He was born in the city of Pisa, which was then part of the Duchy of Florence.
Galileo was a passionate advocate of a heliocentric theory of the universe.
He was the first to use a telescope to study the planet Jupiter.
He discovered four moons of Jupiter, the phases of Venus, and the sunspots.
He was also the first to use the term "satellites" to describe these tiny stars.
The Sidereal Messenger, which Galileo published on March 13, 1610, soon became a popular publication throughout Europe and the world.
Galileo was also fascinated with the science of mechanics, the application of mathematics to kinematics and statics.
His discoveries in this field were his primary focus. However, he was not very interested in astronomy before moving to Padua.