relied completely on what today is understood as the scientific method—direct observation and experimentation—rather than the Bible or received tradition in his study of astronomy. Because he developed the telescope, he was able to study the movement of the planets, discovering the four largest moons of Jupiter and determining that Aristotelean cosmology (a received tradition) was in error, causing a huge stir in the scientific community.

Galileo also studied velocity, dropping balls of different weights (again using the scientific method of direct observation) from the top of the leaning tower of Pisa to time how quickly they fell. He demolished Aristotle's contention that objects of different weights fall at different speeds through experimentation. Stunningly, however, he had no concept of gravity, as Newton, who would discover gravity, had not yet been born.

Galileo's most famous example of himself as exemplar of rationalism and the scientific method came in his bold assertion, based on his years of observation of the planets, that the earth revolved around the sun and not vice versa. This was a radical concept for two reasons: first, the Bible stated that the sun revolved around the earth. The people in the Renaissance were as intelligent as we are and understood that much in the Bible was metaphor, so when scientific evidence refuted Biblical claims, the people of Galileo's time were quite ready to move what they though were literal statements into the category of the metaphoric. (The undeniable realization that the earth was round, for example, moved Biblical references to the four corners of the earth to the realm of metaphor.)

However, there was another problem with Galileo's assertion, in that people had what they thought was the scientific method on their side: the experience of their senses. It seemed completely evident using one's eyes that the the sun proceeding in an orderly orbit around the earth.

Against a deepening backdrop of political trouble in Italy as the pope and the Austro-Hungarian empire suffered losses in the Forty Years war against the German states, a "holy" war that was supposed to assert the supremacy of the universal Roman Catholic church, the pope came under intense pressure to weed out heresy. When Galileo rashly published his theories of heliocentrism (that the planets, including the earth, circled the sun) he became an easy, high profile target to demonstrate that the Church was vigilant about heresy, and he was, under pressure from the Inquisition, forced to retract what he knew from observation, but could not yet (again, remember there was no concept of gravity) prove to be true. Nevertheless, his groundbreaking reliance of the scientific method and courage in asserting his truth have earned him a lasting reputation as the father of modern science.

Most historians tend to associate the beginning of the Scientific Revolution with Copernicus's advocacy of heliocentrism (which placed the Sun, rather than the Earth, at the center of the Solar System). This viewpoint unleashed tremendous controversy within Europe, as it conflicted both with the doctrine of the Church, as well as the older teachings of Aristotle.

Galileo was one of the foremost astronomers of his era, and one of the leading champions of Copernicus's vision of a heliocentric solar system. He was also critical in shaping experimental science, building a telescope to actually observe what was going on in the night sky, which he used to look at and study Jupiter's moons, Saturn's rings, the moon's craters, sunspots, etc. Such astronomical findings were revolutionary.

In addition to his studies of outer space, his experiments also, to quote one historian,

"undermined the Aristotelian theories of motion. He demonstrated that the earth was in perpetual rotation and that balls of various weights will pick up speed at the same rate as they fall, so therefore their speed is not determined by their mass. From such experiments, he developed a theory of inertia" (John Merriman, A History of Modern Europe: Third Edition, New York: W. W. Norton & Co., 2010, 297)

Famous also for his confrontations with the Church, Galileo then emerges as one of the critical participants of the Scientific Revolution.

The Renaissance was a cultural movement that initially began in Florence, Italy, but later spread throughout Europe. It started around 1350 and ended around 1600. During the Renaissance Era (a word that means "rebirth"), people experienced changes in art, science, learning, and many other things.

Galileo Galilei (1564-1642), was considered the father of modern science as he made important contributions to physics, astronomy, mathematics and many other scientific areas during the Renaissance Era. Notably, he improved the telescope and discovered parts of the universe not yet seen before, like Jupiter's moons and many new stars.

Although Galileo was largely disliked by the Catholic Church during this time, he continued his pursuit for correct knowledge about the universe. He agreed with  the heliocentric model of the universe, first proposed by Nicholas Copernicus, and in doing so was placed in jail for the last years of his life.

Galileo set the stage for Issac Newton to create further advancements in science and mathematics.

Galileo Galilei (1564-1642) was an important figure in Renaissance-era Italy, a mathematician and scientist who's contributions to astronomy and physics were outweighed only by his role in advancing the concept of scientific fact as more determinative of reality than dictates handed down by the Church.  His observations of the night sky and contributions to the development of the telescope helped immeasurably in proving that, in contrast to the ancient theories of Aristotle, which were supported by the eminent astronomer Claudius Ptolemy, that the Earth was the center of the universe, that the Earth, as with the other identified planets, orbited the Sun.  The heliocentric theory of the solar system had been most prominently advanced by Nicolas Copernicus, but Galileo's efforts were important in reaffirming his predecessor's theories.  

Galileo conducted numerous experiments and made a number of inventions that further contributed to the advancement of the sciences.  His struggles, as a devout Catholic, to reconcile Church Doctrine with respect to the structure of the universe with his principles as a scientist caused him to repeatedly run afoul of Church authorities.  While he was not subjected to the extreme and extremely painful measures defiance of Church orthodoxy often entailed, he was kept under a great deal of scrutiny for his belief in science-obtained knowledge, but was ultimately confined to house arrest for the final years of his life.

To the extent the Renaissance era was characterized by major advancements in science, as well as the arts, Galileo was an important figure in facilitating those advancements.  

Galileo contributed to the Renaissance by helping to create a new way of thinking.  In this new way of thinking, people did not simply trust in what they had been told by religious authorities or by ancient thinkers like Aristotle.  Instead, they required scientific proof of things if they were to believe them.

Galileo helped bring this sort of idea about by doing many experiments and observations to determine how things really worked.  For example, he did his famous experiment to prove that objects of different weights fell at the same rate.  Galileo also created the first telescope that could be used for astronomy.  Using the telescope, he took observations that he could use, for example, to prove that the planets were moving around the Sun and not around the Earth.