Equant
Ecuante
- Date
- 150 · confidence medium
- Place
- Alexandria, Egypt
- Credited to
- Ptolemy
- Field
- Cosmos & Earth
What it is
An auxiliary mathematical point introduced by Ptolemy to account for the observed changes in speed of planetary motion while preserving the appearance of uniform circular motion.
What it led to
- key element of the Ptolemaic geocentric model for over a thousand years
- object of criticism among Arab and European astronomers
- indirect spur to heliocentric alternatives such as Copernicus's