Death's End

Deterrence Era, Year 62 Gravity, in the Vicinity of the Oort Cloud

Gravity had been pursuing Blue Space for half a century.

It finally approached its target. Only three AU separated the hunter and the hunted. Compared to the 1.5 light-years that the two ships had traversed, this was mere inches.

A decade ago, Gravity had passed through the Oort Cloud. This region, about one light-year from the sun at the edge of the Solar System, was the birthplace of comets. Blue Space and Gravity were the first human spaceships to cross this border. The region didn’t feel anything like a cloud, though. Once in a while, a frozen ball of dirt and ice—a tailless comet—passed tens of thousands or hundreds of thousands of kilometers away, invisible to the naked eye.

Once Gravity left the Oort Cloud behind, the ship entered true outer space. From here, the sun appeared as just another star behind the ship. It lost its reality and became like an illusion. In every direction, all one could see was a bottomless abyss, and the only objects whose existence could be ascertained by the senses were the droplets flying in formation with Gravity. The droplets flanked the ship at a distance of about five kilometers, just visible to the naked eye. Those aboard Gravity liked to gaze at the droplets with telescopes as a source of comfort in the endless emptiness. Observing the droplets was, in a sense, just looking at themselves. The mirrorlike surface of the droplets reflected an image of Gravity. The dimensions were a bit distorted, but due to the perfect smoothness of the surface, the image was particularly clear. With sufficient magnification on their telescopes, the observers could even pick out the porthole, and themselves in it, in the reflection.

Most of the one hundred-plus officers and crew aboard Gravity didn’t experience this solitude because they had spent the majority of the past fifty years in hibernation. During routine cruising, only about five to ten crew members needed to be on duty. As the crew rotated through hibernation, each person was usually on duty for three to five years.

The entire pursuit was a complex game of acceleration between Gravity and Blue Space. First of all, Blue Space couldn’t just accelerate continuously, as doing so would cost it precious fuel and ultimately deprive it of mobility. Even if it managed to escape Gravity, it would be committing suicide in the endless empty desert of outer space if it exhausted its fuel. Although Gravity had more fuel onboard than Blue Space, it had constraints of its own. Since it needed to be prepared for a return voyage, its fuel reserves had to be divided into four equal parts: the acceleration away from the Solar System; the deceleration before its destination; the acceleration toward the Solar System; and the deceleration before arriving at the Earth. Thus, the portion available for acceleration during the pursuit amounted to only one-quarter of the fuel. Based on calculations of Blue Space’s previous maneuvers and intelligence gathered by the sophons, Gravity had an accurate idea of Blue Space’s fuel reserves, but the latter had no information about the former’s stores. Thus, in this game, Gravity knew all the cards held by Blue Space, while Blue Space struggled in ignorance. During pursuit, Gravity consistently maintained a speed higher than Blue Space, but neither ship approached their maximum velocities. Moreover, twenty-five years after the start of the chase, Blue Space stopped accelerating, perhaps because it had used up all the fuel it dared.

During the half century of the hunt, Gravity repeatedly hailed Blue Space, explaining that running was meaningless. Even if the crew of Blue Space somehow escaped the hunters from Earth, the droplets would catch up and destroy them. But if they returned to Earth, they would receive a fair trial. They had the option to greatly shorten the pursuit by surrendering. But Blue Space ignored these entreaties.

A year previously, when Gravity and Blue Space were thirty AU apart, something not entirely unexpected occurred: Gravity and the two accompanying droplets entered a region of space where the sophons lost their quantum ties to home, terminating real-time communications with Earth. Gravity had to communicate with Earth through only neutrinos and radio. Transmissions from Gravity now took a year and three months to reach the Earth, and the ship had to wait an equally long time to receive a reply.

Excerpt from A Past Outside of Time More Indirect Evidence for the Dark Forest: Sophon-Blind Regions