The geocentric model, which places the Earth at the center of the universe, was most highly developed and widely known from the work of Claudius Ptolemy around 150 CE. While the concept of an Earth-centered universe existed before him, it was Ptolemy who formulated the detailed mathematical and observational model known as the Ptolemaic system. His model explained the complex planetary motions, including retrograde motion, using epicycles and was the dominant astronomical paradigm for over 1,500 years.
Earlier contributions to the geocentric idea came from ancient Greek philosophers such as Aristotle, and even earlier, Eudoxus created an initial geocentric model around 380 BCE. However, Ptolemy's systematic and predictive model marked the pinnacle of the geocentric theory before it was eventually replaced by heliocentric models in the 16th century.
