Who proposed a heliocentric model of the solar system in the 16th century?

• A. Ptolemy
• B. Nicolaus Copernicus
• C. Tycho Brahe
• D. Aristotle

Answer: (B)

The main idea tested is the shift from thinking Earth is the center of everything to recognizing the Sun as the center of the solar system. In the 16th century, Nicolaus Copernicus proposed a heliocentric model in which the Sun sits at the center and the planets, including Earth, orbit it. This was a radical change from the long-standing geocentric view associated with Ptolemy and Aristotle, which placed Earth at the center with complex systems of epicycles to explain motion. Copernicus’s idea, articulated in his work De revolutionibus orbium caelestium (published in 1543), helped spark the scientific revolution by offering a simpler framework for understanding planetary motions and retrograde movement. Tycho Brahe proposed a hybrid model rather than a fully heliocentric one, which is why he isn’t the correct answer.