Moon's "tidal lock" rotation theory - What is wrong with it?

The purpose for me in creating this threat is to find a rational explanation, not necessarily a scientific one, for why the moon's rotation is locked to its orbit around the earth.

"Tidal lock" is problematic because, even here on earth, scientists do not have a decent explanation for why there are two tides each day, one on the side close to the Moon, and one on the opposite side. It squarely contradicts our understanding of gravity. (Why do oceans not take an egg-white shape, with the earth being the yolk?) We have been observing the tides for thousands of years yet we cannot explain half of it. To claim that we "know" that the Moon's rotation is caused by "tidal lock" - where we CANNOT observe any tides, much less "tidal forces", is pure hypocrisy, not science.
en.wikipedia.org...

The self-appointed task of science is to observe phenomena and explain them with a theory. But each theory is only valid until ONE contradiction has been found. People need to realize that science only offers theories, NOT knowledge. It is up to everybody themselves to decide which explanation or theory is adequate and which one is not.

en.wikipedia.org...
"torque is defined as the cross product of the lever-arm distance and force, which tends to produce rotation."
To explain my disagreement I will first consider a moon that is solid and has a center of gravity that is away from its axis of rotation. When trying to rotate, gravity will slow it down, because the "torque" on one side would be greater than on the other. When the center of gravity gets to the other side, however, torque will apply the same amount of force to re-accelerate it.

en.wikipedia.org...
IF a moon is a perfect sphere, but has oceans or other liquids, then earth's gravity will pull the liquids closer, thereby causing it to bulge, or be squeezed (hence the name "tidal force"). The elongated shape of molten metal at the core of a moon would essentially make it asymmetric, causing torque forces to be out of balance, and thereby slowing its rotation. Contrary to the above example with the solid moon, the center of gravity will NOT sling to the other side (therefore does not re-accelerate it).

However, this effect of torque would not apply to water. Due to its low "viscosity" (resistance to flow: honey versus water), water flows easily, and, as fast as gravity commands it to. Therefore, the elongated shape will always point directly at earth. With the center of gravity NOT removed off the axis of symmetry, torque forces apply equally to both, the approaching side as they do to the side that is turning away.

en.wikipedia.org...
On the other hand, moving liquids cause friction. With friction, tidal force generates heat, which is a loss of energy, reducing the inertia (tendancy to maintain its speed) of the rotation.

Let's look at our actual Moon. It has a core that is molten to some extent. Due to its small size (relative to its whole body), the high viscosity, and the high pressure that prevents any significant movement, the bulging or any other movement would seem to be minimal. The extent of the bulge needs to be calculated as a function of these factors before one can even look at the torque that it will cause.

Conclusion: To determine how many millions or billions of years it would take for such a bulge to cause a moon or planet to be "tidally locked" requires a monstrous calculation, with many factors being little more than vague estimates. It is hardly something that can be asserted with today's insights and technological abilities to measure. I would consider this our "best available" scientific theory, a plausible assumption, not knowledge.

Where do you think I am correct or incorrect? I hope to get criticism and/or corrections of my explanations and conclusions. I do not need to be told, that I am "obstinate stubborn", or any other mischaracterization for refusing to accept a theory just because it is THE theory deemed "knowledge" by mainstream scientists - yet appears to me to contradict itself or to lack rational, logical reasoning.

Interesting thought. Why is the moon tidally locked to the Earth, yet the Earth is not tidally locked to the Sun?

I'm sure there is a real good reason, but the science is way beyond my pay grade.

So are all moons of all other planets tidally locked to their planets?

Sometimes things seem to be so, well, MANUFACTURED.

reply to post by ThinkingHuman


The moon is not the only causation of tidal influences. The following is a partial excerpt from my Uni thesis about tidal influences.

This thread is also full of relevant information provided by some ATS brainiacs covering your query.

Tides come about because the ocean's waters are mobile (plastic) & are able to respond to the changing tidal generating forces exerted between the earth, Moon & SUN in their orbits.

These forces vary with time because of the changing relative positions of the earth and Moon during the 29-day lunar cycle and the annual cycle of the relative positions of the earth and Sun.

The PRIMARY tidal influence is the Moon - the forces between her & the earth produce an Elliptical envelope with its long axis pointing towards the Moon.

Since the earth is spinning (once/24hrs), the high waters so produced and their intervening lows are progressively moving around the earth to produce a Semi-Diurnal (half daily) tidal pattern involving 2 highs and 2 lows each day. Since the Moon is orbiting the earth each lunar month, it will have moved eastwards about 13 degrees of it's orbit each day. This causes the semi-diurnal tide pattern to repeat itself every 24hrs and 52mins (a lunar day). The net effect is that the tide times move back about an hour a day here on this rock. The latitude on the Earth that the moon is overhead varies about 25 degrees either side of the equator during the lunar month. Because of this resultant shift in the plane of the moon's influence, there is generally an inequality in the 2 highs and 2 lows each day.

Only when the moon is overhead the equator will the highs be equal (and lows be equal) - this happens about once every fortnight. The SUN also exerts similar influences on the tide pattern in similar ways, but to a lesser extent than the moon and over 365-day cycle rather than every lunar month. In theory, the tide that is experienced is a result of the interaction of the Moon's and the Sun's elliptical envelopes.

OTHER TIDAL INFLUENCES:

1. The continents disrupt the free movement and at depths, shapes and current flows in each tidal basin (Pacific ocean for instance) modify the response. These changes can be extreme such that the expected semi-diurnal patterns become only one high and one low each day (diurnal) - Karumba in the Gulf of Carpentaria and Koolan/Cockatoo Islands are prime examples. Again the rises and falls don't occur simultaneously over the surface of the ocean basin but seem to radiate outwards and/or rotate around each basin.

2.Strong and prolonged winds - the effect of wind on tidal heights & times is variable and is, in turn, modified by the coastal topography. In general, it can be said that a strong "onshore" breeze will "pile-up" the water and cause higher tides than predicted; "offshore" breezes will have the opposite effect.

3. Unusually high or low barometric pressures. Low pressure systems tend to raise sea levels - sometimes by more than 2 meters in intense cyclones and high-pressure systems tend to lower them.

S&F for providing some good thoughts in your OP

reply to post by Sublimecraft


Some good info there, thanks. I actually learned something useful here on ATS today! Star for you.

The moon happens to rotate at about the same rate it revolves around the Earth: one month. This is why we see the same side of the moon every night. There is no tidal lock "pattern"; it is not the same for every moon in our solar system. To have a better understanding of how the moon affects tides on Earth, we would probably need a better understanding of how the moon was formed. We know more about Mars' two moons - essentially just two asteroids locked in orbit - than we do our own, for which there are a few competing theories out there.

Im not sure if that is the answer you're looking for, just sharing my two cents and some basics of what I've learned from astronomy classes in Uni and a couple years of space camp.

A better question, in my opinion, would be "why are tides higher during a full moon than during a new moon?"

Originally posted by ThinkingHuman
The purpose for me in creating this threat is to find a rational explanation, not necessarily a scientific one, for why the moon's rotation is locked to its orbit around the earth.

The use of the phrase "not necessarily a scientific one" is going to be the theme of the thread, I fear.

"Tidal lock" is problematic because, even here on earth, scientists do not have a decent explanation for why there are two tides each day, one on the side close to the Moon, and one on the opposite side. It squarely contradicts our understanding of gravity. (Why do oceans not take an egg-white shape, with the earth being the yolk?)

Because that's not the way tidal forces work. Consider a body in orbit. One rock on the near side of the object, one rock on the far side. Left to themselves, these two rocks would orbit at different speeds. The force vectors making them "want" to assume separate orbits is the tidal force. The ones holding them together are the gravitational force of the body (and the tensile strength of the materials, if they're bound together). If the tidal forces exceed these, the body will break up (Roche limit).

Now, if you take the gravitational force vectors of the Moon, and subtract that of the Earth, you'll find there are tidal forces generated both toward and away from the Moon. This causes near and far side water elevation. It's not a mystery, no one really debates that it's happening. This is celestial mechanics 101. It does NOT squarely contradict the understanding of gravity, and in fact while the math is tough for the uninitiated, it's the sort of thing you can solve as a sophomore when you take CM. The effect you're looking at (and dismissing out of hand) is called tidal elongation. There's a nice book on CM online, it's math laden though, you'll find what you're looking for near page 74: linky (pdf)

We have been observing the tides for thousands of years yet we cannot explain half of it. To claim that we "know" that the Moon's rotation is caused by "tidal lock" - where we CANNOT observe any tides, much less "tidal forces", is pure hypocrisy, not science.

Tidal forces are a basic of gravity. That you don't understand the math (or concept) doesn't make it false. "Tides" don't mean oceanic motion, by the way. Ocean tides are caused by tidal forces, but tidal forces don't require oceans.

en.wikipedia.org...
"torque is defined as the cross product of the lever-arm distance and force, which tends to produce rotation."
To explain my disagreement I will first consider a moon that is solid and has a center of gravity that is away from its axis of rotation..

Tidal locking isn't just related to water friction. It is to some extent accentuated by off-center centers of mass, and by masscons. However, if the material of the body isn't infinitely rigid, and rock isn't, then tidal forces will deform the rock and lead to dissipative losses. The phase lag in the deformation causes the torque force that causes tidal locking. Rock is somewhat plastic, it takes time to deform and recover, and Bob's your uncle. The same link I gave you for celestial mechanics shows the math a few pages later under "tidal torque forces".

Then again what if our moon is hollow? Maybe the big round Death Star circle is allways facing away from our Earth. LoL

Originally posted by ThinkingHuman

The self-appointed task of science is to observe phenomena and explain them with a theory. But each theory is only valid until ONE contradiction has been found. People need to realize that science only offers theories, NOT knowledge. It is up to everybody themselves to decide which explanation or theory is adequate and which one is not.

Well here we go another science expert on here that's not a scientist

Science DOESN'T just offer theories if science was so wrong guess what YOU would not have been able to post this thread because we would have NO computers or internet.

Have you heard of the Scientific Method

The scientific method has four steps
1. Observation and description of a phenomenon or group of phenomena.
2. Formulation of an hypothesis to explain the phenomena. In physics, the hypothesis often takes the form of a causal mechanism or a mathematical relation.
3. Use of the hypothesis to predict the existence of other phenomena, or to predict quantitatively the results of new observations.
4. Performance of experimental tests of the predictions by several independent experimenters and properly performed experiments.

Any contradiction as you put it would have to be proved right using the methods above

Originally posted by Bedlam

The force vectors making them "want" to assume separate orbits is the tidal force. The ones holding them together are the gravitational force of the body (and the tensile strength of the materials, if they're bound together). If the tidal forces exceed these, the body will break up (Roche limit).... Ocean tides are caused by tidal forces, but tidal forces don't require oceans.

Thanks for your response (and all the others). Yes, the rocks "want" to assume whatever orbit or path that gravity pulls them. But if they are attached, they cannot. They may break up at some point but this is, for each rock, a one time event.

Now, if you take the gravitational force vectors of the Moon, and subtract that of the Earth, you'll find there are tidal forces generated both toward and away from the Moon. This causes near and far side water elevation.

I am familiar with vectors but I don't follow how subtracting earth from moon vectors will result in vectors pointing in different directions away from the earth. I downloaded the book, give me a day to absorb it but at first glance it looks like a great resource.

Non scientific term? Easy! God did it!......... ok now that is out of the way...


I would like to think that Size what affects the whole Revolution/Rotation and Tidal Lock.

Some Asteroids(spherical) are too small to have their own strength against a planet, so the planets controls it.

When something is big as a moon(ratio to earth)...Earth slightly wins against the gravitational force, thus, Moon revolves around earth, yet, moon is quite larger than an average asteroid, thus it still wants it its way, so we have have 2 forces meet and one force is slightly weak thus we have the tidal lock.

Well that's my look on it.

Originally posted by wmd_2008

Well here we go another science expert on here that's not a scientist

Science DOESN'T just offer theories if science was so wrong guess what YOU would not have been able to post this thread because we would have NO computers or internet.

Science offer many great insights of practical value. I love science but also have come to see its limitation. A scientist may not be happy when his field is criticised but sometimes it is warranted. We will only find those instances if scientists are willing to address the questions raised by outsiders.

I don't see the need to complicate things with oceans, friction, vectors, etc. The simple fact is that the side of the Moon nearest to Earth experiences greater force of attraction than the opposite side. When, in the past, the Moon rotated faster, this difference created a torque that slowed the rotation down.

The Earth hasn't locked to the Moon because it's a lot more massive and requires stronger force to slow down. But this process is "helped" by the tidal bulge of the oceans, which the Earth carries away from the direct Moon-Earth line as it rotates every 24 hrs, and this creates additional torque on our planet. The Earth's spin is slowing down, and this has been measured. This process also boosts the orbital speed of the Moon, causing it to move further and further away from us.

Originally posted by ThinkingHuman
Thanks for your response (and all the others). Yes, the rocks "want" to assume whatever orbit or path that gravity pulls them. But if they are attached, they cannot. They may break up at some point but this is, for each rock, a one time event.

Remember in the thought experiment, one rock was on the far side, one on the near side. Since they're orbiting at different radii, the outer one would want to go more slowly, the inner one more quickly. They'd immediately diverge. This is what I was talking about when I said they'd "want" to assume different orbits. That force is constant and ongoing for something like the moon orbiting the earth. If you slice the moon in your head in a number of disks on a line radial from the center of the earth through the moon, each slice will want to orbit at a different speed, because they're at different orbital radii. Since they can't, as the moon is held together by gravity and the rock's tensile strength, this tendency to orbit at different speeds leads to a deformation force.

This is what gives rise to tidal forces (it's an oversimplification).

Tidal and buoyant forces used to mess with my head. It's sort of contrary to what you expect.

Originally posted by Bedlam
This is what I was talking about when I said they'd "want" to assume different orbits. That force is constant and ongoing for something like the moon orbiting the earth. If you slice the moon in your head in a number of disks on a line radial from the center of the earth through the moon, each slice will want to orbit at a different speed, because they're at different orbital radii. Since they can't, as the moon is held together by gravity and the rock's tensile strength, this tendency to orbit at different speeds leads to a deformation force.

The document you linked put it this way, bottom of page 76: Away from the center of mass, the centrifugal acceleration remains constant, whereas the gravitational acceleration increases with increasing z. Hence, at positive z, the gravitational acceleration is larger than the centrifugal, giving rise to a net acceleration in the +z-direction. Likewise, at negative z, is larger than the gravitational, giving rise to a net acceleration in the −z-direction.

I think this is the same phenomenon you are referring to. It seemed to be a beautiful explanation of "tidal elongation" when I read it but this can only apply to a moon, not to earth. I would be willing to go along with it, except we cannot confirm that the model is accurate for our Moon because of the absence of water tides. And we cannot confirm this model to be accurate for the earth because the same forces do not apply. The only Moon-force that applies to the earth tides is Moon gravity, not a centrifugal force of earth rotating around the Moon.

The centrifugal force caused by the rotation of the earth is a different issue and continuously balanced by the gravitational force of earth. I am aware that earth and Moon rotate around a common center of gravity but this is a 28 day cycle, not a daily one.

Originally posted by ThinkingHuman
I think this is the same phenomenon you are referring to. It seemed to be a beautiful explanation of "tidal elongation" when I read it but this can only apply to a moon, not to earth.

Look at page 77, near the top.

second line

Originally posted by Bedlam
Look at page 77, near the top.

second line

Second line says: It follows that the mass distribution m is subject to a residual acceleration, represented by the second-order variation in Equation (6.58), which acts to elongate it along the z-axis. This effect is known as tidal elongation.

That is still part of the explanation for tidal elongation that I also referred to, and which agrees with what you said.

It says that the elongation is due, not to gravity by itself, but to the difference between gravity and centrifugal force. Those two forces are equal in size at the center but their amounts are, at the closest and furthest points, different from each other - but in opposite directions. Therefore the elongation.

This makes sense but even the line you pointed out does not address what I said, that the earth is not subject to centrifugal force with regards to the Moon. Only the Moon is subject to centrifugal force relative to earth because it is in earth's orbit.

Earth should not experience elongation, at least not because of a difference between gravity and centrifugal forces.

Interesting thought. Why is the moon tidally locked to the Earth, yet the Earth is not tidally locked to the Sun?

The tidal force between Earth and Moon is stronger than the tidal force between Earth and Sun.

One possible answer is that we completely misunderstand Gravity.
We can calculate Gravity or the likely behaviour of Mass in our locality, and all of the calculations seem to predict accurate outcomes, but because we cant see the source we confuse a Force with an Effect.

It is entirely likely that Space itself provides a gradient (based on it's density or quantum state )which provides us with the effects of gravity.

At the centre of each planet there is probably an irregularity in Space (density or phase change) which provides an energy sticking point which forms matter and subsequently mass.

If the Space Gradient between these irregularites in Space (distance between Planets, Moons etc ) is in fact the driving force behind the effects we perceive as Gravity, we might indeed see the effects you describe.

The earth is manifested within Space and the space around it (with all its Quantum irrgularities) effects the surface of the planet as the surface (and everything else) is in fact just a number of quantum correlations that average out to provide us with the world we perceive with our senses and sensors.

These averaged out effects would appear very strange to us but then we look at the chaotic worlds of Weather, Tidal Effects, Quantum Effects, Plate Tectonics etc etc and there are so many unexplained facets it seems possible.


The strangeness of this is only overshadowed by the statisitcal unlikeliness of these quantum effects averaging over to provide an eden such as the Earth with its Magentosphere, protective planets, warming yet stable core, position in relation to Solar, Galactic effects etc etc etc

I understand we are a product of the environment but that environment does seem remarkably well tuned given the almost infinite levels of random events that needs to occur for us to be able to evolve to understand.

Originally posted by Jukiodone
One possible answer is that we completely misunderstand Gravity.

That is possible. Do you have a different suggestion? Curved space? Separate dimension? If others disagree with you, that is okay, we still have the right to express, disagree and STILL respect each other.

So please have the guts to expose yourself to criticism, let us know what is your understanding?

Originally posted by wmd_2008
Well here we go another science expert on here that's not a scientist

Science DOESN'T just offer theories

Since you are such an expert in Science, can you provide a scientific explanation for the two tides on earth?

Bedlam tried by referring to a document prepared by a Physics Professor. But that one did not do the job, so it seems that Bedlam gave up on trying.

If science has no clue about what "tides" do on earth, scientists certainly cannot claim that they "know" how they work on a Moon where they cannot be observed ! And that "tidal forces" cause the rotation lock.

What did you say was the scientific method, did that not include observation?