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From Galileo to Newton
By A. Rupert Hall
Dover Publications, Inc.Copyright © 1981 A. Rupert Hall
All rights reserved.
SCIENCE IN TRANSITION 1630–1650
What if the Sun
Be Center to the World, and other Starrs
By his attractive vertue and thir own
Incited, dance about him various rounds?
Thir wandring course now high, now low, then hid,
Progressive, retrograde, or standing still,
In six thou seest, and what if sev'nth to these
The Planet Earth, so stedfast though she seem,
Insensibly three different. Motions move?
(John Milton, Paradise Lost, VIII, 122–130)
Among the young men admitted to the Mastership of Arts in the University of Cambridge in 1632 was a young scholar and poet who might but for various accidents have spent the rest of his life in academic quiet. About six years later, travelling in Italy, John Milton briefly met Galileo—in enforced retirement at Arcetri outside Florence as a result of the justification of the Copernican hypothesis that he had published in 1632. In 1665, before the Fire of London, Milton finished Paradise Lost, the splendid epic in which the ancient imagery of the Earth-centred universe spent its last creative force. He died nine years later, at a time when Isaac Newton was warmly engaged in defending his optical discoveries. During the years when Milton served republican England, he was also familiar with men who had plunged into science and the business of invention. He corresponded with Henry Oldenburg (1615?–77), who became Secretary of the Royal Society a decade later. He visited the house of Lady Ranelagh, beloved sister of Robert Boyle; he was known to one mathematician, John Pell, and probably to another, John Wallis; he was acquainted with the ambitions of the reforming schemer, Samuel Hartlib, and may have met Comenius when he visited London at Hartlib's instigation in 1641. He lived through the transformation of science in England, though he was himself more concerned with the fleeting transitions of politics, and talked with some of the men who brought it about.
When Milton was born English science descended in almost limpid purity direct from the Middle Ages. When he died the Royal Society was in full course of building a new world, an earthly paradise perhaps though not a heavenly one. He was a man when Galileo was sentenced at Rome; he lived through the whole active life of Descartes; and having gone to school with Aristotle and Ptolemy he could have seen "at Mr Crosse's house in Oxford" the very beginning of the long road that led to Rutherford. Caught between the past and the future Milton's present held the fall of classicism and the rise of modernism, the reluctant yielding of Puritanism before deism, the passage of the new science from diffidence to mastery.
The first thirty years of the seventeenth century had shaken the old order of things but by no means disrupted it. Traditional science so far revealed astonishing resilience and the new had not yet acquired an outlook positive enough to take its place. Schools and universities all over Europe continued to teach the comfortable doctrines of natural philosophy and medicine drawn from classical authors much as they had done for two centuries before. To an ordinary observer of the learned world in Milton's youth only two groups presented themselves as markedly dissident. The more serious consisted of those astronomers who persisted in upholding the belief of Copernicus—still after some eighty years regarded by all but a few enthusiasts as fantastically absurd—that the Earth and planets circle a stationary sun. So feeble had the arguments in favour of Copernicus seemed and so evident the fixity of the Earth that it was only in 1616 that Copernicanism had been condemned by the Catholic Church, save as a calculating device. The real battle between traditional and revolutionary ideas in astronomy had been long delayed, and when it came its violence was largely confined to Italy. Elsewhere the transition from scepticism to acceptance of the heliostatic system occurred peacefully enough in the second quarter of the century; but before 1620 there were few Copernicans anywhere. In France, for instance, Marin Mersenne (1588–1648)—later to become a central figure of the scientific movement in his country—published in 1623 a work in which he showed, very fairly, the weakness of the Copernican hypothesis. He did not change his mind until about 1630. Descartes (1596–1650) had probably swung over rather earlier, yet he always hesitated to avow himself openly a Copernican. Learned opinion in France was broadly of Mersenne's mind.
In England William Gilbert (1540–1603), physicist and physician, had made the rotation of the Earth the pillar of his magnetical philosophy without following Copernicus in setting the Earth free to revolve about the sun. There were others, however, who followed the sixteenth-century example of Thomas Digges in taking the opposite view, among them the Gresham College Professors Briggs and Gellibrand. And Sir Henry Savile, in founding a chair of astronomy at Oxford in 1619, had wisely stipulated that the system of Copernicus should be taught alongside that of Ptolemy. In fact, though few Englishmen as yet subscribed firmly to the new celestial system, many of the well informed recognised the imperfection of the Ptolemaic, and looked for some kind of compromise such as that offered by Tycho Brahe (1546–1601). For Tycho made the five planets spin around the Sun, while the Sun and Moon revolved about the Earth; hence the fixity of the Earth was maintained although the relative motions were the same as in the Copernican system.
It did not follow that—outside Italy—adherence to Copernican ideas was regarded as reprehensible. Moreover, some scholars though sceptical nevertheless made use of Copernican tables and astronomical constants, as Erasmus Reinhold (1511–53) had done years before in compiling his Prutenic Tables. In many places discussion of the rival theories took place without sharpness, and there was no open crisis even in Italy before 1632, despite the cardinals' decision of 1616. The career of the greatest of early seventeenth-century astronomers, Johann Kepler (1571–1630), was not affected by his unconcealed attachment to Copernicus's system. The storms in Kepler's life were not occasioned by his scientific opinions, though indeed when he died two years before Galileo's trial it might have seemed that he had lived in vain. In the strategy of science Kepler's discoveries are among the greatest, and tactically they yielded the most solid support for the heliostatic view that the age could furnish. But no echo of Kepler's laws of planetary motion is perceptible until a decade after his death, while in his lifetime he was best known for fantastical and absurd speculations—and for his optics. Even Galileo (1564–1642), besides failing to elucidate the significance of Kepler's discoveries (in public at any rate), seems to have had little wish to link his own rational defence of Copernicanism with the supposed whims and fancies of the Imperial Astronomer. The Pythagorean mysticism, the farfetched ratios and musical harmonies of Kepler's books repelled many who sought, rather, one single solid reason for supposing the Earth to move.
Galileo's history is very different. Like Kepler a fairly early convert to the new astronomy, in 1597 he confessed his fear of declaring himself lest he should be mocked. Throughout his career he taught his pupils the Ptolemaic system and it is probable that he never lectured publicly on the physical truth of the Copernican. Certainly he denied that he had ever done so. However, he did discuss the old and the new astronomy in private before 1632 (as it was lawful for him to do) and among his pupils he found some notable converts for Copernicus, such as Benedetto Castelli (1577–1644) and Bonaventura Cavalieri (1598–1647). From 1610 onwards he wrote plainly in favour of Copernicus and against any attempt to suppress preference for the new astronomy, or discussion of its tenets. Galileo had become famous throughout Europe as the first to turn the telescope to the heavens, as the discoverer of Jupiter's satellites and the mountains of the moon, of the spots on the sun and the phases of Venus, so that it might seem, with his authority as an investigator reinforced by his vigour as a polemical writer, that Galileo's opinion would have carried great weight in favour of Copernicus even before he published the Dialogues on the Two Chief Systems of the World (1632). This would be too simple a view. Like Kepler, Galileo had won few converts before 1630, most of them among his circle of friends and pupils. His discoveries and writings did two things. They provoked the first really powerful counter-attacks against the new doctrines in astronomy, and they also multiplied the number of these new doctrines. The question was no longer simply whether the mathematical system of Copernicus was physically correct or not. For a time at least the situation, the decision for or against traditional ideas, was not clarified but rather confused by the new discoveries made by Galileo and others.
Criticism of Galileo took three forms. First, there were attacks on the truth and originality of his observations—the former more understandable because it proved very difficult in the early years to repeat them, until Galileo had distributed a number of his own telescopes which were much superior to those bought in the opticians' shops. Secondly, his interpretation of what he saw—that the moon is rugged and mountainous, that the Earth reflects light like the moon, that the sun has dark blemishes whose movement demonstrates its rotation and so forth—was doubted by many who admitted the ocular evidence. And thirdly it was not allowed by his opponents that the new sight of the heavens given by the telescope in any way confirmed the Copernican pattern of celestial motion. Copernicus' innovations in astronomy had been essentially geometrical; Galileo's were essentially physical. It was possible to tie the two together—though Galileo only attempted to do so in detail in theDialogues of 1632—but it was equally possible to avoid doing so. Galileo's critics could quite reasonably hold that the new discoveries did not prove the truth of the Copernican system though they might (and did) destroy the Ptolemaic.
They could take this position by following the example of the great Danish astronomer Tycho Brahe, who had rejected both Ptolemy and Copernicus. Tycho's own system of celestial motions had the merit of being theoretically equivalent to the Copernican, without the apparent defect of ascribing motion to the Earth; it made possible a scientifically adequate geostatic astronomy, irrefutable by any test of observation that Galileo or anyone else could impose upon it. As such it was adopted by many writers, especially by orthodox Catholic astronomers such as Giambaptista Riccioli (1598–1671). The Tychonic system was effectively current long after the Ptolemaic was defunct, surviving until after mid-century. Relying on this modern geostatic conception anti-Copernican and anti-Galilean astronomers like the Jesuit Christopher Scheiner (1575–1650) could not only accept Galileo's physical observations of the new celestial phenomena, but claim them for themselves. In the same fashion Tycho, though anti-Copernican, had argued that there were no celestial spheres and that comets were true celestial bodies. Acceptance of the reality of Jupiter's satellites and of sunspots put the critic in a far stronger and more flexible position than that which had been adopted by Galileo's early traditionalist opponents, who had simply decried everything seen through the telescope. It could now be argued that Aristotle was in error only in so far as he had unfortunately lacked such a device for exploring the sky. Well and good: mountains on the moon prove it is not a perfectly crystalline sphere, but they do not prove that the Earth moves.
In the years just before the publication of Galileo's Dialogues there was little reason to anticipate a violent revolution in astronomical theory. Fresh information had come in swiftly since the first use of the telescope in 1609 but it seemed that its import could be neutralised by accommodating it within the old framework. The spread of Copernican ideas was slow and undramatic. They were still opposed by most learned men and by virtually all the mathematical astronomers except Kepler. The latter's accurate solution of the problems of planetary motion was universally ignored. The innovators themselves were not completely agreed on the new shape of the heavens; Galileo was conservative in denying that comets were heavenly bodies, Kepler in denying that the universe could conceivably be infinite. On lesser matters—the size of the heliocentric orbits, the strange appearance of Saturn, the cause of terrestrial tides—confusion reigned among them. Yet, within about a quarter of a century, the issue was decided in favour of Copernicus and the Earth was henceforward as likely to be considered flat as fixed. The decrees of 1633 were issued at the very moment when they were useless.
The other dissident group that reveals some coherence in the early seventeenth century was in the long run of far less significance in the development of science, and was (perhaps naturally) proportionately more noisy in its own time. The iatrochemists (chemical physicians) distorted a good case against traditional medicine, whereas the astronomers were in the right even though they could not prove it. Just as the latter attacked the authority of Aristotle and Ptolemy, so their companion innovators attacked that of Galen and the whole long line of Graeco-Arab physicians descending from him. In place of Copernicus they had his near-contemporary Paracelsus (1493–1541); for the heliocentric system the therapy of chemically-prepared medicaments; for the mystique of numerical relations the mystique of fire as the sovereign of chemical and bodily action; for the decrees of the Church the condemnations of the established faculties of medicine. And as the war against new ideas in astronomy was hottest in Italy, so the war against them in medicine was hottest in France. Elsewhere—in Germany, the Low Countries, England—Paracelsan ideas (or alternative more rational versions of them) were allowed to make slow headway, just as Copernican notions did.
There was never so marked a change in opinions about the proper kind of remedies to use against disease as that which took place in astronomy. The older herbal medicines—" Galenicals "—continued to hold their place in the pharmacopoeias, if always in retreat. While only a few chemical preparations were admitted into the first edition of the London Pharmacopoeia in 1618, their number increased steadily with each reissue during the seventeenth century. Approaches to medicine, physiology and chemistry proper that owed something to the teaching of Paracelsus reached their maximum influence about mid-century; thereafter the effect of Paracelsus declined again. Elements of mysticism were gradually pruned away till only a rational basis remained, just as happened with the celestial harmonies of Kepler. There was an increasing tendency for alchemy, like astrology the disreputable companion of astronomy, to be set aside as an aberrant variation of true chemical science. For the first matter-of-fact manuals of empirical chemistry had appeared in the first years of the seventeenth century, and their pattern was developed with further elaboration.
The comparison between Paracelsan chemico-medicine and the new astronomy indicates that the struggle between tradition and innovation in science was not necessarily (or simply) one between wrong and right as judged by later standards. The iatrochemists were no less sure of their innovations than were the Copernicans. They argued as tenaciously and more volubly, they were no less ready with experiential proof and philosophical reasoning to justify their case. With no less justice they could resent the dead weight of tradition that opposed them and the intolerance of authorities; they could appeal with no less effect to the virtue of the open, inquiring mind and of the experimental method. If, in the end, their views have been found to hold but a dim perception of the truth it can equally be said of the Copernicans that they had seized upon but the first clue to modern astronomy. Just as certain pages of Kepler, contrasted with the plausible sanity of some anti-Copernican astronomers, cause one to wonder which was the side of the angels, so the Paracelsan insurgence underlines the current of fantasy in the ebullience of seventeenth-century science.
Excerpted from From Galileo to Newton by A. Rupert Hall. Copyright © 1981 A. Rupert Hall. Excerpted by permission of Dover Publications, Inc..
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