Essay About Carl Sagan Death

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What I learned from Carl Sagan

By Phil Plait | December 19, 2006 10:17 pm

Today marks the tenth anniversary of the day we lost Carl Sagan. He was a true skeptic; a man whose mind was open to possibilities, yet able to cut away the chaff of pseudoscience and blind alleys. Even when facing death — a slow, painful, wasting death — he was able to turn it into a series of lessons on science, medicine, and critical thinking. Many people, perhaps most people, would have clung to any idea, no matter how irrational, to make themselves feel better. Carl didn’t do that. He couldn’t. He not only relied on science, he reveled in it.

To celebrate the man, I am writing this essay as part of the Carl Sagan blogathon. I’m very interested and excited to see what others have written (Update: Joel Schlosberg has posted the list). Here’s my submission.

I was contacted recently by a Chinese journalist. He’s writing an article on the tenth anniversary of Carl Sagan’s death, focusing on Sagan’s impact on science, skepticism, and public knowledge, and he wanted my input. The article will run soon, and I’ll link to it if I can when it goes live (Update: here is the story (in Chinese, maybe you can get Rosie O’Donnell to translate) and here is a blurb on the journalist’s blog). He decided to use an abbreviated quote by me, so I thought it might be nice to post my complete answers. His questions to me are in the blockquotes.

First, Dr. Sagan was an outspoken skeptic as you are. So what’s the most valuable legacy that Dr. Sagan left to us who have a natural worldview, who do not believe paranormal claims and would like to examine them strictly?

Sagan made it very clear that we don’t need to examine the Universe as a supernatural creation. It is enough — more than enough — to examine it naturally. The sense of awe, beauty, wonder, and joy we feel when we view a Hubble image of a distant galaxy is a natural product of our sense of discovery. It is more amazing, and ultimately more wonderful, to think about how all these incredible things came about due to the relatively simple laws of physics, rather than try to ascribe supernatural powers behind their creation.

Second, after ten years since Dr. Sagan passed away, the world seems changed a lot. So, I would like to know, what, do you think, is the most important, and valuable insights that Dr. Sagan left to this fragile world?

I don’t think the world has changed much at all. We still have self-claimed psychics, conspiracy theorists, religious fundamentalists, and all manners of conmen whose only purpose is to confuse people about the real world. Many of these people honestly believe that what they are doing is right, but that does not make them right.

Sagan’s insight, his gift to us, is the knowledge that we all have the ability to examine the Universe with all the power of human curiosity, and we need not retreat from the answers we find.

The language of the Universe, as far as we can tell, is science and math, and those remain — and will probably always remain– our best tools to understand it.

CATEGORIZED UNDER: Antiscience, Astronomy, Cool stuff, Piece of mind, Religion, Science, Skepticism

Carl Sagan

Sagan in 1980

BornCarl Edward Sagan
(1934-11-09)November 9, 1934
Brooklyn, New York, U.S.
DiedDecember 20, 1996(1996-12-20) (aged 62)
Seattle, Washington, U.S.
Resting placeIthaca, New York, U.S.
Alma materUniversity of Chicago,
(BA, BS, MS, Ph.D)
Known for
Spouse(s)Lynn Margulis (m. 1957; div. 1965)
Linda Salzman (m. 1968; div. 1981)
Ann Druyan (m. 1981)
Children5, including Dorion and Nick
AwardsKlumpke-Roberts Award (1974)
NASA Distinguished Public Service Medal (1977)
Pulitzer Prize for General Non-Fiction (1978)
Oersted Medal (1990)
Carl Sagan Award for Public Understanding of Science (1993)
National Academy of SciencesPublic Welfare Medal (1994)
Scientific career
Doctoral advisorGerard Kuiper
Doctoral studentsClark Chapman, James B. Pollack, Owen Toon

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.[1]

Sagan published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books.[2] 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.[3] 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,[4] are archived at The Library of Congress.[5]

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 SciencesPublic 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[edit]

Carl Sagan was born in Brooklyn, New York.[6] His father, Samuel Sagan, was an immigrant garment worker from Kamianets-Podilskyi, then in the Russian Empire,[7] 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."[8]

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."[8]:12 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.[8]:2 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."[8]:2

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.[8]:2 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.[8]:2 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.[8]:9 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.[9]

1939 World's Fair[edit]

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!"[8]:14 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?[8]:14

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.[8]:15

World War II[edit]

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."[8]:15 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.[9]

Inquisitiveness about nature[edit]

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.[8]:18

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, American grizzly bear standing on his hind legs, ten or twelve feet tall, and staring me right in the eye.[8]:18

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."[9]

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.[10]

High school years[edit]

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.[8]:23 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.[8]:23 Rahway was an older industrial town, and the Sagans were among its few Jewish families.[8]:23

Sagan was a straight-A student but was bored due to unchallenging classes and uninspiring teachers.[8]:23 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."[8]:24 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.[8]:24 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."[8]:25

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.[11] The subject was considered controversial, but his rhetorical skill won over the judges and they awarded him first prize.[11] By graduation, his classmates had voted him "Most likely to succeed," and put him in line to be valedictorian.[11]


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.[12] 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.[12]

During his time as an honors program undergraduate, Sagan worked in the laboratory of the geneticistH. J. Muller and wrote a thesis on the origins of life with physical chemistHarold Urey. Sagan joined the Ryerson Astronomical Society,[13] received a B.A. degree in 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 the dissertation "Physical Studies of Planets" submitted to the Department of Astronomy and Astrophysics.[14][15][16][17]

He used the summer months of his graduate studies to work with his dissertation director, planetary scientistGerard 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".[18] In 1958, the two worked on the classified military Project A119, the secret Air Force plan to detonate a nuclear warhead on the Moon.[19]

Sagan had a "Top Secret" clearance at the U.S. Air Force and a "Secret" clearance with NASA.[20] 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.[21]

Scientific career[edit]

From 1960 to 1962 Sagan was a Miller Fellow at the University of California, Berkeley.[22] 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.[23]

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.[23] 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.[24] 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.[20] An advisor from his years as an undergraduate student, Harold Urey, wrote a letter to the tenure committee recommending strongly against tenure for Sagan.[10]

Science is more than a body of knowledge; it is a way of thinking. I have a foreboding of an America in my children's or grandchildren's time – when the United States is a service and information economy; when nearly all the key manufacturing industries have slipped away to other countries; when awesome technological powers are in the hands of a very few, and no one representing the public interest can even grasp the issues; when the people have lost the ability to set their own agendas or knowledgeably question those in authority; when, clutching our crystals and nervously consulting our horoscopes, our critical faculties in decline, unable to distinguish between what feels good and what's true, we slide, almost without noticing, back into superstition and darkness.

Carl Sagan, from Demon-Haunted World (1995)[25]

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.[26] 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.[27]

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 Apolloastronauts 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-anodizedplaque, 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.[28]

Scientific achievements[edit]

Former student David Morrison describes Sagan as "an 'idea person' and a master of intuitive physical arguments and 'back of the envelope' calculations,"[20] 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."[20]

Sagan's contributions were central to the discovery of the high surface temperatures of the planet Venus.[1][29] 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 emissions from Venus and concluded that there was a surface temperature of 500 °C (900 °F). As a visiting scientist to NASA's Jet Propulsion Laboratory, he contributed to the first Mariner missions to Venus, working on the design and management of the project. Mariner 2 confirmed his conclusions on the surface conditions of Venus in 1962.

Sagan was among[clarification needed] 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.[30] 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.[31][self-published source]

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.[32] 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[clarification needed] but shifts in surface dust caused by windstorms.

Sagan is best known, however, for his research on the possibilities of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation.[33][34]

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".[35] He was denied membership in the Academy, reportedly because his media activities made him unpopular with many other scientists.[36][37][38]

As of 2017, Sagan is the most cited SETI scientist and one of the most cited planetary scientists.[2]

Cosmos: popularizing science on TV[edit]

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.[3][39][40] The book, Cosmos, written by Sagan, was published to accompany the series.[41]

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.[42]

Each of the 13 episodes was created to focus on a particular subject or person, thereby demonstrating the synergy of the universe.[42] 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[43] along with a Peabody Award, and transformed Sagan from an obscure astronomer into a pop-culture icon.[44]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.[45] In 2000, "Cosmos" was released on a remastered set of DVDs.

"Billions and billions"[edit]

See also: Sagan's number

From Cosmos, he was invited to frequent appearances on The Tonight Show Starring Johnny Carson.[46] Sagan became associated with the catchphrase "billions and billions", although he never actually used the phrase in the Cosmos series.[47] He rather used the term "billions upon billions."[48] Carson, however, would sometimes use the phrase during his parodies of Sagan.[49][a]

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.[51][52][53]

Scientific and critical thinking advocacy[edit]

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.[54]

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.[55][56] 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".[57] 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.[57]

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;[58]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.[28] 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.[20]

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";[60][61] 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.[62][63]

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".[64]

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.[65] 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.[66][67] 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".[66]

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".[66][68] 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.[67] 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.[69]

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.[70]

Popularizing science[edit]

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.[clarification needed] The other reason was the excitement of communicating one's own excitement about science to others.[71]


While Sagan was widely adored by the general public, his reputation in the scientific community was more polarized.[72] Critics sometimes characterized his work as fanciful, non-rigorous, and self-aggrandizing,[73] and others complained in his later years that he neglected his role as a faculty member to foster his celebrity status.[74]

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.[75] 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.[76]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.[75]

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."[75] 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.[75]

Some, like Urey, later came to realize Sagan's popular brand of scientific advocacy was beneficial to the science as a whole.[77] 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."[77]

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.[75]

Social concerns[edit]

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[date missing] 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.[78] 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 PresidentRonald 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.[79]

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.[80]

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.[81] 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".[82] One chapter of his 1993 book, Shadows of Forgotten Ancestors is dedicated to testosterone and its alleged poisonous effects.[83]

Personal life and beliefs[edit]

I have just finished The Cosmic Connection and loved every word of it. You are my idea of a good writer because you have an unmannered style, and when I read what you write, I hear you talking. One thing about the book made me nervous. It was entirely too obvious that you are smarter than I am. I hate that.

Isaac Asimov, in letter to Sagan, 1973[84][85]

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

Photo of Sagan from high school yearbook, 1951
Sagan with a model of the Viking lander that would land on Mars. Sagan examined possible landing sites for Viking along with Mike Carr and Hal Masursky.
Pale Blue Dot: Earth is a bright pixel when photographed from Voyager 1 six billion kilometers out (beyond Pluto). Sagan encouraged NASA to generate this image.

from Pale Blue Dot (1994)

On it, everyone you ever heard of...The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there on a mote of dust, suspended in a sunbeam. . . .

Think of the rivers of blood spilled by all those generals and emperors so that in glory and triumph they could become the momentary masters of a fraction of a dot.

Carl Sagan, Cornell lecture in 1994[59]

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