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Counting the total number is difficult, but estimates are that he created a system just as complicated, or even more so. [16] Koestler, in his history of man's vision of the universe, equates the number of epicycles used by Copernicus at 48. [17] The popular total of about 80 circles for the Ptolemaic system seems to have appeared in 1898.
In graph theory, a Ptolemaic graph is an undirected graph whose shortest path distances obey Ptolemy's inequality, which in turn was named after the Greek astronomer and mathematician Ptolemy. The Ptolemaic graphs are exactly the graphs that are both chordal and distance-hereditary ; they include the block graphs [ 1 ] and are a subclass of the ...
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.
A simple illustration showing the basic elements of Ptolemaic astronomy. It shows a planet rotating on an epicycle which is itself rotating around a deferent inside a crystalline sphere. The center of the system is marked with an X, and the earth is slightly off of the center.
Nederlands: The Ptolemaic system is an ancient astronomical model that posits the Earth as the center of the universe, with the planets, the Sun, and the stars orbiting around it in a series of concentric circles.
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 equant is ...
The term system is polysemic: Robert Hooke (1674) used it in multiple senses, in his System of the World, [7]: p.24 but also in the sense of the Ptolemaic system versus the Copernican system [8]: 450 of the relation of the planets to the fixed stars [9] which are cataloged in Hipparchus' and Ptolemy's Star catalog. [10]
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.