Celestial spheres

The celestial spheres, also known as spherical shells or spherical orbs, are a historical concept that posited that the universe was composed of a series of concentric, transparent spheres, to which stars, planets, and even celestial events such as comets, were attached. This model was widely accepted in ancient Greek philosophy and cosmology, and was later adopted and developed by medieval Islamic and European scholars. In Hebrew, the term is translated as כדורי השמיים (Kdurei HaShamayim). In Arabic, it is known as الكرويات السماوية (Al-Karāwiyyāt Al-Samāwiyyah), and in Latin as sphaerae coelestium. The concept was used to explain the apparent motion of celestial bodies across the sky, with each sphere rotating at a different speed and axis. The outermost sphere, known as the primum mobile, was believed to be responsible for the motion of all the other spheres. This model was eventually superseded by the heliocentric model of the universe proposed by Nicolaus Copernicus in the 16th century.