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The L Factor: Hope and Fear in the
Search for Extraterrestrial Intelligence


Charles T. Rubin




The 'L' factor in the Drake equation, which estimates the period of time a civilization capable of extraterrestrial communication is detectable, is widely understood to account for most of the variance in estimates of the number of ETIs that might be contacted.  It is also among the hardest to quantify on the basis of any empirical information.  Failure to achieve contact to date has led to speculation concerning the propensity of technological civilizations to destroy themselves or to loose interest in communication, thus producing relatively short L’s.  An examination of such discussions of the L factor in the popular and technical SETI literature suggests that attempts to think about L involve a variety of potentially conflicting assumptions about civilizational lifespan that tend to reflect hopes and fears about the human future.  Hopes for an indefinitely prolonged civilization, even if an insular one, is the other side of the coin of fears about self-destruction.  In addition, arguments for short L’s prove to be difficult to square with the assumption of mediocrity and anti-anthropomorphism.



SETI, Drake equation, L-factor, mediocrity.


  • The paper (author Web site)


Principal Author Biography

Dr. Charles T. Rubin is an Associate Professor of Political Science at Duquesne University, Graduate Faculty in Duquesne’s Graduate Center for Social and Public Policy, and an Associate of Duquesne’s Center for Environmental Research and Education.  He is author of The Green Crusade: Rethinking the Roots of Environmentalism (Rowman and Littlefield), and editor of Conservation Reconsidered: Nature, Virtue and American Liberal Democracy (Rowman and Littlefield).  In addition to his work on environmentalism, his studies focus on topics at the intersection of political philosophy and public policy such as sprawl and city planning theory, the problem of earth/asteroid collisions, and the scientific search for extraterrestrial intelligence


Principal Author Affiliation

Charles Rubin
Duquesne University
Department of Political Science
Pittsburgh, PA 15282
Tel: (412) 396-6485
Fax: (412) 396-4285
Email: ctrubin@worldnet.att.net


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