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Book of the Month

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April 2008

Nicolaus Copernicus

Detail from folio 9v from De Revolutionibus showing the sun at the centre of Copernicus' heliocentric "Universe"

 De Revolutionibus

Nuremberg: 1543
Sp Coll Hunterian Cz.1.13

Nicolaus Copernicus (1473-1543) is now recognised as one of the fathers of modern science: his one great work, De Revolutionibus orbium coelestium libri sex (Six books on the Revolutions of the Heavenly Spheres), garnered him immediate, if posthumous, fame. It has been described as a "monument of scientific genius" and marks a huge and important stride forward in human understanding of the natural world. A rare first edition of De Revolutionibus with a fascinating provenance is April's Book of the Month.

Title page of De Revolutionibus

De Revolutionibus famously proposed the heliocentric theory: the (now taken for granted) proposition that the Earth rotates around the Sun rather than vice versa. During Copernicus' lifetime, orthodox opinion asserted the contrary view - that the Earth was fixed, unmoving at the centre of the Universe. This "geo-centric" myth was not easy to de-bunk: it was popularly held to be true by common sense perception supported by two millennia of philosophical tradition, not to mention Biblical scripture.

As with many great "discoverers", Copernicus was not, in fact, the first ever person to conceive of heliocentrism. Although Copernicus' name is now synonymous with the theory, the ancient Greek astronomer Aristarchus of Samos apparently first proposed the theory during the Third Century BC; however, unlike Copernicus, Aristarchus failed to work out the details. Angus Armitage has argued that Copernicus' great contribution to the rise of modern thought was through nature of "choice" rather than "discovery": choosing to believe that his proposition held true and backing up this stance with a vast quantity of supportive data, useful calculations and technical innovation.


Detail from the title page. It was not unusual for people to Latinize their names during
 the Sixteenth Century - thus Kopernik became Copernicus. The final part of the
 author's name, Torinensis, refers to the his place of birth, Toruń.

Mikołaj Kopernik (Copernicus) was born in Toruń in modern day Poland in 1473; he received elementary tuition locally before moving on to attain a well rounded education in the humanistic environment of Kraków University. With the encouragement of his uncle, Bishop Watzenrode of Varmia, Copernicus journeyed south to study Canon Law at Bologna in preparation for a career in the Church. While in Bologna, he researched a wide variety of fields particularly indulging his growing interest in astronomy. Over the following years he continued to read widely, study hard and think about the Universe. Following his experiences in Bologna, he moved to Padua to study medicine before finally graduating and returning to Poland in 1503 to take up a position as Canon of Frombork near the Baltic coast.
Copernicus' work on De Revolutionibus seems to have begun in 1517; however, he was to work quietly on the manuscript for the rest of his life - only publishing it on his death bed after persuasion from his friend and pupil, the young mathematician Joachim Rheticus. Rheticus' role in the publication of the work has been acknowledged as paramount - without his encouragement and willingness to act as a middle man between the author and the Nuremburg printer, Johannes Petreius, the work may never have been published.

Further detail from the title page: this note, added by the publisher proclaims, "You have in this
 recent work, studious reader, the motion of both the fixed stars and the planets restored
 from ancient as well as recent observations, and outfitted with wonderful new and admirable
 hypotheses. You also have most expeditious tables from which you can easily compute the
 positions of the planets for any time. Therefore, buy, read, profit."


A note, in Greek, on the title page warns of the highly technical
 detail contained within: "Ageometretos oudeis eisito"
 - meaning, "Let no one untutored in geometry enter here"

De Revolutionibus is divided into six sections, or "books". The first of these books sets out Copernicus' heliocentric theory as the basis for his cosmology and ongoing calculations; the second book uses trigonometry to solve various motions of heavenly bodies in the sky; book three looks at the motion of the Earth; book four, the motion of the Moon; and books five and six, the motions of the planets. After the initial cosmological chapters, Copernicus' work becomes increasingly complex and mathematical as he attempts to show how his heliocentric cosmology permits astronomers to posit alternative methods from Ptolemy's to account for the motion of heavenly bodies. A very firm grasp of mathematics would have been required for a reader to follow all of his calculations and reasoning.
The astronomical theory in which Copernicus would have been schooled was based on the traditional Aristotelian philosophy of nature as interpreted and modified by later astronomers, notably Ptolemy of Alexandria in the Second Century AD. Aristotle saw the Universe as a spherical space of limited size, with the Earth sitting motionless at the centre. He stated that Heavens and Earth were separated by a spherical dividing wall. On the inside, everything was made from one of four elements: earth, water, air and fire, all constantly metamorphosing in a cycle of decay; on the heavenly side, he believed that everything was made of aether, a superior element which he thought incorruptible and unchanging. He attributed certain dynamic qualities to the elements, noting that stones fell to the ground while flames shot upwards; consequently he proposed that the earthly elements moved in straight lines while the purer, uncorrupted aether moved in perfect circles. His notion that heavenly bodies could only move in perfect circles was to endure for centuries and inform every subsequent attempt by astronomers to interpret what they observed in the skies.

Detail from folio 5v: this section of Copernicus' text refutes Ptolemy's assertion
 that the Earth remains at rest. Copernicus states: " the fear of Ptolemy
 that Earth and all thereon would be disintegrated by a natural rotation..."

Diagram from folio 9v depicting Copernicus' heliocentric cosmology

Detail from the heliocentric diagram showing Earth with its
 Moon orbiting

Early astronomers continually encountered difficulty reconciling what they observed with Aristotle's natural laws. In attempting to explain the erratic movements of the planets he observed, Ptolemy, working in Alexandria during the Second Century AD, employed two stratagems: firstly he supposed that the centre of a planet's orbit was not actually the Earth but was offset a small distance to another point (the equant) to create an excentric orbit (or deferent); secondly, he suggested that while following this excentric orbit, the planet completed a smaller orbit around a central point on the deferent (an epicycle). This theory, although ostensibly satisfying Aristotle's requirement for circular motion and reasonably explaining what was observed in the sky, was never entirely satisfactory to all astronomers. It necessitated that the epicycle orbit would move non-uniformly around the deferent circle - seen as a betrayal of Aristotle's true intention.
In placing the sun at the centre of the cosmos, Copernicus successfully showed that planetary motion could be explained without employing either an equant or the numerous planetary epicycles described by Ptolemy. Owen Gingerich, having studied marginal notes during his decades long census of early editions of De Revolutionibus, is convinced that, "because it satisfied the ancient aesthetic principle that eternal celestial motions should be uniform and circular", the majority of sixteenth century astronomers viewed eliminating the equant as Copernicus' big achievement - not his heliocentric cosmology. Gingerich suggests that many early readers of De Revolutionibus were less interested in Copernicus' correct view of the solar system as heliocentric and more interested in the theory's ability to better satisfy a wrong-headed view of the natural world!

Detail from folio 9v, where Copernicus sets out his cosmology: "In the middle of all sits
 Sun enthroned. In this most beautiful temple could we place this luminary in any better
 position from which he can illuminate the whole at once? ... So the Sun sits as
 upon a royal throne ruling his children the planets which circle round him.
  The Earth has the Moon at her service"


Copernicus' preface: "To the Most Holy Lord,
 Pope Paul III"


The above example shows what a difficult and slow process adherents persuading people to accept the heliocentric world view faced. Another impediment to its acceptance was its apparent contravention of Biblical scripture. Several Biblical passages asserted that the Earth was still and that the heavens moved. Just as Aristotelians attempted to reconcile Copernican ideas within traditional systems, so too did pious believers. Indeed, the majority of European astronomers during the Sixteenth Century, including Copernicus, would have been devout Christians, having been trained in astronomy as part of a general religious education. Educated Christian champions of heliocentrism often advocated a reinterpretation of Biblical scripture from the literal to the allegorical in attempting to make sense of Copernican ideas.

Detail from the preface. Copernicus, fully aware of how controversial his theory is, states:
 "I may well presume, most Holy Father, that certain people, as soon as they hear that
 in this book ... I ascribe movement to the earthly globe, will cry out that,
 holding such views, I should at once be hissed off the stage"

This tension between heliocentric theory and the Bible was clearly a significant worry for contemporary supporters of the theory, not least Copernicus. He decided (perhaps with this concern in mind) to dedicate his work to Pope Paul III, stating in the dedication that he feared attacks upon the heliocentric theory on the part of those who would quote certain Biblical passages "falsely distorted for their purpose". Interestingly, although apparently contradicting the Bible, De Revolutionibus avoided serious censorship until 1616, seventy three years after first publication, when it was placed on the Catholic Church's Index of Prohibited Books. In attempting to explain this it is perhaps necessary to return to the story of the initial printing.

Detail from the head of Osiander's prefatory "Ad lectorem". Note Willebrord Snell's manuscript attribution of authorship
 to Osiander, added below the title.

Andreas Osiander's anonymous "Ad lectorem"

Copernicus' friend Rheticus acted as an agent overseeing the printing of De Revolutionibus in Nuremberg; however, he could not oversee the whole process, so a local Lutheran clergyman, Andreas Osiander, helped in proofreading and liaising with the printer in Rheticus' absence. Not content with simply overseeing the work, Osiander seems to have added an anonymous preface to it, the Ad lectorem (To the reader). This preface states, "it is the duty of an astronomer to record the motion of the heavens with diligent and skilful observations, and then he has to propose their causes or, rather, hypotheses, since he cannot hope to attain the true reasons. . Our author has done both of these very well, for these hypotheses need not be true nor even probable; it is sufficient if the calculations agree with the observations". With this preface, Osiander arguably changed the whole nature of the work, his use of "these hypotheses need not be true nor even probable" moved De Revolutionibus from a true account of the world, to a useful thought-experiment.

Detail from the "Ad lectorem" stating that Copernicus' hypotheses "need not
 be true nor even probable; it is sufficient if the calculations agree
 with the observations"

Willebrord Snell's manuscript note on the title page asserts that, contrary to Osiander's "Ad lectorem",
 Copernicus did intend his work to be a true reflection of the real world: "Because of the inscription of
 Osiander, which Copernicus saw in the last days before he died, when he was already bedridden,
 his spirit was quite disturbed, according to what Rheticus once told Praetorius"

Rheticus seems to have been furious with Osiander's unprompted meddling. Owen Gingerich notes a manuscript comment made by the astronomer Michael Maestlin on a copy of De Revolutionibus now housed in Schaffhausen (Switzerland) which states, "Rheticus . became embroiled in a very bitter wrangle with the printer [over the Ad lectorem]. Rheticus . suspected Osiander had prefaced the work; if he knew this for certain, he declared, he would rough up the fellow so violently that in future he would mind his own business.".

Despite Rheticus' anger, Bruce Wrightsman has more recently argued that the Ad lectorem , "actually permitted the work to be used and pondered during . an extremely tense period of ideological and political conflict". Without Osiander's expedient preface, argues Wrightsman, the work may not have received such a wide readership, despite its usefulness not least for accurately calculating the date of religious festivals. Indeed, the work's eventual censorship seems largely to have been due to later commentators such as Kepler and Gallileo re-asserting its intentions as a true depiction of the natural world.

When placed on the "Index of Prohibited Books" in 1616, "De Revolutionibus" was not banned
 outright; however, in order to conform to Church orthodoxy it required modification to sections
 where it seemed to suggest a model of reality.  For example, the title of Book 1, Chapter 11
 (see above) was mandated to be changed from "The Explication of the three-fold motion
 of the Earth" to "The Hypothesis of the three-fold motion of the Earth"

The featured copy of De Revolutionibus is known to have passed through many hands, none more illustrious than its earliest known owner, the sixteenth century cartographer and polymath Gerhard Mercator (1512-94). Mercator was a fascinating character: he helped map the "New World" during the years of European expansion through foreign exploration and conquest. His globe making was unparalleled; his projection of a three dimensional globe onto a two dimensional map was innovative and revolutionary, while his humanistic appreciation of aesthetics helped spread the use of italic script to northern Europe. Interestingly, our copy of De Revolutionibus boasts both Mercator's calligraphic italic handwriting and his more functional cursive hand. According to Gingerich, he uses the former primarily for captions or isolated index notes, and the latter for other notes. Mercator felt that italic script was more important than mere decoration. In his 1541 volume Litteratum latinarum he remarks that the "Latin language . has a script of its own, elegant easy to write, and far more eligible than any other". Mercator observed that when Latin was written in Greek or Gothic script, it was as unworthy as, "a king [taking] off his purple . to go about in a beggar's clothing unworthy of his royal station".

Detail from folio 69v shows Mercator's distinctive calligraphic italic hand with its trademark capital "E"

Detail from folio 79v shows Mercator's cursive hand

Detail from the foot of folio 79v shows Snell's hand

Following Mercator's death the volume seems to have entered the collection of the Dutch mathematician Willebrord Snell (1580-1626). Snell, a mathematics and astronomy professor at Leiden University, apparently remained an adherent of Ptolemy's "geocentric" theory throughout his life, unconvinced by Copernicus' arguments. The heliocentric theory could only really claim mainstream adherence towards the end of the Seventeenth Century after the publication of Isaac Newton's Principia, following Kepler's earlier modifications.

Detail from the head of the title page confirms Colbert's one time ownership
 of the volume

The book finally arrived in the collections of Glasgow University in 1807 as part of the bequest of the famous Scottish obstetrician and bibliophile William Hunter (1718-83). Hunter bequeathed De Revolutionibus, along with his entire library and museum, to Glasgow University according to the terms of his will.  Prior to Hunter's ownership the volume was listed in the 1728 book sale of the French statesman Jean-Baptiste Colbert (1619-83) whose previous ownership is evidenced by a manuscript note at the head of the title page.  This remarkable volume, having travelled the length and breadth of Europe, surviving the threats of prohibition and the ravages of time, is truly a testament to past generations' pursuit of knowledge and preservation of learning.

Armitage, A. (1972). The World of Copernicus. Wakefiled: S. R. Publishers. Level 5 Main Lib Astronomy A11 1972-A


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Robert MacLean April 2008