Sagan 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
his popular science books and the award-winning television series
Cosmos, which he co-wrote and presented and eventually released
as a book. He also wrote the novel Contact, upon which the 1997
film of the same name starring Jodie Foster was based. In his works,
he frequently advocated the scientific method.
and scientific career
Carl Sagan was born in Brooklyn, New York. His parents were Jewish;
his father, Sam Sagan, was a garment worker and his mother, Rachel
Molly Gruber, was 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. During his time as an undergraduate,
Sagan spent some time working in the laboratory of the geneticist
H. J. Muller.
the early 1960s, no one knew for certain even the basic conditions
of the surface of the planet Venus. He listed the contending possibilities
in a report (which were later depicted for popularization in a
Time-Life book, Planets). His own view was that the planet was
dry and very hot. As a visiting scientist to Caltech's Jet Propulsion
Laboratory, he contributed to the first Mariner missions to the
planet Venus in the design and management of the project, which
confirmed his views with the success of Mariner 2 in 1962.
taught at Harvard University until 1968, when he moved to Cornell
University. He 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 into space was a gold-anodized
plaque, attached to 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.
Sagan was among the first to hypothesize that Saturn's moon Titan
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
furthered insights regarding the atmosphere of Jupiter, seasonal
changes on Mars, and Saturn's moon Titan. 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 gases. He suggested that the 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, rightSagan 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.
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 and
was a member of the SETI Institute Board of Trustees.
was well known as a co-author of the scientific paper that predicted
nuclear winter would follow nuclear war. 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.
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
became more politically active after marrying novelist Ann Druyan,
performing acts of civil disobedience at nuclear weapons sites
during the Nuclear freeze 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.
Sagan was an avid user of marijuana, although he never publicly
admitted it 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. 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. When the
biography, entitled Carl Sagan: A Life, was published in 1999,
the marijuana exposure stirred some media attention.
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 narrated
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)
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 60 countries
and seen by more than 600 million people.
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.
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 the many affectionate impressions
of him. Sagan took this in good humor, and his final book was
entitled Billions and Billions - see below.) The humorous unit
of measurement, the Sagan has now been coined to stand for any
count of at least 4,000,000,000.
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.
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.
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, 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.
arguments against Velikovsky's catastrophism have been criticized
by some of his colleagues. Dr. Robert Jastrow of NASA's Goddard
Institute of 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 in error;
Sagan himself acknowledged his error in print.
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 the scientific method. The compilation, Billions and Billions:
Thoughts on Life and Death at the End of the Millennium, published
after Sagan's death, contains essays written by Sagan, such as
his views on abortion, and Ann Druyan's account of his death as
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
1994, Apple Computer began developing the Power Macintosh 7100.
They chose the internal code name "Carl 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 — 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" (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; still,
the 7100 saw another name change: it was lastly called "LAW"
(Lawyers Are Wimps).
is regarded by most as an atheist, agnostic, or pantheist observing
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."
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
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 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."
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
Dr. Edward Condon, and their still-controversial final report,
formally concluded that there was nothing anomalous about UFO
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 McDonald and Hynek but also skeptics
like astronomers William Hartmann and 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 UFO's:
A Scientific Debate
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, p. 603)
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)
is sometimes noted that Sagan's generally hostile 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.
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."
was likewise inconsistent in his views on interstellar travel
in his 1980 Cosmos series. When scoffing at UFOs, he maintained
that the distance between stars was too great to make interstellar
travel feasible for aliens. Yet in another episode, he said the
stars would "beckon" to humanity, and then again described
the Bussard ramjet as one way humans might do it.
After a long and difficult fight with myelodysplasia, Sagan died
at the age of 62, on 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.
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 also named in his honor.
1997 movie, Contact (see above), based on Sagan's novel of the
same name, and finished after his death, ends with the dedication
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."
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."