Adler Planetarium

15th Annual Webster Lecture on Archaeoastronomy

In 1962, Roderick (Rod) and Marjorie (Madge) Webster discovered a passion for historic scientific instruments when, on a whim, Rod purchased an old sundial while running errands. We’ll never know exactly what prompted him to pick up the dial, but it was serendipitous for the Adler. Rod and Madge’s curiosity led to a 40-year volunteer relationship with the Adler as curators (Rod and Madge) and Chairman of the Board (Rod). Rod’s background as an engineer and Madge’s background as a teacher and archaeologist made them particularly well suited to study and interpret the Adler’s collection, composed of books and objects that combine concepts in math, science, art, and culture. Through their efforts, the Adler is the home of one of the world’s greatest science collections. 

Rod passed away in 1997. Shortly after, Madge endowed three yearly public lectures with the Archaeological Institute of America (AIA) in his memory. Each year, one of the lectures is held at the Adler and focuses on archaeoastronomy – “the study of the astronomical practices, celestial lore, mythologies, religions and world-views of all ancient cultures.” Although Madge passed away in 2002, the lecture series continues and is a yearly reminder of their legacy at the Adler. The speaker for the 15th annual Roderick S. Webster Memorial Lecture, Dr. Susan Milbrath of the Florida Museum of Natural History at the University of Florida, will present “Decoding the Astronomical Narrative in the Codex Borgia.” Using historic astronomical observations, Milbrath proposes a reinterpretation of the Codex Borgia.

“Borgia 30,” 1898 facsimile edition, online at Wikimedia Commons. 

“Borgia 30,” 1898 facsimile edition, online at Wikimedia Commons. 

One of the great masterpieces of ancient Mexico, the Codex Borgia was likely produced sometime between 1496 and 1519 in the Puebla-Tlaxcala Valley in central Mexico. It is comprised of colorful images painted on a long animal hide which folds down to 39 double-sided leaves, accordion-style. Unfolded, it is about 35’ long. The Codex was “discovered” in the collection of Italian Cardinal Stefano Borgia in 1805, although it is unknown when or how the document traveled to Italy from Mexico. Currently in the collection of the Vatican Library in Rome, the Codex Borgia has been studied for centuries. 

Similar codices are understood to be tonalamatl, books of divination used by religious leaders. The Codex Borgia has parallels to these other manuscripts, but stands apart due to its unique references to specific dates and astronomical events observed in Central Mexico. Milbrath proposes that the images on Borgia 29–46 correspond not to standard religious content but to actual astronomical events, including a spectacular solar eclipse that was observed in Central Mexico in 1496. 

To learn more, please attend the lecture on Monday, April 28th at 6:30 pm. Held in the Adler’s Samuel C. Johnson Family Star Theater, the lecture is free and open to the public. Seating is limited and is first come, first serve. Confirm your attendance today! We hope to see you there! 

Written by Lauren Boegen, digital collections manager in the Webster Institute's for the History of Astronomy at the Adler Planetarium.

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