Final answer:
Copernicus's proposal was a theory based on his observations and calculations. It explained the celestial mechanics placing the Sun, not the Earth, at the center of the solar system. His work eventually led to the empirical validation that supported the heliocentric model.
Step-by-step explanation:
Nicolaus Copernicus's proposal that the Sun is the center of the solar system was a theory, not a law. A scientific law describes a consistent phenomenon that occurs in nature under certain conditions, without explaining why. A scientific theory, on the other hand, is a well-substantiated explanation of some aspect of the natural world that can incorporate laws, hypotheses, and facts. Copernicus's heliocentric theory was based on his observations and calculations, and he spent many years refining his ideas, which contrasted sharply with the prevailing geocentric views of the day that continued to be reinforced by religious and philosophical traditions.
In those times, sensory evidence from nature was often deemed unreliable, and Aristotelian philosophy was held in higher regard than empirical experimentation. Copernicus's theory ultimately paved the way for the scientific method that emphasizes observation, experimentation, and evidence-based conclusions. While the heliocentric model could not immediately be tested with the technology of his time, it provided predictions that could differentiate it from the competing geocentric model.
Therefore, the correct answer is b) Theory, as it was based on observation and calculations