2. CONTENTS• Introduction • Definition • Theories • The Equilibrium Theory of Tides • The Dynamic Theory of Tides• Tides are generated by…• Types of tides • Neep tides • Spring tides • Proxigean Spring Tide• Interesting facts• Tidal Energy• References
3. INTRODUCTION• The Greek navigator and explorer Pytheas first wrote the connection between the position of the moon and height of tides (399B.C.), But a full understanding of tides had to await Newton’s analysis of gravitation.
4. DEFINITION “periodic rise and fall of all ocean waters, including those of open sea, gulfs, and bays, resulting from the gravitational attraction of the moon and the sun upon the water and upon the earth itself.” (Microsoft ® Encarta ® Encyclopedia 2005 © 1993-2004 Microsoft Corporation. All rights reserved.)
5. EQUILIBRIUM THEORY• The equilibrium theory of tides explains many characteristics of ocean tides by examining the balance and effects of the forces that allow a planet to stay in a stable orbit around the sun, or the moon to orbit earth.• The equilibrium theory assumes that the seafloor does not influence the tides and that the ocean conforms instantly to the forces that affect the position of its surface.• The ocean surface is presumed always to be in equilibrium (balance) with the forces acting on it.
6. DYNAMIC THEORY OF TIDES• The dynamic theory of tides, first proposed in 1775 by Laplace, added a fundamental understanding of the problems of fluid motion to Newtons breakthrough in celestial mechanics.• The dynamic theory explains the differences between predictions based on Newtons model and the observed behaviors of tides.
7. TIDES ARE GENERATED BY…Gravitational pull of the moon and sun Centripetal force of the rotating Earth
8. TYPES OF TIDESNeep tides•During the moons quarter phases the sun and moon work at right angles, causing thebulges to cancel each other. The result is a smaller difference between high and low tidesand is known as a neap tide.Spring tides• When the moon is full or new, the gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low. This is known as a spring high tide
9. The Proxigean Spring Tide•This is a rare, unusually high tide. This very high tide occurs when the moon is both unusuallyclose to the Earth (at its closest perigee, called the proxigee) and in the New Moon phase (whenthe Moon is between the Sun and the Earth). The proxigean spring tide occurs at most onceevery 1.5 years.
10. INTERESTING FACTS• Spring tides and neap tide levels are about 20% higher or lower than average.• The highest tides in the world are at the Bay of Fundy in Nova Scotia, Canada.• The type of gravitational force that causes tides is know as "Tractive" force.• The suns gravity also produces tides. But since the forces are smaller, as compared to the moon, the effects are greatly decreased.• Moon has 2x greater gravitational pull than the sun• Sun is 10 million x more massive than the moon and is 390 times farther away
11. TIDAL ENERGY• The energy of tides has been harnessed to produce electricity. In the summer of 1966, a tidal power plant with a capacity of 240,000 kw went into operation on the Rance River, an estuary of the English Channel in northwestern France.(Microsoft ® Encarta ® Encyclopedia 2005 © 1993-2004 Microsoft Corporation. All rights reserved)
12. GLOBAL DISTRIBUTION
13. REFERENCES• Microsoft ® Encarta ® Encyclopedia 2005 © 1993-2004 Microsoft Corporation. All rights reservedRetrieved from• http://www.physicalgeography.net/fundamentals/8r.html• http://geography.about.com/od/physicalgeography/a/tides.htm• http://home.hiwaay.net/~krcool/Astro/moon/moontides/• http://www.opportunityenergy.org/?p=316 (14-01-2012)