Hellenistic Astronomy and Geography in Alexandria (3rd–1st centuries BCE)

1. Euclid composes the *Elements* in Alexandria

   Jan 1, 300 BCELabels: Euclid, Elements

   • Britannica
   • Elements

2. Timocharis begins systematic observations at Alexandria

   Jan 1, 290 BCELabels: Timocharis, Alexandria Observatory

   • Timocharis

3. Aristarchus advances a heliocentric hypothesis

   Jan 1, 270 BCELabels: Aristarchus, Heliocentrism

   • Britannica

4. Eratosthenes becomes head librarian at Alexandria

   Jan 1, 255 BCELabels: Eratosthenes, Library of

   • Britannica

5. Conon serves as court astronomer in Alexandria

   Jan 1, 245 BCELabels: Conon, Ptolemy III

   • Britannica

6. Callimachus compiles the *Pinakes* library catalog

   Jan 1, 245 BCELabels: Callimachus, Pinakes

   • Pinakes

7. Eratosthenes measures Earth’s circumference

   Jan 1, 240 BCELabels: Eratosthenes, Earth circumference

   • Britannica
   • OxfordAcad

8. Apollonius develops epicyclic–eccentric equivalence

   Jan 1, 220 BCELabels: Apollonius, Epicyclic models

   • Britannica

9. Eratosthenes outlines world mapping in *Geography*

   Jan 1, 215 BCELabels: Eratosthenes, Geography

   • Strabo
   • Britannica

10. Antikythera Mechanism built with advanced astronomical gearing

    Jan 1, 150 BCELabels: Antikythera Mechanism, Astronomical gearing

    • Antikythera

11. Hipparchus develops chord-based trigonometry

    Jan 1, 140 BCELabels: Hipparchus, Trigonometry

    • Britannica

12. Hipparchus completes a major star catalog

    Jan 1, 129 BCELabels: Hipparchus, Star catalog

    • Britannica
    • Britannica

13. Hipparchus identifies precession of the equinoxes

    Jan 1, 129 BCELabels: Hipparchus, Precession

    • Britannica

14. Posidonius re-estimates Earth’s circumference via Canopus

    Jan 1, 100 BCELabels: Posidonius, Canopus

    • EarthCirc
    • Posidonius