De motu impresso a motore translato. Epistolae duae

GASSENDI, Pierre

Published by Ludovicus de Hequeville, Paris, 1642

THE FIRST PUBLISHED STATEMENT OF THE PRINCIPLE OF INERTIA. First edition, very rare, of this important work, which "contains the first precise published formulation of the principle of inertia" (Jones, p. 63). "Gassendi (1592-1655) did indeed have a deep understanding of Galileo's science and contributed in a crucial way to its dissemination. In his De motu impresso a motore translato (1642) and in the Epistolae de proportione qua gravia decidentia accelerantur (1646), Gassendi integrated in an interesting and original way the content of the Dialogue Concerning the Two Chief World Systems with that of the Two New Sciences, thereby bringing to light the close connection between Galileo's endorsement of the Copernican cosmology and his new science of motion" (Palmerino, p. 267). "On one point - and it is an important one - [Gassendi] was more successful than Galileo: he correctly stated the principle of inertia. The experiment of the De motu impresso a motore translato, performed in 1640 in Marseilles, overthrew the argument of Copernicus's opponents against the movement of the earth. Gassendi arranged to have a weight dropped from the top of a vertical mast on a moving ship in order to demonstrate that it fell at the foot of the mast and not behind it, thus sharing in its fall the forward motion of the ship. Gassendi understood that the composition of motions is a universal phenomenon. Motion is, in itself, a physical state, a measurable quantity, not - as the Scholastics maintained - the change from one state to another. It changes only through the interposition of another movement or of an obstacle" (DSB). "In this regard, Gassendi was able to take a step beyond Galileo's conclusions, drawing from this test a generalized principle of inertia (the Galilean version of inertia was fundamentally circular, given that bodies in motion would trace the earth's curve). Gassendi saw that the motion of the dropped stone at a sustained speed - in the absence of any contrary force or obstacle - is an instance of inertial motion, albeit one where the motion is compositional (describing the parabola). Indeed, neither compositionality nor directionality had any impact on inertial motion, Gassendi concluded: any body set in motion in any direction continues, unless impeded, in a rectilinear path" (Fisher). Gassendi "sent an account of his experiment to his friend and mentor François Luillier. Luillier read Gassendi's letter (which is no longer extant) to a group of erudite friends, among whom was Pierre Dupuy, librarian for the president of the Parliament of Paris. Having heard that Dupuy had expressed some doubts concerning the experimental report, Gassendi wrote him two long letters, in which he provided empirical and theoretical arguments in support of the Galilean principle that 'whatever moves, impresses its motion to all the things that rest on it'" (Palmerino, pp. 267-8). These letters were published as the present work.De motu impresso is also notable for its diagrammatic representations of the mathematics of motion, namely in its abandonment of Galileo's 'triangle of speeds' in favor of "a visually and conceptually different representation based on a lattice of triangles" (Meli, p. 120). OCLC locates U.S. copies at Harvard, Oklahoma, Smithsonian, and New York Society Library. "In the story of mechanics from the time of Aristotle to that of Newton one of the most important and interesting chapters concerns the development of the concept of inertia. The question of what kept projectiles moving was raised from mechanics to cosmology in the Copernican debate and assumed still more importance because of its relevance to the supplantation of Aristotelian physics which was necessitated by Copernicanism. For all his genius, Galileo, the chief founder of that new physics, never was able to shed his preoccupation with circularity and to conceive of inertia as rectilinear. It was Pierre Gassendi, overshadowed by Galileo and Descartes, who prece. Seller Inventory # 6206

Bibliographic Details

Title: De motu impresso a motore translato. ...
Publisher: Ludovicus de Hequeville, Paris
Publication Date: 1642
Edition: First edition.