From the previous book, The Three Body Problem, Chinese scientist Ye Wenjie sent a test message pointed at the sun, which amplified the message and broadcast it to the galaxy. Four years later she received a reply warning in no uncertain terms not to reply so that Earth’s location would remain unknown. Disillusioned in humanity by the trauma of the Cultural Revolution, she immediately replied that she would help them conquer Earth. That civilization, Trisolaris, was immeasurably more advanced that humanity, and had sent supercomputers named sophons folded in eleven dimensions down to lock the state of fundamental physics to its current state. The sophons could only affect things on an atomic scale which was sufficient to actively muddle the results of fundamental physics research. They could observe what humanity was doing, so humanity could have no secrets. The situation was hopeless and Trisolaris was guaranteed to win the Doomsday Battle in four centuries when the fleet arrived.
The book opens with an ant crawling on a tombstone, similar to how The Grapes of Wrath opens with an inter-chapter of a turtle crossing a road. The grave is that of Ye Wenjie’s daughter, where, shortly before her death, Ye Wenjie gave a suggestion to a Dr. Luo Ji, a astrophysicst-turned-sociology professor, that he study “cosmic sociology” and outlined the basic principles for him.
Since the sophons can observe everything written or communicated, the only hope for winning the defense of the planet was a plan hidden in someone’s mind, which they never disclosed. It was for this reason that the UN created the Wallfacer Project. Named after certain Buddhist monks who stare at a wall in search of enlightenment, four members of humanity were chosen to create a plan for the defense of humanity. Within a few limits, they were given carte blanche to do whatever they wished. By this time, Dr. Luo, was a professor doing the minimum to get by and have short-term relationships with women, in chase of the fantasy woman he had created at the request of his first girlfriend and then fallen in love with. He had just escaped being killed by an errant car when inspector Shi Qiang swooped him up and took him to the UN meeting, where he discovered that he had been appointed—to the surprise of almost everyone—as one of the Wallfacers. He told the UN Secretary General after the meeting that he declined, and then experienced his first “Wallfacer smile”: the smile that said “how do I know that this is not part of your plan?” He survived an immediate assassination attempt, although he did meet his assailant in the hospital, and convinced him that he was not a competent Wallfacer. Dr. Luo used his Wallfacer powers to request a retreat in a beautiful part of nature, where he intended to continue ignoring his Wallfacer responsibilities. After a while he had Shi Qiang find him a woman who matched the description of his fantasy woman. Shi found him one of his relatives (and then went into hibernation because he had leukemia which was not curable at that time). They fell in love and had a child, Xia Xia.
The Trisolarians’ brains emitted much stronger electromagentic radiation than our brains, so their communications were direct thoughts, and therefore they did not understand what secrets or deception meant. So the ETO, humans who hated humanity and were helping the Trisolarians destroy humanity, helped the Trisolarians unravel the plans of the Wallfacers. The people who were assigned this task were called Wallbreakers. It was decided that Luo Ji did not need a Wallbreaker; he was his own Wallbreaker.
After a few years had passed, the Wallbreaker for Wallfacer Frederick Tyler (former US Secretary of Defense) appeared to him and explained to him the secrets of his plan (shortly before his disseminations to the media went public). Tyler’s plan was to create a swarm of kamikaze fighters to attack the Trisolarian fleet with hydrogen bombs. They were kamikaze because they needed to detonate quite close to have an chance of working. As he expected, he could not find people to man the fighters, so he planned to man them with pilots from the ETO, who would then turn on the human fleet and destroy it. Then they would pick up chunks of ice as a gift to the Trisolarians, who would be in their dehydrated state and need water to rehydrate, and rendezvous with the Trisolarian fleet. At that point, Tyler would take remote control of the fighters and execute the original plan. The Wallbreaker informed Tyler that “the Lord” (that is, the Trisolarians) were unconcerned by the plan. Tyler told Dr. Luo, then shot himself in despair.
This, the arrival of winter (the season for thinking), and the fact that the UN sent his wife and child into hibernation until the Doomsday Battle in four centuries, galvanized him to actually begin work on the problem. He spent nights looking at the stars and thinking. He had almost seen the answer, but was interrupted, so he went out on the ice of the lake where he was alone like a civilization by itself in the universe. He fell through the ice, and as he did so he understood what Ye Wenjie had been trying to communicate. He managed to pull himself out by spreading out his body to minimize the surface pressure, and then announced himself: “Wallfacer Luo Ji, I am your Wallbreaker”. Then, having developed a terror of the sight of stars, he requested to be moved to an underground bunker in China. Then he drew up a message communicating the exact position of a star 50 light-years away (including the ability to calculate its position in the future, since stars move) and requested that his “spell” be sent into the galaxy (using the amplification of the sun). The Wallfacer Council mocked his request, but did it, and also sent him into hibernation, as requested, to be woken when humanity observed the results of the spell.
It was several decades later that the Wallbreaker for Manuel Rey Diaz (former president of Venezuela) showed up. Diaz had requisitioned the creation of an extremely powerful fusion bomb. Once developed, he requisition a million of these, to be used against the Trisolarian fleet and stockpiled on Mercury. The Wallfacer Council had thought that this was excessive, and some members drafted a proposal to terminate his status. His Wallbreaker informed him that his plan was actually that he thought destroying the fleet was impossible, so he was going to use the bombs to slow down Mercury, causing it to fall into the Sun. This would result in the Sun’s atmosphere expanding to the orbit of Mars, causing drag on the inner planets, slowing them down so that they, too, would fall into the Sun, expanding the atmosphere to Jupiter, whose fall would expand it to Neptune. His plan was to threaten the Trisolarians with mutual annihilation if they did not call off their battle. This Wallbreaker also said that “the Lord” was unconcerned about this. Not only was the plan not concerning, but humanity did not actually have the resources for a million bombs, and even if they did, it was insufficient to cause Mercury to fall into the Sun. Nevertheless, the Wallbreaker congratulated Diaz on his strategy and how difficult it was to work out. When the news hit the media, Diaz was called to the Council, which revoked his status on the basis of crimes against humanity itself. He used the threat of a dead man’s switch to hold the meeting hostage and arrange for a flight back to his country, where he was immediately stoned by the people because of his heinous plan.
Humanity perfected the space elevator, which enabled inexpensive transport into space, and therefore the construction of a space station habitats and a spaceship fleet. The global military was deciding whether to research better propulsion by means of more efficiently expelling matter out the back, or to focus on plasma drives. Chinese naval officer, Zhang Beihai, known for his insistence that the military have people who believed that Earth would triumph (“Triumphalists”), thought that plasma drives were the better choice for the long-term. So he bought some iron meteorites from a collected, used a CNC machine to make them into bullets, and went up to the space conference of the traditional propulsionists. Conference attendees took their picture in space in front of the space station—quite a glamorous shot. In space even a pistol is a rifle; since there is no air resistance, bullets always travel straight. So from a distance away he shot the head researchers, and the investigation suggested that the cause of death was a meteor swarm. This steered humanity towards plasma drives.
About 200 years later, Luo Ji was woken out of hibernation. The world was a very different place: energy was limitless because of fusion and beamed out as microwaves, which any and every device used to power itself. The result was that every surface was now a display and everything was electrified—a sofa would adjust to your exact shape so that each part of your body would experience the same amount of pressure. Humanity mostly lived in underground cities, since the surface had become somewhat of a desert. (Although, Beijing, where Dr. Luo was, is already essentially a desert biome in real life due to its geography.) A sky was projected onto the dome, and people lived in pods suspended from branches coming out of the pillars supporting the dome. Humanity now had two thousand ships, which were capable of traveling faster than the Trisolarian fleet if necessary. The fleets from the three major continents were now considered three separate countries and functioned as a political counterweight to terrestrial humanity. A certainty of victory pervaded humanity, and seemed to Dr. Luo to be, if not hubris, then at least unwarranted, but humanity certainly was in a very different place than it had been two centuries earlier, even if fundamental physics had not advanced due to sophon meddling.
There had been no change in the star that Luo Ji had “cast” his spell on; he had been woken up for the last Wallfacer Council hearing, where the Wallfacer Project was disbanded and he was returned to a private citizen. He was given permission to wake his wife and child, although the chair recommended waiting until he had adjusted to the new culture, as the transition could be difficult. After the meeting was adjured, Wallfacer Bill Hines wife and research partner stood up and announced that she was his Wallbreaker. Hines had directed research into greater intelligence, in order to get around the sophon block. He then hibernated for eight years until computing power was enough to simulate the brain. Having matured for eight years more, when he awoke his wife now understood the look in his eyes that she had not before. He was convinced that humanity would lose the battle, and that the only hope was to flee to Solar System. Before hibernating the second time (this time with his wife), they had been able to model the brain, and had discovered that certain stimulation when a patient was evaluating a simple false statement would create an faith in that statement’s truth. He opened a Faith Center, where someone could gain the Faith in humanity’s victory—as long as they chose willingly and had adequate opportunity to change their mind. It was a success, so he and his wife hibernated. But just as she lost consciousness, his wife understood his plan. When she woke up almost two centuries later, she understood that he had subtly altered the code in the machine so that it created faith in humanity’s losing the battle but being able to win by escaping (generally known as “Escapism”). Escapism was generally seen in a negative light, because whoever would not get to escape was jealous of those who would. He had built four other machines, which would be sufficient redundancy to run for two centuries, and she hypothesized that he had started a faith in the military whose initiation was the acquisition of Faith.
Now that humanity had embraced Triumphalism, they needed to figure out who these Escapists were. So they woke up Zhang Beihai, known for his instance that the military needed Triumphalists, and gave him operational control of the flagship starship—the actual captain would need to relay orders through him. Once given control, he promptly entered in coordinates to a nearby star system with a giant planet for refueling of the hydrogen fuel and accelerated to 0.1c. Four other command ships promptly pursued.
When Dr. Luo had sent his spell, the Trisolarians had launched ten probes, the first of which was just arriving. Since every leader in the three fleets wanted the honor of first contact with the probe, the entire fleet went. An old Chinese scientist was one of two people on the shuttle to rendezvous with the probe. He had a bad feeling and advised the ship he was one to prepare for high-speed acceleration; this ship and one other did so. The probe was reflective on all frequencies and held together by the strong force. This made it as dense and as smooth as a neutron star (but with much less mass). As far as humanity was able to discern, the droplet-shaped probe was perfectly smooth down to the subatomic scale. Shortly afterwards, the probe caused an explosion, and while the ships still thought that the probe had exploded (they had calculated the maximum explosion based on the mass and stayed out of range), the probe quickly accelerated, and moving completely unaffected by the normal limitations in space, went row by row through the formation, ramming through their fusion reactors and causing the ships to explode. The modern humans were not accustomed to thinking on their feet, so it was only two low-level officers who were hibernators that managed to figure out what was going on and escape. The two ships that had been prepared accelerated on a trajectory out of the solar system and the droplet did not pursue them.
It turned out that humanity’s triumphalism had created a complete lack of resilience, and Earth’s population fell into despair and began wrecking themselves. On the Natural Selection, Zhang Beihai exited his spherical cabin expecting to be arrested, but instead, to his surprise, he was hailed as a hero. The pursuing ships joined him in “Starfleet Earth”, and his wisdom in setting a course to refuel, before proceeding to a nearby system to colonize a planet was lauded. But after a short time an emotional malaise settled on the fleet. The psychologists eventually went to Zhang, and discovered that he had locked the weapons on the other four ships of the fleet. There were dust clouds in the way, which would reduce their speed and require 60,000 years to get to the system, which was more than their fuel could support. But they did not have enough fuel to re-accelerate and also decelerate into the system to refuel. So the only option was to reduce the number of people, and use the other ships as spare parts. Zhang was a little too compassionate, though, and did not fire quickly enough, and a pursuing ship won the fight.
Back on Earth, someone finally observed that the system Dr. Luo cast his spell on had been destroyed, by a probe moving at nearly the speed of light flying through the star and triggering an instability that destroyed the system. The UN promptly reinstated him as Wallfacer. Also, his wife and child were denied reawakening. He again refused, because the Trisolarian probe had remained at a Lagrange point of Earth’s, and was sending such a strong signal at the sun that it overwhelmed the amplification layer, which meant that no further spells could be cast. He insisted that there was nothing he could do if he could not cast a spell. Eventually he allowed himself to be talked into managing a project detonating the super bombs scattered in orbit around the sun so that the Earth could detect the Trisolarian fleet (the other nine probes were using propulsion that did not emit light, having learned from the first probe) as it entered the system. He poured his heart into the project, even determining the precise orbits himself. When the project was cancelled, he turned to drink. Originally hailed as a hero, when it became obvious that he had no plan, public sentiment turned against him, and he was exiled from his settlement and even asked to leave the bus he was riding after a passenger recognized him.
He found Ye Wenjie’s daughters grave (another ant was crawling up it), dug a shallow grave, and pointed a pistol at his heart. Then he addressed Trisolaris, who he knew would have a sophon or two observing him. He informed them that he had arranged the dust bombs in such a manner that they would go off in a timed sequence that would cause a dimming of the sun, that would send a message with the coordinates of Trisolaris. Due to their initial communications, this would also reveal the location of the solar system. Thus, they could either both live, or both be annihilated; the logic of cosmic sociology left no other option. The two basic principles were that life is plentiful in the universe and moreover, life expands quickly. It’s primary goal is security and resources for itself. But resources (star systems) are fixed, so every civilization is a potential competitor. Furthermore, because of the explosive growth of technology, and civilization that is known to be harmless might pose a serious threat by the time a probe could reach the system. To make matters worse, the distance makes it impossible for civilizations to trust each other: even if they know the other civilization is peaceful, they do not know what the other civilization knows. So the universe is a dark forest where any light will be killed, and the only rational choice is for civilizations to stay quiet.
The Trisolarians agreed to his demands to turn off the probe’s transmission (enabling the spell to be sent if they renege), and diverting the remaining probes and the fleet from the system. He then referred them to the Earth government, to finally resume has only desire of spending his life with his wife and child. But he did suggest that, since the fleet would not have the fuel to survive (and he prohibited them from entering the Solar System), they might wish to partner with humanity in a tech transfer to enable us to help rescue the fleet. In the end, he has a sophon conversation with the Trisolarian operator who went rogue and sent the original warning message. Dr. Luo had claimed in a speech that only humanity had love, but the Trisolarian disagreed: his civilization had the seed, but it was not conducive to civilization growth and they supressed it, although the seed was hardy and occasionally took root. He suggested that the seed might have taken root elsewhere. Dr. Luo agreed that it would be worth exploring.
The Dark Forest is an interesting sequel and a engaging read. Unfortunately, it seems current to have many parallel story lines (recent Neil Stephenson being partly egregious here), and Liu succumbs to the style. The Wallfacer project is interesting, but the first three are clearly diversions from Luo Ji, who is clearly the only one that Trisolaris is concerned about. Although Zhang Beifang does have a role, it also feels like a diversion. Luo Ji is also the only interesting Wallfacer, having some interesting ideas about beauty and simple enjoyment that would be worth exploring from a philosophical level, in addition to the potential as baffling contrast with the others. So from multiple perspectives, the story would be tighter if it just focused on Luo Ji.
The dark forest idea was the most interesting idea in the book, and was new to me, even though apparently it is on old answer to the Fermi Paradox of why there are millions of planets yet we perceive ourselves to be alone. Unfortunately, it is left as a mystery until the very last pages. This makes it impossible to explore as an idea. It is sort of retrospectively explored because the ships that leave the Solar System have the same dilemma, but because of the ordering, there is no way to explore the iron grip of the logic.
Although the dark forest is not new, nor is it a Chinese idea, nevertheless that way of rationalistic thinking feels particularly mainland Chinese. In business and in foreign relations, the Chinese approach seems to be that others are a threat and need to be preemptively neutralized. (To be fair, the realpolitik view of international relations takes this same approach, and is propounded to wise effect by political science professor John Mearsheimer.) In contrast, traditionally the West, informed by the Judeao-Christian value that all people are made in the image of God, espouses a work-together approach (even as our foreign relations towards rival powers is more similar to China’s). So the preemptive disabling of the other ships is not a foregone conclusion; one could imagine the five captains discussing the problem and coming to a mutual agreement.
But perhaps Liu is subtly critiquing that rationalistic, self-focused, fearful aspect of Chinese society. In the previous book the case for the way people were treated in the Cultural Revolution is directly connected with Ye Wenjie feeling that humanity is beyond redemption, and could be seen as a subtle critique. Likewise, this book ends with the recognition that love is universal, and that there may be a way to transform the dark forest by means of the light of love.
From a compositional analysis, the structure of the book is unremarkable, being diluted with unnecessary side stories, and the main ideas being relegated to the end where their consequences cannot be explored. Traditionally science fiction is about exploring the consequences of the ideas; Liu has written more of a mystery or thriller set it the future. Also, long exposition of a fantasy girlfriend that turns in to a real fantasy wife is rather tiring. However his vision of 200 years in the future is well-done and is a reasonable extrapolation which is nicely fleshed out. And certainly the book is definitely an engaging read.