Il natural desiderio di sapere - Pontifical Academy of Sciences

FEDERICO CESI, THE FIRST ACADEMY, AND UMBRIA 83notes of the Cesi family physician Johann Baptist Winther, and Gabrieli’ssplendid reconstruction, that Galileo, Cesi, and Stelluti considered, especiallyduring the evenings, in long and gripping discussions in front of thefireplace, the central themes of the scientific revolution, first among themthat of inertial physics and the relativistic conception of motion.During his stay in Acquasparta, Galileo did not fail to undertake hisoft planned excursion to the Marmore waterfall,and it was indeed during this excursion that the Tuscan scientistcarried out at Lake Piediluco the first relativistic experiment withheavy objects falling within a moving system of reference forwhich there is direct and documented historical testimony. 112An account of this experiment is contained in a letter written by Stellution 8 January 1633, in which he intended to offer a summary of the Dialogosopra i due massimi sistemi. 113 In brief: to the objection of the Aristotelianswho defended the immobility of the Earth partially by virtue of the experimentin which a rock thrown from a high tower falls at the foot of thetower and not far away from it, as should happen if the Earth were inmotion, and to the Galilean indication in the second day of the Dialogue, inwhich it is held that in reality the rock must fall naturally at the foot of thetower because ithas two movements, one direct in falling downward and the othertransverse caused by the circular motion of the earth, whence therock thrown by us from on high in falling downward makes almosta semi-circle because of the two movements that it has,Stelluti adds,And I saw the experiment, and it is that going with Signor Galileoto Piediluco on the lake with a six-oar boat that was going very fast,and with him sitting on one side and I on the other he asked me ifI had something heavy, and I said I had the key to my room, he tookit; and as the boat moved along rapidly he threw the key up into theair so that I thought it was lost in the water; but, even though the112 L. Conti, Sotto il segno degli astri: lo studio perugino e i Lincei, in G. Sapori, C. Vinti,L. Conti, Il Palazzo Cesi di Acquasparta e la rivoluzione scientifica lincea, op. cit., p. 77; cf.Id., Giuseppe Neri: un matematico aristotelico all’Accademia dei Lincei, op. cit., p. 55.113 The letter can be read in the Appendix to L. Conti, Giuseppe Neri: un matematicoaristotelico all’Accademia dei Lincei, op. cit., pp. 61-65: Francesco Stelluti to unknown(perhaps to Fabio Colonna), Rome 8 January 1633. For an account of the discovery ofthe letter, ibid. p. 56, n. 64.