Galileo Galilei(redirected from Galileo Galilaei)
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Ga·li·le·o Ga·li·lei(găl′ə-lā′ō găl′ə-lā′) 1564-1642.
Italian mathematician and astronomer. Galileo constructed a telescope (1609) with which he discovered the moons of Jupiter and made other astronomical observations. He strongly advocated Copernicus's theory that the earth moves around the sun, which led to his interrogation by the Inquisition (1633) and a life sentence of house arrest.
Ga·li·le·o Ga·li·lei(găl′ə-lā′ō găl′ə-lā′)
1564-1642. Italian astronomer, mathematician, and physicist who was the first to use a telescope to study the stars and planets. He discovered that Jupiter has moons and that Venus has phases like those of Earth's moon, suggesting that Venus orbits the sun.
Biography In 1609 Galileo heard of the invention of the spyglass, a tube with a piece of glass at each end that made objects appear closer and larger when you looked through it. He set about making his own. One night Galileo used his telescope (as they began to be called) to look up at the moon. He was astonished to see its mountains and valleys, since the moon was believed to be perfectly smooth. Galileo continued to observe the heavens, and a few months later he discovered Jupiter's four largest moons. As he studied them, he realized that they were orbiting Jupiter, not Earth. Galileo's observations convinced him that Copernicus had been right when he stated that Earth and all the planets orbit the sun. Many people feared Copernicus's theory, which overthrew the long-held belief that Earth was the center of the universe. Because he openly supported Copernicus's theory, Galileo was called before Church authorities and forced to declare that the theory was false. He was then put under house arrest on his own farm, where he was nonetheless allowed to continue his scientific work until the end of his life.