450 years ago, on December 27, 1571, a mathematician and astronomer, who sought the music of God in the skies, was born in Weil der Stadt, near Stuttgart in Germany: Johannes Kepler.
At the age of 19 he enrolled in the Theological Facoltà of the University of Tübingen, where he studied, in addition to theology, mathematics and astronomy with Michael Mästlin (1580-1635). At 22, Kepler taught mathematics in Graz, southeastern Austria, but, obeying a decree that ordered the expulsion of all Protestants, at the beginning of 1600 he moved to Prague, accepting the invitation of Tycho Brahe (1546-1601). Here he helped the Danish astronomer to prepare planetary tables, the future Tabulæ Rudolphinæ (1627), in honor of Rudolf II (1552-1612), Holy Roman emperor and patron of both.
With Tycho dead, Kepler became Imperial Mathematician and inherited the fruit of the planetary observations made for over twenty years by the Dane with the maximum precision obtainable at the time. Thanks to this material Kepler deduced his famous three laws on the heliocentric movement of the planets. The first — the shape of the planetary orbits is elliptical and the sun occupies one of the two foci — is really Astronomia Nova, as his main work composed in Prague in 1609 is called. Here he dispels the ancient belief that all celestial movements must be circular and of uniform speed. It certainly did not appeal to the Aristotelians but, strangely enough, nor to Galilei. In the midst of the Thirty Years War, which devastated much of Central Europe, Kepler, tormented by material difficulties and family misfortunes, died in Regensburg, southeastern Germany, on November 15, 1630.
It is precisely an indestructible trust in the possibility of tracing the imprint of a geometer and musician in God’s creation that made Kepler a pioneer of astrophysics. In his book of 1619 Harmonices Mundi Libri V, in addition to the third law, we find exposed, complete with numerical tables and musical notation of the sounds of each planet, all his theory on the “music of the celestial spheres”: in the footsteps of Pythagoras and Plato, the discoverer of the laws of the planets considered music as the echo of the movement of the celestial spheres, created by God as the “Surveyor and supreme Musician”.
Johannes Kepler is also the baritone protagonist of two operas: Die Harmonie der Welt (“The Harmony of the World”), completed in May 1957, on his own libretto, by the German composer Paul Hindemith (1895-1963) and Kepler by Philip Glass (b. 1937), American composer among the leaders of musical minimalism, on a libretto in German and Latin by the Austrian Martina Winkel.
The latter had its first performance on September 20, 2009, in Linz, north-central Austria, where our astronomer taught mathematics from 1612 to 1626. “Fragments from the life and ideas of the scientist Johannes Kepler”, we read in the DVD presentation, “are contrasted with segments from the story of creation [from the Book of Genesis] and poems by Andreas Gryphius [1616-1664], which portray Europe during the Thirty Years War.” The text offered to the composer is not dramaturgically generous: in addition to the title role and the choir, almost always on stage, there are three female voices (Soprano 1, Soprano 2 and Mezzo) and three male voices (Tenor, Baritone and Bass), all anonymous. The music is very rhythmic and compelling with varied melodies; the orchestration is rich: 2 flutes, piccolo, oboe, English horn, clarinet, bass clarinet, 2 bassoons, 4 horns, 3 trumpets, 3 trombones, tuba, 5 percussions, celesta, piano, harp and strings.
The opera, which is divided into a prologue and two acts, lasts about two hours. It begins and ends with Kepler’s epitaph, which says in Latin: “I used to measure the skies / Now I measure the shadows of Earth. / Although my mind was sky-bound, / The shadow of my body lies here.” The protagonist explains his intentions in Latin: “I wanted to become theologian. / Behold, God by my work / even in astronomy / is praised, / God / who from the book of nature / wants to be recognized.” Then, Kepler admonishes theologians that: “The Bible doesn’t teach / optics / and astronomy.” The solo voices comment that “God’s counsels are impenetrable / but not his material creation.” The protagonist, then, wants to show: “that the celestial machine / isn’t a divine organism, / but rather a clock, / in which are executed / the movements / of a single / magnetic / and corporeal force.” The solo voices note in Latin that “Geometry is the archetype / of the beauty of the world.” The choir shouts against the transience of things devoured by time, quoting the famous verse from the Book of Ecclesiastes (1:2): Vanitas! Vanitatum Vanitas! The solo voices wonder: “what now / if the earth itself / vanishes into the ether?” Kepler wonders: “Does the cold / Cause / The structure / Of snowflakes?” At the end of the first act the protagonist and the six scholars declare that: “Without perfect knowledge / human life is dead.”
The second act is dedicated to the human aspect of the protagonist. Astrology, which he dealt by making horoscopes, is used to calculate the date of his conception. Amused, the solo voices portray him: “This man / has completely / a dog nature, / […] is greedy / out of order.” Kepler lists his enemies and justifies their actions with astrology; however, he despises it, since: “the will of man, / princeps animæ facultas, / is and remains free!” The protagonist arrives at his most important discovery: “The planetary orbit / is a perfect ellipse. / The sky movements / are nothing else / as perpetual heavenly music, / with the mind / not by ear / perceptible.” Before repeating Kepler’s epitaph, the choir praises God’s creative action in the cosmos, with a Latin text inspired by Psalms 147 and 148.
Kepler and, before him, Tycho Brahe, Galileo, Maimonides, Albert the Great and, after him, even Newton are proof that, to use the words of the German physicist who originated quantum theory, Max Pianck (1858-1947), not only religion and science don’t exclude each other; rather, they mutually complement each other.
Title photo: two pages from Kepler’s Rudolphine Tables showing eclipses of the Sun and Moon, public domain.
 Cf. A. M. Lombardi, Keplero: una biografia scientifica (Codice, Torino 2008), 27.
 Cf. Max Planck, La conoscenza del mondo fisico (Boringhieri, Torino 1993), 64-65.