Final answer:
The Catholic Church initially believed in the geocentric theory but later considered the heliocentric theory when introduced by Nicolaus Copernicus. Galileo's observations and writings further supported the heliocentric theory and convinced many scientists of its validity.
Step-by-step explanation:
The Catholic Church initially believed in the geocentric theory, which stated that Earth was the center of the universe. This belief was based on a long philosophical tradition and the authority of Aristotle and Ptolemy. However, the Church started to consider the heliocentric theory when Nicolaus Copernicus introduced it in the 16th century.
Galileo, a prominent scientist of the time, also supported the heliocentric theory and conducted observations and experiments to provide evidence for it. Although Galileo faced opposition and was accused of heresy by the Church for his ideas, his observations and writings convinced many scientists of the validity of the Copernican theory.