Dear Friends, The International Astronomical Union will be holding its General Assembly in Rome in 2027. The History of Astronomy Commission (C3) is planning to submit a proposal to the IAU executive board to hold a "Focus Meeting"-a two-day specialized gathering inside the big conference-on a topic related to gnomons, sundials, and astronomical instruments. Preliminary ideas were given as a "letter of intent" and are below. By December 1, I need to submit a formal proposal, which will then be part of a competitive selection process.
If you are interested in being part of the Scientific or Local Organizing Committee, or being a speaker, please let me know as soon as possible. You do not need to be a member of the IAU to participate. Best wishes, Sara Sara J. Schechner, PhD, FAAS Curator Emerita, Collection of Historical Scientific Instruments, Harvard University President, International Astronomical Union Commission C3 (History of Astronomy) https://saraschechner.scholars.harvard.edu/ [email protected]<mailto:[email protected]> [email protected]<mailto:[email protected]> Art Quilts and Sundials https://www.altazimutharts.com Focus Meeting for IAU GA XXXIII, August 10-19, 2027, Rome The Sun and the Catholic Church Coordinating Division: C Commission: C3 Scientific Organizing Committee * Sara J. Schechner, Harvard University (USA) (F) * Costantino Sigismondi, International Center for Relativistic Astrophysics (ICRA) (Italy) (M) * More scholars to be added with a balance of different expertise, genders, and nationalities As the IAU GA XXXIII meeting will be in Rome, the center of the Catholic Church, this Focus Meeting will highlight how the Church contributed to astronomy through its buildings, through the instruments developed by its members and collaborators, and through collected and archived data, which have been and continue to be useful for scientific and societal purposes. As our focus, we choose the most ancient of astronomical observations-that of the Sun-and will consider the history of an innovative and initially Italian and Catholic method of using gnomons set out in public forums, built into churches, and brought into palazzos in order to study the Sun's path, seasons, and sunspots, to reform the calendar, to establish standard time, and most recently to demonstrate stellar aberration and special relativity. Use of an obelisk with a meridian line to track the solar year dates back to the Solarium Augusti (10 BCE) in Rome and the Vatican obelisk in St. Peter's Square. Since the 15th century, apertures in the vault of churches have also served as gnomons tracing the Sun's diurnal motion across the pavement below and served as pin-hole cameras. The earliest may be that finished in 1475 by Paolo Toscanelli in the Duomo of Florence. Other early examples of churches as observatories include Pope Gregory's Tower of Winds in Rome-the work of Ignazio Danti (1536-1586), who also placed a gnomon in the interior and solar instruments on the façade of the Santa Maria Novella in Florence--and churches in Bologna, Rome, Palermo, Milan, Paris, etc. Scientific information was also displayed by spectacular sundials such as the 17th century catoptric (reflecting) dials by Minim friar Emmanuel Maignan in the Palazzo Spada and the convent of Trinità dei Monti, both in Rome. The data of these solar instruments were key to the Gregorian calendar reform of 1582 and later astronomical research into sunspot groups and the changing size and position of the solar image on the meridian line. By the 19th century, meridian projects had moved beyond Italy and the Catholic Church. In Belgium, an 1836 Government Decree established 41 meridian lines in Belgian churches and other public buildings. The goal was to standardize timekeeping across the country for the very first double-track railway line on the European continent, which ran from Brussels in an approximate north-south direction. This was therefore a purely secular enterprise, driven entirely by the immediate needs of the industrial revolution. The method, however, was rendered obsolete by the deployment of the electric telegraph less than a decade later. The old gnomons and their data are still of value in the 21st century. Today the meridian lines of the Vatican obelisk and the Basilica of St. Maria degli Angeli in Rome are used for educational purposes, being able to measure stellar aberrations by the transits of the Sun and Sirius. Moreover, the precision of the old archived data can be analyzed in order to tell us whether this vintage data can be reliably used for climate studies. Focus Meeting of 2 days (6 sessions of 1.5 hours each) Outline of sessions: 1. Setting the stage: Early solar observations and introductory talks on the history and principles of gnomons and meridian lines used for astronomy, time finding, and cartography-starting with Greco-Roman obelisks like the Solarium Augusti before the Catholic Church existed. 2. How and why early modern Catholic astronomers and mathematicians focused on making and using time finding and measuring instruments for civil, religious, and astronomical needs. * Talks might discuss people involved-e.g., Danti, Clavius, or Cassini who were tracking the Sun's motion to keep the calendar and liturgical cycle; or the numerous members of Catholic orders-Jesuits, Capuchins, Franciscans, etc.--who wrote extensively on sundial making and designed those to show the seasons, declinations, and feast days. * Spectacular sundials: E.g., the reflecting sun- and moon-dials made for Cardinal Bernardino Spada and the convent of Trinità dei Monti by Emmanuel Maignan between 1636 and 1644. 3. The church as an observatory I--Various Catholic examples in Rome, Florence, Bologna, Milan, Palermo, and Paris. Speakers may frame their talks so as to discuss political, economic, religious, and scientific developments related to the different sites, and how the "church observatories" contributed to the scientific and local communities. 4. The church as an observatory II-Continuation of previous session, but also including non-Catholic examples driven by secular concerns, such the Belgian meridian projects of the 19th century. 1. Historical, archived data * the accuracy and precision of archived data concerning the solar image and its position on the meridian, sunspot groups, the inclination of the ecliptic, etc. * the usefulness of archived data for long-time domain astronomical studies such as changes to obliquity, or astronomically-driven climate changes (e.g., by the Milankovitch cycle or sunspot cycles). 2. Modern work with historical meridians and gnomons * observations of stellar transits, stellar aberrations. * Educational uses of obelisks to introduce students to special relativistic effects like stellar aberration.
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