During the Middle Ages, the scientific understanding of cosmology was a combination of the ideas of Aristotle, Ptolemy, and others. They believed in a fixed, motionless earth at the center of a series of cocentric spheres where there were perfectly spherical planets in circular orbits at a constant speed. This theory is known as the Geocentric model of the universe.
This theory was challenged by Nicolaus Copernicus, who wrote a work called On the Revolutions of the Heavenly Spheres. In his work, Copernicus suggested that the sun, not the earth was the center of the universe. He thought that it was a better way to portray the universe, as there were many obvious problems observed with the geocentric model. One of the problems of the geocentric model was that as many as 80 epicycles had to be added to the model to account for observations of the planetary movements. Copernius’ newer model is known as the Heliocentric model.
However, although Copernicus’ model improved on the geocentric model, it was not completely accurate. Copernicus’ theory required epicycles too, albeit much less. Johannes Kepler, a German astronomer, observed that planets do not move in circular orbits, but elliptical with the sun at one focus. He also discovered that planetary speed increases when closer to the sun and decreases when it gets farther away.
Galileo Galilei, another astronomer, likewise challenged the geocentric model by presenting observations he made with his telescope. Galileo discovered the moons of Jupiter, and observed that they did not orbit earth, but Jupiter. This contradicted the geocentric model, which said that all the planets orbited the earth. He also discovered that the moon was not a perfect sphere, but had craters, mountains, and other features, likewise contradicting the model. Galileo also famously got in trouble with the church, who said that he contradicted church doctrine.
These advances in astronomy were brought to fruition by Isaac Newton, who developed the laws of gravity and motion. He applied these laws to the planets, showing that the reason they orbited the sun was because of gravity, which was likewise the reason people and other objects are held to the earth rather than flying off into space.
Many people believe that during this time there was a war between science and religion. Today, there is a new consensus among science historians that religion did indeed play a large role in the Scientific Revolution, and was not necessarily opposed to science as was previously thought. In fact, a Christan worldview posits an orderly universe, and says that God is a God of order. Some examples of Catholic or Protestant scientists are Nicolaus Steno, who worked with geology, Francesco Grimaldi, Roger Boscovich, Giovanni Cassini, and the aforementioned Isaac Newton and Johannes Kepler.
During the 18th century, a philosophical movement arose known as The Enlightenment. Some common themes among the Enlightenment thinkers was an emphasis on reason and the skepticism of traditional institutions. They also more confidence in human nature than is expressed in Christianity. They said that science was a model for knowledge, as it does not cause conflict like religion does. Many Enlightenment thinkers believed in a form of religion stripped of ritual and miracles, consisting only of wonder at the Author of the universe. They also generally believed in religious toleration for most religious traditions.