Carl Edward Sagan was born on November 9, 1934, in theBensonhurst neighborhood of New York City'sBrooklyn borough.[10][4] His mother, Rachel Molly Gruber (1906–1982), was a housewife from New York City; his father, Samuel Sagan (1905–1979), was a Ukrainian-born garment worker who had emigrated fromKamianets-Podilskyi (then in theRussian Empire).[11] Sagan was named in honor of his maternal grandmother, Chaiya Clara, who had died while giving birth to her second child; she was, in Sagan's words, "the mother she [Rachel] never knew."[12] Sagan's family lived in a modest apartment in Bensonhurst. He later described his family asReform Jews, one of the more liberal of Judaism's four main branches. He and his sister agreed that their father was not especially religious, but that their mother "definitely believed in God, and was active in thetemple [...] and served onlykosher meat."[13] During the worst years of theDepression, his father worked as a movie theater usher.[13]
According to biographer Keay Davidson, Sagan traced his analytical inclinations to his mother, who had been extremely poor as a child in New York City duringWorld War I and the 1920s,[14] and whose later intellectual ambitions were sabotaged by her poverty, status as a woman and wife, andJewish ethnicity. Davidson suggested she "worshipped her only son, Carl" because "he would fulfill her unfulfilled dreams."[14] Sagan traced his sense of wonder to his father, who spent his free time giving apples to the poor or helping soothe tensions between workers and management within New York City's garment industry.[14] Sagan said: "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."[15]
He described a defining moment in his development, when his parents took him to the1939 New York World's Fair. He recalled his vivid memories of several exhibits there. One,Futurama, included a moving map, which, as he recalled, "showed beautiful highways andcloverleaves and littleGeneral Motors cars all carrying people to skyscrapers, buildings with lovely spires, flying buttresses—and it looked great!"[16] Another involved a flashlight shining on aphotoelectric cell, which created a crackling sound, and another showed how the sound from atuning fork became a wave on anoscilloscope. He saw an exhibit of the nascent medium oftelevision. He later wrote: "Plainly, the world held wonders of a kind I had never guessed. Howcould a tone become a picture and light become a noise?"[16] Sagan saw one of the fair's most publicized events: the burial atFlushing Meadows of atime capsule, which contained mementos from the 1930s to be recovered in the far future. Davidson wrote that this "thrilled Carl." As an adult, Sagan and his colleagues would create similar time capsules to be sent out into space.
DuringWorld War II, Sagan's parents worried about the fate of their European relatives, but he was generally unaware of the details of the ongoing war. He wrote, "Sure, we had relatives who were caught up in theHolocaust.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."[17]
He asked people what thestars were, but no one could give him a clear answer. He recalled
As soon as I was old enough, my parents gave me my very first library card. I think the library was on 85th Street, an alien land. Immediately, I asked the librarian for something on stars. She returned with a picture book displaying portraits of men and women with names likeClark Gable andJean Harlow. I complained, and for some reason then obscure to me, she smiled and found another book—the right kind of book. I opened it breathlessly and read until I found it. The book said something astonishing, a very big thought. It said that the stars were suns, but very far away. The Sun was a star, but close up... I was innocent of the notion of theinverse square law for light propagation. I had not the ghost of a chance of calculating the distance to the stars. But I could tell that if the stars were suns, they had to be very far away—farther away than 85th Street, farther away than Manhattan, farther away, probably, than New Jersey. The Cosmos was much bigger than I had guessed.[18]: 180
He said: "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."[19] When he was about six or seven, he and a close friend took trips to theAmerican Museum of Natural History. While there, they visited theHayden Planetarium and walked around exhibits of space objects, such asmeteorites, as well as displays ofdinosaur fossils and naturedioramas. As Sagan later wrote, "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 Americangrizzly bear standing on his hind legs, ten or twelve feet tall, and staring me right in the eye."[19]
Sagan's parents nurtured his growing interest in science, buying him chemistry sets and reading matter. According to biographer Ray Spangenburg, Sagan's efforts in his early years to understand the Cosmos became a "driving force in his life, a continual spark to his intellect, and a quest that would never be forgotten."[15] In 1947,mass hysteria developed about the possibility that extraterrestrial visitors had arrived inflying saucers, and the young Sagan joined in the speculation that the flying "discs" people reported seeing in the sky might be alien spaceships.[20] His fascination with outer space emerged as his primary focus, especially after reading thescience fiction of such writers asJules Verne andH. G. Wells. In 1947, Sagan discovered the magazineAstounding Science Fiction, which introduced him to morehard science fiction speculations.[21]
Sagan attended David A. Boody Junior High School in his native Bensonhurst and had hisbar mitzvah when he turned 13.[22] In 1948, when he was 14, his father's work took the family to the older semi-industrial town ofRahway, New Jersey, where he attendedRahway High School.[22] He was a straight-A student but was bored because his classes did not challenge him and his teachers did not inspire him.[22] His teachers realized this and tried to convince his parents to send him to a private school, with an administrator telling them, "This kid ought to go to a school for gifted children, he has something really remarkable."[23] However, his parents could not afford to do so. Sagan became president of the school's chemistry club, and set up his own laboratory at home. He taught himself aboutmolecules by making cardboard cutouts to help him visualize how they were formed: "I found that about as interesting as doing [chemical] experiments."[23] He was mostly interested in astronomy, studying it in his spare time. In his junior year of high school, he discovered that professional astronomers were paid for doing something he always enjoyed. "That was a splendid day—when I began to suspect that if I tried hard I could do astronomy full-time."[24]
In 1950, Sagan wrote the essay "Space, Time, and the Poet" for his high school newspaper.[25] In it, he mused on man's place in the universe as expressed by poets likeT. S. Eliot andAlfred, Lord Tennyson and "the work containing perhaps the greatest poetry—the Bible."[26] He graduated from Rahway High School in 1951.[22]
In 1954, he was awarded a Bachelor of Liberal Arts with general and special honors[31] in what he quipped was "nothing."[32] In 1955, he earned a Bachelor of Science in physics. He went on to do graduate work at the University of Chicago, earning a Master of Science in physics in 1956 and a Doctor of Philosophy in astronomy and astrophysics in 1960. His doctoral thesis, under the direction ofGerard Kuiper, wasPhysical Studies of the Planets.[33][34][35] During hisgraduate studies, he spent summers working with Kuiper,[3] as well as chemistMelvin Calvin and physicistGeorge Gamow. Sagan's dissertation reflected common interests with Kuiper, who had been president of theInternational Astronomical Union's commission on "Physical Studies of Planets and Satellites" throughout the 1950s.[36] He credited Kuiper with teaching himback-of-the-envelope calculations: "A possible explanation to a problem occurs to you, you pull out an old envelope, appeal to your knowledge of fundamental physics, scribble a few approximate equations on the envelope, and see if your answer comes anywhere near explaining your problem. If not, you look for a different explanation. It cut through nonsense like a knife through butter."[30]: xiv
In 1958, Sagan and Kuiper worked on the classified militaryProject A119, a secretUnited States Air Force plan to detonate a nuclear warhead on the Moon and document its effects.[37] Sagan had aTop Secret clearance at the Air Force and aSecret clearance withNASA.[38] In 1999, an article published in the journalNature revealed that Sagan had included the classified titles of two Project A119 papers in his 1959 application for a scholarship toUniversity of California, Berkeley. A follow-up letter to the journal by project leader Leonard Reiffel confirmed Sagan's security leak.[39]
After the publication of Sagan'sScience article, in 1961,Harvard University astronomersFred Whipple andDonald Menzel offered Sagan the opportunity to give a colloquium at Harvard and subsequently offered him alecturer 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.[42] Sagan lectured, performed research, and advised graduate students at the institution from 1963 until 1968, as well as working at theSmithsonian Astrophysical Observatory, also located inCambridge, Massachusetts.
In 1968, Sagan was deniedacademic tenure at Harvard. He later indicated that the decision was very unexpected.[43] 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.[38] An advisor from his years as an undergraduate student, Harold Urey, wrote a letter to the tenure committee recommending strongly against tenure for Sagan.[20]
Long before the ill-fated tenure process, Cornell University astronomerThomas Gold had courted Sagan to move toIthaca, New York, and join the recently hired astronomerFrank Drake among 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.[44] Following two years as an associate professor, Sagan became afull professor at Cornell in 1970 and directed the Laboratory forPlanetary 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.[45]
Sagan was associated with the U.S. space program from its inception.[46] From the 1950s onward, he worked as an advisor toNASA, where one of his duties included briefing theApolloastronauts before their flights to theMoon. Sagan contributed to many of therobotic spacecraft missions that explored theSolar System, arranging experiments on many of the expeditions. He often challenged the decisions to fund theSpace Shuttle and theInternational Space Station at the expense of further robotic missions.[47] Sagan assembled the first physical message that was sent into space: agold-platedplaque, attached to the space probePioneer 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 theVoyager Golden Record, a sample of the sights and sounds of Earth sent with theVoyager space probes in 1977. Among much else, it features music by Bach,Beethoven andChuck Berry.[48]
Former studentDavid Morrison described Sagan as "an 'idea person' and a master of intuitive physical arguments and 'back of the envelope' calculations",[38] 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."[38]
Sagan's contributions were central to the discovery of the high surface temperatures of the planetVenus.[49][50] 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 aTime Life bookPlanets. His own view was that Venus was dry and very hot as opposed to the balmy paradise others had imagined. He had investigatedradio waves from Venus and concluded that there was a surface temperature of 500 °C (900 °F). As a visiting scientist to NASA'sJet Propulsion Laboratory, he contributed to the firstMariner 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 thatSaturn's moonTitan might possess oceans of liquid compounds on its surface and thatJupiter's moonEuropa might possess subsurface oceans of water. This would make Europa potentially habitable.[51] Europa's subsurface ocean of water was later indirectly confirmed by the spacecraftGalileo. The mystery of Titan's reddish haze was also solved with Sagan's help. The reddish haze was revealed to be due to complexorganic molecules constantly raining down onto Titan's surface.[52]
Sagan further contributed insights regarding the atmospheres of Venus andJupiter, as well as seasonal changes onMars. He also perceivedclimate 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 ofrunaway greenhouse effect.[53] He testified to the US Congress in 1985 that the greenhouse effect would change the Earth's climate system.[54] Sagan and his Cornell colleagueEdwin Ernest Salpeter speculated aboutlife 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 bywindstorms. He argued in favor of the hypothesis, which has since been accepted, that the high surface temperatures ofVenus are the result of thegreenhouse effect.[49]
As of 2017[update], Sagan is the most cited SETI scientist and one of the most cited planetary scientists.[6]
In 1993,Sky & Telescope held a contest to replace the name of theBig Bang model. Suggestions included “Hubble Bubble”, “Bertha D. Universe” and “SAGAN” (“Scientists Awestruck at God’s Awesome Nature”.) The panel, including Sagan,Timothy Ferris andHugh Downs, turned them down.[57]
Sagan's number is the number ofstars in theobservable universe.[58] 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.
Carl Sagan popularized the Cosmic Calendar as a method to visualize thechronology of the universe, scaling itscurrent age of 13.8 billion years to a single year to help intuit it for pedagogical purposes.
Sagan andAnn Druyan co-wrote the 13-partPBS documentaryCosmos: A Personal Voyage. It drew on earlier documentaries, notablyJacob Bronowski'sThe Ascent of Man. The production involved the recreation of theLibrary of Alexandria. It covered an array of scientific subjects, including the evolution of stars and how it is linked to theevolution 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. He travels the earth as well. One moment he is seated in a cafe on the Aegean island ofSamos, home ofPythagoras andAristarchus, explaining the first stirrings of Greek scientific prowess. At another moment, he is strolling through the venerableCavendish 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 is the quintessential schoolmaster; he makes such a classical experiment asChristiaan Huygens’ determination of the distance of the stars with only a perforated brass disc seem as vivid today as when it was performed three centuries ago."[64] 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[7][65][66][67], making it the most widely watched series in the history of American public television untilKen Burns'sThe Civil War in 1990.[61]Cosmos won anEmmy[68] and aPeabody. 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."[69]
Of science popularization, 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.[71] The other reason was the excitement of communicating one's own excitement about science to others.[4]
I have just finishedThe 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.
The Planetary Society members at the organization's founding. Sagan is seated on the right.Pale Blue Dot: Earth is a bright pixel when photographed fromVoyager 1, 6 billion kilometres (3.7 billion miles) away.[81] Sagan encouraged NASA to generate this image.
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.
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... The dumbing down of America is most evident in the slow decay of substantive content in the enormously influential media, the 30 second sound bites (now down to 10 seconds or less), lowest common denominator programming, credulous presentations on pseudoscience and superstition, but especially a kind of celebration of ignorance.[30]: 69
He noted that science'spredictive 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 yourpernicious anemia, or you can takeVitamin B12. If you want to save your child frompolio, you can pray or you caninoculate.”[30]: 30
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.[89] He argued that all of the numerous methods proposed toalter the orbit of an asteroid, including the employment ofnuclear detonations, created adeflection 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.[90][91] In a 1994 paper he co-authored, he ridiculed a three-day-long "Near-Earth Object Interception Workshop" held byLos Alamos National Laboratory (LANL) in 1993 that did not, "even in passing" state that such interception and deflection technologies could have these "ancillary dangers."[90]
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."[90][92] 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 inmining asteroids.[91] His interest in the use of nuclear detonations in space grew out of his work in 1958 for theArmour Research Foundation'sProject A119, concerning the possibility of detonating a nuclear device on the lunar surface.[93]
He was an advocate for pure scientific 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 withantibiotics 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 theX-ray diffractometry ofDNA…"[30]: 398
AfterCosmos aired, Sagan became associated with thecatchphrase "billions and billions", although he never actually said it.[94] He rather used the term "billionsupon billions."[95]
Richard Feynman used the phrase "billions and billions" many times in hisLectures on Physics. However, Sagan's frequent use of the wordbillions 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")[94] made him a favorite target of comic performers, notablyJohnny Carson,[96][97]Gary Kroeger,Mike Myers,Bronson Pinchot,Penn Jillette,Harry Shearer, and others.Frank Zappa satirized the line in the song "Be in My Video", noting as well "atomic light." Sagan took this all in good humor, and his final book was titledBillions 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.[94]
In 1993, engineers atApple Computer code-named thePower Macintosh 7100 "Carl Sagan" in the hope that Apple would make "billions and billions".[10] 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."[98][99] 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."[100]
As a humorous tribute to Sagan and his association with the catchphrase "billions and billions", asagan has been defined as aunit of measurement equivalent to a very large number of anything.[101][102]
While Sagan was widely adored by the general public, his reputation in the scientific community was more polarized.[103] Critics sometimes characterized his work as fanciful, non-rigorous, and self-aggrandizing,[104] and others complained in his later years that he neglected his role as a faculty member to foster his celebrity status.[105]
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.[106] 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.[43]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.[106]
Sagan's Harvard friendLester Grinspoon also stated: "I know Harvard well enough to know there are people there who certainly do not like people who are outspoken."[106] Grinspoon added:[106]
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 believed that Sagan's popular brand of scientific advocacy was beneficial to the science as a whole.[107] Urey especially liked Sagan's 1977 bookThe 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."[107]
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.[106]
At the height of theCold War, Sagan became involved innuclear disarmament efforts by promoting hypotheses on the effects ofnuclear war, whenPaul Crutzen's"Twilight at Noon" concept suggested that a substantial nuclear exchange could trigger anuclear 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 colleagueRichard P. Turco had coined.[108] In 1984, he co-authored the bookThe Cold and the Dark: The World after Nuclear War and in 1990, the bookA Path Where No Man Thought: Nuclear Winter and the End of the Arms Race, which explains the nuclear-winter hypothesis and advocatesnuclear 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 physicistEdward 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."[109] 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.[109]
Sagan believed that theDrake equation suggested that a large number of extraterrestrial civilizations would form, but that the lack of evidence of such civilizations highlighted by theFermi paradox suggeststechnological 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 acataclysm and eventually becoming aspacefaring species. Sagan's deep concern regarding the potential destruction ofhuman civilization in anuclear holocaust was conveyed in a memorable cinematic sequence in the final episode ofCosmos, "Who Speaks for Earth?" Sagan had already resigned[date missing] from theAir Force Scientific Advisory Board's UFO-investigatingCondon Committee and voluntarily surrendered histop-secret clearance in protest over theVietnam War.[110] Following his marriage to his third wife (novelist Ann Druyan) in June 1981, Sagan became more politically active—particularly in opposing escalation of thenuclear arms race under PresidentRonald Reagan.
In March 1983, Reagan announced theStrategic Defense Initiative—a multibillion-dollar project to develop a comprehensivedefense against attack bynuclear 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 throughdecoys and other means—and that its construction would seriously destabilize the "nuclear balance" between the United States and theSoviet Union, making further progress towardnuclear disarmament impossible.[111][112]
When Soviet leaderMikhail Gorbachev declared a unilateral moratorium on thetesting of nuclear weapons, which would begin on August 6, 1985—the 40th anniversary of theatomic bombing ofHiroshima—the Reagan administration dismissed the dramatic move as nothing more than propaganda and refused to follow suit. In response, USanti-nuclear and peace activists staged a series of protest actions at theNevada 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 undergroundOperation Charioteer andUnited States's Musketeer nuclear test series of detonations.[113]
He was an advocate for free speech andcivil liberties. When visiting the Soviet Union, he and Druyan would smuggle in banned books.[30]: 415
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 offree speech and the other freedoms reserved by theBill 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 forus. 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.[115]
Sagan was married three times. In 1957, he married biologistLynn Margulis. The couple had two children, Jeremy andDorion Sagan. According to Margulis, Sagan left her to do the majority of the domestic duties, believing he was above them.[116] Their marriage ended in 1964. Sagan married artistLinda Salzman in 1968 and they had a child together,Nick Sagan, and divorced in 1981. During these marriages, Carl Sagan focused heavily on his career, a factor which may have contributed to Sagan's first divorce.[38] In 1981, Sagan married authorAnn Druyan and they later had two children, Alexandra (known asSasha) and Samuel Sagan. Carl Sagan and Druyan remained married until his death in 1996.[117]
Sagan was a proponent of the search for extraterrestrial life. He urged the scientific community to listen withradio telescopes for signals from potential intelligentextraterrestrial life-forms. Sagan was so persuasive that by 1982 he was able to get a petition advocating SETI published in the journalScience, signed by 70 scientists, including seven Nobel Prize winners. This signaled a tremendous increase in the respectability of a then-controversial field. He may have contributed toFrank Drake'sArecibo message, a radio message beamed into space from theArecibo Observatory on November 16, 1974, aimed at informing potential extraterrestrials about Earth.[118][119]
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 exampleBaruch Spinoza andAlbert 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.[122]
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.[123]
Sagan in 1987
Sagan also commented on Christianity and theJefferson 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 ofPaul.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."[124]
Sagan thought that spirituality should be scientifically informed and that traditional religions should be abandoned and replaced with belief systems that revolve around the scientific method,[125] but also the mystery and incompleteness of scientific fields. 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 anythingoutside 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. So are our feelings in the presence of great art or music or literature, or acts of exemplary selfless courage, such as those ofMohandas Gandhi orMartin Luther King, Jr. The notion that science and spirituality are somehow mutually exclusive does a disservice to both.[30]: 29–30
An environmental appeal, "Preserving and Cherishing the Earth", primarily written by Sagan and signed by him and other noted scientists as well as religious leaders, and published 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."[126]
In reply to a question in 1996 about his religious beliefs, Sagan said he wasagnostic.[127] 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.[128] 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."[129]
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. But, the great thing is that when we were together, for nearly twenty years, we lived with a vivid appreciation of how brief and precious life is. We never trivialized the meaning of death by pretending it was anything other than a final parting.
Every single moment that we were alive and we were together was miraculous-not miraculous in the sense of inexplicable or supernatural. We knew we were beneficiaries of chance... That pure chance could be so generous and so kind... That we could find each other, as Carl wrote so beautifully inCosmos, you know, in the vastness of space and the immensity of time... That we could be together for twenty years. That is something which sustains me and it’s much more meaningful... The way he treated me and the way I treated him, the way we took care of each other and our family, while he lived. That is so much more important than the idea I will see him someday.
I don't think I'll ever see Carl again. But I saw him. We saw each other. We found each other in the cosmos, and that was wonderful.
Late in his life, Sagan's books elaborated on hisnaturalistic view of the world.Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium, published posthumously, contains essays written by him, on topics such as his views on abortion, and also an essay by Ann Druyan about the relationship between his agnostic and freethinking beliefs and his death.
He wrote of the universality of physical law:[30]: 273
We detect the light from distantquasars only because the laws ofelectromagnetism are the same ten billion light years away as here. The spectra of those quasars are recognizable only because the samechemical elements are present there as here, and because the same laws ofquantum mechanics apply. The motion of galaxies around one another follows familiarNewtonian gravity.Gravitational lenses andbinary pulsar spin-downs revealgeneral relativity in the depths of space. Wecould have lived in a universe with different laws in every province, but we do not. This fact cannot but elicit feelings of reverence and awe.
He went on: "Why should a few simple laws of Nature explain so much and hold such sway throughout this vast Universe? Isn’t this just what you might expect from a Creator of the Universe? Why should some religious people oppose the reductionist program in science, except out of some misplaced love of mysticism?"[30]: 274
Sagan was a user and advocate ofmarijuana. Under the pseudonym "Mr. X", he contributed an essay about smoking cannabis to the 1971 bookMarihuana Reconsidered.[131][132] 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 friendLester Grinspoon disclosed this information to Sagan's biographer, Keay Davidson. The publishing of the biographyCarl Sagan: A Life, in 1999 brought media attention to this aspect of Sagan's life.[133][134][135] Not long after his death, his widow Ann Druyan went on to preside over the board of directors of theNational Organization for the Reform of Marijuana Laws (NORML), a non-profit organization dedicated to reforming cannabis laws.[136][137]
In 1947, the year that inaugurated the "flying saucer"craze, the young Sagan suspected the "discs" might be alien spaceships.[20] Sagan's interest inUFO reports prompted him on August 3, 1952, to write a letter to U.S. Secretary of StateDean Acheson to ask how the United States would respond if flying saucers turned out to be extraterrestrial.[138] He later had several conversations on the subject in 1964 withJacques Vallée.[139] 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.
In 1966, Sagan was a member of the Ad Hoc Committee to ReviewProject Blue Book, theU.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 theCondon Committee (1966–68), led by physicistEdward 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.
SociologistRon Westrum writes that "The high point of Sagan's treatment of the UFO question was theAAAS' symposium in 1969. A wide range of educated opinions on the subject were offered by participants, including not only proponents such asJames McDonald andJ. Allen Hynek but also skeptics like astronomersWilliam Hartmann andDonald 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."[139] With physicist Thornton Page, Sagan edited the lectures and discussions given at the symposium; these were published in 1972 asUFO's: A Scientific Debate. Some of Sagan's many books examine UFOs (as did one episode ofCosmos) and he claimed a religious undercurrent to the phenomenon.
He wrote:
Occasionally, I get a letter from someone who is ‘in contact’ with extraterrestrials. I am invited to ‘ask them anything.’ And so, over the years I’ve prepared a list of questions. These extraterrestrials are very advanced, remember. So I ask things like, ‘Please provide a short proof ofFermat’s Last Theorem.’ Or theGoldbach Conjecture. So then I have to explain what these are, because extraterrestrials will not call it Fermat’s Last Theorem. So I write out the simple equations and the exponents I never get an answer. On the other hand, if I ask something like ‘Should we be good?’ I almost always get an answer. Anything vague, especially involving conventional moral judgments, these aliens are extremely happy to respond to. But on anything specific, where there is a chance to find out if they actually know anything beyond what most humans know, there is only silence. Something can be deduced from this differential ability to answer questions.
He noted: "It's a stimulating exercise to think of questions to which no human today knows the answers, but where a correct answer would be immediately recognized as such. It's even more challenging to such formulate such questions in fields other than mathematics. Perhaps we should hold a contest and collect the best responses in 'Ten Questions to Ask an Alien.'"[30]: 100
He received thePublic Welfare Medal, the highest award of theNational Academy of Sciences for "distinguished contributions in the application of science to the public welfare."[143] He was denied membership in the academy, reportedly because his media activities made him unpopular with many other scientists.[144][145][146]
In 1997, theSagan 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 theSciencenter, a hands-on museum. The exhibition was created in memory of Sagan, who was an Ithaca resident and Cornell Professor. Professor Sagan had been a founding member of the museum's advisory board.[166]
On November 9, 2001, on what would have been Sagan's 67th birthday, theAmes 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 AdministratorDaniel Goldin. Ann Druyan was at the center as it opened its doors on October 22, 2006.
On October 21, 2019, the Carl Sagan and Ann Druyan Theater was opened at theCenter for Inquiry West in Los Angeles.[167]
Sagan has at least three awards named in his honor:
TheCarl Sagan Memorial Award presented jointly since 1997 by the American Astronomical Society and The Planetary Society,
TheCarl Sagan Medal for Excellence in Public Communication in Planetary Science presented since 1998 by the American Astronomical Society'sDivision 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
In 2022, Sagan was posthumously awarded the Future of Life Award "for reducing the risk of nuclear war by developing and popularizing the science of nuclear winter." The honor, shared by seven other recipients involved in nuclear winter research, was accepted by his widow, Ann Druyan.[172]
The 1997 filmContact was based on Sagan's novel of the same name. The movie was completed after his death.[173] It ends with the dedication "For Carl." His photo can also be seen in the film.
Sagan's son Nick wrote several episodes in theStar Trek franchise. In an episode ofStar Trek: Enterprise entitled "Terra Prime", a quick shot is shown of the relicroverSojourner, part of theMars Pathfinder mission, placed by a historical marker atCarl 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 studentSteve Squyres led the team that landed the roversSpirit andOpportunity successfully on Mars in 2004.
Beginning in 2009, a musical project known asSymphony of Science sampled several excerpts of Sagan from his seriesCosmos and remixed them toelectronic music. To date, the videos have received over 21 million views worldwide on YouTube.[176]
The 2014 Swedish science fiction short filmWanderers uses excerpts of Sagan's narration of his bookPale Blue Dot, played over digitally-created visuals of humanity's possible future expansion into outer space.[177][178]
In February 2015, the Finnish-basedsymphonic metal bandNightwish released the song "Sagan" as a non-album bonus track for their single "Élan."[179] The song, written by the band's songwriter/composer/keyboardistTuomas Holopainen, is an homage to Sagan's the life and work.
In February 2019, the progressive metal bandDream Theater dedicated their song named "Pale Blue Dot" to Sagan. It opens with an audioclip from Nick Sagan saying "Hello from the children of planet Earth."
In 2019, Sagan's daughter Sasha releasedFor Small Creatures Such as We: Rituals for Finding Meaning in our Unlikely World, which depicts life with her parents and her father's death when she was fourteen.[180] Building on a theme in her father's work, Sasha Sagan argues inFor Small Creatures Such as We that skepticism does not imply pessimism.[181]
In 2022, the audiobook recording of Sagan's 1994 bookPale Blue Dot was selected by the U.S.Library of Congress for inclusion in theNational Recording Registry for being "culturally, historically, or aesthetically significant."[182][183]
Sagan, Carl (1961).Organic Matter and The Moon. Panel on Extra-Terrestrial Life for the Armed Forces – NRC Committee on Bio-Astronautics, Publication 757. Washington, D.C.: National Academy of Sciences—National Research Council.Bibcode:1961orm..book.....S.LCCN61-60064.
^Sagan, Carl (1960).Physical Studies of the Planets (PhD thesis).University of Chicago. p. ii.OCLC20678107.ProQuest301918122.A thesis in four parts submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Astronomy, University of Chicago, June, 1960
^Tatarewicz, Joseph N. (1990),Space Technology & Planetary Astronomy, Science, technology, and society, Bloomington, IN: Indiana University Press, p. 22,ISBN978-0-253-35655-0
^Sagan, Carl (writer/host) (December 14, 1980). "Encyclopaedia Galactica".Cosmos: A Personal Voyage. Episode 12. 01:24 minutes in. PBS.
^Rawson, Hugh (2008)."Sagan's Standard".The Unwritten Laws of Life. CSBC Ltd. Archived fromthe original on January 12, 2012. RetrievedSeptember 1, 2013.
^Quarles, Norma (December 20, 1996)."Carl Sagan dies at 62". CNN.Archived from the original on March 11, 2010. RetrievedDecember 5, 2011.Sagan was a noted astronomer whose lifelong passion was searching for intelligent life in the cosmos.
