A new theory suggests that there is a very good reason why we haven’t been visited by aliens, even though there is a strong chance that they exist, scientists believe. Radio astronomer John A. Ball from the Massachusetts Institute of Technology has put forward the “Zoo Theory,” which promotes the idea that aliens know we’re here, they just choose not to contact us.

Ball thinks that aliens almost certainly exist, but they’ve decided to monitor human activity rather than interact with us. The reason is similar to the reason that us humans merely observe the activities of animals in a zoo, rather than treat them as peers to communicate with, according to this theory.

It’s a theory that might help answer the Fermi Paradox, which describes the contradiction apparent in certain scientific circles where it seems that alien existence seems inevitable, as does interstellar travel, but for some reason they haven’t made contact with us. It’s a wild idea, but it might explain why we’ve seen UFOs but have not made any contact with this alien species.

“The zoo hypothesis speculates as to the assumed behavior and existence of technically advanced extraterrestrial life and the reasons they refrain from contacting Earth and is one of many theoretical explanations for the Fermi paradox,” reads a Wikipedia excerpt on the zoo hypothesis. “The hypothesis is that alien life intentionally avoids communication with Earth, and one of its main interpretations is that it does so to allow for natural evolution and sociocultural development, avoiding interplanetary contamination. The hypothesis seeks to explain the apparent absence of extraterrestrial life despite its generally accepted plausibility and hence the reasonable expectation of its existence.”