1. Carl Sagan was a prolific author.

Carl Sagan papers on display in Washington, D.C.
In November 2013, a collection of Carl Sagan's papers were on display at the Library of Congress in Washington, D.C. | Paul Morigi/Getty Images

Though he frequently appeared on television, Sagan’s written works stand as his most influential contribution to the understanding of astronomy. While not a complete list, some of his more well-known titles include:

  • Other Worlds (1975), which explored the potential for life on other planets.
  • Cosmos (1980), an illustrated journey through the stars and human evolution.
  • Contact (1985), a novel about a scientist who journeys into space to communicate with alien life.
  • A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race (1990), written with Richard Turco, which details the authors’ attempts to warn domestic and foreign leaders of the horrors of nuclear war.
  • Pale Blue Dot: A Vision of the Human Future in Space (1994), a sequel to Cosmos that further explores the role of humans in space.
  • The Demon-Haunted World: Science as a Candle in the Dark (1996), which imparts lessons in skeptical thinking.

2. Carl Sagan created Cosmos because he wanted to make space exploration popular again.

Carl Sagan in a photo with a replica of the Viking lander.
Carl Sagan posing with a model of the Viking lander in Death Valley, California. | JPL, Wikimedia Commons // Public Domain

Carl Sagan attended the University of Chicago, graduating with a bachelor’s and later a master’s degree in physics, and was eventually named director of Cornell’s Laboratory for Planetary Studies in 1968. As a NASA consultant, Sagan was consistently amazed by the work of the space agency and puzzled why the general public didn’t feel the same. When he worked with NASA in 1976 on the Viking Lander Imaging Team project that would gather information from Mars, he decided to combat the lack of media attention with a television series, Cosmos: A Personal Voyage, and a companion book that explored space and human civilization. Both debuted in 1980. The series ran for 13 episodes and helped make Sagan the most famous name and face in the field of science, though it didn’t stick with its original title, Man and the Cosmos. That, Sagan thought, sounded too sexist.

3. Carl Sagan wanted Contact to be an early video game.

Actress Jodie Foster in the movie 'Contact.'
Jodie Foster starred in the movie adaptation of Carl Sagan's book 'Contact' in 1997. | Getty Images

Published in 1985, Contact was Sagan’s departure from science non-fiction. In the novel, astrophysicist Eleanor Arroway discovers a line of communication with extraterrestrial life. The book was later turned into the 1997 feature film of the same name starring Jodie Foster. But if Sagan had his way, there would have been more to the story than just the book. While writing Contact in 1983, Sagan had the idea to turn the premise into a video game, where the player would control an alien coming to Earth with a peaceful message, traveling through the galaxy along the way. The game would also allow players to control a human of the future seeking a new civilization. There wouldn’t have been any battle scenarios, as Sagan wanted to promote a nonviolent game. Sagan had so many ideas for the game that he wondered if it could be split into two titles, but despite his detailed vision, it never materialized.

4. Carl Sagan’s famous “Pale Blue Dot” speech almost never happened.

NASA's Pale Blue Dot photo from 1990.
The famous "Pale Blue Dot" photo taken from Voyager 1, where Earth appears as nothing but a speck against a backdrop of the vastness of space. | NASA, Wikimedia Commons // Public Domain

In 1990, Sagan drew attention to a photograph taken by NASA’s Voyager 1 spacecraft just before it left our solar system to explore interstellar space. In the photo, Earth is seen as a tiny spot in the vast black expanse of the universe. The striking image communicated Earth’s relatively inconsequential physical presence in space, an idea affirmed by Sagan calling it the “pale blue dot.” But the photo was never guaranteed. When Voyager 1 launched in 1977, Sagan implored NASA to take a photo of Earth. Fearing the sun would burn up the camera and compromise its mission to pass Jupiter and Saturn, officials put it off until much later in the mission—Valentine’s Day 1990.

Sagan later wrote a book, 1994’s Pale Blue Dot: A Vision of the Human Future in Space, based on thoughts he had after viewing the photo. He wrote of the seemingly innocuous speck: "Look again at that dot. That’s here. That’s home. That’s us."

5. Carl Sagan's book The Demon-Haunted World debunked alien abductions.

Carl Sagan and his wife, Ann Druyan.
Carl Sagan was married to author and 'Cosmos' co-writer Ann Druyan from 1981 until his death in 1996. | Mickey Adair/Getty Images

Sagan had long held an interest in discussing aliens and UFOs, but by the time he wrote 1996's The Demon-Haunted World: Science as a Candle in the Dark, he felt the time was right to demystify the idea of alien abductions. Denouncing these claims as odd due to the fact most aliens were described as being slightly human in form, Sagan pointed out that a mass plan to abduct people is far less likely than some abductees succumbing to psychological distress and imagining a scenario that never happened.

6. Carl Sagan’s wife helped create the “golden record” for aliens.

NASA's gold record case for Voyager 1 and 2.
The aluminum case for the gold record sent out on Voyager 1 and 2, which Carl Sagan contributed to. | NASA on the Commons, Flickr // No Known Restrictions

Despite Sagan’s doubt over extraterrestrial abductions, he remained open to the possibility of other life in the galaxy. To that end, Sagan and NASA employee Ann Druyan helped compile a “golden record” of audio on a copper phonograph record that went on board the Voyager spacecrafts in 1977. The sounds, which included two people kissing, a mother speaking her first words to her child, music, and greetings in 59 different languages, were intended to be samples for any alien race that might find them. The project also allowed Sagan and Druyan to spend time together. Two days after Voyager 2 launched on August 20, 1977, the two announced their engagement. They remained married until Sagan’s death in 1996.

7. Carl Sagan never actually said his famous “billions and billions” quote.

A photo of Carl Sagan and the other members of The Planetary Society.
Carl Sagan, Bruce Murray (seated), Louis Friedman (standing, left), and Harry Ashmore (standing, right) formed The Planetary Society in 1980. | NASA JPL, Wikimedia Commons // Public Domain

One of Sagan’s most oft-quoted phrases in reference to the number of stars or galaxies in the universe, “billions and billions,” was something the scientist didn’t ever actually say. Sagan protested this attribution in a letter to television host Johnny Carson, who had Sagan on a guest several times and sometimes did an impression of Sagan using the phrase. Carson wrote back: “Even if you didn’t say ‘billions and billions’ you should have—Johnny.” But Sagan did say “billions,” frequently, on Cosmos. He also titled his last book Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium, published in 1997, in a nod to the misattribution.

Famous Carl Sagan quotes.

  • “The surface of the Earth is the shore of the cosmic ocean. From it we have learned most of what we know. Recently, we have waded a little out to sea, enough to dampen our toes or, at most, wet our ankles. The water seems inviting.”
  • “For small creatures such as we, the vastness is bearable only through love.”
  • “Imagination will often carry us to worlds that never were. But without it, we go nowhere.”
  • “The universe is a pretty big place. If it’s just us, seems like an awful waste of space.”
  • "If you wish to make an apple pie from scratch, you must first invent the universe."