Chapter 4, page 10.
4.10 4.1 Two ways of representing the ocean tides.
4.2 Two approaches to explain the ocean tides.
4.3 Values of attraction.
4.4 The direction of the tide waves.
4.5 The continents and the flowing of the tide waves.
4.6 Number of the tide waves.
4.7 Tide waves and sublunar points.
4.8 The physical equation for the ocean tides.
4.9 When Earth, Moon and Sun are aligned.
4.10 Tide cadences.
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On this point, with regard to the same facts, the two approaches bring about two very different explanations. (1) On the criterion to tell the cadence of a tide basin. And (2) on the mechanism which determines the cadence.
THE FACTS.
#06 - The tide cadences.
.1 The cadence, or frequency per day, of a tide wave is not the same in all the basins.
.2 During the time the Earth revolves on its axis one time, in almost all the basins, there are a bit less than two tide waves (semi-diurnal basins), while in just a few basins, there is only one (diurnal basins).
CRITERION TO TELL THE CADENCE.
Number of tide waves per day.
.3 In the current approach, the tide cadence is referred to the cadence of the tide waves reaching the coast.
.4 If during one day, the tide wave reaches the coast twice, one say that the tide cadence of that basin is semi-diurnal. That is the most common occurence.
.5 In a few basin, only one tide wave per day reaches the coast. Then, one say that the cadence of that basin is diurnal.
.6 In the same basin, the tide cadence may vary. As in the lagoon of Venice, where sometimes there is only one tide wave per day, instead of two.
Distinction between generation and tide wave.
.7 (inductive approach) When you have to determine the cadence of a tide basin, the number per day of a tide wave transit, on a coast, is not a reliable datum.
.8 In the inductive way of posing the terms of the question, first of all, the distinction is done between two events: (#18) the frequency of the tide generation (decrease of the water density), and (#23) the times the tide wave components reach the coast.
.9 It is the cadence of the tide generation which gives us the cadence of a basin.
.10 At a given location, the tide generation is clear-cut; it has either a diurnal, or a semi-diurnal cadence. A possible exception is where the cadence change with the season (a topic to settle).
.11 The times of a tide wave are just consequences, to be analysed on a case by case basis.
See a case, where a semi-diurnal basin (two tide waves per day) apparently becomes a diurnal basin (one tide wave per day).
THE CAUSE.
#12 -The Moon declination would be the cause.
.12 (current approach) The cause of the cadences is attributed to the declination of the generating celestial bodies.
In high latitude seas.
.13 Indeed, in seas situated at higher latitudes, where the Moon declination is extreme, we may find diurnal tides.
Inductive approach position.
.14 That means nothing. We may find diurnal tides also in the tropical regions (examples: China sea, Mexico gulf).
.15 With regard to a given tide basin, the declinations of the generating bodies (Moon, Sun) can only modify the times of the local tide generation. It does not change its daily cadence of generation (diurnal; semi-diurnal).
THE CONSTRAINT.
Each basin has its cadence.
.16 The force which brings about the tides appear it could generate a tide, either with a cadence of one per day, or with a cadence of two. It depends on the basin.
Local features.
.17 For the time being, I assume that it is because of local features. The topic will be proposed on the page 6.6.
Conclusion of the chapter.
.18 The subject of the tide cadence is of crucial importance. If you have both one wave per day basins, and two wave per day ones, the classic representation of the ocean tides is no more viable: the two bulges, the two sub-lunar points, the westward direction of the waves, the Earth as one space unit. Everything is to be reconsidered.
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