‘Heavens and earth in one frame’
Cosmography and the form of the earth in the Scientific Revolution.
Jackie Biro
A thesis submitted in fulfilment of the requirements for the degree of Master of Arts (Research)
© Jackie Biro University of New South Wales March 2006.
Abstract
This thesis addresses the role of geography in the Scientific Revolution, a matter yet to be settled by historians of science. Specifically it argues that cosmography, the parent discipline of both astronomy and geography, was central to Copernican natural philosophy in the early modern period. Copernicus, Bruno, Gilbert, Galileo and Descartes all sought to provide a unified picture of the heavens and earth by harmonising ideas in geography and astronomy, according to established principles of cosmography. In addition, using concepts about the earth’s form to build heliocentric cosmological theories was routine amongst Copernican thinkers. Indeed, this analysis demonstrates that Copernicus, Bruno and Gilbert staked their claims about the heavens on their theories of the earth.
Recognising cosmography offers several advantages to historical understanding of the Scientific Revolution. It helps explain the form of Bruno’s argument for an infinite cosmos and a multiplicity of worlds. It provides insights into Gilbert’s interest in the detailed structure of the earth, beyond simply magnetism, and reveals that his argument followed a more traditional path than generally thought. A cosmographic perspective explains why Galileo took such pride in his theory of the tides and clarifies the place of this theory in his case for heliocentrism. From the cosmographic viewpoint, Descartes appears as a radically ambitious cosmographer with his use of a single account of the creation of the heavens and earth, thereby linking geography and astronomy in a single physical theory. Thus, cosmography represented a competitive enterprise among the Copernican natural philosophers. In general, thinking in terms of cosmography helps us understand the manner in which geographical ideas entered into the conceptual developments of the Scientific Revolution.
The main contribution to knowledge in this thesis is its identification of cosmography as a key frame of reference for early modern thinking about cosmology, overlooked in the historical literature.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. i To Dr George and Kitty Biro.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. ii Acknowledgments
I would like to express my gratitude to my supervisor, Associate Professor John Schuster, for his guidance and encouragement throughout the writing of this thesis and for his expert help in orientating to the extensive literature on the period. The work presented here has benefited from many stimulating and lively discussions. I especially appreciate his patience and forbearance over the many years of part-time study. To my close friends and family, your indefatigable support as well as your understanding is cherished.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. iii Table of contents
Abstract i
Table of contents v
Preface vi
Chapter One: Cosmography and the Scientific Revolution 1
1. Historiography and changing visions of the earth 1 1.1 Early modern cosmography defined 1 1.2 Cosmography and geography in the literature on the Scientific Revolution 3
2. The cosmographic tradition 9 2.1 Goldstein, Grant and Randles (GGR) 9 2.2 Beyond GGR—Cosmography before the sixteenth century 13 2.3 Copernicus and the earth in the sixteenth century 21 2.4 Beyond GGR—Cosmography at the beginning of the Scientific Revolution 32 2.5 Why the oversight? 33
3. Contribution of this thesis 37
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. iv Chapter Two: Cosmography and natural philosophy in the late sixteenth century 41
1. Introduction 42
2. Bruno’s cosmographic form of argument 43
3. Gilbert and the cosmographic tradition 46 3.1 Recent approaches to Gilbert 46 3.2 England and the tradition of cosmography 49 3.3 English interpretations of Copernicus 55 3.4 Cosmography in Gilbert 57 3.5 Implications for historiography 62
Chapter Three: Cosmography and natural philosophy in the early–mid seventeenth century 65
1. Introduction 66
2. Galileo and the cosmographic tradition 67 2.1 Recent approaches to Galileo’s theory of the tides 67 2.2 The cosmographic project of Galileo 71 2.3 The place of geognosic opinion in the theory of the tides 85 2.4 Implications for historiography 90
3. Descartes and the tradition of cosmography 91 3.1 Descartes’ natural philosophy 91 3.2 Recent approaches to Descartes 98 3.3 The cosmographic project of René Descartes 99
Conclusion 106
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. v Bibliography 114
Appendix 131
List of figures 133
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. vi Preface
Claudius Ptolemy’s Geographia was recovered in the West at the beginning fifteenth century to great acclaim. It was distributed in Latin, first in manuscript and then from 1475 in printed form. Between 1477 and 1513, the wondrous printing press spilled forth at least twelve editions of Geographia containing maps produced with Ptolemy’s radical cartographic approach. Ten of these editions included modern maps, keeping pace with the rapid growth in geographical knowledge.1 All these editions of the Geographia, and no doubt more, were published before the first printed edition of Ptolemy’s Almagest appeared in 1515, which dealt with astronomy.2 So, to the mind of an early modern thinker, Ptolemy would be associated as much with his method of representing the earth on maps and globes, as with the equants and epicyles that accounted for the movement of the planets and sun around the earth. Yet, as historian of early modern instruments Jim Bennett remarks, ‘were we to judge from the attention given by historians of science, Ptolemy’s influence on the intellectual life of the Renaissance was exercised chiefly through his Almagest’.3 Bennett’s comment in many ways instigated this thesis by highlighting an important but neglected area of research in historiography on the early modern period: how Geographia featured in the intellectual developments of the Scientific Revolution.
1 Mapforum Magazine, ‘Printed editions of Ptolemy containing maps’, MapForum.com, Specialist antique map magazine, Honorary Advisory Board: Peter Barber, Map Librarian of the British Library; Matthew Edney, Faculty Scholar, Osher Map Library; Francis Herbert, Curator of Maps at the Royal Geographical Society (with Institute of British Geographers); Alice Hudson, Chief of the Map Division at the New York Public Library; Peter van der Krogt, Researcher in the History of Cartography, Explokart Research Program, University of Utrecht, viewed on 24 March 2006, http://www.mapforum.com/02/ptolemy.htm#sylvanus. 2 J. Windsor, A Bibliography of Ptolemy’s Geography, Cambridge, Mass. Harvard University Press, 1884 cited in J. Bennett, ‘Practical Geometry and Operative Knowledge’, Configurations, 6 (2), Spring 1998, pp. 195-222, p. 202. 3 J. Bennett, ‘Practical Geometry and Operative Knowledge. Configurations’, p. 202.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. vii I became even more interested in the place of Geographia when I read a little-noticed group of papers by Thomas Goldstein, Edward Grant and W. G. L. Randles. These collectively explored Scholastic dilemmas over Aristotelian doctrine concerning the shape of the earth, the placement of ‘land’ (earth) in relation to water, and the relative volumes of earth and water.4 GGR assert that these debates get overshadowed from outside universities due to the recovery of Ptolemy’s Geographia and the voyages of discovery, leading to the re-emergence of the concept of a ‘terraqueous’ globe (where land and water basins combined form one sphere). GGR conclude by showing that Copernicus is an academic convert to the terraqueous concept of the earth, as reflected in his chapter on the shape of the earth, and that he used the notion to argue that the earth can move with circular motion.
It struck me that the general literature on the Scientific Revolution does not recognise that our modern concept of the earth was new and unproven in Copernicus’s time. Nor does it link the radical position Copernicus took in cosmology to the contemporary debate about the earth. I wondered what became of the debate about the form of the earth later into the Scientific Revolution and how leading Copernicans reacted to these ideas.
Fortunately, historians of science now generally recognise that early modern natural philosophers drew on many diverse fields of knowledge to develop their claims. Recent research into the relations between natural philosophy and other enterprises has found that, in challenging institutionalised scholastic Aristotelian views about the nature of matter and its arrangement in the cosmos, thinkers often co-opted ideas from the various ‘subordinate sciences’ including optics and hydrostatics. Using a similar research framework, and drawing together the findings already mentioned, I began to consider the place of geography in the Scientific Revolution.
This study explores how geographical knowledge entered into the conceptual developments of the Scientific Revolution. It finds several shortcomings in the literature—the neglect of geographic issues in customary accounts of the Scientific Revolution and the narrow focus on method in the literature on early modern geography. I address these by widening the
4 Thomas Goldstein, Edward Grant and W. G. L. Randles will be collectively referred to as GGR.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. viii analysis to consider geographic ideas as well as recognising the neglected topic of cosmography (the field in which natural philosophers placed knowledge in both geography and astronomy). In sum, I argue that theories about the earth were central to natural philosophy during the Scientific Revolution via the field of cosmography.
In Chapter One we briefly explore the status of early modern cosmography. We then trace the bonds that existed in natural philosophy between ideas about the earth’s structure and natural philosophy from the thirteenth century up to the time of Copernicus. We will see that cosmography was a customary part of Scholastic natural philosophy and lived on in Copernicus.
In Chapter Two, we begin our own case studies in the late sixteenth century by exploring the cosmographical tradition in Giordano Bruno and William Gilbert. We find that both staked their claims about the heavens on a particular conceptualisation of the form of the earth. The cosmographic perspective helps us solve key historiographical puzzles about these thinkers.
Finally, in Chapter Three we examine the manner in which two of the most influential pro- Copernicans—Galileo Galilei and René Descartes—were also engaged in cosmography. Our analysis demonstrates that the cosmographic tradition persisted through the Scientific Revolution to the mid seventeenth century. Galileo and Descartes continued the debate about the structure of the earth although by this time the terraqueous globe was no longer in doubt. However, they dealt slightly differently with geognosic opinion compared with earlier thinkers. We find Descartes to be the most ambitious of all the Copernican cosmographers.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. ix Chapter 1 Cosmography and the Scientific Revolution
1. Historiography and changing visions of the earth
1.1 Early modern cosmography defined
In the early modern period, cosmography was that part of natural philosophy that provided within one explanatory framework the relationship between the heavens and earth. As John Dee put it, cosmography “matcheth Heaven, and the Earth, in one frame”.1 Specifically:
Cosmographie, is the whole and perfect description of the heauenly, and also elementall parte of the world, and their homologall application, and mutuall collation necessarie. This Art, requireth Astronomie, Geographie, Hydrographie and Musike. Therefore, it is no small Arte, nor so simple, as in common practise, it is (slightly) considered.2
1 J Dee, ‘John Dee his mathematical praeface’ in The Elements of Geometrie of the Most Auncient Philosopher Euclide of Megara by Euclid, Iohn Daye, London, 1570, Early English Books Online, Cambridge University Library, viewed on 23 October 2005,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 1 Dee clearly considered the field important. Furthermore, while early modern scholars like Dee noted that the ancients sometimes took cosmography and geography to be the same ‘science’, they considered cosmography and geography as different, but related fields of knowledge. Cosmography was the parent field comprising not only geography but also astronomy. For example, Nathanael Carpenter asserted:
Geographie…differs fró Cosmographie, as a part from the whole. Forasmuch as Cosmographie according to the name is a description of the whole world, cóprehending under it as well Geographie,andAstronomie.3
In cosmography, one reasoned from one to the other, so that knowledge of the heavens and of the earth were mutually illuminating. The usual direction of inference in cosmography was from the heavens to the earth. Indeed, William Barlow advised that:
University Library, viewed on 27 September 2005,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 2 The onely good methode of teaching and learning Cosmography (after a fewe principles of Geometry and Arithmetike first knowen) is, to beginne with the Celestiall Globe, and to be perfect therein, before you deale with the Terrestriall: for this dependeth on that, and the former being once reasonably vnderstoode, the other is not two dayes worke.4
Thus, elaborating on our opening definition, cosmography was the part of natural philosophy that explained the relationship between the heavens and earth as well as the nature of both, and often did so by arguing from a view of one to a view of the other, with the typical direction of argument from the heavens to the earth.
1.2 Cosmography and geography in the literature on the Scientific Revolution
Surprisingly, the voluminous historical literature on the Scientific Revolution has not dealt with cosmography. Astronomy, of course, has been discussed at length. So too, as we shall see, has geography. However, historians of science have overlooked that branch of natural philosophy that integrated knowledge from these fields. The omission extends back to the ‘founding fathers’ of historiography on the Scientific Revolution.
Kuhn dealt briefly with geography and its links to astronomy in The Copernican Revolution, first published in 1957.5 He argued that knowledge about the location and extent of landmasses, their ‘products’ and ‘people’ was in a state of ferment during the early modern period, stimulated by the new feats of navigation of the late fifteenth to mid sixteenth centuries.6 The field of astronomy was also flourishing, similarly due to the explorations: new maps and navigational methods called for increased knowledge of the heavens. Kuhn also claimed that the voyages showed scholars that the geographical
4 WBarlow,The Nauigators Supply Conteining Many Things of Principall Importance Belonging to Nauigation, G Bishop, R Newbery and R Barker, London, 1597, viewed 23 October 2005,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 3 knowledge presented in the works of Ptolemy was inaccurate and so prepared an astronomer ‘for changes in his own closely related field.’7 While Kuhn argued, rightly in my view, that geography and astronomy were practically interdependent fields in the early modern period, his prime concern remained conceptual developments in astronomy. Thus, he failed to examine the close relationships between conceptual developments in geography and astronomy and thereby overlooked cosmography, understood as a unified field. Koyré also focused on theoretical developments in astronomy, as well as those in physics, but did not examine the relationships between these fields.8 For example, he noted that Copernicus wrote at length on the structure of the earth but he did not link the discourse to Copernicus’s cosmology.9
Though Kuhn and Koyré could hardly be expected to explore cosmography with their narrow focus on astronomy and (to a lesser degree) physics, the more recent interest in early modern geography has opened the door to such an inquiry. We now have a much- improved understanding of early modern geography and thereby stand better equipped to consider connections made at the time between thinking about the earth and thinking about the heavens. However, as we shall see, no one has taken the opportunity and the field of cosmography remains unexamined.
The work of Lesley Cormack, J. A. Bennett and David N. Livingstone has investigated how geography shaped the Scientific Revolution.10 Their studies conclude, firstly, that
7 T S Kuhn, The Copernican Revolution, p. 125. 8 A Koyré, Galileo Studies, J Mepham (trans), The Harvester Press Limited, Sussex, 1978, originally published as Etudes Galiléennes, Librarie Scientifique Hermann et Cie, Paris, 1939; A. Koyré, From the closed world to the infinite cosmos, John Hopkins Press, Baltimore, 1957; A Koyré, The Astronomical Revolution: Copernicus, Kepler and Borelli, R E W Maddison (trans), Methuen, London, 1973, originally published as La révolution astronomique, Hermann, Paris, 1961. 9 A Koyré, The Astronomical Revolution, p. 58. Koyré’s views on this aspect of the work of Copernicus are further outlined and commented on later this chapter. 10 L Cormack, ‘“Good Fences Make Good Neighbours”’; L Cormack, ‘Geography’ in Wilbur Applebaum (ed) Encyclopedia of the Scientific Revolution: From Copernicus to Newton, Garland Publishing, New York, 2000, pp. 261-264; J A Bennett, ‘The mechanics’ philosophy and the mechanical philosophy’ in History of Science, vol. 24, no. 1, 1986, pp. 1-28; J A Bennett, ‘The challenge of practical mathematics’ in S Pumfrey, P L. Rossi and M Slawinski (eds) Science, Culture and Popular Belief in Renaissance Europe,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 4 Manchester University Press, Manchester, 1991, pp. 176-190; J A Bennett, ‘Practical geometry and operative knowledge’ in Configurations, vol. 6 no. 2, Spring, 1998, pp. 195-222; D Livingstone, ‘Geography’ in R Olby, G Cantor, J Christie and M Hodge (eds) Companion to the History of Modern Science, Routledge, London, 1990, pp. 743-760; D Livingstone, ‘Geography, tradition and the Scientific Revolution: an interpretative essay’ in Transactions of the Institute of British Geographers, vol. 15. no. 3, 1990, pp. 359-373. Determining the fields of knowledge that historically comprised geography appears to be a complex enterprise, even for historians of geography. Discussing the concerns of historians of geography, David Livingstone, a respected historian of science, has argued that many historians “have legitimated, or criticised, such diverse visions as ‘geography as exploration’, ‘geography as map-making’, ‘geography as the study of landforms’, ‘geography as regional description’, ‘geography as society-nature relations’ or ‘geography as spatial science’ ”. Livingstone believes that modern commentators hold such diverse opinions because of the consistently close conceptual links between geography and other academic disciplines and policy agendas, and the predominance of largely presentist, hagiographic chronicles in the discipline’s historiography. D Livingstone, ‘Geography’, quote p. 744, discussion pp. 743-745. Livingstone’s contribution to the history of science is discussed in S Shapin, ‘Science, space, and hermeneutics. Book review’in British Journal for the History of Science, vol. 36, 2003, pp. 89-90. Cormack argues that the discipline of early modern geography in the late sixteenth and early seventeenth century comprised three fields of knowledge, ‘mathematical’, ‘descriptive’ and ‘chorographical’ geography, distinguishable by the scale at which each sought to explain the earth and their method of analyses. Mathematical geography, which is the focus of Cormack, Bennett and Livingstone’s work, investigated the shape and size of the earth, the exact locations of places on the earth, terrestrial gravity and magnetism, and was closely related to cartography and mapmaking. Descriptive geography depicted the physical and political features of other countries and regions, incorporating for example, accounts of European road conditions and anecdotes of unusual places. Chorography (the third sub-discipline of early modern geography) encompassed genealogy, chronology, antiquities, local history and topography. Cormack asserts that this tripartite division was widely discussed, increasingly recognised and, as a result, strengthened during the late sixteenth and early seventeenth centuries by scholars both in England and across the Continent, including John Dee, Thomas Blundeville, Nathanael Carpenter, Bartholomew Keckermann, and William Premble. However, she argues that by 1630 the issue of taxonomy of the sub- disciplines of geography was no longer of primary importance for English writers as the issue had largely been settled within scholarly circles. L Cormack, ‘Geography’, pp. 261-262; L Cormack ‘“Good Fences Make Good Neighbours”’, especially pages 641- 643 including footnote 14. It should be noted that Cormack proposes this conceptualisation of geography in ‘“Good Fences Make Good Neighbours”’, but limits her claims to early modern England. In her later paper, ‘Geography’, she suggests this conceptualisation of early modern geography applied to Europe as a whole (notwithstanding that studies were limited to geography in England, France and Spain). L Cormack, ‘Geography’, fn 5, p. 641. More generally, the literature on early modern geography reflects a recent, growing concern with relations between practical mathematics and natural philosophy. It emanates from an older, broader body of scholarship that views the rise of the practical arts in the fifteenth and sixteenth centuries as central to the Scientific Revolution: what has come to be termed the scholar-craftsman thesis. This body of scholarship considers the coming together of practice (elite craftspeople and practical mathematicians) and theory (scholars) as a key determinant of the Scientific Revolution. The proposition, first made by Hessen in 1931 and elaborated on by Zilsel in the 1940s, was that the collapse of the barriers between artisans and scholars during the end of the sixteenth century, caused by the rise of merchant capitalism, helped bring about the theories proposed by Descartes, Bacon and Newton by providing natural philosophers with the opportunity to adopt and transform artisans’ experience-based ‘rules of thumb’ into theories and to embrace a new ideology of progress through cooperation and the public utility of knowledge.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 5 geography fostered the genesis and growth of a new experimental method, a defining feature of the ‘new science’ of the early modern period.11 For instance, Bennett proposes that the successful use of practical mathematics in exploration, navigation and cartography during the late sixteenth and early seventeenth centuries led those challenging Aristotelianism during the seventeenth century to adopt the tools of practical mathematics: mathematics, experiment and instrumentation.12 The second, related claim in this literature is that geography contributed to the growth of the ideology of the ‘new sciences’, although commentators differ on its nature. Some identify the distinctive ideology of the new science as utilitarian. For example, Cormack states that geography in the early modern period ‘helped to promote an ideology of utility that encouraged public use of scholarly knowledge’.13 Other historians define the ideology of the new science as the willingness to
Important works regarding the scholar-craftsman thesis include: B Hessen, ‘The social and economic roots of Newton’s “Principia”’ in Science at the Crossroads, Papers Presented to the International Congress of the History of Science and Technology Held in London from June 29th to July 3rd, 1931, by the Delegates of the USSR, Kniga (England) Ltd, London, 1931, pp. 149-212; E Zilsel, ‘The sociological roots of science’ in American Journal of Sociology, 1941/1942, pp. 544-562; E Zilsel, ‘The genesis of the concept of scientific progress’ in Journal of the History of Ideas, VI, 1945, pp. 1-32; P Rossi, Philosophy, Technology and the Arts in the Early Modern Era, Harper and Row, New York, 1970; M Biagioli ‘The social status of Italian mathematicians 1450-1600’ in History of Science, vol. xxvii, 1989, pp. 41-51. More recent scholarship drawing on the scholar-craftsman thesis includes: R Westman, ‘The astronomer’s role in the sixteenth century: a preliminary study’ in History of Science, vol. xviii, 1980, pp 105-147; P Dear, Discipline and Experience: The Mathematical Way in the Scientific Revolution, University of Chicago Press Chicago, 1995; K Hill (Neal) ‘“Juglers or Schollers?”: Negotiating the role of a mathematical practioner’ in British Journal for the History of Science, vol. 31, 1998, pp. 253-274; K Neal, ‘The rhetoric of utility: avoiding occult associations for mathematics through profitability and pleasure’ in History of Science, vol. xxxvii, 1999, pp. 151- 178. 11 The term ‘new science’ is used by Cormack in L Cormack, ‘“Good Fences Make Good Neighbours”’, p. 661, and also by J A Bennett, ‘The mechanics’ philosophy and the mechanical philosophy’, p. 2. 12 J A Bennett, ‘The challenge of practical mathematics’, pp. 182-184 and p. 189. Livingstone also sees a connection between geography and the origin and expansion of the experimental method. He proposes geography’s anti-authoritarian emphasis on experience helped advance a new epistemological method that valued only those opinions that were either self-evident or based on logic, mathematics or science. Cormack also sees in early modern geography ‘a new explanation for the growth of experimental science and perhaps of mechanical philosophy in the seventeenth century. D Livingstone, ‘Geography, tradition and the Scientific Revolution: an interpretative essay’, p. 359; L Cormack, ‘ “Good Fences Make Good Neighbours”’, p 640. 13 L Cormack, ‘ “Good Fences Make Good Neighbours”’, p. 661; See also L Cormack, “Utility, imperialism, and the ‘New Science’: The Zilsel thesis revisited”,1998 [the source of this paper is unclear but it may be the paper—‘Mathematical practioners, patronage and the Scientific Revolution: The Zilsel thesis revisited’, a talk to the Department of History, University of Calgary]; L Cormack, ‘Geography’, p. 261. For a more
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 6 challenge classical authority. Gingerich argues the voyages of discovery contributed to the growth of this ideology by demonstrating that the ancient texts could be viewed as fallible.14 In all of this, the emphasis is on the method of the new geography—the utility of instruments, the revision of information and the use of mathematics in cartography and exploration, rather the content of geographic knowledge.
Within the literature, only Cormack’s work addresses the fate of cosmography. Cormack proposes that in the sixteenth century, cosmography stood as an established field from which geography in both Europe and England emerged: ‘[i]n sixteenth-century England geography was developing into a discipline distinct from the older study of cosmography’.15 However, she is not altogether clear on the fate of cosmography. On the one hand she argues that cosmography reduced its scope and simply continued as geography. That is, in the early modern period the field of cosmography transformed into geography. On the other hand, Cormack says nothing about what happened to the broader concerns of cosmography.16 So, although the recent literature has noted two possible conduits between geography and the intellectual developments of the Scientific Revolution (method and
nuanced claim of the extensive use of the rhetoric of utility by mathematicians in England from 1550–1650 and the considerable extent to which its use changed public perception by promoting mathematics as profitable and pleasurable, see K Neal, ‘The rhetoric of utility’. Livingstone highlights a transferral of ideology in the opposite direction: the Scientific Revolution led geographers to seek a separation between the goals and practices of geography from theology. D Livingstone, ‘Geography’, p. 746. 14 Gingerich argues: ‘the discoveries of Columbus helped set the stage for the coming Copernican revolution, for, at the end of the 15th century, the ancient Alexandrian, Claudius Ptolemy, was probably better known as a geographer than as an astronomer. The discovery of America…filled the map with lands never dreamt of by Ptolemy. If Ptolemy as geographer–cosmographer could be challenged, what about Ptolemy as astronomer–cosmologer?’ O Gingerich, ‘Scientific cosmology meets western theology a historical perspective’ in Annals of the New York Academy of Sciences, vol. 950. no. 1, 2001, pp. 28 – 38, p. 29. This view is similar to that expressed by Kuhn in The Copernican Revolution, p. 125. See footnote 24 for an explanation of the contents and dissemination of Geographia. 15 L Cormack, ‘“Good Fences Make Good Neighbours”’, p. 641. See footnote 10 regarding the geographical scope of Cormack’s claims. 16 L Cormack, ‘Geography’, p. 261, L Cormack, ‘“Good Fences Make Good Neighbours”’, p. 641.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 7 ideology), the status of the field of cosmography in the period remains largely unexamined.17
The reason the standard literature has overlooked cosmography is simply because the research question has been inadequately framed: it has focused on geographical methods rather than ideas and knowledge about the earth. Thus, notwithstanding our long-standing grasp of conceptual developments in astronomy and the recent attention given to early modern geography, which theoretically stand us in a better position to inquire into the links between thinking about the earth and thinking about the heavens, the role that knowledge about the earth played in the Scientific Revolution remains largely unexamined.
17 It is worthwhile noting the limited range of evidence deployed in the arguments by the standard literature (that is, Bennett, Livingstone and Cormack). If we are to agree with the claim that geography aided the development of a new experimental method and the distinctive ideology of the new science, then we need to be convinced of the mechanism (or mechanisms) through which the methods and utilitarian approach of this mathematical geography were transmitted to leading thinkers of the Scientific Revolution. However, the literature focuses almost exclusively on showing the considerable infiltration of mathematical techniques into geographical endeavours. The evidence presented by Bennett, for example, largely comprises proof of the infiltration of mathematical techniques into the navigational and geographical program. Only passing attention is given to identifying and demonstrating the transmission mechanisms for the alleged experimental methods and/or ideology of geography. Cormack argues that patronage was a key means through which geographers’ utilitarian ideology was transferred to scholars. While the work contributes to some extent to current interest in patronage as a potential means for the spread of experimental method, her account of the transmission mechanism is quite cursory. These limitations leave the conclusions about how geography shaped the Scientific Revolution largely unsubstantiated. J A Bennett, ‘The challenge of practical mathematics’, pp. 176 – 189; L Cormack, ‘Utility, imperialism and the New Science’, pp. 55-59; L Cormack, ‘Geography’, p. 262; L Cormack, “Good Fences Make Good Neighbours”’, pp. 640, 644-650. It is also important to note that the assumption in the literature that the Scientific Revolution involved a revolution in intellectual approaches (method or ideology) has recently come under critical scrutiny. Commentators such as Schuster and Taylor suggest, rightly in my view, that historians should also regard the declarations made by early modern scholars for experimental method and dramatic ideological shifts (such as towards utilitarianism) as rhetoric aimed at winning collegiate approval within a highly competitive intellectual environment. In addition, certain historians of science challenge the premise underpinning the scholar-craftsman argument of the existence of a revolution in intellectual methods in the late sixteenth and early seventeenth centuries. For example, Grafton argues that Europe was ‘undergoing an intellectual revolution prior to the discovery of the New World’. Although the forms of knowledge and expression in Europe changed to some extent, he proposes there was no sudden rupture in the nature of intellectual life in the early modern period as proposed by the scholar-craftsman thesis. Grafton also casts doubt on the characterisation of the intellectual life of elite artisans as craft-based. The intellectual life of navigators, cartographers and other elite artisans was based on a ‘strong culture of the book’, he asserts. J A Schuster and A B H Taylor, ‘Seized by the spirit of modern science’, MetaScience, vol. 9, pp. 9-26; A Grafton, New Worlds, Ancient Texts. The Power of Traditions and the Shock of Discovery,Harvard University Press, Cambridge Massachusetts, 1992, quote p. 28, pp. 28-35 and pp. 61-68.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 8 The aim of this thesis is to address this substantial gap in our understanding of the early modern period by investigating the status of cosmography during the Scientific Revolution. My findings challenge Cormack’s opinion that cosmography narrowed in scope and continued as geography. I will argue the broader concerns of cosmography persisted and thrived during the mid sixteenth to mid seventeenth centuries. Indeed, I contend that geography played a role in the Scientific Revolution largely as a part of cosmography. To avoid using ‘geography’ anachronistically, to denote the study of the earth of a type that today would fall under our definition of science, instead of using the term ‘geography’ I will use the term ‘geognosic opinion’, by which I mean all ideas and knowledge about the earth’s structure. This correlates to that part of cosmography related chiefly to the earth, keeping in mind it is also related to opinion about the heavens.18
2. The cosmographic tradition
2.1 Goldstein, Grant and Randles
The work of Thomas Goldstein, Edward Grant and W. G. L. Randles (henceforth ‘GGR’) provides considerable insights into cosmography in the early modern period.19 GGR
18 I employ the term ‘geognosic opinion’ as using the term ‘geography’ tempts one, anachronistically, to think of opinion in this field as separate from opinion about the heavens. There is precedent for this, for example, in the late eigtheenth century A. G. Werner, influential geologist, used the term ‘geognosy’ to describe ‘the abstract systemic knowledge of the solid earth’. A M Ospovat, Short Classification and Description of the Various Rocks by Abraham Gottlob Werner, Hafner Publishing Company, New York, 1971, p. 101, cited in J P Tandarich, ‘Wisconsin agricultural geologists: ahead of their time’ in Geoscience Wisconsin, vol. 18, 2001, pp. 21-26. 19 T Goldstein, ‘The renaissance concept of the earth in its influence upon Copernicus’ in Terrae Incognitae, vol. 4, 1972, pp. 19-51; E Grant, ‘In defense of the earth’s centrality and immobility: scholastic reaction to Copernicanism in the 17th century’ in Transactions of the American Philosophical Society, 74, 4, 1984, pp. 20-32; W G L Randles, ‘Classical models of world geography and their transformation following the discovery of America’ in Geography. Cartography and Nautical Science in the Renaissance. The Impact of the Great Discoveries. Ashgate Publishing Ltd, Great Britain, 2000, pp. 5-76. In terms of the relative chronology of Grant and Randles, Grant cites an article in French by Randles dated 1980. This suggests that the concepts in the English version of the work by Randles appeared in the earlier
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 9 examine geognosic opinion from the Middle Ages through to the late sixteenth century and its impact on the Scientific Revolution. By focusing on the role that ideas about the structure of the earth played in the Scientific Revolution (rather than geographical methods) their work begins to fill the gap, just identified, in the literature on early modern science and geography. Moreover, the connections GGR sketch between geognosic opinion and intellectual developments during the period raise a number of propositions that are especially relevant to the present study of cosmography. This section outlines the arguments presented by each commentator and then describes the conclusions about cosmography that arise from their collective work.
W. G. L. Randles examines how geognosic opinion in Europe changed from the thirteenth through to the seventeenth centuries. He argues that in the late fifteenth century, Europe’s educated elite was debating four competing and contrary concepts of the earth, each derived from the classical tradition. The first was inherited from Homer and represented the earth as a ‘single, flat disc’ (the inhabited world as known to the Greeks, the oikoumene, surrounded by the Ocean Sea).20 The second concept was of the earth as a sphere surrounded entirely by a sphere of water, which in turn is surrounded by a sphere of air and then fire. This concept was founded on Aristotle’s sublunary laws of the concentric arrangement of the elements and initially taken to be a theoretical construct.21 The third concept of the earth
French article and therefore Randles’ work predates that of Grant. While subscribing to this as the likely chronology, I hold to the English version of Randles’ work in this thesis. 20 In literature on the history of cartography, David Woodward notes that the representation of the earth in medieval maps, particularly in the ‘T-O’ formation mappaemundi, is often used as evidence for the dominance of the concept of a flat earth in the Middle Ages. He warns against such conclusions on the bases that the mappaemundi were intended as narrative histories, not representations of geographical fact, and of the limited knowledge of projective geometry in the Middle Ages. See D Woodward, ‘Reality, symbolism, time and space in medieval world maps’ in Annals of the Association of American Geographers, vol. 75, no. 4, 1985, pp. 510 – 521. 21 Indeed, Goldstein and Randles’ view is that the Aristotelian system, when it was introduced to Europe from translations of Arab manuscripts in the early thirteenth century, contained two completely different theories about arrangement of the land and the sea. The first theory, just cited, was the subject of substantial inquiry and diversity of opinion in the context of natural philosophical issues. Aristotle’s second, different theory of the earth was of the earth as a sphere of which the sea is an integral part. The earth was conceived of as consisting of five zones (created by the Artic circle, the Tropic of Capricorn, the Equator, the tropic of Cancer, and the Antarctic circle), and only the two temperate zones are habitable.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 10 was that of ‘four small landmasses situated symmetrically on a sphere over the greater part of which flowed two wide river oceans at right angles to one another’, a concept generally credited to the Greek scholar, Crates of Mallos (150 BCE).22 In the fourth concept of the earth, the seas were conceived as discrete lakes lying in the hollows of the earth wherein the earth and waters combined form one sphere. 23 This conceptualisation of the earth, what we would now term a terraqueous globe, was presented in Ptolemy’s Geographia and first introduced to Western Europe in the early fifteenth century.24 Importantly for the present
Based on this second theory of the earth’s structure, Aristotle concluded that, as the earth was small, the ocean that separated the northern land mass was not very wide. This second theory underpinned theologically loaded debates about which parts of the earth were inhabitable. Goldstein and Randles argue these two conceptualisations of the earth were inherently contradictory. The first did not allow for dry land, the second not only allowed for dry land, but also articulated which land was inhabitable. Moreover, the two concepts appeared side by side in Aristotle’s work such as De Caelo. As this thesis is concerned with natural philosophy, attention will focus on Aristotle’s first theory. W G L Randles, ‘Classical models of world geography’, p. 9 and T Goldstein, ‘The Renaissance concept of the earth in its influence upon Copernicus’, pp. 29-30. 22 W G L Randles, ‘Classical models of world geography’, p. 10. 23 W G L. Randles, ‘Classical models of world geography’, p. 16. 24 Randles’ account of the evolution of the Ptolemaic concept of the terraqueous globe, which is explained in detail later in this Chapter, assumes that, amongst the various theories of the earth’s structure, only the model presented in Geographia contained a clear and exact definition of a terraqueous globe. However, it is unlikely that the sole representation of the earth as a terraqueous globe appeared in Geographia,as Randles suggests. Both Aristotle’s second theory of the earth (see footnote 21) and the ‘Cratesian’ theory appear to have relied on a terraqueous concept of the earth. Nevertheless, there are strong grounds for the key propositions by Randles that are utilised in this thesis; namely, that the structure of the earth was in a state of controversy during the sixteenth century. A discussion of the differing presentations of the terraqueous globe in Geographia and Almagest is provided at footnote 38. Geographia was written by Alexandrian Claudius Ptolemy in the second century A.D. and was intended as a guide to drawing maps. Maps were not part of the original manuscript – the aim of the text itself was to explain how to draw maps (one of the whole oikoumen and twenty-six regional maps). The oikoumen in Geographia are divided into three continents: Europe, Liby (our Africa) and Asia. The work included: introductory chapters that gave principles for obtaining the data on which the maps would be based and the circumstances for a good map projection; instructions for drawing a map on both globes and plane surfaces, using two different methods of projections; and an index, which represented the majority of the manuscript, of a multitude of localities to be drawn on the map with their latitudes and longitudes (including coastlines, longer rivers and mountain ranges; cities, small mountains, river mouths, and; the peoples inhabiting small districts); and captions or ‘descriptive labels’ to be written on the maps and how to divide the known world into 26 regional maps. Geographia was recovered in Europe from Byzantium in the fifteenth century, considerably later than Ptolemy’s astronomical treatise Almagest,whichwas rediscovered in Europe in the twelfth century. The first printed edition of Geographia appeared in 1475 with numerous subsequent editions through the late fifteenth and early sixteenth centuries. More than twelve editions were published before the first printed edition of Almagest in 1515, a testament in Bennett’s view to the popularity of Geographia in the early modern period. Randles’ claim that the concept
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 11 study, the support each of these four concepts received from scholars changed considerably over time. The evidence on which Randles bases his case deals with Aristotle and Ptolemy, medieval and Renaissance commentaries on Aristotle, and fifteenth and sixteenth century correspondence and anti-Aristotelian treatises.
Thomas Goldstein examines the status of geognosic opinion in the opening stages of the Scientific Revolution and its place in the work of Copernicus. He proposes that the concept of the earth as a terraqueous globe was new to Renaissance thinkers, developed from the introduction of Ptolemy’s Geographia and the fresh geographical knowledge from the explorations.25 Moreover, this new terraqueous concept of the earth was central to Copernicus’s astronomical and physical arguments, and thereby crucial in the conceptual developments of the Scientific Revolution. The grounds for Goldstein’s argument consist of a careful reading of Book I of De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres) by Copernicus and Aristotle, Sacrobosco and Oresme.26
Edward Grant, an historian of medieval science, asks how theorists in cosmology, particularly Aristotelian Scholastics, situated the centre of the cosmos relative to the centre of the earth from the fourteenth to the late sixteenth centuries. He maintains that the arrangement of the ‘three centres’—the centre of the cosmos, the geometric centre of the earth and the centre of gravity of the earth—was the subject of ongoing argument amongst Scholastic Aristotelians. The problem had its origin in a non-controversial distinction, first
of a terraqueous globe was introduced to Europe through Ptolemy’s Geographia is discussed at footnote 38. J L Berggren and A Jones (eds) ‘Introduction’ in Ptolemy's Geography: an annotated translation of the theoretical chapters, Princeton University Press, Princeton, 2000, pp. xi, 3, 4, 40; C Ptolemy Geographia in J L Berggren and A Jones (eds) Ptolemy's Geography: an annotated translation of the theoretical chapters, Princeton University Press, Princeton, 2000; J A Bennett, ‘The challenge of practical mathematics’, p. 183; J A Bennett, ‘Practical geometry and operative knowledge’, p. 202. The introduction to Geographia by J L Berggren and A Jones provides a comprehensive discussion of the publication and dissemination of Geographia. 25 T Goldstein, ‘The Renaissance Concept of the Earth’, p.20. 26 Goldstein argues, correctly in my view that the reason historians have failed to find a link between geography and cosmology in the early modern period is because both historians of each have treated their fields in isolation.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 12 made in the fourteenth century by Aristotelian John Buridan, between a body’s centre of gravity and its geometric centre.27 For a homogenous body, scholars commonly presumed the centre of gravity coincided with its geometric centre. However, if a body’s composition was varied, they considered that the two centres would be separate. Grant states that centuries of argument ensued when Scholastics applied the issue to the physical earth: did the centre of the cosmos coincide with the earth’s centre of gravity, its geometric centre, or both? His view is that the arrangement of the three centres continued to be a significant concern for leading Scholastic natural philosophers until the late sixteenth century. The evidence Grant provides to support his case comprises fourteenth century Scholastic commentaries, including Buridan and Albert of Saxony, and sixteenth century commentaries, such as those by Clavius, Aversa and Bellutus.
Although GGR do not explicitly examine the status of the field of cosmography during the Scientific Revolution their works raise two propositions that are particularly pertinent to the present study. First, cosmography was an important concern for natural philosophers at least to the late fifteenth century; second, cosmography was crucial to Copernicus’s development of the heliocentric cosmology. In the following sections we examine the grounds for these propositions.
2.2 Beyond GGR—Cosmography before the sixteenth century
The view that emerges from the work of GGR is that, for the period spanning the thirteenth century to the late fifteenth century, there was ongoing inquiry and diversity of opinion amongst the educated elite in Europe about the structure of the earth in general and about the relations between the land and water in particular.28 This thesis does not aim to repeat GGR’s chronology of the discussions and dynamism in geognosic opinion. Rather, it aims to point out that the evidence GGR present demonstrates that cosmography was an active
27 A body’s geometric centre was also referred to as its centre of magnitude 28 GGR’s conclusions beyond the late fifteenth century are discussed in the next section on Copernicus.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 13 field of knowledge throughout the Middle Ages and the early Renaissance, a prospect not addressed by GGR. That is, the ongoing theoretical research in geognosic opinion amongst Scholastics identified by GGR can be understood as the part of a flourishing field of cosmography spanning the thirteenth to the late fifteenth centuries.
During the Middle Ages and early Renaissance scholars concerned with natural philosophy, particularly Aristotelians, engaged in a three-way reconciling; of geognosic opinion, evident truths about the earth (such as the existence of dry land), with certain aspects of natural philosophy (particularly cosmological laws of physics and the arrangement of matter). The key aim was to ensure that Aristotelian natural philosophy provided within one explanatory system the nature of heaven and earth and the relationship between each. To achieve such alignment, Scholastics primarily introduced theoretical modifications to geognosic opinion, chiefly regarding the relations between the land and sea. To a lesser degree, they expanded and modified the application of their natural philosophical laws. Theoretical developments in thirteenth century natural philosophy are a good example. Early in the century, Sacrobosco proposed a view of the earth, derived from a certain reading of Aristotle, in his influential astronomy textbook Incipit tractatus de spera magistri Iohannis de Sacrobosco (The Sphere of Sacrobosco).29 Sacrobosco wrote that the elementary region comprised the element earth, concentrically surrounded by the elements of water, air and fire, as a direct consequence of Aristotle’s sublunary laws of physics. However, he introduced the following, slight amendment to Aristotle’s theory of the four elements to allow for the indubitable existence of dry land:
29 J Sacrobosco, ‘Incipit tractatus de spera magistri Iohannis de Sacrobosco’, c. 1220, in L Thorndike, The Sphere of Sacrobosco and its Commentators, The University of Chicago Press, Chicago, 1949, English translation, pp. 118-142. Universities throughout Europe used ‘The Sphere’ for over three hundred years. At the end of the fourteenth century, it was a required text for an A.B. in the Faculty of Arts in Vienna, the University of Ferrara and for the pre-medical course at Bologna University. The Sphere was required scholarship at the university in Prague for students at the level of Master of Arts and for licentiate students at the university in Paris. In the early fifteenth century students wanting to gain an A.B. at Oxford or a licentiate at Bourges had to study The Sphere. Notwithstanding the Copernican system, the use of The Sphere continued into the seventeenth century. L Thorndike, The Sphere of Sacrobosco, pp. 41-43. On the dating of the Sphere,seep.5.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 14 The elementary region is divided into four…For there is earth, placed, as it were, as the center in the middle of all, about which is water, about water air, about air fire…And these are called the “four elements”… Three of them, in turn, surround the earth on all sides spherically, except in so far as the dry land stays the sea’s tide to protect the life of animate beings.30
Figure 1.1 illustrates Sacrobosco’s conceptualisation. According to Lynn Thorndike, the earth’s structure was of considerable interest to Aristotelian natural philosophers: one of the only four questions common to the commentaries of Michael Scot (c.1230), Robertus Anglicus (1271) and Cecco D’Ascoli (early fourteenth century) was about the arrangement of the land and water.31 Thus, thirteenth century natural philosophers were actively engaged in the project of harmonising geognosic opinion, certain aspects of their natural philosophy systems and the unquestionable existence of dry land, in order to provide within one explanatory system a description of the nature and relationship of the earth and heavens.
30 L Thorndike, The Sphere of Sacrobosco, p. 119. 31 L Thorndike, The Sphere of Sacrobosco, p. 49. The question addressed in each of these commentaries was how dry land exists if the sphere of water surrounds the sphere of earth. A further question in relation to the earth shared by each of these commentaries was whether the earth is inhabitable at the equator. Ironically, each question is based on a different Aristotelian concept of the earth. A discussion of the tradition of commentaries in general and those on Sacrobosco’s The Sphere in particular is contained in L. Thorndike. On the textbook tradition more generally, see P Reif. ‘The textbook tradition in natural philosophy’ in Journal of the History of Ideas, Vol. 30, No. 1, 1969, pp. 17-32; C Schmitt, ‘The rise of the philosophical textbook’ in C Schmitt, Q Skinner and E Kessler (eds) The Cambridge History of Renaissance Philosophy, Cambridge University Press, Cambridge, 1988; C Schmitt, ‘Galilei and the seventeenth-century textbook tradition’ in Reappraisals in Renaissance Thought, Variorum Reprints, London, 1989.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 15 Figure 1.1: Sacrobosco’s model of the earth: engraving from a fifteenth century edition of The Sphere, 32 Venice 1485 and 1490
Cosmography remained a dynamic field during the fourteenth century. One crucial consideration was the proposition that the volume of water was ten times greater than that of the earth, a claim incorrectly attributed to Aristotle by Greco–Roman scholars and inherited by medieval scholars.33 John Buridan adapted the pseudo–Aristotelian theory of the earth emerging from the sphere of water, incorporating the Greek misconception that the sphere of water was ten times larger than the sphere of earth, into what GGR propose became the widely accepted scholarly conceptualisation of the earth—the ‘floating apple’ model.34 This model theorised a small part of the sphere of earth protruding above the
32 Reproduced in W G L Randles, ‘Classical models of world geography’, p. 42. 33 W G L Randles, ‘Classical models of world geography’, p. 9-10. As we shall see, the belief that there was ten times more water than earth (see excerpts in footnote 34) largely drove conceptualisations of the earth’s structure throughout this period and was to become the basis for considerable debate following the voyages of discovery. 34 The educated elite appears to have employed this analogy to explain the model. For instance, in the late fifteenth and early sixteenth centuries, clear references to the ‘floating apple’ model appear in the works of
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 16 considerably larger sphere of water. The lower hemisphere of the earth remained totally submerged. To align the notion that the earth maintained a position above the sphere of water with Aristotelian laws of physics, which required the element of earth to lie below that of water, Buridan proposed that the density of the protruding part of the earth was lightened by its exposure to the air and sun (while the submerged section of the earth continued to be heavier and denser than water).35 Buridan’s floating apple model generated an extremely wide Atlantic Ocean, an important obstacle for Columbus and the evolution of
those challenging the model. Jacob Perez de Valencia, Augustinian friar and academic theologian in Spain, stated in 1484: ‘Some consider that all the seas are interconnected and that the Ocean is much larger than the whole of the earth and that it surrounds it on all sides and that the earth is like a light ball or an apple in a basin full of water of which only the top appears above the water. And they say that God made it so from the beginning…’ Caspar Peucer, teacher of astronomy to Tycho Brahe and German professor of mathematics and medicine at the University of Wittenberg in 1554 and 1556, uses the same analogy even while expressing scepticism. In 1551 he stated: ‘[T]he low lying parts of the earth are not, as some have imagined, encircled by waters like a girth while the higher parts stick out, and that the earth does not float like an apple in the waters, not is the lower hemisphere plunged in the waters while the upper one emerges out of them.’ J P de Valencia Comentum noviter edditim [sic]…in Psalmos, Valencia 1484, quoted in W G L Randles, ‘Classical models of world geography', p. 41-43 and C Peucer, Elementa doctrinae de circulis coelestibus et primo motu, Wittenberg, 1551, quoted in W G L Randles, ‘Classical models of world geography', p. 71. Information on de Valencia from T Rasmussen, ‘Jacob Pérez de Valencia's "Tractatus contra Judeos" (1484) in the light of the medieval anti-Judaic traditions’ in Kenneth Hagen (ed) Augustine, the harvest, and theology (1300-1650). Essays dedicated to Heiko Augustinus Oberman in honor of his sixtieth birthday, Brill, New York, 1990, pp. 41-59, p. 43. Information on Caspar Peucer from The Galileo Project, Rice University, viewed on 30 October 2005, http://galileo.rice.edu/Catalog/NewFiles/brahe.html; S Boettcher, H H von Rezension, G Wartenberg, Caspar Peucer (1525-1602). ‘Wissenschaft, Glaube und Politik im konfessionellen Zeitalter, Leipzig: Evangelische Verlagsanstalt 2005’ in sehepunkte, 5, 2005, viewed on 1 November 2005, http://www.sehepunkte.historicum.net/2005/10/3694.html; P Schaff, The New Schaff-Herzog Encyclopedia of Religious Knowledge, Vol IX, Baker Book House, Michigan, 1953, available on The Christian Classics Ethereal Library, viewed on 6 November 2005, http://www.ccel.org. 35 See E Grant, ‘In defense of the earth’s centrality and immobility’, p. 24-25 and W G L Randles, ‘Classical models of world geography’, p31-33. Buridan stated that: ‘[t]he earth, in the part that is not covered by the water, is altered by the air and the heat of the sun and a large quantity of air is mixed with it and thus this part of the earth becomes less dense and lighter and it has many pores full of air or subtle bodies. But the part of the earth which is covered by the water is not altered by the air and the sun and it remains denser and heavier. And thus if the earth were divided through the middle of its magnitude, one part would be heavier than the other and that part in which the earth is uncovered by water would be much lighter.’ Jean Buridan, Quaestiones super libris quatuor de caelo et mundo quoted in W G L Randles, ‘Classical models of world geography’, pages 32-33.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 17 geognosic opinion into the sixteenth century, as we shall see.36 Buridan’s student, Albert of Saxony, articulated the floating apple model further to ensure it aligned with the cosmological requirement that the centre of the earth lay at the centre of the cosmos. Saxony rejected the notion that the geometric centre of the earth and the centre of the cosmos coincided, like Buridan.37 However, he claimed the point of the earth that lay at the centre of the cosmos was the centre of gravity of the aggregate of the earth and water. Put another way, Albert of Saxony achieves the cosmographic aim of developing one descriptive system in part by arguing from a view of the cosmos to a view of the earth.
Cosmographical matters continued to excite interest through the fifteenth century, although the resolution of Aristotelian physics and cosmology with the floating apple model can be viewed as stable. The field of debate incorporated a new concept of the earth following the recovery of Ptolemy’s Geographia from Byzantium and its rapid dissemination throughout Europe.38 Geographia presented the world as one single globe in which the earth and water
36 The large expanse of ocean resulting in this pseudo-Aristotelian model was contrary to Aristotle’s view (arising from his second theory of the arrangement of the earth and sea) that the Atlantic Ocean was quite narrow. See footnote 21 for an explanation of Aristotle’s second geognosic theory. 37 W G L Randles, ‘Classical models of world geography’, p. 34. Goldstein shares the view held by Randles and Grant that the dominant concept of the earth from the fourteenth to the end of the sixteenth century was premised on there being significantly more water than earth, and on an earth with separate centres of magnitude and gravity. However, it is unclear whether Goldstein also believes the leading concept of the earth in this period was the floating apple conceptualisation. One interpretation is Goldstein believes the accepted concept of the earth during this period was that the element earth produced a small spherical core that sat in the centre of a considerably larger sphere of water. A segment of the earth stretched out from this small central core to emerge above the sphere of water and form the three continental landmasses. On the other hand, Goldstein’s reference to the ‘two-sphere theory of the earth’ suggests he considers the floating apple model was the dominant model of the earth during this period. T Goldstein, ‘The Renaissance concept of the earth in its influence upon Copernicus’, pages 30, 37 and 38. 38 Randles’ account assumes that, of Ptolemy’s works, only the later-rediscovered Geographia contained a clear and exact definition of a terraqueous globe. Randles contends from the phrasing of the text in the astronomical treatise Almagest readers would have understood Ptolemy to be saying the land is spherical and the sea is spherical but not necessarily that they formed one, single sphere. W G L Randles, ‘Classical models of world geography’, pp. 16-18. See also footnote 24. If substantiated, this account by Randles of the crucial contribution of Geographia to the Scientific Revolution address the matter identified by Bennett (and mentioned earlier in the Preface) that: ‘The popular identification of Ptolemy was perhaps even more as a geographer than an astronomer, though in truth it is the case that the two roles were closely intertwined and embedded in a much broader subject domain… Geographia figures significantly at the very heart of this deliberate mathematical
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 18 are co-mingled, as described earlier. Ptolemy wrote that ‘the earth and seas form one continuous sphere’.39 In contrast to the floating apple theory, the Ptolemaic opinion conceived of the water as resting in the hollows of the significantly greater volume of earth. Geognosic opinion in the fifteenth century appears to have incorporated both the floating apple model and Ptolemaic model notwithstanding the inconsistencies between the two.40 For example, the floating apple model was articulated in Pierre d’Ailly’s commentary of The Sphere and illustrated in D’Ailly’s renowned Imago Mundi.41 Aeneas Sylvius Piccolomini, later to become Pope Pius II, wrote in 1477 of the diversity of geognosic opinion of the time that included both the floating apple and Ptolemaic concept of the
revival…Though this is fairly familiar territory for historians of cartography, it still needs to be integrated into the history of science.’ Bennett does not identify cosmography as the ‘broader subject domain’. J A Bennett, ‘Practical geometry and operative knowledge’, pp. 202- 205. My preliminary view of Randles’ claim is that the different subject matter and methods of Almagest and Geographia and the circulation of Geographia during a period of considerable explorations could account for early modern scholars giving more attention to the concepts of the earth contained in Geographia.The view of Berggren and Jones supports this interpretation. They state that although Ptolemy gave some consideration to geographical issues in Almagest, the treatise mainly relates to how to convert the recorded times of observations made at different locations to Alexandrian mean time. That is, ‘Ptolemy’s treatment of matters relating to the observer’s geographical position is almost wholly theoretical’. J L Berggren and A Jones, ‘Introduction’ in Ptolemy's Geography, pp. 17-18. Notwithstanding the possibility that a terraqueous concept of the earth globe could have been construed from Almagest, the subject of the structure of the earth was of secondary importance as it was a means to calculate the movement of celestial bodies. In contrast, Geographia focused on the structure of the earth and places on it. This may well have been an important factor in scholars becoming more aware of Ptolemy’s concept of a terraqueous globe in response to Geographia rather than Almagest. Further research is needed on the issue, although the task of determining how early modern scholars’ interpreted minor differences in text is a difficult one in the absence of any comment from primary sources and a detailed textual and contextual analysis. Regardless of the need to examine the claim by Randles that the dissemination of Geographia was solely responsible for the introduction of the terraqueous globe to early modern scholars, the assertion that there was considerable debate and controversy about the concept of the earth by the sixteenth century is well founded. 39 C Ptolemy, Traité de Géographie, Greek text and French translation by Abbe Halma, Paris, 1828, p. 11, cited in W G L Randles, ‘Classical models of world geography’, p. 16. Randles’ interpretation of the text by Ptolemy is consistent with that implied in the most recent English translation of Geographia,inwhich the cited passage is translated as: ‘the continuous surface of land and water is (as regards its broad features) spherical and concentric with the celestial sphere.’ C Ptolemy, Geographia in J L Berggren and A Jones (eds), Ptolemy's Geography, p. 60. 40 See W G L Randles, ‘Classical models of world geography’, pp. 35-43. 41 W G L Randles, ‘Classical models of world geography’, pp. 38-39.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 19 earth.42 Thus, in the fifteenth century, cosmological matters continued to garner attention although the introduction of an additional, different geognosic model does not appear to have resulted in fresh cosmographical debates.
As the examples I have chosen illustrate, cosmography remained an active field of knowledge and concern to those posing natural philosophical questions from the thirteenth century through to late fifteenth century. Scholastics considered the earth in relation to the cosmos as a whole, and actively engaged in providing within one (Aristotelian) explanatory system the nature and relationship of the earth and heavens. Put another way, a cosmographical problematic had emerged from high Medieval Scholasticism, engaging natural philosophers and framing their discourse about the structure of the earth. One method Scholastics used to address this customary concern was to argue from knowledge about the heavens to knowledge about the earth. Commentators like Albert of Saxony used this form of argument. He reasoned from the cosmological proposition that the earth rests at the centre of the cosmos to the view that the centre of gravity of the aggregate of the spheres of earth and water lies at the centre of the cosmos. Those Scholastics concerned with laws of physics and matter, such as Scot and Buridan, modified geognosic opinion in order to provide for one explanatory system consistent with these laws.43 Thus, the usual direction of cosmographic inference was from the heavens to the earth. As we shall see, the tradition of cosmography—the project itself and the associated method of argument— remained active throughout the sixteenth century.
42 A S Piccolomini, Historia rerum ubique gestarum, venice, 1477, Cap. I, sign. A. i. (v.) - sign a. ii. (r.), cited in Randles, ‘Classical models of world geography’, p. 38. 43 As the laws of physics and matter pertaining to the earth extended only as far as the lunar region, any cosmographic form of argument linking the earth with the cosmos on these matters only dealt with the nature of the cosmos within the extent of the terrestrial region.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 20 2.3 Copernicus and the earth in the sixteenth century
A key link in Copernicus’s line of reasoning for the heliocentric arrangement of the cosmos concerned the structure of the earth. In De Revolutionibus Orbium Coelestium, Copernicus argued that one could more fully account for the motions of the ‘wandering stars’ by attributing motions to the earth than by assuming an immobile earth.44 On this basis, he radically asserted that the sun not the earth rests immobile at the centre of the cosmos and the locus for the revolutions of the planets. Indeed, the earth is a planet and its major movements are a daily axial rotation from west to east and annual revolution around the sun, also from west to east. Countering Aristotelian claims that any motion of the earth would constitute violent motion and thereby result in its disintegration, Copernicus argued that the circular motion of the earth was ‘proper’ to the earth on account of its spherical shape. Copernicus thus co-opted the Scholastic law of celestial physics whereby spherical bodies naturally exhibit circular motion and, radically, applied it to the terrestrial realm.45
GGR make several key points concerning geognosic opinion during the sixteenth century and its place in the work of Copernicus. They claim that: that geognosic opinion was in a state of high controversy during the period; Copernicus argued explicitly for the ascendant concept of the earth as a terraqueous globe; and Copernicus’s argument for a particular shape of the earth was crucial to his cosmological theory. I will turn first to explore GGR’s views on the state of geognosic opinion in the early modern period.
44 N Copernicus, De revolutionibus orbium coelestium, 1543, published in A. M. Duncan (ed) On the Revolutions of the Heavenly Spheres, Newton Abbot, England, 1976, pp. 25-99, especially p. 26. Subsequent references to Copernicus come from this edition, which shall be cited as ‘N Copernicus, On the Revolutions of the Heavenly Spheres’. 45 While Kuhn acknowledges the Scholastic nature of Copernicus’s argument there are substantial shortcomings in his interpretation of Book 1, which are discussed later in this Chapter. T S Kuhn, The Copernican Revolution, p. 148.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 21 GGR argue that the structure of the earth was highly controversial not just when Copernicus was writing De Revolutionibus and considering its publication from the first decade through to the fifth decade of the sixteenth century, but as late as the 1570s.46 As already noted, the GGR position is that in the fourteenth and fifteenth centuries, the floating apple theory stood as the dominant concept of the structure of the earth. During the late fifteenth and early sixteenth centuries, information about the existence and extent of distant landmasses and islands brought back from the ‘voyages of discovery’ cast serious doubt on the floating apple theory. The explorations demonstrated that both the African and South American landmasses extend far into the southern hemisphere, which theoretically required the earth to sit extremely high out of the sphere of water in the floating apple model. Moreover, the discovery of islands far removed from the oikoumene made the floating apple theory implausible since, according to it the sea got deeper and deeper as one travelled east or west. So, from the early sixteenth century scholars and elite practical mathematicians outside Scholastic circles increasingly rejected the floating apple model, arguing for a terraqueous concept of the earth as a single, largely solid sphere of earth and water, a conceptualisation associated with Ptolemy. GGR’s inquiry into geognosic opinion proceeds no further in time than the late sixteenth century.47
Secondly, GGR assert that Copernicus argued explicitly in De Revolutionibus for the ascendant Ptolemaic concept of the earth as a terraqueous globe. That is, Copernicus was one of those outside universities in the early–mid sixteenth century consciously challenging certain Scholastics’ concept of the earth as a floating apple. GGR propose that historians of science should view the opening chapters in Book One as a carefully structured argument
46 Copernicus was formulating his heliocentric views from as early as 1506, completed De Revolutionibus not much later than 1531, and published the treatise in 1543, the year of his death. A Koyré, The Astronomical Revolution, p. 25. 47 GGR’s chronology of thinking about the shape of the earth ends with the late sixteenth century. Accordingly, their claim of the considerable influence of geognosic opinion on the Scientific Revolution is quite narrow in scope: it is based on the central place of the concept of a terraqueous globe in Copernicus’ argument and the role of Copernicus’ work in establishing heliocentrism and in the gradual undermining of Aristotelian natural philosophy.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 22 for the terraqueous concept of the earth.48 We shall return to assess the grounds for this claim shortly.
GGR’s third point is that Copernicus employed the ascendant concept of the earth and water as a single, largely solid sphere in his argument for a heliocentric cosmos.49 Specifically, Copernicus utilised the earth’s perfect sphericity as a key premise in his sequence of arguments for the natural circular motion of the earth in his cosmology, since spherical-shaped bodies are those most suited to circular motion. Thus, GGR claim that Copernicus used the controversial concept of the terraqueous globe as grounds for arguing a certain astronomical view. The evidence strongly suggests GGR are right in each of the three points.
There are substantial grounds for GGR’s first claim; that the concept of the earth was controversial through to sixteenth century. To begin with, the floating apple concept of the earth still found widespread scholarly acceptance. For example, what little evidence there is suggests the Scholastic view of the floating apple model was held by the Spanish boards of cosmographers that considered Columbus’ project for sailing to Asia, as Randles has suggested. In the first meeting to assess the project in Salamanca (1486–87) the Spanish Queen’s cosmographers held the view that only a very small part of the earth lay uncovered since most of the earth was submerged in water.50 At the second meeting at Santa Fe (1491), the cosmographers drew on Paul de Burgos as the authority for the view that the
48 Randles also suggests that the increasing support for a terraqueous concept of the globe weakened Copernicus’ ties to Aristotelian cosmology: ‘It is possible that the formulation of the heliocentric hypothesis depended for Copernicus in his reaching a point where he was sufficiently freed from the weight of Aristotelian tradition and this point was provided by the experience of the navigators showing the untenability of the Scholastic doctrine of the spheres of the water and of the earth.’ W G L Randles, ‘Classical models of world geography', p. 70. 49 T Goldstein, ‘The Renaissance concept of the earth in its influence upon Copernicus’, pp. 23, 26 and 37 and particular fn 9; E Grant, ‘In defense of the earth’s centrality and immobility’ pp. 22-23, fn 69; W G L Randles, ‘Classical models of world geography', pp. 69-70. 50 F Columbus, Le Historie delle vita e dei fatti di Cristoforo Colombo, Venice, 1571, modern edition: Acura di Rinaldo Caddeo, con studio introduttivo, note, carte e incisioni, Milan, 1930, Vol. I, chap XII, pp. 106- 107 and B de Las Casa, Historia de las Indias, Lib. I, Cap. V, Biblioteca de Autores Españoles, Vol. XCV, Madrid, 1957, p111, both cited in W G L Randles, ‘Classical models of world geography', p.46.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 23 entire oikoumene lies between the Canary Islands in the west to China in the east and does not extend far into the southern hemisphere.51
While accepted in certain scholarly circles, the floating apple model had many detractors too. Indeed, humanist scholars ridiculed Scholastics’ prevarications about the floating apple model of the earth. In 1515, Joachim Vadianus, based in Vienna, argued for the concept of the earth as a single, largely solid sphere of earth and water in published correspondence to metallurgist and author Rudolf Agricola. Vadianus wrote:
It might seem thus, Rudolf, to those who believe that on one side the earth emerges from the water like a hilltop rising above the flat surface of a lake or even like an apple floating in it, as some of the ancients have thought. But, by Hercules, to imagine this is the work of a dull mind, given that in reality, things are very different. As the many facts of experience have shown and as George Peurbach, a German very clever at mathematics has recorded in his collected writings on the Sphere of Sacrobosco, the earth together with the waters which surround it, forms a globe in such a way…that together with the waters, it follows a curved globe-like shape.52
This sixteenth century example of support for the terraqueous globe can be readily repeated. For instance, in 1528, Jean Fernal, lecturer of medicine at the College de Cornouailles and eventual physician to Henry II, wrote:
51 AGeraldini,Itinerarium ad regiones sub aequinoctiali constitutas, Rome, 1631, pp. 204-205, cited in W G L Randles, ‘Classical models of world geography', p.46. 52 J Vadianus, Habes lector: hoc libello Rudophi Agricola…ad I. Vadianum…, Vienna, 1515, sign. B. ii (r.). cited in W G L Randles, ‘Classical models of world geography', p. 67. For completeness, it is worthwhile noting that a phrase in Vadianus’ correspondence, not included here, appears initially to be a statement in support of a floating apple model; Vadianus refers to the earth emerging like a ‘like a small clod out of a lake’. However, this should be considered in the context of Vadianus’ clear statements that the earth and water form one globe. The phrase is therefore better understood as an expression of Ptolemy’s concept of the seas being like lakes or hollows in the earth. The lack of clarity arises partly because Vadianus atypically articulates the Ptolemaic concept with the earth as the subject, (‘it emerges like a small clod out of a lake’) rather than the waters as the subject (that is, the waters rest in the hollows of the earth like lakes).
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 24 We need to examine more carefully the reasoning of certain philosophers, most of them modern ones, who are convinced that the centre of magnitude of the earth is different from the centre of the universe…[T]he great number of places they [islands] occupy in the sea amply shows that the part of the earth that is covered by the waters can be said to be at the same distance from the centre of the universe as the other part…One must thus agree that the earth looks like a wooden globe in which there are many hollows in which water can gather.53
Similar arguments for the terraqueous concept of the earth continued through the mid to late sixteenth century and can be found in England as late as 1635.54
53 JFernal,Cosmotheoria, Paris, sign. B. I (v.). cited in , W G L Randles, ‘Classical models of world geography', p. 68. Randles suggests that Fernal uses a Ptolemaic demonstration of the relation of the earth and water, but attributes it to Aristotle (which cannot be substantiated from the sources to which Fernal refers). 54 In 1537, Portuguese mathematician Pedro Nunes argued the earth and waters comprised one, largely solid sphere on the basis of the shape of the earth’s shadow on the moon during an eclipse and the equivalent distance corresponding to a celestial degree on land and sea, points commonly advanced at the time in support of the terraqueous globe. P Nunes, Tratado da Sphera, Lisbon, 1537, facsimile edition by J. Densaude, Munich, sign a. iiii (r.), cited in W G L Randles, ‘Classical models of world geography’, p. 66. Caspar Peucer wrote in 1551 that the discovery of the existence of numerous and vast lands all over the world shows that the southern part of the earth is not submerged. Rather, the earth with the waters together form a single globe-shaped body wherein the two ‘elements’ are merged. C Peucer. Elementa doctrinae de circulis coelestibus et primo motu, Wittenberg, 1551, sign. vii (r.). cited in W G L Randles, ‘Classical models of world geography’, p. 71. In 1635, Nathaniel Carpenter in his geographical treatise— Geographie delineated forth in two bookes Containing the sphericall and topicall parts thereof—presented two ‘theorems’ regarding the earth and water, showing the relations between earth and water were still subject to some debate: ‘1 In the Terrestriall Spheare is more Earth then Water. ‘The Theoreme may bee proued by sundry reasons drawne from Nature and Experience. Whereof the first may bee taken from the depth of the waters, compared with the whole thicknes of the Earth. For the ordinary depth of the Sea is seldome found to be aboue 2 or 3 miles, and in few places 10 furlongs, which make a mile and a quarter. And albeit some late Writers haue imagined the obseruation to be vnderstood only of straight and narrow Seas, and not of the maine Ocean: yet granting it to amount…10, 20 or 30 miles, it cannot each to so great a quantity , as to come neere the greatness of the Earth …Another reason to proue the Earth to be greater in quantity, may bee drawne from the mixture of Earth and Water:forif these two Elements should meet in the same quantity, & challenge an equality; questionlesse the whole Earth would proue ouer-moist... Moreouer the Water being no other than a thin and fluid body, hardly containing it selfe within its own bounds or limits (as Aristotle teacheth vs) must needs require a hard and solid body, whereon to support it selfe, which body must of necessity bee greater in quantity.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 25 Thus, the conceptualisation of the earth was contested widely across Europe throughout the sixteenth century. Main rival views were the Aristotelian-derived floating apple model and the Ptolemaic concept of the earth as a single, largely solid sphere of earth and water. The relative volumes of earth and water and the coincidence or otherwise of the earth’s centre of gravity and geometry featured as leading matters of debate.
Notwithstanding the obvious state of controversy about the relations between the earth and water, further research is required to ascertain the status of the terraqueous globe among sixteenth century Aristotelians. Randles states the long-held Aristotelian support for the floating apple model was brought largely to a close by Clavius’s highly influential commentary on Sacrobosco’s The Sphere, first published in 1570.55 Undoubtedly, however, there was support for a terraqueous concept of the earth amongst some Aristotelians prior to the wide distribution of Clavius’ work. For example, Martín Fernández De Enisco, Spanish navigator and geographer, wrote in 1519 of an Aristotelian
‘2 The Earth and Water together make one Spheare. ‘It may bee probably collected from sundry places of holy Scripture, that in the first Creation, the surface of the Earth; being round and vniforme, was ouerwhelmed and compassed round with Waters, as yet vnfurnished of liuing Creatures. Secondly, it appeares that Almighty GOD afterwards made a separation betwixt the Waters and Dry-Land. This separation (a…farre as reason may bee admitted as Iudge) seemes to bee effected one of these two wayes: Either by giuing super-naturall bounds and limits vnto the Waters, not suffering them to inuade the Dry-land: or els by altering the superficies of the Earth, casting it into inequall parts, so that some-where, some parts of it being taken away, empty channels or concauities might be left to receiue the Waters; other-where by heaping vp the parts so taken away, whence were caused Mountaines and eminent places on the earth. The former of these wayes seemes altogether improbable; forasmuch as it is very vnlikely to imagine, that God in the first institution of Nature, should impose a perpetuall violence vpon Nature, as hereafter in place more conuenient shall bee demonstrated. Wherefore taking the later as more consonant to reason; we shall find that the Water & the Earth separated and diuided, make not two separate and distinct…Globes, but one and the same Spheare; forasmuch as the concauities and hollowgapings of the Earth, are euery-where choaked and filled vp with Water, whose superficies is Sphaericall; and therefore helpes, together with the Earth, to accomplish & perfect this Terrestriall Spheare.’ N Carpenter, Geography Delineated Forth in Two Books Containing the Sphaericall and Topicall Parts Thereof, 1635, Book 1, pp. 7–11 55 The commentary by Clavius on Sacrobosco’s The Sphere went into eighteen editions between 1570 and 1618. W G L Randles, ‘Classical models of world geography', pp. 71-74.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 26 cosmos in the centre of which rested the earth and water together as a single body.56 Leading popular natural philosophical and geographical books before Clavius presented the earth and water as commingled. The image in Peter Apian’s 1540 Cosmographia,for instance, presented the earth and water forming a single sphere within a geocentric cosmos (Figure 1.2). Also, as Grant observes, the Ptolemaic earth did not immediately convert all Aristotelians. Aversa mentioned the Conimbricenses and Ruvio as amongst those who maintained the earth was separate from the waters that enveloped it.57 Finally, diversity of opinion also existed into the seventeenth century amongst Aristotelian supporters of the terraqueous globe. Varied opinions were expressed on the coincidences of the centre of gravity and magnitude in the terraqueous globe.58 Debate further proliferated regarding whether the mountains marred the rotundity of the earth—an issue, which we will see, also affected the case for a moving earth.59
56 M De Enciso, Suma de Geographia, Seville, 1519, sign, A. iij (r.-v.), cited in W G L Randles, ‘Classical models of world geography' . p. 66. Biographical information from The Catholic Encyclopedia, http://www.newadvent.org/cathen,7 November 2005. 57 Aversa, Philosophia, 225, col. 2., referred to in E Grant, ‘In defense of the earth’s centrality and immobility’, p. 27 and fn 92. The Conimbricenses were a group of Jesuits at the University of Coimbra, Portugal, prepared a collection of texts and commentaries on the key works of Aristotle between 1592 - 1598, including a commentary on De Caelo in 1592. The commentaries were dictations to the students by the professors and as such were not originally intended for publication. However, following publication, the Jesuits revised and republished the commentaries. B Schmitt, Q Skinner, J Krayl, E Kessler, J Kraye (eds), The Cambridge History of Renaissance Philosophy, Cambridge University Press, Cambridge, 1990, viewed on 11 September 2005,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 27 Figure 1.2. Image of the cosmos, from Peter Apian’s 1540 Cosmographia (Cosmography)60
60 Image accessed from Exhibits Online, History of Science Department, University of Oklahoma,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 28 Be this as it may, that Clavius chose to mount a detailed argument for the earth and water together forming one, largely solid sphere strongly demonstrates that the concept of the earth as a terraqueous globe was not one that late sixteenth century Scholastics took for granted. By this time, however, it was recognised that the concept of the terraqueous globe could be aligned with Church doctrine.61 Thus, the evidence is strong for the view that in Copernicus’s time and throughout the sixteenth century, the terraqueous globe was a controversial concept: some Scholastics accepted that the earth and oceans constituted a spherical body, and some held alternative models.
GGR are certainly right in their second point: that Copernicus argued carefully for the ascendant concept of the earth as a terraqueous globe. This is shown by a careful reading of Chapters One to Five, Book One of De Revolutionibus in which, at the outset, Copernicus states that the universe is spherical.62 He then maintains that:
The Earth is also [as well as the universe] globe-shaped, because every part of it tends towards the centre.63
Next, Copernicus outlines that the sea is also spherical:
That the waters also tend to the same shape is realised by seafarers, because land which is not in view from a ship is often sighted from the top of the mast.64
61 The view of James M. Lattis on Clavius’s work potentially throws some doubt on this interpretation. Lattis argues that the core concepts in the work by Clavius comprise ‘ideas that a sixteenth century European reader could reasonably be expected to accept with little or no argumentation or debate. That is, Clavius’ presentation rests on assumptions and prejudices with which his audience is already comfortable’ However, Lattis does not enumerate what concepts constitute the nucleus of beliefs in the work. J M Lattis, Between Copernicus and Galileo. Christoph Clavius and the Collapse of Ptolemaic Cosmology, The University of Chicago Press, Chicago, 1994, p. 65. 62 N Copernicus, On the Revolutions of the Heavenly Spheres, pp. 36-41. Goldstein argues the titles of Book I of De Revolutionibus ‘read almost like a capsulized summary of his [Copernicus’] basic argumentation.’ (See footnote 67 for an outline of the chapter titles). Goldstein also compares the topics Copernicus dealt with and those of the medieval debate, and comments on Copernicus’ familiarity with medieval scholars. T Goldstein, ‘The Renaissance concept of the earth in its influence upon Copernicus’, p. 36 fn 33 and p. 23, fn 9, respectively. 63 N Copernicus, On the Revolutions of the Heavenly Spheres, p. 36-37. We can see Copernicus here uses Aristotelian laws of terrestrial physics to mount his geognosic case.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 29 The final step in Copernicus’s argument is to assert that the spherical earth and spherical water in fact form a single sphere. To mount his case, Copernicus engages with the key geognosic controversies of his time, as shown by the following quote:
We should not listen to certain of the Peripatetics who have declared that the total amount of water is ten times greater than the whole Earth…they are mistaken from ignorance of geometry, not knowing that the water cannot be even seven times more, and still allow some of the Earth to remain dry…Further, from the shore of the ocean the depth of the abyss would increase continuously, and because of that no island, nor rock, nor anything of the nature of land would be encountered by seafarers as they voyaged onwards. 65
The most original of Copernicus’s arguments for the terraqueous globe in respect of his contemporaries appears to be his geometrical rebuttal of the floating apple model. Namely, geometry dictates that if the earth is to both protrude above the sphere of water and the centre of gravity of the aggregate earth-water body to reside inside the earth, the amount water could not be more than seven times greater than earth. In the following quote we see that Copernicus’s whole argument is a case for the Ptolemaic earth:
All this seems to me to show that Earth and water both tend towards the same centre of gravity, which is no different from the geometrical centre of the Earth, the clefts in which, as it is heavier, are filled with water, and therefore the quantity of water is limited in comparison with the Earth, although on the surface there may appear to be more of the water…So the Earth…is of a perfect roundness.66
64 N Copernicus, On the Revolutions of the Heavenly Spheres, p. 37. 65 N Copernicus, On the Revolutions of the Heavenly Spheres, p. 37-38. 66 N Copernicus, On the Revolutions of the Heavenly Spheres, p. 37-38. Thus, the concurrence of the centres of gravity and magnitude of the earth are chief amongst Copernicus’s arguments for the earth forming a perfect sphere. Interestingly, in this section of writing Copernicus also cites the moon’s shadow as an argument for the terraqueous globe. This is evidence presented by Aristotle, presumably made redundant by the pseudo-Aristotelian notion that there is ten times as much water as earth and the subsequent floating apple model.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 30 Indeed, the title of the Chapter is ‘how the earth with its Water makes up a single globe’.67 So, Copernicus argued at length in De Revolutionibus for the Ptolemaic concept of the earth as a terraqueous globe.
Finally, the sphericity of the earth plays a key role in Copernicus’s heliocentric theory, as noted by GGR and Kuhn before them. Indeed, Copernicus considered his argument for the earth’s spherical shape to be crucial in his line of reasoning for the possibility of the earth’s circular motions (set out in Chapters Five and Eight of De Revolutionibus). For example, he wrote:
As it has now been shown that the Earth also has the shape of a globe, I believe we must consider whether its motion too follows its shape.68
The following quote is further evidence that Copernicus considered the sphericity of the earth to be critical to his case for the earth’s circular motion:
Why …do we still hesitate to concede movement to that which has a shape naturally fitted for it, rather than believe that the whole universe is shifting, although its limit is unknown and cannot be known.69
So, establishing the sphericity of the earth was crucial in Copernicus’s co-option of the Scholastic law of celestial physics and his radical application of it to the terrestrial realm.
Finally, that Copernicus subscribed to the Ptolemaic earth is further demonstrated by the following quote: ‘the Ocean which surrounds the Earth pours out its seas far and wide and fills the deeper hollows.’ N Copernicus, On the Revolutions of the Heavenly Spheres, p. 37. 67 The title of the first three chapters of Book One of De Revolutionibus are: (1) That the universe is spherical; (2) That the Earth is also spherical; and (3) that the Earth with its water makes up a single globe. Kuhn translates the title of Chapter Three slightly differently, but argumentative intent of this it is still clear. Kuhn’s entitles the Chapter: “How the earth, with the Water on it, forms one Sphere”. T S Kuhn, The Copernican Revolution, p.146. 68 N Copernicus, On the Revolutions of the Heavenly Spheres,p.40 69 N Copernicus, On the Revolutions of the Heavenly Spheres,p.44
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 31 2.4 Beyond GGR—Cosmography at the beginning of the Scientific Revolution
GGR deserve credit for highlighting these three points. Nevertheless, they fail to notice that Copernicus was engaged in cosmography both in terms of content and method. First, his cosmological system explicitly addressed and provided a congruent account of the relations between the heavens and earth. Indeed, Copernicus’s engagement with the tradition of cosmography was recognised in the early modern period. Blundeville in 1594 described Copernicus as a recent ‘furtherer’ of cosmography, for example.70 The cosmographic project in De Revolutionibus extended to the method of argument. From the thirteenth through the late fifteenth centuries, natural philosophers aligned geognosic theories with certain aspects of the hegemonic Aristotelianism and the existence of dry land by modifying and manipulating conceptualisations of the earth’s structure. That is, the cosmographical problematic was often settled by arguing from a particular view of the heavens to the structure of the earth. In contrast, Copernicus argued from a particular structure of the earth to a distinct and radical view of the heavens, using the controversial concept of the terraqueous globe as grounds for this astronomical view. Thus, we can understand Copernicus’s form of argument to be a standard cosmographical one, with the important exception of the reversal of order. Copernicus is therefore radical in his form, marking an important shift in the cosmographic tradition.71
To sum up, historians of science from Kuhn and Koyré down to recent commentators on early modern geography have mostly failed to notice or, in the case of Cormack failed to investigate closely, the field of cosmography. Cosmography can be understood to have been a customary concern of natural philosophy from the thirteenth century through to the late fifteenth century. It was the pathway by which geognosic knowledge entered into the
70 T Blundeville, M. Blundeville his exercises containing sixe treatises, p. 135. Georgus Purbacchius and Johannes de Monte Regio are the others in ‘these latter days’ that had ‘learnedly treated’ and furthered the science of cosmography, according to Blundeville. 71 Whether this reversal is rare or completely unprecedented is a question requiring further research into the form of argument used in late medieval cosmography.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 32 conceptual developments in natural philosophy. This tradition continued into the mid sixteenth century with Copernicus, who actively engaged in addressing the cosmographic problematic and used cosmography as a field of knowledge or form to locate his argument about the earth’s motion with one crucial reversal of order. Thus, during the opening phase of the Scientific Revolution cosmographical discourse not only constituted part of the tradition of natural philosophy but stood as an integral and recognised feature of the cosmological treatise that ignited the Copernican and the Scientific Revolutions.
As we shall see, the tradition of cosmography lived on after Copernicus. For later Copernicans, the cosmographical project had a different scope than it did for Scholastics. For the latter, the earth is indeed very different from heavens in the form and nature of matter (and cause), yet it is variously cosmographically related to the heavens in a ‘unity’. For Copernicans, cosmography and a novel, radical earth provided an opportunity to learn more about the heavens, as laws for the earth and heavens were not necessarily different.
2.5 Why historians have overlooked cosmography
Before turning to the principle part of this thesis, it is appropriate to briefly contemplate how the oversight of cosmography in the literature might have occurred. I suggest presentist bias or assumptions in two areas account for the historiographical neglect of cosmography. First, historians of science from Kuhn and Koyré down to modern commentators assume there was no significant change in geognosic opinion during the early modern period. To illustrate, Kuhn quotes extensively from Book One of De Revolutionibus, including those chapters in which Copernicus makes a case for the earth and water forming one single, solid sphere.72 Even so, Kuhn fails to notice that controversy surrounded the structure of
72 T S Kuhn, The Copernican Revolution, pp. 145 – 150.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 33 the earth, implicitly assuming that all Scholastics conceived of the world as a terraqueous globe. For example, when Kuhn outlines the concept of a two-sphere universe that was advanced in antiquity, inherited by the modern world and from which Copernicus diverged, he offers illustrations wherein the earth appears as a terraqueous globe (Figure 1.3).73 Further evidence of Kuhn’s failure to notice the ongoing debate about the structure of the earth is his interpretation of the geognosic chapters of Book One of De Revolutionibus. A case in point is Kuhn’s commonsense construal of the claim by Copernicus that the volume of water is less than that of earth, which was a not uncontroversial geognosic opinion as we have seen. Kuhn writes:
Presumably he [Copernicus] is looking ahead. Earth breaks up less easily than water when moved; motion of a solid globe is more plausible than a liquid one.74
Thus, Kuhn fails to connect Copernicus’s statements to the long debated subject of the relative volumes of earth and water. Kuhn is aware that Copernicus used the earth’s sphericity as an argument for the natural circular motion of the earth, but since Kuhn overlooks the fact that Copernicus had previously argued for a certain geognosic opinion, he fails to fully appreciate Copernicus’s line of reasoning.75 Furthermore, Kuhn is not alone. Not long after Kuhn’s book was published, Koyré commented (1961) that the sphericity of the earth was ‘a fact not in dispute in his [Copernicus’] time’.76
73 Kuhn’s comments in the preface to the volume strongly imply he accepted the illustrations as an accurate and adequate translation of his communicative intent. See pages ix-x. 74 T S Kuhn, The Copernican Revolution, p.146. 75 T S Kuhn, The Copernican Revolution, p.148 76 A Koyré, The Astronomical Revolution, p58.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 34 Figure 1.3: Illustrations of the astronomical functions of the two-sphere universe and approximate planetary orbits in a two sphere universe from T S Kuhn. 77
77 T S Kuhn, The Copernican Revolution, pages 31 and 53 respectively. Similar representations of the earth as a terraqueous globe within the Aristotelian system appear elsewhere in the work, such as on pages 33, 36, and 156.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 35 Since Koyré and Kuhn, there has been very little change in the views of historians of science’s concerning the genealogy of the terraqueous globe. For example, in his preface to an abridged translation of Galileo’s Dialogo sopra i due massimi sistemi del mondo, Tolemaico e Copernicano (Dialogue Concerning the Two Chief World Systems— Ptolemaic and Copernican), Maurice Finocchiaro, Galilean commentator, wrote:
Although uneducated persons or primitive peoples at the time of Aristotle or Galileo may have believed the earth was flat, scholars had settled the question a long time ago; thus, it should be clear that the Copernican controversy had nothing to do with the shape of the earth but was rather concerned with its behaviour and location.78
Gingerich similarly mistakes belief in a spherical earth in the early modern period as settled: ‘educated people knew the earth was round’, he lightly asserted in 2001.79 As already noted, the literature on early modern geography fails to consider the status of geognosic opinion, instead focusing on method and ideology. Historians of science (other than GGR) who have recognised that medieval Scholastics utilised the floating apple model, such as historian of geology, David Oldroyd, still fail to consider how and when this concept changed and its impact on theoretical developments in the Scientific Revolution.80
78 Finocchiaro also argues that the navigational voyages and geographical discoveries at the end of the 15th century only served to confirm the already existing belief of the earth’s spherical shape. M. Finocchiaro, Galileo on the World Systems. A New Abridged Translation and Guide, University of California Press, Berkley, 1997, quote from page 8, emphasis added. 79 O Gingerich, ‘Scientific cosmology meets western theology’, p. 28. 80 David Oldroyd identifies that a concept of the earth existed in the Middle Ages wherein the sphere of earth protrudes above the sphere of water. He praises Buridan for this ‘ingenious’ and ‘extraordinary’ model. Oldroyd also comments that Albert of Saxony supported the model and Oresme rejected the model. However, he does not examine the significance of this model for cosmology despite publishing subsequently to Goldstein and Grant. While this focus is understandable given Oldroyd’s chief concern is the history of ideas about the earth’s geology, not a history of cosmology, it is a striking example of how disciplinary distinctions within the history of science may have contributed to a situation in which important links between geographical and cosmological ideas have been overlooked, as Grant has noted. D Oldroyd, Thinking about the Earth: A History of Ideas in Geology, The Athlone Press, Cambridge, 1996, pp. 3, 26.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 36 The assumption of stasis in geognosic opinion has, to my mind, been a principal factor in the oversight of early modern cosmography. If historians of science had viewed geognosic opinion as evolving, perhaps more consideration would have been given to how early modern thinkers reconciled shifts in geognosic opinion with other aspects of their natural philosophy.
An even greater presentist assumption pertains to the disciplinary framework of debate about the structure of the earth. Geognosic opinion could not be separated from astronomical (and cosmological) doctrine in the fifteenth and sixteenth centuries. Yet historians of science have generally treated geography as if it were an independent field, as in the present, neglecting the bond with astronomy under the umbrella of cosmography. This bond, as I shall show, persists right through the mid seventeenth century. To sum up, the reason why the problem addressed by this thesis has been overlooked is simply that few historians have understood both that the shape of the earth remained controversial during the sixteenth century and that the issue was a matter of cosmography (not just geography).
3. Contribution of this thesis
Given the issues addressed in this Chapter, we can now point to the detailed aims and content of this thesis. The following chapters seek to establish the role that cosmography played in the intellectual developments of the Scientific Revolution by examining how natural philosophers utilised the relations between the earth and heavens, as well as the nature of each, to form and advance their respective theories. At a secondary level, the thesis also provides insights into the fate of geognosic opinion once the shape of the earth had largely been settled, going further in time than GGR.81 I will argue that the cosmographic project and Copernicus’s inverted cosmographical argument lived on
81 See footnote 47.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 37 through the sixteenth and seventeenth centuries. The harmonisation of heaven and earth was a going concern throughout the Scientific Revolution.
By way of method, I focus on the Copernican natural philosophers and employ four case studies. These comprise selected works of Giordano Bruno, William Gilbert, Galileo and René Descartes. The rationale for the selection of case studies is that historians of science consider that these works impacted greatly on natural philosophical thinking at the time and thereby played an important role in the Scientific Revolution. Moreover, modern commentators opine that, despite substantial scholarship about the theories of these leading Copernicans, quandaries remain in interpreting certain aspects of each: the extent of Bruno’s radicalism, Gilbert’s reversal of neo–Platonic procedure in constructing his natural philosophy from the terrestrial globe outward to the heavens, Galileo’s puzzling theory of the tides, and Descartes’ lengthy account of the formation of the earth. In other words, historians of science still have trouble seeing the coherence of each of these four systems. A greater coherence emerges in each case with the recognition of the field of cosmography.
Considered as a group, Bruno, Gilbert, Galileo and Descartes can be collectively viewed as representative Copernicans. Together with Copernicus they span the period of the Scientific Revolution (mid sixteenth to mid seventeenth centuries). They also represent diverse theoretical agendas present amongst Copernicans: Bruno, radical Neoplatonic; Gilbert, ‘sanitised’ Neoplatonic; Galileo, physico-mathematical and ‘Archimedean’; and Descartes, corpuscular-mechanical. Lastly, considered as a group, Bruno, Gilbert, Galileo and Descartes lived, studied and worked in the key countries involved in the Scientific Revolution. To provide depth, the work of Gilbert and Galileo is examined in considerable detail. Two additional cases, Bruno and Descartes, are offered in less detail in order to make available chronological, theoretical and geographical breadth. The cases are presented chronologically, beginning with the work of Giordano Bruno.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 38 Finally, the concept of the ‘Scientific Revolution’ itself must be addressed. The thesis proceeds from a conceptualisation of the Scientific Revolution as a period of particular ferment in the long-running tradition of natural philosophy All natural philosophical systems proposed: ‘a general theory of nature—that is, the nature of matter and causes, the cosmological structuring and functioning of matter and the proper method for acquiring or justifying knowledge of nature.’82 In the early modern period, Scholastic Aristotelianism was only one, albeit dominant, institutionalised system of natural philosophy. The field of natural philosophy also encompassed atomism, Neoplatonic, Chemical, Magnetic, mechanist and later Newtonian systems.83 This thesis considers the Scientific Revolution as a particularly intense period of contestation within the field of natural philosophy that saw the hegemony of Scholasticism was gradually eroded and varieties of mechanical philosophy became the dominant form of natural philosophy after 1650.84 The concerns of this thesis share themes with the considerable research underway into how natural philosophy claims were located relative to other enterprises, particularly in relation to the
82 P R Anstey and J A Schuster (ed.) The Science of Nature in the Seventeenth Century. Patterns of Change in Early Modern Natural Philosophy, Springer, Dordrecht, 2005, p, i. 83 Previously, many examinations of the Scientific Revolution by historians of science overlook the category of natural philosophy. These accounts view the Scientific Revolution as the conquest of a new and specific ‘essence’, such as scientific method, social norms or a particular view (mechanistic or Newtonian), resulting from developments either internal or external to ‘science’. A more recent approach has been to acknowledge the category of natural philosophy but define it narrowly as Scholastic Aristotelianism. Some recent scholars thereby conclude that the Scientific Revolution involved the demise of natural philosophy and the triumph of the new ‘modern’ science. P. R. Anstey and J. A Schuster, ‘Introduction’ in P. R. Anstey and J. A Schuster (eds.), The Science of Nature in the Seventeenth Century, p. 2. Cohen offers a detailed account of early historiographical approaches to the Scientific Revolution: H F Cohen, The Scientific Revolution. A Historiographical Inquiry, University of Chicago Press, Chicago, 1994. 84 Recent works include: J A Schuster and G Watchirs, ‘Natural philosophy, experiment and discourse in the 18th century: beyond the Kuhn/Bachelard problematic’ in H E. LeGrand (ed) Experimental Inquiries: Historical, Philosophical and Social Studies of Experiment, Dordrecht, Reidel, 1990, pp. 1-48; J A Schuster, ‘The Scientific Revolution’ In R Olby, G Cantor, J Christie, M Hodge (eds) Companion to the History of Modern Science, Routledge, London, 1990, pp. 217 – 242; A Cunningham, ‘How the Principia got its name; or, taking natural philosophy seriously’, History of Science, vol. 24, 1991, p. 377-392; J A Schuster, ‘Saving the Revolution’ in Isis, vol. 88, no. 1, 1997, pp. 118-121; A Cunningham, ‘Getting the game right: some plain words on the identity and invention of science’ in Studies in History and Philosophy of Science, vol. 19, 1998, pp. 365-389; J A Schuster, ‘L’Aristotelismo e le sue Alternative’ in D Garber (ed), La Revoluzione Scientifica, Instituto della Enciclopedia Italiana, Rome, 2002, pp. 337-357; P R Anstey and J A Schuster, ‘Introduction’ in The Science of Nature in the Seventeenth Century, pp. 1-7.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 39 mixed mathematical sciences. This study in particular places cosmography in the natural philosophy of the sixteenth and seventeenth centuries.
Viewing the Scientific Revolution against the background of the nature and dynamics of natural philosophy leads to a certain interpretation of intellectual developments during the period. The different theories and propositions of anti-Aristotelians like Bruno, Gilbert and Galileo are recognised as claims made in an attempt to challenge and replace the institutional hegemony of Scholastic Aristotelianism with their particular brand of natural philosophy. In addition, this perspective of the Scientific Revolution helps illuminate that Copernican natural philosophers contended not only against Aristotelianism but also amongst one another, in part by demonstrating the explanatory power of their own view and imposing new explanatory tasks on their opponents.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 40 Chapter Two Cosmography and natural philosophy in the late sixteenth century
To those men of early times, and as it were, first parents of philosophy, to Aristotle, Theophrastus, Ptolemy, Hippocrates, Galen, be due honor rendered for ever, for from them has knowledge descended to those that have come after them: but our age has discovered and brought to light very many things which they too, were they among the living, would cheerfully adopt. William Gilbert De Magnete1
If you do not seize the good that is near you, How can you find the good which is far away?... [T]he moon is not more heaven for us than we for the moon Giordano Bruno La cena de la ceneri2
1 W Gilbert, De Magnete Magneticisque Corporibus et de Magno Magnete Tellure Physiologio Nova, 1600, published in P F Mottelay (trans) R M Hutchins (ed), On the Lodestone and Magnetic Bodies by William Gilbert, Concerning the Two New Sciences by Galileo Galilei, On the Motion of the Hearth and Blood in Animals. On the Circulation of the Blood. On the Generation of Animals by William Harvey, Great Books of the Western World Series, vol. 28, Encyclopedia Britannica, Chicago, 1952. pp. xi – 121, p.2. Cited hereafter as ‘On the lodestone’ (Hutchins). 2 G Bruno, La cena de le ceneri, 1584, published by E A Goselin and L S Lerner (eds), University of Toronto Press, Toronto, 1995, p. 91.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 41 1. Introduction
The previous chapter demonstrated that cosmography remained a customary part of natural philosophy from the thirteenth through to the mid sixteenth centuries. Medieval and early Renaissance scholars often engaged with this cosmographical project by arguing from a view of the heavens to the earth, or in the case of Copernicus, a view of the earth to the heavens. In this chapter, to understand the role of cosmography in the middle stages of the Scientific Revolution, we explore the place of cosmography in the work of two late sixteenth century Copernican Neoplatonists: Giordano Bruno and William Gilbert.
Historians of science have traditionally identified the mathematical, ‘rational’ approach of Copernicus and others such as Kepler or Brahe as the foremost characteristic of modern science. Enlightenment historians through to modern scholars like Brian Vickers and A. R. Hall have supported this view.3 These commentators have drawn a sharp distinction between modern science and magic. Thus, they have interpreted the occultist thinking of thinkers like Bruno, Gilbert and Campanella and their approach, based on deduction from the animate nature of the cosmos, as antithetical to the development of modern science. In contrast, other historians argue that ‘magical’ attitudes were an important factor in the Scientific Revolution. Frances Yates instigated this revisionist view in the 1960s with her exploration of the impact of the Corpus Hermeticum on early modern thinking.4 Easlea and Walker are among those who have extended the ‘Yates thesis’, while Westman, Copenhaver and McGuire are amongst its
3 B Vickers (ed) Occult and Scientific Mentalities in the Renaissance, Cambridge University Press, Cambridge, 1984, pp. 1 - 55 and pp. 95- 164, especially page 44; A R Hall, ‘Magic, metaphysics and mysticism in the Scientific Revolution’ in Reason, Experiment and Mysticism in the Scientific Revolution, M L R Bonelli and W R Shea (eds), Science History Publications, New York, 1975, pp. 275-282, especially pp. 280-282. 4 F Yates, Giorando Bruno and the Hermetic Tradition, Routledge and K. Paul, London, 1964.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 42 critics.5 The latter group of commentators support Yates’s view that numerous connections existed between natural philosophy and occultism, but argue that Neoplatonism, not Hermetism, was the progressive magical worldview. As a result of this debate, historians of science now routinely incorporate the work of Neoplatonists like Bruno, Gilbert and Campanella into the narrative of the intellectual developments of the Scientific Revolution. Nevertheless, fundamental questions persist such as how these thinkers arrived at their radical theoretical claims, compared to those of their Copernican predecessors and peers. I argue here, through an exploration of Bruno and Gilbert, that some answers to these historiographical puzzles might lie in cosmography.
2. Bruno’s cosmographic form of argument
To historians of science, Giordano Bruno stands as one of the most perplexing Copernicans of the early period of the Scientific Revolution for his sheer radicalness. Bruno made two key cosmological claims in La cena de le ceneri (The Ash Wednesday Supper); the cosmos is infinite and possesses no centre or periphery, and is full of innumerable, inhabited bodies, similar to the earth.6 ‘If we were on the moon,
5 Key works on natural magic and the Scientific Revolution include: B Easlea, Witchhunting, Magic and the New Philosophy, Harvester, Exeter, 1980; B P Copenhaver, ‘Natural magic, hermeticism, and occultism in early modern science’ in D C Lindberg and R S Westman (eds) Reappraisals of the Scientific Revolution, Cambridge University Press, Cambridge, 1990; A P Coudert, ‘Neoplatonism’ in Wilbur Applebaum (ed) Encyclopedia of the Scientific Revolution: from Copernicus to Newton, Garland Publishing, New York, 2000, p. 455-457; K. Hutchinson, ‘Magic and the Scientific Revolution’ in Wilbur Applebaum (ed) Encyclopedia of the Scientific Revolution: from Copernicus to Newton, Garland Publishing, New York, 2000 pp. 382-384; D P Walker, Spiritual and Demonic Magic from Ficino to Campanella, University of Notre Dame Press, Notre Dame, 1975; R S Westman and J E McGuire (eds.) Hermeticism and the Scientific Revolution. Papers read at a Clark Library Seminar, March 9, 1974, William Andrews Clark Memorial Library, University of California, Los Angeles, 1977. 6 G Bruno, La cena de le ceneri,p.13.La cena de le ceneri was published in London in 1584, following Bruno’s departure from Rome, his abandonment of the Dominican order and seven years residence in France. Bruno was the first thinker after Digges’ to claim the cosmos was infinite. He also proposed that the planetary bodies differed from the earth only in their size and that the cosmos contained innumerable other suns, which like ‘ours’, is made of fire. G Bruno, La cena de le ceneri, pp. 52, 91, 153-154 ,152, and 171, fn 73; The Galileo Project, Rice University, viewed 18 November 2005,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 43 or other stars, we would not be in a place very different from this’, Bruno wrote.7 Modern commentators still struggle to explain how as a Neoplatonist Bruno came to make the conceptual leap from the heliocentric but finite cosmos of Copernicus to his infinite cosmos full of a multiplicity of earth-like worlds.
The substantial body of literature on Bruno focuses on the legacy of natural magic in his Hermetic philosophy and will not be revisited in detail here.8 However, a leading critic of the Yates thesis, Robert Westman, has offered an explanation of how Bruno came to propose an infinite cosmos.9 He argues that the concept of sufficient reason constituted a crucial assumption governing the central concepts of Bruno’s philosophy:
For Bruno, the necessary truth that determines all existence is the infinitude of God. Thus, if there is a reason why some finite good should be, there is a still greater reason why an infinite good should be. If divinity exists in us, then there is no reason why it should not exist elsewhere, everywhere. The problem concerns the manner in which God’s infinitude determines the particular attributes of the universe.10
Westman argues that Bruno’s principle of sufficient reason led him to deduce from the narrowly Copernican premise that the earth does not have a fixed, central, privileged position in a heliocentric system the radical Brunonian conclusion that there are no privileged places in space at all. As Westman put it; ‘no limits, no centers, no entities
7 G Bruno, La cena de le ceneri, p. 90. Bruno also responded to the need for a completely new system of physics given a heliocentric cosmos. In La cena de le ceneri, he proposed that a natural, divine impulse within each body causes it to move so as to effect renewal and rebirth. Bruno considered the impetus for motion must come from inside a body; external impetus for motion would constitute undesirable violent motion. The earth moved with four motions: diurnal axial rotation, annually revolution around the sun and motions that account for the procession of the equinoxes and the inclination of the earth’s axis. Bruno proposed humans should seek divinity in things earthly, as the excerpt opening this Chapter demonstrates. G Bruno, La cena de le ceneri, p. 91 (quote) and pp. 155- 156, 208, 213-214, 219-221. 8 The pioneering work was undertaken in 1964 by Frances Yates, as previously cited. Yates subsequently stated that Bruno ‘shows what could be evolved out of an extension and intensification of the Hermetic impulse toward the world’. F A Yates ‘Giordano Bruno’, p. 451. 9 R S Westman ‘Magical reform and astronomical reform: the Yates thesis reconsidered’, pp. 5 – 91, especially pp. 20-32. 10 R S Westman, ‘Magical Reform and Astronomical Reform’, p. 25.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 44 more privileged than others by virtue of spatial location, no limit to the number of worlds God created.’11
I contend that an additional answer to how Bruno arrived at his particular, confronting conclusions rests in cosmography. Bruno also employed a cosmographic form of argument, in the mould of Copernicus, but with one crucial exception. He argued from a particular feature of the earth, its location (that is, its non–central, non–privileged position) to a view of the heavens (containing no centre and no privileged positions). Or, perhaps Bruno arrived at his proposition by slightly different path, applying his view of the earth’s position specifically to the sun, thereby conceiving of the sun as just one amongst many in an infinite cosmos. In both cases, we can recognise the style of argument as a cosmographical one with the same reversal of order used by Copernicus. However, Bruno’s mode of argument differs from Copernicus in one important respect. Whereas Copernicus ennobled the earth by treating it as a celestial body but left heaven untouched, Bruno corrupted the heavens by attributing features of the earth to them.
Bruno’s cosmological claim of a multiplicity of earth–like worlds also depends on the cosmographical style of argument, added to the principle of sufficient reason. We can understand Bruno’s generalisation of the characteristics of the earth to other, distant heavenly bodies as a cosmographical move in the Copernican style. Given this continuity of method, historians might temper the usual view of Bruno’s cosmology as radical, and constituting a discontinuous and substantial conceptual leap from Copernicus. Bruno praised Copernicus for concluding ‘this globe moves with respect to the universe’ but criticised him for not moving far enough away from the ‘vulgar philosophy’.12 Perhaps he was referring to Copernicus’s timidity with respect to further similarities between the earth and heavenly bodies. While the concepts in Bruno vary considerably from those of Copernicus, his method of argument was largely the same. Historians of science have overlooked Bruno’s cosmographic approach in their focus on the natural magical aspects of his program.
11 R S Westman, ‘Magical Reform and Astronomical Reform’, p. 26. It is on the basis of the strong role the principle of sufficient reason plays in Bruno’s infinist theory that Westman challenges Yates’ thesis about the significant influence of passages from Corpus Hermeticum on Bruno, see pp. 27-9. 12 G Bruno, La cena de le ceneri p. 87, 86
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 45 3. Gilbert and the cosmographic tradition
3.1 Recent approaches to Gilbert
If the puzzle for historians with Bruno is his radicalism, then the conundrum with Gilbert is his magnetism. Gilbert, an English physician, started to question Scholastic Aristotelianism in the late 1560s and develop his natural philosophy in the 1580s.13 In De Magnete Magneticisque Corporibus et de Magno Magnete Tellure Physiologio Nova (On the Loadstone and on the Great Magnet the Earth), published in 1600, Gilbert proposed a new system of nature wherein the ‘true’ core regions of the earth, other planets and the moon were composed of magnet, in its purest form.14 Magnet was the foundational material of the cosmos. It was animate and willing the earth and other planetary bodies to move. Regarding the cause of the earth’s axial motion, for example, Gilbert explained:
[W]ere the earth not to revolve with diurnal rotation, the sun would ever hang with its constant light over a given part, and, by long tarrying there, would scorch the earth reduce it to powder, and dissipate its substance, and the uppermost surface of the earth would receive grievous hurt…In all other parts there would be horror, and all things frozen with stiff and cold…And as the earth herself cannot endure so pitiable and so horrid a state of things on either side, with her astral magnetic mind she moves in a circle, to the end there may be, unceasing change of light, a perpetual vicissitude, heat and cold, rise and decline, day and night. So the earth seeks and seeks the sun again, turns from him, by her wondrous magnetical energy.15
13 S Pumfrey, Latitude and the magnetic earth, Icon Books, Cambridge, 2002, p. 18-19, 24. 14 Henceforth referred to as De Magnete. Also, I will consistently use the term ‘magnet’ as a synonym for lodestone. 15 W Gilbert, ‘On the lodestone’ (Hutchins) p. 112-113 (full reference at footnote 1). Gilbert’s views on the motions of the planets have been the subject of critical discussion amongst historians of science. The debate is partly due to the existence of imprecise and contradictory statements in De magnete,and
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 46 The proposition that magnets had an animate soul was founded on the unique and occult nature of the properties of a magnet and reflected Gilbert’s pre-existing Neoplatonic set of values and beliefs. Findings from numerous experiments stood as the evidence for the theory, premised on an alleged correlation between the behaviour of a small lathe- turned spherical magnet (a terrella) and the earth.16 From the nineteenth century through to the 1980s scholars saw Gilbert as a pioneer of experimentalism and a researcher of magnetism.17 More recently, historians of science have considered Gilbert as participant
the placement of these comments within other topic areas. This thesis proceeds from the view that Gilbert considered that all of the planets revolved around the sun, and that the earth and the other planets also rotated on their axes. That is, it shares the opinion of Pumfrey and Freudenthal, that Gilbert was a Copernican rather than an advocate of the modified Tychonic system. S Pumfrey, ‘Was Gilbert a Copernican?’, Paper presented to the Department of Science and Technology, Imperial College, London, undated. G Freudenthal, ‘Theory of matter and cosmology in William Gilbert’s De magnete’inIsis, Vol. 74, No. 1, March, 1983, pp. 22-37. Evidence in De magnete for this position includes: the statement by Gilbert that the earth rotated daily in the same direction as other planets, from west to east; the proposition that the moon rotated on its axis; and the imprecise comment ‘[t]hus each of the moving globes has circular motion, either in a great circular orbit or on its own axis or in both ways’. The following statement provides further grounds for this interpretation: ‘Wonderful is the loadstone shown in many experiments to be, and, as it were, animate… in all globes the effused forms reach out and are projected in a sphere all round, and have their own bounds – hence the order and regularity of all the motions and revolutions of the planets, and their circuits.’ Gilbert also explained the cause of the axial rotations of the planets: first, planets had an innate philanthropic desire to rotate, and second the total magnetic influence created by the magnetic nature of all heavenly bodies caused the axial rotations of the planets. The key claims of Gilbert and his statements on the motions of planetary bodies referred to above can be found in W Gilbert, ‘On the lodestone’ (Hutchins), pp. 23 – 25, 34, 43, 102-105, 106, 108-109, 111- 115, quotes from pages 113 and 104 respectively. For a useful exposition of the concept of the sphere of influence in Gilbert, see discussion in G Edmond, An Attraction for Copernicanism: Reclaiming Gilbert’s De Magnete (1600) For The New Historiography of Science, Thesis for a Bachelor of Arts (Honours), University of Wollongong, Australia, 1992, pp. 69 – 70, 72-73. 16 Four of the six books that constitute De Magnete were intended to be persuasive demonstrations of the earth’s magnetism on the basis that the earth partook in the basic magnetic motions proposed by Gilbert. The magnetic motions that supported the proposition of the earth’s magnetism were the tendency of magnet and iron to attract (Book II) and of a magnetic compass needle to show direction, variation and horizontal dip (Book II, III and IV). The tendency of a spherical magnet to rotate (Book V) was presented as confirmation of the earth’s capacity for motion rather than evidence of its magnetism. 17 Suzanne Kelly, for example, proposed that ‘the combination of a new theory supported by confirming evidence and demonstrations is a Pre-Baconian example of the new experimental philosophy which became popular in the 17th century.’ In this strand of the historiography, what interested historians was Gilbert’s contribution to contemporary thinking about electricity and magnetism (for example Benjamin and Heilbron) and his substantial program of experiment (Mottelay, Kelly, Harré and Zilsel). S Kelly, ‘William Gilbert’ in Charles Coulston Gillispie (ed) The Dictionary of Scientific Biography, vol. 5, Scribner, New York, 1972, pp. 396 – 401, quote p. 399. P Benjamin, A History of Electricity: From Antiquity to the Days of Benjamin Franklin, J. Wiley, New York, 1898 quoted in G Edmond, ‘An attraction for Copernicanism’, pp. 9-11; J L Heilbron, Elements of Early Modern Physics, University of California Press, Berkley, 1982 quoted in G Edmond, ‘An attraction for Copernicanism’, p. 13; R Harré, The Method of Science, Wykeham, London, 1970, quoted in G Edmond, ‘An attraction for Copernicanism’, p. 15-16.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 47 in the discipline of natural philosophy and thereby rendered a more coherent explanation of his program than previously achieved. Pumfrey, Schuster, and Edmond are among those who explore Gilbert’s cosmological beliefs and the discursive aspects of his natural philosophical claims.18 On the view of these latter historians, Gilbert sought to explain what caused the earth’s diurnal rotation, an unanswered question in natural philosophy raised as a result of Copernicus’s work. Indeed, Gilbert himself saw De magnete as a treatise in natural philosophy; a ‘physiologia’.19
While the recent literature provides an improved understanding of Gilbert’s overall aim, a question remains regarding Gilbert’s place in the Neoplatonic tradition. The matter arises in part from the considerable debate about the legacy of the tradition of natural magic instigated by Frances Yates’ analysis of Hermeticism, cited earlier. Yates argued that a new fifteenth century translation of the Corpus Hermeticum considerably hastened the rise of the Copernicanism by strengthening the drive to uncover the harmony of the cosmos, the symbolic significance of the sun, and the belief that the cosmos was full of powers that individuals could use.20 The belief that causality worked from ‘above to below’, from the heavens ‘down and in’ to the earth, constituted one of the key theoretical principles of natural magic, according to Copenhaver.21 However, Gilbert reversed the usual order of causality; the hierarchy of matter in De magnete favoured the centre of the earth and saw all matter being produced there. Typically, commentators attribute Gilbert’s focus on the magnet to the contemporary importance of understanding the earth’s magnetism for English navigation, exploration and trade interests. Pumfrey, for example, claims that the navigational experts and mathematical practioners inspired Gilbert (resulting in part
18 S Pumfrey, Latitude; S Pumfrey, ‘William Gilbert’ in Wilbur Applebaum (ed), Encyclopedia of the Scientific Revolution: from Copernicus to Newton, Garland Publishing, New York, 2000, pp. 266-268; G. Edmond, An attraction for Copernicanism; J. A. Schuster, ‘L’Aristotelismo e le sue Alternative’. 19 W Gilbert, ‘On the lodestone’ (Hutchins), p. 2. Gilbert also referred to discourse promoting a geocentric cosmos as within the discipline of ‘natural philosophy’, see p. 60. 20 FYates,Giorando Bruno and the Hermetic Tradition, and as noted by K. Hutchinson, ‘Magic and the Scientific Revolution’, p. 383. The Corpus Hermeticum is dated between the second to fourth century. 21 B P Copenhaver, ‘Natural magic, hermeticism, and occultism in early modern science’, p. 281. Easlea has suggested that Hermetic natural magicians had an ambivalent attitude to the earth, some seeing it as divine while others regarded it as corrupt. B. Easlea, Witchhunting, Magic and the New Philosophy, p. 94.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 48 from Gilbert’s involvement with the English navy).22 However, an important and enduring question for historians is why Gilbert looked to matter within the earth itself to explain the motions of the earth and other planets when many other Copernican Neoplatonists, such as Kepler, attributed causation for planetary motion to non-terrestrial explanations (forces emanating from the sun in the case of Kepler, for example).23 Notably, none of the recent scholarship examines Gilbert in the context of the tradition of cosmography.24 I argue here that placing Gilbert in the cosmographical tradition helps us understand how he came to challenge the sun- centred legacy of Neoplatonism and make the earth and its magnetism central to his theory of matter and causation.
3.2 England and the tradition of cosmography
Gilbert, an avid consumer of geographical and navigational literature, was aware of the long–running debate about the structure of the earth that preceded him, as De magnete attests. Gilbert referred there to the opinion held by ‘vulgar philosophers’ that there is ten times as much water as there is land, for example.25 Moreover, Gilbert was familiar with the work of key contributors, both Medieval and Renaissance, to the debate about the structure of the earth. He refers to Albertus Magnus, one of the few Medieval Aristotelian commentators to argue that the spheres of the concentric elements may not
22 S Pumfrey, Latitude, pp.23-24. 23 While this is a leading question in scholarship on Gilbert I do not wish to suggest is the only matter subject to critical discussion. Historians of science are also considering: why Gilbert refrained from overtly stating his beliefs about the earth’s annual rotation; the authorship of sections of De Magnete; and why Gilbert proposed that natural philosophy could only progress through new observations revealed through experiment (an approach historians consider avant-garde approach for 1600). 24 Neither the field of cosmography nor geognosic opinion are considered by Pumfrey, Edmond, Freudenthal, Schuster or Henry. S Pumfrey, Latitude; S Pumfrey, ‘William Gilbert’; G Edmond, An attraction for Copernicanism; J A Schuster, ‘L’Aristotelismo e le sue Alternative’; G Freudenthal, ‘Theory of matter and cosmology in William Gilbert’s De magnete’, J Henry, ‘Animism and empiricism: Copernican physics and the origins of William Gilbert’s Experimental Method’ in Journal of the History of Ideas, Vol. 62, No. 1. January 2001, pp. 99-119. For instance, Pumfrey states that ‘Gilbert believed the ideal shape was a sphere, because the Earth was spherical’ but overlooks the diversity of opinion concerning the shape of the earth that persisted into the mid-late sixteenth century. S Pumfrey, Latitude, p. 34-35. 25 W Gilbert, ‘On the lodestone’ (Hutchins), p. 23.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 49 in fact be real.26 Gilbert also knew of the work of the sixteenth century Portuguese mathematician Pedro Nunes and French physician and lecturer Jean Fernal, both advocates of a terraqueous globe (as described in Chapter One).27 So Gilbert knew of the recent state of controversy surrounding the structure of the earth, and that scholastics had difficulties squaring their natural philosophy with geognosic opinion, and probably approached his Copernican program with this in mind.
In addition, Gilbert was aware that the terraqueous globe appeared during the mid to late sixteenth century in certain, influential Aristotelian treatises in both Europe and England. By the closing decades of the sixteenth century, English natural philosophers such as Gilbert must have understood that the Jesuits in Rome had incorporated the terraqueous globe into their theories, through exposure to Clavius’s commentary on The Sphere of Sacrobosco. As described in Chapter One, the lengthy explication of the earth in the commentary by Clavius represented a formal Aristotelian adoption of the terraqueous globe. While universities in England did not use the commentary as a textbook until the beginning of the seventeenth century, the work of Feingold suggests that Gilbert knew of Clavius’s work through his association with William Gent, before De magnete.28 Furthermore, English natural philosophers of Gilbert’s generation were exposed to presentations of scholastic Aristotelianism that incorporated the terraqueous globe. For instance, the Castle of
26 W Gilbert, ‘On the lodestone’ (Hutchins), pp. 6, 13 and 58. 27 Gilbert refers directly to Fernal in De Magnete, W Gilbert, ‘On the lodestone’ (Hutchins), p. 5 while Pumfrey argues for Gilbert’s awareness of the work of Nunes, S Pumfrey, Latitude, p.68. 28 Feingold examined the contents of the personal libraries of Cambridge scholars during Gilbert’s era in his renowned analysis of university instruction in England from 1560–1640. Feingold found that the personal book collection of William Gent (a member of Gloucester Hall from the 1580s and who belonged to a circle that included Gilbert) included a copy of the work of Clavius. Feingold argues convincingly that the networks among the educated elite with an interest science were strong, suggesting the commonplace exchange of seminal works such as that by Clavius. Gent donated this among 400 other works to help found the Bodleian Library in 1600. M Feingold, The Mathematicians' Apprenticeship: Science, Universities and Society in England, 1560-1640, Cambridge, Cambridge University Press, 1984, p. 118, 215.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 50 Knowledge by Robert Recorde presented the earth and water together as one sphere in the 1556 edition.29 Recorde wrote:
Under which the foure elementes succede: first the fier, then the ayer, nexte foloweth the water: which with the earth…Ioyntile annexed, maketh as it were, one sphere only.30
Recorde also asserted the shape of the earth was ‘round exactly like a ball’ and presented illustrations of the earth and water co-joined in one sphere (Figure 2.1).31 According to Feingold, The Castle of Knowledge was one of the main elementary textbooks in use in England from 1560 until the early seventeenth century.32
29 R Record, The Castle of Knowledge, imprinted at London by Reginalde Wolfe, 1556. Early English Books Online, Cambridge University Library, viewed 21 October 2004,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 51 Figure 2.1: ‘An example of the Paralleles in earth agreeably to the Paralleles in the Skye’, in Robert Record, The Castle of Knowledge33
33 R Record, The Castle of Knowledge, p, 62. There are two interesting points to note about this illustration. First, it appears the earth is represented ‘up-side-down’. The large landmass in the northern hemisphere appears to be depicted at the bottom of the diagram, as suggested by the labelling of the water and land (on the basis that the labels apply to the particular parts of the illustration on which they are placed, rather than the more unlikely interpretation that the labels were intended to be read as one phrase). Also, the order of the ‘paralleles’ in the sky is the reverse of what we would now attribute to the parallels on earth, but consistent with the interpretation of the landmass in the northern hemisphere being represented at the bottom of the earth. The reason for this may relate to the diagram attempting to depict correspondences between the celestial and terrestrial realms. Second, the labelling of the parallels is uncommon in Aristotelian illustrations of the cosmos and is particularly informative, for the following reason. In many Aristotelian representations of the cosmos it is not clear whether the illustration was conceived as a side-on representation of the cosmos and earth (i.e. the viewing point is parallel to the equator of the earth) or a ‘top down’ representation (i.e. from above the north pole). The issue of the viewing point is particularly important for interpreting representations of the earth in early modern Aristotelian diagrams. The parallels in this illustration suggest that the cosmos was typically depicted from side-on. This coincides with the viewing point I believe historians of science have implicitly assumed for such illustrations. However, as far as I am aware, the question has not been the subject of detailed inquiry and constitutes a valuable area of further research.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 52 Other examples can be offered, such as Thomas Digges’s 1576 new, amended edition of his father’s treatise on Ptolemaic cosmology, wherein terrestrial region is said to consist of: ‘first Earth and Water whereon we are, then Air and Fire’.34 The accompanying illustration also depicts the elements of earth and water jointly contained in one circle (Figure 2.2). Digges’s treatise went into seven editions between 1576 and 1605 and was well known to natural philosophers (as discussed in the following section).35 Thus, when Gilbert was developing his magnetic theory during the 1580s, he was not only aware of the past controversy about the structure of the earth in Aristotelian theory, but also that certain recent and influential Aristotelian texts, both English and European, had adopted the terraqueous globe into their cosmography. To explore how Gilbert might have interpreted the significance of these shifts in geognosic opinion for Copernican natural philosophy, we need to consider how Gilbert and his contemporaries came to know of, and viewed, the work of Copernicus.
34 L Digges published in T Digges A prognostication euerlastinge of right good … Published by Leonard Digges Gentleman. Lately corrected and augmented by Thomas Digges his sonne…. Imprinted by Thomas Marsh, London, 1576, Folio 17. Early English Books Online, Cambridge University Library, viewed 21 October 2004,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 53 Figure 2.2: Image of the Aristotelian ordering of the cosmos, 36 published in Thomas Digges’ A prognostication euerlastinge of right good effecte 1576
36 T Digges, A prognostication euerlastinge of right good effecte, folio 4.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 54 3.3 English interpretations of Copernicus
Copernicus’s conceptualisation of the earth as a terraqueous globe was amongst the first ideas of Copernicus available to readers, when his work was introduced to England in the 1570s. The educated elite in England first came to know of the ideas of Copernicus through the 1576 treatise by Thomas Digges, mentioned previously.37 While the treatise did not include the relevant chapter of De Revolutionibus (Chapter Three, Book One), it did present Copernicus’s concept of a terraqueous globe by including an analogy used by Copernicus; that the air is joined to the earth just as the oceans are attached to the earth.38 That Digges did not incorporate Copernicus’s lengthy argument for a
37 J Russell, ‘The Copernican system in Great Britain’, p. 193-194. N Copernicus, selected chapters of De Revolutionibus (Book One, chapters seven, eight and ten) published as ‘The Addition’ in T Digges A prognostication euerlastinge of right good … Published by Leonard Digges Gentleman. Lately corrected and augmented by Thomas Digges his sonne…. Imprinted by Thomas Marsh, London, 1576, Folio 17. Early English Books Online, Cambridge University Library, viewed 21 October 2004,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 55 terraqueous globe supports the view that the concept of a terraqueous globe was no longer fundamentally controversial when the treatise was published in 1576.
Copernicus’s novel form of cosmographic argument was also evident in the work published by Digges. The treatise included Chapter Eight of Book One, which contained the specific section of text, previously cited from De Revolutionibus,inwhich Copernicus linked the earth’s shape with the possibility of its circular motion:
Wihye dwe we yet stagger to confesse motion in the Earth beinge most agreeable to hys forme and nature, whose bounes also and circumference wee knowe, rather then to imagine that the whole world should sway and turne, whose ende we know not, be possibly can of any mortall man be knowne.39
The cosmographic line of reasoning is clearly set out to readers: the sphericity of the earth allows the possibility of its circular motion, and, as the universe’s shape is not and cannot be known, the earth’s motion is more probable than that of the primum mobile. Thus, while English natural philosophers were forming their theories in the late sixteenth century, they had an opportunity to understand Copernicus’s form of cosmographic argument and that the concept of the earth as a terraqueous globe played a central role in this argument.
The three chapters of De Revolutionibus in the treatise—chapters seven, eight and ten—were presented in the following order: ten, seven and eight. Chapter ten presented Copernicus’ ordering of the heavenly spheres. Chapter seven contained Copernicus’ summary of Aristotle’s reasons for considering the earth to be immobile at the centre of the cosmos and chapter eight refuted these traditional arguments against the earth’s movement and presented arguments for its mobility. The effect of the selection and ordering of the chapters is a brief presentation of the key elements of Copernicus’ theory. Copernicus argued for the attachment of the air to the earth to answer the contemporary question of whether the air moves together with the earth as it spins on its axis. Detractors of Copernicanism argued that, if the earth moved, a considerable wind would be experienced on the earth as it moved through the immobile sphere of element air. Similarly, birds should be seen flying backwards. They presented both matters as arguments against the earth’s motion. Like Copernicus, many Copernicans refuted this argument by asserting that the air moved with the earth and many made their case by analogy to the attachment of the water to the earth. This is further evidence for the view that the concept of co-joined earth and water was largely accepted but still a matter of some interest at this time. 39 N Copernicus, published as ‘The Addition’, in L Digges, A prognostication euerlastinge of right good effecte, (no page numbers).
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 56 3.4 Cosmography in Gilbert
Gilbert actively engaged in cosmography. He sought to paint a unified picture of the heavens and earth by relating the magnetic nature of the earth with its motions as well as the motions of all other planets in the cosmos. In other words, he staked his cosmological views on a certain view of the earth.40
Most fundamentally, Gilbert conceived of the earth as a terraqueous globe. In De Magnete he wrote: ‘[t]he terrestrial mass which together with the world of waters produces the spherical figure and our globe.’41 The conceptualisation of the earth as a terraqueous globe plays two roles in the magnetic philosophy. First and foremost, Gilbert’s arguments for direction, variation and dip are founded on a terraqueous globe. These ‘magnetic motions’—the tendency of a compass needle to point north as well as on occasion deflect away from the closest pole and dip below the horizon—were fundamental to Gilbert’s argument as they demonstrated that the earth was primarily magnet. A scan of the illustrations accompanying Gilbert’s theory suggests this was the case in showing mountains rising out of the sea and an island (see Figure 2.3). The inability to translate the explanations of the magnetic motions to the floating apple model of the earth provides further demonstration (see Appendix A). Second, Gilbert employed the sphericity of the earth as an argument for its revolution:
[N]ature would seem to have given a motion quite in harmony with the shape of the earth, for the earth being a globe, it is far easier and more fitting that it should revolve on its natural poles, than the whole universe, whose bounds we know not nor can know, should be whirled around.42
40 The magnetic motions relevant to the earth’s magnetic nature were: the tendency of a magnet and iron to attract (coition, Book II) and of a compass needle to show direction, show displacement from the closest pole, and to ‘dip’ below the horizon (verticity, Book III; variation Book IV; and declination, Book IV). 41 W Gilbert, ‘On the lodestone’ (Hutchins), p. 23. For further evidence in the text of Gilbert’s assumption of a terraqueous conceptualisation of the globe, see the earlier discussion about Gilbert’s use of the attachment of the water to land as an analogy for the relationship between the terraqueous globe and air. 42 W Gilbert, ‘On the lodestone’ (Hutchins), p. 110.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 57 Hooper has noted that ‘Gilbert’s language remained very close to Copernicus’s text when he spoke of the larger structure of the world system.’43 Indeed, in the passage just cited, Gilbert restates Copernicus’s proposition; that the motion of the earth is more probable than that of the primum mobile as the shape of the earth is known and spherical, while the shape of the universe is not and cannot be known. The case of Gilbert suggests that the sphericity of the terraqueous globe constituted a premise of all realist Copernican natural philosophies, and perhaps a resource that strengthened their position versus the Scholastics.
Figure 2.3: Gilbert’s diagram for variation44
Be that as it may, Gilbert’s and Copernicus’s treatment of the concept of the terraqueous globe differed in one important respect. Unlike Copernicus, Gilbert did not include lengthy arguments for the earth and water together forming one sphere in De magnete. Rather, he refuted the specific, contemporary claim of certain Aristotelians that the sphericity of the terraqueous earth is marred by the elevation of mountains and the depressions of valleys and seas, and therefore does not provide a basis for the earth’s
43 W Hooper, ‘Seventeenth-Century theories of the tides as a gauge of scientific change’ in C R Palmerino and J M M H Thijssen (eds) The Reception of the Galilean Science of Motion in Seventeenth-Century Europe, Kluwer Academic Publishers, Dordrecht, 2004, p. 212. 44 W Gilbert, ‘On the lodestone’ (Hutchins), p. 80. Gilbert states in the accompanying text that mountains generally rise out of the sea beds and identifies point D as an island, confirming the compass points are meant to illustrate that they are taken at sea.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 58 circular motion. Regarding the seas, for example, Gilbert argued that ‘in view of the earth’s dimensions, such depressions cannot much impair the spheroidal shape of the earth’.45 Gilbert did not consider it necessary to make a case for the idea of a terraqueous globe in order that geognosic opinion align with his natural philosophy, probably because few now disputed the terraqueous concept of the earth (as described earlier in this Chapter). Thus, the sphericity of the earth functioned as auxiliary evidence for the magnetic philosophy, not central evidence as was the case in De revolutionibus.
For Gilbert’s generation, the cosmographical debate had shifted from the shape of the earth to characteristics of a terraqueous globe. In his cosmographic undertaking, Gilbert presented arguments both about the earth’s solidity and weight. First, the depth of the oceans stands out as a major topic in the treatise. Gilbert wrote:
[T]he seas do not but fill certain not very deep hollows, having rarely a depth of a mile, and often not exceeding 100 or 50 fathoms. This appears from the observations of navigators who have with line and sinker explored their bottoms. In view of the earth’s dimension, such depressions cannot much impair the spheroidal shape of the globe.46
Gilbert demoted the importance and impact of water on the terraqueous globe in order to construct the terraqueous globe as a predominantly solid body. He asserted:
The solid mass of earth has the greater volume and holds preeminence in the constitution of our globe. Yet the water is associated with it, though only as something supplementary…the strong foundation of the globe, its great mass, is that terrene body, far surpassing in quantity the whole aggregate of fluids and waters whether in combination with the earth or free, whatever the vulgar philosophers may dream about the magnitudes and proportions of their elements);
45 W Gilbert, ‘On the lodestone’ (Hutchins), p. 114 -115. 46 W Gilbert, ‘On the lodestone’ (Hutchins), p. 23.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 59 and this mass makes up most of the globe, constituting nearly its whole interior framework and of itself taking on a spherical form.47
Gilbert placed this argument for the earth’s solidity immediately prior to his case for magnet (in its purest form) constituting the earth’s core. A largely solid earth constituted a key premise of the analogy between the terrella and the earth and relatedly, the ubiquitous and substantial potency of magnet.
A further cosmographic concern in Gilbert was the earth’s weight. Gilbert proposed the earth as a whole had no weight, defined as the ‘tendence [of the earth] to its centre’, on the basis that parts of the earth had no weight when resting on the earth’s solid surface.48 The mountains and other protuberances had no impact on the earth’s weightlessness, as they too are weightless.49 However, even if protuberances such as mountains did have weight, Gilbert hedged, they would not hinder for the earth’s diurnal revolution as mountains are spread uniformly around the earth’s spherical surface.50 Gilbert addressed the weight of the earth because Aristotelians at the time argued that the heaviness of the earth, as determined by Aristotelian laws of terrestrial physics, precluded its motion. Gilbert asserted:
Thus the whole globe, having a natural axis, is balanced and in equilibrium and is set in motion easily by the slightest cause, but chiefly for the reason that the earth, in its own place, is in no wise heavy nor needs any balancing. Hence no weight hinders the diurnal revolution, and no weight gives to the earth direction or continuance in its place.51
47 W Gilbert, ‘On the lodestone’ (Hutchins), p. 23. The statement about the ‘vulgar philosophers’ refers to those who clung to the ten to one ratio of water to land. Gilbert’s case here is interesting in that he argues for a smaller volume of water irrespective of the specific concept of the arrangement of the earth and water. The statement ‘whether in combination with the earth or free’ could refer to the floating apple model or Aristotelian arguments about the combination (or otherwise) of elements of water and earth. 48 W Gilbert, ‘On the lodestone’ (Hutchins), p. 115, see also 116. 49 Gilbert conceived mountains as constituting ‘parts in union’ with the earth, which he deemed to be also at rest. 50 W Gilbert, ‘On the lodestone’ (Hutchins), p 116. 51 W Gilbert, ‘On the lodestone’ (Hutchins), p. 116.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 60 A balanced, weightless terraqueous globe was necessary for a Copernican moving earth, but independent of Gilbert’s specific proposition of the magnetic nature of the earth that ultimately provides the cause of its rotation. These attempts to reconcile certain aspects of geognosic opinion with the magnetic philosophy demonstrate Gilbert’s concern with providing within one explanatory system for the heavens and earth and their relation. In other words, Gilbert sought to square his geognosic theory with Copernican astronomy.
Gilbert’s involvement with cosmography extended to his form of argument. His explanation of the movement of the planets, his celestial physics, derived from his extension of the earth’s magnetic character to that of heavenly bodies. This Copernican style of cosmographic argument was more radical than Copernicus and more in the style of Bruno. Thus, Gilbert engaged in cosmography, not just by relating the heavens and earth in his magnetic philosophy, but also by utilising a cosmographic form of argument in a Copernican–Brunonian style.
Historians of science have overlooked both aspects of Gilbert’s involvement in cosmography. They generally recognise that the magnetic nature of the earth was the main focus of De Magnete. Indeed, it is not novel to observe that Books Two to Four were intended to be persuasive demonstrations of the earth’s magnetism on the basis that the earth partook in the ‘magnetic motions’. Yet, while modern commentators have traditionally examined Gilbert’s articulation of the magnetic earth, they have largely overlooked his theory of the structure of the earth. For example, historians have little noted Gilbert’s involvement with the topic of the proportions of water and land, although this fundamental geognosic matter had been the subject of debate since as early as the fourteenth century. It is also now commonplace that Gilbert derived his account of the motions of the earth and planets from his claim that the earth is a magnet.52 However, Gilbertian scholars have not identified this form of argument as cosmographic. Historiographical puzzles persist regarding the approach and rhetoric of Gilbert’s magnetic philosophy, and the cosmographic perspective has much to offer.
52 For example, J A Schuster, ‘L’Aristotelismo e le sue Alternative’, p. 340-341.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 61 3.5 Implications for historiography
I contend that understanding the place cosmography occupied in Gilbert greatly improves our comprehension of his work. As noted earlier, commentators are yet to answer how Gilbert came to reverse the customary Neoplatonic order of causality that worked from the heavens ‘down and in’ to the earth. Placing his work in a cosmographical context helps explain his radical approach, for a Neoplatonist. We can understand Gilbert’s approach to causality as the result of his employment of the Copernican mode of cosmographic argument in the service of his particular Neoplatonic worldview. Put another way, Gilbert applied his evident knowledge of Copernicus’s cosmographic form of argument, recently utilised and modified by Bruno. We might even question the interpretation of Gilbert’s magnetic philosophy as radical, given natural philosophy’s long-standing engagement with cosmography and Copernicus’s earlier utilisation and modification of cosmography.
Placing Gilbert in the cosmographical tradition also helps us to understand the rhetoric of De magnete. Recent commentators like Edmond challenge literalist readings of Gilbert’s work, arguing that his claims of ‘experimentalism’ can be viewed as carefully constructed rhetoric. That is, the discursive aspects of De magnete should be understood as claims being built and others refuted to create a persuasive argument for the magnetic philosophy.53 Gilbert frequently asserted that the answers to natural philosophical matters are best found in earthly phenomena. He also, often abrasively, criticised scholastics for searching for answers in the heavens:
So has ever been the wont of mankind: homely things are vile; things from abroad and afar are dear to them and the object of longing.54
We can understand this discourse as Gilbert choosing to make his argument explicit.
53 G Edmond, ‘An attraction for Copernicanism’, pp. 25 - 42. 54 W Gilbert, ‘On the lodestone’ (Hutchins), p. 61.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 62 Next, placing Gilbert in a cosmographical context improves our understanding of how Gilbert may have sourced many of his concepts and methods from the thirteenth century work Epistola de Magnete by Petrus Peregrinus.55 Peregrinus proposed that the (rotating) heavenly spheres were magnetic and provided magnets on earth with their magnetic powers. This particular cosmographic explanation of the origin of magnets contrasted with other contemporary explanations that proposed magnets received their properties from the Pole star or from the location at which they were found. The chief grounds for Peregrinus claim was that a magnet on earth ‘bears in itself the similitude of the heavens’, and he described a number of experiments on small spherical magnets to prove this claim.56 For example, Peregrinus maintained that a spherical magnet lightly suspended on pivots would rotate in unison with the poles of the heavens.57 According to Mottelay, as far back as the seventeenth century historians have debated the influence of Epistola de Magnete on Gilbert.58 Most recently, Pumfrey has argued that Gilbert inverted Peregrinus’s central ideas about the heavens and applied them to the earth to arrive at his magnetic philosophy.59 Pumfrey proposes that such a tactic would only appeal to a Copernican but he fails to address how a Copernican might come to consider
55 P Perigrinus, Epistle of Peter Perigrinus of Maricourt to Sygerus of Foncacourt, soldier, concerning the magnet, 1249, reprinted by Charles Whittingham and Company, Chiswick Press, 1902. 56 P Perigrinus, Epistle of Peter Perigrinus of Maricourt,chapterIV. 57 So confident was Peregrinus in the accurate conferral of heavenly motion to the magnet in this experiment, he claimed: ‘you will be relieved from every kind of clock, for by it you will be able to know the Ascendant at whatever hour you wish and all the other dispositions of the heavens which Astrologers seek after.’ P Perigrinus, Epistle of Peter Perigrinus of Maricourt, quote from chapter X. His key claims, referred to here, are articulated in chapters II, IV, IX and X. 58 P F Mottelay, trans. De magnete, by W Gilbert, Dover Publications, New York, 1958, fn 1, p. 166. 59 Pumfrey highlights the conceptual and methodological similarities between the two works. Gilbert scholars will know that the tendency of a suspended magnet to rotate of its own accord is one of Gilbert’s most important claimed experimental findings. Indeed, Gilbert acknowledged the experiment is that of Peregrinus, but claims it cannot work effectively on earth. S Pumfrey, Latitude, pp. 57, 101- 102. Nevertheless, there are some crucial differences between the claims of the two theories and Pumfrey’s proposition of a mere inversion requires some modification. Certainly, the claim by Gilbert that earth is magnetic can be understood as an inversion of Peregrinus’ proposition that the heavens were magnetic. Further, Gilbert’s claim that magnets gain their magnetic nature from, and move in correspondence with, the earth can be seen as an inversion of the proposition by Peregrinus that magnets gain their magnetic nature and move in sympathy with the heavens. However, Peregrinus did not claim the heaven’s magnetic nature caused the heavens to spin, nor that the heavens had a magnetic soul. An improved interpretation, then, is that Gilbert adopted, inverted and considerably augmented the central claims of Peregrinus in a way that served his broader natural philosophical agenda.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 63 using this method. Certainly, Gilbert appears to have inverted and considerably augmented the central claims of Peregrinus. However, it was the cosmographic direction of inference that Gilbert reversed and perhaps he conceived of doing so because it was already an established strategy amongst Copernicans.
Finally, understanding Gilbert’s utilisation of cosmography offers valuable insights into geognosic opinion in late sixteenth century England, following the general acceptance of a terraqueous globe. That Gilbert argued for the shallowness of the oceans and the weightlessness of the earth suggests these characteristics of the terraqueous globe were open to some interpretation during this time. So, while the educated elite increasingly accepted the concept of the terraqueous globe, certain key characteristics of the terraqueous globe (such as the significance of mountains) had not yet been settled during Gilbert’s time. Historians of science interested in the early modern period could usefully inquire further into contemporary geognosic opinion.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 64 Chapter Three Cosmography and natural philosophy in the early–mid seventeenth century
I hope that from these considerations the world will come to know that if other nations have navigated more, we have not theorized less.
Galileo Galilei ‘To the Discerning Reader’ in the Dialogo1
Sagredo: I am much astonished that among men of sublime intellect, of whom there have been plenty, none have been struck by the incompatibility between the reciprocating motion of the contained waters and the immobility of the containing vessel, a contradiction which now seems so obvious to me.
Galileo Galilei Dialogo2
1 G Galilei, ‘To the Discerning Reader’, in Dialogo sopra i due massimi sistemi del mondo, Tolemaico e Copernicano, 1632, published in A Einstein (ed) S Drake (trans), Dialogue Concerning the Two Chief World Systems – Ptolemaic & Copernican, second edition, University of California Press, Berkeley, 1967, p. 6 and p. 461. Herewith the entire work shall be cited as G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 6. 2 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 461.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 65 1. Introduction
In the previous chapter, I explored how Copernicans built on the cosmographical tradition and, in the case of Gilbert, developed a theory of the earth’s composition, structure and motions. In this final chapter, I will look at the first generations of the seventeenth century. The analysis will concentrate on two of the most important Copernicans and innovators in natural philosophy—Galileo and Descartes—and reveal that they were involved in the same cosmographic project we have been studying, albeit in different ways.
This chapter focuses on Galileo’s theory of the tides, as presented in the 1632 in Dialogo sopra i due massimi sistemi del mondo, Tolemaico e Copernicano (Dialogue Concerning the Two Chief World Systems – Ptolemaic & Copernican), and certain terrestrial aspects of Descartes’ Le Monde, ou Traité de la lumiere (The World, or a Treatise on Light) and Principia Philosophiae (Principles of Philosophy), completed in 1633 and 1644 respectively. In each case, I look how each text deals with the relation between the heavens and earth.
I find that the tradition of cosmography was a central concern for Galileo and Descartes. Both attempted to provide a unified picture of the heavens and earth. I also argue that understanding cosmography helps us answer several hitherto unanswered questions in the literature, such as why Galileo took such pride in his theory of the tides and the origin of Descartes’ extensive explanation of the earth.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 66 2. Galileo and the cosmographic tradition
2.1 Recent approaches to Galileo’s theory of the tides
In 1597 Galileo wrote to Johannes Kepler that he had ‘discovered the causes of many physical effects which are perhaps inexplicable on the common hypothesis’.3 Most modern historiography derives largely from Kepler’s wily construal of Galileo’s statement as referring principally to the tides.4 Indeed, Galileo began developing his ideas on the tides about 1595.5 By the time Galileo wrote Cardinal Orsini in 1616, in which he first put his ideas on the tides down on paper, he had developed the core framework of his tidal argument.6 However, Galileo considered his complete theory of the tides to be the version presented in the Dialogo, printed in 1632.7
3 G Galilei, quoted in S. Drake, Galileo at Work. His Scientific Biography. The University of Chicago Press, Chicago, 1981 edition, p. 41. 4 See,forexample,S.Drake,p.41. 5 W Hooper, ‘Seventeenth-Century theories of the tides as a gauge of scientific change’,; S. Drake, Galileo at Work, pp. 36-37; R Naylor, ‘Galileo, Copernicanism and the origins of the new science of motion’, British Journal for the History of Science, vol. 36, 2003, pp. 151-181, p. 168. For a detailed case for this view, see S. Drake, ‘Galileo’s theory of the tides’ in Galileo Studies: Personality, Tradition and Revolution, University of Michigan Press, Ann Arbor, 1970, pp. 200-213. 6 G Galilei, ‘Discourse on the Tides’, 1616, in M A Finocchiaro (ed and trans) The Galileo Affair. A Documentary History, University of California Press, Berkeley, 1989, pp.119-133. The Discourse contained the core elements of the theory of the tides as published in 1632 in the Dialogo, although Galileo made more circumspect claims about particular tidal effects in the later work. In addition, a considerable proportion of the text in Discourse appears to be reproduced in Dialogo almost verbatim, for example, Galileo’s explanation of the absence of tides in the Red Sea. 7 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition. Westman has usefully shown that, despite suppression by the Catholic Church, the Dialogo was widely circulated at the time to state officials, physicians, academics and men of the Church in France and northern Italy. R S Westman, ‘The reception of Galileo’s “Dialogo”. A partial world census of extant copies’ in Novità Celesti e Crisi del Sapere. Atti del Convegno Internazionale di Studi Galileiani,P. Galluzzi (curator), Supplemento agli Annali dell’Istituto e Museo di Sotria della Scienza, Monografia 7, Istituto e Museo di Sotria della Scienza, Firenze,1983.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 67 Galileo claimed that the tides are caused by the combined effect of the earth’s axial and annual motions. Their existence, he asserted, therefore proves that the earth moves with these two motions (at least).8 Moreover, his account of the tides refuted not just the geocentrist view of the earth’s immobility but also the notion, proposed by advocates of the modified Tychonic system and others, that the earth moves solely with axial rotation.9 In terms of the Dialogo as a whole, Galileo’s theory of the tides stood as one component in a tryptich of evidence for the earth’s motions:
[T]he discussions of these four days provide strong indications in favor of the Copernican system. Among them, three appear to be very convincing: first, the one taken from the stoppings and retrogressions of the planets and their approaching and receding from the earth; second, the one from the sun’s rotation on itself and from what is observed from its spots; and third, the one from the ebb and flow of the sea.10
Crucially, the ebb and flow of the tides was the only proof of the Copernican view derived from the earth.
Historians disagree widely on how to interpret the aim of ‘argument three’ in the Dialogo. However, they generally agree that Galileo’s theory of the tides has problems and hence cannot understand why Galileo took such pride in the theory. Koyré has argued that Galileo sought to transform the philosophical base of physics.11 Galileo’s Dialogo,he
8 G Galilei, Galileo on the World Systems, M. A. Finocchiaro, p. 293. 9 Galileo makes this position clear in the Dialogo, as shown in the following quote, where Salviati wonders how educated men: ‘did not notice that a simple and uniform motion, such as the simple diurnal motion of the terrestrial globe for instance, does not suffice, and that an uneven motion is required, now accelerated and now retarded. For if the motion of the vessels were uniform, the contained water would become habituated to it and would never make any mutations.’ G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 461-462. 10 G Galilei, Galileo on the World Systems, M A Finocchiaro (trans and ed), pp. 304-305. Salviati remarks here that other evidence for the Copernican case could be added in the near future, such as the annual parallax of the fixed stars that Copernicus assumed to be imperceptible. 11 A Koyré, Galileo Studies, The Harvester Press, Sussex, 1978, p. 201-209.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 68 maintained, was more about the role and value of mathematics in the formation of scientific knowledge than the ‘merits of the two astronomical systems.’12 Consistent with Koyré’s interpretation, Shea has proposed that Galileo intended to establish a science wherein the unifying structure of reality could be solely understood by means of a mathematical method.13 Feyerabend has argued that Galileo was seeking to install a new concept of motion. His aim was to replace the well-entrenched conceptual system of motion (built around the category of natural motion as an absolute, goal-directed process for both celestial and terrestrial cases), with a system constructed around the relativity of motion, geometrically described.14 Pitt offers yet another view, claiming that Galileo’s sole aim was to provide a credible theory of the tides and that ‘Galileo became a Copernican because the Copernican theory supported his solution to the tides.’15 Recently, historians like Finocchiaro, Wallace and Naylor have noted that Galileo intended his tidal
12 A Koyré Galileo Studies, p. 201. He states: ‘The question of greatest consequence under discussion throughout the Dialogue and underlying every step in its argument, a question of far greater importance than the of the merits of the two astronomical systems under consideration, which after all was of limited significance, was that of the respective merits of two philosophies. For the resolution of the astronomical problem depends on the constitution of a physical science; and this in its turn presupposes the prerequisite resolution of the philosophical problem of the nature and structure of this science. In practice, this amounts to understanding the role of be played by mathematics in the constitution of scientific knowledge of the real world.’ Koyré proposed that Galileo was playing into a long-running debate between Platonists, such as Galileo, who saw mathematics as having a real value and hence should hold a leading position in physics on the one hand, and Aristotelians who considered ‘science’ should be based on experience, on the other. According to Koyré, the latter gave mathematics a lower value because they believed science could not be based on mathematics ‘because physical reality itself, which is qualitative and indefinite, does not conform to the rigor of mathematical concepts’. A. Koyré Galileo Studies, p. 201- 202. 13 W R J Shea, ‘Galileo’s Claim to Fame: The Proof that the Earth moves from the evidence of the Tides’ in the The British Journal for the History of Science, Vol 5, no 18, 1970, p111-127. Shea argues that: ‘Galileo’s discussion of the tides fails to make sense if we forget that he was more than a physicist. He was a natural philosopher who saw beyond the problem of determining the periods of the tides, about which he did not feel strongly, to the great vision of a science in which the real is described by the ideal, the physical by the mathematical, matter by mind. Shea also provides a useful contrast between the precursor-view and contextual approach to history of science’ pp. 111, 118. 126, 123-4, quote p. 126. 14 P Feyerabend, Against Method, revised edition, Verso, London, 1988, pp. 71-72. Feyerabend asserts that the successful introduction of this new, more speculative kind of experience by Galileo was one way in which opinion shifted away from a geostatic cosmos and towards a heliocentric one. 15 J C Pitt ‘Galileo, Copernicus and the Tides’, Theoria et Historia Scientiarium, Vol. 1, 1991, p. 94.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 69 theory to be a proof of the earth’s dual motions and thus argued against the Tychonic system.16
Many of these and other historians regard Galileo’s account of the tides as intellectually flawed for a range of reasons. For Shea, the shortcomings of the theory lie chiefly in its limited explanatory power: Galileo neglected to take account of all four commonly recognised periods of the tides and ignored discrepancies between the theory and ‘experience’.17 Shea maintains these are all matters of which Galileo would have been aware. Pitt, on the other hand, criticised the logic of the tidal argument on the basis of its reliance on both primary and secondary causes of the tides. In his view, the theory of the tides ‘is a fairly weak defense of Copernicus’ because Galileo does not link the composite motion of the earth and real tidal phenomenon using only one causal step.18 A great deal of the recent condemnation of the tidal theory has centred on Galileo’s aggregation of the two motions of the earth, with historians suggesting the argument is inconsistent with Newtonian physics. The three-year interchange in Isis between Harold Burstyn and EJ Aiton is a renowned example. Burstyn considered Galileo offered ‘good evidence for the motion of the earth around the sun’ and thus the fourth day of ‘the mighty Dialogo shines as brightly as its three predecessors and is just as significant for our understanding of the physics of the seventeenth century.’19 In contrast, Aiton concluded that Newtonian mechanics shows there to be no link between the earth’s dual motions and the tides and thus proposed Galileo’s claim was unfounded.
16 M Finocchiaro, Galileo on the World Systems, W Wallace, Galileo’s logic of discovery and proof,R Naylor, ‘Galileo, Copernicanism and the origins of the new science of motion’ in British Journal for the History of Science, vol. 36, no. 129, 2003, pp. 151-181. 17 W R J Shea, ‘Galileo’s Claim to Fame’, p. 111, 125. 18 See J C. Pitt ‘Galileo, Copernicus and the tides’, p. 89, and J C Pitt, ‘Galileo and rationality: the case of the tides’ in J C Pitt and M Pera (eds), Rational Changes in Science: Essays on Scientific Reasoning, Dordrecht, Boston, 1987, pp. 125-153, p. 135, respectively. A further work is J C Pitt, ‘The untrodden road: rationality and Galileo’s theory of the tides’ in Nature and System,vol. 4, 1982, pp. 87-99. 19 H Burstyn, ‘Galileo’s attempt to prove that the earth moves’ in Isis, Vol. 53, No. 2, 1962, p. 161-185, quotes p. 181 and p.182.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 70 Those who regard the tidal theory as an intended proof of the earth’s motions debate the strength of the tidal theory. Finocchiaro finds that Galileo did not consider the evidence of the tides to be conclusive for Copernicanism but just one in a number of equally strong, mutually reinforcing arguments for the earth’s motions.20 Wallace suggested that Galileo included the tidal theory in the Dialogo only to persuade to those who might already be predisposed to the Copernican position.21 Naylor proposes that Galileo believed that his arguments would not win over Aristotelians and he only intended the Dialogo and the tidal theory to undermine their ‘intellectual credibility’.22 Indeed, it is Pitt’s misgivings about the strength of the argument that led him to suggest Galileo’s purpose rested solely in explaining the tides and not cosmology. In all this, the implication is that the educated elite of the time would not have considered Galileo’s theory of the tides as particularly convincing evidence. In sum, Burstyn’s 1963 characterisation of the tidal theory still holds sway: by and large historians of science still see Galileo’s theory of the tides as ‘the pathetic result of genius gone wrong, the skeleton in the Galilean cupboard’.23
2.2 The cosmographic project of Galileo
Explaining the cause of the tides was a common undertaking in natural philosophy during the Scientific Revolution. Hooper, in his recent chronology of early modern tidal theories, observed that Gilbert, Stevin, Kepler, Descartes, Gassendi, Wallis and Newton all devoted
20 M Finocchiaro, Galileo on the World Systems, pp. 53-54. Finocchiaro’s argument is that if Galileo considered one argument to be strong enough as to be conclusive, for example, the sunspot argument or tidal argument then he would not have presented both. He also points to Galileo’s support of research into stellar parallax as evidence that Galileo realises he has not completely refuted the anti-Copernican argument (the absence of stellar parallax would support the geocentrists). Finocchiaro acknowledges his view is not universally shared and offers alternative readings by Shea and Langford. 21 W Wallace, Galileo’s logic of discovery and proof, pp. 226-228. 22 R Naylor, ‘Galileo, Copernicanism and the origins of the new science of motion’, pp. 151-181, phrase p. 178. 23 H. Burstyn, ‘Galileo and the Earth-Moon System: Reply to Dr Aiton’ in Isis Vol 54, No 3, 1963, pp. 400- 401, p. 401.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 71 lengthy arguments to tidal phenomena.24 Provoked in part by the notion that the earth might move, both Copernican and non-Copernicans began to think of the tides as a potentially significant physical event and widely discussed the extent to which the earth’s motion was imparted to the oceans. Although Hooper usefully noted that theorising about the cause of the tides was customary for Galileo’s generation, he failed to recognise that the traditional connection to astronomy via cosmography.25 Dee considered that ‘Cosmographie… requireth…Hydrographie’, as we noted in Chapter One.26 Like Hooper, other Galilean scholars have either overlooked cosmography altogether or, in the case of Drake, dismissed it as unimportant in understanding Galileo’s agenda.27 In contrast, I will argue that cosmography provides a key to understanding the expectations Galileo was trying to meet with his theory of the tides.
24 W Hooper, ‘Seventeenth-Century Theories of the Tides as a Gauge of Scientific Change’, p. 200-201. Hooper argues: ‘some of the most important authors on world systems and the new physics – Gilbert, Stevin, Galileo, Kepler, Descartes, Gassendi, Wallis, and Newton – devoted paragraphs and sections to the subject [the tides] at critical junctures in their most important works’, W. Hooper, ‘Seventeenth- Century Theories of the Tides as a Gauge of Scientific Change’, p. 200-201. Hooper analyses the nature of and links between the tidal theories proposed by Stevin, Kepler, Galileo, Bacon, Gassendi and Wallis. He argues that Gilbert was the first Copernican to publish views on the tides and initiated the way of addressing the tides that persisted in natural philosophical debates about the motion of the earth up until the time of Newton. Hooper proposes that Galileo developed and modified his theory of the tides in the context of, and in response to, other tidal theories, in particular Bacon’s 1611 tidal treatise. Bacon’s work led Galileo to abandon the claim he made in the 1616 Discourse on the Tides that a twelve-hour tidal period had been observed at Lisbon. When Galileo’s tidal theory appeared in 1632 in the Dialogo Galileo claimed that a six-hour period was most commonly observed period in the Mediterranean. According to Hooper, the comprehensive list of different tidal periods in Bacon’s treatise led Galileo in the Dialogo to include in his tidal theory for the first time an explanation of the monthly and annual tidal periods . 25 Hooper’s account concentrates on providing a chronology of tidal theories. Using a narrow frame of reference, he neglects geognosic discussions that did not relate directly to the tides, the dynamics of natural philosophy and the field of cosmography. Hence, he considers that the discussion of terrestrial matters in Copernicus was brief and inconsequential and proposes that early seventeenth century scholars carefully observed all the ‘salient features’ of the tides. Ultimately his interest lies in describing a perfect trajectory of the theoretical advancement of thinking about the tides, and arguing for a modern legacy in the theory of the tides on the basis of Galileo’s reference to ocean structure. W Hooper, ‘Seventeenth-Century theories of the tides as a gauge of scientific change’, p. 201, 205 and 242. 26 J Dee, ‘John Dee his mathematical praeface’ p. b.iii. 27 Drake has recognised Galileo’s involvement in the field but argued it is of little import. His views are outlined and discussed later in this chapter.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 72 To appreciate the cosmographic content of the tidal theory we need to return to the structure of the argument itself. In other words, we need to closely investigate his method. Galileo’s initial step was to cast doubt on the conceptual frameworks of existing tidal theories. At the outset of Day Four in the Dialogo, Galileo refuted rival tidal theories. He critiqued those who asserted the tides were caused by some sort of change in the water already at a location. For instance, Galileo rejected the view that high tides were due to the moon’s heat causing the water to expand. He argued that the water involved in a high tide had the same salinity, density, temperature and weight as that previously there.28 Galileo also refuted the proposition that high tides in the Mediterranean arose from water entering through the Strait of Gibraltar. Not only was the passage was too narrow for the volume of water needed, he asserted, but the water would need to move at impossible speeds (of over 400 miles per hour) to reach the far side of the Mediterranean.29 Galileo used a more mocking tone to refute the (perhaps imagined) suggestion that an abyss in the sea floor caused the changes in tides. If such a abyss sucked in and expelled water ‘breathing like some immense and monstrous whale’, then water would rise simultaneously at all
28 Galileo reasoned: ‘Such a rise does not derive from the expansion of the water, but rather from new water that has come here, water of the same kind as the old, of the same salinity, of the same density, of the same weight; boats float on it, Simplicio, just as they did on the old water, without subsiding a hair lower…it is as cold as the other, without any change; in short, it is new water that has visibility entered the bay through the narrows of the Lido. Now, you tell me whence and how it has come here.’ G Galilei in M Finocchiaro, Galileo on the World Systems, p. 286-7. Galileo also briefly commented on Kepler’s views on the tides. Galileo commented that ‘although he [Kepler] had a free and penetrating intellect and grasped the motions attributed to the earth, he lent his ear and gave his assent to the dominion of the moon over the water, to occult properties, and to similar childish ideas.’ In addition, Galileo dismissed the proposal of ‘a great Peripatetic’ that the different depths in an ocean cause the tides (as the water sitting at the top of the deeper body replaces the water in the shallower region) on the basis that this would unreasonably require all lakes to have level bottoms. On Kepler see M Finocchiaro, Galileo on the World Systems, p. 304 and on the argument about the depth of oceans, see G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 420. 29 GGalilei,Dialogue Concerning the Two Chief World Systems, second edition, p. 423. Galileo’s argument on this matter is a great example of his use of satire to discredit competing ideas. In referring to the speed of water flowing through the Mediterranean and its effects, he argues: ‘What will happen to the various ships at sea? What will happen to those which might be in the straight, where there would be such a constant and impetuous flow of an immense quantity of water, that, by using a channel no more than eight miles wide, it would provide enough water to flood in six hours an area hundreds of miles wide and thousands of miles long? What tiger or falcon ever flew at such a speed? I mean a speed of 400 and more miles per hour. There are indeed currents along the strait (I do not deny it), but they are so slow that rowboats outrun them, although not without a delay in their course.’ M Finocchiaro, Galileo on the World Systems, pp. 287-288, p. 423.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 73 locations on the Mediterranean, while in reality tides occur at different times throughout.30 Salviati’s statement at the conclusion of these refutations points to Galileo’s strategy: showing the incommensurability between the ebb and flow of tides and the geocentric view:
Who will find a way to pour new water into an immovable vessel and have it rise in one definite place and not others?31
Thus, Galileo set the scene for the introduction of his own theory of the tides.
Galileo’s account of the tides was bound fundamentally to the Copernican view of the dual motions of the earth. The connection derived from the three foundational propositions of the theory: water in a vessel runs from one end to the other when it moves with uneven motion; water in a moving vessel behaves very much like the tides; and the non-uniform motion of the earth causes the tides.32 The case of a barge bringing fresh water to Venice set the template for characterising the tides.33 It was introduced in the opening stages of Day Four, Salviati suggesting that the three friends:
Let us imagine to ourselves such a barge coming along the lagoon with moderate speed, placidly carrying the water with which it is filled, when either by running aground or by striking some obstacle, it becomes greatly retarded. Now the water…will run toward the prow, where it will rise perceptibly, sinking at the stern.34
30 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 423. 31 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 423. 32 This reconstruction draws on that provided in W A Wallace, Galileo’s logic of discovery and proof: the background, content, and use of his appropriated treatises on Aristotle’s Posterior analytics. Dordrecht, Kluwer Academic Publishers, 1992. 33 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 425. 34 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 425.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 74 Readers were asked to note several aspects of the water as the barge accelerated and decelerated. To make the water in the vessel rise at one end, there is no call for new water from outside the vessel (replying to the issues described earlier). Next, the water in the middle of the barge does not perceptibly rise or fall. Critically, the farther the water is from the middle of the barge the more it rises and falls, so that the water at the ends of the barge moves with the greatest vertical motion. Finally, while the water in the middle of the moving vessel does not noticeably rise or fall, it undergoes variation by flowing forward and backward.35
The second chief proposition was that the case of the barge is analogous to the relation between the sea basins and the ebb and flow of the tides. As Salviati put it:
Now, gentlemen, what the barge does with regard to the water it contains, and what the water does with respect to the barge containing in it, is precisely the same as what the Mediterranean basin does with regards to the water contained within it, and what the water contained does with respect to the Mediterranean basin, its container.36
35 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 425. Galileo presented several additional ‘concomitant’ causes that accounted for the particular tidal events at different places and times. These were that: water elevated at one extremity will return to equilibrium of its own accord; the frequency of the oscillations of water correspond to the length of vessels and is inversely proportional to the depth of a vessel; and the extremities of long oceans do not increase and decrease in speed equally nor at the same time. These factors are related to, but different from, the secondary causes in the theory. G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, pp. 428-430. 36 GGalilei,Dialogue Concerning the Two Chief World Systems, second edition, pp. 425-426. It is significant to note that Galileo sometimes makes key claims in terms of all oceans and sometimes in regards to the Mediterranean, reflecting his own mental model (and presumably also that of many of his readers) is based on the Mediterranean. Galileo justifies his use of the Mediterranean as exemplar at several junctures. In one such instance, he argues that: ‘though in other seas remote from us events may take place which do not occur in our Mediterranean, nevertheless the reason and the cause which I shall produce will still be true, provided it is verified and fully satisfied by the events which do take place in out sea; for ultimately one single true and primary cause must hold good for effects which are similar in kind.’ G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 418. At another point, he proposes in relation to the commonly noted six hourly tidal cycles in the Mediterranean that the Mediterranean ‘has been the only place practicable for making observations over many centuries’. This rationalisation appears unconvincing as, if the dual motions of the earth did cause the tides as Galileo contends, then tidal phenomena would be relatively constant over time and observations spanning a short
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 75 Galileo attended carefully to establishing the credibility of this analogy, for example, his argumentative strategy highlighted the very same tidal phenomena that he articulated for the barge.37 The chief evidence for this claim are that the tides at Venice, located at the end of the Adriatic, reach up to five or six feet while those at Rome, Sardinia or Corsica, which are in the middle of the Mediterranean, are much less.38 The analogy between the action of water in a vessel moving non-uniformly and the tides in the centre and at the ends of the seas was made to look like the discovery, or uncovering of a cause.
Thus, the third key proposal in the tidal argument involved demonstrating ‘how and in what manner it happens that the Mediterranean and all other sea basins (in a word, that all the
period of time would also be quite adequate. Quote from G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 433. 37 The credibility of the analogy rested on the fact that Galileo described only a very selective set of tidal events. From the outset he gives primacy to the daily tidal cycle and thereby focuses theoretical conjecture on the daily tides. The monthly and annual periods of tidal changes ‘merely’ alter the magnitude of the daily tidal movements. On the basis of the premise that a single effect can have only one basic cause, he argues that the monthly and annual tidal cycles resulted from irregularities in the composite motion of the earth. G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 418, quote and discussion from p. 445 – 446. To understand Galileo’s argumentative strategy it is also important to note that Galileo shifts his position on the mutual exclusivity of the two chief tidal motions – the rising and falling of the waters, and the horizontal running – during, but very early in his argument on Day Four. At the outset, Galileo claims that both the motions could occur simultaneously at one location: in ‘some places the waters rise and fall without making any forward motion’, in other places the waters run to and fro without any ‘rising or falling’, and in some places ‘the height and course both vary’. However, thereafter Galileo focuses on the existence of only the first two motions. This shift is most clearly illustrated in, and achieved rhetorically through, Galileo’s treatment of the tides at Venice. Galileo initially proposes that Venice experienced both changes in tidal height and the forward and backward running of the tides. However, the horizontal movement was a result of the water ‘terminating on the open shore where it has room to spread out upon rising’. Galileo then (somewhat obscurely) comments that, if the course of the tides at Venice were ‘interrupted by mountains or by very high dikes, they would rise and sink against these without any forward motion.’ That is, the horizontal motion was a particular function of the structure of shorelines. We explore this issue later in the body of the study in regards to the role of geognosic opinion in the theory. In terms of its rationale, however, Galileo introduces this proviso so that a reader might accept his subsequent discussions of the tides at Venice, which concentrated on the rising and falling of the tides. When Galileo compares the tides at Venice with those in the Straits of Messina, for example, he focuses solely on the five to six feet rise in height at Venice. Quotes from G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 419; discussion on p. 418-419 and p. 433. 38 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 433. See also the discussion in the previous footnote regarding Galileo’s careful explanation of the tides at Venice.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 76 parts of the earth) move with a conspicuous uneven motion’.39 Galileo argued that the earth’s dual motions, each of which is uniform and easterly, together result in a non- uniform motion in parts of the earth. He reasoned that the earth (DEFG in Figure 3.1) moves in its annual orbit along the larger circumference, from west to east, from B towards C. In addition, the earth rotates on its axis in twenty-four hours, around B, in the order of the points D, E, F, G. At D, the absolute motion of the earth is very quick as D is subject to two motions in the same direction (to the left)—the annual orbit and axial rotation. On the other hand, the absolute motion of the earth at F ‘is much retarded’, the result of one motion being subtracted from the other.40 As Galileo put it:
in combining this diurnal motion with the other annual one there results an absolute motion of the parts of the terrestrial surface that is sometimes highly accelerated and sometimes retarded by the same amount.41
The theory provided that each part of the earth possesses its own continuously varying absolute motion, determined for any part by adding or subtracting the diurnal rotation and the annual revolution at that point.42
39 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 426. 40 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 426 – 427. 41 G Galilei in Galileo on the World Systems, p. 292. 42 G Galilei in Galileo on the World Systems, p. 291-292. See Finocchiaro’s footnote 20 for critiques of the logic in Galileo’s reasoning.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 77 Figure 3.1: Combining of the two uniform motions of the earth in the theory of the tides G Galilei, Dialogo43
Galileo proposed that the effects of a number of other ‘secondary factors’ ‘mixed’ with the tidal effects arising from this primary cause, causing the specific action and timing of the oscillations of the tides at any one location. Indeed, he drew on secondary causes to explain the observed six-hourly rather than the predicted twelve-hourly cycle of the daily tides. The length, depth, width and orientation of ocean basins, and the volume of river water inflow, played a role in the specific actions of the tides at any one location. However, the non-uniform motion of the earth constituted the primary cause of the tides that brought about the motion of the water. Without it, Galileo maintained, the tides would not occur at all.44 Thus, Galileo’s argument provided a theory that could only account for the tides on the Copernican view and conversely a description of the phenomenon that required dual motions of the earth.
43 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 426. 44 G Galilei in Galileo on the World Systems, p. 293 and p. 298-300, 360. These effects relate to the concomitant causes, described in footnote 35.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 78 The purpose of the Dialogo was to provide both strictly astronomical and other cosmographical proofs for the Copernican view. The role of Day Four was to provide the cosmographic proof, using the tides. The way historians of science typically construe the tidal theory—Galileo argued that tidal effects prove the Copernican view—misses this cosmographic content. If we summarise the theory another way the central place of cosmography becomes evident: only when one views the cosmos as did Copernicus can one explain the tides. The aim of Day Four of the Dialogo was to show that the Copernican theory offers a more satisfying cosmography than the Ptolemaic and modified Tychonic systems.
Galileo himself regarded that the value of the tidal theory lay in cosmography. He insisted that the way the theory provided an integrated picture of heaven and earth was a crucial reason to accept the heliocentric cosmos. For instance, in his 1616 letter to Orsini, Galileo concluded:
This is was what I advanced as the causes of these motions of the sea in my discussion with you, Most Eminent Lord. It was an idea which seemed to harmonize mutually the earth’s motion and the tides, taking the former as cause of the latter, and the latter as a sign of and argument for the former.45
Galileo makes a stronger assertion in 1632 in the Dialogo:
I have arrived at two conclusions…these are that if the terrestrial globe were immoveable, the ebb and flow of the oceans could not occur naturally; and that when we confer upon the globe the movements just assigned to it, the seas are necessarily subjected to an ebb and flow agreeable in all respects with what is to be observed in them.46
45 G Galilei, Discourse on the Tides, p. 131 (emphasis added). 46 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 417, emphasis added.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 79 The claim in 1632 is of an exclusive match between the Copernican view and tidal effects. Thus, Galileo held the same cosmographic ambition to provide a unified picture of the heavens and earth as the thinkers studied in previous chapters.
However, Galileo’s engagement with cosmography differed from the scholastics as well as from Copernicus, Bruno and Gilbert in that he did not use a cosmographic form of argument, of either a traditional or Copernican hue. In other words, Galileo did not argue from a particular view of the earth to the Copernican arrangement of the cosmos or vice versa (unless we regard his assumption of shallow ocean basins as controversial). As described earlier, Galileo used cosmography to verify the heliocentric cosmos, not to discover or describe it.
We also find that Galileo sought pre-eminence among Copernicans on the basis of his approach to cosmography, possibly appealing to educated readers uncommitted to either system. Over the first three days of the Dialogo Galileo tried to neutralise Aristotelian arguments that used terrestrial phenomena to prove the earth’s immobility. He maintained that the arc of projectiles, the action of falling bodies and the flight of birds could equally support the Ptolemaic and Copernican systems, and therefore prove neither:
all terrestrial events from which it is ordinarily held that the earth stands still and the sun and the fixed stars are moving would necessarily appear just the same to us if the earth moved and the others stood still.47
Galileo argued that all terrestrial evidence advanced by the geocentrists was inconclusive regarding cosmology, consistent with either system.
47 GGalilei,Dialogue Concerning the Two Chief World Systems, second edition, p. 416. Galileo’s discussion of these terrestrial matters appears primarily on the Second Day of the Dialogo.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 80 Yet, shortly after Galileo formulated his initial ideas on the tides (1595 to 1597) Gilbert’s De Magnete was published, proposing that the magnetic nature of the earth constituted terrestrial evidence for the earth’s rotation (in that a spherical lodestone showed the tendency to rotate when suspended). Galileo did not let this claim by Gilbert stand. He praised Gilbert’s ideas on the magnetic composition of the earth but rejected the possibility of a suspended, spherical magnet rotating and therefore proving the earth’s motions.48 It was faulty reasoning, Galileo asserted, to conclude that a magnet separated from the earth would rotate while the earth also rotated. This would attribute to such lodestones ‘two motions; a rotation in twenty-four hours about the centre of the whole, and a revolution about their own centres’, which is ‘arbitrary, and there is no reason whatever for introducing it.’49 Galileo lamented:
What I might have wished for in Gilbert would have been more of the mathematician, and especially a thorough grounding in geometry…His reasons, candidly speaking, are not rigorous, and lack that force which must unquestionably be present in those adduced as necessary and eternal scientific conclusions.50
It is significant to note that Galileo dismisses Gilbert’s terrestrial explanation of Copernican arrangement of the cosmos just before he introduces his own theory of the tides.
48 Discussion of Gilbert is at G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, pp. 400-415, and concludes Day Three. 49 GGalilei,Dialogue Concerning the Two Chief World Systems, second edition, p. 414. A sense of the nature of the praise Galileo provides on Gilbert’s exposition on magnets can be sensed throughout Salviati’s explanation Gilbert’s magnetic theory of the earth to Sagredo and Simplicio. For instance, Salviati comments: ‘I frankly admit in the entire magnetic science I have not heard or read anything which gives so cogently the reasons for any of its other remarkable phenomena. If their causes were to be explained to us this clearly, I can think of nothing pleasanter that our intellects could wish for.’ G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 408. 50 GGalilei,Dialogue Concerning the Two Chief World Systems, second edition, p. 406.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 81 With Gilbert’s claim refuted, Galileo sought prestige on the basis that the theory of the tides constituted the first valid terrestrial proof of the earth’s motions. His success, he argued, rested in his choice of the earth’s oceans as evidence. The discussions on Day Four open as follows:
Up to this point the indications of…[the earth’s] mobility have been taken from celestial phenomena, seeing that nothing which takes place on the earth has been powerful enough to establish the one position any more than the other. This we have already examined at length...Among all sublunary things it is only the element of water (as something which is very vast and is not joined and linked with the terrestrial globe as are all its solid parts, but is rather, because of its fluidity, free and separate and a law unto itself) that we may recognize some trace or indication of the earth’s behaviour in regard to motion and rest.51
Galileo claimed that only by focusing on water could one find evidence on earth that suggests an alignment with the Copernican view. Historians of science generally recognise Galileo’s proposition that all the terrestrial phenomena advanced by geocentrists were inconclusive regarding cosmology. However, as far as I am aware, historians have not examined the extent to which Galileo utilised terrestrial claims to compete with fellow Copernicans in cosmology.52 In other words, modern commentators have not noticed that cosmography constituted one of the sites of competition in natural philosophy. Perhaps it was because of his distinctive success in the field of cosmography that Galileo considered the theory of the tides to be his crowning achievement.
From the outset Galileo was steeped in cosmography, a fact little noticed by historians of science. Cosmography was in fact one of the courses he privately tutored in Padua and in
51 GGalilei,Dialogue Concerning the Two Chief World Systems, second edition, p. 416-417.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 82 his commentary on Sacrobosco in the unpublished Trattato della Sfera, ovvero Cosmografia (Treatise on the Sphere, or Cosmography), completed between 1586 and 1587, Galileo wrote about matters concerning both geography and astronomy.53 In his instructor’s notes for the Trattato, Galileo defines the domain of cosmography as:
the number and order of the parts of this world and the shape, size and distance of [each of] these. And especially…their motions, leaving to the Natural Philosophers consideration of the qualities of the said parts of the world.54
In other words, Galileo considered that cosmography concerned the structure and motion, but not the composition of, the earth and the heavenly bodies. The cosmographer, he proposed, reflects on:
52 It is notable, for instance, that Finocchiaro’s abridged translation of the Dialogo does not include both Galileo’s critique of Gilbert and his subsequent claim about the novelty of water as grounds for the Copernican view. 53 Galileo’s account books show he privately tutored in cosmography from 1601-1607, averaging four students each year. S Drake, Galileo at Work. p. 51. Subjects in Trattato della sfera included the size of the earth in relation to the heavens, the meridian circles and the equator, latitude and longitude, the illumination of the moon, the celestial spheres and their motion, and whether the earth constitutes the center of the celestial spheres and is immobile. The treatise, as the long title suggests, also attended to a plethora of practical astronomical matters such as how to divide the circumference of a circle into 360 equal parts and a method for making an instrument to observe the heavens. G Galilei, Trattato della sfera / di Galileo Galilei; con alcune prattiche intorno à quella e modo di fare la figura celeste e suoi direttioni secondo la via rationale di Buonardo Saui, for Nicolò Angelo Tinassi, Roma, 1656, IMSS Digital Library, Istituto e Museo di Storia della Scienza, viewed on 11 February 2006,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 83 the rising and setting of stars; the darkening now of the sun and again of the moon; the latter’s showing herself now cresent, now at quarter, now at full, and again completely dark; the moving of the planets with very different motions; and many such other appearances.55
A notebook from approximately 1590 shows that Galileo was well acquainted with the ideas of the thirteenth century thinker, Albertus Magnus, who refuted the common view of philosophers and mathematicians that the southern hemisphere is completely submerged because the sphere of water is greater than the sphere of earth.56 In sum, by 1586, Galileo was acquainted with thirteenth century Aristotelian cosmographic dilemmas and had began writing a treatise on Sacrobosco’s The Sphere. By 1601, cosmography was amongst a suite of courses he privately tutored.57
Historians have largely overlooked Galileo’s engagement with cosmography. Drake, who did acknowledge it, even argued that historians have little to gain from examining Galileo’s views on the links between astronomy and geography. Regarding the Trattato della Sfera, he comments that ‘except for the opening statement about method it is of little interest’.58 Yet, Galileo was immersed in cosmography at the time he was developing his theory of the tides and this supports the interpretation provided here that he intended the tidal theory as a cosmographic proof of the Copernican view.
55 SDrake,Galileo at Work,p.52. 56 Wallace bases his claim for Galileo’s familiarity with the natural philosophy of Albertus Magnus on the substantial citation of Albertus in one of Galileo’s three early notebooks, written in approximately 1590. W A Wallace, Prelude to Galileo, pp. 265, 281 and 283. On Magnus’s views, see W G L Randles, ‘Classical models of world geography’, p 26-27. 57 SDrake,Galileo at Work,p.51. 58 SDrake,Galileo at Work,p.12.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 84 2.3 The place of geognosic opinion in the theory of the tides
Galileo used geognosic opinion in a different manner to the thinkers investigated in the previous chapters. He certainly presented the earth as a terraqueous globe and, like Gilbert and probably for similar reasons, did not provide a lengthy argument.59 Indeed, there is much in the Dialogo to confirm that the terraqueous conceptualisation of the earth was uncontroversial by this time.60 Rather than argue for aspects of the terraqueous globe Galileo advanced an idealised model of ocean structure and also introduced general and quite specific aspects of geognosic knowledge to demonstrate the explanatory power of this theory.
Galileo asked the reader to imagine that oceans were containers of water, orientated east to west, with smooth beds and vertical sides. These features were all requirements of the theory’s principal line of reasoning. Through the proceedings of Day Four, Galileo subtly sought to build credibility for this idealised model of ocean structure. He concentrated mainly on the notion of oceans as sealed bodies of water, a matter on which some diversity of opinion existed at the time. (As we shall see shortly, Descartes based his theory of the tides on an idealisation of the oceans being interconnected.) Most notably, Galileo employed the terms ‘basins’, ‘vessels’ and ‘containing vessel’ throughout Day Four to
59 Salviati states: ‘The very long basins of the sea… are nothing but certain hollows carved out of the solid terrestrial globe’. G Galilei, Galileo on the World Systems, p. 295. Drake’s translation similarly suggests a terraqueous conceptualisation of the globe: the ‘long sea bottoms…are nothing more than cavities made in the solidity of the terrestrial globe’. G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 429-430. 60 There are a number of grounds to consider the concept of the earth as a terraqueous globe was not controversial by this time. Simplicio, the voice of scholastics, states that the oceans constitute ‘basins containing the waters of the sea’, suggesting that Aristotelian acceptance of the concept of the terraqueous globe at the time. See M Finocchiaro (ed), Galileo on the World Systems, p. 286. In addition, Galileo refers to oceans in a similar way in the Discourse; oceans are “certain hollows carved out of the solid terrestrial globe”. G Galilei, Discourse on the Tides, p. 295. Finally, the acceptance of the concept of a terraqueous globe is suggested by Galileo’s continual reference to the earth as a ‘terrestrial globe’ in Day Four of the Dialogo (in both Drakes and Finocchiaro’s translations), although further evaluation of the original meaning is required.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 85 refer to oceans.61 This type of rhetoric was absent from the 1616 letter to Orsini, suggesting Galileo recognised the benefits of this argumentative strategy in the period between the two works. Within the Dialogo, Galileo began using this rhetoric before introducing the ‘closed system’ of the barge.62 The arguments Galileo made against rival theories, described earlier, also aimed to strengthen his idealisation. For example, by refuting theories that proposed that the tides involved new water flowing into (and out of) the Mediterranean, Galileo framed the conceptual problem as explaining tidal phenomena within contained bodies of water.63
61 [O]f all the causes that have so far been advanced as true ones, there is none from which we can reproduce a similar effect, regardless of what artifices we employ; for by means of the light of the moon, or sun or temperate heat or differences of depth, we will never make the water contained in a motionless vessel artificially run back and forth and go up and down at one place but not another. M Finocchiaro, Galileo on the World Systems, p.p285, emphasis added. 62 Galileo deployed this type of language for the ocean irrespective of whether the points being discussed related to the earth as mobile or immobile. For example Simplicio says: ‘ I know that the latter containers do not move, the entire terrestrial globe being entirely immobile’. G Galilei, Dialogue Concerning the Two Chief World Systems, second edition p. 421. 63 The other features of Galileo’s idealised model of ocean structure, namely the nature of their orientation, shorelines and seabeds, received less explicit attention in Galileo’s argumentative strategy. The reasoning in the tidal argument prescribed a certain orientation for oceans. If the uneven motion of the earth, like that of the barge, acted along the length of oceans, then the logic of the tidal theory required that oceans (in which there which tides) extend east to west. Galileo explicitly acknowledged the need for this geognosic reality and, with some careful rhetoric, implied could be the case in fact: ‘Thus if it is true (and it is most true, as experience shows) that the acceleration and retardation of a vessel’s motion makes the water contained in it run back and forth along its length and rise and fall at its ends, who will want to raise any difficulties about granting that such an effect can (or rather, must necessarily) happen in sea-water, which is contained in various basins subject to similar variations, especially in those whose length stretches out from east to west (which is the direction along which most of these basins move)?’ Of course, Galileo did not provide evidence that most tidal oceans extended east to west. Rather, he utilised the proposition as negative proof, for instance, as an explanation of why the generally north-south orientated Red Sea lacked tides. M Finocchiaro, Galileo on the World Systems, quote p. 292-293. See also p. 299. We can also identify that Galileo had in mind certain features for the shorelines. The subject arises in relation to the nature of the tides at Venice. Galileo initially proposed that the tides at Venice involved changes in the height of water and a forward and backward running. However, he then argued that the horizontal movement was a result of the water ‘terminating on the open shore where it has room to spread out upon rising’. If the coursing of the tides at Venice were ‘interrupted by mountains or by very high dikes’, Galileo remarked‘they would rise and sink against these without any forward motion’. All subsequent claims about the Venetian tides in the Dialogo cite only the vertical motion.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 86 Nonetheless, when the predictions of the idealised model fell short, Galileo introduced ad hoc modifying details to his ideal, simple ocean structure. For example, he argued that the unusually strong currents between Calabria and Sicily, and Africa and Madagascar, were due to the particularly narrow straits in these locations.64 In another instance, he called attention to the smallness of the Black Sea, the large volumes of river water flowing into it, and the narrowness of the passage to explain the atypical, one-directional (southerly) flow of water in the Bosporus.65 Galileo introduced modifying conditions based on geognosic opinion to account not just for location-specific tidal phenomena but also for fundamental tidal phenomena, the six-hourly tides being a prime example.66 In this instance, Galileo was no more specific in the geognosic knowledge used than citing the
Indeed, preliminary thinking about Galileo’s proposal suggests it would require the edges of sea basins to be mostly vertical and extend above the low tide mark. If the sides of oceans had little extension above the low tide mark, the high tides would overrun the sides of oceans and flood neighbouring land. If oceans were thought of as having very long gently sloping edges, the apparent motion of the water at the extremities of oceans would be a horizontal running rather than a vertical rise and fall. While Galileo discussed the impact of sea depth to discount the Aristotelian explanations of the tides and regarding the relation between depth of oceans and the frequency of tidal oscillations, he did not present any clear opinion on actual depth of oceans in the context of his argument for the primary cause of the tides. Nonetheless, the theory is founded on shorelines being largely vertical. The tides at Venice discussed in G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 419 and p. 433, quote from p. 419. A final point is that claims in the tidal theory insinuated a particular quality to ocean beds. Galileo argued that water in an ocean moves unimpeded. It moves separately and freely and ‘is not joined and linked’ to the solid parts of the basin. G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 417. 64 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 433 – 434. 65 G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 435 – 436. Galileo maintained that the earth’s non-uniform motion had little effect on small seas and the ‘superabundance’ of water flowing from the Black Sea into the narrow Bosphorus strait (connecting the Black Sea and the Sea of Marma) contributed to its southerly tidal effect. 66 Galileo recognised that the primary cause of the tides embodied ‘a principle for moving the water only at twelve hour intervals, that is once for the maximum speed of motion and once for the minimum’, not at six hourly tidal periods as was commonly observed. However, he maintained that the common length and depth of ocean ‘vessels’ is such that it generates a six hourly cycle: ‘ the six hour interval is no more proper or natural than other time intervals, although it is perhaps the most commonly observed since it occurs in our Mediterranean.’ M Finocchiaro, Galileo on the World Systems, discussion on the six hourly tides at p. 295, quotes from p. 298. We can identify that Galileo modified his earlier work so as to strengthen his claims about actual tidal phenomena in the Dialogo, with one of the greatest changes being his claims concerning the tidal cycles at Lisbon. Galileo’s position in both the Discourse and Dialogo is that six hours is the most commonly observed tidal period as it is the period that occurs in the Mediterranean. He stated in both works that this
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 87 common length and depth of oceans. So, alongside his idealised model of ocean structure, Galileo used both specific and very broad geognosic claims to demonstrate the explanatory power of the tidal theory.
The role that terrestrial knowledge in general played in the theory of the tides has been widely discussed by historians of science. Prior to the work of Koyré, some historians considered the theory of the tides was motivated by ‘induction from experience’.67 Galileo indeed commented on tidal events at a number of locations and claimed to have based his theory on careful observation of tidal effects.68 But he did not arrive at his theory of the tides from detailed observations. If nothing else, the imprecision of the Galileo’s data demonstrates the point. Galileo only quantified three tidal phenomena: the tides in the Mediterranean ‘are for the most part about six hours each’; at Venice, the tides reached five or six feet; and at Corsica, Sardinia and the coasts at Rome and Leghorn do not exceed half a foot.69
six hourly period is no more “natural” than any other. However, Galileo elaborated considerably on the point in the Discourse, claiming that the Atlantic experiences tidal periods of twelve hours and this has been observed at Lisbon. He noted the Atlantic is twice the length of the Mediterranean implying this accounts for the period of oscillation in the Atlantic being twice the period in the Mediterranean. In the Dialogo, Galileo considerably shortened and generalised his discussion of this point for publication and made no reference to the twelve-hour tidal periods in the Atlantic or at Lisbon. In addition, discussion of the shorter tidal periods in the Sea of Marma and Hellenspont in Dialogo is considerably more generalised, brief and less prominent compared with the Discourse. On the other hand, Galileo made considerable additions in the Dialogo to number of locations whose tidal effects he discussed: claims about the tidal effects at Balearics, Elba, Malta, Crete, Ancona, Genoa, Naples and Dubrovnik do not appear in the earlier work. Most interestingly, the claimed variation of the tides at Venice in the 1616 Discourse is three feet while in the Dialogo it is five to six feet. These additions should be interpreted more as evidence of Galileo taking more care in securing the explanatory power of his theory in the published treatise than Galileo being more precise about tidal effects. On the Lisbon modification, see S. Drake, Galileo at Work, p. 273-274 and p. 296. 67 This view of the chronology in the historiography is mentioned in S. Drake, Galileo at Work, p. xvii. 68 Galileo stated: ‘In questions of natural science like this one at hand, knowledge of the effects is what leads to an investigation and discovery of the causes...before all else it is necessary to have a knowledge of the effects of whose causes we are seeking.’ G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 417. 69 In all, Galileo presented observations from over twenty locations from within the Mediterranean basin and only three locations outside the Mediterranean basin. The locations mentioned by Galileo include: Venice, Straits of Messina, Crete, the Balearics, Corsica, Sardinia, Elba, Sicily, Malta, Crete, Naples, Genoa,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 88 In terms of Galileo’s use of geognosic knowledge specifically, commentators now typically recognise the importance of the barge analogy and considerations of the length and depth of sea basins to the tidal argument.70 The general view, correct in my opinion, is that knowledge about the earth’s structure did not play a leading role in the tidal theory. But the point is not so much whether ‘these disciplines were in a rudimentary state at the time particularly from the point of view of quantative analysis’ as Wallace asserts, but that Galileo constructed his theory so it never relied on detailed geognosic knowledge in the first instance.71 Beside his idealised model of ocean structure, the role of ‘real’ geognosic knowledge in Galileo’s theory of the tides was merely as explanandum, to show the power of the theory for selected well-known tidal phenomena and to demonstrate that he was well versed in geognosy, presumably to contrast himself with the scholastics.
Ancona, Dubrovnik, the Red Sea, Rome, Leghorn, the strait between Africa and Madagascar, the Hellespont (now the Dardanelles), the Straits of Messina, the Black Sea and the Bosphorous strait (between the Black Sea and the Sea of Marma), Pharos and Alexandria, Alexandretta, and the Straits of Gibraltar. Of these, the Red Sea, the channel between Madagascar and Africa, and the Straits of Magellan were outside the Mediterranean. Other than asserting that the currents in the Straits of Magellan were fast, Galileo failed to cite any evidence from the ‘New World’. At most, it would be fair to say that the theory was seemingly inspired by consideration of the interaction of tides between the Adriatic and the Mediterranean. This proposition is based on the discussion of the interaction between the Adriatic Gulf and the Mediterranean towards the conclusion of Day Four where Galileo reflects on why the tides were highest at Venice, which lay at the end of a body of water orientated north-south. G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, pp. 460 – 461. 70 S. Drake in Galileo at Work, p. 37, p. 43; W. Hooper, ‘Seventeenth-Century Theories of the Tides as a Gauge of Scientific Change’, p. 221-222. Finocchiaro, for example, more generally points to the importance of the division for Galileo’s explanation of the six hourly intervals between high and low tides. M Finocchiaro, Galileo on the World Systems, p298, footnote 28. 71 W Wallace, Galileo’s logic of discovery and proof, p. 216.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 89 2.4 Implications for historiography
Placing the theory of the tides in a cosmographic context helps us understand what Galileo hoped to achieve through the theory. The purpose of the Dialogo was to provide both astronomical and cosmographical proofs for the Copernican arrangement of the cosmos. In this, the purpose of the theory of the tides was to offer the cosmographic argument for the Copernican view.. Because historians of science have overlooked the field of cosmography, they have failed to notice this purpose.
The juxtaposition of terrestrial and astronomical evidence in the Dialogo and the subject of the cause of the tides itself was not as extraordinary for the time as historians have anachronistically thought. Natural philosophers at the time were typically concerned with matching the heavens and earth, and with earthly phenomena such as tidal movement. Finally, Galileo’s great pride in his tidal theory derived from cosmography. He claimed that, in the tides, he had provided the first ever cosmographic demonstration for the Copernican view. Moreover, he claimed he had shown that the heliocentric theory could be developed into a successful cosmographic system, a traditional purpose and measure of success of any natural philosophy. We turn now to explore how the natural philosophy of René Descartes dealt with the relation between the heavens and earth.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 90 3. Descartes and the tradition of cosmography
3.1 Descartes’ natural philosophy
In the Principia, Descartes presented the first credible, wide-ranging account of cosmology, physics and matter that was consistent with Copernicus’s heliocentric arrangement of the cosmos.72 In this work, Descartes proposed that the cosmos comprised numerous fixed stars around which rotated whirlpools or vortices of tiny heavenly globular particles (Figure 3.2).73 Each vortex carried the planets around the fixed star at its centre, while the distribution of the size and speeds of the particles kept each planet ‘suspended’ at a certain, constant distance from the star.74 Smaller vortices existed around some planets and were responsible for carrying moons around that planet.75
At the core of Descartes’ natural philosophy was an account of the formation of the cosmos and the earth. This genetic story was a hypothetical one, based on laws of nature Descartes purported to deduce from first principles. Before presenting it, he wrote:
I wish what I shall write later to be taken only as a hypothesis…But, even though these things may be thought to be false, I shall consider that I have achieved a great deal if all the things which are deduced from them are entirely in conformity with the phenomena: for, if this comes about, my hypothesis will be as useful to life as if it were true,{because we will be
72 R Descartes, Principles of Philosophy, V R Miller and R P Miller (trans), D Reidel, Dordrecht, 1983. 73 R Descartes, Principles of Philosophy, p. 96 -98. 74 The manner of the formation of the stars was crucial in accounting for why each planet kept a set distance from its star and why planets collectively kept different distances. See J. A. Schuster, ‘“Waterworld”: Descartes’ Vortical Celestial Mechanics. A gambit in the natural philosophical contest of the early seventeenth century’ in P R Anstey and J. A. Schuster (eds), The Science of Nature in the Seventeenth Century, Springer, Netherlands, 2005, pp. 35-79, pp.41-55. 75 R Descartes, Principles of Philosophy, p. 97-98.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 91 Figure 3.2: Heavens containing vortices with a fixed star at the centre of each (the sun is at S and other fixed stars at f and F in the centre of the 76 vortices IEP, BVEI and AEV respectively).
76 R Descartes, Principles of Philosophy, Plate VI. ‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 92 able to use it in the same way to dispose of natural causes to produce the effects which we desire}.77
Thus, the diachronic story of the formation of the cosmos and the earth was a central device in Descartes’ argument for the nature of the heavens and the earth.
Descartes derived three basic elements of his cosmos and the initial creation of the cosmos, vortices and fixed stars from these elements. ‘All the bodies of this visible world are composed of these three elements: the Sun and the fixed Stars of the first, the Heavens of the second, and the Earth, Planets, and the Comets of the third’, Descartes asserted.78 Descartes hypothesised that all planets were once fixed stars.79 A star became a planet when, being surrounded by sunspots and aether, it is extinguished and descends into a neighbouring vortex until it reached a certain distance from the fixed star at the centre of that vortex and proceeded to revolve around that star. All planets, moons and comets were originally fixed stars in vortices of their own. Indeed, the Earth was once a fixed star that became extinguished and ‘ultimately descended, along with the spots and all the air enveloping it, into another larger vortex in the center of which is the Sun.’80
77 R Descartes, Principles of Philosophy, p. 105. 78 R Descartes, Principles of Philosophy, p. 110. Descartes’ explanation of the nature of matter was fundamentally in accord with the atomist concept of the existence of only one primary matter. Different elements within this primary matter could be distinguished on the basis of shape, size and motion. Descartes additional, defining, premise beyond the atomistic conceptualisation was that there could be no void in nature. This premise was central to his explanation of the nature of matter and its arrangement in the cosmos as it accounted (amongst other things) for the gradual creation of different elements from the primary matter. The first element comprised extremely small, fast moving particles of matter that could be easily divided and change shape and size, and primarily makes up stars The second element consisted of larger, spherical globules, makes up the vortices. The third element comprised slow moving, branch- shaped particles that makes up planets, satellites and all ‘terrestrial’ objects on and of them. Particles of the first element moved into fill the spaces left by the other elements. Descartes argued for the existence of these three elements through a detailed explication of their gradual formation since the ‘beginning’ of matter in a cosmos without void when there were numerous, equally sized and shaped particles. R Descartes, Principles of Philosophy, pp. 109-110, 138-139, quote p. 139. Kuhn addresses the affinity between Copernicanism and atomism in T S Kuhn, The Copernican Revolution, pp. 235-238. 79 R Descartes, Principles of Philosophy, pp. 145 – 151. 80 R Descartes, Principles of Philosophy, quote p. 181-182.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 93 A related component of the genetic story was a diachronic account of how the earth was formed.81 Descartes proposed, again hypothetically, that the earth’s structure resulted from the interaction over time between the elements of matter of which the earth was composed, which itself was a result of the Earth’s star-origins. Shortly before the earth descended towards the sun, it comprised three regions; I, M and A (see Figure 3.3), Region A comprised many particles of the third element mixed with the heavenly matter. Descartes argued that all the bodies found on earth originated in this region. Region I contained heavenly matter of the first element, the same in nature as that comprising the sun, while region M was made up of the second element, the same in nature as sunspots. As the earth approached the vicinity of the sun, the heavenly globules pushed down on the particles of the third element causing region A to gradually separate into four distinct regions B, C, D and E, on the basis of the shape and size of the matter particles (see Figure 3.4).82 Descartes maintained that region D was fluid (it comprised long, cylindrical-shaped particles) while region E was initially a hard, thin, shell-like layer. Over many years, the non-cylindrical particles in D transferred to region E, where they accumulated, causing E to both thicken and develop small fissures. These fissures became larger from the migration and motion of heavenly particles within them (points 2, 3, 4, 5, and 6 in Figure 3.5). Eventually they became so big that E cracked and ‘fell by its own weight’ onto the surface of exterior crust of the earth, C. As the circumference of C was smaller than that of E, when E collapsed onto C some fragments became tilted and leaned on each other, while others fell directly on top of C (Figure 3.6).83
81 R Descartes, Principles of Philosophy, pp. 181- 203. 82 R Descartes, Principles of Philosophy, p. 196 - p. 203. 83 R Descartes, Principles of Philosophy, pp. 181 - 203.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 94 Figure 3.3 The original Earth with three regions84
Figure 3.4: The gradual formation of the regions of the Earth.85 (The sequence of the creation of the Earth takes place anti-clockwise from A)
84 R Descartes, Principles of Philosophy, plate XVI. 85 R Descartes, Principles of Philosophy, plate XVII. ‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 95 Figure 3.5: Cross section of the Earth and its regions, including the hard crust of E with fissures and gap F86
Figure 3.6: Cross section of Earth where E has broken and fallen onto C, forming the oceans and mountains87
86 R Descartes, Principles of Philosophy, plate XVIII, figure i. 87 R Descartes, Principles of Philosophy, plate XVIII, figure ii. ‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 96 All this linked into a discussion of certain physical features of the earth. Descartes proposed that oceans formed when D, which was fluid, moved above the lower parts of E. This created oceans (at 23 and 67), gentle plains (at 89 and VX) and mountains like at 12 and 9, 4 and V). In addition, Descartes accounted for the formation of cliffs (1) and rock shelves (such as at 3 and 6).88 Thus, Descartes’ diachronic story of the production of the earth described the existence of specific physical features of the earth; namely the oceans, mountains, plains and coastlines.
Finally, it is important to note that Descartes accounted for a plethora of ‘things which are seen on the Earth’ on the basis of the behaviour and nature of matter close to the earth, a dead star.89 The issues he explained included: the earth’s composition (the existence of minerals, metals and salt); particular effects (the transformation of water into ice and air, and the ebb and flow of the oceans); the origin of particular features on the earth (including rivers, springs, earthquakes, and volcanoes); and the creation and properties of common terrestrial materials (fire, gunpowder, glass, magnets, steel and iron, and the sphericity of drops of liquid).90 In reference to his genetic account of the formation of the cosmos and the earth, Descartes maintained that, as there ‘was no phenomenon in the distant heavens which has not been sufficiently explained’ and that ‘the causes of all natural things [on earth] can be understood’ by means of that [genetic] hypothesis’, then one could reasonably conclude that their nature ‘is the same as if they had indeed been formed in such a way’.91
88 R Descartes, Principles of Philosophy, p. 203, emphasis added. 89 R Descartes, Principles of Philosophy, p. 181. 90 R Descartes, Principles of Philosophy, pp.181-288. 91 R Descartes, Principles of Philosophy, p. 177 and p. 181.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 97 3.2 Recent approaches to Descartes
In the considerable literature on Descartes, many historians of science observe that Descartes used a genetic story of the production of the cosmos and attempted to account for terrestrial phenomena by using his corpuscular mechanical theory. Gaukroger, Dear, Schuster, Hooper and Hattab are among the recent commentators who mention Descartes’ interest in explaining terrestrial effects by means of the mechanical theory.92 Hooper explores Descartes’ tidal theory while Gaukroger examines both his tidal theory and story of the earth’s formation. Hattab comments that Descartes engaged in ‘universalising’ explanations of everyday phenomena, such as how pebbles become rounded, and then comparing them by analogy to the cosmos.93 While each commentator considers the aspects they highlight to be significant components of Descartes’ theory, they either do not explain why Descartes is so interested in the exposition of these terrestrial matters, or provide any compelling explanations. Gaukroger proposes that Descartes’ description of the earth’s formation was the first occasion in the early modern period in which natural philosophers investigated the earth and its structure and topography.94 As we have seen, while the process of the earth’s formation may have been novel subject matter, the explication of the earth’s structure was not. None of these historians acknowledge the field of cosmography.
92 P Dear, ‘Circular argument. Descartes’ Vortices and Their Crafting as Explanations of Gravity’ in P R Anstey and J A Schuster (eds), The Science of Nature in the Seventeenth Century, Springer, Netherlands, 2005, pp. 81-97, p. 90; S Gaukroger, Descartes’ system of natural philosophy, Cambridge, Cambridge University Press, 2002; J A Schuster, “‘Waterworld’’; H Hattab, ‘From Mechanics to Mechanism. The Questiones Mechanicae and Descartes’ Physics’ in P R Anstey and J A Schuster (eds), The Science of Nature in the Seventeenth Century, Springer, Netherlands, 2005, pp. 99-130, 117-118; W Hooper, Seventeenth Century Theories of the Tides, p. 200. 93 H Hattab, ‘From Mechanics to Mechanism, p. 117 – 118. Hattab describes how Descartes drew an analogy from everyday terrestrial phenomena, such as the rounding of the edges of pebbles in water to larger scale issues, to how the different elements were formed in the universe. Moreover, he ‘universalises’, or expands the scale of claims that can be made from a particular principle, in comparison to Baldi and other commentators on this issue deriving from the (Pseudo-) Aristotelian Mechanical Questions, and applies the expanded claim to the universe.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 98 Nor have historians explored how Descartes used ideas about the earth’s structure in his argumentative strategy. For instance, those examining the tidal theory focus on how Descartes’ thinking changed over time, the important role of the moon in his theory (in contrast to Galileo), and his coverage of tidal effects compared to predecessors and peers.95 However, commentators ignore his conceptualisation of oceans that underpins the theory. We shall, in the following analysis, shine a light on the manner in which Descartes was involved in cosmography and how he utilised geognosic opinion of his day.
3.3 The cosmographic project of René Descartes
We can see that Descartes engaged in cosmography in a manner consistent with earlier Copernicans. That is, he sought to show that his theory of the heavens (both his cosmology and physics) could account for earthly phenomena such as the tides and magnetism. This suggests that Descartes had an eye to the leading natural philosophical concerns regarding geognosic knowledge. Furthermore, like the thinkers we have already investigated, Descartes was actively involved in articulating geognosic opinion for the purpose of providing a unified picture of heavens and earth. To understand how he did this, we need to investigate the theory of the tides Descartes presented in his early work, Le Monde, ou Traité de la lumiere.96
94 S Gaukroger, Descartes’ system of natural philosophy,p.161. 95 Gaukroger notes that: Descartes’ theory accounted for the daily, monthly, half-monthly, yearly, and half- yearly cycles of the tides; the tidal theory in Le Monde and Principia were largely the same; and Descartes was satisfied with his tidal theory and reasonably confident of its success. S Gaukroger, Descartes’ system of natural philosophy, p.18, 169-171. See also Hooper on Descartes’ tidal theory, W Hooper, ‘Seventeenth Century Theories of the Tides’, p. 200. 96 Le Monde was completed in 1633 but published posthumously in 1664. R Descartes, Le Monde, ou Traité de la lumiere, 1664, M S Mahoney (trans. and ed.), Abaris Books Inc., New York, 1979, pp. 139-146. On the date of writing and publication of Le Monde, see the introduction by Mahoney, pp. vii-viii; J A Schuster, ‘“Waterworld”’, p. 35; R Descartes, The World and Other Writings,SGaukroger(ed.), Cambridge University Press, Cambridge, 1998, p. xxii,vii:. Descartes’ abandonment of the publication of Le Monde following condemnation of Galileo’s Dialogo by the Roman Inquisition is discussed by M S Mahoney pp. vii-xiv and more recently in S Gaukroger, Descartes’ system of natural philosophy, pp. 5-6,
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 99 Descartes proposed that the tides were due to the unusually fast movement of the ‘matter of heaven’ (consisting in balls of second element) between the moon and the earth.97 If the moon were immobile at B (Figure 3.7) heavenly matter has less space to pass between the moon and the earth, than it would if the moon were absent (the space between 6 and O with the moon present, compared with the space 6 to B if the moon were not present). Consequently, heavenly matter has to move a little bit faster when it moves between the earth and moon, and in doing so ‘cannot fail to have the force push the whole earth [EFGH] a little bit toward D’.98 That is, the centre of the earth (EFGH) ‘sinks’ to T, away from the centre of heaven ABCD at M.99 The heavenly particles also cause the air (5678) and water (1234) to sink towards T both at sides 6, 2 and also at sides 8,4, because they are both liquids. In response, the water and air rise at 5,1 and 7,3. The fast-moving heavenly particles, in effect, ‘squeeze’ the water and air causing the surface of each to form an oval, while the solid earth remains round.100
The ebb and flow of the tides arise as the earth turns around its axis and the water on different parts of the earth is, in turn, squeezed. After six hours of axial rotation, the point E of the earth and point 1 of the sphere of water would have moved to the position opposite the moon, causing the water at 1 and 3 to be pressed by the force of the heavenly matter (in turn causing the water at these positions to be ‘less high’ where previously it had been ‘higher’) and the water to accumulate at 2 and 4 (where previously it had been ‘lower’).101 Thus, the height of the water at locations on the earth had been reversed over a six-hour period. Descartes maintained that the six-hourly displacement of the water continued over an (approximately) twenty-four hour period as
10 - 23. 97 R Descartes, Le Monde, p. 139. 98 R Descartes, Le Monde, pp. 139, 141. 99 R Descartes, Le Monde, p. 141. 100 R Descartes, Le Monde, p. 141. 101 R Descartes, Le Monde, p. 141.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 100 Figure 3.7: Diagram explaining the tides, R Descartes, Le Monde, 1644.102
102 R Descartes, Le Monde, p. 139.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 101 the earth spins on its axis, causing the sea to have an ebb and flow ‘about this earth once every six hours’.103
Crucially, in his tidal argument of Le Monde Descartes presents an idealised model of the earth completely encircled by water. This is reminiscent of the traditional Aristotelian model. Indeed, Descartes’ notion that water could flow freely between oceans differed from the idealised idea of Galileo of oceans as sealed, separate and unconnected bodies of water. Presumably, Descartes presented his model of a water-encircled earth because it was vital to his tidal argument: it allowed for displaced water to flow freely around the rotating earth.
However, when Descartes explained how the earth was formed in the Principia,he described a different concept of the earth as a terraqueous globe. As described earlier, the oceans formed when the exterior of the earth fell below the water and thus rested within the hollows of the collapsed outer crust (Figure 3.6). So, when Descartes presented the
103 R Descartes, Le Monde, pp. 141, 143. In addition, Descartes claimed that the squeezing of the oceans combined with the easterly axial rotation of the earth causes a continuous travelling of water and air towards the west ‘which, according to the report of our pilots, make navigation on our seas much easier going from the orient to the occident than from the occident to the orient.’ R Descartes, Le Monde,p. 143. As we saw earlier, this experience is also cited in the Dialogo, suggesting it was commonly believed that voyages in a westerly direction were quicker than those in an easterly direction (25% quicker in the Mediterranean, according to Galileo). The explanation in the Dialogo appeals to the ‘fact’ of a constant breeze from the east, noted by sailors in the tropics, which Salviati claims supports the earth’s motion. G Galilei, Dialogue Concerning the Two Chief World Systems, second edition, p. 440-441. Descartes also accounted for the one fifth of an hour lag in the tidal changes (because of the monthly circuit of the moon) and why the ebb and flow of the sea are much greater when the moon is full and new, than when only half full (the moon moves faster at B and D, where it is full or new). R. Descartes, Le Monde, p. 143. He added that the ‘other special properties of the ebb and flow of the sea…depend in part on the diverse situations of the seacoasts and in part on the winds prevailing at the time and at the place they are observed’. R Descartes, Le Monde, p. 145.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 102 tidal theory from Le Monde in the Principia he carefully qualified his concept of a water- enclosed earth.104
In Le Monde, Descartes did not remark on his proposal that the earth was completely surrounded by water:
Because the air 5678 and water 1234 surrounding this earth are liquid bodies, it is evident that the same force that presses the earth in this way must also make them sink towards T, not only from the side 6, 2 but also from its opposite 8, 4, and in recompense cause them to rise in the places 5,1 and 7, 3.105
Descartes did not explain the model in any detail. However, he refined the model for the Principia:
let…1234 [be] the surface of the water, which, for the sake of greater clarity, we are supposing completely covers the Earth; and 5678, the surface of the air encompassing the ocean.106
Descartes argued that the concept of an earth encircled by water was not true in reality but was a useful and appropriate conceptual device:
[I]t must be noted that the ocean does not in fact cover the whole Earth, as we assumed a little earlier; but because the Ocean extends around the Earth’s entire periphery, as far as the general movement of the Ocean’s
104 The case for the cause of the tides in the Principia was largely the same as that in Le Monde. 105 R Descartes, Le Monde, p. 141. 106 R Descartes, Principles of Philosophy, p. 206, emphasis added.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 103 water is concerned, it must be understood as if the Ocean did envelope thewholeEarth.107
In other words, Descartes maintained that, while oceans do not wholly cover the earth, they are continuous to the extent that the westerly flow of water is unhindered as no stretch of land runs completely from north to south. The waters in the oceans can travel freely from east to west as if they covered the whole earth.108
So, Descartes was engaged in the same process of explaining geognosic opinion and terrestrial phenomena that we investigated in earlier chapters to assist the cosmographic project of aligning the heavens and earth. Yet, he deployed two concepts of the earth: a simple, ideal model of a water-encircled earth to explain the tides and a terraqueous globe for the creation of the earth’s physical features. In addition, he accounted for a wide range of terrestrial phenomena, revealing what he regarded as necessary to prove his corpuscular theory. What readers expected of Descartes must have resembled what they expected of Gilbert, except that a generation later, Galileo (and Gassendi, and others) had raised the stakes and a greater display of explanatory power was now called for.
Descartes marks a shift in the Copernican cosmographic discourse of the sixteenth and seventeenth century. He pursued the traditional goals of the cosmography in a much more radical way than previous Copernicans. As we have seen, Copernicans used the ‘heavens to earth’ link to make new claims about the heavens, competing with each other to get
107 R Descartes, Principles of Philosophy, p. 209. 108 This interpretation is supported by the fact that Descartes chose to use a new term for oceans in the theory of the tides, as noted by editors Miller and Miller: ‘The term used at this point [in respect to the tides] in the Latin is ‘Oceanus’ which refers to the collective total of the Earth’s oceans. Previously, when referring to the ocean, the term ‘mare’ (uncapitalized) has been used. The French reflects this change as well.’ In the English edition, they translate ‘Oceanus’ as ‘Ocean’ while ‘mare’ appears as ‘ocean’. R Descartes, Principles of Philosophy, editors’ footnote 41, p. 209. Interestingly, when Descartes comes to explain the absence of tides in lakes and ponds he reasons that waters contained in lakes and ponds is not ‘squeezed’ and displaced by heavenly matter (like the water in oceans) as it is
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 104 more astronomical traction from cosmography. In other words, they argued for particular claims about the heavens from features of the earth (albeit in differing ways and for slightly different strategic reasons). However, Descartes’ cosmographic program was more ambitious: in it the terraqueous earth and all planets were not just theoretically related to the heavens, but both were actually similar products of the same physical laws and celestial processes of star and planet formation. From vortex formation, appearance of a central star, and then a star’s death and its capture in another vortex, Descartes describes the production of terraqueous planets and all other heavenly bodies in a single explanatory frame. In other words, Descartes derived all planets from his vortex dynamics of the heavens and is therefore the ultimate ‘heavens to earth’ cosmographer. He wrote:
[I]f we can devise some principles by which we can demonstrate that the stars and the Earth, and indeed everything which we perceive in this visible world, could have sprung forth … we shall in that way explain their nature much better than if we were to merely describe them as they are now.109
Descartes turned cosmography into a theoretical account of the processes giving rise to the arrangement of the cosmos. His natural philosophy is a triumph of cosmography, but at the same perhaps establishes cosmography’s replacement: physical theory accounting for heavens and earth without distinction.
physical disconnected from the mass of water in the ocean and has only small surface area. R Descartes, Principles of Philosophy, p. 209. 109 R Descartes, Principles of Philosophy, p. 105 -106, emphasis added.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 105 Conclusion
This study started out by examining what historians of science have said about the role of geography in the Scientific Revolution. I noted that modern commentators like Bennett, Livingstone and Cormack have concentrated on the style and methods of early modern geography rather than on knowledge and theories about the earth. I argued that, as a result, while history of science has seen substantial benefits in tracing the methodological connections between natural philosophy and its subordinate disciplines, such as the mixed mathematical sciences, the standard literature has not yet identified a concrete pathway of how geographical discoveries—arising from the rapidly advancing field of navigation and exploration—entered into the conceptual developments of the Scientific Revolution.
To cast light on the place of geography, or rather ‘geognosy’ or knowledge about the earth’s structure, we briefly investigated at the status of cosmography in the early modern period. We found that cosmography was a prominent field of knowledge, considered to be that part of natural philosophy seeking to provide within one explanatory system the relationship between the heavens and earth as well as the nature of each. It was a ‘parent’ discipline, connecting and requiring alignment between the fields of geography and astronomy. We discovered, however, that historians of science have overlooked cosmography (or misconstrued it as in the case of Cormack) and the oversight applies equally to historians focused on astronomy since Kuhn and Koyré, and those concentrated on early modern geography such as Bennett and Livingstone.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 106 So, to investigate cosmography, we examined the bonds between geognosic opinion and natural philosophy from the thirteenth century up to the time of Copernicus. Referring to the work of Goldstein, Grant and Randles, we found that the shape of the earth remained a controversial topic throughout the period. Moreover, natural philosophers customarily sought to fit concepts of the earth’s structure to cosmological theory. In other words, modifying geognosic opinion was a core part of the cosmographic endeavour. In the thirteenth century, Aristotelians Sacrobosco and Scot tried to reconcile terrestrial physics with the indubitable existence of dry land by proposing that the earth emerged slightly from the sphere of water like a floating apple. In fourteenth century, Buridan and Albert of Saxony squared the floating apple model of the earth with the additional pseudo– Aristotelian concept that the sphere of water is ten times larger than that of earth. In the late fifteenth and sixteenth centuries, controversy erupted with thinkers like Vadianus, Fernal, Nunes and Peucer rejecting the floating apple model of the earth on the basis of knowledge gained from the voyages of discovery, and campaigning for the Ptolemaic notion of a spherical, terraqueous globe. Crucially, we found that Copernicus participated in this geognosic debate. Additionally, he used his explication of the spherical shape of the earth to build a matching, albeit radical, heliocentric cosmological theory and did so by reasoning from the earth to the heavens, a form inverting the usual Aristotelian direction of inference. In sum, then, Chapter One demonstrated that cosmography was a customary part of Aristotelian natural philosophy and Copernicus himself engaged with it, although with radical conclusions and in a radical form.
After drawing attention to Copernicus’s cosmography, we began our own case studies in the late sixteenth century with Bruno and Gilbert. Chapter Two argued that both thinkers were actively engaged in cosmography. Bruno painted a unified picture of the heavens and earth by relating the non–central and non–privileged position of the earth to non–
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 107 central and non–privileged position of the sun (and solar system), while Gilbert aligned heaven and earth by linking the magnetic composition of the earth with the movements of the planets around the sun. In addition, he defended the concept of a spherical terraqueous globe and explicated the earth’s solidity and weightlessness for the purpose of his cosmographic project. We also identified that both Bruno and Gilbert adopted Copernicus’s cosmographic style of argument; drawing their cosmological conclusions from their views of the earth, and treating the earth and heavenly bodies as similar. However, the form of argument used by these late sixteenth century Copernicans differed from that of Copernicus in that they extended properties of the earth to celestial bodies, as opposed to applying celestial laws of motion to the earth. Indeed, each may have seen his involvement in cosmography and use of Copernicus’s mode of argument as an expansion of Copernicus’s approach.
Looking at Gilbert and Bruno through a cosmographic lens has cast doubt on the identification by historians of certain features of their thinking as especially radical. Given natural philosophers’ long-standing engagement with cosmography and its use and adaptation by Copernicus, I suggested that historians could regard the approaches of Bruno and Gilbert as instances of a common kind of realist Copernican cosmography, wherein cosmological claims were based on the theory of the earth.
The final chapter moved into the seventeenth century and investigated how two of the most influential Copernicans—Galileo and Descartes—were also engaged in cosmography. It revealed that both thinkers were involved in the same general project we investigated in previous chapters, namely, attempting to provide within one explanatory framework the relationship between the heavens and the earth, and the nature of each. Galileo built on the established cosmographic approach to cosmology. However, he did not argue from a certain view of the earth to his view of the heavens and thus did not employ Copernicus’s cosmographic style of argument. Rather, he utilised the principle
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 108 that claims in cosmology must paint a unified picture of heaven and earth to assert, on the basis of the tides, the Copernican view. In other words, a key way Galileo argued for Copernicanism was by demonstrating the cosmographic superiority of the heliocentric theory. In this, he competed not just with scholastic rivals but also with other Copernicans, such as Gilbert.
The third chapter also characterised Descartes as the most ambitious of the Copernican cosmographers. Descartes proposed that the heavens and earth were related by a single process of generation. Copernicans had not previously explained the processes that created the heavens and earth in their attempt to present a unified picture of the heavens and earth.
To serve cosmography, both Galileo and Descartes addressed aspects of the real structure of oceans and coastlines whilst also employing simple, idealised models of ocean structure. Nonetheless, each built very different models. Galileo’s notion of oceans as vessels emphasised their containment, while Descartes’ concept of an earth encircled by water highlighted their interconnection. Ocean structure was obviously a topic of geognosic controversy in the seventeenth century.
Finally, Chapter Three offered new insights and thereby answered some persistent historiographical questions on these leading seventeenth century Copernicans. It revealed that Galileo intended ‘argument three’ of the Dialogo to be a cosmographical proof of the Copernican view, providing historians with a new explanation of Galileo’s sense of accomplishment. Looking at Descartes from a cosmographic perspective has shown how his cosmographical account, little stressed by historians, sat at the centre of his natural philosophical strategy. It suggested his entire mature work to be a radical move in the tradition of cosmography.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 109 There are some clear similarities among the approaches of the Copernican natural philosophers we investigated. It is significant, that Copernicus, Bruno, Gilbert, Galileo and Descartes were all involved in the cosmographic project and all employed cosmography to argue for the earth’s motions (Bruno, however, did not use cosmography to address the earth’s movement). In addition, all took for granted that natural philosophy had to provide a unified picture of the heavens and earth. Cosmography was a customary, if not central, part of natural philosophy throughout the period of the Scientific Revolution. Lastly, each Copernican—from Copernicus himself through to Descartes—made their cosmography explicit. Galileo was the most outspoken in this regard in his refutation of Gilbert’s proof of the earth’s motion.
We can also identify several trends over time. Whereas late sixteenth century Copernicans used the cosmographic form of argument (with Copernicus’s reversal), the seventeenth century philosophers did not. Galileo did not propose that the form of the earth determined his cosmological view and Descartes argued from a third component (the genetic development of the cosmos) to the nature of both the heavens and earth.1 We can also see a shift in both the type of geognosic knowledge that Copernicans addressed and in the way they did so. While natural philosophers continued to explicate geognosic opinion into the late sixteenth century, by Gilbert’s generation the focus had shifted from the shape of the earth to the characteristics of a terraqueous globe. By this time, the concept of the terraqueous globe per se was generally taken for granted. However, unlike the sixteenth century thinkers we investigated, Galileo and Descartes did not stake their cosmological claims on a specific form of the earth. For Galileo, aside from his simple, idealised model of ocean structure, geognosic opinion and terrestrial phenomenon were things that had to be explained. Descartes took natural philosophical concern with geognosic opinion exponentially further by using a single process of generation to align the heavens and earth.
1 Our earlier reference to Descartes as a ‘heavens to earth’ cosmographer was in the sense that he derived the earth from the processes and bodies of the heavens.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 110 What can we learn from the involvement of leading Copernicans in cosmography? In the first place, it establishes the need for historians of science to recognise cosmography as a key area in which Copernicans developed their natural philosophies during the Scientific Revolution, and to abandon the anachronistic mindset of astronomy and geography as separate sciences. Early modern natural philosophers cannot be taken to be merely astronomers trying to understand the heavens. They were chiefly cosmographers trying to understand the nature of the heavens and the earth, and their relations. So, the rise of geography should not be equated with the demise of cosmography, as suggested by Cormack. Rather, historians should regard cosmography as exactly the kind of geography in which early modern thinkers were involved, as a field of knowledge at the heart of the intellectual agenda and conceptual developments of the Scientific Revolution. When then did cosmography end? Perhaps its demise came with the emergence of physical theories in the modern sense with Descartes, providing a single explanation of the development of the heavens and earth without distinction. Or perhaps, as Edney proposed, the field still existed at least into the eighteenth century, advanced by groups such as the Nuremberg Cosmographical Society (1746–1754) and pursued in enterprises such as determining the size of the earth, longitude at sea and the possibly spheroidal in shape as suggested by Newton.2
Secondly, cosmography offered Copernicans a new opportunity to learn about the heavens via the earth. However, in considering early modern cosmography, historians should be cognisant that the cosmographic project held a different significance for Copernicans and scholastics. It required scholastics to relate heavens and earth in a ‘unity’ in order to ensure, for example, that the terrestrial laws of physics and geocentric cosmology squared with obvious facts about the earth. Theology and other views on correspondences similarly demanded certain alignments between heavens and earth. However, in contrast to Copernicans, because different laws applied to the heavens and earth, cosmography did not see scholastics drawing from geognosic opinion to celestial laws of physics, matter and causation.
2 M. Edney, ‘Mathematical Cosmography and the Social Ideology of British Cartography, 1780-1820’, p. 102-103.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 111 Thirdly, apart from astronomy, to understand the place of geognosic knowledge (or ‘geography’) in the Scientific Revolution, historians of science need to think in terms of the field of cosmography. Natural philosophy had to include cosmography. Geognosic knowledge entered into the intellectual developments of the Scientific Revolution through cosmography. Ideas about the earth’s structure were contested within the discipline of natural philosophy; natural philosophers argued for a particular geognosic view in relation to a particular stance in astronomy. Thus, through this study we have seen the structure of the terraqueous globe becoming increasingly articulated—from Copernicus’s explication of the spherical shape of the earth, to Gilbert’s claim for its solidity, through to Galileo’s and Descartes’ (idealised and real) accounts of the structure and interconnection of oceans, and ultimately with Descartes, the formation of the earth over time. Indeed, views about the form of the earth took on a new importance in Copernican natural philosophy; the earth’s form began to be transferred onto the forms of celestial bodies.
Finally, we can consider the implications of this study for the literature that addresses the Scientific Revolution. For the work by GGR, which traced the history of thinking about the earth’s structure, this analysis has extended their study of the debate about the earth and its relation to Aristotelianism by applying a natural philosophical and cosmographical lens, and has also taken their chronology further in time. Our investigation has also suggested a broader approach to early modern ‘geography’ by looking at ideas about the earth. It has offered a new, concrete means by which geognosic knowledge entered into the Scientific Revolution. In addition, this study has offered insights into the possible origin of modern physical theory: it emerged out of cosmography, in Descartes at least.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 112 Certainly, our analysis has meant modifying interpretations of those like Kuhn and Koyré who argue as if leading thinkers in the Scientific Revolution were only interested in astronomy and ‘physics’. More positively, for those interested in the links between disciplines, it has identified cosmography, a neglected, yet central part of early modern natural philosophy. Understandably, the literature on individual philosophers is affected by these findings. This study has offered new insights into what certain thinkers were doing when they formulated natural philosophies and has thereby solved some persistent historiographical questions.
This thesis is necessarily limited in space and scope, and thus points to further possibilities. Historians might usefully apply a cosmographic perspective to anomalies that remain in our understanding of other great early modern thinkers. For example, Newton’s interest in astrology and alchemy springs to mind. The harmonic work of Kepler (music after all was for some central to cosmography) also demands investigation from a cosmographic perspective: does it depend on any particular features of the sublunary world or does it rather prefigure Descartes with his quest for a single generative account of the cosmos in geometry and harmonics? The research on the Copernicans investigated here could be extended, for instance by exploring Galileo’s work beyond the theory of the tides or the use of terrestrial analogies by many to explain the heavens. Other opportunities lie in examining the use of cosmographic counter- arguments by scholastics against Copernicans and exploring the use of cosmographic- related representations of the cosmos, such as the pairing of celestial and terrestrial globes.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 113 Bibliography
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‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 128 Appendix
A. Gilbert’s reliance on a terraqueous globe
We can understand the great extent to which Gilbert’s argument relied on a terraqueous globe by way of a thought experiment, in which we attempt to graft the arguments of the magnetic philosophy onto the floating apple model of the earth.
In doing this, a key challenge is the behaviour of a compass needle on the earth. This was central to Gilbert’s explanations of variation, direction and dip and thus his proof of the magnetic nature of the earth. Take Gilbert’s case for the magnetic motion of variation as an example. Gilbert proposed that the deflection of a compass needle noted by sailors and navigators, was due to the amount of compass-attracting lodestone in the vicinity of the location of the place of the compass reading. Given that the earth consisted of magnet of various forms, the existence of mountains near a particular place would cause a compass to vary towards those mountains, (see the figure presented in Chapter Two, reproduced below as Figure A).
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 129 Figure A: Illustration in De magnete
showing variation1
In Gilbert’s diagram, points P and M are the poles of the earth represented on a terrella. The compass needles G and N point directly towards pole P, that is they do not experience variation. On the other hand, compasses C, A and L deflect slightly away from pole P as a result of their attraction to mountains F, B and F respectively.
If we translate Gilbert’s theory of variation to the floating apple model of the earth, the effect of mountains on a compass observations at sea to a large degree become inconsequential because the point of observation could be south of the ‘south’ pole.
To illustrate, Figure B shows the sphere of the earth emerging out of the larger sphere of water, on a hypothetical earth/terrella.
1 W. Gilbert, ‘On the lodestone’ (Hutchins), p. 80.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 130 Figure B: Gilbert’s explanation of variation translated hypothetically to the floating apple model of the earth
The poles of the sphere of earth are points P and M and a mountain range is at F. The middle of the sphere of water (that is, the middle of the Atlantic Ocean) is at O. Compasses on vessels at sea at points C and A would not aim to the pole P, as in Gilbert’s theory, but away from the nearer ‘south’ pole M on the sphere of earth. This in itself would have contradicted commonly accepted navigational experience during Gilbert’s time.
Furthermore, because the compass is primarily responding to the south pole M and the distance between the earth and the site of the compass reading are considerably great, given the ratio of water to earth in the model is ten to one (illustrated here), it would be very difficult to argue that any mountains on the earth (such as at F) would have an observable effect and be the sole influence on a compass. The distance from C to the mountains F, for example, is approximately twice the earth’s diameter. While not explicitly stated, commonsense acceptance of Gilbert’s theory of variation relies on landforms being in close proximity to and surrounding the observational point (as
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 131 suggested by his illustrations). So, Gilbert’s theory of variation is incompatible with the floating apple model because any compass observations on open ‘sea’ on the terrella are not taken from the surface of the earth but a considerable distance from the earth’s surface (and hence mountains) and often south of the southern pole.2 As direction and dip similarly rely on observations being taken from the surface of the earth, they too would also be incompatible the floating apple model of the earth. Thus, three of the five motions that comprised Gilbert’s proof of the earth’s magnetic nature—variation, dip and direction—relied on the terraqueous concept of the earth.3
Additionally, Gilbert used the earth’s sphericity as an argument for the ability of the earth to move, drawing on the case of Copernicus, as discussed in Chapter Two. So, in fact the case for four of the five magnetic motions, rotation included, are incompatible with the floating apple model of the earth.
Finally, Gilbert’s argumentative strategy clearly relied on drawing an analogy between the results of ‘experiments’ on the terrella and those which would apply to the earth. Presumably, it would have been very difficult to maintain the use of the solid, spherical terrella as a representation of the world if the earth were conceived as comprising a large sphere of water attached to the sphere of earth, as in the floating apple model of the earth.
This brief analysis demonstrates that Gilbert, like Copernicus, based his theory on the earth as a terraqueous globe wherein the land and sea together formed one sphere.
2 It is conceivable on the floating apple model that once a boat would pass north of the southerly pole, a compass needle would behave as would be expected by pointing north. However, the impact of mountains on compass variation would remain coarse for the reason of the proportions of water to land and the distance between the observational point and the mountains so great that the compass variation associated with a minor shift in longitudinal position would be very small. 3 Gilbert’s explanation of coition did not involve the earth in its explanation and therefore did not rely on a particular premise about the shape of the earth.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 132 List of figures
Figure 1.1: Sacrobosco’s model of the earth, engraving from fifteenth century edition of The Sphere, Venice 1485 and 1490 16 Figure 1.2: Image of the cosmos, from Peter Apian’s 1540 Cosmographia 28 Figure 1.3: Illustrations of the astronomical functions of the two-sphere universe and approximate planetary orbits in a two sphere universe, T. S. Kuhn, The Copernican Revolution.35 Figure 2.1: ‘An example of the Paralleles in earth agreeably to the Paralleles in the Skye’, R Record, The Castle of Knowledge, 1556 52 Figure 2.2: Image of the Aristotelian ordering of the cosmos, T Digges A prognostication euerlastinge of right good effecte 1576 54 Figure 2.3: Gilbert’s diagram for variation, De Magnete, 1600 58 Figure 3.1 Combining of the two uniform motions of the earth in the theory of the tides G Galilei, Dialogo, 1632 78 Figure 3.3 The original Earth with three regions* 92 Figure 3.2: Heavens containing vortices with a fixed star at the centre of each 95 Figure 3.4: The gradual formation of the regions of the Earth 95 Figure 3.5: Cross section of the Earth and its regions, including the hard crust of E with fissures and gap F 96 Figure 3.6: Cross section of Earth where E has broken and fallen onto C, forming the oceans and mountains 96 Figure 3.7: Diagram explaining the tides, R Descartes, Le Monde, 1664 101 Figure A: Illustration in De magnete showing variation 132 Figure B: Gilbert’s explanation of variation translated hypothetically to the floating apple model of the earth 133
* Figures 3.3 – 3.6: R Descartes, Principia, 1644.
‘Heavens and earth in one frame’ Cosmography and the form of the earth in the Scientific Revolution. 133