“…This extended perspective now brings clearly into view the closely-related multi-disciplinary 'sibling' fields of SETI, the Search for Extra-Terrestrial Intelligence (e.g., Ekers et al 2002;Harrison 2009;Morrison, Billingham & Wolfe 1979;Shklovskii & Sagan 1966;Tarter 2001Tarter , 2004Tarter et al 2010), and Astrobiology, the study of how life might arise and evolve in the Universe (e.g., Chyba & Hand 2005;Domagal-Goldman et al 2016;Mix et al 2006). In this expanded conception, then, we are-here on our "pale blue dot" (Sagan 1995)-simply a single 'element' (in the language of set theory) of what may be a set of intelligent technology-using civilisations, which itself forms a sub-set of intelligent lifeforms in general (i.e., not necessarily technology-using), which itself forms a sub-set of lifeforms in general (i.e., not necessarily intelligent), which arise on places/planets where lifeforms could arise (i.e., habitable planets, in general).…”