In [[medieval]] [[Christian]] [[cosmology]], the '''Primum Mobile''' ('first mover') is the outermost sphere of [[Heaven]]. Medieval astronomers extrapolated from the observed motion of the [[planet]]s that the [[Earth]] was surrounded by concentric rotating spheres, each of which contained a planet. The outermost visible sphere contained the fixed stars, and it was conjectured that outside that was a final invisible sphere, the Primum Mobile, which also rotated. Since it was the furthest moving sphere before the [[Empyrean]], the Primum Mobile was thought to be the source of [[time]]. | In [[medieval]] [[Christian]] [[cosmology]], the '''Primum Mobile''' ('first mover') is the outermost sphere of [[Heaven]]. Medieval astronomers extrapolated from the observed motion of the [[planet]]s that the [[Earth]] was surrounded by concentric rotating spheres, each of which contained a planet. The outermost visible sphere contained the fixed stars, and it was conjectured that outside that was a final invisible sphere, the Primum Mobile, which also rotated. Since it was the furthest moving sphere before the [[Empyrean]], the Primum Mobile was thought to be the source of [[time]]. |