the histories

Throwback Thursday: Eclipse of Thales 585 BC

Posted on Updated on

Ancient Origins Total Eclipse Image One
Image Credit: Ancient Origins

Two thousand, six hundred and five years ago, today (roughly speaking)

The eclipse of Thales was a solar eclipse that was, according to The Histories of Herodotus, accurately predicted by the Greek philosopher Thales of Miletus. If Herodotus‘s account is accurate, this eclipse is the earliest recorded (per Isaac Asimov) as being known in advance of its occurrence. How, exactly, Thales predicted the eclipse remains uncertain […].

According to Herodotus, the appearance of the eclipse was interpreted as an omen and, interrupted a battle in a long-standing war between the Medes and the Lydians. The fighting immediately stopped and they agreed to a truce. Because astronomers can calculate the dates of historical eclipses, Isaac Asimov described this battle as the earliest historical event whose date is known with precision to the day and described the prediction as the birth of science.

Ancient Origins Annular Eclipse Image Two
Photo Credit: Ancient Origins

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 […]. [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 night-time […]. [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 7 1/2 minutes.

Moon Blink Eclipse Track Image Three
Eclipse Track
Image Credit: Moon Blink

[What] makes Thales’ prediction [an] 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. [It’s] known [that] Thales studied Egyptian techniques for measuring sections of land with rope […].

Returning [to] the war (mentioned above), after 15 years of fighting, on May 28, 585 BC, the armies of King Aylattes of Lydia were in battle with the forces of King Cyaxares of Medes (or, possibly, Astyages, his son), 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 […]. [The] event ended both the battle and the war.

[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.

Additional Reading & Sources:
The Battle of the Solar Eclipse (Ancient Origins)
Total Solar Eclipse of May 28, 0585 BC (Moon Blink)
Happy Birthday to Science (Web Archive)
Battle of the Eclipse (Wikipedia)
Eclipse of Thales (Wikipedia)
Predicted Solar Eclipse Stops Battle (Wired)