At the Los Alamos National Laboratory in 1950, physicist Enrico Fermi famously posed to his colleagues a simple question borne of complex math: “Where are they?”
He was asking about aliens—intelligent ones, specifically. The Italian-American scientist was puzzled as to why mankind hasn’t detected any signs of intelligent life beyond our planet. He reasoned that even if life is extremely rare, you’d still expect there to be many alien civilizations given the sheer size of the universe. After all, some estimates indicate that there is one septillion, or 1,000,000,000,000,000,000,000,000, stars in the universe, some of which are surrounded by planets that could probably support life.
So, where are they, and why aren’t they talking to us?