Newton also predicts Gravity Waves

[MetaFrizzics]

Yes. Since the Centre of Mass 'method' and Sphere Theorem are only approximations, they also implicitly predict gravitational waves. Therefore the existance of GW is not a strong proof for General Relativity.

 

Comments?

 

Next he'll say Newtonian gravity bends light too!

[ydoaPs]

could you please elaborate how newton predicts gravity wave?

[MetaFrizzics]

For instance,

 

(1) the Centre of Mass 'method'/approximation says that a spinning, free-falling non-spherical body acts as though its mass were concentrated at its centre.

 

(2) However, the error in the approximation means that a rotating body presents a fluctuating gravitational force upon all nearby objects, oscillating at the frequency of relative rotation to the nearby object.

 

(3) The fluctuating force exerts a stress and does work on the surrounding objects. This causes micro-variations in the location of mass nearby when the field strength of the nearby object is large in comparison to neutralizing or averaging counter-forces.

 

So what this guy is saying is that nearby spinning objects act as inexpensive vibrators!

[timo]

Since the Centre of Mass and Sphere Theorems are only approximations, ...

I know what a center of mass is, I know what a sphere is and I know that spherical symmetric mass distributions (outside the distribution) have a gravitational field as if the whole mass was in the center of mass. I do not, however, know about a "center of mass theorem" or a "sphere theorem". What is that supposed to be? The thing about spherical symmetric masses I mentioned above? Afaik, that´s no approx.

 

... they also implicitly predict gravitational waves.

What is a gravitational wave and how is that predicted by these "theorems"?

 

Therefore the existance of GW is not a strong proof for General Relativity

.

Newtonian Gravity has is ruled out by a) the light deviation and b) the non-elliptical orbits of planets. Both effects can also be explained with Newtonian Gravity but with incorrect numbers.

I can not see how the point that Newtonian Gavity predicts gravitational waves (regardless whether it acutally does or not) affects the implication of their existance for GR.

[timo]

For instance' date='

 

(1) the Centre of Mass 'method'/approximation says that a spinning, free-falling non-spherical body acts as though its mass were concentrated at its centre.

 

(2) However, the error in the approximation means that a rotating body presents a fluctuating gravitational force upon all nearby objects, oscillating at the frequency of relative rotation to the nearby object.

 

(3) The fluctuating force exerts a stress and does work on the surrounding objects. This causes micro-variations in the location of mass nearby when the field strength of the nearby object is large in comparison to neutralizing or averaging counter-forces.[/quote']

 

The Newtonian gravitational potential of a particle at position p is something like V(x)=Gm/|x-p|. I can´t see where the velocity of a particle should play a role in there.

EDIT: And since you say "non-spherical" body (didn´t read it the first time). Yes, the center of mass approximation only works for sufficiently large distances, then. As a matter of fact, the non-elliptical orbits of planets can be explained with taking into account that the sun might not be a spherical symmetric mass distribution (adding a quadupole term to the gravitational potential). It still leads to incorrect numbers as I allready said. Plus, it has nothing to do with gravitational waves.

[MetaFrizzics]

The Newtonian gravitational potential of a particle at position p is something like V(x)=Gm/|x-p|. I can´t see where the velocity of a particle should play a role in there.

Its not the velocity of the particle, but the angular velocity of a rigid system of particles that generates the radiation.

 

What kind of spin is he trying to put on this now?

[timo]

Ok, I see what you mean. But that´s nothing else than saying the gravitational potential changes because the point of mass generating it moves. Perhaps I could understand your statement better if I knew what a gravitational wave is supposed to be...

[MetaFrizzics]

Perhaps I could understand your statement better if I knew what a gravitational wave is supposed to be...

What is it that we want from a gravity wave?

A detectable effect. A transfer of energy (through field and/or particle exchange). And that's just what Newton gives us, if we'd only listen.

 

Balanced forces do no work. But unbalanced forces cause energy exchange and motion. Oscillating forces cannot be balanced, except by precise counter-forces or by drowning in a sea of random counter-force.

 

For instance, for a diatomic gas, Newton gives us the effect of a 'virtual particle with 720 degree spin without all the effort of Pauli spin matices etc. If only those German physics students like Heisenberg hadn't been 'Ocktoberfesting' so much, we might have been spared the grief of Quantum Mechanics.

 

What!?! Quit drinking? Drown this traitor!

[timo]

I know I can be a little pedant from time to time but can you be a bit more specific or elaborate more. I understand almost nothing in your last post. Only statement I understand the first paragraph. And considering that one, banging my head against a wall would classify as a gravitational wave because it has a detectable effect and transfers energy (even through a particle exchange if one really wants to treat it with QED).

I mean: You want comments on your statement that Newtonian Gravity predicts gravitational waves but you do not say what a gravitational wave is supposed to be - at least not in a way I´d understand.

[ydoaPs]

bubbles are only for use in GD.

[MetaFrizzics]

... Only statement I understand the first paragraph. And considering that one' date=' banging my head against a wall would classify as a gravitational wave because it has a detectable effect and transfers energy (even through a particle exchange if one really wants to treat it with QED).

I mean: You want comments on your statement that Newtonian Gravity predicts gravitational waves but you do not say what a gravitational wave is supposed to be - at least not in a way I´d understand.[/quote']

Well, suppose we glue a magnet on a rotating wheel. Most would sense that this is now a dipole antenna generating electromagnetic waves.

 

Similarly, a binary star cluster (two stars rotating) is supposed to generate gravitational waves. Now suppose the binary star pair are for all intents and purposes identical. We have no way of telling one star from the other. Although the pair rotates at one velocity (cycle), the gravity wave generated is actually twice the frequency, since half-orbits are identical states.

 

If such a mass system generates gravity waves, then obviously on a smaller scale so does a diatomic gas molecule.

[MetaFrizzics]

bubbles are only for use in GD.

Is that a serious offense? or just a misdimeanor? I am not trying to be funny, (at the moment anyway). I just thought a bit of spice could be fun.

[timo]

But in contrast to Newtonial Gravity, Electromagnetism is a relativistic covariant theory and has wave-equations (d´alambert field = source) as their field equations. Newtonian Gravity´s field equation is a Poisson equation (laplace field = source), if I remember correctly. I can´t see how wave-solutions are to pop out of this.

 

And even though I am risking to be repetitive: I do not think that anyone doubts that moving masses create a change in the gravitational potential in Newtonian gravity. I was just thinking that your were saying more than this, perhaps.

[MetaFrizzics]

And even though I am risking to be repetitive: I do not think that anyone doubts that moving masses create a change in the gravitational potential in Newtonian gravity. I was just thinking that your were saying more than this, perhaps.

I think I would say it this way:

Previous 'field-theory' formulations of Newtonian gravity are premature and fatally flawed. They have been made without looking far enough into the phenomenae actually extant, and without seeing the implications of fundamental axioms of Newtonian gravity itself.

 

If some of the side-effects and ramafications of Newtonian gravitational theory were analyzed more deeply, a different field theory/formulation would result.

So to answer your question, yes I think I am implying more than just the surface statements, and suggesting a second look at just what 'Newtonian' axioms require from a field theory.

[DQW]

Yes. Since the Centre of Mass 'method' and Sphere Theorem are only approximations, they also implicitly predict gravitational waves.

Would you please prove this statement ? It seems you are suggesting that the treatment of the gravitational field due to a spherical mass (of uniform densty) as that due to a point particle of the same mass is only an approximation.

 

Therefore the existance of GW is not a strong proof for General Relativity.

There is enough proof for GR outside of detecting Gravity Waves.

[DQW]

For instance, for a diatomic gas, Newton gives us the effect of a 'virtual particle with 720 degree spin without all the effort of Pauli spin matices etc. If only those German physics students like Heisenberg hadn't been 'Ocktoberfesting' so much, we might have been spared the grief of Quantum Mechanics.

Pauli Spin Matrices have nothing to do with a rotating diatomic molecule.

 

So, this thread is basically saying : "QM and GR are fundamentally flawed/redundant. Everything follows naturally from Newtonian Mechanics."

 

And in this "everything" you include electromagnetism as well, even though Newton knew nothing about the existence of such a thing as "a quantized charge" (not to say that he knew anything quantitative about charge itself).

[timo]

Would you please prove this statement [Newtonian Gravity predicting gravitational waves with whatever implications'] ?

You know, I´ve been trying to get some usefull information for 5 posts, now. But I´m getting bored with it. Perhaps you could take over?

[DQW]

Perhaps you could take over?

Hey, not so fast ! I'm not going to spend time here if all that follows are more unsubstantiated claims and rhetoric. Nor am I going to take the effort to prove Gauss' Law (which, according to the OP, should be wrong).

[MetaFrizzics]

Please, I think we can all stay calm for a few posts. Its just a theoretical chat in the classical mechanics section.

 

Let me take your concerns one at a time:

It seems you are suggesting that the treatment of the gravitational field due to a spherical mass (of uniform densty) as that due to a point particle of the same mass is only an approximation.

This is quite true and no real secret.

While the 'mathematical proof' for the Sphere Theorem is correct as a mathematical theorem, it naturally breaks down due to the discrete spacial quantization of mass.

I'll be happy to start another thread on this do demonstrate the point to anyone's satisfaction. But I won't make the effort either if you are just going to say something like, "well, okay, but so what. It's not important." If you think the Sphere Theorem is an exact and accurate physical theory (or law, or method), then say so now, so there is no humming and hawwing later.

 

The Centre of Mass concept will also be inevitably involved, so lets be clear on this too. It is admitted at this time to be an approximation (albeit a good one) even by introductory physics texts. My point will be that the error terms are inadequately quantified in current theory or at least standard presentations. And I will be happy to show just how wildly inaccurate and unpredictable the CM method is for gravitational forces. But if I do, don't just kiss it off as 'we know its an approximation'.

 

Both concepts fail in special cases (cases where QM effects become important), for different reasons entirely.

Pauli Spin Matrices have nothing to do with a rotating diatomic molecule.

Well, you are certainly right in that this just begs the question. It depends upon one's view of the causal explanation of Spin. By no means is this 'known' according to current QM theory. It is only described.

Everything follows naturally from Newtonian Mechanics."

And in this "everything" you include electromagnetism as well, even though Newton knew nothing about the existence of such a thing as "a quantized charge" (not to say that he knew anything quantitative about charge itself).

I think this is a bit unfair: if you read my posts so far more carefully, you'll see that I, like you think current formulations of Newton/Galilean Gravity theories are inadequate. I don't dispute Newton's lack of knowledge of 20th century atomic theory.

Nor am I going to take the effort to prove Gauss' Law (which, according to the OP, should be wrong).

This also is unfair. Gauss' Law is strictly speaking a mathematical theorem. That it seems to work well with Faraday's 'field lines' in Classical Electromagnetic Theory is not disputed either. As a 'proof' of the physical accuracy of Newton's Sphere Theorem, however, it is a dud.

I can integrate the Sphere as well as the next man. The issue is not mathematical accuracy or beauty but whether or not it applies in a given physical experiment.

 

So tell me how you want to handle things, and I'll cooperate if I can.

[DQW]

I'm sorry Meta, but I think my time here is better spent helping those that are new to science and discussing mainstream physics, than debating your personal ideas, at the end of which I may only feel regret, if you show me that, for instance, the error in the "center of mass theorem" is of order 1 part in 10^23.

[MetaFrizzics]

Not a problem. You are the best judge of how to spend your own time.

 

time here is better spent helping those that are new to science and discussing mainstream physics,

This would be my purpose too.

But it doesn't get more mainstream/introductory than Newtonian gravity.

Maybe I could start a Q and A thread on that.

[DQW]

But it does veer from mainstream when you suggest that :

 

(i) the understanding of the electroweak interaction as provided by the standard model is suspect,

 

(ii) that any of the present formulations of QM could be done away with by applying the Newtonian formulation to microscopic objects,

 

(iii) that SR & GR are redundant to Newtonian gravitation,

 

(iv) that Boltzmann statistics is a scandal, and that all physical laws obey time inversion symmetry,

 

(v) that the Feynman(-Wheeler) formulation of QED is its only renormalized formulation,

 

etc.

[[Tycho?]]

I must admit that my curiosity is piqued by this.

 

Ok, one takes a magnet, and shakes it back and forth. The acceleration of the magnetic field produces a wave.

 

Take a star and shake it back and forth, gravitational waves result, as the gravitational attraction that that star exerts on another object would vary sinosodaly. It does seem like gravitational waves, or at least the appearance of them can be predicted by Newtonian mechanics. Could somebody show me the flaw in this?

[DQW]

'']Take a star and shake it back and forth, gravitational waves result, as the gravitational attraction that that star exerts on another object would vary sinosodaly. It does seem like gravitational waves, or at least the appearance of them can be predicted by Newtonian mechanics. Could somebody show me the flaw in this?

There is no flaw in that argument. It is something that has been known for centuries, and there's ABSOLUTELY nothing new or revolutionary about it.

 

But in the Newtonian framework, you only have a temporal oscillation in the gravitational field - the field here changes with time, and so does the field out there. In the framework of Relativity, you have a real wave that oscillates in space and time. The aplitude out here is different from the amplitude out there, and the wave has a finite wavelength.

 

To have a wave, you need a finite propagation velocity. In the Newtonian framework, gravity propagates instantaneously (with infinite wavelength - so it's not a wave).

[timo]

I still haven´t heard a definition for a gravitational wave in Newtonian Gravity so it´s really hard to give a competent answer. Nevertheless:

''] Ok, one takes a magnet, and shakes it back and forth. The acceleration of the magnetic field produces a wave.

What does "acceleration of a field" mean?

 

Take a star and shake it back and forth, gravitational waves result, as the gravitational attraction that that star exerts on another object would vary sinosodaly.

Why? What is "sinosodaly" ? It´s certainly nothing like A*sin(wt). Or else you´d have to explain to me how the gravitational attraction can change its sign.

 

It does seem like gravitational waves, ...

Perhaps. Depends on what a gravitational wave is supposed to be.

 

Could somebody show me the flaw in this?

There is no flaw in it if one just sufficiently stretches your terminology.