Those are the two main ingredients of being a scientist! Skepticism and a willingness to confront models with observations.
Tides are more complicated than the book explanation, as you have
just discovered with actual tide data. The reason for the difference is
that water has to move around from one place on the earth to another in
order for the water levels to rise and fall. If there weren't any land
on the earth and the oceans were of uniform depth, then the tides would
travel as a gigantic wave with a wavelength of half of the
circumference of the earth. There are continents and the ocean floor
changes depth, so the waves are impeded in their paths. The tides will
come at different times even for places not so far apart, if there are
big impediments to water flow. For example, water flowing into a bay
through a narrow inlet will make the tides lag. Tides propagate some
distance up rivers that open out into the ocean, and these may lag as
well (or exhibit even more interesting behavior, such as single waves
-- "tidal bores").
It may even be that a resonating water sloshing effect goes on in
a closed or mostly closed body of water (like the Mediterranean) that
causes the tides to be more complicated than a simple rise and fall
with the sun and moon -- local harmonics can be important too.
p.s., concerning what the books and teacher say. It really is true
that the moon pulls the water toward it. It does pull hardest on the
part closest, and weakest on the farthest part, and in-between on the
Earth. The complication, as Tom described, is that when you pull on
something it doesn't immediately adjust its position. If you take a
mass on a spring with some friction on it, then push and pull at a
regular rate, you can get:
1, the mass stretched out toward you when you pull
2. the mass moving toward you when you pull, and closest to you in-between pull and push.
3. the mass accelerating toward you when you pull, and closest to you when you push,
or anything in between, depending on the mass, the springiness, and
the friction. As Tom points out, for the tides in different places
there are a range of those conditions.
(republished on 07/13/06)