<P> The biblical roots of Galileo's name and surname were to become the subject of a famous pun . In 1614, during the Galileo affair, one of Galileo's opponents, the Dominican priest Tommaso Caccini, delivered against Galileo a controversial and influential sermon . In it he made a point of quoting Acts 1: 11, "Ye men of Galilee, why stand ye gazing up into heaven?". </P> <P> Despite being a genuinely pious Roman Catholic, Galileo fathered three children out of wedlock with Marina Gamba . They had two daughters, Virginia (born in 1600) and Livia (born in 1601), and a son, Vincenzo (born in 1606). </P> <P> Because of their illegitimate birth, their father considered the girls unmarriageable, if not posing problems of prohibitively expensive support or dowries, which would have been similar to Galileo's previous extensive financial problems with two of his sisters . Their only worthy alternative was the religious life . Both girls were accepted by the convent of San Matteo in Arcetri and remained there for the rest of their lives . Virginia took the name Maria Celeste upon entering the convent . She died on 2 April 1634, and is buried with Galileo at the Basilica of Santa Croce, Florence . Livia took the name Sister Arcangela and was ill for most of her life . Vincenzo was later legitimised as the legal heir of Galileo and married Sestilia Bocchineri . </P> <P> Although Galileo seriously considered the priesthood as a young man, at his father's urging he instead enrolled in 1580 at the University of Pisa for a medical degree . In 1581, when he was studying medicine, he noticed a swinging chandelier, which air currents shifted about to swing in larger and smaller arcs . To him, it seemed, by comparison with his heartbeat, that the chandelier took the same amount of time to swing back and forth, no matter how far it was swinging . When he returned home, he set up two pendulums of equal length and swung one with a large sweep and the other with a small sweep and found that they kept time together . It was not until the work of Christiaan Huygens, almost one hundred years later, that the tautochrone nature of a swinging pendulum was used to create an accurate timepiece . Up to this point, Galileo had deliberately been kept away from mathematics, since a physician earned a higher income than a mathematician . However, after accidentally attending a lecture on geometry, he talked his reluctant father into letting him study mathematics and natural philosophy instead of medicine . He created a thermoscope, a forerunner of the thermometer, and, in 1586, published a small book on the design of a hydrostatic balance he had invented (which first brought him to the attention of the scholarly world). Galileo also studied disegno, a term encompassing fine art, and, in 1588, obtained the position of instructor in the Accademia delle Arti del Disegno in Florence, teaching perspective and chiaroscuro . Being inspired by the artistic tradition of the city and the works of the Renaissance artists, Galileo acquired an aesthetic mentality . While a young teacher at the Accademia, he began a lifelong friendship with the Florentine painter Cigoli, who included Galileo's lunar observations in one of his paintings . </P>

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