"There's a strange contradiction revealed by the naivete and kindness demonstrated by humanity when faced with the universe: On Earth, humankind can step onto another continent, and without a thought, destroy the kindred civilizations found there through warfare and disease. But when they gaze up at the stars, they turn sentimental and believe that if extraterrestrial intelligences exist, they must be civilizations bound by universal, noble, moral constraints, as if cherishing and loving different forms of life are parts of a self-evident universal code of conduct."
— Liu Cixin
Remembrance of Earth's Past (地球往事), occasionally referred to by the title of its first installment The Three-Body Problem, is a Science Fiction novel series by Chinese author Liu Cixin. It details the interactions of humanity with the Trisolarans, an invading alien civilization on the brink of destruction, and chronicles humanity's attempts to survive in a tumultuous universe. It is comprised of the following books:
- The Three-Body Problem (三体): First serialized in 2006, published as a novel in 2008, and translated into English by Ken Liu in 2014.
- The Dark Forest (黑暗森林): First published in 2008 and translated into English by Joel Martinsen in 2015.
- Death's End (死神永生): First published in 2010 and translated into English by Ken Liu in 2016.
Ball Lightning is a pseudo-prequel to the series also written by Liu Cixin.
The Redemption Of Time (观想之宙), a continuation to the series, was published in 2011 and translated in 2019. Not written by Liu Cixin, it originated as an ambitious and hugely popular fanfiction that received the Approval of God, and is officially semi-canonical.
A film adaptation of the first book is stuck in Development Hell. A live-action TV adaptation was developed by Chinese entertainment company Tencent Video. An animated TV adaptation was developed by Yoo Zoo Entertainment. A webtoon adaptation is in progress and the English translation may be found here
. A live-action TV adaptation, 3 Body Problem, was released by Netflix on March 21st, 2024, with David Benioff & D.B. Weiss (Game of Thrones) and Alexander Woo (The Terror: Infamy) as showrunners.
Series-wide tropes:
- Absolute Xenophobe: Under the Dark Forest theory, every single race in the entire universe is ultimately hostile to the existence of any other alien race, and actively works towards the complete destruction of other races. While lesser races engage in galactic wars, advanced god-like races are committing mass genocide on a universal scale by ruthlessly attacking any location suspected of harboring sentient races with incomprehensibly powerful weapons.
- Abusive Precursors: Ancient aliens have used weapons which, among other things, have lowered the speed of light universally and reduced the universe from 10 to 3 dimensions. They continue to do so.
- Aliens Are Bastards:
- The Trisolarans' history bred everything out of their culture except the desperate need to survive at all costs... though there seem to be individual exceptions. By the third book, they have mastered human deception by feeding humans false science to hamper humanity's technological boom, embracing their culture only to deceive and enslave them later, and refusing to give them the means to escape a dark forest strike.
- It's not just the Trisolarans. In the third book it's revealed that casual annihilation of any intelligent race that is discovered is entirely routine; they don't care about the damage their weapons do to the fabric of reality; and the universe is effectively a war ruin as a result of billions of years of conflict and the damage wrought by those weapons. The grand unifying universal sociology theory is built upon this rule.
- It's not all bad. The last chapters of the third book hint at the existence of a greater galactic society, with interstellar trade, alliance, and information exchange all possible. The dark forest theorem is still extremely in effect, however, and it's considered very rude to ask someone where their homeworld is.
- Alien Invasion: Already launched, and due in about 450 years. They have mastered lightspeed travel in the third book and can reach Earth in a few years, but invasion is narrowly averted by the dark forest broadcast.
- Apocalypse How: The author wrote an article discussing apocalypses in the series and their absence in Chinese literature in general.
- From the first book: The present Trisolaran civilisation is the latest in over two hundred, each of which was wiped out after a Planetary Extinction (minimum) caused by the planet's chaotic orbit. Special note goes to number 191, which is destroyed when the planet gets ripped apart by tidal forces after passing close to the suns; the smaller fragment eventually becomes a moon of the larger fragment, still holding visible ruins on its surface. Eleven other planets in the system have already fallen into the suns, and given time Trisolaris will fall in as well.
- From the second book: The "Great Ravine" that occurred off-screen during the Crisis Era is a planetary Societal Disruption, with over half the Earth's population dying out over the course of half a century due to wars, famine and general lack of resources.
- From the third book: The end of (most) life on earth is narrowly averted when the Trisolarans call off their invasion just in time for humanity not to have to eat itself, but Trisolaris is destroyed shortly afterwards. Then later played straight on a 'Total Extinction' scale when the Solar System is converted to two dimensions. The universe itself is implied to be on the way to a universal, metaphysical annihilation if galactic warfare is allowed to continue.
- Applied Phlebotinum: While most of the fictional science in the book is explored in great lengths, the "mathematical language" that allows the first contact between species is hand-waved. We also never get even a hint at how human space technology managed to contain a breathable atmosphere in hangars and launch pads permanently open to the void.
- Bizarre Alien Biology:
- Trisolarans only appear in one scene in the first book and are never given a complete description, but we know a handful of details: they can mummify themselves at will to enter a state of suspended animation, they communicate through flashes of light (and have no real barrier between thinking something and saying it), and reproduce by fusing together and then splitting into several new Trisolarans, which inherit some memories from their parents.
- In The Redemption of Time, Yun Tianming becomes the first and only human to lay eyes on a Trisolaran. Their most salient feature is that they’re no larger than rice grains, which has had profound effects on their intelligence and psychology. The irony of them calling humanity “bugs” is the first thing Yun realizes.
- Big Good: The Returners, who seek to ensure a Big Crunch that will recreate the universe in its original shape, undamaged by endless warfare. They broadcast a message in every possible language encouraging people to return mass from their pocket universes to the greater universe to avoid its mass going below some lower threshold that will prevent it from collapsing into a new singularity. Whether they succeed is left open.
- Born as an Adult: The Trisolarans, technically speaking, thanks to their Bizarre Alien Reproduction. Because they inherit some of the memories and personality traits of their parents, they don't really have a childhood.
- Boring, but Practical: Photoids, projectiles used to carry out dark forest strikes. It's very destructive and also very cheap and boring because it's just a bullet thrown at near-lightspeed, which gives it enough power to tear apart a star. note
- Cosmic Horror Story: The book has strong parallels with the cosmic horror genre by putting humans in a universe where everyone is an enemy, and every enemy is magnitudes upon magnitudes more powerful than they could ever become.
- Crapsack World:
- Trisolaris, with its extremely unpredictable environment and dog-eat-dog population.
- The second and third book reveal that the whole universe is also this. The Dark Forest theory says that every single race in the universe is or will be absolutely hostile to each other, due to the inability to establish trust, the fundamental desire for survival, and the limited resources in the universe. It is a necessity for every single race to enact genocide on every other alien race they encounter, or else they would risk genocide to themselves. Combine the Dark Forest theory, with the fact that Sufficiently Advanced Aliens are everywhere, and the only reason they haven't genocided humanity is because they don't know where the humans are, the entire universe is revealed to be an infinitely bleak one where hope for peaceful survival is impossible.
- Creator Provincialism: With the author being Chinese, it shouldn't come as a surprise that much of the action on Earth is set in China, almost all major characters are Chinese, and most of contemporary and future human civilization has a strong Chinese tint.
- Feeling Oppressed by Their Existence: The series’ portrayal of the Dark Forest hypothesis is this viewpoint taken to its most literal and horrifying extent. The discovery of any intelligent alien civilization by another means the possibility of being outclassed and destroyed by that civilization, and, thus, must be wiped out immediately lest those fears are confirmed.
- Golden Translator: Ken Liu, the English translator, is an award-winning writer in his own right, and his translation of the book is renowned.
- Hand Wave: While most of the fictional science in the books are explored and deconstructed in great lengths, the "mathematical language" that any intelligent species can decipher and use to communicate is taken for granted.
- Happy Ending Override: Inverted. Part of the purpose of book four is to override Happy Ending Override-turned-sad-ending of the third book. Thanks to the manipulations of a Sufficiently Advanced Alien, the universe does undergo a Big Crunch and is reborn, minus five kilograms of matter. This universe is still wracked by dimensional war, but it's better than the last one. Most notably, the chaotic Trisolaris system is now the stable trinary system that Alpha Centauri is in real life, and a very different Trisolaran species has evolved there, meaning there's no more immediate threat to Earth. Yun Tianming, reborn as a new person with the memories of the old, is tasked with visiting other universes to discover how true peace can be achieved... but first, as a warning, he needs to write down the history of the previous. Writing under the name he has in the new universe, Cixin Liu, he decides to call this history Remembrance of Earth's Past, starting with Book 1: The Three-Body Problem.
- Hit So Hard, the Calendar Felt It: The events of The Three-Body Problem trigger the start of the "Crisis Era". Death's End reveals this to be the first of several times the calendar gets reset.
- Hobbes Was Right: Reality is a war of all against all on a universal scale due to difficulties of communication and an inability for trust to be established between races. Game theory requires a civilization to wipe out any other intelligent life it discovers. Any race that rejects this reasoning is destroyed by others who accept it.
- Homeworld Evacuation: The possibility of sending one or more Generation Ships to flee the solar system before the Trisolarans arrive is a recurring plot element in the second and third books. "Escapism" never ends up getting off the ground, not because of technological or logistical problems, but because the question of who gets to go quickly becomes the Berserk Button for humanity, and no politician is willing to risk a massive international backlash by endorsing it.
- Hopeless War: Earth versus Trisolaris is widely expected to be this, given the Trisolarans' much greater technology, which humanity can't hope to match thanks to the sophon block. The point is really driven home in book two when Earth's entire space fleet is wiped out by a single two-meter Trisolaran probe, nine more of which will arrive within three years, followed by a thousand warships in another two centuries.
- Human Popsicle: Hibernation technology features prominently in both sequels, allowing people to step decades or even centuries into the future. It was originally developed to allow people with terminal diseases to sleep until a cure was discovered.
- Humans Advance Swiftly:
- The Trisolarans estimate that in the five centuries it will take them to reach Earth four light-years away, Earth will have far surpassed Trisolaran technology and will easily crush the invasion force... unless Trisolaris can halt Earth's scientific progress.
- Even with the sophon block, humanity makes some astonishingly rapid progress. By the early 23rd century, while the Trisolaran invaders are still two hundred years away, they've built a massive Standard Sci-Fi Fleet and constructed space habitats all over the solar system. And this is in spite of a colossal economic collapse (the "Great Ravine") that pretty much shattered civilization as we know it for decades and halved the population of Earth.
- Humans Are Bastards: Played with. Her experiences during the Cultural Revolution are the cause of Wenjie's nihilism and other experiences of human destructiveness are why many members of the ETO believe humanity deserves to be destroyed. However, in the end it turns out to be the reverse: Humans are too soft and sentimental to survive in a harsh universe ruled by The Dark Forest.
- Humans Need Aliens: Both main ETO factions, for different reasons. The Redemptionists believe humanity can't be trusted to rule itself, and should be subservient to Trisolaran rulers; the Adventists believe that humans have mismanaged the planet we should be lucky to have and deserve to be annihilated.
- Humans Through Alien Eyes: The Trisolarians' view of Earthlings averts the trope that an alien civilization encountering human culture for the first time, would reach conclusions that all agree with. In The Three-Body Problem, upon discovering Earth Trisolaris's leadership begins planning an invasion for the living space of a planet in the permanent golden age of a stable orbit, as well as rooting out a potential rival. Meanwhile, a wave of xenophilia and fascination sweeps through the general populace until the leadership manages to override it.
- Made of Indestructium: Trisolaran tech is impossible to scratch using conventional technologies due to their mastery of the strong interaction. Humanity's space fleets found this out the hard way in book two.
- Magical Computer: The sophons, Sufficiently Advanced computers packed into a space the size of a proton.
- Modern Stasis: Played With. The sophons' purpose is to interfere with human technological development so that they won't be able to halt the Trisolaran invasion when it lands. They do so by detecting particle accelerators and forcing them to give random results so that subatomic physics cannot be discovered. Humanity manages to crawl to Space Age Stasis by using what physics we already understand to the limit, but that's about it.
- Named After Their Planet: The Trisolarans are from... Trisolaris.
- No Kill like Overkill: The races responsible for Dark Forest strikes don’t care about collateral damage or preserving inhabitable planets when they wipe out a race. The basic attack seen twice in the books involves blowing up a star. When that isn’t guaranteed to be effective they escalate to weapons that remove a spatial dimension utterly annihilating everything in the vicinity (and, eventually, the universe).
- "Ray of Hope" Ending: All three books end on this note.
- The Three-Body Problem: Humanity is faced with repelling Technologically-Advanced Alien Invaders in a few centuries, and is trapped in Modern Stasis and therefore unable to develop new weapons to fight them. However, plans are being drawn to fight back all the same, and Shi points out that, if humans have never been able to fully defeat locusts, then surely the Trisolarans won't be able to fully defeat us.
- The Dark Forest: Earth's fleets are completely destroyed, and the universe has been revealed to be a Cosmic Horror Story. However, Luo Ji has managed to scare the Trisolarans into abandoning their invasion, and it's hoped that one day the two species can become friends and, perhaps, even shine some light into the dark forest.
- Death's End: Earth and Trisolaris have been destroyed, the universe is a war ruin well on its way to destruction at the hands of Sufficiently Advanced Aliens, and Cheng Xin and Yun Tianming didn't get their happily-ever-after. However, humans and Trisolarans live on in the descendants of Starship Earth and the First Invasion Fleet, respectively, and there's a Big Good race called the Returners who have a plan to reset the universe and finally bring an end to the wars.
- Ring World Planet: Many of these types of cities are built behind the shadows of the solar system's gas giants during the Bunker Era to protect against a Dark Forest strike.
- Shoot the Dog: A dark forest strike is not an act of malice, but rather one of ruthless self-interest. Because communicating with another civilization leaves you at the mercy of their unknown intentions, and leaving them alone runs the risk of them eventually finding you anyway, the only logical act is to Do Unto Others Before They Do Unto Us.
- Sliding Scale of Idealism Versus Cynicism: The first book is very cynical, the second book drives it all the way into despair-inducing dog-eat-dog hopelessness on a cosmic scale, and the third book takes the scale up even higher by turning the book into a hard-science Cosmic Horror Story. That being said, this only applies on an interstellar scale — it's noted that individuals and even civilizations can still have long, prosperous, happy lives as long as they stay beneath the notice of the wider universe.
- The Social Darwinist: The Trisolarans' hat. Due to having evolved on a Death World, they think nothing of Shooting the Dog to preserve their civilization and are confused by humanity's indecisiveness on the subject. This is best exemplified in book three when, rather than exterminate humanity as originally planned, they decide to deprive us of electricity and demand that we begin cannibalizing each other to survive. This isn't Cruel Mercy, they genuinely intended this as a kindness and are shocked and confused when humanity reacts with panic and rage.
- Star Killing: Apparently the method of choice for dark forest strikes for somebody in the stellar neighborhood is do this by shooting a star with a "photoid", which is essentially just a rock... fired at speeds a significant percentage of the speed of light, so that its energy is a significant fraction of the star's mass. The impact literally blows the star open, spewing its contents onto surrounding planets before the star ultimately collapses. This is what happens to Trisolaris due to the dark forest broadcast.
- Stock Star Systems: Trisolaris orbits the three suns of Alpha Centauri, the nearest system to Sol. Otherwise averted; other systems are referred to by a catalogue number (such as 187J3X1) rather than a familiar name.
- Straw Character: In Liu-land, "environmentalist" means "genocidal misanthrope", as the Big Bad of the first book wants to help aliens exterminate humanity because she read Silent Spring, her primary ally is an environmentalist whose hatred of humanity is shown as entirely intertwined with his environmentalist views, and other members of their organization consider environmentalists to be science-hating fanatics and thus potential allies. All environmentalist characters are evil, and no heroic characters express environmentalist views.
- Arguably deconstructed in the background of the second book, where the ETO's actions have tarnished the very idea of environmental preservation. This, coupled with fear of the Trisolaran invasion, leads to reckless military-industrial buildup on Earth, causing an ecological catastrophe and unprecedented worldwide famine known as the Great Ravine. It's bad enough that when the protagonist wakes up long after the end of the Ravine, the world's population is still less than half what it was in our time.
- Subspace Ansible: The sophons on Earth can communicate instantaneously with their counterparts on Trisolaris via quantum entanglement.
- Sufficiently Advanced Alien:
- Subverted with the Trisolarans. They do have extremely powerful technology, but they use it to fake feats that are beyond even them in order to make humanity believe they are this. For example, they can't actually switch off the background microwave radiation of the universe at will, but they can make it seem like they can by wrapping the planet in an extremely thin shell and having it act as a filter.
- Played straight in book three with the revelation that many civilizations across the galaxy not only have the power to weaponize the laws of physics, but mathematics as well.
- Suicide by Pills: Ye Wenjie's daughter Yang Dong, a genius physicist, kills herself by overdosing on sleeping pills after confirming the experimental discovery that quantum physics is fundamentally unverifiable and unlearnable (as well as that her own mother is in cahoots with the aliens on their way to wipe out humanity).
- Summon Bigger Fish: A dark forest broadcast. Basically, you transmit the location of your enemy's sun to the galaxy at large, and wait for somebody to take it out.
- Technologically Advanced Foe: The Trisolarans have technology far beyond anything humanity can muster. Humans can understand it, to some extent, but beating it is another matter.
- Telepathy: Sort of. Trisolarans' thoughts are transparent to each other, meaning that they can read each others' minds even at significant distances. As a result they have very little experience with deception and political intrigue, forcing them to rely on their human collaborators to deduce Earth's defensive strategies.
- Time Skip: A number of times in the sequels, usually when main characters go into hibernation, with the story later skipping to when they wake.
- Too Dumb to Live: Despite the overwhelming evidence humanity keeps coming up with reasons to reject the Dark Forest interpretation of the universe, can’t quite believe that the Trisolarans really do intend to wipe them out, prohibit attempts to escape from the Solar System and even introduce the death penalty for anyone who tries to develop FTL Technology that would make an escape possible. Ultimately they arrogantly believe, based on only two data points, that they can see a way to survive a photoid strike by hiding behind the gas giants without considering that aliens greater in scope than the Trisolarans who have experience destroying civilizations will know all these tricks and, when appropriate, will use weapons that render them ineffective.
- Ungovernable Galaxy: The Dark Forest doesn’t just mean every alien species is at war with every other alien species, it also means every spacefaring species will likely be at war with itself too. This is first demonstrated when the handful of surviving ships from the destruction of humanity’s space fleet end up fighting each other for fuel and supplies, and again later when the alien species that destroys the solar system is shown to be fighting a civil war between its homeworld and a colony world.
