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NICOLAUS COPERNICUS
S. N. Blazhko.
Dedicated to Prof. V. K. Tserasky.
In the small Prussian town of Thorn, not far from the former Russian border station of Aleksandrovo, a monument has been erected to the reformer of astronomy, Nicolaus Copernicus, with the inscription:
NICOLAUS COPERNICUS THORUNENSIS
TERRAE MOTOR
SOLIS COELIQUE STATOR
- — That is, Nicolaus Copernicus, a native of Thorn, who moved the Earth and set the Sun and the heavens at rest.
This brief and expressive inscription aptly points both to the fundamental idea of Copernicus’s teaching—the immobility of the Sun and the stars and the motion of the Earth—and to the gigantic labor he accomplished, stopping the Sun and the heavens and compelling the Earth to move.
Copernicus was a reformer of astronomy; but to say this is not to say everything. Purely astronomical views of the structure of the universe determine to a considerable degree one’s worldview in general; one answer or another to the purely astronomical question of the position of the Earth in the universe also determines the position of man in the universe and, to some extent, his role on Earth. It is no accident that this question in its time attracted great attention from persons who, it may be, had no concern with astronomy in the narrow sense of the word. And in order properly to understand the role of Copernicus in the history of the development of humanity, it is necessary clearly to imagine the relation of purely astronomical facts and views to general culture, to the general worldview.
From time immemorial people began to gaze at the sky, to note the arrangement of the stars, and to observe that they do not change their mutual positions; on this basis they joined the bright stars with lines—
into groups—constellations, and gave each constellation its own name. Everyone knows the seven-star group of the Great Bear in the form of a dipper; this dipper, in the same form in which we see it, was seen by the ancient Egyptians and Assyrians, and by people who lived before them. Of course, the very first observations pointed to the rotation of the sky, to the fact that the whole sky revolves around us, around the Earth. This rotation of the sky, and in particular the rising and setting of the Sun, determined, at the very beginning of cultural development, the first measure of time—the day. The change of the lunar phases—the lunar month—became the second, larger unit for measuring time, and the day of the first appearance of the “new” Moon in the form of a narrow crescent shortly after sunset in the rays of the evening glow came to be marked as the beginning of a new month; so it is marked to this day among orthodox Muslims. Thus celestial phenomena from the very beginning acquired a purely practical significance for people. But the light and warmth of the Sun so obviously influence the course of life on Earth, for the most part beneficially, but sometimes, during prolonged drought, destructively, that the idea of the power of this luminary naturally arose, later leading to its deification. The luminary of the night—the Moon, with primitive mankind’s tendency to personify everything around it, also in time became a goddess. It was not difficult to notice that the Moon does not remain all the time in one and the same place among the stars, but passes from one constellation to another, making a complete circuit always in one direction, from west to east, through a definite series of constellations in the course of a month, a little faster than the time from one new moon to the next. It was harder to observe that the Sun too moves through the same constellations as the Moon, and always in the same direction, from west to east, but considerably more slowly, so that it makes a complete circuit through these “zodiacal” constellations only in 12 and a half lunar months, or in 365 days; of course, the time of this circuit of the Sun across the sky was not at once determined exactly, and only gradually did it become the third measure of time—the year. It was, of course, observed that each year, in connection with the Sun’s movement through the constellations, certain phenomena recur approximately alike, for example the alternation of cold and warm, or rainy and dry, weather, the flooding of the fertile Nile in Egypt, and the like. But, besides the Sun and the Moon, from time immemorial five other special luminaries were noticed in the sky; in appearance they resemble very bright stars, but differ essentially from them in that, while the stars do not change their mutual arrangement, these luminaries, independently of one another, pass from one zodiacal constellation to the neighboring one and, moreover, do not always move among the stars from west to east, like the Sun and the Moon, but sometimes in the other direction as well: from east to west; some are always not far in the sky from the Sun, whereas others may move away from it to the opposite side of the sky. These “heavenly wanderers” are now known under the name of planets, i.e. wandering,
wandering luminaries. From ancient times their motions attracted the attention of people who were interested in what was happening around them, and who were not content merely to be fed and clothed and to spend their time without care. Of course, at first all observations of the luminaries were made without any instruments—the stars served as reference points in the investigation of the motion of the Sun, the Moon, and the planets; later, as science developed, special instruments too were created. It is understandable that all these observations could have developed not in such a place as, for example, Moscow, where half the year the sky is not visible; our astronomy came to us, above all, from the Greeks, who had received its beginnings from the Egyptians and Chaldeans. There, in the south, where the nights are blacker, where the stars are brighter, astronomy was born, and there it could not but be born.
The unusual motions of the planets naturally led one to suspect that they, like the Sun and the Moon, also have some sort of influence—though an unclear one—on the course of events on Earth, determining by their position in various constellations the character of the weather in one year or another. And since they influence the Earth, it means they are endowed with some supernatural power; it means they possess mighty authority; it means they are gods. Thus arose the deification of the planets. It is no accident that their names are the names of Roman gods. But if so, it is natural to suppose that they influence also the fate of man, in close connection with the belief that a person’s fate is predetermined at the moment of his birth, and with the fate of human undertakings. Thus astrology was born—not invented, not contrived, but the result of insufficient knowledge. In order to judge from the position of the luminaries in the sky about future destiny, one must know that position of the luminaries; and for this one must know their motions, so that for any moment of time one can compute their places among the stars and the arrangement of the luminaries above the horizon of any place on Earth. Thus the purely material side, the desire to know the future, demanded the development of astronomy. Of course, underlying all such considerations there lay a distinctly conscious idea that the Earth is the principal thing in the universe, and man the king of creation. But alongside such a narrowly utilitarian view of astronomy there existed—and in Greece especially manifested itself—a purely scientific attitude toward celestial phenomena. We observe these phenomena from the Earth. How, then, do they take place in reality in heavenly space? How is one to explain the visible motion of the Sun among the stars, the non-uniform speed of this motion during the year; how is one to explain the complex motion of the Moon; how is one to explain the still more complex motion of the planets—now from east to west, now from west to east; now meeting with the Sun in one constellation, now moving away from it to the opposite side of the sky? What principle should be laid at the foundation of astronomical theory? Direct observation of everything taking place on Earth shows its immobility; it would be ridiculous to suppose that the Earth
moves. Thus, it is motionless, and the all too modest observations of the motion of bodies on Earth, the complete absence of experiments, led the Greeks to peculiar proofs of the Earth’s immobility—proofs that, from our point of view, are entirely unconvincing, entirely unscientific. They are sometimes called logical or metaphysical. From the standpoint of present-day natural science, these are not proofs at all. But we must not apply our point of view to past centuries. In their time they corresponded to the general level of natural science and therefore were demonstrative. Thus, the terrestrial globe is motionless.
Further: the Sun, the Moon, the planets move. Along what paths? Can the smooth, solemn motion of these mighty luminaries be nonuniform, and is it not fitting for them to move only along the most perfect curves, i.e., uniformly in circles? This is from the metaphysical point of view. And from a purely geometrical one, every complex motion, even if somewhat similar to circular motion, is naturally to be regarded as composed of simple uniform circular motions. But the apparent irregularities had to be explained. And so, gradually, such a system of the world was created: in the middle of the universe there rests motionless the round Earth; around it the Moon and the Sun move in circles and uniformly, but the centers of these circles do not coincide with the center of the Earth.
For the planets it was necessary to devise a more complex system. Each planet moves along a circle, but the center of this circle itself moves along another circle, whose center is close to the Earth, but does not coincide with its center.
The Greeks were good geometers, and one of them, an outstanding geometer, the Alexandrian scholar Ptolemy, relying on the works of his predecessors, consistently developed this system of the world, derived from observations numerical values for the sizes of all the circles, for the periods of revolution of each point, of each planet, and in the second century A.D. his work The Great Construction became a compendium of all the astronomical science of that time—a great creation that reigned unchallenged right up to Copernicus.
The ideas of this Ptolemaic system of the world, resting on the direct impression of the Earth’s immobility, lay at the foundation of the entire worldview; they entered into the flesh and blood of all who were interested in the heavens and the Earth.
The truth of Ptolemy’s teaching could be doubted no more than the truth of divine revelation; it was supported by the physics of Aristotle. And so the Bible, Aristotle, Ptolemy—three foundations of learning on which science naturally rested when, after many turbulent centuries, schools, universities, and academies began to arise in Western Europe. Any doubt about the truth of the Ptolemaic system was regarded as heresy. But whence could doubts arise? And they did arise. The point is that, for exact agree—
In comparing the Ptolemaic system of circles with observations of the planets, it proved necessary not to confine oneself to the simple scheme of two circles: the primary one, whose center is near the Earth, and a second one, along which the planet moves and whose center moves along the circumference of the first. It became necessary to mount a third circle upon the second, a fourth upon the third, and so on, and in the end the system acquired such complexity that it could naturally give rise to doubts as to its truth. On the other hand, already among the Greeks some had expressed the thought that the life-giving Sun, as manifestly the principal object in the universe, ought to be at the center of everything, and not the Earth, dark and living by the light and warmth of the Sun. Doubts existed. After the revival of classical antiquity, these views of certain Greek philosophers concerning the central position of the Sun became known—vague, mystical, unscientific. What was needed was the appearance of a free, strong, mathematically developed mind, one that not only would dare to go against the obvious, but would be able to develop to the end new ideas that ran counter to the entire worldview, and to put a new system of the world in place of the old. In science the role of personality is beyond doubt: a hundred ordinary scholars cannot replace a single genius. Such a genius, who overthrew the old doctrine, was Copernicus.
Astronomy was born in the south; it matured in the north.
Nicolaus Copernicus was born in 1473 in the small town of Toruń; whether he was of German or Polish origin has not been established, despite extensive investigations of this question; each of these nations considers him its own, the Poles with greater insistence and with greater right. At the age of nine he lost his father, and his upbringing was undertaken by his maternal uncle; he attended lectures at the University of Kraków, then spent ten years at Italian universities, studying mathematics, astronomy, law, and medicine. In Rome he lectured on astronomy. In these Italian years, which gave Copernicus so varied an education, there arose in him the ideas about the structure of the solar system to the detailed development of which he then devoted his whole life. At the age of thirty-three he returned to his homeland and there, in the “most remote corner of the earth,” as he expressed it in the dedication of his work to Pope Paul III, he lived the greater part of his life, until the end of his days in 1543.
He was a member of the Chapter, i.e. of the ecclesiastical administration of the province, in the town of Frauenburg, attached to the cathedral at the altar of St. Bartholomew, but he was not a priest in the strict sense of the word, since he did not have the proper ordination. He took an active part in the administration of the diocese; as a physician he gave aid to the sick, and in the quiet of his study and his modest observatory he recreated the world. Apparently by 1530 he had completed, perhaps already fully, the elaboration of his ideas. He was in no hurry to publish his work, but
reported his researches in letters to his friends, and his fame as a penetrating astronomer, who had created a new explanation of the celestial motions by admitting the motion of the Earth, had already spread through Europe, arousing the laudatory responses of some and the ridicule, and even threats, of others. His friends—Rheticus, professor of mathematics at the University of Wittenberg, Nicholas Schönberg, Cardinal of Capua, Tiedemann Giese, Bishop of Kulm—urged him, however, to publish his work. The manuscript was finally sent to press in Nuremberg and appeared in 1543 under the title: De revolutionibus orbium coelestium, i.e., On the Revolutions of the Celestial Spheres.
In the six parts of his work, the reformer of astronomy, by strict geometrical reasoning, shows that all the visible motions of the Sun, the Moon, the planets, and the stars can be explained with complete accuracy if one takes as the basis of the argument the assumption that the Earth is not some special object in the universe, but that it is a planet, similar to the five other planets in the sense that, like them, it moves around the Sun and, in addition, rotates about one of its diameters, as about an axis. The chief irregularities of the celestial motions are explained with extraordinary simplicity and naturalness by the fact that the Earth rotates and that the actual motions of the planets around the Sun are observed by us from the Earth, which is moving around it.
I cannot, of course, examine this work in detail, but a few excerpts from it will not be superfluous. It is always instructive to become acquainted with the primary sources of our knowledge; it is always interesting to investigate the sources of a great river.
The work is dedicated to Pope Paul III. Here are several passages from the dedication1.
“It seems to me, Most Holy Father, that certain persons, as soon as they learn that in my work on the motions of the celestial spheres I admit the motion of the terrestrial globe, will, without further examination, condemn me and my views. I do not at all hold so high an opinion of my theory as to pay no attention to the opinions of others. Although I know that the thoughts of a philosopher are quite far removed from the judgment of the common people, since the former is obliged in all things to seek truth insofar as it has been given to him by God, nevertheless I believe that one must keep away from an opinion that is remote from the truth. For this reason I considered within myself how absurd it would seem to all who know the opinion, established over so many centuries, concerning the immovable position of the Earth at the center of the universe, if I, on the contrary, were to assert that the Earth moves. I hesitated for a long time whether to make public in print my researches, or whether I should follow the example of the Pythagoreans
NIKOLAI COPERNICUS
and others, who transmitted the secrets of philosophy not in writing, but orally...
“But my friends compelled me to abandon my prolonged delay and hesitation. I should not, they said, out of this fear alone, further postpone the publication of my work for the common benefit of mathematicians. The more senseless at present my teaching on the motion of the earth will seem to many, the more gratitude and wonder it will deserve when my published investigations, thanks to their clear arguments, dispel the haze of apparent contradiction. In this hope, and yielding to these persuasions, I allowed my friends to dispose of the publication of my work, so long awaited by them.
“But perhaps your Holiness will be surprised not so much that I have dared to publish my work, as at the manner in which I dared, contrary to the ancient opinion of mathematicians and contrary, so to speak, to the generally accepted view and common sense, to think about the motion of the earth. I will not conceal from your Holiness that I was led to the thought of devising another method for calculating the motions of the heavenly bodies by nothing other than the circumstance that, with regard to investigations of these motions, mathematicians disagree among themselves...
“Reflecting for a long time on the uncertainty of the mathematical dogmas handed down to us concerning the mutual relation of the motions of the heavenly bodies, I finally began to be annoyed that philosophers, who ordinarily strive to recognize even the most insignificant things, had still not succeeded in explaining with certain accuracy the course of the world-machine, created for us by the best and order-loving Architect. Therefore I took upon myself the labor of rereading the writings of all the philosophers available to me, in order to be convinced whether any of them had admitted a motion other than that which is taught in our schools. And thus I found first in Cicero that Hicetas had admitted the motion of the earth, and from one passage in Plutarch I saw that others had been of the same opinion...
“Encouraged by this, I too, in my turn, began to ponder the motion of the earth, and, although this opinion seemed to me implausible, I nevertheless supposed that, just as before me others had been permitted to devise arbitrary circles for the explanation of celestial phenomena, so I too was permitted to try whether I might not find, for the explanation of these motions, a more plausible account, by assuming the motion of the earth.
“Having admitted those motions which are ascribed to the earth in this work, I, after long and repeated investigations, finally came to the conclusion that if the motions of the other wandering stars are related to the circle along which the earth moves, and on this basis the motions of each luminary are calculated, then not only will the phenomena presented by them follow as consequences, but the luminaries themselves and their paths, in their sequence or magnitude, and the very sky itself will appear in such a ...”
relations among themselves, so that nowhere, in no single part, can anything be changed without entangling the remaining parts and the whole whole...
“If there should be idle babblers who, although by no means versed in the mathematical sciences, allow themselves to judge or refute my undertaking, deliberately distorting some passage of Holy Scripture, then I shall not pay attention to them... Mathematical subjects are written for mathematicians alone...”
In judging this dedication it is necessary to bear in mind that, after all, this is being written in the sixteenth century by an orthodox Catholic cleric to the pope, the head of the Church and his own highest superior. The calm, assured, and frank tone of the dedication clearly shows the author’s confidence in his right to investigate the question he had touched upon from a strictly scientific point of view, his conviction of his own correctness, and completely refutes the supposition that Copernicus put forward his teaching merely as a simple hypothesis. He did not doubt it and presented for it all the proofs available to him.
At the beginning of his work Copernicus says that “the universe has a spherical form, for the sphere is, of all geometrical bodies, the most perfect, needing no support; the sphere encloses the greatest volume, and for this reason the principal bodies, such as the sun, the moon, and the stars, also have a spherical form. And drops of water and of other liquids strive to assume the form of a sphere, seeking to confine themselves. Therefore there can be no doubt that a spherical form is inherent also in the heavenly bodies.”
This reasoning is entirely in the spirit of ancient philosophy: it is a priori, based on analogy; but, nevertheless, Copernicus’ conclusions, as we now know on the basis of observations, are correct with respect to the Sun and the planets, and, insofar as on the basis of all our knowledge of the properties of matter we can judge the stars, they are correct with respect to the stars as well.
Next, the sphericity of the Earth is proved on the basis of observations; the proofs are the same as those still given in elementary astronomy textbooks.
Then Copernicus considers the motion of the heavenly bodies. “All these motions,” he says, “must take place along circumferences having neither beginning nor end. The whole universe seems to us to rotate from east to west, excluding the earth. This motion is the measure of every motion and serves for the measurement of time in days. But we also observe reverse motions, that is, from west to east, of the sun, the moon, and the five planets; the sun and the moon move sometimes faster, sometimes more slowly. The planets, however, appear to us now to move directly, now to stand still, now to move backward. But, nevertheless, it is necessary to admit that these motions are performed either in a circle or in various circles, because this inequality could not be subject to known laws, could not occur periodically, if it were not for
motion was not performed in circles. It cannot be that a simple celestial body should move non-uniformly in a single orbit. The latter can occur only because of the inconstancy of the moving force or the special properties of the moving body, or else the heterogeneity of its parts. But since such an assumption, unworthy of the perfection of creation, is contrary to our reason, it remains to suppose that uniform motion only seems to us to be non-uniform…»
This reasoning is entirely in the spirit of ancient philosophy. Copernicus preserves the idea of the necessity of circular, uniform motion of the celestial bodies and tries to justify it.
Next Copernicus poses the question: does the Earth have circular motion, and what place does it occupy?
“The Earth is a sphere,” he says, “but does motion follow from this? What place does the Earth occupy in space? This is what must be clarified in order to give an account of its motion. Almost all writers agree among themselves that the Earth is immobile; the contrary opinion even seems ridiculous to them. But if one looks more attentively, it turns out that this question cannot at all be considered settled, and that it should by no means be neglected. Every change of position of an object that we observe occurs either as a result of its own motion, or of the motion of the observer, or of their relative motion; if the motions of both are equal, then the displacement is imperceptible. We observe the sky from the Earth: if the latter has motion, then the sky will appear to us to be moving in the opposite direction.
“The entire heavenly vault has a motion from east to west; if we imagine the heavenly vault at rest, and give the Earth motion in the opposite direction, i.e. from west to east, we shall obtain the same phenomena. Since the sky is the container, and the Earth is the contained, there is no apparent reason why it would not be better to ascribe motion to the contained rather than to the container.” Thus the concept of relative motion and of the possibility of “apparent” motions is introduced. In the following chapter, he then speaks of the infinity of the heavenly vault in comparison with the Earth. This is proved by the fact that everywhere on the surface of the Earth the horizon divides the heavenly vault into two equal parts.
“If it is true that the celestial sphere is infinite, then how are we to understand that it revolves in 24 hours? Is it not more natural to suppose that this motion belongs to the Earth and to it alone? Otherwise, if it revolved together with the celestial sphere, but somewhat more slowly than the latter (because of the smaller volume of the Earth), then we would not notice the slightest change in the position of the luminaries on the heavenly vault: the sun and the stars, relative to the observer, would constantly appear at the same angular distance from the meridian. Therefore it is natural to suppose that the Earth rotates about its axis, and that the celestial sphere is immobile.”
Then follows an analysis of the teachings of the ancients on motions.
Earth and water, says Aristotle, as heavier bodies, ought to strive downward and occupy the middle place; air and fire, as the lightest bodies, should be above and strive from the middle upward. “If the earth rotated about its axis,” says Ptolemy, “we would see a phenomenon opposite to the preceding one: the earth would break apart, for what could resist the terrible speed of its rotation? Moreover, no body thrown upward would fall back to its former place along a perpendicular; the clouds and everything borne in the air would seem to us carried from east to west.” Copernicus refutes the opinions of the ancients partly by metaphysical reasoning, partly by facts. “If we allow the rotation of the earth about its axis,” he says, “then we must also allow that this motion is not violent, but natural. Everything forced, violent, caused by external causes, may be torn apart, decomposed; everything natural, however, invariably preserves its original form. Therefore Ptolemy’s fear concerning the rupture of the earth and its dispersal in space is vain. If this could indeed follow from the rotation of the earth, then still more could it happen as a consequence of the daily rotation of the celestial sphere, whose speed, because of the enormous distance of this sphere from the earth, would have to be immeasurably greater than the speed of the earth’s rotation.” After reasoning about the finiteness or infinity of the celestial sphere, Copernicus again turns to the daily motion of the Earth. “It is indisputable,” he says, “that the earth has the form of a sphere; motion is proper to this form; why then should we not admit this motion, without troubling ourselves about what we cannot know? People on a ship attribute its motion to external objects; the same happens with us: the heavens seem to us to rotate because in reality the earth rotates. What, then, shall we now say of the clouds and of all bodies borne through the air, if not that they too participate in the motion of the earth? This motion is common to the whole atmosphere or, at the very least, to that part of it nearest the earth; this part, touching the land and the water, follows the same motion as the whole earth, constantly touching it and not being held back by anything. Although it would seem that the upper parts of the atmosphere also participate in this motion, just as comets participate in the daily motion of the earth, nevertheless, because of their considerable distance from the earth, the upper part of the atmosphere may be considered motionless. The air seems to us perfectly at rest, if it is not disturbed by wind or other causes; is wind in the air anything other than waves in the sea? As for falling bodies, their motion is a composite of rectilinear and circular motion. By their heaviness they fall toward the center of the earth, but, being part of the latter, they also participate in its rotation. Heavy bodies
NIKOLAI COPERNICUS
...fall, while fiery bodies rise upward; flame is fiery smoke. Rectilinear motion belongs only to bodies that have been removed from their natural position. To be out of one’s place contradicts the order of the whole, and therefore these bodies strive to attain their former position. In doing so these bodies move nonuniformly, whereas circular motion is always uniform, having neither beginning nor end. Parts of the earth must participate in this latter motion as well, even during their rectilinear and nonuniform fall to the earth.”
In this discussion of motion and in the refutation of the ancient teachings, it is interesting to note the mixture of entirely correct conclusions from observations—still repeated in textbooks—with considerations that still fully bear the character of ancient reasoning, with its a priori assumptions, which were set forth as obvious.
In the following, tenth, chapter, entitled “On the Order of the Celestial Orbits,” the whole essence of the Copernican system is expounded. “No one doubts,” he says, “that the heaven (the sphere) of the fixed stars is the most remote. The ancient philosophers arranged the planets according to the duration of their revolutions, following the rule that, with a motion equal for all the planets, the most distant planets should appear to us to move the slowest. They believed that the Moon is nearer to us than all the planets, since it completes its revolution in the shortest time; that Saturn must be the most distant planet, for it uses the greatest amount of time for its revolution. Below it they placed Jupiter and then Mars. With regard to Venus and Mercury, opinions were divided, since their distance from the Sun is different from that of the other planets...”
“For all the reasons set forth here, the view deserves attention according to which Venus and Mercury revolve around the Sun, which occupies the middle, and as a result they can recede from it only by an amount corresponding to the radius of their orbits; these planets do not enclose the Earth with their orbits, like the other planets, but their orbits are turned toward it by their convexity. And what does this mean, if not that the Sun is at the center of these orbits? Thus the orbit of Mercury is enclosed within the orbit of Venus, which is more than twice as large, and finds sufficient room for itself. On the basis of these considerations, Saturn, Jupiter, and Mars can without error be referred to the same center; it remains only to give their orbits radii sufficient for these orbits to enclose within themselves the Earth’s orbit.
“These planets, at the time of their opposition, are at the nearest distance from the Earth; at the time of conjunction they are most distant from the Earth, and this serves as sufficient proof that the Sun serves as the center of their orbits, just as we see in ...”
Venus and Mercury. But, having subordinated all these bodies to one middle body, it is necessary to place in the space remaining between the convex orbit of Venus and the concave one of Mars, and around this same center, the sphere or orbit of the earth with its satellite—the moon—and with all that is contained beneath the moon; for we can in no way separate the moon from the earth, so close is it to it, and for it there is in this space a quite sufficient and convenient place. And therefore we shall not be ashamed to admit that the lunar orbit and the center of the earth in the course of a year revolve around the sun along a great orbit, at the center of which is the sun. We shall take the sun as immovable, and on this basis all the apparent motions can be explained by the motion of the earth. The radius of this orbit, however great it may be, is nevertheless quite insignificant in comparison with the distance of the fixed stars; this can be agreed to all the more readily since this space is filled with a multitude of orbits, as is admitted even by those who take the earth as the center. One must take an example from nature, which produces nothing superfluous, nothing useless, but, on the contrary, is able from a single cause to derive a multitude of consequences. All this will seem inconvenient and even incredible; but, with God’s help, we shall prove it more clearly than the sun, at least for those acquainted with mathematics.
“Proceeding from the principle, more acceptable than others, that with the increase of the planets’ orbits the speed of revolution also increases, we obtain the following order of spheres, beginning with the highest: the first of the spheres, containing all the others within itself, is the sphere of the fixed stars; it is immovable, and to it we refer all motions and positions of the stars... Beneath this sphere is the sphere of Saturn, which completes its revolution in 30 years; next follows Jupiter, revolving in 12 years; then Mars, completing its revolution in 2 years, and next the Earth, revolving in 1 year; Venus completes its revolution in 9 months, and, finally, Mercury—in 88 days. In the midst of all these orbits is the sun: for could this splendid luminary be placed in so magnificent a temple in any better place, from which it could illuminate everything with itself? Therefore it was not in vain that some called the sun the soul of the universe, and others the ruler of worlds...” “And thus the sun, as if seated upon a royal throne, governs the family of luminaries revolving around it. The earth makes use of the services of the moon, and at the same time the earth is fertilized by the sun and bears within itself fruit during the year. This order brings about an astonishing symmetry of the universe and such a harmonious relation between the motion and the magnitudes of the orbits as we can find in no other way...”
“All these phenomena in the motions of the planets are conditioned by the motion of the earth. We do not see similar phenomena in the fixed stars, because of their enormous distance, for which the annual displacement of the earth is almost imperceptible. As to what lies between the outermost planet Saturn ...”
and the sphere of fixed stars there exists an immense space, proves the overthrow of the latter, and in this they differ from the planets; and in this consists an important distinction between moving and immobile bodies. So great and divine is the creation of the Almighty!’
It cannot be denied that the character of Copernicus’s proofs is, in essence, ancient; in his time both physics and mechanics had not advanced far in comparison with what they had been among the Greeks. The character of the proofs is the same as before, but the conclusions are opposite. What is essential, however, is that Copernicus’s proofs were in accord with the spirit of the science of physical phenomena of that time, and therefore they seemed sufficient and had significance for his contemporaries; but the conclusions at which he arrived ran counter to the established worldview, they led astronomy out of a dead end onto a broad road, and for this reason his conclusions are valuable for the development of science. It is not important that Copernicus could not provide such proofs of his doctrine as we possess now; he provided proofs convincing enough for his teaching to acquire followers, who developed this teaching further and brought astronomy to the state in which it now stands.
Incidentally, his fundamental idea, of course, undermined astrology at its very root. It brought the Earth down from its exclusive, honorable place in the universe; it compelled a reconsideration also of views on the position of man in the universe. The Earth is a planet; life has developed upon it; living beings inhabit it, and among them are those whom we call rational. The Earth is a planet: perhaps other planets are also earths; perhaps on them too there is life and beings whom we, if we knew them, would not refuse to recognize as rational? To certain objections against the motion of the Earth Copernicus answered by pointing to the enormous distances of the stars from us. In his book, to be sure, there is not a word about what the stars are. But already soon after him the thought naturally began to enter the consciousness of his followers that the stars are suns, similar to our Sun; if so, then around them too there may be cold planets, and on these planets too life and, perhaps, rational beings. True, to this day we can neither affirm this nor deny it. In this question everyone may think as he wishes, but the very thought is such that, of course, it essentially broadens our horizon and fundamentally changes the conception of man’s position in the universe. It is understandable that this thought could especially inflame a lively mind and by its very nature could seem indubitable. One of the most ardent followers of the Copernican doctrine, the philosopher and publicist Giordano Bruno, boldly abandoned the cautious, strictly consistent, and scientific path of Copernicus, became the first ardent preacher of a plurality of inhabited worlds, and, among other things, for these bold preach—
was burned in 1600 in Rome; now the monument on the site of his execution recalls the sacrifice made by a bold defender of the new worldview to the rigidity of the ordinary human mind.
The work of Copernicus was dedicated to the head of the Church. Many clerics, sufficiently educated not only to take an interest in these questions, but also to understand Copernicus’ geometrical arguments, had already earlier shown interest, attention, and sympathy for the new teaching. They did not belong to those of whom Copernicus said that “people who, though ignorant of the mathematical sciences, allow themselves to judge or refute his theory, deliberately distorting some passage of Holy Scripture.” Copernicus’ book, when it appeared, received no prohibition from Rome. It circulated freely, and after 20 years a second edition of it had already appeared. All the more interesting is it to point out that, on the contrary, the reformers in the ecclesiastical sphere met Copernicus’ teaching with resolute condemnation. Luther expressed himself sharply: “Some fool wants to overturn the whole art of astronomy, but, as Holy Scripture says, Jesus Nave commanded the Sun, and not the Earth, to stand still.” The more moderate Melanchthon, the teacher of Germany, did not express himself so crudely, but on the basis of certain texts of the Bible and the physics of Aristotle he did not acknowledge the motion of the Earth and demanded that the teaching of Copernicus be forbidden to be expounded in the universities.
The spread of the new teaching, of course, proceeded slowly, but gradually it embraced an ever wider circle of adherents, who, preserving its basic idea of the motion of the Earth, supplemented it, perfected it, and thereby made it ever more convincing. But outside the circle of specialist astronomers its spread nevertheless proceeded very slowly and has not ceased to this day. For many decades more, as before, even among the educated public there reigned the former anthropocentric, astrological worldview. By way of characterization, here is a small quotation from Torquato Tasso’s poem Jerusalem Delivered, published 40 years after Copernicus’ book. In the 60th stanza of the Ninth Canto it is described how an angel flew to the aid of the Franks1.
“He spread his golden wings
And flew swifter than an instant.
In flight he pierced through fire and light,
The everlasting abodes of blessed souls.
(Localization of paradise.)And farther, through the pure crystal he
Passed through the sphere of the fixed stars.
Not equal either in appearance or in influence
(Astrological views.)
The planets below turn in orderly fashion,
Led by angels in their course,
So that on their path they cannot stray.
This is a peculiar satisfaction of the requirements of mechanics: it was necessary to explain what force makes the planets move without straying from their path; and since the ideas of mechanics had not yet been developed, although already in Copernicus there are hints of the attractive force of the Sun, it was necessary to resort to the intervention of supernatural forces.
And in the following centuries, and in our own century, objections to the motion of the Earth have appeared and continue to appear; an entire anti-Copernican literature has arisen, which, the further it goes, the more clearly confirms the words of Copernicus himself in his dedication: “mathematical things are written for mathematicians,” and the epigraph to his book: “Let no one ignorant of geometry enter.” This does not mean that any profound knowledge of mathematics is required for a complete acquaintance with Copernicus’s teaching. But clear geometrical conceptions are needed above all! These are what the modern “anti-Copernicans” for the most part lack. And astrology? The belief that the future can be known from the stars? Has it really died out entirely? Old ideas live on. It seems as though ideas are inherited, like physical properties, and even the educated part of humanity frees itself only with great difficulty from the ideological legacy of long-past times and is very slowly imbued with new ideas.