Who introduced the heliocentric model?

• A. Nicolaus Copernicus, Poland 1473-1543
• B. Galileo Galilei
• C. Johannes Kepler
• D. Ptolemy

Answer: (A)

Placing the sun at the center and the planets orbiting it marks a major shift in how we understand the solar system. Nicolaus Copernicus, a Polish Renaissance astronomer, is the one who introduced this heliocentric idea and presented a formal model, published in 1543 as De revolutionibus orbium coelestium. His proposal offered a coherent framework that explained how planets move, including retrograde motion, without the complex epicycles of the geocentric system. This work sparked a scientific revolution and set the stage for later confirmations and refinements. Galileo later provided observational support with his telescopic discoveries, and Johannes Kepler refined the model with his laws of planetary motion, showing that orbits are elliptical rather than perfect circles. Before Copernicus, the geocentric model attributed everything to a Earth-centered universe, notably championed by Ptolemy. So, Copernicus is the one who introduced the heliocentric model.