Cixin Liu - Death's End

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.

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.

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.