Join us on April 1st for our next Full Moon-th On-line Meetup!

Our guest will be Giovanni Battista Riccioli (1598–1671) an Italian astronomer, theologian and Jesuit priest. Riccioli is the author of Almagestum Novum, an encyclopedic work that became the standard technical reference book for astronomers all over Europe during his time.

Riccioli is temporally challenged, without access to Zoom, or a time-travel capable computer; his avatar will be reenacted by Vatican Observatory thespian Christopher M. Graney.

Our tradition of hosting online meetups with our Sacred Space Astronomy members and the Vatican Observatory staff, scholars and friends during the Full Moon in Tucson (or thereabout) continues on Wednesday April 1, 2026 at 9:00 AM Tucson time (with daylight savings time), 12:00 Noon ET or 16:00 UTC.

We’ll also discuss the latest astronomy news and an update about the Vatican Advanced Technology Telescope.

Giovanni Battista Riccioli was a prominent Italian Jesuit priest and astronomer who made significant contributions to the fields of experimental physics and lunar studies. In collaboration with Francesco Maria Grimaldi, Riccioli developed the system of lunar nomenclature still in use today, naming prominent features like the Mare Tranquillitatis and assigning craters the names of famous astronomers. He was also the first to precisely measure the acceleration of falling bodies using pendulums for timing, confirming Galileo’s “odd-number” rule while also noting the effects of air resistance.

Despite his extensive scientific achievements, Riccioli was a staunch opponent of the heliocentric theory. In his Almagestum Novum, he famously presented 126 arguments regarding the Earth’s motion—49 in favour and 77 against—ultimately concluding that the Earth remains stationary at the centre of the universe. His scientific objections included the lack of detectable stellar parallax and the absence of observed physical effects, such as the Coriolis effect, which he correctly theorised should be present on a rotating planet. Throughout his life, he balanced his scientific pursuits with his roles as a theologian and teacher in various Jesuit colleges, maintaining a vast correspondence with other leading scholars of the era, including Huygens and Cassini.