May 28, 585 BC: The Battle Of The Solar Eclipse
On this day, 28 May, in 585 BC, a fierce battle was underway in Asia Minor when the light vanished in the middle of the day causing the warring armies to lay down their arms and declare a truce. This famous solar eclipse was allegedly predicted by the Greek mathematician Thales of Miletus, and it provides a debatable calculation point for some major dates in ancient history. But how on Earth did he accomplish this incredible astronomical observation and subsequent prediction?
The Violence of Ancient Astronomy
Greek historian Herodotus wrote that Thales predicted a solar eclipse in a year when “the Medians and the Lydians were at war” and by reverse engineering the methodology used when calculating future eclipses, modern astronomers have been able to calculate precisely when historical eclipses occurred.
According to an entry on Moon Blink a total eclipse of the Sun occurred on 28 May, 0585 BC, Universal Time Old Style, with the maximum eclipse occurring at 14:22 UT, and the event is described as a “dramatic” total eclipse that plunged the Sun into darkness for 6 minutes and 4 seconds at maximum, creating an “amazing spectacle” for observers in a very broad path, 271 km wide at maximum. This spectacular event would have been seen by ancient cultures in central America, France, and northern Mediterranean countries while a partial eclipse would have been visible across the Americas, Europe, north Africa and north-western Asia.
On May 28, 585 BC, a total eclipse was witnesses Americas, Europe, north Africa and north-western Asia. (IgorZh / Adobe Stock)
The Mechanics of a Monumentally Difficult Prediction
The reason this astronomical event is thought of as being so important is that predicting a solar eclipse, compared with a lunar eclipse, is exceptionally difficult. The astronomer must not only calculate when it will occur, but where on Earth’s surface it will be visible and according to NASA, in a lunar eclipse the moon passes through the Earth's sun shadow and the phenomena is visible on the whole side of the Earth that is in nighttime, and they often last longer than an hour. In solar eclipses, however, the moon's shadow falls across the Earth in a comparatively narrow path with a maximum duration at any given location of about 7½ minutes.
So to accurately calculate a solar eclipse the observer requires an intimate understanding of the Moon's orbit around Earth to within fractions of a degree of accuracy, and what makes Thales’ prediction a historical mystery is that historians know early Greeks, at large, didn’t have this essential lunar data and there are no other records of Greek astronomers in this period accurately predicting any other eclipses. Thus, it is thought by historians that the only place Thales’ advanced astronomical knowledge could have come from was Egypt.
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The Birth of Geometry and Astronomy
Historians Herodotus (c. 450 BC) and Strabo (c. 24 BC) both said Greek mathematicians adapted many of the Egyptian calculation and surveying techniques, modifying and developing them with their own sophisticated advancements into a very refined system. Furthermore, it's known Thales studied Egyptian techniques for measuring sections of land with rope, and when his notes were transferred onto clay tablets by Greek geometers, and later codified by Euclid, geometry was born ( Geo -“Earth” and Metry -“Measure” in Greek).
Having learned so many practical mathematical skills, like bisecting angles, trigonometry and calculating passing time using shadows, from Egyptian surveyors, some researchers speculate that Thales may not have made the famous eclipse prediction himself, but may simply have lifted the date from the Egyptians.
Annular solar eclipse in desert with a silhouette of a dromedary camel. Liwa desert, Abu Dhabi, United Arab Emirates. (Kertu / Adobe Stock)
The Astronomical Conclusion of the Battle of the Solar Eclipse
Returning the war described in the opening paragraph, after 15 years of fighting, on 28 May 585 BC, the armies of King Aylattes of Lydia were in battle with the forces of King Cyaxares of Medes, near the River Halys in what is today central Turkey. Chroniclers noted the “heavens darkening” and soldiers on both sides laying down their weapons in awe of the spectacle and that the event ended both the battle and the war. The kings of Cilicia and Babylon intervened and a peace treaty was negotiated and the River Halys, where the “Battle of the Eclipse” was fought became the border between the Lydians and the Medes.
While most astronomers would agree that May 28, 585 BC, is the most likely candidate date for Thales’ predicted eclipse, a Wired article says this famous astronomical event has been debated by hundreds of scholars for nearly two millennia and that some authorities believe Thales’ eclipse may have occurred 25 years earlier in 610 BC. But the reason most agree with the 585 BC date is the record of the famous battle in Asia Minor ending when “the day was suddenly turned to night”.
Top image: The total solar eclipse of May 28 585 caused a cease in fighting between the Medians and the Lydians. Source: zef art / Adobe Stock
By Ashley Cowie