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How did Galileo Galilei’s discovery of Jupiter’s moons support the Copernican model?
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Jupiter
Photograph of Jupiter taken by Voyager 1 on February 1, 1979, at a range of 32.7 million km (20.3 million miles). Prominent are the planet's pastel-shaded cloud bands and Great Red Spot (lower centre).
Galileo Galilei’s discovery of four moons orbiting Jupiter in 1610 provided a fundamental argument in favor of the Copernican model by directly challenging the Ptolemaic system.1
In the geocentric Ptolemaic model, it was believed that all celestial objects must move around Earth. By observing that these satellites revolved around Jupiter, Galileo demonstrated that there could be more than one center of motion in the universe. This observation effectively demoted Earth from its unique, central position in the cosmos, supporting the Copernican view that the Sun serves as the center of the solar system and that Earth is simply another planet in motion.123