Why Do the Tides Rise And Fall ?

The water in the oceans is held close to the earth by gravity. But the Moon and Sun also have some 'pull' on the earth. The Moon's gravity affects water in the oceans. The sea is 'pulled' slightly towards the Moon, causing a bulge, or high tide. On the opposite side, the sea is pushed away, causing a second bulge.

High tided occur twice in about 25 hours. This is because at the same time as the earth is rotating on its axis , the Moon is traveling round the Earth(every 27 days).