Galileo Galilei 1564-1642

Galileo Galilei, (1564-1642), Italian physicist and astronomer whose observations with a telescope revolutionized astronomy was born in Pisa, Italy.

Galileo Galilei

Galileo went to the University of Pisa in 1581 in order to study Medicine. During the studies he got interested in Physics and in 1583 stated the theory of the isochronism of the pendulum, which he guessed by observing the oscillations of a lamp inside the Pisa Cathedral. In 1585 he quit the University, and began his activity in Physics and Mathematics inventing the hydrostatic balance in 1586.

In 1588 he obtained a chair at the Pisa University. He got interested in the motion of the falling bodies and wrote "De Motu". In 1592 Galileo obtained a chair of Mathematics (Geometry and Astronomy) at the Padova University, where he stayed until 1610. In 1606 he invented the thermoscope, a primitive thermometer. In 1604 Galileo observed a supernova, which appeared in the sky during the fall of the year. Galileo invented a calculating compass for the practical solution of mathematical problems.

By December 1609, Galileo had built a telescope of 20 times magnification, and used it in observation and the discovery of sunspots, lunar mountains and valleys, the four largest satellites of Jupiter, and the phases of Venus. He published these findings in March 1610 in The Starry Messenger. He published a book on floating bodies in 1612. In 1613 he published a work on sunspots and predicted victory for the Copernican theory. In 1624 Galileo began a book "Dialogue on the Tides," in which he discussed the Ptolemaic and Copernican hypotheses in relation to the physics of tides. The title was altered to Dialogue on the Two Chief World Systems by the censors and published at Florence in 1632.

Galileo's final book, Discourses Concerning Two New Sciences, which was published at Leiden in 1638, reviews and refines his earlier studies of motion and, in general, the principles of mechanics. The book opened a road that was to lead Newton to the law of universal gravitation that linked Kepler's planetary laws with Galileo's mathematical physics. Galileo's most valuable scientific contribution was his founding of physics on precise measurements rather than on metaphysical principles and formal logic.

Galileo wrote a long, open letter on the irrelevance of biblical passages in scientific arguments, holding that interpretation of the Bible should be adapted to increasing knowledge and that no scientific position should ever be made an article of Roman Catholic faith. Galileo was summoned to Rome by the Inquisition to stand trial for "grave suspicion of heresy." [In October 1992 a papal commission acknowledged the Vatican's error.] He set forth his views on scientific reasoning in a book on comets, The Assayer (1623). Galileo's lifelong struggle to free scientific inquiry from restriction by philosophical and theological interference stands beyond science.

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