The Greek astronomer Hipparchus of Nicaea, working on Rhodes, compared his own star positions with those recorded a century and a half earlier by Timocharis and Aristyllus. He found that the stars had shifted slowly along the ecliptic, and concluded that the point where the Sun crosses the equator at the equinox creeps westward by at least one degree per century. The true figure is about one degree per 72 years, caused by the slow wobble of the Earth's axis. Hipparchus also compiled one of the first star catalogues and developed early trigonometry. His results reached later astronomers through Ptolemy's Almagest.
Before and after
- 141 BCEPaper
- 2nd century BCEVenus de Milo
- 139 BCEZhang Qian's mission opens the Silk Road
- 134 BCETiberius Gracchus is murdered and the Republic enters its crisis
- c. 131 BCEHipparchus discovers the precession of the equinoxes
- from 111 BCE to 105 BCEJugurthine War
- 3 January 106 BCEBirth of Cicero
- 104 BCEEstablishment of Qumran
- 2nd century BCEOrigins of Vienna
More in Science & technology
- 4th century BCEElements
- 3rd century BCEArchimedes' principle
- c. 241 BCEEratosthenes measures the size of the Earth
- 190 BCEBirth of Hipparchus
- 105 CECai Lun reports the invention of paper
- c. 150sPtolemy writes the Almagest
The era
This moment belongs to the Ancient civilizations (3,200 BCE to 500 CE), writing, cities and empires. You can also browse everything in the 2nd century BCE.