Before Foucault

The Proofs of the Earth’s Rotation

Abstract

We are going to trace the ideas and experiments, since Galileo and until Leon Foucault, aimed at proving the Earth’s rotation. Galileo - incorrectly – tried to explain the phenomenon of tidal forward and backward flow with the Earth’s rotation. After Galileo, the cannon shots towards the zenith and the experiments on falling objects were considered reliable evidences. In Florence Vincenzo Viviani observed and described the rotation of pendulums, but he did not realize its scientific importance. At the end of the XVII century, Newton had the idea of showing the Royal Society, through Hooke, the proof of the eastward deflection of a falling body from considerable height. In the XVIII century, new geophysical proofs of the Earth’s rotation were available. At the end of the century, in Italy, Newton’s direct experiment was taken into consideration again. In Bologna, Guglielmini measured the deviations towards the east and south of small leaden balls falling inside the Asinelli Tower.