All the heavens just and true: cultural and historical astronomy in manuscript collections from Georgia

All the heavens just and true: cultural and historical astronomy in manuscript collections from Georgia

Australian Higher Education Graduation Statement (AHEGS):

This study reviews astronomical writings preserved in Georgian manuscripts produced from the 10th to the 20th century. Excerpts of religious treatises, astronomical-meteorological prognostications, calendrical writings, and later technical works are translated from over 350 manuscripts. Two case studies are also presented. Analysis of a 17th-century Georgian brontologion ('thunder book') suggests the christianisation of a 4th-century Georgian king was associated with a solar eclipse. Computer simulations show a solar eclipse in A.D. 319 was visible at the king's presumed location (but not necessarily in the valley below, as later sources recount), five years before the date conventionally held by historians today.

The present study is about premodern astronomy in the former Soviet Republic of Georgia. The focus is on cultural astronomy, which (in broad terms) investigates how people viewed and thought about the sky, in a wider cultural context. I also investigate writings relevant to applied historical astronomy, which uses naked-eye observations to address modern problems in astronomy and geophysics.

The core of this study is a chronological listing and review of astronomical and calendrical written sources in manuscripts comprising the four principal Georgian-language collections (fonds A, H, Q, and S) of the Korneli Kekelidze Georgian National Centre of Manuscripts (GNCM), located in Tbilisi, Georgia. From these approximately 9,000 manuscript codices (out of an estimated 11,000 extant worldwide), I discuss 532 produced in the 10th to early 20th century and translate – most for the first time into English – excerpts from over 350 manuscripts. I also give extended translations of several calendrical or astronomical-prognostication works preserved in Manuscripts (MSS) A-38, A-65, A-85, A-290, and A-620.

This review of Georgian manuscripts reveals written material that enhances our understanding of cultural astronomy as well as data of potentially scientific use to applied historical astronomy. Of the manuscripts with astronomical or calendrical material, those produced before the 18th century are, almost without exception, ecclesiastical in nature, whereas manuscripts devoted to philosophical or scientific topics appear generally only later. Many, if not most, of the writings are duplicated in multiple copies. This material encompasses a variety of religious treatises of an astronomical or chronological nature; prognostications and similar works based on astronomical, meteorological, and other natural phenomena; calendrical writings of varying sophistication; and later technical works, both original and translations into Georgian. Especially noteworthy are King Vakhtang VI's translation efforts, 19th-century observations of total solar eclipses (TSEs), and innovative guides on determining the date of Easter based on the Georgian calendar.

Two case studies are also presented. In the first, I analyse a Georgian brontologion ('thunder book') preserved in MS A-620. For each month of the year starting in January, the brontologion gives succinct, formulaic predictions of political well-being, weather, agriculture, and popular health, based on the occurrence of specific natural phenomena: solar and lunar eclipses and halos, thunder, lightning, rainbows, earthquakes during the day, and earthquakes at night. At times, predictions are left out. In one instance, the syntax of the following prognosis points to an intentional omission, specifically with respect to solar eclipses in July. Whereas solar eclipses typically bade ill, I suggest that the copyist (or earlier redactor) of MS A-620 associated such events in July with miraculous accounts of the christianisation of the royal family of Georgia.

The second case study builds on the first. In the early 4th century, a sudden return of daylight after a darkening of the sky purportedly swayed King Mirian III of eastern Georgia (Kartli) to convert to Christianity. Medieval written sources and modern geophysical models indicate the possibility that Mirian, whilst on a mountain top near the city of Mtskheta, may have observed a TSE. Adjusting for both visibility corrections and constraints on the accumulated clock error known as ΔT, the local circumstances are examined of the TSE of 6 May 319, which Gigolashvili et al. 2007, 2009 have proposed as the most likely natural explanation. If the basis for the legendary accounts of Mirian's conversion is this TSE, then the value of ΔT inferred from written sources agrees well with generally accepted values, such as those derived by Morrison and Stephenson 2004, namely, ΔT ≈ 7,450 ± 180 s in 319. Computer simulations show that the TSE of 6 May 319 would have been visible to the king and his entourage at his presumed location but not to the townspeople in the valley below – a crucial element in later Georgian sources. If it is the TSE of 6 May 319 that ancient and later written sources recount, then the date of Mirian's hunting expedition was five years earlier than 324, the year conventionally held by historians today.