In most places on the earth, where the ocean meets the land, there are two high tides and two low tides each day. This Snack models the equilibrium theory of tides, showing why there are two tide cycles per day, why the heights of the tides change over the course of a month, and why the tides occur about an hour later each day.

astronomy space gravity sun moon gravitational Theory axis equilibrium body cycle High tide celestial cycles Low bodies tieds gravitational forces tidal bulges