Assertion: mercury's motion | /r/CreatedBy | its orbital motion
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Source sentences:
text: The westward motion of the stars due to its rotation is opposite the eastward motion of the Sun caused by its orbital motion, so the Sun's net westward motion is only two degrees per (Earth) day, which is three times slower than the star's six degrees per (Earth) day; therefore, the day ought to be three times longer than the rotation, as it is.