1. A note about terminology: Historically the search for technosignatures was called CETI (communication with extraterrestrial intelligence) in the 1960s and early 70s. It slowly transitioned to SETI (search for extraterrestrial intelligence) shortly after a US‐USSR conference in 1971. Today the term “technosignatures” is becoming favored as a compliment to the term “biosignatures” in exoplanetary research. For historical accuracy this chapter will predominantly use “CETI” when discussing work conducted in the 1960s.
2. Contact with Alien Civilizations