Sublunary sphere

In Aristotelian physics and Greek astronomy, the sublunary sphere is the region of the geocentric cosmos below the Moon, consisting of the four classical elements: earth, water, air, and fire.

Beginning with the Moon, up to the limits of the universe, everything (to classical astronomy) was permanent, regular and unchanging—the region of aether where the planets and stars are located.

Avicenna carried forward into the Middle Ages the Aristotelian idea of generation and corruption being limited to the sublunary sphere.

In their wake, Tycho Brahe's observations of a new star (nova) and of comets in the supposedly unchanging heavens further undermined the Aristotelian view.

[9] Samuel Johnson praised Shakespeare's plays as "exhibiting the real state of sublunary nature, which partakes of good and evil, joy and sorrow, intermingled".