Carl Edward Sagan (November 9, 1934 - December 20, 1996) was an American astronomer who pioneered exobiology and promoted the Search for Extraterrestrial Intelligence (SETI) and science in general. He is less well known for his skepticism.
Carl Sagan with a model of the Viking Lander. ()
Photo credit: Jet Propulsion Laboratory, free for non-commercial use.
He was born in Brooklyn, New York. His father was a Jewish garment worker and his mother a housewife. Sagan attended the University of Chicago, where he received a bachelor's degree (1955) and a master's degree (1956) in physics, before earning his doctorate (1960) in astronomy and astrophysics. He taught at Harvard University until 1968, when he moved to Cornell University.
Sagan became a full professor at Cornell in 1971 and directed a lab there. He contributed to most of the unmanned space missions that explored our solar system. He conceived the idea of adding an unalterable and universal message on spacecraft destined to leave the solar system, that could be understood by any extraterrestrial intelligence that might find it. The first message that was actually sent out into space was a gold-anodized plaque on board of the space probe Pioneer 10. He continued to refine his designs and the most elaborate such message he helped to develop was the Voyager Golden Record that was sent out with the Voyager space probes.
He was well known as a coauthor of the paper that warned of the dangers of nuclear winter. He furthered insights regarding the atmosphere of Venus, seasonal changes on Mars, and Saturn's moon Titan. He established that the atmosphere of Venus is extremely hot and dense. He also perceived global warming as a growing, man-made danger and likened it to the natural development of Venus into a hot life-hostile planet through greenhouse gases. He suggested that Titan and Jupiter's moon Europa may contain oceans (a subsurface ocean in the case of Europa) or lakes that provide the foundations of life. He suggested that the seasonal changes on Mars were due to windblown dust.
His interest in these topics was in large part motivated by his interpretation of the Drake equation and the Fermi paradox. He believed that the Drake Equation suggested that a large number of extraterrestrial civilizations would form, but that the lack of evidence of such civilizations suggests that technological civilizations tend to destroy themselves rather quickly. This stimulated his interest in identifying ways that humanity could destroy itself, with the hope of avoiding such destruction and eventually becoming a space-faring species.
Sagan's capability to convey his ideas allowed many people to better understand the cosmos. He delivered the 1977/1978 Christmas Lectures for Young People at the Royal Institution. He wrote (with Ann Druyan, whom he later married) and narrated the highly popular thirteen part PBS television series Cosmos; he also wrote books to popularize science (The Dragons of Eden (which won a Pulitzer Prize), Broca's Brain, etc.) and a novel, Contact, that was a best-seller and had a film adaptation starring Jodie Foster in 1997. The film won the 1998 Hugo award. From Cosmos Sagan became associated with the catchphrase "billions and billions" which he never actually used in the television series. (He simply often used the word "billions.") He wrote "Pale Blue Dot: A Vision of the Human Future in Space", which was selected as a notable book of 1995 by The New York Times. Under the pseudonym "Mr. X", Sagan wrote an essay concerning pot smoking in the 1971 book "Reconsidering marijuana". Lester Grinspoon (the book's editor), disclosed this to Keay Davidson, Sagan's biographer. Sagan commmented that marijuana encouraged some of his works and enhanced experiences.
Sagan was a proponent for the investigation seeking extraterrestrial life. He urged the scientific community to listen with large radio telescopes for signals from intelligent extraterrestrial lifeforms. He advocated sending probes to other planets. Sagan was Editor in Chief of Icarus (a professional journal concerning planetary research) for 12 years. He cofounded the Planetary Society, a society created to do major research in radio communication with extraterrestrial life, robotic exploration on Mars, the investigation of asteroids near the Earth. Carl Sagan was a member of the SETI Institute Board of Trustees.
Sagan caused mixed reactions among other professional scientists. On the one hand, there was general support for his popularization of science, his efforts to increase scientific understanding among the general public, and his positions in favor of skepticism and against pseudoscience. On the other hand, there was some unease that the public would misunderstand some of the personal positions and interests that Sagan took as being part of the scientific consensus rather than his own personal views, and there was some unease, which some believe to have been motivated in part by professional jealousy, that scientific views contrary to those that Sagan took (such as on the severity of nuclear winter) were not being sufficiently presented to the public.
Sagan did support theories about nuclear winter, global warming, and asteroids impacting the Earth. He was an early supporter of the Global Warming Theory. He also was a proponent of the Nuclear Winter Theory. Both theories are disputed in the scientific community. Some issues he commented on are open to doubt and suspicion (his comments on the Kuwait oil well fires during the first Gulf War were shown later to be in error).
Late in his life, Sagan's books developed his skeptical/atheist view of the world. Works from this period include The Demon-Haunted World: Science as a Candle in the Dark and Billions and Billions: Thoughts on Life and Death at the End of the Millennium, which includes Ann Druyan's account of Sagan's death as a non-believer. He develops tools for testing arguments and detecting fallacious or fraudulent arguments, presented in The Demon-Haunted World. He states that when new ideas are offered for consideration, they should be tested by means of skeptical thinking. If the new ideas continue in existence after examination by the propositions, he states that they should be acknowledged as suppositions. The tools for skeptical thinking essentially are means to construct, understand, reason, and recognize valid and invalid arguments. Conclusions emerging from a premise, and the validity of the premise, should not be discounted or accepted because of favor. Wherever possible there must be independent validation of the concepts whose truth can be proved. He believed that reason and logic would succeed once the truth is known.
Sagan was known to have a bit of an ego. In 1994, Apple Computer began developing the Power Macintosh 7100. They chose the internal code name “Sagan”, in honor of the astronomer. Though the project name was strictly internal and never used in public marketing, when Sagan learned of this internal usage, he sued Apple Computer to use a different project name. Though Sagan lost the suit, Apple engineers complied with his demands anyway, renaming the project "Butthead Astronomer". Sagan sued Apple for libel over the new name, claiming that it subjected him to contempt and ridicule. Sagan lost this lawsuit as well.
After a long and difficult fight with myelodysplasia, Sagan died at the age of 62, on December 20, 1996. Sagan was a significant figure, and his supporters credit his importance to his popularising the natural sciences, opposing both restraints on science and reactionary applications of science, defending democratic traditions, resisting nationalism, defending humanism, and arguing against geocentric and anthropocentric views.
The landing site of the unmanned Mars Pathfinder spacecraft was renamed the Carl Sagan Memorial Station in honor of Dr. Sagan on July 5, 1997. Asteroid 2709 Sagan is named in his honor.
Lynn Margulis was the first wife of Carl Sagan, and mother of Dorion Sagan.
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Awards and Medals
Related Books and Media
External Links
See also : Ann Druyan, Contact, Cosmos: A Personal Voyage, Extraterrestrial life, First contact, Lynn Margulis, Nuclear winter, Voyager Golden Record
