Which discovery did Galileo make to support the theory that the planets, including Earth, orbit the Sun?

Galileo observed that Venus goes through a full set of phases, much like the Moon. This is explained if Venus orbits the Sun, with its changing position showing different amounts of its sunlit side to Earth. The discovery supported the idea that planets, including Earth, orbit the Sun. Elliptical orbits and the rule that planets move faster near the Sun were later described by Kepler.

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