Description: Early models of the Universe were geocentric, placing Earth at the center of the cosmos, with the Moon, Sun, and planets moving around it relative to the "fixed" stars. Geocentric models existed in many cultures in antiquity alongside heliocentric models which put the Sun in the center. An influential geocentric model is the Ptolemaic system, named after Claudius Ptolemy, an astronomer from the 2nd century. This became the most prominent model of the cosmos for over a thousand years in Europe, North Africa, and the Middle East. Late in the 16th century a shift began towards a heliocentric model, which is commonly associated with the name of Nicolaus Copernicus. Today, we know that the Solar System is only one of many such systems, and certainly not the center of the Universe. In practice, geocentric descriptions of the sky are still in use, but only as a way of calculating which astronomical objects are visible from a given location at a given time.

Related Terms:

• Heliocentric Model

Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".