Death's End

Nothing but silence. After a long while, Cheng Xin called out, “Dr. Guan?”

“You’re too… kind-hearted,” Guan Yifan said softly.

“I don’t understand—”

“There’s a way for the attacker to avoid death. Think about it.”

Cheng Xin pondered and then said, “I can’t figure it out.”

“I know you can’t. Because you’re too kind. It’s very simple. The attacker must first transform themselves into life forms that can survive in a low-dimensional universe. For instance, a four-dimensional species can transform itself into three-dimensional creatures, or a three-dimensional species can transform itself into two-dimensional life. After the entire civilization has entered a lower dimension, they can initiate a dimensional strike against the enemy without concern for the consequences.”

Cheng Xin was silent again.

“Are you reminded of anything?” Yifan asked.

Cheng Xin was thinking of more than four hundred years ago, when Blue Space and Gravity had stumbled into the four-dimensional fragment. Yifan had been a member of the small expedition that conversed with the Ring.

Did you build this four-dimensional fragment?

You told me that you came from the sea. Did you build the sea?

Are you saying that for you, or at least for your creators, this four-dimensional space is like the sea for us?

More like a puddle. The sea has gone dry.

Why are so many ships, or tombs, gathered in such a small space?

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.

Are all the fish here?

The fish responsible for drying the sea are not here.

We’re sorry. What you said is really hard to understand.

The fish that dried out the sea went onto land before they did this. They moved from one dark forest to another dark forest.

“Is it worth it to pay such a price for victory in war?” Cheng Xin asked. She could not imagine how it was possible to live in a world of one fewer dimension. In two-dimensional space, the visible world consisted of a few line segments of different lengths. Could anyone who was born in three-dimensional space willingly live in a thin sheet of paper with no thickness? Living in three dimensions must be equally confining and unimaginable for those born to a four-dimensional world.

“It’s better than death,” said Yifan.

While Cheng Xin was still recovering from the shock, Yifan continued, “The speed of light is also frequently used as a weapon. I’m not talking about building light tombs—or, as you call them, black domains. Those are just defensive mechanisms employed by weak worms like us. The gods do not stoop so low. In war, it’s possible to make reduced-lightspeed black holes to seal the enemy inside. But more commonly, the technique is used to construct the equivalents of pits and city walls. Some reduced-lightspeed belts are large enough to traverse an entire arm of a galaxy. In places where the stars are dense, many reduced-lightspeed black holes can be connected together into chains that stretch for tens of millions of light-years. That’s a Great Wall at the scale of the universe. Even the most powerful fleets, once trapped, would not be able to escape. Those barriers are very difficult to cross.”

“What is the ultimate result of all this manipulation of space-time?”

“Dimensional strikes will eventually cause more and more of the universe to become two-dimensional, until one day the entire universe is two-dimensional. Similarly, the construction of fortifications will eventually cause all the reduced-lightspeed areas to connect, until the different lowered lightspeeds all average out: This new average will be the new c for the universe.

“At that time, any scientist from a baby civilization—like us—would think that the speed of light through vacuum is barely a dozen kilometers per second, and this is an ironclad universal constant, just like we now think the same of three hundred thousand kilometers per second.

“Of course, I’ve only brought up two examples. Other universal laws of physics have been used as weapons as well, though we don’t know all of them. It’s very possible that every law of physics has been weaponized. It’s possible that in some parts of the universe, even… Forget it, I don’t even believe that.”

“What were you going to say?”

“The foundation of mathematics.”