Giovanni Battista Baliani

Giovanni Battista Baliani (1582 to 1666) was an Italian mathematician, physicist and astronomer, born in Genoa, who was governor of Savona in 1647 to 1649 and captain of the archers of the Republic of Genoa. For some 25 years he corresponded with Galileo Galilei about the most innovative scientific theories and experiments of the time. In 1630 he wrote to Galileo about a siphon led over a hill about 21 metres high that failed to work, the water in its limb sinking to about 10 metres above the reservoir, which Galileo explained by the power of a vacuum. At Savona he repeated the Tower of Pisa experiment with more precise measurements that showed the effect of air, and he showed the heat generated by a pot of water rotated at high speed. His main work, De motu naturali gravium, fluidorum et solidorum (1638), was the first to enunciate the law of acceleration of a body and to distinguish mass from weight. He also supported Galileo's theory that the tides are generated by the motion of the Earth around the Sun.