Oikumene

The ecumene (US) or oecumene (UK; Greek: οἰκουμένη, oikouménē, lit. "inhabited") was an ancient Greek term for the known world, the inhabited world, or the habitable world. Under the Roman Empire, it came to refer to civilization and the secular and religious imperial administration. In present usage, it is used as the noun form of "ecumenical" and describes the Christian Church as a unified whole or the unified modern world civilization. It is also used in cartography to describe a type of world map (mappa mundi) used in late Antiquity and the Middle Ages.

The Greek term cited above is the feminine present middle participle of the verb οἰκέω (oikéō, "to inhabit") and is a clipped form of οἰκουμένη γῆ (oikouménē gē, "inhabited world").

Eratosthenes of Cyrene (276–196 BC) deduced the circumference of the Earth with remarkable accuracy (within 10% of the correct value). The Greek cartographer Crates created a globe about 150 BC.Claudius Ptolemy (83–161) calculated the Earth's surface in his Geography and described the inhabited portion as spanning 180 degrees of longitude (from the Fortunate Isles in the west to Serae and Serica (China) in the east) and about 80 degrees of latitude (from Thule in the north to anti-Meroë below the equator). Ptolemy was well aware that the Romans knew only about a quarter of the globe and his erroneous belief that the Indian Ocean was landlocked led to expectation of a terra incognita ("unknown land"). In fact, symmetry led him to expect that there should be three other continents to balance the ecumene: Perioeci (lit. "beside the ecumene"), Antoeci ("opposite the ecumene") and the Antipodes (“opposite the feet”).

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