Plenary Lecture: The Ara Pacis and Montecitorio Obelisk of Augustus: A Simpirical Investigation

Presenter: Bernard Frischer (School of Informatics, Indiana University)

This talk first reports on research undertaken to determine the validity of Edmund Buchner’s theory that the Montecitorio obelisk was aligned to the Ara Pacis such that during the day of Augustus’ birthday (September 23, according to Buchner) the shadow of the obelisk proceeded down the equinoctial line of a hypothesized horizontal sundial inscribed on a monumental pavement to or toward the center of the Ara Pacis. The research project developed and utilized: two new, independent surveys of the meridian fragment discovered by Buchner under the building at Via di Campo Marzio 48; the newly-available Edmund Buchner Archive housed at the AEK, Munich; and an interactive computer simulation of this area of the ancient city as well as the apparent path of the sun in the sky during the period 9 BC to 40 AD. The major conclusions reached by the research project are that: (1) Buchner was correct to postulate a solar alignment between the Ara Pacis and the obelisk; (2) Buchner’s positioning of the meridian and obelisk should be corrected; and (3) once these corrections are made, Buchner’s theory is not confirmed. Finally, (4) the computer simulation suggests that an alternative theory may better account for the alignment, viz., that the point was to stand on axis with the east entrance of the Ara Pacis on the Via Flaminia and see the sun’s disk seemingly centered on the top of the pyramidion of the obelisk during the afternoon of October 9. That date is significant: it is the festival day of Apollo Palatinus, a god with whom Augustus had a particularly close relationship. I conclude with some general remarks about simpiricism: a new methodology made possible by interactive simulations of historical monuments and sites. Simpiricism holds great promise for the disciplines of archaeology as well as architectural, art, and cultural history.