"The first modern textbook of physics, a foundation stone in the science of mechanics"

Galilei, Galileo (1564-1642)

Discorsi e dimostrazioni matematiche, intorno a due nuove scienze attenenti alla mecanica & i movimenti locali. del signor Galileo Galilei linceo, filosofo e matematico primario del serenissimo grand duca di Toscana ; con una appendice del centro di grauità d'alcuni solidi.

Leiden: Elzevier Press, 1638


Quarto: 20 x 14 cm. 
 [8], 306 [i.e. 314], [6] p. Collation: *4, A-Z4, Aa-Rr4


A fine copy, bound in contemporary reversed calf, small repair to head of spine, slight wear. With the errata leaf at end, printers' woodcut device on title, numerous woodcut illustrations and diagrams in text, woodcut initials, head- and tailpiece. Text in fine condition throughout with a couple of light blemishes, light soiling to title, a few 18th c. notes in French, and some very mild intermittent spotting.

Galileo's last work, "Discourses and Mathematical Demonstrations concerning Two New Sciences", has been called "the first modern textbook of physics, a foundation stone in the science of mechanics" (Grolier/Horblit).

Like the earlier 'Dialogo' (1632), the 'Discorsi' takes the form of a conversation. There are four dialogues, the latter two of which "are devoted to the treatment of uniform and accelerated motion and the discussion of parabolic trajectories. The first two deal with problems related to the constitution of matter; the nature of mathematics; the place of experiment and reason in science; the weight of air; the nature of sound; the speed of light; and other comments on physics as a whole."(Stillman Drake)

Forbidden by the Inquisition to publish his theories, Galileo had a manuscript of the "Discorsi" smuggled out of Italy to France and, thence, to Leiden, where the book was published by the Elzevirs.

"Mathematicians and physicists of the later seventeenth century, Isaac Newton among them, rightly supposed that Galileo had begun a new era in the science of mechanics. It was upon his foundations that Huygens, Newton and others were able to erect the frame of the science of dynamics, and to extend its range (with the concept of universal gravitation) to the heavenly bodies." (PMM)

Galileo gives "detailed treatments of uniform and accelerated rectilinear motion and the parabolic trajectories of projectiles. Objects falling freely, or descending on an inclined plane, move with uniform acceleration, though they do so only in a vacuum, he states; in a resisting medium such as air, they attain a fixed terminal velocity. He also devotes considerable attention to the swinging motion of the pendulum, whose isochronism was his earliest discovery, giving the relation between its period and its length and pointing out that this period did not depend on the mass of its bob. However, he did not manage to explain the reason for its isochronism.

"In his mathematical discussions, he distinguishes between finite, infinitesimally small, and infinitely large quantities, without flinching from the paradoxes that arise and appear unresolvable. On the subject of infinite quantities, for example, he points out that such concepts as 'less than,' 'greater than,' and 'equal to,' are not necessarily applicable, which he exemplifies by showing that the infinite set of natural numbers can be put into one-to-one correspondence with the set consisting of their squares. These are problems with a definitely modern flavor that would preoccupy mathematicians in the nineteenth-century."

"The primary characteristics of Galileo's approach to physics were, first, his reliance on observational or experimental evidence rather than pure reasoning to demonstrate the truth of a statement about nature. The world we see is, in his opinion, real, not an imperfect image of an ideal Platonic universe that could be constructed by the human mind. Second, he emphasized the mathematical description of observed physical processes. The language of nature, he believed, was mathematics, and it was impossible to understand the natural world without knowing that language. His jealously guarded independence of judgment on matters subject to his own direct observation against the pressures of traditional authority exerted a strong general influence on the educated public all over Europe, as did his support of Copernican astronomy. And although his immediate scientific influence was not very great, in the long run his mode of thinking penetrated deeply into subsequent physics.

"That he felt no need to search for efficient causes of events when a mathematical description was available distinguished him from many of his immediate successors, but this mode of thinking would eventually become dominant and remains fashionable to this day. Galileo's formulation of physical laws in mathematical terms began to transform the idea of a clockwork solar system into a more general view of nature as a whole, run, like a machine, by gears consisting of algorithms (in modern terms, like a computer.) Carried further by the influential René Descartes and by Christiaan Huygens, this transformation led to the work of Isaac Newton, which was the culmination of the first scientific revolution."(Newton, "From Clockwork to Crapshoot: A History of Physics", p. 82-83)

Dibner, Heralds of Science 141; Grolier/Horblit 36; Norman 859; PMM 130; Wellcome 264