Carl Edward Sagan (; November 9, 1934 – December
20, 1996) was an American astronomer, cosmologist,
astrophysicist, astrobiologist, author, science
popularizer, and science communicator in astronomy
and other natural sciences. He is best known
for his work as a science popularizer and
communicator. His best known scientific contribution
is research on extraterrestrial life, including
experimental demonstration of the production
of amino acids from basic chemicals by radiation.
Sagan assembled the first physical messages
sent into space: the Pioneer plaque and the
Voyager Golden Record, universal messages
that could potentially be understood by any
extraterrestrial intelligence that might find
them. Sagan argued the now accepted hypothesis
that the high surface temperatures of Venus
can be attributed to and calculated using
the greenhouse effect.Sagan published more
than 600 scientific papers and articles and
was author, co-author or editor of more than
20 books. He wrote many popular science books,
such as The Dragons of Eden, Broca's Brain
and Pale Blue Dot, and narrated and co-wrote
the award-winning 1980 television series Cosmos:
A Personal Voyage. The most widely watched
series in the history of American public television,
Cosmos has been seen by at least 500 million
people across 60 different countries. The
book Cosmos was published to accompany the
series. He also wrote the science fiction
novel Contact, the basis for a 1997 film of
the same name. His papers, containing 595,000
items, are archived at The Library of Congress.Sagan
advocated scientific skeptical inquiry and
the scientific method, pioneered exobiology
and promoted the Search for Extra-Terrestrial
Intelligence (SETI). He spent most of his
career as a professor of astronomy at Cornell
University, where he directed the Laboratory
for Planetary Studies. Sagan and his works
received numerous awards and honors, including
the NASA Distinguished Public Service Medal,
the National Academy of Sciences Public Welfare
Medal, the Pulitzer Prize for General Non-Fiction
for his book The Dragons of Eden, and, regarding
Cosmos: A Personal Voyage, two Emmy Awards,
the Peabody Award, and the Hugo Award. He
married three times and had five children.
After suffering from myelodysplasia, Sagan
died of pneumonia at the age of 62, on December
20, 1996.
== Early life and education ==
Carl Sagan was born in Brooklyn, New York.
His father, Samuel Sagan, was an immigrant
garment worker from Kamianets-Podilskyi, then
in the Russian Empire, in today's Ukraine.
His mother, Rachel Molly Gruber, was a housewife
from New York. Carl was named in honor of
Rachel's biological mother, Chaiya Clara,
in Sagan's words, "the mother she never knew."He
had a sister, Carol, and the family lived
in a modest apartment near the Atlantic Ocean,
in Bensonhurst, a Brooklyn neighborhood. According
to Sagan, they were Reform Jews, the most
liberal of North American Judaism's four main
groups. Carl and his sister agreed that their
father was not especially religious, but that
their mother "definitely believed in God,
and was active in the temple;... and served
only kosher meat." During the depths of the
Depression, his father worked as a theater
usher.
According to biographer Keay Davidson, Sagan's
"inner war" was a result of his close relationship
with both of his parents, who were in many
ways "opposites." Sagan traced his later analytical
urges to his mother, a woman who had been
extremely poor as a child in New York City
during World War I and the 1920s. As a young
woman she had held her own intellectual ambitions,
but they were frustrated by social restrictions:
her poverty, her status as a woman and a wife,
and her Jewish ethnicity. Davidson notes that
she therefore "worshipped her only son, Carl.
He would fulfill her unfulfilled dreams."However,
he claimed that his sense of wonder came from
his father, who in his free time gave apples
to the poor or helped soothe labor-management
tensions within New York's garment industry.
Although he was awed by Carl's intellectual
abilities, he took his son's inquisitiveness
in stride and saw it as part of his growing
up. In his later years as a writer and scientist,
Sagan would often draw on his childhood memories
to illustrate scientific points, as he did
in his book, Shadows of Forgotten Ancestors.
Sagan describes his parents' influence on
his later thinking:
My parents were not scientists. They knew
almost nothing about science. But in introducing
me simultaneously to skepticism and to wonder,
they taught me the two uneasily cohabiting
modes of thought that are central to the scientific
method.
=== 1939 World's Fair ===
Sagan recalls that one of his most defining
moments was when his parents took him to the
1939 New York World's Fair when he was four
years old. The exhibits became a turning point
in his life. He later recalled the moving
map of the America of Tomorrow exhibit: "It
showed beautiful highways and cloverleaves
and little General Motors cars all carrying
people to skyscrapers, buildings with lovely
spires, flying buttresses—and it looked
great!" At other exhibits, he remembered how
a flashlight that shone on a photoelectric
cell created a crackling sound, and how the
sound from a tuning fork became a wave on
an oscilloscope. He also witnessed the future
media technology that would replace radio:
television. Sagan wrote:
Plainly, the world held wonders of a kind
I had never guessed. How could a tone become
a picture and light become a noise?
He also saw one of the Fair's most publicized
events, the burial of a time capsule at Flushing
Meadows, which contained mementos of the 1930s
to be recovered by Earth's descendants in
a future millennium. "The time capsule thrilled
Carl," writes Davidson. As an adult, Sagan
and his colleagues would create similar time
capsules—capsules that would be sent out
into the galaxy; these were the Pioneer plaque
and the Voyager Golden Record précis, all
of which were spinoffs of Sagan's memories
of the World's Fair.
=== World War II ===
During World War II Sagan's family worried
about the fate of their European relatives.
Sagan, however, was generally unaware of the
details of the ongoing war. He wrote, "Sure,
we had relatives who were caught up in the
Holocaust. Hitler was not a popular fellow
in our household... But on the other hand,
I was fairly insulated from the horrors of
the war." His sister, Carol, said that their
mother "above all wanted to protect Carl...
She had an extraordinarily difficult time
dealing with World War II and the Holocaust."
Sagan's book, The Demon-Haunted World (1996),
included his memories of this conflicted period,
when his family dealt with the realities of
the war in Europe but tried to prevent it
from undermining his optimistic spirit.
=== Inquisitiveness about nature ===
Soon after entering elementary school he began
to express a strong inquisitiveness about
nature. Sagan recalled taking his first trips
to the public library alone, at the age of
five, when his mother got him a library card.
He wanted to learn what stars were, since
none of his friends or their parents could
give him a clear answer:
I went to the librarian and asked for a book
about stars;... And the answer was stunning.
It was that the Sun was a star but really
close. The stars were suns, but so far away
they were just little points of light ... The
scale of the universe suddenly opened up to
me. It was a kind of religious experience.
There was a magnificence to it, a grandeur,
a scale which has never left me. Never ever
left me.
At about age six or seven, he and a close
friend took trips to the American Museum of
Natural History across the East River in Manhattan.
While there, they went to the Hayden Planetarium
and walked around the museum's exhibits of
space objects, such as meteorites, and displays
of dinosaurs and animals in natural settings.
Sagan writes about those visits:
I was transfixed by the dioramas—lifelike
representations of animals and their habitats
all over the world. Penguins on the dimly
lit Antarctic ice; ...a family of gorillas,
the male beating his chest, ...an American
grizzly bear standing on his hind legs, ten
or twelve feet tall, and staring me right
in the eye.
His parents helped nurture his growing interest
in science by buying him chemistry sets and
reading materials. His interest in space,
however, was his primary focus, especially
after reading science fiction stories by writers
such as H. G. Wells and Edgar Rice Burroughs,
which stirred his imagination about life on
other planets such as Mars. According to biographer
Ray Spangenburg, these early years as Sagan
tried to understand the mysteries of the planets
became a "driving force in his life, a continual
spark to his intellect, and a quest that would
never be forgotten."In 1947 he discovered
Astounding Science Fiction magazine, which
introduced him to more hard science fiction
speculations than those in Burroughs's novels.
That same year inaugurated the "flying saucer"
mass hysteria with the young Carl suspecting
the "discs" might be alien spaceships.
=== High school years ===
Sagan had lived in Bensonhurst where he went
to David A. Boody Junior High School. He had
his bar mitzvah in Bensonhurst when he turned
13. The following year, 1948, his family moved
to the nearby town of Rahway, New Jersey for
his father's work, where Sagan then entered
Rahway High School. He graduated in 1951.
Rahway was an older industrial town, and the
Sagans were among its few Jewish families.
Sagan was a straight-A student but was bored
due to unchallenging classes and uninspiring
teachers. His teachers realized this and tried
to convince his parents to send him to a private
school, the administrator telling them, "This
kid ought to go to a school for gifted children,
he has something really remarkable." This
they couldn't do, partly because of the cost.
Sagan was made president of the school's chemistry
club, and at home he set up his own laboratory.
He taught himself about molecules by making
cardboard cutouts to help him visualize how
molecules were formed: "I found that about
as interesting as doing [chemical] experiments,"
he said. Sagan remained mostly interested
in astronomy as a hobby, and in his junior
year made it a career goal after he learned
that astronomers were paid for doing what
he always enjoyed: "That was a splendid day­­­­—when
I began to suspect that if I tried hard I
could do astronomy full-time, not just part-time."Before
the end of high school, he entered an essay
contest in which he posed the question of
whether human contact with advanced life forms
from another planet might be as disastrous
for people on Earth as it was for Native Americans
when they first had contact with Europeans.
The subject was considered controversial,
but his rhetorical skill won over the judges
and they awarded him first prize. By graduation,
his classmates had voted him "Most likely
to succeed," and put him in line to be valedictorian.
=== University education ===
Sagan attended the University of Chicago,
which was one of the few colleges he applied
to that would consider admitting a sixteen-year-old,
despite his excellent high school grades.
Its Chancellor, Robert Hutchins, structured
the school as an "ideal meritocracy," with
no age requirement. The school also employed
a number of the nation's leading scientists,
including Enrico Fermi and Edward Teller,
along with operating the famous Yerkes Observatory.During
his time as an honors program undergraduate,
Sagan worked in the laboratory of the geneticist
H. J. Muller and wrote a thesis on the origins
of life with physical chemist Harold Urey.
Sagan joined the Ryerson Astronomical Society,
received a B.A. degree in laughingly self-proclaimed
"nothing" with general and special honors
in 1954, and a B.S. degree in physics in 1955.
He went on to earn a M.S. degree in physics
in 1956, before earning a Ph.D. degree in
1960 with his thesis Physical Studies of Planets
submitted to the Department of Astronomy and
Astrophysics.He used the summer months of
his graduate studies to work with his dissertation
director, planetary scientist Gerard Kuiper,
as well as physicist George Gamow, and chemist
Melvin Calvin. The title of Sagan's dissertation
reflects his shared interests with Kuiper,
who throughout the 1950s had been president
of the International Astronomical Union's
commission on "Physical Studies of Planets
and Satellites". In 1958, the two worked on
the classified military Project A119, the
secret Air Force plan to detonate a nuclear
warhead on the Moon.Sagan had a "Top Secret"
clearance at the U.S. Air Force and a "Secret"
clearance with NASA. While working on his
doctoral dissertation, Sagan revealed US Government
classified titles of two Project A119 papers
when he applied for a University of California
at Berkeley scholarship in 1959. The leak
was not publicly revealed until 1999, when
it was published in the journal "Nature".
A follow-up letter to the journal by project
leader Leonard Reiffel confirmed Sagan's security
leak.
== Career and research ==
From 1960 to 1962 Sagan was a Miller Fellow
at the University of California, Berkeley.
Meanwhile, he published an article in 1961
in the journal Science on the atmosphere of
Venus, while also working with NASA's Mariner
2 team, and served as a "Planetary Sciences
Consultant" to the RAND Corporation.After
the publication of Sagan's Science article,
in 1961 Harvard University astronomers Fred
Whipple and Donald Menzel offered Sagan the
opportunity to give a colloquium at Harvard,
and they subsequently offered him a lecturer
position at the institution. Sagan instead
asked to be made an assistant professor, and
eventually Whipple and Menzel were able to
convince Harvard to offer Sagan the assistant
professor position he requested. Sagan lectured,
performed research, and advised graduate students
at the institution from 1963 until 1968, as
well as working at the Smithsonian Astrophysical
Observatory, also located in Cambridge, Massachusetts.
In 1968, Sagan was denied tenure at Harvard.
He later indicated the decision was very much
unexpected. The tenure denial has been blamed
on several factors, including that he focused
his interests too broadly across a number
of areas (while the norm in academia is to
become a renowned expert in a narrow specialty),
and perhaps because of his well-publicized
scientific advocacy, which some scientists
perceived as borrowing the ideas of others
for little more than self-promotion. An advisor
from his years as an undergraduate student,
Harold Urey, wrote a letter to the tenure
committee recommending strongly against tenure
for Sagan.
Long before the ill-fated tenure process,
Cornell University astronomer Thomas Gold
had courted Sagan to move to Ithaca, New York
and join the faculty at Cornell. Following
the denial of tenure from Harvard, Sagan accepted
Gold's offer and remained a faculty member
at Cornell for nearly 30 years until his death
in 1996. Unlike Harvard, the smaller and more
laid-back astronomy department at Cornell
welcomed Sagan's growing celebrity status.
Following two years as an associate professor,
Sagan became a full professor at Cornell in
1970, and directed the Laboratory for Planetary
Studies there. From 1972 to 1981, he was associate
director of the Center for Radiophysics and
Space Research (CRSR) at Cornell. In 1976,
he became the David Duncan Professor of Astronomy
and Space Sciences, a position he held for
the remainder of his life.Sagan was associated
with the U.S. space program from its inception.
From the 1950s onward, he worked as an advisor
to NASA, where one of his duties included
briefing the Apollo astronauts before their
flights to the Moon. Sagan contributed to
many of the robotic spacecraft missions that
explored the Solar System, arranging experiments
on many of the expeditions. 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 carrying another copy of
the plaque, was launched the following year.
He continued to refine his designs; the most
elaborate message he helped to develop and
assemble was the Voyager Golden Record that
was sent out with the Voyager space probes
in 1977. Sagan often challenged the decisions
to fund the Space Shuttle and the International
Space Station at the expense of further robotic
missions.
=== Scientific achievements ===
Former student David Morrison describes Sagan
as "an 'idea person' and a master of intuitive
physical arguments and 'back of the envelope'
calculations," and Gerard Kuiper said that
"Some persons work best in specializing on
a major program in the laboratory; others
are best in liaison between sciences. Dr.
Sagan belongs in the latter group."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 Venus' 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 waves 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 would make Europa potentially
habitable. Europa's subsurface ocean of water
was later indirectly confirmed by the spacecraft
Galileo. The mystery of Titan's reddish haze
was also solved with Sagan's help. The reddish
haze was revealed to be due to complex organic
molecules constantly raining down onto Titan's
surface.He further contributed insights regarding
the atmospheres of Venus and Jupiter as well
as seasonal changes on Mars. 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 also known 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". He was denied membership in the
Academy, reportedly because his media activities
made him unpopular with many other scientists.As
of 2017, Sagan is the most cited SETI scientist
and one of the most cited planetary scientists.
=== Cosmos: popularizing science on TV ===
In 1980 Sagan co-wrote and narrated the award-winning
13-part PBS television series, Cosmos: A Personal
Voyage, which became the most widely watched
series in the history of American public television.
The show has been seen by at least 500 million
people across 60 different countries. The
book, Cosmos, written by Sagan, was published
to accompany the series.Because of his earlier
popularity as a science writer from his best-selling
books, including The Dragons of Eden, which
won him a Pulitzer Prize in 1977, he was asked
to write and narrate the show. It was targeted
to a general audience of viewers who Sagan
felt had lost interest in science, partly
due to a stifled educational system.Each of
the 13 episodes was created to focus on a
particular subject or person, thereby demonstrating
the synergy of the universe. They covered
a wide range of scientific subjects including
the origin of life and a perspective of humans'
place on Earth.
The show won an Emmy along with a Peabody
Award, and transformed Sagan from an obscure
astronomer into a pop-culture icon. Time magazine
ran a cover story about Sagan soon after the
show broadcast, referring to him as "creator,
chief writer and host-narrator of the show.
In 2000, "Cosmos" was released on a remastered
set of DVDs.
=== "Billions and billions" ===
Sagan was invited to frequent appearances
on The Tonight Show Starring Johnny Carson.
After Cosmos aired, he became associated with
the catchphrase "billions and billions", although
he never actually used the phrase in the Cosmos
series. He rather used the term "billions
upon billions." Carson, however, would sometimes
use the phrase during his parodies of Sagan.As
a humorous tribute to Sagan and his association
with the catchphrase "billions and billions",
a sagan has been defined as a unit of measurement
equivalent to a very large number – technically
at least four billion (two billion plus two
billion) – of anything.
=== Scientific and critical thinking advocacy
===
Sagan's ability to convey his ideas allowed
many people to understand the cosmos better—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 series of Royal Institution
Christmas Lectures in London.Sagan was a proponent
of the search for extraterrestrial life. He
urged the scientific community to listen with
radio telescopes for signals from potential
intelligent extraterrestrial life-forms. Sagan
was so persuasive 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
signaled a tremendous increase in the respectability
of a then-controversial field. Sagan also
helped Frank Drake write the Arecibo message,
a radio message beamed into space from the
Arecibo radio telescope on November 16, 1974,
aimed at informing potential extraterrestrials
about Earth.
Sagan was chief technology officer of the
professional planetary research journal Icarus
for twelve years. He co-founded The Planetary
Society, 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 (AAAS).
At the height of the Cold War, Sagan became
involved in nuclear disarmament efforts by
promoting hypotheses on the effects of nuclear
war, when Paul Crutzen's "Twilight at Noon"
concept suggested that a substantial nuclear
exchange could trigger a nuclear twilight
and upset the delicate balance of life on
Earth by cooling the surface. In 1983 he was
one of five authors—the "S"—in the follow-up
"TTAPS" model (as the research paper came
to be known), which contained the first use
of the term "nuclear winter", which his colleague
Richard P. Turco had coined. In 1984 he co-authored
the book The Cold and the Dark: The World
after Nuclear War and in 1990 he co-authored
the book A Path Where No Man Thought: Nuclear
Winter and the End of the Arms Race, which
explains the nuclear winter hypothesis and
advocates nuclear disarmament. Sagan received
a great deal of skepticism and disdain for
the use of media to disseminate a very uncertain
hypothesis. In personal correspondence with
Edward Teller c. 1983, although beginning
amicably, with Teller expressing support for
continued research to ascertain the credibility
of the winter hypothesis, Sagan and Teller's
correspondence would ultimately result in
Teller writing "A propagandist is one who
uses incomplete information to produce maximum
persuasion. I can compliment you on being,
indeed, an excellent propagandist remembering
that a propagandist is the better the less
he appears to be one". Biographers of Sagan
would also comment that from a scientific
viewpoint, nuclear winter was a low point
for Sagan, although, politically speaking,
it popularized his image amongst the public.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 in 1985, based on a film treatment
he wrote with his wife in 1979, but he did
not live to see the book's 1997 motion picture
adaptation, which starred Jodie Foster and
won the 1998 Hugo Award for Best Dramatic
Presentation.
Sagan 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's
Charlie Rose program in January 1995. Sagan
also wrote the introduction for Stephen Hawking's
bestseller, 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 death, David
Morrison, a former student of Sagan's, recalled
"Sagan's immense contributions to planetary
research, the public understanding of science,
and the skeptical movement" in Skeptical Inquirer.
Following Saddam Hussein's threats to light
Kuwait's oil wells on fire in response to
any physical challenge to Iraqi control of
the oil assets, Sagan together with his "TTAPS"
colleagues and Paul Crutzen, warned in January
1991 in the Baltimore Sun and Wilmington Morning
Star newspapers that if the fires were left
to burn over a period of several months, enough
smoke from the 600 or so 1991 Kuwaiti oil
fires "might get so high as to disrupt agriculture
in much of South Asia ..." and that this possibility
should "affect the war plans"; these claims
were also the subject of a televised debate
between Sagan and physicist Fred Singer on
22 January, aired on the ABC News program
Nightline. In the televised debate, Sagan
argued that the effects of the smoke would
be similar to the effects of a nuclear winter,
with Singer arguing to the contrary. After
the debate, the fires burnt for many months
before extinguishing efforts were complete.
The results of the smoke did not produce continental-sized
cooling. Sagan later conceded in The Demon-Haunted
World that the prediction did not turn out
to be correct: "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 asteroids/near-Earth
objects (NEOs) that might impact the Earth
but to forestall or postpone developing the
technological methods that would be needed
to defend against them. He argued that all
of the numerous methods proposed to alter
the orbit of an asteroid, including the employment
of nuclear detonations, created a Deflection
Dilemma: if the ability to deflect an asteroid
away from the Earth exists, then one would
also have the ability to divert a non-threatening
object towards Earth, creating an immensely
destructive weapon. In a 1994 paper he co-authored,
he ridiculed a 3-day long "Near-Earth Object
Interception Workshop" held by Los Alamos
National Laboratory (LANL) in 1993 that did
not, "even in passing" state that such interception
and deflection technologies could have these
"ancillary dangers".Sagan remained hopeful
that the natural NEO impact threat, and the
intrinsically double-edged essence of the
methods to prevent these threats, would serve
as a "new and potent motivation to maturing
international relations". Later acknowledging
that, with sufficient international oversight,
in the future a "work our way up" approach
to implementing nuclear explosive deflection
methods could be fielded, and when sufficient
knowledge was gained, to use them to aid in
mining asteroids. His interest in the use
of nuclear detonations in space grew out of
his work in 1958 for the Armour Research Foundation's
Project A119, concerning the possibility of
detonating a nuclear device on the lunar surface.
Sagan was a critic of Plato, having said of
the ancient Greek philosopher: "Science and
mathematics were to be removed from the hands
of the merchants and the artisans. This tendency
found its most effective advocate in a follower
of Pythagoras named Plato" and He (Plato)
believed that ideas were far more real than
the natural world. He advised the astronomers
not to waste their time observing the stars
and planets. It was better, he believed, just
to think about them. Plato expressed hostility
to observation and experiment. He taught contempt
for the real world and disdain for the practical
application of scientific knowledge. Plato's
followers succeeded in extinguishing the light
of science and experiment that had been kindled
by Democritus and the other Ionians.
=== Popularizing science ===
Speaking about his activities in popularizing
science, Sagan said that there were at least
two reasons for scientists to share the purposes
of science and its contemporary state. Simple
self-interest was one: much of the funding
for science came from the public, and the
public therefore had the right to know how
the money was being spent. If scientists increased
public admiration for science, there was a
good chance of having more public supporters.
The other reason was the excitement of communicating
one's own excitement about science to others.
=== Criticisms ===
While Sagan was widely adored by the general
public, his reputation in the scientific community
was more polarized. Critics sometimes characterized
his work as fanciful, non-rigorous, and self-aggrandizing,
and others complained in his later years that
he neglected his role as a faculty member
to foster his celebrity status.One of Sagan's
harshest critics, Harold Urey, felt that Sagan
was getting too much publicity for a scientist
and was treating some scientific theories
too casually. Urey and Sagan were said to
have different philosophies of science, according
to Davidson. While Urey was an "old-time empiricist"
who avoided theorizing about the unknown,
Sagan was by contrast willing to speculate
openly about such matters. Fred Whipple wanted
Harvard to keep Sagan there, but learned that
because Urey was a Nobel laureate, his opinion
was an important factor in Harvard denying
Sagan tenure.Sagan's Harvard friend Lester
Grinspoon also stated, "I know Harvard well
enough to know there are people there who
certainly do not like people who are outspoken."
Grinspoon added:
Wherever you turned, there was one astronomer
being quoted on everything, one astronomer
whose face you were seeing on TV, and one
astronomer whose books had the preferred display
slot at the local bookstore.
Some, like Urey, later came to realize Sagan's
popular brand of scientific advocacy was beneficial
to the science as a whole. Urey especially
liked Sagan's 1977 book, The Dragons of Eden,
and wrote Sagan with his opinion: "I like
it very much and am amazed that someone like
you has such an intimate knowledge of the
various features of the problem...I congratulate
you...You are a man of many talents."Sagan
was accused of borrowing some ideas of others
for his own benefit, and countered these claims
by explaining that the misappropriation was
an unfortunate side effect of his role as
a science communicator and explainer, and
that he attempted to give proper credit whenever
possible.
=== Social concerns ===
Sagan believed that the Drake equation, on
substitution of reasonable estimates, 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 self-destruct. 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?" Sagan had already resigned
from the Air Force Scientific Advisory Board's
UFO investigating Condon Committee and voluntarily
surrendered his top secret clearance in protest
over the Vietnam War. Following his marriage
to his third wife (novelist Ann Druyan) in
June 1981, Sagan became more politically active—particularly
in opposing escalation of the nuclear arms
race under President Ronald Reagan.
In March 1983, Reagan announced the Strategic
Defense Initiative—a multibillion-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 such a system
than it would be for an enemy to defeat it
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, US
anti-nuclear and peace activists staged a
series of protest actions at the Nevada Test
Site, beginning on Easter Sunday in 1986 and
continuing through 1987. Hundreds of people
in the "Nevada Desert Experience" group were
arrested, including Sagan, who was arrested
on two separate occasions as he climbed over
a chain-link fence at the test site during
the underground Operation Charioteer and United
States's Musketeer nuclear test series of
detonations.Sagan was also a vocal advocate
of the controversial notion of testosterone
poisoning, arguing in 1992 that human males
could become gripped by an "unusually severe
[case of] testosterone poisoning" and this
could compel them to become genocidal. In
his review of Moondance magazine writer Daniela
Gioseffi's 1990 book Women on War, he argues
that females are the only half of humanity
"untainted by testosterone poisoning". One
chapter of his 1993 book, Shadows of Forgotten
Ancestors is dedicated to testosterone and
its alleged poisonous effects.
== Personal life and beliefs ==
Sagan was married three times. In 1957, he
married biologist Lynn Margulis. The couple
had two children, Jeremy and Dorion Sagan.
After Carl Sagan and Margulis divorced, he
married artist Linda Salzman in 1968 and they
also had a child together, Nick Sagan. During
these marriages, Carl Sagan focused heavily
on his career, a factor which may have contributed
to Sagan's first divorce. In 1981, Sagan married
author Ann Druyan and they later had two children,
Alexandra and Samuel Sagan. Carl Sagan and
Druyan remained married until his death in
1996. He lived in an Egyptian revival house
in Ithaca perched on the edge of a cliff that
had formerly been the headquarters of a Cornell
secret society.Isaac Asimov described Sagan
as one of only two people he ever met whose
intellect surpassed his own. The other, he
claimed, was the computer scientist and artificial
intelligence expert Marvin Minsky.
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.
For example: 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—for example Baruch Spinoza
and Albert Einstein—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.
In another description of his view on the
concept of God, Sagan emphatically wrote:
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.
On atheism, Sagan commented in 1981: An atheist
is someone who is certain that God does not
exist, someone who has compelling evidence
against the existence of God. I know of no
such compelling evidence. Because God can
be relegated to remote times and places and
to ultimate causes, we would have to know
a great deal more about the universe than
we do now to be sure that no such God exists.
To be certain of the existence of God and
to be certain of the nonexistence of God seem
to me to be the confident extremes in a subject
so riddled with doubt and uncertainty as to
inspire very little confidence indeed.
Sagan also commented on Christianity and the
Jefferson Bible, stating "My long-time view
about Christianity is that it represents an
amalgam of two seemingly immiscible parts,
the religion of Jesus and the religion of
Paul. Thomas Jefferson attempted to excise
the Pauline parts of the New Testament. There
wasn't much left when he was done, but it
was an inspiring document."
Regarding spirituality and its relationship
with science, Sagan stated: 'Spirit' comes
from the Latin word 'to breathe'. What we
breathe is air, which is certainly matter,
however thin. Despite usage to the contrary,
there is no necessary implication in the word
'spiritual' that we are talking of anything
other than matter (including the matter of
which the brain is made), or anything
outside the realm of science. On occasion,
I will feel free to use the word. Science
is not only compatible with spirituality;
it is a profound source of spirituality. When
we recognize our place in an immensity of
light-years and in the passage of ages, when
we grasp the intricacy, beauty, and subtlety
of life, then that soaring feeling, that sense
of elation and humility combined, is surely
spiritual.
An environmental appeal, "Preserving and Cherishing
the Earth", signed by Sagan with other noted
scientists in January 1990, stated that "The
historical record makes clear that religious
teaching, example, and leadership are powerfully
able to influence personal conduct and commitment...
Thus, there is a vital role for religion and
science."
In reply to a question in 1996 about his religious
beliefs, Sagan answered, "I'm agnostic." Sagan
maintained that the idea of a creator God
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's views
on religion have been interpreted as a form
of pantheism comparable to Einstein's belief
in Spinoza's God. His son, Dorion Sagan said,
"My father believed in the God of Spinoza
and Einstein, God not behind nature but as
nature, equivalent to it." His last wife,
Ann Druyan, stated: When my husband died,
because he was so famous and known for not
being a believer, many people would come up
to me—it still sometimes happens—and ask
me if Carl changed at the end and converted
to a belief in an afterlife. They also frequently
ask me if I think I will see him again. Carl
faced his death with unflagging courage and
never sought refuge in illusions. The tragedy
was that we knew we would never see each other
again. I don't ever expect to be reunited
with Carl.
In 2006, Ann Druyan edited Sagan's 1985 Glasgow
Gifford Lectures in Natural Theology into
a 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 is also widely regarded as a freethinker
or skeptic; one of his most famous quotations,
in Cosmos, was, "Extraordinary claims require
extraordinary evidence" (called the "Sagan
standard" by some). This was based on a nearly
identical statement by fellow founder of the
Committee for the Scientific Investigation
of Claims of the Paranormal, Marcello Truzzi,
"An extraordinary claim requires extraordinary
proof." This idea had been earlier aphorized
in Théodore Flournoy's work From India to
the Planet Mars (1899) from a longer quote
by Pierre-Simon Laplace (1749–1827), a French
mathematician and astronomer, as the Principle
of Laplace: "The weight of the evidence should
be proportioned to the strangeness of the
facts."Late in his life, Sagan's books elaborated
on his skeptical, naturalistic view of the
world. In The Demon-Haunted World, 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,
as well as an account by his widow, Ann Druyan,
of his death in relation to his having been
a skeptic, agnostic, and freethinker.
Sagan warned against humans' tendency towards
anthropocentrism. He was the faculty adviser
for the Cornell Students for the Ethical Treatment
of Animals. In the Cosmos chapter "Blues For
a Red Planet", Sagan wrote, "If there is life
on Mars, I believe we should do nothing with
Mars. Mars then belongs to the Martians, even
if the Martians are only microbes."Sagan was
a user and advocate of marijuana. Under the
pseudonym "Mr. X", he contributed an essay
about smoking cannabis to the 1971 book Marihuana
Reconsidered. The essay explained that marijuana
use had helped to inspire some of Sagan's
works and enhance sensual and intellectual
experiences. After Sagan's death, his friend
Lester Grinspoon disclosed this information
to Sagan's biographer, Keay Davidson. The
publishing of the biography, Carl Sagan: A
Life, in 1999 brought media attention to this
aspect of Sagan's life. Not long after his
death, widow Ann Druyan went on to preside
over the board of directors of the National
Organization for the Reform of Marijuana Laws
(NORML), a non-profit organization dedicated
to reforming cannabis laws.In 1994, engineers
at Apple Computer code-named the Power Macintosh
7100 "Carl Sagan" in the hope that Apple would
make "billions and billions" with the sale
of the PowerMac 7100. The name was only used
internally, but Sagan was concerned that it
would become a product endorsement and sent
Apple a cease-and-desist letter. Apple complied,
but engineers retaliated by changing the internal
codename to "BHA" for "Butt-Head Astronomer".
Sagan then sued Apple for libel in federal
court. The court granted Apple's motion to
dismiss Sagan's claims and opined in dicta
that a reader aware of the context would understand
Apple was "clearly attempting to retaliate
in a humorous and satirical way", and that
"It strains reason to conclude that Defendant
was attempting to criticize Plaintiff's reputation
or competency as an astronomer. One does not
seriously attack the expertise of a scientist
using the undefined phrase 'butt-head'." Sagan
then sued for Apple's original use of his
name and likeness, but again lost. Sagan appealed
the ruling. In November 1995, an out-of-court
settlement was reached and Apple's office
of trademarks and patents released a conciliatory
statement that "Apple has always had great
respect for Dr. Sagan. It was never Apple's
intention to cause Dr. Sagan or his family
any embarrassment or concern." Apple's third
and final code name for the project was "LAW",
short for "Lawyers are Wimps".Sagan briefly
served as an adviser on Stanley Kubrick's
film 2001: A Space Odyssey. Sagan proposed
that the film suggest, rather than depict,
extraterrestrial superintelligence.
=== Sagan and UFOs ===
In 1947, the year that inaugurated the "flying
saucer" craze, the young Sagan suspected the
"discs" might be alien spaceships.Sagan's
interest in UFO reports prompted him on August
3, 1952, to write a letter to U.S. Secretary
of State Dean Acheson to ask how the United
States would respond if flying saucers turned
out to be extraterrestrial. He later had several
conversations on the subject in 1964 with
Jacques Vallée. 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 (1966–68), 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.
Sociologist Ron Westrum writes that "The high
point of Sagan's treatment of the UFO question
was the AAAS' 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 UFO's: 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 wrote 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.
=== Sagan's Paradox ===
Sagan's contribution to the 1969 symposium
was an attack on the belief that UFOs are
piloted by extraterrestrial beings: Applying
several logical assumptions (see Drake equation),
Sagan calculated the possible number of advanced
civilizations capable of interstellar travel
to be about one million. He projected that
any civilization wishing to check on all the
others on a regular basis of, say, once a
year would have to launch 10,000 spacecraft
annually. Not only does that seem like an
unreasonable number of launchings, but it
would take all the material in one percent
of the universe's stars to produce all the
spaceships needed for all the civilizations
to seek each other out.
To argue that the Earth was being chosen for
regular visitations, Sagan said, one would
have to assume that the planet is somehow
unique. And that assumption "goes exactly
against the idea that there are lots of civilizations
around. Because if there are then our sort
of civilization must be pretty common. And
if we're not pretty common then there aren't
going to be many civilizations advanced enough
to send visitors."
This argument, which some called "Sagan's
paradox," helped to establish a new school
of thought: the belief that extraterrestrial
life exists but has nothing to do with UFOs.
The new belief had a salutary effect on UFO
studies. It helped separate researchers who
wanted to identify unidentified flying objects
from those who wanted to identify their pilots.
And it gave scientists opportunities to search
the universe for intelligent life unencumbered
by the stigma associated with UFOs.
=== Death ===
After suffering from myelodysplasia for two
years, and receiving three bone marrow transplants
from his sister, Carol, Sagan died of pneumonia
at the age of 62, at the Fred Hutchinson Cancer
Research Center in Seattle, Washington, in
the early morning of December 20, 1996.
Burial took place at Lakeview Cemetery in
Ithaca, New York.
== Awards and honors ==
=== 
Posthumous recognition ===
The 1997 movie Contact, based on Sagan's novel
of the same name and finished after his death,
ends with the dedication "For Carl". His photo
can also be seen at 59:23 in the film.
In 1997 the Sagan Planet Walk was opened in
Ithaca, New York. It is a walking-scale model
of the Solar System, extending 1.2 km from
the center of The Commons in downtown Ithaca
to the Sciencenter, a hands-on museum. The
exhibition was created in memory of Carl Sagan,
who was an Ithaca resident and Cornell Professor.
Professor Sagan had been a founding member
of the museum's advisory board.The landing
site of the unmanned Mars Pathfinder spacecraft
was renamed the Carl Sagan Memorial Station
on July 5, 1997. Asteroid 2709 Sagan is named
in his honor, as is the Carl Sagan Institute
for the search of habitable planets.
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
rovers Spirit and Opportunity successfully
on Mars in 2004.
On November 9, 2001, on what would have been
Sagan's 67th birthday, the 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 has at least three awards named in his
honor:
The Carl Sagan Memorial Award presented jointly
since 1997 by the American Astronomical Society
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 was the
first recipient of the CSSP award in 1993.August
2007 the Independent Investigations Group
(IIG) awarded Sagan posthumously a Lifetime
Achievement Award. This honor has also been
awarded to Harry Houdini and James Randi.Beginning
in 2009, a musical project known as Symphony
of Science sampled several excerpts of Sagan
from his series Cosmos and remixed them to
electronic music. To date, the videos have
received over 21 million views worldwide on
YouTube.The 2014 Swedish science fiction short
film Wanderers uses excerpts of Sagan's narration
of his book Pale Blue Dot, played over digitally-created
visuals of humanity's possible future expansion
into outer space.In February 2015, the Finnish-based
symphonic metal band Nightwish released the
song "Sagan" as a non-album bonus track for
their single "Élan". The song, written by
the band's songwriter/composer/keyboardist
Tuomas Holopainen, is an homage to the life
and work of the late Carl Sagan.
In August 2015, it was announced that a biopic
of Sagan's life was being planned by Warner
Bros.
=== Publications ===
== 
See also ==
Carl Sagan portal
List of peace activists
Sagan effect
Neil deGrasse Tyson
== Notes
