adapted from: http://webexhibits.org/calendars/year-text-Copernicus.html
Nicholas Copernicus
De Revolutionibus (On the Revolutions), 1543 C.E.
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Nicholas Copemicus Copernicus was born into a well-to-do mercantile family in 1473, at Torun, Poland. After the death of his father, he was sponsored by his uncle, Bishop Watzenrode, who sent him first to the University of Krakow, and then to study in Italy at the universities of Bologna, Padua and Ferrara. His concentrations there were law and medicine, but his lectures on the subject at the University of Rome in 1501 already evidenced his interest in astronomy. Returning to Poland, he spent the rest of his life as a church canon under his uncle. In 1514, Copernicus privately circulated an outline of his thesis on planetary motion, but actual publication of De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) containing his mathematical proofs did not occur until 1543, after a supporter named Rheticus had impatiently taken it upon himself to publish a brief description of the Copernican system (Narratio prima) in 1541. |
NICHOLAS COPERNICUS
OF TORUÑ
SIX BOOKS ON
THE REVOLUTIONS OF THE HEAVENLY
SPHERES
Let no one untrained in geometry enter here.
NUREMBERG
JOHANNES PETREIUS
1543
XIX
TO HIS HOLINESS, POPE PAUL III,
NICHOLAS COPERNICUS' PREFACE
TO HIS BOOKS ON THE REVOLUTIONS
I can readily imagine, Holy Father, that as soon as some people hear that in this volume, which I have written about the revolutions of the spheres of the universe, I ascribe certain motions to the terrestrial globe, they will shout that I must be immediately repudiated together with this belief. . . .
But while I hesitated for a long time and even resisted, my friends drew me back. Foremost among them was the cardinal of Capua, Nicholas Schönberg, renowned in every field of learning. Next to him was a man who loves me dearly, Tiedemann Giese, bishop of Chelmno, a close student of sacred letters as well as of all good literature. For he repeatedly encouraged me and, sometimes adding reproaches, urgently requested me to publish this volume….
For a long time, then, I reflected on this confusion in the astronomical traditions concerning the derivation of the motions of the universe's spheres. I began to be annoyed that the movements of the world machine, created for our sake by the best and most systematic Artisan of all, were not understood with greater certainty by the philosophers, who otherwise examined so precisely the most insignificant trifles of this world. For this reason I undertook the task of rereading the works of all the philosophers which I could obtain to learn whether anyone had ever proposed other motions of the universe's spheres than those expounded by the teachers of astronomy in the schools. And in fact first I found in Cicero that Hicetas supposed the earth to move . ..
Therefore, having obtained the opportunity from these sources, I too began to consider the mobility of the earth.. . .
In order that the educated and uneducated alike may see that I do not run away from the judgment of anybody at all, I have preferred dedicating my studies to Your Holiness rather than to anyone else. For even in this very remote comer of the earth where I live you are considered the highest authority by virtue of the loftiness of your office and your love for all literature and astronomy too. Hence by your prestige and judgment you can easily suppress calumnious attacks.
Perhaps there will be babblers who claim to be judges of astronomy although completely ignorant of the subject and, badly distorting some passage of Scripture to their purpose, will dare to find fault with my undertaking and censure it. I disregard them even to the extent of despising their criticism as unfounded. For it is not unknown that Lactantius, otherwise an illustrious writer but hardly an astronomer, speaks quite childishly about the earth's shape, when he mocks those who declared that the earth has the form of a globe. Hence scholars need not be surprised if any such persons will likewise ridicule me. Astronomy is written for astronomers. To them my work too will seem, unless I am mistaken, to make some contribution also to the Church, at the head of which Your Holiness now stands. For not so long ago under Leo X the Lateran Council considered the problem of reforming the ecclesiastical calendar. The issue remained undecided then only because the lengths of the year and month and the motions of the sun and moon were regarded as not yet adequately measured. From that time on, at the suggestion of that most distinguished man, Paul, bishop of Fossombrone, who was then in charge of this matter, I have directed my attention to a more precise study of these topics.
NICHOLAS COPERNICUS'
REVOLUTIONS Book One
INTRODUCTION
Although all the good arts serve to draw man's mind away from vices and lead it toward better things, this function can be more fully performed by this art, which also provides extraordinary intellectual pleasure. For when a man is occupied with things which he sees established in the finest order and directed by divine management, will not the unremitting contemplation of them and a certain familiarity with them stimulate him to the best and to admiration for the Maker of everything, in whom are all happiness and every good? For would not the godly Psalmist [92:4] in vain declare that he was made glad through the work of the Lord and rejoiced in the works of His hand s, were we not drawn to the contemplation of the highest good by this means, as though by a chariot?
However, this divine rather than human science, which investigates the loftiest subjects, is not free from perplexities. The main reason is that its principles and assumptions, called "hypotheses" by the Greeks, have been a source of disagreement, as we see, among most of those who undertook to deal with this subject, and so they did not rely on the same ideas. An additional reason is that the motion of the planets and the revolution of the stars could not be measured with numerical precision and completely understood except with the passage of time and the aid of many earlier observations, through which this knowledge was transmitted to posterity from hand to hand, so to say. To be sure, Claudius Ptolemy of Alexandria, who far excels the rest by his wonderful skill and industry, brought this entire art almost to perfection with the help of observations extending over a period of more than four hundred years, so that there no longer seemed to be any gap which he had not closed. Nevertheless very many things, as we perceive, do not agree with the conclusions which ought to follow from his system, and besides certain other motions have been discovered which were not yet known to him . . . .
I acknowledge that I shall treat many topics differently from my predecessors, and yet I shall do so thanks to them, for it was they who first opened the road to the investigation of these very questions.
HOW EARTH FORMS A SINGLE SPHERE Chapter
3
WITH WATER
In his Geography Ptolemy extended the habitable area halfway around the world. Beyond that meridian, where he left unknown land, the moderns have added Cathay (China) and territory as vast as sixty degrees of longitude, so that now the earth is inhabited over a greater stretch of longitude than is left for the ocean. To these regions, moreover, should be added the islands discovered in our time under the rulers of Spain and Portugal, and especially America, named after the ship's captain who found it….
From all these facts, I think it is clear that land and water together press upon a single center of gravity; that the earth has no other center of magnitude; in that, since earth is heavier, its gaps are filled with water; and that consequently there is little water in comparison with land, even though more water perhaps appears on the surface.
WHY THE ANCIENTS THOUGHT THAT Chapter
7
THE EARTH REMAINED AT REST IN
THE MIDDLE OF THE UNIVERSE AS ITS CENTER
Accordingly, the ancient philosophers sought to establish that the earth remains at rest in the middle of the universe by certain other arguments. As their main reason, however, they adduce heaviness and lightness. Earth is in fact the heaviest element, and everything that has weight is borne toward it in an effort to reach its inmost center….
Therefore, remarks Ptolemy of Alexandria [Syntaxis, 1, 7], if the earth were to move, merely in a daily rotation, the opposite of what was said above would have to occur, since a motion would have to be exceedingly violent and its speed unsurpassable to carry the entire circumference of the earth around in twenty-four hours. But things which undergo an abrupt rotation seem utterly unsuited to gather [bodies to themselves], and seem more likely, if they have been produced by combination, to fly apart unless they are held together by some bond. The earth would long ago have burst asunder, he says, and dropped out of the skies (a quite preposterous notion); and, what is more, living creatures and any other loose weights would by no means remain unshaken.
THE INADEQUACY OF THE PREVIOUS Chapter
8
ARGUMENTS AND A REFUTATION OF THEM
For these and similar reasons forsooth the ancients insist that the earth remains at rest in the middle of the universe, and that this is its status beyond any doubt. Yet if anyone believes that the earth rotates, surely he will hold that its motion is natural, not violent. But what is in accordance with nature produces effects contrary to those resulting from violence, since things to which force or violence is applied must disintegrate and cannot long endure. On the other hand, that which is brought into existence by nature is well-ordered and preserved in its best state. Ptolemy has no cause, then, to fear that the earth and everything earthly will be disrupted by a rotation created through nature’ handiwork, which is quite different from what art or human intelligence can accomplish.
But why does he not feel this apprehension even more for the universe, whose motion must be the swifter, the bigger the heavens are than the earth? Or have the heavens become immense because the indescribable violence of their motion drives them away from the center? Would they also fall apart if they came to a halt? ….
We regard it as a certainty that the earth, enclosed between poles, is bounded by a spherical surface. Why then do we still hesitate to grant it the motion appropriate by nature to its form rather than attribute a movement to the entire universe, whose limit is unknown and unknowable? Why should we not admit, with regard to the daily rotation, that the appearance is in the heavens and the reality in the earth? This situation closely resembles what Vergil's Aeneas says:
Forth from the harbor we sail, and the land and the cities slip backward [Aeneid, III, 72].
For when a ship is floating calmly along, the sailors see its motion mirrored in everything outside, while on the other hand they suppose that they are stationary, together with everything on board. In the same way, the motion of the earth can unquestionably produce the impression that the entire universe is rotating.
THE ORDER OF THE HEAVENLY SPHERES Chapter 10
According to Plato’s followers, all the planets, being dark bodies otherwise, shine because they receive sunlight…. In addition, they argue, the sun must sometimes be eclipsed by the interposition of these planets, and its light cut off in proportion to their size. Since this is never observed, these planets do not pass beneath the sun at all, according to those who follow Plato.
(Others say that) these planets do not eclipse the sun, because it rarely happens that they interfere with our view of the sun, since they generally deviate in latitude. Besides, they are tiny bodies in comparison with the sun. Venus, although bigger than Mercury, can occult barely a hundredth of the sun. So says Al-Battani of Raqqa (an Moslem scientist), who thinks that the sun's diameter is ten times larger [than Venus'], and therefore so minute a speck is not easily descried in the most brilliant light. Yet in his Paraphrase of Ptolemy, Ibn Rushd reports having seen something blackish when he found a conjunction of the sun and Mercury indicated in the tables. And thus these two planets are judged to be moving below the sun's sphere.
But this reasoning also is weak and unreliable. This is obvious from the fact that there are 38 earth-radii to the moon's perigee, according to Ptolemy [Syntaxis, V, 13], but more than 49 according to a more accurate determination, as will be made clear below.
. . . . .
Hence I feel no shame in asserting that this whole region engirdled by the moon, and the center of the earth, traverse this grand circle amid the rest of the planets in an annual revolution around the sun. Near the sun is the center of the universe. Moreover, since the sun remains stationary, whatever appears as a motion of the sun is really due rather to the motion of the earth. In comparison with any other spheres of the planets, the distance from the earth to the sun has a magnitude which is quite appreciable in proportion to those dimensions.
All these statements are difficult and almost inconceivable, being of course opposed to the beliefs of many people. Yet, as we proceed, with God's help I shall make them clearer than sunlight, at any rate to those who are not unacquainted with the science of astronomy.
At rest in the middle of everything is the sun. For in this most beautiful temple, who would place this lamp in another or better position than that from which it can light up the whole thing at the same time?
In this arrangement, therefore, we discover a marvelous symmetry of the universe, and an established harmonious linkage between the motion of the spheres and their size, such as can be found in no other way. . . .
READING QUESTIONS
1. Copernicus knew that his theories were likely to get him in trouble with the church. What steps does he take to make his arguments appear compatible with Christianity?
2. What is Copernicus’ attitude towards authority – both religious and scientific (Ptolemy, etc.)? What authors does he rely on most? Does he make any use of Moslem science?
3. How do Copernicus’ theories about the universe compare to those of modern astronomers? Where was he “correct,” and where “incorrect?”
4.Evaluate Copernicus’ scientific method. How does he test his hypotheses? Are his standards of proof comparable to modern scientists’?
5. As he says himself, Copernicus was not the first to posit a heliocentric solar system. So what was new here? Why was he at the forefront of what will come to be called the “scientific revolution?”
Adapted from Dartmouth College, MATC, Online reader.