epicycle

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epicycle:

see Ptolemaic systemPtolemaic system
, historically the most influential of the geocentric cosmological theories, i.e., theories that placed the earth motionless at the center of the universe with all celestial bodies revolving around it (see cosmology).
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epicycle

(ep -ă-sÿ-kăl) See Ptolemaic system.

Epicycle

(religion, spiritualism, and occult)

When Earth was viewed as the stationary center of the universe, the retrograde motion of the planets was explained in terms of epicycles—smaller orbits that circled in the reverse direction from the planets’ usual motion.

Epicycle

 

an auxiliary circle in Ptolemy’s geocentric system of the world.

Epicycles were introduced to explain the retrograde motions of the planets. It was presumed that a planet moves uniformly along the epicycle while its center E (see Figure 1) moves along another circle, called the deferent, with its center at the earth. Because a deferent with one epicycle could not explain many irregularities in the motions of the planets, systems of epicycles were introduced. It was believed that the center of the second epicycle moved along the first epicycle, while the center of the third epicycle

Figure 1

moved, in turn, along the second epicycle, and so on. The planet is located in the last epicycle.

epicycle

[′ep·ə‚sī·kəl]
(mathematics)
The circle which generates an epicycloid or hypocycloid.
References in periodicals archive ?
The efficiency of the proposed device for controlling speed changes by means of a differential transmission with a closed hydraulic system via the solar gear, in the case where the driving link is the carrier and the driven one is the epicycle, appears as follows
If not for Copernicus' better theory, we would still be trying to improve the accuracy of our epicycles, equants and deferents.
This then required, and correctly so, that the orbits have epicycle components.
The Islamic epicenter was the pivot of the literary epicycles depicting his diverse roles, proving that Islam was no laughing matter after all, but also that the initiative for serious engagement had drained itself in a tide of fabrication of anti-Islamic polemic and mutual Christian recrimination.
7) Here I ignore to what degree Hume's treatment of pre-Copernican astronomy is fair; presumably he has in mind the oft-caricatured tendency to introduce, say, new epicycles in order to 'save' the phenomena in Ptolemaic astronomy.
The basic provision has been extended to violations of other constitutional rights (3) and freighted with innumerable epicycles, and epicycles on epicycles, but it is at bottom straightforward.
For example, even the Ptolemaic theory, with its ad hoc armoury of epicycles, eccentrics and equants, could achieve only approximate consistency with observed celestial motions (Kuhn 1957, 59-73), and it was inconsistent with the observed quantitative variations in the brightness of the planets (Feyerabend 1975, 109-11, 141-43).
The final model by Ptolemy used epicycles, so that planets would go around a small circle that in turn was circling the earth.
While he appears to accept Ptolemy's theory of epicycles in order to account for the retrograde motions of the 'wandering stars' in the course of their revolutions around the earth, Ibn Sina adopts Alexander's view in pointing out the reason behind those irregular and complex motions of the planets.
In Parsifal, Graham diffracts an interlude composed by Wagner's assistant, Engelbert Humperdinck, into an array of musical epicycles for each of the fourteen orchestral parts, the combinations of which would take more than thirty-nine billion years to play out.
When a favorite explanation encounters contradictory evidence, we make an ad hoc adjustment to it to account for this evidence--just like Ptolemy added epicycles to his explanation of the planets' movements.
Part of the trouble here is that the complexities of Bruce's metaphysics, the constant adjustments and nested levels, remind me of nothing so much as the complex epicycles he earlier deemed fatal to Ptolemaic cosmology.