It seems that we are completely alone in the universe. But simple reasoning suggests that there should be an abundance of alien civilizations. Maybe they’re all out there, but they are keeping their distance. Welcome to the zoo (hypothesis).
The story goes that in the summer of 1950, eminent physicist Enrico Fermi was visiting colleagues at Los Alamos National Laboratory. It was the initial peak of UFO mania, and naturally the physicists brought it up over lunch. After a short while, Fermi went silent. Later, well after the conversation had turned to other topics, he exclaimed “Where is everybody?”
Everybody knew what he meant. We know that the universe is capable of producing intelligent life. We’re literally living proof of that. But the cosmos tends to not do things just once. If life happened here, it likely also happened elsewhere. In fact, given the extraordinary age of the universe and the incredible number of stars and planetary systems in any given galaxy, the Milky Way should be abuzz with intelligent space-faring civilizations.
Humanity itself is right on the cusp of developing a sustained interplanetary presence, and our species is still in its youth, at least as cosmic reckoning is concerned. We should see evidence for other intelligent species everywhere: radio signals, megastructures, wandering probes, and so on.
But we’ve got nothing. So where is everybody?
Perhaps the strangest possible solution to Fermi’s paradox, as this conundrum came to be known, is known as the zoo hypothesis. In this idea, alien life is indeed common, as is intelligence. There really is no huge barrier to intelligent creatures developing spaceflight capabilities and spreading themselves throughout the galaxy.
But the reason that we don’t see anybody is that they are intentionally hiding themselves from us. Through their sophisticated observations, they can easily tell that we are intelligent ourselves, but also somewhat dangerous. After all, we have peaceful space rockets and dangerous ICBMs. We are just dipping our toes into space, and we may not be exactly trustworthy.
And so the intelligent civilizations of the galaxy are keeping us in a sort of “zoo.” They are masking themselves and their signals, making us think that we’re all alone, largely confined to our own solar system and a few nearby stars.
Once we prove ourselves, the hypothesis goes, we’ll be welcomed into the larger galactic community with open arms (or tentacles).
The zoo hypothesis is, honestly, a little far-fetched. It assumes not only the existence of alien civilizations, but also their motives and intentions. But we ultimately do not know if we are alone in the universe. And there’s only one way to find out.