Galilei, Galileo. Astronomer and natural philosopher. Born in Pisa in 1564. Was educated first in Florence, but afterwards returned to Pisa to study medicine, for which profession his father designed him. Here, after becoming known as an opponent of the Aristotelian maxims, he discovered, in 1582, the law of the vibrations of the pendulum. Soon afterward he began to study mathematics, and was appointed professor at Pisa when only 25. Thence Galileo removed to Padua in 1592, and during his residence there invented a thermometer and constructed his first telescope, the invention of which he had heard of at Venice. He also made astronomical discoveries, and was reestablished in 1610, at Florence, by his patron Cosimo de' Medici. Here it was that his opposition to traditional views, and especially his advocacy of the Copernican doctrine that the sun was the center of the universe, brought him into conflict with the Inquisition, but proceedings were dropped on Galileo's promise not to teach the doctrine. On the publication, however, in 1632 (17 years after), of his "Dialogue" on the same subject, Galileo was again summoned to Rome, condemned to imprisonment for life, and required to recant his opinion. Galileo was confined at first in the house of one of the Inquisitors, his pupil, but was afterwards allowed to live in Florence, where he died in 1642, having been blind four years.

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