Carl Sagan and space exploration: The effects of popularising science

A photograph of Carl Sagan with a model of the Viking lander.

Image credit: NASA/Public domain.

First published on 6th April 2016. Last updated 1 January 2020 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 as an undergraduate at the University of Chicago[2][3a]. During this time, he organised a lecture series on campus that, decades later, he compared to the television series Cosmos[3b].[3c][4].

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 this time, he began to be quoted by the media[3d].

Sagan's first success with a mainstream scientific journal came with The Planet Venus[5]. That same year, his greenhouse model of Venus made it into the New York Times and Newsweek[3e]. Sagan's views earned him a place at 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.

When Mariner 4 sent back photos showing no evidence of life on Mars in 1965, 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 of Earth from the same distance, showing that evidence of life may not be seen. Sagan later discussed this with Rolling Stone magazine[11].

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].

A 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 Telesc., 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, where he became the show's 'house astronomer'.

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].

Sagan suggested launching robotic probes to Mars when they were not given funding for a crewed mission. Carson helped endorse the view, and they won over the public. Shortly after this, Sagan was profiled by Rolling Stone magazine[3l].

NASA developed the Viking missions to Mars, which contained cameras that could spot moving objects and Sagan talked of "polar bear-sized" creatures. 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]. When Viking 1 reached Mars in 1976, there was no evidence of life.

Sagan began composing data to be attached to the Voyager probes in 1977, having previously helped design the Pioneer plaque, along with Frank Drake and Linda Salzman Sagan.

In 1980, Cosmos aired. 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 was well-received and the accompanying book became a bestseller. It also received critical acclaim from journals and magazines such as Sky Telesc.[17].

Credit: via Ilen hans.

Credit: via 24fpsfan.

Sagan, Bruce Murray, and Louis Friedman founded the Planetary Society in 1980, in order to help fund the SETI program. 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].

A 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].


  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', Sci, 133, pp.849-858.

  6. Schilling, G. and MacRobert, A.M., 1998, 'The Chance of Finding Aliens', Sky Telesc., 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', Nat, 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 Telesc., 61, pp.536.

  18. (a, b) Burns, J. A., 1997, 'Carl Sagan (1934-96) Astronomer and popularizer of science', Nat, 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', Nat, 436, pp.454-455.

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

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