Kepler's Harmonices Mundi

Title page of Kepler's Harmony of the World (Harmonices Mundi). The book was completed in the spring of 1618 and finally published in Linz in 1619. Again of a rather mystical flavor at time, the book contains Kepler's first formulation of his Third Law of planetary motion:

The square of a planet's orbital periods is proportional to the cube of its mean distance to the Sun.

Kepler was to formulate the final versions of his Three Laws of planetary motions much more clearly in book IV of his textbook Epitome of Copernican Astronomy (Epitome astronomiae Copernicanae), published in 1620.

Bibliography:

Stephenson, B. 1994, The Music of the Heavens, Princeton University Press.

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-Written and last revised 20 December 1997 by paulchar@ucar.edu.