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Re: Tidal bulges



I think I may finally have gotten the real point in Jim Green's messages
about tidal bulges, and I think it is a very important one. See if I have this
right, Jim. The issue isn't how do we model tides, but to distinguish cause
and effect. We have forces and response to those forces. We have stress and
stain. Just because the moon creates a fairly simple force gradient on the
earth doesn't mean the earth responds with an equally simple distortion.
The lie is not in what we say about the form of the tides. The lie is to
suggest that stress and strain are so tightly and simply connected. I just
about had a stroke at a recent seminar where we were shown photos taken from
recent planetary missions, because everytime a possible extensional feature
appeared we were told it was tensional. The folks who make these interpretatio
ns seem oblivious to the fact that extension can occur even when all stresses
are compressional, all that is needed is for some stresses to be more
compressional than others.

I guess that in my view, how accurately one wants to model the tides is their
own business and a judgement call, but to suggest that tides or any other
deformation has to look just like the forces that cause it really is bad,
evil, etc. just as Jim says.