In the town of Orvieto during the autumn of 1463, the German philosopher and astronomer Nicolò Cusano completed his treatise De ludo globi** – in which he used the rules of a novel game played with a ball to describe a new vision of the universe. The impetus and movement of the ball was a metaphor for the complex design which regulates the destiny of a new cosmos – from the movement of planets to the exercise of man’s freewill.
Within a few decades, gioco della palla corda (Jeu de Paume), had become a cultural and social phenomenon, enthusiastically adopted by aristocrats at Renaissance Italy’s principal courts. In 1585, Antonio Scaino da Salo, priest, doctor of theology and Aristotelian philosopher, wrote the first treatise on the game’s principles and practices. Like Cusano before him, Scaino could not resist digressions into scientific endeavour: in particular, he noted the complexity of the tennis ball’s motion and its relevance to the emerging science of ballistics.
Although we can’t not know if Galileo read Scaino’s treatise, we do know that palla corda was played at the University of Padua – where Galileo taught mathematics for nearly twenty years. It’s notable that in his most important work, Dialogo sopra i due massimi sistemi del mondo (1632), Galileo chose a familiar subject – the curved trajectory of an expertly-struck ball – to explain a scientific concept in his second dialogue: the combined rotational and translational motion of a mobile.
For the acceptance and dissemination of his revolutionary – at the time, heretical – ideas, Galileo relied heavily upon the patronage and support of two powerful prelates: The Pontiff, Pope Urban VIII – and his nephew, Cardinal Francesco Barberini; The Pope will have been aware of Jeu de Paume’s popularity: the game was adopted by the Clergy long before it caught on with the nobility – indeed, Cardinal Barberini’s Rome palace had two palla corda courts! It’s notable also that Galileo enjoyed the patronage of Florence’s Medici dynasty: Ferdinando de’ Medici was passionate about palla corda.
Galileo’s allusion here to the tennis ball isn’t a mere captatio benevolentiae to his powerful patrons, but rather, the fruit of serious reflection. Tennis provides an effective model with which he could at once explore the phenomenon of combined motion and implicitly corroborate Copernicus’s theory of the earth’s double motion. Furthermore, the ball’s irregular movement and unpredictable trajectory clearly and practically demonstrate the limitations of Aristotle’s theory of motion.
Thus, Galileo adopts a commonly-understood metaphor which provides a lucid translation of his scientific language.
French philosopher and physicist René Descartes recognised the merit of Galileo’s use of palla corda as a device to explain innovative scientific concepts. His work Dioptrique (1638) features some curious engravings which illustrate how a tennis ball’s trajectory alters when struck in different ways.
In a letter to the Royal Society dated February 6, 1671, Isaac Newton addresses the subject of light and colour refraction, likening ‘cut’ or ‘slice’ shots to refracted rays of light. He also explores also the laws of fluid mechanics: how the trajectory of the ball will be affected by the fluid medium (i.e., the air) through which it travels:
“Then I began to suspect, whether the Rays, after their trajection through the Prisme, did not move in curve lines, and according to their more or less curvity tend to divers parts of the wall. And it increased my suspition, when I remembred that I had often seen a Tennis ball, struck with an oblique Racket, describe such a curve line. For, a circular as well as a progressive motion being communicated to it by that stroak, its parts on that side, where the motions conspire, must press and beat the contiguous Air more violently than on the other, and there excite a reluctancy and reaction of the Air proportionably greater.”
Much time has passed since Galileo, Descartes, and Newton used tennis to render their ideas more accessible, but the practise of using tennis to illustrate disparate scientific theories continues: from iatromechanics to probability theory. When it comes to analogy and metaphor, it seems the game of Kings is commonly understood.