Information for Children on Ocean Tides

Gravitational Force Overview

• Provide an overview about gravitational force to help children understand how it functions. Explain to your child that gravity is a force that works between objects, pulling them toward each other based on the size -- or mass -- of the objects, according to the National Aeronautics and Space Administration. The larger an object, the more gravitational force it exerts over other objects. Because the earth is larger than the moon, the earth holds the moon in place, orbiting around the earth. Because the sun is larger than the earth, the sun holds the earth in place orbiting around the sun.

Sun, Earth and Moon Connection

• The gravitational connection between the sun, earth and moon is most evident to people because of the moon̵7;s close proximity to earth and the sun̵7;s size, according to a lesson published by the University of Southern California. As the earth orbits the sun slowly over 365 days, it rotates once every 24 hours, creating a day. As the earth orbits and rotates, the moon simultaneously orbits the earth once every 29 days, creating a lunar month. As this orbiting and rotating occurs, one side of the earth always faces the moon, which creates a pull. The ocean responds to this pull by bulging at the points currently facing the moon. Centrifugal force causes a symmetrical bulge to occur simultaneously to the ocean on the opposite side of the earth. To create these bulges, the ocean displaces water at two opposite points from each bulge. The two bulges create high tides and the two displaced points create low tides.

Ocean Tide Behavior

• Ocean tides occur predictably along shorelines as the earth and moon orbit and revolve. Most high and low tides span a time period of approximately six hours. The highest crest of tide occurs at high tide and the lowest trough occurs at low tide, according to the National Oceanic and Atmospheric Administration website. The distance between the high tide crest and the low tide trough is the ̶0;tidal range.̶1; Different locations have different tidal ranges, with the largest tidal range located at the Bay of Fundy in Canada -- 53 feet and occurring over a six-hour period, states the OneGeology Kids website.

Variations in Tides

• Tides vary according to the moon̵7;s rotation, advises the OneGeology Kids website. During full moons and new moons, oceans experience the highest tides -- spring tides. During quarter moon (waxing) and three-quarter moon (waning), oceans experience the lowest tides -- neap tides.