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    Re: Navigating Around Hills and Dips in the Ocean
    From: Fred Hebard
    Date: 2003 Aug 19, 15:19 -0400

    On Tuesday, Aug 19, 2003, at 14:53 US/Eastern, George Huxtable wrote:
    > However, we have to keep a sense of proportion here. On weather maps,
    > isobars can wander all over the place. Conversely, if the Earth was a
    > uniform sphere, the equipotential shells would be exactly spherical,
    > and
    > so, as it happens, would be our equal-g contours. Even the ellipsoidal
    > effects caused by the Earth's spin give rise to changes which are less
    > than
    > 1%. And the hills and dips, that we've been discussing in such detail,
    > are
    > molehills on that ellipsoid. So the gravity variations that we have
    > been
    > discussing are small, and the surfaces of equal potential and the
    > surfaces
    > of equal gravity, though not spherical shells, are pretty damn near to
    > that.
    So, once again, just how big are these molehills?  200 meters is about
    .001% of the earth's radius, if my calculation is correct, which is
    pretty insignificant.  But that would be a fair-sized skyscraper or

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