SPRINGER BRIEFS IN HISTORY OF SCIENCE AND TECHNOLOGY Ido Yavetz Bodies and Media On the Motion of Inanimate Objects in Aristotle’s Physics and On the Heavens 123 SpringerBriefs in History of Science and Technology More information about this series at http://www.springer.com/series/10085 Ido Yavetz Bodies and Media On the Motion of Inanimate Objects ’ in Aristotle s Physics and On the Heavens 123 Ido Yavetz CohnInstitute for History of Science andIdeas TelAviv University TelAviv Israel ISSN 2211-4564 ISSN 2211-4572 (electronic) SpringerBriefs inHistory ofScience andTechnology ISBN978-3-319-21262-3 ISBN978-3-319-21263-0 (eBook) DOI 10.1007/978-3-319-21263-0 LibraryofCongressControlNumber:2015943847 SpringerChamHeidelbergNewYorkDordrechtLondon ©TheAuthor(s)2015 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfrom therelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authorsortheeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinor foranyerrorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper SpringerInternationalPublishingAGSwitzerlandispartofSpringerScience+BusinessMedia (www.springer.com) For Tomer, Amalia, and Dafna Foreword The purpose of this essay is to present a theory of the motion of inanimate bodies based exclusively on principles laid down by Aristotle in his Physics and On the Heavens.Astheintroductionwillexplainingreaterdetail,thereisnopretensehere to capture the definitive reconstruction of Aristotle’s theory of bodies in motion— animpossibletaskinmyopinion,giventheinformationwecurrentlypossess.Itis, however, a plausible reconstruction, albeit not the only one possible. The essay is meantprimarilyforhistoriansofscienceinterestedintheevolutionofphysicsfrom antiquity to the scientific revolution of the seventeenth century, and to students of Aristotle’s natural philosophy. In order to keep a sharp focus on Aristotle’s texts, andtoremainwithintheusefulformatoftheSpringerBriefsSeries,discussionsand references that pertain to the vast literature on Aristotle’s natural philosophy have been cut down to a bare minimum. Initial motivation forthisprojectoriginatedinagraduateseminar Igavejointly withProf.RivkaFeldhayonGalileo’sDeMotuattheCohnInstituteforHistoryand Philosophy of Science and Ideas in Tel Aviv University. In his De Motu, Galileo attempted to formulate principles of locomotion irrespective of more general ideas regarding natural change. Aristotle’s Physics discusses nature as the realm of all material changes, of which locomotion is but one form. On the Heavens discusses aspects of locomotion to the extent that they pertain to general cosmology. Aristotle’s surviving works do not contain a separate treatise dedicated to locomo- tionalone.Bycontrast,Galileo’sstudyofterrestrialmotion,fromtheDeMotutoits finalevolvedformintheDiscoursesonTwoNewSciences,revealsnointerestinthe wider scope of Aristotle’s terrestrial natural philosophy. Instead, he developed a theoryoflocomotionforitsownsake.However,inthecourseofformulatinghisown ideas, he found numerous occasions to comment at length on various aspects of Aristotle’stheory oflocomotion. Onsome ofthese occasions, Galileo’s comments vii viii Foreword seemed to us either misguided, or somewhat careless, or not representative of a decent interpretation of Aristotle’s texts as we currently know them. The more we discussed these issues in the seminar, the clearer it became that before we could properlyaddressGalileo’sremarks,weneededtodevelopourownunderstandingof Aristotle’s theory of locomotion. This resulted in an outline for a theory of loco- motion with fair capacity to account for a large class of locomotive phenomena, often in mathematical form that Aristotle’s own text indicates. Viewed from this theoretical perspective, Galileo’s law offree fall remains a highly original contri- bution, exposing connections between basic Aristotelian parameters that were pre- viouslytreatedasindependentwithinthetheory.Itisnot,however,aprinciplethat requireswholesaleabandonmentoftheAristoteliantheory.Infact,itcanbeseenasa great new discovery that refines the theory’s ability to account for locomotive phenomena. Developmentoftheideasthatgerminatedduringthejointseminarwasaidedby discussionswithasmallgroupofscholarsandstudentsattheMinervaHumanities Center’s project on migrating knowledge at Tel Aviv University, headed by Prof. Feldhay, to whom I owe my first gratitude. Without her constant encouragement and support this essay would never have developed beyond my lecture notes and PowerPoint presentations. Particular thanks go to Dr. Michael Elazar, for his endless patience and constructively critical examination of this essay’s various aspects.Dr.IvorLudlumhelpedwithsomedifficultiesinvolvingAristotle’sGreek, and Appendix B on the threshold of motion in time would not have been possible without Mr. Avi Aroesti’s generous help. Final shaping of the understandings gained during these years into the present essay was made possible by two scholarships at Department 1 of the Max Planck InstitutefürWissenschaftsgeschichteinBerlin,undertheleadershipofProf.Jürgen Renn, to whom I am indebted for this opportunity. Professor Matteo Valleriani of Department 1 read the entire manuscript, and suggested many useful corrections andimprovements.IhavealsobenefittedfromDr.JoycevanLeeuwen’sextensive familiarity with the pseudo Aristotelian Mechanical Problems. At an advanced stage,selectaspectsofthisworkwerepresentedattheExcellenceClusterTOPOIin Berlin. I thank the informed audience I met there for the relevant feedback. Contents 1 The Three Levels of Aristotle’s Theory of Material Bodies in Forced Motion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Level 1: The Basic Relationship Between Mover, Load, and Speed. . . 1 Level 2: The Medium and Resistance to Motion . . . . . . . . . . . . . . . . 6 Level 3: Why Motion Persists After the Initial Moving Cause Has Been Removed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2 Heaviness, Lightness, Sinking and Floating . . . . . . . . . . . . . . . . . . 15 Summary: The Main Features of Aristotle’s Theory of Terrestrial Locomotion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3 Some Refinements of the Basic Theory . . . . . . . . . . . . . . . . . . . . . 29 The Threshold of Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Segments of Time, Instants of Time, and the Concept of Speed. . . . . . 31 Formal and Dynamical Objections to Motion of Unlimited Extent . . . . 34 Reversal of Motion and Collisions. . . . . . . . . . . . . . . . . . . . . . . . . . 36 Heaviness, Lightness, and “the Dense Is Heavy and the Rare Light”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 The Geometry of Heaviness: On Projectiles that Reach Peak Speed at Midflight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4 The Dynamics of Balance: The Winch and the Lever in the Pseudo Aristotelian Mechanical Problems. . . . . . . . . . . . . . . 55 How to Balance a Winch Using Aristotle’s Physics, VII.V . . . . . . . . . 55 The Winch in the Pseudo-aristotelian Mechanical Problems. . . . . . . . 59 ix x Contents 5 Hipparchus on the Theory of Prolonged Motion . . . . . . . . . . . . . . 67 Appendix A: Do Heavy Objects Become Heavier as they Approach Their Natural Place?. . . . . . . . . . . . . . . . . . . 71 Appendix B: A Threshold of Motion in Time, as well as in Force? . . . 73 Appendix C: A Mathematical Formulation of Aristotle’s Theory of Forced Horizontal Motion. . . . . . . . . . . . . . . 81 Appendix D: A Mathematical Formulation of Aristotle’s Theory of Natural and Forced Vertical Motion . . . . . . . 85 Appendix E: A Mathematical Formulation of Hipparchus’s Theory of Vertical Motion. . . . . . . . . . . . . . . . . . . . . . . 91 Appendix F: Alternative Translations of the Quotations Used in the Main Text. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Bibliography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117