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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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(ep -ă-sÿ-kăl) See Ptolemaic system.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006


(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.




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.



The circle which generates an epicycloid or hypocycloid.
References in periodicals archive ?
A block diagram of possible power losses in the device for controlling speed changes by means of a differential transmission with a closed hydraulic system through an epicycle, where the driving link is the carrier, and the driven one is the epicycle, is shown in fig.
These spurious effects, "dark energy", "dark matter", and "accelerating expansion", are reminiscent of Ptolemy's epicycles when an incorrect model of the solar system was forced to fit the data, rather than using the data to test different models of the solar system.
before protecting it, but that seems like an unnecessary epicycle. It
(7) Thapar points out that according to some scholars, the number 432,000 could be of Babylonian origin, combined with the Greek epicycle theory (15).
giving the gigraha (epicycle) figures for each degree of the
Calmeta manages, while blowing on his pipes, also to sing about the phases of the moon, its epicycle, equant, and deferant, the rules and attributes of the planets ("del rosseggiante Marte, del temperato Giove e del pigro Saturno" Filocolo 5.8.18).
Also, if we allow the center of the epicycle to move at a constant angular speed around a third point on the opposite side of the deferent, one can predict the positions of the planets much more accurately.
The scientist does not observe the system "perched on the epicycle of Mercury" (Skinner, 1974 p.
A planet is carried on an epicycle, a circle whose center moves on the circumference of a larger circle called a deferent.
However, the activity in which composers are involved does not seem to be one of discovery, but one of creation; as Levinson correctly insists, the idea that composers create their compositions is 'one of the most firmly entrenched of our beliefs concerning art'.[10] A Platonist may at this point either bite the bullet, and argue that musical works are indeed discovered,[11] or devise some ingenious epicycle that allows for the possibility that abstract entities are created.
By the time of the next Ellis, The Rules of Attraction (1987), instead of a puppy-novelist, we confronted an epicycle of the Ptolemaic system of hype, according to which the heavens move in eccentric orbits around a vacuous editorial need for gas.