In this system the entire universe was part of a great sphere.
This sphere was split into two sections, an outer celestial realm and an inner terrestrial one.
The dividing line between the two was the orbit of the moon.
While the earth was a place of transition and flux, the heavens were unchanging..
Greek philosophers estimated the distance to the Moon, and even tried to calculate the size of the entire universe.
They believed it was finite.
The outer sphere of the stars carried them on their nightly course around the Earth.
The natural place for earthy material was down at the center of the universe..
In Aristotle's Cosmology, each of these four elements (earth, water, fire and air) had a weight.
Earth was the heaviest, water less so, and air and fire the lightest.
According to Aristotle the lighter substances moved away from the center of the universe and the heaver elements settled into the center..
Greek cosmology.
The first “cosmologies” were based on creation myths in which one or more deities made the universe out of sheer will, or out of their bodily fluids, or of the carcass of some god they defeated, etc.
A few examples of such “theories” of the universe are provided in this chapter..
Anaximander was a pre-Socratic Greek philosopher who is widely referred to as the "father of astronomy" and even as the "father of cosmology" as a result of his works to explain the origin and makeup of the physical universe.
He is regarded as the most important of the Ionian philosophers, and was a pupil of Thales..
Aristotle’s cosmology belonged to the class of steady-state theories in so far that his universe was changeless and eternal
When Einstein in 1917 proposed the first relativistic model of the universe, he unwittingly pictured a universe which had qualitative features in common with Aristotle’s: it was finite in space, but infinite in time
