Carl Sagan
Dr. Carl Edward Sagan (
November 9 1934 â€"
December 20 1996) was an
American astronomer,
astrobiologist, and highly successful science popularizer. 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 television series
Cosmos, the most-watched
PBS program of all time
[ According to nasa.gov, [1], [2] and [3]]. A
book to accompany the program was also published. He also wrote the novel
Contact, upon which the 1997
film of the same name starring
Jodie Foster was based. Throughought his career he wrote more than 400 published scientific and popular articles. In his works, he frequently advocated
skepticism,
humanism, and the
scientific method.
|
Sagan of Astronomy Department, Cornell University, 1969 |
Carl Sagan was born in
Brooklyn,
New York[For biographical information see Carl Sagan: A Life in the Cosmos by William Poundstone. Henry Holt & Company (October 1 1999) ISBN 0-805-05766-8]. His parents were
Jewish; his father, Sam Sagan, was a garment worker and his mother, Rachel Molly Gruber, was a housewife. Carl was named in honor of Rachel's biological mother, Chaiya/ Clara, "the mother she never knew," in Sagan's words. 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. During his time as an undergraduate, Sagan spent some time working in the laboratory of the
geneticist H. J. Muller. From 1962 to 1968, he worked at the
Smithsonian Astrophysical Observatory.
|
Sagan, chairman of the Voyager Golden Record committee in 1977 |
Sagan taught at
Harvard University until 1968, when he moved to
Cornell University. He became a full professor at Cornell in 1971 and directed the Laboratory for
Planetary Studies there. From 1972 to 1981 he was Associate Director of the Center for Radio Physics and Space Research at Cornell.
Sagan contributed to most of the
unmanned space missions that explored the
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. Sagan assembled the first physical message that was sent into
space: a
gold-
anodized plaque, attached to the space probe
Pioneer 10, launched in 1972.
Pioneer 11, also containing the plaque, was launched the following year. He continued to refine his designs and the most elaborate such message he helped to develop and assemble was the
Voyager Golden Record that was sent out with the
Voyager space probes in 1977.
Sagan taught at Cornell a course on critical thinking until the year of his death in 1996. The course had only a limited number of seats, although hundreds of students tried to attend. He chose about 20 students who were allowed to enroll by reading huge piles of application essays. The course was discontinued after his death.
Sagan was 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 Venus' surface and Sagan listed the possibilities in a report (which were later depicted for popularization in a
Time-Life book,
Planets) â€" his own view was that the planet was dry and very hot, as opposed to the balmy paradise others had imagined. 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 views on the conditions of Venus in 1962.
Sagan was among the first to hypothesize that
Saturn's moon
Titan[Much of Sagan's research in the field of planetary science is outlined by William Poundstone (see reference #1, above). Poundstone's biography of Sagan includes an eight page list of Sagan's scientific articles published from 1957 to 1998. Detailed information about Sagan's scientific work comes from the primary research articles. Example: Sagan, C., Thompson, W. R., and Khare, B. N. Titan: A Laboratory for Prebiological Organic Chemistry, Accounts of Chemical Research, volume 25, page 286 (1992). There is commentary on this research article about Titan at The Encyclopedia of Astrobiology, Astronomy, and Spaceflight.] and
Jupiter's moon
Europa may possess oceans (a subsurface ocean, in the case of Europa) or lakes, thus making the hypothesized water ocean on Europa potentially habitable for
life. Europa's subsurface ocean was later indirectly confirmed by the spacecraft
Galileo.
He furthered 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. 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 gasses. Sagan speculated (along with his Cornell colleague
E. E. Salpeter) about life in
Jupiter's clouds, given the planet's dense atmospheric composition rich in
organic molecules. He suggested that the observed seasonal changes on Mars were due to windblown
dust, not to
vegetation changes, as others had proposed.
 |
Planetary Society members at the organization's founding. Carl Sagan seated, right |
Sagan was a proponent of the search for extraterrestrial life. He urged the scientific community to listen with large
radio telescopes for signals from intelligent extraterrestrial lifeforms. So persuasive was he that by 1982, he was able to get a petition advocating
SETI published in the journal
Science, signed by 70 scientists, including seven Nobel Prize winners. This was a tremendous turnaround in the respectability of this controversial field. Sagan also advocated sending
probes to explore the
solar system.
He was editor-in-chief of
Icarus (a professional journal concerning planetary research) for 12 years. He cofounded the
Planetary Society, the largest space-interest group in the world, with over 100,000 members in more than 140 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.
Sagan helped Dr.
Frank Drake write the
Arecibo message, a radio message beamed into space from the
Arecibo radio telescope in 1974, aimed at informing extraterrestrials about Earth.
At the height of the
Cold War, Sagan deliberately ignored the "extraordinary claims" test for evidence when a mathematical climate model suggested that a substantial nuclear exchange could upset the delicate balance of life on
Earth. He was the last of five authors â€" the "S" of the
"TTAPS" report as the research paper came to be known. He eventually co-authored the scientific paper that predicted
nuclear winter[Turco RP, Toon OB, Ackerman TP, Pollack JB, Sagan C. Climate and smoke: an appraisal of nuclear winter, Science, volume 247, pages 166-176 (1990). PubMed abstract | JSTORE link to full text article. Carl Sagan discussed his involvement in the political nuclear winter debates and his erroneous global cooling prediction for the Gulf War fires in his book, The Demon-Haunted World.] would follow
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 famously predicted that smoky
oil fires in Kuwait (set by
Saddam Hussein's army) would cause an ecological disaster of black clouds. Retired
atmospheric physicist Fred Singer dismissed Sagan's prediction as nonsense, predicting that the smoke would dissipate in a matter of days. In his book
The Demon-Haunted World, Sagan gave a list of errors he had made (including his predictions about the effects of the Kuwaiti oil fires) as an example of how science is tentative.
Sagan is also known for being involved as a researcher in
Project A119, a secret
US Air Force operation whose purpose was to drop a bomb on Earth's
Moon.
Sagan believed that the
Drake equation suggested that a large number of extraterrestrial civilizations would form, but that the lack of evidence of such civilizations (the
Fermi paradox) suggests that 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 destruction and eventually becoming a space-faring species.
Sagan became more politically active after marrying novelist
Ann Druyan, performing acts of
civil disobedience at the
Nevada Nuclear Weapons Test Site during the
Nuclear freeze era, for which he was publicly arrested twice, along with
Daniel Ellsberg,
Philip Zimmermann and
Martin Sheen. He was also arrested for participating in an anti-war protest during the
Vietnam era. He spoke out against President
Ronald Reagan's
Strategic Defense Initiative, or the "Star Wars" program, which he felt was technically impossible to build and perfect, far more expensive to create than for an enemy to defeat through decoys and other means, and destabilizing to Cold War
nuclear weapons disarmament progress.
Carl Sagan used
marijuana, although he never admitted this publicly during his life. Under the
pseudonym "Mr. X," he wrote an essay concerning cannabis smoking in the 1971 book
Marihuana Reconsidered, whose editor was
Lester Grinspoon[Marihuana Reconsidered by Lester, M.D. Grinspoon. Publisher: Quick American Archives (2nd edition; April 1 1994) ISBN 0932551130. Sagan's essay is available online.]. In his essay, Sagan commented that marijuana encouraged some of his works and enhanced experiences. After Sagan's death, Grinspoon disclosed this to Sagan's biographer, Keay Davidson
[Carl Sagan: A Life by Keay Davidson. John Wiley & Sons (August 30 1999) ISBN 0471252867]. When the biography, entitled
Carl Sagan: A Life, was published in 1999, the marijuana exposure stirred some media attention
[BBC news story that includes mention of Sagan's marijuana use.].
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 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).
|
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. It won an
Emmy and a
Peabody Award; according to the
NASA Office of Space Science, it has been since broadcast in more than 60 countries and seen by over 600 million people.
Sagan also wrote books to popularize science, such as
Cosmos, which reflected and expanded upon some of the themes of
A Personal Voyage,
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 never lived 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." (He never actually used that phrase in
Cosmos, but his distinctive delivery and frequent use of
billions made this a favorite phrase of
Johnny Carson and others, doing many affectionate impressions of him. Sagan took this in good humor, and his final book was entitled
Billions and Billions â€" see below.) A humorous unit of measurement, the
Sagan, has now been coined to stand for any count of at least 4,000,000,000.
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. Carl Sagan also wrote an introduction for the bestselling book by
Stephen Hawking,
A Brief History of Time.
Sagan presents a speculation concerning the origin of the
swastika symbol in his book,
Comet. Sagan hypothesized that a
comet approached so close to Earth in antiquity that the jets of gas streaming out of it were visible, bent by the comet's rotation. The book
Comet reproduces an ancient
Chinese manuscript that shows comet tail varieties; most are variations on simple comet tails, but the last shows the comet nucleus with four bent arms extending from it, showing a swastika.
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
scientific skepticism and against
pseudoscience; most notably his thorough
debunking of the book
Worlds in Collision by
Immanuel Velikovsky. 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. Some believe this unease 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's arguments against Velikovsky's
catastrophism have been criticized by some of his colleagues.
Robert Jastrow of NASA's
Goddard Institute for Space Studies wrote: "Professor Sagan's calculations, in effect, ignore the law of gravity. Here, Dr. Velikovsky was the better astronomer." His comments on the Kuwait oil well fires during the first
Gulf War were shown later to be incorrect; Sagan himself acknowledged his error in print.
Late in his life, Sagan's books developed 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 1998 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,
atheist and
freethinker.
In 2006, Ann Druyan edited Sagan's 1985 Gifford Lectures into a new book,
Gifford Lectures in Natural Theology, 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.
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. According to an uncited anecdote in
The Independent, Sagan "responded by saying that he wanted editorial control and a percentage of the film's takings, which was rejected"
[ 2001: The secrets of Kubrick's classic" by Anthony Barnes (23 October 2005).].
In 1994,
Apple Computer began developing the
Power Macintosh 7100. They chose the internal code name "Carl Sagan," the joke being that the mid-range PowerMac 7100 would make Apple "billions and billions"
[An account of this lawsuit is given in Carl Sagan: A Life in the Cosmos, pages 363-364 and 374-375.]. 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 â€" other projects had names like "
Cold fusion" and "
Piltdown Man", and he was displeased at being associated with what he considered pseudoscience. Though Sagan lost the suit, Apple engineers complied with his demands anyway, renaming the project "BHA" (
Butt-Head 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; still, the 7100 saw another name change: it was lastly called "LAW" (Lawyers Are Wimps).
Sagan wrote about religion and the relationship between religion and science. He made statements such as: "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."
[A similar quote can be found in Chapter 23 of Sagan's book Broca's Brain. "Some people think God is an outsized, light-skinned male with a long white beard, sitting on a throne somewhere up there in the sky, busily tallying the fall of every sparrow. Others â€" for example Baruch Spinoza and Albert Einstein â€" considered God to be essentially the sum total of the physical laws which describe the universe. I do not know of any compelling evidence for anthropomorphic patriarchs controlling human destiny from some hidden celestial vantage point, but it would be madness to deny the existence of physical laws."] Concerning athiesm, Sagan said: "Atheism is more than just the knowledge that gods do not exist, and that religion is either a mistake or a fraud. Atheism is an attitude, a frame of mind that looks at the world
objectively, fearlessly, always trying to understand all things as a part of nature..." Sagan is also widely considered as a freethinker or skeptic, one of his most famous quotations (as seen in
Cosmos) being, "Extraordinary claims require extraordinary evidence."
Sagan married three times; the famous biologist,
Lynn Margulis (mother of
Dorion Sagan and
Jeremy Sagan) in 1957, artist
Linda Salzman (mother of
Nick Sagan) in 1968, and author Ann Druyan (mother of Sasha and Sam) in 1981, to whom he remained married until his death.
Isaac Asimov described Sagan as one of the only two people he ever met who were just plain smarter than Asimov himself. The other was
computer scientist and expert on
artificial intelligence,
Marvin Minsky.
Sagan had some interest in
UFO reports from at least 1964, when he had several conversations on the subject with
Jacques Vallee (Westrum 37). Though quite skeptical of any extraordinary answer to the UFO question, Sagan thought that science 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" (Appelle 22).
In 1966, Sagan was a member of the Ad Hoc Committee to Review
Project Blue Book. The committee concluded that the U.S. Air Force's
Project Blue Book had been lacking as a scientific study, and recommended a university-based project to give the UFO phenomenon closer scientific scrutiny. The
Condon Committee (1966-1968), lead by physicist
Edward Condon, and their still-controversial final report, formally concluded that there was nothing anomalous about UFO reports.
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 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" (Westrum 37-38). With physicist
Thornton Page, Sagan edited the lectures and discussions given at the symposium; these were published in 1972 as
UFO's: A Scientific Debate.
Jerome Clark writes that Sagan's perspective on UFO's irked Condon: "... though a skeptic, [Sagan] was too soft on UFOs for Condon's taste. In 1971, he considered blackballing Sagan from the prestigious
Cosmos Club" (Clark 603).
Some of Sagan's many books examine UFOs (as did one episode of
Cosmos) and he recognized a
religious undercurrent to the phenomenon. However, Westrum writes that "Sagan spent very little time researching UFOs ... he thought that little evidence existed to show that the UFO phenomenon represented alien spacecraft and that the motivation for interpreting UFO observations as spacecraft was emotional" (Westrum 37).
It is sometimes noted that Sagan's generally skeptical attitude to UFOs conflicted sharply with his views in a 1966 book he wrote with Russian astronomer and astrophysicist
I.S. Shklovskii,
Intelligent Life in the Universe. Here Sagan instead argued that technologically advanced alien civilizations were common and he considered it very probable that Earth had been visited many times in the past.
Yet only a few years later in
UFO's: A Scientific Debate, Sagan was now highly skeptical of interstellar visitation. As to the physical possibility of
interstellar travel, Sagan brought up the proposed
Bussard ramjet as an interstellar vehicle. While not terribly practical, Sagan thought such proposed propulsion systems were nevertheless important because they demonstrated that there were conceivable ways of accomplishing interstellar travel "without bumping into fundamental physical constraints. And this suggests that it is premature to say that interstellar space flight is out of the question." But to this Sagan added, "I believe the numbers work out in such a way that UFO's as interstellar vehicles is extremely unlikely, but I think it is an equally bad mistake to say that interstellar space flight is impossible."
Sagan revealed his views on interstellar travel in his 1980
Cosmos series. Although he scoffed at the idea that UFOs are visiting Earth, maintaining that the distance between stars was too great to make interstellar travel feasible for aliens, in another episode he said the stars would "beckon" to humanity, describing the Bussard ramjet as one way humans might achieve interstellar travel. Sagan pointed out that there is no evidence that aliens have actually visited the Earth, either in the past or present (Sagan, 1995: 81-96, 99-104).
After a long and difficult fight with
myelodysplasia, Sagan died at the age of 62, on Friday,
December 20,
1996, at the
Fred Hutchinson Cancer Research Center in
Seattle, Washington. Sagan was a significant figure, and his supporters credit his importance to his popularization of 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.
|
Sagan in 1996, shortly before his death |
The landing site of 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.
The 1997 movie
Contact (see above), 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.
In 2004, the
electronic music group Sagan released the CD/DVD "Unseen Forces." The music was accompanied by a DVD which featured humorous
music video format homages of many of the historical sketches from
Cosmos.
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."
*
Apollo Achievement Award -
National Aeronautics and Space Administration*
Chicken Little Honorable Mention - 1991 - National Anxiety Center; a
dubious achievement award from an organization which is skeptical about many pessimistic appraisals of the state of the environment
*
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
*
Homer Award - 1997 -
Contact*
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 -
The Cosmic Connection*
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*
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*
Carl Sagan Memorial Award - Named in his honor
* Named 99th "
Greatest American" on the
June 5 2005 "Greatest American" show on the
Discovery Channel.
* Appelle, Stuart: "
Ufology and
Academia: The UFO Phenomenon as a Scholarly Discipline" (pages 7-30 in
UFOs and Abductions: Challenging the Borders of Knowledge, David M. Jacobs, editor; University Press of Kansas, 2000; ISBN)
* Clark, Jeromne:
The UFO Book. Visible Ink Press, 1998, 750 pgs
* Sagan, Carl and Jonathon Norton Leonard and editors of Life,
Planets. Time, Inc., 1966
* Sagan, Carl and
I.S. Shklovskii,
Intelligent Life in the Universe. Random House, 1966
* Sagan, Carl,
UFO's: A Scientific Debate. Cornell University Press, 1972, 310 pgs
* Sagan, Carl,
Communication with Extraterrestrial Intelligence. MIT Press, 1973
* Sagan, Carl, et. al.
Mars and the Mind of Man. Harper & Row, 1973
* Sagan, Carl,
Broca's Brain: Reflections on the Romance of Science. Ballantine Books, 1974, ISBN 0345336895, 416 pgs
* Sagan, Carl,
Other Worlds. Bantam Books, 1975
* Sagan, Carl, et. al.
Murmurs of Earth: The Voyager Interstellar Record. Random House, 1977
* Sagan, Carl,
The Dragons of Eden: Speculations on the Evolution of Human Intelligence. Ballantine Books, 1978, ISBN 0345346297, 288 pgs
* Sagan, Carl,
Cosmos. Random house, 1980. Random House New Edition,
May 7 2002, ISBN 0375508325, 384 pgs
* Sagan, Carl et. al.
The Nuclear Winter: The World After Nuclear War. Sidgwick & Jackson, 1985
* Sagan, Carl and Ann Druyan,
Comet. Ballantine Books, 1985, ISBN 0345412222, 496 pgs
* Sagan, Carl,
Contact. Simon and Schuster, 1985; Reissued August 1997 by Doubleday Books, ISBN 1568654243, 352 pgs
* Sagan, Carl and Richard Turco,
A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race. Random House, 1990
* Sagan, Carl and Ann Druyan,
Shadows of Forgotten Ancestors: A Search for Who We Are. Ballantine Books, October 1993, ISBN 0345384725, 528 pgs
* Sagan, Carl,
Pale Blue Dot: A Vision of the Human Future in Space. Random House, November 1994, ISBN 0679438416, 429 pgs
* Sagan, Carl,
The Demon-Haunted World: Science as a Candle in the Dark. Ballantine Books, March 1996, ISBN 0345409469, 480 pgs
* Sagan, Carl and Ann Druyan,
Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium. Ballantine Books, June 1998, ISBN 0345379187, 320 pgs
* Sagan, Carl and Jerome Agel,
Cosmic Connection: An Extraterrestrial Perspective. Cambridge University Press,
January 15 2000, ISBN 0521783038, 301 pgs
*Westrum, Ron, "Limited Access: Six Natural Scientists and the UFO Phenomenon" (pages 30-55 in Jacobs)
* Zemeckis, Robert,
Contact. Warner Studios, 1997,
IMDB* Davidson, Keay,
Carl Sagan: A Life. John Wiley & Sons,
August 31 2000, ISBN 0471395366, 560 pgs
* Head, Tom (editor),
Conversations with Carl Sagan. University Press of Mississippi, 2005, ISBN 1578067367, 170 pgs
* Sagan, Carl,
Gifford Lectures in Natural Theology, The Varieties of Scientific Experience: A Personal View of the Search for God. Penguin Press, November 2006, 288 pgs
*
CarlSagan.com - homepage of
Cosmos Studios, which sells the
Cosmos series on DVD.
*
"In Memory of Carl Sagan" Skeptic remembers Carl, with tributes from Tom McDonough,
James Randi and
Michael Shermer. Also includes quotations from Sagan's selection works.
*
Charlie Rose May 27, 1996 - interview with Sagan on his book
The Demon-Haunted World.
*
Talk of the Nation May 3, 1996 - Ira Flatow interviews Sagan on his last book.
*
"The Quest for Extraterrestrial Intelligence" - 1979 essay by Carl Sagan.
*
"Can We Know the Universe?" - essay by Carl Sagan, taken from his book
Broca's Brain.
*
"Mr. X" - Sagan's anonymous essay in Lester Grinspoon's
Marihuana Reconsidered, 1971.
*
"Carl Sagan Takes Questions" - from Sagan's 1994 "Wonder and Skepticism" keynote address delivered in Seattle June 23â€"26.
*
"Carl Sagan, Cornell astronomer, dies today (Dec. 20) in Seattle" -
Cornell University press release.
*
The Sagan Planet Walk - New York planetary exhibit created in memory of Carl Sagan.
*
25th Anniversary Rebroadcast of Cosmos on The Science Channel*
Cosmos tribute clip on YouTube*
Carl Sagan on Johnny Carson, circa 1985*
Carl Sagan's Religion of Science - an analysis of Sagan's view of religion as expressed in his writings.
*
Contact Film Review - an analysis of the film and novel, by Larry Klaes.
