Why the sea rises and falls.
Why are there two tidal bulges?
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Why are there two tidal bulges?
Move the Moon and compare the two alignments.
The Moon’s gravitational pull differs between the near and far sides of Earth. These differences produce two tidal bulges. The Sun adds another tidal contribution: alignment strengthens spring tides, while right-angle geometry gives weaker neap tides.
Equilibrium tide schematic with two opposite bulges. Relative lunar amplitude 1 and solar 0.46; normalized range, not metres at a coastline. Differential gravity produces the tide; local ocean geography and timing are omitted.
Arrange a spring-tide alignment and then inspect a neap tide.
Compare spring and neap tide alignments.