text: why does the moon have something to do with high and low tides?   the force (gravity) the moon exerts on the earth morphs the shape of the entire planet by pulling up on it.  since the particles that comprise the earth have mass the gravity acts on them, drawing them towards its "source" (the center of mass/center of the moon here).  water, being fluid, moves more readily than other things like the hard rock that makes up the land masses of the earth so it seems to be more affected by the moon's gravity.  when the moon is overhead it pulls the water (and less noticably everything else) towards it, creating a high tide (as well as one on the opposite side of the planet).  the sun also affects the tides to a lesser degree.