Galileo was born February 15, 1564 in Pisa,  eldest of seven children of Vincenzo Galilei and Giulia Ammannati.  Ammannati, originating in the lands of Pistoia and Pescia, boasted prestigious origins: a Thomas Ammannati (approx 1345 to 1396), was made a cardinal by Pope Clement VII in 1385, while his brother Boniface (c. 1350 to 1399) obtained the Purple in 1397 by one of the successors of Clement, the antipope Benedict XIII, as to James Ammannati Piccolomini (1422 – 1479), cardinal in 1477, was a humanist, who continued the Commentaries of Pius II and author of a Life of the popes who went lost.
It is understandable that Julia did not fail to point out Ammannati the difference in origins to Vincenzo, as were the ancestors of her husband belonged to the middle-class Florentine remembers a Bonaiuti Thomas, who was part of the government of Florence after the expulsion of the Duke of Athens in 1343, and Galileo de ‘Galilei (1370 – ca 1450), medically known in his time, and standard-bearer of justice, whose tomb in the church of Holy Cross became the tomb of his descendants. But Vincent was born in Santa Maria a Monte in 1520, by which time his family and he had fallen, composer of value, had to move to Pisa combining to need more money, exercise the profession of music art trade . On July 9, 1563 Vincent, rents a house in Via dei Mercanti in Pisa by Giuseppe Bocca, while among those with whom he was in business, stands the name of the Pisan nobleman Jacopo della Seta,  a member of the Wake.
Lutenist, teacher and music theorist – had been part of the Florentine Camerata dei Bardi – was in conflict with the classical tradition sustained by his teacher Zarlino, which attributed the harmony between all the sounds and the control of numerical proportions, with his Discourse Opera Messer Zarlino Josephus, from Chioggia and the Dialogue of music ancient and modern, had proposed to return to the melody against the prevailing monodic contrapuntal polyphony.
Of the other six children of Vincenzo and Julia, have been some news of Peter Paul, Virginia, born in 1573, Michelangelo was born in 1575, and Livia, born in 1578, like his brother Michelangelo in Florence, where the Galilei family had moved since 1574. The young Galileo made his first studies at Pisa under Muzio Tedaldi, customs officer of the city, and in Florence, first with his father, then a master of dialectic, and finally in the school of the convent of Santa Maria di Vallombrosa, where he took the habit as a novice until the age of fourteen.
Vincenzo, September 5, 1581, the son enrolled at the University of Pisa with the intention to make him study medicine, as will that Galileo ripercorresse the tradition of his glorious ancestors, and especially to undertake a career that could earn lucrative book, despite its experimental interest in the progress of those years, attention was soon attracted by Galileo’s mathematics, which he began to study the summer of 1583, taking advantage of the opportunity of knowledge made in Florence Hostilius Ricci Still, a follower of the school mathematics Niccolo Tartaglia. Ricci was characteristic of the setting that he gave the teaching of mathematics is not an abstract science, but a science that would serve to solve practical problems related to mechanics and engineering techniques. It is likely that in Pisa Galileo has followed the courses of physics required Aristotelianism Francesco Bonami: confirming the coincidence of arguments between the Juvenile, the notes of physics outlined by Galileo during this period, and ten books of the De motu Bonamico .
During his stay in Pisa, which lasted until 1585, Galileo arrived at his first, personal discovery, the isochronism of swings of the pendulum: the paternity of the discovery as assigned to go to Ibn Junis (950 – 1009), it is certain that the ‘activities quell’astronomo Arabic was still completely unknown in Europe.
And so, after four years, the young Galileo resigned to pursue his medical studies and returned to Pisa to Florence, where he furthered his new scientific interests, dealing with mechanics and hydraulics; in 1586 invented an instrument for the determination of the hydrostatic specific weight of bodies: it describes the details in the short treatise bilancetta, first circulated among his acquaintances and published posthumously in 1644. The influence of Archimedes and the teaching of Ricci is also found in his studies on the center of gravity of solids, expressed in theoremata about centrum gravitatis solidorum, published only in 1638 as an appendix to the Discourses and mathematical demonstrations concerning two new sciences, and found a solution to the problem of Hero of the crown.
Meanwhile, Galileo tried a regular budget accommodation: In addition to giving private lessons in mathematics in Florence and Siena, in 1587 he went to Rome to ask for a recommendation to enter the University of Bologna to the famous mathematician Christoph Clavius,  but to no avail, because in Bologna they preferred to the chair of mathematics at Padua, Giovanni Antonio Magini. At the invitation of the Florentine Academy in 1588 held two lessons about the shape, size and site of Dante’s Inferno, defending the assumptions already made by Antonio Manetti on the topography of Hell by Dante imagined until, in 1589, recommended by Cardinal Francesco Maria Del Monte, brother of the mathematician Guidobaldo, obtained by the Grand Duke Ferdinando I, a three-year contract to hold the chair of mathematics at the University of Pisa.
Teaching in Pisa (1589-1592)
The result of teaching is the Pisan De motu antiquiora manuscript, which contains a series of lectures in which he tries to give an account of the problem of the movement. The basis of his research is his treatise, published in Turin in 1585, Diversarum speculationum mathematicarum liber Blessed John the Baptist, one of the supporters of the physical theory of ‘"momentum" as a cause of "violent motion." Although not known to define the nature of such a force impressed on the bodies, this theory, developed for the first time in the sixth century John Philoponus and then supported by physicists in Paris, while not being able to solve the problem, opposed to the traditional Aristotle’s explanation of the movement as a product of the same medium in which the bodies move.
In Pisa Galileo did not confine himself to scientific pursuits: in fact date back to this period his Considerations on the rate that will be followed up with Apostilles Ariosto: it is spread on sheets of notes and annotations in the margins of its pages in the volumes of the Jerusalem Orlando Furioso, and where, while reproving the rate, "the lack of imagination and the image and slow the monotony of the verse, what he loves nell’Ariosto is not only a variety of beautiful dreams, the rapid change his situation, the living elasticity of rhythm, but the harmonious balance of this, the coherence of the organic unity – even in the variety – of poetic fantasy. "
In the summer of 1591 the father Vincenzo died, leaving the burden to Galileo to take care of keeping the whole family for the wedding of her sister Virginia, who married the same year, Galileo had to provide dowries, contracting debts, as well as will do for the wedding of her sister Livia in 1601 and will have to spend more money to help the needs of the large family of his brother Michelangelo. Not enough the modest salary of sixty crowns a year, and shortly before the expiry of his contract, Galileo again turned to the influential friend Guidobaldo Del Monte, which recommended him to the prestigious University of Padua, where it was still vacant chair of mathematics after his death in 1588 by Professor Giuseppe Moletti.
September 26, 1592 The authorities of the Republic of Venice issued a decree to appoint, with a contract extension, for four years and with a salary of 180 florins a year. On December 7, held in Padua, Galileo introductory speech and after a few days he began a course designed to have a large following among students. He will remain there for 18 years, which define "better them eighteen years of my age."