Source: Digital Library, Museo Galileo

KEPLER, Johannes (1571-1630), Epitome of Copernican Astronomy & Harmonies of the World. Translated from the Latin to English by Charles Glenn Wallis. Amherst, NY: Prometheus Books, 1995.

Original citation: Epitome Astronomiae Copernicanae, usitata forma quaestionum et responsionum conscripta. Linz [Austria]: Johann Planck, 1618-21 [published in three parts].  

Condemned: May 10, 1619. 

Removed from Index: 1822.  

§2: Books including any heresy or schism attempting to destroy religious orthodoxy;

§7: Books engaged in any kind of superstition, fortune-telling, magic, spirit-conjuring, or other similar occult topics.

…there are many wicked folk who despise the arts, and maliciously interpret everything their own dull minds cannot grasp. They fasten harmful laws onto the human race; and many, condemned by those laws, have been swallowed by the [abyss]… 

–Somnium, sive Astronomia lunaris Joannis Kepleri (Translated by Patricia Frueh Kirkwood)


In Greek, the word for planet (πλανήτης — transliterated as planítis or planetes) ultimately traces its meaning to “wanderer” or “wandering.” The planets in our solar system were at first (and understandably) misunderstood by the Greeks as one and the same as stars. The wandering nature of these glowing celestial bodies had also been conceived and explained over the millenia by ancient astronomers from a plethora of civilizations throughout the world; their positions in the night sky were established as both regular and cyclical. This work was, of course, done almost exclusively with the naked eye. This legacy of skygazers includes the second-century AD, Greco-Egyptian Claudius Ptolemy (and his predecessor Hipparchus); the Polish astronomer Copernicus (1473-1543); official mathematician, astronomer, and astrologer to the ruling Hapsburg family of the Holy Roman Empire, Tycho Brahe (1546-1601); and his German pupil and successor, one Johannes Kepler. 

Kepler was something of a wanderer himself. This was manifest in both his traumatic migrations throughout east-central Europe as well as in his massive contributions to an eclectic range of fields, including mathematics, physics, astrophysics, astronomy, philosophy, and even science fiction. “Kepler,” writes scholar Maria Papova, “knew what we habitually forget — that the locus of possibility expands when the unimaginable is imagined and then made real through systematic effort.” A contemporary and correspondent of Galileo Galilei (1564-1642), Kepler was that rare combination of poetic dreamer and meticulous scientist. As a result, he succeeded in bridging the gap of cosmic understanding between his revolutionary (no pun intended) predecessor, Nicolaus Copernicus, and his prolific successor, Sir Isaac Newton. 

Though he published several other books, Kepler’s 1618-1621 three-volume text, Epitome Astronomiae Copernicanae — usually translated into English as Epitome of Copernicus’ or Copernican Astronomy — was the one singled out for inclusion on the Index. This sole citation was not by mere happenstance, but rather inherently linked to its association with the texts of Copernicus and Galileo. The first half — and especially the first quarter — of the seventeenth century constituted a period of particularly extreme reckoning for Church dogma vis-à-vis the rapidly changing scientific conception of the Earth, its nature and dynamics within the solar system, and furthermore those of the greater cosmos. Galileo’s saga of ecclesiastical persecution, censure, and house arrest was a result of his building upon Copernicus’s 1543 bombshell. But the latter was not condemned right away; Copernican heliocentrism was not deemed incompatible with Catholic dogma, at least in the immediate years after its publication. However, as an American Jesuit priest wrote as recently as 1940, “Had [Galileo] advocated [Copernicanism] as such with due respect for the time-honored interpretation of the Book of Books, had he not used bold, sometimes bitter and defying language, no steps would have been taken against him, who until then had been a favorite of the pope and of many dignitaries” (emphasis added). If only. As we have seen, Galileo’s Dialogo remained on the Index from its condemnation in 1634 until the almost mind-bogglingly late date of 1822. 

So too was Johannes Kepler included in the Vatican’s dragnet for thorough, published support of Copernicus. In addition to his previous and continued wranglings with representatives of his own denomination, Lutheranism, Kepler’s listing on the Index was decreed by the Vatican on May 10, 1619, before the second and third volumes of the condemned Epitome could be published. And along with those highly influential works of Galileo and Copernicus, so too was 1822 the year of the Epitome’s highly belated removal. 

The massive threat of works by brilliant thinkers such as Kepler, Galileo, and Copernicus lay, of course, in that they were more rigorously scientific and well documented than most others that had preceded them. That meant that their methods and findings could much more reliably be reproduced by any other person so inclined to make the attempt, per the dictum of the modern scientific method. Kepler and Galileo — contemporaries, recall — also each had at his disposal a powerful tool with which to bolster the discoveries of Copernicus. For Galileo, this tool was his re-designed and enhanced telescope, many times stronger than any other yet invented. Kepler’s secret weapon was the massive trove of astronomical data bestowed upon him by his teacher and mentor, Tycho Brahe, and then later published as the Rudolphine Tables.  

Originally from Denmark, Tycho Brahe (born Tyge Ottesen Brahe in 1546, three years after the publication of Copernicus’ magnum opus) was both a giant of tireless astronomical computational analysis while simultaneously rather cautious in his support for the new and still wildly controversial Copernican model. As such, he proposed his own system, now known as Tychonic, which hedged between the Copernican and the Ptolemaic. 

As both a nobleman and the imperial mathematician to the Hapsburg Emperor Rudolph II at the observatory in Prague, Brahe’s compromise, in a Europe riven by politico-religious strife, is understandable. But upon his death in 1601, Brahe’s assistant and student since the previous year, Johannes Kepler, would go on to stand on his master’s and Copernicus’ shoulders, as it were, to advance human understanding of planetary sizes and distances, orbital mechanics, and beyond. 

The Epitome, far from provocative or scurrilous in its style, is presented as a thoughtful dialogue. A stand-in for the reader asks Kepler straightforward questions and follow-up requests for clarification about his observations and propositions in a gradual, logical sequence: E.g., “What do you judge to be the lay-out of the principal parts of the world?” Charles Glenn Wallis, a twentieth-century translator of Kepler’s Latin into English, notes that the book is “remarkable for the prominence given to ‘physical astronomy’ and for the extension to the Jovian system of the laws recently discovered to regulate planetary motion.” Book I introduces general principles of astronomy; Book II the concept and properties of a sphere; III “the Doctrine of the First Movement — called the Doctrine on the Sphere.” These first three books were all published as one volume in 1618 and, as noted, triggered the full, three-volume text’s blacklisting the following year, despite the final two volumes’ pending publications. Books IV (Volume Two; 1619) and V (Volume Three; 1620) comprise the modern English translation referenced herein and deal with, respectively, the more nuanced principles of the solar system and elliptical (i.e., not circular as previously surmised) orbits of the planets and their moons. This principle of elliptical orbits (Kepler’s First Law) comprises one of the astronomer’s monumental contributions to astrophysics. All three of his laws of planetary motion were essential to Sir Isaac Newton’s (b. 1642) later development of the theory of universal gravitation, the one so popularly — if apocryphally — memorialized by a falling apple hitting him on the head. 

Thanks to Kepler’s copious correspondence and other documentation, we have a good sense as to what he thought of challenging the shared Ptolemaic conservatism of both the Catholic and Protestant authorities in Germany. As Lear notes, “Though not easily intimidated, Kepler did have a deep fear of censorship, which was to come to the surface when the first part of his Epitome of Copernican Astronomy was placed on the Roman Catholic Index…in 1619. His reaction then was to…imagine pending demands that he renounce astronomy as a career in spite of his eminent position.” Though he was to spend the final decade of his life (1620-30) both actively experimenting and writing, much time and attention was also focused on exonerating his mother Katharina from accusations of witchcraft (a dramatic saga in its own right) as well as resolving various debts the imperial treasury owed him since his benefactor Rudolph II was deposed by his brother Matthias in 1611. In addition to these more legal misfortunes, Kepler suffered from several chronic illnesses likely originating from childhood smallpox; witnessed the death of his son, followed quickly by that of his first wife; and in general had the general misfortune of many thoughtful intellectuals: he was often misunderstood and taken advantage of and by others. In late 1630, Johannes Kepler fell sick while traveling and died at the age of fifty-eight; he had been en route to the city of Ravensburg to resolve his outstanding fiscal predicaments with the Imperial Diet. Kepler’s work would live on to this day, however, and his place among the giants in the firmament of scientific discovery is eternally secured. Aptly, a NASA space-telescope project, the Kepler Mission, has discovered more than 2,600 planets outside of our solar system between 2009 and 2018.

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