Complex sentence: It was first observed by astronomers in the late 1600s seaching for stellar parallax, but it first became influential after James Bradley provided the classical explanation for it in 1729 after decades of controversy over its origin.
Split into simpler sentences: It was first observed by astronomers in the late 1600s seaching for stellar parallax. It first became influential in the 18th century after James Bradley provided the classical explanation for it in 1729 after decades of controversy over its origin.