Episode 5: The Search for Signatures

In the search for life and intelligence beyond Earth, astronomers look for telltale “signatures.” These include the chemical elements that we associate with life as we know it and its biological functions (“biosignatures), and indications of technological activity (“technosignatures”) as we would recognize it. At present, the search for signatures is limited by two factors: the limits of our instrumentation, and the limits of our frame of reference.