Death's End

“I think there’s an even more interesting question: Have we encountered them before? Think about the Earth: It’s been careening through space for several billion years. Is it not possible that it had entered a four-dimensional fragment in the past?”

“That would have been an astonishing sight. I find it hard to imagine that humanity had experienced it…. But I wonder if dinosaurs could have located warped points…”

“Why are there bubbles at all? Why are there so many four-dimensional fragments in three-dimensional space?”

“It’s a great mystery.”

“Captain, I think it’s likely a dark secret.”

—————

Blue Space and Gravity began to back out of the fragment. As the ships accelerated, gravity pulled them toward the ships’ sterns. Guan Yifan and the science officers from both ships tried to cram as much research about the fragment as possible into the next few days and spent almost all their time in four-dimensional space. This was only in part due to the requirements of their research—they also found the confinement and claustrophobia of being in three-dimensional space unbearable.

On the fifth day after beginning acceleration, all those in four-dimensional space found themselves back in three-dimensional space in a flash without having passed through a warped point. The electromagnetic sensors on the two ships indicated that there were no more warped points aboard either ship.

Blue Space and Gravity were outside the fragment.

This surprised them. Based on their calculations, they should still be cruising through the fragment for another twenty hours. Their early exit was probably due to one of two reasons: one, the fragment had sped up in a direction opposite to the ships’ current heading. Two, the fragment was shrinking. The crews believed reason number two was more likely. Other than the data, they also remembered the answer from the Ring:

When the sea is drying, the fish have to gather into a puddle. The puddle is also drying, and all the fish are going to disappear.

The two ships stopped accelerating and began to decelerate at full power. Finally, they stopped at the vicinity of the boundary of the four-dimensional fragment, where it was safe.

The edge of the four-dimensional fragment was invisible. The space before them was empty, placid like the surface of a deep pool. The sea of stars that was the Milky Way shone brightly, giving no hint that a great secret was hidden close by.

But soon they did notice a strange and spectacular sight: From time to time, luminous lines appeared in the space before them. Those lines were very thin, and very straight on first appearance. They seemed to have no thickness to the naked eye, and stretched in length between five thousand and thirty thousand kilometers. The lines appeared suddenly. At first, they gave off a blue glow. Then the color gradually shifted to red, and the straight lines curved and broke into many pieces, until they finally vanished. Observation showed that these lines manifested at the edge of the fragment, as though a giant pen constantly marked out the boundary.

They launched an unmanned probe toward the region of space where the lines appeared, and by luck, the probe managed to observe one of the lines when it flashed into existence at close range. The probe was about a hundred kilometers away, rushing toward the line at full speed. By the time it arrived, the line had curled, broken up, and disappeared. The probe detected massive quantities of hydrogen and helium in the vicinity, and also some dust from heavy elements, mainly iron and silicon.

After analyzing the data, Guan and the science officers concluded that the lines were created by four-dimensional matter entering three-dimensional space. As the fragment shrank, four-dimensional matter dropped into three-dimensional space and decayed instantly. Although these bits of matter took up very little volume in four-dimensional space, their decay into three dimensions flattened the fourth dimension, causing their volume to increase greatly and expand into the form of straight lines. By their calculations, a few tens of grams of four-dimensional matter could form a line stretching almost ten thousand kilometers in three dimensions.

Based on the rate at which the boundary of the fragment was receding, in twenty days or so, the Ring would also enter three-dimensional space. The two ships decided to wait to observe such a wonder of the universe—they had plenty of time, after all. Using the glowing decay-lines as markers, the two ships cautiously proceeded, maintaining the same speed as the receding edge of the fragment.