Earth's Place in the Universe
Discoveries Leading To Modern Astronomy
Claudius Ptolemaeus (~100-170 CE), also know simply as Ptolemy, was an Egyptian astronomer, geographer, and mathematician (of Greek descent) who became well known in the Alexandria philosophical community in the 2nd century. Although Ptolemy made a variety of important, if not interesting, contributions to knowledge of his times, perhaps his most significant, and long lasting, was his observations of the orbits of planets and constellations. He promoted the geocentric model, that Earth was the center of the observable Universe. The ancient Greek, Roman, and Muslim astronomers followed the geocentric model (or Ptolemaic system) that described the Universe with the Earth at its center.