Hobbes, Galileo, and the Physics of Simple Circular Motions (original) (raw)

What was Galileo Thinking? III: Galileo on Natural Motion

This is the third of a set of papers in which I endeavor to describe how Galileo thought about the physical world without filtering his work through later physics. The present paper discusses Galileo's account of the fundamental role of circular motion in nature.

“A Certain Correspondence”: The Unification of Motion from Galileo to Huygens

In this work, I focus on one of Galileo's concepts which was neither mathematically nor empirically derived, but instead based on a fundamental intuition regarding the nature of motion: that all mechanical phenomena can be treated in the same way, using the same mathematical and conceptual apparatus. This was Galileo's concept of 'correspondence', and I follow it from its origins at the turn of the 17th century through Thomas Harriot, Marin Mersenne and ultimately to Christiaan Huygens. At the centre of the concept of correspondence was that phenomena which looked similar really were the same; they were separate instances of the same fundamental processes. Hanging chains and projectile trajectories did not form the same curve by coincidence; they formed the same curve because both were produced by the same competition between vertical and horizontal tendencies. Correspondences were one of the major motivating and legitimising factors behind both Galileo and Huygens' desire to treat all of nature mathematically. This conceptual structure justified their treatment of all of mechanics as mathematically the same. Harriot and Mersenne's roles in this story are to show how contemporaries of Galileo could approach the same topic in drastically different ways. Unlike Huygens, neither Harriot nor Mersenne understood the concept of correspondences. While Galileo and Huygens relied crucially on correspondences to understand natural phenomena, both Harriot and Mersenne were able to achieve many important results in mechanics without it. This work is the biography of a concept; one that is contingent, constructed, frequently fruitful but not a historical or scientific necessity.

Idealization and Galileo's Proto-Inertial Principle

Philosophy of Science, 2018

Galileo proposed what has been called a proto-inertial principle, according to which a body in horizontal motion will conserve its motion. This statement is only true in counterfactual circumstances where no impediments are present. This paper analyzes how Galileo could have been justified in ascribing definite properties to this idealized motion. This analysis is then used to better understand the relation of Galileo's proto-inertial principle to the classical inertial principle.

Hobbes's Mechanical Philosophy and Its English Critics

The mechanical philosophy was a new system of natural philosophy developed in the early part of the seventeenth century, and which soon came to be seen as the best replacement for the natural philosophical system of scholasticism (based largely on Aristotelian precepts), which dominated university teaching, but was increasingly seen to be moribund and fundamentally misconceived. Based in large measure on the Ancient atomistic physics of Epicurus, the mechanical philosophy was developed to explain all physical phenomena in terms of the motions and physical interactions of countless invisibly small particles of matter, which were supposed to constitute all bodies. Where the Ancient atomists referred all phenomena to "atoms and the void," the new mechanical philosophers summed up their philosophy in terms of "matter in motion." Their emphasis was upon kinematics-the science of motion-and mechanicsthe understanding of impacts and collisions. United in assuming the particulate nature of matter, they remained divided as to whether the particles moved in void space or were jostled together in a plenum, and whether the particles of matter were indivisible (as atomists claimed) or (at least in principle) infinitely divisible (as those who have come to be designated "corpuscularists" claimed). This new approach to understanding the natural world was prefigured in the work of Galileo (Henry 2011) but was developed in its most powerful, systematic, and historically influential form by René Descartes, in his Principia philosophiae of 1644 (Gaukroger 2002). Although the rival system of mechanical philosophy of Thomas Hobbes did not appear in fully developed form until 1655, in his De corpore, Hobbes was recognized long before that as a leading exponent of this new style of natural philosophy (Brandt 1928). Interacting with Sir Kenelm Digby (who would publish the first system of mechanical philosophy in English in 1644) and other English pioneers in the new c23.

Galileo and the Scientific Revolution:The Importance of His Kinematics

2011

It might even be argued that this is the best that can be said in favour of Galileo: his importance lay not in establishing a new way of philosophizing but in producing a range of new observations and new arguments which pointed the way to a new philosophy, and enabled others to accomplish it. It seems to me, however, that there is another way to sum up Galileo's importance in the history of science. I want to suggest that Galileo's significance for the Scientific Revolution rests upon something as wide ranging and expansive as the experimental method or the mathematization of the world picture but which, as far as I know, has not yet been properly acknowledged by Galileo scholars, although it is certainly implicit in many of their commentaries. What I have in mind might be referred to as «Galileo's science of motion», but by this, I do not simply mean the «new science» of motion which he expounded in the Discorsi. Galileo was one of the seminal figures of the Scientific Revolution, I want to suggest, because he clearly showed his contemporaries how all physical phenomena might be explained in terms of bodies in motion, and nothing more. 4 At a time when the learned all over Europe were recognising that Aristotelianism could no longer be sustained, it became increasingly urgent to establish a new physics on new principles. Although Galileo never succeeded in writing his book on the System of the World which he announces as forthcoming in his Siderius Nuncius, 5 his Dialogo sopra i due massimi sistemi del Mondo, supplemented

On the method in Galileo Galilei’ mechanics

2011

This paper will briefly suggest some historical-epi stemological notes about Galileo Galilei’s method (1564-1642), in his study upon centres of gr avity and the specific problem of the resistance of bodies that the Italian scholar repor ts in Le Mecaniche (1634) and Discorsi e dimostrazioni matematiche (1638).

'MOTION' (Entry for the Encyclopedia of Renaissance Philosophy)

Motion in Renaissance Science

MOTION Abstract Aristotle's ideas, and interpretations of them, dominated theorizing about motion during the Middle ages. However, local motion [motus localis] or locomotion was, according to the 'Philosopher' and his followers, only one of four types of change. In addition to change in location, the Peripatetics distinguished change in substance, in quality and in quantity. Within these four domains of change, change always requires the existence of a potentiality which can be actualized. During the late renaissance, however, the peripatetic views on motion were variously criticized, adapted, rejected and replaced. (Bodnar 2016) Generally speaking, the different kinds of change were all reduced to local motion, and one of the key ideas of the new theory of motion was the principle of inertia. First versions of this concept were introduced by Galileo (1564-1642) and later developed by René Descartes (1596-1650) and Isaac Newton (1643-1727). The seeds of this (r)evolution, though, had already been planted by philosophers such as Johannes Buridanus (c. 1300-1358) during the late Middle Ages, who was himself inspired by the work of John Philoponos (c.490-c.570). In the geocentric cosmos as conceived of by Aristotle (384-322 BC) and Ptolemy (c.100-c.170), there was a strict, ontological distinction between the sublunary world of change and the celestial world of perfect bodies making perfect, circular motions. However, in 1543, Copernicus (1473-1543) published his De revolutionibus which presented a heliocentric model of the universe, supported by Galileo's telescopic observations. The collapse of the traditional worldview was completed when Newton introduced his notion of universal gravitation.

Galileo and Aristotle' s Wheel

At the beginning of his last major work, Galileo tackles an old paradox, Aristotle's Wheel, in order to produce a model of the continuum that explains (at least to him) how line segments of different length could be put into a one-to-one correspondence. His argument seems like a playful digression. However, it is precisely this type of a one-to-one correspondence that he needs to support his work on free fall. In this article, we investigate how Galileo's model for the wheel paradox informs his work on free fall. We also examine some of the reasons his results on free fall-results that were grounded in his notion of the continuumwere not readily accepted in his time.

Kenelm Digby's Two Treatises and the Reception of the Galilean Science of Motion

2020

When Paolo Galluzzi investigated what he called the «second Galileo affaire» in 1993, he looked at the negative reactions to Galileo's laws of motion after his death in 1642. Following the first affaire-the clerical condemnation by Roman clerics of 1633-this second affaire was focused on Paris, and the circle of Marin Mersenne. In his study Galluzzi lists the main protagonists of the affaire: the Jesuits Pierre Le Cazre and Honoré Fabri, Ismaël Bouilliau, Gilles de Roberval, Jacques Alexandre Le Tenneur and-to a lesser extent-René Descartes and Pierre de Fermat. 1 In Galluzzi's view the debate was started by Pierre Gassendi's presentation of Galileo's theory in De motu impresso a motore translato, composed in 1640 two years after the publication of the Discorsi, and published in Paris in 1642. Omitted from Galluzzi's list of protagonists are the names of two Englishman living in Paris in the 1640s, who were both part of Mersenne's extended network: Thomas White and Kenelm Digby. This omission is particularly regrettable given that these two Englishmen were also in the orbit of Thomas Hobbes, who was also in Paris at this time, and it seems likely that Hobbes formulated his own natural philosophical ideas, at least in part, in reaction to the ideas of his English contemporaries, who had both published natural philosophical The authors are most grateful to Professor Carla Rita Palmerino for her helpful comments on a draft of this paper.