Q & A: Low tide, High tide, Spring tide, Neap tide

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Q:

How exactly is the moon envolved with the ocean’s tide
- Chris (age 11)
Roseville, CA U.S.A.

A:

Chris -

The moon is what creates the ocean's tide! When the moon's gravity pulls on the earth, it pulls a little bit harder on the water that's closest to it than on the rest of the planet. This pulls water in that direction, making it a little bit deeper on that side of the planet. The water is also deeper on the opposite side because the moon pulls harder on the earth than on the far oceans. Since the earth is rotating, this means that there are two high-tides and two low-tides each day.



The sun's gravity also helps to create tides, although it is not as important as the moon's gravity (since the sun is so much farther away). When the sun and the moon are lined up to both pull in the same direction or opposite directions, tides are especially strong. This is called a 'spring tide.'



When the sun and the moon are pulling at right anglkes to each other (i.e. 90 degrees to each other), the tides are especially weak. This is called a 'neap tide.'

For more information on tides (and for where I found these pictures), look here.

-Tamara

(published on 10/22/2007)

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