When did ptolemy live?

Ptolemy invented improved projections. It is known that a world map based on the Geography was on display in Autun (France) in late Roman times. read more

Ptolemy was important in the history of astronomy because he A) developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries. B) developed a scientifically accurate model of the universe. C) was the first to believe in an Earth-centered universe. read more

One reason is that Ptolemy estimated the size of the Earth as too small: while Eratosthenes found 700 stadia for a great circle degree on the globe, Ptolemy uses 500 stadia in the Geography. It is highly probable that these were the same stadion, since Ptolemy switched from the former scale to the latter between the Syntaxis and the Geography, and severely readjusted longitude degrees accordingly. read more