Uniform circular motion

Uniform circular motion
Plato argued that the most perfect form should be a circle and therefore motions of the heavens should be made of up combinations of circular motion.

uniform circular motion: The classical belief that the perfect heavens could move only by the combination of constant motion along circular orbits.
valley network: Dry drainage channels resembling streambeds found on Mars.

Their ideas mostly involved uniform circular motion, and were centered on the earth.

This is not true, because Copernicus was able to rid himself of the long-held notion that the Earth was the center of the Solar system, but he did not question the assumption of uniform circular motion.

Their models employed combinations of uniform circular motion and were centered on the earth. An independent philosophical tradition was concerned with the physical causes of such circular motions.

Simplicius of Cilicea comments on Plato’s 1000-year old theory that the heavenly bodies have uniform circular motions.
580 approx ...

The retention, however, by Copernicus of the antique postulate of uniform circular motion impaired the perfection of his plan, since it involved a partial survival of the epicyclical machinery.

Plato claimed that heaven is perfect and circle is the most perfect form. Thus, the heaven is in uniform circular motion with the Earth at the center. This is the beginning of the geocentric model.

He supposed that the Earth was located a short distance from the center of the deferent for each planet and that the center of the planet's deferent and the epicycle described uniform circular motion around what he called the equant, ...

With the benefit of hindsight, we now recognize that the major error lay in the assumption of a geocentric universe. This was compounded by the insistence on uniform circular motion, whose basis was largely philosophical, rather than scientific, ...

He retained the uniform circular motion of the Ptolemaic system, but by placing the sun at the center, he was able to reduce the number of epicycles.

Another way of saying this is that there were uniform circular motions. Ancient astronomers were really hung up on the idea that stuff in the sky had to move in paths that were perfect circles, or associated with circular objects.

See also: Solar, Distance, Earth, Time, Moon