Hello, I'm the OUTDOOR PROFESSOR from DiscoveringTheOutdoors.com/
Here's your outdoor tip on the moon and tides.
Water levels rise and fall creating a motion in the oceans called tides. The simple explanation of the cause for this movement is called gravity—the forces of the Sun and Moon.
As the Earth spins on its axis, ocean levels around the planet are kept at equal levels by the Earth’s gravity pulling inward and centrifugal force pushing outward. The Moon’s gravitational forces are strong enough to disrupt this balance of ocean levels by accelerating the water toward the Moon causing it to bulge. As the moon orbits around the planet, this bulge moves. The areas where the bulging occurs experience a high tide and the other areas experience a low tide.
Now, that’s a simple explanation, but there is more to it than that.
For a different reason, the water on the opposite side of the Earth facing away from the Moon also bulges outward creating a high tide. The Moon and Earth revolve around a common gravitational center, or center of mass. Think of yourself swinging a heavy object attached to a rope around your body as you slowly rotate. You have to lean back to compensate for the outward pull putting the center of the mass between you and the object. Gravity is like this rope that pulls keeping the two bodies together. Centrifugal force keeps them apart. Because the centrifugal force is greater than the Moon’s gravitational pull, oceans on the opposite side of the Earth bulge outward.
These same forces are at work as the Earth revolves around the Sun. The effect is smaller than that of the Moon because the Sun is so far away—380 times farther than the Moon. Because the tides are influenced by the Moon and sun, when the Sun lines up with the Moon and Earth, as during a New Moon or Full Moon, the tidal effect is increased. These are known as “spring tides” because they are higher than normal. Providing the opposite, if the Sun and Moon are 90 degrees apart as during the First Quarter Moon or Third Quarter—called half-moons—high tides are not as high as they would be normally. Despite its distance, the Sun’s mass allows it to exert enough gravitational force on the oceans that it can negate some of the Moon’s pull. This lower high tide is called “neap tide.”
Tides heights can also vary during the month because the Moon is not always the same distance from Earth. As the moon comes closer to earth, its gravitational forces can increase by almost 50 percent leading to high tides. When the Moon is farther away, the tides are not as high.
There is normally a high and low tide each day (called diurnal). Sometimes, there are also two high and low tides each day (called semi-diurnal), but these periods do not happen at the same time each day. This is because the Moon takes more than 23 hours to come into alignment again—usually about 50 minutes later than the one before it.
Many factors are involved in predicting the tides. In addition to the motion of the Moon and Sun, the times that tides occur can also be affected by the Moon’s height above the equator, local geography of a coastline, topography of the ocean floor, the depth of water, and other considerations. Because of this, we cannot exactly predict tides only on the positions of the Sun and Moon. Greatest accuracy in predicting ties comes from integrating data from actual observation over a period of years.
Based on this discussion, you can hopefully understand why you can make general predictions on the level of the tide based on the position of the moon on a given day. However, there are many factors involved in predicting tide level, and understanding the various factors controlling our oceans, gives you allows you to better understand our tides.
This is the OUTDOOR PROFESSOR from DiscoveringTheOutdoors.com/
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References-Additional Reading
Moon Tides
http://home.hiwaay.net/~krcool/Astro/moon/moontides/
The Ocean’s Tides Explained
http://www.moonconnection.com/tides.phtml
Tides and Water Levels
http://oceanservice.noaa.gov/education/kits/tides/tides02_cause.html
Nature Quotient.
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Outdoor Professor’s Tips: Exploring the Wonders of Nature
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