• The Earth's rotation and the gravitational pull of the sun and moon create tides. Because the moon is much closer to Earth than the sun, the moon exerts a much stronger gravitational pull.

    The Earth's oceans respond to the moon's gravitational pull by bulging and dipping as the moon rotates around the Earth. As the ocean bulges toward the moon, a high tide is created. The high tide on the side of the Earth facing the moon is called the high high tide. The high tide caused by the bulge on the opposite side of the Earth is called the low high tide. (A low high tide may be understood as the moon's tidal force pulling the planet—not the ocean—toward it.)

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  • Term Part of Speech Definition Encyclopedic Entry
    Earth Noun

    our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

    		 Encyclopedic Entry: Earth
    exert Verb

    to force or pressure.
    gravitational pull Noun

    physical attraction between two massive objects.
    high high tide Noun

    tide created when the Earth directly faces the moon.
    high tide Noun

    water level that has risen as a result of the moon's gravitational pull on the Earth.
    low high tide Noun

    tide created when the Earth faces away from the moon.
    Moon Noun

    Earth's only natural satellite.
    ocean Noun

    large body of salt water that covers most of the Earth.

    		 Encyclopedic Entry: ocean
    planet Noun

    large, spherical celestial body that regularly rotates around a star.

    		 Encyclopedic Entry: planet
    rotate Verb

    to turn around a center point or axis.
    rotation Noun

    object's complete turn around its own axis.

    		 Encyclopedic Entry: rotation
    sun Noun

    star at the center of our solar system.
    tidal force Noun

    gravitational pull exerted by one object, such as the sun or moon, that raises tides on another object, such as the Earth.
    tide Noun

    rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.

    		 Encyclopedic Entry: tide
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Illustrator

Mary Crooks, National Geographic Society

Producer

Caryl-Sue, National Geographic Society

Last Updated

July 7, 2015

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