Carl Sagan

Carl Sagan
Born	(1934-11-09)November 9, 1934 Brooklyn, New York, U.S.
Died	December 20, 1996(1996-12-20) (aged 62) Seattle, Washington, U.S.
Nationality	American
Alma mater	University of Chicago
Known for	Search for Extra-Terrestrial Intelligence (SETI) Cosmos: A Personal Voyage Voyager Golden Record Pioneer plaque Contact Pale Blue Dot
Awards	Oersted Medal (1990) NASA Distinguished Public Service Medal (twice) Pulitzer Prize for General Non-Fiction (1978) National Academy of Sciences Public Welfare Medal (1994)
Scientific career
Fields	Astronomy and planetary science
Institutions	Cornell University Harvard University

Carl Edward Sagan, Ph.D. (November 9, 1934 – December 20, 1996) was an American astronomer, astrochemist, author, and highly successful popularizer of astronomy, astrophysics and other natural sciences. He pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI).

He is world-famous for writing popular science books and for co-writing and presenting the award-winning 1980 television series Cosmos: A Personal Voyage, which has been seen by more than 600 million people in over 60 countries, making it the most widely watched PBS program in history. A book to accompany the program was also published. He also wrote the novel Contact, the basis for the 1997 Robert Zemeckis film of the same name starring Jodie Foster. During his lifetime, Sagan published more than 600 scientific papers and popular articles and was author, co-author, or editor of more than 20 books. In his works, he frequently advocated skeptical inquiry, secular humanism, and the scientific method.

A pot head atheist who was a dickhole

Scientific achievements

Carl Sagan's contributions were central to the discovery of the high surface temperatures of the planet Venus. In the early 1960s no one knew for certain the basic conditions of that planet's surface, and Sagan listed the possibilities in a report later depicted for popularization in a Time-Life book, Planets. His own view was that Venus was dry and very hot as opposed to the balmy paradise others had imagined. He had investigated radio emissions from Venus and concluded that there was a surface temperature of 500 °C (900 °F). As a visiting scientist to NASA's Jet Propulsion Laboratory, he contributed to the first Mariner missions to Venus, working on the design and management of the project. Mariner 2 confirmed his conclusions on the surface conditions of Venus in 1962.

Sagan was among the first to hypothesize that Saturn's moon Titan might possess oceans of liquid compounds on its surface and that Jupiter's moon Europa might possess subsurface oceans of water. This made Europa potentially habitable for life. Europa's subsurface ocean of water was later indirectly confirmed by the spacecraft Galileo. Sagan also helped solve the mystery of the reddish haze seen on Titan, revealing that it is composed of complex organic molecules constantly raining down onto the moon's surface.

He further contributed insights regarding the atmospheres of Venus and Jupiter as well as seasonal changes on Mars. Sagan established that the atmosphere of Venus is extremely hot and dense with pressures increasing steadily all the way down to the surface. 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 a kind of runaway greenhouse effect. Sagan and his Cornell colleague Edwin Ernest Salpeter speculated about life in Jupiter's clouds, given the planet's dense atmospheric composition rich in organic molecules. He studied the observed color variations on Mars’ surface and concluded that they were not seasonal or vegetational changes as most believed but shifts in surface dust caused by windstorms.

Sagan is best known, however, for his research on the possibilities of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation.

He is also the 1994 recipient of the Public Welfare Medal, the highest award of the National Academy of Sciences for "distinguished contributions in the application of science to the public welfare."

Scientific advocacy

Planetary Society members at the organization's founding. Carl Sagan is seated second from the right.

Sagan was a proponent of the search for extraterrestrial life. He urged the scientific community to listen with radio telescopes for signals from intelligent extraterrestrial life-forms. So persuasive was he that by 1982 he was able to get a petition advocating SETI published in the journal Science and signed by 70 scientists including seven Nobel Prize winners. This was a tremendous turnaround in the respectability of this controversial field. Sagan also helped Dr. Frank Drake write the Arecibo message, a radio message beamed into space from the Arecibo radio telescope on November 16, 1974, aimed at informing extraterrestrials about Earth.

Sagan was chief technology officer of the professional planetary research journal Icarus for twelve years. He co-founded the Planetary Society, the largest space-interest group in the world, with over 1,000,000 members in more than 149 countries, and was a member of the SETI Institute Board of Trustees. Sagan served as Chairman of the Division for Planetary Science of the American Astronomical Society, as President of the Planetology Section of the American Geophysical Union, and as Chairman of the Astronomy Section of the American Association for the Advancement of Science.

At the height of the Cold War, Sagan became involved in public awareness efforts for the effects of nuclear war when a mathematical climate model suggested that a substantial nuclear exchange could upset the delicate balance of life on Earth. He was one of five authors—the "S" of the "TTAPS" report as the research paper came to be known. He eventually co-authored the scientific paper hypothesizing a global nuclear winter following nuclear war. He also co-authored the book A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race, a comprehensive examination of the phenomenon of nuclear winter.

Sagan erroneously predicted in January 1991 that so much smoke from the Kuwaiti oil fires "might get so high as to disrupt agriculture in much of South Asia…" He acknowledged the error in The Demon-Haunted World: "as events transpired, it was pitch black at noon and temperatures dropped 4–6°C over the Persian Gulf, but not much smoke reached stratospheric altitudes and Asia was spared."

In his later years Sagan advocated the creation of an organized search for near Earth objects that would impact the Earth. When others suggested creating large nuclear bombs that could be used to alter the orbit of an NEO that was predicted to hit the Earth, Sagan proposed the Deflection Dilemma: If we create the ability to deflect an asteroid away from the Earth, then we also create the ability to deflect an asteroid towards the Earth—providing an evil power with a true doomsday bomb.

Social concerns

Sagan believed that the Drake equation, on substitution of reasonable guesstimates, suggested that a large number of extraterrestrial civilizations would form, but that the lack of evidence of such civilizations highlighted by the Fermi paradox suggests technological civilizations tend to destroy themselves rather quickly. This stimulated his interest in identifying and publicizing ways that humanity could destroy itself, with the hope of avoiding such a cataclysm and eventually becoming a spacefaring species. Sagan's deep concern regarding the potential destruction of human civilization in a nuclear holocaust was conveyed in a memorable cinematic sequence in the final episode of Cosmos, called "Who Speaks for Earth?". Following his marriage to his third wife (novelist Ann Druyan) in June 1981, Sagan became more politically active—particularly in regard to the escalation of the nuclear arms race under President Ronald Reagan.

In March 1983, hoping to blunt the momentum of the nuclear freeze movement, Reagan announced the Strategic Defense Initiative—a multi-billion dollar project to develop a comprehensive defense against attack by nuclear missiles, which was quickly dubbed the "Star Wars" program. Sagan spoke out against the project, arguing that it was technically impossible to develop a system with the level of perfection required, and far more expensive to build than for an enemy to defeat through decoys and other means—and that its construction would seriously destabilize the nuclear balance between the United States and the Soviet Union, making further progress toward nuclear disarmament impossible.

When Soviet leader Mikhail Gorbachev declared a unilateral moratorium on the testing of nuclear weapons, which would begin on August 6, 1985—the 40th anniversary of the atomic bombing of Hiroshima—the Reagan administration dismissed the dramatic move as nothing more than propaganda, and refused to follow suit. In response, American anti-nuclear and peace activists staged a series of protest actions at the Nevada Test Site, beginning on Easter Sunday of 1986 and continuing through 1987. Hundreds of people were arrested, including Sagan, who (previously being arrested for participating in an anti-war protest during the Vietnam War) was arrested on two separate occasions as he climbed over a chain-link fence at the Test Site.

Popularization of science

Sagan's capability to convey his ideas allowed many people to better understand the cosmos—simultaneously emphasizing the value and worthiness of the human race, and the relative insignificance of the earth in comparison to the universe. He delivered the 1977/1978 Christmas Lectures for Young People at the Royal Institution. He hosted and, with Ann Druyan, co-wrote and co-produced the highly popular thirteen-part PBS television series Cosmos: A Personal Voyage modeled on Jacob Bronowski's The Ascent of Man.

File:Sagan Viking.jpg

Sagan with a model of the Viking Lander probes which would land on Mars. Sagan examined possible landing sites for Viking along with Mike Carr and Hal Masursky.

Cosmos covered a wide range of scientific subjects including the origin of life and a perspective of our place in the universe. The series was first broadcast by the Public Broadcasting Service in 1980, winning an Emmy and a Peabody Award. It has been broadcast in more than 60 countries and seen by over 600 million people, according to the Science Channel.

Sagan also wrote books to popularize science, such as Cosmos, which reflected and expanded upon some of the themes of A Personal Voyage, and became the best-selling science book ever published in English; The Dragons of Eden: Speculations on the Evolution of Human Intelligence, which won a Pulitzer Prize; and Broca's Brain: Reflections on the Romance of Science. Sagan also wrote the best-selling science fiction novel Contact, but did not live to see the book's 1997 motion picture adaptation, which starred Jodie Foster and won the 1998 Hugo Award.

From Cosmos and his frequent appearances on The Tonight Show, Sagan became associated with the catch phrase "billions and billions". As Sagan himself stated, he never actually used the phrase in the Cosmos series. The closest that he ever came was in the book Cosmos, where he talked of "billions upon billions":

A galaxy is composed of gas and dust and stars — billions upon billions of stars.

— Cosmos, chapter 1, page 3, in Carl Sagan

However, his frequent use of the word billions, and distinctive delivery emphasizing the "b" (which he did intentionally, in place of more cumbersome alternatives such as "billions with a 'b'", in order to distinguish the word from "millions" in viewers' minds), made him a favorite target of comic performers including Johnny Carson, Gary Kroeger, Mike Myers, Bronson Pinchot, Harry Shearer, and others. Frank Zappa satirized the line in the song Be In My Video, noting as well 'atomic light.' Sagan took this all in good humor, and his final book was entitled Billions and Billions which opened with a tongue-in-cheek discussion of this catch phrase, observing that Carson himself was an amateur astronomer and that Carson's comic caricature often included real science.

As a humorous tribute to him, a Sagan has been defined as a humorous unit of measurement equal to at least four billion, since the lower bound of a number conforming to the constraint of billions and billions must be two billion plus two billion. Assuming one uses the short scale definition for billion, there are nearly 100 Sagan (400,000,000,000) stars in the Milky Way galaxy.

In 1994, Apple Computer began developing the Power Macintosh 7100. They chose the internal code name "Carl Sagan", the reference being that the mid-range PowerMac 7100 should make Apple "billions and billions." Though the internal project name was never used in public marketing, it did come up in Usenet postings and news of the name grew from there. When Sagan learned of this he sued Apple Computer to force the use of a different project name. Other models released conjointly had code names such as "Cold fusion" and "Piltdown Man", and Sagan was displeased at being associated with what he considered pseudoscience. (He was at the time writing a book discrediting pseudoscience.) Though Sagan lost the lawsuit Apple engineers complied with his demands anyway and renamed the project "BHA" (for Butt-Head Astronomer). Sagan promptly sued Apple for libel over the new name, claiming that it subjected him to contempt and ridicule, but he lost this lawsuit as well. Still, the 7100 saw another name change: it was finally referred to internally as "LAW" (Lawyers Are Wimps).

Whilst Sagan was outspoken about political issues, the popular perception of his characterisation of large cosmic quantities continued to be a sense of wonderment at the numinousness of space and time as in his phrase "The total number of stars in the Universe is larger than all the grains of sand on all the beaches of the planet Earth", however this famous saying was widely misunderstood, as he was in fact referring, in his Cosmos series, to the world being at a "critical branch point in history where our actions will propagate down through the centuries" as in the following quote from Cosmos: A personal Voyage: Episode 8: Journeys in Space and Time:

Those worlds in space are as countless as all the grains of sand on all the beaches of the earth. Each of those worlds is as real as ours and every one of them is a succession of incidents, events, occurrences which influence its future. Countless worlds, numberless moments, an immensity of space and time. And our small planet at this moment, here we face a critical branch point in history, what we do with our world, right now, will propagate down through the centuries and powerfully affect the destiny of our descendants, it is well within our power to destroy our civilisation and perhaps our species as well.

He wrote a sequel to Cosmos, 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. He appeared on PBS' Charlie Rose program in January 1995. Sagan also wrote an introduction for the bestselling book by Stephen Hawking, A Brief History of Time. Sagan was also known for his popularization of science, his efforts to increase scientific understanding among the general public, and his positions in favor of scientific skepticism and against pseudoscience, such as his debunking of the Betty and Barney Hill abduction. To mark the tenth anniversary of Sagan's passing, David Morrison, a former student of Sagan, recalled "Sagan's immense contributions to planetary research, the public understanding of science, and the skeptical movement" in Skeptical Inquirer.

Personal life and beliefs

In 1966, Sagan was asked to contribute an interview about the possibility of extraterrestrials to a proposed introduction to the film 2001: A Space Odyssey. Sagan allegedly responded by saying that he wanted editorial control and a percentage of the film's box office receipts. These terms were rejected.

Sagan wrote frequently about religion and the relationship between religion and science, expressing his skepticism about the conventional conceptualization of God as a sapient being. Sagan once stated, for instance, that:

The idea that God is an oversized white male with a flowing beard, who sits in the sky and tallies the fall of every sparrow is ludicrous. But if by 'God' one means the set of physical laws that govern the universe, then clearly there is such a God. This God is emotionally unsatisfying ... it does not make much sense to pray to the law of gravity."

Sagan is also widely regarded as a freethinker or skeptic; one of his most famous quotations, in Cosmos, was, "Extraordinary claims require extraordinary evidence." This was actually based on a nearly identical earlier quote by fellow CSICOP founder Marcello Truzzi, "Extraordinary claims require extraordinary proof." In turn, those quotes originated with Pierre-Simon Laplace (1749-1827), a French mathematician and astronomer who said, "The weight of evidence for an extraordinary claim must be proportioned to its strangeness." Sagan was, however, not an atheist, expressing that, "An atheist has to know a lot more than I know." In reply to a direct question in 1996 about his religious beliefs, Sagan gave a direct answer: "I'm agnostic." Sagan argued that the idea of a Creator of the Universe was difficult to prove or disprove and that the only conceivable scientific discovery that could challenge it would be an infinitely old universe.

Sagan married three times: to biologist Lynn Margulis, mother of Dorion Sagan and Jeremy Sagan, in 1957; to artist Linda Salzman, mother of Nick Sagan, in 1968; and to author Ann Druyan, mother of Alexandra Rachel (Sasha) and Samuel Democritus (Sam), in 1981. His marriage to Druyan continued until his death in 1996.

Isaac Asimov described Sagan as one of only two people he ever met who were smarter than Asimov himself. The other was the computer scientist and artificial intelligence expert Marvin Minsky.

Sagan was a user of marijuana. Under the pseudonym "Mr. X", he wrote an essay concerning cannabis smoking in the 1971 book Marihuana Reconsidered, written by Sagan's close friend Lester Grinspoon. In his essay, Sagan wrote how marijuana use had helped to inspire some of his works and enhance sensual and intellectual experiences. After Sagan's death, Grinspoon disclosed this to Sagan's biographer, Keay Davidson. The publishing of the biography, Carl Sagan: A Life, in 1999, brought much media attention about this.

Sagan warned against human beings' tendency for anthropocentrism, and was the faculty adviser for the Cornell Students for the Ethical Treatment of Animals. In the COSMOS chapter "Blues For a Red Planet" Sagan states, "If there is life on Mars, then I believe we should do nothing to disturb that life. Mars, then, belongs to the Martians, even if they are microbes."

Late in his life, Sagan's books elaborated on his skeptical, naturalistic view of the world. In The Demon-Haunted World: Science as a Candle in the Dark, he presented tools for testing arguments and detecting fallacious or fraudulent ones, essentially advocating wide use of critical thinking and the scientific method. The compilation, Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium, published in 1997 after Sagan's death, contains essays written by Sagan, such as his views on abortion, and his widow Ann Druyan's account of his death as a skeptic, agnostic, and freethinker.

In 2006, Ann Druyan edited Sagan's 1985 Glasgow Gifford Lectures in Natural Theology into a new book, The Varieties of Scientific Experience: A Personal View of the Search for God, in which he elaborates on his views of divinity in the natural world.

Sagan and UFOs

Sagan had some interest in UFO reports from at least 1964, when he had several conversations on the subject with Jacques Vallee. Though quite skeptical of any extraordinary answer to the UFO question, Sagan thought scientists should study the phenomenon, at least because there was widespread public interest in UFO reports.

Stuart Appelle notes that Sagan "wrote frequently on what he perceived as the logical and empirical fallacies regarding UFOs and the abduction experience. Sagan rejected an extraterrestrial explanation for the phenomenon but felt there were both empirical and pedagogical benefits for examining UFO reports and that the subject was, therefore, a legitimate topic of study."

In 1966, Sagan was a member of the Ad Hoc Committee to Review Project Blue Book, the U.S. Air Force's UFO investigation project. The committee concluded Blue Book had been lacking as a scientific study, and recommended a university-based project to give the UFO phenomenon closer scientific scrutiny. The result was the Condon Committee (1966–1968), led by physicist Edward Condon, and in their final report they formally concluded that UFOs, regardless of what any of them actually were, did not behave in a manner consistent with a threat to national security.

Ron Westrum writes that "The high point of Sagan's treatment of the UFO question was the AAAS's symposium in 1969. A wide range of educated opinions on the subject were offered by participants, including not only proponents such as James McDonald and J. Allen Hynek but also skeptics like astronomers William Hartmann and Donald Menzel. The roster of speakers was balanced, and it is to Sagan's credit that this event was presented in spite of pressure from Edward Condon". With physicist Thornton Page, Sagan edited the lectures and discussions given at the symposium; these were published in 1972 as UFOs: A Scientific Debate. Some of Sagan's many books examine UFOs (as did one episode of Cosmos) and he claimed a religious undercurrent to the phenomenon.

Sagan again revealed his views on interstellar travel in his 1980 Cosmos series. In one of his last written works, Sagan argued that the chances of extraterrestrial spacecraft visiting Earth are vanishingly small. However, Sagan did think it plausible that Cold War concerns contributed to governments misleading their citizens about UFOs, and that "some UFO reports and analyses, and perhaps voluminous files, have been made inaccessible to the public which pays the bills ... It's time for the files to be declassified and made generally available." He cautioned against jumping to conclusions about suppressed UFO data and stressed that there was no strong evidence that aliens were visiting the Earth either in the past or present.

Death and legacy

Stone dedicated to Carl Sagan in the Celebrity Path of the Brooklyn Botanic Garden

After a long and difficult fight with myelodysplasia, which included three bone marrow transplants, Sagan died of pneumonia at the age of 62 at the Fred Hutchinson Cancer Research Center in Seattle, Washington on December 20, 1996. Surviving him were his wife and five children. After landing, the unmanned Mars Pathfinder spacecraft was renamed the Carl Sagan Memorial Station on July 5, 1997. Asteroid 2709 Sagan is also named in his honor. He was buried at Lakeview Cemetery in Ithaca, New York.

The 1997 movie Contact, based on Sagan's novel of the same name and finished after his death, ends with the dedication "For Carl".

On November 9, 2001, on what would have been Sagan's 67th birthday, the NASA Ames Research Center dedicated the site for the Carl Sagan Center for the Study of Life in the Cosmos. "Carl was an incredible visionary, and now his legacy can be preserved and advanced by a 21st century research and education laboratory committed to enhancing our understanding of life in the universe and furthering the cause of space exploration for all time", said NASA Administrator Daniel Goldin. Ann Druyan was at the Center as it opened its doors on October 22, 2006.

Sagan's son, Nick Sagan, wrote several episodes in the Star Trek franchise. In an episode of Star Trek: Enterprise entitled "Terra Prime", a quick shot is shown of the relic rover Sojourner, part of the Mars Pathfinder mission, placed by a historical marker at Carl Sagan Memorial Station on the Martian surface. The marker displays a quote from Sagan: "Whatever the reason you're on Mars, I'm glad you're there, and I wish I was with you." Sagan's student Steve Squyres led the team that landed the Spirit Rover and Opportunity Rover successfully on Mars in 2004.

Sagan has at least three awards named in his honor:

• The Carl Sagan Memorial Award presented jointly since 1997 by the American Astronautical Society (AAS) and the Planetary Society,
• The Carl Sagan Medal for Excellence in Public Communication in Planetary Science presented since 1998 by the American Astronomical Society's Division for Planetary Sciences (AAS/DPS) for outstanding communication by an active planetary scientist to the general public — Carl Sagan was one of the original organizing committee members of the DPS, and
• The Carl Sagan Award for Public Understanding of Science presented by the Council of Scientific Society Presidents (CSSP) — Sagan himself was the first recipient of the CSSP award in 1993.

In 2006, the Carl Sagan Medal was awarded to astrobiologist and author David Grinspoon, the son of Sagan's friend Lester Grinspoon.

On December 20, 2006, the tenth anniversary of Sagan's death, a blogger, Joel Schlosberg, organized a Carl Sagan "blog-a-thon" to commemorate Sagan's death, and the idea was supported by Nick Sagan. Many members of the blogging community participated.

In 2008, Benn Jordan, also known as The Flashbulb, released the album "Pale Blue Dot: A Tribute to Carl Sagan".

Awards and honors

NASA Distinguished Public Service Medal

• Annual Award for Television Excellence - 1981 - Ohio State University - PBS series Cosmos
• Apollo Achievement Award - National Aeronautics and Space Administration
• NASA Distinguished Public Service Medal - National Aeronautics and Space Administration (twice)
• Emmy - Outstanding Individual Achievement - 1981 - PBS series Cosmos
• Emmy - Outstanding Informational Series - 1981 - PBS series Cosmos
• Exceptional Scientific Achievement Medal - National Aeronautics and Space Administration
• Helen Caldicott Leadership Award - Women's Action for Nuclear Disarmament
• Hugo Award - 1981 - Cosmos
• Humanist of the Year - 1981 - Awarded by the American Humanist Association
• In Praise of Reason Award - 1987 - Committee for the Scientific Investigation of Claims of the Paranormal
• Isaac Asimov Award - 1994 - Committee for the Scientific Investigation of Claims of the Paranormal
• John F. Kennedy Astronautics Award - American Astronautical Society
• John W. Campbell Memorial Award - 1974 - Cosmic Connection: An Extraterrestrial Perspective
• Joseph Priestley Award - "For distinguished contributions to the welfare of mankind"
• Klumpke-Roberts Award of the Astronomical Society of the Pacific - 1974
• Konstantin Tsiolkovsky Medal - Awarded by the Soviet Cosmonauts Federation
• Locus Award 1986 - Contact
• Lowell Thomas Award - Explorers Club - 75th Anniversary
• Masursky Award - American Astronomical Society
• Miller Research Fellowship - Miller Institute (1960–1962)
• New Jersey Hall of Fame - 2009 inductee
• Oersted Medal - 1990 - American Association of Physics Teachers
• Peabody Award - 1980 - PBS series Cosmos
• Prix Galbert - The international prize of Astronautics
• Public Welfare Medal - 1994 - National Academy of Sciences
• Pulitzer Prize for General Non-Fiction - 1978 - The Dragons of Eden
• SF Chronicle Award - 1998 - Contact
• Named the "99th Greatest American" on the June 5, 2005, Greatest American show on the Discovery Channel

Bibliography

By Sagan

• Planets (LIFE Science Library), Sagan, Carl, Jonathon Norton Leonard and editors of Life, Time, Inc., 1966
• Intelligent Life in the Universe, I.S. Shklovskii coauthor, Random House, 1966, 509 pgs
• UFO's: A Scientific Debate, Thornton Page coauthor, Cornell University Press, 1972, 310 pgs
• Communication with Extraterrestrial Intelligence. MIT Press, 1973, 428 pgs
• Mars and the Mind of Man, Sagan, Carl, et al., Harper & Row, 1973, 143 pgs
• Cosmic Connection: An Extraterrestrial Perspective, Jerome Agel coauthor, Anchor Press, 1973, ISBN 0-521-78303-8, 301 pgs
• Other Worlds. Bantam Books, 1975
• Murmurs of Earth: The Voyager Interstellar Record, Sagan, Carl, et al., Random House, ISBN 0-394-41047-5, 1978
• The Dragons of Eden: Speculations on the Evolution of Human Intelligence. Ballantine Books, 1978, ISBN 0-345-34629-7, 288 pgs
• Broca's Brain: Reflections on the Romance of Science. Ballantine Books, 1979, ISBN 0-345-33689-5, 416 pgs
• Cosmos. Random house, 1980. Random House New Edition, May 7, 2002, ISBN 0-375-50832-5, 384 pgs
• The Nuclear Winter: The World After Nuclear War, Sagan, Carl et al., Sidgwick & Jackson, 1985
• Comet, Ann Druyan coauthor, Ballantine Books, 1985, ISBN 0-345-41222-2, 496 pgs
• Contact. Simon and Schuster, 1985; Reissued August 1997 by Doubleday Books, ISBN 1-56865-424-3, 352 pgs
• The Varieties of Scientific Experience: A Personal View of the Search for God, Ann Druyan editor, 1985 Gifford lectures, Penguin Press, 2006, ISBN 1-59420-107-2, 304 pgs
• A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race, Richard Turco coauthor, Random House, 1990, ISBN 0-394-58307-8, 499 pgs
• Shadows of Forgotten Ancestors: A Search for Who We Are, Ann Druyan coauthor, Ballantine Books, October 1993, ISBN 0-345-38472-5, 528 pgs
• Pale Blue Dot: A Vision of the Human Future in Space. Random House, November 1994, ISBN 0-679-43841-6, 429 pgs
• The Demon-Haunted World: Science as a Candle in the Dark. Ballantine Books, March 1996, ISBN 0-345-40946-9, 480 pgs (note: the book was first published and copyrighted in 1995 with an errata slip inserted)
• Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium, Ann Druyan coauthor, Ballantine Books, June 1997, ISBN 0-345-37918-7, 320 pgs
• The Varieties of Scientific Experience: A Personal View of the Search for God, Carl Sagan (writer) & Ann Druyan (editor), Penguin Press HC, November 2006, ISBN 1-59420-107-2, 304 pgs

About Sagan

• Davidson, Keay (1999). Carl Sagan: A Life. New York: John Wiley & Sons. pp. 33–41. ISBN 0471252867.
• Head, Tom (ed.) (2005). Conversations with Carl Sagan. Jackson, Mississippi: University Press of Mississippi. ISBN 1578067367. {{cite book}}: |first= has generic name (help); Cite has empty unknown parameter: |coauthors= (help)
• Poundstone, William (1999). Carl Sagan: A Life in the Cosmos. New York: Henry Holt & Company. ISBN 0805057668.
• Morrison, David (2006). Carl Sagan: The People's Astronomer. AmeriQuests, vol. 3. no. 2: <http://ejournals.library.vanderbilt.edu/ameriquests/include/getdoc.php?id=402&article=93&mode=pdf>.
• Achenbach, Joel (1999). Captured by Aliens: the search for life and truth in a very large universe. New York: Simon & Schuster. ISBN 0-684-84856-2. Includes detailed account of Sagan's role in the search for extraterrestrial life.

External links

• The Carl Sagan Portal
• Carl Sagan at IMDb
• Can We Know the Universe? – 1979 essay by Carl Sagan, taken from his book Broca's Brain
• Talk of the Nation – Ira Flatow interviews Sagan on his book The Demon-Haunted World: Science as a Candle in the Dark (May 3, 1996)
• Skeptical Inquirer: Carl Sagan's Life & Legacy (Jan./Feb. 2007)
• We Are Here: The Pale Blue Dot – A short film narrated by Carl Sagan (40 min extended version)
• Carl Sagan Charlie Rose interviews
• Carl Sagan Prize for Science Popularization
• Carl Sagan Medal for Excellence in Public Communication in Planetary Science, presented by the American Astronomical Society's Division for Planetary Sciences (AAS/DPS)
• Cosmos Magazine, an Australian popular science magazine inspired by Carl Sagan and launched in June 2005
• Template:Worldcat id
• Carl Sagan at Find a Grave

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