How does the moon control the tides?

Answer 1

An often-heard explanation is that it's because the Moon's gravity field pulls the water. This can't be the full explanation since the Moon pulls the solid Earth as well and does not pull the water *relatively* to the solid Earth. Also, somewhat contra-intuitively, there's high tide twice per day, namely when the Moon is highest on the sky but also when its on it lowest point below the horizon, when intuition might suggest that the Moon should be pulling water down rather than up.

The correct answer is that the variation in the Moon's field of gravity (stronger the nearer you are to the Moon) causes the Earth to have a minimum of potential energy if it where slightly elliptic. Note that such an ellipsoid has a lower potential energy than a sphere even though the center of mass is the same. While the Oceans take the minimum-energy shape, the solid Earth is too rigid to get deformed into an ellipsoid.

Maybe it's easier to understand this way: The Earth rotates around the common center of gravity for the Earth-Moon system. This rotation produces a centrifugal force directed away from the Moon. This centrifugal force is, on average, balanced by the gravity of the Moon.

The centrifugal field is
F = r omega^2, where omega is the rotational speed of Earth in its orbit around the common center of mass, i.e. it grows linearly with r which is related to the distance from the Moon at a particular point of the Earth's surface, while the lunar gravitational force is
F = - m G /d^2, where m is the mass of the Moon, G the gravitational constant and d is the distance from a particular point on Earth's surface to the Moon. The minus sign because the direction is the opposite as that of the centrifugal force.

Now the total field affecting the ocean becomes
r omega^2 -mG/d^2
differentiating with respect to r gives
F' = omega^2+mG/(3d^3)
which is always positive so that the field in the direction away from the Moon must be stronger the further away you come from the Moon. Since the average field must be zero (the gravitational and centrifugal force must balance eah other to keep the Earth in orbit), the field must be negative (i.e. directed towards the Moon) at thee location nearest to the Moon, and positive (i.e. directed away from the Moon at locations furthest away from the Moon.

Answer 2

Tidal forces in general are caused by the difference in gravitational force experienced between different parts of the same object. When there is a large difference in the forces between the different parts (either because the object is very large or the gravitational field strength changes very rapidly with distance) then there are pulling/stretching forces experienced within the object as well as the overall gravitational attraction the pulls the centre of mass. In the earth/moon system, there is a large distance between the side of the earth near the moon and the side farthest away. This creates a stretching force - so the earth is pulled into a sort of bulging ball shape Of course, the oceans are free, so they also respond to this tidal force - they flow toward the point of maximum gravitational force which is the point where the moon is overhead. That's high tide! On the far side of the earth, the solid planet has moved toward the moon but the tidal force on the water is much lower so effectively the ground falls downward - creating another high tide! That's the very basic idea - the tides are actually very complicated and controlled by things like shape of ocean floor, funnelling in river estuaries etc. The relative orientation of the sun and moon also plays a part. But that's the gist :)

Answer 3

any of the cyclic deformations of one astronomical body caused by the gravitational forces exerted by others. The most familiar are the periodic variations in sea level on the Earth that correspond to changes in the relative positions of the Moon and the Sun.

At the surface of the Earth the gravitational force of the Moon is about 2.2 times greater than that of the Sun. The tide-producing action of the Moon arises from the variations in its gravitational field over the surface of the Earth as compared with its strength at the Earth's centre. The effect is that the water tends to accumulate on the parts of the Earth's surface directly toward and directly opposite the Moon and to be depleted elsewhere. The regions of accumulation move over the surface as the position of the Moon varies relative to the Earth, mainly because of the Earth's rotation but also because of the Moon's orbital motion around the Earth. There are approximately two high and two low tides per day at any given place, but they occur at times that change from day to day; the average interval between consecutive high tides is 12 hours 25 minutes. The effect of the Sun is similar and additive to that of the Moon. Consequently, the tides of largest range or amplitude (spring tides) occur at New Moon, when the Moon and the Sun are in the same direction, and at Full Moon, when they are in opposite directions; the tides of smallest range (neap tides) occur at intermediate phases of the Moon

Answer 4

It exherts its own gravitational pull on the earth. As water is a moveable substance it pulls the water to the point of the Earth that it is nearest to (as the earths crust is too heavy to be pulled towards it) causing tides. As the moon moves around the Earth, the water is pulled by the moon wherever it goes causing low and high tides as it goes.

Answer 5

It's called the Wikipedia effect.

Answer 6

It controls it with it's gravitational pull.

Answer 7

it sends down alpha gamma rays that chat to the ocean ..i commad you to move over and over

Answer 8

gravity