Death's End

Bunker Era, Year 66 Outside the Solar System

A year before Cheng Xin’s awakening, the advance warning system discovered an unknown flying object sweeping past the edge of the Oort Cloud at a speed close to lightspeed. At its closest approach, the object was only 1.3 light-years from the Sun. The object’s volume was immense, and at its near-lightspeed velocity, the radiation generated by its impact with the scattered dust and atoms in space was intense. The advance warning system also observed the object making a small course change during flight to avoid a patch of interstellar dust, before resuming its previous course. It was most certainly an intelligent spaceship.

This was the first time that Solar System humans—as opposed to Galactic humans—had observed another extraterrestrial civilization besides the Trisolarans.

Due to lessons learned from the previous three false alarms, the Federation Government did not publicize this discovery. No more than a thousand people in the entire Bunker World knew about it. During the few days when the spaceship had been closest to the Solar System, these individuals lived in extreme anxiety and terror. In the few tens of space observation units comprising the advance warning system, in the advance warning center (a space city in the Jupiter cluster), in the battle center of Federation Fleet Command, and in the office of the president of the Solar System Federation, people held their breaths and watched the spaceship’s course like a trembling school of fish hiding at the bottom of a pond, waiting for the trawler to pass overhead. These individuals’ terror developed to absurd levels later: They refused to use radio communications, walked noiselessly, and spoke only in whispers…. In reality, everyone understood that these gestures were meaningless, not the least because what the advance warning system observed had happened a year and four months ago. By now, the spaceship was already gone.

After the extraterrestrial spaceship moved farther away, these individuals did not relax. The advance warning system discovered something else that was worrisome. The strange spaceship did not shoot a photoid at the Sun, but did launch something else. This object was also shot at the Sun at lightspeed, but it produced none of the emissions associated with photoids and was completely invisible electromagnetically. The advance warning system only managed to discover it through gravitational waves. The object continuously emitted weak gravitational waves whose strength and frequency remained constant. The waves clearly carried no message, and were probably the result of some physical characteristic of the projectile. When the advance warning system initially discovered these gravitational waves, the source was thought to be the extraterrestrial spaceship. But they soon found that the source was separate from the spaceship, and it was approaching the Solar System at lightspeed.

Further analysis of the observation data revealed that the projectile wasn’t aimed precisely at the Sun. According to its current trajectory, it would sweep past the Sun outside the orbit of Mars. If the intended target had been the Sun, this was a relatively gross error. This showed another way that the projectile was different from a photoid: The data gathered from the previous two photoid strikes all showed that after a photoid was launched, it followed a precise, straight trajectory to the target star (taking into account the motion of the star) and did not require any course correction. It could be surmised that a photoid was essentially a rock flying under inertia at lightspeed. Tracking the gravitational wave source showed that the projectile did not make any course corrections, apparently indicating that its target was not the Sun. This provided some comfort for everyone involved.

When the projectile was about 150 AU from the Sun, the gravitational waves it emitted began to rapidly decrease in frequency. The advance warning system discovered that this was due to its deceleration. Within a few days, the projectile’s velocity went from lightspeed to one-thousandth of lightspeed, and continued to decrease. Such low speed meant that it wasn’t enough to threaten the Sun, which provided further comfort. In addition, at this speed, human spacecraft could keep up with it. In other words, it was possible to send out ships to intercept it.

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Revelation and Alaska departed the Neptune city cluster and flew in formation to investigate the unknown projectile.