Water And Oceanography

Characteristics of Tides



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“Time and Tide Wait For No Man”. This ancient saying shows that a person has no control over nature. The nature of tides has gone on for millions of years.

Donald Simenek, physicist at Lock Haven University, questions the accuracy of textbooks and most web sites. There is no definition of tide. He believes that, without a definition, many misinterpretations of tides are made. Textbooks, he maintains, are wrong in their explanation of tides. His article, “Misconceptions of Tides” gives two definitions: 1. The variation of sea level at a coastal location, which depends strongly on shoreline topography and ocean currents near shore. 2. The deformation of land and water of the Earth due to gravitational forces of the moon and sun acting every part of the Earth.

He believes the second definition of tides as written in textbooks, is erroneous. The meaning clearly is that tides are the result of gravitation, 'without rotation'.

The Sun and Moon's Influence On Tides

The gravitational force of the earth as it spins, in conjunction with gravitational pull of the sun and moon, affects the oceans.

The moon has more influence on tides than the sun because it is closer to earth.

Web Sites Explanations:

The gravitational pull of the sun and moon creates two types of tides: the high tide and low tide. During each 24 hours and 50 minutes, there are two high and two low tides. That is how long it takes the moon to revolve around the Earth. As the moon rotates around Earth, a large wave starts but does not break. It becomes a bulge that follows the moon. On the other side of the world, there is a second bulge. These are high tides. Between high tides, there are low tides.

Siminek's Explanation – Equilibrium Theory of Tides:

The real Earth (not a diagram) has a solid crust with thin layers of ocean bounded by continents. The gravity in the core of Earth causes equilibrium to the gravitational pull of the sun and moon. The tidal bulges are not due to Earth's rotation, but the variation of the moon's gravitational pull. The coastal tides vary locally because of the differences in shoreline slopes and ocean currents. The tides are due to the gravitational field of the sun. If tides formed the way many textbooks describe, water would lag behind and cover continents.

Spring Tides

A new or full moon and the sun combine their gravitational forces. This makes the high tides extraordinarily high, and low tides are extraordinarily low.

Neap Tides

When the moon is at its quarter phase, the earth, the moon, and the sun are at right angles. This causes the bulges to cancel each other. This makes low tides and high tides less obvious.

Tides Around the World

In different parts of the world, there are different tides. For example, tides near the equator show little change. This is because there is a tremendous volume of water that spreads over a large area. Nova Scotia has the highest tides at the Bay of Fundy. The narrow bay causes the ocean rushing in to rise to 65 feet.

Whether or not we accept Dr. Simeneks's equilibrium theory is not important because, in the final analysis, time and tide waits for no man.

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