In the book, Sagan explores 15 billion years of cosmic evolution and the development of science and civilization. Cosmos traces the origins of knowledge and the scientific method, mixing science and philosophy, and speculates to the future of science. The book also discusses the underlying premises of science by providing biographical anecdotes about many prominent scientists throughout history, placing their contributions into the broader context of the development of modern science.The book covers a broad range of topics, comprising Sagan's reflections on anthropological, cosmological, biological, historical, and astronomical matters from antiquity to contemporary times. Sagan reiterates his position on extraterrestrial life—that the magnitude of the universe permits the existence of thousands of alien civilizations, but no credible evidence exists to demonstrate that such life has ever visited earth.

    It is a story that actually begins with the development of telescopes powerful enough to reveal first Uranus, then Neptune, and finally Pluto, the outermost planets of our solar system, which cannot be seen with the naked eye. Thanks to the clues provided by the identification of Uranus and Neptune, and the lucky chance that saw young, self-taught astronomer Clyde Tombaugh working with a new telescope at the Lowell Observatory -one of the few centers where an active planet-seeking program was brewing carried on- Pluto was discovered on February 18th, 1930.Sweet within the larger context of the history and evolution of astronomy, OUT OF THE DARKNESS recaptures all of the tension and excitement of the search for and discovery of Pluto, and explores the controversy about the true nature of this planet, which is still going on today.