BOOK V.
FORMAL ASTRONOMY.
CHAPTER I.
Prelude to Copernicus.
Nicolas of Cus.
I WILL quote the passage, in the writings of this author, which bears upon the subject in question. I translate it from the edition of his book De Docta Ignorantia, from his works published at Basil in 1565. He praises Learned Ignorance—that is, Acknowledged Ignorance—as the source of knowledge. His ground for asserting the motions of the earth is, that there is no such thing as perfect rest, or an exact centre, or a perfect circle, nor perfect uniformity of motion. “Neque verus circulus dabilis est, quinetiam verior dari possit, neque unquam uno tempore sicut alio æqualiter præcisè, aut movetur, aut circulum veri similem, æqualem describit, etiamsi nobis hoc non appareat. Et ubicumque quis fuerit, se in centro esse credit.” (Lib. i. cap. xi. p. 39.) He adds, “The Ancients did not attain to this knowledge, because they were wanting in Learned Ignorance. Now it is manifest to us that the Earth is truly in motion, although this do not appear to us; since we do not apprehend motion except by comparison with something fixed. For if any one were in a boat in the middle of a river, ignorant that the water was flowing, and not seeing the banks, how could he apprehend that the boat was moving? And thus since every one, whether he be in the Earth, or in the Sun, or in any other star, thinks that he is in an immovable centre, and that everything else is moving; he would assign different poles for himself, others as being in the Sun, others in the Earth, and others in the Moon, and so of the rest. Whence the machine of the world is as if it had its centre everywhere and its circumference nowhere.” This train of thought [524] might be a preparation for the reception of the Copernican system; but it is very different from the doctrine that the Sun is the centre of the Planetary Motions.
CHAPTER II.
The Copernican Theory.
The Moon’s Rotation.
I HAVE said, in [page 264], that a confusion of mind produced by the double reference of motion to absolute space, and to a centre of revolution, often leads persons to dispute whether the Moon, while she revolves about the Earth, always turning to it the same face, revolves about her axis or not.
This dispute has been revived very lately, and has been conducted in a manner which shows that popular readers and writers have made little progress in the clearness of their notions during the last two or three centuries; and that they have accepted the Newtonian doctrines in words with a very dim apprehension of their real import.
If the Moon were carried round the Earth by a rigid arm revolving about the Earth as a centre, being rigidly fastened to this arm, as a mimic Moon might be, in a machine constructed to represent her motions, this contrivance, while it made her revolve round the Earth would make her also turn the same face to the Earth: and if we were to make such a machine the standard example of rotation, the Moon might be said not to rotate on her axis.
But we are speedily led to endless confusion by taking this case as the standard of rotation. For the selection of the centre of rotation in a system which includes several bodies is arbitrary. The Moon turns all her faces successively to the Sun, and therefore with regard to the Sun, she does rotate on her axis; and yet she revolves round the Sun as truly as she revolves round the Earth. And the only really simple and consistent mode of speaking of rotation, is to refer the motion not to any relative centre, but to absolute space.
This is the argument merely on the ground of simplicity and consistency. But we find physical reasons, as well as mathematical, for referring the motion to absolute space. If a cup of water be carried round a centre so as to describe a circle, a straw floating on the surface [525] of the water, if it point to the centre of the circle at first, does not continue to do so, but remains parallel to itself during the whole revolution. Now there is no cause to make the water (and therefore the straw) rotate on its axis; and therefore it is not a clear or convenient way of speaking, to say that the water in this case does revolve on its axis. But if the water in this case do not revolve on its axis, a body in the case of the Moon does revolve on its axis.
The difficulty, as I have said in the text, is of the same nature as that which the Copernicans at first found in the parallel motion of the Earth’s axis. In order to make the axis of the Earth’s rotation remain parallel to itself while the Earth revolves about the Sun, in a mechanical representation, some machinery is needed in addition to the machinery which produces the revolution round the centre (the Sun): but the simplest way of regarding the parallel motion is, to conceive that the axis has no motion except that which carries it round the central Sun. And it was seen, when the science of Mechanics was established, that no force was needed in nature to produce this parallelism of the Earth’s axis. It was therefore the only scientific course, to conceive this parallelism as not being a rotation: and in like manner we are to conceive the parallelism of a revolving body as not being a rotation.
M. Foucault’s Proofs of the Earth’s Motion.
It was hardly to be expected that we should discover, in our own day, a new physical proof of the earth’s motion, yet so it has been. The experiments of M. Foucault have enabled us to see the Rotation of the Earth on its axis, as taking place, we may say, before our eyes. These experiments are, in fact, a result of what has been said in speaking of the Moon’s rotation: namely, That the mechanical causes of motion operate with reference to absolute, not relative, space; so that where there is no cause operating to change a motion, it will retain its direction in absolute space; and may on that account seem to change, if regarded relatively in a limited space.
In M. Foucault’s first experiment, the motion employed was that of a pendulum. If a pendulum oscillate quite freely, there is no cause acting to change the vertical plane of oscillation absolutely; for the forces which produce the oscillation are in the vertical plane. But if the vertical plane remain the same absolutely, at a spot on the surface of the revolving Earth, it will change relatively to the spectator. He will see the pendulum oscillate in a vertical plane which gradually [526] turns away from its first position. Now this is what really happens; and thus the revolution of the Earth in absolute space is experimentally proved.
In subsequent experiments, M. Foucault has used the rotation of a body to prove the same thing. For when a body rotates freely, acted upon by no power, there is nothing to change the position of the axis of rotation in absolute space. But if the position of the axis remain the same in absolute space, it will, in virtue of its relative motion, change as seen by a spectator at any spot on the rotating Earth. By taking a heavy disk or globe and making it rotate on its axis rapidly, the force of absolute permanence (as compared with the inevitable casual disturbances arising from the machinery which supports the revolving disk) becomes considerable and hence the relative motion can, in this way also, be made visible.
Mr. De Morgan has said (Comp. to Brit. Alm. 1836, p. 18) that astronomy does not supply any argument for the earth’s motion which is absolutely and demonstrably conclusive, till we come to the Aberration of Light. But we may now venture to say that the experiments of M. Foucault prove the diurnal motion of the Earth in the most conclusive manner, by palpable and broad effects, if we accept the doctrines of the Science of Mechanics: while Aberration proves the annual motion, if we suppose that we can observe the places of the fixed stars to the accuracy of a few seconds; and if we accept, in addition to the doctrines of Mechanics, the doctrine of the motion of light with a certain great velocity.
CHAPTER III.
Sequel to Copernicus.
English Copernicans.
PROFESSOR DE MORGAN has made numerous and interesting contributions to the history of the progress and reception of the Copernican System. These are given mainly in the Companion to the British Almanac; especially in his papers entitled “Old Arguments against the Motion of the Earth” (1836); “English Mathematical and Astronomical Writers” (1837); “On the Difficulty of Correct [527] Description of Books” (1853); “The Progress of the Doctrine of the Earth’s Motion between the Times of Copernicus and Galileo” (1855). In these papers he insists very rightly upon the distinction between the mathematical and the physical aspect of the doctrines of Copernicus: a distinction corresponding very nearly with the distinction which we have drawn between Formal and Physical Astronomy; and in accordance with which we have given the history of the Heliocentric Doctrine as a Formal Theory in [Book v.], and as a Physical Theory in [Book vii.]
Another interesting part of Mr. De Morgan’s researches are the notices which he has given of the early assertors of the heliocentric doctrine in England. These make their appearance as soon as it was well possible they should exist. The work of Copernicus was published, as we have said, in 1543. In September 1556, John Field published an Ephemeris for 1557, “juxta Copernici et Reinholdi Canones,” in the preface to which he avows his conviction of the truth of the Copernican hypothesis. Robert Recorde, the author of various works on Arithmetic, published among others, “The Pathway to Knowledge” in 1551. In this book, the author discusses the question of the “quietnes of the earth,” and professes to leave it undecided: but Mr. De Morgan (Comp. A. 1837, p. 33) conceives that it appears from what is said, that he was really a Copernican, but did not think the world ripe for any such doctrine.
Mr. Joseph Hunter also has brought to notice[29] the claims of Field, whom he designates as the Proto-Copernican of England. He quotes the Address to the Reader prefixed to his first Ephemeris, and dated May 31, 1556, in which he says that, since abler men decline the task, “I have therefore published this Ephemeris of the year 1557, following in it as my authorities, N. Copernicus and Erasmus Reinhold, whose writings are established and founded on true, certain, and authentic demonstrations.” I conceive that this passage, however, only shows that Field had adopted the Copernican scheme as a basis for the calculation of Ephemerides; which, as Mr. De Morgan has remarked, is a very different thing from accepting it as a physical truth. Field, in this same address, makes mention of the errors “illius turbæ quæ Alphonsi utitur hypothesi;” but the word hypothesis is still indecisive.
[29] Ast. Soc. Notices, vol. iii. p. 3 (1833).
As evidence that Field was regarded in his own day as a man who [528] had rendered good service to science, Mr. Hunter notices that, in 1558, the Heralds granted to him the right of using, with his arms, the crest or additional device of a red right arm issuing from the clouds, and presenting a golden armillary sphere.
Recorde’s claims depend upon a passage in a Dialogue between Master and Scholar, in which the Master expounds the doctrine of Copernicus, and the authorities against it; to which the Scholar answers, taking the common view: “Nay, sir, in good faith I desire not to hear such vaine phantasies, so far against common reason, and repugnant to all the learned multitude of wryters, and therefore let it passe for ever and a day longer.” The Master, more sagely, warns him against a hasty judgment, and says, “Another time I will so declare his supposition, that you shall not only wonder to hear it, but also peradventure be as earnest then to credit it, as you now are now to condemne it.” I conceive that this passage proves Mr. De Morgan’s assertion, that Recorde was a Copernican, and very likely the first in England.
In 1555, also, Leonard Digges published his “Prognostication Everlasting;” but this is, as Mr. De Morgan says (Comp. A. 1837, p. 40) a meteorological work. It was republished in 1592 by his son Thomas Digges with additions; and as these have been the occasion of some confusion among those who have written on the history of astronomy, I am glad to be able, through the kindness of Professor Walker of Oxford, to give a distinct account of the editions of the work.
In the Bodleian Library, besides the editions of 1555 and 1592 of the “Prognostication Everlasting,” there is an edition of 1564. It is still decidedly Ptolemaic, and contains a Diagram representing a number of concentric circles, which are marked, in order, as—
“The Earth,
Moone,
Venus,
Mercury,
Sunne,
Mars,
Jupiter,
Saturne,
The Starrie Firmament,
The Crystalline Heavens,
The First Mover,
The Abode of God and the Elect. Here the Learned do approve.” [529]
The third edition, of 1592, contains an Addition, by the son, of twenty pages. He there speaks of having found, apparently among his father’s papers, “A description or modile of the world and situation of Spheres Cœlestiall and elementare according to the doctrine of Ptolemie, whereunto all universities (led thereunto chiefly by the authoritie of Aristotle) do consent.” He adds: “But in this our age, one rare witte (seeing the continuall errors that from time to time more and more continually have been discovered, besides the infinite absurdities in their Theoricks, which they have been forced to admit that would not confesse any Mobilitie in the ball of the Earth) hath by long studye, paynfull practise, and rare invention, delivered a new Theorick or Model of the world, shewing that the Earth resteth not in the Center of the whole world or globe of elements, which encircled and enclosed in the Moone’s orbe, and together with the whole globe of mortalitye is carried yearely round about the Sunne, which like a king in the middest of all, raygneth and giveth lawes of motion to all the rest, sphærically dispersing his glorious beames of light through all this sacred cœlestiall Temple. And the Earth itselfe to be one of the Planets, having his peculiar and strange courses, turning every 24 hours rounde upon his owne centre, whereby the Sunne and great globe of fixed Starres seem to sway about and turne, albeit indeed they remaine fixed—So many ways is the sense of mortal man abused.”
This Addition is headed:
“A Perfit Description of the Cœlestiall Orbes, according to the most ancient doctrine of the Pythagoreans: lately revived by Copernicus, and by Geometrical Demonstrations approved.” Mr. De Morgan, not having seen this edition, and knowing the title-page only as far as the word “Pythagoreans,” says “their astrological doctrines we presume, not their reputed Copernican ones.” But it now appears that in this, as in other cases, the authority of the Pythagoreans was claimed for the Copernican system. Antony a Wood quotes the latter part of the title thus: “Cui subnectitur orbium Copernicarum accurata descriptio;” which is inaccurate. Weidler, still more inaccurately, cites it, “Cui subnectitur operum Copernici accurata descriptio.” Lalande goes still further, attempting, it would seem, to recover the English title-page from the Latin: we find in the Bibl. Astron. the following: “1592 . . Leonard Digges, Accurate Description of the Copernican System to the Astronomical perpetual Prognostication.”
Thomas Digges appears, by others also of his writings, to have been [530] a clear and decided Copernican. In his “Alæ sive Scalæ Mathematicæ,” 1573, he bestows high praise upon Copernicus and upon his system: and appears to have been a believer in the real motion of the Earth, and not merely an admirer of the system of Copernicus as an explanatory hypothesis.
Giordano Bruno.
The complete title of the work referred to is:
“Jordani Bruni Nolani De Monade Numero et Figura liber consequens Quinque De Minimo Magno et Mensura, item De Innumerabilibus, Immenso et Infigurabili; seu De Universo et Mundis libri octo. (Francofurti, 1591.)”
That the Reader may judge of the value of Bruno’s speculations, I give the following quotations:
Lib. iv. c. 11 (Index). “Tellurem totam habitabilem esse intus et extra, et innumerabilia animantium complecti tum nobis sensibilium tum occultorum genera.”
C. 13. “Ut Mundorum Synodi in Universo et particulares Mundi in Synodis ordinentur,’ &c.
He says (Lib. v. c. 1, p. 461): “Besides the stars and the great worlds there are smaller living creatures carried through the etherial space, in the form of a small sphere which has the aspect of a bright fire, and is by the vulgar regarded as a fiery beam. They are below the clouds, and I saw one which seemed to touch the roofs of the houses. Now this sphere, or beam as they call it, was really a living creature (animal), which I once saw moving in a straight path, and grazing as it were the roofs of the city of Nola, as if it were going to impinge on Mount Cicada; which however it went over.”
There are two recent editions of the works of Giordano Bruno; by Adolf Wagner, Leipsick, 1830, in two volumes; and by Gfrörer, Berlin, 1833. Of the latter I do not know that more than one volume (vol. ii.) has appeared.
Did Francis Bacon reject the Copernican System?
Mr. De Morgan has very properly remarked (Comp. B. A. 1855, p. 11) that the notice of the heliocentric question in the Novum Organon must be considered one of the most important passages in his works upon this point, as being probably the latest written and best [531] matured. It occurs in Lib. ii. Aphorism xxxvi., in which he is speaking of Prerogative Instances, of which he gives twenty-seven species. In the passage now referred to, he is speaking of a kind of Prerogative Instances, better known to ordinary readers than most of the kinds by name, the Instantia Crucis: though probably the metaphor from which this name is derived is commonly wrongly apprehended. Bacon’s meaning is Guide-Post Instances: and the Crux which he alludes to is not a Cross, but a Guide-Post at Cross-roads. And among the cases to which such Instances may be applied, he mentions the diurnal motion of the heavens from east to west, and the special motion of the particular heavenly bodies from west to east. And he suggests what he conceives may be an Instantia Crucis in each case. If, he says, we find any motion from east to west in the bodies which surround the earth, slow in the ocean, quicker in the air, quicker still in comets, gradually quicker in planets according to their greater distance from the earth: then we may suppose that there is a cosmical diurnal motion, and the motion of the earth must be denied.
With regard to the special motions of the heavenly bodies, he first remarks that each body not coming quite so far westwards as before, after one revolution of the heavens, and going to the north or the south, does not imply any special motion; since it may be accounted for by a modification of the diurnal motion in each, which produces a defect of the return, and a spiral path; and he says that if we look at the matter as common people[30] and disregard the devices of astronomers, the motion is really so to the senses; and that he has made an imitation of it by means of wires. The instantia crucis which he here suggests is, to see if we can find in any credible history an account of any comet which did not share in the diurnal revolution of the skies.
[30] Et certissimum est si paulisper pro plebeiis nos geramus (missis astronomorum et scholæ commentis, quibus illud in more est, ut sensui in multis immerito vim faciant et obscuriora malint) talem esse motum istum ad sensum qualem diximus.
On his assertion that the motion of each separate planet is, to sense, a spiral, we may remark that it is certainly true; but that the business of science, here, as elsewhere, consists in resolving the complex phenomenon into simple phenomena; the complex spiral motion into simple circular motions.
With regard to the diurnal motion of the earth, it would seem as if Bacon himself had a leaning to believe it when he wrote this passage; for neither is he himself, nor are any of the Anticopernicans, [532] accustomed to assert that the immensely rapid motion of the sphere of the Fixed Stars graduates by a slower and slower motion of Planets, Comets, Air, and Ocean, into the immobility of the Earth. So that the conditions are not satisfied on which he hypothetically says, “tum abnegandus est motus terræ.”
With regard to the proper motions of the planets, this passage seems to me to confirm what I have already said of him; that he does not appear to have seen the full value and meaning of what had been done, up to his time, in Formal Astronomy.
We may however fully agree with Mr. De Morgan; that the whole of what he has said on this subject, when put together, does not justify Hume’s assertion that he rejected the Copernican system “with the most positive disdain.”
Mr. De Morgan, in order to balance the Copernican argument derived from the immense velocity of the stars in their diurnal velocity on the other supposition, has reminded us that those who reject this great velocity as improbable, accept without scruple the greater velocity of light. It is curious that Bacon also has made this comparison, though using it for a different purpose; namely, to show that the transmission of the visual impression may be instantaneous. In Aphorism xlvi. of Book ii. of the Novum Organon he is speaking of what he calls Instantiæ curriculi, or Instantiæ ad aquam, which we may call Instances by the clock: and he says that the great velocity of the diurnal sphere makes the marvellous velocity of the rays of light more credible.
“Immensa illa velocitas in ipso corpore, quæ cernitur in motu diurno (quæ etiam viros graves ita obstupefecit ut mallent credere motum terræ), facit motum illum ejaculationis ab ipsis [stellis] (licet celeritate ut diximus admirabilem) magis credibilem.” This passage shows an inclination towards the opinion of the earth’s being at rest, but not a very strong conviction.
Kepler persecuted.
We have seen ([p. 280]) that Kepler writes to Galileo in 1597—“Be trustful and go forwards. If Italy is not a convenient place for the publication of your views, and if you are likely to meet with any obstacles, perhaps Germany will grant us the necessary liberty.” Kepler however had soon afterwards occasion to learn that in Germany also, the cultivators of science were exposed to persecution. It is true that [533] in his case the persecution went mainly on the broad ground of his being a Protestant, and extended to great numbers of persons at that time. The circumstances of this and other portions of Kepler’s life have been brought to light only recently through an examination of public documents in the Archives of Würtemberg and unpublished letters of Kepler. (Johann Keppler’s Leben und Wirken, nach neuerlich aufgefundenen Manuscripten bearbeitet von J. L. C. Freiherrn v. Breitschwart, K. Würtemberg. Staats-Rath. Stuttgart, 1831.)
Schiller, in his History of the Thirty Years’ War, says that when Ferdinand of Austria succeeded to the Archduchy of Stiria, and found a great number of Protestants among his subjects, he suppressed their public worship without cruelty and almost without noise. But it appears now that the Protestants were treated with great severity. Kepler held a professorship in Stiria, and had married, in 1507, Barbara Müller, who had landed property in that province. On the 11th of June, 1598, he writes to his friend Mæstlin that the arrival of the Prince out of Italy is looked forwards to with terror. In December he writes that the Protestants had irritated the Catholics by attacks from the pulpit and by caricatures; that hereupon the Prince, at the prayer of the Estates, had declared the Letter of License granted by his father to be forfeited, and had ordered all the Evangelical Teachers to leave the country on pain of death. They went to the frontiers of Hungary and Croatia; but after a month, Kepler was allowed to return, on condition of keeping quiet. His discoveries appear to have operated in his favor. But the next year he found his situation in Stiria intolerable, and longed to return to his native country of Würtemberg, and to find some position there. This he did not obtain. He wrote a circular letter to his Brother Protestants, to give them consolation and courage; and this was held to be a violation of the conditions on which his residence was tolerated. Fortunately, at this time he was invited to join Tycho Brahe, who had also been driven from his native country, and was living at Prague. The two astronomers worked together under the patronage of the Emperor Rudolph II.; and when Tycho died in 1601, Kepler became the Imperial Mathematicus.
We are not to imagine that even among Protestants, astronomical notions were out of the sphere of religious considerations. When Kepler was established in Stiria, his first official business was the calculation of the Calendar for the Evangelical Community. They protested against the new Calendar, as manifestly calculated for the furtherance of an impious papistry: and, say they, “We hold the Pope for a [534] horrible roaring Lion. If we take his Calendar, we must needs go into the church when he rings us in.” Kepler however did not fail to see, and to say, that the Papal Reformation of the Calendar was a vast improvement.
Kepler, as court-astronomer, was of course required to provide such observations of the heavens as were requisite for the calculations of the Astrologers. That he considered Astrology to be valuable only as the nurse of Astronomy, he did not hesitate to reveal. He wrote a work with a title of which the following is the best translation which I can give: “Tertius interveniens, or: A Warning to certain Theologi, Medici, Philosophi, that while they reasonably reject star-gazing superstition, they do not throw away the kernel with the shell.[31] 1610.” In this he says, “You over-clever Philosophers blame this Daughter of Astronomy more than is reasonable. Do you not know that she must maintain her mother with her charms? How many men would be able to make Astronomy their business, if men did not cherish the hope to read the Future in the skies?”
[31] The German passage involves a curious image, borrowed, I suppose, from some odd story: “dass sie mit billiger Verwerfung des sternguckerischen Aberglaubens das Kind nicht mit dem Bade ausschütten.” “That they do not throw away the child along with the dirty water of his bath.”
Were the Papal Edicts against the Copernican System repealed?
Admiral Smyth, in his Cycle of Celestial Objects, vol. i. p. 65, says—“At length, in 1818, the voice of truth was so prevailing that Pius VII. repealed the edicts against the Copernican system, and thus, in the emphatic words of Cardinal Toriozzi, ‘wiped off this scandal from the Church.’”
A like story is referred to by Sir Francis Palgrave, in his entertaining and instructive fiction, The Merchant and the Friar.
Having made inquiry of persons most likely to be well informed on this subject, I have not been able to learn that there is any further foundation for these statements than this: In 1818, on the revisal of the Index Expurgatorius, Galileo’s writings were, after some opposition, expunged from that Catalogue.
Monsignor Marino Marini, an eminent Roman Prelate, had addressed to the Romana Accademia di Archeologia, certain historico-critical Memoirs, which he published in 1850, with the title Galileo e l’Inquisizione. In these, he confirms the conclusion which, I think, almost [535] all persons who have studied the facts have arrived at;[32] that Galileo trifled with authority to which he professed to submit, and was punished for obstinate contumacy, not for heresy. M. Marini renders full justice to Galileo’s ability, and does not at all hesitate to regard his scientific attainments as among the glories of Italy. He quotes, what Galileo himself quoted, an expression of Cardinal Baronius, that “the intention of the Holy Spirit was to teach how to go to heaven, not how heaven goes.”[33] He shows that Galileo pleaded (p. 62) that he had not held the Copernican opinion after it had been intimated to him (by Bellarmine in 1616), that he was not to hold it; and that his breach of promise in this respect was the cause of the proceedings against him.
[32] M. Marini (p. 29) mentions Leibnitz, Guizot, Spittler, Eichhorn, Raumer, Ranke, among the “storici eterodossi” who have at last done justice to the Roman Church.
[33] Come si vada al Cielo, e non come vada il Cielo.
Those who admire Galileo and regard him as a martyr because, after escaping punishment by saying “It does not move,” he forthwith said “And yet it does move,” will perhaps be interested to know that the former answer was suggested to him by friends anxious for his safety. Niccolini writes to Bali Cioli (April 9, 1633) that Galileo continued to be so persuaded of the truth of his opinions that “he was resolved (some moments before his sentence) to defend them stoutly; but I (continues Niccolini) exhorted him to make an end of this; not to mind defending them; and to submit himself to that which he sees that they may desire him to believe or to hold about this matter of the motion of the earth. He was extremely afflicted.” But the Inquisition was satisfied with his answers, and required no more.[34]
[34] Marini, p. 61.