattern could be repeating several hundred times per second.” Yifan sighed. Cheng Xin noticed his sorrow, despite his effort to hide it. And she knew why.
She understood that every time the pattern repeated on the broad belt, it meant that the shuttle had completed another orbit around Planet Blue at lightspeed. Even at reduced lightspeed, the demonic rules of the theory of special relativity still held. In the planet’s frame of reference, time was passing tens of millions of times faster than in here, like blood seeping out of her heart.
A moment here; eons there.
Cheng Xin turned away from the porthole and strapped herself into the seat as well. Light flickered through the porthole on the other side. Outside, the sun of this world was alternately a bright line that connected the two ends of the universe, and a ball of light. It was dancing the mad dance of death.
“Cheng Xin.” Yifan called for her softly. “It’s possible that when we wake up, we’ll find the screen telling us that an error has occurred.”
Cheng Xin turned and smiled at him through the visor. “I’m not afraid.”
“I know you’re not afraid. I just want to tell you something in case we don’t... I know about your experience as the Swordholder. I want to let you know that you didn’t do anything wrong. Humanity chose you, which meant they chose to treat life and everything else with love, even if they had to pay a great price. You fulfilled the wish of the world, carried out their values, and executed their choice. You really didn’t do anything wrong.”
“Thank you,” Cheng Xin said.
“I don’t know what happened to you after that, but you still didn’t do anything wrong. Love isn’t wrong. A single individual cannot destroy a world. If that world was doomed, then it was the result of the efforts of everyone, including those living and those who had already died.”
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“Thank you,” Cheng Xin said. Her eyes felt hot and wet.
“As for what will happen next, I’m not afraid either. When I was on Gravity, all those stars in the emptiness made me afraid and tired, and I wanted to stop thinking about the universe. But it was like a drug, and I couldn’t stop. Well, now I can stop.”
“That’s good. You know something? The only thing I’m scared of is that you’ll be afraid.”
“I’m the same.”
They held hands, and as the sun continued its mad dance, they gradually lost consciousness and stopped breathing.
* Translator’s Note: This is a wordplay in Chinese. 幕 (mu), or “curtain,” is a pun for 墓 (mu), or “tomb.”
About Seventeen Billion Years After the Beginning of Time Our Star
It took a long time to wake up.
Cheng Xin recovered her awareness gradually. After her memory and sight came back, she knew right away that the neural computer had booted successfully. A soft light illuminated the inside of the cabin, and she could hear the machines humming reassuringly. The air was warm. The shuttle had been revived.
But Cheng Xin soon realized that the lights inside the cabin came from different fixtures than before—perhaps these were backups designed specifically for reduced-lightspeed use. There were no information windows in the air. It was possible that the reduced lightspeed meant such holographic displays were no longer operable. The interface of the neural computer was limited to that flat screen, which now resembled a color bitmap display from the Common Era.
Guan Yifan was drifting in front of the display, tapping on it with the fingers of a gloveless hand. He turned and smiled at Cheng Xin, made a hand gesture indicating that it was okay to drink, and then handed her a bottle of water.
“It’s been sixteen days,” he said.
The bottle felt warm. Cheng Xin saw that she wasn’t wearing gloves, either. She realized that although she was still wearing the primitive space suit, her helmet had been removed. The temperature and pressure inside the cabin were comfortable.
Since she had recovered enough to move her hands, Cheng Xin unstrapped herself and drifted next to Yifan to look at the screen with him, their space suits squeezed tightly side by side. Several windows were up on the screen, each showing rapidly scrolling numbers: diagnostics on the shuttle’s various systems. Yifan told Cheng Xin that he had established contact with Hunter, whose neural computer had also apparently booted successfully.
Cheng Xin looked up and saw that the two portholes were still open. She drifted over. Guan Yifan dimmed the cabin lights so she could see through them without glare. They anticipated each other’s needs now as though they were a single person.
At first, the universe didn’t appear to have changed from what she had seen before: The ship continued to orbit around Planet Blue at reduced lightspeed; the two star clusters, blue and red, continued to change their shapes erratically at the two ends of the universe; the sun continued to dance madly between being a line and a circle; and color patches continued to whip across Planet Blue’s surface. When Cheng Xin tried to match her gaze to the rapidly flowing surface of Planet Blue, she finally noticed something different: the blue and white patches had been replaced by purple ones.
Yifan pointed to the screen. “The propulsion system self-diagnosis is complete. Everything’s basically working. We can decelerate out of lightspeed anytime.”
“The fusion drive still works?” Cheng Xin asked. Before they entered hibernation, this question had weighed on her mind. She had not asked because she knew that she was likely to receive a disappointing answer, and she didn’t want to give Yifan more to worry about.
“Of course not. With such a reduced lightspeed, nuclear fusion puts out too little power. We have to use the backup antimatter drive.”
“Antimatter? But wouldn’t the containment field be affected by the reduced lightspeed?”
“No problems there. The antimatter engine was designed specifically for reduced-lightspeed conditions. When we’re on long expeditions like this, we equip all our spacecraft with reduced-lightspeed propulsion systems.... Our world puts a lot of effort into developing such technologies. The goal isn’t to solve the problem of accidentally entering trails left by curvature propulsion; rather, it’s because we have to plan for the possibility of having to conceal ourselves inside a light tomb, or a black domain.”
Half an hour later, the shuttle and Hunter both activated their antimatter engines and began decelerating. Cheng Xin and Guan Yifan were pressed against their seats by the hypergravity, and the porthole screens rose to block out the outside. Violent jolts seized the shuttle, but gradually subsided. The deceleration process took less than twenty minutes. Then the engines shut off, and they were again weightless.
“We’re out of lightspeed,” Guan Yifan said. He pressed a button, and the screens over the two portholes retracted.
Through the portholes, Cheng Xin saw that the blue and red star clusters were gone, and the sun was now a normal sun. But the sight of Planet Blue in the porthole on the other side surprised her: Planet Blue was now “Planet Purple.” Other than the ocean, which was still a light yellow, the rest of the planet was covered by purple—even the snow was gone. She was, however, most shocked by the appearance of space itself.
“What are those lines?” Cheng Xin cried out.
“I think they are... stars.” Yifan was as amazed as she.
All the stars in space had turned into thin lines of light. Cheng Xin was actually familiar with such a sight: She had seen plenty of long-exposure photographs taken of the starry sky from Earth. Due to the Earth’s rotation, the stars in the pictures all became concentric arcs of approximately the same length. But now, the stars she saw were segments of different lengths and aligned every which way. The longest few lines, in fact, took up almost a third of the sky. These lines crossed each other at different angles and made space appear far more confusing and chaotic than before.
“I think they’re stars,” repeated Yifan. “A star’s light must pass through two interfaces before getting to us: First, it must go through the interface between regular lightspeed and reduced lightspeed, and then through the event horizon of the black hole. That’s why the stars look so strange to us now.”
“We’re inside the black domain?”
“That’s right. We’re inside the light tomb.”
The DX3906 solar system was now a reduced-lightspeed black hole completely sealed off from the rest of the universe. The starry sky woven by the multitude of crisscrossing silver threads was a dream that could be seen but would never be achieved.
“Let’s go down to the surface,” Yifan said after a long silence.
The shuttle decelerated further and lowered its orbit. With a series of powerful jolts, it entered the atmosphere of the planet and descended toward the surface of this world in which the two of them were doomed to spend the rest of their lives.
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 w
as 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.