Galileo Galilei was an Italian scientist in the 16th century that played a key role in the Scientific Revolution during the Renaissance. He supported Nicolaus Copernicus' finding that the planets of our solar system, including Earth, revolve about the sun and not the other way around. This led to conflicts with the Catholic Church that at this point still believed that the Earth was the centre of the universe. Galileo was tried by the Roman Inquisition and forced to withdraw his support for Copernicus', spending the rest of his life in home arrest.
Penny: So, you and Leonard.
Sheldon: Oh, dear God.
Penny: Little misunderstaning, huh?
Sheldon (outraged): A "little misunderstand—?" Galileo and the Pope had a "little misunderstanding".