Searching for extraterrestrial intelligence across a century

Abstract Exobiology is a burgeoning research field. There is a realistic prospect that in a decade or two we will have the capability to detect biosignatures – non-equilibrium atmospheric chemistry, vegetation etc. – for the nearest exoplanets. But of course what is most interesting of all would be some techno -signatures, indicating not just ‘life’, but intelligent life. This paper offers some introductory comments on this topic.