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The Secret (and Mystery) of Brunelleschi's Cupola

"How are you going to do it?" was the question posed to architect Brunelleschi during the 1418-1420 competition to decide the architect of the octagonal cupola of Santa Maria del Fiore, Florence's cathedral. The project submitted by Brunelleschi was markedly different from the other ten projects received by the committee. It had the significant advantage of proposing a construction without centering, which are wooden structures that support the masonry before completion. But, he never mentioned his strategy to friends or collaborators. A very secretive character, he was afraid that somebody, notably his rival Ghiberti, would steal his ideas and replace him as capomastro of the construction.

How did he do it? Architects and engineers have tried to uncover Brunelleschi's secret. Many have failed. Proposed models of the cupola have collapsed. Five ideas were most likely at the foundation of Brunelleschi's design: the curvature of the arcs, the double cupola, the spinapesce, the use of circumferential rings, and the corda blanda. Three were already outlined in the project presented in 1336 by Neri di Fioravanti. The Romans knew the spinapesce. The corda blanda was Brunelleschi's idea.

In his Athenaeum lecture Professor Mario Martelli will present a new solution explaining the curvature of the two cupolas. A method for producing the corda blanda was recently proposed by an architect and by a former student of Martelli's at the University of Florence. Martelli has slightly modified this interesting solution and will spend next spring taking measurements of the cupola to verify if the changes he proposed are in agreement with the construction. Professor Martelli is a professor of mathematics at Claremont McKenna College, where he has been particularly active in supporting student research. A native of Florence, Professor Martelli received his Ph.D from the University of Florence. He has been awarded the Distinguished Service Award by the Mathematical Association of America and was also a nominee for the USA Teacher of the Year granted by the Carnegie Foundation in 2000. Please join us at the Athenaeum for a fascinating examination of this historical and architectural mystery.