Le mecaniche (review)

The study of mechanics was still in a rudimentary state at the end of the sixteenth century but in Italy it had attracted capable investigators like Niccolò Tartaglia, Giovanni Battista Benedetti, and Guidobaldo del Monte. The principal works in the received canon of mechanics had been written centuries before by Archimedes, Aristotle (so they thought, but really an unknown peripatetic we now call pseudo-Aristotle), Pappus, and Jordanus Nemorarius.

It was quite clear that the canon was riddled with difficulties and inconsistencies. Between 1592–1600, Galileo Galilei, then a young professor at Padua, investigated those difficulties and managed to solve many of them in a short, untitled treatise, now known as Le mecaniche, on the principles of the five simple machines — the lever, the winch (or capstan), the pulley, the screw, and the wedge — and the force of percussion. Galileo never published Le mecaniche, but his students occasionally copied it out during private tutorials. One of those copies found its way to Marin Mersenne, who recognized its importance at once, translated it into French, and published it at Paris in 1634. Then in 1656, Vincenzo Viviani appended a scholium on the force of percussion Galileo had drawn from Le mecaniche to the Manolesi edition of Discorsi matematiche intorno alle due nuove scienze in 1656. Le mecaniche was a formative work for Galileo, and it helped to set the stage for major advances in mechanics that followed before the end of the seventeenth century.

Romano Gatto has just published an excellent critical edition of Le mecaniche — the first new edition to appear in Italian since 1891 despite its importance to historians of science. After a century of reliance on Antonio Favaro's definitive Edizione Nazionale delle Opere di Galileo, (1890–1909, reprinted 1929–39, 1964–66, 1968) historians are now reassessing the original texts of the Galilean corpus. Gatto's project is a fitting complement to recent editions of Galileo's works by other leading Italian scholars who are raising editorial standards to new heights: Enrico Giusti's edition of Discorsi matematiche intorno alle due nuove scienze (1990), for example, or Ottavio Besomi and Mario Helbing's extraordinary editions of Dialogo sopra due massimi sistemi del mondo (1998), and the Discorso delle comete (2002).

It is rare that new insights emerge strongly from careful reexamination of old data, yet Gatto makes an important revelation in this edition. On review of the eighteen extant copies of Le mecaniche, Gatto has established that Galileo wrote two distinct versions of Le mecaniche. Gatto refers to them as the brief version (versione breve) and the long version (versione lunga) and, for the first time, he makes both versions available to the reading public. Gatto maintains that this pair of treatises has been known primarily through the long version, which Favaro published as Le mecaniche in the Opere (1891) after deciding that four shorter variants constituted reductions of a single, original manuscript.

Once we acknowledge the existence and import of two distinct versions, however, Galileo's early Paduan period and its episodes take on interesting new contours. The earlier versione breve (represented in four of the eighteen copies) was devoted to the question of how machines can be used to move greater weights with smaller forces, praeter naturam, and whether nature could be deceived, which Galileo denied. The later versione lunga revisited the five machines but included an analysis of the inclined plane as part of the discussion of the screw. The versione lunga further proposed a mechanical "principle of conservation," principio conservativo, and attempted to establish a rigorous deductive structure for mechanics based on definitions of momento, centro di gravità; and suppositions on how bodies and their centers move in basso.

Gatto's introductory essay on the history of mechanics and the nature of Galileo's innovations in Le mecaniche makes other important contributions to Galileo scholarship in its own right. Gatto's review of the familiar canon of ancient and medieval authors...