Earth-like planets are common.
Metrodorus of Chios quoted by Joel Achenbach. "Life Beyond Earth," National Geographic, Jan 2000.
Seth Shostak.
Sharing the Universe: Perspectives on Extraterrestrial Life,
(Berkeley: Berkeley Hills Books, 1998), 7-11.
Earth is rare.
Donald Brownlee and Peter D. Ward.
Rare Earth: Why Complex Life is Uncommon in the Universe,
(New York: Copernicus Books, 2000), xi.
Geoff Marcy. E-mail with NOVA producer Julia Cort. 7 June 2004.
Mayr, Ernst. "The Search for Extraterrestrial Intelligence."
Extraterrestrials: Where are They? 2nd ed., Eds.
Ben Zuckerman and Michael H. Hart (Cambridge: Press Syndicate of the
University of Cambridge, 1995), 153.
Life flourishes in hostile places.
David Darling.
Life Everywhere: The Maverick Science of Astrobiology, (New
York: Basic Books, 2001), xi.
Robert Ballard.
Explorations: My Quest for Adventure and Discovery Under the
Sea, (New York: Hyperion, 1995).
Life flourishes in hostile places, but not complex life.
Mayr, Ernst. "The Search for Extraterrestrial Intelligence."
Extraterrestrials: Where are They? 2nd ed., Eds.
Ben Zuckerman and Michael H. Hart (Cambridge: Press Syndicate of the
University of Cambridge, 1995), 153.
Ian Crawford, "Where Are They?" Scientific American (July 2000): 43.
Donald Brownlee and Peter D. Ward.
Rare Earth: Why Complex Life is Uncommon in the Universe,
(New York: Copernicus Books, 2000), xxvi.
Intelligence is likely.
David Darling.
Life Everywhere: The Maverick Science of Astrobiology, (New
York: Basic Books, 2001), 140-141
Seth Shostak, "Intelligent Aliens?" Space.com, 30 May 2002, (9 June 2004).
Roger Hanlon, interview by NOVA producer Julia Cort.
Origins: Where Are the Aliens?, NOVA: Public Broadcasting
System, 29 September 2004.
Intelligence is unlikely.
Stephen Jay Gould,
Wonderful Life: The Burgess Shale and the Nature of History,
(New York: W. W. Norton, 1989).
Mayr, Ernst. "The Search for Extraterrestrial Intelligence."
Extraterrestrials: Where are They? 2nd ed., Eds.
Ben Zuckerman and Michael H. Hart (Cambridge: Press Syndicate of the
University of Cambridge, 1995), 154.
Jared Diamond. "Alone in a Crowded Universe,"
Extraterrestrials: Where are They? 2nd ed., Eds.
Ben Zuckerman and Michael H. Hart (Cambridge: Press Syndicate of the
University of Cambridge, 1995), 163.
Peter Ward, NOVA interview by Neil Tyson. 2004.
Alien civilizations are likely to be advanced.
Paul Davies.
Are We Alone? Philosophical Implications of the Discovery of
Extraterrestrial Life. (New York: BasicBooks, 1995), 48.
Seth Shostak.
Sharing the Universe: Perspectives on Extraterrestrial Life,
(Berkeley: Berkeley Hills Books, 1998), 96.
Alien civilizations are likely to be gone.
Joel Achenbach. "Life Beyond Earth," National Geographic, Jan 2000.
Jared Diamond. "Alone in a Crowded Universe,"
Extraterrestrials: Where are They? 2nd ed., Eds.
Ben Zuckerman and Michael H. Hart (Cambridge: Press Syndicate of the
University of Cambridge, 1995), 163.
Donald Brownlee and Peter D. Ward.
Rare Earth: Why Complex Life Is Uncommon in the Universe,
(New York: Copernicus Books, 2000), xxvii.
Aliens haven't visited because they can't or don't want to.
David E. Fisher and Marshall Jon Fisher.
Strangers in the Night (Washington, D.C.: Counterpoint,
1998), 257.
Paul Davies.
Are We Alone? Philosophical Implications of the Discovery of
Extraterrestrial Life. (New York: BasicBooks, 1995), 72.
Seth Shostak.
Sharing the Universe: Perspectives on Extraterrestrial Life,
(Berkeley: Berkeley Hills Books, 1998), 5.
If aliens existed, they would have visited.
Sebastian von Hoerner, "The Likelihood of Interstellar Colonization"
Extraterrestrials: Where are They? 2nd ed., Eds.
Ben Zuckerman and Michael H. Hart (Cambridge: Press Syndicate of the
University of Cambridge, 1995), 30.
Ian Crawford, "Where Are They?" Scientific American (July 2000): 42.
SETI hasn't succeeded because the search has just begun.
David E. Fisher and Marshall Jon Fisher.
Strangers in the Night (Washington, D.C.: Counterpoint,
1998), 260-261
Frank Drake and Dava Sobel. Is Anyone Out There? (New York:
Delacorte Press, 1992), 235-236.
Seth Shostak.
Sharing the Universe: Perspectives on Extraterrestrial Life,
(Berkeley: Berkeley Hills Books, 1998), 12.
SETI's quest is futile
George W. Swenson, Jr., "Intergalactically Speaking," Scientific American: (July 2000), 47.
Paul Davies.
Are We Alone? Philosophical Implications of the Discovery of
Extraterrestrial Life. (New York: BasicBooks, 1995), 71.
Jared Diamond. "Alone in a Crowded Universe,"
Extraterrestrials: Where are They? 2nd ed., Eds.
Ben Zuckerman and Michael H. Hart (Cambridge: Press Syndicate of the
University of Cambridge, 1995), 164.
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