Death's End

“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.