Why two high tides a day instead of one? Tidal forces raise two symmetric bulges, one facing the Moon and one on the opposite side, and the spinning Earth passes through both. As the Moon nears perigee the tidal range grows, while its phase decides between spring and neap tides: the Sun adds roughly 46% of the Moon's tidal pull, reinforcing or cancelling it. All the while the Moon keeps receding 3.8 cm per year.
Why two high tides a day instead of one? Tidal forces raise two symmetric bulges, one facing the Moon and one on the opposite side, and the spinning Earth passes through both. As the Moon nears perigee the tidal range grows, while its phase decides between spring and neap tides: the Sun adds roughly 46% of the Moon's tidal pull, reinforcing or cancelling it. All the while the Moon keeps receding 3.8 cm per year.
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