What established distinction was shattered by the observation that the Moon resembled the Earth?

Answer

The distinction between the corruptible sub-lunar world and the unchanging celestial realm.

The discovery that the Moon had features like mountains and craters, appearing much like Earth, shattered the Aristotelian distinction between the corruptible, changing sub-lunar world and the unchanging, perfect celestial realm.

What established distinction was shattered by the observation that the Moon resembled the Earth?
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