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Loading contentGalileo observed that Venus shows a full cycle of phases like the Moon, including a 'full' phase only possible if it orbits the Sun.
Among the strongest observational evidence for the heliocentric model.
Facts on this topic will be cited from these primary and reference sources.
General reference for the history of astronomy, biographies, and cultural context.
Mission data, planetary science, space telescopes, and public-domain imagery.
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