ZOO HYPOTHESIS, proposition that super-advanced forms of alien life exist but are deliberately hiding from us. It is one attempt to solve the “Fermi paradox.” In 1950 during a lunchtime conversation with colleagues, nuclear physicist Enrico Fermi was speculating aloud about the possibility of high-speed space travel and alien life. All present agreed that, given the vastness of space, the nearly incalculable age of the universe, and the large number of planets orbiting their stars in the so-called habitable zone, the existence of extraterrestrial civilizations capable of interplanetary space travel and communication was not only possible but statistically likely. Whereupon Fermi wondered: “But where is everyone?”
In other words, if aliens have the technological capability to contact us, why haven’t they? Should the absence of such attempts be taken as evidence that no such beings exist, or is there another explanation? Many hypothetical answers to the Fermi paradox have been proffered: that intelligent life exists but is very rare, that advanced societies survive so briefly that overlap between them is unlikely, that aliens have been trying to contact us but with signals we’re unable to read, and even that the impulse to colonial expansion is uniquely human.
The zoo hypothesis, first proposed by astrophysicist John Allen Ball in 1973, posits that advanced alien lifeforms do exist and are aware of Earth, but are deliberately not making contact to avoid disturbing Earth’s natural development. In doing so they are thus acting as a species of zookeeper or wildlife conservationist, protecting Earth from outside interference.
A criticism of this logic is that all alien species would need to share the same motivation. This could only be explained by the existence of some kind of galactic confederation with rules of engagement regarding less technologically advanced societies à la Starfleet’s “Prime Directive” in Star Trek. Another criticism is that the hypothesis is almost impossible to prove or disprove given that the aliens do not want to be discovered and have the technology to remain undetectable.