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In the Hipparchian, Ptolemaic, and Copernican systems of astronomy, the epicycle (from Ancient Greek ἐπίκυκλος (epíkuklos) 'upon the circle', meaning "circle moving on another circle") [1] was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets.
Pages from 1550 Annotazione on Sacrobosco's De sphaera mundi, showing the Ptolemaic system. In the Ptolemaic system, each planet is moved by a system of two spheres: one called its deferent; the other, its epicycle. The deferent is a circle whose center point, called the eccentric and marked in the diagram with an X, is distant from the Earth.
Reigning for 275 years, the Ptolemaic was the longest and last dynasty of ancient Egypt from 305 BC until its incorporation into the Roman Republic in 30 BC. [ 6 ] [ 7 ] Ptolemy , a general and one of the somatophylakes (bodyguard companions) of Alexander the Great , was appointed satrap of Egypt after Alexander's death in 323 BC.
Download as PDF; Printable version; In other projects ... Ptolemaic is the adjective formed from the name Ptolemy, and may refer to: ... Ptolemaic system, ...
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The basic elements of Ptolemaic astronomy, showing a planet on an epicycle (smaller dashed circle), a deferent (larger dashed circle), the eccentric (×) and an equant (•). Equant (or punctum aequans ) is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of the planets.
The Ptolemaic system of celestial motion as depicted in the Harmonia Macrocosmica (1661). Science in classical antiquity encompasses inquiries into the workings of the world or universe aimed at both practical goals (e.g., establishing a reliable calendar or determining how to cure a variety of illnesses) as well as more abstract investigations belonging to natural philosophy.
It was written in three writing systems: Egyptian hieroglyphs, demotic, and koine Greek, on several ancient Egyptian memorial stones, or steles. The inscription is a record of a great assembly of priests held at Canopus, Egypt , on 7 Appellaios (Mac.) = 17 Tybi (E.g.) year 9 of Ptolemy III = Thursday 7 March 238 BC (proleptic Julian calendar).