epicycle

Definitions

  • WordNet 3.6
    • n epicycle a circle that rolls around (inside or outside) another circle; generates an epicycloid or hypocycloid
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Webster's Revised Unabridged Dictionary
    • Epicycle (Mech) A circle which rolls on the circumference of another circle, either externally or internally.
    • Epicycle (Ptolemaic Astron) 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. "The schoolmen were like astronomers which did feign eccentrics, and epicycles , and such engines of orbs."
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Century Dictionary and Cyclopedia
    • n epicycle A circle moving upon or around another circle, as one of a number of wheels revolving round a common axis. See epicyclic train, under epicyclic.
    • n epicycle In the Ptolemaic system of astronomy, a little circle, conceived for the explanation of planetary motion, whose center was supposed to move round in the circumference of a greater circle; a small circle whose center, being fixed in the deferent of a planet, was supposed to be carried along with the deferent, and yet by its own peculiar motion to carry the body of the planet fastened to it round its proper center. Copernicus also made use of epicycles, which, however, were banished by Kepler.
    • n epicycle In mod. astron., sometimes used for the geocentric path of a planet, or its path relative to the earth regarded as fixed.
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Chambers's Twentieth Century Dictionary
    • n Epicycle ep′i-sī-kl a circle having its centre on the circumference of a greater circle on which it moves
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Etymology

Webster's Revised Unabridged Dictionary
L. epicyclus, Gr. ; 'epi` upon + circle. See Cycle
Chambers's Twentieth Century Dictionary
Gr. epi, upon, kyklos, a circle.

Usage

In literature:

The fourth one in order is the yearly revolution which includes the earth with the moon's orbit as an epicycle.
"A History of Science, Volume 2(of 5)" by Henry Smith Williams
In both classes, the action involves the use of some sort of epicyclic train, since the motions to be explained are both orbital and axial.
"Scientific American Supplement, No. 447, July 26, 1884" by Various
The theories of eccentrics and epicycles accomplished the end of explaining all the known phenomena.
"Beacon Lights of History, Volume III" by John Lord
Cycle and epicycle, orb in orb.
"Familiar Quotations" by Various
The moons, of those solar planets which have them, represent the epi-epicyclical orbits of the Ptolemaic theory.
"Harper's New Monthly Magazine, Vol. 3, July, 1851" by Various
Motion still supposed to be in epicycles.
"Pioneers of Science" by Oliver Lodge
Epicycles and eccentrics, Hipparchus's theory of, i.
"History of the Intellectual Development of Europe, Volume II (of 2)" by John William Draper
They even supposed the moon to have one, perhaps two epicycles and we shall find this notion reflected in Chaucer.
"Astronomical Lore in Chaucer" by Florence M. Grimm
To help out of this difficulty, the worst possible mechanical scheme was invented, that known as the epicycle.
"Astronomy" by David Todd
Hang early plummets upon the heels of Pride, and let Ambition have but an Epicycle and narrow circuit in thee.
"The Works of Sir Thomas Browne" by Thomas Browne
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In poetry:

Then burn thy Epicycles, foolish man;
Break all thy spheres, and save thy head;
Faith needs no staffe of flesh, but stoutly can
To heav'n alone both go, and leade.
"Divinitie" by George Herbert

In news:

The "pin and slot" epicyclic system referred to in the text is at 5 o'clock on the bottom gear.
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In science:

Fig. 5.— Radial epicyclic frequency κr as a function of radius for a black hole of spin a = 0.4M and for several values of the parameter ǫ.
Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum. III. Quasi-Periodic Variability
Zeros of the radial epicyclic frequency correspond to marginally stable orbits.
Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum. III. Quasi-Periodic Variability
Stability would be a fluid element that oscillates at the local epicyclic frequency.
Foundations of Black Hole Accretion Disk Theory
In the slender-torus limit, one can write down analytic expressions for a few of the lowest order modes besides just the radial and vertical epicyclic ones.
Foundations of Black Hole Accretion Disk Theory
Here y = (z/H )[γg /(γg − 1)]1/2 is the re-scaled vertical coordinate, γg is the adiabatic index, ˜ω(r) = ωr /ωθ is the ratio of the epicyclic frequencies from Section 2.3, Ψ is the eigenvalue of the (WKB) separation function, and g = (P /Pc )/(ρ/ρc ), where Pc and ρc are the midplane values.
Foundations of Black Hole Accretion Disk Theory
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