Harmonices Mundi (Latin: The Harmony of the Worlds, 1619) is a book by Johannes Kepler. In the work Kepler investigates harmony and congruence in geometrical forms and physical phenomena. The final section of the work relates his discovery of the so-called "Third Law" of planetary motion. Latin was the language originally spoken in the region around Rome called Latium. ... Events May 13 - Dutch statesman Johan van Oldenbarnevelt is executed in The Hague after having been accused of treason. ... Johannes Kepler (December 27, 1571 – November 15, 1630) was a German mathematician, astronomer and astrologer, and a key figure in the 17th century astronomical revolution. ...

Kepler divides The Harmony of the World into five long chapters: the first is on regular polygons; the second is on the congruence of figures; the third is on the origin of harmonic proportions in music; the fourth on is on harmonic configurations in astrology; and the fifth on the harmony of the motions of the planets. In astrology, an aspect is the relative angle between two heavenly bodies. ...

While medieval philosophers spoke metaphorically of the "music of the spheres," Kepler discovered actual, albeit silent, harmonies in planetary motion. He found that the difference between the maximum and minimum angular speeds of planet on its orbit approximates a harmonic proportion. For instance, the maximum angular speed of the Earth as measured from the Sun varies by a semitone (a ratio of 16:15), from mi to fa, between aphelion and perihelion. Venus only varies by a tiny 25:24 interval (called a diesis in musical terms). Kepler explains the reason for the Earth's small harmonic range: The eight planets and three dwarf planets of the Solar System. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ...

The Earth sings Mi, Fa, Mi: you may infer even from the syllables that in this our home misery and famine hold sway.

At very rare intervals all of the planets would sing together in 'perfect concord': Kepler proposed that this may have happened only once in history, perhaps at the time of creation.

Kepler also 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 unharmonic ratio of 18:19. In fact, the cause of Kepler's dissonance might be explained by the fact that the asteroid belt separates those two planetary orbits, as discovered in 1801, 150 years after Kepler's death. Two bodies with a slight difference in mass orbiting around a common barycenter. ... For details on the physical properties of bodies in the asteroid belt see Asteroid and Main-belt comet. ...

Kepler's previous book Astronomia nova, related the discovery of the first two of the principles that we know today as Kepler's laws. The third law, 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, is set out in Chapter 5 of this book, immediately after a long digression on astrology. Astronomia nova (A new astronomy), written by Johannes Kepler and published in 1609, set out the evidence for what came to be known as Keplers laws of planetary motion. ... Johannes Keplers primary contributions to astronomy/astrophysics were his three laws of planetary motion. ... Hand-coloured version of the anonymous Flammarion woodcut (1888). ...

References

• Johannes Kepler, The Harmony of the World. Tr.: Dr Juliet Field. Pub. by The American Philosophical Society, 1997. ISBN 0-87169-209-0
• Johannes Kepler, The Harmony of the World. Tr. Charles Glenn Wallis. Chicago: Great Books of the Western World. Pub. by Encyclopedia Britannica, Inc., 1952.
• "Johannes Kepler," in The New Grove Dictionary of Music and Musicians, Ed. Stanley Sadie. 20 vol. London, Macmillan Publishers Ltd., 1980. ISBN 1-56159-174-2

Further links

• Summary of Kepler's Harmonices Mundi
  • Harmonies of the World, Charles Glenn Wallis tr., etext at sacred-texts.com
• Harmonices mundi ("The Harmony of the Worlds") in fulltext facsimile; Carnegie-Mellon University
• Walter W. Bryant. Kepler, available at Project Gutenberg.
• Electronic facsimile-editions of the rare book collection at the Vienna Institute of Astronomy
• Device denominated technical work of art that combines astronomy, mechanics, melodics and electronics

Project Gutenberg, abbreviated as PG, is a volunteer effort to digitize, archive and distribute cultural works. ...

See also

• Pythagoreanism
• Musica universalis