epicycle

/ep-uh-sahy-kuhl/US // ˈɛp əˌsaɪ kəl //UK // (ˈɛpɪˌsaɪkəl) //

附图,附属物,附属品,附注

Definitions

n.名词 noun

1
- : Astronomy. a small circle the center of which moves around in the circumference of a larger circle: used in Ptolemaic astronomy to account for observed periodic irregularities in planetary motions.
- : Mathematics. a circle that rolls, externally or internally, without slipping, on another circle, generating an epicycloid or hypocycloid.

For the epicycle is a sphere which changes place in the circumference of the large sphere.
The eighth sphere had neither deferent nor epicycle but to it were attached the fixed stars.
Epicycle, a conception of the ancient astronomy used to explain the irregular, and at times retrograde, motions of the planets.
The fourth one in order is the yearly revolution which includes the earth with the moon's orbit as an epicycle.
To correct for these irregularities Copernicus introduced epicycle on epicycle in the lunar orbit.