The Great Filter – Is it just a matter of time?

Abstract The discussion on the second day of the symposium centred on the Great Filter, a concept proposed by Robin Hanson as a way to reframe the analysis of the Fermi Paradox. It asserts that there must be a least one Great Filter – an evolutionary step that is extremely improbable – somewhere along a chain which starts from a lifeless Earth-like planet, followed by the sequential development of simple, complex, intelligent/technological life, and culminating in an explosive phase of readily-detectable galactic colonization. Some 25 years on from Hanson’s proposal, we examine the Great Filter’s continuing usefulness as a concept and current thinking on whether any such filter lies in our past (Early Great Filter), or is waiting in our future (Late Great Filter), and what this means for us and our search for life in the Universe.