Carl Sagan

Carl Edward Sagan (; SAY-gən; November 9, 1934 – December 20, 1996) was a prominent American astronomer, planetary scientist, and science communicator. His academic career commenced as an assistant professor at Harvard, after which he transitioned to Cornell University, where he served as the David Duncan Professor of Astronomy and Space Sciences and directed the Laboratory for Planetary Studies. He actively participated in the Mariner, Viking, and Voyager space programs. Sagan authored over 600 scientific papers and articles, in addition to several popular science books, beginning with The Cosmic Connection. He was awarded the Pulitzer Prize for General Nonfiction for his work, The Dragons of Eden.

Carl Edward Sagan (; SAY-gən; November 9, 1934 – December 20, 1996) was an American astronomer, planetary scientist and science communicator. Initially an assistant professor at Harvard, Sagan later moved to Cornell, where he was the David Duncan Professor of Astronomy and Space Sciences and directed the Laboratory for Planetary Studies. He played an active role in the Mariner, Viking and Voyager programs. He published more than 600 scientific papers and articles and several popular science books, starting with The Cosmic Connection. He won the Pulitzer Prize for General Nonfiction for The Dragons of Eden.

He co-authored and narrated the 1980 documentary series Cosmos: A Personal Voyage, which garnered an audience of at least 500 million individuals across 60 countries and received two Emmy Awards and a Peabody Award. The accompanying volume, Cosmos, became the highest-selling science book of its time.

A lifelong enthusiast of science fiction, Sagan ventured into the genre with his novel Contact, which was subsequently adapted into a film of the same title. He was a co-founder and the inaugural president of the Planetary Society. Furthermore, he proposed the capture of the Pale Blue Dot photograph of Earth by Voyager 1.

Sagan maintained a lifelong interest in the potential for extraterrestrial life, contributing to the Arecibo message and playing a more substantial role in the development of the Pioneer plaques and the Voyager Golden Record. These were designed as universal messages, potentially comprehensible to any intelligent entities that might discover them. He advocated for skepticism and the scientific method, particularly in his penultimate book, The Demon-Haunted World, and popularized a critical thinking toolkit. He famously asserted the maxim, "Extraordinary claims require extraordinary evidence." Although frequently attributed to him, the phrase "Billions and billions" was never uttered by Sagan in its exact form; however, he did employ it as the title for his final publication. Sagan received numerous accolades and honors, including the NASA Distinguished Public Service Medal and the National Academy of Sciences Public Welfare Medal. He was married three times and had five children. Following the development of myelodysplasia, Sagan succumbed to pneumonia at the age of 62 on December 20, 1996.

Early life

Childhood

Carl Edward Sagan was born on November 9, 1934, in the Bensonhurst neighborhood of Brooklyn, New York City. His mother, Rachel Molly Gruber (1906–1982), was a New York City housewife, while his father, Samuel Sagan (1905–1979), was a Ukrainian-born garment worker who had immigrated from Kamianets-Podilskyi, then part of the Russian Empire. Sagan was named in honor of his maternal grandmother, Chaiya Clara, who had died during the birth of her second child; she was, in Sagan's words, "the mother she [Rachel] never knew." The Sagan family resided in a modest apartment in Bensonhurst. He later characterized his family as Reform Jews, one of the more liberal branches of Judaism. Both he and his sister concurred that their father was not particularly religious, but their mother "definitely believed in God, and was active in the temple [...] and served only kosher meat." During the most severe years of the Great Depression, his father worked as a movie theater usher.

According to biographer Keay Davidson, Sagan attributed his analytical inclinations to his mother, who had experienced extreme poverty as a child in New York City during World War I and the 1920s. Her subsequent intellectual aspirations were reportedly hindered by her poverty, gender, marital status, and Jewish ethnicity. Davidson suggested that she "worshipped her only son, Carl" because "he would fulfill her unfulfilled dreams." Sagan traced his sense of wonder to his father, who dedicated his free time to distributing apples to the impoverished or mediating disputes between workers and management within New York City's garment industry. Sagan articulated: "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."

He recounted a pivotal developmental experience when his parents brought him to the 1939 New York World's Fair. He retained distinct recollections of several exhibits there. One, Futurama, featured a moving map that, as he recalled, "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!" Other displays demonstrated a flashlight activating a photoelectric cell to produce a crackling sound, and the visualization of a tuning fork's sound as a waveform on an oscilloscope. He also observed an exhibit on the emerging medium of television. He later articulated his profound realization: "Plainly, the world held wonders of a kind I had never guessed. How could a tone become a picture and light become a noise?" Sagan witnessed a highly publicized event at the fair: the interment of a time capsule at Flushing Meadows, containing 1930s mementos intended for future retrieval. Davidson noted that this experience "thrilled Carl." In his adult career, Sagan and his collaborators would devise analogous time capsules for interstellar transmission.

During World War II, Sagan's parents expressed concern for their European relatives, though he largely remained uninformed about the conflict's specifics. Sagan later recounted, "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, indicated that their mother's primary objective was to "protect Carl," given her "extraordinarily difficult time dealing with World War II and the Holocaust."

He pondered the nature of stars, yet no one could provide a definitive explanation. He recounted:

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 like Clark Gable and Jean 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 the inverse 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.

He articulated this profound realization: "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." During his sixth or seventh year, he and a close companion frequently visited the American Museum of Natural History, where they were captivated by the dinosaur fossil exhibits, nature dioramas, and the Hayden Planetarium. Sagan's parents actively fostered his burgeoning scientific curiosity by providing him with chemistry sets and educational literature. According to biographer Ray Spangenburg, Sagan's aspiration to comprehend the Cosmos evolved into "a driving force in his life, a continual spark to his intellect, and a quest that would never be forgotten." His interest in extraterrestrial realms intensified following his engagement with Edgar Rice Burroughs's John Carter of Mars series. In 1947, he encountered Astounding Science Fiction, which exposed him to more rigorous scientific speculations within the genre. He described his engagement: "Each month I eagerly awaited the arrival of Astounding. I read Verne and Wells, read, cover‐to‐cover, the first two science‐fiction anthologies that I was able to find, devised scorecards, similar to those I was fond of making for baseball, on the quality of the stories I read. Many ranked high in asking interesting questions but low in answering them."

Education

Carl Sagan attended David A. Boody Junior High School in Bensonhurst, his birthplace, and celebrated his bar mitzvah at age 13. In 1948, at 14, his family relocated to Rahway, New Jersey, due to his father's employment, where he subsequently enrolled at Rahway High School. Despite maintaining excellent academic performance, Sagan experienced disengagement, finding his classes unchallenging and his instructors uninspiring. Recognizing his exceptional abilities, his teachers advocated for his enrollment in a private institution, with one administrator remarking, "This kid ought to go to a school for gifted children, he has something really remarkable." Nevertheless, his parents were unable to bear the financial cost. Sagan assumed the presidency of the school's chemistry club and established a personal laboratory at home. He independently studied molecular structures by constructing cardboard models to visualize their formation, noting, "I found that about as interesting as doing [chemical] experiments." His primary academic interest lay in astronomy, which he pursued in his leisure time. During his junior year of high school, he realized that professional astronomers earned a living from an activity he consistently enjoyed, reflecting, "That was a splendid day—when I began to suspect that if I tried hard I could do astronomy full-time."

Prior to completing high school, Sagan participated in an essay competition where he posited that human interaction with advanced extraterrestrial civilizations could prove as catastrophic for Earth's inhabitants as the initial encounters between Native Americans and Europeans had been for indigenous populations. Although the topic was deemed contentious, his persuasive rhetorical abilities secured him first prize from the judges. Nearing his high school graduation, his peers designated him "most likely to succeed" and positioned him as a candidate for valedictorian. In 1950, Sagan authored the essay "Space, Time, and the Poet" for his high school newspaper. This piece reflected on humanity's position within the cosmos, drawing upon the perspectives of poets such as T. S. Eliot and Alfred, Lord Tennyson, and referencing "the work containing perhaps the greatest poetry—the Bible." He successfully graduated from Rahway High School in 1951.

Sagan matriculated at the University of Chicago, which was among the limited number of institutions willing to admit a 16-year-old applicant. The university's chancellor, Robert M. Hutchins, had recently restructured the College of the University of Chicago into an "ideal meritocracy," emphasizing a curriculum centered on Great Books, Socratic dialogue, comprehensive examinations, and provisions for early college admission. He became a member of the Ryerson Astronomical Society. Sagan articulated his collegiate experience as "the fulfillment of my dreams," noting, "I found teachers who not only understood science, but were actually able to explain it. … I was a physics student in a department orbiting around Enrico Fermi; I discovered what true mathematical elegance is from Subrahmanyan Chandrasekhar; I was given the chance to talk chemistry with Harold Urey; over summers I was apprenticed in biology to H. J. Muller at Indiana University; and I learned planetary astronomy from its only full-time practitioner at the time, G. P. Kuiper." The Miller-Urey experiment, performed in 1952, significantly stimulated his interest in abiogenesis. Under Urey's mentorship, he authored "Radiation and the Origin of the Gene." He recollected that "science was presented as an integral part of the gorgeous tapestry of human knowledge," and that "it was considered unthinkable for an aspiring physicist not to know Plato, Aristotle, Bach, Shakespeare, Gibbon, Malinowski and Freud—among many others."

Sagan received a Bachelor of Liberal Arts degree with general and special honors in what he humorously described as "nothing." In 1955, he obtained a Bachelor of Science in physics. Subsequently, he pursued graduate studies at the University of Chicago, completing a Master of Science in physics in 1956 and a Doctor of Philosophy in astronomy and astrophysics in 1960. His doctoral dissertation, supervised by Kuiper, was titled "Physical Studies of the Planets." Throughout his graduate tenure, he dedicated his summers to collaborative work with Kuiper, as well as with chemist Melvin Calvin and physicist George Gamow. He attributed to Kuiper the instruction in "back-of-the-envelope" calculations, explaining the method: "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."

In 1958, Sagan and Kuiper collaborated on Project A119, a classified military initiative by the United States Air Force to detonate a nuclear warhead on the Moon and document its effects. Sagan held a Top Secret clearance with the Air Force and a Secret clearance with NASA. In 1999, an article in the journal Nature disclosed that Sagan had listed the classified titles of two Project A119 documents in his 1959 scholarship application to the University of California, Berkeley. Subsequently, project leader Leonard Reiffel corroborated Sagan's security breach in a letter to the journal.

Career and Research

Between 1960 and 1962, Sagan held a Miller Fellowship at the University of California, Berkeley. During this period, he published an article in Science in 1961 concerning the atmosphere of Venus, concurrently contributing to NASA's Mariner 2 team and serving as a Planetary Sciences Consultant for the RAND Corporation.

Following the 1961 publication of Sagan's article in Science, Harvard University astronomers Fred Whipple and Donald Menzel extended an invitation for him to present a colloquium, subsequently offering a lecturer position. Sagan, however, requested an appointment as an assistant professor, a role Whipple and Menzel ultimately persuaded Harvard to grant. From 1963 to 1968, Sagan lectured, conducted research, and mentored graduate students at Harvard, while also contributing to the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts.

In 1968, Harvard denied Sagan academic tenure, a decision he later described as highly unexpected. Several factors have been cited for this denial, including his broad intellectual pursuits across multiple disciplines—contrasting with the academic norm of specializing in a narrow field—and potentially his prominent scientific advocacy, which some peers viewed as leveraging others' ideas primarily for self-promotion. Notably, Harold Urey, his undergraduate advisor, submitted a letter to the tenure committee strongly opposing Sagan's tenure application.

Prior to the unsuccessful tenure review at Harvard, Thomas Gold, an astronomer at Cornell University, had actively recruited Sagan to relocate to Ithaca, New York, and join the Cornell faculty alongside the recently appointed Frank Drake. After Harvard's tenure denial, Sagan accepted Gold's invitation, remaining a faculty member at Cornell for nearly three decades until his passing in 1996. In contrast to Harvard, Cornell's smaller, more informal astronomy department embraced Sagan's increasing public recognition. After two years as an associate professor, Sagan achieved full professorship at Cornell in 1970 and assumed directorship of the Laboratory for Planetary Studies. From 1972 to 1981, he served as associate director of Cornell's Center for Radiophysics and Space Research (CRSR). In 1976, he was appointed the David Duncan Professor of Astronomy and Space Sciences, a distinguished position he maintained throughout his life.

Sagan maintained a continuous association with the U.S. space program from its earliest stages. Beginning in the 1950s, he served as a NASA advisor, notably briefing Apollo astronauts prior to their lunar missions. He played a significant role in numerous robotic spacecraft missions exploring the Solar System, often designing experiments for these expeditions. Sagan frequently questioned funding allocations for the Space Shuttle and the International Space Station, arguing they diverted resources from further robotic exploration. He conceptualized and assembled the first physical message dispatched into space: a gold-plated plaque affixed to the Pioneer 10 space probe, launched in 1972. A duplicate plaque was carried by Pioneer 11, launched the subsequent year. Sagan further refined these designs, contributing to the Voyager Golden Record, a compendium of Earth's sights and sounds sent aboard the Voyager space probes in 1977, which notably included music by Bach, Beethoven, and Chuck Berry.

Scientific Achievements

David Morrison, a former student, characterized Sagan as a "conceptual innovator" and an adept practitioner of intuitive physical reasoning and rapid estimation techniques, while Gerard Kuiper observed that some individuals excel in specialized laboratory research, whereas others are more effective in interdisciplinary scientific coordination, categorizing Dr. Sagan within the latter group.

Sagan's contributions were instrumental in establishing the high surface temperatures of Venus. In the early 1960s, the fundamental surface conditions of Venus remained uncertain; Sagan enumerated potential scenarios in a report subsequently popularized in the Time Life book Planets. His perspective posited Venus as arid and extremely hot, contrasting with the temperate, paradisiacal environment envisioned by some. Through analysis of radio emissions from Venus, he deduced a surface temperature of 500 °C (900 °F). As a visiting scientist at NASA's Jet Propulsion Laboratory, he played a significant role in the initial Mariner missions to Venus, participating in both project design and management. Mariner 2 corroborated his findings regarding Venus's surface conditions in 1962.

Sagan was a pioneering proponent of the hypothesis that Saturn's moon Titan could harbor surface oceans of liquid compounds and that Jupiter's moon Europa might contain subterranean water oceans, thereby suggesting Europa's potential habitability. Europa's subsurface ocean of water subsequently received indirect confirmation from the spacecraft Galileo. Sagan also contributed to resolving the enigma of Titan's reddish atmospheric haze, which was identified as resulting from the continuous precipitation of complex organic molecules onto Titan's surface.

Sagan additionally provided significant insights into the atmospheres of Venus and Jupiter, as well as seasonal changes on Mars. He recognized anthropogenic climate change as an escalating threat, drawing parallels between this phenomenon and Venus's natural evolution into a scorching, inhospitable planet via a runaway greenhouse effect. In 1985, he presented testimony to the United States Congress, asserting that the greenhouse effect would alter Earth's climate system. Sagan and his Cornell colleague Edwin Ernest Salpeter theorized about the potential for life within Jupiter's clouds, considering the planet's dense, organic-molecule-rich atmospheric composition. He investigated observed Martian surface color variations, concluding that these were attributable to wind-driven shifts in surface dust rather than the commonly accepted seasonal or vegetational alterations. He advocated for the hypothesis, subsequently widely accepted, that Venus's elevated surface temperatures are a consequence of the greenhouse effect.

Sagan is also recognized for his investigations into the potential for extraterrestrial life, notably including experimental evidence for the radiolytic synthesis of amino acids from fundamental chemical precursors.

By 2017, Sagan had become the most frequently cited scientist in the field of SETI and ranked among the most cited planetary scientists.

He served as editor of Icarus from 1975 to 1979. In 1980, he co-established The Planetary Society.

Public Engagement in Science

Sagan authored the Encyclopædia Britannica entry concerning Life, which was subsequently revised by his first wife, biologist Lynn Margulis. His inaugural popular science publication was The Cosmic Connection. He presented the Cosmic Calendar within The Dragons of Eden, a work awarded the 1978 Pulitzer Prize in the General Nonfiction category. He delivered the 1977 Royal Institution Christmas Lectures titled The Planets.

Carl Sagan and Ann Druyan collaboratively authored the 13-part PBS documentary series, Cosmos: A Personal Voyage. This series drew inspiration from preceding documentaries, particularly Jacob Bronowski's The Ascent of Man. Its production notably included the reconstruction of the Library of Alexandria. The documentary encompassed a broad spectrum of scientific disciplines, such as stellar evolution and its intrinsic connection to the development of life. Frederic Golden observed that "The series' title derives from the Greek term for the ordered universe, representing the antithesis of chaos. This selection is highly appropriate. Cosmos constitutes Sagan's profound endeavor to elucidate what many perceive as the profoundly perplexing realm of 20th-century science. To narrate his account, he traverses two millennia of scientific advancement, frequently moving across centuries akin to a Wellsian chrononaut. At one juncture, he is depicted in a café on the Aegean island of Samos, the birthplace of Pythagoras and Aristarchus, expounding upon the nascent stages of Greek scientific achievement. Subsequently, he is shown perambulating through the esteemed Cavendish Laboratories at England's Cambridge University, detailing the genesis of modern atomic physics. Sagan renders scientific concepts as accessible as the apple pie he meticulously slices in a Cambridge University dining room to illustrate a point regarding matter." Sagan presented an optimistic perspective on humanity's position within the cosmos, asserting that "We are a way for the cosmos to know itself." By 1990, Cosmos had garnered an audience of at least 500 million individuals across 60 nations, establishing it as the most extensively viewed series in the annals of American public television until the debut of Ken Burns's The Civil War. The series Cosmos was honored with both an Emmy Award and a Peabody Award. Its soundtrack incorporated compositions by notable artists such as Bach, Vivaldi, and Vangelis.

The companion book, published concurrently, received considerable acclaim. James Michener commented that "Mr. Sagan's essay, an offshoot of his immensely successful television program, presents a skillfully composed and imaginatively illustrated synopsis of his geological, anthropological, biological, historical, and astronomical reflections on our universe. His scholarly references encompass the full breadth of human history. His exposition, though necessarily concise, is distinctly personal. He consistently maintains readability, and given the extensive scope of his intellect, he appears uniquely suited for this undertaking."

Sagan authored the introduction for Stephen Hawking's acclaimed bestseller, A Brief History of Time. In 1988, Magnus Magnusson facilitated a discussion featuring Sagan, Hawking, and Arthur C. Clarke, titled God, the Universe and Everything Else. Subsequently, he penned a sequel to Cosmos, titled Pale Blue Dot. The title of this work alludes to the perspective of Earth as observed from the Voyager spacecraft.

Sagan articulated at least two primary motivations for scientists to disseminate the objectives and discoveries of scientific inquiry. One motivation was pragmatic self-interest: a substantial portion of scientific funding originates from public sources, thereby entitling the public to transparency regarding expenditure. Should scientists successfully cultivate greater public appreciation for science, the likelihood of securing increased public support would significantly improve. The second motivation involved the intrinsic satisfaction derived from conveying one's enthusiasm for scientific endeavors to a broader audience.

Sagan stated: "Among the foremost contemporary scientist-popularizers, I consider Stephen Jay Gould, E. O. Wilson, Lewis Thomas, and Richard Dawkins in the field of biology; Steven Weinberg, Alan Lightman, and Kip Thorne in physics; Roald Hoffmann in chemistry; and the early contributions of Fred Hoyle in astronomy. (Furthermore, despite necessitating a background in calculus, the most consistently stimulating, thought-provoking, and inspiring scientific popularization of recent decades appears to me to be Volume 1 of Richard Feynman's Introductory Lectures on Physics.)"

Science Fiction

Sagan articulated that science fiction served as a foundational influence, guiding him toward a career in science. He further noted that while much of the science fiction he encountered during his formative years did not withstand critical scrutiny, "the pinnacle of science fiction endures as exceptionally meritorious. Certain narratives are so meticulously crafted, so replete with the intricate particulars of an unfamiliar civilization, that they captivate me entirely before I can even engage in critical assessment. Exemplary works of this caliber include Robert Heinlein's The Door into Summer; Alfred Bester's The Stars My Destination and his The Demolished Man; Jack Finney's Time and Again; Frank Herbert's Dune, and Walter M. Miller's A Canticle for Leibowitz."

Sagan's engagement with science fiction fandom was facilitated by his friendship with Isaac Asimov; he delivered a speech at the Nebula Awards ceremony in 1969. Asimov notably characterized Sagan as one of only two individuals whose intellect he considered superior to his own, the other being computer scientist and artificial intelligence expert Marvin Minsky. Sagan provided advisory services for Stanley Kubrick's film, 2001: A Space Odyssey, for a brief period. He advocated for the film to imply, rather than explicitly portray, the existence of extraterrestrial superintelligence. In 1971, he joined a panel discussion concerning Mars alongside Ray Bradbury, Arthur C. Clarke, Bruce C. Murray, and Walter Sullivan; their contributions were subsequently published as Mars and the Mind of Man. Sagan ventured into science fiction writing with his novel, Contact. To facilitate his protagonist, Ellie Arroway's, journey from Earth to Vega, he consulted his colleague Kip Thorne regarding the physics of wormholes. This consultation subsequently prompted Thorne's original research into closed timelike curves.

Skepticism

Sagan actively advocated for scientific skepticism, particularly in opposition to pseudoscience. He attributed the development of his critical thinking skills to Martin Gardner's Fads and Fallacies in the Name of Science and Charles Mackay's Extraordinary Popular Delusions and the Madness of Crowds. In 1974, he initiated a debate challenge against Immanuel Velikovsky. He was a vocal critic of practices such as crystal healing and astrology. Within a column for Parade, he introduced the concept of a "Baloney Detection Kit," a term originated by Arthur Felberbaum, a friend of his wife, Ann Druyan. This concept was further elaborated in his penultimate publication, The Demon-Haunted World. He expressed regret that the majority of newspapers featured daily astrology columns, while very few dedicated even a weekly column to astronomy.

Commemorating the tenth anniversary of Sagan's passing, David Morrison, a former student, highlighted "Sagan's immense contributions to planetary research, the public understanding of science, and the skeptical movement" in an article published in Skeptical Inquirer. Sagan also instructed a Senior Seminar focused on "Critical Thinking."

One of Sagan's most renowned aphorisms, "extraordinary claims require extraordinary evidence," is frequently referred to as the "Sagan standard." This principle derived from a highly similar assertion made by Marcello Truzzi, a co-founder of the Committee for the Scientific Investigation of Claims of the Paranormal: "An extraordinary claim requires extraordinary proof." The underlying concept had been previously encapsulated in Théodore Flournoy's From India to the Planet Mars (1899), originating from a more extensive statement by the French mathematician and astronomer Pierre-Simon Laplace, known as the Principle of Laplace: "The weight of the evidence should be proportioned to the strangeness of the facts."

Sagan observed that the predictive capacity of science served as a key differentiator from pseudoscience, stating: “If you want to know when the next eclipse of the Sun will be, you might try magicians and mystics, but you’ll do much better with scientists. They will tell you where on Earth to stand, when you have to be there, and whether it will be a partial eclipse, a total eclipse, or an annular eclipse. They can routinely predict a solar eclipse, up to the minute, a century in advance. You can go to the witch doctor to lift the spell that causes your pernicious anemia, or you can take Vitamin B12. If you want to save your child from polio, you can pray or you can inoculate.”

Additional Interests

During his later career, Sagan advocated for the systematic identification of near-Earth objects (NEOs) with potential terrestrial impact trajectories, while simultaneously recommending the deferral of technological advancements for planetary defense. He contended that the various proposed strategies for altering asteroid orbits, including the use of nuclear detonations, presented a significant deflection dilemma: the capacity to divert an asteroid away from Earth inherently implies the capability to redirect a non-threatening object towards Earth, thereby constituting an exceptionally destructive weapon. In a co-authored paper from 1994, Sagan critically assessed a three-day "Near-Earth Object Interception Workshop" conducted by Los Alamos National Laboratory (LANL) in 1993, noting its failure to mention, "even in passing," the "ancillary dangers" associated with such interception and deflection technologies.

Sagan maintained optimism that the inherent dual nature of methods to mitigate the natural near-Earth object (NEO) impact threat, alongside the threat itself, would serve as a "new and potent motivation to maturing international relations." He later acknowledged that, with adequate international oversight, an incremental implementation approach to nuclear explosive deflection methods could be deployed in the future. Once sufficient knowledge was acquired, these methods could then be utilized to facilitate asteroid mining. His interest in employing nuclear detonations in space originated from his 1958 work for the Armour Research Foundation's Project A119, which investigated the feasibility of detonating a nuclear device on the lunar surface.

He was a proponent of fundamental research, emphasizing its potential for future practical applications: “Maxwell wasn’t thinking of radio, radar, and television when he first scratched out the fundamental equations of electromagnetism; Newton wasn’t dreaming of space flight or communications satellites when he first understood the motion of the Moon; Roentgen wasn’t contemplating medical diagnosis when he investigated a penetrating radiation so mysterious he called it ‘X-rays’; Curie wasn’t thinking of cancer therapy when she painstakingly extracted minute amounts of radium from tons of pitchblende; Fleming wasn’t planning on saving the lives of millions with antibiotics when he noticed a circle free of bacteria around a growth of mold; Watson and Crick weren’t imagining the cure of genetic diseases when they puzzled over the X-ray diffractometry of DNA…"

Sagan's Number

Sagan's number quantifies the stars within the observable universe. This metric is conceptually well-defined, given the established understanding of stars and the observable universe, yet its precise value is subject to significant uncertainty.

• In 1980, Sagan estimated this quantity to be approximately 10 sextillion (10²²) on the short scale.
• By 2003, it was subsequently estimated at 70 sextillion (7 × 10²²).
• In 2010, the estimate was further refined to reach 300 sextillion (3 × 10²³).

"Billions and billions"

Following the broadcast of Cosmos, Sagan became widely associated with the catchphrase "billions and billions," despite never directly uttering this precise phrase. He instead employed the expression "billions upon billions."

Richard Feynman frequently employed the phrase "billions and billions" in his Lectures on Physics. However, Sagan's frequent use of the term billions, coupled with his distinctive vocal delivery that emphasized the "b" sound (an intentional choice to differentiate it from "millions" rather than using cumbersome alternatives such as "billions with a 'b'"), was famously satirized by Johnny Carson. Sagan was a friend of Carson's and a recurring guest on the Tonight Show.

Other comedians, including Gary Kroeger, Mike Myers, Bronson Pinchot, Penn Jillette, and Harry Shearer, followed Carson's comedic lead. Frank Zappa parodied the phrase in his song "Be in My Video." Sagan received this attention with good humor, culminating in his final book, titled Billions and Billions, which commenced with a lighthearted, self-referential discussion of this catchphrase, noting Carson's amateur astronomical interest and the incorporation of genuine scientific elements into his comedic portrayals.

In 1993, engineers at Apple Computer internally codenamed the Power Macintosh 7100 "Carl Sagan," with the aspiration that Apple would achieve "billions and billions" in sales. Although the name remained an internal designation, Sagan was apprehensive that this association might imply a product endorsement and consequently issued a cease-and-desist letter to Apple. Apple complied with the request; however, engineers subsequently retaliated by altering the internal codename to "BHA," an acronym for "Butt-Head Astronomer." In November 1995, following additional legal proceedings, an out-of-court settlement was achieved, and Apple's office of trademarks and patents issued a conciliatory statement affirming 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."

In a humorous homage to Sagan and his enduring association with the catchphrase "billions and billions," the term sagan has been formally defined as a unit of measurement representing an exceptionally large, indeterminate quantity of any item.

Criticisms

While Sagan was widely adored by the general public, his reputation within the scientific community was more divided. Critics sometimes labeled his work as fanciful, non-rigorous, and self-aggrandizing, and others, in his later years, complained that he prioritized celebrity over his faculty responsibilities.

Harold Urey, a prominent critic of Sagan, believed Sagan received excessive publicity for a scientist and treated certain scientific theories with undue informality. According to Davidson, Urey and Sagan held divergent philosophies of science. Urey, an "old-time empiricist," avoided theoretical speculation about the unknown, whereas Sagan readily engaged in such open conjecture. Fred Whipple advocated for Sagan's retention at Harvard but discovered that Urey's status as a Nobel laureate significantly influenced Harvard's decision to deny Sagan tenure.

Lester Grinspoon, a Harvard colleague and friend of Sagan, also remarked: "I know Harvard well enough to know there are people there who certainly do not like people who are outspoken." Grinspoon further added:

Everywhere one looked, a single astronomer was being quoted on all subjects, featured on television, and had their books prominently displayed in local bookstores.

Subsequently, some individuals, including Urey, came to believe that Sagan's popular approach to scientific advocacy ultimately benefited the scientific community. Urey particularly admired Sagan's 1977 book The Dragons of Eden and conveyed his opinion to Sagan in writing: "I like it very much and am amazed that someone like you has such an intimate knowledge of the various features of the problem... I congratulate you... You are a man of many talents."

Sagan faced accusations of appropriating others' ideas for his own gain. He countered these claims by explaining that such misappropriation was an unfortunate consequence of his role as a science communicator and explainer, asserting that he endeavored to provide proper attribution whenever feasible.

Social Concerns

During the peak of the Cold War, Sagan actively participated in nuclear disarmament initiatives. He promoted hypotheses regarding the potential consequences of nuclear conflict, particularly after Paul Crutzen's "Twilight at Noon" concept suggested that a significant nuclear exchange could induce a nuclear twilight, disrupting Earth's delicate ecological balance through surface cooling. In 1983, Sagan was one of five authors—represented by the "S"—in the subsequent "TTAPS" model, a research article notable for introducing the term "nuclear winter," coined by his colleague Richard P. Turco. He co-authored the book The Cold and the Dark: The World after Nuclear War in 1984 and A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race in 1990, both of which elucidate the nuclear-winter hypothesis and advocate for nuclear disarmament. Sagan encountered considerable skepticism and disapproval for utilizing media to disseminate a highly uncertain hypothesis. A personal correspondence with nuclear physicist Edward Teller, commencing amicably around 1983, initially saw Teller express support for continued research to verify the credibility of the winter hypothesis. However, their exchange ultimately led Teller to write: "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." Sagan's biographers also noted that, from a scientific perspective, nuclear winter represented a low point in his career, although it significantly enhanced his public image politically.

Sagan posited that while the Drake equation indicated the probable existence of numerous extraterrestrial civilizations, the absence of empirical evidence, as underscored by the Fermi paradox, implied a propensity for technological societies to self-destruct. This perspective fueled his dedication to identifying and disseminating information about potential existential threats to humanity, aiming to avert such a catastrophe and facilitate the eventual emergence of a spacefaring civilization. His profound apprehension concerning the potential annihilation of human civilization through nuclear conflict was powerfully articulated in a notable cinematic segment within the concluding episode of Cosmos, titled "Who Speaks for Earth?" Previously, Sagan had resigned from the Air Force Scientific Advisory Board's Condon Committee, which investigated UFOs, and voluntarily relinquished his top-secret clearance as a form of protest against the Vietnam War. Subsequent to his marriage to novelist Ann Druyan in June 1981, Sagan intensified his political engagement, notably advocating against the escalation of the nuclear arms race during President Ronald Reagan's administration.

In March 1983, President Reagan unveiled the Strategic Defense Initiative, a multi-billion-dollar endeavor aimed at establishing a comprehensive defense system against nuclear missile attacks, which rapidly acquired the moniker "Star Wars." Sagan, alongside numerous scientific colleagues, publicly opposed this initiative, contending that the requisite level of technical perfection for such a system was unattainable. Furthermore, they argued that constructing the system would be considerably more costly than an adversary's efforts to circumvent it using decoys and other countermeasures. They also asserted that its implementation would profoundly destabilize the existing "nuclear balance" between the United States and the Soviet Union, thereby precluding any future advancements in nuclear disarmament.

Upon Soviet leader Mikhail Gorbachev's declaration of a unilateral moratorium on nuclear weapons testing, effective August 6, 1985—coinciding with the 40th anniversary of the atomic bombing of Hiroshima—the Reagan administration characterized this significant action as mere propaganda and declined to reciprocate. Consequently, American anti-nuclear and peace activists initiated a series of protest demonstrations at the Nevada Test Site, commencing on Easter Sunday in 1986 and persisting throughout 1987. Among the hundreds of individuals from the "Nevada Desert Experience" group who were apprehended, Sagan was arrested twice for scaling a chain-link fence at the test site during the underground Operation Charioteer and the United States's Musketeer nuclear test series.

Sagan championed free speech and civil liberties. During the McCarthy era, his professor, Edward Condon, faced accusations from the House Un-American Activities Committee (HUAC) of being a "revolutionary in physics." Sagan recounted Condon's response: "I believe in Archimedes’ Principle, formulated in the third century B. C. I believe in Kepler’s laws of planetary motion, discovered in the seventeenth century. I believe in Newton’s laws…," with Condon further citing Bernoulli, Fourier, Ampère, Boltzmann, and Maxwell. This response did not amuse the committee. Sagan further recalled, "But the most they were able to pin on Condon, as I recall, was that in high school he had a job delivering a socialist newspaper door-to-door on his bicycle." During their visits to the Soviet Union, Sagan and Druyan engaged in the clandestine importation of prohibited literature.

During a speech delivered at Monticello on July 4, 1992, Sagan underscored the critical role of science for figures such as Thomas Jefferson, John Adams, and Benjamin Franklin, as well as for the foundational principles of democracy in America:

On this beleaguered planet, it is an observable reality that widespread torture, famine, and systemic governmental corruption are more prevalent under tyrannical regimes than in democratic systems. This disparity arises because leaders in autocratic states face significantly lower probabilities of removal from power for their transgressions compared to their counterparts in democracies. This mechanism constitutes the political system's inherent error correction process.

He observed 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 concluded by stating:

Comprehensive education regarding the intrinsic value of free speech and other liberties enshrined in the Bill of Rights, coupled with an understanding of the consequences of their absence and the methods for their exercise and preservation, constitutes a fundamental prerequisite for citizenship in the United States, and indeed for any nation, particularly where such rights are inadequately protected. A populace unable to engage in independent thought or unwilling to challenge authority becomes susceptible to manipulation by those in power. Conversely, an educated citizenry capable of forming its own judgments ensures that governing bodies are accountable to us. Consequently, the integration of the scientific method and the rationale behind a Bill of Rights into educational curricula globally is imperative, fostering attributes such as decency, humility, and civic solidarity.

Personal Life and Beliefs

Carl Sagan was married on three occasions. His first marriage, in 1957, was to biologist Lynn Margulis, with whom he had two children, Jeremy and Dorion Sagan. Margulis reportedly stated that Sagan delegated most domestic responsibilities to her, believing himself exempt from such duties. This marriage concluded in 1964. In 1968, Sagan married artist Linda Salzman, and they had one child, Nick Sagan, before divorcing in 1981. Sagan's intense focus on his career during these periods is considered a potential contributing factor to his initial divorce. His third marriage, in 1981, was to author Ann Druyan, and they had two children, Alexandra (known as Sasha) and Samuel Sagan. Carl Sagan and Druyan remained married until his passing in 1996.

Sagan was a prominent advocate for the search for extraterrestrial life, actively encouraging the scientific community to utilize radio telescopes for detecting signals from potential intelligent extraterrestrial civilizations. His persuasive efforts culminated in 1982 with the publication of a petition in the journal Science, endorsing SETI (Search for Extraterrestrial Intelligence), which garnered signatures from 70 scientists, including seven Nobel Prize laureates. This publication significantly elevated the credibility of what was then a contentious scientific domain. Furthermore, Sagan is believed to have contributed to Frank Drake's Arecibo message, a radio transmission broadcast into space from the Arecibo Observatory on November 16, 1974, designed to convey information about Earth to potential extraterrestrial recipients.

For 12 years, Sagan served as chief technology officer for the professional planetary research journal Icarus. He co-founded The Planetary Society and was a member of the SETI Institute Board of Trustees. Additionally, Sagan held positions as Chairman of the Division for Planetary Science of the American Astronomical Society, President of the Planetology Section of the American Geophysical Union, and Chairman of the Astronomy Section of the American Association for the Advancement of Science (AAAS).

While instructing at Cornell University, Sagan resided in an Egyptian Revival-style house situated on a cliff edge in Ithaca. During this period, he owned a red Porsche 911 Targa and an orange 1970 Porsche 914, the latter bearing the license plate PHOBOS.

Naturalism

Sagan frequently addressed topics concerning religion and the interplay between religion and science, often expressing skepticism regarding the conventional anthropomorphic conception of God. For instance, he stated:

Some people think God is an outsized, light-skinned male with a long white beard, sitting on a throne somewhere up there in the sky, busily tallying the fall of every sparrow. Others—for example Baruch Spinoza and Albert Einstein—considered God to be essentially the sum total of the physical laws which describe the universe. I do not know of any compelling evidence for anthropomorphic patriarchs controlling human destiny from some hidden celestial vantage point, but it would be madness to deny the existence of physical laws.

In 1981, Sagan offered his perspective on atheism, remarking:

An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence. Because God can be relegated to remote times and places and to ultimate causes, we would have to know a great deal more about the universe than we do now to be sure that no such God exists. To be certain of the existence of God and to be certain of the nonexistence of God seem to me to be the confident extremes in a subject so riddled with doubt and uncertainty as to inspire very little confidence indeed.

Sagan further articulated his perspectives on Christianity and the Jefferson Bible, positing that Christianity constitutes an amalgamation of two ostensibly incompatible components: the teachings of Jesus and the doctrines of Paul. He noted Thomas Jefferson's endeavor to remove the Pauline elements from the New Testament, observing that the resulting text, though significantly reduced, remained a profoundly inspiring document.

Sagan contended that spirituality ought to be grounded in scientific understanding, advocating for the supersession of traditional religious frameworks by belief systems centered on the scientific method, while simultaneously acknowledging the inherent mystery and provisional nature of scientific inquiry. In discussing the interplay between spirituality and science, Sagan articulated:

'Spirit' comes from the Latin word 'to breathe'. What we breathe is air, which is certainly matter, however thin. Despite usage to the contrary, there is no necessary implication in the word 'spiritual' that we are talking of anything other than matter (including the matter of which the brain is made), or anything outside the realm of science. On occasion, I will feel free to use the word. Science is not only compatible with spirituality; it is a profound source of spirituality. When we recognize our place in an immensity of light-years and in the passage of ages, when we grasp the intricacy, beauty, and subtlety of life, then that soaring feeling, that sense of elation and humility combined, is surely spiritual. So are our feelings in the presence of great art or music or literature, or acts of exemplary selfless courage, such as those of Mohandas Gandhi or Martin Luther King, Jr. The notion that science and spirituality are somehow mutually exclusive does a disservice to both.

In January 1990, an environmental appeal titled "Preserving and Cherishing the Earth," primarily authored by Sagan and endorsed by him alongside other prominent scientists and religious leaders, asserted 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."

When questioned about his religious convictions in 1996, Sagan identified as agnostic. He contended that the concept of a creator God for the universe was inherently challenging to either substantiate or refute empirically, suggesting that the sole scientific finding capable of contesting this notion would be the discovery of an infinitely ancient universe. His son, Dorion Sagan, clarified that his father subscribed to the Spinozan and Einsteinian conception of God, viewing divinity not as a force external to nature but as nature itself, its intrinsic equivalent.

In 2006, Ann Druyan compiled and edited Sagan's 1985 Glasgow Gifford Lectures in Natural Theology into a published volume, titled The Varieties of Scientific Experience: A Personal View of the Search for God, wherein Sagan expounds upon his perspectives regarding divinity within the natural world.

Toward the end of his life, Sagan's literary works further developed his naturalistic worldview. His posthumously published collection, Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium, includes his essays on subjects such as abortion, alongside an essay by Ann Druyan exploring the connection between his agnostic and freethinking convictions and his passing.

He articulated the universality of physical laws as follows:

We detect the light from distant quasars only because the laws of electromagnetism are the same ten billion light years away as here. The spectra of those quasars are recognizable only because the same chemical elements are present there as here, and because the same laws of quantum mechanics apply. The motion of galaxies around one another follows familiar Newtonian gravity. Gravitational lenses and binary pulsar spin-downs reveal general relativity in the depths of space. We could 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 continued by posing: "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?"

Advocacy for Marijuana

Carl Sagan utilized and publicly supported marijuana. Writing under the alias "Mr. X," he authored an essay on cannabis use for the 1971 publication Marihuana Reconsidered. This essay detailed how marijuana consumption had contributed to the inspiration for some of Sagan's creative endeavors and augmented his sensory and intellectual perceptions. Following Sagan's passing, his associate Lester Grinspoon revealed this detail to Sagan's biographer, Keay Davidson. The 1999 publication of the biography Carl Sagan: A Life subsequently drew considerable media attention to this facet of Sagan's personal life. Shortly after his demise, his widow, Ann Druyan, assumed the role of presiding over the board of directors for the National Organization for the Reform of Marijuana Laws (NORML), a non-profit entity committed to advocating for cannabis law reform.

Unidentified Flying Objects

In 1947, a pivotal year that initiated the widespread fascination with "flying saucers," a young Carl Sagan theorized that these observed "discs" could potentially be extraterrestrial spacecraft. His engagement with UFO accounts led him, on August 3, 1952, to address a letter to U.S. Secretary of State Dean Acheson, inquiring about the potential governmental response should flying saucers be confirmed as extraterrestrial in origin. Subsequently, in 1964, he engaged in multiple discussions on this topic with Jacques Vallée. Despite his considerable skepticism regarding extraordinary explanations for the UFO phenomenon, Sagan maintained that scientific inquiry into the subject was warranted, primarily due to extensive public interest in UFO reports.

Stuart Appelle observes that Sagan "frequently documented what he identified as the logical and empirical inconsistencies associated with UFOs and the abduction phenomenon." While Sagan dismissed extraterrestrial hypotheses for these phenomena, he contended that investigating UFO reports offered both empirical and pedagogical advantages, thereby establishing the subject as a valid area for academic research.

In 1966, Sagan served as a member of the Ad Hoc Committee tasked with reviewing Project Blue Book, the United States Air Force's initiative for investigating Unidentified Flying Objects. The committee determined that Project Blue Book lacked scientific rigor and proposed the establishment of a university-affiliated project to subject the UFO phenomenon to more thorough scientific examination. This recommendation led to the formation of the Condon Committee (1966–68), chaired by physicist Edward Condon, which formally concluded in its final report that UFOs, irrespective of their actual nature, did not exhibit behaviors indicative of a threat to national security.

Sociologist Ron Westrum asserts that "Sagan's most significant engagement with the UFO question occurred at the 1969 AAAS symposium." Participants presented a diverse array of informed perspectives on the topic, encompassing both advocates such as James McDonald and J. Allen Hynek, and skeptics including astronomers William Hartmann and Donald Menzel. The speaker lineup was meticulously balanced, and the symposium's presentation, despite opposition from Edward Condon, stands as a testament to Sagan's influence. In collaboration with physicist Thornton Page, Sagan edited the symposium's lectures and discussions, which were subsequently published in 1972 under the title UFO's: A Scientific Debate. Several of Sagan's numerous publications explored the subject of UFOs (a theme also addressed in an episode of Cosmos), and he posited a latent religious dimension to the phenomenon.

He articulated:

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 of Fermat’s Last Theorem.’ Or the Goldbach 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 remarked, "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 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.'"

Demise

After a two-year battle with myelodysplasia, during which he underwent three bone marrow transplants from his sister, Sagan succumbed to pneumonia at the age of 62 on December 20, 1996, at the Fred Hutchinson Cancer Research Center in Seattle. His interment took place at Lake View Cemetery in Ithaca, New York.

Legacy

Sagan is widely recognized for inspiring a generation of scientists and individuals engaged in science popularization. Notably, Simon Singh dedicated his work, Big Bang, to "Carl Sagan, James Burke, Magnus Pyke, Heinz Wolff, Patrick Moore, Johnny Ball, Rob Buckman, Miriam Stoppard, Raymond Baxter, and all the science TV producers and directors who inspired my interest in science."

The Sagan Teaching Awards, presented at the University of Chicago, are named in his honor.

Discover Magazine recognized The Cosmic Connection as one of the twenty-five most significant science books ever published.

In 2013, James H. Billington, the Librarian of Congress, participated with Ann Druyan in the inauguration of the Carl Sagan Archives. The event featured speakers such as Carolyn Porco, Bill Nye, and Kip Thorne. Subsequently, in 2014, Druyan and Seth MacFarlane co-produced Cosmos: A Spacetime Odyssey, which was hosted by Neil Degrasse Tyson.

He was awarded the Public Welfare Medal, the National Academy of Sciences' highest distinction, for his "distinguished contributions in the application of science to the public welfare." However, his application for membership in the academy was reportedly rejected due to the perception that his extensive media engagements had alienated numerous fellow scientists.

• Annual Award for Television Excellence (1981) from Ohio State University for the PBS series Cosmos: A Personal Voyage.
• Apollo Achievement Award from the National Aeronautics and Space Administration.
• NASA Distinguished Public Service Medal from the National Aeronautics and Space Administration (1977).
• Emmy Award for Outstanding Individual Achievement (1981) for the PBS series Cosmos: A Personal Voyage.
• Emmy Award for Outstanding Informational Series (1981) for the PBS series Cosmos: A Personal Voyage.
• Fellow of the American Physical Society (1989).
• Exceptional Scientific Achievement Medal from the National Aeronautics and Space Administration.
• Helen Caldicott Leadership Award, conferred by Women's Action for Nuclear Disarmament.
• Hugo Award for Best Dramatic Presentation (1981) for Cosmos: A Personal Voyage.
• Hugo Award for Best Related Non-Fiction Book (1981) for Cosmos.
• Hugo Award for Best Dramatic Presentation (1998) for Contact.
• Humanist of the Year (1981), presented by the American Humanist Association.
• Elected to membership in the American Philosophical Society (1995).
• In Praise of Reason Award (1987) from the Committee for Skeptical Inquiry.
• Isaac Asimov Award (1994) from the Committee for Skeptical Inquiry.
• John F. Kennedy Astronautics Award (1982) from the American Astronautical Society.
• Special Non-Fiction Campbell Memorial Award (1974) for The Cosmic Connection: An Extraterrestrial Perspective.
• Joseph Priestley Award, recognizing "distinguished contributions to the welfare of mankind."
• Klumpke-Roberts Award from the Astronomical Society of the Pacific (1974).
• Golden Plate Award from the American Academy of Achievement (1975).
• Konstantin Tsiolkovsky Medal, bestowed by the Soviet Cosmonauts Federation.
• Locus Award (1986) for Contact.
• Los Angeles Times Book Prize in the Science and Technology category (1996) for The Demon-Haunted World: Science as a Candle in the Dark.
• Lowell Thomas Award from The Explorers Club, commemorating its 75th Anniversary.
• Masursky Award from the American Astronomical Society.
• Miller Research Fellowship from the Miller Institute (1960–1962).
• Oersted Medal (1990) from the American Association of Physics Teachers.
• Peabody Award (1980) for the PBS series Cosmos: A Personal Voyage.
• Le Prix Galabert d'astronautique from the International Astronautical Federation (IAF).
• Public Welfare Medal (1994) from the National Academy of Sciences.
• Pulitzer Prize for General Nonfiction (1978) for The Dragons of Eden.
• Science Fiction Chronicle Award for Dramatic Presentation (1998) for Contact.
• UCLA Medal (1991).
• Inducted into the International Space Hall of Fame in 2004.
• On June 5, 2005, he was designated the "99th Greatest American" during the Greatest American television series broadcast on the Discovery Channel.
• He was conferred honorary membership in the Demosthenian Literary Society on November 10, 2011.
• In 2009, he was inducted into the New Jersey Hall of Fame.
• The Committee for Skeptical Inquiry (CSI) inducted him into its Pantheon of Skeptics in April 2011.
• On November 23, 1998, he received the Grand-Cross of the Order of Saint James of the Sword from Portugal.
• Whittier College awarded him an honorary Doctor of Science (Sc.D.) degree in 1978.
• He was presented with the 2012 Kate Wilhelm Solstice Award by the Science Fiction and Fantasy Writers Association.

Posthumous Recognition

Locations Honoring His Name

In 1993, Sky & Telescope organized a competition to propose alternative names for the Big Bang model. Submissions included "Hubble Bubble," "Bertha D. Universe," and "SAGAN" (an acronym for "Scientists Awestruck at God’s Awesome Nature"). However, the judging panel, which comprised Sagan, Timothy Ferris, and Hugh Downs, rejected all proposals.

The Sagan Planet Walk, a walking-scale representation of the Solar System, commenced operations in Ithaca, New York, in 1997. This exhibit spans 1.2 kilometers, connecting The Commons in downtown Ithaca to the Sciencenter, an interactive museum. The installation commemorates Sagan, who resided in Ithaca and served as a Cornell Professor, having also been a founding member of the museum's advisory board.

On July 5, 1997, the landing site of the uncrewed Mars Pathfinder spacecraft was officially redesignated as the Carl Sagan Memorial Station.

Asteroid 2709 Sagan bears his name, as does the Carl Sagan Institute, dedicated to the exploration of habitable planets.

On November 9, 2001, coinciding with what would have been Sagan's 67th birthday, the Ames Research Center formally dedicated the location for the Carl Sagan Center for the Study of Life in the Cosmos. NASA Administrator Daniel Goldin remarked, "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." Ann Druyan attended the center's official opening on October 22, 2006.

The Carl Sagan and Ann Druyan Theater was inaugurated at the Center for Inquiry West in Los Angeles on October 21, 2019.

His extensive collection of papers, totaling 595,000 items, is preserved within the archives of the Library of Congress.

Awards Bearing His Name

At least three distinct awards have been established in Sagan's honor:

• The Carl Sagan Memorial Award, jointly conferred since 1997 by the American Astronomical Society and The Planetary Society.
• The Carl Sagan Medal for Excellence in Public Communication in Planetary Science, awarded since 1998 by the American Astronomical Society's Division for Planetary Sciences (AAS/DPS) to recognize exceptional public communication by an active planetary scientist. Notably, Carl Sagan was among the initial organizing committee members of the DPS.
• The Carl Sagan Award for Public Understanding of Science, presented by the Council of Scientific Society Presidents (CSSP). Sagan himself was the inaugural recipient of this CSSP award in 1993.

Awards Conferred Upon Him

In August 2007, the Independent Investigations Group (IIG) posthumously bestowed a Lifetime Achievement Award upon Sagan. This esteemed recognition has also been granted to Harry Houdini and James Randi.

In 2022, Sagan posthumously received the Future of Life Award, acknowledging his contributions "for reducing the risk of nuclear war by developing and popularizing the science of nuclear winter." His widow, Ann Druyan, accepted this honor, which was shared among seven other individuals involved in nuclear winter research.

In Popular Culture

Robert Zemeckis's film Contact was adapted from Sagan's novel of the identical title. The production was finalized subsequent to his passing and concludes with the dedication "For Carl." A photograph of Sagan is also featured within the film.

The Beastie Boys honored Sagan in their album To the 5 Boroughs with the lyric: "I've got billions and billions of rhymes to flex / 'Cause I've got more rhymes than Carl Sagan's got turtlenecks."

Nick Sagan, Carl Sagan's son, contributed to the Star Trek franchise by writing multiple episodes. Within the Star Trek: Enterprise episode "Terra Prime," a brief visual features the decommissioned Sojourner rover, a component of the Mars Pathfinder mission, situated alongside a historical marker at the Carl Sagan Memorial Station on Mars. This marker bears a quotation from Sagan: "Whatever the reason you're on Mars, I'm glad you're there, and I wish I was with you." Furthermore, Steve Squyres, a former student of Sagan, headed the team responsible for the successful 2004 landing of the Spirit and Opportunity rovers on Mars.

In September 2008, composer Benn Jordan released Pale Blue Dot, a musical homage dedicated to Sagan's life.

Commencing in 2009, the musical initiative "Symphony of Science" incorporated various excerpts of Sagan's narration from his television series Cosmos, subsequently remixing them into electronic music. These videos have collectively garnered more than 21 million global views on YouTube.

The 2014 Swedish science fiction short film Wanderers features segments of Sagan's narration from his book Pale Blue Dot, which are overlaid onto computer-generated imagery depicting humanity's potential future expansion into space.

In February 2015, the Finnish symphonic metal band Nightwish launched the song "Sagan" as a non-album bonus track accompanying their single "Élan." This composition, penned by the band's songwriter, composer, and keyboardist Tuomas Holopainen, serves as a tribute to Sagan's life and professional contributions.

In February 2019, the progressive metal band Dream Theater dedicated their track "Pale Blue Dot" to Sagan. The song commences with an audio clip featuring Nick Sagan stating, "Hello from the children of planet Earth."

In 2019, Sasha Sagan, Carl Sagan's daughter, published For Small Creatures Such as We: Rituals for Finding Meaning in our Unlikely World, a work that chronicles her upbringing with her parents and the experience of her father's passing when she was fourteen. Expanding upon a central theme from her father's oeuvre, Sasha Sagan posits in For Small Creatures Such as We that skepticism is not synonymous with pessimism.

The Library of Congress recognized Cosmos as one of the "Books That Shaped America." Subsequently, in 2022, the audiobook rendition of Sagan's Pale Blue Dot was inducted into the National Recording Registry, acknowledged for its "culturally, historically, or aesthetically significant" value.

Sagan is prominently featured in Emer Reynolds's documentary The Farthest, which explores the Voyager program.

In 2023, the film Voyagers, directed by Sebastián Lelio, was announced, with Andrew Garfield cast as Sagan and Daisy Edgar-Jones portraying Sagan's third wife, Ann Druyan.

Sagan's recordings and archival video footage were extensively incorporated into two films scheduled for 2025 release: Elio and The Life of Chuck.

Druyan recounts an incident where a porter declined payment from Sagan for handling his luggage, stating, "You gave me the universe."

Publications

A list of peace activists

• List of peace activists
• Neil deGrasse Tyson

Explanatory Notes

References

Citations

Cited References

• Achenbach, Joel (1999). Captured by Aliens: The Search for Life and Truth in a Very Large Universe. New York: Simon & Schuster. ISBN 978-0-684-84856-3. LCCN 99037592. OCLC 41606346.Davidson, Keay (1999). Carl Sagan: A Life. New York: John Wiley & Sons. ISBN 978-0-471-25286-3. LCCN 99036206. OCLC 41580617.Morrison, David (2006). "Carl Sagan: The People's Astronomer." AmeriQuests. 3 (2). doi:10.15695/amqst.v3i2.84. ISSN 1553-4316.Head, Tom, ed. (2006). Conversations with Carl Sagan (1st ed.). Jackson, MS: University Press of Mississippi. ISBN 978-1-57806-736-7. LCCN 2005048747. OCLC 60375648.Poundstone, William (1999). Carl Sagan: A Life in the Cosmos. New York: Henry Holt and Company. ISBN 978-0-8050-5766-9. LCCN 99014615. OCLC 40979822.Spangenburg, Ray; Moser, Kit (2004). Carl Sagan: A Biography. Westport, CT: Greenwood Publishing Group. ISBN 978-0-313-32265-5. LCCN 2004015176. OCLC 55846272.Terzian, Yervant; Bilson, Elizabeth, eds. (1997). Carl Sagan's Universe. Cambridge; New York: Cambridge University Press. ISBN 978-0-521-57603-1. LCCN 96040511. OCLC 36130681.Terzian, Yervant, and Virginia Trimble. "Carl Sagan (1934–1996)." Bulletin of the AAS 29, no. 4 (January 1, 1997).The Seth MacFarlane Collection of the Carl Sagan and Ann Druyan Archive, spanning 1860–2004 with a bulk from 1962–1997, is housed at the Library of Congress.
  • The Seth MacFarlane collection of the Carl Sagan and Ann Druyan archive, 1860-2004 (bulk 1962-1997). The Library of Congress
  • The Carl Sagan Portal
  • Carl Sagan discography at Discogs
  • Morrison, David. "Carl Sagan." Biographical Memoirs of the National Academy of Sciences (2014).
  • David Morrison, "Carl Sagan", Biographical Memoirs of the National Academy of Sciences (2014)
  • Carl Sagan was featured in the BBC Radio program Great Lives on December 15, 2017.
  • Carl Sagan – Great Lives, BBC Radio, December 15, 2017
  • An interview with Carl Sagan, titled "A man whose time has come," conducted by Ian Ridpath, was published in New Scientist on July 4, 1974.
  • David Morrison authored the article "Carl Sagan's Life and Legacy as Scientist, Teacher, and Skeptic" for the Committee for Skeptical Inquiry.
  • In 1962, while at Stanford University, Carl Sagan authored a controversial paper, "Direct Contact Among Galactic Civilizations by Relativistic Interstellar Spaceflight," funded by a NASA research grant. This paper, identified as NASA Technical Reports Server (NTRS) 19630011050, posited that ancient alien intervention might have initiated human civilization.
  • Carl Sagan provided a demonstration illustrating Eratosthenes' method for determining the Earth's spherical shape and its approximate circumference.