The prevailing belief at the time of Galileo was that the Earth was the center of the universe, with the sun and planets going around it, called geocentrism, put forward by Aristotle.
Copernicus first proposed that the Earth and planets revolved around the sun, called heliocentrism. Galileo tried to prove this after making observations on his telescope.
Even scientists of the day had a hard time accepting Galileo’s findings. Aristotle himself had argued that if heliocentrism were true, then there would be observable parallax shifts in the stars’ positions as the earth moved around the sun, but due to the technology of the time, no such shifts could be observed.
Galileo’s theories seemed to contradict the Bible, but the church chose to take a literal interpretation of the Bible, citing verses like 1 Chronicles 16:30: “The world is firmly established, it cannot be moved”, Psalm 93:1 “The world is established, firm and secure”, and Ecclesiastes 1:5 “The sun rises and the sun sets, and hurries back to where it rises”.
It’s easy to see now that these verses are not meant to be taken literally, and actually this is what Galileo argued.
In the end, the church could not accept Galileo’s theories, because at the time they could not be conclusively proven.
Next: Lessons About the Church and Galileo