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Johannes Kepler, Willie Ruff, and John Rodgers: “The Planets from Mercury Outward”

From the album The Harmony of the World: A Realization for the Ear of Johannes Kepler’s Data from Harmonices Mundi (1619)

Most famous for his “first law” declaring that the orbit of planets around the sun traced ellipses, and not circles, as was previously believed, the German astronomer Johannes Kepler (1571-1630) is not usually thought of in connection to music.  But in his 1619 book Harmonices Mundi (The Harmony of the Worlds), Kepler gave the ancient Pythagorean and Platonic notion of the “music of the spheres” a new and precisely empirical formulation.  He compared the angular velocity of the planets at perihelion and aphelion (the orbital points closest to and furthest from the sun), and expressed the relationship between these speeds as musical intervals:

(The interval in question is between the outermost notes of each scale; the inner notes are filled in as a formality.)

Kepler’s calculation of the “music of the spheres” was remarkable for a number of reasons.  First, as explained in Joscelyn Godwin’s excellent book Harmonies of Heaven and Earth, the intervals are calculated not in relation to the Earth, but rather, in accordance with the heliocentric theory of Copernicus, from the auditory perspective of the sun.  Second, although Kepler’s notation could not indicate it, he imagined their tonal ranges as being continuously sounded in the manner of a glissando.  Finally, Kepler’s cosmic music is explicitly polyphonic.  Previous theories were constrained by conventional understandings of what was musically acceptable: Aristotle, for example, rejected the notion that each planet simultaneously sounded the note of a scale, for the result would be cacophony.  But Kepler saw no reason to believe that the music of the spheres would cleave neatly to human notions of musical beauty.  He believed, with his medieval predecessor John Scotus Eriugena, that “all the musical consonances can be made by the eight celestial sounds, not just in the three genera (diatonic, chromatic, and enharmonic), but even in others beyond the conception of mortals.”

Because the time-scale of these planetary motions is exceedingly vast (Saturn’s trip up and down a major third requires no less than 30 years), things have to be accelerated to make these harmonies audible to humans. This is what has been done in this exceptional recording made by Willie Ruff and John Rodgers.  The music you are hearing introduces the planets one by one: first Mercury, high and fast, with its eccentric orbit covering a large interval of a minor 10th; then, both in the treble register, Venus and Earth, whose nearly circular orbits create tones that barely change—Venus oscillates within a quarter-tone, Earth a semitone.  Next enters Mars in the alto range, with a fairly wide ambitus traversed in 10 second cycles. Quite a bit lower, Jupiter sounds its stentorian baritone, spanning a minor third. Finally comes Saturn, a growling bass about an octave below Jupiter.  Its range is a major third.

The outer planets, unknown in Kepler’s time, are represented by rhythmic impulses instead of musical tones: Uranus vacillates between a rapid 9 and 10 pulses per second, Neptune keeps a near-constant rate of 5 per second, and Pluto enters with a slow but irregular beat, which is the last to be heard after all the other voices drop out.

For a similarly inspired piece, check out Greg Fox’s Carmen of the Spheres (2006), which measures the orbital period of each of the planets in seconds, then divides that figure by two (using the principle of octave equivalence) again and again until it represents a frequency within the audible spectrum for humans.  A similar procedure is used to determine the duration of the pitches.  Interesting music, though Mr. Fox’s website is unforgivable.

March 06, 2010, 3:23pm