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Earth-Moon-Sun Tides

What you are seeing: Earth as a 3D sphere with the L=2 tidal bulge made visible. The Moon orbits in the equatorial plane and the Sun lies at +x. As the Moon moves, the bulge moves with it; when the Sun and Moon align (new or full moon) the bulge gets bigger (spring tide); at quadrature it gets smaller (neap tide)

Figure 1. Earth with the lunar + solar L=2 tidal bulge made visible; Moon (gray) at the chosen orbital phase; Sun lies at +x. Method: closed-form L=2 Legendre tidal potential h(theta) = A_lunar P_2(cos theta_M) + A_solar P_2(cos theta_S).
lunar phase (°)60
bulge scale0.08
animation speed2

WHAT TO TRY

  • Move the lunar phase: the L=2 tidal bulge always points along the Earth-Moon line, with a second bulge on the far side, so there are two high tides a day as Earth rotates under them.
  • Watch the Sun line up at new and full moon: the solar and lunar bulges add to give the large spring tides, and at quarter phase they partly cancel into weak neap tides.
  • Raise the bulge scale to exaggerate the deformation: the tide is the difference of the Moon gravity across Earth diameter, a gradient effect, not the Moon pull itself.