We know the moon used to be much closer to Earth. What kind of tides might there have been back then?
• The force causing lunar tides is inversely proportional to the cube of the distance to the moon. So if the moon were twice as close, tides would be eight times higher. If it had once been only a tenth the distance, tides would have been 1000 times higher than those today, if there were seas back then.
Such giant tides would have a proportionally stronger effect on the moon in return, causing it to move away, and so eventually reducing the size of the tides.
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Eric Kvaalen, Les Essarts-le-Roi, France
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