Hipparchus of Nicaea (Ἵππαρχος ὁ Νικαεύς)

Life Hipparchus was a Greek astronomer, geographer, and mathematician, born in Nicaea in Bithynia and active during the 2nd century BCE. His recorded astronomical observations date from 147 to 127 BCE [1]. He conducted most of his work from Rhodes, and his career marks a pivotal shift in Greek astronomy toward systematic observation and mathematical modeling [1].

Works Almost all of Hipparchus’s original writings are lost, known primarily through later sources like Ptolemy’s Almagest [1][2]. His only surviving work is a commentary on the Phaenomena of Aratus and Eudoxus [1][2]. His major contributions, as reported by ancient sources, include a star catalog of roughly 850 stars, studies on the lengths of the year and month, the discovery of the precession of the equinoxes, and works on solar and lunar theory [1][2]. He also wrote a critique, Against the Geography of Eratosthenes, and produced foundational works in trigonometry, including the first known trigonometric table [1][2].

Significance Hipparchus is considered the greatest astronomical observer of antiquity and the founder of trigonometry [1][2]. His meticulous observations and mathematical models, such as the use of epicycles, provided the empirical foundation for Ptolemaic astronomy. His discovery of precession was a monumental achievement, and his critical methodology influenced later science [1][2].

Sources 1. Stanford Encyclopedia of Philosophy: Hipparchus (plato.stanford.edu): https://plato.stanford.edu/entries/hipparchus/ 2. Encyclopædia Britannica: Hipparchus (Greek astronomer) (britannica.com): https://www.britannica.com/biography/Hipparchus-Greek-astronomer