Explain how low and high tide occurs?

Question

Explain how low and high tide occurs?

Answer 1

view of the tides at Halls Harbour on Nova Scotia's Bay of Fundy. This is a time lapse of the tidal rise and fall over a period of six and a half hours. During the next six hours of ebb the fishermen unload their boats on the dock. That's a high tide every 12 and 1/2 hours! There are two high tides every 25 hours.

few more Facts About Lunar Tides  

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The gravitational force of the moon is one ten-millionth that of earth, but when you combine other forces such as the earth's centrifugal force created by its spin, you get tides.

The sun's gravitational force on the earth is only 46 percent that of the moon. Making the moon the single most important factor for the creation of tides.

The sun's gravity also produces tides. But since the forces are smaller, as compared to the moon, the effects are greatly decreased.

Tides are not caused by the direct pull of the moon's gravity. The moon is pulling upwards on the water while the earth is pulling downward. Slight advantage to the moon and thus we have tides.

Whenever the Moon, Earth and Sun are aligned, the gravitational pull of the sun adds to that of the moon causing maximum tides.

Spring tides happen when the sun and moon are on the same side of the earth (New Moon) or when the sun and moon are on opposite sides of the earth (Full Moon).

When the Moon is at first quarter or last quarter phase (meaning that it is located at right angles to the Earth-Sun line), the Sun and Moon interfere with each other in producing tidal bulges and tides are generally weaker; these are called neap tides.

Spring tides and neap tide levels are about 20% higher or lower than average.

Offshore, in the deep ocean, the difference in tides is usually less than 1.6 feet

The surf grows when it approaches a beach, and the tide increases. In bays and estuaries, this effect is amplified. (In the Bay of Fundy, tides have a range of 44.6 ft.)

The highest tides in the world are at the Bay of Fundy in Nova Scotia, Canada.

Because the earth rotates on its axis the moon completes one orbit in our sky every 25 hours (Not to be confused with moon's 27 day orbit around the earth), we get two tidal peaks as well as two tidal troughs. These events are separated by about 12 hours.

Since the moon moves around the Earth, it is not always in the same place at the same time each day. So, each day, the times for high and low tides change by 50 minutes.

The type of gravitational force that causes tides is know as "Tractive" force.

The result is that near the equator, the difference between high tide and low tide is actually rather small, compared to other latitudes. To see this, draw a circle inscribed in an ellipse, with the major axis of the ellipse rotated by 23 degrees with respect to the circle's horizontal diameter. Now measure the height of the elliptical contour just above the 'equator' of the circle. You will see that it is quite small compared to other positions on earth, particularly at latitudes of 23 degrees or so. Even larger differences can occur depending on the shape of a bay or inlet or continental shelf." - Dr. Odenwald's  - ASTRONOMER

The World Ocean is a complex dynamical system. The natural velocity of a water disturbance depends on the depth and salinity of the water at each point it passes. When bodies of land circumscribe bodies of water, they produce a collection of resonating systems that favor water oscillations with certain frequencies over others. From among the 300+ harmonics that can be measured, every port and coastal location has its own unique signature depending on its latitude, longitude, water depth and salinity. The result is that the 'two high two low' tide rule can be strongly modified so that the time between successive high tides can be greater than or less that 12 hours in many cases. The result is that for some locations, there can be days when only one high tide occurs. Looking at the Atlantic and Pacific Coast tide tables for 1995, the data for the various 'Standard Ports' showed that virtually all days had two high tides and two low tides in San Diego, San Francisco, New York and Charleston. There were, however a few days every few months when only a single high tide occurred." - Dr. Odenwald's - ASTRONOMER

"The Moon follows an elliptical path around the Earth which has a perigee distance of 356,400 kilometers, which is about 92.7 percent of its mean distance. Because tidal forces vary as the third power of distance, this little 8 percent change translates into 25 percent increase in the tide- producing ability of the Moon upon the Earth. If the lunar perigee occurs when the Moon is between the Sun and the Earth, it produces unusually high Spring high tides. When it occurs on the opposite side from the Earth that where the Sun is located ( during full moon) it produces unusually low, Neap Tides. The High, High Tide is called the Proxigean Spring Tide and it occurs not more than once every 1.5 years. Some occurrences are more favorable that others.

"It is intuitively easy to understand why the gravitational pull of the Moon should produce a water tide on the Earth in the part of the ocean closest to the moon along the line connecting the center of the Moon with the center of the Earth. But in fact not one but TWO water tides are produced under which the Earth rotates every day to produce about two high tides and two low tides every day

The Sun also causes tides on the Earth because even though it is so far away, it is very massive. These solar tides are about half as strong as the ones produced by the Moon, and they cause the so-called Spring tides and the Neap Tides. When the bulge of ocean water raised by the Moon is added the a similar tidal bulge raised by the Sun, you get a higher, high tide called the Spring Tide. When the solar low tide is added to the lunar low tide, you get the Neap Tide.

There may be even weaker tides caused by the gravitational influences of the planets Mars and Venus, but they are probably lost in the daily noise of individual tides."-

Tides are created because the Earth and the moon are attracted to each other, just like magnets are attracted to each other. The moon tries to pull at anything on the Earth to bring it closer. But, the Earth is able to hold onto everything except the water. Since the water is always moving, the Earth cannot hold onto it, and the moon is able to pull at it. Each day, there are two high tides and two low tides. The ocean is constantly moving from high tide to low tide, and then back to high tide. There is about 12 hours and 25 minutes between the two high tides

...still more.. but... not end...

Answer 2

The gravity of the moon pulls the water along with it. So if the moon is over land there will be a high tide. If it is over the ocean there will be a low tide.

Answer 3

the moons gravity affects tide it rotates around the world pulling water with it

winds blow over the seas in certain directions and times

Answer 4

i think this link will help u out.......

http://www.fhsu.edu/te/facstaff/gtaggart...

Answer 5

Why did you ask twice?

Anyway...

The effect of gravity is distance dependent F = GMm/r^2

So the side of the earth closest to the moon is pulled harder than the middle of the earth, which is pulled harder than the far side.

The oceans are fluid and so can flow to react the the forces.

This results in two bulges in the oceans - one pointing towards the moon, and one poitning in the opposite direction. The opppsite bulge is because the solid earth is being pulled harder than the water on that side!.

Then the earth rotates. The moon orbits the earth slowly, so you can more or less consider it to be stationary for a day.

Now consider the earths rotation. If you start on the side towards the moon, there is a high tide because of the water bulge. 6 hours later you have rotated round to 90degs from the direction to the moon and are away from the bulge and in low tide. 6 hours later you are on the farside of the earth from the moon and back in a bluge and thus a high tide and so on.

Search for BadAstronomy and tides for a good link