The term "geocentric" refers to a model of the universe where the Earth is at the center, and all celestial bodies, including the Sun, Moon, and planets, revolve around it. This view was widely accepted in ancient times and was notably supported by the Greek philosopher Aristotle and later by Ptolemy, who developed a detailed geocentric system. The geocentric model was eventually challenged by the heliocentric model proposed by Nicolaus Copernicus, which placed the Sun at the center of the solar system. This shift in understanding marked a significant change in astronomy and laid the groundwork for modern scientific thought.