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earliest ages. He also concluded that the
line of apses would revolve in the plane of
the lunar orbit also in about nineteen years;
but the observed period is only ten years.
For a long time this was the one weak point
in the Newtonian theory. It was not till
1747 that Clairaut reconciled this with the
theory, and showed why Newton’s calcula-
tion was not exact.
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