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-wrote and narrated the 1980 documentary series Cosmos: A Personal Voyage, which has been seen by at least 500 million people in 60 countries and won two Emmy Awards and a Peabody Award. Cosmos, the companion volume, was the bestselling science book to date.
A lifelong science fiction fan, Sagan entered the genre with Contact, which was adapted as the film of the same name. He was a founding member and first president of the Planetary Society. He proposed the Pale Blue Dot photograph of Earth taken by Voyager 1.
He had a lifelong interest in the possibility of extraterrestrial life and is generally credited with contributions to the Arecibo message, with a much more significant role developing the Pioneer plaques and the Voyager Golden Record, universal messages that could potentially be understood by any intelligence that might find them. He promoted skepticism and the scientific method, particularly in his penultimate book The Demon-Haunted World. He popularized a toolkit for critical thinking. He made famous the maxim "Extraordinary claims require extraordinary evidence." The phrase "Billions and billions" was attributed to him, although he never said it; he did use it as the title of his last book. Sagan received numerous awards and honors, including the NASA Distinguished Public Service Medal and the National Academy of Sciences Public Welfare Medal. He married three times and had five children. After developing myelodysplasia, Sagan died of pneumonia at the age of 62 on December 20, 1996.
Carl Edward Sagan was born on November 9, 1934, in the Bensonhurst neighborhood of New York City's Brooklyn borough. 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 from Kamianets-Podilskyi (then in the Russian Empire). 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." Sagan's family lived in a modest apartment in Bensonhurst. He later described his family as Reform 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 the temple [...] and served only kosher meat." During the worst years of the Great Depression, his father worked as a movie theater usher.
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 during World War I and the 1920s, and whose later intellectual ambitions were sabotaged by her poverty, status as a woman and wife, and Jewish ethnicity. Davidson suggested she "worshipped her only son, Carl" because "he would fulfill her unfulfilled dreams." 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. 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."
He described a defining moment in his development, when his parents took him to the 1939 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 and cloverleaves and little General Motors cars all carrying people to skyscrapers, buildings with lovely spires, flying buttresses—and it looked great!" Another involved a flashlight shining on a photoelectric cell, which created a crackling sound, and another showed how the sound from a tuning fork became a wave on an oscilloscope. He saw an exhibit of the nascent medium of television. He later wrote: "Plainly, the world held wonders of a kind I had never guessed. How could a tone become a picture and light become a noise?" Sagan saw one of the fair's most publicized events: the burial at Flushing Meadows of a time 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.
During World 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 the Holocaust. Hitler was not a popular fellow in our household... but on the other hand, I was fairly insulated from the horrors of the war." His sister, Carol, said that their mother "above all wanted to protect Carl... she had an extraordinarily difficult time dealing with World War II and the Holocaust."
He wondered what the stars 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 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 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." At age six or seven, he and a close friend took trips to the American Museum of Natural History. They were impressed by the displays of dinosaur fossils and nature dioramas and by the Hayden Planetarium. Sagan's parents nurtured his growing interest in science, buying him chemistry sets and reading matter. Per biographer Ray Spangenburg, Sagan's desire 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." His fascination with outer space deepened after reading Edgar Rice Burroughs's John Carter of Mars books. In 1947, he discovered Astounding Science Fiction, which introduced him to more hard science fiction speculations: "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."
Sagan attended David A. Boody Junior High School, in his native Bensonhurst and had his bar mitzvah when he turned 13. In 1948, when he was 14, his father's work took the family to Rahway, New Jersey, where he attended Rahway High School. He was a straight-A student but was bored because his classes did not challenge him and his teachers did not inspire him. 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." 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 about molecules by making cardboard cutouts to help him visualize how they were formed: "I found that about as interesting as doing [chemical] experiments." 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."