Astronomical chronology

Astronomical chronology, or astronomical dating, is a technical method of dating events or artifacts that are associated with astronomical phenomena. Written records of historical events that include descriptions of astronomical phenomena have done much to clarify the chronology of the Ancient Near East; works of art which depict the configuration of the stars and planets and buildings which are oriented to the rising and setting of celestial bodies at a particular time have all been dated through astronomical calculations.

Astronomical dating can be a powerful tool for establishing absolute chronologies, but...
it can easily produce precise and impressive looking results based on invalid assumptions –
results so precise and impressive they may not be questioned by scholars in other fields.

The use of descriptions of astronomical phenomena to date historical events began in the 16th century, a time of a renewed humanistic interest in history and of increasingly precise astronomical tables.Eclipses in particular are relatively infrequent events and can be dated precisely. When the circumstances are not exact and descriptions leave ambiguities, one can often use other details such as the month of the eclipse or the position of other stars and planets to identify the specific eclipse.

Astronomical dating, like other forms of historical interpretation, requires care in interpreting the surviving written records. John Steele has proposed three questions that must be asked when dating an event: Does the record refer to an actual astronomical event, or is this merely a modern assumption? If it does refer to an actual astronomical event, is the source reliable? Can the record provide an unambiguous date without making unwarranted assumptions about ancient astronomical observational methods?

Babylonian astronomical diaries provide detailed and unambiguous accounts of the positions of all the visible planets, often in relation to specific stars, that have been used to provide precise dates of events like the defeat of Darius III by Alexander the Great at the Battle of Gaugamela on 1 October 331 BCE and of Alexander's subsequent death on 11 June 323.

Since the success of this method depends on the reliability of the written sources and the precision of their accounts of astronomical phenomena, attempts to date literary texts which may describe astronomical events loosely or even as metaphors have led researchers to conclusions that appear precise, but rely on invalid assumptions and are consequently less widely accepted. Thus the attempts to date Vedic texts describing the Pleiades as rising "due East" to about 2300 BCE, which is the time when the Pleiades rose "exactly" due East, is complicated by the fact that poetic descriptions need not be taken as reflecting precise astronomical observations, while precession is a very slow process which makes only small changes in the azimuth of a star rising in the East.

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