Timeline of astronomy Rectification of Planetary Theory", eliminated the need for an equant by introducing an extra epicycle, departing from the Ptolemaic system in a way very similar to what Copernicus later also did. Ibn al-Shatir proposed a system that was only approximately geocentric, rather than exactly so, having demonstrated trigonometrically that the Earth was not the exact center of the universe. His rectification is later used in the Copernican model. Nicolaus Copernicus publishes "De revolutionibus orbium coelestium" containing his theory that Earth travels around the Sun. However, he complicates his theory by retaining Plato's perfect circular orbits of the planets. A brilliant
Canticle of the Sun Kõrvits (1969) composed a 12-part "A cappella" piece for mixed choir (SSAATTBB) "The Canticle of the Sun" for Southern Chorale choir in 2014. Pope Francis published his second encyclical Laudato si' on June 18, 2015. The Canticle inspired the encyclical's title, "Praise be to you," and was quoted in the first paragraph, "Praise be to you, Our Lord, through our Sister, Mother Earth, who sustains and governs us, and who produces various fruits, with colored flowers and herbs." The Irish composer Vincent Kennedy was commissioned by the Irish Franciscans to set the Canticle of the Sun for Soprano, Harp and