What does epicycle mean?

Definitions for epicycle
ˈɛp əˌsaɪ kəlepicy·cle

This dictionary definitions page includes all the possible meanings, example usage and translations of the word epicycle.

Princeton's WordNet

  1. epicyclenoun

    a circle that rolls around (inside or outside) another circle; generates an epicycloid or hypocycloid

Wiktionary

  1. epicyclenoun

    A small circle whose centre is on the circumference of a larger circle; in Ptolemaic astronomy it was seen as the basis of revolution of the "seven planets", given a fixed central Earth.

  2. epicyclenoun

    Any circle whose circumference rolls around that of another circle, thus creating a hypocycloid or epicycloid.

  3. Etymology: From epicyclus, from ἐπίκυκλος, from ἐπί + κύκλος.

Samuel Johnson's Dictionary

  1. Epicyclenoun

    A little circle whose center is in the circumference of a greater; or a small orb, which, being fixed in the deferent of a planet, is carried along with its motion; and yet, with its own peculiar motion, carries the body of the planet fastened to it round about its proper center. John Harris

    Etymology: ἐϖὶ and ϰύϰλος.

    In regard of the epicycle, or lesser orb, wherein it moveth, the motion of the moon is various and unequal. Brown.

    Gird the sphere
    With centric and eccentric, scribbl’d o’er;
    Cycle and epicycle, orb in orb. John Milton, Paradise Lost, b. viii.

Wikipedia

  1. epicycle

    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") was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets. In particular it explained the apparent retrograde motion of the five planets known at the time. Secondarily, it also explained changes in the apparent distances of the planets from the Earth. It was first proposed by Apollonius of Perga at the end of the 3rd century BC. It was developed by Apollonius of Perga and Hipparchus of Rhodes, who used it extensively, during the 2nd century BC, then formalized and extensively used by Ptolemy in his 2nd century AD astronomical treatise the Almagest. Epicyclical motion is used in the Antikythera mechanism, an ancient Greek astronomical device for compensating for the elliptical orbit of the Moon, moving faster at perigee and slower at apogee than circular orbits would, using four gears, two of them engaged in an eccentric way that quite closely approximates Kepler's second law. Epicycles worked very well and were highly accurate, because, as Fourier analysis later showed, any smooth curve can be approximated to arbitrary accuracy with a sufficient number of epicycles. However, they fell out of favor with the discovery that planetary motions were largely elliptical from a heliocentric frame of reference, which led to the discovery that gravity obeying a simple inverse square law could better explain all planetary motions.

ChatGPT

  1. epicycle

    An epicycle is a small circle, the center of which moves around the circumference of a larger circle. This concept was primarily used in the geocentric model of planetary motion proposed by the ancient Greek astronomer, Ptolemy, and others to explain the apparent irregular movements of celestial bodies.

Webster Dictionary

  1. Epicyclenoun

    a circle, whose center moves round in the circumference of a greater circle; or a small circle, whose center, being fixed in the deferent of a planet, is carried along with the deferent, and yet, by its own peculiar motion, carries the body of the planet fastened to it round its proper center

  2. Epicyclenoun

    a circle which rolls on the circumference of another circle, either externally or internally

  3. Etymology: [L. epicyclus, Gr. ; 'epi` upon + circle. See Cycle.]

Chambers 20th Century Dictionary

  1. Epicycle

    ep′i-sī-kl, n. a circle having its centre on the circumference of a greater circle on which it moves.—adj. Epicy′clic.—n. Epicy′cloid, a curve described by every point in the plane of a circle moving on the convex circumference of another circle.—adj. Epicycloi′dal. [Gr. epi, upon, kyklos, a circle.]

The Nuttall Encyclopedia

  1. Epicycle

    an expression used in the Ptolemaic (q. v.) system of astronomy; the old belief that the celestial bodies moved in perfect circles round the earth was found to be inadequate to explain the varying position of the planets, a difficulty which led Ptolemy to invent his theory of epicycles, which was to the effect that each planet revolved round a centre of its own, greater or less, but that all these centres themselves moved in procession round the earth, a theory which fell to pieces before the investigations of Kepler and Newton.

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Numerology

  1. Chaldean Numerology

    The numerical value of epicycle in Chaldean Numerology is: 2

  2. Pythagorean Numerology

    The numerical value of epicycle in Pythagorean Numerology is: 6


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"epicycle." Definitions.net. STANDS4 LLC, 2024. Web. 29 Mar. 2024. <https://www.definitions.net/definition/epicycle>.

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