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Over the lunar year the declination of the sun changes: at the equinoxes, the sun is overhead at the equator, so that sun, moon, and earth are nearest to being in a straight line, exerting the maximum gravitational pull. At the solstices, the sun is overhead north or south of the equator, and the moon-earth-sun line deviates most from being straight, resulting in the weakest tide-raising forces.