He was a physicist and philosopher of nature (Pisa 1564 - Arcetri 1642). The eldest son of Vincenzo, a musician and music theorist, and Giulia Ammannati, he spent his childhood between Pisa and Florence (from 1574). On September 5, 1580 (1581 according to the Pisan calendar) he was matriculated among the "artist pupils" at the University of Pisa. Leaving the university in 1585, without obtaining any degree, under the guidance of Ostilio Ricci, a member of the Florentine Academy of Drawing, he undertook the reading of Euclid and Archimedes. He soon progressed so far in his studies that he was in turn able to give private lessons to several students in Florence and Siena. His earliest writings date from this period. In 1589 he was assigned the chair of mathematics in Pisa. A few years later, in 1592, he was assigned the chair of mathematics in Padua. Alongside this teaching activity G. kept a small technical workshop, sent ahead by the mechanic Marcantonio Mazzoleni, where geometrical and military compasses, compasses, squares and other mechanical instruments, later telescopes, were produced and sold. In his later years he worked on determining longitudes, building pendulum clocks, mechanical problems, and moonlight. He died in Arcetri on January 8, 1642. Plans for a solemn burial in Santa Croce were forbidden by Rome and were not realized until 1737.