by Cixin Liu
“The night I finished building the lighthouse, I took my boat out to the sea to look at it from a distance. And all of a sudden I had a thought: Death is the only lighthouse that is always lit. No matter where you sail, ultimately, you must turn toward it. Everything fades in the world, but Death endures.”
It had been twenty minutes since they entered the whirlpool, and the boat had slid about a third of the way down toward the bottom. The boat became more slanted, but due to centrifugal force, the passengers weren’t sliding toward the portside. The wall of water filled their field of view, and they could no longer see the top, even on the other side of the whirlpool. Everyone avoided looking up at the sky because, in the maelstrom, the boat moved along with the spinning wall of water, and it was almost impossible to feel the motion—the boat seemed to adhere to the side of a watery basin. But if they looked up, the motion instantly became evident. The cloud-filled sky spun overhead faster and faster, making them dizzy. Since the centrifugal force was stronger lower in the vortex, the water wall below the boat became even smoother and felt more solid, like ice. The rumbling from the eye of the maelstrom overwhelmed every other sound, and conversation was no longer possible. The Sun in the west peeked out of cracks in the cloud cover, and a ray of golden light shone into the swirling vortex. But the light couldn’t reach the maw at the bottom, and only illuminated a small part of the wall of water, making the bottom appear even more dark and menacing by contrast. Mist and fog swirled out of the eye at the center, forming a rainbow in the ray of sunlight that arced grandly across the rotating abyss.
“I remember Poe describing a rainbow in the maelstrom as well. I think it was even in moonlight. He called it a bridge between Time and Eternity.” Jason was shouting, but no one could hear what he was saying.
The helicopter came to their rescue. Hovering about two or three meters above the boat, it dangled a rope ladder so that everyone in the boat could climb out. Then the empty boat drifted away and continued to circle the monstrous vortex. The unfinished cod on the boat still glowed with the remnants of a blue flame.
The helicopter hovered above the maw of the maelstrom, and as everyone looked down at the spinning funnel, they soon felt nauseated and dizzy. Someone entered directions into the navigation system for the helicopter to spin, matching the whirlpool’s rotation below. This way, the whirlpool appeared still, but the world outside—sky, sea, and mountains—began to spin around them. The maelstrom seemed to become the center of the world, and the observer’s nausea wasn’t reduced in the slightest. AA vomited up all the fish she had eaten.
As she gazed at the whirlpool below, another whirlpool appeared in Cheng Xin’s mind: It was made up of a hundred billion silver stars spinning in the sea that was the universe, taking 250 million years to complete one rotation—it was the Milky Way. The Earth was not even as big as a mote of dust in this whirlpool, and the Moskstraumen was but another mote of dust on the Earth-dust.
Half an hour later, the boat fell into the eye and disappeared abruptly. Amidst the unchanging rumbling, they seemed to detect the sound of the boat being ground apart.
The helicopter dropped Jason off at Mosken, and Cheng Xin promised to compensate him with a new boat as soon as possible. Then they said farewell and the helicopter headed for Oslo, the nearest city with a sophon-free room.
Everyone remained deep in thought through the voyage, not even conversing with their eyes.
The Moskstraumen’s meaning was so obvious that no thought was required.
But the question remained: What did lowering the speed of light have to do with black holes? What did black holes have to do with the cosmic safety notice?
A black hole couldn’t change the speed of light; all it could do was to change the wavelength.
Lowering the speed of light in vacuum to one-tenth, one-hundredth, or even one-thousandth of its natural speed would mean thirty thousand kilometers per second, three thousand kilometers per second, and three hundred kilometers per second, respectively. It was hard to tell how black holes would be involved.
There was a threshold here that had to be crossed—hard to do for normal patterns of thinking, but not so for this group, among the most brilliant minds humanity had to offer. Cao Bin, in particular, was good at unconventional ideas. As a physicist who had crossed three centuries, he knew something else: Back during the Common Era, a research group had successfully reduced the speed of light through a medium in a lab to seventeen meters per second, slower than someone riding a bike. Of course, this was not the same as lowering the speed of light through vacuum, but at least it made what he imagined next seem not so crazy.
What if the speed of light were reduced even further, to thirty kilometers per second? Would that involve black holes? It still seemed essentially the same process as before... wait!
“Sixteen point seven!” Cao Bin shouted. The fire in his eyes quickly set the other eyes around him ablaze.
The third cosmic velocity of the Solar System was 16.7 kilometers per second. A spacecraft from the Earth could not leave the Solar System without exceeding this limit.
It was the same with light.
If the speed of light through vacuum in the Solar System were reduced to below 16.7 kilometers per second, light would no longer be able to escape the gravity of the Sun, and the Solar System would become a black hole. This was an inescapable consequence of the derivation of the Schwarzschild radius of an object, even if the object was the Solar System. More precisely, the necessary speed limit would be even lower if a larger Schwarzschild radius were desired.
Since nothing could exceed the speed of light, if light couldn’t leave the Solar System’s event horizon, nothing else could either. The Solar System would be hermetically sealed off from the rest of the universe.
And therefore completely safe—as far as the rest of the universe was concerned.
How would a distant observer see the Solar System black hole created by lowering the speed of light? There were two possibilities: for technologically primitive observers, the Solar System would simply disappear; and, for technologically advanced observers, they should be able to detect the black hole, but instantly understand that the system was safe.
Take a distant star, a barely visible dot. Anyone casually glancing at it would say: Oh, that star is safe; that star will not threaten us.
This was the cosmic safety notice. The impossible was possible, after all.
The interpreters thought of the Glutton’s Sea, thought of the Storyless Kingdom sealed off from the rest of the universe by the sea. This additional bearing coordinate really wasn’t necessary—they already understood.
Later, people would call a black hole formed by lowering the speed of light a “black domain.” Compared to black holes where the speed of light was unaltered, a reduced-lightspeed black hole had a much larger Schwarzschild radius. The interior was not a space-time singularity, but a fairly open region.
The helicopter continued above the clouds. It was now after 11 P.M., and the sun slowly set in the west, leaving only a slice visible. In the golden light of the midnight sun, everyone tried to imagine life in a world where light moved just below 16.7 kilometers per second, tried to imagine the creeping light of such a sunset.
By now, most of the puzzle pieces in Yun Tianming’s stories had fallen into place. But one piece remained: the paintings of Needle-Eye. The interpreters couldn’t figure out the dual-layer metaphor or find any bearing coordinates. Some thought that the paintings might be another bearing coordinate for the Moskstraumen, symbolizing the event horizon of the black domain. They reasoned that from an outside observer’s perspective, anything entering the black domain would be forever fixed at the event horizon, which resembled being painted into a picture. But most interpreters disagreed. The meaning of the Moskstraumen was very clear, and Tianming had used the Glutton’s Sea to act as a bearing coordinate. There was no need for another.
Ultimately, this last piece of the puzzle could not be deciphered
. Like the missing arms of Venus de Milo, the paintings of Needle-Eye remained mysterious. But as this detail formed the foundation for all three stories and described an elegant ruthlessness, an exquisite cruelty, and a beautiful death, it must have hinted at a great secret of life and death.
Excerpt from A Past Outside of Time Three Paths of Survival for Earth Civilization
I. The Bunker Project: This was the plan with the most hope for success, because it was based entirely on known technologies and involved no theoretical unknowns. In some sense, the Bunker Project could be viewed as a natural continuation of the development of the human race. Even without the threat of a dark forest strike, it was time for humanity to begin colonizing the rest of the Solar System. The Bunker Project just made the effort more focused and the goals clearer.
This was also a plan devised entirely by the Earth itself; it had not been described in the message from Yun Tianming.
II. The Black Domain Plan: This involved transforming the Solar System into a reduced-lightspeed black hole to broadcast a cosmic safety notice. Out of all the choices, this was the most technically challenging. Within a region of space fifty AU (or 7.5 billion kilometers) in radius, a physical constant had to be altered. This was dubbed God’s Engineering Project. The theoretical unknowns were immense.
But if the Black Domain Plan were to succeed, it would provide the most protection for Earth civilization. Setting aside its effect as a cosmic safety notice, the black domain itself would act as a highly effective protective barrier. Any external missile, such as a photoid, would be traveling at a very high velocity to produce the necessary destructive power, and would thus enter the black domain with a speed far in excess of the modified speed of light inside. Under the theory of relativity, such an object would have to proceed at the (new, low) speed of light as soon as it crossed the barrier, and its excess kinetic energy would be converted to mass. The first part of the object entering the black domain would suddenly slow down and acquire a much larger mass, while the rest of the object, still moving at the unaltered speed of light, would run into the first part, thereby destroying the entire missile with the impact. Calculations showed that even objects made of strong-interaction materials such as droplets would be completely shattered at the boundary of the black domain. Thus, a black domain was also dubbed “the cosmic safe.”
There was yet another advantage to the Black Domain Plan: Out of all three choices, it was the only plan that allowed humanity to continue to live on the familiar surface of the Earth and avoid an exile in space.
But Earth civilization would pay a heavy price. The Solar System would be completely divided from the rest of the universe, equivalent to humanity shrinking their universe from 16 billion light-years across to one hundred AU. Moreover, it was impossible to know what life in such a world would be like. It was certain that electronic and quantum computers would have to operate at extremely low speeds, so humanity might regress to a low-technology society. This would be an even more absolute seal than the technology seal imposed by the sophons. Besides being a cosmic safety notice, the Black Domain Plan was also a form of technological self-mutilation. Humans would never be able to escape from this reduced-lightspeed trap.
III. Lightspeed Spaceflight Plan: Although the theoretical foundation for curvature propulsion was unknown, it was clearly easier than the Black Domain Plan.
Lightspeed spaceflight could not, however, provide any security for Earth civilization. It was only good for escape into the stars. Of all three plans, this involved the most unknowns. Even if it succeeded, members of the human race who escaped into the vast emptiness of space faced unpredictable dangers. Also, the dangers of escapism meant that the plan faced numerous political barriers and traps.
Yet a portion of humanity was certain to be obsessed with lightspeed spaceflight for reasons other than survival.
For people of the Broadcast Era, the only smart choice was to carry out all three plans simultaneously.
Broadcast Era, Year 8 Fate’s Choice
Cheng Xin came to the headquarters of the Halo Group.
This was her first time here. She had never participated in its operation because, subconsciously, she never thought of the enormous wealth as truly hers, or Yun Tianming’s. They possessed that star, but the wealth generated by the star belonged to society.
But now, perhaps, the Halo Group could help her realize her dream.
The corporate headquarters occupied an entire giant tree. Interestingly, all the buildings on the tree were transparent. Moreover, as the refractive index in the construction material was close to that of the air, all internal structures were visible. One could see employees moving inside as well as countless information windows. The hanging buildings resembled transparent ant farms with colorful ants milling about inside.
Inside the large conference room at the tip of the tree, Cheng Xin got to meet most of the high-level executives of the Halo Group. They were all young, smart, and vivacious. Most of them had never met Cheng Xin before, and they did not disguise their awe and adoration.
After the meeting, when only Cheng Xin and AA remained in the large, empty room, they began to talk about the future of the company. The message from Yun Tianming and the deciphering progress remained secrets from the public. To protect Tianming, Fleet International and the UN planned to release the results gradually to the public and to make them appear as the fruits of research on Earth. Some deliberate false research results would also be mixed in to further conceal the real origin of the information.
Cheng Xin had gotten used to the transparent floor and no longer felt so acrophobic. A few large information windows drifted in the conference room, displaying live video feeds from a few of the Halo Group’s construction projects in Earth orbit, one of which was the giant cross in geosynchronous orbit. After Tianming’s reappearance, the public’s hopes for a miracle gradually faded, and with the initiation of the Bunker Project, the religious fervor dimmed. The church stopped investing in the giant cross, and it was abandoned. Now it was in the process of being dismantled so that only a giant “1” remained—a rather meaningful sight.
“I don’t like ‘black domain,’” said AA. “It would be more appropriate to call it ‘black tomb,’ a tomb we dig for ourselves.”
Cheng Xin looked at the city below through the transparent floor. “I don’t think of it that way. During the era I was from, the Earth was completely separated from the rest of the universe. Everyone lived on the surface, and very rarely did they glance up at the stars. People had lived that way for five thousand years, and you can’t just say that wasn’t a good life. Even now, the Solar System is basically separated from the rest of the universe. The only people who are in deep space are the thousand or so people on those two spaceships.”
“But I feel that if we separate ourselves from the stars, dreams will die.”
“Not at all. In ancient times there was happiness and joy as well, and they had no fewer dreams than we. Also, even inside a black domain, we would still see the stars, only... who knows what that would look like.... Personally, I don’t like ‘black domain’ either.”
“I know you don’t.”
“I like lightspeed ships.”
“We all like lightspeed ships. The Halo Group should build lightspeed ships!”
“I thought you weren’t going to agree,” Cheng Xin said. “This requires heavy investment in basic research.”
“You think I’m just a capitalist? Well, you’re not wrong. I am, and so are the members of the board of directors. We want to maximize profits. But that doesn’t conflict with lightspeed spaceships. Politically, the government will devote the most resources into the Bunker Project and the black domain, but lightspeed ships will be left to entrepreneurs.... We should put our efforts into the Bunker Project, and then use some of the profits to research lightspeed ships.”
“Here’s my thinking, AA: Curvature propulsion and the black domain probably share some fundamental theories.
We can wait for the government and the World Academy of Sciences to complete that part of the research, then develop it toward curvature propulsion.”
“All right. We should start a Halo Group Academy of Sciences, too, and recruit scientists. Many of them have dreamed about lightspeed spaceflight, but they can’t find such opportunities in national or international projects—”
AA was interrupted by a sudden surge of new information windows. Windows of all sizes appeared in every direction like a colorful avalanche, quickly burying the few original information windows showing feeds from the Halo Group’s projects. A “window avalanche” like this usually indicated the sudden occurrence of some important event, but the flood of information often caused people to be overwhelmed, unable to find out what actually happened. Such was the case with AA and Cheng Xin. They saw that most of the windows were filled with complex text and animated figures, and only those windows that showed pure images could be taken in at a glance. In one of the windows, Cheng Xin saw a few faces looking upwards, then the lens zoomed in until a frightened pair of eyes filled the frame, accompanied by a cacophony of screams....
A new window came to the forefront showing AA’s secretary. She stared at AA and Cheng Xin, her face full of terror and shock.
“A warning! An attack!” she shouted.
“Any specifics?” AA asked.
“They activated the first observation unit in the Solar System advance warning system and found a photoid right away!”
“In what direction? How far?”
“I don’t know. I don’t know anything. All I know—”
