- Aristotle believed the universe to be spherical and finite. The earth was thought to be in the center.
Astronomy
A likely impossibility is always preferable to an unconvincing possibility.
- Four elements made up the central part of the universe: earth, air, fire, and water.
- These elements each have their own place in the universe determined by their heaviness or 'specific gravity.'
- They each move in a straight line towards that place, making terrestrial motion linear, and stopping once reaching their respective proper places.
- Contrary to the central part of the universe, he believed the heavens to move continually in a circle. He determined that it must be of a different element, which he termed aither.
- Aither was defined as incapable of change other than change in location.
