12 Fascinating Facts About Carl Sagan

Carl Sagan was arguably one of America's most beloved scientific visionaries since Albert Einstein. A brilliant astronomy researcher and a gifted communicator, he made the mysteries of the cosmos accessible to the public through his famous TV series Cosmos and works like the Pulitzer Prize–winning Dragons of Eden and Pale Blue Dot. His only novel, Contact, was later adapted into a sci-fi film starring Jodie Foster and Matthew McConaughey. Here are some lesser-known facts about the scientist, TV personality, and amateur turtleneck enthusiast.

1. Harvard turned down Carl Sagan.

After spending five years as an assistant professor at the prestigious university, Harvard refused to grant him tenure in 1967, partly because one of his mentors from the University of Chicago criticized his work as overly verbose and unnecessary. He then accepted a position at Cornell, where he continued to serve as a professor until his passing in 1996.

2. Carl Sagan recorded all his writing using an audio recorder.

Sagan was a passionate self-editor. There are 20 drafts of his 1994 book Pale Blue Dot housed at the Library of Congress, each brimming with handwritten edits, annotations, and revisions by the author. However, he created all his writings—even grant proposals—by dictating his ideas onto a cassette recorder. These tapes were transcribed for him, and the transcriptions were returned for further editing.

3. Carl Sagan once considered writing a children's book titled How Do Birds Fly?

In 1993, Sagan came up with an extensive list of potential children's books for a series based on the theme of 'why?'. Other ideas included Why Is It Warm In Summer?, Why Are There Lakes?, and What Is Air?

4. Carl Sagan was critical of the Space Shuttle program.

Sagan opposed the funding of NASA's Space Shuttle program, advocating instead for more robotic exploration of deep space. 'That’s not space exploration,' he remarked in an interview about the shuttle’s week-long orbits. 'Space exploration is going to other worlds.' He also stated that a space station would only be worthwhile if it were intended to prepare humans for extended space journeys, as he told Charlie Rose in 1995.

5. Carl Sagan was one of the earliest advocates against climate change.

Sagan’s 1960 Ph.D. thesis focused on the atmosphere of Venus. His theoretical model demonstrated that the planet’s extreme surface temperatures were caused by the greenhouse effect of an atmosphere rich in carbon dioxide and water vapor. In his book Cosmos, he wrote, 'The surface environment of Venus is a warning: something disastrous can happen to a planet rather like our own.'

6. Carl Sagan has an archive at the Library of Congress, funded by the creator of Family Guy.

Family Guy creator Seth McFarlane contributed an undisclosed amount to assist the Library of Congress in acquiring more than a thousand boxes of materials preserved by the late scientist and his partner, Ann Druyan. The papers in The Seth MacFarlane Collection of Carl Sagan and Ann Druyan Archive, which opened in 2013, include some of Sagan’s earliest notebooks and report cards.

7. Carl Sagan became famous for a catchphrase he never actually used.

After appearing on the Tonight Show Starring Johnny Carson multiple times, Carson decided to parody the scientist’s iconic style (including his turtleneck) in a comedy sketch.

Carson’s over-the-top use of “billions and billions” would later be wrongly attributed to the astronomer, even though he never actually said it. However, Sagan did frequently discuss large numbers, as shown in this supercut.

8. Carl Sagan and Ann Druyan’s relationship began with a single phone call—and they were engaged before hanging up.

Sagan and Druyan, who would later co-create the TV show Cosmos, developed a romantic connection while working together on the Voyager message. Their brief courtship is vividly described by NPR's Radiolab:

“After tirelessly seeking the perfect piece of Chinese music for the record, Druyan discovered a 2500-year-old song titled ‘Flowing Stream.’ Thrilled, she immediately called Sagan, leaving a message at his hotel. At that point, they were nothing more than professional acquaintances and friends. However, when Sagan returned her call an hour later, something changed. By the end of the call, they were engaged to be married.”

9. Carl Sagan was an advocate for the legalization of marijuana.

Writing under the pseudonym “Mr. X,” Sagan authored a 1969 essay for Time magazine, detailing his personal experiences with cannabis use. At the time, in his mid-30s, he admitted to having smoked throughout the preceding decade. “I find that today a single joint is enough to get me high,” he confessed, adding that marijuana had helped him appreciate art and music more deeply. He concluded, “The illegality of cannabis is outrageous, an impediment to full utilization of a drug which helps produce the serenity and insight, sensitivity and fellowship so desperately needed in this increasingly mad and dangerous world.”

10. Carl Sagan believed that Star Trek lacked racial diversity.

In a future global society, centuries from now, the crew members of interstellar ships are predominantly Anglo-American, which Sagan found quite embarrassing. He noted that only two out of 12 or 14 interstellar vessels were given non-English names, Kongo and Potemkin,” in a 1978 article for The New York Times.

11. Carl Sagan believed we should leave Mars undisturbed.

Despite his enthusiasm for space exploration, Sagan advocated for the conservation of Mars, even if it meant restricting our exploration of the planet. In the series Cosmos, he famously stated:

“If life exists on Mars, I believe we should leave it untouched. Mars belongs to the Martians, even if they are only microbes. The existence of life on a neighboring planet is an invaluable treasure, and preserving that life should take precedence over any other potential use of Mars.”

12. Carl Sagan had a vision for a Contact video game.

In the initial stages of developing what would eventually become Contact, Carl Sagan envisioned the story as a perfect fit for a video game. However, it wasn’t meant to be an action-packed adventure. Instead, players would guide an alien tasked with delivering a message of peace to Earth, while navigating various challenges. The game would also include parts where players would control a human character, with Sagan even contemplating whether this could be turned into multiple games. Sadly, none of these ideas came to life.

This article was first published in 2017; it has been revised and updated for 2021.