only once in history, perhaps at the time of creation. Kepler reminds us that harmonic order is only mimicked by man, but has origin in the alignment of the heavenly bodies: Kepler discovers that all but one of the ratios of the maximum and minimum speeds of planets on neighboring orbits approximate musical harmonies within a margin of error of less than a diesis (a 25:24 interval). The orbits of Mars and Jupiter produce the one exception to this rule, creating the inharmonic ratio of 18:19. Chapter 3 [to be written] Chapter 4 [to be written] Chapter 5 includes a long digression on astrology. This is immediately followed by Kepler's third law of planetary motion, which shows a constant proportionality between the cube of the semi-major axis of a planet's orbit and the square of the time of its orbital period. Kepler's previous book, Astronomia nova, related the discovery of the first two principles now known as Kepler's laws. Recent history A copy of the 1619 edition was stolen from the National Library of Sweden in the 1990s. Use in recent music A small number of recent compositions either make reference to or are based on the concepts of Harmonice Mundi or Harmony of the Spheres. The most notable of these are: Laurie Spiegel: Kepler's Harmony of the Worlds (1977). An excerpt of the piece was selected by Carl Sagan for inclusion on the Voyager Golden Record, launched aboard the Voyager spacecraft. Mike Oldfield, (English musician and composer, born 1953), Music of the Spheres (album released in 2008 by Mercury Records). Joep Franssens (Dutch composer, born 1955), Harmony of the Spheres (cycle in five movements for mixed choir and string orchestra), composed 2001. Philip Glass, American composer, Kepler (opera) (2009), homage to Johannes Kepler, commissioned by the city of Linz, where the astronomer lived. Tim Watts, (English composer, born 1979), Kepler's Trial (2016–2017), premiered at St John's College, Cambridge (2016); revised version performed at the Victoria and Albert Museum, 9 November 2017 Paul Hindemith, German composer Die Harmonie der Welt Symphony (originally entitled Symphonie „Die Harmonie der Welt“ in German), IPH 50, is a symphony composed in 1951, and which served as the basis for the 1957 opera Die Harmonie der Welt. Miriam Monaghan (British recorder player and composer) Kepler’s Planets (2019), written for Palisander Recorder Quartet. Extracts were premiered live on BBC Radio 3 In Tune (October 2019) with