Death's End

by Cixin Liu

  Average distance of incoming formation of strong-interaction space probes: approximately 4.5 million kilometers. The closest one is at three million kilometers. Estimated arrival time at the surface: two minutes.

  Two of the probes are headed for Asia, two others for North America. The last one is aimed at Europe.

  Pressing the switch would end the progress of 3.5 billion years. Everything would disappear in the eternal night of the universe, as though none of it had ever existed.

  That baby seemed to be back in her arms: soft, cuddly, warm, his face moist, smiling sweetly, calling her mama.

  Average distance of incoming formation of strong-interaction space probes: approximately 3 million kilometers. The closest one is at 1.5 million kilometers, and it is rapidly decelerating. Estimated arrival time at the surface: one minute and thirty seconds.

  “No—” Cheng Xin screamed, and threw the switch away. She watched it slide across the ground, as though watching a devil.

  Strong-interaction space probes approaching lunar orbit and continuing to decelerate. Extending their trajectories suggests that their targets are the gravitational wave broadcasting stations in North America, Europe, and Asia, and Gravitational Wave Universal Broadcast System Control Station Zero. Estimated impact on the surface: thirty seconds.

  Like a strand of spider silk, these final moments stretched out endlessly. But Cheng Xin did not vacillate; she had already made up her mind. This wasn’t a decision born of thought, but buried deep in her genes. These genes could be traced to four billion years ago, when the decision was first made. The subsequent billions of years only strengthened it. Right or wrong, she knew she had no other choice.

  It was good that release was at hand.

  A great jolt tumbled her to the ground: The droplets had penetrated the crust. She felt as though the solid rocks around her had vanished, and the Deterrence Center was on top of a giant drumhead. She closed her eyes and imagined the sight of a droplet passing through the crust like a fish swimming through water, waiting for the arrival at cosmic velocity of the perfectly smooth devil that would turn her and everything around her into molten lava.

  But the quaking stopped after a few violent beats, like a drummer punctuating the end of the piece.

  The red light on the screen faded, replaced by the white background from before. The room seemed brighter and more open. A few lines of black text appeared:

  North American gravitational wave transmitter destroyed.

  European gravitational wave transmitter destroyed.

  Asian gravitational wave transmitter destroyed.

  Solar radio-amplification function suppressed on all bands.

  Silence once again reigned over everything, except the faint sound of water trickling somewhere. A pipe had burst during the quake.

  Cheng Xin understood that the droplet attack on the Asian gravitational wave transmitter had caused the earthquake. That antenna was about twenty kilometers from here and was also deeply buried.

  The droplets had not even bothered attacking the Swordholder.

  The black text disappeared. After some moments of blankness, a last screen of text faded in:

  Gravitational wave universal broadcast system cannot be recovered. Dark forest deterrence has been terminated.

  Post-Deterrence Era, First Hour

  A Lost World

  Cheng Xin rode the elevator to the surface. Exiting the elevator station, she saw the plaza where the deterrence handover ceremony had taken place an hour ago. All the attendees had left, and the place was empty save for the long shadows cast by the flagpoles. The flags of the UN and the Solar System Fleet hung from the two tallest poles, and behind them were the flags of the various nations. The flags continued to flap tranquilly in the light breeze. Beyond them was the endless Gobi Desert. A few twittering birds landed in a stand of tamarisk nearby. In the distance, she could see the rolling Qilian Mountains, the snow cover on a few peaks giving them a silvery highlight.

  Everything seemed the same, but this world no longer belonged to humans.

  Cheng Xin didn’t know what to do. No one had contacted her after the end of deterrence. The Swordholder no longer existed, just like deterrence.

  She walked forward aimlessly. When she exited the gates of the compound, two guards saluted her. She was terrified of facing people, but she saw nothing but curiosity in their eyes—they didn’t yet know what had happened. Regulations permitted the Swordholder to come onto the surface for brief intervals, and they must have thought she had come up to investigate the quake. Cheng Xin saw a few military officers standing next to a flying transport parked by the gate. They weren’t even looking at her, merely in the direction she had come from. One of them pointed in that direction.

  She turned around and saw the mushroom cloud on the horizon. Formed by the earth and dust thrown up from deep underground, it was very thick, appearing almost solid. It looked so out of place in the serene scene that it resembled a bad Photoshop job. A closer examination led Cheng Xin to imagine it as an ugly bust showing a strange expression in the setting sun. That was where the droplet had penetrated the Earth.

  Someone called her name. She turned and saw 艾 AA running toward her. Dressed in a white jacket, her hair waving in the wind, she panted and told Cheng Xin that she had come to see her, but the sentries wouldn’t let her in.

  “I’ve brought some flowers for your new place,” she said, pointing at her parked car. Then she turned to the mushroom cloud. “Is that a volcano? Did that cause the earthquake just now?”

  Cheng Xin wanted to pull AA into her arms and cry, but she controlled herself. She wanted to delay the moment when this happy girl found out the truth, wanted to let the reverberations of the good times that had just ended linger a bit longer.

  Excerpt from A Past Outside of Time

  Reflections on the Failure of Dark Forest Deterrence

  The most important factor in the failure of deterrence was, of course, electing the wrong Swordholder. This is a topic that will be addressed elsewhere in a dedicated chapter. For now, let’s focus on the technical weaknesses in the system design that contributed to the failure.

  After the failure, most people immediately pointed to the small number of gravitational wave transmitters as a cause, and blamed people from the early Deterrence Era for dismantling nineteen of the twenty-three completed transmitters. But this reaction represented a failure to grasp the substance of the problem. From data gathered during the droplet attack, a droplet needed slightly more than ten seconds on average to penetrate the crust and destroy a transmitter. Even if the planned one hundred transmitters had been completed and deployed, it wouldn’t have taken long for droplets to destroy the entire system.

  The key was that the system could be destroyed. Humankind had had a chance to build an indestructible gravitational wave universal broadcast system, but hadn’t taken it.

  The problem wasn’t the number of transmitters, but where they were deployed.

  Imagine if the twenty-three transmitters had not been built on or below the surface, but in space—that is, twenty-three spaceships like Gravity. Normally, the ships would be scattered around the Solar System. Even if the droplets had conducted a surprise attack, it would be difficult for them to destroy all of them. One or more of the ships would have time to escape into deep space.

  This would have greatly increased the degree of deterrence for the whole system, in a way that would not have been dependent on the Swordholder. The Trisolarans would have known that they controlled insufficient forces within the Solar System to completely destroy the deterrence system, and would have behaved with far more restraint.

  Regrettably, there was only one Gravity.

  There were two reasons that more ships with transmitters weren’t built: First, there was the “Sons of the Earth” attack on the transmitter in Antarctica. Spaceships were deemed even more vulnerable to threats from extremist humans than underground stations. Second, it was a matter of econom
ics. Since gravitational wave antennas were immense, they had to serve as the hull of the ship itself. Thus, the antenna had to be constructed out of materials that met the requirements of spaceflight, which increased costs many times. Gravity itself cost almost the equivalent of the twenty-three ground-based transmitters added together. Moreover, the hull of the ship itself could not be refreshed; when the vibrating string made of degenerate matter that ran the length of the ship reached its fifty-year half-life limit, a completely new gravitational wave ship had to be built.

  But the deeper root cause could only be found in the minds of humankind. Never explicitly stated, and perhaps not even consciously understood, a gravitational wave ship was too powerful—so powerful that it terrified its creator. If something—a droplet attack or something else—forced such ships to depart for deep space, and they could never return to the Solar System due to the presence of enemy threats, they would turn into copies of Blue Space and Bronze Age, or something even more horrific. Each gravitational wave ship, with its no-longer-human crew, would also possess the power to broadcast to the universe (though limited by the half-life of the vibrating string), thus controlling the fate of humanity. A frightful instability would be permanently scattered among the stars.

  At its root, this fear was a fear of dark forest deterrence itself. This was characteristic of ultimate deterrence: The deterrer and the deteree shared the same terror of deterrence itself.

  Post-Deterrence Era, First Hour

  A Lost World

  Cheng Xin walked toward the officers and asked them to take her to the site of the eruption. A lieutenant colonel in charge of security for the compound immediately dispatched two cars: one to take her, the other to carry a few guards for security. Cheng Xin asked AA to stay and wait for her, but AA insisted on coming and got into the car.

  The flying cars hovered barely above the ground and headed to the mushroom cloud at a low speed. AA asked the driver what was wrong, but he didn’t know. The volcano had erupted twice, a few minutes apart. He thought it might be the first time in recorded history that a volcano had erupted within China’s borders.

  He couldn’t have imagined that the “volcano” had once hidden the strategic fulcrum for the world: the gravitational wave antenna. The first eruption was caused by the impact of the droplet penetrating the crust. After destroying the antenna, it retraced its path and emerged from the ground, causing a second eruption. The eruptions were due to the droplet releasing its tremendous kinetic energy in the ground, not an outburst of material from the mantle, so they were very brief. The extremely high velocity of the droplet meant that it could not be observed by the naked eye as it penetrated or emerged from the ground.

  Small smoking pits dotted the Gobi as it passed beneath the car: mini-impact craters from the lava and heated rocks that had been thrown up by the eruption. As they proceeded, the pits grew denser, and a thick layer of smoke hovered over the Gobi, revealing burning stands of tamarisk here and there. Though few people lived out here they occasionally saw old buildings collapsed by the quake. The whole scene resembled a battlefield where the fighting had just finished.

  The cloud had dissipated a bit by now and no longer looked like a mushroom—it was more like a head of unkempt hair whose tips were colored crimson by the setting sun. A security line stopped the cars as they approached, and they had to land. But Cheng Xin persisted, and the sentries let her through. The soldiers didn’t know that the world had already fallen, and they still respected Cheng Xin’s authority as the Swordholder. They did, however, stop AA, and no matter how she screamed and struggled, they would not let her pass.

  The steady wind had already driven most of the dust away, but the smoke broke the light of the setting sun into a series of flickering shadows. Cheng Xin walked about a hundred meters through the shadows until she reached the edge of a giant crater. Shaped like a funnel, the crater was forty or fifty meters deep at the center. Thick clouds of white smoke still poured out of it, and the bottom of the crater gave off a dim red molten glow: a pool of lava.

  Forty-five kilometers below, the gravitational wave antenna, a cylinder with a length of fifteen hundred meters and a diameter of fifty meters suspended in an underground cave with magnetic levitation, had been smashed into smithereens and swallowed by the red-hot lava.

  This should have been her fate. It would have been the best ending for a Swordholder who had given up the power to deter.

  The red glow at the bottom of the crater attracted Cheng Xin. Just one more step, and she would achieve the release that she desired. As waves of heat buffeted her face, she stared at the dim red pool, mesmerized, until peals of laughter from behind her shook her out of her musing.

  She turned around. In the flickering sunlight filtered by the smoke, a slender figure approached her. She didn’t recognize the newcomer until she was very close: Sophon.

  Other than the pale, lovely face, the robot looked completely different from the last time Cheng Xin had seen her. She was dressed in desert camouflage, and her hair, once tied up in a neat bun decorated with flowers, had been cut in a short and efficient style. Around her neck was the black scarf of a ninja, and on her back was strapped a long katana. She looked valiant and heroic, but the extreme femininity that she exuded had not vanished completely: Her postures and movements were still soft and gentle like water, but now they were also suffused with a glamorous air of killing and death, like a pliant but fatal noose. Even the heat spilling from the crater could not dispel the chill she brought.

  “You acted just as we anticipated,” Sophon said, sneering. “Don’t be too hard on yourself. The fact is that humankind chose you, and they chose this result. Out of all the members of the human race, you’re the only innocent.”

  Cheng Xin’s heart jumped. She didn’t feel comforted, but she had to admit that this lovely devil had a power that penetrated her soul.

  Cheng Xin saw AA approach. She had apparently found out or guessed what had really happened. AA’s eyes burned with fury as she stared at Sophon; she picked up a rock from the ground with both hands and smashed the back of Sophon’s skull with it. But Sophon turned around and brushed the rock away like a mosquito. AA cursed at Sophon using every profane word she could think of, and went for another rock. Sophon unsheathed the katana on her back, easily pushing off the pleading Cheng Xin with her other hand, and twirled the katana. It sliced through the air, faster than the blades of an electric fan, whining loudly. When she stopped, strands of AA’s hair drifted down around her head. AA stood frozen in place, terrified, her shoulders hunched.

  Cheng Xin remembered that she had seen Sophon’s katana in that eastern leaf-house shrouded in fog and cloud. Back then, it, and two shorter swords, had rested on a refined wooden stand next to the tea table, looking more decorative than deadly.

  “Why?” Cheng Xin muttered, as if asking herself.

  “Because the universe is not a fairy tale.”

  Rationally, Cheng Xin understood that, had the balance maintained by deterrence continued, the brighter future belonged to humankind, not Trisolaris. But in her subconscious, the universe remained a fairy tale, a fairy tale about love. Her biggest mistake was not looking at the problem from the perspective of the enemy.

  From Sophon’s gaze, Cheng Xin finally understood why she had been kept alive.

  As the gravitational wave broadcast system had been destroyed and the sun’s ability to amplify radio waves had been suppressed, a living Cheng Xin posed no threat. On the other hand, in the unlikely event that humans still possessed some other method of broadcasting to the universe unknown to Trisolaris, eliminating the Swordholder might cause others to activate the broadcast. As long as the Swordholder was alive, however, the probability of that happening was virtually nil: Others would have a reason and excuse to shirk their responsibility.

  Instead of the deterrer, Cheng Xin had been turned into a safety shield. The enemy had seen through her completely.

  She was a fairy tale.

/>   “Don’t celebrate too early,” AA said to Sophon, having recovered some of her courage. “We still have the spaceship Gravity.”

  Sophon returned the katana to its sheath on her back in a single, smooth motion. “Foolish girl, Gravity has been destroyed. It happened an hour ago, when the handover occurred a light-year away. I regret that I can’t show you the wreckage because the sophons are in a blind zone.”

  The Trisolarans had been planning and preparing for this moment for a long time. The exact time for the handover had been determined five months ago, before the sophons accompanying Gravity had entered the blind zone. The two droplets with Gravity had already received the order to destroy the ship at the moment of the handover.

  “I’m leaving,” said Sophon. “Please convey to Dr. Luo Ji the deepest respect of all of Trisolaris. He was a powerful deterrer, a great warrior. Oh, and if you get the chance, also give Mr. Thomas Wade our regrets.”

  Cheng Xin looked up, surprised.

  “In our personality studies, your degree of deterrence hovered around ten percent, like a worm wriggling on the ground. Luo Ji’s degree of deterrence was always around ninety percent, like a fearsome cobra poised to strike. But Wade—” Sophon gazed at the setting sun behind the smoke, only a sliver of which now was above ground. Terror glinted from her eyes. She shook her head vigorously, as though trying to chase away a mirage in her mind. “He had no curve at all. No matter what the other environmental parameters were, his degree of deterrence stayed at one hundred percent! What a devil! If he had become the Swordholder, none of this would have been possible. This peace would have had to last. We’ve already waited sixty-two years, but we’d have had to keep on waiting, maybe for fifty more years, or even longer. And then Trisolaris would face an Earth equal to us in technology and power. We’d have to compromise.… However, we knew that humanity would choose you.”