Carl Sagan (1934-1996) was an American planetary astronomer known for his strong support of the systematic, scientific search for extraterrestrial life and his popular books and television programmes about science.
Sagan worked for many years on NASA's planetary exploration programmes including Voyager and Viking. He correctly predicted that Venus is heated by the greenhouse effect and that observed changes in Mars's surface features are caused by dust storms, not changes in seasonal vegetation.
Image: Carl Sagan poses with a model of the Viking lander in Death Valley, California (credit: NASA/JPL)
An American astronomer works to popularise science.
Patrick Moore discusses the search for life with Sagan.
Sir Patrick Moore spoke to Dr Carl Sagan in 1974 about the search for other civilisations.
Earth is a tiny blue dot when viewed from the edge of the Solar System.
In 1990, 13 years after leaving the Earth and at a distance of 3.7 billion miles, Voyager 1 turned around to face the Sun and captured images of most of the planets, including the Earth. Voyager scientist Carl Sagan described our planet as a "blue dot".
In 1962 some thought Venusian life was possible.
Prior to Mariner 2's 1962 flyby of Venus, some scientists such as Dr Carl Sagan thought that conditions on the planet might favour life. However, the probe's instruments showed that the cloudy planet's surface was extremely hot, greatly reducing the chance that anything could survive there.
Carl Edward Sagan (/ˈseɪɡən/; November 9, 1934 – December 20, 1996) was an American astronomer, cosmologist, astrophysicist, astrobiologist, author, science popularizer, and science communicator in astronomy and other natural sciences. His contributions were central to the discovery of the high surface temperatures of Venus. However, he is best known for his contributions to the scientific research of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation. Sagan assembled the first physical messages that were sent into space: the Pioneer plaque and the Voyager Golden Record, universal messages that could potentially be understood by any extraterrestrial intelligence that might find them.
He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. Sagan is known for many of his popular science books, such as The Dragons of Eden, Broca's Brain and Pale Blue Dot, and for the award-winning 1980 television series Cosmos: A Personal Voyage, which he narrated and co-wrote. The most widely watched series in the history of American public television, Cosmos has been seen by at least 500 million people across 60 different countries. The book Cosmos was published to accompany the series. He also wrote the science fiction novel Contact, the basis for a 1997 film of the same name.
Sagan always advocated scientific skeptical inquiry and the scientific method, pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI). He spent most of his career as a professor of astronomy at Cornell University, where he directed the Laboratory for Planetary Studies. Sagan and his works received numerous awards and honors, including the NASA Distinguished Public Service Medal, the National Academy of Sciences Public Welfare Medal, the Pulitzer Prize for General Non-Fiction for his book The Dragons of Eden, and, regarding Cosmos: A Personal Voyage, two Emmy Awards, the Peabody Award and the Hugo Award. He married three times and had five children. After suffering from myelodysplasia, Sagan died of pneumonia at the age of 62 on December 20, 1996.