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Originally Posted by kilopi
Originally Posted by Tensor
No "force" is required.
It's a fictional force, but it's a force nonetheless. It's certainly as real as centrifictional force.
Ya'know, I took that out, put it back, took it out, and finally put it back in. I should have just left it out, as you are right, it is a foce, albeit fictional.

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Originally Posted by Gary Redmond
Tensor Thank You.
This has come up more than once, and I believe it needs to be worked on.
Originally Posted by Tensor
"General Relativity describes the tides (in simple terms) as a stretch of spacetime in the direction of the moon or sun and a squeeze at 90 degree angles to that direction"
Questions:
I'll take a swing at answering you, although I am still quite new at
trying to explain GR.

Originally Posted by Gary Redmond
An effect such as the tides must require a cause?
Let me turn it around, are you saying that there is no cause for the tides ?

Originally Posted by Gary Redmond
If no "force" is required, what is the cause?
See my answer to Kilopi. Yes, there is a what you could call a force.

Originally Posted by Gary Redmond
Is it my understanding that the stretch you discribe comes from the gravitational mass of the oceans and is directed toward the "moon or sun"?
Not really. It is the mass of the oceans reacting to the spacetime curvature caused by moon or sun's mass. The earth itself also feels the squeeze and stretch which produces tides on the earth itself, not just the oceans.

Originally Posted by Gary Redmond
The "90 degree squeeze", is that like a rubber band constricting a cone?
Not really. It more like if you have a rubber ball or Nerf ball. Imagine you are the sun or the moon. The middle of the part of the ball you are looking at is the front. Now squeeze each side and the top and bottom at the same time. You will find the front and the back of the ball stretches toward and away from you. Remember, this is an inexact analogy as the squeeze caused by the spacetime curvature is much smother than you can apply to the ball.

Originally Posted by Gary Redmond
Do you have a source for the squeeze other than perhaps the Earth's own constricting mass?
Yes, the moon and sun's gravity curve spacetime. That curvature manifests itself as a stretch in the direction of the moon or sun and a squeeze at 90 degree angles to the direction of the moon or sun.

Originally Posted by Gary Redmond
That would make it more of a squirt than a squeeze would it not?
Well, lets say the squeeze causes the squirt, how's that?

Originally Posted by Gary Redmond
It has been my position since my first post using the Newtonian Law of gravity that the direction of the force is from a mass (the oceans) toward some mid point in the direction of a second mass (moon or sun) or towards the center of the second mass (moon or sun).

Originally Posted by Gary Redmond
The encyclopedias credit the secondary masses as being the cause of the tidal motions.
Yep, if the seconday masses are not there, there would be no tides.

Originally Posted by Gary Redmond
I still say that the tides are caused by the Earth and Earth's oceans, not the bodies to which they attract.
Nope, it's a reaction to the curvature of spacetime caused by the moon or sun.

Originally Posted by Gary Redmond
It shouldn't matter whether gravity is a force, or if it just warps spacetime. It is the source of the gravity, which is the cause of the tides whether that gravity is a force or not.
You're right, it is the source of gravity that causes the tides, but that source is not the earth. The moon and sun cause the curvature of spacetime that the earth moves through. And, as it moves through that curvature, it experiences the stretch and squeeze that causes the tides.

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Originally Posted by Gary Redmond
Solid fuel rockets have some sort of nozzle or engine.
After doing some inquiries, I learned that you can indeed speak of the engine of a rocket. Naturally, this is quite a different beast from an internal combustion engine.
But in the end it makes no difference. Both cars and rockets move according to the same effect: the Principle of Action-Reaction, or Newton’s Third Law. This is in fact a good example to think about. Would you say that the rise of a rocket is caused by the fuel pushing the rocket, or by the rocket pulling itself up?

Originally Posted by Gary Redmond
Without the friction the direction of the cars exhaust pipe will push like a jet engine.
I can’t understand what you mean by that.

Originally Posted by Gary Redmond
I had said the oceans mass several times before, I just got sloppy. I have tried to edit carefully, but sometimes I have to be human.
I have found several places in this book of Newton's where he does similar things. He too was human.
It’s quite possible that Newton used different terms than we currently do. After all, he was writing three centuries ago. But you have no such excuse.

Originally Posted by Gary Redmond
When Newton explained how a "corpuscle" attracted a large body or mass of particles, the resultant of all the separate forces made the large mass become a single point or the center of gravity of the mass.
So the sneaker doesn't particularly attract a Moon-rock. Nor does a Moon-rock attract the sneaker. The sneaker does however attract the Moon's center of gravity, as does the Moon-rock the Earth's center of gravity. The individual particles of one body attract the whole of the other.
You are talking about when Newton showed that a solid sphere of constant density is equivalent to a material point placed on the sphere’s centre of gravity. This is true and important, but it does not tell you anything about the nature of the sphere. It’s only a mathematical result that facilitates computation. It does not mean that a sphere like the Earth is a point, only that it can be replaced by one in certain calculations.
Besides, what does that have to do with tides?

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Tensor, because I asked all the questions let me start here. For every action and reaction there is a cause, or force. That force is often very obscure. The encyclopedias say that the Moon and Sun are the cause of Earth’s tides. (As you seem too)
Originally Posted by Tensor
Nope, it's a reaction to the curvature of spacetime caused by the moon or sun.
I disagree! Here is why.
The Moon has only a small fraction of the Earth's mass, and the Earth only a tiny fraction of the Sun's. To place the Moon and Sun on equal footing as the cause seems a little unfair. The Moon rocks that fell to the Moon at some time, and then were brought to Earth, can now fall to the Earth. Those rocks have gravity; they attract themselves to which ever body they can.
Each particle of each atom of the oceans attract or pull or distort their own spacetime, I believe those particles have the same force (gravity) as the luminaries and that they have the capability to cause their own motion. Like the rocks they attract whatever they can.

Originally Posted by Musashi
I would say that, if the first statement is true, than the second statement is false. It seems that the tides are caused by the attraction between the oceans and the Moon and/or Sun. Not one or the other.
Very good!
"The Universal Law of Gravity" is usually interpreted as a mutual attraction.
If your observation (a mutual attraction) is true, then are the encyclopedias correct when they say the tides are caused by the Moon and/or Sun?
I say no! If the cause is mutual (single force between them) then to specify one or the other is wrong. The cause would be the single force of gravity, located somewhere between them, and belonging to neither. "Newton's Book I, PROPOSITION 61. THEOREM 24" (see my post of 01 Nov 2003) used an imaginary third body that third body became the hitching post to which each of the two bodies in question moved or was attracted. Back on the first page the third post of this thread Cougar described his calculus method, that method is similar to Newton's in that the center of gravity of the two bodies became the point to which the bodies attract themselves.

Originally Posted by kilopi
I have decided, for myself, that one can accept a point of view such that one can say that the encyclopedias are wrong, but then one also has to say that you are wrong too.
A Great Philosopher once said “ “.
Originally Posted by kilopi
So, you're saying that the Earth can attract the water, but the Sun and Moon can't? That's being inconsistent, on your part.
No that is not what I said.
Originally Posted by GR
I still say that the tides are caused by the Earth and Earth's oceans, not the bodies to which they attract.
To attract or pull or contract or implode is a one-way street or force, if the one (attract) force happens to one body, the body may get smaller in volume. Hence Earth's spherical shape and high density.
If that single force happens between two separate bodies, we than have an action and reaction in opposite directions. In the case of attraction the bodies move toward each other. The Earth and Moon fall around or toward each other.
Now for the fun part, we must assign blame or name the cause.
The tides or (particles of the oceans), move or “tend” toward the luminaries or (sun and moon). We have two bodies, tides and luminaries moving in opposite directions. That means there is at least one force to be named or blamed as the cause. The encyclopedias single out the luminaries. I feel that is incorrect.
I say:
The oceans “corpuscles” “attract” the Earth and the “luminaries“.

If my 9 year old grandson goes to the encyclopedia he shouldn't be misinformed. Nor should he have to go through all this junk to find a real cause. As adults it is our job to right the wrongs (if we can) not to perpetuate them because of indifference or worse. It appears that most everyone here knows "The Universal Law of Gravity". It states that any two bodies attract each other. It does not say that only (one body) or only the (other body) attracts. Nor does it say that (both bodies) are attracted by a single mutual force, although Newton used that idea, and Cougar uses a similar method.
The "Law" says "(two bodies) attract (each other)".
Both bodies have gravitational force.
Either body can be the cause of something.
From "Newton's" "Book I, PROPOSITION 61. THEOREM 24" (see my post of 01 Nov 2003) I am convinced that Newton felt that each body was the cause of its own motions; even though the motions appear to be caused by the attraction of an imaginary third body.

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Originally Posted by informant
Would you say that the rise of a rocket is caused by the fuel pushing the rocket, or by the rocket pulling itself up?
This is about a push not a pull force.
When combustion takes place within the rocket the expansion of the gas forces the combustion bi-products out of the rocket. The combustion is the force. The equal and opposite reactions are the rocket and the bi-product (junk). The higher the velocity of the junk the greater the efficency of the engine.

Originally Posted by informant
G R wrote:
Without the friction the direction of the cars exhaust pipe will push like a jet engine.
Originally Posted by informant
I can’t understand what you mean by that.
A jet engine doesn't carry an oxidizer, its combustion needs the air through which it passes. Yet like the rocket, the junk or bi-product of the combustion is the other half of the action reaction.
The very low velocity and junk emision of the car exaust would push under zero friction conditions.

Originally Posted by informant
It’s quite possible that Newton used different terms than we currently do. After all, he was writing three centuries ago.
Newton also wrote in Latin and this book is in English so there has been a couple of translations. As for being human I don't find that an excuse, to not admit it is.

Originally Posted by informant
You are talking about when Newton showed that a solid sphere of constant density is equivalent to a material point placed on the sphere’s centre of gravity. This is true and important, but it does not tell you anything about the nature of the sphere. It’s only a mathematical result that facilitates computation. It does not mean that a sphere like the Earth is a point, only that it can be replaced by one in certain calculations.
Besides, what does that have to do with tides?
When an H2O molecule of the ocean looks up at the Moon it attracts itself to all of the Moon as if the Moon was a single point. It then accelerates itself over, under, around, or through whatever it must to try get to that point.
When an object on the Moon looks at or attracts the Earth it is as if the Earth were a single point.

PS how do we get subscript 2's

6. Originally Posted by Gary Redmond
When an H2O molecule of the ocean looks up at the Moon it attracts itself to all of the Moon as if the Moon was a single point.
When water looks at the moon??
It then accelerates itself over, under, around, or through whatever it must to try get to that point.
When an object on the Moon looks at or attracts the Earth it is as if the Earth were a single point.
That is just false.

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Originally Posted by Gary Redmond
Tensor, because I asked all the questions let me start here. For every action and reaction there is a cause, or force. That force is often very obscure. The encyclopedias say that the Moon and Sun are the cause of Earth’s tides. (As you seem too)
You're right here, I agree with the encyclopedias. What you don't seem to realize is the tides, using Newton's laws, are caused by the difference in gravitational attraction across the width of the earth (as I mentioned, in GR the tides are caused by the strech and squeeze of spacetime. But, it is much easier to calculate using Newton's laws). I noticed that you didn't have any comment on Donnie B's post on the first page of this thread. Would you please go back, read it, and then comment on it?

Originally Posted by Gary Redmond
Originally Posted by Tensor
Nope, it's a reaction to the curvature of spacetime caused by the moon or sun.
I disagree! Here is why.
The Moon has only a small fraction of the Earth's mass, and the Earth only a tiny fraction of the Sun's. To place the Moon and Sun on equal footing as the cause seems a little unfair.
Well, you're right. The sun and moon are not on equal footing, the moon's tides are a bit more than twice the sun's tides (on average).

Originally Posted by Gary Redmond
The Moon rocks that fell to the Moon at some time, and then were brought to Earth, can now fall to the Earth. Those rocks have gravity; they attract themselves to which ever body they can.
Originally Posted by Musashi
I would say that, if the first statement is true, than the second statement is false. It seems that the tides are caused by the attraction between the oceans and the Moon and/or Sun. Not one or the other.
Very good!
"The Universal Law of Gravity" is usually interpreted as a mutual attraction. If your observation (a mutual attraction) is true, then are the encyclopedias correct when they say the tides are caused by the Moon and/or Sun?
I say no! If the cause is mutual (single force between them) then to specify one or the other is wrong.
Look at it this way, the earth's mass is approximately 5.983 X10^24 Kg (I know Kilopi, but I'm quite sure that we will never get this one exact :wink: ). If you take a 1 Kg piece of rock and hold it 1 meter above the earth. Now let it go. There is a mutual attraction between the earth and the rock. But the earth moves 5.983x10-24 meters and the rock moves 1 - 5.983x10^-24 meters. Now can you honestly say that as far as you can tell, the rock didn't fall 1 meter? The only reason someone says the rock falls to the earth is that the distance the earth moves can only be calculated, but not really measured.

edited for grammar

8. Originally Posted by Tensor
I know Kilopi
I know him too.
Man, I wish my Bluewave tagline manager worked here.
Would he work cheap?

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Originally Posted by GrapesOfWrath
Originally Posted by Tensor
I know Kilopi
I know him too.
So I've heard. :wink: Haven't seen you around here in a while, is this going to be a trend?
Originally Posted by GrapesOfWrath
Originally Posted by Tensor
Man, I wish my Bluewave tagline manager worked here.
Would he work cheap?

10. Haven't seen you (GoW) around here in a while, is this going to be a trend?

Only if he finds a way to keep his post count at 3142... 1,000 x pi...

(Which, since he also found a way to post a reply before the question, is probably do-able.)

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NEWS FLASH

I have finish absorbing the "Principia", and I have found what I was looking for.

• BOOK THREE
SYSTEM OF THE WORLD
RULES OF REASONING IN PHILOSOPHY
RULE III
[list:62b588cde4](Paragraph 3 Sentence 1)
[/list:u:62b588cde4]
Originally Posted by Sir Isaac Newton
• Lastly, if it universally appears, by experiments and astronomical observations, that all bodies about the earth gravitate towards the earth, and that in proportion to the quantity of matter which they severally contain; that the moon likewise, according to the quantity of its matter, gravitates towards the earth; that, on the other hand, our sea gravitates towards the moon; and all the planets one towards another; and the comets in like manner towards the sun; we must, in consequence of this rule, universally allow that all bodies whatsoever are endowed with a principle of mutual gravitation.
• It is evident beyond doubt, from the above, that Newton realized the tides were caused by their own possession of the force of gravity. The tides are not caused by the Moon and Sun.
The tides are in-fact or "on the other hand," caused when "our sea gravitates" (attracts itself) "towards the moon".
Newton’s above statement seems to stem from the Earth centered universe concept. He starts with the explanation “that all bodies about the earth gravitate towards the earth”. He includes “the moon likewise” as one of the things which gravitate “towards” the earth. But then, he gives the tides as the first example of something attracting toward another body, with “our sea gravitates towards the moon”.

Gary Redmond

12. Originally Posted by Isaac Newton, in the [i
Principia[/i], Book III, Proposition V, Theorem V, Corollary 3,]All the planets do mutually gravitate towards one another, by Cor. 1 and 2. And hence it is that Jupiter and Saturn, when near their conjunction, by their mutual attractions sensibly disturb each other's motions. So the sun disturbs the motions of the moon; and both sun and moon disturb our sea, as we shall hereafter explain.

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Originally Posted by Tensor
I noticed that you didn't have any comment on Donnie B's post on the first page of this thread. Would you please go back, read it, and then comment on it?
Certainly!
Donnie B. made two posts on page one.

Originally Posted by Donnie B. 1
If the oceans had no mass, they'd fly off in all directions at the speed of light. And we'd all get very thirsty.
AND
Originally Posted by Donnie B. 2
Frankly, GR, I don't see what the big deal is. The entries on the tides are somewhat simplified, sure, but they aren't there to explain gravity. There's another entry for that.

Look at it this way: assume for a moment that there is no Moon or Sun -- nothing, in fact, except the Earth (magically kept warm enough for the oceans to remain liquid). Now there are no tides, right? Earth still has gravity, so it keeps the oceans in place, a nice smooth "water plating" over the crust. That's the "first-order" effect: Earth's gravity holds the oceans down.

Now add in a Moon. All of a sudden we get tides, because now we have gravitational gradients across the diameter of the Earth. This is, technically, due to the gravity of the Earth and Moon acting on each other, but the difference -- the second-order effect of ocean tides, as opposed to the oceans being held quietly in place by Earth's gravity -- is due to the presence of the Moon.

Hence, we can say (in shorthand) that the tides are caused by the Moon's attraction.

Now add in the Sun... same argument. The third-order solar tides can be attributed to the Sun's attraction.

What's so terrible about that? Do you expect encyclopedias to be as thorough as a Physics text?
In the first of those posts it was said that "they'd fly off in all directions at the speed of light". For that to happen there would need to be a source of force causing the acceleration to that speed. Because I had removed the mass there would be no reaction to the action, all considered my silliness followed by more silliness didn't require comment.
The first sentence of that second post is the part to which I did respond.
Originally Posted by Donnie B.
"Frankly, GR, I don't see what the big deal is."
I will repeat my response not in quotations, but in some detail. I truly wish to explain what the "BIG DEAL IS", but I must have some agreement as to where the force that accelerates the oceans, which causes the tides comes from.
Originally Posted by Later in that post Donnie B.
"Earth still has gravity, so it keeps the oceans in place, a nice smooth "water plating" over the crust. That's the "first-order" effect: Earth's gravity holds the oceans down."
That is wrong.
The Earth is composed of trillions of particles. Each of those particles has the property of gravity. Each of those particles attracts itself to each and every other one of those particles. The ocean holds itself down.
That is the "first-order" effect.
As I said, the moon-rock that fell to the Moon, and was brought to earth, is now free to fall to the Earth. It is the Rock which has the force. Without that force the Rock could not fall in either place. Without that force the ocean could not have a tide.

I do not expect encyclopedias to be as thorough as a Physics text, they just need to have the direction correct and place the cause at its proper location, not 240,000 or 93 million miles away.

I will try to say it again.
The oceans particles, consisting of mass, have the property of gravity.
Having that property those particles attract the remaining particles of the universe.
The inertial resistances of the particles (both ocean and universe) determine the action/reaction motions to that attractive force.
The gravitational forces of the oceans are the cause of the tides.
To clarify or make that more precise, you can say the cause of the tides is the oceans own attraction by gravity towards the Moon and Sun.

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Eroica
Thank you.
This is exactly what I was talking about when I said Newton was also human. He repeatedly jumped back and forth with the direction of the force. In his explanation of the tides I almost got the feeling that he had copied the work of others. In Book III Proposition 24. Theorem 19, he mentions observations of Colepress and Sturmy, also Dr. Halley. He also made the miscalculation that the moon was denser than the earth and a few other minor errors, but the majority of his book is excellent.

If we use the same reasoning he did, we also must come to the conclusion that all particles of matter or of mass have the property of gravity.
The oceans consist of particles having that property, which is the property of attraction.

From that we have to logically also reason that the oceans attract or pull on every other particle in the universe, including those of the moon and sun. If we also reason and calculate inertia and mass volume of the sun and moon, then relate that to the mass of a water droplet we can estimate the action-reaction. From that we find the oceans to move toward the moon and sun. Thus we have tides.

If the moon and sun had equal volumes of liquid water they would have tides of similar proportions. The sun tides and moon tides would not be caused by the earth they would be caused by their own attractions.

As I explained to Tensor, the moon-rock that fell to the Moon, and was brought to earth, is now free to fall to the Earth. It is the Rock which has the force.
The oceans have tides because the oceans have the force of gravity.

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Gary,

1. You don't want to understand the current thought concerning the nature of of mass, gravity, or how they interelate or react to each other. You have your own ideas on the matter and won't give up those ideas.

2. You now understand, but don't want to admit you were wrong.

3. You came here just to provoke those that post here.

If it is one of the first two, there is no reason to continue trying to explain things as you will not change your mind. Concerning the third, it falls under the catagory of "Don't feed the trolls". So I leave you to your posts.

16. Originally Posted by Gary Redmond
The tides are in-fact or "on the other hand," caused when "our sea gravitates" (attracts itself) "towards the moon".
There's a problem. Newton uses "gravitates" but you insist that that means "attracts itself". I couldn't find a dictionary that agrees with you. Do you have one that does?

Or is it not only the encyclopedias that have it wrong, but the dictionaries too?

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Originally Posted by Tensor
After reading your reply to Eroica and rereading the rest of your posts on this matter, I have to come to believe one of the following: 1, 2, and 3
Thank you for your contributions; if you are truly gone you'll be missed.
Originally Posted by Tensor
You have your own ideas on the matter and won't give up those ideas.
That statement is absolutely correct. I am quite sure I understand the currently taught basic physics and that I have a good handle on most of Einstein's work although some of the math is over my head. I feel my ideas have been very carefully assembled from the facts, and they are correct in every way to those teachings. I have spent nearly a year researching this and I can find nothing to prove my ideas wrong. Instead everything seems to confirm my accusation. All the facts are the same it is only the conclusion which is different. As you may have noticed no one has given a real reason why I might be wrong other than the encyclopedias say the Moon and Sun, are the cause and I say the oceans are the cause, which that was my original position.

Let me try this again.
Originally Posted by My Physics book
"Newton's law of universal gravitation states that any two bodies in the universe attract each other with a force that is directly proportional to the product of the masses of the two bodies and inversely proportional to the square of the distance between them."
AND
Originally Posted by Here is what Newton
Book III
PROPOSITION 8. THEOREM 8
"In two spheres gravitating each towards the other, if the matter in places on all sides round about and equidistant from the centres is similar, the weight of either sphere towards the other will be inversely as the square of the distance between their centres."
This is perhaps where we (surely) part ways. I say that, this Physics Book is incorrect (WRONG) in having misstated that law in that manner. I don't believe that is what Newton said or meant, and I am sure from a logical stand point it is very WRONG.

This particular Physics book says "attract each other with a force" hopefully you can see and understand how that indicates a singular force located (perhaps) somewhere between the two bodies. That is very very WRONG!
Newton on the other hand specifically states that "two spheres gravitating each towards the other", or he spells out in that fashion that each of the two bodies has the force of gravity, and that one body uses that force to move or attempt to move towards the other body, and the other or second body does likewise, each body with its own force (or forces). Newton also explained how subdividing the sphere (or body) proportionately divides its force. (If you grind a stone to dust the dust still has the force of gravity.)
The gravity between two bodies is not a singular force, but the forces number near infinity in quantity.
I'm certiam that not all Physics books have that law written incorrectly, but this one surely does. You must understand that every author of books tries to do it a little different to not plagiarize and get the copyright to make the buck. Sometimes authors get it wrong.

Originally Posted by kilopi
Or is it not only the encyclopedias that have it wrong, but the dictionaries too?
I just showed my physics book wrong, but my dictionary seems to have the word gravitate correct. My dictionary says the word gravitate is often used with the word 'to' or 'toward'. If you go to a party and you "gravitate to" the punchbowl, were you the cause or was the punchbowl the cause of the gravitation. The mental (non physical) part was the punch attracted you, but the physical part or cause is the source of the force, which brings about the motion. You or more specifically your muscles were the source of the force which moves you (your body) across the room to the punch. You gravitate to the punch.
The first dictionary definition I have for the word gravitate is:
Originally Posted by The American Heritage Dictionary New College Edition
1. To move in response to the force of gravity.
Newton said, "our sea gravitates towards the moon;" or our sea moves in response to the force of gravity towards the moon.
In that statement of fact, Newton did not say where that gravity came from or give a cause other than perhaps gravity itself. He did however say what moved, in which direction it moved, and perhaps by what type force it was moved. So the questions then become or still are; where does the gravity come from, what is its source, or the cause of the tides is what.
To answer that you must go to the "Universal Law of Gravity", which I just, explained to Tensor if he is still listening.
That law according to Newton is "two spheres gravitating each towards the other". In other words both bodies have the force. So once again we are not given a true answer as to the source or cause.

Isn't that correct?

For the true source of the force we must turn to Newton's second law of motion.
Originally Posted by My (bad) Physics Book
If an unbalanced force acts on a body, the body will be accelerated; the magnitude of the acceleration is proportional to the magnitude of the unbalanced force, and the direction of the acceleration is in the direction of the unbalanced force.
Originally Posted by Or Newton
LAW II
"The change of motion is proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed."
We know (as Newton knew) the sea or oceans move toward the Moon and Sun, the acceleration is in the direction of the luminaries. The direction of the unbalanced force, or direction in which the force is impressed, is the direction of the acceleration.
All the above having been said I can only assume the force to move from a greater or stronger source to a lesser source.
That makes the sea the greater source. Therefore the tides are caused by the sea when the sea gravitates itself, or attracts itself to (or towards) the moon, using the force of gravity, which it has.

Originally Posted by This PHYSICS BOOK (regarding the law of gravity)
'This law describes both the magnitude and the direction of the force. The direction of the force is somewhat hidden in the word "attract" in the statement of the law. The direction is made somewhat clearer (if wordier) by recognizing that "attract" means that a body exerts a force on another body that is directed back to the first body along the line joining the two bodies.'

In the above drawing from the Physics Book, the sources of the gravitational forces are the masses M and m. It is not a singular force located between the masses. The direction of the force is from each mass toward the other mass (see the drawing).

Therefore I must once again repeat my statement that the encyclopedias are wrong. They have the direction of the force reversed when they say the luminaries cause the tides.
The oceans (or seas) have or possess the force of gravity, and that force is the true cause of the tides.

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## push to top

so i can find this 1?

PS the Moon(ey) problem I have is to explain why there exists a delay in time
between the day the SUN EARTH &amp; MOON all align (New Moon Full Moon)
and the day upon which the Clam tides occure around here..
{tht is to say WHEN THE MAX - {LOW} tide occurs

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tides are caused by differential gravitation.

You probably saw a picture like this simple one:

&lt;---Earth--->__________&lt;----Moon

Correct?

Where the arrows indicate the direction and magnitude of the forces in play. The ___________Are for spacing.

The real forces at play are a little different than that picture even.

The moon pulls on the near side of the earth harder than any other part, because it is closer (and gravity is stronger as the distance shrinks).

It then pulls on the center a little weaker still (since its further)

And it pulls on the far side the least.

So the forces look like:

-->E 0----> E------>______________&lt;----M

Where E is the edge, 0 is the center, and the arrows point in the direction (and length indicated magnitude) of the forces at play here.

For the net forces, we use a "geocentric" system, basically using the idea that the earth is stationary, or close enough, for our concerns. Espeicially since we want to see how the tides move, relative to the EARTH, and not something else, this is a valid choice.

So we subtract the force on the center of the earth, from the edges. This makes the NET force, if the earth is "stationary", to look like:

&lt;-- E-->

This shows the "apparent" forces, that produce the tides.

In reality it is merely the moon pulling the near side of the earth away from the center. And it pulls the center away from the far side. This creates a bulge towards the moon, and a bulge on the opposite side (since it lags behind, like your head experience whiplash in a collision).

20. Guest

## Sounds correct {I guess}

My #1 Lunar question was ? Why the Clam tide {Max -} does not occur
on the exact same day as the Full or New Moon
-----------------------------------------------------------
but lags some {maybe it even lags a full 1/2 lunar phase+
but even i kind of doubt that.
======================================
however it doeth 4me raise the nother question
how dothe A Person know the tide is NOT being caused by
:::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::
the Previous alignment and not by the current one
or {even the one prior to that {preNulltamate}/?/?/?/ ?
HU?

21. Established Member
Join Date
Apr 2004
Posts
588
clam tide?

I don't know of that type. I've heard of spring tides, where the moon's conjuction an opposition (new and full phases) make the tides more extreme, and Neap tides, where the moon is in a quarter phase, thus making the tides weaker.

If there is a delay, it should only be the standard offset of all tides, due to the inertia of the water, and earth's rotation.

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