is vitally important, for
coastal Navigation, to understanding and be able to predict tidal
The rise and
fall of sea levels are caused
by the gravitational pull of the sun and moon and are also affected by
centrifugal forces generated by the earth’s rotation.
The effect is
subject to the relationship
between the earth, the moon and the sun at any given time.
The moon being
closer to the Earth has a
greater influence on the oceans than the sun.
As the moon
rotates around Earth a tidal
bulge occurs beneath the moon where its gravitational pull is
the opposite side of the
globe, where the moons pull is negative the centrifugal force of the
earth’s rotation creates a second bulge away from the
It is also why
there are normally two
tides every 24 hours and 50 minutes, which is the time it takes for the
rotate around Earth.
are modified by the ‘solar-tides’ caused by the gravitational pull
of the sun.
It is this
reinforcing or partially
canceling out of the ‘lunar-tide’ which causes springs and