Campus Martius, also known as the Campus of Mars, was built by the Roman Senate just outside the ancient Rome city walls back in 9 BCE. It was built to celebrate the peace brought upon the Roman people as a result of Emperor Agustus’s military conquests. Thanks to a complex computer simulation created by the Institute for Digital Intermedia Arts (IDIA) for Indiana University's School of Informatics and Computing, it is now possible to verify if and how solar alignments influenced the positioning of the different objects on site.
While the the original site can be studied directly, the excavation ground is located 20 feet (6.1 m) below today’s ground level. This, and the fact that the key artifacts have been moved from their original locations on the Campus, makes studying solar alignments somewhat difficult.
The bulk of research based on the simulation has so far been focused on the interplay of light and shadow that must have occurred between the Altar of Peace (Ara Pacis) and the 71-foot-high (21.6 m) Obelisk of Montecitorio – a red granite structure removed from Heliopolis in ancient Egypt and brought to Rome by Augustus in 10 BCE.
The simulation has already shed some light on the solar relationship between the two objects. It helped disprove the long-established theory proposed by German scholar Edmund Buchner, who believed that the obelisk, serving as a gnomon (pointer) of a huge sundial on the plaza floor, would cast a shadow exactly towards the middle of the Ara Pacis on September 23 to celebrate the beloved emperor’s birthday.
The modeling (which can be seen in the video at the bottom of the page) shows that although the shadow would indeed fall relatively close to the door opening, an intentional alignment can be ruled out. What then was the logic behind the positioning of the giant obelisk against the altar?
"What’s important is not the shadow of the obelisk, but the sun’s disk seen over the center of the top of the obelisk from a position on the Via Flaminia in front of the Ara Pacis," says Bernard Frisher, an Indiana University Bloomington School of Informatics and Computing professor, and co-author of a paper on the simulation. Via Flaminia, an ancient road from Rome to the Adriatic Sea, was adjacent to the two landmarks in question and positioned in parallel to them.
Ismini Miliaresis, Frisher’s research assistant, investigated the location of the meridian line, a horizontal line aligned with a gnomon on a meridian, used to indicate the day of the year and figure out the length of the solar year. Meanwhile, engineer Paolo Albèri Auber focused on refining the data regarding the obelisk’s original size. The exact position of the sun in Augustus’s times was calculated based on NASA’s Horizons System, which enables scientists to model the position of solar system bodies in the sky at any time in history and in relation to any chosen observation spot on earth.
The resulting dataset was used to digitally recreate the 490-acre (198-hectare) Campus Martius site in unprecedented detail. The Institute for Digital Intermedia Arts Lab of The Ball State University, lead by John Fillwalk, used the Unity game engine to craft an interactive model of the site. Another photorealistic model was built in 3D Studio Max and Autocad by Matthew Brennan, a research scientist at Indiana University School of Informatics, to produce images and videos illustrating the research.
The observations of the resulting simulation lead to the discovery that the actual solar alignment, or the moment when the sun would be placed at the top of the obelisk as seen from Via Flaminia, would occur on October 9. This means that the birthday present was intended not for Augustus but for Apollo. "No other date on the Roman religious calendar would have been as appropriate as this" says Fischer. "And the most lavish new temple Augustus built, the Temple of Palatine Apollo, was dedicated to his patron god and built right next to Augustus’ own home."
The findings were then independently confirmed by astrophysicist David Dearborn from Lawrence Livermore National Laboratory, who arrived at the same conclusions using different software and methods.
"3D modeling can show scholars and, indeed, the general public, what the archaeologist uncovered, and it can be used to provide a view of how the site or object looked when it was new and in subsequent stages of its use and destruction," Frischer added. This year marks the 2,000th anniversary of the death of Emperor Augustus. Let's hope the occasion will be marked by some more discoveries.
Source: Indiana University
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