Galileo Galilei

Galileo pioneered the use of the telescope for astronomical observation, discovering Jupiter's four largest moons, the phases of Venus, and sunspots — all of which supported the Copernican heliocentric model over Church-backed geocentrism. His formulation of the law of falling bodies and the principle of inertia laid the experimental foundations that Newton would later formalize. He is widely regarded as the father of observational astronomy and of the scientific method itself.