Astronomy Practice Exam 2025 – Complete Preparation Guide

Nicolaus Copernicus is known for his revolutionary heliocentric theory, which posited that the Sun is at the center of the solar system and that the Earth, along with other planets, revolves around it. This was a significant shift from the geocentric model that dominated ancient and medieval astronomy, where it was believed that the Earth was the stationary center of the universe and that all celestial bodies, including the Sun and stars, revolved around it.

By placing the Sun at the center, Copernicus was able to provide a more straightforward explanation for the observed movements of the planets. For instance, his model accounted for the retrograde motion of planets in a way that the geocentric model struggled with. Copernicus's ideas laid the groundwork for future astronomers like Kepler and Galileo, who would further develop and provide evidence for the heliocentric theory.

The other choices suggest concepts that contradict Copernican theory. The notion of a flat and stationary Earth, the Earth-centric view of the solar system, and the fixed nature of stars are all ideas rooted in earlier astronomical thinking, which Copernicus’s work challenged and ultimately helped to refute through a more accurate representation of the cosmos.