in ''
Who's Out There?'' (1973), an
award-winning NASA documentary film by
Robert Drew. 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 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
academic tenure at Harvard. He later indicated that the decision was very unexpected. The 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. 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. He often challenged the decisions to fund the
Space Shuttle and the
International Space Station at the expense of further robotic missions. Sagan assembled the first physical message that was sent into space: a
gold-plated 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. He contributed to the
Voyager Golden Record, a sample of the sights and sounds of Earth sent with the
Voyager space probes in 1977.
Among much else, it features music by Bach,
Beethoven and
Chuck Berry.
Scientific achievements Former student
David Morrison described Sagan as "an 'idea person' and a master of intuitive physical arguments and '
back of the envelope' calculations", 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 . 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. Sagan further contributed insights regarding the atmospheres of Venus and
Jupiter, as well as seasonal changes on
Mars. He also perceived
climate change 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. He testified to the US Congress in 1985 that the greenhouse effect would change the Earth's climate system. 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. He argued in favor of the hypothesis, which has since been accepted, that the high surface temperatures of
Venus are the result of the
greenhouse effect. 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. , Sagan is the most cited SETI scientist and one of the most cited planetary scientists. He edited
Icarus from 1975 to 1979. In 1980, he cofounded the
Planetary Society. Sagan's first
popular science book was
The Cosmic Connection. He introduced the
Cosmic Calendar in
The Dragons of Eden, which won the 1978
Pulitzer Prize for General Nonfiction. He delivered the 1977
Royal Institution Christmas Lectures on
The Planets. '' (1980) Sagan and
Ann Druyan co-wrote the 13-part
PBS documentary
Cosmos: A Personal Voyage. It drew on earlier documentaries, notably
Jacob Bronowski's
The Ascent of Man. The production involved the recreation of the
Library of Alexandria. It covered an array of scientific subjects, including the
evolution of stars and how it is linked to the
evolution of life. Frederic Golden wrote "The series' name comes from the Greek word for the ordered universe, the antithesis of chaos. It is an apt choice.
Cosmos is nothing less than Sagan's attempt to make sense out of what is for many people the hopelessly baffling world of 20th century science. To unfold his story he roves through two millennia of scientific progress, often shuttling back and forth over the centuries like some Wellsian time traveler. One moment he is seated in a cafe on the Aegean island of
Samos, home of
Pythagoras and
Aristarchus, explaining the first stirrings of Greek scientific prowess. At another moment, he is strolling through the venerable
Cavendish Laboratories of England's Cambridge University, recounting the birth of modern atomic physics. Sagan makes science as palatable as the apple pie he lovingly cuts up in a Cambridge University dining room in order to make a point about matter." He offers an optimistic and a perspective of humans' place on Earth, arguing that "We are a way for the cosmos to know itself."
Cosmos has been seen by at least 500 million people across 60 countries, making it the most widely watched series in the history of American public television until
Ken Burns's
The Civil War in 1990. and a
Peabody. It featured music by Bach,
Vivaldi,
Vangelis and others. The
accompanying book was well received.
James Michener wrote "Mr. Sagan's essay, a spin-off from his hugely successful television show, is a cleverly written, imaginatively illustrated summary of his geological, anthropological, biological, historical and astronomical ruminations about our universe. His references comprise the entire scope of human history. His treatment, necessarily abbreviated, is highly personal. He is always readable, and because his mind ranges so far and wide, he seems exactly the right man for the job." He wrote the introduction to
Stephen Hawking's bestseller
A Brief History of Time. In 1988,
Magnus Magnusson moderated a discussion between Sagan, Hawking and
Arthur C. Clarke,
God, the Universe and Everything Else. He wrote a sequel to
Cosmos,
Pale Blue Dot. The title refers to the view of Earth from the
Voyager spacecraft. Sagan said that there were at least two reasons for scientists to share the purposes and findings of science. 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 joy of communicating one's own excitement about science to others. He wrote: "Among the best contemporary scientist-popularizers, I think of
Stephen Jay Gould,
E. O. Wilson,
Lewis Thomas and
Richard Dawkins in biology;
Steven Weinberg,
Alan Lightman and
Kip Thorne in physics;
Roald Hoffmann in chemistry; and the early works of
Fred Hoyle in astronomy. (And while requiring
calculus, the most consistently exciting, provocative, and inspiring science popularization of the last few decades seems to me to be Volume 1 of
Richard Feynman's
Introductory Lectures on Physics.)" Asimov described Sagan as one of only two people he ever met whose intellect surpassed his own, the other being
computer scientist and
artificial intelligence expert
Marvin Minsky. Sagan briefly served as an adviser on
Stanley Kubrick's
2001: A Space Odyssey. He proposed that the film suggest, rather than depict, extraterrestrial superintelligence. In 1971, he participated in a panel on Mars with
Ray Bradbury, Arthur C. Clarke,
Bruce C. Murray and
Walter Sullivan, published as
Mars and the Mind of Man. Sagan turned his pen to science fiction with
Contact. He needed a way for his heroine, Ellie Arroway, to get from Earth to
Vega, so he asked his friend Kip Thorne for advice on the physics of
wormholes. This led to original research by Thorne on
closed timelike curves. members at the organization's founding. Sagan is seated on the right.
: Earth is a bright pixel when photographed from Voyager 1'', away. Sagan encouraged NASA to generate this image.
Skepticism Sagan promoted
scientific skepticism against
pseudoscience. He credited
Martin Gardner's
Fads and Fallacies in the Name of Science and
Charles Mackay's
Extraordinary Popular Delusions and the Madness of Crowds with teaching him critical thinking. a phrase coined by Arthur Felberbaum, a friend of his wife Ann Druyan. He expanded on it in his penultimate book,
The Demon-Haunted World. He lamented the fact that most newspapers had a daily column on astrology and very few had even a weekly column on astronomy. One of his most famous quotations, "
extraordinary claims require extraordinary evidence", is called the "Sagan standard" by some. It 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 aphorized in
Théodore Flournoy's
From India to the Planet Mars (1899) from a longer quote by the French mathematician and astronomer
Pierre-Simon Laplace as the Principle of Laplace: "The weight of the evidence should be proportioned to the strangeness of the facts." He noted that science's
predictive power distinguished it from pseudoscience: "If you want to know when the next
eclipse of the Sun will be, you might try magicians and mystics, but you'll do much better with scientists. They will tell you where on Earth to stand, when you have to be there, and whether it will be a partial eclipse, a total eclipse, or an annular eclipse. They can routinely predict a solar eclipse, up to the minute, a century in advance. You can go to the witch doctor to lift the spell that causes your
pernicious anemia, or you can take
Vitamin B12. If you want to save your child from
polio, you can pray or you can
inoculate." 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 three-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." 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. He was an advocate for
basic research, pointing out that it might prove to have practical applications in the future: "
Maxwell wasn't thinking of radio, radar, and television when he first scratched out the fundamental
equations of electromagnetism;
Newton wasn't dreaming of space flight or communications satellites when he first understood the
motion of the Moon;
Roentgen wasn't contemplating medical diagnosis when he investigated a penetrating radiation so mysterious he called it '
X-rays';
Curie wasn't thinking of cancer therapy when she painstakingly extracted minute amounts of
radium from tons of pitchblende;
Fleming wasn't planning on saving the lives of millions with
antibiotics when he noticed a circle free of bacteria around a growth of
mold;
Watson and
Crick weren't imagining the cure of genetic diseases when they puzzled over the
X-ray diffractometry of
DNA…" This number is reasonably well defined, because it is known what stars are and what the observable universe is, but its value is highly uncertain. • In 1980, Sagan estimated it to be 10
sextillion in
short scale (1022). • In 2010, it was estimated to be 300 sextillion (3 × 1023).
"Billions and billions" After
Cosmos aired, Sagan became associated with the
catchphrase "billions and billions", although he never actually said it. He rather used the term "billions
upon billions." Richard Feynman used the phrase "billions and billions" many times in his
Lectures on Physics. However, Sagan's frequent use of the word
billions and distinctive delivery emphasizing the "b" (which he did intentionally, in place of more cumbersome alternatives such as "billions with a 'b, in order to distinguish the word from "millions") Other comedians followed Carson's lead, including
Gary Kroeger,
Mike Myers,
Bronson Pinchot,
Penn Jillette,
Harry Shearer, and others.
Frank Zappa satirized the line in the song "Be in My Video". Sagan took this all in good humor, and his final book was titled
Billions and Billions, which opened with a tongue-in-cheek discussion of this catchphrase, observing that Carson was an amateur astronomer and that Carson's comic caricature often included real science. In November 1995, after further legal battle, 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." 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 of anything.
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: Some, like Urey, later believed that 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 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 article 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, 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. A personal correspondence with nuclear physicist
Edward Teller around 1983 began amicably, with Teller expressing support for continued research to ascertain the credibility of the winter hypothesis. However, 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 among the public. 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. /Russia nuclear stockpiles, in
total number of nuclear bombs/warheads in existence throughout the
Cold War and post-Cold War era 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 "Star Wars". Sagan, along with other scientists, 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. He was an advocate for free speech and
civil liberties. His professor
Edward Condon, during the
McCarthy era, was accused by
HUAC of being a "revolutionary in physics". Sagan quotes Condon as replying: "I believe in
Archimedes' Principle, formulated in the third century B. C. I believe in
Kepler's laws of planetary motion, discovered in the seventeenth century. I believe in
Newton's laws…", going on to invoke
Bernoulli,
Fourier,
Ampère,
Boltzmann, and Maxwell. The committee was not amused. "But the most they were able to pin on Condon, as I recall, was that in high school he had a job delivering a socialist newspaper door-to-door on his bicycle." It is a fact of life on our beleaguered little planet that widespread torture, famine and governmental criminal corruption are more likely to be found in tyrannical than in democratic governments. Why? Because the rulers of the former are much less likely to be thrown out of office for their misdeeds than the rulers of the latter. This is the error correction machinery in politics. He notes that "New ideas, invention, and creativity in general, always spearhead a new kind of freedom—a breaking out from hobbling constraints. Freedom is a prerequisite for continuing the delicate experiment of science—which is one reason the Soviet Union could not remain a totalitarian state and remain technically competitive. At the same time, science—or rather its delicate mix of openness and skepticism, and its encouragement of diversity and debate—is a prerequisite for continuing the delicate experiment of freedom in an industrial and highly technological society." He concludes: Education on the value of
free speech and the other freedoms reserved by the
Bill of Rights, about what happens when you don't have them, and about how to exercise and protect them, should be an essential prerequisite for being an American citizen — or indeed a citizen of any nation, the more so to the degree that such rights remain unprotected. If we can't think for ourselves, if we're unwilling to question authority, then we're just putty in the hands of those in power. But if the citizens are educated and form their own opinions, then those in power work for
us. In every country, we should be teaching our children the scientific method and the reasons for a Bill of Rights. With it comes a certain decency, humility and community spirit. == Personal life and beliefs ==