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Free Online Course on World Geography, Weather, Climate & Regions

Lesson 3: Our Planet: The earth and the universe—where do we fit in?


Figure 3.2.1, The gravitational pull of the moon creates tidal bulges on either side of the earth.

The moon: an influential neighbor

The moon is our closest neighbor and it has a significant influence on the earth. The most noticeable impact is the rise and fall of the ocean tides. The moon's gravitational pull is not as strong as the earth's; however, it is strong enough to exert a pull on the earth. The moon works like a magnet that pulls on the oceans, causing them to bulge out in the direction of the moon, this is called a tidal bulge because it creates ocean tides. The ocean on the other side of the earth has a tidal bulge in the opposite direction, because the earth itself is also being pulled a little bit toward the moon by its gravitational pull and away from the water on the far side, as you can see in Figure 3.2.1. The moon's gravitational pull, combined with the earth's rotation, creates two tides every day. Tides are the ebb and flow of the ocean along the shore—the water rises and then it falls. The strength of the tide depends on where the moon is in its orbit.


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