Final answer:
Copernicus needed reassurance that his work was in line with the Church's teachings due to the contradiction it posed to the Church's geocentric model of the solar system.
Step-by-step explanation:
Copernicus needed to be reassured that his work was for the well-being of the Church because his new theories contradicted the Church's established geocentric model of the solar system, which placed Earth at the center. This challenged the authority and teachings of the Church. By dedicating his manuscript to the pope and emphasizing that his work was in line with the teachings of the Church, Copernicus hoped to mitigate potential backlash and opposition from the Church.