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.
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 Newton's breakthrough in celestial mechanics.
• The dynamic theory explains the differences between predictions
based on Newton's 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 TIDES
Neep tides
•During the moon's quarter phases the sun and moon work at right angles, causing the
bulges to cancel each other. The result is a smaller difference between high and low tides
and 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.
10.
11. The Proxigean Spring Tide
•This is a rare, unusually high tide. This very high tide occurs when the moon is both unusually
close to the Earth (at its closest perigee, called the proxigee) and in the New Moon phase (when
the Moon is between the Sun and the Earth). The proxigean spring tide occurs at most once
every 1.5 years.
12. 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 sun's 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
