Ocean tides are generated by the gravitational attraction of the moon and the sun on the sea. To simplify the problem, imagine the earth as an ocean planet completely covered by water. As the earth orbits around the sun and the moon orbits around the earth, both form their own rotational systems, each system rotating around its own center of mass.
First we will look at the earth-moon system. To keep the gravitational attraction of the earth and moon from pulling them together, another force must counterbalance gravity. This centrifugal force comes from the inertia of the moon's rotation around the earth-moon center of mass. While this balance of forces keep the earth and moon apart, the side of the earth facing the moon experiences a greater gravitational attraction than the remainder of the planet, while the side facing away experiences a lesser gravitational attraction. In the simple case that we have just described, this causes the water to pile up in bulges on both sides of earth facing towards and away from the moon. In what has been called the Equilibrium Theory of Tides, we can envision the earth completing one revolution per 24-hour day, with any point experiencing two high tides per day as it passes under these bulges in the sea surface and two low tides per day when it passes by the position out of phase with these bulges where the gravitational and centrifugal forces on the ocean are in balance.
The same argument as above can be developed for the earth-sun rotational system. However, the sun's influence on the tides is only about half that of the moon. The reason for this is that forces generating the tides increase with the mass of the two bodies, but decrease as the cube of the distance between them. Therefore, even though the sun is much larger than the moon (27 million times more massive), it is also much further away from earth than the moon (387 times further away), and the distance cubed is the more important factor.
To add an additional level of complexity, we need to consider how the moon and sun influence the tides in combination. When the sun and moon are aligned, there are exceptionally strong gravitational forces, causing very high and very low tides. These are called spring tides, and they are associated with the new and full moons.When the alignment of the sun and moon are out of phase, the gravitational forces cancel each other out, and the differences between the high and low tides are minimal. These are called neap tides, and they are associated with the first-quarter and third-quarter moons.
Predicting tides can get much more complicated as we add continents, the geometry of ocean basins, and bottom friction to our conceptual model. In fact, scientists must record tidal data at a particular location for a period of time before they can unravel some of this complexity and accurately predict tides at that location. That is a level of detail we won't go into here, but the above discussion should allow you to understand the general role of the moon, as well as the sun, in generating ocean tides.
2007-03-25 02:10:10
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answer #1
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answered by Smilez 1
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The gravitational force of the moon on the Earth is the same as the gravitational force of the Sun on the Earth.
This is because although the Sun is 440 times bigger than the moon, its also 440 times farther away.
Because the oceans are liquid and not land, they are more susseptable to shape change due to external gravity than the solid earth. So when the Sun or Moon is over-head, the oceans swell, and when this swell reaches land, its comes in the form of the rising tide.
2007-03-25 08:58:50
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answer #2
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answered by Bloke Ala Sarcasm 5
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The moon exerts a strong gravitational pull on the Earth, (and vice versa). As the earth rotates, this pull picks the ocean up a bit, then drops it back down, creating tides- it doesn't quite pull the water up directly under the moon, because this effect is complicated by all the continents and bottom contours of the oceans, as well as the inertia of the water itself. It takes a very large scale body of water to generate this effect, so even the Great Lakes in the US don't have tides...(the planet flexes a bit as well!)
2007-03-25 08:58:36
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answer #3
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answered by Steve E 4
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Grvaitational force, like the above ones said... also note that the moon is relatively close to the earth and very fecking big for a sattelite. I'm not saying it does, but it might have something to do with it.
o.o
2007-03-25 09:30:39
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answer #4
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answered by Anonymous
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whats a sea tider? god i,m thick i should of went to school for longer.
2007-03-25 09:01:25
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answer #5
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answered by kelly69627 2
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It's gravity causes a rise in the sea level on both sides of the earth. See here and choose your topic on the right
http://www.nos.noaa.gov/education/kits/tides/welcome.html
2007-03-25 08:55:53
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answer #6
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answered by Gene 7
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due to moon's gravitational force it attracts the tides and because
earth also has the gravitational force it do not allow the water to go out in the space
2007-03-25 08:54:07
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answer #7
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answered by pokemon maniac 6
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It's gravity pulls on the water.
http://groups.google.co.in/group/neat-astronomy?hl=en
2007-03-25 09:02:20
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answer #8
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answered by chase 3
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THE GRAVITANAL PULL FROM THE MOON.
2007-03-25 09:22:36
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answer #9
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answered by thomas b 3
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it makes the giant whales go crazy
2007-03-25 09:40:03
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answer #10
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answered by fuufingf 5
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