The Dark Forest Theory: The Reason Why We Shouldn’t Be Looking for Aliens

A part of space exploration has always been dedicated to finding extraterrestrial life. After all, in such a big universe, it’s highly unlikely that we’re the only ones living in it. However, aside from a few mystery radio waves and planets that could sustain life due to the presence of water in it, we still have no hard evidence that suggests there are other lifeforms outside Earth.

And according to the Dark Forest theory, it may be in our best interest that it stays that way.

The Dark Forest theory doesn’t deny the existence of aliens; in fact, the theory supports other theories claiming extraterrestrial life exists and that there are more planets and galaxies filled with aliens than we might have imagined. But the reason we haven’t found it has less to do with us not trying hard enough or having the right equipment, but more on the paranoia of other alien civilizations finding evidence of something out there.

And, according to this theory, if we’re as smart as these civilizations, we might want to give up the search for alien lifeforms entirely.


The Dark Forest by Cixin Liu

The theory traces back to the 2008 science fiction novel The Dark Forest written by Cixin Liu. The novel is part of Liu’s hard science fiction trilogy, Remembrance of Earth’s Past, and is the second book and sequel to the first book, The Three-Body Problem. The English version was translated by Joel Martinsen and published in 2015.

Photo from Cixin Liu: “The Dark Forest”, May 2008, Published in August 2015 by Tor Books,; photograph



In the first novel, astrophysicist Ye Wenjie has grown to despise humankind and finds a way to contact an alien from the planet Trisolaris. By communicating with the alien, Ye allows the Trisolaris inhabitants to locate and plan an invasion on Earth that will take them 450 years to reach the planet. Together with the wealthy son of an oil company CEO who is also angry with humanity, they create a semi-secret Earth-Trisolaris Organization (ETO) and recruit educated people disappointed by humanity as their members.

Photo from Tolstoyevsky: “Earth-Trisolaris Organization”, May 2018,; photograph

Decades pass, and nanotechnology professor Wang Miao is inducted to the ETO when he plays the VR video game Three Body (which the ETO uses to recruit members) and figures out how their climate works with three suns. He discovers that the Trisolarans plan on invading and inhabiting Earth as its climate is more inhabitable. Working undercover with detective Shi Qiang, they raid the ETO’s data and discover that the aliens have been spying on Earth and have disrupted the Earth’s particle accelerators to stop humans from making technological advancements that could help them defend themselves against the Trisolaran invasion.


Plot Summary

In The Dark Forest, humankind has 400 years until the Trisolaran invasion. Humans learn that Trisolarans are incapable of internalizing their thoughts and spying on the minds of humans, so the United Nations assigns four “wallfacers,” which are people with access to the UN’s resources tasked with coming up with plans to defend themselves against the Trisolarans – because the plans are limited to the wallfacer’s mind, the Trisolarans cannot spy on these plans. However, defeatism (the belief that mankind should give up and escape the solar system to find a new planet to rebuild) is on the rise, and this is coupled with the ETO’s “wallbreakers” assigned to find out the wallfacers’ plans.

Photo from Stevebidmead, Sept. 12, 2014,; photograph

Sociologist and astronomer Luo Ji accepts the UN’s assignment of being one of the wallfacers. Aside from him, three other men are assigned to be wallfacers and come up with their own plans: Frederick Tyler (who plans to use Kamikaze fighter pilots carrying hydrogen bombs), Manuel Rey Diaz (who researches supermassive hydrogen bombs), and Bill Hines (who researches the human brain to break the Trisolarans’ block that prevents any technological advancements).

Eventually, Tyler’s plan is revealed by a wallbreaker, and the aftermath drives him to commit suicide. Diaz’s wallbreaker reveals his plan was to expand the sun’s surface, which would destroy the Earth so the Trisolarans would not win. After the UN revokes his wallfacer status, he is stoned to death upon his return to Venezuela. Hines and his wife discover a way to remove defeatist beliefs and create an army of people who strongly believe in the Earth’s ability to win against the Trisolarans (called Triumphalism) and the two enter hibernation until the invasion begins.

Desperate to make Luo Ji begin his planning, the UN kidnaps his family and puts them in hibernation. He comes up with a plan that will take a hundred years to verify, which evidently scare the Trisolarans. The ETO nearly kill Luo Ji with an incurable virus, but the UN puts him in hibernation until a cure can be found.

Luo Ji and Hines are awoken centuries later to find that the world has fallen through an ecological collapse and is now a militarized Earth with 3 billion people remaining. While the Earth’s surface is mostly a desert, underground is a technological group of cities. The Earth now has thousands spaceships equipped to fight the Trisolaris, and so the wallfacer project is disbanded. However, Hines’ wife is revealed to be an ETO member and a wallbreaker. She reveals that Hines was a defeatist and, instead of the triumphalist beliefs he claimed to have sealed in soldiers, it was defeatist beliefs in an effort for humanity to escape and preserve their kind.

With heavy losses from the Trisolaran probe and the rest of the ships entering defeatist plans to escape the solar system, Luo Ji realizes what becomes the “Dark Forest Theory:” that if a one civilization finds another civilization, they will never feel safe until the other civilization is destroyed. Luo Ji is tasked by the UN to work for Project Snow, a mission that will track incoming probes. Three years later, Luo Ji comes up with a plan to blackmail the Trisolarans, threatening to release the coordinates of Trisolaris and Earth to rest of the galaxy. The Trisolarans surrender and leave the solar system.


The Dark Forest Theory

The Dark Forest Theory was explained by Luo Ji as the implications of why Ye Wenji’s actions resulted in the Earth and the Trisolarans’ battle. This is due to two axioms: each civilization seeks to survive, and resources are infinite. He compares the universe to a dark forest: when two predators are aware of each other’s presence in the forest, they aren’t sure if the other plans to harm them. Because of this, it is inevitable that these predators will try to destroy the other and evade any other predators before they pose a threat.

The same applies to the Trisolaris and Earth: even if Trisolarans and humans were to deal in peace talks as some characters in the books wanted, humans could never be sure of their true intentions. Trisolarans, on the other hand, know that even if they did leave Earth alone because they weren’t as technologically advanced as they were, it would only be a matter of time before they developed and became a real threat. In the beginning, a Trisolaris alien sympathetic to humans warned Ye that if she tried to contact again, she would be risking the invasion of her planet: this proved to be true in the events of the next two books. To quote The Dark Forest:

“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 another life—another hunter, angel, or a demon, a delicate infant to tottering old man, a fairy or demigod—there’s only one thing he can do: open fire and eliminate them.”

And because Remembrance of Earth’s Past is based on hard science fiction (sci-fi based on existing logic and hard facts), what’s to say that this theory isn’t possible in real life? When you have existing paradoxes and theories that question why we’ve never seen aliens or signs of extraterrestrial lifeforms, the Dark Forest Theory poses a convincing argument: we’re not seeing aliens either because they’re hiding from us, or we’re not meant to see them.


Hidden in the Universe: The Fermi Paradox

Talking about the Dark Forest Theory means we have to briefly talk about the Fermi Paradox. This theory was named by physicist Enrico Fermi, who pointed out the contradiction of the high probability that there are many aliens or extraterrestrial civilization in the Milky Way galaxy alone and the lack of evidence despite of this.

The Fermi Paradox, named for Dr. Enrico Fermi, describes the apparent contradiction between the lack of evidence of extraterrestrial civilizations and the high probability that such alien life exists. AP, June 18, 2018,; photograph

The Fermi Paradox was coined in 1950, but it wasn’t fully formed until Michael H. Hart wrote it in his 1975 paper explaining the paradox. According to Hart, there are billions of stars similar to the sun scattered in the Milky Way. If this is the case, then these suns may have their own planets capable of sustaining intelligent lifeforms. And yet, despite this likeliness, humankind has not yet found sure signs of life on other planets, nor has Earth been visited by extraterrestrial beings. However, credit for this paradox is given to Fermi because, in 1950, Fermi is quoted for being the person to first ask where the aliens are.

According to astrophysicists, the Earth and our solar system is relatively young compared to the rest of the universe. This means that if there are other inhabitable planets and aliens out there, they should have had a head start building their technology. Hence, it’s likely that they have the advanced interstellar travel down unlike humans. This means that they’re more likely to visit us than us visit them in the near future.


So Why Haven’t Aliens Visited Us Yet?

Or for that matter, why have we found no evidence of their existence? Some astrophysicists pose that it’s because of the Dark Forest Theory.

Photo from KELLEPICS, Oct. 17, 2017,; photograph

Luo Ji’s theory implies that if you want your civilization to survive, you will eliminate any other extraterrestrial civilization. Otherwise, it may be a matter of time when the other civilization finds your own civilization and eventually becomes a threat to your survival. As a result, there can be no trust between civilizations because of the paranoia that the other civilization seeks to destroy the other. And like a hunter in a dark forest, one would be more likely to shoot anything that moves before it poses a serious threat. Even if we are technologically behind, aliens may be threatened by our ability to progress, as that progress may lead to us becoming more advanced than they are.


What If Aliens Were Real?

Based on the Drake equation (an equation that estimates the number of possible extraterrestrial civilizations based on a number of factors), there may be at least 20 civilizations within the Milky Way Galaxy including our own. Assuming that the Fermi paradox is real and the Dark Forest Theory holds water, what would be the case if aliens were real?

GIF from Gfycat

Luckily, the Dark Forest Theory is grounded on the assumption that these aliens are real. But we don’t see them or hear from them because, knowing the alternative of discovering other lifeforms or being discovered, they would opt for peace and instead choose to remain ignorant about the truth beyond their own civilization. And to remain ignorant despite their starting advantage in technological advancements is simply them purposefully keeping quiet to avoid catching the attention of other civilizations.


The Prisoner’s Dilemma

When you think about it, it’s a lot like the Prisoner’s Dilemma. It’s a paradox where two individuals who think about their personal interests end up worse off if they had just chosen to act in their mutual interest.

It goes something like this: two robbers are arrested and interrogated in separate rooms, thus are incapable of communicating. With no witnesses, the only way police can arrest them is if one robber turns on the other and agrees to testify.

If both robbers refuse to testify and remain silent, both of them will receive a year imprisonment for very minor charges since the police cannot arrest them for robbery. If one of them testifies and the other remains silent, the one who testifies can avoid jail time while the other person receives a three-year jail sentence. And if both of them testify, they incriminate each other and are sentenced to 2 years of jail each.

The Dark Forest Theory is similar to this paradox in such a way that the lack of communication tempts both parties to act in their own best interests. Because of the distance between civilizations (as well as the fact that an alien civilization is unlikely to speak the same language or have the same cultures as we do), there’s a communication barrier between ours and other civilizations out there. But what we do know about them, based on Fermi and Cixin Liu’s works, is that what they want their own civilization to survive.

Going back to the Prisoner’s Dilemma, that inability to communicate proves to be the prisoners’ downfall. For both parties to get the best outcome, both prisoners would have to keep quiet and have faith that the other will also choose to do the same. But by refusing to testify, however, they are risking getting the short end of the stick if they misplaced their faith on the other robber who chooses to testify against them.

Photo from Ichigo121212, December 3, 2014,; photograph

At the same time, if they want to walk away with the best result (getting no jail time), they are tempted to testify and then hope that their partner chooses not to testify. But because both are at risk for keeping quiet and can benefit from talking, it’s likely that both will talk and result in a much worse outcome had they just chose to keep quiet.

Each scenario in this case can apply to our civilization and any alien civilization out there. Let’s say you have mankind and any alien civilization. Because of the lack of communication, both do not know what the other plans on doing, thus it becomes more difficult to expect that the other party will be peaceful and act in your interests. It’s difficult to expect this, though, and what each party will expect now is that either the other will attack if they try to be peaceful, or they should attack before the other becomes a serious threat to their safety. And when both try to attack, they end up worse off than they could have been had they just chosen to remain silent.

The best result for both parties, therefore, is to simply not see each other at all. In the case of the robbers, neither would be a threat to the other if they were not aware of each other’s’ presence. Let’s try to change the dilemma a bit: if two robbers were apprehended for completely different crimes, the existence of one would not be relevant to the other’s situation. And since their actions do not affect each other, they don’t care about the other person. In that same train of thought, if both civilizations remained unaffected and unaware of the other civilization in the universe, they’re much better off as there’s no need to take an offensive position to ensure their survival.


How Plausible Is the Dark Forest Theory?

When you think about it, it’s a pretty good theory – especially if you believe in aliens but have to explain away why humanity has never found hard evidence of life outside of Earth. A lot of this is purely speculation, but the theory is based on facts and strengthens why we don’t see aliens without completely denying their possible existence.

Photo from Gimono, October 21, 2016,; photograph

Remember when I mentioned in this article how astrophysicists regularly find mysterious radio signals that seem to come out of nowhere? What if that really did come from aliens, but these are aliens who accidentally sent out radio waves and would rather not find out the truth about what lies beyond their own civilization?

And if all alien civilizations are trying hard not to be seen by other civilizations, and mankind is here scattering our probes all around the galaxy, what happens when aliens reach us or we finally find hard proof of extraterrestrial lifeforms?

Perhaps, based on the Dark Forest Theory’s warning, it is best that humanity remains in the dark for now.

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