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The Moon can move within 218,000 miles (351,000 km) of the earth's
surface. This proximity to the earth produces reactions in the
earth's atmosphere, seas and the earth's surface. The most observable
reaction occurs with the ocean's tides. The tides are due to the
gravitational attraction of the Sun and Moon. The Earth's great
oceans are pulled regularly to and fro by the Moon, as well as the
fluids in our very own bodies. High and low tides occur in a
roughly 6 hour cycle, with two high and two low tides
a day. This 6 hour cycle is caused by the gravitational tugging of the
moon upon the earth. |
The Moon's gravity pulls the Earth's water surface into two bulges,
one on the side facing the Moon and the other on the opposite side. The
water on the side of the Earth closest to the Moon is pulled, by the Moon's
gravitational force, much stronger than the mass of the Earth. The water on
the side furthest from the Moon has a weaker pull than the gravitational
force of the Earth. As the earth rotates under this ocean bulge,
it causes a high tide. The height of the tide is determined by
the shape of the coastline and of the nearby continental shelf.
A change in the gravitational force across the body of the earth
produces two bulges, causing us to experience two high tides, and two
low tides each day. The tides make the earth slow down its rotation
around its axis, and when the angular force of the earth decreases the
moon compensates by increasing its angular momentum.
The effect of the Sun's pull also causes similar effects. Twice
a month, at new and full Moon, the Sun and Moon pull in line so
that the tidal bulge occurs on both sides of the earth. One bulge
occurs toward the Moon and the other away from the Moon. The tides
that we see at this time are the result of both pulls. Their tidal
effects combine to produce tides higher than normal called Spring
Tides, because they "spring up".
When the solar low tide and lunar low tides occur simultaneously , it produces what is known as a Neap Tide. This occurs at first or last
quarter, when the Moon is pulling at right angles to the sun. The tidal
effects work against each other and produce tides of a smaller range,
called "neap", or scanty tides. As the earth rotates under these two
bulges, points on its surface experience a cycle of low tides twice a
day. The actual height of the tide is partly determined by the shape
of the coastline and depth of water.
Tidal Information
WWW Tide/Current Predictor
Sourthern California Surfing Conditions
Oregon Inlet Tide Chart
East Coast (USA) Surfing Conditions
Hawaii Weather and Surf
Religious rites and festivals have surrounded the Moon's rhythmic
cycle with many predictions based on this cycle. Fishing predictions
for both fresh and saltwater anglers are based partly on the Moon's
rising and setting times and phases of the moon. If the fishing
is in a saltwater area then predictions are amplified by tidal
flows. The
Old Farmers Almanac has provided planting guides, and other
information based on phases of the Moon since 1792.
Shareware Program, Graphically showing Tides & Fishing Curves
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