Sagan, Carl (1934–1996)

School and Early Research

Sagan was born in Brooklyn, New York, on November 9, 1934. In 1951, he entered the University of Chicago at age 16, and in 1954, he graduated with honors and received his general bachelor of arts degree. At the time, the University of Chicago required all undergraduates to complete a broad liberal arts education before choosing a specialty field. On graduating, Sagan chose to specialize in physics and received his bachelor of science degree in 1955. The following year, he received his master's of science degree in physics and entered the University of Chicago doctorate program in astronomy.

While working on his doctorate, Sagan made two important contributions to the field of planetary science—both of which went against popular belief but proved to be correct. At the 1956 meeting of the American Association for the Advan cement of Science, Sagan courageously disagreed with noted Dutch-born American astronomer Gerard Kuiper's hypothesis about seasonal vegetation changes causing the variation in dark areas on the surface of Mars. Instead, Sagan postulated that the variation could be caused by giant dust storms blowing light-colored dust across areas of dark lava, which was later confirmed to be the case.

Sagan also disagreed with the popular view of Venus as Earth's twin. At the time, many people believed that under Venus's atmosphere was a warm, lush planet harboring life. After hearing about new radio telescope data showing strong microwave readings from Venus, however, Sagan postulated that Venus was subject to a runaway greenhouse effect caused by carbon dioxide and water vapor in its atmosphere that made it extremely hot—with an estimated surface temperature of around 600 degrees Fahrenheit. Although the scientific community initially resisted the idea, Sagan's hypothesis was later confirmed by robotic spacecraft measurements. The actual surface temperature of Venus was found to be 864 degrees Fahrenheit—an environment way too hostile for the lush life once thought to exist there.

In 1960, Sagan received his doctorate degree in astronomy and astrophysics from the University of Chicago with a thesis titled “Physical Studies of Planets.” The next year, Sagan's Venus paper was [Page 670]published in Science—one of the most respected peer-reviewed journals. This attracted the attention of Harvard University, and he was offered and accepted the position of assistant professor of astronomy in 1963. Around this time, Sagan also began consulting for the National Academy of Sciences and the National Aeronautics and Space Administration (NASA) on planetary missions and continued to do so for the rest of his career.

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