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Kepler Fest

Reversing the Notion of Circular Motion

February 17–18, SANTA FE

William Donahue stands with a facsimile of Kepler's original manuscript.
William Donahue displays a facsimile of Kepler’s original manuscript.

Astronomer Johannes Kepler (1571-1630) will be lauded at Kepler Fest on the Santa Fe campus of St. John’s College. Kepler Fest celebrates a newly retranslated and revised edition of Kepler’s landmark book, Astronomia Nova, authored by tutor emeritus William Donahue.

Schedule of Events

All events will be held in Peterson Student Center, Great Hall

Friday, February 17

3:30 p.m. Owen Gingerich Workshop: “Plotting Earth’s Orbit” 

Gingerich will lead a high-level workshop that plots the orbit of Earth using Kepler’s original technique.

Gingerich is an emeritus professor of astronomy and the history of science at Harvard University and an emeritus senior astronomer at the Smithsonian Astrophysical Observatory. He has received the rare honor of having an asteroid named after him: 2658 Gingerich.

7:30 p.m. William Donahue Lecture: “A Page of Kepler”

This lecture will feature facsimiles of Kepler’s original handwritten manuscript, preceded by a presentation of the Kepler Essay Prize.

Donahue will share his experience of identifying Kepler’s “eureka” moment, which Donahue encountered while reading the original handwritten manuscript in St. Petersburg, Russia. As Kepler was working through calculations for the orbit of Mars, he was plagued by a discrepancy in the numbers. It was canonical that the orbit be perfectly circular, and yet… Kepler drew a line across his calculations, and began furiously working out his new idea fresh on the page. It was one moment, the drawing of this single line, which separated a new vision of the cosmos from the old one. Abandoning circular motion was necessary to make the math balance out.

As Donahue explains, “It suddenly occurred to him that if you squeezed the circle in a little bit on the sides, you could eliminate those nine minutes of discrepancy. This is the moment when he leaps, and is no longer committed to circularity. So instead of finishing the computation which was going to happen here on the page, he drew a line along here, and started writing down new physics for the orbit.”

Saturday, February 18

10:30 a.m. Peter Pesic lecture: “Kepler and Music: The New Cosmic Polyphony”

This will be followed by a Small Chorus performance of Orlande de Lassus’s “In Me Transierunt,” led by Andy Kingston

Tutor Emeritus Peter Pesic will explore the many connections between music and physics, as discussed in his book Music and the Making of Modern Science (MIT Press, 2014).

As part of this lecture, the Small Chorus will sing the motet “In Me Transierunt,” to which Kepler refers repeatedly in his book Harmony of the World as exemplifying polyphonic music and universal harmonics.

2 p.m. Owen Gingerich lecture: “Kepler’s Elusive Eccentricity”

Gingerich writes: “For Kepler himself, it was the physics that pointed to the ellipse; we know now that Kepler’s physics was defective, lacking the concept of inertia, but his insistence on physical reasoning paved the way for Newton, even though Newton sniffed, ‘Kepler guessed it was an ellipse, but I have proved it.’”