Mind-Benders of Greek & Roman History
A Greek measured the Earth's 26,000-year wobble
Around 129 BCE the astronomer Hipparchus compiled one of antiquity's first great star catalogues, and by comparing his star positions with observations recorded about 150 years earlier he detected the precession of the equinoxes — the slow wobble of Earth's axis that completes a full cycle only every ~26,000 years. He inferred a cycle tens of thousands of years long from barely a century and a half of records, by eye and without a telescope.
How we know
Hipparchus c. 190–120 BCE; catalogue c. 129 BCE, compared with Timocharis' observations (~150 years earlier) → discovery of precession; the modern cycle is ~25,800 years.
One of many fact-checked wonders across eight traditions at The Spring of Wisdom.