Galileo was one of the first scientists to use a telescope, make substantial improvements, and point it at the stars and moon. He published his observations in his “Starry Message” (Sidereus Nuncius) memo in 1610 — causing shockwaves through Italy and the rest of Europe.
At the time, everyone believed that the Earth was the center of the universe (geocentrism) and everything else orbited around it. But Galileo, building on theories from Kepler and Copernicus, took heliocentrism (Earth revolves around the Sun) as fact. This didn’t sit well with the Catholic church, which saw the idea as heresy. In 1633, Galileo was tried by the Inquisition, found guilty, and sentenced to life imprisonment under house arrest. Any future publications of his were banned.
He was forced to recant his belief in heliocentrism. But, legend has it, afterward, he muttered the phrase, Eppur si muove — “And yet it moves.”