The Fermi paradox is the apparent contradiction between high
estimates of the probability of the existence of
extraterrestrial civilizations and the lack of evidence for, or
contact with, such civilizations. As Enrico Fermi asked if the
Universe is conducive to intelligent life, “Where is everybody?”
“Intelligent species might reasonably worry about the possible
dangers of self-advertisement and hence incline towards
discretion” -- the “Undetectability Conjecture,” put forth by
Beatriz Gato-Rivera, a theoretical physicist at the Instituto de
Fisica Fundamental (previously Instituto de Matematicas y Fisica
Fundamental) of the CSIC (Spanish Scientific Research Council)
in Madrid. According to Gato-Rivera, we may find ourselves in a
universe in which there exist intelligent technological
civilizations but they have chosen to be undetectable,
camouflaging themselves mainly for security reasons (because
advanced civilizations could also be aggressive). “Evolutionary
selection, acting on a cosmic scale," Kent adds.