Thales of Miletus | Internet Encyclopedia of Philosophy

On May 25, 585 BC, Thales of Greece makes the first known prediction of a solar eclipse. From the article:

"Thales is acclaimed for having predicted an eclipse of the sun which occurred on 28 May 585 B.C.E. The earliest extant account of the eclipse is from Herodotus: 'On one occasion [the Medes and the Lydians] had an unexpected battle in the dark, an event which occurred after five years of indecisive warfare: the two armies had already engaged and the fight was in progress, when day was suddenly turned into night. This change from daylight to darkness had been foretold to the Ionians by Thales of Miletus, who fixed the date for it within the limits of the year in which it did, in fact, take place' (Hdt. I.74). The vital points are: Thales foretold a solar eclipse; it did occur within the period he specified. How Thales foretold the eclipse is not known but there is strong opinion that he was able to perform this remarkable feat through knowledge of a cycle known as the Saros, with some attributing his success to use of the Exeligmos cycle. It is not known how Thales was able to predict the Eclipse, if indeed he did, but he could not have predicted the Eclipse by using the Saros or the Exeligmos cycles.

In addition to Herodotus, the successful prediction of the eclipse was accepted by Eudemus in his History of Astronomy and acknowledged by a number of other writers of ancient times (Cicero, Pliny, Dercyllides, Clement, Eusebius). This is how Diogenes Laertius recorded the event: '[Thales] seems by some accounts to have been the first to study astronomy, the first to predict eclipses of the sun, and to fix the solstices; so Eudemus in his History of Astronomy. It was this which gained for him the admiration of Xenophanes and Herodotus and the notice of Heraclitus and Democritus' (D.L. I.23). Diogenes asserted that Herodotus knew of Thales's work, and in naming Xenophanes, Heraclitus, and Democritus, he nominated three of the great pre-Socratics, eminent philosophers who were familiar with the work of Thales.

Modern astronomy confirms that the eclipse did occur, and was total. According to Herodotus's report, the umbra of the eclipse of Thales must have passed over the battle field. The "un-naturalness" of a solar eclipse is eerie and chilling. All becomes hushed and there is a strong uncanny sensation of impending disaster, of being within the control of some awful power. In ancient times, the awesome phenomenon must have aroused great fear, anxiety and wonder. The combatants saw the eclipse as disapproval of their warfare, and as a warning. They ceased fighting and a peace agreement was reached between the two kings."