Death's End (The Three-Body Problem)

by Cixin Liu

  The camera continued to fall toward the plane. Cheng Xin stared at the approaching two-dimensional city, hoping to find signs of movement in the city. But no, other than the distortion caused by the plasma flames earlier, everything in the flat city was still. Similarly, the two-dimensional bodies did not move at all, and gave no signs of being alive.

  This was a dead world. A dead picture.

  The camera moved still closer to the plane, falling toward a two-dimensional body. The body’s limbs soon filled the whole image, and then came the complicated patterns of muscle fibers and blood vessels. Perhaps it was just an illusion, but Cheng Xin seemed to see red, two-dimensional blood flowing through two-dimensional blood vessels. In a flash, the picture was gone.

  Cheng Xin and AA began their second trip to retrieve more artifacts. They both felt the mission was likely to be meaningless. After observing the two-dimensionalized cities, they understood that the process preserved most of the information from the three-dimensional world. Any information loss would be at the atomic level. Due to the nonoverlapping principle used in projection, the flattened Pluto’s crust wouldn’t be commingled with the artifacts in the museum, and so the information in the artifacts should be preserved. But since they had accepted this mission, they would finish it. Like Cao Bin said, doing something was better than doing nothing.

  They exited Halo and saw the two flattened planets still suspended overhead, but now they were much dimmer. This made the new long, glowing belt that appeared below the planets even more noticeable. The light belt went from one end of the sky to the other, like a necklace formed from numerous individual glowing spots.

  “Is that the asteroid belt?” Cheng Xin asked.

  “Yes. Mars will be next,” said AA.

  “Mars is on this side of the Sun right now.”

  The two fell silent. Without looking at the flattened asteroid belt, they walked toward the black monolith.

  The Earth was next.

  In the great hall of the museum, they saw that Luo Ji had already prepped a bunch of additional artifacts for them. Many of them were Chinese-brush-painting scrolls. AA unrolled one of them: Along the River During the Qingming Festival.

  Cheng Xin and AA no longer had the initial awe and delight of seeing such precious works of art—compared to the grandeur of the destruction in process outside, this was nothing more than an old painting. When future explorers arrived at the great painting that was the flattened Solar System, they would have trouble imagining that this twenty-four-centimeter-by-five-meter rectangle was once very special.

  Cheng Xin and AA asked Luo Ji to come onto Halo. Luo Ji said he would like to see it, and went to look for a space suit.

  As the three of them carried the artifacts out of the monolith, the sight of a flattening Earth greeted them.

  The Earth was the first solid planet to collapse into two dimensions. Compared to Neptune and Saturn, the “tree rings” in the two-dimensionalized Earth were even more replete with fine details—the yellow mantle gradually shifted over to the deep red nickel-iron core—but the overall area was much smaller than the gas giants.

  Unlike in their imagination, they couldn’t see any hint of blue.

  “What happened to our oceans?” Luo Ji asked.

  “They should be near the outside... But two-dimensionalized water is transparent, so we can’t see it,” AA said.

  The three carried the artifacts to Halo in silence. They couldn’t feel the grief yet, like one didn’t immediately feel the pain of a fresh wound cut by a sharp knife.

  But the flattened Earth did show her own wonders. At her outermost rim, a white ring gradually appeared. At first it was barely visible, but soon it stood out sharply against the black backdrop of space. The white ring was pure, flawless, but seemed uneven in its makeup, like it was formed from countless small white grains.

  “That’s our ocean!” Cheng Xin said.

  “The water froze in two-dimensional space,” said AA. “It’s cold there.”

  “Oh—” Luo Ji wanted to stroke his beard, but the visor got in the way of his hand.

  The three carried the boxes of artifacts onto Halo. Luo Ji seemed familiar with the ship’s layout, heading for the ship’s hold without instruction from Cheng Xin or AA. The ship’s AI also recognized him, and accepted his orders. After they secured the artifacts, the three returned to the yacht’s living quarters. Luo Ji asked the AI for a cup of hot tea, and soon, a little robot that Cheng Xin and AA had never seen before brought it to him. Clearly, Luo Ji had some history with this ship that the two women did not know about. They were curious about the story, though more urgent matters had to be taken care of first.

  Cheng Xin asked the AI to play some news from the Earth, but the AI said that it had received only a few transmissions from the planet, and the visual and audio content was essentially impossible to make sense of. They looked at the few open information windows and saw only blurred images taken by unmanned cameras. The AI added that it could provide the video taken by the spacecraft monitoring system near the Earth. A new, large window popped up and the flatted Earth filled the screen.

  The three immediately thought the image looked unreal, even suspecting that the AI had synthesized the image to fool them.

  “What in the world is this?” AA cried out.

  “It’s the Earth about seven hours ago. The camera is fifty astronomical units away, and angular magnification is four hundred and fifty times.”

  They looked more closely at the holographic video taken by the telescopic lens. The body of the flattened Earth appeared very clearly, and the “tree rings” were even denser than when observed with the naked eye. The collapse had probably already been completed, and the two-dimensional Earth was dimming. But what really shocked them was the frozen two-dimensional ocean—the white ring around the rim of the Earth. They could clearly make out the grains forming the ring: snowflakes! These were unimaginably large snowflakes, hexagonal in plan, but each with unique crystal branches—exquisite, lovely beyond words. To see snowflakes from fifty AU away was already extremely surreal, and these immense snowflakes were arranged side by side on the plane with no overlap, which further enhanced the feeling of unreality. They seemed to be purely artistic portrayals of snowflakes, powerfully decorative, turning the frozen two-dimensional sea into a piece of stage art.

  “How big are the snowflakes?” AA asked.

  “Most have diameters between four thousand and five thousand kilometers.” The ship’s AI, incapable of wonder, continued to speak in a serene tone.

  “Bigger than the moon!” Cheng Xin said.

  The AI opened a few other windows, and each showed a zoomed-in snowflake. In these images, the sense of scale was lost, and they seemed to be tiny spirits under a magnifying lens, each snowflake ready to turn into a tiny droplet as soon as it touched down on a palm.

  “Oh—” Luo Ji stroked his beard again, and this time, succeeded.

  “How are they formed?” AA asked.

  “I don’t know,” the AI said. “I can’t find any information about the crystallization of water at astronomical scales.”

  In three-dimensional space, snowflakes formed in accordance with the laws of ice-crystal growth. Theoretically, these laws did not restrict the size of snowflakes. The largest snowflake previously on record was thirty-eight centimeters in diameter.

  No one knew the laws of ice crystal growth in two-dimensional space. Whatever they were, they permitted ice crystals in two dimensions to grow to five thousand kilometers.

  “There’s water on Neptune and Saturn, and ammonia can also form crystals. Why didn’t we see large snowflakes there?” Cheng Xin asked.

  The AI said it didn’t know.

  Luo Ji squinted his eyes and enjoyed the two-dimensional version of the Earth. “The ocean looks rather nice this way, don’t you think? Only the Earth is worthy of such a lovely wreath.”

  “I really want to know what the forests look like, what the grasslands look lik
e, what the ancient cities look like,” Cheng Xin said slowly.

  Grief finally struck them, and AA began to sob. Cheng Xin turned her eyes away from the snowflake ocean and made no sound as her eyes filled with tears. Luo Ji shook his head, sighed, and continued to sip his tea. Their grief was moderated to some extent by the thought that the two-dimensional space would also be their home in the end.

  They would attain their eternal rest alongside Mother Earth on that plane.

  The three decided to begin their third cargo trip. They exited Halo, gazed up at the sky, and saw the three two-dimensional planets. Neptune, Saturn, and the Earth had grown even larger, and the asteroid belt was wider. This was no hallucination. They asked the AI about it.

  “The navigation system has detected a split in the Solar System’s navigational frame of reference. Frame of reference one continues as before. The navigational markers within this system—the Sun, Mercury, Mars, Jupiter, Uranus, Pluto, and some asteroids and Kuiper Belt objects—still satisfy the recognition criteria. Frame of reference two, however, has transformed dramatically. Neptune, Saturn, the Earth, and some asteroids have lost their characteristics as navigational markers. Frame of reference one is moving toward frame of reference two, which leads to the phenomenon you’ve observed.”

  In the sky in the other direction, many moving points of light appeared before the stars—the fleet of ships seeking to escape the Solar System. Some of the glowing blue lights dragged long tails behind them. Some of the ships swept by the three of them, fairly close. The bright lights of their engines operating at maximum capacity cast moving shadows of the three observers on the ground. None of the ships tried to land on Pluto.

  But it was impossible to escape from the collapsing zone. Halo’s AI was trying to say this: The three-dimensional space of the Solar System was like a large carpet that was being pulled by invisible hands into a two-dimensional abyss. These ships were nothing more than worms on the carpet inching along—they couldn’t extend their already limited allotment of time by much.

  “Go ahead by yourselves,” Luo Ji said. “Just take a few more objects. I want to wait here. I don’t want to miss it.” Cheng Xin and AA understood what he meant by “it,” but they had no desire to witness the scene.

  After returning to the underground hall, Cheng Xin and AA, not in the mood to pick and choose, randomly gathered a collection of artifacts. Cheng Xin wanted to take along a Neanderthal skull, but AA tossed it aside.

  “You’ll have plenty of skulls on this picture,” AA said.

  Cheng Xin acknowledged that she was right. The earliest Neanderthals had lived no more than a few hundred thousand years ago. Optimistically, the flattened Solar System would not have visitors until a few hundred thousand years from now. In their eyes, Neanderthals and modern humans would appear to be the same species. Cheng Xin looked around at the other artifacts, and none excited her. For themselves in the present, and for those unimaginable observers in the far future, nothing here mattered as much as the world that was dying outside.

  They took a last look at the dim hall and left with the artifacts. Mona Lisa watched them leave, smiling sinisterly and eerily.

  On the surface, they saw that yet another two-dimensional planet had appeared in the sky: Mercury (Venus was on the other side of the Sun at this moment). It looked smaller than the two-dimensional Earth, but the light generated by its recent collapse into two dimensions made it very bright.

  After they packed the artifacts in the hold, Cheng Xin and AA came out of Halo. Luo Ji, who was waiting outside, leaning on his cane, said, “All right. I think that’s enough. It’s meaningless to carry more, anyway.”

  The women agreed. They stood together with Luo Ji on the Plutonian ground and waited for the most magnificent scene of the play: the flattening of the Sun.

  At this moment, Pluto was forty-five AU from the Sun. Earlier, since both Pluto and the Sun were in the same region of three-dimensional space, the distance between them hadn’t changed. But when the Sun came into contact with the plane, it ceased to move, while Pluto continued to fall toward it, along with the space around it, causing the distance between them to shrink rapidly.

  When the Sun began to two-dimensionalize, the naked eye could only see that its brightness and size appeared to increase suddenly. The latter was due to the rapid expansion of the flattened portion of the Sun on the plane, but from a distance it appeared as though the Sun itself was growing. Halo’s AI projected a large information window outside the ship to show a holographic feed from a telescopic lens, but as Pluto pulled closer to the Sun, even the naked eye could see the grand spectacle of a star collapsing into two dimensions.

  As soon as the Sun began to two-dimensionalize, a circle expanded on the plane. Soon, the planar Sun’s diameter exceeded the diameter of the remaining part of the Sun. This process took only thirty seconds. Based on the mean solar radius of seven hundred thousand kilometers, the rim of the two-dimensional Sun grew at the rate of twenty thousand kilometers per second. The planar Sun continued to grow, forming a sea of fire on the plane, and the three-dimensional Sun sank slowly into this blood-red sea of fire.

  Four centuries ago, Ye Wenjie had stood on the peak of Red Coast Base and watched such a sunset during the last moments of her life. Her heart had struggled to beat like a zither string about to break, and a black fog had begun to cloud her eyes. On the western horizon, the Sun that was falling into the sea of clouds seemed to melt, and the Sun’s blood seeped into the clouds and the sky, creating a large crimson swath. She had called it humanity’s sunset.

  And now, the Sun really was melting, its blood seeping into the deadly plane. This was the last sunset.

  In the distance, white fog rose from the ground outside the landing field. Pluto’s solid nitrogen and ammonia sublimated, and the fresh, thin atmosphere began to scatter the sunlight. The sky no longer appeared pure black, but showed hints of purple.

  While the three-dimensional Sun was setting, the two-dimensional Sun was rising. A flat star could still radiate its light inside the plane, so the two-dimensional Solar System received its first sunlight. The sides of the four two-dimensional planets facing the sun—Neptune, Saturn, the Earth, and Mercury—all took on a golden glow, though the light only fell along a one-dimensional curved edge. The giant snowflakes that surrounded the Earth melted and turned into white vapor, which was blown by two-dimensional solar wind into two-dimensional space. Some of the vapor soaked up the golden sunlight and appeared as if the Earth had hair that drifted with the wind.

  An hour later, the Sun had completely collapsed into two dimensions.

  From Pluto, the Sun appeared as a giant oval. The two-dimensional planets were tiny fragments compared to it. Unlike the planets, the Sun did not display clear “tree rings” but was separated into three concentric sections around a core. The center was very bright, and no details could be seen—probably corresponding to the core of the original Sun. The wide ring outside the core probably corresponded to the original radiation zone—a boiling, two-dimensional, bright red ocean where countless cell-like structures rapidly formed, split, combined, and disappeared in a manner that seemed chaotic and agitated when viewed locally, but followed grand patterns and order when viewed as a whole. Outside that was the original Sun’s convection zone. Like in the original Sun, currents of solar material transferred heat into space. But unlike the chaotic radiation zone, the new convection zone revealed clear structure, as many ring-shaped convection loops, similar in shape and size, arranged themselves side by side in neat order. The outermost layer was the solar atmosphere. Golden currents leapt away from the circular rim and formed a large number of two-dimensional prominences, resembling graceful dancers cavorting wantonly around the Sun. Some of the “dancers” even escaped the Sun and drifted far into the two-dimensional universe.

  “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.