Famous historically for his battle with the Catholic Church over the validity of his scientific theory, Galileo was a 16th and 17th century astronomer who helped to further the theory proposed by Nicolaus Copernicus that Earth and all other planets revolved around the sun.
Born in February 1564 in Pisa, Italy, Galileo Galilei moved with his family to Florence at the age of six so that his education could begin at a monastery near the town. Instructed by his inflexible father to become a doctor, Galileo began his studies at the University of Pisa in 1581, taking courses heavy in medicine and in Aristotelian philosophy.
Not pleased with the field of medicine, Galileo convinced his father after just four years to allow him to take up instead mathematics, a subject for which he had a particular flair. After tutoring several years in Florence, Galileo was appointed a professor of mathematics at the University of Padua. During his teaching years, which ended at Padua in 1610, Galileo made most of his scientific discoveries.
While studying the theory of Greek astronomer Ptolemy that all planets revolved around Earth, Galileo also encountered the elegant explanation of Copernicus. During his days as a student in the early 17th century, the field of astronomy was dominated by two clashing factions: followers of the Copernican heliocentric (sun as the center of a solar system) theory v. the classical geocentric (Earth as a stationary center) theory.
Records indicate that Galileo proclaimed his support for the theory of Copernicus in 1604. At the time, he had no way of supporting his claim, but in time he would offer his own proof.
Many sources claim that Galileo invented the telescope. In fact, though, Galileo did not invent the telescope, but he was so vitally important to its development that he is often credited with the discovery. At the time, telescopic devices were being used for reconnaissance in wartime. Galileo was the first to turn these "spy-glass" telescopes towards the sky and to use them for astronomical observation. He also made great refinements to the telescope and built greatly improved models, larger and more powerful, popularizing the instrument for astronomical purposes. But, at the same time, it should be made clear that he did not invent the telescope.
While using the telescope to investigate the Copernican theory, Galileo himself made several important discoveries about celestial bodies which further emphasized the importance of the telescope:
As well as making personal discoveries, Galileo had also collected proof that Copernicus was correct in his theory about the earth orbiting around the sun. His scheme to win over the Medicis worked, for he even studied for a time as their official mathematician in Florence! By this time, Galileo had formed many of his conclusions and collected much of the evidence he needed for an assault on Ptolemy's geocentric theory.
In a biting letter written in 1613, Galileo ridiculed supporters of Ptolemy's theory and attempted to illustrate that Copernicus's theory was both correct and consistent with the Roman Catholic Church's interpretation of the Bible. For his controversial letter, Galileo was brought to Rome to testify about his views but was cleared of heresy charges. Still, the Church gave him strict orders never to propose Copernican theory as fact.
In 1623, the Pope died and was succeeded by Urban VIII, who looked favorably upon Galileo and who quietly hinted that the restriction on Galileo's teaching would be relaxed. In 1632, Galileo published his great work, Dialogue Concerning the Two Chief World Systems, the massive conclusion, six years in the writing, to his exhaustive investigation. The book put the theory of Copernicus side-by-side with those of Aristotle and Ptolemy, and he demonstrated through comparison that Copernicus's explanation was impeccable in its logic and validated by his own findings.
Though Galileo had perceived a friendlier environment in the Church, Dialogue was received angrily, and he was summoned to Rome for breaking his pledge about the teaching of Copernicus. After these hearings, Galileo was convicted and forced to spend his final dying years in poor health in house arrest outside of Florence.
Historians have pointed out that many in Rome at the time were hesitant to prosecute Galileo because his violation was a questionable one; his sentence of house arrest was actually a considerably lenient one. It should also be noted that Galileo, like Kepler, was deeply religious and that he never felt that he was compromising his faith by conducting scientific investigations.
Galileo made far-reaching contributions beyond those in astronomy, especially in his defense and promotion of the so-called scientific method. Forever thinking and testing, Galileo would first reduce complex problems to simple terms based on logic. He then approached each individual problem with mathematical reasoning. Though historians dispute his title as the "founder of modern experimental science" because they argue that experimentation had little to do with his discoveries, Galileo's name will forever be attached to the concept of scientific method.
Galileo was vital to astronomy, not only for his discovery of Jupiter's moons and for his popularization of the telescope, but primarily because he had presented observations to support the theory that the earth revolved around the sun. He had taken a large step towards proving the Copernican theory and had helped to make way for the theories of the great Isaac Newton.
At once, Galileo is far too complex a character for us to pass judgment on his actions after just a brief introduction. But we feel that there is -- and well should be -- a compassion and sympathy for his firm stance on behalf of scientific method and for his willingness to sacrifice his liberty for his idealistic belief in truth. Indeed, he was one of the earliest to fight hard for freedom of thought. Pardoned by a humiliated Catholic Church only hundreds of years after his death, Galileo is a truly inspirational scientific figure.