Astronomer Biography Galileo

About the astronomer Galileo, history and biography of the man who first used the telescope.



(1564-1642, Italy)

Major Discoveries: Features on the surface of the moon, phases of Venus, Jupiter's moons, starry nature of the Milky Way.

Means of Observation: Telescope (its first use in astronomy).

His Story: As a poor medical student in Pisa, the city of his birth, Galileo chanced to overhear a lesson in geometry. The accident changed his life and the course of history. He took up the study of mathematics, and although he had to leave the university because he ran out of money, his brilliant treatises on physical laws earned him a series of teaching posts at Italian universities. Contrary to popular legend, there is no proof that he once dropped two different weights from the Leaning Tower of Pisa to prove they would strike the ground at the same time. Galileo proved it, but on paper.

Early in his life Galileo became convinced that the 2,000-year-old theory of Ptolemy, that the sun revolved around the earth, was wrong, but since to believe otherwise was heretical, he kept his mouth shut in public.

In the spring of 1609, while teaching in Padua, Galileo learned of the recent invention of the telescope in Holland. He completely redesigned and improved the instrument in one day. He was the first to turn the telescope toward the heavens and thus was the first to see many things, including the rings of Saturn. His observations of the movement of spots across the sun conclusively proved the Copernican theory. He believed that the world could wait no longer to hear that it was not the center of the universe. He made a series of visits to Rome and finally, in 1624, received permission from the pope to write about the "systems of the world," both Copernican and Ptolemaic. Although his masterwork, Dialogue Concerning the Two Chief World Systems, published in 1632, was acknowledged throughout Europe as a literary and philosophical landmark, it would cost Galileo dearly. The Roman Catholic Church, reeling under the Protestant Reformation, considered the work to be more damaging than "Luther and Calvin put together." A faked document that forbade Galileo from discussing Copernicanism "in any way" was conveniently "discovered" in Rome.

Galileo was arrested, brought before the Inquisition, twice threatened with torture, made to recant, and placed under house arrest on his estate near Florence. He nevertheless continued to experiment, observe, and write. He completed his Dialogue Concerning Two New Sciences, which summed up his work in physics and mechanics. It was published by Protestants in the Netherlands in 1638 and is considered by many to be his most notable achievement. Galileo died four years later at the age of 78, blind, exhausted, and still confined to his house. But he died with the knowledge that he, as he put it, had enlarged "this heaven, this earth, this universe . . . a hundred thousand times beyond the belief of the wise men of bygone ages."

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