New Light on the Relationship between the Montecitorio Obelisk and Ara Pacis of Augustus

Abstract

The article takes as its point of departure recent work [Frischer forthcoming] critiquing the theory of Edmund Buchner about the relationship of the gnomonical instrument known as the Horologium Augusti and the Ara Pacis Augustae. As a result of this critique, the Montecitorio Obelisk could be situated with greater precision on the map of the city. A computer simulation showed that Buchner erred in positing that the shadow of the Montecitorio Obelisk went into the center of the Ara Pacis on Augustus' birthday. In this article, computer simulations are used to develop a post-Buchnerian interpretation of the relationship of the obelisk and altar. Over 230 hitherto unrecognized solar and shadow alignments are reported. The first part of the article defines four zones around the monuments where the solar and shadows observations were made. In the second part of the article, specialists interpret the significance of the annual solar and shadow spectacle from various points of view. The conclusion synthesizes the results, arguing that the monuments were intentionally aligned and situated in order to propagate the same message as the one inscribed on two sides of the Montecitorio Obelisk [CIL 6.702 = ILS 91]: that Augustus was a devoted worshipper of the sun god (Sol), who brings Rome victory in time of war, and prosperity in time of peace through his earthly representative, the emperor. From 13 to 9 BC Augustus initiated projects in the Northern Campus Martius to erect the Ara Pacis, Montecitorio Obelisk, and the gnomonical device generally known as the Horologium Augusti.2 The projects had two motivations closely related to the two ways we can couple the monuments: obelisk-gnomonical device and obelisk-Ara Pacis. The obelisk-gnomonical device pair is functionally bound, serving the purposes of accurate time-keeping. The obelisk supported a sphere on a rod attached to the top of its pyramidion, and the shadow of the sphere hit a crosshatch inscribed on the meridian line at local noon each day of the year. The obelisk-Ara Pacis pair appears to have served the purpose of expressing the symbolism of imperial ideology, since the two monuments are visually bound but have no functional connection. They have a similar orientation, and the obelisk stands athwart an extension westward of the altar's axis of symmetry. In recent years, the attention of scholars has been concentrated more on the first than on the second pair. This paper shifts the focus to the second pair and its motivation. It has two goals: to present a series of recently discovered solar and shadow axial alignments between the sun, the Ara Pacis, and the Montecitorio Obelisk that could be seen in the Campus Martius and Campus Agrippae during the reign of Augustus and beyond (for the location of these monuments, see the map on figure 1), and to interpret these alignments from various, mutually reinforcing points of view. We shall argue that the major motivation in erecting the monuments and siting them as they were was to create a recurrent sun and shadow spect...

Horologium Augusti and the Reckoning of Time

“…Actually, it is not clear from [17], what is the uncertainty of this result (at the same time, it is not given the uncertainty of the 3D model). Let us remember that the uncertainty is the experimenter's estimate of how far an experimental quantity might be from the "true value."…”

“…A third reason is coming from some recent simulations proposed in [16,17], made by a team led by Bernard Frischer, Indiana University Bloomington. The result is the following.…”

“…The model of that part of the Campus where the Ara Pacis was placed is based on the excavation and reconstruction of the altar made by Giuseppe Moretti and Guglielmo Gatti, in 1937-38. For what concerns the obelisk, the positioning of it within the reconstruction required "an inferential method, whose results can be controlled by the data produced by unpublished corings undertaken by Edmund Buchner" [17]. As previously told, the Frischer's simulations in his 3D reconstruction of the Campus Martius is giving another date, October 9, and not the equinox.…”

“…In [17], we can read that the simulation was made on year 9 BC. A note of the article tells that the team was aware of the fact "that in that year, the calendar had not yet been re-synched to the leap year.…”

Reconciling the dissonance between Historic Preservation and Virtual Reality through a Place-based Virtual Heritage system.

“…Both these projects serve as constructivist tools for educating students in archeology and historic preservation (Frischer 2008;Frischer 2017). The former project enabled archaeology students to virtual travel through time from the present archaeological site to reconstructed landscapes of the past.…”