Who used his telescope to prove the heliocentric theory?

Galileo Galilei used his telescope to provide crucial evidence supporting the heliocentric theory, which posits that the Earth and other planets orbit the Sun. His observations of celestial bodies, such as the phases of Venus and the moons of Jupiter, challenged the geocentric model and helped establish the validity of Copernicus's earlier work. Galileo's findings were significant in advancing the scientific revolution and changing our understanding of the cosmos.