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Written by gaby
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Saturday, 09 May 2009 |
Understanding Tidal Influences
Throughout all history, mankind has searched for explanations of this natural phenomena in order to be able to utilise and predict them accurately. In the case of the tides, this necessity is driven by common activities such as agriculture or fishing, since any animate entity, due to its water content, is influenced by this astral phenomenon. In this section, we try to offer a guide to the cycles of the tides.
Introduction to the tides:
As we are all aware, the Earth turns around its axis in a complete spin every 24 hours, but the Moon also turns in the same direction in its orbit around the Earth and makes a complete revolution in 24 hours 50 minutes, resulting in a high water every 12 hours and 25 minutes, due to gravitational pull or attraction. The cycle of lunar phases is governed by the lunar month of 27 days 6 hours in which the four phases take place: New Moon, first quarter, Full Moon and last quarter.
'Spring' tides:
When the positions of the three bodies, the Sun, Moon and Earth are in-line, thus combining their forces of attraction or gravitational pull, the high waters are of consequently greater value and the low tides are lower than average.
'Neap' tides:
When the Moon and the Sun form an angle of 90º with the Earth's centre, the Moon is in its first quarter, or decline, in the case of flood resembling a C exactly and when resembling a D it is in its last quarter. In this circumstance, the attraction forces are reduced and is the reason why the greater attraction of the Moon is diminished by effect of the Sun and resulting in tides of smaller magnitude than the average. Consequently, the currents - flood (from the sea) and ebb (out to sea) flows -will result in a smaller volume of water being transferred in the same time.
Equinoctial tides:
The highest tides of the year take place when the Sun is in the equinoxes, that is, on the Equator (21st March and 23rd September) and additionally are high ('Springs') at Full and New Moon. These tides are referred to as High/Low Astronomical Tides.
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Last Updated ( Saturday, 09 May 2009 )
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