Parmenides and the Origins of the Heavenly Sphere in Ancient Greek Cosmology.

Aristotle presented an influential conception of the universe consisting of a sphere of fixed stars with a spherical Earth at its centre. A spherical conception of heaven and Earth appears also in Plato's writings. In presocratic cosmology, the idea of a spherical universe appears probably first in the thoughts of the Pythagoreans and Parmenides. But while there is no surviving evidence for the cosmology of early Pythagoreans, various sources mention in relation to Parmenides a solid surrounding part and a spherical Earth at the centre of the universe. Being, which Parmenides had likened to a sphere, may have moreover in a cosmological sense referred to 'heaven.' Furthermore, we can observe in presocratic cosmologies a development which shows that the cosmology of heavenly sphere appeared in the fifth century BCE. Although Parmenides is commonly thought to have influenced especially ontology, one can argue that it was he who introduced the concept of a heavenly sphere to cosmology, a notion which in Aristotle's thought evolved into the notion of a sphere of fixed stars forming the boundary of the world. [ABSTRACT FROM AUTHOR]