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Dark-forest.gmi (7024B)

The Dark Forest is book two of a trilogy by Chinese author 刘慈欣 (Liu Cixin). I really loved this trilogy! It was one of my favorite sci-fi reads in a long time, and one of the rare books that I read more than once. The first book provided a fascinating first-hand glimpse into the Cultural Revolution's impact on Chinese conciousness, and the trilogy as a whole was an exciting exploration of near-future (and far-future) scifi on a grand scale. However, as much as I enjoyed these books, the Dark Forest hypothesis, which serves as the foundation of the narrative, has weighed on me ever since I read it.
I will be discussing spoilers for the Three Body Problem and the Dark Forest in this post. If you have not read them, please go do that!
The Dark Forest hypothesis is an answer to the famous Fermi Paradox: why are we seemingly alone in the universe? For my part, I don't take the Fermi Paradox, and especially the Drake Equation, very seriously. But a lot of people do, and the Dark Forest explanation has captivated many of them.
This hypothesis is derived from the following "axioms" of interstellar civilization, as stated in the English translation:
> First, survival is the primary need of civilization. Second, civilization continuously grows and expands, but the total matter in the universe remains constant.
From these axioms, the nature of interstellar society is derived, and the motivation for the Trisolaran invasion is revealed. So the logic goes, each civilization, removed from each other by literal light-years in space, and figurative light-years in culture and philosophy, lacks the tools for meaningful communication with one another. Furthermore, these civilizations are in competition for resources, as each is expected to grow exponentially to consume more and more of the finite resources the universe has on offer. Thus, we have established that each civilization constitutes a threat to the others, and lacks access to diplomatic options.
So ubiquitous is this truth in Liu's universe that it is leveraged to strategic ends. For instance, humanity constructs a gravitational wave transmitter¹ which will broadcast the location of Earth to the galaxy as a whole, assuring mutual destruction should the Trisolaran's threaten humanity. Furthermore, the theory is weaponized: by broadcasting the coordinates of a distant star into space, a character instigates a higher interstellar civilization to pre-emptively attack and destroy the star under the presumption that life exists there, and was foolish enough to let everyone else know about it.
This paints a grim understanding of the universe and our role in it, and it makes me uncomfortable when people treat this fictional plot device as a truth about our own universe. The problem lies with the second axiom:
> Civilization continuously grows and expands, but the total matter in the universe remains constant.
Sure, the total amount of matter in the universe is constant. But does civilization actually grow and expand continuously? No evidence is provided to support this assertion.
In practice, we actually see that the opposite is true. Life seeks to endure, but humanity — the only known sample of intelligent civilization — does not grow without bound. Population growth is already slowing, and the scientific consensus is that the world population will stabilize within the 21st century. Social and economic development, along with a higher standard of living — all of which I would take as a pre-requisite of any higher civilization — is strongly associated with lower birth rates in humans.²
Furthermore, the situation presented in the novels is very unusual, something the novels themselves emphasize. The Trisolaran civilization is under pressure due to their unfortunate circumstances within a trinary star system's chaotic gravity well, which drives them to invade Earth. Even within the novel's axioms, this situation would be very rare! The usual outcome, per the hypothesis, would be that humanity is simply destroyed from afar should it be foolish enough to broadcast its location to the universe, not that it is invaded for its resources.
But why should the universe be so cruel? Even within our solar system, we posess stunning access to resources. The sun alone has a power output of 3.83×10^26 watts! Humanity today uses only 2.1×10^12 watts, so we must by 100,000,000,000,000× before we would have to consider going somewhere else for energy. That assumes we make zero gains in the efficiency of our machines, too. We have three other rocky planets to occupy, and plenty of moons, plus the asteroid belt, and countless objects in the Oort cloud, collectively representing an area many times larger than the Earth: there's no shortage of real estate. There are 2.784×10^27 kg of mass here that we can mine to get material resources, too. Even assuming that nearby stars are also occupied, and therefore we cannot exploit their resources, we can grow for a very, very long time — and science tells us that we probably won't!
Here's what I think would actually happen in the scenario presented by the books: the greatest refugee crisis in history. Humanity is not great at dealing with these, for sure, but the situation changes when the stakes are different. The Trisolarans are a more advanced civilization than humanity, and has a lot of technology to tempt us with. Moreover, they're armed. We would see an international humanitarian (or... gentiatarian?) movement to prepare for their arrival. The Trisolarans would send us instructions on how to prepare suitable accomodations for them on Mars or in the outer solar system, and we would get to work. We have no shortage of resources, and it will take hundreds of years for them to arrive. Ultimately, the incentives would favor an empathetic approach more than any other.
And what of a more realistic scenario, where intelligent life is more distant, and not looking towards Earth as a solution to their crisis? Well, our communication may be limited, but certainly not to the extent the novel implies. Over a great enough distance, we can communicate much faster than we can send colony ships or intertial mass weapons. The book itself works with the concept of self-describing messages that can be studied on the remote end to establish communication without bi-directional language: such systems can work in reality, too, and thus communications can be established with alien, remote civilizations. And what threat do we really pose to each other? Each of us enjoys a boundless wealth in our slice of the universe. If life out there is anything like us — and remember, we are the only kind of life that we can prove is possible — we should be able to get along with each other.
¹ Side note: how the heck is /that/ supposed to work?
² Aside: a lot of racist people use alarmist views on population growth to justify some horrible ideas. Should you encounter such arguments, you can trivially dismiss them with this fact.