Using an Eclipse to Understand the Past.

Did you know that there will be 11,898 eclipses of the sun between the years 2000 BC and 3000 AD? This time period of 5000 years, which includes both past and future, witnesses a variety of different solar eclipses. 4,200 partial eclipses, 3956 annular eclipses, 3173 total eclipses, and 569 hybrid eclipses. 1 We usually think about predicting future eclipses, but what about the knowledge of past eclipses?

Using a Historical Eclipse to Determine Time.

Previous Solar Eclipse’s exact times and locations can be calculated very precisely. These exact times can be cross-referenced with historical records of events, and used to very accurately predict the time of such events. Using a combination of historical context, estimated time ranges, and a degree of interpretation, one can use the exact date of an eclipse as a "landmark" (or "timemark" in this case).

One of the major challenges is determining if the reports throughout history are actually accounts of total solar eclipses. "In some cases, a darkening of the Sun that was first interpreted as a solar eclipse is now believed to have been caused by a meteorological phenomenon."2 While the calculations of the past eclipses are extremely precise, the historical accounts of humans are often misinterpreted. This is increasingly true as you go back further in history.

There are numerous quotes from ancient texts dated before 0 AD, which contain very reasonable (and sometimes very direct) descriptions of an eclipse sighting. Some of the oldest quotes discovered go back as far as 2136 BC or 2159 BC. You can more than 200 quotes from this webpage: [Eclipse Quotations] compiled by David Le Conte. The quotes are chronologically ordered, ranging from ancient to modern times.

For those who might be interested, here’s a good starting point for learning more about eclipses throughout history: [https://en.wikipedia.org/wiki/Solar_eclipse#Historical_eclipses]

Examples of Quotes about Historical Eclipses


"Here lie the bodies of Ho and Hi, Whose fate, though sad, is risible; Being slain because they could not spy Th’ eclipse which was invisible."

Author unknown Said to refer to the Chinese eclipse of 2136 BC, October 21.


"On day kuei-yu (the 10th day of a 60-day cycle), it was inquired (by divination): ‘The Sun was eclipsed in the evening; is it good?’ On day kuei-yu it was inquired: ‘The Sun was eclipsed in the evening; is it bad?’"

From: the An-yang oracle bones of the Shang dynasty, China (c. 1550-1050 BC). Quoted in Encyclopaedia Britannica CD 98.


"On the day of the new moon, in the month of Hiyar, the Sun was put to shame, and went down in the daytime, with Mars in attendance."

Early Mesopotamian Records. Ugarit Eclipse of 1374 May 03 (1375 BCE)


To learn more, check out this NASA webpage: Solar Eclipses of Historical Interest by Fred Espenak. It has a table of historical eclipses and their "reference text", including links to the calculations of eclipse times and paths.

Eclipse of the Peloponnesian War

"the sun assumed the shape of a crescent and became full again, and during the eclipse some stars became visible."

Thucydides

Perhaps one of the most interesting historical eclipses was that which occurred during the Peloponnesian War. The Median and Lydian armies were fighting a battle, and upon witnesses a solar eclipse, stopped fighting and declared a peace.

"just as the battle was growing warm, day was on a sudden changed into night. This event had been foretold by Thales, the Milesian, who forewarned the Ionians of it, fixing for it the very year in which it actually took place. The Medes and Lydians, when they observed the change, ceased fighting, and were alike anxious to have terms of peace agreed on.""

[The Histories by Herodotus]

There are records of the approximate location of the battle, an estimate time period, and the fact that there was solar eclipse. Given these three pieces of information, you can then make an educated guess about which eclipse was seen. You can calculate the exact dates that each eclipse occurred at that location in that time frame. The eclipse of May 28, 585 BC (sometimes called the "Eclipse of Thales") corresponds well with the historical records, and therefore we now have an exact date for the battle.

Thales of Miletus is the astronomer mentioned by Herodotus. There is much debate on whether or not Thales actually predicted the eclipse3, but the fact remains that we are definitely able to now, and it has provided valuable insight into the dates of historical events.

Learn more from [Wikipedia: Eclipse of Thales] and [Wikipedia: History of the Peloponnesian War]

In Conclusion

The significance of eclipses has been felt throughout history, whether seen as an omen or an natural process of nature and planetary mechanics. I hope the reader appreciates the this perspective and thinks about how eclipses can be used as a "landmark in time", and that this property of time keeping applies to other aspects of astronomy.

Despite changing calendars throughout the ages, the properties of the cosmos have remained the same. Whether it is a pulsar, an eclipse, or the summer solstice, many of our greatest clocks are not created by humans, but are elements of the world beyond Earth.

References

"Mesopotamian Astronomy & Astrology: Astronomical Chronology", Staff.science.uu.nl, 2017. [Online]. Available: http://www.staff.science.uu.nl/~gent0113/babylon/babybibl_chronology.htm. [Accessed: 03- Jul- 2017].

F. Espenak, "NASA – Solar Eclipses of History", Eclipse.gsfc.nasa.gov, 2017. [Online]. Available: https://eclipse.gsfc.nasa.gov/SEhistory/SEhistory.html. [Accessed: 03- Jul- 2017].

"NASA – Total Solar Eclipse of 2017 Aug 21", Eclipse.gsfc.nasa.gov, 2017. [Online]. Available: https://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2017Aug21Tgoogle.html. [Accessed: 03- Jul- 2017].

"NASA Technical Publication TP-2006-214141", Eclipse.gsfc.nasa.gov, 2017. [Online]. Available: https://eclipse.gsfc.nasa.gov/SEpubs/5MCSE.html. [Accessed: 03- Jul- 2017].

"NASA Eclipse Web Site", Eclipse.gsfc.nasa.gov, 2017. [Online]. Available: https://eclipse.gsfc.nasa.gov/eclipse.html. [Accessed: 03- Jul- 2017].

"Thales biography", Www-groups.dcs.st-and.ac.uk, 2017. [Online]. Available: http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Thales.html. [Accessed: 03- Jul- 2017].


  1. Five Millennium Canon of Solar Eclipses: -1999 to +3000. "NASA Technical Publication TP-2006-214141" by Fred Espenak and Jean Meeus

  2. "Mesopotamian Astronomy & Astrology: Astronomical Chronology"

  3. http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Thales.html

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