What evidence helped prove the heliocentric model was better than the geocentric model?

• A. Galileo's observation of moons orbiting Jupiter
• B. Eratosthenes measuring Earth's circumference
• C. The discovery of Neptune
• D. The existence of Pluto

Answer: (A)

The main idea here is that observational evidence can show that Earth isn’t the fixed center of all motion in the sky. Galileo’s discovery that Jupiter has moons shows that there are centers of motion other than Earth—moons orbit a planet, and planets themselves orbit the Sun in a larger system. This directly challenges a strictly geocentric view where everything must revolve around Earth, and it fits with the heliocentric idea that the Sun is the central body in the solar system. The other options don’t target this central question: measuring Earth’s circumference demonstrates that Earth is a sphere but doesn’t address who orbits whom; Neptune’s discovery and Pluto’s existence reveal more about the solar system’s outer members and come from later reasoning, not direct evidence against Earth as the center. So the moons around Jupiter best illustrate that not all celestial motion centers on Earth, strengthening the case for a Sun-centered model.