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If a planet passed near the moon and caused its orbit to decay down to earth- how long could it take and how would that effect the visible phases of the moon on earth?

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    $\begingroup$ The devil is in the detail. This is impossible to answer without a very detailed (numerical) set of data to start from. It might not be workable even then. $\endgroup$ – StephenG Sep 4 '17 at 15:52
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    $\begingroup$ The latter question is easy: visible phases are purely a matter of the relative angular positions of the sun, earth, and moon (leaving out eclipses), so pretty much nothing would change. $\endgroup$ – Carl Witthoft Sep 5 '17 at 12:54