The Dark Forest Hypothesis: Aliens are Either Quiet or Dead
And Earth is loud.
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Science fiction writer Liu Cixin has cemented himself in science fiction history with his modern classic, the Remembrance of Earth’s Past trilogy. The first book, The Three Body Problem, was recently adapted into a Netflix show by David Benioff and D.B. Weiss, the creators of Game of Thrones.
The second book, The Dark Forest, revolves around the greatest secret of the alien invaders. This secret, now named the dark forest hypothesis after Cixin’s book, is the concept that there are two types of civilizations: quiet ones and dead ones.
The loud ones, calling out to the cosmos? The dark forest hypothesis proclaims that these worlds will ultimately be destroyed by a technologically superior civilization. It’s the principle that the Universe is fundamentally hostile. Destroy or be destroyed.
Consider where humanity fits into this picture. We are shouting at the universe with radio waves. The dark forest hypothesis would have chilling implications for us.
Why does the dark forest hypothesis exist?
The hypothesis stems from our apparent isolation in the universe. Ages ago, our uniqueness in the universe was understood. After all, everything revolves around the Earth! Well, turns out: the geocentric model is wrong. The Earth revolves around the Sun. Oh, and by the way, the Sun isn’t an outlier among the two sextillion stars within the observable Universe. And the universe, on a large scale, is isotropic and homogeneous. So we’re extra not special.
In cosmology, this is known as the Copernican principle. Humans on Earth are not privileged observers. There is no reason we should be the only form of intelligent life in the universe. With so many stars and so many Earth-like planets—not to mention other potential habitats for life—we stumble upon a paradox. The Fermi paradox: where is everybody?
The Drake Equation provides a rough estimate of the number of technologically advanced alien civilizations in the Milky Way:
Figure source: NASA Science Editorial Team
The Drake Equation is a much more of a discussion starter than a formula. It might be off by several orders of magnitude, and the variables are difficult to quantify. Still, estimates suggest thousands of intelligent civilizations in this galaxy.
The dark forest hypothesis provides a possible solution to the Fermi paradox.
Since space communication to resolve conflict is difficult, all civilizations will be presumed, by at least one alien world, to have hostile intent. Liu Cixin calls these communication difficulties “chains of suspicion.” On Earth, miscommunication is easily resolved. We are much more alike than different. There is some shared culture, community, and biology. Shared humanity.
Between alien worlds, there is no guarantee of any common characteristics, making communication difficult and resolving miscommunication near impossible. Consider the time that space communication takes. Even quickly resolved disputes could drag on for centuries! The hypothesis suggests that communication is not worth risking extinction, and all worlds must be considered hostile. Even if not presently hostile, all life poses a future threat.
Actually, there’s no need for an existential crisis!
Tarter et al. (2010) is often referenced in these discussions: our search for life beyond Earth is like taking a glass of water from the Earth’s oceans and expecting to find fish. A 2018 study (Wright et al.) found that we’ve actually searched roughly the volume of a small swimming pool out of the Earth’s oceans. Clearly, we are nowhere close to concluding there is no communicating extraterrestrial life.
So, take the dark forest idea with a very large grain of salt. It makes for great science fiction! But that’s all it is: science fiction.
We will keep calling.
Are we more terrified of the vastness of space or its apparent silence? Both, actually. We are terrified of the apparent silence in this vastness of space.
We are afraid to call out, but we still do.
Science fiction writer Arthur Clarke famously said, “Two possibilities exist: either we are alone in the Universe or we are not.”
This is one of the greatest endeavors: to find out the truth about our aloneness.
In the ocean of the universe, we have only observed the volume of a small pool. It will be an egregious disservice to humanity if we do not search further. If we do not call out. If we do not proclaim our place in the universe, on this little blue dot in an ordinary star system, in what may now seem like a dark forest.
Written by Chloe Xu
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