Ptolemy's Almagest
A geocentric model so accurate it holds for 1,400 years.
- When
- Known to
- ± 20 years
- Era
- Classical, Holocene
Writing in Alexandria around 150 CE, Ptolemy assembles Greek astronomy into a mathematical system that predicts planetary positions using epicycles and equants with genuine accuracy. It is wrong about the arrangement of the solar system and right about a great deal else, and it works — which is why it survives until Copernicus and beyond. His Geography, with coordinates for 8,000 places, shapes mapmaking for as long.