The Dark Forest

The Dark Forest is a 2008 science fiction novel by the Chinese writer Liu Cixin. It is the sequel to the Hugo Award-winning novel The Three-Body Problem in the trilogy titled Remembrance of Earth's Past, but Chinese readers generally refer to the series by the title of the first novel. The English version, translated by Joel Martinsen, was published in 2015. The novel is about the dark forest hypothesis (which was named after the novel), a possible solution to the Fermi paradox, though similar theories have been described as early as 1983.

Plot
In a flashback, Chinese sociology professor Luo Ji has a chance meeting with Ye Wenjie, the astrophysicist from The Three Body Problem who first contacted the Trisolarans and encouraged their invasion. She suggests he study "cosmic sociology" based on a set of axioms that she shares with him.

In the present day, the UN is trying to find a way to survive the invasion of the Trisolaran fleet, which will arrive in about 421 years. Their prime difficulty is the sophons: super-smart subatomic machines sent from Trisolaris that see everything on Earth and block advances in fundamental physics, while communicating with Trisolaris in real time through quantum entanglement. The UN must also deal with an organization of Trisolaran loyalists on Earth who support the invasion and carry out acts of sabotage based on instructions from the sophons.

The sophons can overhear any conversation and intercept any written or digital communication but cannot read human thoughts, so the UN devises a countermeasure by initiating the "Wallfacer" Program. Four individuals are granted vast resources and tasked with generating and fulfilling strategies that must never leave their own heads. Three of the Wallfacers are famous for their military, political, psychological and/or scientific expertise; the fourth is the obscure professor Luo Ji, who does not initially understand why he was chosen.

Trisolarans have evolved so that their thoughts transmit openly, and as a result the entire species is unfamiliar with concepts like lies, misdirection and subterfuge. To overcome this weakness, the Trisolarans select three loyalist humans dubbed "Wallbreakers," who are given full access to the information collected by the sophons and tasked with deducing the plans of the Wallfacers. Within a few years, two of the Wallbreakers successfully ruin the strategies of their respective Wallfacers. The third Wallfacer enters hibernation to continue his efforts in a future era, but ultimately his strategy also fails.

Luo doesn't view himself as capable and refuses the position of Wallfacer, but finds himself unable to do so. All his actions, including announcing his resignation, are interpreted as a ruse in service of his ultimate strategy. Selfishly, he takes advantage of his power in order to secure an isolated paradise and an idealised partner, with whom he starts a family. After several years of peace and happiness, Luo's wife takes his daughter, and they go into hibernation until the Trisolaran fleet arrives. UN Secretary General Say tells Luo that this hibernation had always been a UN contigency plan to motivate Luo to perform his Wallfacer duties.

Luo learns that he was chosen as a Wallfacer because he is the only human that the Trisolarans have ever directly targeted for assassination (and failed), suggesting that the aliens fear him for some unknown reason. Luo concludes that he must have been targeted because of his conversation with Ye Wenjie, which the sophons presumably overheard. After reflecting on the conversation, he comes to a realization. Luo arranges for the location of a star 49.5 light-years away to be broadcast throughout the galaxy, without explaining his purpose. He then enters hibernation, asking to be woken if an effect on the star is noticed. Soon after the broadcast is sent, the Trisolaran fleet launches a series of probes with faster acceleration that will reach the Solar System much sooner than the rest of the invasion force.

Luo is revived 200 years later in a wealthier, more advanced society and is told that the Wallfacer program has been terminated. Though its technology has been limited by sophon sabotage, Earth has still managed to build a fleet of ships that are larger and faster than the Trisolaran vessels, and world leaders are confident that they can defeat the invasion force. This triumphalism is shattered by the arrival of the Trisolaran's first probe, which proves to be far more technologically sophisticated and annihilates humanity's combined fleet in minutes. Earth collapses into mass hysteria and the few ships that weren't destroyed flee the Solar System to form new civilizations.

The UN discovers that the star whose location Luo had broadcast has been eliminated by an unknown hyper-advanced civilization, and his Wallfacer status is quickly restored. However, Luo says his strategy has already been foiled. After destroying the fleet, the Trisolaran probe stations itself near Earth and begins transmitting a steady jamming signal, preventing any further interstellar communication.

Privately, Luo explains the dark forest hypothesis that underpinned his strategy, which he came to understand after reflecting on his conversation with Ye Wenjie: There is life everywhere in the galaxy, but since growth is constant and resources are finite, each galactic civilization is strongly incentivized to destroy any others upon discovery. The only defense against this is to remain unnoticed, thus explaining the Fermi paradox.

Luo had intended to force the Trisolarans into a truce by threatening to broadcast their home planet's location to the galaxy, creating a mutual assured destruction scenario. With the Trisolaran probe thwarting such communication, a forlorn Luo spends his time on a UN project involving distributing nuclear bombs throughout the outer solar system in order to create cosmic dust that will help detect, but not prevent, the arrival of the main Trisolaran fleet.

However, this is a ruse. His true goal is to circumvent the probe's transmission jamming. Luo reveals to the sophons that the bombs have been programmed and arranged in such a way that the cosmic dust pattern created by their detonation will reveal to all observers Trisolaris' location in the form of Morse code. In exchange for leaving the bombs undetonated, Trisolaris accepts the truce, diverts its fleet, and agrees to aid human scientific progress.

Years later, Luo, reunited with his wife and daughter, converses briefly with the pacifist Trisolaran who had made first contact with Ye Wenjie. They agree that it may be possible for galactic civilizations to brighten the "dark forest" and engage in peaceful relations.

Characters

 * Ye Wenjie (叶文洁)
 * Astrophysicist who initiated initial contact between Earth and Trisolaris. Spiritual leader of the Earth Trisolaris Organization.


 * Mike Evans (麦克·伊文斯)
 * ETO financial backer and key leader, killed in The Three-Body Problem.


 * Wu Yue (吴岳)
 * Captain in the PLA Navy.


 * Zhang Beihai (章北海)
 * Political commissar in the PLA Navy. Assassinates proponents of media-drive research in order to guarantee the development of drives more capable of interstellar travel. He is hibernated because his seeming unimpeachable triumphalism is required in the future. When he's woken, he's appointed acting commander of one of humanity's most advanced ships so that he can screen existing fleet officers and ensure they are not defeatists. In a twist, it turns out he himself is a defeatist who knows a military victory is impossible and wants mankind to survive by fleeing the solar system. Thanks to him, many ships do escape. However, it is later revealed that he knows the crew of each ship will independently conclude that it's highly unlikely all of them can make it to a star system before running out of fuel. To maximize the chance of humans surviving their potentially endless voyage, a single ship should kill the crews of the other ships and strip them for resources. Hesitating before he starts this process, another ship attacks the one he is operating. The battle, which leaves only a single ship alive in each of the two fleets, is used by Luo Ji to explain how the "dark forest" operates in reality. An important character in the novel, Zhang's story is told in detail and serves as a parallel to the main plot. In some ways, he is a rogue Wallfacer.


 * Chang Weisi (常伟思)
 * General in the PLA and Zhang Beihai's co-worker. First commander of humanity's space force and a defeatist who envies Zhang's Triumphalism.


 * George Fitzroy
 * US General; coordinator at the Planetary Defense Council; military liaison to Hubble II project.


 * Albert Ringier
 * Hubble II astronomer.


 * Yang Jinwen (杨晋文)
 * Retired middle school teacher in Beijing.


 * Miao Fuquan (苗福全)
 * Shanxi coal boss; neighbor to Zhang and Yang.


 * Zhang Yuanchao (张援朝)
 * Recently retired chemical plant worker in Beijing.


 * Shi Qiang (史强)
 * Also nicknamed Da Shi (大史), a returning character from The Three-Body Problem. Wallfacer Head of Security who becomes a close ally to Luo Ji. Afflicted by leukemia and hibernates to the doomsday battle with Luo Ji where he saves his life multiple times from an assassin computer virus.


 * Shi Xiaoming (史晓明)
 * Shi Qiang's son.


 * Kent (坎特)
 * Liaison to the PDC. Wallfacer Security Staff for Luo Ji. Despite his best efforts at physically securing Luo Ji in an underground bunker, he passes on the Bed Flu bioweapon to Luo Ji. Dies of old age in Luo Ji's estate.


 * Say
 * Secretary General of the United Nations, oversees the creation of the Wallfacer project and selects Luo Ji, gambling that his importance to Trisolaris might generate success for humanity. Attempts to create a Human Memorial Project to catalogue human culture, which is destroyed for being defeatist by the Planetary Defense Council.


 * Yamasugi Keiko (山杉恵子)
 * Japanese neuroscientist and the wife of Bill Hines; later revealed to be her husband's Wallbreaker


 * Garanin
 * PDC rotating chair.


 * Ding Yi (丁仪)
 * Theoretical physicist, returning from The Three-Body Problem.


 * Zhuang Yan (庄颜)
 * Graduate of the Central Academy of Fine Arts, she later becomes Luo Ji's wife.


 * Ben Jonathan
 * Fleet Joint Conference special commissioner.


 * Dongfang Yanxu (东方延绪)
 * Captain of space warship Natural Selection. Relieved of command due to a scan of fleet command for evidence of mental seal use, unable to prevent Zhang Beihai from taking complete control of the flagship and fleeing Earth. Attempts to initiate a first strike against the other vessels due to the conclusion that there are not enough supplies among the ships to make the interstellar journey. Killed by a faster first strike made by Ultimate Law.


 * Major Xizi
 * Science officer of Quantum.

Wallfacers

 * Frederick Tyler (弗雷德里克·泰勒)
 * Former US Secretary of Defense. On the surface, his plan was to make a massive swarm of kamikaze fighter craft to combat the Trisolaran fleet. In reality, the plan was to remotely control that fighter craft swarm to destroy Earth's other ships and, to make the ruse of being a turncoat fleet more effective, transport a massive quantity of water to the incoming Trisolarans. Having managed to get within point blank range, the swarm fleet would then detonate hydrogen bombs. Informed by his Wallbreaker that his plan to betray Earth in the first instance would be revealed to the world, he experiences despair. Then, unable to resign from Wallfacer status because it can't be proven that his revealed plan was his true plan, he commits suicide.


 * Manuel Rey Diaz (曼努尔·雷迪亚兹)
 * Former President of Venezuela. On the surface, his plan was to develop very powerful hydrogen bombs that would combat the Trisolaran fleet. In reality, the plan was to create so many bombs that he would have the power to slow down Mercury's orbit and cause a chain reaction where all planets in the Solar System would be consumed by the Sun. The idea was to force the Trisolaran fleet to surrender by threatening mutual destruction – they would not have the fuel to get to another habitable planet system. His Wallbreaker explained he would never have gotten the number of bombs required, and the nature of his plan was too scandalous for the world. He then blackmails the UN with fake nuclear bombs so he can return to Venezuela where he is promptly stoned to death by his own people for threatening the destruction of the Solar System.


 * Bill Hines (比尔·希恩斯)
 * English neuroscientist and former president of the EU. His outward facing plan was to boost human intelligence to a high enough level to overcome the scientific block on particle physics by the sophons. This wasn't possible due to limitations on computing. His true plan was to instill an incorruptible state of defeatism in humanity's military, forcing humanity to develop plans to escape the solar system rather than stay and fight.


 * Luo Ji (罗辑)
 * Astronomer and sociologist. Given the initial axioms of cosmic sociology by Ye Wenjie prior to the events of the series. He is his own Wallbreaker when he concludes that the axioms result in the Dark Forest state of the universe, and thus the only strategic option against the Trisolarans is mutually assured destruction through broadcast of their interstellar coordinates.

Videos

 * Waterdrop, referring to the Trisolaran droplet probe, is a 14-minute tribute film produced by Wang Ren, who was then a graduate student studying Architecture in Columbia University. The author Liu Cixin commented, "This is the kind of film I have in mind. If the feeling of such an atmosphere can be delivered in a Three Body Problem film, I would rest in peace after I die."
 * MC Three Body - The Dark Forest is an animation series produced by a group of Chinese fans. Initially a machinima series produced using the video game Minecraft, they later switched to using professional animation software. The series was released online at the beginning of 2018.
 * A Chinese animated series based on The Dark Forest aired from December 10, 2022 to March 25, 2023.
 * A three-part documentary series entitled Rendezvous with the Future which explores the science behind Liu Cixin's science fiction was produced by BBC Studios and released by Bilibili in China in November 2022. The second episode covers many ideas featured in The Dark Forest such as the space elevator and artificial hibernation. An international version of the series has not yet been released.