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    Re: Global oceanic tides,
    From: E.R.Kooi
    Date: 2003 Aug 24, 16:44 +0200

    Dear navigator's, now that George tells us that explaining "two tides
    per day" requires a lot of waving arms and legs, it makes me curious to
    know why.
    My simple understanding is that the centres of gravities of both earth
    and moon, disregarding the sun, should remain at unchanged distances.
    Therefore, when the moon pulls the water mass to one side of the earth,
    it has to be compensated such that the centre of gravity remains
    unchanged. That can be obtained by having an equal displacement of water
    on the opposite side of the earth. I do recall that that opposite mass
    is not precisely of the same shape, due to land masses disturbing the
    I am sure there is a lot more to it, but the prime reason suffices for
    most people, I guess.
    With fr. Gr. Eppo R. Kooi.
    > -----Original Message-----
    > From: Navigation Mailing List
    > On Behalf Of George Huxtable
    > Sent: zondag 24 augustus 2003 15:38
    > ............
    > Geoff, tantalisingly, adds-
    > >.. only leaving the question of why there are two tides per day
    > than one to be explained!
    > Geoff's contribution sounds rather authoritative, and I wonder if he
    > be prepared to respond to his own suggestion, in explaining the two
    > Otherwise, perhaps I could recall (or reinvent) some of the arguments
    > learned half-a-century ago, if anyone is really interested enough to
    > to understand why there are two tides per day. If any listmembers
    > find that a puzzle, and seek an explanation, I'm quite prepared to
    have a
    > go if requested.
    > However, it usually needs several diagrams and much waving of hands in
    > air, so it would be something of a challenge to do it in words only.
    > George.

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