What if the Dark Forest is full of extraterrestrial civilizations?

Cixin Liu’s (recently Netflix-adapted) trilogy The Three-Body Problem describes a dangerous universe, teeming with hostile civilisations. In contrast, Karim Jebari and Andrea Asker argue in The Monist that the idea of a galaxy full of civilizations should be a source of comfort rather than concern.

This text was written by Karim Jebari and originally published in Swedish on svenskfilosofi.se

Is there life on other planets in our part of the galaxy? We don’t know, but we can't yet rule out the possibility. There are approximately 5,000 stars within a hundred light-years from our sun, and some of these could have planets where extraterrestrial life exists. If so, some of those planets could also harbor an extraterrestrial civilization.

Several extensive projects have been dedicated to searching for these potential civilizations, but none have found anything so far. Therefore, some scientists have suggested that we should not only passively listen to the night sky for traces of civilizations that may have sent signals in our direction, but actively send out radio signals to nearby stars (within a hundred light-years) where Earth-like planets have been found.

A problem with actively sending out signals in this way is that it could reveal our existence to extraterrestrial civilizations, which could be risky if they were hostile and technologically more advanced than we are.

The problem is exacerbated by the fact that it may be difficult, or even impossible, to translate a message from one language to another without a translation manual or the ability to interact over an extended period. According to a common belief in the philosophy of language, the meaning of a phrase lies not in the phrase itself but in how language users’ behavior relates to the phrase. If this is true, it would mean that language confusion is inevitable when attempting to communicate with extraterrestrial civilizations, since we would not have access to observable behavior.

The economist Thomas Schelling formulated a game theoretical model that is similar to the situation that may become manifest in an interaction between humans and an extraterrestrial civilization. In the model, two entities are in contact with each other but lack the ability to communicate and cannot rule out that the other has the ability and intention to act with hostility. The situation is known as the “Hobbesian Trap”, after the philosopher Thomas Hobbes.

Here's an example: Suppose you wake up in the middle of the night and hear a burglar in your home. Armed with a revolver, you step into the hallway and come face to face with the armed intruder. You don’t want to shoot the burglar, but you also don't want to be shot. You worry that the burglar might think you will shoot first to avoid being shot first, but you realize that the burglar is worried that you're worried, and so on. An initial suspicion of bad intentions can lead you and the burglar into mutually reinforcing reasoning that inevitably leads to both of you shooting, even though both of you would have preferred that no one shot.

Normally, these situations are avoided by communicating with each other and signaling peaceful intentions. This can build trust, which facilitates communication and potentially prevents both parties from falling into the trap. But if the parties cannot communicate with each other, as may be the case with humanity and an extraterrestrial civilization, then we have little chance of avoiding the trap.

However, all hope is not lost, as Andrea Asker and I argue in a newly published article. If it is true that there is an extraterrestrial civilization in our immediate vicinity (a hundred light-years), then it must reasonably mean that extraterrestrial civilizations are incredibly numerous. The galaxy is a hundred thousand light-years in diameter, and it would be extremely coincidental if there were extraterrestrials just in our vicinity and nowhere else. 

But if there are indeed so many extraterrestrial civilizations, then at least some of these must already be aware of our existence. It's possible to remain unseen in the galaxy for a while if the nearest civilization is far away (thousands of light years). But if the galaxy is teeming with life, it's improbable that our existence has escaped other civilizations. With the James Webb telescope, humanity already has the technological means to observe and measure the prevalence of various gasses in the atmospheres of nearby exoplanets in ways that can identify life and even an industrial civilisation. This, in turn, poses a question: If there are so many extraterrestrial civilizations, why are we still here? Why hasn't any extraterrestrial civilization attacked us?

The explanation that they are too far away cannot hold, in the scenario under consideration. If we assume that there is at least one nearby civilization, it's reasonable to assume that there are several of them nearby. Instead, there must be at least one other explanation for why extraterrestrial civilizations have spared us. What that explanation might be, we don't know. Whatever reason or combination of reasons that prevent extraterrestrials from attacking each other must be universal, in a non-metaphorical sense. Thus, we have good reason to believe that it holds true for us and for the hypothetical extraterrestrial civilization that we assume might exist in our vicinity. 

If we know this fact, we can use that knowledge to be less worried about being attacked and less worried that others will think we are going to attack them. This should make us even less worried about assaults.

In Cixin Liu's novel trilogy "The Three-Body Problem," the "Dark Forest" is a metaphorical description of a galaxy of constant war of all against all, a place where "armed hunters creep through the trees like ghosts." If we are correct, the opposite is true. If we live in a galaxy where a multitude of civilizations exist in the darkness, then we can hope that contact with such a civilization will not lead to our destruction. The invisible powers of the dark forest should fill us with hope, not with horror.

Read the article “Saved by the Dark Forest: How a Multitude of Extraterrestrial Civilizations Can Prevent a Hobbesian Trap” by Karim Jebari and Andrea Asker.