Measuring Time with the Sun: the Astronomical Use of Basilicas in Italy

Wednesday, April 30, 2014 at the Italian Cultural Institute of the Italian Embassy 3000 Whitehaven St., NW, Washington, DC 20008

Measuring Time with the Sun: the Astronomical Use of Basilicas in Italy

by Professor Costantino Sigismondi

Costantino Sigismondi is an astronomer and astrophysicist, currently professor of physics at Galileo Ferraris Institute in Rome and visiting researcher and teaching fellow at Brazil’s National Observatory in Rio de Janeiro. His research interests include eclipses, planetary transits, meridian transits, meteor showers and the history of astronomy among others. Sigismondi has participated in research projects in astrometry at La Sapienza in Rome (from which he was awarded a PhD in Theoretical Physics in 1998), Yale

University, the Astronomical Observatory of Rome, and institutions and universities in Italy, France, Korea, China and Brazil. His publications in professional journals number more than one hundred. He also founded a journal and maintains research interests in the history of Medieval Science.

ABSTRACT From the Italian Renaissance through the 18th century the great basilicas of Italy were not only places of worship but also played an important role in the history of astronomy. Toscanelli in Florence, Danti and Cassini in Bologna and Bianchini in Rome made great advances in determining midday to a half-second, the altitudes of the solstices and highly accurate measurements of the days of the year. Their principal tools were pinhole openings in the domes or roofs of churches and meridian lines incised on the church pavements. The Italian tradition in solar astrometry paved the way for further progress--two Roman observatories built on earlier work to advance solar physics and map the solar diameter. Since the smallest variations in solar diameter have consequences on solar radiation and on climate, Sigismondi will conclude by providing a brief summary of current research.


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