Carl Sagan and space exploration: The effects of popularising science

Photograph of Carl Sagan with a model of the Viking lander.

Image credit: NASA/Public domain.

First published on 6th April 2016. Last updated on 5th June 2017 by Dr Helen Klus

In the 1960s, science journalism in the United States was sparse and mostly performed by journalists with little or no scientific background[1]. Science was perceived as minimising the need for pseudoscience, but it didn't fill the spiritual void this left in people. Eugenics and nuclear warfare had shown how scientific progress can lead to destruction, and science did not seem to offer hope for humanity.

These problems were challenged by American astronomer Carl Sagan. Sagan tried to present the universe as such a beautiful and exciting place that people would not need pseudoscience in order to believe in something extraordinary.

Sagan began writing to scientific journals in his late teens, and his suggestion that organisms could exist on Mars was mentioned in an article in the New York Times in 1956, while he was still an undergraduate at the University of Chicago[2][3a].

Sagan later organised a lecture series on campus that, decades later, he compared to the television series Cosmos[3b]. Sagan presented the planets as physical places to be explored rather than points of light in the sky, and talked of going to new places in the spirit of adventure, discovering new lands and perhaps even new wildlife[3c].

This idea was reflected in the logo for The Planetary Society, which Sagan formed with fellow American physicists Bruce Murray and Louis Friedman in 1980[4].

Photograph of the night sky. A diagram of the planets is overlaid with a sailboat leaving the 3rd planet, Earth.

Image credit: NASA/Jon Lomberg/Public domain.

Sagan completed his PhD at the University of Chicago in 1960. He then became a Fellow at the University of California, Berkeley.

While at Berkeley, Sagan involved himself in three experiments that would later influence his most powerful arguments for planetary exploration. These were: NASA's the Stratoscope balloon project, and origin of life experiments, both conducted in 1960, and the Mariner 2 space probe to Venus, which launched in 1962. During his time on these projects, Sagan wrote scientific articles, gave speeches, and began to be quoted by the media[3d].

Sagan's first success with a mainstream scientific journal came with The Planet Venus, published in Science in 1961[5]. That same year, Sagan's greenhouse model of Venus, along with the suggestion of 'terraforming' it, a term he borrowed from Jack Williamson's science fiction of the 1940's, made it into the New York Times and Newsweek[3e].

Sagan's views earned him a place at the 1961 Green Bank convention, which became known as the first SETI (Search for Extra Terrestrial Intelligence) meeting[6].

In 1962, Sagan began working for the Smithsonian Astrophysical Observatory in Massachusetts.

Sagan became involved in the civil rights movement in the 1960s, travelling to Alabama for a march in 1963, and lecturing at Alabama's all-black Tuskegee Institute in 1965[3f].

Sagan spoke out against the Vietnam War[7a] and nuclear warfare[8], and by the mid-1960s, he no longer wanted to be associated with the military in any capacity. This led him to resign from the US Air Force Scientific Advisory Board Geophysics Panel in 1966[7b].

Sagan also smoked marijuana "nearly every day", and opposed pseudoscience when it came to the 'war on drugs'[9].

Sagan's approach allowed his message to be spread to a vast number of people who may have had every reason to believe that in the USA, science was only accessible to patriotic, white men.

In 1965, when Mariner 4 sent back photos showing the 'dead' surface of Mars, Sagan fought to keep interest alive by further involving himself with the media. In an article for Icarus[10], Sagan juxtaposed the images of Mars with photographs showing the Earth from the same distance, making it clear that evidence of life might not be observed. Sagan latter discussed this with Rolling Stone magazine[11].

Sagan had a direct effect on NASA's expenditure by bringing publicity, and therefore funding, to the projects he was interested in. By 1965, Sagan held a $198,000 NASA grant to study the 'biochemical actuaries of terrestrial microorganisms in simulated planetary environments' and a $134,684 two year grant to study exobiology[3g].

In his first 'mainstream' book, Planets, which was first published in 1966, Sagan toured the Solar System, explaining the reasons for visiting each planet and citing Russian astronomer Iosif Shklovsky's suggestion that there could be "libraries and museums" on Mars' moon Phobos[12].

Photograph of Carl Sagan in front of a backdrop showing numerous planets. Sagan appears to be sitting on the planet Earth.

Image credit: NASA/Cosmos Studies/Public domain.

In 1968, Sagan became editor of Icarus. Sagan embraced the philosophy of Austrian-British philosopher Karl Popper, who stated that science can be distinguished from pseudoscience by the fact that science makes unique predictions that can be proven false. Icarus became a medium for scientists to present controversial and speculative hypothesis, and this allowed Sagan to show a more speculative side of space exploration[3h].

That same year, Sagan helped found the American Astronomical Society's Division for Planetary Sciences, whose membership increased from 100 shortly after he joined, to 1400 at the time of his death[13a].

Media coverage of NASA plunged in 1972, after the Apollo missions ended with evidence for life on the Moon looking more and more unlikely. Sagan aimed to change this by selling science in the same way that the media sells products. These intentions came into effect when publisher Jerome Agel suggested Sagan write a book on the cosmos. After seventeen rejections, this was published in 1973 as The Cosmic Connection: An Extraterrestrial Perspective. Sagan dictated the book, often while high[3i], and it was full of inspirational metaphors and imagery:

“There is a place with four suns in the sky - red, white, blue, and yellow;
two of them are so close together that they touch, and star-stuff flows between them.
I know of a world with a million moons.
I know of a sun the size of the Earth - and made of diamond.
There are atomic nuclei a few miles across which rotate thirty times a second.
There are tiny grains between the stars, with the size and atomic composition of bacteria.
There are stars leaving the Milky Way. There are immense gas clouds falling into the Milky Way.
There are turbulent plasmas writhing with X - and gamma - rays and mighty stellar explosions.
There are, perhaps, places outside of our universe”[14].

The Cosmic Connection contains three chapters on the necessity and benefits of planetary exploration, and was championed by Sky and Telescope, Time magazine, and Patrick Moore, among others[3j]. New Scientist proclaimed:

"if aliens come tomorrow, and ask for our leader, we shall take them to this man"[15].

Sagan made a number of television appearances to promote the already very successful book, including an appearance on Johnny Carson's The Tonight Show. He went on to become the show's 'house astronomer' and hence became one of the most famous American scientists of the time.

This upset many more-distinguished scientists. Sagan was accused of simplifying science to bias his personal claims, which were then presented as representing the views of the entire establishment. Other astronomers, such as Robert Jastrow, had previously appeared on the Tonight Show without such success and there may have been a touch of resentment that the voice of popular science was not that of the most accomplished scientist. Sagan's popularity led him to a $50,000 advance for a new book: Other Worlds[3k].

When NASA was refused funding for a crewed mission to Mars, due to inflation caused by the Vietnam War, Sagan suggested launching robotic probes to land on the surface instead, and made it his crusade to win over the public. Carson helped endorse the view, and the success of this project led to an article in TV Guide, a less prestigious magazine than scientists were used to, but one with 10 million readers. Shortly after this, Sagan was profiled by Rolling Stone magazine[3l].

Sagan's influence meant that the Viking missions went ahead and contained cameras capable of spotting moving objects. Sagan made what were seen as outrageous claims about the possibility of "polar bear-sized" animals on the surface. This kind of talk ignited the imagination of the public, but scientists worried he was setting them up for a fall and feared the backlash[3m]. The first view of the Martian sky came from Viking 1 in 1976. There was no sign of life.

In 1977, Sagan became involved with composing data to be sent out of the Solar System with the Voyager probes, having previously helped design the Pioneer plaque, along with Frank Drake and Linda Salzman Sagan.

The 13-part television series Cosmos aired in 1980. Cosmos was written by Sagan, Ann Druyan, and Steven Soter. It was preceded by a large media campaign and within a few weeks, Sagan appeared on the cover of Time magazine as "The Showman of Science"[16].

Cosmos received mixed reviews and the kind of fame that led to spoofs and impersonations. The show won a number of awards and the accompanying book became a New York Times best seller for over 70 weeks. It also received critical acclaim from journals and magazines such as Sky and Telescope[17].

Credit: via Ilen hans.

Credit: via 24fpsfan.

By 1980, the SETI program was severely underfunded, and so Sagan, Murray, and Friedman founded The Planetary Society in order to fund it privately. The Society was opened by Steven Spielberg in 1981 and allowed the public to become actively involved in lobbying congress for funding[18a]. That same year, Sagan received a $2 million advance to write the science fiction novel Contact[19]. The book was, among other things, an assault on critics of the SETI program.

Photograph of Louis Friedman, Harry Ashmore, Bruce Murray, and Carl Sagan.

Louis Friedman (standing, left), Harry Ashmore (standing, right), Bruce Murray (seated left), and Carl Sagan (seated right). Friedman, Murray, and Sagan are the founders of The Planetary Society, and Ashmore, a Pulitzer Prize winning journalist, was an advisor. Image credit: NASA JPL/Public domain.

Sagan also fought for the inclusion of women in science. Sagan was a member of The Explorers Club, and in 1981, when IBM stopped supporting the club due to their policy of excluding women, Sagan wrote an impassioned letter to every other member[20].

Sagan also criticised the government of the United States for its laws on abortion and its lack of socialised medicine. In his final book, Billions & Billions: Thoughts on Life and Death at the Brink of the Millennium, Sagan and Druyan stated that "[l]egislative prohibitions on abortion arouse the suspicion that their real intent is to control the independence and sexuality of women"[21].

Credit: via Reddy Greens.

Sagan's vision inspired many planetary scientists including David Goldin, the administrator of NASA from 1992 until 2001. Goldin regularly consulted Sagan for advice, he witnessed the Mars Pathfinder land and proposed interstellar probes, an idea taken from Sagan's book Pale Blue Dot[13b].

Sagan also produced a generation of successful explorers in his students. David Morrison went on to become a Senior Scientist at the NASA Ames Research Centre in California[22]. Steven Squyres headed the NASA team behind Mars' Spirit and Opportunity Rovers[23], and Christopher Chyba chaired the cancelled Europa Orbiter mission, which he proposed in 1998 as a continuum of Sagan's legacy[13c]. The current president of the National Academy of Sciences, Ralph Cicerone, continues to promote space exploration in Sagan's memory[24][25].

After his death in 1996, Nature described Sagan as:

"the greatest populariser of the 20th century"[18b].


  1. Fleischman, J. and Szalinski, C., 2014, 'So you want to be a science writer', Molecular biology of the cell, 25, pp.1938-1941.

  2. New York Times, December 29th 1956, pp.6.

  3. (a, b, c, d, e, f, g, h, i, j, k, l, m) Davidson, K. and Sagan, C., 1999, 'Carl Sagan: a life', Wiley.

  4. The Planetary Society, 'Our Founders', last accessed 01-06-17.

  5. Sagan, C., 1961, 'The Planet Venus: Recent observations shed light on the atmosphere, surface, and possible biology of the nearest planet', Science, 133, pp.849-858.

  6. Schilling, G. and MacRobert, A.M., 1998, 'The Chance of Finding Aliens', Sky and Telescope, pp.36-42.

  7. (a, b) Borisovna, G., 2014, 'Carl Sagan', The Rosen Publishing Group.

  8. Sagan, C., 1985, 'On Minimizing the Consequences of Nuclear War', Nature, 317, pp.485-488.

  9. Angell, T., 2014, 'Carl Sagan's Long Lost Deep Thoughts On The War On Drugs', Popular Resistance, last accessed 01-06-17.

  10. Kilston, S. D., Drummond, R. R. and Sagan, C., 1966, 'A search for life on Earth at kilometer resolution', Icarus, 5, pp.79-98.

  11. Ferris, T., 1973, 'Carl Sagan: Life on Other Planets?', Rolling Stone, last accessed 01-06-17.

  12. Sagan, C., and Leonard, J. N., 1966, 'Planets', Time, Incorporated.

  13. (a, b, c) Broad, W. J., 1998, 'Even in Death, Carl Sagan's Influence Is Still Cosmic', New York Times, last accessed 01-06-17.

  14. Sagan, C., 1973, 'Cosmic Connection: An Extraterrestrial Perspective', Cambridge University Press.

  15. Ridpath, I., 1974, 'A man whose time has come', New Scientist.

  16. Time, 1980, 'The Showman of Science'.

  17. Devorkin, D. H., 1981, 'Book-Review - Cosmos', Sky and Telescope, 61, pp.536.

  18. (a, b) Burns, J. A., 1997, 'Carl Sagan (1934-96) Astronomer and popularizer of science', Nature, 385, pp.400.

  19. McDowell, E., 1981, 'Sagan sells first novel to Simon & Schuster', New York Times.

  20. Sagan, C., 1981, 'Letter to The Explorers Club'.

  21. Sagan, C., and Druyan, A., 2011, 'Abortion: Is it Possible to be both "Pro-life" and "Pro-Choice"?', in 'Billions & Billions: Thoughts on Life and Death at the Brink of the Millennium', Random House Publishing Group.

  22. NASA, 'David Morrison, Senior Scientist', last accessed 01-06-17.

  23. NASA, 'Dr. Steven W. Squyres, Ph. D.', last accessed 01-06-17.

  24. Marris, E., 2005, 'In defence of data', Nature, 436, pp.454-455.

  25. National Academy of Sciences, 'Ralph J. Cicerone', last accessed 01-06-17.

Back to top

The Star Garden is a science news and science education website run by Dr Helen Klus.

How we came to know the cosmos covers the history of physics focusing on space and time, light and matter, and the mind. It explains the simple discoveries we made in prehistoric times, and how we built on them, little by little, until the conclusions of modern theories seem inevitable. This is shown in a timeline of the universe.

The Star Garden covers the basics for KS3, KS4, and KS5 science revision including SATs, GCSE science, and A-level physics.