Primum Mobile
(重定向自Dodecatemory)

In classical, medieval and Renaissance astronomy, the Primum Mobile, or "first moved," was the outermost moving sphere in the geocentric model of the universe.
The concept was introduced by Ptolemy to account for the apparent daily movement of the heavens around the Earth, producing the east-to-west rising and setting of the sun and stars, and reached Western Europe via Avicenna.