"Nav" wrote in message
...


Jeff Morris wrote:
....

Yes that's right but the bulges would be small. I think the problem
probably stems back to Newton who suggested that gravity could explain
the tides. There is no doubt that gravity can produce tidal forces but
we are talking about the real tides on Earth. These are produced by the
imbalance of gravity and centrifugal (inertial) forces. This model
predicts larger tides than are seen but that leads to greater insight
too. The tides are smaller than expected because of friction and land
masses. While your differential gravity explanation can produce a tide
"similar" to that observed it does not explain it -unless you assume the
land masses don't exist. Do you see my point of view now?



Are you really claiming that the "open ocean" tides are over 100 feet, but
the
land masses reduce them to under 10 feet?

No, I'm not saying the tides are 100 foot. Where did you get that
idea/number from?

The differential gravity equations predict tides in the range of 2-3 feet. Your
equations predict a force 65 times greater. While I'm not ready to work out how
that affects the equipotential prolate ellipsoid, its a reasonable guess that
the predicted tides would be much higher, perhaps 100 feet. What's our guess?

What I'm saying is that the land masses and shallow
water impede water flow and reduce global tidal heights. This is a big
effect in oceanography.

Yes, it is a big effect. It's generally held that shallow water and land masses
build the tides higher. Why you think the open water tides are huge when they
hit shallow water they get reduced is beyond me.




The tides have been studied in
considerable detail for the last few hundred years, and the scientists have
been
quite happy with the "differential" model. Do you really think that a
different
model that gives a radically different answer could actually be correct?

Scientists who model the oceans use a model in which the tides are
produced by the difference in centrifugal and gravity forces.

It is possible to look at it that way. My point (shared by the vast majority of
physicists) is that the centrifugal force is constant and cancelled by the net
gravitational pull. There are numerous minor terms, including the centrifugal
force from the daily rotation. But the primary effect, the one that cause the
"two tides a day," is differential gravity.

Their
equations explicity include the orbital period of the moon -it's neither
negligible comaprted to "differential gravity" nor does it just cancel
leaving only gravity terms in the equations (that is the result of
ignoring the higher order terms whose magnitudes are comparable to the
tidal effect itself). Look at the NOAA pages to see what causes the
tides Jeff! :-)

You have to be more selective in your surfing. The NOAA pages you're refering
to (I believe) are frequently pointed to as good examples of "bad science."