You make it sound as if the gravitational forces explains the bulge
under the moon and the centrifugal forces explains the bulge on the
side of the earth that turns away from the moon.
That is not right.

The gravitational difference alone can explain that there are bulges
on both side of the earth. That's why it is sometimes the only factor
mentioned when trying to keep the explanation simple.
The centrifugal element can only explain that there is a bulge on the
part of the earth that turns away from the moon.
That is why it is one of the elements (and there are others), that is
sometimes left out of the explanation.

While I think that in some cases it is a good idea to include the
centrifugal element in the explanation, I don't know exactly how many
elements one should include to make it a good explanation - but I
haven't yet seen a complete explanation in a popular publication.

Peter S/Y Anicula
Sailor
The seven seas


"Nav" skrev i en meddelelse
...
Hi Phil

Keep up the good work! But there is an error on your pages where you
describe how the moon forms two tides. You cannot explain this
correctly
without noting that the earth-moon pair rotate about a common point.
It
is this rotation that causes the two tides. If you like, you can
explain
it as a centrifugal force acting to throw water out while gravity
pulls
the water to water the moon. Since the gravity term is weaker on the
outside of the earth the centrifugal term dominates and the result
is
two tides.

Many regards

Mark Cannell
Professor,
University of Auckland.