Alignments of Greek temples and the full moon: an astronomical perspective on the openings in the gable of the Artemision in Magnesia – Sara Wanek

Magnesia at the Maiandros is situated in Asia Minor, more precisely between the two ancient cities Tralleis and Ephesus. After being afflicted by floodings and epidemics, the city was refounded in 397 BC near the river Lethaios. The pseudodipteral temple of Artemis Leukophryene and its architect Hermogenes were already mentioned in Vitruvius de architectura. Even tough Hermogenes is unlikely to be the inventor of the pseudodipteral construction of Greek temples; the building generated great interest in the archaeological community. That led to the first excavations in that area starting in 1830 lasting to this day. In 1890 C. Humann documented the temples features in detail. To this day these drafts remain the most adequate source where the structure of the Artemision is concerned. Besides the temple the agora, the temple of Zeus, the theatre, the so-called theatron, the so-called market basilica, two gymnasiums and the stadium have been excavated.
Although the streets of Magnesia were arranged following the Hippodamian grid plan, the temple district does not fit this pattern. In addition to the temple, the district includes an altar with a separate space for sacrificial animals and an area that has been interpreted as a holy spring.
Looking at the temple, its remarkable features consisting of three distinctive windows in its gable, immediately attract attention. Ever since the time of the first expansive documentation of the building by C. Humann, the meaning, as well as the function, of these openings have been discussed controversially. These striking features can also be found in other buildings. Among these are the younger dipteros of Artemis in Ephesus, the so-called Serapeion in Ephesus, the temple of Augustus in Antiocheia and the so-called temple of Jupiter in Baalbek. The origin of these windows cannot be unambiguously traced and even more difficulty poses the interpretation of their function. A common explication for the design of the gable is the improvement of the statics. Furthermore, the possibility to access the temple for cleansing and air supply for the roof dealt as interpretations. The most widely acclaimed explaining tries to combine the function of the openings with rituals that are connected with the cult of Artemis. It was assumed that on some days the cult statue was shown through the windows. O. Bingöl follows an astronomical approach. He assumed that the windows are aligned with the full moon of the month of artemision (March or April) to illuminate a statue inside the temple. This phenomenon is supposed to have taken place as part of special festivities around the spring equinox. The hypothesis served as a basic concept for the examination of full moon alignments of Greek temples.
First of all, ancient astronomical knowledge concerning the moon and its orbit had to be examined. In comparison with the sun, the moon does not show an identical position in the sky on a specific day every year. Added to this, the earth’s moon has its characteristic phases that make correct predictions even more difficult. As there are two different approaches for dating the Artemision at the very beginning of the 2nd century BC and in the years between 150 and 130 BC, the 2nd century BC has been considered for the existing astronomical expertise. Thus, it can be said that the astronomical and mathematical foundation for carrying out a full moon alignment existed already at that time. To name but a few, Anaxagoras and Aristarchus, were able to explain and predict the phases of the moon. Already in the 5th century BC the foundation for astronomical time keeping had been laid. Since Eudoxus of Cnidus mathematical models have been used for predictions, in addition to observations of the sky. Additionally, the rules for intercalary years, which where used for calendars, show a profound astronomical knowledge. Exact measurements, which are required for correct alignments could have been realized as well. This can be seen at the extraordinary water supply system at Samos designed by Eupalinos.
After dealing with the astronomical foundations, a 3D model was designed by using the example of the Artemision in Magnesia. In order to analyse the alignment, the appearance of the temple has been simplified. The challenging parts of the reconstruction were the design of the ceiling and the height of the columns, as they are only fragmentarily preserved. Furthermore, the size of the cult statue can only be estimated. The examination of the model showed a line of sights between the opening and the statue. These discoveries led to a further astronomical investigation of the temple, which was carried out with Stellarium, a virtual planetarium programme. The experiment shows that windows with the same dimensions as found in Magnesia can easily be aligned with the full moon. Using the measurements of O. Bingöl it can be seen, that the light of the full moon phase shines through the window at least two times a year, in spring and autumn. The study was carried out for the whole 2nd century BC, as the dating of the temple is still discussed. For Magnesia it is therefore likely, that the function of the gable openings has to be associated with the moon. This fact cannot be transferred without further ado as an interpretation for all other windows in gables. As the astronomical studies were carried out with data by C. Humann and O. Bingöl further measurements and a landscape model are still necessary to exclude any doubt which might be awoken by the full moon alignment theory.