**
Graziano & Raulin**

**Research Methods (8th edition)**

**Claudius Ptolemy** (2nd Century A.D.) was an Alexandrian
astronomer, mathematician, and geographer.

Ptolemy is best known for his development of a mathematical system of the order and function of the heavenly bodies. In his system the Earth was viewed as the stationary center of the universe, around which orbited the moon, the five then-known planets, and the sun. Surrounding this system were the fixed stars.

Ptolemy’s model was a true scientific theory that had been
developed with careful reason and mathematical precision. It was
successful in bringing together many astronomical observations into
a single unified theoretical model and depicted the complex set of
phenomena (planetary motion) as being controlled by a precise and
fairly simple law. This **geocentric system** (i.e.,
Earth-centered) was the major theory of planetary motion for 1300
years. It was eventually supplanted by the **Copernican
heliocentric system** (sun-centered) in the 16th Century.