## 1. Life and Works



Nicolaus Copernicus was born on 19 February 1473, the youngest of four
children of Nicolaus Copernicus, Sr., a well-to-do merchant who had
moved to Torun from Cracow, and Barbara Watzenrode, the daughter of a
leading merchant family in Torun. The city, on the Vistula River, had
been an important inland port in the Hanseatic League. However,
fighting between the Order of the Teutonic Knights and the Prussian
Union in alliance with the Kingdom of Poland ended in 1466, and West
Prussia, which included Torun, was ceded to Poland, and Torun was
declared a free city of the Polish kingdom. Thus the child of a German
family was a subject of the Polish crown.



The father died in 1483, and the children's maternal uncle,
Lucas Watzenrode (1447-1512), took them under his protection.
Watzenrode was a very successful cleric - he was to become
bishop of Warmia (Ermland in German) in 1489 - and he both
facilitated his nephew's advancement in the church and directed
his education. In 1491 Copernicus enrolled in the University of
Cracow. There is no record of his having obtained a degree, which was
not unusual at the time as he did not need a bachelor's degree
for his ecclesiastical career or even to study for a higher degree.
But the University of Cracow offered courses in mathematics,
astronomy, and astrology (see Goddu 25-33 on all the university
offerings), and Copernicus's interest was sparked, which is
attested to by his acquisition of books in these subjects while at
 Cracow.[1]



In 1495 Watzenrode arranged Copernicus's election as canon of
the chapter of Frombork (Frauenberg in German) of the Cathedral
Chapter of Warmia, an administrative position just below that of
bishop. He assumed the post two years later, and his financial
situation was secure for life. In the meantime, following in his
uncle's footsteps, Copernicus went to the University of Bologna
in 1496 to study canon law (see Goddu part 2 on what Copernicus may
have encountered in Italy). While at Bologna he lived with the
astronomy professor Domenico Maria Novara and made his first
astronomical observations. In addition, as Rosen (1971, 323) noted,
"In establishing close contact with Novara, Copernicus met,
perhaps for the first time in his life, a mind that dared to challenge
the authority of [Ptolemy] the most eminent ancient writer in his
chosen fields of study." Copernicus also gave a lecture on
mathematics in Rome, which may have focused on astronomy.



Copernicus's studies at Bologna provided an advantage he did not
have at Cracow - a teacher of Greek. Humanism began to
infiltrate the Italian universities in the fifteenth century. As
Grendler (510) remarked, "By the last quarter of the century,
practically all universities had one or several humanists, many of
them major scholars." Antonio Cortesi Urceo, called Codro,
became professor at Bologna in 1482 and added Greek several years
later. Copernicus may have studied with him, for Copernicus translated
into Latin the letters of the seventh-century Byzantine author
Theophylactus Simocatta (*MW* 27-71) from the 1499
edition of a collection of Greek letters produced by the Venetian
humanist printer Aldus Manutius. Aldus had dedicated his edition to
Urceo. Copernicus had his translation printed in 1509, his only
publication prior to the *On the Revolutions* (*De
revolutionibus*). It is important to note that Copernicus's
acquisition of a good reading knowledge of Greek was critical for his
studies in astronomy because major works by Greek astronomers,
including Ptolemy, had not yet been translated into Latin, the
language of the universities at the time.



Copernicus left Bologna for Frombork in 1501 without having obtained
his degree. The chapter then approved another leave of absence for
Copernicus to study medicine at the University of Padua. The medical
curriculum did not just include medicine, anatomy, and the like when
Copernicus studied it. Siraisi (1990, 16) noted that "the
reception in twelfth-century western Europe of Greek and Islamic
technical astronomy and astrology fostered the development of medical
astrology...the actual practice of medical astrology was greatest
in the West between the fourteenth and the sixteenth centuries."
Astrology was taught in the medical schools of Italy. "The
importance attached to the study of the stars in medieval medical
education derived from a general and widely held belief that the
heavenly bodies play an intermediary role in the creation of things
here below and continue to influence them throughout their existence.
The actual uses of astrology in medical diagnosis and treatment by
learned physicians were many and various. 'Astrological
medicine' is a vague and unsatisfactory term that can embrace
any or all of the following: first, to pay attention to the supposed
effect of astrological birth signs or signs at conception on the
constitution and character of one's patients; second, to vary
treatment according to various celestial conditions...third, to
connect the doctrine of critical days in illness with astrological
features, usually phases of the moon; and fourth, to predict or
explain epidemics with reference to planetary conjunctions, the
appearance of comets, or weather conditions" (Siraisi 1981,
141-42). It is true that astrology required that medical
students acquire some grounding in astronomy; nevertheless, it is
likely that Copernicus studied astrology while at the University of
 Padua.[2]



Copernicus did not receive his medical degree from Padua; the degree
would have taken three years, and Copernicus had only been granted a
two-year leave of absence by his chapter. Instead he matriculated in
the University of Ferrara, from which he obtained a doctorate in canon
law. But he did not return to his chapter in Frombork; rather he went
to live with his uncle in the episcopal palace in Lidzbark-Warminski
(Heilsberg in German). Although he made some astronomical
observations, he was immersed in church politics, and after his
elderly uncle became ill in 1507, Copernicus was his attending
physician. Rosen (1971, 334-35) reasonably conjectured that the
bishop may have hoped that his nephew would be his successor, but
Copernicus left his uncle because his duties in Lidzbark-Warminski
interfered with his continuing pursuit of his studies in astronomy. He
took up residence in his chapter of Frombork in 1510 and stayed there
the rest of his life.



Not that leaving his uncle and moving to Frombork exempted Copernicus
from continued involvement in administrative and political duties. He
was responsible for the administration of various holdings, which
involved heading the provisioning fund, adjudicating disputes,
attending meetings, and keeping accounts and records. In response to
the problem he found with the local currency, he drafted an essay on
coinage (*MW* 176-215) in which he deplored the
debasement of the currency and made recommendations for reform. His
manuscripts were consulted by the leaders of both Prussia and Poland
in their attempts to stabilize the currency. He was a leader for West
Prussia in the war against the Teutonic Knights, which lasted from
1520-1525. He was physician for the bishop (his uncle had died
in 1512) and members of the chapter, and he was consulting physician
for notables in East and West Prussia.



Nevertheless, Copernicus began to work on astronomy on his own.
Sometime between 1510 and 1514 he wrote an essay that has come to be
known as the *Commentariolus* (*MW* 75-126) that
introduced his new cosmological idea, the heliocentric universe, and
he sent copies to various astronomers. He continued making
astronomical observations whenever he could, hampered by the poor
position for observations in Frombork and his many pressing
responsibilities as canon. Nevertheless, he kept working on his
manuscript of *On the Revolutions*. He also wrote what is known
as *Letter against Werner* (*MW* 145-65) in 1524,
a critique of Johann Werner's "Letter concerning the
Motion of the Eighth Sphere" (*De motu octavae sphaerae
tractatus primus*). Copernicus claimed that Werner erred in his
calculation of time and his belief that before Ptolemy the movement of
the fixed stars was uniform, but Copernicus's letter did not
refer to his cosmological ideas.



In 1539 a young mathematician named Georg Joachim Rheticus
(1514-1574) from the University of Wittenberg came to study with
Copernicus. Rheticus brought Copernicus books in mathematics, in part
to show Copernicus the quality of printing that was available in the
German-speaking cities. He published an introduction to
Copernicus's ideas, the *Narratio prima* (First Report).
Most importantly, he convinced Copernicus to publish *On the
Revolutions*. Rheticus oversaw most of the printing of the book,
and on 24 May 1543 Copernicus held a copy of the finished work on his
deathbed.


## 2. Astronomical Ideas and Writings


### 2.1 Pre-Copernican Astronomy



Classical astronomy followed principles established by Aristotle.
Aristotle accepted the idea that there were four physical elements
- earth, water, air, and fire. He put the earth in the center of
the universe and contended that these elements were below the moon,
which was the closest celestial body. There were seven planets, or
wandering stars, because they had a course through the zodiac in
addition to traveling around the earth: the moon, Mercury, Venus, the
sun, Mars, Jupiter. Beyond that were the fixed stars. The physical
elements, according to Aristotle moved vertically, depending on their
'heaviness' or 'gravity'; the celestial bodies
were not physical but a 'fifth element' or
'quintessence' whose nature was to move in perfect circles
around the earth, making a daily rotation. Aristotle envisioned the
earth as the true center of all the circles or 'orbs'
carrying the heavenly bodies around it and all motion as
'uniform,' that is, unchanging.



But observers realized that the heavenly bodies did not move as
Aristotle postulated. The earth was not the true center of the orbits
and the motion was not uniform. The most obvious problem was that the
outer planets seemed to stop, move backwards in
'retrograde' motion for a while, and then continue
forwards. By the second century, when Ptolemy compiled his
*Almagest* (this common name of Ptolemy's
*Syntaxis* was derived from its Arabic title), astronomers had
developed the concept that the orbit moves in 'epicycles'
around a 'deferrent,' that is, they move like a flat
heliacal coil around a circle around the earth. The earth was also
off-center, on an 'eccentric,' as the heavenly bodies
moved around a central point. Ptolemy added a point on a straight line
opposite the eccentric, which is called the 'equalizing
point' or the 'equant,' and around this point the
heavenly bodies moved uniformly. Moreover, unlike the Aristotelian
model, Ptolemy's *Almagest* did not describe a unified
universe. The ancient astronomers who followed Ptolemy, however, were
not concerned if his system did not describe the 'true'
motions of the heavenly bodies; their concern was to 'save the
phenomena,' that is, give a close approximation of where the
heavenly bodies would be at a given point in time. And in an age
without professional astronomers, let alone the telescope, Ptolemy did
a good job plotting the courses of the heavenly bodies.



Not all Greek astronomical ideas followed this geocentric system.
Pythagoreans suggested that the earth moved around a central fire (not
the sun). Archimedes wrote that Aristarchus of Samos actually proposed
that the earth rotated daily and revolved around the
 sun.[3]



During the European Middle Ages, the Islamic world was the center of
astronomical thought and activity. During the ninth century several
aspects of Ptolemy's solar theory were recalculated. Ibn
al-Haytham in the tenth-eleventh century wrote a scathing critique of
Ptolemy's work: "Ptolemy assumed an arrangement that
cannot exist, and the fact that this arrangement produces in his
imagination the motions that belong to the planets does not free him
from the error he committed in his assumed arrangement, for the
existing motions of the planets cannot be the result of an arrangement
that is impossible to exist" (quoted in Rosen 1984, 174).
Swerdlow and Neugebauer (46-48) stressed that the
thirteenth-century Maragha school was also important in finding errors
and correcting Ptolemy: "The method of the Maragha planetary
models was to break up the equant motion in Ptolemy's models
into two or more components of uniform circular motion, physically the
uniform rotation of spheres, that together control the direction and
distance of the center of the epicycle, so that it comes to lie in
nearly the same position it would have in Ptolemy's model, and
always moves uniformly with respect to the equant." They found
that Copernicus used devices that had been developed by the Maragha
astronomers Nasir al-Din Tusi (1201-1274), Muayyad al-Din
al-Urdi (d. 1266), Qutb al-Din al-Shirazi (1236-1311), and Ibn
al-Shatir (1304-1375). In addition, Ragep, 2005, has shown that
a theory for the inner planets presented by Regiomontanus that enabled
Copernicus to convert the planets to eccentric models had been
developed by the fifteenth-century, Samarqand-trained astronomer ali
Qushji
 (1403-1474).[4]



Renaissance humanism did not necessarily promote natural philosophy,
but its emphasis on mastery of classical languages and texts had the
side effect of promoting the sciences. Georg Peurbach
(1423-1461) and (Johannes Muller) Regiomontanus
(1436-1476) studied Greek for the purpose of producing an
outline of Ptolemaic astronomy. By the time Regiomontanus finished the
work in 1463, it was an important commentary on the *Almagest*
as well, pointing out, for example, that Ptolemy's lunar theory
did not accord with observations. He noted that Ptolemy showed the
moon to be at various times twice as far from the earth as at other
times, which should make the moon appear twice as big. At the time,
moreover, there was active debate over Ptolemy's deviations from
Aristotle's requirement of uniform circular motion.


### 2.2 The *Commentariolus*



It is impossible to date when Copernicus first began to espouse the
heliocentric theory. Had he done so during his lecture in Rome, such a
radical theory would have occasioned comment, but there was none, so
it is likely that he adopted this theory after 1500. Further,
Corvinus, who helped him print his Latin translation in 1508-09,
expressed admiration for his knowledge of astronomy, so that
Copernicus's concept may have still been traditional at this
point. His first heliocentric writing was his *Commentariolus*.
It was a small manuscript that was circulated but never printed. We do
not know when he wrote this, but a professor in Cracow cataloged his
books in 1514 and made reference to a "manuscript of six leaves
expounding the theory of an author who asserts that the earth moves
while the sun stands still" (Rosen, 1971, 343; *MW* 75).
Thus, Copernicus probably adopted the heliocentric theory sometime
between 1508 and 1514. Rosen (1971, 345) suggested that
Copernicus's "interest in determining planetary positions
in 1512-1514 may reasonably be linked with his decisions to
leave his uncle's episcopal palace in 1510 and to build his own
outdoor observatory in 1513." In other words, it was the result
of a period of intense concentration on cosmology that was facilitated
by his leaving his uncle and the attendant focus on church politics
and medicine.



It is impossible to know exactly why Copernicus began to espouse the
heliocentric cosmology. Despite his importance in the history of
philosophy, there is a paucity of primary sources on Copernicus. His
only astronomical writings were the *Commentariolus*, the
*Letter against Werner*, and *On the Revolutions*; he
published his translation of Theophylactus's letters and wrote
the various versions of his treatise on coinage; other writings relate
to diocesan business, as do most of the few letters that survive.
Sadly, the biography by Rheticus, which should have provided scholars
with an enormous amount of information, has been lost. Therefore, many
of the answers to the most interesting questions about
Copernicus's ideas and works have been the result of conjecture
and inference, and we can only guess why Copernicus adopted the
heliocentric system.



Most scholars believe that the reason Copernicus rejected Ptolemaic
cosmology was because of Ptolemy's
 equant.[5]
 They assume this because of what Copernicus wrote in the
*Commentariolus*:



> 
> Yet the widespread [planetary theories], advanced by Ptolemy and most
> other [astronomers], although consistent with the numerical [data],
> seemed likewise to present no small difficulty. For these theories
> were not adequate unless they also conceived certain equalizing
> circles, which made the planet appear to move at all times with
> uniform velocity neither on its deferent sphere nor about its own
> [epicycle's] center...Therefore, having become aware of
> these [defects], I often considered whether there could perhaps be
> found a more reasonable arrangement of circles, from which every
> apparent irregularity would be derived while everything in itself
> would move uniformly, as is required by the rule of perfect motion.
> (*MW* 81).
> 



Goddu (381-84) has plausibly maintained that while the initial
motivation for Copernicus was dissatisfaction with the equant, that
dissatisfaction may have impelled him to observe other violations of
uniform circular motion, and those observations, not the rejection of
the equant by itself, led to the heliocentric theory. Blumenberg (254)
has pointed out that the mobility of the earth may have been
reinforced by the similarity of its spherical shape to those of the
heavenly bodies.



As the rejection of the equant suggests a return to the Aristotelian
demand for true uniform circular motion of the heavenly bodies, it is
unlikely that Copernicus adopted the heliocentric model because
philosophies popular among Renaissance humanists like Neoplatonism and
Hermetism compelled him in that
 direction.[6]
 Nor should we attribute Copernicus's desire for uniform
circular motions to an aesthetic need, for this idea was philosophical
not aesthetic, and Copernicus's replacing the equant with
epicyclets made his system more complex than Ptolemy's. Most
importantly, we should bear in mind what Swerdlow and Neugebauer (59)
asserted:



> 
> Copernicus arrived at the heliocentric theory by a careful analysis of
> planetary models - and as far as is known, he was the only
> person of his age to do so - and if he chose to adopt it, he did
> so on the basis of an equally careful analysis.
> 



In the *Commentariolus* Copernicus listed assumptions that he
believed solved the problems of ancient astronomy. Bardi has suggested
that these assumptions are non-Euclidean axioms. Copernicus stated
that the earth is only the center of gravity and center of the
moon's orbit; that all the spheres encircle the sun, which is
close to the center of the universe; that the universe is much larger
than previously assumed, and the earth's distance to the sun is
a small fraction of the size of the universe; that the apparent motion
of the heavens and the sun is created by the motion of the earth; and
that the apparent retrograde motion of the planets is created by the
earth's motion. Although the Copernican model maintained
epicycles moving along the deferrent, which explained retrograde
motion in the Ptolemaic model, Copernicus correctly explained that the
retrograde motion of the planets was only apparent not real, and its
appearance was due to the fact that the observers were not at rest in
the center. The work dealt very briefly with the order of the planets
(Mercury, Venus, earth, Mars, Jupiter, and Saturn, the only planets
that could be observed with the naked eye), the triple motion of the
earth (the daily rotation, the annual revolution of its center, and
the annual revolution of its inclination) that causes the sun to seem
to be in motion, the motions of the equinoxes, the revolution of the
moon around the earth, and the revolution of the five planets around
the sun.


### 2.3 *On the Revolutions*



The *Commentariolus* was only intended as an introduction to
Copernicus's ideas, and he wrote "the mathematical
demonstrations intended for my larger work should be omitted for
brevity's sake..." (*MW* 82). In a sense it
was an announcement of the greater work that Copernicus had begun. The
*Commentariolus* was never published during Copernicus's
lifetime, but he sent manuscript copies to various astronomers and
philosophers. He received some discouragement because the heliocentric
system seemed to disagree with the Bible, but mostly he was
encouraged. Although Copernicus's involvement with official
attempts to reform the calendar was limited to a no longer extant
letter, that endeavor made a new, serious astronomical theory welcome.
Fear of the reaction of ecclesiastical authorities was probably the
least of the reasons why he delayed publishing his
 book.[7]
 The most important reasons for the delay was that the larger work
required both astronomical observations and intricate mathematical
proofs. His administrative duties certainly interfered with both the
research and the writing. He was unable to make the regular
observations that he needed and Frombork, which was often fogged in,
was not a good place for those observations. Moreover, as Gingerich
(1993, 37) pointed out,



> 
> [Copernicus] was far from the major international centers of printing
> that could profitably handle a book as large and technical as *De
> revolutionibus*. On the other [hand], his manuscript was still
> full of numerical inconsistencies, and he knew very well that he had
> not taken complete advantage of the opportunities that the
> heliocentric viewpoint offered...Furthermore, Copernicus was far
> from academic centers, thereby lacking the stimulation of technically
> trained colleagues with whom he could discuss his work.
> 



The manuscript of *On the Revolutions* was basically complete
when Rheticus came to visit him in 1539. The work comprised six books.
The first book, the best known, discussed what came to be known as the
Copernican theory and what is Copernicus's most important
contribution to astronomy, the heliocentric universe (although in
Copernicus's model, the sun is not truly in the center). Book 1
set out the order of the heavenly bodies about the sun: "[The
sphere of the fixed stars] is followed by the first of the planets,
Saturn, which completes its circuit in 30 years. After Saturn, Jupiter
accomplishes its revolution in 12 years. The Mars revolves in 2 years.
The annual revolution takes the series' fourth place, which
contains the earth...together with the lunar sphere as an
epicycle. In the fifth place Venus returns in 9 months. Lastly, the
sixth place is held by Mercury, which revolves in a period of 80
days" (*Revolutions*, 21-22). This established a
relationship between the order of the planets and their periods, and
it made a unified system. This may be the most important argument in
favor of the heliocentric model as Copernicus described
 it.[8]
 It was far superior to Ptolemy's model, which had the planets
revolving around the earth so that the sun, Mercury, and Venus all had
the same annual revolution. In book 1 Copernicus also insisted that
the movements of all bodies must be circular and uniform, and noted
that the reason they may appear nonuniform to us is "either that
their circles have poles different [from the earth's] or that
the earth is not at the center of the circles on which they
revolve" (*Revolutions*, 11). Particularly notable for
Copernicus was that in Ptolemy's model the sun, the moon, and
the five planets seemed ironically to have different motions from the
other heavenly bodies and it made more sense for the small earth to
move than the immense heavens. But the fact that Copernicus turned the
earth into a planet did not cause him to reject Aristotelian physics,
for he maintained that "land and water together press upon a
single center of gravity; that the earth has no other center of
magnitude; that, since earth is heavier, its gaps are filled with
water..." (*Revolutions*, 10). As Aristotle had
asserted, the earth was the center toward which the physical elements
gravitate. This was a problem for Copernicus's model, because if
the earth was no longer the center, why should elements gravitate
toward it?



The second book of *On the Revolutions* elaborated the concepts
in the first book; book 3 dealt with the precession of the equinoxes
and solar theory; book 4 dealt with the moon's motions; book 5
dealt with the planetary longitude and book 6 with
 latitude.[9]
 Copernicus depended very much on Ptolemy's observations, and
there was little new in his mathematics. He was most successful in his
work on planetary longitude, which, as Swerdlow and Neugebauer (77)
commented, was "Copernicus's most admirable, and most
demanding, accomplishment...It was above all the decision to
derive new elements for the planets that delayed for nearly half a
lifetime Copernicus's continuation of his work - nearly
twenty years devoted to observation and then several more to the most
tedious kind of computation - and the result was recognized by
his contemporaries as the equal of Ptolemy's accomplishment,
which was surely the highest praise for an astronomer."
Surprisingly, given that the elimination of the equant was so
important in the *Commentariolus*, Copernicus did not mention
it in book 1, but he sought to replace it with an epicyclet throughout
*On the Revolutions*. Nevertheless, he did write in book 5 when
describing the motion of Mercury:



> 
> ...the ancients allowed the epicycle to move uniformly only
> around the equant's center. This procedure was in gross conflict
> with the true center [of the epicycle's motion], its relative
> [distances], and the prior centers of both [other
> circles]...However, in order that this last planet too may be
> rescued from the affronts and pretenses of its detractors, and that
> its uniform motion, no less than that of the other aforementioned
> planets, may be revealed in relation to the earth's motion, I
> shall attribute to it too, [as the circle mounted] on its eccentric,
> an eccentric instead of the epicycle accepted in antiquity
> (*Revolutions*, 278-79).
> 


### 2.4 Rheticus and the *Narratio prima*



Although Copernicus received encouragement to publish his book from
his close friend, the bishop of Chelmo Tiedemann Giese
(1480-1550), and from the cardinal of Capua Nicholas
Schonberg (1472-1537), it was the arrival of Georg Joachim
Rheticus in Frombork that solved his needs for a supportive and
stimulating colleague in mathematics and astronomy and for access to
an appropriate printer. Rheticus was a professor of mathematics at the
University of Wittenberg, a major center for the student of
mathematics as well as for Lutheran theology. In 1538 Rheticus took a
leave of absence to visit several famous scholars in the fields of
astronomy and mathematics. It is not known how Rheticus learned about
Copernicus's theory; he may have been convinced to visit
Copernicus by one of the earlier scholars he had visited, Johann
Schoner, though, as Swerdlow and Neugebauer (16) noted, by
"the early 1530's knowledge of Copernicus's new
theory was circulating in Europe, even reaching the high and learned
circles of the Vatican." Rheticus brought with him some
mathematical and astronomical volumes, which both provided Copernicus
with some important material and showed him the quality of the
mathematical printing available in the German centers of
 publishing.[10]
 Rheticus's present of the 1533 edition of Regiomontanus's
*On all Kinds of Triangles* (*De triangulis omnimodis*),
for example, convinced Copernicus to revise his section on
trigonometry. But Rheticus was particularly interested in showing
Copernicus the work of the Nuremberg publisher Johann Petreius as a
possible publisher of Copernicus's volume. Swerdlow and
Neugebauer (25) plausibly suggested that "Petreius was offering
to publish Copernicus's work, if not advertising by this notice
that he was already committed to do so." Rheticus wrote the
*Narratio prima* in 1540, an introduction to the theories of
Copernicus, which was published and circulated. This further
encouraged Copernicus to publish his *Revolutions*, which he
had been working on since he published the
*Commentariolus*.



The *Narratio prima* was written in 1539 and took the form of a
letter to Johann Schoner announcing Copernicus's findings
and describing the contents of the *Revolutions*. He dealt with
such topics as the motions of the fixed stars, the tropical year, the
obliquity of the ecliptic, the problems resulting from the motion of
the sun, the motions of the earth and the other planets, librations,
longitude in the other five planets, and the apparent deviation of the
planets from the ecliptic. He asserted that the heliocentric universe
should have been adopted because it better accounted for such
phenomena as the precession of the equinoxes and the change in the
obliquity of the ecliptic; it resulted in a diminution of the
eccentricity of the sun; the sun was the center of the deferents of
the planets; it allowed the circles in the universe to revolve
uniformly and regularly; it satisfied appearances more readily with
fewer explanations necessary; it united all the spheres into one
system. Rheticus added astrological predictions and number mysticism,
which were absent from Copernicus's work.



The *Narratio prima* was printed in 1540 in Gdansk (then
Danzig); thus, it was the first printed description of the Copernican
thesis. Rheticus sent a copy to Achilles Pirmin Gasser of Feldkirch,
his hometown in modern-day Austria, and Gasser wrote a foreword that
was published with a second edition that was produced in 1541 in
Basel. It was published again in 1596 as an appendix to the first
edition of Johannes Kepler's *Mysterium cosmographicum*
(Secret of the Universe), the first completely Copernican work by an
adherent since the publications by Copernicus and Rheticus.


### 2.5 Printing *On the Revolutions* and Osiander's Preface



The publication of Rheticus's *Narratio prima* did not
create a big stir against the heliocentric thesis, and so Copernicus
decided to publish *On the Revolutions*. He added a dedication
to Pope Paul III (r. 1534-1549), probably for political reasons,
in which he expressed his hesitancy about publishing the work and the
reasons he finally decided to publish it. He gave credit to
Schonberg and Giese for encouraging him to publish and omitted
mention of Rheticus, but it would have been insulting to the pope
during the tense period of the Reformation to give credit to a
Protestant
 minister.[11]
 He dismissed critics who might have claimed that it was against the
Bible by giving the example of the fourth-century Christian apologist
Lactantius, who had rejected the spherical shape of the earth, and by
asserting, "Astronomy is written for astronomers"
(*Revolutions*,
 5).[12]
 In other words, theologians should not meddle with it. He pointed to
the difficulty of calendar reform because the motions of the heavenly
bodies were inadequately known. And he called attention to the fact
that "if the motions of the other planets are correlated with
the orbiting of the earth, and are computed for the revolution of each
planet, not only do their phenomena follow therefrom but also the
order and size of all the planets and spheres, and heaven itself is so
linked together that in no portion of it can anything be shifted
without disrupting the remaining parts and the universe as a
whole" (*Revolutions*, 5).



Rheticus returned to Wittenberg in 1541 and the following year
received another leave of absence, at which time he took the
manuscript of the *Revolutions* to Petreius for publishing in
Nuremberg. Rheticus oversaw the printing of most of the text. However,
Rheticus was forced to leave Nuremberg later that year because he was
appointed professor of mathematics at the University of Leipzig. He
left the rest of the management of printing the *Revolutions*
to Andrew Osiander (1498-1552), a Lutheran minister who was also
interested in mathematics and astronomy. Though he saw the project
through, Osiander appended an anonymous preface to the work. In it he
claimed that Copernicus was offering a hypothesis, not a true account
of the working of the heavens: "Since he [the astronomer] cannot
in any way attain to the true causes, he will adopt whatever
suppositions enable the motions to be computed correctly from the
principles of geometry for the future as well as for the past
...these hypotheses need not be true nor even probable"
(*Revolutions, xvi*). This clearly contradicted the body of the
work. Both Rheticus and Giese protested, and Rheticus crossed it out
in his copy.


### 2.6 Sixteenth Century Reactions to *On the Revolutions*



Copernicus's fame and book made its way across Europe over the
next fifty years, and a second edition was brought out in
 1566.[13]
 As Gingerich's census of the extant copies showed, the book was
read and commented on by astronomers (for a fuller discussion of
reactions, see Omodeo). Gingerich (2004, 55) noted "the majority
of sixteenth-century astronomers thought eliminating the equant was
Copernicus' big achievement."



While Martin Luther may have made negative comments about Copernicus
because the idea of the heliocentric universe seemed to contradict the
 Bible,[14]
 Philip Melanchthon (1497-1560), who presided over the
curriculum at the University of Wittenberg, eventually accepted the
importance of teaching Copernicus's ideas, perhaps because
Osiander's preface made the work more palatable. His son-in-law
Caspar Peucer (1525-1602) taught astronomy there and began
teaching Copernicus's work. As a result, the University of
Wittenberg became a center where Copernicus's work was studied.
But Rheticus was the only Wittenberg scholar who accepted the
heliocentric idea. Robert Westman (1975a, 166-67; 2011, chap. 5)
suggested that there was a 'Wittenberg Interpretation':
astronomers appreciated and adopted some of Copernicus's
mathematical models but rejected his cosmology, and some were pleased
with his replacement of the equant by epicyclets. One of these was
Erasmus Reinhold (1511-1553), a leading astronomer at Wittenberg
who became dean and rector. He produced a new set of planetary tables
from Copernicus's work, the Prutenic Tables. Although, as
Gingerich (1993, 232) pointed out, "there was relatively little
to distinguish between the accuracy of the *Alfonsine Tables*
and the *Prutenic Tables*," the latter were more widely
adopted; Gingerich plausibly suggested that the fact that the Prutenic
Tables more accurately predicted a conjunction between Jupiter and
Saturn in 1563 made the difference. Reinhold did not accept the
heliocentric theory, but he admired the elimination of the equant. The
Prutenic Tables excited interest in Copernicus's work.



Tycho Brahe (1546-1601) was the greatest astronomical observer
before the invention of the telescope. He called Copernicus a
'second Ptolemy' (quoted in Westman 1975, 307) and
appreciated both the elimination of the equant and the creation of a
planetary system. But Tycho could not adopt the Copernican system,
partly for the religious reason that it went against what the Bible
seemed to preach. He, therefore, adopted a compromise, the
'geoheliostatic' system in which the two inner planets
revolved around the sun and that system along with the rest of the
planets revolved around the earth.



Among Catholics, Christoph Clavius (1537-1612) was the leading
astronomer in the sixteenth century. A Jesuit himself, he incorporated
astronomy into the Jesuit curriculum and was the principal scholar
behind the creation of the Gregorian calendar. Like the Wittenberg
astronomers, Clavius adopted Copernican mathematical models when he
felt them superior, but he believed that Ptolemy's cosmology
- both his ordering of the planets and his use of the equant
- was correct.



Pope Clement VII (r. 1523-1534) had reacted favorably to a talk
about Copernicus's theories, rewarding the speaker with a rare
manuscript. There is no indication of how Pope Paul III, to whom
*On the Revolutions* was dedicated reacted; however, a trusted
advisor, Bartolomeo Spina of Pisa (1474-1546) intended to
condemn it but fell ill and died before his plan was carried out (see
Rosen, 1975). Thus, in 1600 there was no official Catholic position on
the Copernican system, and it was certainly not a heresy. When
Giordano Bruno (1548-1600) was burned at the stake as a heretic,
it had nothing to do with his writings in support of Copernican
cosmology, and this is clearly shown in Finocchiaro's
reconstruction of the accusations against Bruno (see also
Blumenberg's part 3, chapter 5, titled "Not a Martyr for
Copernicanism: Giordano Bruno").



Michael Maestlin (1550-1631) of the University of Tubingen
was the earliest astronomer after Rheticus to adopt Copernicus's
heliocentricism. Although he wrote a popular textbook that was
geocentric, he taught his students that the heliocentric system was
superior. He also rejected Osiander's preface. Maestlin's
pupil Johannes Kepler wrote the first book since the publication of
*On the Revolutions* that was openly heliocentric in its
orientation, the *Mysterium cosmographicum* (Secret of the
Universe). And, of course, Kepler eventually built on
Copernicus's work to create a much more accurate description of
the solar system.