🚀 go-pugleaf

On 25 Apr 1995, Donald E. Simanek wrote:

>
> It isn't the 'pull' that matters, it's the 'difference' in the
> gravitational force on the near and far sides of the earth that matters.
> I.e., it's not the force, but the gradient of the force which causes tides.
> This is where many attempts at a simple description of the tides go
> wrong, by failing to deal with the force gradient--a calculus concept.
>
>         -- Donald

You also have to deal with the fact that the moon does not orbit around a
stationary earth. In fact the two bodies spin around a point called the
barycenter (sorry if I spelled that wrong my resource book is at
school).  That means that the water on the side away from the moon is
farther from this point of rotation than any of the other water on the
earth as well as being at the low end of the force gradient.

Second note.
The sun produces a second set of tides.  When the sun and moon line up
(new moon or full moon) the effects are additive and called spring
tides.  When they are at right angles to each other you can have two high
and two low tides each day with the moons tide be the larger.

On top of all that there are a large number of other factors that
control the tides at any given shore.  The simple way to deal with it is
to discuss a spherical earth covered with a uniform layer of water and a
moon that orbits in the plane of earths orbit.

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