Italian scientist (1564-1642). He saw objects never seen by other astronomers, and was almost condemned to death by claiming that the earth was not the center of the universe.
The first astronomer to make frequent and systematic use of a telescope, Galileo Galilei began a new era in the history of astronomy. Born in Pisa, Italy, son of mathematician Vincenzo Galilei, as a teenager he studied physics and wrote a treatise on the specific gravity of solid bodies. At 24, he became a math teacher in Pisa. It was in this city that he developed the theory that two objects of different weights fell at the same speed. And, it is said, although there is no record of this fact, he would have demonstrated his theory of the famous Leaning Tower of Pisa, from which he simultaneously shot a metal ball and a wooden ball that hit the ground at the same time.
Between 1592 and 1610, Galileo was a professor at the University of Padua. In 1609 he built a telescope based on what had been invented some time before by Hans Lippershey (1570-1619) in the Netherlands. Pointing his telescope skyward, Galileo saw objects no one had ever observed before. On January 7, 1610, he discovered Io, Europa, Ganymede, and Callisto, the four largest moons of Jupiter. Three of them, by the way, are even larger than the moon that orbits around our planet.
Galileo stated that Jupiter, like Mars and Venus, was a spherical body. He also investigated Saturn. On each side of the planet, he observed what appeared to be two moons that never changed position. But what he really saw was the edges of Saturn's great ring system. With his telescope, Galileo could see the rings, but his instrument was not so accurate in determining exactly what those points were. He also studied the surface of the moon and found spots on the surface of the sun, which helped to prove that the star also rotated about an axis.
Galileo accepted, and publicly defended, Nicholas Copernicus's theory that the sun, not the earth, was the center of our solar system. In 1616, the Catholic Church, which held the opposite view (ie, that the center was the earth), prohibited Galileo from spreading or teaching his ideas. In 1632, in a defiant attitude, he published his Dialogue on the Two Largest Systems of the Universe, which attracted the wrath of the Church. Placed in a kind of house arrest, Galileo lived the rest of his life in a village near Florence investigating the skies.
On January 8, 1642, he died. He was almost blinded by observing sunspots without eye protection. Three hundred and fifty years later - on October 31, 1992 - his theories were formally recognized by Pope John Paul II.