Eclipses and history: from Thales to Christopher Columbus
The battle halted in 585 BC, the ruin of Nicias at Syracuse, Columbus's ruse in Jamaica: the eclipses that have left their mark on history.
Eclipses do not belong to astronomy alone. Because of their sudden and spectacular nature they have halted battles, influenced military decisions and allowed those who could predict them to wield extraordinary power. Ancient and modern sources preserve some famous episodes that show how heavily the sky has weighed on human affairs, from Asia Minor to Sicily and the Caribbean.
The battle of the eclipse
Herodotus, in the first book of his Histories, relates that during a war between the Lydians and the Medes, in the sixth year of fighting, day suddenly turned into night in the middle of a battle. The two armies, terrified, stopped fighting and made peace, sealed by a marriage between the two royal houses. The historian adds that Thales of Miletus had foretold this change to the Ionians, naming the year in which it would occur.
Modern astronomers usually identify the phenomenon with the total solar eclipse of 28 May 585 BC, visible in Asia Minor. How Thales could have predicted it remains debated: perhaps he knew cycles of Babylonian origin, but a precise prediction of where it would be visible was beyond the knowledge of the time, and some scholars doubt the historicity of the episode.
Nicias at Syracuse
Thucydides, in the seventh book of the History of the Peloponnesian War, tells one of the most dramatic episodes linked to a lunar eclipse. In the summer of 413 BC the Athenian army was besieging Syracuse without success and its commander Nicias had decided to withdraw. Just then the Moon was eclipsed. Nicias, much given to omens, accepted the advice of the soothsayers, who counselled waiting «thrice nine days» before moving.
The delay was fatal. The Syracusans blocked the harbour, the Athenian fleet was destroyed and the army, retreating overland, was wiped out; Nicias himself was put to death. The eclipse, dated by astronomers to 27 August 413 BC, has remained a textbook case in which the interpretation of a celestial phenomenon had decisive military consequences.
Columbus in Jamaica
In 1503, during his fourth voyage, Christopher Columbus was stranded in Jamaica with his ships damaged. After some months the island's inhabitants stopped supplying the Spaniards with food. According to the account of his son Ferdinand, Columbus knew from an astronomical almanac, usually identified with Regiomontanus' Ephemerides, that there would be a lunar eclipse on 29 February 1504, and announced that God would show his anger by darkening the Moon. When the Moon did grow dark, the provisions began to arrive again.
Eclipses as documents
Eclipses recorded in ancient sources are also precious for chronology. Since their date can be calculated precisely, they make it possible to fix events that would otherwise be uncertain. A solar eclipse mentioned in the Assyrian eponym lists, commonly identified with that of 15 June 763 BC, is one of the cornerstones of the chronology of the ancient Near East, because it anchors an entire sequence of years to an absolute date.
Comparing the eclipses recorded in Babylon, in China and in the Greek world with theoretical predictions has also allowed modern astronomers to measure the slow slowing of the Earth's rotation over the millennia. An eclipse described by a scribe or a historian thus becomes a scientific datum, able to speak across a distance of more than two thousand years.
From Thales to Columbus, the history of eclipses is also the history of knowledge as a form of power. Those who knew the cycles of the sky could turn terror into prediction, and prediction into authority; those who did not remained at the mercy of an omen, as happened to the Athenians before Syracuse and to the people of Jamaica before Columbus's ships.