De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) is the seminal work on the heliocentric theory of the astronomer Nicolaus Copernicus (1473–1543 CE). The book, first printed in 1543 CE in Nuremberg, Holy Roman Empire, offered an alternative model of the universe to Ptolemy's geocentric system, which had been widely accepted since ancient times.
History
Copernicus initially outlined his system in a short, untitled, anonymous manuscript that he distributed to several friends, referred to as the Commentariolus. A physician's library list dating to 1514 includes a manuscript whose description matches the Commentariolus, so Copernicus must have begun work on his new system by that time. Most historians believe that he wrote the Commentariolus after his return from Italy, possibly only after 1510. At this time, Copernicus anticipated that he could reconcile the motion of the Earth with the perceived motions of the planets easily, with fewer motions than were necessary in the version of the Ptolemaic system current at the time. Among other techniques, the heliocentric Copernican model made use of the Urdi Lemma developed in the 13th century by the Arab astronomer Mu'ayyad al-Din al-'Urdi, the first of the Maragha astronomers to develop a geocentric but non-Ptolemaic model of planetary motion.Saliba (1979).
Observations of Mercury by Bernhard Walther (1430–1504) of Nuremberg, a pupil of Regiomontanus, were made available to Copernicus by Johannes Schöner, 45 observations in total, 14 of them with longitude and latitude. Copernicus used three of them in De revolutionibus, giving only longitudes, and erroneously attributing them to Schöner. Copernicus' values differed slightly from the ones published by Schöner in 1544 in Observationes XXX annorum a I. Regiomontano et B. Walthero Norimbergae habitae, [4°, Norimb. 1544].
A manuscript of De revolutionibus in Copernicus' own hand has survived. After his death, it was given to his pupil, Rheticus, who for publication had only been given a copy without annotations. Via Heidelberg, it ended up in Prague, where it was rediscovered and studied in the 19th century. Close examination of the manuscript, including the different types of paper used, helped scholars construct an approximate timetable for its composition. Apparently Copernicus began by making a few astronomical observations to provide new data to perfect his models. He may have begun writing the book while still engaged in observations. By the 1530s a substantial part of the book was complete, but Copernicus hesitated to publish. In 1536, Cardinal Nikolaus von Schönberg wrote to Copernicus and urged him to publish his manuscript.
In 1539, Georg Joachim Rheticus, a young mathematician from Wittenberg, arrived in Frauenburg (Frombork) to study with him. Rheticus read Copernicus' manuscript and immediately wrote a non-technical summary of its main theories in the form of an open letter addressed to Schöner, his astrology teacher in Nürnberg; he published this letter as the Narratio Prima in Danzig in 1540. Rheticus' friend and mentor Achilles Gasser published a second edition of the Narratio in Basel in 1541. Due to its friendly reception, Copernicus finally agreed to publication of more of his main work—in 1542, a treatise on trigonometry, which was taken from the second book of the still unpublished De revolutionibus. Rheticus published it in Copernicus' name.
Under strong pressure from Rheticus, and having seen that the first general reception of his work had not been unfavorable, Copernicus finally agreed to give the book to his close friend, Bishop Tiedemann Giese, to be delivered to Rheticus in Wittenberg for printing by Johannes Petreius at Nürnberg (Nuremberg). It was published just before Copernicus' death, in 1543.
Copernicus kept a copy of his manuscript which, sometime after his death, was sent to Rheticus in the attempt to produce an authentic, unaltered version of the book. The plan failed but the copy was found during the 18th century and was published later.Teresa Borawska, The history of the original manuscript of "De revolutionibus" It is kept at the Jagiellonian University Library in Kraków, where it remains bearing the library number BJ 10 000.
Contents
From the first edition, Copernicus' book was prefixed with an anonymous preface which argues that the following is a calculus consistent with the observations, and cannot resolve philosophical truths. Only later was this revealed to be the unauthorized interjection by Lutheran preacher Andreas Osiander, who lived in Nuremberg when the first edition was printed there. This is followed by Copernicus' own preface, where he dedicates his work to Pope Paul III and appeals to the latter's skill as a mathematician to recognize the truth of Copernicus' hypothesis.
De revolutionibus is divided into six "books" (sections or parts), following closely the layout of Ptolemy's Almagest which it updated and replaced: Book I chapters 1–11 are a general vision of the heliocentric theory, and a summarized exposition of his cosmology. The world (heavens) is spherical, as is the Earth, and the land and water make a single globe. The celestial bodies, including the Earth, have regular circular and everlasting movements. The Earth rotates on its axis and around the Sun. Answers to why the ancients thought the Earth was central. The order of the planets around the Sun and their periodicity. Chapters 12–14 give theorems for chord geometry as well as a table of chords. Book II describes the principles of spherical astronomy as a basis for the arguments developed in the following books and gives a comprehensive catalogue of the fixed stars. Book III describes his work on the precession of the equinoxes and treats the apparent movements of the Sun and related phenomena. Book IV is a similar description of the Moon and its orbital movements. Book V explains how to calculate the positions of the wandering stars based on the heliocentric model and gives tables for the five planets. Book VI deals with the digression in latitude from the ecliptic of the five planets.
Copernicus argued that the universe comprised eight spheres. The outermost consisted of motionless, fixed stars, with the Sun motionless at the center. The known planets revolved about the Sun, each in its own sphere, in the order: Mercury, Venus, Earth, Mars, Jupiter, Saturn. The Moon, however, revolved in its sphere around the Earth. What appeared to be the daily revolution of the Sun and fixed stars around the Earth was actually the Earth's daily rotation on its own axis.
Copernicus adhered to one of the standard beliefs of his time, namely that the motions of celestial bodies must be composed of uniform circular motions. For this reason, he was unable to account for the observed apparent motion of the planets without retaining a complex system of epicycles similar to those of the Ptolemaic system. Despite Copernicus' adherence to this aspect of ancient astronomy, his radical shift from a geocentric to a heliocentric cosmology was a serious blow to Aristotle's science—and helped usher in the Scientific Revolution.
Ad lectorem
Rheticus left Nürnberg to take up his post as professor in Leipzig. Andreas Osiander had taken over the task of supervising the printing and publication. In an effort to reduce the controversial impact of the book Osiander added his own unsigned letter Ad lectorem de hypothesibus huius operis (To the reader concerning the hypotheses of this work)Wallis's translation (1952, p.505) printed in front of Copernicus' preface which was a dedicatory letter to Pope Paul III and which kept the title "Praefatio authoris" (to acknowledge that the unsigned letter was not by the book's author). Osiander's letter stated that Copernicus' system was mathematics intended to aid computation and not an attempt to declare literal truth:
As even Osiander's defenders point out, the Ad lectorem "expresses views on the aim and nature of scientific theories at variance with Copernicus' claims for his own theory".Andreas Osiander's Contribution to the Copernican Achievement, by Bruce Wrightsman, Section VII, The Copernican Achievement, ed. Robert S. Westman, University of California Press, Los Angeles, 1975 Many view Osiander's letter as a betrayal of science and Copernicus, and an attempt to pass his own thoughts off as those of the book's author. An example of this type of claim can be seen in the Catholic Encyclopedia, which states "Fortunately for him [the dying Copernicus], he could not see what Osiander had done. This reformer, knowing the attitude of Luther and Melanchthon against the heliocentric system ... without adding his own name, replaced the preface of Copernicus by another strongly contrasting in spirit with that of Copernicus."
While Osiander's motives behind the letter have been questioned by many, he has been defended by historian Bruce Wrightsman, who points out he was not an enemy of science. Osiander had many scientific connections including "Johannes Schoner, Rheticus's teacher, whom Osiander recommended for his post at the Nurnberg Gymnasium; Peter Apian of Ingolstadt University; Hieronymous Schreiber...Joachim Camerarius...Erasmus Reinhold...Joachim Rheticus...and finally, Hieronymous Cardan."
The historian Wrightsman put forward that Osiander did not sign the letter because he "was such a notorious [Protestant] reformer whose name was well-known and infamous among Catholics", so that signing would have likely caused negative scrutiny of the work of Copernicus (a loyal Catholic canon and scholar). Copernicus himself had communicated to Osiander his "own fears that his work would be scrutinized and criticized by the 'peripatetics and theologians'," and he had already been in trouble with his bishop, Johannes Dantiscus, on account of his former relationship with his mistress and friendship with Dantiscus's enemy and suspected heretic, Alexander Scultetus. It was also possible that Protestant Nurnberg could fall to the forces of the Holy Roman Emperor and since "the books of hostile theologians could be burned...why not scientific works with the names of hated theologians affixed to them?" Wrightsman also holds that this is why Copernicus did not mention his top student, Rheticus (a Lutheran) in the book's dedication to the Pope.
Osiander's interest in astronomy was theological, hoping for "improving the chronology of historical events and thus providing more accurate apocalyptic interpretations of the Bible... [he shared in] the general awareness that the calendar was not in agreement with astronomical movement and therefore, needed to be corrected by devising better models on which to base calculations." In an era before the telescope, Osiander (like most of the era's mathematical astronomers) attempted to bridge the "fundamental incompatibility between Ptolemaic astronomy and Aristotelian physics, and the need to preserve both", by taking an 'instrumentalist' position. Only the handful of "Philosophical purists like the Averroists... demanded physical consistency and thus sought for realist models."