I was looking at an article the astronomy teacher was handing out to her class (9th grade earth science) which claimed that the second high tide in a day was caused by the fact that the earth does not rotate around its geometric center but that the earth and moon each revolve around their common center of mass. The article said, basically, that it is a centrifugal effect. I am suspicious of this explanation (as I am with most explanations in earth science texts). My suspicion does not lie in how the earth-moon system rotates, but that this could cause a "tidal bulge" on the side of the earth opposite the moon.
I have searched the archives of this list and found volumes on tides but none mentioned this effect (that I saw). Any comments?