Death's End

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.

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