Researchers using 3D modeling and data from NASA think they've discovered the true purpose of the Obelisk of Montecitorio—upending a theory that has stood for decades. The 71-foot-tall ancient Egyptian obelisk was brought to Rome by Emperor Augustus, and would have stood across a plaza from the Ara Pacis, the "Altar of Peace" built to commemorate the Pax Romana. Historians have long accepted scholar Edmund Buchner's theory that the obelisk was positioned so that its shadow would point to the altar on Augustus' birthday, Sept. 23.
But when Bernie Frischer from Indiana University Bloomington built a computer model using NASA's Horizon System, which provides details on the locations of celestial bodies as seen from any point on Earth at any time, he found a "big surprise," he tells LiveScience: "Buchner was wrong." What mattered, the model suggested, was not the shadow, but the position of the sun over the obelisk as seen from in front of the Ara Pacis. They would line up perfectly on the festival of the Temple of Palatine Apollo, which makes sense because Augustus dedicated the obelisk to Apollo. "I think Buchner erred because he was too concentrated on Augustus' birthday, and so only made one calculation," Frischer says, whereas his simulation "can instantaneously calculate" lighting positions over a 40-year period.