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Unformatted text preview: What Are Tides?
0. Tides are periodic, short-term changes in the height of the ocean surface at a particular place caused by a combination of gravitational force of the moon and the sun and the motion of earth. Newton's Gravitational Model Of Tides
1. The Greek navigator and explorer Pytheas first wrote about the connection between the position of the moon and the height of a tide around 300 B.C., but a full understanding of tides had to await Newton's analysis of gravitation 2. Newton's central finding was that the pull of gravity between two bodies is proportional to the masses of the bodies, but inversely proportional to the square of the distance between them. 3. Heavy bodies attract each other more strongly than light bodies do. 4. Gravitational attraction quickly weakens as the distance grows larger The Moon and Tides
0. Contrary to what you might think, the moon does not revolve around the center of the Earth. 1. The Earth-Moon system revolves once a month around the system's center of mass. 2. Since Earth is 81 times that of the moon, this common center of mass is located not in space but 1650 kilometers inside the Earth. 0. When the moon is new or full, tides rise higher than normal. 1. When the moon is at its quarter phases, tides are lower than normal. 2. This is caused by gravity. 3. The moon rises about 50 minutes later each day, and so do the tides The Moon and Tides The Moon and Tides
0. The moon's gravity attracts the ocean surface toward the moon. The Moon and Tides
1. Earth's motion around the center of mass of the Earth-moon system throws up a bulge on the opposite side of Earth. The Moon and Tides
2. Two tidal bulges result. High Tide and Low Tide
3. Every 24 hours and 50 minutes, any given point on Earth rotates through these two bulges. Thus, every day, most coastal locations experience two high tides known as flood tides, and two low tides known as ebb tides. Spring Tides
0. The sun has the same type of effect on the oceans as the moon, but on a smaller scale because it is so far away. 1. However, when the sun is in line with the moon and Earth, high tides are very high, and low tides are very low. 2. tides. This occurs twice a month and is known as spring Neap Tides
3. At quarter phases, the moon and the sun are not in line with Earth, and the sun's tidemaking effect is subtracted from the moon's. When this occurs, high tides are not very high, and low tides are not very low. 4. tides. This also occurs twice a month and is known as neap The Sun and Tides Tidal Range
4. The difference in the water level between high tide and low tide is called the tidal range. 5. The largest tidal ranges occur at the edges of the largest ocean basins. Power From Tides
5. Using trapped high-tide water to generate electricity has many advantages: 0. 1. 2. Operating costs are low The source of power is free No carbon dioxide or other pollutants are released into the atmosphere. Tidal Bores
0. When river mouths are exposed to very large tidal fluctuation, a tidal bore will sometimes form. 1. This is a true tidal wave - A steep wave moving upstream generated by the arrival of the tide crest in an enclosed river mouth. Tidal Bores Pororoca in the Amazon ...
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This note was uploaded on 11/13/2008 for the course GEO 1000 taught by Professor ? during the Spring '03 term at Baylor.
- Spring '03