[Colin2B]

The water bulges up at one side of the bowl as you move it in a circle, but it does the exact opposite at the other side of the bowl - not a bulge, but a dip. That doesn't match up with the behaviour of tides.

You’re correct if thinking of earth without land masses. What is being described here is the basin effect eg North Atlantic which results in a rotating tidal wave around a node.

[rmolnav]

Imagine that we only have the Earth and the moon, and that the Earth rotates at a speed that keeps the same side facing the moon at all times. What's would be the result? No tides.

I need more time to properly refute several things on your post ... For now, just something about what quoted.
That imaginary case is the real case of the moon, because it is tidal locked to our planet.
And there tides, in the exact way we have them here, certainly doesn´t happen, but tidal effects do, including a stretching, kind of bulges.
Moon is rotating around the barycenter, and centripetal (mainly earth pull) and centrifugal forces do happen at different parts of it. And also own moon gravitational forces.
At closer moon half, earth attraction prevails. At further moon half, earth pull is insufficient to supply the centripetal force necessary for the rotation ... Own moon gravity has to supply the deficit, and all those further parts kind of lighten, due to same reasons explained on:
https://www.lockhaven.edu/~dsimanek/scenario/centrip.htm
"The figure shows the force vectors W and mg, which are the only forces acting on the man. The vector F is their sum. W is directed along the radius of the Earth. Being the radial component of the net force (it is the net force in this case), its size is a = v2/R (the centripetal force). Now compare these two cases. On the non-rotating Earth the man's weight was of size mg. Remember, the weight of an object is the force required to support it, i.e., the force exerted upward by the weighing scale. With the Earth rotating, that force is smaller than before. The contact force between the man's feet and the scale is reduced. But all other such stress forces are reduced as well, within the man, within the scale's springs, within the body of the Earth itself. This causes a slight decompression of these materials, a relaxation of the spring in the scales. In fact, the entire body of the earth expands slightly and the man and scale move outward from the axis of rotation slightly, until forces come into balance with the requirements of rotational stability at the new radius. This is the reason for the equatorial bulge of the Earth due to its own axial rotation"

[rmolnav]

The water bulges up at one side of the bowl as you move it in a circle, but it does the exact opposite at the other side of the bowl - not a bulge, but a dip. That doesn't match up with the behaviour of tides.

I started with your 2nd paragraph, but that does´t mean I agree with 1st one !
In the first place, an analogy is just that, an analogy. Scenarios can´t be identical.
In my analogy, we were supposed to move the bowl with our hands ... But if ("forgetting" the mass of the bowl), we imagined the bowl water molecules pulled horizontally by some "magic" magnet (attracting water), following a circular path similarly to moon-earth case, and forces were properly balanced, we would also see water rising at closer bowl side (magnet pull would prevail at that side), as well as the one at further side. Now it would be smaller than when we move the bowl with our hands (for identical radius and angular speed), because water pressure there would rise due to only the excess of centrifugal force, in comparison to the smaller magnet pull there ...

[David Cooper]

The water bulges up at one side of the bowl as you move it in a circle, but it does the exact opposite at the other side of the bowl - not a bulge, but a dip. That doesn't match up with the behaviour of tides.

You’re correct if thinking of earth without land masses. What is being described here is the basin effect eg North Atlantic which results in a rotating tidal wave around a node.

The issue under discussion in this particular case is the imagined centrifugal effect of the Earth moving in a circle once a month as the moon goes around it, which, if there was such an effect acting, would lead to one high tide per day on a planet with no continents and even sea depth all the way round.

[David Cooper]

Moon is rotating around the barycenter, and centripetal (mainly earth pull) and centrifugal forces do happen at different parts of it. And also own moon gravitational forces.

The whole moon is being pulled by the Earth's gravity, and that removes the opportunity for centripetal force to apply. For centrifugal/centripetal force to apply, you'd need to have something like a string connecting the Earth and moon to apply the force instead of gravity, and that string would only apply the force at one point with all the rest of the material feeling as if it's being pulled outwards relative to it. That would produce one bulge if it attached to the centre, but it would produce two bulges if it was attached to the nearest point, and given that the gravity is highest at the closest point, something not unlike that is actually happening, so I might just be about to change my mind on this whole issue...

At closer moon half, earth attraction prevails. At further moon half, earth pull is insufficient to supply the centripetal force necessary for the rotation ... Own moon gravity has to supply the deficit, and all those further parts kind of lighten, due to same reasons explained on:

I can see now that you could regard this as centrifugal/centripetal force on the basis that the change in gravitational strength does produce a situation similar to the moon and Earth being connected by a string, except that there's an elastic string connecting to every atom which applies less force to the atoms that are furthest away and more force to the ones that are nearer. You then have pull forces acting within the moon and planet to hold them together, these being provided by locally generated gravity, so nothing feels stressed other than by the changing deformation as they rotate. So, on that basis, tides arguably do have something to do with centripetal force and can be said to be entirely caused by it. It all comes down to whether we decide to class this as centripetal or not. Up until now, I would certainly not have done, but now I'm not so sure. It will come down to definition, and the distinctions may be arbitrary.

Imagine a case where there's a planet and a "moon", but there is no orbiting - the planet is being pulled along on a string in a straight line by a powerful spaceship and is accelerating, while the moon is being pulled along behind it by gravity such that it keeps up and maintains separation. The moon's gravity is causing two bulges in the planet's ocean, but there is no rotation involved in the system at all, so are the bulges driven by centripetal force in a case such as this one? No. When you get "flung back" by acceleration in a car, that is also like centripetal force, but without any rotation. Ultimately, all these cases are the same phenomenon, and the primary cause is the greater phenomenon, not dependent on rotation. It is caused by different amounts of force being applied to different material in different places.

If we accelerate an object in a straight line by pulling it on a string, we create an equivalent of swinging it round and round on the end of a string. In the latter case, it's centripetal force. In the former, it isn't, and yet it's really the same thing. Centripetal/centrifugal force is a subset of the greater phenomenon.

With a moon going round a planet, or both of them going round the same point, we have the same relationship to the case where the planet is being pulled by a spaceship while the moon is pulled along behind it by gravity. The greater phenomenon is the cause of both cases, but in the former case it could be attributed to the subset of that greater phenomenon called centripetal. However, there may be a problem with the definition of centripetal if it excludes "gravitational string", and I've no idea whether using forces as "string" has ever been used in the definition of centripetal to settle the argument, either by including or excluding its role. Everything thus rests on a technical definition and it's a matter of luck as to who is officially right.

[rmolnav]

Imagine a case where there's a planet and a "moon", but there is no orbiting - the planet is being pulled along on a string in a straight line by a powerful spaceship and is accelerating, while the moon is being pulled along behind it by gravity such that it keeps up and maintains separation. The moon's gravity is causing two bulges in the planet's ocean, but there is no rotation involved in the system at all, so are the bulges driven by centripetal force in a case such as this one? No

You yourself answered your question: No.
But, I´d rather say "no" to the very question: if the powerful spaceship would be making the earth accelerate, and with the moon back at current distance, earth deformation would depend on the way the spaceship force were transmitted to earth:
1) If somehow it were transmitted pulling on earth c.g., we wouln´t have two bulges: forward hemisphere would get flatter.
2) If the spaceship pushed on earth back side, the whole earth would get flatter (if pushing through a sufficiently big flat surface): no bulges at all.
3) Only if pulling from forward earth parts, we would get two bulges. But forward bulge would not be due only to less gravitational pull from more distant moon, but also to the very spaceship direct pull ...
We could even draw a parallel with our real case. In your imaginary case, the agent which causes moon-earth distance doesn´t diminish, is the mega-spaceship ... In the real case, similarly the agent is a kind of "hidden" force ("centrifugal" f., or at least "outward" force), due to inertia and the fact that all earth parts try to follow the tangent, and moon-earth dance, through invisible "gravity strings", is continuously "bending" the trajectories of all those earth parts ...
Without mentioned dynamic effects of that earth-moon dance, we could not even be here discussing the issue, because they were paramount in the very history of our planet evolution and the beginning of life !

[David Cooper]

But, I´d rather say "no" to the very question: if the powerful spaceship would be making the earth accelerate, and with the moon back at current distance, earth deformation would depend on the way the spaceship force were transmitted to earth: ...

I didn't design that bit of the system well enough, and you've taken it in the wrong direction, missing the point as a result.

Let's have the spaceship apply an even force to the whole of the Earth and all the water on it with a tractor beam so that the Earth simply accelerates and the moon accelerates after it. In this case, there are two bulges in the water with one ahead and the other behind. The bulges in this case are not caused by any kind of rotation, but the mechanism for forming them is the same as it is in the real case of the Earth with the moon orbiting it - it's the difference in the moon's gravitational attraction acting on the Earth as it reduces with distance. The important point is that the cause occurs in a straight line case with no rotation, so it is not caused by centripetal force. Take away the spaceship and the moon will fall into the Earth, and as it does so there will be an amplification of the two bulges, again not caused by centripetal force. This clearly shows the real mechanism behind the tides.

In the case of the Earth with the moon orbiting it, rotation is present and is part of the mechanism for maintaining the bulges indefinitely (with the orbit making sure the Earth and moon don't collide), but it is not that rotation that causes the bulges - they are already there from the mere proximity of Earth and moon and the reduction of gravitational force over distance. I now think I was wrong about it being a matter of technical definition as to who is right - centrifugal/centripetal force is not part of the cause of tides, but merely plays a peripheral role.

I said before that we could see gravity as being like strings linking every atom of the Earth and sea to the moon, but with them being elastic so that some can pull with more force than others. The difference in strengths of pull in different places leads to the deformation, and that makes it similar to a case where a string is attached to the nearest point and not to any other, leading to it seeming possible that it could be equivalent to the case of a ball being swung round in circles on the end of a string. But if you stop the ball going round on the string (do this in deep space where there's no gravity worth speaking of), it just sits there at the end of the string with no deformation. If you do the same thing with the elastic gravity "strings" linking to every atom of Earth and sea from the moon, they continue to pull and the bulges are maintained when the rotation is removed. The rotation therefore did not cause the bulges, so their cause cannot be attributed to centripetal/centrifugal force.

[rmolnav]

Let's have the spaceship apply an even force to the whole of the Earth and all the water on it with a tractor beam so that the Earth simply accelerates and the moon accelerates after it. In this case, there are two bulges in the water with one ahead and the other behind. The bulges in this case are not caused by any kind of rotation, but the mechanism for forming them is the same as it is in the real case of the Earth with the moon orbiting it - it's the difference in the moon's gravitational attraction acting on the Earth as it reduces with distance

Your model has really improved … Now both bulges would be identical to real, natural ones (disregarding effects due to sun and other celestial objects) …
But in that scenario bulges wouldn´t be due to "the difference in the moon's gravitational attraction acting on the Earth as it reduces with distance” as you say, because massive stuff can react only to forces exerted on it, either gravity from more or less distant matter, or direct pulls or pushes (even share stresses) exerted by contiguous material. It cannot directly react to gravitational attraction differences between positions thousands of km apart !! How “on earth” could it ??
The behind bulge would actually be due to the fact that there backward pull from moon, at any given position, is bigger than forward pull from the spacecraft. And ahead bulge would be due to the fact that there moon backward pull is smaller than forward pull from the spaceship !! 
Your new model makes possible to also improve the parallel I drew: now we would be exerting on our planet an artificial, uniform and outward (relative to moon-earth couple) force with the spaceship, which is actually replacing the also uniform and outward force that, in the real case with earth revolving around the barycenter, is exerted by nature. How? … As I previously said, moon-earth dance is continuously bending the trajectory of each earth molecule (forcing it to be circular). ALL earth material points are continuously at farthest distance from moon (within its respective circular trajectory), what implies centripetal and centrifugal forces inherent to that revolving are all parallel to the straight line between earth and moon centers of mass.

Take away the spaceship and the moon will fall into the Earth, and as it does so there will be an amplification of the two bulges, again not caused by centripetal force.

That is another prove of the impossibility of having the tides we have had for billions of years without mentioned inertial effects due to the revolving of earth and the rotation of moon, both logically around their common center of mass.
What quoted would not happen if, exactly at the moment of disconnection of the spaceship, somehow we could give earth and moon the “tangential” real velocity vectors they got in nature. The barycenter would follow its previous straight trajectory, at the speed acquired until that moment, and earth-moon couple would dance again, the earth with the two bulges that in your model were artificially originated ... 

[David Cooper]

Your model has really improved … Now both bulges would be identical to real, natural ones (disregarding effects due to sun and other celestial objects) …
But in that scenario bulges wouldn´t be due to "the difference in the moon's gravitational attraction acting on the Earth as it reduces with distance” as you say, because massive stuff can react only to forces exerted on it, either gravity from more or less distant matter, or direct pulls or pushes (even share stresses) exerted by contiguous material. It cannot directly react to gravitational attraction differences between positions thousands of km apart !! How “on earth” could it ??

What's the problem with this being the mechanism? Gravity's strong enough to make the moon orbit the Earth, and the moon's gravity is strong enough to make the Earth wander round in a circle. Why shouldn't the difference in the strength of the moon's gravity as it falls off over distance also be enough to raise the sea a little on the nearest and furthest sides? If there was no difference in the gravitational strength over distance, each body would act on the other just like the spaceship's tractor beam with no bulges being generated in the ocean at all.

The behind bulge would actually be due to the fact that there backward pull from moon, at any given position, is bigger than forward pull from the spacecraft.

If you don't think the fall off in gravitational strength over distance is enough to account for the tides, the moon would apply it's backward pull to the whole Earth and its ocean and pull them all backward equally rather than doing so more strongly on the nearest part (creating a bulge there) and less strongly on the furthest part (creating a bulge there too).

And ahead bulge would be due to the fact that there moon backward pull is smaller than forward pull from the spaceship !!

You're describing the same mechanism as mine while claiming mine is wrong and yours is right - it is the fall off in gravitational strength that is doing the job of creating the bulges.

Your new model makes possible to also improve the parallel I drew: now we would be exerting on our planet an artificial, uniform and outward (relative to moon-earth couple) force with the spaceship, which is actually replacing the also uniform and outward force that, in the real case with earth revolving around the barycenter, is exerted by nature. How? …

The spaceship is only needed in the linear case to stop the moon catching the Earth and colliding with it. If we have the moon orbiting the Earth instead, they won't collide, so we can do away with it. We don't need it though anyway to see the mechanism for tides because it's all there on show until they collide, and the height of the bulges grows as they near each other.

As I previously said, moon-earth dance is continuously bending the trajectory of each earth molecule (forcing it to be circular). ALL earth material points are continuously at farthest distance from moon (within its respective circular trajectory), what implies centripetal and centrifugal forces inherent to that revolving are all parallel to the straight line between earth and moon centers of mass.

You haven't taken in what I said at the end of my previous post. If you stop the Earth and moon (and all the water of the ocean) in an instant by applying uniform forces to each body, what happens to the bulges? They don't disappear, but are maintained (and will grow as the two bodies accelerate towards each other). If you are whirling a ball round your head on a string and then apply uniform forces to eliminate the movement in the same way, what happens to the bulges? They disappear as the ball springs back into a sphere. In the case of the ball on the string, the centripetal force has been removed, so the bulges disappear. In the case of the Earth and moon, there is no centripetal force to remove, so the bulges remain - they are caused by something else.

Take away the spaceship and the moon will fall into the Earth, and as it does so there will be an amplification of the two bulges, again not caused by centripetal force.

That is another prove of the impossibility of having the tides we have had for billions of years without mentioned inertial effects due to the revolving of earth and the rotation of moon, both logically around their common center of mass.

The only difference is that an orbit prevents a collision, so the system continues to function for much longer.

What quoted would not happen if, exactly at the moment of disconnection of the spaceship, somehow we could give earth and moon the “tangential” real velocity vectors they got in nature. The barycenter would follow its previous straight trajectory, at the speed acquired until that moment, and earth-moon couple would dance again, the earth with the two bulges that in your model were artificially originated ...

If the spaceship can tow the Earth in the manner I described, there is no reason why the same advanced technology couldn't apply forces to Earth (including ocean) and moon to send them in the right directions to establish an orbit, but the bulges are caused by the same mechanism before and after these changes - it is not the orbit that produces them.

[rmolnav]

What's the problem with this being the mechanism? Gravity's strong enough to make the moon orbit the Earth, and the moon's gravity is strong enough to make the Earth wander round in a circle. Why shouldn't the difference in the strength of the moon's gravity as it falls off over distance also be enough to raise the sea a little on the nearest and furthest sides?

Imaging three tennis ball size pieces of earth stuff, one were earth c.g. (E),  another just under the moon (M), and the other at the antipodes (A).
If we had them without the rest of our planet, they would be free to react to forces such as moon gravity … M would accelerate the most, and A the least. Distances between M and E, and between E and A, would increase, though M and A don´t even “know” moon pull on E. And certainly without needing any rotation or revolving.
But in the real case, M and A neither are free whatsoever, nor “know” how much E is pulled by the moon, let alone that material stuff “knows” how to subtract pull vectors, in order to directly react to gravitational differences !!
Our planet own gravity, many, many million times grater than moon gravity differences, together with rigidity where solid parts, “forces” them to move basically together … That causes internal stresses, what also depends on the way the planet globally reacts to the pull of the moon.
As you say, "the moon's gravity is strong enough to make the Earth wander round in a circle”, but that movement also requires suitable initial “tangential” speeds of both earth and moon. And those speeds, and their continuous change of direction due to the rotation/revolving, also affect internal stresses, what inevitably intervenes on tides.
You cannot say tides are due only to moon pull differences. The ways M and A react to the pull of the moon at their different distances depend on the let us say  degree of freedom the rest of the planet allows them …
If, e.g., we analyzed tidal effects at the moon, we would find that the answer of the whole moon to earth¨s gravity is different than the opposite we are dealing with. Moon is tidal locked to earth, and further parts of it require bigger centripetal acceleration than closer ones, for its actual rotation. But earth only revolves around the barycenter: all its parts require identical centripetal force.
Therefore, distribution of internal stresses due to those not equal “ global” movements is utterly different, and that also affects tides. 
A single cause such as gravitational differences can´t be the unique reason of tides, because  in mentioned two cases the field of total force acting on each unit of mass of the earth are the result of differently caused individual forces ...

If you don't think the fall off in gravitational strength over distance is enough to account for the tides, the moon would apply it's backward pull to the whole Earth and its ocean and pull them all backward equally rather than doing so more strongly on the nearest part (creating a bulge there) and less strongly on the furthest part (creating a bulge there too).

That´s logically flawed. What I say is that gravitational differences can´t be the UNIQUE cause of tides, that they intervene on the formation of tides, but only as one of the sides of a more complex “coin”.
And it is absurd to deduce from that, if it were right, "the moon would apply it's backward pull to the whole Earth and its ocean and pull them all backward equally …”

You haven't taken in what I said at the end of my previous post. If you stop the Earth and moon (and all the water of the ocean) in an instant by applying uniform forces to each body, what happens to the bulges? They don't disappear, but are maintained (and will grow as the two bodies accelerate towards each other).

We could imagine bizarre situations applying artificial forces to change the scenario, and get something similar to actual tides for a short period of time … But that wouldn´t mean our billions of year old natural tides are due only to causes identical to the ones at those situations ... 

If you are whirling a ball round your head on a string and then apply uniform forces to eliminate the movement in the same way, what happens to the bulges? They disappear as the ball springs back into a sphere.

That is erroneous, because outer parts of the ball require bigger centripetal force than inner ones (the ball rotates, as moon´s case …).
But, curiously, inner bulge would be bigger than outer one, because internal tensile stresses (interactions between contiguous material), caused also by centripetal and centrifugal forces, kind of accumulate inwards ...
To make the bulges disappear you would need to apply opposite forces varying proportionally to the radius (required centripetal force: ω²r)
And if we made the ball rotate with a sling (pushing inwards on its outer side), instead of bulges the ball would get slightly flatter. As before, required centripetal force would be bigger at outer side, but the now compression internal stresses would be also bigger there, because they accumulate outwards …
All that shows how much the distribution and type of forces causing the circular movement affect internal stresses, and logically deformations and tidal effects.

In the case of the Earth and moon, there is no centripetal force to remove, so the bulges remain - they are caused by something else.

That is also erroneous! The whole earth, in order to be able of making the moon rotate, is revolving around the barycenter, similarly to the waist movement of a child playing “hulla-hoop” …
And centripetal forces (and centrifugal ones) necessarily have to be present, they affect internal stresses, and due to that also affects the dynamics of tides.

[rmolnav]

(required centripetal force: ω²r)

Sorry ... That´s actually the required centripetal acceleration. It could also be considered as centripetal force ... but per unit of rotating mass !!

[David Cooper]

But in the real case, M and A neither are free whatsoever, nor “know” how much E is pulled by the moon, let alone that material stuff “knows” how to subtract pull vectors, in order to directly react to gravitational differences !!

The Earth's material applies a gravitational pull upon itself, pulling it into a ball. Its rotation causes an equatorial bulge and polar flattening. The moon's gravitational pull then adds to this and causes two bulges on opposite sides. They all add together and none of the material knows or cares where the gravity comes from that is acting on it - it simply moves to where the total force takes it.

As you say, "the moon's gravity is strong enough to make the Earth wander round in a circle”, but that movement also requires suitable initial “tangential” speeds of both earth and moon. And those speeds, and their continuous change of direction due to the rotation/revolving, also affect internal stresses, what inevitably intervenes on tides.

If you apply an even force to something, you don't get any such effect. you only get the tidal bulges because it is not an even force, but one that falls off over distance. The bulk of the force on each point is the same and generates no stresses - it's only the excess at the near side and deficit at the far side that causes them.

You cannot say tides are due only to moon pull differences. The ways M and A react to the pull of the moon at their different distances depend on the let us say  degree of freedom the rest of the planet allows them …

The Earth's tidal bulges are precisely caused by the differences caused by the moon and sun's gravity. All the other distortions which these add on top of are not included as tidal effects. As the Earth rotates, the tidal bulges move, but the other distortions remain (ignoring the stresses caused by the mass of water changing as the bulges move - where I live, the land I'm standing on bends downwards measurably at high tide under the weight of the mass of water).

If, e.g., we analyzed tidal effects at the moon, we would find that the answer of the whole moon to earth¨s gravity is different than the opposite we are dealing with. Moon is tidal locked to earth, and further parts of it require bigger centripetal acceleration than closer ones, for its actual rotation. But earth only revolves around the barycenter: all its parts require identical centripetal force.

It is not centripetal force - the force remains in place when rotation is removed. The moon is tidally locked to the Earth by the same mechanism of the Earth's gravity falling away over distance. The moon has no ocean to produce bulges, but it has the equivalent set in stone in its mass distribution, thereby allowing its rate of spin to be locked at one rotation per orbit. Because its orbit isn't circular, it doesn't rotate at a constant rate, but wobbles, and the corrections are made by the gravitational tidal forces. Because the Earth's gravity is much stronger than the moon, the difference in force across the moon is bigger than the difference in force across the Earth, so if the moon had an ocean it would have much bigger tide bulges. It doesn't though, so all we have is a wobbling rock which is continually moving away from its average alignment and being corrected back towards it, with stresses generated as a consequence.

A single cause such as gravitational differences can´t be the unique reason of tides, because  in mentioned two cases the field of total force acting on each unit of mass of the earth are the result of differently caused individual forces ...

The tidal part is entirely driven by the gravitational force from the other body decreasing over distance. Any other forces acting are not contributing to tides - the tides are acting on the top of those.

If you don't think the fall off in gravitational strength over distance is enough to account for the tides, the moon would apply it's backward pull to the whole Earth and its ocean and pull them all backward equally rather than doing so more strongly on the nearest part (creating a bulge there) and less strongly on the furthest part (creating a bulge there too).

That´s logically flawed.

No - your understanding of it may be logically flawed, but what I said is correct. If the moon's gravitational force acts so evenly across the whole Earth that it isn't responsible for the tides, there will be no bulges produced by placing the two bodies close to each other (while they fall together), and, incidentally, you also lose spaghettification of objects falling into black holes. If we put the two in orbit around each other instead, again there will be no tidal bulges because the moon's gravitational force will be too even across the whole Earth and its ocean to produce them. There is no centripetal force to make up the difference because acceleration by an even force field does not produce centripetal force. Remember the glass of water on a desk being accelerated sideways by such a field from zero to 100m/s in an instant and back to zero again the next - the water would not slosh about at all, but would sit with a flat surface at the top throughout. The same applies if you move this glass of water round in a circle by applying an even force field to it, and you should realise that when you repeat the straight line version of this experiment to move the glass north, then east, then west, then south in quick succession, each time doing so by applying an even force field to it. The glass moves round the corners of this square without the water moving relative to it at all. No centripetal forces are acting in a case like this. To send the glass round in a circle at a constant speed of 100m/s, all we need to is apply two force fields to it at 90 degrees to each other, each one accelerating it up to 100m/s on one axis, then decelerating it to zero on that same axis, then to -100m/s on that same axis, then back to zero again. No sloshing of the water - the surface remains flat at all times. That is what happens with the moon and Earth's gravity when they act on each other, except for the crucial difference that the strength of that gravity diminishes with distance, and that's what generates the bulges in the ocean.

(Incidentally, the bulges on an Earth with no land and equally deep water everywhere would be tiny - we only have big bulges where they run up against coasts. I've heard that at Fiji there is no noticeable tide at all.)

What I say is that gravitational differences can´t be the UNIQUE cause of tides, that they intervene on the formation of tides, but only as one of the sides of a more complex “coin”.

If you take away the gravitational difference caused by it diminishing over distance, you will have no tides at all. The complexities that you are imagining do not contribute to the tides, even though centripetal bulge does add to to the degree to which the sea bulges away from a spherical shape - the tides are just the distortions added to that already-distorted surface and are not the total distortion away from a sphere.

And it is absurd to deduce from that, if it were right, "the moon would apply it's backward pull to the whole Earth and its ocean and pull them all backward equally …”

You may find it absurd, but it is correct regardless. I refer you back to the glass of water experiment with the even force field being applied - no bulges and no sloshing. You simply aren't modelling this correctly in your head, and that's why you're imagining absurdities where there are none.

We could imagine bizarre situations applying artificial forces to change the scenario, and get something similar to actual tides for a short period of time … But that wouldn´t mean our billions of year old natural tides are due only to causes identical to the ones at those situations ... 

These bizarre situations are designed to pin down precisely which parts of a system are responsible for which results. The bulges are caused by precisely the same thing, and that is the difference in gravitational pull over distance in accordance with the inverse square law. The only reason tides continue in a relatively constant way (in terms of bulge size) for millions of years is that the moon's orbit prevents it being ended by a collision. If we were to put the moon into an orbit where it comes much more directly towards the Earth, then swings round it and heads back out to the far point again, we would see the bulges in our ocean grow in size as the moon sweeps in towards us, then they'd diminish as the moon leaves, and if you then change the orbit again to make it a straight line leading to a collision, the bulges would grow in a near-identical way as the moon approaches even though all the rotation has been removed from the system. And we know this, because if the force was evenly applied instead, there would be no bulges generated in any of these cases, just like the glass of water being moved around by even force fields.

If you are whirling a ball round your head on a string and then apply uniform forces to eliminate the movement in the same way, what happens to the bulges? They disappear as the ball springs back into a sphere.

That is erroneous, because outer parts of the ball require bigger centripetal force than inner ones (the ball rotates, as moon´s case …).

Then stop the movement with a force that acts more strongly on the furthest out part of the ball - the aim is simply to stop the orbit to reveal the truth about what was causing the distortion. When you stop the orbit of the ball on the string, it pings back to a spherical shape. When you do the equivalent with the Earth and moon, no such return to spherical shape would occur because the cause of the distortion is still applying in full.

To make the bulges disappear you would need to apply opposite forces varying proportionally to the radius (required centripetal force: ω²r)

To make the bulges disappear from the ball, it is sufficient to stop it moving and have the string go slack.

All that shows how much the distribution and type of forces causing the circular movement affect internal stresses, and logically deformations and tidal effects.

What it shows is how centripetal force acts on things, and you're the one proposing that it causes tides. It doesn't have any role in causing tides though, so none of these complications apply.

In the case of the Earth and moon, there is no centripetal force to remove, so the bulges remain - they are caused by something else.

That is also erroneous!

The error is not in what I said, but in your understanding.

The whole earth, in order to be able of making the moon rotate, is revolving around the barycenter, similarly to the waist movement of a child playing “hulla-hoop” …
And centripetal forces (and centrifugal ones) necessarily have to be present, they affect internal stresses, and due to that also affects the dynamics of tides.

That's where your entire misunderstanding comes from. You have recognised a similarity between two systems and made the mistake of imagining that they must work the same way, but they don't. An even force field being applied to something does not generate any stresses in it and does not distort it. This makes it possible to move something in a circle without anything being flung outwards or pulled in by centrifugal/centripetal force.

[rmolnav]

I consider you talk a load of rubbish ! ...
I´m not going to refute all that. It´d be useless. I thought we could "solve" our Physics differences, but I see we have also a quite different mind set, and I can´t agree with your Logics. That is much more difficult to solve ...
Just one question. You say:
"If you take away the gravitational difference caused by it diminishing over distance, you will have no tides at all. The complexities that you are imagining do not contribute to the tides, even though centripetal bulge does add to to the degree to which the sea bulges away from a spherical shape - the tides are just the distortions added to that already-distorted surface and are not the total distortion away from a sphere".
You seem to refer ("already-distorted surface") to the equatorial bulge caused by daily earth spinning.
That is caused by inertial effects. Water, with a linear speed tangent to equator (if exactly there), tends to follow the tangent. But own earth gravity obliges the water to follow a circular path.
In this case, without any significant gravity differences, we have a relatively huge permanent bulge, because centripetal/centrifugal forces are proportional to the square of angular speed, some 29 times bigger than in the moon-earth "dance"
Somewhere you say tides occur on top of that permanent equatorial bulge. Quite right.
But, why earth daily spinning can cause that permanent equatorial bulge, and (according to you) the some 29 day revolving of the earth around the barycenter (please don´t mix with daily earth rotation !!), besides actual gravity forces on each location, can´t intervene in tides formation ??
In this last earth movement, water (and solid parts too) are also somehow obliged to follow circular paths, instead their inertial tendency to follow the tangents ... Therefore, centripetal and centrifugal forces are also present, and they do intervene on the 29 day cycle of moon-éarth dynamics, and on lunar related tides !!
There is an image:
main-qimg-851d9284749b378191c8ae87e4e2e4c2
that can help guys understand better moon-earth dance, especially earth revolving around the barycenter.
By the way: the image has a detail a little bit erroneous ... Any guess?

[rmolnav]

There is an image:
main-qimg-851d9284749b378191c8ae87e4e2e4c2
that can help guys understand better moon-earth dance, especially earth revolving around the barycenter.
By the way: the image has a detail a little bit erroneous ... Any guess?

A Google page appears. Please click on images ...

[David Cooper]

I consider you talk a load of rubbish ! ...

That's why the world's in such a mess - the people who talk the most sense aren't recognised by the masses who can't work out what makes sense and what doesn't, so all the decisions are made by majorities of people with faulty understandings.

I´m not going to refute all that. It´d be useless.

To try to correct something correct is indeed a fruitless endeavour (unless you realise that it is correct).

I thought we could "solve" our Physics differences, but I see we have also a quite different mind set, and I can´t agree with your Logics. That is much more difficult to solve ...

If you aren't prepared to break down the system into component mechanisms properly to find out precisely what causes what, how are you ever going to know if you're right or wrong? I'm just trying to help you do that. The key thing for you to understand is that when an even force field is applied to an object that's free to move, every single particle in it will be pulled with equal force, so this adds no stress within that object at all. You could use such an even force field to make the object travel in a circle, and all the particles would respond exactly the same amount and move in exactly the same direction without generating any stress at all. That's what an orbit essentially does using gravity (except for the fall off in strength of gravity over distance, without which there would be no tides). That's all you need to understand to see why centripetal force is not part of the mechanism.

But, why earth daily spinning can cause that permanent equatorial bulge, and (according to you) the some 29 day revolving of the earth around the barycenter (please don´t mix with daily earth rotation !!), besides actual gravity forces on each location, can´t intervene in tides formation ??

The daily spinning has already had its full effect - the Earth's rotation causes a distortion and that distortion is fairly constant, only diminishing very gradually over time as the rotation slows. The revolving around the barycentre is irrelevant for the reason set out in my previous paragraph - an even force being applied gives no scope for stresses to be generated in the material to which it is applied if all that material is free to move. The Earth and moon are both free to move, so you cannot put any stress into them by applying an even force to either of them, and that means you can't distort them that way - no bulges.

In this last earth movement, water (and solid parts too) are also somehow obliged to follow circular paths, instead their inertial tendency to follow the tangents ... Therefore, centripetal and centrifugal forces are also present, and they do intervene on the 29 day cycle of moon-éarth dynamics, and on lunar related tides !!

The reason you think I'm talking nonsense is that you have put a faulty idea into your model of reality which is causing you to make mistakes whenever you try to build on top of it. None of the material of the Earth of moon feels as if it's travelling round anything in a circle - it all feels as if it's going in a straight line (ignoring spin). Imagine a case where the spin is removed. All the material of the moon is following a circular path which is exactly the same shape and size for ever single particle of the moon, and all the material of the Earth is following a much smaller circular path which is exactly the same shape and size for every single particle of the Earth. If you imagine this orbiting system is maintained by an even gravitational force being applied to each body by the other, you have no means whatsoever of generating tidal bulges. You incorrectly suppose that the mere fact of these bodies moving along circular paths will try to fling material outwards in the same way as happens with a ball on a string being whirled round your head, but that is based on a fundamental misunderstanding where you equate two different mechanisms and assume that the stresses generated by one must also be generated by the other, but they aren't. There is no location on a non-spinning planet or moon where the orbital path of that body would be detectable by any apparatus designed to measure stress if the gravitational force was applied evenly.

I very much doubt you'll believe that even now, so I'll give you even more help. Imagine four rockets in a square formation near a little asteroid with insufficient gravitational strength for them to orbit it in any useful amount of time. If we want the four rockets to travel round it in a circle while maintaining their square formation and without rotating that formation, what do we do? We make them all put out the same amount of thrust in the same direction at all times, so they maintain the same distances to each other and the square maintains its alignment with the stars while it travels round and round the asteroid. The square does not bulge. Now compare that with a non-spinning moon and non-spinning planet with an even gravity field being applied by each to the other, and you have exactly the same thing - no bulges appear because every particle has the same force applied to it from the other body (and applied in the same direction). We have the two bodies moving on circular paths without centrifugal/centripetal force having any ability to act.

Now replace the even gravity field with one that falls away in strength over distance, and what happens? Tidal bulges suddenly appear, and we can see very clearly the mechanism that drives them. Take away the orbits and the bulges are maintained by the mere proximity of the two bodies alone, revealing that the bulges are not caused by the circular paths. If you were to take the moon further away from the Earth and then release it to let it fall onto the Earth, the bulges in the ocean would grow as the moon falls towards the Earth, and at the point where the moon and Earth are 250,000 miles apart, these bulges would be the same size as they are when the moon is orbiting the Earth at that distance.

You can lead a horse to water, but you can't make it drink. I have taken you to the water and there's nothing more that I can do for you if you aren't able to drink.

[rmolnav]

As I did yesterday, I´ll quote only one paragraph from all that rubbish, today the first one.

That's why the world's in such a mess - the people who talk the most sense aren't recognised by the masses who can't work out what makes sense and what doesn't, so all the decisions are made by majorities of people with faulty understandings.

You are wrong even on the “social” history of the issue.
What actually happens is the other way around. Your model is even called by many the standard model, because many people like you, physicists included, keep in their minds erroneous ideas already corrected by the few … My stand here, since my very first post #20 on 29/05/2015 (!!), has most frequently gone against the grain, always defending the importance of centrifugal force on the existence of tides, especially on the hemisphere furthest from the moon.
But I´m not alone, what in its case would clearly mean I was the wrong. In several moments I even contacted eminent scientists, directly by email, to discuss some details or ask some questions. And I discovered interesting details of the huge confusion that exists, and has existed, out there ...
Just as an example, the first reply from a NOAA scientist was: 
"Based on the topics and points of discussion, you are obviously someone with a high level of science, physics, and mathematical education, training and understanding.
Unfortunately, this level of knowledge and understanding can sometimes work against you - as you look for a "deeper" level of explanation, or do not understand why some concepts that you understand are not included in the descriptions.
The publication you are referring to is "Our Restless Tides", a 10-page pamphlet developed in the 1950's to provide a basic description of the forces which create the tides.  It's intended audience were the grade school children and adults of that time.  It used terminology of science and forces which were common in the 1950s.  Such as centrifugal force.  Centrifugal force was always an "imaginary force" (not a real / measurable force).  But that type of description made the concepts easier to understand and explain.  That  description and use of centrifugal force continued to be common practice until the 1970-80's.  At that point, the terminology shifted and the textbooks used in grade schools were changed to use a more modern terminology and description of this "effect" being a result of inertia rather than an "imaginary force”.[/b]
I´m afraid your model is somehow “contaminated” by ideas which are several decades out of date, what added to your to me "absurd" logic make you say all that rubbish !!
By the way, without entering the amazing ideas of Einstein on deep nature of gravity, we should not forget he started from his idea that inertia and gravity are the same (I´d personally rather say “almost” the same …), derived from their almost identical effects …
Once again, how gravity forces could intervene on the formation of tides, but inertial ones (such as centrifugal forces inherent in circular movements) could not ??

[David Cooper]

As I did yesterday, I´ll quote only one paragraph from all that rubbish, today the first one.

What rubbish? I've analysed the system for you and I've done so correctly, illustrating each point carefully. Just labelling it "rubbish" isn't adequate. You need to pick it apart and show where it's broken, but you'll find that you can't because it isn't broken. When I tell you that an even gravitational field applied to an object acts equally upon every single particle of that object, I mean exactly that, and I'm also right. Such a field does not generate stresses in that object if the object can move freely - the object simply accelerates in the direction the force makes it move in and it does so without taking on any distortion. That makes it possible for the object to move in a circular path without any tidal bulges because there is no centripetal/centrifugal force involved at all. The way to produce the bulges is to change it from an even force to one that varies over distance (as it spreads out away from the source), and that is how tides are generated. It's that simple, but you are incapable of understanding that because you are determined that your explanation must be right and that any rival explanation therefore must be wrong because it opposes yours. You're shackled in your thinking by your inability to reject an incorrect idea that you are so emotionally tied to that you cannot let it go, no matter how clearly it is shown to you that you're wrong.

Now, you could make that same accusation to me in an attempt to defend your position, but I'm not emotionally tied to this - I don't care what wins out as the cause of tides other than wanting that winner to be the correct answer, and I approach everything else in science and every other field on the exact same basis - you should never develop an emotional bond to a theory, but be ready to ditch it in an instant as soon as a fatal flaw appears with it. That means that I test the proposed mechanisms to see if they really do what's claimed of them. If you look back a few posts (to reply #144), you'll see that this is absolutely true - I shifted position radically when I realised why you thought centrifutal/centripetal force had a role in tides because I suddenly saw such a strong parallel between the two systems (ball swinging round in circles at end of a string, and planet/moon held in orbit by gravity acting like invisible strings) that I thought the difference in the proposed mechanism might be an artificial one caused by an inadequate technical definition of centripetal/centrifugal, and I was happy to think that you might therefore be right. However, when I wrote my next post (reply #146), I ruled that out because I realised that there was a key difference between the two cases in that the bulges remain in the gravity case when the rotation is removed, thereby proving that it cannot be driven by centripetal/centrifugal force. That was the point where the case was proved, and everything since then is about you failing to get that point while you remain superglued to a disproved position.

You are wrong even on the “social” history of the issue.

No I'm not - I see monkeys making bad decisions practically everywhere. There's a reason why China is heading for world domination, because they have people with a significantly higher level of expertise making decisions there without having to pander to people of lesser minds. They still make woeful decisions most of the time, of course, because even those people with higher expertise are poor thinkers, but they are better than average, and that adds up to a big economic advantage over time.

What actually happens is the other way around. Your model is even called by many the standard model, because many people like you, physicists included, keep in their minds erroneous ideas already corrected by the few …

You don't have to look far around this forum to find that I do not follow the herd. When it comes to gravity, I am now leaning most strongly towards the idea of it not being a force - it is just a slowing of the speed of light in the proximity of mass, as that's all it takes to change the course of objects (and of light), and to change their speed of travel (so there is no need for it to curve space in the way proposed by GR). When I refer to gravity as being a force in this thread, it doesn't mean that I believe it is a force, but the way a force acts would create the same results as the more complicated explanation without getting bogged down in unnecessary technical details as to the actual mechanism by which gravity produces orbits. (In the same way, a believer in GR might also use the idea of gravity being a force in this discussion rather than going into unnecessary complications about curved space and the orbiting body moving in a straight path at all times through non-Euclidean Spacetime.)

My stand here, since my very first post #20 on 29/05/2015 (!!), has most frequently gone against the grain, always defending the importance of centrifugal force on the existence of tides, especially on the hemisphere furthest from the moon.

Lovely, but who cares about the grain? I don't care how much support (or how little) an idea gets from troops of monkeys. The only thing that matters is whether it's right or not, and to find that out it's necessary to test the idea properly to see where it breaks (or doesn't). Your idea breaks at the point where the tidal bulges remain after the orbital rotation is removed from the system, thereby revealing that the rotation from the orbit had absolutely no role in producing the bulges, with the result that the cause cannot be attributed to centripetal/centrifugal force.

But I´m not alone, what in its case would clearly mean I was the wrong. In several moments I even contacted eminent scientists, directly by email, to discuss some details or ask some questions. And I discovered interesting details of the huge confusion that exists, and has existed, out there ...

There are many eminent scientists who are wrong on many things. Nothing can be taken on trust on the basis of authority - everything has to be tested for what it is itself without biasing the results by factoring in dogma and other baggage.

Just as an example, the first reply from a NOAA scientist was: 
"Based on the topics and points of discussion, you are obviously someone with a high level of science, physics, and mathematical education, training and understanding.

That is a standard, polite wording. The thought going through the mind of the author of such phrases runs along the lines of, "How can I get rid of this tiresome pest while pretending to respect him?"

The publication you are referring to is "Our Restless Tides", a 10-page pamphlet developed in the 1950's to provide a basic description of the forces which create the tides.  It's intended audience were the grade school children and adults of that time.  It used terminology of science and forces which were common in the 1950s.  Such as centrifugal force.

It is common in education to provide false explanations of things in an attempt to simplify them, so the higher you go with your studies, the more times you will have such explanations thrown out for you to be replaced with better false explanations, and if you get far enough you might eventually be lucky enough to be see some true explanations.

Centrifugal force was always an "imaginary force" (not a real / measurable force).  But that type of description made the concepts easier to understand and explain.  That  description and use of centrifugal force continued to be common practice until the 1970-80's.  At that point, the terminology shifted and the textbooks used in grade schools were changed to use a more modern terminology and description of this "effect" being a result of inertia rather than an "imaginary force”.[/i]

Here, we see that the scientist may not have a firm understanding of the tides himself though - all he's doing here is trying to get rid of the idea of centrifugal force by referring to the real mechanism that is behind centrifugal force, but he hasn't realised that this isn't the mechanism behind the tides.

I´m afraid your model is somehow “contaminated” by ideas which are several decades out of date, what added to your to me "absurd" logic make you say all that rubbish !!

I can't work out if that's still part of what the scientist said to you, or if you're saying it to me. What I'm giving you is direct analysis where I look at the role of rotation (the orbit) and see what happens when that orbit is removed. The tidal bulges remain, so the rotation cannot have a role in producing them, and that means centipedal/centrifungal force has no role in causing tides.

By the way, without entering the amazing ideas of Einstein on deep nature of gravity, we should not forget he started from his idea that inertia and gravity are the same (I´d personally rather say “almost” the same …), derived from their almost identical effects …

Einstein saw a parallel and read too much into it, just as you have done. SR and GR both fail to function correctly in accordance with their specifications - all simulations of them have to cheat as a result in order to maintain the pretence that the model works. But we don't need to go into that side issue - it is sufficient to prove the case that the tidal bulges remain when there is no rotation at all.

Once again, how gravity forces could intervene on the formation of tides, but inertial ones (such as centrifugal forces inherent in circular movements) could not ??

Centrifugal forces are not inherent in all circular movements - that's where you're continuing to fail to understand this. You are trying to have them act in a case where they do not act. A ball whirling round your head on the end of a string feels a force - the whole of it feels the force. A moon going round a planet would not feel any force acting on it at all if the force between them was even, acting with the same strength on each particle (and applying in the same direction to each). It's only when you make that force uneven that you get distortion, and that distortion is not dependent on orbiting - the exact same distortion applies in a straight line system.

[rmolnav]

There are many eminent scientists who are wrong on many things. Nothing can be taken on trust on the basis of authority - everything has to be tested for what it is itself without biasing the results by factoring in dogma and other baggage

When I said I directly contacted several scientists to discuss details of the issue, I meant I did tell them the things they had said I didn´t agree with, or at least I didn´t understand ... And what I´ve been telling you is the result of both my initial ideas, and all those discussions, some of them really fruitful ... It´s not just "trust on the basis of authority" !! I do know "There are many eminent scientists who are wrong on many things" …
Though I wonder if you really think a scientist who ...
" ... spent most of his career in NOAA and much of his time working on tide related
problems as a specialty even while tackling jobs with a much broader scope ..."
and held positions at NOAA such as:
"Chief Scientist of the National Ocean Service; Director of the Coast Survey Development Laboratory; Director of the World Data Center for Oceanography; Principal Investigator for the NOAA Global Sea Level Program; and head of the U.S. national tides and currents program (in a earlier organizational form before it became CO-OPS)",
if being clearly on my side (about the discussed issue), instead of on yours, still he could be wrong on the very core of the issue ...
And what you also said:
"Just labelling it "rubbish" isn't adequate. You need to pick it apart and show where it's broken, but you'll find that you can't because it isn't broken”
should not be applied to my case. I´ve been refuting many single things said by you (#136,138,141,142,145,147,149,152… - only then i started mentioning the word “rubbish”! ), but you keep on repeating same things, without any change connected to what I´d previously said … It seems you have not read all my posts !!
By the way, you said too:
"The key thing for you to understand is that when an even force field is applied to an object that's free to move, every single particle in it will be pulled with equal force, so this adds no stress within that object at all" ...
I´d rather say, as I´ve said many times, but with other words:
"The key things for you to understand are that” …, even if moon´s pull were uniform across our planet,
1) earth, as it´s not “free to move” (moon and earth c.g.s have to keep their distance, and the barycenter has to follow its orbit around the sun), it would experience additional internal stresses ...
2) if due to initial conditions earth parts were somehow following not rectilinear paths, centripetal and centrifugal forces would be occurring ...
3) if those paths were as they actually are (circumferences with ALL earth parts continuosly at maximum distance from the moon), inertia would tend to make water follow the tangent, earth own gravity would avoid it … and we would get the further hemisphere bulge ... as I said even if moon pull there were the “uniform” average !!   

[Le Repteux]

Hi David,

I agree with you about the bulges, but it is not clear how a small vertical motion in the middle of the oceans can transform into huge ones on the coasts. That's what tsunamis do, but they are considered as a fast wave that breaks on shallow waters, so they can break in any direction from the impact point, while the two opposing tidal bulges are only going west and could only break on eastern coasts if they were a wave, which is not what is observed. I didn't read all the thread, so maybe you already talked about that, but if not, can you give me your explanation please?

[David Cooper]

Though I wonder if you really think a scientist who ... if being clearly on my side (about the discussed issue), instead of on yours, still he could be wrong on the very core of the issue ...

It would be fully possible for a scientist who's an expert on tides to have a gap in his knowledge about the fundamental cause of them (or for his knowledge to be built upon an error which makes no importance to the science that he's doing). It isn't clear from your quote though whether he has such a gap or fault, because what you quoted was simply him objecting to centrifugal force being regarded as a real force, so he wasn't actually addressing the issue of the cause of tides.

If you want to find out who's right about the fundamental cause of tides, you need to produce a model that replicates tides when you run a simulation of them, and that model has to be compatible with reality rather than contradicting it. If you apply an even force to an object in a simulation and the object is free to move, it won't distort - you can send it round a circular path with such a force being applied from the centre and there will be no bulges produced. You can also simulate the way the bulges grow as the moon moves towards the Earth on a straight path and show that no rotation is necessary to generate them. I can do this in my head without difficulty, but I know that this is a skill which is not shared by everyone, and indeed that only a tiny minority can do it well.

And what you also said:
"Just labelling it "rubbish" isn't adequate. You need to pick it apart and show where it's broken, but you'll find that you can't because it isn't broken”
should not be applied to my case. I´ve been refuting many single things said by you (#136,138,141,142,145,147,149,152… - only then i started mentioning the word “rubbish”! ), but you keep on repeating same things, without any change connected to what I´d previously said … It seems you have not read all my posts !!

The reason I keep repeating things is that you keep repeating the same incorrect things instead of fixing your mistakes, so I keep trying to help you recognise where you're wrong by spelling things out more and more clearly for you. I can't force you to recognise an error if you're incapable of recognising it though, so there is no guarantee that you will ever understand this stuff. It appears that running simulations with precision in your head is not something you can handle, so perhaps we need to move to using computer programs to run the models openly instead so that it's harder for you to go on denying reality.

...even if moon´s pull were uniform across our planet,
1) earth, as it´s not “free to move” (moon and earth c.g.s have to keep their distance, and the barycenter has to follow its orbit around the sun), it would experience additional internal stresses ...

Of course it's free to move! The Earth's sitting in space without being moored to anything - it will simply accelerate towards anything that applies a gravitational force to it. The Earth, moon, sun, other planets, etc. are all falling through space without any strings tied to them - they are free to go wherever they're flung. They don't have to keep their distance from each other, but simply fall uncontrolled, but fortunately, if they miss each other at closest approach, they naturally produce orbits which keep repeating the same pattern.

2) if due to initial conditions earth parts were somehow following not rectilinear paths, centripetal and centrifugal forces would be occurring ...

Why? With an even force applying, there is no centrifugal force involved because every particle is accelerated the same amount in the same direction, thereby ensuring that no stress is generated.

3) if those paths were as they actually are (circumferences with ALL earth parts continuosly at maximum distance from the moon), inertia would tend to make water follow the tangent, earth own gravity would avoid it … and we would get the further hemisphere bulge ... as I said even if moon pull there were the “uniform” average !![/b]

Why should water follow the tangent when the Earth doesn't follow the tangent? Why are you applying one rule to the Earth and a different rule to the water sitting on it?