A tide –generating force has two dynamic properties. One of them is a property as a vector with magnitude and direction, the other is a periodicity of force acting with a cycle of about 12 hours. If the tide-generating force is a periodic external force, the tides must be a kind of forced oscillation phenomena. Three proposals regarding the origin of tides will be suggested in this article.
(1) The ocean tides can be divided into three types by the depth. They are ‘out of phase’ type (shallower than 22,000m), ‘in phase’ type (deeper than 22,000m) and ‘resonance’ type (equal to 22,000m). The actual ocean tides are classified into the ‘out of phase’ type. On the other hand, the Earth tides occurring on the solid Earth are classified into the ‘in phase’ type.
(2) Dynamic movement pictures of each type of tides have been determined. Unlike the widely accepted explanation, the global form of the ocean surface repeats an oval and a circle in turn according to the Moon’s position. As a result, the tidal movements of the ocean will occur in fixed four areas with an angular distance of 90 degrees apart along the equator, and four spots escaping any tidal movements will appear between them.
(3) A new concept of ‘tide burst’ is deduced and its scientific meanings are discussed. Judging from the delay of Earth’s rotation period, the tide burst will happen in the ocean about 4.5 billion years from the present.
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