Question

explain how Galileo's observations of the phases of Venus was the "nail in the coffin" for geocentrism identifying what he observed to support his claims.

Answer 1

As per geocentrism, earth was at the center and all other planets, sun and all the stars move around it in their respective orbit. However,  Using his telescope, Galileo found that Venus went through phases, just like our Moon. But, the nature of these phases could only be explained by Venus going around the Sun, not the Earth. Galileo concluded that Venus must travel around the Sun, passing at times behind and beyond it, rather than revolving directly around the Earth. Galileo's observations of the phases of Venus virtually proved that the Earth was not the center of the universe

The Catholic Church believed that the Earth did not move and was the center of the universe. Galileo was summoned to the court and was only let go until he accepted that he was wrong and earth does not move. However, after his book got publishesd, he was house arrested and was not allowed to leave and died under house arrest due to ill health.