Tides are caused by a gravitational tug-of-war
between the sun, moon, and earth. All objects exert gravitational pull on each
other. The closer they are, or the larger they are, the greater the pull. All
of the planets exert some gravitational pull on the earth. However, the pull of
the moon and sun are most noticeable because the moon is so close to us and the
sun is so big. It takes the earth 365 days to revolve around the sun. As it
revolves around the sun, it spins, or rotates on its axis once every 24 hours.
At the same time, the moon revolves around the earth once every 29 days. The
gravitational pull of the sun holds the earth in orbit, while the gravitational
pull of the earth keeps the moon in orbit.As a result of this gravitational
attraction between the earth and the moon, the side of the earth facing the
moon is pulled towards it. Solid objects like the ground and buildings are not
distorted as much as liquids like the ocean. A bulge of water occurs on the
side of the earth facing the moon. As the earth rotates around the sun,
centrifugal force causes an equal bulge of water on the opposite side of the
earth. Water is pulled away from these two sides of the earth to form these
bulges, or high tides. This leaves a depression, or low spot, in the oceans
between. These are the areas of low tides.
