Cixin Liu - Death's End

“Is the Sun still alive in two dimensions?” asked AA. She spoke for the hope of all three. They all wished for the Sun to continue to give light and heat to the planar Solar System, even if there was no more life in it.

But her hope was soon dashed.

The flattened Sun began to dim. The light from the core diminished rapidly and soon it was possible to see fine annular structures within. The radiation zone was also quieting, and the boiling calmed down, turning into a viscous peristalsis. The loops in the convection zone distorted, broke apart, and soon disappeared. The golden dancers around the rim of the Sun wilted like dried leaves and lost their vivaciousness. Now it was possible to tell that at least gravity continued to function in the two-dimensional universe. The dancing solar prominences lost the support of solar radiation and began to be dragged back to the edge of the Sun by its gravity. Finally, the dancers yielded to gravity and fell lethargically, until the Sun’s atmosphere was no more than a thin, smooth ring wrapped around the Sun. As the Sun went out, the golden arcs at the edges of the planets also dimmed, and the Earth’s two-dimensional hair, formed from the sublimated ocean, lost its golden glow.

Everything in the three-dimensional world died after collapsing into two dimensions. Nothing survived in a painting with no thickness.

Perhaps a two-dimensional universe could possess its own sun, planets, and life, but they would have to be created and operate under completely different principles.

While the three were focused on the flattening Sun, Venus and Mars collapsed into the plane as well. Compared to the Sun, however, the two-dimensionalization of these two terrestrial planets was rather unremarkable. The flattened Mars and Venus were very similar to the Earth in terms of their “tree ring” structure. There were many hollow areas near the rim of Mars, places in the Martian crust that contained water, suggesting that Mars had possessed far more water than people thought. After a while, the water also turned an opaque white, but no giant snowflakes appeared. There were giant snowflakes around the flattened Venus, but they weren’t anywhere as numerous as the ones near the Earth, and the Venusian snowflakes were yellow in hue, indicating that they were not water crystals. A while later, the asteroids on that side of the Sun were also flattened, completing the other half of the Solar System necklace.

Tiny snowflakes—three-dimensional ones—now fell from the light purple Plutonian sky. These were the nitrogen and ammonia that had sublimated in the burst of energy during the Sun’s flattening, and which were now freezing into snow as the temperature plummeted following the Sun’s extinguishment. The snow fell more heavily, and soon accumulated a thick layer over the monolith and Halo . Although there were no clouds, the heavy snow blurred Pluto’s sky, and the two-dimensional Sun and the planets turned hazy behind a curtain of snow. The world looked smaller.

“Don’t you feel at home?” AA lifted both hands and spun in the snow.

“I was just thinking the same thing,” Cheng Xin said, and nodded. She had also thought of snow as something unique to the Earth, and the giant snowflakes around the flattened Earth had confirmed this feeling. The snow falling on this cold, dark world on the edge of the Solar System surprisingly provided her a trace of the warmth of home.

Luo Ji watched as AA and Cheng Xin tried to catch the snow. “Hey, you two! Don’t even think about taking off your gloves!”

Cheng Xin did feel an impulse to take off her gloves and catch the snow with her bare hands. She wanted to feel the slight chill, and watch the crystalline snowflakes melt with her own body heat…. but of course she had enough presence of mind to not indulge the impulse. The nitrogen-ammonia snowflakes were at a temperature of minus-210-degrees Celsius. If she really took off her gloves, her hand would turn as fragile and hard as glass and the feeling of being on Earth would disappear instantaneously.

“There’s no more home,” Luo Ji said, shaking his head and leaning against his cane. “Home is now just a picture.”

The nitrogen-ammonia snow didn’t last long. The snowflakes thinned out and the purple haze from the nitrogen-ammonia atmosphere faded. The sky was once again perfectly transparent and dark. They saw that the Sun and the planets had grown even bigger, indicating that Pluto had moved even closer to that two-dimensional abyss.

When the snow stopped, a bright glowing light appeared near the horizon. The intensity of the light grew rapidly, and soon overwhelmed the fading two-dimensional Sun. Although they couldn’t see the details, they knew that it was Jupiter, the Solar System’s largest planet, falling into the plane. Pluto spun slowly, and part of the flattened Solar System had fallen below the horizon, so they thought they wouldn’t get to witness Jupiter’s collapse, but it appeared that the rate of fall into two dimensions was accelerating.

They asked Halo ’s AI to look for transmissions from Jupiter. Very few images and videos were being transmitted now, and most were indecipherable. Almost all of the messages they got were audio only. Every communication channel was filled with noise, mostly human voices, as though all the remaining space in the Solar System had been filled with a frenzied sea of people. The voices cried, screamed, sobbed, laughed hysterically… and some even sang. The chaotic background noise made it impossible to tell what they were singing, only that it was many voices singing in harmony. The music was solemn, slow, like a hymn. Cheng Xin asked the AI whether it was possible to receive any official broadcasts from the Federation Government. The AI said that all official communications from the government had terminated when the Earth was flattened. The Federation Government couldn’t fulfill the promise to carry out its duties until the end of the Solar System after all.

Ships trying to escape continued to stream by the vicinity of Pluto.

“Children, it’s time to go,” said Luo Ji.

“Let’s go together,” said Cheng Xin.

“What’s the point?” Luo Ji shook his head and smiled. He pointed at the monolith with his cane. “I’m more comfortable over there.”

“All right. We’ll wait until Uranus is flattened so that we get to spend more time with you,” AA said. There really didn’t seem to be any point in insisting. Even if Luo Ji got on Halo, it would only delay the inevitable by another hour. He didn’t need that bit of time. Indeed, if Cheng Xin and AA didn’t have a mission to carry out, they wouldn’t care for that bit of time either.

“No. You must go now!” Luo Ji said. He struck the ground with his cane forcefully, which made him float up under the low gravity. “No one knows how much faster the collapse is happening now. Carry out your mission! We can stay in contact, and that’s no different from being together.”

Cheng Xin hesitated for a moment, then nodded. “All right. We’ll leave. Stay in contact!”

“Of course.” Luo Ji lifted his cane in farewell and turned to walk toward the monolith. With the light gravity, he almost floated over the snow on the ground and had to use the cane to slow himself. Cheng Xin and AA watched until the aged figure of this Wallfacer, Swordholder, and humanity’s final grave keeper disappeared behind the door of the monolith.

Cheng Xin and AA went back inside Halo . The yacht took off right away, its thrusters tossing up snow everywhere. Soon, the ship achieved Pluto’s escape velocity—just a hair above one kilometer per second—and reached orbit. From the porthole and the monitor they could see that swaths of white now joined the blue and black patches of the Plutonian surface. The giant words “Earth Civilization,” written in multiple scripts and languages, had been covered by the snow and were almost illegible. Halo passed through the gap between Pluto and Charon as though flying through a canyon, the two celestial bodies were so close.