Final answer:
Galileo used the phases of Venus and the discovery of Jupiter's four moons as evidence to support the heliocentric model, challenging the geocentric view.
Step-by-step explanation:
Galileo Galilei significantly contributed to the scientific revolution of the Renaissance period with his support of the Copernican heliocentrism. The two crucial pieces of evidence he used to support the claim that the Earth is not the center of the universe can be attributed to his astronomical observations through the telescope he improved.
Firstly, Galileo observed the phases of Venus, which could only be explained if Venus were orbiting the Sun, not the Earth. Secondly, he discovered the four moons of Jupiter, demonstrating that not all celestial bodies revolve around the Earth.
These observations were revolutionary because they directly contradicted the then-accepted geocentric model and provided strong support for the heliocentric model.