Fermi paradox
Michael H. Hart published in 1975 a detailed examination of the paradox, which has since become a theoretical reference point for much of the research into what is now sometimes known as the Fermi–Hart paradox. Geoffrey A. Landis prefers that name on the grounds that "while Fermi is credited with first asking the question, Hart was the first to do a rigorous analysis showing that the problem is not trivial, and also the first to publish his results". Robert H. Gray argues that the term "Fermi paradox" is a misnomer, since in his view it is neither a paradox nor due to Fermi; he instead prefers the name Hart–Tipler argument, acknowledging Michael Hart as its originator, but also the substantial contribution of Frank J. Tipler in extending Hart's arguments.
Future of Humanity Institute
A recurring theme in FHI's research is the Fermi paradox, the surprising absence of observable alien civilizations. Robin Hanson has argued that there must be a "Great Filter" preventing space colonization to account for the paradox. That filter may lie in the past, if intelligence is much more rare than current biology would predict; or it may lie in the future, if existential risks are even larger than is currently recognized.