Michael H. Hart (born April 27, 1932) is an American astrophysicist and author, most notably of The 100: A Ranking of the Most Influential Persons in History.
Hart published in 1975 a detailed examination of the Fermi paradox: the contrast between the extreme likelihood of extraterrestrial life somewhere in the universe and the total absence of any evidence for this. Hart’s work has since become a theoretical reference point for much of the research into what is now sometimes known as the Fermi-Hart paradox. Concerning Hart's contributions to the study of the paradox, Geoffrey A. Landis writes: "A more proper name for [the paradox] would be the Fermi-Hart paradox, since 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; he argues that it is not the work of Fermi, nor is it an actual paradox (rather an argument). He views Hart as the proper originator of this argument, in his 1975 paper. Gray therefore proposes, that instead of the (standard, but in his view incorrect) name Fermi paradox, it should be known as the Hart-Tipler argument–acknowledging Hart's priority as the argument's originator, but also acknowledging Frank J. Tipler's substantial extension of Hart's arguments in his 1980 paper Extraterrestrial intelligent beings do not exist.
Hart is an advocate of the Rare Earth hypothesis; he proposed a very narrow habitable zone based on climate studies. He advocated for this hypothesis in the influential book which he co-edited, "Extraterrestrials: Where are They", in particular in the chapter he contributed to it "Atmospheric Evolution, the Drake Equation and DNA: Sparse Life in an Infinite Universe".
Hart's first book was The 100: A Ranking of the Most Influential Persons in History (1978), which has sold more than 500,000 copies and been translated into many languages. The first person on Hart's list was Muhammad, chosen over Jesus or Moses. Hart attributes this to the fact that Muhammad was "supremely successful" in both the religious and secular realms. He also accredits Muhammad for his role in the development of Islam, far more influential than Jesus' contribution to the development of Christianity. Hart claims that St. Paul was more pivotal than Jesus to the growth of Christianity.
His fourth book, Understanding Human History, was called "racist" by the Southern Poverty Law Center.
Hart has described himself as a white separatist and is active in white separatist causes. In 1996, Hart addressed a conference organized by Jared Taylor's white separatist organization, New Century Foundation, publisher of American Renaissance. He proposed partitioning the United States into four states: a white state, a black state, a Hispanic state, and an integrated mixed-race state.
At the 2006 American Renaissance conference, Hart, who is Jewish, had a public confrontation with David Duke, the former Grand Wizard of the Ku Klux Klan and former Louisiana state representative, over Duke's antisemitic remarks. Accounts of the conference say that Hart stood up, called Duke a Nazi (with expletive) and stormed out.
Hart organized a conference held in Baltimore in 2009 with the title, Preserving Western Civilization. It was billed as addressing the need to defend "America's Judeo-Christian heritage and European identity." Invited speakers included: Lawrence Auster, Peter Brimelow, Steven Farron, Julia Gorin, Lino A. Graglia, Henry C. Harpending, Roger D. McGrath, Pat Richardson, J. Philippe Rushton, Srdja Trifković, and Brenda Walker.