Astronomical Images : Representation of the lunar eclipse of Gaugamela

Peter Apian

Astronomical Images

As part of his ambitious work, Astronomicum caesareum, Peter Apian proposed a method of using astronomical calculation to improve the dating of significant historical events. In this way, he drew not only on existing astronomical traditions, but also on the traditions of Christian chronology as established by Eusebius and others. Tabular chronologies of the sort introduced by Eusebius lined up important events in the different ancient states, synchronising the lives of rulers from various dynasties. These chronologies, however, offered approximate dates only; besides operating only in whole years, rather than months or days, the events were presented sequentially and thus an incorrect date could throw off the accuracy of all subsequent dates in a given chronicle. Appreciating these inherent problems, Apian conceived of his work as offering a basis for a radical transformation of historical scholarship, arguing that attention to dateable eclipses recorded in the historical sources could provide an enhanced level of precision. To support this argument, he included in his Astronomicum caesareum detailed treatments of past, present, and future eclipses. The image seen here is a representation of the first eclipse discussed by Apian - that associated with Alexander's defeat of Darius at Gaugamela. This event was thought to have particular historical and theological significance. According to Biblical exegesis, there were to be four, and only four, empires between the Flood and the coming of the Messiah: the Assyrian, the Medo-Persian, the Greek, and the Roman. The defeat of Darius (and therefore Persia) by Alexander thus represented a crucial event in this historical narrative, midway between the Flood and the Millennium. But like other dates in the medieval chronologies, this event was only dated approximately in reference to a previous event; Eusebius, for example, placed it 4871 years after Creation. Using Plutarch's assertion that the defeat occurred eleven days after a total lunar eclipse in the Athenian month of Boedromion, Apian was able to examine possible full moons and claim that only the one on 28 June 326 BC could have undergone an eclipse in question. By thus applying his astronomical knowledge to historical chronology, Apian was able to fix the change of empires not only to a year, but to a month and day. (It is worth noting, however, that calendrical and historical accounts not considered by Apian show that the actual eclipse of Gaugamela took place five years before the date given by Apian, on 20 September 331 BC.) It was by this method of examining celestial events in relation to terrestrial ones that Apian hoped to offer a greater level of precision in historical dating.