When the Earth Moved
Copernicus and his Heliocentric System of the Universe
by Dr. Severyn Żołędziowski
The following is the edited text of a presentation made on October 20, 1993 at a joint meeting of the Polish Arts Club of Buffalo and the Buffalo Museum of Science in commemoration of the 450th anniversary of the first printing of Nicholas Copernicus' immortal work which revolutionized astronomy|
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Copernicus; The Formative Years
In commemorating this important historical milestone, I will review the life and work of the great Polish astronomer, give the history behind the writing of the book and its later fates, and say a few words about the Copernican model of the universe.The heliocentric model of the universe, which is now universally accepted and included in all science curricula taught in schools and colleges, was not always acknowledged by scholars. The history of Copernicanism, as this cosmological theory is called, is a case study in the evolution of human thinking and the difficulty encountered in challenging well-established traditions.
Copernicus (Mikołaj Kopernik) had to develop and demonstrate the validity of the mathematical model which reflected the physical reality of the solar system. He also had to overcome centuries-old and well entrenched concepts of the universe.
In order to put Copernicus' work into historical perspective let us first review the cosmology to which Copernicus was exposed as a student. We will then give a description of how the concept of the Copernican universe evolved, and end with a short history of the writing and publication of the book, its initial criticism and its final recognition.
Cosmology and the Calendar
Observations of the sky have been conducted since the dawn of time. Initially, the solar day was used for short term time keeping and longer periods were measured by tracking the phases of the moon. The main purpose of such long-term time keeping was to develop a means of predicting natural phenomena such as the seasons, the flooding of the Nile, lunar eclipses, etc., and to develop a calendar which could be used for scheduling religious feasts and festivals. Problems arose when the sun begun to be used as a reference point for long-term time keeping.The earliest solar calendars were based on a year which bad 360 days, a nice round number in the hexadecimal numbering system (one based on base number of 16 rather than 10). However, as we now know, the year has 365 days, hence "New Year's Day" gradually crept around the cycle of seasons. The calendar was scarcely useful over long periods of time, because important seasonal events, such as the flooding of the Nile in Egypt, occurred at later and later dates in successive years. To keep in step with the seasons, the Egyptians added five extra days, a holiday season, to their original year.
It turned out that the 365 day year was also too short and after 40 years the Egyptian calendar was again out of step with the seasons, this time by 10 days. Therefore, with the help of Egyptian astronomers, Julius Caesar reformed the calendar. He based the new calendar upon a year of 365¬ days: three years of 365 days followed by one year of 366 days. This calendar was used throughout Europe from 45 BC until after the death of Copernicus. But the seasonal year is actually 11 mi and 14 sec shorter than 365¬, therefore by Copernicus' lifetime, the vernal equinox had moved backward from March 21 to March 11.
The resulting demand for calendar reform provided an important motive for the reform of astronomy itself. The Catholic Church was interested in the development of science in general and supported the work of astronomers. This is also true about Copernicus whose studies were sponsored by his uncle, the bishop, and whose work gained him recognition even in Vatican circles. During Copernicus' lifetime, Pope Leo X started work on the reform of the calendar. Copernicus was invited to take part in the studies but did not participate at the conference in person. We know from preserved documents that he did submit a paper, but unfortunately, it has not been found so we will never know for sure what Copernicus wrote. There are some indications, however, that he expressed an opinion that the existing models of the universe were inadequate to create a "long term calendar" which would be synchronized with the seasons. The reform that gave the Western world its modern calendar followed the publication of De Revolutionbus by only thirty-nine years. The new calendar, called the Gregorian calendar after Pope Gregory XIII during whose pontificate it was introduced, suppresses a leap year three times every four hundred years. The year 1600 was a leap year and the year 2000 will be a leap year, but 1700, 1800 and 1900 had only 365 days.
The Earth: Center of the Universe
The cosmological theory which was universally accepted in Copernicus' time placed the earth in the center of the universe. It was based on the Almagest (The Great Compilation), a book written by Ptolemy in the second century BC. According to this geocentric model of the universe the earth was surrounded by eight spheres which encircled it. For over 12 centuries the model served astronomers, scientists and theologians. The moon, sun, planets and stars each occupied a separate sphere which moved in accordance with the perceived motion of the celestial body occupying it. The model envisioned that the moon occupied the first sphere, Mercury the second, Venus the third, then came the sun, followed by Mars, Jupiter and Saturn. The fixed stars occupied the eighth sphere. Theologians placed heaven on the ninth sphere, and by symmetry, placed nine rings of hell below the surface of the earth.To place Copernicus' work in a historical perspective, reference can be made to a time-line which lists Copernicus together with other famous astronomers and scholars and gives their dates of birth and death.
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Copernicus; The Formative Years
Copernicus was born in Toruń on February 19, 1473 as the fourth child of a wealthy merchant. The spelling of his name, takes on a number of forms ranging from Koppernigk to Kopernik, but best known is the Latinized version: Copernicus.His mother died when he was a young boy and shortly thereafter, his father also passed away. The children were left in the care of their maternal uncle Lucas Watzenrode (Waczelrodt) who later became bishop of Warmia (Ermiand) a Polish Bishopric on the Baltic. Uncle Lucas, who himself had a doctorate, saw to it that Nicolas and his brother obtained a good education, first at the cathedral school in Wrocławek and later at the University of Cracow where they were matriculated in 1491. The two brothers then went on to Italy for graduate studies. In 1496 Nicolas studied liberal arts in Bologna, then medicine in Padua and in 1503 he obtained a doctorate in Canon Law from the University of Ferrara.
In 1497 Copernicus was elected (by proxy) a canon at the cathedral of Frombork in Warmia. This post was an administrative position which did not require that Copernicus be an ordained priest but did require that he have higher education; it provided him with a steady source of income during his studies in Italy.
After completing his studies Copernicus returned to Poland and became an advisor and physician of his uncle the bishop. After his uncle's death in 1512, the Frombork Cathedral Chapter made Copernicus administrator of two small Warmia districts, Meizak and Olsztyn. For four years he made the Olsztyn castle his headquarters. in 1520, during a war between the Polish King Zygmunt Stary and the Teutonic Knights, he defended the castle against a siege by the Knights. In 1525 he retired from his duties and devoted his time to astronomy and his book - De Revolutionibus.
Copernicus The Astronomer
Copernicus' interest in astronomy developed during his studies at the University of Cracow, which at that time was a recognized center of higher education. He studied there under professor Adalbert Brudzewski (Wojciech of Brudzewo, c. 1445 - 1495), a renowned mathematician, astronomer and astrologer.While in Italy, he became acquainted with Domenico Maria de Novara (1454 1504) with whom he conducted astronomical observations. These gave him the opportunity to examine by direct observation a small but very important detail of the existing cosmological system. It concerned the motions of the moon. The occultation of Aldebaran (the brightest star in the constellation of Taurus) offered an excellent occasion for this examination. Copernicus calculated that the phenomenon would take place on the evening of March 9, 1497. His calculations, made with the greatest precision, turned out to be a success. They proved that, in contradiction to Ptolemaic theory, the distance between the earth and the moon is the same no matter whether the moon is full or in one of its quarters.
These memorable observations began the period of his research. Copernicus started to read diligently various ancient authors: Aristotle, Plato, Euclid, Pliny, Ptolemy, Averroes (Ibn Rashid) and others, searching for clues of other concepts of the universe, besides those of Ptolemy. He discovered that in the writings of Cicero, Plutarch and other ancients there were some statements concerning certain Greek philosophers, especially those of the ń school, who thought the earth might be moving.
After returning from Italy to Warmia, Copernicus assumed his duties as canon of the duchy-bishopric of Warmia. In his leisure time, he continued his astronomical observations and studies.
The instruments which Copernicus had at his disposal were rather primitive and did not provide a greater accuracy than the instruments of the ancient astronomers. Also, the data base which was available to Copernicus was not much larger or better than the one which was available to the ancients. He developed the heliocentric model because his innovative and revolutionary thought process allowed him to break away from the accepted norms.
From about 1510 to 1514, Copernicus developed the first general outline of his new heliocentric system and presented it in a short manuscript, the Commentariolus, or to give its full title, Nicolai Copernici de hypothesibus motuum coelestium a se constitutis commentariolus (Nicholas Copernicus' little treatise on the hypothesis formulated by himself for the heavenly motions). The work was not written to be published. Rather it was distributed among his closest friends in manuscript form.
Copernicus began to write the first book of De Revolutionibus about 1515. The principle aim of this work was to develop the ideas he had been outlined in the Commentariolus. As the work progressed, he found that the mechanism of celestial motion was more complicated than that which he had described in the Commentariolus.
For instance, he discovered that the orbit of the Earth had variable eccentricity and that the apogee of the Sun moved towards the fixed stars. Because of this, the writing of De Revolutionibus was much delayed and became the subject of many changes and corrections. And even when all the books were completed, Copernicus did not consider them ready for print, but perused them over and over again verifying all the details and calculations with new calculations.
Concerned about the implications of his discovery, its novelty and inconceivableness, he preferred to keep the results of his labors for himself and for a few close friends. However, word of his work spread among the circles of mathematicians and astronomers.
Lectures on the principles expounded in the Commentariolus were given in Rome in 1533 before Pope Clement VII who approved of the theory. A formal request to publish was made by Nicholas Schonberg, Cardinal of Capua. From Rome he sent Copernicus a letter, dated November 1, 1536, encouraging him to publish the work or at least to send him a copy of the manuscript. Copernicus declined the request. Others also urged him to publish De Revolutionibus. The most ardent among them was his good friend, Tiedeman Giese, then bishop of Chełmno (Kulm) and earlier canon of the Warmia chapter.
These endeavors might have been fruitless had it not been for the intervention of a young Wittemberg mathematician and astronomer George Joachim Rheticus (1514 - 1574). Having heard of Copernicus and his original new system of the world, Rheticus, on the advice of fellow Protestant mathematicians and astronomers such as Johannes Schoener, Erasmus Reinhold and particularly Philip Melachthon, went to Frombork to learn from the master himself the secret of his theory. He arrived in May 1539 and at once won the confidence and sympathy of the aged astronomer. Thanks to his own and Giese's persuasions, the doubts and scruples that had kept Copernicus from publishing the work were overcome.
Copernicus commissioned Rheticus to publish a summary of his work in order to prepare the minds for his new revolutionary idea. Narratio Prima was printed in Gdansk in 1540. A second edition was published in Basel the following year.
The Book
In 1541 Rheticus left Warmia for Nuremberg taking with him a manuscript copy of De Revolutionibus Orbium Coelestium Libri VI (Six books on the Revolutions of Heavenly Spheres) in order to have it printed in the printing shop of Johannes Pretrejus. Andreas Osiander a Lutheran theologian and mathematician was entrusted with its proofreading. However, Osiander did more then proofread the book. He first tried to persuade Copernicus to write a preface to his work presenting the new astronomical theory as a mere hypothesis, useful for astronomical calculations but not necessarily true. Copernicus rejected his request and by way of reasserting the truth of his system wrote (in June 1542) a splendid dedicatory letter to Pope Paul Ill to be printed as a foreword to the book. Nevertheless, De Revolutionibus was published with a Preface which was for a time attributed to Copernicus.An exchange of letters between Copernicus' friends, Rheticus and Giese, clearly indicates that Copernicus did not write the Preface and was in fact opposed to labeling his theory as a mere mathematical model and not a reflection of the real world. Preserved documents of that period indicate that the Preface was written by Osiander who surreptitiously turned it over to the printer together with Copernicus' manuscript.
In retrospect, Osiander's Preface probably helped the book more than it harmed it for it made possible the publication of two editions before major objections from scientific and religious circles arose. Yet, the world eventually found out about the mystification and Copernicus got full credit for recognizing the mechanism of the solar system.
A copy of the great work is believed to have been brought to Copernicus at Frombork on the last day of his life when he died in a coma on May 24, 1543.
De Revolutionibus is composed of six books. All but the introductory First Book are too mathematical to read with understanding by anyone except a technically proficient astronomer. It could and actually it did serve for many years as a text book for astronomers. The logical and meticulous approach employed can be glimpsed from the chapter headings of Book I, to whit:
- The universe is spherical ů The earth too is spherical
- The Earth forms a single sphere with water
- The motion of the heavenly bodies is uniform, eternal and circular or compounded of circular motions
- Does circular motion suit the Earth? What is its position?
- The immensity of the heavens compared with the size of the earth
- Why the ancients thought that the earth remained at rest in the middle of the universe as its center
- The inadequacy of the previous arguments and a refutation of them
- Can several motions be attributed to the earth? the center of the universe
- The order of the heavenly spheres ů Proof of the earth's triple motion
Theological Problems
Upon the Nuremberg publication of the first edition (a printing of 1000 copies), the book gained instant popularity. Scholars were immediately divided into proponents and opponents of the new theory. The theologians, particularly some Protestant ones were vehemently opposed to a theory which set the Earth in motion "in contradiction of the scriptures". Among the first and most ardent opponents of the theory are prominent Protestants such as Martin Luther, Philipp Melanchton and Calvin.Initially the Roman Catholic church had not opposed the theory, possibly because of its specialized scientific content (which the Church supported), possibly because of Osiander's Preface. The latter suggested that the heliocentric theory was only a mathematical model which simplified computations but did not necessarily insist that the Earth was not the center of the Universe.
The second edition was published in Basel in 1566 without any major opposition. However, around the turn of the century anti-Copernican sentiments started to grow. It spurred fundamentalist clergymen of many persuasions to search the Bible, line by line, for new passages that would confound the adherents of the Earth's motion. With growing frequency Copernicans were labeled "infidel" and "atheist." When, 67 years after the publication of the first edition, the Catholic Church officially joined the battle against Copernicanism in 1610, the formal charge was heresy.
On March 5, 1616 the Sacred Congregation of the Index recognized the scientific value of De Revolutionibus but placed it on the Index Librorum Prohibitorum, that is the list of books forbidden as dangerous to the faith or morals of Catholics. It also decreed that, if the book was to be used, a number of "corrections" must be made. The decree was not promulgated until after the 1617 publication of the third edition in Amsterdam.
One of the most famous victims of the Inquisition was Galileo Galilei who was persecuted for his support of the Copernican theory. He had been given permission by his friend, Pope Urban VIII, to write a book about the Copernican and the Ptolemaic system provided he discusses both systems noncommittally. The Inquisition, however, found him guilty of teaching Copernicanism in the resulting book, Dialogue Concerning the two Chief World Systems: Ptolemaic and Copernican. His sentence was commuted by the Pope to house arrest under which he spent the last eight years of his life.
I think that Coperrncanism was caught in the middle of the ideological battle between the Protestant and Catholic Churches. The Protestant fundamentalists found it inconceivable to accept a model of the universe which, in their opinion, contradicted the scriptures. The Catholic Church at first followed its old tradition of accepting new scientific discoveries and reconciling them with the teachings of the Bible. However, fear that the Catholic Church may be losing to the Reformation on this count, spurred criticism of the new cosmology.
By the middle of the seventeenth century it was difficult to find an important astronomer who was not a Copernican; by the end of the century it was impossible. During the closing decades of the seventeenth century, Copernican, Ptolemaic and Tichonic astronomy was taught side by side in many prominent Protestant universities. During the eighteenth century the last two systems were gradually dropped. The triumph of Copernicanism was a gradual process. Not until 1822 did the Catholic Church permit the printing of the book that treated the earth's motion as physically real. By then all but the most rigidly orthodox Protestants had long been persuaded.
The next edition of De Revolutionibus was not published until 1854, that is, not until after it had been removed from the Index in 1835. It was published in Warsaw. The next edition, the fifth, was published in Toruń, Copernicus' birth place, in 1873 to commemorate the 400 anniversary of his birth. The sixth edition was published in Munich in 1949, and the seventh again in Warsaw in 1972, this time to commemorate the 500 anniversary of his birth.
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