Running into an alien on the bus would be strange — but it’s almost equally strange that humankind has never encountered aliens. The universe is vast. Can we really be alone in it?
Think about it: What are the chances that life on Earth is the only life in the impossibly gigantic universe? There are probably 100 Earth-like planets for every grain of sand in the world, yet we’ve never even heard from an extraterrestrial life form. No “Hey” — not even a “U up?” Why?
We’re not the first people to wonder. Enrico Fermi, a Nobel Prize-winning physicist, also thought it was odd. As he famously put it to his friends in the cafeteria one day: “Where is everybody?” In 1950, this became formalized as the Fermi paradox. How can we have not one scrap of evidence aliens exist, when it’s overwhelmingly likely that they do?
You might assume aliens are just too far away, but Fermi wasn’t swayed by that argument. An alien civilization with a solid space program could make rapid imperial progress, Fermi argued. He estimated it would take just 10 million years for an alien civilization to take over our entire galaxy. They’ve had tons of chances when you consider that the Milky Way Galaxy has been around for 10 billion years.
One explanation of the Fermi paradox is the zoo hypothesis. It’s admittedly a freaky situation to consider, but here it is: aliens know we earthlings are here, but they’re purposely avoiding contact with us, opting to study us from afar instead.
This hypothesized answer to the Fermi Paradox was proposed by MIT astronomer John A. Ball in 1973. It’s named the zoo hypothesis because it suggests that all life on Earth is just like an animal (or, you know, a few billion animals) at the zoo — look, but don’t touch! Ball suggests that maybe alien civilizations are advanced enough to know not to influence our primitive society, or not to get involved with other intelligent lifeforms.
Overall, Ball laid out 10 possible solutions to Fermi’s Paradox. The zoo hypothesis covers just two of them: in one, aliens find us “of some interest” and study us casually; in the other, aliens find us “interesting” and pay closer attention. In both scenarios, though, they’re actively avoiding us. Harsh.
In an even harsher solution, outside the zoo hypothesis, aliens know about us and don’t care. In this scenario, “We pose no threat, and we have nothing they want,” Ball writes. “This is a likely but a very unpopular answer, for it seems to downgrade mankind’s importance, and we do like to feel important.”
A more popular answer to the Fermi Paradox is that alien life is still very primitive or has already come and gone. At this point, it’s really anyone’s guess. So if you want to assume we’re a Very Important Species, at this point, go ahead. Why not?