Alberti, Leone Battista
Baif, Lazare de
Baliani, Giovanni Battista
Benedetti, Giovanni Battista
Borelli, Giovanni Alfonso
Cicero, M. Tullius
Foscarini, Paolo Antonio
Guevara, Giovanni di
Jordanus de Nemore
Marci of Kronland, Johannes Marcus
Monantheuil, Henri de
Monte, Guidobaldo del
Schreck, Johann Terrenz
Stelliola, Niccolò Antonio
Wolff, Christian von
Baliani, Giovanni Battista
born 1582 in Genoa, died 1666 in Genoa, Italian mathematician and physicist
Baliani was the son of a Genovese senator and, as a lawyer, held public office nearly his entire life. He appears to have occupied himself with questions of science from around 1612, when he was prefect of the fortress in Savona, where it struck him that cannonballs, although they have different weights, always fall to the earth at the same speed. At this time he also built a pot of iron that rotated in an iron vessel and that was so warmed by frictional heat that it was possible to cook inside it.
Through Filippo Salviati, who met Baliani in 1613, Galilei Galileo began corresponding with Baliani, primarily about the determination of the weight of air. In 1615 Baliani traveled to Florence, where he visited Galileo and also met with Benedetto Castelli. This correspondence, which continued sporadically for many years, shows that he was skilled at experimenting and an ingenious thinker. In 1623 he became governor in Sarzana and in July 1624, senator in Genoa. In 1630 he reported to Galileo about the failure of a hoisting pump that was to pump water to an elevation of sixty feet. Baliana attributed the fact that the pumps used to raise water at that time worked to the pressure of the earth’s atmosphere, but doubted that the total weight of an air column many miles high could be less than that of a thirty-foot high water column. Galileo had already noted the failure of pumps to raise water to this height.
In his 1638 tract De motu naturali gravium solidorum he describes the correct laws of gravity, movement on inclined planes and the movements of pendula. In the greatly expanded edition of 1646 he expresses the supposition that the distances traveled in immeasurably miniscule consecutive times by a falling body behave like the natural numbers, whereby he assumes that the bodies sustain very short impacts in quick succession, and that the resulting impulses remain in the bodies and accumulate there. He attributes the difference between the way a ball of iron and a ball of wax fall to air resistance. Moreover, Baliani already differentiated between the mass of a body and its weight.
In Trattato della pestilenza, published in 1647, he proposes a chemical explanation for the symptoms of the plague and its great contagiousness. In this book he also deliberates about the connection between population growth and the existing food resources, even attempting a quantitative analysis of this connection. In 1653 a second edition of this work appeared with a new introduction, in which he also describes his research in physics.
In 1647 Baliani returned to Savon as governor of the fortress and remained in this office until 1649. Thereafter he joined the Supreme Council of Genoa, where he lived until his death.
After his death, his previously unpublished works were collected and published in 1666. A subsequent edition including a biography of Baliani was published by G. Francelli in 1792. Volumes XII – XVIII of the national Galileo edition include Baliani’s correspondence with Galileo; his correspondence with Mersenne is contained in the edition of Mersenne correspondence. Baliani’s direct influence on other scholars of his age appears not to have been major, probably because he worked as an amateur and because his primary area of interest was dominated by Galileo and his pupils. His formulation of the law of gravity is not independent of Galileo, although the explanation using the impacts sustained while falling and the resulting accumulating impulses is his own. However, a similar analysis had been provided by G.B. Bendetti in 1585. Baliani never failed to emphasize his scientific independence from Galileo.