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Uranus should stay on the dashed ring. It doesn’t.
The sun pulls. The path should be tidy. The real walk is a little fat, then a little thin.
People already knew how a planet ought to walk around the sun. Uranus refused. Sometimes it was ahead of the dashed line. Sometimes behind. Not by much. Enough that the tidy picture was wrong, and nobody had dropped a telescope on the reason.
Drag the tug. At zero, Uranus behaves. Turn it up, and the walk leaves the ring.