Eclipse of Thales stops a battle

In the account of the Greek historian Herodotus, the Lydians under King Alyattes and the Medes under King Cyaxares had been at war in Anatolia (modern Turkey) for five years without a decisive result. In the sixth year, in the middle of a battle, day suddenly turned to night. Both armies stopped fighting, and the kings agreed to peace. The agreement was sealed by a marriage between Alyattes' daughter Aryenis and Cyaxares' son Astyages, and the Halys River became the border. Herodotus adds that Thales of Miletus had told the Ionian Greeks in advance which year the darkness would come.¹

Astronomers who have computed ancient eclipse paths find that a total eclipse of the Sun crossed Anatolia on May 28, 585 BCE, which makes it the best match. That turns a story into one of the earliest firm dates in Greek and Near Eastern history, and scholars use it to date Thales and the Lydian and Median kingdoms. How Thales could have known is unclear. Babylonian astronomers had kept eclipse records for centuries (see the Babylonian astronomical diaries) and may have noticed that eclipses repeat after a cycle of about 18 years, later called the Saros, though it was probably not yet reliable for prediction. But a cycle tells you an eclipse is possible somewhere, not that it will be total over a particular country, so many historians doubt that any real prediction was possible.²³

Herodotus wrote about 150 years after the event, so the tale may have grown in the telling, and some older studies proposed other eclipses. Even so, later Greek writers made it the founding story of Greek science: a thinker who could read the sky without gods or omens. The eclipse itself remains a rare case where a physical event fixes a date for the ancient world.¹³