The Dark Forest
Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.
Sir Arthur C. Clarke
The Three-Body Problem by Cixin Liu is probably my all time favorite Sci-Fi saga (with a recent, suprisingly good Netflix adaptation). Not only is it packed with mind blowing technological concepts, it explores dark and existential questions. How would you react if you learned about an incoming alien invasion fleet that will arrive in 300 years? How would society and nation states prepare?
One of the most intriguing concepts in the books is the fictional field of cosmic sociology, which explains the Fermi Paradox (why we haven’t detected any aliens) via the “dark forest” hypothesis.
Below, I will briefly summarize the idea. It is elegant, logical, simple, and yet contrary to everything we have come to believe when we think about Science Fiction.
The Game Theory
We are starting out with two simple, seemingly trivial axioms:
Survival is the primary need of any civilization.
Civilizations continuously grow and expand, but the total matter in the universe remains constant.
We can observe this on Earth. From an evolutionary perspective the dominant species must develop traits that favour survival (against other predators) and expansion (to secure resources) to develop a civilization in the first place.
Given some starting knowledge about the size of the universe and the speed of light, we can derive two key points of cosmic sociology:
- Chain of suspicion: Unlike civilizations on earth, cosmic civilizations have no realistic way of communication due to the vast distances and time delays. We can thus only assume that an alien civilization is either hostile or benevolent, without any way to verify it. Even if we assume that the aliens are benevolent, they might assume we are not, and thus attack us first. This leads to an infinite regression: They might think that we think that they think we are hostile… In conclusion, game theory suggests its the safer bet to assume everyone is hostile.
- Technological explosion: From the development of fire (~1 million years ago) to industrialization (18th century) progress was slow. However, the jump to electricity, computers, the internet, and space travel took only 200 years. Thus, since advancements can occur unpredictably fast, a seemingly harmless pre-industrial civilization might surpass and threaten a more advance civilization by the time a radio signal would have travelled over cosmic distances.
Together, these considerations lead to a chilling conclusion: The universe is a “dark forest” where every civilization is an armed hunter, stealthily avoiding detection. Revelaing your position invites preemtive destruction, and the safest strategy is to eliminate potential threats immediately.
Flaws in the Dark Forest Hypothesis
When I first encountered the theory, its clever and contrarian nature completely won me over. However, it’s easy to fall in love with a theory and become blind to its flaws.
Isaac Arthur has a great youtube channel, discussing concepts in science and futurism and provides some convincing arguments against the dark forest hypothesis:
Is the galaxy a dark forest full of unknowns?
No. In fact, it is a brightly lit place where stealth is incredibly hard. Earth has shown astronomically visible tell-tale signs of life far longer than we had fire or technology. Certainly far longer than it would take any probe to get to us and report back. Any aliens at our scientific level or above could easily spot expolanets with signs of life.
Thus, the parameters in the game theory completely change when you cannot hide your existense.
Even if we developed a technology to “cloak” us, we could not do so retroactively, we have been detected millions of years ago.
This opens up alternative questions and thoughts:
- If we’ve been detected long ago, why haven’t we already been attacked?
- What would be the point in staying silent and trying to hide? It would seem strange that those aliens would suddenly murder as if we say hello, when they haven’t done so before.
- Other aliens would come to the same conclusion that there must be older civilizations out there which, for some reason, haven’t attacked them. Would committing genocide be a smart move or put them at risk from these older civilizations?
Other flaws with the game theory
Game theory often oversimplifies the reality. Here, it assumes static behaviour over huge time scales with changing actors.
It may make sense in the early stages of space travel to be cautious and stay under the radar. In the long run, however, it would inhibit a civilizations ability to grow in strength. As stated before this is the default evolutionary objective and generally a good survival strategy.
As stated, it is not feasible to hide an entire civilization for millions of years anyways.
Consider an actual forest on earth: It would be much easier for a predator to hide there. Yet, their strategy is not to hide but do clearly declare their territory. A strategy that avoids many more potential conflicts.
Conclusion
In the end, the dark forest hypothesis, while intriguing, crumbles under the weight of its own assumptions, revealing a universe where openness and resilience might outweigh the risks of silence. Perhaps the real cosmic challenge is not hiding but finding the courage to connect across the stars.