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Originally Posted by JohnD
I accept your point about the effect of the Earth's rotation on its shape, and accurate satellite observations have confirmed that the Earth is 'shorter that it is wide'. But I cannot work out how closely that observation coincides with the predicted flattening from rotation.
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The equatorial bulge is 20,000 meters, whereas the tidal bulge is less than a meter.
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Anyway, that flattening is at right angles to the tidal effect, which will be superimposed on the equatorial bulge.
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Yes, that is why Sawicki states that the rotation doesn't affect the conclusion about tides.
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I have to confess that I have only today read Sawicki's explanation of tides ("gravity vectors"?). I noted two things, first he makes clear that he neglects the effects of the Earth's rotation "as they do not affect our conclusions" and that his model is of an Earth free-falling towards the Sun, not one in orbit. This is a model some way short of reality
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Earth in orbit is in "free-fall," so that comment is wrong.
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Maybe that is why I favour "different orbits", a more intuitive way of thinking about tides that does not need mathematics, though as Eroica shows, the maths work out, confirming intuition.
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Changing reference frames is valid--but ignoring an effect is not.
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In case you are not plotting my downfall (!), will you please try to reconcile these two views? Can you calculate from this model the size of the force 'lifting' the ocean into the tidal bulges? If this value corresponds with Sawicki's calculated 0.515 x 10^-7g, then either point of view is just that, a point of view, a world-picture, NOT a "New Theory Of Tides".
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Any point of view is valid--but you do have to be careful that you are not ignoring effects, or attributing to tides an effect that is caused by rotation.