Ptolemy, an ancient Greek astronomer and mathematician, believed in the geocentric model of the universe, which placed Earth at the center with the Sun, Moon, planets, and stars orbiting around it. This model, known as the Ptolemaic system, was detailed in his work Almagest and was the dominant astronomical theory for over a thousand years.
Key Features of Ptolemy’s Model:
- Earth-Centered Universe – Earth was stationary at the center.
- Epicycles and Deferents – To explain the apparent retrograde motion of planets, Ptolemy introduced epicycles (small circular orbits) on top of deferents (larger circular orbits).
- Perfect Circles – He believed celestial bodies moved in perfect circles, following the philosophical ideas of Aristotle.
- Fixed Stars – The stars were thought to be embedded in a fixed outer sphere that rotated around Earth.
This model remained widely accepted until the heliocentric model proposed by Copernicus in the 16th century challenged it.