This posting follows: Copernicus and the Church
By claiming that the sun, and not the earth, was at the center of the universe, Copernicus directly challenged the Church's sacred Aristotelian worldview. But while Copernicus was the first one to publicly challenge the Church's view of the world, many followed. What he had started not even the Inquisition could stop.
Johannes Kepler (1571-1630), a German astronomer, expanded on the Copernican worldview, and developed it into a mathematical model. The three laws of planetary motion he conceived are still in use nowadays. These mathematical laws, based on elliptical motion, accurately explained all planetary observations. However, by suggesting that the planets were moving in elliptical orbits and not in the heavenly perfect circular motion, Kepler deviated even further from the Aristotelian model. He was excommunicated from the Lutheran Church in 1612.
Kepler's contemporary, the Italian scientist and astronomer Galileo Galilei (1564-1642), in his most renowned experiment dropped two bodies of different weights from the Leaning Tower of Pisa, and demonstrated, once and for all, that all bodies fall at the same speed regardless of their weight. This was the first time that an experiment was used to determine scientific truth, and the result was an indisputable proof that Aristotle's theory and the Church's dogma were fundamentally mistaken.
But this was not enough for Galileo. Being the first person to apply the telescope to the study of the heavenly bodies, Galileo also revolutionized astronomy. His observations led him to discover the moons of Jupiter and the phases of the planet Venus, and convinced him that Copernicus' heliocentric model, with the sun at the center of the universe, was the correct one. In 1633, Galileo was brought before the Inquisition for a grave suspicion of heresy. He was forced to formally renounce his beliefs, and was sentenced to life-long house arrest.