On November 9, the world will mark Carl Sagan's 90th birthday. Sagan died in 1996 at the age of 62. Most people remember Sagan as the co-creator and host of the 1980 "Cosmos" television series, which was watched worldwide by hundreds of millions of people. Others remember him for his best-selling science fiction novel "Contact" or his Pulitzer Prize-winning nonfiction book "The Dragons of Eden." Millions more saw Carl Sagan popularize astronomy on "The Tonight Show."
Sagan was an unequaled science communicator, astute advocate, prolific writer, and outstanding scientist. What most people don't know about Carl Sagan, and what has been somewhat obscured by his fame, is the far-reaching impact of his science, which resonates to this day. He propelled science forward in at least three important ways: he produced notable results and insights described in over 600 scientific papers, he enabled new scientific disciplines to flourish, and he inspired multiple generations of scientists.
Jean-Luc Margot, a planetary astronomer, believes such a combination of talents and accomplishments is rare and may occur only once in a lifetime. In the 1960s, very little was known about Venus. Carl Sagan investigated how the greenhouse effect in Venus's carbon dioxide atmosphere might explain the unbearably high temperature on Venus, approximately 870 degrees Fahrenheit (465 degrees Celsius). His research on Venus remains a cautionary tale about the dangers of fossil fuel emissions on Earth.
Carl Sagan proposed a compelling explanation for seasonal changes in the brightness of Mars, which had been incorrectly attributed to vegetation or volcanic activity. He explained that wind-blown dust was responsible for the mysterious variations in Mars's brightness. With unusual breadth in astronomy, physics, chemistry, and biology, Carl Sagan pushed forward the nascent discipline of astrobiology—the study of life in the universe.
Together with research scientist Bishun Khare at Cornell University, Carl Sagan conducted pioneering laboratory experiments. They showed that certain ingredients of prebiotic chemistry, called tholins, and certain building blocks of life, known as amino acids, form naturally in laboratory environments that mimic planetary settings. Carl Sagan modeled the delivery of prebiotic molecules to early Earth by asteroids and comets. He was deeply engaged in the biological experiments onboard the Mars Viking landers and speculated about the possibility of balloon-shaped organisms floating in the atmospheres of Venus and Jupiter.
His passion for finding life elsewhere extended far beyond the solar system. Carl Sagan was a champion of the search for extraterrestrial intelligence, also known as SETI. He helped fund and participated in a systematic search for extraterrestrial radio beacons by scanning 70% of the sky with physicist and electrical engineer Paul Horowitz. Carl Sagan proposed and co-designed the plaques and the "Golden Records" now affixed to humanity's most distant ambassadors, the Pioneer and Voyager spacecraft. It is unlikely that extraterrestrials will ever find these artifacts, but Carl Sagan wanted people to contemplate the possibility of communication with other civilizations.
Carl Sagan's scientific output repeatedly led him to become an eloquent advocate on issues of societal and scientific significance. He testified before Congress about the dangers of climate change. Carl Sagan was an antinuclear activist and spoke out against the Strategic Defense Initiative, also known as "Star Wars." He urged collaborations and a joint space mission with the Soviet Union in an attempt to improve U.S.-Soviet relations. He spoke directly with members of Congress about the search for extraterrestrial intelligence and organized a petition signed by dozens of prominent scientists urging support for the search for extraterrestrial intelligence.
His most important gift to society was his promotion of truth-seeking and critical thinking. Carl Sagan encouraged people to muster the humility and discipline to confront their most cherished beliefs and to rely on evidence to obtain a more accurate view of the world. His most cited book, "The Demon-Haunted World: Science as a Candle in the Dark," is a precious resource for anyone trying to navigate this age of disinformation.
A scientist's impact can sometimes be gauged by the number of times their scholarly work is cited by other scientists. According to Carl Sagan's Google Scholar page, his work continues to accumulate more than 1,000 citations per year. His current citation rate exceeds that of many members of the National Academy of Sciences, who are "elected by their peers for outstanding contributions to research," according to the academy's website, and being elected is "one of the highest honors a scientist can receive."
Carl Sagan was nominated for election into the National Academy of Sciences during the 1991-1992 cycle, but his nomination was challenged at the annual meeting. More than one-third of the members voted to keep Carl Sagan out, which doomed his admission. An observer at that meeting wrote to Carl Sagan, "It is the worst of human frailties that keeps you out: jealousy," according to The Conversation. This belief was affirmed by others in attendance. In Jean-Luc Margot's opinion, the National Academy of Sciences' failure to admit Carl Sagan remains an enduring stain on the organization.
No amount of jealousy can diminish Carl Sagan's profound and wide-ranging legacy. In addition to his scientific accomplishments, he has inspired generations of scientists and brought an appreciation of science to countless nonscientists. Carl Sagan has demonstrated what is possible in the realms of science, communication, and advocacy. Those accomplishments required truth-seeking, hard work, and self-improvement. On the 90th anniversary of Carl Sagan's birth, a renewed commitment to these values would honor his memory.
Sources: The Conversation, Mirage News, morningagclips.com, Phys.org
This article was written in collaboration with generative AI company Alchemiq