Astronomy Books

"Then what is it which makes the planets move around the sun, each planet within the boundaries of its own region, if there are not any solid spheres, and if the globes themselves cannot be fastened to anything else and made to stick there, and if without solid spheres they cannot be moved from place to place by any soul? Even if things are very far removed from us and... are difficult to explain and give rise to... uncertain judgements... if we follow probability and... not to postulate anything... contrary to us, it will... be clear that no mind is to be introduced which should turn the planets by the dictation of reason and... that no soul is to be put in charge of this revolution, in order that it should impress something into the globes by the balanced contest of the forces, as takes place in the revolution around the axis; but that there is one only solar body, which is situated at the centre of the whole universe, and to which this movement of the primary planets around the body of the sun can be ascribed."

"[T]he truth concerning the mutable nature of the heavens can be taught conveniently... [I]t is not without its use in explaining even those parts of the philosophy of Aristotle which are clearly false, as Book VIII of the Physics concerning celestial movement and Book II of On the Heavens concerning the eternity of the heavens—so... a comparison could be made between the philosophy of the gentiles and the truth of Christian dogma."

"[I]t would be first in my program... to warn... of the distinction between the love—or thirst, to use the Aristotelian word—for the knowledge of natural things and the lust for contradicting and holding the opposite opinion. All philosophers... and all the poets... recognize a divine ravishment in investigating the works of God: and not merely in investigating them privately but even in teaching them publicly: and... the false charge of esoteric novelty-hunting cannot cling to this ravishment.There is God in us, and our warmth comes from His movements: This Spirit has descended from the heavenly seats."

"Why do you say that a celestial body, which is unchanging with respect to its matter, cannot be moved by assent alone? For if the celestial bodies are neither heavy nor light, but most suited for circular movement, then do they resist the motor mind? Even if a celestial globe is not heavy in the way in which a stone on the earth is... and is not light in the way in which among us fire is... nevertheless by reason of its matter it has a natural... powerlessness of crossing from place to place, and it has a natural inertia or rest whereby it rests... where it is placed alone. ...[I]n order that it may be moved out of its... rest, it has need of some power... stronger than its matter and its naked body, and which should overcome its natural inertia. For such a faculty is above the capacity of nature and is a sprout of form, or a sign of life."

"[I]f... even this inquiry is accused of being esoteric... the head of astronomy is struck off. And since astronomy is studied either for its own sake as a philosophy or for the sake of making astronomical predictions... the taking away from me of the primary end slays this whole subtle astronomy and plainly makes it useless."

"You can count few academies in which it is a part of the program to explain the Metaphysics of Aristotle: yet Aristotle wrote the Metaphysics too, a very useful work..."

"Aristotle... in the Metaphysics, Book XII, Chapter 8... built... the most sublime part of his philosophy... concerning the gods... who... sends his students to the astronomers and who defers to the astronomers in respect to their authority and... testitimony...[H]e would never have scorned or... myself, if... necessity... had made us contemporaries. For he orders his students "to read through both,"...[i.e.,] Eudoxus and , for the one had corrected the errors of the other; and today that would be to read both Ptolemy and Tycho: "but to follow" not, he says, the more ancient, but "the more accurate." And so... if the astronomer, using the arguments which modern times have put forward concerning the heavens, has indicated that creatures arose in the heavens and will disappear once more—in opposition to the opinion of him who alleges experience, but experience not sufficiently long."

"But this kind of argument against Aristotle will perhaps seem too contentious. Therefore let us use his own testimony... for he is not everywhere consistent: in the Metaphysics he attributes movement to the celestial bodies for its own sake and teaches "that they are moved in order that they may be moved"; but in On the Heavens, being admonished by the things themselves, he attributes something... like the terrestrial... multiplex and turbulent to the stars or... their movers, who by... these mechanisms and movements seek another end... in this way... he adduces the fewness of movements in the moon as... the inferior... closer kinship to the Earth."

"I now descend to the work... the Harmonies... [H]e who condemns the itch to devise new things and the presumption to profess new and grandiose things will find in the epilogue to the Fifth Book that which he will mark critically. For here the sun-spots and little flames are brought forward as evidence of there being exhalations from the sun which are analogous to exhalations from the Earth: here things corresponding to the generation of animals... in the planets—here the confines of the mysteries of Christian religion are touched: we knock at the doors of the science of the , of , of the idolatry of the Persians, and of those who worship the sun as god—as the interjection of frequent warnings does not dissimulate. ...[R]eason ...leads "from the Muses to Apollo": nevertheless, since the other parts of the work are established by means of their proper demonstrations, the chapter, or epilogue, can be considered as cut off from the rest."

"State the opinion of the ancient astronomers as to how the planets move. The ancients, Eudoxus and , and their follower Ptolemy did not advance beyond circles... for in Book XIII of the ', Chapter 2, Ptolemy writes as follows:"But let no one judge that these interweavings of circles which we postulate are difficult, on the ground that... manual imitation of these interweavings is... intricate. For it is not right for our human things to be compared on a basis of equality with the immortal gods, and for us to seek the evidence for very lofty things from examples of very unlike things. ...Indeed we must try hard to fit the most simple hypotheses to the celestial movements... but if that is not successful, whatever sort of hypotheses can be used. ...[W]e should not judge what is simple in celestial bodies by the examples of things which seem to us to be simple ...For ...he who wishes to judge celestial things in this way will not recognize as simple any of those movements which take place in the heavens, not even the invariable constancy of the first movement: because it is ...impossible to find among men this thing (namely, something which stays in the same state perpetually). Therefore we must not form our judgement upon terrestrial things, but upon the natures of the things which are in the heavens and upon the unchanging steadfastness of their movements. So... in this way all the movements are seen to be simple, and much more simple than those movements which seem to us to be simple. For we are unable to suspect them of any labor or any difficulty in their revolutions." So [says] Ptolemy."

"For... it is disclosed by the telescope... and can be seen... that the solar body is covered with spots, which cross the disk of the sun or its lower hemisphere within 12 or 13 or 14 days, slowly at the beginning and at the end, but rapidly in the middle, which argues that they are stuck to the surface of the sun and turn with it..."

"These extracts from the letter, most of which have to do with the investigation of very hidden causes which is to be viewed in this little book, should be spoken and understood. And now it is time for the reader to pass on to the little book."

"I build my whole astronomy upon Copernicus' hypotheses concerning the world, upon the observations of , and lastly upon the Englishman, William Gilbert's philosophy of magnetism."

"[T]he philosophers speak of the visible heavens; and Christ of the invisible heavens, or, as the schools say, of the , or, as the simple Christians take it, of the blessed seats, which no corruption will ever touch: since not Tycho, not I, but Christ Himself pronounces concerning this visible world: "Heaven and Earth shall pass away," and the Psalmist, "they shall grow old like a garment"; and Peter, "They shall be destroyed root and all, and be consumed by burning in the fire.""

"[A] comparison was undertaken between this book—or the related work On the Harmonies...—and Aristotle's books ' and Metaphysics... I have nothing to worry about in the case of Aristotle... His Most Serene Highness cannot dislike whatever is the more convincing, whether it be that the world was first made at a fixed beginning in time as was my work On the Harmonies, or will be destroyed at some time, or is merely liable to destruction, like the alterations of the ether and the celestial atmosphere; nor will he ever prefer the Master Aristotle to the truth of which Aristotle was ignorant."

"Then, as in each and every planet there is a very fast movement and a very slow movement and in a fixed proportion... and... Saturn and Jupiter have middling eccentricities, Mars a great eccentricity, the Sun and Venus slight eccentricities, and Mercury a very great eccentricity... I also brought forward a solution... and I took my solution from the Archetype of the harmonic cosmos: whence it is established that this cosmos cannot be better... and that it is impossible that the world should not have been created at a fixed beginning in time. This attempt of mine... should have been brought forth into the light with strength of mind... the highest confidence in the visible works of God... or at the exhortation of Aristotle himself, who judged that in these questions you should not suppress or be silent about probabilities any more than... certainties."

"Accordingly, if certain subtleties which are difficult to grasp should not be laid before beginners, or if they should not be preferred to the accepted and necessary teachings, it does not follow that... those things should neither be written nor read privately."

"And that will occur in order that the alterations in the heavens should not destroy their eternity, if there should be such an eternity, just as the terrestrial alterations, which are perrennial and return in a circle, destroy the Earth’s eternity which was equally believed by Aristotle."

"I even in private free myself from the blame of seeking after novelty by suitable proofs: let my doctrines say whether there is love of truth in me or love of glory: for most of the ones I hold have been taken from other writers..."

"[B]ecause certain people cannot grasp the subtleties of things, they lay the charge of novelty-hunting upon me."

"[T]his work of mine, the Harmonies, is nothing except... a certain picture of the edifice of astronomy; and though it may be erased at the pleasure of him who spits upon it, nevertheless the house called astronomy stands by itself: and I know that astronomy is not condemned by His Most Serene Highness but is held of great value on account of its certitude in predicting movements: perhaps, therefore, he will judge its architect—who is almost the only renovator after the Master Tycho and who thought it worth while to devote his life to this work—to be not unworthy of his favour."

"Why do you call them the proper movements of the planets? 1. Because the apparent daily movement—with which the doctrine on the sphere is concerned—and which is common to both the planets and the fixed stars, and so to the whole world, is seen to travel from the east to the west; but the far slower single movements of the single planets travel in the opposite direction from west to east; and therefore it is certain that these movements cannot depend upon that common movement of the world—which we have discussed so far—but should be assigned to the planets themselves, and thus they are generically proper to the planets."

"The most interesting person in this group of Pythagoreans was... Kepler... a technical astronomer well versed in the mathematical arcana of the subject, who knew how to construct an... argument on the basis of observations. ...[A] ...style of argument ...reveals an underlying view of the world similar to... Fludd and Kircher. Kepler recognized harmonies... as correspondences among the different parts of the universe. ...[I]n arguing for Copernican cosmology—the central sun, the outer sphere of the fixed stars, and the intermediate region of the planets—with the Trinity. Kepler... compare[d] the sun with the common sense of animals... in the head, the globes that surround the sun with... sense organs, and the fixed stars with sensible objects. He... compared the sun with the central fireplace... the heart of the world, the seat of reason and life... reminiscent of... Paracelsus and the chymical philosophers..."

"The Epitome Astronomiae Copernicanae, contains much of the material from Kepler's earlier works... It was written for a more general audience, and... gained a relatively wide readership. ...[Here] Kepler's mature physics, metaphysics, and astronomy were presented together for the first time. ...[I]t is an invaluable resource for exploring the evolution of Kepler's thought, fleshing out his conception of the relationship between physics, metaphysics, and astronomy, and—since... intended as a textbook—uncovering what Kepler believed he needed to do to promote his new astronomy."

"By what reasons are you led to make the sun the moving cause or the source of movement for the planets? 1. Because it is apparent that in so far as any planet is more distant from the sun... it moves the more slowly—so that the ratio of the periodic times is the ratio of the 34th powers of the distances from the sun. Therefore we reason from this that the sun is the source of movement. 2. Below we shall hear the same... use in the case of the single planets—so that the closer any one planet approaches the sun during any time, it is borne with an increase of velocity in exactly the ratio of the square.3. Nor is the dignity or the fitness of the solar body opposed to this, because it is... beautiful... of a perfect roundness... very great and is the source of light and heat, whence all life flows out into the vegetables: to such an extent that heat and light can be judged to be... instruments fitted to the sun for causing movement in the planets. 4. But in especial... the sun’s rotation in its own space around its immobile axis, in the same direction in which all the planets proceed: and in a shorter period than Mercury, the nearest to the sun and fastest of all the planets."

"What is the subject of the doctrine of the schemata? The proper movements of the planets; we call them the secondary movements; and the planets, the secondary movables."

"[T]he following thesis is upheld by incontrovertible demonstrations: that in the farthest movements of any two planets, the universe was stamped with the adornment of harmonic proportions; and, accordingly, in order that this adornment might be brought into concord with the movements, the eccentricities which fell to the lot of each planet had to be brought into concord. ...[H]ow great an addition this makes in illustrating the glory of the fabric of the world, and of God the Architect."

"[F]or me there is so much importance in the true doctrine of others or even in correcting the doctrines which are not... well established, that my mind is never at leisure for the game of inventing new doctrines that are contrary to the true."

"Antiquity teaches us... how vainly man sets up boundary posts where God has not set them... how severely all the astronomers were blamed by the first Christians. ...Yet today we set up academies everywhere: we order that philosophy be taught, that astronomy be taught, that the antipodes be taught."

"[T]he boundary posts of investigation should not be set up in the narrow minds of a few... "The world is a petty thing, unless everyone finds the whole world in that which he is seeking," as Seneca says. ...[T]he boundary posts of true speculation are the same as those of the fabric of the world; but the Christian religion has put up some fences around false speculation... in order that error may not rush headlong but may become... harmless..."

"Astronomers should not be granted excessive license to conceive anything they please without reason: on the contrary, it is also necessary for you to establish the probable causes of your Hypotheses which you recommend as the true causes of the Appearances. Hence you must first establish the principles of your Astronomy in a higher science, namely Physics and Metaphysics."

"It has been ten years since I published my Commentaries on the Movements of the Planet Mars. As only a few copies of the book were printed, and as it had so to speak hidden the teaching about celestial causes in thickets of calculations and the rest of the astronomical apparatus, and since the more delicate readers were frightened away by the price... too; it seemed... that I should be doing right and fulfilling my responsibilities, if I should write an epitome, wherein a summary of both the physical and astronomical teaching concerning the heavens would be set forth in plain and simple speech and with the boredom of the demonstrations alleviated."

"Aristotle is the man... who in On the Heavens... Chapter 9... asks: "Do the stars give forth sounds which are modulated harmonically? and answers no: ...I grant that no sounds are given forth but I affirm and demonstrate that the movements are modulated according to harmonic proportions."

"I... led on by... thirst for philosophy, first wiped away from the eyes of astronomy those mists of the multiplicity of movements in the single planets: then I gave a demonstration... that the movement of the planet is not uniform throughout its whole circuit—as Aristotle argued in Chapters 6 and 7; but that... the movement is increased and decreased at places in its period which are fixed and are opposite to one another; and I explained the efficient or instrumental causes... between the planet and the sun... as from what source..."

"As regards the academies, they are... concerned not to have the program of teaching change very often... the things which have to be chosen are not those which are most true but those which are most easy."

"It sufficeth not to know that it [the nature of a body falling downwards] is streight, but its requi­site to know whether it be uniform, or irregular; that is, whe­ther it maintain alwayes one and the same velocity, or else goeth retarding or accelerating. ...Neither doth this suffice, but its requisite to know ac­cording to what proportion such accelleration is made; a Pro­blem, that I believe was never hitherto understood by any Phi­losopher or Mathematician; although Philosophers, and particu­larly the Peripateticks, have writ great and entire Volumes, touching motion."

"No thought can comprehend what ought to be the solidity of that immense Sphere, whose depth so stedfastly holdeth fast such a multitude of Stars... Or else, supposing the Heavens to be fluid, as we are with more reason to believe, so as that every Star wandereth to and fro in it, by wayes of its own, what rules shall regulate their motions, and to what pur­pose, so, as that being beheld from the Earth, they appear as if they were made by one onely Sphere? ...nor can I see how the Earth, a pendent body, and equilibrated upon its centre, exposed indif­ferently to either motion or rest, and environed with a liquid am­bient, should not yield also as the rest, and be carried about."

"We speak of the peice of Ordinance mounted per­pendicular to the Horizon, that is, of a shot towards our vertical point, and to conclude, of the return of the ball by the same line unto the same peice, though that in the long time which it is se­parated from the peice, the earth hath transported it many miles towards the East; now it seemeth, that the ball ought to fall a like distance from the peice towards the West; the which doth not happen: therefore the peice without having been moved did stay expecting the same. The answer is the same with that of the stone falling from the Tower; and all the fallacy, and equivocati­on consisteth in supposing still for true, that which is in question; for the Opponent hath it still fixed in his conceit that the ball departs from its rest, being discharged by the fire from the piece; and the departing from the state of rest, cannot be, unlesse the immobility of the Terrestrial Globe be presupposed, which is the conclusion of that was in dispute; Therefore, I reply, that those who make the Earth moveable, answer, that the piece, and the ball that is in it, partake of the same motion with the Earth; nay that they have this together with her from nature; and that therefore the ball departs in no other manner from its quiescence, but conjoyned with its motion about the cen­tre, the which by its projection upwards, is neither taken away, nor hindered; and in this manner following, the universal motion of the Earth towards the East, it alwayes keepeth perpendicular over the said piece, as well in its rise as in its return. And the same you see to ensue, in making the experiment in a ship with a bullet shot upwards perpendicularly with a Crosse-bow, which returneth to the same place whether the ship doth move, or stand still."

"The Ptolomaique Hypothesis... most unreasonably confoundeth the order, which we assuredly see to be amongst those Cœlestial Bodies, the circumgyration of which is not questionable, but most certain. And that Order is, that according as an Orb is greater, it finisheth its revolution in a longer time, and the lesser, in shorter. ...but if you would have the Earth immoveable, it is necessary, that when you have past from the short period of the Moon, to the others successively bigger, until you come to that of Mars in two years, and from thence to that of the bigger Sphere of Jupiter in twelve years, and from this to the other yet bigger of Saturn, whose period is of thirty years, it is necessary, I say, that you passe to another Sphere incomparably greater still than that, and make this to ac­complish an entire revolution in twenty four hours. ...But the motion of the Earth being granted, the order of the pe­riods will be exactly observed, and from the very slow Sphere of Saturn, we come to the fixed Stars, which are wholly immovea­ble."

"If you will ascribe this Great Motion to Heaven, you must of necessity make it contrary to the particular motion of all the Orbs of the Planets, each of which without controversie hath its peculiar motion from the West towards the East, and this but very easie and moderate: and then you make them to be hurried to the contrary part, i. e. from East to West, by this most furious diurnal motion: whereas, on the contrary, making the Earth to move in it self, the contrariety of motions is taken away, and the onely motion from West to East is accom­modated to all appearances, and exactly satisfieth every Phœno­menon."

"If the Starry Sphere be supposed moveable [there is an] immense disparity between the motions of those stars themselves; of which some would come to move most swiftly in most vast cir­cles, others most slowly in circles very small, according as those or these should be found nearer, or more remote from the Poles. ... And not onely the magnitudes of the circles, and conse­quently the velocity of the motions of these Stars, shall be most different from the circles and motions of those others, but... the self-same Stars shall successively vary its circles and velocities: For that those, which two thousand years since were in the Equinoctial, and consequently did with their motion describe very vast cir­cles, being in our dayes many degrees distant from thence, must of necessity become more slow of motion, and be reduced to move in lesser circles, and it is not altogether impossible but that a time may come, in which some of them which in aforetime had continually moved, shall be reduced by uniting with the Pole, to a state of rest, and then after some time of cessation, shall return to their motion again."

"I would not do so much wrong to Plato, but yet I may truly say with Aristotle, that he too much lost himself in, and too much doted upon that, his Geometry: for that in conclusion these Mathematical subtilties, Salviatus, are true in abstract, but applied to sensible and Physical matter, they hold not good. For the Mathematicians will very well demonstrate for example, that Sphæra tangit planum in puncto [the sphere touches the plane at the point]; a position like to that in dispute, but when one cometh to the matter, things succeed quite another way. And so I may say of these angles of contact, and these proportions; which all evaporate into Air, when they are applied to things material and sensible."

"I hold it [the concept or relative motion] to be much more antient: and suspect that Aristotle in receiving it from some good School, did not fully under­stand it, and that therefore, having delivered it with some altera­tion, it hath been an occasion of confusion amongst those, who would defend whatever he saith. And when he writ, that what­ soever moveth, doth move upon something immoveable, I suppose that he equivocated, and meant, that whatever moveth, moveth in respect to something immoveable; which proposition admitteth no doubt, and the other many."

"Motion is so far Motion, and as Motion operateth, by how far it hath relation to things which want Motion: but in those things which all equally partake thereof it hath nothing to do, and is as if it never were. And thus the Merchandises with which a ship is laden, so far move, by how far leaving London, they pass by France, Spain, Italy, and sail to Aleppo, which London, France, Spain &c. stand still, not moving with the ship: but as to the Chests, Bales and other Parcels, wherewith the ship is stow'd and and laden, and in respect of the ship it self, the Motion from Lon­don to Syria is as much as nothing; and nothing altereth the re­lation which is between them: and this, because it is common to all, and is participated by all alike: and of the Cargo which is in the ship, if a Bale were romag'd from a Chest but one inch onely, this alone would be in that Cargo, a greater Motion in respect of the Chest, than the whole Voyage of above three thousand miles, made by them as they were stived together."

"We having divided the Universe into two parts, one of which is necessarily moveable, and the other immoveable; for the obtaining of whatsoever may depend upon, or be required from such a motion, it may as well be done by making the Earth alone, as by making all the rest of the World to move: for that the operation of such a motion consists in nothing else, save in the relation or habitude which is between the Cœlestial Bodies, and the Earth, the which relation [with an exchange in the two terms] is all that is changed. Now if for the obtaining of the same effect ad unguem [to a nail's thickness], it be all one whe­ther the Earth alone moveth, the rest of the Universe standing still; or that, the Earth onely standing still, the whole Universe moveth with one and the same motion; who would believe, that Nature (which by common consent, doth not that by many things, which may be done by few) hath chosen to make an innumerable number of most vast bodies move, and that with an unconceivable velocity, to perform that, which might be done by the moderate motion of one alone about its own Centre? ...which self same effect falls out exactly in the same manner, if, without troubling so great a part of the Universe."

"Whatsoever motion may be ascribed to the Earth, it is necessary that it be to us, (as inhabitants upon it, and conse­quently partakers of the same) altogether imperceptible, and as if it were not at all, so long as we have regard onely to terrestrial things..."

"If we consider onely the immense magnitude of the Starry Sphere, compared to the smalness of the Terrestrial Globe, contained therein so many mil­lions of times; and moreover weigh the velocity of the motion which must in a day and night make an entire revolution thereof, I cannot perswade my self, that there is any man who believes it more reasonable and credible, that the Cœlestial Sphere turneth round, and the Terrestrial Globe stands still."

"We need a Guid in unknown and uncouth wayes, but in champion places, and open plains, the blind only stand in need of a Leader; and for such, it is better that they stay at home. But he that hath eyes in his head, and in his mind, him should a man choose for his Guid. Yet mistake me not, thinking that I speak this, for that I am against hearing of Aristotle; for on the contrary, I commend the reading, and diligently studying of him; and onely blame the servile giving ones self up a slave unto him, so, as blindly to subscribe to what ever he delivers, and without search of any farther reason thereof, to receive the same for an inviolable decree. Which is an abuse, that carrieth with it ano­ther great inconvenience, to wit, that others will no longer take pains to understand the validity of his Demonstrations. And what is more shameful, than in the middest of publique disputes, whilest one person is treating of demonstrable conclusions, to hear another interpose with a passage of Aristotle, and not sel­dome writ to quite another purpose, and with that to stop the mouth of his opponent? But if you will continue to study in this manner, I would have you lay aside the name of Philosophers; and call your selves either Historians or Doctors of Memory, for it is not sit, that those who never philosophate, should usurp the honourable title of Philosophers."

"Because it is more easie for a man to sculk under anothers shield than to shew himself openly, they tremble, and are affraid to stir one step from him; and rather than they will admit some alterations in the Heaven of Aristotle, they will impertinently de­ny those they behold in the Heaven of Nature."

"Therefore Simplicius, come either with arguments and demonstrations of your own, or of Aristotle, and bring us no more Texts and na­ked authorities, for our disputes are about the Sensible World, and not one of Paper."