Galileo Galilei

Galileo Galilei was born on 15 February 1564 in Pisa, the eldest child of Vincenzo Galilei, a lutenist and music theorist who tested the vibration of strings by experiment. Sent to the monastery school at Vallombrosa and then to the University of Pisa to study medicine, he drifted to mathematics and left in 1585 without a degree. By 1589 he held the chair of mathematics at Pisa, and in 1592 he moved to Padua, where he stayed eighteen years, lecturing, tutoring, building instruments and working out the laws of falling bodies. In 1609 he heard of a Dutch spyglass, built a far stronger one and turned it on the sky. The Starry Messenger (1610) reported mountains on the Moon and four moons circling Jupiter, which he named for the Medici, and it won him a post as court mathematician in Florence. His sunspot letters and his defence of Copernicus drew the notice of the Church, and in 1616 Cardinal Bellarmine warned him not to hold or defend the motion of the Earth. In 1623 his friend Maffeo Barberini became Pope Urban VIII, and Galileo got leave to write about the two systems if he treated them even-handedly. The Dialogue Concerning the Two Chief World Systems appeared in Florence in 1632 and was summoned to Rome within months. In 1633 the Inquisition found him vehemently suspect of heresy, made him abjure, and sentenced him to imprisonment that became house arrest, first at Siena and then at his villa in Arcetri, near the convent where his daughter Virginia lived as a nun until her death in 1634. Blind by 1638, he finished the Discourses on Two New Sciences, printed in Leiden, which laid the groundwork of modern mechanics. He died at Arcetri on 8 January 1642, aged seventy-seven.

On 22 June 1633, aged sixty-nine, Galileo knelt in the Dominican convent of Santa Maria sopra Minerva in Rome and read aloud a formula abjuring the belief that the Earth moves. The Inquisition had found him vehemently suspect of heresy for his Dialogue. The sentence of imprisonment was commuted to house arrest, which lasted the rest of his life.