Galileo was born in Pisa, Italy in the late 1500’s. He eventually became a mathematics teacher despite having no degree, and it was here that his famous future was first hinted. Galileo the math teacher made his first step into Galileo Galilei astronomy when he demonstrated to his students that Aristotle was wrong about object of different weights falling at different speeds. He wasn’t invited back to teach, and so moved to a position at the University of Padua. Galileo contributions to astronomy would come to fruition there.
In Padua, Galileo invented the compass and began studying physics. He discovered the law of falling bodies and the parabolic path of projectiles. These became very important in later Galileo Galilei astronomy. But at the time Galileo claimed to have no interest in the subject other than that he believed the work of Copernicus rather than that of Aristotle and Ptolemy. Copernicus had proposed that the solar system is heliocentric, that is that the planets rotate around the sun. Aristotle and Ptolemy held that the solar system was centered around the Earth, and even the sun rotated around our home. The model Copernicus proposed for the order of planets around the sun has been proven. And today we know Copernicus was completely correct.
Galileo was the first to look at the night sky through a spyglass, thus using the first telescope. With a magnification of 20, this telescope helped Galileo discover mountains and craters on the moon. Galileo also determined that individual stars made up what was called the Milky Way. Next he found the four largest moons of Jupiter. After publishing this information, he was named the royal mathematician in the court at Florence. No longer having to earn a living teaching, he could spend more time exploring. It took him only 9 months to discover Saturn’s phases. This was another nail in the coffin for Ptolemy’s and Aristotle’s ideas about the solar system.
Galileo had a long standing feud with Aristotle’s beliefs and teachings. Many scientists agreed with Galileo, and so published his findings. But because Aristotle’s work elevated man to key position in all the universe, the church supported his work. In 1614 a priest in Florence denounced Galileo Galilei Astronomy. Galileo responded by writing a letter proclaiming the bible irrelevant to science. In 1616 the church censored Galileo’s books, and a cardinal instructed him to stop teaching that the Earth moves. Galileo continued with other studies but in regard to the solar system, obeyed the order. Galileo signed a document proclaiming his agreement with the Earth centered solar system, one in which the Earth doesn’t move. But he had one more thing to say on the subject. “I would say here something that was heard from an ecclesiastic of the most eminent degree; “And yet … it moves.”