Context
Aristotle’s model of the universe was a geocentric one where perfect celestial spheres revolved around the earth in a perfect circle in a uniform fashion. The universe was set to be made out of 4 elements – earth, air, fire, and water. Each of the elements was assigned a comparative weight and the theory believed that the heavies element sunk to the center of the universe. Since earth and water were the heavies, it justified the presence of earth at the center. This was the main accepted theory until the arrival of the Ptolemaic model.
Ptolemy in the 12th century Alexandria forwarded his own theory of planetary motion. He also placed the earth at the center, but his theory used epicycles and that the celestial bodies were present on rotating spheres. He further introduced the 5th element to Aristotle’s theory – quintessence. This model of the universe was extremely complicated and difficult to use to calculate exact planetary motion. Nonetheless, this theory became the dominant one until the turn of the 17th century.
Following the publication of Copernicus’ On the Revolutions of Heavenly Spheres, the heliocentric model of Copernicus failed to take flight. Believers in the theories were few. Proponents in the 16th century only had limited conversations about this new approach to planetary motion. The people that did believe in the theory hailed Copernicus as a revolutionary, although his theory was no less complicated than the Ptolemaic one. Furthermore, it was not just inconsistent with the geocentric thought, but it also made very little common sense since if the earth was revolving and rotating, then we humans should have felt some form of movement. Inertia wasn’t yet formulized. It also failed to produce stellar parallaxes and assigned the Sun to be motionless, all ideas that opponents brought up.
The acceptance of the theory changed after the invention of the Telescope. Galileo was the first person to invent high-magnification telescopes that could view celestial bodies. Increments in magnification on a regular basis allowed Galileo to observe these spheres in details unavailable to any other human prior. He could see that the planet Venus had phases just like the moon and that the moon wasn’t a perfect celestial body – it had craters. This discovery made Galileo a supporter of the Copernican system. Although the Catholic Church was interested in the heliocentric approach early in its development, the Church later joined the protestant Christians in its opposition to the Copernican system. Furthermore, the publication of Galileo’s discovery was heavily criticized and rejected by the church. The church relied on the Aristotelian and the Ptolemaic models of the universe. Essentially, the main belief of the church was that god is perfect and all his creations are perfect. Perfection was an important quality of everything around the world. The planets, orbits, etc. needed to be perfect – and hence, no imperfections like craters on the moon were classified as heresy.
Galileo was going to be questioned by the church because of his beliefs and faith in the Copernican model. To avoid complications, Galileo claimed that he was still a religious individual with a deep belief in the geocentric approach but he argued that there should be scientific debates about the heliocentric approach as well. Secretly, he did very much believe in the Copernican system. In 1616, the Roman Catholic Church banned Copernicus’ book. The church inquisitioned Galileo in 1633 who had already published multiple discoveries that conflicted with the church’s beliefs. He was sentenced to house arrest for the rest of his remaining life.