Enrico Fermi (1901–1954)
em 1950, ao contestar a idéia que poderiam existir inúmeras formas de vida alienígenas espalhadas pela galáxia. <br class="br">citado em "Where are They? Maybe we are alone in the galaxy after all" by Ian Crawford in Scientific American (Julho de 2000), p. 38-43 (PDF document) http://www.cc.nctu.edu.tw/~tseng327/nctu-origin/article/sc200007a.pdf; veja também "Our Galaxy Should Be Teeming With Civilizations, But Where Are They?" by Seth Shostak at Space.com (25 de outubro de 2001) http://web.archive.org/web/20011107185016/http://www.space.com/searchforlife/shostak_paradox_011024.html