Called "America's most effective salesman of science" by Time magazine, astronomer Carl Sagan spent much of his career translating technical scientific explanations to make them easily digestible by the general public. Described as a natural teacher, he educated not only through classroom lectures but also through interviews and on television shows. His 13-part TV series, “Cosmos,” has been seen by over 600 million people in more than 60 countries. The show was so popular it returned to television in 2005. [See also our overview of Famous Astronomers and great scientists from many fields who have worked in astronomy.]

Carl Sagan at the Very Large Array in New Mexico.
Carl Sagan at the Very Large Array in New Mexico.
Credit: Cosmos/Discovery

Life on the Pale Blue Dot

Carl Edward Sagan was born Nov. 9, 1934 in Brooklyn, New York. He attended college at the University of Chicago, where he attained a Ph.D. in astronomy and astrophysics. After doing his postdoctoral work, he taught at Harvard. When he wasn't granted tenure, he moved on to Cornell University in New York, serving as the director for the Laboratory for Planetary Studies and the Associate Director of the Center for Radio Physics and Space Research.

He was married three times, and had a total of five children.

Diagnosed with the rare bone marrow disease myelodysplasia, Sagan underwent three bone marrow transplants over the course of his life. Complications from the disease resulted in  his contracting pneumonia, which led to his death on Dec. 20, 1996. He was 62 years old.

Making science interesting

Although Sagan was most widely known for his scientific communication with the general public, he made many significant contributions to the field of science directly.

While Sagan attended graduate school, the planet Venus was often considered to be similar to Earth. As part of his thesis, Sagan computed the first greenhouse model for Venus' atmosphere, which revealed a higher temperature than previously suspected. He suggested that the seasonal changes observed on Mars was caused by dust storms on the planet, and wrote a series of papers on the organic chemistry of Jupiter's atmosphere.

Serving as an advisor to NASA, Sagan helped to design and manage the Mariner 2 mission to Venus, the Mariner 9 and Viking trips to Mars, the Voyager system to the outer solar system, and the Galileo mission to Jupiter. He also helped to brief astronauts prior to their trips to the moon.

But Sagan was far more visible as a scientific educator than he was as a researcher. He was gifted at breaking down scientific concepts into explanations that the public could readily understand, without seeming to talk down to them. He authored hundreds of popular articles and more than two dozen books, frequently appeared in Time magazine — landing the cover on at least one occasion. And was a guest on The Tonight Show with Johnny Carson 26 times, calling it "the biggest classroom in history." His 13-hour miniseries, Cosmos, was loved by countless children and adults, and his nonfiction and fiction books were widely read.

Sagan helped lay the groundwork for two new scientific disciplines in the course of his lifetime: planetary science and exobiology. He was the first president and one of the founders of The Planetary Society, an organization  dedicated to inspiring and involving the public in space exploration. He promoted the Search for Extraterrestrial Intelligence (SETI), where he served as a trustee.

Describing him in October of 1980, Time magazine wrote, "Sagan sends out an exuberant message: science is not only vital for humanity's future well being, but it is rousing good fun as well."

Sagan’s books and TV episodes

In 1977, Sagan began work on the television series “Cosmos: A Personal Voyage,” serving as writer and presenter. The show aired on the Public Broadcasting Service in October of 1980 and was the most widely watched series on American public television for nearly a decade. The show won an Emmy and a Peabody award and was broadcast around the world. The accompanying book of the same name was on the New York Times best seller list for 70 weeks, and was the best-selling science book ever published in the English language.

This narrow-angle color image of the Earth s a part of the first ever "portrait" of the solar system taken by Voyager 1. The spacecraft acquired a total of 60 frames for a mosaic of the solar system from a distance of more than 4 billion miles from Earth and about 32 degrees above the ecliptic. Image released Feb. 14, 1990.
This narrow-angle color image of the Earth s a part of the first ever "portrait" of the solar system taken by Voyager 1. The spacecraft acquired a total of 60 frames for a mosaic of the solar system from a distance of more than 4 billion miles from Earth and about 32 degrees above the ecliptic. Image released Feb. 14, 1990.
Credit: NASA/JPL

At Sagan’s request, NASA commanded its Voyager 1 spacecraft to turn its camera on Earth, creating an image that came to be known as the Pale Blue Dot, one of the most famous pictures of Earth from space ever taken. Sagan used that name as the title of a book. The sequel to “Cosmos,” “The Pale Blue Dot,” toured the solar system and the galaxy, arguing for the necessity of planetary science and the exploration of Earth's closest neighbors. It, too, was widely and well received by the general public.

An earlier nonfiction book by Sagan, “The Dragons of Eden: Speculations on the Evolution of Human Intelligence,” focused on the evolution of human intelligence. It received the 1978 Pulitzer Prize.

Although the majority of Sagan's work was nonfiction, he also used fiction to present scientific principles when he published the fiction novel “Contact” in 1985. Based on interactions between the human race and an advanced species of extraterrestrials, the novel sold over a million copies in its first two years of publication. In 1997, it was released as a movie starring Jodi Foster.

Carl Sagan quotes

Advances in medicine and agriculture have saved vastly more lives than have been lost in all the wars in history.
The Demon-Haunted World: Science as a Candle in the Dark (1997), 11.

At the heart of science is an essential balance between two seemingly contradictory   attitudes—an openness to new ideas, no matter how bizarre or counterintuitive they may be, and the most ruthless skeptical scrutiny of all ideas, old and new. This is how deep truths are winnowed from deep nonsense.
The Demon-Haunted World: Science as a Candle in the Dark (1997), 304.

Every kid starts out as a natural-born scientist, and then we beat it out of them. A few trickle through the system with their wonder and enthusiasm for science intact.
Psychology Today (Jan 1996).

For myself, I like a universe that, includes much that is unknown and, at the same time, much that is knowable. A universe in which everything is known would be static and dull, as boring as the heaven of some weak-minded theologians. A universe that is unknowable is no fit place for a thinking being. The ideal universe for us is one very much like the universe we inhabit. And I would guess that this is not really much of a coincidence.
—'Can We know the Universe?' in M. Gardner (ed.), The Sacred Beetle and Other Great Essays in Science (1985), 109.

In a lot of scientists, the ratio of wonder to skepticism declines in time. That may be connected with the fact that in some fields—mathematics, physics, some others—the great discoveries are almost entirely made by youngsters.
Psychology Today (Jan 1996).

It is sometimes said that scientists are unromantic, that their passion to figure out robs the world of beauty and mystery. But is it not stirring to understand how the world actually works—that white light is made of colors, that color is the way we perceive the wavelengths of light, that transparent air reflects light, that in so doing it discriminates among the waves, and that the sky is blue for the same reason that the sunset is red? It does no harm to the romance of the sunset to know a little bit about it.
Pale Blue Dot: A Vision of the Human Future in Space (1994), 159

It is the responsibility of scientists never to suppress knowledge, no matter how awkward that knowledge is, no matter how it may bother those in power; we are not smart enough to decide which pieces of knowledge are permissible, and which are not. …
—Lily Splane, Quantum Consciousness (2004), 80.

It is the tension between creativity and skepticism that has produced the stunning and unexpected findings of science.
Broca's Brain: Reflections on the Romance of Science (1974, 1986), 73.

Our passion for learning ... is our tool for survival.
Cosmos (1980, 1985), 230-231

The cure for a fallacious argument is a better argument, not the suppression of ideas.
The Demon Haunted World: Science as a Candle in the Dark (1997), 429

The fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright brothers. But they also laughed at Bozo the clown.
— Carl Sagan, In Broca's Brain: Reflections on the Romance of Science (1980), 34.

— Nola Taylor Redd

More information: