"In this forest, hell is other people."
— Luo Ji
The Dark Forest (黑暗森林) is a Science Fiction novel and the second in the Remembrance of Earth's Past trilogy by Liu Cixin. It was first published in 2008 and translated into English by Joel Martinsen in 2015. It is preceded by The Three-Body Problem and followed by Death's End.
In response to the impending Alien Invasion, Earth forms the Planetary Defense Council (PDC) and fasttracks technological development. However, the Trisolarans have already sent subatomic artificial intelligences called sophons that interfere with humanity's progress. In response, the PDC appoints four Wallfacers, whose task is to develop their own secret strategies to defeat the enemy. Though the other three are brilliant elites, the fourth is unremarkable professor Luo Ji. To everyone's surprise, however, Luo Ji might just discover the thing that can save humanity.
An animated TV adaptation (under the name The Three-Body Problem) was developed by Chinese entertainment company Yoo Zoo Entertainment.
Tropes:
- Artistic License – Physics: The Droplet's properties, namely it registering at Absolute Zero and being Made of Indestructium, are said to be due to a force field that counteracts the electromagnetic repulsion between particles. This allows the Strong Force to "spill out" and effectively nail the particles into place without altering the distances between them. While the Strong Force holds atomic nuclei together at ranges of 0.8 femtometers, it loses strength rapidly and becomes insignificant past only 2.5 femtometers, which has nothing to do with electromagnetism.
- Beneath Notice: In Shi's lecture to Luo Ji near the start of the book, he identifies this as the foundation of real shrewdness. This becomes key to Luo Ji's ultimate plan at the end of the book, when he convinces everyone around him, including the Trisolarans, that he has no way to stop the invasion, and is only working on an ultimately meaningless project in order to escape reality.
- Bittersweet Ending: Luo Ji does succeed in the end. The problem is that the Trisolarans still knows where humanity is and there's more advanced civilizations out there looking for prey. It's now a race for humanity to become strong enough to defend themselves from the next threat while hiding from all other civilizations in the meantime. Meanwhile, humanity has to keep a constant dead man's switch on it to sell out the Trisolarans' location in the event that they attempt to come back and that the Trisolarans won't be able to relocate or bypass the system. Slightly downplayed as the Trisolarans seem genuinely impressed and more or less promise to stop messing with Earth. Hopefully...
- Cannot Tell a Lie: Played with: the Trisolarans can lie over their communications, but the fact that their thoughts are broadcast to everyone around them in person means that their society and mindset has no experience of doing so. It turns out that the huge amount of information they gave about their society, development and scientific capabilities in the previous book was because it simply didn't occur to them that it would be prudent to conceal things from the civilization you're trying to destroy.
- The Chessmaster: Zhang Beihai who, along with his father, predicts the future development of human society under sophon lockdown and successfully executes a centuries long plot to ensure that at least some humans escape.
- Crapsack Universe: The book is named after the titular "dark forest theory". The theory is that all advanced civilizations hide from each other out of fear of being destroyed. In the end, Luo Ji figures out how to send an interstellar message that will alert other species of the Trisolarans' presence. This locks both sides in a stalemate because if one wins, the other will alert more advanced aliens to destroy the winner. However, since humanity was the weaker civilization, it's treated as a victory either way.
- Curb-Stomp Battle: In order to make a statement, Earth deploys thousands of powerful warships to engage the first small Trisolaran probe which enters our Solar System. Unfortunately for Earth, the probe easily destroys the entire fleet in a matter of hours while taking no damage; the only Earth ships that survive were nowhere near there.
- Despair Event Horizon: After his Wallbreaker cracks his strategy, the pressure of being unable to save the world (along with the reality that no matter what he says and does, everyone will assume that it's part of his genius strategy) catches up to Tyler. He ends up shooting himself.
- The Dreaded: Luo Ji is feared by Trisolaris, for reasons absolutely nobody can fathom. It's because he's close to figuring out that the universe is a dark forest and that he can beat Trisolaris by threatening to Summon Bigger Fish.
- Driven to Suicide: Frederick Tyler, the first Wallfacer, crosses the Despair Event Horizon after his strategy is exposed and he eventually shoots himself.
- Everything Trying to Kill You: Said word-for-word; this is the effect of the computer virus targeted at Luo Ji while in hibernation; any device that gets infected will attempt to kill him somehow. Combined with Everything Is Online, it gets to a point where even sofas are a danger.
- Failed Future Forecast: The book was originally published in 2008.
- It has a meeting 20 Minutes into the Future between a former American secretary of defense and an aged Islamic fundamentalist hiding out in Afghanistan who is clearly intended to be — but not named as — Osama bin Laden. The English translation of the book didn't appear until 2015, meaning that the mess-up was baked into it from the start.
- It has Hugo Chavez's successor as being a highly competent and popular leader who turned Venezuela into the most powerful state in South America.
- Fake Defector: Tyler planned to have his Space Fighters seemingly defect to the Trisolarans, only to blow themselves up in a suicide attack and take them out. His Wallbreaker manages to figure out the strategy before it gets very far, though, and later events show that it wouldn't have worked anyway.
- Four Is Death: Inverted. Four "Wallfacers" are tasked with formulating the strategy to defeat Trisolaris. The fourth, Luo Ji, is the one who succeeds.
- Graceful Loser: The Trisolarans take Luo Ji's checkmating them with surprisingly good grace. Furthermore, (assuming their capacity to manipulate or conceal information hasn't improved over 200 years,) their openness in communication suggests the grace is genuine, rather than an attempt to manipulate him.
- Humans Advance Swiftly: At the climax of the book Luo Ji is able to turn this into a positive reason for the Trisolarans to share their technology with humans and stop blocking their progress; with the Trisolaran fleet being forced to divert into deep space with limited resources and no ability for the Trisolarans to help them, the fleet's only hope of rescue is for the humans to come up with something.
- It's All About Me: Luo Ji for the first half of the book. His cynicism runs so deep that for a good while he genuinely doesn't care what happens to humanity, instead using his Wallfacer privileges to enjoy a hedonistic lifestyle for himself. Even when trying to act heroically, he still has elements of this; he assumes that the droplet is headed to Earth to kill him to prevent any dark forest plan from working, and he gets far away from other people to minimise collateral damage, but in fact it's taking the far more far-sighted approach of blocking Earth's ability to use the sun as an amplifier again.
- Ramming Always Works: Earth's entire fleet is wiped out by a "droplet," a two-meter long Trisolaran probe. Simply enough, they figured out they'd figured out how to use the strong atomic force to make their technology indestructable and made the droplets essentially a reusable spear which destroys each ship in Earth's collected fleet by ramming right through them one at a time.
- Sacrificial Planet: Luo Ji unleashes a dark forest strike on a (hopefully uninhabited) system fifty light-years from Earth to test the Dark Forest theory.
- Shout-Out:
- Rey Diaz's Wallbreaker bears a strong resemblance to Christopher Reeve, and he mentions that people call him Superman a lot.
- The alien perfection of the monoliths from the novel version of 2001: A Space Odyssey is explicitly referenced when the Droplets are introduced close-up.
- One of the North American warships that pursues the Natural Selection is named Enterprise.
- Sinister Surveillance: The sophons can monitor any location on Earth and transmit their findings back to Trisolaris in real-time thanks to quantum entanglement. This has profound implications for Earth, who are forced to plan their counterattacks with the knowledge that Trisolaris knows everything they're doing. The Wallfacers are intended to work around this by formulating bizarre strategies known only to them.
- Standard Sci-Fi Fleet: Earth builds a very impressive fleet consisting of two thousand ships armed with gamma-ray lasers, hydrogen bombs, railguns, and Space Fighters, and capable of reaching ten percent of light-speed. Unfortunately, the Trisolarans, being a Technologically Advanced Foe, have technology that is literally Made of Indestructium, and Earth's whole fleet is destroyed by a single probe that rams each ship one by one. In other words, this trope only makes sense when Space Age Stasis is in effect for both sides.
- Stop, or I Shoot Myself!: Luo Ji manages to scare Trisolaris into calling off their invasion by threatening to kill himself, which would trigger a dead man's switch and send out an improvised dark forest broadcast targeting Trisolaris.
- Unspoken Plan Guarantee: Justified. The sophons can eavesdrop on any spoken or written communication anywhere in the world. The four people tasked with resisting the Trisolarans have to put their plans into effect without explaining the meaning of their orders or giving instructions which make their plan obvious, or the Trisolarans will simply counter them. Two of the four fail in relatively short order, the third one has his own goal other than resisting the Trisolarans, and the Trisolarans figure it out anyway. The fourth plan eventually succeeds, playing the trope straight as the reader doesn't learn the truth until Luo Ji explains it to Trisolaris.
- Weirdness Coupon: Luo Ji is among the four people tasked with resisting the Trisolaran invasion, and he uses this power to make a series of bizarre demands. The Earth government can't ask him to explain what he is actually trying to accomplish and goes along with it for some time. Eventually they come to believe he actually doesn't have a plan and increasingly restrict what he is allowed to do. Earth is right at first, but Luo Ji's increasing irrelevance means the Trisolarans miss their chance to stop him when he does finally come up with a plan.
- You Are Worth Hell: When Zhang Beihai is about to nuke the rest of Starship Earth to protect the Natural Selection.Zhang Beihai: Children, let me do this.
Dongfang Yanxu: You mean, 'If I don't go to hell, who will'? Is that it?
Zhang Beihai: From the moment I became a soldier, I was prepared to go there if necessary.
Dongfang Yanxu: Let's go together. Let me in. I'll go to hell with you!
