![]() However, the height of the shoreline tide is known to be influenced by local topographical and bathymetrical features and that the tidal elevation in midocean is not the same as at the land/sea interface. Use of harmonic analysis, which has been substantially accelerated by the application of digital processing, allows appropriate tidal predictions to be made, which are generally fit for purpose at any one location. The results of the tide-producing, astronomical forces can easily be measured at the shoreline, and tabulated data have been produced for hundreds of years at certain sites, particularly those of interest to naval powers. These tidal waves, being of astronomical origin, have no connection with a tsunami, an event that is often erroneously referred to as a tidal wave. This compares with the equatorial lunar speed of about 450 m s −1, thus demonstrating that the Earth's oceans simply cannot keep up with the lunar track. ![]() A typical wave in an average ocean of 4000 m depth would travel at about 200 m s −1. The tidal waves created by the Earth/Moon/Sun system propagate as long waves, and their speed is dependent on water depth. The further reading section offers a range of suitable publications for an in-depth mathematical analysis of tidal forces. ![]() These cycles are themselves modified by the evective influence of the Sun and occasionally other planets within our solar system, depending on their relative positions. The Moon is responsible for the largest proportion of the tidal forces applied to the Earth, but it is not independent on its influence, as not only does the Sun affect the tidal forces but also the Moon's own tidal influence is modified by the Sun's gravitational field. It is these offsets in combination with the superimposed rotational patterns of the Earth/Moon/Sun system that create the complex forces that drive the Earth's tides. The plane of the Earth's path around the Sun is known as the ecliptic, from which the Earth's axis is inclined 66 degrees 30′ and the Moon's orbit is inclined 5 degrees 9′, which, in combination, allows the Moon's declination to reach 28 degrees 30′ every 18.6 years.
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