Death's End (Remembrance of Earth’s Past, #3)

by Liu Cixin

The Second Trisolaran Fleet is heading for Earth at lightspeed, and should arrive in four years.” Chu Yan looked at Gravity’s crew with caring eyes, as though sorry that he had to deliver this news.

Based on information provided by Gravity, that was the scheduled time for the Swordholder to transfer his authority to his successor. This was the opportunity Trisolaris had been waiting for for half a century. The two droplets had clearly been given orders before entering the blind zone. This was a long-planned, coordinated attack.

“It’s been sixty years since you left home, and fifty for us. Everything on Earth has changed. Deterrence made a comfortable cradle, and as humanity napped inside, it regressed from an adult to a child.” “Don’t you know that there are no more men on Earth?” someone from Gravity shouted.

“Humans on Earth lost the ability to maintain dark forest deterrence,” Chu Yan said. “We had planned to capture Gravity and re-establish dark forest deterrence. But we’ve just found out that due to decay in the antenna, the ability to broadcast gravitational waves will only last two more months. Believe me, this has been an incredible blow to all of us. We have only one choice: immediately activate the universal broadcast.”

It’s very likely that the genocide of the human race is underway. “Activating the universal broadcast would give the Earth one last chance. If the location of the Solar System is revealed, it would no longer have any value to Trisolaris because it could be destroyed at any moment. This would force the Trisolarans to leave the Solar System, and their lightspeed fleet would have to turn away. We may be able to save the human race from immediate annihilation. To give them more time, our broadcast will include only the location of Trisolaris.”

Three hundred fifteen years had passed since that morning in the twentieth century when Ye Wenjie had pushed another red button. The gravitational wave broadcast began.

“Was it Blue Space?” “No one knows the details, not even Sophon. But Trisolaris received the universal broadcast, and it was initiated a year ago, when deterrence failed.” “Can you let me be by myself for a while?” “All right, Dr. Cheng. But you should be happy. They did what you needed to do.”

“It’s possible to detect the warped points using the naked eye,” Chu Yan said. “But the best way is to monitor the electromagnetic radiation. The emission from these points is very faint, but it has a distinct spectral signature. The regular sensors on our ships can detect and locate them. Typically, a volume of space as large as a ship in this region contains one to two warped points, but we once found twelve at once. Look, right now there are three.”

All who had experienced it agree that the sensation of being in four-dimensional space was indescribable. They would even say that it was the only thing encountered by humanity thus far that absolutely could not be captured by language.

Imagine a race of flat beings living inside a two-dimensional picture. No matter how rich or colorful the picture was, the flat people could only see the profile of the world around them. In their eyes, everything consisted of line segments of various lengths. Only when such a two-dimensional being was taken up out of the picture into three-dimensional space and looking down on the world could he see the entirety of the image. This analogy simply expressed in some more detail the indescribability of experiencing four-dimensional space.

Only from four-dimensional space could he see the picture as a whole. He would describe it this way: Nothing blocked whatever was placed behind it. Even the interiors of sealed spaces were laid open. This seemed a simple change, but when the world was displayed this way, the visual effect was utterly stunning. When all barriers and concealments were stripped away, and everything was exposed, the amount of information entering the viewer’s eyes was hundreds of millions times greater than when he was in three-dimensional space. The brain could not even process so much information right away.

Given this description, those who had never experienced four-dimensional space might get the wrong impression that they were seeing everything “through” the hull. But no, they were not seeing “through” anything. Everything was laid out in the open, just like when we look at a circle drawn on a piece of paper, we can see the inside of the circle without looking “through” anything.

One could see the interior of solids, such as the bulkheads or a piece of metal or a rock—one could see all the cross sections at once!

But when one viewed the three-dimensional world from four-dimensional space, all concealed and hidden details were revealed simultaneously, since three-dimensional objects were laid open at every level. Take a sealed container as an example: One could see not only what was inside, but also the interiors of the objects inside.

even when observing some specific object, such as a cup or a pen, they saw infinite details, and the information received by their visual systems was incalculable. Even a lifetime would not be enough to take in the shape of any one of these objects in four-dimensional space.

When an object was revealed at all levels in four-dimensional space, it created in the viewer a vertigo-inducing sensation of depth, like a set of Russian nesting dolls that went on without end. Bounded in a nutshell but counting oneself a king of infinite space was no longer merely a metaphor.

They saw bodies revealed at every level with the details displayed in parallel: They could see bones, organs, the marrow inside the bones, the blood flowing through the ventricles and atria of the heart, the openings and closings of the mitral and tricuspid valves. When gazing at each other, they could see clearly the interior structure of the lenses of the eyes.…

Morovich and Guan quickly learned how to avoid touching inner organs. By moving in a certain direction, they could grasp someone’s hand instead of the bones inside the hand. To touch the bones or organs required exertion in another direction—a direction that didn’t exist in three-dimensional space.

During spacewalks, they were at least enclosed by space suits, but now, nothing stood between space and them. The ship that revealed infinite details did not shield them from space. In the fourth dimension, the ship lay in parallel with all of space.

Once their attention was no longer completely absorbed by the inexhaustible details of the environment around them, they sensed space itself, or sensed the fourth dimension. Later, people would call this feeling “high-dimensional spatial sense.”

Concepts like “vastness” or “boundlessness” in three-dimensional space were replicated an infinite number of times in four-dimensional space in a direction that did not exist in three-dimensional space.

two mirrors facing each other: In either mirror one could see a boundless multitude of replicated mirrors, a hall of mirrors that extended into infinity. In this analogy, each mirror in the hall was a three-dimensional space. In other words, the vastness that one experienced in three-dimensional space was but a cross-section of the vastness of four-dimensional space.

The difficulty of describing high-dimensional spatial sense lay in the fact that for observers situated in four-dimensional space, the space they could see was empty and uniform, but there was a depth to it that could not be captured by language. This depth w...

Guan Yifan’s exclamation later became a classic quote: “A bottomless abyss...

“How did all this happen?” Morovich tore open his collar and gasped. “We entered a region of space where space has four dimensions. That’s it. We call this region a four-dimensional fragment.”

“Let me propose a model,” said Guan excitedly. “The entirety of our three-dimensional space is a large, thin sheet of paper, sixteen billion light-years across. Somewhere on this sheet of paper is a tiny, four-dimensional soap bubble.”

“Though we were in four-dimensional space just now, our bodies remained three-dimensional,” Morovich said. “That’s right. We were flat, three-dimensional people drifting in four-dimensional space. It’s not clear how our bodies are able to survive in four-dimensional space, given that the physical laws are likely different. There are many such mysteries.”

“The three-dimensional sheet of paper is not completely flat everywhere. Some places are warped, reaching into the fourth dimension. That’s what a warped point is: a tunnel from lower dimensions into higher dimensions. We can get into four-dimensional space by jumping into them.”

Some are much bigger. There’s one mystery we’ve never been able to solve: We once observed that the rear third of Gravity had warped into four-dimensional space, and stayed there for several minutes.

“It’s not possible to look into the fourth dimension from three-dimensional space. But it is possible to be in four-dimensional space and see everything happening in three-dimensional space and to affect things in it. We were able to lay an ambush against the droplets from four-dimensional space. No matter how powerful the strong-interaction probes were, they were still three-dimensional objects.

We approached it from the fourth dimension, and, without understanding its principles of operation, sabotaged its internal mechanisms—completely exposed—at random.

“The soap bubble—uh, four-dimensional fragment—how big is it?” “Talking about the size of four-dimensional space from three-dimensional space is kind of meaningless. We can only discuss how big the projection of the fragment is in three dimensions.

“How could a four-dimensional fragment appear in three-dimensional space?” Guan Yifan muttered to himself. “No one knows. Doctor, this is your puzzle to solve.”

In three-dimensional space, this region appeared very empty and showed no irregularities. Much of the exploration had to be conducted in four-dimensional space. Since releasing probes into four-dimensional space was no trivial matter, most of the research was conducted by inserting a telescope into the fragment through a warped point.

Through the telescope, they discovered a ring-shaped object. Since it was impossible to determine its distance from the ship, it was also impossible to estimate its size.

Navigating through four-dimensional space was fraught with risks. To precisely fix one’s location required four coordinates, but equipment brought from three-dimensional space could only determine three coordinates. This meant three-dimensional explorers could not determine the location of any object in four-dimensional space with precision. An explorer could not ascertain the location or distance of the Ring using instrumentation or visual observation, so it would be possible to collide with the Ring at any moment.

As the two ships sailed deeper into the four-dimensional fragment, the density of micrometeoroid strikes increased, and even larger meteoroids, visible to the naked eye, passed near the ships. Their velocity relative to the ships was several times the third cosmic velocity. In three-dimensional space, the critical parts of the ships were wrapped in layers of protection, but here, they lay exposed to the fourth dimension, completely defenseless.

Guan Yifan raged against this decision. “The greatest mystery in the universe is right in front of us. The answers to all our cosmological questions may be found here. How can we leave?” “Are you talking about the three and three hundred thousand syndrome? The fragment did remind me of it.”

the longest voyage in four-dimensional space had been the attack on the droplets and Gravity. During the attack, a pinnace had sailed through four-dimensional space to approach Gravity, and then three people, including Lieutenant Commander Park Ui-gun, had entered Gravity via a warped point to reconnoiter. Thereafter, more than sixty marines had boarded Gravity in three separate waves. The attack on the droplets had relied on smaller shuttles. But this voyage of discovery to the Ring would be far longer.

Lieutenant Zhuo piloted the pinnace using voice commands or by moving the cursor with his gaze—it was a good idea to avoid using hands and risking contact with some sensitive piece of equipment that now lay exposed in four dimensions.

Due to the extra unmeasurable dimension, visual judgments of distance were completely unreliable. The Ring might be as far away as an astronomical unit or as close as the pinnace’s bow.

“You’ve got to remember that we’re basically blind in the fourth dimension,” Lieutenant Zhuo said. He decreased their speed again.

What they were seeing wasn’t just a Ring, but an infinity of Rings all stacked together in concealment. This sensation of four-dimensionality impressed itself upon the soul, and gave the observers the experience of seeing the mountain contained in a mustard seed described in Buddhist parables.

Lieutenant Zhuo and Guan were both glad to have West with them. The psychologist did seem to have some skills when it came to establishing communications with unknown intelligences.

The last message consisted of four Chinese characters: I am a tomb. The Rosetta System was written in a language that mixed English with Chinese. It would make sense that the Ring would use the same language to communicate with them.

Guan Yifan typed a question into the floating window, and began the conversation between humanity and the Ring. Whose tomb is this? The tomb of those who created it. Is this a spaceship? It used to be a spaceship. But now it’s dead, and so it’s a tomb. Who are you? Who is conversing with us? I am the tomb. It is the tomb speaking to you. I’m dead.

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.

The fish responsible for drying the sea are not here. We’re sorry. What you said is really hard to understand. The fish who dried the sea went onto land before they did this. They moved from one dark forest to another dark forest.

Are you going to attack us? I’m a tomb; I’m dead; I won’t attack anyone. There is no dark forest state between spaces of different dimensions. The lower-dimensional space cannot threaten the higher-dimensional space, and the resources of the lower-dimensional space are of no use to the higher-dimensional space. But the dark forest exists everywhere between those sharing the same dimensions.

“I go back to the analogy I made before. The probability that we managed to stumble into the only soap bubble with a diameter of forty to fifty astronomical units on the surface of a sheet of paper sixteen billion light-years across is so minuscule that it might as well be zero. I’m certain that there are other soap bubbles, probably many more.”