Glossary term: Geocentric Model

Description: Early models of the Universe were geocentric, placing Earth at the center of the world, orbited by the Moon, Sun, and planets, with the stars as lights on a spherical shell surrounding that whole arrangement. An influential model of this kind is the Ptolemaic system, named after Claudius Ptolemy. Late in the 16th century a shift began towards a heliocentric model, which puts the Sun in the center and 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, and where.

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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".