Hi, I'd like to know why we only observe a tide in a sea or ocean? Why it does not occur in a glass of water?

Question

Although I know that tides are due to moon attraction, I don't understand why it can only have an influence on the oceans and seas. What makes sea and ocean water react differently from rivers and lacs when it comes to moon attraction?

thank you for your answers.

Answer 1

because the ocean and sea have alot of mass that can be displaced to increase the water level on beaches from the moons gravity. Your glass of water will never have more mass than you put into it, there for its never going to increase in its level.

Answer 2

Tidal force
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Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiter's tidal forces.The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational field is not constant across a body's diameter. When a body (body 1) is acted on by the gravity of another body (body 2), the field can vary significantly on body 1 between the side of the body facing body 2 and the side facing away from body 2. This causes strains on both bodies and may distort them or even, in extreme cases, break one or the other apart. These strains would not occur if the gravitational field is uniform, since a uniform field only causes the entire body to accelerate together in the same direction and at the same rate.


Saturn's rings are inside the orbits of its moons. Tidal forces prevented the material in the rings from coalescing gravitationally to form moons.The figure shows Comet Shoemaker-Levy 9 after it had broken up under the influence of Jupiter's tidal forces. The comet was falling into Jupiter, and the parts of the comet closest to Jupiter fell with a greater acceleration, due to the greater gravitational force. From the point of view of an observer riding on the comet, it would appear that the parts in front split off in the forward direction, while the parts in back split off in the backward direction. In reality, however, all parts of the comet were accelerating toward Jupiter, but at different rates.

In the case of an elastic sphere, the effect of a tidal force is to distort the shape of the body without any change in volume. The sphere becomes an ellipsoid, with two bulges, pointing towards and away from the other body. This is essentially what happens to the Earth's oceans. Although the Earth is not falling along a line directly toward the moon, the Earth is continuously accelerating due to the moon's gravitational forces, causing it to wobble around their common center of mass. All parts of the Earth accelerate in response to the moon's gravitational forces, but to an observer on the Earth, it appears that the Earth's center remains at rest, while water in the oceans is redistributed to form bulges on the sides near the moon and far from the moon.

When a body rotates while subject to tidal forces, internal friction results in the gradual dissipation of its rotational kinetic energy as heat. If the body is close enough to its primary, this can result in a rotation which is tidally locked to the orbital motion, as in the case of the Earth's moon. Tidal heating produces dramatic volcanic effects on Jupiter's moon Io.


Keep in mind that water in a glass or other container is constrained by that container.

Answer 3

The glass full of water is not big enough to be affected by the tidal pulls of the moon. Also, if you think of some lakes aroung the world, like Lake Titicaca in Central America, they are not affected by the tides.

Answer 4

Ever spun around with your arms extended? Then you have experienced a "tidal" force yourself. A tidal force is a relative effect, due to the difference in the pull on an object over the size of the object. To see the effect of a tide, the force must vary detectably over distances of the order of the size of the object.

When you spin around, the centripetal eaaceleration of your body varies from zero (at your axis) to its maximum (at your hands). It's easily detectable in the heaviness of your hands. The gravitational forces on the water in the glass are, to a high approximation, pretty constant over the dimensions of the glass. So the tidal force is correspondingly very difficult to detect.

Answer 5

I don't think the gravitational pull of the moon will ever make water come spilling out of your glass. And it has nothing to do with the composition of ocean salt water.

Answer 6

There is an affect on the glass of water but it is so miniscule as to be undetected also there is no additional inflow of water in a glass, unlike an ocean or large lake.

Answer 7

It does occur in a glass of water. BUT, the effect is so infinitesimal that you need some very sensitive (and very ex$pen$ive) instruments to measure it.

The rules of physics don't change just because it is a glass of water.

Answer 8

I learned that the gravity pull on the SIDES of the earth are greater in larger bodies of water,such as the seven seas.

Answer 9

Apparently you have to have a certain amount of water for the moon to affect it or the affect is so slight in smaller bodies of water you don't notice.

Answer 10

due to larger mass of water the gravitational force which is directly proportional to mass increases considerably in large water bodies