Tides

The tide is the greatest synchronised movement of matter on our planet. Every drop of seawater takes part in tidal motion, driven by the gravitational pull of the moon and sun. At the coast, we see the tide as a twice-daily rise and fall of sea level that moves the edge of the sea up and down a beach or cliff-face. In some places, the tide is small but at others it can rise in a few hours by the h...