People have been discussing the "dark forest hypothesis", a potential solution to the Fermi paradox, finding it either cool, terrifying, or hilarious.
If you haven't heard of the Fermi paradox, this is the simple version: with all the stars, space, and time in the universe allowing for the possibility of alien life, how come we have not found any signs of it? If there is intelligent life out there, why has nobody got in touch?
Answers range from the frustrating (the oxygen bottleneck could keep aliens trapped in the stone age) to the terrifying (what if there is no paradox at all). The dark forest hypothesis, a piece of speculation on the topic outlined in Liu Cixin's sci-fi novel The Dark Forest, falls towards the creepier end of the spectrum.
In the book, the second in the Three Body Problem series (also known as Remembrance of Earth's Past), conversations take place between a sociology professor and former astronomer, and their dead friend's mother.
The professor states that life will always strive to stay alive, and there is no way of knowing the intentions of other alien species. Some could be benevolent, some could be hostile. Even if the life out there isn't hostile, it will still be expanding in a universe with limited resources, increasing the likelihood of conflict with others who need those same resources.
Given these factors, the book suggests, all intelligent life is left with the safest course of action: to wipe out any other lifeforms before they can do the same to them.
“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 other life – another hunter, an angel or a demon, a delicate infant or a tottering old man, a fairy or a demigod – there’s only one thing he can do: open fire and eliminate them," a key passage from the book reads.
"In this forest, hell is other people. An eternal threat that any life that exposes its own existence will be swiftly wiped out. This is the picture of cosmic civilization. It’s the explanation for the Fermi Paradox.”
This doesn't mean that we haven't heard from other species because they have all been wiped out, the book argues. If even one species out there acts like this, destroying others for resources or sport, it makes sense for all others to keep quiet, and not advertise their existence to others.
Which, as people are pointing out, is not what humans have been doing.
As Greg Bear's sci-fi book The Forge of God put it when killer probes are found, "We’ve been sitting in our tree chirping like foolish birds for over a century now, wondering why no other birds answered. The galactic skies are full of hawks, that’s why."
However there is one factor that the book expands on – that though wiping out others before they can do the same to you is the most rational course of action, aliens may not do it for practical reasons. Say you send out a fleet of destroyers to another star system. By the time it gets there, your fleet will remain at the same technological level you sent it, while the people you are attacking will have advanced by centuries or even millennia.
As such, it may be beneficial to most civilizations to simply sit out there like many other forms of benevolent lifeforms, all hiding themselves in the forest in fear.
An earlier version of this article was published in April 2021.