“Two possibilities exist,” physicist and science-fiction author Arthur C. Clarke once wrote. “Either we are alone in the universe or we are not. Both are equally terrifying.” Chinese science-fiction author Liu Cixin begs to differ. In his mind-bending trilogy Remembrance of Earth’s Past, adapted by Game of Thrones showrunners David Benioff and D. B. Weiss as 3 Body Problem for Netflix, he convincingly argues that we’d be better off if we were alone in the universe and, barring that, that we should hide from whoever or whatever might be out there.
Remembrance of Earth’s Past divides the history of humanity into two halves: before and after first contact with an intelligent alien civilization. It tells a fictionalized history of that second half, from the moment of first contact until 17 billion years after the beginning of time.
It starts with a world-breaking revolt against the Communist Party of China. Disillusioned and misanthropic physicist Ye Wenjie works at a secret Chinese military installation, tasked with searching for extraterrestrial intelligence and broadcasting greetings from Earth in a language that includes its own decoding key based on universal mathematics. One day, she receives an answer from another world in that same language. Despondent about humanity’s failings in general, and Chinese totalitarianism in particular, she invites the beings of that world to conquer our own and offers to help. She does not yet know—because she cannot know—that she’s speaking to a technologically advanced but dying world in a triple-star (three-body) system, later dubbed Trisolaris, buffeted by chaotic orbital mechanics and such violent climate extremes that the surface of the planet is repeatedly frozen and melted. Trisolaris, with no fewer than 200 dead civilizations in its past and desperate for a benign and stable planet in a single-star system, builds a fleet of a thousand ships and sails toward Earth with colonization—and ultimately, genocide—as its objective.
Each book in Cixin’s trilogy is progressively bigger, better, and more ambitious than the last. The first, The Three-Body Problem, is a fascinating but difficult mess, told out of chronological order and featuring a cast of characters who don’t know or interact with one another—problems that Benioff and Weiss resolve in the Netflix adaptation with some plot tidying and character modification. The first book, like the first Netflix season, mostly takes places in the modern era, and it’s merely the setup for the real story, one of galactic conflict hundreds of years in the future in books two and three, The Dark Forest and Death’s End, when the violent clash between Earth and Trisolaris unfolds. Books two and three are easier to digest and exhilarating to read. They’re better plotted, show deeper character development, tackle bigger ideas, and take place in settings as exotic as deep space, the moons of Jupiter, the surface of Pluto, interstellar warships, a planetary system hundreds of light-years away, Earth’s past during the time of the Byzantine Empire, and splinter universe 647. Death’s End is such a wild, unpredictable ride that I couldn’t spoil it if I tried.
As sweeping as the trilogy is, it starts small, during one of the most wrenching periods in Chinese history. And since Cixin lives and works in China, it’s surprising that Beijing’s rulers let anybody read this. The English translation, like the Netflix adaptation, opens with a harrowing “struggle session” during the Cultural Revolution (1966–76), when a cadre of Mao Zedong’s Red Guards murders a science teacher in front of a deranged mob for daring to teach Albert Einstein’s “imperialist” theory of relativity. Why begin there? Because the story’s inciting incident, when Ye Wenjie invites Trisolaris to invade, requires that she first lose all faith in humanity; the murdered teacher was her father. When she contacts technologically superior aliens, she assumes (with zero evidence) that they must also be morally superior and capable of saving humanity from itself.
The Chinese Communist Party grudgingly tolerates criticism of the Cultural Revolution, which Cixin describes as “the years of madness,” but his publishers, fearful of government censorship, cajoled him into moving the opening scene to the middle of the book, hoping that the regime wouldn’t notice it, or would at least complain about it less obstreperously. But Wenjie’s character arc doesn’t make sense if that scene is rendered as a flashback in the middle. She must lose faith in humanity before anyone can believe that she would betray humanity. No good editor would suggest reversing cause and effect in the story like this, but Cixin’s publishing house had something other than literary craft on its mind.
Not until Ken Liu translated the novel into English did the scene find its rightful place, at the beginning—and then only in the translated edition and Netflix adaptation. Cixin bristles so much at the hatchet job done to his original manuscript that he recommends the translated edition even to Chinese readers if they can read English. “Usually when Chinese literature gets translated to a foreign language, it tends to lose something,” he said to Alexandra Alter at the New York Times Magazine in 2019. “I don’t think that happened with The Three-Body Problem. I think it gained something.”
Cixin isn’t a dissident, and he doesn’t criticize his homeland’s ruling party when somebody asks him about politics, a subject he hates. But his deepest values seem clear. All references to politics in his books are antitotalitarian when they aren’t specifically anti-Communist. Late in the first book comes an amusing scene, with regime officials wanting to broadcast Communist propaganda into outer space. “This is utter crap!” one character says. “It’s enough to put up [propaganda] posters everywhere on the ground, but we should not send them into space.” Once the Trisolaran crisis gets going, when the entire human race knows that it’s targeted for annihilation by a more powerful species, Earth civilization unites to face its common enemy. When that happens, all authoritarian and totalitarian regimes—presumably, including the Communist Party of China, though Cixin doesn’t explicitly say so—are swept aside and replaced with democracies.
Some Chinese nationalists are furious at the Netflix adaptation, accusing the platform of deliberately making China look bad. Few people enjoy seeing one of the worst episodes in their nation’s history vividly portrayed in a foreign television series, especially when it happens during the opening scene—but a Chinese author wrote this, he’s beloved in his home country, he won China’s prestigious Nebula Award, and all the Netflix scenes set in Communist China unfold exactly as portrayed in that novel. And in the real world, the Maoist state and the Red Guards were every bit as deranged as Cixin depicts them on the page and Netflix portrays them on screen. If anything, the series barely scratches the surface of the horror, since it follows only a few characters during that period; the Cultural Revolution killed at least 1 million people, perhaps 2 million.
Writers ruled by oppressive regimes have long sought refuge in science fiction. Tyrannical censors everywhere are dim-witted, unable to parse literature in any genre or language. Allegory, dual meanings, subtext—all are lost on these people, which makes it easy to comment indirectly on current affairs by changing the place and time and lambasting some fictional regime instead of the real one. “In China,” Cixin’s translator said at a panel discussion in New York, “there’s this official propaganda position that science fiction is about imagination and this is what the future is all about. In reality, much of the most interesting science fiction is much more subversive. It is a kind of wry commentary on what is happening in society. And because so many things are changing in China so rapidly, science fiction feels like oftentimes the most realistic way to describe what’s happening.”
Even so, Cixin insists that this is not what he’s up to. In his postscript for the American edition of The Three-Body Problem, he writes: “As a science fiction writer who began as a fan, I do not use my fiction as a disguised way to criticize the reality of the present.” You might think, well, he would say that if he wants to stay out of trouble and continue publishing books; but I believe him because most of his work consists of deep dives into ideas that transcend modern politics. “The stories of science are far more magnificent, grand, involved, profound, thrilling, strange, terrifying, mysterious, and even emotional, compared to the stories told by literature,” he observes. “Only, these wonderful stories are locked in cold equations that most do not know how to read.”
He’s more, though, than just a science nerd geeking out about things like quantum entanglement and 11-dimensional physics. Cixin’s biggest ideas, those that deserve the widest possible audience beyond the core of science-fiction fans, involve our place in the universe and what it means to be human.
Hoping to take an educated stab at how many intelligent alien civilizations might exist in our galaxy, astrobiologist (yes, that’s a real job) Frank Drake formulated the eponymous Drake Equation. It considers the number of stars in the Milky Way, the fraction of stars that have planets, the fraction of planets where life could exist, the fraction of those planets where life does exist, the fraction of those planets where intelligent life exists, the fraction of those planets with a civilization capable of communicating with other planets, and the duration of time that a typical such civilization survives. The values for all but two of these variables are guesses, of course; but even with conservative estimates, thousands of advanced civilizations could exist in our galaxy alone. With billions of galaxies in the observable universe, trillions upon trillions of intelligent civilizations could be out there. Yet we have no evidence that anyone or anything else is out there. Which brings us to the Fermi Paradox, named after Italian American physicist Enrico Fermi: If the universe teems with life, where is everybody?
No shortage of hypotheses are on offer, ranging from the simple (distances are so vast that communication is impossible) to the unlikely (there will be lots of intelligent civilizations, but ours is the first). Cixin’s answer to the Fermi Paradox in the second book in his trilogy, The Dark Forest, is one of the most chilling.
His astronomer character Luo Ji (renamed Saul Durand in the Netflix series), at the urging of a repentant Ye Wenjie after she understands the hell that she has unleashed by enabling the Trisolaran invasion, develops a “cosmic sociology” with four main axioms:
Survival is the primary need of civilization.
Civilization continuously grows and expands, but the total matter in the universe remains constant.
Civilizations that cannot interact with each other in real time will be suspicious of each other.
Technology advances at an explosive rate.
All four of these axioms are inarguably correct. And taken together, what Luo Ji ultimately calls “the dark forest nature of the universe” becomes frighteningly clear.
Say you have two civilizations, light-years apart. Earth learns that an advanced civilization on Planet X exists but knows nothing else about it, least of all whether Planet X is benign or malicious. Earth has two options: communicate or remain quiet.
Reaching out to say hello would be risky, yes, but Earth civilization is benign. We didn’t establish SETI (search for extraterrestrial intelligence) because we want to find aliens and kill them. Maybe other advanced civilizations will be benign for the same reasons we are. There’s no way to know, but let’s say that Earth is willing to roll the dice and hope for the best—which is basically what Ye Wenjie does in The Three-Body Problem.
Once Planet X receives the message, it will know that Earth exists, and it will know that Earth knows that Planet X exists. Now what does Planet X do? There’s no way to know whether Earth is benign or malicious. Earth could say that it’s benign, but it could be a trap. When the stakes are low, risking cooperation is possible. When the stakes are existential, and when guessing wrong is catastrophic, the only truly safe course of action is to destroy the other world, if possible—and to do so immediately upon discovery without initiating communication in case the other world decides to strike first.
This is basically an interstellar example of the “sequential and incomplete information game” in game theory. Friendship and cooperation are built on trust, and trust is impossible over vast distances. Here on Earth, nations can forge friendships and alliances because we can commingle and communicate in real time. We can visit other countries, verify whether what foreign peoples say about themselves is true, and establish relationships based on mutual values, common interests, or both. None of this is possible at interstellar distances because it takes years, decades, centuries, or even longer to receive a single message.
You might think that another world is benign, but that’s not good enough because you can’t prove that you yourself are benign. You know what you think about the other world, but you don’t know what the other world thinks about you. And the other world doesn’t truly know what you think about it. “That’s the chain of suspicion,” astronomer Luo Ji says to another character, Da Shi (played by the terrific Benedict Wong in the Netflix adaptation), as he explains his theory of cosmic sociology. “It’s something that you don’t see on Earth. Humanity’s shared species, cultural similarities, interconnected ecosystem, and close distances mean that, in this environment, the chain of suspicion will only extend a level or two before it’s resolved through communication.”
Besides—and Cixin doesn’t make this point, but I’m adding it here—a civilization can be benign in one era and malicious in another. That happens on Earth all the time. From the United States’ point of view, Germany started out benign, became an enemy during World War I, became utterly malicious under Nazi rule, and then became benign again. “In actual cosmic civilization, the biological differences between different groups might be as high as the kingdom level, and cultural differences are even further beyond our imagining,” Luo Ji explains. “Add to this the vast distances between them, and you have chains of suspicion that are practically indestructible.”
Let’s say that we discover an intelligent yet militarily weak civilization, one that’s no threat to us. We’d be fools to discount the technological explosion. If we observe another world that’s hundreds of light-years away, we will be observing its past. We’ll have no idea what its current capabilities are. And technological progress grows at an exponential rate, at least here on Earth, with our scientific and innovative culture.
So it’s dangerous to establish communication with another world. We should keep quiet then, right? That’s not necessarily good enough if we ever discover another civilization. If I can see you, you can see me. While Planet X may not know that Earth exists, once we discover Planet X, we’ll know that Planet X will eventually be able to discover Earth.
It’s certainly possible for two advanced civilizations to break through the chain of suspicion and form a friendship. Perhaps they’re both benign and trusting of others. Maybe most civilizations are like this. But in a universe with a septillion stars—that’s a one followed by 24 zeros—and potentially trillions of inhabited worlds, the likelihood that all of them are inherently benign and trusting is nil.
Here is Luo Ji again, warning the human race—too late!—about the nature of the universe:
The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound. Even breathing is done with care. The hunter has to be careful, because everywhere in the forest are stealthy hunters like him. If he finds other life—another hunter, an angel or a demon, a delicate infant or a tottering old man, a fairy or a demigod—there’s only one thing he can do: open fire and eliminate them. In this forest, hell is other people. An eternal threat that any life that exposes its own existence will be swiftly wiped out. This is the picture of cosmic civilization. It’s the explanation for the Fermi Paradox. But in this dark forest, there’s a stupid child called humanity, who has built a bonfire and is standing beside it shouting, “Here I am! Here I am!”
In Fred Saberhagen’s 1960s-era Berserker novels, self-replicating doomsday machines, forged by an extraterrestrial civilization embroiled in a galactic war, seek out and destroy all other life in the universe as part of a genocidal self-defense strategy. Earth is menaced by similar machines in Greg Bear’s apocalyptic novel The Forge of God, and one character laments—again, too late—that humanity brought this on itself. “There once was an infant lost in the woods, crying its heart out, wondering why no one answered, drawing down the wolves.” Phrased another way: “We’ve been sitting in our tree chirping like foolish birds for over a century now, wondering why no other birds answered. The galactic skies are full of hawks, that’s why. Planetisms that don’t know enough to keep quiet, get eaten.”
I’m not personally worried that the galaxy is crawling with genocidal machines. No doubt you, too, have more urgent things to think about. But in a noted 1983 research paper, “The Great Silence: The Controversy Concerning Extraterrestrial Intelligent Life,” astrophysicist and science-fiction author David Brin argues that this may be less of a stretch than it first seems:
Let us say many advanced ETIS [extraterrestrial intelligences] . . . fill the void with messages of brotherhood. Then suppose that for every 100 or 1,000 or 10,000 “sane” ETIS, there is one that is xenophobic, paranoid even. Such a race might program its self-replicating emissaries to add powerful bombs to their repertoire, and command them to home in on any unrecognized source of modulated electromagnetic radiation. . . . There is no need to struggle to suppress the elements of the Drake equation in order to explain the Great Silence, nor need we suggest that no ETIS anywhere would bear the cost of interstellar travel. It need only happen once for the results of this scenario to become the equilibrium conditions in the Galaxy. We would not have detected extra-terrestrial radio traffic—nor would any ETIS have ever settled on Earth—because all were killed shortly after discovering radio.
No need to panic just because humans are broadcasting radio messages into space. In The Three-Body Problem novel, Cixin makes it clear that a radio signal from another world does not by itself indicate that world’s location, but only the direction. Point your finger at any random spot in the sky, and countless stars and planets (even galaxies) are in that direction. The only way to pinpoint a message’s source location would be if some kind of dialogue opens between the two worlds. If, for instance, it takes 50 years to respond to a message, we can assume that the other world is 25 light-years away. Radio waves travel at the speed of light, and a 25-light-year round trip would take 50 years. If you know the direction and the distance of whatever world you’re communicating with, you can pinpoint the location on a three-dimensional star map. So sending radio waves into the universe (and weak ones, at that, which is all we’re currently capable of) in a one-way monologue won’t necessarily reveal our location to anything watching and listening from a great distance.
Space journalist Matt Williams at Universe Today sees a possible flaw in Brin’s hypothesis and also, perhaps, in Cixin’s dark-forest theory: “A species of robots that have become so pervasive that they would have eliminated any ETIs in our corner of the galaxy would have surely left undeniable signs of its existence.” Fair enough. But human astronomers have been studying the sky for an infinitesimal blip of galactic time, which makes even geologic time seem as though it’s unspooling on fast-forward. Our sun orbits the supermassive black hole Sagittarius A* at the center of the Milky Way at 130 miles per second, yet it takes 212 million years to complete a single rotation. With that kind of time scale, arguing that we’ll probably never see something if we haven’t already seen it is like the old joke about the guy who falls from a skyscraper and, halfway down, thinks, “So far, so good.”
In his Substack newsletter, economist Noah Smith, criticizing the dark-forest idea, says that we “don’t necessarily have to wait for aliens to send . . . radio messages in order to detect them. You can just build a space telescope and look for them. Already, we humans are starting to observe many of the alien worlds out there in the cosmos. As telescopes get bigger and better, we’ll be able to see with greater and greater resolution.” But it’s impossible to build a single lens large enough to see an exoplanet in detail greater than one pixel. The only option is to use astronomical interferometry to create a virtual telescope, placing multiple smaller telescopes vast distances apart and pointing them at the same object simultaneously.
Physics professor Z. N. Osmanov at the Free University of Tbilisi in Georgia calculates that, to see the Great Pyramids of Giza from 3,000 light-years away, you’d need a virtual telescope millions of miles wide. “Such huge megastructures might be built only by Type-II civilizations but not by Type-I alien societies,” Osmanov writes. On the Kardashev scale, a hypothetical measure of a society’s level of technological advancement, a Type II civilization is one that consumes and expends an amount of energy equivalent to that produced by an entire sun—meaning that it must first encase that sun in something like a gigantic Dyson sphere that captures all solar energy in every direction, not just the trivial amount that reaches a planet. We don’t know how many such civilizations exist, if any, but our immediate neighborhood likely isn’t dense with them. (We don’t yet even merit the distinction of being a Type I civilization, which can harness and store all the energy available to a planet from its parent star.) Anyway, there’s nothing we can do to prevent someone (or something) from seeing the surface of our planet if it is able to look using gravitational lensing and interferometry on a staggering scale. All we can do is avoid going out of our way to draw more attention to ourselves.
In Death’s End, the last book in the Remembrance of Earth’s Past trilogy, is a remarkable scene from the point of view of a third alien civilization that’s observing the war between Trisolaris and Earth. The alien character perfectly understands Cixin’s dark-forest sociology—how, in a Darwinian struggle on a galactic scale, civilizations that hide themselves and destroy others upon discovery will naturally dominate in the long run. The character reduces the strategy for survival to five words: “Hide yourself well; cleanse well.” He, she, or it seems almost amused to discover that neither Earth nor Trisolaris has both “the hiding gene” and “the cleansing gene.”
In The Dark Forest, Luo Ji says hopefully, “I have a dream that one day brilliant sunlight will illuminate the dark forest.” But in the final book, an older and wiser Trisolaran character says, “The universe is not a fairy tale.”
What does it mean to be human in such a cutthroat universe? Cixin argues that it’s as much environmental as it is biological. In other words, we are Earth. We could not be who and what we are if we arose anywhere else—say, in the atmosphere of a gas giant or at the bottom of an ocean or a moon at the edge of the solar system. Not only could we not become who and what we are if we arose on a world with different conditions; we won’t be able to remain who and what we are if we ever leave. “Life reached an evolutionary milestone when it climbed onto land from the ocean, but those first fish that climbed onto land ceased to be fish. Similarly, when humans truly enter space and are freed from the Earth, they cease to be human.”
When Trisolarans learn about Earth civilization, its history, its climate, and its global culture (such as it is), they figure that we must live in paradise, as if our entire existence is a vacation at a spa resort compared with their life in a triple-star system with deadly climate extremes and chronic mass-extinction events. Earth civilization may not seem benign to us—big wars happen periodically, small wars are constantly happening somewhere, and not until recently did “human rights” even exist as a concept—but Trisolaran civilization is brutal. Mere survival is such a monumental struggle that the society is inherently totalitarian. Earth affords at least some of us the ability to pursue and enjoy love, peace, literature, high culture, and much else that we don’t strictly need to survive. Trisolarans cannot even imagine these things, and it’s impossible not to feel some empathy for these fictional beings, though they want to conquer our planet. Would we be better if we switched places? What would we become? The fish that climbed out of the sea and ceased to be fish.
This is exactly what happens in The Dark Forest after a nightmarish battle at the edge of the solar system, when several Earth ships are seemingly lost forever in space. Cut off from their home world, without enough shipboard resources to maintain everyone’s survival long enough to find a new home, the microcosmic human society swiftly and murderously terminates all vestiges of democracy and human rights and subordinates the individual right even to live to the survival of the group. Cixin chillingly describes their descent with 12 blunt words: “Humans lost in space will create a totalitarian society in five minutes.”
Some critics of Cixin’s Remembrance of Earth’s Past trilogy bristle at its bleak message. I, too, felt existential dread when reading this story, especially during the last 100 pages of The Dark Forest and the harrowing climax of Death’s End. It hasn’t made me afraid of the night sky, but it hardly inspires me to expect a Star Trek future of interstellar cooperation if one day we do manage to discover alien civilizations and leave our home planet.
Cixin’s worst detractors accuse him of xenophobia. Yes, if we define “xenophobia” as the fear of alien worlds rather than of fellow human beings born on the other side of a border. But he’s no more a xenophobe under the standard definition—which would have him dread and loathe Westerners, Africans, even Mongolians and Koreans—than he is a Maoist.
Cixin makes this clear not only in the stories he tells but also in the scraps of nonfiction he writes. “When you read or make science fiction,” he observes in the introduction to his short-story collection To Hold Up the Sky, “your sympathy automatically moves away from ideas of ethnicity and nation and toward a higher idea of humanity as a whole; from this vantage, humanity naturally becomes a collective unit, rather than an assembly of different parts divided by ethnicity and nation.” And in the author’s note for the English translation of The Three-Body Problem, he writes: “Let’s turn the kindness we show toward the stars to members of the human race on Earth and build up the trust and understanding between the different peoples and civilizations that make up humanity. But for the universe outside the solar system, we should be ever vigilant, and be ready to attribute the worst of intentions to any Others that might exist in space. For a fragile civilization like ours, this is without a doubt the most responsible path.”
Top Photo: Illustration by David Hollenbach