Cixin Liu - Death's End

“These are probably the darkest things in the universe,” Cheng Xin said. The death lines showed no details except an exceptional blackness showing the boundaries of the zero-lightspeed region, with no real surface. Looking up, the lines showed up clearly even against the dark backdrop of space.

“These are the deadest things in the universe as well,” said Guan Yifan. “Zero-lightspeed means absolute, one hundred percent death. Inside it, every fundamental particle, every quark is dead. There is no vibration. Even without a source of gravity inside, each death line is a black hole. A zero-gravity black hole. Anything that falls in cannot reemerge.”

Yifan picked up a rock and tossed it toward one of the death lines. The rock disappeared inside the absolute darkness.

“Can your lightspeed ships produce death lines?” Cheng Xin asked.

“Far from it.”

“So you’ve seen these before, then?”

“Yes, but only rarely.”

Cheng Xin gazed up at the giant black columns reaching into space. They lifted up the domed sky and seemed to turn the universe into a Palace of Death. Is this the ultimate end for everything?

In the sky, Cheng Xin could see the end of the columns. She pointed in that direction. “So the ships entered lightspeed at the end?”

“That’s right. These are only about a hundred kilometers high. We’ve seen columns even shorter than these, presumably left by ships that entered lightspeed almost instantaneously.”

“Are these the most advanced lightspeed ships?”

“Maybe. But this is a rarely seen technique. Death lines are usually the products of Zero-Homers.”

“Zero-Homers?”

“They’re also called Resetters. Maybe they’re a group of intelligent individuals, or a civilization, or a group of civilizations. We don’t know exactly who they are, but we’ve confirmed their existence. The Zero-Homers want to reset the universe and return it to the Garden of Eden.”

“How?”

“By moving the hour hand of the clock past twelve. Take spatial dimensions as an example. It’s practically impossible to drag a universe in lower dimensions back into higher dimensions, so maybe it’s better to work forward in the other direction. If the universe can be lowered into zero dimensions and then beyond, the clock might be reset and everything returned to the beginning. The universe might possess ten macroscopic dimensions again.”

“Zero dimensions! Have you seen such a thing done?”

“No. We’ve only witnessed two-dimensionalization. We’ve never even seen one-dimensionalization. But somewhere, some Zero-Homers must be trying. No one knows if they’ve ever succeeded. Comparatively, it’s easier to lower the speed of light to zero, so we’ve seen more evidence of such attempts to lower the speed of light past zero and return it to infinity.”

“Is that even theoretically possible?”

“We don’t know. Maybe the Zero-Homers have theories that say yes, but I don’t think so. Zero-lightspeed is an impassable wall. Zero-lightspeed is absolute death for all existence, the cessation of all motion. Under such conditions, the subjective cannot influence the objective in any way, so how can the ‘hour hand’ be shifted past it? I think the Zero-Homers are practicing a kind of religion, a kind of performance art.”

Cheng Xin stared at the death lines, her terror mixed with awe. “If these are trails, why don’t they spread?”

Guan Yifan clutched Cheng Xin’s arm. “I was just getting to that. We’ve got to get out of here. Leave not just Planet Gray, but the entire system. This is a very dangerous place. Death lines are not like regular trails. Without disturbance, they’ll stay like this, with a diameter equal to the effective surface of the curvature engine. But if they’re disturbed, they’ll spread very rapidly. A death line of this size can expand to cover a region the size of a solar system. Scientists call this phenomenon a death line rupture.”

“Does a rupture make the speed of light zero in the entire region?”

“No, no. After rupture, it turns into a regular trail. The speed of light inside goes up as the trail dissipates over a wider region, but it will never be much more than a dozen meters per second. After these death lines expand, this entire system might turn into a reduced-lightspeed black hole, or a black domain…. Let’s go.”

Cheng Xin and Guan Yifan turned toward the shuttle and began to run and leap.

“What kind of disturbance makes them spread?” Cheng Xin asked. She turned to give the death lines another glance. Behind them, the five death lines cast long shadows that stretched across the plain to the horizon.

“We’re not sure. Some theories suggest that the appearance of other curvature trails nearby would cause disturbance. We’ve confirmed that curvature trails within a short distance can influence each other.”

“So, if Halo accelerates—”

“That’s why we must get farther away using only the fusion engine before engaging the curvature engine. We’ve got to move… using your units of measurement… at least forty astronomical units away.”

After the shuttle took off, Cheng Xin continued to stare at the receding death lines. She said, “The Zero-Homers give me a bit of hope.”

Yifan said, “The universe contains multitudes. You can find any kind of ‘people’ and world. There are idealists like the Zero-Homers, pacifists, philanthropists, and even civilizations dedicated only to art and beauty. But they’re not the mainstream; they cannot change the direction of the universe.”

“It’s just like the world of humans.”

“At least the Zero-Homers’ task will ultimately be completed by the cosmos itself.”

“You mean the end of the universe?”

“That’s right.”

“But based on what I know, the universe will continue to expand, and become sparser and colder forever.”

“That’s the old cosmology you know, but we’ve disproved it. The amount of dark matter had been underestimated. The universe will stop expanding and then collapse under gravity, finally forming a singularity and initiating another big bang. Everything will return to zero, or home. And so Nature remains the final victor.”

“Will the new universe have ten dimensions?”

“Who knows? There are infinite possibilities. That’s a brand-new universe, and a brand-new life.”

The trip back to Planet Blue was as uneventful as the trip to Planet Gray. Most of the time, Cheng Xin and Guan Yifan remained asleep under the sleep-aid machines. By the time they were awakened, Hunter was in orbit around Planet Blue. Looking down at the blue-and-white world, Cheng Xin almost thought she was home.

AA hailed them, and Yifan replied. “ Hunter here. What’s wrong?”

AA’s voice was agitated. “I’ve called you multiple times, and the ship’s AI refused to wake you!”

“I told you we have to maintain radio silence. What happened?”

“Yun Tianming is here!”

Cheng Xin was thunderstruck. The last traces of sleep left her, and even Yifan’s jaw hung open.

“What?” Cheng Xin said softly.

“Yun Tianming is here! His ship landed three hours ago.”

“Oh,” Cheng Xin answered mechanically.

“He’s still young, as young as you!”

“Really?” Cheng Xin’s voice seemed to come from far away, even to herself.

“He brought a gift for you.”

“He already gave me a gift. We’re inside his gift now.”

“That’s nothing. Let me tell you, this is an awesome gift, and much bigger…. He’s outside right now. Let me get him.”

Yifan interrupted. “No. We’re coming down right now. So much radio transmission is dangerous. I’m cutting it off.”