Dark forest hypothesis
The dark forest hypothesis is the conjecture that many alien civilizations exist throughout the universe, but they are both silent and hostile, maintaining their undetectability for fear of being destroyed by another hostile and undetected civilization.[1] It is one of many possible explanations of the Fermi paradox, which contrasts the lack of contact with alien life with the potential for such contact. The hypothesis derives its name from Liu Cixin's 2008 novel The Dark Forest,[2] although the concept predates the novel.[3][4][5]
Concept[edit]
The "dark forest" hypothesis presumes that any space-faring civilization would view any other intelligent life as an inevitable threat and thus destroy any nascent life that makes itself known. As a result, the electromagnetic spectrum would be relatively quiet, without evidence of any intelligent alien life.[9][10]
A similar hypothesis, under the name "deadly probes", was described by astronomer and author David Brin in his 1983 summary of the arguments for and against the Fermi paradox.[11]
The name of the hypothesis derives from Liu Cixin’s 2008 novel The Dark Forest,[12] as in a "dark forest" filled with "armed hunter(s) stalking through the trees like ghosts".[13][14] Since the intentions of any newly contacted civilisation can never be known with certainty, meaning that, if one is encountered, it is best to shoot first and ask questions later, in order to avoid the potential extinction of one’s own species. The novel provides a detailed investigation of Liu's concerns about alien contact.[2]
Relationship to other proposed Fermi paradox solutions[edit]
The Berserker hypothesis, also known as the deadly probes scenario, proposes self-reproducing machines seek to destroy organic life.[3]: 112 The name derives from short stories by Fred Saberhagen written in the 1960s. The dark forest hypothesis is distinct from the Berserker hypothesis in that under the former, many alien civilizations could still exist provided they keep silent. The former can be viewed as a special case of the latter, if the deadly probes are (e.g. due to resource scarcity) only sent to star systems that show signs of intelligent life.[9]
Game theory[edit]
The dark forest hypothesis is a special case of the "sequential and incomplete information game" in game theory.[15][10][16]
In game theory, a "sequential and incomplete information game" is one in which all players act in sequence, one after the other, and none are aware of all available information.[17] In the case of this particular game, the only win condition is continued survival.[9] An additional constraint in the special case of the "dark forest" is the scarcity of vital resources.[10] The "dark forest" can be considered an extensive-form game with each "player" possessing the following possible actions: destroy another civilization known to the player; broadcast and alert other civilizations of one's existence; or do nothing.[15]