Geocentric model Geocentric model In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under the geocentric model, the Sun, Moon, stars, and planets all orbited Earth. The geocentric model served as the predominant description of the cosmos in many ancient civilizations, such as those of Aristotle and Ptolemy. Two observations supported the idea that Earth was the center of the Universe. First, from anywhere on Earth, the Sun appears to revolve around Earth once per day. While the Moon and the planets have their own motions,
Encyclopedia of the Central Intelligence Agency if he would instead be interested in writing an encyclopedia detailing the history of the CIA. Smith agreed as he felt the CIA was highly relevant to military history. "Encyclopedia of the Central Intelligence Agency" was first published in 2003 by Facts on File. It was released in both hardcover and paperback formats. An eBook edition was published the same year. Additionally an eBook was also published in 2003 in Great Britain. In the "Encyclopedia of the Central Intelligence Agency", Smith discusses and defines key concepts relating to intelligence gathering, including "clandestine mentality", a colloquial term used to characterize what